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1

Water Dynamics in Salt Solutions Studied with Ultrafast Two-Dimensional Infrared (2D IR)  

E-Print Network (OSTI)

Water Dynamics in Salt Solutions Studied with Ultrafast Two-Dimensional Infrared (2D IR RECEIVED ON FEBRUARY 3, 2009 C O N S P E C T U S Water is ubiquitous in nature, but it exists as pure water infrequently. From the ocean to biology, water molecules interact with a wide variety of dissolved species

Fayer, Michael D.

2

MOBILITY OF THE 2 D ADSORBED PHASES. STUDY OF THE MOBILITY Ol? AN HYPERCRITICAL TWO-DIMENSIONAL  

E-Print Network (OSTI)

MOBILITY OF THE 2 D ADSORBED PHASES. STUDY OF THE MOBILITY Ol? AN HYPERCRITICAL TWO the diffusion coefficient of the two-dimensional hypercritical fluid of methane adsorbed on the graphite basal to measure the dynamical properties of the two-dimensional (2 D) adsorbed fluids pointed out a few years ago

Boyer, Edmond

3

Development of models for the two-dimensional, two-fluid code for sodium boiling NATOF-2D  

E-Print Network (OSTI)

Several features were incorporated into NATOF-2D, a twodimensional, two fluid code developed at M.I.T. for the purpose of analysis of sodium boiling transients under LMFBR conditions. They include improved interfacial mass, ...

Zielinski, R. G.

1981-01-01T23:59:59.000Z

4

Two?dimensional nuclear magnetic resonance studies on a single crystal of l?alanine. Separation of the local dipolar fields; and 2D exchange spectroscopy of the 1 4N relaxation processes  

Science Journals Connector (OSTI)

Two types of 2DNMR techniques namely separated local field 2DNMR (SLF 2DNMR) and 2D exchange NMR spectroscopy were applied to a single crystal of l?alanine at room temperature. In the SLF 2DNMR experiments we found that the 1 3C–1H dipolar field at the C?carbon nucleus could be separated not only from the chemical shift interaction but also from the 1 3C?–1 4N dipolar field. The angular variation of the 1 3C?–1H dipolar splitting was measured when the static magnetic field was rotated about three orthogonal axes (a b and c axes). The 1 3C??1H dipolar coupling tensor was determined and the C?–H bond length was evaluated to be 1.073 Ĺ. In the 2D exchange NMR experiment for C?carbon nucleus the off?diagonal cross peaks due to the single quantum and the double quantum transitions for the spin?lattice relaxation processes of the adjacent 1 4N nucleus were observed. The single quantum transition rate constant was evaluated to be 0.8 s? 1 and the double quantum transition rate constant was estimated to be much smaller. Inspection of the experimental results of the 2D exchange NMR together with the theory indicates that (1) the double quantum cross peaks which appeared when a long mixing time (? m =1.0 s) was used is brought about by two consecutive single quantum processes and (2) the main spin?lattice relaxation process of the NH+ 3 nitrogen nucleus is the fluctuation of 1 4N–1H dipolar interaction rather than the fluctuation of 1 4N quadrupole interaction.

A. Naito; P. B. Barker; C. A. McDowell

1984-01-01T23:59:59.000Z

5

A compact chaotic laser device with a two-dimensional external cavity structure  

SciTech Connect

We propose a compact chaotic laser device, which consists of a semiconductor laser and a two-dimensional (2D) external cavity for delayed optical feedback. The overall size of the device is within 230??m?×?1?mm. A long time delay sufficient for chaos generation can be achieved with the small area by the multiple reflections at the 2D cavity boundary, and the feedback strength is controlled by the injection current to the external cavity. We experimentally demonstrate that a variety of output properties, including chaotic output, can be selectively generated by controlling the injection current to the external cavity.

Sunada, Satoshi, E-mail: sunada@se.kanazawa-u.ac.jp; Adachi, Masaaki [Faculty of Mechanical Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192 (Japan); Fukushima, Takehiro [Department of Information and Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); Shinohara, Susumu; Arai, Kenichi [NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Harayama, Takahisa [NTT Communication Science Laboratories, NTT Corporation, 2-4 Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Department of Mechanical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)

2014-06-16T23:59:59.000Z

6

Ultra-Shallow Imaging Using 2D & 3D Seismic Reflection Methods  

E-Print Network (OSTI)

Dome in Brazoria County, Texas, in late 1926 (Weatherby, 1948). A successful discovery well that was drilled based on this information helped the reflection seismograph to gain acceptance. At the time, recording trucks had only one channel...

Sloan, Steven D.

2008-01-01T23:59:59.000Z

7

Introduction Two-dimensional (2D) methods for  

E-Print Network (OSTI)

need 3D structures in order to implement complex designs. These re- quirements have stimulated or printing. PDMS is inexpen- sive, homogeneous, optically transparent, nontoxic, and commercially available. The flexibility of the PDMS replicas also al- lows patterning by microcontact printing or micromolding

Prentiss, Mara

8

Two-dimensional river modeling  

E-Print Network (OSTI)

flow conditions. This thesis investigates the application of a recently developed two- dimensional river model system. The microcomputer version of FESWMS-2DH was developed for the Federal Highway Administration by the U. S. Geological Survey. Four... simulations are used to examine the performance of the two- dimensional river modeling system: flow in a simple channel, flow in a strongly curved channel bend, flow in a meandering creek, and flow in Buckhorn Creek, a single opening bridge crossing of a...

Thompson, James Cameron

2012-06-07T23:59:59.000Z

9

On the Decomposition of Two-Dimensional Behaviors  

Science Journals Connector (OSTI)

In the paper, a decomposition theorem for autonomous two-dimensional (2D) behaviors, stating that every such behavior can be expressed as the sum of a (uniquely determined) square autonomous behavior and of some finite dimensional autonomous behavior, ... Keywords: Autonomous/controllable behaviors, Laurent varieties, characteristic cones, square/finite dimensional autonomous behaviors

Maria Elena Valcher

2000-04-01T23:59:59.000Z

10

Ray tracing of multiple transmitted/reflected/converted waves in 2-D/3-D layered anisotropic TTI media and application to crosswell traveltime tomography  

Science Journals Connector (OSTI)

......waves in 2-D/3-D layered anisotropic TTI media and application...reflections (or conversions) in anisotropic media, we have extended the...case Next we consider a 3-D anisotropic TTI medium of extent 10km...is 50 m. The uniform Clay Shale model (Thomsen 1986), was......

Chao-Ying Bai; Guo-Jiao Huang; Xiao-Ling Li; Bing Zhou; Stewart Greenhalgh

2013-01-01T23:59:59.000Z

11

H? repetitive control of linear systems based on Two-Dimensional model  

Science Journals Connector (OSTI)

This paper concerns with the H? repetitive control of linear system based on Two-Dimensional (2D) system theory. First, a 2D model is established to describe the control behaviour within a repetition ... Keywords: 2D system, H-infinity repetitive control, LMI, linear matrix inequality, linear systems, stability, state feedback control

Yong-Hong Lan; Min Wu; Jin-Hua She

2009-08-01T23:59:59.000Z

12

Two-dimensional 1,3,5-Tris(4-carboxyphenyl)benzene self-assembly at  

E-Print Network (OSTI)

Two-dimensional 1,3,5-Tris(4-carboxyphenyl)benzene self-assembly at the 1-phenyloctane and published work see http://pubs.rsc.org/en/journals/journalissues/tc. Two-dimensional (2D) self-assembly storage, selective ion exchange, high den- sity data storage, etc. Molecular self-assembly offers unique

Paris-Sud XI, Université de

13

Two-Dimensional Numerical Simulations of High Efficiency Silicon Solar Cells  

Science Journals Connector (OSTI)

This paper presents for the first time the use of two-dimensional (2D) device simulation for optimising design parameters of high-efficiency silicon solar cells of practical dimensions. We examine the...

G. Heiser; A. G. Aberle; S. R. Wenham…

1993-01-01T23:59:59.000Z

14

Multi-mode two-dimensional infrared spectroscopy of peptides and proteins  

E-Print Network (OSTI)

In this thesis, a methodology for understanding structural stability of proteins through multi-mode two-dimensional infrared (2D IR) spectroscopy is developed. The experimental framework for generation of broadband infrared ...

DeFlores, Lauren P

2008-01-01T23:59:59.000Z

15

A two-dimensional volatility basis set – Part 2: Diagnostics of organic-aerosol evolution  

E-Print Network (OSTI)

We discuss the use of a two-dimensional volatility-oxidation space (2-D-VBS) to describe organic-aerosol chemical evolution. The space is built around two coordinates, volatility and the degree of oxidation, both of which ...

Donahue, N. M.

16

Simulating Flood Propagation in Urban Areas using a Two-Dimensional Numerical Model.  

E-Print Network (OSTI)

??A two-dimensional numerical model (RiverFLO-2D) has been enhanced to simulate flooding of urban areas by developing an innovative wet and dry surface algorithm, accounting for… (more)

Gonzalez-Ramirez, Noemi

2010-01-01T23:59:59.000Z

17

A nanoscale probe of the quasiparticle band structure for two dimensional electron systems  

E-Print Network (OSTI)

The advent of a broad class of two-dimensional (2D) electronic materials has provided avenues to create and study designer electronic quantum phases. The coexistence of superconductivity, magnetism, density waves, and other ...

Soumyanarayanan, Anjan

2013-01-01T23:59:59.000Z

18

Two-dimensional photonic crystals as selective emitters for thermophotovoltaic power conversion applications  

E-Print Network (OSTI)

This research investigates the use of two-dimensional (2D) photonic crystals (PhC) as selective emitters and means of achieving higher efficiencies in combustion-driven thermophotovoltaic (TPV) systems intended as auxiliary ...

Jovanovic, Natalija Zorana

2005-01-01T23:59:59.000Z

19

Electron localization function for two-dimensional systems E. Rsnen,* A. Castro, and E. K. U. Gross  

E-Print Network (OSTI)

Electron localization function for two-dimensional systems E. Räsänen,* A. Castro, and E. K. U The concept of the electron localization function ELF is extended to two-dimensional 2D electron systems. We systems focusing on semiconductor quantum dots that effectively correspond to a confined 2D electron gas

Gross, E.K.U.

20

Two-dimensional Imaging Velocity Interferometry: Technique and Data Analysis  

SciTech Connect

We describe the data analysis procedures for an emerging interferometric technique for measuring motion across a two-dimensional image at a moment in time, i.e. a snapshot 2d-VISAR. Velocity interferometers (VISAR) measuring target motion to high precision have been an important diagnostic in shockwave physics for many years Until recently, this diagnostic has been limited to measuring motion at points or lines across a target. We introduce an emerging interferometric technique for measuring motion across a two-dimensional image, which could be called a snapshot 2d-VISAR. If a sufficiently fast movie camera technology existed, it could be placed behind a traditional VISAR optical system and record a 2d image vs time. But since that technology is not yet available, we use a CCD detector to record a single 2d image, with the pulsed nature of the illumination providing the time resolution. Consequently, since we are using pulsed illumination having a coherence length shorter than the VISAR interferometer delay ({approx}0.1 ns), we must use the white light velocimetry configuration to produce fringes with significant visibility. In this scheme, two interferometers (illuminating, detecting) having nearly identical delays are used in series, with one before the target and one after. This produces fringes with at most 50% visibility, but otherwise has the same fringe shift per target motion of a traditional VISAR. The 2d-VISAR observes a new world of information about shock behavior not readily accessible by traditional point or 1d-VISARS, simultaneously providing both a velocity map and an 'ordinary' snapshot photograph of the target. The 2d-VISAR has been used to observe nonuniformities in NIF related targets (polycrystalline diamond, Be), and in Si and Al.

Erskine, D J; Smith, R F; Bolme, C; Celliers, P; Collins, G

2011-03-23T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Morphology Development in Model Polyethylene via Two-Dimensional Correlation Analysis  

SciTech Connect

Two-dimensional (2D) correlation analysis is applied to synchrotron X-ray scattering data to characterize morphological regimes during nonisothermal crystallization of a model ethylene copolymer (hydrogenated polybutadiene, HPBD). The 2D correlation patterns highlight relationships among multiple characteristics of structure evolution, particularly the extent to which separate features change simultaneously versus sequentially. By visualizing these relationships during cooling, evidence is obtained for two separate physical processes occurring in what is known as 'irreversible crystallization' in random ethylene copolymers. Initial growth of primarily lamellae into unconstrained melt ('primary-irreversible crystallization') is distinguished from subsequent secondary lamellae formation in the constrained, noncrystalline regions between the primary lamellae ('secondary-irreversible crystallization'). At successively lower temperatures ('reversible crystallization'), growth of the crystalline reflections is found to occur simultaneously with the change in shape of the amorphous halo, which is inconsistent with the formation of an additional phase. Rather, the synchronous character supports the view that growth of frustrated crystals distorts the adjacent noncrystalline material. Furthermore, heterocorrelation analysis of small-angle and wide-angle X-ray scattering data from the reversible crystallization regime reveals that the size of new crystals is consistent with fringed-micellar structures (9 nm). Thus, 2D correlation analysis provides new insights into morphology development in polymeric systems.

D Smirnova; J Kornfield; D Lohse

2011-12-31T23:59:59.000Z

22

Applicability of 2-D Time-Lapse High-Resolution Seismic Reflection Approach to Image Natural Salt-Dissolution and Subsidence in Central Kansas and Improved Post-Processed Vibroseis Data Characteristics  

E-Print Network (OSTI)

The effectiveness of 2-D time-lapse imaging for monitoring natural dissolution of the Hutchinson Salt in eastern Reno County, Kansas was shown to be restricted when comparing high-resolution seismic reflection data acquired ...

Rice, Daniel

2009-01-12T23:59:59.000Z

23

Integrable models and degenerate horizons in two-dimensional gravity  

Science Journals Connector (OSTI)

We analyze an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in the conformal gauge. Its general solution represents a pair of “mirror” black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild–de Sitter case. The existence of ?=const solutions and their relation to the solution given by the 2D Birkhoff theorem is then investigated in a more general context. We also point out some interesting features of the semiclassical theory of our model and the similarity with the behavior of AdS2 black holes.

J. Cruz; A. Fabbri; D. J. Navarro; J. Navarro-Salas

1999-12-20T23:59:59.000Z

24

Integrable models and degenerate horizons in two-dimensional gravity  

E-Print Network (OSTI)

We analyse an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in conformal gauge. Its general solution represents a pair of ``mirror'' black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild-de Sitter case. The existence of $\\phi=const.$ solutions and their relation with the solution given by the 2D Birkhoff's theorem is then investigated in a more general context. We also point out some interesting features of the semiclassical theory of our model and the similarity with the behaviour of AdS$_2$ black holes.

J. Cruz; A. Fabbri; D. J. Navarro; J. Navarro-Salas

1999-06-24T23:59:59.000Z

25

The Two-Dimensional Ising Model  

Science Journals Connector (OSTI)

The two-dimensional Ising model is probably one of the most ... bosonic field theory, made of two independent Ising models. In this bosonic formulation, the ... we also present the solution of the continuum Ising

Philippe Di Francesco; Pierre Mathieu; David Sénéchal

1997-01-01T23:59:59.000Z

26

Computer simulations of two dimensional quasicrystals  

E-Print Network (OSTI)

COMPUTER SIMULATIONS OF TWO DIMENSIONAL QUASICRYSTALS A Thesis by STEVEN LEE JOHNSON Submitted to the Oflice of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August... 1989 Major Subject: Physics COMPUTER SIMULATIONS OF TWO DIMENSIONAL QUASICRYSTALS A Thesis by STEVEN LEE JOHNSON Approved to st e std(d c tent by: C M. V. ric (Chair of Committee) R. Bryan (Member) . Perry (Wilember) R. Arnowitt (Head...

Johnson, Steven Lee

2012-06-07T23:59:59.000Z

27

Movement behaviour of traditionally managed cattle in the Eastern Province of Zambia: investigations using two-dimensional motion sensors   

E-Print Network (OSTI)

Two-dimensional (2-D) motion sensors are activity motion sensors that use electronic accelerometers to record the lying, standing and walking behaviour of animals. They were used in this study with the aim of monitoring and quantifying the movement...

Lubaba, Caesar Himbayi

2011-06-27T23:59:59.000Z

28

Ground Ring Of Two Dimensional String Theory  

E-Print Network (OSTI)

String theories with two dimensional space-time target spaces are characterized by the existence of a ``ground ring'' of operators of spin $(0,0)$. By understanding this ring, one can understand the symmetries of the theory and illuminate the relation of the critical string theory to matrix models. The symmetry groups that arise are, roughly, the area preserving diffeomorphisms of a two dimensional phase space that preserve the fermi surface (of the matrix model) and the volume preserving diffeomorphisms of a three dimensional cone. The three dimensions in question are the matrix eigenvalue, its canonical momentum, and the time of the matrix model.

Edward Witten

1991-08-16T23:59:59.000Z

29

Criticality in the two-dimensional random-bond Ising model Department of Physics, University of California, Santa Barbara, California 93106  

E-Print Network (OSTI)

Criticality in the two-dimensional random-bond Ising model Sora Cho Department of Physics of California, Santa Barbara, California 93106 Received 25 July 1996 The two-dimensional 2D random-bond Ising temperatures and disorder strength. We study the associated critical properties, by mapping the random 2D Ising

30

Renormalization of two-dimensional Ising systems with irrelevant, marginal and relevant aperiodic (dis)order  

E-Print Network (OSTI)

Renormalization of two-dimensional Ising systems with irrelevant, marginal and relevant aperiodic Morgenstelle 14, D-72076 Tubingen, Germany Abstract We introduce a class of 2d Ising models with aperiodic: quasicrystals, aperiodic order, renormalization group, Ising spin systems 1. Introduction One important question

Baake, Michael

31

Two-Dimensional Electronic Correlation and Relaxation Spectra:? Theory and Model Calculations  

Science Journals Connector (OSTI)

Two-Dimensional Electronic Correlation and Relaxation Spectra:? Theory and Model Calculations ... Calculated 2D spectra for a two-level Bloch model, an underdamped Brownian oscillator, and a few models of polar solvent dynamics based on the correlation function approach to the nonlinear response developed by Mukamel and co-workers are presented. ...

Sarah M. Gallagher Faeder; David M. Jonas

1999-11-12T23:59:59.000Z

32

Shear viscosity of two-dimensional Yukawa systems in liquid state  

E-Print Network (OSTI)

The shear viscosity of a two-dimensional (2D) liquid was calculated using equilibrium molecular dynamics simulations with a Yukawa potential. The shear viscosity has a minimum, at a Coulomb coupling parameter of about 17, arising from the temperature dependence of the kinetic and potential contributions. Previous calculations of 2D viscosity were less extensive, and for a different potential. The stress autocorrelation function was found to decay rapidly, contrary to some earlier work. These results are useful for 2D condensed matter systems and are compared to a recent dusty plasma experiment.

Bin Liu; J. Goree

2005-01-31T23:59:59.000Z

33

Large two-dimensional electronic systems: Self-consistent energies and densities at low cost  

Science Journals Connector (OSTI)

We derive a self-consistent local variant of the Thomas-Fermi approximation for (quasi-) two-dimensional (2D) systems by localizing the Hartree term. The scheme results in an explicit orbital-free representation of the electron density and energy in terms of the external potential, the number of electrons, and the chemical potential determined upon normalization. We test the method over a variety 2D nanostructures by comparing to the Kohn-Sham 2D local-density approximation (LDA) calculations up to 600 electrons. Accurate results are obtained in view of the negligible computational cost. We also assess a local upper bound for the Hartree energy.

E. Räsänen; S. Pittalis; G. Bekçio?lu; I. Makkonen

2013-01-31T23:59:59.000Z

34

Theory for two dimensional electron emission between parallel flat electrodes  

SciTech Connect

The electron emission in space charge is limited for the case of a planar cathode; such emission is generated by using an approximation that models electric field formation by a dipole, which generates an oscillatory symmetrical density current j(x), minimum value is moved around the origin and calculated throughout the Poisson equation. Such value has been previously calculated based upon the already stated conditions for the two dimensional (2D) case. In our matter under study, it is stated that a symmetric oscillatory potential, namely, mu(x,y) is invariably generated; because of that the boundary conditions represented by both a barrier potential and a square potential will satisfy this potential as well. For the case of the square potential, it is taking into account either a potential is attractive or repulsive. In this study one of the principal problems is discussed. It is when the space charge creates a potential barrier that prohibits steady-state beam propagation. In this paper it is claimed to have found the boundary conditions that fully satisfy the potential, and the potential satisfies approximately the Poisson equation for the 2D case, and the electron emission is generated through a finite strip due to electrical dipole formation.

Torres-Cordoba, Rafael [Universidad Autonoma de Cd. Juarez, Av. Del Charro 450 Norte, Cd. Juarez, Chihuahua C.P. 32310 (Mexico)

2009-12-15T23:59:59.000Z

35

Two dimensional invisibility cloaking via transformation optics  

E-Print Network (OSTI)

We investigate two-dimensional invisibility cloaking via transformation optics approach. The cloaking media possess much more singular parameters than those having been considered for three-dimensional cloaking in literature. Finite energy solutions for these cloaking devices are studied in appropriate weighted Sobolev spaces. We derive some crucial properties of the singularly weighted Sobolev spaces. The invisibility cloaking is then justified by decoupling the underlying singular PDEs into one problem in the cloaked region and the other one in the cloaking layer. We derive some completely novel characterizations of the finite energy solutions corresponding to the singular cloaking problems. Particularly, some `hidden' boundary conditions on the cloaking interface are shown for the first time. We present our study for a very general system of PDEs, where the Helmholtz equation underlying acoustic cloaking is included as a special case.

Hongyu Liu; Ting Zhou

2010-06-07T23:59:59.000Z

36

Graphene forms template for two-dimensional hybrid materials...  

NLE Websites -- All DOE Office Websites (Extended Search)

Graphene forms template for two-dimensional hybrid materials January 17, 2014 Researchers have developed a new technique for forming a two-dimensional, single-atom sheet of two...

37

Localized electrons in the metallic phase of the two-dimensional electron system at ,,Al,Ga...As-GaAs heterojunctions  

E-Print Network (OSTI)

Localized electrons in the metallic phase of the two-dimensional electron system at ,,Al, United Kingdom Received 29 October 1996 Using the effect of electron focusing we measure the Fermi wave vector of the delocalized electrons in a two-dimensional 2D electron system. After obtaining the total

Ludwig-Maximilians-Universität, München

38

Abstract A method is proposed which combines the two dimensional (2D) orthogonal discrete wavelet transform  

E-Print Network (OSTI)

, and permits selective Mixed­D filter­ ing of the subband signals depending upon the energy content within results which compare favourably in terms of arithmetic complexity, storage requirements with approximately constant velocity along a linear trajectory. It can be shown that the spectral energy

Bartley, Norm

39

Hopkinson bar simulation using DYNA2D  

SciTech Connect

A finite-element simulation of a Split Hopkinson's bar (Kolsky apparatus) technique involving mortar specimens is accomplished with DYNA2D, an explicit two-dimensional finite-element code. Calculations are compared with experimental results contained in a University of Florida report Dynamic Response of Concrete and Concrete Structures, and with analytic solutions of the appropriate wave propagation problem.

Smith, J.A.; Glover, T.A.

1985-01-08T23:59:59.000Z

40

Onsager-Kraichnan Condensation in Decaying Two-Dimensional Quantum Turbulence  

E-Print Network (OSTI)

A negative-temperature statistical equilibrium state of two-dimensional quantum vortices can exhibit clustering of same-circulation vortices and a macroscopic accumulation of kinetic energy at the system length scale, which we term an Onsager-Kraichnan condensate (OKC). We develop a method for microcanonical sampling of equilibrium vortex configurations in the homogeneous 2D Gross-Pitaevskii theory. Varying the system energy at fixed vortex number, we characterize the possible states of vortex matter in a bulk superfluid, from the vortex-dipole gas at positive temperature, to negative-temperature OKC states exhibiting macroscopic vortex clustering and kinetic energy condensation. Dynamical simulations reveal that negative-temperature OKC states emerge as the end states of decaying two-dimensional quantum turbulence. Our work provides the first realization of Onsager's point-vortex model, and its negative temperature states, in a microscopic theory of a 2D superfluid.

Billam, Thomas P; Anderson, Brian P; Bradley, Ashton S

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Convergence of two-dimensional Fourier series  

E-Print Network (OSTI)

), then the two-dimensional Fourier series equivalent to f(x, y) is Co CO Co Co f(x, y) = L' L' A sin(nx) sin (my) + Z Z B sin(@x)cos(my) n=l m=1 n=l m=1 1 CG Co co + ? F, B sin(nx) + Z Z C cos (nx) sin(my) + ? Z C sin(my) 2 1 n, o n, m 2 I OIm Co Co OO... 1 + g P D cos(nx)cos(my)+ ? Z D cos(nx) ? g D cos(my) n, m 2 1 n 0 2 o, m + ? D 1 4 o, o where A 1 n, m ? w B 1 n, m 2 w B 1 n, o 2 w C 1 n, m 2 w (w, w) f(x, y) sin (nx) sin(my) d(x, y) (-w, -w) (w, w) f(x, y) sin (nx) cos...

Kidd, Robert Henry, III

2012-06-07T23:59:59.000Z

42

Extensivity of two-dimensional turbulence  

E-Print Network (OSTI)

This study is concerned with how the attractor dimension of the two-dimensional Navier--Stokes equations depends on characteristic length scales, including the system integral length scale, the forcing length scale, and the dissipation length scale. Upper bounds on the attractor dimension derived by Constantin--Foias--Temam are analysed. It is shown that the optimal attractor-dimension estimate grows linearly with the domain area (suggestive of extensive chaos), for a sufficiently large domain, if the kinematic viscosity and the amplitude and length scale of the forcing are held fixed. For sufficiently small domain area, a slightly ``super-extensive'' estimate becomes optimal. In the extensive regime, the attractor-dimension estimate is given by the ratio of the domain area to the square of the dissipation length scale defined, on physical grounds, in terms of the average rate of shear. This dissipation length scale (which is not necessarily the scale at which the energy or enstrophy dissipation takes place) can be identified with the dimension correlation length scale, the square of which is interpreted, according to the concept of extensive chaos, as the area of a subsystem with one degree of freedom. Furthermore, these length scales can be identified with a ``minimum length scale'' of the flow, which is rigorously deduced from the concept of determining nodes.

Chuong V. Tran; Theodore G. Shepherd; Han-Ru Cho

2004-03-03T23:59:59.000Z

43

Turbulent equipartitions in two dimensional drift convection  

SciTech Connect

Unlike the thermodynamic equipartition of energy in conservative systems, turbulent equipartitions (TEP) describe strongly non-equilibrium systems such as turbulent plasmas. In turbulent systems, energy is no longer a good invariant, but one can utilize the conservation of other quantities, such as adiabatic invariants, frozen-in magnetic flux, entropy, or combination thereof, in order to derive new, turbulent quasi-equilibria. These TEP equilibria assume various forms, but in general they sustain spatially inhomogeneous distributions of the usual thermodynamic quantities such as density or temperature. This mechanism explains the effects of particle and energy pinch in tokamaks. The analysis of the relaxed states caused by turbulent mixing is based on the existence of Lagrangian invariants (quantities constant along fluid-particle or other orbits). A turbulent equipartition corresponds to the spatially uniform distribution of relevant Lagrangian invariants. The existence of such turbulent equilibria is demonstrated in the simple model of two dimensional electrostatically turbulent plasma in an inhomogeneous magnetic field. The turbulence is prescribed, and the turbulent transport is assumed to be much stronger than the classical collisional transport. The simplicity of the model makes it possible to derive the equations describing the relaxation to the TEP state in several limits.

Isichenko, M.B.; Yankov, V.V. [Univ. of California, Santa Barbara, CA (United States). Inst. for Theoretical Physics

1995-07-25T23:59:59.000Z

44

Broadband optical coupling between microstructured fibers and photonic band gap circuits: Two-dimensional paradigms  

E-Print Network (OSTI)

simple two-dimensional design models. We demonstrate an effective large- bandwidth small-footprint beam platform for integrated optics. Unlike conventional paradigms such as silicon on insulator SOI waveguides that guide light on a chip by total internal reflection index guiding , PBG-based microcircuits can guide

John, Sajeev

45

Finite-temperature phase transitions in quasi-two-dimensional spin-1 Bose gases  

SciTech Connect

Recently, the Berezinskii-Kosterlitz-Thouless transition was found to be mediated by half-quantum vortices (HQVs) in two-dimensional (2D) antiferromagnetic Bose gases [S. Mukerjee, C. Xu, and J. E. Moore, Phys. Rev. Lett. 97, 120406 (2006)]. We study the thermal activation of HQVs in the experimentally relevant trapped quasi-2D system and find a crossover temperature at which free HQVs proliferate at the center of the trap. Above the crossover temperature, we observe transitions corresponding to the onset of a coherent condensate and a quasicondensate and discuss the absence of a fragmented condensate.

Pietilae, Ville [Department of Applied Physics/COMP, Aalto University, Post Office Box 15100, FI-00076 Aalto (Finland); Australian Research Council Centre of Excellence for Quantum Computer Technology, School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney NSW 2052 (Australia); Simula, Tapio P. [Department of Physics, Okayama University, Okayama 700-8530 (Japan); School of Physics, Monash University, Victoria 3800 (Australia); Moettoenen, Mikko [Department of Applied Physics/COMP, Aalto University, Post Office Box 15100, FI-00076 Aalto (Finland); Australian Research Council Centre of Excellence for Quantum Computer Technology, School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney NSW 2052 (Australia); Low Temperature Laboratory, Aalto University, Post Office Box 13500, FI-00076 Aalto (Finland)

2010-03-15T23:59:59.000Z

46

Magnetotransport in Zener tunneling regime in a high-mobility two-dimensional hole gas  

Science Journals Connector (OSTI)

In a high-mobility two-dimensional hole gas (2DHG) in C-doped (001) GaAs/Al0.4Ga0.6As quantum wells, we observe sharp features in the differential magnetoresistance, which we interpret as the Zener-tunneling peak and valley associated with the commensuration transition of Landau orbits. Comparison of data with that in GaAs/Al0.3Ga0.7As 2D electron gas suggests that the amplitude of Zener oscillations in a 2DHG is strongly damped. The data indicate the significant role of band structures in nonlinear transport in 2D electronic systems.

Yanhua Dai; Z. Q. Yuan; C. L. Yang; R. R. Du; M. J. Manfra; L. N. Pfeiffer; K. W. West

2009-07-20T23:59:59.000Z

47

Unification of BKT and BEC Phase Transitions in a Trapped Two-Dimensional Bose Gas  

E-Print Network (OSTI)

We study the critical point for the emergence of coherence in a harmonically trapped two-dimensional (2d) Bose gas with tuneable interactions. Over a wide range of interaction strengths we find excellent agreement with predictions based on the Berezinskii-Kosterlitz-Thouless (BKT) theory of 2d superfluidity. This allows us to quantitatively show, without any free parameters, that the interaction-driven BKT transition smoothly converges onto the purely statistical Bose-Einstein condensation (BEC) transition in the limit of vanishing interactions.

Fletcher, Richard J; Man, Jay; Navon, Nir; Smith, Robert P; Viebahn, Konrad; Hadzibabic, Zoran

2015-01-01T23:59:59.000Z

48

Two-dimensional excitons in three-dimensional hexagonal boron nitride  

SciTech Connect

The recombination processes of excitons in hexagonal boron nitride (hBN) have been probed using time-resolved photoluminescence. It was found that the theory for two-dimensional (2D) exciton recombination describes well the exciton dynamics in three-dimensional hBN. The exciton Bohr radius and binding energy deduced from the temperature dependent exciton recombination lifetime is around 8?Ĺ and 740?meV, respectively. The effective masses of electrons and holes in 2D hBN deduced from the generalized relativistic dispersion relation of 2D systems are 0.54m{sub o}, which are remarkably consistent with the exciton reduced mass deduced from the experimental data. Our results illustrate that hBN represents an ideal platform to study the 2D optical properties as well as the relativistic properties of particles in a condensed matter system.

Cao, X. K.; Lin, J. Y., E-mail: hx.jiang@ttu.edu; Jiang, H. X., E-mail: jingyu.lin@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Clubine, B.; Edgar, J. H. [Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 (United States)] [Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 (United States)

2013-11-04T23:59:59.000Z

49

Two-Dimensional Gas of Massless Dirac Fermions in Graphene  

E-Print Network (OSTI)

Electronic properties of materials are commonly described by quasiparticles that behave as non-relativistic electrons with a finite mass and obey the Schroedinger equation. Here we report a condensed matter system where electron transport is essentially governed by the Dirac equation and charge carriers mimic relativistic particles with zero mass and an effective "speed of light" c* ~10^6m/s. Our studies of graphene - a single atomic layer of carbon - have revealed a variety of unusual phenomena characteristic of two-dimensional (2D) Dirac fermions. In particular, we have observed that a) the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; b) graphene's conductivity never falls below a minimum value corresponding to the conductance quantum e^2/h, even when carrier concentrations tend to zero; c) the cyclotron mass m of massless carriers with energy E in graphene is described by equation E =mc*^2; and d) Shubnikov-de Haas oscillations in graphene exhibit a phase shift of pi due to Berry's phase.

K. S. Novoselov; A. K. Geim; S. V. Morozov; D. Jiang; M. I. Katsnelson; I. V. Grigorieva; S. V. Dubonos; A. A. Firsov

2005-09-13T23:59:59.000Z

50

Holography: 2D or not 2D?  

Science Journals Connector (OSTI)

As was recently pointed out by Cadoni, a certain class of two-dimensional gravitational theories will exhibit a (black hole) thermodynamic behavior that is reminiscent of a free field theory. In the current Rapid Communication, a direct correspondence is established between these two-dimensional models and the strongly curved regime of (arbitrary-dimensional) anti–de Sitter gravity. On this basis, we go on to speculatively argue that two-dimensional gravity may ultimately be utilized for identifying and perhaps even understanding holographic dualities.

A.J.M. Medved

2004-03-22T23:59:59.000Z

51

Two-dimensional polymer synthesis : towards a two-dimensional replicating system for nanostructures  

E-Print Network (OSTI)

The general concept of a replicating monolayer system is introduced as a new method of nanostructure synthesis. One possible implementation of a 2-D replicating system is pursued which uses a diacetylene moiety for ...

Mosley, David W

2005-01-01T23:59:59.000Z

52

Microwave rectification of the current at the metal-metal junction for dilute two-dimensional metals  

Science Journals Connector (OSTI)

Within a quasiclassical transport theory for two-dimensional (2D) electron system, we analyze a recently observed effect of microwave rectification at the boundary between two 2D metals of different carrier densities. A nonlinear response is employed to explain the effect. It is shown that the effect of rectification arises due to the inhomogeneity of the electron density, which breaks the space symmetry of the system. The results agree with the above-noted experiments.

Natalya A. Zimbovskaya

2003-09-12T23:59:59.000Z

53

Periodic wave patterns of two-dimensional Boussinesq systems  

E-Print Network (OSTI)

Feb 9, 2006 ... Abstract. We prove the existence of a large family of two-dimensional travelling wave patterns for a Boussinesq system which describes.

2006-06-09T23:59:59.000Z

54

Two-dimensional simulation of the Raft River geothermal reservoir...  

Open Energy Info (EERE)

favorably with the test data. Authors Kettenacker and W. C. Published DOE Information Bridge, 311977 DOI 10.21727290699 Citation Kettenacker, W. C. . 311977. Two-dimensional...

55

Linear steady flows in a two-dimensional Boussinesq  

E-Print Network (OSTI)

Linear steady flows in a two-dimensional Boussinesq fluid driven by thermal forcing P.A.J. van Melick De Bilt | 2010 | Stageverslag #12;#12;Linear steady flows in a two-dimensional Boussinesq fluid-rotating, small-amplitude and Boussinesq flow. A step-by-step approach has been used towards a smooth localized

Stoffelen, Ad

56

Detection of slow modulation wave diffusion in incommensurate barium sodium niobate by 93Nb two-dimensional exchange NMR  

Science Journals Connector (OSTI)

93Nb two-dimensional (2D) exchange NMR was used to study ultraslow motions in incommensurate barium sodium niobate (BSN) in the temperature range 500–560 K. These 2D exchange data provide strong evidence for diffusionlike motion of the modulation wave in BSN. Such motions in BSN had been previously detected by using a complementary NMR experiment, the Hahn spin-echo decay. However, since the Hahn spin-echo decay technique cannot always distinguish unambiguously between different motional mechanisms, this 2D experiment provides definitive confirmation of modulation wave diffusion and rules out other possible motional mechanisms for the Hahn spin-echo decay in this system.

Ligia Muntean and David C. Ailion

2000-12-11T23:59:59.000Z

57

Delay-dependent robust $$H_\\infty $$ control for 2-D discrete nonlinear systems with state delays  

Science Journals Connector (OSTI)

This paper investigates the problem of robust $$H_\\infty $$ control for a class of 2-D (two-dimensional) discrete state delayed systems with sector nonlinearity ... Keywords: $$H_\\infty $$ performance, 2D discrete systems, Exponential stability, State delays

Shipei Huang; Zhengrong Xiang

2014-10-01T23:59:59.000Z

58

Effective field theory and integrability in two-dimensional Mott transition  

SciTech Connect

Highlights: > Mott transition in 2d lattice fermion model. > 3D integrability out of 2D. > Effective field theory for Mott transition in 2d. > Double Chern-Simons. > d-Density waves. - Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a quantum group symmetry as a consequence of a recently found solution of the Zamolodchikov tetrahedron equation. A projection (from three to two space-time dimensions) property of the solution is used to identify the symmetry of the model at the Mott critical point as U{sub q}(sl(2)-circumflex)xU{sub q}(sl(2)-circumflex), with deformation parameter q = -1. Based on this result, the low-energy effective field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the effective filed theory methods, we show that the Mott transition that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.

Bottesi, Federico L. [Facultad de Ingenieria Pontificia Universidad Catolica Argentina, Av. Alicia Moreau de Justo 1500, 1428 Buenos Aires (Argentina); Physics Department, Comision Nacional de Energia Atomica, Av. Libertador 8250, 1429 Buenos Aires (Argentina); Zemba, Guillermo R., E-mail: zemba@tander.cnea.gov.ar [Facultad de Ingenieria Pontificia Universidad Catolica Argentina, Av. Alicia Moreau de Justo 1500, 1428 Buenos Aires (Argentina); Physics Department, Comision Nacional de Energia Atomica, Av. Libertador 8250, 1429 Buenos Aires (Argentina)

2011-08-15T23:59:59.000Z

59

Two-dimensional Detector for High Resolution Soft X-ray Imaging  

SciTech Connect

A new two-dimensional (2D) detector for detecting soft X-ray (SX) images was developed. The detector has a scintillator plate to convert a SX image into a visible (VI) one, and a relay optics to magnify and detect the converted VI image. In advance of the fabrication of the detector, quantum efficiencies of scintillators were investigated. As a result, a Ce:LYSO single crystal on which Zr thin film was deposited was used as an image conversion plate. The spatial resolution of fabricated detector is 3.0 {mu}m, and the wavelength range which the detector has sensitivity is 30-6 nm region.

Ejima, Takeo; Ogasawara, Shodo; Hatano, Tadashi; Yanagihara, Mihiro; Yamamoto, Masaki [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University (Japan)

2010-06-23T23:59:59.000Z

60

Spin Dynamics in Two-Dimensional Arrays of Quantum Dots with Local Ordering of Nanoclusters  

SciTech Connect

Electron paramagnetic resonance (EPR) is used to probe the spin dynamics in two-dimensional (2D) quantum dot (QD) arrays with local ordering of nanoclusters. A careful examination of EPR line shape, width and g-factor values allow us to attribute this signal to the electrons localized in the strain-induced potential wells in Si in the vicinity of the Ge dots. The strong orientation dependence of EPR line width is defined by changing localization degree of electrons at different magnetic field directions. The theoretical approximation of orientation dependence of EPR line width allows estimating the effective radius of electron localization, as {approx}80 nm.

Zinovieva, A. F.; Dvurechenskii, A. V.; Stepina, N. P.; Nikiforov, A. I.; Lyubin, A. S. [Institute of Semiconductor Physics, 630090 Novosibirsk, pr. Lavrentieva 13 (Russian Federation); Sobolev, N.; Carmo, M. C. [Departamento de Fisica e I3N, Universidade de Aveiro, Aveiro (Portugal)

2011-12-23T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Social applications of two-dimensional Ising models  

Science Journals Connector (OSTI)

I review three socio-economic models of economic opinions urban segregation and language change and show that the well-known two-dimensional Ising model gives about the same results in each case.

D. Stauffer

2008-01-01T23:59:59.000Z

62

Entropy of the two-dimensional Ising model  

Science Journals Connector (OSTI)

A numerical calculation of the entropy of the two-dimensional Ising model is described, for nonzero external field. The calculation makes use of the Monte Carlo method to simulate a kind of microcanonical ensemble.

Daniel R. Stump

1987-11-01T23:59:59.000Z

63

Exact Partition Function for the Two-Dimensional Ising Model  

Science Journals Connector (OSTI)

We present a relatively simple derivation based on Burgoyne's combinational method of the Onsager formula for the partition function of the two-dimensional square Ising model.

M. Lawrence Glasser

1970-01-01T23:59:59.000Z

64

Single particle spectrum of the two dimensional electron gas  

E-Print Network (OSTI)

Accurate spectroscopy has driven advances in chemistry, materials science, and physics. However, despite their importance in the study of highly correlated systems, two-dimensional systems (2DES) have proven difficult to ...

Dial, Oliver Eugene, III

2007-01-01T23:59:59.000Z

65

Regional statistics in confined two-dimensional decaying turbulence  

Science Journals Connector (OSTI)

...evolution of Eulerian statistics of vorticity and pressure...Gaussian vorticity probability distribution function...study, the Lagrangian statistics of the same problem...85.752 ) Regional statistics in confined two-dimensional...Boltzmann method. The probability density function...

2011-01-01T23:59:59.000Z

66

Two dimensional properties of methane adsorbed on porous silicon  

E-Print Network (OSTI)

TWO DIMENSIONAL PROPERTIES OF METHANE ADSORBED ON POROUS SILICON A Thesis by RICHARD FRANKLIN TENNIS Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE May 1989 Major Subject: Physics TWO DIMENSIONAL PROPERTIES OF METHANE ADSORBED ON POROUS SILICON A Thesis by RICHARD FRANKLIN TENNIS Approved as to style and content by: P. Kirk (C ir of Committee) Glenn olet (M er) Da J. Ernst...

Tennis, Richard Franklin

2012-06-07T23:59:59.000Z

67

Two?dimensional magnetohydrodynamic calculations of the plasma focus  

Science Journals Connector (OSTI)

Two?dimensional magnetohydrodynamic calculations on plasma focus experiments in the Mather geometry are described. The properties of the two?dimensional numerical solutions are discussed. Detailed results are given for a specific problem which compares favorably with experiment. The numerical solution for the plasma focus previously given by Potter has been rerun with substantial disagreement. Arguments are given to show that the Potter code is incorrect.

Stephen Maxon; James Eddleman

1978-01-01T23:59:59.000Z

68

Two-dimensional relativistic space charge limited current flow in the drift space  

SciTech Connect

Relativistic two-dimensional (2D) electrostatic (ES) formulations have been derived for studying the steady-state space charge limited (SCL) current flow of a finite width W in a drift space with a gap distance D. The theoretical analyses show that the 2D SCL current density in terms of the 1D SCL current density monotonically increases with D/W, and the theory recovers the 1D classical Child-Langmuir law in the drift space under the approximation of uniform charge density in the transverse direction. A 2D static model has also been constructed to study the dynamical behaviors of the current flow with current density exceeding the SCL current density, and the static theory for evaluating the transmitted current fraction and minimum potential position have been verified by using 2D ES particle-in-cell simulation. The results show the 2D SCL current density is mainly determined by the geometrical effects, but the dynamical behaviors of the current flow are mainly determined by the relativistic effect at the current density exceeding the SCL current density.

Liu, Y. L.; Chen, S. H., E-mail: chensh@ncu.edu.tw [Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Koh, W. S. [A-STAR Institute of High Performance Computing, Singapore 138632 (Singapore)] [A-STAR Institute of High Performance Computing, Singapore 138632 (Singapore); Ang, L. K. [Engineering Product Development, Singapore University of Technology and Design, Singapore 138682 (Singapore)] [Engineering Product Development, Singapore University of Technology and Design, Singapore 138682 (Singapore)

2014-04-15T23:59:59.000Z

69

Modeling two-dimensional magnetic resonance measurements in coupled pore systems  

Science Journals Connector (OSTI)

We present numerical simulations of a two-dimensional (2D) nuclear magnetic resonance process, T2-storage-T2, on a simple mixed porosity system, the micrograin consolidation (?GC) model. The results of these calculations are compared with predictions based on the analytic two-site exchange model, for which we have independently established numerical values for all the input parameters. Although there is qualitative and semiquantitative agreement between the two models, we identify specific instances where the two-site model fails to properly describe the combined effects of relaxation and diffusion. Generally, these instances occur when a gradient in magnetization within the large pores of the ?GC model is established during the initial phase of the 2D process. The two-site model assumes that the magnetization is spatially uniform within each of its subpore systems and thus cannot describe such effects.

L. M. Schwartz; D. L. Johnson; J. Mitchell; T. C. Chandrasekera; E. J. Fordham

2013-09-30T23:59:59.000Z

70

Optimal design of switched reluctance motor using two-dimensional finite element method  

Science Journals Connector (OSTI)

Switched reluctance motor (SRM) has some advantages such as low cost high torque density etc. but SRM has essentially high torque ripple due to its salient structure. To apply SRM to the industrial field we have to minimize torque ripple which is the weak point of SRM. This article introduces optimal design process of SRM using a numerical method such as two-dimensional (2D) finite element method. The electrical and geometrical design parameters have been adopted as 2D design variables. From this work we can obtain the optimal design which minimizes the torque ripple. We also can obtain the optimal design which maximizes the average torque. Finally this article presents performance comparison of two optimal designs the minimized torque ripple and the maximized average torque.

Youn-Hyun Kim; Jae-Hak Choi; Sung-In Jung; Sol Kim; Ju Lee; Min-Sik Chu; Kyung-Jin Hong; Dong-Hoon Choi

2002-01-01T23:59:59.000Z

71

Three-Dimensionality in Quasi-Two Dimensional Flows: the Barrel Effects  

E-Print Network (OSTI)

A scenario is put forward for the appearance of three-dimensionality both in quasi-2D rotating flows and quasi-2D magnetohydrodynamic (MHD) flows. We distinguish two forms of threedimensionalities, establish how both are ignited by the presence of walls, and how they relate to each other. One form involves velocities or currents along the rotation direction or the magnetic field, while the other leads to quadratic variations of these quantities along this direction. It is shown that the common tendency of these flows to two-dimensionality and the mechanisms of the first form of three-dimensionality can be explained through a single formal analogy between rotating flows, MHD flows and a wider class of flows, whereas the second form involves a distinct mechanism. Because of this trans-disciplinary character, these phenomena are active in such diverse flows as those in atmospheres, oceans and the cooling blankets of nuclear fusion reactors.

Pothérat, Alban

2011-01-01T23:59:59.000Z

72

An Ant Colony Optimization Algorithm for the 2D HP Protein Folding Problem  

E-Print Network (OSTI)

An Ant Colony Optimization Algorithm for the 2D HP Protein Folding Problem Alena Shmygelska, Rosal, the two dimensional hydrophobic-polar (2D HP) protein folding problem. We introduce an ant colony algorithm closely approaches that of specialised, state-of-the methods for 2D HP protein folding. 1

Hoos, Holger H.

73

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy  

SciTech Connect

One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO){sub 3} and CpFe(CO){sub 2} have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO){sub 5}[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO){sub 5} have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.

Cahoon, James Francis

2008-12-16T23:59:59.000Z

74

Temperature-jump 2D IR spectroscopy to study protein conformational dynamics  

E-Print Network (OSTI)

Temperature-jump (T-jump) two-dimensional infrared spectroscopy (2D IR) is developed, characterized, and applied to the study of protein folding and association. In solution, protein conformational changes span a wide range ...

Jones, Kevin C. (Kevin Chapman)

2012-01-01T23:59:59.000Z

75

Hydrogen Bond Rearrangements in Water Probed with Temperature-Dependent 2D IR  

E-Print Network (OSTI)

We use temperature-dependent two-dimensional infrared spectroscopy (2D IR) of dilute HOD in H2O to investigate hydrogen bond rearrangements in water. The OD stretching frequency is sensitive to its environment, and loss ...

Nicodemus, Rebecca A.

76

Can one and two-dimensional solid-state NMR fingerprint zeolite framework topology?  

Science Journals Connector (OSTI)

Abstract In this contribution, we have explored the potential and strength of one-dimensional (1D) 29Si and two-dimensional (2D) 29S–29Si and 29Si–17O NMR as invariants of non-oriented graph for fingerprinting zeolite frameworks. 1D and 2D 29Si NMR can indeed provide indications on the graph vertices, edges and allow the construction of the adjacency matrix, i.e. the set of connections between the graph vertices. From the structural data, hypothetical 1D 29Si and 2D 29Si–29Si NMR signatures for 193 of the zeolite frameworks reported in the Atlas of Zeolite Structures have been generated. Comparison between all signatures shows that thanks to the 1D 29Si NMR data only, almost 20% of the known zeolite frameworks could be distinguished. Further NMR signatures were generated by taking into account 2D 29Si–29Si and 29Si–17O correlations. By sorting and comparison of all the NMR data, up to 80% of the listed zeolites could be unambiguously discriminated. This work indicates that (i) solid-state NMR data indeed represent a rather strong graph invariant for zeolite framework, (ii) despite their difficulties and costs (isotopic labeling is often required, the NMR measurements can be long), 29Si and 17O NMR measurements are worth being investigated in the frame of zeolites structure resolution. This approach could also be generalized to other zeolite-related materials containing NMR-measurable nuclides.

Charlotte Martineau; Sandrine Vial; Dominique Barth; Franck Quessette; Francis Taulelle

2014-01-01T23:59:59.000Z

77

Equilibrium state of a trapped two-dimensional Bose gas  

Science Journals Connector (OSTI)

We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional Rb87 Bose gas and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in situ measurements and quantum Monte Carlo simulations, which we attribute to a nonlinear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time of flight, taking advantage of their self-similarity in a two-dimensional expansion.

Steffen P. Rath, Tarik Yefsah, Kenneth J. Günter, Marc Cheneau, Rémi Desbuquois, Markus Holzmann, Werner Krauth, and Jean Dalibard

2010-07-12T23:59:59.000Z

78

Superfluid Mutual-friction Coefficients from Vortex Dynamics in the Two-dimensional Galerkin-truncated Gross-Pitaevskii Equation  

E-Print Network (OSTI)

We present algorithms for the ab-initio determination of the temperature ($T$) dependence of the mutual-friction coefficients $\\alpha$ and $\\alpha'$ and the normal-fluid density $\\rho_{\\rm n}$ in the two-dimensional (2D) Galerkin-truncated Gross-Pitaevskii system. Our algorithms enable us to determine $\\alpha(T)$, even though fluctuations in 2D are considerably larger than they are in 3D. We also examine the implications of our measurements of $\\alpha'(T)$ for the Iordanskii force, whose existence is often questioned.

Vishwanath Shukla; Marc Brachet; Rahul Pandit

2014-11-23T23:59:59.000Z

79

condmat/9801215 Crossovers in the Two Dimensional Ising Spin Glass  

E-Print Network (OSTI)

cond­mat/9801215 v2 26 Jan 1998 Crossovers in the Two Dimensional Ising Spin Glass of extensive computer simulations we analyze in detail the two dimen­ sional \\SigmaJ Ising spin glass Introduction At present it is clear that the lower critical dimension of Edwards­Anderson Ising spin glasses

Roma "La Sapienza", UniversitĂ  di

80

Anomalous Hall effect in a two-dimensional electron gas  

E-Print Network (OSTI)

transport theory or the diagrammatic approach based on the Kubo- Streda linear-response formalism. The equivalence of these two methods for the two-dimensional Dirac-band graphene system has recently been shown by Sinitsyn et al.,10 who explicitly...

Nunner, Tamara S.; Sinitsyn, N. A.; Borunda, Mario F.; Dugaev, V. K.; Kovalev, A. A.; Abanov, Artem; Timm, Carsten; Jungwirth, T.; Inoue, Jun-ichiro; MacDonald, A. H.; Sinova, Jairo.

2007-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

High Order Hybrid Numerical Simulations of Two Dimensional Detonation Waves  

E-Print Network (OSTI)

High Order Hybrid Numerical Simulations of Two Dimensional Detonation Waves Wei Cai Department detonation waves, we have devel- oped a high order numerical scheme suitable for calculating the detailed transverse wave structures of multidimensional detonation waves. The numerical algorithm uses a multi

Cai, Wei

82

Lattice Boltzmann scheme for two-dimensional magnetohydrodynamics  

Science Journals Connector (OSTI)

It is shown that the lattice Boltzmann equation arising from the basic lattice-gas scheme for Navier-Stokes equations can be extended in such a way as to include the effects of a two-dimensional magnetic field. This offers the possibility of developing new computational schemes for the efficient simulation of incompressible magnetohydrodynamic flows.

S. Succi; M. Vergassola; R. Benzi

1991-04-15T23:59:59.000Z

83

Two-DIMENSIONAL WATER FLOOD AND MUDFLOW SIMULATION  

E-Print Network (OSTI)

Two-DIMENSIONAL WATER FLOOD AND MUDFLOW SIMULATION By J. S. O'Brien, 1 P. Y. Julien, 2 and W. T by the Federal Emergency Management Agency (FEMA) (FAN, 1990). Since the FEMA method doesn't simulate flood. Fullerton, 3 Members, ASCE ABSTRACT: FLO-2Dis a two-dimensionalfinite differencemodel that simulates clear

Julien, Pierre Y.

84

Two-dimensional optimization of free-electron-laser designs  

DOE Patents (OSTI)

Off-axis, two-dimensional designs for free electron lasers are described that maintain correspondence of a light beam with a synchronous electron at an optimal transverse radius r > 0 to achieve increased beam trapping efficiency and enhanced laser beam wavefront control so as to decrease optical beam diffraction and other deleterious effects.

Prosnitz, D.; Haas, R.A.

1982-05-04T23:59:59.000Z

85

Two-dimensional optimization of free electron laser designs  

DOE Patents (OSTI)

Off-axis, two-dimensional designs for free electron lasers that maintain correspondence of a light beam with a "synchronous electron" at an optimal transverse radius r>0 to achieve increased beam trapping efficiency and enhanced laser beam wavefront control so as to decrease optical beam diffraction and other deleterious effects.

Prosnitz, Donald (Walnut Creek, CA); Haas, Roger A. (Pleasanton, CA)

1985-01-01T23:59:59.000Z

86

IDENTIFICATION OF MATERIAL DAMAGE IN TWO DIMENSIONAL DOMAINS  

E-Print Network (OSTI)

IDENTIFICATION OF MATERIAL DAMAGE IN TWO DIMENSIONAL DOMAINS USING SQUID BASED NDE SYSTEM H on such problems entails quantitative nondestructive evaluation methods in SQUID-based NDE system [1]. It is well, SQUID based nondestructive evaluation (NDE) systems using injection current methods have been recently

87

IDENTIFICATION OF MATERIAL DAMAGE IN TWO DIMENSIONAL DOMAINS  

E-Print Network (OSTI)

IDENTIFICATION OF MATERIAL DAMAGE IN TWO DIMENSIONAL DOMAINS USING SQUID BASED NDE SYSTEM H#ort on such problems entails quantitative nondestructive evaluation methods in SQUID­based NDE system [1]. It is well nondestructive evaluation (NDE) systems using injection current methods have been recently developed [3, 4

88

Experiments on a two–dimensional laminar separation bubble  

Science Journals Connector (OSTI)

...disturbances in the bubble was found to be exponen...simulation and linear stability calculations), where...two-dimensional laminar separation bubble 3205 This work was supported...transitional separation bubbles. TRITA-MEK tech...1993 Experiments on the stability of Tollmien{Schlichting...

2000-01-01T23:59:59.000Z

89

Optical implementability of the two-dimensional Quantum Walk  

E-Print Network (OSTI)

We propose an optical cavity implementation of the two-dimensional coined quantum walk on the line. The implementation makes use of only classical resources, and is tunable in the sense that a large number of different unitary transformations can be implemented by tuning some parameters of the device.

Eugenio Roldan; J. C. Soriano

2005-03-07T23:59:59.000Z

90

Nesting of two-dimensional irregular parts: an integrated approach  

E-Print Network (OSTI)

Nesting of two-dimensional irregular parts: an integrated approach S. Q. XIE*{, G. G. WANG{ and Y The present paper reports an intelligent computer-aided nesting (CAN) system for optimal nesting of two the utilization ratio of sheet materials. This paper also systemically reviews the nesting algorithms that were

Wang, Gaofeng Gary

91

Electronic Control of a Two-Dimensional, Knee-less,  

E-Print Network (OSTI)

of the two dimensional, knee-less, bipedal walker was originally created by Gosse [1] in 1998. Energy and prepare dozens of discrete components, the Robot Controller combines a programmable chip, programming port Power Approx. 1W Low power consumption means greater robot efficiency and longer walking time Size 3

Ruina, Andy L.

92

Fast approximate Duplicate Detection for 2D-NMR Spectra  

E-Print Network (OSTI)

, the one-dimensional plots at the axes are projections of the original two-dimensional intensity function the influences of two different atom types at the same time, e.g. 1 H (hydrogen) and 13 C (carbon). The result of a 2D-NMR measurement can be seen as an intensity function measured over two independent variables3

Hinneburg, Alexander

93

Hopkinson bar simulation using DYNA2D. Revision 1  

SciTech Connect

A finite-element simulation of a Split Hopkinson's bar (Kolsky apparatus) technique involving mortar specimens is accomplished with DYNA2D, an explicit two-dimensional finite-element code. Calculations are compared with experimental results contained in a University of Florida report Dynamic Response of Concrete and Concrete Structures, and with analytic solutions of the appropriate wave propagation problem.

Smith, J.A.; Glover, T.A.

1985-05-01T23:59:59.000Z

94

Weakly interacting two-dimensional system of dipoles: Limitations of the mean-field theory  

Science Journals Connector (OSTI)

We consider a homogeneous two-dimensional Bose gas with repulsive dipole-dipole interactions. The ground-state equation of state, calculated using the diffusion Monte Carlo method, shows quantitative differences from the predictions of the commonly used Gross-Pitaevskii mean-field theory. The static structure factor, pair distribution function, and condensate fraction are calculated in a wide range of the gas parameter. Differences from mean-field theory are reflected in the frequency of the lowest “breathing” mode for harmonically trapped systems.

G. E. Astrakharchik, J. Boronat, J. Casulleras, I. L. Kurbakov, and Yu. E. Lozovik

2007-06-29T23:59:59.000Z

95

Two-dimensional materials as a new platform for atomically thin electronics and optoelectronics  

E-Print Network (OSTI)

M. S. Electronics and optoelectronics of two-dimensionalGraphene photonics and optoelectronics. Nat. Photon. 4, 611–M. S. Electronics and optoelectronics of two-dimensional

Cheng, Rui

2014-01-01T23:59:59.000Z

96

E-Print Network 3.0 - analysis ii two-dimensional Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

Washington, Seattle, WA, United States Two-dimensional turbulence appears... of the phenomenology of two-dimensional turbulence as well as recent theoretical breakthroughs by...

97

Consideration of a ultracold neutron source in two-dimensional cylindrical geometry by taking simulated boundaries  

SciTech Connect

A new idea to calculate ultracold neutron (UCN) production by using Monte Carlo simulation method to calculate the cold neutron (CN) flux and an analytical approach to calculate the UCN production from the simulated CN flux was given. A super-thermal source (UCN source) was modeled based on an arrangement of D{sub 2}O and solid D{sub 2} (sD{sub 2}). The D{sub 2}O was investigated as the neutron moderator, and sD{sub 2} as the converter. In order to determine the required parameters, a two-dimensional (2D) neutron balance equation written in Matlab was combined with the MCNPX simulation code. The 2D neutron-transport equation in cylindrical (? ? z) geometry was considered for 330 neutron energy groups in the sD{sub 2}. The 2D balance equation for UCN and CN was solved using simulated CN flux as boundary value. The UCN source dimensions were calculated for the development of the next UCN source. In the optimal condition, the UCN flux and the UCN production rate (averaged over the sD{sub 2} volume) equal to 6.79?×?10{sup 6} cm{sup ?2}s{sup ?1} and 2.20 ×10{sup 5} cm{sup ?3}s{sup ?1}, respectively.

Gheisari, R., E-mail: gheisari@pgu.ac.ir [Physics Department, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Nuclear Energy Research Center, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Firoozabadi, M. M.; Mohammadi, H. [Department of Physics, University of Birjand, Birjand 97175 (Iran, Islamic Republic of)] [Department of Physics, University of Birjand, Birjand 97175 (Iran, Islamic Republic of)

2014-01-15T23:59:59.000Z

98

Conductance characteristics between a normal metal and a two-dimensional Fulde-Ferrell-Larkin-Ovchinnikov superconductor: The Fulde-Ferrell state  

E-Print Network (OSTI)

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state has received renewed interest recently due to the experimental indication of its presence in CeCoIn5, a quasi-two-dimensional (2D) d-wave superconductor. However direct evidence of the spatial...

Cui, Qinghong; Hu, Chia-Ren; Wei, J. Y. T.; Yang, Kun.

2006-01-01T23:59:59.000Z

99

Volume 168, number 3,4 CHEMICAL PHYSICS LETTERS 4 May 1990 HOLE BURNING LINE SHAPES IN A TWO-DIMENSIONAL GLASS  

E-Print Network (OSTI)

-DIMENSIONAL GLASS A MODEL FOR HOLE BURNING LINE SHAPES OF MOLECULES ON SURFACES Dee William PACK ' and Michael D of molecules in a two-dimensional glass in presented. An extension of the standard dynamic model for three-dimensional glasses is employed. A calculation of the 2-D spatial average with the proper correlation function

Fayer, Michael D.

100

THERM: Two-Dimensional Building Heat-Transfer Modeling  

NLE Websites -- All DOE Office Websites (Extended Search)

5 5 THERM: Two-Dimensional Building Heat-Transfer Modeling For more information and to download THERM, please visit our website: http://windows.lbl.gov/software/therm The Windows and Daylighting Group's two-year-old computer program THERM 1.0 is a state-of-the-art tool for modeling two-dimensional heat-transfer effects in building components. The thermal property information THERM provides is important for the design and application of building components such as windows, walls, foundations, roofs and doors. This Microsoft Windows-based program has great potential to users such as building component manufacturers, educators, students, architects, engineers and others who are interested in assessing the heat-transfer properties of single products, product interactions, or integrated systems. THERM

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse  

SciTech Connect

Abstract Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 m in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their atomic resolution structure were characterized. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

Li, Xufan [ORNL; Lin, Ming-Wei [ORNL; Zhang, Huidong [University of Tennessee, Knoxville (UTK); Puretzky, Alexander A [ORNL; Idrobo Tapia, Juan C [ORNL; Ma, Cheng [ORNL; Chi, Miaofang [ORNL; Yoon, Mina [ORNL; Rouleau, Christopher M [ORNL; Kravchenko, Ivan I [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

2014-01-01T23:59:59.000Z

102

Two-dimensional elastic wave propagation in a duraluminum sheet  

E-Print Network (OSTI)

/receiver separations. The purpose of this study is to investigate the propagation of elastic waves in a thin-sheet model simulating a horizontal layer (Figure 2). Source and receiver transducers sre placed on the edge of the sheet. Elastic waves are generated...TWO-DIMENSIONAL ELASTIC WAVE PROPAGATION IN A DURALUMINUM SHEET A Thesis DAVID PAUL CEFOLA Submitted to the Graduate College of Texas AIM University in partial fulfillment of the requirement for the degree of' MASTER OF SCIENCE August 1982...

Cefola, David Paul

1982-01-01T23:59:59.000Z

103

Suspended two-dimensional electron and hole gases  

SciTech Connect

We report on the fabrication of fully suspended two-dimensional electron and hole gases in III-V heterostructures. Low temperature transport measurements verify that the properties of the suspended gases are only slightly degraded with respect to the non-suspended gases. Focused ion beam technology is used to pattern suspended nanostructures with minimum damage from the ion beam, due to the small width of the suspended membrane.

Kazazis, D.; Bourhis, E.; Gierak, J.; Gennser, U. [Laboratoire de Photonique et de Nanostructures, CNRS-LPN, Route de Nozay, 91460 Marcoussis (France); Bourgeois, O. [Institut Néel, CNRS-UJF, BP 166, 38042 Grenoble Cedex 9 (France); Antoni, T. [Laboratoire de Photonique et de Nanostructures, CNRS-LPN, Route de Nozay, 91460 Marcoussis, France and Laboratoire Kastler Brossel, Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris (France)

2013-12-04T23:59:59.000Z

104

Two?dimensional modeling of the formation of spheromak configurations  

Science Journals Connector (OSTI)

A reduced set of two?dimensional magnetohydrodynamic equations has been derived describing the axisymmetric time evolution of a stable plasma evolving slowly due to resistive diffusion and changing boundary conditions. The equations are restricted to low b but allow changing topology. They are integrated in time to demonstrate a possible spheromak formation method. External circuit equations are integrated simultaneously with the plasma equations to determine the electromagnetic boundary conditions self?consistently. The effects of a finite conductivity vacuum chamber are included.

S. C. Jardin; W. Park

1981-01-01T23:59:59.000Z

105

Quantum Hamilton-Jacobi Approach to Two Dimensional Singular Oscillator  

E-Print Network (OSTI)

We have obtained the solutions of two dimensional singular oscillator which is known as the quantum Calogero-Sutherland model both in cartesian and parabolic coordinates within the framework of quantum Hamilton Jacobi formalism. Solvability conditions and eigenfunctions are obtained by using the singularity structures of quantum momentum functions under some conditions. New potentials are generated by using the first two states of singular oscillator for parabolic coordinates.

Ozlem Yesiltas; Bengu Demircioglu

2007-08-20T23:59:59.000Z

106

Hall effect in the two-dimensional Luttinger liquid  

Science Journals Connector (OSTI)

The temperature dependence of the Hall effect in the normal state is a commom theme of all the cuprate superconductors and has been one of the more puzzling observations on these puzzling materials. We describe a general scheme within the Luttinger liquid theory of these two-dimensional quantum fluids which corrrelates the anomalous Hall and resistivity observations on a wide variety of both pure and doped single crystals, especially the data in the accompanying Letter of Chien, Wang, and Ong.

P. W. Anderson

1991-10-07T23:59:59.000Z

107

Two-dimensional modeling of sodium boiling in a simulated LMFBR loss-of-flow test  

SciTech Connect

Loss-of-flow (LOF) accidents are of major importance in LMFBR safety. Tests have been performed to simulate the simultaneous failure of all primary pumps and reactor shutdown systems in a 37-pin electrically heated test bundle installed in the KNS sodium boiling loop at the Institute of Reactor Development, Karlsruhe. The tests simulated LOF conditions of the German prototype LMFBR, the SNR 300. The main objectives of these tests were to characterize the transient boiling development to cladding dryout and to provide data for validation of sodium boiling codes. One particular LOF test, designated L22, at full power was selected as a benchmark exercise for comparison of several codes at the Eleventh Meeting of the Liquid Metal Boiling Working Group (LMBWG) held in Grenoble, France, in October 1984. In this paper, the results of the calculations performed at ORNL with the two-dimensional (2-D) boiling code THORAX are presented.

Rose, S.D.

1984-01-01T23:59:59.000Z

108

Effects of some common geological features on two-dimensional variably saturated flow  

SciTech Connect

This paper presents results of unsaturated flow simulations undertaken as an auxiliary analysis for the Iterative Performance Assessment (IPA) project, one of the approaches adopted by the U.S. NRC to develop repository license application review capabilities. The effects on flow of common geological features, such as nonhorizontal stratification and vertical or near-vertical fault zones intersecting the strata, in a two-dimensional (2D) domain are studied. Results indicate that the presence of layers and crosscutting fault zones tend to induce three-dimensional (3D) unstable flows in the unsaturated zone. The instability is manifested in our simulations by an oscillatory behavior of steady state. This numerical instability imposes extremely stringent criteria on the time step used in the simulation. Finally, once stable steady-state solutions are attained, the effect of the crossing point in the matrix-fault unsaturated hydraulic conductivity curve on groundwater flux vectors and moisture content distributions is studied.

Bagtzoglou, A.C.; Ababou, R.; Sagar, B.; Islam, M.R. [Southwest Research Institute, San Antonio, TX (United States)

1993-12-31T23:59:59.000Z

109

Interactions between colloidal inclusions in two-dimensional smectic-C* films  

Science Journals Connector (OSTI)

We report an experimental study of colloidal inclusions in free-standing films of smectic-C* liquid crystal. The inclusions are cholesteric droplets that form above the bulk smectic-C*-7cholesteric transition temperature. Each droplet confined in a two-dimensional (2D) system, is accompanied by a topological defect. The distortions of the in-plane orientational order of the smectic-C* film induce elastic interactions between the droplets. As in 3D water nematic emulsions, a short-range repulsion and a long-range dipolar attraction govern the stability of the inclusions and lead to their organization in chainlike structures. Our results are in agreement with recent theoretical predictions.

P. Cluzeau; P. Poulin; G. Joly; H. T. Nguyen

2001-02-21T23:59:59.000Z

110

Large-eddy simulation of flows over two-dimensional idealised street canyons with height variation  

Science Journals Connector (OSTI)

A series of large-eddy simulation (LES) models consisting of two-dimensional (2D) idealised street canyons with building height variability (BHV) are examined. Building blocks with two different heights are placed alternately in the computational domains, constructing repeated street canyons of building-height-to-street-width (aspect) ratio (AR) = 1, 0.5, 0.25 and 0.125 together with BHV = 0.2, 0.4 and 0.6. LES results show that the air exchange rate (ACH) increases with increasing aerodynamic resistance. Apart from AR, BHV is another factor affecting the aerodynamic resistance and thus the ACH. The (vertical) dispersion coefficient ?z of plume transport is also closely related to the aerodynamic resistance, suggesting that introducing BHV in urban areas could help improve the air quality.

Colman C.C. Wong; Chun-Ho Liu

2014-01-01T23:59:59.000Z

111

Three-dimensional liver motion tracking using real-time two-dimensional MRI  

SciTech Connect

Purpose: Combined magnetic resonance imaging (MRI) systems and linear accelerators for radiotherapy (MR-Linacs) are currently under development. MRI is noninvasive and nonionizing and can produce images with high soft tissue contrast. However, new tracking methods are required to obtain fast real-time spatial target localization. This study develops and evaluates a method for tracking three-dimensional (3D) respiratory liver motion in two-dimensional (2D) real-time MRI image series with high temporal and spatial resolution. Methods: The proposed method for 3D tracking in 2D real-time MRI series has three steps: (1) Recording of a 3D MRI scan and selection of a blood vessel (or tumor) structure to be tracked in subsequent 2D MRI series. (2) Generation of a library of 2D image templates oriented parallel to the 2D MRI image series by reslicing and resampling the 3D MRI scan. (3) 3D tracking of the selected structure in each real-time 2D image by finding the template and template position that yield the highest normalized cross correlation coefficient with the image. Since the tracked structure has a known 3D position relative to each template, the selection and 2D localization of a specific template translates into quantification of both the through-plane and in-plane position of the structure. As a proof of principle, 3D tracking of liver blood vessel structures was performed in five healthy volunteers in two 5.4 Hz axial, sagittal, and coronal real-time 2D MRI series of 30 s duration. In each 2D MRI series, the 3D localization was carried out twice, using nonoverlapping template libraries, which resulted in a total of 12 estimated 3D trajectories per volunteer. Validation tests carried out to support the tracking algorithm included quantification of the breathing induced 3D liver motion and liver motion directionality for the volunteers, and comparison of 2D MRI estimated positions of a structure in a watermelon with the actual positions. Results: Axial, sagittal, and coronal 2D MRI series yielded 3D respiratory motion curves for all volunteers. The motion directionality and amplitude were very similar when measured directly as in-plane motion or estimated indirectly as through-plane motion. The mean peak-to-peak breathing amplitude was 1.6 mm (left-right), 11.0 mm (craniocaudal), and 2.5 mm (anterior-posterior). The position of the watermelon structure was estimated in 2D MRI images with a root-mean-square error of 0.52 mm (in-plane) and 0.87 mm (through-plane). Conclusions: A method for 3D tracking in 2D MRI series was developed and demonstrated for liver tracking in volunteers. The method would allow real-time 3D localization with integrated MR-Linac systems.

Brix, Lau, E-mail: lau.brix@stab.rm.dk [Department of Procurement and Clinical Engineering, Region Midt, Olof Palmes Allé 15, 8200 Aarhus N, Denmark and MR Research Centre, Aarhus University Hospital, Skejby, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark)] [Department of Procurement and Clinical Engineering, Region Midt, Olof Palmes Allé 15, 8200 Aarhus N, Denmark and MR Research Centre, Aarhus University Hospital, Skejby, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark); Ringgaard, Steffen [MR Research Centre, Aarhus University Hospital, Skejby, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark)] [MR Research Centre, Aarhus University Hospital, Skejby, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark); Sřrensen, Thomas Sangild [Department of Computer Science, Aarhus University, Aabogade 34, 8200 Aarhus N, Denmark and Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark)] [Department of Computer Science, Aarhus University, Aabogade 34, 8200 Aarhus N, Denmark and Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, 8200 Aarhus N (Denmark); Poulsen, Per Rugaard [Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, 8200 Aarhus N, Denmark and Department of Oncology, Aarhus University Hospital, Nřrrebrogade 44, 8000 Aarhus C (Denmark)] [Department of Clinical Medicine, Aarhus University, Brendstrupgaardsvej 100, 8200 Aarhus N, Denmark and Department of Oncology, Aarhus University Hospital, Nřrrebrogade 44, 8000 Aarhus C (Denmark)

2014-04-15T23:59:59.000Z

112

July 24, 2011 15:30 World Scientific Review Volume -9.75in x 6.5in HadzibabicDalibard BKT physics with two-dimensional atomic gases  

E-Print Network (OSTI)

, and the more conventional Bose­Einstein condensation that is expected for an ideal 2D Bose gas confined quasi two-dimensional (2D) samples by freezing out one degree of freedom with laser beams, and we de of the gas, monitor the occurrence of a BKT-driven phase transition, and observe thermally activated

Dalibard, Jean

113

4D-2D projection of Lorentz-violating Myers-Pospelov QED  

Science Journals Connector (OSTI)

We consider the four-dimensional quantum electrodynamics extended with Myers-Pospelov Lorentz-violating dimension-five operators to investigate 4D-2D projection. In projecting out the 4D theory down to a 2D theory, we get analogs of these operators. Namely, we obtain a new two-dimensional theory with corresponding scalar and fermionic 2D Myers-Pospelov Lorentz-violating dimension-three operators. New defect structures can also be found from this new projected-out 2D scalar sector. Furthermore, we also show that this 2D scalar sector can also be radiatively induced through the new 2D fermionic sector.

F. A. Brito; M. S. Guimaraes; E. Passos; P. Sampaio; C. Wotzasek

2012-11-20T23:59:59.000Z

114

GLOBAL WELL-POSEDNESS FOR THE 2D BOUSSINESQ SYSTEM WITHOUT HEAT DIFFUSION AND WITH EITHER  

E-Print Network (OSTI)

GLOBAL WELL-POSEDNESS FOR THE 2D BOUSSINESQ SYSTEM WITHOUT HEAT DIFFUSION AND WITH EITHER: 612/626-7370 URL: http://www.ima.umn.edu #12;GLOBAL WELL-POSEDNESS FOR THE 2D BOUSSINESQ SYSTEM for the two-dimensional non-diffusive Boussinesq system with viscosity only in the horizontal direction, which

115

Dynamics of quasi-two-dimensional turbulent jets  

E-Print Network (OSTI)

In turbulent jets, fluid is driven by momentum from an orifice into an environ- ment filled with similar fluid. The complexity of this flow, which has been studied for more than 80 years (see e.g. List, 1982, for a detailed review), resides in its turbulent... in time with an accuracy of approximately 1 %. We conducted two distinct sets of experiments using two qualitatively different techniques: dye tracking and particle image velocimetry (PIV). 7 2 Meandering and self-similarity of quasi-two-dimensional jets x...

Landel, Julien Rémy Dominique Gérard

2012-11-13T23:59:59.000Z

116

Nonlinear Cascades in Two-Dimensional Turbulent Magnetoconvection  

SciTech Connect

The dynamics of spectral transport in two-dimensional turbulent convection of electrically conducting fluids is studied by means of direct numerical simulations in the frame of the magnetohydrodynamic Boussinesq approximation. The system performs quasioscillations between two different regimes of small-scale turbulence: one dominated by nonlinear magnetohydrodynamic interactions; the other governed by buoyancy forces. The self-excited change of turbulent states is reported here for the first time. The process is controlled by the ideal invariant cross helicity, H{sup C}=SdSv{center_dot}b. The observations are explained by the interplay of convective driving with the nonlinear spectral transfer of total magnetohydrodynamic energy and cross helicity.

Skandera, Dan; Mueller, Wolf-Christian [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany)

2009-06-05T23:59:59.000Z

117

Magnus force in discrete and continuous two-dimensional superfluids  

SciTech Connect

Motion of vortices in two-dimensional superfluids in the classical limit is studied by solving the Gross-Pitaevskii equation numerically on a uniform lattice. We find that, in the presence of a superflow directed along one of the main lattice periods, vortices move with the superflow on fine lattices but perpendicular to it on coarse ones. We interpret this result as a transition from the full Magnus force in a Galilean-invariant limit to vanishing effective Magnus force in a discrete system, in agreement with the existing experiments on vortex motion in Josephson junction arrays.

Gecse, Z.; Khlebnikov, S. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States)

2005-08-01T23:59:59.000Z

118

Two-dimensional random walk in a bounded domain  

E-Print Network (OSTI)

In a recent Letter Ciftci and Cakmak [EPL 87, 60003 (2009)] showed that the two dimensional random walk in a bounded domain, where walkers which cross the boundary return to a base curve near origin with deterministic rules, can produce regular patterns. Our numerical calculations suggest that the cumulative probability distribution function of the returning walkers along the base curve is a Devil's staircase, which can be explained from the mapping of these walks to a non-linear stochastic map. The non-trivial probability distribution function(PDF) is a universal feature of CCRW characterized by the fractal dimension d=1.75(0) of the PDF bounding curve.

Mahashweta Basu; P. K. Mohanty

2009-10-30T23:59:59.000Z

119

Integrable models and degenerate horizons in two-dimensional gravity  

E-Print Network (OSTI)

We analyse an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in conformal gauge. Its general solution represents a pair of ``mirror'' black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild-de Sitter case. The existence of Birkhoff's theorem is then investigated in a more general context. We also point out some interesting features of the semiclassical theory of our model and the similarity with the behaviour of AdS$_2$ black holes.

Cruz, J; Navarro, D J; Navarro-Salas, J

2000-01-01T23:59:59.000Z

120

Focused two-dimensional antiscatter grid for mammography.  

SciTech Connect

We are developing freestanding high-aspect-ratio, focused, two-dimensional antiscatter grids for mammography using deep x-ray lithography and copper electroforming. The exposure is performed using x-rays from bending magnet beamline 2-BM at the Advanced Photon Source (APS) of Argonne National Laboratory. A 2.8-mm-thick prototype freestanding copper antiscatter grid with 25 {micro}m-wide parallel cell walls and 550 {micro}m periodicity has been fabricated. The progress in developing a dynamic double-exposure technique to create the grid with the cell walls aligned to a point x-ray source of the mammography system is discussed.

Makarova, O. V.; Moldovan, N.; Tang, C.-M.; Mancini, D. C.; Divan, R.; Zyryanov, V. N.; Ryding, D. C.; Yaeger, J.; Liu, C.; Creatv MicroTech Inc.

2002-09-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Two-dimensional random walk in a bounded domain  

E-Print Network (OSTI)

In a recent Letter Ciftci and Cakmak [EPL 87, 60003 (2009)] showed that the two dimensional random walk in a bounded domain, where walkers which cross the boundary return to a base curve near origin with deterministic rules, can produce regular patterns. Our numerical calculations suggest that the cumulative probability distribution function of the returning walkers along the base curve is a Devil's staircase, which can be explained from the mapping of these walks to a non-linear stochastic map. The non-trivial probability distribution function(PDF) is a universal feature of CCRW characterized by the fractal dimension d=1.75(0) of the PDF bounding curve.

Basu, Mahashweta

2010-01-01T23:59:59.000Z

122

Two-dimensional imaging of fuel-vapour concentration by  

Science Journals Connector (OSTI)

The laser-induced exciplex fluorescence (LIEF) technique, which is based on spectrally resolved two-colour fluorescent emissions, has been applied to an evaporating diesel spray for the simultaneous separation of liquid and vapour phases on the two-dimensional images. The exciplex system is based on the TMPD/naphthalene system proposed by Melton. The temporal and spatial distribution of liquid and vapour phases during the mixture formation process was detected by this technique. In the LIEF technique, the vapour phase is detected by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. It is able to provide quantitative information on the diffusion state for applying the statistical entropy concept. This concept was put into practice in the image sets obtained through LIEF measurement in order to investigate the diffusion process of vapour phase in the evaporating diesel spray. The laser shadowgraph was taken to deduce the effect of turbulent mixing on the ignition. The experiments were conducted in a direct injection diesel engine with optical access required for the two-dimensional laser imaging. From the results, it is found that ignition occurs in the region where turbulent mixing has advanced a nearly homogeneous mixture of fuel vapour and air. Multi-sectional images obtained by LIEF indicate that there is a spatial dependence of ignition on the vapour-phase fuel in the combustion chamber.

Hajime Fujimoto; Dae Choi; Yuta Shima; Jiro Senda

2002-01-01T23:59:59.000Z

123

Two-dimensional gravity with a dynamical aether  

Science Journals Connector (OSTI)

We investigate the two-dimensional behavior of gravity coupled to a dynamical unit timelike vector field, i.e. “Einstein-aether theory.” The classical solutions of this theory in two dimensions depend on one coupling constant. When this coupling is positive the only solutions are (i) flat spacetime with constant aether, (ii) de Sitter or anti-de Sitter spacetimes with a uniformly accelerated unit vector invariant under a two-dimensional subgroup of SO(2,1) generated by a boost and a null rotation, and (iii) a nonconstant curvature spacetime that has no Killing symmetries and contains singularities. In this case the sign of the curvature is determined by whether the coupling is less or greater than one. When instead the coupling is negative only solutions (i) and (iii) are present. This classical study of the behavior of Einstein-aether theory in 1+1 dimensions may provide a starting point for further investigations into semiclassical and fully quantum toy models of quantum gravity with a dynamical preferred frame.

Christopher Eling and Ted Jacobson

2006-10-23T23:59:59.000Z

124

High-Accuracy 2D Digital Image Correlation Measurements with Bilateral Telecentric Lenses: Error Analysis and Experimental Verification  

Science Journals Connector (OSTI)

By comparing two digital images of a test planar specimen surface recorded in different configurations, two-dimensional digital image correlation (2D-DIC) provides full-field displacements to sub-pixel accurac...

Bing Pan; Liping Yu; Dafang Wu

2013-11-01T23:59:59.000Z

125

Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers  

SciTech Connect

The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles.

Maingi, R. [North Carolina State Univ., Raleigh, NC (United States)

1992-08-01T23:59:59.000Z

126

Effect of disorder on the superfluid transition in two-dimensional systems  

SciTech Connect

In recent experiments on thin {sup 4}He films absorbed to rough surfaces Luhman and Hallock [Phys. Rev. Lett. 93, 086106 (2004)] attempted to observe Kosterlitz-Thouless (KT) features of the superfluid-normal transition of this strongly disordered two-dimensional (2D) bosonic system. It came as a surprise that while peak of dissipation was measured for a wide range of surface roughness there were no indications of the theoretically expected universal jump of the areal superfluid density for the strongly disordered samples. We test the hypothesis that this unusual behavior is a manifestation of finite-size effects by numerical study of the corresponding 2D bosonic model with strong diagonal disorder. We demonstrate that the discontinuous features of the underlying KT transition are severely smoothed out for finite system sizes (or finite frequency measurements). We resolve the universal discontinuity of the areal superfluid density by fitting our data to the KT renormalization group equations for finite systems. In analogy to our simulations, we suggest that in experiments on strongly disordered 2D bosonic systems the very existence of the KT scenario can and should be revealed only from a proper finite-size scaling of the data (for {sup 4}He films finite-size scaling can be effectively controlled by the scaling of finite frequency of measurements). We also show relevance of our conclusions for a wider class of systems, such as superconducting granular films, Josephson junction arrays, and ultracold atomic gases, where similar difficulties appear in experiments designed to verify KT transition (especially in disordered cases)

Balabanyan, Karen G. [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States)

2007-04-01T23:59:59.000Z

127

Specific heat of a superconducting multilayer: 2D fluctuations and 2D-0D crossover  

Science Journals Connector (OSTI)

We have measured the specific heat of multilayers of superconducting amorphous Mo77Ge23 layers separated by insulating amorphous germanium. We observe a fluctuation regime in quantitative agreement with predictions for two-dimensional superconductivity. The fluctuation peak is rapidly suppressed by the application of small magnetic fields perpendicular to the layers, and the transition becomes extremely broad as the field is increased. The transition widths scale as expected for a field-induced 2D to 0D crossover, and are in excellent agreement with the exact result for 0D fluctuations.

J. S. Urbach; W. R. White; M. R. Beasley; A. Kapitulnik

1992-10-19T23:59:59.000Z

128

Possible diminution of impurity pair breaking for triplet pairing superconductivity in two-dimensional or quasi-two-dimensional, weakly localized, nearly magnetic systems  

SciTech Connect

We propose a conjecture according to which, as a consequence of weak localization in two-dimensional, nearly magnetic itinerant paramagnets, the pair-breaking parameter due to normal impurity scattering, in triplet pairing superconductivity, may be reduced at low enough temperature. It might then, in principle, become easier to observe triplet pairing superconductivity in dirty two-dimensional or quasi-two-dimensional metals, than in three-dimensional ones; thus some recently observed puzzling superconductive behaviors should be reexamined.

Beal-Monod, M.T.; Ebisawa, H.; Fukuyama, H.

1984-08-01T23:59:59.000Z

129

Conductance of two-dimensional disordered Voronoi networks  

Science Journals Connector (OSTI)

Resistor networks constructed from Voronoi polygons are models for transport by diffusive motion across local interfaces where both the interface strength and the local coordination number can be distributed. Computer simulations were performed on a series of two-dimensional networks with increasing degree of disorder, starting from a regular lattice. We find nonmonotonic behavior of the overall network conductance as a function of disorder. The observed increase of network conductance G as the random lattice is approached shows the importance of taking local topology variations into account in the description of disordered media. We discuss a general and simple way to estimate G from a particular, network-specific percentile of the distribution of local conductances.

A. Priolo; H. M. Jaeger; A. J. Dammers; S. Radelaar

1992-12-01T23:59:59.000Z

130

Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence  

SciTech Connect

The statistical study of magnetic reconnection events in two-dimensional turbulence has been performed by comparing numerical simulations of magnetohydrodynamics (MHD) and Hall magnetohydrodynamics (HMHD). The analysis reveals that the Hall term plays an important role in turbulence, in which magnetic islands simultaneously reconnect in a complex way. In particular, an increase of the Hall parameter, the ratio of ion skin depth to system size, broadens the distribution of reconnection rates relative to the MHD case. Moreover, in HMHD the local geometry of the reconnection region changes, manifesting bifurcated current sheets and quadrupolar magnetic field structures in analogy to laminar studies, leading locally to faster reconnection processes in this case of reconnection embedded in turbulence. This study supports the idea that the global rate of energy dissipation is controlled by the large scale turbulence, but suggests that the distribution of the reconnection rates within the turbulent system is sensitive to the microphysics at the reconnection sites.

Donato, S.; Servidio, S.; Carbone, V. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Dmitruk, P. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Fisica de Buenos Aires, CONICET, Buenos Aires (Argentina); Shay, M. A.; Matthaeus, W. H. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Cassak, P. A. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States)

2012-09-15T23:59:59.000Z

131

Quantum Emission from Two-Dimensional Black Holes  

E-Print Network (OSTI)

We investigate Hawking radiation from two-dimensional dilatonic black holes using standard quantization techniques. In the background of a collapsing black hole solution the Bogoliubov coefficients can be exactly determined. In the regime after the black hole has settled down to an `equilibrium' state but before the backreaction becomes important these give the known result of a thermal distribution of Hawking radiation at temperature lambda/(2pi). The density matrix is computed in this regime and shown to be purely thermal. Similar techniques can be used to derive the stress tensor. The resulting expression agrees with the derivation based on the conformal anomaly and can be used to incorporate the backreaction. Corrections to the thermal density matrix are also examined, and it is argued that to leading order in perturbation theory the effect of the backreaction is to modify the Bogoliubov transformation, but not in a way that restores information lost to the black holes.

Steven B. Giddings; W. M. Nelson

2009-11-27T23:59:59.000Z

132

Electromagnetic two-dimensional analysis of trapped-ion eigenmodes  

SciTech Connect

A two-dimensional electromagnetic analysis of the trapped-ion instability for the tokamak case with ..beta.. not equal to 0 has been made, based on previous work in the electrostatic limit. The quasineutrality condition and the component of Ampere's law along the equilibrium magnetic field are solved for the perturbed electrostatic potential and the component of the perturbed vector potential along the equilibrium magnetic field. The general integro-differential equations are converted into a matrix eigenvalue-eigenfunction problem by expanding in cubic B-spline finite elements in the minor radius and in Fourier harmonics in the poloidal angle. A model MHD equilibrium with circular, concentric magnetic surfaces and large aspect ratio is used which is consistent with our assemption that B << 1. The effect on the trapped-ion mode of including these electromagnetic extensions to the calculation is considered, and the temperature (and ..beta..) scaling of the mode frequency is shown and discussed.

Kim, D.; Rewoldt, G.

1984-11-01T23:59:59.000Z

133

High speed two-dimensional optical beam position detector  

SciTech Connect

Disclosed is the design of a high speed two-dimensional optical beam position detector which outputs the X and Y displacement and total intensity linearly. The experimental detector measures the displacement from DC to 123 MHz and the intensity of an optical spot in a similar way as a conventional quadrant photodiode detector. The design uses four discrete photodiodes and simple dedicated optics for the position decomposition which enables higher spatial accuracy and faster electronic processing than conventional detectors. Measurements of the frequency response and the spatial sensitivity demonstrate high suitability for atomic force microscopy, scanning probe data storage applications, and wideband wavefront sensing. The operation principle allows for position measurements up to 20 GHz and more in bandwidth.

Rutten, Paul Edmond [Maypa B.V., Bijsters 2, 5131 NW, Alphen (Netherlands)

2011-07-15T23:59:59.000Z

134

Investigating Coherent Structures of Quasi Two-Dimensional Flows Subject  

E-Print Network (OSTI)

and Future work #12;L. Moubarak 3 2D turbulence in nuclear fusion Fusion requirements: · High energy due and Motivation - Experimental setups, the square and cylindrical container & diagnostics: tracers, laser sheet for the laser sheet. #12;L. Moubarak 12 The Magnetic field Axial magnetic field Axial magnetic field ·Almost

Shihadeh, Alan

135

A two-dimensional matrix correction for off-axis portal dose prediction errors  

SciTech Connect

Purpose: This study presents a follow-up to a modified calibration procedure for portal dosimetry published by Bailey et al. ['An effective correction algorithm for off-axis portal dosimetry errors,' Med. Phys. 36, 4089-4094 (2009)]. A commercial portal dose prediction system exhibits disagreement of up to 15% (calibrated units) between measured and predicted images as off-axis distance increases. The previous modified calibration procedure accounts for these off-axis effects in most regions of the detecting surface, but is limited by the simplistic assumption of radial symmetry. Methods: We find that a two-dimensional (2D) matrix correction, applied to each calibrated image, accounts for off-axis prediction errors in all regions of the detecting surface, including those still problematic after the radial correction is performed. The correction matrix is calculated by quantitative comparison of predicted and measured images that span the entire detecting surface. The correction matrix was verified for dose-linearity, and its effectiveness was verified on a number of test fields. The 2D correction was employed to retrospectively examine 22 off-axis, asymmetric electronic-compensation breast fields, five intensity-modulated brain fields (moderate-high modulation) manipulated for far off-axis delivery, and 29 intensity-modulated clinical fields of varying complexity in the central portion of the detecting surface. Results: Employing the matrix correction to the off-axis test fields and clinical fields, predicted vs measured portal dose agreement improves by up to 15%, producing up to 10% better agreement than the radial correction in some areas of the detecting surface. Gamma evaluation analyses (3 mm, 3% global, 10% dose threshold) of predicted vs measured portal dose images demonstrate pass rate improvement of up to 75% with the matrix correction, producing pass rates that are up to 30% higher than those resulting from the radial correction technique alone. As in the 1D correction case, the 2D algorithm leaves the portal dosimetry process virtually unchanged in the central portion of the detector, and thus these correction algorithms are not needed for centrally located fields of moderate size (at least, in the case of 6 MV beam energy).Conclusion: The 2D correction improves the portal dosimetry results for those fields for which the 1D correction proves insufficient, especially in the inplane, off-axis regions of the detector. This 2D correction neglects the relatively smaller discrepancies that may be caused by backscatter from nonuniform machine components downstream from the detecting layer.

Bailey, Daniel W. [Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260 (United States); Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Kumaraswamy, Lalith; Bakhtiari, Mohammad [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Podgorsak, Matthew B. [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214 (United States)

2013-05-15T23:59:59.000Z

136

Two dimensional metallic photonic crystals for light trapping and anti-reflective coatings in thermophotovoltaic applications  

SciTech Connect

We report the development of a front-side contact design for thermophotovoltaics that utilizes metallic photonic crystals (PhCs). While this front-side grid replacement covers more surface area of the semiconductor, a higher percentage of photons is shown to be converted to usable power in the photodiode. This leads to a 30% increase in the short-circuit current of the gallium antimonide thermophotovoltaic cell.

Shemelya, Corey; DeMeo, Dante F.; Vandervelde, Thomas E. [The Renewable Energy and Applied Photonics Laboratories, Electrical and Computer Engineering, Tufts University, Medford, Massachusetts 02155 (United States)

2014-01-13T23:59:59.000Z

137

Two-dimensional kinetic model of short high-current vacuum-arc discharge  

Science Journals Connector (OSTI)

A two-dimensional mathematical model of a short high-current vacuum-arc discharge is developed, according to which magnetized electrons ... a free flight regime in a two-dimensional electric field. The proposed m...

Ya. I. Londer; K. N. Ul’yanov

2010-03-01T23:59:59.000Z

138

Femtosecond X-ray diffraction from two-dimensional protein crystals  

Science Journals Connector (OSTI)

Bragg diffraction achieved from two-dimensional protein crystals using femtosecond X-ray laser snapshots is presented.

Frank, M.

2014-02-28T23:59:59.000Z

139

Radiative heat transfer in 2D Dirac materials  

E-Print Network (OSTI)

We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene. Neglecting spatial dispersion, we derive both numerically and analytically the short-distance asymptotics of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. We argue that this scaling law for the near-field heat transfer is generic for any two-dimensional systems.

Pablo Rodriguez-Lopez; Wang-Kong Tse; Diego A. R. Dalvit

2014-10-16T23:59:59.000Z

140

THE EFFECT OF A SHEAR FLOW ON CONVECTION NEAR A TWO-DIMENSIONAL HOT-PATCH  

Science Journals Connector (OSTI)

......CONVECTION NEAR A TWO-DIMENSIONAL HOT-PATCH I. C. WALTON Department of Mathematics...takes the form of a two-dimensional hot-patch. Ingersoll's (6) results for uniform...CONVECTION NEAR A TWO-DIMENSIONAL HOT-PATCH By I. C. WALTON (Department of Mathematics......

I. C. WALTON

1985-11-01T23:59:59.000Z

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141

Shallow quantum well excitons: 2D or 3D?  

Science Journals Connector (OSTI)

A new regime is obtained in semiconductor heterostructures with constituents of nearly identical band gaps. Previously, it has been shown that even extremely shallow quantum wells (SHQWs) exhibit excitonic and electroabsorption properties typical of a 2D system, but 3D transport features. We show that, surprisingly, even when carriers are two-dimensionally confined in SHQWs, the hole spin relaxation is extremely fast (?400 fsec) as in the bulk (3D) limit and that a 2D-3D transition in the hole spin dynamics in GaAs/AlxGa1-xAs SHQWs takes place at x?5%.

I. Brener; W. H. Knox; K. W. Goossen; J. E. Cunningham

1993-01-18T23:59:59.000Z

142

2D-1D Coupling in Cleaved Edge Overgrowth  

Science Journals Connector (OSTI)

We study the scattering properties of an interface between a one-dimensional (1D) wire and a two-dimensional (2D) electron gas. Experiments were conducted in the highly controlled geometry provided by molecular bean epitaxy overgrowth onto the cleaved edge of a high quality GaAs /AlGaAs quantum well. Such structures allow for the creation of variable length 1D-2D coupling sections. We find ballistic 1D electron transport through these interaction regions with a mean free path as long as 6 ?m. Our results explain the origin of the puzzling nonuniversal conductance quantization observed previously in such 1D wires.

R. de Picciotto; H. L. Stormer; A. Yacoby; L. N. Pfeiffer; K. W. Baldwin; K. W. West

2000-08-21T23:59:59.000Z

143

Method and apparatus for two-dimensional spectroscopy  

DOE Patents (OSTI)

Preferred embodiments of the invention provide for methods and systems of 2D spectroscopy using ultrafast, first light and second light beams and a CCD array detector. A cylindrically-focused second light beam interrogates a target that is optically interactive with a frequency-dispersed excitation (first light) pulse, whereupon the second light beam is frequency-dispersed at right angle orientation to its line of focus, so that the horizontal dimension encodes the spatial location of the second light pulse and the first light frequency, while the vertical dimension encodes the second light frequency. Differential spectra of the first and second light pulses result in a 2D frequency-frequency surface equivalent to double-resonance spectroscopy. Because the first light frequency is spatially encoded in the sample, an entire surface can be acquired in a single interaction of the first and second light pulses.

DeCamp, Matthew F. (Swarthmore, PA); Tokmakoff, Andrei (Lexington, MA)

2010-10-12T23:59:59.000Z

144

Persistent exciton-type many-body interactions in GaAs quantum wells measured using two-dimensional optical spectroscopy  

Science Journals Connector (OSTI)

Studies have shown that many-body interactions among semiconductor excitons can produce distinct features in two-dimensional optical spectra. However, to the best of our knowledge, the dynamics of many-body interactions have not been measured in two-dimensional (2D) spectroscopy studies. Here we measure 2D spectra of GaAs quantum wells at many different “waiting” times and study the time dependence of the spectral features. Characteristic signatures of exciton polarization correlations manifest in the diagonal peaks decay at the exciton dephasing rate, consistent with theoretical predictions. Other many-body interactions manifest in off-diagonal features decay much more slowly. These persistent off-diagonal features must be due to many-body interactions involving exciton populations, and their persistence cannot be predicted by theoretical descriptions restricted to the coherent limit.

Daniel B. Turner; Patrick Wen; Dylan H. Arias; Keith A. Nelson; Hebin Li; Galan Moody; Mark E. Siemens; Steven T. Cundiff

2012-05-15T23:59:59.000Z

145

Kolmogorov flow in two dimensional strongly coupled dusty plasma  

SciTech Connect

Undriven, incompressible Kolmogorov flow in two dimensional doubly periodic strongly coupled dusty plasma is modelled using generalised hydrodynamics, both in linear and nonlinear regime. A complete stability diagram is obtained for low Reynolds numbers R and for a range of viscoelastic relaxation time ?{sub m} [0?

Gupta, Akanksha; Ganesh, R., E-mail: ganesh@ipr.res.in; Joy, Ashwin [Institute for Plasma Research, Bhat Gandhinagar, Gujarat 382 428 (India)

2014-07-15T23:59:59.000Z

146

Quasi-two-dimensional excitons in finite magnetic fields  

Science Journals Connector (OSTI)

We present a theoretical and experimental investigation of the effects of a magnetic field on quasi-two-dimensional excitons. We calculate the internal structures and dispersion relations of spatially direct and indirect excitons in single and coupled quantum wells in a magnetic field perpendicular to the well plane. We find a sharp transition from a hydrogenlike exciton to a magnetoexciton with increasing the center-of-mass momentum at fixed weak field. At that transition the mean electron-hole separation increases sharply and becomes ?P/B?, where P is the magnetoexciton center-of-mass momentum and B? is the magnetic field perpendicular to the quantum well plane. The transition resembles a first-order phase transition. The magnetic-field–exciton momentum phase diagram describing the transition is constructed. We measure the magnetoexciton dispersion relations and effective masses in GaAs/Al0.33Ga0.67As coupled quantum wells using tilted magnetic fields. The calculated dispersion relations and effective masses are in agreement with the experimental data. We discuss the impact of magnetic field and sample geometry on the condition for observing exciton condensation.

Yu. E. Lozovik, I. V. Ovchinnikov, S. Yu. Volkov, L. V. Butov, and D. S. Chemla

2002-05-24T23:59:59.000Z

147

Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks  

SciTech Connect

Here we explore pulsed laser deposition (PLD), a well known and versatile synthesis method principally used for epitaxial oxide thin film growth, for the synthesis of functional metal chalcogenide (GaSe) nanosheet networks by stoichiometric transfer of laser vaporized material from bulk GaSe targets in Ar background gas. Uniform coverage of interconnected, crystalline, few-layer, photoresponsive GaSe nanosheets in both in-plane and out-of-plane orientations were achieved under different ablation plume conditions over ~1.5 cm2 areas. Plume propagation was characterized by in situ ICCD-imaging. High (1 Torr) Ar background gas pressures were found to be crucial for the stoichiometric growth of GaSe nanosheet networks. Individual 1-3 layer GaSe triangular nanosheets of ~ 200 nm domain size were formed within 30 laser pulses, coalescing to form nanosheet networks in as few as 100 laser pulses. The thickness of the deposited networks increased linearly with pulse number, adding layers in a two-dimensional (2D) growth mode while maintaining a surface roughness of 2 GaSe layers for increasing overall thickness. Field effect transistors using these interconnected crystalline GaSe networks showed p-type semiconducting characteristics with mobilities reaching as high as 0.1 cm2V-1s-1. Spectrally-resolved photoresponsivities and external quantum efficiencies ranged from 0.4 AW-1 and 100% at 700 nm, to 1.4 AW-1 and 600 % at 240 nm, respectively. Pulsed laser deposition under these conditions appears to provide a versatile and rapid approach to stoichiometrically transfer and deposit photoresponsive networks of 2D nanosheets with digital thickness control and substrate-scale uniformity for a variety of applications.

Mahjouri-Samani, Masoud [ORNL; Gresback, Ryan G [ORNL; Tian, Mengkun [ORNL; Puretzky, Alexander A [ORNL; Rouleau, Christopher M [ORNL; Eres, Gyula [ORNL; Ivanov, Ilia N [ORNL; Xiao, Kai [ORNL; McGuire, Michael A [ORNL; Duscher, Gerd [University of Tennessee, Knoxville (UTK); Geohegan, David B [ORNL

2014-01-01T23:59:59.000Z

148

Two-Dimensional Kinetic Turbulence in the Solar Wind  

Science Journals Connector (OSTI)

We present the first 2D hybrid-Vlasov simulations of turbulence in the solar wind that describe the evolution of the energy spectra in a range of two decades of wavelengths around the ion inertial scale. Several previous magnetohydrodynamics and particle-in-cell simulations in the range of large (fluid) wavelengths showed a marked anisotropy of the energy spectra in the direction perpendicular to the mean magnetic field. Here we give evidence that the parallel direction can also be a privileged way for turbulence to develop towards short scales, where kinetic effects govern the plasma dynamics.

F. Valentini; F. Califano; P. Veltri

2010-05-17T23:59:59.000Z

149

Two-dimensional oscillator in a magnetic field  

SciTech Connect

The energy and eigenstate spectrum of a charged particle in the electric field of a 2D anisotropic oscillator and in a uniform magnetic field is considered. The exact analytic solution to the problem is obtained for an arbitrary magnetic field strength. The characteristic features of variation of the energy spectrum depending on the magnetic field strength are analyzed. The results of this study are of interest for the quantum-mechanical theory of magnetism and can be used to simulate the magnetic properties of atoms and molecules.

Rebane, T. K., E-mail: trebane@mail.ri [St. Petersburg University, Fock Research Institute of Physics (Russian Federation)

2012-02-15T23:59:59.000Z

150

Two dimensional NMR and NMR relaxation studies of coal structure  

SciTech Connect

This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have concentrated on a theoretical treatment of pairs of tightly coupled spin {1/2} nuclei under magic angle spinning conditions. The average Hamiltonian theory developed here is required for a quantitative understanding of two dimensional NMR experiments of such spin pairs in solids. These experiments in turn provide a means of determining connectivities between resonances in solid state NMR spectra. Development of these techniques will allow us to establish connectivities between functional components in coals. The complete description of these spin dynamics has turned out to be complex, and is necessary to provide a foundation upon which such experiments may be quantitatively interpreted in complex mixtures such as coals. 25 refs., 4 figs., 3 tabs.

Zilm, K.W.

1990-01-01T23:59:59.000Z

151

Criterion based Two Dimensional Protein Folding Using Extended GA  

E-Print Network (OSTI)

Abstract — In the dynamite field of biological and protein research, the protein fold recognition for long pattern protein sequences is a great confrontation for many years. With that consideration, this paper contributes to the protein folding research field and presents a novel procedure for mapping appropriate protein structure to its correct 2D fold by a concrete model using swarm intelligence. Moreover, the model incorporates Extended Genetic Algorithm (EGA) with concealed Markov model (CMM) for effectively folding the protein sequences that are having long chain lengths. The protein sequences are preprocessed, classified and then, analyzed with some parameters (criterion) such as fitness, similarity and sequence gaps for optimal formation of protein structures. Fitness correlation is evaluated for the determination of bonding strength of molecules, thereby involves in efficient fold recognition task. Experimental results have shown that the proposed method is more adept in 2D protein folding and outperforms the existing algorithms. Index Terms — classification, CMM, criterion analysis, EGA, protein folding, sequence gaps I.

T. Kalai Chelvi; P. Rangarajan

152

Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals  

SciTech Connect

This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group. The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected to model a photonic-crystal combiner for an integrated multi-wavelength-source laser.

Mario Agio

2002-12-31T23:59:59.000Z

153

Results from laboratory tests of the two-dimensional Time-Encoded Imaging System.  

SciTech Connect

A series of laboratory experiments were undertaken to demonstrate the feasibility of two dimensional time-encoded imaging. A prototype two-dimensional time encoded imaging system was designed and constructed. Results from imaging measurements of single and multiple point sources as well as extended source distributions are presented. Time encoded imaging has proven to be a simple method for achieving high resolution two-dimensional imaging with potential to be used in future arms control and treaty verification applications.

Marleau, Peter; Brennan, James S.; Brubaker, Erik; Gerling, Mark D; Le Galloudec, Nathalie Joelle

2014-09-01T23:59:59.000Z

154

2D-3D transition of gold cluster anions resolved  

Science Journals Connector (OSTI)

Small gold cluster anions Aun? are known for their unusual two-dimensional (2D) structures, giving rise to properties very different from those of bulk gold. Previous experiments and calculations disagree about the number of gold atoms nc where the transition to 3D structures occurs. We combine trapped ion electron diffraction and state of the art electronic structure calculations to resolve this puzzle and establish nc=12. It is shown that theoretical studies using traditional generalized gradient functionals are heavily biased towards 2D structures. For a correct prediction of the 2D-3D crossover point it is crucial to use density functionals yielding accurate jellium surface energies, such as the Tao-Perdew-Staroverov-Scuseria (TPSS) functional or the Perdew-Burke-Ernzerhof functional modified for solids (PBEsol). Further, spin-orbit effects have to be included, and large, flexible basis sets employed. This combined theoretical-experimental approach is promising for larger gold and other metal clusters.

Mikael P. Johansson; Anne Lechtken; Detlef Schooss; Manfred M. Kappes; Filipp Furche

2008-05-19T23:59:59.000Z

155

Postoperative Radiotherapy for Lung Cancer: Improvement in Locoregional Control Using Three-Dimensional Compared With Two-Dimensional Technique  

SciTech Connect

Purpose: To determine whether lung cancer patients treated with three-dimensional (3D) postoperative radiotherapy (PORT) have more favorable outcomes than those treated with two-dimensional (2D) PORT. Patients and Methods: We retrospectively analyzed the charts of 153 lung cancer patients who underwent PORT with curative intent at our center between 1995 and 2007. The patients were grouped according to the RT technique; 66 patients were in the 2D group and 87 in the 3D group. The outcomes included locoregional control, survival, and secondary effects. All patients were treated using a linear accelerator at a total dose of approximately 50 Gy and 2 Gy/fraction. A few patients (21%) also received chemotherapy. Most tumors were in the advanced stage, either Stage II (30%) or Stage III (65%). The main clinical indications for PORT were positive resection margins (23%) and Stage pN2 (52%) and pN1 (22%). The patient characteristics were comparable in both groups. Results: Kaplan-Meier analysis showed that the 3D technique significantly improved the locoregional control rate at 5 years compared with the 2D technique (81% vs. 56%, p = .007 [Cox]). The 2D technique was associated with a more than twofold increased risk of locoregional recurrence (hazard ratio, 2.7; 95% confidence interval, 1.3-5.5; p = .006). The overall survival rate did not differ at 5 years (38% vs. 20%, p = .3 [Cox]). The toxicities were also similar and acceptable in both groups. Conclusion: The 3D technique for conformal PORT for lung cancer improved the locoregional control rates of patients compared with the 2D technique.

Masson-Cote, Laurence [Department of Radiation Oncology, Centre Hospitalier Universitaire de Quebec-L'Hotel-Dieu de Quebec, Quebec City, QC (Canada); Couture, Christian [Departments of Anatomic Pathology and Cytology, Institut Universitaire de Cardiologie et de Pneumologie de Quebec (Hopital Laval), Quebec City, QC (Canada); Fortin, Andre [Department of Radiation Oncology, Centre Hospitalier Universitaire de Quebec-L'Hotel-Dieu de Quebec, Quebec City, QC (Canada); Dagnault, Anne, E-mail: anne.dagnault@mail.chuq.qc.ca [Department of Radiation Oncology, Centre Hospitalier Universitaire de Quebec-L'Hotel-Dieu de Quebec, Quebec City, QC (Canada)

2011-07-01T23:59:59.000Z

156

Ab initio modeling of the two-dimensional energy landscape of screw dislocations in bcc transition metals  

Science Journals Connector (OSTI)

A density functional theory (DFT) study of the 1/2?111? screw dislocation was performed in the following body-centered cubic transition metals: V, Nb, Ta, Cr, Mo, W, and Fe. The energies of the easy, hard, and split core configurations, as well as the pathways between them, were investigated and used to generate the two-dimensional (2D) Peierls potential, i.e. the energy landscape seen by the dislocation as a function of its position in the (111) plane. In all investigated elements, the nondegenerate easy core is the minimum energy configuration, while the split core configuration, centered in the immediate vicinity of a ?111? atomic column, has a high energy near or above that of the hard core. This unexpected result yields 2D Peierls potentials very different from the usually assumed landscapes. The 2D Peierls potential in Fe differs from the other transition metals, with a monkey saddle instead of a local maximum located at the hard core. An estimation of the Peierls stress from the shape of the Peierls barrier is presented in all investigated metals. A strong group dependence of the core energy is also evidenced, related to the position of the Fermi level with respect to the minimum of the pseudogap of the electronic density of states.

L. Dezerald; Lisa Ventelon; E. Clouet; C. Denoual; D. Rodney; F. Willaime

2014-01-15T23:59:59.000Z

157

RADIAL STELLAR PULSATION AND THREE-DIMENSIONAL CONVECTION. II. TWO-DIMENSIONAL CONVECTION IN FULL AMPLITUDE RADIAL PULSATION  

SciTech Connect

We have developed a three-dimensional radiation hydrodynamics code to simulate the interaction of convection and radial pulsation in classical variable stars. One key goal is the ability to carry these simulations to full amplitude in order to compare them with observed light curves. Previous multi-dimensional calculations were prevented from reaching full amplitude because of drift in the radial coordinate system, due to the algorithm defining radial movement of the coordinate system during the pulsation cycle. We have removed this difficulty by defining our radial coordinate flow algorithm to require that the mass in a spherical shell remain constant for every time step throughout the pulsation cycle. We have used our new code to perform two-dimensional (2D) simulations of the interaction of radial pulsation and convection. We have made comparisons between light curves from our 2D convective simulations with observed light curves and find that our 2D simulated light curves are better able to match the observed light curve shape near the red edge of the RR Lyrae instability strip than light curves from previous one-dimensional time-dependent convective models.

Geroux, Chris M.; Deupree, Robert G., E-mail: geroux@astro.ex.ac.uk [Institute for Computational Astrophysics and Department of Astronomy and Physics, Saint Mary's University, Halifax, NS B3H 3C3 (Canada)

2013-07-10T23:59:59.000Z

158

Deconfinement in a 2D Optical Lattice of Coupled 1D Boson Systems  

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We show that a two-dimensional (2D) array of 1D interacting boson tubes has a deconfinement transition between a 1D Mott insulator and a 3D superfluid for commensurate fillings and a dimensional crossover for the incommensurate case. We determine the phase diagram and excitations of this system and discuss the consequences for Bose condensates loaded in 2D optical lattices.

A. F. Ho; M. A. Cazalilla; T. Giamarchi

2004-04-02T23:59:59.000Z

159

Two dimensional electron gases in polycrystalline MgZnO/ZnO heterostructures grown by rf-sputtering process  

SciTech Connect

This paper reports the formation of two-dimensional electron gas (2DEG) in rf-sputtered defective polycrystalline MgZnO/ZnO heterostructure via the screening of grain boundary potential by polarization-induced charges. As the MgZnO thickness increases, the sheet resistance reduces rapidly and then saturates. The enhancement of the interfacial polarization effect becomes stronger, corresponding to a larger amount of resistance reduction, when the Mg content in the cap layer increases. Monte Carlo method by including grain boundary scattering effect as well as 2D finite-element-method Poisson and drift-diffusion solver is applied to analyze the polycrystalline heterostructure. The experimental and Monte Carlo simulation results show good agreement. From low temperature Hall measurement, the carrier density and mobility are both independent of temperature, indicating the formation of 2DEG with roughness scattering at the MgZnO/ZnO interface.

Chin, Huai-An; Cheng, I-Chun; Huang, Chih-I; Wu, Yuh-Renn [Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan (China); Lu, Wen-Sen; Lee, Wei-Li [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Chen, Jian Z. [Institute of Applied Mechanics, National Taiwan University, Taipei 10617, Taiwan (China); Chiu, Kuo-Chuang; Lin, Tzer-Shen [Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China)

2010-09-15T23:59:59.000Z

160

GENERALIZED 2D EULER-BOUSSINESQ EQUATIONS WITH A SINGULAR VELOCITY  

E-Print Network (OSTI)

GENERALIZED 2D EULER-BOUSSINESQ EQUATIONS WITH A SINGULAR VELOCITY DURGA KC, DIPENDRA REGMI a system of equations generalizing the two-dimensional incompressible Boussinesq equa- tions. The velocity- value problem of this generalized Boussinesq equations when the velocity is "double logarithmically

Wu, Jiahong

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

An Efficient Genetic Algorithm for Predicting Protein Tertiary Structures in the 2D HP Model  

E-Print Network (OSTI)

, predicting its tertiary structure is known as the protein folding problem. This problem has been widely genetic algo- rithm for the protein folding problem under the HP model in the two-dimensional square Genetic Algorithm, Protein Folding Problem, 2D HP Model 1. INTRODUCTION Amino acids are the building

Istrail, Sorin

162

Signatures of correlated excitonic dynamics in two-dimensional spectroscopy of the Fenna-Matthew-Olson photosynthetic complex  

SciTech Connect

Long-lived excitonic coherence in photosynthetic proteins has become an exciting area of research because it may provide design principles for enhancing the efficiency of energy transfer in a broad range of materials. In this publication, we provide new evidence that long-lived excitonic coherence in the Fenna-Mathew-Olson pigment-protein (FMO) complex is consistent with the assumption of cross correlation in the site basis, indicating that each site shares bath fluctuations. We analyze the structure and character of the beating crosspeak between the two lowest energy excitons in two-dimensional (2D) electronic spectra of the FMO Complex. To isolate this dynamic signature, we use the two-dimensional linear prediction Z-transform as a platform for filtering coherent beating signatures within 2D spectra. By separating signals into components in frequency and decay rate representations, we are able to improve resolution and isolate specific coherences. This strategy permits analysis of the shape, position, character, and phase of these features. Simulations of the crosspeak between excitons 1 and 2 in FMO under different regimes of cross correlation verify that statistically independent site fluctuations do not account for the elongation and persistence of the dynamic crosspeak. To reproduce the experimental results, we invoke near complete correlation in the fluctuations experienced by the sites associated with excitons 1 and 2. This model contradicts ab initio quantum mechanic/molecular mechanics simulations that observe no correlation between the energies of individual sites. This contradiction suggests that a new physical model for long-lived coherence may be necessary. The data presented here details experimental results that must be reproduced for a physical model of quantum coherence in photosynthetic energy transfer.

Caram, Justin R.; Lewis, Nicholas H. C.; Fidler, Andrew F.; Engel, Gregory S. [Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States)

2012-03-14T23:59:59.000Z

163

A New Exact Method for Solving the Two-Dimensional Ising Model  

Science Journals Connector (OSTI)

A New Exact Method for Solving the Two-Dimensional Ising Model ... We have used the two-dimensional Ising model with a limited number of rows, but with the coordination number of four for each site, to set up the transfer matrix for the model. ... The Ising Problem ...

Sh. Ranjbar; G. A. Parsafar

1999-08-12T23:59:59.000Z

164

Unimodal Maps as Boundary-Restrictions of Two-Dimensional Full-Folding Maps  

E-Print Network (OSTI)

Unimodal Maps as Boundary-Restrictions of Two-Dimensional Full-Folding Maps Hideki TSUIKI tsuiki-75-753-6744, Fax:+81-75-753-6694 Abstract It is shown that every unimodal map is realized as a restriction of a simple map defined on the unit disc to a part of its boundary. Our two-dimensional map is called a full

Tsuiki, Hideki

165

Shear viscosity and shear thinning in two-dimensional Yukawa , J. Goree2  

E-Print Network (OSTI)

Shear viscosity and shear thinning in two-dimensional Yukawa liquids Z. Donk´o1 , J. Goree2 , P using two different nonequi- librium molecular dynamics simulation methods. Shear viscosity values.e., the viscosity diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas

Goree, John

166

Two-Dimensional NMR Spectroscopy Elimination of Zero-Quantum Interference in  

E-Print Network (OSTI)

the sample is large enough, the net result will be cancelation of the zero-quantum coherence. A simpleTwo-Dimensional NMR Spectroscopy Elimination of Zero-Quantum Interference in Two-Dimensional NMR and homonuclear zero-quantum coherence, which is invariably present. The zero-quantum coherence gives rise to anti

Keeler, James

167

Quantitative assessment of collagen fibre orientations from two-dimensional images of soft biological tissues  

Science Journals Connector (OSTI)

...extracted from two-dimensional images. Specifically...distribution with a standard deviation of 35...Canham 1995 Three-dimensional collagen organization...J. R. Soc. Interface 3, 15-35. 10...Srihari 2002 On measuring the distance between...orientations from two-dimensional images of soft...

2012-01-01T23:59:59.000Z

168

Argonne CNM Highlight: Self-Assembly Kinetics of Two-Dimensional  

NLE Websites -- All DOE Office Websites (Extended Search)

Self-Assembly Kinetics of Two-Dimensional Nanocrystal Superlattices Self-Assembly Kinetics of Two-Dimensional Nanocrystal Superlattices Two-dimensional nanocrystal superlattices Two-dimensional assembly of gold nanocrystals at a toluene-air interface during colloidal droplet evaporation process: in situ optical microscopy (top panel, inset is a TEM image of the array after drying) and time-resolved GISAXS (bottom panel a-b). Self-assembly of a crystalline phase with quasi-long-range positional order for two-dimensional nanocrystal superlattice (NSC) domains at the liquid-air interface during droplet evaporation has been observed. The NSCs were formed by depositing a colloidal suspension of highly monodisperse dodecanethiol-ligated gold nanocrystals. The kinetics of the self-assembly were immediately captured by in situ time-resolved grazing-incidence

169

2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe  

SciTech Connect

A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

Chen, Y. H.; Yang, X. Y.; Lin, C., E-mail: linchen0812@pku.edu.cn, E-mail: cjxiao@pku.edu.cn; Wang, X. G.; Xiao, C. J., E-mail: linchen0812@pku.edu.cn, E-mail: cjxiao@pku.edu.cn [State Key Lab of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wang, L. [Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190 (China); Xu, M. [Center for Fusion Science of Southwestern Institute of Physics, P. O. Box 432, Chengdu 610041 (China)

2014-11-15T23:59:59.000Z

170

Crossover from 2D to 3D in a Weakly Interacting Fermi Gas  

Science Journals Connector (OSTI)

We have studied the transition from two to three dimensions in a low temperature weakly interacting Li6 Fermi gas. Below a critical atom number N2D only the lowest transverse vibrational state of a highly anisotropic oblate trapping potential is occupied and the gas is two dimensional. Above N2D the Fermi gas enters the quasi-2D regime where shell structure associated with the filling of individual transverse oscillator states is apparent. This dimensional crossover is demonstrated through measurements of the cloud size and aspect ratio versus atom number.

P. Dyke; E. D. Kuhnle; S. Whitlock; H. Hu; M. Mark; S. Hoinka; M. Lingham; P. Hannaford; C. J. Vale

2011-03-11T23:59:59.000Z

171

THE ANGULAR MOMENTUM OF MAGNETIZED MOLECULAR CLOUD CORES: A TWO-DIMENSIONAL-THREE-DIMENSIONAL COMPARISON  

SciTech Connect

In this work, we present a detailed study of the rotational properties of magnetized and self-gravitating dense molecular cloud (MC) cores formed in a set of two very high resolution three-dimensional (3D) MC simulations with decaying turbulence. The simulations have been performed using the adaptative mesh refinement code RAMSES with an effective resolution of 4096{sup 3} grid cells. One simulation represents a mildly magnetically supercritical cloud and the other a strongly magnetically supercritical cloud. We identify dense cores at a number of selected epochs in the simulations at two density thresholds which roughly mimic the excitation densities of the NH{sub 3} (J - K) = (1,1) transition and the N{sub 2}H{sup +} (1-0) emission line. A noticeable global difference between the two simulations is the core formation efficiency (CFE) of the high-density cores. In the strongly supercritical simulations, the CFE is 33% per unit free-fall time of the cloud (t{sub ff,cl}), whereas in the mildly supercritical simulations this value goes down to {approx}6 per unit t{sub ff,cl}. A comparison of the intrinsic specific angular momentum (j{sub 3D}) distributions of the cores with the specific angular momentum derived using synthetic two-dimensional (2D) velocity maps of the cores (j{sub 2D}) shows that the synthetic observations tend to overestimate the true value of the specific angular momentum by a factor of {approx}8-10. We find that the distribution of the ratio j{sub 3D}/j{sub 2D} of the cores peaks at around {approx}0.1. The origin of this discrepancy lies in the fact that contrary to the intrinsic determination of j which sums up the individual gas parcels' contributions to the angular momentum, the determination of the specific angular momentum using the standard observational procedure which is based on a measurement on the global velocity gradient under the hypothesis of uniform rotation smoothes out the complex fluctuations present in the 3D velocity field. Our results may well provide a natural explanation for the discrepancy by a factor of {approx}10 observed between the intrinsic 3D distributions of the specific angular momentum and the corresponding distributions derived in real observations. We suggest that previous and future measurements of the specific angular momentum of dense cores which are based on the measurement of the observed global velocity gradients may need to be reduced by a factor of {approx}10 in order to derive a more accurate estimate of the true specific angular momentum in the cores. We also show that the exponent of the size-specific angular momentum relation is smaller ({approx}1.4) in the synthetic observations than their values derived in the 3D space ({approx}1.8).

Dib, Sami; Csengeri, Timea; Audit, Edouard [Service d'Astrophysique, DSM/Irfu, CEA/Saclay, F-91191, Gif-sur-Yvette Cedex (France); Hennebelle, Patrick [Laboratoire de Radioastronomie, UMR CNRS 8112, Ecole Normale Superieure, Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Pineda, Jaime E.; Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bontemps, Sylvain, E-mail: sami.dib@cea.f [CNRS/INU, Laboratoire d'Astrophysique de Bordeaux, UMR 5804, BP 89, 33271, Floirac, Cedex (France)

2010-11-01T23:59:59.000Z

172

Two-dimensional Vlasov solution for a collisionless plasma jet across transverse magnetic field lines with a sheared bulk velocity  

Science Journals Connector (OSTI)

We consider a two-dimensional (2D) stationary stream of a collisionless plasma injected across an external stationary magnetic field and a background stagnant plasma. The solution is found by solving the Vlasov equation for each species (electrons and protons), the Maxwell-Ampere equation for the magnetic vector potential, and the equation of plasma quasineutrality for the electrostatic potential. The solution of the stationary Vlasov equation is given in terms of two constants of motion and one adiabatic invariant. The partial charge and current densities are given by analytical expressions of the moments of the velocity distribution functions for each particle species. The 2D distribution of the plasma bulk velocity, Vx(y,z), is roughly uniform inside the jet. There is no plasma bulk flow in the direction of the magnetic field. Inside the boundary layer interfacing the jet and the stagnant plasma, the bulk velocity has gradients (i.e., shears) in the direction parallel as well perpendicular to the magnetic field. The parallel component of this gradient, ??V?, produces a nonzero electric field component parallel to the magnetic field lines, E?B?0. The parallel electric field within the transition layer is a basic element allowing plasma elements to be transported across magnetic field lines in astrophysical systems as well as in laboratory experiments where plasmoids are injected across magnetic fields.

Marius M. Echim and Joseph F. Lemaire

2005-09-13T23:59:59.000Z

173

Ethylene adsorbed on Ni(110): An experimental and theoretical determination of the two-dimensional band structure  

Science Journals Connector (OSTI)

We have investigated the saturated ethylene layer on Ni(110) by low-energy electron diffraction (LEED), angle-resolved ultraviolet photoemission spectroscopy (ARUPS), and near-edge x-ray-absorption fine structure (NEXAFS). This layer exhibits a c(2×4) LEED pattern that corresponds to a structure containing two adsorbates per primitive unit cell. The ethylene molecules are adsorbed with the molecular plane parallel to the surface and the C-C axis preferentially aligned along the [11Ż0] direction of the substrate, as is independently determined from the ARUPS and NEXAFS experiments. The two-dimensional (2D) adsorbate band structure is determined from the ARUPS spectra at various photon energies. Except for the ? orbital, all ethylene-derived bands show significant dispersion (up to 2 eV), but no splitting as would be expected for a structure with two molecules per unit cell. The experimentally determined band structure is reproduced in all details by extended-Hückel-theory calculations for an unsupported ethylene layer. The structural model derived from LEED, ARUPS, and NEXAFS is confirmed both by force field and by the 2D band-structure calculations. This indicates that the adsorbate-adsorbate interactions are essentially decoupled from the adsorbate-substrate interaction, that is responsible for the chemisorption bond.

M. Weinelt; W. Huber; P. Zebisch; H.-P. Steinrück; B. Reichert; U. Birkenheuer; N. Rösch

1992-07-15T23:59:59.000Z

174

Sputter deposition of multilayer thermoelectric films: An approach to the fabrication of two-dimensional quantum wells  

SciTech Connect

The relative efficiency of a thermoelectric material is measured in terms of a dimensionless figure of merit, ZT. Though all known thermoelectric materials are believed to have ZT{le}1, recent theoretical results predict that thermoelectric devices fabricated as two-dimensional quantum wells (2D QWs) or onedimensional (1D) quantum wires could have ZT{ge}3. Multilayers with the dimensions of 2D QWs have been synthesized by alternately sputtering Bi{sub 0.9}Sb{sub 0.1} and PbTe{sub 0.8}Se{sub 0.2} onto a moving single-crystal sapphire substrate from dual magnetrons. These materials have been used to test the thermoelectric quantum-well concept and gain insight into relevant transport mechanisms. If successful, this research could lead to thermoelectric devices that have efficiencies close to that of an ideal Carnot engine. Ultimately, such devices could be used to replace conventional heat engines and mechanical refrigeration systems.

Farmer, J.C.; Barbee, T.W. Jr.; Chapline, G.C. Jr.; Foreman, R.J.; Summers, L.J. [Lawrence Livermore National Lab., CA (United States); Dresselhaus, M.S.; Hicks, L.D. [Massachusetts Institute of Technology, Boston, MA (United States). Dept. of Physics

1994-07-01T23:59:59.000Z

175

Two-Dimensional EPR Spectroscopic Studies on the Radicals in Argonne Premium Coals  

Science Journals Connector (OSTI)

Two-Dimensional EPR Spectroscopic Studies on the Radicals in Argonne Premium Coals ... Both coals showed nuclear modulation effects due to1H and naturally abundant 13C nuclear spins. ...

Tadaaki Ikoma; Osamu Ito; Shozo Tero-Kubota; Kimio Akiyama

1998-07-11T23:59:59.000Z

176

Shock-Fitted Numerical Solutions of One- and Two-Dimensional Detonation.  

E-Print Network (OSTI)

??One- and two- dimensional detonation problems are solved using a conservative shock-fitting numerical method which is formally fifth order accurate. The shock-fitting technique for a… (more)

Henrick, Andrew Koldewey

2011-01-01T23:59:59.000Z

177

Electronic and magnetic properties of Fe and Mn doped two dimensional hexagonal germanium sheets  

SciTech Connect

Using first principles density functional theory calculations, the present paper reports systematic total energy calculations of the electronic properties such as density of states and magnetic moment of pristine and iron and manganese doped two dimensional hexagonal germanium sheets.

Soni, Himadri R., E-mail: himadri.soni@gmail.com; Jha, Prafulla K., E-mail: himadri.soni@gmail.com [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364001 (India)

2014-04-24T23:59:59.000Z

178

X-RAY DIFFRACTION FROM A TWO-DIMENSIONAL SOLID T. CEVA and C. MARTI (*)  

E-Print Network (OSTI)

the liquid two-dimensional phase of xenon on graphite could be seen. We present here some preliminary results be less disturbing. The cryostat uses liquid nitrogen flow; a liquid nitrogen tank (with automatic

Paris-Sud XI, Université de

179

Roughening and superroughening in the ordered and random two-dimensional sine-Gordon models  

E-Print Network (OSTI)

Roughening and superroughening in the ordered and random two-dimensional sine-Gordon models Angel S called roughening tem- perature (TR ), thermal uctuations e#11;ectively suppress the e#11;ect

Moro, Esteban

180

Bispectral Analysis of Energy Transfer within the Two-Dimensional Oceanic Internal Wave Field  

Science Journals Connector (OSTI)

Bispectral analysis of the numerically reproduced spectral responses of the two-dimensional oceanic internal wave field to the incidence of the low-mode semidiurnal internal tide is performed. At latitudes just equatorward of 30°, the low-mode ...

Naoki Furuichi; Toshiyuki Hibiya; Yoshihiro Niwa

2005-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Excitation of two-dimensional plasma wakefields by trains of equidistant particle bunches  

SciTech Connect

Nonlinear effects responsible for elongation of the plasma wave period are numerically studied with the emphasis on two-dimensionality of the wave. The limitation on the wakefield amplitude imposed by detuning of the wave and the driver is found.

Lotov, K. V. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk, Russia and Novosibirsk State University, 630090 Novosibirsk (Russian Federation)] [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk, Russia and Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

2013-08-15T23:59:59.000Z

182

E-Print Network 3.0 - asymmetric two-dimensional magnetic Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

of asymmetric magnetic field reconnection Summary: of the Figure 2. Magnetic field lines in a two-dimensional plane for asymmetric reconnection. A00C03 MOZER ET AL......

183

Initial Testing of a Two-Dimensional Finite Element Model for Floodplain Inundation  

Science Journals Connector (OSTI)

8 January 1994 research-article Initial Testing of a Two-Dimensional Finite Element Model for Floodplain...expectations and the need for improved data acquisition for model testing is highlighted. On the basis of these numerical experiments...

1994-01-01T23:59:59.000Z

184

Modeling of acoustic wave scattering from a two-dimensional fracture  

E-Print Network (OSTI)

In this paper, we model the acoustic scattering from a two dimensional fracture that is simulated by two different physical models. We calculate the scattering from the fractures with different properties based on these ...

Wang, Ping

2010-01-01T23:59:59.000Z

185

Uniqueness, stability and Hessian eigenvalues for two-dimensional bubble clusters  

Science Journals Connector (OSTI)

A recent conjecture on two-dimensional foams suggested that for fixed topology with given bubble areas there is a unique state of ... counter-examples, consisting of a ring of bubbles around a central one, which ...

D. Weaire; S.J. Cox; F. Graner

2002-02-01T23:59:59.000Z

186

Mechanical fault interaction within the Los Angeles Basin: A two-dimensional analysis using mechanical efficiency  

E-Print Network (OSTI)

Mechanical fault interaction within the Los Angeles Basin: A two-dimensional analysis using mechanical efficiency Michele L. Cooke Geosciences Department, University of Massachusetts-Amherst, Amherst July 2002. [1] Mechanical models examine deformation within eight different structural cross sections

Cooke, Michele

187

E-Print Network 3.0 - angle-resolved two-dimensional mapping...  

NLE Websites -- All DOE Office Websites (Extended Search)

Rettig... in an energy- and angle-resolved manner. To achieve this, a field free drift tube with an acceptance angle... of 22 is combined with two-dimensional position-sensitive...

188

Two-Dimensional Hybrid Spatial Audio Systems with User Variable Controls of Sound Source Attributes  

Science Journals Connector (OSTI)

This paper presents two novel hybrid spatial audio systems demonstrated for use in two-dimensional ... further creative freedom to a composer, sound engineer or sound designer. The systems are principally ... bas...

Martin J. Morrell; Joshua D. Reiss

2013-01-01T23:59:59.000Z

189

Shear viscosity and shear thinning in two-dimensional Yukawa liquids  

E-Print Network (OSTI)

A two-dimensional Yukawa liquid is studied using two different nonequilibrium molecular dynamics simulation methods. Shear viscosity values in the limit of small shear rates are reported for a wide range of Coulomb coupling parameter and screening length. At high shear rates it is demonstrated that this liquid exhibits shear thinning, i.e., the viscosity $\\eta$ diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas will exhibit this effect.

Z. Donkó; J. Goree; P. Hartmann; K. Kutasi

2006-03-24T23:59:59.000Z

190

An analysis of the connectivity of two-dimensional fracture patterns at Yucca Mountain, Nevada  

E-Print Network (OSTI)

AN ANALYSIS OF THE CONNECTIVITY OF TWO-DIMENSIONAL FRACTURE PATTERNS AT YUCCA MOUNTAIN, NEVADA A Thesis by HANS WOLFGANG MEINARDUS Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1991 Major Subject: Geology AN ANALYSIS OF THE CONNECTIVITY OF TWO-DIMENSIONAL FRACTURE PATTERNS AT YUCCA MOUNTAIN, NEVADA A Thesis by HANS WOLFGANG MEINARDUS Approved as to style and content by: Patrick A...

Meinardus, Hans Wolfgang

2012-06-07T23:59:59.000Z

191

Two dimensional finite element analysis of homogenization and failure in plain weave textile composites  

E-Print Network (OSTI)

TWO DIMENSIONAL FINITE ELEMENT ANALYSIS OF HOMOGENIZATION AND FAILURE IN PLAIN WEAVE TEXTILE COMPOSITES A Thesis by VEERARAGHAVA GOPAL KONDAGUNTA Submitted to the Office of Graduate Studies of Texas ARM University In partial fulffllment... of the requirements for the degree of MASTER OF SCIENCE August 1993 Major Subject: Aerospace Engineering TWO DIMENSIONAL FINITE ELEMENT ANALYSIS OF HOMOGENIZATION AND FAILURE IN PLAIN WEAVE TEXTILE COMPOSITES A Thesis by VEERARAGHAVA GOPAL KONDAGUNTA...

Kondagunta, Veeraraghava Gopal

2012-06-07T23:59:59.000Z

192

Evaluation of new techniques for two dimensional finite element analysis of woven composites  

E-Print Network (OSTI)

EVALUATION OF NEW TECHNIQUES FOR TWO DIMENSIONAL FINITE ELEMENT ANALYSIS OF WOVEN COMPOSITES A Thesis by SITARAM CHOWDARY GUNDAPANENI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE DECEMBER 1992 Major Subject: Aerospace Engineering EVALUATION OF NEW TECHNIQUES FOR TWO DIMENSIONAL FINITE ELEMENT ANALYSIS OF WOVEN COMPOSITES A Thesis by SITARAM CHOWDARY GUNDAPANENI Approved...

Gundapaneni, Sitaram Chowdary

2012-06-07T23:59:59.000Z

193

Evaluation of wrist strength limitations in two-dimensional biochemical modeling  

E-Print Network (OSTI)

EVALUATION OF WRIST STRENGTH LIMITATIONS IN TWO-DIMENSIONAL BIOMECHANICAL MODELING A Thesis by KHALED WALID AL-EISAWI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1994 Major Subject: Industrial Engineering EVALUATION OF WRIST STRENGTH LIMITATIONS IN TWO-DIMENSIONAL BIOMECHANICAL MODELING A Thesis by KHALED WALID AL-EISAWI Submitted to Texas A&M University in partial...

Al-Eisawi, Khaled Walid

2012-06-07T23:59:59.000Z

194

Effect of the block-spin configuration on the location of ?c in two-dimensional Ising modelsin two-dimensional Ising models  

Science Journals Connector (OSTI)

We consider the nearest neighbor Ising model on the 2D square lattice and...? c ...is close to 1, which, compared to the original nearest neighbor Ising? ...

Mohamed Ould-Lemrabott

1997-03-01T23:59:59.000Z

195

MESH2D GRID GENERATOR DESIGN AND USE  

SciTech Connect

Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j{sub 0}) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations. The overall mesh is constructed from grid zones that are typically then subdivided into a collection of smaller grid cells. The grid zones usually correspond to distinct materials or larger-scale geometric shapes. The structured grid zones are identified through uppercase indices (I,J). Subdivision of zonal regions into grid cells can be done uniformly, or nonuniformly using either a polynomial or geometric skewing algorithm. Grid cells may be concentrated backward, forward, or toward both ends. Figure 1 illustrates the above concepts in the context of a simple four zone grid.

Flach, G.; Smith, F.

2012-01-20T23:59:59.000Z

196

Two-dimensional simulation of the Raft River geothermal reservoir and  

Open Energy Info (EERE)

dimensional simulation of the Raft River geothermal reservoir and dimensional simulation of the Raft River geothermal reservoir and wells. (SINDA-3G program) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Report: Two-dimensional simulation of the Raft River geothermal reservoir and wells. (SINDA-3G program) Details Activities (1) Areas (1) Regions (0) Abstract: Computer models describing both the transient reservoir pressure behavior and the time dependent temperature response of the wells at the Raft River, Idaho, Geothermal Resource were developed. A horizontal, two-dimensional, finite-difference model for calculating pressure effects was constructed to simulate reservoir performance. Vertical, two-dimensional, finite-difference, axisymmetric models for each of the three existing wells at Raft River were also constructed to describe the

197

Two-dimensional modeling of sodium boiling transients in simulated LMFBR fuel bundles  

SciTech Connect

A two-dimensional code for analysis of sodium boiling in LMFBR fuel assemblies has been developed at ORNL. This code, THORAX, has been used to analyze tests in 19- and 61-pin electrically-heated, simulated LMFBR fuel assemblies in the THORS facility. THORAX has simulated well the transient growth of the two-dimensional boiling region and the resulting static flow instability leading to dryout. Extrapolation of results to a full size fuel pin bundle shows that two-dimensional effects are reduced but still significant. The code will be extended to include a loop model in support of forthcoming tests in the THORS-SHRS Assembly 1 loop, which will include two parallel 19-pin simulated driver bundles.

Rose, S.D.; Dearing, J.F; Carbajo, J.J.; Levin, A.E.; Montgomery, B.H.; Wantland, J.L.

1982-01-01T23:59:59.000Z

198

Stability analysis for two-dimensional ion-acoustic waves in quantum plasmas  

SciTech Connect

The quantum hydrodynamic model is applied to two-dimensional ion-acoustic waves in quantum plasmas. The two-dimensional quantum hydrodynamic model is used to obtain a deformed Kortewegde Vries (dKdV) equation by reductive perturbation method. By using the solution of auxiliary ordinary equations, a extended direct algebraic method is described to construct the exact solutions for nonlinear quantum dKdV equation. The present results are describing the generation and evolution of such waves, their interactions, and their stability.

Seadawy, A. R., E-mail: Aly742001@yahoo.com [Mathematics Department, Faculty of Science, Taibah University, Al-Ula (Saudi Arabia); Mathematics Department, Faculty of Science, Beni-Suef University (Egypt)

2014-05-15T23:59:59.000Z

199

Calculation of electronic states of a two-dimensional electron gas in a periodic magnetic field  

E-Print Network (OSTI)

CALCULATION OF ELECTRONIC STATES OF A TWO-DIMENSIONAL ELECTRON GAS IN A PERIODIC MAGNETIC FIELD A Thesis ANISI. L HAOEE Submitted to the Office ol' Graduate Studies of Texas A&M I. , niversity in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE, May 1992 Major Subject: Electricaj Engineering CALCULATION OF ELECTRONIC STATES OF A TWO-DIMENSIONAL ELECTRON GAS IN A PERIODIC MAGNETIC FIEI D A Thesis by ANISIlL HAOLtE 8L~ M. H. Weichold (Chair of Oornmittee) D...

Haque, Anisul

2012-06-07T23:59:59.000Z

200

ARM - Datastreams - sonicwind2d  

NLE Websites -- All DOE Office Websites (Extended Search)

Datastreamssonicwind2d Datastreamssonicwind2d Documentation Data Quality Plots ARM Data Discovery Browse Data Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send Datastream : SONICWIND2D Horizontal wind speed and direction from ultrasonic wind sensor (Vaisala WS425), 2m above ground on Barrow MET tower Active Dates 2003.10.31 - 2008.09.16 Measurement Categories Atmospheric State Originating Instrument ultrasonic wind sensor (SONICWIND) Measurements Only measurements considered scientifically relevant are shown below by default. Show all measurements Measurement Units Variable Horizontal wind Wind direction vector mean deg SonicWD_DU_WVT ( time ) Wind direction vector mean standard deviation deg SonicWD_SDU_WVT ( time ) Horizontal wind Wind speed arithmetic mean m/s SonicWS_S_WVT ( time )

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

STP Resources for Statistical & Thermal Physics Density of States of the Two-Dimensional Ising Model  

E-Print Network (OSTI)

STP Resources for Statistical & Thermal Physics Density of States of the Two-Dimensional Ising Model: STP IsingDensityOfStates FIG. 1: Plot of the density of states generated by stp IsingDensityOfStates. I. INTRODUCTION The STP IsingDensityOfStates program computes the density of states of the two

Holzwarth, Natalie

202

Large-scale Simulation of the Two-dimensional Kinetic Ising Model  

E-Print Network (OSTI)

Large-scale Simulation of the Two-dimensional Kinetic Ising Model Andreas Linke, Dieter W. Heermann-dimensional kinetic Ising model using a lattice of size 106 106 spins. We used Glauber as well as Metropolis dynamics for the Ising model because of its simplicity and its model character as a representant for a universality class

Heermann, Dieter W.

203

Two-dimensional numerical methods in electromagnetic hypersonics including fully coupled Maxwell equations  

E-Print Network (OSTI)

the magnetic field source (solenoid or permanent magnet). To test the technique, we show the results obtainedTwo-dimensional numerical methods in electromagnetic hypersonics including fully coupled Maxwell Keplerlaan 1, 2200 AG Noordwijk, The Netherlands We describe a numerical technique for solving the coupled

D'Ambrosio, Domenic

204

Asymptotic Behavior of the Newton-Boussinesq Equation in a Two-Dimensional Channel  

E-Print Network (OSTI)

We prove the existence of a global attractor for the Newton-Boussinesq equation defined in a two-dimensional channel. The asymptotic compactness of the equation is derived by the uniform estimates on the tails of solutions. We also establish the regularity of the global attractor.

Guglielmo Fucci; Bixiang Wang; Preeti Singh

2007-05-24T23:59:59.000Z

205

Two-Dimensional Lattice for Four-Dimensional = 4 Supersymmetric Yang-Mills  

Science Journals Connector (OSTI)

......intriguing scenario leading to four-dimensional N = 4 SYM...In order to realize the four-dimensional theory...appropriately. The crucial point is that one takes the...theory first) and then lifts the two-dimensional continuum theory to four dimensions using a matrix......

Masanori Hanada; So Matsuura; Fumihiko Sugino

2011-10-01T23:59:59.000Z

206

A SIMPLE PREDICTION ALGORITHM FOR THE LAGRANGIAN MOTION IN TWO-DIMENSIONAL TURBULENT FLOWS  

E-Print Network (OSTI)

with the mean square error of a prediction algorithm. The mathematical framework we set up here is as followsA SIMPLE PREDICTION ALGORITHM FOR THE LAGRANGIAN MOTION IN TWO-DIMENSIONAL TURBULENT FLOWS LEONID I Vol. 63, No. 1, pp. 116­148 Abstract. A new algorithm is suggested for prediction of a Lagrangian

Ozgökmen, Tamay M.

207

A first order two-dimensional melting transition : methane adsorbed on (0001) graphite (*)  

E-Print Network (OSTI)

L-543 A first order two-dimensional melting transition : methane adsorbed on (0001) graphite (*) A. Abstract. 2014 The variation of long range order of a registered solid submonolayer of methane adsorbed for various solid mono- layers adsorbed on graphite indicates that solid- fluid phase transitions are more

Paris-Sud XI, Université de

208

Electrostatic Structures in Space Plasmas: Properties of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes  

E-Print Network (OSTI)

Electrostatic Structures in Space Plasmas: Properties of Two-dimensional Magnetic Bernstein-Greene theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes of their properties, including its energy content, temperature and velocity distribution, and stability. This work

Ng, Chung-Sang

209

Numerical Studies of Collective Phenomena in Two-Dimensional Electron and Cold Atom Systems  

SciTech Connect

Numerical calculations were carried out to investigate a number of outstanding questions in both two-dimensional electron and cold atom systems. These projects aimed to increase our understanding of the properties of and prospects for non-Abelian states in quantum Hall matter.

Rezayi, Edward

2013-07-25T23:59:59.000Z

210

An Accurate Deterministic Projection Method for Two-Dimensional Stiff Detonation Waves  

E-Print Network (OSTI)

An Accurate Deterministic Projection Method for Two-Dimensional Stiff Detonation Waves Yunlong Chen detonation waves. We demonstrate the robustness of the proposed approach on a number of numerical experiments. Key words: stiff detonation waves, reactive Euler equations, splitting method, deterministic

Kurganov, Alexander

211

Surface-Skimming Stoneflies and Mayflies: The Taxonomic and Mechanical Diversity of Two-Dimensional Aerodynamic  

E-Print Network (OSTI)

-Dimensional Aerodynamic Locomotion* James H. Marden Brigid C. O'Donnell Michael A. Thomas Jesse Y. Bye Department be used to accomplish two-dimensional aerodynamic locomotion on the surface of water. Here we extend, horizontal velocity, and the verticality of aerodynamic force production increase as the body orientation

Marden, James

212

Two Dimensional Radiation Pressure Tactile Display Takayuki Iwamoto, Yoshimichi Ikeda, and Hiroyuki Shinoda  

E-Print Network (OSTI)

Two Dimensional Radiation Pressure Tactile Display Takayuki Iwamoto, Yoshimichi Ikeda, and Hiroyuki Shinoda The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan {iwa, ikeda, shino, radiation pressure 1. Introduction One of the difficulties in designing tactile displays is to find

Shinoda, Hiroyuki

213

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Window Frames  

E-Print Network (OSTI)

1 Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer Arasteh and Dragan Curcija ABSTRACT Accurately analyzing heat transfer in window frame cavities radiation heat-transfer effects.) We examine three representative complex cavity cross-section profiles

214

ccsd00001226 Ultracold atoms con ned in rf-induced two-dimensional trapping potentials  

E-Print Network (OSTI)

into this trap, starting either from thermal samples or Bose{Einstein condensates. In the latter case, technical along one direction to produce a two-dimensional atomic gas. We transferred ultracold atoms.50.Vk, 03.75.-b, 32.80.Pj It is well known that Bose{Einstein condensation (BEC) of homogeneous gases

215

SURFACE TENSION AND DEFORMATIONS OF MEMBRANE STRUCTURES : RELATION TO TWO-DIMENSIONAL PHASE TRANSITIONS  

E-Print Network (OSTI)

1099 SURFACE TENSION AND DEFORMATIONS OF MEMBRANE STRUCTURES : RELATION TO TWO-DIMENSIONAL PHASE les molécules sont en contact avec un réservoir. Dans le premier cas, la tension de surface est nulle tension de surface finie et les fluctuations sont très réduites. Ce résultat est en accord avec des

Boyer, Edmond

216

Physica D 136 (2000) 245265 Dynamics of kinks in two-dimensional hyperbolic models  

E-Print Network (OSTI)

indicative of the tendency of the free energy to decay towards a minimum. In the case of a non-conserved, and non-negative, and f () a real odd function with positive maximum equal to , negative minimum equal. With f () = sin , Eq. (1) is a two-dimensional generalization of the standard model of a large area

Rotstein, Horacio G.

217

Two-dimensional simulations of extreme floods on a large watershed  

E-Print Network (OSTI)

Two-dimensional simulations of extreme floods on a large watershed John F. England Jr. a,*, Mark L-dimensional, Runoff, Erosion and Export (TREX) model to simulate extreme floods on large watersheds in semi, validation and simulation of extreme storms and floods on the 12,000 km2 Arkansas River watershed above

Julien, Pierre Y.

218

Simulations of the Two-Dimensional Electronic Spectroscopy of the Photosystem II Reaction Center  

E-Print Network (OSTI)

for spectroscopic study. A purified PSII preparation capable of evolving oxygen consists of so-called BBY particlesSimulations of the Two-Dimensional Electronic Spectroscopy of the Photosystem II Reaction Center K spectroscopy of the Qy band of the D1-D2-Cyt b559 photosystem II reaction center at 77 K. We base

Mukamel, Shaul

219

Long-range orientational order in two-dimensional microfluidic dipoles  

E-Print Network (OSTI)

-range orientational order of droplet velocities in disordered two-dimensional microfluidic droplet ensembles. Droplet-droplet correlation can be explained by representing the entire ensemble as a third droplet. The correlation amplitude in capillaries13 , protein diffusion in membranes14 , and microfluidic droplets15,16 , the hydrodynamic

Loss, Daniel

220

Discrete-ordinates solution of short-pulsed laser transport in two-dimensional turbid media  

E-Print Network (OSTI)

of the hyperbolic transient radiative-transport equation are not known. Ku- mar et al.4 considered the solution-pulsed laser transport is transient radiative-transfer theory. Complete an- alytical solutionsDiscrete-ordinates solution of short-pulsed laser transport in two-dimensional turbid media

Guo, Zhixiong "James"

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Symmetry operators for Dirac's equation on two-dimensional spin manifolds  

E-Print Network (OSTI)

It is shown that the second order symmetry operators for the Dirac equation on a general two-dimensional spin manifold may be expressed in terms of Killing vectors and valence two Killing tensors. The role of these operators in the theory of separation of variables for the Dirac equation is studied.

Lorenzo Fatibene; Raymond G. McLenaghan; Giovanni Rastelli; Shane N. Smith

2008-12-11T23:59:59.000Z

222

hal-00177251,version1-6Oct2007 Derivation of asymptotic two-dimensional  

E-Print Network (OSTI)

by Boussinesq [1], allows to derive several shallow-water equations, which are named "Boussinesq-type equations. The KdV [6] and BBM [7] equations can also be derived in the case of unidirectional waves; this approachhal-00177251,version1-6Oct2007 Derivation of asymptotic two-dimensional time-dependent equations

Paris-Sud XI, Université de

223

Singular limits of a two-dimensional boundary value problem arising in corrosion modelling  

E-Print Network (OSTI)

Singular limits of a two-dimensional boundary value problem arising in corrosion modelling Juan D boundary . A very common boundary condition arising in corrosion modelling in a planar sample represented u on . We refer the reader to [11] and [4] for the derivation of this and related corrosion models

Ceragioli, Francesca

224

Two-Dimensional Numerical Modeling of Radio-Frequency Ion Engine Discharge  

E-Print Network (OSTI)

Two-Dimensional Numerical Modeling of Radio-Frequency Ion Engine Discharge Michael Meng-Tsuan Tsay-Frequency Ion Engine Discharge Michael Meng-Tsuan Tsay, Manuel Martinez-Sanchez August 2010 SSL # 14 Modeling of Radio-Frequency Ion Engine Discharge by Michael Meng-Tsuan Tsay Submitted to the Department

225

Two-dimensional Electron Liquid State at Oxide Interfaces J. Mannhart  

E-Print Network (OSTI)

Two-dimensional Electron Liquid State at Oxide Interfaces J. Mannhart Max Planck InstituteAlO3 #12;LaAlO3 - SrTiO3 YBa2Cu3O7 G. Hammerl #12;Interfaces with Standard Semiconductors: Space Charge;Conductance-voltage characteristics It/ Vs Vs were measured using a standard lock-in technique.24 Simulta

Yeh, Nai-Chang

226

Two dimensional thermoelectric platforms for thermocapillary droplet Man-Chi Liu,ac  

E-Print Network (OSTI)

the cooling function relies on the natural conduction and/or convection. A thermoelectric (TE) chipTwo dimensional thermoelectric platforms for thermocapillary droplet actuation Man-Chi Liu,ac Jin be driven to the cooler regions via surface tension modulation by varying the temperature. The usual method

Lin, Pei-Chun

227

Signatures of the Protein Folding Pathway in Two-Dimensional Ultraviolet Spectroscopy  

E-Print Network (OSTI)

Signatures of the Protein Folding Pathway in Two-Dimensional Ultraviolet Spectroscopy Jun Jiang of the signals provides a quantitative marker of protein folding status, accessible by both theoretical calculations and experiments. SECTION: Biophysical Chemistry and Biomolecules Protein folding is an important

Mukamel, Shaul

228

Radiation by Moving Shells in Curved Two-Dimensional Space-Time  

Science Journals Connector (OSTI)

......by the shell, which is then compared to that by a moving mirror. It also leads to a physically lucid expression for the stress...pp. 1126-1139 Quantum Field Theory in Two-Dimensional Schwarzschild-de Sitter Spacetime. II Shin-ichi Tadaki and Shin Takagi......

Kousuke Shizume; Shin Takagi

1988-03-01T23:59:59.000Z

229

Ultra-sensitive Calorimetry for Microwave Cyclotron Resonance in a Two-Dimensional Electron Gas  

E-Print Network (OSTI)

GP-B-1 Ultra-sensitive Calorimetry for Microwave Cyclotron Resonance in a Two-dimensional electron in GaAs quantum wells. We construct a differential nano-calorimetry which can operate at 300 mK the sensitivity for detecting CR heating to several nano-watts. This ultra-sensitive technique opens up

230

Analysis of Biodiesel/Petroleum Diesel Blends with Comprehensive Two-Dimensional Gas Chromatography  

Science Journals Connector (OSTI)

......Comprehensive two-dimensional gas chromatography (GC GC...assembled from a conventional gas chromatograph fitted with...bined with the high cost of crude oil, has sparked...interest in biodiesel production and distribution. Biodiesel...methods use single column gas chromatography (GC......

John V. Seeley; Stacy K. Seeley; Elise K. Libby; James D. McCurry

231

Quasi-equilibrium phase diagram and optical response in two-dimensional electron-hole system  

SciTech Connect

We study two dimensional electron-hole system in quasi-equilibrium. By using the self-consistent screened T matrix approximation, we present density dependence of ionization ratio. We also discuss the photoluminescence spectra, which are compared with experiment over the wide carrier density range.

Yoshioka, Takuya; Asano, Kenichi [Department of Physics, Osaka University, Toyonaka, Osaka, 560-0064 (Japan)

2013-12-04T23:59:59.000Z

232

Photocathode source for studying two-dimensional fluid phenomena with magnetized electron columns  

E-Print Network (OSTI)

Photocathode source for studying two-dimensional fluid phenomena with magnetized electron columns D have been generated with thermionic sources, typically limiting the initial electron distribution a new electron source based on a cesium antimonide photocathode that can generate more complicated

Fajans, Joel

233

Vortex-vacancy interactions in two-dimensional easy-plane magnets G. M. Wysin  

E-Print Network (OSTI)

Vortex-vacancy interactions in two-dimensional easy-plane magnets G. M. Wysin Department of Physics of a magnetic vacancy site on a nearby magnetic vortex are analyzed on square, hexagonal and triangular lattices. When the vortex is centered on a vacancy, the critical anisotropies where the stable vortex structure

Wysin, Gary

234

Magnetoabsorption and radiation-induced resistance oscillations in two-dimensional electron systems  

SciTech Connect

Magnetoabsorption and resistance oscillations in two-dimensional systems are calculated in the framework of the same theory: the microwave driven Larmor orbit model. On the one hand, this theory allows to obtain resistance oscillations with multiple peaks, depending on the microwave frequency. On the other hand, it permits also to calculate the microwave magnetoabsorption..

Inarrea, J. [Escuela Politecnica Superior, Universidad Carlos III, Leganes, Madrid, 28911 (Spain) and Instituto de Ciencia de Materiales, CSIC, Cantoblanco, Madrid, 28049 (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, Cantoblanco, Madrid, 28049 (Spain)

2011-12-23T23:59:59.000Z

235

Asymptotic Behavior of Energy Solutions to a Two Dimensional Semilinear Problem with Mixed  

E-Print Network (OSTI)

Asymptotic Behavior of Energy Solutions to a Two Dimensional Semilinear Problem with Mixed Boundary with the asymptotic behavior of the energy solutions of the mixed boundary value problem u + up = 0 in u = 0 on 0 School of Mathematics, University of Minnesota Minneapolis, MN 55455 Key words and phrases: Mixed

Ren, Xiaofeng

236

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities  

E-Print Network (OSTI)

the two-dimensional heat transfer through building products.Gustavsen, A. 2001. Heat transfer in window frames withand CFD Simulations of Heat Transfer in Horizontal Window

Gustavsen, Arlid

2008-01-01T23:59:59.000Z

237

Correlation energy of finite two-dimensional systems: Toward nonempirical and universal modeling  

Science Journals Connector (OSTI)

The capability of density-functional theory to deal with the ground state of strongly correlated low-dimensional systems, such as semiconductor quantum dots, depends on the accuracy of functionals developed for the exchange and correlation energies. Here we extend a successful approximation for the correlation energy of the three-dimensional inhomogeneous electron gas, originally introduced by Becke [J. Chem. Phys. 88, 1053 (1988)], to the two-dimensional case. The approach is based on nonempirical modeling of the correlation-hole functions satisfying a set of exact properties. Furthermore, the electron current and spin are explicitly taken into account. As a result, good performance is obtained in comparison with numerically exact data for quantum dots with varying external magnetic field, and for the homogeneous two-dimensional electron gas, respectively.

S. Pittalis; E. Räsänen; C. R. Proetto; E. K. U. Gross

2009-02-24T23:59:59.000Z

238

Quantization of the Reduced Phase Space of Two-Dimensional Dilaton Gravity  

E-Print Network (OSTI)

We study some two-dimensional dilaton gravity models using the formal theory of partial differential equations. This allows us to prove that the reduced phase space is two-dimensional without an explicit construction. By using a convenient (static) gauge we reduce the theory to coupled \\ode s and we are able to derive for some potentials of interest closed-form solutions. We use an effective (particle) Lagrangian for the reduced field equations in order to quantize the system in a finite-dimensional setting leading to an exact partial differential Wheeler-DeWitt equation instead of a functional one. A WKB approximation for some quantum states is computed and compared with the classical Hamilton-Jacobi theory. The effect of minimally coupled matter is examined.

W. M. Seiler; R. W. Tucker

1995-06-19T23:59:59.000Z

239

Two-Dimensional Density-Matrix Topological Fermionic Phases: Topological Uhlmann Numbers  

E-Print Network (OSTI)

We construct a topological invariant that classifies density matrices of symmetry-protected topological orders in two-dimensional fermionic systems. As it is constructed out of the previously introduced Uhlmann phase, we refer to it as the topological Uhlmann number ${\\rm n}_{\\rm U}$. With it, we study thermal topological phases in several two-dimensional models of topological insulators and superconductors, computing phase diagrams where the temperature $T$ is on an equal footing with the coupling constants in the Hamiltonian. Moreover, we find novel thermal-topological transitions between two non-trivial phases in a model with high Chern numbers. At small temperature we recover the standard topological phases as the Uhlmann number approaches to the Chern number.

O. Viyuela; A. Rivas; M. A. Martin-Delgado

2014-05-23T23:59:59.000Z

240

Resonant tunneling device with two-dimensional quantum well emitter and base layers  

DOE Patents (OSTI)

A double electron layer tunneling device is presented. Electrons tunnel from a two dimensional emitter layer to a two dimensional tunneling layer and continue traveling to a collector at a lower voltage. The emitter layer is interrupted by an isolation etch, a depletion gate, or an ion implant to prevent electrons from traveling from the source along the emitter to the drain. The collector is similarly interrupted by a backgate, an isolation etch, or an ion implant. When the device is used as a transistor, a control gate is added to control the allowed energy states of the emitter layer. The tunnel gate may be recessed to change the operating range of the device and allow for integrated complementary devices. Methods of forming the device are also set forth, utilizing epoxy-bond and stop etch (EBASE), pre-growth implantation of the backgate or post-growth implantation. 43 figs.

Simmons, J.A.; Sherwin, M.E.; Drummond, T.J.; Weckwerth, M.V.

1998-10-20T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
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241

Inorganic Graphenylene: A Porous Two-Dimensional Material With Tunable Band Gap  

E-Print Network (OSTI)

By means of ab initio calculations we investigate the possibility of existence of a boron nitride (BN) porous two-dimensional nanosheet which is geometrically similar to the carbon allotrope known as biphenylene carbon. The proposed structure, which we called Inorganic Graphenylene (IGP), is formed spontaneously after selective dehydrogenation of the porous Boron Nitride (BN) structure proposed by Ding et al. We study the structural and electronic properties of both porous BN and IGP and it is shown that, by selective substitution of B and N atoms with carbon atoms in these structures, the band gap can be significantly reduced, changing their behavior from insulators to semiconductors, thus opening the possibility of band gap engineering for this class of two-dimensional materials.

Perim, Eric; Atreto, Pedro Alves da Silva; Galvăo, Douglas

2014-01-01T23:59:59.000Z

242

Electron-electron relaxation in two-dimensional and layered superconductors  

Science Journals Connector (OSTI)

The electron-electron relaxation in two-dimensional and layered superconductors is studied. The calculations go beyond the random-phase approximation in the lowest order of perturbation theory for any relation between the screening momentum ? and the Fermi momentum pF. Besides the Coulomb electron-electron interaction we also include all possible channels of the electron-electron interaction in a superconductor. We show that the electron relaxation rate in the superconducting state acquires the logarithmic factor similar to the normal state. The electron relaxation drastically changes in two-dimensional d-wave superconductors in comparison with the three-dimensional case. We also show that in a superconductor–normal-metal system the recombination relaxation rate in the superconducting layer in the low-temperature region strongly increased (by the exponential factor), what may be important for superconducting radiation detectors.

Michael Reizer

1998-01-01T23:59:59.000Z

243

Resonant tunneling device with two-dimensional quantum well emitter and base layers  

DOE Patents (OSTI)

A double electron layer tunneling device is presented. Electrons tunnel from a two dimensional emitter layer to a two dimensional tunneling layer and continue traveling to a collector at a lower voltage. The emitter layer is interrupted by an isolation etch, a depletion gate, or an ion implant to prevent electrons from traveling from the source along the emitter to the drain. The collector is similarly interrupted by a backgate, an isolation etch, or an ion implant. When the device is used as a transistor, a control gate is added to control the allowed energy states of the emitter layer. The tunnel gate may be recessed to change the operating range of the device and allow for integrated complementary devices. Methods of forming the device are also set forth, utilizing epoxy-bond and stop etch (EBASE), pre-growth implantation of the backgate or post-growth implantation.

Simmons, Jerry A. (Sandia Park, NM); Sherwin, Marc E. (Rockville, MD); Drummond, Timothy J. (Tijeras, NM); Weckwerth, Mark V. (Pleasanton, CA)

1998-01-01T23:59:59.000Z

244

Theory of microwave-induced zero-resistance states in two-dimensional electron systems  

SciTech Connect

The phenomena of microwave-induced zero-resistance states (MIZRS) and microwave-induced resistance oscillations (MIRO) were discovered in ultraclean two-dimensional electron systems in 2001-2003 and have attracted great interest from researchers. In spite of numerous theoretical efforts, the true origin of these effects remains unknown so far. We show that the MIRO-ZRS phenomena are naturally explained by the influence of the ponderomotive forces which arise in the near-contact regions of two-dimensional electron gas under the action of microwaves. The proposed analytical theory is in agreement with all experimental facts accumulated so far and provides a simple and self-evident explanation of the microwave frequency, polarization, magnetic field, mobility, power, and temperature dependencies of the observed effects.

Mikhailov, S. A. [Institute of Physics, University of Augsburg, D-86135 Augsburg (Germany)

2011-04-15T23:59:59.000Z

245

2D gravity and the extended formalism  

Science Journals Connector (OSTI)

The role of SL(2,R) symmetry in two-dimensional gravity is investigated in the context of the extended Hamiltonian formalism. Using our results we clarify previous works on the subject.

Fernando P. Devecchi

1998-07-10T23:59:59.000Z

246

Large scale two-dimensional arrays of magnesium diboride superconducting quantum interference devices  

SciTech Connect

Magnetic field sensors based on two-dimensional arrays of superconducting quantum interference devices were constructed from magnesium diboride thin films. Each array contained over 30?000 Josephson junctions fabricated by ion damage of 30?nm weak links through an implant mask defined by nano-lithography. Current-biased devices exhibited very large voltage modulation as a function of magnetic field, with amplitudes as high as 8?mV.

Cybart, Shane A., E-mail: scybart@ucsd.edu; Dynes, R. C. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Wong, T. J.; Cho, E. Y. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Beeman, J. W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Yung, C. S.; Moeckly, B. H. [Superconductor Technologies Inc., Santa Barbara, California 93111 (United States)

2014-05-05T23:59:59.000Z

247

TWIST: a transient two-dimensional intra-subassembly thermal hydraulics model for LMFBRs  

SciTech Connect

Mathematical models and numerical methods for a two-dimensional porous body simulation of steady state and transient thermal-hydraulics conditions in LMFBR subassemblies resulting in the TWIST computer code are presented. Comparison of calculated results to steady state and transient out-of-pile sodium experiments show good agreement for cross-assembly temperature distributions for a wide range of heat transfer and flow conditions.

Khatib-Rahbar, M.; Cazzoli, E.G.

1984-06-03T23:59:59.000Z

248

World Sheet and Space Time Physics in Two Dimensional (Super) String Theory  

E-Print Network (OSTI)

We show that tree level ``resonant'' $N$ tachyon scattering amplitudes, which define a sensible ``bulk'' S -- matrix in critical (super) string theory in any dimension, have a simple structure in two dimensional space time, due to partial decoupling of a certain infinite set of discrete states. We also argue that the general (non resonant) amplitudes are determined by the resonant ones, and calculate them explicitly, finding an interesting analytic structure. Finally, we discuss the space time interpretation of our results.

P. Di Francesco; D. Kutasov

1991-09-04T23:59:59.000Z

249

Inverse fixed energy scattering problem for the two-dimensional nonlinear Schroedinger operator  

E-Print Network (OSTI)

This work studies the direct and inverse fixed energy scattering problem for two-dimensional Schroedinger equation with rather general nonlinear index of refraction. In particular, using the Born approximation we prove that all singularities of the unknown compactly supported potential from $L^2$-space can be obtained uniquely by the scattering data with fixed positive energy. The proof is based on the new estimates for the Faddeev-Green's function in $L^\\infty$-space.

Georgios Fotopoulos; Valery Serov

2014-12-01T23:59:59.000Z

250

Two Dimensional Integration of Ring Cavity Surface Emitting Quantum Cascade Lasers  

SciTech Connect

The continual improvements over the last fifteen years have made quantum cascade lasers reliable and versatile light sources in the mid infrared and the terahertz spectral regions. In this work we present our latest results regarding the implementation of these light sources for forming broad band emitting two-dimensional laser arrays. A spectral tuning range of 180 cm{sup -1} around the centered wavelength of 8.2 {mu}m could be shown.

Schwarzer, Clemens; Mujagic, Elvis; Zederbauer, Tobias; Detz, Hermann; Andrews, Aaron M.; Schrenk, Werner; Strasser, Gottfried [Institute for Solid State Electronics, Vienna University of Technology, 1040 Vienna (Austria); Yao Yu; Chen Jianxin; Gmachl, Claire [Department of Electrical Engineering, Princeton University, Princeton, NJ 08544 (United States)

2011-12-26T23:59:59.000Z

251

Coulomb reacceleration as a clock for nuclear reactions: A two-dimensional model  

Science Journals Connector (OSTI)

Reacceleration effects in the Coulomb breakup of nuclei are modeled with the two-dimensional time-dependent Schrödinger equation, extending a previous one-dimensional study. The present model better describes the individual contributions of longitudinal and transverse forces to the breakup and reacceleration. Reacceleration effects are found to preserve a strong memory of the pre-breakup phase of the reaction, as was concluded with the one-dimensional model.

C. A. Bertulani and G. F. Bertsch

1994-05-01T23:59:59.000Z

252

Preliminary results for a two-dimensional simulation of the working process of a Stirling engine  

SciTech Connect

Stirling engines have several potential advantages over existing types of engines, in particular they can use renewable energy sources for power production and their performance meets the demands on the environmental security. In order to design Stirling Engines properly, and to put into effect their potential performance, it is important to more accurately mathematically simulate its working process. At present, a series of very important mathematical models are used for describing the working process of Stirling Engines and these are, in general, classified as models of three levels. All the models consider one-dimensional schemes for the engine and assume a uniform fluid velocity, temperature and pressure profiles at each plane of the internal gas circuit of the engine. The use of two-dimensional CFD models can significantly extend the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes which occur in the internal gas circuit, as well as in the external circuit of the engine. In this paper a two-dimensional simplified frame (no construction walls) calculation scheme for the Stirling Engine has been assumed and the standard {kappa}-{var{underscore}epsilon} turbulence model has been used for the analysis of the engine working process. The results obtained show that the use of two-dimensional CFD models gives the possibility of gaining a much greater insight into the fluid flow and heat transfer processes which occur in Stirling Engines.

Makhkamov, K.K.; Ingham, D.B.

1998-07-01T23:59:59.000Z

253

Rashba spin splitting and cyclotron resonance in strained InGaAs/InP heterostructures with a two-dimensional electron gas  

SciTech Connect

Cyclotron resonance and magnetic transport in InP/InGaAs/InP heterostructures with axially symmetric quantum wells are studied experimentally at 4.2 K. An increase in the cyclotron mass at the Fermi level from 0.047m{sub 0} to 0.057m{sub 0} with an increase in the concentration of two-dimensional electrons from 5.5 Multiplication-Sign 10{sup 11} to 2.1 Multiplication-Sign 10{sup 12} cm{sup -3} is shown. The values of the Rashba spin splitting at the Fermi level are determined from Fourier analysis of the beats of Shubnikov-de Haas oscillations. The obtained experimental data are compared with the theoretical results of self-consistent calculations of the energy spectrum and cyclotron masses of 2D electrons performed using the eight-band k {center_dot} p Hamiltonian.

Kalinin, K. P., E-mail: kirill.kalinin@mail.ru; Krishtopenko, S. S.; Maremyanin, K. V.; Spirin, K. E.; Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Biryukov, A. A.; Baidus, N. V.; Zvonkov, B. N. [Lobachevskyi State University, Physical-Technical Research Institute (Russian Federation)] [Lobachevskyi State University, Physical-Technical Research Institute (Russian Federation)

2013-11-15T23:59:59.000Z

254

Formulation of the MFS for the two-dimensional Laplace equation with an added constant and constraint  

Science Journals Connector (OSTI)

Abstract Motivated by the incompleteness of single-layer potential approach for the interior problem with a degenerate-scale domain and the exterior problem with bounded potential at infinity, we revisit the method of fundamental solutions (MFS). Although the MFS is an easy method to implement, it is not complete for solving not only the interior 2D problem in case of a degenerate scale but also the exterior problem with bounded potential at infinity for any scale. Following Fichera?s idea for the boundary integral equation, we add a free constant and an extra constraint to the traditional MFS. The reason why the free constant and extra constraints are both required is clearly explained by using the degenerate kernel for the closed-form fundamental solution. Since the range of the single-layer integral operator lacks the constant term in the case of a degenerate scale for a two dimensional problem, we add a constant to provide a complete base. Due to the rank deficiency of the influence matrix in the case of a degenerate scale, we can promote the rank by simultaneously introducing a constant term and adding an extra constraint to enrich the MFS. For an exterior problem, the fundamental solution does not contain a constant field in the degenerate kernel expression. To satisfy the bounded potential at infinity, the sum of all source strengths must be zero. The formulation of the enriched MFS can solve not only the degenerate-scale problem for the interior problem but also the exterior problem with bounded potential at infinity. Finally, three examples, a circular domain, an infinite domain with two circular holes and an eccentric annulus were demonstrated to see the validity of the enriched MFS.

Jeng-Tzong Chen; Jheng-Lin Yang; Ying-Te Lee; Yu-Lung Chang

2014-01-01T23:59:59.000Z

255

PHYSICAL REVIEW E 87, 043303 (2013) Numerically exact correlations and sampling in the two-dimensional Ising spin glass  

E-Print Network (OSTI)

-dimensional Ising spin glass Creighton K. Thomas1 and A. Alan Middleton2 1 Department of Materials Science existing technique for evaluating statistical mechanical quantities in two-dimensional Ising models of inverse matrices and exact sampling, a method and computer code for studying two-dimensional Ising models

Middleton, Alan

256

Electron Transport in a Two-Dimensional Electron Gas at GaAs/AlGaAs Heterointerface  

E-Print Network (OSTI)

in condensed matters. Two-dimensional electron gas (2DEG) at the GaAs/AlGaAs hetero-interface o ersThesis Electron Transport in a Two-Dimensional Electron Gas at GaAs/AlGaAs Heterointerface under of the art samples, the mean free path of electrons exceeds 10;4 m at low temperature. The achievement

Katsumoto, Shingo

257

2D Gauge Field Theory  

SciTech Connect

We show from the action integral that under the assumption of longitudinal dominance and transverse confinement, QCD4 in (3+1) dimensional space-time can be approximately compactified into QCD2 in (1+1) dimensional space-time. In such a process, we find the relation between the coupling constant $g(2D)$ in QCD2 and the coupling constant $g(4D)$ in QCD4. We also show that quarks and gluons in QCD2 acquire masses as a result of the compactification.

Koshelkin, Andrey V. [Moscow Institute for Physics and Engineering, Russia] [Moscow Institute for Physics and Engineering, Russia; Wong, Cheuk-Yin [ORNL] [ORNL

2012-01-01T23:59:59.000Z

258

Transparent Conducting Electrodes based on 1D and 2D Ag Nanogratings for Organic Photovoltaics  

E-Print Network (OSTI)

The optical and electrical properties of optically-thin one-dimensional (1D) Ag nanogratings and two-dimensional (2D) Ag nanogrids are studied, and their use as transparent electrodes in organic photovoltaics are explored. A large broadband and polarization-insensitive optical absorption enhancement in the organic light-harvesting layers is theoretically and numerically demonstrated using either single-layer 2D Ag nanogrids or two perpendicular 1D Ag nanogratings, and is attributed to the excitation of surface plasmon resonances and plasmonic cavity modes. Total photon absorption enhancements of 150% and 200% are achieved for the optimized single-layer 2D Ag nanogrids and double (top and bottom) perpendicular 1D Ag nanogratings, respectively.

Zeng, Beibei; Bartoli, Filbert J

2014-01-01T23:59:59.000Z

259

Two-Dimensional Melts:? Polymer Chains at the Air?Water Interface  

Science Journals Connector (OSTI)

Grant T. Gavranovic ,† Joshua M. Deutsch ,‡ and Gerald G. Fuller *† ... Both physical surface rheology and computer simulation experiments were performed to understand the conformation of polymers in 2D systems. ...

Grant T. Gavranovic; Joshua M. Deutsch; Gerald G. Fuller

2005-06-25T23:59:59.000Z

260

Two-dimensional full wavefield inversion of wide-aperture marine seismic streamer data  

Science Journals Connector (OSTI)

......Developments in the field of high performance computing facilities supporting parallel...University of Cambridge High Performance Computing Facility. The 2-D wavefield...data set. Access to the High Performance Computing Facility at the University......

Richard M. Shipp; Satish C. Singh

2002-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Plasmon mass and Drude weight in strongly spin-orbit-coupled two-dimensional electron gases  

E-Print Network (OSTI)

) spin- orbit-coupled 2D electron and hole gases, which are promising candidates for semiconductor spintronics,1 (ii) graphene2 (a monolayer of carbon atoms arranged in a 2D honeycomb lattice), which has attracted a great deal of interest because..., in the case of graphene) degree of freedom. This coupling, being of relativistic origin,12 naturally breaks Galilean invariance and is thus the basic reason for a quite sensitive dependence of several observables on electron-electron interactions, even...

Agarwal, Amit; Chesi, Stefano; Jungwirth, T.; Sinova, Jairo; Vignale, G.; Polini, Marco.

2011-01-01T23:59:59.000Z

262

An implicit logarithmic finite-difference technique for two dimensional coupled viscous Burgers’ equation  

SciTech Connect

This article describes a new implicit finite-difference method: an implicit logarithmic finite-difference method (I-LFDM), for the numerical solution of two dimensional time-dependent coupled viscous Burgers’ equation on the uniform grid points. As the Burgers’ equation is nonlinear, the proposed technique leads to a system of nonlinear systems, which is solved by Newton's iterative method at each time step. Computed solutions are compared with the analytical solutions and those already available in the literature and it is clearly shown that the results obtained using the method is precise and reliable for solving Burgers’ equation.

Srivastava, Vineet K., E-mail: vineetsriiitm@gmail.com [ISRO Telemetry, Tracking and Command Network (ISTRAC), Bangalore-560058 (India); Awasthi, Mukesh K. [Department of Mathematics, University of Petroleum and Energy Studies, Dehradun-248007 (India)] [Department of Mathematics, University of Petroleum and Energy Studies, Dehradun-248007 (India); Singh, Sarita [Department of Mathematics, WIT- Uttarakhand Technical University, Dehradun-248007 (India)] [Department of Mathematics, WIT- Uttarakhand Technical University, Dehradun-248007 (India)

2013-12-15T23:59:59.000Z

263

From antiferromagnetism to d-wave superconductivity in the two-dimensional t-J model  

Science Journals Connector (OSTI)

We have found that the two dimensional t-J model, for the physical parameter range J/t=0.4 reproduces the main experimental qualitative features of high-Tc copper oxide superconductors: d-wave superconducting correlations are strongly enhanced upon small doping and clear evidence of off-diagonal long-range order is found at the optimal doping ??0.15. On the other hand, antiferromagnetic long-range order, clearly present at zero hole doping, is suppressed at small hole density with clear absence of antiferromagnetism at ?>?0.1.

Matteo Calandra and Sandro Sorella

2000-05-01T23:59:59.000Z

264

Recursion relations for the matrix elements of the two-dimensional harmonic oscillator  

E-Print Network (OSTI)

RECURSION RELATIONS FOR THE HAYRIX ELEi~iENTS OF THE T410- DiI&NSIONAL HAiB'lONIC OSCILLATOR A Thesis ABNER HERMAN FERESTEH Subraitted to the Graduate College of Texas A &: Yi University in. partial fulfillment of the requirement.... lid 0 ~~rt e t Hem. r~ ember August i/70 Becursion Belations for the Natrix Elements of the Two- Dimensional Harmon1c Oscillator. (August 1970) Avner Herman Ferester, B. B. A. , The City College of New York; Directed by: Professor J. B. Coon...

Ferester, Avner Herman

1970-01-01T23:59:59.000Z

265

Phonon blocking by two dimensional electron gas in polar CdTe/PbTe heterojunctions  

SciTech Connect

Narrow-gap lead telluride crystal is an important thermoelectric and mid-infrared material in which phonon functionality is a critical issue to be explored. In this Letter, efficient phonon blockage by forming a polar CdTe/PbTe heterojunction is explicitly observed by Raman scattering. The unique phonon screening effect can be interpreted by recent discovery of high-density two dimensional electrons at the polar CdTe/PbTe(111) interface which paves a way for design and fabrication of thermoelectric devices.

Zhang, Bingpo; Cai, Chunfeng; Zhu, He; Wu, Feifei; Ye, Zhenyu; Chen, Yongyue; Li, Ruifeng; Kong, Weiguang; Wu, Huizhen, E-mail: hzwu@zju.edu.cn [Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027 (China)

2014-04-21T23:59:59.000Z

266

CURRENT - A Computer Code for Modeling Two-Dimensional, Chemically Reaccting, Low Mach Number Flows  

SciTech Connect

This report documents CURRENT, a computer code for modeling two- dimensional, chemically reacting, low Mach number flows including the effects of surface chemistry. CURRENT is a finite volume code based on the SIMPLER algorithm. Additional convergence acceleration for low Peclet number flows is provided using improved boundary condition coupling and preconditioned gradient methods. Gas-phase and surface chemistry is modeled using the CHEMKIN software libraries. The CURRENT user-interface has been designed to be compatible with the Sandia-developed mesh generator and post processor ANTIPASTO and the post processor TECPLOT. This report describes the theory behind the code and also serves as a user`s manual.

Winters, W.S.; Evans, G.H.; Moen, C.D.

1996-10-01T23:59:59.000Z

267

Ionized-impurity scattering of quasi-two-dimensional quantum-confined carriers  

Science Journals Connector (OSTI)

Hall-effect measurements of electron mobility in anti-modulation-doped GaAs/AlGaAs quantum wells indicate that the ionized-impurity scattering of a quasi-two-dimensional electron gas immersed in the identical concentration of ionized impurities is greater than that of a bulk electron gas of the same density. This enhancement results from an increase of the overlap of the electronic wave function with the impurities, a decrease in screening, and an increase in large-angle scattering. The enhanced scattering rate may be further increased by confining the dopant ions to a deltalike doping profile in the center of the well.

W. Ted Masselink

1991-03-18T23:59:59.000Z

268

Bounds on the length of magnetic field lines in a two-dimensional plasma  

Science Journals Connector (OSTI)

Magnetic field lines in ideal turbulent plasmas tend to become quite complicated and their length to grow in time. Diffusivity allows for reconnection and possible shortening, but this fact has not so far been rigorously quantified. We show that in a two-dimensional diffusive plasma the mean length of field lines stays bounded for all time. Moreover, these estimates are local, in the sense that the mean values of magnetic field and velocity in the neighborhood of a ball determine bounds for length within the ball, without recourse to external magnitudes.

Manuel Núńez

2001-02-27T23:59:59.000Z

269

A Quasi-Two-Dimensional Electrochemistry Modeling Tool for Planar Solid Oxide Fuel Cell Stacks  

SciTech Connect

A two-dimensional numerical model is presented for the efficient computation of the steady-state current density, species concentration, and temperature distributions in planar solid oxide fuel cell stacks. The model reduction techniques, engineering approximations, and numerical procedures used to simulate the stack physics while maintaining adequate computational speed are discussed. The results of the model for benchmark cases with and without on-cell methane reformation are presented with comparisons to results from other research described in the literature. The capabilities, performance, and scalability of the model for the study of large multi-cell stacks are then demonstrated.

Lai, Canhai; Koeppel, Brian J.; Choi, Kyoo Sil; Recknagle, Kurtis P.; Sun, Xin; Chick, Lawrence A.; Korolev, Vladimir N.; Khaleel, Mohammad A.

2011-03-15T23:59:59.000Z

270

Variable enstrophy flux and energy spectrum in two-dimensional turbulence with Ekman friction  

E-Print Network (OSTI)

Experiments and numerical simulations reveal that in the forward cascade regime, the energy spectrum of two-dimensional turbulence with Ekman friction deviates from Kraichnan's prediction of $k^{-3}$ power spectrum. In this letter we explain this observation using an analytic model based on variable enstrophy flux arising due to Ekman friction. We derive an expression for the enstrophy flux which exhibits a logarithmic dependence in the inertial range for the Ekman-friction dominated flows. The energy spectrum obtained using this enstrophy flux shows a power law scaling for large Reynolds number and small Ekman friction, but has an exponential behaviour for large Ekman friction and relatively small Reynolds number.

Mahendra K. Verma

2012-03-23T23:59:59.000Z

271

Ultra-low-temperature cooling of two-dimensional electron gas  

Science Journals Connector (OSTI)

A new design has been used for cooling GaAs/AlxGa1?xAs sample to ultra-low-temperatures. The sample, with electrical contacts directly soldered to the sintered silver powder heat exchangers, was immersed in liquid  3He, which was cooled by a PrNI5 nuclear refrigerator. The data analysis shows that the two-dimensional electron gas (2DEG) was cooled to 4.0 mK at the refrigerator base temperature Tb of 2.0 mK. The design with heat exchanger cooling is applicable to any ultra-low-temperature transport measurements of 2DEG system.

J.S Xia; E.D Adams; V Shvarts; W Pan; H.L Stormer; D.C Tsui

2000-01-01T23:59:59.000Z

272

Biexcitons in two-dimensional systems with spatially separated electrons and holes  

Science Journals Connector (OSTI)

The binding energy and wave functions of two-dimensional indirect biexcitons are studied analytically and numerically. It is proven that stable biexcitons exist only when the distance between electron and hole layers is smaller than a certain critical threshold. Numerical results for the biexciton binding energies are obtained using the stochastic variational method and compared with the analytical asymptotics. The threshold interlayer separation and its uncertainty are estimated. The results are compared with those obtained by other techniques, in particular, the diffusion Monte Carlo method and the Born-Oppenheimer approximation.

A. D. Meyertholen and M. M. Fogler

2008-12-10T23:59:59.000Z

273

Unitary transformations of a family of two-dimensional anharmonic oscillators  

E-Print Network (OSTI)

In this paper we analyze a recent application of perturbation theory by the moment method to a family of two-dimensional anharmonic oscillators. By means of straightforward unitary transformations we show that two of the models studied by the authors are separable. Other is unbounded from below and therefore cannot be successfully treated by perturbation theory unless a complex harmonic frequency is introduced in the renormalization process. We calculate the lowest resonance by means of complex-coordinate rotation and compare its real part with the eigenvalue estimated by the authors. A pair of the remaining oscillators are equivalent as they can be transformed into one another by unitary transformations.

Francisco M. Fernández; Javier Garcia

2014-09-24T23:59:59.000Z

274

Observation of audio-frequency edge magnetoplasmons in the classical two-dimensional electron gas  

Science Journals Connector (OSTI)

The electric admittance of a two-dimensional electron gas on liquid helium measured at audio frequencies ? is observed to oscillate as a function of magnetic field at strong magnetic fields. The oscillations can be attributed to the propagation of very-low-frequency (???10-6, ? scattering time; ?/?c?10-8, ?c cyclotron frequency) edge magnetoplasmons. The directly determined dispersion relation agrees with theory and quantitatively with measurements in the collisionless regime (???1). The attenuation, theoretically obtained by incorporating the screening in a simple local-capacitance model, agrees well with experiments.

P. J. M. Peters; M. J. Lea; A. M. L. Janssen; A. O. Stone; W. P. N. M. Jacobs; P. Fozooni; R. W. van der Heijden

1991-10-14T23:59:59.000Z

275

Unparticle Example in 2D  

Science Journals Connector (OSTI)

We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

Howard Georgi and Yevgeny Kats

2008-09-25T23:59:59.000Z

276

Local dissipation effects in two-dimensional quantum Josephson junction arrays with a magnetic field  

SciTech Connect

We study the quantum phase transitions in two-dimensional arrays of Josephson-couples junctions with short range Josephson couplings (given by the Josephson energy E{sub J}) and the charging energy E{sub C}. We map the problem onto the solvable quantum generalization of the spherical model that improves over the mean-field theory method. The arrays are placed on the top of a two-dimensional electron gas separated by an insulator. We include effects of the local dissipation in the presence of an external magnetic flux f={phi}/{phi}{sub 0} in square lattice for several rational fluxes f=0,(1/2),(1/3),(1/4), and (1/6). We also have examined the T=0 superconducting-insulator phase boundary as a function of a dissipation {alpha}{sub 0} for two different geometry of the lattice: square and triangular. We have found a critical value of the dissipation parameter independent on geometry of the lattice and presence magnetic field.

Polak, T.P.; Kopec, T.K. [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Strasse 38, 01187 Dresden (Germany); Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, POB 1410, 50-950 Wroclaw 2 (Poland)

2005-07-01T23:59:59.000Z

277

Spectral effects simulation with two-dimensional magnetohydrodynamic models of the solar photosphere  

E-Print Network (OSTI)

To study the structure of spatially unresolved features of the solar photosphere, we calculated the Stokes profiles of seven photospheric iron lines using two-dimensional nonstationary MHD models of solar granulation for various amounts of magnetic flux (0, 10, 20, 30 mT). We investigate variations in the absolute wavelength shifts and bisectors of the I profiles, as well as variations in the zero-crossing wavelength shifts, amplitude and area asymmetry of the V profiles as functions of magnetic field strength and time. The center-to-limb variations of the Stokes profiles are analyzed. The iron abundance is found to be 7.57, with the photosphere inhomogeneities taken into account. Although most of the spectral effects simulated within the scope of the two-dimensional MHD models are in satisfactory agreement with observational data, these models cannot always give a quantitative agreement. The absolute wavelength shifts of the Stokes profiles of Fe II lines calculated with the MHD models are substantially smal...

Atroshchenko, I N; 10.3103/50884591305030022

2012-01-01T23:59:59.000Z

278

Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids  

SciTech Connect

We study the ground-state properties of a two-dimensional spin-polarized fluid of dipolar fermions within the Euler–Lagrange Fermi-hypernetted-chain approximation. Our method is based on the solution of a scattering Schrödinger equation for the “pair amplitude” ?(g(r)), where g(r) is the pair distribution function. A key ingredient in our theory is the effective pair potential, which includes a bosonic term from Jastrow–Feenberg correlations and a fermionic contribution from kinetic energy and exchange, which is tailored to reproduce the Hartree–Fock limit at weak coupling. Very good agreement with recent results based on quantum Monte Carlo simulations is achieved over a wide range of coupling constants up to the liquid-to-crystal quantum phase transition. Using the fluctuation–dissipation theorem and a static approximation for the effective inter-particle interactions, we calculate the dynamical density–density response function, and furthermore demonstrate that an undamped zero-sound mode exists for any value of the interaction strength, down to infinitesimally weak couplings. -- Highlights: •We have studied the ground state properties of a strongly correlated two-dimensional fluid of dipolar fermions. •We have calculated the effective inter-particle interaction and the dynamical density–density response function. •We have shown that an undamped zero sound mode exists at any value of the interaction strength.

Abedinpour, Saeed H., E-mail: abedinpour@iasbs.ac.ir [Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731 (Iran, Islamic Republic of); School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531 (Iran, Islamic Republic of); Asgari, Reza [School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531 (Iran, Islamic Republic of)] [School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531 (Iran, Islamic Republic of); Tanatar, B. [Department of Physics, Bilkent University, Bilkent, 06800 Ankara (Turkey)] [Department of Physics, Bilkent University, Bilkent, 06800 Ankara (Turkey); Polini, Marco [NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56126 Pisa (Italy)] [NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56126 Pisa (Italy)

2014-01-15T23:59:59.000Z

279

Two dimensional invisibility cloaking for Helmholtz equation and non-local boundary conditions  

E-Print Network (OSTI)

Transformation optics constructions have allowed the design of cloaking devices that steer electromagnetic, acoustic and quantum waves around a region without penetrating it, so that this region is hidden from external observations. The material pa- rameters used to describe these devices are anisotropic, and singular at the interface between the cloaked and uncloaked regions, making physical realization a challenge. These singular material parameters correspond to singular coefficient functions in the partial differential equations modeling these constructions and the presence of these singularities causes various mathematical problems and physical effects on the interface surface. In this paper, we analyze the two dimensional cloaking for Helmholtz equation when there are sources or sinks present inside the cloaked region. In particular, we consider nonsingular approximate invisibility cloaks based on the truncation of the singular transformations. Using such truncation we analyze the limit when the approximate cloaking approaches the ideal cloaking. We show that, surprisingly, a non-local boundary condition appears on the inner cloak interface. This effect in the two dimensional (or cylindrical) invisibility cloaks, which seems to be caused by the infinite phase velocity near the interface between the cloaked and uncloaked regions, is very different from the earlier studied behavior of the solutions in the three dimensional cloaks.

Matti Lassas; Ting Zhou

2010-11-09T23:59:59.000Z

280

A two dimensional thermal network model for a photovoltaic solar wall  

SciTech Connect

A two dimensional thermal network model is proposed to predict the temperature distribution for a section of photovoltaic solar wall installed in an outdoor room laboratory in Concordia University, Montreal, Canada. The photovoltaic solar wall is constructed with a pair of glass coated photovoltaic modules and a polystyrene filled plywood board as back panel. The active solar ventilation through a photovoltaic solar wall is achieved with an exhaust fan fixed in the outdoor room laboratory. The steady state thermal network nodal equations are developed for conjugate heat exchange and heat transport for a section of a photovoltaic solar wall. The matrix solution procedure is adopted for formulation of conductance and heat source matrices for obtaining numerical solution of one dimensional heat conduction and heat transport equations by performing two dimensional thermal network analyses. The temperature distribution is predicted by the model with measurement data obtained from the section of a photovoltaic solar wall. The effect of conduction heat flow and multi-node radiation heat exchange between composite surfaces is useful for predicting a ventilation rate through a solar ventilation system. (author)

Dehra, Himanshu [1-140 Avenue Windsor, Lachine, Quebec (Canada)

2009-11-15T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Application of the static fluctuation approximation to the computation of the thermodynamic properties of an interacting trapped two-dimensional hard-sphere Bose gas  

SciTech Connect

The static fluctuation approximation (SFA) is applied to compute the thermodynamic properties of a trapped two-dimensional (2D) interacting hard-sphere (HS) Bose gas in the weakly and strongly interacting regime. A mean-field approach involving a variational wave function is used to compute the mean-field energy as a function of temperature for each harmonic oscillator (HO) state plugged into the SFA technique. In the variational approach, a parameter {alpha} is introduced into the harmonic oscillator wave function in order to take into account the changes in the width when the repulsive interactions between the bosons are increased. In the weakly interacting regime, below the critical temperature, the total energy of all HO states (evaluated by our model) matches the noninteracting result very well. However, beyond the critical temperature, we 'fit' our energies to the classical limit for 2D bosons in a trap by using a suitably proposed weighting function. We compare our results to earlier results of mean-field theory. Further, we evaluate the density matrix arising from correlations between the HO orbitals.

Sakhel, Asaad R. [Al-Balqa Applied University, Faculty of Engineering Technology, Amman 11134 (Jordan); Qashou, Saleem I. [Department of Physics, Faculty of Science and Information Technology, Zarqa Private University, Zarqa 13132 (Jordan); Sakhel, Roger R. [Department of Basic Sciences, Faculty of Information Technology, Al-Isra University, Amman 11622 (Jordan); Ghassib, Humam B. [Department of Physics, University of Jordan, Amman (Jordan)

2010-12-15T23:59:59.000Z

282

Polaron-molecule transitions in a two-dimensional Fermi gas  

SciTech Connect

We address the problem of a single 'spin-down' impurity atom interacting attractively with a spin-up Fermi gas in two dimensions (2D). We consider the case where the mass of the impurity is greater than or equal to the mass of a spin-up fermion. Using a variational approach, we resolve the questions raised by previous studies and show that there is, in fact, a transition between polaron and molecule (dimer) ground states in 2D. For the molecule state, we use a variational wave function with a single particle-hole excitation on the Fermi sea and we find that its energy matches that of the exact solution in the limit of infinite impurity mass. Thus, we expect the variational approach to provide a reliable tool for investigating 2D systems.

Parish, Meera M. [Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)

2011-05-15T23:59:59.000Z

283

Experimental investigation of the thermal-hydraulics of gas jet expansion In a two-dimensional liquid pool  

E-Print Network (OSTI)

Gas jet blowdown in a two-dimensional liquid pool has been experimentally investigated. Two sets of experiments were performed: a set of hydrodynamic experiments, where a non-condensible gas is injected into a subcooled ...

Rothrock, Ray Alan

1978-01-01T23:59:59.000Z

284

Calculation of Solar P-mode Oscillation Frequency Splittings Based on a Two-dimensional Solar Model  

E-Print Network (OSTI)

We compute the p-mode oscillation frequencies and frequency splittings that arise in a two-dimensional model of the Sun that contains toroidal magnetic fields in its interior.

Linghuai Li; Sarbani Basu; Sabatino Sofia; Pierre Demarque

2008-10-27T23:59:59.000Z

285

Optical properties of Ag nanoparticle-polymer composite film based on two-dimensional Au nanoparticle array film  

Science Journals Connector (OSTI)

The nanocomposite polyvinyl pyrrolidone (PVP) films containing Ag nanoparticles and Rhodamine 6G are prepared on the two-dimensional distinctive continuous ultrathin gold nanofilms. We investigate the optical pro...

Long-De Wang; Tong Zhang; Xiao-Yang Zhang; Yuan-Jun Song…

2014-03-01T23:59:59.000Z

286

Electronic properties of the AlGaN/GaN heterostructure and two-dimensional electron gas observed by electroreflectance  

Science Journals Connector (OSTI)

A contacted electroreflectance technique was used to investigate AlGaN/GaN heterostructures and their intrinsic electric field-induced properties. By studying variations in the electroreflectance with applied field spectral features associated with the AlGaN barrier the two-dimensional electron gas at the interface and bulk GaN were identified. Barrier-layer composition and electric field were determined from the AlGaN Franz–Keldysh oscillations. For a high mobilityheterostructure grown on SiC measured AlGaN polarizationelectric field and two-dimensional electron gas density approached values predicted by a standard bandstructure model. The two-dimensional electron gas produced a broad field-tunable first derivative electroreflectance feature. With a dielectric function calculation we describe the line shape and relative amplitude of the two-dimensional electron gas electroreflectance feature for a wide range of electron density and applied field values.

S. R. Kurtz; A. A. Allerman; D. D. Koleske; A. G. Baca; R. D. Briggs

2004-01-01T23:59:59.000Z

287

Generation and control of ultrashort-wavelength two-dimensional surface acoustic waves at nanoscale interfaces  

Science Journals Connector (OSTI)

In this work, we generate and probe the shortest wavelength surface acoustic waves to date, at 45 nm, by diffracting coherent extreme ultraviolet beams from a suboptical phononic crystal. The short acoustic wavelengths correspond to penetration depths of approximately 10 nm. We also measure the acoustic dispersion in two-dimensional nanostructured phononic crystals down to this wavelength for the first time, showing that it is strongly influenced by the ultrashort acoustic penetration depth, and that advanced finite-element analysis is required to model the dispersion. Finally, we use pulse sequences to control surface acoustic wave generation in one-dimensional nanostructured gratings, to preferentially enhance higher-order surface waves, while suppressing lower frequency waves. This allows us to reduce the generated surface acoustic wavelength by a factor of two for a defined nanostructure period.

Qing Li; Kathleen Hoogeboom-Pot; Damiano Nardi; Margaret M. Murnane; Henry C. Kapteyn; Mark E. Siemens; Erik H. Anderson; Olav Hellwig; Elizabeth Dobisz; Bruce Gurney; Ronggui Yang; Keith A. Nelson

2012-05-15T23:59:59.000Z

288

Laser induced reentrant freezing in two-dimensional attractive colloidal systems  

E-Print Network (OSTI)

The effects of an externally applied one-dimensional periodic potential on the freezing/melting behaviour of two-dimensional systems of colloidal particles with a short-range attractive interaction are studied using Monte Carlo simulations. In such systems, incommensuration results when the periodicity of the external potential does not match the length-scale at which the minimum of the attractive potential occurs. To study the effects of this incommensuration, we consider two different models for the system. Our simulations for both these models show the phenomenon of reentrant freezing as the strength of the periodic potential is varied. Our simulations also show that different exotic phases can form when the strength of the periodic potential is high, depending on the length-scale at which the minimum of the attractive pair-potential occurs.

Pinaki Chaudhuri; Chinmay Das; Chandan Dasgupta; H. R. Krishnamurthy; A. K. Sood

2005-09-11T23:59:59.000Z

289

Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U  

SciTech Connect

A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.

Faust, I.; Parker, R. R. [MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Delgado-Aparicio, L.; Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Tritz, K. [The Johns Hopkins University, Baltimore, Maryland 21209 (United States); Stratton, B. C. [MIT - Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)

2014-11-15T23:59:59.000Z

290

Two-dimensional model of a reaction-diffusion system as a typewriter  

Science Journals Connector (OSTI)

Pattern formation is a common phenomenon, which appears in biological systems, especially in cell differentiation processes. The proper level for understanding the creation of patterns seems to be a physicochemical description. The most fundamental models should be based on systems, in which only chemical reactions and diffusion transport occur (reaction-diffusion systems). In order to present a richness of patterns, we show here the asymptotic patterns in the form of capital letters obtained in two-dimensional reaction-diffusion systems with zero-flux boundary conditions. All capital letters are obtained in the same model, but initial conditions and sizes of the systems are different for each letter. The chemical model consists of elementary reactions and is realistic. It can be realized experimentally in continuous-flow unstirred reactor with an enzymatic reaction allosterically inhibited by an excess of its reactant and product.

Andrzej L. Kawczy?ski and Bart?omiej Legawiec

2001-10-09T23:59:59.000Z

291

Spectral-domain phase microscopy with improved sensitivity using two-dimensional detector arrays  

SciTech Connect

In this work we demonstrate the use of two-dimensional detectors to improve the signal-to-noise ratio (SNR) and sensitivity in spectral-domain phase microscopy for subnanometer accuracy measurements. We show that an increase in SNR can be obtained, from 82 dB to 105 dB, using 150 pixel lines of a low-cost CCD camera as compared to a single line, to compute an averaged axial scan. In optimal mechanical conditions, phase stability as small as 92 {mu}rad, corresponding to 6 pm displacement accuracy, could be obtained. We also experimentally demonstrate the benefit of spatial-averaging in terms of the reduction of signal fading due to an axially moving sample. The applications of the improved system are illustrated by imaging live cells in culture.

Singh, K.; Dion, C.; Ozaki, T. [Centre de Recherche, Hopital Maisonneuve-Rosemont, Montreal, Quebec (Canada); Institut National de la Recherche Scientifique, Energie, Materiaux et Telecommunications, Varennes, Quebec (Canada); Lesk, M. R. [Centre de Recherche, Hopital Maisonneuve-Rosemont, Montreal, Quebec (Canada); Departement d'Ophtalmologie, Universite de Montreal, Montreal, Quebec (Canada); Costantino, S. [Centre de Recherche, Hopital Maisonneuve-Rosemont, Montreal, Quebec (Canada); Departement d'Ophtalmologie, Universite de Montreal, Montreal, Quebec (Canada); Institut de Genie Biomedical, Universite de Montreal, Montreal, Quebec (Canada)

2011-02-15T23:59:59.000Z

292

Wilson line correlators in two-dimensional noncommutative Yang-Mills theory  

Science Journals Connector (OSTI)

We study the correlator of two parallel Wilson lines in two-dimensional non-commutative Yang-Mills theory, following two different approaches. We first consider a perturbative expansion in the large-N limit and resum all planar diagrams. The second approach is non perturbative: we exploit the Morita equivalence, mapping the two open lines on the non-commutative torus (which eventually gets decompacted) in two closed Wilson loops winding around the dual commutative torus. Planarity allows us to single out a suitable region of the variables involved, where a saddle-point approximation of the general Morita expression for the correlator can be performed. In this region the correlator nicely compares with the perturbative result, exhibiting an exponential increase with respect to the momentum p.

Antonio Bassetto; Federica Vian

2002-01-01T23:59:59.000Z

293

Bose-Einstein condensation and heat capacity of two-dimensional spin-polarized atomic hydrogen  

SciTech Connect

The static fluctuation approximation (SFA) is used to study the condensate fraction and the specific heat capacity of finite two-dimensional spin-polarized atomic hydrogen. It is found that Bose-Einstein condensation occurs in this system. The transition temperature at different densities decreases as the number of particles of the system increases. At low density, a sharp peak in the specific heat capacity is observed at the transition temperature. On the other hand, as the density of the system increases, the transition temperature becomes no longer well-defined, and a hump is observed in the specific heat capacity around the transition temperature. A qualitative comparison of our results to published results for finite Bose systems shows good agreement.

Al-Sugheir, M. K. [Department of Physics, Hashemite University, Zarqa (Jordan); Ghassib, H. B. [Department of Physics, University of Jordan, Amman (Jordan); Awawdeh, M. [Department of Physics, Yarmouk University, Irbid (Jordan)

2011-07-15T23:59:59.000Z

294

SAS4A simulation of the OPERA-15 two-dimensional voiding experiment. [LMFBR  

SciTech Connect

A major effort is currently being pursued to validate the SAS4A LMFBR accident analysis code. Part of this effort involves SAS4A analysis of both in-pile and out-of-pile safety experiments. Such an experiment is the fifteen-pin Out-of-Pile Explusion and Reentry Apparatus (OPERA) test run at Argonne National Laboratory. This test uses a fifteen-pin triangular-shaped bundle of simulant fuel pins to demonstrate two-dimensional voiding behavior in a LMFBR subassembly during a Loss-of-Flow (LOF) accident. This experiment was chosen for SAS4A analysis both for its value in code validation and its usefulness in evaluating the limitations of the one-dimensional SAS4A sodium voiding model in accident analysis.

Briggs, L.L.

1984-01-01T23:59:59.000Z

295

Two-dimensional spectroscopy for the study of ion Coulomb crystals  

E-Print Network (OSTI)

Ion Coulomb crystals are currently establishing themselves as a highly controllable test-bed for mesoscopic systems of statistical mechanics. The detailed experimental interrogation of the dynamics of these crystals however remains an experimental challenge. In this work, we show how to extend the concepts of multi-dimensional nonlinear spectroscopy to the study of the dynamics of ion Coulomb crystals. The scheme we present can be realized with state-of-the-art technology and gives direct access to the dynamics, revealing nonlinear couplings even in systems with many ions and in the presence of thermal excitations. We illustrate the advantages of our proposal showing how two-dimensional spectroscopy can be used to detect signatures of a structural phase transition of the ion crystal, as well as resonant energy exchange between modes. Furthermore, we demonstrate in these examples how different decoherence mechanisms can be identified.

A. Lemmer; C. Cormick; C. T. Schmiegelow; F. Schmidt-Kaler; M. B. Plenio

2014-07-03T23:59:59.000Z

296

Numerical simulation of the two-dimensional flow in high pressure catalytic combustor for gas turbine  

Science Journals Connector (OSTI)

The objective of this paper is modeling the mechanism of high pressure and high temperature catalytic oxidation of natural gas, or methane. The model is two-dimensional steady-state, and includes axial and radial convection and diffusion of mass, momentum and energy, as well as homogeneous (gas phase) and heterogeneous (gas surface) single step irreversible chemical reactions within a catalyst channel. Experimental investigations were also made of natural gas, or methane combustion in the presence of Mn-substituted hexaaluminate catalysts. Axial profiles of catalyst wall temperature, and gas temperature and gas composition for a range of gas turbine combustor operating conditions have been obtained for comparison with and development of a computer model of catalytic combustion. Numerical calculation results for atmospheric pressure agree well with experimental data. The calculations have been extended for high pressure (10 atm) operating conditions of gas turbine.

Y. Tsujikawa; S. Fujii; H. Sadamori; S. Ito; S. Katsura

1995-01-01T23:59:59.000Z

297

Two?dimensional simulation of the formation of the Princeton spheromak  

Science Journals Connector (OSTI)

Various schemes proposed for the creation of the spheromak in the Princeton S1 experiment are simulated by our two?dimensional time?dependent compressible resistive hydromagnetic code. In these schemes the toroidal fields and poloidal currents in the plasma are induced by a solenoidal discharge in a core while a toroidal coil inside the core produces the major part of the initial poloidal fields as well as the main plasma toroidal current. Poloidal fields are reversed by programming current reversal in the toroidal coil. Poloidal field reconnection toroidal field compression and plasma accumulation into a spheromak geometry are achieved in the various schemes with or without the aid of pinching coils. For several schemes using proper programming of currents realistic parameter values give effective spheromak formation.

H. C. Lui; C. K. Chu; A. Aydemir

1981-01-01T23:59:59.000Z

298

Two-dimensional charge fluctuation in ?-Na0.33V2O5  

Science Journals Connector (OSTI)

We have investigated the critical phenomena of the metal-to-insulator (MI) transition of ?-Na0.33V2O5. The critical exponent ? of 0.226(3) and anisotropic diffuse scattering suggest that the MI transition of ?-Na0.33V2O5 is two dimensional in nature and that the dimension of the order parameter is not Ising. The non-Ising-like order parameter indicates that the MI transition is not a simple order-disorder type such as that of ??-NaV2O5 but charge-density-wave like, where the valence at each V site is continuous and the arrangement is modulated. This closely corresponds to the situation predicted by neutron diffraction measurements [Nagai et al., J. Phys. Soc. Jpn. 74, 1297 (2005)] and NMR measurements [Itoh et al., Phys. Rev. B 74, 054434 (2006)].

Kenji Ohwada, Touru Yamauchi, Yasuhiko Fujii, and Yutaka Ueda

2012-04-06T23:59:59.000Z

299

Measurement of two-dimensional small angle deviation with a prism interferometer  

SciTech Connect

A new technique for the measurement of two-dimensional small angular deviation is presented. A compound prism, which effectively produces a combination of two right-angled prisms in orthogonal directions, and plane reference surfaces have been utilized for the measurement of the orthogonal components of the angular tilt of an incident plane wavefront. Each orthogonal component of the angular tilt is separately measured from the angular rotation of the resultant wedge fringes between two plane wavefronts generated due to splitting of the incident plane wavefront by the corresponding set of right-angled prism and plane reference surface. The technique is shown to have high sensitivity for the measurement of small angle deviation. A monolithic prism interferometer, which is practically insensitive to vibration, is also proposed. Results obtained for the measurement of a known tilt angle are presented.

Chatterjee, Sanjib; Kumar, Y. Pavan

2008-09-20T23:59:59.000Z

300

Two-dimensional computational modeling of sodium boiling in simulated LMFBR fuel-pin bundles  

SciTech Connect

Extensive sodium boiling tests have been carried out in two simulated LMFBR fuel pin bundles in the Thermal-Hydraulic Out-of-Reactor Safety (THORS) Facility at Oak Ridge National Laboratory. Experimental results from a 19-pin bundle (THORS Bundle 6A) have been previously reported, and experimental results from a 61-pin bundle (THORS Bundle 9) will be reported soon. The results discussed here are from the 19-pin bundle. Preliminary analysis has shown that the computational methods used and conclusions reached are equally valid for the 61-pin bundle, as well as the 19-pin in-reactor Sodium Loop Safety Facility (SLSF) W-1 experiment. The main result of THORS sodium boiling experimentation is that boiling behavior is determined by two-dimensional effects, i.e., the rates of mass, momentum and energy transfer in the direction perpendicular to the axes of the fuel pins.

Dearing, J.F.

1981-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

One-dimensional half-metallic interfaces of two-dimensional honeycomb insulators  

Science Journals Connector (OSTI)

We study zigzag interfaces between insulating compounds that are isostructural to graphene, specifically II-VI, III-V, and IV-IV two-dimensional honeycomb insulators. We show that these one-dimensional interfaces are polar, with a net density of excess charge that can be simply determined by using the ideal (integer) formal valence charges, regardless of the predominant covalent character of the bonding in these materials. We justify this finding on fundamental physical grounds by analyzing the topology of the formal polarization lattice in the parent bulk materials. First-principles calculations elucidate an electronic compensation mechanism not dissimilar to oxide interfaces, which is triggered by a Zener-like charge transfer between interfaces of opposite polarity. In particular, we predict the emergence of one-dimensional electron and hole gases, which in some cases are ferromagnetic half metallic.

N. C. Bristowe; Massimiliano Stengel; P. B. Littlewood; Emilio Artacho; J. M. Pruneda

2013-10-30T23:59:59.000Z

302

Two-dimensional space-resolved emission spectroscopy of laser ablation plasma in water  

SciTech Connect

We developed a method for two-dimensional space-resolved emission spectroscopy of laser-induced plasma in water to investigate the spatial distribution of atomic species involved in the plasma. Using this method, the laser ablation plasma produced on a Cu target in 5 mM NaCl aqueous solution was examined. The emission spectrum varied considerably depending on the detecting position. The temperature and the atomic density ratio N{sub Na}/N{sub Cu} at various detecting positions were evaluated by fitting emission spectra to a theoretical model based on the Boltzmann distribution. We are successful in observing even a small difference between the distributions of the plasma parameters along the directions vertical and horizontal to the surface. The present approach gives direct information for sound understanding of the behavior of laser ablation plasma produced on a solid surface in water.

Matsumoto, Ayumu; Tamura, Ayaka; Fukami, Kazuhiro; Ogata, Yukio H. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Sakka, Tetsuo [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan)

2013-02-07T23:59:59.000Z

303

Classical and Quantum Implications of the Causality Structure of Two-Dimensional Spacetimes with Degenerate Metrics  

E-Print Network (OSTI)

The causality structure of two-dimensional manifolds with degenerate metrics is analysed in terms of global solutions of the massless wave equation. Certain novel features emerge. Despite the absence of a traditional Lorentzian Cauchy surface on manifolds with a Euclidean domain it is possible to uniquely determine a global solution (if it exists), satisfying well defined matching conditions at the degeneracy curve, from Cauchy data on certain spacelike curves in the Lorentzian region. In general, however, no global solution satisfying such matching conditions will be consistent with this data. Attention is drawn to a number of obstructions that arise prohibiting the construction of a bounded operator connecting asymptotic single particle states. The implications of these results for the existence of a unitary quantum field theory are discussed.

Jonathan Gratus; Robin W Tucker

1996-06-21T23:59:59.000Z

304

Linear stability of two-dimensional combined buoyant-thermocapillary flow in cylindrical liquid bridges  

Science Journals Connector (OSTI)

The combined buoyant-thermocapillary flow in cylindrical liquid bridges of unit aspect ratio is calculated by a mixed finite-difference–Chebyshev-collocation method. Gravity is assumed to be parallel or antiparallel to the cylinder's axis. For dominating thermocapillarity the two-dimensional basic flow is unique at the onset of instability. It is shown that additional buoyant body forces act stabilizing on the axisymmetric flow in high Prandtl number fluids for both heating and cooling from below. For heating from below, the onset of time-dependent convection is delayed to higher Marangoni numbers than for cooling from below, in agreement with previously unexplained experimental findings. In the absence of thermocapillary effects two axisymmetric convective solutions bifurcate from the conducting basic state. This perfect pitchfork bifurcation is perturbed by weak thermocapillary forces. The linear stability of all three axisymmetric base states is investigated numerically for Pr=4, a Prandtl number typical for model experiments.

M. Wanschura, H. C. Kuhlmann, and H. J. Rath

1997-06-01T23:59:59.000Z

305

Two-dimensional thermo-mechanical finite element model for laser cladding  

SciTech Connect

Temperature and stress fields during Laser Cladding determine, respectively, the microstructure and residual stress induced deformation and crack formation. As laser cladding processes find application in manufacturing, understanding of the temperature and stress fields becomes crucial for development of the relationship between process parameters and service behavior. A two-dimensional model of laser cladding is developed, using the finite element software package ABAQUS. It enables an investigation of the temperature field that develops at the center plane of the material. This temperature field provides the input for a thermal stress analysis, for which generalized plane strain was assumed. The goal of the present paper is to perform a quantitative evaluation of the residual stresses that develop at the two-layered material, as a function of process parameters such as scanning speed, laser power and powder feed rate. Results of the model are presented, as applied to cladding of C95600 on AA333.

Deus, A.M. de; Mazumder, J. [Univ. of Illinois, Urbana-Champaign, IL (United States)

1996-12-31T23:59:59.000Z

306

The friction factor of two-dimensional rough-boundary turbulent soap film flows  

E-Print Network (OSTI)

We use momentum transfer arguments to predict the friction factor $f$ in two-dimensional turbulent soap-film flows with rough boundaries (an analogue of three-dimensional pipe flow) as a function of Reynolds number Re and roughness $r$, considering separately the inverse energy cascade and the forward enstrophy cascade. At intermediate Re, we predict a Blasius-like friction factor scaling of $f\\propto\\textrm{Re}^{-1/2}$ in flows dominated by the enstrophy cascade, distinct from the energy cascade scaling of $\\textrm{Re}^{-1/4}$. For large Re, $f \\sim r$ in the enstrophy-dominated case. We use conformal map techniques to perform direct numerical simulations that are in satisfactory agreement with theory, and exhibit data collapse scaling of roughness-induced criticality, previously shown to arise in the 3D pipe data of Nikuradse.

Nicholas Guttenberg; Nigel Goldenfeld

2008-08-11T23:59:59.000Z

307

Two-dimensional nanostructured Y{sub 2}O{sub 3} particles for viscosity modification  

SciTech Connect

Nanoparticle additives have been shown to improve the mechanical and transport phenomena of various liquids; however, little has been done to try and explain the rheological modifications provided from such modifications from a theoretical standpoint. Here, we report a non-Einstein-like reduction of viscosity of mineral oil with the utilization of yttrium oxide nanosheet additives. Experimental results, coupled with generalized smoothed-particle hydrodynamics simulations, provide insight into the mechanism behind this reduction of fluid shear stress. The ordered inclination of these two-dimensional nanoparticle additives markedly improves the lubricating properties of the mineral oil, ultimately reducing the friction, and providing a way in designing and understanding next generation of lubricants.

He, Xingliang; Xiao, Huaping; Liang, Hong, E-mail: hliang@tamu.edu [Department of Mechanical Engineering, Texas A and M University, College Station, Texas 77843-3123 (United States); Kyle, Jonathan P.; Terrell, Elon J. [Department of Mechanical Engineering, Columbia University, New York, New York 10027 (United States)

2014-04-21T23:59:59.000Z

308

Photonic-band-gap effects in two-dimensional polycrystalline and amorphous structures  

SciTech Connect

We study numerically the density of optical states (DOS) in two-dimensional photonic structures with short-range positional order and observe a transition from polycrystalline to amorphous photonic systems. In polycrystals, photonic band gaps (PBGs) are formed within individual domains, which leads to a depletion of the DOS similar to that in periodic structures. In amorphous photonic media, the domain sizes are too small to form PBGs, thus the depletion of the DOS is weakened significantly. The critical domain size that separates the polycrystalline and amorphous regimes is determined by the attenuation length of Bragg scattering, which depends not only on the degree of positional order but also the refractive-index contrast of the photonic material. Even with relatively low-refractive-index contrast, we find that modest short-range positional order in photonic structures enhances light confinement via collective scattering and interference.

Yang, Jin-Kyu; Noh, Heeso; Liew, Seng-Fatt [Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8482 (United States); Schreck, Carl [Department of Physics, Yale University, New Haven, Connecticut 06520-8120 (United States); Guy, Mikhael I. [Science and Research Software Core, Yale University, New Haven, Connecticut 06520-8286 (United States); O'Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520-8286 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520-8120 (United States); Cao, Hui [Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8482 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520-8120 (United States)

2010-11-15T23:59:59.000Z

309

Electronic structure of two-dimensional hexagonal diselenides: Charge density waves and pseudogap behavior  

SciTech Connect

We theoretically study the electronic structure (spectral functions and Fermi surfaces) of incommensurate pseudogap and charge density wave (CDW) and commensurate CDW phases of quasi-two-dimensional diselenides 2H-TaSe{sub 2} and 2H-NbSe{sub 2}. The incommensurate pseudogap regime is described within the scenario based on short-range-order CDW fluctuations, considered within the static Gaussian random field model. In contrast, e.g., to high-T{sub c} cuprates, layered dichalcogenides have several different CDW scattering vectors and an electronic spectrum with two bands at the Fermi level. For this, we present a theoretical background for the description of multiple scattering processes within a multiple-band electronic spectrum. Theoretical spectral functions and Fermi surfaces thus obtained are compared with recent ARPES experimental data, demonstrating rather good qualitative agreement.

Kuchinskii, E. Z., E-mail: kuchinsk@iep.uran.ru; Nekrasov, I. A., E-mail: nekrasov@iep.uran.ru; Sadovskii, M. V. [Russian Academy of Sciences, Institute for Electrophysics, Ural Branch (Russian Federation)

2012-04-15T23:59:59.000Z

310

Magnetic field control of the intraband optical absorption in two-dimensional quantum rings  

SciTech Connect

Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field B are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity B changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency is calculated as a function of the magnetic field and levels' broadening.

Olendski, O., E-mail: oolendski@ksu.edu.sa [King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2454, Riyadh 11451 (Saudi Arabia); Barakat, T., E-mail: tbarakat@ksu.edu.sa [Department of Physics, King Saud University, P.O. Box 2454, Riyadh 11451 (Saudi Arabia)

2014-02-28T23:59:59.000Z

311

Potential Energy Landscape of the Two-Dimensional XY Model: Higher-Index Stationary Points  

E-Print Network (OSTI)

The application of numerical techniques to the study of energy landscapes of large systems relies on sufficient sampling of the stationary points. Since the number of stationary points is believed to grow exponentially with system size, we can only sample a small fraction. We investigate the interplay between this restricted sample size and the physical features of the potential energy landscape for the two-dimensional $XY$ model in the absence of disorder with up to $N=100$ spins. Using an eigenvector-following technique, we numerically compute stationary points with a given Hessian index $I$ for all possible values of $I$. We investigate the number of stationary points, their energy and index distributions, and other related quantities, with particular focus on the scaling with $N$. The results are used to test a number of conjectures and approximate analytic results for the general properties of energy landscapes.

Dhagash Mehta; Ciaran Hughes; Michael Kastner; David J Wales

2014-12-10T23:59:59.000Z

312

Differential Resistance of Two Dimensional Electron Systems Subject to Microwave Radiation  

SciTech Connect

We present the expression for differential resistance of a disordered two-dimensional electron gas placed in a perpendicular magnetic field and subject to microwave irradiation. We demonstrate that in strong dc electric fields the current oscillates as a function of the strength of the applied constant electric field. We demonstrate that the amplitude of oscillations of the differential resistivity is characterized by the back-scattering rate off disorder. We argue that the dominant contribution to the non-linearity in strong electric fields originates from the modification of electron scattering off disorder by electric fields, or so-called 'displacement' mechanism. The non-equilibrium mechanism, which is related to modification of electron distribution function by electric fields turns out to be inefficient in strong electric fields, although it describes current in weak electric fields. We further analyze the positions of maxima and minima of the differential resistance as a function of the applied electric field and frequency of microwave radiation.

Khodas, M.; Vavilov, M.G.

2008-11-03T23:59:59.000Z

313

Negative differential resistance in electron tunneling in ultrathin films near the two-dimensional limit  

SciTech Connect

We report on our observation of negative differential resistance (NDR) in electron tunneling conductance in atomic-scale ultrathin Ag films on Si(111) substrates. NDR was observed by scanning tunneling spectroscopy measurements. The tunneling conductance depends on the electronic local density of states (LDOS) of the sample. We show that the sample bias voltage, at which negative differential resistance and peak negative conductance occur, depends on the film thickness. This can be understood from the variation in the LDOS of the Ag films as a function of film thickness down to the two-dimensional limit of one atomic layer. First principles density functional theory calculations have been used to explain the results.

Batabyal, R.; Abdul Wasey, A. H. M.; Mahato, J. C.; Das, Debolina; Roy, A.; Das, G. P.; Dev, B. N. [Department of Materials Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032 (India)

2013-01-21T23:59:59.000Z

314

Two-dimensional electronic spectroscopy and photosynthesis: Fundamentals and applications to photosynthetic light-harvesting  

Science Journals Connector (OSTI)

In natural light harvesting systems, pigment-protein complexes are able to harvest sunlight with near unity quantum efficiency. These complexes exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this perspective, we focus on how two-dimensional electronic spectroscopy (2DES) can provide an incisive tool to probe the electronic, energetic, and spatial landscapes that must be understood to describe photosynthetic light-harvesting. We review the theoretical and experimental principles of 2DES, and demonstrate its application to the study of the Photosystem II supercomplex of green plants. We illustrate several capabilities of 2DES, including monitoring energy transfer pathways, observing excitonic coherence, determining excitonic geometry, and informing on the atomic structure.

Gabriela S. Schlau-Cohen; Akihito Ishizaki; Graham R. Fleming

2011-01-01T23:59:59.000Z

315

Coherence and population dynamics of chlorophyll excitations in FCP complex: Two-dimensional spectroscopy study  

E-Print Network (OSTI)

The energy transfer processes and coherent phenomena in the fucoxanthin-chlorophyll protein complex, which is responsible for the light harvesting function in marine algae diatoms, were investigated at 77 K by using two-dimensional electronic spectroscopy. Experiments performed on the femtosecond and picosecond timescales led to separation of spectral dynamics, witnessing evolutions of coherence and population states of the system in the spectral region of ${\\rm Q}_{y}$ transitions of chlorophylls $a$ and $c$. Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) $a$ and fucoxanthin intramolecular vibrations dominating over the first few picoseconds. Closer inspection of the spectral region of the ${\\rm Q}_{y}$ transition of Chl $c$ revealed previously not identified mutually non-interacting chlorophyll $c$ states participating in femtosecond or picosecond energy transfer to the Chl $a$ molecules. Consideration of separated coherent and incoherent dynamics allowed us to hypothesize the v...

Butkus, Vytautas; Augulis, Ram?nas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius

2015-01-01T23:59:59.000Z

316

Fabrication of two-dimensional photonic crystals in a chalcogenide glass  

Science Journals Connector (OSTI)

Two-dimensional photonic band gap structures consisting of air holes arranged to form a hexagonal lattice were patterned into chalcogenide glass thin films by Focused Ion Beam (FIB) milling. The dimensional parameters for these structures, namely type of lattice, lattice parameter and radius of the holes, were chosen so as to show a photonic band gap relevant to the infrared range, aiming at their subsequent use in the field of chemical sensing and biosensing. The optical behaviour of these structures was determined by calculating the band structure for the TM (magnetic field in-plane) and TE (electric field in-plane) modes. Furthermore, FIB milling was used to fabricate input and output waveguides coupled to the photonic crystals. The transmission spectra of the resulting structures for the TE and TM modes with two different orientations were also calculated.

Raul J. Martin-Palma; Trevor E. Clark; Carlo G. Pantano

2009-01-01T23:59:59.000Z

317

Conductivity and Hall effect in the two-dimensional Hubbard model  

Science Journals Connector (OSTI)

A path-integral field-theoretic derivation of electromagnetic linear response for the two-dimensional Hubbard model is given. We find, remarkably, that changes in the Fermi-surface topology associated with incommensurate planar spin-density-wave saddle points induce a change in sign of the Hall coefficient at dopings ?H=0.02–0.5 for U/t=2–10. The change in sign is not affected by short-range magnetic domains. We delinate from first principles an anomalous temperature dependence of the Hall carrier density at dopings close to ?H. An additional anisotropic component to the usual dc conductivity is nonvanishing for certain types of spirals. The paper extends the Bloch-Boltzmann theory to the case of untraditional Fermi liquids where the damping of the quasiparticles is ?(?)?max(kBT,?).

Puru Voruganti; Andrey Golubentsev; Sajeev John

1992-06-15T23:59:59.000Z

318

Collision-dependent power law scalings in two dimensional gyrokinetic turbulence  

SciTech Connect

Nonlinear gyrokinetics provides a suitable framework to describe short-wavelength turbulence in magnetized laboratory and astrophysical plasmas. In the electrostatic limit, this system is known to exhibit a free energy cascade towards small scales in (perpendicular) real and/or velocity space. The dissipation of free energy is always due to collisions (no matter how weak the collisionality), but may be spread out across a wide range of scales. Here, we focus on freely decaying two dimensional electrostatic turbulence on sub-ion-gyroradius scales. An existing scaling theory for the turbulent cascade in the weakly collisional limit is generalized to the moderately collisional regime. In this context, non-universal power law scalings due to multiscale dissipation are predicted, and this prediction is confirmed by means of direct numerical simulations.

Cerri, S. S., E-mail: silvio.sergio.cerri@ipp.mpg.de; Bańón Navarro, A.; Told, D. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Jenko, F. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Max-Planck/Princeton Center for Plasma Physics (Germany)

2014-08-15T23:59:59.000Z

319

Microbunching Instability in a Chicane: Two-Dimensional Mean Field Treatment  

SciTech Connect

We study the microbunching instability in a bunch compressor by a parallel code with some improved numerical algorithms. The two-dimensional charge/current distribution is represented by a Fourier series, with coefficients determined through Monte Carlo sampling over an ensemble of tracked points. This gives a globally smooth distribution with low noise. The field equations are solved accurately in the lab frame using retarded potentials and a novel choice of integration variables that eliminates singularities. We apply the scheme with parameters for the first bunch compressor system of FERMI{at}Elettra, with emphasis on the amplification of a perturbation at a particular wavelength. Gain curves agree with those of the linearized Vlasov model at long wavelengths, but show some deviation at the smallest wavelengths treated.

Bassi, G.; Ellison, James A.; Heinemann, Klaus; Warnock, Robert; /Liverpool U. /Cockroft Inst. /New Mexico U. /SLAC /LBL, Berkeley

2009-01-27T23:59:59.000Z

320

A two-dimensional deformable phantom for quantitatively verifying deformation algorithms  

SciTech Connect

Purpose: The incorporation of deformable image registration into the treatment planning process is rapidly advancing. For this reason, the methods used to verify the underlying deformation algorithms must evolve equally fast. This manuscript proposes a two-dimensional deformable phantom, which can objectively verify the accuracy of deformation algorithms, as the next step for improving these techniques. Methods: The phantom represents a single plane of the anatomy for a head and neck patient. Inflation of a balloon catheter inside the phantom simulates tumor growth. CT and camera images of the phantom are acquired before and after its deformation. Nonradiopaque markers reside on the surface of the deformable anatomy and are visible through an acrylic plate, which enables an optical camera to measure their positions; thus, establishing the ground-truth deformation. This measured deformation is directly compared to the predictions of deformation algorithms, using several similarity metrics. The ratio of the number of points with more than a 3 mm deformation error over the number that are deformed by more than 3 mm is used for an error metric to evaluate algorithm accuracy. Results: An optical method of characterizing deformation has been successfully demonstrated. For the tests of this method, the balloon catheter deforms 32 out of the 54 surface markers by more than 3 mm. Different deformation errors result from the different similarity metrics. The most accurate deformation predictions had an error of 75%. Conclusions: The results presented here demonstrate the utility of the phantom for objectively verifying deformation algorithms and determining which is the most accurate. They also indicate that the phantom would benefit from more electron density heterogeneity. The reduction of the deformable anatomy to a two-dimensional system allows for the use of nonradiopaque markers, which do not influence deformation algorithms. This is the fundamental advantage of this verification technique.

Kirby, Neil; Chuang, Cynthia; Pouliot, Jean [Department of Radiation Oncology, University of California San Francisco, San Francisco, California 94143-1708 (United States)

2011-08-15T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
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321

Two-dimensional plasmon in a metallic monolayer on a semiconductor surface: Exchange-correlation effects  

E-Print Network (OSTI)

Department of Materials Science and Technology, Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Appelstrasse 2, D-30167, Hannover, Germany Received 9 July 2002; published 30 December 2002 Taking account on the clean Si(111)-(7 7) surface, though the reconstruction from an ideally truncated surface into a (7 7

Hasegawa, Shuji

322

High-resolution models of solar granulation: the two-dimensional case  

Science Journals Connector (OSTI)

......at observing the solar atmosphere in high...in the Sunrise project (see Schussler...simulations of solar granulation and...for momentum and energy balance in 2D...the amount of energy flux appropriate for the solar case enters the......

H. J. Muthsam; B. Löw-Baselli; Chr. Obertscheider; M. Langer; P. Lenz; F. Kupka

2007-10-01T23:59:59.000Z

323

Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe  

E-Print Network (OSTI)

, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors. T wo-generation electronic and optoelectronic devices. Although most research has focused on 2D transition metal

Geohegan, David B.

324

Instabilities in two-dimensional flower and chain clusters of bubbles M. A. Fortes1  

E-Print Network (OSTI)

, clusters, Surface Evolver, bubbles, foams 1 #12;1.Introduction Considerable attention has been given multiplied by the film energy per unit length or film tension . We therefore identify cells with bubbles the stability of the equilibria of two types of 2D finite clusters of bubbles: 1) flower clusters with N shells

Cox, Simon

325

Retrieval of Aerosol Optical Depth in Vicinity of Broken Clouds from Reflectance Ratios: Sensitivity Study  

SciTech Connect

We conducted a sensitivity study to better understand the potential of a new method for retrieving aerosol optical depth (AOD) under partly cloudy conditions. This method exploits reflectance ratios in the visible spectral range and provides an effective way to avoid three-dimensional (3D) cloud effects. The sensitivity study is performed for different observational conditions and random errors in input data. The results of the sensitivity study suggest that this ratio method has the ability to detect clear pixels even in close proximity to clouds. Such detection does not require a statistical analysis of the two-dimensional (2D) horizontal distribution of reflected solar radiation, and thus it could be customized for operational retrievals. In comparison with previously suggested approaches, the ratio method has the capability to increase the "harvest" of clear pixels. Similar to the traditional Independent Pixel Approximation (IPA), the ratio method has a low computational cost for retrieving AOD. In contrast to the IPA method, the ratio method provides much more accurate estimations of the AOD values under broken cloud conditions: pixel-based and domain-averaged estimations of errors in AOD are about 25% and 10%, respectively. Finally, both the ratio-based cloud screening and the accuracy of domain-averaged ratio-based AOD values do not suffer greatly when 5% random errors are introduced in the reflectances.

Kassianov, Evgueni I.; Ovtchinnikov, Mikhail; Berg, Larry K.; McFarlane, Sally A.; Flynn, Connor J.

2009-09-01T23:59:59.000Z

326

Form 2D | Open Energy Information  

Open Energy Info (EERE)

Form 2DLegal Abstract Form 2D: Application for Permit to Discharge Process Wastewater - New Industrial Facilities, current through August 14, 2014. Published NA Year...

327

Orientational Ordering of a Bent-Core Mesogen by Two-Dimensional 13C NMR Spectroscopy  

Science Journals Connector (OSTI)

The C?H dipolar couplings obtained from the separated local field (SLF) experiment for the aromatic rings are used to find the local order parameter tensors. ... 2D separated local field (SLF) NMR spectroscopy has been used to measure and assign C?H dipolar couplings. ... 30-32 In the SLF method, a 13C spin evolves under the influence of dipolar local fields produced by the surrounding protons. ...

J. Xu; K. Fodor-Csorba; Ronald Y. Dong

2005-02-12T23:59:59.000Z

328

Staring 2-D hadamard transform spectral imager  

DOE Patents (OSTI)

A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.

Gentry, Stephen M. (Albuquerque, NM); Wehlburg, Christine M. (Albuquerque, NM); Wehlburg, Joseph C. (Albuquerque, NM); Smith, Mark W. (Albuquerque, NM); Smith, Jody L. (Albuquerque, NM)

2006-02-07T23:59:59.000Z

329

Bifurcations from periodic solution in a simplified model of two-dimensional magnetoconvection  

SciTech Connect

A two-dimensional Boussinesq fluid with nonlinear interaction between Rayleigh--Benard convection and an external magnetic field is investigated numerically and analytically. A simplified model consisting of a fifth-order system of nonlinear ordinary differential equations with five parameters is introduced and integrated numerically in certain parameter regions. Various types of bifurcations from periodic solutions are found numerically: period-doubling bifurcation, heteroclinic bifurcation, intermittency, and saddle-node bifurcation. A normal form equation is also derived from the fifth-order system, and center manifold theory is applied to it. An expression for the renormalized Holmes--Melnikov boundary for the evaluation of the numerical results is given. It is shown from the normal form equation that each property of the two phase portraits described by the Duffing equation and the van der Pol equation emanates from one common attractor in the five-dimensional space of the fifth-order system. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Bekki, N.; Karakisawa, T. [College of Engineering, Nihon University, Koriyama, Fukushima 963 (Japan)] [College of Engineering, Nihon University, Koriyama, Fukushima 963 (Japan)

1995-08-01T23:59:59.000Z

330

Non–Oberbeck-Boussinesq effects in two-dimensional Rayleigh-Bénard convection in glycerol  

Science Journals Connector (OSTI)

We numerically analyze Non–Oberbeck-Boussinesq (NOB) effects in two-dimensional Rayleigh-Bénard flow in glycerol, which shows a dramatic change in the viscosity with temperature. The results are presented both as functions of the Rayleigh number Ra up to 108 (for fixed temperature difference ? between the top and bottom plates) and as functions of ? ("non-Oberbeck-Boussinesqness" or "NOBness") up to 50?K (for fixed Ra). For this large NOBness the center temperature Tc is more than 5?K larger than the arithmetic mean temperature Tm between top and bottom plate and only weakly depends on Ra. To physically account for the NOB deviations of the Nusselt numbers from its Oberbeck-Boussinesq values, we apply the decomposition of NuNOB/NuOB into the product of two effects, namely first the change in the sum of the top and bottom thermal BL thicknesses, and second the shift of the center temperature Tc as compared to Tm. While for water the origin of the Nu deviation is totally dominated by the second effect (cf. Ahlers G. et al., J. Fluid Mech., 569 (2006) 409) for glycerol the first effect is dominating, in spite of the large increase of Tc as compared to Tm.

K. Sugiyama; E. Calzavarini; S. Grossmann; D. Lohse

2007-01-01T23:59:59.000Z

331

Nonlinear transverse cascade and two-dimensional magnetohydrodynamic subcritical turbulence in plane shear flows  

E-Print Network (OSTI)

We find and investigate via numerical simulations self-sustained two-dimensional turbulence in a magnetohydrodynamic flow with a maximally simple configuration: plane, noninflectional (with a constant shear of velocity) and threaded by a parallel uniform background magnetic field. This flow is spectrally stable, so the turbulence is subcritical by nature and hence it can be energetically supported just by transient growth mechanism due to shear flow nonnormality. This mechanism appears to be essentially anisotropic in spectral (wavenumber) plane and operates mainly for spatial Fourier harmonics with streamwise wavenumbers less than a ratio of flow shear to the Alfv\\'{e}n speed, $k_y < S/u_A$ (i.e., the Alfv\\'{e}n frequency is lower than the shear rate). We focused on the analysis of the character of nonlinear processes and underlying self-sustaining scheme of the turbulence, i.e., on the interplay between linear transient growth and nonlinear processes, in spectral plane. Our study, being concerned with a ...

Mamatsashvili, G R; Chagelishvili, G D; Horton, W

2014-01-01T23:59:59.000Z

332

Observation of Spin Coulomb Drag in a Two-Dimensional Electron Gas  

SciTech Connect

An electron propagating through a solid carries spin angular momentum in addition to its mass and charge. Of late there has been considerable interest in developing electronic devices based on the transport of spin, which offer potential advantages in dissipation, size, and speed over charge-based devices. However, these advantages bring with them additional complexity. Because each electron carries a single, fixed value (-e) of charge, the electrical current carried by a gas of electrons is simply proportional to its total momentum. A fundamental consequence is that the charge current is not affected by interactions that conserve total momentum, notably collisions among the electrons themselves. In contrast, the electron's spin along a given spatial direction can take on two values, {+-} {h_bar}/2 (conventionally {up_arrow}, {down_arrow}), so that the spin current and momentum need not be proportional. Although the transport of spin polarization is not protected by momentum conservation, it has been widely assumed that, like the charge current, spin current is unaffected by electron-electron (e-e) interactions. Here we demonstrate experimentally not only that this assumption is invalid, but that over a broad range of temperature and electron density, the flow of spin polarization in a two-dimensional gas of electrons is controlled by the rate of e-e collisions.

Weber, C.P.

2011-08-19T23:59:59.000Z

333

Method for laser-based two-dimensional navigation system in a structured environment  

DOE Patents (OSTI)

A low power, narrow laser beam, generated by a laser carried by a mobile vehicle, is rotated about a vertical reference axis as the vehicle navigates within a structured environment. At least three stationary retroreflector elements are located at known positions, preferably at the periphery of the structured environment, with one of the elements having a distinctive retroreflection. The projected rotating beam traverses each retroreflector in succession, and the corresponding retroreflections are received at the vehicle and focussed on a photoelectric cell to generate corresponding electrical signals. The signal caused by the distinctive retroreflection serves as an angle-measurement datum. An angle encoder coupled to the apparatus rotating the projected laser beam provides the angular separation from this datum of the lines connecting the mobile reference axis to successive retroreflectors. This real-time angular data is utilized with the known locations of the retroreflectors to trigonometrically compute using three point resection, the exact real-time location of the mobile reference axis (hence the navigating vehicle) vis-a-vis the structured environment, e.g., in terms of two-dimensional Cartesian coordinates associated with the environment.

Boultinghouse, Karlan D. (Sandia Park, NM); Schoeneman, J. Lee (Albuquerque, NM); Tise, Bertice L. (Albuquerque, NM)

1989-01-01T23:59:59.000Z

334

Molecular-dynamics simulation of compressible fluid flow in two-dimensional channels  

Science Journals Connector (OSTI)

We study compressible fluid flow in narrow two-dimensional channels using a molecular-dynamics simulation method. In the simulation area, an upstream source is maintained at constant density and temperature while a downstream reservoir is kept at vacuum. The channel is sufficiently long in the direction of the flow that the finite length has little effect on the properties of the fluid in the central region. The simulated system is represented by an efficient data structure, whose internal elements are created and manipulated dynamically in a layered fashion. Consequently the computer code is highly efficient and manifests completely linear performance in simulations of large systems. We obtain the steady-state velocity, temperature, and density distributions in the system. The velocity distribution across the channel is very nearly a quadratic function of the distance from the center of the channel and reveals velocity slip at the boundaries; the temperature distribution is only approximately a quartic function of this distance from the center to the channel. The density distribution across the channel is nonuniform. We attribute this nonuniformity to the relatively high Mach number, approximately 0.5, in the fluid flow. An equation for the density distribution based on simple compressibility arguments is proposed; its predictions agree well with the simulation results. The validity of the concept of local dynamic temperature and the variation of the temperature along the channel are discussed.

M. Sun and C. Ebner

1992-10-15T23:59:59.000Z

335

Deformation-Driven Diffusion and Plastic Flow in Two-Dimensional Amorphous Granular Pillars  

E-Print Network (OSTI)

We report a combined experimental and simulation study of deformation-induced diffusion in compacted two-dimensional amorphous granular pillars, in which thermal fluctuations play negligible role. The pillars, consisting of bidisperse cylindrical acetal plastic particles standing upright on a substrate, are deformed uniaxially and quasistatically by a rigid bar moving at a constant speed. The plastic flow and particle rearrangements in the pillars are characterized by computing the best-fit affine transformation strain and non-affine displacement associated with each particle between two stages of deformation. The non-affine displacement exhibits exponential crossover from ballistic to diffusive behavior with respect to the cumulative deviatoric strain, indicating that in athermal granular packings, the cumulative deviatoric strain plays the role of time in thermal systems and drives effective particle diffusion. We further study the size-dependent deformation of the granular pillars by simulation, and find that different-sized pillars follow self-similar shape evolution during deformation. In addition, the yield stress of the pillars increases linearly with pillar size. Formation of transient shear lines in the pillars during deformation becomes more evident as pillar size increases. The width of these elementary shear bands is about twice the diameter of a particle, and does not vary with pillar size.

Wenbin Li; Jennifer M. Rieser; Andrea J. Liu; Douglas J. Durian; Ju Li

2015-02-04T23:59:59.000Z

336

Apparatus and method for reading two-dimensional electrophoretograms containing .beta.-ray-emitting labeled compounds  

DOE Patents (OSTI)

Apparatus and method for electronically reading planar two dimensional .beta.-ray emitter-labeled gel electrophoretograms. A single, flat rectangular multiwire proportional chamber is placed in close proximity to the gel and the assembly placed in an intense uniform magnetic field disposed in a perpendicular manner to the rectangular face of the proportional chamber. Beta rays emitted in the direction of the proportional chamber are caused to execute helical motions which substantially preserve knowledge of the coordinates of their origin in the gel. Perpendicularly oriented, parallel wire, parallel plane cathodes electronically sense the location of the .beta.-rays from ionization generated thereby in a detection gas coupled with an electron avalanche effect resulting from the action of a parallel wire anode located therebetween. A scintillator permits the present apparatus to be rendered insensitive when signals are generated from cosmic rays incident on the proportional chamber. Resolution for concentrations of radioactive compounds in the gel exceeds 700 .mu.m. The apparatus and method of the present invention represent a significant improvement over conventional autoradiographic techniques in dynamic range, linearity and sensitivity of data collection. A concentration and position map for gel electrophoretograms having significant concentrations of labeled compounds and/or highly radioactive labeling nuclides can generally be obtained in less than one hour.

Anderson, Herbert L. (Santa Fe, NM); Kinnison, W. Wayne (Los Alamos, NM); Lillberg, John W. (Los Alamos, NM)

1987-01-01T23:59:59.000Z

337

Dirac-Weyl fermions with arbitrary spin in two-dimensional optical superlattices  

SciTech Connect

Dirac-Weyl fermions are massless relativistic particles with a well-defined helicity which arise in the context of high-energy physics. Here we propose a quantum simulation of these paradigmatic fermions using multicomponent ultracold atoms in a two-dimensional square optical lattice. We find that laser-assisted spin-dependent hopping, specifically tuned to the (2s+1)-dimensional representations of the su(2) Lie algebra, directly leads to a regime where the emerging massless excitations correspond to Dirac-Weyl fermions with arbitrary pseudospin s. We show that this platform hosts two different phases: a semimetallic phase that occurs for half-integer s, and a metallic phase that contains a flat zero-energy band at integer s. These phases host a variety of interesting effects, such as a very rich anomalous quantum Hall effect and a remarkable multirefringent Klein tunneling. In addition, we show that these effects are directly related to the number of underlying Dirac-Weyl species and zero modes.

Lan, Z.; Lu, W.; Oehberg, P. [SUPA, Department of Physics, Heriot-Watt University, EH14 4AS, Edinburgh (United Kingdom); Goldman, N. [Center for Nonlinear Phenomena and Complex Systems - Universite Libre de Bruxelles, 231, Campus Plaine, B-1050 Brussels (Belgium); Bermudez, A. [Departamento de Fisica Teorica I, Universidad Complutense, E-28040 Madrid (Spain); Institut fuer Theoretische Physik, Albert-Einstein Allee 11, Universitaet Ulm, 89069 Ulm (Germany)

2011-10-15T23:59:59.000Z

338

Computational Model of the Mark-IV Electrorefiner: Two-Dimensional Potential and Current Distributions  

SciTech Connect

A computational model of the Mark-IV electrorefiner is currently being developed as a joint project between Idaho National Laboratory, Korea Atomic Energy Research Institute, Seoul National University, and the University of Idaho. As part of this model, the two-dimensional potential and current distributions within the molten salt electrolyte are calculated for U3+ , Zr4+ , and Pu3+ along with the total distributions, using the partial differential equation solver of the commercial Matlab software. The electrical conductivity of the electrolyte solution is shown to depend primarily on the composition of the electrolyte and to average 205 mho/m with a standard deviation of 2.5 × 10-5% throughout the electrorefining process. These distributions show that the highest potential gradients (thus, the highest current) exist directly between the two anodes and cathode. The total, uranium, and plutonium potential gradients are shown to increase throughout the process, with a slight decrease in that of zirconium. The distributions also show small potential gradients and very little current flow in the region far from the operating electrodes.

Supathorn Phongikaroon; Steven Herrmann; Michael F. Simpson

2011-02-01T23:59:59.000Z

339

Two-dimensional flow of foam around an obstacle: force measurements  

E-Print Network (OSTI)

A Stokes experiment for foams is proposed. It consists in a two-dimensional flow of a foam, confined between a water subphase and a top plate, around a fixed circular obstacle. We present systematic measurements of the drag exerted by the flowing foam on the obstacle, \\emph{versus} various separately controlled parameters: flow rate, bubble volume, bulk viscosity, obstacle size, shape and boundary conditions. We separate the drag into two contributions, an elastic one (yield drag) at vanishing flow rate, and a fluid one (viscous coefficient) increasing with flow rate. We quantify the influence of each control parameter on the drag. The results exhibit in particular a power-law dependence of the drag as a function of the bulk viscosity and the flow rate with two different exponents. Moreover, we show that the drag decreases with bubble size, and increases proportionally to the obstacle size. We quantify the effect of shape through a dimensioned drag coefficient, and we show that the effect of boundary conditions is small.

Benjamin Dollet; Florence Elias; Catherine Quilliet; Christophe Raufaste; Miguel Aubouy; Francois Graner

2004-10-13T23:59:59.000Z

340

Two-dimensional flows of foam: drag exerted on circular obstacles and dissipation  

E-Print Network (OSTI)

A Stokes experiment for foams is proposed. It consists in a two-dimensional flow of a foam, confined between a water subphase and a top plate, around a fixed circular obstacle. We present systematic measurements of the drag exerted by the flowing foam on the obstacle, \\emph{versus} various separately controlled parameters: flow rate, bubble volume, solution viscosity, obstacle size and boundary conditions. We separate the drag into two contributions, an elastic one (yield drag) at vanishing flow rate, and a fluid one (viscous coefficient) increasing with flow rate. We quantify the influence of each control parameter on the drag. The results exhibit in particular a power-law dependence of the drag as a function of the solution viscosity and the flow rate with two different exponents. Moreover, we show that the drag decreases with bubble size, increases with obstacle size, and that the effect of boundary conditions is small. Measurements of the streamwise pressure gradient, associated to the dissipation along the flow of foam, are also presented: they show no dependence on the presence of an obstacle, and pressure gradient depends on flow rate, bubble volume and solution viscosity with three independent power laws.

Benjamin Dollet; Florence Elias; Catherine Quilliet; Arnaud Huillier; Miguel Aubouy; Francois Graner

2004-11-22T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Apparatus for reading two-dimensional electrophoretograms containing. beta. -ray-emitting labeled compounds  

DOE Patents (OSTI)

An apparatus and method for electronically reading planar two-dimensional ..beta..-ray emitter-labeled gel electrophoretograms. A single, flat rectangular multiwire proportional chamber is placed in close proximity to the gel and the assembly placed in an intense uniform magnetic field disposed in a perpendicular manner to the rectangular face of the proportional chamber. Beta rays emitted in the direction of the proportional chamber are caused to execute helical motions which substantially preserve knowledge the coordinates of their origin in the gel. Perpendicularly oriented, parallel wire, parallel plane cathodes electronically sense the location of the ..beta..-rays from ionization generated thereby in a detection gas coupled with an electron avalanche effect resulting from the action of a parallel wire anode located therebetween. A scintillator permits the present apparatus to be rendered insensitive when signals are generated from cosmic rays incident on the proportional chamber. Resolution for concentrations of radioactive compounds in the gel exceeds 700-..mu..m. The apparatus and method of the present invention represent a significant improvement over conventional autoradiographic techniques in dynamic range, linearity and sensitivity of data collection. A concentration and position map for gel electrophoretograms having significant concentrations of labeled compounds and/or highly radioactive labeling nuclides can generally be obtained in less than one hour.

Anderson, H.L.; Kinnison, W.W.; Lillberg, J.W.

1985-04-30T23:59:59.000Z

342

Microscopic measurement of the linear compressibilities of two-dimensional fatty acid mesophases  

E-Print Network (OSTI)

The linear compressibility of two-dimensional fatty acid mesophases has determined by grazing incidence x-ray diffraction. Surface pressure vs molecular area isotherms were reconstructed from these measurements, and the linear compressibility (relative distortion along a given direction for isotropic applied stress) was determined both in the sample plane and in a plane normal to the aliphatic chain director (transverse plane). The linear compressibilities range over two orders of magnitude from 0.1 to 10 m/N and are distributed depending on their magnitude in 4 different sets which we are able to associate with different molecular mechanisms. The largest compressibilities (10m/N) are observed in the tilted phases. They are apparently independent of the chain length and could be related to the reorganization of the headgroup hydrogen-bounded network, whose role should be revalued. Intermediate compressibilities are observed in phases with quasi long-range order (directions normal to the molecular tilt in L_2 or L_2' phases, S phase), and could be related to the ordering of these phases. The lowest compressibilities are observed in the solid untilted CS phase and for 1 direction of the S and L_2'' phases. They are similar to the compressibility of crystalline polymers and correspond to the interactions between methyl groups in the crystal. Finally, negative compressibilities are observed in the transverse plane for L_2' and L_2'' phases and can be traced to subtle reorganizations upon untilting.

C. Fradin; J. Daillant; A. Braslau; D. Luzet; M. Alba; M. Goldmann

1997-08-22T23:59:59.000Z

343

Electrostatics on the sphere with applications to Monte Carlo simulations of two dimensional polar fluids  

E-Print Network (OSTI)

We present two methods for solving the electrostatics of point charges and multipoles on the surface of a sphere, \\textit{i.e.} in the space $\\mathcal{S}_{2}$, with applications to numerical simulations of two-dimensional polar fluids. In the first approach, point charges are associated with uniform neutralizing backgrounds to form neutral pseudo-charges, while, in the second, one instead considers bi-charges, \\textit{i.e.} dumbells of antipodal point charges of opposite signs. We establish the expressions of the electric potentials of pseudo- and bi-charges as isotropic solutions of the Laplace-Beltrami equation in $\\mathcal{S}_{2}$. A multipolar expansion of pseudo- and bi-charge potentials leads to the electric potentials of mono- and bi-multipoles respectively. These potentials constitute non-isotropic solutions of the Laplace-Beltrami equation the general solution of which in spherical coordinates is recast under a new appealing form. We then focus on the case of mono- and bi-dipoles and build the theory...

Caillol, Jean-Michel

2015-01-01T23:59:59.000Z

344

Detection of point sources on two-dimensional images based on peaks  

E-Print Network (OSTI)

This article considers the detection of point sources in two dimensional astronomical images. The detection scheme we propose is based on peak statistics. We discuss the example of the detection of far galaxies in Cosmic Microwave Background experiments throughout the paper, although the method we present is totally general and can be used in many other fields of data analysis. We assume sources with a Gaussian profile --that is a fair approximation of the profile of a point source convolved with the detector beam in microwave experiments-- on a background modeled by a homogeneous and isotropic Gaussian random field characterized by a scale-free power spectrum. Point sources are enhanced with respect to the background by means of linear filters. After filtering, we identify local maxima and apply our detection scheme, a Neyman-Pearson detector that defines our region of acceptance based on the a priori pdf of the sources and the ratio of number densities. We study the different performances of some linear fil...

Lopez-Caniego, M; Sanz, J L; Barreiro, R B

2005-01-01T23:59:59.000Z

345

Detection of point sources on two-dimensional images based on peaks  

E-Print Network (OSTI)

This article considers the detection of point sources in two dimensional astronomical images. The detection scheme we propose is based on peak statistics. We discuss the example of the detection of far galaxies in Cosmic Microwave Background experiments throughout the paper, although the method we present is totally general and can be used in many other fields of data analysis. We assume sources with a Gaussian profile --that is a fair approximation of the profile of a point source convolved with the detector beam in microwave experiments-- on a background modeled by a homogeneous and isotropic Gaussian random field characterized by a scale-free power spectrum. Point sources are enhanced with respect to the background by means of linear filters. After filtering, we identify local maxima and apply our detection scheme, a Neyman-Pearson detector that defines our region of acceptance based on the a priori pdf of the sources and the ratio of number densities. We study the different performances of some linear filters that have been used in this context in the literature: the Mexican Hat wavelet, the matched filter and the scale-adaptive filter. We consider as well an extension to two dimensions of the biparametric scale adaptive filter (BSAF). The BSAF depends on two parameters which are determined by maximizing the number density of real detections while fixing the number density of spurious detections. For our detection criterion the BSAF outperforms the other filters in the interesting case of white noise.

M. Lopez-Caniego; D. Herranz; J. L. Sanz; R. B. Barreiro

2005-03-07T23:59:59.000Z

346

Kinetic cascade beyond MHD of solar wind turbulence in two-dimensional hybrid simulations  

E-Print Network (OSTI)

The nature of solar wind turbulence in the dissipation range at scales much smaller than the large MHD scales remains under debate. Here a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented, which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime, the numerical system is initialized by assuming a superposition of isotropic Alfv\\'en waves with amplitudes that follow the empirically confirmed spectral law of Kolmogorov. Then turbulence develops and energy cascades into the dispersive spectral range, where also dissipative effects occur. Under typical solar wind conditions, weak turbulence develops as a superposition of normal modes in the kinetic regime. Spectral analysis in the direction parallel to the background magnetic field reveals a cascade of left-handed Alfv\\'en/ion-cyclotron waves up to wave vectors where their resonant absorption sets in, as well as a cont...

Verscharen, Daniel; Motschmann, Uwe; Müller, Joachim

2012-01-01T23:59:59.000Z

347

Kinetic cascade beyond magnetohydrodynamics of solar wind turbulence in two-dimensional hybrid simulations  

Science Journals Connector (OSTI)

The nature of solar windturbulence in the dissipation range at scales much smaller than the large magnetohydrodynamic (MHD) scales remains under debate. Here a two-dimensional model based on the hybrid code abbreviated as A.I.K.E.F. is presented which treats massive ions as particles obeying the kinetic Vlasov equation and massless electrons as a neutralizing fluid. Up to a certain wavenumber in the MHD regime the numerical system is initialized by assuming a superposition of isotropic Alfvén waves with amplitudes that follow the empirically confirmed spectral law of Kolmogorov. Then turbulence develops and energy cascades into the dispersive spectral range where also dissipative effects occur. Under typical solar wind conditions weak turbulence develops as a superposition of normal modes in the kinetic regime. Spectral analysis in the direction parallel to the background magnetic field reveals a cascade of left-handed Alfvén/ion-cyclotron waves up to wave vectors where their resonant absorption sets in as well as a continuing cascade of right-handed fast-mode and whistler waves. Perpendicular to the background field a broad turbulent spectrum is found to be built up of fluctuations having a strong compressive component. Ion-Bernstein waves seem to be possible normal modes in this propagation direction for lower driving amplitudes. Also signatures of short-scale pressure-balanced structures (very oblique slow-mode waves) are found.

D. Verscharen; E. Marsch; U. Motschmann; J. Müller

2012-01-01T23:59:59.000Z

348

A two-dimensional regional basin model of Williston basin hydrocarbon systems  

SciTech Connect

Institut Francais du Petrole`s two-dimensional model, TEMISPACK, is used to discuss the functioning of petroleum systems in the Williston basin along a 330-km-long section, focusing on four regional source intervals: Ordovician Yeoman formation, Lower Devonian Winnipegosis Formation, Upper Devonian-Lower Mississippian Bakken Formation, and Mississippian Lodgepole formation. Thermal history calibration against present temperature and source rock maturity profiles suggests that the Williston basin can be divided into a region of constant heat flow of about 55 mW/m{sup 2} away from the Nesson anticline, and a region of higher heat flow and enhanced thermal maturity in the vicinity of the Nesson anticline. Original kinetic parameters used in the calibration were derived for each of the four source rocks from Rock-Eval yield curves. Bakken overpressures are entirely due to oil generation, not compaction disequilibrium. Very low Bakken vertical permeabilities range from 0.01 to 0.001 and are matched against observed overpressures, whereas Bakken porosities based on the model and confirmed by measurements are inferred to be also unusually low, around 3%.

Burrus, J.; Wolf, S.; Doligez, B. [Institut Francais due Petrole, Rueil-Malmaison (France)] [and others

1996-02-01T23:59:59.000Z

349

Chiral operators in two-dimensional (0,2) theories and a test of triality  

E-Print Network (OSTI)

In this paper we compute spaces of chiral operators in general two-dimensional (0,2) nonlinear sigma models, both in theories twistable to the A/2 or B/2 model, as well as in non-twistable theories, and apply them to check recent duality conjectures. The fact that in a nonlinear sigma model, the Fock vacuum can act as a section of a line bundle on the target space plays a crucial role in our (0,2) computations, so we begin with a review of this property. We also take this opportunity to show how even in (2,2) theories, the Fock vacuum encodes in this way choices of target space spin structures, and discuss how such choices enter the A and B model topological field theories. We then compute chiral operators in general (0,2) nonlinear sigma models, and apply them to test the recent Gadde-Gukov-Putrov triality proposal, which says that certain triples of (0,2) GLSMs should RG flow to nontrivial IR fixed points. We find that different UV theories in the same proposed universality class do not necessarily have the...

Guo, J; Sharpe, E

2015-01-01T23:59:59.000Z

350

Magnetotransport theory in quantum dots: 3D-0D and 2D-0D tunneling and angular momentum selection rules  

Science Journals Connector (OSTI)

A study of magnetotransport through quantum dots is presented. The model allows one to analyze tunneling both from bulk-like contacts and from 2D accumulation layers. The fine features in the I-V characteristics due to the quantum dot states are known to be shifted to different voltages depending upon the value of the magnetic field. While this effect is also well reproduced by our calculations, in this work we concentrate on the amplitude of each current resonance as a function of the magnetic field. Such amplitudes show oscillations reflecting the variation of the density of states at the Fermi energy in the emitter. Furthermore the amplitude increases as a function of the magnetic field for certain features while it decreases for others. In particular, we demonstrate that the behavior of the amplitude of the current resonances is linked to the value of the angular momentum of each dot level through which tunneling occurs. We show that a selection rule on the angular momentum must be satisfied. As a consequence, tunneling through specific dot states is strongly suppressed and sometimes prohibited altogether by the presence of the magnetic field. This will allow to extract from the experimental curves detailed information on the nature of the quantum-dot wave functions involved in the electronic transport. Furthermore, when tunneling occurs from a two-dimensional accumulation layer to the quantum dot, the presence of a magnetic field hugely increases the strength of some resonant features. This effect is predicted by our model and, to the best of our knowledge, has never been observed.

B. Jouault; M. Boero; G. Faini; J. C. Inkson

1999-02-15T23:59:59.000Z

351

Neutron Reflectivity  

Science Journals Connector (OSTI)

Neutron Reflectivity ... This article is part of the Neutron Reflectivity special issue. ... The articles in this special issue on neutron reflectivity cover a broad range of the applications of this technique and the related X-ray and neutron scattering experiments of SAXS, SANS, GISAXS, and GISANS. ...

Jeffrey Penfold

2009-03-31T23:59:59.000Z

352

Order?Disorder Transformation in RuBr3 and MoBr3:? A Two-Dimensional Ising Model  

Science Journals Connector (OSTI)

Order?Disorder Transformation in RuBr3 and MoBr3:? A Two-Dimensional Ising Model ... We suggest that an equal spanning of the metals in the columns, as proposed by previous authors for the hexagonal phase, is never realized in any compound with the TiI3 structure type and present a possible mechanism of the order?disorder phase transition in this class of compounds and discuss it within the frame of a two-dimensional Ising model. ... 5. Ising Model ...

Stefano Merlino; Luca Labella; Fabio Marchetti; Simone Toscani

2004-09-09T23:59:59.000Z

353

Si deposition rates in a two-dimensional CVD (chemical vapor deposition) reactor and comparisons with model calculations  

SciTech Connect

Deposition rates are presented for silicon from silane in a helium carrier gas using a tubular CVD reactor with a two-dimensional flow geometry. Measured surface-temperature profiles, inlet gas velocities, total pressures, and silane/helium concentrations are reported, providing exact boundary conditions that can be used in a two-dimensional numerical CVD model. Comparisons are made between this data and two variations of a model by Coltrin, Kee, and Miller in which different empirical expressions for the silane and disilane reactive sticking coefficient are used.

Breiland, W.G.; Coltrin, M.E.

1989-10-01T23:59:59.000Z

354

Tile-Based Fisher-Ratio Software for Improved Feature Selection Analysis of Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry Data  

SciTech Connect

Two-dimensional (2D) gas chromatography coupled with time-of-flight mass spectrometry (GC × GC – TOFMS) is a highly capable instrumental platform that produces complex and information-rich multi-dimensional chemical data. The complex data can be overwhelming, especially when many samples (of various sample classes) are analyzed with multiple injections for each sample. Thus, the data must be analyzed in such a way to extract the most meaningful information. The pixel-based and peak table-based algorithmic use of Fisher ratios has been used successfully in the past to reduce the multi-dimensional data down to those chemical compounds that are changing between classes relative to those that are not (i.e., chemical feature selection). We report on the initial development of a computationally fast novel tile-based Fisher-ratio software that addresses challenges due to 2D retention time misalignment without explicitly aligning the data, which is a problem for both pixel-based and peak table- based methods. Concurrently, the tile-based Fisher-ratio software maximizes the sensitivity contrast of true positives against a background of potential false positives and noise. To study this software, eight compounds, plus one internal standard, were spiked into diesel at various concentrations. The tile-based F-ratio software was able to discover all spiked analytes, within the complex diesel sample matrix with thousands of potential false positives, in each possible concentration comparison, even at the lowest absolute spiked analyte concentration ratio of 1.06.

Marney, Luke C.; Siegler, William C.; Parsons, Brendon A.; Hoggard, Jamin C.; Wright, Bob W.; Synovec, Robert E.

2013-10-15T23:59:59.000Z

355

Remarkable effect of bromide ion upon two-dimensional faradaic phase transition of dibenzyl viologen on an HOPG electrode surface: Emergence of two-step transition  

Science Journals Connector (OSTI)

Abstract We found that dibenzyl viologen (dBV) on an HOPG electrode undergoes a two-step first order faradaic phase transition at high concentrations of bromide ion (Br?). Results of voltammetric and electroreflectance measurements were used to describe the mechanism of the two-step transition processes. When [Br?] > 180 mM, the transition step at less negative potential was ascribed to a phase transition between a gas-like adsorption layer of dBV dication (dBV2+) and a mesophase of dBV radical cation (dBV+). Most likely, the mesophase is a two-dimensional (2D) ordered phase composed of co-adsorbed dBV+ and Br? where both are in direct contact with the HOPG surface. The transition step at more negative potential was ascribed to a phase transition between the dBV+ Br? mesophase and a 2D condensed phase of dBV+. In the condensed phase being denser than the mesophase, dBV+ molecules are ?-stacked due to face-to-face interaction between bipyridinium radical cations. This transition step involves also a reduction process of dBV2+ to dBV+ followed by its incorporation into the condensed phase. The two-step transition was not observed in \\{KCl\\} solution of any concentration, either in \\{KBr\\} solution of [Br?] transition but single-step one. The nature of the transition, especially in the [Br?] range from 75 to 180 mM, was closely analyzed.

Tomohiro Higashi; Takamasa Sagara

2013-01-01T23:59:59.000Z

356

NUCLEOSYNTHESIS IN TWO-DIMENSIONAL DELAYED DETONATION MODELS OF TYPE Ia SUPERNOVA EXPLOSIONS  

SciTech Connect

For the explosion mechanism of Type Ia supernovae (SNe Ia), different scenarios have been suggested. In these, the propagation of the burning front through the exploding white dwarf (WD) star proceeds in different modes, and consequently imprints of the explosion model on the nucleosynthetic yields can be expected. The nucleosynthetic characteristics of various explosion mechanisms are explored based on three two-dimensional explosion simulations representing extreme cases: a pure turbulent deflagration, a delayed detonation following an approximately spherical ignition of the initial deflagration, and a delayed detonation arising from a highly asymmetric deflagration ignition. Apart from this initial condition, the deflagration stage is treated in a parameter-free approach. The detonation is initiated when the turbulent burning enters the distributed burning regime. This occurs at densities around 10{sup 7} g cm{sup -3}-relatively low as compared to existing nucleosynthesis studies for one-dimensional spherically symmetric models. The burning in these multidimensional models is different from that in one-dimensional simulations as the detonation wave propagates both into unburned material in the high-density region near the center of a WD and into the low-density region near the surface. Thus, the resulting yield is a mixture of different explosive burning products, from carbon-burning products at low densities to complete silicon-burning products at the highest densities, as well as electron-capture products synthesized at the deflagration stage. Detailed calculations of the nucleosynthesis in all three models are presented. In contrast to the deflagration model, the delayed detonations produce a characteristic layered structure and the yields largely satisfy constraints from Galactic chemical evolution. In the asymmetric delayed detonation model, the region filled with electron capture species (e.g., {sup 58}Ni, {sup 54}Fe) is within a shell, showing a large off-set, above the bulk of {sup 56}Ni distribution, while species produced by the detonation are distributed more spherically.

Maeda, K. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Roepke, F.K.; Fink, M.; Hillebrandt, W.; Travaglio, C. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching (Germany); Thielemann, F.-K., E-mail: keiichi.maeda@ipmu.j [Department Physik, Universitaet Basel, CH-4056 Basel (Switzerland)

2010-03-20T23:59:59.000Z

357

Carbon monoxide in the solar atmosphere I. Numerical method and two-dimensional models  

E-Print Network (OSTI)

The radiation hydrodynamic code CO5BOLD has been supplemented with the time-dependent treatment of chemical reaction networks. Advection of particle densities due to the hydrodynamic flow field is also included. The radiative transfer is treated frequency-independently, i.e. grey, so far. The upgraded code has been applied to two-dimensional simulations of carbon monoxide (CO) in the non-magnetic solar photosphere and low chromosphere. For this purpose a reaction network has been constructed, taking into account the reactions which are most important for the formation and dissociation of CO under the physical conditions of the solar atmosphere. The network has been strongly reduced to 27 reactions, involving the chemical species H, H2, C, O, CO, CH, OH, and a representative metal. The resulting CO number density is highest in the cool regions of the reversed granulation pattern at mid-photospheric heights and decreases strongly above. There, the CO abundance stays close to a value of 8.3 on the usual logarithmic abundance scale with [H]=12 but is reduced in hot shock waves which are a ubiquitous phenomenon of the model atmosphere. For comparison, the corresponding equilibrium densities have been calculated, based on the reaction network but also under assumption of instantaneous chemical equilibrium by applying the Rybicki & Hummer (RH) code by Uitenbroek (2001). Owing to the short chemical timescales, the assumption holds for a large fraction of the atmosphere, in particular the photosphere. In contrast, the CO number density deviates strongly from the corresponding equilibrium value in the vicinity of chromospheric shock waves. Simulations with altered reaction network clearly show that the formation channel via hydroxide (OH) is the most important one under the conditions of the solar atmosphere.

S. Wedemeyer-Boehm; I. Kamp; J. Bruls; B. Freytag

2005-03-23T23:59:59.000Z

358

Screening properties of a classical two-dimensional Coulomb gas from the sine-Gordon equation  

Science Journals Connector (OSTI)

The free energy and the static dielectric function at small wave vectors of a classical two-dimensional Coulomb gas (CG) is obtained for small densities through a fully microscopic calculations which utilizes the equivalence between the CG and the sine-Gordon (SG) equation. The existence of three distinct regions in the temperature-density (T-n) phase diagram of the CG at low densities is confirmed. In the hightemperature (metallic) region the CG is a fully ionized plasma, characterized by the screening length (?) versus density (n) relation ?=a(T)n-12 where a is a regular function of T. As T?? the Debye-Hückel result a(T)=(T2?)12 is obtained trivially from the Klein-Gordon limit of the SG theory. At lower temperatures an "intermediate" region characterized by the coexistence of both charged particles and neutral molecular pairs occurs. In this region, the low-density relation ??(n?)-12, where ? is a function of T which varies continuously from 1 to ? with decreasing temperature, holds. Here n?, the effective density of charged particles available for screening, is less than the actual particle density n owing to the existence of neutral pairs. The divergence of ? signals a phase transition into the low-temperature (insulating) region, characterized by an infinite screening length. At the temperature defining the boundary between the metallic and intermediate phases the CG dielectric function is obtained for all wave vectors through an analogy between the CG and a one-dimensional free-fermion theory. Leading corrections to the low-density results give here are estimated.

P. Minnhagen, A. Rosengren, and G. Grinstein

1978-08-01T23:59:59.000Z

359

A CMOS neuroelectronic interface based on two-dimensional transistor arrays with monolithically-integrated circuitry  

Science Journals Connector (OSTI)

The ability to monitor and to elicit neural activity with a high spatiotemporal resolution has grown essential for studying the functionality of neuronal networks. Although a variety of microelectrode arrays (MEAs) has been proposed, very few \\{MEAs\\} are integrated with signal-processing circuitry. As a result, the maximum number of electrodes is limited by routing complexity, and the signal-to-noise ratio is degraded by parasitics and noise interference. This paper presents a single-chip neuroelectronic interface integrating oxide-semiconductor field-effect transistors (OSFETs) with signal-processing circuitry. After the chip was fabricated with the standard complementary-metal-oxide-semiconductor (CMOS) process, polygates of specific transistors were etched at die-level to form OSFETs, while metal layers were retained to connect the \\{OSFETs\\} into two-dimensional arrays. The complete removal of polygates was confirmed by high-resolution image scanners, and the reliability of \\{OSFETs\\} was examined by measuring their electrical characteristics. Through a gate oxide of only 7 nm thick, each OSFET can record and stimulate neural activity extracellularly by capacitive coupling. The capability of the full chip in neural recording and stimulation was further experimented using the well-characterised escape circuit of the crayfish. Experimental results indicate that the OSFET-based neuroelectronic interface can be used to study neuronal networks as faithfully as conventional electrophysiological tools. Moreover, the proposed simple, die-level fabrication process of the \\{OSFETs\\} underpins the development of various field-effect biosensors on a large scale with on-chip circuitry.

C.H. Chang; S.R. Chang; J.S. Lin; Y.T. Lee; S.R. Yeh; H. Chen

2009-01-01T23:59:59.000Z

360

Two-dimensional iterative region-of-interest (ROI) reconstruction from truncated projection data  

SciTech Connect

A small detector or limited gantry rotation angles may cause data truncation, in which case the entire object cannot be completely reconstructed. However, a small region of interest (ROI) may be recoverable in certain truncation situations. Two analytical methods have been proposed for exact ROI reconstruction. Here we evaluate the capability of ROI reconstruction using an maximum-likelihood expectation-maximization (ML-EM) method, which directly solves the inverse problem of the system equations. ROI reconstruction using the ML-EM method is compared with that using the two analytical methods. Comparisons are based on reconstructions of four specifically designed, computer-simulated truncation cases. In the simulation, each reconstructed ROI is coupled with its counterpart in the nontruncated case to evaluate the accuracy of the reconstructed ROI. We found that, (a) in two truncation situations the ROI can be reconstructed by both the analytical methods and the two-dimensional ML-EM method, but the ML-EM method may produce a larger ROI; (b) for a truncation case that neither analytical algorithm is applicable, the ML-EM method provides a quantitative ROI reconstruction; and (c) for the well-known 'interior' truncation problem, neither the analytical methods nor the ML-EM method can perform an exact ROI reconstruction, but the ML-EM method provides informative ROI images. We also propose an analysis using the truncated projection matrix and its Moore-Penrose inverse matrix which can help to determine the recoverable ROI using iterative methods for a given truncation situation.

Zhang, B.; Zeng, G. L. [Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84108 (United States)

2007-03-15T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Bond-propagation algorithm for thermodynamic functions in general two-dimensional Ising Y. L. Loh and E. W. Carlson  

E-Print Network (OSTI)

Bond-propagation algorithm for thermodynamic functions in general two-dimensional Ising models Y. L-propagation algorithm for calculating the partition func- tion and correlation functions of random-bond Ising models for Ising systems. We conclude with a discussion on the outlook for applying similar algorithms to other

Carlson, Erica

362

ISIT2000, Sorrento, Italy, June 25{30, 2000 Constellation Mappings For Two-Dimensional Non-Uniform Signaling  

E-Print Network (OSTI)

that constel- lation mappings which minimize the average symbol energy and, given this, maximize the decoding-QAM constellation with a mapping M1 . For p > 0:5, the mapping M1 minimizes the average symbol energyISIT2000, Sorrento, Italy, June 25{30, 2000 Constellation Mappings For Two-Dimensional Non

Linder, Tamás

363

Long-range adsorbate interactions mediated by a two-dimensional electron gas N. Knorr,1,2  

E-Print Network (OSTI)

Long-range adsorbate interactions mediated by a two-dimensional electron gas N. Knorr,1,2 H. Brune 8 March 2002 We report on long-range interactions between adsorbates on metal surfaces with a surface state. A compari- son of three adsorbate/substrate systems Cu/Cu 111 , Co/Cu 111 , and Co/Ag 111

Brune, Harald

364

Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using Particle-in-Cell Simulations  

E-Print Network (OSTI)

Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using Particle theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes of their properties, including its energy content, temperature and velocity distribution, and stability. This work

Ng, Chung-Sang

365

Roughening and super-roughening in the ordered and random two-dimensional sine-Gordon models  

E-Print Network (OSTI)

Roughening and super-roughening in the ordered and random two-dimensional sine-Gordon models Angel the super-roughening transition in the random sine-Gordon model. We also find evidence supporting . Above the so-called roughening temperature (TR), thermal fluctuations effectively suppress the effect

Sánchez, Angel "Anxo"

366

Magneto-electric coupling in a two-dimensional ballistic Josephson junction with in-plane magnetic texture  

E-Print Network (OSTI)

Magneto-electric coupling in a two-dimensional ballistic Josephson junction with in-plane magnetic, Germany (Dated: August 20, 2014) We study a Josephson junction made with a spin-textured bridge, when both-dimensional ballistic Josephson junction close to the critical temperature of the heterostructure, when an anomalous

Boyer, Edmond

367

Probing Conformational Disorder in Neurotensin by Two-Dimensional Solid-State NMR and Comparison to Molecular Dynamics Simulations  

E-Print Network (OSTI)

Probing Conformational Disorder in Neurotensin by Two-Dimensional Solid-State NMR and Comparison is introduced to characterize conformational ensembles of intrinsically unstructured peptides on the atomic simulations. For neurotensin, a peptide that binds with high affinity to a G-protein coupled receptor

de Groot, Bert

368

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability  

E-Print Network (OSTI)

Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability Milos 25, 1998; In Final Form: October 19, 1998 Various patterns of standing waves are found beyond the onset of the short-wave instability in a model reaction- diffusion system. These include plain

Epstein, Irving R.

369

Self-assembly of two-dimensional nanoclusters observed with STM: From surface molecules to surface superstructure  

E-Print Network (OSTI)

Self-assembly of two-dimensional nanoclusters observed with STM: From surface molecules to surface on the Si 111 - 3 3-Ag surface at submonolayer Au coverage. Self-assembly of these Au nanoclusters leads nanoclus- ter are discussed in terms of a substrate-mediated interaction among the Au adatoms, and the self-assembling

Hasegawa, Shuji

370

PHYSICAL REVIEW E 84, 046201 (2011) Reconstruction of two-dimensional phase dynamics from experiments on coupled oscillators  

E-Print Network (OSTI)

phase modeling methods to quantify the dynamics of pairs of coupled electrochemical oscillators, based electrochemical oscillators. We discuss the basic theory, which we apply for our system of two oscillators with noise and connect the two-dimensional and one-dimensional models [6,8,9]. We calculate the natural

Potsdam, Universität

371

Evidence for two-dimensional solitary sound waves in a lipid controlled interface and its implications for biological signalling  

Science Journals Connector (OSTI)

...property of the interface (such as...means for measuring state changes...advantages over standard fluorescence...state of the interface was controlled...trough while measuring the lateral...FRET at an interface. In an ordered two-dimensional medium...

2014-01-01T23:59:59.000Z

372

Quantum Field Theory in Two-Dimensional Schwarzschild-de Sitter Spacetime. II: Space with a Collapsing Star  

Science Journals Connector (OSTI)

......uniformly accelerated mirror does not radiate.S...region I, then the Schwarzschild null coordinates (u...in-basis' in the case of a mirror eternally accelerated...an initially static mirror eternally accelerated...in Two-Dimensional Schwarzschild-de Sitter Spacetime......

Shin-ichi Tadaki; Shin Takagi

1990-06-01T23:59:59.000Z

373

Two-dimensional position-sensitive gaseous detectors for high-resolution neutron and X-ray diffraction  

Science Journals Connector (OSTI)

Two-dimensional position-sensitive gaseous detectors have been developed at the Geesthacht Neutron Facility (GeNF) for high-resolution...2, 3He/CF4 and Xe/CO2, respectively. One neutron detector is used at the AR...

M. Marmotti; M. Haese-Seiller; R. Kampmann

2002-12-01T23:59:59.000Z

374

Two dimensional assembly of triblock Janus particles into crystal phases in the two bond per patch limit  

E-Print Network (OSTI)

Two dimensional assembly of triblock Janus particles into crystal phases in the two bond per patch]. Here, we assess the ability of a simple two-patch effective potential to reproduce the experimental mimicking hydrophobic interactions and a patch width that allows for a maximum of two contacts per patch. We

Sciortino, Francesco

375

PHYSICAL REVIEW E 87, 032204 (2013) Energy equipartition in two-dimensional granular systems with spherical intruders  

E-Print Network (OSTI)

- and S-wave energy densities equilibrate in a unique way that is independent of the detailsPHYSICAL REVIEW E 87, 032204 (2013) Energy equipartition in two-dimensional granular systems, Technion City, Haifa 3200, Israel (Received 21 June 2012; published 14 March 2013) We study the effects

Daraio, Chiara

376

Programmed Automation of Modulator Cold Jet Flow for Comprehensive Two-Dimensional Gas Chromatographic Analysis of Vacuum Gas Oils  

Science Journals Connector (OSTI)

......2007 642 naphthalene region of a straight run VGO sample analyzed by TOFMS...con- tour plot image of the same straight run VGO feed sample in which a template...and total aromatic compounds in gasoline by comprehensive two-dimensional......

Wayne Rathbun

377

2D Boussinesq Equations with Logarithmically Super-Critical Conditions.  

E-Print Network (OSTI)

??This thesis focuses on the regularity problem of two generalized two dimensional Boussinesq equations. The rst model contains the critical level of diusion and a… (more)

Tao, Lizheng

2013-01-01T23:59:59.000Z

378

On the influence of low initial pressure and detonation stochastic nature on Mach reflection of gaseous detonation waves  

Science Journals Connector (OSTI)

The two-dimensional, time-dependent and reactive Navier–Stokes equations were solved to obtain an insight into Mach reflection of gaseous detonation in a stoichiometric hydrogen-oxygen mixture diluted ... argon. ...

C. J. Wang; C. M. Guo

2014-09-01T23:59:59.000Z

379

Plastic Deformation of 2D Crumpled Wires  

E-Print Network (OSTI)

When a single long piece of elastic wire is injected trough channels into a confining two-dimensional cavity, a complex structure of hierarchical loops is formed. In the limit of maximum packing density, these structures are described by several scaling laws. In this paper it is investigated this packing process but using plastic wires which give origin to completely irreversible structures of different morphology. In particular, it is studied experimentally the plastic deformation from circular to oblate configurations of crumpled wires, obtained by the application of an axial strain. Among other things, it is shown that in spite of plasticity, irreversibility, and very large deformations, scaling is still observed.

M A F Gomes; V P Brito; A S O Coelho; C C Donato

2008-11-17T23:59:59.000Z

380

Advances in experimental technique for quantitative two-dimensional dopant profiling by scanning capacitance microscopy  

Science Journals Connector (OSTI)

Several advances have been made toward the achievement of quantitative two-dimensional dopant and carrier profiling. To improve the dielectric and charge properties of the oxide–silicon interface a method of low temperature heat treatment has been developed which produces an insulating layer with consistent quality and reproducibility. After a standard polishing procedure is applied to cross-sectional samples the samples are heated to 300?°C for 30 min under ultraviolet illumination. This additional surface treatment dramatically improves dielectric layer uniformity scanning capacitancemicroscopy (SCM) signal to noise ratio and C–V curve flat band offset. Examples of the improvement in the surface quality and comparisons of converted SCM data with secondary ion mass spectrometry(SIMS) data are shown. A SCM tip study has also been performed that indicates significant tip depletion problems can occur. It is shown that dopedsilicon tips are often depleted by the applied SCM bias voltage causing errors in the SCM measured profile. Worn metalcoated and silicided silicon tips also can cause similar problems. When these effects are tested for and eliminated excellent agreement can be achieved between quantitative SCM profiles and SIMS data over a five-decade range of dopant density using a proper physical model. The impact of the tip size and shape on SCM spatial accuracy is simulated. A flat tip model gives a good agreement with experimental data. It is found that the dc offset used to compensate the C–V curve flat band shift has a consistently opposite sign on p- and n-type substrates. This corresponds to a positive surface on p-type silicon and to a negative surface on n-type silicon. Rectification of the large capacitance probing voltage is considered as a mechanism responsible for the apparent flat band shift of (0.4–1) V measured on the samples after heating under UV irradiation. To explain the larger flat band shift of (1–5) V tip induced charging of water-related traps is proposed and discussed.

V. V. Zavyalov; J. S. McMurray; C. C. Williams

1999-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Dynamics of the Solar Magnetic Network: Two-dimensional MHD Simulations  

E-Print Network (OSTI)

The aim of this work is to identify the physical processes that occur in the network and contribute to its dynamics and heating. We model the network as consisting of individual flux tubes with a non-potential field structure that are located in intergranular lanes. With a typical horizontal size of 200 km at the base of the photosphere, they expand upward and merge with their neighbors at a height of about 600 km. Above a height of approximately 1000 km the magnetic field starts to become uniform. Waves are generated in this medium by means of motions at the lower boundary. We focus on transverse driving, which generates both fast and slow waves within a flux tube and acoustic waves at the interface of the tube and the field-free medium. The acoustic waves at the interface are due to compression of the gas on one side of the flux tube and expansion on the other. These waves travel upward along the two sides of the (2D) flux tube and enter it, where they become longitudinal waves. For impulsive excitation with a time constant of 120 s, we find that a dominant feature is the creation of vortical motions that propagate upward. We have identified an efficient mechanism for the generation of longitudinal waves and shock formation in the chromospheric part of the flux concentration. We examine some broad implications of our results.

S. S. Hasan; A. A. van Ballegoiijen; W. Kalkofen; O. Steiner

2005-03-24T23:59:59.000Z

382

Geothermal helical heat exchangers: Comparison and use of two-dimensional axisymmetric models  

Science Journals Connector (OSTI)

Abstract This study concerns near-surface geothermic heat pumps applied to the heating or the cooling of buildings, and more especially the modeling of new helical heat exchangers buried in the subsoil between 1 and 4 m depth. Two 2D axisymmetric models are considered for the exchangers: a horizontal rings model and an annular cylindrical conduit model. The models are described, and successfully compared with literature results applied to ground thermal energy storage. The 2 models give comparable results. The simulations run significantly faster when modeling the exchanger as an annular cylindrical conduit. The ability of the thermal model of the subsoil to simulate the earth freezing is validated by comparison to experimental results. The influence of the liquid fraction included into the ground on the thermal response of the geothermic heat pumps is analyzed. It has a significant impact on the return temperature from the geothermal heat exchangers because of the phase change phenomena and the increase of the conductivity due to the soil freezing.

Xavier Moch; Marc Palomares; Fabrice Claudon; Bernard Souyri; Benoît Stutz

2014-01-01T23:59:59.000Z

383

Three- to two-dimensional transition in electrostatic screening of point charges at semiconductor surfaces studied by scanning tunneling microscopy  

Science Journals Connector (OSTI)

The electrostatic screening of localized electric charges on semiconductor surfaces is investigated quantitatively by statistically analyzing the spatial distribution of thermally formed positively charged anion surface vacancies on GaAs and InP(110) surfaces. Two screening regimes are found: at low vacancy concentrations the vacancy charges are found to be three-dimensionally screened by bulk charge carriers. The corresponding screening length, which increases strongly with decreasing carrier concentration, is best described by the classical bulk screening length evaluated with a surface dielectric constant. With increasing vacancy concentration at given bulk carrier concentration, a three- to two-dimensional screening transition occurs. At high vacancy concentrations, the screening is found to be governed by charge carriers located in a two-dimensional surface vacancy defect band, which is partially filled due to the vacancy-induced surface band bending.

A. Laubsch, K. Urban, and Ph. Ebert

2009-12-14T23:59:59.000Z

384

Magnetic-field effects on quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells  

Science Journals Connector (OSTI)

We have used the variational procedure in the effective-mass and nondegenerate parabolic band approximations in order to investigate the effects of a magnetic field on the exciton effective mass and dispersion in semiconductor heterostructures. Calculations are performed for bulk GaAs, and two-dimensional and quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells for applied magnetic fields perpendicular to the layers. A simple hydrogenlike envelope wave function provides the expected behavior for the exciton dispersion in a wide range of the center-of-mass momenta, and an analytical expression for the exciton effective mass is obtained. Present results lead to a magnetic-field dependent exciton effective mass and dispersion in quite good agreement with available experimental measurements in coupled GaAs?(Ga,Al)As quantum wells.

E. Reyes-Gómez, L. E. Oliveira, and M. de Dios-Leyva

2005-01-14T23:59:59.000Z

385

Development of an energy-saving glass using two-dimensional periodic nano-structures  

Science Journals Connector (OSTI)

Abstract A new type of energy-saving glass, Ag inlaid with SiO2 nano-structures (Inlay SiO2), is numerically developed here to offer modern buildings a passive but promising way of saving power under sunlight. The profile of glass is identified after optimizing optical responses using the genetic algorithm and a fitness function. Wavelength-selective reflectance (R) and transmittance (T) are demonstrated with validated programs based on the rigorous coupled-wave analysis algorithm. The high T and low R in the visible range not only saves energy for lighting but diminishes reflected and stray light. The low T and high R in the near-infrared reduce the cost for air-conditioning. Besides the cost can be further reduced, the superiority of this glass over current commercially available products includes the material commonness, light weight, and freedom from adhesion as well as oxidation. The fabrication tolerance of each dimension is further investigated to determine the key one. Other structure configurations are also approached to explore possibilities of alternates.

Chih-Ling Huang; Chi-Chun Ho; Yu-Bin Chen

2014-01-01T23:59:59.000Z

386

Two-Dimensional Property Distributions, Ohmic Losses, and Power Consumption within a Fuel Cell Polymer Electrolyte Membrane  

Science Journals Connector (OSTI)

Two-Dimensional Property Distributions, Ohmic Losses, and Power Consumption within a Fuel Cell Polymer Electrolyte Membrane ... The land provides both mechanical support and electrical contact to the porous transport layer (PTL), while the fuel and oxidant are distributed to the catalyst layer (CL) through the channels, again via the PTL. ... The anisotropic nature of the distributions suggest that there may be localized “hot spots” where an increased rate of power consumption could heat the membrane and cause it to fail. ...

Venkateshwar R. Devulapalli; Aaron V. Phoenix

2010-06-24T23:59:59.000Z

387

Magnetic phases of the quasi-two-dimensional compounds FexCo1-xTa2O6  

E-Print Network (OSTI)

Magnetic phases of the quasi-two-dimensional compounds FexCo1-xTa2O6 E G Santos1 , S R de Oliveira, 49100-000 S~ao Crist´ov~ao, SE, Brazil Abstract. We report new results about magnetic properties of the FexCo1-xTa2O6 series of compounds. Using essentially neutron diffraction and magnetic measurements we

Boyer, Edmond

388

The calculation of the thermal properties of graphene under a magnetic field via the two-dimensional Dirac oscillator  

E-Print Network (OSTI)

In this paper, we show, by using the approach of effective mass, that the model of a two-dimensional Dirac oscillator can be used to describe the thermal properties of graphene under an uniform magnetic field. All thermal quantities of graphene, such as the free energy, the mean energy, the entropy and the specific heat, have been found by using an approach based on the zeta function.

Abdelmalek Boumali

2014-10-10T23:59:59.000Z

389

Low-temperature scanning tunneling microscopy and transport measurements on adsorbate-induced two-dimensional electron systems  

SciTech Connect

We have performed not only magnetotransport measurements on two-dimensional electron systems (2DESs) formed at the cleaved surfaces of p-InAs but also observations of the surface morphology of the adsorbate atoms, which induced the 2DES at the surfaces of narrow band-gap semiconductors, with use of a scanning tunneling microscopy. The electron density of the 2DESs is compared to the atomic density of the isolated Ag adatoms on InAs surfaces.

Masutomi, Ryuichi; Triyama, Naotaka; Okamoto, Tohru [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-12-04T23:59:59.000Z

390

Coupled plasma waves in a system of two two-dimensional superlattices in the presence of a quantizing electric field  

SciTech Connect

The effect of a dc electric field on coupled plasma waves in a system of two two-dimensional super-lattices is studied. In the case of high temperatures, a dispersion relation is obtained and the fundamental and resonant modes of the plasma waves are numerically studied. The calculations are performed based on the quantum theory of plasma waves in the random phase approximation taking into account umklapp processes.

Glazov, S. Yu., E-mail: ser-glazov@yandex.ru; Kubrakova, E. S. [Volgograd State Social Pedagogical University (Russian Federation)] [Volgograd State Social Pedagogical University (Russian Federation); Mescheryakova, N. E. [Volgograd Institute of Business (Russian Federation)] [Volgograd Institute of Business (Russian Federation)

2013-10-15T23:59:59.000Z

391

Suppression of electron magnetotunneling between parallel two-dimensional GaAs/InAs electron systems by the correlation interaction  

SciTech Connect

Magnetotunneling between two-dimensional GaAs/InAs electron systems in vertical resonant tunneling GaAs/InAs/AlAs heterostructures is studied. A new-type of singularity in the tunneling density of states, specifically a dip at the Fermi level, is found; this feature is drastically different from that observed previously for the case of tunneling between two-dimensional GaAs tunnel systems in terms of both the kind of functional dependence and the energy and temperature parameters. As before, this effect manifests itself in the suppression of resonant tunneling in a narrow range near zero bias voltage in a high magnetic field parallel to the current direction. Magnetic-field and temperature dependences of the effect's parameters are obtained; these dependences are compared with available theoretical and experimental data. The observed effect can be caused by a high degree of disorder in two-dimensional correlated electron systems as a result of the introduction of structurally imperfect strained InAs layers.

Khanin, Yu. N.; Vdovin, E. E., E-mail: vdov62@yandex.ru [Russian Academy of Sciences, Institute of Microelectronics Technology and High Purity Materials (Russian Federation); Makarovsky, O. [University of Nottingham, School of Physics and Astronomy (United Kingdom)] [University of Nottingham, School of Physics and Astronomy (United Kingdom); Henini, M. [University of Nottingham, School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Center (United Kingdom)] [University of Nottingham, School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Center (United Kingdom)

2013-09-15T23:59:59.000Z

392

Exploring size and state dynamics in CdSe quantum dots using two-dimensional electronic spectroscopy  

SciTech Connect

Development of optoelectronic technologies based on quantum dots depends on measuring, optimizing, and ultimately predicting charge carrier dynamics in the nanocrystal. In such systems, size inhomogeneity and the photoexcited population distribution among various excitonic states have distinct effects on electron and hole relaxation, which are difficult to distinguish spectroscopically. Two-dimensional electronic spectroscopy can help to untangle these effects by resolving excitation energy and subsequent nonlinear response in a single experiment. Using a filament-generated continuum as a pump and probe source, we collect two-dimensional spectra with sufficient spectral bandwidth to follow dynamics upon excitation of the lowest three optical transitions in a polydisperse ensemble of colloidal CdSe quantum dots. We first compare to prior transient absorption studies to confirm excitation-state-dependent dynamics such as increased surface-trapping upon excitation of hot electrons. Second, we demonstrate fast band-edge electron-hole pair solvation by ligand and phonon modes, as the ensemble relaxes to the photoluminescent state on a sub-picosecond time-scale. Third, we find that static disorder due to size polydispersity dominates the nonlinear response upon excitation into the hot electron manifold; this broadening mechanism stands in contrast to that of the band-edge exciton. Finally, we demonstrate excitation-energy dependent hot-carrier relaxation rates, and we describe how two-dimensional electronic spectroscopy can complement other transient nonlinear techniques.

Caram, Justin R.; Zheng, Haibin; Rolczynski, Brian S.; Griffin, Graham B.; Engel, Gregory S., E-mail: gsengel@uchicago.edu [Department of Chemistry, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dahlberg, Peter D. [Graduate Program in the Biophysical Sciences, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Graduate Program in the Biophysical Sciences, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dolzhnikov, Dmitriy S.; Talapin, Dmitri V. [Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)

2014-02-28T23:59:59.000Z

393

Two-dimensional heterogeneous model for a reticulated-foam photocatalytic reactor  

SciTech Connect

A 2-D heterogeneous convection reaction model for a gas-solid lamp-in-tube annular photocatalytic reactor is presented. The catalyst (TiO{sub 2}) is supported on a reticulated-foam monolithic structure placed in the annular space between the UV lamp and the reactor wall. Mass balances for individual species are coupled through the reaction-rate expression that appears in the boundary condition at the fluid-solid interface in heterogeneous catalytic reactor models. The heterogeneous reaction rate is modeled using semiempirical Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics with adsorption constants for various species. The local volumetric rate of energy absorption (LVREA) term in the rate expression was computed using a 3-D polychromatic radiation-field model. The overall system of nonlinear partial differential equations was solved using a combination of the Crank-Nicolson method and the globally convergent Newton-Raphson method. The apparent, average quantum yield in the LHHW kinetic rate form is the single adjustable parameter in the model. Isopropanol (IPA) was chosen as the test contaminant to conduct experimental performance measurements for model validation. Model-predicted radial and axial profiles for bulk and surface concentration reveal that the extent to which mass transport influences the operation of a photocatalytic reactor is determined largely by the local magnitude of the LVREA. Similitude in the scale-up of an annular lamp-in-tube heterogeneous photocatalytic reactor is achieved only when the dimensionless radial radiation profile, as well as corresponding magnitudes of a geometric number, the Peclet number, the Stanton number, and the photocatalytic analog of the Damkoehler number, are identical.

Changrani, R.G.; Raupp, G.B.

2000-04-01T23:59:59.000Z

394

Excited states of exciton-polariton condensates in 2D and 1D harmonic traps  

Science Journals Connector (OSTI)

We present a theoretical description of Bogolyubov-type excitations of exciton-polariton Bose-Einstein condensates (BECs) in semiconductor microcavities. For a typical two-dimensional (2D) BEC we focus on two limiting cases, the weak- and strong-coupling regimes, where a perturbation theory and the Thomas-Fermi approximation, respectively, are valid. We calculate integrated scattering intensity spectra for probing the collective excitations of the condensate in both considered limits. Moreover, in relation to recent experiments on optical modulation allowing localization of condensates in a trap with well-controlled shape and dimensions, we study the quasi-one-dimensional (1D) motion of the BEC in microwires and report the corresponding Bogolyubov excitation spectrum. We show that in the 1D case the characteristic polariton-polariton interaction constant is expressed as g1=3?N/(2Ly) (? is the 2D polariton-polariton interaction parameter in the cavity, N the number of the particles, and Ly the wire cavity width). We reveal some interesting features for 2D and 1D Bogolyubov spectra for both repulsive (?>0) and attractive (?<0) interactions.

C. Trallero-Giner; M. V. Durnev; Y. Núńez Fernández; M. I. Vasilevskiy; V. López-Richard; A. Kavokin

2014-05-27T23:59:59.000Z

395

2-D Temperature Mapping in Fluorocarbon Plasmas  

SciTech Connect

Two-dimensional maps of rotational temperature in CF4 plasmas were determined using planar laser-induced fluorescence measurements of CF A2{sigma}+ - X2{pi} (1,0). Rotational temperatures are expected to be in equilibrium with gas temperatures under the present conditions. Experiments were performed in a capacitively-coupled, parallel-plate reactor at pressures from 27 Pa to 107 Pa and powers of 10 W to 30 W. The effects of electrode cooling and having a wafer present were also examined. Measured temperatures ranged between 273 K{+-}15 K and 480 K{+-}15 K. The strong temperature gradients found in these plasmas can have serious effects on density measurements that probe a single rotational level, as well as on reaction rate constants and interpretation of density gradients.

Steffens, Kristen L.; Sobolewski, Mark A. [Process Measurements Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)

2005-09-09T23:59:59.000Z

396

Physica 65 (1973) 73-88 0 North-Holland Publishing Co. SURFACE TENSION IN THE TWO-DIMENSIONAL ISING MODEL  

E-Print Network (OSTI)

Physica 65 (1973) 73-88 0 North-Holland Publishing Co. SURFACE TENSION IN THE TWO-DIMENSIONAL ISING of surface tension between oppositely magnetised phases in the two-dimensional Ising model. With nearest?) defined and calculated exactly a surface tension. This was later shown by Fisher and Ferdinand5

Roma "La Sapienza", UniversitĂ  di

397

2d Affine XY-Spin Model/4d Gauge Theory Duality and Deconfinement  

SciTech Connect

We introduce a duality between two-dimensional XY-spin models with symmetry-breaking perturbations and certain four-dimensional SU(2) and SU(2) = Z{sub 2} gauge theories, compactified on a small spatial circle R{sup 1,2} x S{sup 1}, and considered at temperatures near the deconfinement transition. In a Euclidean set up, the theory is defined on R{sup 2} x T{sup 2}. Similarly, thermal gauge theories of higher rank are dual to new families of 'affine' XY-spin models with perturbations. For rank two, these are related to models used to describe the melting of a 2d crystal with a triangular lattice. The connection is made through a multi-component electric-magnetic Coulomb gas representation for both systems. Perturbations in the spin system map to topological defects in the gauge theory, such as monopole-instantons or magnetic bions, and the vortices in the spin system map to the electrically charged W-bosons in field theory (or vice versa, depending on the duality frame). The duality permits one to use the two-dimensional technology of spin systems to study the thermal deconfinement and discrete chiral transitions in four-dimensional SU(N{sub c}) gauge theories with n{sub f} {ge} 1 adjoint Weyl fermions.

Anber, Mohamed M.; Poppitz, Erich; /Toronto U.; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept. /San Francisco State U.

2012-08-16T23:59:59.000Z

398

Two-Dimensional Polaronic Behavior in the Binary Oxides m-HfO2 and m-ZrO2  

SciTech Connect

We demonstrate that the three-dimensional (3D) binary monoclinic oxides HfO{sub 2} and ZrO{sub 2} exhibit quasi-2D polaron localization and conductivity, which results from a small difference in the coordination of two oxygen sublattices in these materials. The transition between a 2D large polaron into a zero-dimensional small polaron state requires overcoming a small energetic barrier. These results demonstrate how a small asymmetry in the lattice structure can determine the qualitative character of polaron localization and significantly broaden the realm of quasi-2D polaron systems.

McKenna, K. P.; Wolf, M. J.; Shluger, A. L.; Lany, S.; Zunger, A.

2012-03-16T23:59:59.000Z

399

2D Joint Inversion Of Dc And Scalar Audio-Magnetotelluric Data In The  

Open Energy Info (EERE)

Joint Inversion Of Dc And Scalar Audio-Magnetotelluric Data In The Joint Inversion Of Dc And Scalar Audio-Magnetotelluric Data In The Evaluation Of Low Enthalpy Geothermal Fields Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: 2D Joint Inversion Of DC And Scalar Audio-Magnetotelluric Data In The Evaluation Of Low Enthalpy Geothermal Fields Details Activities (0) Areas (0) Regions (0) Abstract: Audio-magnetotelluric (AMT) and resistivity (dc) surveys are often used in environmental, hydrological and geothermal evaluation. The separate interpretation of those geophysical data sets assuming two-dimensional models frequently produces ambiguous results. The joint inversion of AMT and dc data is advocated by several authors as an efficient method for reducing the ambiguity inherent to each of those

400

Determining Transition State Geometries in Liquids Using 2D-IR  

SciTech Connect

Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.

Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.

2007-12-11T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

A Fast Algorithm for Eye Detection Using Two-Dimensional CSP Akiko SUZUKI Tetsuya TAKIGUCHI Yasuo ARIKI  

E-Print Network (OSTI)

CSP A Fast Algorithm for Eye Detection Using Two-Dimensional CSP Akiko SUZUKI Tetsuya TAKIGUCHI Yasuo ARIKI 1. , CSP Crosspower-Spectrum Phase 2 [1] [2][3] CSP 2. W Ă? H I(x, y) w Ă? h T(i, j) R(x, y) R(x, y) (4) 3. CSP 1 CSP I(x, y) T(i, j) I(1, 2) = x,y I(x, y)e-j1x e-j2y (5) T(1, 2) = i,j T(i, j)e-j1

Takiguchi, Tetsuya

402

Optimized Use of a 50 ?m Internal Diameter Secondary Column in a Comprehensive Two-Dimensional Gas Chromatography System  

Science Journals Connector (OSTI)

Optimized Use of a 50 ?m Internal Diameter Secondary Column in a Comprehensive Two-Dimensional Gas Chromatography System ... The primary GC (GC1) was equipped with an AOC-20i autoinjector and a split?splitless injector (280 °C). ... The unmodulated applications carried out at ?15, 20, 25, 30, and 35 cm/s, analyzing a C17 alkane at an isothermal temperature of 155 °C (n = 3), generated N values of circa 122?600, 149?600, 147?600, 140?800, and 119?400, respectively. ...

Peter Quinto Tranchida; Giorgia Purcaro; Lanfranco Conte; Paola Dugo; Giovanni Dugo; Luigi Mondello

2009-09-17T23:59:59.000Z

403

Finite-size effects on the phase diagram of difermion condensates in two-dimensional four-fermion interaction models  

SciTech Connect

We investigate finite-size effects on the phase structure of chiral and difermion condensates at finite temperature and density in the framework of the two-dimensional large-N Nambu-Jona-Lasinio model. We take into account size-dependent effects by making use of zeta-function and compactification methods. The thermodynamic potential and the gap equations for the chiral and difermion condensed phases are then derived in the mean-field approximation. Size-dependent critical lines separating the different phases are obtained considering antiperiodic boundary conditions for the spatial coordinate.

Abreu, L. M.; Malbouisson, J. M. C. [Instituto de Fisica, Universidade Federal da Bahia, 40210-340, Salvador, BA (Brazil); Malbouisson, A. P. C. [Centro Brasileiro de Pesquisas Fisicas, MCT, 22290-180, Rio de Janeiro, RJ (Brazil)

2011-01-15T23:59:59.000Z

404

Theory of two-dimensional macroscopic quantum tunneling in a Josephson junction coupled with an LC circuit  

E-Print Network (OSTI)

We investigate classical thermal activation (TA) and macroscopic quantum tunneling (MQT) for a Josephson junction coupled with an LC circuit theoretically. The TA and MQT escape rate are calculated analytically by taking into account the two-dimensional nature of the classical and quantum phase dynamics. We find that the MQT escape rate is largely suppressed by the coupling to the LC circuit. On the other hand, this coupling gives rise to slight reduction of the TA escape rate. These results are relevant for the interpretation of a recent experiment on the MQT and TA phenomena in grain boundary YBCO Josephson junctions.

Shiro Kawabata; Takeo Kato; Thilo Bauch

2009-12-17T23:59:59.000Z

405

A two-dimensional numerical simulation of shock-enhanced mixing in a rectangular scramjet flowfield with parallel hydrogen injection  

SciTech Connect

The effect of shock impingement on the mixing and combustion of a reacting shear-layer is numerically simulated. Hydrogen fuel is injected at sonic velocity behind a backward facing step in a direction parallel to a supersonic freestream vitiated with H{sub 2}O. The two-dimensional Navier-Stokes equations are solved and explicitly coupled to a chemistry package employing a global, two-step combustion model. The results show that shock impingement enhances the mixing and combustion. 17 refs.

Domel, N.D.; Thompson, D.S. (Texas Univ., Arlington (USA))

1991-01-01T23:59:59.000Z

406

Energy-loss rate of a fast particle in two-dimensional semiconductors with Rashba spin-orbit coupling  

SciTech Connect

The energy-loss rate (ELR) of a charged particle in a two-dimensional semiconductor with Rashba spin-orbit coupling is studied. Our model takes into account of the temperature and density dependence of the electronic properties of the Rashba system. The energy and temperature dependence of the ELR are presented. It is found that a finite Rashba spin-orbit coupling offers a mechanism of tuning the mean scattering time in narrow-gap semiconductors. With a change of Rashba parameter of around 3 times, the mean scattering time can change by one to two orders of magnitude.

Feng, W. [Department of Physics, Jiangsu University, Zhenjiang, Jiangsu (China)] [Department of Physics, Jiangsu University, Zhenjiang, Jiangsu (China); Tawfiq, Asya [School of Physics, University of Wollongong, New South Wales 2522 (Australia)] [School of Physics, University of Wollongong, New South Wales 2522 (Australia); Cao, J. C. [Key Laboratory of Terahertz Solid State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai (China)] [Key Laboratory of Terahertz Solid State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai (China); Zhang, C. [School of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522 (Australia)] [School of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522 (Australia)

2013-02-04T23:59:59.000Z

407

One- and two-dimensional infrared spectroscopic studies of solution-phase homogeneous catalysis and spin-forbidden reactions  

SciTech Connect

Understanding chemical reactions requires the knowledge of the elementary steps of breaking and making bonds, and often a variety of experimental techniques are needed to achieve this goal. The initial steps occur on the femto- through picosecond time-scales, requiring the use of ultrafast spectroscopic methods, while the rate-limiting steps often occur more slowly, requiring alternative techniques. Ultrafast one and two-dimensional infrared and step-scan FTIR spectroscopies are used to investigate the photochemical reactions of four organometallic complexes. The analysis leads to a detailed understanding of mechanisms that are general in nature and may be applicable to a variety of reactions.

Sawyer, Karma Rae

2008-12-12T23:59:59.000Z

408

2-D discrete element modeling of unconsolidated sandstones  

E-Print Network (OSTI)

developed in this thesis is compared to the results of triaxial tests performed in cylindrical core samples of unconsolidated sandstones saturated with heavy oil. The discrete element model treats the sand as a two dimensional assembly of particles...

Franquet Barbara, Javier Alejandro

2012-06-07T23:59:59.000Z

409

The actuated Workbench : 2D actuation in tabletop tangible interfaces  

E-Print Network (OSTI)

The Actuated Workbench is a new actuation mechanism that uses magnetic forces to control the two-dimensional movement of physical objects on flat surfaces. This mechanism is intended for use with existing tabletop Tangible ...

Pangaro, Gian Antonio, 1976-

2003-01-01T23:59:59.000Z

410

GBL-2D Version 1.0: a 2D geometry boolean library.  

SciTech Connect

This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.

McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R.; Meyers, Ray J. (Elemental Technologies, American Fort, UT)

2006-11-01T23:59:59.000Z

411

A scalable 2-D parallel sparse solver  

SciTech Connect

Scalability beyond a small number of processors, typically 32 or less, is known to be a problem for existing parallel general sparse (PGS) direct solvers. This paper presents a parallel general sparse PGS direct solver for general sparse linear systems on distributed memory machines. The algorithm is based on the well-known sequential sparse algorithm Y12M. To achieve efficient parallelization, a 2-D scattered decomposition of the sparse matrix is used. The proposed algorithm is more scalable than existing parallel sparse direct solvers. Its scalability is evaluated on a 256 processor nCUBE2s machine using Boeing/Harwell benchmark matrices.

Kothari, S.C.; Mitra, S. [Iowa State Univ., Ames, IA (United States)

1995-12-01T23:59:59.000Z

412

Two-Temperature Two-Dimensional Non Chemical Equilibrium Modeling of Ar–CO2–H2 Induction Thermal Plasmas at Atmospheric Pressure  

Science Journals Connector (OSTI)

Here the authors developed a two-dimensional two-temperature chemical non-equilibrium (2T-NCE) model of Ar–...2–H2 inductively coupled thermal plasmas (ICTP) around atmospheric pressure (760 torr). Assuming 22 di...

Sharif Abdullah Al-Mamun; Yasunori Tanaka…

2010-02-01T23:59:59.000Z

413

Dissipative flows of 2D foams  

E-Print Network (OSTI)

We analyze the flow of a liquid foam between two plates separated by a gap of the order of the bubble size (2D foam). We concentrate on the salient features of the flow that are induced by the presence, in an otherwise monodisperse foam, of a single large bubble whose size is one order of magnitude larger than the average size. We describe a model suited for numerical simulations of flows of 2D foams made up of a large number of bubbles. The numerical results are successfully compared to analytical predictions based on scaling arguments and on continuum medium approximations. When the foam is pushed inside the cell at a controlled rate, two basically different regimes occur: a plug flow is observed at low flux whereas, above a threshold, the large bubble migrates faster than the mean flow. The detailed characterization of the relative velocity of the large bubble is the essential aim of the present paper. The relative velocity values, predicted both from numerical and from analytical calculations that are discussed here in great detail, are found to be in fair agreement with experimental results.

Isabelle Cantat; Renaud Delannay

2005-07-21T23:59:59.000Z

414

On the nonlinear stability of a quasi-two-dimensional drift kinetic model for ion temperature gradient turbulence  

E-Print Network (OSTI)

We study a quasi-two-dimensional electrostatic drift kinetic system as a model for near-marginal ion temperature gradient (ITG) driven turbulence. A proof is given of the nonlinear stability of this system under conditions of linear stability. This proof is achieved using a transformation that diagonalizes the linear dynamics and also commutes with nonlinear $E\\times B$ advection. For the case when linear instability is present, a corollary is found that forbids nonlinear energy transfer between appropriately defined sets of stable and unstable modes. It is speculated that this may explain the preservation of linear eigenmodes in nonlinear gyrokinetic simulations. Based on this property, a dimensionally reduced ($\\infty\\times\\infty \\rightarrow 1$) system is derived that may be useful for understanding dynamics around the critical gradient of Dimits.

Plunk, G G

2015-01-01T23:59:59.000Z

415

Photovoltaic oscillations due to edge-magnetoplasmon modes in a very high-mobility two-dimensional electron gas  

Science Journals Connector (OSTI)

Using very high-mobility GaAs?AlxGa1?xAs two-dimensional electron Hall bar samples, we have experimentally studied the photoresistance and/or photovoltaic oscillations induced by microwave irradiation in the regime where both 1?B and B-periodic oscillations can be observed. In the frequency range between 27 and 130GHz, we found that these two types of oscillations are decoupled from each other, consistent with the respective models that 1?B oscillations occur in bulk while the B oscillations occur along the edges of the Hall bars. In contrast to the original report of this phenomenon [I. V. Kukushkin et al., Phys. Rev. Lett. 92, 236803 (2004)], the periodicity of the B oscillations in our samples is found to be independent of L, the length of the Hall bar section between voltage measuring leads.

K. Stone, C. L. Yang, Z. Q. Yuan, R. R. Du, L. N. Pfeiffer, and K. W. West

2007-10-16T23:59:59.000Z

416

Effect of interactions on two-dimensional fermionic symmetry-protected topological phases with Z2 symmetry  

Science Journals Connector (OSTI)

We study the effect of interactions on two-dimensional fermionic symmetry-protected topological (SPT) phases using the recently proposed braiding statistics approach. We focus on a simple class of examples: superconductors with a Z2 Ising symmetry. Although these systems are classified by Z in the noninteracting limit, our results suggest that the classification collapses to Z8 in the presence of interactions—consistent with previous work that analyzed the stability of the edge. Specifically, we show that there are at least eight different types of Ising superconductors that cannot be adiabatically connected to one another, even in the presence of strong interactions. In addition, we prove that each of the seven nontrivial superconductors have protected edge modes.

Zheng-Cheng Gu and Michael Levin

2014-05-19T23:59:59.000Z

417

A new two-dimensional X-ray drift chamber for diffraction studies with pulsed synchroton radiation  

Science Journals Connector (OSTI)

A two-dimensional position-sensitive detector (drift-chamber) for X-ray difraction experiments with pulsed synchrotron radiation is described. For the measurements of drift direction (x), the small drift chamber uses a reference signal generated by the electron bunches circulating in the storage ring. A flat geometry delay-line, inductively connected to the anode, detects the position of avalanche electrons on the anode wire (y-direction). The main features are: spatial resolution in drift direction (x), 100 ?m for 5 keV photons; spatial resolution in y direction, 400 ?m; maximum counting-rate 5×105 cps; quantum efficiency ar 5 keV, 52%. The systems has been succesfully tested at the ADONE storage ring at Frascati by measuring the small-angle diffraction spectrum of a dry tendon collagen.

Mario Iannuzzi; Andrea La Monaca

1982-01-01T23:59:59.000Z

418

Spin-polarized currents in the tunnel contact of a normal conductor and a two-dimensional topological insulator  

SciTech Connect

The spin filtering of electrons tunneling from the edge states of a two-dimensional topological insulator into a normal conductor under a magnetic field (external or induced due to proximity to a magnetic insulator) is studied. Calculations are performed for a tunnel contact of finite length between the topological insulator and an electronic multimode quantum strip. It is shown that the flow of tunneling electrons is split in the strip, so that spin-polarized currents arise in its left and right branches. These currents can be effectively controlled by the contact voltage and the chemical potential of the system. The presence of a magnetic field, which splits the spin subbands of the electron spectrum in the strip, gives rise to switching of the spin current between the strip branches.

Sukhanov, A. A., E-mail: AASukhanov@yandex.ru; Sablikov, V. A. [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino branch) (Russian Federation)] [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino branch) (Russian Federation)

2013-11-15T23:59:59.000Z

419

Anharmonic OH vibrations in Mg ( OH ) 2 (brucite): Two-dimensional calculations and crystal-induced blueshift  

Science Journals Connector (OSTI)

A two-dimensional quantum-mechanical vibrational model has been used to calculate the anharmonic OH vibrational frequencies in the layered Mg ( OH ) 2 (brucite) crystal. The underlying potential energy surface was generated by density functional theory(DFT) calculations. The resulting OH frequencies are upshifted (blueshifted) by about + 75 ? cm ? 1 with respect to the gas-phase OH frequency ( + 120 ? cm ? 1 in experiments; the discrepancy is mainly due to inadequacies in the DFT and pseudopotential models). The Raman-IR split is about 50 ? cm ? 1 both in the calculations and in experiments. We find that the blueshift phenomenon in brucite can qualitatively be explained by a parabolalike “OH frequency versus electric field” correlation curve pertaining to an OH ? ion exposed to an electric field. We also find that it is primarily the neighbors within the Mg ( OH ) 2 layer that induce the blueshift while the interlayer interaction gives a smaller (and redshifting) contribution.

Kersti Hermansson; Michael M. Probst; Grzegorz Gajewski; Pavlin D. Mitev

2009-01-01T23:59:59.000Z

420

A method for the frequency control in time-resolved two-dimensional gigahertz surface acoustic wave imaging  

SciTech Connect

We describe an extension of the time-resolved two-dimensional gigahertz surface acoustic wave imaging based on the optical pump-probe technique with periodic light source at a fixed repetition frequency. Usually such imaging measurement may generate and detect acoustic waves with their frequencies only at or near the integer multiples of the repetition frequency. Here we propose a method which utilizes the amplitude modulation of the excitation pulse train to modify the generation frequency free from the mentioned limitation, and allows for the first time the discrimination of the resulted upper- and lower-side-band frequency components in the detection. The validity of the method is demonstrated in a simple measurement on an isotropic glass plate covered by a metal thin film to extract the dispersion curves of the surface acoustic waves.

Kaneko, Shogo; Tomoda, Motonobu; Matsuda, Osamu, E-mail: omatsuda@eng.hokudai.ac.jp [Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan)] [Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan)

2014-01-15T23:59:59.000Z

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421

Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses  

E-Print Network (OSTI)

We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles which readily permit variation of sample packing fraction. At each packing fraction, the particle displacement covariance matrix is measured and used to extract the vibrational spectrum of the "shadow" colloidal glass (i.e., the particle network with the same geometry and interactions as the sample colloid but absent damping). Rearrangements are induced by successive, small reductions in packing fraction. The experimental results suggest that low-frequency quasi-localized phonon modes in colloidal glasses, i.e., modes that present low energy barriers for system rearrangements, are spatially correlated with rearrangements in this thermal system.

K. Chen; M. L. Manning; P. J. Yunker; W. G. Ellenbroek; Z. Zhang; Andrea J. Liu; A. G. Yodh

2011-03-11T23:59:59.000Z

422

Two-dimensional hybrid simulations of the oblique electromagnetic alpha/proton instability in the solar wind  

Science Journals Connector (OSTI)

In the solar wind alpha particles are observed to flow faster than the core protons. In this paper two-dimensional hybrid simulations are performed to investigate the nonlinear evolution of oblique Alfvén waves excited by an alpha/proton beam instability in a low beta plasma. The propagation angles of the excited waves are within a finite range suggesting the generation of oblique Alfvén waves. During the nonlinear evolution both the wave numbers and frequencies of the waves drift to smaller values and the propagation angles decrease. At the same time the propagation angle of the dominant mode also changes. Eventually the plasma system reaches a marginally stable state according to linear theory.

Quanming Lu; Aimin Du; Xing Li

2009-01-01T23:59:59.000Z

423

A two-dimensional simulation of tritium transport in the vadose zone at the Nevada Test site  

SciTech Connect

The site of a 0.75-kiloton underground nuclear explosion, the Cambric event, was selected for the study of radionuclide transport in the hydrologic environment. Water samples from RNM-2S, a well located 91 m from Cambric, have been analyzed for tritium and other radionuclides since the initiation of pumping. Water from RNM-2S flows to Frenchman Lake via an unlined canal. Flume data indicate canal transmission losses of approximately 2m{sup 3}/day/meter of canal. To determine if infiltrating canal water might be recirculated by RNM-2S, and therefore provide an additional radionuclide input to water samples collected at RNM-2S, a two-dimensional variably saturated solute transport computer model (SATURN, Huyakorn et al., 1983) was used to simulate the movement of tritium from the canal to the water table. Results indicate that recirculated canal water has not had a significant effect on the breakthrough of tritium at RNM-2S.

Ross, W.C.; Wheatcraft, S.W.

1994-09-01T23:59:59.000Z

424

Superfluidity at the BEC-BCS crossover in two-dimensional Fermi gases with population and mass imbalance  

Science Journals Connector (OSTI)

We explore the zero-temperature phase behavior of a two-dimensional two-component atomic Fermi gas with population and mass imbalance in the regime of the BEC-BCS crossover. Working in the mean-field approximation, we show that the normal and homogeneous balanced superfluid phases are separated by an inhomogeneous superfluid phase of Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) type. We obtain an analytical expression for the line of continuous transitions separating the normal and inhomogeneous FFLO phases. We further show that the transition from the FFLO phase to the homogeneous balanced superfluid is discontinuous leading to phase separation. If the species have different masses, the superfluid phase is favored when the lighter species is in excess. We explore the implications of these findings for the properties of the two-component Fermi gas in the atomic trap geometry. Finally, we compare and contrast our findings with the predicted phase behavior of the electron-hole bilayer system.

G. J. Conduit; P. H. Conlon; B. D. Simons

2008-05-29T23:59:59.000Z

425

Two-dimensional velocity models for paths from Pahute Mesa and Yucca Flat to Yucca Mountain; Yucca Mountain Project  

SciTech Connect

Vertical acceleration recordings of 21 underground nuclear explosions recorded at stations at Yucca Mountain provide the data for development of three two-dimensional crystal velocity profiles for portions of the Nevada Test Site. Paths from Area 19, Area 20 (both Pahute Mesa), and Yucca Flat to Yucca Mountain have been modeled using asymptotic ray theory travel time and synthetic seismogram techniques. Significant travel time differences exist between the Yucca Flat and Pahute Mesa source areas; relative amplitude patterns at Yucca Mountain also shift with changing source azimuth. The three models, UNEPM1, UNEPM2, and UNEYF1, successfully predict the travel time and amplitude data for all three paths. 24 refs., 34 figs., 8 tabs.

Walck, M.C.; Phillips, J.S.

1990-11-01T23:59:59.000Z

426

Kinetic Monte Carlo Simulation ofKinetic Monte Carlo Simulation of TwoTwo--dimensional Semiconductordimensional Semiconductor  

E-Print Network (OSTI)

­ KMC 2D Growth Model ­ Growth Parameters Dependence of QDs Shape and Distribution · Temperature Parameters Dependence of QDs Shape and Distribution · Temperature ---- T · Surface coverage ---- c · Flux Melissa SunMelissa Sun Peter ChungPeter Chung Computer Modeling and Simulation Group The University

Pan, Ernie

427

Scaling behavior of universal pinch-off in two-dimensional foam Chin-Chang Kuo, and Michael Dennin  

E-Print Network (OSTI)

of significant study and are rele- vant to a wide range of applications such as sprays, droplet formation modes in fluids, the details of which depend on issues including the relative role of viscosity[1 with a relatively large viscosity [9]. For 2D inviscid fluids, simulations and analytic studies indicate

Dennin, Michael

428

Energy-dependent scattering and the Gross-Pitaevskii equation in two-dimensional Bose-Einstein condensates  

Science Journals Connector (OSTI)

We consider many-body effects on particle scattering in one-, two-, and three-dimensional (3D) Bose gases. We show that at T=0 these effects can be modeled by the simpler two-body T matrix evaluated off the energy shell. This is important in 1D and 2D because the two-body T matrix vanishes at zero energy and so mean-field effects on particle energies must be taken into account to obtain a self-consistent treatment of low-energy collisions. Using the off-shell two-body T matrix we obtain the energy and density dependence of the effective interaction in 1D and 2D and the appropriate Gross-Pitaevskii equations for these dimensions. Our results provide an alternative derivation of those of Kolomeisky and co-workers. We present numerical solutions of the Gross-Pitaevskii equation for a 2D condensate of hard-sphere bosons in a trap. We find that the interaction strength is much greater in 2D than for a 3D gas with the same hard-sphere radius. The Thomas-Fermi regime is, therefore, approached at lower condensate populations and the energy required to create vortices is lowered compared to the 3D case.

M. D. Lee; S. A. Morgan; M. J. Davis; K. Burnett

2002-04-10T23:59:59.000Z

429

Two-Dimensional Hydrodynamic Core-Collapse Supernova Simulations with Spectral Neutrino Transport II. Models for Different Progenitor Stars  

E-Print Network (OSTI)

1D and 2D supernova simulations for stars between 11 and 25 solar masses are presented, making use of the Prometheus/Vertex neutrino-hydrodynamics code, which employs a full spectral treatment of the neutrino transport. Multi-dimensional transport aspects are treated by the ``ray-by-ray plus'' approximation described in Paper I. Our set of models includes a 2D calculation for a 15 solar mass star whose iron core is assumed to rotate rigidly with an angular frequency of 0.5 rad/s before collapse. No important differences were found depending on whether random seed perturbations for triggering convection are included already during core collapse, or whether they are imposed on a 1D collapse model shortly after bounce. Convection below the neutrinosphere sets in about 40 ms p.b. at a density above 10**12 g/cm^3 in all 2D models, and encompasses a layer of growing mass as time goes on. It leads to a more extended proto-neutron star structure with accelerated lepton number and energy loss and significantly higher muon and tau neutrino luminosities, but reduced mean energies of the radiated neutrinos, at times later than ~100 ms p.b. In case of an 11.2 solar mass star we find that low (l = 1,2) convective modes cause a probably rather weak explosion by the convectively supported neutrino-heating mechanism after ~150 ms p.b. when the 2D simulation is performed with a full 180 degree grid, whereas the same simulation with 90 degree wedge fails to explode like all other models. This sensitivity demonstrates the proximity of our 2D models to the borderline between success and failure, and stresses the need of simulations in 3D, ultimately without the axis singularity of a polar grid. (abridged)

R. Buras; H. -Th. Janka; M. Rampp; K. Kifonidis

2005-12-07T23:59:59.000Z

430

Pauli matrices and 2D electron gas  

E-Print Network (OSTI)

In the present paper it will be argued that transport in a 2D electron gas can be implemented as 'local hidden instrument based' variables. With this concept of instrumentalism it is possible to explain the quantum correlation, the particle-wave duality and Wheeler's 'backward causation of a particle'. In the case of quantum correlation the spin measuring variant of the Einstein Podolsky and Rosen paradox is studied. In the case of particle-wave duality the system studied is single photon Mach-Zehnder (MZ) interferometry with a phase shift size $\\delta$. The idea that the instruments more or less neutrally may show us the way to the particle will be replaced by the concept of laboratory equipment contributing in an unexpected way to the measurement.

J. F. Geurdes

2012-10-22T23:59:59.000Z

431

Lie symmetries and 2D Material Physics  

E-Print Network (OSTI)

Inspired from Lie symmetry classification, we establish a correspondence between rank two Lie symmetries and 2D material physics. The material unit cell is accordingly interpreted as the geometry of a root system. The hexagonal cells, appearing in graphene like models, are analyzed in some details and are found to be associated with A_2 and G_2 Lie symmetries. This approach can be applied to Lie supersymmetries associated with fermionic degrees of freedom. It has been suggested that these extended symmetries can offer a new way to deal with doping material geometries. Motivated by Lie symmetry applications in high energy physics, we speculate on a possible connection with (p,q) brane networks used in the string theory compactification on singular Calabi-Yau manifolds.

Adil Belhaj; Moulay Brahim Sedra

2014-04-18T23:59:59.000Z

432

2D 3D * iklee)@yonsei.ac.kr  

E-Print Network (OSTI)

1 2012 2D 3D * 0 , 1 , 2 0,2 1 ( 0 skrcjstk, 2 iklee)@yonsei.ac.kr 1 rinthel Science, Yonsei University. 1 Dept. of Information Media, The University of Suwon. 2D 3D . 2D - , 3D (Disparity) 3D . . 1. 3D 3D . 3D 3D [1

Lee, In-Kwon

433

Real time two?dimensional temperature imaging for guidance and monitoring of high?intensity focused ultrasound beams.  

Science Journals Connector (OSTI)

We have recently introduced a fully real time 2?D temperature imaging system using diagnostic ultrasound. A SonixRP is used to collect beamformed M2D mode data with frame rates in the 200–400 fps during the application of pulsed high?intensity focused ultrasound (pHIFU). M2D mode is a modification on the SonixRP allowing for maximizing the number of scanlines per frame for a specified frame rate. This allows for capturing the full range of tissue motions during the application of the pHIFU beams including native motions due to breathing and pulsations radiation forces due to pHIFU and temperature?induced strains. In this paper we demonstrate the use of this image?guidance mode in the control of the pHIFU exposure in real time with millisecond temporal resolution. Results from heating and lesion formation experiments in the hindlimb of nude mice in vivo will be presented. Temperature imaging results during the application of subtherapeutic pHIFU beams before therapeutic pHIFU lesion formation will demonstrate the advantages of this approach in the guidance and dose estimation. In addition temperature imaging of subtherapeutic pHIFU after lesion formation allows for the measurement of changes in tissue properties that may be used as indicators of irreversible tissue damage.

Dalong Liu; John R. Ballard; Alyona Haritonova; Jing Jiang; John C. Bischof; Emad S. Ebbini

2010-01-01T23:59:59.000Z

434

Orientation of a b-Hairpin Antimicrobial Peptide in Lipid Bilayers from Two-Dimensional Dipolar Chemical-Shift Correlation NMR  

E-Print Network (OSTI)

-dimensional (2D) separated-local field (SLF) spectroscopy correlating the 15 N chemical shift with 15 N-1 H and the helical axis, the 2D SLF spectra of multiply 15 N-labeled helical peptides give characteristic wheel

Hong, Mei

435

Using comprehensive two-dimensional gas chromatography to explore the geochemistry of the Santa Barbara oil seeps  

SciTech Connect

The development of comprehensive two-dimensional gas chromatography (GC x GC) has expanded the analytical window for studying complex mixtures like oil. Compared to traditional gas chromatography, this technology separates and resolves at least an order of magnitude more compounds, has a much larger signal to noise ratio, and sorts compounds based on their chemical class; hence, providing highly refined inventories of petroleum hydrocarbons in geochemical samples that was previously unattainable. In addition to the increased resolution afforded by GC x GC, the resulting chromatograms have been used to estimate the liquid vapor pressures, aqueous solubilities, octanol-water partition coefficients, and vaporization enthalpies of petroleum hydrocarbons. With these relationships, powerful and incisive analyses of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment are available. For example, GC x GC retention data has been used to quantitatively deconvolve the effects of phase transfer processes such as water washing and evaporation. In short, the positive attributes of GC x GC-analysis have led to a methodology that has revolutionized the analysis of petroleum hydrocarbons. Overall, this research has opened numerous fields of study on the biogeochemical "?genetics"ť (referred to as petroleomics) of petroleum samples in both subsurface and surface environments. Furthermore, these new findings have already been applied to the behavior of oil at other seeps as well, for petroleum exploration and oil spill studies.

Reddy, Christopher; Nelson, Robert

2013-03-27T23:59:59.000Z

436

Solvent viscosity mismatch between the solute plug and the mobile phase: Considerations in the applications of two-dimensional HPLC  

SciTech Connect

Understanding the nature of viscosity contrast induced flow instabilities is an important aspect in the design of two-dimensional HPLC separations. When the viscosity contrast between the sample plug and the mobile phase is sufficiently large, the phenomenon known as viscous fingering can be induced. Viscous fingering is a flow instability phenomenon that occurs at the interface between two fluids with different viscosities. In liquid chromatography, viscous fingering results in the solute band undergoing a change in form as it enters into the chromatography column. Moreover, even in the absence of viscous fingering, band shapes change shape at low viscosity contrasts. These changes can result in a noticeable change in separation performance, with the result depending on whether the solvent pushing the solute plug has a higher or lower viscosity than the solute plug. These viscosity induced changes become more important as the solute injection volume increases and hence understanding the process becomes critical in the implementation of multidimensional HPLC techniques, since in these techniques the sample injection plug into the second dimension is an order of magnitude greater than in one-dimensional HPLC. This review article assesses the current understanding of the viscosity contrast induced processes as they relate to liquid chromatographic separation behaviour.

Shalliker, R. Andrew [University of Western Sydney, Australia; Guiochon, Georges A [ORNL

2010-01-01T23:59:59.000Z

437

Automated Classification of Stellar Spectra. II: Two-Dimensional Classification with Neural Networks and Principal Components Analysis  

E-Print Network (OSTI)

We investigate the application of neural networks to the automation of MK spectral classification. The data set for this project consists of a set of over 5000 optical (3800-5200 AA) spectra obtained from objective prism plates from the Michigan Spectral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry Draper Catalogue, were used to develop supervised neural network classifiers. We show that neural networks can give accurate spectral type classifications (sig_68 = 0.82 subtypes, sig_rms = 1.09 subtypes) across the full range of spectral types present in the data set (B2-M7). We show also that the networks yield correct luminosity classes for over 95% of both dwarfs and giants with a high degree of confidence. Stellar spectra generally contain a large amount of redundant information. We investigate the application of Principal Components Analysis (PCA) to the optimal compression of spectra. We show that PCA can compress the spectra by a factor of over 30 while retaining essentially all of the useful information in the data set. Furthermore, it is shown that this compression optimally removes noise and can be used to identify unusual spectra.

Coryn A. L. Bailer-Jones; Mike Irwin; Ted von Hippel

1998-03-05T23:59:59.000Z

438

Two-dimensional particle-in-cell Monte Carlo simulation of a miniature inductively coupled plasma source  

SciTech Connect

Two-dimensional axisymmetric particle-in-cell simulations with Monte Carlo collision calculations (PIC-MCC) have been conducted to investigate argon microplasma characteristics of a miniature inductively coupled plasma source with a 5-mm-diameter planar coil, where the radius and length are 5 mm and 6 mm, respectively. Coupling the rf-electromagnetic fields to the plasma is carried out based on a collisional model and a kinetic model. The former employs the cold-electron approximation and the latter incorporates warm-electron effects. The numerical analysis has been performed for pressures in the range 370-770 mTorr and at 450 MHz rf powers below 3.5 W, and then the PIC-MCC results are compared with available experimental data and fluid simulation results. The results show that a considerably thick sheath structure can be seen compared with the plasma reactor size and the electron energy distribution is non-Maxwellian over the entire plasma region. As a result, the distribution of the electron temperature is quite different from that obtained in the fluid model. The electron temperature as a function of rf power is in a reasonable agreement with experimental data. The pressure dependence of the plasma density shows different tendency between the collisional and kinetic model, implying noncollisional effects even at high pressures due to the high rf frequency, where the electron collision frequency is less than the rf driving frequency.

Takao, Yoshinori; Kusaba, Naoki; Eriguchi, Koji; Ono, Kouichi [Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)

2010-11-15T23:59:59.000Z

439

Magnonic band structure, complete bandgap, and collective spin wave excitation in nanoscale two-dimensional magnonic crystals  

SciTech Connect

We present the observation of a complete bandgap and collective spin wave excitation in two-dimensional magnonic crystals comprised of arrays of nanoscale antidots and nanodots, respectively. Considering that the frequencies dealt with here fall in the microwave band, these findings can be used for the development of suitable magnonic metamaterials and spin wave based signal processing. We also present the application of a numerical procedure, to compute the dispersion relations of spin waves for any high symmetry direction in the first Brillouin zone. The results obtained from this procedure have been reproduced and verified by the well established plane wave method for an antidot lattice, when magnetization dynamics at antidot boundaries are pinned. The micromagnetic simulation based method can also be used to obtain iso–frequency contours of spin waves. Iso–frequency contours are analogous of the Fermi surfaces and hence, they have the potential to radicalize our understanding of spin wave dynamics. The physical origin of bands, partial and full magnonic bandgaps have been explained by plotting the spatial distribution of spin wave energy spectral density. Although, unfettered by rigid assumptions and approximations, which afflict most analytical methods used in the study of spin wave dynamics, micromagnetic simulations tend to be computationally demanding. Thus, the observation of collective spin wave excitation in the case of nanodot arrays, which can obviate the need to perform simulations, may also prove to be valuable.

Kumar, D.; Barman, A., E-mail: abarman@bose.res.in [Thematic Unit of Excellence on Nanodevice Technology, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); K?os, J. W.; Krawczyk, M. [Faculty of Physics, Adam Mickiewicz University in Poznan, Umultowska 85, Pozna? 61-614 (Poland)

2014-01-28T23:59:59.000Z

440

Apparatus and method for heterodyne-generated two-dimensional detector array using a single element detector  

DOE Patents (OSTI)

Apparatus and method for heterodyne-generated, two-dimensional detector array using a single detector. Synthetic-array heterodyne detection, permits a single-element optical detector to behave as though it were divided into an array of separate heterodyne detector elements. A fifteen-element synthetic array has successfully been experimentally realized on a single-element detector, permitting all of the array elements to be read out continuously and in parallel from one electrical connection. A CO.sub.2 laser and a single-element HgCdTe photodiode are employed. A different heterodyne local oscillator frequency is incident upon the spatially resolvable regions of the detector surface. Thus, different regions are mapped to different heterodyne beat frequencies. One can determine where the photons were incident on the detector surface even though a single electrical connection to the detector is used. This also prevents the destructive interference that occurs when multiple speckles are imaged (similar to spatial diversity), In coherent LIDAR this permits a larger field of view. An acoustooptic modulator generates the local oscillator frequencies and can achieve adequate spatial separation of optical frequencies of the order of a megahertz apart.

Strauss, Charlie E. (Santa Fe, NM)

1997-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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441

Apparatus and method for heterodyne-generated two-dimensional detector array using a single element detector  

DOE Patents (OSTI)

Apparatus and method are disclosed for heterodyne-generated, two-dimensional detector array using a single detector. Synthetic-array heterodyne detection, permits a single-element optical detector to behave as though it were divided into an array of separate heterodyne detector elements. A fifteen-element synthetic array has successfully been experimentally realized on a single-element detector, permitting all of the array elements to be read out continuously and in parallel from one electrical connection. A CO{sub 2} laser and a single-element HgCdTe photodiode are employed. A different heterodyne local oscillator frequency is incident upon the spatially resolvable regions of the detector surface. Thus, different regions are mapped to different heterodyne beat frequencies. One can determine where the photons were incident on the detector surface even though a single electrical connection to the detector is used. This also prevents the destructive interference that occurs when multiple speckles are imaged (similar to spatial diversity), In coherent LIDAR this permits a larger field of view. An acoustooptic modulator generates the local oscillator frequencies and can achieve adequate spatial separation of optical frequencies of the order of a megahertz apart. 4 figs.

Strauss, C.E.

1997-11-18T23:59:59.000Z

442

Unitary limit and quantum interference effect in disordered two-dimensional crystals with nearly half-filled bands  

Science Journals Connector (OSTI)

Based on the self-consistent T-matrix approximation, the quantum interference (QI) effects are studied with the diagrammatic technique in weakly disordered two-dimensional crystals with nearly half-filled bands. In addition to the usual 0-mode cooperon and diffuson, there exists ?-mode cooperon and diffuson in the unitary limit due to the particle-hole symmetry. The diffusive ? modes are gapped by the deviation from the exactly nested Fermi surface. The conductivity diagrams with the gapped ?-mode cooperon or diffuson are found to give rise to unconventional features of the QI effects. Besides inelastic scattering, thermal fluctuation is also shown to be an important dephasing mechanism in the QI processes related to the diffusive ? modes. In the proximity of the nesting case, a power-law antilocalization effect appears due to the ?-mode diffuson. For large deviation from the nested Fermi surface, this antilocalization effect is suppressed, and the conductivity remains to have the usual logarithmic weak-localization correction contributed by the 0-mode cooperon. As a result, the dc conductivity in the unitary limit becomes a nonmonotonic function of the temperature or the sample size, which is quite different from the prediction of the usual weak-localization theory.

Y. H. Yang; Y. G. Wang; M. Liu; D. Y. Xing

2003-07-29T23:59:59.000Z

443

LIFTING THE VEIL OF DUST FROM NGC 0959: THE IMPORTANCE OF A PIXEL-BASED TWO-DIMENSIONAL EXTINCTION CORRECTION  

SciTech Connect

We present the results of a study of the late-type spiral galaxy NGC 0959, before and after application of the pixel-based dust extinction correction described in Tamura et al. (Paper I). Galaxy Evolution Explorer far-UV, and near-UV, ground-based Vatican Advanced Technology Telescope, UBVR, and Spitzer/Infrared Array Camera 3.6, 4.5, 5.8, and 8.0 {mu}m images are studied through pixel color-magnitude diagrams and pixel color-color diagrams (pCCDs). We define groups of pixels based on their distribution in a pCCD of (B - 3.6 {mu}m) versus (FUV - U) colors after extinction correction. In the same pCCD, we trace their locations before the extinction correction was applied. This shows that selecting pixel groups is not meaningful when using colors uncorrected for dust. We also trace the distribution of the pixel groups on a pixel coordinate map of the galaxy. We find that the pixel-based (two-dimensional) extinction correction is crucial for revealing the spatial variations in the dominant stellar population, averaged over each resolution element. Different types and mixtures of stellar populations, and galaxy structures such as a previously unrecognized bar, become readily discernible in the extinction-corrected pCCD and as coherent spatial structures in the pixel coordinate map.

Tamura, K.; Jansen, R. A.; Windhorst, R. A. [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Eskridge, P. B.; Cohen, S. H., E-mail: ktamura@asu.ed [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States)

2010-06-15T23:59:59.000Z

444

A two-dimensional pseudospectral Hartree-Fock method for low-Z atoms in intense magnetic fields  

E-Print Network (OSTI)

The energy levels of the first few low-lying states of helium and lithium atoms in intense magnetic fields up to $\\approx 10^8-10^9$~T are calculated in this study. A pseudospectral method is employed for the computational procedure. The methodology involves computing the eigenvalues and eigenvectors of the generalized two-dimensional Hartree-Fock partial differential equations for these two- and three-electron systems in a self-consistent manner. The method exploits the natural symmetries of the problem without assumptions of any basis functions for expressing the wave functions of the electrons or the commonly employed adiabatic approximation. It is seen that the results obtained here for a few of the most tightly bound states of each of the atoms, helium and lithium, are in good agreement with findings elsewhere. In this regard, we report new data for two new states of lithium that have not been studied thus far in the literature. It is also seen that the pseudospectral method employed here is considerably more economical, from a computational point of view, than previously employed methods such as a finite-element based approach. The key enabling advantage of the method described here is the short computational times which are on the order of seconds for obtaining accurate results for heliumlike systems.

Anand Thirumalai; Jeremy S. Heyl

2014-04-24T23:59:59.000Z

445

Response to Halatek and Frey: Effective two-dimensional model does account for geometry sensing by self-organized proteins patterns  

E-Print Network (OSTI)

The Min proteins from Escherichia coli can self-organize into traveling waves on supported lipid bilayers. In Proc. Natl. Acad. Sci. USA 109, 15283 (2012) we showed that these waves are guided along the boundaries of membrane patches. We introduced an effective two-dimensional model reproducing the observed patterns. In arXiv:1403.5934v1, Jacob Halatek and Erwin Frey contest the ability of our effective two-dimensional model to describe the dynamics of Min proteins on patterned supported lipid bilayers. We thank Halatek and Frey for their interest in our work and for again highlighting the importance of dimensionality and geometry for pattern formation by the Min proteins. Here we reply in detail to the objections by Halatek and Frey and show that (1) our effective two-dimensional model reproduces the observed patterns on isolated patches and that (2) a three-dimensional version of our model produces similar patterns on square patches.

Mike Bonny; Jakob Schweizer; Martin Loose; Ingolf Mönch; Petra Schwille; Karsten Kruse

2014-06-05T23:59:59.000Z

446

Exact two-dimensional plasma pair-correlation function in the Singwi-Tosi-Land-Sjolander approximation. I. k-space solutions and thermodynamic properties  

Science Journals Connector (OSTI)

The Singwi-Tosi-Land-Sjolander (STLS) nonlinear integral equation for the plasma pair-correlation function g is adapted to two-dimensional one-component plasma (ocp) systems whose Coulombic interactions are characterized by the logarthmic potential. The two-dimensional STLS integral equation has the remarkable property that it can be exactly solved. The resulting expressions for g(k) are extensively analyzed and are shown to be negative definite for all values of k and the coupling strength. The implication here is that in the STLS approximation, the ocp liquid can never undergo a phase transition. Exact expressions for g enable us to evolve exact formulas for the correlation energy and heat capacity. Finally, we demonstrate that the STLS approximation scheme exactly reproduces the correct equation of state for the two-dimensional ocp liquid.

R. Calinon, K. I. Golden, G. Kalman, and D. Merlini

1979-07-01T23:59:59.000Z

447

2D grating simulation for X-ray phase-contrast and dark-field imaging with a Talbot interferometer  

SciTech Connect

Talbot interferometry is a recently developed and an extremely powerful X-ray phase-contrast imaging technique. Besides giving access to ultra-high sensitivity differential phase contrast images, it also provides the dark field image, which is a map of the scattering power of the sample. In this paper we investigate the potentialities of an improved version of the interferometer, in which two dimensional gratings are used instead of standard line grids. This approach allows to overcome the difficulties that might be encountered in the images produced by a one dimensional interferometer. Among these limitations there are the phase wrapping and quantitative phase retrieval problems and the directionality of the differential phase and dark-field signals. The feasibility of the 2D Talbot interferometer has been studied with a numerical simulation on the performances of its optical components under different circumstances. The gratings can be obtained either by an ad hoc fabrication of the 2D structures or by a superposition of two perpendicular linear grids. Through this simulation it has been possible to find the best parameters for a practical implementation of the 2D Talbot interferometer.

Zanette, Irene; Weitkamp, Timm [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble (France); David, Christian; Rutishauser, Simon [Paul Scherrer Insitute, 5232 Villigen PSI (Switzerland)

2010-04-06T23:59:59.000Z

448

Two-dimensional superconformal gravity with the local symmetry supergroups OSP(1?2)×OSP(2?2) and SP(2)×OSP(2?2)  

Science Journals Connector (OSTI)

The algebra of OSP(1?2)×OSP(2?2) is given and all its matter multiplets are constructed. It is shown that only one multiplet can be used to form a two-dimensional superconformal gravity theory. The SP(2)×OSP(2?2) two-dimensional superconformal gravity is also constructed with the normal spin (0,1/2) matter multiplet as well as with a constrained multiplet that transforms nontrivially only under a subgroup of the SP(2)×OSP(2?2) group. These theories are quantized, and some of the consequences of anomalies in the conformal symmetries are analyzed in detail.

J. McCabe

1986-08-15T23:59:59.000Z

449

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions  

Science Journals Connector (OSTI)

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector describing traditional spin-density-wave or spiral magnetic states. These one-electron spinor wave functions have the distinguishing property that they are antiperiodic along a closed path encircling any elementary plaquette of the lattice. This corresponds to a 2? rotation of the internal coordinate frame of the electron as it encircles the plaquette. The possibility of spinor wave functions with spatial antiperiodicity is a direct consequence of the two-valuedness of the internal electronic wave function defined on the space of Euler angles describing its spin. This internal space is the topologically, doubly-connected, group manifold of SO(3). Formally, these antiperiodic wave functions may be described by passing a flux which couples to spin (rather than charge) through each of the elementary plaquettes of the lattice. When applied to the two-dimensional Hubbard model with one electron per site, this new topological magnetic state exhibits a relativistic spectrum for charged, quasiparticle excitations with a suppressed one-electron density of states at the Fermi level.For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number ? associated with the vortex rotation of the background magnetic moment field by a phase angle 2?? along a path encircling the soliton. Such solitons also carry a spin flux of ?? through the plaquette on which they are centered. The ?=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the ?=1 and 2 solitons. The spectrum of localized states is symmetric about E=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

Sajeev John and Andrey Golubentsev

1995-01-01T23:59:59.000Z

450

Phase transitions in the two-dimensional single-ion anisotropic Heisenberg model with long-range interactions  

Science Journals Connector (OSTI)

Abstract In the present work, we investigate the effects of long-range interactions on the phase transitions of a two-dimensional Heisenberg model with single-ion anisotropy at zero and finite temperatures. The Hamiltonian is given by H = ? i ? j J ij ( S i x S j x + S i y S j y + ? S i z S j z ) + D ? i ( S i z ) 2 , where J ij = ? J | r j ? r i | ? p ( p ? 3 ) is a long-range ferromagnetic interaction ( J > 0 ) , 0 ? ? ? 1 is an anisotropic constant and D is the single-ion anisotropic constant. It is well-known that the single-ion anisotropy D creates a competition between an ordered state (favored by the exchange interaction) and a disordered state, even at zero temperature. For small values of D, the system has a spontaneous magnetization m z ? 0 , while in the large-D phase mz=0 because a state with ? S z ? ? 0 is energetically unfavorable. Therefore a phase transition takes a place in some critical value Dc due to quantum fluctuations. For systems with short-range interaction Dc?6 J (depending of ? constant) but in our model we have found larger values of D due to the higher cost to flip a spin. Since low-dimensional magnetic systems with long range interaction can be ordered at finite temperature, we also have analyzed the thermal phase transitions (similar to the BKT transition). The model has been studied by using a Schwinger boson formalism as well as the self-consistent harmonic approximation (SCHA) and both methods provide according results.

A.R. Moura

2014-01-01T23:59:59.000Z

451

Two-dimensional lattice-Boltzmann simulation of size exclusion effects during colloidal transport in pore-scale flow channels  

SciTech Connect

Experimental investigations indicate that colloidal particles are transported more rapidly than soluble tracers through porous and fractured media. The prevailing in- terpretation is that colloids are confined to larger pores, larger channels or regions within channels where flow is more rapid. A lattice-Boltzmann modeling approach was used to analyze how size-dependent exclusion from low velocity fields in chan- nels can lead to accelerated transport of an inert non-Brownian colloidal particle in low-Reynolds number flows in two-dimensional smooth-walled and rough-walled channels. The simulations were based on pore-scale particle-fluid hydrodynamics without direct interactions between the particle surface and the channel surface. For the smooth-walled channel, the particle consistently drifted towards the center- line and traveled faster than the average fluid velocity. In rough-walled channels, differences between the velocity of the particle and the average velocity of the fluid displayed stronger variations than in the smooth-walled channel. Surface roughness increased the residence time of the particle in the flow channel and modified its trajectories differently in each flow regime. The final position (at the channel exit) and the average velocity of the particle in the rough-walled flow channel were sen- sitive to the release location of the particle, the flow strength, and the magnitude of the surface roughness in the channel. Under all flow conditions investigated, a large particle had a longer residence time in rough-walled flow channels, but drifted Preprint submitted to Elsevier Science 19 September 2006 toward the centerline more strongly than a smaller particle as it approached the channel walls.

H. Basagaoglu; Meakin, P.; S. Succi; Redden, George D; T.R. Ginn

2008-05-01T23:59:59.000Z

452

Photorefractive holography for 2D mechanical vibrations measurement  

Science Journals Connector (OSTI)

We report an efficient holographic setup for the real time measurement of 2D mechanical vibration modes in surfaces, based on the time-average holographic interferometry technique...

de Oliveira, Ivan; Frejlich, Jaime

453

Digital Transfer Growth of Patterned 2D Metal Chalcogenides by...  

NLE Websites -- All DOE Office Websites (Extended Search)

for Energy Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation October 28, 2014 (a) Illustration of the digital transfer growth...

454

Self-interfering matter-wave patterns generated by a moving laser obstacle in a two-dimensional Bose-Einstein condensate inside a power trap cut off by box potential boundaries  

SciTech Connect

We report the observation of highly energetic self-interfering matter-wave (SIMW) patterns generated by a moving obstacle in a two-dimensional Bose-Einstein condensate (BEC) inside a power trap cut off by hard-wall box potential boundaries. The obstacle initially excites circular dispersive waves radiating away from the center of the trap which are reflected from hard-wall box boundaries at the edges of the trap. The resulting interference between outgoing waves from the center of the trap and reflected waves from the box boundaries institutes, to the best of our knowledge, unprecedented SIMW patterns. For this purpose we simulated the time-dependent Gross-Pitaevskii equation using the split-step Crank-Nicolson method and the obstacle was modelled by a moving impenetrable Gaussian potential barrier. Various trapping geometries are considered in which the dynamics of the spatial and momentum density, as well as the energy, are considered. The momentum dynamics reveal an oscillatory behavior for the condensate fraction, indicative of excitations out of and de-excitations back into the condensate state. An oscillatory pattern for the energy dynamics reveals the presence of solitons in the system. Some vortex features are also obtained.

Sakhel, Roger R. [Department of Basic Sciences, Faculty of Information Technology, Isra University, Amman 11622 (Jordan); Sakhel, Asaad R. [Department of Applied Sciences, Faculty of Engineering Technology, Al-Balqa Applied University, Amman 11134 (Jordan); Ghassib, Humam B. [Department of Physics, The University of Jordan, Amman 11942 (Jordan)

2011-09-15T23:59:59.000Z

455

IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL. 48, NO. 2, FEBRUARY 2000 517 Image Classification by a Two-Dimensional Hidden  

E-Print Network (OSTI)

, the dependency in two dimensions is reflected simultaneously. The HMM parameters are estimated by the EM Foundation under NSF Grant MIP-931190 and by gifts from Hewlett-Packard, Inc. and SK Telecom, Inc, Stanford University, Stanford, CA 94305 USA (e-mail: jiali@isl.stanford.edu; zaalim

Li, Jia

456

Impurity Profiling of a Chemical Weapon Precursor for Possible Forensic Signatures by Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry and Chemometrics  

Science Journals Connector (OSTI)

Impurity Profiling of a Chemical Weapon Precursor for Possible Forensic Signatures by Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry and Chemometrics ... DMMP is a widely used flame retardant(6, 7) that is listed as a schedule 2 compound by the Chemical Weapons Convention (CWC) because it is a well-known CW precursor and not produced in large quantities for commercial purposes. ...

Jamin C. Hoggard; Jon H. Wahl; Robert E. Synovec; Gary M. Mong; Carlos G. Fraga

2009-12-16T23:59:59.000Z

457

Self-organization of bouncing oil drops: Two-dimensional lattices and spinning clusters Suzanne I. Lieber, Melissa C. Hendershott, Apichart Pattanaporkratana, and Joseph E. Maclennan  

E-Print Network (OSTI)

Self-organization of bouncing oil drops: Two-dimensional lattices and spinning clusters Suzanne I Received 16 October 2006; published 18 May 2007 Multiple oil drops bouncing on the surface of a vertically vibrating bath of the same oil exhibit self- organization behavior in two dimensions S. Protière, Y. Couder

Weeks, Eric R.

458

The 19th international conference on Electronic Properties of Two-Dimensional Systems (EP2DS19) and the 15th  

E-Print Network (OSTI)

2010 The 19th international conference on Electronic Properties of Two-Dimensional Systems (EP2DS19) and the 15th conference on Modulated Semiconductor Structures (MSS 15). July 25-29, 2011 Tallahassee, FL EP2DS19/MSS15Scope of conferences EP2DS emphasizes the fundamental physics, including transport

Weston, Ken

459

Bandgap Engineering in Disordered Graphene Two-dimensional atomic crystals attract attention due to their unique low-dimensional electron transport  

E-Print Network (OSTI)

Bandgap Engineering in Disordered Graphene ­Two-dimensional atomic crystals attract attention due-gap semiconductor graphene. The relativistic Dirac dispersion of electrons in graphene leads to an anomalous four large compared to electron Fermi wavelength. In high magnetic fields, the cleanest graphene samples

Weston, Ken

460

Analysis of two-dimensional high-energy photoelectron momentum distributions in the single ionization of atoms by intense laser pulses  

E-Print Network (OSTI)

, using longer pulses at lower intensities. The energy spectra above 4Up, where Up is the ponderomotive energy, have been found to vary rapidly with small changes in laser intensities 10,11 when laser pulseAnalysis of two-dimensional high-energy photoelectron momentum distributions in the single

Lin, Chii-Dong

Note: This page contains sample records for the topic "two-dimensional 2d reflection" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Glass transition of two-dimensional binary soft-disk mixtures with large size ratios Rei Kurita* and Eric R. Weeks  

E-Print Network (OSTI)

Glass transition of two-dimensional binary soft-disk mixtures with large size ratios Rei Kurita the glass transition. The "fragility" quantifies how sensitively the relaxation time scale depends.20.Ja, 64.60.My I. INTRODUCTION Many liquids can form glasses if they are cooled rapidly, and glassy

Weeks, Eric R.

462

ABSTRACT FINAL ID: SM13A-2029 TITLE: Particle-in-Cell Simulations of Two-dimensional Bernstein-Greene-Kruskal (BGK)  

E-Print Network (OSTI)

ABSTRACT FINAL ID: SM13A-2029 TITLE: Particle-in-Cell Simulations of Two-dimensional Bernstein, University of Alaska Fairbanks, Fairbanks, AK, United States. Title of Team: ABSTRACT BODY: Electrostatic with modulations having frequency of the order of electron cyclotron frequency. This work is supported

Ng, Chung-Sang

463

Design and development of a silicon-segmented detector for 2D dose measurements in radiotherapy  

Science Journals Connector (OSTI)

Modern radiotherapy treatment techniques, such as intensity Modulated Radiation Therapy (IMRT) and protontherapy, require detectors with specific features, usually not available in conventional dosimeters. IMRT dose measurements, for instance, must face non-uniform beam fluences as well as a time-varying dose rate. Two-dimensional detectors present a great interest for dosimetry in beams with steep dose gradients, but they must satisfy a number of requirements and, in particular, they must exhibit high spatial resolution. With the aim of developing a dosimetric system adequate for 2D pre-treatment dose verifications, we designed a modular dosimetric device based on a monolithic silicon-segmented module. State and results of this work in progress are described in this article. The first 441 pixels, 6.29×6.29 cm2 silicon module has been produced by ion implantation on a 50 ?m thick p-type epitaxial layer. This sensor has been connected to a discrete readout electronics performing current integration, and has been tested with satisfactory results. In the final configuration, nine silicon modules will be assembled together to cover an area close to 20×20 cm2 with 3969 channels. In this case, the readout electronics will be based on an ASIC capable to read 64 channels by performing current-to-frequency conversion.

David Menichelli; Mara Bruzzi; Marta Bucciolini; Cinzia Talamonti; Marta Casati; Livia Marrazzo; Mauro Tesi; Claudio Piemonte; Alberto Pozza; Nicola Zorzi; Mirko Brianzi; Antonio De Sio

2007-01-01T23:59:59.000Z

464

Two-dimensional simulations of thermonuclear burn in ignition-scale inertial confinement fusion targets under compressed axial magnetic fields  

SciTech Connect

We report for the first time on full 2-D radiation-hydrodynamic implosion simulations that explore the impact of highly compressed imposed magnetic fields on the ignition and burn of perturbed spherical implosions of ignition-scale cryogenic capsules. Using perturbations that highly convolute the cold fuel boundary of the hotspot and prevent ignition without applied fields, we impose initial axial seed fields of 20–100 T (potentially attainable using present experimental methods) that compress to greater than 4 × 10{sup 4} T (400 MG) under implosion, thereby relaxing hotspot areal densities and pressures required for ignition and propagating burn by ?50%. The compressed field is high enough to suppress transverse electron heat conduction, and to allow alphas to couple energy into the hotspot even when highly deformed by large low-mode amplitudes. This might permit the recovery of ignition, or at least significant alpha particle heating, in submarginal capsules that would otherwise fail because of adverse hydrodynamic instabilities.

Perkins, L. J.; Logan, B. G.; Zimmerman, G. B.; Werner, C. J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2013-07-15T23:59:59.000Z

465

Impacts of elevation data spatial resolution on two-dimensional dam break flood simulation and consequence assessment  

SciTech Connect

A grid resolution sensitivity analysis using a two-dimensional flood inundation model has been presented in this paper. Simulations for 6 dam breaches located randomly in the United States were run at 10,30,60,90, and 120 meter resolutions. The dams represent a range of topographic conditions, ranging from 0% slope to 1.5% downstream of the dam. Using 10 meter digital elevation model (DEM) simulation results as the baseline, the coarser simulation results were compared in terms of flood inundation area, peak depths, flood wave travel time, daytime and nighttime population in flooded area, and economic impacts. The results of the study were consistent with previous grid resolution studies in terms of inundated area, depths, and velocity impacts. The results showed that as grid resolution is decreased, the relative fit of inundated area between the baseline and coarser resolution decreased slightly. This is further characterized by increasing over prediction as well as increasing under prediction with decreasing resolution. Comparison of average peak depths showed that depths generally decreased as resolution decreased, as well as the velocity. It is, however, noted that the trends in depth and velocity showed less consistency than the inundation area metrics. This may indicate that for studies in which velocity and depths must be resolved more accurately (urban environments when flow around buildings is important in the calculation of drag effects), higher resolution DEM data should be used. Perhaps the most significant finding from this study is the perceived insensitivity of socio-economic impacts to grid resolution. The difference in population at risk (PAR) and economic cost generally remained within 10% of the estimated impacts using the high resolution DEM. This insensitivity has been attributed to over estimated flood area and associated socio-economic impacts compensating for under estimated flooded area and associated socio-economic impacts. The United States has many dams that are classified as high-hazard potential that need an emergency action plan (EAP). It has been found that the development of EAPs for all high-hazard dams is handicapped due to funding limitations. The majority of the cost associated with developing an EAP is determining the flooded area. The results of this study have shown that coarse resolution dam breach studies can be used to provide an acceptable estimate of the inundated area and economic impacts, with very little computational cost. Therefore, the solution to limited funding may be to perform coarse resolution dam breach studies on high-hazard potential dams and use the results to help prioritize the order in which detailed EAPs should be developed.

Judi, David R [Los Alamos National Laboratory; Mcpherson, Timothy N [Los Alamos National Laboratory; Burian, Steven J [UNIV OF UTAH

2009-01-01T23:59:59.000Z

466

Spin and charge dynamics of the ferromagnetic and antiferromagnetic two-dimensional half-filled Kondo lattice model  

Science Journals Connector (OSTI)

We present a detailed numerical study of ground state and finite temperature spin and charge dynamics of the two-dimensional Kondo lattice model with hopping t and exchange J. Our numerical results stem from auxiliary field quantum Monte Carlo simulations formulated in such a way that the sign problem is absent at half-band filling thus allowing us to reach lattice sizes up to 12×12. At T=0 and antiferromagnetic couplings J>0 the competition between the Ruderman-Kittel-Kasuya-Yosida interaction and the Kondo effect triggers a quantum phase transition between antiferromagnetically ordered and magnetically disordered insulators: Jc/t=1.45±0.05. At J0, the single-particle spectral function A(k?,?) shows a dispersion relation following that of hybridized bands as obtained in the noninteracting periodic Anderson model. In the ordered phase this feature is supplemented by shadows, thus allowing an interpretation in terms of the coexistence of Kondo screening and magnetic ordering. In contrast, at J<0 the single-particle dispersion relation follows that of noninteracting electrons in a staggered external magnetic field. At finite temperatures spin TS and charge TC scales are defined by locating the maximum in the charge and spin uniform susceptibilities. For weak to intermediate couplings, TS marks the onset of antiferromagnetic fluctuations—as observed by a growth of the staggered spin susceptibility—and follows a J2 law. At strong couplings TS scales as J. On the other hand TC scales as J both in the weak- and strong-coupling regime. At and slightly below TC we observe (i) the onset of screening of the magnetic impurities, (ii) a rise in the resistivity as a function of decreasing temperature, (iii) a dip in the integrated density of states at the Fermi energy, and finally (iv) the occurrence of hybridized bands in A(k?,?). It is shown that in the weak-coupling limit, the charge gap of order J is formed only at TS and is hence of magnetic origin. The specific heat shows a two-peak structure. The low-temperature peak follows TS and is hence of magnetic origin. Our results are compared to various mean-field theories.

S. Capponi and F. F. Assaad

2001-03-30T23:59:59.000Z

467

CFD Modelling of Particle Mixtures in a 2D CFB  

Science Journals Connector (OSTI)

The capability of Fluent 6.2.16 to simulate particle mixtures in a laboratory scale 2D circulating fluidized bed (CFB) unit has been tested. In the ... 40 cm wide and 3 m high 2D CFB was modeled using a grid with...

M. Seppälä; S. Kallio

2010-01-01T23:59:59.000Z

468

P2Q2Iso2D = 2D ISOPARAMETRIC FEM IN MATLAB S. BARTELS, C. CARSTENSEN  

E-Print Network (OSTI)

P2Q2Iso2D = 2D ISOPARAMETRIC FEM IN MATLAB S. BARTELS, C. CARSTENSEN , AND A. HECHT Abstract. A short Matlab implementation realizes a flexible isoparametric finite element method up to quadratic a short Matlab implementation of this finite element method for the Laplace equation in two dimensions

Bartels, Soeren

469

OECD/MCCI 2-D Core Concrete Interaction (CCI) tests : final report February 28, 2006.  

SciTech Connect

Although extensive research has been conducted over the last several years in the areas of Core-Concrete Interaction (CCI) and debris coolability, two important issues warrant further investigation. The first issue concerns the effectiveness of water in terminating a CCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. This safety issue was investigated in the EPRI-sponsored Melt Attack and Coolability Experiments (MACE) program. The approach was to conduct large scale, integral-type reactor materials experiments with core melt masses ranging up to two metric tons. These experiments provided unique, and for the most part repeatable, indications of heat transfer mechanism(s) that could provide long term debris cooling. However, the results did not demonstrate definitively that a melt would always be completely quenched. This was due to the fact that the crust anchored to the test section sidewalls in every test, which led to melt/crust separation, even at the largest test section lateral span of 1.20 m. This decoupling is not expected for a typical reactor cavity, which has a span of 5-6 m. Even though the crust may mechanically bond to the reactor cavity walls, the weight of the coolant and the crust itself is expected to periodically fracture the crust and restore contact with the melt. Although crust fracturing does not ensure that coolability will be achieved, it nonetheless provides a pathway for water to recontact the underlying melt, thereby allowing other debris cooling mechanisms to proceed. A related task of the current program, which is not addressed in this particular report, is to measure crust strength to check the hypothesis that a corium crust would not be strong enough to sustain melt/crust separation in a plant accident. The second important issue concerns long-term, two-dimensional concrete ablation by a prototypic core oxide melt. As discussed by Foit the existing reactor material database for dry cavity conditions is solely one-dimensional. Although the MACE Scoping Test was carried out with a two-dimensional concrete cavity, the interaction was flooded soon after ablation was initiated to investigate debris coolability. Moreover, due to the scoping nature of this test, the apparatus was minimally instrumented and therefore the results are of limited value from the code validation viewpoint. Aside from the MACE program, the COTELS test series also investigated 2-D CCI under flooded cavity conditions. However, the input power density for these tests was quite high relative to the prototypic case. Finally, the BETA test series provided valuable data on 2-D core concrete interaction under dry cavity conditions, but these tests focused on investigating the interaction of the metallic (steel) phase with concrete. Due to these limitations, there is significant uncertainty in the partition of energy dissipated for the ablation of concrete in the lateral and axial directions under dry cavity conditions for the case of a core oxide melt. Accurate knowledge of this 'power split' is important in the evaluation of the consequences of an ex-vessel severe accident; e.g., lateral erosion can undermine containment structures, while axial erosion can penetrate the basemat, leading to ground contamination and/or possible containment bypass. As a result of this uncertainty, there are still substantial differences among computer codes in the prediction of 2-D cavity erosion behavior under both wet and dry cavity conditions. In light of the above issues, the OECD-sponsored Melt Coolability and Concrete Interaction (MCCI) program was initiated at Argonne National Laboratory. The project conducted reactor materials experiments and associated analysis to achieve the following technical objectives: (1) resolve the ex-vessel debris coolability issue through a program that focused on providing both confirmatory evidence and test data for the coolability mechanisms identified in MACE integral effects tests, and (2) address remaining uncertainties relat

Farmer, M. T.; Lomperski, S.; Kilsdonk, D. J.; Aeschlimann, R. W.; Basu, S. (Nuclear Engineering Division); (NRC)

2011-05-23T23:59:59.000Z

470

The simulation of 3D microcalcification clusters in 2D digital mammography and breast tomosynthesis  

SciTech Connect

Purpose: This work proposes a new method of building 3D models of microcalcification clusters and describes the validation of their realistic appearance when simulated into 2D digital mammograms and into breast tomosynthesis images. Methods: A micro-CT unit was used to scan 23 breast biopsy specimens of microcalcification clusters with malignant and benign characteristics and their 3D reconstructed datasets were segmented to obtain 3D models of microcalcification clusters. These models were then adjusted for the x-ray spectrum used and for the system resolution and simulated into 2D projection images to obtain mammograms after image processing and into tomographic sequences of projection images, which were then reconstructed to form 3D tomosynthesis datasets. Six radiologists were asked to distinguish between 40 real and 40 simulated clusters of microcalcifications in two separate studies on 2D mammography and tomosynthesis datasets. Receiver operating characteristic (ROC) analysis was used to test the ability of each observer to distinguish between simulated and real microcalcification clusters. The kappa statistic was applied to assess how often the individual simulated and real microcalcification clusters had received similar scores (''agreement'') on their realistic appearance in both modalities. This analysis was performed for all readers and for the real and the simulated group of microcalcification clusters separately. ''Poor'' agreement would reflect radiologists' confusion between simulated and real clusters, i.e., lesions not systematically evaluated in both modalities as either simulated or real, and would therefore be interpreted as a success of the present models. Results: The area under the ROC curve, averaged over the observers, was 0.55 (95% confidence interval [0.44, 0.66]) for the 2D study, and 0.46 (95% confidence interval [0.29, 0.64]) for the tomosynthesis study, indicating no statistically significant difference between real and simulated lesions (p > 0.05). Agreement between allocated lesion scores for 2D mammography and those for the tomosynthesis series was poor. Conclusions: The realistic appearance of the 3D models of microcalcification clusters, whether malignant or benign clusters, was confirmed for 2D digital mammography images and the breast tomosynthesis datasets; this database of clusters is suitable for use in future observer performance studies related to the detectability of microcalcification clusters. Such studies include comparing 2D digital mammography to breast tomosynthesis and comparing different reconstruction algorithms.

Shaheen, Eman; Van Ongeval, Chantal; Zanca, Federica; Cockmartin, Lesley; Marshall, Nicholas; Jacobs, Jurgen; Young, Kenneth C.; Dance, David R.; Bosmans, Hilde [Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium); National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, GU2 7XX (United Kingdom); Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium)

2011-12-15T23:59:59.000Z

471

High precision two-dimensional strain mapping in semiconductor devices using nanobeam electron diffraction in the transmission electron microscope  

SciTech Connect

A classical method used to characterize the strain in modern semiconductor devices is nanobeam diffraction (NBD) in the transmission electron microscope. One challenge for this method lies in the fact that the smaller the beam becomes, the more difficult it becomes to analyze the resulting diffraction spot pattern. We show that a carefully designed fitting algorithm enables us to reduce the sampling area for the diffraction patterns on the camera chip dramatically (?1/16) compared to traditional settings without significant loss of precision. The resulting lower magnification of the spot pattern permits the presence of an annular dark field detector, which in turn makes the recording of images for drift correction during NBD acquisition possible. Thus, the reduced sampling size allows acquisition of drift corrected NBD 2D strain maps of up to 3000 pixels while maintaining a precision of better than 0.07%. As an example, we show NBD strain maps of a modern field effect transistor (FET) device. A special filtering feature used in the analysis makes it is possible to measure strain in silicon devices even in the presence of other crystalline materials covering the probed area, which is important for the characterization of the next generation of devices (Fin-FETs).

Baumann, Frieder H., E-mail: fhbauman@us.ibm.com [IBM Microelectronics Division, 2070 Route 52, Hopewell Junction, New York 12533 (United States)

2014-06-30T23:59:59.000Z

472

New results of ultra-low temperature experiments in the second Landau level of a two-dimensional electron system.  

SciTech Connect

In the second Landau level around {nu} = 5/2 filling of an extremely high quality 2D electron system and at temperatures T down to 9 mK we observe a very strong even-denominator fractional quantum Hall effect at Landau level filling {nu} = 5/2 and its energy gap is large and {Delta} {approx} 0.45 K. A clear FQHE state is seen at {nu} = 2+2/5, with well-quantized R{sub xy}. A novel, even denominator FQHE state at {nu} = 2+3/8 seems to develop, as deduced from the T-dependence of dR{sub xy}/dB. In addition, four fully developed re-entrant integral quantum Hall effect (RIQHE) states are also observed. At low temperatures, the wide RIQHE plateau around at {nu} = 2+2/7 is interrupted by a dip, indicating an additional reentrance. Finally, the tilted magnetic field experiment at an ultra-low temperature of 10 mK was carried out to examine the spin-polarization of the {nu} = 5/2 FQHE state.

Pan, Wei; Vicente, C. (University of Florida); Stormer, H. L. (Columbia University); Sullivan, N. S. (University of Florida); Xia, J. S. (University of Florida); Adams, E. D. (University of Florida); West, Ken W. (Bell Labs, Lucent Technologies); Tsui, Daniel Chee (Princeton University, Princeton, NJ); Pfeiffer, Loren N. (Bell Labs, Lucent Technologies); Baldwin, K. W. (Bell Labs, Lucent Technologies)

2003-07-01T23:59:59.000Z

473

Comparison of 2D and 3D gamma analyses  

SciTech Connect

Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must be noted that clinical 2D versus 3D datasets may have additional differences—for example, if 2D measurements are made with a different dosimeter than 3D measurements. Factors such as inherent dosimeter differences may be an important additional consideration to the extra dimension of available data that was evaluated in this study.

Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F., E-mail: sfkry@mdanderson.org [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030 (United States); Bosca, Ryan [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030 (United States)] [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030 (United States); O’Daniel, Jennifer [Department of Radiation Oncology, Duke University, Durham, North Carolina 27705 (United States)] [Department of Radiation Oncology, Duke University, Durham, North Carolina 27705 (United States)

2014-02-15T23:59:59.000Z

474

Characterization of Volatile Compounds of Indian Cress Absolute by GC-Olfactometry/VIDEO-Sniff and Comprehensive Two-Dimensional Gas Chromatography  

Science Journals Connector (OSTI)

Characterization of Volatile Compounds of Indian Cress Absolute by GC-Olfactometry/VIDEO-Sniff and Comprehensive Two-Dimensional Gas Chromatography ... During the sniffing sessions, the sniffers were instructed (a) to signal each odor perceived by pressing a push button for as long as the odor lasted, (b) to describe the odors orally, and (c) to quantify their intensity on a five-point scale (2). ...

Katharina Breme; Pascal Tournayre; Xavier Fernandez; Uwe J. Meierhenrich; Hugues Brevard; Daniel Joulain; Jean Louis Berdague?

2009-11-18T23:59:59.000Z

475

Multi-locality and fusion rules on the generalized structure functions in two-dimensional and three-dimensional Navier-Stokes turbulence  

E-Print Network (OSTI)

Using the fusion rules hypothesis for three-dimensional and two-dimensional Navier-Stokes turbulence, we generalize a previous non-perturbative locality proof to multiple applications of the nonlinear interactions operator on generalized structure functions of velocity differences. The resulting cross-terms pose a new challenge requiring a new argument and the introduction of a new fusion rule that takes advantage of rotational symmetry.

Eleftherios Gkioulekas

2014-10-23T23:59:59.000Z

476

An analog computer study of the transition from fully developed turbulent smooth wall flow to fully developed turbulent rough wall flow in a two-dimensional channel  

E-Print Network (OSTI)

investigation of the change in the boundary layer in a two-dimensional flew chamber caused by a sudden change 1n wall shear stress. Jacobs first attempted to sol~e the boundary layer equation 1n the d1rection of motion by using finite differences..., Jacobs calculated shear stress dis- tzibutions. He then developed an empirical equation for his calculated shear stress, which varied between the linearly smooth and the linearly rough distributions ~ Clauser (2) in 1956 reported an investigation...

Sheppard, Donald Max

2012-06-07T23:59:59.000Z

477

Optoelectronics of 2D Materials | MIT-Harvard Center for Excitonics  

NLE Websites -- All DOE Office Websites (Extended Search)

University of Washington focuses on creation, control, and understanding of novel optoelectronic devices based on two-dimensional quantum materials. Selected awards include DAPRA...

478

2D Ising model for hydrated protein surfaces  

Science Journals Connector (OSTI)

To understand the nature of the glassy dielectric relaxation recently observed in hydrated protein powders, we model the protein surface as a 2D Ising square net, and identify frustration at the...

G. Careri

479

Ising-Bloch transition in 2D degenerate wave mixing  

Science Journals Connector (OSTI)

We show experimentally and theoretically the existence of a 2D Ising-Bloch transition in the field generated by degenerate four wave mixing in a BaTiO3-resonator.

Larionova, Yevgeniya; Peschel, Ulf; Esteban-Martin, Adolfo; Weiss, Carl Otto

480

Unfolding Square Root Singularities in the 2D Boussinesq Equations  

E-Print Network (OSTI)

Unfolding Square Root Singularities in the 2D Boussinesq Equations Russel Caflisch October 13 in the complex plane for Boussinesq. 1 Boussineq Equations The Boussinesq equations in stream function

Soatto, Stefano

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481

Tripyrrylmethane based 2D porous structure for hydrogen storage  

Science Journals Connector (OSTI)

The key to hydrogen storage is to design new materials with light ... explored Ti-tripyrrylmethane based 2D porous structure for hydrogen storage using density functional theory. We have found ... and the exposed...

Xiao Zhou ??; Jian Zhou ??; Qiang Sun ??

2011-06-01T23:59:59.000Z

482

4d/2d correspondence : instantons and W-algebras.  

E-Print Network (OSTI)

?? In this thesis, we study the 4d/2d correspondence of Alday-Gaiotto-Tachikawa, which relates the class of 4-dimensional N=2 gauge theories (theories of class S) to… (more)

Song, Jaewon

2012-01-01T23:59:59.000Z

483

The Branching of Graphs in 2-d Quantum Gravity  

E-Print Network (OSTI)

The branching ratio is calculated for three different models of 2d gravity, using dynamical planar phi-cubed graphs. These models are pure gravity, the D=-2 Gaussian model coupled to gravity and the single spin Ising model coupled to gravity. The ratio gives a measure of how branched the graphs dominating the partition function are. Hence it can be used to estimate the location of the branched polymer phase for the multiple Ising model coupled to 2d gravity.

M. G. Harris

1996-07-16T23:59:59.000Z