For comprehensive and current results, perform a real-time search at Science.gov.

1

Stabilization of two-dimensional spatial solitons in dissipative media

NASA Astrophysics Data System (ADS)

This work analyzes the dynamics of two-dimensional spatial solitons in dissipative media. Stable solitons are formed in a two-dimensional medium with constant dissipation due to the balancing between dissipation and the instabilities due to nonlinearity. The dynamics have also been studied for linear, quadratic and exponential loss profiles. When a beam propagates in media with dissipation, where dissipation is a function of distance, it becomes compressed. A linear loss profile results in higher compression, while compression is minimal for an exponential profile.

Aysha Muhsina, K.; Subha, P. A.

2014-07-01

2

Two-dimensional spatial, solitons in nematic liquid crystals

We have observed, for the first to the best of our knowledge, time 2+1\\u000a dimensional spatial solitons with an Argon-ion beam in planar cells\\u000a containing an undoped nematic liquid crystal, The cells provided planar\\u000a anchoring for the liquid crystal molecules, with transparent electrodes\\u000a for applying an external voltage across the 75 mum-thick crystal. The\\u000a voltage allowed to pre-orientate the director

M Peccianti; C Umeton; IC Khoo; A deRossi; G Assanto

2001-01-01

3

NASA Astrophysics Data System (ADS)

We report the observation of incoherent collisions between two-dimensional bright photorefractive screening solitons. The solitons remain intact and do not exchange energy whenever the collision angle exceeds the critical angle for guidance in the waveguide that each soliton induces, which is, in turn, fully controlled by the soliton parameters. When the collision angle is much smaller than the critical angle the solitons fuse to form a single beam.

Shih, Ming-Feng; Segev, Mordechai

1996-10-01

4

Fully localized two-dimensional embedded solitons

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

5

Controllable branching of optical beams by quasi-two-dimensional dark spatial solitons

,6 The product Ioa2 is found to be a constant for the ODSS's, where I0 is the background-beam intensity holograms in liquid-crystal spatial light modulators7 ; (ii) by varying the background-beam inten- sity and and photorefractive9 nonlinear media. The photovoltaic pho- torefractive media do not require external electrical

6

Two-dimensional solitons in a quintic-septimal medium

NASA Astrophysics Data System (ADS)

We report an observation of spatial solitons in a medium managed to present fifth-seventh (focusing-defocusing) refractive nonlinearities with suppressed third-order nonlinearity. Propagation of two-dimensional bright spatial solitons for ˜10 Rayleigh lengths was observed and characterized in a suspension of silver nanoparticles in acetone using the scattered light imaging method. Numerical calculations based on a nonlinear Schrödinger-type equation, including contributions up to the seventh-order susceptibility, were performed showing good agreement with the experimental results.

Reyna, Albert S.; Jorge, Kelly C.; de Araújo, Cid B.

2014-12-01

7

Two-dimensional interaction of ion-acoustic solitons

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

8

Two-dimensional stability of ion-acoustic solitons

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

9

We report results of systematic numerical studies of two-dimensional matter-wave soliton families supported by an external potential, in a vicinity of the junction between stable and unstable branches of the families, where the norm of the solution attains a minimum, facilitating the creation of the soliton. The model is based on the Gross-Pitaevskii equation for the self-attractive condensate loaded into a quasiperiodic (QP) optical lattice (OL). The same model applies to spatial optical solitons in QP photonic crystals. Dynamical properties and stability of the solitons are analyzed with respect to variations of the depth and wave number of the OL. In particular, it is found that the single-peak solitons are stable or not in exact accordance with the Vakhitov-Kolokolov (VK) criterion, while double-peak solitons, which are found if the OL wave number is small enough, are always unstable against splitting. PMID:23004912

Burlak, Gennadiy; Malomed, Boris A

2012-05-01

10

Dragging two-dimensional discrete solitons by moving linear defects

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

11

Interaction forces among two-dimensional bright solitons and many-soliton molecules.

We consider two-dimensional bright matter-wave solitons in two-dimensional Bose-Einstein condensates. From the asymptotic form of their wave function, we derive an analytic expression for the force of interaction between solitons in the large separation limit, which turns out to decay with solitons separation ? as F(?)?exp(-?)/??. Simulating the dynamics of two solitons using the relevant Gross-Pitaevskii equation, we obtain the force of the interaction for the full range of ?, which turns out to be of molecular type. We show that many-soliton molecules can exist as a result of such a molecular-type of interaction. These include string-shaped, ring-shaped, or regular-lattice-shaped soliton molecules. By calculating their binding energy, we investigate the stability of these structures. Contrary to one-dimensional soliton molecules, which have no binding energy, two-dimensional molecules of a lattice of solitons with alternating phases are robust and have a negative binding energy. Lattices of size larger than 2 × 2 solitons have many discrete equilibrium values of the separation between two neighboring solitons. PMID:23004892

Al Khawaja, U

2012-05-01

12

One- and two-dimensional solitons supported by singular modulation of quadratic nonlinearity

We introduce a model of one- and two-dimensional (1D and 2D) optical media with the $\\chi ^{(2)}$ nonlinearity whose local strength is subject to cusp-shaped spatial modulation, $\\chi ^{(2)}\\sim r^{-\\alpha }$, with $\\alpha >0$, which can be induced by spatially nonuniform poling. Using analytical and numerical methods, we demonstrate that this setting supports 1D and 2D fundamental solitons, at $\\alpha 0.5$. 2D solitary vortices are found too. They are unstable, splitting into a set of fragments, which eventually merge into a single fundamental soliton pinned to the cusp. Spontaneous symmetry breaking of solitons is studied in the 1D system with a symmetric pair of the cusp-modulation peaks.

Lutsky, Vitaly

2015-01-01

13

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

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.

Luz, H. L. F. da; Gammal, A. [Instituto de Fisica, Universidade de Sao Paulo, 05508-090 Sao Paulo, Sao Paulo (Brazil); Abdullaev, F. Kh. [CFTC, Complexo Interdisciplinar, Universidade Lisboa, Avenida Professor Gama Pinto, 2, P-1649-003 Lisboa (Portugal); Salerno, M. [Dipartimento di Fisica 'E.R. Caianiello', CNISM and INFN-Gruppo Collegato di Salerno, Universita di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy); Tomio, Lauro [Instituto de Fisica, Universidade Federal Fluminense, 24210-346 Niteroi, Rio de Janeiro (Brazil); Instituto de Fisica Teorica, Universidade Estadual Paulista (UNESP), 01140-070 Sao Paulo, Sao Paulo (Brazil)

2010-10-15

14

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

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

15

OPTICAL SOLITONS: Excitation of two-dimensional soliton matrices by fundamental Gaussian beams

NASA Astrophysics Data System (ADS)

The excitation of two-dimensional periodic structures of fields of the first and second radiation harmonics due to the modulation instability of fundamental Gaussian beams is studied in a medium with a quadratic nonlinearity. The distances are found at which soliton matrix structures with a specified period are formed and destroyed. Optical gratings formed due to nonlinear aberration of broad Gaussian beams are considered.

Borovkova, O. V.; Chuprakov, D. A.; Sukhorukov, Anatolii P.

2005-01-01

16

Spatial resource analysis of two dimensional barcodes

It cannot be denied that documents in the form of hardcopy are still being used, especially important documents such as land titles, application forms, contracts and tickets. However there are reports of forgery cases over the years and as such, it is imperative to have a mechanism for integrity verification of hardcopy document. This research proposed the usage of two-dimensional

Teoh Chin Yew; S. Mazleena; I. Subariah

2008-01-01

17

Two-dimensional solitons in Bose-Einstein condensates with a disk-shaped trap

We consider, both analytically and numerically, the evolution of two-dimensional (2D) nonlinear matter-wave pulses in a Bose-Einstein condensate with a disk-shaped trap and repulsive atom-atom interactions. Due to the strong confinement in the axial direction the sound speed of the system is c=(1/2{sup 1/4})c{sub 0}, where c{sub 0} is the corresponding value without the trap. From the 3D order-parameter equation of the condensate, we derive a soliton-bearing Kadomtsev-Petriashvili equation with positive dispersion. When the trapping potential is weak in two transverse directions, a low-depth plane dark soliton can propagate in the condensate with a changing profile but preserving its structure down to the boundary of the condensate. We show that high-depth plane dark solitons are unstable to long-wavelength transverse disturbances. The instability appears as a longitudinal modulation of the soliton amplitude decaying into vortices. We also show how a dark lumplike 2D nonlinear excitation can be excited in the system. Furthermore, a dark lump decaying algebraically in two spatial directions can propagate rather stable in the condensate, but disappears near the boundary of the condensate where two vortices are nucleated. The vortices move in opposite directions along the boundary and when meeting merge creating a new lump. Finally, we also provide results for head-on and oblique collisions of two lumps in the system.

Huang Guoxiang [Key Laboratory for Optical and Magnetic Resonance Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Abdus Salam International Center for Theoretical Physics, P.O. Box 586, Strada Costiera 11, Trieste 34100 (Italy); Makarov, Valeri A. [Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII, No. 1, Madrid 28040 (Spain); Velarde, Manuel G. [Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII, No. 1, Madrid 28040 (Spain); International Center for Mechanical Sciences (CISM), Palazzo del Torso, Piazza Garibaldi, Udine 33100 (Italy)

2003-02-01

18

Sharp waveguide bends induced by spatial solitons

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

19

Temporal modulation of spatial optical solitons.

A variational method is used to investigate temporal effects that are experimentally observed in the propagation of spatial solitons in planar systems. These effects appear when the laser beam used to reach the soliton propagation regime is pulsed. In the absence of dispersion, the three-dimensional equation of propagation, including two space and one time variable, becomes a two-dimensional spatial equation. Time is included as a parameter that determines the initial value problem. The main effect derived is a temporal modulation on the spatial width of the soliton. This modulation depends crucially on the temporal envelope shape. The interest of these results is concerned with the potential use of spatial solitons for making gradient-index systems with a controllable index profile. PMID:20885715

Michinel, H; Fuente, R de L; Liñares, J

1994-06-01

20

Two-dimensional skyrmions and other solitonic structures in confinement-frustrated chiral nematics

NASA Astrophysics Data System (ADS)

We explore spatially localized solitonic configurations of a director field, generated using optical realignment and laser-induced heating, in frustrated chiral nematic liquid crystals confined between substrates with perpendicular surface anchoring. We demonstrate that, in addition to recently studied torons and Hopf-fibration solitonic structures (hopfions), one can generate a host of other axially symmetric stable and metastable director field configurations where local twist is matched to the surface boundary conditions through introduction of point defects and loops of singular and nonsingular disclinations. The experimentally demonstrated structures include the so-called "baby-skyrmions" in the form of double twist cylinders oriented perpendicular to the confining substrates where their double twist field configuration is matched to the perpendicular boundary conditions by loops of twist disclinations. We also generate complex textures with arbitrarily large skyrmion numbers. A simple back-of-the-envelope theoretical analysis based on free energy considerations and the nonpolar nature of chiral nematics provides insights into the long-term stability and diversity of these inter-related solitonic field configurations, including different types of torons, cholestric-finger loops, two-dimensional skyrmions, and more complex structures comprised of torons, hopfions, and various disclination loops that are experimentally observed in a confinement-frustrated chiral nematic system.

Ackerman, Paul J.; Trivedi, Rahul P.; Senyuk, Bohdan; van de Lagemaat, Jao; Smalyukh, Ivan I.

2014-07-01

21

Two-dimensional skyrmions and other solitonic structures in confinement-frustrated chiral nematics.

We explore spatially localized solitonic configurations of a director field, generated using optical realignment and laser-induced heating, in frustrated chiral nematic liquid crystals confined between substrates with perpendicular surface anchoring. We demonstrate that, in addition to recently studied torons and Hopf-fibration solitonic structures (hopfions), one can generate a host of other axially symmetric stable and metastable director field configurations where local twist is matched to the surface boundary conditions through introduction of point defects and loops of singular and nonsingular disclinations. The experimentally demonstrated structures include the so-called "baby-skyrmions" in the form of double twist cylinders oriented perpendicular to the confining substrates where their double twist field configuration is matched to the perpendicular boundary conditions by loops of twist disclinations. We also generate complex textures with arbitrarily large skyrmion numbers. A simple back-of-the-envelope theoretical analysis based on free energy considerations and the nonpolar nature of chiral nematics provides insights into the long-term stability and diversity of these inter-related solitonic field configurations, including different types of torons, cholestric-finger loops, two-dimensional skyrmions, and more complex structures comprised of torons, hopfions, and various disclination loops that are experimentally observed in a confinement-frustrated chiral nematic system. PMID:25122322

Ackerman, Paul J; Trivedi, Rahul P; Senyuk, Bohdan; van de Lagemaat, Jao; Smalyukh, Ivan I

2014-07-01

22

Two-dimensional solitons in triangular photonic lattices with parity-time symmetry

NASA Astrophysics Data System (ADS)

We report the existence and stability of two-dimensional (2D) fundamental, dipole-mode, vortex, and multipole solitons in parity-time (PT) symmetric triangular lattices with the Kerr self-focusing nonlinearity. It is demonstrated that the structure of such complex lattice potentials strongly affects the shape of the solitons, enabling the formation of stable out-of-phase dipole and multipole solitons, as well as vortices. The solitons of all these species have their stability regions in the semi-infinite gap. We also identify the point of the PT-symmetry-breaking phase transition in this lattice.

Wang, Hong; Shi, Shuang; Ren, Xiaoping; Zhu, Xing; Malomed, Boris A.; Mihalache, Dumitru; He, Yingji

2015-01-01

23

Two-dimensional spatial compounding with warping.

Spatial compounding aims to improve image quality through signal averaging, but speed-of-sound (SoS) and refraction errors can misalign the component frames and blur the compound image. A 2-D compounding system is demonstrated that uses a nonrigid registration (warping) to realign the frames before compounding. Block-based estimates of local misalignments are interpolated smoothly to compute the warp vectors. Simulations and a specialized phantom, both with a 9% SoS distortion, were created, and compound images with and without warping were compared to the conventional image. Image sharpness was compared by measuring the diameter of point targets and directional edge sharpness. The average registration accuracy was 0.06 to 0.07 mm (approximately one pixel). The diameter of point targets increased only 2% with warping vs. 32% without warping and directional edge sharpness dropped 3.7% vs. 20.0%. Furthermore, most of the speckle reduction due to compounding is retained when warping is used. The tests on simulated and phantom data demonstrate that the method is capable of making a small, but significant, improvement to image quality. The examinations in vitro and in vivo show the correct operation of the method with real tissue features. Further clinical studies should be performed to compare spatial compounding with and without warping to see which applications would benefit from the small improvement. PMID:15313325

Groves, Adrian R; Rohling, Robert N

2004-07-01

24

NASA Astrophysics Data System (ADS)

The Manakov soliton is a two-component soliton that was first considered by Manakov in the early 1970s.1 Based on the work of Zakharov and Shabat,2 Manakov found that the coupled nonlinear Schrodinger (CNSE) equations with special choice of the coefficients in front of nonlinear terms can be solved exactly. This system is integrable and solitons have therefore a number of special properties which might be useful in practice. In particular, for same total power, the soliton of a single nonlinear Schrodinger equation and the Manakov soliton behave similarly. There are certain conditions for the integrability of the CNSE. Namely, for the coupled set of equations with cubic nonlinearity, the ratio between the self-phase modulation (SPM) to the cross-phase modulation coefficients has to be equal to unity, and the SPM coefficients need to be equal for the two polarizations. Moreover, the energy exchange terms or four-wave mixing (FWM) terms must be zero. Physically, the Manakov soliton is a mutually trapped state of two orthogonally polarized beams where each component of the soliton experiences exactly the same index potential which is proportional to the total intensity of the beam. There are no crystal symmetries that a priori lead to a SPM/XPM ratio of unity. Thus, the Manakov soliton has not been observed experimentally prior to the work we reported.3 Based on our previous work, we found that in AlGaAs, for photon energies just below half the band gap, the conditions for integrability can be satisfied. This led to the first experimental observation of spatial Manakov solitons.

Kang, J. U.; Stegeman, G. I.; Aitchison, J. S.; Akhmediev, N.

1996-12-01

25

NASA Astrophysics Data System (ADS)

We introduce one- and two-dimensional (1D and 2D) models of parity-time (PT)-symmetric couplers with the mutually balanced linear gain and loss applied to the two cores and cubic-quintic (CQ) nonlinearity acting in each one. The 2D and 1D models may be realized in dual-core optical wave guides in the spatiotemporal and spatial domains, respectively. Stationary solutions for PT-symmetric solitons in these systems reduce to their counterparts in the usual coupler. The most essential problem is the stability of the solitons, which become unstable against symmetry breaking with the increase of the energy (norm) and retrieve the stability at still larger energies. The boundary value of the intercore-coupling constant, above which the solitons are completely stable, is found by means of an analytical approximation, based on the cw (zero-dimensional) counterpart of the system. The approximation demonstrates good agreement with numerical findings for the 1D and 2D solitons. Numerical results for the stability limits of the 2D solitons are obtained by means of the computation of eigenvalues for small perturbations, and verified in direct simulations. Although large parts of the soliton families are unstable, the instability is quite weak. Collisions between 2D solitons in the PT-symmetric coupler are studied by means of simulations. Outcomes of the collisions are inelastic but not destructive, as they do not break the PT symmetry.

Burlak, Gennadiy; Malomed, Boris A.

2013-12-01

26

High-order-mode soliton structures in two-dimensional lattices with defocusing nonlinearity.

While fundamental-mode discrete solitons have been demonstrated with both self-focusing and defocusing nonlinearity, high-order-mode localized states in waveguide lattices have been studied thus far only for the self-focusing case. In this paper, the existence and stability regimes of dipole, quadrupole, and vortex soliton structures in two-dimensional lattices induced with a defocusing nonlinearity are examined by the theoretical and numerical analysis of a generic envelope nonlinear lattice model. In particular, we find that the stability of such high-order-mode solitons is quite different from that with self-focusing nonlinearity. As a simple example, a dipole ("twisted") mode soliton with adjacent excited sites which may be stable in the focusing case becomes unstable in the defocusing regime. Our results may be relevant to other two-dimensional defocusing periodic nonlinear systems such as Bose-Einstein condensates with a positive scattering length trapped in optical lattices. PMID:17280161

Kevrekidis, P G; Susanto, H; Chen, Z

2006-12-01

27

High-order-mode soliton structures in two-dimensional lattices with defocusing nonlinearity

NASA Astrophysics Data System (ADS)

While fundamental-mode discrete solitons have been demonstrated with both self-focusing and defocusing nonlinearity, high-order-mode localized states in waveguide lattices have been studied thus far only for the self-focusing case. In this paper, the existence and stability regimes of dipole, quadrupole, and vortex soliton structures in two-dimensional lattices induced with a defocusing nonlinearity are examined by the theoretical and numerical analysis of a generic envelope nonlinear lattice model. In particular, we find that the stability of such high-order-mode solitons is quite different from that with self-focusing nonlinearity. As a simple example, a dipole (“twisted”) mode soliton with adjacent excited sites which may be stable in the focusing case becomes unstable in the defocusing regime. Our results may be relevant to other two-dimensional defocusing periodic nonlinear systems such as Bose-Einstein condensates with a positive scattering length trapped in optical lattices.

Kevrekidis, P. G.; Susanto, H.; Chen, Z.

2006-12-01

28

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

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

Two-dimensional B-spline finite elements and their application to the computation of solitons

Contents In this paper we investigate the interaction of localized solutions with stable shape and constant velocity, so called solitons, of the Kadomtsev-Petviashvili-equation by numberical methods. B-spline finite elements turn out to be well suited for this purpose. The concept of two-dimensional B-spline finite elements and their numerical implementation is presented. In order to test the method, a diffusion problem

S. Wendel; H. Maisch; H. Karl; G. Lehner

1993-01-01

30

Spatial solitons in photorefractive media

It is shown that photorefractive media can support a new type of spatial soliton, in which the diffraction is balanced by the self-scattering (two-wave mixing) of the beam spatial frequency components. This photorefractive soliton possesses some unique properties, such as independence of the absolute light intensity, and can experience absorption (or gain) with no change in its transverse structure.

Mordechai Segev; Bruno Crosignani; Amnon Yariv; Baruch Fischer

1992-01-01

31

Two-dimensional solitons and vortices in normal and anomalous dispersive media.

We study solitons and vortices described by the (2+1)-dimensional fourth-order generalized nonlinear Schrödinger equation with cubic-quintic nonlinearity. Necessary conditions for the existence of such structures are investigated analytically using conservation laws and asymptotic behavior of localized solutions. We derive the generalized virial relation, which describes the combined influence of linear and nonlinear effects on the evolution of the wave packet envelope. By means of refined variational analysis, we predict the main features of steady soliton solutions, which have been shown to be in good agreement with our numerical results. Soliton and vortex stability is investigated by linear analysis and direct numerical simulations. We show that stable bright solitons exist in nonlinear Kerr media both in anomalous and normal dispersive regimes, even if only the fourth-order dispersive effect is taken into account. Vortices occur robust with respect to symmetry-breaking azimuthal instability only in the presence of additional defocusing quintic nonlinearity in the strongly nonlinear regime. We apply our results to the theoretical explanation of whistler self-induced waveguide propagation in plasmas, and discuss possible applications to light beam propagation in cubic-quintic optical materials and to solitons in two-dimensional molecular systems. PMID:12636817

Davydova, T A; Yakimenko, A I; Zaliznyak, Yu A

2003-02-01

32

Solitons as baryons and qualitons as constituent quarks in two-dimensional QCD

We study the soliton type solutions arising in two-dimensional quantum chromodynamics (QCD$_{2}$). The so-called generalized sine-Gordon model (GSG) arises as the low-energy effective action of bosonized QCD$_{2}$ for unequal quark mass parameters, and it has been shown that the relevant solitons describe the normal and exotic baryonic spectrum of QCD$_{2}$ [JHEP(03)(2007)(055)]. In the first part of this chapter we classify the soliton and kink type solutions of the sl(3) GSG model. Related to the GSG model we consider the sl(3) affine Toda model coupled to matter fields (Dirac spinors) (ATM). It has been shown the confinement of the spinors inside the solitons and kinks of the GSG model providing an extended hadron model for "quark" confinement [JHEP(01)(2007)(027)]. In the second part of this chapter we discuss the appearance of the constituent quarks in the context of bosonized QCD$_{2}$ and the relevance of the $sl(2)$ ATM model in order to describe the confinement of the color degrees of freedom. We have shown that QCD$_{2}$ has quark soliton solutions if the quark mass is sufficiently large.

H. Blas; H. L. Carrion

2008-03-04

33

Spatial Solitons in Algaas Waveguides

NASA Astrophysics Data System (ADS)

In this work, by measuring the two-, three-photon absorption, and the nonlinear refractive index coefficients, a useful bandwidth for an all-optical switching applications in the AlGaAs below half the band gap is identified. Operating in this material system, several types of spatial solitons such as fundamental bright solitons, Vector solitons, and Manakov solitons are experimentally demonstrated. The propagation and the interaction behaviors of these solitons are studied experimentally and numerically. The distinct properties of each soliton are discussed along with some possible applications. Some applications, such as all -optical switching based on spatial soliton dragging and the efficient guiding of orthogonally polarized femtosecond pulses by a bright spatial soliton, are experimentally demonstrated. The signal gain due to an ultrafast polarization coupling, better known as Four Wave Mixing (FWM) is demonstrated in a channel waveguide. The effects of FWM are studied experimentally and numerically. This effect is also used to demonstrate polarization switching. The linear and nonlinear properties of AlGaAs/GaAs multiple quantum well waveguides are measured. Anisotropic two photon absorption and nonlinear refractive indices near half the band gap are measured along with the linear birefringence for several different quantum well structures. The usefulness of multiple quantum well structures for an all -optical switching because of anisotropic nature of this material system is discussed.

Kang, Jin Ung

34

Collision properties of quasi-one-dimensional spin wave envelope solitons propagating in narrow ferrite film waveguides and of two-dimensional self-focused spin wave packets (spin wave bullets) propagating in wide ferrite film samples are studied both experimentally and numerically. The experiments, performed by means of a space- and time-resolved Brillouin light scattering technique, have shown that quasi-one-dimensional spin wave envelope solitons retain their shapes after collisions, while two-dimensional spin wave bullets are destroyed in collisions. The experiments have also shown that the introduction of a fixed phase shift between the colliding envelope solitons leads to a qualitative change in their interaction at the collision point. Numerical modeling of head-on collisions of nonlinear spin wave packets based on two different approaches provides a good qualitative description of the observed collision phenomena. PMID:12777134

Slavin, A N; Büttner, O; Bauer, M; Demokritov, S O; Hillebrands, B; Kostylev, M P; Kalinikos, B A; Grimalsky, V V; Rapoport, Yu

2003-06-01

35

NASA Astrophysics Data System (ADS)

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector describing traditional spin-density-wave or spiral magnetic states. These one-electron spinor wave functions have the distinguishing property that they are antiperiodic along a closed path encircling any elementary plaquette of the lattice. This corresponds to a 2? rotation of the internal coordinate frame of the electron as it encircles the plaquette. The possibility of spinor wave functions with spatial antiperiodicity is a direct consequence of the two-valuedness of the internal electronic wave function defined on the space of Euler angles describing its spin. This internal space is the topologically, doubly-connected, group manifold of SO(3). Formally, these antiperiodic wave functions may be described by passing a flux which couples to spin (rather than charge) through each of the elementary plaquettes of the lattice. When applied to the two-dimensional Hubbard model with one electron per site, this new topological magnetic state exhibits a relativistic spectrum for charged, quasiparticle excitations with a suppressed one-electron density of states at the Fermi level. For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number ? associated with the vortex rotation of the background magnetic moment field by a phase angle 2?? along a path encircling the soliton. Such solitons also carry a spin flux of ?? through the plaquette on which they are centered. The ?=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the ?=1 and 2 solitons. The spectrum of localized states is symmetric about E=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

John, Sajeev; Golubentsev, Andrey

1995-01-01

36

Terahertz relativistic spatial solitons in doped graphene metamaterials

We propose an electrically tunable graphene-based metamaterial showing a large nonlinear optical response at THz frequencies, which we calculate analytically for the first time to our knowledge and arises from the intraband current. The structure sustains a novel type of stable two-dimensional spatial solitary wave, a relativistic version of the Townes soliton. These results can be also applied to any material exhibiting a conical dispersion with massless Dirac fermions.

Haiming Dong; Claudio Conti; Fabio Biancalana

2011-07-28

37

Spatial weak-light ring soliton in self-assembled quantum dots

NASA Astrophysics Data System (ADS)

By using semiclassical theory combined with multiple-scale method, we analytically study the linear absorption and the nonlinear dynamical properties in a lifetime broadened ?-type three-level self-assembled quantum dots. It is found that this system can exhibit the transparency, and the width of the transparency window becomes wider with the increase of control light field. Interestingly, a weak probe light beam can form spatial weak-light dark solitons. When it propagates along the axial direction, the soliton will transform into a steady spatial weak-light ring dark soltion. In addition, the stability of two-dimensional spatial optical solitons is testified numerically.

Chen, Qiu-Cheng

2014-12-01

38

The propagation of a nonlinear low-frequency mode in two-dimensional (2D) monolayer hexagonal dusty plasma crystal in presence of external magnetic field and dust-neutral collision is investigated. The standard perturbative approach leads to a 2D Korteweg-de Vries (KdV) soliton for the well-known dust-lattice mode. However, the Coriolis force due to crystal rotation and Lorentz force due to magnetic field on dust particles introduce a linear forcing term, whereas dust-neutral drag introduce the usual damping term in the 2D KdV equation. This new nonlinear equation is solved both analytically and numerically to show the competition between the linear forcing and damping in the formation of quasilongitudinal soliton in a 2D strongly coupled complex (dusty) plasma. Numerical simulation on the basis of the typical experimental plasma parameters and the analytical solution reveal that the neutral drag force is responsible for the usual exponential decay of the soliton, whereas Coriolis and/or Lorentz force is responsible for the algebraic decay as well as the oscillating tail formation of the soliton. The results are discussed in the context of the plasma crystal experiment. PMID:25314548

Ghosh, Samiran

2014-09-01

39

NASA Technical Reports Server (NTRS)

We present what are to our knowledge first-time calculations from vector nonlinear Maxwell's equations of femtosecond soliton propagation and scattering, including carrier waves, in two-dimensional dielectric waveguides. The time integration efficiently implements linear and nonlinear convolutions for the electric polarization, and the nonlinear convolution accounts for two quantum effects, the Kerr and Raman interactions. By retaining the optical carrier, the new method solves for fundamental quantities - optical electric and magnetic fields in space and time - rather than a nonphysical envelope function. It has the potential to provide an unprecedented two- and three-dimensional modeling capability for millimeter-scale integrated-optical circuits with submicrometer engineered inhomogeneities.

Joseph, Rose M.; Goorjian, Peter M.; Taflove, Allen

1993-01-01

40

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

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

41

Spatial solitons rays in periodic optical lattices

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 a new perturbative approach of the Maxwell equation. These findings are then demonstrated to compare well to the eikonal law of light ray propagation (nonlinearity compensates diffraction).

Ramaz Khomeriki; Jerome Leon

2009-09-17

42

Two-dimensional spatial profiles of plasma parameters during the DC magnetron sputtering process of an indium-tin-oxide (ITO) target in Ar\\/O2 are studied. Two-dimensional spatial profiles of sputtered indium atoms in the ground state and of argon and indium atoms in their excited states are measured by two-dimensional laser induced fluorescence (2D-LIF) and two-dimensional optical emission spectroscopy (2D-OES), respectively. The 2D-OES profiles

M. Muta; S. Ohgushi; Y. Matsuda; H. Fujiyama

1999-01-01

43

Various kinds of spatial solitons associated with photoisomerization

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

44

We present what are to our knowledge first-time calculations from vector nonlinear Maxwell's equations of femtosecond soliton propagation and scattering, including carrier waves, in two-dimensional dielectric waveguides. The time integration efficiently implements linear and nonlinear convolutions for the electric polarization, and the nonlinear convolution accounts for two quantum effects, the Kerr and Raman interactions. By retaining the optical carrier, the new method solves for fundamental quantities-optical electric and magnetic fields in space and time-rather than a nonphysical envelope function. It has the potential to provide an unprecedented two- and three-dimensional modeling capability for millimeter-scale integrated-optical circuits with submicrometer engineered inhomogeneities. PMID:19802177

Joseph, R M; Goorjian, P M; Taflove, A

1993-04-01

45

Discrete solitons and vortices on two-dimensional lattices of 𝒫𝒯 -symmetric couplers

NASA Astrophysics Data System (ADS)

We introduce a 2D network built of $\\mathcal{PT}$-symmetric dimers with on-site cubic nonlinearity, the gain and loss elements of the dimers being linked by parallel square-shaped lattices. The system may be realized as a set of $\\mathcal{PT}$-symmetric dual-core waveguides embedded into a photonic crystal. The system supports $\\mathcal{PT}$-symmetric and antisymmetric fundamental solitons (FSs) and on-site-centered solitary vortices (OnVs). Stability of these discrete solitons is the central topic of the consideration. Their stability regions in the underlying parameter space are identified through the computation of stability eigenvalues, and verified by direct simulations. Symmetric FSs represent the system's ground state, being stable at lowest values of the power, while anti-symmetric FSs and OnVs are stable at higher powers. Symmetric OnVs, which are also stable at lower powers, are remarkably robust modes: on the contrary to other PT-symmetric states, unstable OnVs do not blow up, but spontaneously rebuild themselves into stable FSs.

Chen, Zhaopin; Liu, Jingfeng; Fu, Shenhe; Li, Yongyao; Malomed, Boris A.

2014-12-01

46

Discrete solitons and vortices on two-dimensional lattices of -symmetric couplers.

We introduce a 2D network built of -symmetric dimers with on-site cubic nonlinearity, the gain and loss elements of the dimers being linked by parallel square-shaped lattices. The system may be realized as a set of -symmetric dual-core waveguides embedded into a photonic crystal. The system supports -symmetric and antisymmetric fundamental solitons (FSs) and on-site-centered solitary vortices (OnVs). Stability of these discrete solitons is the central topic of the consideration. Their stability regions in the underlying parameter space are identified through the computation of stability eigenvalues, and verified by direct simulations. Symmetric FSs represent the system's ground state, being stable at lowest values of the power, while anti-symmetric FSs and OnVs are stable at higher powers. Symmetric OnVs, which are also stable at lower powers, are remarkably robust modes: on the contrary to other -symmetric states, unstable OnVs do not blow up, but spontaneously rebuild themselves into stable FSs. PMID:25606899

Chen, Zhaopin; Liu, Jingfeng; Fu, Shenhe; Li, Yongyao; Malomed, Boris A

2014-12-01

47

Dark (bright) steady-state spatial solitons are predicted in one dimension for a series circuit consisting of two photorefractive crystals of which at least one must be photovoltaic. Each crystal can support a spatial soliton. The two solitons are known collectively as a separate spatial soliton pair with three types: bright–bright, bright–dark and dark–dark. In the limit in which the spatial

Jinsong Liu

2002-01-01

48

We address the problem of directional mobility of discrete solitons in two-dimensional rectangular lattices, in the framework of a discrete nonlinear Schrödinger model with saturable on-site nonlinearity. A numerical constrained Newton-Raphson method is used to calculate two-dimensional Peierls-Nabarro energy surfaces, which describe a pseudopotential landscape for the slow mobility of coherent localized excitations, corresponding to continuous phase-space trajectories passing close to stationary modes. Investigating the two-parameter space of the model through independent variations of the nonlinearity constant and the power, we show how parameter regimes and directions of good mobility are connected to the existence of smooth surfaces connecting the stationary states. In particular, directions where solutions can move with minimum radiation can be predicted from flatter parts of the surfaces. For such mobile solutions, slight perturbations in the transverse direction yield additional transverse oscillations with frequencies determined by the curvature of the energy surfaces, and with amplitudes that for certain velocities may grow rapidly. We also describe how the mobility properties and surface topologies are affected by inclusion of weak lattice anisotropy. PMID:21517610

Naether, Uta; Vicencio, Rodrigo A; Johansson, Magnus

2011-03-01

49

NASA Astrophysics Data System (ADS)

We introduce a system with competing self-focusing (SF) and self-defocusing (SDF) terms, which have the same scaling dimension. In the one-dimensional (1D) system, this setting is provided by a combination of the SF cubic term multiplied by the delta function ? (x) and a spatially uniform SDF quintic term. This system gives rise to the most general family of 1D Townes solitons, with the entire family being unstable. However, it is completely stabilized by a finite-width regularization of the ? function. The results are produced by means of numerical and analytical methods. We also consider the system with a symmetric pair of regularized ? functions, which gives rise to a wealth of symmetric, antisymmetric, and asymmetric solitons, linked by a bifurcation loop, that accounts for the breaking and restoration of the symmetry. Soliton families in two-dimensional (2D) versions of both the single- and double-?-functional systems are also studied. The 1D and 2D settings may be realized for spatial solitons in optics and in Bose-Einstein condensates.

Viet Hung, Nguyen; Trippenbach, Marek; Infeld, Eryk; Malomed, Boris A.

2014-08-01

50

Incoherent spatial solitons in nematic liquid crystals

Spatial solitons are generated in nematic liquid crystals taking\\u000a advantage of their reorientational response with increase in refractive\\u000a index. Such response is saturable and can therefore prevent\\u000a Filamentation even in the fully three-dimensional case. To sustain a\\u000a soliton, a linearly polarized optical field exerts a torque on the\\u000a (pre-aligned) induced molecular dipoles of a positive uniaxial liquid\\u000a crystal, orienting them

Marco Peccianti; Antonio DeLuca; Gaetano Assanto

2001-01-01

51

NASA Astrophysics Data System (ADS)

We propose a simple and straightforward method to generate spatially variant lattice structures by optical interference lithography method. Using this method, it is possible to independently vary the orientation and period of the two-dimensional lattice. The method consists of two steps which are: numerical synthesis of corresponding phase mask by employing a two-dimensional integrated gradient calculations and experimental implementation of synthesized phase mask by making use of a phase only spatial light modulator in an optical 4f Fourier filtering setup. As a working example, we provide the experimental fabrication of a spatially variant square lattice structure which has the possibility to guide a Gaussian beam through a 90° bend by photonic crystal self-collimation phenomena. The method is digitally reconfigurable, is completely scalable, and could be extended to other kind of lattices as well.

Kumar, Manish; Joseph, Joby

2014-08-01

52

We consider the existence, stability and dynamics of the nodeless state and fundamental nonlinear excitations, such as vortices, for a quasi-two-dimensional polariton condensate in the presence of pumping and nonlinear damping. We find a series of interesting features that can be directly contrasted to the case of the typically energy-conserving ultracold alkali-atom Bose-Einstein condensates (BECs). For sizeable parameter ranges, in line with earlier findings, the nodeless state becomes unstable towards the formation of stable nonlinear single or multi-vortex excitations. The potential instability of the single vortex is also examined and is found to possess similar characteristics to those of the nodeless cloud. We also report that, contrary to what is known, e.g., for the atomic BEC case, stable stationary gray ring solitons (that can be thought of as radial forms of Nozaki-Bekki holes) can be found for polariton condensates in suitable parametric regimes. In other regimes, however, these may also suffer symmetry-breaking instabilities. The dynamical, pattern-forming implications of the above instabilities are explored through direct numerical simulations and, in turn, give rise to waveforms with triangular or quadrupolar symmetry. PMID:24674920

Rodrigues, A S; Kevrekidis, P G; Carretero-González, R; Cuevas-Maraver, J; Frantzeskakis, D J; Palmero, F

2014-04-16

53

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 [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2013-05-15

54

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

55

Subwavelength spatial solitons in inhomogeneous Kerr media

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

56

Impaired spatial selectivity and intact phase precession in two-dimensional virtual reality.

During real-world (RW) exploration, rodent hippocampal activity shows robust spatial selectivity, which is hypothesized to be governed largely by distal visual cues, although other sensory-motor cues also contribute. Indeed, hippocampal spatial selectivity is weak in primate and human studies that use only visual cues. To determine the contribution of distal visual cues only, we measured hippocampal activity from body-fixed rodents exploring a two-dimensional virtual reality (VR). Compared to that in RW, spatial selectivity was markedly reduced during random foraging and goal-directed tasks in VR. Instead we found small but significant selectivity to distance traveled. Despite impaired spatial selectivity in VR, most spikes occurred within ?2-s-long hippocampal motifs in both RW and VR that had similar structure, including phase precession within motif fields. Selectivity to space and distance traveled were greatly enhanced in VR tasks with stereotypical trajectories. Thus, distal visual cues alone are insufficient to generate a robust hippocampal rate code for space but are sufficient for a temporal code. PMID:25420065

Aghajan, Zahra M; Acharya, Lavanya; Moore, Jason J; Cushman, Jesse D; Vuong, Cliff; Mehta, Mayank R

2015-01-01

57

Quantized quasi-two-dimensional Bose-Einstein condensates with spatially modulated nonlinearity

We investigate the localized nonlinear matter waves of the quasi-two-dimensional Bose-Einstein condensates with spatially modulated nonlinearity in the harmonic potential. It is shown that all of the Bose-Einstein condensates, similar to the linear harmonic oscillator, can have an arbitrary number of localized nonlinear matter waves with discrete energies, which are mathematically exact orthogonal solutions of the Gross-Pitaevskii equation. Their properties are determined by the principal quantum number n and secondary quantum number l: the parity of the matter wave functions and the corresponding energy levels depend only on n, and the numbers of density packets for each quantum state depend on both n and l, which describe the topological properties of the atom packets. We also give an experimental protocol to observe these phenomena in future experiments.

Wang Dengshan; Hu Xinghua; Liu, W. M. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Hu Jiangping [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States)

2010-02-15

58

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. PMID:21712569

Foldes, S T; Taylor, D M

2011-08-01

59

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

60

On two-dimensional temporal modes in spatially evolving open flows: the flat-plate boundary layer

Temporal linear stability modes depending on two space directions are computed for a two-dimensional boundary-layer flow along a flat plate. The spatial structure of each individual temporally stable mode is shown to be reminiscent of the spatial exponential growth of perturbations along the flat plate, as predicted by local analyses. It is shown using an optimal temporal growth analysis, that

Uwe Ehrenstein; François Gallaire

2005-01-01

61

ERIC Educational Resources Information Center

We investigated whether and how student performance on three types of spatial cognition tasks differs when worked with two-dimensional or stereoscopic representations. We recruited nineteen middle school students visiting a planetarium in a large Midwestern American city and analyzed their performance on a series of spatial cognition tasks in…

Price, Aaron; Lee, Hee-Sun

2010-01-01

62

It is commonly known that two-dimensional mean-field models of optical and matter waves with cubic self-attraction cannot produce stable solitons in free space because of the occurrence of collapse in the same setting. By means of numerical analysis and variational approximation, we demonstrate that the two-component model of the Bose-Einstein condensate with the spin-orbit Rashba coupling and cubic attractive interactions gives rise to solitary-vortex complexes of two types: semivortices (SVs, with a vortex in one component and a fundamental soliton in the other), and mixed modes (MMs, with topological charges 0 and ±1 mixed in both components). These two-dimensional composite modes can be created using the trapping harmonic-oscillator (HO) potential, but remain stable in free space, if the trap is gradually removed. The SVs and MMs realize the ground state of the system, provided that the self-attraction in the two components is, respectively, stronger or weaker than the cross attraction between them. The SVs and MMs which are not the ground states are subject to a drift instability. In free space (in the absence of the HO trap), modes of both types degenerate into unstable Townes solitons when their norms attain the respective critical values, while there is no lower existence threshold for the stable modes. Moving free-space stable solitons are also found in the present non-Galilean-invariant system, up to a critical velocity. Collisions between two moving solitons lead to their merger into a single one. PMID:24730926

Sakaguchi, Hidetsugu; Li, Ben; Malomed, Boris A

2014-03-01

63

We investigate exact nonlinear matter wave functions with odd and even parities in the framework of quasi-two-dimensional Bose-Einstein condensates (BECs) with spatially modulated cubic-quintic nonlinearities and harmonic potential. The existence condition for these exact solutions requires that the minimum energy eigenvalue of the corresponding linear Schroedinger equation with harmonic potential is the cutoff value of the chemical potential {lambda}. The competition between two-body and three-body interactions influences the energy of the localized state. For attractive two-body and three-body interactions, the larger the matter wave order number n, the larger the energy of the corresponding localized state. A linear stability analysis and direct simulations with initial white noise demonstrate that, for the same state (fixed n), increasing the number of atoms can add stability. A quasi-stable ground-state matter wave is also found for repulsive two-body and three-body interactions. We also discuss the experimental realization of these results in future experiments. These results are of particular significance to matter wave management in higher-dimensional BECs. - Highlights: > 2D Bose-Einstein condensates (BECs) with spatially modulated cubic-quintic nonlinearities and the harmonic potential are discussed. > 2D exact quantized nonlinear matter wave functions with the odd and even parities are obtained. > The 2D ground-state matter wave with attractive two-body and repulsive three-body interactions is stable. > Experimental realization of our results in future experiments is proposed.

Dai Chaoqing, E-mail: dcq424@126.com [School of Sciences, Zhejiang A and F University, Lin'an, Zhejiang 311300 (China); Wang Dengshan [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang Liangliang [Institute of Nonlinear Physics, Zhejiang Normal University, Jinhua, Zhejiang, 321004 (China); Zhang Jiefang [Institute of Nonlinear Physics, Zhejiang Normal University, Jinhua, Zhejiang, 321004 (China); Zhejiang University of Media and Communications, Hangzhou 310018, Zhejiang (China); Liu, W.M. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2011-09-15

64

Very high spatial resolution two-dimensional solar spectroscopy with video CCDs

NASA Technical Reports Server (NTRS)

We have developed techniques for recording and reducing spectra of solar fine structure with complete coverage of two-dimensional areas at very high spatial resolution and with a minimum of seeing-induced distortions. These new techniques permit one, for the first time, to place the quantitative measures of atmospheric structure that are afforded only by detailed spectral measurements into their proper context. The techniques comprise the simultaneous acquisition of digital spectra and slit-jaw images at video rates as the solar scene sweeps rapidly by the spectrograph slit. During data processing the slit-jaw images are used to monitor rigid and differential image motion during the scan, allowing measured spectrum properties to be remapped spatially. The resulting quality of maps of measured properties from the spectra is close to that of the best filtergrams. We present the techniques and show maps from scans over pores and small sunspots obtained at a resolution approaching 1/3 arcsec in the spectral region of the magnetically sensitive Fe I lines at 630.15 and 630.25 nm. The maps shown are of continuum intensity and calibrated Doppler velocity. More extensive spectral inversion of these spectra to yield the strength of the magnetic field and other parameters is now underway, and the results of that analysis will be presented in a following paper.

Johanneson, A.; Bida, T.; Lites, B.; Scharmer, G. B.

1992-01-01

65

Single-atom interferometer based on two-dimensional spatial adiabatic passage

NASA Astrophysics Data System (ADS)

In this work, we propose a single-atom interferometer based on a fully two-dimensional spatial adiabatic passage process using a system of three identical harmonic traps in a triangular geometry. While the transfer of a single atom from the ground state of one trap to the ground state of the most distant one can successfully be achieved in a robust way for a broad range of parameter values, we point out the existence of a specific geometrical configuration of the traps for which a crossing of two energy eigenvalues occurs and the transfer of the atom fails. Instead, the wave function is robustly split into a coherent superposition between two of the traps. We show that this process can be used to construct a single-atom interferometer and discuss its performance in terms of the final population distribution among the asymptotic eigenstates of the individual traps. This interferometric scheme could be used to study space-dependent fields from ultrashort to relatively large distances, or the decay of the coherence of superposition states as a function of the distance.

Menchon-Enrich, R.; McEndoo, S.; Busch, Th.; Ahufinger, V.; Mompart, J.

2014-05-01

66

Combined Akhmediev breather and Kuznetsov–Ma solitons in a two-dimensional graded-index waveguide

NASA Astrophysics Data System (ADS)

We study the (2 + 1)-dimensional coupled nonlinear Schrödinger equation with variable coefficients in a graded-index waveguide, and present a combined Akhmediev breather and Kuznetsov–Ma soliton solution with nonautonomous characteristics for certain functional relations. From this solution, by modulating the relation between the maximum effective propagation distance Zmax and the periodic locations Zm based on the maximum amplitude of soliton solution, different types of controllable excitation behaviors such as limitation excitation, maintenance and postponement are demonstrated.

Zhu, Hai-Ping; Pan, Zhen-Huan

2014-04-01

67

Two-dimensional spatial-discretization methods on a Lagrangian mesh

Methods for efficiently solving the two-dimensional multigroup transport equation for orthogonal (x,y) or (r,z) geometries are generally well-developed. The extension to regular triangular meshes in (x,y) and (r,z) geometries has been done. However, some complex geometries cannot be accurately described with these methods. Furthermore, it is often desirable to couple neutronics with hydrodynamics calculations. It is desirable to perform the neutronics calculations directly on a distorted Lagrangian mesh, rather than mapping the material properties onto an orthogonal mesh. This paper will describe some of the Los Alamos work on solving the transport equation on an arbitrary Lagrangian mesh, with emphasis on the spatial differencing schemes used. The angular variable is treated by the standard discrete-ordinates approximation, using the diamond-difference approximation for curved geometry. Before the calculation is begun, a large (packed) ordering array of size: (number of spatial mesh cell x number of discrete-ordinates directions) is computed to specify the order of sweeping the mesh cells for each direction. This can be done in a very efficient fashion for near-spherical meshes. By writing a conservation equation for each triangular or quadrilateral mesh cell, and using additional diamond-difference-like relationships, depending upon the number of sides visible, an equation for the cell-centered angular flux can be derived. This scheme suffers from the same difficulties as the standard diamond difference in orthogonal geometries, in addition to other deficiencies unique to Lagrangian meshes. Schemes for fix-ups of negative fluxes and boomerangs will be described. Two temporary triangular subzoning schemes will be outlined.

Hill, T.R.; Paternoster, R.R.

1982-01-01

68

nonlinear matter waves of the quasi-two-dimensional Bose-Einstein condensates with spatially modulated to the linear harmonic oscillator, can have an arbitrary number of localized nonlinear matter waves of the matter wave functions and the corresponding energy levels depend only on n, and the numbers of density

Hu, Jiangping

69

NASA Astrophysics Data System (ADS)

A photovoltaic dark spatial soliton is generated in a planar waveguide produced by the implantation of protons into a copper-doped lithium niobate crystal. Stationary soliton regimes are achieved at powers 90 and 30 ?W at wavelengths 633 and 532 nm, respectively.

Kruglov, V. G.; Shandarov, V. M.; Tan, Ya; Chen, F.; Kip, D.

2008-11-01

70

Dark spatial solitons splitting in logarithmically saturable nonlinear media

NASA Astrophysics Data System (ADS)

We numerically simulate the evolution of the dark-notch-bearing optical beam in the logarithmically saturable nonlinear media based on beam propagation method (BPM). The simulation results indicate that the multiple dark spatial solitons are deep, possible in this type of nonlinear media. The number of multiple dark spatial solitons depends on the width of the dark notch, the initial conditions and the peak intensity of the initial input beam. Under the odd and even initial conditions, the odd and even number sequence of multiple dark spatial solitons can be obtained, respectively. For an input beam with fixed optical intensity, the number of dark solitons increases with the width of the initial input dark notch. The behavior of the multiple dark solitons in this type of media is similar to that in a photorefractive nonlinear crystal.

Zhang, Yuhong; Liu, Baoyuan; Lu, Keqing; Liu, Wangyun; Han, Jun

2014-12-01

71

NASA Astrophysics Data System (ADS)

This work presents advances on error estimation of three spatial approximations of the Discrete Ordinates (DO) method for solving the neutron transport equation. The three methods considered are the Diamond Difference (DD) method, the Arbitrarily High Order Transport method of the Nodal type (AHOT-N), and of the Characteristic type (AHOT-C). The AHOT-N method is employed in constant, linear, quadratic and cubic orders of spatial approximation. The AHOT-C is used in constant, linear and quadratic approximations. Error norms for different problems in non-scattering or isotropic scattering media over two dimensional Cartesian geometries are evaluated. The problems are characterized with different levels of differentiability of the exact solution of the DO equations. The cell-wise error is computed as the difference between the cell-averaged flux calculated by each method and the cell-averaged exact value. The cell error values are used to determine L1, L2, and Linfinity discrete error norms. The results of this analysis demonstrate that while integral error norms, i.e. L1 and L 2, converge to zero with mesh refinement, the cell-wise, Linfinity, norm may not converge when the exact flux possesses discontinuities across the Singular Characteristic (SC). The results suggest that smearing (numerical diffusion) across the SC is the major source of error on the global scale. To mitigate the adverse effect of the smearing, we propose a new Singular Characteristic Tracking (SCT) algorithm which achieves cell-wise convergence even for the cases with discontinuous exact flux. Convergence is restored by hindering numerical diffusion across the SC when resolving the streaming operator in the standard inner sweep iterations. SCT solves two separate Step Characteristics stencils for two sub-cell defined by the intersection of the SC with a mesh cell. Compared to the standard DD, DD-SCT increases the L1 error norm rate of convergence (based on cell size) from 0.5 to 2 for uncollided discontinuous exact flux, and from 0.3 to 1.3 for discontinuous exact flux with isotropic scattering. To provide a confidence level to the spatial resolution of the DO equations, we have casted the AHOT-N method as a Discontinuous Petrov-Galerkin method. Within the mathematical framework of Finite Element Methods (FEM), we have derived an a posteriori error estimator that furnishes a bound on the global L2 error norm. When sufficient regularity is assumed of the adjoint solution, the error estimator is written as a function of the numerical solution's volume and surface residuals, and cell edges discontinuities, for which we present easily computable approximations. As a direct application of decomposing the global error norm estimator into local indicators, we have tested an Adaptive Mesh Refinement (AMR) strategy to enhance computational efficiency without compromising accuracy. In a Shielding Benchmark problem, we show that for the same level of tolerance in the L2 error norm, we can decrease the required number of unknowns (degrees of freedom) by a factor of 10 when comparing AMR to uniform refinement.

Duo, Jose Ignacio

2008-10-01

72

Photorefractive spatial solitons as waveguiding elements for optical telecommunication

NASA Astrophysics Data System (ADS)

Spatial solitons permit optical waveguiding. This holds true for the soliton write beam (i.e. the driving laser beam), as well as for additional probe beams, which may carry optically encoded information. This feature of spatial solitons is of significant interest for applications in optical telecommunication. We present systematic experimental investigations on single and multiple spatial solitons in the infrared spectral regime (i.e. around optical telecommunication wavelengths), applied as controllable all-optical devices. In particular, we present the implementations of a Y-coupler as an optical signal divider, a switchable Y-coupler as an optical add multiplexer, and a novel design for a 1 × 3 optical beam switch, i.e. applied as a router for infrared signal beams. We report large waveguiding efficiencies up to 40% and transmission rates of 90 Tbit/s in our setups. The presented experimental data are confirmed by numerical simulations.

Tiemann, M.; Halfmann, T.; Tschudi, T.

2009-09-01

73

Two-dimensional (2D) optimal filter for highly nonstationary 2D signal estimation is developed. It is based on the real-time results of space\\/spatial-fre quency (S\\/SF) analysis, on the correspondence of filter's region of support (FRS) to the signal's local frequency (LF) and on the real time LF estimation algorithm, also proposed in this paper. The filter permits multiple FRS detection in the

Veselin N. Ivanovic; Nevena Radovic; Srdjan Jovanovski

2011-01-01

74

Spatial distributions of sputtered particles during the dc planar magnetron sputtering of indium-tin-oxide (ITO) target in 5 mTorr Ar\\/O2 were measured by two-dimensional optical emission spectroscopy (2D-OES) and laser induced fluorescence spectroscopy (2D-LIF). Absolute number density of sputtered In atoms was determined by calibrating the LIF signal with Rayleigh scattering signal from Ar. The flux of atomic species onto the

Y. Matsuda; M. Muta; H. Fujiyama

1999-01-01

75

NASA Astrophysics Data System (ADS)

A new two dimensional codes family, namely two dimensional multi-diagonal (2D-MD) codes, is proposed for spectral/spatial non-coherent OCDMA systems based on the one dimensional MD code. Since the MD code has the property of zero cross correlation, the proposed 2D-MD code also has this property. So that, the multi-access interference (MAI) is fully eliminated and the phase induced intensity noise (PIIN) is suppressed with the proposed code. Code performance is analyzed in terms of bit error rate (BER) while considering the effect of shot noise, PIIN, and thermal noise. The performance of the proposed code is compared with the related MD, modified quadratic congruence (MQC), two dimensional perfect difference (2D-PD) and two dimensional diluted perfect difference (2D-DPD) codes. The analytical and the simulation results reveal that the proposed 2D-MD code outperforms the other codes. Moreover, a large number of simultaneous users can be accommodated at low BER and high data rate.

Kadhim, Rasim Azeez; Fadhil, Hilal Adnan; Aljunid, S. A.; Razalli, Mohamad Shahrazel

2014-10-01

76

Waveguides formed by quasi-steady-state photorefractive spatial solitons

NASA Astrophysics Data System (ADS)

We show that a quasi-steady-state photorefractive spatial soliton forms a waveguide structure in the bulk of a photorefractive material. Although the optically induced waveguide is formed by a very low-power (microwatts) soliton beam, it can guide a powerful (watt) beam of a longer wavelength at which the medium is nonphotosensitive. Furthermore, the waveguide survives, either in the dark or when guiding the longer-wavelength beam, for a long time after the soliton beam is turned off. We take advantage of the solitons' property of evolution from a relatively broad input beam into a narrow channel and show that the soliton induces a tapered waveguide (an optical funnel) that improves the coupling efficiency of light into the waveguiding structure.

Morin, Matthew; Duree, Galen; Salamo, Gregory; Segev, Mordechai

1995-10-01

77

Interactions of spatial solitons with fused couplers

NASA Astrophysics Data System (ADS)

We study dynamical and stationary states of solitons in dual-core waveguides which are locally coupled (fused) at one or several short segments. The model applies to planar optical waveguides, and to Bose-Einstein condensate in dual traps. Collisions of an incident soliton with single and double locally fused couplers are investigated by means of systematic simulations and several analytical methods (quasilinear, fast-soliton, and adiabatic approximations). Excitation dynamics of a soliton trapped by a local coupler is studied by means of the variational approximation, and verified by simulations. Shuttle motion of a soliton trapped in a cavity between two local couplers, and in a finite array of couplers, is studied too.

Harel, Alon; Malomed, Boris A.

2014-04-01

78

Spatial solitons and instabilities in nonlinear optical media

NASA Astrophysics Data System (ADS)

Optics has the intrinsic capability of dramatically improving the fundamental performance of computers. Because silicon-based computing is expected to approach its technological limits in one or two decades, a new computation concept, Solitonic Gateless Computing, has been proposed. This approach is based on the unique collision properties of spatial solitons, i.e. optical beams that propagate without change of shape due to the balance of diffraction and material nonlinearity. Spatial solitons have commanded a great deal of attention because of their unusual physical properties, such as their remarkable stability and particle-like behavior upon collisions. A detailed investigation of various existing and new classes of solitons is important in order to assess their value for computing and other applications. The investigation of instabilities of solitons is also critical. For example, polarization instability can limit the stability of various solitons against polarization fluctuations. On the other hand, seeding with an interference pattern can generate via modulational instabilities a periodic array of spatial solitons, a feature that could be used for computing. In this dissertation, the construction, optimization and full characterization of a versatile tunable picosecond light source for soliton studies-an optical parametric generator-amplifier is described first. Subsequently, spatial noise initiated modulational instability (MI) in media with Kerr (third-order) and quadratic (second-order) nonlinearities in a one dimensional geometry, i.e. slab waveguides, is investigated and the results are compared to analytical theories and numerical simulations. Seeded MI is also studied and the MI gain was measured in lithium niobate waveguides with a quadratic nonlinearity. A closely related phenomenon, fission into multiple solitons, was observed in both lithium niobate waveguides at 1.32 microns and periodically poled lithium niobate waveguides at 1.58 microns. The interaction between birefringence and Kerr nonlinearity leads ultimately to a polarization instability that places an upper limit on the intensity of Kerr and Vector solitons. This effect was investigated experimentally and numerically in aluminum gallium arsenide waveguides. Lastly, the generation and properties of Type I quadratic solitons, that contain two frequency components and form an especially rich family, in bulk non-critically phase- matched potassium niobate is reported.

Malendevich, Roman

2001-11-01

79

NASA Astrophysics Data System (ADS)

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:LiNbO3 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.

Frolova, M. N.; Borodin, M. V.; Shandarov, S. M.; Shandarov, V. M.; Larionov, Yu M.

2003-11-01

80

What types of spatial soliton can be formed based on two-photon-isomerisation?

NASA Astrophysics Data System (ADS)

In this paper we answer the question: “what types of spatial soliton can be formed based on two-photon-isomerisation (TPI)”. The conclusion that anti-dark solitons are not supported by monotonic nonlinearity should cast light on the notion of fundamental spatial solitons. The idea to obtain a bright TPI soliton with the joining of a background light or with the coupling of a dark soliton offers new schemes of light-controlling-light.

Liang, J. C.; Cai, Z. B.; Sun, Y. Z.; Yi, L.; Wang, H. C.

2009-12-01

81

Oscillation modes of Spatial Soliton Arrays in Waveguides with Nonlinear Boundaries Jacob Scheuer-4-8294641, Fax. 972-4-8323041, E-mail: scheuerj@tx.technion.ac.il Propagation of arrays of spatial soliton;Oscillation modes of Spatial Soliton Arrays in Waveguides with Nonlinear Boundaries Jacob Scheuer and Meir

Scheuer, Jacob (Koby)

82

NASA Astrophysics Data System (ADS)

A new class of nuclear magnetic resonance (NMR) pulses that provides simultaneous spatially selective inversion of nuclear spins in two dimensions following a single pulse application is described and demonstrated. The two-dimensional selective pulses consist of a single square- or amplitude-modulated ? rf pulse applied in the presence of an amplitude-modulated magnetic field gradient that reorients through the two dimensions during the rf pulse. For example, square and Gaussian rf pulses produce sharply peaked sombrero-, egg-carton-, and stalagmite-shaped profiles of spin inversion in the xz plane when applied in the presence of a gradient that rotates or describes a figure eight in the xz plane. The theoretical profiles, computed by numerical integration of the Bloch equation, are in good agreement with experimental results obtained by incorporating the pulses into a conventional NMR imaging sequence. The pulses are directly applicable to restricted field-of-view high-resolution imaging for the amelioration of aliasing signal artifacts, and when combined with one-dimensional localized phosphorus (31P) chemical shift spectroscopy techniques that employ surface detection coils, should permit complete three-dimensionally localized 31P NMR spectroscopy. The ? pulses provide similar two-dimensional spatial selectivity of the transverse nuclear magnetization when used for refocusing Hahn spin echoes.

Bottomley, Paul A.; Hardy, Christopher J.

1987-11-01

83

Two-dimensional periodic and quasiperiodic spatial structures in microchip laser resonator

The spatially periodic 2D patterns at output mirror of solid state microchip laser with high Fresnel number (100-1000) are discussed in view of numerical modeling with split-step FFT code comprising nonlinear gain, relaxation of inversion and paraxial diffraction.

Okulov, A Yu

2014-01-01

84

Noncoherent Spatial/Spectral Optical CDMA System With Two-Dimensional Perfect Difference Codes

NASA Astrophysics Data System (ADS)

In this paper, the family of newly constructed codes, named 2-D perfect difference codes, is proposed to suppress the phase-induced intensity noise (PIIN) in noncoherent spatial/spectral optical code division multiple access (OCDMA) systems. A novel spatial/spectral transceiver structure employing the new codes to eliminate the multiuser interference (MUI) by using the MUI cancellation property of the new codes is also presented. Compared with the systems employing modified quadratic congruence codes (MQC codes) and maximal-area matrices codes (M-matrices codes), numerical results verify that our proposed system can more effectively suppress the PIIN and eliminate MUI. Hence, the number of simultaneous users and total transmission rate increase significantly.

Lin, Cheing-Hong; Wu, Jingshown; Yang, Chun-Liang

2005-12-01

85

This work presents advances on error estimation of three spatial approximations of the Discrete Ordinates (DO) method for solving the neutron transport equation. The three methods considered are the Diamond Difference (DD) method, the Arbitrarily High Order Transport method of the Nodal type (AHOT-N), and of the Characteristic type (AHOT-C). The AHOT-N method is employed in constant, linear, quadratic and

Jose Ignacio Duo

2008-01-01

86

Metamaterials for remote generation of spatially controllable two dimensional array of microplasma.

Since the initial demonstration of negative refraction and cloaking using metamaterials, there has been enormous interest and progress in making practical devices based on metamaterials such as electrically small antennas, absorbers, modulators, detectors etc that span over a wide range of electromagnetic spectrum covering microwave, terahertz, infrared (IR) and optical wavelengths. We present metamaterial as an active substrate where each unit cell serves as an element for generation of plasma, the fourth state of matter. Sub-wavelength localization of incident electromagnetic wave energy, one of the most interesting properties of metamaterials is employed here for generating high electric field to ignite and sustain microscale plasmas. Frequency selective nature of the metamaterial unit cells make it possible to generate spatially localized microplasma in a large array using multiple resonators. A dual resonator topology is shown for the demonstration. Since microwave energy couples to the metamaterial through free space, the proposed approach is naturally wireless. Such spatially controllable microplasma arrays provide a fundamentally new material system for future investigations in novel applications, e.g. nonlinear metamaterials. PMID:25098976

Singh, Pramod K; Hopwood, Jeffrey; Sonkusale, Sameer

2014-01-01

87

Metamaterials for Remote Generation of Spatially Controllable Two Dimensional Array of Microplasma

Since the initial demonstration of negative refraction and cloaking using metamaterials, there has been enormous interest and progress in making practical devices based on metamaterials such as electrically small antennas, absorbers, modulators, detectors etc that span over a wide range of electromagnetic spectrum covering microwave, terahertz, infrared (IR) and optical wavelengths. We present metamaterial as an active substrate where each unit cell serves as an element for generation of plasma, the fourth state of matter. Sub-wavelength localization of incident electromagnetic wave energy, one of the most interesting properties of metamaterials is employed here for generating high electric field to ignite and sustain microscale plasmas. Frequency selective nature of the metamaterial unit cells make it possible to generate spatially localized microplasma in a large array using multiple resonators. A dual resonator topology is shown for the demonstration. Since microwave energy couples to the metamaterial through free space, the proposed approach is naturally wireless. Such spatially controllable microplasma arrays provide a fundamentally new material system for future investigations in novel applications, e.g. nonlinear metamaterials. PMID:25098976

Singh, Pramod K.; Hopwood, Jeffrey; Sonkusale, Sameer

2014-01-01

88

Metamaterials for Remote Generation of Spatially Controllable Two Dimensional Array of Microplasma

NASA Astrophysics Data System (ADS)

Since the initial demonstration of negative refraction and cloaking using metamaterials, there has been enormous interest and progress in making practical devices based on metamaterials such as electrically small antennas, absorbers, modulators, detectors etc that span over a wide range of electromagnetic spectrum covering microwave, terahertz, infrared (IR) and optical wavelengths. We present metamaterial as an active substrate where each unit cell serves as an element for generation of plasma, the fourth state of matter. Sub-wavelength localization of incident electromagnetic wave energy, one of the most interesting properties of metamaterials is employed here for generating high electric field to ignite and sustain microscale plasmas. Frequency selective nature of the metamaterial unit cells make it possible to generate spatially localized microplasma in a large array using multiple resonators. A dual resonator topology is shown for the demonstration. Since microwave energy couples to the metamaterial through free space, the proposed approach is naturally wireless. Such spatially controllable microplasma arrays provide a fundamentally new material system for future investigations in novel applications, e.g. nonlinear metamaterials.

Singh, Pramod K.; Hopwood, Jeffrey; Sonkusale, Sameer

2014-08-01

89

NASA Astrophysics Data System (ADS)

Two-dimensional steady groundwater flow in a confined aquifer with spatially variable transmissivity T is analyzed stochastically using spectral analysis and the theory of intrinsic random functions. Conditions that ensure a stationary (statistically homogeneous) head process are derived, and using two convenient forms for the covariance function of the ln T process, the head covariance function is studied. In addition, the head variogram is obtained for a particular nonstationary case, and the asymptotic head variogram is derived under very general conditions. Results are compared to those obtained by Gelhar (1976) for one- and two-dimensional phreatic flow and Bakr et al. (1978) for one- and three-dimensional confined flow. Multidimensional flow analysis results in a significantly reduced head variance. The head correlation remains high over much greater distances than the ln T correlation. The variogram obtained when stationary heads are assumed is identical to that obtained for nonstationary heads for dimensionless lag distances up to 2½ times the correlation scale of the log transmissivity. The variogram for nonstationary heads continues to grow logarithmically as lag distance increases, independent of the form of the input covariance in the nonstationary case. The conditions for stationarity are contrasted with the corresponding results obtained for the one- and three-dimensional cases of Gutjahr and Gelhar (1981). The head variance calculated from the stationary theory is found to agree with that of previous Monte Carlo simulations.

Mizell, Steve A.; Gutjahr, Allan L.; Gelhar, Lynn W.

1982-08-01

90

MR thermometry can be a very challenging application, as good resolution may be needed along spatial, temporal as well as temperature axes. Given that the heated foci produced during thermal therapies are typically much smaller than the anatomy being imaged, much of the imaged FOV is not actually being heated and may not require temperature monitoring. In the present work, many-fold improvements were obtained in terms of temporal resolution and/or 3D spatial coverage by sacrificing some of the in-plane spatial coverage. To do so, three fast-imaging approaches were jointly implemented with a spoiled gradient echo sequence: 1) two-dimensional spatially-selective RF excitation, 2) unaliasing by Fourier-encoding the overlaps using the temporal dimension (UNFOLD), and 3) parallel imaging. The sequence was tested during experiments with focused ultrasound heating in ex-vivo tissue and a tissue-mimicking phantom. Temperature maps were estimated from phase-difference images based on the water proton resonance frequency shift. Results were compared to those obtained from a spoiled gradient echo sequence, using a t-test. Temporal resolution was increased by 24-fold, with temperature uncertainty less than 1°C, while maintaining accurate temperature measurements (mean difference between measurements, as observed in gel, = 0.1°C ± 0.6; R = 0.98; P > 0.05). PMID:21337421

Mei, Chang-Sheng; Panych, Lawrence P.; Yuan, Jing; McDannold, Nathan J.; Treat, Lisa H.; Jing, Yun; Madore, Bruno

2011-01-01

91

Splitting after collision of high-order bright spatial solitons in Kerr media.

By numerically studying the collision between (1 + 1)-Dimensional high order bright spatial solitons in a Kerr nonlinear media we show that after the collision, the high order solitons split into a number of first order solitons that corresponds to its order. Two different collision scenarios are considered: collision between two independent high order solitons and a collision with a virtual soliton simulated by the reflection at an angle of a high order soliton at a linear interface. The results demonstrate that in both cases the high order solitons split showing minor differences. PMID:25607025

Castillo, M D Iturbe; Cerda, S Chavez; Martinez, D Ramirez

2014-12-15

92

Soliton gyroscopes in media with spatially growing repulsive nonlinearity

We find that the recently introduced model of self-trapping supported by a spatially growing strength of a repulsive nonlinearity gives rise to robust vortex-soliton tori, i.e., three-dimensional vortex solitons, with topological charges S. The family with S=1 is completely stable, while the one with S=2 has alternating regions of stability and instability. The families are nearly exactly reproduced in an analytical form by the Thomas-Fermi approximation (TFA). Unstable states with S=2 and 3 split into persistently rotating pairs or triangles of unitary vortices. Application of a moderate torque to the vortex torus initiates a persistent precession mode, with the torus' axle moving along a conical surface. A strong torque heavily deforms the vortex solitons, but, nonetheless, they restore themselves with the axle oriented according to the vectorial addition of angular momenta.

Driben, Rodislav; Malomed, Boris A; Meier, Torsten; Torner, Lluis

2013-01-01

93

We describe the relations between active maintenance of the hand at various positions in a two-dimensional space and the frequency of single cell discharge in motor cortex (n = 185) and area 5 (n = 128) of the rhesus monkey. The steady-state discharge rate of 124/185 (67%) motor cortical and 105/128 (82%) area 5 cells varied with the position in which the hand was held in space ("static spatial effect"). The higher prevalence of this effect in area 5 was statistically significant. In both structures, static effects were observed at similar frequencies for cells that possessed as well as for those that lacked passive driving from the limb. The results obtained by a quantitative analysis were similar for neurons of the two cortical areas studied. It was found that of the neurons with a static effect, the steady-state discharge rate of 78/124 (63%) motor cortical and 63/105 (60%) area 5 cells was a linear function of the position of the hand across the two-dimensional space, so that the neuronal "response surface" was adequately described by a plane (R2 greater than or equal to 0.7, p less than 0.05, F-test in analysis of variance). The preferred orientations of these response planes differed for different cells. These results indicate that individual cells in these areas do not relate uniquely a particular position of the hand in space. Instead, they seem to encode spatial gradients at certain orientations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6723864

Georgopoulos, A P; Caminiti, R; Kalaska, J F

1984-01-01

94

Recent research has shown that KCl:Eu²? has great potential for use in megavoltage radiation therapy dosimetry because this material exhibits excellent storage performance and is reusable due to strong radiation hardness. This work reports the authors' attempts to fabricate 2D KCl:Eu²? storage phosphor films (SPFs) using both a physical vapor deposition (PVD) method and a tape casting method. X-ray diffraction analysis showed that a 10 µm thick PVD sample was composed of highly crystalline KCl. No additional phases were observed, suggesting that the europium activator had been completely incorporated into the KCl matrix. Photostimulated luminescence and photoluminescence spectra suggested that F (Cl(-)) centers were the electron storage centers post x-ray irradiation and that Eu²? cations acted as luminescence centers in the photostimulation process. The 150 µm thick casted KCl:Eu²? SPF showed sub-millimeter spatial-resolution. Monte Carlo simulations further demonstrated that the admixture of 20% KCl:Eu²? and 80% low Z polymer binder exhibited almost no energy-dependence in a 6 MV beam. KCl:Eu²? pellet samples showed a large dynamic range from 0.01 cGy to 60 Gy dose-to-water, and saturated at approximately 500 Gy as a result of KCl's intrinsic high radiation hardness. Taken together, this work provides strong evidence that KCl:Eu²?-based SPF with associated readout apparatus could result in a novel electronic film system that has all the desirable features associated with classic radiographic film and, importantly, water equivalence and the capability of permanent identification of each detector. PMID:24651448

Li, H Harold; Driewer, Joseph P; Han, Zhaohui; Low, Daniel A; Yang, Deshan; Xiao, Zhiyan

2014-04-21

95

This work describes the design and use of an optical apparatus to measure the far-field elastic light-scattering pattern for a single particle over two angular-dimensions. A spatial filter composed of a mirror with a small through-hole is used to enable collection of the pattern uncommonly close to the forward direction; to within tenths of a degree. Minor modifications of the design allow for the simultaneous measurement of a particle's image along with its two-dimensional scattering pattern. Example measurements are presented involving single micrometer-sized glass spherical particles confined in an electrodynamic trap and a dilute suspension of polystyrene latex particles in water. A small forward-angle technique, called Guinier analysis, is used to determine a particle-size estimate directly from the measured pattern without a priori knowledge of the particle refractive index. Comparison of these size estimates to those obtained by fitting the measurements to Mie theory reveals relative errors low as 2%. PMID:20588794

Berg, Matthew J; Hill, Steven C; Videen, Gorden; Gurton, Kristan P

2010-04-26

96

We present a new method for the determination of the two-dimensional (2D) projected spatial distribution of globular clusters (GCs) in external galaxies. This method is based on the K-Nearest Neighbor density estimator of Dressler, complemented by Monte-Carlo simulations to establish the statistical significance of the results. We apply this method to NGC 4261, a ''test galaxy'' where significant 2D anisotropy in the GC distribution has been reported. We confirm that the 2D distribution of GC is not azimuthally isotropic. Moreover, we demonstrate that the 2D distribution departures from the average GC radial distribution results in highly significant spiral-like or broken shell features. Overall, the same perturbations are found in ''red'' and ''blue'' GCs, but with some differences. In particular, we observe a central feature, roughly aligned with the minor axis of NGC 4261, composed of red and most luminous GCs. Blue and fainter GCs are more frequent at large radial distances and follow the spiral-like features of the overall density structure. These results suggest a complex merging history for NGC 4261.

D'Abrusco, R.; Fabbiano, G.; Zezas, A.; Mineo, S.; Fragos, T.; Kim, D.-W. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Strader, J. [Department of Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824-2320 (United States); Bonfini, P. [Physics Department and Institute of Theoretical and Computational Physics, University of Crete, 71003 Heraklion, Crete (Greece); Luo, B. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); King, A. [Department of Physics and Astronomy, University of Leicester, Leicester (United Kingdom)

2013-08-20

97

H NMR resonances of [cyclo (9----18) Lys1, Gly6]bradykinin (CBK) in (CD3)2SO and H2O solution have been assigned by combined analysis of two-dimensional COSY and NOESY spectra. The presence of two slowly interchangeable conformers of CBK in (CD3)2SO is established, the minor conformer not exceeding 15% in the population. The minor conformer is absent from the aqueous solution, chemical shifts of the CBK and bradykinin NH and C alpha H protons differ insignificantly. The major CBK conformer contains at least two X-Pro trans-peptide groups and three amide protons NH Phe5, NH Arg9 and N zeta H Lys1 protected from solvent. A system of cross-peaks from the NOESY spectra of CBK in (CD3)2SO has been analysed and the maximum distance between backbone protons and neighbouring amino acid residues evaluated. The experimental data agree well with the assumed type II beta-bend in the sequence Pro2-Pro3-Gly4-Phe5. Spatial structure models for the backbone fragment 6-9 of CBK containing two intramolecular hydrogen bonds that involve the NH Arg9 and N zeta H Lys1 protons and the carbonyl groups of Phe5 and Gly4 are proposed. PMID:4062989

Saulitis, Iu B; Liepin'sh, E E; Sekatsis, I P; Shenderovich, M D; Mutulis, F K

1985-08-01

98

Controlled transport of matter waves in two-dimensional optical lattices.

We propose a method for achieving dynamically controllable transport of highly mobile matter-wave solitons in a driven two-dimensional optical lattice. Our numerical analysis based on the mean-field model and the theory based on the time-averaging approach demonstrate that a fast time-periodic rocking of the two-dimensional optical lattice enables efficient stabilization and manipulation of spatially localized matter wave packets via induced reconfigurable mobility channels. PMID:20868140

Abdullaev, Jasur; Poletti, Dario; Ostrovskaya, Elena A; Kivshar, Yuri S

2010-08-27

99

Controlled Transport of Matter Waves in Two-Dimensional Optical Lattices

We propose a method for achieving dynamically controllable transport of highly mobile matter-wave solitons in a driven two-dimensional optical lattice. Our numerical analysis based on the mean-field model and the theory based on the time-averaging approach demonstrate that a fast time-periodic rocking of the two-dimensional optical lattice enables efficient stabilization and manipulation of spatially localized matter wave packets via induced reconfigurable mobility channels.

Abdullaev, Jasur; Ostrovskaya, Elena A.; Kivshar, Yuri S. [Nonlinear Physics Centre and ARC Centre of Excellence for Quantum-Atom Optics, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Poletti, Dario [Centre for Quantum Technologies, National University of Singapore, Singapore 117542 (Singapore)

2010-08-27

100

Quantum fluctuations and correlations of spatial scalar or multimode vector solitons in Kerr media

We apply the Green's function method to determine the global degree of squeezing and the transverse spatial distribution of quantum fluctuations of solitons in Kerr media. We show that both scalar bright solitons and multimode vector solitons experience strong squeezing on the optimal quadrature. For vector solitons, this squeezing is shown to result from an almost perfect anti-correlation between the fluctuations on the two incoherently-coupled circular polarisations.

Eric Lantz; Thibaut Sylvestre; Herve Maillote; Nicolas Treps; Claude Fabre

2003-11-13

101

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

102

Controlled Transport of Matter Waves in Two-Dimensional Optical Lattices Jasur Abdullaev,1

Controlled Transport of Matter Waves in Two-Dimensional Optical Lattices Jasur Abdullaev,1 Dario a method for achieving dynamically controllable transport of highly mobile matter-wave solitons in a driven-dimensional optical lattice enables efficient stabilization and manipulation of spatially localized matter wave

103

Beating the spatial standard quantum limits via adiabatic soliton expansion

Spatial quantum enhancement effects are studied under a unified framework. It is shown that the multiphoton absorption rate of photons with a quantum-enhanced lithographic resolution is reduced, not enhanced, contrary to popular belief. The use of adiabatic soliton expansion is proposed to beat the standard quantum limit on the optical beam displacement accuracy, as well as to engineer an arbitrary multiphoton interference pattern for quantum lithography. The proposed scheme provides a conceptually simple method that works for an arbitrary number of photons.

Mankei Tsang

2006-05-09

104

NASA Astrophysics Data System (ADS)

For noninvasive and quantitative measurements of global two-dimensional (2D) heart wall motion, speckle tracking methods have been developed and applied. These methods overcome the limitation of tissue Doppler imaging (TDI), which is susceptible to aliasing, by directly tracking backscattered echoes by pattern matching techniques, i.e., the cross-correlation or the sum of absolute differences, in real time. In these conventional methods, the frame rate (FR) is limited to about 200 Hz, corresponding to the sampling period of 5 ms. However, myocardial function during the isovolumic contraction period obtained by these conventional speckle tracking methods remains unclear owing to low temporal and spatial resolutions of these methods. Moreover, the accuracy of the speckle tracking method depends on an important parameter, i.e., the size of the correlation kernel. To track backscattered echoes accurately, it is necessary to determine the optimal kernel size. However, the optimal kernel size has not been thoroughly investigated. In this study, correlation kernel size, which determines the tracking accurately, was optimized by evaluating root mean squared (RMS) errors in the lateral and axial displacements of a phantom estimated by speckle tracking methods at high spatial and temporal resolutions. For this purpose, the RF data from the longitudinal-axis cross-sectional view for the interventricular septum (IVS) were acquired on the basis of parallel beam forming (PBF) to improve temporal and spatial resolutions. A wide transmit beam scanned in 7 different directions sparsely and 16 receiving beams were generated for each transmission. The RF data of the phantom and the heart wall were obtained at high spatial (angle intervals of scan lines: 0.375 degrees) and temporal [frame rate (FR): 1020 Hz] resolutions. The determined optimal size of the correlation kernel was 7.9{\\degree} × 4.8 mm. Estimated displacements of the phantom were in good agreement with the actual displacement at an RMS error of 0.34 mm. Furthermore, the IVS motion during the isovolumic contraction (IC) was analyzed in detail. The speckle tracking method using the optimal kernel size 7.9{\\degree} × 4.8 mm was applied to multiple points in IVS to estimate 2D displacements during the IC period. In this period, a rapid displacement of IVS at a small amplitude of 1.5 mm, which suggests the expansion of the left ventricle and has not been measured by conventional tracking methods at a low temporal resolution, was detected by 2D tracking. Furthermore, the displacement on the apical side was found to be delayed by 10 ms compared with that on the basal side. These results indicate the potential of this method in the high-accuracy estimation of 2D displacements and detailed analyses of physiological function of the myocardium.

Yasunori Honjo,; Hideyuki Hasegawa,; Hiroshi Kanai,

2010-07-01

105

NASA Astrophysics Data System (ADS)

For noninvasive and quantitative measurements of global two-dimensional (2D) heart wall motion, speckle tracking methods have been developed and applied. These methods overcome the limitation of tissue Doppler imaging (TDI), which is susceptible to aliasing, by directly tracking backscattered echoes by pattern matching techniques, i.e., the cross-correlation or the sum of absolute differences, in real time. In these conventional methods, the frame rate (FR) is limited to about 200 Hz, corresponding to the sampling period of 5 ms. However, myocardial function during the isovolumic contraction period obtained by these conventional speckle tracking methods remains unclear owing to low temporal and spatial resolutions of these methods. Moreover, the accuracy of the speckle tracking method depends on an important parameter, i.e., the size of the correlation kernel. To track backscattered echoes accurately, it is necessary to determine the optimal kernel size. However, the optimal kernel size has not been thoroughly investigated. In this study, correlation kernel size, which determines the tracking accurately, was optimized by evaluating root mean squared (RMS) errors in the lateral and axial displacements of a phantom estimated by speckle tracking methods at high spatial and temporal resolutions. For this purpose, the RF data from the longitudinal-axis cross-sectional view for the interventricular septum (IVS) were acquired on the basis of parallel beam forming (PBF) to improve temporal and spatial resolutions. A wide transmit beam scanned in 7 different directions sparsely and 16 receiving beams were generated for each transmission. The RF data of the phantom and the heart wall were obtained at high spatial (angle intervals of scan lines: 0.375 degrees) and temporal [frame rate (FR): 1020 Hz] resolutions. The determined optimal size of the correlation kernel was 7.9° ×4.8 mm. Estimated displacements of the phantom were in good agreement with the actual displacement at an RMS error of 0.34 mm. Furthermore, the IVS motion during the isovolumic contraction (IC) was analyzed in detail. The speckle tracking method using the optimal kernel size 7.9° ×4.8 mm was applied to multiple points in IVS to estimate 2D displacements during the IC period. In this period, a rapid displacement of IVS at a small amplitude of 1.5 mm, which suggests the expansion of the left ventricle and has not been measured by conventional tracking methods at a low temporal resolution, was detected by 2D tracking. Furthermore, the displacement on the apical side was found to be delayed by 10 ms compared with that on the basal side. These results indicate the potential of this method in the high-accuracy estimation of 2D displacements and detailed analyses of physiological function of the myocardium.

Honjo, Yasunori; Hasegawa, Hideyuki; Kanai, Hiroshi

2010-07-01

106

Weak-beam trapping by bright spatial solitons in AlGaAs planar waveguides

NASA Astrophysics Data System (ADS)

We demonstrate experimentally the trapping and spatial wave breaking of weak signal beams by orthogonally polarized bright spatial solitons. Experiments were performed in an AlGaAs planar waveguide excited at a wavelength of 1.55 mu m .

Kang, J. U.; Stegeman, G. I.; Aitchison, J. S.

1995-10-01

107

Material figures of merit for spatial soliton interactions in the presence of absorption

NASA Astrophysics Data System (ADS)

The effects of linear and two-photon absorption on bright spatial soliton propagation are studied. A spatial soliton switch that achieves gain through the novel mechanism of colliding, dragging, or trapping of two fundamental solitons of different widths is proposed. Figures of merit for use in evaluating the suitability of absorbing nonlinear media for soliton switching applications are presented. The main effect of linear absorption is to limit the propagation distance, which places an upper bound on the width of the soliton in order to fit sufficient characteristic soliton propagation lengths within the device. The optical limiting nature of two-photon absorption places an upper bound on the gain that an interaction can achieve. The combined effects of linear and two-photon absorption are to reduce the gain upper bound imposed by two-photon absorption alone with the addition of the soliton width constraint. A maximized gain upper bound is determined solely by material parameters and is compared among three promising nonlinear materials. It is shown numerically that the spatial soliton dragging interaction requires shorter propagation distances and achieves greater gain than the collision interaction and that both are tolerant to the presence of absorption and can provide, with high contrast, gains of three or greater using measured material parameters. These results warrant pursuing the implementation of spatial soliton-based logic gates. .

Blair, Steve; Wagner, Kelvin H.; McLeod, Robert

1996-10-01

108

Observation of the commutation between bright and dark spatial optical solitons

NASA Astrophysics Data System (ADS)

We report a new experimental technique on generation of both dark and bright optical spatial solitons in liquid crystals doped with organic dyes. In our recent works we have demonstrated that in some liquid crystals (LC's) the effective nonlinear refraction index (?) is polarization dependent. Moreover, under certain conditions it is possible to realize inversion of ?, from ? > 0 to ? < 0, by proper adjustment of incident lightwave polarization. In this work we present experimental evidence that this LC is capable of supporting both bright and dark spatial solitons. The experimental setup used for characterization of solitons used two CCD cameras, which allowed us to analyze the longitudinal and transverse propagation characteristics of solitons in a glass cell containing a LC. It was possible to observe a clear correlation between the phase and the polarization state of incident light and the characteristic profile of the dark or bright soliton. The extreme values of the effective nonlinear refraction index were measured to be ? = -4.68 × 10-10 cm2/W (dark spatial soliton case), and ? = 2.80 × 10-10 cm2/W (bright spatial soliton). The key parameters of spatial solitons were estimated by using the nonlinear Schrödinger equation.

Rodríguez-Rosales, A. A.; Ordoñez, E.; Ortega-Martínez, R.; Román, C. J.; Kolokoltsev, O.

2011-09-01

109

Spatiotemporal electromagnetic soliton and spatial ring formation in nonlinear metamaterials

We present a systematic investigation of ultrashort electromagnetic pulse propagation in metamaterials (MMs) with simultaneous cubic electric and magnetic nonlinearity. We predict that spatiotemporal electromagnetic solitons may exist in the positive-index region of a MM with focusing nonlinearity and anomalous group velocity dispersion (GVD), as well as in the negative-index region of the MM with defocusing nonlinearity and normal GVD. The experimental circumstances for generating and manipulating spatiotemporal electromagnetic solitons can be created by elaborating appropriate MMs. In addition, we find that, in the negative-index region of a MM, a spatial ring may be formed as the electromagnetic pulse propagates for focusing nonlinearity and anomalous GVD; while the phenomenon of temporal splitting of the electromagnetic pulse may appear for the same case except for the defocusing nonlinearity. Finally, we demonstrate that the nonlinear magnetization makes the sign of effective electric nonlinear effect switchable due to the combined action of electric and magnetic nonlinearity, exerting a significant influence on the propagation of electromagnetic pulses.

Zhang Jinggui; Wen Shuangchun; Xiang Yuanjiang; Wang Youwen; Luo Hailu [Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, School of Computer and Communication, Hunan University, Changsha 410082 (China)

2010-02-15

110

Spatiotemporal electromagnetic soliton and spatial ring formation in nonlinear metamaterials

NASA Astrophysics Data System (ADS)

We present a systematic investigation of ultrashort electromagnetic pulse propagation in metamaterials (MMs) with simultaneous cubic electric and magnetic nonlinearity. We predict that spatiotemporal electromagnetic solitons may exist in the positive-index region of a MM with focusing nonlinearity and anomalous group velocity dispersion (GVD), as well as in the negative-index region of the MM with defocusing nonlinearity and normal GVD. The experimental circumstances for generating and manipulating spatiotemporal electromagnetic solitons can be created by elaborating appropriate MMs. In addition, we find that, in the negative-index region of a MM, a spatial ring may be formed as the electromagnetic pulse propagates for focusing nonlinearity and anomalous GVD; while the phenomenon of temporal splitting of the electromagnetic pulse may appear for the same case except for the defocusing nonlinearity. Finally, we demonstrate that the nonlinear magnetization makes the sign of effective electric nonlinear effect switchable due to the combined action of electric and magnetic nonlinearity, exerting a significant influence on the propagation of electromagnetic pulses.

Zhang, Jinggui; Wen, Shuangchun; Xiang, Yuanjiang; Wang, Youwen; Luo, Hailu

2010-02-01

111

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

112

NASA Astrophysics Data System (ADS)

A coaxial backward wave oscillator with a two-dimensional Bragg structure mounted at the exit from the interaction space is studied theoretically and experimentally. Azimuthal wave fluxes arising in this structure permit one to synchronize radiation of different fractions of a tubular relativistic electron beam with a large diameter. A narrowband radiation of the 8-mm range with a megawatt level of power has been obtained in the experimental prototype of the backward wave oscillator. The prototype was implemented on the basis of the Saturn accelerator (300 keV/200 A/1 ?s), as the perimeter of the system constituted more than 15 wavelengths.

Ginzburg, N. S.; Zaslavskii, V. Yu.; Ilyakov, E. V.; Kulagin, I. S.; Peskov, N. Yu.; Sergeev, A. S.

2013-06-01

113

Exact solutions for bright and dark solitons in spatially inhomogeneous nonlinearity

NASA Astrophysics Data System (ADS)

We present exact analytical results for bright and dark solitons in a type of one-dimensional spatially inhomogeneous nonlinearity. We show that the competition between a homogeneous self-defocusing (SDF) nonlinearity and a localized self-focusing (SF) nonlinearity supports stable fundamental bright solitons. For a specific choice of the nonlinear parameters, exact analytical solutions for fundamental bright solitons have been obtained. By applying both variational approximation and Vakhitov-Kolokolov stability criterion, it is found that exact fundamental bright solitons are stable. Our analytical results are also confirmed numerically. Additionally, we show that a homogeneous SF nonlinearity modulated by a localized SF nonlinearity allows the existence of exact dark solitons, for certain special cases of nonlinear parameters. By making use of linear stability analysis and direct numerical simulation, it is found that these exact dark solitons are linearly unstable.

Xie, Qiongtao

2014-12-01

114

NASA Astrophysics Data System (ADS)

The propagation of intensity-modulated laser radiation in a barium—sodium niobate crystal is studied in an external electric field. The possibility of controlling a nonlinear local response of the crystal is demonstrated. It is shown experimentally that the conditions of formation of a one-dimensional spatial soliton can be changed by varying the nonlinear response of the crystal.

Assel'born, S. A.; Kundikova, N. D.; Novikov, I. V.

2008-09-01

115

NASA Astrophysics Data System (ADS)

The interaction of two coupled binary matter wave bright solitons is investigated by means of the variational approach in the presence of spatially varying nonlinearity. The effective potential characterizing the interaction between the two solitons is obtained. It is shown that the effective potential is composed of three parts, related to the spatially modulated nonlinearity, the external trapping potential and the interaction of the two coupled solitons. The spatially modulated nonlinearity induces a pseudo-potential and the solitons can be accelerated by the spatially modulated nonlinearity. The effect depends on the sign and value of the spatially modulated coefficient. The interaction of two coupled binary matter wave bright solitons is of short range, and may be attractive or repulsive depending on the sign of the interspecies interactions. Under the appropriate condition, the two coupled solitons can evolve stably and do not coalesce. The neighbouring binary Bose-Einstein condensates are also available as media to create symbiotic bright solitons. The validity of the theoretical predictions is verified by the numerical integration of the coupled Gross-Pitaevskii equations.

Cheng, Yongshan

2009-10-01

116

In this paper, we investigate code acquisition in the delay and angular domain in environments where interference and noise are nonuniformly distributed in the spatial (angular) domain. It is seen that performance is clearly degraded by the presence of nonuniform spatial distributions of interference. The degree of impairment is related to the actual shape of the distribution and becomes more

Marcos Katz; Jari H. Iinatti; Savo G. Glisic

2004-01-01

117

A scattering mechanism related to the Schottky barrier height (SBH) spatial fluctuation of the two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures is presented. We find that the low field mobility is on the order of 10{sup 4}–10{sup 6} cm{sup 2}/Vs. The 2DEG transport properties are found to be influenced by both the mobility and 2DEG density variations caused by the SBH fluctuation. Our results indicate that a uniform Schottky contact is highly desired to minimize the influence of SBH inhomogeneity on the device performance.

Li, Huijie; Liu, Guipeng, E-mail: liugp@semi.ac.cn; Wei, Hongyuan; Jiao, Chunmei; Wang, Jianxia; Zhang, Heng; Dong Jin, Dong; Feng, Yuxia; Yang, Shaoyan, E-mail: sh-yyang@semi.ac.cn; Wang, Lianshan; Zhu, Qinsheng; Wang, Zhan-Guo [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)] [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

2013-12-02

118

Some search strategies for code acquisition in the delay and angular domains in radio environments with colored spatial distribution of interference are studied . The basic strategies comprise the fix angle sweep delay and fix delay sweep angle approaches to search the uncertainty region. A simple algorithm combining the fix angle sweep delay scheme with an ordered search according to

Marcos Katz; Jari Iinatti; Savo Glisic

2001-01-01

119

Spatial solitons in a three-level atomic medium supported by a Laguerre-Gaussian control beam

We investigate the existence and stability of various types of spatial solitons in a three-level atomic medium with Laguerre-Gaussian control beam. Radial and azimuthal modulations of the medium properties, introduced by the control beam, provide possibilities for existence of diverse soliton patterns and dynamics. Beam diffraction provides additional soliton controllability. All types of solitons can be generated at very low input energy at a few-photon level.

Hang Chao [Centro de Fisica Teorica e Computacional, Faculdade de Ciencias, Universidade de Lisboa, Avenida Professor Gama Pinto 2, Lisboa PT-1649-003 (Portugal); Department of Physics and State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai CN-200062 (China); Konotop, V. V. [Centro de Fisica Teorica e Computacional, Faculdade de Ciencias, Universidade de Lisboa, Avenida Professor Gama Pinto 2, Lisboa PT-1649-003 (Portugal); Departamento de Fisica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, Piso 6, Lisboa PT-1749-016 (Portugal)

2011-05-15

120

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

121

Propagation of spatial optical solitons in a dielectric with adjustable nonlinearity

We investigate spatial optical solitons propagating in a medium with a saturable but adjustable nonlinearity and a fixed degree of nonlocality. We employ nematic liquid crystals in a planar cell with optical properties tuned by an external voltage and solitons excited in the near infrared. We also demonstrate soliton self-bending versus excitation due to nonlinear variations in walk-off. A theoretical model accounting for the longitudinal derivatives is employed to compute the refractive index distribution and is found in excellent agreement with the experimental data.

Alberucci, A.; Piccardi, A.; Peccianti, M.; Assanto, G. [Nonlinear Optics and OptoElectronics Laboratory (NooEL), University ROMA TRE, Via della Vasca Navale 84, I-00146 Rome (Italy); Kaczmarek, M. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2010-08-15

122

A Kentech x-ray streak camera was run at the LLNL compact multipulse terawatt (COMET) laser to record simultaneous space- and time-resolved measurements of picosecond laser-produced plasmas. Four different x-ray energy channels were monitored using broadband filters to record the time history of Cu targets heated at irradiances of 10(16)-10(19) W?cm(2). Through the Cu filter channel, a time-resolution below 3 ps was obtained. Additionally, an array of 10 ?m diameter pinholes was placed in front of the camera to produce multiple time-resolved x-ray images on the photocathode and time-integrated images on the phosphor with 10 and 15 times magnification, respectively, with spatial resolution of < 13 ?m. PMID:23127011

Steel, A B; Nagel, S R; Dunn, J; Baldis, H A

2012-10-01

123

NASA Astrophysics Data System (ADS)

Gravel-bed braided rivers are characterized by shallow, branching flow across low relief, complex, and mobile bed topography. These conditions present a major challenge for the application of higher dimensional hydraulic models, the predictions of which are nevertheless vital to inform flood risk and ecosystem management. This paper demonstrates how high-resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynamic simulations in braided rivers. Specifically, we detail applications of the shallow water model, Delft3d, to the Rees River, New Zealand, at two nested scales: a 300 m braid bar unit and a 2.5 km reach. In each case, terrestrial laser scanning was used to parameterize the topographic boundary condition at hitherto unprecedented resolution and accuracy. Dense observations of depth and velocity acquired from a mobile acoustic Doppler current profiler (aDcp), along with low-altitude aerial photography, were then used to create a data-rich framework for model calibration and testing at a range of discharges. Calibration focused on the estimation of spatially uniform roughness and horizontal eddy viscosity, ?H, through comparison of predictions with distributed hydraulic data. Results revealed strong sensitivity to ?H, which influenced cross-channel velocity and localization of high shear zones. The high-resolution bed topography partially accounts for form resistance, and the recovered roughness was found to scale by 1.2-1.4 D84 grain diameter. Model performance was good for a range of flows, with minimal bias and tight error distributions, suggesting that acceptable predictions can be achieved with spatially uniform roughness and ?H.

Williams, R. D.; Brasington, J.; Hicks, M.; Measures, R.; Rennie, C. D.; Vericat, D.

2013-09-01

124

We study analytically and numerically a kind of diffractive resonant radiation emitted by spatial solitons, which is generated in waveguide arrays with Kerr nonlinearity. The phase matching condition between soliton and radiation is derived and agrees well with direct pulse propagation simulations. The folded dispersion due to the Brillouin zone leads to a peculiar anomalous soliton recoil that we describe in detail. A linear potential applied across the array generates the analogue of the Raman self-frequency shift in optical fibers, only now applied to the wavenumber. We demonstrate that it is possible to mimic closely temporal fiber-optical dynamics, unveiling the new effects of wavenumber-supercontinuum generation and the compensation of the 'soliton self-wavenumber shift' by the emitted diffractive radiation. This work paves the way for designing unique optical devices that generate spectrally broad supercontinua with a controllable directionality.

Tran, Truong X

2012-01-01

125

Two-component vector solitons in defocusing Kerr-type media with spatially modulated nonlinearity

NASA Astrophysics Data System (ADS)

We present a class of exact solutions to the coupled (2 + 1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity and a special external potential, which describe the evolution of two-component vector solitons in defocusing Kerr-type media. We find a robust soliton solution, constructed with the help of Whittaker functions. For specific choices of the topological charge, the radial mode number and the modulation depth, the solitons may exist in various forms, such as the half-moon, necklace-ring, and sawtooth vortex-ring patterns. Our results show that the profile of such solitons can be effectively controlled by the topological charge, the radial mode number, and the modulation depth.

Zhong, Wei-Ping; Beli?, Milivoj

2014-12-01

126

Spatiotemporal electromagnetic soliton and spatial ring formation in nonlinear metamaterials

We present a systematic investigation of ultrashort electromagnetic pulse propagation in metamaterials (MMs) with simultaneous cubic electric and magnetic nonlinearity. We predict that spatiotemporal electromagnetic solitons may exist in the positive-index region of a MM with focusing nonlinearity and anomalous group velocity dispersion (GVD), as well as in the negative-index region of the MM with defocusing nonlinearity and normal GVD.

Jinggui Zhang; Shuangchun Wen; Yuanjiang Xiang; Youwen Wang; Hailu Luo

2010-01-01

127

We report on the design, fabrication process and characterization of liquid crystal cells for investigation of optical spatial solitons. Controlling of the director orientation at the input interface, as well as in the bulk, allows to obtain configurations that can produce distinct optical phenomena in a light beam propagating in the cell. For a particular director configuration, it is possible

Antonio de Luca; Gianluca Coschignano; Cesare Umeton; Marco Morabito

2006-01-01

128

Spatially periodic modulation of the intersite coupling in two-dimensional (2D) nonlinear lattices modifies the eigenvalue spectrum by opening mini-gaps in it. This work aims to build stable localized modes in the new bandgaps. Numerical analysis shows that single-peak and composite two- and four-peak discrete static solitons and breathers emerge as such modes in certain parameter areas inside the mini-gaps of the 2D superlattice induced by the periodic modulation of the intersite coupling along both directions. The single-peak solitons and four-peak discrete solitons are stable in a part of their existence domain, while unstable stationary states (in particular, two-soliton complexes) may readily transform into robust localized breathers. PMID:24985438

Gligori?, Goran; Maluckov, Aleksandra; Hadžievski, Ljup?o; Malomed, Boris A

2014-06-01

129

We show that transverse electromagnetic waves propagating along an external static electric field in liquid metacrystal (LMC) can provoke spontaneous rearrangement of elongated meta-atoms that changes the direction of the anisotropy axis of the LMC. This kind of instability may reorient the meta-atoms from the equilibrium state parallel to a static field to the state along a high-frequency field and back at the different threshold intensities of electromagnetic waves in such a way that bistability in the system takes place. Reorientation of meta-atoms causes a change in the effective refraction index of LMC that creates, in turn, the conditions for the formation of bright spatial solitons. Such spatial solitons are the self-consistent domains of redirected meta-atoms with trapped photons. We find that the instability thresholds as well as energy flux captured by the spatial soliton can be easily managed by variation of the static electric field applied to the LMC. We study the effects of soliton excitation and collisions via numerical simulations. PMID:25215843

Zharov, Alexander A; Zharov, Alexander A; Zharova, Nina A

2014-08-01

130

NASA Astrophysics Data System (ADS)

We present experimental evidence obtained in the generation and variation of dark to bright optical spatial solitons due the change of polarization plane of He-Ne laser beam incident in the sample of liquid crystals 5CB doped with methyl red at 0.1% wt inside a cell of 15 ?m widths. This work is based in previous papers about the variation of nonlinear refraction index ? in liquid crystals, where we have demonstrated that under certain conditions it is possible to realize inversion of ?, from ? > 0 to ? < 0, by proper adjustment of incident light wave polarization and the theoretical and experimental characterization of spatial solitons. It was possible to observe a clear correlation between the polarization state of incident light and the characteristic profile of dark or bright soliton; we shows here the experimental setup, the results in photographs and their related graphics. The experimental results will open the design of a new system that will generate in the same material a controlled dark or bright spatial optical solitons. We consider this new phenomena very important and as well as its potential technological application in all-optical switching in telecommunications and optoelectronic.

Rodríguez-Rosales, A. A.; Román Moreno, C. J.; Ortega-Martínez, R.

2013-11-01

131

Large phase shift of (1+1)-dimensional nonlocal spatial solitons in lead glass

NASA Astrophysics Data System (ADS)

The large phase shift of strongly nonlocal spatial optical soliton (SNSOS) in the (1+1)-dimensional [(1+1)D] lead glass is investigated using the perturbation method. The fundamental soliton solution of the nonlocal nonlinear Schödinger equation (NNLSE) under the 2nd order approximation in strongly nonlocal case is obtained. It is found that the phase shift rate along the propagation direction of such soliton is proportional to the degree of nonlocality, which indicates that one can realize ?-phase-shift within one Rayleigh distance in (1+1)D lead glass. A full comprehension of the nonlocality enhancement to the phase shift rate of SNSOS is reached via quantitative comparisons of phase shift rates in different nonlocal systems. This can help us to conclude that, compared with SNSOSs in other nonlocal systems, SNSOS in (1+1)D lead glass is a most promising candidate which can experience large phase shift within the shortest propagation distance.

Shou, Qian; Wu, Miao; Guo, Qi

2015-03-01

132

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

133

Tablets of amorphous indomethacin were compressed at 10, 25, 50, or 100 MPa using either an unlubricated or a lubricated die and stored individually at 35 °C in sealed Mylar pouches. At selected time points, tablets were analyzed by two-dimensional X-ray diffractometry (2D-XRD), which enabled us to profile the extent of drug crystallization in tablets, in both the radial and axial directions. To evaluate the role of lubricant, magnesium stearate was used as "internal" and/or "external" lubricant. Indomethacin crystallization propensity increased as a function of compression pressure, with 100 MPa pressure causing crystallization immediately after compression (detected using synchrotron radiation). However, the drug crystallization was not uniform throughout the tablets. In unlubricated systems, pronounced crystallization at the radial surface could be attributed to die wall friction. The tablet core remained substantially amorphous, irrespective of the compression pressure. Lubrication of the die wall with magnesium stearate, as external lubricant, dramatically decreased drug crystallization at the radial surface. The spatial heterogeneity in drug crystallization, as a function of formulation composition and compression pressure, was systematically investigated. When formulating amorphous systems as tablets, the potential for compression induced crystallization warrants careful consideration. Very low levels of crystallization on the tablet surface, while profoundly affecting product performance (decrease in dissolution rate), may not be readily detected by conventional analytical techniques. Early detection of crystallization could be pivotal in the successful design of a dosage form where, in order to obtain the desired bioavailability, the drug may be in a high energy state. Specialized X-ray diffractometric techniques (2D; use of high intensity synchrotron radiation) enabled detection of very low levels of drug crystallization and revealed the heterogeneity in crystallization within the tablet. PMID:25438193

Thakral, Naveen K; Mohapatra, Sarat; Stephenson, Gregory A; Suryanarayanan, Raj

2015-01-01

134

NASA Astrophysics Data System (ADS)

Bacterial growth and its interaction with water flow was investigated in a two-dimensional flow field in a saturated porous medium. A flow cell (56×44×1 cm) was filled with glass beads and operated under a continuous flow of a mineral medium containing nitrate as electron acceptor. A glucose solution was injected through an injection port, simulating a point source contamination. Visible light transmission was used to observe the distribution of the growing biomass and water flow during the experiment. At the end of the experiment (on day 31), porous medium samples were destructively collected and analyzed for abundance of total and active bacterial cells, bacterial cell volume and concentration of polysaccharides and proteins. Microbial growth was observed in two stripes along the length of the flow cell, starting at the glucose injection port, where highest biomass concentrations were obtained. The spatial distribution of biomass indicated that microbial activity was limited by transverse mixing between glucose and nitrate media, as only in the mixing zone between the media high biological activities were achieved. The ability of the biomass to change the flow pattern in the flow cell was observed, indicating that the biomass was locally reducing the hydraulic conductivity of the porous medium. This bioclogging effect became evident when the injection of the glucose solution was turned off and water flow still bypassed the area around the glucose injection port, preserving the flow pattern as it was during the injection of the glucose solution. As flow bypass was possible in this system, the average hydraulic properties of the flow cell were not affected by the produced biomass. Even in the vicinity of the injection port, the total volume of the bacterial cells remained below 0.01% of the pore space and was unlikely to be responsible for the bioclogging. However, the bacteria produced large amounts of extracellular polymeric substances (EPS), which likely caused the observed bioclogging effects.

Thullner, Martin; Mauclaire, Laurie; Schroth, Martin H.; Kinzelbach, Wolfgang; Zeyer, Josef

2002-10-01

135

To improve the reliability of two-dimensional information, codes that can correct two-dimensional bursts (or spots) may be useful. In this paper a class of two-dimensional burst-correcting codes, called two-dimensional Fire codes, is proposed. The definition of these codes is a natural extension of that of the conventional Fire codes. The two-dimensional Fire code is a two-dimensional cyclic code designed for

H. Imai

1973-01-01

136

NASA Astrophysics Data System (ADS)

Two-dimensional time-dependent finite-difference equations of the surface harmonics method (SHM) for the description of the neutron transport are derived for square-lattice reactors. These equations are implemented in the SUHAM-TD code. Verification of the derived equations and the developed code are performed by the example of known test problems, and the potential and efficiency of the SHM as applied to the solution of the time-dependent neutron transport equation in the diffusion approximation in two-dimensional geometry are demonstrated. These results show the substantial advantage of SHM over direct finite-difference modeling in computational costs.

Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A.

2014-12-01

137

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

138

NASA Astrophysics Data System (ADS)

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, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.

2010-09-01

139

NASA Astrophysics Data System (ADS)

Within the framework of the study a two dimensional hydrodynamic high-resolution model of the energy, H2O, CO2 turbulent exchange was developed and applied to describe effect of the horizontal and vertical heterogeneity of a forest canopy on CO2exchange between soil surface, forest stand and the atmosphere under different weather conditions. Most attention in the study was paid to analyze the influence of forest clearing, windthrow of different sizes, forest edges, etc. on turbulent exchange rate and CO2 flux partitioning between forest overstorey, understorey and soil surface. The modeling experiments were provided under different wind conditions, thermal stratification of the atmospheric boundary layer, incoming solar radiation, etc. To quantify effect of spatial heterogeneity on total ecosystem fluxes the modeling results were compared with CO2 fluxes modeled for a spatially uniform forest canopy under similar ambient conditions. The averaged system of hydrodynamic equations is used for calculating the components of the mean velocity ?V = {V1, V2}: ( ( ) ) ?Vi+ V ?Vi= - 1-??P- - -?- ? E - K ?Vi-+ ?Vj- + F, ?Vi = 0, ?t j?xj ?0 ?xi ?xj ij ?xj ?xi i ?xi where E is the turbulent kinetic energy (TKE), K is the turbulent diffusivity, ?P is the deviation of pressure from the hydrostatic distribution and ?0?F is the averaged force of air flow interaction with vegetation. F? was parameterized as ?F = -cd ·LAD ·| | ||V?||·?V, where cd is the drag coefficient and LAD is the leaf area density. The turbulent diffusivity K can be expressed by means of TKE and the velocity of TKE dissipation ? as follows: K = C?E2?-1, where C? is the proportionality coefficient. One of the ways to obtain E and ? is to solve the additional system of two differential equations of diffusion-transport type: ( ) ( ) ?E- -?E- -?- -K-?E- ?-? ??- -?- K-?? -? ( 1 2 ) ?t +Vj?xj = ?xi ?E ?xi +PE - ?, ?t +Vj ?xj = ?xi ???xi +E C ?PE - C?? - ? ?, where ?E and ?? are the Prandtl numbers, PE is the TKE production by shear, C?1 and C?2 are the model constants. The term ?? = ?- E(C ?1 - C?2) · 12C?1/2c dLAD||? || |V |E describes the increase of TKE dissipation due to the interaction with vegetation elements. The function ? can be any of the following variables: ?, ?/ E, or El, where l is the mixing length. Detailed analysis of these equations performed by Sogachev (Sogachev, Panferov, 2006) showed that for ? = ?/ E the model is less sensible to the errors of the input data. Transfer equation for CO2 within and above a plant canopy can be written as: ( ) ?C- -?C- -?- -K-?C- ?t + Vj?xj = ?xi ?C ?xi + FC, where C is CO2 concentration, ?C is the Prandtl number, and the term FC describes the sources/sinks of CO2 in the vegetation and soil. For parameterization of the photosynthesis rate in the forest canopy the Monsi and Saeki approach (Monsi M., Saeki T., 1953) was applied. Stem respiration was ignored in the study. The CO2 emission from the soil surface into the atmosphere was assumed to be constant for entire forest area. This study was supported by grants of the Russian Foundation for Basic Research (RFBR 14-04-01568-a).

Mukhartova, Yulia; Olchev, Alexander; Shapkina, Natalia

2014-05-01

140

We propose what we believe to be a newly developed optical fiber management and testing system with a view to reducing the operation, administration, and maintenance (OA&M) cost for PON. Identification technologies using a mobile access terminal with a two-dimensional code scanner, and fault isolation technologies using a high-spatial-resolution optical time-domain reflectometer (OTDR) enhance the functions for the registration, administration,

Yoshitaka Enomoto; Hisashi Izumita; Masahito Arii

2007-01-01

141

NASA Astrophysics Data System (ADS)

We developed a two-dimensional gradiometer that detects the gradient of a magnetic field in two orthogonal directions to measure the biomagnetic signal in an unshielded environment. We based the gradiometer on a low-Tc superconducting quantum interference device (SQUID) and wire-wound pickup coil. The gradiometer we developed detects both the axial-second-order and planar-first-order gradient of a magnetic field. The experimental results revealed that its noise-reduction ratio (NRR) was 54 dB from 0.5 to 49 Hz and 14 dB (5 times) larger than that of the axial-second-order gradiometer. Moreover, by using the new gradiometer, we obtained a clear magnetocardiography (MCG) waveform in real time without averaging under an unshielded environment (noise level: 3.8 nT/\\sqrt{Hz} at 1 Hz; 150 pT/\\sqrt{Hz} at 10 Hz).

Seki, Yusuke; Kandori, Akihiko

2007-06-01

142

Multipole plasmonic lattice solitons

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

143

Two-Dimensional Modulation Codes

A new class of run-length-limited codes in introduced. These codes are called two-dimensional or multitrack modulation codes. Two-dimensional modulation codes provide substantial data storage density increases for multitrack recording systems by operating on multiple tracks in parallel. Procedures for computing the capacity of these new codes are given along with fast algorithms for implementing these procedures. Examples of two-dimensional codes

Michael W. Marcellin; Harold J. Weber

1992-01-01

144

Bright dipolar Bose-Einstein-condensate soliton mobile in a direction perpendicular to polarization

NASA Astrophysics Data System (ADS)

We demonstrate stable, robust, bright one-dimensional dipolar Bose-Einstein-condensate (BEC) solitons, moving in a direction perpendicular to the polarization direction, formed due to dipolar interaction for repulsive contact interaction. At medium velocity the head on collision of two such solitons is found to be quasielastic with practically no deformation. Upon small perturbation the solitons are found to exhibit sustained breathing oscillation. The findings are illustrated by numerical simulation using the three-dimensional mean-field Gross-Pitaevskii equation and a reduced two-dimensional model in three and two spatial dimensions employing realistic interaction parameters for a dipolar 164Dy BEC.

Adhikari, S. K.

2014-11-01

145

Gray and dark spatial solitons supported by two-photon isomerization

NASA Astrophysics Data System (ADS)

A theory is presented to show that gray and dark solitons can exist in bulk polymers with two-photon isomerization (TPI) nonlinearity. The soliton FWHM, intensity and phase profiles are discussed in detail. In addition, the stability properties of these TPI solitons are also investigated by employing the stability criterion based on the renormalized momentum.

Wang, Hongcheng; Zhang, Bingzhi; Yan, Lifen; Li, Yanggang; Zheng, Guoliang; She, Weilong

2007-07-01

146

NASA Astrophysics Data System (ADS)

Spatial rocking is a kind of resonant forcing able to convert a self-oscillatory system into a phase-bistable, pattern forming system, whereby the phase of the spatially averaged oscillation field locks to one of two values differing by ?. We propose the spatial rocking in an experimentally relevant system—the vertical-cavity surface-emitting laser (VCSEL)—and demonstrate its feasibility through analytical and numerical tools applied to a VCSEL model. We show phase bistability, spatial patterns, such as roll patterns, domain walls, and phase (dark-ring) solitons, which could be useful for optical information storage and processing purposes.

Fernandez-Oto, C.; de Valcárcel, G. J.; Tlidi, M.; Panajotov, K.; Staliunas, K.

2014-05-01

147

propagate as a spatial soliton [1Â6]. The ease of their formation and manipulation using very low laser switching and manipulation. This concept is based on the ability to implement logic operations by allowing and propagation of screening solitons in photorefractive media. Section 3 describes the basic experimental

Saffman, Mark

148

NASA Astrophysics Data System (ADS)

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 40×40 channels exhibited a temporal response of ˜100ns (pulse width of the amplified signal) and a spatial resolution of 0.9 and 1.4mm (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 CF4.

Tanaka, Hiroki; Nakamura, Tatsuya; Yamagishi, Hideshi; Soyama, Kazuhiko; Aizawa, Kazuya

2005-09-01

149

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

150

Two-Dimensional Visual Language Grammar

\\u000a Visual language refers to the idea that communication occurs through visual symbols, as opposed to verbal symbols or words.\\u000a Contrast to a sentence construction in spoken language with a linear ordering of words, a visual language has a simultaneous\\u000a structure with a parallel temporal and spatial configuration. Inspired by Deikto [5], we propose a two-dimensional string\\u000a or sentence construction of

Siska Fitrianie; Léon J. M. Rothkrantz

2006-01-01

151

2D 1H-NMR spectra of des-Gly9-[Arg8]vasopressin in dimethylsulfoxide have been taken and the 1H resonances have been assigned. The coupling constants and amide proton temperature coefficients (delta delta/delta T) have been measured and the NOE cross-peaks in the NOESY spectrum have been analyzed. The most essential information on the spatial structure of des-Gly9-[Arg8]vasopressin is extracted from the low delta delta/delta T value for Asn5 amide proton and from the NOE between the Cys1 and Cys6 alpha-protons. A diminished accessibility of the Asn5 NH proton for the solvent is ascribed to the presence of a beta-turn in the fragment 2-5. The distance between the Cys1 and Cys6 C alpha H protons seems to be less than 4 A. These constraints were taken into account in the conformational analysis of the title peptide. The derived set of the low-energy backbone conformations was analyzed against the background of the all available NMR data. The most probable conformation of the cyclic moiety in des-Gly9-[Arg8]vasopressin was found to be the type III beta-turn. The corner positions are occupied by the residues 3, 4, while the residues 1-2 and 5-6 are at the extended sites. Some NMR data indicate that this structure is in a dynamic equilibrium with other minor conformers. PMID:4062995

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

1985-09-01

152

Matched infrared soliton pairs in graphene under Landau quantization via four-wave mixing

NASA Astrophysics Data System (ADS)

We investigate a type of matched infrared soliton pairs based on four-wave mixng (FWM) in Landau-quantized graphene by using density-matrix method and perturbation theory. The linear and nonlinear dynamical properties of the graphene system are first discussed, and, in particular, we focus on the signatures of nonlinear optical response. Then we present analytical solutions for the fundamental bright and dark solitons, as well as bright two-soliton, which are in good agreement with the results of numerical simulations. Moreover, due to the unusual dispersion relation and chiral character of electron states, we find that the matched spatial soliton pairs can propagate through a two-dimensional crystal of graphene and their carrier frequencies are adjustable within the infrared frequency regimes. Our proposed scheme may provide a route to explore the applications of matched infrared soliton pairs in telecommunication and optical information processing.

Ding, Chunling; Yu, Rong; Li, Jiahua; Hao, Xiangying; Wu, Ying

2014-10-01

153

NASA Astrophysics Data System (ADS)

Dynamics of solitons is considered in the framework of an extended nonlinear Schrödinger equation (NLSE), which is derived from a system of the Zakharov's type for the interaction between high- and low-frequency (HF and LF) waves. The resulting NLSE includes a pseudo-stimulated-Raman-scattering (pseudo-SRS) term, i.e., a spatial-domain counterpart of the SRS term, which is a known ingredient of the temporal-domain NLSE in optics. Inhomogeneity of the spatial second-order dispersion (SOD) and linear losses of HF waves was also included. It is shown that wavenumber downshift by the pseudo-SRS may be compensated by the upshift provided by SOD whose local strength is an exponentially decaying function of the coordinate. An analytical soliton solution with a permanent shape is found in an approximate form, and is verified by the comparison with numerical results.

Gromov, E. M.; Malomed, B. A.

2014-06-01

154

Two-dimensional material nanophotonics

NASA Astrophysics Data System (ADS)

Two-dimensional materials exhibit diverse electronic properties, ranging from insulating hexagonal boron nitride and semiconducting transition metal dichalcogenides such as molybdenum disulphide, to semimetallic graphene. In this Review, we first discuss the optical properties and applications of various two-dimensional materials, and then cover two different approaches for enhancing their interactions with light: through their integration with external photonic structures, and through intrinsic polaritonic resonances. Finally, we present a narrow-bandgap layered material -- black phosphorus -- that serendipitously bridges the energy gap between the zero-bandgap graphene and the relatively large-bandgap transition metal dichalcogenides. The plethora of two-dimensional materials and their heterostructures, together with the array of available approaches for enhancing the light-matter interaction, offers the promise of scientific discoveries and nanophotonics technologies across a wide range of the electromagnetic spectrum.

Xia, Fengnian; Wang, Han; Xiao, Di; Dubey, Madan; Ramasubramaniam, Ashwin

2014-12-01

155

Observation of soliton ridge states for the self-imprinting of fiber-slab couplers

NASA Astrophysics Data System (ADS)

We investigate experimentally the energy exchange patterns and consequent propagation dynamics of an extended hybrid-dimensional interaction between a one-dimensional and a two-dimensional spatial soliton in a biased photorefractive crystal. Results show that conditions can be found in which the coupling manifests propagation invariant features. The mechanism hinges on mutual distortion through spatially nonlocal components of response, as opposed to standard wave overlap, which would lead to a diffusion of the needle into the slab mode. These nonlocal-nonlinearity-driven ridge modes represent the instrument for writing fiber-slab couplers, the key to attaining soliton-based wavelength selectivity with electroactivated features.

DelRe, Eugenio; D'Ercole, Angelo; Palange, Elia; Agranat, Aharon J.

2005-05-01

156

Optical solitons in metamaterials

Metamaterials can be designed to have desirable linear and nonlinear electromagnetic responses to light waves, thus become a new candidate for generating and manipulating solitons. Here, we present a review of optical solitons in metamaterials, focusing on the new properties of temporal, spatial and spatiotemporal solitons relating to the unique electromagnetic property of metamaterials.

Shuangchun Wen; Jingui Zhang; Yuanjiang Xiang; Xiaoyu Dai; Xi Cheng; Wei Zhou; Binxian Zhuang

2008-01-01

157

Anderson Localization of Solitons

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

158

A spatial envelope soliton model of the electron - propagating within a fictitious waveguide

The paper proposes an envelope soliton model of the electron. The soliton propagates within a waveguide which size varies with the potential. The soliton is the solution of the Schroedinger equation with the addition of a nonlinear term that is the negative of Bohm's Quantum potential. This potential is interpreted as representing the dispersion of the linear equation. The model is based on de Broglie's original wave-particle concept, which is based on the Special theory of relativity. The model thus illustrates that theory.

Roald Ekholdt

2008-03-04

159

Two-dimensional thermofield bosonization

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

160

Two-Dimensional Thermofield Bosonization

The main objective of this paper is 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. In order 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.

R. L. P. G. Amaral; L. V. Belvedere; K. D. Rothe

2005-04-01

161

Two-dimensional flexible nanoelectronics

NASA Astrophysics Data System (ADS)

2014/2015 represents the tenth anniversary of modern graphene research. Over this decade, graphene has proven to be attractive for thin-film transistors owing to its remarkable electronic, optical, mechanical and thermal properties. Even its major drawback--zero bandgap--has resulted in something positive: a resurgence of interest in two-dimensional semiconductors, such as dichalcogenides and buckled nanomaterials with sizeable bandgaps. With the discovery of hexagonal boron nitride as an ideal dielectric, the materials are now in place to advance integrated flexible nanoelectronics, which uniquely take advantage of the unmatched portfolio of properties of two-dimensional crystals, beyond the capability of conventional thin films for ubiquitous flexible systems.

Akinwande, Deji; Petrone, Nicholas; Hone, James

2014-12-01

162

Two-dimensional river modeling

conveyance of the section would not reflect the inertial effects influencing this variation in the channel and overbank velocity. The water surface elevation is presented as water surface contours in Figure 12 and as a three-dimensional surface in Figure... OF FIGURES INTRODUCTION One-Dimensional and Two-Dimensional River Modeling Description of the Modeling System GOVERNING EQUATIONS Three-Dimensional Equations of Motion Effects of Turbulence Depth-Averaged Equations of Motion Non-conservative Equations...

Thompson, James Cameron

1988-01-01

163

Two-dimensional optical storage

With storage capacities increasing much faster than data rates, fast read-out of content is becoming a bottleneck for the convenient use of optical storage devices. Two-dimensional optical storage (TwoDOS) is a new concept that solves this data-rate problem by using a multi-spot parallel readout system. In addition, the storage capacity is increased with a factor of at least 2. Using

W. M. J. Coene; D. M. Bruls; A. H. J. Immink; A. M. van der Lee; A. P. Hekstra; J. Riani; S. van Beneden; M. Ciacci; J. W. M. Bergmans; M. Furuki

2005-01-01

164

Observability for two dimensional systems

NASA Technical Reports Server (NTRS)

Sufficient conditions that a two-dimensional system with output is locally observable are presented. Known results depend on time derivatives of the output and the inverse function theorem. In some cases, no informaton is provided by these theories, and one must study observability by other methods. The observability problem is dualized to the controllability problem, and the deep results of Hermes on local controllability are applied to prove a theorem concerning local observability.

Hunt, L. R.; Su, R.

1981-01-01

165

Two-Dimensional Colloidal Alloys

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

166

Two-dimensional colloidal alloys.

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

2011-03-25

167

Ultrafast deflection of spatial solitons in AlxGa1-xAs slab waveguides

laser pulse. A separate ultrashort pump pulse is focused onto the top of the waveguide, introducing cladding, both with x=0.24. The pulses used to generate and steer the solitons are obtained from an ultrafast laser system: a 250 kHz optical parametric amplifi

Van Driel, Henry M.

168

REVIEW ARTICLE: Experiments on partially coherent photorefractive solitons

We provide an overview of experimental studies on partially coherent spatial solitons in photorefractive materials, including the first experimental demonstration of bright and dark incoherent solitons, incoherent vortex solitons, Y-junction dark solitons and anti-dark solitons, and pixel-like incoherent soliton arrays. These solitons are created with partially spatially incoherent light beams by using the non-instantaneous photorefractive screening nonlinearity. Experimental results on

Zhigang Chen; Mordechai Segev; Demetrios N. Christodoulides

2003-01-01

169

Solitons on Tori and Soliton Crystals

NASA Astrophysics Data System (ADS)

Necessary conditions for a soliton on a torus to be a soliton crystal, that is, a spatially periodic array of topological solitons in stable equilibrium, are derived. The stress tensor of the soliton must be L 2 orthogonal to , the space of parallel symmetric bilinear forms on TM, and, further, a certain symmetric bilinear form on , called the hessian, must be positive. It is shown that, for baby Skyrme models, the first condition actually implies the second. It is also shown that, for any choice of period lattice ?, there is a baby Skyrme model which supports a soliton crystal of periodicity ?. For the three-dimensional Skyrme model, it is shown that any soliton solution on a cubic lattice which satisfies a virial constraint and is equivariant with respect to (a subgroup of) the lattice symmetries automatically satisfies both tests. This verifies, in particular, that the celebrated Skyrme crystal of Castillejo et al., and Kugler and Shtrikman, passes both tests.

Speight, J. M.

2014-11-01

170

This is a sequel to a recent work of Gaudin, who studied the classical equilibrium statistical mechanics of the two-dimensional Coulomb gas on a lattice at a special value of the coupling constant Gamma such that the model is exactly solvable. This model is briefly reviewed, and it is shown that the correlation functions obey the sum rules that characterize a conductive phase. A related model in which the particles are constrained to move on an array of equidistant parallel lines has simpler mathematics, and the asymptotic behavior of its correlation functions is studied in some detail. In the low-density limit, the lattice model is expected to have the same properties as a system of charged, hard disks; the correlation functions, internal energy, and specific heat of the latter are discussed.

Cornu, F.; Jancovici, B.

1987-10-01

171

Two-dimensional NMR spectroscopy

Written for chemists and biochemists who are not NMR spectroscopists, but who wish to use the new techniques of two-dimensional NMR spectroscopy, this book brings together for the first time much of the practical and experimental data needed. It also serves as information source for industrial, academic, and graduate student researchers who already use NMR spectroscopy, but not yet in two dimensions. The authors describe the use of 2-D NMR in a wide variety of chemical and biochemical fields, among them peptides, steroids, oligo- and poly-saccharides, nucleic acids, natural products (including terpenoids, alkaloids, and coal-derived heterocyclics), and organic synthetic intermediates. They consider throughout the book both the advantages and limitations of using 2-D NMR.

Croasmun, W.R.; Carlson, R.M.K.

1987-01-01

172

Inverse velocity statistics in two dimensional turbulence

We present a numerical study of two-dimensional turbulent flows in the enstrophy cascade regime, with different large-scale forcings and energy sinks. In particular, we study the statistics of more-than-differentiable velocity fluctuations by means of two recently introduced sets of statistical estimators, namely {\\it inverse statistics} and {\\it second order differences}. We show that the 2D turbulent velocity field, $\\bm u$, cannot be simply characterized by its spectrum behavior, $E(k) \\propto k^{-\\alpha}$. There exists a whole set of exponents associated to the non-trivial smooth fluctuations of the velocity field at all scales. We also present a numerical investigation of the temporal properties of $\\bm u$ measured in different spatial locations.

L. Biferale; M. Cencini; A. Lanotte; D. Vergni

2002-04-10

173

NASA Astrophysics Data System (ADS)

We study analytically the properties of the optical absorption and the spatial weak-light solitons in a quantum dot molecule system with the interdot tunneling coupling (ITC). It is shown that, for the linear case, there exists tunneling induced transparency (TIT) in the context of a weak ITC, while the TIT can be replaced by Autler-Townes splitting in the presence of a strong ITC. For the nonlinear case, it is probable to realize the spatial optical solitons even under weak light intensity. Interestingly, we find that there appears transformation behavior between the bright and dark solitons by properly turning both the ITC strength and the detuning of the probe field. Meanwhile, the transformation condition of the bright and dark solitons is obtained. Additionally it is also found that the amplitude of the solitons first descends and then rises with the increasing of ITC strength. Our results may have potential applications for nonlinear optical experiments and optical telecommunication engineering in solid systems.

Zeng, Kuanhong; Wang, Denglong; She, Yanchao; Luo, Xiaoqin

2013-11-01

174

Collage of two-dimensional words

We consider a new operation on one-dimensional (resp. two-dimensional) word lan- guages, obtained by piling up, one on top of the other, words of a given recognizable language (resp. two-dimensional recognizable language) on a previously empty one- dimensional (resp. two-dimensional) array. The resulting language is the set of words \\

Christian Choffrut; Berke Durak

2005-01-01

175

Interaction of spatial solitons with a gapless stripe embedded into a Bragg-grating area

NASA Astrophysics Data System (ADS)

We introduce a model in which the grating is absent in a finite-width stripe in the waveguide, thus creating a gapless channel in the gapped medium. Two semi-infinite grating separated by the plain stripe may have a relative phase shift. This system modifies the Bragg bandgap, creating intra-gap defect modes (DFs) which are pinned to the gapless channel. A DF solution in the linear system is found analytically. Further, numerical analysis of the full nonlinear system demonstrates that the shape and stability of Bragg solitons are also strongly affected by the presence of the gapless channel, and by the possible phase shift between the two semi-infinite gratings. In particular, asymmetric and flat-top solitons appear.

Mayteevarunyoo, Thawatchai; Malomed, Boris A.

2015-01-01

176

Spatial vector soliton and its collisions in isotropic self-defocusing Kerr media.

A fairly general form of the two-component (dark-dark) vector one-soliton solution of the integrable coupled nonlinear Schrödinger equation (Manakov model) with self-defocusing nonlinearity is obtained by using the Hirota method. It couples two dark components with the same envelope width, envelope speed, and envelope trough location using two complex arbitrary parameters not only in the envelope amplitude but also in the complex modulation. Although it has the freedom to change its pulse width without affecting its speed, it can also tune its grayness (depth of the pulse relative to background) without disturbing the envelope width and speed. The variations in peak power against the depth of localization of two dark components are investigated with and without a parametric restriction. The collision between many dark-dark vector solitons has also been studied by constructing a multisoliton solution with more free parameters. PMID:17677374

Radhakrishnan, R; Aravinthan, K

2007-06-01

177

Two-Dimensional Ratchets with Non-Conservative Impulsive Force

We discuss the directed motion of overdamped Brownian particles based on a two-dimensional ratchet model with a non-conservative impulsive force field. We consider the combined effects on the stationary current due to local spatial asymmetry in the longitudinal direction as well as the constrained harmonic force in the transverse direction. We notice that the current reversal is induced by the

Tong-Jun Zhao; Yi-Zhong Zhuo; Yong Zhan; Qing Ji; Tian-Guang Cao

2002-01-01

178

Image transmission by two-dimensional contour coding

The results of a computer simulation of an image transmission system are reported. A reduction in the total number of bits required to describe a picture by a factor of 4 to 23 is possible as compared with 6-bit PCM. In this system an image is treated as a two-dimensional signal of the spatial coordinates x and y. The large

DONALD NORMAN GRAHAM

1967-01-01

179

Kubo conductivity of a strongly magnetized two-dimensional plasma.

NASA Technical Reports Server (NTRS)

The Kubo formula is used to evaluate the bulk electrical conductivity of a two-dimensional guiding-center plasma in a strong dc magnetic field. The particles interact only electrostatically. An ?anomalous' electrical conductivity is derived for this system, which parallels a recent result of Taylor and McNamara for the coefficient of spatial diffusion.

Montgomery, D.; Tappert, F.

1971-01-01

180

NASA Astrophysics Data System (ADS)

We report the generation of three-dimensional bright spatial solitary waves by the breakup of an optical vortex in a saturable self-focusing nonlinear medium. An elliptical Gaussian beam from a Ti:sapphire laser containing a singly charged on-axis vortex was passed through a nonlinear medium consisting of rubidium vapor at low concentrations. The modulational instability resulted in the formation of a pair of out-of-phase solitonlike beams, which spiraled away from each other during propagation as a result of the repulsive nature of their interaction. The rate of rotation and separation of the two soliton beams could be controlled by the parameters of the medium and the laser intensity. Numerical analysis of the propagation based on a model nonlinearity corresponding to a strongly saturated two-level system showed good quantitative agreement with the experimental data. Copyright (c) 1995 Optical Society of America

Tikhonenko, Vladimir; Christou, Jason; Luther-Daves, Barry

1995-11-01

181

Inelastic collision of spherical ion-acoustic solitons

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

182

Bright vector solitons in cross-defocusing nonlinear media

We study two-dimensional soliton-soliton vector pairs in media with self-focusing nonlinearities and defocusing cross interactions. The general properties of the stationary states and their stability are investigated. The different scenarios of instability are observed using numerical simulations. The quasistable propagation regime of the high-power vector solitons is revealed.

Yakimenko, A. I. [Department of Physics, Taras Shevchenko National University, Kiev 03022 (Ukraine); Institute for Nuclear Research, Kiev 03680 (Ukraine); Prikhodko, O. O.; Vilchynskyi, S. I. [Department of Physics, Taras Shevchenko National University, Kiev 03022 (Ukraine)

2010-07-15

183

Soliton dynamics in modulated Bessel photonic lattices

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

184

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

185

Soliton dynamics in the multiphoton plasma regime

Soliton dynamics in the multiphoton plasma regime Chad A. Husko1 *, Sylvain CombrieÂ´2 , Pierre, to gap solitons for dispersionless slow-light, and discrete spatial solitons in lattices, amongst others W/cm2 . Here we report the first phase-resolved observations of femtosecond optical solitons

Hone, James

186

Two-dimensional supersonic nonlinear Schroedinger flow past an extended obstacle

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

187

Delayed-action interaction and spin-orbit coupling between solitons.

We report on new fundamental phenomena in soliton interactions: delayed-action interaction and "spin"-orbit coupling upon collision between two-dimensional composite solitons carrying topological charges. PMID:11177943

Musslimani, Z H; Soljaci?, M; Segev, M; Christodoulides, D N

2001-01-29

188

Influence of iron doping on spatial soliton formation and fixing in lithium niobate crystals

NASA Astrophysics Data System (ADS)

We analyse the feasibility of using iron-doping in lithium niobate in order to stabilize and permanently fix light-induced integrated structures. General 3D optical interconnections were realized in bulk lithium niobate crystals by means of soliton waveguides exploiting the enhanced photorefractive properties obtainable using specific iron doping. We report an enhancement of the photorefractive properties in doped crystals that can be considered for permanently fixing the integrated circuits. This work opens new directions for realizing permanent self-assembled and self-aligned integrated electro-optic devices and photonic circuits.

Fazio, E.; Zaltron, A.; Belardini, A.; Argiolas, N.; Sada, C.

2014-11-01

189

Nematic liquid crystal cells for optical spatial solitons (Nematicons) - art. no. 64870R

The study of optical solitons and light filaments steering in liquid\\u000a crystals requires utilization of particular cells designed for top view\\u000a investigation and realized with an input interface which enables both to\\u000a control the molecular director configuration and to prevent light\\u000a scattering. Up to now, the director orientation imposed by this\\u000a additional interface has been only estimated by experimental\\u000a observations.

A. De Luca; A. Veltri; L. Pezzi; G. Coschignano; C. Umeton; A. Alberucci; C. Conti; M. Peccianti; G. Assanto

2007-01-01

190

Turbulent equipartitions in two dimensional drift convection

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

Mathematical frontiers in optical solitons

Solitons are localized concentrations of field energy, resulting from a balance of dispersive and nonlinear effects. They are ubiquitous in the natural sciences. In recent years optical solitons have arisen in new and exciting contexts that differ in many ways from the original context of coherent propagation in a uniform medium. We review recent developments in incoherent spatial solitons and in gap solitons in periodic structures. PMID:11687646

Bronski, Jared C.; Segev, Mordechai; Weinstein, Michael I.

2001-01-01

192

An explicit, supersymmetric solution to the low-energy heterotic string field equations representing an extended soliton with five spatial dimensions is found. This 5-brane is dual to heterotic strings in 10 dimensions in the same sense that magnetic charges are dual to electric charges in 4 dimensions. The 5-brane core is essentially a Yang-Mills instanton. The worldbrane field theory which describes

Andrew Strominger

1990-01-01

193

Two-dimensional nozzle plume characteristics

NASA Technical Reports Server (NTRS)

Future high performance aircraft will likely feature asymmetric or two-dimensional nozzles with or without ejectors. In order to design two-dimensional nozzle/ejector systems of minimum size and weight, the plume decay and spreading characteristics of basic two-dimensional nozzles must first be established. The present work deals with the experimental analyses of these plume characteristics and includes the effects of nozzle aspect ratio and flow conditions (jet Mach number and temperature) on the plume decay and spreading of two-dimensional nozzles. Correlations including these variables are developed in a manner similar to those previously developed successfully for conic and dual-flow plumes.

Von Glahn, Uwe H.

1987-01-01

194

Class of compound dissipative solitons as a result of collisions in one and two spatial dimensions

NASA Astrophysics Data System (ADS)

We study the interaction of quasi-one-dimensional (quasi-1D) dissipative solitons (DSs). Starting with quasi-1D solutions of the cubic-quintic complex Ginzburg-Landau (CGL) equation in their temporally asymptotic state as the initial condition, we find, as a function of the approach velocity and the real part of the cubic interaction of the two counterpropagating envelopes: interpenetration, one compound state made of both envelopes or two compound states. For the latter class both envelopes show DSs superposed at two different locations. The stability of this class of compound states is traced back to the quasilinear growth rate associated with the coupled system. We show that this mechanism also works for 1D coupled cubic-quintic CGL equations. For quasi-1D states that are not in their asymptotic state before the collision, a breakup along the crest can be observed, leading to nonunique results after the collision of quasi-1D states.

Descalzi, Orazio; Brand, Helmut R.

2014-08-01

195

Class of compound dissipative solitons as a result of collisions in one and two spatial dimensions.

We study the interaction of quasi-one-dimensional (quasi-1D) dissipative solitons (DSs). Starting with quasi-1D solutions of the cubic-quintic complex Ginzburg-Landau (CGL) equation in their temporally asymptotic state as the initial condition, we find, as a function of the approach velocity and the real part of the cubic interaction of the two counterpropagating envelopes: interpenetration, one compound state made of both envelopes or two compound states. For the latter class both envelopes show DSs superposed at two different locations. The stability of this class of compound states is traced back to the quasilinear growth rate associated with the coupled system. We show that this mechanism also works for 1D coupled cubic-quintic CGL equations. For quasi-1D states that are not in their asymptotic state before the collision, a breakup along the crest can be observed, leading to nonunique results after the collision of quasi-1D states. PMID:25215679

Descalzi, Orazio; Brand, Helmut R

2014-08-01

196

Two-dimensional Brownian vortices

NASA Astrophysics Data System (ADS)

We introduce a stochastic model of 2D Brownian vortices associated with the canonical ensemble. The point vortices evolve through their usual mutual advection but they experience in addition a random velocity and a systematic drift generated by the system as a whole. The statistical equilibrium state of this stochastic model is the Gibbs canonical distribution. We consider a single species system and a system made of two types of vortices with positive and negative circulations. At positive temperatures, like-sign vortices repel each other (“plasma” case) and at negative temperatures, like-sign vortices attract each other (“gravity” case). We derive the stochastic equation satisfied by the exact vorticity field and the Fokker-Planck equation satisfied by the N-body distribution function. We present the BBGKY-like hierarchy of equations satisfied by the reduced distribution functions and close the hierarchy by considering an expansion of the solutions in powers of 1/N, where N is the number of vortices, in a proper thermodynamic limit. For spatially inhomogeneous systems, we derive the kinetic equations satisfied by the smooth vorticity field in a mean field approximation valid for N?+?. For spatially homogeneous systems, we study the two-body correlation function, in a Debye-Hückel approximation valid at the order O(1/N). The results of this paper can also apply to other systems of random walkers with long-range interactions such as self-gravitating Brownian particles and bacterial populations experiencing chemotaxis. Furthermore, for positive temperatures, our study provides a kinetic derivation, from microscopic stochastic processes, of the Debye-Hückel model of electrolytes.

Chavanis, Pierre-Henri

2008-12-01

197

Phase Transitions in Two-Dimensional Superconductors

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

Ali Yazdani

1995-01-01

198

Scanning of two-dimensional space groups.

Tables of the scanning of two-dimensional space groups are presented to determine the frieze-group symmetry of lines that transect two-dimensional crystals. It is shown how these tables can be used to predict the (001) projection symmetries of migration-related segments of coincidence site lattice tilt boundaries with [001] tilt axis. PMID:25537394

Litvin, Daniel B

2015-01-01

199

The two-dimensional derivative-coupling model revisited

NASA Astrophysics Data System (ADS)

Using the operator approach we reexamine the two-dimensional model describing a massive Fermi field interacting via derivative couplings with two massless Bose fields, one scalar and the other pseudoscalar. Performing a canonical transformation on the Bose field algebra, the Fermi field operator is written in terms of the Mandelstam soliton operator and the derivative-coupling (DC) model is mapped into the massive Thirring model with two vector-current-scalar-derivative interactions (Schroer-Thirring model). The DC model with massless fermions can be mapped into the massless Rothe-Stamatescu model with a Thirring interaction (massless Rothe-Stamatescu-Thirring model). Within the present approach the weak equivalence between the fermionic sector of the DC model and the massive Thirring model is exhibited compactly.

Belvedere, L. V.; Rodrigues, A. F.

2007-05-01

200

Nonlinear compressional waves in a two-dimensional Yukawa lattice.

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

2003-10-01

201

Two-soliton interaction as an elementary act of soliton turbulence in integrable systems

Two-soliton interaction as an elementary act of soliton turbulence in integrable systems E Novgorod, Russia 3 Department of Mathematical Sciences, Loughborough University, UK Abstract Two-soliton characteristics of the nonlinear wave field of soliton turbulence we study properties of the spatial moments

202

Two-dimensional code acquisition using antenna arrays

An extension of conventional (delay domain) code acquisition to the delay-angle domain is studied. The two-dimensional uncertainty region is serially searched in an angle-delay or delay-angle fashion. Under the assumption that the signal is seen from one out of m possible angular directions and the interference can be modeled as temporarily and spatially white we show that there exist an

Marcos Katz; Jari Iinatti; Savo Glisic

2000-01-01

203

Two-dimensional amorphous silicon image sensor arrays

Large two-dimensional amorphous silicon image sensor arrays offer an advantage for high speed document scanning and medical X-ray imaging. We describe our page sized 200 spot per inch imager and the accompanying high speed readout electronics. The spatial resolution performance for white light and X-ray imaging is illustrated. We discuss how the important issues of noise and resolution depend on

X. D. Wu; R. Weisfield; S. Ready; R. Apte; M. Ngyuen; W. B. Jackson; P. Nylen

1996-01-01

204

Two dimensional prolate spheroidal wave functions for MRI

The tradeoff between spatial and temporal resolution is often used to increase data acquisition speed for dynamic MR imaging. Reduction of the k-space sampling area, however, leads to stronger partial volume and truncation effects. A two dimensional prolate spheroidal wave function (2D-PSWF) method is developed to address these problems. Utilizing prior knowledge of a given region of interest (ROI) and

Qing X. Yang; Martin A Lindquist; Lawrence Shepp; Cun-Hui Zhang; Jianli Wang; Michael B Smith

2002-01-01

205

Mars Pathfinder Two-Dimensional Model

NSDL National Science Digital Library

This activity is about the Mars Pathfinder spacecraft. Using cardboard and other materials, learners will create a two dimensional model of the spacecraft. A diagram with approximate measures of each component is provided.

2012-08-03

206

Two-Dimensional Planetary Surface Lander

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

207

Two-dimensional order and disorder thermofields

The main objective of this paper was to obtain the two-dimensional order and disorder thermal operators using the Thermofield Bosonization formalism. We show that the general property of the two-dimensional world according with the bosonized Fermi field at zero temperature can be constructed as a product of an order and a disorder variables which satisfy a dual field algebra holds at finite temperature. The general correlation functions of the order and disorder thermofields are obtained.

Belvedere, L. V. [Instituto de Fisica - Universidade Federal Fluminense, Av. Litora circumflex nea S/N, Boa Viagem Niteroi, CEP 24210-340 Rio de Janeiro (Brazil)

2006-11-15

208

Two-dimensional dispersion-managed light bullets in Kerr media

We propose a scheme for stabilizing spatiotemporal solitons (STSs) in media with cubic self-focusing nonlinearity and ``dispersion management,'' i.e., a layered structure inducing periodically alternating normal and anomalous group-velocity dispersion. We develop a variational approximation for the STS, and verify results by direct simulations. A stability region for the two-dimensional (2D) STS (corresponding to a planar waveguide) is identified. At

M. Matuszewski; M. Trippenbach; B. A. Malomed; E. Infeld; A. A. Skorupski

2004-01-01

209

A different spatial soliton-bearing wave equation is introduced, the Helmholtz-Manakov (HM) equation, for describing the evolution of broad multicomponent self-trapped beams in Kerr-type media. By omitting the slowly varying envelope approximation, the HM equation can describe accurately vector solitons propagating and interacting at arbitrarily large angles with respect to the reference direction. The HM equation is solved using Hirota's method, yielding four different classes of Helmholtz soliton that are vector generalizations of their scalar counterparts. General and particular forms of the three invariants of the HM system are also reported. PMID:17280167

Christian, J M; McDonald, G S; Chamorro-Posada, P

2006-12-01

210

Static topologically-nontrivial configurations in sigma-models, for spatial\\u000adimension D \\\\geq 2, are unstable. The question addressed here is whether such\\u000asigma-model solitons can be stabilized by steady rotation in internal space;\\u000athat is, rotation in a global SO(2) symmetry. This is the mechanism which\\u000astabilizes Q-balls (non-topological solitons). The conclusion is that the\\u000aQ-mechanism can stabilize topological solitons in D=2

R. S. Ward

2003-01-01

211

Solitons and ionospheric modification

NASA Technical Reports Server (NTRS)

The possibility of Langmuir soliton formation and collapse during ionospheric modification is investigated. Parameters characterizing former facilities, existing facilities, and planned facilities are considered, using a combination of analytical and numerical techniques. At a spatial location corresponding to the exact classical reflection point of the modifier wave, the Langmuir wave evolution is found to be dominated by modulational instability followed by soliton formation and three-dimensional collapse. The earth's magnetic field is found to affect the shape of the collapsing soliton. These results provide an alternative explanation for some recent observations.

Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.; Weatherall, J. C.; Goldman, M. V.

1982-01-01

212

Talbot image of two-dimensional fractal grating

NASA Astrophysics Data System (ADS)

Talbot effect of two-dimensional fractal grating built by square aperture arrays is studied theoretically and experimentally in this paper. The amplitude fractal gratings are produced by use of the spatial light modulator, and the diffraction intensity distributions of fractal gratings with different fractal level in Fresnel diffraction field are measured with the help of the two-dimensional CCD. Talbot images of fractal gratings with 1-level and 2-level fractal are obtained in practical experiment. The analytic expression of Fresnel diffraction intensity of the fractal gratings is derived through decomposing fractal gratings into the sum of many periodic gratings. Theoretic results predict the self-image of fractal grating reappears at some certain distance. The numerical calculations also show the Talbot image and the fractional Talbot image of fractal grating. These results may extend the application of fractal grating in the optical processing of information and laser measurement.

Teng, Shuyun; Wang, Junhong; Li, Furui; Zhang, Wei

2014-03-01

213

Accessible solitons in diffusive media.

We investigate spatial solitons in nonlocal media with a nonlinear index well modeled by a diffusive equation. We address the role of nonlocality and its interplay with boundary conditions, shedding light on the behavior of accessible solitons in real samples and discussing the accuracy of the highly nonlocal approximation. We find that symmetric solitons exist only above a power threshold, with an existence region that grows larger and larger with nonlocality in the plane width power. PMID:25078166

Alberucci, Alessandro; Jisha, Chandroth P; Assanto, Gaetano

2014-08-01

214

Classically spinning and isospinning solitons

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

215

Solitons on tori and soliton crystals

Necessary conditions for a soliton on a torus $M=\\R^m/\\Lambda$ to be a soliton crystal, that is, a spatially periodic array of topological solitons in stable equilibrium, are derived. The stress tensor of the soliton must be $L^2$ orthogonal to $\\ee$, the space of parallel symmetric bilinear forms on $TM$, and, further, a certain symmetric bilinear form on $\\ee$, called the hessian, must be positive. It is shown that, for baby Skyrme models, the first condition actually implies the second. It is also shown that, for any choice of period lattice $\\Lambda$, there is a baby Skyrme model which supports a soliton crystal of periodicity $\\Lambda$. For the three-dimensional Skyrme model, it is shown that any soliton solution on a cubic lattice which satisfies a virial constraint and is equivariant with respect to (a subgroup of) the lattice symmetries automatically satisfies both tests. This verifies in particular that the celebrated Skyrme crystal of Castillejo {\\it et al.}, and Kugler and Shtrikman, passes both tests.

J. M. Speight

2014-02-24

216

Singularity-free two-dimensional cosmologies

NASA Astrophysics Data System (ADS)

We present a class of theories of two-dimensional gravity which admits homogeneous and isotropic solutions that are nonsingular and asymptotically approach a FRW matter-dominated universe at late times. These models are generalizations of two-dimensional dilaton gravity and both vacuum solutions and those including conformally coupled matter are investigated. In each case our construction leads to an inflationary stage driven by the gravitational sector. Our work comprises a simple example of the ``nonsingular universe'' constructions of Brandenberger and co-workers.

Moessner, R.; Trodden, M.

1995-03-01

217

Singularity-free two-dimensional cosmologies

We present a class of theories of two-dimensional gravity which admits homogeneous and isotropic solutions that are nonsingular and asymptotically approach a FRW matter-dominated universe at late times. These models are generalizations of two-dimensional dilaton gravity and both vacuum solutions and those including conformally coupled matter are investigated. In each case our construction leads to an inflationary stage driven by the gravitational sector. Our work comprises a simple example of the nonsingular universe'' constructions of Brandenberger and co-workers.

Moessner, R.; Trodden, M. (Department of Physics, Brown University, Providence, Rhode Island 02912 (United States))

1995-03-15

218

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

219

Crossflow in two-dimensional asymmetric nozzles

NASA Technical Reports Server (NTRS)

An experimental investigation of the crossflow effects in three contoured, two-dimensional asymmetric nozzles is described. The data were compared with theoretical predictions of nozzle flow by using an inviscid method of characteristics solution and two-dimensional turbulent boundary-layer calculations. The effect of crossflow as a function of the nozzle maximum expansion angle was studied by use of oil-flow techniques, static wall-pressure measurements, and impact-pressure surveys at the nozzle exit. Reynolds number effects on crossflow were investigated.

Sebacher, D. I.; Lee, L. P.

1975-01-01

220

Two-Dimensional Clifford Windowed Fourier Transform

NASA Astrophysics Data System (ADS)

Recently several generalizations to higher dimension of the classical Fourier transform (FT) using Clifford geometric algebra have been introduced, including the two-dimensional (2D) Clifford-Fourier transform (CFT). Based on the 2D CFT, we establish the two-dimensional Clifford windowed Fourier transform (CWFT). Using the spectral representation of the CFT, we derive several important properties such as shift, modulation, a reproducing kernel, isometry, and an orthogonality relation. Finally, we discuss examples of the CWFT and compare the CFT and CWFT.

Bahri, Mawardi; Hitzer, Eckhard M. S.; Adji, Sriwulan

221

KP solitons, total positivity, and cluster algebras

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. PMID:21562211

Kodama, Yuji; Williams, Lauren K.

2011-01-01

222

KP solitons, total positivity, and cluster algebras

Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili 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 non-negative 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.

Yuji Kodama; Lauren Williams

2011-05-20

223

Reconfigurable soliton networks optically-induced by arrays of nondiffracting Bessel

Reconfigurable soliton networks optically- induced by arrays of nondiffracting Bessel beams Zhiyong.Kartashov@icfo.es Abstract: We address the propagation of solitons in reconfigurable two- dimensional networks induced optically by arrays of nondiffracting Bessel beams in Kerr-type nonlinear media. We show that broad soliton

224

A nonsingular two dimensional black hole

NASA Astrophysics Data System (ADS)

We construct a model of gravity in 1 + 1 spacetime dimensions in which the solutions approach the Schwarzschild metric at large r and de Sitter space far inside the horizon. Our model may be viewed as a two dimensional application of the ``Limiting Curvature Construction'' of Mukhanov and Brandenberger [Phys. Rev. Lett. 68 (1992) 1969].

Trodden, M.; Mukhanov, V. F.; Brandenberger, R. H.

1993-10-01

225

High Capacity Colored Two Dimensional Codes

Barcodes enable automated work processes without human intervention, and are widely deployed because they are fast and accurate, eliminate many errors and often save time and money. In order to increase the data capacity of barcodes, two dimensional (2D) code were developed; the main challenges of 2D codes lie in their need to store more information and more character types

Antonio Grillo; Alessandro Lentini; Marco Querini; Giuseppe F. Italiano

2010-01-01

226

On the two-dimensional associativity equation

We consider the two-dimensional associativity (or WDVV) equation u_yyy - u_xxy^2 + u_xxx u_xyy=0 and describe all integrable structures related to it (i.e., Hamiltonian, symplectic, and recursion operators). Infinite hierarchies of symmetries and conservation laws are constructed as well.

Kersten, Paul; Verbovetsky, Alexander; Vitolo, Raffaele

2011-01-01

227

Fractal two-dimensional electromagnetic bandgap structures

Fractal two-dimensional electromagnetic bandgap (EBG) materials are proposed and studied by means of a full-wave method developed for diffraction gratings. Such technique allows us to characterize, In an accurate and rapidly convergent way, the transmission and reflection properties of periodic fractal structures with an arbitrary geometry in the unit cell. Both polarization cases can be treated. A validation of the

Fabrizio Frezza; Lara Pajewski; Giuseppe Schettini

2004-01-01

228

Two-dimensional rotating heat pipe analysis

A detailed transient numerical simulation of rotating heat pipes is presented. This two-dimensional, axisymmetric formulation accounts for the thin liquid condensate film on the inner surface of the rotating pipe wall, the vapor flow in the vapor space, and the unsteady heat conduction in the pipe wall. The thin liquid film is coupled to the vapor velocity at the liquid-vapor

C. Harley; A. Faghri

1995-01-01

229

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

230

Two dimensional gas turbine engine exhaust nozzle

A two-dimensional variable area gas turbine engine exhaust nozzle is described having thrust reversing capability, the nozzle including spaced apart side wall means and upper and lower flap assemblies connected to the side wall means defining an exhaust gas flow path wihtin the nozzle, the nozzle having a centerline.

Thayer, E.B.; McLafferty, G.H.

1988-06-28

231

NASA Astrophysics Data System (ADS)

The main purpose of the paper is to provide a survey of our recent studies on soliton solutions of the Kadomtsev-Petviashvili (KP) equation. The KP equation describes weakly dispersive and small amplitude wave propagation in a quasi-two-dimensional framework. Recently, a large variety of exact soliton solutions of the KP equation has been found and classified. These solutions are localized along certain lines in a two-dimensional plane and decay exponentially everywhere else, and are called line-solitons. The classification is based on the far-field patterns of the solutions which consist of a finite number of line-solitons. Each soliton solution is then defined by a point of the totally non-negative Grassmann variety which can be parametrized by a unique derangement of the symmetric group of permutations. Our study also includes certain numerical stability problems of those soliton solutions. Numerical simulations of the initial value problems indicate that certain classes of initial waves asymptotically approach to these exact solutions of the KP equation. We discuss an application of our theory to the Mach reflection problem in shallow water. This problem describes the resonant interaction of solitary waves appearing in the reflection of an obliquely incident wave onto a vertical wall, and it predicts an extraordinary fourfold amplification of the wave at the wall. There are several numerical studies confirming the prediction, but all indicate disagreements with the KP theory. Contrary to those previous numerical studies, we find that the KP theory actually provides an excellent model to describe the Mach reflection phenomena when the higher order corrections are included in the quasi-two-dimensional approximation. We also present laboratory experiments of the Mach reflection recently carried out by Yeh and his colleagues, and show how precisely the KP theory predicts this wave behavior.

Kodama, Yuji

2010-10-01

232

Two dimensional prolate spheroidal wave functions for MRI

NASA Astrophysics Data System (ADS)

The tradeoff between spatial and temporal resolution is often used to increase data acquisition speed for dynamic MR imaging. Reduction of the k-space sampling area, however, leads to stronger partial volume and truncation effects. A two dimensional prolate spheroidal wave function (2D-PSWF) method is developed to address these problems. Utilizing prior knowledge of a given region of interest (ROI) and the spatial resolution requirement as constraints, this method tailors the k-space sampling area with a matching 2D-PSWF filter so that optimal signal concentration and minimal truncation artifacts are achieved. The k-space sampling area is reduced because the shape and size of the sampling area match the resolution posed by the non-rectangular shape of a convex ROI. The 2D-PSWF method offers an efficient way for spatial and temporal tradeoff with minimal penalty due to truncation, and thus, it promises a wide range of applications in MRI research.

Yang, Qing X.; Lindquist, Martin A.; Shepp, Lawrence; Zhang, Cun-Hui; Wang, Jianli; Smith, Michael B.

2002-09-01

233

Oblique collision of plane ion-acoustic solitons

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

234

Numerical simulations of Kadomtsev-Petviashvili soliton interactions

The Kadomtsev-Petviashvili equation generalizes that of Korteweg and de Vries to two space dimensions and arises in various weakly dispersive media. Two very different species of soliton solutions are known for one variant, KPI. The first species to be discovered are line solitons, the second are two dimensional lumps. This paper describes numerical simulations, consistent with all constraints of the

E. Infeld; A. Senatorski; A. A. Skorupski

1995-01-01

235

Oblique collision of plane ion-acoustic solitons

The nonlinear evolution of oblique collisions are 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.

Nishida, Y.; Nagasawa, T.

1980-11-17

236

Two-dimensional visualization of cluster beams by microchannel plates

An advanced technique for a two-dimensional real time visualization of cluster beams in vacuum as well as of the overlap volume of cluster beams with particle accelerator beams is presented. The detection system consists of an array of microchannel plates (MCP) in combination with a phosphor screen which is read out by a CCD camera. This setup together with the ionization of a cluster beam by an electron or ion beam allows for spatial resolved investigations of the cluster beam position, size, and intensity. Moreover, since electrically uncharged clusters remain undetected, the operation in an internal beam experiment opens the way to monitor the overlap region and thus the position and size of an accelerator beam crossing an originally electrically neutral cluster jet. The observed intensity distribution of the recorded image is directly proportional to the convolution of the spatial ion beam and cluster beam intensities and is by this a direct measure of the two-dimensional luminosity distribution. This information can directly be used for the reconstruction of vertex positions as well as for an input for numerical simulations of the reaction zone. The spatial resolution of the images are dominated by the granularity of the complete MCP device and was found to be in the order of \\sigma~100 \\mu m.

Alfons Khoukaz; Daniel Bonaventura; Silke Grieser; Ann-Katrin Hergemöller; Esperanza Köhler; Alexander Täschner

2013-07-23

237

Inviscid dynamics of two-dimensional shear layers

NASA Astrophysics Data System (ADS)

The dynamics of unconfined, spatially developing shear layers is studied by numerical solutions of the time-dependent Euler equations using a second-order Godunov scheme. Effects of density and velocity variations between the two streams of the shear layer are studied and color graphics is used to show more clearly the entrainment process of the surrounding streams. The calculations demonstrated that the evolution of the mean flow was dominated by two-dimensional, inviscid effects. The rms fluctuating velocity and density profiles were found to be in good agreement with the measurements of Oster and Wygnanski and of Konrad, except for the peak value of the v-prime profile.

Chien, Kuei-Yuan; Ferguson, Ralph E.; Kuhl, Allen L.; Glaz, Harland M.; Colella, Philip

1991-06-01

238

Two-dimensional high temperature strain measurement system

NASA Technical Reports Server (NTRS)

Two-dimensional optical strain measurements on high temperature test specimens are presented. This two-dimensional capability is implemented through a rotatable sensitive strain axis. Three components of surface strain can be measured automatically, from which the first and second principal strains are calculated. One- and two-dimensional strain measurements at temperatures beyond 750 C with a resolution of 15 microstrain are demonstrated. The system is based on a one-dimensional speckle shift technique. The speckle shift technique makes use of the linear relationship between surface strain and the differential shift of laser speckle patterns in the diffraction plane. Laser speckle is a phase effect that occurs when spatially coherent light interacts with an optically rough surface. Since speckle is generated by any diffusely reflecting surface, no specimen preparation is needed to obtain a good signal. Testing was done at room temperature on a flat specimen of Inconel 600 mounted in a fatigue testing machine. A load cell measured the stress on the specimen before and after acquiring the speckle data. Strain components were measured at 0 C (parallel to the load axis) and at plus or minus 45 C, and plots indicate the calculated values of the first and second principal strains. The measured values of Young's modulus and Poisson's ratio are in good agreement with handbook values. Good linearity of the principal strain moduli at high temperatures indicate precision and stability of the system. However, a systematic error in the high-temperature test setup introduced a scale factor in the slopes of the two-dimensional stress-strain curves. No high temperature effects, however, have been observed to degrade speckle correlation.

Lant, Christian T.; Barranger, John P.

1989-01-01

239

A Two-dimensional Magnetoseismic Network in the United States

NASA Astrophysics Data System (ADS)

Supported through several projects a series of ground magnetometers deployed in the past few years have formed a two-dimensional magnetoseismic network in the United States. This network includes the nine-station Mid-continent MAgnetoseismic Chain (McMAC) along the 330th magnetic meridian and the Falcon chain spanning from Maryland to Alaska. Sampling at 2 Hz the high-resolution fluxgate magnetometers located at these ground stations detect magnetospheric perturbations in the ULF frequencies and transmit the data through the Internet for analysis. In this presentation we focus on the ULF wave activities, including the resonances of magnetospheric field lines and the impulsive signals, observed by this two-dimensional magnetoseismic network in conjunction with other magnetometer arrays in North America. In sounding the plasmaspheric density, the gradient method can make use of the two-dimensional array to identify field line resonance (FLR) signatures from station pairs that are not strictly aligned in the same meridian but are separated by up to 20 degrees in longitude. Using the observations from the two-dimensional magnetoseismic network we found the spatial variations of plasmaspheric density in local time that would otherwise be unidentifiable by only the data from a single meridian chain. In timing the substorm onsets in the magnetotail, the magnetometer network can measure the different arrival times of magnetic impulses induced by substorm onsets and infer the start time and location of the associated reconnection in the magnetotail. A future plan on enhancing the capability of this magnetoseismic network in space weather monitoring and the coordination with space missions will be discussed.

Chi, P. J.; Bristow, W. A.; Chun, F. K.; Engebretson, M. J.; Hairston, M. R.; Jorgensen, A. M.; McHarg, M. G.; Mynatt, D.; Petit, N.; Russell, C. T.; Scherrer, D. K.; Takahashi, K.; Wing, S.; Winkler, L. I.; Cruz-Abeyro, J. L.

2010-12-01

240

Two-dimensional turbulence: a physicist approach

NASA Astrophysics Data System (ADS)

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 subjects are presented: coherent structures, statistical theories, inverse cascade of energy, condensed states, Richardson law, direct cascade of enstrophy, and the inter-play between cascades and coherent structures. The review offers a physicist's view on two-dimensional turbulence in the sense that experimental facts play an important role in the presentation, technical issues are described without much detail, sometimes in an oversimplified form, and physical arguments are given whenever possible. I hope this bias does not jeopardize the interest of the presentation for whoever wishes to visit the fascinating world of Flatland.

Tabeling, Patrick

2002-05-01

241

Graphane: A two-dimensional hydrocarbon

NASA Astrophysics Data System (ADS)

We predict the stability of an extended two-dimensional hydrocarbon on the basis of first-principles total-energy calculations. The compound that we call graphane is a fully saturated hydrocarbon derived from a single graphene sheet with formula CH. All of the carbon atoms are in sp3 hybridization forming a hexagonal network and the hydrogen atoms are bonded to carbon on both sides of the plane in an alternating manner. Graphane is predicted to be stable with a binding energy comparable to other hydrocarbons such as benzene, cyclohexane, and polyethylene. We discuss possible routes for synthesizing graphane and potential applications as a hydrogen storage material and in two-dimensional electronics.

Sofo, Jorge O.; Chaudhari, Ajay S.; Barber, Greg D.

2007-04-01

242

Graphane: a two-dimensional hydrocarbon

NASA Astrophysics Data System (ADS)

We predict the stability of a new extended two-dimensional hydrocarbon on the basis of first-principles total energy calculations. The compound that we call graphane is a fully saturated hydrocarbon derived from a single graphene sheet with formula CH. All of the carbon atoms are in sp^3 hybridization forming a hexagonal network and the hydrogen atoms are bonded to carbon on both sides of the plane in an alternating manner. Graphane is predicted to be stable with a binding energy comparable to other hydrocarbons such as benzene, cyclohexane, and polyethylene. We discuss possible routes for synthesizing graphane and potential applications as a hydrogen storage material and in two dimensional electronics.

Sofo, Jorge; Chaudhari, Ajay; Barber, Greg

2007-03-01

243

Electronics based on two-dimensional materials

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

244

Electronics based on two-dimensional materials.

The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments. PMID:25286272

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

2014-10-01

245

Two-dimensional structures in the magnetopause

NASA Astrophysics Data System (ADS)

A brief review is presented of a recently developed technique for reconstruction of two-dimensional structures in the magnetopause current layer. The method is based on numerical integration of the Grad-Shafranov (GS) equation, using as spatial initial conditions magnetic field and plasma velocity/pressure data measured by a single spacecraft as it traverses the structures. The method is benchmarked as follows, by use of data from the four Cluster II spacecraft: A reconstructed field map, based on data from one spacecraft, is used to predict what should be seen at the other three. These predictions are then compared with what was actually measured. The correlation coefficient between measured and predicted field components can reach values as high as 0.98. The method is then modified to allow ingestion of data from all four spacecraft, the result being field maps that no longer exactly satisfy the GS equation but produce correlation coefficients between measured and predicted field components that are substantially better: values as high as 0.994 have been reached. The reconstruction method is now used to study a few magnetopause encounters, occurring at the fairly high latitudes dictated by the Cluster orbit. Included are events that show no indications of reconnection as well as events that involve incipient reconnection and flux transfer events (FTEs). Even without any of the standard reconnection signatures, the reconstructed magnetopause maps usually display significant internal structure of the layer, in the form of magnetic islands separated by X points. The significance of such structures is discussed. Maps of FTEs indicate that, by the time they reach Cluster, they have often become fossil in the sense that reconnection activity has essentially stopped and the cross section has evolved toward a rounded final state. The axial "core" field in the FTEs is substantial, so that the FTE has the appearance of a somewhat flattened flux rope, embedded in the magnetopause. The core field and motion of the FTEs appear to require that they were generated by component merging at lower latitude and then convected past the observation site at high latitude. The orientation of the invariant axis of the FTEs is fairly well determined in the reconstruction technique, by a process of optimizing the correlation coefficient. In a test case, it shows good agreement with the orientation found from an earlier method [Khrabrov and Sonnerup, JGR, June, 1998], which technique is applicable when a spacecraft has an encounter with the external field, draped over an FTE bulge. The axis orientation of an FTE should provide an indication of the orientation of the reconnection line at which it was created. The orientations found are reasonably consistent with this expectation. The closed magnetic flux in the direction perpendicular to the FTE axis, i.e., in the reconstruction plane, can be calculated from the map and, using the time separation between FTEs, can be used to estimate the average reconnection electric field during the creation of the FTE. The results are in reasonable agreement with expectations.

Sonnerup, B.; Hasegawa, H.

246

Solitary waves bifurcated from Bloch-band edges in two-dimensional periodic media.

Solitary waves bifurcated from edges of Bloch bands in two-dimensional periodic media are determined both analytically and numerically in the context of a two-dimensional nonlinear Schrödinger equation with a periodic potential. Using multiscale perturbation methods, the envelope equations of solitary waves near Bloch bands are analytically derived. These envelope equations reveal that solitary waves can bifurcate from edges of Bloch bands under either focusing or defocusing nonlinearity, depending on the signs of the second-order dispersion coefficients at the edge points. Interestingly, at edge points with two linearly independent Bloch modes, the envelope equations lead to a host of solitary wave structures, including reduced-symmetry solitons, dipole-array solitons, vortex-cell solitons, and so on-many of which have not been reported before to our knowledge. It is also shown analytically that the centers of envelope solutions can be positioned at only four possible locations at or between potential peaks. Numerically, families of these solitary waves are directly computed both near and far away from the band edges. Near the band edges, the numerical solutions spread over many lattice sites, and they fully agree with the analytical solutions obtained from the envelope equations. Far away from the band edges, solitary waves are strongly localized, with intensity and phase profiles characteristic of individual families. PMID:17677181

Shi, Zuoqiang; Yang, Jianke

2007-05-01

247

Fermions near two-dimensional surfaces

We review work on constrained systems in which (3+1)-dimensional field theories are reduced to effective (2+1)-dimensional ones. Known results are extended to encompass the Dirac equation and the nonrelativistic limit is examined. We discuss to what extent this system can really be made two dimensional and obtain a lower bound on the thickness. Some comments are made about recent theories

Mark Burgess; Bjørn Jensen

1993-01-01

248

Deeply subrecoil two-dimensional Raman cooling

We report the implementation of a two-dimensional Raman cooling scheme using sequential excitations along the orthogonal axes. Using square pulses, we have cooled a cloud of ultracold cesium atoms down to an rms velocity spread of 0.39(5) recoil velocities, corresponding to an effective transverse temperature of 30 nK (0.15T{sub rec}). This technique can be useful to improve cold-atom atomic clocks and is particularly relevant for clocks in microgravity.

Boyer, V.; Phillips, W.D. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Lising, L.J.; Rolston, S.L. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2004-10-01

249

Statistical Mechanics of Two-dimensional Foams

The methods of statistical mechanics are applied to two-dimensional foams under macroscopic agitation. A new variable -- the total cell curvature -- is introduced, which plays the role of energy in conventional statistical thermodynamics. The probability distribution of the number of sides for a cell of given area is derived. This expression allows to correlate the distribution of sides ("topological disorder") to the distribution of sizes ("geometrical disorder") in a foam. The model predictions agree well with available experimental data.

Marc Durand

2010-09-07

250

Two-dimensional arrays for medical ultrasound

The design, fabrication and evaluation of two-dimensional transducer arrays are described for medical ultrasound imaging. A 4×32, 2.8-MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging. Laboratory measurements from typical array elements showed 50 ? insertion loss of -56 dB, -6 dB fractional bandwidth of 43%,

S. W. Smith; G. E. Trahey; O. T. von Ramm

1991-01-01

251

Two-dimensional dense gas dynamics

Certain polyatomic fluids with large molecular weights referred to as dense gases exhibit unusual thermodynamic and flow properties in the region of the thermodynamic critical point. A computer program developed to solve two-dimensional flow fields is used to analyze non- classical dense gas phenomena in the single-phase gas region. A two-step, flux-limited, total variation diminishing scheme solves the time-dependent Euler

Brady Polk Brown

1997-01-01

252

Two dimensional wedge/translating shroud nozzle

NASA Technical Reports Server (NTRS)

A jet propulsion exhaust nozzle is reported for multi-engine installations which produces high internal/external, thrust-minus-drag, performance for transonic cruise or transonic acceleration as well as improved performance at subsonic and supersonic speeds. A two dimensional wedge/translating shroud provides the variable nozzle exit geometry needed to achieve high engine performance over a wide range of throttle power settings.

Maiden, D. L. (inventor)

1978-01-01

253

Two-dimensional electrophoresis of membrane proteins

One third of all genes of various organisms encode membrane proteins, emphasizing their crucial cellular role. However, due\\u000a to their high hydrophobicity, membrane proteins demonstrate low solubility and a high tendency for aggregation. Indeed, conventional\\u000a two-dimensional gel electrophoresis (2-DE), a powerful electrophoretic method for the separation of complex protein samples\\u000a that applies isoelectric focusing (IEF) in the first dimension and

Ralf J. Braun; Norbert Kinkl; Monika Beer; Marius Ueffing

2007-01-01

254

Two-Dimensional Half-Rate Codes Using Two-Dimensional Finite-Field Filter Banks

This correspondence introduces two-dimensional (2-D) filter bank codes (TDFBCs). The synthesis bank of a two-channel two-dimensional filter bank over a finite field is used to design the 2-D code, and the corresponding analysis bank is used to generate the syndrome of the code. First, we study the encoder of half-rate TDFBCs and show that these linear codes are lattice-cyclic. It

Mina Sartipi; Farshid Delgosha; Faramarz Fekri

2007-01-01

255

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

256

Two-dimensional visualization of cluster beams by microchannel plates

An advanced technique for a two-dimensional real time visualization of cluster beams in vacuum as well as of the overlap volume of cluster beams with particle accelerator beams is presented. The detection system consists of an array of microchannel plates (MCP) in combination with a phosphor screen which is read out by a CCD camera. This setup together with the ionization of a cluster beam by an electron or ion beam allows for spatial resolved investigations of the cluster beam position, size, and intensity. Moreover, since electrically uncharged clusters remain undetected, the operation in an internal beam experiment opens the way to monitor the overlap region and thus the position and size of an accelerator beam crossing an originally electrically neutral cluster jet. The observed intensity distribution of the recorded image is directly proportional to the convolution of the spatial ion beam and cluster beam intensities and is by this a direct measure of the two-dimensional luminosity distribution. This inf...

Khoukaz, Alfons; Grieser, Silke; Hergemöller, Ann-Katrin; Köhler, Esperanza; Täschner, Alexander

2013-01-01

257

Transversely stable soliton trains in photonic lattices

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

258

Two families of Gaussian-type soliton solutions of the (n+1)-dimensional Schrödinger equation with cubic and power-law nonlinearities in -symmetric potentials are analytically derived. As an example, we discuss some dynamical behaviors of two dimensional soliton solutions. Their phase switches, powers and transverse power-flow densities are discussed. Results imply that the powers flow and exchange from the gain toward the loss regions in the cell. Moreover, the linear stability analysis and the direct numerical simulation are carried out, which indicates that spatial Gaussian-type soliton solutions are stable below some thresholds for the imaginary part of -symmetric potentials in the defocusing cubic and focusing power-law nonlinear medium, while they are always unstable for all parameters in other media. PMID:25542020

Chen, Yi-Xiang; Xu, Fang-Qian

2014-01-01

259

Kinetic theory of a two-dimensional magnetized plasma.

NASA Technical Reports Server (NTRS)

Several features of the equilibrium and nonequilibrium statistical mechanics of a two-dimensional plasma in a uniform dc magnetic field are investigated. The charges are assumed to interact only through electrostatic potentials. The problem is considered both with and without the guiding-center approximation. With the guiding-center approximation, an appropriate Liouville equation and BBGKY hierarchy predict no approach to thermal equilibrium for the spatially uniform case. For the spatially nonuniform situation, a guiding-center Vlasov equation is discussed and solved in special cases. For the nonequilibrium, nonguiding-center case, a Boltzmann equation, and a Fokker-Planck equation are derived in the appropriate limits. The latter is more tractable than the former, and can be shown to obey conservation laws and an H-theorem, but contains a divergent integral which must be cut off on physical grounds. Several unsolved problems are posed.

Vahala, G.; Montgomery, D.

1971-01-01

260

Formation and dynamics of dark solitons and vortices in quantum electron plasmas.

We present simulation studies of the formation and dynamics of dark solitons and vortices in quantum electron plasmas. The electron dynamics in the latter is governed by a pair of equations comprising the nonlinear Schrödinger and Poisson system of equations, which conserves the number of electrons as well as their momentum and energy. The present governing equations in one spatial dimension admit stationary solutions in the form a dark envelope soliton. The dynamics of the latter reveals its robustness. Furthermore, we numerically demonstrate the existence of cylindrically symmetric two-dimensional quantum electron vortices, which survive during collisions. The nonlinear structures presented here may serve the purpose of transporting information at quantum scales in ultracold micromechanical systems and dense plasmas, such as those created during intense laser-matter interactions. PMID:16907249

Shukla, P K; Eliasson, B

2006-06-23

261

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

262

Two dimensional echocardiographic diagnosis of situs.

At present there is no reliable method of recognising atrial isomerism by two dimensional echocardiography. We therefore used two dimensional echocardiography to examine 158 patients including 25 with atrial isomerism and four with situs inversus. Particular attention was paid to the short and long axis subcostal scans of the abdomen. Using the position of the inferior vena cava and the aorta with respect to the spine it was possible to separate those with situs solitus from the others. Two false positives for abnormal situs had exomphalos. In situs solitus the aorta lay to the left of the spine and the inferior vena cava lay to the right. One patient with situs solitus and azygos continuation of the inferior vena cava also had inferior vena cava to right atrial connection. In the four patients with situs inversus the mirror image of the normal pattern was present. In nine patients with right isomerism the inferior vena cava and aorta ran together on one or other side of the spine. The inferior vena cava, anterior to the aorta at the level of the diaphragm, received at least the right hepatic veins (normal or partial anomalous hepatic venous connection). Of the 16 patients with left isomerism, 14 had azygos continuation of the inferior vena cava which was visualised posterior to the aorta in all but two. All patients with left isomerism had total anomalous hepatic venous connection to one or both atria via one or two separate veins. Two dimensional echocardiography therefore provides the means of detecting abnormal atrial situs and of diagnosing right or left isomerism in the great majority of patients, if not all. Images PMID:7093090

Huhta, J C; Smallhorn, J F; Macartney, F J

1982-01-01

263

Two-dimensional heat flow apparatus

NASA Astrophysics Data System (ADS)

We have created an apparatus to quantitatively measure two-dimensional heat flow in a metal plate using a grid of temperature sensors read by a microcontroller. Real-time temperature data are collected from the microcontroller by a computer for comparison with a computational model of the heat equation. The microcontroller-based sensor array allows previously unavailable levels of precision at very low cost, and the combination of measurement and modeling makes for an excellent apparatus for the advanced undergraduate laboratory course.

McDougall, Patrick; Ayars, Eric

2014-06-01

264

Two dimensional foam rheology with viscous drag

We formulate and apply a continuum model that incorporates elasticity, yield stress, plasticity and viscous drag. It is motivated by the two-dimensional foam rheology experiments of Debregeas et al. [G. Debregeas, H. Tabuteau, and J.-M. di Meglio, Phys. Rev. Lett. 87, 178305 (2001)] and Wang et al [Y. Wang, K. Krishan, and M. Dennin, Phys. Rev. E 73, 031401 (2006)], and is successful in exhibiting their principal features an exponentially decaying velocity profile and strain localisation. Transient effects are also identified.

E. Janiaud; D. Weaire; S. Hutzler

2006-07-18

265

Diffusive transport in two-dimensional nematics

We discuss a dynamical theory for nematic liquid crystals describing the stage of evolution in which the hydrodynamic fluid motion has already equilibrated and the subsequent evolution proceeds via diffusive motion of the orientational degrees of freedom. This diffusion induces a slow motion of singularities of the order parameter field. Using asymptotic methods for gradient flows, we establish a relation between the Doi-Smoluchowski kinetic equation and vortex dynamics in two-dimensional systems. We also discuss moment closures for the kinetic equation and Landau-de Gennes-type free energy dissipation.

Ibrahim Fatkullin; Valeriy Slastikov

2014-03-02

266

Coherent matter waves of a dipolar condensate in two-dimensional optical lattices

The coherent matter waves of a dipolar condensate in deep two-dimensional (2D) tilted and nontilted optical lattices are studied both analytically and numerically. It is shown that, in tilted lattices, by properly designing the sign and the magnitude of the contact interaction and the dipolar interaction, it is possible to control the decoherence of Bloch oscillations. Contrary to the usual short-range interacting Bose system, long-lived Bloch oscillations of the dipolar condensate are achieved when the dipolar interaction, the contact interaction, and the lattice dimension satisfy an analytical condition. Furthermore, we predict that, in untilted lattices, stable coherent 2D moving soliton and breather states of the dipolar condensate exist. This fact is very different from the purely short-range interacting Bose system (where the moving soliton cannot be stabilized in high-dimensional lattices). The dipolar interaction can lead to some novel phenomena that can not appear in short-range interacting BEC system.

Zhang Aixia; Xue Jukui [Physics and Electronics Engineering College, Northwest Normal University, Lanzhou 730070 (China)

2010-07-15

267

The optical properties of two-dimensional Scarff parity-time symmetric potentials

NASA Astrophysics Data System (ADS)

We investigate the optical properties with two-dimensional (2D) Scarff parity-time (PT) symmetric potentials, including linear case, and self-focusing and self-defocussing nonlinear cases. For linear case, the PT-breaking points, the eigenvalues and eigenfunction for different modulated depths of 2D Scarff PT symmetry complex potential are obtained numerically. The PT-breaking points increase linearly with increasing the real part of the modulated depths of PT potential. Below the PT-breaking points, the eigenvalues of linear modes are real, however, eigenvalues of linear modes are complex above the PT-breaking points. For nonlinear cases, the existence of fundamental and multipole solitons is studied in self-focusing and self-defocussing media. The eigenvalue for linear case is equal to the critical propagation constant bc of soliton existing.

Hu, Sumei; Chen, Haibo

2014-08-01

268

Ultrashort light bullets described by the two-dimensional sine-Gordon equation

By using a reductive perturbation technique applied to a two-level model, this study puts forward a generic two-dimensional sine-Gordon evolution equation governing the propagation of femtosecond spatiotemporal optical solitons in Kerr media beyond the slowly varying envelope approximation. Direct numerical simulations show that, in contrast to the long-wave approximation, no collapse occurs, and that robust (2+1)-dimensional ultrashort light bullets may form from adequately chosen few-cycle input spatiotemporal wave forms. In contrast to the case of quadratic nonlinearity, the light bullets oscillate in both space and time and are therefore not steady-state lumps.

Leblond, Herve [Laboratoire de Photonique d'Angers, EA 4464 Universite d'Angers, 2 Bd. Lavoisier, FR-49045 Angers Cedex 01 (France); Mihalache, Dumitru [Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 407 Atomistilor, RO-077125 Magurele-Bucharest (Romania); Academy of Romanian Scientists, 54 Splaiul Independentei, RO-050094 Bucharest (Romania)

2010-06-15

269

Spatial coherence of a polariton condensate.

We perform Young's double-slit experiment to study the spatial coherence properties of a two-dimensional dynamic condensate of semiconductor microcavity polaritons. The coherence length of the system is measured as a function of the pump rate, which confirms a spontaneous buildup of macroscopic coherence in the condensed phase. An independent measurement reveals that the position and momentum uncertainty product of the condensate is close to the Heisenberg limit. An experimental realization of such a minimum uncertainty wave packet of the polariton condensate opens a door to coherent matter-wave phenomena such as Josephson oscillation, superfluidity, and solitons in solid state condensate systems. PMID:17930529

Deng, Hui; Solomon, Glenn S; Hey, Rudolf; Ploog, Klaus H; Yamamoto, Yoshihisa

2007-09-21

270

Two-dimensional vortices in superconductors

NASA Astrophysics Data System (ADS)

Superconductors have two key characteristics: they expel magnetic field and they conduct electrical current with zero resistance. However, both properties are compromised in high magnetic fields, which can penetrate the material and create a mixed state of quantized vortices. The vortices move in response to an electrical current, dissipating energy and destroying the zero-resistance state. One of the central problems for applications of high-temperature superconductivity is the stabilization of vortices to ensure zero electrical resistance. We find that vortices in the anisotropic superconductor Bi2Sr2CaCu2O8+? (Bi-2212) have a phase transition from a liquid state, which is inherently unstable, to a two-dimensional vortex solid. We show that at high field the transition temperature is independent of magnetic field, as was predicted theoretically for the melting of an ideal two-dimensional vortex lattice. Our results indicate that the stable solid phase can be reached at any field, as may be necessary for applications involving superconducting magnets. The vortex solid is disordered, as suggested by previous studies at lower fields. But its evolution with increasing magnetic field exhibits unexpected threshold behaviour that needs further investigation.

Chen, Bo; Halperin, W. P.; Guptasarma, Prasenjit; Hinks, D. G.; Mitrovi?,

2007-04-01

271

Decoherence in two-dimensional quantum walks

NASA Astrophysics Data System (ADS)

We analyze the decoherence in quantum walks in two-dimensional lattices generated by broken-link-type noise. In this type of decoherence, the links of the lattice are randomly broken with some given constant probability. We obtain the evolution equation for a quantum walker moving on two-dimensional (2D) lattices subject to this noise, and we point out how to generalize for lattices in more dimensions. In the nonsymmetric case, when the probability of breaking links in one direction is different from the probability in the perpendicular direction, we have obtained a nontrivial result. If one fixes the link-breaking probability in one direction, and gradually increases the probability in the other direction from 0 to 1, the decoherence initially increases until it reaches a maximum value, and then it decreases. This means that, in some cases, one can increase the noise level and still obtain more coherence. Physically, this can be explained as a transition from a decoherent 2D walk to a coherent 1D walk.

Oliveira, A. C.; Portugal, R.; Donangelo, R.

2006-07-01

272

Two dimensional and linear scintillation detectors for fast neutron imaging — comparative analysis

NASA Astrophysics Data System (ADS)

The paper was aimed to compare performance capabilities of two types of scintillation detectors commonly used for fast neutron imaging: two dimensional and linear ones. Best-case values of quantum efficiency, spatial resolution and capacity were estimated for detectors with plastic converter-screen in case of 14 MeV neutrons. For that there were examined nuclear reactions produced in converter-screen by fast neutrons, spatial distributions of energy release of emerged charged particles and amplitude distributions of scintillations generated by these particles. The paper shows that the efficiency of the linear detector is essentially higher and this detector provides potentially better spatial resolution in comparison with the two dimensional detector. But, the two dimensional detector surpasses the linear one in capacity. The presented results can be used for designing radiographic fast neutron detectors with organic scintillators.

Mikerov, V. I.; Koshelev, A. P.; Ozerov, O. V.; Sviridov, A. S.; Yurkov, D. I.

2014-05-01

273

Soliton scattering in the Darboux transformation formalism

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

274

Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions

NASA Astrophysics Data System (ADS)

Two-dimensional layered semiconductors such as MoS2 and WSe2 have attracted considerable interest in recent times. Exploring the full potential of these layered materials requires precise spatial modulation of their chemical composition and electronic properties to create well-defined heterostructures. Here, we report the growth of compositionally modulated MoS2–MoSe2 and WS2–WSe2 lateral heterostructures by in situ modulation of the vapour-phase reactants during growth of these two-dimensional crystals. Raman and photoluminescence mapping studies demonstrate that the resulting heterostructure nanosheets exhibit clear structural and optical modulation. Transmission electron microscopy and elemental mapping studies reveal a single crystalline structure with opposite modulation of sulphur and selenium distributions across the heterostructure interface. Electrical transport studies demonstrate that the WSe2–WS2 heterojunctions form lateral p–n diodes and photodiodes, and can be used to create complementary inverters with high voltage gain. Our study is an important advance in the development of layered semiconductor heterostructures, an essential step towards achieving functional electronics and optoelectronics.

Duan, Xidong; Wang, Chen; Shaw, Jonathan C.; Cheng, Rui; Chen, Yu; Li, Honglai; Wu, Xueping; Tang, Ying; Zhang, Qinling; Pan, Anlian; Jiang, Jianhui; Yu, Ruqing; Huang, Yu; Duan, Xiangfeng

2014-12-01

275

Two-dimensional phased array probe shape corrections

NASA Astrophysics Data System (ADS)

The availability of non-destructive testing hardware capable of controlling large numbers of elements has made possible forays into two-dimensional ultrasonic arrays. Here, we explore two such arrays. The first is a conical matrix array for three-dimensional imaging of fastener holes in aircraft wing structures, and the second is an annular-sectorial array with a compound radius of curvature for the inspection of aircraft engine grade billets. In both prototypes, significant departures of the true shape of the probe face from its ideal value are observed. Since the shape aberrations are many wavelengths in magnitude, it is impossible to arrive at the desired beam profile using the beamforming parameters for the ideal probe shape. We detail our approach for correcting the beamforming process. It is based on a combination of parametric representations of probe shape families and experimental measurements with specially designed targets. While exposing current limitations in the probe manufacturing process, our results demonstrate that complicated probe malformations of many wavelengths in magnitude can easily be corrected and that the spatially disjoint nature of two-dimensional arrays becomes an opportunity for such corrections.

Lupien, Vincent; Cancre, Fabrice; Lacroix, Benolt; Miller, Ted; Selman, John; Kinney, Andy; Duffy, Tim; Herzog, Pamela G.

2002-05-01

276

Rationally synthesized two-dimensional polymers.

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. PMID:23695626

Colson, John W; Dichtel, William R

2013-06-01

277

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

278

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

279

Transport in Two-Dimensional Disordered Semimetals

NASA Astrophysics Data System (ADS)

We theoretically study transport in two-dimensional semimetals. Typically, electron and hole puddles emerge in the transport layer of these systems due to smooth fluctuations in the potential. We calculate the electric response of the electron-hole liquid subject to zero and finite perpendicular magnetic fields using an effective medium approximation and a complementary mapping on resistor networks. In the presence of smooth disorder and in the limit of a weak electron-hole recombination rate, we find for small but finite overlap of the electron and hole bands an abrupt upturn in resistivity when lowering the temperature but no divergence at zero temperature. We discuss how this behavior is relevant for several experimental realizations and introduce a simple physical explanation for this effect.

Knap, Michael; Sau, Jay D.; Halperin, Bertrand I.; Demler, Eugene

2014-10-01

280

Two-dimensional fourier transform spectrometer

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

281

Intrinsic two-dimensional features as textons

NASA Technical Reports Server (NTRS)

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.

Barth, E.; Zetzsche, C.; Rentschler, I.

1998-01-01

282

From two-dimensional materials to heterostructures

NASA Astrophysics Data System (ADS)

Graphene, hexagonal boron nitride, molybdenum disulphide, and layered transition metal dichalcogenides (TMDCs) represent a class of two-dimensional (2D) atomic crystals with unique properties due to reduced dimensionality. Stacking these materials on top of each other in a controlled fashion can create heterostructures with tailored properties that offers another promising approach to design and fabricate novel electronic devices. In this report, we attempt to review this rapidly developing field of hybrid materials. We summarize the fabrication methods for different 2D materials, the layer-by-layer growth of various vertical heterostructures and their electronic properties. Particular interests are given to in-situ stack aforementioned 2D materials in controlled sequences, and the TMDCs heterostructures.

Niu, Tianchao; Li, Ang

2015-02-01

283

Two-dimensional layered composite photocatalysts.

Two-dimensional (2D) layered nanostructure composites are promising candidates for conducting high-performance energy conversion and environmental remediation. The construction of 2D layered composite photocatalysts can generate many unique properties that do not exist in other kinds of semiconductor composite photocatalyst, which are beneficial for photocatalytic performance enhancement, band gap tuning, heterojunction formation, etc. Recently, these advantages have greatly stimulated the study of 2D layered composite photocatalysts in the field of photocatalysis. This feature article summarizes the recent developments of 2D layered composite photocatalysts for photocatalytic applications, such as photocatalytic hydrogen production, bacterial disinfection, and pollutant degradation. Finally, perspectives on the challenges and opportunities for the future exploration of 2D layered composite photocatalysts are put forward. PMID:24964375

Low, Jingxiang; Cao, Shaowen; Yu, Jiaguo; Wageh, Swelm

2014-09-25

284

Two-dimensional virtual impactors. Final report

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

285

Internal tide generation by arbitrary two-dimensional topography

To date, analytical models of internal tide generation by two-dimensional ridges have considered only idealized shapes. Here, we advance the Green function approach to address the generation of internal tides by two-dimensional ...

Peacock, Thomas

286

Microwave near-field imaging of two-dimensional semiconductors.

Optimizing new generations of two-dimensional devices based on van der Waals materials will require techniques capable of measuring variations in electronic properties in situ and with nanometer spatial resolution. We perform scanning microwave microscopy (SMM) imaging of single layers of MoS2 and n- and p-doped WSe2. By controlling the sample charge carrier concentration through the applied tip bias, we are able to reversibly control and optimize the SMM contrast to image variations in electronic structure and the localized effects of surface contaminants. By further performing tip bias-dependent point spectroscopy together with finite element simulations, we distinguish the effects of the quantum capacitance and determine the local dominant charge carrier species and dopant concentration. These results underscore the capability of SMM for the study of 2D materials to image, identify, and study electronic defects. PMID:25625509

Berweger, Samuel; Weber, Joel C; John, Jimmy; Velazquez, Jesus M; Pieterick, Adam; Sanford, Norman A; Davydov, Albert V; Brunschwig, Bruce; Lewis, Nathan S; Wallis, Thomas M; Kabos, Pavel

2015-02-11

287

Electron capture imaging of two-dimensional materials

NASA Astrophysics Data System (ADS)

We demonstrate that electron transfer induced by fast ion impact can be used as an imaging technique of two-dimensional materials. Applied to a keV proton beam passing through a graphene surface, it is shown that coherent single-electron capture gives a sub-ångström-scale spatial resolution image of the electronic structure of a single sheet. This imaging scheme is shown to be particularly effective, resolving missing atoms (vacancies) in the lattice, in a narrow projectile 5-10-keV energy region, where the capture probability exhibits a minimum at the center of the hexagonal cells. This geometry-dependent phenomenon is caused by the coupling dynamic between the initial state and a multi-electron entangled one-hole state and is therefore highly sample selective.

Labaigt, G.; Dubois, A.; Hansen, J. P.

2014-06-01

288

Research on Generation Algorithm of Network Two-Dimensional Code

Two-dimensional code is a new and developing code which has gradually entered people's life. In foreign countries, one-dimensional barcode has been replaced with two-dimensional code in many respects: such as ID card, driver's license, military certificate, etc. But it is not so extensive to use two-dimensional code in China. However, with the development of information technology, the use of two-dimensional

Wei Zhang

2008-01-01

289

An improved two-dimensional code encoding approach for publications

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

290

????????????????????? Consideration on Two Dimensional Constraint Codes with Honeycomb Structure

Recently, two-dimensional recording system has developed in order to record information on very high density. Two-dimensional constraint codes also have stud- ied since such recording system requires the constraint with two-dimensionality. It has discussed only about the square lattice as the basic structure of a two-dimensional recording system. In this paper, we propose to use regular hexagonal as basic structure,

Shogo Usami; Akira Watanabe; Tadashi Wadayama

291

Packet Classification Using Two-Dimensional Multibit Tries

We develop fast algorithms to construct space-optimal contrained two-dimensional multibit tries for Internet packet classifier applications. Experimental evidence suggests that using the same memory budget, space-optimal two-dimensional multibit tries require 1\\/4 to 1\\/3 the memory accesses required by two-dimensional one-bit tries for table lookup. A heuristic for two-dimensional multibit tries with switch pointers also is proposed.

Wencheng Lu; Sartaj Sahni

2005-01-01

292

Two-Dimensional Weight-Constrained Codes through Enumeration Bounds

Two-Dimensional Weight-Constrained Codes through Enumeration Bounds Erik Ordentlich i into An m at a rate H( );( m =m);( n =n). Keywords: Two-dimensional coding Weight-constrained codes Balanced is motivated primarily by the coding problem of two-dimensional balanced binary n m arrays, in which each row

Roth, Ronny

293

E cient Code Constructions for Certain Two-Dimensional Constraints

E cient Code Constructions for Certain Two-Dimensional Constraints Roman Talyanskyy Tuvi Etzionz, there have been several results reported on two-dimensional runlength-limited coding 7], 8], coding of constraints on two- dimensional binary arrays. The rst constraint considered is that of t-conservative arrays

Roth, Ronny

294

Encorporation of Two Dimensional FrontTracking into

in Computational Science (PICS) GCT code, version 1.0. This merge adds a two dimensional, discontinuity tracking is the November 92 upgrade of the Stony Brook Code. This version is a two dimensional fully parallel (node only) CÂcodeEncorporation of Two Dimensional FrontÂTracking into PICS GCT 1.0 \\Lambda B. Bielefeld, B

New York at Stoney Brook, State University of

295

Spectral tunneling of lattice nonlocal solitons

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

296

Two dimensional prolate spheroidal wave functions for MRI.

The tradeoff between spatial and temporal resolution is often used to increase data acquisition speed for dynamic MR imaging. Reduction of the k-space sampling area, however, leads to stronger partial volume and truncation effects. A two dimensional prolate spheroidal wave function (2D-PSWF) method is developed to address these problems. Utilizing prior knowledge of a given region of interest (ROI) and the spatial resolution requirement as constraints, this method tailors the k-space sampling area with a matching 2D-PSWF filter so that optimal signal concentration and minimal truncation artifacts are achieved. The k-space sampling area is reduced because the shape and size of the sampling area match the resolution posed by the non-rectangular shape of a convex ROI. The 2D-PSWF method offers an efficient way for spatial and temporal tradeoff with minimal penalty due to truncation, and thus, it promises a wide range of applications in MRI research. PMID:12419670

Yang, Qing X; Lindquist, Martin A; Shepp, Lawrence; Zhang, Cun-Hui; Wang, Jianli; Smith, Michael B

2002-01-01

297

Implementations of two-dimensional liquid chromatography

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

298

Helmholtz solitons at nonlinear interfaces.

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

299

Elongation of moving noncommutative solitons

NASA Astrophysics Data System (ADS)

We discuss the characteristic properties of noncommutative solitons moving with constant velocity. As noncommutativity breaks the Lorentz symmetry, the shape of moving solitons is affected not just by the Lorentz contraction along the velocity direction, but also sometimes by additional `elongation' transverse to the velocity direction. We explore this in two examples: noncommutative solitons in a scalar field theory on two spatial dimension and `long stick' shaped noncommutative /U(2) magnetic monopoles. However the elongation factors of these two cases are different, and so not universal.

Bak, D.; Lee, K.

2000-12-01

300

Spontaneously walking discrete cavity solitons.

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

301

Seismic isolation of two dimensional periodic foundations

NASA Astrophysics Data System (ADS)

Phononic crystal is now used to control acoustic waves. When the crystal goes to a larger scale, it is called periodic structure. The band gaps of the periodic structure can be reduced to range from 0.5 Hz to 50 Hz. Therefore, the periodic structure has potential applications in seismic wave reflection. In civil engineering, the periodic structure can be served as the foundation of upper structure. This type of foundation consisting of periodic structure is called periodic foundation. When the frequency of seismic waves falls into the band gaps of the periodic foundation, the seismic wave can be blocked. Field experiments of a scaled two dimensional (2D) periodic foundation with an upper structure were conducted to verify the band gap effects. Test results showed the 2D periodic foundation can effectively reduce the response of the upper structure for excitations with frequencies within the frequency band gaps. When the experimental and the finite element analysis results are compared, they agree well with each other, indicating that 2D periodic foundation is a feasible way of reducing seismic vibrations.

Yan, Y.; Laskar, A.; Cheng, Z.; Menq, F.; Tang, Y.; Mo, Y. L.; Shi, Z.

2014-07-01

302

Two-dimensional detector of thermal neutrons

NASA Astrophysics Data System (ADS)

A two-dimensional detector of thermal neutrons has been designed and constructed for neutron diffraction experiments at the St. Petersburg Nuclear Physics Institute. It is based on a multiwire proportional chamber (MWPC) with cathode strip delay line readout and has a sensitive area of 170×300 mm 2 and anode wire spacing is 4 mm. It operates with a gas mixture of 1.5 bar 3He+2 bar CF 4. To improve the gas purity by a few orders of magnitude, a new technology for fabrication of the detector's electrodes has been developed. An intrinsic resolution of 0.6 mm (FWHM) and a differential nonlinearity of ±5% are achieved. It was shown that the detector, whose efficiency is about 60% for 9 Å neutrons, has a resolution of 2.5 mm along the fine axis and about 4 mm for the perpendicular discrete axis. The dependence of the measured pulse height spectra from the applied high voltage and the electric field in the drift regions has been investigated. It turns out that for thermal neutrons the measured spectra are very similar to those obtained with proportional neutron counters filled with 10 bar 3He.

Andreev, V.; Ganzha, G.; Ilyin, D.; Ivanov, E.; Kovalenko, S.; Krivshich, A.; Nadtochy, A.; Runov, V.

2007-10-01

303

An atlas of two-dimensional materials.

The discovery of graphene and other two-dimensional (2D) materials together with recent advances in exfoliation techniques have set the foundations for the manufacturing of single layered sheets from any layered 3D material. The family of 2D materials encompasses a wide selection of compositions including almost all the elements of the periodic table. This derives into a rich variety of electronic properties including metals, semimetals, insulators and semiconductors with direct and indirect band gaps ranging from ultraviolet to infrared throughout the visible range. Thus, they have the potential to play a fundamental role in the future of nanoelectronics, optoelectronics and the assembly of novel ultrathin and flexible devices. We categorize the 2D materials according to their structure, composition and electronic properties. In this review we distinguish atomically thin materials (graphene, silicene, germanene, and their saturated forms; hexagonal boron nitride; silicon carbide), rare earth, semimetals, transition metal chalcogenides and halides, and finally synthetic organic 2D materials, exemplified by 2D covalent organic frameworks. Our exhaustive data collection presented in this Atlas demonstrates the large diversity of electronic properties, including band gaps and electron mobilities. The key points of modern computational approaches applied to 2D materials are presented with special emphasis to cover their range of application, peculiarities and pitfalls. PMID:24825454

Miró, Pere; Audiffred, Martha; Heine, Thomas

2014-09-21

304

Compact Two-Dimensional Spectrometer Optics

NASA Technical Reports Server (NTRS)

The figure is a simplified depiction of a proposed spectrometer optical unit that would be suitable for incorporation into a remote-sensing instrumentation system. Relative to prior spectrometer optical assemblies, this unit would be compact and simple, largely by virtue of its predominantly two-dimensional character. The proposed unit would be a combination of two optical components. One component would be an arrayed-waveguide grating (AWG) an integrated-optics device, developed for use in wavelength multiplexing in telecommunications. The other component would be a diffraction grating superimposed on part of the AWG. The function of an AWG is conceptually simple. Input light propagates along a single-mode optical waveguide to a point where it is split to propagate along some number (N) of side-by-side waveguides. The lengths of the optical paths along these waveguides differ such that, considering the paths in a sequence proceeding across the array of waveguides, the path length increases linearly. These waveguides launch quasi-free-space waves into a planar waveguide-coupling region. The waves propagate through this region to interfere onto an array of output waveguides. Through proper choice of key design parameters (waveguide lengths, size and shape of the waveguide coupling region, and lateral distances between waveguides), one can cause the input light to be channeled into wavelength bins nominally corresponding to the output waveguides.

Hong, John

2008-01-01

305

Dynamics of two-dimensional dipole systems

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

306

Two-dimensional transition metal carbides.

Herein we report on the synthesis of two-dimensional transition metal carbides and carbonitrides by immersing select MAX phase powders in hydrofluoric acid, HF. The MAX phases represent a large (>60 members) family of ternary, layered, machinable transition metal carbides, nitrides, and carbonitrides. Herein we present evidence for the exfoliation of the following MAX phases: Ti(2)AlC, Ta(4)AlC(3), (Ti(0.5),Nb(0.5))(2)AlC, (V(0.5),Cr(0.5))(3)AlC(2), and Ti(3)AlCN by the simple immersion of their powders, at room temperature, in HF of varying concentrations for times varying between 10 and 72 h followed by sonication. The removal of the "A" group layer from the MAX phases results in 2-D layers that we are labeling MXenes to denote the loss of the A element and emphasize their structural similarities with graphene. The sheet resistances of the MXenes were found to be comparable to multilayer graphene. Contact angle measurements with water on pressed MXene surfaces showed hydrophilic behavior. PMID:22279971

Naguib, Michael; Mashtalir, Olha; Carle, Joshua; Presser, Volker; Lu, Jun; Hultman, Lars; Gogotsi, Yury; Barsoum, Michel W

2012-02-28

307

Two-dimensional flow magnetophoresis of microparticles.

A new two-dimensional micro-flow magnetophoresis device was constructed in a superconducting magnet (10 T) using triangular shaped pole pieces, which could apply a magnetic strength, B(dB/dx), in the range of ca. 0-14,000 T(2) m(-1) across a capillary cell. Polystyrene particles with diameters of 1, 3, and 6 ?m were used as test samples in a paramagnetic medium of 1 M MnCl(2) to evaluate the performance of this method. Microparticles migrated across the capillary along the edge of the pole pieces, and then flowed through the gap in the pole piece at a position defined as the migration distance, depending on the magnetic susceptibility and the size of particles as well as the flow rate. The most effective flow rate to exhibit the largest resolution among the particles was theoretically predicted and experimentally confirmed. By this method, the magnetic susceptibilities of individual deoxygenated and non-deoxygenated red blood cells were measured from the relative migration distance. PMID:22618326

Kawano, Makoto; Watarai, Hitoshi

2012-07-01

308

Nonlinear tunneling in two-dimensional lattices

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

309

ERIC Educational Resources Information Center

Investigated the development among fourth-graders of two-dimensional space concepts within a mathematics unit on grids, coordinates, and rectangles. Found that students' knowledge of grid and coordinate systems related to levels of competence in number sense, spatial-geometric relationships, and the ability to discriminate and integrate the two…

Sarama, Julie; Clements, Douglas H.; Swaminathan, Sudha; McMillen, Sue; Gonzalez Gomez, Rosa M.

2003-01-01

310

Two-dimensional atomic lithography by submicrometer focusing of atomic beams

of secondary maxima that can lead to atom localization in rings surrounding the central peak. In this paper weTwo-dimensional atomic lithography by submicrometer focusing of atomic beams Will Williams and M optical focusing of a colli- mated atomic beam. A spatial light modulator is used in a side illumination

Saffman, Mark

311

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

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

M. Z. Hasan; R. W. Conn

1986-01-01

312

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

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

M. Z. Hasan; R. W. Conn

1987-01-01

313

Development of a new two-dimensional Cartesian geometry nodal multigroup discrete ordinates method

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques respectively. The basic approach is to (1) approximate the

Pevey

1982-01-01

314

Solution and Study of the Two-Dimensional Nodal Neutron Transport Equation

In the last decade Vilhena and coworkers reported an analytical solution to the two-dimensional nodal discrete-ordinates approximations of the neutron transport equation in a convex domain. The key feature of these works was the application of the combined collocation method of the angular variable and nodal approach in the spatial variables. By nodal approach we mean the transverse integration of

Ruben Panta Pazos; Eliete Biasotto Hauser; Marco Tullio de Vilhena

2002-01-01

315

Development of a new two-dimensional Cartesian geometry nodal multigroup discrete-ordinates method

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques, respectively. The resulting FORTRAN computer code is designed to

Pevey

1982-01-01

316

Two-Dimensional Optical Proximity Effects

NASA Astrophysics Data System (ADS)

In projection printing the proximity effects between adjacent two-dimensional features such as concentric elbows can be the limiting factor in designing layout rules. An aerial image simulation code based on the imaging algorithms in SAMPLE has been developed and used to investigate these proximity effects. The program accepts arbitrary polygonal shapes constructed of rectangular and triangular patches. The image is calculated using Hopkins transmission cross coefficient formulation and uses rapid integral evaluation techniques. The cpu time for this FORTRAN F77 program depends on the size of the mask and the partial coherence factor as 0.25[(1 + ?) 2A(NA/?)2]2 seconds on a DEC VAX 11/780 using double precision, where A is the mask area, ? the coherence factor, NA the numerical aperture and ? the wavelength. The output intensity can be displayed with graphics tools such as UNIGRAFIX or cross-sectioned for input to SAMPLE development simulation along critical paths. Proximity effects in critical regions between features such as nested elbows, contacts near contacts and lines, and lines near large pads are studied. For small contacts studies show that a contact hole can be placed as close as 0.5?/NA microns to another contact hole. For nested elbows the critical effect is the variation in intensity in the straight regions just adjacent to the corner. This undesirable variation is primarily due to the intrafeature intensity interactions and is not greatly influenced by the proximity of another nested elbow. For general feature shapes the proximity effects are reduced by increasing the partial coherence factor to 0.5 or higher but at the cost of reducing contrast and peak intensity. For contact masks a partial coherence of 0.3 is recommended for higher edge slope and peak intensities. Proximity effects of small defects are also illustrated.

Flanner, Philip D.; Subramanian, Shankar; Neureuther, Andrew R.

1986-08-01

317

Coherence Controlled Soliton Interactions Ting-Sen Ku,1

Coherence Controlled Soliton Interactions Ting-Sen Ku,1 Ming-Feng Shih,1 Andrey A. Sukhorukov,2 theoretically and subsequently observe in experiment a novel type of soliton interaction when a pair of closely spaced spatial optical solitons as a whole is made partially incoherent. We explain how the character

318

Soliton interactions and transformations in colloidal media Michal Matuszewski,1

Soliton interactions and transformations in colloidal media Michal Matuszewski,1 Wieslaw the existence and properties of one-dimensional self-trapped beams spatial optical solitons in such media and demonstrate the existence of a bistability regime. The solitons corresponding to the two bistable branches

319

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

320

TWO DIMENSIONAL COMPUTER SIMULATION OF PLASMA IMMERSION

for treating complex shaped objects Â·requires complex target manipulation Â·high production cost #12;Plasma Â·low cost Â·shorter implantation time Disadvantages Â·spatial dose uniformity is a priori not guaranteed. Probabilistic Monte-Carlo collision algorithm is employed to simulate the ionization process. Actual mass of N2

321

[Improved diagnosis and therapy of pericardial effusion with two-dimensional echocardiography].

M-mode echocardiography has until now been the method of choice for the diagnosis of pericardial effusion in general clinical practice. Incidences of false positive and false negative findings have nonetheless been reported in the literature. A vastly simplified diagnosis with greater sensitivity and specificity has been achieved with the spatial orientation provided by a combination of two-dimensional echocardiography and M-mode echocardiography. With these two-dimensional techniques, pericardial puncture is rendered simpler and safer for the patient. PMID:6880217

Zenker, G; Harnoncourt, K; Forche, G

1983-06-15

322

Two-dimensional material confined water.

Conspectus The interface between water and other materials under ambient conditions is of fundamental importance due to its relevance in daily life and a broad range of scientific research. The structural and dynamic properties of water at an interface have been proven to be significantly difference than those of bulk water. However, the exact nature of these interfacial water adlayers at ambient conditions is still under debate. Recent scanning probe microscopy (SPM) experiments, where two-dimensional (2D) materials as ultrathin coatings are utilized to assist the visualization of interfacial water adlayers, have made remarkable progress on interfacial water and started to clarify some of these fundamental scientific questions. In this Account, we review the recently conducted research exploring the properties of confined water between 2D materials and various surfaces under ambient conditions. Initially, we review the earlier studies of water adsorbed on hydrophilic substrates under ambient conditions in the absence of 2D coating materials, which shows the direct microscopic results. Subsequently, we focus on the studies of water adlayer growth at both hydrophilic and hydrophobic substrates in the presence of 2D coating materials. Ice-like water adlayers confined between hydrophobic graphene and hydrophilic substrates can be directly observed in detail by SPM. It was found that the packing structure of the water adlayer was determined by the hydrophilic substrates, while the orientation of intercalation water domains was directed by the graphene coating. In contrast to hydrophilic substrates, liquid-like nanodroplets confined between hydrophobic graphene and hydrophobic substrates appear close to step edges and atomic-scale surface defects, indicating that atomic-scale surface defects play significant roles in determining the adsorption of water on hydrophobic substrates. In addition, we also review the phenomena of confined water between 2D hydrophilic MoS2 and the hydrophilic substrate. Finally, we further discuss researchers taking advantage of 2D graphene coatings to stabilize confined water nanodroplets to manipulate nanofluidics through applying an external force by using novel SPM techniques. Moreover, for future technology application purposes, the doping effect of confined water is also discussed. The use of 2D materials as ultrathin coatings to investigate the properties of confined water under ambient conditions is developing and recognized as a profound approach to gain fundamental knowledge of water. This ideal model system will provide new opportunities in various research fields. PMID:25539031

Li, Qiang; Song, Jie; Besenbacher, Flemming; Dong, Mingdong

2015-01-20

323

January 1, 1991 / Vol. 16, No. 1 / OPTICS LETTERS 15 Experimental observation ofspatial soliton optical solitons in a nonlinear glasswaveguide. Both attraction and repulsion wereobserved,depending on the relative phase between the solitons. Spatial optical solitons are self-trapped optical beams that propagate

Purdue University

324

Embedded solitons: solitary waves in resonance with the linear spectrum

It is commonly held that a necessary condition for the existence of solitons in nonlinear-wave systems is that the soliton’s frequency (spatial or temporal) must not fall into the continuous spectrum of radiation modes. However, this is not always true. We present a new class of codimension-one solitons (i.e., those existing at isolated frequency values) that are embedded into the

A. R. Champneys; B. A. Malomed; J. Yang; D. J. Kaup

2001-01-01

325

Modulational instability and solitons in nonlocal media with competing nonlinearities

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

326

Packet Classification Using Pipelined Two-Dimensional Multibit Tries

We propose heuristics for the construction of fixed- and variable-stride two-dimensional multibit tries. These multibit tries are suitable for the classification of Internet packets using a pipelined architecture. The pipelined two-dimensional multibit tries constructed by our proposed heuristics are superior, for pipelined architectures, to two-dimensional multibit tries constructed by the best algorithms proposed for non-pipelined architectures.

Wencheng Lu; Sartaj Sahni

2006-01-01

327

Two-Dimensional Finite Element Ablative Thermal Response Analysis of an Arcjet Stagnation Test

NASA Technical Reports Server (NTRS)

The finite element ablation and thermal response (FEAtR, hence forth called FEAR) design and analysis program simulates the one, two, or three-dimensional ablation, internal heat conduction, thermal decomposition, and pyrolysis gas flow of thermal protection system materials. As part of a code validation study, two-dimensional axisymmetric results from FEAR are compared to thermal response data obtained from an arc-jet stagnation test in this paper. The results from FEAR are also compared to the two-dimensional axisymmetric computations from the two-dimensional implicit thermal response and ablation program under the same arcjet conditions. The ablating material being used in this arcjet test is phenolic impregnated carbon ablator with an LI-2200 insulator as backup material. The test is performed at the NASA, Ames Research Center Interaction Heating Facility. Spatially distributed computational fluid dynamics solutions for the flow field around the test article are used for the surface boundary conditions.

Dec, John A.; Laub, Bernard; Braun, Robert D.

2011-01-01

328

By incorporating a length of single-mode, polarization-preserving fiber into the feedback loop of a mode-locked color-center laser (lambdaapprox.1.4--1.6 ..mu..m), we have created a device that we call the soliton laser. Pulse width (2.0 to 0.21 psec obtained to data) is determined by fiber length, in accordance with N = 2 soliton behavior. Production of <50-fsec-wide pulses is indicated for compression

L. F. Mollenauer; R. H. Stolen

1984-01-01

329

We review the status of solitons in superstring theory, with a view to understanding the strong coupling regime. These solitonic solutions are non-singular field configurations which solve the empty-space low-energy field equations (generalized, whenever possible, to all orders in ??), carry a non-vanishing topological “magnetic” charge and are stabilized by a topological conservation law. They are compared and contrasted with

M. J. Duff; Ramzi R. Khuri; J. X. Lu

1995-01-01

330

Soliton form factors from lattice simulations

The form factor provides a convenient way to describe properties of topological solitons in the full quantum theory, when semiclassical concepts are not applicable. It is demonstrated that the form factor can be calculated numerically using lattice Monte Carlo simulations. The approach is very general and can be applied to essentially any type of soliton. The technique is illustrated by calculating the kink form factor near the critical point in 1+1-dimensional scalar field theory. As expected from universality arguments, the result agrees with the exactly calculable scaling form factor of the two-dimensional Ising model.

Arttu Rajantie; David J. Weir

2011-01-06

331

The main purpose of the paper is to provide a survey of our recent studies on soliton solutions of the Kadomtsev-Petviashvili (KP) equation. The classification is based on the far-field patterns of the solutions which consist of a finite number of line-solitons. Each soliton solution is then defined by a point of the totally non-negative Grassmann variety which can be parametrized by a unique derangement of the symmetric group of permutations. Our study also includes certain numerical stability problems of those soliton solutions. Numerical simulations of the initial value problems indicate that certain class of initial waves asymptotically approach to these exact solutions of the KP equation. We then discuss an application of our theory to the Mach reflection problem in shallow water. This problem describes the resonant interaction of solitary waves appearing in the reflection of an obliquely incident wave onto a vertical wall, and it predicts an extra-ordinary four-fold amplification of the wave at the wall. There are several numerical studies confirming the prediction, but all indicate disagreements with the KP theory. Contrary to those previous numerical studies, we find that the KP theory actually provides an excellent model to describe the Mach reflection phenomena when the higher order corrections are included to the quasi-two dimensional approximation. We also present laboratory experiments of the Mach reflection recently carried out by Yeh and his colleagues, and show how precisely the KP theory predicts this wave behavior.

Yuji Kodama

2010-04-26

332

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 10T(m) (T(m) being the melting temperature of the crystal), while the motions due to long-wavelength phonons decrease only linearly in temperature. PMID:23214781

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

2012-11-01

333

The classical solutions of two-dimensional gravity

The solutions of two-dimensional gravity following from a non-linear Lagrangian L = f(R) are classified, and their symmetry and singularity properties are described. Then a conformal transformation is applied to rewrite these solutions as analogous solutions of two-dimensional Einstein-dilaton gravity and vice versa.

Hans - Juergen Schmidt

1999-05-15

334

Completeness through Flatness in Two-Dimensional Temporal Logic

] for an overview) to develop two-dimensional modal logics taking care of the linguistic phenomenon that the truth (Venema [26]) which is based on the idea that in its semantics, transitions (arrows) do not link the possible worlds, they are the possible worlds. Two-dimensional arrow logic arises if we see transitions

Venema, Yde

335

Two-dimensional simulation of the polarization switching in ferroelectrics

NASA Astrophysics Data System (ADS)

The main switching properties in ferroelectrics are simulated within the framework of the extended Ishibashi dipole-lattice model including the dipole-dipole interaction in a two-dimensional case. The mechanism of the polarization reversal is modeled in the two-dimensional case. The results of the modeling are in a good agreement with experimental data for the set of materials.

Bakaleinikov, L. A.; Gordon, A.

2009-12-01

336

Automatic identification technology — Application of two-dimensional code

With the modern development of intelligent information society, automatic identification technology will be a research priority. This article focuses on one field of automatic identification technology - two-dimensional code technology. By studying the application of two-dimensional codes, the application of certain areas could be promoted, so as to improve the development of automatic identification technology in China, promote China's economic

Tao Sun; Di Zhou

2011-01-01

337

Two-Dimensionally Isotropic High Index Metamaterials Yushin Kim1

Two-Dimensionally Isotropic High Index Metamaterials Yushin Kim1 , Muhan Choi1,2 , Seung Hoon Lee1 of Korea bmin@kaist.ac.kr Abstract: We fabricated two-dimensionally isotropic high index metamaterials indices in the terahertz frequency range. OCIS codes: (160.3918) Metamaterials; (300.6495) Spectroscopy

Park, Namkyoo

338

Two-dimensional wavelet compression of ion mobility spectra

A two-dimensional wavelet compression method has been developed as a tool for portable ion mobility sensors. Ion mobility spectrometry (IMS) offers chemical sensors with low detection limits and rapid response for many compounds. Two-dimensional wavelet compression yields compressions greater than 99% without significant loss of information. A method has also been developed and evaluated to optimize the compression. The compression

Aaron A. Urbas; Peter B. Harrington

2001-01-01

339

Adiabatic Single Scan Two-Dimensional NMR Spectrocopy Philippe Pelupessy*,

on the use adiabatic pulses, for single scan two-dimensional NMR experiments (Frydman et al., Proc. Nat. Acad- and heteronuclear experiments are presented. Introduction The introduction of two-dimensional (2D) experiments has revolutionized the field of nuclear magnetic resonance (NMR).1,2 Unfortunately, these experiments are inherently

340

Two-Dimensional Signal Transmission for Networked Sensing

Transmission (2DST)" for connecting a large number of devices, using microwave propagation localized in a thin in which signals are conveyed by microwave propagation localized within a two-dimensional signal. In this paper, first we analyze two dimensional propagation of electromagnetic wave in a thin layer. We show

Shinoda, Hiroyuki

341

PRESSURE MEASUREMENT IN A TWO DIMENSIONAL UNSTEADY FLOW

PRESSURE MEASUREMENT IN A TWO DIMENSIONAL UNSTEADY FLOW William Walker Virginia Polytechnic to obtain unsteady aerodynamic data from a two dimensional wing, and analyzing the pressure variations with time over the wing surface. The data was gathered by using electronic pressure transducers

Patil, Mayuresh

342

Information technologies for comprehensive two-dimensional gas chromatography

Review Information technologies for comprehensive two-dimensional gas chromatography Stephen E December 2003 Available online 8 March 2004 Abstract Comprehensive two-dimensional gas chromatography (GC Ã?-dimensional gas chromatography; GCÃ?GC; Information technology; Image processing; Visualization; Computer

Reichenbach, Stephen E.

343

Freely decaying turbulence in two-dimensional electrostatic gyrokinetics

In magnetized plasmas, a turbulent cascade occurs in phase space at scales smaller than the thermal Larmor radius ('sub-Larmor scales') [Tatsuno et al., Phys. Rev. Lett. 103, 015003 (2009)]. When the turbulence is restricted to two spatial dimensions perpendicular to the background magnetic field, two independent cascades may take place simultaneously because of the presence of two collisionless invariants. In the present work, freely decaying turbulence of two-dimensional electrostatic gyrokinetics is investigated by means of phenomenological theory and direct numerical simulations. A dual cascade (forward and inverse cascades) is observed in velocity space as well as in position space, which we diagnose by means of nonlinear transfer functions for the collisionless invariants. We find that the turbulence tends to a time-asymptotic state, dominated by a single scale that grows in time. A theory of this asymptotic state is derived in the form of decay laws. Each case that we study falls into one of three regimes (weakly collisional, marginal, and strongly collisional), determined by a dimensionless number D{sub *}, a quantity analogous to the Reynolds number. The marginal state is marked by a critical number D{sub *}=D{sub 0} that is preserved in time. Turbulence initialized above this value become increasingly inertial in time, evolving toward larger and larger D{sub *}; turbulence initialized below D{sub 0} become more and more collisional, decaying to progressively smaller D{sub *}.

Tatsuno, T. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Department of Communication Engineering and Informatics, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Plunk, G. G. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Max-Planck-Institut fuer Plasmaphysik, 17491 Greifswald (Germany); Barnes, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dorland, W. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Numata, R. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Graduate School of Simulation Studies, University of Hyogo, Kobe, Hyogo 650-0047 (Japan)

2012-12-15

344

The Thirring interaction in the two-dimensional axial-current-pseudoscalar derivative coupling model

We reexamine the two-dimensional model of massive fermions interacting with a massless pseudoscalar field via axial-current derivative coupling. The hidden Thirring interaction in the axial-derivative coupling model is exhibited compactly by performing a canonical field transformation on the Bose field algebra and the model is mapped into the Thirring model with an additional vector-current-scalar derivative interaction (Schroer-Thirring model). The Fermi field operator is rewritten in terms of the Mandelstam soliton operator coupled to a free massless scalar field. The charge sectors of the axial-derivative model are mapped into the charge sectors of the massive Thirring model. The complete bosonized version of the model is presented. The bosonized composite operators of the quantum Hamiltonian are obtained as the leading operators in the Wilson short distance expansions.

Belvedere, L.V. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea S/N, Boa Viagem, Niteroi, CEP 24210-340, Rio de Janeiro (Brazil)]. E-mail: belve@if.uff.br; Rodrigues, A.F. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea S/N, Boa Viagem, Niteroi, CEP 24210-340, Rio de Janeiro (Brazil)]. E-mail: armflavio@if.uff.br

2006-12-15

345

Transfer of optical signals around bends in two-dimensional linear photonic networks

NASA Astrophysics Data System (ADS)

The ability to navigate light signals in two-dimensional networks of waveguide arrays is a prerequisite for the development of all-optical integrated circuits for information processing and networking. In this article, we present a theoretical analysis of bending losses in linear photonic lattices with engineered couplings, and discuss possible ways for their minimization. In contrast to previous work in the field, the lattices under consideration operate in the linear regime, in the sense that discrete solitons cannot exist. The present results suggest that the functionality of linear waveguide networks can be extended to operations that go beyond the recently demonstrated point-to-point transfer of signals, such as blocking, routing, logic functions, etc.

Nikolopoulos, G. M.

2015-02-01

346

Quantum holographic encoding in a two-dimensional electron gas

The advent of bottom-up atomic manipulation heralded a new horizon for attainable information density, as it allowed a bit of information to be represented by a single atom. The discrete spacing between atoms in condensed matter has thus set a rigid limit on the maximum possible information density. While modern technologies are still far from this scale, all theoretical downscaling of devices terminates at this spatial limit. Here, however, we break this barrier with electronic quantum encoding scaled to subatomic densities. We use atomic manipulation to first construct open nanostructures - 'molecular holograms' - which in turn concentrate information into a medium free of lattice constraints: the quantum states of a two-dimensional degenerate Fermi gas of electrons. The information embedded in the holograms is transcoded at even smaller length scales into an atomically uniform area of a copper surface, where it is densely projected into both two spatial degrees of freedom and a third holographic dimension mapped to energy. In analogy to optical volume holography, this requires precise amplitude and phase engineering of electron wavefunctions to assemble pages of information volumetrically. This data is read out by mapping the energy-resolved electron density of states with a scanning tunnelling microscope. As the projection and readout are both extremely near-field, and because we use native quantum states rather than an external beam, we are not limited by lensing or collimation and can create electronically projected objects with features as small as {approx}0.3 nm. These techniques reach unprecedented densities exceeding 20 bits/nm{sup 2} and place tens of bits into a single fermionic state.

Moon, Christopher

2010-05-26

347

Polarization scattering by soliton-soliton collisions

NASA Astrophysics Data System (ADS)

We have discovered experimentally that soliton-soliton collisions in wavelength division multiplexing significantly alter the polarization states of the colliding solitons. Analysis shows that the change in polarization is according to the cross product of the Stokes vectors of the colliding solitons. Birefringence of the fiber spans can turn this polarization scattering into a significant source of timing jitter.

Mollenauer, L. F.; Gordon, J. P.; Heismann, F.

1995-10-01

348

Propagative phase shielding solitons in inhomogeneous media

NASA Astrophysics Data System (ADS)

Dissipative solitons in parametrically driven systems propagating in a spatial inhomogeneous medium are investigated. Recently, a family of dissipative solitons with an unexpected shell-type phase structure has been reported. In the present work, we show that the phase configuration moves rigidly along with the modulus after some transient state. Such a transient state is characterized for a self-adaptation of the phase front symmetry and its relative distance to the soliton. The described dynamical behavior is analytically predicted, showing good agreement with numerical simulations. A mechanism of control and manipulation of these structures based on spatial inhomogeneities is proposed.

Clerc, Marcel G.; Garcia-Ñustes, Mónica A.; Zárate, Yair

2014-02-01

349

Laser-excited shear waves in solid and liquid two-dimensional dusty plasmas

The propagation of transverse waves in a two-dimensional particle suspension in a plasma is studied in the solid and liquid phase. The different states of the suspension are realized by raising the kinetic temperature of the dust particles with a new laser method. An additional laser beam is used to excite shear waves and the wave is observed by videomicroscopy in terms of the individual velocities of the dust particles. For recovering the spatial wave patterns the method of singular value decomposition is applied and compared with the method of spatial Fourier analysis of complex wave numbers. In the solid phase, weakly damped waves are found which follow the expected dispersion relation. In the liquid phase the existence of strongly damped waves is demonstrated. The real part of the wave number is in overall agreement with the predictions of the Quasi Localized Charge Approximation model for a two-dimensional system. The damping of the waves is discussed.

Piel, A.; Nosenko, V.; Goree, J. [IEAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa (United States)

2006-04-15

350

Pinned modes in two-dimensional lossy lattices with local gain and nonlinearity.

We introduce a system with one or two amplified nonlinear sites ('hot spots', HSs) embedded into a two-dimensional linear lossy lattice. The system describes an array of evanescently coupled optical or plasmonic waveguides, with gain applied to selected HS cores. The subject of the analysis is discrete solitons pinned to the HSs. The shape of the localized modes is found in quasi-analytical and numerical forms, using a truncated lattice for the analytical consideration. Stability eigenvalues are computed numerically, and the results are supplemented by direct numerical simulations. In the case of self-focusing nonlinearity, the modes pinned to a single HS are stable and unstable when the nonlinearity includes the cubic loss and gain, respectively. If the nonlinearity is self-defocusing, the unsaturated cubic gain acting at the HS supports stable modes in a small parametric area, whereas weak cubic loss gives rise to a bistability of the discrete solitons. Symmetric and antisymmetric modes pinned to a symmetric set of two HSs are also considered. PMID:25246677

Ding, Edwin; Tang, A Y S; Chow, K W; Malomed, Boris A

2014-10-28

351

Spin and Valley Noise in Two-Dimensional Dirac Materials

NASA Astrophysics Data System (ADS)

We develop a theory for optical Faraday rotation noise in two-dimensional Dirac materials. In contrast to spin noise in conventional semiconductors, we find that the Faraday rotation fluctuations are influenced not only by spins but also the valley degrees of freedom attributed to intervalley scattering processes. We illustrate our theory with two-dimensional transition-metal dichalcogenides and discuss signatures of spin and valley noise in the Faraday noise power spectrum. We propose optical Faraday noise spectroscopy as a technique for probing both spin and valley relaxation dynamics in two-dimensional Dirac materials.

Tse, Wang-Kong; Saxena, A.; Smith, D. L.; Sinitsyn, N. A.

2014-07-01

352

Two-dimensional array codes correcting rectangular burst errors

Two-dimensional array codes correcting rectangular burst errors are considered. We give a construction and examples of linear\\u000a two-dimensional array codes correcting rectangular burst errors of size b\\u000a 1 b\\u000a 2 with minimum redundancy r = 2b\\u000a 1\\u000a b\\u000a 2. We present constructions of cyclic two-dimensional array codes correcting phased and arbitrary rectangular burst errors;\\u000a their encoding and decoding algorithms are

I. M. Boyarinov

2006-01-01

353

Thermal relaxation of a two dimensional plasma in a dc magnetic field. Part 2: Numerical simulation

NASA Technical Reports Server (NTRS)

The thermal relaxation process for a spatially uniform two dimensional plasma in a uniform dc magnetic field is simulated numerically. Thermal relaxation times are defined in terms of the time necessary for the numerically computer Boltzman H-function to decrease through a given part of the distance to its minimum value. Dependence of relaxation time on two parameters is studied: number of particles per Debye square and ratio of gyrofrequency to plasma frequency.

Hsu, J. Y.; Joyce, G.; Montgomery, D.

1974-01-01

354

Design of a new family of two-dimensional codes for fiber-optic CDMA networks

We report the design of a new family of two-dimensional codes for fiber-optic CDMA networks. These newly designed temporary\\/spatial single-pulse-per-row (T\\/S SPR) codes have out-of-phase autocorrelation zero and cross correlation equal to one. Optical orthogonal codes (OOCs) have the lowest out-of-phase autocorrelation and cross-correlation values (both equal to one) among the one-dimensional codes. We compare the performance of our codes

E. S. Shivaleela; Kumar N. Sivarajan; A. Selvarajan

1998-01-01

355

There exist otolith-sensitive vestibular nuclei neurons with spatio-temporal properties that can be described by two response vectors that are in temporal and spatial quadrature. These neurons respond to the component of a stimulus vector on a plane rather than a single axis. It is demonstrated here that these “two-dimensional” linear accelerometer neurons can function as one-dimensional angular velocity detectors. The

Dora E. Angelaki

1992-01-01

356

Reconstruction of two-dimensional coherent MHD structures in a space plasma: The theory

We develop basic theory for the reconstruction of two-dimensional, time-stationary, ideal, compressible MHD structures in a space plasma from data taken by a single spacecraft as the structures move past it. The MHD equations are solved as a spatial initial-value problem in a manner similar to that used in so-called Grad-Shafranov (GS) reconstruction (e.g., Sonnerup et al., 2006), the difference

Bengt U. Ö. Sonnerup; Wai-Leong Teh

2008-01-01

357

Local Electron Correlations in a Two-Dimensional Hubbard Model on the Penrose Lattice

NASA Astrophysics Data System (ADS)

We study electron correlations in the half-filled Hubbard model on a two-dimensional Penrose lattice. Applying real-space dynamical mean-field theory to large clusters, we discuss how low-temperature properties are affected by a quasiperiodic structure. By calculating the double occupancy and renormalization factor at each site, we clarify the existence of the Mott transition. The spatially dependent renormalization characteristic of a geometrical structure is also addressed.

Takemori, Nayuta; Koga, Akihisa

2015-02-01

358

Stability analysis of two-dimensional models of three-dimensional convection

Analytical and numerical methods are used to study the linear stability of spatially periodic solutions for various two-dimensional equations which model thermal convection in fluids. This analysis suggests new model equations that will be useful for investigating questions such as wave number selection, pattern formation, and the onset of turbulence in large aspect ratio Rayleigh-Benard systems. In particular, we construct a nonrelaxational model that has stability boundaries similar to those calculated for intermediate Prandtl number fluids.

Greenside, H.S.; Cross, M.C.

1984-12-01

359

Solitonic axion condensates modeling dark matter halos

Instead of fluid type dark matter (DM), axion-like scalar fields with a periodic self-interaction or some truncations of it are analyzed as a model of galaxy halos. It is probed if such cold Bose–Einstein type condensates could provide a viable soliton type interpretation of the DM ‘bullets’ observed by means of gravitational lensing in merging galaxy clusters. We study solitary waves for two self-interacting potentials in the relativistic Klein–Gordon equation, mainly in lower dimensions, and visualize the approximately shape-invariant collisions of two ‘lump’ type solitons. -- Highlights: •An axion model of dark matter is considered. •Collision of axion type solitons are studied in a two dimensional toy model. •Relations to dark matter collisions in galaxy clusters are proposed.

Castañeda Valle, David, E-mail: casvada@gmail.com; Mielke, Eckehard W., E-mail: ekke@xanum.uam.mx

2013-09-15

360

Experiments on ion-acoustic solitons in plasmas

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 with a modified KdV equation and numerical results. Oblique collisions and their evolution, including overtaking and head-on collisions of two planar, cylindrical, or spherical solitons are described. Reflection, diffraction, and other topics related with ion-acoustic solitons are presented.

Yoshiharu, N.

1982-09-01

361

Soliton gating and switching in liquid crystal light valve

NASA Astrophysics Data System (ADS)

Using a photoconductive light valve with nematic liquid crystals, we introduce a versatile platform for the excitation and routing of spatial optical solitons, with external beams controlling the whereabouts of the underlying all-optically induced waveguides and their spatial dynamics. Using this all-optical control of soliton trajectory, we demonstrate a NOR gate, an XNOR, and a Boolean half-adder.

Piccardi, Armando; Alberucci, Alessandro; Bortolozzo, Umberto; Residori, Stefania; Assanto, Gaetano

2010-02-01

362

Coherent atomic soliton molecules for matter-wave switching

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

363

Scattering of solitons in the formalism of the Darboux transform

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

364

Scattering of solitons in the formalism of the Darboux transform

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

365

Local curvature and stability of two-dimensional systems

We propose a fast method to determine the local curvature in two-dimensional (2D) systems with arbitrary shape. The curvature information, combined with elastic constants obtained for a planar system, provides an accurate ...

Guan, Jie

366

Quasiparticle Energy and Excitons in Two-Dimensional Structures.

??Two-dimensional materials, such as graphene-related structures, transition metal dichalcogenides, are attracting enormous interest in nowadays condensed matter physics. They not only serve as ideal testbeds… (more)

Liang, Yufeng

2014-01-01

367

Single particle spectrum of the two dimensional electron gas

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

Dial, Oliver Eugene, III

2007-01-01

368

Optical properties of two-dimensional transition metal dichalcogenides

The re-discovery of the atomically thin transition metal dichalcogenides (TMDs), which are mostly semiconductors with a wide range of band gaps, has diversified the family of two-dimensional materials and boosted the ...

Lin, Yuxuan, S.M. Massachusetts Institute of Technology

2014-01-01

369

Design and analysis of a two-dimensional camera array

I present the design and analysis of a two-dimensional camera array for virtual studio applications. It is possible to substitute conventional cameras and motion control devices with a real-time, light field camera array. ...

Yang, Jason C. (Jason Chieh-Sheng), 1977-

2005-01-01

370

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

371

Healing of defects in a two-dimensional granular crystal

Using a macroscopic analog for a two dimensional hexagonal crystal, we perform an experimental investigation of the self-healing properties of circular grain defects with an emphasis on defect orientation. A circular grain ...

Rice, Marie C

2014-01-01

372

Two-dimensional signal processing with application to image restoration

NASA Technical Reports Server (NTRS)

A recursive technique for modeling and estimating a two-dimensional signal contaminated by noise is presented. A two-dimensional signal is assumed to be an undistorted picture, where the noise introduces the distortion. Both the signal and the noise are assumed to be wide-sense stationary processes with known statistics. Thus, to estimate the two-dimensional signal is to enhance the picture. The picture representing the two-dimensional signal is converted to one dimension by scanning the image horizontally one line at a time. The scanner output becomes a nonstationary random process due to the periodic nature of the scanner operation. Procedures to obtain a dynamical model corresponding to the autocorrelation function of the scanner output are derived. Utilizing the model, a discrete Kalman estimator is designed to enhance the image.

Assefi, T.

1974-01-01

373

Near-Surface Geophysics: Two-Dimensional Resistivity

USGS hydrologist conducts a two-dimensional (2D) resistivity survey to investigate and characterize the shallow subsurface. The survey was conducted as part of an applied research effort by the USGS Office of Groundwater Branch of Geophysics in 2006....

374

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

375

Quantization of two-dimensional gravity with dynamical torsion

NASA Astrophysics Data System (ADS)

We consider two-dimensional gravity with dynamical torsion in the BV (Batalin-Vilkovisky) and BLT (Batalin-Lavrov-Tyutin) formalisms of gauge theory quantization, as well as in the background field method.

Lavrov, P. M.; Moshin, P. Yu

1999-07-01

376

NASA Technical Reports Server (NTRS)

Theoretical and numerical works in atmospheric turbulence have used the Navier-Stokes fluid equations exclusively for describing large-scale motions. Controversy over the existence of an average temperature gradient for the very large eddies in the atmosphere suggested that a new theoretical basis for describing large-scale turbulence was necessary. A new soliton formalism as a fluid analogue that generalizes the Schrodinger equation and the Zakharov equations has been developed. This formalism, processing all the nonlinearities including those from modulation provided by the density fluctuations and from convection due to the emission of finite sound waves by velocity fluctuations, treats large-scale turbulence as coalescing and colliding solitons. The new soliton system describes large-scale instabilities more explicitly than the Navier-Stokes system because it has a nonlinearity of the gradient type, while the Navier-Stokes has a nonlinearity of the non-gradient type. The forced Schrodinger equation for strong fluctuations describes the micro-hydrodynamical state of soliton turbulence and is valid for large-scale turbulence in fluids and plasmas where internal waves can interact with velocity fluctuations.

Tchen, C. M.

1986-01-01

377

Two-dimensional hydrodynamic model of St. Lucie Estuary

A two-dimensional hydrodynamic model of St. Lucie Estuary was developed to assess the impact of drainage canal discharge and storm water runoff. Water surface elevation, two-dimensional velocity field and salinity are collected during 1998--1998 ENSO episode. The data sets cover an eight months period that includes both wet ad dry weather conditions. The model has been applied to St. Lucie Estuary salinity study. It will also provide flow fields to a water quality model.

Hu, G.G.

1999-07-01

378

Shell Model of Two-dimensional Turbulence in Polymer Solutions

We address the effect of polymer additives on two dimensional turbulence, an issue that was studied recently in experiments and direct numerical simulations. We show that the same simple shell model that reproduced drag reduction in three-dimensional turbulence reproduces all the reported effects in the two-dimensional case. The simplicity of the model offers a straightforward understanding of the all the major effects under consideration.

Roberto Benzi; Nizan Horesh; Itamar Procaccia

2003-10-13

379

Sensor Networking based on Two-Dimensional Signal Transmission Technology

This paper introduces our project of sensor networking technology called two-dimensional signal transmission (2DST). 2DST is a new form of room-size communication, in which the signal energy is confined in thin sheets. The sheet is composed of a dielectric layer sandwiched between a conductive mesh and a continuous conductive layer, typically. Signals are sent by microwaves propagating in the two-dimensional

Hiroyuki Shinoda

2006-01-01

380

The Two-Dimensional Bar Code Application in Book Management

Two-dimensional bar code is one of the most basic and key technologies to achieve the process of identifying information technology for the Internet of things. This paper focuses on book management based on two-dimensional bar code through Visual Basic.NET and SQL Server databases. It can achieve anti-counterfeiting, automatic book information entry, reader identification and library lending management. It can also

He Xuechen

2010-01-01

381

Two-dimensional QCD as a string theory

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

382

Ground ring of two-dimensional string theory

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

383

Numerical modeling of two-dimensional confined flows

NASA Technical Reports Server (NTRS)

A numerical model of two-dimensional confined flows is presented. The flow in the duct is partitioned into finite streams. The difference equations are then obtained by applying conservation principles directly to the individual streams. A listing of a computer code based on this approach in FORTRAN 4 language is presented. The code computes two dimensional compressible turbulent flows in ducts when the duct area along the flow is specified and the pressure gradient is unknown.

Greywall, M. S.

1979-01-01

384

On GID-testable two-dimensional iterative arrays

A new approach is presented for easily testable two-dimensional iterative arrays. It is an improvement on GI-testability (Group\\u000a Identical testability) and is referred to as GID-testability (Group Identical and Different testability). In a GID-testable\\u000a two-dimensional array, the primaryx andy outputs are organized into groups and every group has more than one output. This is similar to the GI-testable arrays. However,

Weikang Huang; F. Lombard

1994-01-01

385

Two-dimensional thermomechanical analysis of continuous casting process

In this work the two-dimensional analysis of continuous casting of low carbon steel was presented. The interaction between moved ingot, copper mould and transport rolls was modeling. The influence of liquid steel ferrostatic pressure and coupled between temperature and deformation fields were taken into consideration.For thermal analysis (with phase change), the two-dimensional unsteady-state heat conduction equation with enthalpy convention was

M. Janik; H. Dyja; S. Berski; G. Banaszek

2004-01-01

386

C-Testability of Two-Dimensional Iterative Arrays

The issue of testing two-dimensional iterative arrays with a constant number of test vectors independent of the array size (C-testability) is discussed in this paper. Sufficient conditions for C-testability are stated. It is shown that any two-dimensional array can be modified to become C-testable. An extension to systolic (synchronous) arrays is made. The approach simplifies testing systolic arrays by using

Hasan Elhuni; Anastasios Vergis; Larry L. Kinney

1986-01-01

387

Two-dimensional aperture coding for magnetic sector mass spectrometry.

In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off. To provide a viable path to miniaturization for harsh environment field applications, we are investigating similar concepts in sector mass spectrometry. Recently, we demonstrated the viability of 1D aperture coding and here we provide a first investigation of 2D coding. In coded optical spectroscopy, 2D coding is preferred because of increased measurement diversity for improved conditioning and robustness of the result. To investigate its viability in mass spectrometry, analytes of argon, acetone, and ethanol were detected using a custom 90-degree magnetic sector mass spectrometer incorporating 2D coded apertures. We developed a mathematical forward model and reconstruction algorithm to successfully reconstruct the mass spectra from the 2D spatially coded ion positions. This 2D coding enabled a 3.5× throughput increase with minimal decrease in resolution. Several challenges were overcome in the mass spectrometer design to enable this coding, including the need for large uniform ion flux, a wide gap magnetic sector that maintains field uniformity, and a high resolution 2D detection system for ion imaging. Furthermore, micro-fabricated 2D coded apertures incorporating support structures were developed to provide a viable design that allowed ion transmission through the open elements of the code. PMID:25510933

Russell, Zachary E; Chen, Evan X; Amsden, Jason J; Wolter, Scott D; Danell, Ryan M; Parker, Charles B; Stoner, Brian R; Gehm, Michael E; Brady, David J; Glass, Jeffrey T

2015-02-01

388

Two dimensional NMR of liquids and oriented molecules

Chapter 1 discusses the quantum mechanical formalism used for describing the interaction between magnetic dipoles that dictates the appearance of a spectrum. The NMR characteristics of liquids and liquid crystals are stressed. Chapter 2 reviews the theory of multiple quantum and two dimensional NMR. Properties of typical spectra and phase cycling procedures are discussed. Chapter 3 describes a specific application of heteronuclear double quantum coherence to the removal of inhomogeneous broadening in liquids. Pulse sequences have been devised which cancel out any contribution from this inhomogeneity to the final spectrum. An interpretation of various pulse sequences for the case of /sup 13/C and /sup 1/H is given, together with methods of spectral editing by removal or retention of the homo- or heteronuclear J coupling. The technique is applied to a demonstration of high resolution in both frequency and spatial dimensions with a surface coil. In Chapter 4, multiple quantum filtered 2-D spectroscopy is demonstrated as an effective means of studying randomly deuterated molecules dissolved in a nematic liquid crystal. Magnitudes of dipole coupling constants have been determined for benzene and hexane, and their signs and assignments found from high order multiple quantum spectra. For the first time, a realistic impression of the conformation of hexane can be estimated from these results. Chapter 5 is a technical description of the MDB DCHIB-DR11W parallel interface which has been set up to transfer data between the Data General Nova 820 minicomputer, interfaced to the 360 MHz spectrometer, and the Vax 11/730. It covers operation of the boards, physical specifications and installation, and programs for testing and running the interface.

Gochin, M.

1987-02-01

389

Two-dimensional ionization chamber arrays for IMRT plan verification

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

390

While a two-dimensional electrophoresis (2-DE) database is a relatively old concept, in recent years it generated renewed interest within the 2-DE community due to two main factors: (i) The high reproducibility of the current 2-DE method allows 2-DE images to be exchanged and compared between laboratories. (ii) The recent development of faster and more powerful techniques for protein identification such as microsequencing, matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) and amino acid composition makes the production of reference protein maps and 2-DE databases cost- and time-effective. Additionally, the Internet network's current increase in popularity, combined with the rapid growth of Internet-connected laboratories, provides a straightforward means of publishing and sharing 2-DE data. While a small number of laboratories have already successfully published their data over the net, the increasing number of 2-DE database servers that are currently being set up will sooner or later require some kind of standardization. Unfortunately, standardization can be a long and cumbersome process inevitably leading to undesirable compromises. A federated database offers a simple and efficient way to publish and share 2-DE data without the need for standardization. Taking advantage of Internet protocols such as World Wide Web, they allow each laboratory to maintain their own database and to interconnect it with other similar databases through the use of active cross-references. This paper first presents guidelines for building a federated 2-DE database that may easily be followed by most laboratories. It then briefly reviews the state-of-the-art in networked 2-DE databases, and finally describes the SWISS-2DPAGE database which fully implements the concept of a federated 2-DE database. PMID:8740178

Appel, R D; Bairoch, A; Sanchez, J C; Vargas, J R; Golaz, O; Pasquali, C; Hochstrasser, D F

1996-03-01

391

Finite Differences and Collocation Methods for the Solution of the Two Dimensional Heat Equation

NASA Technical Reports Server (NTRS)

In this paper we combine finite difference approximations (for spatial derivatives) and collocation techniques (for the time component) to numerically solve the two dimensional heat equation. We employ respectively a second-order and a fourth-order schemes for the spatial derivatives and the discretization method gives rise to a linear system of equations. We show that the matrix of the system is non-singular. Numerical experiments carried out on serial computers, show the unconditional stability of the proposed method and the high accuracy achieved by the fourth-order scheme.

Kouatchou, Jules

1999-01-01

392

Two-Dimensional Grammars And Their Applications To Artificial Intelligence

NASA Astrophysics Data System (ADS)

During the past several years, the concepts and techniques of two-dimensional grammars1,2 have attracted growing attention as promising avenues of approach to problems in picture generation as well as in picture description3 representation, recognition, transformation and manipulation. Two-dimensional grammar techniques serve the purpose of exploiting the structure or underlying relationships in a picture. This approach attempts to describe a complex picture in terms of their components and their relative positions. This resembles the way a sentence is described in terms of its words and phrases, and the terms structural picture recognition, linguistic picture recognition, or syntactic picture recognition are often used. By using this approach, the problem of picture recognition becomes similar to that of phrase recognition in a language. However, describing pictures using a string grammar (one-dimensional grammar), the only relation between sub-pictures and/or primitives is the concatenation; that is each picture or primitive can be connected only at the left or right. This one-dimensional relation has not been very effective in describing two-dimensional pictures. A natural generaliza-tion is to use two-dimensional grammars. In this paper, two-dimensional grammars and their applications to artificial intelligence are presented. Picture grammars and two-dimensional grammars are introduced and illustrated by examples. In particular, two-dimensional grammars for generating all possible squares and all possible rhombuses are presented. The applications of two-dimensional grammars to solving region filling problems are discussed. An algorithm for region filling using two-dimensional grammars is presented together with illustrative examples. The advantages of using this algorithm in terms of computation time are also stated. A high-level description of a two-level picture generation system is proposed. The first level is the picture primitive generation using two-dimensional grammars. The second level is picture generation using either string description or entity-relationship (ER) diagram description. Illustrative examples are also given. The advantages of ER diagram description together with its comparison to string description are also presented. The results obtained in this paper may have useful applications in artificial intelligence, robotics, expert systems, picture processing, pattern recognition, knowledge engineering and pictorial database design. Furthermore, examples related to satellite surveillance and identifications are also included.

Lee, Edward T.

1987-05-01

393

An accurate medium modeling method of discretized granular medium with non-magnetic grain boundaries using a discrete Voronoi diagram is proposed for two-dimensional magnetic recording. A simple closed-form representation of a double-shielded reader sensitivity function is also proposed for modeling the reading process. Moreover, a two-dimensional neural network equalizer (2D-NNE) is proposed to mitigate the influence of intertrack interference and jitter-like

Masato Yamashita; Hisashi Osawa; Yoshihiro Okamoto; Yasuaki Nakamura; Yoshio Suzuki; Kenji Miura; Hiroaki Muraoka

2011-01-01

394

Dynamics of matter solitons in weakly modulated optical lattices

It is shown that matter solitons can be effectively managed by means of smooth variations of parameters of optical lattices in which the condensate is loaded. The phenomenon is based on the effect of lattice modulations on the carrier wave transporting the soliton and that is why it is well understood in terms of the effective mass approach, where a particular spatial configuration of the band structure is of primary importance. Linear, parabolic, and spatially localized modulations are considered as case examples. It is shown that these defects can originate an accelerating and oscillating motion of matter solitons as well as they can simulate soliton interactions with attractive and repulsive defects.

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, Universidade de Lisboa, Campo Grande, Edificio C8, Piso 6, Lisbon 1749-016 (Portugal); Kuzmiak, V. [Institute of Radio Engineering and Electronics, Czech Academy of Sciences, Chaberska 57, 182 51 Prague 8 (Czech Republic)

2004-10-01

395

Ion acoustic solitons in Earth's upward current region

The formation and evolution of ion acoustic solitons in Earth's auroral upward current region are studied using one- and two-dimensional (2D) electrostatic particle-in-cell simulations. The one-dimensional simulations are confined to processes that occur in the auroral cavity and include four plasma populations: hot electrons, H{sup +} and O{sup +} anti-earthward ion beams, and a hot H{sup +} background population. Ion acoustic solitons are found to form for auroral-cavity ion beams consistent with acceleration through double-layer (DL) potentials measured by FAST. A simplified one-dimensional model simulation is then presented in order to isolate the mechanisms that lead to the formation of the ion acoustic soliton. Results of a two-dimensional simulation, which include both the ionosphere and the auroral cavity, separated by a low-altitude DL, are then presented in order to confirm that the soliton forms in a more realistic 2D geometry. The 2D simulation is initialized with a U-shaped potential structure that mimics the inferred shape of the low altitude transition region based on observations. In this simulation, a soliton localized perpendicular to the geomagnetic field is observed to form and reside next to the DL. Finally, the 2D simulation results are compared with FAST data and it is found that certain aspects of the data can be explained by assuming the presence of an ion acoustic soliton.

Main, D. S.; Scholz, C. [Department of Physics, John Brown University, Siloam Springs, Arkansas 72761 (United States); Newman, D. L. [Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80309 (United States); Ergun, R. E. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303 (United States)

2012-07-15

396

Two-dimensional Fourier representation used in the bioelectric forward problem.

The objective of this paper is the application of two-dimensional discrete Fourier transformation for solving the integral equation of the bioelectric forward problem. Therefore, the potential, the source term, and the integral equation kernel are assumed to be sampled at evenly spaced intervals. Thus the continuous functions of the problem domain can be expressed by their two-dimensional discrete Fourier transform in the spatial frequency domain. The method is applied to compute the surface potential generated by an eccentric dipole in a homogeneous spherical conducting medium. The integral equation for the potential is solved in the spatial frequency domain and the value of the potential at the sampling points is obtained from inverse Fourier transformation. The solution of the presented method is compared to both, an analytic solution and a solution gained from applying the boundary element method. Isoparametric quadrilateral boundary elements are used for modeling the spherical volume conductor in the boundary element solution, while in the two-dimensional Fourier transformation method the volume conductor is represented by a parametric boundary surface approximation. PMID:10520531

Wach, P; Lafer, G; Tilg, B; Modre, R

1999-09-01

397

We find classically stable solitons (instantons) in odd (even) dimensional scalar non-commutative field theories whose scalar potential, V(phi), has at least two minima. These solutions are bubbles of the false vacuum whose size is set by the scale of noncommutativity. Our construction uses the correspondence between non-commutative fields and operators on a single particle Hilbert space. In the case of

Rajesh Gopakumar; Shiraz Minwalla; Andrew Strominger

2000-01-01

398

Phase correlations and quasicondensate in a two-dimensional ultracold Fermi gas

NASA Astrophysics Data System (ADS)

The interplay between dimensionality, coherence and interaction in superfluid Fermi gases is analyzed by the phase correlation function of the field of fermionic pairs. We calculate this phase correlation function for a two-dimensional superfluid Fermi gas with s-wave interactions within the Gaussian pair fluctuation formalism. The spatial behavior of the correlation function is shown to exhibit a rapid (exponential) decay at short distances and a characteristic algebraic decay at large distances, with an exponent matching that expected from the Berezinskii-Kosterlitz-Thouless theory of 2D Bose superfluids. We conclude that the Gaussian pair fluctuation approximation is able to capture the physics of quasi-long-range order in two-dimensional Fermi gases.

Tempere, J.; Klimin, S. N.

2015-02-01

399

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

NASA Astrophysics Data System (ADS)

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 Journal for Numerical Methods in Fluids 1999; 29(2):143)) and this paper describes the extension of these ideas to the two-dimensional equations and the application of the method to complex geometries using unstructured triangular grids. Computational results are presented for two standard test problems and a realistic harbour model. Copyright

Walkley, Mark; Berzins, Martin

2002-08-01

400

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

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. copyright 1987 Academic Press, Inc.

Hasan, M.Z.; Conn, R.W.

1987-08-01

401

Two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

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

402

A Two-Dimensional Finite Element Multigroup Diffusion Theory for Neutral Atom Transport in Plasmas

NASA Astrophysics Data System (ADS)

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, Mohammad Z.; Conn, Robert W.

1987-08-01

403

Hamiltonian formalism of two-dimensional Vlasov kinetic equation.

In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented. PMID:25484603

Pavlov, Maxim V

2014-12-01

404

Two dimensional convolute integers for machine vision and image recognition

NASA Technical Reports Server (NTRS)

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

Edwards, Thomas R.

1988-01-01

405

Quantum Walks on Two Kinds of Two-Dimensional Models

NASA Astrophysics Data System (ADS)

In this paper, we numerically study quantum walks on two kinds of two-dimensional graphs: cylindrical strip and Mobius strip. The two kinds of graphs are typical two-dimensional topological graph. We study the crossing property of quantum walks on these two models. Also, we study its dependence on the initial state, size of the model. At the same time, we compare the quantum walk and classical walk on these two models to discuss the difference of quantum walk and classical walk.

Li, Dan; Mc Gettrick, Michael; Zhang, Wei-Wei; Zhang, Ke-Jia

2015-01-01

406

A two-dimensional nematic phase of magnetic nanorods

NASA Astrophysics Data System (ADS)

We report a hybrid mesophase consisting of magnetic nanorods confined between the non-ionic surfactant bilayers of a lamellar phase. The magnetic field-induced ordering of the nanorods was measured experimentally and modeled by a two-dimensional Onsager theory including the third virial coefficient. The nanorods are strongly confined in layers, with no orientational coupling from one layer to the next. At high volume concentration they exhibit spontaneous in-plane orientational ordering and form a stack of independent two-dimensional nematic systems. This isotropic-nematic transition is first-order.

Slyusarenko, Kostyantyn; Constantin, Doru; Davidson, Patrick

2014-03-01

407

A two-dimensional nematic phase of magnetic nanorods.

We report a hybrid mesophase consisting of magnetic nanorods confined between the non-ionic surfactant bilayers of a lamellar phase. The magnetic field-induced ordering of the nanorods was measured experimentally and modeled by a two-dimensional Onsager theory including the third virial coefficient. The nanorods are strongly confined in layers, with no orientational coupling from one layer to the next. At high volume concentration they exhibit spontaneous in-plane orientational ordering and form a stack of independent two-dimensional nematic systems. This isotropic-nematic transition is first-order. PMID:24628202

Slyusarenko, Kostyantyn; Constantin, Doru; Davidson, Patrick

2014-03-14

408

[A two-dimensional double dispersed hadamard transform spectrometer].

A kind of two-dimensional hadamard transform spectrometer was developed. A grating was used for chromatic dispersion of orders and a prism was used for spectral dispersion. Quite different from traditional CCD detection method, a digital micromirror device (DMD) was applied for optical modulation, and a simple point detector was used as the sensor. Compared with traditional two-dimensional spectrometer, it has the advantage of high resolution and signal-noise-ratio, which was proved by theoretical calculation and computer simulation. PMID:22870674

Liu, Jia; Shi, Lei; Li, Kai; Zheng, Xin-Wen; Zeng, Li-Bo; Wu, Qiong-Shui

2012-06-01

409

A new diffusion synthetic acceleration scheme is developed for solving the two-dimensional S[sub n] equations in x - y geometry with bilinear-discontinuous finite element spatial discretization. This method differs from previous methods in that it is unconditionally efficient for problems with isotropic or weakly anisotropic scattering. Computational results are given that demonstrate this property.

Morel, J.E.; Dendy, J.E. Jr.; Wareing, T.A. (Los Alamos National Lab., NM (United States))

1993-12-01

410

Development of a new two-dimensional Cartesian geometry nodal multigroup discrete ordinates method

The purpose of this work is the development and testing of a new family of methods for calculating the spatial dependence of the neutron density in nuclear systems described in two-dimensional Cartesian geometry. The energy and angular dependence of the neutron density is approximated using the multigroup and discrete ordinates techniques respectively. The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. The three methods which were developed differ in the detail of the spatial description: (1) the first method expands the two-dimensional intranode neutron flux as two separable one-dimensional expansions in the x- and y-dimensions and represents the edge fluxes as constant; (2) the second method is the same as the first in the interior of each node, but represents the edge fluxes as one-dimensional expansions in the basis function set; and (3) the third method is the same as the second on the edges, but represents the interior flux shape in a full two-dimensional expansion in the x- and y-dependent basis functions. In order to test the accuracy versus computer time of the three methods, five sample problems were run and the results compared with those of the finite-difference code DOT4.2.

Pevey, R.E.

1982-01-01

411

Soliton matter as a model of dense nuclear matter

We employ the hybrid soliton model of the nucleon consisting of a topological meson field and deeply bound quarks to investigate the behavior of the quarks in soliton matter as a function of density. To organize the calculation, we place the solitons on a spatial lattice. The model suggests the transition of matter from a color insulator to a color conductor above a critical density of a few times normal nuclear density. 9 references, 5 figures.

Glendenning, N.K.

1985-01-01

412

Higher order corrections to dust-acoustic ZK-solitons in a magnetized quantum dusty plasma

NASA Astrophysics Data System (ADS)

Nonlinear propagation of two dimensional dust-acoustic solitary waves in a magnetized quantum dusty plasma whose constituents are electrons, ions, and negatively charged heavy dust particles are investigated using quantum hydrodynamic model. The Zakharov-Kuznetsov (ZK) equation is derived by using reductive perturbation technique (RPT). The higher order inhomogeneous ZK-type differential equation is obtained for the correction to ZK- soliton. The dynamical equation for dressed soliton is solved by using renormalization method. The effects of obliqueness ( l x ) of the wave vector, magnetic field strength ( B 0), quantum parameter for ions ( H i ), soliton velocity ( ?) and Fermi temperature ratio ( ?) on amplitudes and widths of the ZK-soliton and as well as of the dressed soliton are investigated. The conditions for the validity of the higher order correction are described. Suitable parameter ranges for the existence of compressive and rarefactive dressed solitons are also discussed.

Ghorui, Malay Kumar; Mondal, Ganesh; Chatterjee, Prasanta

2013-07-01

413

A two-dimensional Helmhotlz equation solution for the multiple ...

Feb 1, 2013 ... inlet ducts or cavity-backed antennas can dominate the total radar cross section. .... We focus on a two-dimensional geometry by assuming that the ... Here j2 ¼ x2el0, where x is the angular frequency and j is known as the wavenumber. ...... by micro strip patch antennas and arrays residing in a cavity, IEEE.

Peijun Li

2013-02-19

414

Matrix characteristics for two dimensional nongroup Cellular Automata

In this paper we explore the properties of two dimensional Cellular Automata based on its matrix characteristics. In general, Cellular Automata is divided into two classes: group and nongroup Cellular Automata, each of which has its own matrix characteristics with the different properties. In this paper we restrict our study to nongroup Cellular Automata because of its uniqueness properties. The

J. Santoso; O. Slamet Santoso; B. Riyanto Trilaksono

2011-01-01

415

Statistical Transmutation and Phases of Two-Dimensional Quantum Matter

After surveying the quantum kinematics and dynamics of statistical transmutation, I show how this concept suggests a phase diagram for the two-dimensional matter in a magnetic field, as a function of quantum statistics. I discuss the fundamental properties of quasiparticles in the different phases, and briefly suggest {\\it gedanken\\/} -- but not manifestly infeasible -- experiments to show up these properties.

Frank Wilczek

1995-09-14

416

CHAPTER 6 COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY ( GC × GC )

Comprehensive two-dimensional gas chromatography (GC × GC) is one of the most powerful analytical tools for the analysis of organic compounds in complex matrices. The technique is based on continuous collection of the effluent from a GC column and periodic reinjection of small portions of the effluent to a second column of different properties. The process is repeated at a

Tadeusz Górecki; James Harynuk

417

Quantum of optical absorption in two-dimensional semiconductors

Quantum of optical absorption in two-dimensional semiconductors Hui Fanga,b,c , Hans A. Bechteld semiconductor, where is the fine structure con- stant and nc is an optical local field correction factor quantitative examination of the intrinsic absorption properties of free-standing 2D semiconductor thin films

California at Irvine, University of

418

Defects activated photoluminescence in two-dimensional semiconductors

Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China, 3, Berkeley, California 94720, United States. Point defects in semiconductors can trap free charge carriers

Wu, Junqiao

419

Stationary Axisymmetric Fields as Two-Dimensional Geodesics

Einstein's equations for stationary axisymmetric fields are reformulated as the equations for affine geodesics in a two--dimensional space. The affine collineations of this space are investigated and used to relate explicit solutions of Einstein's equations with different physical properties. Particularly, the solutions describing the exterior fields of a dyon and a slowly rotating body are discussed.

D. Nunez; H. Quevedo

1993-10-08

420

Two-dimensional black holes in accelerated frames: quantum aspects

By considering charged black hole solutions of a one parameter family of two dimensional dilaton gravity theories, one finds the existence of quantum mechanically stable gravitational kinks with a simple mass to charge relation. Unlike their Einsteinian counterpart (i.e. extreme Reissner-Nordstr\\"om), these have nonvanishing horizon surface gravity.

R. Balbinot; A. Fabbri

1996-07-04

421

Coherent addition of two dimensional array of fiber lasers

Configurations for efficient free space coherent addition of four separate fiber lasers arranged in two dimensional array are presented. They include compact and robust interferometric combiners that can be inserted either inside or outside the cavity of the combined lasers system. The results reveal that over 85% combining efficiency can be obtained.

Fridman, Moti; Davidson, Nir; Friesem, Asher A; Luria, Elena; Krupkin, Vladimir

2008-01-01

422

Sound waves in two-dimensional ducts with sinusoidal walls

NASA Technical Reports Server (NTRS)

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

Nayfeh, A. H.

1974-01-01

423

Two-dimensional structure of auroral poleward boundary intensifications

We investigate the two-dimensional structure of auroral poleward boundary intensifications (PBIs). PBIs are a nightside auroral intensification that has been studied primarily with ground-based meridian scanning photometers (MSPs). They have a signature that in the MSP data, appears as an increase in intensity at or near the magnetic separatrix and is often seen to extend equatorward. They are also associated

E. Zesta; E. Donovan; L. Lyons; G. Enno; J. S. Murphree; L. Cogger

2002-01-01

424

The Two-Dimensional Lattice Gas with Nearest Neighbor Interaction

The transfer matrix for the two-dimensional lattice gas with nearest neighbor interaction u is investigated. After some preliminary work, it is shown that the transfer matrix can be partially diagonalized, not only when the number of rows is prime, but also when it is non-prime. Equations are given for computing the size of the transfer matrix, and the largest submatrix

James Lawrence Bighouse

1988-01-01

425

Chaotic dynamics for two-dimensional tent maps

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

426

A two-dimensional ideal gas finite element

The formulation of a family of two-dimensional finite elements that model an ideal gas is presented. The elements support nonlinear analysis and represent either a plane strain or axisymmetric condition. The family of elements is intended for use with conventional elasticity-type elements to perform structural analysis of insulated glass units, pressure vessels, and other systems for which the interaction between

Richard J. Schmidt; Keith R. Fulton

2001-01-01

427

Resonant Proximity Connector for Two-Dimensional Sensor Implantation

In this paper, we propose a stable proximity connector RFC (resonant proximity connector) to TDC (two-dimensional communication) sheet. RFC is an electrode whose length is a quarter of the electromagnetic wavelength. The induced resonance around the electrode reduces the impedance between the connector and TDC sheet, which allows sensor chips to communicate with TDC sheet stably. Since the resonance depends

Hiromasa Chigusa; Yasutoshi Makino; Hiroyuki Shinoda

2006-01-01

428

A survey of two-dimensional codes for optical CDMA

The paper presents the implementation of an optical CDMA system with two-dimensional coding using wavelength channels and time chips to create the codeword. Computer simulations have been performed in order to analyze and optimize the electronic circuits. The experimental work has been designed in order to investigate and evaluate the capabilities ofthe implemented optical CDMA system.

Petre Stroica; Marian Vladescu; Ovidiu Iancu

2007-01-01

429

Two-Dimensional Computational Fluid Dynamics and Conduction

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer were performed, two with a CFD code and four with a building- component thermal-simulation tool using) simulations with detailed radiation modeling are used as a reference. Four different frames were studied. Two

430

Potential for two-dimensional codes in automated manufacturing

Linear barcodes have found wide acceptance in all sectors of industry as machine-readable part identifiers, but their low data density limits practical data capacity to some 20 characters. Two-dimensional codes, however, have a much higher data density, and can contain significant volumes of data in compact symbols that can be printed or marked directly on to small parts. When used

Keith A. Osman; Anthony Furness

2000-01-01

431

Random and guided generation of coherent two-dimensional codes

Two-dimensional codes play a central role for many optical applications. Such codes are distributions of weighted points; a code is good if its autocorrelation closely approximates a multiple of the delta-function. This paper treats coherent codes with weights +1 and -1, shows their significant improvement compared with the incoherent codes which have only weights of +1, and outlines a method

K. Pasedach; E. Haase

1981-01-01

432

Towards a two dimensional code of anisotropic Godunov type

A two dimensional code of Godunov type is developed for solving gas dynamic equations. In the Godunov type code interaction between neighbor meshes are analyzed by using a Riemann problem solution. Special attention is given to the problem of anisotropy: the scheme gives different responses depending on the orientation of the meshes. The analysis is performed under Lagrangian concepts for

B. Meltz; J. K. Dukowicz

1987-01-01

433

Two-dimensional coded classification schemes in wireless sensor networks

This work proposes a novel fault-tolerant classification system based on distributed detection and two-dimensional channel coding. A rule is then derived to reduce the search space such that the optimal code matrix can be found. Simulation results reveal that the proposed scheme has higher classification reliability and better capability of fault tolerance than previous methods. Moreover, a code matrix using

Hung-ta Pai; Yunghsiang S. Han; Jing-tian Sung

2008-01-01

434

Two-dimensional vortex motion and 'negative temperatures.'

NASA Technical Reports Server (NTRS)

Explanation of the novel phenomenon, tentatively identified as the 'ergodic boundary' in a space of initial conditions for turbulent flow, suggested by the recent numerical integration of the two-dimensional Navier-Stokes equations at high Reynolds numbers reported by Deem and Zabusky (1971). The proposed explanation is presented in terms of negative temperatures for a point vortex model.

Montgomery, D.

1972-01-01

435

Two-dimensional vortex motion and ``negative temperatures''

A recent numerical integration of the two-dimensional Navier-Stokes equations has tentatively identified an ``ergodic boundary'' in the space of initial conditions for the turbulent flow. An explanation is suggested in terms of negative temperatures, for a point vortex model. The author acknowledges valuable discussions with Drs. F. Tapert and R. Hardin.

D. Montgomery

1972-01-01

436

Algebraic analysis of a model of two-dimensional gravity

An algebraic analysis of the Hamiltonian formulation of the model two-dimensional gravity is performed. The crucial fact is an exact coincidence of the Poisson brackets algebra of the secondary constraints of this Hamiltonian formulation with the SO(2,1)-algebra. The eigenvectors of the canonical Hamiltonian $H_{c}$ are obtained and explicitly written in closed form.

A. M. Frolov; N. Kiriushcheva; S. V. Kuzmin

2009-01-22

437

FLOW AND DISPERSION OF POLLUTANTS WITHIN TWO-DIMENSIONAL VALLEYS

Wind-tunnel experiments and a theoretical model concerning the flow structure and pollutant diffusion over two-dimensional valleys of varying aspect ratio are described and compared. hree model valleys were used, having small, medium, and steep slopes. Measurements of mean and tu...

438

A fast two-dimensional median filtering algorithm

We present a fast algorithm for two-dimensional median filtering. It is based on storing and updating the gray level histogram of the picture elements in the window. The algorithm is much faster than conventional sorting methods. For a window size of m × n, the computer time required is 0(n).

Thomas S. Huang; George J. Yang; Gregory Y. Tang

1979-01-01

439

Distributions of the Two-Dimensional DCT Coefficients for Images

For a two-dimensional discrete cosine transform (DCT) image coding system, there have been different assumptions concerning the distributions of the transform coefficients. This paper presents results of distribution tests that indicate that for many images the statistics of the coefficients are best approximated by a Gaussian distribution for the DC coefficient and a Laplacian distribution for the other coefficients. Furthermore,

R. Reininger; J. Gibson

1983-01-01

440

Exact two-dimensional superconformal R symmetry and c extremization.

We uncover a general principle dubbed c extremization, which determines the exact R symmetry of a two-dimensional unitary superconformal field theory with N=(0,2) supersymmetry. To illustrate its utility, we study superconformal theories obtained by twisted compactifications of four-dimensional N=4 super-Yang-Mills theory on Riemann surfaces and construct their gravity duals. PMID:23432232

Benini, Francesco; Bobev, Nikolay

2013-02-01

441

Light absorption by a two-dimensional quantum dot superlattice

The monochromatic light absorption in an ideal two-dimensional quantum dot superlattice (QDSL) is considered theoretically. Calculations of the absorption coefficient are done in both the absence and presence of a homogeneous DC electric field with rational and irrational orientations. The explicit dependencies of the absorption coefficient on the frequency of the light, the QDSL parameters and the strength of the

Manuk G. Barseghyan; Albert A. Kirakosyan

2005-01-01

442

Adapting Grids For Computing Two-Dimensional Flows

NASA Technical Reports Server (NTRS)

SAGE2D is two-dimensional implementation of Self Adaptive Grid Evolution computer program that intelligently redistributes initial grid points on basis of initial flow-field solution. Grids modified according to initial computed flows enabling recomputation at greater accuracy. Written in FORTRAN 77.

Davies, Carol B.; Venkatapathy, Ethiraj

1992-01-01

443

Two-Dimensional Diverging Shocks in a Nonuniform Medium

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

444

A two-dimensional global study of tropospheric ozone production

The ozone production in the troposphere has been studied by means of a zonally averaged model which consists of a two-dimensional transport model, a description of the emissions, wet and dry deposition, and chemical processes of importance for the ozone production in the troposphere. The transport model describes a closed circulation in the meridional plane below 10 hPa and has

Asbjørn Strand; Ø. Hov

1994-01-01

445

Two-dimensional NMR spectroscopy with temperature-sweep.

Two-dimensional nuclear magnetic resonance (NMR) spectroscopy is useful for studying temperature-dependent effects on molecular structure. However, experimental time is usually long, because sampling is repeated at several temperatures. A novel solution to the problem is proposed, in which signal sampling is performed in parallel to the linear temperature-sweep. PMID:24863674

Bermel, Wolfgang; Dass, Rupashree; Neidig, Klaus-Peter; Kazimierczuk, Krzysztof

2014-08-01

446

Two-dimensional group lattices with a twist

NASA Astrophysics Data System (ADS)

We study a statistical mechanics system defined on a particular two-dimensional group lattice. The lattice has local abstract dislocation defects. The partition function is explicitly computed and the phase transition points are enumerated. We consider several applications to physical systems.

Samuel, Stuart

1991-08-01

447

A recursive exact algorithm for weighted two-dimensional cutting

Gilmore and Gomory's algorithm is one of the better actually known exact algorithms for solving unconstrained guillotine two-dimensional cutting problems. Herz's algorithm is more effective, but only for the unweighted case. We propose a new exact algorithm adequate for both weighted and unweighted cases, which is more powerful than both algorithms. The algorithm uses dynamic programming procedures and one-dimensional knapsack

M. Hifi; V. Zissimopoulos

1996-01-01

448

Two-Dimensional Fourier Transform Analysis of Helicopter Flyover Noise

NASA Technical Reports Server (NTRS)

A method to separate main rotor and tail rotor noise from a helicopter in flight is explored. Being the sum of two periodic signals of disproportionate, or incommensurate frequencies, helicopter noise is neither periodic nor stationary. The single Fourier transform divides signal energy into frequency bins of equal size. Incommensurate frequencies are therefore not adequately represented by any one chosen data block size. A two-dimensional Fourier analysis method is used to separate main rotor and tail rotor noise. The two-dimensional spectral analysis method is first applied to simulated signals. This initial analysis gives an idea of the characteristics of the two-dimensional autocorrelations and spectra. Data from a helicopter flight test is analyzed in two dimensions. The test aircraft are a Boeing MD902 Explorer (no tail rotor) and a Sikorsky S-76 (4-bladed tail rotor). The results show that the main rotor and tail rotor signals can indeed be separated in the two-dimensional Fourier transform spectrum. The separation occurs along the diagonals associated with the frequencies of interest. These diagonals are individual spectra containing only information related to one particular frequency.

SantaMaria, Odilyn L.; Farassat, F.; Morris, Philip J.

1999-01-01

449

Numerical simulation of two?dimensional tsunami runup

The hydrodynamic and mathematical problems connected with discontinuity between wet and dry domains, nonlinearity, friction, and computational instability are the main problems that have to be sorted out in the runup computation. A variety of runup models are analyzed, including the boundary conditions used to move the shoreline. Based on the initial experiments one?dimensional and two?dimensional algorithms are constructed. These

Z. Kowalik; T. S. Murty

1993-01-01

450

Numerical Modelling of induction heating for two dimensional geometries.

Numerical Modelling of induction heating for two dimensional geometries. P. Dreyfuss J. Rappaz Summary We present both a mathematical model and a numerical method for simulating induction heating and infinite in one direction. Thus the induction heating problem can be studied in a plane perpendicular

Dreyfuss, Pierre

451

TWO DIMENSIONAL IMMERSED BOUNDARY SIMULATIONS OF SWIMMING JELLYFISH

TWO DIMENSIONAL IMMERSED BOUNDARY SIMULATIONS OF SWIMMING JELLYFISH by Haowen Fang B.Eng., Nanjing Simulations Of Swim- ming Jellyfish Examining Committee: Dr. Weiran Sun, Assistant Professor Chair Dr. John iii #12;Abstract The swimming behavior of jellyfish, driven by the periodic contraction of body

Stockie, John

452

Disorder and Magnetism in Two Dimensional Quantum Systems

Introduction 1 References 10 2 Kondo Lattice Scenario in Semiconductor Heterostructures 11 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 Two dimensional Kondo model . . . . . . . . . . . . . . . . . . . . . 17 2.2.1 One impurity . . . . . . . . . . . . . . . . . . . . . . . . 23 2.2.3 Lattice of impurity spins . . . . . . . . . . . . . . . . . . . . . 25 2.3 Summary

453

Area two-dimensional converging\\/diverging nozzle

A two-dimensional variable area exhaust nozzle assembly is described for a gas turbine engine, the engine having an axis and comprising: exhaust duct means having opposed, fixed, side walls; variable position exhaust nozzle means disposed within the exhaust duct means, the nozzle means including upper flap means and lower flap means opposed to the upper flap means, the upper and

1986-01-01

454

Vessel Segmentation and Tracking Using a Two-Dimensional Model

The segmentation and analysis of blood vessels in retinal images is of immense interest for study of diseases involving vasculature changes. An algorithm to segment blood vessels in colour retinal images by tracking of vessels is described. This algorithm proceeds by fitting a physically inspired two-dimensional model of the vessel profile to a local region of the vessel. By fitting

M. J. Cree; D. Cornforth; H. F. Jelinek

455

Two-dimensional parallel thinning algorithms based on critical kernels

Two-dimensional parallel thinning algorithms based on critical kernels G. Bertrand and M. Couprie complexes for the study of parallel thinning in any dimension. The most fundamental result in this framework to simple local characterizations, we are able to express thinning algorithms by the way of sets of masks

Boyer, Edmond

456

Symmetries in two-dimensional dilaton gravity with matter

The symmetries of generic two-dimensional (2D) dilaton models of gravity with (and without) matter are studied in some detail. It is shown that delta2, one of the symmetries of the matterless models, can be generalized to the case where matter fields of any kind are present. The general (classical) solution for some of these models, in particular, those coupled to

Miguel Navarro; F ´ õsica; Teorica y Computacional

1997-01-01

457

Higgs algebraic symmetry in the two-dimensional Dirac equation

The dynamical symmetry algebra of the two-dimensional Dirac Hamiltonian with equal scalar and vector Smorodinsky-Winternitz potentials is constructed. It is the Higgs algebra, a cubic polynomial generalization of SU(2). With the help of the Casimir operators, the energy levels are derived algebraically.

Fu-Lin Zhang; Bo Fu; Jing-Ling Chen

2009-07-04

458

Finite-volume application of high-order ENO schemes to two-dimensional boundary-value problems

Finite-volume applications of high-order accurate ENO schemes to two-dimensional boundary-value problems are studied. These schemes achieve high-order spatial accuracy, in smooth regions, by a piecewise polynomial approximation of the solution from cell averages. In addition, this spatial operation involves an adaptive stencil algorithm in order to avoid the oscillatory behavior that is associated with interpolation across steep gradients. High-order TVD

Jay Casper

1991-01-01

459

Laguerre and Hermite Soliton Clusters in Nonlocal Nonlinear Media Daniel Buccoliero,1,2

Laguerre and Hermite Soliton Clusters in Nonlocal Nonlinear Media Daniel Buccoliero,1,2 Anton S classes of higher-order spatial optical solitons in analogy with Laguerre-Gaussian and Hermite-Gaussian linear eigenmodes. We reveal that stable higher-order optical solitons can exist in nonlocal nonlinear

460

The Role of Sleep in Forming a Memory Representation of a Two-Dimensional Space

There is ample evidence from human and animal models that sleep contributes to the consolidation of newly learned information. The precise role of sleep for integrating information into interconnected memory representations is less well understood. Building on prior findings that following sleep (as compared to wakefulness) people are better able to draw inferences across learned associations in a simple hierarchy, we ask how sleep helps consolidate relationships in a more complex representational space. We taught 60 subjects spatial relationships between pairs of buildings, which (unknown to participants) formed a two-dimensional grid. Critically, participants were only taught a subset of the many possible spatial relations, which allowed them to potentially infer the remainder. After a 12 h period that either did or did not include a normal period of sleep, participants returned to the lab. We examined the quality of each participant's map of the two-dimensional space, and their knowledge of relative distances between buildings. After 12 h with sleep, subjects could more accurately map the full space than subjects who experienced only wakefulness. The incorporation of untaught, but inferable, associations was particularly improved. We further found that participants' distance judgment performance related to self-reported navigational style, but only after sleep. These findings demonstrate that consolidation over a night of sleep begins to integrate relations into an interconnected complex representation, in a way that supports spatial relational inference. PMID:23780782

Coutanche, Marc N.; Gianessi, Carol A.; Chanales, Avi J.H.; Willison, Kate W.; Thompson-Schill, Sharon L.

2014-01-01

461

Two-dimensional atom localization in a four-level tripod system in laser fields

We propose a scheme for two-dimensional (2D) atom localization in a four-level tripod system under an influence of two orthogonal standing-wave fields. Position information of the atom is retained in the atomic internal states by an additional probe field either of a standing or of a running wave. It is shown that the localization factors depend crucially on the atom-field coupling that results in such spatial structures of populations as spikes, craters, and waves. We demonstrate a high-precision localization due to measurement of population in the upper state or in any ground state.

Ivanov, Vladimir [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FIN-20014 Turku (Finland); Saint Petersburg State University of Information Technologies, Mechanics and Optics, 197101 St. Petersburg (Russian Federation); Rozhdestvensky, Yuri [Saint Petersburg State University of Information Technologies, Mechanics and Optics, 197101 St. Petersburg (Russian Federation)

2010-03-15

462

Synchronization of particle motion induced by mode coupling in a two-dimensional plasma crystal.

The kinematics of dust particles during the early stage of mode-coupling induced melting of a two-dimensional plasma crystal is explored. It is found that the formation of the hybrid mode causes the particle vibrations to partially synchronize at the hybrid frequency. Phase- and frequency-locked hybrid particle motion in both vertical and horizontal directions (hybrid mode) is observed. The system self-organizes in a rhythmic pattern of alternating in-phase and antiphase oscillating chains of particles. The spatial orientation of the synchronization pattern correlates well with the directions of the maximal increment of the shear-free hybrid mode. PMID:25353905

Couëdel, L; Zhdanov, S; Nosenko, V; Ivlev, A V; Thomas, H M; Morfill, G E

2014-05-01

463

Synchronization of particle motion induced by mode coupling in a two-dimensional plasma crystal

NASA Astrophysics Data System (ADS)

The kinematics of dust particles during the early stage of mode-coupling induced melting of a two-dimensional plasma crystal is explored. It is found that the formation of the hybrid mode causes the particle vibrations to partially synchronize at the hybrid frequency. Phase- and frequency-locked hybrid particle motion in both vertical and horizontal directions (hybrid mode) is observed. The system self-organizes in a rhythmic pattern of alternating in-phase and antiphase oscillating chains of particles. The spatial orientation of the synchronization pattern correlates well with the directions of the maximal increment of the shear-free hybrid mode.

Couëdel, L.; Zhdanov, S.; Nosenko, V.; Ivlev, A. V.; Thomas, H. M.; Morfill, G. E.

2014-05-01

464

Two-dimensional computer code for design assessment of SRM aft closure environment. [space shuttle

NASA Technical Reports Server (NTRS)

A general interpolants method for constructing numerical analogs of the partial differential equations of continuum mechanics and which combines the best features of both finite element and finite difference methods was used in a two dimensional axisymmetric analysis of the space shuttle solid motor aft closure region flowfield. The numerical technique used is discussed as well as the results of the analysis. A steady state solution for the submerged nozzle nose region indicates the development of an area gas flow recirculation near the propellant burning surface boundary and in the region of the underside of the nozzle nose. This recirculation region remains spatially fixed for successive iterations (greater than 800) of the solution.

Freeman, J. A.

1978-01-01

465

Quantized phase optimization of two-dimensional Fourier kinoforms by a genetic algorithm

NASA Astrophysics Data System (ADS)

We have developed a phase optimization method of a quantized kinoform by a genetic algorithm. Because the genetic algorithm inherently deals with discrete values, the quantized phase of the kinoform can be easily estimated. The two-dimensional Fourier kinoform can utilize effectively the periodicity of the discrete Fourier transform in the genetic algorithm. This condition enables us to perform the crossover process that is one of the processes in genetic algorithm without a spatial bandwidth of the kinoform. The optimization has been performed successfully in computer simulation. The optically reconstructed image agrees well with the theoretical one.

Yoshikawa, N.; Itoh, M.; Yatagai, T.

1995-04-01

466

Two-dimensional propagation of magnetocardiac T wave signals for characterizing myocardial ischemia

NASA Astrophysics Data System (ADS)

Instead of detecting electrical signals for diagnosing cardiac abnormalities, a promising alternative is to detect the magnetic signals generated from cardiac electrical currents. The system utilizing 64 low-transition-temperature superconducting quantum interference devices was tested to detect the time-dependent magnetocardiac signals that are spatially distributed over the heart. To achieve efficient acquisition and analysis, we propose a method to detect two-dimensionally, the T wave propagation of electromagnetic signals of beating hearts. In addition to characterizing the propagating behaviors, the differences between normal hearts and those with coronary artery disease were investigated.

Wu, C. C.; Huang, H. C.; Liu, Y. B.; Lin, L. C.; Lin, L. Y.; Chen, M. F.; Tsai, M. C.; Gao, Y. L.; Yang, S. Y.; Horng, H. E.; Yang, H. C.; Tseng, W. K.; Lee, T. L.; Hsuan, C. F.; Pan, Y. F.; Lee, Y. H.

2008-05-01

467

In situ two-dimensional imaging quick-scanning XAFS with pixel array detector

Quick-scanning X-ray absorption fine structure (XAFS) measurements were performed in transmission mode using a PILATUS 100K pixel array detector (PAD). The method can display a two-dimensional image for a large area of the order of a centimetre with a spatial resolution of 0.2?mm at each energy point in the XAFS spectrum. The time resolution of the quick-scanning method ranged from 10?s to 1?min per spectrum depending on the energy range. The PAD has a wide dynamic range and low noise, so the obtained spectra have a good signal-to-noise ratio. PMID:21997918

Tanida, Hajime; Yamashige, Hisao; Orikasa, Yuki; Oishi, Masatsugu; Takanashi, Yu; Fujimoto, Takahiro; Sato, Kenji; Takamatsu, Daiko; Murayama, Haruno; Arai, Hajime; Matsubara, Eiichiro; Uchimoto, Yoshiharu; Ogumi, Zempachi

2011-01-01

468

NASA Astrophysics Data System (ADS)

It is shown that optical solitons in nonlinear fibre-optic communication systems and soliton lasers can be represented as nonlinear Bloch waves in periodic structures. The Bloch theorem is proved for solitons of the nonlinear Schrodinger equation in systems with the dispersion, the nonlinearity, and the gain (absorption coefficient) periodically changing over the length. The dynamics of formation and interaction, as well as stability of the coupled states of nonlinear Bloch waves are investigated. It is shown that soliton Bloch waves exist only under certain self-matching conditions for the basic parameters of the system and reveal a structural instability with respect to the mismatch between the periods of spatial modulation of the dispersion, nonlinearity or gain.

Serkin, Vladimir N.; Belyaeva, T. L.

2001-11-01

469

Helmholtz solitons in power-law optical materials

A nonlinear Helmholtz equation for optical materials with regimes of power-law type of nonlinearity is proposed. This model captures the evolution of broad beams at any angle with respect to the reference direction in a wide range of media, including some semiconductors, doped glasses, and liquid crystals. Exact analytical soliton solutions are presented for a generic nonlinearity, within which known Kerr solitons comprise a subset. Three general conservation laws are also reported. Analysis and numerical simulations examine the stability of the Helmholtz power-law solitons. A propagation feature, associated with spatial solitons in power-law media, constituting a class of oscillatory solution, is identified.

Christian, J. M.; McDonald, G. S.; Potton, R. J.; Chamorro-Posada, P. [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); Departamento de Teoria de la Senal y Comunicaciones e Ingenieria Telematica, Universidad de Valladolid, ETSI Telecomunicacion, Campus Miguel Delibes s/n, 47011 Valladolid (Spain)

2007-09-15

470

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

471

Strong localization effect in magnetic two-dimensional hole systems

We report an extensive study of the magnetotransport properties of magnetically doped two-dimensional hole systems. Inverted manganese modulation doped InAs quantum wells with localized manganese ions providing a magnetic moment of S=5/2 were grown by molecular beam epitaxy. Strong localization effect found in low-field magnetotransport measurements on these structures can either be modified by the manganese doping density or by tuning the two-dimensional hole density p via field effect. The data reveal that the ratio between p and manganese ions inside or in close vicinity to the channel enlarges the strong localization effect. Moreover, asymmetric broadening of the doping layer due to manganese segregation is significantly influenced by strain in the heterostructure.

Wurstbauer, U. [Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg (Germany); Institute of Applied Physics, University of Hamburg, 20355 Hamburg (Germany); Knott, S.; Zolotaryov, A.; Hansen, W. [Institute of Applied Physics, University of Hamburg, 20355 Hamburg (Germany); Schuh, D. [Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg (Germany); Wegscheider, W. [Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg (Germany); Solid State Physics Laboratory, ETH Zurich, 8093 Zurich (Switzerland)

2010-01-11

472

Multigrid Navier-Stokes calculation for two dimensional cascades

NASA Astrophysics Data System (ADS)

A fast and accurate numerical method for solving the two dimensional Reynolds averaged Navier-Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based on an explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D Navier-Stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.

Yang, Ce; Lao, Dazhong; Jiang, Zikang

1998-03-01

473

Two-dimensional Raman-terahertz spectroscopy of water

Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water. PMID:24297930

Savolainen, Janne; Ahmed, Saima; Hamm, Peter

2013-01-01

474

Automatic measurement method of two-dimensional complex geometric features

NASA Astrophysics Data System (ADS)

To realize automatic measurement of two-dimensional complex geometric features on parts with high-precision, the characteristics and advantages of five types of machine vision measurement methods are analyzed. The technological challenges that each method faces in dealing with high-precise automatic measurement of complex geometric features are indicated. To solve the problem, a machine vision measurement method with cooperation of multi field of view, which has a hierarchical structure, is proposed. Its principle and procedures are introduced. The experimental results show that the relative error is less than 0.025% using the method to gauge conventional scale parts. Its outstanding advantage is that the measuring accuracy is NOT influenced by ambient temperature and the precision of machine systems compared with traditional CMM. Therefore, it is an effective method that can be applied in industrial spot to automatically measure normal and large scale two-dimensional complex geometric characteristics with high-precision.

He, Boxia; He, Yong; Ren, Fu-long; Xue, Rong

2013-01-01

475

Overlap distributions in two-dimensional spin glasses

NASA Astrophysics Data System (ADS)

Numerical results are presented for overlaps of configurations of two-dimensional Ising spin glasses. At low temperatures, the correlation length greatly exceeds the system size, so that spin-spin correlations are relatively long range and domain wall energies exhibit sensitive dependence to temperature,as seen in the low temperature phase of three-dimensional spin glasses. Exact sampling algorithms are used so that there is no doubt of equilibration. High statistics runs are carried out, with tens of thousands of samples of size L^2=256^2 simulated. The results of the size-dependent spin overlap distribution P(q) are evaluated using statistics recently developed by Yucesoy, Katzgraber and Machta. The statistics for two-dimensional models at low temperature are found to be quite similar to those of three-dimensional spin glasses at finite temperatures below the spin-glass transition.

Middleton, A. Alan

2013-03-01

476

Silicon-based two dimensional tunable photonic crystal devices

NASA Astrophysics Data System (ADS)

Photonic crystal devices are capable of controlling the flow of light in ultra compact scales. Silicon two dimensional (2D) nanostructures are well developed in the integrated circuit (IC) industry. Silicon is transparent to infrared light and has high refractive index which makes silicon an ideal material for photonic crystals in the infrared spectrum. Silicon 2D photonic crystals have attracted a lot of interest for showing feasibility of photonic integrated circuits. Typical photonic crystal devices are waveguides or cavities, which were developed as mostly passive devices. Various methods can be used to make photonic crystals tunable. In this work, silicon 2D tunable photonic crystal devices are studied using thermo-optic effect of silicon. In addition, this research presents one-step lithography to form micro and nano combined structures for the two-dimensional slab photonic crystals.

Choi, Kyung-Hak

477

Disordered quantum walks in two-dimensional lattices plink

NASA Astrophysics Data System (ADS)

The properties of the two-dimensional quantum walk with point, line, and circle disorders in phase are reported. Localization is observed in the two-dimensional quantum walk with certain phase disorder and specific initial coin states. We give an explanation of the localization behavior via the localized stationary states of the unitary operator of the walker + coin system and the overlap between the initial state of the whole system and the localized stationary states. Project supported by the National Natural Science Foundation of China (Grant No. 11174052), the National Basic Research Program of China (Grant No. 2011CB921203), and the Open Fund from the State Key Laboratory of Precision Spectroscopy of East China Normal University.

Zhang, Rong; Xu, Yun-Qiu; Xue, Peng

2015-01-01

478

High-speed, two-dimensional filtering using residue arithmetic

NASA Astrophysics Data System (ADS)

An operation common to many applications of high-speed, real-time signal processing is two-dimensional filtering. Recent advances in memory technology and residue arithmetic allow high-speed implementation. A two-dimensional five-by-five matrix convolution filter for pulse matching was implemented in residue arithmetic using programmable read only memory (PROM). The simple architecture of this all-PROM filter permits easy pipeline design and the inherent modular structure of residue arithmetic minimized the design overhead. The filter operates at 20 million operations per second with emitter coupled logic (ECL) PROMs. This filter has options such as elementary error detection, multiple patterns matching and adaptive filtering. An Intel 8086 microproprocessor was used as a controller to the filter.

Huang, C. H.

1980-01-01

479

Two-dimensional turbulence in the inverse cascade range.

Numerical and physical experiments on forced two-dimensional Navier-Stokes equations show that transverse velocity differences are described by "normal" Kolmogorov scaling <(deltav)(2n)> proportional r(2n/3) and obey Gaussian statistics. Since nontrivial scaling is a sign of the strong nonlinearity of the problem, these two results seem to contradict each other. A theory explaining these observations is presented in this paper. The derived self-consistent expression for the pressure gradient contributions leads to the conclusion that small-scale transverse velocity differences are governed by a linear Langevin-like equation, stirred by a nonlocal, universal, solution-dependent Gaussian random force. This explains the experimentally observed Gaussian statistics of transverse velocity differences and their Kolmogorov scaling. The solution for the PDF of longitudinal velocity differences is based on the numerical smallness of the energy flux in two-dimensional turbulence. The theory makes a few quantitative predictions that can be tested experimentally. PMID:11970429

Yakhot, V

1999-11-01

480

Tunable refraction in a two dimensional quantum metamaterial

In this paper we consider a two-dimensional metamaterial comprising an array of qubits (two level quantum objects). Here we show that a two-dimensional quantum metamaterial may be controlled, e.g. via the application of a magnetic flux, so as to provide controllable refraction of an input signal. Our results are consistent with a material that could be quantum birefringent (beam splitter) or not dependent on the application of this control parameter. We note that quantum metamaterials as proposed here may be fabricated from a variety of current candidate technologies from superconducting qubits to quantum dots. Thus the ideas proposed in this work would be readily testable in existing state of the art laboratories.

M. J. Everitt; J. H. Samson; S. E. Savelev; T. P. Spiller; R. Wilson; A. M. Zagoskin

2012-08-22

481

Two-dimensional Simulations of Correlation Reflectometry in Fusion Plasmas

A two-dimensional wave propagation code, developed specifically to simulate correlation reflectometry in large-scale fusion plasmas is described. The code makes use of separate computational methods in the vacuum, underdense and reflection regions of the plasma in order to obtain the high computational efficiency necessary for correlation analysis. Simulations of Tokamak Fusion Test Reactor (TFTR) plasma with internal transport barriers are presented and compared with one-dimensional full-wave simulations. It is shown that the two-dimensional simulations are remarkably similar to the results of the one-dimensional full-wave analysis for a wide range of turbulent correlation lengths. Implications for the interpretation of correlation reflectometer measurements in fusion plasma are discussed.

E.J. Valeo; G.J. Kramer; R. Nazikian

2001-07-05

482

A two-dimensional dam-break flood plain model

A simple two-dimensional dam-break model is developed for flood plain study purposes. Both a finite difference grid and an irregular triangle element integrated finite difference formulation are presented. The governing flow equations are approximately solved as a diffusion model coupled to the equation of continuity. Application of the model to a hypothetical dam-break study indicates that the approach can be used to predict a two-dimensional dam-break flood plain over a broad, flat plain more accurately than a one-dimensional model, especially when the flow can break-out of the main channel and then return to the channel at other downstream reaches. ?? 1985.

Hromadka, T.V., II; Berenbrock, C.E.; Freckleton, J.R.; Guymon, G.L.

1985-01-01

483

On comparing helioseismic two-dimensional inversion methods

NASA Technical Reports Server (NTRS)

We consider inversion techniques for investigating the structure and dynamics of the solar interior as functions of radius and latitude. In particular, we look at the problem of inferring the radial and latitudinal dependence of the Sun's internal rotation, using a fully two-dimensional least-squares inversion algorithm. Concepts such as averaging kernels, measures of resolution, and trade-off curves, which have previously been used in the one-dimensional case, are generalized to facilitate a comparison of two-dimensional methods. We investigate the weighting given to different modes and discuss the implications of this for observational strategies. As an illustration we use a mode set whose properties are similar to those expected for data from the GONG network.

Schou, J.; Christensen-Dalsgaard, J.; Thompson, M. J.

1994-01-01

484

Two-dimensional semi-parametric alignment of chromatograms.

We present a comprehensive alignment algorithm that extends the semi-parametric approach to two dimensions. The algorithm is based on modeling shifts with a two-dimensional "warp function" such that the sample chromatogram - its shifts corrected with the warp function - is adjusted to the reference chromatogram by minimizing the squared intensity difference. A warp function approach has the advantage that overlapping peaks are easily dealt with compared to other proposed two-dimensional algorithms. Another advantage is that missing peaks are allowed if the absence of these peaks has little numerical effect on the warp function computation and if these peaks occur between existing peaks. Performance of the algorithm is demonstrated using GC×GC data from three batches of three diesel oil samples and LC-MS data from a mouse breast cancer data set. PMID:24794941

de Boer, Wim P H; Lankelma, Jan

2014-06-01

485

Wavelength scale terahertz two-dimensional photonic crystal waveguides.

A terahertz-scale two-dimensional photonic-crystal waveguide based on a silicon-on-insulator was fabricated, and the optical transmission spectrum was measured. Terahertz beam propagation characteristics were observed using a thermal imaging camera, with incident light in the 10.1-10.7 microm range. The measured transmission spectrum was in good agreement with a three-dimensional finite-difference time-domain calculation. PMID:19488208

Lin, Chunchen; Chen, Caihua; Schneider, Garrett; Yao, Peng; Shi, Shouyuan; Sharkawy, Ahmed; Prather, Dennis

2004-11-15

486

Suspended two-dimensional electron and hole gases

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

Kazazis, D.; Bourhis, E.; Gierak, J.; Gennser, U. [Laboratoire de Photonique et de Nanostructures, CNRS-LPN, Route de Nozay, 91460 Marcoussis (France); Bourgeois, O. [Institut Néel,