FireStem2D A Two-Dimensional Heat Transfer Model for Simulating Tree Stem Injury in Fires
FireStem2D A Two-Dimensional Heat Transfer Model for Simulating Tree Stem Injury in Fires, et al. (2013) FireStem2D A Two-Dimensional Heat Transfer Model for Simulating Tree Stem Injury
Water Dynamics in Salt Solutions Studied with Ultrafast Two-Dimensional Infrared (2D IR)
Fayer, Michael D.
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
Bill2d -- a software package for classical two-dimensional Hamiltonian systems
Solanpää, Janne; Räsänen, Esa
2015-01-01T23:59:59.000Z
We present Bill2d, a modern and efficient C++ package for classical simulations of two-dimensional Hamiltonian systems. Bill2d can be used for various billiard and diffusion problems with one or more charged particles with interactions, different external potentials, an external magnetic field, periodic and open boundaries, etc. The software package can also calculate many key quantities in complex systems such as Poincar\\'e sections, survival probabilities, and diffusion coefficients. While aiming at a large class of applicable systems, the code also strives for ease-of-use, efficiency, and modularity for the implementation of additional features. The package comes along with a user guide, a developer's manual, and a documentation of the application program interface (API).
Embrechts, M.J.; Dudziak, D.J.; Urban, W.T.
1983-01-01T23:59:59.000Z
Sensitivity and uncertainty analyses implement the information obtained from a transport code by providing a reasonable estimate for the uncertainty of a particular design parameter and a better understanding of the nucleonics involved. The toroidal geometry of many fusion devices motivates a two-dimensional calculation capability. A two-dimensional cross-section and secondary energy distribution (SED) sensitivity and uncertainty analysis code, SENSIT-2D, has been developed that allows modeling of a toroidal geometry. Two-dimensional and one-dimensional sensitivity analyses for the heating and the copper d.p.a. of the TF coil for a conceptual FED blanket/shield design were performed. The uncertainties from the two-dimensional analysis are of the same order of magnitude as those obtained from the one-dimensional study. The largest uncertainties were caused by the cross-section covariances for chromium.
2D Seismic Reflection Data across Central Illinois
Smith, Valerie; Leetaru, Hannes
2014-09-30T23:59:59.000Z
In a continuing collaboration with the Midwest Geologic Sequestration Consortium (MGSC) on the Evaluation of the Carbon Sequestration Potential of the Cambro-Ordovician Strata of the Illinois and Michigan Basins project, Schlumberger Carbon Services and WesternGeco acquired two-dimensional (2D) seismic data in the Illinois Basin. This work included the design, acquisition and processing of approximately 125 miles of (2D) seismic reflection surveys running west to east in the central Illinois Basin. Schlumberger Carbon Services and WesternGeco oversaw the management of the field operations (including a pre-shoot planning, mobilization, acquisition and de-mobilization of the field personnel and equipment), procurement of the necessary permits to conduct the survey, post-shoot closure, processing of the raw data, and provided expert consultation as needed in the interpretation of the delivered product. Three 2D seismic lines were acquired across central Illinois during November and December 2010 and January 2011. Traversing the Illinois Basin, this 2D seismic survey was designed to image the stratigraphy of the Cambro-Ordovician sections and also to discern the basement topography. Prior to this survey, there were no regionally extensive 2D seismic data spanning this section of the Illinois Basin. Between the NW side of Morgan County and northwestern border of Douglas County, these seismic lines ran through very rural portions of the state. Starting in Morgan County, Line 101 was the longest at 93 miles in length and ended NE of Decatur, Illinois. Line 501 ran W-E from the Illinois Basin – Decatur Project (IBDP) site to northwestern Douglas County and was 25 miles in length. Line 601 was the shortest and ran N-S past the IBDP site and connected lines 101 and 501. All three lines are correlated to well logs at the IBDP site. Originally processed in 2011, the 2D seismic profiles exhibited a degradation of signal quality below ~400 millisecond (ms) which made interpretation of the Mt. Simon and Knox sections difficult. The data quality also gradually decreased moving westward across the state. To meet evolving project objectives, in 2012 the seismic data was re-processed using different techniques to enhance the signal quality thereby rendering a more coherent seismic profile for interpreters. It is believed that the seismic degradation could be caused by shallow natural gas deposits and Quaternary sediments (which include abandoned river and stream channels, former ponds, and swamps with peat deposits) that may have complicated or changed the seismic wavelet. Where previously limited by seismic coverage, the seismic profiles have provided valuable subsurface information across central Illinois. Some of the interpretations based on this survey included, but are not limited to: - Stratigraphy generally gently dips to the east from Morgan to Douglas County. - The Knox Supergroup roughly maintains its thickness. There is little evidence for faulting in the Knox. However, at least one resolvable fault penetrates the entire Knox section. - The Eau Claire Formation, the primary seal for the Mt. Simon Sandstone, appears to be continuous across the entire seismic profile. - The Mt. Simon Sandstone thins towards the western edge of the basin. As a result, the highly porous lowermost Mt. Simon section is absent in the western part of the state. - Overall basement dip is from west to east. - Basement topography shows evidence of basement highs with on-lapping patterns by Mt. Simon sediments. - There is evidence of faults within the lower Mt. Simon Sandstone and basement rock that are contemporaneous with Mt. Simon Sandstone deposition. These faults are not active and do not penetrate the Eau Claire Shale. It is believed that these faults are associated with a possible failed rifting event 750 to 560 million years ago during the breakup of the supercontinent Rodinia.
Development of models for the two-dimensional, two-fluid code for sodium boiling NATOF-2D
Zielinski, R. G.
1981-01-01T23:59:59.000Z
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, ...
Weston, Ken
in monolayer graphene and topological insulators. Our results imply that a wide range of bulk crystals with Bi found so far in 2D materials such as graphene and topological insulators. Relativistic Fermions
Seismic isolation of two dimensional periodic foundations
Yan, Y.; Mo, Y. L., E-mail: yilungmo@central.uh.edu [University of Houston, Houston, Texas 77004 (United States); Laskar, A. [Indian Institute of Technology Bombay, Powai, Mumbai (India); Cheng, Z.; Shi, Z. [Beijing Jiaotong University, Beijing (China); Menq, F. [University of Texas, Austin, Texas 78712 (United States); Tang, Y. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2014-07-28T23:59:59.000Z
Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5?Hz to 50?Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.
Ridgley, Jennie; Taylor, David J.; Huffman, Jr., A. Curtis
2000-06-08T23:59:59.000Z
Multichannel surface seismic reflection data recording is a standard industry tool used to examine various aspects of geology, especially the stratigraphic characteristics and structural style of sedimentary formations in the subsurface. With the help of the Jicarilla Apache Tribe and the Bureau of Indian Affairs we were able to locate over 800 kilometers (500 miles) of multichannel seismic reflection data located on the Jicarilla Apache Indian reservation. Most of the data was received in hardcopy form, but there were data sets where either the demultiplexed digital field data or the processed data accompanied the hardcopy sections. The seismic data was acquired from the mid 1960's to the early 1990's. The most extensive seismic coverage is in the southern part of the reservation, although there are two good surveys located on the northeastern and northwestern parts of the reservation. Most of the data show that subsurface formations are generally flat-lying in the southern and western portion of the reservation. There is, however, a significant amount of structure imaged on seismic data located over the San Juan Basin margin along the east-central and northern part of the reservation. Several west to east trending lines in these areas show a highly faulted monoclinal structure from the deep basin in the west up onto the basin margin to the east. Hydrocarbon exploration in flat lying formations is mostly stratigraphic in nature. Where there is structure in the subsurface and indications are that rocks have been folded, faulted, and fractured, exploration has concentrated on structural traps and porosity/permeability "sweet spots" caused by fracturing. Therefore, an understanding of the tectonics influencing the entire section is critical in understanding mechanisms for generating faults and fractures in the Cretaceous. It is apparent that much of the hydrocarbon production on the reservation is from fracture porosity in either source or reservoir sequences. Therefore it is important to understand the mechanism that controls the location and intensity of the fractures. A possible mechanism may be deep seated basement faulting that has been active through time. Examining the basement fault patterns in this part of the basin and their relation to fracture production may provide a model for new plays on the Jicarilla Indian Reservation. There are still parts of the reservation where the subsurface has not been imaged geophysically with either conventional two-dimensional or three-dimensional reflection seismic techniques. These methods, especially 3-D seismic, would provide the best data for mapping deep basement faulting. The authors would recommend that 3-D seismic be acquired along the Basin margin located along the eastern edge of the reservation and the results be used to construct detailed fault maps which may help to locate areas with the potential to contain highly fractured zones in the subsurface.
Two-dimensional Photonic Crystals Fabricated by Nanoimprint Lithography
Chen, A.
We report on the process parameters of nanoimprint lithography (NIL) for the fabrication of two-dimensional (2-D) photonic crystals. The nickel mould with 2-D photonic crystal patterns covering the area up to 20mm² is ...
Alternative structures for two-dimensional MEMS optical switches [Invited
Wai, Ping-kong Alexander
Two-dimensional (2-D) microelectromechanical system (MEMS) optical switches have the merits of easy technologies have been proposed for building OXCs. Microelectromechanical system (MEMS) optical switches haveAlternative structures for two-dimensional MEMS optical switches [Invited] Victor O. K. Li
Electronic transport in two-dimensional graphene S. Das Sarma
Rossi, Enrico
. Monolayer graphene 409 2. Bilayer graphene 411 3. 2D Semiconductor structures 412 C. Elementary electronicElectronic transport in two-dimensional graphene S. Das Sarma Condensed Matter Theory Center; published 16 May 2011) A broad review of fundamental electronic properties of two-dimensional graphene
Wideband radar cross section reduction using two-dimensional phase gradient metasurfaces
Li, Yongfeng; Qu, Shaobo; Wang, Jiafu; Chen, Hongya [College of Science, Air Force Engineering University, Xi'an, Shaanxi 710051 (China); Zhang, Jieqiu [College of Science, Air Force Engineering University, Xi'an, Shaanxi 710051 (China); Electronic Materials Research Laboratory, Key Laboratory of Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China); Xu, Zhuo [Electronic Materials Research Laboratory, Key Laboratory of Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China); Zhang, Anxue [School of Electronics and Information Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 (China)
2014-06-02T23:59:59.000Z
Phase gradient metasurface (PGMs) are artificial surfaces that can provide pre-defined in-plane wave-vectors to manipulate the directions of refracted/reflected waves. In this Letter, we propose to achieve wideband radar cross section (RCS) reduction using two-dimensional (2D) PGMs. A 2D PGM was designed using a square combination of 49 split-ring sub-unit cells. The PGM can provide additional wave-vectors along the two in-plane directions simultaneously, leading to either surface wave conversion, deflected reflection, or diffuse reflection. Both the simulation and experiment results verified the wide-band, polarization-independent, high-efficiency RCS reduction induced by the 2D PGM.
A compact chaotic laser device with a two-dimensional external cavity structure
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
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.
Plasmonics with Two-Dimensional Conductors Hosang Yoon1
Ham, Donhee
in GaAs/AlGaAs two-dimensional (2D) electron gas (2DEG) and graphene, where electrons are perfectly, such as semiconductor heterojunction and graphene, contrast the surface plasmonic waves on bulk metals, as the former. Furthermore, the 2D plasmons can achieve much greater subwavelength confinement [5-7] with their velocity
Introduction Two-dimensional (2D) methods for
Prentiss, Mara
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
Two-dimensional river modeling
Thompson, James Cameron
1988-01-01T23:59:59.000Z
: Civil Engineering TWO-DIMENSIONAL RIVER MODELING A Thesis by JAMES CAMERON THOMPSON Approved as to style and content by: Wesl (Co-Chair J f C mittee) alph A. Wurbs (Co-Chair of Committee) R. 0. Reid (Member) ames . . Yao (Head of D rtment... 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...
Barros, E. B.
We propose a third-order time-dependent perturbation theory approach to describe the chemical surface-enhanced Raman spectroscopy of molecules interacting with two-dimensional (2D) surfaces such as an ideal 2D metal and ...
Quantum of optical absorption in two-dimensional semiconductors
California at Irvine, University of
Quantum of optical absorption in two-dimensional semiconductors Hui Fanga,b,c , Hans A. Bechteld semiconductor, where is the fine structure con- stant and nc is an optical local field correction factor quantitative examination of the intrinsic absorption properties of free-standing 2D semiconductor thin films
Two dimensional unstable scar statistics.
Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)
2006-12-01T23:59:59.000Z
This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.
Two-dimensional fourier transform spectrometer
DeFlores, Lauren; Tokmakoff, Andrei
2013-09-03T23:59:59.000Z
The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.
Two-dimensional defects in amorphous materials
Michael Moshe; Eran Sharon; Ido Levin; Hillel Aharoni; Raz Kupferman
2014-09-09T23:59:59.000Z
We present a new definition of defects which is based on a Riemannian formulation of incompatible elasticity. Defects are viewed as local deviations of the material's reference metric field, $\\bar{\\mathfrak{g}}$, from a Euclidian metric. This definition allows the description of defects in amorphous materials and the formulation of the elastic problem, using a single field, $\\bar{\\mathfrak{g}}$. We provide a multipole expansion of reference metrics that represent a large family of two-dimensional (2D) localized defects. The case of a dipole, which corresponds to an edge dislocation is studied analytically, experimentally and numerically. The quadrupole term, which is studied analytically, as well as higher multipoles of curvature carry local deformations. These multipoles are good candidates for fundamental strain carrying entities in plasticity theories of amorphous materials and for a continuous modeling of recently developed meta-materials.
Correlation energy of finite two-dimensional systems: Toward nonempirical and universal modeling
Gross, E.K.U.
in quasi-2D structures such as semiconductor layers and sur- faces, quantum-Hall systems, graphene gradient approximations, orbital functionals, and hybrid functionals.2 Such efforts for two- dimensional 2D, and various types of quantum dots3 QDs . When using DFT, QDs are most commonly treated using the 2D
Two-dimensional QCD and strings
D. J. Gross; W. Taylor
1993-11-12T23:59:59.000Z
A review is given of recent research on two-dimensional gauge theories, with particular emphasis on the equivalence between these theories and certain string theories with a two-dimensional target space. Some related open problems are discussed.
Energy and enstrophy transfer in numerical simulations of two-dimensional' turbulence
Vallis, Geoff
Energy and enstrophy transfer in numerical simulations of two-dimensional' turbulence Mathew E a significant fraction of the flow field,w and energy spectra from these simulations have slopes significantly October 1992; accepted 25 March 1993) Numerical simulations of statistically steady two-dimensional (2-D
Meju, Max
Joint two-dimensional DC resistivity and seismic travel time inversion with cross to evaluate the structural features common to both methods. The cross-gradients function is incorporated method. The resultant iterative two-dimensional (2-D) joint inversion scheme is successfully applied
Nanoscience and Quantum Physics Two-dimensional atomic crystals, best exemplified by
Furui, Sadaoki
Nanoscience and Quantum Physics 22 Two-dimensional atomic crystals, best exemplified by graphene will first discuss the physics and material aspect of graphene. Drawing from our experiences in graphene the doping and dimensionality of the 2D systems are modulated. Two-dimensional materials beyond graphene
Two Dimensional QCD is a String Theory
David J. Gross; Washington Taylor
1993-01-18T23:59:59.000Z
The partition function of two dimensional QCD on a Riemann surface of area $A$ is expanded as a power series in $1/N$ and $A$. It is shown that the coefficients of this expansion are precisely determined by a sum over maps from a two dimensional surface onto the two dimensional target space. Thus two dimensional QCD has a simple interpretation as a closed string theory.
Jovanovic, Natalija Zorana
2005-01-01T23:59:59.000Z
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 ...
A tale of coupled vibrations in solution told by coherent two-dimensional infrared spectroscopy
Khalil, Munira, 1975-
2004-01-01T23:59:59.000Z
Coherent two-dimensional infrared (2D IR) spectroscopy is used as a tool for investigating the molecular structure and dynamics of coupled vibrations in solution on a picosecond timescale. The strongly coupled asymmetric ...
Multi-mode two-dimensional infrared spectroscopy of peptides and proteins
DeFlores, Lauren P
2008-01-01T23:59:59.000Z
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 ...
A nanoscale probe of the quasiparticle band structure for two dimensional electron systems
Soumyanarayanan, Anjan
2013-01-01T23:59:59.000Z
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 ...
Two-dimensional plasmon in a surface-state band Tadaaki Nagao a,b,c,*, Torsten Hildebrandt d
Hasegawa, Shuji
Two-dimensional plasmon in a surface-state band Tadaaki Nagao a,b,c,*, Torsten Hildebrandt d well with the plasmon dispersion calculated from two-dimensional (2D) nearly free-electron theory. As hallmarked from these observations, we identify the measured loss as a longitudinal intraband 2D plasmon
O'Sullivan, Joseph A.
1 Data Detection for Two-Dimensional ISI Channels Joseph A. O'Sullivan, Naveen Singla, Yunxiang Wu-mail:{jao, singla, ywu, rsi}@ee.wustl.edu Introduction Two-dimensional (2-D) inter symbol interference (ISI) arises-D ISI channels. The motivation for considering 2-D recording is two fold; firstly, as 1-D recording
Electronic transport in two-dimensional high dielectric constant nanosystems
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Ortuńo, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.
2015-04-10T23:59:59.000Z
There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screeningmore »length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.« less
Two-Dimensional Chalcogenide Nanoplates as Tunable Metamaterials via Chemical Intercalation
Cui, Yi
Following the success of graphene and boron nitride, two- dimensional (2D) layered metal chalcogenides. Here, we explore 2D metal chalcogenides as a potential material platform for plasmonic and photonic include metamaterials with a gain medium,15,16 intermetallics,17 heavily doped semiconductors with carrier
Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R.; Salmassi, Farhad; Warwick, Tony
2005-07-12T23:59:59.000Z
The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It was shown that these three techniques provide essentially consistent results. For the stainless steel mirror, an envelope over all measured PSD distributions can be described with an inverse power-law PSD function. It is also shown that the measurements can be corrected for the specific spatial frequency dependent systematic errors of the instruments. The AFM and the X-ray scattering measurements were used to determine the modulation transfer function of the interferometric microscope. The corresponding correction procedure is discussed in detail. Lower frequency investigation of the 2D PSD distribution was also performed with a long trace profiler and a ZYGO GPI interferometer. These measurements are in some contradiction, suggesting that the reliability of the measurements has to be confirmed with additional investigation. Based on the crosscheck of the performance of all used methods, we discuss the ways for improving the 2D PSD characterization of X-ray optics.
Rapid heating and cooling in two-dimensional Yukawa systems
Yan Feng; Bin Liu; J. Goree
2011-04-19T23:59:59.000Z
Simulations are reported to investigate solid superheating and liquid supercooling of two-dimensional (2D) systems with a Yukawa interparticle potential. Motivated by experiments where a dusty plasma is heated and then cooled suddenly, we track particle motion using a simulation with Langevin dynamics. Hysteresis is observed when the temperature is varied rapidly in a heating and cooling cycle. As in the experiment, transient solid superheating, but not liquid supercooling, is observed. Solid superheating, which is characterized by solid structure above the melting point, is found to be promoted by a higher rate of temperature increase.
Two-dimensional materials for electronic applications
Wang, Han, Ph. D. Massachusetts Institute of Technology
2013-01-01T23:59:59.000Z
The successful isolation of graphene in 2004 has attracted great interest to search for potential applications of this unique material and other members of the two-dimensional materials family in electronics, optoelectronics ...
Remarks on the KLB theory of two-dimensional turbulence
Chuong V. Tran; Theodore G. Shepherd
2004-12-10T23:59:59.000Z
We study the inverse energy transfer in forced two-dimensional (2D) Navier--Stokes turbulence in a doubly periodic domain. It is shown that an inverse energy cascade that carries a nonzero fraction of the injected energy to the large scales via a power-law energy spectrum $\\propto k^{-\\alpha}$ requires that $\\alpha\\ge5/3$. This result is consistent with the classical theory of 2D turbulence that predicts a $k^{-5/3}$ inverse-cascading range, thus providing for the first time a rigorous basis for this important feature of the theory. We derive bounds for the Kolmogorov constant $C$ in the classical energy spectrum $E(k)=C\\epsilon^{2/3}k^{-5/3}$, where $\\epsilon$ is the energy injection rate. Issues related to Kraichnan's conjecture of energy condensation and to power-law spectra as the quasi-steady dynamics become steady are discussed.
Soliton nanoantennas in two-dimensional arrays of quantum dots
Gligori?, G; Had˛ievski, Lj; Slepyan, G Ya; Malomed, B A
2015-01-01T23:59:59.000Z
We consider two-dimensional (2D) arrays of self-organized semiconductor quantum dots (QDs) strongly interacting with electromagnetic field in the regime of Rabi oscillations. The QD array built of two-level states is modelled by two coupled systems of discrete nonlinear Schr\\"{o}dinger equations. Localized modes in the form of single-peaked fundamental and vortical stationary Rabi solitons and self-trapped breathers have been found. The results for the stability, mobility and radiative properties of the Rabi modes suggest a concept of a self-assembled 2D \\textit{% soliton-based nano-antenna}, which should be stable against imperfections In particular, we discuss the implementation of such a nano-antenna in the form of surface plasmon solitons in graphene, and illustrate possibilities to control their operation by means of optical tools.
Xie, Xiaoliang Sunney
Two-Dimensional Reaction Free Energy Surfaces of Catalytic Reaction: Effects of Protein Form: October 23, 2007 We introduce a two-dimensional (2D) multisurface reaction free energy space representing different states of the cycle, which is constructed according to the free energy
Novel Phases and Reentrant Melting of Two Dimensional Colloidal Crystals
Leo Radzihovsky; Erwin Frey; David R. Nelson
2000-08-11T23:59:59.000Z
We investigate two-dimensional (2d) melting in the presence of a one-dimensional (1d) periodic potential as, for example, realized in recent experiments on 2d colloids subjected to two interfering laser beams. The topology of the phase diagram is found to depend primarily on two factors: the relative orientation of the 2d crystal and the periodic potential troughs, which select a set of Bragg planes running parallel to the troughs, and the commensurability ratio p= a'/d of the spacing a' between these Bragg planes to the period d of the periodic potential. The complexity of the phase diagram increases with the magnitude of the commensurabilty ratio p. Rich phase diagram, with ``modulated liquid'', ``floating'' and ``locked floating'' solid and smectic phases are found. Phase transitions between these phases fall into two broad universality classes, roughening and melting, driven by the proliferation of discommensuration walls and dislocations, respectively. We discuss correlation functions and the static structure factor in these phases and make detailed predictions of the universal features close to the phase boundaries. We predict that for charged systems with highly screened short-range interactions these melting transitions are generically reentrant as a function of the strength of the periodic potential, prediction that is in accord with recent 2d colloid experiments. Implications of our results for future experiments are also discussed.
Drag Law of Two Dimensional Granular Fluids
Satoshi Takada; Hisao Hayakawa
2015-04-19T23:59:59.000Z
Drag force law acting on a moving circular disk in a two-dimensional granular medium is analyzed based on the discrete element method (DEM). It is remarkable that the drag force on the moving disk in moderate dense and pure two-dimensional granular medium can be well reproduced by a perfect fluid with separation from the boundary. A yield force, being independent of the moving speed of the disk, appears if a dry friction between the granular disks and the bottom plate exists. The perfect fluidity is violated in this case. The yield force and the drag force diverge at the jamming point.
Cosmologies with Two-Dimensional Inhomogeneity
A. Feinstein; J. Ibįńez; Ruth Lazkoz
1995-11-27T23:59:59.000Z
We present a new generating algorithm to construct exact non static solutions of the Einstein field equations with two-dimensional inhomogeneity. Infinite dimensional families of $G_1$ inhomogeneous solutions with a self interacting scalar field, or alternatively with perfect fluid, can be constructed using this algorithm. Some families of solutions and the applications of the algorithm are discussed.
Two-dimensional simulations of pulsational pair-instability supernovae...
Office of Scientific and Technical Information (OSTI)
Two-dimensional simulations of pulsational pair-instability supernovae Citation Details In-Document Search Title: Two-dimensional simulations of pulsational pair-instability...
Two-Dimensional Superconducting Fluctuations in Stripe-Ordered La1:875Ba0:125CuO4 Q. Li, M. Hu of two-dimensional (2D) fluctuating superconductivity, which eventually reaches a 2D superconducting˙xBaxCuO4 frustrates three-dimensional superconducting phase order, but is fully compatible with 2D
On-chip silicon optical phased array for two-dimensional beam steering
Chen, Ray
and thermo-optic phase shifting with a switching power of P 20 mW per channel. Using a silicon waveguide-channel un- equally spaced OPA [3]. However, for many applications two-dimensional (2D) steering, rib waveguides are needed for single-mode operation, thereby adding additional pat- terning steps
PHYSICAL REVIEW E 87, 013106 (2013) Longitudinal viscosity of two-dimensional Yukawa liquids
Goree, John
2013-01-01T23:59:59.000Z
is obtained for a two-dimensional (2D) liquid using a Green-Kubo method with a molecular dynamics simulation characterize energy dissipation in a fluid. Bulk viscosity is for energy dissipation due to compression, in contrast, is for energy dissipation due to a gradient in the flow velocity. In the latter case, the energy
DOI: 10.1002/anie.201105439 Fabrication of Large-Area Two-Dimensional Colloidal Crystals**
Asher, Sanford A.
Polymers DOI: 10.1002/anie.201105439 Fabrication of Large-Area Two-Dimensional Colloidal Crystals-dimensional crystalline colloidal arrays (CCAs) have numerous applications, such as photonic crystal materials and sensors to prepare close-packed 2D colloidal crystals by floating and re-deposit- ing colloidal monolayers at the air
Transitions in two-dimensional patterns in a ferrocyanideiodatesulfite reaction Ge Li,a) Qi-dimensional 2D spatial patterns were investigated in a ferrocyanideiodate sulfite FIS reaction in a circular.20.6 mm , reservoir residence time 0.64 min , and ferrocyanide concentration 1280 mM . Iodate
Francos, Joseph M.
IEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL. 47, NO. 7, JULY 1999 1795 Parameter Estimation of 2-D Abstract--Phase information has fundamental importance in many two-dimensional (2-D) signal processing one- and two-dimensional (1-D and 2-D) signal process- ing problems. When dealing with 2-D signals
Fully localized two-dimensional embedded solitons
Yang Jianke [Department of Mathematics and Statistics, University of Vermont, Burlington, Vermont 05401 (United States)
2010-11-15T23:59:59.000Z
We report the prediction of fully localized two-dimensional embedded solitons. These solitons are obtained in a quasi-one-dimensional waveguide array which is periodic along one spatial direction and localized along the orthogonal direction. Under appropriate nonlinearity, these solitons are found to exist inside the Bloch bands (continuous spectrum) of the waveguide and thus are embedded solitons. These embedded solitons are fully localized along both spatial directions. In addition, they are fully stable under perturbations.
Statistical Mechanics of Two-dimensional Foams
Marc Durand
2010-09-07T23:59:59.000Z
The methods of statistical mechanics are applied to two-dimensional foams under macroscopic agitation. A new variable -- the total cell curvature -- is introduced, which plays the role of energy in conventional statistical thermodynamics. The probability distribution of the number of sides for a cell of given area is derived. This expression allows to correlate the distribution of sides ("topological disorder") to the distribution of sizes ("geometrical disorder") in a foam. The model predictions agree well with available experimental data.
Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R.; Salmassi, Farhad; Warwick, Tony
2005-04-17T23:59:59.000Z
The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It was shown that these three techniques provide essentially consistent results. For the stainless steel mirror, an envelope over all measured PSD distributions can be described with an inverse power-law PSD function. It is also shown that the measurements can be corrected for the specific spatial frequency dependent systematic errors of the instruments. The AFM and the X-ray scattering measurements were used to determine the modulation transfer function of the interferometric microscope. The corresponding correction procedure is discussed in detail. Lower frequency investigation of the 2D PSD distribution was also performed with a long trace profiler and a ZYGO GPI interferometer. These measurements are in some contradiction, suggesting that the reliability of the measurements has to be confirmed with additional investigation. Based on the crosscheck of the performance of all used methods, we discuss the ways for improving the 2D PSD characterization of X-ray optics.
Two-dimensional stimulated resonance Raman spectroscopy of molecules with broadband x-ray pulses
Biggs, Jason D.; Zhang Yu; Healion, Daniel; Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States)
2012-05-07T23:59:59.000Z
Expressions for the two-dimensional stimulated x-ray Raman spectroscopy (2D-SXRS) signal obtained using attosecond x-ray pulses are derived. The 1D- and 2D-SXRS signals are calculated for trans-N-methyl acetamide (NMA) with broad bandwidth (181 as, 14.2 eV FWHM) pulses tuned to the oxygen and nitrogen K-edges. Crosspeaks in 2D signals reveal electronic Franck-Condon overlaps between valence orbitals and relaxed orbitals in the presence of the core-hole.
Stability of Two-Dimensional Soft Quasicrystals
Kai Jiang; Jiajun Tong; Pingwen Zhang; An-Chang Shi
2015-05-26T23:59:59.000Z
The relative stability of two-dimensional soft quasicrystals is examined using a recently developed projection method which provides a unified numerical framework to compute the free energy of periodic crystal and quasicrystals. Accurate free energies of numerous ordered phases, including dodecagonal, decagonal and octagonal quasicrystals, are obtained for a simple model, i.e. the Lifshitz-Petrich free energy functional, of soft quasicrystals with two length-scales. The availability of the free energy allows us to construct phase diagrams of the system, demonstrating that, for the Lifshitz-Petrich model, the dodecagonal and decagonal quasicrystals can become stable phases, whereas the octagonal quasicrystal stays as a metastable phase.
Two-dimensional electronic spectroscopy signatures of the glass transition
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lewis, K. L .M.; Myers, J. A.; Fuller, F.; Tekavec, P. F.; Ogilvie, J. P.
2010-01-01T23:59:59.000Z
Two-dimensional electronic spectroscopy is a sensitive probe of solvation dynamics. Using a pump–probe geometry with a pulse shaper [Optics Express15(2007), 16681-16689;Optics Express16(2008), 17420-17428], we present temperature dependent 2D spectra of laser dyes dissolved in glass-forming solvents. At low waiting times, the system has not yet relaxed, resulting in a spectrum that is elongated along the diagonal. At longer times, the system loses its memory of the initial excitation frequency, and the 2D spectrum rounds out. As the temperature is lowered, the time scale of this relaxation grows, and the elongation persists for longer waiting times. This can be measured inmore »the ratio of the diagonal width to the anti-diagonal width; the behavior of this ratio is representative of the frequency–frequency correlation function [Optics Letters31(2006), 3354–3356]. Near the glass transition temperature, the relaxation behavior changes. Understanding this change is important for interpreting temperature-dependent dynamics of biological systems.« less
Theory for two dimensional electron emission between parallel flat electrodes
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
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.
Two dimensional Sen connections in general relativity
L. B. Szabados
1994-02-01T23:59:59.000Z
The two dimensional version of the Sen connection for spinors and tensors on spacelike 2-surfaces is constructed. A complex metric $\\gamma_{AB}$ on the spin spaces is found which characterizes both the algebraic and extrinsic geometrical properties of the 2-surface $\\$ $. The curvature of the two dimensional Sen operator $\\Delta_e$ is the pull back to $\\$ $ of the anti-self-dual part of the spacetime curvature while its `torsion' is a boost gauge invariant expression of the extrinsic curvatures of $\\$ $. The difference of the 2 dimensional Sen and the induced spin connections is the anti-self-dual part of the `torsion'. The irreducible parts of $\\Delta_e$ are shown to be the familiar 2-surface twistor and the Weyl--Sen--Witten operators. Two Sen--Witten type identities are derived, the first is an identity between the 2 dimensional twistor and the Weyl--Sen--Witten operators and the integrand of Penrose's charge integral, while the second contains the `torsion' as well. For spinor fields satisfying the 2-surface twistor equation the first reduces to Tod's formula for the kinematical twistor.
Internal tide generation by arbitrary two-dimensional topography
Peacock, Thomas
To date, analytical models of internal tide generation by two-dimensional ridges have considered only idealized shapes. Here, we advance the Green function approach to address the generation of internal tides by two-dimensional ...
Using Two-Dimensional Colloidal Crystals to Understand Crystallography
Loening, Niko
Using Two-Dimensional Colloidal Crystals to Understand Crystallography Instructor Notes Geometric). #12;Using Two-Dimensional Colloidal Crystals to Understand Crystallography Instructions for Students the patterns that result from the diffraction of electromagnetic radiation by a crystal provides structural
Graphene forms template for two-dimensional hybrid materials...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (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...
Fan, Shanhui
GaN-based two-dimensional surface-emitting photonic crystal lasers with AlN/GaN distributed Bragg 14 December 2007; published online 11 January 2008 GaN-based two-dimensional 2D surface-emitting photonic crystal PC lasers with AlN/GaN distributed Bragg reflectors are fabricated and demonstrated
Economou, Demetre J.
Simulation of a two-dimensional sheath over a flat insulatorconductor interface on a radio-frequency the two-dimensional 2D sheath over a flat insulator/conductor interface on a radio-frequency rf biased is no longer one dimen- sional. The extent of sheath ``disturbance'' depends on the thickness of the sheath
Cui, Qinghong; Hu, Chia-Ren; Wei, J. Y. T.; Yang, Kun.
2006-01-01T23:59:59.000Z
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 ...
Bartley, Norm
, 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
Convergence of two-dimensional Fourier series
Kidd, Robert Henry, III
1962-01-01T23:59:59.000Z
), 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...
Dynamics of two-dimensional dipole systems
Golden, Kenneth I.; Kalman, Gabor J.; Hartmann, Peter; Donko, Zoltan [Department of Mathematics and Statistics, Department of Physics, University of Vermont, Burlington, Vermont 05401 (United States); Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary and Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States)
2010-09-15T23:59:59.000Z
Using a combined analytical/molecular dynamics approach, we study the current fluctuation spectra and longitudinal and transverse collective mode dispersions of the classical two-dimensional (point) dipole system (2DDS) characterized by the {phi}{sub D}(r)={mu}{sup 2}/r{sup 3} repulsive interaction potential; {mu} is the electric dipole strength. The interest in the 2DDS is twofold. First, the quasi-long-range 1/r{sup 3} interaction makes the system a unique classical many-body system, with a remarkable collective mode behavior. Second, the system may be a good model for a closely spaced semiconductor electron-hole bilayer, a system that is in the forefront of current experimental interest. The longitudinal collective excitations, which are of primary interest for the liquid phase, are acoustic at long wavelengths. At higher wave numbers and for sufficiently high coupling strength, we observe the formation of a deep minimum in the dispersion curve preceded by a sharp maximum; this is identical to what has been observed in the dispersion of the zero-temperature bosonic dipole system, which in turn emulates so-called roton-maxon excitation spectrum of the superfluid {sup 4}He. The analysis we present gives an insight into the emergence of this apparently universal structure, governed by strong correlations. We study both the liquid and the crystalline solid state. We also observe the excitation of combination frequencies, resembling the roton-roton, roton-maxon, etc. structures in {sup 4}He.
Two-Dimensional Ferroelectric Photonic Crystals: Optics and Band Structure
Simsek, Sevket; Ozbay, Ekmel
2013-01-01T23:59:59.000Z
In this report we present an investigation of the optical properties and band structure calculations for the photonic structures based on the functional materials- ferroelectrics. A theoretical approach to the optical properties of the 2D and 3D photonic crystals which yields further insight in the phenomenon of the reflection from different families of lattice planes in relation to the presence of photonic gaps or photonic bands. We calculate the photonic bands and optical properties of LiNbO3 based photonic crystals. Calculations of reflection and transmission spectra show the features correspond to the onset of diffraction, as well as to additional reflectance structures at large values of the angle of incidence.
Heisler, Ismael A., E-mail: i.heisler@uea.ac.uk; Moca, Roberta; Meech, Stephen R., E-mail: s.meech@uea.ac.uk [School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ (United Kingdom); Camargo, Franco V. A. [School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ (United Kingdom); CAPES Foundation, Ministry of Education of Brazil, Brasķlia - DF 70040-020 (Brazil)
2014-06-15T23:59:59.000Z
We report an improved experimental scheme for two-dimensional electronic spectroscopy (2D-ES) based solely on conventional optical components and fast data acquisition. This is accomplished by working with two choppers synchronized to a 10 kHz repetition rate amplified laser system. We demonstrate how scattering and pump-probe contributions can be removed during 2D measurements and how the pump probe and local oscillator spectra can be generated and saved simultaneously with each population time measurement. As an example the 2D-ES spectra for cresyl violet were obtained. The resulting 2D spectra show a significant oscillating signal during population evolution time which can be assigned to an intramolecular vibrational mode.
Two-dimensional excitons in three-dimensional hexagonal boron nitride
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
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?Å 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.
Two-Dimensional Gas of Massless Dirac Fermions in Graphene
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
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.
Two-dimensional polymer synthesis : towards a two-dimensional replicating system for nanostructures
Mosley, David W
2005-01-01T23:59:59.000Z
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 ...
Pandey, Ravi
. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4892798] I. INTRODUCTION Two dimensional (2D the semiconductor-to-metal transition. Application of the external electric fields, on the other hand, shows- liation technique similar to one applied to graphene. The layered TMDs are the class of materials
Wavelet Analysis of Two Dimensional Quantum Scattering A thesis presented
Heller, Eric
Wavelet Analysis of Two Dimensional Quantum Scattering A thesis presented by Jonathan Dillwyn discretization based on the discrete wavelet transformation, which uses basis elements that can readily adapt
Du, Yuchen; Yang, Lingming; Liu, Han; Ye, Peide D., E-mail: yep@purdue.edu [School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)
2014-09-01T23:59:59.000Z
Layered two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) have been widely isolated, synthesized, and characterized recently. Numerous 2D materials are identified as the potential candidates as channel materials for future thin film technology due to their high mobility and the exhibiting bandgaps. While many TMD filed-effect transistors (FETs) have been widely demonstrated along with a significant progress to clearly understand the device physics, large contact resistance at metal/semiconductor interface still remain a challenge. From 2D device research point of view, how to minimize the Schottky barrier effects on contacts thus reduce the contact resistance of metals on 2D materials is very critical for the further development of the field. Here, we present a review of contact research on molybdenum disulfide and other TMD FETs from the fundamental understanding of metal-semiconductor interfaces on 2D materials. A clear contact research strategy on 2D semiconducting materials is developed for future high-performance 2D FETs with aggressively scaled dimensions.
Two-dimensional quantum propagation using wavelets in space and time
Sparks, Douglas K.; Johnson, Bruce R. [Department of Chemistry, Rice Quantum Institute and Laboratory for Nanophotonics, Rice University, Houston, Texas 77005 (United States)
2006-09-21T23:59:59.000Z
A recent method for solving the time-dependent Schroedinger equation has been developed using expansions in compact-support wavelet bases in both space and time [H. Wang et al., J. Chem. Phys. 121, 7647 (2004)]. This method represents an exact quantum mixed time-frequency approach, with special initial temporal wavelets used to solve the initial value problem. The present work is a first extension of the method to multiple spatial dimensions applied to a simple two-dimensional (2D) coupled anharmonic oscillator problem. A wavelet-discretized version of norm preservation for time-independent Hamiltonians discovered in the earlier one-dimensional investigation is verified to hold as well in 2D and, by implication, in higher numbers of spatial dimensions. The wavelet bases are not restricted to rectangular domains, a fact which is exploited here in a 2D adaptive version of the algorithm.
Handling Database Updates in Two-dimensional Temporal Logic
Finger, Marcelo
Handling Database Updates in Two-dimensional Temporal Logic Marcelo Finger y Department (Draft version 0.2) Abstract This paper deals with the description of the evolution of the understanding in database systems due to updates. For this purpose, we introduce a two-dimensional temporal logic
Plastic flow in two-dimensional solids Akira Onuki
Plastic flow in two-dimensional solids Akira Onuki Department of Physics, Kyoto University, Kyoto-Landau model of plastic deformation in two-dimensional solids is presented. The fundamental dynamic variables in uniaxial stretching. High-density dislocations produced in plastic flow do not disappear even if the flow
Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures
Azad, Abul K [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Han, Jiaguang [OSU; Lu, Xinchao [OSU; Zhang, Weili [OSU
2009-01-01T23:59:59.000Z
The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.
Two-dimensional cross-section and SED uncertainty analysis for the Fusion Engineering Device (FED)
Embrechts, M.J.; Urban, W.T.; Dudziak, D.J.
1982-01-01T23:59:59.000Z
The theory of two-dimensional cross-section and secondary-energy-distribution (SED) sensitivity was implemented by developing a two-dimensional sensitivity and uncertainty analysis code, SENSIT-2D. Analyses of the Fusion Engineering Design (FED) conceptual inboard shield indicate that, although the calculated uncertainties in the 2-D model are of the same order of magnitude as those resulting from the 1-D model, there might be severe differences. The more complex the geometry, the more compulsory a 2-D analysis becomes. Specific results show that the uncertainty for the integral heating of the toroidal field (TF) coil for the FED is 114.6%. The main contributors to the cross-section uncertainty are chromium and iron. Contributions to the total uncertainty were smaller for nickel, copper, hydrogen and carbon. All analyses were performed with the Los Alamos 42-group cross-section library generated from ENDF/B-V data, and the COVFILS covariance matrix library. The large uncertainties due to chromium result mainly from large convariances for the chromium total and elastic scattering cross sections.
Time slices from two-dimensional seismic surveys
Miller, M.H. Jr.; French, W.S.
1988-02-01T23:59:59.000Z
Two-dimensional seismic programs commonly are laid out repeatedly over the same prospect during the course of several years. Many seismic base maps reveal a network of two-dimensional seismic lines whose total mileage approaches that of a modern three-dimensional survey. A modern three-dimensional processing system can interpolate these two-dimensional networks onto a three-dimensional data volume followed by three-dimensional migration. This process has been conducted with varying degrees of success in a number of areas. The authors are not suggesting that the method replaces the need for modern three-dimensional surveys because detail not recorded during acquisition cannot be restored by processing. However, their method does provide a valuable new way to interpret the old two-dimensional network of lines in cases where new three-dimensional acquisition is not possible or economical. As the gaps between the two-dimensional lines increase, the resolution of the final product decreases. Generally, a few new two-dimensional lines can be shot to eliminate the large gaps in old two-dimensional networks.
Characterization of metal contacts for two-dimensional MoS{sub 2} nanoflakes
Walia, Sumeet, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au; Balendhran, Sivacarendran; Sriram, Sharath; Bhaskaran, Madhu, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au [Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria 3000 (Australia) [Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria 3000 (Australia); School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000 (Australia); Wang, Yichao; Ab Kadir, Rosmalini; Sabirin Zoolfakar, Ahmad; Atkin, Paul; Zhen Ou, Jian; Kalantar-zadeh, Kourosh, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000 (Australia)] [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000 (Australia)
2013-12-02T23:59:59.000Z
While layered materials are increasingly investigated for their potential in nanoelectronics, their functionality and efficiency depend on charge injection into the materials via metallic contacts. This work explores the characteristics of different metals (aluminium, tungsten, gold, and platinum) deposited on to nanostructured thin films made of two-dimensional (2D) MoS{sub 2} flakes. Metals are chosen based on their work functions relative to the electron affinity of MoS{sub 2}. It is observed, and analytically verified that lower work functions of the contact metals lead to smaller Schottky barrier heights and consequently higher charge carrier injection through the contacts.
An Ant Colony Optimization Algorithm for the 2D HP Protein Folding Problem
Hoos, Holger H.
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
Two-dimensional ultrasonic computed tomography of growing bones.
Paris-Sud XI, Université de
Two-dimensional ultrasonic computed tomography of growing bones. P. Lasaygues, E. Franceschini, R: Ultrasonic Computed Tomography, Bone imaging, Born approximation, iterative distorted method I. INTRODUCTION imaging process, using ultrasonic computed tomography. Although this method is known to provide
Healing of defects in a two-dimensional granular crystal
Rice, Marie C
2014-01-01T23:59:59.000Z
Using a macroscopic analog for a two dimensional hexagonal crystal, we perform an experimental investigation of the self-healing properties of circular grain defects with an emphasis on defect orientation. A circular grain ...
Transformation optics scheme for two-dimensional materials
Kumar, Anshuman
Two-dimensional optical materials, such as graphene, can be characterized by surface conductivity. So far, the transformation optics schemes have focused on three-dimensional properties such as permittivity ? and permeability ...
Complex Interplay and Hierarchy of Interactions in Two-Dimensional
Brune, Harald
Complex Interplay and Hierarchy of Interactions in Two-Dimensional Supramolecular Assemblies Marta, Freiestrasse 3, 3012 Bern, Switzerland, and Empa, Swiss Federal Laboratories for Materials Science potential implementation of self- assembled supramolecular struc- tures in molecular electronic devices asks
Notes on the two-dimensional fractional Brownian motion
Baudoin, Fabrice; Nualart, David
2006-02-17T23:59:59.000Z
We study the two-dimensional fractional Brownian motion with Hurst parameter H>½. In particular, we show, using stochastic calculus, that this process admits a skew-product decomposition and deduce from this representation some asymptotic properties...
Wavelet Analysis of Two Dimensional Quantum Scattering A thesis presented
Heller, Eric
Wavelet Analysis of Two Dimensional Quantum Scattering A thesis presented by Jonathan Dillwyn the local nature of the scattering. We present an alternative discretization based on the discrete wavelet
Optical properties of two-dimensional transition metal dichalcogenides
Lin, Yuxuan, S.M. Massachusetts Institute of Technology
2014-01-01T23:59:59.000Z
The re-discovery of the atomically thin transition metal dichalcogenides (TMDs), which are mostly semiconductors with a wide range of band gaps, has diversified the family of two-dimensional materials and boosted the ...
Two-dimensional relativistic space charge limited current flow in the drift space
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
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.
A Minimal description of morphological hierarchy in two-dimensional aggregates
Tamoghna Das; T. Lookman; M. M. Bandi
2015-02-11T23:59:59.000Z
A dimensionless parameter $\\Lambda$ is proposed to describe a hierarchy of morphologies in two-dimensional (2D) aggregates formed due to varying competition between short-range attraction and long-range repul- sion. Structural transitions from finite non-compact to compact to percolated structures are observed in the configurations simulated by molecular dynamics at a constant temperature and density. Configurational randomness across the transition, measured by the two-body excess entropy $S_2$, exhibits data collapse with the average potential energy $\\bar{\\mathcal{E}}$ of the systems. Independent master curves are presented among $S_2$, the reduced second virial coefficient $B_2^*$ and $\\Lambda$, justifying this minimal description. This work lays out a coherent basis for the study of 2D aggregate morphologies relevant to diverse nano- and bio-processes.
Intrinsic Magnetism of Grain Boundaries in Two-dimensional Metal Dichalcogenides
Zhang, Zhuhua; Crespi, Vincent H; Yakobson, Boris I
2013-01-01T23:59:59.000Z
Grain boundaries (GBs) are structural imperfections that typically degrade the performance of materials. Here we show that dislocations and GBs in two-dimensional (2D) metal dichalcogenides MX2 (M = Mo, W; X = S, Se) can actually improve the material by giving it a qualitatively new physical property: magnetism. The dislocations studied all have a substantial magnetic moment of ~1 Bohr magneton. In contrast, dislocations in other well-studied 2D materials are typically non-magnetic. GBs composed of pentagon-heptagon pairs interact ferromagnetically and transition from semiconductor to half-metal or metal as a function of tilt angle and/or doping level. When the tilt angle exceeds 47{\\deg} the structural energetics favor square-octagon pairs and the GB becomes an antiferromagnetic semiconductor. These exceptional magnetic properties arise from an interplay of dislocation-induced localized states, doping, and locally unbalanced stoichiometry. Purposeful engineering of topological GBs may be able to convert MX2 ...
Hydrogen Bond Rearrangements in Water Probed with Temperature-Dependent 2D IR
Nicodemus, Rebecca A.
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 ...
Cahoon, James Francis
2008-12-16T23:59:59.000Z
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.
Hexatic phase and cluster crystals of two-dimensional GEM4 spheres
Santi Prestipino; Franz Saija
2014-11-17T23:59:59.000Z
Two-dimensional crystals of classical particles are very peculiar in that melting may occur in two steps, in a continuous fashion, via an intermediate hexatic fluid phase exhibiting quasi-long-range orientational order. On the other hand, three-dimensional spheres repelling each other through a fast-decaying bounded potential of generalized-exponential shape (GEM4 potential) can undergo freezing into cluster crystals, allowing for more that one particle per lattice site. We hereby study the combined effect of low spatial dimensionality and extreme potential softness, by investigating the phase behavior of the two-dimensional (2D) GEM4 system. Using a combination of density-functional theory and numerical free-energy calculations, we show that the 2D GEM4 system displays one ordinary and several cluster triangular-crystal phases, and that only the ordinary crystal first melts into a hexatic phase. Upon heating, the difference between the various cluster crystals fades away, eventually leaving a single undifferentiated cluster phase with a pressure-modulated site occupancy.
Li, Xufan [ORNL; Basile Carrasco, Leonardo A [ORNL; Yoon, Mina [ORNL; Ma, Cheng [ORNL; Puretzky, Alexander A [ORNL; Lee, Jaekwang [ORNL; Idrobo Tapia, Juan Carlos [ORNL; Chi, Miaofang [ORNL; Rouleau, Christopher M [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL
2015-01-01T23:59:59.000Z
Characterizing and controlling the interlayer orientations and stacking order of bilayer two-dimensional (2D) crystals and van der Waals (vdW) heterostructure is crucial to optimize their electrical and optoelectronic properties. The four polymorphs of layered gallium selenide (GaSe) that result from different layer stacking provide an ideal platform to study the stacking configurations in bilayer 2D crystals. Here, through a controllable vapor-phase deposition method we selectively grow bilayer GaSe crystals and investigate their two preferred 0 or 60 interlayer rotations. The commensurate stacking configurations (AA and AB-stacking) in as-grown 2D bilayer GaSe crystals are clearly observed at the atomic scale and the Ga-terminated edge structure are identified for the first time by using atomic-resolution scanning transmission electron microscopy (STEM). Theoretical analysis of the interlayer coupling energetics vs. interlayer rotation angle reveals that the experimentally-observed orientations are energetically preferred among the bilayer GaSe crystal polytypes. The combined experimental and theoretical characterization of the GaSe bilayers afforded by these growth studies provide a pathway to reveal the atomistic relationships in interlayer orientations responsible for the electronic and optical properties of bilayer 2D crystals and vdW heterostructures.
Vishwanath Shukla; Marc Brachet; Rahul Pandit
2014-11-23T23:59:59.000Z
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.
M-Theory and Two-Dimensional Effective Dynamics
N. D. Lambert; P. C. West
1999-08-09T23:59:59.000Z
We calculate from M-theory the two-dimensional low energy effective dynamics of various brane configurations. In the first part we study configurations that have a dual description in type IIA string theory as two-dimensional (4,0) Yang-Mills theories with gauge group SU(N_1)xSU(N_2) and chiral fermions in the bi-fundamental representation. In the second part we derive related equations of motion which describe the low energy internal dynamics of a supersymmetric black hole in four-dimensional N=1 supergravity, obtained as an M-fivebrane wrapped on a complex four-cycle.
A two-dimensional nematic phase of magnetic nanorods
Kostyantyn Slyusarenko; Doru Constantin; Patrick Davidson
2015-04-04T23:59:59.000Z
We report a hybrid mesophase consisting of magnetic nanorods confined between the non-ionic surfactant bilayers of a lamellar phase. The magnetic field-induced ordering of the nanorods was measured experimentally and modeled by a two-dimensional Onsager theory including the third virial coefficient. The nanorods are strongly confined in layers, with no orientational coupling from one layer to the next. At high volume concentration they exhibit spontaneous in-plane orientational ordering and form a stack of independent two-dimensional nematic systems. This isotropic-nematic transition is first-order.
Performance and Error Analysis of Knill's Postselection Scheme in a Two-Dimensional Architecture
Ching-Yi Lai; Gerardo Paz; Martin Suchara; Todd A. Brun
2013-05-31T23:59:59.000Z
Knill demonstrated a fault-tolerant quantum computation scheme based on concatenated error-detecting codes and postselection with a simulated error threshold of 3% over the depolarizing channel. %We design a two-dimensional architecture for fault-tolerant quantum computation based on Knill's postselection scheme. We show how to use Knill's postselection scheme in a practical two-dimensional quantum architecture that we designed with the goal to optimize the error correction properties, while satisfying important architectural constraints. In our 2D architecture, one logical qubit is embedded in a tile consisting of $5\\times 5$ physical qubits. The movement of these qubits is modeled as noisy SWAP gates and the only physical operations that are allowed are local one- and two-qubit gates. We evaluate the practical properties of our design, such as its error threshold, and compare it to the concatenated Bacon-Shor code and the concatenated Steane code. Assuming that all gates have the same error rates, we obtain a threshold of $3.06\\times 10^{-4}$ in a local adversarial stochastic noise model, which is the highest known error threshold for concatenated codes in 2D. We also present a Monte Carlo simulation of the 2D architecture with depolarizing noise and we calculate a pseudo-threshold of about 0.1%. With memory error rates one-tenth of the worst gate error rates, the threshold for the adversarial noise model, and the pseudo-threshold over depolarizing noise, are $4.06\\times 10^{-4}$ and 0.2%, respectively. In a hypothetical technology where memory error rates are negligible, these thresholds can be further increased by shrinking the tiles into a $4\\times 4$ layout.
Quasi-two Dimensional Hydrodynamics and Interaction of Vortex Tubes
Zakharov, Vladimir
Quasi-two Dimensional Hydrodynamics and Interaction of Vortex Tubes Vladimir Zakharov 1 but a careful study of the dynamics of the vortex tubes or their systems in a real 3-dimentional nonstationary for description of this type of flow looks very timely. Another motivation is the vortex dynamics
condmat/9801215 Crossovers in the Two Dimensional Ising Spin Glass
Roma "La Sapienza", Universitą di
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 with ferromagnetic nextnearestneighbor interactions. We found a crossover from ferromagnetic to ``spin glass'' like
Defects activated photoluminescence in two-dimensional semiconductors
Wu, Junqiao
Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China, 3, Berkeley, California 94720, United States. Point defects in semiconductors can trap free charge carriers
A MULTIPOLE BOUNDARY ELEMENT METHOD FOR TWO DIMENSIONAL ELASTOSTATICS 3
Yamamoto, Hirosuke
A MULTIPOLE BOUNDARY ELEMENT METHOD FOR TWO DIMENSIONAL ELASTOSTATICS 3 YOSIHIRO YAMADAy z AND KEN. To avoid these problems, Rokhlin proposed the multipole method for the potential prob- lem. This paper requires O(N log N) work and memory. Theoretical error estimates for the multipole expansions are also
Two-dimensional optimization of free electron laser designs
Prosnitz, Donald (Walnut Creek, CA); Haas, Roger A. (Pleasanton, CA)
1985-01-01T23:59:59.000Z
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.
Two-dimensional optimization of free-electron-laser designs
Prosnitz, D.; Haas, R.A.
1982-05-04T23:59:59.000Z
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.
Electronic, Vibrational and Thermoelectric Properties of Two-Dimensional Materials
Wickramaratne, Darshana
2015-01-01T23:59:59.000Z
properties of van der Waals materials exhibiting ring shapedmonochalco- genides B 2D Material Database B.1 Retrievingstudies conducted on these materials are currently hosted on
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Mahmood, Qasim [Department of Chemical Engineering, College of Engineering, Kyung Hee University (Republic of Korea); Bak, Seong-Min [Brookhaven National Laboratory (BNL), Upton, NY (United States); Kim, Min G. [Beamline Research Division, Pohang Accelerator Laboratory, Pohang (Republic of Korea); Yun, Sol [School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon (Republic of Korea); Yang, Xiao-Qing [Brookhaven National Laboratory (BNL), Upton, NY (United States); Shin, Hyeon S. [Department of Energy Engineering, Department of Chemistry, and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology(UNIST) (Republic of Korea); Kim, Woo S. [Department of Chemical Engineering, College of Engineering, Kyung Hee University (Republic of Korea); Braun, Paul V. [Department of Materials Science and Engineering Materials Research Laboratory and Beckman Institute, University of Illinois at Urbana?Champaign, Urbana, Illinois (United States); Park, Ho S. [School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon (Republic of Korea)
2015-04-08T23:59:59.000Z
Two-dimensional (2D) heteronanosheets are currently the focus of intense study due to the unique properties that emerge from the interplay between two low-dimensional nanomaterials with different properties. However, the properties and new phenomena based on the two 2D heteronanosheets interacting in a 3D hierarchical architecture have yet to be explored. Here, we unveil the surface redox charge storage mechanism of surface-exposed WS2 nanosheets assembled in a 3D hierarchical heterostructure using in situ synchrotron X-ray absorption and Raman spectroscopic methods. The surface dominating redox charge storage of WS2 is manifested in a highly reversible and ultrafast capacitive fashion due to the interaction of heteronanosheets and the 3D connectivity of the hierarchical structure. In contrast, compositionally identical 2D WS2 structures fail to provide a fast and high capacitance with different modes of lattice vibration. The distinctive surface capacitive behavior of 3D hierarchically structured heteronanosheets is associated with rapid proton accommodation into the in-plane W–S lattice (with the softening of the E2g bands), the reversible redox transition of the surface-exposed intralayers residing in the electrochemically active 1T phase of WS2 (with the reversible change in the interatomic distance and peak intensity of W–W bonds), and the change in the oxidation state during the proton insertion/deinsertion process. This proposed mechanism agrees with the dramatic improvement in the capacitive performance of the two heteronanosheets coupled in the hierarchical structure.
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
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.
Surface Science Letters The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of
Goodman, Wayne
Surface Science Letters The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO online 7 May 2011 Keywords: Graphene Ru(0001) STM 2-D Au CO adsorption IRAS The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied
Transport behavior of water molecules through two-dimensional nanopores
Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2014-11-14T23:59:59.000Z
Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ?15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.
Point Defect Dynamics in Two-Dimensional Colloidal Crystals
A. Libal; C. Reichhardt; C. J. Olson Reichhardt
2006-12-16T23:59:59.000Z
We study the topological configurations and dynamics of individual point defect vacancies and interstitials in a two-dimensional colloidal crystal. Our Brownian dynamics simulations show that the diffusion mechanism for vacancy defects occurs in two phases. The defect can glide along the crystal lattice directions, and it can rotate during an excited topological transition configuration to assume a different direction for the next period of gliding. The results for the vacancy defects are in good agreement with recent experiments. For the interstitial point defects, which were not studied in the experiments, we find several of the same modes of motion as in the vacancy defect case along with two additional diffusion pathways. The interstitial defects are more mobile than the vacancy defects due to the more two-dimensional nature of the diffusion of the interstitial defects.
X-ray tests of a two-dimensional stigmatic imaging scheme with variable magnifications
Lu, J., E-mail: jlu@pppl.gov [Key Laboratory of Optoelectronic Technology and System of Ministry of Education, Chongqing University, Chongqing 400030 (China); Bitter, M.; Hill, K. W.; Delgado-Aparicio, L. F.; Efthimion, P. C.; Pablant, N. A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Beiersdorfer, P. [Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Caughey, T. A.; Brunner, J. [Inrad Optics, 181 Legrand Avenue, Northvale, New Jersey 07647 (United States)
2014-11-15T23:59:59.000Z
A two-dimensional stigmatic x-ray imaging scheme, consisting of two spherically bent crystals, one concave and one convex, was recently proposed [M. Bitter et al., Rev. Sci. Instrum. 83, 10E527 (2012)]. The Bragg angles and the radii of curvature of the two crystals of this imaging scheme are matched to eliminate the astigmatism and to satisfy the Bragg condition across both crystal surfaces for a given x-ray energy. In this paper, we consider more general configurations of this imaging scheme, which allow us to vary the magnification for a given pair of crystals and x-ray energy. The stigmatic imaging scheme has been validated for the first time by imaging x-rays generated by a micro-focus x-ray source with source size of 8.4 ?m validated by knife-edge measurements. Results are presented from imaging the tungsten L?1 emission at 8.3976 keV, using a convex Si-422 crystal and a concave Si-533 crystal with 2d-spacings of 2.21707 Å and 1.65635 Å and radii of curvature of 500 ± 1 mm and 823 ± 1 mm, respectively, showing a spatial resolution of 54.9 ?m. This imaging scheme is expected to be of interest for the two-dimensional imaging of laser produced plasmas.
Quantum Hamilton-Jacobi Approach to Two Dimensional Singular Oscillator
Ozlem Yesiltas; Bengu Demircioglu
2008-04-27T23:59:59.000Z
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.
Dynamics of quasi-two-dimensional turbulent jets
Landel, Julien Rémy Dominique Gérard
2012-11-13T23:59:59.000Z
of the core. To understand the transport and dispersion properties of quasi-two-dimensional jets we use a time-dependent advection–diffusion equation, with a mixing length hypothesis accounting for the turbulent eddy diffusivity. The model is supported... problems, such as sediment transport and coastal erosion (Joshi & Taylor, 1983), as well as environ- mental pollution. In the event of a spillage of pollutants in rivers, the prediction and monitoring of the transport and dispersion of the pollutants...
Accelerating universe in two-dimensional noncommutative dilaton cosmology
Wontae Kim; Myung Seok Yoon
2006-12-01T23:59:59.000Z
We show that the phase transition from the decelerating universe to the accelerating universe, which is of relevance to the cosmological coincidence problem, is possible in the semiclassically quantized two-dimensional dilaton gravity by taking into account the noncommutative field variables during the finite time. Initially, the quantum-mechanically induced energy from the noncommutativity among the fields makes the early universe decelerate and subsequently the universe is accelerating because the dilaton driven cosmology becomes dominant later.
Harmonic lattice behavior of two-dimensional colloidal crystals
P. Keim; G. Maret; U. Herz; H. H. von Grünberg
2004-02-17T23:59:59.000Z
Using positional data from video-microscopy and applying the equipartition theorem for harmonic Hamiltonians, we determine the wave-vector-dependent normal mode spring constants of a two-dimensional colloidal model crystal and compare the measured band-structure to predictions of the harmonic lattice theory. We find good agreement for both the transversal and the longitudinal mode. For $q\\to 0$, the measured spring constants are consistent with the elastic moduli of the crystal.
A detailed two-dimensional stellar population study of M32
C. del Burgo; R. F. Peletier; A. Vazdekis; S. Arribas; E. Mediavilla
2000-09-01T23:59:59.000Z
We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region of M32 obtained with the 2D_FIS fibre spectrograph installed at the William Herschel Telescope. From these spectra line strength maps have been reconstructed for about 20 absorption lines, mostly belonging to the Lick system. We find good agreement with long-slit line strength profiles in the literature. In contrast with previous studies, indices were azimuthally averaged along continuum isophotes of M32. A remarkable result is that no gradients are presented in the spectral indices. So, we have fitted the mean values of each spectral index and central colours to the models of Vazdekis et al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and metallicity similar to solar (Z=0.02) are the best fitted values for the innermost region of M32.
Procedures for two-dimensional electrophoresis of proteins
Tollaksen, S.L.; Giometti, C.S.
1996-10-01T23:59:59.000Z
High-resolution two-dimensional gel electrophoresis (2DE) of proteins, using isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) in the second, was first described in 1975. In the 20 years since those publications, numerous modifications of the original method have evolved. The ISO-DALT system of 2DE is a high-throughput approach that has stood the test of time. The problem of casting many isoelectric focusing gels and SDS-PAGE slab gels (up to 20) in a reproducible manner has been solved by the use of the techniques and equipment described in this manual. The ISO-DALT system of two-dimensional gel electrophoresis originated in the late 1970s and has been modified many times to improve its high-resolution, high-throughput capabilities. This report provides the detailed procedures used with the current ISO-DALT system to prepare, run, stain, and photograph two-dimensional gels for protein analysis.
Novel Logic Devices based on 2D Crystal Semiconductors: Opportunities and Challenges
Novel Logic Devices based on 2D Crystal Semiconductors: Opportunities and Challenges (Invited Paper that the advent of 2D crystal semiconductors has caused excitement in the field [2]. These materials can: djena@nd.edu Abstract Two-dimensional crystal semiconductors such as graphene, BN, and the transition
Ab initio simulations of two-dimensional electronic spectra: The SOS//QM/MM approach
Rivalta, I; Nenov, A; Cerullo, G; Mukamel, S; Garavelli, M; Garavelli, M
2013-01-01T23:59:59.000Z
calculations. Conclusions Two-dimensional electronic spectroscopy holds great potential for studying structure, dynamics,
Two-Step Growth of Two-Dimensional WSe2/MoSe2 Heterostructures
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Gong, Yongji; Lei, Sidong; Lou, Jun; Liu, Zheng; Vajtai, Robert; Zhou, Wu; Ajayan, Pullikel M
2015-08-03T23:59:59.000Z
Two dimensional (2D) materials have attracted great attention due to their unique properties and atomic thickness. Although various 2D materials have been successfully synthesized with different optical and electrical properties, a strategy for fabricating 2D heterostructures must be developed in order to construct more complicated devices for practical applications. Here we demonstrate for the first time a two-step chemical vapor deposition (CVD) method for growing transition-metal dichalcogenide (TMD) heterostructures, where MoSe2 was synthesized first and followed by an epitaxial growth of WSe2 on the edge and on the top surface of MoSe2. Compared to previously reported one-step growth methods, thismore »two-step growth has the capability of spatial and size control of each 2D component, leading to much larger (up to 169 ?m) heterostructure size, and cross-contamination can be effectively minimized. Furthermore, this two-step growth produces well-defined 2H and 3R stacking in the WSe2/MoSe2 bilayer regions and much sharper in-plane interfaces than the previously reported MoSe2/WSe2 heterojunctions obtained from one-step growth methods. The resultant heterostructures with WSe2/MoSe2 bilayer and the exposed MoSe2 monolayer display rectification characteristics of a p-n junction, as revealed by optoelectronic tests, and an internal quantum efficiency of 91% when functioning as a photodetector. A photovoltaic effect without any external gates was observed, showing incident photon to converted electron (IPCE) efficiencies of approximately 0.12%, providing application potential in electronics and energy harvesting.« less
Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases
Lianyi He; Haifeng Lv; Gaoqing Cao; Hui Hu; Xia-Ji Liu
2015-08-14T23:59:59.000Z
We present a theoretical study of the ground state of the BCS-BEC crossover in dilute two-dimensional Fermi gases. While the mean-field theory provides a simple and analytical equation of state, the pressure is equal to that of a noninteracting Fermi gas in the entire BCS-BEC crossover, which is not consistent with the features of a weakly interacting Bose condensate in the BEC limit and a weakly interacting Fermi liquid in the BCS limit. The inadequacy of the 2D mean-field theory indicates that the quantum fluctuations are much more pronounced than those in 3D. In this work, we show that the inclusion of the Gaussian quantum fluctuations naturally recovers the above features in both the BEC and the BCS limits. In the BEC limit, the missing logarithmic dependence on the boson chemical potential is recovered by the quantum fluctuations. Near the quantum phase transition from the vacuum to the BEC phase, we compare our equation of state with the known grand canonical equation of state of 2D Bose gases and determine the ratio of the composite boson scattering length $a_{\\rm B}$ to the fermion scattering length $a_{\\rm 2D}$. We find $a_{\\rm B}\\simeq 0.56 a_{\\rm 2D}$, in good agreement with the exact four-body calculation. We compare our equation of state in the BCS-BEC crossover with recent results from the quantum Monte Carlo simulations and the experimental measurements and find good agreements.
Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases
Lianyi He; Haifeng Lv; Gaoqing Cao; Hui Hu; Xia-Ji Liu
2015-06-23T23:59:59.000Z
We present a theoretical study of the ground state of the BCS-BEC crossover in dilute two-dimensional Fermi gases. While the mean-field theory provides a simple and analytical equation of state, the pressure is equal to that of a noninteracting Fermi gas in the entire BCS-BEC crossover, which is not consistent with the features of the weakly interacting Bose condensate in the BEC limit and the weakly interacting Fermi liquid in the BCS limit. The inadequacy of the 2D mean-field theory indicates that the quantum fluctuations are much more pronounced than those in 3D. In this work, we show that the inclusion of the Gaussian quantum fluctuations naturally recovers the above features in both the BEC and BCS limits. In the BEC limit, the missing logarithmic dependence on the boson chemical potential is recovered by the quantum fluctuations. Near the quantum phase transition from the vacuum to the BEC phase, we compare our equation of state with the known grand canonical equation of state of 2D Bose gases and determine the ratio of the composite boson scattering length $a_{\\rm B}$ to the fermion scattering length $a_{\\rm 2D}$. We find $a_{\\rm B}\\simeq 0.56 a_{\\rm 2D}$, in good agreement with the exact four-body calculation. We compare our equation of state in the BCS-BEC crossover with recent results from the quantum Monte Carlo simulations and the experimental measurements and find good agreements.
2D protrusion but not motility predicts growth factor–induced cancer cell migration in 3D collagen
Meyer, Aaron Samuel
Growth factor–induced migration is a critical step in the dissemination and metastasis of solid tumors. Although differences in properties characterizing cell migration on two-dimensional (2D) substrata versus within ...
A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures
Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.
1998-12-14T23:59:59.000Z
We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.
Thin films versus 2D sheets in layered structures: graphene and 2D metallic sheets
Bo E. Sernelius
2012-09-19T23:59:59.000Z
We study an interface between two media separated by a strictly 2D sheet. We show how the amplitude reflection coefficient can be modeled by that for an interface where the 2D sheet has been replaced by a film of small but finite thickness. We give the relationship between the 3D dielectric function of the thin film and the 2D dielectric function of the sheet. We choose graphene and a 2D metallic sheet as illustrative examples. This approach turns out to be very useful when treating graphene or graphene like sheets in non-planar structures
Testability of non-autonomous two dimensional iterative logic array
Nagumo, Hideo
1991-01-01T23:59:59.000Z
' SCIENCE August III91 Major Subject: Electrical Engineering TESTABILITY OF NON-AUTONOMOUS T'A'0 DIMENSIONAL ITERATIVE LOGIC ARRAY A Thesis by HIDEO NAGUMO Approved as to style and content by: . . ed~ I(aran L. watson (Chair of Committee) Mi Lu... (Member) William G. Bliss (Member) Donald K. Friesen (Member) Jo Howze (Head of Department) August 1991 ABSTRACT Testability of i%on-Autonomous Two-Dimensional Iterative Logic Array. (August 1991) Hideo iX'agumo, B. S. , Shinshu University...
Anomalous Hall effect in a two-dimensional electron gas
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
Anomalous Hall effect in a two-dimensional electron gas Tamara S. Nunner,1 N. A. Sinitsyn,2,3 Mario F. Borunda,2 V. K. Dugaev,4 A. A. Kovalev,2 Ar. Abanov,2 Carsten Timm,5 T. Jungwirth,6,7 Jun-ichiro Inoue,8 A. H. MacDonald,9 and Jairo Sinova2...,6 1Institut f?r Theoretische Physik, Freie Universit?t Berlin, Arnimallee 14, 14195 Berlin, Germany 2Department of Physics, Texas A&M University, College Station, Texas 77843-4242, USA 3CNLS/CCS-3, Los Alamos National Laboratory, Los Alamos, New...
Laminar flame and acoustic waves in two-dimensional flow
Zaytsev, M. L., E-mail: mlzaytsev@gmail.com; Akkerman, V. B., E-mail: slava.akkerman@gmail.com [Russian Academy of Sciences, Nuclear Safety Institute (Russian Federation)
2011-03-15T23:59:59.000Z
The complete system of fluid dynamics equations describing the development of instability of a reaction front in a two-dimensional flow in reversed time are reduced to a closed system of equations of front dynamics by using Lagrangian variables and integrals of motion. The system can be used to analyze processes behind the front without solving the complete system of fluid dynamics and chemical kinetics equations. It is demonstrated how the gas density disturbances induced by the moving front can be described in the adiabatic approximation.
Optical and electronic properties of two dimensional graphitic silicon carbide
Lin, Xiao; Lin, Shisheng; Hakro, Ayaz Ali; Cao, Te; Chen, Hongsheng; Zhang, Baile
2012-01-01T23:59:59.000Z
Optical and electronic properties of two dimensional few layers graphitic silicon carbide (GSiC), in particular monolayer and bilayer, are investigated by density functional theory and found different from that of graphene and silicene. Monolayer GSiC has direct bandgap while few layers exhibit indirect bandgap. The bandgap of monolayer GSiC can be tuned by an in-plane strain. Properties of bilayer GSiC are extremely sensitive to the interlayer distance. These predictions promise that monolayer GSiC could be a remarkable candidate for novel type of light-emitting diodes utilizing its unique optical properties distinct from graphene, silicene and few layers GSiC.
Two-dimensional flux-corrected transport solver for convectively dominated flows
Baer, M.R.; Gross, R.J.
1986-01-01T23:59:59.000Z
A numerical technique designed to solve a wide class of convectively dominated flow problems is presented. An attractive feature of the technique is its ability to resolve the behavior of field quantities possessing large gradients and/or shocks. The method is a finite-difference technique known as flux-corrected transport (FCT) that maintains four important numerical considerations - stability, accuracy, monotonicity, and conservation. The theory and methodology of two-dimensional FCT is presented. The method is applied in demonstrative example calculations of a 2-D Riemann problem with known exact solutions and to the Euler equations in a study of classical Rayleigh-Taylor and Kelvin-Helmholtz instability problems. The FCT solver has been vectorized for execution on the Cray 1S - a typical call with a 50 by 50 mesh requires about 0.00428 cpu seconds of execution time per call to the routine. Additionally, we have maintained a modular structure for the solver that eases its implementation. Fortran listings of two versions of the 2-D FCT solvers are appended with a driver main program illustrating the call sequence for the modules. 59 refs., 49 figs.
Guo, Hongxuan, E-mail: Guo.hongxuan@nims.go.jp, E-mail: msxu@zju.edu.cn [Global Research Center for Environment and Energy Based on Nanomaterials Science National Institute for Materials Science (NIMS) 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Gao, Jianhua; Ishida, Nobuyuki [International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Xu, Mingsheng, E-mail: Guo.hongxuan@nims.go.jp, E-mail: msxu@zju.edu.cn [State Key Laboratory of Silicon Materials, Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Fujita, Daisuke [Advanced Key Technologies Division, Global Research Center for Environment and Energy Based on Nanomaterials Science, and International Center for Young Scientists, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)
2014-01-20T23:59:59.000Z
Characterization of the structural and physical properties of two-dimensional (2D) materials, such as layer number and inelastic mean free path measurements, is very important to optimize their synthesis and application. In this study, we characterize the layer number and morphology of hexagonal boron nitride (h-BN) nanosheets on a metallic substrate using field emission scanning electron microscopy (FE-SEM) and scanning helium ion microscopy (HIM). Using scanning beams of various energies, we could analyze the dependence of the intensities of secondary electrons on the thickness of the h-BN nanosheets. Based on the interaction between the scanning particles (electrons and helium ions) and h-BN nanosheets, we deduced an exponential relationship between the intensities of secondary electrons and number of layers of h-BN. With the attenuation factor of the exponential formula, we calculate the inelastic mean free path of electrons and helium ions in the h-BN nanosheets. Our results show that HIM is more sensitive and consistent than FE-SEM for characterizing the number of layers and morphology of 2D materials.
Two-dimensional nuclear magnetic resonance of quadrupolar systems
Wang, Shuanhu
1997-09-17T23:59:59.000Z
This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combining the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.
Phonons in two-dimensional soft colloidal crystals
Ke Chen; Tim Still; Samuel Schoenholz; Kevin B. Aptowicz; Michael Schindler; A. C. Maggs; Andrea J. Liu; A. G. Yodh
2013-09-11T23:59:59.000Z
The vibrational modes of pristine and polycrystalline monolayer colloidal crystals composed of thermosensitive microgel particles are measured using video microscopy and covariance matrix analysis. At low frequencies, the Debye relation for two dimensional harmonic crystals is observed in both crystal types; at higher frequencies, evidence for van Hove singularities in the phonon density of states is significantly smeared out by experimental noise and measurement statistics. The effects of these errors are analyzed using numerical simulations. We introduce methods to correct for these limitations, which can be applied to disordered systems as well as crystalline ones, and we show that application of the error correction procedure to the experimental data leads to more pronounced van Hove singularities in the pristine crystal. Finally, quasi-localized low-frequency modes in polycrystalline two-dimensional colloidal crystals are identified and demonstrated to correlate with structural defects such as dislocations, suggesting that quasi-localized low-frequency phonon modes may be used to identify local regions vulnerable to rearrangements in crystalline as well as amorphous solids.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Mahmood, Qasim; Bak, Seong-Min; Kim, Min G.; Yun, Sol; Yang, Xiao-Qing; Shin, Hyeon S.; Kim, Woo S.; Braun, Paul V.; Park, Ho S.
2015-04-08T23:59:59.000Z
Two-dimensional (2D) heteronanosheets are currently the focus of intense study due to the unique properties that emerge from the interplay between two low-dimensional nanomaterials with different properties. However, the properties and new phenomena based on the two 2D heteronanosheets interacting in a 3D hierarchical architecture have yet to be explored. Here, we unveil the surface redox charge storage mechanism of surface-exposed WS2 nanosheets assembled in a 3D hierarchical heterostructure using in situ synchrotron X-ray absorption and Raman spectroscopic methods. The surface dominating redox charge storage of WS2 is manifested in a highly reversible and ultrafast capacitive fashion due to themore »interaction of heteronanosheets and the 3D connectivity of the hierarchical structure. In contrast, compositionally identical 2D WS2 structures fail to provide a fast and high capacitance with different modes of lattice vibration. The distinctive surface capacitive behavior of 3D hierarchically structured heteronanosheets is associated with rapid proton accommodation into the in-plane W–S lattice (with the softening of the E2g bands), the reversible redox transition of the surface-exposed intralayers residing in the electrochemically active 1T phase of WS2 (with the reversible change in the interatomic distance and peak intensity of W–W bonds), and the change in the oxidation state during the proton insertion/deinsertion process. This proposed mechanism agrees with the dramatic improvement in the capacitive performance of the two heteronanosheets coupled in the hierarchical structure.« less
Spin from defects in two-dimensional quantum field theory
Sebastian Novak; Ingo Runkel
2015-06-24T23:59:59.000Z
We build two-dimensional quantum field theories on spin surfaces starting from theories on oriented surfaces with networks of topological defect lines and junctions. The construction uses a combinatorial description of the spin structure in terms of a triangulation equipped with extra data. The amplitude for the spin surfaces is defined to be the amplitude for the underlying oriented surface together with a defect network dual to the triangulation. Independence of the triangulation and of the other choices follows if the line defect and junctions are obtained from a Delta-separable Frobenius algebra with involutive Nakayama automorphism in the monoidal category of topological defects. For rational conformal field theory we can give a more explicit description of the defect category, and we work out two examples related to free fermions in detail: the Ising model and the so(n) WZW model at level 1.
Spin from defects in two-dimensional quantum field theory
Novak, Sebastian
2015-01-01T23:59:59.000Z
We build two-dimensional quantum field theories on spin surfaces starting from theories on oriented surfaces with networks of topological defect lines and junctions. The construction uses a combinatorial description of the spin structure in terms of a triangulation equipped with extra data. The amplitude for the spin surfaces is defined to be the amplitude for the underlying oriented surface together with a defect network dual to the triangulation. Independence of the triangulation and of the other choices follows if the line defect and junctions are obtained from a Delta-separable Frobenius algebra with involutive Nakayama automorphism in the monoidal category of topological defects. For rational conformal field theory we can give a more explicit description of the defect category, and we work out two examples related to free fermions in detail: the Ising model and the so(n) WZW model at level 1.
Incoherent control and entanglement for two-dimensional coupled systems
R. Romano; D. D'Alessandro
2005-10-03T23:59:59.000Z
We investigate accessibility and controllability of a quantum system S coupled to a quantum probe P, both described by two-dimensional Hilbert spaces, under the hypothesis that the external control affects only P. In this context accessibility and controllability properties describe to what extent it is possible to drive the state of the system S by acting on P and using the interaction between the two systems. We give necessary and sufficient conditions for these properties and we discuss the relation with the entangling capability of the interaction between S and P. In particular, we show that controllability can be expressed in terms of the SWAP operator, acting on the composite system, and its square root.
Quantum Emission from Two-Dimensional Black Holes
Steven B. Giddings; W. M. Nelson
2009-11-27T23:59:59.000Z
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.
A ballistic two-dimensional-electron-gas Andreev interferometer
Amado, M., E-mail: mario.amadomontero@sns.it; Fornieri, A.; Sorba, L.; Giazotto, F., E-mail: f.giazotto@sns.it [NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa (Italy); Biasiol, G. [CNR-IOM, Laboratorio TASC, Area Science Park, I-34149 Trieste (Italy)
2014-06-16T23:59:59.000Z
We report the realization and investigation of a ballistic Andreev interferometer based on an InAs two dimensional electron gas coupled to a superconducting Nb loop. We observe strong magnetic modulations in the voltage drop across the device due to quasiparticle interference within the weak-link. The interferometer exhibits flux noise down to ?80???{sub 0}/?(Hz) and a robust behavior in temperature with voltage oscillations surviving up to ?7?K. Besides this remarkable performance, the device represents a crucial first step for the realization of a fully-tunable ballistic superconducting magnetometer and embodies a potential advanced platform for the investigation of Majorana bound states, non-local entanglement of Cooper pairs, as well as the manipulation and control of spin triplet correlations.
Exit time distribution in spherically symmetric two-dimensional domains
Rupprecht, J -F; Grebenkov, D S; Voituriez, R
2014-01-01T23:59:59.000Z
The distribution of exit times is computed for a Brownian particle in spherically symmetric two- dimensional domains (disks, angular sectors, annuli) and in rectangles that contain an exit on their boundary. The governing partial differential equation of Helmholtz type with mixed Dirichlet- Neumann boundary conditions is solved analytically. We propose both an exact solution relying on a matrix inversion, and an approximate explicit solution. The approximate solution is shown to be exact for an exit of vanishing size and to be accurate even for large exits. For angular sectors, we also derive exact explicit formulas for the moments of the exit time. For annuli and rectangles, the approximate expression of the mean exit time is shown to be very accurate even for large exits. The analysis is also extended to biased diffusion. Since the Helmholtz equation with mixed boundary conditions is encountered in microfluidics, heat propagation, quantum billiards, and acoustics, the developed method can find numerous appl...
Reconnection events in two-dimensional Hall magnetohydrodynamic turbulence
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
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.
Two-dimensional AMR simulations of colliding flows
Niklaus, Markus; Niemeyer, Jens C
2009-01-01T23:59:59.000Z
Colliding flows are a commonly used scenario for the formation of molecular clouds in numerical simulations. Due to the thermal instability of the warm neutral medium, turbulence is produced by cooling. We carry out a two-dimensional numerical study of such colliding flows in order to test whether statistical properties inferred from adaptive mesh refinement (AMR) simulations are robust with respect to the applied refinement criteria. We compare probability density functions of various quantities as well as the clump statistics and fractal dimension of the density fields in AMR simulations to a static-grid simulation. The static grid with 2048^2 cells matches the resolution of the most refined subgrids in the AMR simulations. The density statistics is reproduced fairly well by AMR. Refinement criteria based on the cooling time or the turbulence intensity appear to be superior to the standard technique of refinement by overdensity. Nevertheless, substantial differences in the flow structure become apparent. In...
M. B. Isichenko; A. V. Gruzinov
1996-09-06T23:59:59.000Z
The long-time relaxation of ideal two dimensional magnetohydrodynamic turbulence subject to the conservation of two infinite families of constants of motion---the magnetic and the "cross" topology invariants--is examined. The analysis of the Gibbs ensemble, where all integrals of motion are respected, predicts the initial state to evolve into an equilibrium, stable coherent structure (the most probable state) and decaying Gaussian turbulence (fluctuations) with a vanishing, but always positive temperature. The non-dissipative turbulence decay is accompanied by decrease in both the amplitude and the length scale of the fluctuations, so that the fluctuation energy remains finite. The coherent structure represents a set of singular magnetic islands with plasma flow whose magnetic topology is identical to that of the initial state, while the energy and the cross topology invariants are shared between the coherent structure and the Gaussian turbulence. These conservation laws suggest the variational principle of iso-topological relaxation which allows us to predict the appearance of the final state from a given initial state. For a generic initial condition having X points in the magnetic field, the coherent structure has universal types of singularities: current sheets terminating at Y points. These structures, which are similar to those resulting from the 2D relaxation of magnetic field frozen into an ideally conducting viscous fluid, are observed in the numerical experiment of Biskamp and Welter. The Gibbs ensemble method developed in this work admits extension to other Hamiltonian systems with invariants not higher than quadratic in the highest-order-derivative variables. The turbulence in two dimensional Euler fluid is of a different nature: there the coherent structures are also formed, but the fluctuations about these structures are non-Gaussian.
Coexistence of Fermi arcs with two-dimensional gapless Dirac states
Grushin, Adolfo G.
We present a physical scenario in which both Fermi arcs and two-dimensional gapless Dirac states coexist as boundary modes at the same two-dimensional surface. This situation is realized in topological insulator–Weyl ...
The Electronic Structure of a Two-Dimensional Pure Copper Oxide...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
The Electronic Structure of a Two-Dimensional Pure Copper Oxide Lattice The Electronic Structure of a Two-Dimensional Pure Copper Oxide Lattice Print Monday, 27 October 2014 09:44...
Pan, Kuo-Chuan; Hempel, Matthias; Thielemann, Friedrich-Karl
2015-01-01T23:59:59.000Z
The neutrino mechanism of core-collapse supernova is investigated via non-relativistic, two-dimensional (2D), neutrino radiation-hydrodynamic simulations. For the transport of electron flavor neutrinos, we use the interaction rates defined by Bruenn (1985) and the isotropic diffusion source approximation (IDSA) scheme, which decomposes the transported particles into trapped particle and streaming particle components. Heavy neutrinos are described by a leakage scheme. Unlike the "ray-by-ray" approach in other multi-dimensional IDSA implementations in spherical coordinates, we use cylindrical coordinates and solve the trapped particle component in multiple dimensions, improving the proto-neutron star resolution and the neutrino transport in angular and temporal directions. We perform Newtonian 1D and 2D ab initio simulations from prebounce core collapse to several hundred milliseconds postbounce with 11, 15, 21, and 27 $M_\\odot$ progenitors from Woosley et al.~(2002) with the HS(DD2) equation of state. We obtai...
2D microwave imaging reflectometer electronics
Spear, A. G.; Domier, C. W., E-mail: cwdomier@ucdavis.edu; Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C. [Electrical and Computer Engineering, University of California, Davis, California 95616 (United States); Tobias, B. J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2014-11-15T23:59:59.000Z
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.
Entropy and Kinetics of Point-Defects in Two-Dimensional Dipolar Crystals
Wolfgang Lechner; David Polster; Georg Maret; Christoph Dellago; Peter Keim
2015-02-18T23:59:59.000Z
We study in experiment and with computer simulation the free energy and the kinetics of vacancy and interstitial defects in two-dimensional dipolar crystals. The defects appear in different local topologies which we characterize by their point group symmetry; $C_n$ is the n-fold cyclic group and $D_n$ is the dihedral group, including reflections. The frequency of different local topologies is not determined by their almost degenerate energies but dominated by entropy for symmetric configurations. The kinetics of the defects is fully reproduced by a master equation in a multi-state Markov model. In this model, the system is described by the state of the defect and the time evolution is given by transitions occurring with particular rates. These transition rate constants are extracted from experiments and simulations using an optimisation procedure. The good agreement between experiment, simulation and master equation thus provides evidence for the accuracy of the model.
Method and apparatus for two-dimensional spectroscopy
DeCamp, Matthew F. (Swarthmore, PA); Tokmakoff, Andrei (Lexington, MA)
2010-10-12T23:59:59.000Z
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.
Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals
Stavroula Foteinopoulou
2003-12-12T23:59:59.000Z
In this dissertation, they have undertaken the challenge to understand the unusual propagation properties of the photonic crystal (PC). The photonic crystal is a medium where the dielectric function is periodically modulated. These types of structures are characterized by bands and gaps. In other words, they are characterized by frequency regions where propagation is prohibited (gaps) and regions where propagation is allowed (bands). In this study they focus on two-dimensional photonic crystals, i.e., structures with periodic dielectric patterns on a plane and translational symmetry in the perpendicular direction. They start by studying a two-dimensional photonic crystal system for frequencies inside the band gap. The inclusion of a line defect introduces allowed states in the otherwise prohibited frequency spectrum. The dependence of the defect resonance state on different parameters such as size of the structure, profile of incoming source, etc., is investigated in detail. For this study, they used two popular computational methods in photonic crystal research, the Finite Difference Time Domain method (FDTD) and the Transfer Matrix Method (TMM). The results for the one-dimensional defect system are analyzed, and the two methods, FDTD and TMM, are compared. Then, they shift their attention only to periodic two-dimensional crystals, concentrate on their band properties, and study their unusual refractive behavior. Anomalous refractive phenomena in photonic crystals included cases where the beam refracts on the ''wrong'' side of the surface normal. The latter phenomenon, is known as negative refraction and was previously observed in materials where the wave vector, the electric field, and the magnetic field form a left-handed set of vectors. These materials are generally called left-handed materials (LHM) or negative index materials (NIM). They investigated the possibility that the photonic crystal behaves as a LHM, and how this behavior relates with the observed negatively refractive phenomena. They found that in the PC system, negative refraction is neither a prerequisite nor guarantees left-handed behavior. They examined carefully the condition to obtain left-handed behavior in the PC. They proposed a wedge type of experiment, in accordance with the experiment performed on the traditional LHM, to test these conditions. They found that for certain frequencies the PC shows left-handed behavior and acts in some respects like a homogeneous medium with a negative refractive index. they used the realistic PC system for this case to show how negative refraction occurs at the interface between a material with a positive and a material with a negative refractive index. Their findings indicate that the formation of the negatively refracted beam is not instantaneous and involves a transient time. With this time-dependent analysis, they were able to address previous controversial issues about negative refraction concerning causality and the speed of light limit. Finally, they attempt a systematic study of anomalous refractive phenomena that can occur at the air-PC interface. They observe cases where only a single refracted beam (in the positive or negative direction) is present, as well as cases with birefringence. they classify these different effects according to their origin and type of propagation (left-handed or not). For a complete study of the system, they also obtain expressions for the energy and group velocities, and show their equality. For cases with very low index contrast, band folding becomes an artificiality. They discuss the validity of their findings when they move to the limit of photonic crystals with a low index modulation.
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
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.
Kolmogorov flow in two dimensional strongly coupled dusty plasma
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
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?
Ferromagnetism in the two-dimensional periodic Anderson model
Batista, C. D.; Bonca, J.; Gubernatis, J. E.
2001-05-01T23:59:59.000Z
Using the constrained-path Monte Carlo method, we studied the magnetic properties of the two-dimensional periodic Anderson model for electron fillings between 1/4 and 1/2. We also derived two effective low-energy theories to assist in interpreting the numerical results. For 1/4 filling, we found that the system can be a Mott or a charge-transfer insulator, depending on the relative values of the Coulomb interaction and the charge-transfer gap between the two noninteracting bands. The insulator may be a paramagnet or antiferromagnet. We concentrated on the effect of electron doping on these insulating phases. Upon doping we obtained a partially saturated ferromagnetic phase for low concentrations of conduction electrons. If the system were a charge-transfer insulator, we would find that the ferromagnetism is induced by the well-known Ruderman-Kittel-Kasuya-Yosida interaction. However, we found a novel correlated hopping mechanism inducing the ferromagnetism in the region where the nondoped system is a Mott insulator. Our regions of ferromagnetism spanned a much smaller doping range than suggested by recent slave boson and dynamical mean-field theory calculations, but they were consistent with that obtained by density-matrix renormalization group calculations of the one-dimensional periodic Anderson model.
Acoustic dispersion in a two-dimensional dipole system
Golden, Kenneth I.; Kalman, Gabor J.; Donko, Zoltan; Hartmann, Peter [Department of Mathematics and Statistics, College of Engineering and Mathematical Sciences, University of Vermont, Burlington, Vermont 05401-1455 (United States); Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States); Research Institute for Solid State Physics and Optics of the Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary)
2008-07-15T23:59:59.000Z
We calculate the full density response function and from it the long-wavelength acoustic dispersion for a two-dimensional system of strongly coupled point dipoles interacting through a 1/r{sup 3} potential at arbitrary degeneracy. Such a system has no random-phase-approximation (RPA) limit and the calculation has to include correlations from the outset. We follow the quasilocalized charge (QLC) approach, accompanied by molecular-dynamics (MD) simulations. Similarly to what has been recently reported for the closely spaced classical electron-hole bilayer [G. J. Kalman et al., Phys. Rev. Lett. 98, 236801 (2007)] and in marked contrast to the RPA, we report a long-wavelength acoustic phase velocity that is wholly maintained by particle correlations and varies linearly with the dipole moment p. The oscillation frequency, calculated both in an extended QLC approximation and in the Singwi-Tosi-Land-Sjolander approximation [Phys. Rev. 176, 589 (1968)], is invariant in form over the entire classical to quantum domains all the way down to zero temperature. Based on our classical MD-generated pair distribution function data and on ground-state energy data generated by recent quantum Monte Carlo simulations on a bosonic dipole system [G. E. Astrakharchik et al., Phys. Rev. Lett. 98, 060405 (2007)], there is a good agreement between the QLC approximation kinetic sound speeds and the standard thermodynamic sound speeds in both the classical and quantum domains.
Classical Symmetries of Some Two-Dimensional Models
John H. Schwarz
1995-03-27T23:59:59.000Z
It is well-known that principal chiral models and symmetric space models in two-dimensional Minkowski space have an infinite-dimensional algebra of hidden symmetries. Because of the relevance of symmetric space models to duality symmetries in string theory, the hidden symmetries of these models are explored in some detail. The string theory application requires including coupling to gravity, supersymmetrization, and quantum effects. However, as a first step, this paper only considers classical bosonic theories in flat space-time. Even though the algebra of hidden symmetries of principal chiral models is confirmed to include a Kac--Moody algebra (or a current algebra on a circle), it is argued that a better interpretation is provided by a doubled current algebra on a semi-circle (or line segment). Neither the circle nor the semi-circle bears any apparent relationship to the physical space. For symmetric space models the line segment viewpoint is shown to be essential, and special boundary conditions need to be imposed at the ends. The algebra of hidden symmetries also includes Virasoro-like generators. For both principal chiral models and symmetric space models, the hidden symmetry stress tensor is singular at the ends of the line segment.
Two-dimensional simulations of pulsational pair-instability supernovae
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5 TablesExports to3,1,50022,3,,0,,6,1,SeparationConnect1.08]Te[subscriptM-PACEResponses to aConnect TowardsTestConnect(2D-CARS):(Journal
Optical properties of two-dimensional metamaterial photonic crystals
Mejķa-Salazar, J. R. [Departamento de Fķsica, Universidad del Valle, AA 25360, Cali, Colombia and Instituto de Fķsica, UNICAMP, Campinas-SP 13083-859 (Brazil)
2013-12-14T23:59:59.000Z
In the present work, we theoretically study a 2D photonic crystal (PC) comprised by double negative (DNG) metamaterial cylinders, showing that such a system presents a superior light-matter interaction when compared with their single negative (SNG) plasmonic PC counterparts, suggesting a route to enhance the performance of sensors and photovoltaic cells. On the other hand, we have observed that depending on the frequency, the mode symmetry resembles either the case of SNG electric (SNG-E) or SNG magnetic (SNG-M) PC, suggesting that either the electric or magnetic character of the DNG metamaterial dominates in each case.
Tamoghna Das; T. Lookman; M. M. Bandi
2015-05-21T23:59:59.000Z
Two-dimensional (2D) particulate aggregates formed due to competing interactions exhibit a range of non-equilibrium steady state morphologies from finite-size compact crystalline structures to non-compact string-like conformations. We report a transition in heterogeneous microscopic dynamics across this morphological hierarchy as a function of decreasing long-range repulsion relative to short-range attraction at a constant {\\it low} density and temperature. Following a very slow cooling protocol to form steady state aggregates, we show that geometric frustration inherent to competing interactions assures non-ergodicity of the system, which in turn results in long-time sub diffusive relaxation of the same. Analysing individual particle trajectories generated by molecular dynamics, we identify {\\it caging} dynamics of particles in compact clusters in contrast to the {\\it bonding} scenario for non-compact ones. Finally, by monitoring temperature dependence, we present a generic relation between diffusivity and structural randomness of the aggregates, irrespective of their thermodynamic equilibrium.
Prasad Perlekar; Nairita Pal; Rahul Pandit
2015-06-29T23:59:59.000Z
We study two-dimensional (2D) binary-fluid turbulence by carrying out an extensive direct numerical simulation (DNS) of the forced, statistically steady turbulence in the coupled Cahn-Hilliard and Navier-Stokes equations. In the absence of any coupling, we choose parameters that lead (a) to spinodal decomposition and domain growth, which is characterized by the spatiotemporal evolution of the Cahn-Hilliard order parameter $\\phi$, and (b) the formation of an inverse-energy-cascade regime in the energy spectrum $E(k)$, in which energy cascades towards wave numbers $k$ that are smaller than the energy-injection scale $k_{inj}$ in the turbulent fluid. We show that the Cahn-Hilliard-Navier-Stokes coupling leads to an arrest of phase separation at a length scale $L_c$, which we evaluate from $S(k)$, the spectrum of the fluctuations of $\\phi$. We demonstrate that (a) $L_c \\sim L_H$, the Hinze scale that follows from balancing inertial and interfacial-tension forces, and (b) $L_c$ is independent, within error bars, of the diffusivity $D$. We elucidate how this coupling modifies $E(k)$ by blocking the inverse energy cascade at a wavenumber $k_c$, which we show is $\\simeq 2\\pi/L_c$. We compare our work with earlier studies of this problem.
Two-dimensional defect modes in optically induced photonic lattices
Wang Jiandong; Yang Jianke; Chen Zhigang [Department of Mathematics and Statistics, University of Vermont, Burlington, Vermont 05401 (United States); Department of Physics and Astronomy, San Francisco State University, San Francisco, California 94132 (United States)
2007-07-15T23:59:59.000Z
In this article, localized linear defect modes due to band gap guidance in two-dimensional photonic lattices with localized or nonlocalized defects are investigated theoretically. First, when the defect is localized and weak, eigenvalues of defect modes bifurcated from edges of Bloch bands are derived analytically. It is shown that in an attractive (repulsive) defect, defect modes bifurcate out from Bloch-band edges with normal (anomalous) diffraction coefficients. Furthermore, distances between defect-mode eigenvalues and Bloch-band edges decrease exponentially with the defect strength, which is very different from the one-dimensional case where such distances decrease quadratically with the defect strength. It is also found that some defect-mode branches bifurcate not from Bloch-band edges, but from quasiedge points within Bloch bands, which is very unusual. Second, when the defect is localized but strong, defect modes are determined numerically. It is shown that both the repulsive and attractive defects can support various types of defect modes such as fundamental, dipole, quadrupole, and vortex modes. These modes reside in various band gaps of the photonic lattice. As the defect strength increases, defect modes move from lower band gaps to higher ones when the defect is repulsive, but remain within each band gap when the defect is attractive, similar to the one-dimensional case. The same phenomena are observed when the defect is held fixed while the applied dc field (which controls the lattice potential) increases. Lastly, if the defect is nonlocalized (i.e., it persists at large distances in the lattice), it is shown that defect modes can be embedded inside the continuous spectrum, and they can bifurcate out from edges of the continuous spectrum algebraically rather than exponentially.
Periodic trajectories for a two-dimensional nonintegrable Hamiltonian
Baranger, M.; Davies, K.T.R.
1987-08-01T23:59:59.000Z
A numerical study is made of the classical periodic trajectories for the two-dimensional nonintegrable Hamiltonian H = 1/2(p/sup 2//sub x/+p/sup 2//sub y/)+(y-1/2x/sup 2/)/sup 2/+0.05 x/sup 2/. In addition to x--y pictures of the trajectories, E--tau (energy--period) plots of the periodic families are presented. Efforts have been ade to include all trajectories with short periods and all simple branchings of these trajectories. The monodromy matrix has been calculated in all cases, and from it the stability properties are derived. The topology of the E--tau plot has been explored, with the following results. One family may have several stable regions. The plot is not completely connected; there are islands. The plot is not a tree; there are cycles. There are isochronous branchings, period-doublings, and period-multiplyings of higher orders, and examples of each of these are presented. There is often more than one branch issuing from a branch point. Some general empirical rules are inferred. In particular, the existence of isochronous branching is seen to be a consequence of the symmetry of the Hamiltonian. All these results agree with the general classification of possible branchings derived in Ref. (10). (M. A. M. de Aguiar, C. P. Malta, M. Baranger, and K. T. R. Davies, in preparation). Finally, some nonperiodic trajectories are calculated to illustrate the fact that stable periodic trajectories lie in ''regular'' regions of phase space, while unstable ones lie in ''chaotic'' regions.
Quantum holographic encoding in a two-dimensional electron gas
Moon, Christopher
2010-05-26T23:59:59.000Z
The advent of bottom-up atomic manipulation heralded a new horizon for attainable information density, as it allowed a bit of information to be represented by a single atom. The discrete spacing between atoms in condensed matter has thus set a rigid limit on the maximum possible information density. While modern technologies are still far from this scale, all theoretical downscaling of devices terminates at this spatial limit. Here, however, we break this barrier with electronic quantum encoding scaled to subatomic densities. We use atomic manipulation to first construct open nanostructures - 'molecular holograms' - which in turn concentrate information into a medium free of lattice constraints: the quantum states of a two-dimensional degenerate Fermi gas of electrons. The information embedded in the holograms is transcoded at even smaller length scales into an atomically uniform area of a copper surface, where it is densely projected into both two spatial degrees of freedom and a third holographic dimension mapped to energy. In analogy to optical volume holography, this requires precise amplitude and phase engineering of electron wavefunctions to assemble pages of information volumetrically. This data is read out by mapping the energy-resolved electron density of states with a scanning tunnelling microscope. As the projection and readout are both extremely near-field, and because we use native quantum states rather than an external beam, we are not limited by lensing or collimation and can create electronically projected objects with features as small as {approx}0.3 nm. These techniques reach unprecedented densities exceeding 20 bits/nm{sup 2} and place tens of bits into a single fermionic state.
Lyo, Sungkwun Kenneth; Pan, Wei; Reno, John Louis; Wendt, Joel Robert; Barton, Daniel Lee
2008-09-01T23:59:59.000Z
We have investigated the physics of Bloch oscillations (BO) of electrons, engineered in high mobility quantum wells patterned into lateral periodic arrays of nanostructures, i.e. two-dimensional (2D) quantum dot superlattices (QDSLs). A BO occurs when an electron moves out of the Brillouin zone (BZ) in response to a DC electric field, passing back into the BZ on the opposite side. This results in quantum oscillations of the electron--i.e., a high frequency AC current in response to a DC voltage. Thus, engineering a BO will yield continuously electrically tunable high-frequency sources (and detectors) for sensor applications, and be a physics tour-de-force. More than a decade ago, Bloch oscillation (BO) was observed in a quantum well superlattice (QWSL) in short-pulse optical experiments. However, its potential as electrically biased high frequency source and detector so far has not been realized. This is partially due to fast damping of BO in QWSLs. In this project, we have investigated the possibility of improving the stability of BO by fabricating lateral superlattices of periodic coupled nanostructures, such as metal grid, quantum (anti)dots arrays, in high quality GaAs/Al{sub x}Ga{sub 1-x}As heterostructures. In these nanostructures, the lateral quantum confinement has been shown theoretically to suppress the optical-phonon scattering, believed to be the main mechanism for fast damping of BO in QWSLs. Over the last three years, we have made great progress toward demonstrating Bloch oscillations in QDSLs. In the first two years of this project, we studied the negative differential conductance and the Bloch radiation induced edge-magnetoplasmon resonance. Recently, in collaboration with Prof. Kono's group at Rice University, we investigated the time-domain THz magneto-spectroscopy measurements in QDSLs and two-dimensional electron systems. A surprising DC electrical field induced THz phase flip was observed. More measurements are planned to investigate this phenomenon. In addition to their potential device applications, periodic arrays of nanostructures have also exhibited interesting quantum phenomena, such as a possible transition from a quantum Hall ferromagnetic state to a quantum Hall spin glass state. It is our belief that this project has generated and will continue to make important impacts in basic science as well as in novel solid-state, high frequency electronic device applications.
Robust and Efficient Adaptive Moving Mesh Solution of the 2-D Euler equations
Zegeling, Paul
to track individual features of the physi- cal solutions, such as shocks and emerging instabilities [2] in which the difficult choice of a user-defined adaptivity constant in the monitor function lists our conclusions. 2 The 2D Euler equations The two-dimensional Euler equations of gas dynamics
An Efficient Genetic Algorithm for Predicting Protein Tertiary Structures in the 2D HP Model
Istrail, Sorin
, 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
Chuong V. Tran; Theodore G. Shepherd
2002-02-06T23:59:59.000Z
We study two-dimensional turbulence in a doubly periodic domain driven by a monoscale-like forcing and damped by various dissipation mechanisms of the form $\
TWO-DIMENSIONAL CORE-COLLAPSE SUPERNOVA MODELS WITH MULTI-DIMENSIONAL...
Office of Scientific and Technical Information (OSTI)
NEUTRINOS; DIFFUSION; GRAVITATIONAL COLLAPSE; HYDRODYNAMICS; MASS; STAR MODELS; SUPERNOVAE; TWO-DIMENSIONAL CALCULATIONS; VARIATIONS Word Cloud More Like This Full Text...
A characterization of causal automorphisms on two-dimensional Minkowski spacetime
Do-Hyung Kim
2013-04-08T23:59:59.000Z
It is shown that causal automorphisms on two-dimensional Minkowski spacetime can be characterized by the invariance of the wave equations.
Two-dimensional liquid chromatography system for online top-down...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
liquid chromatography system for online top-down mass spectrometry. Two-dimensional liquid chromatography system for online top-down mass spectrometry. Abstract: An online...
Signatures of the protein folding pathway in two-dimensional ultraviolet spectroscopy
Jiang, J; Jiang, J; Lai, Z; Wang, J; Wang, J; Mukamel, S
2014-01-01T23:59:59.000Z
2) Dobson, C. M. Protein Folding and Misfolding. Naturethe Complexity of Protein Folding. Curr. Opin. Struct. Biol.Signatures of the Protein Folding Pathway in Two-Dimensional
Two-dimensional elastic wave propagation in a duraluminum sheet
Cefola, David Paul
1982-01-01T23:59:59.000Z
dimensions should be propor- tional to r eL, where r is the separation between the source and receiver and L is the distance the wave has traveled. along the lower interface. Newlands (1952) investigated the theoretical behavior of refracted waves trs.... 96 313. 17 179. 1a aal. aZ '89. 7a al. , 8 231. 66 236, 9$ ? ? o 52. 12 J J. S9 a. 6, , U 53 where T is the arrival time, X is the source/receiver separation, and. V is the wave velocity. For reflected-P waves in the model, the traveltime...
Surface energies in a two-dimensional mass-spring model for crystals
Theil, Florian
Surface energies in a two-dimensional mass-spring model for crystals Florian Theil Mathematics an atomistic pair potential-energy E(n)(y) that describes the elastic behavior of two- dimensional crystals analysis of the ground state energy as n tends to infinity. We show in a suitable scaling regime where
Shear viscosity and shear thinning in two-dimensional Yukawa , J. Goree2
Goree, John
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
TWO-DIMENSIONAL TRANSIENT RADIATIVE HEAT TRANSFER USING DISCRETE ORDINATES METHOD
Guo, Zhixiong "James"
TWO-DIMENSIONAL TRANSIENT RADIATIVE HEAT TRANSFER USING DISCRETE ORDINATES METHOD Zhixiong Guo for the first time to solve transient radiative heat transfer in a two-dimensional rectangular enclosure of solution method of radiative heat transfer in participating media in recent decades. However, the analysis
Phonons in two-dimensional soft colloidal crystals Ke Chen,1, 2
Schindler, Michael
Phonons in two-dimensional soft colloidal crystals Ke Chen,1, 2 Tim Still,1 Samuel Schoenholz,1 and polycrystalline monolayer colloidal crystals composed of thermosensitive microgel particles are measured using-frequency modes in polycrystalline two-dimensional colloidal crystals are identified and demonstrated to correlate
Two-Dimensional NMR Spectroscopy Elimination of Zero-Quantum Interference in
Keeler, James
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
Gusev, Guennady
Negative linear classical magnetoresistance in a corrugated two-dimensional electron gas N. M (Received 18 August 2004; published 20 December 2004) Large linear negative magnetoresistance (LNMR) was measured in a GaAs/AlxGa1-xAs two-dimensional electron system with nonplanar topography, caused by random
An Experimental Study of Critical Heat Flux in Narrow Gap With Two-Dimensional Slices
Yong Hoon Kim; Suh, Kune Y. [Seoul National University, San56-1 Shinrim-dong, Gwanak-gu, Seoul, 151-742 (Korea, Republic of); Rae Joon Park; San Baek Kim; Hee Dong Kim [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)
2002-07-01T23:59:59.000Z
A cooling mechanism due to boiling in a gap between the debris crust and the reactor pressure vessel (RPV) wall was proposed for the TMI-2 reactor accident analysis. If there is enough heat transfer through the gap to cool the outer surface of the debris and the inner surface of the wall, the RPV wall may preserve its integrity during a severe core melt accident. If the heat removal through gap cooling relative to the counter-current flow limitation (CCFL) is pronounced, the safety margin of the reactor can be far greater than what had been previously known in the severe accident management arena. Should a severe accident take place, the RPV integrity will be maintained because of the inherent nature of degraded core coolability inside the lower head due to boiling in a narrow gap between the debris crust and the RPV wall. As a defense-in-depth measure, the heat removal capability by gap cooling coupled with external cooling can be examined for the Korean Standard Nuclear Power Plant (KSNPP) and the Advanced Power Reactor 1400 MWe (APR1400) in light of the TMI-2 vessel survival. A number of studies were carried out to investigate the complex heat transfer mechanisms for the debris cooling in the lower plenum. However, these heat transfer mechanisms have not been clearly understood yet. The CHFG (Critical Heat Flux in Gap) experiments at KAERI were carried out to develop the critical heat flux (CHF) correlation in a hemispherical gap, which is the upper limit of the heat transfer. According to the CHFG experiments performed with a pool boiling condition, the CHF in a parallel gap was reduced by 1/30 compared with the value measured in the open pool boiling condition. The correlation developed from the CHFG experiment is based on the fact that the CHF in a hemispherical gap is governed by the CCFL and a Kutateladze type CCFL parameter correlates CCFL data well in hemispherical gap geometry. However, the results of the CHFG experiments appear to be limited in their value because the power of the heaters was restricted by the three-dimensional (3D) geometry. The two-dimensional (2D) geometry relative to the 3D geometry enables the heaters to produce higher power. Experiments were conducted to develop the CHF correlation for gap cooling with the 2D slices. The experimental facility consisted of a heater, a pressure vessel, a heat exchanger and the pressure and temperature measurement system. Tests were carried out in the pressure range of 0.1 to 1 MPa for the gap sizes of 1 mm and 2 mm using demineralized water. (authors)
Two-dimensional Insect Flight on an Air-Water Interface is a Chaotic Oscillator
Mukundarajan, Haripriya; Prakash, Manu
2014-01-01T23:59:59.000Z
Two-dimensional flapping wing insect flight on an air-water interface provides a successful foraging strategy to explore an ecological niche on the surface of a pond. However, the complex interplay of surface tension, aerodynamic forces, biomechanics and neural control that enables two-dimensional flight is unknown. Here we report the discovery of two-dimensional flight in the waterlily beetle Galerucella nymphaeae, which is the fastest reported propulsion mode for an insect on a fluid interface. Using kinematics derived from high-speed videography coupled with analytical models, we demonstrate that two-dimensional flight is a chaotic interfacial oscillator, thus significantly constraining the possible range of flight parameters. Discovery of this complex dynamics in two-dimensional flight on time scales similar to neural responses indicates the challenge of evolving active flight control on a fluid interface.
2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe
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
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.
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
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.
MESH2D GRID GENERATOR DESIGN AND USE
Flach, G.; Smith, F.
2012-01-20T23:59:59.000Z
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.
Two-Dimensional Image Rotation Ivan Sterling 1 and Thomas Sterling 2
Sterling, Ivan
Two-Dimensional Image Rotation Ivan Sterling 1 and Thomas Sterling 2 1 Department of Mathematics scanning of a document, such as an engineering drawing. When the drawing is fed into the scanner, it may
Comparative Visualization of Two-Dimensional Flow Data Using Moment Invariants
Hamann, Bernd
Comparative Visualization of Two-Dimensional Flow Data Using Moment Invariants author1, author2 affiliation1 affiliation2 Email: {author1,author2}@affiliation Abstract The analysis of time-dependent data
Turner, Daniel B.
We use fifth-order two-dimensional electronic spectroscopy to measure coherent four-particle dynamics in a semiconductor nanostructure. By using optical polarization control in two-quantum measurements enabled by the COLBERT ...
Modeling of acoustic wave scattering from a two-dimensional fracture
Wang, Ping
2010-01-01T23:59:59.000Z
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 ...
Electronic and magnetic properties of Fe and Mn 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
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.
Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using PIC Simulations
Ng, Chung-Sang
Stability Studies of Two-dimensional Magnetic Bernstein- Greene-Kruskal Modes using PIC Simulations of these solutions, as well as Particle-in-Cell (PIC) simulations, we will present further studies of the stability
Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs
Harris, C. Thomas (Charles Thomas)
2010-01-01T23:59:59.000Z
The electrical characteristics of high-mobility, two-dimensional electron gas (2DEG) systems, such as GaAs quantum wells, have been well-studied at low frequencies and in extreme conditions of high magnetic fields and ...
An experimental study of unsteady separation in a two-dimensional flow
Coral Pinto, Raul Javier
2005-01-01T23:59:59.000Z
An experimental study of flow separation in an incompressible two-dimensional unsteady flow was undertaken with the aim of validating recently developed flow separation criteria, which are based on kinematic principles. ...
Cooke, Michele
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
Infinite energy solutions of the two-dimensional Navier-Stokes equations
Gallay, Thierry
Infinite energy solutions of the two-dimensional Navier-Stokes equations Thierry Gallay Universit-Martin-d'H`eres, France Thierry.Gallay@ujf-grenoble.fr Abstract These notes are based on a series of lectures delivered
Parametric resonance of a two-dimensional electron gas under bichromatic irradiation Christian Joas
von Oppen, Felix
Parametric resonance of a two-dimensional electron gas under bichromatic irradiation Christian Joas driving ac fields (bichromatic irradiation). Compared to the case of monochromatic irradiation, which's theorem, gives rise to new qualitative effects specific to bichromatic irradiation. Namely, when
Development and validation of a vertically two-dimensional mesoscale numerical model
Walters, Michael Kent
1985-01-01T23:59:59.000Z
DEVELOPMENT AND VALIDATION OF A VERTICALLY TWO-DIMENSIONAL MESOSCALE NUMERICAL MODEL A Thesis by MICHAEL KENT WALTERS Submitted to the Graduate College of Texas AsM University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE August 1985 Major Subject: Meteorology DEVELOPMENT AND VALIDATION OF A VERTICALLY TWO-DIMENSIONAL MESOSCALE NUMERICAL MODEL A Thesis by MICHAEL KENT WALTERS Approved as to style and content by: Dusan Djuric (Chair of Committee) WP...
Lyapunov Modes and Time-Correlation Functions for Two-Dimensional Systems
Tooru Taniguchi; Gary P. Morriss
2005-09-27T23:59:59.000Z
The relation between the Lyapunov modes (delocalized Lyapunov vectors) and the momentum autocorrelation function is discussed in two-dimensional hard-disk systems. We show numerical evidence that the smallest time-oscillating period of the Lyapunov modes is twice as long as the time-oscillating period of momentum autocorrelation function for both square and rectangular two-dimensional systems with hard-wall boundary conditions.
Patterned Arrays of Lateral Heterojunctions within Monolayer 2D Semiconductors
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; Lupini, Andrew R; Lee, Jaekwang; Basile Carrasco, Leonardo A; Rouleau, Christopher M; Boulesbaa, Abdelaziz; Puretzky, Alexander A; Ivanov, Ilia N; et al
2015-01-01T23:59:59.000Z
The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversionmore »process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.« less
Patterned Arrays of Lateral Heterojunctions within Monolayer 2D Semiconductors
Mahjouri-Samani, Masoud [ORNL; Lin, Ming-Wei [ORNL; Wang, Kai [ORNL; Lupini, Andrew R [ORNL; Lee, Jaekwang [ORNL; Basile Carrasco, Leonardo A [ORNL; Boulesbaa, Abdelaziz [ORNL; Rouleau, Christopher [Oak Ridge National Laboratory (ORNL); Puretzky, Alexander A [ORNL; Ivanov, Ilia N [ORNL; Xiao, Kai [ORNL; Yoon, Mina [ORNL; Geohegan, David B [ORNL
2015-01-01T23:59:59.000Z
The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.
% function dirfield2d % This program plots a direction field for an ODE x'=Ax, where A is % a 2x2 matrix, with the option of also plotting solution curves to % initial ...
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kozuka, Y.; Tsukazaki, A.; Maryenko, D.; Falson, J.; Bell, C.; Kim, M.; Hikita, Y.; Hwang, H. Y.; Kawasaki, M.
2012-02-01T23:59:59.000Z
We investigate the spin susceptibility (g*m*) of dilute two-dimensional (2D) electrons confined at the MgxZn1-xO/ZnO heterointerface. Magnetotransport measurements show a four-fold enhancement of g*m*, dominated by the increase in the Landé g-factor. The g-factor enhancement leads to a ferromagnetic instability of the electron gas as evidenced by sharp resistance spikes. At high magnetic field, the large g*m* leads to full spin polarization, where we found sudden increase in resistance around the filling factors of half-integer, accompanied by complete disappearance of fractional quantum Hall (QH) states. Along with its large effective mass and the high electron mobility, our result indicates thatmore »the ZnO 2D system is ideal for investigating the effect of electron correlations in the QH regime.« less
Otsuji, Taiichi; Hanabe, Mitsuhiro; Ogawara, Osamu [Kyushu Institute of Technology, Graduate School of Computer Science and Systems Engineering, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502 (Japan)
2004-09-13T23:59:59.000Z
We have observed the frequency dependence of the plasma resonant intensity in the terahertz range for a short gate-length InGaP/InGaAs/GaAs pseudomorphic high-electron-mobility transistor. The plasma resonance excitation was performed by means of interband photoexcitation using the difference-frequency component of a photomixed laser beam. Under sufficient density of two-dimensional (2D) conduction electrons (>10{sup 12} cm{sup -2}) and a moderate modulation index (the ratio of the density of photoexcited electrons to the initial density of the 2D electrons) we clearly observed the plasma-resonant peaks at 1.9 and 5.8 THz corresponding to the fundamental and third-harmonic resonance at room temperature, which is in good agreement with theory.
Canas-Ventura, M. E.; Klappenberger, F.; Clair, S.; Pons, S.; Kern, K.; Brune, H.; Strunskus, T.; Woell, Ch.; Fasel, R.; Barth, J. V. [Institut de Physique des Nanostructures, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland) and Lehrstuhl fuer Physikalische Chemie I, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany) and Empa, Swiss Federal Laboratories for Materials Testing and Research, Nanotech at surfaces Laboratory, CH-3602 Thun (Switzerland); Department of Chemistry, University of British Columbia, BC V6T 1Z4 Vancouver (Canada) and Department of Physics and Astronomy, University of British Columbia, BC V6T 1Z4 Vancouver (Canada)
2006-11-14T23:59:59.000Z
The adsorption of terephthalic acid [C{sub 6}H{sub 4}(COOH){sub 2}, TPA] on a Pd(111) surface has been investigated by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure spectroscopy under ultrahigh vacuum conditions at room temperature. We find the coexistence of one- (1D) and two-dimensional (2D) molecular ordering. Our analysis indicates that the 1D phase consists of intact TPA chains stabilized by a dimerization of the self-complementary carboxyl groups, whereas in the 2D phase, consisting of deprotonated entities, the molecules form lateral ionic hydrogen bonds. The supramolecular growth dynamics and the resulting structures are explained by a self-limiting deprotonation process mediated by the catalytic activity of the Pd surface. Our models for the molecular ordering are supported by molecular mechanics calculations and a simulation of high resolution STM images.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kozuka, Y.; Tsukazaki, A.; Maryenko, D.; Falson, J.; Bell, C.; Kim, M.; Hikita, Y.; Hwang, H. Y.; Kawasaki, M.
2012-02-01T23:59:59.000Z
We investigate the spin susceptibility (g*m*) of dilute two-dimensional (2D) electrons confined at the MgxZn1-xO/ZnO heterointerface. Magnetotransport measurements show a four-fold enhancement of g*m*, dominated by the increase in the Landé g-factor. The g-factor enhancement leads to a ferromagnetic instability of the electron gas as evidenced by sharp resistance spikes. At high magnetic field, the large g*m* leads to full spin polarization, where we found sudden increase in resistance around the filling factors of half-integer, accompanied by complete disappearance of fractional quantum Hall (QH) states. Along with its large effective mass and the high electron mobility, our result indicates that the ZnO 2D system is ideal for investigating the effect of electron correlations in the QH regime.
Zhukov, Alexander V., E-mail: alex-zhukov@sutd.edu.sg; Bouffanais, Roland [Singapore University of Technology and Design, 20 Dover Drive, Singapore 138682 (Singapore); Fedorov, E. G. [Volgograd State University of Architecture and Civil Engineering, 400074 Volgograd (Russian Federation); Belonenko, Mikhail B. [Laboratory of Nanotechnology, Volgograd Institute of Business, 400048 Volgograd (Russian Federation)
2014-05-28T23:59:59.000Z
Propagation of ultrashort laser pulses through various nano-objects has recently became an attractive topic for both theoretical and experimental studies due to its promising perspectives in a variety of problems of modern nanoelectronics. Here, we study the propagation of extremely short two-dimensional bipolar electromagnetic pulses in a heterogeneous array of semiconductor carbon nanotubes. Heterogeneity is defined as a region of enhanced electron density. The electromagnetic field in an array of nanotubes is described by Maxwell's equations, reduced to a multidimensional wave equation. Our numerical analysis shows the possibility of stable propagation of an electromagnetic pulse in a heterogeneous array of nanotubes. Furthermore, we establish that, depending on its speed of propagation, the pulse can pass through the area of increased electron concentration or be reflected therefrom.
Wu, Tianmin; Zhang, Ruiting; Li, Huanhuan; Zhuang, Wei, E-mail: wzhuang@dicp.ac.cn, E-mail: lijiangy@pku.edu.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning (China)] [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning (China); Yang, Lijiang, E-mail: wzhuang@dicp.ac.cn, E-mail: lijiangy@pku.edu.cn [College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871 (China)] [College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871 (China)
2014-02-07T23:59:59.000Z
We analyzed, based on the theoretical spectroscopic modeling, how the differences in the folding landscapes of two ?-hairpin peptides trpzip2 and trpzip4 are reflected in their thermal unfolding infrared measurements. The isotope-edited equilibrium FTIR and two dimensional infrared spectra of the two peptides were calculated, using the nonlinear exciton propagation method, at a series of temperatures. The spectra calculations were based on the configuration distributions generated using the GB{sup OBC} implicit solvent MD simulation and the integrated tempering sampling technique. Conformational analysis revealed the different local thermal stabilities for these two peptides, which suggested the different folding landscapes. Our study further suggested that the ellipticities of the isotope peaks in the coherent IR signals are more sensitive to these local stability differences compared with other spectral features such as the peak intensities. Our technique can thus be combined with the relevant experimental measurements to achieve a better understanding of the peptide folding behaviors.
The Landau-Zener transition and the surface hopping method for the 2D Dirac equation for graphene
Jin, Shi
The Landau-Zener transition and the surface hopping method for the 2D Dirac equation for graphene dimensional massless Dirac equation for Graphene with an electrostatic potential, in the semiclassical regime in a single graphene layer. This material is a two-dimensional flat monolayer of carbon atoms which displays
2D Seismic Reflection Survey Crump Geyser Geothermal Prospect Warner
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on DeliciousPlasmaP a gHigh4-FD-a < RAPIDā€ˇcommunication facilities | Open EnergyEnergy2-M Probe20 CCR2327 CCRValley,
2D Seismic Reflection Survey Crump Geyser Geothermal Prospect...
Additional Info Field Value Author Nevada Geothermal Power Company Maintainer Nicole Smith bureaucode 019:20 Catalog DOE harvestobjectid d542f4da-f04b-4172-ac22-483b3b5ff60a...
A New Proof on Net Upscale Energy Cascade in 2D and QG Turbulence
Eleftherios Gkioulekas; Ka Kit Tung
2006-09-30T23:59:59.000Z
A general proof that more energy flows upscale than downscale in two-dimensional (2D) turbulence and barotropic quasi-geostrophic (QG) turbulence is given. A proof is also given that in Surface QG turbulence, the reverse is true. Though some of these results are known in restricted cases, the proofs given here are pedagogically simpler, require fewer assumptions and apply to both forced and unforced cases.
GRAPHICS PROGRAMMING Section B Java 2D
Hill, Gary
GRAPHICS PROGRAMMING Section B Java 2D 20 - Graphics2D: Introduction 21 - Graphics2D: Shapes 22 2D: General Path Curves 29 - Graphics 2D: Constructive Area Geometry Gary Hill December 2003 Java 2 Java initially through the Abstract Window Toolkit, which was extended to include swing, shortly
Two-dimensional TBR calculations for conceptual compact reversed-field pinch reactor blanket
Davidson, J.W.; Battat, M.E.; Dudziak, D.J.
1985-01-01T23:59:59.000Z
A detailed two-dimensional nucleonic analysis was performed for a conceptual first wall, blanket, and shield design for the Compact Reversed-Field Pinch Reactor. The design includes significant two-dimensional aspects presented by the limiter, vacuum ducts, and coolant manifolds; these aspects seriously degrade the tritium-breeding reaction (TBR) predicted by one-dimensional calculations. A range of design change to increase the TBR were investigated within the two-dimensional analysis. The results of this investigation indicated that an adequate TBR could be achieved with a thinner copper first wall, a /sup 6/Li enrichment near 90%, the proper selection of reflector, and a small addition to the blanket thickness, determined by the one-dimensional analysis.
Van der Waals Epitaxial Growth of Single-Crystal Two-Dimensional GaSe on Graphene
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Li, Xufan; Basile, Leonardo; Huang, Bing; Ma, Cheng; Lee, Jaekwang; Vlassiouk, Ivan V.; Puretzky, Alexander A.; Lin, Ming-Wei; Chi, Miaofang; Idrobo Tapia, Juan Carlos; et al
2015-07-22T23:59:59.000Z
Two-dimensional (2D) van der Waals (vdW) heterostructures are a family of artificially-structured materials that promise tunable optoelectronic properties for devices with enhanced functionalities. Compared to stamping, direct epitaxy of vdW heterostructures is ideal for clean interlayer interfaces and scalable device fabrication. Here, we explore the synthesis and preferred orientations of 2D GaSe atomic layers on graphene (Gr) by vdW epitaxy. Guided by the wrinkles on graphene, GaSe nuclei form that share a predominant lattice orientation. Due to vdW epitaxial growth many nuclei grow as perfectly aligned crystals and coalesce to form large (tens of microns), single-crystal flakes. Through theoretical investigationsmore »of interlayer energetics, and measurements of preferred orientations by atomic-resolution STEM and electron diffraction, a 10.9 interlayer rotation of the GaSe lattice with respect to the underlying graphene is found to be the most energetically preferred vdW heterostructure with the largest binding energy and the longest-range ordering. These GaSe/Gr vdW heterostructures exhibit an enhanced Raman E21g band of monolayer GaSe along with highly-quenched photoluminescence due to strong charge transfer. Despite the very large lattice mismatch of GaSe/Gr through vdW epitaxy, the predominant orientation control and convergent formation of large single-crystal flakes demonstrated here is promising for the scalable synthesis of large-area vdW heterostructures for the development of new optical and optoelectronic devices.« less
Du, X. Z.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Frye, C. D.; Edgar, J. H. [Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506-5102 (United States)
2014-02-07T23:59:59.000Z
Hexagonal boron nitride (hBN) is an emerging material for the exploration of new physics in two-dimensional (2D) systems that are complementary to graphene. Nanotubes with a diameter (?60?nm) that is much larger than the exciton binding energy in hBN have been synthesized and utilized to probe the fundamental optical transitions and the temperature dependence of the energy bandgap of the corresponding 2D hBN sheets. An excitonic transition at 5.901?eV and its longitudinal optical phonon replica at 5.735?eV were observed. The excitonic emission line is blue shifted by about 130?meV with respect to that in hBN bulk crystals due to the effects of reduced dimensionality. The temperature evolution of the excitonic emission line measured from 300 to 800?K revealed that the temperature coefficient of the energy bandgap of hBN nanotubes with large diameters (or equivalently hBN sheets) is about 0.43?meV/{sup 0}K, which is a factor of about 5 times smaller than the theoretically predicted value for the transitions between the ? and ?* bands in hBN bulk crystals and 6 times smaller than the measured value in AlN epilayers with a comparable energy bandgap. The observed weaker temperature dependence of the bandgap than those in 3D hBN and AlN is a consequence of the effects of reduced dimensionality in layer-structured hBN.
Yuan, Long; Yang, Jinlong
2012-01-01T23:59:59.000Z
Recently, a new kind of spintronics materials, bipolar magnetic semiconductor (BMS), has been proposed. The spin polarization of BMS can be conveniently controlled by a gate voltage, which makes it very attractive in device engineering. Now, the main challenge is finding more BMS materials. In this article, we propose that hydrogenated wurtzite SiC nanofilm is a two-dimensional BMS material. Its BMS character is very robust under the effect of strain, substrate, or even a strong electric field. The proposed two-dimensional BMS material paves the way to use this promising new material in an integrated circuit.
E. Brezin; S. Hikami
1992-04-08T23:59:59.000Z
In the usual matrix-model approach to random discretized two-dimensional manifolds, one introduces n Ising spins on each cell, i.e. a discrete version of 2D quantum gravity coupled to matter with a central charge n/2. The matrix-model consists then of an integral over $2^{n}$ matrices, which we are unable to solve for $n>1$. However for a fixed genus we can expand in the cosmological constant g for arbitrary values of n, and a simple minded analysis of the series yields for n=0,1 and 2 the expected results for the exponent $\\gamma_{string}$ with an amazing precision given the small number of terms that we considered. We then proceed to larger values of n. Simple tests of universality are successfully applied; for instance we obtain the same exponents for n=3 or for one Ising model coupled to a one dimensional target space. The calculations are easily extended to states Potts models, through an integration over $q^{n}$ matrices. We see no sign of the tachyonic instability of the theory, but we have only considered genus zero at this stage.
Extended two-dimensional characteristic framework to study nonrotating black holes
W. Barreto
2014-07-07T23:59:59.000Z
We develop a numerical solver, that extends the computational framework considered in [Phys. Rev. D 65, 084016 (2002)], to include scalar perturbations of nonrotating black holes. The nonlinear Einstein-Klein-Gordon equations for a massless scalar field minimally coupled to gravity are solved in two spatial dimensions (2D). The numerical procedure is based on the ingoing light cone formulation for an axially and reflection symmetric spacetime. The solver is second order accurate and was validated in different ways. We use for calibration an auxiliary 1D solver with the same initial and boundary conditions and the same evolution algorithm. We reproduce the quasinormal modes for the massless scalar field harmonics $\\ell = 0$, $1$ and $2$. For these same harmonics, in the linear approximation, we calculate the balance of energy between the black hole and the world tube. As an example of nonlinear harmonic generation, we show the distortion of a marginally trapped two-surface approximated as a q-boundary and based upon the harmonic $\\ell=2$. Additionally, we study the evolution of the $\\ell = 8$ harmonic in order to test the solver in a spacetime with a complex angular structure. Further applications and extensions are briefly discussed.
VAM2D: Variably saturated analysis model in two dimensions
Huyakorn, P.S.; Kool, J.B.; Wu, Y.S. (HydroGeoLogic, Inc., Herndon, VA (United States))
1991-10-01T23:59:59.000Z
This report documents a two-dimensional finite element model, VAM2D, developed to simulate water flow and solute transport in variably saturated porous media. Both flow and transport simulation can be handled concurrently or sequentially. The formulation of the governing equations and the numerical procedures used in the code are presented. The flow equation is approximated using the Galerkin finite element method. Nonlinear soil moisture characteristics and atmospheric boundary conditions (e.g., infiltration, evaporation and seepage face), are treated using Picard and Newton-Raphson iterations. Hysteresis effects and anisotropy in the unsaturated hydraulic conductivity can be taken into account if needed. The contaminant transport simulation can account for advection, hydrodynamic dispersion, linear equilibrium sorption, and first-order degradation. Transport of a single component or a multi-component decay chain can be handled. The transport equation is approximated using an upstream weighted residual method. Several test problems are presented to verify the code and demonstrate its utility. These problems range from simple one-dimensional to complex two-dimensional and axisymmetric problems. This document has been produced as a user's manual. It contains detailed information on the code structure along with instructions for input data preparation and sample input and printed output for selected test problems. Also included are instructions for job set up and restarting procedures. 44 refs., 54 figs., 24 tabs.
computing machine (CCM) called Splash- 2, a computation speed of 180 Mflops and a speed-up of 23 times over on the Splash-2 FPGA-based custom computing machine (CCM). This application requires the abil- ity to do. An advantage of using a CCM for floating point is the ability to customize the format and algorithm data flow
Structural Health Monitoring of Composite Materials Using the Two Dimensional Fast Fourier
Nemat-Nasser, Sia
Structural Health Monitoring of Composite Materials Using the Two Dimensional Fast Fourier. This work is part of an effort to develop smart composite materials that monitor their own health using the health of composite materials. Submitted to: Smart Materials and Structures #12;Structural Health
Two dimensional representation of the Dirac equation in Non associative algebra
S. Hamieh; H. Abbas
2011-04-18T23:59:59.000Z
In this note a simple extension of the complex algebra to higher dimension is proposed. Using the postulated algebra a two dimensional Dirac equation is formulated and its solution is calculated. It is found that there is a sub-algebra where the associative nature can be recovered.
Soljačię, Marin
Solar thermophotovoltaic energy conversion systems with two-dimensional tantalum photonic crystal) systems convert solar energy into electricity via thermally radiated photons at tailored wavelengths highly scalable for a wide range of power capacities, have no moving parts, and allow solar energy
Edge-spin accumulation in semiconductor two-dimensional hole gases RID E-5081-2010
Nomura, K.; Wunderlich, J.; Sinova, Jairo; Kaestner, B.; MacDonald, AH; Jungwirth, T.
2005-01-01T23:59:59.000Z
The controlled generation of localized spin densities is a key enabler of semiconductor spintronics In this work, we study spin Hall effect induced edge-spin accumulation in a two-dimensional hole gas with strong spin orbit interactions. We argue...
Plasmon mass and Drude weight in strongly spin-orbit-coupled two-dimensional electron gases
Agarwal, Amit; Chesi, Stefano; Jungwirth, T.; Sinova, Jairo; Vignale, G.; Polini, Marco.
2011-01-01T23:59:59.000Z
Spin-orbit-coupled two-dimensional electron gases (2DEGs) are a textbook example of helical Fermi liquids, i.e., quantum liquids in which spin (or pseudospin) and momentum degrees of freedom at the Fermi surface have a well-defined correlation. Here...
Two-dimensional Gibbsian point processes with continuous spin-symmetries
Thomas Richthammer
2004-07-13T23:59:59.000Z
We consider two-dimensional marked point processes which are Gibbsian with a two-body-potential U. U is supposed to have an internal continuous symmetry. We show that under suitable continuity conditions the considered processes are invariant under the given symmetry. We will achieve this by using Ruelle`s superstability estimates and percolation arguments.
The anomaly-free quantization of two-dimensional relativistic string. I
S. N. Vergeles
1998-12-21T23:59:59.000Z
An anomaly-free quantum theory of a relativistic string is constructed in two-dimensional space-time. The states of the string are found to be similar to the states of a massless chiral quantum particle. This result is obtained by generalizing the concept of an ``operator'' in quantum field theory.
Optimization of a Flyback Transformer Winding Considering Two-Dimensional Field Effects, Cost
Optimization of a Flyback Transformer Winding Considering Two-Dimensional Field Effects, Cost and perhaps miti- gated. And both the cost and the loss in the litz-wire winding are strong functions and cost. In this paper, we address just such a case: a flyback trans- 1Although high-frequency winding
Transformation Property of the Caputo Fractional Differential Operator in Two Dimensional Space
Ehab Malkawi
2013-05-06T23:59:59.000Z
The transformation property of the Caputo fractional derivative operator of a scalar function under rotation in two dimensional space is derived. The study of the transformation property is essential for the formulation of fractional calculus in multi-dimensional space. The inclusion of fractional calculus in the Lagrangian and Hamiltonian dynamics relies on such transformation. An illustrative example is given.
Two-dimensional topological field theories coupled to four-dimensional BF theory
Merced Montesinos; Alejandro Perez
2007-11-19T23:59:59.000Z
Four dimensional BF theory admits a natural coupling to extended sources supported on two dimensional surfaces or string world-sheets. Solutions of the theory are in one to one correspondence with solutions of Einstein equations with distributional matter (cosmic strings). We study new (topological field) theories that can be constructed by adding extra degrees of freedom to the two dimensional world-sheet. We show how two dimensional Yang-Mills degrees of freedom can be added on the world-sheet, producing in this way, an interactive (topological) theory of Yang-Mills fields with BF fields in four dimensions. We also show how a world-sheet tetrad can be naturally added. As in the previous case the set of solutions of these theories are contained in the set of solutions of Einstein's equations if one allows distributional matter supported on two dimensional surfaces. These theories are argued to be exactly quantizable. In the context of quantum gravity, one important motivation to study these models is to explore the possibility of constructing a background independent quantum field theory where local degrees of freedom at low energies arise from global topological (world-sheet) degrees of freedom at the fundamental level.
Quantum dots and etch-induced depletion of a silicon two-dimensional electron gas
Coppersmith, Susan N.
Quantum dots and etch-induced depletion of a silicon two-dimensional electron gas L. J. Klein, K. L coupled quantum dots containing individual electrons whose spins act as qubits.4 We have made recent in a silicon quantum dot can be held constant for up to 11 hours. This fulfills an important milestone towards
Signatures of the Protein Folding Pathway in Two-Dimensional Ultraviolet Spectroscopy
Mukamel, Shaul
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
Davies, John H.
Modeling the patterned two-dimensional electron gas: Electrostatics John H. Davies and Ivan A. V. Sukhorukov Institute of Problems of Microelectronics Technology, Academy of Science of Russia, Chernogolovka, Moscow district, Russia, 142432 (Dated: February 21, 2005) Abstract We present analytical
Carvalho, Joćo Luiz
TWO-DIMENSIONAL COMPRESSION OF SURFACE ELECTROMYOGRAPHIC SIGNALS USING COLUMN-CORRELATION SORTING of Computer Science. chaffim@gmail.com INTRODUCTION Surface Electromyographic (S-EMG) signals are important different approaches have been proposed for compression of electromyographic signals, including DPCM [3
SOME OBSERVATIONS OF TWO-DIMENSIONAL SMOLDERING AND THE TRANSITION TO FLAMING
Tse, Stephen D.
process from slow smoldering to rapid flaming (fast, exothermic, gas-phase reactions) is also689 SOME OBSERVATIONS OF TWO-DIMENSIONAL SMOLDERING AND THE TRANSITION TO FLAMING Stephen D. Tse and the phenomenon of transition to flaming of a porous combustible material in the presence of an air
RANDOM WALK IN RANDOM ENVIRONMENT IN A TWO-DIMENSIONAL STRATIFIED MEDIUM WITH ORIENTATIONS
Paris-Sud XI, Université de
RANDOM WALK IN RANDOM ENVIRONMENT IN A TWO-DIMENSIONAL STRATIFIED MEDIUM WITH ORIENTATIONS ALEXIS oriented lattices, random walk in random environment, random walk in random scenery, functional limit-00634636,version2-24Nov2012 #12;RWRE IN A STRATIFIED ORIENTED MEDIUM 2 We denote by E and E
RANDOM WALK IN RANDOM ENVIRONMENT IN A TWO-DIMENSIONAL STRATIFIED MEDIUM WITH ORIENTATIONS
Pčne, Franēoise
RANDOM WALK IN RANDOM ENVIRONMENT IN A TWO-DIMENSIONAL STRATIFIED MEDIUM WITH ORIENTATIONS ALEXIS walk in random environment, random walk in random scenery, functional limit theorem, transience. This research was supported by the french ANR project MEMEMO2. 1 #12;RWRE IN A STRATIFIED ORIENTED MEDIUM 2 Our
Determining energy relaxation length scales in two-dimensional electron gases
Billiald, Jordan; Backes, Dirk; Farrer, Ian; Ritchie, David; Narayan, Vijay; König, Jürgen
2015-01-01T23:59:59.000Z
We present measurements of the energy relaxation length scale l in two-dimensional electron gases (2DEGs). A temperature gradient is established in the 2DEG by means of a heating current, and then the elevated electron temperature Te is estimated...
Sedimenting discs in a two-dimensional foam I. T. Davies, S. J. Cox
Cox, Simon
Sedimenting discs in a two-dimensional foam I. T. Davies, S. J. Cox Institute of Mathematics and Physics, Aberystwyth University, Ceredigion SY23 3BZ, UK Abstract The sedimentation of circular discs. In the second scenario, the upper disc falls into the wake of the lower, after which the discs sediment as one
Fast transport, atom sample splitting and single-atom qubit supply in two-dimensional arrays
Birkl, Gerhard
Fast transport, atom sample splitting and single-atom qubit supply in two-dimensional arrays architecture for neutral atom quantum information processing, quantum simulation and the manipulation of ultra-cold implemented functions. We introduce piezo-actuator-based transport of atom ensembles over distances of more
Two-dimensional 1,3,5-Tris(4-carboxyphenyl)benzene self-assembly at
Paris-Sud XI, Université de
Two-dimensional 1,3,5-Tris(4-carboxyphenyl)benzene self-assembly at the 1-phenyloctane-assembly of star-shaped 1,3,5-Tris(4-carboxyphenyl)benzene molecules is investigated. Scanning tunneling microscopy.22 showed that 1,3,5-Tris(4-carboxyphenyl)benzene star-shaped molecules can form two distinc self
Implementing Per Bak's Sand Pile Model as a Two-Dimensional Cellular Automaton
Tesfatsion, Leigh
Implementing Per Bak's Sand Pile Model as a Two-Dimensional Cellular Automaton Leigh Tesfatsion 21 January 2009 Econ 308 Presentation Outline · Brief review: What is a Cellular Automaton? · Sand piles and "self-organized criticality" · Algorithmic description of Per Bak's sand pile model as a two
A THz transverse electromagnetic mode two-dimensional interconnect layer incorporating quasi-optics
of transmitting subpicosecond pulses in the transverse electromagnetic TEM mode over arbitrarily long paths near the cutoff fre- quency. Such pulse broadening does not occur for the trans- verse electromagneticA THz transverse electromagnetic mode two-dimensional interconnect layer incorporating quasi
Teaching Sequence for Two Dimensional Motion R. A. Morse, St. Albans School, Washington, DC
Steinberg, Richard N.
Teaching Sequence for Two Dimensional Motion R. A. Morse, St. Albans School, Washington, DC robert in understanding. Final teaching sequence 1992- 2000 4. Developed sequence of discussion, simulation use, written questions and class discussions designed to engage students throughout sequence. Results now pretty good
Integrated digital inverters based on two-dimensional anisotropic ReS? field-effect transistors
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Liu, Erfu; Fu, Yajun; Wang, Yaojia; Feng, Yanqing; Liu, Huimei; Wan, Xiangang; Zhou, Wei; Wang, Baigeng; Shao, Lubin; Ho, Ching -Hwa; et al
2015-05-07T23:59:59.000Z
Semiconducting two-dimensional transition metal dichalcogenides are emerging as top candidates for post-silicon electronics. While most of them exhibit isotropic behaviour, lowering the lattice symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here we present atomically thin rhenium disulfide (ReS?) flakes with unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated monolayer and few-layer ReS? field-effect transistors, which exhibit competitive performance with large current on/off ratios (~10?) and low subthreshold swings (100 mV per decade). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known two-dimensional semiconductingmore »materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS? anisotropic field-effect transistors, suggesting the promising implementation of large-scale two-dimensional logic circuits. Our results underscore the unique properties of two-dimensional semiconducting materials with low crystal symmetry for future electronic applications.« less
A TWO-DIMENSIONAL FEM CODE FOR THE ANALYSIS OF LARGE DEFORMATIONS OF
Zabaras, Nicholas J.
A TWO-DIMENSIONAL FEM CODE FOR THE ANALYSIS OF LARGE DEFORMATIONS OF HYPERELASTIC VISCOPLASTIC SOLIDS S. Badrinarayanan and N. Zabaras Sibley School of Mechanical and Aerospace Engineering 188 and the kinematic problem, are formulated and solved. The constitutive problem involves determining the stress
Mukasyan, Alexander
Combustion/micropyretic synthesis of atomically thin two-dimensional materials for energy unique inexpensive combustion-based approaches have been developed to prepare the nanomaterials. This article specifically aims to be an overview of current trends and as a perspective of combustion synthesis
Accurate Multipole Analysis for Leaky Microcavities in Two-dimensional Photonic Crystals
Lu, Ya Yan
1 Accurate Multipole Analysis for Leaky Microcavities in Two-dimensional Photonic Crystals Shaojie Li and Ya Yan Lu Abstract--A multipole method is presented to analyze leaky microcavities in finite expansions. Index Terms--Optical cavities, photonic crystals, numerical methods, multipole method. I
Theory of vortex crystal formation in two-dimensional turbulence* Dezhe Z. Jin
California at San Diego, University of
Theory of vortex crystal formation in two-dimensional turbulence* Dezhe Z. Jin and Daniel H. E are symmetric arrays of strong vortices within a background of weaker vorticity. This paper presents a theory, a theory is advanced that allows us to predict from the initial conditions the approximate number
ENERGY-PRESERVING AND STABLE APPROXIMATIONS FOR THE TWO-DIMENSIONAL SHALLOW WATER EQUATIONS
ENERGY-PRESERVING AND STABLE APPROXIMATIONS FOR THE TWO-DIMENSIONAL SHALLOW WATER EQUATIONS EITAN water equations 13 5.1. Energy stable schemes 13 5.2. Energy preserving schemes 17 6. Numerical TADMOR AND WEIGANG ZHONG Abstract. We present a systematic development of energy-stable approximations
Likos, Christos N.
Crystal Structures of Two-Dimensional Binary Mixtures of Dipolar Colloids in Tilted External that lie parallel to the in-plane projection of the field. I. Introduction The crystallization of colloids to petrochemicals and pharmaceuticals. Unlike particles in the bulk, the effective in- teractions between colloidal
Supplementary information to "Phonons in two-dimensional soft colloidal crystals"
Schindler, Michael
Supplementary information to "Phonons in two-dimensional soft colloidal crystals" Ke Chen et al. S1. Characterization of colloidal crystals. Colloidal crystals are characterized by sample lattice structure. Figure S1 of low frequency modes obtained from pristine colloidal crystals exhibit features of plane waves
Two-dimensional imaging of continuous-wave terahertz radiation using electro-optic detection
Heinz, Tony F.
image the two-dimensional properties of a THz beam focused into a 110 ZnTe electro-optic detection- though x-ray imaging has found significant application in medical diagnostics. As one moves further as a function of the spatial posi- tion of the beam. In order to create an image, one then mea- sures
Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using PIC
Ng, Chung-Sang
Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using PIC Simulations + + + + + + + - - - - - - - - #12;General Form of Exact Solutions #12;One Particular Solution #12;Solution with very small e #12;PIC simulations using OOPIC Pro ce = 10 pe See http://www.gi.alaska.edu/~chungsangng/bgk/bgk_b10_xyphs.mov #12;PIC
Energy landscape analysis of the two-dimensional nearest-neighbor 4 Dhagash Mehta
Hauenstein, Jonathan
Physics (NITheP), Stellenbosch 7600, South Africa and Institute of Theoretical Physics, University of Stellenbosch, Stellenbosch 7600, South Africa Jonathan D. Hauenstein Department of Mathematics, Texas AEnergy landscape analysis of the two-dimensional nearest-neighbor 4 model Dhagash Mehta Department
Numerical Studies of Collective Phenomena in Two-Dimensional Electron and Cold Atom Systems
Rezayi, Edward
2013-07-25T23:59:59.000Z
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.
Insertion of a Two-Dimensional Iron-Chloride Network between Perovskite Blocks. Synthesis and
Spinu, Leonard
Insertion of a Two-Dimensional Iron-Chloride Network between Perovskite Blocks. Synthesis between the perovskite blocks of a double-layered Dion-Jacobson compound. The product, (FeCl)- LaNb2O7, contains iron coordinated by two apical oxygens from the perovskite layer and four in-plane chlorines
Nonexistence of Coherent Structures in Two-Dimensional Inviscid Channel Flow
Kalisch, Henrik
Abstract Two-dimensional inviscid channel flow of an incompressible fluid is considered. It is shown to the study of transition from laminar flow to turbulence [25]. It follows from the result of this note that this kind of steady flow cannot exist in an inviscid fluid. Imagine a fluid contained in a horizontal
Formation of Two-Dimensional Sand Ripples under Laminar Shear Flow Vincent Langlois and Alexandre sand bed patterns under a laminar and steady shear flow. Several issues are addressed here: (i fluid is investigated theoretically. The sand transport is described taking into account both the local
Stability and Interaction of Vortices in Two-Dimensional Viscous Flows
Gallay, Thierry
Stability and Interaction of Vortices in Two-Dimensional Viscous Flows Thierry Gallay UniversitĀ´e de Grenoble I Institut Fourier, UMR CNRS 5582 B.P. 74 F-38402 Saint-Martin-d'H`eres, France Thierry.Gallay
Reichenbach, Stephen E.
2005-01-01T23:59:59.000Z
non-linear pattern variations and changes in gas pressure generate nearly linear pattern variations Abstract Identifying compounds of interest for peaks in data generated by comprehensive two-dimensional gas and inlet gas pressure and evaluates two types of affine transformations for matching peak patterns
Two-dimensional simulations of extreme floods on a large watershed
Julien, Pierre Y.
Two-dimensional simulations of extreme floods on a large watershed John F. England Jr. a,*, Mark L. Velleux b , Pierre Y. Julien c a Bureau of Reclamation, Flood Hydrology, 86-68530, Denver Federal Center September 2007; accepted 14 September 2007 KEYWORDS Flash floods; Flood design; Rainfall runoff; Extreme
Modelling dynamics of piezoelectric solids in the two-dimensional case
Melnik, Roderick
that may not be attained by purely electronic means. These new horizons of piezoelectric applicationsModelling dynamics of piezoelectric solids in the two-dimensional case R.V.N. Melnik a,*, K; Hollow piezoceramic cylinders; Corner points; Accuracy estimates 1. Introduction In many applications
Takanobu Amano; Masahiro Hoshino
2008-09-02T23:59:59.000Z
Electron acceleration mechanism at high Mach number collisionless shocks propagating in a weakly magnetized medium is investigated by a self-consistent two-dimensional particle-in-cell simulation. Simulation results show that strong electrostatic waves are excited via the electron-ion electrostatic two-stream instability at the leading edge of the shock transition region as in the case of earlier one-dimensional simulations. We observe strong electron acceleration that is associated with the turbulent electrostatic waves in the shock transition region. The electron energy spectrum in the shock transition region exhibits a clear power-law distribution with spectral index of $2.0 {\\rm -} 2.5$. By analyzing the trajectories of accelerated electrons, we find that the acceleration mechanism is very similar to shock surfing acceleration of ions. In contrast to the ion shock surfing, however, the energetic electrons are reflected by electron-scale electrostatic fluctuations in the shock transition region, but not by the ion-scale cross-shock electrostatic potential. The reflected electrons are then accelerated by the convective electric field in front of the shock. We conclude that the multidimensional effects as well as the self-consistent shock structure are essential for the strong electron acceleration at high Mach number shocks.
Description of Collective Motion in Two-Dimensional Nuclei; Tomonaga's Method Revisited
Seiya Nishiyama; Joao da Providencia
2015-02-09T23:59:59.000Z
Four decades ago, Tomonaga proposed the elementary theory of quantum mechanical collective motion of two-dimensional nuclei of N nucleons. The theory is based essentially on the neglect of 1/sqrtN against unity. Very recently we have given exact canonically conjugate momenta to quadrupole-type collective coordinates under some subsidiary conditions and have derived nuclear quadrupole-type collective Hamiltonian. Even in the case of simple two-dimensional nuclei, we have a subsidiary condition to obtain exact canonical variables. Particularly the structure of the collective subspace satisfying the subsidiary condition is studied in detail. This subsidiary condition is important to investigate what is a structure of the collective subspace.
Computational prediction of two-dimensional group-IV mono-chalcogenides
Singh, Arunima K.; Hennig, Richard G., E-mail: rhennig@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)
2014-07-28T23:59:59.000Z
Density functional calculations determine the structure, stability, and electronic properties of two-dimensional materials in the family of group-IV monochalcogenides, MX (M?=?Ge, Sn, Pb; X?=?O, S, Se, Te). Calculations with a van der Waals functional show that the two-dimensional IV-VI compounds are most stable in either a highly distorted NaCl-type structure or a single-layer litharge type tetragonal structure. Their formation energies are comparable to single-layer MoS{sub 2}, indicating the ease of mechanical exfoliation from their layered bulk structures. The phonon spectra confirm their dynamical stability. Using the hybrid HSE06 functional, we find that these materials are semiconductors with bandgaps that are generally larger than for their bulk counterparts due to quantum confinement. The band edge alignments of monolayer group IV-VI materials reveal several type-I and type-II heterostructures, suited for optoelectronics and solar energy conversion.
Resonant tunneling device with two-dimensional quantum well emitter and base layers
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
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.
Quantization of the Reduced Phase Space of Two-Dimensional Dilaton Gravity
W. M. Seiler; R. W. Tucker
1995-06-19T23:59:59.000Z
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.
Emergence of coherence in a uniform quasi-two-dimensional Bose gas
Lauriane Chomaz; Laura Corman; Tom Bienaimé; Rémi Desbuquois; Christof Weitenberg; Sylvain Nascimbčne; Jérōme Beugnon; Jean Dalibard
2014-11-13T23:59:59.000Z
Phase transitions are ubiquitous in our three-dimensional world. By contrast most conventional transitions do not occur in infinite uniform two-dimensional systems because of the increased role of thermal fluctuations. Here we explore the dimensional crossover of Bose-Einstein condensation (BEC) for a weakly interacting atomic gas confined in a novel quasi-two-dimensional geometry, with a flat in-plane trap bottom. We detect the onset of an extended phase coherence, using velocity distribution measurements and matter-wave interferometry. We relate this coherence to the transverse condensation phenomenon, in which a significant fraction of atoms accumulate in the ground state of the motion perpendicular to the atom plane. We also investigate the dynamical aspects of the transition through the detection of topological defects that are nucleated in a quench cooling of the gas, and we compare our results to the predictions of the Kibble-Zurek theory for the conventional BEC second-order phase transition.
Locality and stability of the cascades of two-dimensional turbulence.
Gkioulekas, Eleftherios - Department of Mathematics, University of Texas
chemical combustion Stabilize plasma in a nuclear fusion reactor Propagation of laser through turbulence;Outline Why study turbulence? Brief overview of K41 theory (3D turbulence) Frisch reformulation of K41 theory. KLB theory (2D turbulence). My reformulation of Frisch to address 2D turbulence Locality
Coulomb reacceleration as a clock for nuclear reactions: A two-dimensional model
Bertulani, C.A. (Gesellschaft fuer Schwerionenforschung, KPII, Planckstrasse 1, D-64291 Darmstadt (Germany)); Bertsch, G.F. (Department of Physics and Institute for Nuclear Theory FM-15, University of Washington, Seattle, Washington 98195 (United States))
1994-05-01T23:59:59.000Z
Reacceleration effects in the Coulomb breakup of nuclei are modeled with the two-dimensional time-dependent Schroedinger 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.
Two Dimensional Integration of Ring Cavity Surface Emitting Quantum Cascade Lasers
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
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.
Inverse fixed energy scattering problem for the two-dimensional nonlinear Schroedinger operator
Georgios Fotopoulos; Valery Serov
2014-12-01T23:59:59.000Z
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.
Sanchez, Dario Ferreira; Weleguela, Monica Larissa Djomeni; Audoit, Guillaume; Grenier, Adeline; Gergaud, Patrice; Bleuet, Pierre [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA/LETI, MINATEC Campus, F-38054 Grenoble (France); Laloum, David [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA/LETI, MINATEC Campus, F-38054 Grenoble (France); ST Microelectronics, 850 Rue Jean Monnet, F-38920 Crolles (France); Ulrich, Olivier; Micha, Jean-Sébastien; Robach, Odile [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA/INAC and CNRS, SPrAM, 17 rue des Martyrs, F-38054 Grenoble (France); Lorut, Frédéric [ST Microelectronics, 850 Rue Jean Monnet, F-38920 Crolles (France)
2014-10-28T23:59:59.000Z
Here, white X-ray ?-beam Laue diffraction is developed and applied to investigate elastic strain distributions in three-dimensional (3D) materials, more specifically, for the study of strain in Cu 10??m diameter–80??m deep through-silicon vias (TSVs). Two different approaches have been applied: (i) two-dimensional ?-Laue scanning and (ii) ?-beam Laue tomography. 2D ?-Laue scans provided the maps of the deviatoric strain tensor integrated along the via length over an array of TSVs in a 100??m thick sample prepared by Focused Ion Beam. The ?-beam Laue tomography analysis enabled to obtain the 3D grain and elemental distribution of both Cu and Si. The position, size (about 3??m), shape, and orientation of Cu grains were obtained. Radial profiles of the equivalent deviatoric strain around the TSVs have been derived through both approaches. The results from both methods are compared and discussed.
Remarks on the two-dimensional power correction in the soft wall model
Tao Huang; Fen Zuo
2009-09-15T23:59:59.000Z
We present a direct derivation of the two-point correlation function of the vector current in the soft wall model by using the AdS/CFT dictionary. The resulting correlator is exactly the same as the one previously obtained from dispersion relation with the same spectral function as in this model. The coefficient $C_2$ of the two-dimensional power correction is found to be $C_2=-c/2$ with $c$ the slope of the Regge trajectory, rather than $C_2=-c/3$ derived from the strategy of first quantized string theory. Taking the slope of the $\\rho$ trajectory $c\\approx0.9{GeV}^2$ as input, we then get $C_2\\approx-0.45{GeV}^2$. The gluon condensate is found to be $\\approx0.064{GeV}^4$, which is almost identical to the QCD sum rule estimation. By comparing these two equivalent derivation of the correlator of scalar glueball operator, we demonstrate that the two-dimensional correction can't be eliminated by including the non-leading solution in the bulk-to-boundary propagator, as was done in \\cite{Colangelo2}. In other words, the two-dimensional correction does exist in the scalar glueball case. Also it is manifest by using the dispersion relation that the minus sign of gluon condensate and violation of the low energy theorem are related to the subtraction scheme.
Two-dimensional numerical model of underground oil-shale retorting
Travis, B.J.; Hommert, P.J.; Tyner, C.E.
1983-01-01T23:59:59.000Z
A two-dimensional numerical model of underground oil shale retorting, which fully couples retorting chemistry with fluid and heat flow, has been developed. The model solves the time-dependent, two-dimensional mass, momentum, and energy balance equations for a nine-component fluid (O/sub 2/, N/sub 2/, H/sub 2/, CO/sub 2/, CO, CH/sub 4/, CH/sub x/, H/sub 2/O, and oil). Water and oil can flow in the liquid and/or vapor phases. Retort chemistry includes kerogen pyrolysis, carbonate decomposition, char reactions, and combustion. Also, detailed modeling of heat flow and chemistry inside shale particles allows large rubble sizes as well as small sizes to be considered. The model is compared to one-dimensional experimental data obtained from Lawrence Livermore National Laboratory. The model can be used to examine the effect of two-dimensional variations in shale grade, rubble size, permeability, porosity, geometry, inflow gas composition, etc. on retorting efficiency and process optimization. A sample calculation is presented.
Transparent Conducting Electrodes based on 1D and 2D Ag Nanogratings for Organic Photovoltaics
Zeng, Beibei; Bartoli, Filbert J
2014-01-01T23:59:59.000Z
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.
Optical Tweezers as a Micromechanical Tool for Studying Defects in 2D Colloidal Crystals
Sungcheol Kim; Lichao Yu; Stephanie Huang; Alexandros Pertsinidis; Xinsheng Sean Ling
2011-08-09T23:59:59.000Z
This paper reports on some new results from the analyses of the video microscopy data obtained in a prior experiment on two-dimensional (2D) colloidal crystals. It was reported previously that optical tweezers can be used to create mono- and di-vacancies in a 2D colloidal crystal. Here we report the results on the creation of a vacancy-interstitial pair, as well as tri-vacancies. It is found that the vacancy-interstitial pair can be long-lived, but they do annihilate each other. The behavior of tri-vacancies is most intriguing, as it fluctuates between a configuration of bound pairs of dislocations and that of a locally amorphous state. The relevance of this observation to the issue of the nature of 2D melting is discussed.
Zhang, Jun
A Family of Fourth Order Difference Schemes on Rotated Grid for Two Dimensional Convection a family of fourth order finite difference schemes on the rotated grid for the two dimensional convection values of the convection coefficients. We also compare the fourth order schemes with the nine point
Two-dimensional calculation of eddy currents on external conducting walls induced by low-n external 1997; accepted 8 December 1997 The results of two-dimensional calculations of eddy currents induced on external conducting walls surrounding a tokamak are reported. The computed eddy currents are generated
ccsd-00085042,version1-11Jul2006 A Two-dimensional eddy current model using thin
Paris-Sud XI, Université de
ccsd-00085042,version1-11Jul2006 A Two-dimensional eddy current model using thin inductors Youcef a mathematical model for eddy currents in two dimensional geometries where the conductors are thin domains. We Mathematical modelling of eddy current problems often involves multiple conductors with various sizes
Wijngaarden, Rinke J.
Influence of the driving rate in a two-dimensional rice pile model Kinga A. Lrincz and Rinke J the influence of the driving rate in the two-dimensional Oslo rice pile model. We find that the usual power are the Bak-Tang- Wiesenfeld BTW sandpile model 1,7 , the rice pile models the Oslo model 8 and the Amaral
Dobrosavljevic, Vladimir
Linear temperature dependence of the conductivity in Si two-dimensional electrons near the apparent mobility two-dimensional electron system in Si, near the critical density, nc=0.32 1011 cm-2 , of the apparent metal-to-insulator transition, the conductivity displays a linear temperature T dependence around
Knight, S; Darakchieva, V; Kühne, P; Carlin, J -F; Grandjean, N; Herzinger, C M; Schubert, M; Hofmann, T
2015-01-01T23:59:59.000Z
The effect of a tunable, externally coupled Fabry-P\\'{e}rot cavity to resonantly enhance the optical Hall effect signatures at terahertz frequencies produced by a traditional Drude-like two-dimensional electron gas is shown and discussed in this communication. As a result, the detection of optical Hall effect signatures at conveniently obtainable magnetic fields, for example by neodymium permanent magnets, is demonstrated. An AlInN/GaN-based high electron mobility transistor structure grown on a sapphire substrate is used for the experiment. The optical Hall effect signatures and their dispersions, which are governed by the frequency and the reflectance minima and maxima of the externally coupled Fabry-P\\'{e}rot cavity, are presented and discussed. Tuning the externally coupled Fabry-P\\'{e}rot cavity strongly modifies the optical Hall effect signatures, which provides a new degree of freedom for optical Hall effect experiments in addition to frequency, angle of incidence and magnetic field direction and stren...
Goldberg, L.F. [Univ. of Minnesota, Minneapolis, MN (United States)
1990-08-01T23:59:59.000Z
The activities described in this report do not constitute a continuum but rather a series of linked smaller investigations in the general area of one- and two-dimensional Stirling machine simulation. The initial impetus for these investigations was the development and construction of the Mechanical Engineering Test Rig (METR) under a grant awarded by NASA to Dr. Terry Simon at the Department of Mechanical Engineering, University of Minnesota. The purpose of the METR is to provide experimental data on oscillating turbulent flows in Stirling machine working fluid flow path components (heater, cooler, regenerator, etc.) with particular emphasis on laminar/turbulent flow transitions. Hence, the initial goals for the grant awarded by NASA were, broadly, to provide computer simulation backup for the design of the METR and to analyze the results produced. This was envisaged in two phases: First, to apply an existing one-dimensional Stirling machine simulation code to the METR and second, to adapt a two-dimensional fluid mechanics code which had been developed for simulating high Rayleigh number buoyant cavity flows to the METR. The key aspect of this latter component was the development of an appropriate turbulence model suitable for generalized application to Stirling simulation. A final-step was then to apply the two-dimensional code to an existing Stirling machine for which adequate experimental data exist. The work described herein was carried out over a period of three years on a part-time basis. Forty percent of the first year`s funding was provided as a match to the NASA funds by the Underground Space Center, University of Minnesota, which also made its computing facilities available to the project at no charge.
Quantum State Transfer in a Two-dimensional Regular Spin Lattice of Triangular Shape
Hiroshi Miki; Satoshi Tsujimoto; Luc Vinet; Alexei Zhedanov
2012-03-12T23:59:59.000Z
Quantum state transfer in a triangular domain of a two-dimensional, equally-spaced, spin lat- tice with non-homogeneous nearest-neighbor couplings is analyzed. An exact solution of the one- excitation dynamics is provided in terms of 2-variable Krawtchouk orthogonal polynomials that have been recently defined. The probability amplitude for an excitation to transit from one site to another is given. For some values of the parameters, perfect transfer is shown to take place from the apex of the lattice to the boundary hypotenuse.
Quantum State Transfer in a Two-dimensional Regular Spin Lattice of Triangular Shape
Miki, Hiroshi; Vinet, Luc; Zhedanov, Alexei
2012-01-01T23:59:59.000Z
Quantum state transfer in a triangular domain of a two-dimensional, equally-spaced, spin lat- tice with non-homogeneous nearest-neighbor couplings is analyzed. An exact solution of the one- excitation dynamics is provided in terms of 2-variable Krawtchouk orthogonal polynomials that have been recently defined. The probability amplitude for an excitation to transit from one site to another is given. For some values of the parameters, perfect transfer is shown to take place from the apex of the lattice to the boundary hypotenuse.
Ground State of Magnetic Dipoles on a Two-Dimensional Lattice: Structural Phases in Complex Plasmas
Feldmann, J. D.; Kalman, G. J. [Department of Physics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, Massachusetts, 02467 (United States); Hartmann, P. [Research Institute for Solid State Physics and Optics of the Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Rosenberg, M. [Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, California, 92093 (United States)
2008-02-29T23:59:59.000Z
We study analytically and by molecular dynamics simulations the ground state configuration of a system of magnetic dipoles fixed on a two-dimensional lattice. We find different phases, in close agreement with previous results. Building on this result and on the minimum energy requirement we determine the equilibrium lattice configuration, the magnetic order (ferromagnetic versus antiferromagnetic), and the magnetic polarization direction of a system of charged mesoscopic particles with magnetic dipole moments, in the domain where the strong electrostatic coupling leads to a crystalline ground state. Orders of magnitudes of the parameters of the system relevant to possible future dusty plasma experiments are discussed.
Unitary transformations of a family of two-dimensional anharmonic oscillators
Francisco M. Fernįndez; Javier Garcia
2014-09-24T23:59:59.000Z
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.
Jain, Piyush; Cinti, Fabio; Boninsegni, Massimo [Department of Physics, University of Alberta, Edmonton, Alberta (Canada)
2011-07-01T23:59:59.000Z
Low-temperature properties of harmonically confined two-dimensional assemblies of dipolar bosons are systematically investigated by Monte Carlo simulations. Calculations carried out for different numbers of particles and strengths of the confining potential yield evidence of a quantum phase transition from a superfluid to a crystal-like phase, consistently with what is observed in the homogeneous system. It is found that the crystal phase nucleates in the center of the trap, as the density increases. Bose-Einstein condensation vanishes at T=0 upon entering the crystalline phase, concurrently with the disappearance of the superfluid response.
Heat transfer coefficients in two-dimensional Yukawa systems (numerical simulations)
Khrustalyov, Yu. V., E-mail: yuri.khrustalyov@gmail.com; Vaulina, O. S. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)
2013-05-15T23:59:59.000Z
New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data.
Observations of indirect exciton trapping in one- and two-dimensional magnetic lattices
Ahmed M. Abdelrahman; Byoung S. Ham
2012-02-23T23:59:59.000Z
A simple method to create and control magnetic potentials onto coupled quantum wells is demonstrated for indirect-exciton magnetic confinement. Localized inhomogeneous magnetic potentials with periodically distributed local minima and maxima, known as magnetic lattices, are projected into the plane of the coupled quantum wells and used for the spatially distributed two-dimensional indirect-exciton trapping, in which case localized indirect-excitons are observed. The indirect-exciton trapping mechanism is examined by controlling external magnetic field bias resulting in a shift of the localized excitonic lattice.
Zhan, H. F.; Bell, J. M.; Gu, Y. T., E-mail: yuantong.gu@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George St., Brisbane, Queensland 4000 (Australia); Zhang, G. [Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, Singapore 138632 (Singapore)
2014-10-13T23:59:59.000Z
We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architecture, which can be constructed through welding of single-wall CNTs by electron beam. Using large-scale nonequilibrium molecular dynamics simulations, the thermal conductivity is found to vary with different junction types due to their different phonon scatterings at the junction. The strong length and strain dependence of the thermal conductivity suggests an effective avenue to tune the thermal transport properties of the CNT-based architecture, benefiting the design of nanoscale thermal rectifiers or phonon engineering.
Two dimensional flow of a compressible gas in a thin passage
Desai, Anantkumar Ratanji
1971-01-01T23:59:59.000Z
) (Member) (Member) (Me ber) (Member) August 1971 ABSTRACT Two Dimensional Flow of a Compressible Gas in a Thin Passage (August 1971) Anantkumar Ratangi Desai, B. E. , University of Bombay; Directed by: Dr. Meherwan P. Boyce The present report... assumptions that restrict its applicability. The equations describing the flow are: 2 n ? - ~+ 3 u 3 2 Bx By p u ? + v ? (1) (Navier-Stokes Eqn. ) r 3 3 3 Bx By J 3, /Bu u ? + p ? + Bx ( Bx (2) (Continuity-Eqn. ) BT BD pCpu ? u ~ Bx Bx (3) (Energy...
Variable enstrophy flux and energy spectrum in two-dimensional turbulence with Ekman friction
Mahendra K. Verma
2012-03-23T23:59:59.000Z
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.
Two-dimensional analysis of the Split-Hopkinson Pressure Bar
Sharp, Richard Norton
1973-01-01T23:59:59.000Z
1973 Ma/or Sub)ect: Aerospace Engineering TWO-DIMENSIONAL ANALYSIS OF THE SPLIT- HOPKINSON PRESSURE BAR A Thesis by RICHARD NORTON SHARP Approved as to sty1e and content by: ( airman of Committee) Hea of Department (Member (Nsmber) December... System, " Sandia Labora- tories, Code Development Division, 5162, 1971. 14 Holt, D. L. , Babcock, S. G. , Green, S. J. , Maiden, C. J ~ , The It Strain-Rate Dependence of the Flow Stress in Some Aluminum Alloys, " 1' t ~01, 01. 60, 0. 1, 1, 1067. 15 M...
Universal Velocity Profile for Coherent Vortices in Two-Dimensional Turbulence
M. Chertkov; I. Kolokolov; V. Lebedev
2009-12-29T23:59:59.000Z
Two-dimensional turbulence generated in a finite box produces large-scale coherent vortices coexisting with small-scale fluctuations. We present a rigorous theory explaining the $\\eta=1/4$ scaling in the $V\\propto r^{-\\eta}$ law of the velocity spatial profile within a vortex, where $r$ is the distance from the vortex center. This scaling, consistent with earlier numerical and laboratory measurements, is universal in its independence of details of the small-scale injection of turbulent fluctuations and details of the shape of the box.
On the Classical Solutions of Two Dimensional Inviscid Rotating Shallow Water System
Bin Cheng; Chunjing Xie
2009-07-01T23:59:59.000Z
We prove global existence and asymptotic behavior of classical solutions for two dimensional inviscid Rotating Shallow Water system with small initial data subject to the zero-relative-vorticity constraint. One of the key steps is a reformulation of the problem into a symmetric quasilinear Klein-Gordon system, for which the global existence of classical solutions is then proved with combination of the vector field approach and the normal forms. We also probe the case of general initial data and reveal a lower bound for the lifespan that is almost inversely proportional to the size of the initial relative vorticity.
Interface Tensions and Perfect Wetting in the Two-Dimensional Seven-State Potts Model
B. Grossmann; Sourendu Gupta
1993-10-25T23:59:59.000Z
We present a numerical determination of the order-disorder interface tension, \\sod, for the two-dimensional seven-state Potts model. We find $\\sod=0.0114\\pm0.0012$, in good agreement with expectations based on the conjecture of perfect wetting. We take into account systematic effects on the technique of our choice: the histogram method. Our measurements are performed on rectangular lattices, so that the histograms contain identifiable plateaus. The lattice sizes are chosen to be large compared to the physical correlation length. Capillary wave corrections are applied to our measurements on finite systems.
A two-dimensional numerical investigation of stratified wind flow over escarpments
Fikes, Jay Stanley
1981-01-01T23:59:59.000Z
A TWO-DIMENSIONAL NUMERICAL INVESTIGATION OF STRATIFIED WIND FLOW OVER ESCARPMENTS A Thesis by JAY STANLEY FIKES, JR. Approved as to sty1e and content by: (Chairman of Committee) / (Member) (Member) (Head o& Department) May 1981 ABSTRACT... A Two-Dimens1onal Numerical Investigation of Stratified Wind Flow Over Escarpments (May 1981) Jay Stanley Fi kes, Jr. , B . S. , Texas ASM University Cha1rman of Advisory Committee: Dr. David J. Norton Long's nonl1near equat1on is solved...
Running Coupling Constants in 2D Gravity
Christof Schmidhuber
1993-08-26T23:59:59.000Z
The renormalization group flow in two--dimensional field theories that are coupled to gravity is discussed at the example of the sine-Gordon model. In order to derive the phase diagram in agreement with the matrix model results, it is necessary to generalize the theory of David, Distler and Kawai.
Particle dynamics in two-dimensional random energy landscapes - experiments and simulations
Florian Evers; Christoph Zunke; Richard D. L. Hanes; Joerg Bewerunge; Imad Ladadwa; Andreas Heuer; Stefan U. Egelhaaf
2013-06-13T23:59:59.000Z
The dynamics of individual colloidal particles in random potential energy landscapes were investigated experimentally and by Monte Carlo simulations. The value of the potential at each point in the two-dimensional energy landscape follows a Gaussian distribution. The width of the distribution, and hence the degree of roughness of the energy landscape, was varied and its effect on the particle dynamics studied. This situation represents an example of Brownian dynamics in the presence of disorder. In the experiments, the energy landscapes were generated optically using a holographic set-up with a spatial light modulator, and the particle trajectories were followed by video microscopy. The dynamics are characterized using, e.g., the time-dependent diffusion coefficient, the mean squared displacement, the van Hove function and the non-Gaussian parameter. In both, experiments and simulations, the dynamics are initially diffusive, show an extended sub-diffusive regime at intermediate times before diffusive motion is recovered at very long times. The dependence of the long-time diffusion coefficient on the width of the Gaussian distribution agrees with theoretical predictions. Compared to the dynamics in a one-dimensional potential energy landscape, the localization at intermediate times is weaker and the diffusive regime at long times reached earlier, which is due to the possibility to avoid local maxima in two-dimensional energy landscapes.
Solutions of Two Dimensional Viscous Accretion and Winds In Kerr Black Hole Geometry
S. K. Chakrabarti
1996-11-04T23:59:59.000Z
We extend our previous studies of shock waves and shock-free solutions in thin accretion and winds in pseudo-Newtonian geometry to the case when the flow is ``two-dimensional'' and around a ``Kerr black hole''. We present equations for fully general relativistic viscous transonic flows and classify the parameter space according to whether or not shocks form in an inviscid flow. We discuss the behaviors of shear, angular momentum distribution, heating and cooling in viscous flows. We obtain a very significant result: we find that in weak viscosity limit the presence of the standing shock waves is more generic in the sense that flows away from the equatorial plane can produce shock waves in a wider range of parameter space. Similar conclusion also holds when the angular momentum of the black hole is increased. Generally, our conclusions regarding the shape of the shock waves are found to agree with results of the existing numerical simulations of the two dimensional accretion in Schwarzschild geometry. In a strong viscosity limit, the shocks may be located farther out or disappear completely as in the pseudo-Newtonian geometry.
Detector-Response Correction of Two-Dimensional ? -Ray Spectra from Neutron Capture
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.
2015-05-28T23:59:59.000Z
The neutron-capture reaction produces a large variety of ?-ray cascades with different ?-ray multiplicities. A measured spectral distribution of these cascades for each ?-ray multiplicity is of importance to applications and studies of ?-ray statistical properties. The DANCE array, a 4? ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture ?-rays. The high granularity of DANCE enables measurements of high-multiplicity ?-ray cascades. The measured two-dimensional spectra (?-ray energy, ?-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. Themore »detector-response correction problem becomes more difficult for a 4? detection system than for a single detector. A trial and error approach and an iterative decomposition of ?-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional ?-ray spectra measured at DANCE from ?-ray sources and from the 10B(n, ?) and 113Cd(n, ?) reactions.« less
Asymmetric Two-dimensional Magnetic Lattices for Ultracold Atoms Trapping and Confinement
A. Abdelrahman; P. Hannaford M. Vasiliev; K. Alameh
2009-10-27T23:59:59.000Z
A new method to implement an asymmetrical two-dimensional magnetic lattice is proposed. The asymmetrical two-dimensional magnetic lattice can be created by periodically distributing magnetic minima across the surface of magnetic thin film where the periodicity can be achieved by milling $n\\times n$ square holes on the surface of the film. The quantum device is proposed for trapping and confining ultracold atoms and quantum degenerate gases prepared in the low magnetic field seeking-state at low temperature, such as the Bose-Einstein Condensate (BEC) and ultracold fermions. We present detailed analysis of the analytical expressions and the numerical simulation procedure used to calculate the external magnetic field. We also, describe the magnetic band gap structure exhibited by the asymmetric effect of the magnetic minima and show some of the possible application. We analyze the effect of changing the characteristic parameters of the magnetic lattice, such as the separating periodicity length and the hole size along with the applications of the external magnetic bias fields to maintain and allocate a suitable non-zero magnetic local minima at effective $z$-distance above the thin film surface. Suitable values are shown which keep the trapped ultracold atoms away from the thermal Majorana spin-flip and the surface Casimir-Polder effect.
A two dimensional thermal network model for a photovoltaic solar wall
Dehra, Himanshu [1-140 Avenue Windsor, Lachine, Quebec (Canada)
2009-11-15T23:59:59.000Z
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)
Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids
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
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.
Local dissipation effects in two-dimensional quantum Josephson junction arrays with a 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
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.
Rothrock, Ray Alan
1978-01-01T23:59:59.000Z
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 ...
Marocchino, A.; Atzeni, S.; Schiavi, A. [Dipartimento SBAI, Universitą di Roma “La Sapienza” and CNISM, Roma 00161 (Italy)] [Dipartimento SBAI, Universitą di Roma “La Sapienza” and CNISM, Roma 00161 (Italy)
2014-01-15T23:59:59.000Z
In some regions of a laser driven inertial fusion target, the electron mean-free path can become comparable to or even longer than the electron temperature gradient scale-length. This can be particularly important in shock-ignited (SI) targets, where the laser-spike heated corona reaches temperatures of several keV. In this case, thermal conduction cannot be described by a simple local conductivity model and a Fick's law. Fluid codes usually employ flux-limited conduction models, which preserve causality, but lose important features of the thermal flow. A more accurate thermal flow modeling requires convolution-like non-local operators. In order to improve the simulation of SI targets, the non-local electron transport operator proposed by Schurtz-Nicolaļ-Busquet [G. P. Schurtz et al., Phys. Plasmas 7, 4238 (2000)] has been implemented in the DUED fluid code. Both one-dimensional (1D) and two-dimensional (2D) simulations of SI targets have been performed. 1D simulations of the ablation phase highlight that while the shock profile and timing might be mocked up with a flux-limiter; the electron temperature profiles exhibit a relatively different behavior with no major effects on the final gain. The spike, instead, can only roughly be reproduced with a fixed flux-limiter value. 1D target gain is however unaffected, provided some minor tuning of laser pulses. 2D simulations show that the use of a non-local thermal conduction model does not affect the robustness to mispositioning of targets driven by quasi-uniform laser irradiation. 2D simulations performed with only two final polar intense spikes yield encouraging results and support further studies.
Accurate two-dimensional IMRT verification using a back-projection EPID dosimetry method
Wendling, Markus; Louwe, Robert J.W.; McDermott, Leah N.; Sonke, Jan-Jakob; Herk, Marcel van; Mijnheer, Ben J. [Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Department of Radiation Oncology, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands)
2006-02-15T23:59:59.000Z
The use of electronic portal imaging devices (EPIDs) is a promising method for the dosimetric verification of external beam, megavoltage radiation therapy--both pretreatment and in vivo. In this study, a previously developed EPID back-projection algorithm was modified for IMRT techniques and applied to an amorphous silicon EPID. By using this back-projection algorithm, two-dimensional dose distributions inside a phantom or patient are reconstructed from portal images. The model requires the primary dose component at the position of the EPID. A parametrized description of the lateral scatter within the imager was obtained from measurements with an ionization chamber in a miniphantom. In addition to point dose measurements on the central axis of square fields of different size, we also used dose profiles of those fields as reference input data for our model. This yielded a better description of the lateral scatter within the EPID, which resulted in a higher accuracy in the back-projected, two-dimensional dose distributions. The accuracy of our approach was tested for pretreatment verification of a five-field IMRT plan for the treatment of prostate cancer. Each field had between six and eight segments and was evaluated by comparing the back-projected, two-dimensional EPID dose distribution with a film measurement inside a homogeneous slab phantom. For this purpose, the {gamma}-evaluation method was used with a dose-difference criterion of 2% of dose maximum and a distance-to-agreement criterion of 2 mm. Excellent agreement was found between EPID and film measurements for each field, both in the central part of the beam and in the penumbra and low-dose regions. It can be concluded that our modified algorithm is able to accurately predict the dose in the midplane of a homogeneous slab phantom. For pretreatment IMRT plan verification, EPID dosimetry is a reliable and potentially fast tool to check the absolute dose in two dimensions inside a phantom for individual IMRT fields. Film measurements inside a phantom can therefore be replaced by EPID measurements.
Magnetic relaxation of superconducting quantum dot: two-dimensional false vacuum decay
D. R. Gulevich; F. V. Kusmartsev
2006-09-11T23:59:59.000Z
Quantum tunneling of vortices has been found to be an important novel phenomena for description of low temperature creep in high temperature superconductors (HTSCs). We speculate that quantum tunneling may be also exhibited in mesoscopic superconductors due to vortices trapped by the Bean-Livingston barrier. The London approximation and method of images is used to estimate the shape of the potential well in superconducting HTSC quantum dot. To calculate the escape rate we use the instanton technique. We model the vortex by a quantum particle tunneling from a two-dimensional ground state under magnetic field applied in the transverse direction. The resulting decay rates obtained by the instanton approach and conventional WKB are compared revealing complete coincidence with each other.
Study of vaneless diffuser rotating stall based on two-dimensional inviscid flow analysis
Tsujimoto, Yoshinobu; Yoshida, Yoshiki [Osaka Univ., Toyonaka, Osaka (Japan); Mori, Yasumasa [Mitsubishi Motors Corp., Ohta, Tokyo (Japan)
1996-03-01T23:59:59.000Z
Rotating stalls in vaneless diffusers are studied from the viewpoint that they are basically two-dimensional inviscid flow instability under the boundary conditions of vanishing velocity disturbance at the diffuser inlet and of vanishing pressure disturbance at the diffuser outlet. The linear analysis in the present report shows that the critical flow angle and the propagation velocity are functions of only the diffuser radius ratio. It is shown that the present analysis can reproduce most of the general characteristics observed in experiments: critical flow angle, propagation velocity, velocity, and pressure disturbance fields. It is shown that the vanishing velocity disturbance at the diffuser inlet is caused by the nature of impellers as a resistance and an inertial resistance, which is generally strong enough to suppress the velocity disturbance at the diffuser inlet. This explains the general experimental observations that vaneless diffuser rotating stalls are not largely affected by the impeller.
Finite-time barriers to front propagation in two-dimensional fluid flows
Mahoney, John R
2015-01-01T23:59:59.000Z
Recent theoretical and experimental investigations have demonstrated the role of certain invariant manifolds, termed burning invariant manifolds (BIMs), as one-way dynamical barriers to reaction fronts propagating within a flowing fluid. These barriers form one-dimensional curves in a two-dimensional fluid flow. In prior studies, the fluid velocity field was required to be either time-independent or time-periodic. In the present study, we develop an approach to identify prominent one-way barriers based only on fluid velocity data over a finite time interval, which may have arbitrary time-dependence. We call such a barrier a burning Lagrangian coherent structure (bLCS) in analogy to Lagrangian coherent structures (LCSs) commonly used in passive advection. Our approach is based on the variational formulation of LCSs using curves of stationary "Lagrangian shear", introduced by Farazmand, Blazevski, and Haller [Physica D 278-279, 44 (2014)] in the context of passive advection. We numerically validate our techniqu...
Experimental test of a trace formula for two-dimensional dielectric resonators
S. Bittner; E. Bogomolny; B. Dietz; M. Miski-Oglu; P. Oria Iriarte; A. Richter; F. Schäfer
2010-06-21T23:59:59.000Z
Resonance spectra of two-dimensional dielectric microwave resonators of circular and square shapes have been measured. The deduced length spectra of periodic orbits were analyzed and a trace formula for dielectric resonators recently proposed by Bogomolny et al. [Phys. Rev. E 78, 056202 (2008)] was tested. The observed deviations between the experimental length spectra and the predictions of the trace formula are attributed to a large number of missing resonances in the measured spectra. We show that by taking into account the systematics of observed and missing resonances the experimental length spectra are fully understood. In particular, a connection between the most long-lived resonances and certain periodic orbits is established experimentally.
Thermoelectric probe for Rashba spin-orbit interaction strength in a two dimensional electron gas
S. K. Firoz Islam; Tarun Kanti Ghosh
2012-07-18T23:59:59.000Z
Thermoelectric coefficients of a two dimensional electron gas with the Rashba spin-orbit interaction are presented here. In absence of magnetic field, thermoelectric coefficients are enhanced due to the Rashba spin-orbit interaction. In presence of magnetic field, the thermoelectric coefficients of spin-up and spin-down electrons oscillate with different frequency and produces beating patterns in the components of the total thermoelectric power and the total thermal conductivity. We also provide analytical expressions of the thermoelectric coefficients to explain the beating pattern formation. We obtain a simple relation which determines the Rashba SOI strength if the magnetic fields corresponding to any two successive beat nodes are known from the experiment.
Photonic-band-gap effects in two-dimensional polycrystalline and amorphous structures
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
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.
Yulianti, Yanti [Dept. of Physics, Universitas Lampung (UNILA), Jl. Sumantri Brojonegor No.1 Bandar Lampung (Indonesia); Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Su'ud, Zaki; Waris, Abdul; Khotimah, S. N. [Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Shafii, M. Ali [Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Dept. of Physics, Universitas Andalas (UNAND), Kampus Limau Manis, Padang, Sumatera Barat (Indonesia)
2010-12-23T23:59:59.000Z
The research about fast transient and spatially non-homogenous nuclear reactor accident analysis of two-dimensional nuclear reactor has been done. This research is about prediction of reactor behavior is during accident. In the present study, space-time diffusion equation is solved by using direct methods which consider spatial factor in detail during nuclear reactor accident simulation. Set of equations that obtained from full implicit finite-difference discretization method is solved by using iterative methods ADI (Alternating Direct Implicit). The indication of accident is decreasing macroscopic absorption cross-section that results large external reactivity. The power reactor has a peak value before reactor has new balance condition. Changing of temperature reactor produce a negative Doppler feedback reactivity. The reactivity will reduce excess positive reactivity. Temperature reactor during accident is still in below fuel melting point which is in secure condition.
Transfer of optical signals around bends in two-dimensional linear photonic networks
Georgios M. Nikolopoulos
2014-11-13T23:59:59.000Z
The ability to navigate light signals in two-dimensional networks of waveguide arrays is a prerequisite for the development of all-optical integrated circuits for information processing and networking. In this article, we present a theoretical analysis of bending losses in linear photonic lattices with engineered couplings, and discuss possible ways for their minimization. In contrast to previous work in the field, the lattices under consideration operate in the linear regime, in the sense that discrete solitons cannot exist. The present results suggest that the functionality of linear waveguide networks can be extended to operations that go beyond the recently demonstrated point-to-point transfer of signals, such as blocking, routing, logic functions, etc.
Scaling properties of generalized two-dimensional Kuramoto-Sivashinsky equations
Vaidas Juknevicius
2015-05-09T23:59:59.000Z
This paper presents numerical results for the two-dimensional isotropic Kuramoto-Sivashinsky equation (KSE) with an additional nonlinear term and a single independent parameter. Surfaces generated by this equation exhibit a certain dependence of the average saturated roughness on the system size that indicates power-law shape of the surface spectrum for small wave numbers. This leads to a conclusion that although cellular surface patterns of definite scale dominate in the range of short distances, there are also scale-free long-range height variations present in the large systems. The dependence of the spectral exponent on the equation parameter gives some insight into the scaling behavior for large systems.
Laboratory setup and results of experiments on two-dimensional multiphase flow in porous media
McBride, J.F. (ed.) (Pacific Northwest Lab., Richland, WA (USA)); Graham, D.N. (ed.); Schiegg, H.O. (SIMULTEC Ltd., Meilen/Zurich (Switzerland))
1990-10-01T23:59:59.000Z
In the event of an accidental release into earth's subsurface of an immiscible organic liquid, such as a petroleum hydrocarbon or chlorinated organic solvent, the spatial and temporal distribution of the organic liquid is of great interest when considering efforts to prevent groundwater contamination or restore contaminated groundwater. An accurate prediction of immiscible organic liquid migration requires the incorporation of relevant physical principles in models of multiphase flow in porous media; these physical principles must be determined from physical experiments. This report presents a series of such experiments performed during the 1970s at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland. The experiments were designed to study the transient, two-dimensional displacement of three immiscible fluids in a porous medium. This experimental study appears to be the most detailed published to date. The data obtained from these experiments are suitable for the validation and test calibration of multiphase flow codes. 73 refs., 140 figs.
Two-dimensional spectroscopy for the study of ion Coulomb crystals
A. Lemmer; C. Cormick; C. T. Schmiegelow; F. Schmidt-Kaler; M. B. Plenio
2015-05-04T23:59:59.000Z
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 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.
Implementation of the Log-Conformation Formulation for Two-Dimensional Viscoelastic Flow
Jensen, K E; Okkels, F
2015-01-01T23:59:59.000Z
We have implemented the log-conformation method for two-dimensional viscoelastic flow in COMSOL, a commercial high-level finite element package. The code is verified for an Oldroyd-B fluid flowing past a confined cylinder. We are also able to describe the well-known bistability of the viscoelastic flow in a cross-slot geometry for a FENE-CR fluid, and we describe the changes required for performing simulations with the Phan-Thien-Tanner (PTT), Giesekus and FENE-P models. Finally, we calculate the flow of a FENE-CR fluid in a geometry with three in- and outlets. The implementation is included in the supplementary material, and we hope that it can inspire new as well as experienced researchers in the field of differential constitutive equations for viscoelastic flow.
Statistical Mechanics of Two-dimensional Foams: Physical Foundations of the Model
Marc Durand
2015-07-16T23:59:59.000Z
In a recent series of papers [1--3], a statistical model that accounts for correlations between topological and geometrical properties of a two-dimensional shuffled foam has been proposed and compared with experimental and numerical data. Here, the various assumptions on which the model is based are exposed and justified: the equiprobability hypothesis of the foam configurations is argued. The range of correlations between bubbles is discussed, and the mean field approximation that is used in the model is detailed. The two self-consistency equations associated with this mean field description can be interpreted as the conservation laws of number of sides and bubble curvature, respectively. Finally, the use of a "Grand-Canonical" description, in which the foam constitutes a reservoir of sides and curvature, is justified.
Two-dimensional cylindrical ion-acoustic solitary and rogue waves in ultrarelativistic plasmas
Ata-ur-Rahman [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan) [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Centre for Physics at QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics at QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan)] [National Centre for Physics at QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said 42521 (Egypt)] [Department of Physics, Faculty of Science, Port Said University, Port Said 42521 (Egypt); Mushtaq, A. [National Centre for Physics at QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan) [National Centre for Physics at QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan)
2013-07-15T23:59:59.000Z
The propagation of ion-acoustic (IA) solitary and rogue waves is investigated in a two-dimensional ultrarelativistic degenerate warm dense plasma. By using the reductive perturbation technique, the cylindrical Kadomtsev–Petviashvili (KP) equation is derived, which can be further transformed into a Korteweg–de Vries (KdV) equation. The latter admits a solitary wave solution. However, when the frequency of the carrier wave is much smaller than the ion plasma frequency, the KdV equation can be transferred to a nonlinear Schrödinger equation to study the nonlinear evolution of modulationally unstable modified IA wavepackets. The propagation characteristics of the IA solitary and rogue waves are strongly influenced by the variation of different plasma parameters in an ultrarelativistic degenerate dense plasma. The present results might be helpful to understand the nonlinear electrostatic excitations in astrophysical degenerate dense plasmas.
A two-dimensional thermomechanical simulation of a gas metal arc welding process
Ortega, A.R.
1990-08-01T23:59:59.000Z
A low heat input gas metal arc (GMA) weld overlay process is being investigated as a possible means to repair Savannah River nuclear reactor tanks in the event cracks are detected in the reactor walls. Two-dimensional thermomechanical simulations of a GMA welding process were performed using the finite element code ABAQUS to assist in the design of the upcoming weld experiments on helium-charged specimens. The thermal model correlated well with existing test data, i.e., fusion zone depth and thermocouple data. In addition, numerical results revealed that after cool-down the final deformation of the workpiece was qualitatively similar to the shape observed experimentally. Based on these analyses, conservative recommendations were made for the workpiece dimensions, weld pass spacing, and thermomechanical boundary conditions to ensure the experiments would be as representative as possible of welding on the reactor walls. 12 refs., 13 figs.
Perturbative quantization of two-dimensional space-time noncommutative QED
Ghasemkhani, M.; Sadooghi, N. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of)
2010-02-15T23:59:59.000Z
Using the method of perturbative quantization in the first order approximation, we quantize a nonlocal QED-like theory including fermions and bosons whose interactions are described by terms containing higher order space-time derivatives. As an example, the two-dimensional space-time noncommutative QED (NC-QED) is quantized perturbatively up to O(e{sup 2},{theta}{sup 3}), where e is the NC-QED coupling constant and {theta} is the noncommutativity parameter. The resulting modified Lagrangian density is shown to include terms consisting of first order time-derivative and higher order space-derivatives of the modified field variables that satisfy the ordinary equal-time commutation relations up to O(e{sup 2},{theta}{sup 3}). Using these commutation relations, the canonical current algebra of the modified theory is also derived.
Davis, Benjamin L; Shields, Douglas W; Kennefick, Julia; Kennefick, Daniel; Seigar, Marc S; Lacy, Claud H S; Puerari, Ivānio
2012-01-01T23:59:59.000Z
A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.
Hydration of an apolar solute in a two-dimensional waterlike lattice fluid
C. Buzano; E. De Stefanis; M. Pretti
2005-01-11T23:59:59.000Z
In a previous work, we investigated a two-dimensional lattice-fluid model, displaying some waterlike thermodynamic anomalies. The model, defined on a triangular lattice, is now extended to aqueous solutions with apolar species. Water molecules are of the "Mercedes Benz" type, i.e., they possess a D3 (equilateral triangle) symmetry, with three equivalent bonding arms. Bond formation depends both on orientation and local density. The insertion of inert molecules displays typical signatures of hydrophobic hydration: large positive transfer free energy, large negative transfer entropy (at low temperature), strong temperature dependence of the transfer enthalpy and entropy, i.e., large (positive) transfer heat capacity. Model properties are derived by a generalized first order approximation on a triangle cluster.
Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U
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
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.
Topological Patterns in Two-dimensional Gel Electrophoresis of DNA Knots
Michieletto, Davide; Orlandini, Enzo
2015-01-01T23:59:59.000Z
Gel electrophoresis is a powerful experimental method to probe the topology of DNA and other biopolymers. While there is a large body of experimental work which allows us to accurately separate different topoisomers of a molecule, a full theoretical understanding of these experiments has not yet been achieved. Here we show that the mobility of DNA knots depends crucially and subtly on the physical properties of the gel, and in particular on the presence of dangling ends. The topological interactions between these and DNA molecules can be described in terms of an "entanglement number", and yield a non-monotonic mobility at moderate fields. Consequently, in two-dimensional electrophoresis, gel bands display a characteristic arc pattern; this turns into a straight line when the density of dangling ends vanishes. We also provide a novel framework to accurately predict the shape of such arcs as a function of molecule length and topological complexity, which may be used to inform future experiments.
Epitaxial two-dimensional nitrogen atomic sheet in GaAs
Harada, Yukihiro, E-mail: y.harada@eedept.kobe-u.ac.jp; Yamamoto, Masuki; Baba, Takeshi; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)
2014-01-27T23:59:59.000Z
We have grown an epitaxial two-dimensional nitrogen (N) atomic sheet in GaAs by using the site-controlled N ?-doping technique. We observed a change of the electronic states in N ?-doped GaAs from the isolated impurity centers to the delocalized impurity band at 1.49?eV with increasing N-doping density. According to the excitation-power- and temperature-dependent photoluminescence (PL) spectra, the emission related to localized levels below the impurity band edge was dominant at low excitation power and temperature, whereas the effects of the localized levels can be neglected by increasing the excitation power and temperature. Furthermore, a clear Landau shift of the PL-peak energy was observed at several Tesla in the Faraday configuration, in contrast to the case in the impurity limit.
A Priori Estimates for Two-Dimensional Water Waves with Angled Crests
Kinsey, Rafe H
2014-01-01T23:59:59.000Z
We consider the two-dimensional water wave problem in the case where the free interface of the fluid meets a vertical wall at a possibly non-right angle; our problem also covers interfaces with angled crests. We assume that the fluid is inviscid, incompressible, and irrotational, with no surface tension and with air density zero. We construct a low-regularity energy and prove a closed energy estimate for this problem. Our work differs from earlier work in that, in our case, only a degenerate Taylor stability criterion holds, with $-\\frac{\\partial P}{\\partial {\\bf n}} \\ge 0$, instead of the strong Taylor stability criterion $-\\frac{\\partial P}{\\partial {\\bf n}} \\ge c > 0$.
Carr, Sam T. [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie, 76128 Karlsruhe (Germany); DFG Center for Functional Nanostructures, Karlsruher Institut fuer Technologie, 76128 Karlsruhe (Germany); Quintanilla, Jorge [School of Physical Sciences, University of Kent, Canterbury CT2 7NH (United Kingdom); ISIS Spallation Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX (United Kingdom); Betouras, Joseph J. [Department of Physics, Loughborough University, Loughborough LE11 3TU (United Kingdom)
2010-07-15T23:59:59.000Z
We consider a two-dimensional model of noninteracting chains of spinless fermions weakly coupled via a small interchain hopping and a repulsive interchain interaction. The phase diagram of this model has a surprising feature: an abrupt change in the Fermi surface as the interaction is increased. We study in detail this metanematic transition and show that the well-known 2(1/2)-order Lifshitz transition is the critical end point of this first-order quantum phase transition. Furthermore, in the vicinity of the end point, the order parameter has a nonperturbative BCS-type form. We also study a competing crystallization transition in this model and derive the full phase diagram. This physics can be demonstrated experimentally in dipolar ultracold atomic or molecular gases. In the presence of a harmonic trap, it manifests itself as a sharp jump in the density profile.
Khater, A.H.; Moawad, S.M.; Callebaut, D.K. [Department of Mathematics, Faculty of Science, Cairo University, Beni-Suef (Egypt); Departement Natuurkunde, Campus Drie Eiken, Universiteit Antwerpen - UA, B-2610 Antwerpen (Belgium)
2005-01-01T23:59:59.000Z
The equilibrium and Lyapunov stability properties for two-dimensional ideal magnetohydrodynamic (MHD) plasmas with incompressible and homogeneous (i.e., constant density) flows are investigated. In the unperturbed steady state, both the velocity and magnetic field are nonzero and have three components in a Cartesian coordinate system with translational symmetry (i.e., one ignorable spatial coordinate). It is proved that (a) the solutions of the ideal MHD steady state equations with incompressible and homogeneous flows in the plane are also valid for equilibria with the axial velocity component being a free flux function and the axial magnetic field component being a constant (b) the conditions of linearized Lyapunov stability for these MHD flows in the planar case (in which the fields have only two components) are also valid for symmetric equilibria that have a nonplanar velocity field component as well as a nonplanar magnetic field component. On using the method of convexity estimates, nonlinear stability conditions are established.
The friction factor of two-dimensional rough-boundary turbulent soap film flows
Nicholas Guttenberg; Nigel Goldenfeld
2009-03-25T23:59:59.000Z
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.
Two-dimensional modeling of the cathode sheath formation during the streamer-cathode interaction
Yan, Wen; Sang, Chaofeng; Wang, Dezhen, E-mail: wangdez@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Liu, Fucheng [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)] [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)
2014-01-15T23:59:59.000Z
In this paper, a computational simulation of the sheath formation during the streamer-surface interaction at atmospheric pressure is presented. A two-dimensional fluid model of a point-to-plane configuration is applied to investigate the evolution of the discharge in the vicinity of cathode plane. The effects of the surfaces on the properties of streamer have been studied for three cases, i.e., conductive surface with secondary electron emission (SEE), conductive surface without SEE, and dielectric surface. In all cases, we found that the axial propagation velocity of the streamer front decreases as the streamer arrives at the boundary of the cathode sheath. And the simulation results showed that the properties of the surface have a significant effect on the streamer. Besides the influences, the secondary emission coefficient and the relative permittivity on the streamer-surface interactions are also studied.
Butkus, Vytautas; Augulis, Ram?nas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius
2015-01-01T23:59:59.000Z
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...
Device for two-dimensional gas-phase separation and characterization of ion mixtures
Tang, Keqi (Richland, WA); Shvartsburg, Alexandre A. (Richland, WA); Smith, Richard D. (Richland, WA)
2006-12-12T23:59:59.000Z
The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.
Thermoelectric probe for Rashba spin-orbit interaction strength in a two dimensional electron gas
Islam, S K Firoz
2012-01-01T23:59:59.000Z
Thermoelectric coefficients of a two dimensional electron gas with the Rashba spin-orbit interaction are presented here. In absence of magnetic field, thermoelectric coefficients are enhanced due to the Rashba spin-orbit interaction. In presence of magnetic field, the thermoelectric coefficients of spin-up and spin-down electrons oscillate with different frequency and produces beating patterns in the components of the total thermoelectric power and the total thermal conductivity. We also provide analytical expressions of the thermoelectric coefficients to explain the beating pattern formation. We obtain a simple relation which determines the Rashba SOI strength if the magnetic fields corresponding to any two successive beat nodes are known from the experiment.
Collision-dependent power law scalings in two dimensional gyrokinetic turbulence
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
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.
Laser induced reentrant freezing in two-dimensional attractive colloidal systems
Pinaki Chaudhuri; Chinmay Das; Chandan Dasgupta; H. R. Krishnamurthy; A. K. Sood
2005-09-11T23:59:59.000Z
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.
Freezing of a two dimensional fluid in to a crystalline phase : Density functional approach
Anubha Jaiswal; Swarn L. Singh; Yashwant Singh
2012-10-02T23:59:59.000Z
A free-energy functional for a crystal proposed by Singh and Singh (Europhys. Lett. {\\bf {88}}, 16005 (2009)) and which contains both the symmetry conserved and symmetry broken parts of the direct pair correlation function has been used to investigate the crystallization of a two-dimensional fluid. The results found for fluids interacting via the inverse power potential $ u(r)= \\epsilon ({\\sigma}/{r})^{n} $ for n= 3, 6 and 12 are in good agreement with experimental and simulation results. The contribution made by the symmetry broken part to the grand thermodynamic potential at the freezing point is found to increase with the softness of the potential. Our results explain why the Ramakrishnan-Yussouff (Phys. Rev. B {\\bf 19}, 2775 (1979)) free-energy functional gave good account of freezing transitions of hard-core potentials but failed for potentials that have soft core and/or attractive tail.
Motion of fluxons in distributed two-dimensional Josephson tunnel junctions
Nevirkovets, I.P.; Rudenko, E.M.
1984-01-01T23:59:59.000Z
A strong asymmetry is observed in the current--voltage characteristics of distributed two-dimensional Sn--I--Sn, Sn--I--Pb tunnel junctions with dimensions L>>lambda/sub J/ when an external magnetic field is applied in the plane of the junction perpendicular to the L dimension for different orientations of the field. A resistive section in the form of an almost vertical step appears in the IVC in one orientation of the field and is absent in the opposite orientation. It is shown that the appearance of the steps is related to the conditions of motion of Josephson vortices in tunnel junctions under the action of the Lorentz force in the presence of a current domain at the edge of the distributed junction.
Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials
Lotz, Mikkel R.; Boll, Mads; Bųggild, Peter; Petersen, Dirch H., E-mail: dirch.petersen@nanotech.dtu.dk [Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Hansen, Ole [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Danish National Research Foundation's Center for Individual Nanoparticle Functionality (CINF), Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Kjęr, Daniel [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); CAPRES A/S, Scion-DTU, Building 373, DK-2800 Kgs. Lyngby (Denmark)
2014-08-04T23:59:59.000Z
The presence of defects in graphene have for a long time been recognized as a bottleneck for its utilization in electronic and mechanical devices. We recently showed that micro four-point probes may be used to evaluate if a graphene film is truly 2D or if defects in proximity of the probe will lead to a non-uniform current flow characteristic of lower dimensionality. In this work, simulations based on a finite element method together with a Monte Carlo approach are used to establish the transition from 2D to quasi-1D current transport, when applying a micro four-point probe to measure on 2D conductors with an increasing amount of line-shaped defects. Clear 2D and 1D signatures are observed at low and high defect densities, respectively, and current density plots reveal the presence of current channels or branches in defect configurations yielding 1D current transport. A strong correlation is found between the density filling factor and the simulation yield, the fraction of cases with 1D transport and the mean sheet conductance. The upper transition limit is shown to agree with the percolation threshold for sticks. Finally, the conductance of a square sample evaluated with macroscopic edge contacts is compared to the micro four-point probe conductance measurements and we find that the micro four-point probe tends to measure a slightly higher conductance in samples containing defects.
Improved bends for two-dimensional photonic crystal , Ya Yan Lu b
Lu, Ya Yan
is a three-dimensional (3D) structure with a 2D periodicity. Typically, it is a dielectric slab. Keywords: Optical waveguides, photonic crystal waveguides, waveguide bends, optimal design, numerical material to realize such waveguide bends. Mekis et al. [2] first theoretically demonstrated high
Graphene/MoS2 Hybrid Technology for Large-Scale Two-Dimensional Electronics
Walsworth, Ronald L.
mechanical flexibility, optical transparency, and favorable transport properties for realizing electronic and circuits based on this 2D heterostructure pave the way for practical flexible transparent electronics, flexible and transparent As Moore's law approaches its physical limit in Si-based electronics, the device
Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots
Zhang, Jian-Shi (Shanghai, CN); Giometti, Carol S. (Glenview, IL); Tollaksen, Sandra L. (Montgomery, IL)
1989-01-01T23:59:59.000Z
After two-dimensional electrophoresis of proteins or the like, resulting in a polyacrylamide gel slab having a pattern of protein gel spots thereon, an individual protein gel spot is cored out from the slab, to form a gel spot core which is placed in an extraction tube, with a dialysis membrane across the lower end of the tube. Replicate gel spots can be cored out from replicate gel slabs and placed in the extraction tube. Molten agarose gel is poured into the extraction tube where the agarose gel hardens to form an immobilizing gel, covering the gel spot cores. The upper end portion of the extraction tube is filled with a volume of buffer solution, and the upper end is closed by another dialysis membrane. Upper and lower bodies of a buffer solution are brought into contact with the upper and lower membranes and are provided with electrodes connected to the positive and negative terminals of a DC power supply, thereby producing an electrical current which flows through the upper membrane, the volume of buffer solution, the agarose, the gel spot cores and the lower membrane. The current causes the proteins to be extracted electrophoretically from the gel spot cores, so that the extracted proteins accumulate and are contained in the space between the agarose gel and the upper membrane. A high percentage extraction of proteins is achieved. The extracted proteins can be removed and subjected to partial digestion by trypsin or the like, followed by two-dimensional electrophoresis, resulting in a gel slab having a pattern of peptide gel spots which can be cored out and subjected to electrophoretic extraction to extract individual peptides.
2D Fokker-Planck models of rotating clusters
J. Fiestas; R. Spurzem; E. Kim
2006-09-04T23:59:59.000Z
Globular clusters rotate significantly, and with the increasing amount of detailed morphologicaland kinematical data obtained in recent years on galactic globular clusters many interesting features show up. We show how our theoretical evolutionary models of rotating clusters can be used to obtain fits, which at least properly model the overall rotation and its implied kinematics in full 2D detail (dispersions, rotation velocities). Our simplified equal mass axisymmetric rotatingmodel provides detailed two-dimensional kinematical and morphological data for star clusters. The degree of rotation is not dominant in energy, but also non-negligible for the phase space distribution function, shape and kinematics of clusters. Therefore the models are well applicable for galactic globular clusters. Since previously published papers on that matter by us made it difficult to do detailed comparisons with observations we provide a much more comprehensive and easy-to-use set of data here, which uses as entries dynamical age and flattening of observed cluster andthen offers a limited range of applicable models in full detail. The method, data structure and some exemplary comparison with observations are presented. Future work will improve modelling anddata base to take a central black hole, a mass spectrum and stellar evolution into account.
Coexistence of Magnetic Order and Two-dimensional Superconductivity at LaAlO3/SrTiO3 Interfaces
Li, Lu
A two dimensional electronic system forms at the interface between the band insulators LaAlO[subscript 3]
Staring 2-D hadamard transform spectral imager
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
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.
Annotated Bibliography of EDGE2D Use
J.D. Strachan and G. Corrigan
2005-06-24T23:59:59.000Z
This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.
Enyashin, A.N.; Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru
2013-11-15T23:59:59.000Z
The structural, electronic properties and stability of the new MXene compounds—two-dimensional pristine carbonitrides Ti{sub 3}C{sub 2?x}N{sub x} and their hydroxylated derivatives Ti{sub 3}C{sub 2?x}N{sub x}(OH){sub 2} are studied by means of DFTB calculations. The genesis of the properties is discussed in the sequence: binary MXenes Ti{sub 3}C{sub 2} (Ti{sub 3}N{sub 2})?hydroxylated forms Ti{sub 3}C{sub 2}(OH){sub 2} (Ti{sub 3}N{sub 2}(OH){sub 2})?pristine MXene Ti{sub 3}C{sub 2?x}N{sub x}?hydroxylated Ti{sub 3}C{sub 2?x}N{sub x}(OH){sub 2}. All examined materials are metallic-like. The most favorable type of OH-covering is presented by the occupation of the hollow sites between three neighboring carbon (nitrogen) atoms. Two-dimensional MXene carbonitrides with random distribution of C and N atoms are found to be thermodynamically more favorable. - Graphical abstract: The side views of the optimized atomic structures of some examined hydroxylated derivatives of MXene Ti{sub 3}CN and their electronic band structures. Display Omitted - Highlights: • Very recently 2D titanium carbonitrides have been synthesized. • Structural, electronic properties and stability for these materials were evaluated. • The hydroxylated derivatives of 2D titanium carbonitrides are examined.
Bosons in Disc-Shaped Traps: From 3D to 2D
K. Schnee; J. Yngvason
2006-10-16T23:59:59.000Z
We present a mathematically rigorous analysis of the ground state of a dilute, interacting Bose gas in a three-dimensional trap that is strongly confining in one direction so that the system becomes effectively two-dimensional. The parameters involved are the particle number, $N\\gg 1$, the two-dimensional extension, $\\bar L$, of the gas cloud in the trap, the thickness, $h\\ll \\bar L$ of the trap, and the scattering length $a$ of the interaction potential. Our analysis starts from the full many-body Hamiltonian with an interaction potential that is assumed to be repulsive, radially symmetric and of short range, but otherwise arbitrary. In particular, hard cores are allowed. Under the premisses that the confining energy, $\\sim 1/h^2$, is much larger than the internal energy per particle, and $a/h\\to 0$, we prove that the system can be treated as a gas of two-dimensional bosons with scattering length $a_{\\rm 2D}= h\\exp(-(\\hbox{\\rm const.)}h/a)$. In the parameter region where $a/h\\ll |\\ln(\\bar\\rho h^2)|^{-1}$, with $\\bar\\rho\\sim N/\\bar L^2$ the mean density, the system is described by a two-dimensional Gross-Pitaevskii density functional with coupling parameter $\\sim Na/h$. If $|\\ln(\\bar\\rho h^2)|^{-1}\\lesssim a/h$ the coupling parameter is $\\sim N |\\ln(\\bar\\rho h^2)|^{-1}$ and thus independent of $a$. In both cases Bose-Einstein condensation in the ground state holds, provided the coupling parameter stays bounded.
Two-dimensional double layer in plasma in a diverging magnetic field
Saha, S. K.; Raychaudhuri, S.; Chowdhury, S.; Janaki, M. S.; Hui, A. K. [Plasma Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)
2012-09-15T23:59:59.000Z
Plasma created by an inductive RF discharge is allowed to expand along a diverging magnetic field. Measurement of the axial plasma potential profile reveals the formation of an electric double layer near the throat of the expansion chamber. An accelerated ion beam has been detected in the downstream region, confirming the presence of the double layer. The 2-D nature of the ion energy distribution function of the downstream plasma has been studied by a movable ion energy analyser, which shows that the beam radius increases along the axial distance. The 2-D structure of the plasma potential has been studied by a movable emissive probe. The existence of a secondary lobe in the contour plot of plasma equipotential is a new observation. It is also an interesting observation that the most diverging magnetic field line not intercepting the junction of the discharge tube and the expansion chamber has an electric field aligned with it.
Two-dimensional single-stream electron motion in a coaxial diode with magnetic insulation
Fuks, Mikhail I.; Schamiloglu, Edl [Department of Electrical and Computer Engineering, MSC01 1100, University of New Mexico, Albuquerque, New Mexico 87131-0001 (United States)] [Department of Electrical and Computer Engineering, MSC01 1100, University of New Mexico, Albuquerque, New Mexico 87131-0001 (United States)
2014-05-15T23:59:59.000Z
One of the most widespread models of electrons drifting around the cathode in magnetrons is the single-stream state, which is the Brillouin stream with purely azimuthal motion. We describe a single-stream state in which electrons not only move in the azimuthal direction, but also along the axial direction, which is useful for consideration, for example, of relativistic magnetrons, MILOs, and coaxial transmission lines. Relations are given for the conditions of magnetic insulation for 2D electron motion, for 1D azimuthal and axial motion, and for synchronism of these streams with the operating waves of M-type microwave sources. Relations are also provided for the threshold of generation in magnetrons with 2D electron motion.
PAD, a computer-aided molecular model building system utilizing two-dimensional graphical input
White, William Gerald
1980-01-01T23:59:59.000Z
and an artist. CONTENTS CHAPTER I. BACKGROUND: INTERFACING COMPUTER AND CHEMIcT Graphical Input Hardware Evolution. . . . . Software Systems: Using the Hardware, , Chemical Applications. Program PAD xn Perspective. CHAPTER II. YATERIA' S AND METHODS... are used. The 2-D coordinates of each atom input by the user are stored permanently in XS and YS, after temporary storage in IX and IY. Arrays XS and YS are each 99 elements long, as are all other arrays storing information about input atoms; therefore...
Two-dimensional Electron Liquid State at Oxide Interfaces J. Mannhart
Yeh, Nai-Chang
AlO3 (4 unit cells) interface electron system SrTiO3 M. Breitschaft et al., PRB 81, 153414 (2010) #12 Interface M. Breitschaft et al., PRB 81, 153414 (2010) #12;E - EF (eV) VS (V) E - EV (eV) E - EF (eV) VS (V al., PRB 81, 153414 (2010) U is needed, interface system is a 2D-electron liquid #12;LaAlOAlxGa1-x
Two-dimensional inverse planning and delivery with a preclinical image guided microirradiator
Stewart, James M. P. [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E2, Canada and Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9 (Canada)] [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E2, Canada and Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9 (Canada); Lindsay, Patricia E. [Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9, Canada and Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 3E2 (Canada)] [Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9, Canada and Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Jaffray, David A. [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E2 (Canada) [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9 (Canada); Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); The Techna Institute for the Advancement of Technology for Health, Toronto, Ontario M5G 1P5 (Canada)
2013-10-15T23:59:59.000Z
Purpose: Recent advances in preclinical radiotherapy systems have provided the foundation for scaling many of the elements of clinical radiation therapy practice to the dimensions and energy demanded in small animal studies. Such systems support the technical capabilities to accurately deliver highly complex dose distributions, but methods to optimize and deliver such distributions remain in their infancy. This study developed an optimization method based on empirically measured two-dimensional dose kernel measurements to deliver arbitrary planar dose distributions on a recently developed small animal radiotherapy platform.Methods: A two-dimensional dose kernel was measured with repeated radiochromic film measurements for the circular 1 mm diameter fixed collimator of the small animal radiotherapy system at 1 cm depth in a solid water phantom. This kernel was utilized in a sequential quadratic programming optimization framework to determine optimal beam positions and weights to deliver an arbitrary desired dose distribution. The positions and weights were then translated to a set of stage motions to automatically deliver the optimized dose distribution. End-to-end efficacy of the framework was quantified through five repeated deliveries of two dosimetric challenges: (1) a 5 mm radius bullseye distribution, and (2) a “sock” distribution contained within a 9 × 13 mm bounding box incorporating rectangular, semicircular, and exponentially decaying geometric constructs and a rectangular linear dose gradient region. These two challenges were designed to gauge targeting, geometric, and dosimetric fidelity.Results: Optimization of the bullseye and sock distributions required 2.1 and 5.9 min and utilized 50 and 77 individual beams for delivery, respectively. Automated delivery of the resulting optimized distributions, validated using radiochromic film measurements, revealed an average targeting accuracy of 0.32 mm, and a dosimetric delivery error along four line profiles taken through the sock distribution of 3.9%. Mean absolute delivery error across the 0–1 Gy linear dose gradient over 7.5 mm was 0.01 Gy.Conclusions: The work presented here demonstrates the potential for complex dose distributions to be planned and automatically delivered with millimeter scale heterogeneity at submillimeter accuracy. This capability establishes the technical foundation for preclinical validation of biologically guided radiotherapy investigations and development of unique radiobiological experiments.
Danila, Bogdan; Mocanu, Gabriela
2015-01-01T23:59:59.000Z
We investigate the transition to Self Organized Criticality in a two-dimensional model of a flux tube with a background flow. The magnetic induction equation, represented by a partial differential equation with a stochastic source term, is discretized and implemented on a two dimensional cellular automaton. The energy released by the automaton during one relaxation event is the magnetic energy. As a result of the simulations we obtain the time evolution of the energy release, of the system control parameter, of the event lifetime distribution and of the event size distribution, respectively, and we establish that a Self Organized Critical state is indeed reached by the system. Moreover, energetic initial impulses in the magnetohydrodynamic flow can lead to one dimensional signatures in the magnetic two dimensional system, once the Self Organized Critical regime is established. The applications of the model for the study of Gamma Ray Bursts is briefly considered, and it is shown that some astrophysical paramet...
Simulations of spray autoignition and flame establishment with two-dimensional CMC
Wright, Y.M.; Boulouchos, K. [Aerothermochemistry and Combustion Technology Laboratory, ETH Zurich (Switzerland); De Paola, G.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)
2005-12-01T23:59:59.000Z
The unsteady two-dimensional conditional moment closure (CMC) model with first-order closure of the chemistry and supplied with standard models for the conditional convection and turbulent diffusion terms has been interfaced with a commercial engine CFD code and analyzed with two numerical methods, an 'exact' calculation with the method of lines and a faster fractional-step method. The aim was to examine the sensitivity of the predictions to the operator splitting errors and to identify the extent to which spatial transport terms are important for spray autoignition problems. Despite the underlying simplifications, solution of the full CMC equations allows a single model to be used for the autoignition, flame propagation ('premixed mode'), and diffusion flame mode of diesel combustion, which makes CMC a good candidate model for practical engine calculations. It was found that (i) the conditional averages have significant spatial gradients before ignition and during the premixed mode and (ii) that the inclusion of physical-space transport affects the calculation of the autoignition delay time, both of which suggest that volume-averaged CMC approaches may be inappropriate for diesel-like problems. A balance of terms in the CMC equation before and after autoignition shows the relative magnitude of spatial transport and allows conjectures on the structure of the premixed phase of diesel combustion. Very good agreement with available experimental data is found concerning ignition delays and the effect of background air turbulence on them.
Two dimensional Sen connections and quasi-local energy-momentum
L. B. Szabados
1994-02-02T23:59:59.000Z
The recently constructed two dimensional Sen connection is applied in the problem of quasi-local energy-momentum in general relativity. First it is shown that, because of one of the two 2 dimensional Sen--Witten identities, Penrose's quasi-local charge integral can be expressed as a Nester--Witten integral.Then, to find the appropriate spinor propagation laws to the Nester--Witten integral, all the possible first order linear differential operators that can be constructed only from the irreducible chiral parts of the Sen operator alone are determined and examined. It is only the holomorphy or anti-holomorphy operator that can define acceptable propagation laws. The 2 dimensional Sen connection thus naturally defines a quasi-local energy-momentum, which is precisely that of Dougan and Mason. Then provided the dominant energy condition holds and the 2-sphere S is convex we show that the next statements are equivalent: i. the quasi-local mass (energy-momentum) associated with S is zero; ii.the Cauchy development $D(\\Sigma)$ is a pp-wave geometry with pure radiation ($D(\\Sigma)$ is flat), where $\\Sigma$ is a spacelike hypersurface whose boundary is S; iii. there exist a Sen--constant spinor field (two spinor fields) on S. Thus the pp-wave Cauchy developments can be characterized by the geometry of a two rather than a three dimensional submanifold.
Basin boundary, edge of chaos, and edge state in a two-dimensional model
J. Vollmer; T. M. Schneider; B. Eckhardt
2008-08-19T23:59:59.000Z
In shear flows like pipe flow and plane Couette flow there is an extended range of parameters where linearly stable laminar flow coexists with a transient turbulent dynamics. When increasing the amplitude of a perturbation on top of the laminar flow, one notes a a qualitative change in its lifetime, from smoothly varying and short one on the laminar side to sensitively dependent on initial conditions and long on the turbulent side. The point of transition defines a point on the edge of chaos. Since it is defined via the lifetimes, the edge of chaos can also be used in situations when the turbulence is not persistent. It then generalises the concept of basin boundaries, which separate two coexisting attractors, to cases where the dynamics on one side shows transient chaos and almost all trajectories eventually end up on the other side. In this paper we analyse a two-dimensional map which captures many of the features identified in laboratory experiments and direct numerical simulations of hydrodynamic flows. The analysis of the map shows that different dynamical situations in the edge of chaos can be combined with different dynamical situations in the turbulent region. Consequently, the model can be used to develop and test further characterisations that are also applicable to realistic flows.
Anderson, H.L.; Kinnison, W.W.; Lillberg, J.W.
1985-04-30T23:59:59.000Z
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.
Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots
Zhang, Jian-Shi; Giometti, C.S.; Tollaksen, S.L.
1987-09-04T23:59:59.000Z
After two-dimensional electrophoresis of proteins or the like, resulting in a polyacrylamide gel slab having a pattern of protein gel spots thereon, an individual protein gel spot is cored out from the slab, to form a gel spot core which is placed in an extraction tube, with a dialysis membrane across the lower end of the tube. Replicate gel spots can be cored out from replicate gel slabs and placed in the extraction tube. Molten agarose gel is poured into the extraction tube where the agarose gel hardens to form an immobilizing gel, covering the gel spot cores. The upper end portion of the extraction tube is filled with a volume of buffer solution, and the upper end is closed by another dialysis membrane. Upper and lower bodies of a buffer solution are brought into contact with the upper and lower membranes and are provided with electrodes connected to the positive and negative terminals of a dc power supply, thereby producing an electrical current which flows through the upper membrane, the volume of buffer solution, the agarose, the gel spot cores and the lower membrane. The current causes the proteins to be extracted electrophoretically from the gel spot cores, so that the extracted proteins accumulate and are contained in the space between the agarose gel and the upper membrane. 8 figs.
Variational representations for the Parisi functional and the two-dimensional Guerra-Talagrand bound
Wei-Kuo Chen
2015-01-27T23:59:59.000Z
The validity of the Parisi formula in the Sherrington-Kirkpatrick (SK) model was initially proved by Talagrand [12]. The central argument relied on a careful study of the coupled free energy using the Guerra-Talagrand (GT) replica symmetry breaking bound. It is believed that this bound is highly related to the conjectures of chaos and ultrametricity in the SK model, but a completely investigation is still far from been reached. Motivated by the theory of optimal stochastic control, we present a new approach to analysing the Parisi functional and the two-dimensional GT bound in the mixed p-spin model. We first compute the directional derivative of the Parisi functional and obtain equivalent criteria for the Parisi measure. Next we demonstrate how our approach provides an efficient control for the GT bound and yield several results on the positivity of the overlap and disorder chaos problem. In particular, these include new examples of the models containing odd p-spin interactions.
The MHD Kelvin-Helmholtz instability a two-dimensional numerical study
Frank, A I; Ryu, D; Gaalaas, J B; Frank, Adam; Ryu, Dongsu; Gaalaas, Joseph B
1995-01-01T23:59:59.000Z
Using a new numerical code we have carried out two-dimensional simulations of the nonlinear evolution of unstable sheared magnetohydrodynamic flows. We considered two cases: a strong magnetic field (Alfven Mach number, M_a = 2.5) and a weak field (M_a =5). Each flow rapidly evolves until it reaches a nearly steady condition, which is fundamentally different from the analogous gasdynamic state. Both MHD flows relax to a stable, laminar flow on timescales less than or of the order of 15 linear growth times, measured from saturation of the instability. That timescale is several orders of magnitude less than the nominal dissipation time for these simulated flows, so this condition represents an quasi-steady relaxed state. The strong magnetic field case reaches saturation as magnetic tension in the displaced flow boundary becomes sufficient to stabilize it. That flow then relaxes in a straightforward way to the steady, laminar flow condition. The weak magnetic field case, on the other hand, begins development of t...
Pinned modes in two-dimensional lossy lattices with local gain and nonlinearity
Ding, Edwin; Chow, K W; Malomed, Boris A
2014-01-01T23:59:59.000Z
We introduce a system with one or two amplified nonlinear sites ("hot spots", HSs) embedded into a two-dimensional linear lossy lattice. The system describes an array of evanescently coupled optical or plasmonic waveguides, with gain applied at selected HS cores. The subject of the analysis is discrete solitons pinned to the HSs. The shape of the localized modes is found in quasi-analytical and numerical forms, using a truncated lattice for the analytical consideration. Stability eigenvalues are computed numerically, and the results are supplemented by direct numerical simulations. In the case of self-focusing nonlinearity, the modes pinned to a single HS are stable or unstable when the nonlinearity includes the cubic loss or gain, respectively. If the nonlinearity is self-defocusing, the unsaturated cubic gain acting at the HS supports stable modes in a small parametric area, while weak cubic loss gives rise to a bistability of the discrete solitons. Symmetric and antisymmetric modes pinned to a symmetric se...
Diagnosing hyperuniformity in two-dimensional disordered jammed-packings of soft spheres
Remi Dreyfus; Ye Xu; Tim Still; Lawrence A. Hough; A. G. Yodh; Salvatore Torquato
2014-08-20T23:59:59.000Z
Hyperuniformity characterizes a state of matter for which density fluctuations diminish towards zero at the largest length scales. However, the task of determining whether or not an experimental system is hyperuniform is experimentally challenging due to finite-resolution, noise and sample-size effects that influence characterization measurements. Here we explore these issues, employing video optical microscopy to study hyperuniformity phenomena in disordered two-dimensional jammed packings of soft spheres. Using a combination of experiment and simulation we characterize the detrimental effects of particle polydispersity, image noise, and finite-size effects on the assignment of hyperuniformity, and we develop a methodology that permits improved diagnosis of hyperuniformity from real-space measurements. The key to this improvement is a simple packing reconstruction algorithm that incorporates particle polydispersity to minimize free volume. In addition, simulations show that hyperuniformity can be ascertained more accurately in direct space than in reciprocal space as a result of finite sample-size. Finally, experimental colloidal packings of soft polymeric spheres are shown to be hyperuniform.
Symmetry properties and spectra of the two-dimensional quantum compass model
Wojciech Brzezicki; Andrzej M. Ole?
2013-06-04T23:59:59.000Z
We use exact symmetry properties of the two-dimensional quantum compass model to derive nonequivalent invariant subspaces in the energy spectra of $L\\times L$ clusters up to L=6. The symmetry allows one to reduce the original $L\\times L$ compass cluster to the $(L-1)\\times (L-1)$ one with modified interactions. This step is crucial and enables: (i) exact diagonalization of the $6\\times 6$ quantum compass cluster, and (ii) finding the specific heat for clusters up to L=6, with two characteristic energy scales. We investigate the properties of the ground state and the first excited states and present extrapolation of the excitation energy with increasing system size. Our analysis provides physical insights into the nature of nematic order realized in the quantum compass model at finite temperature. We suggest that the quantum phase transition at the isotropic interaction point is second order with some admixture of the discontinuous transition, as indicated by the entropy, the overlap between two types of nematic order (on horizontal and vertical bonds) and the existence of the critical exponent. Extrapolation of the specific heat to the $L\\to\\infty$ limit suggests the classical nature of the quantum compass model and high degeneracy of the ground state with nematic order.
Strain-induced energy band gap opening in two-dimensional bilayered silicon film
Ji, Zhonghang; Voon, Lok C Lew Yan; Zhuang, Yan
2015-01-01T23:59:59.000Z
This work presents a theoretical study of the structural and electronic properties of bilayered silicon films under in-plane biaxial strain/stress using density functional theory. Atomic structures of the two-dimensional silicon films are optimized by using both the local-density approximation and generalized gradient approximation. In the absence of strain/stress, five buckled hexagonal honeycomb structures of the bilayered silicon film have been obtained as local energy minima and their structural stability has been verified. These structures present a Dirac-cone shaped energy band diagram with zero energy band gaps. Applying tensile biaxial strain leads to a reduction of the buckling height. Atomically flat structures with zero bucking height have been observed when the AA-stacking structures are under a critical biaxial strain. Increase of the strain between 10.7% ~ 15.4% results in a band-gap opening with a maximum energy band gap opening of ~168.0 meV obtained when 14.3% strain is applied. Energy band d...
Spectral properties of a hybrid-qubit model based on a two-dimensional quantum dot
Alba Y. Ramos; Omar Osenda
2015-03-27T23:59:59.000Z
The design and study of hybrid qubits is driven by their ability to get along the best of charge qubits and of spin qubits, {\\em i.e.} the speed of operation of the former and the very slow decoherence rates of the latter ones. There are several proposals to implement hybrid qubits, this works focuses on the spectral properties of an one-electron hybrid qubit. By design, the information would be stored in the electronic spin and the switching between the qubit basis states would be achieved using an external ac electric field. The electron is confined in a two-dimensional quantum dot, whose confining potential is given by a quartic potential, features that are typical of GaAS quantum dots. Besides the confining potential that characterizes the quantum dot there are two static magnetic fields applied to the system, one is a large constant Zeeman field and the other one has a constant gradient. We study the spectral properties of the model Hamiltonian, a Scr\\"odinger-Pauli Hamiltonian with realistic parameters, using the Ritz method. In particular, we look for regions of the parameter space where the lowest eigenenergies and their eigenfunctions allow to define a qubit which is stable under perturbations to the design parameters. We put special attention to the constraints that the design imposes over the magnetic fields, the tuning of the energy gap between the qubit states and the expectation value of the spin operator where the information would be stored.
Development of a new two-dimensional Cartesian geometry nodal multigroup discrete-ordinates method
Pevey, R.E.
1982-07-01T23:59:59.000Z
The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques, respectively. The resulting FORTRAN computer code is designed to handle an arbitrary number of spatial, energy, and angle subdivisions. Any degree of scattering anisotropy can be handled by the code for either external source or fission systems. The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. In the general case the calculation is iterative due to neutron sources which depend on the neutron density itself, such as scattering interactions.
Design, testing and two-dimensional flow modeling of a multiple-disk fan
Engin, Tahsin; Oezdemir, Mustafa; Cesmeci, Sevki [Department of Mechanical Engineering, The University of Sakarya, Esentepe Campus, 54187 Sakarya (Turkey)
2009-11-15T23:59:59.000Z
A multiple-disk Tesla type fan has been designed, tested and analyzed two-dimensionally using the conservation of angular momentum principle. Experimental results showed that such multiple-disk fans exhibited exceptionally low performance characteristics, which could be attributed to the low viscosity, tangential nature of the flow, and large mechanical energy losses at both suction and discharge sections that are comparable to the total input power. By means of theoretical analysis, local and overall shearing stresses on the disk surfaces have been determined based on tangential and radial velocity distributions of the air flow of different volume flow rates at prescribed disk spaces and rotational speeds. Then the total power transmitted by rotating disks to air flow, and the power acquired by the air flow in the gap due to transfer of angular momentum have been obtained by numerically integrating shearing stresses over the disk surfaces. Using the measured shaft and hydraulic powers, these quantities were utilized to evaluate mechanical energy losses associated with the suction and discharge sections of the fan. (author)
Simple models for two-dimensional tunable colloidal crystals in rotating ac electric fields
Nils Elsner; C. Patrick Royall; Brian Vincent; David RE Snoswell
2009-04-18T23:59:59.000Z
We compare the behavior of a new two-dimensional aqueous colloidal model system with a simple numerical treatment. To the first order the attractive interaction between the colloids induced by an in-plane rotating ac electric field is dipolar, while the charge stabilization leads to a shorter ranged, Yukawa-like repulsion. In the crystal-like 'rafts' formed at sufficient field strengths, we find quantitative agreement between experiment and Monte Carlo simulation, except in the case of strongly interacting systems, where the well depth of the effective potential exceeds 250 times the thermal energy. The 'lattice constant' of the crystal-like raft is located approximately at the minimum of the effective potential, resulting from the sum of the Yukawa and dipolar interactions.The experimental system has display applications, owing to the possibility of tuning the lattice spacing with the external electric field. Limitations in the applied field strength and relative range of the electrostatic interactions of the particles result in a reduction in tunable lattice spacing for small and large particles, respectively. The optimal particle size for maximizing the lattice spacing tunability was found to be around 1000 nm.
Displacement fields of point defects in two-dimensional colloidal crystals
Wolfgang Lechner; Elisabeth Schöll-Paschinger; Christoph Dellago
2008-05-20T23:59:59.000Z
Point defects such as interstitials, vacancies, and impurities in otherwise perfect crystals induce complex displacement fields that are of long-range nature. In the present paper we study numerically the response of a two-dimensional colloidal crystal on a triangular lattice to the introduction of an interstitial particle. While far from the defect position the resulting displacement field is accurately described by linear elasticity theory, lattice effects dominate in the vicinity of the defect. In comparing the results of particle based simulations with continuum theory, it is crucial to employ corresponding boundary conditions in both cases. For the periodic boundary condition used here, the equations of elasticity theory can be solved in a consistent way with the technique of Ewald summation familiar from the electrostatics of periodically replicated systems of charges and dipoles. Very good agreement of the displacement fields calculated in this way with those determined in particle simulations is observed for distances of more than about 10 lattice constants. Closer to the interstitial, strongly anisotropic displacement fields with exponential behavior can occur for certain defect configurations. Here we rationalize this behavior with a simple bead-spring that relates the exponential decay constant to the elastic constants of the crystal.
Dirac-Weyl fermions with arbitrary spin in two-dimensional optical superlattices
Z. Lan; N. Goldman; A. Bermudez; W. Lu; P. Ohberg
2011-12-31T23:59:59.000Z
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 $\\mathfrak{su}$(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.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kanel, S. R.; Clement, T. P.; Barnett, M. O.; Goltz, M. N.
2011-01-01T23:59:59.000Z
Synthetic nano-scale hydroxyapatite (NHA) was prepared and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The XRD data confirmed that the crystalline structure and chemical composition of NHA correspond to Ca5OH(PO4)3. The SEM data confirmed the size of NHA to be less than 50?nm. A two-dimensional physical model packed with saturated porous media was used to study the transport characteristics of NHA under constant flow conditions. The data show that the transport patterns of NHA were almost identical to tracer transport patterns. This result indicates that the NHA material can move with water like a tracer, andmore »its movement was neither retarded nor influenced by any physicochemical interactions and/or density effects. We have also tested the reactivity of NHA with 1?mg/L hexavalent uranium (U(VI)) and found that complete removal of U(VI) is possible using 0.5?g/L NHA at pH?5 to 6. Our results demonstrate that NHA has the potential to be injected as a dilute slurry forin situtreatment of U(VI)-contaminated groundwater systems.« less
Deformation-Driven Diffusion and Plastic Flow in Two-Dimensional Amorphous Granular Pillars
Wenbin Li; Jennifer M. Rieser; Andrea J. Liu; Douglas J. Durian; Ju Li
2015-02-04T23:59:59.000Z
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.
Hybrid Vlasov-Maxwell simulations of two-dimensional turbulence in plasmas
Valentini, F.; Servidio, S.; Veltri, P. [Dipartimento di Fisica, Universitą della Calabria, I-87036 Rende (CS) (Italy); Perrone, D. [LESIA, Observatoire de Paris, 92190 Meudon (France); Califano, F. [Dipartimento di Fisica and CNISM, Universitą di Pisa, 56127 Pisa (Italy); Matthaeus, W. H. [Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States)
2014-08-15T23:59:59.000Z
Turbulence in plasmas is a very challenging problem since it involves wave-particle interactions, which are responsible for phenomena such as plasma dissipation, acceleration mechanisms, heating, temperature anisotropy, and so on. In this work, a hybrid Vlasov-Maxwell numerical code is employed to study local kinetic processes in a two-dimensional turbulent regime. In the present model, ions are treated as a kinetic species, while electrons are considered as a fluid. As recently reported in [S. Servidio, Phys. Rev. Lett. 108, 045001 (2012)], nearby regions of strong magnetic activity, kinetic effects manifest through a deformation of the ion velocity distribution function that consequently departs from the equilibrium Maxwellian configuration. Here, the structure of turbulence is investigated in detail in phase space, by evaluating the high-order moments of the particle velocity distribution, i.e., temperature, skewness, and kurtosis. This analysis provides quantitative information about the non-Maxwellian character of the system dynamics. This departure from local thermodynamic equilibrium triggers several processes commonly observed in many astrophysical and laboratory plasmas.
Serena Cenatiempo; Alessandro Giuliani
2014-07-18T23:59:59.000Z
We present a renormalization group construction of a weakly interacting Bose gas at zero temperature in the two-dimensional continuum, both in the quantum critical regime and in the presence of a condensate fraction. The construction is performed within a rigorous renormalization group scheme, borrowed from the methods of constructive field theory, which allows us to derive explicit bounds on all the orders of renormalized perturbation theory. Our scheme allows us to construct the theory of the quantum critical point completely, both in the ultraviolet and in the infrared regimes, thus extending previous heuristic approaches to this phase. For the condensate phase, we solve completely the ultraviolet problem and we investigate in detail the infrared region, up to length scales of the order $(\\lambda^3 \\rho_0)^{-1/2}$ (here $\\lambda$ is the interaction strength and $\\rho_0$ the condensate density), which is the largest length scale at which the problem is perturbative in nature. We exhibit violations to the formal Ward Identities, due to the momentum cutoff used to regularize the theory, which suggest that previous proposals about the existence of a non-perturbative non-trivial fixed point for the infrared flow should be reconsidered.
Marney, Luke C.; Siegler, William C.; Parsons, Brendon A.; Hoggard, Jamin C.; Wright, Bob W.; Synovec, Robert E.
2013-10-15T23:59:59.000Z
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.
Finite Heat conduction in 2D Lattices
Lei Yang; Yang Kongqing
2001-07-30T23:59:59.000Z
This paper gives a 2D hamonic lattices model with missing bond defects, when the capacity ratio of defects is enough large, the temperature gradient can be formed and the finite heat conduction is found in the model. The defects in the 2D harmonic lattices impede the energy carriers free propagation, by another words, the mean free paths of the energy carrier are relatively short. The microscopic dynamics leads to the finite conduction in the model.
A Turbulent Constitutive Law for the Two-Dimensional Inverse Energy Cascade
Gregory L. Eyink
2005-12-10T23:59:59.000Z
We develop a fundamental approach to a turbulent constitutive law for the 2D inverse cascade, based upon a convergent multi-scale gradient (MSG) expansion. To first order in gradients we find that the turbulent stress generated by small-scale eddies is proportional not to strain but instead to `skew-strain,' i.e. the strain tensor rotated by $45^\\circ.$ The skew-strain from a given scale of motion makes no contribution to energy flux across eddies at that scale, so that the inverse cascade cannot be strongly scale-local. We show that this conclusion extends a result of Kraichnan for spectral transfer and is due to absence of vortex-stretching in 2D. This `weakly local' mechanism of inverse cascade requires a relative rotation between the principal directions of strain at different scales and we argue for this using both the dynamical equations of motion and also a heuristic model of `thinning' of small-scale vortices by an imposed large-scale strain. Carrying out our expansion to second-order in gradients, we find two additional terms in the stress that can contribute to energy cascade. The first is a Newtonian stress with an `eddy-viscosity' due to differential strain-rotation, and the second is a tensile stress exerted along vorticity contour-lines. The latter was anticipated by Kraichnan for a very special model situation of small-scale vortex wave-packets in a uniform strain field. We prove a proportionality in 2D between the mean rates of differential strain-rotation and of vorticity-gradient stretching, analogous to a similar relation of Betchov for 3D. According to this result the second-order stresses will also contribute to inverse cascade when, as is plausible, vorticity contour-lines lengthen on average by turbulent advection.
Kondagunta, Veeraraghava Gopal
1993-01-01T23:59:59.000Z
contains one repeating pattern of fabric design. The elastic analysis of one such structure yields all the 3D moduli of the composite. There have also been a few papers in the area of damage mechanics of textile composites. Li et. al. [21] used 2D finite... are considered. The understanding gained from this two dimen- sional study can be used to extend these techniques for a complete 3D analysis. The high degree of inhomogeneity in textile composites due to the coarse microstructure makes the O ~ eel 0 Cl CD...
Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5 TablesExports to3,1,50022,3,,0,,6,1,SeparationConnect1.08]Te[subscriptM-PACEResponses to aConnect TowardsTestConnect(2D-CARS): simultaneous
Two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5 TablesExports to3,1,50022,3,,0,,6,1,SeparationConnect1.08]Te[subscriptM-PACEResponses to aConnect TowardsTestConnect(2D-CARS):
Nakajima, Akira, E-mail: a-nakajima@aist.go.jp; Ogura, Masahiko; Makino, Toshiharu; Nishizawa, Shin-ichi; Ohashi, Hiromichi; Yamasaki, Satoshi [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Liu, Pucheng; Kakushima, Kuniyuki; Iwai, Hiroshi [Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori, Yokohama, Kanagawa 226-8503 (Japan)
2014-04-21T23:59:59.000Z
The electrical properties of two-dimensional hole gases (2DHGs) in GaN/AlGaN/GaN double heterostructures were investigated. The layers were grown on sapphire substrates and a high-quality bulk GaN substrate. The coexistence of 2DHG and 2D electron gases on both sides of the AlGaN layer was confirmed by Hall effect measurements at 80–460?K. It was also verified that the 2DHGs were generated by negative polarization at the undoped GaN/AlGaN interface, which did not have a doped Mg acceptor. It was also demonstrated that the 2DHG density could be controlled by varying the AlGaN layer thickness and was inversely related to the 2DHG mobility. The measured relation indicated that the 2DHG mobility is mainly limited by phonon scatterings at around room temperature. As a result, the maximum 2DHG mobility of 16 cm{sup 2}/Vs at 300?K was achieved with a density of 1?×?10{sup 13}?cm{sup ?2}.
Buss, R.J.; Ho, P. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States)
1996-02-01T23:59:59.000Z
Low-temperature plasmas are used for a wide variety of materials processing applications, especially in the fabrication of microelectronic devices. Thus plasma processes, such as etching, deposition, and cleaning, are the subject of much current research. However, achieving a detailed understanding of such systems, especially for computer simulations, requires a great deal of kinetic information about the physics and chemistry. One particular aspect, the reactions of radicals generated in the plasma at the surfaces of the substrates, is important in determining the performance of a plasma process. However, such reactions are not well studied because there are few experimental techniques available that can directly probe them. Here, two-dimensional (2-D) imaging is a significant improvement to the IRIS (imaging of radicals interacting with surfaces) technique for measuring the reactivity of plasma-generated radicals at surfaces. Several interesting phenomena resulting from the effects of saturation of the optical transition and of molecular translation during the radiative lifetime of OH have now been observed directly.
Li, Kai; Gao, Tianyou; Peng, Shi-Guo; Jiang, Kaijun
2015-01-01T23:59:59.000Z
Trapping lithium with a big number in a simplified experimental setup has difficulties and challenges today. In this paper, we experimentally demonstrate the enhancement of \\textsuperscript{6}Li trapping efficiency in a three-dimensional magneto-optical trap (3D MOT) by using the multiple-sideband cooling in a two-dimensional magneto-optical trap (2D MOT). To improve the number of trapped atoms, we broaden the cooling light spectrum to 102 MHz composed of seven frequency components and then trap atoms with a number of $6.0\\times10^8$ which is about 4 times compared to that in the single-frequency cooling. The capture velocity and dependence of atomic number on the laser detuning have been analyzed, where the experimental result has a good agreement with the theoretical prediction based on a simple two-level model. We also analyze the loss rate of alkali metals due to fine-structure exchanging collisions and find that the multiple-sideband cooling is special valid for lithium.
Plastic Deformation of 2D Crumpled Wires
M A F Gomes; V P Brito; A S O Coelho; C C Donato
2008-11-17T23:59:59.000Z
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.
Curvature-induced cross-hatched order in two-dimensional semiflexible polymer networks
Cyril Vrusch; Cornelis Storm
2015-07-14T23:59:59.000Z
A recurring motif in the organization of biological tissues are networks of long, fibrillar protein strands effectively confined to cylindrical surfaces. Often, the fibers in such curved, quasi-2D geometries adopt a characteristic order: the fibers wrap around the central axis at an angle which varies with radius and, in several cases, is strongly bimodally distributed. In this Letter, we investigate the general problem of a 2D crosslinked network of semiflexible fibers confined to a cylindrical substrate, and demonstrate that in such systems the trade-off between bending and stretching energies, very generically, gives rise to cross-hatched order. We discuss its general dependency on the radius of the confining cylinder, and present an intuitive model that illustrates the basic physical principle of curvature-induced order. Our findings shed new light on the potential origin of some curiously universal fiber orientational distributions in tissue biology, and suggests novel ways in which synthetic polymeric soft materials may be instructed or programmed to exhibit preselected macromolecular ordering.
Hossein Ghaffarnejad
2015-04-29T23:59:59.000Z
Aim of the paper is to obtain 2d analogue of the backreaction equation which will be useful to study final state of quantum perturbed spherically symmetric curved space times. Thus we take Einstein-massless-scalar $\\psi$ tensor gravity model described on class of spherically symmetric curved space times. We rewrite the action functional in 2d analogue in terms of dimensionless dilaton-matter field $(\\chi=\\Phi\\psi)$ where dilaton field $\\Phi$ is conformal factor of 2-sphere. Then we seek renormalized expectation value of quantum dilaton-matter field stress tensor operator by applying Hadamard rennormalization prescription. Singularity of the Green function is assumed to be has logarithmic form. Covariantly conservation condition on the renormalized quantum dilaton-matter stress tensor demands to input a variable cosmological parameter $\\lambda(x)$. Energy conditions (weak, strong and null) is studied on the obtained renormalized stress tensor leading to dynamical equations for $\\lambda(x), \\Phi$ and quantum vacuum state $W_0(x)=_{ren}.$ In weak quantum field limits our obtained trace anomaly corresponds to one which obtained from zeta function regularization method. Setting null-like apparent horizon equation $\
Two-dimensional simulations of explosive eruptions of Kick-em Jenny and other submarine volcanos
Gisler, Galen R.; Weaver, R. P. (Robert P.); Mader, Charles L.; Gittings, M. L. (Michael L.)
2004-01-01T23:59:59.000Z
Kick-em Jenny, in the Eastern Caribbean, is a submerged volcanic cone that has erupted a dozen or more times since its discovery in 1939. The most likely hazard posed by this volcano is to shipping in the immediate vicinity (through volcanic missiles or loss-of-buoyancy), but it is of interest to estimate upper limits on tsunamis that might be produced by a catastrophic explosive eruption. To this end, we have performed two-dimensional simulations of such an event in a geometry resembling that of Kick-em Jenny with our SAGE adaptive mesh Eulerian multifluid compressible hydrocode. We use realistic equations of state for air, water, and basalt, and follow the event from the initial explosive eruption, through the generation of a transient water cavity and the propagation of waves away from the site. We find that even for extremely catastrophic explosive eruptions, tsunamis from Kick-em Jenny are unlikely to pose significant danger to nearby islands. For comparison, we have also performed simulations of explosive eruptions at the much larger shield volcano Vailuluu in the Samoan chain, where the greater energy available can produce a more impressive wave. In general, however, we conclude that explosive eruptions do not couple well to water waves. The waves that are produced from such events are turbulent and highly dissipative, and don't propagate well. This is consistent with what we have found previously in simulations of asteroid-impact generated tsunamis. Non-explosive events, however, such as landslides or gas hydrate releases, do couple well to waves, and our simulations of tsunamis generated by subaerial and sub-aqueous landslides demonstrate this.
Fast chemical reaction in two-dimensional Navier-Stokes flow: Initial regime
Farid Ait-Chaalal; Michel S. Bourqui; Peter Bartello
2012-04-05T23:59:59.000Z
This paper studies an infinitely fast bimolecular chemical reaction in a two-dimensional bi-periodic Navier-Stokes flow. The reactants in stoichiometric quantities are initially segregated by infinite gradients. The focus is placed on the initial stage of the reaction characterized by a well-defined one dimensional material contact line between the reactants. Particular attention is given to the effect of the diffusion of the reactants. This study is an idealized framework for isentropic mixing in the lower stratosphere and is motivated by the need to better understand the effect of resolutionon stratospheric chemistry in Climate-Chemistry Models. Adopting a Lagrangian stretching theory approach, we relate theoretically the ensemble mean of the length of the contact line, of the gradients along it and of the modulus of the rate of decrease of the space averaged reactant concentrations (here called the chemical speed) to the joint statistics of the finite time Lyapunov exponent with two equivalent times. The inverse of the Lyapunov exponent measures the stretching time scale of a Lagrangian parcel on a chaotic orbit up to a finite time t, while the first equivalent time measures it in the recent past before t and the second equivalent time in the early part of the trajectory. We show that the chemical speed scales like the square root of the diffusion and that its time evolution is determined by rare large events in the finite time Lyapunov exponent distribution. The case of smooth initial gradients is also discussed. The theoretical results are tested with an ensemble of direct numerical simulations (DNS) using a pseudospectral model.
Two dimensional point of use fuel cell : a final LDRD project report.
Zavadil, Kevin Robert; Hickner, Michael A. (Pennsylvania State University, University Park, PA); Gross, Matthew L. (Pennsylvania State University, University Park, PA)
2011-03-01T23:59:59.000Z
The Proliferation Assessment (program area - Things Thin) within the Defense Systems and Assessment Investment Area desires high energy density and long-lived power sources with moderate currents (mA) that can be used as building blocks in platforms for the continuous monitoring of chemical, biological, and radiological agents. Fuel cells can be an optimum choice for a power source because of the high energy densities that are possible with liquid fuels. Additionally, power generation and fuel storage can be decoupled in a fuel cell for independent control of energy and power density for customized, application-driven power solutions. Direct methanol fuel cells (DMFC) are explored as a possible concept to develop into ultrathin or two-dimensional power sources. New developments in nanotechnology, advanced fabrication techniques, and materials science are exploited to create a planar DMFC that could be co-located with electronics in a chip format. Carbon nanotubes and pyrolyzed polymers are used as building block electrodes - porous, mechanically compliant current collectors. Directed assembly methods including surface functionalization and layer-by-layer deposition with polyelectrolytes are used to pattern, build, and add functionality to these electrodes. These same techniques are used to incorporate nanoscale selective electrocatalyst into the carbon electrodes to provide a high density of active electron transfer sites for the methanol oxidation and oxygen reduction reactions. The resulting electrodes are characterized in terms of their physical properties, electrocatalytic function, and selectivity to better understand how processing impacts their performance attributes. The basic function of a membrane electrode assembly is demonstrated for several prototype devices.
Narayanan, Vinod
1997-01-01T23:59:59.000Z
nozzle. A new two-dimensional reattachment nozzle, entitled 'Slot Jet Reattachment' (SJR) nozzle was designed and built with four exit angles of-10[], O[], +20[] and +45. This nozzle is a modification of the slot jet nozzle commonly used in industries...
Huang, Jiaxing
) is a promising precursor for preparing graphene-based composites and electronics applications. Like graphene, GO-dimensional assemblies over large areas is discussed. Figure 1. a) Typical preparation of graphene oxide (GO). PristineGraphene Oxide: Surface Activity and Two-Dimensional Assembly By Franklin Kim, Laura J. Cote
Kenji Nakahira; Tsuyoshi Sasaki Usuda
2015-01-26T23:59:59.000Z
We study the discrimination of multipartite quantum states by local operations and classical communication. We derive that any optimal discrimination of quantum states spanning a two-dimensional Hilbert space in which each party's space is finite dimensional is possible by local operations and one-way classical communication, regardless of the optimality criterion used and how entangled the states are.
Integrated digital inverters based on two-dimensional anisotropic ReS2 field-effect transistors
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Liu, Erfu; Fu, Yajun; Wang, Yaojia; Feng, Yanqing; Liu, Huimei; Wan, Xiangang; Zhou, Wei; Wang, Baigeng; Shao, Lubin; Ho, Ching-Hwa; et al
2015-05-07T23:59:59.000Z
Semiconducting two-dimensional transition metal dichalcogenides are emerging as top candidates for post-silicon electronics. While most of them exhibit isotropic behaviour, lowering the lattice symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here we present atomically thin rhenium disulfide (ReS2) flakes with unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated monolayer and few-layer ReS2 field-effect transistors, which exhibit competitive performance with large current on/off ratios (~107) and low subthreshold swings (100 mV per decade). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known two-dimensional semiconductingmore »materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS2 anisotropic field-effect transistors, suggesting the promising implementation of large-scale two-dimensional logic circuits. Our results underscore the unique properties of two-dimensional semiconducting materials with low crystal symmetry for future electronic applications.« less
Sedimentation of an elliptical object in a two-dimensional foam I.T. Davies, S.J. Cox1
Cox, Simon
Sedimentation of an elliptical object in a two-dimensional foam I.T. Davies, S.J. Cox1 Institute of Mathematics and Physics, Aberystwyth University, Ceredigion SY23 3BZ, UK Abstract The sedimentation laterally. A larger, more eccentric, ellipse rotates more quickly. Key words: foam, ellipse, sedimentation 1
Avrutsky, Ivan
June 15, 1999 / Vol. 24, No. 12 / OPTICS LETTERS 817 Two-dimensional colloidal crystal corrugated colloidal crystals. We report experimental studies of light coupling into and out of the waveguide structure colloidal crystals. Self-assembly of colloid particles occurs on the surface of a planar waveguide
A is injected. Light emission from the injected beam by electron impact ex- citation (LiI/670.8 nm) is collected the emission of the injected neutral lithium beam by electron impact excitation. It can probe plasmas fromTwo-dimensional diagnostics of edge and divertor region of toroidal helical plasmas using a lithium
Baba, Toshihiko
Efficiency enhancement in a light-emitting diode with a two-dimensional surface grating photonic 21 November 2003 We demonstrate a light-emitting diode exhibiting 1.72.7-fold enhancement in light light emitting diode LED , the ef- ficiency is limited to several percents by a low light extrac- tion
Sprott, Julien Clinton
2008-01-01T23:59:59.000Z
to the logistic map. Bounded solutions exist for the H´enon map over a range of a and b values, and a portion introduces a two-dimensional, C discrete bounded map capable to generating "multi- fold" strange attractors sin x, and we study this model for all values of a and b. The essential motivation for this work
Sprott, Julien Clinton
2008-01-01T23:59:59.000Z
to the logistic map. Bounded solutions exist for the H´enon map over a range of a and b values, and a portion introduces a two-dimensional, C discrete bounded map capable of generating "multi- fold" strange attractors sin x, and we study this model for all values of a and b. The essential motivation for this work
Horovitz, Baruch
Freezing transitions and the density of states of two-dimensional random Dirac Hamiltonians Baruch dimensions that allows us to treat nonperturbative freezing phenomena. For purely random gauge disorder in the context of random gauge XY models1218 and in particular the freezing transitions that occur
MacKinnon, Angus
Two-dimensional electron gas in a linearly varying magnetic field: Quantization of the electron of electron and current densities. We investigate the case where the magnetic field varies linearly properties of a noninteracting electron gas in a linearly varying magnetic field, we consider the following
Electron-beam-induced domain poling in LiNbO3 for two-dimensional nonlinear frequency conversion
Arie, Ady
Electron-beam-induced domain poling in LiNbO3 for two-dimensional nonlinear frequency conversion to achieve noncollinear second-harmonic generation. The sample was fabricated using an electron-beam indirect electron-beam poling,1 electric-field poling,2 and high-voltage atomic force microscop AFM .3
Markovic, Miljenko, E-mail: markovic@livemail.uthscsa.edu; Stathakis, Sotirios; Mavroidis, Panayiotis; Jurkovic, Ines-Ana; Papanikolaou, Nikos [Department of Radiation Oncology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas 78229 (United States)] [Department of Radiation Oncology, University of Texas Health Sciences Center at San Antonio, San Antonio, Texas 78229 (United States)
2014-05-15T23:59:59.000Z
Purpose: The purpose of the study is to investigate the characteristics of a two-dimensional (2D) liquid-filled ion chamber detector array, which is used for the verification of radiotherapy treatment plans that use small field sizes of up to 10 × 10 cm. Methods: The device used in this study was Octavius 1000 SRS model (PTW, Freiburg, Germany). Its 2D array of detectors consists of 977 liquid-filled ion chambers arranged over an area of 11 × 11 cm. The size of the detectors is 2.3 × 2.3 × 0.5 mm (volume of 0.003 cm{sup 3}) and their spacing in the inner area of 5.5 × 5.5 cm is 2.5 mm center-to-center, whereas in the outer area it is 5 mm center-to-center. The detector reproducibility, dose linearity, and sensitivity to positional changes of the collimator were tested. Also, the output factors of field sizes ranging from 0.5 × 0.5 to 10 × 10 cm{sup 2} both for open and wedged fields have been measured and compared against those measured by a pin-point ionization chamber, liquid filled microchamber, SRS diode, and EDR2 film. Results: Its short-term reproducibility was within 0.2% and its medium and long-term reproducibility was within 0.5% (verified with air ionization chamber absolute dose measurements), which is an excellent result taking into account the daily fluctuation of the linear accelerator and the errors in the device setup reproducibility. The dose linearity and dose rate dependence were measured in the range of 0.5–85 Gy and 0.5–10 Gy?min{sup ?1}, respectively, and were verified with air ionization chamber absolute dose measurements was within 3%. The measurements of the sensitivity showed that the 2D Array could detect millimetric collimator positional changes. The measured output factors showed an agreement of better than 0.3% with the pinpoint chamber and microliquid filled chamber for the field sizes between 3 × 3 and 10 × 10 cm{sup 2}. For field sizes down to 1 × 1 cm{sup 2}, the agreement with SRS diode and microliquid filled chamber is better than 2%. The measurements of open and wedge-modulated field profiles were compared to the film and ionization chamber in water measurements. Conclusions: The Octavius Detector 1000 SRS is an accurate, precise, and reliable detector, very useful for the daily performance of the patient specific quality assurance of radiotherapy treatment plans.
LaTiO?/KTaO? interfaces: A new two-dimensional electron gas system
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Zou, K.; Ismail-Beigi, Sohrab; Kisslinger, Kim; Shen, Xuan; Su, Dong; Walker, F. J.; Ahn, C. H.
2015-03-01T23:59:59.000Z
We report a new 2D electron gas (2DEG) system at the interface between a Mott insulator, LaTiO?, and a band insulator, KTaO?. For LaTiO?/KTaO? interfaces, we observe metallic conduction from 2 K to 300 K. One serious technological limitation of SrTiO?-based conducting oxide interfaces for electronics applications is the relatively low carrier mobility (0.5-10 cm²/V s) of SrTiO? at room temperature. By using KTaO?, we achieve mobilities in LaTiO?/KTaO? interfaces as high as 21 cm²/V s at room temperature, over a factor of 3 higher than observed in doped bulk SrTiO?. By density functional theory, we attribute the higher mobilitymore »in KTaO? 2DEGs to the smaller effective mass for electrons in KTaO?.« less
A two-dimensional particle simulation of the magnetopause current layer
Berchem, J.; Okuda, H.
1988-11-01T23:59:59.000Z
We have developed a 2/1/2/-D (x, y, v/sub x/, v/sub y/, v/sub z/) electromagnetic code to study the formation and the stability of the magnetopause current layer. This code computes the trajectories of ion and electron particles in their self-consistently generated electromagnetic field and an externally imposed 2-D vacuum dipolar magnetic field. The results presented here are obtained for the simulation of the solar wind-magnetosphere interaction in the subsolar region of the equatorial plane. We observe the self-consistent establishment of a current layer resulting from both diamagnetic drift and E /times/ B drift due to the charge separation. The simulation results show that during the establishment of the current layer, its thickness is of the order of the hybrid gyroradius /rho//sub H/ = ..sqrt../rho//sub i//rho//sub e/ predicted by the Ferraro-Rosenbluth model. However, diagnostics indicate that the current sheet is subject to an instability which broadens the width of the current layer. Ripples with amplitudes of the order of the ion gyroradius appear at the interface between the field and the particles. These pertubations are observed both on the electrostatic field and on the compressional component of the magnetic field. This instability has a frequency of the order of the local ion cyclotron frequency. However, the modulation propagates in the same direction as the electron diamagnetic drift which indicates that the instability is not a classical gradient-driven instability, such as the lower hybrid or ion drift cyclotron instabilities. The nonlinear phase of the instability is characterized by the filamentation of the current layer which causes anomalous diffusion inside the central current sheet. 79 refs., 7 figs.
Two-Dimensional Simulation Analysis of the Standing-wave Free-electron Laser Two-Beam Accelerator
Wang, C.
2008-01-01T23:59:59.000Z
and S. Yu, "Relativistic klystron simulations using RKTW2D,"dimensional relativistic klystron code, developed by Ryneand the relativistic klystron two-beam accelerator. In this
Animation : 2D versus 3D and their combined effect
Au, Kristin C
2014-01-01T23:59:59.000Z
This thesis studies the differences in the perception of space and character movement between 2D and 3D animation. 2D animation is defined by elements constructed in a 2D environment while 3D animation by elements constructed ...
Gadgil, A.J.
2008-01-01T23:59:59.000Z
radiation, S(24) = IDN * CCM. S(24) = SOLAR FACTOR 'A' *in the calculation IBUF CCM CODE COOLIT AIRINF CCC CCLATsurface, S(22) = BS * CCM. = diffuse ground reflected
Simulating the collapse transition of a two-dimensional semiflexible lattice polymer
Jie Zhou; Zhong-Can Ou-Yang; Haijun Zhou
2008-01-07T23:59:59.000Z
It has been revealed by mean-field theories and computer simulations that the nature of the collapse transition of a polymer is influenced by its bending stiffness $\\epsilon_{\\rm b}$. In two dimensions, a recent analytical work demonstrated that the collapse transition of a partially directed lattice polymer is always first-order as long as $\\epsilon_{\\rm b}$ is positive [H. Zhou {\\em et al.}, Phys. Rev. Lett. {\\bf 97}, 158302 (2006)]. Here we employ Monte Carlo simulation to investigate systematically the effect of bending stiffness on the static properties of a 2D lattice polymer. The system's phase-diagram at zero force is obtained. Depending on $\\epsilon_{\\rm b}$ and the temperature $T$, the polymer can be in one of three phases: crystal, disordered globule, or swollen coil. The crystal-globule transition is discontinuous, the globule-coil transition is continuous. At moderate or high values of $\\epsilon_{\\rm b}$ the intermediate globular phase disappears and the polymer has only a discontinuous crystal-coil transition. When an external force is applied, the force-induced collapse transition will either be continuous or discontinuous, depending on whether the polymer is originally in the globular or the crystal phase at zero force. The simulation results also demonstrate an interesting scaling behavior of the polymer at the force-induced globule-coil transition.
Equilibrium and dynamical properties of two dimensional self-gravitating systems
Alessandro Torcini; Mickael Antoni
1998-08-07T23:59:59.000Z
A system of N classical particles in a 2D periodic cell interacting via long-range attractive potential is studied. For low energy density $U$ a collapsed phase is identified, while in the high energy limit the particles are homogeneously distributed. A phase transition from the collapsed to the homogeneous state occurs at critical energy U_c. A theoretical analysis within the canonical ensemble identifies such a transition as first order. But microcanonical simulations reveal a negative specific heat regime near $U_c$. The dynamical behaviour of the system is affected by this transition : below U_c anomalous diffusion is observed, while for U > U_c the motion of the particles is almost ballistic. In the collapsed phase, finite $N$-effects act like a noise source of variance O(1/N), that restores normal diffusion on a time scale diverging with N. As a consequence, the asymptotic diffusion coefficient will also diverge algebraically with N and superdiffusion will be observable at any time in the limit N \\to \\infty. A Lyapunov analysis reveals that for U > U_c the maximal exponent \\lambda decreases proportionally to N^{-1/3} and vanishes in the mean-field limit. For sufficiently small energy, in spite of a clear non ergodicity of the system, a common scaling law \\lambda \\propto U^{1/2} is observed for any initial conditions.
Fedorczak, N. [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego, California 92093 (United States); CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Manz, P. [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego, California 92093 (United States); Max-Planck-Institut feur Plasmaphysik, Association Euratom-IPP, 85748Garching (Germany); Thakur, S. C.; Xu, M.; Tynan, G. R. [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego, California 92093 (United States); Xu, G. S.; Liu, S. C. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)
2012-12-15T23:59:59.000Z
Time delay estimation (TDE) techniques are frequently used to estimate the flow velocity from fluctuating measurements. Tilted structures carried by the flow lead to misinterpretation of the time delays in terms of velocity direction and amplitude. It affects TDE measurements from probes, and is also intrinsically important for beam emission spectroscopy and gas puff imaging measurements. Local eddy shapes estimated from 2D fluctuating field are necessary to gain a more accurate flow estimate from TDE, as illustrated by Langmuir probe array measurements. A least square regression approach is proposed to estimate both flow field and shaping parameters. The technique is applied to a test case built from numerical simulation of interchange fluctuations. The local eddy shape does not only provide corrections for the velocity field but also quantitative information about the statistical interaction mechanisms between local eddies and E Multiplication-Sign B flow shear. The technique is then tested on gaz puff imaging data collected at the edge of EAST tokamak plasmas. It is shown that poloidal asymmetries of the fluctuation fields-velocity and eddy shape-are consistent at least qualitatively with a ballooning type of turbulence immersed in a radially sheared equilibrium flow.
2d Affine XY-Spin Model/4d Gauge Theory Duality and Deconfinement
Anber, Mohamed M.; Poppitz, Erich; /Toronto U.; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept. /San Francisco State U.
2012-08-16T23:59:59.000Z
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.
Two-loop calculation of the scaling behavior of two-dimensional forced Navier-Stokes equation
J. Honkonen; Yu. S. Kabrits; M. V. Kompaniets
2002-01-15T23:59:59.000Z
Asymptotic properties of the solution of two-dimensional randomly forced Navier-Stokes equation with long-range correlations of the driving force are analyzed in the two-loop order of perturbation theory with the use of renormalization group. Kolmogorov constant of the energy spectrum is calculated for both the inverse energy cascade and the direct enstrophy cascade in the second order of the $\\epsilon$ expansion.
Abdelmalek Boumali
2014-10-10T23:59:59.000Z
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.
Closed loop engine control for regulating NOx emissions, using a two-dimensional fuel-air curve
Bourn, Gary D.; Smith, Jack A.; Gingrich, Jess W.
2007-01-30T23:59:59.000Z
An engine control strategy that ensures that NOx emissions from the engine will be maintained at an acceptable level. The control strategy is based on a two-dimensional fuel-air curve, in which air manifold pressure (AMP) is a function of fuel header pressure and engine speed. The control strategy provides for closed loop NOx adjustment to a base AMP value derived from the fuel-air curve.
Zhang, Kou-Lin, E-mail: klzhang@yzu.edu.cn [Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu Province, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zhang, Jing-Bo; Jing, Chu-Yue; Zhang, Lei [Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu Province, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Walton, Richard I. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom); Zhu, Peizhi, E-mail: pzzhu@yzu.edu.cn [Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu Province, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Ng, Seik Weng [Department of Chemistry, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2014-03-15T23:59:59.000Z
Four 2D coordination polymers (CPs) with different structures containing the multifunctional ligand 5-hydroxyisophthalate (5-OH-BDC{sup 2?}), [Zn(5-OH-BDC)(btb)]·2H{sub 2}O (1), [Cd(5-OH-BDC)(btp)(H{sub 2}O)]·3H{sub 2}O (2), [Cd(5-OH-BDC)(bth){sub 2}(H{sub 2}O)]·H{sub 2}O (3) and [Pb(5-OH-BDC)]·H{sub 2}O (4) [btp=1, 3-bis(1,2,4-triazol-1-yl)propane, btb=1,4-bis(1,2,4-triazol-1-yl)butane, bth=1, 6-bis(1,2,4-triazol-1-yl)hexane] were obtained. 1–3 were synthesised hydrothermally, while 4 was obtained under ambient condition. The adjacent (2D?2D) polycatenated 2D layers of 1 polythread in a parallel manner to form an unusual 2D?3D polythreaded framework. 2 contains an undulated 2D (4, 4) network and further extends into an “embracing” double-layer structure through the C–H···? and ?···? stacking interactions. 3 exhibits a non-interpenetrating 2D (4, 4)-network. 4 exhibits a 2D double-layered binodal (4, 4)-net containing oblong nanochannels with symbol (4{sup 3}6{sup 3}){sub 2}. Reversible dehydration–rehydration is observed in 1, 2 and 4, which fall within the category of “recoverable collapsing” and “guest-induced re-formation” frameworks, while 3 exhibits irreversible dehydration–rehydration behaviour. The solid state fluorescent properties of 1–4 have been investigated. -- Graphical abstract: Among four 2D CPs reported, 1 is an unusual 2D?3D polythreaded framework. 4 exhibits 2D double-layered binodal (4, 4)-net containing nanochannels. Reversible dehydration–rehydration is observed in 1, 2 and 4. Highlights: • Four 2D CPs based on 5-hydroxyisophthalate with d{sup 10} and Pb(II) ions were reported. • 1 is an unusual 2D?3D polythreaded framework. • 4 shows a binodal (4, 4)-connected 2D double-layer network with nanochannels. • The materials 1, 2 and 4 show reversible dehydration–rehydration behaviours. • Solid state fluorescent properties were investigated.
Cheng, Juan, E-mail: cheng_juan@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Shu, Chi-Wang, E-mail: shu@dam.brown.edu [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)
2014-09-01T23:59:59.000Z
In applications such as astrophysics and inertial confinement fusion, there are many three-dimensional cylindrical-symmetric multi-material problems which are usually simulated by Lagrangian schemes in the two-dimensional cylindrical coordinates. For this type of simulation, a critical issue for the schemes is to keep spherical symmetry in the cylindrical coordinate system if the original physical problem has this symmetry. In the past decades, several Lagrangian schemes with such symmetry property have been developed, but all of them are only first order accurate. In this paper, we develop a second order cell-centered Lagrangian scheme for solving compressible Euler equations in cylindrical coordinates, based on the control volume discretizations, which is designed to have uniformly second order accuracy and capability to preserve one-dimensional spherical symmetry in a two-dimensional cylindrical geometry when computed on an equal-angle-zoned initial grid. The scheme maintains several good properties such as conservation for mass, momentum and total energy, and the geometric conservation law. Several two-dimensional numerical examples in cylindrical coordinates are presented to demonstrate the good performance of the scheme in terms of accuracy, symmetry, non-oscillation and robustness. The advantage of higher order accuracy is demonstrated in these examples.
Matter-wave 2D solitons in crossed linear and nonlinear optical lattices
H. L. F. da Luz; F. Kh. Abdullaev; A. Gammal; M. Salerno; Lauro Tomio
2010-11-08T23:59:59.000Z
It is demonstrated the existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with linear OL in the $x-$direction and nonlinear OL (NOL) in the $y-$direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance. In particular, we show that such crossed linear and nonlinear OL allows to stabilize two-dimensional (2D) solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach (VA), with the Vakhitov-Kolokolov (VK) necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation (GPE). Very good agreement of the results corresponding to both treatments is observed.
Likos, Christos N.
Crystal structures of two-dimensional magnetic colloids in tilted external magnetic fields V. A; published 30 December 2003 The stability of different crystal lattices of two-dimensional superparamagnetic the colloidal particles along its direction, whose strength can be controlled by the amplitude of the external
Likos, Christos N.
Anisotropic mean-square displacements in two-dimensional colloidal crystals of tilted dipoles V. A the crystal aniso- tropy or not. Here we study an anisotropic two-dimensional colloidal crystal composed; revised manuscript received 7 February 2005; published 31 March 2005 Superparamagnetic colloidal particles
Capacity and Coding for 2D Channels
Khare, Aparna
2011-02-22T23:59:59.000Z
: : : : : : : : : : : : : : : : : : : : : : 3 2 Signal ow : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 3 Bayer pattern : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7 4 Example of a Tanner graph : : : : : : : : : : : : : : : : : : : : : : : 13 5 LDPC code... much data we can pack onto a given area of paper. 3 (a) Aztec code (b) Maxicode (c) QR code (d) Data matrix Fig. 1. 2D barcodes used in practice 4 D. Outline of the dissertation In Chapter II, we discuss the channel model. First, we consider the model...
The actuated Workbench : 2D actuation in tabletop tangible interfaces
Pangaro, Gian Antonio, 1976-
2003-01-01T23:59:59.000Z
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 ...
GBL-2D Version 1.0: a 2D geometry boolean library.
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
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.
Two-Dimensional Optical Measurement of Waves on Liquid Lithium Jet Simulating IFMIF Target Flow
Kazuhiro Itoh; Hiroyuki Koterazawa [University of Hyogo, 1-3-3, Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo (Japan); Taro Itoh; Yutaka Kukita [Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi, 464-8603 (Japan); Hiroo Kondo; Nobuo Yamaoka; Hiroshi Horiike [Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871 (Japan); Mizuho Ida; Hideo Nakamura; Hiroo Nakamura [Japan Atomic Energy Agency (Japan); Takeo Muroga [National Institute for Fusion Science, 322-6, Oroshi-cho, Toki, GIFU, 509-5292 (Japan)
2006-07-01T23:59:59.000Z
Waves on a liquid-lithium jet flow, simulating a proposed high-energy beam target design, have been measured using an optical technique based on specular reflection of a single laser beam on the jet surface. The stream-wise and spanwise fluctuations of the local free-surface slope were least-square fitted with a sinusoidal curve to makeup the signals lost due to the constriction in the optical arrangement. The waveform was estimated with an assumption that wave phase speed can be calculated using the dispersion relation for linear capillary-gravity waves. The direction of propagation on the jet surface was also evaluated so that the wave amplitudes, calculated by integral of slope angle signal, agree consistently in stream-wise and spanwise direction. These measurements and analyses show that the waves at the measurement location for a jet velocity of 1.2 m/s can best be represented by oblique waves with an inclination of 1.23 rad, a wavelength of 3.8 mm and a wave amplitude of about 0.05 mm. (authors)
Two-dimensional PIC simulations of ion-beam instabilities in Supernova-driven plasma flows
M. E. Dieckmann; A. Meli; P. K. Shukla; L. O. C. Drury; A. Mastichiadis
2008-04-16T23:59:59.000Z
Supernova remnant (SNR) blast shells can reach the flow speed $v_s = 0.1 c$ and shocks form at its front. Instabilities driven by shock-reflected ion beams heat the plasma in the foreshock, which may inject particles into diffusive acceleration. The ion beams can have the speed $v_b \\approx v_s$. For $v_b \\ll v_s$ the Buneman or upper-hybrid instabilities dominate, while for $v_b \\gg v_s$ the filamentation and mixed modes grow faster. Here the relevant waves for $v_b \\approx v_s$ are examined and how they interact nonlinearly with the particles. The collision of two plasma clouds at the speed $v_s$ is modelled with particle-in-cell (PIC) simulations, which convect with them magnetic fields oriented perpendicular to their flow velocity vector. One simulation models equally dense clouds and the other one uses a density ratio of 2. Both simulations show upper-hybrid waves that are planar over large spatial intervals and that accelerate electrons to $\\sim$ 10 keV. The symmetric collision yields only short oscillatory wave pulses, while the asymmetric collision also produces large-scale electric fields, probably through a magnetic pressure gradient. The large-scale fields destroy the electron phase space holes and they accelerate the ions, which facilitates the formation of a precursor shock.
Li, J; Deng, M; Voronine, DV; Mukamel, S; Jiang, J
2015-01-01T23:59:59.000Z
G. R. Evidence for Wavelike Energy Transfer through QuantumBath Fluctuations and Energy Transfer in 2D Spectroscopy ofCenter of Chemistry for Energy Materials, School of
Li Linghuai; Sofia, Sabatino; Basu, Sarbani; Demarque, Pierre [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Ventura, Paolo [INAF, Osservatorio Astronomico di Roma, 00040 Monteporzio Catone (Italy); Penza, Valentina [Universita Di Roma 'Tor Vergata', Via Della Ricerca Scientifica 1, 00133 Roma (Italy); Bi Shaolan [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)], E-mail: li@astro.yale.edu
2009-06-15T23:59:59.000Z
In the second paper of this series we pursue two objectives. First, in order to make the code more sensitive to small effects, we remove many approximations made in Paper I. Second, we include turbulence and rotation in the two-dimensional framework. The stellar equilibrium is described by means of a set of five differential equations, with the introduction of a new dependent variable, namely the perturbation to the radial gravity, that is found when the nonradial effects are considered in the solution of the Poisson equation. Following the scheme of the first paper, we write the equations in such a way that the two-dimensional effects can be easily disentangled. The key concept introduced in this series is the equipotential surface. We use the underlying cause-effect relation to develop a recurrence relation to calculate the equipotential surface functions for uniform rotation, differential rotation, rotation-like toroidal magnetic fields, and turbulence. We also develop a more precise code to numerically solve the two-dimensional stellar structure and evolution equations based on the equipotential surface calculations. We have shown that with this formulation we can achieve the precision required by observations by appropriately selecting the convergence criterion. Several examples are presented to show that the method works well. Since we are interested in modeling the effects of a dynamo-type field on the detailed envelope structure and global properties of the Sun, the code has been optimized for short timescales phenomena (down to 1 yr). The time dependence of the code has so far been tested exclusively to address such problems.
Sawyer, Karma Rae
2008-12-12T23:59:59.000Z
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.
Hill, James Robert
1981-01-01T23:59:59.000Z
models in ex1stence, many schemes are very similar in the fin1te-d1fference methodology as well as the grid structure. Realizing th1s fact, the study of a representative cross section of exist1ng models seems suff'icient to gain some ins1ght into two... (December 1981) James Robert Hill B. S. , The Ohio State University Chairman of Advisory Committee: Dr. David R. Basco The depth averaged conservation form of the equations of motion is used to develop a two-dimensional numerical model. This particular...
Hu, C.H.; Koterayama, Wataru [Kyushu Univ., Kasuga (Japan)
1994-12-31T23:59:59.000Z
A two-dimensional incompressible viscous flow around a fixed or elastically supported circular cylinder with a splitter plate of attached rigid, hinged or elastic types, has been simulated by a finite difference method, to study the effect of splitter plate on drag and vortex shedding frequency of the cylinder. The computation is carried out at R{sub e} = 1,000, and the results show in good accordance with the available experimental data. The relationship between the unsteady flow patterns and hydrodynamic force coefficients is also discussed.
Takiguchi, Tetsuya
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 × H I(x, y) w × 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
Two-dimensional imaging of gas-to-particle transition in flames by laser-induced nanoplasmas
Zhang, Yiyang [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Li, Shuiqing, E-mail: lishuiqing@tsinghua.edu.cn; Ren, Yihua; Yao, Qiang [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Law, Chung K. [Center for Combustion Energy, Tsinghua University, Beijing 100084 (China); Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263 (United States)
2014-01-13T23:59:59.000Z
Two-dimensional imaging of gas/particle phase transition of metal oxides in their native high-temperature flow conditions, using laser-driven localized nanoplasmas, was obtained by utilizing the gap between the excitation energies of the gas and particle phases such that only the Ti atoms in the particle phase were selectively excited without detectable Bremsstrahlung background. These in situ images of the particle phase Ti distribution allow the quantitative visualization of the transition of the gas precursors to the nanoparticle phase across the flame sheet as well as diffusion of the particle concentration in the post-flame zone.
Nicolas Destainville
2007-11-29T23:59:59.000Z
It has recently been proposed, with the help of numerical investigations, that fluorescence correlation spectroscopy at variable observation area can reveal the existence of a meshgrid of semi-permeable barriers hindering the two-dimensional diffusion of tagged particles, such as plasmic membrane constituents. We present a complete theory confirming and accounting for these findings. It enables a reliable, quantitative exploitation of experimental data from which the sub-wavelength mesh size can be extracted. Time scales at which fluorescence correlation spectroscopy must be performed experimentally are discussed in detail.
Lo, Shun-Tsung; Hsu, Chang-Shun [Graduate Institute of Applied Physics, National Taiwan University, Taipei 10617, Taiwan (China); Lin, Y. M.; Lin, S.-D.; Lee, C. P. [Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Ho, Sheng-Han; Chuang, Chiashain; Wang, Yi-Ting [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Liang, C.-T. [Graduate Institute of Applied Physics, National Taiwan University, Taipei 10617, Taiwan (China); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)
2014-07-07T23:59:59.000Z
We study interference and interactions in an InAs/InAsSb two-dimensional electron system. In such a system, spin-orbit interactions are shown to be strong, which result in weak antilocalization (WAL) and thereby positive magnetoresistance around zero magnetic field. After suppressing WAL by the magnetic field, we demonstrate that classical positive magnetoresistance due to spin-orbit coupling plays a role. With further increasing the magnetic field, the system undergoes a direct insulator-quantum Hall transition. By analyzing the magnetotransport behavior in different field regions, we show that both electron-electron interactions and spin-related effects are essential in understanding the observed direct transition.
Large-$q$ expansion of the specific heat for the two-dimensional $q$-state Potts model
H. Arisue; K. Tabata
1998-07-03T23:59:59.000Z
We have calculated the large-$q$ expansion for the specific heat at the phase transition point in the two-dimensional $q$-state Potts model to the 23rd order in $1/\\sqrt{q}$ using the finite lattice method. The obtained series allows us to give highly convergent estimates of the specific heat for $q>4$ on the first order transition point. The result confirm us the correctness of the conjecture by Bhattacharya et al. on the asymptotic behavior of the specific heat for $q \\to 4_+$.
Radozycki, Tomasz
2015-01-01T23:59:59.000Z
The Lorentz transformation properties of the equal-time bound-state Bethe-Salpeter amplitude in the two-dimensional massless quantum electrodynamics (the so called Schwinger Model) are considered. It is shown that while boosting a bound state (a `meson') this amplitude is subject to approximate Lorentz contraction. The effect is exact for large separations of constituent particles (`quarks'), while for small distances the deviation is more significant. For this phenomenon to appear, the full} function, i.e. with the inclusion of all instanton contributions has to be considered. The amplitude in each separate topological sector does not exhibit such properties.
Tomasz Radozycki
2015-08-31T23:59:59.000Z
The Lorentz transformation properties of the equal-time bound-state Bethe-Salpeter amplitude in the two-dimensional massless quantum electrodynamics (the so called Schwinger Model) are considered. It is shown that while boosting a bound state (a `meson') this amplitude is subject to approximate Lorentz contraction. The effect is exact for large separations of constituent particles (`quarks'), while for small distances the deviation is more significant. For this phenomenon to appear, the full} function, i.e. with the inclusion of all instanton contributions has to be considered. The amplitude in each separate topological sector does not exhibit such properties.
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The Hanle Effect in 1D, 2D and 3D
R. Manso Sainz; J. Trujillo Bueno
2007-10-29T23:59:59.000Z
This paper addresses the problem of scattering line polarization and the Hanle effect in one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) media for the case of a two-level model atom without lower-level polarization and assuming complete frequency redistribution. The theoretical framework chosen for its formulation is the QED theory of Landi Degl'Innocenti (1983), which specifies the excitation state of the atoms in terms of the irreducible tensor components of the atomic density matrix. The self-consistent values of these density-matrix elements is to be determined by solving jointly the kinetic and radiative transfer equations for the Stokes parameters. We show how to achieve this by generalizing to Non-LTE polarization transfer the Jacobi-based ALI method of Olson et al. (1986) and the iterative schemes based on Gauss-Seidel iteration of Trujillo Bueno and Fabiani Bendicho (1995). These methods essentially maintain the simplicity of the Lambda-iteration method, but their convergence rate is extremely high. Finally, some 1D and 2D model calculations are presented that illustrate the effect of horizontal atmospheric inhomogeneities on magnetic and non-magnetic resonance line polarization signals.
The 2D surfaces that generate Newtonian and general relativistic orbits with small eccentricities
Chad A. Middleton
2015-06-09T23:59:59.000Z
Embedding diagrams prove to be quite useful when learning general relativity as they offer a way of visualizing spacetime curvature through warped two dimensional (2D) surfaces. In this manuscript we present a different 2D construct that also serves as a useful conceptual tool for gaining insight into gravitation, in particular, orbital dynamics - namely the cylindrically symmetric surfaces that generate Newtonian and general relativistic orbits with small eccentricities. Although we first show that no such surface exists that can exactly reproduce the arbitrary bound orbits of Newtonian gravitation or of general relativity (or, more generally, of any spherically symmetric potential), surfaces do exist that closely approximate the resulting orbital motion for small eccentricities; exactly the regime that describes the motion of the solar system planets. These surfaces help to illustrate the similarities, as well as the differences, between the two theories of gravitation (i.e. stationary elliptical orbits in Newtonian gravitation and precessing elliptical-like orbits in general relativity) and offer, in this age of 3D printing, an opportunity for students and instructors to experimentally explore the predictions made by each.
Brummans, Boris H. J. M.
2005-02-17T23:59:59.000Z
analysis suggests that the studied scholars enact these games to understand a more or less common object of knowledge, but also to constitute a more or less identifiable position in this given social space. Reflection on the ontological complicity between...
Feenstra, Randall
-surface region. In particular, the technique of low-energy electron diffraction (LEED) has been developed by many workers, both experimentally and theoretically.1 , 2 In a conventional LEED instrument, a mono diffracted beam can be labeled by one (or more) reciprocal lattice vector(s), ),( yx ggg . These diffraction
The Seismic Analyzer: Interpreting and Illustrating 2D Seismic Data Daniel Patel, Christopher for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel
Pauli matrices and 2D electron gas
J. F. Geurdes
2013-02-07T23:59:59.000Z
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.
Chen, A.
The fabrication process of two-dimensional photonic crystals in an AlGaInP/GaInP multi-quantum-well membrane structure is developed. The process includes high resolution electron-beam lithography, pattern transfer into ...
Dutkiewicz, Stephanie.
We describe the coupling of a three-dimensional ocean circulation model, with explicit thermodynamic seaice and ocean carbon cycle representations, to a two-dimensional atmospheric/land model. This coupled system has been ...
Aris, John P.
" in tightly sealed and parafilmed 500 ml glass bottle. Add 250 mls of buffer "B" to tank, and pre + 165 mls ddH2O + 5 ml concentrated NH4OH. Store "A" in tightly sealed and parafilmed 500 ml glass bottle. Add 250 mls of buffer "A" to tank, and pre-equilibrate for 24 hours at room temperature. Run
Waveform tomography at a groundwater contamination site: Surface reflection data
Pratt, R. Gerhard
acoustic-waveform tomography to 45 2D seismic profiles to image the 3D geometry of a buried pale- ochannel the shallowest groundwater system in the study area. The 2D profiles were extracted from a 3D surface reflection the channel showed marked vertical and lat- eral velocity heterogeneity. Traveltime tomography and waveform
M. Hassan Farshbaf-Shaker; Christian Heinemann
2015-02-10T23:59:59.000Z
In this work we investigate a phase field model for damage processes in two-dimensional viscoelastic media with nonhomogeneous Neumann data describing external boundary forces. In the first part we establish global-in-time existence, uniqueness, a priori estimates and continuous dependence of strong solutions on the data. The main difficulty is caused by the irreversibility as well as boundedness of the phase field variable which results in a doubly constrained PDE system. In the last part we consider an optimal control problem where a cost functional penalizes maximal deviations from prescribed damage profiles. The goal is to minimize the cost functional with respect to exterior forces acting on the boundary which play the role of the control variable in the considered model. To this end, we prove existence of minimizers and study a family of "local" approximations via adapted cost functionals.
Chou, Yen; Li, Hsiang-Wei; Yin, Yu-Feng; Wang, Yu-Ting; Lin, Yen-Chen; Wu, Yuh-Renn; Huang, Jian Jang, E-mail: jjhuang@ntu.edu.tw [Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan (China); Lin, Da-Wei; Kuo, Hao-Chung [Department of Photonics and Electro-Optical Engineering, National Chiao-Tung University, Hsinchu, Taiwan (China)
2014-05-21T23:59:59.000Z
Fabricating photonic crystals (PhCs) on GaN based non-polar light emitting diodes (LEDs) is an effective way to increase light extraction and meanwhile to preserve or improve polarization ratio. In this work, a-plane GaN LEDs with two-dimensional PhCs were demonstrated. With the E // m polarized modes (which mean the optical polarization with the electric field parallel to m-axis) as the target of diffraction, we matched E//m modes to the photonic bands and aligned E//c modes to fall within the photonic band gap. The results show stronger E//m but weaker E//c mode diffractions on both c- and m-axes. At the vertical direction, the polarization ratio is enhanced from 45.8% for the planar device to 52.3% for the LEDs with PhCs.
M. Hassan Farshbaf-Shaker; Christian Heinemann
2015-07-08T23:59:59.000Z
In this work we investigate a phase field model for damage processes in two-dimensional viscoelastic media with nonhomogeneous Neumann data describing external boundary forces. In the first part we establish global-in-time existence, uniqueness, a priori estimates and continuous dependence of strong solutions on the data. The main difficulty is caused by the irreversibility of the phase field variable which results in a constrained PDE system. In the last part we consider an optimal control problem where a cost functional penalizes maximal deviations from prescribed damage profiles. The goal is to minimize the cost functional with respect to exterior forces acting on the boundary which play the role of the control variable in the considered model. To this end, we prove existence of minimizers and study a family of "local" approximations via adapted cost functionals.
Two-dimensional resonant magnetic excitation in BaFe1.84Co0.16As2
Lumsden, Mark D [ORNL; Christianson, Andrew D [ORNL; Parshall, Daniel [ORNL; Stone, Matthew B [ORNL; Nagler, Stephen E [ORNL; Mook Jr, Herbert A [ORNL; Lokshin, Konstantin A [ORNL; Egami, Takeshi [ORNL; Abernathy, Douglas L [ORNL; Goremychkin, E. A. [ISIS Facility, Rutherford Appleton Laboratory; Osborn, R. [Argonne National Laboratory (ANL); McGuire, Michael A [ORNL; Safa-Sefat, Athena [ORNL; Jin, Rongying [ORNL; Sales, Brian C [ORNL; Mandrus, David [ORNL
2009-01-01T23:59:59.000Z
Inelastic neutron scattering measurements on single crystals of superconducting BaFe1.84Co0.16As2 clearly reveal a magnetic excitation located at wavevectors (1/2 1/2 L) in tetragonal notation. The scattering is much broader in L than are spin waves observed in the parent compound BaFe2As2 indicating that the excitations in the superconducting material are more two-dimensional in nature. The excitation appears gapless for T > TC and becomes gapped on cooling below TC. The observed gap energy is approximately 9.6 meV corresponding to 5 kBTC which is remarkably similar to the canonical value for the resonance energy in the cuprates.
Ramanayaka, A. N.; Mani, R. G. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Wegscheider, W. [Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich (Switzerland)
2013-12-04T23:59:59.000Z
We extract the electron temperature in the microwave photo-excited high mobility GaAs/AlGaAs two dimensional electron system (2DES) by studying the influence of microwave radiation on the amplitude of Shubnikov-de Haas oscillations (SdHOs) in a regime where the cyclotron frequency, ?{sub c}, and the microwave angular frequency, ?, satisfy 2? ? ?{sub c} ? 3.5? The results indicate that increasing the incident microwave power has a weak effect on the amplitude of the SdHOs and therefore the electron temperature, in comparison to the influence of modest temperature changes on the dark-specimen SdH effect. The results indicate negligible electron heating under modest microwave photo-excitation, in good agreement with theoretical predictions.
Klein, Avraham [The Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 (Israel); Aleiner, Igor L., E-mail: aleiner@phys.columbia.edu [Physics Department, Columbia University, New York, NY 10027 (United States); Agam, Oded [The Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 (Israel); Physics Department, Columbia University, New York, NY 10027 (United States)
2014-07-15T23:59:59.000Z
We analyze the motion of quantum vortices in a two-dimensional spinless superfluid within Popov’s hydrodynamic description. In the long healing length limit (where a large number of particles are inside the vortex core) the superfluid dynamics is determined by saddle points of Popov’s action, which, in particular, allows for weak solutions of the Gross–Pitaevskii equation. We solve the resulting equations of motion for a vortex moving with respect to the superfluid and find the reconstruction of the vortex core to be a non-analytic function of the force applied on the vortex. This response produces an anomalously large dipole moment of the vortex and, as a result, the spectrum associated with the vortex motion exhibits narrow resonances lying within the phonon part of the spectrum, contrary to traditional view.
Y-shape spin-separator for two-dimensional group-IV nanoribbons based on quantum spin hall effect
Gupta, Gaurav, E-mail: a0089293@nus.edu.sg; Abdul Jalil, Mansoor Bin; Liang, Gengchiau, E-mail: elelg@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Lin, Hsin [Graphene Research Centre and Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Bansil, Arun [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Huang, Cheng-Yi; Tsai, Wei-Feng [Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China)
2014-01-20T23:59:59.000Z
An efficient spin-separator that operates in quantum spin hall phase has been investigated for two-dimensional group-IV materials. A three-terminal Y-shaped device has been simulated via non-equilibrium Green Function to demonstrate the separation of unpolarized current at source terminal into spin-polarized current of opposite polarity at the two drain terminals. Device controls, i.e., tunable buckling and perpendicular magnetic field have been modeled comprehensively to evaluate the device feasibility and performance. It is shown that these controls can preferentially steer current between the two drains to create a differential charge current with complementary spin polarization, thus enabling a convenient regulation of output signal.
Yan, Wen; Sang, Chaofeng; Wang, Dezhen, E-mail: wangdez@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Liu, Fucheng [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)
2014-06-15T23:59:59.000Z
In this paper, a computational study of two counter-propagating helium plasma jets in ambient air is presented. A two-dimensional fluid model is applied to investigate the physical processes of the two plasma jets interaction (PJI) driven by equal and unequal voltages, respectively. In all studied cases, the PJI results in a decrease of both plasma bullets propagation velocity. When the two plasma jets are driven by equal voltages, they never merge but rather approach each other around the middle of the gas gap at a minimum approach distance, and the minimal distance decreases with the increase of both the applied voltages and initial electron density, but increases with the increase of the relative permittivity. When the two plasma jets are driven by unequal voltages, we observe the two plasma jets will merge at the position away from the middle of the gas gap. The effect of applied voltage difference on the PJI is also studied.
Mirizzi, Alessandro
2015-01-01T23:59:59.000Z
Self-induced flavor conversions of supernova (SN) neutrinos have been characterized in the spherically symmetric "bulb model", reducing the neutrino evolution to a one dimensional problem along a radial direction. We lift this assumption, presenting a two-dimensional model where neutrinos are launched from a spherical neutrino-sphere with many zenithal angles and two azimuthal angles. We also assume that self-induced conversions are not suppressed by large matter effects. In this situation we find that self-interacting neutrinos spontaneously break axial and spherical symmetries. As a result the flavor content and the lepton number of the neutrino gas would acquire seizable direction-dependent variations, breaking the coherent behavior found in the spherically symmetric case. This finding would suggest that the previous results of the self-induced flavor evolution obtained in one-dimensional models should be critically re-examined.
Shear Viscosity of Two-Dimensional Yukawa Systems in the Liquid State Bin Liu and J. Goree
Goree, John
with liquids, including liquids near freezing, composed of molecules or particles that interact with a Yukawa a few reports of transport coef- ficients computed for 2D liquids using molecular dynamics (MD simulation uses an equilibrium method to calculate . Under equilibrium conditions, momentum transport arises
Pan, Ernie
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
Matsui, H.; Koike, Makoto; Kondo, Yutaka; Fast, Jerome D.; Takigawa, M.
2014-09-30T23:59:59.000Z
Number concentrations, size distributions, and mixing states of aerosols are essential parameters for accurate estimation of aerosol direct and indirect effects. In this study, we developed an aerosol module, designated Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS), that can represent these parameters explicitly by considering new particle formation (NPF), black carbon (BC) aging, and secondary organic aerosol (SOA) processes. A two-dimensional bin representation is used for particles with dry diameters from 40 nm to 10 µm to resolve both aerosol size (12 bins) and BC mixing state (10 bins) for a total of 120 bins. The particles with diameters from 1 to 40 nm are resolved using an additional 8 size bins to calculate NPF. The ATRAS module was implemented in the WRF-chem model and applied to examine the sensitivity of simulated mass, number, size distributions, and optical and radiative parameters of aerosols to NPF, BC aging and SOA processes over East Asia during the spring of 2009. BC absorption enhancement by coating materials was about 50% over East Asia during the spring, and the contribution of SOA processes to the absorption enhancement was estimated to be 10 – 20% over northern East Asia and 20 – 35% over southern East Asia. A clear north-south contrast was also found between the impacts of NPF and SOA processes on cloud condensation nuclei (CCN) concentrations: NPF increased CCN concentrations at higher supersaturations (smaller particles) over northern East Asia, whereas SOA increased CCN concentrations at lower supersaturations (larger particles) over southern East Asia. Application of ATRAS to East Asia also showed that the impact of each process on each optical and radiative parameter depended strongly on the process and the parameter in question. The module can be used in the future as a benchmark model to evaluate the accuracy of simpler aerosol models and examine interactions between NPF, BC aging, and SOA processes under different meteorological conditions and emissions.
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AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5(Million Cubic Feet) Oregon (Including Vehicle Fuel) (MillionStructural Basis of WntSupportBRAP-focused topicsTwodimensional time resolved measurements
Fabio Deelan Cunden; Anna Maltsev; Francesco Mezzadri
2015-06-26T23:59:59.000Z
We study the distribution of the mean radial displacement of charges of a 2D one-component plasma in the thermodynamic limit $N\\to\\infty$ at finite temperature $\\beta>0$. We compute explicitly the large deviation functions showing the emergence of a fourth-order phase transition as a consequence of a change of topology in the plasma distribution. This weak phase transition occurs exactly at the ground state of the plasma. These results have been compared with the integrable case (finite $N$) of plasma parameter $\\beta q^2=2$. In this case the problem can be mapped to the stationary properties of 2D Dyson Brownian particles and to a non-Hermitian matrix model.
Ultra-Shallow Imaging Using 2D & 3D Seismic Reflection Methods
Sloan, Steven D.
2008-01-01T23:59:59.000Z
.3 Fold map comparison of rolling spreads 16 Figure 2.4 Offset-distribution plot 18 Figure 2.5 Offset-redundancy plot 20 Figure 2.6 High-fold CMP gather with poor offset distribution 21 Figure 2.7 Azimuth-distribution plot 21... that of the entire survey area since the total fold is the sum of the nominal fold of multiple patches and increases as the patch is rolled across the survey areas in the inline and crossline directions. Because the fold tapers at the edges of the survey, the S...
van Vliet, Lucas J.
with oblique internal layering, best imaged on seismic reflection profiles, where three geometric elementsHigh-resolution clinoform characterization by 2-D model-driven seismic Bayesian inversion Daria of seismic data always presents an inversion problem. Instead of analyzing the data trace by trace, we
Jun'ichi Sato; Keisuke Sawada; Naofumi Ohnishi
2003-04-14T23:59:59.000Z
Two-dimensional numerical simulations of an accretion flow in a close binary system are performed by solving the Euler equations with radiative transfer. In the present study, the specific heat ratio is assumed to be constant while radiative cooling effect is included as a non-adiabatic process. The cooling effect of the disc is considered by discharging energy in the vertical directions from the top and bottom surfaces of the disc. We use the flux-limited diffusion approximation to calculate the radiative heat flux values. Our calculations show that a disc structure appears and the spiral shocks are formed on the disc. These features are similar to that observed in the case of an adiabatic gas with a lower specific heat ratio, $\\gamma=1.01$. It is found that when radiative cooling effect is accounted for, the mass of the disc becomes larger than that assuming $\\gamma=5/3$, and smaller than that assuming $\\gamma=1.01$. It is concluded that employing an adiabatic gas with a lower specific heat ratio is almost a valid assumption for simulating accretion disc with radiative cooling effect.
Reddy, Christopher; Nelson, Robert
2013-03-27T23:59:59.000Z
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"¯ (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.
Strauss, Charlie E. (Santa Fe, NM)
1997-01-01T23:59:59.000Z
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.
Luo, Xiaoguang, E-mail: 276718626@qq.com; Long, Kailin; Wang, Jun; Qiu, Teng, E-mail: tqiu@seu.edu.cn [Department of Physics, Southeast University, Nanjing 211189 (China); He, Jizhou [Department of Physics, Nanchang University, Nanchang 330031 (China); Liu, Nian [Department of Physical and Electronics, Anhui Science and Technology University, Bengbu 233100 (China)
2014-06-28T23:59:59.000Z
Theoretical thermoelectric nanophysics models of low-dimensional electronic heat engine and refrigerator devices, comprising two-dimensional hot and cold reservoirs and an interconnecting filtered electron transport mechanism have been established. The models were used to numerically simulate and evaluate the thermoelectric performance and energy conversion efficiencies of these low-dimensional devices, based on three different types of electron transport momentum-dependent filters, referred to herein as k{sub x}, k{sub y}, and k{sub r} filters. Assuming the Fermi-Dirac distribution of electrons, expressions for key thermoelectric performance parameters were derived for the resonant transport processes, in which the transmission of electrons has been approximated as a Lorentzian resonance function. Optimizations were carried out and the corresponding optimized design parameters have been determined, including but not limited to the universal theoretical upper bound of the efficiency at maximum power for heat engines, and the maximum coefficient of performance for refrigerators. From the results, it was determined that k{sub r} filter delivers the best thermoelectric performance, followed by the k{sub x} filter, and then the k{sub y} filter. For refrigerators with any one of three filters, an optimum range for the full width at half maximum of the transport resonance was found to be <2k{sub B}T.
Nikolay Kuznetsov
2015-03-07T23:59:59.000Z
The coupled motion is investigated for a mechanical system consisting of water and a body freely floating in it. Water occupies either a half-space or a layer of constant depth into which an infinitely long surface-piercing cylinder is immersed, thus allowing us to study two-dimensional modes. Under the assumption that the motion is of small amplitude near equilibrium, a linear setting is applicable and for the time-harmonic oscillations it reduces to a spectral problem with the frequency of oscillations as the spectral parameter. It is essential that one of the problem's relations is linear with respect to the parameter, whereas two others are quadratic with respect to it. Within this framework, it is shown that the total energy of the water motion is finite and the equipartition of energy holds for the whole system. On this basis, it is proved that no wave modes can be trapped provided their frequencies exceed a bound depending on cylinder's properties, whereas its geometry is subject to some restrictions and, in some cases, certain restrictions are imposed on the type of mode.