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1

Robust two-dimensional spatial solitons in liquid carbon disulfide.  

PubMed

The excitation of near-infrared (2+1)D solitons in liquid carbon disulfide is demonstrated due to the simultaneous contribution of the third- and fifth-order susceptibilities. Solitons propagating free from diffraction for more than 10 Rayleigh lengths although damped, were observed to support the proposed soliton behavior. Numerical calculations using a nonlinear Schrödinger-type equation were also performed. PMID:23383790

Falcăo-Filho, Edilson L; de Araújo, Cid B; Boudebs, Georges; Leblond, Hervé; Skarka, Vladimir

2013-01-02

2

Fully localized two-dimensional embedded solitons  

SciTech Connect

We report the prediction of fully localized two-dimensional embedded solitons. These solitons are obtained in a quasi-one-dimensional waveguide array which is periodic along one spatial direction and localized along the orthogonal direction. Under appropriate nonlinearity, these solitons are found to exist inside the Bloch bands (continuous spectrum) of the waveguide and thus are embedded solitons. These embedded solitons are fully localized along both spatial directions. In addition, they are fully stable under perturbations.

Yang Jianke [Department of Mathematics and Statistics, University of Vermont, Burlington, Vermont 05401 (United States)

2010-11-15

3

Exact vortex solitons in a quasi-two-dimensional Bose-Einstein condensate with spatially inhomogeneous cubic-quintic nonlinearity  

NASA Astrophysics Data System (ADS)

The exact vortex soliton solutions of the quasi-two-dimensional cubic-quintic Gross-Pitaevskii equation with spatially inhomogeneous nonlinearities are constructed by similarity transformation. It is demonstrated that spatially inhomogeneous cubic-quintic nonlinearity can support exact vortex solitons in which there are two quantum numbers S and m. The radius structures and density distributions of these vortex solitons are studied, and it is shown that the number of ring structure of the vortex solitons increases by one with increasing the "radial quantum number" m by one.

Wang, Deng-Shan; Zeng, Xin; Ma, Yu-Quan

2012-10-01

4

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Self-Similar Hermite-Gaussian Spatial Solitons in Two-Dimensional Nonlocal Nonlinear Media  

NASA Astrophysics Data System (ADS)

We study analytically and numerically the propagation of spatial solitons in a two-dimensional strongly nonlocal nonlinear medium. Exact analytical solutions in the form of self-similar spatial solitons are obtained involving higher-order Hermite-Gaussian functions. Our theoretical predictions provide new insights into the low-energy spatial soliton transmission with high fidelity.

Yang, Bin; Zhong, Wei-Ping; Beli?, Milivoj R.

2010-05-01

5

Chaotic spatial soliton rays in smooth two-dimensional optical lattices.  

PubMed

The light ray of a spatial soliton in an optical film whose refractive index is smoothly modulated (wavelength much larger than the typical soliton width) in both spatial directions is shown to possess chaotic regimes for which the propagation is erratic. This is interpreted as a parametric driven pendulum, obtained by what we believe to be a new perturbative approach of the Maxwell's equation. These findings are then demonstrated to compare well to the eikonal law of light ray propagation (nonlinearity compensates diffraction). PMID:19881599

Khomeriki, R; Leon, J

2009-11-01

6

Two-dimensional interaction of ion-acoustic solitons  

Microsoft Academic Search

The two-dimensional nonlinear interaction of two planar ion-acoustic solitons has been studied experimentally. When the angle between the wave vectors of the two interacting solitons is small and the soliton amplitudes approach a critical value, a resonant three-soliton interaction occurs.

P. A. Folkes; H. Ikezi; R. Davis

1980-01-01

7

Two-dimensional stability of ion-acoustic solitons  

Microsoft Academic Search

Two dimensional generalizations of the Korteweg-de Vries equation appropriate to the propagation of nonlinear ion-acoustic waves are obtained. Soliton solutions are found to exist and they are shown to be stable to two dimensional perturbations.

M. Kako; G. Rowlands

1976-01-01

8

Two dimensional diffraction managed soliton in cubic-quintic nonlinear media  

Microsoft Academic Search

The nonlinear Schrodinger equation which governs the dy- namics of two dimensional spatial solitons in cubic-quintic media with vary- ing diffraction coefficient is analyzed in this paper using variational ap- proach and numerical studies. The variational equations are solved numer- ically and the phase portraits reveal that diffraction management prevents the collapse of solitons. The direct partial differential equation solution

P. A. Subha; C. P. Jisha; V. C. Kuriakose

9

Pairing of Solitons in Two-Dimensional S=1 Magnets  

SciTech Connect

We study a general model of isotropic two-dimensional spin-1 magnet, which is relevant for the physics of ultracold atoms with hyperfine S=1 spins in an optical lattice at odd filling. We demonstrate a novel mechanism of soliton pairing occurring in the vicinity of a special point with an enhanced SU(3) symmetry: upon perturbing the SU(3) symmetry, solitons with odd CP{sup 2} topological charge are confined into pairs that remain stable objects.

Ivanov, B. A. [Institute of Magnetism, National Academy of Sciences and Ministry of Education, 03142 Kiev (Ukraine); T. Shevchenko Kiev National University, 03127 Kiev (Ukraine); Khymyn, R. S. [T. Shevchenko Kiev National University, 03127 Kiev (Ukraine); Kolezhuk, A. K. [Institut fuer Theoretische Physik C, RWTH Aachen, D-52056 Aachen (Germany)

2008-02-01

10

Exciton-Polariton Gap Solitons in Two-Dimensional Lattices  

NASA Astrophysics Data System (ADS)

We report on the two-dimensional gap-soliton nature of exciton-polariton macroscopic coherent phases (PMCP) in a square lattice with a tunable amplitude. The resonantly excited PMCP forms close to the negative mass M point of the lattice band structure with energy within the lattice band gap and its wave function localized within a few lattice periods. The PMCPs are well described as gap solitons resulting from the interplay between repulsive polariton-polariton interactions and effective attractive forces due to the negative mass. The solitonic nature accounts for the reduction of the PMCP coherence length and optical excitation threshold with increasing lattice amplitude.

Cerda-Méndez, E. A.; Sarkar, D.; Krizhanovskii, D. N.; Gavrilov, S. S.; Biermann, K.; Skolnick, M. S.; Santos, P. V.

2013-10-01

11

Dragging two-dimensional discrete solitons by moving linear defects  

SciTech Connect

We study the mobility of small-amplitude solitons attached to moving defects which drag the solitons across a two-dimensional (2D) discrete nonlinear Schroedinger lattice. Findings are compared to the situation when a free small-amplitude 2D discrete soliton is kicked in a uniform lattice. In agreement with previously known results, after a period of transient motion the free soliton transforms into a localized mode pinned by the Peierls-Nabarro potential, irrespective of the initial velocity. However, the soliton attached to the moving defect can be dragged over an indefinitely long distance (including routes with abrupt turns and circular trajectories) virtually without losses, provided that the dragging velocity is smaller than a certain critical value. Collisions between solitons dragged by two defects in opposite directions are studied too. If the velocity is small enough, the collision leads to a spontaneous symmetry breaking, featuring fusion of two solitons into a single one, which remains attached to either of the two defects.

Brazhnyi, Valeriy A.; Malomed, Boris A. [Centro de Fisica do Porto, Faculdade de Ciencias, Universidade do Porto, Rua Campo Alegre 687, Porto P-4169-007 (Portugal); Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel) and ICFO-Institut de Ciencies Fotoniques and Universitat Politecnica de Catalunya, Mediterranean Technology Park, E-08860 Castelldefels, Barcelona (Spain)

2011-07-15

12

Dragging two-dimensional discrete solitons by moving linear defects  

NASA Astrophysics Data System (ADS)

We study the mobility of small-amplitude solitons attached to moving defects which drag the solitons across a two-dimensional (2D) discrete nonlinear Schrödinger lattice. Findings are compared to the situation when a free small-amplitude 2D discrete soliton is kicked in a uniform lattice. In agreement with previously known results, after a period of transient motion the free soliton transforms into a localized mode pinned by the Peierls-Nabarro potential, irrespective of the initial velocity. However, the soliton attached to the moving defect can be dragged over an indefinitely long distance (including routes with abrupt turns and circular trajectories) virtually without losses, provided that the dragging velocity is smaller than a certain critical value. Collisions between solitons dragged by two defects in opposite directions are studied too. If the velocity is small enough, the collision leads to a spontaneous symmetry breaking, featuring fusion of two solitons into a single one, which remains attached to either of the two defects.

Brazhnyi, Valeriy A.; Malomed, Boris A.

2011-07-01

13

Dissipative vortex solitons in two-dimensional lattices  

SciTech Connect

We report the existence of stable symmetric vortex-type solutions for two-dimensional nonlinear discrete dissipative systems governed by a cubic-quintic complex Ginzburg-Landau equation. We construct a whole family of vortex solitons with a topological charge S=1. Surprisingly, the dynamical evolution of unstable solutions of this family does not significantly alter their profile, but instead their phase distribution completely changes; they transform into two-charge swirl-vortex solitons. We dynamically excite this structure showing its experimental feasibility.

Mejia-Cortes, C.; Soto-Crespo, J. M. [Instituto de Optica, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Molina, Mario I.; Vicencio, Rodrigo A. [Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Center for Optics and Photonics, Universidad de Concepcion, Casilla 4016, Concepcion (Chile)

2010-12-15

14

Two-dimensional solitons in media with stripe-shaped nonlinearity modulation  

SciTech Connect

We introduce a model of media with the cubic attractive nonlinearity concentrated along a single or double stripe in the two-dimensional (2D) plane. The model can be realized in terms of nonlinear optics (in the spatial and temporal domains alike) and BEC. It is known from recent works that search for stable 2D solitons in models with a spatially localized self-attractive nonlinearity is a challenging problem. We make use of the variational approximation (VA) and numerical methods to investigate conditions for the existence and stability of solitons in the present setting. The result crucially depends on the transverse shape of the stripe: while the rectangular profile supports stable 2D solitons, its smooth Gaussian-shaped counterpart makes all the solitons unstable. This difference is explained, in particular, by the VA. The double stripe with the rectangular profile admits stable solitons of three distinct types: symmetric and asymmetric ones with a single-peak, and double-peak symmetric solitons. The shape and stability of the single-peak solitons of either type are accurately predicted by the VA. Collisions between identical stable solitons are briefly considered too, by means of direct simulations. Depending on the collision velocity, we observe excitation of intrinsic oscillations of the solitons, or their decay, or the collapse (catastrophic self-focusing).

Hung, Nguyen Viet; Zin, Pawel [Soltan Institute for Nuclear Studies, Hoza 69, PL-00-681 Warsaw (Poland); Trippenbach, Marek [Institute of Theoretical Physics, Physics Department, Warsaw University, Hoza 69, PL-00-681 Warsaw (Poland); Malomed, Boris A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)

2010-10-15

15

Matter-wave two-dimensional solitons in crossed linear and nonlinear optical lattices  

NASA Astrophysics Data System (ADS)

The existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with a linear optical lattice (LOL) in the x direction and a nonlinear optical lattice (NOL) in the y direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance is demonstrated. In particular, we show that such crossed LOLs and NOLs allow for stabilizing two-dimensional solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach, with the Vakhitov-Kolokolov necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation. Very good agreement of the results corresponding to both treatments is observed.

da Luz, H. L. F.; Abdullaev, F. Kh.; Gammal, A.; Salerno, M.; Tomio, Lauro

2010-10-01

16

Delayed-action interaction between two-dimensional composite solitons  

Microsoft Academic Search

Summary form only given. Soliton interactions are universal, displaying features common to all solitons, in spite of the diversity of the physical systems in which solitons are found. The reason for this universality is the fact that solitons can be viewed as modes of their own induced waveguide. The simplest case arises when the self-induced waveguide has only one mode

Z. H. Musslimani; M. Soljacic; M. Segev; D. N. Christodoulides

2001-01-01

17

Stabilization of two-dimensional solitons in cubic-saturable nonlinear lattices  

SciTech Connect

We consider soliton dynamics and stability in a nonlinear lattice formed by alternating domains with focusing cubic and saturable nonlinearities. We find that in such lattices, solitons centered on cubic domains may be stabilized even in two-dimensional geometries, in spite of their intrinsic catastrophic instability in the absence of the lattice. Solitons centered on saturable domains are always unstable.

Borovkova, Olga V.; Kartashov, Yaroslav V.; Torner, Lluis [ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain)

2010-06-15

18

Self-trapping of two-dimensional vector dipole solitons in nonlocal media  

SciTech Connect

We study the self-trapping of the superposition of two-dimensional vector dipole solitons in nonlocal media with an arbitrary degree of nonlocality. We apply the variational approach to find the exact solution of such vector dipole solitons and investigate their stability by using directly numerical simulations. The dynamics of such vector solitons are also compared with a scalar vortex. We show the nonlocality induces an attractive force which can completely stabilize the vector dipole solitons.

Shen, M.; Ding, H.; Ruan, L.; Pang, S.; Shi, J.; Wang, Q. [Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China); Kong, Q. [Laser Physics Center, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia); Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

2010-10-15

19

Sharp waveguide bends induced by spatial solitons  

SciTech Connect

We experimentally demonstrate the ability of a self-guided laser beam to induce waveguides with sharp bends. The beam is a two-dimensional photorefractive screening-photovoltaic bright spatial soliton generated inside a biased lithium-niobate crystal shaped as a prism. The soliton robustness against total internal reflections is shown to leave place to a low-loss unimodal waveguide undergoing multiple zero-radius 90 deg. turns.

Jaeger, Robert; Gorza, Simon-Pierre; Cambournac, Cyril; Haelterman, Marc; Chauvet, Mathieu [Universite libre de Bruxelles, Service d'optique et acoustique, B-1050 Brussels (Belgium); Institut Femto-ST, Departement d'optique P-M. Duffieux, UMRS CNRS 6174/Universite de Franche-Comte 6174, F-25030 Besancon cedex (France)

2006-02-06

20

Two-dimensional multipeak gap solitons supported by parity-time-symmetric periodic potentials.  

PubMed

We report on the existence and stability of the two-dimensional multipeak gap solitons in a parity-time-symmetric periodic potential with defocusing Kerr nonlinearity. We investigate the multipeak solitons with all the peaks of the real parts in-phase. It is found that these solitons can be stable in the first gap. The system can support not only the stable solitons with even number peaks, but also the stable solitons with odd number peaks. The transverse energy flow vector of these solitons is also studied. PMID:23903123

Zhu, Xing; Wang, Hong; Li, Huagang; He, Wei; He, Yingji

2013-08-01

21

Subwavelength solitons and Faraday waves in two-dimensional lattices of metal nanoparticles.  

PubMed

We demonstrate that optically driven two-dimensional lattices of nonlinear metal nanoparticles can support a variety of dissipative localized modes including Faraday ripples, trapped and walking solitons, oscillons, and switching waves connecting different polarization states. PMID:23939109

Noskov, Roman E; Smirnova, Daria A; Kivshar, Yuri S

2013-07-15

22

Quantum Quasi-Solitons in the Two-Dimensional Ferromagnetic Lattice with AN External Field  

NASA Astrophysics Data System (ADS)

Based on the quantum theory and a simplified version of the multiple-scale method, the nonlinear excitations in a two-dimensional ferromagnetic lattice with an external magnetic field are analytically investigated. The standard two-dimensional nonlinear Schrödinger equation is obtained. Results show that the quantum quasi-soliton can exist in the two-dimensional ferromagnetic lattice. In addition, when the group velocity is equal to zero, at the boundary of the Brillouin zone, the quantum quasi-soliton becomes the quantum intrinsic localized mode.

Li, De-Jun; Tang, Bing; Hu, Ke; Tang, Yi

2013-04-01

23

Asymmetric spatial soliton dragging.  

PubMed

A new low-latency, cascadable optical logic gate with gain, high contrast, and three-terminal input-output isolation is introduced. The interaction between two orthogonally polarized spatial solitons brought into coincidence at the boundary of a saturating nonlinear medium and propagating in different directions results in the phase-insensitive spatial dragging of a strong pump soliton by a weaker signal. As a result, the strong pump is transmitted through an aperture when the weak signal is not present, and it is dragged to the side by more than a beam width and blocked in the presence of the weak signal, thus implementing an inverter with gain. A multi-input, logically complete NOR gate also can be implemented in a cascaded system. PMID:19855703

Blair, S; Wagner, K; McLeod, R

1994-12-01

24

Vortex and dipole solitons in complex two-dimensional nonlinear lattices  

NASA Astrophysics Data System (ADS)

Using computational methods, it is found that the two-dimensional nonlinear Schrödinger (NLS) equation with a quasicrystal lattice potential admits multiple dipole and vortex solitons. The linear and the nonlinear stability of these solitons is investigated using direct simulations of the NLS equation and its linearized equation. It is shown that certain multiple vortex structures on quasicrystal lattices can be linearly unstable but nonlinearly stable. These results have application to investigations of localized structures in nonlinear optics and Bose-Einstein condensates.

Ablowitz, Mark J.; Antar, Nalan; Bak?rta?, ?lkay; Ilan, Boaz

2012-09-01

25

Collapse suppression and stabilization of dipole solitons in two-dimensional media with anisotropic semilocal nonlinearity  

SciTech Connect

We consider the impact of anisotropic nonlocality on the arrest of the collapse and stabilization of dipole-mode (DM) solitons in two-dimensional (2D) models of optical media with the diffusive nonlinearity. The nonlocal nonlinearity is made anisotropic through elliptic diffusivity. The medium becomes semilocal in the limit case of 1D diffusivity. Families of fundamental and DM solitons are found by means of the variational approximation and in a numerical form. We demonstrate that the collapse of 2D beams is arrested even in the semilocal system. The anisotropic nonlocality readily stabilizes the DM solitons, which are completely unstable in the isotropic medium.

Ye Fangwei; He Yingji [Department of Physics, Centre for Nonlinear Studies, and Beijing-Hong Kong Singapore Joint Centre for Nonlinear and Complex Systems, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Malomed, Boris A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Hu Bambi [Department of Physics, Centre for Nonlinear Studies, and Beijing-Hong Kong Singapore Joint Centre for Nonlinear and Complex Systems, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Department of Physics, University of Houston, Houston, Texas 77204-5005 (United States)

2010-04-15

26

Two-dimensional solitons with hidden and explicit vorticity in bimodal cubic-quintic media  

NASA Astrophysics Data System (ADS)

We demonstrate that two-dimensional two-component bright solitons of an annular shape, carrying vorticities (m,ąm) in the components, may be stable in media with the cubic-quintic nonlinearity, including the hidden-vorticity (HV) solitons of the type (m,-m) , whose net vorticity is zero. Stability regions for the vortices of both (m,ąm) types are identified for m=1 , 2, and 3, by dint of the calculation of stability eigenvalues, and in direct simulations. In addition to the well-known symmetry-breaking (external) instability, which splits the ring soliton into a set of fragments flying away in tangential directions, we report two new scenarios of the development of weak instabilities specific to the HV solitons. One features charge flipping, with the two components exchanging angular momentum and periodically reversing the sign of their spins. The composite soliton does not directly split in this case; therefore, we identify such instability as an intrinsic one. Eventually, the soliton splits, as weak radiation loss drives it across the border of the ordinary strong (external) instability. Another scenario proceeds through separation of the vortex cores in the two components, each individual core moving toward the outer edge of the annular soliton. After expulsion of the cores, there remains a zero-vorticity breather with persistent internal vibrations.

Desyatnikov, A. S.; Mihalache, D.; Mazilu, D.; Malomed, B. A.; Denz, C.; Lederer, F.

2005-02-01

27

Impurity-Pinned Solitons in the Two-Dimensional Antiferromagnet Detected by Electron Paramagnetic Resonance  

NASA Astrophysics Data System (ADS)

It is shown that the introduction of a very small amount of nonmagnetic impurities into the magnetic sites of a classical two-dimensional antiferromagnet creates a new type of static (impurity-pinned) soliton that affects the Arrhenius, exp\\(-E/T\\), temperature-dependent electron paramagnetic resonance linewidth by drastically changing the parameter E. Data just above the transition temperature for \\(C3H7NH3\\)2MxMn1-xCl4 confirm the existence of these impurity-pinned solitons.

Subbaraman, K.; Zaspel, C. E.; Drumheller, John E.

1998-03-01

28

Two-dimensional solitons at interfaces between binary superlattices and homogeneous lattices  

SciTech Connect

We report on the experimental observation of two-dimensional surface solitons residing at the interface between a homogeneous square lattice and a superlattice that consists of alternating 'deep' and 'shallow' waveguides. By exciting single waveguides in the first row of the superlattice, we show that solitons centered on deep sites require much lower powers for their excitation than their respective counterparts centered on shallow sites. Despite the fact that the average refractive index of the superlattice waveguides is equal to the refractive index of the homogeneous lattice, the interface results in clearly asymmetric output patterns.

Heinrich, M.; Ramirez, L. P. R.; Dreisow, F.; Keil, R.; Nolte, S.; Tuennermann, A. [Institute of Applied Physics, Friedrich-Schiller-University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Kartashov, Y. V.; Vysloukh, V. A.; Torner, L. [ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain); Szameit, A. [Physics Department and Solid State Institute, Technion, 32000 Haifa (Israel)

2009-12-15

29

Bright spatial solitons in defocusing Kerr media with PT-symmetric potentials  

SciTech Connect

We show that defocusing Kerr media with parity-time-symmetric potentials can support one- and two-dimensional bright spatial solitons. These solitons are found to be stable over the wide range where they exist. More importantly, we discover an exact one-dimensional solution and a closed two-dimensional solution in the structure.

Shi, Zhiwei; Jiang, Xiujuan [School of Information Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Zhu, Xing [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275 (China); Li, Huagang [Department of Physics, Guangdong Institute of Education, Guangzhou 510303 (China)

2011-11-15

30

Two-dimensional spatial light modulators: a tutorial  

Microsoft Academic Search

Two-dimensional spatial light modulators (SLMs) modulate one of the properties of an optical wavefront (amplitude, phase, polarization) as a function of two spatial dimensions and time in response to information-bearing control signals that may be either optical or electrical. These devices form a critical part of optical information processing systems, serving as input transducers as well as performing several basic

J. A. Neff; RAVINDRA A. ATHALE; SING H. LEE

1990-01-01

31

Delay feedback induces a spontaneous motion of two-dimensional cavity solitons in driven semiconductor microcavities  

NASA Astrophysics Data System (ADS)

We consider a broad area vertical-cavity surface-emitting laser (VCSEL) operating below the lasing threshold and subject to optical injection and time-delayed feedback. We derive a generalized delayed Swift-Hohenberg equation for the VCSEL system, which is valid close to the nascent optical bistability. We first characterize the stationary-cavity solitons by constructing their snaking bifurcation diagram and by showing clustering behavior within the pinning region of parameters. Then, we show that the delayed feedback induces a spontaneous motion of two-dimensional (2D) cavity solitons in an arbitrary direction in the transverse plane. We characterize moving cavity solitons by estimating their threshold and calculating their velocity. Numerical 2D solutions of the governing semiconductor laser equations are in close agreement with those obtained from the delayed generalized Swift-Hohenberg equation.

Tlidi, M.; Averlant, E.; Vladimirov, A.; Panajotov, K.

2012-09-01

32

Energy Transfer through Photorefractive Spatial Soliton Interaction  

NASA Astrophysics Data System (ADS)

In this research, we investigate the interaction between colliding photorefractive spatial solitons. The energy transfer from a vector soliton to a scalar soliton is quantitatively investigated. The energy exchange efficiency increases as the input intensity ratio of the vector soliton increases, while it decreases as the collision angle increases. It is also found that the spatial solitons interact with each other like particles, and the energy of each soliton is conserved after the collision. This observation provides preliminary data for optical computation applications via photorefractive spatial solitons.

Liang, Bao-Lai; Guo, Qing-Lin; Jiang, Yi-Hui; Wang, Ying; Zhang, Su-Heng; Fu, Guang-Sheng

2013-06-01

33

Arresting soliton collapse in two-dimensional nonlinear Schrödinger systems via spatiotemporal modulation of the external potential  

NASA Astrophysics Data System (ADS)

We predict stable, collapse-free solitonslike structures in two-dimensional nonlinear Schrödinger systems in subdiffractive regimes, accomplished by a spatiotemporal modulation of the external potential. We investigate the scaling laws, the stability, and the dynamical properties of these subdiffractive solitons.

Staliunas, Kestutis; Herrero, Ramon; de Valcárcel, Germán J.

2007-01-01

34

Dark and bright photovoltaic spatial solitons  

SciTech Connect

Dark (bright) planar spatial solitons are predicted for photovoltaic photorefractive materials when the diffraction of an optical beam is exactly compensated by nonlinear self-defocusing (focusing) due to the photovoltaic field and electro-optic effect. These solitons may have steady-state irradiances of microwatts to milliwatts per square centimeter and widths as small as 10 [mu]m in lithium niobate. Optical control is provided by incoherent illumination, and the nonlinear index of a dark soliton may be used to trap a bright soliton by rotating the plane of polarization of the soliton field.

Valley, G.C. (Hughes Research Laboratories, Malibu, California 90265 (United States)); Segev, M.; Crosignani, B.; Yariv, A. (California Institute of Technology, Pasadena, California 91125 (United States)); Fejer, M.M.; Bashaw, M.C. (Stanford University, Stanford, California 94305 (United States))

1994-12-01

35

Band-gap boundaries and fundamental solitons in complex two-dimensional nonlinear lattices  

SciTech Connect

Nonlinear Schroedinger (NLS) equation with external potentials (lattices) possessing crystal and quasicrystal structures are studied. The fundamental solitons and band gaps are computed using a spectral fixed-point numerical scheme. Nonlinear and linear stability properties of the fundamental solitons are investigated by direct simulations and the linear stability properties of the fundamental solitons are confirmed by analysis the linearized eigenvalue problem.

Ablowitz, Mark J.; Antar, Nalan; Bakirtas, Ilkay; Ilan, Boaz [Department of Applied Mathematics, University of Colorado, Colorado 80309-0526 (United States); Istanbul Technical University, Maslak 34469, Istanbul (Turkey); School of Natural Sciences, University of California at Merced, Merced, California 95344 (United States)

2010-03-15

36

Solitons supported by spatially inhomogeneous nonlinear losses.  

PubMed

We uncover that, in contrast to the common belief, stable dissipative solitons exist in media with uniform gain in the presence of nonuniform cubic losses, whose local strength grows with coordinate ? (in one dimension) faster than |?|. The spatially-inhomogeneous absorption also supports new types of solitons, that do not exist in uniform dissipative media. In particular, single-well absorption profiles give rise to spontaneous symmetry breaking of fundamental solitons in the presence of uniform focusing nonlinearity, while stable dipoles are supported by double-well absorption landscapes. Dipole solitons also feature symmetry breaking, but under defocusing nonlinearity. PMID:22330503

Borovkova, Olga V; Kartashov, Yaroslav V; Vysloukh, Victor A; Lobanov, Valery E; Malomed, Boris A; Torner, Lluis

2012-01-30

37

Spatial solitons in nonlinear liquid waveguides  

Microsoft Academic Search

Spatial solitons are studied in a planar waveguide filled with nonlinear liquids. Spectral and spatial measurements for different\\u000a geometries and input power of the laser beam show the influence of different nonlinear effects as stimulated scatterings on\\u000a the soliton propagation and in particular on the beam polarization. The stimulated scattering can be used advantageously to\\u000a couple the two polarization components.

R. Barillé; G. Rivoire

2001-01-01

38

Various kinds of spatial solitons associated with photoisomerization  

SciTech Connect

It is predicted that the fundamental spatial solitons, namely bright, dark, and gray solitons associated with photoisomerization, can be formed stably except for antidark solitons. The soliton solutions and the relative properties of these solitons are given in detail. Incoherently coupled bright-dark soliton pairs are also investigated. Both the cases indicate that although the formation of a spontaneous bright soliton based on photoisomerization is impossible, it is, however, possible to form a bright soliton with the joining of a background light or the coupling of another dark soliton. The results provide possible methods of controlling a light with another light.

Liang Jianchu; Cai Zebin; Sun Yunzhou; Xu Siliu; Yi Lin [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2009-01-15

39

Two-Dimensional Bright Solitons in Dipolar Bose-Einstein Condensates  

NASA Astrophysics Data System (ADS)

We analyze the physics of bright solitons in 2D dipolar Bose-Einstein condensates. These solitons, which are not possible in short-range interacting gases, constitute the first realistic proposal of fully mobile stable 2D solitons in ultracold gases. In particular, we discuss the necessary conditions for the existence of stable 2D bright solitary waves by means of a 3D analysis of the lowest-lying excitations. We show that the anisotropy of the dipolar potential is crucial, since sufficiently large dipolar interactions can destabilize the 2D soliton. Additionally, we study the scattering of solitary waves, which, contrary to the contact-interacting case, is inelastic and could lead to fusion of the waves. Finally, the experimental possibilities for observability are discussed.

Pedri, P.; Santos, L.

2005-11-01

40

Dynamically Stabilized Bright Solitons in a Two-Dimensional Bose-Einstein Condensate  

NASA Astrophysics Data System (ADS)

We demonstrate that a matter-wave bright soliton can be stabilized in 2D free space by causing the strength of interactions to oscillate rapidly between repulsive and attractive by using, e.g., Feshbach resonance.

Saito, Hiroki; Ueda, Masahito

2003-01-01

41

Symmetric and asymmetric solitons and vortices in linearly coupled two-dimensional waveguides with the cubic-quintic nonlinearity  

NASA Astrophysics Data System (ADS)

It is well known that the two-dimensional (2D) nonlinear Schrödinger equation (NLSE) with the cubic-quintic (CQ) nonlinearity supports a family of stable fundamental solitons, as well as solitary vortices (alias vortex rings), which are stable for sufficiently large values of the norm. We study stationary localized modes in a symmetric linearly coupled system of two such equations, focusing on asymmetric states. The model may describe “optical bullets” in dual-core nonlinear optical waveguides (including spatiotemporal vortices that have not been discussed before), or a Bose-Einstein condensate (BEC) loaded into a “dual-pancake” trap. Each family of solutions in the single-component model has two different counterparts in the coupled system, one symmetric and one asymmetric. Similarly to the earlier studied coupled 1D system with the CQ nonlinearity, the present model features bifurcation loops, for fundamental and vortex solitons alike: with the increase of the total energy (norm), the symmetric solitons become unstable at a point of the direct bifurcation, which is followed, at larger values of the energy, by the reverse bifurcation restabilizing the symmetric solitons. However, on the contrary to the 1D system, both the direct and reverse bifurcation may be of the subcritical type, at sufficiently small values of the coupling constant, ?. Thus, the system demonstrates a double bistabilityfor the fundamental solitons. The stability of the solitons is investigated via the computation of instability growth rates for small perturbations. Vortex rings, which we study for two values of the “spin”, s=1 and 2, may be subject to the azimuthal instability, like in the single-component model. In particular, complete destabilization of asymmetric vortices is demonstrated for a sufficiently strong linear coupling. With the decrease of ?, a region of stable asymmetric vortices appears, and a single region of bistability for the vortices is found. We also develop a quasi-analytical approach to the description of the bifurcations diagrams, based on the variational approximation. Splitting of asymmetric vortices, induced by the azimuthal instability, is studied by means of direct simulations. Interactions between initially quiescent solitons of different types are studied too. In particular, we confirm the prediction of the reversal of the sign of the interaction (attractive/repulsive for in-phase/out-of-phase pairs) for the solitons with the odd spin, s=1, in comparison with the even values, s=0and 2.

Dror, Nir; Malomed, Boris A.

2011-03-01

42

One- and two-dimensional solitons in second-harmonic-generating lattices.  

PubMed

In a model of a dynamical lattice with the on-site second-harmonic-generating nonlinearity and harmonic intersite couplings (that may be equal or different for the fundamental and second harmonics), various solitary-wave solutions are considered in one and two dimensions (1D and 2D). Fundamental (single-hump) solitons are identified in either dimension and their stability is examined and compared to previous results as well as to what is known for the model's continuum counterpart. Stability limits in terms of the coupling constants, which depend on the value of the phase-mismatch parameter, are found for solitons of the twisted-mode type in the 1D lattice, and for their counterparts of two different types (one being a discrete vortex) in the 2D lattice. When the twisted-mode soliton is unstable, the instability, which may be either oscillatory or due to imaginary eigenfrequency pairs, transforms the unstable soliton into a stable fundamental one, in both 1D and 2D cases. PMID:12059730

Malomed, Boris A; Kevrekidis, P G; Frantzeskakis, D J; Nistazakis, H E; Yannacopoulos, A N

2002-04-30

43

Learning Two-Dimensional Spatial Dynamics from Experimental Data  

NASA Astrophysics Data System (ADS)

This thesis discusses the analysis of complex spatial dynamics using a computer learning algorithm. The goal is to model experimental data, the dendritic solidification of ammonium bromide crystals, using a learning algorithm to search through a space of possible models in order to find an optimal description of the data. The space of possible models is a class of probabilistic cellular automaton rules, a rule which is inherently local. The traditional definition of a cellular automaton has been enhanced here to include information which is non-local in both space and time thus allowing the models to reproduce a greater variety of complex spatial dynamics. The learning algorithm performing the stochastic search through the model space is a variation of the genetic algorithm. The technique is first applied to pattern data generated by deterministic models for the solidification process. Simple cellular automata and more complicated generalizations of cellular automata are used to generate test data for the learning algorithm. Video images of solidifying ammonium bromide dendrites are then modeled using the genetic algorithm, and the results are compared to the test cases.

Richards, Fred Christian

1991-02-01

44

Propagation, collision, and fusion of spatial optical soliton, in three-dimensional media with saturable nonlinear refractive index change  

Microsoft Academic Search

Summary form only given. In this talk we present an extensive study of the properties of two-dimensional spatial solitons in 2+1 dimensions in a media with saturable nonlinearity. In particular the theory describes the properties of spatial photorefractive screening solitons. The refractive index change resulting from the electro-optic effect induced by an applied voltage V and influenced by the space-charge

S. Gatz; J. Hermann

1996-01-01

45

Two-dimensional s-polarized solitary waves in plasmas. II. Stability, collisions, electromagnetic bursts, and post-soliton evolution  

SciTech Connect

The dynamics of two-dimensional s-polarized solitary waves is investigated with the aid of particle-in-cell (PIC) simulations. Instead of the usual excitation of the waves with a laser pulse, the PIC code was directly initialized with the numerical solutions from the fluid plasma model. This technique allows the analysis of different scenarios including the theoretical problems of the solitary wave stability and their collision as well as features already measured during laser-plasma experiments such as the emission of electromagnetic bursts when the waves reach the plasma-vacuum interface, or their expansion on the ion time scale, usually named post-soliton evolution. Waves with a single density depression are stable whereas multihump solutions decay to several waves. Contrary to solitons, two waves always interact through a force that depends on their relative phases, their amplitudes, and the distance between them. On the other hand, the radiation pattern at the plasma-vacuum interface was characterized, and the evolution of the diameter of different waves was computed and compared with the ''snow plow'' model.

Sanchez-Arriaga, G.; Lefebvre, E. [CEA, DAM, DIF, F-91297 Arpajon (France)

2011-09-15

46

Two-dimensional s-polarized solitary waves in plasmas. II. Stability, collisions, electromagnetic bursts, and post-soliton evolution.  

PubMed

The dynamics of two-dimensional s-polarized solitary waves is investigated with the aid of particle-in-cell (PIC) simulations. Instead of the usual excitation of the waves with a laser pulse, the PIC code was directly initialized with the numerical solutions from the fluid plasma model. This technique allows the analysis of different scenarios including the theoretical problems of the solitary wave stability and their collision as well as features already measured during laser-plasma experiments such as the emission of electromagnetic bursts when the waves reach the plasma-vacuum interface, or their expansion on the ion time scale, usually named post-soliton evolution. Waves with a single density depression are stable whereas multihump solutions decay to several waves. Contrary to solitons, two waves always interact through a force that depends on their relative phases, their amplitudes, and the distance between them. On the other hand, the radiation pattern at the plasma-vacuum interface was characterized, and the evolution of the diameter of different waves was computed and compared with the "snow plow" model. PMID:22060510

Sánchez-Arriaga, G; Lefebvre, E

2011-09-09

47

Two-dimensional radiation in a cylinder with spatially varying albedo  

Microsoft Academic Search

The 'discrete ordinates', or S(N) method is presently used to develop a general, accurate scheme for determining two-dimensional radiative transfer in an axisymmetric cylindrical enclosure that contains an absorbing, emitting, and anisotropically scattering medium with spatially varying albedo. The spatial variation of albedo is noted to have significant effects on the heat flux for the optically thick case; for the

M. N. Ozisik; J. R. Tsai; H. Y. Li

1992-01-01

48

Watermarking in the space\\/spatial-frequency domain using two-dimensional Radon-Wigner distribution  

Microsoft Academic Search

A two-dimensional (2-D) signal with a variable spatial frequency is proposed as a watermark in the spatial domain. This watermark is characterized by a linear frequency change. It can be efficiently detected by using 2-D space\\/spatial-frequency distributions. The projections of the 2-D Wigner distribution-the 2-D Radon-Wigner distribution, are used in order to emphasize the watermark detection process. The watermark robustness

Srdjan Stankovic ´; Igor Djurovic; Ioannis Pitas

2001-01-01

49

Subwavelength spatial solitons in inhomogeneous Kerr media  

SciTech Connect

Propagation of a narrow beam in a periodic Kerr medium is analyzed for an arbitrary relation between the beam width, modulation period, and optical wavelength. Maxwell's equations used to obtain solutions describing spatial optical solitons, and their basic properties are determined. The results are compared with those obtained by solving the paraxial nonlinear Schoedinger equation. Conditions are found under which these models are mutually inconsistent.

Aleshkevich, V. A.; Grigor'ev, A. V.; Zhukarev, A. S. [Moscow State University (Russian Federation); Kartashov, Ya. V. [Mediterranean Technology Park, and Universitat Politecnica de Catalunya, ICFO-Institut de Ciencies Fotoniques (Spain)], E-mail: Yaroslav.Kartashov@icfo.es

2008-07-15

50

Vortex solitons in defocusing media with spatially inhomogeneous nonlinearity.  

PubMed

The analytical two- and three-dimensional vortex solitons with arbitrary values of vorticity are constructed in the cubic defocusing media with spatially inhomogeneous nonlinearity. The values of the nonlinearity coefficients are zero near the center and increase rapidly toward the periphery. In addition to the analytical ones, a number of vortex solitons are found numerically. It is shown that analytical vortex solitons are stable. Also, the stability region of the numerically constructed vortex solitons are given. PMID:23004891

Tian, Qing; Wu, Lei; Zhang, Yonghao; Zhang, Jie-Fang

2012-05-11

51

Spatially structured oscillations in a two-dimensional excitatory neuronal network with synaptic depression  

Microsoft Academic Search

We study the spatiotemporal dynamics of a two-dimensional excitatory neuronal network with synaptic depression. Coupling between populations of neurons is taken to be nonlocal, while depression is taken to be local and presynaptic. We show that the network supports a wide range of spatially structured oscillations, which are suggestive of phenomena seen in cortical slice experiments and in vivo. The

Zachary P. Kilpatrick; Paul C. Bressloff

2010-01-01

52

Deconvolution method for two-dimensional spatial-response mapping of lithographic infrared antennas.  

PubMed

The spatial impulse response of antenna-coupled infrared detectors with dimensions comparable with the wavelength is obtained from a two-dimensional scan of a tightly focused CO(2)-laser beam. The method uses an experimental setup with submicrometer resolution and an iterative deconvolution algorithm. The measured spatial response is compared with numerically computed near-field distributions of a dipole antenna, with good agreement. PMID:18323874

Alda, J; Fumeaux, C; Codreanu, I; Schaefer, J A; Boreman, G D

1999-07-01

53

Using two-dimensional spatial information in decomposition of surface EMG signals.  

PubMed

Recently, high-density surface EMG electrode grids and multi-channel amplifiers became available for non-invasive recording of human motor units (MUs). We present a way to decompose surface EMG signals into MU firing patterns, whereby we concentrate on the importance of two-dimensional spatial differences between the MU action potentials (MUAPs). Our method is exemplified with high-density EMG data from the vastus lateralis muscle of a single subject. Bipolar and Laplacian spatial filtering was applied to the monopolar raw signals. From the single recording in this subject six different simultaneously active MUs could be distinguished using the spatial differences between MUAPs in the direction perpendicular to the muscle fiber direction. After spike-triggered averaging, 125-channel two-dimensional MUAP templates were obtained. Template-matching allowed tracking of all MU firings. The impact of spatial information was measured by using subsets of the MUAP templates, either in parallel or perpendicular to the muscle fiber direction. The use of one-dimensional spatial information perpendicular to the muscle fiber direction was superior to the use of a linear array electrode in the longitudinal direction. However, to detect the firing events of the MUs with a high accuracy, as needed for instance for estimation of firing synchrony, two-dimensional information from the complete grid electrode appears essential. PMID:16904342

Kleine, Bert U; van Dijk, Johannes P; Lapatki, Bernd G; Zwarts, Machiel J; Stegeman, Dick F

2006-08-10

54

Spatial solitons in two-photon photorefractive media  

SciTech Connect

We provide a theory for spatial solitons due to the two-photon photorefractive effect based on the Castro-Camus model [Opt. Lett. 28, 1129 (2003)]. We present the evolution equation of one-dimensional spatial solitons in two-photon photorefractive media. In steady state and under appropriate external bias conditions, we obtain the dark and bright soliton solutions of the optical wave evolution equation, and also discuss the self-deflection of the bright solitons theoretically by taking into account the diffusion effect.

Hou Chunfeng; Pei Yanbo; Zhou Zhongxiang; Sun Xiudong [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China)

2005-05-15

55

Using two-dimensional spatial information in decomposition of surface EMG signals  

Microsoft Academic Search

Recently, high-density surface EMG electrode grids and multi-channel amplifiers became available for non-invasive recording of human motor units (MUs). We present a way to decompose surface EMG signals into MU firing patterns, whereby we concentrate on the importance of two-dimensional spatial differences between the MU action potentials (MUAPs). Our method is exemplified with high-density EMG data from the vastus lateralis

Bert U. Kleine; Johannes P. van Dijk; Bernd G. Lapatki; Machiel J. Zwarts; Dick F. Stegeman

2007-01-01

56

Perfect optical solitons: spatial Kerr solitons as exact solutions of Maxwell's equations  

Microsoft Academic Search

We prove that spatial Kerr solitons, usually obtained in the frame of a nonlinear Schrödinger equation valid in the paraxial approximation, can be found in a generalized form as exact solutions of Maxwell's equations. In particular, they are shown to exist, both in the bright and dark version, as TM, linearly polarized, exactly integrable one-dimensional solitons and to reduce to

Alessandro Ciattoni; Bruno Crosignani; Paolo di Porto; Amnon Yariv

2005-01-01

57

Spatial Solitons: Mutual Interactions and Magneto Optic Surfaces.  

National Technical Information Service (NTIS)

There has been a lot of recent activity on spatial solitons, including some very interesting work on soliton interactions. The latter work relies entirely upon the linear theory of rays in a graded index medium. This is a valuable viewpoint but since spat...

A. D. Boardman K. Xie

1992-01-01

58

Dark photovoltaic spatial solitons: experiment and numerical solution  

Microsoft Academic Search

We generated dark photovoltaic spatial solitons in the iron doped lithium niobate, and we studied the generation process with a numerical model. The Schrodinger nonlinear equation was simulated with BPM (beam propagation method). This numerical method is also called symmetrical split-step Fourier method. For the generation of dark solitons, we used both the amplitude mask and the phase mask. The

Michal Bodnar

2007-01-01

59

Finding exact spatial soliton profiles in nematic liquid crystals.  

PubMed

Finding exact analytical soliton profile solutions is only possible for certain types of non-linear media. In most cases one must resort to numerical techniques to find the soliton profile. In this work we present numerical calculations of spatial soliton profiles in nematic liquid crystals. The nonlinearity is governed by the optical-field-induced liquid crystal director reorientation, which is described by a system of coupled nonlinear partial differential equations. The soliton profile is found using an iterative scheme whereby the induced waveguide and mode profiles are calculated alternatively until convergence is achieved. In this way it is also possible to find higher order solitons. The results in this work can be used to accurately design all-optical interconnections with soliton beams. PMID:20389338

Beeckman, J; Neyts, K; Vanbrabant, P J M; James, R; Fernandez, F A

2010-02-15

60

Solitons supported by singular spatial modulation of the Kerr nonlinearity  

NASA Astrophysics Data System (ADS)

We introduce a setting based on the one-dimensional nonlinear Schrödinger equation (NLSE) with the self-focusing cubic term modulated by a singular function of the coordinate |x|-?. It may be additionally combined with the uniform self-defocusing (SDF) nonlinear background, and with a similar singular repulsive linear potential. The setting, which can be implemented in optics and Bose-Einstein condensates, aims to extend the general analysis of the existence and stability of solitons in NLSEs. Results for fundamental solitons are obtained analytically and verified numerically. The solitons feature a quasicuspon shape, with the second derivative diverging at the center, and are stable in the entire existence range, which is 0??<1. Dipole (odd) solitons are also found. They are unstable in the infinite domain, but stable in the semi-infinite one. In the presence of the SDF background, there are two subfamilies of fundamental solitons, one stable and one unstable, which exist together above a threshold value of the norm (total power of the soliton). The system, which additionally includes the singular repulsive linear potential, emulates solitons in a uniform space of the fractional dimension, 0two-dimensional extension of the system, based on the quadratic (?(2)) nonlinearity, is also formulated.

Borovkova, Olga V.; Lobanov, Valery E.; Malomed, Boris A.

2012-02-01

61

New physics and applications of Kerr spatial solitons  

NASA Astrophysics Data System (ADS)

Spatial solitons arise as a result of the interplay between diffraction and a Kerr-like nonlinearity. They are the spatial analog of the better known temporal solitons, which exist e.g. in optical fibers and result in pulse propagation without change of pulse shape. Similarly, spatial solitons are beams that do not change their shape upon propagation. In an introductory part of this work, the basic concept of spatial solitons will be reviewed and a number of properties that make them attractive for optical switching and routing devices will be described. Special emphasis will be put on the favorable properties of the AlGaAs material system in the spectral region below in the half bandgap, which were crucial for the experiments performed. One such device, a soliton steering element, has been realized and tested in AlGaAs samples. The device design and the experimental results will be presented in detail. The work performed is intended to demonstrate the basic feasibility of reconfigurable switching devices based on spatial solitons. Sufficient steering for the separation of four channels was achieved. Furthermore, one of the most interesting features of solitons is their robustness against perturbations. In birefringent media, however, the interaction between birefringence and nonlinearity leads ultimately to a polarization instability. This effect was investigated numerically and experimentally, and a radiation related polarization instability was observed for the first time. Additional work that is related to the field of Kerr spatial solitons and their generation, specifically an investigation of the linear parameters of a novel nonlinear material, the polydiacetylene p-toluene sulfonate (PTS), and the construction of a color center laser system used for the soliton experiments, are described in two appendices.

Friedrich, Lars

1999-12-01

62

Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas.  

PubMed

A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing. PMID:23742549

Kim, Young-Cheol; Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook

2013-05-01

63

Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas  

NASA Astrophysics Data System (ADS)

A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing.

Kim, Young-Cheol; Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook

2013-05-01

64

Implementation of a spatial two-dimensional quantum random walk with tunable decoherence  

NASA Astrophysics Data System (ADS)

We put forward a versatile and highly scalable experimental setup for the realization of discrete two-dimensional quantum random walks with a single-qubit coin and tunable degree of decoherence. The proposed scheme makes use of a small number of simple optical components arranged in a multipath Mach-Zehnder-like configuration, where a weak coherent state is injected. Environmental effects (decoherence) are generated by a spatial light modulator, which introduces pure dephasing in the transverse spatial plane perpendicular to the direction of propagation of the light beam. By controlling the characteristics of this dephasing, one can explore a great variety of scenarios of quantum random walks: pure quantum evolution (ballistic spread), fast fluctuating environment leading to a diffusive classical random walk, and static disorder resulting in the observation of Anderson localization.

Svozilík, J.; León-Montiel, R. de J.; Torres, J. P.

2012-11-01

65

Fast Transient And Spatially Non-Homogenous Accident Analysis Of Two-Dimensional Cylindrical Nuclear Reactor  

SciTech Connect

The research about fast transient and spatially non-homogenous nuclear reactor accident analysis of two-dimensional nuclear reactor has been done. This research is about prediction of reactor behavior is during accident. In the present study, space-time diffusion equation is solved by using direct methods which consider spatial factor in detail during nuclear reactor accident simulation. Set of equations that obtained from full implicit finite-difference discretization method is solved by using iterative methods ADI (Alternating Direct Implicit). The indication of accident is decreasing macroscopic absorption cross-section that results large external reactivity. The power reactor has a peak value before reactor has new balance condition. Changing of temperature reactor produce a negative Doppler feedback reactivity. The reactivity will reduce excess positive reactivity. Temperature reactor during accident is still in below fuel melting point which is in secure condition.

Yulianti, Yanti [Dept. of Physics, Universitas Lampung (UNILA), Jl. Sumantri Brojonegor No.1 Bandar Lampung (Indonesia); Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Su'ud, Zaki; Waris, Abdul; Khotimah, S. N. [Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Shafii, M. Ali [Dept. of Physics, Institut Teknologi Bandung (ITB), Jl. Ganesha 10 Bandung (Indonesia); Dept. of Physics, Universitas Andalas (UNAND), Kampus Limau Manis, Padang, Sumatera Barat (Indonesia)

2010-12-23

66

Two-dimensional bending vector sensing based on spatial cascaded orthogonal long period fiber.  

PubMed

A novel bending vector sensor based on spatial cascaded orthogonal long period fiber gratings (SCO-LPFGs) written by high-frequency CO(2) laser pulses has been proposed, and two-dimensional bending vector sensing characteristics based on the simple SCO-LPFGs have been experimentally demonstrated. A three-dimensional orthogonal sensing coordinate system has been established, and the measurement results of the proposed SCO-LPFGs sensor based on the above coordinate system is given, and furthermore both of curvature and bending-direction could be intuitively solved according to the three-dimensional orthogonal sensing coordinates. The research work presented in this paper would be helpful to improve the practicability of fiber vector sensors due to the distinguished characteristics such as simple structure, low-cost, ease of fabrication. PMID:23263093

Geng, Pengcheng; Zhang, Weigang; Gao, Shecheng; Zhang, Hao; Li, Jieliang; Zhang, Shanshan; Bai, Zhiyong; Wang, Li

2012-12-17

67

Dissipative soliton excitability induced by spatial inhomogeneities and drift.  

PubMed

We show that excitability is generic in systems displaying dissipative solitons when spatial inhomogeneities and drift are present. Thus, dissipative solitons in systems which do not have oscillatory states, such as the prototypical Swift-Hohenberg equation, display oscillations and type I and II excitability when adding inhomogeneities and drift to the system. This rich dynamical behavior arises from the interplay between the pinning to the inhomogeneity and the pulling of the drift. The scenario presented here provides a general theoretical understanding of oscillatory regimes of dissipative solitons reported in semiconductor microresonators. Our results open also the possibility to observe this phenomenon in a wide variety of physical systems. PMID:23432247

Parra-Rivas, P; Gomila, D; Matías, M A; Colet, P

2013-02-05

68

Offline comparison of spatial filters for two-dimensional movement control with noninvasive field potentials  

NASA Astrophysics Data System (ADS)

Paralyzed individuals can control the movement of an assistive device using changes in electroencephalographic (EEG) power resulting from attempted movements. Simultaneous, proportional control of two-dimensional (2D) device movements can be achieved with the concurrent modulation of brain activity that is associated with the attempted movement and rest of two independent body parts. Movement control may be improved by spatial filtering methods that recombine raw EEGs to form new signals with more focused information about the underlying brain activity. This study compared spatial filters offline for improving simultaneous proportional 2D movement commands from EEGs. Filtering options evaluated were common average referencing, Laplacian, independent component analysis, principle component analysis, and two novel ways of applying common spatial pattern (CSP) analysis. CSP analysis is a supervised algorithm that optimally recombines EEGs collected under two known conditions. Both CSP options resulted in more accurate movement prediction than the other filtering options. CSP was particularly advantageous when separating EEGs associated with neighboring or overlapping areas on the motor homunculus. Finally, CSP performed well using smaller subsets of filtered signals, thus making CSP practical and efficient for simultaneous 2D control. A 2D online cursor control example using CSP filtering is included to show CSP's utility.

Foldes, S. T.; Taylor, D. M.

2011-08-01

69

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions  

SciTech Connect

For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number [mu] associated with the vortex rotation of the background magnetic moment field by a phase angle 2[pi][mu] along a path encircling the soliton. Such solitons also carry a spin flux of [mu][pi] through the plaquette on which they are centered. The [mu]=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the [mu]=1 and 2 solitons. The spectrum of localized states is symmetric about [ital E]=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

John, S.; Golubentsev, A. (Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 (Canada))

1995-01-01

70

Observation of spatially ordered structures in a two-dimensional Rydberg gas.  

PubMed

The ability to control and tune interactions in ultracold atomic gases has paved the way for the realization of new phases of matter. So far, experiments have achieved a high degree of control over short-range interactions, but the realization of long-range interactions has become a central focus of research because it would open up a new realm of many-body physics. Rydberg atoms are highly suited to this goal because the van der Waals forces between them are many orders of magnitude larger than those between ground-state atoms. Consequently, mere laser excitation of ultracold gases can cause strongly correlated many-body states to emerge directly when atoms are transferred to Rydberg states. A key example is a quantum crystal composed of coherent superpositions of different, spatially ordered configurations of collective excitations. Here we use high-resolution, in situ Rydberg atom imaging to measure directly strong correlations in a laser-excited, two-dimensional atomic Mott insulator. The observations reveal the emergence of spatially ordered excitation patterns with random orientation, but well-defined geometry, in the high-density components of the prepared many-body state. Together with a time-resolved analysis, this supports the description of the system in terms of a correlated quantum state of collective excitations delocalized throughout the gas. Our experiment demonstrates the potential of Rydberg gases to realize exotic phases of matter, thereby laying the basis for quantum simulations of quantum magnets with long-range interactions. PMID:23128229

Schauß, Peter; Cheneau, Marc; Endres, Manuel; Fukuhara, Takeshi; Hild, Sebastian; Omran, Ahmed; Pohl, Thomas; Gross, Christian; Kuhr, Stefan; Bloch, Immanuel

2012-11-01

71

Two-dimensional spatial coherence of excitons in semicrystalline polymeric semiconductors: Effect of molecular weight  

NASA Astrophysics Data System (ADS)

The electronic properties of macromolecular semiconductor thin films depend profoundly on their solid-state microstructure, which in turn is governed, among other things, by the processing conditions selected and the polymer's chemical nature and molecular weight. Specifically, low-molecular-weight materials form crystalline domains of cofacially ?-stacked molecules, while the usually entangled nature of higher-molecular-weight polymers leads to microstructures comprised of molecularly ordered crystallites interconnected by amorphous regions. Here, we examine the interplay between extended exciton states delocalized along the polymer backbones and across polymer chains within the ? stack, depending on the structural development with molecular weight. Such two-dimensional excitations can be considered as Frenkel excitons in the limit of weak intersite coupling. We combine optical spectroscopies, thermal probes, and theoretical modeling, focusing on neat poly(3-hexylthiophene) (P3HT)—one of the most extensively studied polymeric semiconductors—of weight-average molecular weight (Mw) of 3-450 kg/mol. In thin-film structures of high-molecular-weight materials (Mw > 50 kg/mol), a balance of intramolecular and intermolecular excitonic coupling results in high exciton coherence lengths along chains (˜4.5 thiophene units), with interchain coherence limited to ˜2 chains. In contrast, for structures of low-Mw P3HT (<50 kg/mol), the interchain exciton coherence is dominant (˜30% higher than in architectures formed by high-molecular-weight materials). In addition, the spatial coherence within the chain is significantly reduced (by nearly 25%). These observations give valuable structural information; they suggest that the macromolecules in aggregated regions of high-molecular-weight P3HT adopt a more planar conformation compared to low-molecular-weight materials. This results in the observed increase in intrachain exciton coherence. In contrast, shorter chains seem to lead to torsionally more disordered architectures. A rigorous, fundamental description of primary photoexcitations in ?-conjugated polymers is hence developed: two-dimensional excitons are defined by the chain-length dependent molecular arrangement and interconnectivity of the conjugated macromolecules, leading to interplay between intramolecular and intermolecular spatial coherence.

Paquin, Francis; Yamagata, Hajime; Hestand, Nicholas J.; Sakowicz, Maciej; Bérubé, Nicolas; Côté, Michel; Reynolds, Luke X.; Haque, Saif A.; Stingelin, Natalie; Spano, Frank C.; Silva, Carlos

2013-10-01

72

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions  

Microsoft Academic Search

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1\\/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector

Sajeev John; Andrey Golubentsev

1995-01-01

73

Generation and dynamics of quadratic birefringent spatial gap solitons  

SciTech Connect

A method is proposed to generate and study the dynamics of spatial light solitons in a birefringent medium with quadratic nonlinearity. Although no analytical expression for propagating solitons has been obtained, our numerical simulations show the existence of stable localized spatial solitons in the frequency forbidden band gap of the medium. The dynamics of these objects is quite rich and manifests for instance elastic reflections, or inelastic collisions where two solitons merge and propagate as a single solitary wave. We derive the dynamics of the slowly varying envelopes of the three fields (second harmonic pump and two-component signal) and study this new system theoretically. We show that it does present a threshold for nonlinear supratransmission that can be calculated from a series expansion approach with a very high accuracy. Specific physical implications of our theoretical predictions are illustrated on LiGaTe{sub 2} (LGT) crystals. Once irradiated by a cw laser beam of 10 {mu}m wavelength, at an incidence beyond the extinction angle, such crystals will transmit light, in the form of spatial solitons generated in the nonlinear regime above the nonlinear supratransmission threshold.

Anghel-Vasilescu, P. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, D-01187 Dresden (Germany); Dorignac, J.; Geniet, F.; Leon, J. [Laboratoire Charles Coulomb, Departement de Physique Theorique, UMR 5221 CNRS-UM2, Universite Montpellier 2, F-34095 Montpellier Cedex 5 (France); Taki, A. [Laboratoire de Physique des Lasers, Atomes et Molecules, CNRS-INP-UMR8523, Universite des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq (France)

2011-04-15

74

Note: Interpolation for evaluation of a two-dimensional spatial profile of plasma densities at low gas pressures  

SciTech Connect

An interpolation algorithm for the evaluation of the spatial profile of plasma densities in a cylindrical reactor was developed for low gas pressures. The algorithm is based on a collisionless two-dimensional fluid model. Contrary to the collisional case, i.e., diffusion fluid model, the fitting algorithm depends on the aspect ratio of the cylindrical reactor. The spatial density profile of the collisionless fitting algorithm is presented in two-dimensional images and compared with the results of the diffusion fluid model.

Oh, Se-Jin; Kim, Young-Chul; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2011-02-15

75

The geometry of percolation fronts in two-dimensional lattices with spatially varying densities  

NASA Astrophysics Data System (ADS)

Percolation theory is usually applied to lattices with a uniform probability p that a site is occupied or that a bond is closed. The more general case, where p is a function of the position x, has received less attention. Previous studies with long-range spatial variations in p(x) have only investigated cases where p has a finite, non-zero gradient at the critical point pc. Here we extend the theory to two-dimensional cases in which the gradient can change from zero to infinity. We present scaling laws for the width and length of the hull (i.e. the boundary of the spanning cluster). We show that the scaling exponents for the width and the length depend on the shape of p(x), but they always have a constant ratio 4/3 so that the hull's fractal dimension D = 7/4 is invariant. On this basis, we derive and verify numerically an asymptotic expression for the probability h(x) that a site at a given distance x from pc is on the hull.

Gastner, Michael T.; Oborny, Beáta

2012-10-01

76

Numerical simulation of two-dimensional sine-Gordon solitons via a local weak meshless technique based on the radial point interpolation method (RPIM)  

NASA Astrophysics Data System (ADS)

In this paper the meshless local radial point interpolation method (LRPIM) is adopted to simulate the two-dimensional nonlinear sine-Gordon (S-G) equation. The meshless LRPIM is one of the “truly meshless” methods since it does not require any background integration cells. In this case, all integrations are carried out locally over small quadrature domains of regular shapes, such as circles or squares in two dimensions and spheres or cubes in three dimensions. A technique is proposed to construct shape functions using radial basis functions. These shape functions which are constructed by point interpolation method using the radial basis functions have delta function property. The time derivatives are approximated by the time-stepping method. In order to eliminate the nonlinearity, a simple predictor-corrector scheme is performed. Numerical results are obtained for various cases involving line and ring solitons. Also the conservation of energy in undamped sine-Gordon equation is investigated.

Dehghan, Mehdi; Ghesmati, Arezou

2010-04-01

77

Anomalous spatial modifications of beams diffracted by two-dimensional periodic media  

NASA Astrophysics Data System (ADS)

Beams diffracted by planar surfaces having a two-dimensional (2-D) periodicity may exhibit strong spatial modifications that cannot be explained in terms of conventional geometric arguments. These effects include 2-D longitudinal and transverse lateral displacements, focal shifts, beam waist modifications, and angular deflections for each of the diffracted beams. We perform a rigorous analysis of these phenomena by first developing a formalism for plane-wave scattering by 2-D periodic impedance surfaces, and applying it to investigate the diffraction of Gaussian beams in the paraxial regime. Some of the beam modification effects due to the 2-D grating action are analogous to those for uniform or 1-D periodic surfaces. However, these effects acquire a complexity that involves novel features generated by the 2-D aspect of the periodic scattering surface. For plane-wave scattering, we satisfy the periodic boundary conditions at the surface and obtain an infinite set of coupled recurrence equations whose solution yields the scattered field expansion coefficients. We present numerical results that compare favorably with those previously published for copolarized returns. We also show that no depolarization occurs for the diffracted orders that propagate in the same plane of the incident wave and incidence is in a symmetry plane of 2-D periodic structure. Using the plane-wave formalism, the geometrical properties of Gaussian beams diffracted by a 2-D periodic impedance plane are first analyzed by neglecting variations in the scattering function. We thus show that, in general, waist values are unequal in the two transverse directions across the beam and they appear along different locations along the beam axis, i.e., the diffracted beams are astigmatic. Spatial modification effects are derived by accounting for the actual scattering function describing the spectral contents of each diffracted field. The formal solution for those fields is a coherent superposition of Gaussian beams arising from the principal and cross polarized returns. Each one of these beams may undergo anomalous spatial modifications which are expressed in terms of derivatives of the scattering function. We obtain analytic expressions for these effects by developing a Pade approximant scattering model and demonstrate its surprising accuracy. The 2-D effects are shown to exhibit a greater complexity and include additional features that are absent in the simpler 1-D grating situation.

Falco, Frank

78

Temporal behavior of bidimensional photorefractive bright spatial solitons  

Microsoft Academic Search

The time behavior of bright spatial solitons in biased photorefractive media is investigated within the framework of a bidimensional band transport model. Biasing the photorefractive media requires an externally applied electric field or the presence of a photovoltaic effect. These two basically different phenomena are shown to be equivalent and additive. The mechanism of space-charge field buildup is analytically expressed,

N. Fressengeas; J. Maufoy; G. Kugel

1996-01-01

79

Spatial Thirring-type solitons via electromagnetically induced transparency  

NASA Astrophysics Data System (ADS)

We show that the giant Kerr nonlinearity in the regime of electromagnetically induced transparency in vapor can give rise to the formation of Thirring-type spatial solitons, which are supported solely by cross-phase modulation that couples the two copropagating light beams.

Friedler, Inbal; Kurizki, Gershon; Cohen, Oren; Segev, Mordechai

2005-12-01

80

Gray spatial solitons in biased photorefractive media  

Microsoft Academic Search

Summary form only given. Recently, soliton splitting has been successfully used to write permanent Y-waveguide structures (3-dB splitters) in the bulk of a photorefractive crystal. Such Y-junctions can then be employed to guide other intense beams at less photosensitive wavelengths (~1.5 ?m) or can be permanently impressed (fixed) into the crystalline lattice. An investigation of the properties of these Y-junction

A. G. Grandpierre; T. H. Coskun; D. N. Christodoulides; M. Segev; Y. S. Kivshar

2000-01-01

81

The Effect of Two-dimensional and Stereoscopic Presentation on Middle School Students’ Performance of Spatial Cognition Tasks  

Microsoft Academic Search

We investigated whether and how student performance on three types of spatial cognition tasks differs when worked with two-dimensional\\u000a or stereoscopic representations. We recruited nineteen middle school students visiting a planetarium in a large Midwestern\\u000a American city and analyzed their performance on a series of spatial cognition tasks in terms of response accuracy and task\\u000a completion time. Results show that

Aaron Price; Hee-Sun Lee

2010-01-01

82

Design and realization of a two-dimensional spatial magnetic field mapping apparatus to measure magnetic fields of metamaterials  

Microsoft Academic Search

The two-dimensional (2D) spatial electric-field mapping apparatus [Opt. Express 14, 8694 (2006)] plays an important role in experiments involving metamaterials, such as the verification of free-space and ground-plane invisibility cloaks. However, such an apparatus is valid only for the transverse-electric (TE) mode and is invalid for the transverse-magnetic (TM) mode, as it requires perfectly magnetic conducting (PMC) planes, which do

Quan Jiang; Xiao Yang Zhou; Jessie Yao Chin; Tie Jun Cui

2011-01-01

83

Mapping Spatial Tracer Gases Concentration Profiles on a Two-Dimensional Plane by OP-FTIR Remote Sensing  

Microsoft Academic Search

The mapping methods of the trace gas concentration profiles are proposed in this paper. Path Integrated Concentration (PIC) data, measured by an Open?Path Fourier Transform Infrared (OP?FTIR) Remote Sensing system, was utilized to reconstruct spatial maps of three hazardous volatile organic compounds (chloroform, acetone, and methylene chloride) on a two?dimensional plane. The results illustrate that the measured concentration data for

Zhonghua Huang; Junde Wang; Yan Li

2003-01-01

84

Waveguide properties of the asymmetric collision between two bright spatial solitons in Kerr media.  

PubMed

In this work, we numerically characterize the waveguide properties of the asymmetric collision between two bright spatial solitons in a nonlinear Kerr media. The results demonstrate that the energy carried by a probe beam guided by one soliton can be transferred after the collision to the waveguide created by the other soliton depending on the initial separation between the solitons, the angle of their collision, and in some cases, the particular soliton that initially guides the probe beam. The observed behavior is equivalent to that obtained for the symmetrical collision when there is an initial relative phase between the solitons. PMID:23187598

Martínez, D Ramírez; Otero, M M Méndez; Carrasco, M L Arroyo; Castillo, M D Iturbe

2012-11-19

85

All-optical polarization modulator based on spatial soliton coupling  

Microsoft Academic Search

The possibility of realizing an all-optical polarization modulator is theoretically demonstrated. Basic device exploits the cross-phase modulation effect involving spatial solitons in a Kerr-like nonlinear material. It is shown that a weak wave (modulating signal) can be used to control a stronger wave (pump signal), in such a way to obtain a polarization switch, if their input phase difference is

Giovanni Cancellieri; Franco Chiaraluce; E. Gambi; Paola Pierleoni

1996-01-01

86

Vortex Spatial Solitons to a Nonlinear Schrödinger Equation with Varying Coefficients  

NASA Astrophysics Data System (ADS)

Based on homogeneous balance method, soliton solutions to a generalized nonlinear Schrödinger equation (NLSE) with varying coefficients have been gotten. Our results indicate that a new family of vortex or petal-like spatial solitons can be formed in the Kerr nonlinear media in the cylindrical symmetric geometry. It is shown by numerical simulation that these soliton profiles are stable.

Xu, Si-Liu; Liang, Jian-Chu; Li, Zhong-Ming

2011-12-01

87

Evolution of spatial optical solitons in biased photorefractive media under steady state conditions  

Microsoft Academic Search

The dynamical evolution of bright spatial solitons in biased photorefractive crystals is investigated under steady-state conditions. Our numerical study indicates that these optical solitons are stable against small perturbations whereas optical beams that significantly differ from soliton solutions tend to experience larger cycles of compression and expansion. The influence of loss in a typical photorefractive material like SBN:60 is studied

S. R Singh; D. N Christodoulides

1995-01-01

88

Uncertainty relation for resolution in space, spatial frequency, and orientation optimized by two-dimensional visual cortical filters.  

PubMed

Two-dimensional spatial linear filters are constrained by general uncertainty relations that limit their attainable information resolution for orientation, spatial frequency, and two-dimensional (2D) spatial position. The theoretical lower limit for the joint entropy, or uncertainty, of these variables is achieved by an optimal 2D filter family whose spatial weighting functions are generated by exponentiated bivariate second-order polynomials with complex coefficients, the elliptic generalization of the one-dimensional elementary functions proposed in Gabor's famous theory of communication [J. Inst. Electr. Eng. 93, 429 (1946)]. The set includes filters with various orientation bandwidths, spatial-frequency bandwidths, and spatial dimensions, favoring the extraction of various kinds of information from an image. Each such filter occupies an irreducible quantal volume (corresponding to an independent datum) in a four-dimensional information hyperspace whose axes are interpretable as 2D visual space, orientation, and spatial frequency, and thus such a filter set could subserve an optimally efficient sampling of these variables. Evidence is presented that the 2D receptive-field profiles of simple cells in mammalian visual cortex are well described by members of this optimal 2D filter family, and thus such visual neurons could be said to optimize the general uncertainty relations for joint 2D-spatial-2D-spectral information resolution. The variety of their receptive-field dimensions and orientation and spatial-frequency bandwidths, and the correlations among these, reveal several underlying constraints, particularly in width/length aspect ratio and principal axis organization, suggesting a polar division of labor in occupying the quantal volumes of information hyperspace.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:4020513

Daugman, J G

1985-07-01

89

Effect of four-wave mixing on copropagating spatial solitons  

NASA Astrophysics Data System (ADS)

It is known that in the absence of four-wave mixing, spatial solitons of two frequencies can copropagate stably in a Kerr-law nonlinear medium. We investigate the effect of including four-wave mixing. We show that when phase-matching conditions are satisfied, Stokes and anti-Stokes waves can be generated to produce a new steady-state solution consisting of four copropagating beams. On the other hand, if weak signal beams are injected along with the pump beams, then four-wave mixing can be used to amplify those side beams. When phase-matching conditions are not satisfied, the Stokes and anti-Stokes waves simply propagate as linear modes in the effective waveguides induced by the pump solitons.

Ansari, Nadeem A.; Sammut, Rowland A.; Tran, Hai-Tan

1996-07-01

90

Construction and initial evaluation of an apparatus for spatial comprehensive two-dimensional liquid-phase separations.  

PubMed

Spatial comprehensive two-dimensional chromatography is discussed as a potentially alternative to the conventional column-based approach. In "spatial" separations each analyte ends up in a specific location, rather than being eluted at a specific time. Ultimately, higher peak-capacity-production rates (peak capacity per unit time) may be attained by spatial two- and three-dimensional separations. While low-pressure planar chromatography is well developed, the high-pressure equivalent is still in its infancy. We discuss the requirements for a device for high-pressure spatial two-dimensional chromatography and we describe a possible design. A prototype instrument has been constructed in-house. The preparation of a polymer monolithic separation body and a valve configuration that allows manual sample injection are described. Initial tests of this study included the investigation of the homogeneity of the monolith and the flow profile through the separation body. Furthermore, in order to evaluate the current chromatographic performance of the device, a mixture of dyes was separated in one dimension within 30 s. PMID:21763814

Vanhoutte, Dominique J D; Eeltink, Sebastiaan; Kok, Wim Th; Schoenmakers, Peter J

2011-06-13

91

Observation of multi-component spatial vector solitons of four-wave mixing.  

PubMed

We report the observation of multi-component dipole and vortex vector solitons composed of eight coexisting four-wave mixing (FWM) signals in two-level atomic system. The formation and stability of the multi-component dipole and vortex vector solitons are observed via changing the experiment parameters, including the frequency detuning, powers, and spatial configuration of the involved beams and the temperature of the medium. The transformation between modulated vortex solitons and rotating dipole solitons is observed at different frequency detunings. The interaction forces between different components of vector solitons are also investigated. PMID:22714480

Wang, Ruimin; Wu, Zhenkun; Zhang, Yiqi; Zhang, Zhaoyang; Yuan, Chenzhi; Zheng, Huaibin; Li, Yuanyuan; Zhang, Jinhai; Zhang, Yanpeng

2012-06-18

92

Projectile motion of spatial soliton in photorefractive medium with drift and diffusion nonlinearity  

NASA Astrophysics Data System (ADS)

Dynamics of (1+1)D spatial solitons in photorefractive medium with drift and diffusion nonlinearity is investigated. Propagation of solitons is analyzed theoretically by means of effective-particle approach method. The explicit formula of acceleration of soltion is derived. Analytical results show that the solitons evolve with a constant acceleration along a parabolic trajectory. The acceleration is determined by the input soliton and the diffusion nonlinearity. We also simulate the propagation of solitons numerically and excellent agreements are obtained between the theoretical and numerical results.

Ma, Lihong; Dong, Liangwei; Wang, Hui

2007-10-01

93

Interaction of spatial solitons in biased photorefractive photovoltaic media  

Microsoft Academic Search

Numerical investigations of the interactions among bright screening-photovoltaic solitons are performed in detail by using the Crank-Nicholson scheme. The numerical results show that a number of parameters, such as the initial separation and phase difference between solitons, can determine the interaction forces of solitons. The numerical study indicates that two in-phase solitons attract each other, and soliton fusions do occur

Chen Shuyu; Yali Qin; Yang Juan; Hongliang Ren

2008-01-01

94

Two-dimensional selection of optical spatial frequencies by acousto-optic methods  

NASA Astrophysics Data System (ADS)

We theoretically and experimentally examine the selection of spatial frequencies of optical beams carried out by acousto-optic methods. Control of the optical rays is provided in two orthogonal directions with the help of a single acousto-optic cell fabricated of a birefringent paratellurite single crystal. The investigation is performed using a cell of a tunable acousto-optic filter illuminated by coherent radiation of a He- Ne laser at optical wavelength (gamma) equals 633 nm. The filter is capable of a 2-D selection of optical beams propagating all over the range of spatial frequencies vx equals vy equals

Voloshinov, Vitaly B.; Babkina, T. M.; Molchanov, Vladimir Y.

2002-06-01

95

Reduced FOV Single-Shot Fast Spin Echo Imaging Using Two-dimensional Spatially-Selective RF Pulses  

PubMed Central

Purpose To demonstrate reduced field-of-view (RFOV) single-shot fast spin echo (SS-FSE) imaging based on the use of two-dimensional spatially-selective RF pulses. Materials and Methods 2DRF pulses were incorporated into a SS-FSE sequence for RFOV imaging in both phantoms and the human brain on a 1.5 T whole-body MR system with the aim of demonstrating improvements in terms of shorter scan time, reduced blurring and higher spatial resolution compared to full FOV imaging. Results For phantom studies, scan time gains of up to 4.2 fold were achieved as compared to the full FOV imaging. For human studies, the spatial resolution was increased by a factor of 2.5 (from 1.7 mm/pixel to 0.69 mm/pixel) for RFOV imaging within a scan time (0.7s) similar to full FOV imaging. A 2.2-fold shorter scan time along with a significant reduction of blurring was demonstrated in RFOV images compared to full FOV images for a target spatial resolution of 0.69 mm/pixel. Conclusion RFOV SS-FSE imaging using a 2DRF pulse shows advantages in scan time, blurring, and SAR reduction along with true spatial resolution increase compared to full FOV imaging. This approach is promising to benefit fast imaging applications such as image guided therapy.

Yuan, Jing; Zhao, Tzu-Cheng; Tang, Yi; Panych, Lawrence P.

2010-01-01

96

High spatial resolution two-dimensional position sensitive detector for the performance of coincidence experiments  

SciTech Connect

A position sensitive detector (PSD) adapted to the technical and mechanical specifications of our angle and energy resolved electron-ion(s) coincidence experiments is described in this article. The device, whose principle is very similar to the one detailed by J. H. D. Eland [Meas. Sci. Technol. 5, 1501 (1994)], is composed by a set of microchannel plates and a delay line anode. The originality comes from the addition in front of the encoding surface of a ceramic disk covered by a resistive surface. The capacitive coupling between the anode and the resistive plane has the double advantage of eliminating the spatial modulations due to the lattice of the anode and also of sensitizing a greater number of electrodes, increasing thus considerably the accuracy of the position measurements. The tests carried out with a time to digital conversion module of 250 ps resolution showed that a spatial resolution better than 50 {mu}m and a dead time of 160 ns can be achieved. Typical images obtained with the help of the EPICEA and DELICIOUS coincidence setups are also shown.

Ceolin, D.; Chaplier, G.; Lemonnier, M.; Garcia, G.A.; Miron, C.; Nahon, L.; Simon, M.; Leclercq, N.; Morin, P. [Laboratoire LURE, Bat. 209D, BP 34, Universite Paris-Sud, 91898 Orsay Cedex (France); Laboratoire LURE, Bat. 209D, BP 34, Universite Paris-Sud, 91898 Orsay Cedex, France CEA/DSM/DRECAM/SPAM, Laboratoire Francis Perrin, CNRS URA 2453, Bat. 522, CE Saclay, 91191 Gif-sur-Yvette Cedex (France); Laboratoire LURE, Bat. 209D, BP 34, Universite Paris-Sud, 91898 Orsay Cedex, France Laboratoire de Chimie Physique-Matiere et Rayonnement, CNRS, 11 Rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France)

2005-04-01

97

High spatial resolution two-dimensional position sensitive detector for the performance of coincidence experiments  

NASA Astrophysics Data System (ADS)

A position sensitive detector (PSD) adapted to the technical and mechanical specifications of our angle and energy resolved electron-ion(s) coincidence experiments is described in this article. The device, whose principle is very similar to the one detailed by J. H. D. Eland [Meas. Sci. Technol. 5, 1501 (1994)], is composed by a set of microchannel plates and a delay line anode. The originality comes from the addition in front of the encoding surface of a ceramic disk covered by a resistive surface. The capacitive coupling between the anode and the resistive plane has the double advantage of eliminating the spatial modulations due to the lattice of the anode and also of sensitizing a greater number of electrodes, increasing thus considerably the accuracy of the position measurements. The tests carried out with a time to digital conversion module of 250 ps resolution showed that a spatial resolution better than 50 ?m and a dead time of 160 ns can be achieved. Typical images obtained with the help of the EPICEA and DELICIOUS coincidence setups are also shown.

Céolin, D.; Chaplier, G.; Lemonnier, M.; Garcia, G. A.; Miron, C.; Nahon, L.; Simon, M.; Leclercq, N.; Morin, P.

2005-04-01

98

Modelling of ceramic matrix composite microstructure using a two-dimensional fractal spatial particle distribution  

NASA Astrophysics Data System (ADS)

Particulate composite reinforcements are good candidates for the fracture toughness of ceramics. In order to predict mechanical response of ceramic matrix composites, an efficient method capable of modelling their complex microstructure is needed. The purpose of this research is the development of such a model using fractal spatial particle distribution. A review of different toughness mechanisms for particulate composites and associated models for deriving their constitutive relationships is presented in chapter 2. These different toughening mechanisms as well constitutive properties depend on particle shape, size and spatial distribution, which lend themselves to a self-similar fractal based modelling approach. A self-similar distribution of particles linked to the fractal geometry is proposed. Fractal geometry provides an ideal tool for describing the randomness and disorder of the system. Its foundations are reviewed in chapter three with emphasis on iterated function systems that are subsequently used to obtain the particle configurations in the proposed model. For the sake of completeness, a review of fractal structure in science is given to illustrate possible applications. Derivation of the volume fraction associated with self similar distributions is provided in chapter 4. This is followed by a description of the numerical model and the boundary conditions. A Finite Element simulation is performed for different volume fractions, generators and number of particles for different displacements (two uniaxial and biaxial cases) and 2-D stress state cases. From these simulations the inverse distribution of the maximum principal stress is computed. Then the self similar models are compared with the model obtained by the Yang Teriari Gokhale (Y.T.G.) method and model obtained by only one iteration. Fractal dimension for real microstructure are computed and microstructure based on the fractal dimension and number of particle is simulated. It can be derived that the fractal dimension can be related to the average radius of circular particle in special cases. General conclusion and recommendation for future work brings this investigation to a close.

Cottet, Arnaud J.

99

Properties of optical spatial solitons in photorefractive crystals with special emphasis to two-photon photorefractive nonlinearity  

NASA Astrophysics Data System (ADS)

We have reviewed recent developments of some aspects of optical spatial solitons in photorefractive media. Underlying principles governing the dynamics of photorefractive nonlinearity have been discussed using band transport model. Nonlinear dynamical equations for propagating solitons have been derived considering single as well as two-photon photorefractive processes. Fundamental properties of screening and photovoltaic solitons have been considered. For each type of solitons, three different configurations i.e., bright, dark and gray varieties have been considered. Mechanisms of formation of these solitons due to single as well as two-photon photorefractive processes have been considered and their self bending discussed. Vector solitons, particularly, incoherently coupled solitons due to single photon and two-photon photorefractive phenomena have been highlighted. Existence of some missing solitons have been also pointed out. In addition, incoherent solitons and discrete spatial solitons in optically-induced photorefractive lattices are also discussed.

Konar, S.; Biswas, Anjan

2013-10-01

100

Monte Carlo simulation of the spatial resolution and depth sensitivity of two-dimensional optical imaging of the brain  

PubMed Central

Absorption or fluorescence-based two-dimensional (2-D) optical imaging is widely employed in functional brain imaging. The image is a weighted sum of the real signal from the tissue at different depths. This weighting function is defined as “depth sensitivity.” Characterizing depth sensitivity and spatial resolution is important to better interpret the functional imaging data. However, due to light scattering and absorption in biological tissues, our knowledge of these is incomplete. We use Monte Carlo simulations to carry out a systematic study of spatial resolution and depth sensitivity for 2-D optical imaging methods with configurations typically encountered in functional brain imaging. We found the following: (i) the spatial resolution is <200 ?m for NA ?0.2 or focal plane depth ?300 ?m. (ii) More than 97% of the signal comes from the top 500 ?m of the tissue. (iii) For activated columns with lateral size larger than spatial resolution, changing numerical aperature (NA) and focal plane depth does not affect depth sensitivity. (iv) For either smaller columns or large columns covered by surface vessels, increasing NA and?or focal plane depth may improve depth sensitivity at deeper layers. Our results provide valuable guidance for the optimization of optical imaging systems and data interpretation.

Tian, Peifang; Devor, Anna; Sakadzic, Sava; Dale, Anders M.; Boas, David A.

2011-01-01

101

A new family of Thirring type optical spatial solitons via electromagnetically induced transparency  

NASA Astrophysics Data System (ADS)

We report the existence of a very large new family of two-component composite optical Thirring solitons which is solely supported by cross focusing of two optical beams, that is due to giant Kerr nonlinearity in the regime of electromagnetically induced transparency in vapor. We identify a wide parameter space of power and spatial widths, which permits the existence of such stationary solitons. Direct numerical simulations of the coupled nonlinear equations that describe such solitons have substantiated analytical results.

Jana, Soumendu; Konar, S.

2007-03-01

102

FDTD Computational Electromagnetics Modeling of Spatial Optical Solitons  

NASA Astrophysics Data System (ADS)

The frontier for computing and telecommunications holds the prospects for a significant development in terms of speed and capability. This is clearly apparent in the wealth of research findings in nanophotonics technology over the last ten years. Electronic-based processors and traditional transmission lines find an ultimate limit on their capability as frequencies are pushed higher. Moving to an all-optical processor architecture where operation at micron- and smaller wavelengths would offer incredible speed capabilities approaching the speed of light. The primary limitations to realize important optical computing technologies would be manipulating and generating lightwave signals on the nanometer scale. Whereas analytical methods can reveal tradeoffs in simplified problems of optical signal processing, and prototype experimentation can demonstrate real-world behavior of designs, these represent two extremes of the design process in terms of time and cost. The best solution between these is that of a computational model, offering deeper insight to the complex physics of the problem but still performed in a virtual environment. The finite-difference time-domain (FDTD) method is a computational electromagnetic modeling tool that powerfully analyzes practical photonics problems by iterative solution of Maxwell's equations directly. It holds an advantage over other methods of computation (e.g., method of moments) in that it can show the evolution of transient effects, show broadband physical behavior, and conveniently accommodate complex material properties. This thesis summarizes research on FDTD applied to nanophotonics, specifically to the problem of light manipulation on the nanometer scale. Exploiting nonlinearity in optics is an attractive endeavor because light beams---known as solitons---can be made to retain their transverse profile over long propagation distances, overcoming diffraction. This offers the ability to preserve signal quality and ease the manipulation process in optical switching applications. In this work we explore the application of specialized FDTD nonlinear optics algorithms to modeling the control and exotic phenomena of spatial solitons. For the first time FDTD is used to simulate unique soliton guided optics problems of interest, as well as soliton interaction with metals. This work is very relevant and useful towards the quest for progressing an all-optical computing architecture.

Lubin, Zachary

103

Design and realization of a two-dimensional spatial magnetic field mapping apparatus to measure magnetic fields of metamaterials  

NASA Astrophysics Data System (ADS)

The two-dimensional (2D) spatial electric-field mapping apparatus [Opt. Express 14, 8694 (2006)] plays an important role in experiments involving metamaterials, such as the verification of free-space and ground-plane invisibility cloaks. However, such an apparatus is valid only for the transverse-electric (TE) mode and is invalid for the transverse-magnetic (TM) mode, as it requires perfectly magnetic conducting (PMC) planes, which do not exist in nature. In this paper, we propose a 2D spatial magnetic-field mapping apparatus based on artificial magnetic conductor (AMC) plates. The AMC structure is designed using periodically perfectly electrical conducting patches with a sub-wavelength size on a dielectric substrate backed with the ground plane, which can simulate a PMC plane. Using two parallel PMC plates to form a TM-wave planar waveguide, we realize the 2D spatial magnetic-field mapping apparatus in order to measure the external and internal magnetic fields of metamaterials. Two types of excitations, a plane-wave source and a magnetic dipole, are used to feed the system. In order to validate the performance of the magnetic-field mapper, two gradient-index metamaterial lenses are measured, and the experimental results are in good agreement with the full-wave simulations.

Jiang, Quan; Zhou, Xiao Yang; Chin, Jessie Yao; Cui, Tie Jun

2011-07-01

104

Dark spatial optical solitons in planar gradient waveguides in the Z-cut of the 3m symmetry crystals  

SciTech Connect

The propagation of light beams is studied in a planar photorefractive waveguide fabricated by high-temperature diffusion of metal ions in the Z-cut substrate of the 3m symmetry crystal. The wave equations are obtained for single-mode light beams with TE and TM polarisations in planar diffusion waveguides, which take into account the two-dimensional distribution of the optical field. Expressions are found for a nonlinear change in the refractive index when the photovoltaic mechanism makes a dominant contribution to the photorefractive effect. The propagation of single-mode light beams is analysed numerically for a Ti:Fe:LiNbO{sub 3} waveguide fabricated by the successive diffusion of titanium and iron into lithium niobate. It is shown that single-mode light beams with a smooth amplitude envelope can propagate without significant changes in the region of a dip in the intensity modelling a dark soliton. The relations between the amplitude and width of a dark spatial soliton are obtained for the TM modes of a photorefractive planar waveguide. (solitons)

Frolova, M N; Borodin, M V; Shandarov, S M; Shandarov, V M; Larionov, Yu M [Tomsk State University, Tomsk (Russian Federation)

2003-11-30

105

New all-optical wavelength auto-router based on spatial solitons.  

PubMed

We propose a novel all-optical wavelength auto-router based on spatial solitons. By using the swing effect of spatial solitons in a Kerr-type nonlinear medium, the proposed nonlinear waveguide structure could function as a self-routing wavelength division multiplexer (WDM). It could be a potential key component in the applications of ultra-high-speed and ultra-high-capacity optical communications and optical data processing systems. PMID:19483961

Wu, Yaw-Dong

2004-09-01

106

Two-dimensional spatial survey of the plasma potential and electric field in a pulsed bipolar magnetron discharge  

SciTech Connect

Emissive and Langmuir probe techniques have been used to obtain two-dimensional (2D) spatial maps of the plasma potential V{sub p}, electric field E, and ion trajectories in a pulsed bipolar magnetron discharge. The magnetron was pulsed at a frequency of 100 kHz, with a 50% duty cycle and operated at an argon pressure of 0.74 Pa. The pulse wave form was characterized by three distinct phases: the 'overshoot', 'reverse', and 'on' phases. In the 'on' phase of the pulse, when the cathode voltage is driven to -670 V, the 2D spatial distribution of V{sub p} has a similar form to that in dc magnetron, with significant axial and radial electric fields in the bulk plasma, accelerating ions to the sheath edge above the cathode racetrack region. During the 'overshoot' phase (duration 200 ns), V{sub p} is raised to values greater than +330 V, more than 100 V above the cathode potential, with E pointing away from the target. In the 'reverse' phase V{sub p} has a value of +45 V at all measured positions, 2 V more positive than the target potential. In this phase there is no electric field present in the plasma. In the bulk of the plasma, the results from Langmuir probe and the emissive probe are in good agreement, however, in one particular region of the plasma outside the radius of the cathode, the emissive probe measurements are consistently more positive (up to 45 V in the 'on' time). This discrepancy is discussed in terms of the different frequency response of the probes and their perturbation of the plasma. A simple circuit model of the plasma-probe system has been proposed to explain our results. A brief discussion of the effect of the changing plasma potential distribution on the operation of the magnetron is given.

Vetushka, A.; Karkari, S.K.; Bradley, J.W. [Department of Physics, UMIST, Sackville Street, Manchester, M60 1QD (United Kingdom)

2004-11-01

107

Delivery of two-dimensional spatially-slowly-varying intensity-modulated beams by jaws only (JO) in rotate-translate mode.  

PubMed

IMRT can be delivered by jaws only (JO) provided some compromises are accepted. In this letter it is shown how the use of a rotate-translate methodology (ROTJO), also employing only jaws, can lead to the delivery of a two-dimensional intensity-modulated beam wherein the modulation is spatially slowly varying. PMID:20348607

Webb, S; Poludniowski, G

2010-03-26

108

Self-deflection of steady-state bright spatial solitons in biased photorefractive crystals  

Microsoft Academic Search

The self-bending process of steady-state bright spatial solitons in biased photorefractive media is investigated by taking into account diffusion effects. By integrating numerically the nonlinear propagation equation, it is found that the soliton beam evolution is approximately adiabatic. The self-deflection process is further studied using perturbation analysis, which predicts that the center of the optical beam moves on a parabolic

M. I. Carvalho; S. R. Singh; D. N. Christodoulides

1995-01-01

109

Numerical simulation of two-dimensional sine-Gordon solitons via a local weak meshless technique based on the radial point interpolation method (RPIM)  

Microsoft Academic Search

In this paper the meshless local radial point interpolation method (LRPIM) is adopted to simulate the two-dimensional nonlinear sine-Gordon (S-G) equation. The meshless LRPIM is one of the “truly meshless” methods since it does not require any background integration cells. In this case, all integrations are carried out locally over small quadrature domains of regular shapes, such as circles or

Mehdi Dehghan; Arezou Ghesmati

2010-01-01

110

Bright solitons in defocusing media with spatial modulation of the quintic nonlinearity.  

PubMed

It has been recently demonstrated that self-defocusing (SDF) media with cubic nonlinearity, whose local coefficient grows from the center to the periphery fast enough, support stable bright solitons without the use of any linear potential. Our objective is to test the genericity of this mechanism for other nonlinearities, by applying it to one- and two-dimensional (1D and 2D) quintic SDF media. The models may be implemented in optics (in particular, in colloidal suspensions of nanoparticles), and the 1D model may be applied to the description of the Tonks-Girardeau gas of ultracold bosons. In 1D, the nonlinearity-modulation function is taken as g0+sinh2(?x). This model admits a subfamily of exact solutions for fundamental solitons. Generic soliton solutions are constructed in a numerical form and also by means of the Thomas-Fermi and variational approximations (TFA and VA). In particular, a new ansatz for the VA is proposed, in the form of "raised sech," which provides for an essentially better accuracy than the usual Gaussian ansatz. The stability of all the fundamental (nodeless) 1D solitons is established through the computation of the corresponding eigenvalues for small perturbations and also verified by direct simulations. Higher-order 1D solitons with two nodes have a limited stability region, all the modes with more than two nodes being unstable. It is concluded that the recently proposed inverted Vakhitov-Kolokolov stability criterion for fundamental bright solitons in systems with SDF nonlinearities holds here too. Particular exact solutions for 2D solitons are produced as well. PMID:23031045

Zeng, Jianhua; Malomed, Boris A

2012-09-24

111

Dark and bright vector spatial solitons in biased photorefractive media  

Microsoft Academic Search

We show that the vector beam evolution equations in properly oriented biased photorefractive media can exhibit bright-dark soliton pair solutions under steady-state conditions. These wave pairs are obtained perturbatively provided that the intensities of the two optical beams are approximately equal. Our analysis indicates that these bright-dark vector solitons exist irrespective of the polarity of the external bias field. The

M. I. Carvalho; S. R. Singh; D. N. Christodoulides; R. I. Joseph

1996-01-01

112

Mechanisms of crossing for an X-junction based on dark spatial solitons  

NASA Astrophysics Data System (ADS)

We present a fundamental study on the capability of a crossing of two optical waveguides based on dark spatial solitons to act as a controllable optical beam splitter. Our study is based on the fact that the guided beam is diffracted at the waveguide crossing by an effective phase screen formed by the soliton collision profile. We find that when the two dark solitons are immersed into the same finite bright background, the energy of a guided beam can be split into the desired optical channel according to the collision angle. We also found that even the corresponding phase diffractive screen possesses a quite different structure in the bright and dark soliton cases; the physics involved is the same. The authors would like to dedicate this work to the memory of G E Torres-Cisneros.

Torres-Cisneros, M.; Aguilera-Cortés, L. A.; Meneses-Nava, M. A.; Sánchez-Mondragón, J. J.; Torres-Cisneros, G. E.

2004-05-01

113

(1 + 2)-Dimensional sub-strongly nonlocal spatial optical solitons: Perturbation method  

NASA Astrophysics Data System (ADS)

By extending the (1 + 1)-dimensional [(1 + 1)-D] perturbation method suggested by Ouyang et al. [S. Ouyang, Q. Guo, W. Hu, Phys. Rev. E. 74 (2006) 036622] to the (1 + 2)-D case, we obtain a fundamental soliton solution to the (1 + 2)-D nonlocal nonlinear Schrödinger equation (NNLSE) with a Gaussian-type response function for the sub-strongly nonlocal case. Numerical simulations show that the soliton solution obtained in this paper can describe the soliton states in both the sub-strongly nonlocal case and the strongly nonlocal case. It is found that the phase constant and the power of the (1 + 2)-D strongly nonlocal spatial optical soliton with a Gaussian-type response function are both in inverse proportion to the 4th power of its beam width.

Ren, Hongyan; Ouyang, Shigen; Guo, Qi; Wu, Lijun

2007-07-01

114

Langmuir wave solitons and spatial collapse in plasma physics  

Microsoft Academic Search

We discuss recent new results concerning coherent nonlinear structures associated with electron plasma or ``Langmuir'' waves. In the one-dimensional, adiabatic, and Hamiltonian limit, the envelope of such waves obeys a simple cubic nonlinear Schrödinger equation which possesses a well-known exact solution containing nonlinear entities such as solitons and breathers. Our emphasis in this paper is on the effects of: dissipation

Martin V. Goldman

1986-01-01

115

CLASSICAL AREAS OF PHENOMENOLOGY: The (1+1)-dimensional spatial solitons in media with weak nonlinear nonlocality  

NASA Astrophysics Data System (ADS)

We study the propagation of (1+1)-dimensional spatial soliton in a nonlocal Kerr-type medium with weak non-locality. First, we show that an equation for describing the soliton propagation in weak nonlocality is a nonlinear Schrödinger equation with perturbation terms. Then, an approximate analytical solution of the equation is found by the perturbation method. We also find some interesting properties of the intensity profiles of the soliton.

Ding, Na; Guo, Qi

2009-10-01

116

Simultaneous compensation for spatial and temporal dispersion of acousto-optical deflectors for two-dimensional scanning with a single prism.  

PubMed

The dispersive nature of the acousto-optical deflector (AOD) presents a challenge to applications of two sequential orthogonal AODs (a two-dimensional AOD) as XY scanners in multiphoton microscopy. Introducing a prism before the two-dimensional (2D) AOD allows both temporal and spatial dispersion to be compensated for simultaneously. A 90 fs laser pulse was broadened to 572 fs without compensation, and 143 fs with compensation. The ratio of long axis to short axis of the exiting laser beam spot was 3.50 without compensation and 1.14 with compensation. The insertion loss was 37%. Two-photon fluorescence microscopy used the compensated 2D AOD scanner to image a fluorescent microsphere, which improves signal intensity -15-fold compared with the uncompensated scanner. PMID:16625913

Zeng, Shaoqun; Lv, Xiaohua; Zhan, Chen; Chen, Wei R; Xiong, Wenhui; Jacques, Steven L; Luo, Qingming

2006-04-15

117

Simultaneous compensation for spatial and temporal dispersion of acousto-optical deflectors for two-dimensional scanning with a single prism  

NASA Astrophysics Data System (ADS)

The dispersive nature of the acousto-optical deflector (AOD) presents a challenge to applications of two sequential orthogonal AODs (a two-dimensional AOD) as XY scanners in multiphoton microscopy. Introducing a prism before the two-dimensional (2D) AOD allows both temporal and spatial dispersion to be compensated for simultaneously. A 90fs laser pulse was broadened to 572fs without compensation, and 143fs with compensation. The ratio of long axis to short axis of the exiting laser beam spot was 3.50 without compensation and 1.14 with compensation. The insertion loss was 37%. Two-photon fluorescence microscopy used the compensated 2D AOD scanner to image a fluorescent microsphere, which improves signal intensity ~15-fold compared with the uncompensated scanner.

Zeng, Shaoqun; Lv, Xiaohua; Zhan, Chen; Chen, Wei R.; Xiong, Wenhui; Jacques, Steven L.; Luo, Qingming

2006-04-01

118

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Spatial Soliton Solutions in a Harmonic Potential  

NASA Astrophysics Data System (ADS)

The F-expansion technique and the homogeneous nonlinear balance principle have been applied for solving a general (1+1)-dimensional nonlinear Schrödinger equation (NLSE) with varying coefficients and a harmonic potential. A family of (1+1)D spatial solitons has been obtained. The evolution features of exact solutions have been investigated.

Xu, Si-Liu; Liang, Jian-Chu; Yi, Lin

2009-07-01

119

Lie Symmetries and Solitons in Nonlinear Systems with Spatially Inhomogeneous Nonlinearities  

SciTech Connect

Using Lie group theory and canonical transformations, we construct explicit solutions of nonlinear Schroedinger equations with spatially inhomogeneous nonlinearities. We present the general theory, use it to show that localized nonlinearities can support bound states with an arbitrary number solitons, and discuss other applications of interest to the field of nonlinear matter waves.

Belmonte-Beitia, Juan; Perez-Garcia, Victor M.; Vekslerchik, Vadym; Torres, Pedro J. [Departamento de Matematicas, Escuela Tecnica Superior de Ingenieros Industriales, and Instituto de Matematica Aplicada a la Ciencia y la Ingenieria (IMACI), Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Departamento de Matematica Aplicada, Universidad de Granada, Campus de Fuentenueva s/n, 18071 Granada (Spain)

2007-02-09

120

Optical spatial soliton supported by photoisomerization nonlinearity in a polymer with a background beam  

SciTech Connect

We present detailed theoretical studies of optical spatial solitons (SSs) supported by photoisomerization nonlinearity in a polymer sample. One-dimensional dark and bright SSs and their existence curves are presented. Several combinations of polarizations of the signal and background beams can be used to form the SSs.

Wang Xiaosheng; She Weilong; Lee Wingkee [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen (Zhongshan) University, Guangzhou 510275 (China); Department of Physics, Chinese University of Hong Kong, Shatin, Hong Kong (China)

2006-10-15

121

Soliton dynamics in media with space stimulated Raman scattering and synchronic spatial variation of dispersion and self-phase modulation.  

PubMed

Solitons dynamics in the frame of the extended nonlinear Schro?dinger equation taking into account space stimulated Raman scattering (SSRS), synchronic spatial variation of inhomogeneous second-order dispersion (SOD), and self-phase modulation (SPM) is considered both analytically and numerically. Compensation of soliton Raman self-wave number down shift by synchronically increasing SOD and SPM is shown. Analytical soliton solution as a result of the equilibrium of SSRS and increasing both SOD and SPM is found. Regime of the dynamical equilibrium of SSRS and inhomogeneous media with periodical variation of soliton's parameters is found. Analytical and numerical results are in a good agreement. PMID:23556980

Aseeva, N V; Gromov, E M; Tyutin, V V

2013-03-01

122

Bright solitons in quasi-one-dimensional dipolar condensates with spatially modulated interactions  

NASA Astrophysics Data System (ADS)

We introduce a model for the condensate of dipolar atoms or molecules, in which the dipole-dipole interaction (DDI) is periodically modulated in space due to a periodic change of the local orientation of the permanent dipoles, imposed by the corresponding structure of an external field (the necessary field can be created, in particular, by means of magnetic lattices, which are available to the experiment). The system represents a realization of a nonlocal nonlinear lattice, which has a potential to support various spatial modes. By means of numerical methods and variational approximation (VA), we construct bright one-dimensional solitons in this system and study their stability. In most cases, the VA provides good accuracy and correctly predicts the stability by means of the Vakhitov-Kolokolov criterion. It is found that the periodic modulation may destroy some solitons, which exist in the usual setting with unmodulated DDI and can create stable solitons in other cases, not verified in the absence of modulations. Unstable solitons typically transform into persistent localized breathers. The solitons are often mobile, with inelastic collisions between them leading to oscillating localized modes.

Abdullaev, F. Kh.; Gammal, A.; Malomed, B. A.; Tomio, Lauro

2013-06-01

123

Impacts of elevation data spatial resolution on two-dimensional dam break flood simulation and consequence assessment  

SciTech Connect

A grid resolution sensitivity analysis using a two-dimensional flood inundation model has been presented in this paper. Simulations for 6 dam breaches located randomly in the United States were run at 10,30,60,90, and 120 meter resolutions. The dams represent a range of topographic conditions, ranging from 0% slope to 1.5% downstream of the dam. Using 10 meter digital elevation model (DEM) simulation results as the baseline, the coarser simulation results were compared in terms of flood inundation area, peak depths, flood wave travel time, daytime and nighttime population in flooded area, and economic impacts. The results of the study were consistent with previous grid resolution studies in terms of inundated area, depths, and velocity impacts. The results showed that as grid resolution is decreased, the relative fit of inundated area between the baseline and coarser resolution decreased slightly. This is further characterized by increasing over prediction as well as increasing under prediction with decreasing resolution. Comparison of average peak depths showed that depths generally decreased as resolution decreased, as well as the velocity. It is, however, noted that the trends in depth and velocity showed less consistency than the inundation area metrics. This may indicate that for studies in which velocity and depths must be resolved more accurately (urban environments when flow around buildings is important in the calculation of drag effects), higher resolution DEM data should be used. Perhaps the most significant finding from this study is the perceived insensitivity of socio-economic impacts to grid resolution. The difference in population at risk (PAR) and economic cost generally remained within 10% of the estimated impacts using the high resolution DEM. This insensitivity has been attributed to over estimated flood area and associated socio-economic impacts compensating for under estimated flooded area and associated socio-economic impacts. The United States has many dams that are classified as high-hazard potential that need an emergency action plan (EAP). It has been found that the development of EAPs for all high-hazard dams is handicapped due to funding limitations. The majority of the cost associated with developing an EAP is determining the flooded area. The results of this study have shown that coarse resolution dam breach studies can be used to provide an acceptable estimate of the inundated area and economic impacts, with very little computational cost. Therefore, the solution to limited funding may be to perform coarse resolution dam breach studies on high-hazard potential dams and use the results to help prioritize the order in which detailed EAPs should be developed.

Judi, David R [Los Alamos National Laboratory; Mcpherson, Timothy N [Los Alamos National Laboratory; Burian, Steven J [UNIV OF UTAH

2009-01-01

124

Pareto-optimality study into the comparison of the separation potential of comprehensive two-dimensional liquid chromatography in the column and spatial modes.  

PubMed

The expected performance of spatial ("flat-bed") two-dimensional liquid chromatography ((x)LC×(x)LC) has been calculated using the Pareto-optimality strategy. This approach allowed different objectives (total peak capacity, total analysis time, and total dilution) to be considered simultaneously and to establish optimal parameters (pressure drop, particle size, bed length, and initial spot size). The performance of spatial two-dimensional chromatographic systems was compared with that of conventional on-line, real-time two-dimensional column-liquid-chromatography systems ((t)LC×(t)LC). The potential gain in peak capacity and/or analysis time of the spatial configuration was confirmed. By restricting the spatial parameters to realistic chromatographic conditions (limiting the stress, as counterbalance for the pressure drop through the sorbent bed, to 2500 kg) it was found that (x)LC×(x)LC is attractive for very fast analysis of complex samples, rather than for extremely efficient separations. For example, a peak capacity of 780 may be achieved in only 2.7 min using a 100×100 mm sorbent bed of a quality currently encountered thin-layer chromatography. Furthermore, if beds can be packed as efficiently as contemporary columns, the predicted peak capacity increases to around 1000, corresponding to a peak-production rate of about 6.3 peaks/s. Possibilities to boost the performance of (x)LC×(x)LC further are briefly discussed. Unless we can overcome the severe stress requirements of high-performance (x)LC×(x)LC, conventional (t)LC×(t)LC may be more amenable to very complex separations, thanks to the very high peak capacities. However, (t)LC×(t)LC separations will require long analysis times (e.g. 10,000 peaks in 37 h, corresponding to 0.075 peaks/s at a pressure drop of 40 MPa). The best trade-off between total peak capacity, total analysis time, and total dilution under restricted (realistic) conditions was obtained using high pressures, small chromatographic beds, small particles, and relatively large sample spots. PMID:22424732

Vanhoutte, Dominique J D; Vivó-Truyols, Gabriel; Schoenmakers, Peter J

2012-01-25

125

Cascaded Raman slow light and optical spatial solitons in Kerr media  

NASA Astrophysics Data System (ADS)

We provide a complete experimental and numerical investigation of nonlinear beam propagation in a carbon disulfide liquid-filled Kerr slab waveguide using picosecond pulsed light. A first spatial analysis shows the generation of a multicolor solitary wave through the combined effects of cascaded Raman scattering and cross-phase modulation. The impact of temporal effects on this self-trapped optical beam is further studied through a spatiotemporal analysis. It is shown in particular how cascaded Raman slow light induces optical delays between the solitonic components which prevents higher-order spatial soliton and provides a remarkable beam stability. Experimental observations are in very good agreement with numerical simulations of the spatiotemporal (1+1D) nonlinear Schrödinger equation including the Raman scattering.

Fanjoux, Gil; Michaud, Jérémy; Maillotte, Hervé; Sylvestre, Thibaut

2013-03-01

126

On the Structure of the Two-Dimensional Spatially Periodic Inner Transition Layers in a Gas-Discharge Plasma  

SciTech Connect

We investigate the structure of the spatially periodic inner boundary layers in the plasma of a positive glow-discharge column produced in a long cylindrical tube with an electropositive gas inside. Asymptotic methods, namely, the method of boundary functions, are used to analyze the initial mathematical model. We consider the formation of contrast burst-type structures. We have found all principal terms of the boundary-layer asymptotics of the solution. The results obtained are compared with the available probe measurements of basic physical parameters of ionization waves (strata) in neon at low pressures.

Voronov, A.Ya. [Russian Federal Nuclear Center, All-Russia Scientific-Research Institute of Experimental Physics, Sarov, Nizhni Novgorod oblast, 607190 (Russian Federation)

2005-07-01

127

Two-Dimensional Patterns of Poly(N-isopropylacrylamide) Microgels to Spatially Control Fibroblast Adhesion and Temperature-Responsive Detachment.  

PubMed

Thermoresponsive poly(N-isopropyl acrylamide) (PNIPAM) microgels were patterned on polystyrene substrates via dip coating, creating cytocompatible substrates that provided spatial control over cell adhesion. This simple dip-coating method, which exploits variable substrate withdrawal speeds forming particle suspension stripes of densely packed PNIPAM microgels, while spacings between the stripes contained sparsely distributed PNIPAM microgels. The assembly of three different PNIPAM microgel patterns, namely, patterns composed of 50 ?m stripe/50 ?m spacing, 50 ?m stripe/100 ?m spacing, and 100 ?m stripe/100 ?m spacing, was verified using high-resolution optical micrographs and ImageJ analysis. PNIPAM microgels existed as monolayers within stripes and spacings, as revealed by atomic force microscopy (AFM). Upon cell seeding on PNIPAM micropatterned substrates, NIH3T3 fibroblast cells preferentially adhered within spacings to form cell patterns. Three days after cell seeding, cells proliferated to form confluent cell layers. The thermoresponsiveness of the underlying PNIPAM microgels was then utilized to recover fibroblast cell sheets from substrates simply by lowering the temperature without disrupting the underlying PNIPAM microgel patterns. Harvested cell sheets similar to these have been used for multiple tissue engineering applications. Also, this simple, low-cost, template-free dip-coating technique can be utilized to micropattern multifunctional PNIPAM microgels, generating complex stimuli-responsive substrates to study cell-material interactions and allow drug delivery to cells in a spatially and temporally controlled manner. PMID:23968193

Tsai, Hsin-Yi; Vats, Kanika; Yates, Matthew Z; Benoit, Danielle S W

2013-09-17

128

Lie Symmetries and Solitons in Nonlinear Systems with Spatially Inhomogeneous Nonlinearities  

Microsoft Academic Search

Using Lie group theory and canonical transformations we construct explicit\\u000asolutions of nonlinear Schrodinger equations with spatially inhomogeneous\\u000anonlinearities. We present the general theory, use it to show that localized\\u000anonlinearities can support bound states with an arbitrary number solitons and\\u000adiscuss other applications of interest to the field of nonlinear matter waves.

Juan Belmonte-Beitia; Víctor M. Pérez-García; Vadym Vekslerchik; Pedro J. Torres

2007-01-01

129

Optical switching with long-range interactions between strongly nonlocal spatial optical solitons  

SciTech Connect

With a (1+1)D strongly nonlocal model, we present an analytical solution of the interaction of two long-range Gaussian beams with an arbitrary phase and arbitrary injected angles. As the basic optical devices, an all-optical(AO) switching with long-range interactions between strongly nonlocal spatial optical solitons which is independent on the wavelength is accessed. The optimal design of this optical device is discussed.

Zhang Xiaping [Department of Physics, Nanjing Xiaozhuang University, Nanjing 210017 (China)

2010-03-08

130

Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with spatially modulated nonlinearity  

SciTech Connect

We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.

Zhang Jiefang; Meng Jianping; Wu Lei [Institute of Nonlinear Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li Yishen [Department of Mathematics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Malomed, Boris A. [Department of Physical Electronics, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)

2010-09-15

131

Exact solutions of the Gross-Pitaevskii equation for stable vortex modes in two-dimensional Bose-Einstein condensates  

SciTech Connect

We construct exact solutions of the Gross-Pitaevskii equation for solitary vortices, and approximate ones for fundamental solitons, in two-dimensional models of Bose-Einstein condensates with a spatially modulated nonlinearity of either sign and a harmonic trapping potential. The number of vortex-soliton (VS) modes is determined by the discrete energy spectrum of a related linear Schroedinger equation. The VS families in the system with the attractive and repulsive nonlinearity are mutually complementary. Stable VSs with vorticity S{>=}2 and those corresponding to higher-order radial states are reported, in the case of the attraction and repulsion, respectively.

Wu Lei; Zhang Jiefang [Institute of Nonlinear Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li Lu [Institute of Theoretical Physics, Shanxi University, Taiyuan, Shanxi 030006 (China); Mihalache, Dumitru [Horia Hulubei National Institute for Physics and Nuclear Engineering, R-077125 Magurele-Bucharest (Romania); Malomed, Boris A. [Department of Physical Electronics, Faculty of Engineering, Tel Aviv University, IL-69978 Tel Aviv (Israel); Liu, W. M. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2010-06-15

132

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Incoherently Coupled Grey-Grey Spatial Soliton Pairs in Biased Two-Photon Photovoltaic Photorefractive Crystals  

NASA Astrophysics Data System (ADS)

The incoherently coupled grey-grey screening-photovoltaic spatial soliton pairs are predicted in biased two-photon photovoltaic photorefractive crystals under steady-state conditions. These grey-grey screening-photovoltaic soliton pairs can be established provided that the incident beams have the same polarization, wavelength, and are mutually incoherent. The grey-grey screening-photovoltaic soliton pairs can be considered as the united form of grey-grey screening soliton pairs and open or closed-circuit grey-grey photovoltaic soliton pairs.

Su, Yan-Li; Jiang, Qi-Chang; Ji, Xuan-Mang

2010-05-01

133

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS Temporal Behavior of Low-Amplitude Grey Spatial Solitons in Biased Two-Photon Photorefractive Crystals  

NASA Astrophysics Data System (ADS)

The temporal property of grey screening spatial solitons due to two-photon photorefractive effect in low-amplitude regime is analyzed. The results indicate that a broad solitons is generated at the beginning, and as time evolves, the intensity width of grey solitons decreases monotonically to a minimum value toward steady state. In the same propagation time, the FWHM of solitons decreases with ? increasing or m decreasing. Moreover, the formation time of solitons is independent of ? and m. The time is close to a constant determined by the dielectric relaxation time.

Jiang, Qi-Chang; Su, Yan-Li; Ji, Xuan-Mang

2010-12-01

134

Two-dimensional plasmonic metamaterials  

Microsoft Academic Search

The fabrication of three-dimensional photonic metamaterials faces numerous technological challenges. Many new concepts and\\u000a ideas in the optics of metamaterials may be more easily tested in two spatial dimensions using the planar optics of surface\\u000a plasmon polaritons. In this paper we review recent progress in this direction. Two-dimensional photonic crystals exhibiting\\u000a either positive or negative refraction, and strongly anisotropic metamaterials,

I. I. Smolyaninov

2007-01-01

135

Multipole plasmonic lattice solitons  

SciTech Connect

We theoretically demonstrate a variety of multipole plasmonic lattice solitons, including dipoles, quadrupoles, and necklaces, in two-dimensional metallic nanowire arrays with Kerr-type nonlinearities. Such solitons feature complex internal structures with an ultracompact mode size approaching or smaller than one wavelength. Their mode sizes and the stability characteristics are studied in detail within the framework of coupled mode theory. The conditions to form and stabilize these highly confined solitons are within the experimentally achievable range.

Kou Yao; Ye Fangwei; Chen Xianfeng [Department of Physics, State Key Laboratory on Fiber Optic Local Area Communication Networks and Advanced Optical Communication Systems, Shanghai Jiao Tong University, Shanghai 200240 (China)

2011-09-15

136

Topological Solitons in Physics.  

ERIC Educational Resources Information Center

A broad definition of solitons and a discussion of their role in physics is given. Vortices and magnetic monopoles which are examples of topological solitons in two and three spatial dimensions are described in some detail. (BB)

Parsa, Zohreh

1979-01-01

137

Accessible solitons in complex Ginzburg-Landau media  

NASA Astrophysics Data System (ADS)

We construct dissipative spatial solitons in one- and two-dimensional (1D and 2D) complex Ginzburg-Landau (CGL) equations with spatially uniform linear gain; fully nonlocal complex nonlinearity, which is proportional to the integral power of the field times the harmonic-oscillator (HO) potential, similar to the model of “accessible solitons;” and a diffusion term. This CGL equation is a truly nonlinear one, unlike its actually linear counterpart for the accessible solitons. It supports dissipative spatial solitons, which are found in a semiexplicit analytical form, and their stability is studied semianalytically, too, by means of the Routh-Hurwitz criterion. The stability requires the presence of both the nonlocal nonlinear loss and diffusion. The results are verified by direct simulations of the nonlocal CGL equation. Unstable solitons spontaneously spread out into fuzzy modes, which remain loosely localized in the effective complex HO potential. In a narrow zone close to the instability boundary, both 1D and 2D solitons may split into robust fragmented structures, which correspond to excited modes of the 1D and 2D HOs in the complex potentials. The 1D solitons, if shifted off the center or kicked, feature persistent swinging motion.

He, Yingji; Malomed, Boris A.

2013-10-01

138

Anisotropic plasma crystal solitons.  

PubMed

An analytical two-dimensional model for weakly dispersive and weakly nonlinear longitudinal and transverse shear waves propagating in an ideal two-dimensional hexagonal Yukawa crystal is presented. The model takes into account the nonlinear terms up to the third order. Both compressional and shear soliton solutions are found in the long-wavelength approximation. It is shown that the compressional solitons are always supersonic and weakly anisotropic. The shear solitons, on the other hand, exhibit strong anisotropy and can be both subsonic and supersonic, depending on the direction of propagation. In the model, shear solitons cannot propagate along the main axes. The role of weak damping as well as formation of multiple solitons is analyzed. The results are discussed in connection with wave and Mach cone experiments in a monolayer hexagonal plasma crystal, and a diagnostic method is proposed to measure both the charge of the microparticles and the lattice parameter. PMID:12241301

Zhdanov, S K; Samsonov, D; Morfill, G E

2002-08-26

139

Storage by trapping and spatial staggering of multiple interacting solitons in {Lambda}-type media  

SciTech Connect

In this paper we investigate the properties of self-induced transparency (SIT) solitons, propagating in a {Lambda}-type medium. We find that the interaction between SIT solitons can lead to trapping with their phases preserved in the ground-state coherence of the medium. These phases can be altered in a systematic way by the application of appropriate light fields, such as additional SIT solitons. Furthermore, multiple independent SIT solitons can be made to propagate as bisolitons through their mutual interaction with a separate light field. Finally, we demonstrate that control of the SIT soliton phase can be used to implement an optical exclusive-or (xor) gate.

Beeker, Willem P.; Lee, Chris J.; Boller, Klaus J. [Laser Physics and Nonlinear Optics Group, MESA Research Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Can, Edip [Physics of Fluids Group, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands)

2010-11-15

140

Two Dimensional Schrodinger Equation  

NSDL National Science Digital Library

The Two Dimensional Schrodinger Equation model simulates the time evolution of a two-dimensional wave packet as it moves towards a slit with an obstacle in it, both with variable widths. By changing three parameters via sliders provided, slit width, obstacle width, and initial position of the wave packet, different behaviors can be explored. These phenomena include interference, diffraction produced by a slit, a corner, and an obstacle, and bouncing of the wave packet. In addition, the angle of propagation for the diffracted part of the wave packet can be measured. This simulation is described by a paper in the European Journal of Physics, "A versatile applet to explore the wave behaviour of particles, " J I FernĂĄndez Palop, 2009 Eur. J. Phys. 30 771, which outlines the simulation and how the usefulness of the simulation has been tested in the subject of quantum physics. The Two Dimensional Schrodinger Equation model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_schrodinger2d.jar file will run the program if Java is installed.

Palop, Jose I.

2010-07-16

141

Coherent two-dimensional nanoscopy.  

PubMed

We introduce a spectroscopic method that determines nonlinear quantum mechanical response functions beyond the optical diffraction limit and allows direct imaging of nanoscale coherence. In established coherent two-dimensional (2D) spectroscopy, four-wave-mixing responses are measured using three ingoing waves and one outgoing wave; thus, the method is diffraction-limited in spatial resolution. In coherent 2D nanoscopy, we use four ingoing waves and detect the final state via photoemission electron microscopy, which has 50-nanometer spatial resolution. We recorded local nanospectra from a corrugated silver surface and observed subwavelength 2D line shape variations. Plasmonic phase coherence of localized excitations persisted for about 100 femtoseconds and exhibited coherent beats. The observations are best explained by a model in which coupled oscillators lead to Fano-like resonances in the hybridized dark- and bright-mode response. PMID:21835982

Aeschlimann, Martin; Brixner, Tobias; Fischer, Alexander; Kramer, Christian; Melchior, Pascal; Pfeiffer, Walter; Schneider, Christian; Strüber, Christian; Tuchscherer, Philip; Voronine, Dmitri V

2011-08-11

142

Anderson Localization of Solitons  

SciTech Connect

At low temperature, a quasi-one-dimensional ensemble of atoms with an attractive interaction forms a bright soliton. When exposed to a weak and smooth external potential, the shape of the soliton is hardly modified, but its center-of-mass motion is affected. We show that in a spatially correlated disordered potential, the quantum motion of a bright soliton displays Anderson localization. The localization length can be much larger than the soliton size and could be observed experimentally.

Sacha, Krzysztof; Zakrzewski, Jakub [Instytut Fizyki imienia Mariana Smoluchowskiego and Mark Kac Complex Systems Research Center, Uniwersytet Jagiellonski, ulica Reymonta 4, PL-30-059 Krakow (Poland); Laboratoire Kastler-Brossel, UPMC, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France); Mueller, Cord A. [Laboratoire Kastler-Brossel, UPMC, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France); Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Delande, Dominique [Laboratoire Kastler-Brossel, UPMC, ENS, CNRS, 4 Place Jussieu, F-75005 Paris (France)

2009-11-20

143

Anderson localization of solitons.  

PubMed

At low temperature, a quasi-one-dimensional ensemble of atoms with an attractive interaction forms a bright soliton. When exposed to a weak and smooth external potential, the shape of the soliton is hardly modified, but its center-of-mass motion is affected. We show that in a spatially correlated disordered potential, the quantum motion of a bright soliton displays Anderson localization. The localization length can be much larger than the soliton size and could be observed experimentally. PMID:20366020

Sacha, Krzysztof; Müller, Cord A; Delande, Dominique; Zakrzewski, Jakub

2009-11-17

144

Two dimensional vernier  

NASA Astrophysics Data System (ADS)

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.

Juday, Richard D.

1992-01-01

145

Spin Statistics and CPT for Solitons  

Microsoft Academic Search

Conditions are analysed under which the statistics of soliton sectors of massive two-dimensional field theories can be properly defined. A soliton field algebra is defined as a crossed product with the group of soliton sectors. In this algebra, the nonlocal commutation relations are determined and weak locality, spin statistics and CPT theorems are proven. These theorems depart from their usual

Karl-Henning Rehren

1998-01-01

146

Modelling a two-dimensional spatial distribution of mycotoxin concentration in bulk commodities to design effective and efficient sample selection strategies  

Microsoft Academic Search

Mycotoxins in agricultural commodities are a hazard to human and animal health. Their heterogeneous spatial distribution in bulk storage or transport makes it particularly difficult to design effective and efficient sampling plans. There has been considerable emphasis on identifying the different sources of uncertainty associated with mycotoxin concentration estimations, but much less on identifying the effect of the spatial location

M. Rivas Casado; D. J. Parsons; R. M. Weightman; N. Magan; S. Origgi

2009-01-01

147

Dissipative solitons  

Microsoft Academic Search

The present review summarizes experimental and theoretical work dealing with self-organized solitary localized structures (LSs) that are observed in spatially extended nonlinear dissipative systems otherwise exhibiting translational and rotational symmetry. Thereby we focus on those LSs that essentially behave like particles and that we call dissipative solitons (DSs). Such objects are also solutions of corresponding nonlinear evolution equations and it

H.-G. Purwins; H. U. Bödeker; Sh. Amiranashvili

2010-01-01

148

Two-dimensional dispersive shock waves in dissipative optical media.  

PubMed

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, generation of extended shock waves containing multiple intensity oscillations in the "upstream" region, and gradually vanishing oblique dark solitons in the "downstream" region for input tilts exceeding critical one. The generation of stable dispersive shock waves is possible only below certain critical defect strength. PMID:23455300

Kartashov, Yaroslav V; Kamchatnov, Anatoly M

2013-03-01

149

Two-dimensional nanolithography using atom interferometry  

SciTech Connect

We propose a scheme for the lithography of arbitrary, two-dimensional nanostructures via matter-wave interference. The required quantum control is provided by a {pi}/2-{pi}-{pi}/2 atom interferometer with an integrated atom lens system. The lens system is developed such that it allows simultaneous control over the atomic wave-packet spatial extent, trajectory, and phase signature. We demonstrate arbitrary pattern formations with two-dimensional {sup 87}Rb wave packets through numerical simulations of the scheme in a practical parameter space. Prospects for experimental realizations of the lithography scheme are also discussed.

Gangat, A.; Pradhan, P.; Pati, G.; Shahriar, M.S. [Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

2005-04-01

150

A two-dimensional gas detector with individual readouts for neutron detection with a high spatial resolution and fast temporal response  

SciTech Connect

A gaseous neutron-imaging detector with individual signal readouts was developed for a high spatial resolution and a fast temporal response. The system comprises a multiwire head, a gas chamber with 541 channels, fast amplifier-shaper-discriminator boards, a logic circuit for position calculation and encoding, and a fast data-acquisition system. The developed prototype detector incorporating 40x40 channels exhibited a temporal response of {approx}100 ns (pulse width of the amplified signal) and a spatial resolution of 0.9 and 1.4 mm (full width at half maximum) in the x- and y-directions, respectively, with a gas pressure of 4.2-atm helium with 1.8-atm CF{sub 4}.

Tanaka, Hiroki; Nakamura, Tatsuya; Yamagishi, Hideshi; Soyama, Kazuhiko; Aizawa, Kazuya [Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

2005-09-15

151

Spatial variation in vegetation structure coupled to plant available water determined by two-dimensional soil resistivity profiling in a Brazilian savanna  

Microsoft Academic Search

Tropical savannas commonly exhibit large spatial heterogeneity in vegetation structure. Fine-scale patterns of soil moisture,\\u000a particularly in the deeper soil layers, have not been well investigated as factors possibly influencing vegetation patterns\\u000a in savannas. Here we investigate the role of soil water availability and heterogeneity related to vegetation structure in\\u000a an area of the Brazilian savanna (Cerrado). Our objective was

Joice N. Ferreira; Mercedes Bustamante; Diana C. Garcia-Montiel; Kelly K. Caylor; Eric A. Davidson

2007-01-01

152

The electrical soliton oscillator  

Microsoft Academic Search

Solitons are a special class of pulse-shaped waves that propagate in nonlinear dispersive media while maintaining their spatial confinement. They are found throughout nature where the proper balance between nonlinearity and dispersion is achieved. Examples of the soliton phenomena include shallow water waves, vibrations in a nonlinear spring-mass lattice, acoustic waves in plasma, and optical pulses in fiber optic cable.

David Shawn Ricketts

2006-01-01

153

Shaping solitons by lattice defects  

SciTech Connect

We demonstrate the existence of shape-preserving self-localized nonlinear modes in a two-dimensional photonic lattice with a flat-topped defect that covers several lattice sites. The balance of diffraction, defocusing nonlinearity, and optical potential induced by lattices with various forms of defects results in novel families of solitons featuring salient properties. We show that the soliton shape can be controlled by varying the shape of lattice defects. The existence domains of fundamental and vortex solitons in the semi-infinite gap expand with the defect amplitude. Vortex solitons in the semi-infinite gap with rectangular intensity distributions will break into dipole solitons when the propagation constant exceeds a critical value. In the semi-infinite and first-finite gaps, we find that lattices with rectangular defects can support stable vortex solitons which exhibit noncanonical phase structure.

Dong Liangwei [Institute of Information Optics of Zhejiang Normal University, Jinhua 321004 (China); Ye Fangwei [Department of Physics, Centre for Nonlinear Studies, and the Beijing-Hong Kong-Singapore Joint Centre for Nonlinear and Complex Systems (Hong Kong), Hoongkong Baptist University, Kowloon Tong (Hong Kong)

2010-11-15

154

Incoherent solitons  

Microsoft Academic Search

This thesis investigates the dynamical and soliton-like behavior of spatially-partially incoherent light beams in non-instantaneous nonlinear materials. Self-trapping of incoherent beams and their coherence properties are studied in great detail. Two complimentary approaches are developed in order to explain the observed incoherent self-focusing behavior in biased photorefractive media; namely the coherent density approach and the self- consistent incoherent multimode method.

Tamer Coskun

2000-01-01

155

Linearized two-dimensional fluid transients  

NASA Astrophysics Data System (ADS)

A numerical analysis of low-velocity two-dimensional transient fluid flow problems is presented. The method is similar in concept to the one-dimensional method of characteristics, but does not follow the traditional characteristics theory for two spatial dimensions. Distinct paths are defined in the three-dimensional space-time domain along which compatibility equations are integrated. The explicit procedure is explained, and validated by comparisons with analytical solutions.

Wylie, E. B.

1984-06-01

156

Two Dimensional Unstable Scar Statistics.  

National Technical Information Service (NTIS)

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. Thi...

J. D. Kotulski K. S. H. Lee L. K. Warne R. E. Jorgensen

2006-01-01

157

Two-Dimensional Critical Phenomena.  

National Technical Information Service (NTIS)

Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on...

H. Saleur

1987-01-01

158

Change in the refractive index of a photorefractive crystal during formation of a spatially screened soliton  

SciTech Connect

A change in the refractive index of a photorefractive barium-sodium niobate crystal in an alternating electric field during the propagation of intensity-modulated coherent radiation in it is studied. It is shown experimentally that a change in the refractive index in the soliton regime in a photorefractive crystal with a small nonlocal response is independent of the external-field amplitude and intensity-modulation depth. (nonlinear-optics phenomena)

Assel'born, Sergei A; Kundikova, Nataliya D; Novikov, Igor' V [University Academic Division of Nonlinear Optics, Institute of Electrophysics, Ural Division, Russian Academy of Sciences, South Ural State University, Chelyabinsk (Russian Federation)

2010-02-28

159

Soliton dynamics in modulated Bessel photonic lattices  

SciTech Connect

We address the existence and the controlled stability of two-dimensional solitons in modulated Bessel lattices (MBL) induced by a superposition of nondiffracting Bessel beams. We show that variation of the modulation parameter of the lattice and the initial transverse momentum of the soliton significantly modify the behavior of the solitons. We find that, under suitable and well-identified conditions, solitons propagating in the MBL exhibit six regimes of transverse mobility: stationary, oscillatory, rotating, unbounded or escape, transitional, and unstable. These results report propagating solitons that can develop these dynamics of transverse motion.

Ruelas, Adrian; Lopez-Aguayo, Servando; Gutierrez-Vega, Julio C. [Photonics and Mathematical Optics Group, Tecnologico de Monterrey, Monterrey, Mexico 64849 (Mexico)

2010-12-15

160

Inelastic collision of spherical ion-acoustic solitons  

Microsoft Academic Search

The collision of spherical ion-acoustic solitons having different centers of symmetry is studied. Unlike one-dimensional collisions, the solitons are significantly changed by the collision. A new two-dimensional nonlinear object is found to be created. Remnants of the solitons that survive are found to be shifted in phase and reduced in amplitude.

Frederic Ze; Noah Hershkowitz; Chung Chan; K. E. Lonngren

1979-01-01

161

Two-dimensional optimal sensor placement  

SciTech Connect

A method for determining the optimal two-dimensional spatial placement of multiple sensors participating in a robot perception task is introduced in this paper. This work is motivated by the fact that sensor data fusion is an effective means of reducing uncertainties in sensor observations, and that the combined uncertainty varies with the relative placement of the sensors with respect to each other. The problem of optimal sensor placement is formulated and a solution is presented in the two dimensional space. The algebraic structure of the combined sensor uncertainty with respect to the placement of sensor is studied. A necessary condition for optimal placement is derived and this necessary condition is used to obtain an efficient closed-form solution for the global optimal placement. Numerical examples are provided to illustrate the effectiveness and efficiency of the solution. 11 refs.

Zhang, H. [Univ. of Alberta, Edmonton, Alberta (Canada)

1995-05-01

162

Cloaking two-dimensional fermions  

SciTech Connect

A cloaking theory for a two-dimensional spin-(1/2) fermion is proposed. It is shown that the spinor of the two-dimensional fermion can be cloaked perfectly through controlling the fermion's energy and mass in a specific manner moving in an effective vector potential inside a cloaking shell. Different from the cloaking of three-dimensional fermions, the scaling function that determines the invisible region is uniquely determined by a nonlinear equation. It is also shown that the efficiency of the cloaking shell is unaltered under the Aharonov-Bohm effect.

Lin, De-Hone [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2011-09-15

163

Optical Solitons  

NASA Astrophysics Data System (ADS)

1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

Taylor, J. R.

1992-04-01

164

Optical Solitons  

NASA Astrophysics Data System (ADS)

1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

Taylor, J. R.

2005-08-01

165

Two-dimensional solvable chaos  

NASA Astrophysics Data System (ADS)

Two methods are proposed to construct two-dimensional chaotic maps. Several examples of exactly solvable chaotic maps and their invariant measures are obtained. They are isomorphic maps of square to square, plane to plane and circle to circle having various symmetry such as uniform, rotational and the quartic rotational symmetry.

Sogo, Kiyoshi; Masumizu, Atsushi

2011-09-01

166

Investigation of the spatial structure of des-Gly/sup 9/-(Arg/sup 8/)vasopressin by the methods of two-dimensional NMR spectroscopy and theoretical conformational analysis  

SciTech Connect

An assignment of the /sup 1/H NMR signals of des-Gly/sup 9/-(Arg/sup 8/)vasopressin in dimethyl sulfoxide has been made by 2D spectroscopy. The SSCCs and temperature coefficients ..delta..delta/..delta.. T have been obtained for the amide protons and the system of NOE cross-peaks in the two-dimensional NOESY spectrum has been analyzed. The most important information on the spatial structure of des-Gly/sup 9/-(Arg/sup 8/)vasopressin is given by the low value of the temperature coefficient ..delta..delta/..delta.. T of the Asn/sup 5/ amide proton and the NOE between the ..cap alpha..-protons of Cys/sup 1/ and Cys/sup 6/. It is assumed that the screening of the NH proton of the Asn/sup 5/ residue from the solvent is connected with a ..beta..-bend of the backbone in the 2-5 sequence, and the distance between the C/sup ..cap alpha../H atoms of the Cys/sup 1/ and Cys/sup 6/ residues does not exceed 4 A. Bearing these limitations in mind, a theoretical conformational analysis of the molecule has been made. The group of low-energy conformations of the backbone obtained has been compared with the complete set of NMR characteristics.

Shenderovich, M.D.; Sekatsis, I.P.; Liepin'sh, E.E.; Nikiforovich, G.V.; Papsuevich, O.S.

1986-07-01

167

Defect-mediated discrete solitons in optically induced photorefractive lattices  

SciTech Connect

Theoretical analysis to the defect mediated discrete solitons in one- and two-dimensional periodical waveguide lattices is presented. The waveguide arrays with these functional defects are assumed to respond to the light field as an optically induced photorefraction and they are patterned by a holographic technique. It is found that the spatial energy distributions of the solitary waves can be controlled by the defects in the waveguide arrays, and this gives rise to an additional freedom to externally shaping the light field distribution to a special shape.

Li Yongyao [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); Department of Applied Physics, South China Agricultural University, Guangzhou 510642 (China); Pang Wei [Department of Experiment, Guangdong University of Technology, Guangzhou 510006 (China); Chen Yongzhu [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); School of Electro-Mechanic Engineering, Guangdong Polytechnic Normal University, Guangzhou 510665 (China); Yu Zhiqiang; Zhou Jianying; Zhang Huarong [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China)

2009-10-15

168

Two-dimensional thermofield bosonization  

SciTech Connect

The main objective of this paper was to obtain an operator realization for the bosonization of fermions in 1 + 1 dimensions, at finite, non-zero temperature T. This is achieved in the framework of the real-time formalism of Thermofield Dynamics. Formally, the results parallel those of the T = 0 case. The well-known two-dimensional Fermion-Boson correspondences at zero temperature are shown to hold also at finite temperature. To emphasize the usefulness of the operator realization for handling a large class of two-dimensional quantum field-theoretic problems, we contrast this global approach with the cumbersome calculation of the fermion-current two-point function in the imaginary-time formalism and real-time formalisms. The calculations also illustrate the very different ways in which the transmutation from Fermi-Dirac to Bose-Einstein statistics is realized.

Amaral, R.L.P.G. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea S/N, Boa Viagem, Niteroi, CEP, 24210-340 Rio de Janeiro (Brazil)]. E-mail: rubens@if.uff.br; Belvedere, L.V. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea S/N, Boa Viagem, Niteroi, CEP, 24210-340 Rio de Janeiro (Brazil); Rothe, K.D. [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)

2005-12-15

169

Finding two-dimensional peaks  

Microsoft Academic Search

Two-dimensional generalization of the original peak finding algorithm suggested earlier is given. The ideology of the algorithm\\u000a emerged from the well-known quantum mechanical tunneling property which enables small bodies to penetrate through narrow potential\\u000a barriers. We merge this “quantum” ideology with the philosophy of Particle Swarm Optimization to get the global optimization\\u000a algorithm which can be called Quantum Swarm Optimization.

Z. K. Silagadze

2007-01-01

170

Dynamical and topological solitons in a ferromagnet  

NASA Astrophysics Data System (ADS)

The paper is a review of the authors' results in the theory of non-linear excitations in ferromagnets. For the one-dimensional ferromagnet a new class of two-parameter dynamical solitons has been described. In the two-dimensional case a topological soliton (magnetic vortex) has been shown to exist. In the three-dimensional ferromagnet dynamical magnetic solitons of the magnon drop type have been analyzed. In addition, the possibility of existence of a three-dimensional topological soliton has been proven.

Kosevich, A. M.; Ivanov, B. A.; Kovalev, A. S.

1981-07-01

171

Superpower free electron lasers with two-dimensional distributed feedback  

Microsoft Academic Search

Using time domain analysis we have studied the processes of oscillation build-up and spatial synchronization in FELs with two-dimensional distributed feedback driven by large size sheet and tubular relativistic electron beams. It is proved that the proposed feedback mechanism ensures powerful spatially coherent radiation when the ratio between the transverse sized of the electron beam and the wavelength is up

N. S. Ginzburg; N. Yu. Peskov; A. S. Sergeev; A. V. Arzhannikov; S. L. Sinitsky

1995-01-01

172

Classically spinning and isospinning solitons  

SciTech Connect

We investigate classically spinning topological solitons in (2+1)- and (3+1)-dimensional models; more explicitely spinning sigma model solitons in 2+1 dimensions and Skyrme solitons in 2+1 and 3+1 dimensions. For example, such types of solitons can be used to describe quasiparticle excitations in ferromagnetic quantum Hall systems or to model spin and isospin states of nuclei. The standard way to obtain solitons with quantised spin and isospin is the semiclassical quantization procedure: One parametrizes the zero-mode space - the space of energy-degenerate soliton configurations generated from a single soliton by spatial translations and rotations in space and isospace - by collective coordinates which are then taken to be time-dependent. This gives rise to additional dynamical terms in the Hamiltonian which can then be quantized following semiclassical quantization rules. A simplification which is often made in the literature is to apply a simple adiabatic approximation to the (iso)rotational zero modes of the soliton by assuming that the soliton's shape is rotational frequency independent. Our numerical results on classically spinning arbitrarily deforming soliton solutions clearly show that soliton deformation cannot be ignored.

Battye, Richard A.; Haberichter, Mareike [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

2012-09-26

173

Application of the two-dimensional Fourier transform to nonlinear wave propagation phenomena  

Microsoft Academic Search

A new technique based on the two-dimensional Fourier transform is presented and applied to the study of nonlinear wave propagation phenomena in one-dimensional, finite, nonlinear transmission lines. The technique permits determining the effects of nonlinearities and boundary conditions on the Fourier transform and identifying incident and reflected waves and solitons which may propagate through the transmission line at constant speed.

I. Molina-Fernandez; C. Camacho-Penalosa; Juan I. Ramos

1994-01-01

174

Two-dimensional colloidal alloys.  

PubMed

We study the structure of mixed monolayers of large (3 ?m diameter) and small (1 ?m diameter) very hydrophobic silica particles at an octane-water interface as a function of the number fraction of small particles ?. We find that a rich variety of two-dimensional hexagonal super-lattices of large (A) and small (B) particles can be obtained in this system due to strong and long-range electrostatic repulsions through the nonpolar octane phase. The structures obtained for the different compositions are in good agreement with zero temperature calculations and finite temperature computer simulations. PMID:21517357

Law, Adam D; Buzza, D Martin A; Horozov, Tommy S

2011-03-24

175

Two-dimensional stationary Schroedinger equation via the {partial_derivative}-dressing method: New exactly solvable potentials, wave functions, and their physical interpretation  

SciTech Connect

The classes of exactly solvable multiline soliton potentials and corresponding wave functions of two-dimensional stationary Schroedinger equation via {partial_derivative}-dressing method are constructed and their physical interpretation is discussed.

Dubrovsky, V. G.; Topovsky, A. V.; Basalaev, M. Yu. [Novosibirsk State Technical University, Karl Marx prosp. 20, Novosibirsk 630092 (Russian Federation)

2010-09-15

176

KP solitons, total positivity, and cluster algebras  

PubMed Central

Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili [Kadomtsev BB, Petviashvili VI (1970) Sov Phys Dokl 15:539–541] proposed a two-dimensional nonlinear dispersive wave equation now known as the KP equation. It is well-known that the Wronskian approach to the KP equation provides a method to construct soliton solutions. The regular soliton solutions that one obtains in this way come from points of the totally nonnegative part of the Grassmannian. In this paper we explain how the theory of total positivity and cluster algebras provides a framework for understanding these soliton solutions to the KP equation. We then use this framework to give an explicit construction of certain soliton contour graphs and solve the inverse problem for soliton solutions coming from the totally positive part of the Grassmannian.

Kodama, Yuji; Williams, Lauren K.

2011-01-01

177

Occurrence conditions for two-dimensional Borromean systems  

NASA Astrophysics Data System (ADS)

We search for Borromean three-body systems of identical bosons in two dimensional geometry, i.e. we search for bound three-boson system without bound two-body subsystems. Unlike three spatial dimensions, in two-dimensional geometry the two- and three-body thresholds often coincide ruling out Borromean systems. We show that Borromean states can only appear for potentials with substantial attractive and repulsive parts. Borromean states are most easily found when a barrier is present outside an attractive pocket. Extensive numerical search did not reveal Borromean states for potentials without an outside barrier. We outline possible experimental setups to observe Borromean systems in two spatial dimensions.

Volosniev, Artem G.; Fedorov, Dmitri V.; Jensen, Aksel S.; Zinner, Nikolaj T.

2013-05-01

178

Interacao efetiva soliton-soliton. (Soliton-soliton effective interaction).  

National Technical Information Service (NTIS)

A scheme of semi-phenomenological quantization is proposed for the collision process of two equal size envelopes-solitons provided by nonlinear Schroedinger equation. The time advance due to two envelopes-solitons collision was determined. Considering the...

J. N. Maki

1986-01-01

179

Two-dimensional supersonic nonlinear Schrödinger flow past an extended obstacle.  

PubMed

Supersonic flow of a superfluid past a slender impenetrable macroscopic obstacle is studied in the framework of the two-dimensional (2D) defocusing nonlinear Schrödinger (NLS) equation. This problem is of fundamental importance as a dispersive analog of the corresponding classical gas-dynamics problem. Assuming the oncoming flow speed is sufficiently high, we asymptotically reduce the original boundary-value problem for a steady flow past a slender body to the one-dimensional dispersive piston problem described by the nonstationary NLS equation, in which the role of time is played by the stretched x coordinate and the piston motion curve is defined by the spatial body profile. Two steady oblique spatial dispersive shock waves (DSWs) spreading from the pointed ends of the body are generated in both half planes. These are described analytically by constructing appropriate exact solutions of the Whitham modulation equations for the front DSW and by using a generalized Bohr-Sommerfeld quantization rule for the oblique dark soliton fan in the rear DSW. We propose an extension of the traditional modulation description of DSWs to include the linear "ship-wave" pattern forming outside the nonlinear modulation region of the front DSW. Our analytic results are supported by direct 2D unsteady numerical simulations and are relevant to recent experiments on Bose-Einstein condensates freely expanding past obstacles. PMID:19905446

El, G A; Kamchatnov, A M; Khodorovskii, V V; Annibale, E S; Gammal, A

2009-10-26

180

Two-dimensional supersonic nonlinear Schrödinger flow past an extended obstacle  

NASA Astrophysics Data System (ADS)

Supersonic flow of a superfluid past a slender impenetrable macroscopic obstacle is studied in the framework of the two-dimensional (2D) defocusing nonlinear Schrödinger (NLS) equation. This problem is of fundamental importance as a dispersive analog of the corresponding classical gas-dynamics problem. Assuming the oncoming flow speed is sufficiently high, we asymptotically reduce the original boundary-value problem for a steady flow past a slender body to the one-dimensional dispersive piston problem described by the nonstationary NLS equation, in which the role of time is played by the stretched x coordinate and the piston motion curve is defined by the spatial body profile. Two steady oblique spatial dispersive shock waves (DSWs) spreading from the pointed ends of the body are generated in both half planes. These are described analytically by constructing appropriate exact solutions of the Whitham modulation equations for the front DSW and by using a generalized Bohr-Sommerfeld quantization rule for the oblique dark soliton fan in the rear DSW. We propose an extension of the traditional modulation description of DSWs to include the linear “ship-wave” pattern forming outside the nonlinear modulation region of the front DSW. Our analytic results are supported by direct 2D unsteady numerical simulations and are relevant to recent experiments on Bose-Einstein condensates freely expanding past obstacles.

El, G. A.; Kamchatnov, A. M.; Khodorovskii, V. V.; Annibale, E. S.; Gammal, A.

2009-10-01

181

Two-dimensional supersonic nonlinear Schroedinger flow past an extended obstacle  

SciTech Connect

Supersonic flow of a superfluid past a slender impenetrable macroscopic obstacle is studied in the framework of the two-dimensional (2D) defocusing nonlinear Schroedinger (NLS) equation. This problem is of fundamental importance as a dispersive analog of the corresponding classical gas-dynamics problem. Assuming the oncoming flow speed is sufficiently high, we asymptotically reduce the original boundary-value problem for a steady flow past a slender body to the one-dimensional dispersive piston problem described by the nonstationary NLS equation, in which the role of time is played by the stretched x coordinate and the piston motion curve is defined by the spatial body profile. Two steady oblique spatial dispersive shock waves (DSWs) spreading from the pointed ends of the body are generated in both half planes. These are described analytically by constructing appropriate exact solutions of the Whitham modulation equations for the front DSW and by using a generalized Bohr-Sommerfeld quantization rule for the oblique dark soliton fan in the rear DSW. We propose an extension of the traditional modulation description of DSWs to include the linear ''ship-wave'' pattern forming outside the nonlinear modulation region of the front DSW. Our analytic results are supported by direct 2D unsteady numerical simulations and are relevant to recent experiments on Bose-Einstein condensates freely expanding past obstacles.

El, G. A.; Khodorovskii, V. V. [Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU (United Kingdom); Kamchatnov, A. M. [Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow Region (Russian Federation); Annibale, E. S.; Gammal, A. [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil)

2009-10-15

182

Optimum Allocation of Two-Dimensional Shapes.  

National Technical Information Service (NTIS)

The optimum two-dimensional allocation problem consists in taking a two-dimensional resource and cutting it into a number of two-dimensional shapes in such a way that some objective function is optimized. The paper describes an investigation into methods ...

M. Adamowicz

1971-01-01

183

The electrical soliton oscillator  

NASA Astrophysics Data System (ADS)

Solitons are a special class of pulse-shaped waves that propagate in nonlinear dispersive media while maintaining their spatial confinement. They are found throughout nature where the proper balance between nonlinearity and dispersion is achieved. Examples of the soliton phenomena include shallow water waves, vibrations in a nonlinear spring-mass lattice, acoustic waves in plasma, and optical pulses in fiber optic cable. In electronics, the nonlinear transmission line (NLTL) serves as a nonlinear dispersive medium that propagates voltage solitons. Electrical solitons on the NLTL have been actively investigated over the last 40 years, particularly in the microwave domain, for sharp pulse generation applications and for high-speed RF and microwave sampling applications. In these past studies the NLTL has been predominantly used as a 2-port system where a high-frequency input is required to generate a sharp soliton output through a transient process. One meaningful extension of the past 2-port NLTL works would be to construct a 1-port self-sustained electrical soliton oscillator by properly combining the NLTL with an amplifier (positive active feedback). Such an oscillator would self-start by growing from ambient noise to produce a train of periodic soliton pulses in steady-state, and hence would make a self-contained soliton generator not requiring an external high-frequency input. While such a circuit may offer a new direction in the field of electrical pulse generation, there has not been a robust electrical soliton oscillator reported to date to the best of our knowledge. In this thesis we introduce the first robust electrical soliton oscillator, which is able to self-generate a stable, periodic train of electrical solitons. This new oscillator is made possible by combining the NLTL with a unique nonlinear amplifier that is able to "tame" the unruly dynamics of the NLTL. The principle contribution of this thesis is the identification of the key instability mechanisms of solitons in a closed-loop oscillator and the development of the necessary stabilizing mechanisms. Demonstration of the concepts developed were in the form of three prototypes: a low MHz discrete prototype, a microwave discrete prototype, and a chip-scale, GHz prototype.

Ricketts, David Shawn

184

Inelastic Soliton-Soliton Interaction in Coninin Models.  

National Technical Information Service (NTIS)

The field equations with nonlinearity proportional to Vertical BarPSIVertical Barsup(- alpha )PSI, alpha >0 (model 1 of Simonov-Tjon) are solved in one spatial dimension with initial conditions corresponding to two colliding solitons. One or several breat...

Y. A. Simonov A. I. Veselov

1980-01-01

185

Two-dimensional particle-in-cell simulations of plasma cavitation and bursty Brillouin backscattering for nonrelativistic laser intensities  

Microsoft Academic Search

Two-dimensional particle-in-cell simulations of laser-plasma interaction using a plane-wave geometry show strong bursty stimulated Brillouin backscattering, rapid filamentation, and subsequent plasma cavitation. It is shown that the cavitation is not induced by self-focusing. The electromagnetic fields below the plasma frequency that are excited are related to transient soliton-like structures. At the origin of these solitons is a three-wave decay process

C. Riconda; S. Weber; V. T. Tikhonchuk; J.-C. Adam; A. Heron

2006-01-01

186

Spatial Solutions in Photorefractive Media.  

National Technical Information Service (NTIS)

Light solitons in space spatial soliton) have been under an intensive theoretical and experimental research in the last three decades. The solitons evolve from nonlinear changes in the refractive index of the material, due to the light intensity distribut...

M. Segev A. Saa'r A. Yariv

1992-01-01

187

Stabilization of one-dimensional solitons against the critical collapse by quintic nonlinear lattices  

NASA Astrophysics Data System (ADS)

It has recently been discovered that stabilization of two-dimensional (2D) solitons against the critical collapse in media with cubic nonlinearity by means of nonlinear lattices (NLs) is a challenging problem. We address the one-dimensional (1D) version of the problem, i.e., the nonlinear-Schrödinger equation (NLSE) with quintic or cubic-quintic (CQ) terms, the coefficients in front of which are periodically modulated in space. The models may be realized in optics and Bose-Einstein condensates (BECs). Stability diagrams for the solitons are produced by means of numerical methods and analytical approximations. It is found that the sinusoidal NL stabilizes solitons supported by the quintic-only nonlinearity in a narrow stripe in the respective parameter plane, contrary to the case of the cubic nonlinearity in 2D, where the stabilization of solitons by smooth spatial modulations is not possible at all. The stability region is much broader in the 1D CQ model, where higher-order solitons may be stable too.

Zeng, Jianhua; Malomed, Boris A.

2012-02-01

188

A new two-dimensional millimeter wave imaging radiometer  

Microsoft Academic Search

Synthetic aperture radiometer has the potential to meet the spatial resolution requirement of passive microwave remote sensing from space. This paper introduces a prototype of two-dimensional imaging radiometer at millimeter wave (MMW) band. A G Matrix calibration approach and an iterative gradient inversion method are presented to obtain the brightness temperature image. Total least squares (TLS) image processing algorithms for

Yuanyuan Liu; Lu Zhu; Shan Wang

2010-01-01

189

A two-dimensional Prony's method for spectral estimation  

Microsoft Academic Search

The problem of estimating the parameters of a model for bidimensional data made up by a linear combination of damped two-dimensional sinusoids is considered. Frequencies, amplitudes, phases, and damping factors are estimated by applying a generalization of the monodimensional Prony's method to spatial data. This procedure finds the desired quantities after an autoregressive model fitting to the data, a polynomial

M. M. Barbieri; P. Barone

1992-01-01

190

Turbulent equipartitions in two dimensional drift convection  

SciTech Connect

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

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

1995-07-25

191

Oblique collision of plane ion-acoustic solitons  

Microsoft Academic Search

The nonlinear evolution of oblique collisions is investigated experimentally on plane ion-acoustic solitons in two-dimensional space. Many of the observed characteristics of inelastic collisions of solitons are found to be similar to those of resonance interactions described by nonlinear ion-acoustic waves.

Yasushi Nishida; Takeshi Nagasawa

1980-01-01

192

Four-wave-mixing gap solitons  

SciTech Connect

We report an experimental demonstration of generating gap soliton trains in a four-wave-mixing (FWM) signal. Such spatial FWM surfacelike gap soliton trains are induced in a periodically modulated self-defocusing atomic medium by the cross-phase modulation, which can be reshaped under different experimental conditions, such as different atomic densities, nonlinear dispersions, and dressing fields. Controlling spatial gap solitons can have important applications in image memory, processing, and communication.

Zhang Yanpeng; Wang Zhiguo; Zheng Huaibin; Yuan Chenzhi; Li Changbiao; Lu Keqing [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049 (China); Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2010-11-15

193

Influence of Forcing Structure on Two-Dimensional Weak Turbulence  

NASA Astrophysics Data System (ADS)

The dependence of the dynamics of two-dimensional turbulence on its forcing topology is an interesting and practical question for experiments. We generate quasi-two-dimensional flows in thin layers of salt water with a forcing geometry that is either a lattice of alternating vortices or an array of alternating shear bands. We observe that the vortex flow has more fluctuating energy, but that the shear flow has larger spatial gradients. We attribute these differences to the fact that shear forcing imposes fewer constraints on the flow and allows the production of smaller length scales.

Liao, Yang; Kelley, Douglas; Ouellette, Nicholas

2011-11-01

194

Equilibrium state of a trapped two-dimensional Bose gas  

SciTech Connect

We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional {sup 87}Rb Bose gas and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in situ measurements and quantum Monte Carlo simulations, which we attribute to a nonlinear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time of flight, taking advantage of their self-similarity in a two-dimensional expansion.

Rath, Steffen P.; Yefsah, Tarik; Guenter, Kenneth J.; Cheneau, Marc; Desbuquois, Remi; Dalibard, Jean [Laboratoire Kastler Brossel, CNRS, Universite Pierre et Marie Curie, Ecole Normale Superieure, 24 rue Lhomond, F-75005 Paris (France); Holzmann, Markus [Laboratoire de Physique Theorique de la Matiere Condensee, CNRS, Universite Pierre et Marie Curie, 4 Place Jussieu, F-75005 Paris, France, and Laboratoire de Physique et Modelisation des Milieux Condenses, CNRS, Universite Joseph Fourier, BP 166, F-38042 Grenoble (France); Krauth, Werner [Laboratoire de Physique Statistique, CNRS, Universite Pierre et Marie Curie, Universite Paris Diderot, Ecole Normale Superieure, 24 rue Lhomond, F-75005 Paris (France)

2010-07-15

195

Nonlinear compressional waves in a two-dimensional Yukawa lattice.  

PubMed

A modified Korteweg-de Vries (KdV) equation is obtained for studying the propagation of nonlinear compressional waves and pulses in a chain of particles including the effect of damping. Suitably altering the linear phase velocity makes this equation useful also for the problem of phonon propagation in a two-dimensional (2D) lattice. Assuming a Yukawa potential, we use this method to model compressional wave propagation in a 2D plasma crystal, as in a recent experiment. By integrating the modified KdV equation the pulse is allowed to evolve, and good agreement with the experiment is found. It is shown that the speed of a compressional pulse increases with its amplitude, while the speed of a rarefactive pulse decreases. It is further discussed how the drag due to the background gas has a crucial role in weakening nonlinear effects and preventing the emergence of a soliton. PMID:14683049

Avinash, K; Zhu, P; Nosenko, V; Goree, J

2003-10-08

196

TWO-DIMENSIONAL BELIEF CHANGE An Advertisement  

Microsoft Academic Search

In this paper I compare two dierent the models of two-dimensional belief change, namely 'revision by comparison' (Ferme and Rott, Artifi- cial Intelligence 157, 2004) and 'bounded revision' (Rott, in Hommagea Wlodek, Uppsala 2007). These revision operations are two-dimensional in the sense that they take as arguments pairs consisting of an input sentence and a reference sentence. Two-dimensional revision operations

Hans Rott

197

Transversely stable soliton trains in photonic lattices  

SciTech Connect

We report the existence of transversely stable soliton trains in optics. These stable soliton trains are found in two-dimensional square photonic lattices when they bifurcate from X-symmetry points with saddle-shaped diffraction inside the first Bloch band and their amplitudes are above a certain threshold. We also show that soliton trains with low amplitudes or bifurcated from edges of the first Bloch band ({Gamma} and M points) still suffer transverse instability. These results are obtained in the continuous lattice model and are further corroborated by the discrete model.

Yang Jianke [Department of Mathematics and Statistics, University of Vermont, Burlington, Vermont 05401 (United States)

2011-09-15

198

Solitons of axion-dilaton gravity  

SciTech Connect

We use soliton techniques of the two-dimensional reduced {beta}-function equations to obtain nontrivial string backgrounds from flat space. These solutions are characterized by two integers ({ital n},{ital m}) referring to the soliton numbers of the metric and axion-dilaton sectors, respectively. We show that the Nappi-Witten universe associated with the SL(2){times}SU(2)/SO(1,1){times}U(1) CFT coset arises as a (1,1) soliton in this fashion for certain values of the moduli parameters, while for other values of the soliton moduli we arrive at the SL(2)/SO(1,1){times}SO(1,1){sup 2} background. Ordinary four-dimensional black holes arise as two-dimensional (2,0) solitons, while the Euclidean wormhole background is described as a (0,2) soliton on flat space. The soliton transformations correspond to specific elements of the string Geroch group. These could be used as a starting point for exploring the role of {ital U} dualities in string compactifications to two dimensions. {copyright} {ital 1996 The American Physical Society.}

Bakas, I. [Theory Division, European Organization for Nuclear Research (CERN), 1211 Geneva 23, Switzerl]|[and Department of Physics, University of Patras, 26110 Patras (Greece)

1996-11-01

199

Information Extraction by Two Dimensional Parser  

Microsoft Academic Search

This paper proposes a learning algorithm for a two dimensional parser. The parser is designed to analyze page layout of documents and extract information using both textual and layout information. The parsing rules are expressed by an extended stochastic context free grammar that decomposes tokens located in two dimensional space both horizontally and vertically. In this paper we focus on

Atsuhiro Takasu

2008-01-01

200

Universal theory of steady-state one-dimensional photorefractive solitons  

Microsoft Academic Search

A universal theory of steady-state one-dimensional photorefractive spatial solitons is developed which applies to the steady-state one-dimensional photorefractive solitons under various realizations, including the screening solitons in a biased photorefractive medium, the photovoltaic solitons in open- and closed-circuit photovoltaic-photorefractive media and the screening-photovoltaic solitons in biased photovoltaic-photorefractive media. Previous theories advanced individually elsewhere for these solitons can be obtained by

Jin-song Liu

2001-01-01

201

On clutter modeling and the spectra of two-dimensional Gauss-Markov random signals  

NASA Astrophysics Data System (ADS)

The spectral properties of two-dimensional isotropic clutter signals are examined for the cases in which (1) the clutter has an exponential spatial autocorrelation function, and (2) the clutter is a two-dimensional Gauss-Markov random signal. The one- and two-dimensional power spectral densities before and after antenna filtering are obtained, and some of the differences and similarities between these two models are discussed in the context of spectral analysis.

Blanco, M. A.

1982-03-01

202

Fusion of necklace-ring patterns into vortex and fundamental solitons in dissipative media.  

PubMed

We demonstrate that necklace-shaped arrays of localized spatial beams can merge into stable fundamental or vortex solitons in a generic model of laser cavities, based on the two-dimensional complex Ginzburg-Landau equation with the cubic-quintic nonlinearity. The outcome of the fusion is controlled by the number of "beads" in the initial necklace, 2N, and its topological charge, M. We predict and confirm by systematic simulations that the vorticity of the emerging soliton is |N-M|. Threshold characteristics of the fusion are found and explained too. If the initial radius of the array (R(0)) is too large, it simply keeps the necklace shape (if R(0) is somewhat smaller, the necklace features a partial fusion), while, if R(0) is too small, the array disappears. PMID:19551043

He, Y J; Malomed, Boris A; Wang, H Z

2007-12-24

203

Controlling the transverse instability of dark solitons and nucleation of vortices by a potential barrier  

SciTech Connect

We study possibilities to suppress the transverse modulational instability (MI) of dark-soliton stripes in two-dimensional Bose-Einstein condensates (BEC's) and self-defocusing bulk optical waveguides by means of quasi-one-dimensional structures. Adding an external repulsive barrier potential (which can be induced in BEC by a laser sheet, or by an embedded plate in optics), we demonstrate that it is possible to reduce the MI wave number band, and even render the dark-soliton stripe completely stable. Using this method, we demonstrate the control of the number of vortex pairs nucleated by each spatial period of the modulational perturbation. By means of the perturbation theory, we predict the number of the nucleated vortices per unit length. The analytical results are corroborated by the numerical computation of eigenmodes of small perturbations, as well as by direct simulations of the underlying Gross-Pitaevskii/nonlinear Schroedinger equation.

Ma Manjun [College of Science, China Jiliang University, Hangzhou, Zhejiang, 310018 (China); Carretero-Gonzalez, R. [Nonlinear Physics Group, Departamento de Fisica Aplicada I, Universidad de Sevilla, Avda. Reina Mercedes s/n., E-41012 Sevilla (Spain); Kevrekidis, P. G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515 (United States); Frantzeskakis, D. J. [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 15784 (Greece); Malomed, B. A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv IL-69978 (Israel)

2010-08-15

204

Helmholtz solitons at nonlinear interfaces.  

PubMed

Reflection and refraction of spatial solitons at dielectric interfaces, accommodating arbitrarily angles of incidence, is studied. Analysis is based on Helmholtz soliton theory, which eliminates the angular restriction associated with the paraxial approximation. A novel generalization of Snell's law is discovered that is valid for collimated light beams and the entire angular domain. Our new theoretical predictions are shown to be in excellent agreement with full numerical simulations. New qualitative features of soliton refraction and limitations of previous paraxial analyses are highlighted. PMID:17410257

Sánchez-Curto, J; Chamorro-Posada, P; McDonald, G S

2007-05-01

205

Spontaneously walking discrete cavity solitons.  

PubMed

We study the dynamics of oscillating discrete solitons in an array of coupled Kerr-nonlinear cavities. They emanate from stationary discrete cavity solitons due to Hopf instability and are very robust. We show that these oscillating solitons can spontaneously lose their spatial symmetry and start rocking around the equilibrium position. Moreover they can suddenly jump to adjacent resonators starting a chaotic motion along the array, resembling the Brownian motion of particles. We also identify the parameter domain where they move with constant velocity across the array. PMID:23546226

Egorov, O A; Lederer, F

2013-04-01

206

Transition from discrete to continuous Townes solitons in periodic media  

SciTech Connect

We present a comprehensive analysis of how the properties of two-dimensional lattice (''discrete'') solitons in a Kerr medium are influenced by their peak intensity and width. We are able to quantitatively relate the Townes solution for solitons in a two-dimensional, homogeneous media to two distinct regimes of the lattice solitons: to narrow, high-intensity, highly nonlinear solitons and to broad, low-intensity, weakly nonlinear solitons, which experience the periodic potential as an effective homogeneous medium. Both regimes, although they support a different power flow and are affected by completely different diffraction dynamics, are thus traced back to the same physical phenomenon. They are separated by a range of unstable and stable solutions, directly caused by the periodicity of the lattice.

Eilenberger, Falk; Pertsch, Thomas [Institute for Applied Physics, Friedrich Schiller University, Max-Wien-Platz 1, D-07743 Jena (Germany); Szameit, Alexander [Physics Department and Solid State Institute, Technion-Israel Institute of Technology, 32000 Haifa (Israel)

2010-10-15

207

Soliton scattering in the Darboux transformation formalism  

SciTech Connect

The Darboux transformation technique is applied to derive soliton scattering formulas for the Kadomtsev-Petviashvili equation, the KdV equation, the nonlocal KdV equation, the two-dimensionalized Toda chain and its periodic reductions, in particular the sine-Gordon equation.

Matveev, V.B.; Sall', M.A.

1987-05-20

208

Current injection into a two-dimensional anisotropic bidomain.  

PubMed Central

A two-dimensional sheet of anisotropic cardiac tissue is represented with the bidomain model, and the finite element method is used to solve the bidomain equations. When the anisotropy ratios of the intracellular and extracellular spaces are not equal, the injection of current into the tissue induces a transmembrane potential that has a complicated spatial dependence, including adjacent regions of depolarized and hyperpolarized tissue. This behavior may have important implications for the electrical stimulation of cardiac tissue and for defibrillation.

Sepulveda, N G; Roth, B J; Wikswo, J P

1989-01-01

209

Spectral tunneling of lattice nonlocal solitons  

SciTech Connect

We address spectral tunneling of walking spatial solitons in photorefractive media with nonlocal diffusion component of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where solitons traveling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending, solitons survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.

Kartashov, Yaroslav V.; Torner, Lluis [ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain); Vysloukh, Victor A. [Departamento de Fisica y Matematicas, Universidad de las Americas-Puebla, Santa Catarina Martir, 72820 Puebla (Mexico)

2010-07-15

210

Discrete solitons in coupled active lasing cavities.  

PubMed

We examine the existence and stability of discrete spatial solitons in coupled nonlinear lasing cavities (waveguide resonators), addressing the case of active defocusing media, where the gain exceeds damping in the low-amplitude limit. A new family of stable localized structures is found: these are bright and gray cavity solitons representing the connections between homogeneous and inhomogeneous states. Solitons of this type can be controlled by discrete diffraction and are stable when the bistability of homogenous states is absent. PMID:23164851

Prilepsky, Jaroslaw E; Yulin, Alexey V; Johansson, Magnus; Derevyanko, Stanislav A

2012-11-15

211

Azimuthal instability of spinning spatiotemporal solitons  

PubMed

We find one-parameter families of three-dimensional spatiotemporal bright vortex solitons (doughnuts, or spinning light bullets), in dispersive quadratically nonlinear media. We show that they are subject to a strong instability against azimuthal perturbations, similarly to the previously studied (2+1)-dimensional bright spatial vortex solitons. The instability breaks the spinning soliton into several fragments, each being a stable nonspinning light bullet. PMID:11088714

Mihalache; Mazilu; Crasovan; Malomed; Lederer

2000-08-01

212

Superconductivity, Spin and Charge Density Structures in One and Two-Dimensional Self-Consistent Models  

NASA Astrophysics Data System (ADS)

We review some analytical results of our studies of the charge- and spin density modulations (CDW and SDW) in a one- and two-dimensional electron systems. Self-consistent solutions of Bogoliubov- de Gennes equations for spin-charge solitonic superstructure and superconducting state are obtained in the framework of one and two-dimensional extended Hubbard models. Possible correspondence of the theory with experimental data on stripe phase in high Tc cuprates is discussed. We found various solutions for the two-dimensional self-consistent model of superconductors with d_gt;x2-y2 symmetry of the order parameter, taking into account spin and charge distributions. Analytical solutions for spin-charge density wave phases in the absence of the superconductivity ("stripe" and "checkerboard" structures) are presented. Analytical solutions for coexisting superconductivity and stripe-phase modulations in the cores of the Abrikosov's vortices are also found.

Matveenko, S. I.

2010-12-01

213

Superconductivity, Spin and Charge Density Structures in One and Two-Dimensional Self-Consistent Models  

NASA Astrophysics Data System (ADS)

We review some analytical results of our studies of the charge- and spin density modulations (CDW and SDW) in a one- and two-dimensional electron systems. Self-consistent solutions of Bogoliubov- de Gennes equations for spin-charge solitonic superstructure and superconducting state are obtained in the framework of one and two-dimensional extended Hubbard models. Possible correspondence of the theory with experimental data on stripe phase in high Tc cuprates is discussed. We found various solutions for the two-dimensional self-consistent model of superconductors with dx2-y2 symmetry of the order parameter, taking into account spin and charge distributions. Analytical solutions for spin-charge density wave phases in the absence of the superconductivity ("stripe" and "checkerboard" structures) are presented. Analytical solutions for coexisting superconductivity and stripe-phase modulations in the cores of the Abrikosov's vortices are also found.

Matveenko, S. I.

214

Electronic properties of two-dimensional systems  

Microsoft Academic Search

The electronic properties of inversion and accumulation layers at semiconductor-insulator interfaces and of other systems that exhibit two-dimensional or quasi-two-dimensional behavior, such as electrons in semiconductor heterojunctions and superlattices and on liquid helium, are reviewed. Energy levels, transport properties, and optical properties are considered in some detail, especially for electrons at the (100) silicon-silicon dioxide interface. Other systems are discussed

Tsuneya Ando; Alan B. Fowler; Frank Stern

1982-01-01

215

Parametric amplification of soliton steering in optical lattices  

NASA Astrophysics Data System (ADS)

We report on the effect of parametric amplification of spatial soliton swinging in Kerr-type nonlinear media with longitudinal and transverse periodic modulation of the linear refractive index. The parameter areas are found where the soliton center motion is analogous to the motion of a parametrically driven pendulum. This effect has potential applications for controllable soliton steering.

Kartashov, Yaroslav V.; Torner, Lluis; Vysloukh, Victor A.

2004-05-01

216

Noncommutative Solitons  

SciTech Connect

Solitonic objects play a central role in gauge and string theory (as, e.g., monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a noncommutative deformation of the low-energy effective field theory, which allows for new types of solitonic solutions. I present the construction, moduli spaces and dynamics of Moyal-deformed solitons, exemplified in the 2+1 dimensional Yang-Mills-Higgs theory and its Bogomolny system, which is gauge-fixed to an integrable chiral sigma model (the Ward model). Noncommutative solitons for various 1+1 dimensional integrable systems (such as sine-Gordon) easily follow by dimensional and algebraic reduction. Supersymmetric extensions exist as well and are related to twistor string theory.

Lechtenfeld, Olaf [Theory Division, Physics Department, CERN, CH-1211 Geneva 23, Switzerland on leave from: Institut fuer Theoretische Physik, Leibniz Universitaet Hannover (Switzerland)

2008-03-06

217

Traveling dark solitons in superfluid Fermi gases  

SciTech Connect

Families of dark solitons exist in superfluid Fermi gases. The energy-velocity dispersion and number of depleted particles completely determine the dynamics of dark solitons on a slowly varying background density. For the unitary Fermi gas, we determine these relations from general scaling arguments and conservation of local particle number. We find solitons to oscillate sinusoidally at the trap frequency reduced by a factor of 1/{radical}(3). Numerical integration of the time-dependent Bogoliubov-de Gennes equation determines spatial profiles and soliton-dispersion relations across the BEC-BCS crossover, and proves consistent with the scaling relations at unitarity.

Liao Renyuan; Brand, Joachim [New Zealand Institute for Advanced Study and Centre for Theoretical Chemistry and Physics, Massey University, Private Bag 102904 NSMC, Auckland 0745 (New Zealand)

2011-04-15

218

Vibrational properties of small two-dimensional classical crystals  

SciTech Connect

Recent computer simulations have stressed the dependence of transport properties on boundary conditions in two dimensions, where fluctuations and boundary conditions are equally important effects of order {ital N}{sup 1/2}. Elastically isotropic harmonic crystals provide a test case in which these two effects can be studied precisely without sacrificing realism. We investigate the boundary dependence of spatial fluctuations in two-dimensional crystals. Our results confirm the expected boundary independence of the extensive vibrational entropy. We find also that clamped crystal boundaries significantly alter the rate of divergence of the root-mean-square (rms) displacement with crystal size, but do not alter the [logarithmic] functional form, which is known to dominate vibrational fluctuations in periodic two-dimensional crystals. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Hoover, W.G.; Kum, O. [Department of Applied Science, University of California at Davis/Livermore and Lawrence Livermore National Laboratory, Livermore, California 94551-7808 (United States)

1995-07-22

219

Adaptive rezoner in a two-dimensional Lagrangian hydrodynamic code  

SciTech Connect

In an effort to increase spatial resolution without adding additional meshes, an adaptive mesh was incorporated into a two-dimensional Lagrangian hydrodynamics code along with two-dimensional flux corrected (FCT) remapper. The adaptive mesh automatically generates a mesh based on smoothness and orthogonality, and at the same time also tracks physical conditions of interest by focusing mesh points in regions that exhibit those conditions; this is done by defining a weighting function associated with the physical conditions to be tracked. The FCT remapper calculates the net transportive fluxes based on a weighted average of two fluxes computed by a low-order scheme and a high-order scheme. This averaging procedure produces solutions which are conservative and nondiffusive, and maintains positivity. 10 refs., 12 figs.

Pyun, J.J.; Saltzman, J.S.; Scannapieco, A.J.; Carroll, D.

1985-01-01

220

Superconductivity at the Two-dimensional Limit  

NASA Astrophysics Data System (ADS)

Superconductivity in the extreme two-dimensional limit is studied on ultra-thin lead (Pb) films down to two atomic layers, where only a single channel of quantum well states exist. Scanning tunneling spectroscopy reveals that local superconducting order remains robust until two atomic layers, where the transition temperature abruptly plunges to lower values depending sensitively on the exact atomic structure of the film. Our result shows that Cooper pairs can still form in the last two dimensional channel of electron states, although their binding are strongly affected by the substrate [1]. In this presentation, I will also discuss this new result in comparison with several recent experimental results on ultra-thin metallic films performed using local STS probes and macroscopic transport measurements.[4pt] [1] ``Superconductivity at the Two-dimensional Limit,'' Shengyong Qin, Jungdae Kim, Qian Niu and Chih-Kang Shih, Science 324, 1314 (2009).

Shih, Chih-Kang

2010-03-01

221

Characterization, dynamics and stabilization of diffractive domain walls and dark ring cavity solitons in parametric oscillators  

NASA Astrophysics Data System (ADS)

Mean field models of spatially extended degenerate optical parametric oscillators possess one-dimensional stable domain wall solutions in the presence of diffraction. We characterize these structures as spiral heteroclinic connections and study the spatial frequency of the local oscillations of the signal intensity which distinguish them from diffusion kinks. Close to threshold, at resonance or with positive detunings, the dynamics of two-dimensional diffractive domain walls is ruled by curvature effects with a t1/2 growth law, and coalescence of domains is observed. In this regime, we show how to stabilize regular and irregular distributions of two-dimensional domain walls by injection of a helical wave at the pump frequency. Further above threshold the shrinking of domains of one phase embedded in the other is stopped by the interaction of the oscillatory tails of the domain walls, leading to cavity solitons surrounded by a characteristic dark ring. We investigate the nature and stability of these localized states, provide evidence of their solitonic character, show that they correspond to spiral homoclinic orbits and find that their threshold of appearance lowers with increasing pump cavity finesse.

Oppo, Gian-Luca; Scroggie, Andrew J.; Firth, William J.

2001-06-01

222

Phase Transitions in Two-Dimensional Superconductors  

NASA Astrophysics Data System (ADS)

In this thesis, we describe a number of experiments which are designed to explore the theoretically predicted phase transitions for two-dimensional superconductors. We first examine the behavior of a two-dimensional superconductor in the absence of a magnetic field, where the fluctuations in the phase of the superconducting order parameter results in the reduction of the superconducting transition temperature for a two-dimensional superconductor below the mean field transition temperature. The experimental results presented show the importance of the vortex unbinding mechanism; however they challenge some of the predictions of the current theoretical model for the normal/superconducting transition. We then turn our attention to the behavior of two-dimensional superconductors in the presence of a magnetic field. In this case, our experimental results show that vortices in weakly disordered two-dimensional superconducting films freeze into locally correlated areas at temperatures below the mean field transition temperature. The experimentally measured phase boundary between the liquid phase and the locally ordered solid phase for the vortices in our samples shows good agreement with that predicted by the dislocation unbinding melting mechanism for the two-dimensional vortex lattice. For this transition, we have also done a detailed study of the correlations in the vortex lattices as a function of the strength of pinning in our samples and established a connection between the melting theory and collective pinning theory for vortices in two dimensions. To fully examine the phase diagram of a two-dimensional superconductor we have extended our studies of the properties of this system to the limit of strong disorder, where superconductivity is weak. In this limit, we report experimental evidence for a zero temperature field-tuned superconducting-insulating phase transition driven by quantum fluctuation of the phase of the superconducting order parameter. Overall, the results of this thesis provide an experimental bases for a number of phase transitions in two-dimensional superconductors, thereby establishing a rich phase diagram for this system as a function of the temperature, the magnetic field, and the amount of disorder.

Yazdani, Ali

1995-01-01

223

Modulational instability and solitons in nonlocal media with competing nonlinearities  

SciTech Connect

We investigate analytically and numerically propagation and spatial localization of light in nonlocal media with competing nonlinearities. In particular, we discuss conditions for the modulational instability of plane waves and formation of spatial solitons. We show that the competing focusing and defocusing nonlinearities enable coexistence of dark or bright spatial solitons in the same medium by varying the intensity of the beam.

Esbensen, B. K.; Bache, M.; Bang, O. [DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Wlotzka, A. [Department of Physics, Institut fuer Theoretische Festkoerperphysik, University of Karlsruhe, D-76128 Karlsruhe (Germany); Krolikowski, W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2011-11-15

224

Two-Dimensional Turbulence in Magnetized Plasmas  

ERIC Educational Resources Information Center

|In an inhomogeneous magnetized plasma the transport of energy and particles perpendicular to the magnetic field is in general mainly caused by quasi two-dimensional turbulent fluid mixing. The physics of turbulence and structure formation is of ubiquitous importance to every magnetically confined laboratory plasma for experimental or industrial…

Kendl, A.

2008-01-01

225

Two-Dimensional Motions of Rockets  

ERIC Educational Resources Information Center

|We analyse the two-dimensional motions of the rockets for various types of rocket thrusts, the air friction and the gravitation by using a suitable representation of the rocket equation and the numerical calculation. The slope shapes of the rocket trajectories are discussed for the three types of rocket engines. Unlike the projectile motions, the…

Kang, Yoonhwan; Bae, Saebyok

2007-01-01

226

Two-dimensional Markovian holonomy fields  

Microsoft Academic Search

We define a notion of Markov process indexed by curves drawn on a compact surface and taking its values in a compact Lie group. We call such a process a two-dimensional Markovian holonomy field. The prototype of this class of processes, and the only one to have been constructed before the present work, is the canonical process under the Yang-Mills

Thierry Lévy

2008-01-01

227

Two-dimensional turbulence: a physicist approach  

Microsoft Academic Search

Much progress has been made on two-dimensional turbulence, these last two decades, but still, a number of fundamental questions remain unanswered. The objective of the present review is to collect and organize the available information on the subject, emphasizing on aspects accessible to experiment, and outlining contributions made on simple flow configurations. Whenever possible, open questions are made explicit. Various

Patrick Tabeling

2002-01-01

228

Imaging Properties of Two-Dimensional Microlenses  

Microsoft Academic Search

Despite strong experimental and theoretical evidence supporting superresolution imaging based on microlenses, imaging mechanisms involved are not well understood. Based on the transformation optics approach, we demonstrate that microlenses may act as two-dimensional fisheye or Eaton lenses. An asymmetric Eaton lens may exhibit considerable image magnification, which has been confirmed experimentally.

Vera N. Smolyaninova; Igor I. Smolyaninov; Alexander V. Kildishev; Vladimir M. Shalaev

2010-01-01

229

Two dimensional quantum gravity coupled to matter  

NASA Astrophysics Data System (ADS)

A classical two dimensional theory of gravity which has a number of interesting features (including a newtonian limit, black holes and gravitational collapse) is quantized using conformal field theoretic techniques. The critical dimension depends upon Newton's constant, permitting models with d = 4. The constraint algebra and scaling properties of the model are computed.

Mann, R. B.

1992-11-01

230

Constitutive Theory for Two Dimensional Liquid Crystals  

Microsoft Academic Search

Two dimensional liquid crystal are considered as mathematical surfaces of discontinuity of the bulk fields. The equations of motion for the relevant surface fields in the presence of electromagnetic fields are summarized. These are the mechanical balance equations, Maxwell's equations, and an equation of motion for the second order alignment tensor. The restrictions to constitutive functions implied by the Second

C. Papenfuss; W. Muschik

1995-01-01

231

Two-dimensional Penrose lattice: dc conductivity  

Microsoft Academic Search

The dc conductivity for a tight-binding Hamiltonian on a two-dimensional Penrose lattice is computed numerically for finite systems from Kubo's formula using the recursion method. Results are suggestive of a weak metallic behavior where states are more localized than in the case of a pure crystal, in agreement with recent conjectures by Sutherland.

T. C. Choy

1987-01-01

232

Cooperative two-dimensional directed transport  

Microsoft Academic Search

A mechanism for the cooperative directed transport in two-dimensional ratchet potentials is proposed. With the aid of mutual couplings among particles, coordinated unidirectional motion along the ratchet direction can be achieved by transforming the energy from the transversal rocking force (periodic or stochastic) to the work in the longitude direction. Analytical predictions on the relation between the current and other

Zhigang Zheng; Hongbin Chen

2010-01-01

233

The Two-Dimensional Random Walk  

NSDL National Science Digital Library

This is the description and instructions for the Two-Dimensional Random Walk applet. This applet, presented by Boston University's Center for Polymer Studies, relates random coin-flipping to random motion but in more than one direction (dimension). It covers mean squared distance in the discussion. Overall, this is a nice interactive resource for a statistics classroom.

Trunfio, Paul; Mcgath, Gary

2008-12-29

234

Two-dimensional FLD for face recognition  

Microsoft Academic Search

This paper presents a new scheme of face image feature extraction, namely, the two-dimensional Fisher linear discriminant. Experiments on the ORL and the UMIST face databases show that the new scheme outperforms the PCA and the conventional PCA+FLD schemes, not only in its computational efficiency, but also in its performance for the task of face recognition.

Huilin Xiong; M. N. S. Swamy; M. Omair Ahmad

2005-01-01

235

Manipulating solitons by antisymmetric inhomogeneous loss in the complex Ginzburg–Landau model  

NASA Astrophysics Data System (ADS)

We study the dynamics of dissipative spatial solitons by using antisymmetric-type spatially inhomogeneous loss that locally modulates an optical medium described by the complex Ginzburg–Landau model. We reveal soliton dynamics by launching input solitons at different positions of the spatial modulation loss profile, including its zero value and positive value. The soliton transverse drift exhibits tilt straightaway propagation except for the oscillation in initial stage. The tilt angle of the soliton drift can be controlled by the modulation parameters. We also investigate the dependences of the tilt angle of the soliton drift on the amplitude of the inhomogeneous loss and the linear loss coefficient.

Wang, Hongcheng; Zhu, Weiling; Liu, Jinglin; Ling, Dongxiong; He, Yingji

2013-10-01

236

Two-dimensional spatial analysis of the seismic b-value and the Bouguer gravity anomaly in the southeastern part of the Zagros Fold-and-Thrust Belt, Iran: Tectonic implications  

NASA Astrophysics Data System (ADS)

Environmental managers and protection agencies try to assess the magnitudes of earthquakes in regions of seismic activity. For several decades they have used the seismic b-values and Bouguer anomalies for evaluating the crustal character and stress regimes. We have analyzed geostatistically data on both variables to map their spatial distributions in the southeast of the Zagros of Iran. We found a strong correlation between the distribution of the b-value and the Bouguer gravity anomaly in the region. The large Bouguer gravity anomaly values and small b-values all accord with there being a thinner crustal root and a larger concentration of stress in the center. The small to moderate Bouguer gravity anomaly values and intermediate to large b-values accord with the thicker crustal root and the smaller concentration of stress in the northeast. We conclude the southeast of the Zagros, consists of heterogeneous crust, such that accounts for its varied tectonics.

Sarkarinejad, Khalil; Mehdi Zadeh, Rezvan; Webster, Richard

2013-01-01

237

Toward two-dimensional search engines  

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

238

Cooperative two-dimensional directed transport  

NASA Astrophysics Data System (ADS)

A mechanism for the cooperative directed transport in two-dimensional ratchet potentials is proposed. With the aid of mutual couplings among particles, coordinated unidirectional motion along the ratchet direction can be achieved by transforming the energy from the transversal rocking force (periodic or stochastic) to the work in the longitude direction. Analytical predictions on the relation between the current and other parameters for the ac-driven cases are given, which are in good agreement with numerical simulations. Stochastic driving forces can give rise to the resonant directional transport. The effect of the free length, which has been explored in experiments on the motility of bipedal molecular motors, is investigated for both the single- and double-channel cases. The mechanism and results proposed in this letter may both shed light on the collective locomotion of molecular motors and open ways on studies in two-dimensional collaborative ratchet dynamics.

Zheng, Zhigang; Chen, Hongbin

2010-11-01

239

Two-dimensional microfabricated electrostatic einzel lens  

Microsoft Academic Search

A two-dimensional electrostatic einzel lens fabricated using microfabrication technology is described. The lens consists of cylindrical electrodes mounted in on two oxidised, silicon substrates, which are held apart by two cylindrical spacers. V-shaped grooves formed by anisotropic wet chemical etching are used to locate the electrodes and the spacers. The electrodes are metal-coated glass rods that are soldered to metal

R. R. A. Syms; L. Michelutti; M. M. Ahmad

2003-01-01

240

Two-dimensional synthesis of anisotropic nanoparticles  

Microsoft Academic Search

A novel approach for the synthesis of nanoparticles has been introduced in which nanoparticles are fabricated via decomposition of an insoluble precursor compound in a monolayer at the gas\\/liquid interface, and nanoparticle growth is an example of a two-dimensional (2-D) process where true 2-D diffusion of precursor molecules, active intermediates, metal atoms and its complexes, nucleus and growing nanoparticles, surfactants

Gennady B Khomutov

2002-01-01

241

Stochastic models of two-dimensional fracture  

NASA Astrophysics Data System (ADS)

Two statistical models of (strictly two-dimensional) layer destruction are presented. The first is built as a strict percolation model with an added ``conservation law'' (conservation of mass) as physical constraint. The second allows for damped or limited fracture. Two successive fracture crack thresholds are considered. Percolation (i.e., fracture) probability and cluster distributions are studied by use of numerical simulations. Different fractal dimension, critical exponents for cluster distribution, and universality laws characterize both models.

Ausloos, M.; Kowalski, J. M.

1992-06-01

242

Imaging Properties of Two-Dimensional Microlenses  

Microsoft Academic Search

Despite strong experimental and theoretical evidence supporting\\u000asuperresolution imaging based on microlenses, imaging mechanisms involved are\\u000anot well understood. Based on the transformation optics approach, we\\u000ademonstrate that microlenses may act as two-dimensional fisheye or Eaton\\u000alenses. An asymmetric Eaton lens may exhibit considerable image magnification,\\u000awhich has been confirmed experimentally.

Vera N. Smolyaninova; Igor I. Smolyaninov; Alexander V. Kildishev; Vladimir M. Shalaev

2010-01-01

243

Topics in two-dimensional string theory  

Microsoft Academic Search

We explore various topics in two-dimensional string theory. Firstly, we study particle production in time-dependent backgrounds of the c = 1 matrix model, a holographic description of bosonic string theory in 1+1 dimensions. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum

Joshua L. Davis

2006-01-01

244

Superinsulator Phase of Two-Dimensional Superconductors  

Microsoft Academic Search

Using path-integral quantum Monte Carlo we study the low-temperature phase diagram of a two-dimensional superconductor within a phenomenological model, where vortices have a finite mass and move in a dissipative environment modeled by a Caldeira-Leggett term. The quantum vortex liquid at high magnetic fields exhibits superfluidity and thus corresponds to a superinsulating phase which is characterized by a nonlinear voltage-current

A. Krämer; S. Doniach

1998-01-01

245

Superdiffusion in two-dimensional Yukawa liquids  

SciTech Connect

Superdiffusion of two-dimensional (2D) liquids was studied using an equilibrium molecular dynamics simulation. At intermediate temperatures, the mean-squared displacement, probability distribution function (PDF), and velocity autocorrelation function (VACF) all indicate superdiffusion; the VACF has a long-time tail; and the PDF indicates no Levy flights. These effects are predicted to occur in 2D dusty plasmas and other 2D liquids that can be modeled with a long-range repulsive potential.

Liu Bin; Goree, J. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)

2007-01-15

246

Real time multiple two dimensional barcode reader  

Microsoft Academic Search

The proposed work describes a system that can be used to detect and decode multiple Two-Dimensional (2D) barcodes (i.e. Datamatrix). The proposed system is capable of detecting and decoding of barcodes covered by polyethylene foiling in moving images. The foiling causes reflection on the captured images and hence provides challenges to detection\\/decoding. Similarly the proposed system addresses the problem of

I. Zafar; U. Zakir; E. A. Edirisinghe

2010-01-01

247

Homogeneous Cotton solitons  

NASA Astrophysics Data System (ADS)

Left-invariant Cotton solitons on homogeneous manifolds are determined. Moreover, algebraic Cotton solitons are studied providing examples of non-invariant Cotton solitons, both in the Riemannian and Lorentzian homogeneous settings.

Calvińo-Louzao, E.; Hervella, L. M.; Seoane-Bascoy, J.; Vázquez-Lorenzo, R.

2013-07-01

248

Interactions between two vector solitons  

Microsoft Academic Search

Summary form only given. Photorefractive spatial screening solitons exist in biased photorefractive media where the incident beam modifies the index of refraction in such a way that the beam becomes the first guided mode of its own self-induced waveguide. A beam of a given intensity (in units of the equivalent dark irradiance or of the background illumination) self traps in

C. Anasrassiou; M. Mitchell; Ming-Feng Shih; J. Giormaine; J. Martin; M. Segev

1999-01-01

249

A Two-dimensional TSVD Resolution Enhancement for EO Ocean Applications  

NASA Astrophysics Data System (ADS)

A two-dimensional truncated singular value decomposi-tion (TSVD) technique is first proposed to enhance spa-tial resolution of earth observation (EO) products re- lated to ocean-atmosphere interaction. The technique is based on the assumption that the gain function is a two-dimensional tensor product. To set the value of the truncation parameter the Generalized Cross Validation is adopted. Experiments undertaken on a data set of simulated two- dimensional radiometer measurements show the robust- ness of the technique against the additive noise level and its effectivenes

Lenti, F.; Migliaccio, M.; Nunziata, F.; Rodriguez, G.

2012-03-01

250

Interactions of spatiotemporal solitons and vortices in fiber bundles  

NASA Astrophysics Data System (ADS)

We report results of a systematic numerical analysis of collisions between localized three-dimensional (3D) semidiscrete complexes, viz., rhombus-shaped vortices, quadrupoles, and fundamental solitons, in the model of a bundle of fiberlike waveguides. The model also describes a 3D self-attractive Bose-Einstein condensate (BEC) loaded into a deep two-dimensional optical lattice. We identify four outcomes of the collisions: rebound of slow solitons, fusion, splitting, and, finally, quasielastic interactions of fast solitons. Diagrams which demonstrate regions of the different outcomes are reported for collisions between vortices, with equal or opposite topological charges, and quadrupoles.

Leblond, Hervé; Malomed, Boris A.; Mihalache, Dumitru

2009-03-01

251

Multipole-mode interface solitons in quadratic nonlinear photonic lattices  

NASA Astrophysics Data System (ADS)

We address the properties of nonlinear multipole modes supported by an interface between two distinct optical lattices imprinted in two-dimensional nonlinear quadratic media. Such multipole-mode solitons feature out of phase between neighboring lobes, which may be located in two different sides of the lattices. We analyze the impact of guiding parameters of lattices on the existence and stability of multipole-mode interface solitons in different phase mismatching conditions. Remarkably, our results show that multipole-mode interface solitons have the highly asymmetric shape and they are stable in the broad range of system parameters.

Xu, Zhiyong

2009-11-01

252

Two-Dimensional Fractal Characteristics of the Martian Surface  

NASA Astrophysics Data System (ADS)

We present global maps of two-dimensional fractal statistics for Mars topography calculated by applying the two-dimensional Fourier spectral approach to MOLA altimetry measurements over spatial scales extending from approximately 450 meters to 15 kilometers. Three global maps were generated: 1) surface (two-dimensional) fractal dimension, 2) roughness amplitude at a scale of one kilometer, and 3) linear model fit error in the log-log relation of mean power spectral density to radial wavenumber. The linear model fit error is a convenient way to judge the appropriateness of the fractal model. Examination of the fractal dimension and model error maps reveals that a majority of the surface is well modeled by fractal geometry. This is evidenced by minimal systematic spatial variation in fractal dimension and low model fit errors, with the northern plains exhibiting slightly higher overall error than the cratered highlands. There are also several spatially coherent regions in the fractal dimension map that have enhanced values. These regions include Amazonis Planitia and southeast Elysium Planitia. On the other hand, Isidis Planitia and portions of the Olympus Mons aureole exhibit high model fit errors which imply a lower applicability of fractal geometry to these terrains. The one kilometer roughness amplitude map exhibits a tremendous amount of spatial detail and clearly delineates differing roughness terrains. The portions of Amazonis Planitia and southeast Elysium Planitia with enhanced fractal dimension have roughness amplitudes significantly below the global mean, while the Valles Marineris system, the circum-Argyre region, and the chaotic and heavily eroded terrains located along the crustal dichotomy boundary exhibit elevated roughness values. The Tharsis region is particularly rich in detail, displaying a wide range of spatially contiguous roughness provinces that are traceable to known surface units. Comparison of the roughness amplitude map to the MOLA pulse width-derived roughness data (75 meter baseline) reveals a strong correlation with a few notable exceptions. The circum-polar debris mantle located 30 to 45 degrees bilaterally from the equator and a small yet distinct terrain located northwest of Olympus Mons are both evident in the 75 m pulse width data but are not expressed in the longer wavelength roughness amplitude map. This implies that the surface processes responsible for producing these terrains are dominant only at shorter length scales.

Seelos, F. P.; Deal, K. S.; Arvidson, R. E.; Neumann, G. A.

2003-12-01

253

High speed two-dimensional optical beam position detector  

SciTech Connect

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

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

2011-07-15

254

High speed two-dimensional optical beam position detector.  

PubMed

Disclosed is the design of a high speed two-dimensional optical beam position detector which outputs the X and Y displacement and total intensity linearly. The experimental detector measures the displacement from DC to 123 MHz and the intensity of an optical spot in a similar way as a conventional quadrant photodiode detector. The design uses four discrete photodiodes and simple dedicated optics for the position decomposition which enables higher spatial accuracy and faster electronic processing than conventional detectors. Measurements of the frequency response and the spatial sensitivity demonstrate high suitability for atomic force microscopy, scanning probe data storage applications, and wideband wavefront sensing. The operation principle allows for position measurements up to 20 GHz and more in bandwidth. PMID:21806187

Rutten, Paul Edmond

2011-07-01

255

Measurements of two-dimensional vector velocity using image fiber bundle and two rotating gratings  

Microsoft Academic Search

Use of an image fiber bundle is proposed in the two-dimensional vector velocimeter based on the time-varying spatial filter method using two rotating transmission gratings. The spatial filtering characteristics of both the gratings and the image fiber bundle are theoretically analyzed by using power spectral density functions. Two methods are investigated theoretically and experimentally to eliminate the signal generated by

J. Ritonga; T. Ushizaka; T. Asakura

1989-01-01

256

Flow and Solute Transport in a Single Fracture. A Two-Dimensional Statistical Model.  

National Technical Information Service (NTIS)

A two-dimensional model for a single fracture with variable apertures is presented. The spatial variation of the apertures in the fracture is defined by the aperture density distribution and the spatial correlation length. Flow and solute transport in the...

L. Moreno I. Neretnieks Y. Tsang C. F. Tsang

1988-01-01

257

Two-dimensional fluid model of high density inductively coupled plasma sources  

Microsoft Academic Search

A two-dimensional (r,z) fluid model has been developed to study plasma transport in inductively coupled plasmas (ICP). Electron heating is treated by assuming a fixed, spatially varing power deposition profile in the electron energy balance equation. A high aspect ration ICP reactor geometry has been studied, with two assumed power profiles: spatially uniform and localized to within several skin depths

R. A. Steward; D. B. Graves; P. Vitello

1994-01-01

258

Interface roughening in two-dimensional quasicrystals  

NASA Astrophysics Data System (ADS)

The equilibrium fluctuations of interfaces in two-dimensional quasi-periodic lattices, such as Penrose tilings, are considered. By a transfer-matrix formulation, this problem is mapped to the one-dimensional Schroedinger equation with a quasi-periodic potential; from the scaling properties of the eigenstates near the band edge, it is possible to extract the exponent zeta characterizing the interface roughness. For a cosine potential, a true roughening transition in d = 2 dimensions is found. For a Fibonacci tiling, which approximates the Penrose tiling, zeta is nonuniversal, zeta less than 1/2, and zeta goes to 0 continuously as T goes to 0.

Henley, Christopher L.; Lipowsky, Reinhard

1987-10-01

259

Spontaneous trimerization in two-dimensional antiferromagnets.  

PubMed

In this paper, we propose an exotic quantum paramagnetic state in two-dimensional antiferromagnets-the spontaneous trimer state-which is the direct product state of the trimers of spins. Each trimer is a singlet state formed by three neighboring spins with SU(3) symmetry. A frustrated spin-1 Heisenberg model in the kagome lattice is investigated. By analogy to the pseudo-potential approach in the fractional quantum Hall effect (FQHE), we find that the trimer state provides a good description for the exact ground state of this model. Other interesting properties, such as the local excitations as well as magnetization plateaus have also been investigated. PMID:21694029

Cai, Zi; Chen, Shu; Wang, Yupeng

2009-10-23

260

Two dimensional mixtures at water surface  

NASA Astrophysics Data System (ADS)

Thiol capped gold nanoparticles (Au NPs) form a simple two dimensional (2D) liquid on water surface but this thin film is unstable under compression. Amphiphilic stearic acid (StA) molecules on water surface, on the other hand, form a complex and more stable 2D liquid. We have initiated a study on a mixture of StA and Au NPs in a monolayer through Surface Pressure (?) - Specific Molecular Area (A) isotherms and Brewster Angle Microscopy (BAM). A mixture of Stearic Acid and Au nanoparticles (10% by weight) produces a monolayer on water surface that acts as a 2D liquid with phases that are completely reversible with negligible hysteresis.

Choudhuri, Madhumita; Datta, Alokmay

2013-02-01

261

Two-dimensional photonic band gap crystals  

NASA Astrophysics Data System (ADS)

A photonic crystal is a periodic dielectric structure that possesses a band of frequencies in which propagating electromagnetic waves are forbidden. Two-dimensional photonic crystals exhibit a band gap for waves traveling in the crystal plane, a property that offers promise for improved operation of optoelectronic devices including semiconductor lasers, light-emitting diodes, and frequency filters. A theoretical investigation of two-dimensional photonic band gap crystals has been performed. The plane-wave expansion method is used to solve Maxwell's equations for the electromagnetic frequency bands in several square (Laue group 4mm) and triangular (Laue group 6mm) crystal structures. The size of absolute band gaps is often limited by band degeneracies at lattice symmetry points. By reducing the lattice symmetry, these degeneracies can be lifted to increase the size of existing photonic band gaps, or to create new gaps where none existed for the more symmetric structure. Symmetry analysis also offers a rational approach for exploring and designing new photonic crystal structures. Gap maps for several important crystal structures are presented as a useful reference guide for experimentalists. The utility of photonic crystals for many applications is enhanced through the introduction of a defect into the crystal structure, which creates localized frequency states within the photonic band gap. Defect modes in two- dimensional square photonic crystal structures were studied using a supercell approach. By changing the radius of a single rod, several defect modes with complex electromagnetic field patterns appear within the photonic band gap. The mode frequencies can be tuned by varying the size of the defect rod. The double-rod square structure has two rod types per unit cell, yielding different defect characteristics depending on which rod is altered. In addition, anisotropic etching of patterned silicon has been investigated experimentally using a hyperthermal neutral fluorine atom beam generated by laserinduced detonation of SF6. The detrimental effects of surface charging are eliminated by the use of charge-neutral etch species; however, inelastic scattering of energetic reactive species has a significant effect on the development of the etch profiles, especially at high aspect ratios. Etch profile anomalies including microtrenching and undercutting are observed.

Anderson, Cheryl Marie

1999-07-01

262

Continuous compression waves in the two-dimensional Riemann problem  

NASA Astrophysics Data System (ADS)

The interaction between a plane shock wave in a plate and a wedge is considered within the framework of the nondissipative compressible fluid dynamic equations. The wedge is filled with a material that may differ from that of the plate. Based on the numerical solution of the original equations, self-similar solutions are obtained for several versions of the problem with an iron plate and a wedge filled with aluminum and for the interaction of a shock wave in air with a rigid wedge. The behavior of the solids at high pressures is approximately described by a two-term equation of state. In all the problems, a two-dimensional continuous compression wave develops as a wave reflected from the wedge or as a wave adjacent to the reflected shock. In contrast to a gradient catastrophe typical of one-dimensional continuous compression waves, the spatial gradient of a two-dimensional compression wave decreases over time due to the self-similarity of the solution. It is conjectured that a phenomenon opposite to the gradient catastrophe can occur in an actual flow with dissipative processes like viscosity and heat conduction. Specifically, an initial shock wave is transformed over time into a continuous compression wave of the same amplitude.

Charakhch'yan, A. A.

2009-10-01

263

Two-dimensional fourier transform spectrometer  

DOEpatents

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.

DeFlores, Lauren; Tokmakoff, Andrei

2013-09-03

264

Strongly Interacting Two-Dimensional Bose Gases  

NASA Astrophysics Data System (ADS)

We prepare and study strongly interacting two-dimensional Bose gases in the superfluid, the classical Berezinskii-Kosterlitz-Thouless (BKT) transition, and the vacuum-to-superfluid quantum critical regimes. A wide range of the two-body interaction strength 0.05

Ha, Li-Chung; Hung, Chen-Lung; Zhang, Xibo; Eismann, Ulrich; Tung, Shih-Kuang; Chin, Cheng

2013-04-01

265

Quantum Groups in Two-Dimensional Physics  

NASA Astrophysics Data System (ADS)

This book is an introduction to integrability and conformal field theory in two dimensions using quantum groups. The book begins with a brief introduction to S-matrices, spin chains and vertex models as a prelude to the study of Yang-Baxter algebras and the Bethe ansatz. The authors then introduce the basic ideas of integrable systems, giving particular emphasis to vertex and face models. They give special attention to the underlying mathematical tools, including braid groups, knot invariants, and towers of algebras. The authors then go on to give a detailed introduction to quantum groups before addressing integrable models, two-dimensional conformal field theories, and superconformal field theories. The book contains many diagrams and exercises to illustrate key points in the text and will be appropriate for researchers and graduate students in theoretical physics and mathematics.

Gómez, Cisar; Ruiz-Altaba, Martín; Sierra, German

1996-04-01

266

Intrinsic two-dimensional features as textons.  

PubMed

We suggest that intrinsic two-dimensional (i2D) features, computationally defined as the outputs of nonlinear operators that model the activity of end-stopped neurons, play a role in preattentive texture discrimination. We first show that for discriminable textures with identical power spectra the predictions of traditional models depend on the type of nonlinearity and fail for energy measures. We then argue that the concept of intrinsic dimensionality, and the existence of end-stopped neurons, can help us to understand the role of the nonlinearities. Furthermore, we show examples in which models without strong i2D selectivity fail to predict the correct ranking order of perceptual segregation. Our arguments regarding the importance of i2D features resemble the arguments of Julesz and co-workers regarding textons such as terminators and crossings. However, we provide a computational framework that identifies textons with the outputs of nonlinear operators that are selective to i2D features. PMID:9656473

Barth, E; Zetzsche, C; Rentschler, I

1998-07-01

267

Two-Dimensional Speckle Strain Imaging  

PubMed Central

Two-dimensional speckle-tracking strain imaging (speckle strain imaging) is useful for evaluating left ventricular myocardial function in patients with ischemic heart disease and cardiomyopathy, including hypertrophic and dilated phenotypes. The usefulness of speckle strain imaging in patients with pheochromocytoma who are undergoing adrenal surgery has been described, but we found no reports of the use of this method to evaluate ventricular dysfunction longitudinally in children. Herein, we describe the case of a 10-year-old girl with a paraganglioma, acute junctional tachycardia, and myocardial dysfunction. After control of the tachycardia and partial resection of the tumor, speckle strain imaging enabled clinical management that led to substantial improvement in the patient's initially diffuse myocardial dysfunction. Because conventional echocardiographic methods alone may be inadequate to guide the management of pediatric patients with partially resected neuroendocrine tumors, we recommend speckle strain imaging as an additional noninvasive option for treatment guidance and monitoring of cardiac tissue response.

Pignatelli, Ricardo; Law, Mark A.; Martinez, Hugo; Altman, Carolyn; Ayres, Nancy; Jefferies, John L.; Ganame, Javier

2012-01-01

268

Thermodynamics of two-dimensional magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

A two-dimensional magnetic particle in the presence of an external magnetic field is studied. Equilibrium thermodynamical properties are derived by evaluating analytically the partition function. When the external field is applied perpendicular to the anisotropy axis the system exhibits a second-order phase transition with order parameter being the magnetization parallel to the field. In this case the system is isomorph to a mechanical system consisting of a particle moving without friction in a circle rotating about its vertical diameter. Contrary to a paramagnetic particle, equilibrium magnetization shows a maximum at finite temperature. It is also shown that uniaxial anisotropy in a system of noninteracting particles can be misinterpreted as a ferromagnetic or antiferromagnetic coupling among magnetic particles, depending on the angle between the anisotropy axes and magnetic field.

Vargas, P.; Altbir, D.; Knobel, M.; Laroze, D.

2002-05-01

269

Two-dimensional MHD generator model  

NASA Astrophysics Data System (ADS)

A steady state, two dimensional MHD generator code, GEN, is presented. The code solves the equations of conservation of mass, momentum, and energy, using a Von Mises transformation and a local linearization of the equations. By splitting the source terms into a part proportional to the axial pressure gradient and a part independent of the gradient, the pressure distribution along the channel is easily obtained to satisfy various criteria. Thus, the code can run effectively in both design modes, where the channel geometry is determined, and analysis modes, where the geometry is previously known. The code also employs a mixing length concept for turbulent flows, Cebeci and Chang's wall roughness model, and an extension of that model to the effective thermal diffusivities. Results on code validation, as well as comparisons of skin friction and Stanton number calculations with experimental results, are presented.

Geyer, H. K.; Ahluwalia, R. K.; Doss, E. D.

1980-09-01

270

Two-Dimensional Melting under Quenched Disorder  

NASA Astrophysics Data System (ADS)

We study the influence of quenched disorder on the two-dimensional melting behavior of superparamagnetic colloidal particles, using both video microscopy and computer simulations of repulsive parallel dipoles. Quenched disorder is introduced by pinning a fraction of the particles to an underlying substrate. We confirm the occurrence of the Kosterlitz-Thouless-Halperin-Nelson-Young scenario and observe an intermediate hexatic phase. While the fluid-hexatic transition remains largely unaffected by disorder, the hexatic-solid transition shifts to lower temperatures with increasing disorder. This results in a significantly broadened stability range of the hexatic phase. In addition, we observe spatiotemporal critical(like) fluctuations, which are consistent with the continuous character of the phase transitions. Characteristics of first-order transitions are not observed.

Deutschländer, Sven; Horn, Tobias; Löwen, Hartmut; Maret, Georg; Keim, Peter

2013-08-01

271

New Two-Dimensional Ice Models  

NASA Astrophysics Data System (ADS)

This paper presents a new approach for enumerating all hydrogen bond arrangements of ice-like systems with periodic boundary conditions. It is founded on a topological procedure for the dimensional reduction and a new variant of the transfer matrix method based on small conditional transfer matrices. We consider a couple of new two-dimensional ice models on very unusual lattices. One of them is the twisted square ice model with crossing H-bonds. The other is the digonal-hexagonal model with double H-bonds. In spite of their uncommonness, these models are quite realistic, because from the standpoint of combinatorics and topology they are equivalent to the layers of usual hexagonal ice Ih under periodic boundary conditions in one of the directions. The exact proton configuration statistics for a number of 2D-expanded unit cells of hexagonal ice Ih and the residual entropy of the new ice models in the large system limit are presented.

Kirov, Mikhail V.

2012-11-01

272

Rationally synthesized two-dimensional polymers  

NASA Astrophysics Data System (ADS)

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.

Colson, John W.; Dichtel, William R.

2013-06-01

273

Two-dimensional Quantum Random Walk  

NASA Astrophysics Data System (ADS)

We analyze several families of two-dimensional quantum random walks. The feasible region (the region where probabilities do not decay exponentially with time) grows linearly with time, as is the case with one-dimensional QRW. The limiting shape of the feasible region is, however, quite different. The limit region turns out to be an algebraic set, which we characterize as the rational image of a compact algebraic variety. We also compute the probability profile within the limit region, which is essentially a negative power of the Gaussian curvature of the same algebraic variety. Our methods are based on analysis of the space-time generating function, following the methods of Pemantle and Wilson (J. Comb. Theory, Ser. A 97(1):129-161, 2002).

Baryshnikov, Yuliy; Brady, Wil; Bressler, Andrew; Pemantle, Robin

2011-01-01

274

Two-dimensional Quantum Random Walk  

NASA Astrophysics Data System (ADS)

We analyze several families of two-dimensional quantum random walks. The feasible region (the region where probabilities do not decay exponentially with time) grows linearly with time, as is the case with one-dimensional QRW. The limiting shape of the feasible region is, however, quite different. The limit region turns out to be an algebraic set, which we characterize as the rational image of a compact algebraic variety. We also compute the probability profile within the limit region, which is essentially a negative power of the Gaussian curvature of the same algebraic variety. Our methods are based on analysis of the space-time generating function, following the methods of Pemantle and Wilson (J. Comb. Theory, Ser. A 97(1):129-161, 2002).

Baryshnikov, Yuliy; Brady, Wil; Bressler, Andrew; Pemantle, Robin

2010-12-01

275

Graphene: the new two-dimensional nanomaterial.  

PubMed

Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties. PMID:19784976

Rao, C N R; Sood, A K; Subrahmanyam, K S; Govindaraj, A

2009-01-01

276

Two-dimensional motions of rockets  

NASA Astrophysics Data System (ADS)

We analyse the two-dimensional motions of the rockets for various types of rocket thrusts, the air friction and the gravitation by using a suitable representation of the rocket equation and the numerical calculation. The slope shapes of the rocket trajectories are discussed for the three types of rocket engines. Unlike the projectile motions, the descending parts of the trajectories tend to be gentler and straighter slopes than the ascending parts for relatively large launching angles due to the non-vanishing thrusts. We discuss the ranges, the maximum altitudes and the engine performances of the rockets. It seems that the exponential fuel exhaustion can be the most potent engine for the longest and highest flights.

Kang, Yoonhwan; Bae, Saebyok

2007-01-01

277

Two-dimensional Gel Electrophoresis (2DE)  

NASA Astrophysics Data System (ADS)

The chemical compounds, which are present in the environment, increasingly cause bad effects on health. The most serious effects are tumors and various mutations at the cellular level. Such compounds, from the analytical point of view, can serve the function of biomarkers, constituting measurable changes in the organism's cells and biochemical processes occurring therein. The challenge of the twenty-first century is therefore searching for effective and reliable methods of identification of biomarkers as well as understanding bodily functions, which occur in living organisms at the molecular level. The irreplaceable tool for these examinations is proteomics, which includes both quality and quantity analysis of proteins composition, and also makes it possible to learn their functions and expressions. The success of proteomics examinations lies in the usage of innovative analytical techniques, such as electromigration technique, two-dimensional electrophoresis in polyacrylamide gel (2D PAGE), liquid chromatography, together with high resolution mass spectrometry and bio-informatical data analysis. Proteomics joins together a number of techniques used for analysis of hundreds or thousands of proteins. Its main task is not the examination of proteins inside the particular tissue but searching for the differences in the proteins' profile between bad and healthy tissues. These differences can tell us a lot regarding the cause of the sickness as well as its consequences. For instance, using the proteomics analysis it is possible to find relatively fast new biomarkers of tumor diseases, which in the future will be used for both screening and foreseeing the course of illness. In this chapter we focus on two-dimensional electrophoresis because as it seems, it may be of enormous importance when searching for biomarkers of cancer diseases.

K?odzi?ska, Ewa; Buszewski, Bogus?aw

278

Elastic properties of two-dimensional quasicrystals.  

PubMed

Quasicrystals (QC) with two-dimensional quasiperiodic and one-dimensional periodic structure are considered. Their symmetry can be described by embedding the three-dimensional physical space V(E) in a five-dimensional superspace V, which is the direct sum of V(E) and a two-dimensional internal space V(I). A displacement v in V can be written as v = u + w, where u in V(E) and w in V(I). If the QC has a point group P in V(E) that is crystallographic, it is assumed that w and a vector u' in V(E) lying in the plane in which the crystal is quasiperiodic transform under equivalent representations of P, inequivalent ones if the point group is 5-, 8-, 10- or 12-gonal. From the Neumann principle follow restrictions on the form of the phonon, phason and phonon-phason coupling contributions to the elastic stiffness matrix that can be determined by combining the restrictions obtained for a set of elements generating the point group of interest. For the phonon part, the restrictions obtained for the generating elements do not depend on the system to which the point group belongs. This remains true for the phason and coupling parts in the case of crystallographic point groups but, in general, breaks down for the non-crystallographic ones. The form of the symmetric 12 x 12 matrix giving the phonon, phason and phonon-phason coupling contributions to the elastic stiffness is presented in graphic notation. PMID:18560162

Grimmer, Hans

2008-05-12

279

Two-dimensional crystallization of bovine rhodopsin.  

PubMed

Bovine rhodopsin has been clustered into two-dimensional crystals in highly purified native rod disk membranes and studied with negative staining and transmission electron microscopy. The lattice is P2(1) with dimensions of 8.3 X 7.9 nm and interaxis angles of 86 +/- 3 degrees. 110 images of ordered areas were digitized and aligned with computer-correlation methods to calculate an average image with diffraction to the fourth order. The images were computer-filtered and reconstructed to approx. 2 nm resolution. When crystals appeared they covered 20-40% of the surface of the preparation and, since rhodopsin is at least 95% of the protein, there is no doubt that the crystals were due to rhodopsin. There appear to be two rhodopsin dimers per unit cell. Each rhodopsin molecules takes up about 7.5 nm2 of membrane area and is estimated to be associated with about 12 lipids on each side of the membrane. The membrane area found for bovine rhodopsin supports the rhodopsin origin of rarely seen but more highly ordered two-dimensional crystals found in detergent-treated frog rod membranes (Corless, J.M., McCaslin, D.R. and Scott, B.L. (1982) Proc. Natl. Acad. Sci. USA 79, 1116-1120). Furthermore, the rhodopsin membrane area is close to that of bacteriorhodopsin and is consistent with a seven transmembrane helix structure proposed for rhodopsin (for references see Dratz, E.A. and Hargrave, D.A. (1983) Trends Biochem. Sci. 8, 128-131). Crystallization was accomplished by lowering the pH to 5.5 near the isoelectric point of rhodopsin, raising the salt concentration of 2 M (NH4)2SO4, adding 5% glucose and 0.02% Hibitane (Ayerst), a cationic amphipathic antiseptic that favored crystal growth. PMID:4074754

Dratz, E A; Van Breemen, J F; Kamps, K M; Keegstra, W; Van Bruggen, E F

1985-12-20

280

Two-dimensional virtual impactors. Final report  

SciTech Connect

Theoretical predictions using both potential flow analyses and solutions to Navier-Stokes equations are made for the operating characteristics of a two-dimensional virtual impactor. Experiments were performed with 2.5 ..mu..m, uranine tagged, di-octylphthalate (DOP) oil droplets for a wide range of prototype geometries to measure the magnitude of internal losses and to fully characterize the instrument response. The influence of geometry including the throat angle (38/sup 0/ less than or equal to ..beta../sub 0/ less than or equal to 58.2/sup 0/) and normalized void width (0.7 less than or equal to h/w less than or equal to 1.5) on the particle cutoff diameter, efficiency curve steepness and properties of the internal particle loss factor are presented for fixed instrument Reynolds numbers Re = 1540 and bleed flow f = 0.1. The theory, supported by trends in the empirical data, predicts that internal particle losses reduce to zero as the normalized void width increases to h/w = 1.4 +- .1 while the data show a minimum at h/w = 1.6 +- .1. Increasing the void width, however, is shown to substantially reduce the steepness of the particle efficiency curves. Visual observations of the onset of fluid separation for two-dimensional jets impinging upon a void were conducted with a scaled-up water model and correlated with theory. It was found that the limiting void width h/sub lim//w marking the onset of fluid instabilities peaked for an intermediate value of the fluid deflecting plate angle ..beta.. approx. = 80/sup 0/ with larger values of h/sub lim//w corresponding to smaller throat angles ..beta../sub 0/. The limiting void width h/sub lim//w also increased with larger bleed flows into the void. These instabilities may make it difficult to correlate experimental virtual impactor data with theory.

Forney, L.J.; Ravenhall, D.G.

1980-12-01

281

Coherent atomic soliton molecules for matter-wave switching  

SciTech Connect

We discuss the dynamics of interacting dark-bright two-dimensional vector solitons in multicomponent immiscible bulk Bose-Einstein condensates. We describe matter-wave molecules without a scalar counterpart that can be seen as bound states of vector objects. We also analyze the possibility of using these structures as building blocks for the design of matter-wave switchers.

Yin, Chenyun; Berloff, Natalia G. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA (United Kingdom); Perez-Garcia, Victor M. [Departamento de Matematicas, Escuela Tecnica Superior de Ingenieros Industriales (E.T.S.I.I.), Universidad de Castilla La Mancha 13071 Ciudad Real (Spain); Novoa, David; Carpentier, Alicia V.; Michinel, Humberto [Area de Optica, Facultade de Ciencias, Universidade de Vigo, As Lagoas s/n, Ourense, E-32004 (Spain)

2011-05-15

282

Discrete solitons in photorefractive optically-induced photonic crystals  

Microsoft Academic Search

We show that one- and two-dimensional discrete solitons are in fact possible in biased photorefractive media. This can be accomplished in optically induced photonic crystals\\/waveguides by exploiting the photorefractive screening nonlinearity. In this case, the 2-D lattice is created in the bulk, by appropriately interfering polarized plane-wave pairs.

N. K. Efremidis; D. N. Christodoulides; S. Sears; M. Segev

2002-01-01

283

Scattering of solitons in the formalism of the Darboux transform  

SciTech Connect

By means of the technique of Darboux transformations formules are obtained which describe the scattering of solitons in the Kadomtsev-Petviashvili equations; the KdV equation, the nonlocal KdV equation, the two-dimensionalized Toda lattice and its periodic reductions, and, in particular, the Sine-Gordon equation.

Matveev, V.B.; Sall, M.A.

1986-09-01

284

Scattering of solitons in the formalism of the Darboux transform  

SciTech Connect

By means of the technique of Darboux transformations formulas are obtained which describe the scattering of solitons in the Kadomtsev-Petviashvili equations; the KdV equation, the nonlocal KdV equation, the two-dimensionalized Toda lattice and its periodic reductions, and, in particular, the sine-Gordon equation.

Matveev, V.B.; Sall', M.A.

1986-09-10

285

Two-dimensional angular transmission characterization of CPV modules.  

PubMed

This paper proposes a fast method to characterize the two-dimensional angular transmission function of a concentrator photovoltaic (CPV) system. The so-called inverse method, which has been used in the past for the characterization of small optical components, has been adapted to large-area CPV modules. In the inverse method, the receiver cell is forward biased to produce a Lambertian light emission, which reveals the reverse optical path of the optics. Using a large-area collimator mirror, the light beam exiting the optics is projected on a Lambertian screen to create a spatially resolved image of the angular transmission function. An image is then obtained using a CCD camera. To validate this method, the angular transmission functions of a real CPV module have been measured by both direct illumination (flash CPV simulator and sunlight) and the inverse method, and the comparison shows good agreement. PMID:21165081

Herrero, R; Domínguez, C; Askins, S; Antón, I; Sala, G

2010-11-01

286

Modeling complexly magnetized two-dimensional bodies of arbitrary shape  

SciTech Connect

A method has been devised for the forward computation of magnetic anomalies due to two-dimensional (2-D) polygonal bodies with heterogeneously directed magnetization. The calculations are based on the equivalent line source approach wherein the source is subdivided into discrete elements that vary spatially in their magnetic properties. This equivalent dipole line method provides a fast and convenient means of representing and computing magnetic anomalies for bodies possessing complexly varying magnitude and direction of magnetization. The algorithm has been tested and applied to several generalized cases to verify the accuracy of the computation. The technique has also been used to model observed aeromagnetic anomalies associated with the structurally deformed, remanently magnetized Keweenawan volcanic rocks in eastern Lake Superior. This method is also easily adapted to the calculation of anomalies due to two and one-half-dimensional (2.5-D) and three-dimensional (3-D) heterogeneously magnetized sources.

Mariano, J.; Hinze, W.J. (Purdue Univ., West Lafayette, IN (United States). Dept. of Earth and Atmospheric Sciences)

1993-05-01

287

Approaches to verification of two-dimensional water quality models  

SciTech Connect

The verification of a water quality model is the one procedure most needed by decision making evaluating a model predictions, but is often not adequate or done at all. The results of a properly conducted verification provide the decision makers with an estimate of the uncertainty associated with model predictions. Several statistical tests are available for quantifying of the performance of a model. Six methods of verification were evaluated using an application of the BETTER two-dimensional water quality model for Chickamauga reservoir. Model predictions for ten state variables were compared to observed conditions from 1989. Spatial distributions of the verification measures showed the model predictions were generally adequate, except at a few specific locations in the reservoir. The most useful statistics were the mean standard error of the residuals. Quantifiable measures of model performance should be calculated during calibration and verification of future applications of the BETTER model. 25 refs., 5 figs., 7 tabs.

Butkus, S.R. (Tennessee Valley Authority, Chattanooga, TN (USA). Water Quality Dept.)

1990-11-01

288

Polariton condensation in an optically induced two-dimensional potential  

NASA Astrophysics Data System (ADS)

We demonstrate experimentally the condensation of exciton polaritons through optical trapping. The nonresonant pump profile is shaped into a ring and projected to a high quality factor microcavity where it forms a two-dimensional repulsive optical potential originating from the interactions of polaritons with the excitonic reservoir. Increasing the population of particles in the trap eventually leads to the emergence of a confined polariton condensate that is spatially decoupled from the decoherence inducing reservoir, before any buildup of coherence on the excitation region. In a reference experiment, where the trapping mechanism is switched off by changing the excitation intensity profile, polariton condensation takes place for excitation densities more than two times higher and the resulting condensate is subject to much stronger dephasing and depletion processes.

Askitopoulos, A.; Ohadi, H.; Kavokin, A. V.; Hatzopoulos, Z.; Savvidis, P. G.; Lagoudakis, P. G.

2013-07-01

289

Propagating and evanescent modes in two-dimensional wire media.  

PubMed

Electromagnetic waves in an artificial medium formed by two mutually orthogonal lattices of thin ideally conducting straight wires (referred to as a two-dimensional wire medium) are considered. An effective medium approach and a full-wave method based on the dyadic Green's function and the method of moments are developed. Effects of spatial dispersion, such as the appearance of anisotropy in a square lattice and an additional extraordinary wave, as in crystal optics, are demonstrated. Evanescent waves with complex propagation constants are found. The case when both forward and backward extraordinary waves with respect to an interface exist simultaneously is observed and discussed. The effect of birefringence, so that one extraordinary wave has the wave vector making a positive angle to the interface and the other has the wave vector making a negative angle to the interface, is illustrated. PMID:15903811

Nefedov, I S; Viitanen, A J; Tretyakov, S A

2005-04-29

290

An inexpensive rhizotron design for two-dimensional, horizontal root ...  

Treesearch

Title: An inexpensive rhizotron design for two-dimensional, horizontal root ... that supports two-dimensional, horizontal root growth measurements over time ... and (3) acquiring novel rooting data that can be input to a plant growth model.

291

Synergy dynamics of vortices and solitons in an atomic Bose-Einstein condensate excited by an oscillating potential  

SciTech Connect

The hydrodynamics of quantized vortices and solitons in an atomic Bose-Einstein condensate excited by an oscillating potential are studied by numerically solving the two-dimensional Gross-Pitaevskii equation. The oscillating potential keeps nucleating vortex dipoles, whose impulses alternately change their direction synchronously with the oscillation of the potential. This leads to synergy dynamics of vortices and solitons in quantum fluids.

Fujimoto, Kazuya; Tsubota, Makoto [Department of Physics, Osaka City University, Sumiyoshi-ku, Osaka 558-8585 (Japan)

2010-10-15

292

An improved two-dimensional code encoding approach for publications  

Microsoft Academic Search

Nowadays, the publishing industry has begun to use the two-dimensional code in cell phones, but the standard is not defined. Compared with single-dimensional bar code, two-dimensional code contains more information and functions. Nowadays, two-dimensional code has been broadly used in some industries, such as mobile communication, logistics and advertising, but not in publishing. This paper introduces an improved two-dimensional code

Wang Liang; Liu Xiaodan

2010-01-01

293

Self-consistent turbulence in the two-dimensional nonlinear Schrödinger equation with a repulsive potential.  

PubMed

The dynamics of dark solitons (vortices) with the same topological charge (vorticity) in the two-dimensional nonlinear Schrödinger (NLS) equation in a defocusing medium is studied. The dynamics differ from those in incompressible media due to the possibility of energy and angular momentum radiation. The problem of the breakup of a multicharged dark soliton, which is a local decrease of the wave function intensity, into a number of chaotically moving vortices with single charge, is studied both analytically and numerically. After an initial period of intensive wave radiation, there emerges a nonuniform, steady turbulent self-organized motion of these vortices which is restricted in space by the size of the potential well of the initial multicharged dark soliton. Separate orbits of finite widths arise in this turbulent motion. That is, the statistical probability to observe a vortex in a given point has maxima near certain points (orbit positions). In spite of the fact that numerical calculations were performed in a finite region, the turbulent distributions of the vortices do not depend on the size of the container when its radius is larger than the size of the potential well of the primary multicharged dark soliton. The steady turbulent distribution of vortices on these orbits can be obtained as the extremal of the Lyapunov functional of the NLS equation, and obeys some simple rules. The first is the absence of Cherenkov resonance with linear (sound) waves. The second is the condition of a potential energy maximum in the region of vortex motion. These conditions give an approximately equidistant disposition of orbits of the same number of vortices on each orbit, which corresponds to a constant rotating velocity. The magnitude of this velocity is mainly determined by the sound velocity. An integral estimation of the self-consistent rotation of the vortex zone is given. PMID:11969787

Ivonin, I A; Pavlenko, V P; Persson, H

1999-07-01

294

Implementations of two-dimensional liquid chromatography  

SciTech Connect

Today scientists must deal with complex samples that either cannot be adequately separated using one-dimensional chromatography or that require an inordinate amount of time for separation. For these cases we need two-dimensional chromatography because it takes far less time to generate a peak capacity n{sub c} twice in a row than to generate a peak capacity n{sub c}{sup 2} once. Liquid chromatography has been carried out successfully on thin layers of adsorbents and along tubes filled with various adsorbents. The first type of separation sorts out the sample components in a physical separation space that is the layer of packing material. The analysis time is the same for all the components of the sample while their migration distance increases with decreasing retention. The resolution between two components having a certain separation factor (a) increases with increasing migration distance, i.e., from the strongly to the weakly retained compounds. In the second type of separation, the sample components are eluted from the column and separated in the time space, their migration distances are all the same while their retention times increase from the unretained to the strongly retained compounds. Separation efficiency varies little with retention, as long as the components are eluted from the column. We call these two types of separation the chromatographic separations in space (LC{sup x}) and the chromatographic separations in time (LC{sup t}), respectively. In principle, there are four ways to combine these two modes and do two-dimensional chromatographic separations, LC{sup t} x LC{sup t}, LC{sup x} x LC{sup t}, LC{sup t} x LC{sup x}, and LC{sup x} x LC{sup x}. We review, discuss and compare the potential performance of these combinations, their advantages, drawbacks, problems, perspectives and results. Currently, column-based combinations (LC{sup t} x LC{sup t}) are the most actively pursued. We suggest that the combination LC{sup x} x LC{sup t} shows exceptional promise because it permits the simultaneous second-dimension separations of all the fractions separated in the first-dimension, thus providing remarkable time saving.

Guiochon, Georges A [ORNL; Marchetti, Nicola [University of Tennessee, Knoxville (UTK); Mriziq, Khaled S [ORNL; Shalliker, R. Andrew [University of Western Sydney, Australia

2008-01-01

295

Helical rays in two-dimensional resonant wave conversion  

SciTech Connect

The process of resonant wave conversion (often called linear mode conversion) has traditionally been analyzed with a spatially one-dimensional slab model, for which the rays propagate in a two-dimensional phase space. However, it has recently been shown [E. R. Tracy and A. N. Kaufman, Phys. Rev. Lett. 91, 130402 (2003)] that multidimensional rays have a helical structure for conversion in two or more spatial dimensions (if their dispersion matrix is generic). In that case, a one-dimensional model is inadequate; a correct analysis requires two spatial dimensions and, thus, four-dimensional phase space. A cold-plasma model is introduced in this paper which exhibits ray helicity in conversion regions where the density and magnetic field gradients are significantly nonparallel. For illustration, such regions are identified in a model of the poloidal plane of a deuterium-tritium tokamak plasma. In each conversion region, characterized by a six-sector topology, rays in the sector for incident and reflected magnetosonic waves exhibit significant helicity. A detailed analytic and numerical study of helical rays in this sector is developed for a 'symmetric-wedge' model.

Kaufman, Allan N.; Tracy, Eugene R.; Brizard, Alain J. [Lawrence Berkeley National Laboratory and Physics Department, University of California, Berkeley, California 94720 (United States); Physics Department, College of William and Mary, Williamsburg, Virginia 23187-8795 (United States); Department of Chemistry and Physics, Saint Michael's College, Colchester, Vermont 05439 (United States)

2005-02-01

296

Helical rays in two-dimensional resonant wave conversion  

SciTech Connect

The process of resonant wave conversion (often called linear mode conversion) has traditionally been analyzed with a spatially one-dimensional slab model, for which the rays propagate in a two-dimensional phase space. However, it has recently been shown [E.R. Tracy and A.N. Kaufman, Phys. Rev. Lett. 91, 130402 (2003)] that multidimensional rays have a helical structure for conversion in two or more spatial dimensions (if their dispersion matrix is generic). In that case, a one-dimensional model is inadequate; a correct analysis requires two spatial dimensions and, thus, four-dimensional phase space. In this paper we show that a cold plasma model will exhibit ray helicity in conversion regions where the density and magnetic field gradients are significantly non-parallel. For illustration, we examine a model of the poloidal plane of a deuterium-tritium tokamak plasma, and identify such a region. In this region, characterized by a six-sector topology, rays in the sector for incident and reflected magnetosonic waves exhibit significant helicity. We introduce a ''symmetric-wedge'' model, to develop a detailed analytic and numerical study of helical rays in this sector.

Kaufman, Allan N.; Tracy, Eugene R.; Brizard, Alain J.

2004-12-08

297

Helical rays in two-dimensional resonant wave conversion  

SciTech Connect

The process of resonant wave conversion (often called linear mode conversion) has traditionally been analyzed with a spatially one-dimensional slab model, for which the rays propagate in a two-dimensional phase space. However, it has recently been shown [E.R. Tracy and A.N. Kaufman, Phys. Rev. Lett. 91, 130402 (2003)] that multidimensional rays have a helical structure for conversion in two or more spatial dimensions (if their dispersion matrix is generic). In that case, a one-dimensional model is inadequate; a correct analysis requires two spatial dimensions and, thus, four-dimensional phase space. In this paper we show that a cold plasma model will exhibit ray helicity in conversion regions where the density and magnetic field gradients are significantly non-parallel. For illustration, we examine a model of the poloidal plane of a deuterium-tritium tokamak plasma, and identify such a region. In this region, characterized by a six-sector topology, rays in the sector for incident and reflected magnetosonic waves exhibit significant helicity. We introduce a ''symmetric-wedge'' model, to develop a detailed analytic and numerical study of helical rays in this sector.

Kaufman, Allan N.; Tracy, Eugene R.; Brizard, Alain J.

2004-09-14

298

Dynamics of two-dimensional dipole systems  

SciTech Connect

Using a combined analytical/molecular dynamics approach, we study the current fluctuation spectra and longitudinal and transverse collective mode dispersions of the classical two-dimensional (point) dipole system (2DDS) characterized by the {phi}{sub D}(r)={mu}{sup 2}/r{sup 3} repulsive interaction potential; {mu} is the electric dipole strength. The interest in the 2DDS is twofold. First, the quasi-long-range 1/r{sup 3} interaction makes the system a unique classical many-body system, with a remarkable collective mode behavior. Second, the system may be a good model for a closely spaced semiconductor electron-hole bilayer, a system that is in the forefront of current experimental interest. The longitudinal collective excitations, which are of primary interest for the liquid phase, are acoustic at long wavelengths. At higher wave numbers and for sufficiently high coupling strength, we observe the formation of a deep minimum in the dispersion curve preceded by a sharp maximum; this is identical to what has been observed in the dispersion of the zero-temperature bosonic dipole system, which in turn emulates so-called roton-maxon excitation spectrum of the superfluid {sup 4}He. The analysis we present gives an insight into the emergence of this apparently universal structure, governed by strong correlations. We study both the liquid and the crystalline solid state. We also observe the excitation of combination frequencies, resembling the roton-roton, roton-maxon, etc. structures in {sup 4}He.

Golden, Kenneth I.; Kalman, Gabor J.; Hartmann, Peter; Donko, Zoltan [Department of Mathematics and Statistics, Department of Physics, University of Vermont, Burlington, Vermont 05401 (United States); Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary and Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States)

2010-09-15

299

Nonlinear tunneling in two-dimensional lattices  

SciTech Connect

We present a thorough analysis of the nonlinear tunneling of Bose-Einstein condensates in static and accelerating two-dimensional lattices within the framework of the mean-field approximation. We deal with nonseparable lattices, considering different initial atomic distributions in highly symmetric states. For an analytical description of the condensate before instabilities develop, we derive several few-mode models, analyzing essentially both nonlinear and quasilinear regimes of tunneling. By direct numerical simulations, we show that two-mode models provide an accurate description of tunneling when either initially two states are populated or tunneling occurs between two stable states. Otherwise, a two-mode model may give only useful qualitative hints for understanding tunneling, but does not reproduce many features of the phenomenon. This reflects the crucial role of instabilities developed due to two-body interactions resulting in a non-negligible population of the higher bands. This effect becomes even more pronounced in the case of accelerating lattices. In the latter case we show that the direction of the acceleration is a relevant physical parameter which affects the tunneling by changing the atomic rates at different symmetric states and by changing the numbers of bands involved in the atomic transfer.

Brazhnyi, V. A. [Centro de Fisica Teorica e Computacional, Universidade de Lisboa, Complexo Interdisciplinar, Avenida Professor Gama Pinto 2, Lisbon 1649-003 (Portugal); Konotop, V. V. [Centro de Fisica Teorica e Computacional, Universidade de Lisboa, Complexo Interdisciplinar, Avenida Professor Gama Pinto 2, Lisbon 1649-003 (Portugal); Departamento de Fisica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, Piso 6, Lisbon 1749-016 (Portugal); Kuzmiak, V. [Institute of Photonics and Electronics, v.v.i., Czech Academy of Sciences, Chaberska 57, 182 51 Prague 8 (Czech Republic); Shchesnovich, V. S. [Instituto de Fisica, Universidade Federal de Alagoas, Maceio AL 57072-970 (Brazil)

2007-08-15

300

Pressure Fluctuations in Two-dimensional Turbulence  

NASA Astrophysics Data System (ADS)

We investigate pressure fluctuations in two-dimensional (2D) turbulence driven electromagnetically in a freely suspended soap film. The reduced probability distribution function (PDF), P(p/?p), is found to be universal for different Reynolds numbers and consists of asymmetrical exponential wings, where ?p?/?p^3˜-0.5 is significantly smaller than predictions by simple 2D models (Holzer and Siggia, Phys. Fluids A5, 2525 (1993)) but surprisingly close to 3D calculations using a random velocity field with a Kolmogorov energy spectrum E(k)k-5/3. The pressure spectrum Epp(k) scales approximately as Epp(k)k-7/3 in the energy inverse-cascade subrange and k-5 in the enstrophy cascade subrange. These observations suggest that pressure fluctuations is essentially a large-scale phenomenon and the presence of an enstrophy cascade has no effect on the tails of P(p/?p).

Jun, Yonggun; Wu, X. L.

2007-03-01

301

Order Parameters for Two-Dimensional Networks  

NASA Astrophysics Data System (ADS)

We derive methods that explain how to quantify the amount of order in ``ordered'' and ``highly ordered'' porous arrays. Ordered arrays from bee honeycomb and several from the general field of nanoscience are compared. Accurate measures of the order in porous arrays are made using the discrete pair distribution function (PDF) and the Debye-Waller Factor (DWF) from 2-D discrete Fourier transforms calculated from the real-space data using MATLAB routines. An order parameter, OP3, is defined from the PDF to evaluate the total order in a given array such that an ideal network has the value of 1. When we compare PDFs of man-made arrays with that of our honeycomb we find OP3=0.399 for the honeycomb and OP3=0.572 for man's best hexagonal array. The DWF also scales with this order parameter with the least disorder from a computer-generated hexagonal array and the most disorder from a random array. An ideal hexagonal array normalizes a two-dimensional Fourier transform from which a Debye-Waller parameter is derived which describes the disorder in the arrays. An order parameter S, defined by the DWF, takes values from [0, 1] and for the analyzed man-made array is 0.90, while for the honeycomb it is 0.65. This presentation describes methods to quantify the order found in these arrays.

Kaatz, Forrest; Bultheel, Adhemar; Egami, Takeshi

2007-10-01

302

Plastic flow in two-dimensional solids.  

PubMed

A time-dependent Ginzburg-Landau model of plastic deformation in two-dimensional solids is presented. The fundamental dynamic variables are the displacement field u and the lattice velocity v=delta(u)/delta(t). Damping is assumed to arise from the shear viscosity in the momentum equation. The elastic energy density is a periodic function of the shear and tetragonal strains, which enables the formation of slips at large strains. In this work we neglect defects such as vacancies, interstitials, or grain boundaries. The simplest slip consists of two edge dislocations with opposite Burgers vectors. The formation energy of a slip is minimized if its orientation is parallel or perpendicular to the flow in simple shear deformation and if it makes angles of +/-pi/4 with respect to the stretched direction in uniaxial stretching. High-density dislocations produced in plastic flow do not disappear even if the flow is stopped. Thus large applied strains give rise to structurally disordered states, which are metastable due to the Peierls potential. We divide the elastic energy into an elastic part due to affine deformation and a defect part. The latter represents degree of disorder and is nearly constant in plastic flow under cyclic straining. PMID:14754207

Onuki, Akira

2003-12-11

303

Adaptive two-dimensional microgas chromatography.  

PubMed

We proposed and investigated a novel adaptive two-dimensional (2-D) microgas chromatography system, which consists of one 1st-dimensional column, multiple parallel 2nd-dimensional columns, and a decision-making module. The decision-making module, installed between the 1st- and 2nd-dimensional columns, normally comprises an on-column nondestructive vapor detector, a flow routing system, and a computer that monitors the detection signal from the detector and sends out the trigger signal to the flow routing system. During the operation, effluents from the 1st-dimensional column are first detected by the detector and, then, depending on the signal generated by the detector, routed to one of the 2nd-dimensional columns sequentially for further separation. As compared to conventional 2-D GC systems, the proposed adaptive GC scheme has a number of unique and advantageous features. First and foremost, the multiple parallel columns are independent of each other. Therefore, their length, stationary phase, flow rate, and temperature can be optimized for best separation and maximal versatility. In addition, the adaptive GC significantly lowers the thermal modulator modulation frequency and hence power consumption. Finally, it greatly simplifies the postdata analysis process required to reconstruct the 2-D chromatogram. In this paper, the underlying working principle and data analysis of the adaptive GC was first discussed. Then, separation of a mixture of 20 analytes with various volatilities and polarities was demonstrated using an adaptive GC system with a single 2nd-dimensional column. Finally, an adaptive GC system with dual 2nd-dimensional columns was employed, in conjunction with temperature ramping, in a practical application to separate a mixture of plant emitted volatile organic compounds with significantly shortened analysis time. PMID:22468727

Liu, Jing; Khaing Oo, Maung Kyaw; Reddy, Karthik; Gianchandani, Yogesh B; Schultz, Jack C; Appel, Heidi M; Fan, Xudong

2012-04-10

304

Two-dimensional Full Waveform Inversion  

NASA Astrophysics Data System (ADS)

A two-dimensional full wavefield inversion for direct imaging of compressional wave and out-of-plane standing wave (SH) velocity distribution is developed, tested and implemented. The inversion is base on the finite difference solution of the full two-dimension scalar wave equation in the time-distance domain and operates on wide-aperture, common-shot data. The computational kernel fully utilizes the reverse-time image reconstruction principles. No travel-time picking and phase identification are required for full waveform inversion. For each shot records, gradients of misfit function (Frechét derivative) are dynamically determined by cross-correlation of the recorded forward propagating wavefield and backward propagating residual wavefield at each time step. Convergence to local minima can be avoided by gradually increasing the wavenumber bandwidth in the estimated velocity distribution and to increase the inversion resolution as iterations proceed. Synthetic examples show that the effects of the multiples, scattering, artificial boundary reflection waves, or noise do not contaminate the final results and convergences successfully to the correct solution. Using full two-way waveform approach for seismic imaging simplifies un-necessary skeleton seismic processing procedures. Furthermore, the resolution of inversion result is limited by the bandwidth of field recordings, source wavelet and dominant frequency. Convergence rate and stability of our in-house development of inversion algorithm is highly depends on step length and the complexity of subsurface structure associate with the steepest decent direction. For land data, near-surface effects including topography, lateral velocity variation, source and receiver static corrections are automatically included. For marine seismic data, multiples generated by water layer can be effectively suppressed through wavefield based seismic processing approach.

Li, K.; Chen, H.

2005-12-01

305

Motion, relaxation dynamics, and diffusion processes in two-dimensional colloidal crystals confined between walls  

NASA Astrophysics Data System (ADS)

The dynamical behavior of single-component two-dimensional colloidal crystals confined in a slit geometry is studied by Langevin dynamics simulation of a simple model. The colloids are modeled as pointlike particles, interacting with the repulsive part of the Lennard-Jones potential, and the fluid molecules in the colloidal suspension are not explicitly considered. Considering a crystalline strip of triangular lattice structure with n=30 rows, the (one-dimensional) walls confining the strip are chosen as two rigidly fixed crystalline rows at each side, commensurate with the lattice structure and, thus, stabilizing long-range order. The case when the spacing between the walls is incommensurate with the ideal triangular lattice is also studied, where (due to a transition in the number of rows, n?n-1) the confined crystal is incommensurate with the confining boundaries, and a soliton staircase forms along the walls. It is shown that mean-square displacements (MSDs) of particles as a function of time show an overshoot and then saturate at a horizontal plateau in the commensurate case, the value of the plateau being largest in the center of the strip. Conversely, when solitons are present, MSDs are largest in the rows containing the solitons, and all MSDs do not settle down at well-defined plateaus in the direction parallel to the boundaries, due to the lack of positional long-range order in ideal two-dimensional crystals. The MSDs of the solitons (which can be treated like quasiparticles at very low temperature) have also been studied and their dynamics are found to be about an order of magnitude slower than that of the colloidal particles themselves. Finally, transport of individual colloidal particles by diffusion processes is studied: both standard vacancy-interstitial pair formation and cooperative ring rotation processes are identified. These processes require thermal activation, with activation energies of the order of 10Tm (Tm being the melting temperature of the crystal), while the motions due to long-wavelength phonons decrease only linearly in temperature.

Wilms, Dorothea; Virnau, Peter; Snook, Ian K.; Binder, Kurt

2012-11-01

306

Characterizing the Two-Dimensional Thermal Conductivity Distribution in a Sand and Gravel Aquifer  

Microsoft Academic Search

Both hydrologic and thermal transport properties play a significant role in the movement of heat through permeable sedimentary material; however, the thermal conductivity is rarely characterized in detailed spatial resolution. As part of a study of the movement of thermal plumes through a sand and gravel aquifer, we have constructed a two-dimensional profile of thermal conductivity. This work consisted of:

Jeff M. Markle; Robert A. Schincariol; John H. Sass; John W. Molson

2006-01-01

307

Delocalizing transition of Bose-Einstein condensates in two-dimensional optical lattices  

Microsoft Academic Search

A Bose-Einstein condensate trapped in a two-dimensional optical lattice exhibits an abrupt transition manifested by the macroscopic wavefunction changing character from spatially localized to extended. This transition takes place as the interwell potential barrier is adiabatically decreased below a critical value and is irreversible since increasing the interwell barrier back to its initial value does not restore localization. This is

George Kalosakas; Kim O. Rasmussen; Alan R. Bishop

2003-01-01

308

Improved coupled wave analysis of two-dimensional planar multiple gratings  

Microsoft Academic Search

An improved coupled wave approach is presented for the analysis of diffraction behavior of a two-dimensional spatially periodic or almost periodic dielectric layer illuminated by TE polarized plane waves. This method applies to any simultaneous composition of arbitrarily modulated planar transmission gratings with any permittivity in neighboring regions. Two major improvements have been made. In the first part, the eigenvalues

Babak Momeni; Bizhan Rashidian

2004-01-01

309

Two-dimensional calculation of finite-beta modifications of drift and trapped-electron modes  

SciTech Connect

A previous electrostatic calculation for the two-dimensional spatial structure of drift and trapped-electron modes is extended to include finite-..beta.. effects. Specifically, the parallel perturbed vector potential and the parallel Ampere's law are added to the calculation. Illustrative results are presented.

Rewoldt, G.; Tang, W.M.; Frieman, E.A.

1980-05-01

310

Watching Dark Solitons Decay into Vortex Rings in a Bose-Einstein Condensate  

Microsoft Academic Search

We have created spatial dark solitons in two-component Bose-Einstein\\u000acondensates in which the soliton exists in one of the condensate components and\\u000athe soliton nodal plane is filled with the second component. The filled\\u000asolitons are stable for hundreds of milliseconds. The filling can be\\u000aselectively removed, making the soliton more susceptible to dynamical\\u000ainstabilities. For a condensate in a

B. P. Anderson; P. C. Haljan; C. A. Regal; D. L. Feder; L. A. Collins; C. W. Clark; E. A. Cornell

2001-01-01

311

Self-bending of dark and gray photorefractive solitons  

Microsoft Academic Search

We investigate the effects of diffusion on the evolution of steady-state dark and gray spatial solitons in biased photorefractive media. Numerical integration of the nonlinear propagation equation shows that the soliton beams experience a modification of their initial trajectory, as well as a variation of their minimum intensity. This process is further studied using perturbation analysis, which predicts that the

M. I. Carvalho; M. Facăo; D. N. Christodoulides

2007-01-01

312

The Peregrine soliton in nonlinear fibre optics  

NASA Astrophysics Data System (ADS)

The Peregrine soliton is a localized nonlinear structure predicted to exist over 25 years ago, but not so far experimentally observed in any physical system. It is of fundamental significance because it is localized in both time and space, and because it defines the limit of a wide class of solutions to the nonlinear Schrödinger equation (NLSE). Here, we use an analytic description of NLSE breather propagation to implement experiments in optical fibre generating femtosecond pulses with strong temporal and spatial localization, and near-ideal temporal Peregrine soliton characteristics. In showing that Peregrine soliton characteristics appear with initial conditions that do not correspond to the mathematical ideal, our results may impact widely on studies of hydrodynamic wave instabilities where the Peregrine soliton is considered a freak-wave prototype.

Kibler, B.; Fatome, J.; Finot, C.; Millot, G.; Dias, F.; Genty, G.; Akhmediev, N.; Dudley, J. M.

2010-10-01

313

Engineering optical soliton bistability in colloidal media  

NASA Astrophysics Data System (ADS)

We consider a mixture consisting of two species of spherical nanoparticles dispersed in a liquid medium. We show that with an appropriate choice of refractive indices and particle diameters, it is possible to observe the phenomenon of optical soliton bistability in two spatial dimensions in a broad beam power range. Previously, this possibility was ruled out in the case of a single-species colloid. As a particular example, we consider the system of hydrophilic silica particles and gas bubbles generated in the process of electrolysis in water. The interaction of two soliton beams can lead to switching of the lower branch solitons to the upper branch, and the interaction of solitons from different branches is phase independent and always repulsive.

Matuszewski, Micha?

2010-01-01

314

The practical significance of two-dimensional deconvolution in echography.  

PubMed

This paper evaluates deconvolution (inverse filtering) as applied to ultrasonic imaging systems, and discusses the obstacles which are encountered employing the technique in practice. A minicomputer is used to generate artificial echo signals, simulating rf signals resulting from a set of point reflectors in a homogeneous medium, as recorded by an electronically focused group-steered linear array scanner. Two-dimensional deconvolution in combination with a Wiener noise reduction filter (i.e., a Wiener-Inverse filter) is applied to these simulated rf signals, which were contaminated with white noise. The efficacy of the Wiener-Inverse filter is defined in terms of its ability to resolve two point reflectors with a lateral spacing equal to the local -6 dB width of the ultrasonic beam. In favorable circumstances, the targets are resolved at signal-to-noise ratios (SNR) better than 20 dB, where SNR is defined as the maximum signal power divided by the average noise power level. Nonlinear effects due to quantization or signal clipping are investigated. In order to improve the resolution of an rf signal with a dynamic range of 40 dB, the input signal should be digitized at a minimum of 12 bits. The problem of signal clipping can be circumvented by oversampling. The two-dimensional Wiener-Inverse filter is defined in terms of both temporal and spatial properties of the insonification. Effects of wave diffraction give rise to a depth-dependent ultrasonic beam. As a result of a misfit of the Wiener-Inverse filter and the local properties of the ultrasonic beam, erroneous noisy texture arises in the image. Adaptation of the Wiener-Inverse filter with respect to the beam properties gives acceptable results, at the expense of a rather large computational effort. PMID:3318076

Jeurens, T J; Somer, J C; Smeets, F A; Hoeks, A P

1987-04-01

315

Spiraling elliptic solitons in nonlocal nonlinear media without anisotropy  

NASA Astrophysics Data System (ADS)

The spatial optical solitons with ellipse-shaped spots have generally been considered to be a result of either linear or nonlinear anisotropy. We investigate a class of spiraling elliptic solitons in nonlocal nonlinear media without both linear and nonlinear anisotropy. The spiraling elliptic solitons carry the orbital angular momentum (OAM), which plays a key role in the formation of such solitons, and are stable for any degree of nonlocality except the local case if the response function is Gaussian. During the propagation of such solitons, the rate of decay of the OAM is extremely low. The formation of such solitons can be attributed to effective anisotropic diffraction (linear anisotropy) resulting from the OAM. Our variational analytical result is confirmed by direct numerical simulation of the nonlocal nonlinear Schrödinger equation.

Liang, Guo; Guo, Qi

2013-10-01

316

Two-dimensional neutron detector based on a position-sensitive photomultiplier  

Microsoft Academic Search

A new type of two-dimensional neutron scintillation detector with high spatial resolution based on a position-sensitive photomultiplier has been investigated. With a 6Li glass scintillator a spatial resolution of 1.0 mm was measured. The integral linearity over the detection area of 55 × 45 mm2 is <=1.5 mm. The detector homogeneity is within 10% at a discriminator level at 60%

R. Kurz; R. Reinartz; S. Widdau; J. Schelten; A. Scholz; W. Schäfer

1988-01-01

317

Optical realization of the wavelet transform for two-dimensional objects  

Microsoft Academic Search

The authors implement a real-time wavelet transformations of two-dimensional objects by using of the conventional coherent correlator with a multireference matched filter. The different daughter wavelets are spatially multiplexed with different reference-beam directions. Results of two experiments are described, one of them with a spatial light modulator at the input plane in order to enable the real-time property.

David Mendlovic

1993-01-01

318

Optical realization of the wavelet transform for two-dimensional objects  

NASA Astrophysics Data System (ADS)

The authors implement a real-time wavelet transformations of two-dimensional objects by using of the conventional coherent correlator with a multireference matched filter. The different daughter wavelets are spatially multiplexed with different reference-beam directions. Results of two experiments are described, one of them with a spatial light modulator at the input plane in order to enable the real-time property.

Konforti, Nami; Mendlovic, David

1993-11-01

319

Ultrafast Time-to-Two-Dimensional-Space Conversion System Using SHG Crystal  

Microsoft Academic Search

We propose an ultrafast optical time-to-two-dimensional (2-D) space conversion system using a crystal of ?-BaB2O4. The proposed system can optically retrieve a 2-D spatial distribution (an image signal) from an ultra-short laser pulse modulated by an image. The fundamentals are the time-to-space transform and the spatial time-frequency transform. Optical time gating using a nonlinear optical crystal is applied for the

Yoshinori Oshita; Tsuyoshi Konishi; Yoshiki Ichioka

2002-01-01

320

Responses of V1 Neurons to Two-Dimensional Hermite Functions  

PubMed Central

Neurons in primary visual cortex are widely considered to be oriented filters or energy detectors that perform one-dimensional feature analysis. The main deviations from this picture are generally thought to include gain controls and modulatory influences. Here we investigate receptive field (RF) properties of single neurons with localized two-dimensional stimuli, the two-dimensional Hermite functions (TDHs). TDHs can be grouped into distinct complete orthonormal bases that are matched in contrast energy, spatial extent, and spatial frequency content but differ in two-dimensional form, and thus can be used to probe spatially specific nonlinearities. Here we use two such bases: Cartesian TDHs, which resemble vignetted gratings and checkerboards, and polar TDHs, which resemble vignetted annuli and dartboards. Of 63 isolated units, 51 responded to TDH stimuli. In 37/51 units, we found significant differences in overall response size (21/51) or apparent RF shape (28/51) that depended on which basis set was used. Because of the properties of the TDH stimuli, these findings are inconsistent with simple feedforward nonlinearities and with many variants of energy models. Rather, they imply the presence of nonlinearities that are not local in either space or spatial frequency. Units showing these differences were present to a similar degree in cat and monkey, in simple and complex cells, and in supragranular, infragranular, and granular layers. We thus find a widely distributed neurophysiological substrate for two-dimensional spatial analysis at the earliest stages of cortical processing. Moreover, the population pattern of tuning to TDH functions suggests that V1 neurons sample not only orientations, but a larger space of two-dimensional form, in an even-handed manner.

Victor, Jonathan D.; Mechler, Ferenc; Repucci, Michael A.; Purpura, Keith P.; Sharpee, Tatyana

2010-01-01

321

TASI Lectures on Solitons  

Microsoft Academic Search

These lectures cover aspects of solitons with focus on applications to the quantum dynamics of supersymmetric gauge theories and string theory. The lectures consist of four sections, each dealing with a different soliton. We start with instantons and work down in co-dimension to monopoles, vortices and, eventually, domain walls. Emphasis is placed on the moduli space of solitons and, in

David Tong

2005-01-01

322

Soliton excitation in superlattice.  

National Technical Information Service (NTIS)

Excitation of soliton in superlattice has been investigated theoretically. It is noted that the soliton velocity u and the length L depend on the amplitude E(sub 0) and that an increase in the amplitude causes soliton width L to approach zero and the velo...

S. Y. Mensah F. K. A. Allotey N. G. Mensah A. K. Twum

1995-01-01

323

Melting of a two-dimensional crystal of electrons  

Microsoft Academic Search

Experiments show that a sheet of electrons in image-potential-induced states outside a helium surface forms at low temperatures a two-dimensional crystal (the classical, two-dimensional analog of a Wigner crystal). At higher temperatures the electron crystal melts to form a two-dimensional, classical, one-component plasma. The melting transition occurs at Gammam = 131 +\\/- 7 where Gamma is a measure of the

C. C. Grimes

1981-01-01

324

Lie algebra contractions on two-dimensional hyperboloid  

SciTech Connect

The Inoenue-Wigner contraction from the SO(2, 1) group to the Euclidean E(2) and E(1, 1) group is used to relate the separation of variables in Laplace-Beltrami (Helmholtz) equations for the four corresponding two-dimensional homogeneous spaces: two-dimensional hyperboloids and two-dimensional Euclidean and pseudo-Euclidean spaces. We show how the nine systems of coordinates on the two-dimensional hyperboloids contracted to the four systems of coordinates on E{sub 2} and eight on E{sub 1,1}. The text was submitted by the authors in English.

Pogosyan, G. S., E-mail: pogosyan@ysu.am; Yakhno, A. [Universidad de Guadalajara, Departamento de Matematicas, CUCEI (Mexico)

2010-03-15

325

Solitons in nonlinear optics  

SciTech Connect

The classic examples of optical phenomena resulting in the appearance of solitons are self-focusing, self-induced transparency, and parametric three-wave interaction. To date, the list of the fields of nonlinear optics and models where solitons play an important role has significantly expanded. Now long-lived or stable solitary waves are called solitons, including, for example, dissipative, gap, parametric, and topological solitons. This review considers nonlinear optics models giving rise to the appearance of solitons in a narrow sense: solitary waves corresponding to the solutions of completely integrable systems of equations basic for the models being discussed. (review)

Maimistov, Andrei I [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation)

2010-11-13

326

Formation of Quantum Turbulence from Dark Solitons in Atomic Bose-Einstein Condensates  

NASA Astrophysics Data System (ADS)

We theoretically propose a new method of making quantum turbulence from many dark solitons in atomic Bose-Einstein condensates. We solve numerically the two-dimensional Gross-Pitaevskii equation. We set initially many solitons so that they can form a square grid. A dark soliton is known to be stable in one-dimensional systems, but unstable in two- or three-dimensional systems and decay to vortices. Our simulation shows that these solitons decay to a lot of vortices which move around in the system and eventually lead to two-dimensional quantum turbulence. The probability distribution function of the superfluid velocity obeys a Gaussian distribution in the low-velocity region and a power-law distribution in the high-velocity region. The decay of the total number of vortices obeys a power-law for a relatively long period. This scenario may be experimentally realized through interference of Bose-Einstein condensates in a trap potential.

Kusumura, Takuya; Tsubota, Makoto; Takeuchi, Hiromitsu

2012-12-01

327

From Solitons to Knots and Links  

NASA Astrophysics Data System (ADS)

Development in the theory of solvable (integrable) models is reviewed. It covers from basic knowledge on completely integrable systems to recent work by the authors. First, soliton theory is briefly summarized. Through the inverse scattering method and its quantum extension, a central concept, commuting transfer matrices, and a key relation, the Yang-Baxter relation, are introduced. Second, it is shown that there exists at least ? × ? number of solvable models in two-dimensional statistical mechanics. Third, quantum spin chains corresponding to solvable statistical mechanical models are discussed. In particular, finite temperature extension of Baxter's formula is given. Fouth, a new approach is presented to the classification problem of knots and links. It is shown that link polynomial, topological invariant for knots and links, can be associated with any solvable model in statistical mechanics. In the presentation, universality of the soliton picture in field theory, spin systems and statistical mechanics is observed.

Wadati, M.; Akutsu, Y.

328

Stable topological modes in two-dimensional Ginzburg-Landau models with trapping potentials  

SciTech Connect

Complex Ginzburg-Landau (CGL) models of laser media (with cubic-quintic nonlinearity) do not contain an effective diffusion term, which makes all vortex solitons unstable in these models. Recently, it has been demonstrated that the addition of a two-dimensional periodic potential, which may be induced by a transverse grating in the laser cavity, to the CGL equation stabilizes compound (four-peak) vortices, but the most fundamental 'crater-shaped' vortices (CSVs), alias vortex rings, which are essentially squeezed into a single cell of the potential, have not been found before in a stable form. In this work we report on families of stable compact CSVs with vorticity S=1 in the CGL model with the external potential of two different types: an axisymmetric parabolic trap and the periodic potential. In both cases, we identify a stability region for the CSVs and for the fundamental solitons (S=0). Those CSVs which are unstable in the axisymmetric potential break up into robust dipoles. All the vortices with S=2 are unstable, splitting into tripoles. Stability regions for the dipoles and tripoles are identified, too. The periodic potential cannot stabilize CSVs with S{>=}2 either; instead, families of stable compact square-shaped quadrupoles are found.

Mihalache, D.; Mazilu, D. [Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 407 Atomistilor, Magurele-Bucharest, RO-077125 (Romania); Skarka, V.; Leblond, H. [Laboratoire de Photonique d'Angers, EA 4464 Universite d'Angers, 2 Boulevard Lavoisier, F-49045 Angers Cedex 01 (France); Malomed, B. A. [Department of Physical Electronics, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Aleksic, N. B. [Institute of Physics, Pregrevica 118, 11000 Belgrade (Serbia); Lederer, F. [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-077743 Jena (Germany)

2010-08-15

329

Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear.  

PubMed

Langevin dynamics simulations are used to study the effect of shear on a two-dimensional colloidal crystal (with implicit solvent) confined by structured parallel walls. When walls are sheared very slowly, only two or three crystalline layers next to the walls move along with them, while the inner layers of the crystal are only slightly tilted. At higher shear velocities, this inner part of the crystal breaks into several pieces with different orientations. The velocity profile across the slit is reminiscent of shear banding in flowing soft materials, where liquid and solid regions coexist; the difference, however, is that in the latter case the solid regions are glassy while here they are crystalline. At even higher shear velocities, the effect of the shearing becomes smaller again. Also the effective temperature near the walls (deduced from the velocity distributions of the particles) decreases again when the wall velocity gets very large. When the walls are placed closer together, thereby introducing an incommensurability between the periodicity of the confined crystal and the walls, a structure containing a soliton staircase arises in simulations without shear. Introducing shear increases the disorder in these systems until no solitons are visible anymore. Instead, similar structures like in the case without mismatch result. At high shear rates, configurations where the incommensurability of the crystalline structure is compensated by the creation of holes become relevant. PMID:23005095

Wilms, D; Virnau, P; Sengupta, S; Binder, K

2012-06-18

330

Cavity solitons in semiconductor devices  

NASA Astrophysics Data System (ADS)

Cavity solitons appear as bright spots in the transverse intensity profile. They are similar to spatial solitons, but arise in dissipative systems. Here we consider a broad area vertical cavity resonator, driven by an external coherent field, at room temperature. The active material is constituted either by bulk GaAs, or by a Multiple Quantum Well GaAs/AlGaAs structure (MQW). A general model valid for both configurations is presented and a set of nonlinear dynamical equations is derived. The linear stability analysis of the homogeneous steady states is performed in a general form, holding for the two cases. Then, the nonlinear susceptibilities are specified: in the bulk case, we basically work in the free-carrier approximation, with some phenomenological corrections, such as the Urbach tail and the band-gap renormalization. For the bulk case, some numerical results concerning spatial pattern formation and cavity solitons are given. In the MQW case, on the contrary, we derive a full many-body theory, with the Coulomb enhancement treated in the Pade approximation.

Brambilla, Massimo; Lugiato, Luigi A.; Maggipinto, Tommaso; Spinelli, Lorenzo; Tissoni, Giovanna

2000-07-01

331

Vortex solitons of the discrete Ginzburg-Landau equation  

SciTech Connect

We have found several families of vortex soliton solutions in two-dimensional discrete dissipative systems governed by the cubic-quintic complex Ginzburg-Landau equation. There are symmetric and asymmetric solutions, and some of them have simultaneously two different topological charges for two different closed loops encircling, i.e., centered at, the singularity. Their regions of existence and stability are determined. Additionally, we have analyzed the relationship between dissipation and stability for a number of solutions, finding that dissipation favors the stability of the vortex soliton solutions.

Mejia-Cortes, C.; Soto-Crespo, J. M.; Vicencio, Rodrigo A.; Molina, Mario I. [Instituto de Optica, C.S.I.C., Serrano 121, 28006 Madrid (Spain); Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile and Center for Optics and Photonics, Universidad de Concepcion, Casilla 4016, Concepcion (Chile)

2011-04-15

332

Soliton dynamics in the multiphoton plasma regime  

NASA Astrophysics Data System (ADS)

Solitary waves have consistently captured the imagination of scientists, ranging from fundamental breakthroughs in spectroscopy and metrology enabled by supercontinuum light, to gap solitons for dispersionless slow-light, and discrete spatial solitons in lattices, amongst others. Recent progress in strong-field atomic physics include impressive demonstrations of attosecond pulses and high-harmonic generation via photoionization of free-electrons in gases at extreme intensities of 1014 W/cm2. Here we report the first phase-resolved observations of femtosecond optical solitons in a semiconductor microchip, with multiphoton ionization at picojoule energies and 1010 W/cm2 intensities. The dramatic nonlinearity leads to picojoule observations of free-electron-induced blue-shift at 1016 cm-3 carrier densities and self-chirped femtosecond soliton acceleration. Furthermore, we evidence the time-gated dynamics of soliton splitting on-chip, and the suppression of soliton recurrence due to fast free-electron dynamics. These observations in the highly dispersive slow-light media reveal a rich set of physics governing ultralow-power nonlinear photon-plasma dynamics.

Husko, Chad A.; Combrié, Sylvain; Colman, Pierre; Zheng, Jiangjun; de Rossi, Alfredo; Wong, Chee Wei

2013-01-01

333

Theory of slow-light solitons  

NASA Astrophysics Data System (ADS)

In the framework of the nonlinear ? model we investigate propagation of solitons in atomic vapors and Bose-Einstein condensates. We show how the complicated nonlinear interplay between fast solitons and slow-light solitons in the ? -type media points to the possibility to create optical gates and, thus, to control the optical transparency of the ? -type media. We provide an exact analytic description of decelerating, stopping and reaccelerating of slow-light solitons in atomic media in the nonadiabatic regime. Dynamical control over slow-light solitons is realized via a controlling field generated by an auxiliary laser. For a rather general time dependence of the field; we find the dynamics of the slow-light soliton inside the medium. We provide an analytical description for the nonlinear dependence of the velocity of the signal on the controlling field. If the background field is turned off at some moment of time, the signal stops. We find the location and shape of the spatially localized memory bit imprinted into the medium. We discuss physically interesting features of our solution, which are in a good agreement with recent experiments.

Rybin, A. V.; Vadeiko, I. P.; Bishop, A. R.

2005-08-01

334

Soliton self-routing in a finite photonic potential.  

PubMed

We investigate power-dependent routing of one-dimensional Kerr-like spatial solitons in the presence of a finite photonic potential. Large self-deflections can be obtained using a trapping index well of limited length. PMID:23938980

Alberucci, Alessandro; Jisha, Chandroth P; Lee, Ray-Kuang; Assanto, Gaetano

2013-06-15

335

Soap film flows: Statistics of two-dimensional turbulence  

SciTech Connect

Soap film flows provide a very convenient laboratory model for studies of two-dimensional (2-D) hydrodynamics including turbulence. For a gravity-driven soap film channel with a grid of equally spaced cylinders inserted in the flow, we have measured the simultaneous velocity and thickness fields in the irregular flow downstream from the cylinders. The velocity field is determined by a modified digital particle image velocimetry method and the thickness from the light scattered by the particles in the film. From these measurements, we compute the decay of mean energy, enstrophy, and thickness fluctuations with downstream distance, and the structure functions of velocity, vorticity, thickness fluctuation, and vorticity flux. From these quantities we determine the microscale Reynolds number of the flow R{sub {lambda}}{approx}100 and the integral and dissipation scales of 2D turbulence. We also obtain quantitative measures of the degree to which our flow can be considered incompressible and isotropic as a function of downstream distance. We find coarsening of characteristic spatial scales, qualitative correspondence of the decay of energy and enstrophy with the Batchelor model, scaling of energy in {ital k} space consistent with the k{sup {minus}3} spectrum of the Kraichnan{endash}Batchelor enstrophy-scaling picture, and power-law scalings of the structure functions of velocity, vorticity, vorticity flux, and thickness. These results are compared with models of 2-D turbulence and with numerical simulations. {copyright} {ital 1999 American Institute of Physics.}

Vorobieff, P.; Rivera, M.; Ecke, R.E. [Center for Nonlinear Studies and Condensed Matter and Thermal Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1999-08-01

336

Bimodal detection of underground contamination in two-dimensional systems  

NASA Astrophysics Data System (ADS)

Widespread contamination of underground environments with dense non-aqueous phase liquids (DNAPLs) is of great concern to the public, military, and industrial sectors. Proper management of contaminated sites requires detection and monitoring of the contaminants, and accurate knowledge of their transport behavior in underground environments. Over the last years we have done great efforts to develop and integrate technologies that serve to locate contamination and monitor transport mechanism underground. In this paper, we describe a two-dimensional multiphase flow experiment to develop and evaluate two modes of concurrent detection and monitoring technologies: Cross Well Radar (CWR) and Image Analysis (IA). Loop antennas preset at specific locations in the tank are used to evaluate wave scattering properties of the soil under different conditions, while color images are acquired. The electromagnetic response in the CWR antennas and IA are used to establish the relation between electrical soil properties variations and changes spatial and temporal mass of water and contaminants. The technologies used in this research are both in development, but they can be successful tools for the detection, monitoring and imagining of underground contaminants and process. Once develop, the technology may be applied for detecting and monitoring other buried objects.

Serrano-Guzmán, Maria F.; Padilla, Ingrid; Rodriguez, Rafael

2007-04-01

337

Universal topological phase of two-dimensional stabilizer codes  

NASA Astrophysics Data System (ADS)

Topological phases can be defined in terms of local equivalence: two systems are in the same topological phase if it is possible to transform one into the other by a local reorganization of its degrees of freedom. The classification of topological phases therefore amounts to the classification of long-range entanglement. Such local transformation could result, for instance, from the adiabatic continuation of one system's Hamiltonian to the other. Here, we use this definition to study the topological phase of translationally invariant stabilizer codes in two spatial dimensions, and show that they all belong to one universal phase. We do this by constructing an explicit mapping from any such code to a number of copies of Kitaev's code. Some of our results extend to some two-dimensional (2D) subsystem codes, including topological subsystem codes. Error correction benefits from the corresponding local mappings. In particular, it enables us to use decoding algorithm developed for Kitaev's code to decode any 2D stabilizer code and subsystem code.

Bombin, H.; Duclos-Cianci, Guillaume; Poulin, David

2012-07-01

338

Two-dimensional spectroscopy of electronic couplings in photosynthesis  

NASA Astrophysics Data System (ADS)

Time-resolved optical spectroscopy is widely used to study vibrational and electronic dynamics by monitoring transient changes in excited state populations on a femtosecond timescale. Yet the fundamental cause of electronic and vibrational dynamics-the coupling between the different energy levels involved-is usually inferred only indirectly. Two-dimensional femtosecond infrared spectroscopy based on the heterodyne detection of three-pulse photon echoes has recently allowed the direct mapping of vibrational couplings, yielding transient structural information. Here we extend the approach to the visible range and directly measure electronic couplings in a molecular complex, the Fenna-Matthews-Olson photosynthetic light-harvesting protein. As in all photosynthetic systems, the conversion of light into chemical energy is driven by electronic couplings that ensure the efficient transport of energy from light-capturing antenna pigments to the reaction centre. We monitor this process as a function of time and frequency and show that excitation energy does not simply cascade stepwise down the energy ladder. We find instead distinct energy transport pathways that depend sensitively on the detailed spatial properties of the delocalized excited-state wavefunctions of the whole pigment-protein complex.

Brixner, Tobias; Stenger, Jens; Vaswani, Harsha M.; Cho, Minhaeng; Blankenship, Robert E.; Fleming, Graham R.

2005-03-01

339

Microwave tomography: two-dimensional system for biological imaging.  

PubMed

Microwave tomographic imaging is one of the new technologies which has the potential for important applications in medicine. Microwave tomographically reconstructed images may potentially provide information about the physiological state of tissue as well as the anatomical structure of an organ. A two-dimensional (2-D) prototype of a quasi real-time microwave tomographic system was constructed. It was utilized to reconstruct images of physiologically active biological tissues such as an explanted canine perfused heart. The tomographic system consisted of 64 special antennae, divided into 32 emitters and 32 receivers which were electronically scanned. The cylindrical microwave chamber had an internal diameter of 360 mm and was filled with various solutions, including deionized water. The system operated on a frequency of 2.45 GHz. The polarization of the incident electromagnetic field was linear in the vertical direction. Total acquisition time was less than 500 ms. Both accurate and approximation methods of image reconstruction were used. Images of 2-D phantoms, canine hearts, and beating canine hearts have been achieved. In the worst-case situation when the 2-D diffraction model was used for an attempt to "slice" three-dimensional (3-D) object reconstruction, we still achieved spatial resolution of 1 to 2 cm and contrast resolution of 5%. PMID:9214802

Semenov, S Y; Svenson, R H; Boulyshev, A E; Souvorov, A E; Borisov, V Y; Sizov, Y; Starostin, A N; Dezern, K R; Tatsis, G P; Baranov, V Y

1996-09-01

340

Two-dimensional Chebyshev pseudospectral modelling of cardiac propagation.  

PubMed

Bidomain or monodomain modelling has been used widely to study various issues related to action potential propagation in cardiac tissue. In most of these previous studies, the finite difference method is used to solve the partial differential equations associated with the model. Though the finite difference approach has provided useful insight in many cases, adequate discretisation of cardiac tissue with realistic dimensions often requires a large number of nodes, making the numerical solution process difficult or impossible with available computer resources. Here, a Chebyshev pseudospectral method is presented that allows a significant reduction in the number of nodes required for a given solution accuracy. The new method is used to solve the governing nonlinear partial differential equation for the monodomain model representing a two-dimensional homogeneous sheet of cardiac tissue. The unknown transmembrane potential is expanded in terms of Chebyshev polynomial trial functions and the equation is enforced at the Gauss-Lobatto grid points. Spatial derivatives are obtained using the fast Fourier transform and the solution is advanced in time using an explicit technique. Numerical results indicate that the pseudospectral approach allows the number of nodes to be reduced by a factor of sixteen, while still maintaining the same error performance. This makes it possible to perform simulations with the same accuracy using about twelve times less CPU time and memory. PMID:10912348

Zhan, Z; Ng, K T

2000-05-01

341

Two-dimensional spectroscopy of electronic couplings in photosynthesis.  

PubMed

Time-resolved optical spectroscopy is widely used to study vibrational and electronic dynamics by monitoring transient changes in excited state populations on a femtosecond timescale. Yet the fundamental cause of electronic and vibrational dynamics--the coupling between the different energy levels involved--is usually inferred only indirectly. Two-dimensional femtosecond infrared spectroscopy based on the heterodyne detection of three-pulse photon echoes has recently allowed the direct mapping of vibrational couplings, yielding transient structural information. Here we extend the approach to the visible range and directly measure electronic couplings in a molecular complex, the Fenna-Matthews-Olson photosynthetic light-harvesting protein. As in all photosynthetic systems, the conversion of light into chemical energy is driven by electronic couplings that ensure the efficient transport of energy from light-capturing antenna pigments to the reaction centre. We monitor this process as a function of time and frequency and show that excitation energy does not simply cascade stepwise down the energy ladder. We find instead distinct energy transport pathways that depend sensitively on the detailed spatial properties of the delocalized excited-state wavefunctions of the whole pigment-protein complex. PMID:15800619

Brixner, Tobias; Stenger, Jens; Vaswani, Harsha M; Cho, Minhaeng; Blankenship, Robert E; Fleming, Graham R

2005-03-31

342

Fluctuations and symmetries in two-dimensional active gels.  

PubMed

Motivated by the unique physical properties of biological active matter, e.g., cytoskeletal dynamics in eukaryotic cells, we set up effective two-dimensional (2d) coarse-grained hydrodynamic equations for the dynamics of thin active gels with polar or nematic symmetries. We use the well-known three-dimensional (3d) descriptions (K. Kruse et al., Eur. Phys. J. E 16, 5 (2005); A. Basu et al., Eur. Phys. J. E 27, 149 (2008)) for thin active-gel samples confined between parallel plates with appropriate boundary conditions to derive the effective 2d constitutive relations between appropriate thermodynamic fluxes and generalised forces for small deviations from equilibrium. We consider three distinct cases, characterised by spatial symmetries and boundary conditions, and show how such considerations dictate the structure of the constitutive relations. We use these to study the linear instabilities, calculate the correlation functions and the diffusion constant of a small tagged particle, and elucidate their dependences on the activity or nonequilibrium drive. PMID:21533956

Sarkar, N; Basu, A

2011-04-29

343

Beginning Introductory Physics with Two-Dimensional Motion  

ERIC Educational Resources Information Center

|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…

Huggins, Elisha

2009-01-01

344

Hitting lines with two-dimensional Brownian motion  

NASA Astrophysics Data System (ADS)

This paper consists of the computation of several hitting time and hitting place distributions for two-dimensional Brownian motion. The motivation for this study is two-fold: first, to get a diffusion model for the firing behavior of a simple network of neurons, and second, to get an interesting two-dimensional version of the inverse Gaussian distribution.

Iyengar, Satish

1990-05-01

345

New two-dimensional quantum models with shape invariance  

SciTech Connect

Two-dimensional quantum models which obey the property of shape invariance are built in the framework of polynomial two-dimensional supersymmetric quantum mechanics. They are obtained using the expressions for known one-dimensional shape invariant potentials. The constructed Hamiltonians are integrable with symmetry operators of fourth order in momenta, and they are not amenable to the conventional separation of variables.

Cannata, F. [INFN, Via Irnerio 46, 40126 Bologna (Italy); Ioffe, M. V. [Saint-Petersburg State University, 198504 St.-Petersburg (Russian Federation); Nishnianidze, D. N. [Saint-Petersburg State University, 198504 St.-Petersburg (Russian Federation); Akaki Tsereteli State University, 4600 Kutaisi (Georgia)

2011-02-15

346

A Two-Dimensional Haar-Like Transform.  

National Technical Information Service (NTIS)

The report concerns a transform based on a set of two-dimensional Haarlike functions. Series expansions of two-dimensional functions in terms of this set have convergence properties that are analogous to those of Haar series. Following a brief review of H...

J. E. Shore

1973-01-01

347

Soybean Drying by Two-Dimensional Spouted Bed  

Microsoft Academic Search

Urease activity, cracking, and breakage are important factors in considering the quality of raw soybean for feed meal industries. A two-dimensional spouted bed dryer was investigated to determine its capability for thermally inactivating the urease enzyme and maintaining its other qualities. The experimental results have shown that the drying kinetics of soybean in a two-dimensional spouted bed dryer are of

Songchai Wiriyaumpaiwong; Somchart Soponronnarit; Somkiat Prachayawarakorn

2003-01-01

348

Constrained optimization with use of two-dimensional maximum neurons  

Microsoft Academic Search

A special neuron, which we call two-dimensional maximum neuron is proposed. This type of neuron can eliminate the row and column constraints that occur in many problems, such as the stable marriage problem. A parallel processing algorithm to find the stable marriage matching using the proposed two-dimensional maximum neurons is described and the result is now reported

P. P. C. Yip; Y. Takefuji

1994-01-01

349

MIRAS, a two-dimensional aperture synthesis radiometer  

Microsoft Academic Search

Based on the experimented potential use of aperture synthesis (Le Vine, 1990), the European Space Agency has initiated the study of a spaceborne Microwave Interferometric Radiometer with Two-Dimensional Aperture Synthesis (MIRAS) as well as the development of an airborne version of this instrument. The objective of this radiometer is to study and demonstrate the feasibility of two-dimensional interferometry for measuring

M. Martin-Neira; Y. Menard; J. M. Goutoule; U. Kraft

1994-01-01

350

Nonlinear, two-dimensional magnetohydrodynamic calculations  

SciTech Connect

A nonlinear, time-dependent, hydromagnetic model is developed. The model is based on the eight partial differential equations of resistive magnetohydrodynamics (MHD). The equations are expressed as a set of conservation laws which are written in general, orthogonal, curvilinear coordinates in two space dimensions. No assumption about the ordering of terms is made. The resulting equations are then solved by the method of finite differences on an Eulerian mesh. We develop spatial finite-difference techniques which guarantee the simultaneous conservation of the desired physical quantities throughout the course of the calculation. Conservative boundary conditions on thermodynamic quantities at a conducting boundary are derived, and special algorithms are developed for advancing the solution at a singular boundary. For the temporal differencing, we use the Alternating Direction Implicit (ADI) method. We apply our model to the difficult case of resistive instabilities. We present results relevant to the nonlinear evolution of these modes in three distinct coordinate systems. One of these cases depends on finite plasma pressure, and can be studied only with a general model such as that presented here.

Schnack, D.; Killeen, J.

1980-03-15

351

Two dimensional model for coherent synchrotron radiation  

NASA Astrophysics Data System (ADS)

Understanding coherent synchrotron radiation (CSR) effects in a bunch compressor requires an accurate model accounting for the realistic beam shape and parameters. We extend the well-known 1D CSR analytic model into two dimensions and develop a simple numerical model based on the Liénard-Wiechert formula for the CSR field of a coasting beam. This CSR numerical model includes the 2D spatial dependence of the field in the bending plane and is accurate for arbitrary beam energy. It also removes the singularity in the space charge field calculation present in a 1D model. Good agreement is obtained with 1D CSR analytic result for free electron laser (FEL) related beam parameters but it can also give a more accurate result for low-energy/large spot size beams and off-axis/transient fields. This 2D CSR model can be used for understanding the limitation of various 1D models and for benchmarking fully electromagnetic multidimensional particle-in-cell simulations for self-consistent CSR modeling.

Huang, Chengkun; Kwan, Thomas J. T.; Carlsten, Bruce E.

2013-01-01

352

Two-dimensional distribution of refractive-index changes in Ti-diffused LiNbO3 strip waveguides  

Microsoft Academic Search

A method is reported for determining the two-dimensional distribution of refractive-index changes in Ti-diffused LiNbO3 strip waveguides. The measurement process was as follows. Distributions of diffused Ti concentration in LiNbO3 were measured using an x-ray microanalyzer. Using calibration curves the Ti concentrations were then converted into refractive-index changes. To obtain high spatial resolution in the two-dimensional XMA measurement the electron

Makoto Minakata; Shoichi Saito; Masashi Shibata

1979-01-01

353

The Kadomtsev-Petviashvili(KP) equation for ion acoustic soliton in weakly relativistic electron-positron-ion plasma with finite ion temperature  

Microsoft Academic Search

The ion acoustic soliton in weakly a relativistic electron-positron-ion plasma with finite ion temperature have been investigated. Such plasmas is frequently occur in astrophysical environment. Using reductive perturbation method we have derived the two dimensional Kadomtsev- Petviashvili(KP) equation to study the characteristics of ion-acoustic soliton in three component plasma at different plasma temperature. The soliton solution of KP equation is

Amandeep Singh Bains; Harvinder Kaur; Tarsem Singh Gill; Nareshpal Singh Saini

2008-01-01

354

Dynamical trapping and transmission of matter-wave solitons in a collisionally inhomogeneous environment  

SciTech Connect

We investigate bright matter-wave solitons in the presence of a spatially varying scattering length. It is demonstrated that a soliton can be confined due to the inhomogeneous collisional interactions. Moreover, we observe the enhanced transmission of matter-wave solitons through potential barriers for suitably chosen spatial variations of the scattering length. The results indicate that the manipulation of atomic interactions can become a versatile tool to control matter-wave dynamics.

Theocharis, G.; Frantzeskakis, D. J. [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 157 84 (Greece); Schmelcher, P. [Theoretische Chemie, Institut fuer Physikalische Chemie, Universitaet Heidelberg, INF 229, D-69120 Heidelberg (Germany); Physikalisches Institut, Philosophenweg 12, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Kevrekidis, P. G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003-4515 (United States)

2006-11-15

355

Magnetoconductivity of two-dimensional electron systems  

NASA Astrophysics Data System (ADS)

The conductivity sigmaxx(o) of a low-density nondegenerate 2D electron gas is investigated under conditions where hoc ? kBT ? hgamma (oc is the cyclotron frequency and hgamma is the disorder-induced width of the Landau level). Such conditions have been met for electrons on helium surface, and can also be achieved in ultra high quality heterostructures. Because of the random potential of defects, single-electron states of the lowest Landau level form a band of a width hgamma ? hoc. Almost all of these states are localized. Therefore, for ho c ? kBT ? hgamma, the static single-electron conductivity sigma xx(0) may be expected to be equal to zero. Since for o ? gamma the conductivity should decay, on the whole sigma xx(o) has a peak at a finite frequency. From scaling arguments, we show that in the single-electron approximation sigma xx(o) ? omu for o ? 0, with the exponent mu in the range from 0.21 to 0.22, whereas the frequency dependence of the cyclotron resonance absorption peak is non-critical. The far tails of the conductivity peaks are obtained using the method of optimal fluctuation and are shown to be Gaussian. In order to investigate the shape of the low frequency peak and cyclotron resonance absorption peak, we use the method of moments (MOM). In MOM, the low-frequency conductivity is restored from its 14 spectral moments, whereas the cyclotron resonance absorption is restored from the calculated 10 spectral moments using the continuous fraction expansion. In combination with the analytical asymptotics, both expansions converge rapidly with increasing number of included moments, and give numerically accurate results throughout the region of interest. The effect of electron-electron interaction (EEI) on the low frequency conductivity is also investigated. EEI makes the static conductivity finite. For a low-density system, the effect can be described using the notion of a fluctuational field Efl which drives an electron because of electron density fluctuations. Due to this field, spatial diffusion of electrons in a (comparatively strong) random potential of defects gives rise to energy diffusion of each individual electron, with a diffusion coefficient Depsilon = gammae2< E2fl >h/mo c. In combination with the known power-law asymptotic of the single-electron conductivity for sigmase(o) for o ? 0, this allows us to find the static many-electron conductivity sigma me.

Kuehnel, Frank Oliver

356

Two-dimensional imaging with a single-sided NMR probe.  

PubMed

A new low field unilateral NMR sensor equipped with a two-dimensional gradient coil system was built. A new NMR-MOUSE concept using a simple bar magnet instead of the classical U-shaped geometry was used to produce magnetic field profiles comparatively homogeneous in extended lateral planes defining a suitable field of view for 2D spatial localization. Slice selection along the depth direction is obtained by means of the highly constant static magnetic field gradient produced by this magnet geometry. Implementing a two-dimensional phase-encoding imaging method 2D cross sections of objects were obtained with high spatial resolution. By retuning the probe it was possible to change the depth of the selected slice obtaining a 3D imaging method. The details of the construction of the new device are presented together with imaging tests to show the quality of space encoding. PMID:12852905

Casanova, F; Blümich, B

2003-07-01

357

Third sound in one and two dimensional modulated structures  

SciTech Connect

An experimental technique is developed to study acoustic transmission in one and two dimensional modulated structures by employing third sound of a superfluid helium film. In particular, the Penrose lattice, which is a two dimensional quasiperiodic structure, is studied. In two dimensions, the scattering of third sound is weaker than in one dimension. Nevertheless, the authors find that the transmission spectrum in the Penrose lattice, which is a two dimensional prototype of the quasicrystal, is observable if the helium film thickness is chosen around 5 atomic layers. The transmission spectra in the Penrose lattice are explained in terms of dynamical theory of diffraction.

Komuro, T.; Kawashima, H., Shirahama, K.; Kono, K. [Univ. of Tokyo, Tokyo (Japan)

1996-02-01

358

Dynamics of two-dimensional and quasi-two-dimensional polymers.  

PubMed

The dynamic properties of dense two-dimensional (2D) polymer melts are studied using discontinuous molecular dynamics simulations. Both strictly 2D and quasi-2D systems are investigated. The strictly 2D model system consists of a fluid of freely jointed tangent hard disc chains. The translational diffusion coefficient, D, is strongly system size dependent with D ? ln?L where L is the linear dimension of the square simulation cell. The rotational correlation time, ?rot, is, however, independent of system size. The dynamics is consistent with Rouse behavior with D?ln?L ? N(-1) and ?rot ? N(2) for all area fractions. Analysis of the intermediate scattering function, Fs(k, t), shows that the dynamics becomes slow for N = 256 and the area fraction of 0.454 and that there might be a glass transition for long polymers at sufficiently high area fractions. The polymer mobility is not correlated with the conformation of the molecules. In the quasi-2D system hard sphere chains are confined between corrugated surfaces so that chains cannot go over each other or into the surfaces. The conformational properties are identical to the 2D case, but D and ?rot are independent of system size. The scaling of D and ?rot with N is similar to that of strictly 2D systems. The simulations suggest that 2D polymers are never entangled and follow Rouse dynamics at all densities. PMID:23802982

Sung, Bong June; Yethiraj, Arun

2013-06-21

359

Surface defect kink solitons  

NASA Astrophysics Data System (ADS)

We reveal the existence of dynamically stable nonlinear defect kink modes at an interface separating a defocusing Kerr medium and an imprinted semi-infinite lattice with a positive or negative defect covering single or several lattice sites. Increasing the number of defect sites equivalently results in a band-gap shift of lattice which in return alters the existence domains and stability properties of defect solitons. Comparing with the uniform semi-infinite lattice, the instability of kink soliton in lattice with a negative defect is significantly suppressed, especially for in-phase soliton. Our results provide an effective way for the realization of stable in-phase kink solitons.

Zhong, Shunsheng; Huang, Changming; Li, Chunyan; Dong, Liangwei

2012-08-01

360

Two-dimensional potential profile measurement of GaAs HEMT's by Kelvin probe force microscopy  

Microsoft Academic Search

Two-dimensional (2-D) potential profile of GaAs HEMT's under bias voltage has been successfully measured by combining Kelvin probe force microscopy with cleavage of the HEMT's. The spatial resolution evaluated by measuring GaAs-AlAs multiquantum-well structure was less than 70 nm. The measured depth profile of the potential shows a potential knee, which probably originates from the charge trapped at the interface

Takashi Mizutani; Masashi Arakawa; Shigeru Kishimoto

1997-01-01

361

Quantitative two-dimensional instantaneous Raman concentration measurements in a laminar methane jet.  

PubMed

We have achieved quantitative two-dimensional Raman measurements of the concentration of methane in a laminar methane jet into nitrogen without multipassing the incident laser sheet with a coaxial flash-lamp-pumped dye laser. The measurements are compared with the results of direct numerical simulation for the particular flow field. We conclude that the accuracy of the technique is determined by limitations in the dynamic range and in the spatial resolution of the data acquired with an intensified camera. PMID:18354691

Kyritsis, D C; Felton, P G; Huang, Y; Bracco, F V

2000-12-20

362

A finite element method for the two-dimensional extended Boussinesq equations  

Microsoft Academic Search

A new numerical method for Nwogu's (ASCE Journal of Waterway, Port, Coastal and Ocean Engineering 1993; 119:618)two-dimensional extended Boussinesq equations is presented using a linear triangular finite element spatial discretization coupled with a sophisticated adaptive time integration package. The authors have previously presented a finite element method for the one-dimensional form of these equations (M. Walkley and M. Berzins (International

Mark Walkley; Martin Berzins

2002-01-01

363

Two-dimensional imaging with a single-sided NMR probe  

Microsoft Academic Search

A new low field unilateral NMR sensor equipped with a two-dimensional gradient coil system was built. A new NMR-MOUSE concept using a simple bar magnet instead of the classical U-shaped geometry was used to produce magnetic field profiles comparatively homogeneous in extended lateral planes defining a suitable field of view for 2D spatial localization. Slice selection along the depth direction

F. Casanova; B. Blümich

2003-01-01

364

Two-dimensional metal-insulator transition in smooth random magnetic fields  

Microsoft Academic Search

We re-examine the delocalization problem of two-dimensional electrons in the presence of random magnetic fields. By introducing short-range spatial correlations among random fluxes, a well-defined metal-insulator transition characterized by a two-branch scaling of conductance has been demonstrated numerically. Critical conductance is found non-universal with a value around e2\\/h. Interesting connections of this system with the recently observed B = 0

D. N. Sheng; Z. Y. Weng

2000-01-01

365

Two-dimensional thermographic phosphor thermometry using a CMOS high speed camera system  

Microsoft Academic Search

In the present study, a CMOS high speed camera system was employed for two-dimensional thermographic phosphor thermometry.\\u000a By the pixelwise evaluation of the luminescence lifetimes, a temperature map of a phosphor layer can be obtained. Using spatially\\u000a and temporally isothermal conditions in a tube furnace, a temperature lifetime characteristic was determined for the phosphor\\u000a Mg4FGeO6: Mn and was compared with

T. Kissel; E. Baum; A. Dreizler; J. Brübach

2009-01-01

366

Two-dimensional simulation of a miniaturized inductively coupled plasma reactor  

Microsoft Academic Search

A two-dimensional self-consistent simulation of a miniaturized inductively coupled plasma (mICP) reactor was developed. The coupled equations for plasma power deposition, electron temperature, and charged and neutral species densities, were solved to obtain the spatial distribution of an argon discharge. The effect of control parameters, such as power and pressure, on the evolution of plasma density and electron temperature was

Sang Ki Nam; Demetre J. Economou

2004-01-01

367

A Model for second harmonic generation in a TWO-Dimensional array of quantum dots  

NASA Astrophysics Data System (ADS)

We present a model for second harmonic generation in a two-dimensional array of quantum dots. We show that the combined effect of the electromagnetic local field of the array and the intrinsic electronic resonances due to the spatial confinement in the quantum dot produce giant enhancements of the second order non-linear susceptibilities, hence giving a very large efficiency in the second harmonic generation.

Mendoza, Bernardo S.

1994-01-01

368

Phenomenological theory of free two-dimensional vortex dynamics in layered superconductors  

Microsoft Academic Search

Using an analogy with electron-hole plasma in semiconductors we derive equations describing the dynamics of free two-dimensional vortices and antivortices in layered superconductors near the Kosterlitz-Thouless transition temperature KKT. It is found that even a weak external magnetic field He normal to layers penetrates into the sample due to a spatial redistribution of vortices. We study also the passage of

A. F. Volkov

1990-01-01

369

Analysis of two-dimensional electromagnetic scattering from nonplanar periodic surfaces using a strip current model  

Microsoft Academic Search

A method-of-moments solution is presented for the problem of two-dimensional transverse magnetic scattering of a plane wave from a nonplanar periodic surface separating two contrasting homogeneous media. The moment solution uses fictitious spatially periodic and properly modulated electric current strips to simulate the field scattered by the surface and the field penetrating the surface. The fields radiated by the current

Amir Boag; Yehuda Leviatan; Alona Boag

1989-01-01

370

Alternating direction implicit schemes for the two-dimensional fractional sub-diffusion equation  

Microsoft Academic Search

New numerical techniques are presented for the solution of a two-dimensional anomalous sub-diffusion equation with time fractional derivative. In these methods, standard central difference approximation is used for the spatial discretization, and, for the time stepping, two new alternating direction implicit (ADI) schemes based on the L1 approximation and backward Euler method are considered. The two ADI schemes are constructed

Ya-Nan Zhang; Zhi-Zhong Sun

2011-01-01

371

Two-dimensional imaging of excited analyte species in electrothermal vaporizers  

Microsoft Academic Search

Applications of a charge-coupled device (CCD) imaging spectrometer as a detection system for the determination of two-dimensional images of transient atomization events in a furnace atomization plasma emission spectrometric (FAPES) source are reviewed. Spectrally, spatially and temporally resolved images of the emission from analyte species (Ag(I), Ca(I) and Ca(II)) and plasma support gas (He(I)) in a 50 W He rf

R. E. Sturgeon; V. Pavski; C. L. Chakrabarti

1996-01-01

372

GAUGE; two-dimensional, few-group, neutron diffusion in hexagonal geometries. [UNIVAC1108; FORTRAN IV  

Microsoft Academic Search

The two-dimensional few-group neutron diffusion theory equations for a uniform triangular mesh are solved to obtain the multiplication factor and the spatial flux and power distribution of reactors with hexagonal core configuration. Complete reactor life histories with partial refuelling at a number of reload time-points can be calculated. At each discrete time-point a control rod search may be performed to

2008-01-01

373

Optical soliton: first paper and the history that resulted from it  

NASA Astrophysics Data System (ADS)

A quarter of a century ago, the lightwave envelope in an optical fiber was shown to be described by the nonlinear Schrodinger Equation. A localized stationary and stable optical pulse (optical soliton) found as its solution was suggested as a carrier of ultra-high speed data transmission. Now the soliton based ultra-high speed communication is vigorously pursued around the world. Furthermore, the nonlinear Schrodinger equation model is widely used as the simulator of information transmission in fibers in general not limited to solitons. Looking back the historical development of optical soliton research is an interesting case study of how an abstract mathematical concept is put into practical use. This development is a consequence of combined efforts of prominent scientists and engineers around the world. However the most significant factor that has contributed to this success is the appropriateness of the god given physical parameters in fibers. Thus it is a sin not to take advantage of this rear opportunity. History of application of optical solitons for high speed signal transmission in fibers may be divided into five stages, (1) historical background and the discovery of the optical soliton, (2) idea and demonstration of all optical soliton transmission systems, (3) identification of possible problems, (4) demonstration of soliton control and (5) Discovery of Dispersion Managed Optical Solitons. In addition, other application of solitons such as modulational instability, dark solitons, spatial solitons are currently vigorously pursued.

Hasegawa, Akira

1999-04-01

374

Positioning cavity solitons with a phase mask  

NASA Astrophysics Data System (ADS)

Nonlinear interaction between a coherent electric field and a semiconductor medium inside a high Fresnel number cavity may give rise to the formation of cavity solitons. It is theoretically predicted that the position of these structures, mutually independent and bistable, can be controlled by gradients in the injection beam. Using a liquid crystal light valve to spatially modulate the phase of a coherent beam injected into a broad area vertical cavity semiconductor laser, the authors create reconfigurable arrays of cavity solitons. Fast time scales associated with semiconductor lasers and plasticity of localized structures suggest their potential for optical data processing.

Pedaci, F.; Genevet, P.; Barland, S.; Giudici, M.; Tredicce, J. R.

2006-11-01

375

Symmetry-breaking instability of quadratic soliton bound states  

SciTech Connect

We study both numerically and experimentally two-dimensional soliton bound states in quadratic media and demonstrate their symmetry-breaking instability. The experiment is performed in a potassium titanyl phosphate crystal in a type-II configuration. The bound state is generated by the copropagation of the antisymmetric fundamental beam locked in phase with the symmetrical second harmonic one. Experimental results are in good agreement with numerical simulations of the nonlinear wave equations.

Delque, Michaeel [Service OPERA-photonique, CP194/5, Universite Libre de Bruxelles U.L.B. Avenue F.D. Roosevelt, B-1050 Bruxelles (Belgium); Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon (France); Fanjoux, Gil; Maillotte, Herve; Kockaert, Pascal; Sylvestre, Thibaut; Haelterman, Marc [Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon (France)

2011-01-15

376

Index theorems and supersymmetry in the soliton sector  

NASA Astrophysics Data System (ADS)

For arbitrary two-dimensional supersymmetric theories with soliton solutions, we use the Callias-Bott-Seeley trace theorem to calculate the O(h) correction to the soliton mass. At the same order the Bogomolny bound is shown, by an explicit computation, to be saturated. The non-vanishing of the mass correction is traced to the existence of supersymmetry violating surface terms in the soliton lagrangian, while the saturation of the Bogomolny bound is a consequence of the absence of spontaneous breaking of N = 1/2 supersymmetry in a related lagrangian. We argue that this supersymmetry remains unbroken to all orders in perturbation theory. Topological arguments ŕ la Witten are not able to exclude non-perturbative breaking. Present address: Tata Institute of Fundamental Research, Bombay, India.

Imbimbo, Camillo; Mukhi, Sunil

1984-12-01

377

Development of Structure and Strategy in Two-Dimensional Pictures.  

ERIC Educational Resources Information Center

|The development of two structural principles, hierarchical complexity and interruption, was examined in a new domain: two-dimensional pictures. Subjects were 60 4-to 5 1/2-year-old children. (Author/MP)|

Beagles-Roos, Jessica; Greenfield, Patricia Marks

1979-01-01

378

Decoherence in a Landau Quantized Two Dimensional Electron Gas  

NASA Astrophysics Data System (ADS)

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.

Curtis, Jeremy A.; Tokumoto, Takahisa; Cherian, Judy; Sangala, Bagvanth; McGill, Stephen A.; Hilton, David J.

2013-03-01

379

Two-Dimensional Thomson Scattering System for ATF.  

National Technical Information Service (NTIS)

A two-dimensional Thomson scattering system is being designed for the ATF torsatron experiment. This system will provide electron temperature and density measurements at fifteen points along a vertical chord with each shot from a ruby laser. By relocating...

R. R. Kindsfather D. A. Rasmussen M. Murakami C. E. Thomas S. L. Painter

1986-01-01

380

Model of a Negatively Curved Two-Dimensional Space.  

ERIC Educational Resources Information Center

Describes the construction of models of two-dimensional surfaces with negative curvature that are used to illustrate differences in the triangle sum rule for the various Big Bang Theories of the universe. (JRH)

Eckroth, Charles A.

1995-01-01

381

Two-dimensional electronic femtosecond stimulated Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We report two-dimensional electronic spectroscopy with a femtosecond stimulated Raman scattering probe. The method reveals correlations between excitation energy and excited state vibrational structure following photoexcitation. We demonstrate the method in rhodamine 6G.

Wilcox, D. E.; Ogilvie, J. P.

2013-03-01

382

Dynamical Properties of Two-Dimensional Josephson Junction Arrays.  

National Technical Information Service (NTIS)

We have investigated the dynamical properties of two dimensional (2D) Josephson junction arrays at temperatures below the Kosterlitz-Thouless phase transition. We have completed a comprehensive study, based on experiments and simulations, of the effects o...

S. P. Benz

1990-01-01

383

Two-dimensional hydrologic modeling to evaluate aquatic habitat ...  

Treesearch

Title: Two-dimensional hydrologic modeling to evaluate aquatic habitat conditions ... physical and biological parameters such as temperature, dissolved oxygen, ... Government employees on official time, and is therefore in the public domain.

384

Two Dimensional Stochastic Model of a Heterogeneous Geologic System.  

National Technical Information Service (NTIS)

Models based on probabilistic laws are increasingly being employed to simulate heterogeneous geologic systems. One such model, the 'Poisson lines' model, is discussed. This is a two dimensional stochastic model with Markovian properties which is generated...

M. J. Lippmann

1973-01-01

385

Model of a Negatively Curved Two-Dimensional Space.  

ERIC Educational Resources Information Center

|Describes the construction of models of two-dimensional surfaces with negative curvature that are used to illustrate differences in the triangle sum rule for the various Big Bang Theories of the universe. (JRH)|

Eckroth, Charles A.

1995-01-01

386

Difficulties that Students Face with Two-Dimensional Motion  

ERIC Educational Resources Information Center

|Some difficulties that students face with two-dimensional motion are addressed. The difficulties addressed are the vectorial representation of velocity, acceleration and force, the force-energy theorem and the understanding of the radius of curvature.|

Mihas, P.; Gemousakakis, T.

2007-01-01

387

A two-dimensional polymer prepared by organic synthesis  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

388

Time harmonic scar statistics in two dimensional cavities.  

SciTech Connect

This paper examined the high frequency time harmonic localization of modal fields in two dimensional cavities along unstable periodic orbits. The elliptic formalism, combined with the random phase approach, allowed the treatment of both convex and concave boundary geometries.

Warne, Larry Kevin; Kotulski, Joseph Daniel; Jorgenson, Roy E.; Lee, Kelvin S. H. (ITT Industries/AES, Westwood, CA)

2007-01-01

389

Two-Dimensional Thin-Layer Chromatographic Separation of Steroids.  

National Technical Information Service (NTIS)

A two-dimensional thin-layer chromatographic method was described for the separation of steroids in purified organ extracts. Eighteen steroids were investigated using Merck's silica gel G plates and chloroform/acetone mixtures as chromatographic solvents....

W. Schink H. Struck

1973-01-01

390

CHARACTERISTICS OF TWO-DIMENSIONAL PARTICLE EDDY DIFFUSION INOFFICE SPACE  

EPA Science Inventory

The paper discusses the development of a two-dimensional turbulentkinetic energy - dissipation rate (k-epsilon) turbulence model inthe form of vorticity and stream functions. his turbulence modelprovides the distribution of turbulent kinematic viscosity, used tocalculate the effe...

391

Quadrantal symmetry associated with two-dimensional digital transfer functions  

Microsoft Academic Search

The class of two-dimensional (2-D) digital transfer functions which possess quadrantal symmetry in their frequency responses is derived. Application of this class in the design of 2-D recursive digital filters is indicated.

P. Karivaratharajan; M. Swamy

1978-01-01

392

Nonstationarity of a two-dimensional perpendicular shock: Competing mechanisms  

NASA Astrophysics Data System (ADS)

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 ? 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.

Lembčge, Bertrand; Savoini, Philippe; Hellinger, Petr; Trávní?ek, Pavel M.

2009-03-01

393

Soliton Communication Beyond the Average-Soliton Regime.  

National Technical Information Service (NTIS)

We study semianalytically soliton dynamics in a soliton based communication line for which the amplifier spacing is larger than the soliton period (referred to as the quasi-adiabatic regime). This regime allows us to overcome the limit on the soliton dura...

R. J. Essiambre G. P. Agrawal

1995-01-01

394

Doppler Radar Return from Two-Dimensional Random Rough Surfaces  

Microsoft Academic Search

Doppler return from the general case of a two-dimensional random rough surface is investigated. This is an extension of work recently reported for a special case of rough surface. Helmholtz integral approach is used, employing Kirchhoff's approximations in order to evaluate the integral for the plane-wave case. Two-dimensional transmitter\\/receiver gain function and reflection coefficients are used. The shape of the

Malkiat Sohel; Harbhajan Hayre

1972-01-01

395

Kinetic properties of two-dimensional metal systems  

Microsoft Academic Search

The two-dimensional degenerate Fermi gas of electrons interacting with phonons is considered. The basic mechanisms of momentum relaxation in such a system, associated with electron-phonon, phonon-phonon and electron-electron collisions, are shown to be qualitatively different from similar mechanisms in an ordinary three-dimensional metal. The physical explanation for this is that the two-dimensional system of interacting electrons and phonons breaks down

R. N. Gurzhi; A. I. Kopeliovich; S. B. Rutkevich

1987-01-01

396

Two-dimensional wreath product group-based image processing  

Microsoft Academic Search

This paper is intended to complement and extend this earlier work in the directionof a two-dimensional (2-D) finite group-based theory, again with an intent of applyingthis work to image processing. Historically, the notion of a 2-D transform almost alwaysentails a representation of the signal f as a two-dimensional array so that the transformis given by a matrix multiplication of the

Richard Foote; Gagan Mirchandani; Daniel N. Rockmore

2004-01-01

397

Global spherical harmonic computation by two-dimensional Fourier methods  

Microsoft Academic Search

A method is presented for performing global spherical harmonic computation by two-dimensional Fourier transformations. The method goes back to old literature (Schuster 1902) and tackles the problem of non-orthogonality of Legendre-functions, when discretized on an equi-angular grid. Both analysis and synthesis relations are presented, which link the spherical harmonic spectrum to a two-dimensional Fourier spectrum. As an alternative, certain functions

Nico Sneeuw; Richard Bun

1996-01-01

398

Two-dimensional QCD as a string theory  

Microsoft Academic Search

I explore the possibility of finding an equivalent string representation of\\u000atwo dimensional QCD. I develop the large N expansion of the ${\\\\rm QCD_2}$\\u000apartition function on an arbitrary two dimensional Euclidean manifold. If this\\u000ais related to a two-dimensional string theory then many of the coefficients of\\u000athe ${1\\\\over N}$ expansion must vanish. This is shown to be true

David J. Gross

1993-01-01

399

Ground ring of two-dimensional string theory  

Microsoft Academic Search

String theories with two-dimensional space-time target spaces are characterized by the existence of a ``ground ring'' of operators of spin (0, 0). By understanding this ring, one can understand the symmetries of the theory and illuminate the relation of the critical string theory to matrix models. The symmetry groups that arise are, roughly, the area-preserving diffeomorphisms of a two-dimensional phase

Edward Witten

1992-01-01

400

Quasinormal modes of a two-dimensional black hole  

NASA Astrophysics Data System (ADS)

For a two-dimensional black hole we determine the quasinormal frequencies of the Klein-Gordon and Dirac fields. In contrast to the well known examples whose spectrum of quasinormal frequencies is discrete, for this black hole we find a continuous spectrum of quasinormal frequencies, but there are unstable quasinormal modes. In the framework of the Hod and Maggiore proposals we also discuss the consequences of these results on the form of the entropy spectrum for the two-dimensional black hole.

Estrada-Jiménez, S.; Gómez-Díaz, J. R.; López-Ortega, A.

2013-11-01

401

New critical point for two dimensional XY-type models  

Microsoft Academic Search

A new critical point is established through Monte Carlo simulations for a class of two dimensional XY models with a modified nearest-neighbor spin interaction. The critical exponents found are nu~=1.4, beta~=0.6, and an alpha<0, consistent with hyperscaling. The phase transition is interpreted as a vortex-unbinding transition. Comparisons are made with the phase diagram of the two dimensional Coulomb gas and

Anna Jonsson; Petter Minnhagen; Mats Nylén

1993-01-01

402

Quasinormal modes of a two-dimensional black hole  

NASA Astrophysics Data System (ADS)

For a two-dimensional black hole we determine the quasinormal frequencies of the Klein-Gordon and Dirac fields. In contrast to the well known examples whose spectrum of quasinormal frequencies is discrete, for this black hole we find a continuous spectrum of quasinormal frequencies, but there are unstable quasinormal modes. In the framework of the Hod and Maggiore proposals we also discuss the consequences of these results on the form of the entropy spectrum for the two-dimensional black hole.

Estrada-Jiménez, S.; Gómez-Díaz, J. R.; López-Ortega, A.

2013-08-01

403

Two-dimensional flag-transitive planes revisited  

Microsoft Academic Search

This paper shows that the odd order two-dimensional flag-transitive planes constructed by Kantor-Suetake constitute the same family of planes as those constructed by Baker-Ebert. Moreover, for orders satisfying a modest number theoretical assumption this family consists of all possible such planes of that order. In particular, it is shown that the number of isomorphism classes of (non-Desarguesian) two-dimensional flag-transitive affine

R. D. Baker; G. L. Ebert

1996-01-01

404

Two-Dimensional Effects in Laser Ablation of Carbon  

Microsoft Academic Search

This article studies the importance of two-dimensional effects in laser ablation of carbon. It describes the process by using the kinetic theory model of laser ablation based on the moment solution of the Boltzmann equation for arbitrary strong evaporation, and compares the predictions of the full two-dimensional model and of the two other models that use quasi-one-dimensional approximation in the

Michael Shusser

2009-01-01

405

Two-Dimensional Imaging of Gauge Fields in Optical Lattices  

SciTech Connect

We propose a scheme to generate an arbitrary Abelian vector potential for atoms trapped in a two-dimensional optical lattice. By making the optical lattice potential dependent on the atomic state, we transform the problem into that of a two-dimensional imaging. It is shown that an arbitrarily fine pattern of the gauge field in the lattice can be realized without need of diffraction-limited imaging.

Cho, Jaeyoon; Kim, M. S. [QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW (United Kingdom)

2011-12-23

406

Rotation-managed dissipative solitons.  

PubMed

We show that when spatially localized gain landscape performs accelerated motion in the transverse plane, i.e., when it rotates or oscillates around the light propagation axis, the effective gain experienced by the light beam considerably reduces with an increase of the amplitude of oscillations or frequency of rotation of the localized gain. In the presence of uniform background losses and defocusing nonlinearity, such gain landscapes may support dynamically oscillating gain-managed solitons, but if the amplitude of oscillations or the frequency of rotation of the localized gain exceeds a threshold, stable attractors disappear and any input beam decays. PMID:23811914

Kartashov, Yaroslav V; Torner, Lluis

2013-07-01

407

Two-dimensional ionization chamber arrays for IMRT plan verification  

SciTech Connect

In this paper we describe a concept for dosimetric treatment plan verification using two-dimensional ionization chamber arrays. Two different versions of the 2D-ARRAY (PTW-Freiburg, Germany) will be presented, a matrix of 16x16 chambers (chamber cross section 8 mmx8 mm; the distance between chamber centers, 16 mm) and a matrix of 27x27 chambers (chamber cross section 5 mmx5 mm; the distance between chamber centers is 10 mm). The two-dimensional response function of a single chamber is experimentally determined by scanning it with a slit beam. For dosimetric plan verification, the expected two-dimensional distribution of the array signals is calculated via convolution of the planned dose distribution, obtained from the treatment planning system, with the two-dimensional response function of a single chamber. By comparing the measured two-dimensional distribution of the array signals with the expected one, a distribution of deviations is obtained that can be subjected to verification criteria, such as the gamma index criterion. As an example, this verification method is discussed for one sequence of an IMRT plan. The error detection capability is demonstrated in a case study. Both versions of two-dimensional ionization chamber arrays, together with the developed treatment plan verification strategy, have been found to provide a suitable and easy-to-handle quality assurance instrument for IMRT.

Poppe, Bjoern; Blechschmidt, Arne; Djouguela, Armand; Kollhoff, Ralf; Rubach, Antje; Willborn, Kay C.; Harder, Dietrich [Klinik fuer Strahlentherapie und Internistische Onkologie, Pius-Hospital, Oldenburg, Germany, and Carl-von-Ossietzky-Universitaet Oldenburg, Oldenburg (Germany); Carl-von-Ossietzky-Universitaet Oldenburg, Oldenburg (Germany); Klinik fuer Strahlentherapie und Internistische Onkologie, Pius-Hospital, Oldenburg (Germany); Georg-August-Universitaet Goettingen, Goettingen (Germany)

2006-04-15

408

Spectral scaling of the Leray-? model for two-dimensional turbulence  

NASA Astrophysics Data System (ADS)

We present data from high-resolution numerical simulations of the Navier-Stokes-? and the Leray-? models for two-dimensional turbulence. It was shown previously (Lunasin et al 2007 J. Turbul. 8 30) that for wavenumbers k such that k? Gt 1, the energy spectrum of the smoothed velocity field for the two-dimensional Navier-Stokes-? (NS-?) model scales as k-7. This result is in agreement with the scaling deduced by dimensional analysis of the flux of the conserved enstrophy using its characteristic time scale. We therefore hypothesize that the spectral scaling of any ?-model in the sub-? spatial scales must depend only on the characteristic time scale and dynamics of the dominant cascading quantity in that regime of scales. The data presented here, from simulations of the two-dimensional Leray-? model, confirm our hypothesis. We show that for k? Gt 1, the energy spectrum for the two-dimensional Leray-? scales as k-5, as expected by the characteristic time scale for the flux of the conserved enstrophy of the Leray-? model. These results lead to our conclusion that the dominant directly cascading quantity of the model equations must determine the scaling of the energy spectrum.

Lunasin, Evelyn; Kurien, Susan; Titi, Edriss S.

2008-08-01

409

Investigations of photosynthetic light harvesting by two-dimensional electronic spectroscopy  

NASA Astrophysics Data System (ADS)

Photosynthesis begins with the harvesting of sunlight by antenna pigments, organized in a network of pigment-protein complexes that rapidly funnel energy to photochemical reaction centers. The intricate design of these systems---the widely varying structural motifs of pigment organization within proteins and protein organization within a larger, cooperative network---underlies the remarkable speed and efficiency of light harvesting. Advances in femtosecond laser spectroscopy have enabled researchers to follow light energy on its course through the energetic levels of photosynthetic systems. Now, newly-developed femtosecond two-dimensional electronic spectroscopy reveals deeper insight into the fundamental molecular interactions and dynamics that emerge in these structures. The following chapters present investigations of a number of natural light-harvesting complexes using two-dimensional electronic spectroscopy. These studies demonstrate the various types of information contained in experimental two-dimensional spectra, and they show that the technique makes it possible to probe pigment-protein complexes on the length- and time-scales relevant to their functioning. New methods are described that further extend the capabilities of two-dimensional electronic spectroscopy, for example, by independently controlling the excitation laser pulse polarizations. The experiments, coupled with theoretical simulation, elucidate spatial pathways of energy flow, unravel molecular and electronic structures, and point to potential new quantum mechanical mechanisms of light harvesting.

Read, Elizabeth Louise

410

The scaling properties of two-dimensional compressible magnetohydrodynamic turbulence  

SciTech Connect

Understanding the phenomenology captured in direct numerical simulation (DNS) of magnetohydrodynamic (MHD) turbulence rests upon models and assumptions concerning the scaling of field variables and dissipation. Here compressible MHD turbulence is simulated in two spatial dimensions by solving the isothermal equations of resistive MHD on a periodic square grid. In these simulations it is found that the energy spectrum decreases more slowly with k, and the viscous cutoff length is larger, than would be expected from the 1941 phenomenology of Kolmogorov (K41). Both these effects suggest that the cascade time is modified by the presence of Alfven waves as in the phenomenology of Iroshnikov and Kraichnan (IK). Motivated by this, these scaling exponents are compared with those of the IK-based model of Politano and Pouquet [Phys. Rev. E 52, 636 (1995)], which is an extension of the model of She and Leveque [Phys. Rev. Lett. 72, 336 (1994)]. However, the scaling exponents from these simulations are not consistent with the model of Politano and Pouquet, so that neither IK nor K41 models would appear to describe the simulations. The spatial intermittency of turbulent activity in such simulations is central to the observed phenomenology and relates to the geometry of structures that dissipate most intensely via the scaling of the local rate of dissipation. The framework of She and Leveque implies a scaling relation that links the scaling of the local rate of dissipation to the scaling exponents of the pure Elsaesser field variables (z{sup {+-}}=v{+-}B/{radical}({mu}{sub o}{rho})). This scaling relation is conditioned by the distinct phenomenology of K41 and IK. These distinct scaling relations are directly tested using these simulations and it is found that neither holds. This deviation suggests that additional measures of the character of the dissipation may be required to fully capture the turbulent scaling, for example, pointing towards a refinement of the phenomenological models. It may also explain why previous attempts to predict the scaling exponents of the pure Elsaesser fields in two-dimensional magnetohydrodynamic turbulence by extending the theory of She and Leveque have proved unsuccessful.

Merrifield, J.A.; Arber, T.D.; Chapman, S.C.; Dendy, R.O. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); UKAEA Culham Division, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

2006-01-15

411

Interactions of vector solitons  

NASA Astrophysics Data System (ADS)

In this paper, we study the interaction of two widely separated vector solitons in the nonintegrable coupled nonlinear Schrödinger (NLS) equations. Using a modification of Karpman-Solov'ev perturbation method, we derive dynamical equations for the evolution of both solitons' internal parameters. We show that these dynamical equations allow fixed points that correspond to stationary two-vector-soliton bound states if these solitons have the same phase in one component (same sign) and ?-phase difference in the other component (opposite sign). However, linear stability analysis indicates that these bound states are always unstable due to a phase-related unstable eigenvalue. We also investigate vector-soliton interactions and show that, in contrast to soliton interactions in the single NLS equation, vector solitons repel or attract each other depending not only on their relative phases but also on their initial position separation. Lastly, interaction of an arbitrary number of vector solitons is also studied in brief. All our analytical results are supported by direct numerical simulations.

Yang, Jianke

2001-08-01

412

A Comprehensive Two-Dimensional Retention Time Alignment Algorithm To Enhance Chemometric Analysis of Comprehensive Two-Dimensional Separation Data  

Microsoft Academic Search

A comprehensive two-dimensional (2D) retention time alignment algorithm was developed using a novel indexing scheme. The algorithm is termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the separation information in both dimensions. Although the algorithm is demonstrated by correcting comprehensive two-dimensional gas chromatography (GC x GC) data, the algorithm is designed to

Karisa M. Pierce; Lianna F. Wood; Bob W. Wright; Robert E. Synovec

2005-01-01

413

Generation of polygonal soliton clusters and fundamental solitons in dissipative systems by necklace-ring beams with radial-azimuthal phase modulation.  

PubMed

We demonstrate that, in a two-dimensional dissipative medium described by the cubic-quintic (CQ) complex Ginzburg-Landau (CGL) equation with the viscous (spectral-filtering) term, necklace rings carrying a mixed radial-azimuthal phase modulation can evolve into polygonal or quasipolygonal stable soliton clusters, and into stable fundamental solitons. The outcome of the evolution is controlled by the depth and azimuthal anharmonicity of the phase-modulation profile, or by the radius and number of "beads" in the initial necklace ring. Threshold characteristics of the evolution of the patterns are identified and explained. Parameter regions for the formation of the stable polygonal and quasipolygonal soliton clusters, and of stable fundamental solitons, are identified. The model with the CQ terms replaced by the full saturable nonlinearity produces essentially the same set of basic dynamical scenarios; hence this set is a universal one for the CGL models. PMID:23005195

He, Yingji; Mihalache, Dumitru; Malomed, Boris A; Qiu, Yunli; Chen, Zhanxu; Li, Yifang

2012-06-20

414

Modeling two-dimensional water flow and bromide transport in a heterogeneous lignitic mine soil  

SciTech Connect

Water and solute fluxes in lignitic mine soils and in many other soils are often highly heterogeneous. Here, heterogeneity reflects dumping-induced inclined structures and embedded heterogeneous distributions of sediment mixtures and of lignitic fragments. Such two-scale heterogeneity effects may be analyzed through the application of two-dimensional models for calculating water and solute fluxes. The objective of this study was to gain more insight to what extent spatial heterogeneity of soil hydraulic parameters contributes to preferential flow at a lignitic mine soil. The simulations pertained to the 'Barenbrucker Hohe' site in Germany where previously water fluxes and applied tracers had been monitored with a cell lysimeter, and from where a soil block had been excavated for detailed two-dimensional characterization of the hydraulic parameters using pedotransfer functions. Based on those previous studies, scenarios with different distributions of hydraulic parameters were simulated. The results show that spatial variability of hydraulic parameters alone can hardly explain the observed flow patterns. The observed preferential flow at the site was probably caused by additional factors such as hydrophobicity, the presence of root channels, anisotropy in the hydraulic conductivity, and heterogeneous root distributions. To study the relative importance of these other factors by applying two-dimensional flow models to such sites, the experimental database must be improved. Single-continuum model approaches may be insufficient for such sites.

Buczko, U.; Gerke, H.H. [Brandenburg University of Technology, Cottbus (Germany)

2006-02-15

415

Oblique half-solitons and their generation in exciton-polariton condensates  

SciTech Connect

We describe oblique half-solitons, a new type of topological defects in a two-dimensional spinor Bose-Einstein condensate. A realistic protocol based on the optical spin Hall effect is proposed toward their generation within an exciton-polariton system.

Flayac, H.; Solnyshkov, D. D.; Malpuech, G. [Clermont Universite, Universite Blaise Pascal, LASMEA, BP10448, F-63000 Clermont-Ferrand, France CNRS, UMR6602, LASMEA, F-63177 Aubiere (France)

2011-05-15

416

Drift ion acoustic solitons in an inhomogeneous 2-D quantum magnetoplasma  

Microsoft Academic Search

Linear and nonlinear propagation characteristics of quantum drift ion acoustic waves are investigated in an inhomogeneous two-dimensional plasma employing the quantum hydrodynamic (QHD) model. In this regard, the dispersion relation of the drift ion acoustic waves is derived and limiting cases are discussed. In order to study the drift ion acoustic solitons, nonlinear quantum Kadomstev–Petviashvilli (KP) equation in an inhomogeneous

W. Masood

2009-01-01

417

Subcritical patterns and dissipative solitons due to intracavity photonic crystals  

SciTech Connect

Manipulation of the bifurcation structure of nonlinear optical systems via intracavity photonic crystals is demonstrated. In particular, subcritical regions between spatially periodic states are stabilized by modulations of the material's refractive index. An family of dissipative solitons within this bistability range due to the intracavity photonic crystal is identified and characterized in both one and two transverse dimensions. Nontrivial snaking of the modulated-cavity soliton solutions is also presented.

Gomila, Damia [SUPA and Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow, G4 0NG, Scotland (United Kingdom); Instituto de Fisica Interdisciplinar y Sistemas Complejos (IFISC, CSIC-UIB), Campus Universitat Illes Balears, 07122 Palma de Mallorca (Spain); Oppo, Gian-Luca [SUPA and Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow, G4 0NG, Scotland (United Kingdom)

2007-10-15

418

Subcritical patterns and dissipative solitons due to intracavity photonic crystals  

NASA Astrophysics Data System (ADS)

Manipulation of the bifurcation structure of nonlinear optical systems via intracavity photonic crystals is demonstrated. In particular, subcritical regions between spatially periodic states are stabilized by modulations of the material’s refractive index. An family of dissipative solitons within this bistability range due to the intracavity photonic crystal is identified and characterized in both one and two transverse dimensions. Nontrivial snaking of the modulated-cavity soliton solutions is also presented.

Gomila, Damiŕ; Oppo, Gian-Luca

2007-10-01

419

Drift ion acoustic solitons in an inhomogeneous 2-D quantum magnetoplasma  

NASA Astrophysics Data System (ADS)

Linear and nonlinear propagation characteristics of quantum drift ion acoustic waves are investigated in an inhomogeneous two-dimensional plasma employing the quantum hydrodynamic (QHD) model. In this regard, the dispersion relation of the drift ion acoustic waves is derived and limiting cases are discussed. In order to study the drift ion acoustic solitons, nonlinear quantum Kadomstev-Petviashvilli (KP) equation in an inhomogeneous quantum plasma is derived using the drift approximation. The solution of quantum KP equation using the tangent hyperbolic (tanh) method is also presented. The variation of the soliton with the quantum Bohm potential, the ratio of drift to soliton velocity in the co-moving frame, vu, and the increasing magnetic field are also investigated. It is found that the increasing number density decreases the amplitude of the soliton. It is also shown that the fast drift soliton (i.e., v>u) decreases whereas the slow drift soliton (i.e., vsoliton. Finally, it is shown that the increasing magnetic field increases the amplitude of the quantum drift ion acoustic soliton. The stability of the quantum KP equation is also investigated. The relevance of the present investigation in dense astrophysical environments is also pointed out.

Masood, W.

2009-04-01

420

Cubic-quintic solitons in the checkerboard potential  

SciTech Connect

We introduce a two-dimensional (2D) model which combines a checkerboard potential, alias the Kronig-Penney (KP) lattice, with the self-focusing cubic and self-defocusing quintic nonlinear terms. The beam-splitting mechanism and soliton multistability are explored in this setting, following the recently considered 1D version of the model. Families of single- and multi-peak solitons (in particular, five- and nine-peak species naturally emerge in the 2D setting) are found in the semi-infinite gap, with both branches of bistable families being robust against perturbations. For single-peak solitons, the variational approximation (VA) is developed, providing for a qualitatively correct description of the transition from monostability to the bistability. 2D solitons found in finite band gaps are unstable. Also constructed are two different species of stable vortex solitons, arranged as four-peak patterns ('oblique' and 'straight' ones). Unlike them, compact 'crater-shaped' vortices are unstable, transforming themselves into randomly walking fundamental beams.

Driben, Rodislav; Zyss, Joseph [Laboratoire de Photonique Quantique et Moleculaire, CNRS, Ecole Normale Superieure de Cachan, UMR 8537, 94235 Cachan (France); Malomed, Boris A.; Gubeskys, Arthur [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)

2007-12-15

421

Coherent imaging with two-dimensional focal-plane arrays: design and applications  

SciTech Connect

Scanned, single-channel optical heterodyne detection has been used in a variety of lidar applications from ranging and velocity measurements to differential absorption spectroscopy. We describe the design of a coherent camera system that is based on a two-dimensional staring array of heterodyne receivers for coherent imaging applications. Experimental results with a single HgCdTe detector translated in the image plane to form a synthetic two-dimensional array demonstrate the ability to obtain passive heterodyne images of chemical vapor plumes that are invisible to normal video infrared cameras. We describe active heterodyne imaging experiments with use of focal-plane arrays that yield hard-body Doppler lidar images and also demonstrate spatial averaging to reduce speckle effects in static coherent images. {copyright} 1997 Optical Society of America

Simpson, M.L.; Bennett, C.A.; Emery, M.S.; Hutchinson, D.P.; Miller, G.H.; Richards, R.K.; Sitter, D.N. [Instrumentation and Controls Division, Lockheed Martin Energy Research Corporation, Building 3500, MS-6006, P. O. Box 2008, Bethel Valley Road, Oak Ridge, Tennessee 37831-6004 (United States)

1997-09-01

422

Vortex dynamics in two-dimensional underdamped, classical Josephson-junction arrays  

SciTech Connect

We present a systematic experimental study on vortex dynamics in two-dimensional Josephson-junction arrays built of underdamped single junctions in which charging effects can be neglected. Arrays in both square and triangular geometries are measured in small magnetic fields at low temperatures. We find that the whole picture of the spatial dynamics of vortices in two-dimensional arrays is analogous to the dynamics of the phase in a single junction. We study in detail the depinning current, the flux-flow resistance, and the maximum velocity of propagating vortices. Our data show that vortices in underdamped arrays, when driven with a current, experience more damping than can be explained by Ohmic-dissipation alone. A simple semiquantitative model, in which the energy lost to junctions in the wake of the moving vortices is taken into account, explains our data very well. The model shows that vortices will always experience damping no matter how underdamped the single junctions are.

van der Zant, H.S.J. (Department of Applied Physics, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands) Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Fritschy, F.C. (Department of Applied Physics, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands)); Orlando, T.P. (Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Mooij, J.E. (Department of Applied Physics, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands))

1993-01-01

423

Alternating direction implicit method for solving two-dimensional cubic nonlinear Schrödinger equation  

NASA Astrophysics Data System (ADS)

In this paper, four alternating direction implicit (ADI) schemes are presented for solving two-dimensional cubic nonlinear Schrödinger equations. Firstly, we give a Crank-Nicolson ADI scheme and a linearized ADI scheme both with accuracy O(?t+h), with the same method, use fourth-order Padé compact difference approximation for the spatial discretization; two HOC-ADI schemes with accuracy O(?t+h) are given. The two linearized ADI schemes apply extrapolation technique to the real coefficient of the nonlinear term to avoid iterating to solve. Unconditionally stable character is verified by linear Fourier analysis. The solution procedure consists of a number of tridiagonal matrix equations which make the computation cost effective. Numerical experiments are conducted to demonstrate the efficiency and accuracy, and linearized ADI schemes show less computational cost. All schemes given in this paper also can be used for two-dimensional linear Schrödinger equations.

Xu, Yiqiang; Zhang, Luming

2012-05-01

424

Optical imaging process based on two-dimensional Fourier transform for synthetic aperture imaging ladar  

NASA Astrophysics Data System (ADS)

The synthetic aperture imaging ladar (SAIL) systems typically generate large amounts of data difficult to compress with digital method. This paper presents an optical SAIL processor based on compensation of quadratic phase of echo in azimuth direction and two dimensional Fourier transform. The optical processor mainly consists of one phase-only liquid crystal spatial modulator(LCSLM) to load the phase data of target echo and one cylindrical lens to compensate the quadratic phase and one spherical lens to fulfill the task of two dimensional Fourier transform. We show the imaging processing result of practical target echo obtained by a synthetic aperture imaging ladar demonstrator. The optical processor is compact and lightweight and could provide inherent parallel and the speed-of-light computing capability, it has a promising application future especially in onboard and satellite borne SAIL systems.

Sun, Zhiwei; Zhi, Ya'nan; Liu, Liren; Sun, Jianfeng; Zhou, Yu; Hou, Peipei

2013-09-01

425

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas  

SciTech Connect

Solution of the energy dependent diffusion equation in two dimensions is formulated by multigroup approximation of the energy variable and general triangular mesh, finite element discretization of the spatial domain. Finite element formulation is done by Galerkin's method. Based on this formulation, a two-dimensional multigroup finite element diffusion theory code, FENAT, has been developed for the transport of neutral atoms in fusion plasmas. FENAT solves the multigroup diffusion equation in X-Y cartesian and R-Z cylindrical/toroidal geometries. Use of the finite element method allows solution of problems in which the plasma cross-section has an arbitrary shape. The accuracy of FENAT has been verified by comparing results to those obtained using the two-dimensional discrete ordinate transport theory code, DOT-4.3. Results of application of FENAT to the transport of limiter-originated neutral atoms in a tokamak fusion machine are presented.

Hasan, M.Z.; Conn, R.W.

1986-02-01

426

Complexity and efficient approximability of two dimensional periodically specified problems  

SciTech Connect

The authors consider the two dimensional periodic specifications: a method to specify succinctly objects with highly regular repetitive structure. These specifications arise naturally when processing engineering designs including VLSI designs. These specifications can specify objects whose sizes are exponentially larger than the sizes of the specification themselves. Consequently solving a periodically specified problem by explicitly expanding the instance is prohibitively expensive in terms of computational resources. This leads one to investigate the complexity and efficient approximability of solving graph theoretic and combinatorial problems when instances are specified using two dimensional periodic specifications. They prove the following results: (1) several classical NP-hard optimization problems become NEXPTIME-hard, when instances are specified using two dimensional periodic specifications; (2) in contrast, several of these NEXPTIME-hard problems have polynomial time approximation algorithms with guaranteed worst case performance.

Marathe, M.V. [Los Alamos National Lab., NM (United States); Hunt, H.B. III; Stearns, R.E. [State Univ. of New York, Albany, NY (United States). Dept. of Computer Science

1996-09-01

427

Generation of two-dimensional plasmonic bottle beams.  

PubMed

By analogy to the three dimensional optical bottle beam, we introduce the plasmonic bottle beam: a two dimensional surface wave which features a lattice of plasmonic bottles, i.e. alternating regions of bright focii surrounded by low intensities. The two-dimensional bottle beam is created by the interference of a non-diffracting beam, a cosine-Gaussian beam, and a plane wave, thus giving rise to a non-diffracting complex intensity distribution. By controlling the propagation constant of the cosine-Gauss beam, the size and number of plasmonic bottles can be engineered. The two dimensional lattice of hot spots formed by this new plasmonic wave could have applications in plasmonic trapping. PMID:23609739

Genevet, Patrice; Dellinger, Jean; Blanchard, Romain; She, Alan; Petit, Marlene; Cluzel, Benoit; Kats, Mikhail A; de Fornel, Frederique; Capasso, Federico

2013-04-22

428

Power-Dependent Reflection, Transmission, and Trapping Dynamics of Lattice Solitons at Interfaces  

NASA Astrophysics Data System (ADS)

Surface soliton formation and lattice soliton dynamics at an interface between two inhomogeneous periodic media are studied in terms of an effective particle approach. The global reflection, transmission, and trapping characteristics are obtained in direct analogy to linear Snell’s laws for homogeneous media. Interesting dynamics related to soliton power-dependent formation of potential barriers and wells suggest a spatial filtering functionality of the respective structures.

Kominis, Y.; Hizanidis, K.

2009-04-01

429

Experiments on Ion-Acoustic Solitons in Plasmas Invited Review Article  

Microsoft Academic Search

Experiments on ion-acoustic solitons are reviewed. Theories and numerical simulations which are relevant to experimental results are also presented. The measured velocity and width of planar solitons are compared with the predictions of the Korteweg-deVries (KdV) equation which includes a finite ion temperature. The spatial evolution of compressive or rarefactive pulses is discussed. Cylindrical and spherical solitons are introduced together

Yoshiharu Nakamura

1982-01-01

430

Instabilities of optical solitons and Hamiltonian singular solutions in a medium of finite extension  

SciTech Connect

We analyze the role of soliton solutions and Hamiltonian singularities in the dynamics of counterpropagating waves in a medium of finite spatial extension. The soliton solution can become unstable due to the finite extension of the system. We show that the spatiotemporal dynamics then relaxes toward a Hamiltonian singular state of a nature different than that of the soliton state. This phenomenon can be explained through a geometrical analysis of the singularities of the stationary Hamiltonian system.

Assemat, E.; Picozzi, A.; Jauslin, H. R.; Sugny, D. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 5209 CNRS-Universite de Bourgogne, 9 Avenue A. Savary, Boite Postale 47 870, F-21078 Dijon Cedex (France)

2011-07-15

431

Two-dimensional lattice Boltzmann model for magnetohydrodynamics.  

PubMed

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. PMID:12443375

Schaffenberger, Werner; Hanslmeier, Arnold

2002-10-09

432

Quasi-two-dimensional acoustic metamaterial with negative bulk modulus  

NASA Astrophysics Data System (ADS)

We present the experimental realization and characterization of an acoustic metamaterial with negative bulk modulus. The metamaterial consists of a two-dimensional array of cylindrical cavities, and the bulk modulus is controlled by their radius size and length. Experiments are performed in a two-dimensional waveguide where a slab of seven layers is used to extract the parameters of the metamaterial. A complete characterization of the constructed structure is reported, including the dispersion relation of the acoustic bands and the skin depth effect, which both have been measured, and the data are well supported by semianalytical models and by finite-element simulations.

García-Chocano, V. M.; Graciá-Salgado, R.; Torrent, D.; Cervera, F.; Sánchez-Dehesa, J.

2012-05-01

433

Bulk-Edge Correspondence for Two-Dimensional Topological Insulators  

NASA Astrophysics Data System (ADS)

Topological insulators can be characterized alternatively in terms of bulk or edge properties. We prove the equivalence between the two descriptions for two-dimensional solids in the single-particle picture. We give a new formulation of the {{Z}2}-invariant, which allows for a bulk index not relying on a (two-dimensional) Brillouin zone. When available though, that index is shown to agree with known formulations. The method also applies to integer quantum Hall systems. We discuss a further variant of the correspondence, based on scattering theory.

Graf, Gian Michele; Porta, Marcello

2013-10-01

434

On Periodicity of Generalized Two-Dimensional Words  

Microsoft Academic Search

A generalized two-dimensional word is a function on ?2 with finite number of values. The main problem we are interested in is periodicity of two-dimensional words satisfying some\\u000a local conditions. Let \\u000a $\\\\sum\\\\limits_{\\\\scriptsize {c} (y_1, y_2): \\\\\\\\ 0\\\\sum\\\\limits_{\\\\scriptsize \\\\begin{array}{c} (y_1, y_2): \\\\\\\\ 0\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a for every integers x\\u000a 1, x\\u000a 2. We prove that every bounded generalized centered function of radius r?>?1

Svetlana Puzynina

2008-01-01

435

Density fluctuation spectrum of two-dimensional correlated fermion systems  

NASA Astrophysics Data System (ADS)

Density fluctuation spectrum of two-dimensional fermions that interact with short-range repulsive interaction is calculated with the self-consistent perturbation theory. The spectrum extends beyond the particle-hole continuum band in the noninteracting case because of the multiparticle excitations. At a large wave vector, a peak develops in the spectrum near the lower threshold of the particle-hole continuum. These results are compared with the recent inelastic neutron scattering experiment on two-dimensional 3He adsorbed on graphite.

Kotani, Akihiro; Hirashima, Dai

2012-12-01

436

Pulsed atomic soliton laser  

SciTech Connect

It is shown that simultaneously changing the scattering length of an elongated, harmonically trapped Bose-Einstein condensate from positive to negative and inverting the axial portion of the trap, so that it becomes expulsive, results in a train of self-coherent solitonic pulses. Each pulse is itself a nondispersive attractive Bose-Einstein condensate that rapidly self-cools. The axial trap functions as a waveguide. The solitons can be made robustly stable with the right choice of trap geometry, number of atoms, and interaction strength. Theoretical and numerical evidence suggests that such a pulsed atomic soliton laser can be made in present experiments.

Carr, L.D.; Brand, J. [JILA, National Institute for Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany)

2004-09-01

437

Cavity soliton billiards  

SciTech Connect

The motion of a self-propelled cavity soliton in a laser where the pump profile acts as a square billiard is investigated. In the long-term dynamics, only closed trajectories are possible, exhibiting nonspecular reflections with striking similarities to walking droplets in a vibrated liquid bath. Open orbits can be achieved either by introducing scattering defects in the pump profile or in the presence of more than two solitons, due to their interaction. Such dynamical properties can be exploited for applications such as a compact soliton-force microscope.

Prati, F.; Lugiato, L. A. [CNISM and Dipartimento di Fisica e Matematica, Universita dell'Insubria, Via Valleggio 11, I-22100 Como (Italy); Tissoni, G. [Institut Non Lineaire de Nice, UMR 6618, Universite de Nice Sophia Antipolis,1361 Route des Lucioles, F-06560 Valbonne (France); Brambilla, M. [CNISM and Dipartimento Interateneo di Fisica, Universita e Politecnico di Bari, Via Amendola 173, I-70123 Bari (Italy)

2011-11-15

438

The Anisotropic Characters in Two-Dimensional Lattice  

NASA Astrophysics Data System (ADS)

The anisotropic characters of simple cubic lattice are investigated in this paper. Both the linear and nonlinear wave propagating in this lattice have been studied. The dispersion relation has been studied numerically. It is shown that the dispersion relation strongly depends on the directions of wave propagation. Generally, the direction of waves has the inclination angle ? with respect to particle displacement. There are compressional waves ? = 0 or transverse waves ? = ?/2 only for some special cases. The nonlinear waves in this lattice have also been studied. The anisotropic characters of this lattice for the nonlinear waves have also been shown. The compressional and transverse nonlinear solitons have also been studied. The characters of both solitons, such as amplitude and width, have been investigated.

Yang, Yang; Lin, Mai-Mai; Duan, Wen-Shan

2013-03-01

439

Application of the differential evolution algorithm to the optimization of two-dimensional synthetic aperture microwave radiometer circle array  

Microsoft Academic Search

A new optimization technique based on the differential evolution algorithm is presented for the design of two-dimensional synthetic aperture microwave radiometer circle array. The object function is designed by minimizing redundant array and maximizing the distance between spatial frequency coverage samples and the optimal results of 16~32 elements circle array are obtained. Compare with simulated annealing algorithm and symmetrical distribution

Kun Chao; Zhenwei Zhao; Zhensen Wu; Rui Lang

2010-01-01

440

Two-dimensional spectroscopy for a two-dimensional rotator coupled to a Gaussian-Markovian noise bath  

NASA Astrophysics Data System (ADS)

The dynamics of a system in the condensed phase are more clearly characterized by multitime correlation functions of physical observables than by two-time ones. We investigate a two-dimensional motion of a rigid rotator coupled to a Gaussian-Markovian harmonic oscillator bath to probe this issue. The analytical expression of a four-time correlation function of a dipole that is the observable of two-dimensional microwave or far-infrared spectroscopy is obtained from a generating functional approach. The spectra in the absence of damping are discrete and reveal transitions between eigenstates of the angular momentum quantized due to the cyclic boundary condition. For a weakly damped case, the two-dimensional spectrum predicts three echolike peaks corresponding to transition processes between the rotational energy levels, which cannot be observed in one-dimensional (linear-absorption) spectroscopy related to the two-time correlation function of the dipole [J. Phys. Soc. Jpn. 71, 2414 (2002)]. The two-dimensional spectra are more sensitive to the noise effects than the one-dimensional spectra. It is because the effects of the initial thermal distribution determine the profile of the continuous line shape in one-dimensional spectroscopy, while such thermal effects are canceled through the higher-order optical transition process in two-dimensional spectroscopy. If the rotator system is strongly coupled to the colored noise bath, the system exhibits one overdamped and other oscillatory motions. We observe peaks arising from interaction between these two modes in the two-dimensional spectra, which are difficult to distinguish in one-dimensional spectra.

Suzuki, Yoko; Tanimura, Yoshitaka

2003-07-01

441

Two-Dimensional Diverging Shocks in a Nonuniform Medium  

SciTech Connect

An analytic solution is derived from the time evolution of a two- dimensional diverging shock in r - z geometry. The shock propagates through a condensed medium characterized by a Mie-Gruneisen equation of state with a nonzero density gradient in the axial direction.

Roy A. Axford

1998-08-01

442

Extended de Sitter theory of two-dimensional gravitational forces  

SciTech Connect

We present a simple unifying gauge-theoretical formulation of gravitational theories in two-dimensional spacetime. This formulation includes the effects of a novel matter-gravity coupling which leads to an extended de Sitter symmetry algebra on which the gauge theory is based. Contractions of this theory encompass previously studied cases.

Cangemi, D. (Center for Theoretical Physics, Laboratory for Nuclear Science, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Dunne, G. (Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States))

1993-12-15

443

There is no two dimensional analogue of Lamé's equation  

Microsoft Academic Search

this paper is to prove that there is nonon-trivial two-dimensional analogue of this phenomenon. To make the laststatement precise, we begin with a review of the basic properties of the Lameequation.Fix ! 1 ; ! 2 > 0 . Let}(z) =1

Joel Feldman; Horst Knörrer; Eugene Trubowitz

1992-01-01

444

Progress in two-dimensional plasma edge modelling  

Microsoft Academic Search

A review is given of the status of various approaches dealing with tokamak edge related issues by employing two-dimensional numerical fluid codes for the main components of the edge plasma. The predictive capabilities of these models are assessed, in particular with regard to their completeness and the reliability of the transport coefficients. As the plasma edge characteristics in the favourable

D. Reiter

1992-01-01

445

Multibeam two-dimensional binary optics laser scanner  

NASA Astrophysics Data System (ADS)

We have developed a two-dimensional, multibeam, binary optic based scanner for transmission/receiver functions for LADAR and other applications under a Small Business Innovation Research (SBIR) contract from Eglin Air Force Base. Multibeam scan provides many unique advantages including: increased data rate for pulsed lasers; increased scan coverage; and programmable broadcasting for optical interconnect applications.

Jain, Anil K.

1994-06-01

446

Optimal entropic uncertainty relation in two-dimensional Hilbert space  

NASA Astrophysics Data System (ADS)

The exact lower bound on the sum of the information entropies is obtained for arbitrary pairs of observables in two-dimensional Hilbert space. The result coincides with that given by Garrett and Gull for the particular case of real transformation matrices and state vectors. A weaker analytical bound is also obtained.

Sánches-Ruiz, Jorge

1998-07-01

447

Optimal entropic uncertainty relation in two-dimensional Hilbert space  

Microsoft Academic Search

The exact lower bound on the sum of the information entropies is obtained for arbitrary pairs of observables in two-dimensional Hilbert space. The result coincides with that given by Garrett and Gull for the particular case of real transformation matrices and state vectors. A weaker analytical bound is also obtained.

Jorge Sánches-Ruiz

1998-01-01

448

Two-dimensional heat transfer analysis of radiating plates  

Microsoft Academic Search

The strongly implicit procedure is used to solve nonlinear elliptical two-dimensional heat conduction in radiating plates. A uniform heat flux is applied at one end of the plate which dissipates heat by radiation from one end into a vacuum at 0 K and into an ambient at temperature T(i) from the other. The results are presented with reference to four

K. Badari Narayana; S. U. Kumari

1988-01-01

449

Steady two-dimensional groundwater flow through many elliptical inhomogeneities  

Microsoft Academic Search

A new analytic element solution has been derived for steady two-dimensional groundwater flow through an aquifer that contains an arbitrary number of elliptical inhomogeneities. The hydraulic conductivity of each inhomogeneity is homogeneous and differs from the conductivity of the homogeneous background. In addition to elliptical inhomogeneities, other elements (such as wells and line sinks) may be present. The method is

Raghavendra Suribhatla; Mark Bakker; Karl Bandilla; Igor Jankovic

2004-01-01

450

Two-dimensional flow through large numbers of circular inhomogeneities  

Microsoft Academic Search

An implicit analytic solution is presented for two-dimensional groundwater flow through a large number of non-intersecting circular inhomogeneities in the hydraulic conductivity. The locations, sizes and conductivity of the inhomogeneities may be arbitrarily selected. The influence of each inhomogeneity is expanded in a series that satisfies the Laplace equation exactly. The unknown coefficients in this expansion are related to the

R. Barnes; I. Jankovi?

1999-01-01

451

Two-dimensional electron gas near full polarization  

Microsoft Academic Search

We establish the consistency of the Fermi liquid description and find a relation between the Fermi liquid constants for a two-dimensional electron system near the point of full polarization due to a parallel magnetic field H. Our results enable us to predict connections between different thermodynamic properties of the system. In particular, we find that near the point of full

G. Zala; B. N. Narozhny; I. L. Aleiner; Vladimir I. Fal'Ko

2004-01-01

452

Two-Dimensional Chirality in Three-Dimensional Chemistry.  

ERIC Educational Resources Information Center

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)

Wintner, Claude E.

1983-01-01

453

A two dimensional field theory for motion computation  

Microsoft Academic Search

The local extraction of motion information from brightness patterns by individual movement detectors of the correlation-type is considered in the first part of the paper. A two-dimensional field theory of movement detection is developed by treating the distance between two adjacent photoreceptors as a differential. In the first approximation of the theory we only consider linear terms of the time

W. E. Reichardt; R. W. Schlögl

1988-01-01

454

Two-dimensional high speed flow of a radiating gas  

Microsoft Academic Search

In high speed gas dynamics the analysis of two-dimensional flows of hot gases, where the effect of radiation as a mode of energy transfer cannot be neglected, is extremely difficult due to the integro-differential nature of the governing equations. To date, most of the existing literature on radiation gas dynamics is confined to the study of the two asymptotic cases

Prem K. Khosla

1968-01-01

455

Two-Dimensional Flat-Earth Trajectory Computer Program.  

National Technical Information Service (NTIS)

This technical report describes a two-dimensional, flat-earth trajectory computer program written in FORTRAN IV. The report is intended to serve as a complete user's manual and includes a description of the program structure and capabilities, a sample inp...

V. L. Olivier J. C. Vaughan

1968-01-01

456

On the Integrability of Two-Dimensional Flows  

Microsoft Academic Search

This paper deals with the notion of integrability of flows or vector fields on two-dimensional manifolds. We consider the following two key points about first integrals: (1) They must be defined on the whole domain of definition of the flow or vector field, or defined on the complement of some special orbits of the system; (2) How are they computed?

Javier Chavarriga; Hector Giacomini; Jaume Giné; Jaume Llibre

1999-01-01

457

A maximum likelihood approach to two-dimensional crystals  

Microsoft Academic Search

Maximum likelihood (ML) processing of transmission electron microscopy images of protein particles can produce reconstructions of superior resolution due to a reduced reference bias. We have investigated a ML processing approach to images centered on the unit cells of two-dimensional (2D) crystal images. The implemented software makes use of the predictive lattice node tracking in the MRC software, which is

Xiangyan Zeng; Henning Stahlberg; Nikolaus Grigorieff

2007-01-01

458

Equilibrium structural properties of two-dimensional nonideal systems  

NASA Astrophysics Data System (ADS)

The pair correlation functions and the mean squared displacements of charged dust particles were studied experimentally for quasi-two-dimensional (2D) nonideal systems. The experiments were carried out in a plasma of a capacitive radio-frequency (RF-) discharge in argon for monolayers of monodispersed (melamine formaldehyde) spheres. A comparison with the existing theoretical and numerical data is presented.

Vaulina, O. S.; Vasilieva, E. V.; Petrov, O. F.; Fortov, V. E.

2011-12-01

459

Strong exchange narrowing in new two-dimensional paramagnetic systems  

Microsoft Academic Search

Single crystals of (CH3NH3)2 MnCl4 and (C2H5NH3)2 MnCl4 have a strong angular and temperature dependent ESR line width narrowed by exchange interaction. They are very probable two-dimensional paramagnets down to about 50°K.

H. R. Boesch; U. Schmocker; F. Waldner; K. Emerson; J. E. Drumheller

1971-01-01

460

Nonlinear elastic behavior of two-dimensional molybdenum disulfide  

NASA Astrophysics Data System (ADS)

This research explores the nonlinear elastic properties of two-dimensional molybdenum disulfide. We derive a thermodynamically rigorous nonlinear elastic constitutive equation and then calculate the nonlinear elastic response of two-dimensional MoS2 with first-principles density functional theory (DFT) calculations. The nonlinear elastic properties are used to predict the behavior of suspended monolayer MoS2 subjected to a spherical indenter load at finite strains in a multiple-length-scale finite element analysis model. The model is validated experimentally by indenting suspended circular MoS2 membranes with an atomic force microscope. We find that the two-dimensional Young's modulus and intrinsic strength of monolayer MoS2 are 130 and 16.5 N/m, respectively. The results approach Griffith's predicted intrinsic strength limit of ?int˜(E)/(9), where E is the Young's modulus. This study reveals the predictive power of first-principles density functional theory in the derivation of nonlinear elastic properties of two-dimensional MoS2. Furthermore, the study bridges three main gaps that hinder understanding of material properties: DFT to finite element analysis, experimental results to DFT, and the nanoscale to the microscale. In bridging these three gaps, the experimental results validate the DFT calculations and the multiscale constitutive model.

Cooper, Ryan C.; Lee, Changgu; Marianetti, Chris A.; Wei, Xiaoding; Hone, James; Kysar, Jeffrey W.

2013-01-01

461

Two-dimensional representation of a delayed dynamical system  

Microsoft Academic Search

A nonlinear system with delayed feedback, whenever the delay time is much longer than the intrinsic correlation time, displays two widely separated time scales. In such a case, a two-dimensional representation becomes appropriate, because it discloses features otherwise hidden in the one-dimensional sequence of data, and allows use of recognition algorithms developed for spatiotemporal chaos. As an illustration, chaotic time

F. T. Arecchi; G. Giacomelli; A. Lapucci; R. Meucci

1992-01-01

462

Hexagonal structures for two-dimensional photonic crystals  

Microsoft Academic Search

Periodic dielectric structures have been recently proposed to inhibit spontaneous emission in semiconductors. From this suggestion, the new concepts of photonic band gap and photonic crystal have been developed. Zero-threshold lasers, waveguides, antenna substrates, filters and polarizers are promising applications. We propose a new class of two-dimensional periodic dielectric structures with hexagonal symmetry. We study the gap opening according to

D. Cassagne; C. Jouanin; D. Bertho

1996-01-01

463

Torsional springs for two-dimensional dynamic unstructured fluid meshes  

Microsoft Academic Search

Dynamic fluid grids are commonly used for the solution of flow problems with moving boundaries. They are often represented by a network of fictitious lineal springs that can become unreliable when the fluid mesh undergoes large displacements and\\/or deformations. In this paper, we propose to control the arbitrary motion of two-dimensional dynamic unstructured fluid grids with additional torsional springs. We

C. Farhat; C. Degand; B. Koobus; M. Lesmoinne

1998-01-01

464

Predictions of axisymmetric and two-dimensional impinging turbulent jets  

Microsoft Academic Search

The k ? ? turbulence model and a version of a second-moment closure, modified to include the effect of pressure reflections from a solid surface, have been used as the basis of predictions of the flow that results from the orthogonal impingement of circular and two-dimensional (2-D) jets on a flat surface. Comparison of model predictions has been made with

W. P. Jones

1996-01-01

465

A two-dimensional model for quantum gravity  

Microsoft Academic Search

Two-dimensional quantum gravity coupled to conformally invariant matter is a good model for the physics of higher-dimensional gravity, provided the central charge of the matter theory is greater than 25. In particular, the theory has a euclidean saddle point of large negative action, analogous to that considered by Baum, Hawking and Coleman in d = 4. Further, the theory is

Joseph Polchinski

1989-01-01

466

Inexpensive two-dimensional measuring device for cryogenic temperatures  

Microsoft Academic Search

A simple device for measuring thermal deformations in two-dimensional samples cooled to liquid nitrogen temperatures is described. The measurement consists of adding liquid nitrogen to a transparent quartz tray, and then scanning the sample from the bottom with a flatbed scanner. As a test of the device, the thermal contraction of aluminum from room temperature to 77 K is measured.

A. Grau Carles

2005-01-01

467

A two-dimensional damaged finite element for fracture applications  

Microsoft Academic Search

A novel finite element was developed for fatigue and fracture applications. The new element is two-dimensional with an embedded edge crack. The crack is not physically modeled within the element, but instead, its influence on the local flexibility of the structure is accounted for by the reduction of the element stiffness as a function of the crack length. The components

G. P. Potirniche; J. Hearndon; S. R. Daniewicz; D. Parker; P. Cuevas; P. T. Wang; M. F. Horstemeyer

2008-01-01

468

Two dimensional frustrated magnets in high magnetic field  

Microsoft Academic Search

Frustrated magnets in high magnetic field have a long history of offering beautiful surprises to the patient investigator. Here we present the results of extensive classical Monte Carlo simulations of a variety of models of two dimensional magnets in magnetic field, together with complementary spin wave analysis. Striking results include (i) a massively enhanced magnetocaloric effect in antiferromagnets bordering on

L. Seabra; N. Shannon; P. Sindzingre; T. Momoi; B. Schmidt; P. Thalmeier

2009-01-01

469

Online Shopping Using a Two Dimensional Product Map  

Microsoft Academic Search

In this paper, we propose a user interface for online shopping that uses a two dimensional product map to present products. This map is created using multidimensional scaling (MDS). Dissimilarities between products are computed using an adapted version of Gower's coecient of similarity based on the attributes of the product. The user can zoom in and out by drawing rectangles.

Martijn Kagie; Michiel C. Van Wezel; Patrick J. F. Groenen

2007-01-01

470

An efficient architecture for two-dimensional discrete wavelet transform  

Microsoft Academic Search

This paper proposes an efficient architecture for the two-dimensiona