WorldWideScience

Sample records for two-dimensional vector plane

  1. Two-dimensional magnetostriction under vector magnetic characteristic

    Science.gov (United States)

    Wakabayashi, D.; Enokizono, M.

    2015-05-01

    This paper presents two-dimensional magnetostriction of electrical steel sheet under vector magnetic characteristic. In conventional measurement method using Single Sheet Tester, the magnetic flux density, the magnetic field strength, and the magnetostriction have been measured in one direction. However, an angle between the magnetic flux density vector and the magnetic field strength vector exists because the magnetic property is vector quantity. An angle between the magnetic flux density vector and the direction of maximum magnetostriction also exists. We developed a new measurement method, which enables measurement of these angles. The vector magnetic characteristic and the two-dimensional magnetostriction have been measured using the new measurement method. The BH and Bλ curves considering the angles are shown in this paper. The analyzed results considering the angles are also made clear.

  2. On the existence of two-dimensional nonlinear steady states in plane Couette flow

    CERN Document Server

    Rincon, Francois

    2007-01-01

    The problem of two-dimensional steady nonlinear dynamics in plane Couette flow is revisited using homotopy from either plane Poiseuille flow or from plane Couette flow perturbed by a small symmetry-preserving identity operator. Our results show that it is not possible to obtain the nonlinear plane Couette flow solutions reported by Cherhabili and Ehrenstein [Eur. J. Mech. B/Fluids, 14, 667 (1995)] using their Poiseuille-Couette homotopy. We also demonstrate that the steady solutions obtained by Mehta and Healey [Phys. Fluids, 17, 4108 (2005)] for small symmetry-preserving perturbations are influenced by an artefact of the modified system of equations used in their paper. However, using a modified version of their model does not help to find plane Couette flow solution in the limit of vanishing symmetry-preserving perturbations either. The issue of the existence of two-dimensional nonlinear steady states in plane Couette flow remains unsettled.

  3. TWO-DIMENSIONAL PLANE WATER FLOW AND WATER QUALITY DISTRIBUTION IN BOSTEN LAKE

    Institute of Scientific and Technical Information of China (English)

    Feng Min-quan; Zhou Xiao-de; Zheng Bang-min; Min Tao; Zhao Ke-yu

    2003-01-01

    The two-dimensional plane water flow and water quality was developed by using the techniques of coordinate transformation, alternating directions, staggered grid, linear recurrence, and implicit scheme in the study of large water body in lakes. The model was proved to be suitable for treating the irregular boundary and predicting quickly water flow and water quality. The application of the model to the Bosten Lake in Xinjiang Uygur Autonomous Region of China shows that it is reasonable and practicable.

  4. The PLSI Method of Stabilizing Two-Dimensional Nonsymmetric Half-Plane Recursive Digital Filters

    OpenAIRE

    Gangatharan N; Reddy PS

    2003-01-01

    Two-dimensional (2D) recursive digital filters find applications in image processing as in medical X-ray processing. Nonsymmetric half-plane (NSHP) filters have definitely positive magnitude characteristics as opposed to quarter-plane (QP) filters. In this paper, we provide methods for stabilizing the given 2D NSHP polynomial by the planar least squares inverse (PLSI) method. We have proved in this paper that if the given 2D unstable NSHP polynomial and its PLSI are of the same degree, the P...

  5. Static investigation of a two-dimensional convergent-divergent exhaust nozzle with multiaxis thrust-vectoring capability

    Science.gov (United States)

    Taylor, John G.

    1990-01-01

    An investigation was conducted in the Static Test Facility of the NASA Langley 16-Foot Transonic Tunnel to determine the internal performance of two-dimensional convergent-divergent nozzles designed to have simultaneous pitch and yaw thrust vectoring capability. This concept utilized divergent flap rotation of thrust vectoring in the pitch plane and deflection of flat yaw flaps hinged at the end of the sidewalls for yaw thrust vectoring. The hinge location of the yaw flaps was varied at four positions from the nozzle exit plane to the throat plane. The yaw flaps were designed to contain the flow laterally independent of power setting. In order to eliminate any physical interference between the yaw flap deflected into the exhaust stream and the divergent flaps, the downstream corners of both upper and lower divergent flaps were cut off to allow for up to 30 deg of yaw flap deflection. The impact of varying the nozzle pitch vector angle, throat area, yaw flap hinge location, yaw flap length, and yaw flap deflection angle on nozzle internal performance characteristics, was studied. High-pressure air was used to simulate jet exhaust at nozzle pressure ratios up to 7.0. Static results indicate that configurations with the yaw flap hinge located upstream of the exit plane provide relatively high levels of thrust vectoring efficiency without causing large losses in resultant thrust ratio. Therefore, these configurations represent a viable concept for providing simultaneous pitch and yaw thrust vectoring.

  6. Multi-perspective views of students’ difficulties with one-dimensional vector and two-dimensional vector

    Science.gov (United States)

    Fauzi, Ahmad; Ratna Kawuri, Kunthi; Pratiwi, Retno

    2017-01-01

    Researchers of students’ conceptual change usually collects data from written tests and interviews. Moreover, reports of conceptual change often simply refer to changes in concepts, such as on a test, without any identification of the learning processes that have taken place. Research has shown that students have difficulties with vectors in university introductory physics courses and high school physics courses. In this study, we intended to explore students’ understanding of one-dimensional and two-dimensional vector in multi perspective views. In this research, we explore students’ understanding through test perspective and interviews perspective. Our research study adopted the mixed-methodology design. The participants of this research were sixty students of third semester of physics education department. The data of this research were collected by testand interviews. In this study, we divided the students’ understanding of one-dimensional vector and two-dimensional vector in two categories, namely vector skills of the addition of one-dimensionaland two-dimensional vector and the relation between vector skills and conceptual understanding. From the investigation, only 44% of students provided correct answer for vector skills of the addition of one-dimensional and two-dimensional vector and only 27% students provided correct answer for the relation between vector skills and conceptual understanding.

  7. A discussion of $Bl$ conservation on a two dimensional magnetic field plane in watt balances

    CERN Document Server

    Li, Shisong; Huang, Songling

    2015-01-01

    The watt balance is an experiment being pursued in national metrology institutes for precision determination of the Planck constant $h$. In watt balances, the $1/r$ magnetic field, expected to generate a geometrical factor $Bl$ independent to any coil horizontal displacement, can be created by a strict two dimensional, symmetric (horizontal $r$ and vertical $z$) construction of the magnet system. In this paper, we present an analytical understanding of magnetic field distribution when the $r$ symmetry of the magnet is broken and the establishment of the $Bl$ conservation is shown. By using either Gauss's law on magnetism with monopoles or conformal transformations, we extend the $Bl$ conservation to arbitrary two dimensional magnetic planes where the vertical magnetic field component equals zero. The generalized $Bl$ conservation allows a relaxed physical alignment criteria for watt balance magnet systems.

  8. Discriminating image textures with the multiscale two-dimensional complexity-entropy causality plane

    CERN Document Server

    Zunino, Luciano

    2016-01-01

    The aim of this paper is to further explore the usefulness of the two-dimensional complexity-entropy causality plane as a texture image descriptor. A multiscale generalization is introduced in order to distinguish between different roughness features of images at small and large spatial scales. Numerically generated two-dimensional structures are initially considered for illustrating basic concepts in a controlled framework. Then, more realistic situations are studied. Obtained results allow us to confirm that intrinsic spatial correlations of images are successfully unveiled by implementing this multiscale symbolic information-theory approach. Consequently, we conclude that the proposed representation space is a versatile and practical tool for identifying, characterizing and discriminating image textures.

  9. PLANE ELASTICITY PROBLEM OF TWO-DIMENSIONAL OCTAGONAL QUASICRYSTALS AND CRACK PROBLEM

    Institute of Scientific and Technical Information of China (English)

    ZHOU WANG-MIN; FAN TIAN-YOU

    2001-01-01

    The plane elasticity theory of two-dimensional octagonal quasicrystals is developed in this paper. The plane elasticity problem of quasicrystals is reduced to a single higher-order partial differential equation by introducing a displacement function. As an example, the exact analytic solution of a Mode I Griffith crack in the material is obtained by using the Fourier transform and dual integral equations theory, then the displacement and stress fields, stress intensity factor and strain energy release rate can be calculated. The physical significance of the results relative to the phason and the difference between the mechanical behaviours of the crack problem in crystals and quasicrystals are figured out.These provide important information for studying the deformation and fracture of the new solid phase.

  10. The PLSI Method of Stabilizing Two-Dimensional Nonsymmetric Half-Plane Recursive Digital Filters

    Directory of Open Access Journals (Sweden)

    Gangatharan N

    2003-01-01

    Full Text Available Two-dimensional (2D recursive digital filters find applications in image processing as in medical X-ray processing. Nonsymmetric half-plane (NSHP filters have definitely positive magnitude characteristics as opposed to quarter-plane (QP filters. In this paper, we provide methods for stabilizing the given 2D NSHP polynomial by the planar least squares inverse (PLSI method. We have proved in this paper that if the given 2D unstable NSHP polynomial and its PLSI are of the same degree, the PLSI polynomial is always stable, irrespective of whether the coefficients of the given polynomial have relationship among its coefficients or not. Examples are given for 2D first-order and second-order cases to prove our results. The generalization is done for the th order polynomial.

  11. Approximate Ad Hoc Parametric Solutions for Nonlinear First-Order PDEs Governing Two-Dimensional Steady Vector Fields

    Directory of Open Access Journals (Sweden)

    M. P. Markakis

    2010-01-01

    Full Text Available Through a suitable ad hoc assumption, a nonlinear PDE governing a three-dimensional weak, irrotational, steady vector field is reduced to a system of two nonlinear ODEs: the first of which corresponds to the two-dimensional case, while the second involves also the third field component. By using several analytical tools as well as linear approximations based on the weakness of the field, the first equation is transformed to an Abel differential equation which is solved parametrically. Thus, we obtain the two components of the field as explicit functions of a parameter. The derived solution is applied to the two-dimensional small perturbation frictionless flow past solid surfaces with either sinusoidal or parabolic geometry, where the plane velocities are evaluated over the body's surface in the case of a subsonic flow.

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

    Science.gov (United States)

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

    2014-04-01

    We find and investigate via numerical simulations self-sustained two-dimensional turbulence in a magnetohydrodynamic flow with a maximally simple configuration: plane, noninflectional (with a constant shear of velocity), and threaded by a parallel uniform background magnetic field. This flow is spectrally stable, so the turbulence is subcritical by nature and hence it can be energetically supported just by a transient growth mechanism due to shear flow non-normality. This mechanism appears to be essentially anisotropic in the spectral (wave-number) plane and operates mainly for spatial Fourier harmonics with streamwise wave numbers less than the ratio of flow shear to Alfvén speed, kymagnetohydrodynamic (MHD) turbulence research. We find similarity of the nonlinear dynamics to the related dynamics in hydrodynamic flows: to the bypass concept of subcritical turbulence. The essence of the analyzed nonlinear MHD processes appears to be a transverse redistribution of kinetic and magnetic spectral energies in the wave-number plane [as occurs in the related hydrodynamic flow; see Horton et al., Phys. Rev. E 81, 066304 (2010)] and differs fundamentally from the existing concepts of (anisotropic direct and inverse) cascade processes in MHD shear flows.

  13. Two-dimensional modeling of stepped planing hulls with open and pressurized air cavities

    Directory of Open Access Journals (Sweden)

    Konstantin I. Matveev

    2012-06-01

    Full Text Available A method of hydrodynamic discrete sources is applied for two-dimensional modeling of stepped planing surfaces. The water surface deformations, wetted hull lengths, and pressure distribution are calculated at given hull attitude and Froude number. Pressurized air cavities that improve hydrodynamic performance can also be modeled with the current method. Presented results include validation examples, parametric calculations of a single-step hull, effect of trim tabs, and performance of an infinite series of periodic stepped surfaces. It is shown that transverse steps can lead to higher lift-drag ratio, although at reduced lift capability, in comparison with a stepless hull. Performance of a multi-step configuration is sensitive to the wave pattern between hulls, which depends on Froude number and relative hull spacing.

  14. Static internal performance including thrust vectoring and reversing of two-dimensional convergent-divergent nozzles

    Science.gov (United States)

    Re, R. J.; Leavitt, L. D.

    1984-01-01

    The effects of geometric design parameters on two dimensional convergent-divergent nozzles were investigated at nozzle pressure ratios up to 12 in the static test facility. Forward flight (dry and afterburning power settings), vectored-thrust (afterburning power setting), and reverse-thrust (dry power setting) nozzles were investigated. The nozzles had thrust vector angles from 0 deg to 20.26 deg, throat aspect ratios of 3.696 to 7.612, throat radii from sharp to 2.738 cm, expansion ratios from 1.089 to 1.797, and various sidewall lengths. The results indicate that unvectored two dimensional convergent-divergent nozzles have static internal performance comparable to axisymmetric nozzles with similar expansion ratios.

  15. Static internal performance of a two-dimensional convergent-divergent nozzle with thrust vectoring

    Science.gov (United States)

    Bare, E. Ann; Reubush, David E.

    1987-01-01

    A parametric investigation of the static internal performance of multifunction two-dimensional convergent-divergent nozzles has been made in the static test facility of the Langley 16-Foot Transonic Tunnel. All nozzles had a constant throat area and aspect ratio. The effects of upper and lower flap angles, divergent flap length, throat approach angle, sidewall containment, and throat geometry were determined. All nozzles were tested at a thrust vector angle that varied from 5.60 tp 23.00 deg. The nozzle pressure ratio was varied up to 10 for all configurations.

  16. Two-dimensional confined jet thrust vector control: Operating mechanisms and performance

    Science.gov (United States)

    Caton, Jeffrey L.

    1989-03-01

    An experimental investigation of two-dimensional confined jet thrust vector control nozzles was performed. Thrust vector control was accomplished by using secondary flow injection in the diverging section of the nozzle. Schlieren photographs and video tapes were used to study flow separation and internal shock structures. Nozzle performance parameters were determined for nozzle flow with and without secondary flows. These parameters included nozzles forces, vector angles, thrust efficiencies, and flow switching response times. Vector angles as great as 18 degrees with thrust efficiencies of 0.79 were measured. Several confined jet nozzles with variations in secondary flow port design were tested and results were compared to each other. Converging-diverging nozzles of similar design to the confined jet nozzles were also tested and results were compared to the confined jet nozzle results. Existing prediction models for nozzle side to axial force ratio were evaluated. A model for nozzle total forces based on shock losses that predicted values very close to actual results was developed.

  17. An In-Plane Epitaxial Heterostructure of Two-Dimensional Crystals

    Science.gov (United States)

    Gu, Gong

    2015-03-01

    By adapting the concept of epitaxy to two-dimensional (2D) space, a single-atomic-layer, in-plane heterostructure of a prototypical material system, graphene and hexagonal boron nitride (h-BN), has been grown. It is shown by multiple complementary experimental techniques that monolayer crystalline h-BN grows from fresh edges of monolayer graphene with lattice coherence, forming an abrupt 1D interface. The challenges of obtaining truly 2D heterostructures with lattice coherence and sharp interface unassisted by templates in the third dimension will be discussed. Importantly, the h-BN lattice orientation is solely determined by the graphene, forgoing configurations favored by the supporting substrate, a polycrystalline Cu foil with an exclusively (100) surface. To illustrate this important feature of heteroepitaxy in 2D, this talk will briefly discuss the graphene/Cu(100) and h-BN/Cu(100) orientational relations when the two materials are grown alone on Cu foils. For a counterintuitive reason, when grown alone, h-BN strictly aligns to Cu(100) exhibiting four and only four symmetrically equivalent orientations, while graphene shows a wide spread of rotations. The energetically favored h-BN/Cu(100) orientational alignment is overridden when h-BN is grown as an ``epistrip'' templated by a graphene edge. This talk will allude to the interesting physics of the 1D boundary states that has been theoretically predicted, such as spin polarization. As an intermediate step towards establishing the long-predicted physical properties, the boundary states have been observed by atomic-resolution scanning tunneling microscopy and tunneling spectrum mapping, although the sought-after spin polarization is destroyed by the presence of the Cu substrate. This work was partially supported by DARPA (approved for public release; distribution is unlimited) and NSF (ECCS-1231808). A portion of this research was conducted at the Center for Nanophase Materials Sciences (CNMS), sponsored at Oak

  18. Experimental study of two-dimensional turbulence properties in a plane duct in an azimuthal magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Votsish, A.D.; Kolesnikov, Yu.B.

    1977-01-01

    Results are given for an experimental study of two-dimensional turbulent flow with shifts in a plane duct in an azimuthal magnetic field. The turbulent flow was shown to become practically equal to zero in a sufficiently strong field whereas the intensity of the pulsation rate has a finite value. This is explained by the fact that the magnetic field transforms the structure of turbulence into a two-dimensional structure whose maintenance merely requires an insignificant portion of medium flow energy. 4 illustrations, 8 references.

  19. Vector meson masses in two-dimensional SU(NC) lattice gauge theory with massive quarks

    Institute of Scientific and Technical Information of China (English)

    JIANG Jun-Qin

    2008-01-01

    Using an improved lattice Hamiltonian with massive Wilson quarks a variational method is applied to study the dependence of the vector meson mass Mv on the quark mass m and the Wilson parameter r in in the scaling window 1 ≤ 1/g2 ≤ 2, Mv/g is approximately linear in m, but Mv/g obviously does not depend on r (this differs from the quark condensate). Particularly for m → 0 our numerical results agree very well with Bhattacharya's analytical strong coupling result in the continuum, and the value of ((e)Mv/(e)m) |mm=0 in two-dimensional SU(NC) lattice gauge theory is very close to that in Schwinger model.

  20. Spatiotemporal vector pulse shaping of femtosecond laser pulses with a multi-pass two-dimensional spatial light modulator.

    Science.gov (United States)

    Esumi, Y; Kabir, M D; Kannari, F

    2009-10-12

    A novel non-interferometric vector pulse-shaping scheme is developed for femtosecond laser pulses using a two-dimensional spatial light modulator (2D-SLM). By utilizing spatiotemporal pulse shaping obtainable by the 2D-SLM, we demonstrate spatiotemporal vector pulse shaping for the first time.

  1. Design Enhancements of the Two-Dimensional, Dual Throat Fluidic Thrust Vectoring Nozzle Concept

    Science.gov (United States)

    Flamm, Jeffrey D.; Deere, Karen A.; Mason, Mary L.; Berrier, Bobby L.; Johnson, Stuart K.

    2006-01-01

    A Dual Throat Nozzle fluidic thrust vectoring technique that achieves higher thrust-vectoring efficiencies than other fluidic techniques, without sacrificing thrust efficiency has been developed at NASA Langley Research Center. The nozzle concept was designed with the aid of the structured-grid, Reynolds-averaged Navier-Stokes computational fluidic dynamics code PAB3D. This new concept combines the thrust efficiency of sonic-plane skewing with increased thrust-vectoring efficiencies obtained by maximizing pressure differentials in a separated cavity located downstream of the nozzle throat. By injecting secondary flow asymmetrically at the upstream minimum area, a new aerodynamic minimum area is formed downstream of the geometric minimum and the sonic line is skewed, thus vectoring the exhaust flow. The nozzle was tested in the NASA Langley Research Center Jet Exit Test Facility. Internal nozzle performance characteristics were defined for nozzle pressure ratios up to 10, with a range of secondary injection flow rates up to 10 percent of the primary flow rate. Most of the data included in this paper shows the effect of secondary injection rate at a nozzle pressure ratio of 4. The effects of modifying cavity divergence angle, convergence angle and cavity shape on internal nozzle performance were investigated, as were effects of injection geometry, hole or slot. In agreement with computationally predicted data, experimental data verified that decreasing cavity divergence angle had a negative impact and increasing cavity convergence angle had a positive impact on thrust vector angle and thrust efficiency. A curved cavity apex provided improved thrust ratios at some injection rates. However, overall nozzle performance suffered with no secondary injection. Injection holes were more efficient than the injection slot over the range of injection rates, but the slot generated larger thrust vector angles for injection rates less than 4 percent of the primary flow rate.

  2. Backward and forward Monte Carlo method for vector radiative transfer in a two-dimensional graded index medium

    Science.gov (United States)

    Qian, Lin-Feng; Shi, Guo-Dong; Huang, Yong; Xing, Yu-Ming

    2017-10-01

    In vector radiative transfer, backward ray tracing is seldom used. We present a backward and forward Monte Carlo method to simulate vector radiative transfer in a two-dimensional graded index medium, which is new and different from the conventional Monte Carlo method. The backward and forward Monte Carlo method involves dividing the ray tracing into two processes backward tracing and forward tracing. In multidimensional graded index media, the trajectory of a ray is usually a three-dimensional curve. During the transport of a polarization ellipse, the curved ray trajectory will induce geometrical effects and cause Stokes parameters to continuously change. The solution processes for a non-scattering medium and an anisotropic scattering medium are analysed. We also analyse some parameters that influence the Stokes vector in two-dimensional graded index media. The research shows that the Q component of the Stokes vector cannot be ignored. However, the U and V components of the Stokes vector are very small.

  3. Two-dimensional calculus

    CERN Document Server

    Osserman, Robert

    2011-01-01

    The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

  4. Stochastic Vortex Dynamics in Two-Dimensional Easy Plane Ferromagnets: Multiplicative Versus Additive Noise

    Energy Technology Data Exchange (ETDEWEB)

    Kamppeter, T.; Mertens, F.G.; Moro, E.; Sanchez, A.; Bishop, A.R.

    1998-09-01

    We study how thermal fluctuations affect the dynamics of vortices in the two-dimensional anisotropic Heisenberg model depending on their additive or multiplicative character. Using a collective coordinate theory, we analytically show that multiplicative noise, arising from fluctuations in the local field term of the Landau-Lifshitz equations, and Langevin-like additive noise have the same effect on vortex dynamics (within a very plausible assumption consistent with the collective coordinate approach). This is a highly non-trivial result as multiplicative and additive noises usually modify the dynamics in very different ways. We also carry out numerical simulations of both versions of the model finding that they indeed give rise to very similar vortex dynamics.

  5. Measurement of Turbulence Energy Balance in a Two-Dimensional Wall Jet along a Plane Surface

    OpenAIRE

    藤沢, 延行; 白井, 紘行

    1987-01-01

    The sructure of turbulence in a wall jet along a plane surface is investigated by measuring the balance of turbulence energy. With the aid of a hot-wire anemometer system, convection velocities of small-scale turbulent motion are measured as well as other time-averaged flow properties and turbulence characteristics. It is found that the convection velocity of small-scale turbulence deviates significantly from the mean flow velocity, that is, Taylor's hypothesis is not valid for the present wa...

  6. A Hybrid Support Vector Machines and Two-dimensional Risk Matrix Model for Supply Chain Risk Assessment

    OpenAIRE

    Fan Jiang; Junfei Chen

    2014-01-01

    In recent years, the supply chain managements have been paid more and more attention. The supply chain risk management is an important content for enterprises implementing supply chain management. Therefore, how to measure the risk of supply chain is quite important. In this study, a supply chain risk evaluation model based on support vector machines and two-dimensional risk matrix is proposed. The index system of supply chain risk assessment which includes 14 indices is established. The case...

  7. Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma

    KAUST Repository

    Cheng, Chia-Chin

    2016-09-10

    Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach-using a remote hydrogen-plasma process-to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. © 2016 Elsevier Ltd.

  8. Real-space and plane-wave hybrid method for electronic structure calculations for two-dimensional materials

    Science.gov (United States)

    Do, V. Nam; Le, H. Anh; Vu, V. Thieu

    2017-04-01

    We propose a computational approach to combining the plane-wave method and the real-space treatment to describe the periodic variation in the material plane and the decay of wave functions from the material surfaces. The proposed approach is natural for two-dimensional material systems and thus may circumvent some intrinsic limitations involving the artificial replication of material layers in traditional supercell methods. In particular, we show that the proposed method is easy to implement and, especially, computationally effective since low-cost computational algorithms, such as iterative and recursive techniques, can be used to treat matrices with block tridiagonal structure. Using this approach we show first-principles features that supplement the current knowledge of some fundamental issues in bilayer graphene systems, including the coupling between the two graphene layers, the preservation of the σ band of monolayer graphene in the electronic structure of the bilayer system, and the differences in low-energy band structure between the AA- and AB-stacked configurations.

  9. Influence of out-of-plane response on optical properties of two-dimensional materials: First principles approach

    Science.gov (United States)

    Matthes, Lars; Pulci, Olivia; Bechstedt, Friedhelm

    2016-11-01

    The ab initio calculation of optical spectra of sheet crystals usually arranges them in a three-dimensional superlattice with a sufficiently large interlayer distance. We show how the resulting frequency-dependent dielectric tensor is related to the anisotropic optical conductivity of an individual sheet or to the dielectric tensor of a corresponding film with thickness d . Their out-of-plane component is taken into account, in contrast to usual treatments. We demonstrate that the generalized transfer-matrix method to model the optical properties of a layer system containing a sheet crystal accounts for all tensor components. As long as d ≪λ (λ -wavelength of light) this generalized formulation of the optical properties for anisotropic two-dimensional (2D) systems of arbitrary thickness reproduces the limits found in literature that are based either on electromagnetic boundary conditions for a conducting surface or on an isotropic dielectric tensor. For s -polarized light, the results are independent of the sheet description. For oblique incidence of p -polarized light, the tensor nature of the optical conductivity (or the dielectric function) of the sheet crystal strongly impacts on reflectance, transmittance, and absorbance due to the out-of-plane optical conductivity. The limit d →0 should be taken in the final expressions. Example spectra are given for the group-IV honeycomb 2D crystals graphene and silicene.

  10. Static investigation of two fluidic thrust-vectoring concepts on a two-dimensional convergent-divergent nozzle

    Science.gov (United States)

    Wing, David J.

    1994-01-01

    A static investigation was conducted in the static test facility of the Langley 16-Foot Transonic Tunnel of two thrust-vectoring concepts which utilize fluidic mechanisms for deflecting the jet of a two-dimensional convergent-divergent nozzle. One concept involved using the Coanda effect to turn a sheet of injected secondary air along a curved sidewall flap and, through entrainment, draw the primary jet in the same direction to produce yaw thrust vectoring. The other concept involved deflecting the primary jet to produce pitch thrust vectoring by injecting secondary air through a transverse slot in the divergent flap, creating an oblique shock in the divergent channel. Utilizing the Coanda effect to produce yaw thrust vectoring was largely unsuccessful. Small vector angles were produced at low primary nozzle pressure ratios, probably because the momentum of the primary jet was low. Significant pitch thrust vector angles were produced by injecting secondary flow through a slot in the divergent flap. Thrust vector angle decreased with increasing nozzle pressure ratio but moderate levels were maintained at the highest nozzle pressure ratio tested. Thrust performance generally increased at low nozzle pressure ratios and decreased near the design pressure ratio with the addition of secondary flow.

  11. A PARALIND Decomposition-Based Coherent Two-Dimensional Direction of Arrival Estimation Algorithm for Acoustic Vector-Sensor Arrays

    Science.gov (United States)

    Zhang, Xiaofei; Zhou, Min; Li, Jianfeng

    2013-01-01

    In this paper, we combine the acoustic vector-sensor array parameter estimation problem with the parallel profiles with linear dependencies (PARALIND) model, which was originally applied to biology and chemistry. Exploiting the PARALIND decomposition approach, we propose a blind coherent two-dimensional direction of arrival (2D-DOA) estimation algorithm for arbitrarily spaced acoustic vector-sensor arrays subject to unknown locations. The proposed algorithm works well to achieve automatically paired azimuth and elevation angles for coherent and incoherent angle estimation of acoustic vector-sensor arrays, as well as the paired correlated matrix of the sources. Our algorithm, in contrast with conventional coherent angle estimation algorithms such as the forward backward spatial smoothing (FBSS) estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, not only has much better angle estimation performance, even for closely-spaced sources, but is also available for arbitrary arrays. Simulation results verify the effectiveness of our algorithm. PMID:23604030

  12. Coherent Excitonic Wavepackets in Two-Dimensional Square Dot-Arrays Driven by an In-Plane Uniform Electric Field

    Institute of Scientific and Technical Information of China (English)

    李秀平; 阎维贤

    2004-01-01

    We investigate the evolution behaviour of electron-hole pair wavepacket in optically excited square quantum-dot arrays driven by in-plane (x-y plane) uniform electric field E (viz, E = Exex + Eyey, ex,ey are unit vectors along x and y directions respectively), in the time domain. It is found that if the ratio of the x-component electric field Ex to the y-component electric field Ey is a rational p/q (p and q being coprime integer numbers),the wavepackets undergo a time-periodic breathing mode, with the period 2πp/ωBx, where ωBx = eExa/h, with a being the lattice constant of square dot arrays, h being Planck's constant, e being the electron charge. This finding provides a time-domain demonstration of the recent spectral result [Phys. Rev. Lett. 86 (2001)3116].

  13. A Hybrid Support Vector Machines and Two-dimensional Risk Matrix Model for Supply Chain Risk Assessment

    Directory of Open Access Journals (Sweden)

    Fan Jiang

    2014-03-01

    Full Text Available In recent years, the supply chain managements have been paid more and more attention. The supply chain risk management is an important content for enterprises implementing supply chain management. Therefore, how to measure the risk of supply chain is quite important. In this study, a supply chain risk evaluation model based on support vector machines and two-dimensional risk matrix is proposed. The index system of supply chain risk assessment which includes 14 indices is established. The case study shows that the proposed model is reasonable, effective and it can provide an important reference for supply chain risk management.

  14. Multiple-scattering theory for out-of-plane propagation of elastic waves in two-dimensional phononic crystals.

    Science.gov (United States)

    Mei, Jun; Liu, Zhengyou; Qiu, Chunyin

    2005-06-29

    We extend the multiple-scattering theory (MST) to out-of-plane propagating elastic waves in 2D periodical composites by taking into account the full vector character. The formalism for both the band structure calculation and the reflection and transmission coefficient calculation for finite slabs is presented. The latter is based on a double-layer scheme, which obtains the reflection and transmission matrix elements for the multilayer slab from those of a single layer. Being more rapid in both the band structure and the transmission coefficient calculations for out-of-plane propagating elastic waves, our approach especially shows great advantages in handling the systems with mixed solid and fluid components, for which the conventional plane wave approach fails. As the applications of the formalism, we calculate the band structure as well as the transmission coefficients through finite slabs for systems with lead rods in an epoxy host, steel rods in a water host and water rods in a PMMA host.

  15. Study on the Interface Effects Based on Two-Dimensional Green's Functions for the Fluid and Pyroelectric Two-Phase Plane under a Line Heat Source

    Directory of Open Access Journals (Sweden)

    Peng-Fei Hou

    2014-11-01

    Full Text Available Two-dimensional Green's functions for a line heat source applied in the fluid and pyroelectric two-phase plane are presented in this paper. By virtue of the two-dimensional general solutions which are expressed in harmonic functions, six newly introduced harmonic functions with undetermined constants are constructed. Then, all the pyroelectric components in the fluid and pyroelectric two-phase plane can be derived by substituting these harmonic functions into the corresponding general solutions. And the undetermined constants can be obtained by the interface compatibility conditions and the mechanical, electric, and thermal equilibrium conditions. Numerical results are given graphically by contours.

  16. Two-dimensional direction finding for low altitude target based on intensity measurement using an acoustic vector-sensor

    Institute of Scientific and Technical Information of China (English)

    CHEN Huawei; ZHAO Junwei

    2004-01-01

    A method of two-dimensional direction of arrival (DOA) estimation for low altitude target, which is based on intensity measurement using a three-dimensional differential pressure acoustic vector-sensor, is presented. With the perfect characteristics of acoustic vector sensor in the low frequency band, accurate DOA estimation is achieved under small array size. The validity of the proposed method was assessed by experiments on the noise signals radiated by a helicopter. The influence of acoustic sensor size, integral time and signal to noise ratio to the accuracy of DOA estimation were investigated, respectively. The performance comparisons demonstrated that it outperformed the traditional time-delay measurement based method for a small acoustic array.

  17. Myocardial Strain Imaging Based on Two-Dimensional Displacement Vector Measurement

    Science.gov (United States)

    Nitta, Naotaka; Shiina, Tsuyoshi

    2004-05-01

    The abnormalities of myocardial wall motion caused by changes in wall stiffness often appear in the early stage of ischemic heart disease. Since the myocardium exhibits complex and large motion, a two-dimensional (2D) or three-dimensional (3D) assessment of stiffness distribution is required for accurate diagnosis. Although a 3D assessment is ultimately required, as a stepped approach for practical use, we propose novel methods for tracking the 2D motion using a one-dimensional (1D) phased array and for assessing myocardial malfunction by visualizing the invariant of a strain tensor. The feasibilities of the proposed methods were evaluated by numerically simulating the short-axis imaging of a 3D myocardial model. This model includes a hard infarction located between 1 and 3 o’clock, which is difficult to detect by conventional tissue Doppler and strain rate imaging, and the motions of the model were assigned by referring to actual myocardial motion. These results revealed that the proposed imaging methods clearly depicted the hard infarction area which conventional imaging could not detect.

  18. Static internal performance of a thrust vectoring and reversing two-dimensional convergent-divergent nozzle with an aft flap

    Science.gov (United States)

    Re, R. J.; Leavitt, L. D.

    1986-01-01

    The static internal performance of a multifunction nozzle having some of the geometric characteristics of both two-dimensional convergent-divergent and single expansion ramp nozzles has been investigated in the static-test facility of the Langley 16-Foot Transonic Tunnel. The internal expansion portion of the nozzle consisted of two symmetrical flat surfaces of equal length, and the external expansion portion of the nozzle consisted of a single aft flap. The aft flap could be varied in angle independently of the upper internal expansion surface to which it was attached. The effects of internal expansion ratio, nozzle thrust-vector angle (-30 deg. to 30 deg., aft flap shape, aft flap angle, and sidewall containment were determined for dry and afterburning power settings. In addition, a partial afterburning power setting nozzle, a fully deployed thrust reverser, and four vertical takeoff or landing nozzle, configurations were investigated. Nozzle pressure ratio was varied up to 10 for the dry power nozzles and 7 for the afterburning power nozzles.

  19. Fractional Killing-Yano Tensors and Killing Vectors Using the Caputo Derivative in Some One- and Two-Dimensional Curved Space

    Directory of Open Access Journals (Sweden)

    Ehab Malkawi

    2014-01-01

    Full Text Available The classical free Lagrangian admitting a constant of motion, in one- and two-dimensional space, is generalized using the Caputo derivative of fractional calculus. The corresponding metric is obtained and the fractional Christoffel symbols, Killing vectors, and Killing-Yano tensors are derived. Some exact solutions of these quantities are reported.

  20. Slow Oscillations of In-plane Magnetoresistance in Strongly Anisotropic Quasi-Two-Dimensional Rare-Earth Tritellurides

    Science.gov (United States)

    Sinchenko, A. A.; Grigoriev, P. D.; Monceau, P.; Lejay, P.; Zverev, V. N.

    2016-12-01

    The slow oscillations of intralayer magnetoresistance in the quasi-2D metallic compounds TbTe_3 and GdTe_3 have been observed for the first time. These oscillations do not originate from small Fermi-surface pockets, as revealed usually by Shubnikov-de Haas oscillations, but from the entanglement of close frequencies due to a finite interlayer transfer integral t_z, either between the two Te planes forming a bilayer or between two adjacent bilayers, which allows to estimate its values. For TbTe_3 and GdTe_3, we obtain the estimate t_ z≈ 1 meV.

  1. In- and out-of-plane dynamic flexural behaviors of two-dimensional ensembles of vertically aligned single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kiani, Keivan, E-mail: k_kiani@kntu.ac.ir

    2014-09-15

    Useful nonlocal discrete and continuous models are developed to explain free vibration of two-dimensional (2D) ensembles of single-walled carbon nanotubes (SWCNTs) in bending. For this purpose, the models are constructed based on the nonlocal Rayleigh, Timoshenko, and higher-order beam theories. In contrast to an individual SWCNT exhibits identical bending behavior in different directions, for 2D ensemble networks of SWCNTs, it is shown that such a fact is completely dissimilar. Such an important issue leads to the definition of in-plane and out-of-plane flexural behaviors for such nanostructures. Subsequently, their corresponding fundamental frequencies are evaluated based on the proposed nonlocal models. The capabilities of the proposed nonlocal continuous models in predicting flexural frequencies of SWCNTs' ensembles with different numbers of SWCNTs as well as various levels of slenderness ratios are then explained. Such investigations confirm the high efficiency of the proposed continuous models. This matter would be of great importance in vibration analysis of highly populated ensembles of SWCNTs in which the discrete models may suffer from the size of the governing equations. The roles of the number of SWCNTs, slenderness ratio, intertube distance, small-scale parameter, and radius of the SWCNT on both in-plane and out-of-plane fundamental frequencies are addressed.

  2. Conformal Killing Vectors Of Plane Symmetric Four Dimensional Lorentzian Manifolds

    CERN Document Server

    Khan, Suhail; Bokhari, Ashfaque H; Khan, Gulzar Ali; Mathematics, Department of; Peshawar, University of; Pakhtoonkhwa, Peshawar Khyber; Pakistan.,; Petroleum, King Fahd University of; Minerals,; 31261, Dhahran; Arabia, Saudi

    2015-01-01

    In this paper, we investigate conformal Killing's vectors (CKVs) admitted by some plane symmetric spacetimes. Ten conformal Killing's equations and their general forms of CKVs are derived along with their conformal factor. The existence of conformal Killing's symmetry imposes restrictions on the metric functions. The conditions imposing restrictions on these metric functions are obtained as a set of integrability conditions. Considering the cases of time-like and inheriting CKVs, we obtain spacetimes admitting plane conformal symmetry. Integrability conditions are solved completely for some known non-conformally flat and conformally flat classes of plane symmetric spacetimes. A special vacuum plane symmetric spacetime is obtained, and it is shown that for such a metric CKVs are just the homothetic vectors (HVs). Among all the examples considered, there exists only one case with a six dimensional algebra of special CKVs admitting one proper CKV. In all other examples of non-conformally flat metrics, no proper ...

  3. In-plane anisotropy in two-dimensional electron gas at LaAlO3/SrTiO3(110) interface

    Science.gov (United States)

    Sheng-Chun, Shen; Yan-Peng, Hong; Cheng-Jian, Li; Hong-Xia, Xue; Xin-Xin, Wang; Jia-Cai, Nie

    2016-07-01

    A systematic study of the two-dimensional electron gas at LaAlO3/SrTiO3(110) interface reveals an anisotropy along two specific directions, [001] and . The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin-orbit coupling, and the spin relaxation mechanism along both directions belongs to D’yakonov-Perel’ (DP) scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions. Project supported by the Ministry of Science and Technology of China (Grant Nos. 2013CB921701, 2013CBA01603, and 2014CB920903), the National Natural Science Foundation of China (Grant Nos. 10974019, 51172029, 91121012, 11422430, 11374035, 11474022, and 11474024), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (Grant No. NCET-13-0054), and the Beijing Higher Education Young Elite Teacher Project, China (Grant No. YETP0238).

  4. Modeling of Lamb wave propagation in plate with two-dimensional phononic crystal layer coated on uniform substrate using plane-wave-expansion method

    Energy Technology Data Exchange (ETDEWEB)

    Hou Zhilin [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)], E-mail: zhilin.hou@lpmi.uhp-nancy.fr; Assouar, Badreddine M. [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)

    2008-03-17

    We show that the conversional three-dimensional plane wave expansion method can be revised to investigate the lamb wave propagation in the plate with two-dimensional phononic crystal layer coated on uniform substrate. We find that an imaginary three-dimensional periodic system can be constructed by stacking the studied plates and vacuum layers alternately, and then the Fourier series expansion can be performed. The difference between our imaginary periodic system and the true three-dimensional one is that, in our system, the Bloch feature of the wave along the thickness direction is broken. Three different systems are investigated by the proposed method as examples. The principle and reliability of the method are also discussed.

  5. Two-dimensional percolation transition at finite temperature: Phase boundary for in-plane magnetism in films with two atomic layers of Fe on W(110)

    Science.gov (United States)

    Belanger, R.; Venus, D.

    2017-02-01

    A two-dimensional (2D) percolation transition in Fe/W(110) ultrathin magnetic films occurs when islands in the second atomic layer percolate and resolve a frustrated magnetic state to produce long-range in-plane ferromagnetic order. Novel measurements of percolation using the magnetic susceptibility χ (θ ) as the films are deposited at a constant temperature, allow the long-range percolation transition to be observed as a sharp peak consistent with a critical phase transition. The measurements are used to trace the paramagnetic-to-ferromagnetic phase boundary between the T =0 percolation magnetic transition and the thermal Curie magnetic transition of the undiluted film. A quantitative comparison to critical scaling theory is made by fitting the functional form of the phase boundary. The fitted parameters are then used in theoretical expressions for χ (T ) in the critical region of the paramagnetic state to provide an excellent, independent representation of the experimental measurements.

  6. Conformal killing vectors of plane symmetric four dimensional lorentzian manifolds

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Suhail; Hussain, Tahir; Khan, Gulzar Ali [University of Peshawar, Department of Mathematics, Peshawar, Khyber Pakhtoonkhwa (Pakistan); Bokhari, Ashfaque H. [King Fahd University of Petroleum and Minerals, Department of Mathematics and Statistics, Dhahran (Saudi Arabia)

    2015-11-15

    In this paper, we investigate conformal Killing vectors (CKVs) admitted by some plane symmetric spacetimes. Ten conformal Killing's equations and their general forms of CKVs are derived along with their conformal factor. The existence of conformal Killing symmetry imposes restrictions on the metric functions. The conditions imposing restrictions on these metric functions are obtained as a set of integrability conditions. Considering the cases of time-like and inheriting CKVs, we obtain spacetimes admitting plane conformal symmetry. Integrability conditions are solved completely for some known non-conformally flat and conformally flat classes of plane symmetric spacetimes. A special vacuum plane symmetric spacetime is obtained, and it is shown that for such a metric CKVs are just the homothetic vectors (HVs). Among all the examples considered, there exists only one case with a six dimensional algebra of special CKVs admitting one proper CKV. In all other examples of non-conformally flat metrics, no proper CKV is found and CKVs are either HVs or Killing's vectors (KVs). In each of the three cases of conformally flat metrics, a fifteen dimensional algebra of CKVs is obtained of which eight are proper CKVs. (orig.)

  7. Leibniz operad on symplectic plane and cohomological vector fields

    CERN Document Server

    Uchino, K

    2011-01-01

    By using help of algebraic operad theory, Leibniz algebra theory and symplectic geometry are connected. We introduce the notion of cohomological vector field defined on nongraded symplectic plane. It will be proved that the cohomological vector fields induce the finite dimensional Leibniz algebras by the derived bracket construction. This proposition is a Leibniz analogue of the cohomological field theory in the category of Lie algebras. The basic properties of the cohomological fields will be studied, in particular, we discuss a factorization problem with the cohomological fields and introduce the notion of double-algebra in the category of Leibniz algebras.

  8. Derivatization technique to increase the spectral selectivity of two-dimensional Fourier transform infrared focal plane array imaging: analysis of binder composition in aged oil and tempera paint.

    Science.gov (United States)

    Zumbühl, Stefan; Scherrer, Nadim C; Eggenberger, Urs

    2014-01-01

    The interpretation of standard Fourier transform infrared spectra (FT-IR) on oil-based paint samples often suffers from interfering bands of the different compounds, namely, binder, oxidative aging products, carboxylates formed during aging, and several pigments and fillers. The distinction of the aging products such as ketone and carboxylic acid functional groups pose the next problem, as these interfere with the triglyceride esters of the oil. A sample preparation and derivatization technique using gaseous sulfur tetrafluoride (SF4), was thus developed with the aim to discriminate overlapping signals and achieve a signal enhancement on superposed compounds. Of particular interest in this context is the signal elimination of the broad carboxylate bands of the typical reaction products developing during the aging processes in oil-based paints, as well as signal interference originating from several typical pigments in this spectral range. Furthermore, it is possible to distinguish the different carbonyl-containing functional groups upon selective alteration. The derivatization treatment can be applied to both microsamples and polished cross sections. It increases the selectivity of the infrared spectroscopy technique in a fundamental manner and permits the identification and two-dimensional (2D) localization of binder components in aged paint samples at the micrometer scale. The combination of SF4 derivatization with high-resolution 2D FT-IR focal plane array (FPA) imaging delivers considerable advances to the study of micro-morphological processes involving organic compounds.

  9. Composite x-ray image assembly for large-field digital mammography with one- and two-dimensional positioning of a focal plane array

    Science.gov (United States)

    Halama, G.; McAdoo, J.; Liu, H.

    1998-01-01

    To demonstrate the feasibility of a novel large-field digital mammography technique, a 1024 x 1024 pixel Loral charge-coupled device (CCD) focal plane array (FPA) was positioned in a mammographic field with one- and two-dimensional scan sequences to obtain 950 x 1800 pixel and 3600 x 3600 pixel composite images, respectively. These experiments verify that precise positioning of FPAs produced seamless composites and that the CCD mosaic concept has potential for high-resolution, large-field imaging. The proposed CCD mosaic concept resembles a checkerboard pattern with spacing left between the CCDs for the driver and readout electronics. To obtain a complete x-ray image, the mosaic must be repositioned four times, with an x-ray exposure at each position. To reduce the patient dose, a lead shield with appropriately patterned holes is placed between the x-ray source and the patient. The high-precision motorized translation stages and the fiber-coupled-scintillating-screen-CCD sensor assembly were placed in the position usually occupied by the film cassette. Because of the high mechanical precision, seamless composites were constructed from the subimages. This paper discusses the positioning, image alignment procedure, and composite image results. The paper only addresses the formation of a seamless composite image from subimages and will not consider the effects of the lead shield, multiple CCDs, or the speed of motion.

  10. Two-Dimensional DOA and Polarization Estimation for a Mixture of Uncorrelated and Coherent Sources with Sparsely-Distributed Vector Sensor Array.

    Science.gov (United States)

    Si, Weijian; Zhao, Pinjiao; Qu, Zhiyu

    2016-05-31

    This paper presents an L-shaped sparsely-distributed vector sensor (SD-VS) array with four different antenna compositions. With the proposed SD-VS array, a novel two-dimensional (2-D) direction of arrival (DOA) and polarization estimation method is proposed to handle the scenario where uncorrelated and coherent sources coexist. The uncorrelated and coherent sources are separated based on the moduli of the eigenvalues. For the uncorrelated sources, coarse estimates are acquired by extracting the DOA information embedded in the steering vectors from estimated array response matrix of the uncorrelated sources, and they serve as coarse references to disambiguate fine estimates with cyclical ambiguity obtained from the spatial phase factors. For the coherent sources, four Hankel matrices are constructed, with which the coherent sources are resolved in a similar way as for the uncorrelated sources. The proposed SD-VS array requires only two collocated antennas for each vector sensor, thus the mutual coupling effects across the collocated antennas are reduced greatly. Moreover, the inter-sensor spacings are allowed beyond a half-wavelength, which results in an extended array aperture. Simulation results demonstrate the effectiveness and favorable performance of the proposed method.

  11. Two-Dimensional DOA and Polarization Estimation for a Mixture of Uncorrelated and Coherent Sources with Sparsely-Distributed Vector Sensor Array

    Directory of Open Access Journals (Sweden)

    Weijian Si

    2016-05-01

    Full Text Available This paper presents an L-shaped sparsely-distributed vector sensor (SD-VS array with four different antenna compositions. With the proposed SD-VS array, a novel two-dimensional (2-D direction of arrival (DOA and polarization estimation method is proposed to handle the scenario where uncorrelated and coherent sources coexist. The uncorrelated and coherent sources are separated based on the moduli of the eigenvalues. For the uncorrelated sources, coarse estimates are acquired by extracting the DOA information embedded in the steering vectors from estimated array response matrix of the uncorrelated sources, and they serve as coarse references to disambiguate fine estimates with cyclical ambiguity obtained from the spatial phase factors. For the coherent sources, four Hankel matrices are constructed, with which the coherent sources are resolved in a similar way as for the uncorrelated sources. The proposed SD-VS array requires only two collocated antennas for each vector sensor, thus the mutual coupling effects across the collocated antennas are reduced greatly. Moreover, the inter-sensor spacings are allowed beyond a half-wavelength, which results in an extended array aperture. Simulation results demonstrate the effectiveness and favorable performance of the proposed method.

  12. Towards two-dimensional search engines

    CERN Document Server

    Ermann, Leonardo; Shepelyansky, Dima L

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Information flow properties on PageRank-CheiRank plane are analyzed for networks of British, French and Italian Universities, Wikipedia, Linux Kernel, gene regulation and other networks. Methods of spam links control are also analyzed.

  13. Toward two-dimensional search engines

    Science.gov (United States)

    Ermann, L.; Chepelianskii, A. D.; Shepelyansky, D. L.

    2012-07-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank-CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed.

  14. Segment-orientated analysis of two-dimensional strain and strain rate as assessed by velocity vector imaging in patients with acute myocardial infarction

    Directory of Open Access Journals (Sweden)

    Thomas Butz, Corinna N. Lang, Marc van Bracht, Magnus W. Prull, Hakan Yeni, Petra Maagh, Gunnar Plehn, Axel Meissner, Hans-Joachim Trappe

    2011-01-01

    Full Text Available Aims: Strain rate imaging techniques have been proposed for the detection of ischemic or viable myocardium in coronary artery disease, which is still a challenge in clinical cardiology. This retrospective comparative study analyzed regional left ventricular function and scaring with two-dimensional strain (2DS in the first 4 to 10 days after acute anterior myocardial infarction (AMI.Methods and results: The study population consisted of 32 AMI patients with an LAD occlusion and successful reperfusion. The assessment of peak systolic 2DS and peak systolic strain rate (SR was performed segment-oriented with the angle-independent speckle tracking algorithm Velocity Vector Imaging (VVI. The infarcted, adjacent and non-infarcted segments were revealed by late enhancement MRI (LE-MRI, which was used as reference for the comparison with 2DS. The infarcted segments showed a significant decrease of tissue velocities, 2DS and SR in comparison to the non-affected segments.Conclusion: 2DS and SR as assessed by VVI seem to be a suitable approach for echocardiographic quantification of global and regional myocardial function as well as a promising tool for multimodal risk stratification after anterior AMI.

  15. Breakthrough in three-dimensional scoliosis diagnosis: significance of horizontal plane view and vertebra vectors

    OpenAIRE

    Illés, Tamás; Tunyogi-Csapó, Miklós; Somoskeöy, Szabolcs

    2010-01-01

    Scoliosis is a multifactorial three-dimensional (3D) spinal deformity with integral and directly related vertebral deviations in the coronal, sagittal and horizontal planes. Current classification and diagnostic methods rely on two-dimensional (2D) frontal and lateral X-ray images; no routine methods are available for the visualization and quantitative evaluation of deviations in the horizontal plane. The EOS 2D/3D system presented here is a new, low-dose, orthopedic radiodiagnostic device ba...

  16. Size Controlled Two-dimensional Co3O4 with Exposure of {111} Plane: Synthesis and Catalytic Properties for Photooxidation of Organics

    Science.gov (United States)

    The size controlled 2D hexagonal structured Co3O4 with exposure of the {111} plane was fabricated, and the catalytic properties for photooxidation of organics using as-prepared samples were investigated. 2D hexagonal structured Co3O4 with the size of 3 m displays higher photocat...

  17. Size Controlled Two-dimensional Co3O4 with Exposure of {111} Plane: Synthesis and Catalytic Properties for Photooxidation of Organics

    Science.gov (United States)

    The size controlled 2D hexagonal structured Co3O4 with exposure of the {111} plane was fabricated, and the catalytic properties for photooxidation of organics using as-prepared samples were investigated. 2D hexagonal structured Co3O4 with the size of 3 m displays higher photocat...

  18. The Generalized Two Dimensional Thermal-Electro-Elastic Solution for the Cracked-Half-Elliptical-Hole Problem in a Half Plane

    Directory of Open Access Journals (Sweden)

    Wang Y. J.

    2015-06-01

    Full Text Available The half elliptical hole with an edge crack in a thermopiezoelectric material is studied by using the complex variable method. First, the mapping function which maps the outside of the elliptical hole and the crack in the right half plane into the outside of a circular hole in a full plane is given by the method of conformal mapping. Then, the complex potential functions and the field intensity factors (FIF are presented according to the boundary conditions, respectively. Some useful results can be found by numerical analysis: 1 The influence of the heat flux on FIF depends on the model of the crack; 2 The shape and the size of the hole possess a significant effect on the field distribution at the crack tip.

  19. Wiimote Experiments: 3-D Inclined Plane Problem for Reinforcing the Vector Concept

    Science.gov (United States)

    Kawam, Alae; Kouh, Minjoon

    2011-01-01

    In an introductory physics course where students first learn about vectors, they oftentimes struggle with the concept of vector addition and decomposition. For example, the classic physics problem involving a mass on an inclined plane requires the decomposition of the force of gravity into two directions that are parallel and perpendicular to the…

  20. State-Vector Space and Canonical Coherent States in Noncommutative Plane

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The structure of the state-vector space of identical bosons in noncommutative spaces is investigated. To maintain Bose-Einstein statistics the commutation relations of phase space variables should simultaneously include coordinate-coordinate non-commutativity and momentum-momentum non-commutativity, which leads to a kind of de-formed Heisenberg-Weyl algebra. Although there is no ordinary number representation in this state-vector space, several set of orthogonal and complete state-vectors can be derived which are common eigenvectors of corresponding pairs of commuting Hermitian operators. As a simple application of this state-vector space, an explicit form of two-dimensional canonical coherent state is constructed and its properties are discussed.

  1. An experimental investigation of thrust vectoring two-dimensional convergent-divergent nozzles installed in a twin-engine fighter model at high angles of attack

    Science.gov (United States)

    Capone, Francis J.; Mason, Mary L.; Leavitt, Laurence D.

    1990-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine thrust vectoring capability of subscale 2-D convergent-divergent exhaust nozzles installed on a twin engine general research fighter model. Pitch thrust vectoring was accomplished by downward rotation of nozzle upper and lower flaps. The effects of nozzle sidewall cutback were studied for both unvectored and pitch vectored nozzles. A single cutback sidewall was employed for yaw thrust vectoring. This investigation was conducted at Mach numbers ranging from 0 to 1.20 and at angles of attack from -2 to 35 deg. High pressure air was used to simulate jet exhaust and provide values of nozzle pressure ratio up to 9.

  2. Predicting Two-Dimensional Silicon Carbide Monolayers.

    Science.gov (United States)

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  3. A new two-dimensional approach to quantitative prediction for collision cross-section of more than 110 singly protonated peptides by a novel moecular electronegativity-interaction vector through quantitative structure-spectrometry relationship studies

    Institute of Scientific and Technical Information of China (English)

    ZHOU Peng; MEI Hu; TIAN Feifei; WANG Jiaona; WU Shirong; LI Zhiliang

    2007-01-01

    Based on two-dimensional topological characters,a novel method called molecular electronegativityinteraction vector(MEIV)is proposed to parameterize molecular structures.Applying MEIV into quantitative structure-spectrometry relationship studies on ion mobility spectrometry collision cross-sections of 113 singly protonated peptides,three models were strictly obtained,with correlative coefficient r and leave-one-out cross-validation q of 0.983,0.979,0.981,0.979 and 0.980,0.978,respectively.Thus,the MEIV is confirmed to be potent to structural characterizations and property predictions for organic and biologic molecules.

  4. Simplified single plane echocardiography is comparable to conventional biplane two-dimensional echocardiography in the evaluation of left atrial volume: a study validated by three-dimensional echocardiography in 143 individuals.

    Science.gov (United States)

    Vieira-Filho, Normando G; Mancuso, Frederico J N; Oliveira, Wercules A A; Gil, Manuel A; Fischer, Cláudio H; Moises, Valdir A; Campos, Orlando

    2014-03-01

    The left atrial volume index (LAVI) is a biomarker of diastolic dysfunction and a predictor of cardiovascular events. Three-dimensional echocardiography (3DE) is highly accurate for LAVI measurements but is not widely available. Furthermore, biplane two-dimensional echocardiography (B2DE) may occasionally not be feasible due to a suboptimal two-chamber apical view. Simplified single plane two-dimensional echocardiography (S2DE) could overcome these limitations. We aimed to compare the reliability of S2DE with other validated echocardiographic methods in the measurement of the LAVI. We examined 143 individuals (54 ± 13 years old; 112 with heart disease and 31 healthy volunteers; all with sinus rhythm, with a wide range of LAVI). The results for all the individuals were compared with B2DE-derived LAVIs and validated using 3DE. The LAVIs, as determined using S2DE (32.7 ± 13.1 mL/m(2)), B2DE (31.9 ± 12.7 mL/m(2)), and 3DE (33.1 ± 13.4 mL/m(2)), were not significantly different from each other (P = 0.85). The S2DE-derived LAVIs correlated significantly with those obtained using both B2DE (r = 0.98; P < 0.001) and 3DE (r = 0.93; P < 0.001). The mean difference between the S2DE and B2DE measurements was <1.0 mL/m(2). Using the American Society of Echocardiography criteria for grading LAVI enlargement (normal, mild, moderate, severe), we observed an excellent agreement between the S2DE- and B2DE-derived classifications (κ = 0.89; P < 0.001). S2DE is a simple, rapid, and reliable method for LAVI measurement that may expand the use of this important biomarker in routine echocardiographic practice.

  5. Two dimensional vernier

    Science.gov (United States)

    Juday, Richard D. (Inventor)

    1992-01-01

    A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.

  6. Elastic Wave Scattering by Two-Dimensional Periodical Array of Cylinders

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We extend the multiple-scattering theory (MST) for elastic wave scattering and propagating in two-dimensional composite. The formalism for the band structure calculation is presented by taking into account the full vector character of the elastic wave. As a demonstration of application of the formalism, we calculate the band structure of elastic wave propagating in a two-dimensional periodic arrangement of cylinders. The results manifest that the MST shows great promise in complementing the plane-wave (PW) approach for the study of elastic wave.

  7. An Analysis of Different Representations for Vectors and Planes in R[superscript 3]: Learning Challenges

    Science.gov (United States)

    Sandoval, Ivonne; Possani, Edgar

    2016-01-01

    The purpose of this paper is to present an analysis of the difficulties faced by students when working with different representations of vectors, planes and their intersections in R[superscript 3]. Duval's theoretical framework on semiotic representations is used to design a set of evaluating activities, and later to analyze student work. The…

  8. Spectral Anisotropy of Els\\"asser Variables in Two Dimensional Wave-vector Space as Observed in the Fast Solar Wind Turbulence

    CERN Document Server

    Yan, Limei; Zhang, Lei; Tu, Chuanyi; Marsch, Eckart; Chen, Christopher H K; Wang, Xin; Wang, Linghua; Wicks, Robert T

    2016-01-01

    Intensive studies have been conducted to understand the anisotropy of solar wind turbulence. However, the anisotropy of Els\\"asser variables ($\\textbf{Z}^\\pm$) in 2D wave-vector space has yet to be investigated. Here we first verify the transformation based on the projection-slice theorem between the power spectral density PSD$_{2D}(k_\\parallel,k_\\perp )$ and the spatial correlation function CF$_{2D} (r_\\parallel,r_\\perp )$. Based on the application of the transformation to the magnetic field and the particle measurements from the WIND spacecraft, we investigate the spectral anisotropy of Els\\"asser variables ($\\textbf{Z}^\\pm$), and the distribution of residual energy E$_{R}$, Alfv\\'en ratio R$_{A}$ and Els\\"asser ratio R$_{E}$ in the $(k_\\parallel,k_\\perp)$ space. The spectra PSD$_{2D}(k_\\parallel,k_\\perp )$ of $\\textbf{B}$, $\\textbf{V}$, and $\\textbf{Z}_{major}$ (the larger of $\\textbf{Z}^\\pm$) show a similar pattern that PSD$_{2D}(k_\\parallel,k_\\perp )$ is mainly distributed along a ridge inclined toward t...

  9. Two-dimensional optical spectroscopy

    CERN Document Server

    Cho, Minhaeng

    2009-01-01

    Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.

  10. Achievable Angles Between two Compressed Sparse Vectors Under Norm/Distance Constraints Imposed by the Restricted Isometry Property: A Plane Geometry Approach

    CERN Document Server

    Chang, Ling-Hua

    2012-01-01

    The angle between two compressed sparse vectors subject to the norm/distance constraints imposed by the restricted isometry property (RIP) of the sensing matrix plays a crucial role in the studies of many compressive sensing (CS) problems. Assuming that (i) u and v are two sparse vectors separated by an angle thetha, and (ii) the sensing matrix Phi satisfies RIP, this paper is aimed at analytically characterizing the achievable angles between Phi*u and Phi*v. Motivated by geometric interpretations of RIP and with the aid of the well-known law of cosines, we propose a plane geometry based formulation for the study of the considered problem. It is shown that all the RIP-induced norm/distance constraints on Phi*u and Phi*v can be jointly depicted via a simple geometric diagram in the two-dimensional plane. This allows for a joint analysis of all the considered algebraic constraints from a geometric perspective. By conducting plane geometry analyses based on the constructed diagram, closed-form formulae for the m...

  11. Two-dimensional Thrust Vectoring Nozzle Design and Numerical Simulation Based on Single Secondary Injection%基于单缝射流的二元推力矢量喷管设计及数值模拟

    Institute of Scientific and Technical Information of China (English)

    王伟; 宋文艳; 罗飞腾; 李宁

    2011-01-01

    喷管是发动机产生推力的主要部件,其气动性能对发动机的性能具有决定性的影响。本文利用简化特征线法设计二元收敛-扩张(2DCD)推力矢量喷管模型;采用RNGk-ε湍流模型和非平衡壁面函数对单缝二次流喷射后的喷管流场进行数值模拟,分析了射流位置、主流落压比(NPR)、二次流与主流总压比(SPR)等参数对矢量喷管气动性能的影响。计算结果表明:二次射流位置对激波强度及推力矢量角有较大影响,开缝位置越接近喷管出口,推力矢量越大;喷射位置固定,激波强度和推力矢量角主要受SPR影响;SPR相同,随着NPR的增加,存在着一个最大推力矢量角。%Nozzle is the main component of an engine,which produces thrust.Its aerodynamic performance is of a decisive influence to engine performance.A Two-Dimensional Convergent-Divergent(2DCD) thrust vectoring nozzle model with fixed length is designed by the simplified method of characteristics in this paper.The full flow-field of the 2DCD thrust vectoring nozzle with single secondary injection are numerically simulated by CFD method,with the RNG turbulence model and non-equilibrium wall functions employed.The influence of secondary injection locations,Nozzle Pressure Ratio(NPR) and Secondary Pressure Ratio(SPR) on aerodynamic performance of thrust vectoring nozzle are examined.The numerical results indicate that:the secondary injection location is of significant effect on shock intensity and thrust vectoring angle,the thrust vectoring angle gradually increase when secondary injection location is transferred toward the nozzle;at the same secondary injection location,the shock intensity and thrust vectoring angle are mainly affected by SPR;at the same of SPR,there exists a maximum thrust vectoring angle as NPR increasing.

  12. Towards two-dimensional search engines

    OpenAIRE

    Ermann, Leonardo; Chepelianskii, Alexei D.; Shepelyansky, Dima L.

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Statistical properties of inf...

  13. Contributions in anomalous fermion momenta of neutral vector boson in plane-wave field

    CERN Document Server

    Klimenko, E Y

    2002-01-01

    The contributions of the neutral vector boson to the anomalous magnetic and electric momenta of the polarized fermion moving in the plane-wave electromagnetic field are considered in this paper. The contributions are divided by the fermion spin polarization states, which makes it possible to investigate the important problem on the contributions to the fermion anomalous momenta, coming from the the fermion transition to the intermediate state spin-nonflip or spin flip of fermion

  14. CONTROL OF TWO DIMENSIONAL JETS USING MINIATURE ZERO MASS FLUX JETS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Zero mass flux jets, synthesized by acoustic actuators, have been used for the purpose of jet mixing enhancement and jet vectoring. Zero mass flux jets composed of entirely entrained fluid allow momentum transfer into the embedding flow. In the present experiments, miniature-scale high aspect ratio actuator jets are placed along the long sides and near the exit plane of a primary two-dimensional jet. In different modes, the primary jet can be vectored either towards or away from the actuator jets and the jet mixing is enhanced. The disturbance of the excitation frequency is developed while the unstable frequency of the primary jet is completely suppressed.

  15. Interaction of two-dimensional magnetoexcitons

    Science.gov (United States)

    Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.

    2017-04-01

    We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .

  16. Horizontal Coriolis Vector: When Can We Neglect It?: A f-Plane Analysis

    Science.gov (United States)

    Yano, Jun-Ichi

    2016-04-01

    Under the traditional approximations, the horizontal component of the Coriolis vector is neglected in large-scale atmospheric modelling. [A major exception to this rule is the UK Met Office Unified Model.] Almost any standard textbook assures us this is a valid approximation. A simple scale analysis can just suggest us that so long as the aspect ratio of the atmosphere is small enough (as the case with the standard parameters) this horizontal Coriolis vector can be neglected. However, a straight linear-wave analysis on the f-plane shows that the wave dispersion relationship is clearly different in large-scale limit (i.e., limit of vanishing horizontal wavenumber) between the cases with and without the horizontal component of the Coriolis vector. For this reason, Gerkema and Shrira (2005, JFM) suggest that the effect of the horizontal Coriolis vector constitutes a singular perturbation. The goal of the present talk is to elucidate what kind of singularities is involved for generating such an unintuitive wave-dispersion behavior. The key starting point of the analysis is to realize that in the large-scale limit, all the waves reduce to the inertial oscillations without horizontal structures specified. This is a state of degeneracy in the same sense as in the classical quasi-geostrophic problem. In order to resolve this degeneracy, we have to proceed to a higher-order of the equation system, to that order the horizontal Coriolis vector plays a critical role. The full analysis will be presented during the talk.

  17. Two-dimensional Kagome photonic bandgap waveguide

    DEFF Research Database (Denmark)

    Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou;

    2000-01-01

    The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

  18. Band structure of absorptive two-dimensional photonic crystals

    Science.gov (United States)

    van der Lem, Han; Tip, Adriaan; Moroz, Alexander

    2003-06-01

    The band structure for an absorptive two-dimensional photonic crystal made from cylinders consisting of a Drude material is calculated. Absorption causes the spectrum to become complex and form islands in the negative complex half-plane. The boundaries of these islands are not always formed by the eigenvalues calculated for Bloch vectors on the characteristic path, and we find a hole in the spectrum. For realistic parameter values, the real part of the spectrum is hardly influenced by absorption, typically less than 0.25%. The employed method uses a Korringa-Kohn-Rostoker procedure together with analytical continuation. This results in an efficient approach that allows these band-structure calculations to be done on a Pentium III personal computer.

  19. Two dimensional fermions in four dimensional YM

    CERN Document Server

    Narayanan, R

    2009-01-01

    Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.

  20. Bound states of two-dimensional relativistic harmonic oscillators

    Institute of Scientific and Technical Information of China (English)

    Qiang Wen-Chao

    2004-01-01

    We give the exact normalized bound state wavefunctions and energy expressions of the Klein-Gordon and Dirac equations with equal scalar and vector harmonic oscillator potentials in the two-dimensional space.

  1. A two-dimensional Dirac fermion microscope

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-01

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  2. A two-dimensional Dirac fermion microscope.

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-09

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  3. Plane-wave transverse oscillation for high-frame-rate 2-D vector flow imaging.

    Science.gov (United States)

    Lenge, Matteo; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Liebgott, Hervé

    2015-12-01

    Transverse oscillation (TO) methods introduce oscillations in the pulse-echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse-echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of -3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented.

  4. Spatial dispersion in two-dimensional plasmonic crystals: Large blueshifts promoted by diffraction anomalies

    DEFF Research Database (Denmark)

    David, Christin; Christensen, Johan; Mortensen, N. Asger

    2016-01-01

    We develop a methodology to incorporate nonlocal optical response of the free electron gas due to quantum-interaction effects in metal components of periodic two-dimensional plasmonic crystals and study the impact of spatial dispersion on promising building blocks for photonic circuits. Within th...... at normal incidence and the surprisingly large structural parameters at which finite blueshifts are observable, which we attribute to diffraction that offers nonvanishing in-plane wave vector components and increases the penetration depth of longitudinal (nonlocal) modes....

  5. Two-dimensional relativistic electromagnetic dromion-like soliton in a cold transparent plasma

    Institute of Scientific and Technical Information of China (English)

    Wang Yun-Liang; Zhou Zhong-Xiang; Yuan Cheng-Xun; Jiang Xiang-Qian; Qin Ru-Hu

    2006-01-01

    By using a standard multiple scale method, a Davey-Stewartson (DS) equation has been derived and also applied to a multi-dimensional analytical investigation on the interaction of an ultra-intense laser pulse with a cold unmagnetized transparent electron-ion plasma. The regions of instability are found by considering the modulation instability of a plane wave solution of the DS equation. The DS equation is just of the Daveylution, i.e. a two-dimensional (2D) dromion soliton decaying exponentially in all spatial directions. A 2D relativistic electromagnetic dromion-like soliton (2D REDLS) is derived for a vector potential.

  6. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    of this thesis is on online comprehensive two-dimensional liquid chromatography (online LC×LC) with reverse phase in both dimensions (online RP×RP). Since online RP×RP has not been attempted before within this research group, a significant part of this thesis consists of knowledge and experience gained...

  7. Acoustic excitation of diffusion flames with coherent structure in a plane shear layer. ; Application of active combustion control to two-dimensional phase-locked arranging measurements. Soshiki kozo wo tomonau heimen sendai kakusan kaen no onkyo reiki. ; Nijigen iso heikin bunpu sokutei eno active nensho seigyo no oyo

    Energy Technology Data Exchange (ETDEWEB)

    Ishino, Y.; Kojima, T.; Oiwa, N.; Yamaguchi, S. (Nagoya Institute of Technology, Nagoya (Japan))

    1993-11-25

    The acoustic excitation of a plane diffusion flame enhances the periodicity of organized eddy controlled combustion. In this study, to clarify an effectiveness of application of active combustion control, phase characteristics of the excited eddy flames with high periodicity have been examined. A computer-aided phase-locked averaging method was employed to obtain graphical two-dimensional contour maps of the instantaneous profiles of temperature and CH emission. Both maps consisting of eight consecutive phases indicated clearly not only the periodic behavior of the organized eddy flame, but also the gas dynamic properties peculiar to those flames with coherent structure. In addition, the profiles of local contribution of the sound field to the combustion process were examined by calculating the two-dimensional distribution of the local Rayleigh index. Calculation results of the two-dimensional distribution of the local Rayleigh index indicated that the organized eddy flames have high sensitivity to sound, and play an important role in an interaction of sound and flame. 6 refs., 9 figs.

  8. Two dimensional unstable scar statistics.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Two-Dimensional Vernier Scale

    Science.gov (United States)

    Juday, Richard D.

    1992-01-01

    Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.

  10. Two-dimensional elasticity solutions for in-plane free vibration of annular plates with elastically restrained edges%弹性约束边界圆环板面内自由振动的二维弹性解

    Institute of Scientific and Technical Information of China (English)

    蒲育; 赵海英; 滕兆春; 韩国强; 杨晔

    2016-01-01

    Based on the two-dimension theory of linear elasticity and applying Hamilton's principle,the in-plane free vibration of governing differential equations for annular plates are obtained.Applying differential quadrature method (DQM),the frequencies of in-plane free vibration of annular plates with elastically restrained edges are investigated.All the classical boundary for in-plane displacements can be simulated by setting the stiffnesses of the restraining springs to either zero or infinite.The results presented in this paper has illustrated the analytical method was effective and accurate by comparison of previously reported results with those published in literatures.Finally,The influence of the boundary conditions,geometrical parameter,and stiffness coefficients on the dimensionless frequencies of the annular plates are fully investigated.%基于二维线弹性理论,应用哈密顿原理导出弹性约束边界圆环板面内自由振动的控制微分方程。采用微分求积法(DQM)数值研究了弹性约束边界圆环板面内自由振动的频率特性。通过设置弹性刚度系数为0或∞,问题退化为四种典型边界圆环板的面内自由振动,与已有文献的计算数值结果进行比较,证实本文的分析求解方法行之有效。最后全面考虑了圆环板边界条件、几何系数及刚度系数对自振频率的影响。

  11. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    Two-dimensional liquid chromatography has received increasing interest due to the rise in demand for analysis of complex chemical mixtures. Separation of complex mixtures is hard to achieve as a simple consequence of the sheer number of analytes, as these samples might contain hundreds or even...... dimensions. As a consequence of the conclusions made within this thesis, the research group has, for the time being, decided against further development of online LC×LC systems, since it was not deemed ideal for the intended application, the analysis of the polar fraction of oil. Trap-and...

  12. Two-dimensional capillary origami

    Energy Technology Data Exchange (ETDEWEB)

    Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

    2016-01-08

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  13. Three-dimensional isotropic fat-suppressed proton density-weighted MRI at 3 tesla using a T/R-coil can replace multiple plane two-dimensional sequences in knee imaging

    Energy Technology Data Exchange (ETDEWEB)

    Homsi, R.; Luetkens, J.A. [Bonn Univ. (Germany). Dept. of Radiology; Gieseke, J. [Philips Healthcare, Hamburg (Germany); and others

    2016-10-15

    To evaluate whether a 3D proton density-weighted fat-suppressed sequence (PDwFS) of the knee is able to replace multiplanar 2D-PDwFS. 52 patients (26 men, mean age: 41.9±14.5 years) underwent magnetic resonance imaging (MRI) of the knee at 3.0 Tesla using a T/R-coil. The imaging protocol included 3 planes of 2D-PDwFS (acquisition time (AT): 6:40 min; voxel sizes: 0.40-0.63 x 0.44-0.89 x 3 mm{sup 3}) and a 3D-PDwFS (AT: 6:31 min; voxel size: 0.63 x 0.68 x 0.63 mm{sup 3}). Homogeneity of fat suppression (HFS), artifacts, and image sharpness (IS) were evaluated on a 5-point scale (5[excellent] - 1[non-diagnostic]). The sum served as a measure for the overall image quality (OIQ). Contrast ratios (CR) compared to popliteal muscle were calculated for the meniscus (MEN), anterior (ACL) and posterior cruciate ligaments (PCL). In 13 patients who underwent arthroscopic knee surgery, two radiologists evaluated the presence of meniscal, ligamental and cartilage lesions to estimate the sensitivity and specificity of lesion detection. The CR was higher in the ACL, PCL and MEN in 3D- PDwFS compared to 2D-PDwFS (p<0.01 for ACL and PCL; p=0.07 for MEN). Compared to 2D images, the OIQ was rated higher in 3D-PDwFS images (p<0.01) due to fewer artifacts and HFS despite the lower IS (p<0.01). The sensitivity and specificity of lesion detection in 3D- and 2D-PDwFS were similar. Compared to standard multiplanar 2D-PDwFS knee imaging, isotropic high spatial resolution 3D-PDwFS of the knee at 3.0T can be acquired with high image quality in a reasonable scan time. Multiplanar reformations in arbitrary planes may serve as an additional benefit of 3D-PDwFS.

  14. FACE RECOGNITION USING TWO DIMENSIONAL LAPLACIAN EIGENMAP

    Institute of Scientific and Technical Information of China (English)

    Chen Jiangfeng; Yuan Baozong; Pei Bingnan

    2008-01-01

    Recently,some research efforts have shown that face images possibly reside on a nonlinear sub-manifold. Though Laplacianfaces method considered the manifold structures of the face images,it has limits to solve face recognition problem. This paper proposes a new feature extraction method,Two Dimensional Laplacian EigenMap (2DLEM),which especially considers the manifold structures of the face images,and extracts the proper features from face image matrix directly by using a linear transformation. As opposed to Laplacianfaces,2DLEM extracts features directly from 2D images without a vectorization preprocessing. To test 2DLEM and evaluate its performance,a series of ex-periments are performed on the ORL database and the Yale database. Moreover,several experiments are performed to compare the performance of three 2D methods. The experiments show that 2DLEM achieves the best performance.

  15. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

    Science.gov (United States)

    Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N; Strano, Michael S

    2012-11-01

    The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. TMDCs such as MoS(2), MoSe(2), WS(2) and WSe(2) have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. We review the historical development of TMDCs, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.

  16. Low-frequency scattering from two-dimensional perfect conductors

    DEFF Research Database (Denmark)

    Hansen, Thorkild; Yaghjian, A.D

    1991-01-01

    Exact expressions have been obtained for the leading terms in the low-frequency expansions of the far fields scattered from three different types of two-dimensional perfect conductors: a cylinder with finite cross section, a cylindrical bump on an infinite ground plane, and a cylindrical dent...

  17. Piezoelectricity and Piezomagnetism: Duality in two-dimensional checkerboards

    Science.gov (United States)

    Fel, Leonid G.

    2002-05-01

    The duality approach in two-dimensional two-component regular checkerboards is extended to piezoelectricity and piezomagnetism. The relation between the effective piezoelectric and piezomagnetic moduli is found for a checkerboard with the p6'mm'-plane symmetry group (dichromatic triangle).

  18. Zero sound in a two-dimensional dipolar Fermi gas

    NARCIS (Netherlands)

    Lu, Z.K.; Matveenko, S.I.; Shlyapnikov, G.V.

    2013-01-01

    We study zero sound in a weakly interacting two-dimensional (2D) gas of single-component fermionic dipoles (polar molecules or atoms with a large magnetic moment) tilted with respect to the plane of their translational motion. It is shown that the propagation of zero sound is provided by both mean-f

  19. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  20. Two-dimensional capillary origami

    Science.gov (United States)

    Brubaker, N. D.; Lega, J.

    2016-01-01

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid.

  1. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  2. Spatio-temporal Rich Model Based Video Steganalysis on Cross Sections of Motion Vector Planes.

    Science.gov (United States)

    Tasdemir, Kasim; Kurugollu, Fatih; Sezer, Sakir

    2016-05-11

    A rich model based motion vector steganalysis benefiting from both temporal and spatial correlations of motion vectors is proposed in this work. The proposed steganalysis method has a substantially superior detection accuracy than the previous methods, even the targeted ones. The improvement in detection accuracy lies in several novel approaches introduced in this work. Firstly, it is shown that there is a strong correlation, not only spatially but also temporally, among neighbouring motion vectors for longer distances. Therefore, temporal motion vector dependency along side the spatial dependency is utilized for rigorous motion vector steganalysis. Secondly, unlike the filters previously used, which were heuristically designed against a specific motion vector steganography, a diverse set of many filters which can capture aberrations introduced by various motion vector steganography methods is used. The variety and also the number of the filter kernels are substantially more than that of used in previous ones. Besides that, filters up to fifth order are employed whereas the previous methods use at most second order filters. As a result of these, the proposed system captures various decorrelations in a wide spatio-temporal range and provides a better cover model. The proposed method is tested against the most prominent motion vector steganalysis and steganography methods. To the best knowledge of the authors, the experiments section has the most comprehensive tests in motion vector steganalysis field including five stego and seven steganalysis methods. Test results show that the proposed method yields around 20% detection accuracy increase in low payloads and 5% in higher payloads.

  3. Classifying Two-dimensional Hyporeductive Triple Algebras

    CERN Document Server

    Issa, A Nourou

    2010-01-01

    Two-dimensional real hyporeductive triple algebras (h.t.a.) are investigated. A classification of such algebras is presented. As a consequence, a classification of two-dimensional real Lie triple algebras (i.e. generalized Lie triple systems) and two-dimensional real Bol algebras is given.

  4. Singular analysis of two-dimensional bifurcation system

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Bifurcation properties of two-dimensional bifurcation system are studied in this paper.Universal unfolding and transition sets of the bifurcation equations are obtained.The whole parametric plane is divided into several different persistent regions according to the type of motion,and the different qualitative bifurcation diagrams in different persistent regions are given.The bifurcation properties of the two-dimensional bifurcation system are compared with its reduced one-dimensional system.It is found that the system which is reduced to one dimension has lost many bifurcation properties.

  5. Field analysis of two-dimensional focusing grating couplers

    Science.gov (United States)

    Borsboom, P.-P.; Frankena, H. J.

    1995-05-01

    A different technique was developed by which several two-dimensional dielectric optical gratings, consisting 100 or more corrugations, were treated in a numerical reliable approach. The numerical examples that were presented were restricted to gratings made up of sequences of waveguide sections symmetric about the x = 0 plane. The newly developed method was effectively used to investigate the field produced by a two-dimensional focusing grating coupler. Focal-region fields were determined for three symmetrical gratings with 19, 50, and 124 corrugations. For focusing grating coupler with limited length, high-frequency intensity variations were noted in the focal region.

  6. Self-assembly of two-dimensional DNA crystals

    Institute of Scientific and Technical Information of China (English)

    SONG Cheng; CHEN Yaqing; WEI Shuai; YOU Xiaozeng; XIAO Shoujun

    2004-01-01

    Self-assembly of synthetic oligonucleotides into two-dimensional lattices presents a 'bottom-up' approach to the fabrication of devices on nanometer scale. We report the design and observation of two-dimensional crystalline forms of DNAs that are composed of twenty-one plane oligonucleotides and one phosphate-modified oligonucleotide. These synthetic sequences are designed to self-assemble into four double-crossover (DX) DNA tiles. The 'sticky ends' of these tiles that associate according to Watson-Crick's base pairing are programmed to build up specific periodic patterns upto tens of microns. The patterned crystals are visualized by the transmission electron microscopy.

  7. Equivalency of two-dimensional algebras

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S. [Universidade Federal da Bahia (UFBA), BA (Brazil). Inst. de Fisica

    2011-07-01

    Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)

  8. Two-dimensional function photonic crystals

    CERN Document Server

    Wu, Xiang-Yao; Liu, Xiao-Jing; Liang, Yu

    2016-01-01

    In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals.

  9. Collective charge excitations of the two-dimensional electride Ca2N

    Science.gov (United States)

    Cudazzo, Pierluigi; Gatti, Matteo

    2017-09-01

    Ca2N is a layered material that has been recently identified as a two-dimensional (2D) electride, an unusual ionic compound in which electrons serve as anions. The electronic properties of 2D electrides attract considerable interest as the anionic electrons, which form a 2D layer sandwiched between atomic planes, are highly mobile as they are not attached to any ion. Here, on the basis of first-principles time-dependent density-functional theory calculations, we investigate the collective excitations of the electrons—i.e., the plasmons—in Ca2N as a function of wave vector q . Our calculations reveal an intrinsic negative in-plane dispersion of the anionic plasmon, in striking contrast with the homogeneous electron gas. Moreover, for wave vectors q normal to the planes, we find a long-lived plasmon that continues to exist well beyond the first Brillouin zone. This is a mark of the electronic inhomogeneities in the charge response that Ca2N shares with other layered materials like transition-metal dichalcogenides and MgB2. Finally, we compare the plasmon properties of Ca2N in its bulk and monolayer forms, which shows the effect of the different electronic structures and dimensionalities.

  10. Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals

    Energy Technology Data Exchange (ETDEWEB)

    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

  11. A two-dimensional spin liquid in quantum kagome ice.

    Science.gov (United States)

    Carrasquilla, Juan; Hao, Zhihao; Melko, Roger G

    2015-06-22

    Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.

  12. Synthetic Aperture Vector Flow Imaging

    DEFF Research Database (Denmark)

    Oddershede, Niels

    2008-01-01

    of the thesis considers a method for estimating the two-dimensional velocity vector within the image plane. This method, called synthetic aperture vector flow imaging, is first shortly reviewed. The main contribution of this work is partly an analysis of the method with respect to focusing effects, motion...... estimation. The method can be used for increasing the frame rate of color flow maps or alternatively for a new imaging modality entitled quadroplex imaging, featuring a color flow map and two independent spectrograms at a high frame rate. The second is an alternative method for ultrasonic vector velocity...

  13. Hadamard States and Two-dimensional Gravity

    CERN Document Server

    Salehi, H

    2001-01-01

    We have used a two-dimensional analog of the Hadamard state-condition to study the local constraints on the two-point function of a linear quantum field conformally coupled to a two-dimensional gravitational background. We develop a dynamical model in which the determination of the state of the quantum field is essentially related to the determination of a conformal frame. A particular conformal frame is then introduced in which a two-dimensional gravitational equation is established.

  14. Topological defects in two-dimensional crystals

    OpenAIRE

    Chen, Yong; Qi, Wei-Kai

    2008-01-01

    By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.

  15. Spirals and Skyrmions in two dimensional oxide heterostructures.

    Science.gov (United States)

    Li, Xiaopeng; Liu, W Vincent; Balents, Leon

    2014-02-14

    We construct the general free energy governing long-wavelength magnetism in two dimensional oxide heterostructures, which applies irrespective of the microscopic mechanism for magnetism. This leads, in the relevant regime of weak but non-negligible spin-orbit coupling, to a rich phase diagram containing in-plane ferromagnetic, spiral, cone, and Skyrmion lattice phases, as well as a nematic state stabilized by thermal fluctuations.

  16. Spatial dispersion in two-dimensional plasmonic crystals: Large blueshifts promoted by diffraction anomalies

    Science.gov (United States)

    David, Christin; Christensen, Johan; Mortensen, N. Asger

    2016-10-01

    We develop a methodology to incorporate nonlocal optical response of the free electron gas due to quantum-interaction effects in metal components of periodic two-dimensional plasmonic crystals and study the impact of spatial dispersion on promising building blocks for photonic circuits. Within the framework of the hydrodynamic model, we observe significant changes with respect to the commonly employed local-response approximation, but also in comparison with homogeneous metal films where nonlocal effects have previously been considered. Notable are the emergence of a contribution from nonlocality at normal incidence and the surprisingly large structural parameters at which finite blueshifts are observable, which we attribute to diffraction that offers nonvanishing in-plane wave vector components and increases the penetration depth of longitudinal (nonlocal) modes.

  17. High frame-rate blood vector velocity imaging using plane waves: simulations and preliminary experiments

    DEFF Research Database (Denmark)

    Udesen, J.; Gran, F.; Hansen, K.L.

    2008-01-01

    Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1...... carotid artery of a healthy male was scanned with a scan sequence that satisfies the limits set by the Food and Drug Administration. Vector velocity images were obtained with a frame-rate of 100 Hz where 40 speckle images are used for each vector velocity image. It was found that the blood flow...... approximately followed the vessel wall, and that maximum velocity was approximately 1 m/s, which is a normal value for a healthy person. To further evaluate the method, the test person was scanned with magnetic resonance (MR) angiography. The volume flow derived from the MR scanning was compared with that from...

  18. Absolute band gaps in two-dimensional graphite photonic crystal

    Institute of Scientific and Technical Information of China (English)

    Gaoxin Qiu(仇高新); Fanglei Lin(林芳蕾); Hua Wang(王华); Yongping Li(李永平)

    2003-01-01

    The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photoniccrystal structure was studied using transfer matrix method. Transmission spectra calculations indicatethat such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizationsand for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2Dgraphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some propertiesof a three-dimensional (3D) photonic crystal.

  19. Two -Dimensional Wavelength Selective Diffraction by High-Order Three-Dimensional Composite Grating

    Institute of Scientific and Technical Information of China (English)

    Kohji; Furuhashi; Hideaki; Okayama; Hirochika; Nakajima

    2003-01-01

    We propose a wavelength selective diffraction using reflectors placed on three-dimensional grid cross points. Different wavelengths are separated into spots distributed in two-dimensional plane. Compact device with high port counts is attainable.

  20. Strongly interacting two-dimensional Dirac fermions

    NARCIS (Netherlands)

    Lim, L.K.; Lazarides, A.; Hemmerich, Andreas; de Morais Smith, C.

    2009-01-01

    We show how strongly interacting two-dimensional Dirac fermions can be realized with ultracold atoms in a two-dimensional optical square lattice with an experimentally realistic, inherent gauge field, which breaks time reversal and inversion symmetries. We find remarkable phenomena in a temperature

  1. Topology optimization of two-dimensional waveguides

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Sigmund, Ole

    2003-01-01

    In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....

  2. Vectores

    OpenAIRE

    2016-01-01

    Documento que contiene la explicación sobre las temáticas de Sistemas coordenados, Cantidades vectoriales y escalares, Algunas propiedades de los vectores, Componentes de un vector y vectores unitarios

  3. High Frame-Rate Blood Vector Velocity Imaging Using Plane Waves: Simulations and Preliminary Experiments

    DEFF Research Database (Denmark)

    Udesen, Jesper; Gran, Fredrik; Hansen, Kristoffer Lindskov;

    2008-01-01

    Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1......) The ultrasound is not focused during the transmissions of the ultrasound signals; 2) A 13-bit Barker code is transmitted simultaneously from each transducer element; and 3) The 2-D vector velocity of the blood is estimated using 2-D cross-correlation. A parameter study was performed using the Field II program......, and performance of the method was investigated when a virtual blood vessel was scanned by a linear array transducer. An improved parameter set for the method was identified from the parameter study, and a flow rig measurement was performed using the same improved setup as in the simulations. Finally, the common...

  4. Fast Plane Wave 2-D Vector Flow Imaging Using Transverse Oscillation and Directional Beamforming

    DEFF Research Database (Denmark)

    Jensen, Jonas; Villagómez Hoyos, Carlos Armando; Stuart, Matthias Bo

    2017-01-01

    Several techniques can estimate the 2-D velocity vector in ultrasound. Directional beamforming (DB) estimates blood flow velocities with a higher precision and accuracy than transverse oscillation (TO), but at the cost of a high beamforming load when estimating the flow angle. In this paper......, it is proposed to use TO to estimate an initial flow angle, which is then refined in a DB step. Velocity magnitude is estimated along the flow direction using cross-correlation. It is shown that the suggested TO-DB method can improve the performance of velocity estimates compared to TO, and with a beamforming...... but within 4% for TO-DB. The same trends are observed in measurements although with a slightly larger bias. Simulations of realistic flow in a carotid bifurcation model provide visualization of complex flow, and the spread of velocity magnitude estimates is 7.1 cm/s for TO-DB, while it is 11.8 cm/s using...

  5. Prediction of DC Corona Onset Voltage for Rod-Plane Air Gaps by a Support Vector Machine

    Science.gov (United States)

    Jin, Shuo; Ruan, Jiangjun; Du, Zhiye; Zhu, Lin; Shu, Shengwen

    2016-10-01

    This paper proposes a new method to predict the corona onset voltage for a rod-plane air gap, based on the support vector machine (SVM). Because the SVM is not limited by the size, dimension and nonlinearity of the samples, this method can realize accurate prediction with few training data. Only electric field features are chosen as the input; no geometric parameter is included. Therefore, the experiment data of one kind of electrode can be used to predict the corona onset voltages of other electrodes with different sizes. With the experimental data obtained by ozone detection technology, and experimental data provided by the reference, the efficiency of the proposed method is validated. Accurate predicted results with an average relative less than 3% are obtained with only 6 experimental data. supported by National Natural Science Foundation of China (No. 51477120)

  6. Augmented reality simulator for training in two-dimensional echocardiography.

    Science.gov (United States)

    Weidenbach, M; Wick, C; Pieper, S; Quast, K J; Fox, T; Grunst, G; Redel, D A

    2000-02-01

    In two-dimensional echocardiography the sonographer must synthesize multiple tomographic slices into a mental three-dimensional (3D) model of the heart. Computer graphics and virtual reality environments are ideal to visualize complex 3D spatial relationships. In augmented reality (AR) applications, real and virtual image data are linked, to increase the information content. In the presented AR simulator a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to establish spatial and temporal congruence. The heart model, together with an animated ultrasound sector represents a reference scenario, which displays the currently selected two-dimensional echocardiographic cutting plane calculated from the volume data set. Modifications of the cutting plane within the echocardiographic data are transferred and visualized simultaneously and in real time within the reference scenario. The trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by an animated ultrasound probe, whose position is controlled by an electromagnetic tracking system. The tracking system is attached to a dummy transducer and placed on a plastic puppet to give a realistic impression of a two-dimensional echocardiographic examination.

  7. Two Dimensional Plasmonic Cavities on Moire Surfaces

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.

  8. Two-dimensional function photonic crystals

    Science.gov (United States)

    Liu, Xiao-Jing; Liang, Yu; Ma, Ji; Zhang, Si-Qi; Li, Hong; Wu, Xiang-Yao; Wu, Yi-Heng

    2017-01-01

    In this paper, we have studied two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , that can become true easily by electro-optical effect and optical kerr effect. We calculated the band gap structures of TE and TM waves, and found the TE (TM) wave band gaps of function photonic crystals are wider (narrower) than the conventional photonic crystals. For the two-dimensional function photonic crystals, when the dielectric constant functions change, the band gaps numbers, width and position should be changed, and the band gap structures of two-dimensional function photonic crystals can be adjusted flexibly, the needed band gap structures can be designed by the two-dimensional function photonic crystals, and it can be of help to design optical devices.

  9. Two-Dimensional Planetary Surface Lander

    Science.gov (United States)

    Hemmati, H.; Sengupta, A.; Castillo, J.; McElrath, T.; Roberts, T.; Willis, P.

    2014-06-01

    A systems engineering study was conducted to leverage a new two-dimensional (2D) lander concept with a low per unit cost to enable scientific study at multiple locations with a single entry system as the delivery vehicle.

  10. Topological defect motifs in two-dimensional Coulomb clusters

    CERN Document Server

    Radzvilavičius, A; 10.1088/0953-8984/23/38/385301

    2012-01-01

    The most energetically favourable arrangement of low-density electrons in an infinite two-dimensional plane is the ordered triangular Wigner lattice. However, in most instances of contemporary interest one deals instead with finite clusters of strongly interacting particles localized in potential traps, for example, in complex plasmas. In the current contribution we study distribution of topological defects in two-dimensional Coulomb clusters with parabolic lateral confinement. The minima hopping algorithm based on molecular dynamics is used to efficiently locate the ground- and low-energy metastable states, and their structure is analyzed by means of the Delaunay triangulation. The size, structure and distribution of geometry-induced lattice imperfections strongly depends on the system size and the energetic state. Besides isolated disclinations and dislocations, classification of defect motifs includes defect compounds --- grain boundaries, rosette defects, vacancies and interstitial particles. Proliferatio...

  11. Perpendicular magnetic anisotropy of two-dimensional Rashba ferromagnets

    Science.gov (United States)

    Kim, Kyoung-Whan; Lee, Kyung-Jin; Lee, Hyun-Woo; Stiles, M. D.

    2016-11-01

    We compute the magnetocrystalline anisotropy energy within two-dimensional Rashba models. For a ferromagnetic free-electron Rashba model, the magnetic anisotropy is exactly zero regardless of the strength of the Rashba coupling, unless only the lowest band is occupied. For this latter case, the model predicts in-plane anisotropy. For a more realistic Rashba model with finite band width, the magnetic anisotropy evolves from in-plane to perpendicular and back to in-plane as bands are progressively filled. This evolution agrees with first-principles calculations on the interfacial anisotropy, suggesting that the Rashba model captures energetics leading to anisotropy originating from the interface provided that the model takes account of the finite Brillouin zone. The results show that the electron density modulation by doping or an external voltage is more important for voltage-controlled magnetic anisotropy than the modulation of the Rashba parameter.

  12. Interpolation by two-dimensional cubic convolution

    Science.gov (United States)

    Shi, Jiazheng; Reichenbach, Stephen E.

    2003-08-01

    This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.

  13. Two-dimensional dispersive shock waves in dissipative optical media

    CERN Document Server

    Kartashov, Yaroslav V

    2013-01-01

    We study generation of two-dimensional dispersive shock waves and oblique dark solitons upon interaction of tilted plane waves with negative refractive index defects embedded into defocusing material with linear gain and two-photon absorption. Different evolution regimes are encountered including the formation of well-localized disturbances for input tilts below critical one, and generation of extended shock waves containing multiple intensity oscillations in the "upstream" region and gradually vanishing oblique dark solitons in "downstream" region for input tilts exceeding critical one. The generation of stable dispersive shock waves is possible only below certain critical defect strength.

  14. Two-dimensionally confined topological edge states in photonic crystals

    Science.gov (United States)

    Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad

    2016-11-01

    We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters.

  15. Two-Dimensionally Confined Topological Edge States in Photonic Crystals

    CERN Document Server

    Barik, Sabyasachi; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad

    2016-01-01

    We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters.

  16. Mean flow generation in rotating anelastic two-dimensional convection

    CERN Document Server

    Currie, Laura K

    2016-01-01

    We investigate the processes that lead to the generation of mean flows in two-dimensional anelastic convection. The simple model consists of a plane layer that is rotating about an axis inclined to gravity. The results are two-fold: firstly we numerically investigate the onset of convection in three-dimensions, paying particular attention to the role of stratification and highlight a curious symmetry. Secondly, we investigate the mechanisms that drive both zonal and meridional flows in two dimensions. We find that, in general, non-trivial Reynolds stresses can lead to systematic flows and, using statistical measures, we quantify the role of stratification in modifying the coherence of these flows.

  17. Complex Saddles in Two-dimensional Gauge Theory

    CERN Document Server

    Buividovich, P V; Valgushev, S N

    2015-01-01

    We study numerically the saddle point structure of two-dimensional (2D) lattice gauge theory, represented by the Gross-Witten-Wadia unitary matrix model. The saddle points are in general complex-valued, even though the original integration variables and action are real. We confirm the trans-series/instanton gas structure in the weak-coupling phase, and identify a new complex-saddle interpretation of non-perturbative effects in the strong-coupling phase. In both phases, eigenvalue tunneling refers to eigenvalues moving off the real interval, into the complex plane, and the weak-to-strong coupling phase transition is driven by saddle condensation.

  18. TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)

    2015-11-20

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.

  19. Two dimensional topology of cosmological reionization

    CERN Document Server

    Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan

    2015-01-01

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.

  20. Two-dimensional capillary electrophoresis using tangentially connected capillaries.

    Science.gov (United States)

    Sahlin, Eskil

    2007-06-22

    A novel type of fused silica capillary system is described where channels with circular cross-sections are tangentially in contact with each other and connected through a small opening at the contact area. Since the channels are not crossing each other in the same plane, the capillaries can easily be filled with different solutions, i.e. different solutions will be in contact with each other at the contact point. The system has been used to perform different types of two-dimensional separations and the complete system is fully automated where a high voltage switch is used to control the location of the high voltage in the system. Using two model compounds it is demonstrated that a type of two-dimensional separation can be performed using capillary zone electrophoresis at two different pH values. It is also shown that a compound with acid/base properties can be concentrated using a dynamic pH junction mechanism when transferred from the first separation to the second separation. In addition, the system has been used to perform a comprehensive two-dimensional capillary electrophoresis separation of tryptic digest of bovine serum albumin using capillary zone electrophoresis followed by micellar electrokinetic chromatography.

  1. Two-dimensional x-ray diffraction

    CERN Document Server

    He, Bob B

    2009-01-01

    Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

  2. Matching Two-dimensional Gel Electrophoresis' Spots

    DEFF Research Database (Denmark)

    Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza

    2012-01-01

    This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...

  3. Mobility anisotropy of two-dimensional semiconductors

    Science.gov (United States)

    Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong

    2016-12-01

    The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.

  4. Vectors

    DEFF Research Database (Denmark)

    Boeriis, Morten; van Leeuwen, Theo

    2017-01-01

    This article revisits the concept of vectors, which, in Kress and van Leeuwen’s Reading Images (2006), plays a crucial role in distinguishing between ‘narrative’, action-oriented processes and ‘conceptual’, state-oriented processes. The use of this concept in image analysis has usually focused...... on the most salient vectors, and this works well, but many images contain a plethora of vectors, which makes their structure quite different from the linguistic transitivity structures with which Kress and van Leeuwen have compared ‘narrative’ images. It can also be asked whether facial expression vectors...... should be taken into account in discussing ‘reactions’, which Kress and van Leeuwen link only to eyeline vectors. Finally, the question can be raised as to whether actions are always realized by vectors. Drawing on a re-reading of Rudolf Arnheim’s account of vectors, these issues are outlined...

  5. TWO-DIMENSIONAL PARTICLE IMAGE VELOCIMETRY(PIV) MEASUREMENTS IN A TRANSPARENT CENTRIFUGAL PUMP

    Institute of Scientific and Technical Information of China (English)

    Yang Hua; Gu Chuangang; Wang Tong

    2005-01-01

    A special transparent centrifugal pump is designed. Detailed optical measurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pump impeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow is surveyed at three load conditions qv/qνd = 0.4, qν/qνd = 1.0, qν/qνd = 1.5, respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub and shroud of the impeller are presented. At design load, the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow without separation. The distributions of the relative velocity on different plane along the pump shaft are very different and there is always a low velocity zone near the pressure-side of the blade at both low and design flow rate, but the low-velocity-zone at the low flow rate is much larger than that at the design one. The study demonstrates that the PIV technique is efficient in providing reliable and detailed velocity data over a full impeller passage.

  6. Spin-orbit or Aharonov-Casher edge states in semiconductor two-dimensional systems

    Science.gov (United States)

    Xu, L. L.; Heremans, J. J.; Gaspe, C. K.; Vijeyaragunathan, S.; Mishima, T. D.; Santos, M. B.

    2012-02-01

    In semiconductors with spin-orbit interaction we experimentally search for edge states induced by the Aharonov-Casher vector potential or Rashba-type spin-orbit interaction. The Aharonov-Casher effect is electromagnetically dual to the Aharonov-Bohm effect and is predicted to lead to a possibly helical edge state structure at two-dimensional sample edges. We use InGaAs/InAlAs heterostructures patterned into mesoscopic side-gated channel structures, where the edge states can be induced, and where backscattering between edge states can be experimentally measured in the resistance. Sweeping side-gate voltage, low temperature resistances are measured across such mesoscopic closed-path structures at either low applied magnetic field, in-plane or normal to the plane, or at fixed magnetic filling factors of 5, 6, 7, and 8 to obtain states of defined spin. Resistance oscillations are observed at low magnetic fields and around filling factor 6 as function of side-gate voltage, and we analyze the oscillations in the light of the search for the edge states (DOE DE-FG02-08ER46532, NSF DMR-0520550).

  7. Anisotropic electronic conduction in stacked two-dimensional titanium carbide

    Science.gov (United States)

    Hu, Tao; Zhang, Hui; Wang, Jiemin; Li, Zhaojin; Hu, Minmin; Tan, Jun; Hou, Pengxiang; Li, Feng; Wang, Xiaohui

    2015-11-01

    Stacked two-dimensional titanium carbide is an emerging conductive material for electrochemical energy storage which requires an understanding of the intrinsic electronic conduction. Here we report the electronic conduction properties of stacked Ti3C2T2 (T = OH, O, F) with two distinct stacking sequences (Bernal and simple hexagonal). On the basis of first-principles calculations and energy band theory analysis, both stacking sequences give rise to metallic conduction with Ti 3d electrons contributing most to the conduction. The conduction is also significantly anisotropic due to the fact that the effective masses of carriers including electrons and holes are remarkably direction-dependent. Such an anisotropic electronic conduction is evidenced by the I-V curves of an individual Ti3C2T2 particulate, which demonstrates that the in-plane electrical conduction is at least one order of magnitude higher than that vertical to the basal plane.

  8. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao

    2015-02-25

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

  9. Kronecker Product of Two-dimensional Arrays

    Institute of Scientific and Technical Information of China (English)

    Lei Hu

    2006-01-01

    Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.

  10. Two-Dimensional Toda-Heisenberg Lattice

    Directory of Open Access Journals (Sweden)

    Vadim E. Vekslerchik

    2013-06-01

    Full Text Available We consider a nonlinear model that is a combination of the anisotropic two-dimensional classical Heisenberg and Toda-like lattices. In the framework of the Hirota direct approach, we present the field equations of this model as a bilinear system, which is closely related to the Ablowitz-Ladik hierarchy, and derive its N-soliton solutions.

  11. A novel two dimensional particle velocity sensor

    NARCIS (Netherlands)

    Pjetri, Olti; Wiegerink, Remco J.; Lammerink, Theo S.; Krijnen, Gijs J.

    2013-01-01

    In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabrica

  12. Two-dimensional microstrip detector for neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.

  13. Two-dimensional magma-repository interactions

    NARCIS (Netherlands)

    Bokhove, O.

    2001-01-01

    Two-dimensional simulations of magma-repository interactions reveal that the three phases --a shock tube, shock reflection and amplification, and shock attenuation and decay phase-- in a one-dimensional flow tube model have a precursor. This newly identified phase ``zero'' consists of the impact of

  14. Two-dimensional subwavelength plasmonic lattice solitons

    CERN Document Server

    Ye, F; Hu, B; Panoiu, N C

    2010-01-01

    We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai

  15. A two-dimensional Dirac fermion microscope

    DEFF Research Database (Denmark)

    Bøggild, Peter; Caridad, Jose; Stampfer, Christoph

    2017-01-01

    in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2...

  16. Quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$

    OpenAIRE

    Wang, Kefeng; Graf, D.; Petrovic, C.

    2016-01-01

    We report quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$. The band structure shows several narrow bands with nearly linear energy dispersion and Dirac-cone-like points at the Fermi level. The quantum oscillation experiments revealed one quasi-two-dimensional Fermi pocket and another complex pocket with small cyclotron resonant mass. The in-plane transverse magnetoresistance exhibits a crossover at a critical field $B^*$ from semiclassical weak-field $B^2$ dep...

  17. Jamming patterns in a two-dimensional hopper

    Indian Academy of Sciences (India)

    Kiwing To

    2005-06-01

    We report experimental studies of jamming phenomenon of monodisperse metal disks falling through a two-dimensional hopper when the hopper opening is larger than three times the size of the disks. For each jamming event, the configuration of the arch formed at the hopper opening is studied. The cumulative distribution functions () for hoppers of opening size d are measured. (Here is the horizontal component of the arch vector, which is defined as the displacement vector from the center of the first disk to the center of the last disk in the arch.) We found that the distribution of () can be collasped into a master curve () = ()() that decays exponentially for > 4. The scaling factor () is a decreasing function of d and is approximately proportional to the jamming probability.

  18. Anomaly matching condition in two-dimensional systems

    CERN Document Server

    Dubinkin, O; Gubankova, E

    2016-01-01

    Based on Son-Yamamoto relation obtained for transverse part of triangle axial anomaly in ${\\rm QCD}_4$, we derive its analog in two-dimensional system. It connects the transverse part of mixed vector-axial current two-point function with diagonal vector and axial current two-point functions. Being fully non-perturbative, this relation may be regarded as anomaly matching for conductivities or certain transport coefficients depending on the system. We consider the holographic RG flows in holographic Yang-Mills-Chern-Simons theory via the Hamilton-Jacobi equation with respect to the radial coordinate. Within this holographic model it is found that the RG flows for the following relations are diagonal: Son-Yamamoto relation and the left-right polarization operator. Thus the Son-Yamamoto relation holds at wide range of energy scales.

  19. Sufficient Controllability Condition for Affine Systems with Two-Dimensional Control and Two-Dimensional Zero Dynamics

    Directory of Open Access Journals (Sweden)

    D. A. Fetisov

    2015-01-01

    Full Text Available The controllability conditions are well known if we speak about linear stationary systems: a linear stationary system is controllable if and only if the dimension of the state vector is equal to the rank of the controllability matrix. The concept of the controllability matrix is extended to affine systems, but relations between affine systems controllability and properties of this matrix are more complicated. Various controllability conditions are set for affine systems, but they deal as usual either with systems of some special form or with controllability in some small neighborhood of the concerned point. An affine system is known to be controllable if the system is equivalent to a system of a canonical form, which is defined and regular in the whole space of states. In this case, the system is said to be feedback linearizable in the space of states. However there are examples, which illustrate that a system can be controllable even if it is not feedback linearizable in any open subset in the space of states. In this article we deal with such systems.Affine systems with two-dimensional control are considered. The system in question is assumed to be equivalent to a system of a quasicanonical form with two-dimensional zero dynamics which is defined and regular in the whole space of states. Therefore the controllability of the original system is equivalent to the controllability of the received system of a quasicanonical form. In this article the sufficient condition for an available solution of the terminal problem is proven for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. The condition is valid in the case of an arbitrary time interval and arbitrary initial and finite states of the system. Therefore the controllability condition is set for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. An example is given which illustrates how the proved

  20. Electronics based on two-dimensional materials.

    Science.gov (United States)

    Fiori, Gianluca; Bonaccorso, Francesco; Iannaccone, Giuseppe; Palacios, Tomás; Neumaier, Daniel; Seabaugh, Alan; Banerjee, Sanjay K; Colombo, Luigi

    2014-10-01

    The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

  1. Two-dimensional ranking of Wikipedia articles

    Science.gov (United States)

    Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.

    2010-10-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  2. Two-Dimensional NMR Lineshape Analysis

    Science.gov (United States)

    Waudby, Christopher A.; Ramos, Andres; Cabrita, Lisa D.; Christodoulou, John

    2016-04-01

    NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions.

  3. Two-Dimensional Scheduling: A Review

    Directory of Open Access Journals (Sweden)

    Zhuolei Xiao

    2013-07-01

    Full Text Available In this study, we present a literature review, classification schemes and analysis of methodology for scheduling problems on Batch Processing machine (BP with both processing time and job size constraints which is also regarded as Two-Dimensional (TD scheduling. Special attention is given to scheduling problems with non-identical job sizes and processing times, with details of the basic algorithms and other significant results.

  4. String breaking in two-dimensional QCD

    CERN Document Server

    Hornbostel, K J

    1999-01-01

    I present results of a numerical calculation of the effects of light quark-antiquark pairs on the linear heavy-quark potential in light-cone quantized two-dimensional QCD. I extract the potential from the Q-Qbar component of the ground-state wavefunction, and observe string breaking at the heavy-light meson pair threshold. I briefly comment on the states responsible for the breaking.

  5. Two-dimensional supramolecular electron spin arrays.

    Science.gov (United States)

    Wäckerlin, Christian; Nowakowski, Jan; Liu, Shi-Xia; Jaggi, Michael; Siewert, Dorota; Girovsky, Jan; Shchyrba, Aneliia; Hählen, Tatjana; Kleibert, Armin; Oppeneer, Peter M; Nolting, Frithjof; Decurtins, Silvio; Jung, Thomas A; Ballav, Nirmalya

    2013-05-07

    A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Fourier solution of two-dimensional Navier Stokes equation with periodic boundary conditions and incompressible flow

    CERN Document Server

    Kuiper, Logan K

    2016-01-01

    An approximate solution to the two dimensional Navier Stokes equation with periodic boundary conditions is obtained by representing the x any y components of fluid velocity with complex Fourier basis vectors. The chosen space of basis vectors is finite to allow for numerical calculations, but of variable size. Comparisons of the resulting approximate solutions as they vary with the size of the chosen vector space allow for extrapolation to an infinite basis vector space. Results suggest that such a solution, with the full basis vector space and which would give the exact solution, would fail for certain initial velocity configurations when initial velocity and time t exceed certain limits.

  7. Holographic R\\'enyi entropy for two-dimensional $\\mathcal{N}$=(2,2) superconformal field theory

    CERN Document Server

    Li, Zhibin

    2016-01-01

    We investigate the holographic R\\'enyi entropy for two-dimensional $\\mathcal N=(2,2)$ superconformal field theory (SCFT), which is dual to $\\mathcal N=2$ supergravity in AdS$_3$ background. In SCFT we have the stress tensor, current, and their supersymmetric partners, and in supergravity we have the graviton, vector field, and two gravitinos. We get the R\\'enyi mutual information of two short intervals on complex plane in expansion by the cross ratio $x$ to order $x^4$, and R\\'enyi entropy of one interval on torus in expansion by $q=\\exp(-2\\pi\\beta/L)$, with $\\beta$ being the inverse temperature and $L$ being the spatial period, to order $q^2$. We calculate in both the supergravity and SCFT sides, and find matches of the results.

  8. Two dimensional echocardiographic detection of intraatrial masses.

    Science.gov (United States)

    DePace, N L; Soulen, R L; Kotler, M N; Mintz, G S

    1981-11-01

    With two dimensional echocardiography, a left atrial mass was detected in 19 patients. Of these, 10 patients with rheumatic mitral stenosis had a left atrial thrombus. The distinctive two dimensional echocardiographic features of left atrial thrombus included a mass of irregular nonmobile laminated echos within an enlarged atrial cavity, usually with a broad base of attachment to the posterior left atrial wall. Seven patients had a left atrial myxoma. Usually, the myxoma appeared as a mottled ovoid, sharply demarcated mobile mass attached to the interatrial septum. One patient had a right atrial angiosarcoma that appeared as a nonmobile mass extending from the inferior vena caval-right atrial junction into the right atrial cavity. One patient had a left atrial leiomyosarcoma producing a highly mobile mass attached to the lateral wall of the left atrium. M mode echocardiography detected six of the seven myxomas, one thrombus and neither of the other tumors. Thus, two dimensional echocardiography appears to be the technique of choice in the detection, localization and differentiation of intraatrial masses.

  9. Axisymmetric Thermo-elastic Deformation of the Cylinder with Two-dimensional Inhomogeneity of Material

    Directory of Open Access Journals (Sweden)

    Andreev V.I.

    2016-01-01

    Full Text Available The article discusses the use of a numerical method the calculation of finite cylinders into account the dependence of physical and mechanical properties of the material on temperature. If we have two-dimensional temperature field characteristics of the material depends on two coordinates. - r and z from which follows that the problem of thermoelasticity is also a two-dimensional. Using the numerical method allows to solve the problem for any state of the cylinder (plane stress or plane strain and consider arbitrary boundary conditions at its ends.

  10. Left ventricular hypertrophy index based on a combination of frontal and transverse planes in the ECG and VCG: Diagnostic utility of cardiac vectors

    Science.gov (United States)

    Bonomini, Maria Paula; Juan Ingallina, Fernando; Barone, Valeria; Antonucci, Ricardo; Valentinuzzi, Max; Arini, Pedro David

    2016-04-01

    The changes that left ventricular hypertrophy (LVH) induces in depolarization and repolarization vectors are well known. We analyzed the performance of the electrocardiographic and vectorcardiographic transverse planes (TP in the ECG and XZ in the VCG) and frontal planes (FP in the ECG and XY in the VCG) to discriminate LVH patients from control subjects. In an age-balanced set of 58 patients, the directions and amplitudes of QRS-complexes and T-wave vectors were studied. The repolarization vector significantly decreased in modulus from controls to LVH in the transverse plane (TP: 0.45±0.17mV vs. 0.24±0.13mV, p<0.0005 XZ: 0.43±0.16mV vs. 0.26±0.11mV, p<0.005) while the depolarization vector significantly changed in angle in the electrocardiographic frontal plane (Controls vs. LVH, FP: 48.24±33.66° vs. 46.84±35.44°, p<0.005, XY: 20.28±35.20° vs. 19.35±12.31°, NS). Several LVH indexes were proposed combining such information in both ECG and VCG spaces. A subset of all those indexes with AUC values greater than 0.7 was further studied. This subset comprised four indexes, with three of them belonging to the ECG space. Two out of the four indexes presented the best ROC curves (AUC values: 0.78 and 0.75, respectively). One index belonged to the ECG space and the other one to the VCG space. Both indexes showed a sensitivity of 86% and a specificity of 70%. In conclusion, the proposed indexes can favorably complement LVH diagnosis

  11. Weakly disordered two-dimensional Frenkel excitons

    Science.gov (United States)

    Boukahil, A.; Zettili, Nouredine

    2004-03-01

    We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.

  12. Two-dimensional photonic crystal surfactant detection.

    Science.gov (United States)

    Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A

    2012-08-07

    We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants.

  13. Theory of two-dimensional transformations

    OpenAIRE

    Kanayama, Yutaka J.; Krahn, Gary W.

    1998-01-01

    The article of record may be found at http://dx.doi.org/10.1109/70.720359 Robotics and Automation, IEEE Transactions on This paper proposes a new "heterogeneous" two-dimensional (2D) transformation group ___ to solve motion analysis/planning problems in robotics. In this theory, we use a 3×1 matrix to represent a transformation as opposed to a 3×3 matrix in the homogeneous formulation. First, this theory is as capable as the homogeneous theory, Because of the minimal size, its implement...

  14. Two-dimensional ranking of Wikipedia articles

    CERN Document Server

    Zhirov, A O; Shepelyansky, D L

    2010-01-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists {\\it ab aeterno}. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. We analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  15. Mobility anisotropy of two-dimensional semiconductors

    CERN Document Server

    Lang, Haifeng; Liu, Zhirong

    2016-01-01

    The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.

  16. Sums of two-dimensional spectral triples

    DEFF Research Database (Denmark)

    Christensen, Erik; Ivan, Cristina

    2007-01-01

    construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly......, the Dixmier trace induces a multiple of the Lebesgue integral but the growth of the number of eigenvalues is different from the one found for the standard differential operator on the unit interval....

  17. Binding energy of two-dimensional biexcitons

    DEFF Research Database (Denmark)

    Singh, Jai; Birkedal, Dan; Vadim, Lyssenko;

    1996-01-01

    Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....

  18. Dynamics of film. [two dimensional continua theory

    Science.gov (United States)

    Zak, M.

    1979-01-01

    The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.

  19. Fabrication of two-dimensional micro patterns for adaptive optics by using laser interference lithography

    Science.gov (United States)

    Li, Xinghui; Cai, Yindi; Aihara, Ryo; Shimizu, Yuki; Ito, So; Gao, Wei

    2015-07-01

    This paper presents a fabrication method of two-dimensional micro patterns for adaptive optics with a micrometric or sub-micrometric period to be used for fabrication of micro lens array or two-dimensional diffraction gratings. A multibeam two-axis Lloyd's mirror interferometer is employed to carry out laser interference lithography for the fabrication of two-dimensional grating structures. In the proposed instrument, the optical setup consists of a light source providing a laser beam, a multi-beam generator, two plane mirrors to generate a two-dimensional XY interference pattern and a substrate on which the XY interference pattern is to be exposed. In this paper, pattern exposure tests are carried out by the developed optical configuration optimized by computer simulations. Some experimental results of the XY pattern fabrication will be reported.

  20. Symmetry breaking of solitons in two-dimensional complex potentials

    CERN Document Server

    Yang, Jianke

    2014-01-01

    Symmetry breaking is reported for continuous families of solitons in the nonlinear Schr\\"odinger equation with a two-dimensional complex potential. This symmetry-breaking bifurcation is forbidden in generic complex potentials. However, for a special class of partially parity-time-symmetric potentials, such symmetry breaking is allowed. At the bifurcation point, two branches of asymmetric solitons bifurcate out from the base branch of symmetry-unbroken solitons. Stability of these solitons near the bifurcation point are also studied, and two novel stability properties for the bifurcated asymmetric solitons are revealed. One is that at the bifurcation point, zero and simple imaginary linear-stability eigenvalues of asymmetric solitons can move directly into the complex plane and create oscillatory instability. The other is that the two bifurcated asymmetric solitons, even though having identical powers and being related to each other by spatial mirror reflection, can possess different types of unstable eigenval...

  1. Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs

    Science.gov (United States)

    Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D.; Alducin, Diego; Myers, Benjamin D.; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R.; Hersam, Mark C.; Guisinger, Nathan P.

    2016-01-01

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes.Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. PMID:26680195

  2. Two-dimensional Numerical Modeling Research on Continent Subduction Dynamics

    Institute of Scientific and Technical Information of China (English)

    WANG Zhimin; XU Bei; ZHOU Yaoqi; XU Hehua; HUANG Shaoying

    2004-01-01

    Continent subduction is one of the hot research problems in geoscience. New models presented here have been set up and two-dimensional numerical modeling research on the possibility of continental subduction has been made with the finite element software, ANSYS, based on documentary evidence and reasonable assumptions that the subduction of oceanic crust has occurred, the subduction of continental crust can take place and the process can be simplified to a discontinuous plane strain theory model. The modeling results show that it is completely possible for continental crust to be subducted to a depth of 120 km under certain circumstances and conditions. At the same time, the simulations of continental subduction under a single dynamical factor have also been made, including the pull force of the subducted oceanic lithosphere, the drag force connected with mantle convection and the push force of the mid-ocean ridge. These experiments show that the drag force connected with mantle convection is critical for continent subduction.

  3. Two dimensional radiated power diagnostics on Alcator C-Moda)

    Science.gov (United States)

    Reinke, M. L.; Hutchinson, I. H.

    2008-10-01

    The radiated power diagnostics for the Alcator C-Mod tokamak have been upgraded to measure two dimensional structure of the photon emissivity profile in order to investigate poloidal asymmetries in the core radiation. Commonly utilized unbiased absolute extreme ultraviolet (AXUV) diode arrays view the plasma along five different horizontal planes. The layout of the diagnostic set is shown and the results from calibrations and recent experiments are discussed. Data showing a significant, 30%-40%, inboard/outboard emissivity asymmetry during ELM-free H-mode are presented. The ability to use AXUV diode arrays to measure absolute radiated power is explored by comparing diode and resistive bolometer-based emissivity profiles for highly radiative L-mode plasmas seeded with argon. Emissivity profiles match in the core but disagree radially outward resulting in an underprediction of Prad of nearly 50% by the diodes compared to Prad determined using resistive bolometers.

  4. Two-dimensional gauge theoretic supergravities

    Science.gov (United States)

    Cangemi, D.; Leblanc, M.

    1994-05-01

    We investigate two-dimensional supergravity theories, which can be built from a topological and gauge invariant action defined on an ordinary surface. One is the N = 1 supersymmetric extension of the Jackiw-Teitelboim model presented by Chamseddine in a superspace formalism. We complement the proof of Montano, Aoaki and Sonnenschein that this extension is topological and gauge invariant, based on the graded de Sitter algebra. Not only do the equations of motion correspond to the supergravity ones and do gauge transformations encompass local supersymmetries, but we also identify the ∫-theory with the superfield formalism action written by Chamseddine. Next, we show that the N = 1 supersymmetric extension of string-inspired two-dimensional dilaton gravity put forward by Park and Strominger cannot be written as a ∫-theory. As an alternative, we propose two topological and gauge theories that are based on a graded extension of the extended Poincaré algebra and satisfy a vanishing-curvature condition. Both models are supersymmetric extensions of the string-inspired dilaton gravity.

  5. Two-Dimensional Theory of Scientific Representation

    Directory of Open Access Journals (Sweden)

    A Yaghmaie

    2013-03-01

    Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.

  6. Two-dimensional shape memory graphene oxide

    Science.gov (United States)

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-06-01

    Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices.

  7. Two-Dimensional (2D) Polygonal Electromagnetic Cloaks

    Institute of Scientific and Technical Information of China (English)

    LI Chao; YAO Kan; LI Fang

    2009-01-01

    Transformation optics offers remarkable control over electromagnetic fields and opens an exciting gateway to design 'invisible cloak devices' recently.We present an important class of two-dimensional (2D) cloaks with polygon geometries.Explicit expressions of transformed medium parameters are derived with their unique properties investigated.It is found that the elements of diagonalized permittivity tensors are always positive within an irregular polygon cloak besides one element diverges to plus infinity and the other two become zero at the inner boundary.At most positions,the principle axes of permittivity tensors do not align with position vectors.An irregular polygon cloak is designed and its invisibility to external electromagnetic waves is numerically verified.Since polygon cloaks can be tailored to resemble any objects,the transformation is finally generalized to the realization of 2D cloaks with arbitrary geometries.

  8. Effective-range dependence of two-dimensional Fermi gases

    Science.gov (United States)

    Schonenberg, L. M.; Verpoort, P. C.; Conduit, G. J.

    2017-08-01

    The Feshbach resonance provides precise control over the scattering length and effective range of interactions between ultracold atoms. We propose the ultratransferable pseudopotential to model effective interaction ranges -1.5 ≤kF2Reff2≤0 , where Reff is the effective range and kF is the Fermi wave vector, describing narrow to broad Feshbach resonances. We develop a mean-field treatment and exploit the pseudopotential to perform a variational and diffusion Monte Carlo study of the ground state of the two-dimensional Fermi gas, reporting on the ground-state energy, contact, condensate fraction, momentum distribution, and pair-correlation functions as a function of the effective interaction range across the BEC-BCS crossover. The limit kF2Reff2→-∞ is a gas of bosons with zero binding energy, whereas ln(kFa )→-∞ corresponds to noninteracting bosons with infinite binding energy.

  9. Current fluctuations in a two dimensional model of heat conduction

    Science.gov (United States)

    Pérez-Espigares, Carlos; Garrido, Pedro L.; Hurtado, Pablo I.

    2011-03-01

    In this work we study numerically and analytically current fluctuations in the two-dimensional Kipnis-Marchioro-Presutti (KMP) model of heat conduction. For that purpose, we use a recently introduced algorithm which allows the direct evaluation of large deviations functions. We compare our results with predictions based on the Hydrodynamic Fluctuation Theory (HFT) of Bertini and coworkers, finding very good agreement in a wide interval of current fluctuations. We also verify the existence of a well-defined temperature profile associated to a given current fluctuation which depends exclusively on the magnitude of the current vector, not on its orientation. This confirms the recently introduced Isometric Fluctuation Relation (IFR), which results from the time-reversibility of the dynamics, and includes as a particular instance the Gallavotti-Cohen fluctuation theorem in this context but adds a completely new perspective on the high level of symmetry imposed by timereversibility on the statistics of nonequilibrium fluctuations.

  10. Compact triplexer in two-dimensional hexagonal lattice photonic crystals

    Institute of Scientific and Technical Information of China (English)

    Hongliang Ren; Jianping Ma; Hao Wen; Yali Qin; Zhefu Wu; Weisheng Hu; Chun Jiang; Yaohui Jin

    2011-01-01

    We design a contpact triplexer based on two-dimensional (2D) hexagonal lattice photonic crystals (PCs). A folded directional coupler (FDC) is introduced in the triplexer beside the point-defect micro-cavities and line-defect waveguides. Because of the reflection feedback of the FDC, high channel drop efficiency can be realized and a compact size with the order of micrometers can be maintained. The proposed device is analyzed using the plane wave expansion method, and its transmission characteristics are calculated using the finites-difference time-domain method. The footprint of the triplexer is about 12× 9 μm, and its extinction ratios are less than -20 dB for 1310 nm, approximately -20 dB for 1490 nm, and under -4O dB for 1550 nm, making it a potentially essential device ii future fiber-to-the-home networks.%@@ We design a compact triplexer based on two-dimensional (2D) hexagonal lattice photonic crystals (PCs).A folded directional coupler (FDC) is introduced in the triplexer beside the point-defect micro-cavities and line-defect waveguides.Because of the reflection feedback of the FDC, high channel drop efficiency can be realized and a compact size with the order of micrometers can be maintained.The proposed device is analyzed using the plane wave expansion method, and its transmission characteristics are calculated using the finite-difference time-domain method.The footprint of the triplexer is about 12×9 μm, and its extinction ratios are less than -20 dB for 1310 nm, approximately -20 dB for 1490 nm, and under -40 dB for 1550 nm, making it a potentially essential device in future fiber-to-the-home networks.

  11. Characteristics of local photonic state density in an infinite two-dimensional photonic crystal

    Institute of Scientific and Technical Information of China (English)

    Zhou Yun-Song; Wang Xue-Hua; Gu Ben-Yuan; Wang Fu-He

    2005-01-01

    The local density of photonic states (LDPS) of an infinite two-dimensional (2D) photonic crystal (PC) composed of rotated square-pillars in a 2D square lattice is calculated in terms of the plane-wave expansion method in a combination with the point group theory. The calculation results show that the LDPS strongly depends on the spatial positions.The variations of the LDPS as functions of the radial coordinate and frequency exhibit "mountain chain" structures with sharp peaks. The LDPS with large value spans a finite area and falls abruptly down to small value at the position corresponding to the interfaces between two different refractive index materials. The larger/lower LDPS occurs inward the lower/larger dielectric-constant medium. This feature can be well interpreted by the continuity of electricdisplacement vector at the interface. In the frequency range of the pseudo-PBG (photonic band gap), the LDPS keeps very low value over the whole Wiger-Seitz cell. It indicates that the spontaneous emission in 2D PCs cannot be prohibited completely, but it can be inhibited intensively when the resonate frequency falls into the pseudo-PBG.

  12. Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices

    Institute of Scientific and Technical Information of China (English)

    XU Quan; TIAN Qiang

    2007-01-01

    Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.

  13. Two-dimensional coupled electron-hole layers in high magnetic fields

    NARCIS (Netherlands)

    Parlangeli, Andrea

    2000-01-01

    In solids, it is nowadays possible to create structures in which electrons are confined into a two-dimensional (2D) plane. The physics of a 2D electron gas (2DEG) has proved to be very rich, in particular in the presence of a transverse magnetic field. The Quantum Hall Effect, i.e. the quantization

  14. Calculation of the electrical of induction heating coils in two dimensional axissymmetric geometry

    Energy Technology Data Exchange (ETDEWEB)

    Nerg, J.; Partanen, J. [Lappeenranta University of Technology (Finland). Department of Energy Technology, Laboratory of Electrical Engineering

    1997-12-31

    The effect of the workpiece temperature on the electrical parameters of a plane, spiral inductor is discussed. The effect of workpiece temperature on the electrical efficiency, power transfer to the workpiece and electromagnetic distortion are also presented. Calculation is performed in two dimensional axissymmetric geometry using a FEM program. (orig.) 5 refs.

  15. Geotechnical applications of a two-dimensional elastodynamic displacement discontinuity method

    CSIR Research Space (South Africa)

    Siebrits, E

    1993-12-01

    Full Text Available A general two-dimensional elastodynamic displacement discontinuity method is used to model a variety of application problems. The plane strain problems are: the elastodynamic motions induced on a cavity by shear slip on a nearby crack; the dynamic...

  16. Applying Clustering to Statistical Analysis of Student Reasoning about Two-Dimensional Kinematics

    Science.gov (United States)

    Springuel, R. Padraic; Wittman, Michael C.; Thompson, John R.

    2007-01-01

    We use clustering, an analysis method not presently common to the physics education research community, to group and characterize student responses to written questions about two-dimensional kinematics. Previously, clustering has been used to analyze multiple-choice data; we analyze free-response data that includes both sketches of vectors and…

  17. Optimal excitation of two dimensional Holmboe instabilities

    CERN Document Server

    Constantinou, Navid C

    2010-01-01

    Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified environments. However these instabilities occur in tongues for a limited range of parameters. We perform Generalized Stability analysis of the two dimensional perturbation dynamics of an inviscid Boussinesq stratified shear layer and show that Holmboe instabilities at high Richardson numbers can be excited by their adjoints at amplitudes that are orders of magnitude larger than by introducing initially the unstable mode itself. We also determine the optimal growth that obtains for parameters for which there is no instability. We find that there is potential for large transient growth regardless of whether the background flow is exponentially stable or not and that the characteristic structure of the Holmboe instability asymptotically emerges for parameter values ...

  18. Phonon hydrodynamics in two-dimensional materials.

    Science.gov (United States)

    Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola

    2015-03-06

    The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.

  19. Probabilistic Universality in two-dimensional Dynamics

    CERN Document Server

    Lyubich, Mikhail

    2011-01-01

    In this paper we continue to explore infinitely renormalizable H\\'enon maps with small Jacobian. It was shown in [CLM] that contrary to the one-dimensional intuition, the Cantor attractor of such a map is non-rigid and the conjugacy with the one-dimensional Cantor attractor is at most 1/2-H\\"older. Another formulation of this phenomenon is that the scaling structure of the H\\'enon Cantor attractor differs from its one-dimensional counterpart. However, in this paper we prove that the weight assigned by the canonical invariant measure to these bad spots tends to zero on microscopic scales. This phenomenon is called {\\it Probabilistic Universality}. It implies, in particular, that the Hausdorff dimension of the canonical measure is universal. In this way, universality and rigidity phenomena of one-dimensional dynamics assume a probabilistic nature in the two-dimensional world.

  20. Two-dimensional position sensitive neutron detector

    Indian Academy of Sciences (India)

    A M Shaikh; S S Desai; A K Patra

    2004-08-01

    A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons. The detector is tested with 0.5 bar 3He + 1.5 bar krypton gas mixture in active chamber and 2 bar 4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼ 25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in the range of 0.02–0.25 Å-1.

  1. Two-dimensional heterostructures for energy storage

    Science.gov (United States)

    Pomerantseva, Ekaterina; Gogotsi, Yury

    2017-07-01

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  2. Rationally synthesized two-dimensional polymers.

    Science.gov (United States)

    Colson, John W; Dichtel, William R

    2013-06-01

    Synthetic polymers exhibit diverse and useful properties and influence most aspects of modern life. Many polymerization methods provide linear or branched macromolecules, frequently with outstanding functional-group tolerance and molecular weight control. In contrast, extending polymerization strategies to two-dimensional periodic structures is in its infancy, and successful examples have emerged only recently through molecular framework, surface science and crystal engineering approaches. In this Review, we describe successful 2D polymerization strategies, as well as seminal research that inspired their development. These methods include the synthesis of 2D covalent organic frameworks as layered crystals and thin films, surface-mediated polymerization of polyfunctional monomers, and solid-state topochemical polymerizations. Early application targets of 2D polymers include gas separation and storage, optoelectronic devices and membranes, each of which might benefit from predictable long-range molecular organization inherent to this macromolecular architecture.

  3. Janus Spectra in Two-Dimensional Flows

    Science.gov (United States)

    Liu, Chien-Chia; Cerbus, Rory T.; Chakraborty, Pinaki

    2016-09-01

    In large-scale atmospheric flows, soap-film flows, and other two-dimensional flows, the exponent of the turbulent energy spectra, α , may theoretically take either of two distinct values, 3 or 5 /3 , but measurements downstream of obstacles have invariably revealed α =3 . Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which α transitions from 3 to 5 /3 for the streamwise fluctuations but remains equal to 3 for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows.

  4. Local doping of two-dimensional materials

    Science.gov (United States)

    Wong, Dillon; Velasco, Jr, Jairo; Ju, Long; Kahn, Salman; Lee, Juwon; Germany, Chad E.; Zettl, Alexander K.; Wang, Feng; Crommie, Michael F.

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to locally doping two-dimensional (2D) materials. In one aspect, an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a 2D material disposed on the second insulator is formed. A first voltage is applied between the 2D material and the substrate. With the first voltage applied between the 2D material and the substrate, a second voltage is applied between the 2D material and a probe positioned proximate the 2D material. The second voltage between the 2D material and the probe is removed. The first voltage between the 2D material and the substrate is removed. A portion of the 2D material proximate the probe when the second voltage was applied has a different electron density compared to a remainder of the 2D material.

  5. Two-dimensional fourier transform spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    DeFlores, Lauren; Tokmakoff, Andrei

    2016-10-25

    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.

  6. Two-dimensional fourier transform spectrometer

    Science.gov (United States)

    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.

  7. Investigation on the properties of omnidirectional photonic band gaps in two-dimensional plasma photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hai-Feng, E-mail: hanlor@163.com [Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China); Liu, Shao-Bin; Li, Bing-Xiang [Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2016-01-15

    The properties of omnidirectional photonic band gaps (OBGs) in two-dimensional plasma photonic crystals (2D PPCs) are theoretically investigated by the modified plane wave expansion method. In the simulation, we consider the off-plane incident wave vector. The configuration of 2D PPCs is the triangular lattices filled with the nonmagnetized plasma cylinders in the homogeneous and isotropic dielectric background. The calculated results show that the proposed 2D PPCs possess a flatbands region and the OBGs. Compared with the OBGs in the conventional 2D dielectric-air PCs, it can be obtained more easily and enlarged in the 2D PPCs with a similar structure. The effects of configurational parameters of the PPCs on the OBGs also are studied. The simulated results demonstrate that the locations of OBGs can be tuned easily by manipulating those parameters except for changing plasma collision frequency. The achieved OBGs can be enlarged by optimizations. The OBGs of two novel configurations of PPCs with different cross sections are computed for a comparison. Both configurations have the advantages of obtaining the larger OBGs compared with the conventional configuration, since the symmetry of 2D PPCs is broken by different sizes of periodically inserted plasma cylinders or connected by the embedded plasma cylinders with thin veins. The analysis of the results shows that the bandwidths of OBGs can be tuned by changing geometric and physical parameters of such two PPCs structures. The theoretical results may open a new scope for designing the omnidirectional reflectors or mirrors based on the 2D PPCs.

  8. Two-dimensional multiferroics in monolayer group IV monochalcogenides

    Science.gov (United States)

    Wang, Hua; Qian, Xiaofeng

    2017-03-01

    Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with giant strongly-coupled in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their great potentials for tunable multiferroic functional devices by manipulating external electrical, mechanical, and optical field to control the internal responses, and enable the development of four device concepts including 2D ferroelectric memory, 2D ferroelastic memory, and 2D ferroelastoelectric nonvolatile photonic memory as well as 2D ferroelectric excitonic photovoltaics.

  9. Ab Initio Prediction of Piezoelectricity in Two-Dimensional Materials.

    Science.gov (United States)

    Blonsky, Michael N; Zhuang, Houlong L; Singh, Arunima K; Hennig, Richard G

    2015-10-27

    Two-dimensional (2D) materials present many unique materials concepts, including material properties that sometimes differ dramatically from those of their bulk counterparts. One of these properties, piezoelectricity, is important for micro- and nanoelectromechanical systems applications. Using symmetry analysis, we determine the independent piezoelectric coefficients for four groups of predicted and synthesized 2D materials. We calculate with density-functional perturbation theory the stiffness and piezoelectric tensors of these materials. We determine the in-plane piezoelectric coefficient d11 for 37 materials within the families of 2D metal dichalcogenides, metal oxides, and III-V semiconductor materials. A majority of the structures, including CrSe2, CrTe2, CaO, CdO, ZnO, and InN, have d11 coefficients greater than 5 pm/V, a typical value for bulk piezoelectric materials. Our symmetry analysis shows that buckled 2D materials exhibit an out-of-plane coefficient d31. We find that d31 for 8 III-V semiconductors ranges from 0.02 to 0.6 pm/V. From statistical analysis, we identify correlations between the piezoelectric coefficients and the electronic and structural properties of the 2D materials that elucidate the origin of the piezoelectricity. Among the 37 2D materials, CdO, ZnO, and CrTe2 stand out for their combination of large piezoelectric coefficient and low formation energy and are recommended for experimental exploration.

  10. Two-dimensional magnetic ordering in a multilayer structure

    Indian Academy of Sciences (India)

    M K Mukhopadhyay; M K Sanyal

    2006-07-01

    The effect of confinement from one, two or from all three directions on magnetic ordering has remained an active field of research for almost 100 years. The role of dipolar interactions and anisotropy are important to obtain, the otherwise forbidden, ferromagnetic ordering at finite temperature for ions arranged in two-dimensional (2D) arrays (monolayers). We have demonstrated that conventional low-temperature magnetometry and polarized neutron scattering measurements can be performed to study short-range ferromagnetic ordering of in-plane spins in 2D systems using a multilayer stack of non-interacting monolayers of gadolinium ions formed by Langmuir–Blodgett (LB) technique. The spontaneous magnetization could not be detected in the heterogeneous magnetic phase observed here and the saturation value of the net magnetization was found to depend on the sample temperature and applied magnetic field. The net magnetization rises exponentially with lowering temperature and then reaches saturation following a ln( ) dependence. The ln( ) dependence of magnetization has been predicted from spin-wave theory of 2D in-plane spin system with ferromagnetic interaction. The experimental findings reported here could be explained by extending this theory to a temperature domain of < 1.

  11. Procedure for measuring photon and vector meson circular polarization variation with respect to the reaction plane in relativistic heavy-ion collisions

    Science.gov (United States)

    Tang, A. H.; Wang, G.

    2016-08-01

    The electromagnetic (EM) field pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system and causes photons emitted in upper and lower hemispheres to have different preferences in the circular polarization. Similar helicity separation for massive particles, owing to the global vorticity, is also possible. In this paper, we lay out a procedure to measure the variation of the circular polarization with respect to the reaction plane in relativistic heavy-ion collisions for massless photons, as well as similar polarization patterns for vector mesons decaying into two daughters. We propose to study the yield differentially and compare the yield between upper and lower hemispheres to identify and quantify such effects.

  12. On numerical evaluation of two-dimensional phase integrals

    DEFF Research Database (Denmark)

    Lessow, H.; Rusch, W.; Schjær-Jacobsen, Hans

    1975-01-01

    The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated.......The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated....

  13. Two dimensional discriminant neighborhood preserving embedding in face recognition

    Science.gov (United States)

    Pang, Meng; Jiang, Jifeng; Lin, Chuang; Wang, Binghui

    2015-03-01

    One of the key issues of face recognition is to extract the features of face images. In this paper, we propose a novel method, named two-dimensional discriminant neighborhood preserving embedding (2DDNPE), for image feature extraction and face recognition. 2DDNPE benefits from four techniques, i.e., neighborhood preserving embedding (NPE), locality preserving projection (LPP), image based projection and Fisher criterion. Firstly, NPE and LPP are two popular manifold learning techniques which can optimally preserve the local geometry structures of the original samples from different angles. Secondly, image based projection enables us to directly extract the optimal projection vectors from twodimensional image matrices rather than vectors, which avoids the small sample size problem as well as reserves useful structural information embedded in the original images. Finally, the Fisher criterion applied in 2DDNPE can boost face recognition rates by minimizing the within-class distance, while maximizing the between-class distance. To evaluate the performance of 2DDNPE, several experiments are conducted on the ORL and Yale face datasets. The results corroborate that 2DDNPE outperforms the existing 1D feature extraction methods, such as NPE, LPP, LDA and PCA across all experiments with respect to recognition rate and training time. 2DDNPE also delivers consistently promising results compared with other competing 2D methods such as 2DNPP, 2DLPP, 2DLDA and 2DPCA.

  14. SCAPS, a two-dimensional ion detector for mass spectrometer

    Science.gov (United States)

    Yurimoto, Hisayoshi

    2014-05-01

    Faraday Cup (FC) and electron multiplier (EM) are of the most popular ion detector for mass spectrometer. FC is used for high-count-rate ion measurements and EM can detect from single ion. However, FC is difficult to detect lower intensities less than kilo-cps, and EM loses ion counts higher than Mega-cps. Thus, FC and EM are used complementary each other, but they both belong to zero-dimensional detector. On the other hand, micro channel plate (MCP) is a popular ion signal amplifier with two-dimensional capability, but additional detection system must be attached to detect the amplified signals. Two-dimensional readout for the MCP signals, however, have not achieve the level of FC and EM systems. A stacked CMOS active pixel sensor (SCAPS) has been developed to detect two-dimensional ion variations for a spatial area using semiconductor technology [1-8]. The SCAPS is an integrated type multi-detector, which is different from EM and FC, and is composed of more than 500×500 pixels (micro-detectors) for imaging of cm-area with a pixel of less than 20 µm in square. The SCAPS can be detected from single ion to 100 kilo-count ions per one pixel. Thus, SCAPS can be accumulated up to several giga-count ions for total pixels, i.e. for total imaging area. The SCAPS has been applied to stigmatic ion optics of secondary ion mass spectrometer, as a detector of isotope microscope [9]. The isotope microscope has capabilities of quantitative isotope images of hundred-micrometer area on a sample with sub-micrometer resolution and permil precision, and of two-dimensional mass spectrum on cm-scale of mass dispersion plane of a sector magnet with ten-micrometer resolution. The performance has been applied to two-dimensional isotope spatial distribution for mainly hydrogen, carbon, nitrogen and oxygen of natural (extra-terrestrial and terrestrial) samples and samples simulated natural processes [e.g. 10-17]. References: [1] Matsumoto, K., et al. (1993) IEEE Trans. Electron Dev. 40

  15. Two-Dimensional Rotorcraft Downwash Flow Field Measurements by Lidar-Based Wind Scanners with Agile Beam Steering

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Angelou, Nikolas; Hansen, Per

    2014-01-01

    position; all points in space within a cone with a full opening angle of 1208 can be reached from about 8mout to some hundred meters depending on the range resolution required. The first two-dimensional mean wind fields measured in a horizontal plane and in a vertical plane below a hovering search...

  16. Perspective: Two-dimensional resonance Raman spectroscopy

    Science.gov (United States)

    Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.

    2016-11-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.

  17. Janus spectra in two-dimensional flows

    CERN Document Server

    Liu, Chien-Chia; Chakraborty, Pinaki

    2016-01-01

    In theory, large-scale atmospheric flows, soap-film flows and other two-dimensional flows may host two distinct types of turbulent energy spectra---in one, $\\alpha$, the spectral exponent of velocity fluctuations, equals $3$ and the fluctuations are dissipated at the small scales, and in the other, $\\alpha=5/3$ and the fluctuations are dissipated at the large scales---but measurements downstream of obstacles have invariably revealed $\\alpha = 3$. Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which $\\alpha$ has transitioned from $3$ to $5/3$ for the streamwise fluctuations but remains equal to $3$ for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows...

  18. Comparative Two-Dimensional Fluorescence Gel Electrophoresis.

    Science.gov (United States)

    Ackermann, Doreen; König, Simone

    2018-01-01

    Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.

  19. Two-dimensional hexagonal semiconductors beyond graphene

    Science.gov (United States)

    Nguyen, Bich Ha; Hieu Nguyen, Van

    2016-12-01

    The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WS2, WSe2 as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.

  20. Two-Dimensional Phononic Crystals: Disorder Matters.

    Science.gov (United States)

    Wagner, Markus R; Graczykowski, Bartlomiej; Reparaz, Juan Sebastian; El Sachat, Alexandros; Sledzinska, Marianna; Alzina, Francesc; Sotomayor Torres, Clivia M

    2016-09-14

    The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.

  1. Two-dimensional topological photonic systems

    Science.gov (United States)

    Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng

    2017-09-01

    The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.

  2. Radiation effects on two-dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)

    2016-12-15

    The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Photodetectors based on two dimensional materials

    Science.gov (United States)

    Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen

    2016-09-01

    Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

  4. Asymptotics for Two-dimensional Atoms

    DEFF Research Database (Denmark)

    Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip

    2012-01-01

    We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....

  5. Isoperimetry in two-dimensional percolation

    OpenAIRE

    Biskup, Marek; Louidor, Oren; Procaccia, Eviatar B.; Rosenthal, Ron

    2012-01-01

    We consider the unique infinite connected component of supercritical bond percolation on the square lattice and study the geometric properties of isoperimetric sets, i.e., sets with minimal boundary for a given volume. For almost every realization of the infinite connected component we prove that, as the volume of the isoperimetric set tends to infinity, its asymptotic shape can be characterized by an isoperimetric problem in the plane with respect to a particular norm. As an application we t...

  6. Two-dimensional materials and their prospects in transistor electronics.

    Science.gov (United States)

    Schwierz, F; Pezoldt, J; Granzner, R

    2015-05-14

    During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.

  7. Efficient Two-Dimensional Direction Finding via Auxiliary-Variable Manifold Separation Technique for Arbitrary Array Structure

    Directory of Open Access Journals (Sweden)

    Guang Hua

    2015-01-01

    Full Text Available A polynomial rooting direction of arrival (DOA algorithm for multiple plane waves incident on an arbitrary array structure that combines the multipolynomial resultants and matrix computations is proposed in this paper. Firstly, a new auxiliary-variable manifold separation technique (AV-MST is used to model the steering vector of arbitrary array structure as the product of a sampling matrix (dependent only on the array structure and two Vandermonde-structured wavefield coefficient vectors (dependent on the wavefield. Then the propagator operator is calculated and used to form a system of bivariate polynomial equations. Finally, the automatically paired azimuth and elevation estimates are derived by polynomial rooting. The presented algorithm employs the concept of auxiliary-variable manifold separation technique which requires no sector by sector array interpolation and thus does not suffer from any mapping errors. In addition, the new algorithm does not need any eigenvalue decomposition of the covariance matrix and exhausted search over the two-dimensional parameter space. Moreover, the algorithm gives automatically paired estimates, thus avoiding the complex pairing procedure. Therefore, the proposed algorithm shows low computational complexity and high robustness performance. Simulation results are shown to validate the effectiveness of the proposed method.

  8. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Science.gov (United States)

    Yang, Luyi

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This thesis presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly suppressed

  9. Two-dimensional gain cross-grating based on spatial modulation of active Raman gain

    Science.gov (United States)

    Wang, Li; Zhou, Feng-Xue; Guo, Hong-Ju; Niu, Yue-Ping; Gong, Shang-Qing

    2016-11-01

    Based on the spatial modulation of active Raman gain, a two-dimensional gain cross-grating is theoretically proposed. As the probe field propagates along the z direction and passes through the intersectant region of the two orthogonal standing-wave fields in the x-y plane, it can be effectively diffracted into the high-order directions, and the zero-order diffraction intensity is amplified at the same time. In comparison with the two-dimensional electromagnetically induced cross-grating based on electromagnetically induced transparency, the two-dimensional gain cross-grating has much higher diffraction intensities in the first-order and the high-order directions. Hence, it is more suitable to be utilized as all-optical switching and routing in optical networking and communication. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274112 and 11347133).

  10. SAR IMAGING SIMULATION OF HORIZONTAL FULLY TWO-DIMENSIONAL INTERNAL WAVES

    Institute of Scientific and Technical Information of China (English)

    SHEN Hui; HE Yi-Jun

    2006-01-01

    Based on the research of Lynett and Liu, a new horizontal fully two-dimensional internal wave propagation model with rotation effect was deduced, which can be used to simulate the characteristics of internal waves in a horizontal fully two-dimensional plane. By combining the imaging mechanism of Synthetic Aperture Radar(SAR), a simulation procedure was fatherly acquired, which can simulate the propagation characteristics of oceanic internal waves into SAR images. In order to evaluate the validity of the proposed simulation procedure, case studies are performed in South China Sea and results from simulation procedure are analyzed in detail. A very good consistency was found between the simulation results and satellite images. The proposed simulation procedure will be a possible foundation for the quantitative interpretation of internal waves from fully two-dimensional satellite images.

  11. Two dimensional fermions in three dimensional YM

    CERN Document Server

    Narayanan, R

    2010-01-01

    Dirac fermions in the fundamental representation of $SU(N)$ live on the surface of a cylinder embedded in $R^3$ and interact with a three dimensional $SU(N)$ Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the circumference of the cylinder is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit at a typical bulk scale. Replacing three dimensional YM by four dimensional YM introduces non-trivial renormalization effects.

  12. Extending models for two-dimensional constraints

    DEFF Research Database (Denmark)

    Forchhammer, Søren

    2009-01-01

    Random fields in two dimensions may be specified on 2 times 2 elements such that the probabilities of finite configurations and the entropy may be calculated explicitly. The Pickard random field is one example where probability of a new (non-boundary) element is conditioned on three previous...... elements. To extend the concept we consider extending such a field such that a vector or block of elements is conditioned on a larger set of previous elements. Given a stationary model defined on 2 times 2 elements, iterative scaling is used to define the extended model. The extended model may be used...

  13. Ultrafast two dimensional infrared chemical exchange spectroscopy

    Science.gov (United States)

    Fayer, Michael

    2011-03-01

    The method of ultrafast two dimensional infrared (2D IR) vibrational echo spectroscopy is described. Three ultrashort IR pulses tuned to the frequencies of the vibrational transitions of interest are directed into the sample. The interaction of these pulses with the molecular vibrational oscillators produces a polarization that gives rise to a fourth pulse, the vibrational echo. The vibrational echo pulse is combined with another pulse, the local oscillator, for heterodyne detection of the signal. For fixed time between the second and third pulses, the waiting time, the first pulse is scanned. Two Fourier transforms of the data yield a 2D IR spectrum. The waiting time is increased, and another spectrum is obtained. The change in the 2D IR spectra with increased waiting time provides information on the time evolution of the structure of the molecular system under observation. In a 2D IR chemical exchange experiment, two species A and B, are undergoing chemical exchange. A's are turning into B's, and B's are turning into A's, but the overall concentrations of the species are not changing. The kinetics of the chemical exchange on the ground electronic state under thermal equilibrium conditions can be obtained 2D IR spectroscopy. A vibration that has a different frequency for the two species is monitored. At very short time, there will be two peaks on the diagonal of the 2D IR spectrum, one for A and one for B. As the waiting time is increased, chemical exchange causes off-diagonal peaks to grow in. The time dependence of the growth of these off-diagonal peaks gives the chemical exchange rate. The method is applied to organic solute-solvent complex formation, orientational isomerization about a carbon-carbon single bond, migration of a hydrogen bond from one position on a molecule to another, protein structural substate interconversion, and water hydrogen bond switching between ions and water molecules. This work was supported by the Air Force Office of Scientific

  14. Molecular assembly on two-dimensional materials

    Science.gov (United States)

    Kumar, Avijit; Banerjee, Kaustuv; Liljeroth, Peter

    2017-02-01

    Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy. The review covers three aspects of the self-assembly. The first one focuses on non-covalent self-assembly dealing with site-selectivity due to inherent moiré pattern present on 2D materials grown on substrates. We also see that modification of intermolecular interactions and molecule–substrate interactions influences the assembly drastically and that 2D materials can also be used as a platform to carry out covalent and metal-coordinated assembly. The second part deals with the electronic properties of molecules adsorbed on 2D materials. By virtue of being inert and possessing low density of states near the Fermi level, 2D materials decouple molecules electronically from the underlying metal substrate and allow high-resolution spectroscopy and imaging of molecular orbitals. The moiré pattern on the 2D materials causes site-selective gating and charging of molecules in some cases. The last section covers the effects of self-assembled, acceptor and donor type, organic molecules on the electronic properties of graphene as revealed by spectroscopy and electrical transport measurements. Non-covalent functionalization of 2D materials has already been applied for their application as catalysts and sensors. With the current surge of activity on building van der Waals heterostructures from atomically thin crystals, molecular self-assembly has the potential to add an extra level of flexibility and functionality for applications ranging

  15. Two-dimensional materials based transparent flexible electronics

    Science.gov (United States)

    Yu, Lili; Ha, Sungjae; El-Damak, Dina; McVay, Elaine; Ling, Xi; Chandrakasan, Anantha; Kong, Jing; Palacios, Tomas

    2015-03-01

    Two-dimensional (2D) materials have generated great interest recently as a set of tools for electronics, as these materials can push electronics beyond traditional boundaries. These materials and their heterostructures offer excellent mechanical flexibility, optical transparency, and favorable transport properties for realizing electronic, sensing, and optical systems on arbitrary surfaces. These thin, lightweight, bendable, highly rugged and low-power devices may bring dramatic changes in information processing, communications and human-electronic interaction. In this report, for the first time, we demonstrate two complex transparent flexible systems based on molybdenum disulfide (MoS2) grown by chemical vapor method: a transparent active-matrix organic light-emitting diode (AMOLED) display and a MoS2 wireless link for sensor nodes. The 1/2 x 1/2 square inch, 4 x 5 pixels AMOLED structures are built on transparent substrates, containing MoS2 back plane circuit and OLEDs integrated on top of it. The back plane circuit turns on and off the individual pixel with two MoS2 transistors and a capacitor. The device is designed and fabricated based on SPICE simulation to achieve desired DC and transient performance. We have also demonstrated a MoS2 wireless self-powered sensor node. The system consists of as energy harvester, rectifier, sensor node and logic units. AC signals from the environment, such as near-field wireless power transfer, piezoelectric film and RF signal, are harvested, then rectified into DC signal by a MoS2 diode. CIQM, CICS, SRC.

  16. Nonstationarity of a two-dimensional perpendicular shock: Competing mechanisms

    Science.gov (United States)

    Lembège, Bertrand; Savoini, Philippe; Hellinger, Petr; Trávníček, Pavel M.

    2009-03-01

    Two-dimensional particle-in-cell (PIC) simulations are used for analyzing in detail different nonstationary behaviors of a perpendicular supercritical shock. A recent study by Hellinger et al. (2007) has shown that the front of a supercritical shock can be dominated by the emission of large-amplitude whistler waves. These waves inhibit the self-reformation driven by the reflected ions; then, the shock front appears almost ``quasi-stationary.'' The present study stresses new complementary results. First, for a fixed β i value, the whistler waves emission (WWE) persists for high M A above a critical Mach number (i.e., M A >= M A WWE). The quasi-stationarity is only apparent and disappears when considering the full 3-D field profiles. Second, for lower M A , the self-reformation is retrieved and becomes dominant as the amplitude of the whistler waves becomes negligible. Third, there exists a transition regime in M A within which both processes compete each other. Fourth, these results are observed for a strictly perpendicular shock only as B 0 is within the simulation plane. When B 0 is out of the simulation plane, no whistler waves emission is evidenced and only self-reformation is recovered. Fifth, the occurrence and disappearance of the nonlinear whistler waves are well recovered in both 2-D PIC and 2-D hybrid simulations. The impacts on the results of the mass ratio (2-D PIC simulations), of the resistivity and spatial resolution (2-D hybrid simulations), and of the size of the simulation box along the shock front are analyzed in detail.

  17. Two-dimensional state in driven magnetohydrodynamic turbulence.

    Science.gov (United States)

    Bigot, Barbara; Galtier, Sébastien

    2011-02-01

    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(∥)=0 and in the area k(∥)>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 Alfvénic 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.

  18. Gate-induced superconductivity in two-dimensional atomic crystals

    Science.gov (United States)

    Saito, Yu; Nojima, Tsutomu; Iwasa, Yoshihiro

    2016-09-01

    Two-dimensional (2D) crystals are attracting growing interest in condensed matter physics, since these systems exhibit not only rich electronic and photonic properties but also exotic electronic phase transitions including superconductivity and charge density wave. Moreover, owing to the recent development of transfer methods after exfoliation and electric-double-layer transistors, superconducting 2D atomic crystals, the thicknesses of which are below 1-2 nm, have been successfully obtained. Here, we present a topical review on the recent discoveries of 2D crystalline superconductors by ionic-liquid gating and a series of their novel properties. In particular, we highlight two topics; quantum metallic states (or possible metallic ground states) and superconductivity robust against in-plane magnetic fields. These phenomena can be discussed with the effects of weakened disorder and/or broken spacial inversion symmetry leading to valley-dependent spin-momentum locking (spin-valley locking). These examples suggest the superconducting 2D crystals are new platforms for investigating the intrinsic quantum phases as well as exotic nature in 2D superconductors.

  19. Stability and electronic properties of two-dimensional indium iodide

    Science.gov (United States)

    Wang, Jizhang; Dong, Baojuan; Guo, Huaihong; Yang, Teng; Zhu, Zhen; Hu, Gan; Saito, Riichiro; Zhang, Zhidong

    2017-01-01

    Based on ab initio density functional calculations, we studied the stability and electronic properties of two-dimensional indium iodide (InI). The calculated results show that monolayer and few-layer InI can be as stable as its bulk counterpart. The stability of the monolayer structure is further supported by examining the electronic and dynamic stability. The interlayer interaction is found to be fairly weak (˜160 meV/atom) and mechanical exfoliation to obtain monolayer and few-layer structures will be applicable. A direct band gap of 1.88 eV of the bulk structure is obtained from the hybrid functional method, and is comparable to the experimental one (˜2.00 eV). The electronic structure can be tuned by layer stacking and external strain. The size of the gap is a linear function of an inverse number of layers, suggesting that we can design few-layer structures for optoelectronic applications in the visible optical range. In-plane tensile or hydrostatic compressive stress is found to be useful not only in varying the gap size to cover the whole visible optical range, but also in inducing a semiconductor-metal transition with an experimentally accessible stress. The present result strongly supports the strategy of broadening the scope of group-V semiconductors by looking for isoelectronic III-VII atomic-layered materials.

  20. Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures

    Science.gov (United States)

    Mital, Subodh K.; Goldberg, Robert K.; Bonacuse, Peter J.

    2012-01-01

    A research program has been developed to quantify the effects of the microstructure of a woven ceramic matrix composite and its variability on the effective properties and response of the material. In order to characterize and quantify the variations in the microstructure of a five harness satin weave, chemical vapor infiltrated (CVI) SiC/SiC composite material, specimens were serially sectioned and polished to capture images that detailed the fiber tows, matrix, and porosity. Open source quantitative image analysis tools were then used to isolate the constituents, from which two dimensional finite element models were generated which approximated the actual specimen section geometry. A simplified elastic-plastic model, wherein all stress above yield is redistributed to lower stress regions, is used to approximate the progressive damage behavior for each of the composite constituents. Finite element analyses under in-plane tensile loading were performed to examine how the variability in the local microstructure affected the macroscopic stress-strain response of the material as well as the local initiation and progression of damage. The macroscopic stress-strain response appeared to be minimally affected by the variation in local microstructure, but the locations where damage initiated and propagated appeared to be linked to specific aspects of the local microstructure.

  1. Two-dimensional screening of the Wageningen chicken BAC library.

    Science.gov (United States)

    Crooijmans, R P; Vrebalov, J; Dijkhof, R J; van der Poel, J J; Groenen, M A

    2000-05-01

    We have constructed a Bacterial Artificial Chromosome (BAC) library that provides 5.5-fold redundant coverage of the chicken genome. The library was made by cloning partial HindIII-digested high-molecular-weight (HMW) DNA of a female White Leghorn chicken into the HindIII site of the vector pECBAC1. Several modifications of standard protocols were necessary to clone efficiently large partial HindIII DNA fragments. The library consists of 49,920 clones arranged in 130 384-well plates. An average insert size of 134 kb was estimated from the analysis of 152 randomly selected BAC clones. The average number of NotI restriction sites per clone was 0.77. After individual growth, DNA was isolated of the pooled clones of each 384-well plate, and subsequently DNA of each plate was isolated from the individual row and column pools. Screening of the Wageningen chicken BAC library was performed by two-dimensional PCR with 125 microsatellite markers. For 124 markers at least one BAC clone was obtained. FISH experiments of 108 BAC clones revealed chimerism in less than 1%. The number of different BAC clones per marker present in the BAC library was examined for 35 markers which resulted in a total of 167 different BAC clones. Per marker the number of BAC clones varied from 1 to 11, with an average of 4.77. The chicken BAC library constitutes an invaluable tool for positional cloning and for comparative mapping studies.

  2. The influence of the Rashba spin-orbit coupling on the two-dimensional magnetoexcitons

    Energy Technology Data Exchange (ETDEWEB)

    Hakioglu, T [Department of Physics, Bilkent University, 06800 Ankara (Turkey); Liberman, M A [Department of Physics, Uppsala University, Box 530, SE-751 21, Uppsala (Sweden); Moskalenko, S A; Podlesny, I V [Institute of Applied Physics, Academy of Sciences of Moldova, 5, Academiei street, MD-2028, Chisinau (Moldova, Republic of)

    2011-08-31

    The influence of the Rashba spin-orbit coupling (RSOC) on the two-dimensional (2D) electrons and holes in a strong perpendicular magnetic field leads to different results for the Landau quantization in different spin projections. In the Landau gauge the unidimensional wave vector describing the free motion in one in-plane direction is the same for both spin projections, whereas the numbers of Landau quantization levels are different. For an electron in an s-type conduction band they differ by one, as was established earlier by Rashba (1960 Fiz. Tverd. Tela 2 1224), whereas for heavy holes in a p-type valence band influenced by the 2D symmetry of the layer they differ by three. The shifts and the rearrangements of the 2D hole Landau quantization levels on the energy scale are much larger in comparison with the case of conduction electron Landau levels. This is due to the strong influence of the magnetic field on the RSOC parameter. At sufficiently large values of this parameter the shifts and rearrangements are comparable with the hole cyclotron energy. There are two lowest spin-split Landau levels for electrons as well as four lowest ones for holes in the case of small RSOC parameters. They give rise to eight lowest energy bands of the 2D magnetoexcitons, as well as of the band-to-band quantum transitions. It is shown that three of them are dipole-active, three are quadrupole-active and two are forbidden. The optical orientation under the influence of circularly polarized light leads to optical alignment of the magnetoexcitons with different orbital momentum projections in the direction of the external magnetic field. (paper)

  3. The convolution theorem for two-dimensional continuous wavelet transform

    Institute of Scientific and Technical Information of China (English)

    ZHANG CHI

    2013-01-01

    In this paper , application of two -dimensional continuous wavelet transform to image processes is studied. We first show that the convolution and correlation of two continuous wavelets satisfy the required admissibility and regularity conditions ,and then we derive the convolution and correlation theorem for two-dimensional continuous wavelet transform. Finally, we present numerical example showing the usefulness of applying the convolution theorem for two -dimensional continuous wavelet transform to perform image restoration in the presence of additive noise.

  4. Surface plasmon hurdles leading to a strongly localized giant field enhancement on two-dimensional (2D) metallic diffraction gratings.

    Science.gov (United States)

    Brûlé, Yoann; Demésy, Guillaume; Gralak, Boris; Popov, Evgeny

    2015-04-01

    An extensive numerical study of diffraction of a plane monochromatic wave by a single gold cone on a plane gold substrate and by a periodical array of such cones shows formation of curls in the map of the Poynting vector. They result from the interference between the incident wave, the wave reflected by the substrate, and the field scattered by the cone(s). In case of a single cone, when going away from its base along the surface, the main contribution in the scattered field is given by the plasmon surface wave (PSW) excited on the surface. As expected, it has a predominant direction of propagation, determined by the incident wave polarization. Two particular cones with height approximately 1/6 and 1/3 of the wavelength are studied in detail, as they present the strongest absorption and field enhancement when arranged in a periodic array. While the PSW excited by the smaller single cone shows an energy flux globally directed along the substrate surface, we show that curls of the Poynting vector generated with the larger cone touch the diopter surface. At this point, their direction is opposite to the energy flow of the PSW, which is then forced to jump over the vortex regions. Arranging the cones in a two-dimensional subwavelength periodic array (diffraction grating), supporting a specular reflected order only, resonantly strengthens the field intensity at the tip of cones and leads to a field intensity enhancement of the order of 10 000 with respect to the incident wave intensity. The enhanced field is strongly localized on the rounded top of the cones. It is accompanied by a total absorption of the incident light exhibiting large angular tolerances. This strongly localized giant field enhancement can be of much interest in many applications, including fluorescence spectroscopy, label-free biosensing, surface-enhanced Raman scattering (SERS), nonlinear optical effects and photovoltaics.

  5. Multi-Symplectic Splitting Method for Two-Dimensional Nonlinear Schriidinger Equation

    Institute of Scientific and Technical Information of China (English)

    陈亚铭; 朱华君; 宋松和

    2011-01-01

    Using the idea of splitting numerical methods and the multi-symplectic methods, we propose a multisymplectic splitting (MSS) method to solve the two-dimensional nonlinear Schrodinger equation (2D-NLSE) in this paper. It is further shown that the method constructed in this way preserve the global symplectieity exactly. Numerical experiments for the plane wave solution and singular solution of the 2D-NLSE show the accuracy and effectiveness of the proposed method.

  6. Applications of FEM and BEM in two-dimensional fracture mechanics problems

    Science.gov (United States)

    Min, J. B.; Steeve, B. E.; Swanson, G. R.

    1992-08-01

    A comparison of the finite element method (FEM) and boundary element method (BEM) for the solution of two-dimensional plane strain problems in fracture mechanics is presented in this paper. Stress intensity factors (SIF's) were calculated using both methods for elastic plates with either a single-edge crack or an inclined-edge crack. In particular, two currently available programs, ANSYS for finite element analysis and BEASY for boundary element analysis, were used.

  7. Quadrature two-dimensional correlation spectroscopy (Q-2DCOS)

    Science.gov (United States)

    Noda, Isao

    2016-11-01

    Quadrature 2D correlation spectroscopy (Q-2DCOS) is introduced. The technique incorporates the effect of the perturbation into the traditional 2DCOS analysis by building a multivariate model, merging the information of the perturbation variable and spectral responses. By employing factors which are 90° out of phase with each other, pertinent coincidental and sequential spectral intensity variations are adequately captured for the subsequent 2D correlation analysis. Almost complete replication of the original 2DCOS results based on such a simple rank 2 model of experimental spectra suggests that only the dominant spectral intensity variation patterns in combination with its quadrature counterpart seems to be utilized in 2DCOS analysis. Using the linear perturbation variable itself as the basis for generating the primary score vector is equivalent to the least squares fitting of a quadratic polynomial with spectral intensity variations. Q-2DCOS analysis may be displayed in terms of a graphical plot on a phase plane in the vector space, so that coincidental and sequential matching of the patterns of spectral intensity variations is represented simply by the phase angle difference between two vectors. Q-2DCOS analysis is closely related to other established ideas and practices in the 2D correlation spectroscopy field, such as dynamic 2D IR dichroism, PCA 2D, quadrature orthogonal signal correction (Q-OSC), and perturbation correlation moving window (PCMW) analyses.

  8. Applying clustering to statistical analysis of student reasoning about two-dimensional kinematics

    Directory of Open Access Journals (Sweden)

    R. Padraic Springuel

    2007-12-01

    Full Text Available We use clustering, an analysis method not presently common to the physics education research community, to group and characterize student responses to written questions about two-dimensional kinematics. Previously, clustering has been used to analyze multiple-choice data; we analyze free-response data that includes both sketches of vectors and written elements. The primary goal of this paper is to describe the methodology itself; we include a brief overview of relevant results.

  9. Applying clustering to statistical analysis of student reasoning about two-dimensional kinematics

    Directory of Open Access Journals (Sweden)

    John R. Thompson

    2007-12-01

    Full Text Available We use clustering, an analysis method not presently common to the physics education research community, to group and characterize student responses to written questions about two-dimensional kinematics. Previously, clustering has been used to analyze multiple-choice data; we analyze free-response data that includes both sketches of vectors and written elements. The primary goal of this paper is to describe the methodology itself; we include a brief overview of relevant results.

  10. Errors in using two dimensional methods for ergonomic assessment of motion in three dimensional space

    Energy Technology Data Exchange (ETDEWEB)

    Hollerbach, K.; Van Vorhis, R.L. [Lawrence Livermore National Lab., CA (United States); Hollister, A. [Louisiana State Univ., Shreveport, LA (United States)

    1996-03-01

    Wrist posture and rapid wrist movements are risk factors for work related musculoskeletal disorders. Measurement studies frequently involve optoelectronic methods in which markers are placed on the subject`s hand and wrist and the trajectories of the markers are tracked in three dimensional space. A goal of wrist posture measurements is to quantitatively establish wrist posture orientation. Accuracy and fidelity of the measurement data with respect to kinematic mechanisms are essential in wrist motion studies. Fidelity with the physical kinematic mechanism can be limited by the choice of kinematic modeling techniques and the representation of motion. Frequently, ergonomic studies involving wrist kinematics make use of two dimensional measurement and analysis techniques. Two dimensional measurement of human joint motion involves the analysis of three dimensional displacements in an obersver selected measurement plane. Accurate marker placement and alignment of joint motion plane with the observer plane are difficult. In nature, joint axes can exist at any orientation and location relative to an arbitrarily chosen global reference frame. An arbitrary axis is any axis that is not coincident with a reference coordinate. We calculate the errors that result from measuring joint motion about an arbitrary axis using two dimensional methods.

  11. Quasi-two-dimensional complex plasma containing spherical particles and their binary agglomerates

    CERN Document Server

    Chaudhuri, M; Nosenko, V; Thomas, H M

    2015-01-01

    A new type of quasi-two-dimensional complex plasma system was observed which consisted of monodisperse microspheres and their binary agglomerations (dimers). The particles and their dimers levitated in a plasma sheath at slightly different heights and formed two distinct sublayers. The sys- tem did not crystallize and may be characterized as disordered solid. The dimers were identified based on their characteristic appearance in defocused images, i.e., rotating interference fringe pat- terns. The in-plane and inter-plane particle separations exhibit nonmonotonic dependence on the discharge pressure which agrees well with theoretical predictions.

  12. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Subir Sachdev

    2002-02-01

    We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.

  13. Two-dimensional hydrodynamic flow focusing in a microfluidic platform featuring a monolithic integrated glass micronozzle

    Science.gov (United States)

    Liu, Yifan; Shen, Yusheng; Duan, Lian; Yobas, Levent

    2016-10-01

    Two-dimensional hydrodynamic flow focusing is demonstrated through a microfluidic device featuring a monolithic integrated glass micronozzle inside a flow-focusing geometry. Such a coaxial configuration allows simple one-step focusing of a sample fluid stream, jetted from the micronozzle tip, in both in-plane and out-of-plane directions. The width of the focused filament can be precisely controlled and further scaled down to the submicrometer regime to facilitate rapid hydrodynamic mixing. Fluorescence quenching experiments reveal ultra-fast microsecond mixing of the denaturant into the focused filament. This device offers new possibilities to a set of applications such as the study of protein folding kinetics.

  14. The kinetic magnetoelectric effect in laterally boundary-confined ballistic two-dimensional hole gases

    Institute of Scientific and Technical Information of China (English)

    Huang Hai-Tao; Hu Liang-Bin; Zhang Xin-Ding; Zhu Shi-Liang

    2009-01-01

    A theoretical investigation is presented on the characteristics of the kinetic magnetoelectric effect in laterally boundary-confined ballistic two-dimensional hole gases.It was shown that,though the momentum-dependent effective magnetic fields felt by charge carriers due to the spin-orbit interaction are in-plane orientated in such systems,both in-plane polarized and normal polarized nonequilibrium spin polarization densities could be electrically induced by the kinetic magnetoelectric effect,and the induced nonequilibrium spin polarizations exhibit some interesting characteristics.The characteristics we found indicate that there may be some possible relation between this effect and some recent experimental findings.

  15. Negative static permittivity and violation of Kramers-Kronig relations in quasi-two-dimensional crystals

    Science.gov (United States)

    Nazarov, V. U.

    2015-10-01

    We investigate the wave vector and frequency-dependent screening of the electric field in atomically thin (quasi-two-dimensional) crystals. For graphene and hexagonal boron nitride we find that, above a critical wave vector qc, the static permittivity ɛ (q >qc,ω =0 ) becomes negative and the Kramers-Kronig relations do not hold for ɛ (q >qc,ω ) . Thus, in quasi-two-dimensional crystals, we reveal the physical confirmation of a proposition put forward decades ago [D. A. Kirzhnits, Sov. Phys. Usp. 19, 530 (1976), 10.1070/PU1976v019n06ABEH005268], allowing for the breakdown of Kramers-Kronig relations and for negative static permittivity. In the vicinity of the critical wave vector, we find a giant growth of the permittivity. Our results, obtained in the ab initio calculations using both the random-phase approximation and the adiabatic time-dependent local-density approximation, and further confirmed with a simple slab model, allow us to argue that the above properties, being exceptional in the three-dimensional case, are common to quasi-two-dimensional systems.

  16. THE UNCONDITIONAL STABLE DIFFERENCE METHODS WITH INTRINSIC PARALLELISM FOR TWO DIMENSIONAL SEMILINEAR PARABOLIC SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Guangwei Yuan; Longjun Shen

    2003-01-01

    In this paper we are going to discuss the difference schemes with intrinsic parallelismfor the boundary value problem of the two dimensional semilinear parabolic systems. Theunconditional stability of the general finite difference schemes with intrinsic parallelismis justified in the sense of the continuous dependence of the discrete vector solution ofthe difference schemes on the discrete data of the original problems in the discrete W2(2,1)norms. Then the uniqueness of the discrete vector solution of this difference scheme followsas the consequence of the stability.

  17. The Chandrasekhar's Equation for Two-Dimensional Hypothetical White Dwarfs

    CERN Document Server

    De, Sanchari

    2014-01-01

    In this article we have extended the original work of Chandrasekhar on the structure of white dwarfs to the two-dimensional case. Although such two-dimensional stellar objects are hypothetical in nature, we strongly believe that the work presented in this article may be prescribed as Master of Science level class problem for the students in physics.

  18. Beginning Introductory Physics with Two-Dimensional Motion

    Science.gov (United States)

    Huggins, Elisha

    2009-01-01

    During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…

  19. Spatiotemporal surface solitons in two-dimensional photonic lattices.

    Science.gov (United States)

    Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S

    2007-11-01

    We analyze spatiotemporal light localization in truncated two-dimensional photonic lattices and demonstrate the existence of two-dimensional surface light bullets localized in the lattice corners or the edges. We study the families of the spatiotemporal surface solitons and their properties such as bistability and compare them with the modes located deep inside the photonic lattice.

  20. Explorative data analysis of two-dimensional electrophoresis gels

    DEFF Research Database (Denmark)

    Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine;

    2004-01-01

    Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...

  1. Mechanics of Apparent Horizon in Two Dimensional Dilaton Gravity

    CERN Document Server

    Cai, Rong-Gen

    2016-01-01

    In this article, we give a definition of apparent horizon in a two dimensional general dilaton gravity theory. With this definition, we construct the mechanics of the apparent horizon by introducing a quasi-local energy of the theory. Our discussion generalizes the apparent horizons mechanics in general spherically symmetric spactimes in four or higher dimensions to the two dimensional dilaton gravity case.

  2. Topological aspect of disclinations in two-dimensional crystals

    Institute of Scientific and Technical Information of China (English)

    Qi Wei-Kai; Zhu Tao; Chen Yong; Ren Ji-Rong

    2009-01-01

    By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.

  3. Invariant Subspaces of the Two-Dimensional Nonlinear Evolution Equations

    Directory of Open Access Journals (Sweden)

    Chunrong Zhu

    2016-11-01

    Full Text Available In this paper, we develop the symmetry-related methods to study invariant subspaces of the two-dimensional nonlinear differential operators. The conditional Lie–Bäcklund symmetry and Lie point symmetry methods are used to construct invariant subspaces of two-dimensional differential operators. We first apply the multiple conditional Lie–Bäcklund symmetries to derive invariant subspaces of the two-dimensional operators. As an application, the invariant subspaces for a class of two-dimensional nonlinear quadratic operators are provided. Furthermore, the invariant subspace method in one-dimensional space combined with the Lie symmetry reduction method and the change of variables is used to obtain invariant subspaces of the two-dimensional nonlinear operators.

  4. Two-dimensional metal-insulator transition as a strong localization induced crossover phenomenon

    Science.gov (United States)

    Das Sarma, S.; Hwang, E. H.

    2014-06-01

    Low-disorder and high-mobility two-dimensional (2D) electron (or hole) systems confined in semiconductor heterostructures undergo an apparent metal-insulator transition (MIT) at low temperatures as the carrier density (n) is varied. In some situations, the 2D MIT can be caused at a fixed low carrier density by changing an externally applied in-plane magnetic field parallel to the 2D layer. The goal of the current work is to obtain the critical density (nc) for the 2D MIT with the system being an effective metal (Anderson insulator) for density n above (below) nc. We study the 2D MIT phenomenon theoretically as a possible strong localization induced crossover process controlled by the Ioffe-Regel criterion, kFl=1, where kF(n) is the 2D Fermi wave vector and l (n) is the disorder-limited quantum mean free path on the metallic side. Calculating the quantum mean free path in the effective metallic phase from a realistic Boltzmann transport theory including disorder scattering effects, we solve the integral equation (with l depending on n through multidimensional integrals) defined by the Ioffe-Regel criterion to obtain the nonuniversal critical density nc as a function of the applicable physical experimental parameters including disorder strength, in-plane magnetic field, spin and valley degeneracy, background dielectric constant and carrier effective mass, and temperature. The key physics underlying the nonuniversal parameter dependence of the critical density is the density dependence of the screened Coulomb disorder. Our calculated results for the crossover critical density nc appear to be in qualitative and semiquantitative agreement with the available experimental data in different 2D semiconductor systems lending credence to the possibility that the apparent 2D MIT signals the onset of the strong localization crossover in disordered 2D systems. We also compare the calculated critical density obtained from the Ioffe-Regel criterion with that obtained from a

  5. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Luyi [Univ. of California, Berkeley, CA (United States)

    2013-05-17

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly

  6. Two-dimensional stress—magnetization effects of grain-oriented silicon steel sheets

    Science.gov (United States)

    Saito, Akihiko; Murashige, Shinichi; Uehara, Yuji

    1994-05-01

    Changes in the magnetization vector due to tensile stress under a constant magnetic field for grain-oriented silicon-iron sheet strip samples cut at various angles from the rolling direction have been investigated. In a low magnetic field, where the magnetization is less than 1.5 T, the magnetization vector lies in the direction of the sample length and the magnetization decreases with the application of tension. Beyond that magnetic field, the magnetization vector showed a two-dimensional hysteresis loop due to the application of tension. The maximum transverse magnetization change appeared in a 10° sample, where the rotation angle of the magnetization vector was 2.5°.

  7. Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice

    Institute of Scientific and Technical Information of China (English)

    XU Quan; QIANG Tian

    2009-01-01

    We study the existence and stability of two-dimensional discrete breathers in a two-dimensional discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling.Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive)and the center of the two-dimensional gap breather (on a light or a heavy atom).

  8. Band Gap Computation of Two Dimensional Photonic Crystal for High Index Contrast Grating Application

    Directory of Open Access Journals (Sweden)

    Gagandeep Kaur

    2014-05-01

    Full Text Available Two Dimensional Photonic Crystal (PHc is convenient type of PHc, It refers to the fact that the dielectric is periodic in Two directions. The study of photonic structure by a simulation method is extremely momentous. At optical frequencies the optical density contained by two dimensional PHc changes periodically. They have the property to strong effect the propagation of light waves at these optical frequencies. A typical linearization method which solves the common nonlinear Eigen values difficulties has been used to achieve structures of the photonic band. There are two method plane wave expansion method (PWE and Finite Difference Time Domain method (FDTD. These Methods are most widely used for band gap calculation of PHc’s. FDTD Method has more smoothness and directness and can be explored effortlessly for simulation of the field circulation inside the photonic structure than PWE method so we have used FDTD Method for Two dimensional PHc’s calculation. In simulation of Two Dimensional band structures, silicon material has 0.543nm lattice constant and 1.46refractive index.

  9. Exact solutions and conservation laws of the system of two-dimensional viscous Burgers equations

    Science.gov (United States)

    Abdulwahhab, Muhammad Alim

    2016-10-01

    Fluid turbulence is one of the phenomena that has been studied extensively for many decades. Due to its huge practical importance in fluid dynamics, various models have been developed to capture both the indispensable physical quality and the mathematical structure of turbulent fluid flow. Among the prominent equations used for gaining in-depth insight of fluid turbulence is the two-dimensional Burgers equations. Its solutions have been studied by researchers through various methods, most of which are numerical. Being a simplified form of the two-dimensional Navier-Stokes equations and its wide range of applicability in various fields of science and engineering, development of computationally efficient methods for the solution of the two-dimensional Burgers equations is still an active field of research. In this study, Lie symmetry method is used to perform detailed analysis on the system of two-dimensional Burgers equations. Optimal system of one-dimensional subalgebras up to conjugacy is derived and used to obtain distinct exact solutions. These solutions not only help in understanding the physical effects of the model problem but also, can serve as benchmarks for constructing algorithms and validation of numerical solutions of the system of Burgers equations under consideration at finite Reynolds numbers. Independent and nontrivial conserved vectors are also constructed.

  10. Use of real Dirac matrices in two-dimensional coupled linear optics

    Science.gov (United States)

    Baumgarten, C.

    2011-11-01

    The Courant-Snyder theory for two-dimensional coupled linear optics is presented, based on the systematic use of the real representation of the Dirac matrices. Since any real 4×4 matrix can be expressed as a linear combination of these matrices, the presented ansatz allows for a comprehensive and complete treatment of two-dimensional linear coupling. A survey of symplectic transformations in two dimensions is presented. A subset of these transformations is shown to be identical to rotations and Lorentz boosts in Minkowski space-time. The transformation properties of the classical state vector are formulated and found to be analog to those of a Dirac spinor. The equations of motion for a relativistic charged particle—the Lorentz force equations—are shown to be isomorph to envelope equations of two-dimensional linear coupled optics. A universal and straightforward method to decouple two-dimensional harmonic oscillators with constant coefficients by symplectic transformations is presented, which is based on this isomorphism. The method yields the eigenvalues (i.e., tunes) and eigenvectors and can be applied to a one-turn transfer matrix or directly to the coefficient matrix of the linear differential equation.

  11. Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway

    Science.gov (United States)

    2012-09-01

    ER D C/ CH L TR -1 2 -2 0 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway C oa st al a n d H yd ra u lic s La b or at...distribution is unlimited. ERDC/CHL TR-12-20 September 2012 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway Stephen H. Scott, Jeremy A...A two-dimensional Adaptive Hydraulics (AdH) hydrodynamic model was developed to simulate the Moose Creek Floodway. The Floodway is located

  12. RESEARCH ON TWO-DIMENSIONAL LDA FOR FACE RECOGNITION

    Institute of Scientific and Technical Information of China (English)

    Han Ke; Zhu Xiuchang

    2006-01-01

    The letter presents an improved two-dimensional linear discriminant analysis method for feature extraction. Compared with the current two-dimensional methods for feature extraction, the improved two-dimensional linear discriminant analysis method makes full use of not only the row and the column direction information of face images but also the discriminant information among different classes. The method is evaluated using the Nanjing University of Science and Technology (NUST) 603 face database and the Aleix Martinez and Robert Benavente (AR) face database. Experimental results show that the method in the letter is feasible and effective.

  13. ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES

    Directory of Open Access Journals (Sweden)

    Nikola Stefanović

    2007-06-01

    Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.

  14. A Two-Dimensional Photonic Crystal Slab Mirror with Silicon on Insulator for Wavelength 1.3μm

    Institute of Scientific and Technical Information of China (English)

    TANG Hai-Xia; ZUO Yu-Hua; YU Jin-Zhong; WANG Qi-Ming

    2006-01-01

    @@ A concrete two-dimensional photonic crystal slab with triangular lattice used as a mirror for the light at wavelength 1.3μm with a silicon-on-insulator (SOI) substrate is designed by the three-dimensional plane wave expansion method.

  15. Formation of two-dimensional nonspreading atomic wave packets in the field of two standing light waves

    NARCIS (Netherlands)

    Efremov, MA; Petropavlovsky, SV; Fedorov, MV; Schleich, WP; Yakovlev, VP

    2005-01-01

    The formation of two-dimensional nonspreading atomic wave packets produced in the interaction of a beam of two-level atoms with two standing light waves polarised in the same plane is considered. The mechanism providing a dispersionless particle dynamics is the balance of two processes: a rapid deca

  16. A study of two-dimensional magnetic polaron

    Institute of Scientific and Technical Information of China (English)

    LIU; Tao; ZHANG; Huaihong; FENG; Mang; WANG; Kelin

    2006-01-01

    By using the variational method and anneal simulation, we study in this paper the self-trapped magnetic polaron (STMP) in two-dimensional anti-ferromagnetic material and the bound magnetic polaron (BMP) in ferromagnetic material. Schwinger angular momentum theory is applied to changing the problem into a coupling problem of carriers and two types of Bosons. Our calculation shows that there are single-peak and multi-peak structures in the two-dimensional STMP. For the ferromagnetic material, the properties of the two-dimensional BMP are almost the same as that in one-dimensional case; but for the anti-ferromagnetic material, the two-dimensional STMP structure is much richer than the one-dimensional case.

  17. UPWIND DISCONTINUOUS GALERKIN METHODS FOR TWO DIMENSIONAL NEUTRON TRANSPORT EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    袁光伟; 沈智军; 闫伟

    2003-01-01

    In this paper the upwind discontinuous Galerkin methods with triangle meshes for two dimensional neutron transport equations will be studied.The stability for both of the semi-discrete and full-discrete method will be proved.

  18. Two-Dimensionally-Modulated, Magnetic Structure of Neodymium Metal

    DEFF Research Database (Denmark)

    Lebech, Bente; Bak, P.

    1979-01-01

    The incipient magnetic order of dhcp Nd is described by a two-dimensional, incommensurably modulated structure ("triple-q" structure). The ordering is accompanied by a lattice distortion that forms a similar pattern....

  19. Entanglement Entropy for time dependent two dimensional holographic superconductor

    CERN Document Server

    Mazhari, N S; Myrzakulov, Kairat; Myrzakulov, R

    2016-01-01

    We studied entanglement entropy for a time dependent two dimensional holographic superconductor. We showed that the conserved charge of the system plays the role of the critical parameter to have condensation.

  20. Decoherence in a Landau Quantized Two Dimensional Electron Gas

    Directory of Open Access Journals (Sweden)

    McGill Stephen A.

    2013-03-01

    Full Text Available We have studied the dynamics of a high mobility two-dimensional electron gas as a function of temperature. The presence of satellite reflections in the sample and magnet can be modeled in the time-domain.

  1. Quantization of Two-Dimensional Gravity with Dynamical Torsion

    CERN Document Server

    Lavrov, P M

    1999-01-01

    We consider two-dimensional gravity with dynamical torsion in the Batalin - Vilkovisky and Batalin - Lavrov - Tyutin formalisms of gauge theories quantization as well as in the background field method.

  2. Spatiotemporal dissipative solitons in two-dimensional photonic lattices.

    Science.gov (United States)

    Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S

    2008-11-01

    We analyze spatiotemporal dissipative solitons in two-dimensional photonic lattices in the presence of gain and loss. In the framework of the continuous-discrete cubic-quintic Ginzburg-Landau model, we demonstrate the existence of novel classes of two-dimensional spatiotemporal dissipative lattice solitons, which also include surface solitons located in the corners or at the edges of the truncated two-dimensional photonic lattice. We find the domains of existence and stability of such spatiotemporal dissipative solitons in the relevant parameter space, for both on-site and intersite lattice solitons. We show that the on-site solitons are stable in the whole domain of their existence, whereas most of the intersite solitons are unstable. We describe the scenarios of the instability-induced dynamics of dissipative solitons in two-dimensional lattices.

  3. A two-dimensional polymer prepared by organic synthesis.

    Science.gov (United States)

    Kissel, Patrick; Erni, Rolf; Schweizer, W Bernd; Rossell, Marta D; King, Benjamin T; Bauer, Thomas; Götzinger, Stephan; Schlüter, A Dieter; Sakamoto, Junji

    2012-02-05

    Synthetic polymers are widely used materials, as attested by a production of more than 200 millions of tons per year, and are typically composed of linear repeat units. They may also be branched or irregularly crosslinked. Here, we introduce a two-dimensional polymer with internal periodicity composed of areal repeat units. This is an extension of Staudinger's polymerization concept (to form macromolecules by covalently linking repeat units together), but in two dimensions. A well-known example of such a two-dimensional polymer is graphene, but its thermolytic synthesis precludes molecular design on demand. Here, we have rationally synthesized an ordered, non-equilibrium two-dimensional polymer far beyond molecular dimensions. The procedure includes the crystallization of a specifically designed photoreactive monomer into a layered structure, a photo-polymerization step within the crystal and a solvent-induced delamination step that isolates individual two-dimensional polymers as free-standing, monolayered molecular sheets.

  4. Second invariant for two-dimensional classical super systems

    Indian Academy of Sciences (India)

    S C Mishra; Roshan Lal; Veena Mishra

    2003-10-01

    Construction of superpotentials for two-dimensional classical super systems (for ≥ 2) is carried out. Some interesting potentials have been studied in their super form and also their integrability.

  5. Extreme paths in oriented two-dimensional percolation

    OpenAIRE

    Andjel, E. D.; Gray, L. F.

    2016-01-01

    International audience; A useful result about leftmost and rightmost paths in two dimensional bond percolation is proved. This result was introduced without proof in \\cite{G} in the context of the contact process in continuous time. As discussed here, it also holds for several related models, including the discrete time contact process and two dimensional site percolation. Among the consequences are a natural monotonicity in the probability of percolation between different sites and a somewha...

  6. Two Dimensional Nucleation Process by Monte Carlo Simulation

    OpenAIRE

    T., Irisawa; K., Matsumoto; Y., Arima; T., Kan; Computer Center, Gakushuin University; Department of Physics, Gakushuin University

    1997-01-01

    Two dimensional nucleation process on substrate is investigated by Monte Carlo simulation, and the critical nucleus size and its waiting time are measured with a high accuracy. In order to measure the critical nucleus with a high accuracy, we calculate the attachment and the detachment rate to the nucleus directly, and define the critical nucleus size when both rate are equal. Using the kinematical nucleation theory by Nishioka, it is found that, our obtained kinematical two dimensional criti...

  7. Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

    Science.gov (United States)

    2016-06-15

    polymers . 2. Introduction . Research objectives: This research aims to study the physical (van der Waals forces: crystal epitaxy and π-π...AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY...Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-14-1-4054 5c.  PROGRAM ELEMENT

  8. Two-Dimensional Weak Pseudomanifolds on Eight Vertices

    Indian Academy of Sciences (India)

    Basudeb Datta; Nandini Nilakantan

    2002-05-01

    We explicitly determine all the two-dimensional weak pseudomanifolds on 8 vertices. We prove that there are (up to isomorphism) exactly 95 such weak pseudomanifolds, 44 of which are combinatorial 2-manifolds. These 95 weak pseudomanifolds triangulate 16 topological spaces. As a consequence, we prove that there are exactly three 8-vertex two-dimensional orientable pseudomanifolds which allow degree three maps to the 4-vertex 2-sphere.

  9. Two-dimensional analysis of gold nanoparticle effects on dye molecule system

    Energy Technology Data Exchange (ETDEWEB)

    Qaradaghi, Vahid [School of Electrical and Computer Engineering, Tarbiat Modares University (TMU), P.O. Box 14115-194, Tehran (Iran, Islamic Republic of); Fathi, Davood, E-mail: davfathi@modares.ac.ir [School of Electrical and Computer Engineering, Tarbiat Modares University (TMU), P.O. Box 14115-194, Tehran (Iran, Islamic Republic of)

    2013-01-15

    This paper presents a two-dimensional analysis of a dye molecule system in the presence of a gold nanoparticle (AuNP). This configuration has been used widely for the practical applications such as optoelectronics and also the biomedical applications such as cancer. The effects of coupling between the nanoparticle (AuNP) and dye molecules around it are simulated and studied in a two-dimensional plane. The three relative momentum polarizations of dye molecule near the AuNP (perpendicular, parallel and random) are considered. With the change of nanoparticle radius and its distances from the dye molecules, the output fluorescence signal will be changed. The obtained results show that, the perpendicular polarized dye w.r.t. the AuNP surface leads to the increase of output fluorescence signal nearly 1.5 times the input intensity.

  10. Two dimensional tunable photonic crystal defect based drop filter at communication wavelength

    Science.gov (United States)

    D'souza, Nirmala Maria; Mathew, Vincent

    2017-07-01

    We propose a two dimensional photonic crystal (PhC) based drop filter, at communication wavelength with more than 90% transmission. The filtering is achieved by introducing two line defects and three point defects in a two dimensional triangular array of ferroelectric rods in air. Using the electro-optic property of the ferroelectric, about 32 nm tuning in the resonance wavelength is obtained. For the calculation of transmission, finite difference time domain (FDTD) simulations were performed. The operating frequency range is explored via the band structure which is obtained by the implementation of plane wave expansion (PWE) method. The influence of the radius of various rods on the filter wavelength as well as efficiency is also analyzed. The different possible configurations of this filter are also considered.

  11. Two-Dimensional Rotating Stall Analysis in a Wide Vaneless Diffuser

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available We report a numerical study on the vaneless diffuser core flow instability in centrifugal compressors. The analysis is performed for the purpose of better understanding of the rotating stall flow mechanism in radial vaneless diffusers. Since the analysis is restricted to the two-dimensional core flow, the effect of the wall boundary layers is neglected. A commercial code with the standard incompressible viscous flow solver is applied to model the vaneless diffuser core flow in the plane parallel to the diffuser walls. At the diffuser inlet, rotating jet-wake velocity pattern is prescribed and at the diffuser outlet constant static pressure is assumed. Under these circumstances, two-dimensional rotating flow instability similar to rotating stall is found to exist. Performed parameter analysis reveals that this instability is strongly influenced by the diffuser geometry and the inlet and outlet flow conditions.

  12. Giant perpendicular magnetic anisotropy of an individual atom on two-dimensional transition metal dichalcogenides

    Science.gov (United States)

    Odkhuu, Dorj

    2016-08-01

    Exploring magnetism and magnetic anisotropy in otherwise nonmagnetic two-dimensional materials, such as graphene and transition metal dichalcogenides, is at the heart of spintronics research. Herein, using first-principles calculations we explore the possibility of reaching an atomic-scale perpendicular magnetic anisotropy by carefully exploring the large spin-orbit coupling, orbital magnetism, and ligand field in a suitable choice of a two-dimensional structure with transition metal adatoms. More specifically, we demonstrate perpendicular magnetic anisotropy energies up to an order of 100 meV per atom in individual ruthenium and osmium adatoms at a monosulfur vacancy in molybdenum disulfide. We further propose a phenomenological model where a spin state transition that involves hybridization between molybdenum a1 and adatomic e' orbitals is a possible mechanism for magnetization reversal from an in-plane to perpendicular orientation.

  13. Tuning of band gaps for a two-dimensional piezoelectric phononic crystal with a rectangular lattice

    Institute of Scientific and Technical Information of China (English)

    Yize Wang; Fengming Li; Yuesheng Wang; Kikuo Kishimoto; Wenhu Huang

    2009-01-01

    In this paper, the elastic wave propagation in a two-dimensional piezoelectric phononic crystal is studied by considering the mechanic-electric coupling. The gener-alized eigenvalue equation is obtained by the relation of the mechanic and electric fields as well as the Bloch-Floquet the-orem. The band structures of both the in-plane and anti-plane modes are calculated for a rectangular lattice by the plane-wave expansion method. The effects of the lattice constant ratio and the piezoelectricity with different filling fractions are analyzed. The results show that the largest gap width is not always obtained for a square lattice. In some situations, a rectangular lattice may generate larger gaps. The band gap characteristics are influenced obviously by the piezoelectric-ity with the larger lattice constant ratios and the filling frac-tions.

  14. Two-Dimensional Materials for Sensing: Graphene and Beyond

    Directory of Open Access Journals (Sweden)

    Seba Sara Varghese

    2015-09-01

    Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.

  15. Berezinskii-Kosterlitz-Thouless phase transitions in two-dimensional non-Abelian spin models.

    Science.gov (United States)

    Borisenko, Oleg; Chelnokov, Volodymyr; Cuteri, Francesca; Papa, Alessandro

    2016-07-01

    It is argued that two-dimensional U(N) spin models for any N undergo a Berezinskii-Kosterlitz-Thouless (BKT)-like phase transition, similarly to the famous XY model. This conclusion follows from the Berezinskii-like calculation of the two-point correlation function in U(N) models, approximate renormalization group analysis, and numerical investigations of the U(2) model. It is shown, via Monte Carlo simulations, that the universality class of the U(2) model coincides with that of the XY model. Moreover, preliminary numerical results point out that two-dimensional SU(N) spin models with the fundamental and adjoint terms and N>4 exhibit two phase transitions of BKT type, similarly to Z(N) vector models.

  16. Growth and electronic properties of two-dimensional systems on (110) oriented GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F.

    2005-07-01

    As the only non-polar plane the (110) surface has a unique role in GaAs. Together with Silicon as a dopant it is an important substrate orientation for the growth of n-type or p-type heterostructures. As a consequence, this thesis will concentrate on growth and research on that surface. In the course of this work we were able to realize two-dimensional electron systems with the highest mobilities reported so far on this orientation. Therefore, we review the necessary growth conditions and the accompanying molecular process. The two-dimensional electron systems allowed the study of a new, intriguing transport anisotropy not explained by current theory. Moreover, we were the first growing a two-dimensional hole gas on (110) GaAs with Si as dopant. For this purpose we invented a new growth modulation technique necessary to retrieve high mobility systems. In addition, we discovered and studied the metal-insulator transition in thin bulk p-type layers on (110) GaAs. Besides we investigated the activation process related to the conduction in the valence band and a parallelly conducting hopping band. The new two-dimensional hole gases revealed interesting physics. We studied the zero B-field spin splitting in these systems and compared it with the known theory. Furthermore, we investigated the anisotropy of the mobility. As opposed to the expectations we observed a strong persistent photoconductivity in our samples. Landau levels for two dimensional hole systems are non-linear and can show anticrossings. For the first time we were able to resolve anticrossings in a transport experiment and study the corresponding activation process. Finally, we compared these striking results with theoretical calculations. (orig.)

  17. Statistics of the inverse-cascade regime in two-dimensional magnetohydrodynamic turbulence.

    Science.gov (United States)

    Banerjee, Debarghya; Pandit, Rahul

    2014-07-01

    We present a detailed direct numerical simulation of statistically steady, homogeneous, isotropic, two-dimensional magnetohydrodynamic turbulence. Our study concentrates on the inverse cascade of the magnetic vector potential. We examine the dependence of the statistical properties of such turbulence on dissipation and friction coefficients. We extend earlier work significantly by calculating fluid and magnetic spectra, probability distribution functions (PDFs) of the velocity, magnetic, vorticity, current, stream-function, and magnetic-vector-potential fields, and their increments. We quantify the deviations of these PDFs from Gaussian ones by computing their flatnesses and hyperflatnesses. We also present PDFs of the Okubo-Weiss parameter, which distinguishes between vortical and extensional flow regions, and its magnetic analog. We show that the hyperflatnesses of PDFs of the increments of the stream function and the magnetic vector potential exhibit significant scale dependence and we examine the implication of this for the multiscaling of structure functions. We compare our results with those of earlier studies.

  18. Two dimensional soft material: new faces of graphene oxide.

    Science.gov (United States)

    Kim, Jaemyung; Cote, Laura J; Huang, Jiaxing

    2012-08-21

    Graphite oxide sheets, now called graphene oxide (GO), can be made from chemical exfoliation of graphite by reactions that have been known for 150 years. Because GO is a promising solution-processable precursor for the bulk production of graphene, interest in this old material has resurged. The reactions to produce GO add oxygenated functional groups to the graphene sheets on their basal plane and edges, and this derivatization breaks the π-conjugated network, resulting in electrically insulating but highly water-dispersible sheets. Apart from making graphene, GO itself has many intriguing properties. Like graphene, GO is a two-dimensional (2D) sheet with feature sizes at two abruptly different length scales. The apparent thickness of the functionalized carbon sheet is approximately 1 nm, but the lateral dimensions can range from a few nanometers to hundreds of micrometers. Therefore, researchers can think of GO as either a single molecule or a particle, depending on which length scale is of greater interest. At the same time, GO can be viewed as an unconventional soft material, such as a 2D polymer, highly anisotropic colloid, membrane, liquid crystal, or amphiphile. In this Account, we highlight the soft material characteristics of GO. GO consists of nanographitic patches surrounded by largely disordered, oxygenated domains. Such structural characteristics effectively make GO a 2D amphiphile with a hydrophilic periphery and largely hydrophobic center. This insight has led to better understanding of the solution properties of GO for making thin films and new applications of GO as a surfactant. Changes in pH and sheet size can tune the amphiphilicity of GO, leading to intriguing interfacial activities. In addition, new all-carbon composites made of only graphitic nanostructures using GO as a dispersing agent have potential applications in photovoltaics and energy storage. On the other hand, GO can function as a 2D random diblock copolymer, one block graphitic and

  19. Error compensation of IQ modulator using two-dimensional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, Takashi, E-mail: ohshima@spring8.or.jp [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Maesaka, Hirokazu [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Matsubara, Shinichi [Japan Synchrotron Radiation Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Otake, Yuji [RIKEN, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2016-06-01

    It is important to precisely set and keep the phase and amplitude of an rf signal in the accelerating cavity of modern accelerators, such as an X-ray Free Electron Laser (XFEL) linac. In these accelerators an acceleration rf signal is generated or detected by an In-phase and Quadrature (IQ) modulator, or a demodulator. If there are any deviations of the phase and the amplitude from the ideal values, crosstalk between the phase and the amplitude of the output signal of the IQ modulator or the demodulator arises. This causes instability of the feedback controls that simultaneously stabilize both the rf phase and the amplitude. To compensate for such deviations, we developed a novel compensation method using a two-dimensional Discrete Fourier Transform (DFT). Because the observed deviations of the phase and amplitude of an IQ modulator involve sinusoidal and polynomial behaviors on the phase angle and the amplitude of the rf vector, respectively, the DFT calculation with these basis functions makes a good approximation with a small number of compensation coefficients. Also, we can suppress high-frequency noise components arising when we measure the deviation data. These characteristics have advantages compared to a Look Up Table (LUT) compensation method. The LUT method usually demands many compensation elements, such as about 300, that are not easy to treat. We applied the DFT compensation method to the output rf signal of a C-band IQ modulator at SACLA, which is an XFEL facility in Japan. The amplitude deviation of the IQ modulator after the DFT compensation was reduced from 15.0% at the peak to less than 0.2% at the peak for an amplitude control range of from 0.1 V to 0.9 V (1.0 V full scale) and for a phase control range from 0 degree to 360 degrees. The number of compensation coefficients is 60, which is smaller than that of the LUT method, and is easy to treat and maintain.

  20. A two-dimensional Segmented Boundary Algorithm for complex moving solid boundaries in Smoothed Particle Hydrodynamics

    Science.gov (United States)

    Khorasanizade, Sh.; Sousa, J. M. M.

    2016-03-01

    A Segmented Boundary Algorithm (SBA) is proposed to deal with complex boundaries and moving bodies in Smoothed Particle Hydrodynamics (SPH). Boundaries are formed in this algorithm with chains of lines obtained from the decomposition of two-dimensional objects, based on simple line geometry. Various two-dimensional, viscous fluid flow cases have been studied here using a truly incompressible SPH method with the aim of assessing the capabilities of the SBA. Firstly, the flow over a stationary circular cylinder in a plane channel was analyzed at steady and unsteady regimes, for a single value of blockage ratio. Subsequently, the flow produced by a moving circular cylinder with a prescribed acceleration inside a plane channel was investigated as well. Next, the simulation of the flow generated by the impulsive start of a flat plate, again inside a plane channel, has been carried out. This was followed by the study of confined sedimentation of an elliptic body subjected to gravity, for various density ratios. The set of test cases was completed with the simulation of periodic flow around a sunflower-shaped object. Extensive comparisons of the results obtained here with published data have demonstrated the accuracy and effectiveness of the proposed algorithms, namely in cases involving complex geometries and moving bodies.

  1. Standardization of the two-dimensional transcoelomic echocardiographic examination in the central bearded dragon (Pogona vitticeps).

    Science.gov (United States)

    Silverman, S; Sanchez-Migallon Guzman, D; Stern, J; Gustavsen, K A; Griffiths, L G

    2016-06-01

    To objectively and subjectively describe the normal spectrum of two-dimensional echocardiographic findings in the central bearded dragon (Pogona vitticeps). Sixteen central bearded dragons. Central bearded dragons were prospectively evaluated under manual restraint in right and left lateral recumbency to identify imaging planes for reproducible measurements of cardiac chambers, subjective two-dimensional analysis and color Doppler assessment. Echocardiography can be performed through windows in the left and right axillae. The window in the left axilla allows for a subjective and objective assessment of cardiac structure and function. The right axillary window allows for evaluation of pulmonary artery flow. Both views provide data for the presence of pericardial effusion or valvular insufficiency. With optimized imaging planes, cardiac chambers and fractional area change along with fractional shortening in the longitudinal and transverse planes can be calculated. Body weight and cardiac chamber dimensions of males were significantly larger than females. Ventricular fractional area change was the most consistent functional assessment. The majority of animals were found to have no evidence of valvular insufficiency, while approximately half had evidence of pericardial fluid. Pulmonary artery flow was assessed in all patients. Left and right aortic velocities cannot be reliably obtained. This study is the first to generate reference values for cardiac structure and function in clinically healthy central bearded dragons. Valvular insufficiency is not a normal finding in central bearded dragons, while mild pericardial effusion may be. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. High-temperature superconductivity in space-charge regions of lanthanum cuprate induced by two-dimensional doping

    Science.gov (United States)

    Baiutti, F.; Logvenov, G.; Gregori, G.; Cristiani, G.; Wang, Y.; Sigle, W.; van Aken, P. A.; Maier, J.

    2015-10-01

    The exploitation of interface effects turned out to be a powerful tool for generating exciting material properties. Such properties include magnetism, electronic and ionic transport and even superconductivity. Here, instead of using conventional homogeneous doping to enhance the hole concentration in lanthanum cuprate and achieve superconductivity, we replace single LaO planes with SrO dopant planes using atomic-layer-by-layer molecular beam epitaxy (two-dimensional doping). Electron spectroscopy and microscopy, conductivity measurements and zinc tomography reveal such negatively charged interfaces to induce layer-dependent superconductivity (Tc up to 35 K) in the space-charge zone at the side of the planes facing the substrate, where the strontium (Sr) profile is abrupt. Owing to the growth conditions, the other side exhibits instead a Sr redistribution resulting in superconductivity due to conventional doping. The present study represents a successful example of two-dimensional doping of superconducting oxide systems and demonstrates its power in this field.

  3. Two-dimensional dynamics of a free molecular chain with a secondary structure

    DEFF Research Database (Denmark)

    Zolotaryuk, Alexander; Christiansen, Peter Leth; Savin, A.V.

    1996-01-01

    A simple two-dimensional (2D) model of an isolated (free) molecular chain with primary and secondary structures has been suggested and investigated both analytically and numerically. This model can be considered as the simplest generalization of the well-known Fermi-Pasta-Ulam model...... of an anharmonic chain in order to include transverse degrees of freedom of the chain molecules. Both the structures are provided by the first- and second-neighbor intermolecular bonds, respectively, resulting in a regular zig-zag (''20 helix'') chain on a plane. The set of two coupled nonlinear field equations...

  4. Two-dimensional microwave band-gap structures of different dielectric materials

    Indian Academy of Sciences (India)

    E D V Nagesh; G Santosh Babu; V Subramanian; V Sivasubramanian; V R K Murthy

    2005-12-01

    We report the use of low dielectric constant materials to form two-dimensional microwave band-gap structures for achieving high gap-to-midgap ratio. The variable parameters chosen are the lattice spacing and the geometric structure. The selected geometries are square and triangular and the materials chosen are PTFE ( = 2.1), PVC ( = 2.38) and glass ( = 5.5). Using the plane-wave expansion method, proper lattice spacing is selected for each structure and material. The observed experimental results are analyzed with the help of the theoretical prediction.

  5. Complex Path Integrals and Saddles in Two-Dimensional Gauge Theory.

    Science.gov (United States)

    Buividovich, P V; Dunne, Gerald V; Valgushev, S N

    2016-04-01

    We study numerically the saddle point structure of two-dimensional lattice gauge theory, represented by the Gross-Witten-Wadia unitary matrix model. The saddle points are, in general, complex valued, even though the original integration variables and action are real. We confirm the trans-series and instanton gas structure in the weak-coupling phase, and we identify a new complex-saddle interpretation of nonperturbative effects in the strong-coupling phase. In both phases, eigenvalue tunneling refers to eigenvalues moving off the real interval, into the complex plane, and the weak-to-strong coupling phase transition is driven by saddle condensation.

  6. Bessel-Modal Method for Finite-Height Two-Dimensional Photonic Crystal

    Institute of Scientific and Technical Information of China (English)

    SHI Jun-Feng; HUANG Sheng-Ye; WANG Dong-Sheng

    2005-01-01

    @@ By applying the dyadic Green function, the dispersion relation of two-dimensional photonic crystal can be ex pressed as the cylindrical wave expansions of eigenmodes. With the aid of Green's theorem, the plane-wavecoefficients of eigenmodes are reconstructed and employed to formulate the scattering matrix of finite-height twodimensional photonic crystal. These operations make the convergence rate very rapid, and reduce the dimension of the scattering matrix. As a demonstration, we present the transmission and electromagnetic field distributions for an InGaAsIn photonic crystal, and investigate their convergence.

  7. Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer

    Science.gov (United States)

    Siegel, R.

    1974-01-01

    Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential. The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates, the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.

  8. Competitive irreversible random one-, two-, three-, . . . point adsorption on two-dimensional lattices

    Science.gov (United States)

    Evans, J. W.; Nord, R. S.

    1985-02-01

    An analytic treatment of competitive, irreversible (immobile) random one-, two-, three-, . . . point adsorption (or monomer, dimer, trimer, . . . filling) on infinite, uniform two-dimensional lattices is provided by applying previously developed truncation schemes to the hierarchial form of the appropriate master equations. The behavior of these processes for two competing species is displayed by plotting families of ``filling trajectories'' in the partial-coverage plane for various ratios of adsorption rates. The time or coverage dependence of various subconfiguration probabilities can also be analyzed. For processes where no one-point (monomer) adsorption occurs, the lattice cannot fill completely; accurate estimates of the total (and partial) saturation coverages can be obtained.

  9. High applicability of two-dimensional phosphorous in Kagome lattice predicted from first-principles calculations

    OpenAIRE

    Peng-Jen Chen; Horng-Tay Jeng

    2016-01-01

    A new semiconducting phase of two-dimensional phosphorous in the Kagome lattice is proposed from first-principles calculations. The band gaps of the monolayer (ML) and bulk Kagome phosphorous (Kagome-P) are 2.00 and 1.11 eV, respectively. The magnitude of the band gap is tunable by applying the in-plane strain and/or changing the number of stacking layers. High optical absorption coefficients at the visible light region are predicted for multilayer Kagome-P, indicating potential applications ...

  10. Modelling and design of complete photonic band gaps in two-dimensional photonic crystals

    Indian Academy of Sciences (India)

    Yogita Kalra; R K Sinha

    2008-01-01

    In this paper, we investigate the existence and variation of complete photonic band gap size with the introduction of asymmetry in the constituent dielectric rods with honeycomb lattices in two-dimensional photonic crystals (PhC) using the plane-wave expansion (PWE) method. Two examples, one consisting of elliptical rods and the other comprising of rectangular rods in honeycomb lattices are considered with a view to estimate the design parameters for maximizing the complete photonic band gap. Further, it has been shown that complete photonic band gap size changes with the variation in the orientation angle of the constituent dielectric rods.

  11. Spin transport of the frustrated quasi-two-dimensional XY-like antiferromagnet

    Science.gov (United States)

    Lima, L. S.

    2017-01-01

    We use the Self Consistent Harmonic Approximation together with the Kubo formalism of the Linear Response Theory to study the spin transport in the two-dimensional frustrated Heisenberg antiferromagnet in a square lattice with easy-plane ion single anisotropy. The regular part of the spin conductivity σreg(ω) is determined for several values of the critical ion single parameter Dc, that separates the low D region from the large D quantum paramagnetic phase. We have obtained an abrupt change in the spin conductivity in the discontinuity points of the graphic Dc vs. η, where the system presents a quantum phase transition.

  12. On the algebraic structure of rotationally invariant two-dimensional Hamiltonians on the noncommutative phase space

    Science.gov (United States)

    Falomir, H.; Pisani, P. A. G.; Vega, F.; Cárcamo, D.; Méndez, F.; Loewe, M.

    2016-02-01

    We study two-dimensional Hamiltonians in phase space with noncommutativity both in coordinates and momenta. We consider the generator of rotations on the noncommutative plane and the Lie algebra generated by Hermitian rotationally invariant quadratic forms of noncommutative dynamical variables. We show that two quantum phases are possible, characterized by the Lie algebras {sl}(2,{{R}}) or su(2) according to the relation between the noncommutativity parameters, with the rotation generator related with the Casimir operator. From this algebraic perspective, we analyze the spectrum of some simple models with nonrelativistic rotationally invariant Hamiltonians in this noncommutative phase space, such as the isotropic harmonic oscillator, the Landau problem and the cylindrical well potential.

  13. On the algebraic structure of rotationally invariant two-dimensional Hamiltonians on the noncommutative phase space

    CERN Document Server

    Falomir, H; Vega, F; Cárcamo, D; Méndez, F; Loewe, M

    2015-01-01

    We study two-dimensional Hamiltonians in phase space with noncommutativity both in coordinates and momenta. We consider the generator of rotations on the noncommutative plane and the Lie algebra generated by Hermitian rotationally invariant quadratic forms of noncommutative dynamical variables. We show that two quantum phases are possible, characterized by the Lie algebras $sl(2,\\mathbb{R})$ or $su(2)$ according to the relation between the noncommutativity parameters. From this perspective, we analyze the spectrum of some simple models with nonrelativistic rotationally invariant Hamiltonians in this noncommutative phase space, as the isotropic harmonic oscillator, the Landau problem and the cylindrical well potential.

  14. Cyclotron resonance in two-dimensional electron system with self-organized antidots

    CERN Document Server

    Suchalkin, S D; Zundel, M; Nachtwei, G; Klitzing, K V; Eberl, K

    2001-01-01

    The data on the experimental study on the cyclotron resonance in the two-dimensional electron system with the random scattering potential, conditioned by the massif of the AlInAs self-organized quantum islands, formed in the AlGaAs/GaAs heterotransition plane, are presented. The sharp narrowing of the cyclotron resonance with increase in the magnetic field, explained by the charge scattering peculiarities in the given potential is established. The obtained results suggest the strongly correlated electron state in the strong magnetic fields by the carriers concentrations lesser than the antidots concentrations

  15. Quasiparticle GW calculations for solids, molecules, and two-dimensional materials

    DEFF Research Database (Denmark)

    Hüser, Falco; Olsen, Thomas; Thygesen, Kristian Sommer

    2013-01-01

    We present a plane-wave implementation of the GW approximation within the projector augmented wave method code GPAW. The computed band gaps of ten bulk semiconductors and insulators deviate on average by 0.2eV (~5%) from the experimental values, the only exception being ZnO where the calculated...... band gap is around 1eV too low. Similar relative deviations are found for the ionization potentials of a test set of 32 small molecules. The importance of substrate screening for a correct description of quasiparticle energies and Fermi velocities in supported two-dimensional (2D) materials...

  16. Modeling of pressure sensors based on two-dimensional photonic crystals

    Institute of Scientific and Technical Information of China (English)

    Xuehui XIONG; Ping LU; Deming LIU

    2009-01-01

    A pressure sensor based on the two-dimensional photonic crystal (2D PC) has been proposed. Under the condition of different pressure, the photonic band gap of the sensor has been studied by means of the plane wave expansion method (PWM). The results show that there is a good linear relation between the cutoff wavelength and the pressure. Apart from being easily implemented, the presented 2D PC pressure sensor holds many characteristics such as high-pressure sensitivity and convenience in achieving demanded pressure range.

  17. Left-Handed Properties in Two-Dimensional Photonic Crystals Formed by Holographic Lithography

    Institute of Scientific and Technical Information of China (English)

    SHEN Xiao-Xia; YANG Xiu-Lun; CAI Lv-Zhong; WANG Yu-Rong; DONG Guo-Yan; MENG Xiang-Feng; XU Xian-Feng

    2008-01-01

    We give an analysis of the frequency distribution trends in the four lowest bands of two-dimensional square lattices formed by holographic lithography (HL) and in the lattices of the same kind but with regular dielectric columns with increasing filling ratios, and then present a comparative study on the left-handed properties in these two kinds of structures using plane wave expansion method and finite-difference time-domain (FDTD) simulations.The results show that the left-handed properties are more likely to exist in structures with large high-epsilon filling ratios or in a connected lattice.

  18. Central charges and boundary fields for two dimensional dilatonic black holes

    CERN Document Server

    Pinamonti, N

    2003-01-01

    In this paper we first show that within the Hamiltonian description of general relativity, the central charge of a near horizon asymptotic symmetry group is zero, and therefore that the entropy of the system cannot be estimated using Cardy's formula. This is done by mapping a static black hole to a two dimensional plane. We explain how such a charge can only appear to a static observer who chooses to stay permanently outside the black hole. Then an alternative argument is given for the presence of a universal central charge. Finally we suggest an effective quantum theory on the horizon that is compatible with the thermodynamics behaviour of the black hole.

  19. Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

    KAUST Repository

    Ghosh, S.

    2017-01-24

    We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

  20. Batalin-Vilkovisky algebras and two-dimensional topological field theories

    CERN Document Server

    Getzler, E

    1994-01-01

    Batalin-Vilkovisky algebras are a new type of algebraic structure on graded vector spaces, which first arose in the work of Batalin and Vilkovisky on gauge fixing in quantum field theory. In this article, we show that there is a natural structure of a Batalin-Vilkovisky algebra on the cohomology of a topological field theory in two dimensions. Lian and Zuckerman have constructed this Batalin-Vilkovisky structure, in the setting of topological chiral field theories, and shown that the structure is non-trivial in two-dimensional string theory. Our approach is to use algebraic topology, whereas their proofs have a more algebraic character.

  1. Effects of external fields on two-dimensional Klein-Gordon particle under pseudoharmonic oscillator interaction

    CERN Document Server

    Ikhdair, Sameer M

    2012-01-01

    We study the effects of the perpendicular magnetic and Aharonov-Bohm (AB) flux fields on the energy levels of a two-dimensional (2D) Klein-Gordon (KG) particle subjects to equal scalar and vector pseudo-harmonic oscillator (PHO). We calculate the exact energy eigenvalues and normalized wave functions in terms of chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by means of the Nikiforov-Uvarov (NU) method. The non-relativistic limit, PHO and harmonic oscillator solutions in the existence and absence of external fields are also obtained.

  2. On the Classical Solutions of Two Dimensional Inviscid Rotating Shallow Water System

    CERN Document Server

    Cheng, Bin

    2009-01-01

    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.

  3. Tracking dynamics of two-dimensional continuous attractor neural networks

    Science.gov (United States)

    Fung, C. C. Alan; Wong, K. Y. Michael; Wu, Si

    2009-12-01

    We introduce an analytically solvable model of two-dimensional continuous attractor neural networks (CANNs). The synaptic input and the neuronal response form Gaussian bumps in the absence of external stimuli, and enable the network to track external stimuli by its translational displacement in the two-dimensional space. Basis functions of the two-dimensional quantum harmonic oscillator in polar coordinates are introduced to describe the distortion modes of the Gaussian bump. The perturbative method is applied to analyze its dynamics. Testing the method by considering the network behavior when the external stimulus abruptly changes its position, we obtain results of the reaction time and the amplitudes of various distortion modes, with excellent agreement with simulation results.

  4. Hamiltonian formalism of two-dimensional Vlasov kinetic equation.

    Science.gov (United States)

    Pavlov, Maxim V

    2014-12-08

    In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.

  5. Control Operator for the Two-Dimensional Energized Wave Equation

    Directory of Open Access Journals (Sweden)

    Sunday Augustus REJU

    2006-07-01

    Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.

  6. Two-Dimensional Electronic Spectroscopy Using Incoherent Light: Theoretical Analysis

    CERN Document Server

    Turner, Daniel B; Sutor, Erika J; Hendrickson, Rebecca A; Gealy, M W; Ulness, Darin J

    2012-01-01

    Electronic energy transfer in photosynthesis occurs over a range of time scales and under a variety of intermolecular coupling conditions. Recent work has shown that electronic coupling between chromophores can lead to coherent oscillations in two-dimensional electronic spectroscopy measurements of pigment-protein complexes measured with femtosecond laser pulses. A persistent issue in the field is to reconcile the results of measurements performed using femtosecond laser pulses with physiological illumination conditions. Noisy-light spectroscopy can begin to address this question. In this work we present the theoretical analysis of incoherent two-dimensional electronic spectroscopy, I(4) 2D ES. Simulations reveal diagonal peaks, cross peaks, and coherent oscillations similar to those observed in femtosecond two-dimensional electronic spectroscopy experiments. The results also expose fundamental differences between the femtosecond-pulse and noisy-light techniques; the differences lead to new challenges and opp...

  7. Spectral Radiative Properties of Two-Dimensional Rough Surfaces

    Science.gov (United States)

    Xuan, Yimin; Han, Yuge; Zhou, Yue

    2012-12-01

    Spectral radiative properties of two-dimensional rough surfaces are important for both academic research and practical applications. Besides material properties, surface structures have impact on the spectral radiative properties of rough surfaces. Based on the finite difference time domain algorithm, this paper studies the spectral energy propagation process on a two-dimensional rough surface and analyzes the effect of different factors such as the surface structure, angle, and polarization state of the incident wave on the spectral radiative properties of the two-dimensional rough surface. To quantitatively investigate the spatial distribution of energy reflected from the rough surface, the concept of the bidirectional reflectance distribution function is introduced. Correlation analysis between the reflectance and different impact factors is conducted to evaluate the influence degree. Comparison between the theoretical and experimental data is given to elucidate the accuracy of the computational code. This study is beneficial to optimizing the surface structures of optoelectronic devices such as solar cells.

  8. Two dimensional convolute integers for machine vision and image recognition

    Science.gov (United States)

    Edwards, Thomas R.

    1988-01-01

    Machine vision and image recognition require sophisticated image processing prior to the application of Artificial Intelligence. Two Dimensional Convolute Integer Technology is an innovative mathematical approach for addressing machine vision and image recognition. This new technology generates a family of digital operators for addressing optical images and related two dimensional data sets. The operators are regression generated, integer valued, zero phase shifting, convoluting, frequency sensitive, two dimensional low pass, high pass and band pass filters that are mathematically equivalent to surface fitted partial derivatives. These operators are applied non-recursively either as classical convolutions (replacement point values), interstitial point generators (bandwidth broadening or resolution enhancement), or as missing value calculators (compensation for dead array element values). These operators show frequency sensitive feature selection scale invariant properties. Such tasks as boundary/edge enhancement and noise or small size pixel disturbance removal can readily be accomplished. For feature selection tight band pass operators are essential. Results from test cases are given.

  9. Optical modulators with two-dimensional layered materials

    CERN Document Server

    Sun, Zhipei; Wang, Feng

    2016-01-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that two-dimensional layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this review, we cover the state-of-the-art of optical modulators based on two-dimensional layered materials including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as two-dimensional heterostructures, plasmonic structures, and silicon/fibre integrated structures. We also take a look at future perspectives and discuss the potential of yet relatively unexplored mechanisms such as magneto-optic and acousto-optic modulation.

  10. Unstable manifold computations for the two-dimensional plane Poiseuille flow

    Energy Technology Data Exchange (ETDEWEB)

    Casas, Pablo S. [Universidad Politecnica de Cataluna, Departamento de Matematica Aplicada I, Barcelona (Spain); Jorba, Angel [Universidad de Barcelona, Departamento de Matematica Aplicada y Analisis, Barcelona (Spain)

    2004-11-01

    We follow the unstable manifold of periodic and quasi-periodic solutions in time for the Poiseuille problem, using two formulations: holding a constant flux or mean pressure gradient. By means of a numerical integrator of the Navier-Stokes equations, we let the fluid evolve from an initially perturbed unstable solution until the fluid reaches an attracting state. Thus, we detect several connections among different configurations of the flow such as laminar, periodic, quasi-periodic with two or three basic frequencies, and more complex sets that we have not been able to classify. These connections make possible the location of new families of solutions, usually hard to find by means of numerical continuation of curves, and show the richness of the dynamics of the Poiseuille flow. (orig.)

  11. Full two-dimensional rotor plane inflow measurements by a spinner-integrated wind lidar

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Pedersen, Anders Tegtmeier; Angelou, Nikolas

    2013-01-01

    Introduction Wind turbine load reduction and power performance optimization via advanced control strategies is an active area in the wind energy community. In particular, feed-forward control using upwind inflow measurements by lidar (light detection and ranging) remote sensing instruments has at...

  12. Full two-dimensional rotor plane inflow measurements by a spinner-integrated wind lidar

    OpenAIRE

    Sjöholm, Mikael; Pedersen, Anders Tegtmeier; Angelou, Nikolas; Foroughi Abari, Farzad; Mikkelsen, Torben; Harris, Michael; Slinger, Chris; Kapp, Stefan

    2013-01-01

    IntroductionWind turbine load reduction and power performance optimization via advanced control strategies is an active area in the wind energy community. In particular, feed-forward control using upwind inflow measurements by lidar (light detection and ranging) remote sensing instruments has attracted an increasing interest during the last couple of years. So far, the reported inflow measurements have been along a few measurement directions or at most on a circle in front of the turbine, whi...

  13. Two-dimensional superconductors with atomic-scale thickness

    Science.gov (United States)

    Uchihashi, Takashi

    2017-01-01

    Recent progress in two-dimensional superconductors with atomic-scale thickness is reviewed mainly from the experimental point of view. The superconducting systems treated here involve a variety of materials and forms: elemental metal ultrathin films and atomic layers on semiconductor surfaces; interfaces and superlattices of heterostructures made of cuprates, perovskite oxides, and rare-earth metal heavy-fermion compounds; interfaces of electric-double-layer transistors; graphene and atomic sheets of transition metal dichalcogenide; iron selenide and organic conductors on oxide and metal surfaces, respectively. Unique phenomena arising from the ultimate two dimensionality of the system and the physics behind them are discussed.

  14. TreePM Method for Two-Dimensional Cosmological Simulations

    Indian Academy of Sciences (India)

    Suryadeep Ray

    2004-09-01

    We describe the two-dimensional TreePM method in this paper. The 2d TreePM code is an accurate and efficient technique to carry out large two-dimensional N-body simulations in cosmology. This hybrid code combines the 2d Barnes and Hut Tree method and the 2d Particle–Mesh method. We describe the splitting of force between the PM and the Tree parts. We also estimate error in force for a realistic configuration. Finally, we discuss some tests of the code.

  15. Critical Behaviour of a Two-Dimensional Random Antiferromagnet

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.

    1976-01-01

    A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphou...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....

  16. Nonlinear excitations in two-dimensional molecular structures with impurities

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth

    1995-01-01

    We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence of the imp......We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....

  17. Vortices in the Two-Dimensional Simple Exclusion Process

    Science.gov (United States)

    Bodineau, T.; Derrida, B.; Lebowitz, Joel L.

    2008-06-01

    We show that the fluctuations of the partial current in two dimensional diffusive systems are dominated by vortices leading to a different scaling from the one predicted by the hydrodynamic large deviation theory. This is supported by exact computations of the variance of partial current fluctuations for the symmetric simple exclusion process on general graphs. On a two-dimensional torus, our exact expressions are compared to the results of numerical simulations. They confirm the logarithmic dependence on the system size of the fluctuations of the partial flux. The impact of the vortices on the validity of the fluctuation relation for partial currents is also discussed in an Appendix.

  18. Two-dimensional hazard estimation for longevity analysis

    DEFF Research Database (Denmark)

    Fledelius, Peter; Guillen, M.; Nielsen, J.P.

    2004-01-01

    the two-dimensional mortality surface. Furthermore we look at aggregated synthetic population metrics as 'population life expectancy' and 'population survival probability'. For Danish women these metrics indicate decreasing mortality with respect to chronological time. The metrics can not directly be used......We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface...... for analysis of economic implications arising from mortality changes....

  19. Dynamics of vortex interactions in two-dimensional flows

    DEFF Research Database (Denmark)

    Juul Rasmussen, J.; Nielsen, A.H.; Naulin, V.

    2002-01-01

    a critical value, a(c). Using the Weiss-field, a(c) is estimated for vortex patches. Introducing an effective radius for vortices with distributed vorticity, we find that 3.3 a(c) ...The dynamics and interaction of like-signed vortex structures in two dimensional flows are investigated by means of direct numerical solutions of the two-dimensional Navier-Stokes equations. Two vortices with distributed vorticity merge when their distance relative to their radius, d/R-0l. is below...

  20. Two-dimensional assignment with merged measurements using Langrangrian relaxation

    Science.gov (United States)

    Briers, Mark; Maskell, Simon; Philpott, Mark

    2004-01-01

    Closely spaced targets can result in merged measurements, which complicate data association. Such merged measurements violate any assumption that each measurement relates to a single target. As a result, it is not possible to use the auction algorithm in its simplest form (or other two-dimensional assignment algorithms) to solve the two-dimensional target-to-measurement assignment problem. We propose an approach that uses the auction algorithm together with Lagrangian relaxation to incorporate the additional constraints resulting from the presence of merged measurements. We conclude with some simulated results displaying the concepts introduced, and discuss the application of this research within a particle filter context.

  1. Two-dimensional lattice Boltzmann model for magnetohydrodynamics.

    Science.gov (United States)

    Schaffenberger, Werner; Hanslmeier, Arnold

    2002-10-01

    We present a lattice Boltzmann model for the simulation of two-dimensional magnetohydro dynamic (MHD) flows. The model is an extension of a hydrodynamic lattice Boltzman model with 9 velocities on a square lattice resulting in a model with 17 velocities. Earlier lattice Boltzmann models for two-dimensional MHD used a bidirectional streaming rule. However, the use of such a bidirectional streaming rule is not necessary. In our model, the standard streaming rule is used, allowing smaller viscosities. To control the viscosity and the resistivity independently, a matrix collision operator is used. The model is then applied to the Hartmann flow, giving reasonable results.

  2. Quasinormal frequencies of asymptotically flat two-dimensional black holes

    CERN Document Server

    Lopez-Ortega, A

    2011-01-01

    We discuss whether the minimally coupled massless Klein-Gordon and Dirac fields have well defined quasinormal modes in single horizon, asymptotically flat two-dimensional black holes. To get the result we solve the equations of motion in the massless limit and we also calculate the effective potentials of Schrodinger type equations. Furthermore we calculate exactly the quasinormal frequencies of the Dirac field propagating in the two-dimensional uncharged Witten black hole. We compare our results on its quasinormal frequencies with other already published.

  3. Spin dynamics in a two-dimensional quantum gas

    DEFF Research Database (Denmark)

    Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank

    2014-01-01

    We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...

  4. Aspects of QCD current algebra on a null plane

    Science.gov (United States)

    Beane, S. R.; Hobbs, T. J.

    2016-09-01

    Consequences of QCD current algebra formulated on a light-like hyperplane are derived for the forward scattering of vector and axial-vector currents on an arbitrary hadronic target. It is shown that current algebra gives rise to a special class of sum rules that are direct consequences of the independent chiral symmetry that exists at every point on the two-dimensional transverse plane orthogonal to the lightlike direction. These sum rules are obtained by exploiting the closed, infinite-dimensional algebra satisfied by the transverse moments of null-plane axial-vector and vector charge distributions. In the special case of a nucleon target, this procedure leads to the Adler-Weisberger, Gerasimov-Drell-Hearn, Cabibbo-Radicati and Fubini-Furlan-Rossetti sum rules. Matching to the dispersion-theoretic language which is usually invoked in deriving these sum rules, the moment sum rules are shown to be equivalent to algebraic constraints on forward S-matrix elements in the Regge limit.

  5. On some classes of two-dimensional local models in discrete two-dimensional monatomic FPU lattice with cubic and quartic potential

    Institute of Scientific and Technical Information of China (English)

    Xu Quan; Tian Qiang

    2009-01-01

    This paper discusses the two-dimensional discrete monatomic Fermi-Pasta-Ulam lattice, by using the method of multiple-scale and the quasi-discreteness approach. By taking into account the interaction between the atoms in the lattice and their nearest neighbours, it obtains some classes of two-dimensional local models as follows: two-dimensional bright and dark discrete soliton trains, two-dimensional bright and dark line discrete breathers, and two-dimensional bright and dark discrete breather.

  6. Mapping two-dimensional polar active fluids to two-dimensional soap and one-dimensional sandblasting

    Science.gov (United States)

    Chen, Leiming; Lee, Chiu Fan; Toner, John

    2016-07-01

    Active fluids and growing interfaces are two well-studied but very different non-equilibrium systems. Each exhibits non-equilibrium behaviour distinct from that of their equilibrium counterparts. Here we demonstrate a surprising connection between these two: the ordered phase of incompressible polar active fluids in two spatial dimensions without momentum conservation, and growing one-dimensional interfaces (that is, the 1+1-dimensional Kardar-Parisi-Zhang equation), in fact belong to the same universality class. This universality class also includes two equilibrium systems: two-dimensional smectic liquid crystals, and a peculiar kind of constrained two-dimensional ferromagnet. We use these connections to show that two-dimensional incompressible flocks are robust against fluctuations, and exhibit universal long-ranged, anisotropic spatio-temporal correlations of those fluctuations. We also thereby determine the exact values of the anisotropy exponent ζ and the roughness exponents χx,y that characterize these correlations.

  7. Excitation, detection, and electrostatic manipulation of terahertz-frequency range plasmons in a two-dimensional electron system

    CERN Document Server

    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.

  8. Theoretical and numerical investigation of HF elastic wave propagation in two-dimensional periodic beam lattices

    Science.gov (United States)

    Tie, B.; Tian, B. Y.; Aubry, D.

    2013-12-01

    The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the Bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in which, both the in-plane (with respect to the lattice plane) and out-of-plane waves are considered. The dispersion relations are obtained by calculating the Bloch eigenfrequencies and eigenmodes. The frequency bandgaps are observed and the influence of the elastic and geometric properties of the primitive cell on the bandgaps is studied. By analyzing the phase and the group velocities of the Bloch wave modes, the anisotropic behaviors and the dispersive characteristics of the hexagonal beam lattice with respect to the wave propagation are highlighted in high frequency domains. One important result presented herein is the comparison between the first Bloch wave modes to the membrane and bending/transverse shear wave modes of the classical equivalent homogenized orthotropic plate model of the hexagonal beam lattice. It is shown that, in low frequency ranges, the homogenized plate model can correctly represent both the in-plane and out-of-plane dynamic behaviors of the beam lattice, its frequency validity domain can be precisely evaluated thanks to the Bloch modal analysis. As another important and original result, we have highlighted the existence of the retropropagating Bloch wave modes with a negative group velocity, and of the corresponding "retro-propagating" frequency bands.

  9. Two-Dimensional Multiferroics: Ferroelasticity, Ferroelectricity, Domain Wall, and Potential Mechano-Opto-Electronic Applications

    CERN Document Server

    Wang, Hua

    2016-01-01

    Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer Group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with strongly coupled giant in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their ...

  10. Experimentally determining the exchange parameters of quasi-two dimensional Heisenbert magnets

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, John [Los Alamos National Laboratory; Sengupta, P [Los Alamos National Laboratory; Mcdonald, R D [Los Alamos National Laboratory; Cox, S [Los Alamos National Laboratory; Harrison, N [Los Alamos National Laboratory; Goddard, P A [UNIV OF OXFORD; Lancaster, T [UNIV OF OXFORD; Blundell, S J [UNIV OF OXFORD; Pratt, F L [RUTHERFORD APPLETON LAB; Manson, J L [EASTERN WASHINGTON UNIV; Southerland, H I [EASTERN WASHINGTON UNIV; Schlueter, J A [ANL

    2008-01-01

    Though long-range magnetic order cannot occur at temperatures T > 0 in a perfect two-dimensional (2D) Heisenberg magnet, real quasi-2D materials will invariably possess nonzero inter-plane coupling J{sub {perpendicular}} driving the system to order at elevated temperatures. This process can be studied using quantum Monte Carlo calculations. However, it is difficult to test the results of these calculations experimentally since for highly anisotropic materials in which the in-plane coupling is comparable with attainable magnetic fields J{sub {perpendicular}} is necessarily very small and inaccessible directly. In addition, because of the large anisotropy, the Neel temperatures are low and difficult to determine from thermodynamic measurements. Here, we present an elegant method of assessing the calculations via two independent experimental probes: pulsed-field magnetization in fields of up to 85 T, and muon-spin rotation.

  11. Two-dimensional Fermi surfaces in Kondo insulator SmB₆.

    Science.gov (United States)

    Li, G; Xiang, Z; Yu, F; Asaba, T; Lawson, B; Cai, P; Tinsman, C; Berkley, A; Wolgast, S; Eo, Y S; Kim, Dae-Jeong; Kurdak, C; Allen, J W; Sun, K; Chen, X H; Wang, Y Y; Fisk, Z; Li, Lu

    2014-12-05

    In the Kondo insulator samarium hexaboride (SmB6), strong correlation and band hybridization lead to an insulating gap and a diverging resistance at low temperature. The resistance divergence ends at about 3 kelvin, a behavior that may arise from surface conductance. We used torque magnetometry to resolve the Fermi surface topology in this material. The observed oscillation patterns reveal two Fermi surfaces on the (100) surface plane and one Fermi surface on the (101) surface plane. The measured Fermi surface cross sections scale as the inverse cosine function of the magnetic field tilt angles, which demonstrates the two-dimensional nature of the conducting electronic states of SmB6. Copyright © 2014, American Association for the Advancement of Science.

  12. |m| Partial wave treatment for two-dimensional Coulomb-scattering and Regge pole

    Institute of Scientific and Technical Information of China (English)

    WANG; Jing; ZENG; Jinyan

    2004-01-01

    The symmetry and |m| partial-wave analysis for two-dimensional (2D) Coulomb-scattering is investigated. As a function of energy E, the |m| partial-wave scattering amplitude f|m|(θ) is analytically continuated to the negative E (complex k) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles of f|m|(θ) on the positive imaginary k axis as is expected. In addition, as a function of |m|, f|m|(θ) is analytically continuated to the complex |m| plane, the bound state energy eigenvalues are just located at the poles of f|m|(θ) on the positive real |m| axis.

  13. Optical devices combining an organic semiconductor crystal with a two-dimensional inorganic diffraction grating

    Energy Technology Data Exchange (ETDEWEB)

    Kitazawa, Takenori; Yamao, Takeshi, E-mail: yamao@kit.ac.jp; Hotta, Shu [Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2016-02-01

    We have fabricated optical devices using an organic semiconductor crystal as an emission layer in combination with a two-dimensional (2D) inorganic diffraction grating used as an optical cavity. We formed the inorganic diffraction grating by wet etching of aluminum-doped zinc oxide (AZO) under a 2D cyclic olefin copolymer (COC) diffraction grating used as a mask. The COC diffraction grating was fabricated by nanoimprint lithography. The AZO diffraction grating was composed of convex prominences arranged in a triangular lattice. The organic crystal placed on the AZO diffraction grating indicated narrowed peaks in its emission spectrum under ultraviolet light excitation. These are detected parallel to the crystal plane. The peaks were shifted by rotating the optical devices around the normal to the crystal plane, which reflected the rotational symmetries of the triangular lattice through 60°.

  14. Positioning with stationary emitters in a two-dimensional space-time

    CERN Document Server

    Coll, B; Morales, J A; Coll, Bartolom\\'{e}; Ferrando, Joan Josep; Morales, Juan Antonio

    2006-01-01

    The basic elements of the relativistic positioning systems in a two-dimensional space-time have been introduced in a previous work [Phys. Rev. D {\\bf 73}, 084017 (2006)] where geodesic positioning systems, constituted by two geodesic emitters, have been considered in a flat space-time. Here, we want to show in what precise senses positioning systems allow to make {\\em relativistic gravimetry}. For this purpose, we consider stationary positioning systems, constituted by two uniformly accelerated emitters separated by a constant distance, in two different situations: absence of gravitational field (Minkowski plane) and presence of a gravitational mass (Schwarzschild plane). The physical coordinate system constituted by the electromagnetic signals broadcasting the proper time of the emitters are the so called {\\em emission coordinates}, and we show that, in such emission coordinates, the trajectories of the emitters in both situations, absence and presence of a gravitational field, are identical. The interesting...

  15. Waiting Time Dynamics in Two-Dimensional Infrared Spectroscopy

    NARCIS (Netherlands)

    Jansen, Thomas L. C.; Knoester, Jasper

    We review recent work on the waiting time dynamics of coherent two-dimensional infrared (2DIR) spectroscopy. This dynamics can reveal chemical and physical processes that take place on the femto- and picosecond time scale, which is faster than the time scale that may be probed by, for example,

  16. The partition function of two-dimensional string theory

    Science.gov (United States)

    Dijkgraaf, Robbert; Moore, Gregory; Plesser, Ronen

    1993-04-01

    We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c = 1 system to KP flow nd W 1 + ∞ constraints. Moreover we derive a Kontsevich-Penner integral representation of this generating functional.

  17. The partition function of two-dimensional string theory

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, R. (School of Natural Sciences, Inst. for Advanced Study, Princeton, NJ (United States) Dept. of Mathematics, Univ. Amsterdam (Netherlands)); Moore, G.; Plesser, R. (Dept. of Physics, Yale Univ., New Haven, CT (United States))

    1993-04-12

    We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c=1 system to KP flow and W[sub 1+[infinity

  18. Two-Dimensional Electronic Spectroscopy of a Model Dimer System

    Directory of Open Access Journals (Sweden)

    Prokhorenko V.I.

    2013-03-01

    Full Text Available Two-dimensional spectra of a dimer were measured to determine the timescale for electronic decoherence at room temperature. Anti-correlated beats in the crosspeaks were observed only during the period corresponding to the measured homogeneous lifetime.

  19. Torque magnetometry studies of two-dimensional electron systems

    NARCIS (Netherlands)

    Schaapman, Maaike Ruth

    2004-01-01

    This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting

  20. Two-Dimensional Mesoscale-Ordered Conducting Polymers

    NARCIS (Netherlands)

    Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang

    2016-01-01

    Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assem

  1. Specification of a Two-Dimensional Test Case

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    This paper describes the geometry and other boundary conditions for a test case which can be used to test different two-dimensional CFD codes in the lEA Annex 20 work. The given supply opening is large compared with practical openings. Therefore, this geometry will reduce the need for a high number...... of grid points in the wall jet region....

  2. Operator splitting for two-dimensional incompressible fluid equations

    CERN Document Server

    Holden, Helge; Karper, Trygve K

    2011-01-01

    We analyze splitting algorithms for a class of two-dimensional fluid equations, which includes the incompressible Navier-Stokes equations and the surface quasi-geostrophic equation. Our main result is that the Godunov and Strang splitting methods converge with the expected rates provided the initial data are sufficiently regular.

  3. Chaotic dynamics for two-dimensional tent maps

    Science.gov (United States)

    Pumariño, Antonio; Ángel Rodríguez, José; Carles Tatjer, Joan; Vigil, Enrique

    2015-02-01

    For a two-dimensional extension of the classical one-dimensional family of tent maps, we prove the existence of an open set of parameters for which the respective transformation presents a strange attractor with two positive Lyapounov exponents. Moreover, periodic orbits are dense on this attractor and the attractor supports a unique ergodic invariant probability measure.

  4. Divorticity and dihelicity in two-dimensional hydrodynamics

    DEFF Research Database (Denmark)

    Shivamoggi, B.K.; van Heijst, G.J.F.; Juul Rasmussen, Jens

    2010-01-01

    A framework is developed based on the concepts of divorticity B (≡×ω, ω being the vorticity) and dihelicity g (≡vB) for discussing the theoretical structure underlying two-dimensional (2D) hydrodynamics. This formulation leads to the global and Lagrange invariants that could impose significant...

  5. Spin-orbit torques in two-dimensional Rashba ferromagnets

    NARCIS (Netherlands)

    Qaiumzadeh, A.; Duine, R. A.|info:eu-repo/dai/nl/304830127; Titov, M.

    2015-01-01

    Magnetization dynamics in single-domain ferromagnets can be triggered by a charge current if the spin-orbit coupling is sufficiently strong. We apply functional Keldysh theory to investigate spin-orbit torques in metallic two-dimensional Rashba ferromagnets in the presence of spin-dependent

  6. Numerical blowup in two-dimensional Boussinesq equations

    CERN Document Server

    Yin, Zhaohua

    2009-01-01

    In this paper, we perform a three-stage numerical relay to investigate the finite time singularity in the two-dimensional Boussinesq approximation equations. The initial asymmetric condition is the middle-stage output of a $2048^2$ run, the highest resolution in our study is $40960^2$, and some signals of numerical blowup are observed.

  7. Exact two-dimensional superconformal R symmetry and c extremization.

    Science.gov (United States)

    Benini, Francesco; Bobev, Nikolay

    2013-02-08

    We uncover a general principle dubbed c extremization, which determines the exact R symmetry of a two-dimensional unitary superconformal field theory with N=(0,2) supersymmetry. To illustrate its utility, we study superconformal theories obtained by twisted compactifications of four-dimensional N=4 super-Yang-Mills theory on Riemann surfaces and construct their gravity duals.

  8. Topology optimization of two-dimensional elastic wave barriers

    DEFF Research Database (Denmark)

    Van Hoorickx, C.; Sigmund, Ole; Schevenels, M.

    2016-01-01

    Topology optimization is a method that optimally distributes material in a given design domain. In this paper, topology optimization is used to design two-dimensional wave barriers embedded in an elastic halfspace. First, harmonic vibration sources are considered, and stiffened material is insert...

  9. Non perturbative methods in two dimensional quantum field theory

    CERN Document Server

    Abdalla, Elcio; Rothe, Klaus D

    1991-01-01

    This book is a survey of methods used in the study of two-dimensional models in quantum field theory as well as applications of these theories in physics. It covers the subject since the first model, studied in the fifties, up to modern developments in string theories, and includes exact solutions, non-perturbative methods of study, and nonlinear sigma models.

  10. Thermodynamics of Two-Dimensional Black-Holes

    OpenAIRE

    Nappi, Chiara R.; Pasquinucci, Andrea

    1992-01-01

    We explore the thermodynamics of a general class of two dimensional dilatonic black-holes. A simple prescription is given that allows us to compute the mass, entropy and thermodynamic potentials, with results in agreement with those obtained by other methods, when available.

  11. Influence of index contrast in two dimensional photonic crystal lasers

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Christiansen, Mads Brøkner;

    2010-01-01

    The influence of index contrast variations for obtaining single-mode operation and low threshold in dye doped polymer two dimensional photonic crystal (PhC) lasers is investigated. We consider lasers made from Pyrromethene 597 doped Ormocore imprinted with a rectangular lattice PhC having a cavit...

  12. Magnetic order in two-dimensional nanoparticle assemblies

    NARCIS (Netherlands)

    Georgescu, M

    2008-01-01

    This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the

  13. Dynamical phase transitions in the two-dimensional ANNNI model

    Energy Technology Data Exchange (ETDEWEB)

    Barber, M.N.; Derrida, B.

    1988-06-01

    We study the phase diagram of the two-dimensional anisotropic next-nearest neighbor Ising (ANNNI) model by comparing the time evolution of two distinct spin configurations submitted to the same thermal noise. We clearly se several dynamical transitions between ferromagnetic, paramagnetic, antiphase, and floating phases. These dynamical transitions seem to occur rather close to the transition lines determined previously in the literature.

  14. Two-dimensional static black holes with pointlike sources

    CERN Document Server

    Melis, M

    2004-01-01

    We study the static black hole solutions of generalized two-dimensional dilaton-gravity theories generated by pointlike mass sources, in the hypothesis that the matter is conformally coupled. We also discuss the motion of test particles. Due to conformal coupling, these follow the geodesics of a metric obtained by rescaling the canonical metric with the dilaton.

  15. Magnetic order in two-dimensional nanoparticle assemblies

    NARCIS (Netherlands)

    Georgescu, M

    2008-01-01

    This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the r

  16. Two-Dimensional Chirality in Three-Dimensional Chemistry.

    Science.gov (United States)

    Wintner, Claude E.

    1983-01-01

    The concept of two-dimensional chirality is used to enhance students' understanding of three-dimensional stereochemistry. This chirality is used as a key to teaching/understanding such concepts as enaniotropism, diastereotopism, pseudoasymmetry, retention/inversion of configuration, and stereochemical results of addition to double bonds. (JN)

  17. Field analysis of two-dimensional focusing grating

    NARCIS (Netherlands)

    Borsboom, P.P.; Frankena, H.J.

    1995-01-01

    The method that we have developed [P-P. Borsboom, Ph.D. dissertation (Delft University of Technology, Delft, The Netherlands); P-P. Borsboom and H. J. Frankena, J. Opt. Soc. Am. A 12, 1134–1141 (1995)] is successfully applied to a two-dimensional focusing grating coupler. The field in the focal regi

  18. Torque magnetometry studies of two-dimensional electron systems

    NARCIS (Netherlands)

    Schaapman, Maaike Ruth

    2004-01-01

    This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting

  19. Two-Dimensional Mesoscale-Ordered Conducting Polymers

    NARCIS (Netherlands)

    Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang

    2016-01-01

    Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of

  20. Vibrations of Thin Piezoelectric Shallow Shells: Two-Dimensional Approximation

    Indian Academy of Sciences (India)

    N Sabu

    2003-08-01

    In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.

  1. Two-dimensional effects in nonlinear Kronig-Penney models

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim

    1997-01-01

    An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...

  2. Forensic potential of comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.

    2016-01-01

    In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o

  3. Easy interpretation of optical two-dimensional correlation spectra

    NARCIS (Netherlands)

    Lazonder, K.; Pshenichnikov, M.S.; Wiersma, D.A.

    2006-01-01

    We demonstrate that the value of the underlying frequency-frequency correlation function can be retrieved from a two-dimensional optical correlation spectrum through a simple relationship. The proposed method yields both intuitive clues and a quantitative measure of the dynamics of the system. The t

  4. Two Dimensional F(R) Horava-Lifshitz Gravity

    CERN Document Server

    Kluson, J

    2016-01-01

    We study two-dimensional F(R) Horava-Lifshitz gravity from the Hamiltonian point of view. We determine constraints structure with emphasis on the careful separation of the second class constraints and global first class constraints. We determine number of physical degrees of freedom and also discuss gauge fixing of the global first class constraints.

  5. Localization of Tight Closure in Two-Dimensional Rings

    Indian Academy of Sciences (India)

    Kamran Divaani-Aazar; Massoud Tousi

    2005-02-01

    It is shown that tight closure commutes with localization in any two-dimensional ring of prime characteristic if either is a Nagata ring or possesses a weak test element. Moreover, it is proved that tight closure commutes with localization at height one prime ideals in any ring of prime characteristic.

  6. Cryptanalysis of the Two-Dimensional Circulation Encryption Algorithm

    Directory of Open Access Journals (Sweden)

    Bart Preneel

    2005-07-01

    Full Text Available We analyze the security of the two-dimensional circulation encryption algorithm (TDCEA, recently published by Chen et al. in this journal. We show that there are several flaws in the algorithm and describe some attacks. We also address performance issues in current cryptographic designs.

  7. New directions in science and technology: two-dimensional crystals

    Energy Technology Data Exchange (ETDEWEB)

    Neto, A H Castro [Graphene Research Centre, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Novoselov, K, E-mail: phycastr@nus.edu.sg, E-mail: konstantin.novoselov@manchester.ac.uk [School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2011-08-15

    Graphene is possibly one of the largest and fastest growing fields in condensed matter research. However, graphene is only one example in a large class of two-dimensional crystals with unusual properties. In this paper we briefly review the properties of graphene and look at the exciting possibilities that lie ahead.

  8. Boundary-value problems for two-dimensional canonical systems

    NARCIS (Netherlands)

    Hassi, Seppo; De Snoo, H; Winkler, Henrik

    2000-01-01

    The two-dimensional canonical system Jy' = -lHy where the nonnegative Hamiltonian matrix function H(x) is trace-normed on (0,∞) has been studied in a function-theoretic way by L. de Branges. We show that the Hamiltonian system induces a closed symmetric relation which can be reduced to a, not necess

  9. On the continua in two-dimensional nonadiabatic magnetohydrodynamic spectra

    NARCIS (Netherlands)

    De Ploey, A.; Van der Linden, R. A. M.; Belien, A. J. C.

    2000-01-01

    The equations for the continuous subspectra of the linear magnetohydrodynamic (MHD) normal modes spectrum of two-dimensional (2D) plasmas are derived in general curvilinear coordinates, taking nonadiabatic effects in the energy equation into account. Previously published derivations of continuous sp

  10. Dislocation climb in two-dimensional discrete dislocation dynamics

    NARCIS (Netherlands)

    Davoudi, K.M.; Nicola, L.; Vlassak, J.J.

    2012-01-01

    In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows dislocations to escape from dislocation pile-ups and reduces the strain-hardening r

  11. SAR Processing Based On Two-Dimensional Transfer Function

    Science.gov (United States)

    Chang, Chi-Yung; Jin, Michael Y.; Curlander, John C.

    1994-01-01

    Exact transfer function, ETF, is two-dimensional transfer function that constitutes basis of improved frequency-domain-convolution algorithm for processing synthetic-aperture-radar, SAR data. ETF incorporates terms that account for Doppler effect of motion of radar relative to scanned ground area and for antenna squint angle. Algorithm based on ETF outperforms others.

  12. Sound waves in two-dimensional ducts with sinusoidal walls

    Science.gov (United States)

    Nayfeh, A. H.

    1974-01-01

    The method of multiple scales is used to analyze the wave propagation in two-dimensional hard-walled ducts with sinusoidal walls. For traveling waves, resonance occurs whenever the wall wavenumber is equal to the difference of the wavenumbers of any two duct acoustic modes. The results show that neither of these resonating modes could occur without strongly generating the other.

  13. Confined two-dimensional fermions at finite density

    CERN Document Server

    De Francia, M; Loewe, M; Santangelo, E M; De Francia, M; Falomir, H; Loewe, M; Santangelo, E M

    1995-01-01

    We introduce the chemical potential in a system of two-dimensional massless fermions, confined to a finite region, by imposing twisted boundary conditions in the Euclidean time direction. We explore in this simple model the application of functional techniques which could be used in more complicated situations.

  14. Imperfect two-dimensional topological insulator field-effect transistors

    Science.gov (United States)

    Vandenberghe, William G.; Fischetti, Massimo V.

    2017-01-01

    To overcome the challenge of using two-dimensional materials for nanoelectronic devices, we propose two-dimensional topological insulator field-effect transistors that switch based on the modulation of scattering. We model transistors made of two-dimensional topological insulator ribbons accounting for scattering with phonons and imperfections. In the on-state, the Fermi level lies in the bulk bandgap and the electrons travel ballistically through the topologically protected edge states even in the presence of imperfections. In the off-state the Fermi level moves into the bandgap and electrons suffer from severe back-scattering. An off-current more than two-orders below the on-current is demonstrated and a high on-current is maintained even in the presence of imperfections. At low drain-source bias, the output characteristics are like those of conventional field-effect transistors, at large drain-source bias negative differential resistance is revealed. Complementary n- and p-type devices can be made enabling high-performance and low-power electronic circuits using imperfect two-dimensional topological insulators. PMID:28106059

  15. Bounds on the capacity of constrained two-dimensional codes

    DEFF Research Database (Denmark)

    Forchhammer, Søren; Justesen, Jørn

    2000-01-01

    Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run...

  16. Miniature sensor for two-dimensional magnetic field distributions

    NARCIS (Netherlands)

    Fluitman, J.H.J.; Krabbe, H.W.

    1972-01-01

    Describes a simple method of production of a sensor for two-dimensional magnetic field distributions. The sensor consists of a strip of Ni-Fe(81-19), of which the magnetoresistance is utilized. Typical dimensions of the strip, placed at the edge of a glass substrate, are: length 100 mu m, width 2 or

  17. Forensic potential of comprehensive two-dimensional gas chromatography

    NARCIS (Netherlands)

    Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.

    2016-01-01

    In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o

  18. Spontaneous emission in two-dimensional photonic crystal microcavities

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2000-01-01

    The properties of the radiation field in a two-dimensional photonic crystal with and without a microcavity introduced are investigated through the concept of the position-dependent photon density of states. The position-dependent rate of spontaneous radiative decay for a two-level atom with random...

  19. Linkage analysis by two-dimensional DNA typing

    NARCIS (Netherlands)

    te Meerman, G J; Mullaart, E; van der Meulen, M A; den Daas, J H; Morolli, B; Uitterlinden, A G; Vijg, J

    1993-01-01

    In two-dimensional (2-D) DNA typing, genomic DNA fragments are separated, first according to size by electrophoresis in a neutral polyacrylamide gel and second according to sequence by denaturing gradient gel electrophoresis, followed by hybridization analysis using micro- and minisatellite core pro

  20. Phase conjugated Andreev backscattering in two-dimensional ballistic cavities

    NARCIS (Netherlands)

    Morpurgo, A.F.; Holl, S.; Wees, B.J.van; Klapwijk, T.M; Borghs, G.

    1997-01-01

    We have experimentally investigated transport in two-dimensional ballistic cavities connected to a point contact and to two superconducting electrodes with a tunable macroscopic phase difference. The point contact resistance oscillates as a function of the phase difference in a way which reflects

  1. Two-dimensional manifold with point-like defects

    CERN Document Server

    Gani, Vakhid A; Rubin, Sergei G

    2014-01-01

    We study a class of two-dimensional extra spaces isomorphic to the $S^2$ sphere in the framework of the multidimensional gravitation. We show that there exists a family of stationary metrics that depend on the initial (boundary) conditions. All these geometries have a singular point. We also discuss the possibility for these deformed extra spaces to be considered as dark matter candidates.

  2. Instability of two-dimensional heterotic stringy black holes

    CERN Document Server

    Azreg-Ainou, M

    1999-01-01

    We solve the eigenvalue problem of general relativity for the case of charged black holes in two-dimensional heterotic string theory, derived by McGuigan et al. For the case of $m^{2}>q^{2}$, we find a physically acceptable time-dependent growing mode; thus the black hole is unstable. The extremal case $m^{2}=q^{2}$ is stable.

  3. Two Dimensional Tensor Product B-Spline Wavelet Scaling Functions for the Solution of Two-Dimensional Unsteady Diffusion Equations

    Institute of Scientific and Technical Information of China (English)

    XIONG Lei; LI haijiao; ZHANG Lewen

    2008-01-01

    The fourth-order B spline wavelet scaling functions are used to solve the two-dimensional unsteady diffusion equation. The calculations from a case history indicate that the method provides high accuracy and the computational efficiency is enhanced due to the small matrix derived from this method.The respective features of 3-spline wavelet scaling functions, 4-spline wavelet scaling functions and quasi-wavelet used to solve the two-dimensional unsteady diffusion equation are compared. The proposed method has potential applications in many fields including marine science.

  4. Two-grain nanoindentation using the quasicontinuum method: Two-dimensional model approach

    Energy Technology Data Exchange (ETDEWEB)

    Iglesias, Rodrigo A. [Instituto de Investigaciones en Fisicoquimica de Cordoba (INFIQC), Consejo Nacional de Investigaciones, Cientificas y Tecnicas (CONICET), Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Edificio Integrador, Ciudad Universitaria, Cordoba, CP 5000 (Argentina)]. E-mail: riglesias@mail.fcq.unc.edu.ar; Leiva, Ezequiel P.M. [Instituto de Investigaciones en Fisicoquimica de Cordoba (INFIQC), Consejo Nacional de Investigaciones, Cientificas y Tecnicas (CONICET), Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Edificio Integrador, Ciudad Universitaria, Cordoba, CP 5000 (Argentina)

    2006-06-15

    The quasicontinuum method (two-dimensional) developed by Tadmor et al. [Tadmor EB, Ortiz M, Phillips R. Philos Mag 1996;73:1529] is applied to an indentation process taking account of the atomic structure of the indenter and the substrate subject to indentation. Slip vectors, dislocation nucleation and nanostructure formation are analyzed for different indenter materials (Ag, Cu and Pd) and indenter crystal orientations. Slip vectors near to the contact region show that, depending on the material and orientation of the indenter, plastic deformations occur either inside the indenter or the substrate. Long-range material deformations appear during the indentation or retraction of the indenter. All of these aspects mainly dictate the formation of nanoclusters or nanoholes on the substrate surface.

  5. Band Gap Optimization of Two-Dimensional Photonic Crystals Using Semidefinite Programming and Subspace Methods

    CERN Document Server

    Men, Han; Freund, Robert M; Parrilo, Pablo A; Peraire, Jaume

    2009-01-01

    In this paper, we consider the optimal design of photonic crystal band structures for two-dimensional square lattices. The mathematical formulation of the band gap optimization problem leads to an infinite-dimensional Hermitian eigenvalue optimization problem parametrized by the dielectric material and the wave vector. To make the problem tractable, the original eigenvalue problem is discretized using the finite element method into a series of finite-dimensional eigenvalue problems for multiple values of the wave vector parameter. The resulting optimization problem is large-scale and non-convex, with low regularity and non-differentiable objective. By restricting to appropriate eigenspaces, we reduce the large-scale non-convex optimization problem via reparametrization to a sequence of small-scale convex semidefinite programs (SDPs) for which modern SDP solvers can be efficiently applied. Numerical results are presented for both transverse magnetic (TM) and transverse electric (TE) polarizations at several fr...

  6. A stable "flat" form of two-dimensional crystals: could graphene, silicene, germanene be minigap semiconductors?

    Science.gov (United States)

    O'Hare, A; Kusmartsev, F V; Kugel, K I

    2012-02-08

    The discovery of a flat two-dimensional crystal known as graphene has contradicted Landau-Peierls-Mermin-Wagner arguments that there is no stable flat form of such crystals. Here, we show that the "flat" shape of graphene arises due to a microscopic buckling at the smallest possible interatomic scale. We show that the graphene, silicene, and other two-dimensional crystals are stable due to transverse short-range displacements of appropriate atoms. The distortions are small and form various patterns, which we describe in a framework of Ising model with competing interactions. We show that when temperature decreases, two transitions, disorder into order and order into disorder, arise. The ordered state has a form of stripes where carbon atoms are shifted regularly with respect to the plane. The flat graphene, silicene, or germanene planes look like a microscopic "washboard" with the wavelength of about couple of interatomic spacing of appropriate sublattices, which for graphene is about 1.8-3.6 Å. At lower temperatures, the ordered state transforms into a glass. Because of up-down asymmetry in buckled graphene, silicene and other two-dimensional crystals deposited on substrate, a minibandgap may arise. We derive a criterion for the minigap formation and show how it is related to the buckling and to the graphene-substrate interaction. Because of the bandgap, there may arise new phenomena and in particular a rectification of ac current induced by microwave or infrared radiation. We show that the amplitude of direct current arising at wave mixing of two harmonics of microwave electromagnetic radiation is huge. Moreover, we predict the existence of miniexcitons and a new type of fermionic minipolaritons whose behavior can be controlled by the microwave and terahertz radiation.

  7. Two dimensional thermo-optic beam steering using a silicon photonic optical phased array

    Science.gov (United States)

    Mahon, Rita; Preussner, Marcel W.; Rabinovich, William S.; Goetz, Peter G.; Kozak, Dmitry A.; Ferraro, Mike S.; Murphy, James L.

    2016-03-01

    Components for free space optical communication terminals such as lasers, amplifiers, and receivers have all seen substantial reduction in both size and power consumption over the past several decades. However, pointing systems, such as fast steering mirrors and gimbals, have remained large, slow and power-hungry. Optical phased arrays provide a possible solution for non-mechanical beam steering devices that can be compact and lower in power. Silicon photonics is a promising technology for phased arrays because it has the potential to scale to many elements and may be compatible with CMOS technology thereby enabling batch fabrication. For most free space optical communication applications, two-dimensional beam steering is needed. To date, silicon photonic phased arrays have achieved two-dimensional steering by combining thermo-optic steering, in-plane, with wavelength tuning by means of an output grating to give angular tuning, out-of-plane. While this architecture might work for certain static communication links, it would be difficult to implement for moving platforms. Other approaches have required N2 controls for an NxN element phased array, which leads to complexity. Hence, in this work we demonstrate steering using the thermo-optic effect for both dimensions with a simplified steering mechanism requiring only two control signals, one for each steering dimension.

  8. Two-dimensional refractive index modulation by phased array transducers in acousto-optic deflectors.

    Science.gov (United States)

    Wang, Tiansi; Zhang, Chong; Aleksov, Aleksandar; Salama, Islam; Kar, Aravinda

    2017-01-20

    Acousto-optic deflectors are photonic devices that are used for scanning high-power laser beams in advanced microprocessing applications such as marking and direct writing. The operation of conventional deflectors mostly relies on one-dimensional sinusoidal variation of the refractive index in an acousto-optic medium. Sometimes static phased array transducers, such as step configuration or planar configuration transducer architecture, are used to tilt the index modulation planes for achieving higher performance and higher resolution than a single transducer AO device. However, the index can be modulated in two dimensions, and the modulation plane can be tilted arbitrarily by creating dynamic phase gratings in the medium using phased array transducers. This type of dynamic two-dimensional acousto-optic deflector can provide better performance using, for example, a large deflection angle and high diffraction efficiency. This paper utilizes an ultrasonic beam steering approach to study the two-dimensional strain-induced index modulation due to the photoelastic effect. The modulation is numerically simulated, and the effects of various parameters, such as the operating radiofrequency of the transducers, the ultrasonic beam steering angle, and different combinations of pressure on each element of the transducer array, are demonstrated.

  9. Two-dimensional surface river flow patterns measured with paired RiverSondes

    Science.gov (United States)

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.

    2008-01-01

    Two RiverSondes were operated simultaneously in close proximity in order to provide a two-dimensional map of river surface velocity. The initial test was carried out at Threemile Slough in central California. The two radars were installed about 135 m apart on the same bank of the channel. Each radar used a 3-yagi antenna array and determined signal directions using direction finding. The slough is approximately 200 m wide, and each radar processed data out to about 300 m, with a range resolution of 15 m and an angular resolution of 1 degree. Overlapping radial vector data from the two radars were combined to produce total current vectors at a grid spacing of 10 m, with updates every 5 minutes. The river flow in the region, which has a maximum velocity of about 0.8 m/s, is tidally driven with flow reversals every 6 hours, and complex flow patterns were seen during flow reversal. The system performed well with minimal mutual interference. The ability to provide continuous, non-contact two-dimensional river surface flow measurements will be useful in several unique settings, such as studies of flow at river junctions where impacts to juvenile fish migration are significant. Additional field experiments are planned this year on the Sacramento River. ?? 2007 IEEE.

  10. Two-dimensional relative peripheral refractive error induced by Fractal Contact Lenses for myopia control

    CERN Document Server

    Rodriguez-Vallejo, Manuel; Monsoriu, Juan A; Ferrando, Vicente; Furlan, Walter D

    2016-01-01

    Purpose: To assess the peripheral refraction induced by Fractal Contact Lenses (FCLs) in myopic eyes by means of a two-dimensional Relative Peripheral Refractive Error (RPRE) map. Methods: FCLs prototypes were specially manufactured and characterized. This study involved twenty-six myopic subjects ranging from -0.50 D to -7.00 D. The two-dimensional RPRE was measured with an open-field autorefractor by means of tracking targets distributed in a square grid from -30 degrees (deg) nasal to 30 deg temporal and 15 deg superior to -15 deg inferior. Corneal topographies were taken in order to assess correlations between corneal asphericity, lens decentration and RPRE represented in vector components M, J0 and J45. Results: The mean power of the FCLs therapeutic zones was 1.32 +/- 0.28 D. Significant correlations were found between the corneal asphericity and vector components of the RPRE in the nacked eyes. FCLs were decentered a mean of 0.7 +/- 0.19 mm to the temporal cornea. M decreased asymmetrically between nas...

  11. Production of stereoscopic two-dimensional animation%立体二维动画片的制作

    Institute of Scientific and Technical Information of China (English)

    贾寒阳

    2011-01-01

    This paper firstly explains the concept of stereoscopic two-dimensional animation, focusing on analysis the contradiction between " stereoscopic" and plane (two-dimensional) animation and how to make clever use of this contradiction to produce stereoscopic two-dimensional animation. Then from a practical level, it summarizes how to design and produce a stereoscopic two-Dimensional animation. Finally concludes a new idea of creating a stereoscopic two-dimensional animation in a theoretical way.%首先从理论上阐释了立体二维动画片的概念,重点剖析了“立体”与平面(二维)动画片的矛盾,以及如何巧妙运用该矛盾制作立体二维动画片.其次从具体实践的层面上总结了如何构思然后制作一部立体二维动画片.最后,在理论上总结二维动画片创作的一个新思路.

  12. Charge Transport in Antiferromagnetic Insulating Phase of Two-Dimensional Organic Conductor λ-(BETS)2FeCl4

    Science.gov (United States)

    Sugiura, Shiori; Shimada, Kazuo; Tajima, Naoya; Nishio, Yutaka; Terashima, Taichi; Isono, Takayuki; Kobayashi, Akiko; Zhou, Biao; Kato, Reizo; Uji, Shinya

    2016-06-01

    Resistance and dielectric constants have been measured in the antiferromagnetic insulating phase of the quasi-two-dimensional organic conductor λ-(BETS)2FeCl4 to understand charge transport. Nonlinear current-voltage characteristics are observed at low temperatures, which are explained by a charge transport model based on the electric-field dependent Coulomb potential between the thermally excited electron and hole. A small dip in the magnetic field dependence of the resistance is found at 1.2 T, which is ascribed to a spin-flop transition. The large difference between the in-plane and out-of-plane dielectric constants shows the two-dimensionality of the Coulomb potential, which is consistent with the charge transport model. The angular dependence of the metal-insulator transition field is determined, which suggests that the Zeeman effect of the 3d spins of the Fe ions plays an essential role.

  13. Vector geometry

    CERN Document Server

    Robinson, Gilbert de B

    2011-01-01

    This brief undergraduate-level text by a prominent Cambridge-educated mathematician explores the relationship between algebra and geometry. An elementary course in plane geometry is the sole requirement for Gilbert de B. Robinson's text, which is the result of several years of teaching and learning the most effective methods from discussions with students. Topics include lines and planes, determinants and linear equations, matrices, groups and linear transformations, and vectors and vector spaces. Additional subjects range from conics and quadrics to homogeneous coordinates and projective geom

  14. Stress Wave Propagation in Two-dimensional Buckyball Lattice

    Science.gov (United States)

    Xu, Jun; Zheng, Bowen

    2016-11-01

    Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices.

  15. The separation of whale myoglobins with two-dimensional electrophoresis.

    Science.gov (United States)

    Spicer, G S

    1988-10-01

    Five myoglobins (sperm whale, Sei whale, Hubbs' beaked whale, pilot whale, and Amazon River dolphin) were examined using two-dimensional electrophoresis. Previous reports indicated that none of these proteins could be separated by using denaturing (in the presence of 8-9 M urea) isoelectric focusing. This result is confirmed in the present study. However, all the proteins could be separated by using denaturing nonequilibrium pH-gradient electrophoresis in the first dimension. Additionally, all the myoglobins have characteristic mobilities in the second dimension (sodium dodecyl sulfate), but these mobilities do not correspond to the molecular weights of the proteins. We conclude that two-dimensional electrophoresis can be more sensitive to differences in primary protein structure than previous studies indicate and that the assessment seems to be incorrect that this technique can separate only proteins that have a unit charge difference.

  16. Entanglement Entropy in Two-Dimensional String Theory.

    Science.gov (United States)

    Hartnoll, Sean A; Mazenc, Edward A

    2015-09-18

    To understand an emergent spacetime is to understand the emergence of locality. Entanglement entropy is a powerful diagnostic of locality, because locality leads to a large amount of short distance entanglement. Two-dimensional string theory is among the very simplest instances of an emergent spatial dimension. We compute the entanglement entropy in the large-N matrix quantum mechanics dual to two-dimensional string theory in the semiclassical limit of weak string coupling. We isolate a logarithmically large, but finite, contribution that corresponds to the short distance entanglement of the tachyon field in the emergent spacetime. From the spacetime point of view, the entanglement is regulated by a nonperturbative "graininess" of space.

  17. The Persistence Problem in Two-Dimensional Fluid Turbulence

    CERN Document Server

    Perlekar, Prasad; Mitra, Dhrubaditya; Pandit, Rahul

    2010-01-01

    We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter {\\Lambda} to distinguish between vortical and extensional regions. We then use a direct numerical simulation (DNS) of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with a universal exponent {\\theta} = 3.1 \\pm 0.2.

  18. On Dirichlet eigenvectors for neutral two-dimensional Markov chains

    CERN Document Server

    Champagnat, Nicolas; Miclo, Laurent

    2012-01-01

    We consider a general class of discrete, two-dimensional Markov chains modeling the dynamics of a population with two types, without mutation or immigration, and neutral in the sense that type has no influence on each individual's birth or death parameters. We prove that all the eigenvectors of the corresponding transition matrix or infinitesimal generator \\Pi\\ can be expressed as the product of "universal" polynomials of two variables, depending on each type's size but not on the specific transitions of the dynamics, and functions depending only on the total population size. These eigenvectors appear to be Dirichlet eigenvectors for \\Pi\\ on the complement of triangular subdomains, and as a consequence the corresponding eigenvalues are ordered in a specific way. As an application, we study the quasistationary behavior of finite, nearly neutral, two-dimensional Markov chains, absorbed in the sense that 0 is an absorbing state for each component of the process.

  19. Statistical mechanics of two-dimensional and geophysical flows

    CERN Document Server

    Bouchet, Freddy

    2011-01-01

    The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter's troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. The equilibrium microcanonical measure is built from the Liouville theorem. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equi...

  20. Two-dimensional hazard estimation for longevity analysis

    DEFF Research Database (Denmark)

    Fledelius, Peter; Guillen, M.; Nielsen, J.P.

    2004-01-01

    We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface...... the two-dimensional mortality surface. Furthermore we look at aggregated synthetic population metrics as 'population life expectancy' and 'population survival probability'. For Danish women these metrics indicate decreasing mortality with respect to chronological time. The metrics can not directly be used...... for prediction purposes. However, we suggest that life insurance companies use the estimation technique and the cross-validation for bandwidth selection when analyzing their portfolio mortality. The non-parametric approach may give valuable information prior to developing more sophisticated prediction models...

  1. Analysis of one dimensional and two dimensional fuzzy controllers

    Institute of Scientific and Technical Information of China (English)

    Ban Xiaojun; Gao Xiaozhi; Huang Xianlin; Wu Tianbao

    2006-01-01

    The analytical structures and the corresponding mathematical properties of the one dimensional and two dimensional fuzzy controllers are first investigated in detail.The nature of these two kinds of fuzzy controllers is next probed from the perspective of control engineering. For the one dimensional fuzzy controller, it is concluded that this controller is a combination of a saturation element and a nonlinear proportional controller, and the system that employs the one dimensional fuzzy controller is the combination of an open-loop control system and a closedloop control system. For the latter case, it is concluded that it is a hybrid controller, which comprises the saturation part, zero-output part, nonlinear derivative part, nonlinear proportional part, as well as nonlinear proportional-derivative part, and the two dimensional fuzzy controller-based control system is a loop-varying system with varying number of control loops.

  2. Extension of modified power method to two-dimensional problems

    Science.gov (United States)

    Zhang, Peng; Lee, Hyunsuk; Lee, Deokjung

    2016-09-01

    In this study, the generalized modified power method was extended to two-dimensional problems. A direct application of the method to two-dimensional problems was shown to be unstable when the number of requested eigenmodes is larger than a certain problem dependent number. The root cause of this instability has been identified as the degeneracy of the transfer matrix. In order to resolve this instability, the number of sub-regions for the transfer matrix was increased to be larger than the number of requested eigenmodes; and a new transfer matrix was introduced accordingly which can be calculated by the least square method. The stability of the new method has been successfully demonstrated with a neutron diffusion eigenvalue problem and the 2D C5G7 benchmark problem.

  3. Two Dimensional Lattice Boltzmann Method for Cavity Flow Simulation

    Directory of Open Access Journals (Sweden)

    Panjit MUSIK

    2004-01-01

    Full Text Available This paper presents a simulation of incompressible viscous flow within a two-dimensional square cavity. The objective is to develop a method originated from Lattice Gas (cellular Automata (LGA, which utilises discrete lattice as well as discrete time and can be parallelised easily. Lattice Boltzmann Method (LBM, known as discrete Lattice kinetics which provide an alternative for solving the Navier–Stokes equations and are generally used for fluid simulation, is chosen for the study. A specific two-dimensional nine-velocity square Lattice model (D2Q9 Model is used in the simulation with the velocity at the top of the cavity kept fixed. LBM is an efficient method for reproducing the dynamics of cavity flow and the results which are comparable to those of previous work.

  4. Transport behavior of water molecules through two-dimensional nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-11-14

    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.

  5. Transport behavior of water molecules through two-dimensional nanopores

    Science.gov (United States)

    Zhu, Chongqin; Li, Hui; Meng, Sheng

    2014-11-01

    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.

  6. Thermodynamics of two-dimensional Yukawa systems across coupling regimes

    Science.gov (United States)

    Kryuchkov, Nikita P.; Khrapak, Sergey A.; Yurchenko, Stanislav O.

    2017-04-01

    Thermodynamics of two-dimensional Yukawa (screened Coulomb or Debye-Hückel) systems is studied systematically using molecular dynamics (MD) simulations. Simulations cover very broad parameter range spanning from weakly coupled gaseous states to strongly coupled fluid and crystalline states. Important thermodynamic quantities, such as internal energy and pressure, are obtained and accurate physically motivated fits are proposed. This allows us to put forward simple practical expressions to describe thermodynamic properties of two-dimensional Yukawa systems. For crystals, in addition to numerical simulations, the recently developed shortest-graph interpolation method is applied to describe pair correlations and hence thermodynamic properties. It is shown that the finite-temperature effects can be accounted for by using simple correction of peaks in the pair correlation function. The corresponding correction coefficients are evaluated using MD simulation. The relevance of the obtained results in the context of colloidal systems, complex (dusty) plasmas, and ions absorbed to interfaces in electrolytes is pointed out.

  7. Topological states in two-dimensional hexagon lattice bilayers

    Science.gov (United States)

    Zhang, Ming-Ming; Xu, Lei; Zhang, Jun

    2016-10-01

    We investigate the topological states of the two-dimensional hexagon lattice bilayer. The system exhibits a quantum valley Hall (QVH) state when the interlayer interaction t⊥ is smaller than the nearest neighbor hopping energy t, and then translates to a trivial band insulator state when t⊥ / t > 1. Interestingly, the system is found to be a single-edge QVH state with t⊥ / t = 1. The topological phase transition also can be presented via changing bias voltage and sublattice potential in the system. The QVH states have different edge modes carrying valley current but no net charge current. The bias voltage and external electric field can be tuned easily in experiments, so the present results will provide potential application in valleytronics based on the two-dimensional hexagon lattice.

  8. CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION

    Directory of Open Access Journals (Sweden)

    Toth Reka

    2010-12-01

    Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.

  9. Phase separation under two-dimensional Poiseuille flow.

    Science.gov (United States)

    Kiwata, H

    2001-05-01

    The spinodal decomposition of a two-dimensional binary fluid under Poiseuille flow is studied by numerical simulation. We investigated time dependence of domain sizes in directions parallel and perpendicular to the flow. In an effective region of the flow, the power-law growth of a characteristic length in the direction parallel to the flow changes from the diffusive regime with the growth exponent alpha=1/3 to a new regime. The scaling invariance of the growth in the perpendicular direction is destroyed after the diffusive regime. A recurrent prevalence of thick and thin domains which determines log-time periodic oscillations has not been observed in our model. The growth exponents in the infinite system under two-dimensional Poiseuille flow are obtained by the renormalization group.

  10. Two-dimensional localized structures in harmonically forced oscillatory systems

    Science.gov (United States)

    Ma, Y.-P.; Knobloch, E.

    2016-12-01

    Two-dimensional spatially localized structures in the complex Ginzburg-Landau equation with 1:1 resonance are studied near the simultaneous presence of a steady front between two spatially homogeneous equilibria and a supercritical Turing bifurcation on one of them. The bifurcation structures of steady circular fronts and localized target patterns are computed in the Turing-stable and Turing-unstable regimes. In particular, localized target patterns grow along the solution branch via ring insertion at the core in a process reminiscent of defect-mediated snaking in one spatial dimension. Stability of axisymmetric solutions on these branches with respect to axisymmetric and nonaxisymmetric perturbations is determined, and parameter regimes with stable axisymmetric oscillons are identified. Direct numerical simulations reveal novel depinning dynamics of localized target patterns in the radial direction, and of circular and planar localized hexagonal patterns in the fully two-dimensional system.

  11. Enstrophy inertial range dynamics in generalized two-dimensional turbulence

    Science.gov (United States)

    Iwayama, Takahiro; Watanabe, Takeshi

    2016-07-01

    We show that the transition to a k-1 spectrum in the enstrophy inertial range of generalized two-dimensional turbulence can be derived analytically using the eddy damped quasinormal Markovianized (EDQNM) closure. The governing equation for the generalized two-dimensional fluid system includes a nonlinear term with a real parameter α . This parameter controls the relationship between the stream function and generalized vorticity and the nonlocality of the dynamics. An asymptotic analysis accounting for the overwhelming dominance of nonlocal triads allows the k-1 spectrum to be derived based upon a scaling analysis. We thereby provide a detailed analytical explanation for the scaling transition that occurs in the enstrophy inertial range at α =2 in terms of the spectral dynamics of the EDQNM closure, which extends and enhances the usual phenomenological explanations.

  12. Folding two dimensional crystals by swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2014-12-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.

  13. Explorative data analysis of two-dimensional electrophoresis gels

    DEFF Research Database (Denmark)

    Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine

    2004-01-01

    Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...... of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine...... if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots...

  14. Thermal Stability and Anisotropic Sublimation of Two-Dimensional Colloidal Bi2Te3 and Bi2Se3 Nanocrystals

    CERN Document Server

    Buha, Joka; Castillo, Antonio Esau Del Rio; Bonaccorso, Francesco; Manna, Liberato

    2016-01-01

    The structural and compositional stabilities of two dimensional 2D Bi2Te3 and Bi2Se3 nanocrystals, produced by both colloidal synthesis and by liquid phase exfoliation, were studied by in situ transmission electron microscopy TEM during annealing at temperatures between 350 and 500 C. The sublimation process induced by annealing is structurally and chemically anisotropic and takes place through the preferential dismantling of the prismatic 011-0 type planes, and through the preferential sublimation of Te or Se.

  15. Two-dimensional superconductivity of SmFeAsO0.85 single crystals: A fluctuation-conductivity study

    Science.gov (United States)

    Lee, Hyun-Sook; Park, Jae-Hyun; Lee, Jae-Yeap; Kim, Ju-Young; Sung, Nak-Heon; Cho, B. K.; Lee, Hu-Jong

    2010-12-01

    Temperature dependence of the in-plane conductance of a SmFeAsO0.85 single crystal is measured in c-axis and planar magnetic fields up to 7 T. The conductivity near the superconducting transition is well described by two-dimensional (2D) thermal-fluctuation theory. The 2D superconductivity arises as the c-axis coherence length is much shorter than the spacing between neighboring FeAs layers.

  16. Parallel finite difference beam propagation method based on message passing interface: application to MMI couplers with two-dimensional confinement

    Institute of Scientific and Technical Information of China (English)

    Chaojun Yan; Wenbiao Peng; Haijun Li

    2007-01-01

    @@ The alternate-direction implicit finite difference beam propagation method (FD-BPM) is used to analyze the two-dimensional (2D) symmetrical multimode interference (MMI) couplers. The positions of the images at the output plane and the length of multimode waveguide are accurately determined numerically. In order to reduce calculation time, the parallel processing of the arithmetic is implemented by the message passing interface and the simulation is accomplished by eight personal computers.

  17. On calculation of quasi-two-dimensional divergence-free projections for visualization of three-dimensional incompressible flows

    OpenAIRE

    Gelfgat, Alexander

    2015-01-01

    A visualization of three-dimensional incompressible flows by divergence-free quasi-two-dimensional projections of the velocity field on three coordinate planes was recently proposed. The projections were calculated using divergence-free Galerkin bases, which resulted in the whole procedure being complicated and CPU-time consuming. Here we propose an alternative way based on the Chorin projection combined with a SIMPLE-like iteration. The approach proposed is much easier in realization, allows...

  18. Instability of a two-dimensional Bose–Einstein condensate with Rashba spin–orbit coupling at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    He, Pei-Song, E-mail: hepeisong@th.btbu.edu.cn; Zhao, Jia; Geng, Ai-Cong; Xu, Deng-Hui; Hu, Rong

    2013-11-01

    We prove that in a two-dimensional homogeneous boson system with Rashba spin–orbit coupling, Bose–Einstein condensate with plane-wave order is unstable at finite temperature. The calculations are based on a nonlinear sigma model scheme. The density wave contributions to the thermal deletions are divergent in the infrared limit. The behavior of the divergence is different from that without spin–orbit coupling.

  19. Two-dimensional model of elastically coupled molecular motors

    Institute of Scientific and Technical Information of China (English)

    Zhang Hong-Wei; Wen Shu-Tang; Chen Gai-Rong; Li Yu-Xiao; Cao Zhong-Xing; Li Wei

    2012-01-01

    A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins.Extensive Langevin simulations of the model are performed.We discuss the dependences of motion and efficiency on the model parameters,including the external force and the temperature.A good qualitative agreement with the expected behavior is observed.

  20. Conductivity of a two-dimensional guiding center plasma.

    Science.gov (United States)

    Montgomery, D.; Tappert, F.

    1972-01-01

    The Kubo method is used to calculate the electrical conductivity of a two-dimensional, strongly magnetized plasma. The particles interact through (logarithmic) electrostatic potentials and move with their guiding center drift velocities (Taylor-McNamara model). The thermal equilibrium dc conductivity can be evaluated analytically, but the ac conductivity involves numerical solution of a differential equation. Both conductivities fall off as the inverse first power of the magnetic field strength.

  1. Minor magnetization loops in two-dimensional dipolar Ising model

    Energy Technology Data Exchange (ETDEWEB)

    Sarjala, M. [Aalto University, Department of Applied Physics, P.O. Box 14100, FI-00076 Aalto (Finland); Seppaelae, E.T., E-mail: eira.seppala@nokia.co [Nokia Research Center, Itaemerenkatu 11-13, FI-00180 Helsinki (Finland); Alava, M.J., E-mail: mikko.alava@tkk.f [Aalto University, Department of Applied Physics, P.O. Box 14100, FI-00076 Aalto (Finland)

    2011-05-15

    The two-dimensional dipolar Ising model is investigated for the relaxation and dynamics of minor magnetization loops. Monte Carlo simulations show that in a stripe phase an exponential decrease can be found for the magnetization maxima of the loops, M{approx}exp(-{alpha}N{sub l}) where N{sub l} is the number of loops. We discuss the limits of this behavior and its relation to the equilibrium phase diagram of the model.

  2. Cryptography Using Multiple Two-Dimensional Chaotic Maps

    Directory of Open Access Journals (Sweden)

    Ibrahim S. I. Abuhaiba

    2012-08-01

    Full Text Available In this paper, a symmetric key block cipher cryptosystem is proposed, involving multiple two-dimensional chaotic maps and using 128-bits external secret key. Computer simulations indicate that the cipher has good diffusion and confusion properties with respect to the plaintext and the key. Moreover, it produces ciphertext with random distribution. The computation time is much less than previous related works. Theoretic analysis verifies its superiority to previous cryptosystems against different types of attacks.

  3. A UNIVERSAL VARIATIONAL FORMULATION FOR TWO DIMENSIONAL FLUID MECHANICS

    Institute of Scientific and Technical Information of China (English)

    何吉欢

    2001-01-01

    A universal variational formulation for two dimensional fluid mechanics is obtained, which is subject to the so-called parameter-constrained equations (the relationship between parameters in two governing equations). By eliminating the constraints, the generalized variational principle (GVPs) can be readily derived from the formulation. The formulation can be applied to any conditions in case the governing equations can be converted into conservative forms. Some illustrative examples are given to testify the effectiveness and simplicity of the method.

  4. Nonlocal bottleneck effect in two-dimensional turbulence

    CERN Document Server

    Biskamp, D; Schwarz, E

    1998-01-01

    The bottleneck pileup in the energy spectrum is investigated for several two-dimensional (2D) turbulence systems by numerical simulation using high-order diffusion terms to amplify the effect, which is weak for normal diffusion. For 2D magnetohydrodynamic (MHD) turbulence, 2D electron MHD (EMHD) turbulence and 2D thermal convection, which all exhibit direct energy cascades, a nonlocal behavior is found resulting in a logarithmic enhancement of the spectrum.

  5. Level crossings in complex two-dimensional potentials

    Indian Academy of Sciences (India)

    Qing-Hai Wang

    2009-08-01

    Two-dimensional $\\mathcal{PT}$-symmetric quantum-mechanical systems with the complex cubic potential 12 = 2 + 2 + 2 and the complex Hénon–Heiles potential HH = 2 + 2 + (2 − 3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the $\\mathcal{PT}$ symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.

  6. Extraction of plant proteins for two-dimensional electrophoresis

    OpenAIRE

    Granier, Fabienne

    1988-01-01

    Three different extraction procedures for two-dimensional electrophoresis of plant proteins are compared: (i) extraction of soluble proteins with a nondenaturing Tris-buffer, (ii) denaturing extraction in presence of sodium dodecyl sulfate at elevated temperature allowing the solubilization of membrane proteins in addition to a recovery of soluble proteins, and (iii) a trichloroacetic acid-acetone procedure allowing the direct precipitation of total proteins.

  7. Lyapunov Computational Method for Two-Dimensional Boussinesq Equation

    CERN Document Server

    Mabrouk, Anouar Ben

    2010-01-01

    A numerical method is developed leading to Lyapunov operators to approximate the solution of two-dimensional Boussinesq equation. It consists of an order reduction method and a finite difference discretization. It is proved to be uniquely solvable and analyzed for local truncation error for consistency. The stability is checked by using Lyapunov criterion and the convergence is studied. Some numerical implementations are provided at the end of the paper to validate the theoretical results.

  8. Complex dynamical invariants for two-dimensional complex potentials

    Indian Academy of Sciences (India)

    J S Virdi; F Chand; C N Kumar; S C Mishra

    2012-08-01

    Complex dynamical invariants are searched out for two-dimensional complex potentials using rationalization method within the framework of an extended complex phase space characterized by $x = x_{1} + ip_{3}. y = x_{2} + ip_{4}, p_{x} = p_{1} + ix_{3}, p_{y} = p_{2} + ix_{4}$. It is found that the cubic oscillator and shifted harmonic oscillator admit quadratic complex invariants. THe obtained invariants may be useful for studying non-Hermitian Hamiltonian systems.

  9. Two-dimensional hydrogen negative ion in a magnetic field

    Institute of Scientific and Technical Information of China (English)

    Xie Wen-Fang

    2004-01-01

    Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H- in a magnetic field. The results show that the ground and low-excited states of H- in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.

  10. А heuristic algorithm for two-dimensional strip packing problem

    OpenAIRE

    Dayong, Cao; Kotov, V.M.

    2011-01-01

    In this paper, we construct an improved best-fit heuristic algorithm for two-dimensional rectangular strip packing problem (2D-RSPP), and compare it with some heuristic and metaheuristic algorithms from literatures. The experimental results show that BFBCC could produce satisfied packing layouts than these methods, especially for the large problem of 50 items or more, BFBCC could get better results in shorter time.

  11. Chronology Protection in Two-Dimensional Dilaton Gravity

    CERN Document Server

    Mishima, T; Mishima, Takashi; Nakamichi, Akika

    1994-01-01

    The global structure of 1 + 1 dimensional compact Universe is studied in two-dimensional model of dilaton gravity. First we give a classical solution corresponding to the spacetime in which a closed time-like curve appears, and show the instability of this spacetime due to the existence of matters. We also observe quantum version of such a spacetime having closed timelike curves never reappear unless the parameters are fine-tuned.

  12. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M

    1993-01-01

    Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  13. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175

    2009-01-01

    We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  14. SU(1,2) invariance in two-dimensional oscillator

    CERN Document Server

    Krivonos, Sergey

    2016-01-01

    Performing the Hamiltonian analysis we explicitly established the canonical equivalence of the deformed oscillator, constructed in arXiv:1607.03756[hep-th], with the ordinary one. As an immediate consequence, we proved that the SU(1,2) symmetry is the dynamical symmetry of the ordinary two-dimensional oscillator. The characteristic feature of this SU(1,2) symmetry is a non-polynomial structure of its generators written it terms of the oscillator variables.

  15. Multiple Potts Models Coupled to Two-Dimensional Quantum Gravity

    CERN Document Server

    Baillie, C F

    1992-01-01

    We perform Monte Carlo simulations using the Wolff cluster algorithm of {\\it multiple} $q=2,3,4$ state Potts models on dynamical phi-cubed graphs of spherical topology in order to investigate the $c>1$ region of two-dimensional quantum gravity. Contrary to naive expectation we find no obvious signs of pathological behaviour for $c>1$. We discuss the results in the light of suggestions that have been made for a modified DDK ansatz for $c>1$.

  16. Multiple Potts models coupled to two-dimensional quantum gravity

    Science.gov (United States)

    Baillie, C. F.; Johnston, D. A.

    1992-07-01

    We perform Monte Carlo simulations using the Wolff cluster algorithm of multiple q=2, 3, 4 state Potts models on dynamical phi-cubed graphs of spherical topology in order to investigate the c>1 region of two-dimensional quantum gravity. Contrary to naive expectation we find no obvious signs of pathological behaviour for c>1. We discuss the results in the light of suggestions that have been made for a modified DDK ansatz for c>1.

  17. Colloidal interactions in two-dimensional nematic emulsions

    Indian Academy of Sciences (India)

    N M Silvestre; P Patrício; M M Telo Da Gama

    2005-06-01

    We review theoretical and experimental work on colloidal interactions in two-dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions between colloids and fluid (deformable) interfaces and the shape of fluid colloids in smectic-C films.

  18. Thermal diode from two-dimensional asymmetrical Ising lattices.

    Science.gov (United States)

    Wang, Lei; Li, Baowen

    2011-06-01

    Two-dimensional asymmetrical Ising models consisting of two weakly coupled dissimilar segments, coupled to heat baths with different temperatures at the two ends, are studied by Monte Carlo simulations. The heat rectifying effect, namely asymmetric heat conduction, is clearly observed. The underlying mechanisms are the different temperature dependencies of thermal conductivity κ at two dissimilar segments and the match (mismatch) of flipping frequencies of the interface spins.

  19. Numerical Study of Two-Dimensional Viscous Flow over Dams

    Institute of Scientific and Technical Information of China (English)

    王利兵; 刘宇陆; 涂敏杰

    2003-01-01

    In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.

  20. Acoustic Bloch oscillations in a two-dimensional phononic crystal.

    Science.gov (United States)

    He, Zhaojian; Peng, Shasha; Cai, Feiyan; Ke, Manzhu; Liu, Zhengyou

    2007-11-01

    We report the observation of acoustic Bloch oscillations at megahertz frequency in a two-dimensional phononic crystal. By creating periodically arrayed cavities with a decreasing gradient in width along one direction in the phononic crystal, acoustic Wannier-Stark ladders are created in the frequency domain. The oscillatory motion of an incident Gaussian pulse inside the sample is demonstrated by both simulation and experiment.

  1. Exact analytic flux distributions for two-dimensional solar concentrators.

    Science.gov (United States)

    Fraidenraich, Naum; Henrique de Oliveira Pedrosa Filho, Manoel; Vilela, Olga C; Gordon, Jeffrey M

    2013-07-01

    A new approach for representing and evaluating the flux density distribution on the absorbers of two-dimensional imaging solar concentrators is presented. The formalism accommodates any realistic solar radiance and concentrator optical error distribution. The solutions obviate the need for raytracing, and are physically transparent. Examples illustrating the method's versatility are presented for parabolic trough mirrors with both planar and tubular absorbers, Fresnel reflectors with tubular absorbers, and V-trough mirrors with planar absorbers.

  2. Tricritical behavior in a two-dimensional field theory

    Science.gov (United States)

    Hamber, Herbert

    1980-05-01

    The critical behavior of a two-dimensional scalar Euclidean field theory with a potential term that allows for three minima is analyzed using an approximate position-space renormalization-group transformation on the equivalent quantum spin Hamiltonian. The global phase diagram shows a tricritical point separating a critical line from a line of first-order transitions. Other critical properties are examined, and good agreement is found with results on classical spin models belonging to the same universality class.

  3. Quantum entanglement in a two-dimensional ion trap

    Institute of Scientific and Technical Information of China (English)

    王成志; 方卯发

    2003-01-01

    In this paper, we investigate the quantum entanglement in a two-dimensional ion trap system. We discuss the quantum entanglement between the ion and phonons by using reduced entropy, and that between two degrees of freedom of the vibrational motion along x and y directions by using quantum relative entropy. We discuss also the influence of initial state of the system on the quantum entanglement and the relation between two entanglements in the trapped ion system.

  4. Coll Positioning systems: a two-dimensional approach

    CERN Document Server

    Ferrando, J J

    2006-01-01

    The basic elements of Coll positioning systems (n clocks broadcasting electromagnetic signals in a n-dimensional space-time) are presented in the two-dimensional case. This simplified approach allows us to explain and to analyze the properties and interest of these relativistic positioning systems. The positioning system defined in flat metric by two geodesic clocks is analyzed. The interest of the Coll systems in gravimetry is pointed out.

  5. Two-dimensional correlation spectroscopy in polymer study

    Science.gov (United States)

    Park, Yeonju; Noda, Isao; Jung, Young Mee

    2015-01-01

    This review outlines the recent works of two-dimensional correlation spectroscopy (2DCOS) in polymer study. 2DCOS is a powerful technique applicable to the in-depth analysis of various spectral data of polymers obtained under some type of perturbation. The powerful utility of 2DCOS combined with various analytical techniques in polymer studies and noteworthy developments of 2DCOS used in this field are also highlighted. PMID:25815286

  6. Interior design of a two-dimensional semiclassic black hole

    CERN Document Server

    Levanony, Dana; 10.1103/PhysRevD.80.084008

    2009-01-01

    We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. The field equations admit two types of singularities, and their local asymptotic structure is investigated. One of these singularities is found to develop, as a spacelike singularity, inside the black hole. We then study the internal structure of the evaporating black hole from the horizon to the singularity.

  7. Towards a two dimensional model of surface piezoelectricity

    OpenAIRE

    Monge Víllora, Oscar

    2016-01-01

    We want to understand the behaviour of flexoelectricity and surface piezoelectricity and distinguish them in order to go deep into the controversies of the filed. This motivate the construction of a model of continuum flexoelectric theory. The model proposed is a two-dimensional model that integrates the electromechanical equations that include the elastic, dielectric, piezoelectric and flexoelectric effect on a rectangular sample. As the flexoelectric and the surface piezoelectric effects ap...

  8. Velocity Statistics in the Two-Dimensional Granular Turbulence

    OpenAIRE

    Isobe, Masaharu

    2003-01-01

    We studied the macroscopic statistical properties on the freely evolving quasi-elastic hard disk (granular) system by performing a large-scale (up to a few million particles) event-driven molecular dynamics systematically and found that remarkably analogous to an enstrophy cascade process in the decaying two-dimensional fluid turbulence. There are four typical stages in the freely evolving inelastic hard disk system, which are homogeneous, shearing (vortex), clustering and final state. In the...

  9. Statistical study of approximations to two dimensional inviscid turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Glaz, H.M.

    1977-09-01

    A numerical technique is developed for studying the ergodic and mixing hypotheses for the dynamical systems arising from the truncated Fourier transformed two-dimensional inviscid Navier-Stokes equations. This method has the advantage of exactly conserving energy and entropy (i.e., total vorticity) in the inviscid case except for numerical error in solving the ordinary differential equations. The development of the mathematical model as an approximation to a real physical (turbulent) flow and the numerical results obtained are discussed.

  10. Static Structure of Two-Dimensional Granular Chain

    Institute of Scientific and Technical Information of China (English)

    WEN Ping-Ping; LI Liang-Sheng; ZHENG Ning; SHI Qing-Fan

    2010-01-01

    @@ Static packing structures of two-dimensional granular chains are investigated experimentally.It is shown that the packing density approximates the saturation with the exponential law as the length of chain increases.The packing structures are globally disordered,while the local square crystallization is found by using the radial distribution function.This characteristic phase of chain packing is similar to a liquid crystal state,and has properties between a conventional liquid and solid crystal.

  11. THE DEGENERACY PROBLEM OF TWO-DIMENSIONAL LINEAR RECURRING ARRAYS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The degeneracy degree and degeneracy position sets of a wo-dimensional linear recurrence relation set are characterized. The fact that a linear recurring array is essentially a doubly periodic array is shown. By using the Grbner base theory, a calculation formula for degeneracy degree is given and the existence of a special degeneracy position set is proved. In the present paper, the degeneracy problem of the two-dimensional linear recurring arrays is completely solved.

  12. Slipping and Rolling on an Inclined Plane

    Science.gov (United States)

    Aghamohammadi, Cina; Aghamohammadi, Amir

    2011-01-01

    In the first part of the paper, using a direct calculation two-dimensional motion of a particle sliding on an inclined plane is investigated for general values of friction coefficient ([mu]). A parametric equation for the trajectory of the particle is also obtained. In the second part of the paper, the motion of a sphere on the inclined plane is…

  13. Two-Dimensional Identification of Fetal Tooth Germs.

    Science.gov (United States)

    Seabra, Mariana; Vaz, Paula; Valente, Francisco; Braga, Ana; Felino, António

    2017-03-01

      To demonstrate the efficiency and applicability of two-dimensional ultrasonography in the identification of tooth germs and in the assessment of potential pathology.   Observational, descriptive, cross-sectional study.   Prenatal Diagnosis Unit of Centro Hospitalar de Vila Nova de Gaia / Espinho-Empresa Pública in Portugal.   A total of 157 white pregnant women (median age, 32 years; range, 14 to 47 years) undergoing routine ultrasound exams.   Description of the fetal tooth germs, as visualized by two-dimensional ultrasonography, including results from prior fetal biometry and detailed screening for malformations.   In the first trimester group, ultrasonography identified 10 tooth germs in the maxilla and 10 tooth germs in the mandible in all fetuses except for one who presented eight maxillary tooth germs. This case was associated with a chromosomal abnormality (trisomy 13) with a bilateral cleft palate. In the second and third trimesters group, ultrasonography identified a larger range of tooth germs: 81.2% of fetuses showed 10 tooth germs in the maxilla and 85.0% of fetuses had 10 tooth germs in the mandible. Hypodontia was more prevalent in the maxilla than in the mandible, which led us to use qualitative two-dimensional ultrasonography to analyze the possible association between hypodontia and other variables such as fetal pathology, markers, head, nuchal, face, and spine.   We recommend using this method as the first exam to evaluate fetal morphology and also to help establish accurate diagnosis of abnormalities in pregnancy.

  14. Electromagnetically induced two-dimensional grating assisted by incoherent pump

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang, E-mail: wrg@snnu.edu.cn

    2017-04-25

    We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication. - Highlights: • Two-dimensional grating is coherently induced in four-level atoms. • Phase and gain-phase gratings are obtained assisted by incoherent pump. • The diffraction power is improved due to the enhanced refraction modulation. • The gratings can be utilized as multi-channel all-optical splitter and router.

  15. a First Cryptosystem for Security of Two-Dimensional Data

    Science.gov (United States)

    Mishra, D. C.; Sharma, Himani; Sharma, R. K.; Kumar, Naveen

    In this paper, we present a novel technique for security of two-dimensional data with the help of cryptography and steganography. The presented approach provides multilayered security of two-dimensional data. First layer security was developed by cryptography and second layer by steganography. The advantage of steganography is that the intended secret message does not attract attention to itself as an object of scrutiny. This paper proposes a novel approach for encryption and decryption of information in the form of Word Data (.doc file), PDF document (.pdf file), Text document, Gray-scale images, and RGB images, etc. by using Vigenere Cipher (VC) associated with Discrete Fourier Transform (DFT) and then hiding the data behind the RGB image (i.e. steganography). Earlier developed techniques provide security of either PDF data, doc data, text data or image data, but not for all types of two-dimensional data and existing techniques used either cryptography or steganography for security. But proposed approach is suitable for all types of data and designed for security of information by cryptography and steganography. The experimental results for Word Data, PDF document, Text document, Gray-scale images and RGB images support the robustness and appropriateness for secure transmission of these data. The security analysis shows that the presented technique is immune from cryptanalytic. This technique further provides security while decryption as a check on behind which RGB color the information is hidden.

  16. A Two-dimensional Magnetohydrodynamics Scheme for General Unstructured Grids

    Science.gov (United States)

    Livne, Eli; Dessart, Luc; Burrows, Adam; Meakin, Casey A.

    2007-05-01

    We report a new finite-difference scheme for two-dimensional magnetohydrodynamics (MHD) simulations, with and without rotation, in unstructured grids with quadrilateral cells. The new scheme is implemented within the code VULCAN/2D, which already includes radiation hydrodynamics in various approximations and can be used with arbitrarily moving meshes (ALEs). The MHD scheme, which consists of cell-centered magnetic field variables, preserves the nodal finite difference representation of divB by construction, and therefore any initially divergence-free field remains divergence-free through the simulation. In this paper, we describe the new scheme in detail and present comparisons of VULCAN/2D results with those of the code ZEUS/2D for several one-dimensional and two-dimensional test problems. The code now enables two-dimensional simulations of the collapse and explosion of the rotating, magnetic cores of massive stars. Moreover, it can be used to simulate the very wide variety of astrophysical problems for which multidimensional radiation magnetohydrodynamics (RMHD) is relevant.

  17. Procedures for two-dimensional electrophoresis of proteins

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. A two-dimensional analytical model of petroleum vapor intrusion

    Science.gov (United States)

    Yao, Yijun; Verginelli, Iason; Suuberg, Eric M.

    2016-02-01

    In this study we present an analytical solution of a two-dimensional petroleum vapor intrusion model, which incorporates a steady-state diffusion-dominated vapor transport in a homogeneous soil and piecewise first-order aerobic biodegradation limited by oxygen availability. This new model can help practitioners to easily generate two-dimensional soil gas concentration profiles for both hydrocarbons and oxygen and estimate hydrocarbon indoor air concentrations as a function of site-specific conditions such as source strength and depth, reaction rate constant, soil characteristics and building features. The soil gas concentration profiles generated by this new model are shown in good agreement with three-dimensional numerical simulations and two-dimensional measured soil gas data from a field study. This implies that for cases involving diffusion dominated soil gas transport, steady state conditions and homogenous source and soil, this analytical model can be used as a fast and easy-to-use risk screening tool by replicating the results of 3-D numerical simulations but with much less computational effort.

  19. Strongly correlated two-dimensional plasma explored from entropy measurements.

    Science.gov (United States)

    Kuntsevich, A Y; Tupikov, Y V; Pudalov, V M; Burmistrov, I S

    2015-06-23

    Charged plasma and Fermi liquid are two distinct states of electronic matter intrinsic to dilute two-dimensional electron systems at elevated and low temperatures, respectively. Probing their thermodynamics represents challenge because of lack of an adequate technique. Here, we report a thermodynamic method to measure the entropy per electron in gated structures. Our technique appears to be three orders of magnitude superior in sensitivity to a.c. calorimetry, allowing entropy measurements with only 10(8) electrons. This enables us to investigate the correlated plasma regime, previously inaccessible experimentally in two-dimensional electron systems in semiconductors. In experiments with clean two-dimensional electron system in silicon-based structures, we traced entropy evolution from the plasma to Fermi liquid regime by varying electron density. We reveal that the correlated plasma regime can be mapped onto the ordinary non-degenerate Fermi gas with an interaction-enhanced temperature-dependent effective mass. Our method opens up new horizons in studies of low-dimensional electron systems.

  20. Experimental realization of two-dimensional boron sheets.

    Science.gov (United States)

    Feng, Baojie; Zhang, Jin; Zhong, Qing; Li, Wenbin; Li, Shuai; Li, Hui; Cheng, Peng; Meng, Sheng; Chen, Lan; Wu, Kehui

    2016-06-01

    A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp(2) hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.

  1. Two-dimensional oxides: multifunctional materials for advanced technologies.

    Science.gov (United States)

    Pacchioni, Gianfranco

    2012-08-13

    The last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low-dimensionality of the oxide layer, which sometimes leads to truly two-dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two-dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two-dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal-oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. The Bargmann type reduction for some Lax integrable two-dimensional generalization of the relativistic Toda lattice

    Directory of Open Access Journals (Sweden)

    O. Ye. Hentosh

    2016-01-01

    Full Text Available The possibility of applying the method of reducing upon finite-dimensional invariant subspaces, generated by the eigenvalues of the associated spectral problem, to some two-dimensional generalization of the relativistic Toda lattice with the triple matrix Lax type linearization is investigated. The Hamiltonian property and Lax-Liouville integrability of the vector fields, given by this system, on the invariant subspace related with the Bargmann type reduction are found out.

  3. The focusing effect of electromagnetic waves in two-dimensional photonic crystals with gradually varying lattice constant

    Directory of Open Access Journals (Sweden)

    F Bakhshi Garmi

    2016-02-01

    Full Text Available In this paper we studied the focusing effect of electromagnetic wave in the two-dimensional graded photonic crystal consisting of Silicon rods in the air background with gradually varying lattice constant. The results showed that graded photonic crystal can focus wide beams on a narrow area at frequencies near the lower edge of the band gap, where equal frequency contours are not concave. For calculation of photonic band structure and equal frequency contours, we have used plane wave expansion method and revised plane wave expansion method, respectively. The calculation of the electric and magnetic fields was performed by finite difference time domain method.

  4. Two-Dimensional Breather Lattice Solutions and Compact-Like Discrete Breathers and Their Stability in Discrete Two-Dimensional Monatomic β-FPU Lattice

    Institute of Scientific and Technical Information of China (English)

    XU Quan; TIAN Qiang

    2009-01-01

    We restrict our attention to the discrete two-dimensional monatomic β-FPU lattice. We look for twodimensional breather lattice solutions and two-dimensional compact-like discrete breathers by using trying method and analyze their stability by using Aubry's linearly stable theory. We obtain the conditions of existence and stability of two-dimensional breather lattice solutions and two-dimensional compact-like discrete breathers in the discrete twodimensional monatomic β-FPU lattice.

  5. The characters of nonlinear vibration in the two-dimensional discrete monoatomic lattice

    Institute of Scientific and Technical Information of China (English)

    XU Quan; TIAN Qiang

    2005-01-01

    The two-dimensional discrete monoatomic lattice is analyzed. Taking nearest-neighbor interaction into account, the characters of the nonlinear vibration in two-dimensional discrete monoatomic lattice are described by the two-dimensional cubic nonlinear Schrodinger equation. Considering the quartic nonlinear potential, the two-dimensional discrete-soliton trains and the solutions perturbed by the neck mode are presented.

  6. Nonlinear acoustic propagation in two-dimensional ducts

    Science.gov (United States)

    Nayfeh, A. H.; Tsai, M.-S.

    1974-01-01

    The method of multiple scales is used to obtain a second-order uniformly valid expansion for the nonlinear acoustic wave propagation in a two-dimensional duct whose walls are treated with a nonlinear acoustic material. The wave propagation in the duct is characterized by the unsteady nonlinear Euler equations. The results show that nonlinear effects tend to flatten and broaden the absorption versus frequency curve, in qualitative agreement with the experimental observations. Moreover, the effect of the gas nonlinearity increases with increasing sound frequency, whereas the effect of the material nonlinearity decreases with increasing sound frequency.

  7. Three-dimensional versus two-dimensional vision in laparoscopy

    DEFF Research Database (Denmark)

    Sørensen, Stine Maya Dreier; Savran, Mona M; Konge, Lars;

    2016-01-01

    BACKGROUND: Laparoscopic surgery is widely used, and results in accelerated patient recovery time and hospital stay were compared with laparotomy. However, laparoscopic surgery is more challenging compared with open surgery, in part because surgeons must operate in a three-dimensional (3D) space...... through a two-dimensional (2D) projection on a monitor, which results in loss of depth perception. To counter this problem, 3D imaging for laparoscopy was developed. A systematic review of the literature was performed to assess the effect of 3D laparoscopy. METHODS: A systematic search of the literature...

  8. The Rare Two-Dimensional Materials with Dirac Cones

    OpenAIRE

    Wang, Jinying; Deng, Shibin; Liu, Zhongfan; Liu, Zhirong

    2014-01-01

    Inspired by the great development of graphene, more and more works have been conducted to seek new two-dimensional (2D) materials with Dirac cones. Although 2D Dirac materials possess many novel properties and physics, they are rare compared with the numerous 2D materials. To provide explanation for the rarity of 2D Dirac materials as well as clues in searching for new Dirac systems, here we review the recent theoretical aspects of various 2D Dirac materials, including graphene, silicene, ger...

  9. Magnetic reconnection in two-dimensional magnetohydrodynamic turbulence.

    Science.gov (United States)

    Servidio, S; Matthaeus, W H; Shay, M A; Cassak, P A; Dmitruk, P

    2009-03-20

    Systematic analysis of numerical simulations of two-dimensional magnetohydrodynamic turbulence reveals the presence of a large number of X-type neutral points where magnetic reconnection occurs. We examine the statistical properties of this ensemble of reconnection events that are spontaneously generated by turbulence. The associated reconnection rates are distributed over a wide range of values and scales with the geometry of the diffusion region. Locally, these events can be described through a variant of the Sweet-Parker model, in which the parameters are externally controlled by turbulence. This new perspective on reconnection is relevant in space and astrophysical contexts, where plasma is generally in a fully turbulent regime.

  10. Logarithmic divergent thermal conductivity in two-dimensional nonlinear lattices.

    Science.gov (United States)

    Wang, Lei; Hu, Bambi; Li, Baowen

    2012-10-01

    Heat conduction in three two-dimensional (2D) momentum-conserving nonlinear lattices are numerically calculated via both nonequilibrium heat-bath and equilibrium Green-Kubo algorithms. It is expected by mainstream theories that heat conduction in such 2D lattices is divergent and the thermal conductivity κ increases with lattice length N logarithmically. Our simulations for the purely quartic lattice firmly confirm it. However, very robust finite-size effects are observed in the calculations for the other two lattices, which well explain some existing studies and imply the extreme difficulties in observing their true asymptotic behaviors with affordable computation resources.

  11. Theories on Frustrated Electrons in Two-Dimensional Organic Solids

    Directory of Open Access Journals (Sweden)

    Chisa Hotta

    2012-08-01

    Full Text Available Two-dimensional quarter-filled organic solids are a promising class of materials to realize the strongly correlated insulating states called dimer Mott insulator and charge order. In their conducting layer, the molecules form anisotropic triangular lattices, harboring geometrical frustration effect, which could give rise to many interesting states of matter in the two insulators and in the metals adjacent to them. This review is concerned with the theoretical studies on such issue over the past ten years, and provides the systematic understanding on exotic metals, dielectrics, and spin liquids, which are the consequences of the competing correlation and fluctuation under frustration.

  12. Wake-induced bending of two-dimensional plasma crystals

    Energy Technology Data Exchange (ETDEWEB)

    Röcker, T. B., E-mail: tbr@mpe.mpg.de; Ivlev, A. V., E-mail: ivlev@mpe.mpg.de; Zhdanov, S. K.; Morfill, G. E. [Max Planck Institute for Extraterrestrial Physics, 85741 Garching (Germany); Couëdel, L. [CNRS, Aix-Marseille-Université, Laboratoire de Physique des Interactions Ioniques et Moléculaires, UMR 7345, 13397 Marseille Cedex 20 (France)

    2014-07-15

    It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.

  13. Wake-induced bending of two-dimensional plasma crystals

    CERN Document Server

    Röcker, T B; Zhdanov, S K; Couëdel, L; Morfill, G E

    2014-01-01

    It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.

  14. Corner wetting transition in the two-dimensional Ising model

    Science.gov (United States)

    Lipowski, Adam

    1998-07-01

    We study the interfacial behavior of the two-dimensional Ising model at the corner of weakened bonds. Monte Carlo simulations results show that the interface is pinned to the corner at a lower temperature than a certain temperature Tcw at which it undergoes a corner wetting transition. The temperature Tcw is substantially lower than the temperature of the ordinary wetting transition with a line of weakened bonds. A solid-on-solid-like model is proposed, which provides a supplementary description of the corner wetting transition.

  15. Dynamic Multiscaling in Two-dimensional Fluid Turbulence

    CERN Document Server

    Ray, Samriddhi Sankar; Perlekar, Prasad; Pandit, Rahul

    2011-01-01

    We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.

  16. Kinetic analysis of two dimensional metallic grating Cerenkov maser

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Ding [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-08-15

    The dispersion relation of two dimensional metallic grating Cerenkov maser has been given by using kinetic analysis, in which the influence of electron movement is directly considered without using an equivalent dielectric medium assumption. The effects of structural parameters and beam state on the interaction gain and synchronous frequency have also been investigated in detail by numerical calculations. To an illustrative case, the quantitative relations produced from varying the gap distance between electron beam and metallic grating, beam current, electron transverse to axial velocity ratio, and electron axial velocity spread have been obtained. The developed method can be used to predict the real interaction system performances.

  17. Duality, Monodromy and Integrability of Two Dimensional String Effective Action

    CERN Document Server

    Das, A; Melikyan, A; Das, Ashok

    2002-01-01

    The monodromy matrix, ${\\hat{\\cal M}}$, is constructed for two dimensional tree level string effective action. The pole structure of ${\\hat{\\cal M}}$ is derived using its factorizability property. It is found that the monodromy matrix transforms non-trivially under the non-compact T-duality group, which leaves the effective action invariant and this can be used to construct the monodromy matrix for more complicated backgrounds starting from simpler ones. We construct, explicitly, ${\\hat{\\cal M}}$ for the exactly solvable Nappi-Witten model, both when B=0 and $B\

  18. Homogenization of Two-Dimensional Phononic Crystals at Low Frequencies

    Institute of Scientific and Technical Information of China (English)

    NI Qing; CHENG Jian-Chun

    2005-01-01

    @@ Effective velocities of elastic waves propagating in two-dimensional phononic crystal at low frequencies are analysed theoretically, and exact analytical formulas for effective velocities of elastic waves are derived according to the method presented by Krokhin et al. [Phys. Rev. Lett. 91 (2003) 264302]. Numerical calculations for phononic crystals consisted of array of Pb cylinders embedded in epoxy show that the composites have distinct anisotropy at low filling fraction. The anisotropy increases as the filling fraction increases, while as the filling fraction closes to the limitation, the anisotropy decreases.

  19. Electronic Transmission Properties of Two-Dimensional Quasi-Lattice

    Institute of Scientific and Technical Information of China (English)

    侯志林; 傅秀军; 刘有延

    2002-01-01

    In the framework of the tight binding model, the electronic transmission properties of two-dimensional Penrose lattices with free boundary conditions are studied using the generalized eigenfunction method (Phys. Rev. B 60(1999)13444). The electronic transmission coefficients for Penrose lattices with different sizes and widths are calculated, and the result shows strong energy dependence because of the quasiperiodic structure and quantum coherent effect. Around the Fermi level E = 0, there is an energy region with zero transmission amplitudes,which suggests that the studied systems are insulating. The spatial distributions of several typical electronic states with different transmission coefficients are plotted to display the propagation process.

  20. Two-dimensional conformal field theory and the butterfly effect

    CERN Document Server

    Roberts, Daniel A

    2014-01-01

    We study chaotic dynamics in two-dimensional conformal field theory through out-of-time order thermal correlators of the form $\\langle W(t)VW(t)V\\rangle$. We reproduce bulk calculations similar to those of [1], by studying the large $c$ Virasoro identity block. The contribution of this block to the above correlation function begins to decrease exponentially after a delay of $\\sim t_* - \\frac{\\beta}{2\\pi}\\log \\beta^2E_w E_v$, where $t_*$ is the scrambling time $\\frac{\\beta}{2\\pi}\\log c$, and $E_w,E_v$ are the energy scales of the $W,V$ operators.