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. Many of these species are charged. In the ocean, water interacts with dissolved salts. In biological systems, water interacts with dissolved salts as well as charged amino acids, the zwitterionic head groups
Bill2d -- a software package for classical two-dimensional Hamiltonian systems
Solanpää, Janne; Räsänen, Esa
2015-01-01
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).
Yeng, Yi Xiang
We demonstrate designs of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. ...
2D Seismic Reflection Data across Central Illinois
Smith, Valerie; Leetaru, Hannes
2014-09-30
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.
1981-01-01
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, ...
Aris, John P.
119 Two-Dimensional Thin Layer Chromatography (2D-TLC) 1. Resuspend RNA pellet in 5 µl ddH2O. Place and pellet any insoluble material. · If a pellet is visible, carefully transfer supernatant to fresh tube. 3
Seismic isolation of two dimensional periodic foundations
Yan, Y.; Mo, Y. L.; Laskar, A.; Cheng, Z.; Shi, Z.; Menq, F.; Tang, Y.
2014-07-28
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.
Effective mass enhancement of two-dimensional electrons in a one-dimensional superlattice potential
Rokhinson, Leonid
Effective mass enhancement of two-dimensional electrons in a one-dimensional superlattice potential effective mass enhancement of two-dimensional 2D electrons in an atomically precise one-dimensional Al reveal that the mobility of the 2D electrons increases with electron density n2D . At low densities (n2D
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
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
Wideband radar cross section reduction using two-dimensional phase gradient metasurfaces
Li, Yongfeng; Qu, Shaobo; Wang, Jiafu; Chen, Hongya; Zhang, Jieqiu; Xu, Zhuo; Zhang, Anxue
2014-06-02
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 Adachi, Masaaki; Fukushima, Takehiro; Shinohara, Susumu; Arai, Kenichi; Harayama, Takahisa
2014-06-16
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.
Two-dimensional river modeling
Thompson, James Cameron
1988-01-01
heavily vegetated flood plain. It is found that the two-dimensional model can determine the flow more completely and more accurately than a corresponding one- dimensional model. Two-dimensional models are best applied where the flow conditions... committee, W. P. James, R. A. Wurbs, and R. 0. Reid, for their support and interest in this research. Dr. James, in particular, has shown great foresight in supporting broader use of two-dimensional river modeling. Dave Froehlich deserves much...
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
The Electronic Structure of a Two-Dimensional Pure Copper Oxide...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
the two-dimensional (2D) CuO2 planes. By growing epitaxial films with the pulsed-laser deposition facility available on Beamline 7.0.1, researchers could stabilize a 2D version...
Nonlinear Optical Processes in Two-Dimensional Semiconductor Structures
Wang, Yongrui
2015-07-28
The optical properties of two types of two-dimensional (2D) semiconductor structures are studied. One of them is for structures based on quantum wells (QWs), and the other is graphene. We study the dynamics of optically excited electron-hole plasma...
Two dimensional unstable scar statistics.
Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)
2006-12-01
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
2013-09-03
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.
Renormalization of two-dimensional XQCD
Hidenori Fukaya; Ryo Yamamura
2015-10-15
Recently, Kaplan proposed an interesting extension of QCD named Extended QCD or XQCD with bosonic auxiliary fields [1]. While its partition function is kept exactly the same as that of QCD, XQCD naturally contains properties of low-energy hadrons. We apply this extension to the two-dimensional QCD in the large $N_c$ limit ('t Hooft model) [2]. In this solvable model, it is possible to directly examine the hadronic picture of the 2d XQCD and analyze its renormalization group flow to understand how the auxiliary degrees of freedom behave in the low energy region. We confirm that the additional scalar fields can become dynamical acquiring the kinetic term, and its parity-odd part becomes dominant in the low energy region. This renomalization of XQCD provides an "extension" of the renormalization scheme of QCD, inserting different field variables from those in the original theory, without any changes in physical observables.
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
Phase-sensitive two-dimensional neutron shearing interferometer and Hartmann sensor
Baker, Kevin
2015-12-08
A neutron imaging system detects both the phase shift and absorption of neutrons passing through an object. The neutron imaging system is based on either of two different neutron wavefront sensor techniques: 2-D shearing interferometry and Hartmann wavefront sensing. Both approaches measure an entire two-dimensional neutron complex field, including its amplitude and phase. Each measures the full-field, two-dimensional phase gradients and, concomitantly, the two-dimensional amplitude mapping, requiring only a single measurement.
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
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
A tale of coupled vibrations in solution told by coherent two-dimensional infrared spectroscopy
Khalil, Munira, 1975-
2004-01-01
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 ...
A two-dimensional volatility basis set – Part 2: Diagnostics of organic-aerosol evolution
Donahue, Neil M.
We discuss the use of a two-dimensional volatility-oxidation space (2-D-VBS) to describe organic-aerosol chemical evolution. The space is built around two coordinates, volatility and the degree of oxidation, both of which ...
Jovanovic, Natalija Zorana
2005-01-01
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 ...
Volumetric reconstruction of tissue structure from two-dimensional microscopy images
Cruz, Francisco (Francisco Ui)
2006-01-01
Cell morphology of tissue is naturally three-dimensional. Most current methods for tissue analysis use two dimensional histological images of the tissue samples, restricting the analysis to 2D. Existing approaches do not ...
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)
Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.
2015-04-10
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
Two-dimensional Imaging Velocity Interferometry: Technique and Data Analysis
Erskine, D J; Smith, R F; Bolme, C; Celliers, P; Collins, G
2011-03-23
We describe the data analysis procedures for an emerging interferometric technique for measuring motion across a two-dimensional image at a moment in time, i.e. a snapshot 2d-VISAR. Velocity interferometers (VISAR) measuring target motion to high precision have been an important diagnostic in shockwave physics for many years Until recently, this diagnostic has been limited to measuring motion at points or lines across a target. We introduce an emerging interferometric technique for measuring motion across a two-dimensional image, which could be called a snapshot 2d-VISAR. If a sufficiently fast movie camera technology existed, it could be placed behind a traditional VISAR optical system and record a 2d image vs time. But since that technology is not yet available, we use a CCD detector to record a single 2d image, with the pulsed nature of the illumination providing the time resolution. Consequently, since we are using pulsed illumination having a coherence length shorter than the VISAR interferometer delay ({approx}0.1 ns), we must use the white light velocimetry configuration to produce fringes with significant visibility. In this scheme, two interferometers (illuminating, detecting) having nearly identical delays are used in series, with one before the target and one after. This produces fringes with at most 50% visibility, but otherwise has the same fringe shift per target motion of a traditional VISAR. The 2d-VISAR observes a new world of information about shock behavior not readily accessible by traditional point or 1d-VISARS, simultaneously providing both a velocity map and an 'ordinary' snapshot photograph of the target. The 2d-VISAR has been used to observe nonuniformities in NIF related targets (polycrystalline diamond, Be), and in Si and Al.
Rapid heating and cooling in two-dimensional Yukawa systems
Yan Feng; Bin Liu; J. Goree
2011-04-19
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
2013-01-01
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 ...
Soliton nanoantennas in two-dimensional arrays of quantum dots
Gligori?, G; Hadžievski, Lj; Slepyan, G Ya; Malomed, B A
2015-01-01
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
Two-dimensional state in driven magnetohydrodynamic turbulence
Bigot, Barbara; Galtier, Sebastien
2011-02-15
The dynamics of the two-dimensional (2D) state in driven three-dimensional (3D) incompressible magnetohydrodynamic turbulence is investigated through high-resolution direct numerical simulations and in the presence of an external magnetic field at various intensities. For such a flow the 2D state (or slow mode) and the 3D modes correspond, respectively, to spectral fluctuations in the plane k{sub ||}=0 and in the area k{sub ||}>0. It is shown that if initially the 2D state is set to zero it becomes nonnegligible in few turnover times, particularly when the external magnetic field is strong. The maintenance of a large-scale driving leads to a break for the energy spectra of 3D modes; when the driving is stopped, the previous break is removed and a decay phase emerges with Alfvenic fluctuations. For a strong external magnetic field the energy at large perpendicular scales lies mainly in the 2D state, and in all situations a pinning effect is observed at small scales.
Superfluid behaviour of a two-dimensional Bose gas
Desbuquois, Rémi; Yefsah, Tarik; Léonard, Julian; Beugnon, Jérôme; Weitenberg, Christof; Dalibard, Jean
2012-01-01
Two-dimensional (2D) systems play a special role in many-body physics. Because of thermal fluctuations, they cannot undergo a conventional phase transition associated to the breaking of a continuous symmetry. Nevertheless they may exhibit a phase transition to a state with quasi-long range order via the Berezinskii-Kosterlitz-Thouless (BKT) mechanism. A paradigm example is the 2D Bose fluid, such as a liquid helium film, which cannot Bose-condense at non-zero temperature although it becomes superfluid above a critical phase space density. Ultracold atomic gases constitute versatile systems in which the 2D quasi-long range coherence and the microscopic nature of the BKT transition were recently explored. However, a direct observation of superfluidity in terms of frictionless flow is still missing for these systems. Here we probe the superfluidity of a 2D trapped Bose gas with a moving obstacle formed by a micron-sized laser beam. We find a dramatic variation of the response of the fluid, depending on its degre...
Cosmologies with Two-Dimensional Inhomogeneity
A. Feinstein; J. Ibáñez; Ruth Lazkoz
1995-11-27
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.
Synthesis of Two-Dimensional Materials by Selective Extraction
Abdelmalak, Michael Naguib; Gogotsi, Yury
2015-01-01
Two-dimensional (2D) materials have attracted much attention in the past decade. They offer high specific surface area, as well as electronic structure and properties that differ from their bulk counterparts due to the low dimensionality. Graphene is the best known and the most studied 2D material, but metal oxides and hydroxides (including clays), dichalcogenides, boron nitride (BN), and other materials that are one or several atoms thick are receiving increasing attention. They may deliver a combination of properties that cannot be provided by other materials. The most common synthesis approach in general is by reacting different elements or compounds to form a new compound. However, this approach does not necessarily work well for low-dimensional structures, since it favors formation of energetically preferred 3D (bulk) solids. Many 2D materials are produced by exfoliation of van der Waals solids, such as graphite or MoS2, breaking large particles into 2D layers. However, these approaches are not universal; for example, 2D transition metal carbides cannot be produced by any of them. An alternative but less studied way of material synthesis is the selective extraction process, which is based on the difference in reactivity and stability between the different components (elements or structural units) of the original material. It can be achieved using thermal, chemical, or electrochemical processes. Many 2D materials have been synthesized using selective extraction, such as graphene from SiC, transition metal oxides (TMO) from layered 3D salts, and transition metal carbides or carbonitrides (MXenes) from MAX phases. Selective extraction synthesis is critically important when the bonds between the building blocks of the material are too strong (e.g., in carbides) to be broken mechanically in order to form nanostructures. Unlike extractive metallurgy, where the extracted metal is the goal of the process, selective extraction of one or more elements from the precursor materials releases 2D structures. In this Account, in addition to graphene and TMO, we focused on MXenes as an example for the use of selective extraction synthesis to produce novel 2D materials. About 10 new carbides and carbonitrides of transition metals have been produced by this method in the past 3 years. They offer an unusual combination of metallic conductivity and hydrophilicity and show very attractive electrochemical properties. We hope that this Account will encourage researchers to extend the use of selective extraction to other layered material systems that in turn will result in expanding the world of nanomaterials in general and 2D materials in particular, generating new materials that cannot be produced by other means.
Universal entanglement entropy in two-dimensional conformal quantum...
Office of Scientific and Technical Information (OSTI)
two-dimensional conformal quantum critical systems, i.e., systems with scale-invariant wave functions. They include two-dimensional generalized quantum dimer models on bipartite...
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
PHYSICAL REVIEW E 87, 013106 (2013) Longitudinal viscosity of two-dimensional Yukawa liquids
Goree, John
2013-01-01
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
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
Statistical Mechanics of Two-dimensional Foams
Marc Durand
2010-09-07
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.
Fully localized two-dimensional embedded solitons
Yang Jianke [Department of Mathematics and Statistics, University of Vermont, Burlington, Vermont 05401 (United States)
2010-11-15
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.
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)
2012-05-07
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
2015-05-26
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.
2010-01-01
Two-dimensional electronic spectroscopy is a sensitive probe of solvation dynamics. Using a pump–probe geometry with a pulse shaper [ Optics Express 15 (2007), 16681-16689; Optics Express 16 (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 longermore »waiting times. This can be measured in 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 Letters 31 (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
Flow transitions in two-dimensional foams
Christopher Gilbreth; Scott Sullivan; Michael Dennin
2006-08-08
For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three dimensional foam. Recent work in three-dimensional foam has identified three distinct regimes of flow [S. Rodts, J. C. Baudez, and P. Coussot, Europhys. Lett. {\\bf 69}, 636 (2005)]. Two of these regimes are identified with continuum behavior (full flow and shear-banding), and the third regime is identified as a discrete regime exhibiting extreme localization. In this paper, the discrete regime is studied in more detail using a model two dimensional foam: a bubble raft. We characterize the behavior of the bubble raft subjected to a constant rate of strain as a function of time, system size, and applied rate of strain. We observe localized flow that is consistent with the coexistence of a power-law fluid with rigid body rotation. As a function of applied rate of strain, there is a transition from a continuum description of the flow to discrete flow when the thickness of the flow region is approximately 10 bubbles. This occurs at an applied rotation rate of approximately $0.07 {\\rm s^{-1}}$.
Two dimensional Sen connections in general relativity
L. B. Szabados
1994-02-01
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.
Canonical structure of 2D black holes
Navarro-Salas, J; Talavera, C F
1994-01-01
We determine the canonical structure of two-dimensional black-hole solutions arising in $2D$ dilaton gravity. By choosing the Cauchy surface appropriately we find that the canonically conjugate variable to the black hole mass is given by the difference of local (Schwarzschild) time translations at right and left spatial infinities. This can be regarded as a generalization of Birkhoff's theorem.
Couette Flow of Two-Dimensional Foams
G. Katgert; B. P. Tighe; M. E. Möbius; M. van Hecke
2010-04-26
We experimentally investigate flow of quasi two-dimensional disordered foams in Couette geometries, both for foams squeezed below a top plate and for freely floating foams. With the top-plate, the flows are strongly localized and rate dependent. For the freely floating foams the flow profiles become essentially rate-independent, the local and global rheology do not match, and in particular the foam flows in regions where the stress is below the global yield stress. We attribute this to nonlocal effects and show that the "fluidity" model recently introduced by Goyon {\\em et al.} ({\\em Nature}, {\\bf 454} (2008)) captures the essential features of flow both with and without a top plate.
Sieving hydrogen isotopes through two dimensional crystals
M. Lozada-Hidalgo; S. Hu; O. Marshall; A. Mishchenko; A. N. Grigorenko; R. A. W. Dryfe; B. Radha; I. V. Grigorieva; A. K. Geim
2015-11-20
One-atom-thick crystals are impermeable to atoms and molecules, but hydrogen ions (thermal protons) penetrate through them. We show that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes. Employing electrical measurements and mass spectrometry, we find that deuterons permeate through these crystals much slower than protons, resulting in a separation factor of 10 at room temperature. The isotope effect is attributed to a difference of about 60 meV between zero-point energies of incident protons and deuterons, which translates into the equivalent difference in the activation barriers posed by two dimensional crystals. In addition to providing insight into the proton transport mechanism, the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment.
Sieving hydrogen isotopes through two dimensional crystals
Lozada-Hidalgo, M; Marshall, O; Mishchenko, A; Grigorenko, A N; Dryfe, R A W; Radha, B; Grigorieva, I V; Geim, A K
2015-01-01
One-atom-thick crystals are impermeable to atoms and molecules, but hydrogen ions (thermal protons) penetrate through them. We show that monolayers of graphene and boron nitride can be used to separate hydrogen ion isotopes. Employing electrical measurements and mass spectrometry, we find that deuterons permeate through these crystals much slower than protons, resulting in a separation factor of 10 at room temperature. The isotope effect is attributed to a difference of about 60 meV between zero-point energies of incident protons and deuterons, which translates into the equivalent difference in the activation barriers posed by two dimensional crystals. In addition to providing insight into the proton transport mechanism, the demonstrated approach offers a competitive and scalable way for hydrogen isotope enrichment.
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 ...
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...
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
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
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.
2006-01-01
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 ...
Turbulent equipartitions in two dimensional drift convection
Isichenko, M.B.; Yankov, V.V.
1995-07-25
Unlike the thermodynamic equipartition of energy in conservative systems, turbulent equipartitions (TEP) describe strongly non-equilibrium systems such as turbulent plasmas. In turbulent systems, energy is no longer a good invariant, but one can utilize the conservation of other quantities, such as adiabatic invariants, frozen-in magnetic flux, entropy, or combination thereof, in order to derive new, turbulent quasi-equilibria. These TEP equilibria assume various forms, but in general they sustain spatially inhomogeneous distributions of the usual thermodynamic quantities such as density or temperature. This mechanism explains the effects of particle and energy pinch in tokamaks. The analysis of the relaxed states caused by turbulent mixing is based on the existence of Lagrangian invariants (quantities constant along fluid-particle or other orbits). A turbulent equipartition corresponds to the spatially uniform distribution of relevant Lagrangian invariants. The existence of such turbulent equilibria is demonstrated in the simple model of two dimensional electrostatically turbulent plasma in an inhomogeneous magnetic field. The turbulence is prescribed, and the turbulent transport is assumed to be much stronger than the classical collisional transport. The simplicity of the model makes it possible to derive the equations describing the relaxation to the TEP state in several limits.
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)
2010-09-15
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
2013-01-01
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, Brasília - DF 70040-020 (Brazil)
2014-06-15
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 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
2005-09-13
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
2005-01-01
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 ...
Two-Dimensional Self-Assembly in Diblock Copolymers
Hosoi, A.E.
2005-06-20
Diblock copolymers confined to a two-dimensional surface may produce uniform features of macromolecular dimensions (10 â?? 100 nm). We present a mathematical model for nanoscale pattern
Two-dimensional simulation of the Raft River geothermal reservoir...
and the time dependent temperature response of the wells at the Raft River, Idaho, Geothermal Resource were developed. A horizontal, two-dimensional, finite-difference model...
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
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)
2014-09-01
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.
Hydration of ions in two dimensional water
S. Dutta; Yongjin Lee; Y. S. Jho
2015-11-11
We present a 2D lattice model of water to study the effects of ion hydration on the properties of water. We map the water molecules as lattice particles consisting of a single Oxygen at the center of a site and two Hydrogen atoms on each side. The internal state of the system, such as the dipole moment at a site, is defined with respect to the location of the Hydrogen atoms at the site depending on their role in Hydrogen bonds (H-bonds) being a donor or an acceptor. We study the influence of the charge and the radius of the ion on the insertion energy and on the H-bonds in the first and second hydration layers around the ion and in the bulk. In particular we analyze how the competing interactions of the short-ranged H-bonds and the long-ranged electrostatics influence the hydration properties. The role of the ion both as a source of the electrostatic interactions as well as a defect is also discussed. Our model also shows the well known fact that the polarizability of the water molecules destroys the hydrogen bond network and increases the dipole moment of the molecules near the ion.
Hydration of ions in two dimensional water
Dutta, S; Jho, Y S
2015-01-01
We present a 2D lattice model of water to study the effects of ion hydration on the properties of water. We map the water molecules as lattice particles consisting of a single Oxygen at the center of a site and two Hydrogen atoms on each side. The internal state of the system, such as the dipole moment at a site, is defined with respect to the location of the Hydrogen atoms at the site depending on their role in Hydrogen bonds (H-bonds) being a donor or an acceptor. We study the influence of the charge and the radius of the ion on the insertion energy and on the H-bonds in the first and second hydration layers around the ion and in the bulk. In particular we analyze how the competing interactions of the short-ranged H-bonds and the long-ranged electrostatics influence the hydration properties. The role of the ion both as a source of the electrostatic interactions as well as a defect is also discussed. Our model also shows the well known fact that the polarizability of the water molecules destroys the hydrogen...
Dynamical Mechanism of Two-Dimensional Plasmon Launching by Swift Electrons
Xiao Lin; Xihang Shi; Fei Gao; Ido Kaminer; Zhaoju Yang; Zhen Gao; Hrvoje Buljan; John D. Joannopoulos; Marin Solja?i?; Hongsheng Chen; Baile Zhang
2015-07-30
Launching of surface plasmons by swift electrons has long been utilized to investigate plasmonic properties of ultrathin, or two-dimensional (2D), electron systems, including graphene plasmons recently. However, spatio-temporal dynamics of this process has never been clearly revealed. This is because the impact of an electron will generate not only plasmons, but also photons, demanding both space and time. Here we address this issue within the framework of classical electromagnetics by showing the dynamical process of 2D plasmon launching by swift electrons on graphene. The launching of 2D plasmons on graphene is not immediate, but is delayed after a hydrodynamic splashing-like process, which occurs during the formation time of transition radiation caused by the electron's impact. This newly revealed process also implies that all previous estimates on the yields of graphene plasmons in electron-energy-loss-spectroscopy have been overestimated.
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
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
Sensor Networking Using Two-Dimensional Electromagnetic Wave Yasutoshi Makino*
Shinoda, Hiroyuki
causes wastes of energy and interferences of communication. Since intense elec- tromagnetic waveSensor Networking Using Two-Dimensional Electromagnetic Wave Yasutoshi Makino* , Kouta Minamizawa* , and Hiroyuki Shinoda* In this paper, we propose a new technology for sensor networks named "Two Dimensional
Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures
Azad, Abul K; Chen, Houtong; Taylor, Antoinette; O' Hara, John F; Han, Jiaguang; Lu, Xinchao; Zhang, Weili
2009-01-01
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.
Exploring two-dimensional electron gases with two-dimensional Fourier transform spectroscopy
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Paul, J.; Dey, P.; Tokumoto, T.; Reno, J. L.; Hilton, D. J.; Karaiskaj, D.
2014-10-07
The dephasing of excitons in a modulation doped single quantum well was carefully measured using time integrated four-wave mixing (FWM) and two-dimensional Fourier transform (2DFT) spectroscopy. These are the first 2DFT measurements performed on a modulation doped single quantum well. The inhomogeneous and homogeneous excitonic line widths were obtained from the diagonal and cross-diagonal profiles of the 2DFT spectra. The laser excitation density and temperature were varied and 2DFT spectra were collected. A very rapid increase of the dephasing decay, and as a result, an increase in the cross-diagonal 2DFT linewidths with temperature was observed. The lineshapes of the 2DFTmore »spectra suggest the presence of excitation induced dephasing and excitation induced shift.« less
Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.
2015-01-21
Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.
Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
Kamaraju, N. Taylor, A. J.; Prasankumar, R. P.; Pan, W.; Reno, J.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.
2015-01-19
Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also find that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.
Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdi?, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.
2015-01-21
Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG,more »in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.« less
Effective field theory and integrability in two-dimensional Mott transition
Bottesi, Federico L.; Zemba, Guillermo R.
2011-08-15
Highlights: > Mott transition in 2d lattice fermion model. > 3D integrability out of 2D. > Effective field theory for Mott transition in 2d. > Double Chern-Simons. > d-Density waves. - Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a quantum group symmetry as a consequence of a recently found solution of the Zamolodchikov tetrahedron equation. A projection (from three to two space-time dimensions) property of the solution is used to identify the symmetry of the model at the Mott critical point as U{sub q}(sl(2)-circumflex)xU{sub q}(sl(2)-circumflex), with deformation parameter q = -1. Based on this result, the low-energy effective field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the effective filed theory methods, we show that the Mott transition that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.
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)
2013-12-02
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
Healing of defects in a two-dimensional granular crystal
Rice, Marie C
2014-01-01
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 ...
Optical properties of two-dimensional transition metal dichalcogenides
Lin, Yuxuan, S.M. Massachusetts Institute of Technology
2014-01-01
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 ...
Chiral Jacobians and two-dimensional QED at finite temperature
Reuter, M.; Dittrich, W.
1985-07-15
We show that in massless two-dimensional QED there is no restoration of gauge symmetry at finite temperature (because the boson mass is temperature independent), using zeta-function techniques to solve the fermionic determinant exactly.
Design and analysis of a two-dimensional camera array
Yang, Jason C. (Jason Chieh-Sheng), 1977-
2005-01-01
I present the design and analysis of a two-dimensional camera array for virtual studio applications. It is possible to substitute conventional cameras and motion control devices with a real-time, light field camera array. ...
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 ...
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.
2007-01-01
The anomalous Hall effect in a magnetic two-dimensional electron gas with Rashba spin-orbit coupling is studied within the Kubo-Streda formalism in the presence of pointlike potential impurities. We find that all contributions ...
Notes on the two-dimensional fractional Brownian motion
Baudoin, Fabrice; Nualart, David
2006-02-17
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...
Two-dimensional relativistic space charge limited current flow in the drift space
Liu, Y. L.; Chen, S. H.; Koh, W. S.; Ang, L. K.
2014-04-15
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.
Orientation, Flow, and Clogging in a Two-Dimensional Hopper: Ellipses vs. Disks
Junyao Tang; Robert P. Behringer
2015-10-29
Two-dimensional (2D) hopper flow of disks has been extensively studied. Here, we investigate hopper flow of ellipses with aspect ratio $\\alpha = 2$, and we contrast that behavior to the flow of disks. We use a quasi-2D hopper containing photoelastic particles to obtain stress/force information. We simultaneously measure the particle motion and stress. We determine several properties, including discharge rates, jamming probabilities, and the number of particles in clogging arches. For both particle types, the size of the opening, $D$, relative to the size of particles, $\\ell$ is an important dimensionless measure. The orientation of the ellipses plays an important role in flow rheology and clogging. The alignment of contacting ellipses enhances the probability of forming stable arches. This study offers insight for applications involving the flow of granular materials consisting of ellipsoidal shapes, and possibly other non-spherical shapes.
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
2008-12-16
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
2014-11-17
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; Basile Carrasco, Leonardo A; Yoon, Mina; Ma, Cheng; Puretzky, Alexander A; Lee, Jaekwang; Idrobo Tapia, Juan Carlos; Chi, Miaofang; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai
2015-01-01
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
2014-11-23
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.
Quantum of optical absorption in two-dimensional semiconductors
California at Berkeley, University of
. Absorptance quantization appears to be universal in 2D systems including IIIV quantum wells and graphene quantitative examination of the intrinsic absorption properties of free-standing 2D semiconductor thin films work has shown that graphene, a 2D semimetal, has a universal value of light absorption, namely , where
M-Theory and Two-Dimensional Effective Dynamics
N. D. Lambert; P. C. West
1999-08-09
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
2015-04-04
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
2013-05-31
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.
Two-dimensional optimization of free electron laser designs
Prosnitz, Donald (Walnut Creek, CA); Haas, Roger A. (Pleasanton, CA)
1985-01-01
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.
1982-05-04
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.
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", Università 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
: A TWO-DIMENSIONAL BATHYMETRY BASED UNSTRUCTURED TRIANGULAR GRID GENERATOR
unstructured triangular grid refinement algorithms, including the recent "off-centers" method, is providedBATTRI* : A TWO-DIMENSIONAL BATHYMETRY BASED UNSTRUCTURED TRIANGULAR GRID GENERATOR FOR FINITE utilities to check and improve grid quality. The final output mesh node locations, node depths and element
Numerical Study of Two-Dimensional Viscous, Chemically Reacting Flow
Texas at Arlington, University of
A computational fluid dynamics code for two-dimensional, multi-species, laminar Navier- Stokes equations is developed to simulate a pulsed detonation based propulsion system and to analyze its performance. The stiffness due to coupling the fluid dynamics and the chem- ical kinetics is properly taken care of by using
Dynamical confinement in bosonized two-dimensional QCD
Ferrando, A. ); Vento, V. )
1994-03-15
In the bosonized version of two-dimensional theories nontrivial boundary conditions (topology) play a crucial role. They are inevitable if one wants to describe nonsinglet states. In Abelian bosonization, color is the charge of a topological current in terms of a nonlinear meson field. We show that confinement appears as the dynamical collapse of the topology associated with its nontrivial boundary conditions.
Weakly interacting two-dimensional system of dipoles: Limitations of the mean-field theory
Astrakharchik, G. E.; Boronat, J.; Casulleras, J.; Kurbakov, I. L.; Lozovik, Yu. E.
2007-06-15
We consider a homogeneous two-dimensional Bose gas with repulsive dipole-dipole interactions. The ground-state equation of state, calculated using the diffusion Monte Carlo method, shows quantitative differences from the predictions of the commonly used Gross-Pitaevskii mean-field theory. The static structure factor, pair distribution function, and condensate fraction are calculated in a wide range of the gas parameter. Differences from mean-field theory are reflected in the frequency of the lowest ''breathing'' mode for harmonically trapped systems.
Ramon Becar; P. A. Gonzalez; Joel Saavedra; Yerko Vasquez
2014-12-19
We study massive charged fermionic perturbations in the background of a charged two-dimensional dilatonic black hole, and we solve the Dirac equation analytically. Then, we compute the reflection and transmission coefficients and the absorption cross section for massive charged fermionic fields, and we show that the absorption cross section vanishes at the low and high frequency limits. However, there is a range of frequencies where the absorption cross section is not null. Furthermore, we study the effect of the mass and electric charge of the fermionic field over the absorption cross section.
Electronic, Vibrational and Thermoelectric Properties of Two-Dimensional Materials
Wickramaratne, Darshana
2015-01-01
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)
2015-04-08
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.
Zhang, Wei-Bing; Zhu, Peng; Lam, Chi-Hang
2015-01-01
Two-dimensional (2D) intrinsic ferromagnetic (FM) semiconductors are crucial to develop low-dimensional spintronic devices. Using density functional theory, we show that single-layer chromium trihalides (SLCTs) (CrX$_3$,X=F, Cl, Br and I) constitute a series of stable 2D intrinsic FM semiconductors. A free-standing SLCT can be easily exfoliated from the bulk crystal, due to a low cleavage energy and a high in-plane stiffness. Electronic structure calculations using the HSE06 functional indicate that both bulk and single-layer CrX$_3$ are half semiconductors with indirect band gaps. The valence bands and conduction bands are fully spin-polarized in the same spin direction. The energy gaps and absorption edges of CrBr$_3$ and CrI$_3$ are found to be in the visible frequency range, which implies possible opt-electronic applications. Furthermore, these 2D crystals are found to possess a large magnetic moment of 3$\\mu_B$ per formula unit and a sizable magnetic anisotropy energy. The magnetic exchange constants of ...
Puretzky, Alexander A; Liang, Liangbo; Li, Xufan; Xiao, Kai; Wang, Kai; Mahjouri-Samani, Masoud; Basile, Leonardo; Idrobo Tapia, Juan Carlos; Sumpter, Bobby G; Meunier, Vincent; Geohegan, David B
2015-01-01
Stacked monolayers of two-dimensional (2D) materials present a new class of hybrid materials with tunable optoelectronic properties determined by their stacking orientation, order, and atomic registry. Atomic-resolution Z-contrast scanning transmission electron microscopy (AR-Z-STEM) and electron energy loss spectroscopy (EELS) can be used to determine the exact atomic registration between different layers, in few-layer 2D stacks, however fast optical characterization techniques are essential for rapid development of the field. Here, using two- and three-layer MoSe2 and WSe2 crystals synthesized by chemical vapor deposition we show that the generally unexplored low frequency (LF) Raman modes (< 50 cm-1) that originate from interlayer vibrations can serve as fingerprints to characterize not only the number of layers, but also their stacking configurations. Ab initio calculations and group theory analysis corroborate the experimental assignments determined by AR-Z-STEM and show that the calculated LF mode fingerprints are related to the 2D crystal symmetries.
Gheisari, R.; Firoozabadi, M. M.; Mohammadi, H.
2014-01-15
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.
Transport behavior of water molecules through two-dimensional nanopores
Zhu, Chongqin; Li, Hui; Meng, Sheng
2014-11-14
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
2006-12-16
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.
Quantum Hamilton-Jacobi Approach to Two Dimensional Singular Oscillator
Ozlem Yesiltas; Bengu Demircioglu
2008-04-27
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.
The Study of Two-dimensional Polytropic Stars
Sanchari De; Somenath Chakrabarty
2015-10-09
In this article we have studied the structure of hypothetical two-dimensional polytropic stars. Considering some academic interest, we have developed a formalism to investigate some of the gross properties of such stellar objects. However, we strongly believe that the formalism developed here may be prescribed as class problem for post-graduate level students in physics or a post-graduate dissertation project work in physics.
Harmonic lattice behavior of two-dimensional colloidal crystals
P. Keim; G. Maret; U. Herz; H. H. von Grünberg
2004-02-17
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.
Accelerating universe in two-dimensional noncommutative dilaton cosmology
Wontae Kim; Myung Seok Yoon
2006-12-01
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.
X-ray tests of a two-dimensional stigmatic imaging scheme with variable magnifications
Lu, J.; Bitter, M.; Hill, K. W.; Delgado-Aparicio, L. F.; Efthimion, P. C.; Pablant, N. A.; Beiersdorfer, P.; Caughey, T. A.; Brunner, J.
2014-11-15
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.
On the transition between 2D and 3D dunes JEREMY G. VENDITTI*1
Venditti, Jeremy G.
On the transition between 2D and 3D dunes JEREMY G. VENDITTI*1 , MICHAEL CHURCH* and SEAN J the processes that transform the bed configuration from two-dimensional (2D) dunes to three- dimensional (3D) dunes. A narrowly graded, 500 lm size sand was subjected to a 0Æ15 m deep, non-varying mean flow ranging
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
Procedures for two-dimensional electrophoresis of proteins
Tollaksen, S.L.; Giometti, C.S.
1996-10-01
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.
A detailed two-dimensional stellar population study of M32
C. del Burgo; R. F. Peletier; A. Vazdekis; S. Arribas; E. Mediavilla
2000-09-01
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.
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
2013-01-01
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.
2015-08-03
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. As a result, 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
2015-08-14
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.
One- and two-dimensional simulations of ultra-short-pulse reflectometry
Cohen, B.I.; Kaiser, T.B.; Garrison, J.C.
1997-02-01
Ultra-short-pulse reflectometry is studied by means of the numerical integration of one- and two-dimensional full-wave equations for ordinary and extraordinary modes propagating in a plasma. The numerical calculations illustrate the use of the reflection of ultra-short-pulse microwaves as an effective probe of the density or magnetic profile in the presence of density or magnetic fluctuations in the plasma. Bragg resonance effects can be identified in the reflected signals, which give information on fluctuations. It is also demonstrated that ultra-short-pulse reflectometry can be used to perform correlation reflectometry measurements in which correlation lengths for density fluctuations are deduced from the observed cross-correlation function of phase shifts as a function of frequency. {copyright} {ital 1997 American Institute of Physics.}
One- and two-dimensional simulations of ultra-short-pulse reflectometry
Cohen, B.I.; Kaiser, T.B.; Garrison, J.C.
1997-01-01
Ultra-short-pulse reflectometry is studied by means of the numerical integration of one- and two-dimensional full-wave equations for ordinary and extraordinary modes propagating in a plasma. The numerical calculations illustrate the use of the reflection of ultra-short-pulse microwaves as an effective probe of the density or magnetic profile in the presence of density or magnetic fluctuations in the plasma. Bragg resonance effects can be identified in the reflected signals, which give information on fluctuations. It is also demonstrated that ultra-short-pulse reflectometry can be used to perform correlation reflectometry measurements in which correlation lengths for density fluctuations are deduced from the observed cross-correlation function of phase shifts as a function of frequency. {copyright} {ital 1997 American Institute of Physics.}
Testable Signatures of Quantum Nonlocality in a Two-Dimensional...
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of topological excitations--the odd-winding number vortices--in a spinless 2D chiral p-wave (psub x+ipsub y) superconductor traps Majorana fermion states in the vortex...
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)
2011-03-15
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.
Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases
He, Lianyi; Cao, Gaoqing; Hu, Hui; Liu, Xia-Ji
2015-01-01
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 deter...
Ultrafast Photo-Induced Charge Transfer Unveiled by Two-Dimensional Electronic Spectroscopy
Bixner, Oliver; Mancal, Tomas; Hauer, Juergen; Milota, Franz; Fischer, Michael; Pugliesi, Igor; Bradler, Maximilian; Schmid, Walther; Riedle, Eberhard; Kauffmann, Harald F; Christensson, Niklas
2012-01-01
The interaction of exciton and charge transfer (CT) states plays a central role in photo-induced CT processes in chemistry, biology and physics. In this work, we use a combination of two-dimensional electronic spectroscopy (2D-ES), pump-probe measurements and quantum chemistry to investigate the ultrafast CT dynamics in a lutetium bisphthalocyanine dimer in different oxidation states. It is found that in the anionic form, the combination of strong CT-exciton interaction and electronic asymmetry induced by a counter-ion enables CT between the two macrocycles of the complex on a 30 fs timescale. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra, and we monitor how the excited state charge density ultimately localizes on the macrocycle closest to the counter-ion within 100 fs. A comparison with the dynamics in the radical species further elucidates how CT states modulate the electronic structure and tune fs-reac...
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
2013-09-11
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.
2015-03-03
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
Technical Review of the UNET2D Hydraulic Model
Perkins, William A.; Richmond, Marshall C.
2009-05-18
The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a speci?c 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.
A two-dimensional matrix correction for off-axis portal dose prediction errors
Bailey, Daniel W.; Kumaraswamy, Lalith; Bakhtiari, Mohammad; Podgorsak, Matthew B.
2013-05-15
Purpose: This study presents a follow-up to a modified calibration procedure for portal dosimetry published by Bailey et al. ['An effective correction algorithm for off-axis portal dosimetry errors,' Med. Phys. 36, 4089-4094 (2009)]. A commercial portal dose prediction system exhibits disagreement of up to 15% (calibrated units) between measured and predicted images as off-axis distance increases. The previous modified calibration procedure accounts for these off-axis effects in most regions of the detecting surface, but is limited by the simplistic assumption of radial symmetry. Methods: We find that a two-dimensional (2D) matrix correction, applied to each calibrated image, accounts for off-axis prediction errors in all regions of the detecting surface, including those still problematic after the radial correction is performed. The correction matrix is calculated by quantitative comparison of predicted and measured images that span the entire detecting surface. The correction matrix was verified for dose-linearity, and its effectiveness was verified on a number of test fields. The 2D correction was employed to retrospectively examine 22 off-axis, asymmetric electronic-compensation breast fields, five intensity-modulated brain fields (moderate-high modulation) manipulated for far off-axis delivery, and 29 intensity-modulated clinical fields of varying complexity in the central portion of the detecting surface. Results: Employing the matrix correction to the off-axis test fields and clinical fields, predicted vs measured portal dose agreement improves by up to 15%, producing up to 10% better agreement than the radial correction in some areas of the detecting surface. Gamma evaluation analyses (3 mm, 3% global, 10% dose threshold) of predicted vs measured portal dose images demonstrate pass rate improvement of up to 75% with the matrix correction, producing pass rates that are up to 30% higher than those resulting from the radial correction technique alone. As in the 1D correction case, the 2D algorithm leaves the portal dosimetry process virtually unchanged in the central portion of the detector, and thus these correction algorithms are not needed for centrally located fields of moderate size (at least, in the case of 6 MV beam energy).Conclusion: The 2D correction improves the portal dosimetry results for those fields for which the 1D correction proves insufficient, especially in the inplane, off-axis regions of the detector. This 2D correction neglects the relatively smaller discrepancies that may be caused by backscatter from nonuniform machine components downstream from the detecting layer.
2D microwave imaging reflectometer electronics
Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.
2014-11-15
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.
Spin from defects in two-dimensional quantum field theory
Sebastian Novak; Ingo Runkel
2015-06-24
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
2015-01-01
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.
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)
2012-09-15
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.
Incoherent control and entanglement for two-dimensional coupled systems
R. Romano; D. D'Alessandro
2005-10-03
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.
High speed two-dimensional optical beam position detector
Rutten, Paul Edmond
2011-07-15
Disclosed is the design of a high speed two-dimensional optical beam position detector which outputs the X and Y displacement and total intensity linearly. The experimental detector measures the displacement from DC to 123 MHz and the intensity of an optical spot in a similar way as a conventional quadrant photodiode detector. The design uses four discrete photodiodes and simple dedicated optics for the position decomposition which enables higher spatial accuracy and faster electronic processing than conventional detectors. Measurements of the frequency response and the spatial sensitivity demonstrate high suitability for atomic force microscopy, scanning probe data storage applications, and wideband wavefront sensing. The operation principle allows for position measurements up to 20 GHz and more in bandwidth.
Quantum Emission from Two-Dimensional Black Holes
Steven B. Giddings; W. M. Nelson
2009-11-27
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.
Dynamics of a Two-Dimensional System of Quantum Dipoles
Mazzanti, F.; Astrakharchik, G. E.; Boronat, J.; Zillich, R. E.
2009-03-20
A detailed microscopic analysis of the dynamic structure function S(k,{omega}) of a two-dimensional Bose system of dipoles polarized along the direction perpendicular to the plane is presented and discussed. Starting from ground-state quantities obtained using a quantum diffusion Monte Carlo algorithm, the density-density response is evaluated in the context of the correlated basis functions (CBF) theory. CBF predicts a sharp peak and a multiexcitation component at higher energies produced by the decay of excitations. We discuss the structure of the phonon-roton peak and show that the Feynman and Bogoliubov predictions depart from the CBF result already at low densities. We finally discuss the emergence of a roton in the spectrum, but find the roton energy not low enough to make the system unstable under density fluctuations up to the highest density considered that is close to the freezing point.
Approaches to verification of two-dimensional water quality models
Butkus, S.R. . Water Quality Dept.)
1990-11-01
The verification of a water quality model is the one procedure most needed by decision making evaluating a model predictions, but is often not adequate or done at all. The results of a properly conducted verification provide the decision makers with an estimate of the uncertainty associated with model predictions. Several statistical tests are available for quantifying of the performance of a model. Six methods of verification were evaluated using an application of the BETTER two-dimensional water quality model for Chickamauga reservoir. Model predictions for ten state variables were compared to observed conditions from 1989. Spatial distributions of the verification measures showed the model predictions were generally adequate, except at a few specific locations in the reservoir. The most useful statistics were the mean standard error of the residuals. Quantifiable measures of model performance should be calculated during calibration and verification of future applications of the BETTER model. 25 refs., 5 figs., 7 tabs.
Two-Dimensional Electron Gas in Monolayer InN Quantum Wells....
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Two-Dimensional Electron Gas in Monolayer InN Quantum Wells. Citation Details In-Document Search Title: Two-Dimensional Electron Gas in Monolayer InN Quantum Wells. Abstract not...
Designing and Testing a New Shack-Hartmann High Bandwidth Two-Dimensional Wave front Sensor
Gordeyev, Stanislav
Designing and Testing a New Shack-Hartmann High Bandwidth Two-Dimensional Wave front Sensor Shaddy Dame, Notre Dame, IN 46656 A novel Shack-Hartmann high bandwidth two-dimensional wave front sensor
Entropy and Kinetics of Point-Defects in Two-Dimensional Dipolar Crystals
Wolfgang Lechner; David Polster; Georg Maret; Christoph Dellago; Peter Keim
2015-02-18
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)
2010-10-12
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
2003-12-12
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)
2014-01-13
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.
Unexpected Stable Two-dimensional Silicon Phosphides with Different Stoichiometries
Huang, Bing; Zhuang, Houlong; Yoon, Mina; Wei, Su-Huai; Sumpter, Bobby G
2015-01-01
The discovery of stable two-dimensional, earth-abundant, semiconducting materials is of great interest and may impact future electronic technologies. By combining global structural prediction and first-principles calculations, we have theoretically discovered several previously unknown semiconducting silicon phosphides (SixPy) monolayers, which could be formed stably at the stoichiometries of y/x1. Unexpectedly, some of these compounds, i.e., P-6m2 Si1P1 and Pm Si1P2, have comparable or even lower formation enthalpies than their previously known bulk allotropes. The band gaps (Eg) of SixPy compounds can be dramatically tuned in an extremely wide range (0< Eg < 3 eV) by simply changing the number of layers or applying an in-plane strain. Moreover, we find that carrier doping can drive the ground state of C2/m Si1P3 from a nonmagnetic state into a robust half-metallic spin-polarized state, originating from its unique valence band structure, which can extend the use of Si-related compounds for spintronics.
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)
2014-07-15
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.
2001-05-01
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)
2008-07-15
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
1995-03-27
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 photochemical model of the troposphere. Master's thesis
Carlson, M.W.
1990-01-01
An experiment using a time-dependent, two-dimensional photochemical model of the troposphere to model the vertical and zonal distribution of ozone and its precursors is presented. The experiment examines two cases. Case I simulates vertical transport due to diffusion and zonal transport due to advection, with surface emissions of ozone precursors in the center of the model domain representing an urban environment with light wind conditions favorable for the formation of ozone in concentrations greater than 80 parts per billion by volume (ppbv). In Case II, an elevated source of ozone and its precursors is introduced at the upstream boundary in order to investigate the role of advection of these chemical species on ozone concentrations. the first simulation produces surface ozone concentrations greater than 120 ppbv in the air above the urban area, and the second simulation produces an increase of 3 - 10 percent in this region. A comparison of Case I and Case II results shows that enhanced photochemical production of ozone due to the addition of ozone's precursors play an important role in this increase.
Optical properties of two-dimensional metamaterial photonic crystals
Mejía-Salazar, J. R.
2013-12-14
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.
Two-dimensional simulations of pulsational pair-instability supernovae
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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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.Theory of rare Kaon and(Conference) | SciTech(2D-CARS): simultaneous planar
Tamoghna Das; T. Lookman; M. M. Bandi
2015-05-21
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
2015-06-29
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.
Perlekar, Prasad; Pandit, Rahul
2015-01-01
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, o...
Two-dimensional N=(2,2) super Yang-Mills theory on computer
Hiroshi Suzuki
2007-09-05
We carry out preliminary numerical study of Sugino's lattice formulation \\cite{Sugino:2004qd,Sugino:2004qdf} of the two-dimensional $\\mathcal{N}=(2,2)$ super Yang-Mills theory (2d $\\mathcal{N}=(2,2)$ SYM) with the gauge group $\\SU(2)$. The effect of dynamical fermions is included by re-weighting a quenched ensemble by the pfaffian factor. It appears that the complex phase of the pfaffian due to lattice artifacts and flat directions of the classical potential are not problematic in Monte Carlo simulation. Various one-point supersymmetric Ward-Takahashi (WT) identities are examined for lattice spacings up to $a=0.5/g$ with the fixed physical lattice size $L=4.0/g$, where $g$ denotes the gauge coupling constant in two dimensions. WT identities implied by an exact fermionic symmetry of the formulation are confirmed in fair accuracy and, for most of these identities, the quantum effect of dynamical fermions is clearly observed. For WT identities expected only in the continuum limit, the results seem to be consistent with the behavior expected from supersymmetry, although we do not see clear distintion from the quenched simulation. We measure also the expectation values of renormalized gauge-invariant bi-linear operators of scalar fields.
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)
2007-07-15
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.
Optical Properties and Wave Propagation in Semiconductor-Based Two-Dimensional Photonic Crystals
Mario Agio
2002-12-31
This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group. The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected to model a photonic-crystal combiner for an integrated multi-wavelength-source laser.
Rice, Daniel
2009-01-12
acquired in 2001 across an active subsidence feature. Seismic reflection data were acquired in both 2001 and 2008 across an active sinkhole at the intersection of U.S. Highway 50 and Victory Road in Hutchinson, KS as part of a comprehensive study...
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
Results from laboratory tests of the two-dimensional Time-Encoded Imaging System.
Marleau, Peter; Brennan, James S.; Brubaker, Erik; Gerling, Mark D; Le Galloudec, Nathalie Joelle
2014-09-01
A series of laboratory experiments were undertaken to demonstrate the feasibility of two dimensional time-encoded imaging. A prototype two-dimensional time encoded imaging system was designed and constructed. Results from imaging measurements of single and multiple point sources as well as extended source distributions are presented. Time encoded imaging has proven to be a simple method for achieving high resolution two-dimensional imaging with potential to be used in future arms control and treaty verification applications.
A characterization of causal automorphisms on two-dimensional Minkowski spacetime
Do-Hyung Kim
2013-04-08
It is shown that causal automorphisms on two-dimensional Minkowski spacetime can be characterized by the invariance of the wave equations.
Signatures of the protein folding pathway in two-dimensional ultraviolet spectroscopy
Jiang, J; Jiang, J; Lai, Z; Wang, J; Wang, J; Mukamel, S
2014-01-01
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
Amoudache, Samira; Pennec, Yan Djafari Rouhani, Bahram; Khater, Antoine; Lucklum, Ralf; Tigrine, Rachid
2014-04-07
We theoretically investigate the potentiality of dual phononic-photonic (the so-called phoxonic) crystals for liquid sensing applications. We study the transmission through a two-dimensional (2D) crystal made of infinite cylindrical holes in a silicon substrate, where one row of holes oriented perpendicular to the propagation direction is filled with a liquid. The infiltrated holes may have a different radius than the regular holes. We show, in the defect structure, the existence of well-defined features (peaks or dips) in the transmission spectra of acoustic and optical waves and estimate their sensitivity to the sound and light velocity of the analyte. Some of the geometrical requirements behave in opposite directions when searching for an efficient sensing of either sound or light velocities. Hence, a compromise in the choice of the parameters may become necessary in making the phoxonic sensor.
Magnetoconductivity of two-dimensional electrons on liquid helium: Experiments in the fluid phase
Fang-Yen, Christopher
Magnetoconductivity of two-dimensional electrons on liquid helium: Experiments in the fluid phase M of Electronics and Computer Science, University of Southampton, SO17 1BJ, England Received 16 May 1996; revised manuscript received 25 November 1996 The magnetoconductivity (B) of two-dimensional electrons on liquid
Flow transitions in two-dimensional foams Christopher Gilbreth, Scott Sullivan, and Michael Dennin
Dennin, Michael
Flow transitions in two-dimensional foams Christopher Gilbreth, Scott Sullivan, and Michael Dennin: November 21, 2006) For sufficiently slow rates of strain, flowing foam can exhibit inhomogeneous flows. The nature of these flows is an area of active study in both two-dimensional model foams and three
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
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
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
Energy localization and transport in two-dimensional electrical L.Q. English1
Carretero, Ricardo
Energy localization and transport in two-dimensional electrical lattices L.Q. English1 , F. Palmero and characterized in two-dimensional nonlinear electrical lattices which were driven by a spatially-uniform voltage-dimensional, damped-driven electrical lattices (see also Ref. [12]). We characterize these breather states
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
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)
2002-07-01
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
2014-01-01
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.
KIVA: a comprehensive model for 2D and 3D engine simulations
Amsden, A.A.; Butler, T.D.; O'Rourke, P.J.; Ramshaw, J.D.
1985-01-01
This paper summarizes a comprehensive numerical model that represents the spray dynamics, fluid flow, species transport, mixing, chemical reactions, and accompanying heat release that occur inside the cylinder of an internal combustion engine. The model is embodied in the KIVA computer code. The code calculates both two-dimensional (2D) and three-dimensional (3D) situations. It is an outgrowth of the earlier 2D CONCHAS-SPRAY computer program. Sample numerical calculations are presented to indicate the level of detail that is available from these simulations. These calculations are for a direct injection stratified charge engine with swirl. Both a 2D and a 3D example are shown.
2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe
Chen, Y. H.; Yang, X. Y.; Lin, C. E-mail: cjxiao@pku.edu.cn; Wang, X. G.; Xiao, C. J. E-mail: cjxiao@pku.edu.cn; Wang, L.; Xu, M.
2014-11-15
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
1994-07-01
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.
Exact solutions of a two-dimensional Kemmer oscillator in the gravitational field of cosmic string
Nadjette. Messai; Abdelmalek. Boumali
2015-04-21
The two dimensional Kemmer oscillator under the influence of the gravitational field produced by a topology such as the cosmic string spacetime and in the presence of a uniform magnetic field as well as without magnetic field are investigated.
Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs
Harris, C. Thomas (Charles Thomas)
2010-01-01
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 ...
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
Diagnosing Chaos Using Four-Point Functions in Two-Dimensional Conformal Field Theory
Stanford, Douglas
We study chaotic dynamics in two-dimensional conformal field theory through out-of-time-order thermal correlators of the form ?W(t)VW(t)V?. We reproduce holographic calculations similar to those of Shenker and Stanford, ...
An experimental study of unsteady separation in a two-dimensional flow
Coral Pinto, Raul Javier
2005-01-01
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. ...
Traveling Wave Solutions for Systems of ODEs on a Two-Dimensional Spatial Lattice
Van Vleck, Erik; Mallet-Paret, John; Cahn, John W.
1999-03-05
We consider infinite systems of ODEs on the two-dimensional integer lattice, given by a bistable scalar ODE at each point, with a nearest neighbor coupling between lattice points. For a class of ideal nonlinearities, we ...
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 ...
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
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
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, a hyper elastic formulation was considered by Weber and Anand 3]. In this work, the elasticity is modelled
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
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
Long-wavelength anomalous diffusion mode in the two-dimensional XY dipole magnet
Abanov, Artem; Kashuba, A.; Pokrovsky, Valery L.
1997-01-01
In a two-dimensional XY ferromagnet the dipole force induces a strong interaction between spin waves in the long-wavelength limit. The major effect of this interaction is the transformation of a propagating spin wave into ...
Two dimensional electron transport in modulation-doped In{sub...
Office of Scientific and Technical Information (OSTI)
Two dimensional electron transport in modulation-doped Insub 0.53Gasub 0.47AsAlAssub 0.56Sbsub 0.44 ultrathin quantum wells Citation Details In-Document Search Title: Two...
Modeling of acoustic wave scattering from a two-dimensional fracture
Wang, Ping
2010-01-01
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. Jha, Prafulla K.
2014-04-24
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.
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
2015-01-01
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; 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; Xiao, Kai; Yoon, Mina; Geohegan, David B
2015-01-01
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.
Correlational properties of two-dimensional solvable chaos on the unit circle
Aki-Hiro Sato; Ken Umeno
2012-08-30
This article investigates correlational properties of two-dimensional chaotic maps on the unit circle. We give analytical forms of higher-order covariances. We derive the characteristic function of their simultaneous and lagged ergodic densities. We found that these characteristic functions are described by three types of two-dimensional Bessel functions. Higher-order covariances between x and y and those between y and y show non-positive values. Asymmetric features between cosine and sine functions are elucidated.
Development and validation of a vertically two-dimensional mesoscale numerical model
Walters, Michael Kent
1985-01-01
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
2005-09-27
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.
TOPAZ2D heat transfer code users manual and thermal property data base
Shapiro, A.B.; Edwards, A.L.
1990-05-01
TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependent boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available. The material thermal property data base, Chapter 4, included in this manual was originally published in 1969 by Art Edwards for use with his TRUMP finite difference heat transfer code. The format of the data has been altered to be compatible with TOPAZ2D. Bob Bailey is responsible for adding the high explosive thermal property data.
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.
2012-02-03
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
Chang, W.Z.; Kley, E.B.; Fuchs, H.J.; Schnabel, B.; Foerster, E.; Chukhovskii, F.N.
1995-12-31
Theoretical investigations for obtaining x-ray point focusing by using crystals with two-dimensionally modulated surfaces are carried out. Based on the Bragg and Fresnel diffraction principles, formulae of modulated surfaces (structures) are derived for both flat and bent crystals for focusing x-rays to micron or submicron size. It is found that elliptically-shaped and linearly modulated structures are suitable for flat and cylindrically bent crystals, respectively. For the given Ti K{alpha} radiation and geometric parameters, Si(111) and InSb(111) reflections are used for the calculations of flat and bent crystals in terms of their focus characteristics, namely the focusing efficiency and the focus width. The influence of the distribution of the Bragg amplitude on flat and bent crystals is also discussed.
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)
2014-02-07
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.
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)
2014-05-28
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.
Ensemble Kalman filter based state estimation in 2D shallow water equations using Lagrangian method for two- dimensional shallow water equations in rivers using Lagrangian drifter positions of the state of the river. This information is incorporated into shallow water equations by using Ensemble
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
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
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 80f3a9f1-e224-4a02-951b-229cd8e273fd...
AdS solutions to the 2D type 0A effective action David Mattoon Thompson*
Romps, David M.
AdS solutions to the 2D type 0A effective action David Mattoon Thompson* Jefferson Physical November 2004) We present a two-parameter family of AdS solutions to the two-dimensional type 0A effective action. DOI: 10.1103/PhysRevD.70.106001 PACS numbers: 11.25.Mj I. INTRODUCTION AdS backgrounds of string
Huang, J Q; Wu, C F; Zhang, J W; Feng, Y Y; Wang, L J
2015-01-01
We report our studies on an intense source of cold cesium atoms based on a two-dimensional magneto-optical trap with independent axial cooling and pushing. The new-designed source, proposed as 2D-HP MOT, uses hollow laser beams for axial cooling and a thin pushing laser beam for cold atomic beam extraction. Regulated independently by the pushing beam, the atomic flux can be substantially optimized. The atomic flux maximum obtained in the 2D-HP MOT is $4.02\\times 10^{10}$ atoms/s, increased by 60 percent compared to the traditional 2D$^+$ MOT in our experiment. Moreover, with the pushing power 10 $\\mu$W and detuning $0\\Gamma$, the 2D-HP MOT can generate a rather intense cold cesium atomic beam with the concomitant light shift suppressed by 20 times in magnitude. The axial velocity distribution of the cold cesium beams centers at 6.8 m/s with a FMHW of about 2.8 m/s. The dependences of the atomic flux on the pushing power and detuning are studied. The experimental results are in good agreement with the theoreti...
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
2015-07-22
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
Van der Waals epitaxial growth of two-dimensional single-crystalline GaSe domains 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
2015-07-22
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
Two-dimensional electron gas in monolayer InN quantum wells
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Pan, Wei; Dimakis, Emmanouil; Wang, George T.; Moustakas, Theodore D.; Tsui, Daniel C.
2014-11-24
We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in monolayer InN quantum wells embedded in GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5×1015 cm-2 and 420 cm2 /Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES.
Quantum Monte Carlo simulation of a two-dimensional Bose gas
Pilati, S.; Boronat, J.; Casulleras, J.; Giorgini, S.
2005-02-01
The equation of state of a homogeneous two-dimensional Bose gas is calculated using quantum Monte Carlo methods. The low-density universal behavior is investigated using different interatomic model potentials, both finite ranged and strictly repulsive and zero ranged, supporting a bound state. The condensate fraction and the pair distribution function are calculated as a function of the gas parameter, ranging from the dilute to the strongly correlated regime. In the case of the zero-range pseudopotential we discuss the stability of the gaslike state for large values of the two-dimensional scattering length, and we calculate the critical density where the system becomes unstable against cluster formation.
Schiek, Richard (Albuquerque, NM)
2006-06-20
A method of generating two-dimensional masks from a three-dimensional model comprises providing a three-dimensional model representing a micro-electro-mechanical structure for manufacture and a description of process mask requirements, reducing the three-dimensional model to a topological description of unique cross sections, and selecting candidate masks from the unique cross sections and the cross section topology. The method further can comprise reconciling the candidate masks based on the process mask requirements description to produce two-dimensional process masks.
Yuan, Long; Yang, Jinlong
2012-01-01
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.
Jiang, F.-J.; Wiese, U.-J.
2011-04-15
The two-dimensional (2D) spin-(1/2) Heisenberg antiferromagnet with exchange coupling J is investigated on a periodic square lattice of spacing a at very small temperatures using the loop-cluster algorithm. Monte Carlo data for the staggered and uniform susceptibilities are compared with analytic results obtained in the systematic low-energy effective field theory for the staggered magnetization order parameter. The low-energy parameters of the effective theory, i.e., the staggered magnetization density M{sub s}=0.307 43(1)/a{sup 2}, the spin stiffness {rho}{sub s}=0.180 81(11)J, and the spin wave velocity c=1.6586(3)Ja, are determined with very high precision. Our study may serve as a test case for the comparison of lattice quantum chromodynamics Monte Carlo data with analytic predictions of the chiral effective theory for pions and nucleons, which is vital for the quantitative understanding of the strong interaction at low energies.
E. Brezin; S. Hikami
1992-04-08
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.
Ahmed, Zeeshan
2010-01-01
Designing and developing quality based computer game is always a challenging task for developers. In this paper I briefly discuss aero fighting war game based on simple 2D gaming concepts and developed in C & C++ programming languages, using old bitmapping concepts. Going into the details of the game development, I discuss the designed strategies, flow of game and implemented prototype version of game, especially for beginners of game programming.
Symmetry operators for Dirac's equation on two-dimensional spin manifolds
Lorenzo Fatibene; Raymond G. McLenaghan; Giovanni Rastelli; Shane N. Smith
2008-12-17
It is shown that the second order symmetry operators for the Dirac equation on a general two-dimensional spin manifold may be expressed in terms of Killing vectors and valence two Killing tensors. The role of these operators in the theory of separation of variables for the Dirac equation is studied.
Gravity Effects on Steady Two-Dimensional Partially Premixed MethaneAir Flames
Aggarwal, Suresh K.
Gravity Effects on Steady Two-Dimensional Partially Premixed MethaneAir Flames ZHUANG SHU, CHUN W, University of Illinois at Chicago, Chicago, IL 60607-7022 Under normal-gravity conditions the flame heat is only weakly affected by gravity, the outer flame shows significant spatial differences for the two
Soljaèiæ, 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
Cut-wire-pair structures as two-dimensional magnetic metamaterials
Cut-wire-pair structures as two-dimensional magnetic metamaterials David A. Powell, Ilya V-dimensional metamaterial suitable for scaling to optical frequencies. We fabricate the cut-wire metamaterial operating. © 2008 Optical Society of America OCIS codes: (160.3918) Metamaterials; (350.4010) Microwaves References
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
PennyPacking and TwoDimensional Codes * R. L. Graham and N. J. A. Sloane
Sloane, Neil J. A.
design, when the points P 1 , . . . , P n form a twodimensional code [3], [4], [7], U measures of the best packings known for n £ 500. For large n, U ~ Ö``3 n 2 / (4p). _______________ * This appeared diameter d, let P 1 , . . . , P n be their centers and P __ = n - 1 S P i their centroid. Then the problem
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.
2005-01-01
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...
Two-dimensional Gibbsian point processes with continuous spin-symmetries
Thomas Richthammer
2004-07-13
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
1998-12-21
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.
Two-dimensional Thermomechanical Analysis and Optimization of Functionally Graded Materials
Vel, Senthil
Two-dimensional Thermomechanical Analysis and Optimization of Functionally Graded Materials Andrew optimization of heat resisting metal/ceramic functionally graded materials (FGMs). The plane stress static thermoelastic behavior of a FGM is analyzed using the element-free Galerkin method. The effective material
Vel, Senthil
Two-dimensional optimization of material composition of functionally graded materials using-dimensional simulation and optimization of material distribution of functionally graded materials for thermomechanical to optimize the material composition for two model problems. In the first problem, we minimize the peak
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
Two-dimensional high-bandwidth Shack-Hartmann wavefront sensor
Gordeyev, Stanislav
Two-dimensional high-bandwidth Shack-Hartmann wavefront sensor: design guidelines and evaluation-dimensional high-bandwidth Shack-Hartmann wavefront sensor was designed and tested, addressing the high tempo- ral Engineers. DOI: 10.1117/1.3454383 Subject terms: aero-optics; Shack-Hartmann; wavefront sensor; adaptive
Two dimensional silicon nanowalls for lithium ion Jiayu Wan,a
Li, Teng
batteries are one of the most important electrochemical energy storage devices and are widely usedTwo dimensional silicon nanowalls for lithium ion batteries Jiayu Wan,a Alex F. Kaplan,b Jia Zheng with silicon for Li-ion batteries. Excellent performance for the first Coulombic efficiency (CE) has been
Patterning Proteins and Cells Using Two-Dimensional Arrays of Colloids
Aksay, Ilhan A.
Patterning Proteins and Cells Using Two-Dimensional Arrays of Colloids Nathaniel J. Gleason with proteins are deposited onto coverslips coated with gold using a combination of gravitational settling of particles on the substrate. Surface coverage ranged from an essentially continuous coating of protein
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
Passive tracer patchiness and particle trajectory stability in incompressible two-dimensional flows
Olascoaga, Maria Josefina
Passive tracer patchiness and particle trajectory stability in incompressible two-dimensional flows in Geophysics (2003) 1:18 Nonlinear Processes in Geophysics c European Geophysical Society 2003 Passive tracer." This leads to patchiness in the evolution of passive tracer distribu- tions. Also, it is argued
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
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
Numerical Studies of Collective Phenomena in Two-Dimensional Electron and Cold Atom Systems
Rezayi, Edward
2013-07-25
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.
Fifth-order electronically non-resonant Raman scattering: two-dimensional Fourier deconvolution
Kaufman, Laura
Fifth-order electronically non-resonant Raman scattering: two-dimensional Fourier deconvolution information on the direct ®fth-order nuclear response as well as the hyper- polarizability responses can-resonant Raman scattering is one of the new multi-dimensional spectroscopic techniques that oers information
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
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
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, João 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
The critical velocity for vortex existence in a two dimensional rotating Bose-Einstein condensate
Ignat, Radu
The critical velocity for vortex existence in a two dimensional rotating Bose-Einstein condensate-Einstein condensate. It consists in minimizing a Gross-Pitaevskii functional defined in R2 under the unit mass constraint. We estimate the critical rotational speed 1 for vortex existence in the bulk of the condensate
Electrostatic Structures in Space Plasmas: Properties of Two-dimensional Magnetic
Ng, Chung-Sang
Electrostatic Structures in Space Plasmas: Properties of Two-dimensional Magnetic Bernstein-Greene without background B #12;Electron dynamics with uniform ion background #12;Solutions with only energy, it actually has less total energy than that of a Maxwellian plasma. Difference in total energy between
Ng, Chung-Sang
Electrostatic Structures in Space Plasmas: Properties of Two-dimensional Magnetic Bernstein-Greene theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes of their properties, including its energy content, temperature and velocity distribution, and stability. This work
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
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
Huang, Huaxiong
Stability Analysis of the Immersed Boundary Method for a Two-dimensional Membrane with Bending Rigidity Zhaoxin Gong1 , Huaxiong Huang1,2 and Chuanjing Lu1 Abstract: In this paper, we analyse with bending rigidity. The smoothed version, using a standard regularization technique for the singular force
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
Investigation of transient, two-dimensional coupled heat and moisture flow in soils
Shen, L.S.W.
1986-01-01
A two-dimensional finite difference numerical model has been developed to study coupled heat and moisture flow in the soil surrounding an earth-sheltered construction. The model is based on a mechanistic approach formulated by Milly and developed from the work of Philip and deVries. Using soil temperatures and matric potentials as the dependent variables, the model is capable of simulating unsaturated/saturated flow conditions in heterogeneous soil domains. The model is a fully implicit, integrated finite difference approach based on the Patankar Spalding method. The numerical modeling of the governing heat and moisture equations was validated against a number of analytical and quasi-analytical solutions. An axisymmetric, two-dimensional experiment was then defined to which the numerical model could be compared. The experimental apparatus was composed of a cylinder filled with a dredged Mississippi River sand. A series of one and two dimensional heat and moisture flow experiments were run, using boundary conditions consistent with those that occur in the soil surrounding a building. Soil properties used in the model were either calculated from theoretical models or measured experimentally. Agreement between the model and experiments were good, with an error of 10-15% obtained for the two-dimensional coupled heat and moisture flow experiment.
The stability of a two-dimensional vorticity filament under uniform strain
Wirosoetisno, Djoko
The stability of a two-dimensional vorticity filament under uniform strain Article Published-dimensional vorticity filament under uniform strain. Journal of Fluid Mechanics, 230 (1). pp. 647-665. ISSN 0022-dimensional vorticity filament under uniform strain By D. G. DRITSCHEL, P.H. HAYNES, M. N. JUCKES? AND T. G. SHEPHERDS
Fractures in heterogeneous two-dimensional systems Antonio Politi1,2,
Politi, Antonio
Fractures in heterogeneous two-dimensional systems Antonio Politi1,2, * and Maria Zei2,3,4, 1 disorder is used as a testing ground for fracture behavior in heterogeneous materials in strain and different breaking thresholds. We study the strain range where the fracture progressively develops from
BATTRI: A TWO-DIMENSIONAL BATHYMETRY BASED UNSTRUCTURED TRIANGULAR GRID GENERATOR
of Delaunay unstructured triangular grid refinement algorithms, including the recent "off-centers" method Delaunay scheme, called "off-centers" [10], on reducing the number of grid nodes without sacrificingBATTRI: A TWO-DIMENSIONAL BATHYMETRY BASED UNSTRUCTURED TRIANGULAR GRID GENERATOR FOR FINITE
38 | OPN December 2006 www.osa-opn.org Molding Light in Two-Dimensional
38 | OPN December 2006 www.osa-opn.org Molding Light in Two-Dimensional Photonic Lattices Robert, these approaches may only allow limited flexibility in the light molding and rout- ing that is inherently state selects itself the propagation direction in defect-free periodic struc- tures. The symmetry
Transformation Property of the Caputo Fractional Differential Operator in Two Dimensional Space
Ehab Malkawi
2013-05-06
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.
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
Two dimensional representation of the Dirac equation in Non associative algebra
S. Hamieh; H. Abbas
2011-04-18
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.
A Two-Dimensional Model of Chemical Vapor Infiltration With Radio Frequency Heating
Economou, Demetre J.
by a finite element method to study carbon chemical vapor infiltration in a cylindrical carbon preformA Two-Dimensional Model of Chemical Vapor Infiltration With Radio Frequency Heating Vikas Midha studied. The power density distribution in the pre- form evolves in a complex manner as densified regions
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
Three-dimensional and two-dimensional deployment analysis for underwater acoustic sensor networks q
Pompili, Dario
Three-dimensional and two-dimensional deployment analysis for underwater acoustic sensor networks q t i c l e i n f o Article history: Received 8 October 2007 Received in revised form 11 February 2008 Accepted 23 July 2008 Available online 7 August 2008 Keywords: Underwater acoustic sensor networks
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
2015-05-07
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
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
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 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
Two dimensional thermoelectric platforms for thermocapillary droplet Man-Chi Liu,ac
Lin, Pei-Chun
Two dimensional thermoelectric platforms for thermocapillary droplet actuation Man-Chi Liu,ac Jin the cooling function relies on the natural conduction and/or convection. A thermoelectric (TE) chip a novel approach utilizing a 5 6 5 array of thermoelectric (TE) chips. The advantage of using TE chips
Stable Segmentation of 2D Curves
Fitzgibbon, Andrew WJ
This thesis deals with the specific subproblem of converting sequences of two-dimensional data points into higher level descriptions in terms of curved shape primitives. This is an important member of the wider family ...
Takanobu Amano; Masahiro Hoshino
2008-09-02
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.
ARM - Datastreams - sonicwind2d
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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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Comments? We wouldDatastreamsnoaaradbrwDatastreamssonicwind2d Documentation Data Quality Plots ARM Data Discovery
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)
1998-01-01
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.
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
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.
2011-01-01
-coupled 2D electron and hole gases, which are promising candidates for semiconductor spintronics,1 (ii) graphene2 (a monolayer of carbon atoms arranged in a 2D honeycomb lattice), which has attracted a great deal of interest because of the massless...
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)
2011-12-26
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.
Spin-orbit interaction controlled properties of two-dimensional superlattices: Spintronic crystals
Peter Foldi; Viktor Szaszko-Bogar; F. M. Peeters
2015-03-03
The band structure of two-dimensional artificial superlattices in the presence of (Rashba-type) spin-orbit interaction (SOI) is presented. The position and shape of the energy bands in these spintronic crystals depend on the geometry as well as the strength of the SOI, which can be tuned by external gate voltages. For finite mesoscopic arrays we show that their conductance properties can be understood from these spin-dependent band diagrams.
Cybart, Shane A. Dynes, R. C.; Wong, T. J.; Cho, E. Y.; Beeman, J. W.; Yung, C. S.; Moeckly, B. H.
2014-05-05
Magnetic field sensors based on two-dimensional arrays of superconducting quantum interference devices were constructed from magnesium diboride thin films. Each array contained over 30?000 Josephson junctions fabricated by ion damage of 30?nm weak links through an implant mask defined by nano-lithography. Current-biased devices exhibited very large voltage modulation as a function of magnetic field, with amplitudes as high as 8?mV.
Inverse fixed energy scattering problem for the two-dimensional nonlinear Schroedinger operator
Georgios Fotopoulos; Valery Serov
2014-12-01
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.
Instantons and the fixed point topological charge in the two-dimensional O(3) {sigma} model
Blatter, M.; Burkhalter, R.; Hasenfratz, P.; Niedermayer, F.
1996-01-01
We define a fixed point topological charge for the two-dimensional O(3) lattice {sigma} model which is free of topological defects. We use this operator in combination with the fixed point action to measure the topological susceptibility for a wide range of correlation lengths. The results strongly suggest that it is not a physical quantity in this model. The procedure, however, can be applied to other asymptotically free theories as well. {copyright} {ital 1996 The American Physical Society.}
Transparent Conducting Electrodes based on 1D and 2D Ag Nanogratings for Organic Photovoltaics
Zeng, Beibei; Bartoli, Filbert J
2014-01-01
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
2011-08-09
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.
Magnetohydrodynamic waves in two-dimensional prominences embedded in coronal arcades
Terradas, J.; Soler, R.; Díaz, A. J.; Oliver, R.; Ballester, J. L.
2013-11-20
Solar prominence models used so far in the analysis of MHD waves in two-dimensional structures are quite elementary. In this work, we calculate numerically magnetohydrostatic models in two-dimensional configurations under the presence of gravity. Our interest is in models that connect the magnetic field to the photosphere and include an overlying arcade. The method used here is based on a relaxation process and requires solving the time-dependent nonlinear ideal MHD equations. Once a prominence model is obtained, we investigate the properties of MHD waves superimposed on the structure. We concentrate on motions purely two-dimensional, neglecting propagation in the ignorable direction. We demonstrate how, by using different numerical tools, we can determine the period of oscillation of stable waves. We find that vertical oscillations, linked to fast MHD waves, are always stable and have periods in the 4-10 minute range. Longitudinal oscillations, related to slow magnetoacoustic-gravity waves, have longer periods in the range of 28-40 minutes. These longitudinal oscillations are strongly influenced by the gravity force and become unstable for short magnetic arcades.
Remarks on the two-dimensional power correction in the soft wall model
Tao Huang; Fen Zuo
2009-09-15
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.
Preliminary results for a two-dimensional simulation of the working process of a Stirling engine
Makhkamov, K.K.; Ingham, D.B.
1998-07-01
Stirling engines have several potential advantages over existing types of engines, in particular they can use renewable energy sources for power production and their performance meets the demands on the environmental security. In order to design Stirling Engines properly, and to put into effect their potential performance, it is important to more accurately mathematically simulate its working process. At present, a series of very important mathematical models are used for describing the working process of Stirling Engines and these are, in general, classified as models of three levels. All the models consider one-dimensional schemes for the engine and assume a uniform fluid velocity, temperature and pressure profiles at each plane of the internal gas circuit of the engine. The use of two-dimensional CFD models can significantly extend the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes which occur in the internal gas circuit, as well as in the external circuit of the engine. In this paper a two-dimensional simplified frame (no construction walls) calculation scheme for the Stirling Engine has been assumed and the standard {kappa}-{var{underscore}epsilon} turbulence model has been used for the analysis of the engine working process. The results obtained show that the use of two-dimensional CFD models gives the possibility of gaining a much greater insight into the fluid flow and heat transfer processes which occur in Stirling Engines.
Two-dimensional numerical model of underground oil-shale retorting
Travis, B.J.; Hommert, P.J.; Tyner, C.E.
1983-01-01
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.
Ludwig-Maximilians-Universität, München
Relaxation of hot electrons in a degenerate two-dimensional electron system: transition to one, 2011) The energy relaxation channels of hot electrons far from thermal equilibrium in a degenerate two-dimensional electron system are investigated in transport experiments in a mesoscopic three- terminal device. We
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
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
Lapeyre, Guillaume
Comment on ``Finding finite-time invariant manifolds in two-dimensional velocity fields'' Chaos 10 for transport and mixing in periodic and aperi- odic flows. For aperiodic two-dimensional flows, several the hyperbolic point. He further claims that this is generally sufficient to accurately identify the hyper- bolic
On the boundary conditions for EG-methods applied to the two-dimensional wave equation system
On the boundary conditions for EG-methods applied to the two-dimensional wave equation system M Galerkin methods (EG) which are applied for the two-dimensional wave equation system. Di#11;erent known of hyperbolic equations, see, e.g. Grote and Keller [5, 6, 7], En- gquist and Majda [3], Higdon [9], Thompson
Two-dimensional model problem to explain counter-rotating vortex pair formation in a transverse jet
Mahesh, Krishnan
Two-dimensional model problem to explain counter-rotating vortex pair formation in a transverse jet A two-dimensional model problem is used to study the evolution of the cross section of a transverse jet and the counter-rotating vortex pair CVP . The solution to the model problem shows deformation of the jet similar
Fofang, Nicholas Ndeh
1996-01-01
ProMAX 2D, a software for the interactive and batch processing of two dimensional seismic data, was used to process approximately 25 km of seismic data from line FFI-161 of the Brazos-Galveston area of the Gulf of Mexico. ...
TWO-DIMENSIONAL CORE-COLLAPSE SUPERNOVA MODELS WITH MULTI-DIMENSIONAL...
Office of Scientific and Technical Information (OSTI)
diffusion (MGFLD) neutrino transport, including all relevant O(vc) terms. Our main motivation for carrying out this study is to compare with recent 2D models produced by other...
Twisted conformal symmetry in noncommutative two-dimensional quantum field theory
Lizzi, Fedele; Vitale, Patrizia; Vaidya, Sachindeo
2006-06-15
By twisting the commutation relations between creation and annihilation operators, we show that quantum conformal invariance can be implemented in the 2-d Moyal plane. This is an explicit realization of an infinite dimensional symmetry as a quantum algebra.
Goldberg, L.F.
1990-08-01
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.
Current Statistics for Quantum Transport through Two-Dimensional Open Chaotic Billiards
Alexander I. Saichev; Hiromu Ishio; Almas F. Sadreev; Karl-Fredrik Berggren
2001-11-03
The probability current statistics of two-dimensional open chaotic ballistic billiards is studied both analytically and numerically. Assuming that the real and imaginary parts of the scattering wave function are both random Gaussian fields, we find a universal distribution function for the probability current. In by-passing we recover previous analytic forms for wave function statistics. The expressions bridge the entire region from GOE to GUE type statistics. Our analytic expressions are verified numerically by explicit quantum-mechanical calculations of transport through a Bunimovich billiard.
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)
2014-10-13
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.
On the Classical Solutions of Two Dimensional Inviscid Rotating Shallow Water System
Bin Cheng; Chunjing Xie
2009-07-01
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.
The Energy Eigenvalues of the Two Dimensional Hydrogen Atom in a Magnetic Field
Soylu, A; Boztosun, I
2006-01-01
In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the no magnetic field case analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for $n=2-10$ and $m=0-1$ states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.
The Energy Eigenvalues of the Two Dimensional Hydrogen Atom in a Magnetic Field
A. Soylu; O. Bayrak; I. Boztosun
2007-03-13
In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the no magnetic field case analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for $n=2-10$ and $m=0-1$ states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.
Jain, Piyush; Cinti, Fabio; Boninsegni, Massimo [Department of Physics, University of Alberta, Edmonton, Alberta (Canada)
2011-07-01
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.
Kondagunta, Veeraraghava Gopal
1993-01-01
and continuity[7]. The model is still two-dimensional and the actual three-dimension- al cross-sectional shape of the fiber bundles was not considered. The fiber undulation model could analyze the knee behavior in plain-weave composites. Ishikawa and Chou [7... is discussed. 23 III. 2 Micromechanics model for calculating fiber tow properties One of the most basic problems in the analysis of the behavior of composite materials is the prediction of effective or average macroscopic properties in terms...
Vacuum Instability in Chern-Simons Theory, Null Vectors and Two-Dimensional Logarithmic Operators
Ian I. Kogan; Alex Lewis
1998-03-13
A new relation between two-dimensional conformal field theories and three-dimensional topologically massive gauge theories is found, where the dynamical nature of the 3d theory is ultimately important. It is shown that the those primary states in CFT which have non-unitary descendants correspond in the 3d theory to supercritical charges and cause vacuum instability. It is also shown that logarithmic operators separating the unitary sector from a non-unitary one correspond to an exact zero energy ground state in which case the 3d Hamiltonian naturally has a Jordan structure.
One- and two-dimensional nuclear magnetic resonance spectroscopy with a diamond quantum sensor
J. M. Boss; K. Chang; J. Armijo; K. Cujia; T. Rosskopf; J. R. Maze; C. L. Degen
2015-12-10
We report on Fourier spectroscopy experiments performed with near-surface nitrogen-vacancy centers in a diamond chip. By detecting the free precession of nuclear spins rather than applying a multipulse quantum sensing protocol, we are able to unambiguously identify the NMR species devoid of harmonics. We further show that by engineering different Hamiltonians during free precession, the hyperfine coupling parameters as well as the nuclear Larmor frequency can be selectively measured with high precision (here 5 digits). The protocols can be combined to demonstrate two-dimensional Fourier spectroscopy. The technique will be useful for mapping nuclear coordinates in molecules en route to imaging their atomic structure.
Quantum State Transfer in a Two-dimensional Regular Spin Lattice of Triangular Shape
Miki, Hiroshi; Vinet, Luc; Zhedanov, Alexei
2012-01-01
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.
Observations of indirect exciton trapping in one- and two-dimensional magnetic lattices
Ahmed M. Abdelrahman; Byoung S. Ham
2012-02-23
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.
Quantum State Transfer in a Two-dimensional Regular Spin Lattice of Triangular Shape
Hiroshi Miki; Satoshi Tsujimoto; Luc Vinet; Alexei Zhedanov
2012-03-12
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.
Interface Tensions and Perfect Wetting in the Two-Dimensional Seven-State Potts Model
B. Grossmann; Sourendu Gupta
1993-10-25
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.
Guiochon, Georges A; Shalliker, R. Andrew
2010-01-01
An algorithm was developed for 2DHPLC that automated the process of peak recognition, measuring their retention times, and then subsequently plotting the information in a two-dimensional retention plane. Following the recognition of peaks, the software then performed a series of statistical assessments of the separation performance, measuring for example, correlation between dimensions, peak capacity and the percentage of usage of the separation space. Peak recognition was achieved by interpreting the first and second derivatives of each respective one-dimensional chromatogram to determine the 1D retention times of each solute and then compiling these retention times for each respective fraction 'cut'. Due to the nature of comprehensive 2DHPLC adjacent cut fractions may contain peaks common to more than one cut fraction. The algorithm determined which components were common in adjacent cuts and subsequently calculated the peak maximum profile by interpolating the space between adjacent peaks. This algorithm was applied to the analysis of a two-dimensional separation of an apple flesh extract separated in a first dimension comprising a cyano stationary phase and an aqueous/THF mobile phase as the first dimension and a second dimension comprising C18-Hydro with an aqueous/MeOH mobile phase. A total of 187 peaks were detected.
Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas
Bahar, M. K.; Soylu, A.
2015-05-15
In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.
Two-dimensional numerical simulation of boron diffusion for pyramidally textured silicon
Ma, Fa-Jun Duttagupta, Shubham; Shetty, Kishan Devappa; Meng, Lei; Hoex, Bram; Peters, Ian Marius; Samudra, Ganesh S.
2014-11-14
Multidimensional numerical simulation of boron diffusion is of great relevance for the improvement of industrial n-type crystalline silicon wafer solar cells. However, surface passivation of boron diffused area is typically studied in one dimension on planar lifetime samples. This approach neglects the effects of the solar cell pyramidal texture on the boron doping process and resulting doping profile. In this work, we present a theoretical study using a two-dimensional surface morphology for pyramidally textured samples. The boron diffusivity and segregation coefficient between oxide and silicon in simulation are determined by reproducing measured one-dimensional boron depth profiles prepared using different boron diffusion recipes on planar samples. The established parameters are subsequently used to simulate the boron diffusion process on textured samples. The simulated junction depth is found to agree quantitatively well with electron beam induced current measurements. Finally, chemical passivation on planar and textured samples is compared in device simulation. Particularly, a two-dimensional approach is adopted for textured samples to evaluate chemical passivation. The intrinsic emitter saturation current density, which is only related to Auger and radiative recombination, is also simulated for both planar and textured samples. The differences between planar and textured samples are discussed.
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.
2015-05-28
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
Solutions of Two Dimensional Viscous Accretion and Winds In Kerr Black Hole Geometry
S. K. Chakrabarti
1996-11-04
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.
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
2013-06-13
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.
Ground-state and dynamical properties of two-dimensional dipolar Fermi liquids
Abedinpour, Saeed H.; Asgari, Reza; Tanatar, B.; Polini, Marco
2014-01-15
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.
Asymmetric Two-dimensional Magnetic Lattices for Ultracold Atoms Trapping and Confinement
A. Abdelrahman; P. Hannaford M. Vasiliev; K. Alameh
2009-10-27
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.
Rothrock, Ray Alan
1978-01-01
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 ...
Derrida, Bernard
Volume 80A, number 4 PHYSICSLETTERS 8 December 1980 FEIGENBAUM'S RATIOS OF TWO-DIMENSIONAL AREA preserv- ing case [10] 217 #12;Volume 80A, number 4 PHYSICS LETTERS 8 December 1980 G(x,y) = (1 -//x 2 +y
Camp, Philip J.
2003-01-01
The structure and phase behavior of a two-dimensional system with purely repulsive core-softened and long-range interactions are studied using Monte Carlo computer simulations. The pair interactions are of the form, u(r)= ...
Marocchino, A.; Atzeni, S.; Schiavi, A. [Dipartimento SBAI, Università di Roma “La Sapienza” and CNISM, Roma 00161 (Italy)] [Dipartimento SBAI, Università di Roma “La Sapienza” and CNISM, Roma 00161 (Italy)
2014-01-15
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-Nicolaï-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)
2006-02-15
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.
2D Fokker-Planck models of rotating clusters
J. Fiestas; R. Spurzem; E. Kim
2006-09-04
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.
Spectral evolution of two-dimensional kinetic plasma turbulence in the wavenumber-frequency domain
Comi?el, H.; Institute for Space Sciences, Atomi?tilor 409, P.O. Box MG-23, Bucharest-M?gurele RO-077125 ; Verscharen, D.; Narita, Y.; Motschmann, U.; Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Rutherfordstr. 2, D-12489 Berlin
2013-09-15
We present a method for studying the evolution of plasma turbulence by tracking dispersion relations in the energy spectrum in the wavenumber-frequency domain. We apply hybrid plasma simulations in a simplified two-dimensional geometry to demonstrate our method and its applicability to plasma turbulence in the ion kinetic regime. We identify four dispersion relations: ion-Bernstein waves, oblique whistler waves, oblique Alfvén/ion-cyclotron waves, and a zero-frequency mode. The energy partition and frequency broadening are evaluated for these modes. The method allows us to determine the evolution of decaying plasma turbulence in our restricted geometry and shows that it cascades along the dispersion relations during the early phase with an increasing broadening around the dispersion relations.
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)
2006-12-12
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.
Butkus, Vytautas; Augulis, Ram?nas; Gall, Andrew; Büchel, Claudia; Robert, Bruno; Zigmantas, Donatas; Valkunas, Leonas; Abramavicius, Darius
2015-01-01
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...
Photonic-band-gap effects in two-dimensional polycrystalline and amorphous structures
Yang, Jin-Kyu; Noh, Heeso; Liew, Seng-Fatt; Schreck, Carl; Guy, Mikhael I.; O'Hern, Corey S.; Cao, Hui
2010-11-15
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.
Carr, Sam T.; Quintanilla, Jorge; Betouras, Joseph J.
2010-07-15
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.
Analytical and numerical solution of one- and two-dimensional steady heat transfer in a coldplate
Jones, G.F.; Bennett, G.A.; Bultman, D.H.
1987-01-01
We develop analytical models for steady-state, one- and two-dimensional heat transfer in a single-material, flat-plate coldplate. Discrete heat sources are mounted on one side of the plate and heat transfer to a flowing fluid occurs on the other. The models are validated numerically using finite differences. We propose a simple procedure for estimating maximum coldplate temperature at the location of each heat source which includes thermal interaction among the sources. Results from one model are compared with data obtained for a composite coldplate operated in the laboratory. We demonstrate the utility of the models as diagnostic tools to be used for predicting the existence and extent of void volumes and delaminations in the composite material that can occur with coldplates of this type. Based on our findings, recommendations for effective coldplate design are given.
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
2010-06-21
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.
Transfer of optical signals around bends in two-dimensional linear photonic networks
Georgios M. Nikolopoulos
2014-11-13
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
2015-05-09
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.
Passive tracer in a flow corresponding to a two dimensional stochastic Navier Stokes equations
Tomasz Komorowski; Szymon Peszat; Tomasz Szarek
2012-04-26
In this paper we prove the law of large numbers and central limit theorem for trajectories of a particle carried by a two dimensional Eulerian velocity field. The field is given by a solution of a stochastic Navier--Stokes system with a non-degenerate noise. The spectral gap property, with respect to Wasserstein metric, for such a system has been shown in [9]. In the present paper we show that a similar property holds for the environment process corresponding to the Lagrangian observations of the velocity. In consequence we conclude the law of large numbers and the central limit theorem for the tracer. The proof of the central limit theorem relies on the martingale approximation of the trajectory process.
Laser induced reentrant freezing in two-dimensional attractive colloidal systems
Pinaki Chaudhuri; Chinmay Das; Chandan Dasgupta; H. R. Krishnamurthy; A. K. Sood
2005-09-11
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
2012-10-02
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.
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))
1990-10-01
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.
Wannier-Stark states in double-periodic lattices II: two-dimensional lattices
E. N. Bulgakov; D. N. Maksimov; A. R. Kolovsky
2014-11-24
We analyze the Wannier-Stark spectrum of a quantum particle in tilted two-dimensional lattices with the Bloch spectrum consisting of two subbands, which could be either separated by a finite gap or connected at the Dirac points. For rational orientations of the static field given by an arbitrary superposition of the translation vectors the spectrum is a ladder of energy bands. We obtain asymptotic expressions for the energy bands in the limit of large and weak static fields and study them numerically for intermediate field strength. We show that the structure of energy bands determines the rate of spreading of a localized wave packets which is the quantity measured in laboratory experiments. It is shown that wave-packet dispersion becomes a fractal function of the field orientation in the long-time regime of ballistic spreading.
Two-dimensional spectroscopy for the study of ion Coulomb crystals
A. Lemmer; C. Cormick; C. T. Schmiegelow; F. Schmidt-Kaler; M. B. Plenio
2015-05-04
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.
The friction factor of two-dimensional rough-boundary turbulent soap film flows
Nicholas Guttenberg; Nigel Goldenfeld
2009-03-25
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.
Implementation of the Log-Conformation Formulation for Two-Dimensional Viscoelastic Flow
Jensen, K E; Okkels, F
2015-01-01
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
2015-07-16
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.
Dynamical generation of two-dimensional matter-wave discrete solitons
Artem M. Dudarev; Roberto B. Diener; Qian Niu
2004-02-21
We suggest a method to experimentally obtain two-dimensional matter-wave discrete solitons with a {\\it self-repulsive} BEC in optical lattices. At the edge of the Brillouin zone, a wave packet effective mass is negative which could be treated as inversion of the nonlinearity sign. Above critical nonlinearity this makes the wave packets collapse partially into localized modes with a chemical potential located in the gap between the first and the second bands. This critical nonlinearity is also associated with the smallest nonlinearity for which the discrete solitons are possible in the gap. Extensive numerical simulations for square and asymmetric honeycomb lattices in continuous model illustrate every stage of the process.
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)
2014-01-15
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.
Quantum Phase Transition in a Two-Dimensional System of Dipoles
Astrakharchik, G. E.; Boronat, J.; Kurbakov, I. L.; Lozovik, Yu. E.
2007-02-09
The ground-state phase diagram of a two-dimensional Bose system with dipole-dipole interactions is studied by means of a quantum Monte Carlo technique. Our calculation predicts a quantum phase transition from a gas to a solid phase when the density increases. In the gas phase, the condensate fraction is calculated as a function of the density. Using the Feynman approximation, the collective excitation branch is studied and the appearance of a roton minimum is observed. The results of the static structure factor at both sides of the gas-solid phase are also presented. The Lindemann ratio at the transition point becomes {gamma}=0.230(6). The condensate fraction in the gas phase is estimated as a function of the density.
Two-dimensional water quality modeling of Town Creek embayment on Guntersville Reservoir
Bender, M.D.; Shiao, Ming C.; Hauser, G.E. . Engineering Lab.); Butkus, S.R. . Water Quality Dept.)
1990-09-01
TVA investigated water quality of Town Creek embayment using a branched two-dimensional model of Guntersville Reservoir. Simulation results were compared in terms of algal biomass, nutrient concentrations, and volume of embayment with depleted dissolved oxygen. Stratification and flushing play a significant role in the embayment water quality. Storms introduce large loadings of organics, nutrients, and suspended solids. Dissolved oxygen depletion is most severe after storms followed by low flow that fails to flush the embayment. Embayment water quality responses to potential animal waste and erosion controls were explored. Modeling indicated animal waste controls were much more cost-effective than erosion controls. Erosion controls will decrease embayment suspended solids and thereby increase algal biomass due to greater light penetration. 29 refs., 16 figs., 4 tabs.
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)
2005-01-01
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.
A Priori Estimates for Two-Dimensional Water Waves with Angled Crests
Kinsey, Rafe H
2014-01-01
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 $-\\frac{\\partial P}{\\partial {\\bf n}} \\ge c > 0$.
Two-dimensional positive column structure in a discharge tube with radius discontinuity
Zobnin, A. V. Usachev, A. D.; Petrov, O. F.; Fortov, V. E.
2014-11-15
The low-pressure (40 and 90?Pa) low-current (4 and 10?mA) direct current discharge in a tube with a sharp change of its radius is studied both numerically and experimentally. A fully self-consistent hybrid numerical model of a two-dimensional non-uniform positive column in neon is developed using a nonlocal approach. The model combines kinetic simulation of the electrons (under two-terms approach) and fluid description of the neon ions and permits to calculate the distribution of all plasma parameters in the direct current discharges in the cameras with cylindrical geometry and radius discontinuity. The simulation results are compared with the measured 585.3?nm neon spectral line absolute intensities and excited 1s{sub 3} metastable neon atom number densities. Non-local electron kinetics in the transition region and formation of standing strata are discussed.
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)
2014-11-15
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.
Finite-time barriers to front propagation in two-dimensional fluid flows
Mahoney, John R
2015-01-01
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...
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)
2014-01-27
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.
Fuel-air mixing and combustion in a two-dimensional Wankel engine
Shih, T.I.P.; Schock, H.J.; Ramos, J.I.
1987-01-01
The effects of mixture stratification at the intake port and gaseous fuel injection on the flow field and fuel-air mixing in a two-dimensional rotary engine model have been investigated by means of a two-equation model of turbulence, an algebraic grid generation method and an approximate factorization time-linearized numerical technique. It is shown that the fuel distribution in the combustion chamber is a function of the air-fuel mixture fluctuations at the intake port. The fuel is advected by the flow field induced by the rotor and is concentrated near the leading apex during the intake stroke. During compression, the fuel concentration is highest near the trailing apex and lowest near the rotor. The penetration of gaseous fuel injected into the combustion chamber during the compression stroke increases with the injection velocity.
Collision-dependent power law scalings in two dimensional gyrokinetic turbulence
Cerri, S. S. Bañón Navarro, A.; Told, D.; Jenko, F.
2014-08-15
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.
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)
1996-03-01
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.
Thermoelectric probe for Rashba spin-orbit interaction strength in a two dimensional electron gas
S. K. Firoz Islam; Tarun Kanti Ghosh
2012-07-18
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.
NANO EXPRESS Open Access Half metal in two-dimensional hexagonal
Simons, Jack
for spintronics application. Keywords: Half metal; 2D hexagonal organometallic framework; Triphenyl-transition metal; Spintronics device Background Half metals, which act as conductor for electrons of one spin-resolved electric current, holding great promise for future spintronics and nanoelectronic devices. Most known half
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
Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials
Lotz, Mikkel R.; Boll, Mads; Bøggild, 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); Kjær, 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)
2014-08-04
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.
On the diagonal susceptibility of the two-dimensional Ising model
Tracy, Craig A.; Widom, Harold
2013-12-15
We consider the diagonal susceptibility of the isotropic 2D Ising model for temperatures below the critical temperature. For a parameter k related to temperature and the interaction constant, we extend the diagonal susceptibility to complex k inside the unit disc, and prove the conjecture that the unit circle is a natural boundary.
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
Effective Viscosity of Dilute Bacterial Suspensions: A Two-Dimensional Model
Berlyand, Leonid
State University, 418 McAllister Building, University Park, PA 16802 2 Materials Science Division. This formula includes the two terms that are found in the 2D version of Einstein's classical result for passive interactions between bacteria (or passive particles) are often ignored as the interparticle distance exceeds
Third order nite volume evolution Galerkin (FVEG) methods for two-dimensional wave equation system
Galerkin schemes, recovery stage, #12;nite volume. 1 Introduction Evolution Galerkin methods (EG and Warnecke constructed further EG-schemes, namely EG1, EG2 and EG3. In [14] Zahaykah derived the approximate these results new 2D EG schemes, namely FREG, SREG and EG4 schemes were de- rived, cf. [14]. These methods were
X-ray tests of a two-dimensional stigmatic imaging scheme with...
Office of Scientific and Technical Information (OSTI)
of Publication: United States Language: English Subject: 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BRAGG REFLECTION;...
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]
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)
2014-05-15
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.
Two-dimensional double layer in plasma in a diverging magnetic field
Saha, S. K.; Raychaudhuri, S.; Chowdhury, S.; Janaki, M. S.; Hui, A. K.
2012-09-15
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.
PAD, a computer-aided molecular model building system utilizing two-dimensional graphical input
White, William Gerald
1980-01-01
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...
Testable Signatures of Quantum Nonlocality in a Two-Dimensional Chiral p-Wave Superconductor
Tewari, Sumanta; Zhang Chuanwei; Das Sarma, S.; Nayak, Chetan; Lee, Dung-Hai
2008-01-18
A class of topological excitations--the odd-winding number vortices--in a spinless 2D chiral p-wave (p{sub x}+ip{sub y}) superconductor traps Majorana fermion states in the vortex cores. For a dilute gas of such vortices, the lowest energy fermionic eigenstates are intrinsically nonlocal. We predict two testable signatures of this unusual quantum nonlocality in quasiparticle tunneling experiments. We discuss why the associated teleportationlike phenomenon does not imply the violation of causality.
Two-dimensional inverse planning and delivery with a preclinical image guided microirradiator
Stewart, James M. P.; Lindsay, Patricia E.; Jaffray, David A.; Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario M5G 2M9; Department of Radiation Oncology, Faculty of Medicine, University of Toronto, Toronto, Ontario M5S 3E2; Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9; The Techna Institute for the Advancement of Technology for Health, Toronto, Ontario M5G 1P5
2013-10-15
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
2015-01-01
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...
Wu, Jingbo; Wood, Christopher D; Mistry, Divyang; Li, Lianhe; Muchenje, Wilson; Rosamond, Mark C; Chen, Li; Linfield, Edmund H; Davies, A Giles; Cunningham, John E
2015-01-01
Terahertz time domain spectroscopy employing free-space radiation has frequently been used to probe the elementary excitations of low-dimensional systems. The diffraction limit blocks its use for the in-plane study of individual laterally defined nanostructures, however. Here, we demonstrate a planar terahertz-frequency plasmonic circuit in which photoconductive material is monolithically integrated with a two-dimensional electron system. Plasmons with a broad spectral range (up to ~400 GHz) are excited by injecting picosecond-duration pulses, generated and detected by a photoconductive semiconductor, into a high mobility two-dimensional electron system. Using voltage modulation of a Schottky gate overlying the two-dimensional electron system, we form a tuneable plasmonic cavity, and observe electrostatic manipulation of the plasmon resonances. Our technique offers a direct route to access the picosecond dynamics of confined transport in a broad range of lateral nanostructures.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kanel, S. R.; Clement, T. P.; Barnett, M. O.; Goltz, M. N.
2011-01-01
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 Ca 5 OH(PO 4 ) 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 canmore »move with water like a tracer, and 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 for in situ treatment of U(VI)-contaminated groundwater systems. « less
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)
2005-12-01
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
1994-02-02
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.
The Massive Goldstone (Higgs) Mode in Two-Dimensional Ultra-cold Atomic Lattice Systems
Liu, Longxiang; Endres, Manuel; Deng, Youjin; Pollet, Lode; Prokof'ev, Nikolay
2015-01-01
We discuss how to reveal the massive Goldstone mode, often referred to as the Higgs amplitude mode, near the Superfluid-to-Insulator quantum critical point (QCP) in a system of two-dimensional ultra-cold bosonic atoms in optical lattices. The spectral function of the amplitude response is obtained by analytic continuation of the kinetic energy correlation function calculated by Monte Carlo methods. Our results enable a direct comparison with the recent experiment [M. Endres, T. Fukuhara, D. Pekker, M. Cheneau, P. Schau{\\ss}, C. Gross, E. Demler, S. Kuhr, and I. Bloch, Nature 487, 454-458 (2012)], and demonstrate a good agreement for temperature shifts induced by lattice modulation. Based on our numerical analysis, we formulate the necessary conditions in terms of homogeneity, detuning from the QCP and temperature in order to reveal the massive Goldstone resonance peak in spectral functions experimentally. We also propose to apply a local modulation at the trap center to overcome the inhomogeneous broadening c...
Basin boundary, edge of chaos, and edge state in a two-dimensional model
J. Vollmer; T. M. Schneider; B. Eckhardt
2008-08-19
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.
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
2015-02-04
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.
Coherent Structures in Turbulent Flow over Two-Dimensional River Dunes
Omidyeganeh, Mohammad
2011-01-01
We performed large-eddy simulations of the flow over a typical two-dimensional dune geometry at laboratory scale (the Reynolds number based on the average channel height and mean velocity is 18,900) using the Lagrangian dynamic eddy-viscosity subgrid-scale model. The flow separates at the dune crest and reattaches downstream on the bed (at x=5.7h). A favorable pressure gradient accelerates the flow over the stoss-side (the upward-sloping region for x > 8h) and an unfavorable gradient for x dune. Due to the separation of the flow, a shear layer is generated after the crest that expands in the wake region towards the next dune. The outer-layer turbulence structures are visualized through isosurfaces of pressure fluctuations colored by distance to the surface. Spanwise vortices are generated in the shear layer separating from the crest due to the Kelvin-Helmholtz instability. They are convected downstream and either interact with the wall or rise to the surfa...
Universal Conductivity in a Two-dimensional Superfluid-to-Insulator Quantum Critical System
Chen, Kun; Deng, Youjin; Pollet, Lode; Prokof'ev, Nikolay
2013-01-01
We compute the universal conductivity of the (2+1)-dimensional XY universality class, which is realized for a superfluid-to-Mott insulator quantum phase transition at constant density. Based on large-scale Monte Carlo simulations of the classical (2+1)-dimensional $J$-current model and the two-dimensional Bose-Hubbard model, we can precisely determine the conductivity on the quantum critical plateau, $\\sigma(\\infty)=0.359(4)\\sigma_Q$ with $\\sigma_Q$ the conductivity quantum. The universal conductivity is the schoolbook example of where the AdS/CFT correspondence from string theory can be tested and made to use. The shape of our $\\sigma(i\\omega_n)- \\sigma(\\infty)$ function in the Matsubara representation is accurate enough for a conclusive comparison and establishes the particle-like nature of charge transport. We find that the holographic gauge/gravity duality theory for transport properties can be made compatible with the data if temperature of the horizon of the black brane is different from the temperature...
Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots
Zhang, Jian-Shi; Giometti, C.S.; Tollaksen, S.L.
1987-09-04
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.
Kuznetsov, E A
2015-01-01
Statistical characteristics of the Kraichnan direct cascade for two-dimensional hydrodynamic turbulence are numerically studied (with spatial resolution $8192\\times 8192$) in the presence of pumping and viscous-like damping. It is shown that quasi-shocks of vorticity and their Fourier partnerships in the form of jets introduce an essential influence in turbulence leading to strong angular dependencies for correlation functions. The energy distribution as a function of modulus $k$ for each angle in the inertial interval has the Kraichnan behavior, $\\sim k^{-4}$, and simultaneously a strong dependence on angles. However, angle average provides with a high accuracy the Kraichnan turbulence spectrum $E_k=C_K\\eta^{2/3} k^{-3}$ where $\\eta$ is enstrophy flux and the Kraichnan constant $C_K\\simeq 1.3$, in correspondence with the previous simulations. Familiar situation takes place for third-order velocity structure function $S_3^L$ which, as for the isotropic turbulence, gives the same scaling with respect to separa...
E. A. Kuznetsov; E. V. Sereshchenko
2015-10-30
Statistical characteristics of the Kraichnan direct cascade for two-dimensional hydrodynamic turbulence are numerically studied (with spatial resolution $8192\\times 8192$) in the presence of pumping and viscous-like damping. It is shown that quasi-shocks of vorticity and their Fourier partnerships in the form of jets introduce an essential influence in turbulence leading to strong angular dependencies for correlation functions. The energy distribution as a function of modulus $k$ for each angle in the inertial interval has the Kraichnan behavior, $\\sim k^{-4}$, and simultaneously a strong dependence on angles. However, angle average provides with a high accuracy the Kraichnan turbulence spectrum $E_k=C_K\\eta^{2/3} k^{-3}$ where $\\eta$ is enstrophy flux and the Kraichnan constant $C_K\\simeq 1.3$, in correspondence with the previous simulations. Familiar situation takes place for third-order velocity structure function $S_3^L$ which, as for the isotropic turbulence, gives the same scaling with respect to separation length $R$ and $\\eta$, $S_3^L=C_3\\eta R^3$, but the mean over angles and time $\\bar {C_3}$ differs from its isotropic value.
Nazir, Safdar; Behtash, Maziar; Yang, Kesong
2015-03-21
We explore the possibility of achieving highly confined two-dimensional electron gas (2DEG) within one single atomic layer through a comprehensive comparison study on three prototypical perovskite heterostructures, LaAlO{sub 3}/ATiO{sub 3} (A = Ca, Sr, and Ba), using first-principles electronic structure calculations. We predict that the heterostructure LaAlO{sub 3}/BaTiO{sub 3} has a highly confined 2DEG within a single atomic layer of the substrate BaTiO{sub 3}, and exhibits relatively higher interfacial charge carrier density and larger magnetic moments than the well-known LaAlO{sub 3}/SrTiO{sub 3} system. The long Ti-O bond length in the ab-plane of the LaAlO{sub 3}/BaTiO{sub 3} heterostructure is responsible for the superior charge confinement. We propose BaTiO{sub 3} as an exceptional substrate material for 2DEG systems with potentially superior properties.
Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics
Fathi, Kambiz; Falcón-Barroso, Jesús; Beckman, John E; Hernandez, Olivier; Daigle, Olivier; Carignan, Claude; de Zeeuw, Tim
2007-01-01
We study the two-dimensional kinematics of the H-alpha-emitting gas in the nearby barred Scd galaxy, NGC 6946, in order to determine the pattern speed of the primary m=2 perturbation mode. The pattern speed is a crucial parameter for constraining the internal dynamics, estimating the impact velocities of the gravitational perturbation at the resonance radii, and to set up an evolutionary scenario for NGC 6946. Our data allows us to derive the best fitting kinematic position angle and the geometry of the underlying gaseous disk, which we use to derive the pattern speed using the Tremaine-Weinberg method. We find a main pattern speed Omega_p=22 km/s/kpc, but our data clearly reveal the presence of an additional pattern speed Omega_p=47 km/s/kpc in a zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we deduce the location of the resonance radii and confirm that inside the outer Inner Lindblad Resonance radius of the main oval, a primary bar has formed rotating at more than twice the outer p...
Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics
Kambiz Fathi; Silvia Toonen; Jesús Falcón-Barroso; John E. Beckman; Olivier Hernandez; Olivier Daigle; Claude Carignan; Tim de Zeeuw
2007-08-08
We study the two-dimensional kinematics of the H-alpha-emitting gas in the nearby barred Scd galaxy, NGC 6946, in order to determine the pattern speed of the primary m=2 perturbation mode. The pattern speed is a crucial parameter for constraining the internal dynamics, estimating the impact velocities of the gravitational perturbation at the resonance radii, and to set up an evolutionary scenario for NGC 6946. Our data allows us to derive the best fitting kinematic position angle and the geometry of the underlying gaseous disk, which we use to derive the pattern speed using the Tremaine-Weinberg method. We find a main pattern speed Omega_p=22 km/s/kpc, but our data clearly reveal the presence of an additional pattern speed Omega_p=47 km/s/kpc in a zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we deduce the location of the resonance radii and confirm that inside the outer Inner Lindblad Resonance radius of the main oval, a primary bar has formed rotating at more than twice the outer pattern speed. We further confirm that a nuclear bar has formed inside the Inner Lindblad Resonance radius of the primary bar, coinciding with the inner Inner Lindblad Resonance radius of the large-scale m=2 mode oval.
Natural abundance 17O DNP two-dimensional and surface-enhanced NMR spectroscopy
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Perras, Frédéric A.; Kobayashi, Takeshi; Pruski, Marek
2015-06-22
Due to its extremely low natural abundance and quadrupolar nature, the 17O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to 17O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from 1H. Here, we demonstrate new DNP-based measurements that extend 17O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional 1H–17O cross-polarization greatly improves the sensitivity and enables the facile measurementmore »of undistorted line shapes and two-dimensional 1H–17O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone 17O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. As a result, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the 17O nuclide.« less
Hollow cathode theory and experiment. II. A two-dimensional theoretical model of the emitter region
Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.
2005-12-01
Despite their long history and wide range of applicability that includes electric propulsion, detailed understanding of the driving physics inside orificed hollow cathodes remains elusive. The theoretical complexity associated with the multicomponent fluid inside the cathode, and the difficulty of accessing empirically this region, have limited our ability to design cathodes that perform better and last longer. A two-dimensional axisymmetric theoretical model of the multispecies fluid inside an orificed hollow cathode is presented. The level of detail attained by the model is allowed by its extended system of governing equations not solved for in the past within the hollow cathode. Such detail is motivated in part by the need to quantify the effect(s) of the plasma on the emitter life, and by the need to build the foundation for future modeling that will assess erosion of the keeper plate. Results from numerical simulations of a 1.2-cm-diam cathode operating at a discharge current of 25 A and a gas flow rate of 5 SCCM show that approximately 10 A of electron current, and 3.45 A of ion current return back to the emitter surface. The total emitted electron current is 33.8 A and the peak emitter temperature is found to be 1440 K. Comparisons with the measurements suggest that anomalous heating of the plasma is possible near the orifice region. The model predicts heavy species temperatures as high as 2034 K and peak voltage drops near the emitting surface not exceeding 8 V.
MHD wave propagation in the neighbourhood of a two-dimensional null point
J. A. McLaughlin; A. W. Hood
2007-12-11
The nature of fast magnetoacoustic and Alfv\\'en waves is investigated in a zero $\\beta$ plasma. This gives an indication of wave propagation in the low $\\beta$ solar corona. It is found that for a two-dimensional null point, the fast wave is attracted to that point and the front of the wave slows down as it approaches the null point, causing the current density to accumulate there and rise rapidly. Ohmic dissipation will extract the energy in the wave at this point. This illustrates that null points play an important role in the rapid dissipation of fast magnetoacoustic waves and suggests the location where wave heating will occur in the corona. The Alfv\\'en wave behaves in a different manner in that the wave energy is dissipated along the separatrices. For Alfv\\'en waves that are decoupled from fast waves, the value of the plasma $\\beta$ is unimportant. However, the phenomenon of dissipating the majority of the wave energy at a specific place is a feature of both wave types.
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)
2009-11-15
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)
Anderson, H.L.; Kinnison, W.W.; Lillberg, J.W.
1985-04-30
An apparatus and method for electronically reading planar two-dimensional ..beta..-ray emitter-labeled gel electrophoretograms. A single, flat rectangular multiwire proportional chamber is placed in close proximity to the gel and the assembly placed in an intense uniform magnetic field disposed in a perpendicular manner to the rectangular face of the proportional chamber. Beta rays emitted in the direction of the proportional chamber are caused to execute helical motions which substantially preserve knowledge the coordinates of their origin in the gel. Perpendicularly oriented, parallel wire, parallel plane cathodes electronically sense the location of the ..beta..-rays from ionization generated thereby in a detection gas coupled with an electron avalanche effect resulting from the action of a parallel wire anode located therebetween. A scintillator permits the present apparatus to be rendered insensitive when signals are generated from cosmic rays incident on the proportional chamber. Resolution for concentrations of radioactive compounds in the gel exceeds 700-..mu..m. The apparatus and method of the present invention represent a significant improvement over conventional autoradiographic techniques in dynamic range, linearity and sensitivity of data collection. A concentration and position map for gel electrophoretograms having significant concentrations of labeled compounds and/or highly radioactive labeling nuclides can generally be obtained in less than one hour.
Anderson, Herbert L. (Santa Fe, NM); Kinnison, W. Wayne (Los Alamos, NM); Lillberg, John W. (Los Alamos, NM)
1987-01-01
Apparatus and method for electronically reading planar two dimensional .beta.-ray emitter-labeled gel electrophoretograms. A single, flat rectangular multiwire proportional chamber is placed in close proximity to the gel and the assembly placed in an intense uniform magnetic field disposed in a perpendicular manner to the rectangular face of the proportional chamber. Beta rays emitted in the direction of the proportional chamber are caused to execute helical motions which substantially preserve knowledge of the coordinates of their origin in the gel. Perpendicularly oriented, parallel wire, parallel plane cathodes electronically sense the location of the .beta.-rays from ionization generated thereby in a detection gas coupled with an electron avalanche effect resulting from the action of a parallel wire anode located therebetween. A scintillator permits the present apparatus to be rendered insensitive when signals are generated from cosmic rays incident on the proportional chamber. Resolution for concentrations of radioactive compounds in the gel exceeds 700 .mu.m. The apparatus and method of the present invention represent a significant improvement over conventional autoradiographic techniques in dynamic range, linearity and sensitivity of data collection. A concentration and position map for gel electrophoretograms having significant concentrations of labeled compounds and/or highly radioactive labeling nuclides can generally be obtained in less than one hour.
Development of a new two-dimensional Cartesian geometry nodal multigroup discrete-ordinates method
Pevey, R.E.
1982-07-01
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.
Spectral properties of a hybrid-qubit model based on a two-dimensional quantum dot
Alba Y. Ramos; Omar Osenda
2015-03-27
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.
Strain-induced energy band gap opening in two-dimensional bilayered silicon film
Ji, Zhonghang; Voon, Lok C Lew Yan; Zhuang, Yan
2015-01-01
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...
Simple models for two-dimensional tunable colloidal crystals in rotating ac electric fields
Nils Elsner; C. Patrick Royall; Brian Vincent; David RE Snoswell
2009-04-18
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
2008-05-20
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.
Plastic Deformation of 2D Crumpled Wires
M A F Gomes; V P Brito; A S O Coelho; C C Donato
2008-11-17
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.
Marney, Luke C.; Siegler, William C.; Parsons, Brendon A.; Hoggard, Jamin C.; Wright, Bob W.; Synovec, Robert E.
2013-10-15
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.
A Turbulent Constitutive Law for the Two-Dimensional Inverse Energy Cascade
Gregory L. Eyink
2005-12-10
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.
Determining energy relaxation length scales in two-dimensional electron gases
Billiald, Jordan; Backes, Dirk; Farrer, Ian; Ritchie, David; Narayan, Vijay; König, Jürgen
2015-01-01
3 is obtained by substituting the Drude ex- pression ? = npe2?e/m for the electrical conductivity into Eq. 1. Here np is the 2D number density of charge car- riers in section p, ?e is the Drude elastic scattering time, m is the effective mass... -dimensional systems and nanostructures. These insights will be vital for practical design considerations of future nanoelectronic circuits. There currently exist well-established methods to probe the low-temperature (low-T ) electrical and ther- moelectric properties...
Image excitons and plasmon-exciton strong coupling in two-dimensional perovskite semiconductors
Niu, Wendy; Ibbotson, Lindsey A.; Leipold, David; Runge, Erich; Prakash, G. Vijaya; Baumberg, Jeremy J.
2015-04-10
-inorganic perovskite semiconductors have attracted a great deal of attention for their optical and electrical properties1–13. 3D perovskites have re- cently been used to produce solar cells with efficiencies of up to 15%1–4, while 2D per- ovskites are known to form... frequency of ?FP = 65meV, the simple scaling above predicts ?SPP ? ?FP ? (22/72).(407/22)=156meV, in excellent agreement with our measurements. Using SPPs to strongly couple to the excitons thus dramatically reduces the cavity length, thus enhancing...
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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.Theory of rare Kaon and(Conference) | SciTech(2D-CARS): simultaneous planar imaging
Ginzburg, N. S.; Zaslavsky, V. Yu.; Institute of Applied Physics of Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 ; Malkin, A. M.; Sergeev, A. S.
2013-11-15
Within the framework of a quasi-optical approach, we develop 2D and 3D self-consistent theory of relativistic surface-wave oscillators. Presenting the radiation field as a sum of two counter-propagating wavebeams coupled on a shallow corrugated surface, we describe formation of an evanescent slow wave. Dispersion characteristics of the evanescent wave following from this method are in good compliance with those found from the direct cst simulations. Considering excitation of the slow wave by a sheet electron beam, we simulate linear and nonlinear stages of interaction, which allows us to determine oscillation threshold conditions, electron efficiency, and output coupling. The transition from the model of surface-wave oscillator operating in the ?-mode regime to the canonical model of relativistic backward wave oscillator is considered. We also described a modified scheme of planar relativistic surface-wave oscillators exploiting two-dimensional periodic gratings. Additional transverse propagating waves emerging on these gratings synchronize the emission from a wide sheet rectilinear electron beam allowing realization of a Cherenkov millimeter-wave oscillators with subgigawatt output power level.
Li, Kai; Gao, Tianyou; Peng, Shi-Guo; Jiang, Kaijun
2015-01-01
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.
Magnetic Correlations in the Quasi-Two-Dimensional Semiconducting Ferromagnet CrSiTe3
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Williams, Travis J.; Aczel, Adam A.; Lumsden, Mark D.; Nagler, Stephen E.; Stone, Matthew B.; Yan, Jiaqiang -Q.; Mandrus, D.
2015-10-02
Intrinsic, 2D ferromagnetic semiconductors are an important class of materials for overcoming dilute magnetic semiconductors’ limitations for spintronics. CrSiTe3 is a particularly interesting material of this class, since it can likely be exfoliated to single layers, for which Tc is predicted to increase dramatically. Establishing the nature of the bulk material’s magnetism is necessary for understanding the thin-film magnetic behavior and the material’s possible applications. In this work, we use elastic and inelastic neutron scattering to measure the magnetic properties of single crystalline CrSiTe3. We find a very small single ion anisotropy that favors magnetic ordering along the c-axis andmore »that the measured spin waves fit well to a model in which the moments are only weakly coupled along that direction. Then, we find that both static and dynamic correlations persist within the ab-plane up to at least 300 K, which is strong evidence of the material's 2D characteristics that are relevant for future studies on thin film and monolayer samples.« less
Curvature-induced cross-hatched order in two-dimensional semiflexible polymer networks
Cyril Vrusch; Cornelis Storm
2015-07-14
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.
Two dimensional point of use fuel cell : a final LDRD project report.
Zavadil, Kevin Robert; Hickner, Michael A.; Gross, Matthew L.
2011-03-01
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.
Fast chemical reaction in two-dimensional Navier-Stokes flow: Initial regime
Farid Ait-Chaalal; Michel S. Bourqui; Peter Bartello
2012-04-05
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.
A new look at the collapse of two-dimensional polymers
Eric Vernier; Jesper Lykke Jacobsen; Hubert Saleur
2015-09-05
We study the collapse of two-dimensional polymers, via an O($n$) model on the square lattice that allows for dilution, bending rigidity and short-range monomer attractions. This model contains two candidates for the theta point, $\\Theta_{\\rm BN}$ and $\\Theta_{\\rm DS}$, both exactly solvable. The relative stability of these points, and the question of which one describes the `generic' theta point, have been the source of a long-standing debate. Moreover, the analytically predicted exponents of $\\Theta_{\\rm BN}$ have never been convincingly observed in numerical simulations. In the present paper, we shed a new light on this confusing situation. We show in particular that the continuum limit of $\\Theta_{\\rm BN}$ is an unusual conformal field theory, made in fact of a simple dense polymer decorated with {\\sl non-compact degrees of freedom}. This implies in particular that the critical exponents take continuous rather than discrete values, and that corrections to scaling lead to an unusual integral form. Furthermore, discrete states may emerge from the continuum, but the latter are only normalizable---and hence observable---for appropriate values of the model's parameters. We check these findings numerically. We also probe the non-compact degrees of freedom in various ways, and establish that they are related to fluctuations of the density of monomers. Finally, we construct a field theoretic model of the vicinity of $\\Theta_{\\rm BN}$ and examine the flow along the multicritical line between $\\Theta_{\\rm BN}$ and $\\Theta_{\\rm DS}$.
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.)
2004-01-01
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.
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
Eisenstein, Jim
Surface acoustic wave propagation and inhomogeneities in low-density two-dimensional electron) in a low-density regime (!1010 cmK2 ) at zero magnetic field. The interaction of the surface acoustic wave systems; D. Metalinsulator transition; E. Surface acoustic waves The apparent metalinsulator transition
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
Thermoacoustic modeling and uncertainty analysis of two-dimensional conductive membranes Jonghoon-dimensional model for thermoacoustic engines J. Acoust. Soc. Am. 111, 2076 (2002); 10.1121/1.1467675 [This article://scitation.aip.org/termsconditions. Downloaded to ] IP: 146.201.18.83 On: Fri, 13 Feb 2015 15:46:28 #12;Thermoacoustic modeling and uncertainty
Bastatas, Lyndon D.; Bornales, Jinky B.
2008-06-18
White noise path integral prescription is applied to solve the Dirac equation for a two-dimensional Dirac oscillator in a uniform magnetic field. The energy spectrum obtained agrees with the result obtained by Villalba and Maggiolo using the differential approach.
Kenji Nakahira; Tsuyoshi Sasaki Usuda
2015-01-26
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.
Sprott, Julien Clinton
2008-01-01
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
2008-01-01
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
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
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
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
Biologically-Inspired Self-Assembly of Two-Dimensional Shapes Using Global-to-Local Compilation
Batzoglou, Serafim
Biologically-Inspired Self-Assembly of Two-Dimensional Shapes Using Global-to-Local Compilation by decentralized, identically- programmed agents. Our system compiles a prede- termined global shape into a program. In the global- to-local compilation phase, an input shape is de- composed into a network of covering
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
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
2015-05-07
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
V. M. Villalba; R. Pino
2001-01-23
We compute, via a variational mixed-base method, the energy spectrum of a two dimensional relativistic atom in the presence of a constant magnetic field of arbitrary strength. The results are compared to those obtained in the non-relativistic and spinless case. We find that the relativistic spectrum does not present $s$ states.
Ng, Chung-Sang
Stability Studies of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes using Particle theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes of their properties, including its energy content, temperature and velocity distribution, and stability. This work
Liang, Chi-Te; Lin, Li-Hung; Chen, Kuang Yao; Lo, Shun-Tsung; Wang, Yi-Ting; Lo, Dong-Sheng; Kim, Gil-Ho; Chang, Yuan Huei; Ochiai, Yuichi; Aoki, Nobuyuki; Chen, Jeng Chung; Lin, Yiping; Huang, Chun Feng; Lin, Sheng-Di; Richie, David A
2011-02-11
, Nicholls JT, Frost JEF, Linfield EH, Pepper M, Ford CJB, Ritchie DA, Jones GAC, Kogan E, Kaveh M: Magnetic-field-induced insulator-quantum Hall-insulator transition in a disordered two- dimensional electron gas. J Phys Condens Matter 1994, 6:4763. 6...
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
Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability
Epstein, Irving R.
Standing Waves in a Two-Dimensional Reaction-Diffusion Model with the Short-Wave Instability Milos 25, 1998; In Final Form: October 19, 1998 Various patterns of standing waves are found beyond with rotational symmetry in systems with circular geometry. We also find standing waves consisting of periodic
Dobkins, Karen R.
Integration of one- and two-dimensional motion signals in infants: Evidence from the barber-pole into a coherent global motion percept by studying the ``barber-pole illusion''; when a one-dimensional moving study, we used barber-pole stimuli to investigate the develop- ment of motion mechanisms that integrate
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; Nanjing University, Nanjing; Su, Dong; Walker, F. J.; Ahn, C. H.
2015-03-01
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.
1988-11-01
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.
Elastic interactions between 2D geometric defects
Michael Moshe; Eran Sharon; Raz Kupferman
2015-10-13
In this paper, we introduce a methodology applicable to a wide range of localized two-dimensional sources of stress. This methodology is based on a geometric formulation of elasticity. Localized sources of stress are viewed as singular defects---point charges of the curvature associated with a reference metric. The stress field in the presence of defects can be solved using a scalar stress function that generalizes the classical Airy stress function to the case of materials with nontrivial geometry. This approach allows the calculation of interaction energies between various types of defects. We apply our methodology to two physical systems: shear-induced failure of amorphous materials and the mechanical interaction between contracting cells.
Gauge Dressing of 2D Field Theories
Ian I. Kogan; Alex Lewis; Oleg A. Soloviev
1996-07-05
By using the gauge Ward identities, we study correlation functions of gauged WZNW models. We show that the gauge dressing of the correlation functions can be taken into account as a solution of the Knizhnik-Zamolodchikov equation. Our method is analogous to the analysis of the gravitational dressing of 2D field theories.
Two-Dimensional Simulation Analysis of the Standing-wave Free-electron Laser Two-Beam Accelerator
Wang, C.
2008-01-01
and S. Yu, "Relativistic klystron simulations using RKTW2D,"dimensional relativistic klystron code, developed by Ryneand the relativistic klystron two-beam accelerator. In this
Li, Jing
commonly employed in the synthesis of numerous solid-state inorganic materials. ComparablyTwo-Dimensional Coordination Polymers with One-Dimensional Magnetic Chains: Hydrothermal Synthesis
2d Affine XY-Spin Model/4d Gauge Theory Duality and Deconfinement
Anber, Mohamed M.; Poppitz, Erich; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept. /San Francisco State U.
2012-08-16
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.
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)
2012-12-15
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.
Angular dependence of the spin textures in two-dimensional chiral magnets
Tang, Dan; Qi, Yang
2015-05-28
The angular dependence of spin textures in thin helimagnetic films is investigated by a Monte Carlo simulation. When an external field is applied at an angle relative to the film normal, we find that the skyrmion states with broken axis-symmetric structure are able to persist over a wide range of angles by changing the spin orientation. In addition, the uniaxial anisotropy is able to stabilize the distorted skyrmions. This behavior reflects the robust topological stability of skyrmion states in helimagnets and favors their application in spintronic devices.
Abdelmalek Boumali
2014-10-10
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.
2007-01-30
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; Zhang, Jing-Bo; Jing, Chu-Yue; Zhang, Lei; Walton, Richard I.; Zhu, Peizhi; Ng, Seik Weng
2014-03-15
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)
2014-09-01
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.
Tur, A.; Fruit, G.; Louarn, P.
2014-03-15
In the general context of understanding the possible destabilization of a current sheet with applications to magnetospheric substorms or solar flares, a kinetic model is proposed for studying the resonant interaction between electromagnetic fluctuations and trapped bouncing electrons in a 2D current sheet. Tur et al. [A. Tur et al., Phys. Plasmas 17, 102905 (2010)] and Fruit et al. [G. Fruit et al., Phys. Plasmas 20, 022113 (2013)] already used this model to investigate the possibilities of electrostatic instabilities. Here, the model is completed for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly strechted current, undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet half thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in ??=?B{sub z}/B{sub lobes}, the mode becomes explosive with typical growth rate of a few tens of seconds. The free energy contained in the bouncing motion of the electrons may trigger an electromagnetic instability able to disrupt the cross-tail current in a few seconds. This new instability–electromagnetic electron-bounce instability–may explain fast and global scale destabilization of current sheets as required to describe substorm phenomena.
Translating 2D German expressionist woodcut artwork into 3D
Musha, Elona
2006-10-30
This thesis involves the study of four woodcuts from the twentieth century German Expressionist movement. The study of these woodcuts inspires and informs the translation of these artworks from two-dimensional works on ...
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 suspensions that are confined to a planar liquid-gas interface and exposed to a tilted external magnetic field
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
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)
2006-11-01
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.
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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
2008-04-16
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.
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)
2006-07-01
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)
Radozycki, Tomasz
2015-01-01
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
2015-08-31
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.
Large-$q$ expansion of the specific heat for the two-dimensional $q$-state Potts model
H. Arisue; K. Tabata
1998-07-03
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 $q \\to 4_+$.
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)
2014-07-07
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.
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
Hill, James Robert
1981-01-01
(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... 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...
The 2D surfaces that generate Newtonian and general relativistic orbits with small eccentricities
Chad A. Middleton
2015-06-09
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.
Pauli matrices and 2D electron gas
J. F. Geurdes
2013-02-07
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.
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 VEX RADIATION MODULE: 2D RADIATION TRANSPORT WITH MIMETIC...
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THE VEX RADIATION MODULE: 2D RADIATION TRANSPORT WITH MIMETIC DIFFUSION FOR EXAFLAG Citation Details In-Document Search Title: THE VEX RADIATION MODULE: 2D RADIATION TRANSPORT WITH...
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 ...
Two-dimensional resonant magnetic excitation in BaFe1.84Co0.16As2
Lumsden, Mark D; Christianson, Andrew D; Parshall, Daniel; Stone, Matthew B; Nagler, Stephen E; Mook Jr, Herbert A; Lokshin, Konstantin A; Egami, Takeshi; Abernathy, Douglas L; Goremychkin, E. A.; Osborn, R.; McGuire, Michael A; Safa-Sefat, Athena; Jin, Rongying; Sales, Brian C; Mandrus, David
2009-01-01
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.