Coulomb Final State Interactions for Gaussian Wave Packets

CERN Document Server

Wiedemann, Urs Achim; Heinz, Ulrich W

1999-01-01

Two-particle like-sign and unlike-sign correlations including Coulomb final state interactions are calculated for Gaussian wave packets emitted from a Gaussian source. We show that the width of the wave packets can be fully absorbed into the spatial and momentum space widths of an effective emission function for plane wave states, and that Coulomb final state interaction effects are sensitive only to the latter, but not to the wave packet width itself. Results from analytical and numerical calculations are compared with recently published work by other authors.

Wave-packet revivals for quantum systems with nondegenerate energies

International Nuclear Information System (INIS)

Bluhm, R.; Tudose, B.

1996-01-01

The revival structure of wave packets is examined for quantum systems having energies that depend on two nondegenerate quantum numbers. For such systems, the evolution of the wave packet is controlled by two classical periods and three revival times. These wave packets exhibit quantum beats in the initial motion as well as new types of long-term revivals. The issue of whether fractional revivals can form is addressed. We present an analytical proof showing that at certain times equal to rational fractions of the revival times the wave packet can reform as a sum of subsidiary waves and that both conventional and new types of fractional revivals can occur. (orig.)

Microwave Ionization of an Atomic Electron Wave Packet

International Nuclear Information System (INIS)

Noel, Michael W.; Ko, Lung; Gallagher, T. F.

2001-01-01

A short microwave pulse is used to ionize a lithium Rydberg wave packet launched from the core at a well-defined phase of the field. We observe a strong dependence on the relative phase between the motion of the wave packet and the oscillations of the field. This phase dependent ionization is also studied as a function of the relative frequency. Our experimental observations are in good qualitative agreement with a one-dimensional classical model of wave packet ionization

A time-frequency analysis of wave packet fractional revivals

International Nuclear Information System (INIS)

Ghosh, Suranjana; Banerji, J

2007-01-01

We show that the time-frequency analysis of the autocorrelation function is, in many ways, a more appropriate tool to resolve fractional revivals of a wave packet than the usual time-domain analysis. This advantage is crucial in reconstructing the initial state of the wave packet when its coherent structure is short-lived and decays before it is fully revived. Our calculations are based on the model example of fractional revivals in a Rydberg wave packet of circular states. We end by providing an analytical investigation which fully agrees with our numerical observations on the utility of time-frequency analysis in the study of wave packet fractional revivals

Dispersionless wave packets in Dirac materials

International Nuclear Information System (INIS)

Jakubský, Vít; Tušek, Matěj

2017-01-01

We show that a wide class of quantum systems with translational invariance can host dispersionless, soliton-like, wave packets. We focus on the setting where the effective, two-dimensional Hamiltonian acquires the form of the Dirac operator. The proposed framework for construction of the dispersionless wave packets is illustrated on silicene-like systems with topologically nontrivial effective mass. Our analytical predictions are accompanied by a numerical analysis and possible experimental realizations are discussed.

Electron Rydberg wave packets in one-dimensional atoms

Indian Academy of Sciences (India)

produced by the application of a single impulsive kick was explicitly demonstrated. The undulation of ..... In this context, let us divide the wave packet .... wave packet with special attention to the time evolution of its components associ- ated with ...

Aeroacoustic directivity via wave-packet analysis of mean or base flows

Science.gov (United States)

Edstrand, Adam; Schmid, Peter; Cattafesta, Louis

2017-11-01

Noise pollution is an ever-increasing problem in society, and knowledge of the directivity patterns of the sound radiation is required for prediction and control. Directivity is frequently determined through costly numerical simulations of the flow field combined with an acoustic analogy. We introduce a new computationally efficient method of finding directivity for a given mean or base flow field using wave-packet analysis (Trefethen, PRSA 2005). Wave-packet analysis approximates the eigenvalue spectrum with spectral accuracy by modeling the eigenfunctions as wave packets. With the wave packets determined, we then follow the method of Obrist (JFM, 2009), which uses Lighthill's acoustic analogy to determine the far-field sound radiation and directivity of wave-packet modes. We apply this method to a canonical jet flow (Gudmundsson and Colonius, JFM 2011) and determine the directivity of potentially unstable wave packets. Furthermore, we generalize the method to consider a three-dimensional flow field of a trailing vortex wake. In summary, we approximate the disturbances as wave packets and extract the directivity from the wave-packet approximation in a fraction of the time of standard aeroacoustic solvers. ONR Grant N00014-15-1-2403.

Wave packet construction in three-dimensional quantum billiards

Indian Academy of Sciences (India)

We examine the dynamical evolution of wave packets in a cubical billiard where three quantum numbers (, , ) determine its energy spectrum and consequently its dynamical behaviour. We have constructed the wave packet in the cubical billiard and have observed its time evolution for various closed orbits.

Quantum wave-packet revivals in circular billiards

International Nuclear Information System (INIS)

Robinett, R.W.; Heppelmann, S.

2002-01-01

We examine the long-term time dependence of Gaussian wave packets in a circular infinite well (billiard) system and find that there are approximate revivals. For the special case of purely m=0 states (central wave packets with no momentum) the revival time is T rev (m=0) =8μR 2 /(ℎ/2π)π, where μ is the mass of the particle, and the revivals are almost exact. For all other wave packets, we find that T rev (m≠0) =(π 2 /2)T rev (m=0) ≅5T rev (m=0) and the nature of the revivals becomes increasingly approximate as the average angular momentum or number of m≠0 states is increased. The dependence of the revival structure on the initial position, energy, and angular momentum of the wave packet and the connection to the energy spectrum is discussed in detail. The results are also compared to two other highly symmetrical two-dimensional infinite well geometries with exact revivals, namely, the square and equilateral triangle billiards. We also show explicitly how the classical periodicity for closed orbits in a circular billiard arises from the energy eigenvalue spectrum, using a WKB analysis

Angular momentum transport with twisted exciton wave packets

Science.gov (United States)

Zang, Xiaoning; Lusk, Mark T.

2017-10-01

A chain of cofacial molecules with CN or CN h symmetry supports excitonic states with a screwlike structure. These can be quantified with the combination of an axial wave number and an azimuthal winding number. Combinations of these states can be used to construct excitonic wave packets that spiral down the chain with well-determined linear and angular momenta. These twisted exciton wave packets can be created and annihilated using laser pulses, and their angular momentum can be optically modified during transit. This allows for the creation of optoexcitonic circuits in which information, encoded in the angular momentum of light, is converted into excitonic wave packets that can be manipulated, transported, and then reemitted. A tight-binding paradigm is used to demonstrate the key ideas. The approach is then extended to quantify the evolution of twisted exciton wave packets in a many-body, multilevel time-domain density functional theory setting. In both settings, numerical methods are developed that allow the site-to-site transfer of angular momentum to be quantified.

Exact wave packet decoherence dynamics in a discrete spectrum environment

International Nuclear Information System (INIS)

Tu, Matisse W Y; Zhang Weimin

2008-01-01

We find an exact analytical solution of the reduced density matrix from the Feynman-Vernon influence functional theory for a wave packet in an environment containing a few discrete modes. We obtain two intrinsic energy scales relating to the time scales of the system and the environment. The different relationship between these two scales alters the overall form of the solution of the system. We also introduce a decoherence measure for a single wave packet which is defined as the ratio of Schroedinger uncertainty over the delocalization extension of the wave packet and characterizes the time-evolution behaviour of the off-diagonal reduced density matrix element. We utilize the exact solution and the decoherence measure to study the wave packet decoherence dynamics. We further demonstrate how the dynamical diffusion of the wave packet leads to non-Markovian decoherence in such a microscopic environment.

Turbulent Spot Pressure Fluctuation Wave Packet Model

Energy Technology Data Exchange (ETDEWEB)

Dechant, Lawrence J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-05-01

Wave packet analysis provides a connection between linear small disturbance theory and subsequent nonlinear turbulent spot flow behavior. The traditional association between linear stability analysis and nonlinear wave form is developed via the method of stationary phase whereby asymptotic (simplified) mean flow solutions are used to estimate dispersion behavior and stationary phase approximation are used to invert the associated Fourier transform. The resulting process typically requires nonlinear algebraic equations inversions that can be best performed numerically, which partially mitigates the value of the approximation as compared to a more complete, e.g. DNS or linear/nonlinear adjoint methods. To obtain a simpler, closed-form analytical result, the complete packet solution is modeled via approximate amplitude (linear convected kinematic wave initial value problem) and local sinusoidal (wave equation) expressions. Significantly, the initial value for the kinematic wave transport expression follows from a separable variable coefficient approximation to the linearized pressure fluctuation Poisson expression. The resulting amplitude solution, while approximate in nature, nonetheless, appears to mimic many of the global features, e.g. transitional flow intermittency and pressure fluctuation magnitude behavior. A low wave number wave packet models also recover meaningful auto-correlation and low frequency spectral behaviors.

Do Free Quantum-Mechanical Wave Packets Always Spread?

Science.gov (United States)

Klein, James R.

1980-01-01

The spreading or shrinking of free three-dimensional quantum-mechanical wave packets is addressed. A seeming paradox concerning the time evolution operator and nonspreading wave packets is discussed, and the necessity of taking into account the appropriate mathematical structure of quantum mechanics is emphasized. Teaching implications are given.…

Transfer of a wave packet in double-well potential

Science.gov (United States)

Yang, Hai-Feng; Hu, Yao-Hua; Tan, Yong-Gang

2018-04-01

Energy potentials with double-well structures are typical in atoms and molecules systems. A manipulation scheme using Half Cycles Pulses (HCPs) is proposed to transfer a Gaussian wave packet between the two wells. On the basis of quantum mechanical simulations, the time evolution and the energy distribution of the wave packet are evaluated. The effect of time parameters, amplitude, and number of HCPs on spatial and energy distribution of the final state and transfer efficiency are investigated. After a carefully tailored HCPs sequence is applied to the initial wave packet localized in one well, the final state is a wave packet localized in the other well and populated at the lower energy levels with narrower distribution. The present scheme could be used to control molecular reactions and to prepare atoms with large dipole moments.

Energy and Information Transfer Via Coherent Exciton Wave Packets

Science.gov (United States)

Zang, Xiaoning

associated excitations were dubbed twisted excitons. Twisted exciton packets can be manipulated as they travel down molecular chains, and this has applications in quantum information science as well. In each setting considered, exciton dynamics were initially studied using a simple tight-binding formalism. This misses the actual many-body interactions and multiple energy levels associated real systems. To remedy this, I adapted an existing time-domain Density Functional Theory code and applied it to study the dynamics of exciton wave packets on quasi-one-dimensional systems. This required the use of high-performance computing and the construction of a number of key auxiliary codes. Establishing the requisite methodology constituted a substantial part of the entire thesis. Surprisingly, this effort uncovered a computational issue associated with Rabi oscillations that had been incorrectly characterized in the literature. My research elucidated the actual problem and a solution was found. This new methodology was an integral part of the overall computational analysis. The thesis then takes up the a detailed consideration of the prospect for creating systems that support a strong measure of transport coherence. While physical implementations include molecular assemblies, solid-state superlattices, and even optical lattices, I decided to focus on assemblies of nanometer-sized silicon quantum dots. First principles computational analysis was used to quantify reorganization within individual dots and excitonic coupling between dots. Quantum dot functionalizations were identified that make it plausible to maintain a measure of excitonic coherence even at room temperatures. Attention was then turned to the use of covalently bonded bridge material to join quantum dots in a way that facilitates efficient exciton transfer. Both carbon and silicon structures were considered by considering the way in which subunits might be best brought together. This resulted in a set of design criteria

Numerical simulation of the nonlinear dynamics of packets of spiral density waves

International Nuclear Information System (INIS)

Korchagin, V.I.

1987-01-01

In a numerical experiment, the behavior of nonlinear packets of spiral density waves in a gas disk has been investigated for different initial wave amplitudes. If the amplitude of the density perturbations is small (<5%), the wave packet is drawn toward the center or toward the periphery of the disk in accordance with the linear theory. The behavior of linear packets of waves with wavelength comparable to the disk radius (R/sub d//lambda = 4) exhibits good agreement with the conclusions of the linear theory of tightly wound spiral waves. The dynamics of wave packets with initial density amplitudes 16, 30, 50% demonstrates the nonlinear nature of the behavior. THe behavior is governed by whether or not the nonlinear effects of higher than third order in the wave amplitude play a part. If the wave packet dynamics is determined by the cubic nonlinearity, the results of the numerical experiment are in qualitative and quantitative agreement with the nonlinear theory of short waves, although the characteristic scale of the packet and the wavelength are of the order of the disk radius. In the cases when the nonlinear effects of higher orders in the amplitude play an important part, the behavior of a packet does not differ qualitatively from the behavior predicted by the theory of cubic nonlinearity, but the nonlinear spreading of the packet takes place more rapidly

Runge-Lenz wave packet in multichannel Stark photoionization

International Nuclear Information System (INIS)

Texier, F.

2005-01-01

In a previous slow photoionization experiment, modulations of ionization rings were manifested for Xe in a constant electric field. The present quantum calculation reveals that the modulation is an effect of the multichannel core scattering and of tunneling waves through the Coulomb-Stark potential barrier: the barrier reduces the number of oscillations that is observed relatively to the number of oscillations of the short range wave functions, and the nonhydrogenic core phase shifts modify the position of the ionization rings. We find a hidden difference, in the ionization process, for two close values of the energy depending on the resonance with the barrier. The ionization intensity is interpreted as a Runge-Lenz wave packet; thus, we can relate the quantum modulation to the classical Coulomb-Stark trajectories. The Runge-Lenz wave packet differs from a usual temporal wave packet because its components are eigenstates of the Runge-Lenz vector z projection and its evolution is not temporal but spatial

Observation of moving wave packets reveals their quantum state

International Nuclear Information System (INIS)

Leonhardt, U.; Raymer, M.G.

1996-01-01

We show how to infer the quantum state of a wave packet from position probability distributions measured during the packet close-quote s motion in an arbitrary potential. We assume a nonrelativistic one-dimensional or radial wave packet. Temporal Fourier transformation and spatial sampling with respect to a newly found set of functions project the density-matrix elements out of the probability distributions. The sampling functions are derivatives of products of regular and irregular wave functions. We note that the ability to infer quantum states in this way depends on the structure of the Schroedinger equation. copyright 1996 The American Physical Society

The Evolution and Revival Structure of Localized Quantum Wave Packets

OpenAIRE

Bluhm, Robert; Kostelecky, Alan; Porter, James

1995-01-01

Localized quantum wave packets can be produced in a variety of physical systems and are the subject of much current research in atomic, molecular, chemical, and condensed-matter physics. They are particularly well suited for studying the classical limit of a quantum-mechanical system. The motion of a localized quantum wave packet initially follows the corresponding classical motion. However, in most cases the quantum wave packet spreads and undergoes a series of collapses and revivals. We pre...

Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

Science.gov (United States)

Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

2016-04-22

We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.

Zeno dynamics in wave-packet diffraction spreading

Energy Technology Data Exchange (ETDEWEB)

Porras, Miguel A. [Departamento de Fisica Aplicada, Universidad Politecnica de Madrid, Rios Rosas 21, ES-28003 Madrid (Spain); Luis, Alfredo; Gonzalo, Isabel [Departamento de Optica, Facultad de Ciencias Fisicas, Universidad Complutense, ES-28040 Madrid (Spain); Sanz, Angel S. [Instituto de Fisica Fundamental-CSIC, Serrano 123, ES-28006 Madrid (Spain)

2011-11-15

We analyze a simple and feasible practical scheme displaying Zeno, anti-Zeno, and inverse-Zeno effects in the observation of wave-packet spreading caused by free evolution. The scheme is valid both in spatial diffraction of classical optical waves and in time diffraction of a quantum wave packet. In the optical realization, diffraction spreading is observed by placing slits between a light source and a light-power detector. We show that the occurrence of Zeno or anti-Zeno effects depends just on the frequency of observations between the source and detector. These effects are seen to be related to the diffraction mode theory in Fabry-Perot resonators.

Quantum chaos induced by nonadiabatic coupling in wave-packet dynamics

International Nuclear Information System (INIS)

Higuchi, Hisashi; Takatsuka, Kazuo

2002-01-01

The effect of nonadiabatic coupling due to breakdown of the Born-Oppenheimer approximation on chaos is investigated. A couple of measures (indicators) that detect the extent of chaos in wave-packet dynamics on coupled potential functions are devised. Using them, we show that chaos is indeed induced by a nonadiabatic coupling in individual time-dependent wave-packet dynamics. This chaos is genuinely of quantum nature, since it arises from bifurcation and merging of a wave packet at the quasicrossing region of two coupled potential functions

Strongly nonlinear evolution of low-frequency wave packets in a dispersive plasma

Science.gov (United States)

Vasquez, Bernard J.

1993-01-01

The evolution of strongly nonlinear, strongly modulated wave packets is investigated in a dispersive plasma using a hybrid numerical code. These wave packets have amplitudes exceeding the strength of the external magnetic field, along which they propagate. Alfven (left helicity) wave packets show strong steepening for p Schrodinger (DNLS) equation.

Evolution of a wave packet scattered by a one-dimensional potential

International Nuclear Information System (INIS)

Khachatrian, A Zh; Alexanyan, Al G; Khoetsyan, V A; Alexanyan, N A

2013-01-01

We consider the evolution of a wave packet that is made up of a group of the wave functions describing the stationary scattering process and tunnels through a one-dimensional potential of arbitrary form. As the main characteristics of the time difference of the tunnelling process, use is made of the propagation speed of the wave-packet maximum. We show that the known Hartman formula for the tunnelling time corresponds to the wave packet with a wavenumber-uniform spectral composition in the case, when the phase and transmission coefficient modulus dispersions are taken into account only in the linear approximation. The amplitude of the main peak of the transmitted wave intensity is proven to be independent of the tunnelling time and is determined by the transmission coefficient of the spectral component at the carrier frequency and the spectral width of the wave packet. In the limit of an infinitely wide potential barrier the amplitude of the wave-packet maximum is shown to tend to zero slower than the tunnelling time tends to its asymptotic value, i.e., indeed we deal with the paradox of an infinitely large propagation speed of a wave disturbance through the barrier. (propagation of wave fronts)

Evolution of a wave packet scattered by a one-dimensional potential

Energy Technology Data Exchange (ETDEWEB)

Khachatrian, A Zh; Alexanyan, Al G; Khoetsyan, V A; Alexanyan, N A

2013-06-30

We consider the evolution of a wave packet that is made up of a group of the wave functions describing the stationary scattering process and tunnels through a one-dimensional potential of arbitrary form. As the main characteristics of the time difference of the tunnelling process, use is made of the propagation speed of the wave-packet maximum. We show that the known Hartman formula for the tunnelling time corresponds to the wave packet with a wavenumber-uniform spectral composition in the case, when the phase and transmission coefficient modulus dispersions are taken into account only in the linear approximation. The amplitude of the main peak of the transmitted wave intensity is proven to be independent of the tunnelling time and is determined by the transmission coefficient of the spectral component at the carrier frequency and the spectral width of the wave packet. In the limit of an infinitely wide potential barrier the amplitude of the wave-packet maximum is shown to tend to zero slower than the tunnelling time tends to its asymptotic value, i.e., indeed we deal with the paradox of an infinitely large propagation speed of a wave disturbance through the barrier. (propagation of wave fronts)

Manifestations of wave packet revivals in the moments of observables

International Nuclear Information System (INIS)

Sudheesh, C.; Lakshmibala, S.; Balakrishnan, V.

2004-01-01

Using a generic Hamiltonian that models wave packet propagation in a Kerr-like medium, matter wave field dynamics in Bose-Einstein condensation, etc., we show that distinctive signatures of wave packet revivals and fractional revivals are displayed by the time evolution of the expectation values of appropriate observables, enabling selective identification of different fractional revivals

Long-term evolution and revival structure of Rydberg wave packets

International Nuclear Information System (INIS)

Bluhm, R.

1995-01-01

It is known that, after formation, a Rydberg wave packet undergoes a series of collapses and revivals within a time period called the revival time, t rev , at the end of which it is close to its original shape. We study the behavior of Rydberg wave packets on time scales much greater than t rev . We show that after a few revival cycles the wave packet ceases to reform at multiples of the revival time. Instead, a new series of collapses and revivals commences, culminating after a time period t sr >>t rev with the formation of a wave packet that more closely resembles the initial packet than does the full revival at time t rev . Furthermore, at times that are rational fractions of t sr , the square of the autocorrelation function exhibits large peaks with periodicities that can be expressed as fractions of the revival time t rev . These periodicities indicate a new type of fractional revival occurring for times much greater than t rev . A theoretical explanation of these effects is outlined. ((orig.))

Trajectory description of the quantum–classical transition for wave packet interference

Energy Technology Data Exchange (ETDEWEB)

Chou, Chia-Chun, E-mail: ccchou@mx.nthu.edu.tw

2016-08-15

The quantum–classical transition for wave packet interference is investigated using a hydrodynamic description. A nonlinear quantum–classical transition equation is obtained by introducing a degree of quantumness ranging from zero to one into the classical time-dependent Schrödinger equation. This equation provides a continuous description for the transition process of physical systems from purely quantum to purely classical regimes. In this study, the transition trajectory formalism is developed to provide a hydrodynamic description for the quantum–classical transition. The flow momentum of transition trajectories is defined by the gradient of the action function in the transition wave function and these trajectories follow the main features of the evolving probability density. Then, the transition trajectory formalism is employed to analyze the quantum–classical transition of wave packet interference. For the collision-like wave packet interference where the propagation velocity is faster than the spreading speed of the wave packet, the interference process remains collision-like for all the degree of quantumness. However, the interference features demonstrated by transition trajectories gradually disappear when the degree of quantumness approaches zero. For the diffraction-like wave packet interference, the interference process changes continuously from a diffraction-like to collision-like case when the degree of quantumness gradually decreases. This study provides an insightful trajectory interpretation for the quantum–classical transition of wave packet interference.

Square-integrable wave packets from the Volkov solutions

International Nuclear Information System (INIS)

Zakowicz, Stephan

2005-01-01

Rigorous mathematical proofs of some properties of the Volkov solutions are presented, which describe the motion of a relativistic charged Dirac particle in a classical, plane electromagnetic wave. The Volkov solutions are first rewritten in a convenient form, which clearly reveals some of the symmetries of the underlying Dirac equation. Assuming continuity and boundedness of the electromagnetic vector potential, it is shown how one may construct square-integrable wave packets from momentum distributions in the space C 0 ∞ (R 3 ) 4 . If, in addition, the vector potential is C 1 and the derivative is bounded, these wave packets decay in space faster than any polynomial and fulfill the Dirac equation. The mapping which takes momentum distributions into wave packets is shown to be isometric with respect to the L 2 (R 3 ) 4 norm and may therefore be continuously extended to a mapping from L 2 (R 3 ) 4 . For a momentum function in L 1 (R 3 ) 4 intersection L 2 (R 3 ) 4 , an integral representation of this extension is presented

Square-Integrable Wave Packets from the Volkov Solutions

CERN Document Server

Zakowicz, S

2004-01-01

Rigorous mathematical proofs of some properties of the Volkov solutions are presented, which describe the motion of a relativistic charged Dirac particle in a classical, plane electromagnetic wave. The Volkov solutions are first rewritten in a convenient form, which clearly reveals some of the symmetries of the underlying Dirac equation. Assuming continuity and boundedness of the electromagnetic vector potential, it is shown how one may construct square-integrable wave packets from momentum distributions in the space $\\mathcal{C}^{\\infty}_0(\\mathbb{R}^3)^4$. If, in addition, the vector potential is $\\mathcal{C}^1$ and the derivative is bounded, these wave packets decay in space faster than any polynomial and fulfill the Dirac equation. The mapping which takes momentum distributions into wave packets is shown to be isometric with respect to the $L^2(\\mathbb{R}^3)^4$ norm and may therefore be continuously extended to a mapping from $L^2(\\mathbb{R}^3)^4$. For a momen! tum function in $L^1(\\mathbb{R}^3)^4 \\cap L^...

Wave packet formulation of the boomerang model for resonant electron--molecule scattering

International Nuclear Information System (INIS)

McCurdy, C.W.; Turner, J.L.

1983-01-01

A time-dependent formulation of the boomerang model for resonant electron--molecule scattering is presented in terms of a wave packet propagating on the complex potential surface of the metastable anion. The results of calculations using efficient semiclassical techniques for propagating the wave packet are found to be in excellent agreement with full quantum-mechanical calculations of vibrational excitation cross sections in e - --N 2 scattering. The application of the wave packet formulation as a computational and conceptual approach to the problem of resonant collisions with polyatomic molecules is discussed in the light of recent wave packet calculations on polyatomic photodissociation and Raman spectra

Antisymmetrized molecular dynamics of wave packets with stochastic incorporation of Vlasov equation

International Nuclear Information System (INIS)

Ono, Akira; Horiuchi, Hisashi.

1996-01-01

The first purpose of this report is to present an extended AMD model which can generally describe such minor branching processes by removing the restriction on the one-body distribution function. This is done not by generalizing the wave packets to arbitrary single-particle wave functions but by representing the diffused and/or deformed wave packet as an ensemble of Gaussian wave packets. In other words, stochastic displacements are given to the wave packets in phase space so that the ensemble-average of the time evolution of the one-body distribution function is essentially equivalent to the solution of Vlasov equation which does not have any restriction on the shape of wave packets. This new model is called AMD-V. Although AMD-V is equivalent to Vlasov equation in the instantaneous time evolution of the one-body distribution function for an AMD wave function, AMD-V describes the branching into channels and the fluctuation of the mean field which are caused by the spreading or the splitting of the single-particle wave function. The second purpose of this report is to show the drastic effect of this new stochastic process of wave packet splitting on the dynamics of heavy ion collisions, especially in the fragmentation mechanism. We take the 40 Ca + 40 Ca system at the incident energy 35 MeV/nucleon. It will be shown that the reproduction of data by the AMD-V calculation is surprisingly good. We will see that the effect of the wave packet diffusion is crucially important to remove the spurious binary feature of the AMD calculation and to enable the multi-fragment final state. (J.P.N.)

Controlling the spreading of wave packets of a dissociating molecule

DEFF Research Database (Denmark)

Tiwari, Ashwani Kumar; Møller, Klaus Braagaard; Henriksen, Niels Engholm

2007-01-01

A first-order perturbation theoretic approach within the electric-dipole approximation is used to study the time evolution of wave packets created by linearly chirped laser pulses on a repulsive potential of Br-2. Our calculations show that negatively chirped pulses focus the wave packet in the F...

Simulation of the collapse and dissipation of Langmuir wave packets

International Nuclear Information System (INIS)

Newman, D.L.; Winglee, R.M.; Robinson, P.A.; Glanz, J.; Goldman, M.V.

1990-01-01

The collapse of isolated Langmuir wave packets is studied numerically in two dimensions using both particle-in-cell (PIC) simulations and by integrating the Zakharov partial differential equations (PDE's). The initial state consists of a localized Langmuir wave packet in an ion background that either is uniform or has a profile representative of the density wells in which wave packets form during strong plasma turbulence. Collapse thresholds are determined numerically and compared to analytical estimates. A model in which Langmuir damping is significantly stronger than Landau damping is constructed which, when included in the PDE simulations, yields good agreement with the collapse dynamics observed in PIC simulations for wave packets with initial wave energy densities small compared to the thermal level. For more intense initial Langmuir fields, collapse is arrested in PIC simulations at lower field strengths than in PDE simulations. Neither nonlinear saturation of the density perturbation nor fluid electron nonlinearities can account for the difference between simulation methods in this regime. However, at these wave levels inhomogeneous electron heating and coherent jets of transit-time accelerated electrons in phase space are observed, resulting in further enhancement of wave damping and the consequent reduction of fields in the PIC simulations

Comparison of a noncausal with a causal relativistic wave-packet evolution

International Nuclear Information System (INIS)

Castro, A.N. de; Jabs, A.

1991-01-01

In order to study causality violation in more detail we contrast the Klein-Gordon wave packet of Rosenstein und Usher with the Dirac wave packet of Bakke and Wergeland. Both packets are initially localized with exponentially bounded tails but just outside the condition of the general Hegerfeldt theorem for causality violation. It turns out that the wave packet of Bakke and Wergeland exhibits all the features investigated by Rosenstein and Usher, except that it never violates relativistic causality. Thus none of those features, in particular the back- and forerunners emerging from the light cone, can be held responsible for causality violation, and the Ruijsenaars integral is not necessarily a measure of the amount of causality violation. (orig.)

Coherent wave packet dynamics in a double-well potential in cavity

Science.gov (United States)

Zheng, Li; Li, Gang; Ding, Ming-Song; Wang, Yong-Liang; Zhang, Yun-Cui

2018-02-01

We investigate the coherent wave packet dynamics of a two-level atom trapped in a symmetric double-well potential in a near-resonance cavity. Prepared on one side of the double-well potential, the atom wave packet oscillates between the left and right wells, while recoil induced by the emitted photon from the atom entangles the atomic internal and external degrees of freedom. The collapse and revival of the tunneling occurs. Adjusting the width of the wave packets, one can modify the tunneling frequency and suppress the tunneling.

Dynamics of an atomic wave packet in a standing-wave cavity field: A cavity-assisted single-atom detection

International Nuclear Information System (INIS)

Chough, Young-Tak; Nha, Hyunchul; Kim, Sang Wook; An, Kyungwon; Youn, Sun-Hyun

2002-01-01

We investigate the single-atom detection system using an optical standing-wave cavity, from the viewpoint of the quantized center-of-mass motion of the atomic wave packet. We show that since the atom-field coupling strength depends upon the overlap integral of the atomic wave packet and the field mode function, the effect of the wave-packet spreading via the momentum exchange process brings about a significant effect in the detection efficiency. We find that, as a result, the detection efficiency is not sensitive to the individual atomic trajectory for reasonably slow atoms. We also address an interesting phenomenon of the atomic wave-packet splitting occurring when an atom passes through a node of the cavity field

Mesoscopic states in graphene in magnetic field: collapse and revival of wave packets

International Nuclear Information System (INIS)

Demikhovskij, V.Ya.; Telezhnikov, A.V.; Frolova, E.V.; Kravets, N.A.

2013-01-01

The effects of wave packet collapse and revival in monolayer and bilayer graphene at an external perpendicular magnetic field are described. The evolution of electron wave packets, which are a superposition of the states with quantum numbers n around that of some Landau level n 0 was studied. The probability densities as well as average velocities of the packet center were calculated analytically and then visualized. The initial wave packet consisting only of positive energy decomposed into several subpackets at the moments t = (m/n)T R , where T R is the revival time and m, n are the mutually prime integers. Besides, it is shown that the behavior of a wave packet containing the states of both energy bands (with E n > 0 and E n < 0) is more complicated. Such packet splits into two parts, which rotate with a cyclotron frequency in the opposite directions, and then experience collapse and revival. The structure of multipole electromagnetic radiation of these packets is analyzed.

Geometrical aspects in optical wave-packet dynamics.

Science.gov (United States)

Onoda, Masaru; Murakami, Shuichi; Nagaosa, Naoto

2006-12-01

We construct a semiclassical theory for propagation of an optical wave packet in a nonconducting medium with a periodic structure of dielectric permittivity and magnetic permeability, i.e., a nonconducting photonic crystal. We employ a quantum-mechanical formalism in order to clarify its link to those of electronic systems. It involves the geometrical phase, i.e., Berry's phase, in a natural way, and describes an interplay between orbital motion and internal rotation. Based on the above theory, we discuss the geometrical aspects of the optical Hall effect. We also consider a reduction of the theory to a system without periodic structure and apply it to the transverse shift of an optical beam at an interface reflection or refraction. For a generic incident beam with an arbitrary polarization, an identical result for the transverse shift of each reflected or transmitted beam is given by the following different approaches: (i) analytic evaluation of wave-packet dynamics, (ii) total angular momentum (TAM) conservation for individual photons, and (iii) numerical simulation of wave-packet dynamics. It is consistent with a result by classical electrodynamics. This means that the TAM conservation for individual photons is already taken into account in wave optics, i.e., classical electrodynamics. Finally, we show an application of our theory to a two-dimensional photonic crystal, and propose an optimal design for the enhancement of the optical Hall effect in photonic crystals.

Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

International Nuclear Information System (INIS)

Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

2005-01-01

We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

On wave-packet dynamics in a decaying quadratic potential

DEFF Research Database (Denmark)

Møller, Klaus Braagaard; Henriksen, Niels Engholm

1997-01-01

We consider the time-dependent Schrodinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight in particular, the signatures of classical mechanics in the wave packet dynamics.......We consider the time-dependent Schrodinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight in particular, the signatures of classical mechanics in the wave packet dynamics....

Dynamics of electron wave packet in a disordered chain with delayed nonlinear response

International Nuclear Information System (INIS)

Zhu Hongjun; Xiong Shijie

2010-01-01

We investigate the dynamics of one electron wave packet in a linear chain with random on-site energies and a nonadiabatic electron-phonon interaction which is described by a delayed cubic nonlinear term in the time-dependent Schroedinger equation. We show that in the regime where the wave packet is delocalized in the case with only the delayed nonlinearity, the wave packet becomes localized when the disorder is added and the localization is enhanced by increasing the disorder. In the regime where the self-trapping phenomenon occurs in the case with only the delayed nonlinearity, by adding the disorder the general dynamical features of the wave packet do not change if the nonlinearity parameter is small, but the dynamics shows the subdiffusive behavior if the nonlinearity parameter is large. The numerical results demonstrate complicated wave packet dynamics of systems with both the disorder and nonlinearity.

Massachusetts Bay - Internal wave packets digitized from SAR imagery

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This feature class contains internal wave packets digitized from SAR imagery at 1:350,000 scale in Massachusetts Bay. Internal waves are nonsinusoidal waves that...

Nonspreading Wave Packets for Rydberg Electrons in Rotating Molecules with Electric Dipole Moments

International Nuclear Information System (INIS)

Bialynicki-Birula, I.; Bialynicka-Birula, Z.

1996-01-01

Nonspreading wave packets for Rydberg electrons are predicted in rotating molecules with electric dipole moments. We have named them the Trojan wave packets since their stability is due to the same mechanism that governs the motion of the Trojan asteroids in the Sun-Jupiter system. Unlike all previously predicted Trojan wave packets in atoms, molecular Trojan states do not require external fields for their existence

Cherenkov Radiation Control via Self-accelerating Wave-packets.

Science.gov (United States)

Hu, Yi; Li, Zhili; Wetzel, Benjamin; Morandotti, Roberto; Chen, Zhigang; Xu, Jingjun

2017-08-18

Cherenkov radiation is a ubiquitous phenomenon in nature. It describes electromagnetic radiation from a charged particle moving in a medium with a uniform velocity larger than the phase velocity of light in the same medium. Such a picture is typically adopted in the investigation of traditional Cherenkov radiation as well as its counterparts in different branches of physics, including nonlinear optics, spintronics and plasmonics. In these cases, the radiation emitted spreads along a "cone", making it impractical for most applications. Here, we employ a self-accelerating optical pump wave-packet to demonstrate controlled shaping of one type of generalized Cherenkov radiation - dispersive waves in optical fibers. We show that, by tuning the parameters of the wave-packet, the emitted waves can be judiciously compressed and focused at desired locations, paving the way to such control in any physical system.

Traveling-wave photodetector

Science.gov (United States)

Hietala, V.M.; Vawter, G.A.

1993-12-14

The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size. 4 figures.

Dynamical behavior of the wave packets on adiabatic potential surfaces observed by femtosecond luminescence spectroscopy

International Nuclear Information System (INIS)

Suemoto, Tohru; Nakajima, Makoto; Matsuoka, Taira; Yasukawa, Keizo; Koyama, Takeshi

2007-01-01

The wave packet dynamics on adiabatic potential surfaces studied by means of time-resolved luminescence spectroscopy is reviewed and the advantages of this method are discussed. In quasi-one-dimensional bromine-bridged platinum complexes, a movie representing the time evolution of the wave packet motion and shape was constructed. A two-dimensional Lissajous-like motion of the wave packet was suggested in the same material at low temperature. In F-centers in KI, evidence for tunneling of the wave packet between the adjacent adiabatic potential surfaces was found. Selective observation of the wave packet motion on the excited state was demonstrated for F-centers in KBr and compared with the results from pump-and-probe experiments in literature

Pump-dump iterative squeezing of vibrational wave packets.

Science.gov (United States)

Chang, Bo Y; Sola, Ignacio R

2005-12-22

The free motion of a nonstationary vibrational wave packet in an electronic potential is a source of interesting quantum properties. In this work we propose an iterative scheme that allows continuous stretching and squeezing of a wave packet in the ground or in an excited electronic state, by switching the wave function between both potentials with pi pulses at certain times. Using a simple model of displaced harmonic oscillators and delta pulses, we derive the analytical solution and the conditions for its possible implementation and optimization in different molecules and electronic states. We show that the main constraining parameter is the pulse bandwidth. Although in principle the degree of squeezing (or stretching) is not bounded, the physical resources increase quadratically with the number of iterations, while the achieved squeezing only increases linearly.

Traveling wave laser system

International Nuclear Information System (INIS)

Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

1975-01-01

The invention broadly involves a method and means for generating a traveling wave laser pulse and is basically analogous to a single pass light amplifier system. However, the invention provides a traveling wave laser pulse of almost unlimited energy content, wherein a gain medium is pumped in a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

Squeezing a wave packet with an angular-dependent mass

Energy Technology Data Exchange (ETDEWEB)

Schmidt, Alexandre G M [Departamento de Ciencias Exatas, Universidade Federal Fluminense, Av. dos Trabalhadores 420, Volta Redonda RJ, CEP 27255-125 (Brazil)], E-mail: agmschmidt@gmail.com, E-mail: agmschmidt@pq.cnpq.br

2009-06-19

We present a new effect of position-dependent mass (PDM) systems: the possibility of creating squeezed wave packets at the partial revival times. We solve exactly the PDM Schroedinger equation for the two-dimensional quantum rotor with two effective masses {mu}({theta}), both free and interacting with a uniform electric field, and present their energy eigenvalues and eigenfunctions in terms of Mathieu functions. For the first one, in order to squeeze the wave packet it is necessary to apply an electric field; for the second one such an effect can be achieved without the field.

Squeezing a wave packet with an angular-dependent mass

International Nuclear Information System (INIS)

Schmidt, Alexandre G M

2009-01-01

We present a new effect of position-dependent mass (PDM) systems: the possibility of creating squeezed wave packets at the partial revival times. We solve exactly the PDM Schroedinger equation for the two-dimensional quantum rotor with two effective masses μ(θ), both free and interacting with a uniform electric field, and present their energy eigenvalues and eigenfunctions in terms of Mathieu functions. For the first one, in order to squeeze the wave packet it is necessary to apply an electric field; for the second one such an effect can be achieved without the field

Extracting continuum information from Ψ(t) in time-dependent wave-packet calculations

International Nuclear Information System (INIS)

Madsen, L. B.; Nikolopoulos, L. A. A.; Kjeldsen, T. K.; Fernandez, J.

2007-01-01

The theory of measurement projection operators in grid-based time-dependent wave-packet calculations involving electronic continua in atoms and molecules is discussed. A hierarchy of projection operators relevant in their individual restricted configuration spaces is presented. At asymptotically large distances from the scattering or interaction center the projection operators involve plane waves only. To reach this asymptotic regime, however, large propagation times and large boxes may be required. At somewhat smaller distances from the scattering center, the projection operators are expressed in terms of analytical single-center Coulomb scattering waves with incoming wave boundary conditions. If propagation of the wave packet to these asymptotic regimes is impeded, the projection operators involve the exact scattering states which are not readily available in the wave-packet calculation and hence must be supplied by an additional, typically very demanding, calculation. The present approach suggests an exact way of analyzing the timely problem of the one-electron continuum in nonperturbative calculations. A key feature is that the propagated wave packet includes every interaction of the full Hamiltonian. The practicality of the proposed method is illustrated by the nontrivial example of strong-field ionization of the molecular hydrogen ion. Finally, the extension of the presented ideas to single and double ionization of two-electron systems is discussed

Traveling wave laser system

International Nuclear Information System (INIS)

Gregg, D.W.; Kidder, R.E.; Biehl, A.T.

1975-01-01

A method is described for generating a traveling wave laser pulse of almost unlimited energy content wherein a gain medium is pumped into a traveling wave mode, the traveling wave moving at essentially the velocity of light to generate an amplifying region or zone which moves through the medium at the velocity of light in the presence of directed stimulating radiation, thereby generating a traveling coherent, directed radiation pulse moving with the amplification zone through the gain medium. (U.S.)

Resonance-assisted decay of nondispersive wave packets

OpenAIRE

Wimberger, S.; Schlagheck, P.; Eltschka, C.; Buchleitner, A.

2006-01-01

We present a quantitative semiclassical theory for the decay of nondispersive electronic wave packets in driven, ionizing Rydberg systems. Statistically robust quantities are extracted combining resonance assisted tunneling with subsequent transport across chaotic phase space and a final ionization step.

Scattering of wave packets with phases

Energy Technology Data Exchange (ETDEWEB)

Karlovets, Dmitry V. [Department of Physics, Tomsk State University, Lenina Ave. 36, 634050 Tomsk (Russian Federation)

2017-03-09

A general problem of 2→N{sub f} scattering is addressed with all the states being wave packets with arbitrary phases. Depending on these phases, one deals with coherent states in (3+1) D, vortex particles with orbital angular momentum, the Airy beams, and their generalizations. A method is developed in which a number of events represents a functional of the Wigner functions of such states. Using width of a packet σ{sub p}/〈p〉 as a small parameter, the Wigner functions, the number of events, and a cross section are represented as power series in this parameter, the first non-vanishing corrections to their plane-wave expressions are derived, and generalizations for beams are made. Although in this regime the Wigner functions turn out to be everywhere positive, the cross section develops new specifically quantum features, inaccessible in the plane-wave approximation. Among them is dependence on an impact parameter between the beams, on phases of the incoming states, and on a phase of the scattering amplitude. A model-independent analysis of these effects is made. Two ways of measuring how a Coulomb phase and a hadronic one change with a transferred momentum t are discussed.

The Generation Mechanism of Airy—Bessel Wave Packets in Free Space

International Nuclear Information System (INIS)

Ren Zhi-Jun; Ying Chao-Fu; Fan Chang-Jiang; Wu Qiong

2012-01-01

Localized optical Airy—Bessel configuration wave packets were first generated on the basis of a grating-telescope combination [Nat. Photon. 4(2010) 103]. By studying the spatially induced group velocity dispersion effect of ultrashort pulsed Bessel beams during propagation, we find the universal physical foundation of generating Airy—Bessel wave packets (ABWs) in free space. The research results are expected to open up more common channels for generating stable linear localized ABWs

Wave packet fractional revivals in a one-dimensional Rydberg atom

International Nuclear Information System (INIS)

Veilande, Rita; Bersons, Imants

2007-01-01

We investigate many characteristic features of revival and fractional revival phenomena via derived analytic expressions for an autocorrelation function of a one-dimensional Rydberg atom with weighting probabilities modelled by a Gaussian or a Lorentzian distribution. The fractional revival phenomenon in the ionization probabilities of a one-dimensional Rydberg atom irradiated by two short half-cycle pulses is also studied. When many states are involved in the formation of the wave packet, the revival is lower and broader than the initial wave packet and the fractional revivals overlap and disappear with time

Isolated drops from capillary jets by means of Gaussian wave packets

Science.gov (United States)

Garcia, Francisco Javier; Gonzalez, Heliodoro; Castrejon-Pita, Alfonso Arturo; Castrejon-Pita, Jose Rafael; Gomez-Aguilar, Francisco Jose

2017-11-01

The possibility of obtaining isolated drops from a continuous liquid jet through localized velocity perturbations is explored analytically, numerically and experimentally. We show that Gaussian wave packets are appropriate for this goal. A temporal linear analysis predicts the early evolution of these wave packets and provides an estimate of the breakup length of the jet. Non-linear numerical simulations allow us both to corroborate these results and to obtain the shape of the surface of the jet prior to breakup. Finally, we show experimental evidence that stimulating with a Gaussian wave packet can lead to the formation of an isolated drop without disturbing the rest of the jet. The authors acknowledge support from the Spanish Government under Contract No. FIS2014-25161, the Junta de Andalucia under Contract No. P11-FQM-7919, the EPSRC-UK via the Grant EP/P024173/1, and the Royal Society.

The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

Directory of Open Access Journals (Sweden)

S.-D. Zhang

2000-10-01

Full Text Available By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

Parsimonious wave-equation travel-time inversion for refraction waves

KAUST Repository

Fu, Lei

2017-02-14

We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N geophones evenly deployed along the line. These two reciprocal shots contain approximately 2N refraction travel times, which can be spawned into O(N2) refraction travel times by an interferometric transformation. Then, these virtual refraction travel times are used with a source wavelet to create N virtual refraction shot gathers, which are the input data for wave-equation travel-time inversion. Numerical results show that the parsimonious wave-equation travel-time tomogram has about the same accuracy as the tomogram computed by standard wave-equation travel-time inversion. The most significant benefit is that a reciprocal survey is far less time consuming than the standard refraction survey where a source is excited at each geophone location.

On the definition of the momentum of an Alfven wave packet

International Nuclear Information System (INIS)

Khudik, V.N.

1993-01-01

The different definitions of the momentum of a wave disturbance are considered, corresponding to the invariance of the Lagrangian with respect to different kinds of translation in magnetohydrodynamics. It is shown that the value of the momentum of an Alfven wave packet calculated using the definition accepted in the electrodynamics of continuous media is not the same as the total momentum of the particles in the medium and the electromagnetic field in the region within which the packet is localized. 5 refs., 2 figs

State reconstruction of one-dimensional wave packets

Science.gov (United States)

Krähmer, D. S.; Leonhardt, U.

1997-12-01

We review and analyze the method [U. Leonhardt, M.G. Raymer: Phys. Rev. Lett. 76, 1985 (1996)] for quantum-state reconstruction of one-dimensional non-relativistic wave packets from position observations. We illuminate the theoretical background of the technique and show how to extend the procedure to the continuous part of the spectrum.

Structure of Langmuir and electromagnetic collapsing wave packets in two-dimensional strong plasma turbulence

International Nuclear Information System (INIS)

Alinejad, H.; Robinson, P. A.; Cairns, I. H.; Skjaeraasen, O.; Sobhanian, S.

2007-01-01

Nucleating and collapsing wave packets relevant to electromagnetic strong plasma turbulence are studied theoretically in two dimensions. Model collapsing Langmuir and transverse potentials are constructed as superpositions of approximate eigenstates of a spherically symmetric density well. Electrostatic and electromagnetic potentials containing only components with azimuthal quantum numbers m=0, 1, 2 are found to give a good representation of the electric fields of nucleating collapsing wave packets in turbulence simulations. The length scales of these trapped states are related to the electron thermal speed v e and the length scale of the density well. It is shown analytically that the electromagnetic trapped states change with v e and that for v e e > or approx. 0.17c, the Langmuir and transverse modes remain coupled during collapse, with autocorrelation lengths in a constant ratio. An investigation of energy transfer to packets localized in density wells shows that the strongest power transfer to the nucleating state occurs for Langmuir waves. Energy transitions between different trapped and free states for collapsing wave packets are studied, and the transition rate from trapped Langmuir to free plane electromagnetic waves is calculated and related to the emission of electromagnetic waves at the plasma frequency

Coherent structural trapping through wave packet dispersion during photoinduced spin state switching

DEFF Research Database (Denmark)

Lemke, Henrik T.; Kjær, Kasper Skov; Hartsock, Robert

2017-01-01

The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation...... is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing. Throughout the structural trapping, the dispersion of the wave packet along the reaction coordinate reveals details of intramolecular vibronic...

Dispersionless wave packets in Dirac materials

Czech Academy of Sciences Publication Activity Database

Jakubský, Vít; Tušek, M.

2017-01-01

Roč. 378, MAR (2017), s. 171-182 ISSN 0003-4916 R&D Projects: GA ČR(CZ) GJ15-07674Y; GA ČR GA17-01706S Institutional support: RVO:61389005 Keywords : quantum systems * wave packets * dispersion * dirac materials Subject RIV: BE - Theoretical Physics OBOR OECD: Atomic, molecular and chemical physics ( physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect) Impact factor: 2.465, year: 2016

Universal potential-barrier penetration by initially confined wave packets

International Nuclear Information System (INIS)

Granot, Er'el; Marchewka, Avi

2007-01-01

The dynamics of an initially sharp-boundary wave packet in the presence of an arbitrary potential barrier is investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wave function and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics is governed solely by the initial value of the wave function at the boundary

Universal potential-barrier penetration by initially confined wave packets

Science.gov (United States)

Granot, Er'El; Marchewka, Avi

2007-07-01

The dynamics of an initially sharp-boundary wave packet in the presence of an arbitrary potential barrier is investigated. It is shown that the penetration through the barrier is universal in the sense that it depends only on the values of the wave function and its derivatives at the boundary. The dependence on the derivatives vanishes at long distances from the barrier, where the dynamics is governed solely by the initial value of the wave function at the boundary.

Wave-packet treatment of reactor neutrino oscillation experiments and its implications on determining the neutrino mass hierarchy

Energy Technology Data Exchange (ETDEWEB)

Chan, Yat-Long; Chu, M.C.; Xu, Jianyi [The Chinese University of Hong Kong, Department of Physics, Shatin (China); Tsui, Ka Ming [University of Tokyo, RCCN, ICRR, Kashiwa, Chiba (Japan); Wong, Chan Fai [Sun Yat-Sen University, Guangzhou (China)

2016-06-15

We derive the neutrino flavor transition probabilities with the neutrino treated as a wave packet. The decoherence and dispersion effects from the wave-packet treatment show up as damping and phase-shifting of the plane-wave neutrino oscillation patterns. If the energy uncertainty in the initial neutrino wave packet is larger than around 0.01 of the neutrino energy, the decoherence and dispersion effects would degrade the sensitivity of reactor neutrino experiments to mass hierarchy measurement to lower than 3 σ confidence level. (orig.)

Quantum mechanical analysis of the equilateral triangle billiard: Periodic orbit theory and wave packet revivals

International Nuclear Information System (INIS)

Doncheski, M.A.; Robinett, R.W.

2002-01-01

Using the fact that the energy eigenstates of the equilateral triangle infinite well (or billiard) are available in closed form, we examine the connections between the energy eigenvalue spectrum and the classical closed paths in this geometry, using both periodic orbit theory and the short-term semi-classical behavior of wave packets. We also discuss wave packet revivals and show that there are exact revivals, for all wave packets, at times given by T rev =9μa 2 /4(h/2π) where a and μ are the length of one side and the mass of the point particle, respectively. We find additional cases of exact revivals with shorter revival times for zero-momentum wave packets initially located at special symmetry points inside the billiard. Finally, we discuss simple variations on the equilateral (60 deg. -60 deg. -60 deg. ) triangle, such as the half equilateral (30 deg. -60 deg. -90 deg.) triangle and other 'foldings', which have related energy spectra and revival structures

Collective neutrino oscillations and neutrino wave packets

Energy Technology Data Exchange (ETDEWEB)

Akhmedov, Evgeny; Lindner, Manfred [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Kopp, Joachim, E-mail: akhmedov@mpi-hd.mpg.de, E-mail: jkopp@uni-mainz.de, E-mail: lindner@mpi-hd.mpg.de [PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Johannes Gutenberg University, 55099 Mainz (Germany)

2017-09-01

Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation—one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.

Energy-flux characterization of conical and space-time coupled wave packets

International Nuclear Information System (INIS)

Lotti, A.; Couairon, A.; Faccio, D.; Trapani, P. Di

2010-01-01

We introduce the concept of energy density flux as a characterization tool for the propagation of ultrashort laser pulses with spatiotemporal coupling. In contrast with calculations for the Poynting vector, those for energy density flux are derived in the local frame moving at the velocity of the envelope of the wave packet under examination and do not need knowledge of the magnetic field. We show that the energy flux defined from a paraxial propagation equation follows specific geometrical connections with the phase front of the optical wave packet, which demonstrates that the knowledge of the phase fronts amounts to the measurement of the energy flux. We perform a detailed numerical study of the energy density flux in the particular case of conical waves, with special attention paid to stationary-envelope conical waves (X or O waves). A full characterization of linear conical waves is given in terms of their energy flux. We extend the definition of this concept to the case of nonlinear propagation in Kerr media with nonlinear losses.

Delocalization of charge and current in a chiral quasiparticle wave packet

Science.gov (United States)

Sarkar, Subhajit

2018-03-01

A chiral quasiparticle wave packet (c-QPWP) is defined as a conventional superposition of chiral quasiparticle states corresponding to an interacting electron system in two dimensions (2D) in the presence of Rashba spin-orbit coupling (RSOC). I investigate its internal structure via studying the charge and the current densities within the first-order perturbation in the electron-electron interaction. It is found that the c-QPWP contains a localized charge which is less than the magnitude of the bare charge and the remaining charge resides at the system boundary. The amount of charge delocalized turns out to be inversely proportional to the degenerate Fermi velocity v0(=√{α2+2 μ /m }) when RSOC (with strength α ) is weak, and therefore externally tunable. For strong RSOC, the magnitudes of both the delocalized charge and the current further strongly depend on the direction of propagation of the wave packet. Both the charge and the current densities consist of an anisotropic r-2 tail away from the center of the wave packet. Possible implications of such delocalizations in real systems corresponding to 2D semiconductor heterostructure are also discussed within the context of particle injection experiments.

The pump-probe coupling of matter wave packets to remote lattice states

DEFF Research Database (Denmark)

Sherson, Jacob F; Park, Sung Jong; Pedersen, Poul Lindholm

2012-01-01

containing a Bose–Einstein condensate. The evolution of these wave packets is monitored in situ and their six-photon reflection at a band gap is observed. In direct analogy with pump–probe spectroscopy, a probe pulse allows for the resonant de-excitation of the wave packet into states localized around...... selected lattice sites at a long, controllable distance of more than 100 lattice sites from the main component. This precise control mechanism for ultra-cold atoms thus enables controlled quantum state preparation and splitting for quantum dynamics, metrology and simulation....

Determination of the effective transverse coherence of the neutron wave packet as employed in reflectivity investigations of condensed-matter structures. II. Analysis of elastic scattering using energy-gated wave packets with an application to neutron reflection from ruled gratings

Science.gov (United States)

Berk, N. F.

2014-03-01

We present a general approach to analyzing elastic scattering for those situations where the incident beam is prepared as an incoherent ensemble of wave packets of a given arbitrary shape. Although wave packets, in general, are not stationary solutions of the Schrödinger equation, the analysis of elastic scattering data treats the scattering as a stationary-state problem. We thus must gate the wave packet, coherently distorting its shape in a manner consistent with the elastic condition. The resulting gated scattering amplitudes (e.g., reflection coefficients) thus are weighted coherent sums of the constituent plane-wave scattering amplitudes, with the weights determined by the shape of the incident wave packet as "filtered" by energy gating. We develop the gating formalism in general and apply it to the problem of neutron scattering from ruled gratings described by Majkrzak et al. in a companion paper. The required exact solution of the associated problem of plane-wave reflection from gratings also is derived.

Effects of delayed nonlinear response on wave packet dynamics in one-dimensional generalized Fibonacci chains

International Nuclear Information System (INIS)

Zhang, Jianxin; Zhang, Zhenjun; Tong, Peiqing

2013-01-01

We investigate the spreading of an initially localized wave packet in one-dimensional generalized Fibonacci (GF) lattices by solving numerically the discrete nonlinear Schrödinger equation (DNLSE) with a delayed cubic nonlinear term. It is found that for short delay time, the wave packet is self-trapping in first class of GF lattices, that is, the second moment grows with time, but the corresponding participation number does not grow. However, both the second moment and the participation number grow with time for large delay time. This illuminates that the wave packet is delocalized. For the second class of GF lattices, the dynamic behaviors of wave packet depend on the strength of on-site potential. For a weak on-site potential, the results are similar to the case of the first class. For a strong on-site potential, both the second moment and the participation number does not grow with time in the regime of short delay time. In the regime of large delay time, both the second moment and the participation number exhibit stair-like growth

Effects of delayed nonlinear response on wave packet dynamics in one-dimensional generalized Fibonacci chains

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jianxin; Zhang, Zhenjun [Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023 (China); Tong, Peiqing, E-mail: pqtong@njnu.edu.cn [Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023 (China); Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems, Nanjing Normal University, Nanjing 210023 (China)

2013-07-15

We investigate the spreading of an initially localized wave packet in one-dimensional generalized Fibonacci (GF) lattices by solving numerically the discrete nonlinear Schrödinger equation (DNLSE) with a delayed cubic nonlinear term. It is found that for short delay time, the wave packet is self-trapping in first class of GF lattices, that is, the second moment grows with time, but the corresponding participation number does not grow. However, both the second moment and the participation number grow with time for large delay time. This illuminates that the wave packet is delocalized. For the second class of GF lattices, the dynamic behaviors of wave packet depend on the strength of on-site potential. For a weak on-site potential, the results are similar to the case of the first class. For a strong on-site potential, both the second moment and the participation number does not grow with time in the regime of short delay time. In the regime of large delay time, both the second moment and the participation number exhibit stair-like growth.

Negative group delay for Dirac particles traveling through a potential well

International Nuclear Information System (INIS)

Chen Xi; Li Chunfang

2003-01-01

The properties of group delay for Dirac particles traveling through a potential well are investigated. A necessary condition is put forward for the group delay to be negative. It is shown that this negative group delay is closely related to its anomalous dependence on the width of the potential well. In order to demonstrate the validity of stationary-phase approach, numerical simulations are made for a Gaussian-shaped temporal wave packet. A restriction to the potential-well's width is obtained that is necessary for the wave packet to remain distortionless in the traveling. Numerical comparison shows that the relativistic group delay is larger than its corresponding nonrelativistic one

Extended wave-packet model to calculate energy-loss moments of protons in matter

Science.gov (United States)

Archubi, C. D.; Arista, N. R.

2017-12-01

In this work we introduce modifications to the wave-packet method proposed by Kaneko to calculate the energy-loss moments of a projectile traversing a target which is represented in terms of Gaussian functions for the momentum distributions of electrons in the atomic shells. These modifications are introduced using the Levine and Louie technique to take into account the energy gaps corresponding to the different atomic levels of the target. We use the extended wave-packet model to evaluate the stopping power, the energy straggling, the inverse mean free path, and the ionization cross sections for protons in several targets, obtaining good agreements for all these quantities on an extensive energy range that covers low-, intermediate-, and high-energy regions. The extended wave-packet model proposed here provides a method to calculate in a very straightforward way all the significant terms of the inelastic interaction of light ions with any element of the periodic table.

Traveling Wave Resonance and Simplified Analysis Method for Long-Span Symmetrical Cable-Stayed Bridges under Seismic Traveling Wave Excitation

Directory of Open Access Journals (Sweden)

Zhong-ye Tian

2014-01-01

Full Text Available The seismic responses of a long-span cable-stayed bridge under uniform excitation and traveling wave excitation in the longitudinal direction are, respectively, computed. The numerical results show that the bridge’s peak seismic responses vary significantly as the apparent wave velocity decreases. Therefore, the traveling wave effect must be considered in the seismic design of long-span bridges. The bridge’s peak seismic responses do not vary monotonously with the apparent wave velocity due to the traveling wave resonance. A new traveling wave excitation method that can simplify the multisupport excitation process into a two-support excitation process is developed.

Following dynamic nuclear wave packets in N2,O2, and CO with few-cycle infrared pulses

International Nuclear Information System (INIS)

De, S.; Magrakvelidze, M.; Bocharova, I. A.; Ray, D.; Cao, W.; Li, H.; Wang, Z.; Laurent, G.; Thumm, U.; Ben-Itzhak, I.; Cocke, C. L.; Znakovskaya, I.; Kling, M. F.; Litvinyuk, I. V.

2011-01-01

We study the evolution of nuclear wave packets launched in molecular nitrogen, oxygen, and carbon monoxide by intense 8-fs infrared pulses. We use velocity map imaging to measure the momentum of the ion fragments when these wave packets are interrogated by a second such pulse after a variable time delay. Both quasibound and dissociative wave packets are observed. For the former, measurements of bound-state oscillations are used to identify the participating states and, in some cases, extract properties of the relevant potential-energy surfaces. Vibrational structure is resolved in both energy and oscillation frequencies for the cations of oxygen and carbon monoxide, displaying the same quantum wave-packet motion in both energy and time domains. In addition, vibrational structure is seen in the dication of carbon monoxide in a situation where the energy resolution by itself is inadequate to resolve the structure.

Following dynamic nuclear wave packets in N2,O2, and CO with few-cycle infrared pulses

Science.gov (United States)

de, S.; Magrakvelidze, M.; Bocharova, I. A.; Ray, D.; Cao, W.; Znakovskaya, I.; Li, H.; Wang, Z.; Laurent, G.; Thumm, U.; Kling, M. F.; Litvinyuk, I. V.; Ben-Itzhak, I.; Cocke, C. L.

2011-10-01

We study the evolution of nuclear wave packets launched in molecular nitrogen, oxygen, and carbon monoxide by intense 8-fs infrared pulses. We use velocity map imaging to measure the momentum of the ion fragments when these wave packets are interrogated by a second such pulse after a variable time delay. Both quasibound and dissociative wave packets are observed. For the former, measurements of bound-state oscillations are used to identify the participating states and, in some cases, extract properties of the relevant potential-energy surfaces. Vibrational structure is resolved in both energy and oscillation frequencies for the cations of oxygen and carbon monoxide, displaying the same quantum wave-packet motion in both energy and time domains. In addition, vibrational structure is seen in the dication of carbon monoxide in a situation where the energy resolution by itself is inadequate to resolve the structure.

Steering dissociation of Br2 molecules with two femtosecond pulses via wave packet interference.

Science.gov (United States)

Han, Yong-Chang; Yuan, Kai-Jun; Hu, Wen-Hui; Yan, Tian-Min; Cong, Shu-Lin

2008-04-07

The dissociation dynamics of Br2 molecules induced by two femtosecond pump pulses are studied based on the calculation of time-dependent quantum wave packet. Perpendicular transition from X 1Sigma g+ to A 3Pi 1u+ and 1Pi 1u+ and parallel transition from X 1Sigma g+ to B 3Pi 0u+, involving two product channels Br (2P3/2)+Br (2P3/2) and Br (2P3/2)+Br* (2P1/2), respectively, are taken into account. Two pump pulses create dissociating wave packets interfering with each other. By varying laser parameters, the interference of dissociating wave packets can be controlled, and the dissociation probabilities of Br2 molecules on the three excited states can be changed to different degrees. The branching ratio of Br*/(Br+Br*) is calculated as a function of pulse delay time and phase difference.

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

Science.gov (United States)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

2018-01-01

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future.

Propagation of arbitrary initial wave packets in a quantum parametric oscillator: Instability zones for higher order moments

Science.gov (United States)

Biswas, Subhadip; Chattopadhyay, Rohitashwa; Bhattacharjee, Jayanta K.

2018-05-01

We consider the dynamics of a particle in a parametric oscillator with a view to exploring any quantum feature of the initial wave packet that shows divergent (in time) behaviour for parameter values where the classical motion dynamics of the mean position is bounded. We use Ehrenfest's theorem to explore the dynamics of nth order moment which reduces exactly to a linear non autonomous differential equation of order n + 1. It is found that while the width and skewness of the packet is unbounded exactly in the zones where the classical motion is unbounded, the kurtosis of an initially non-gaussian wave packet can become infinitely large in certain additional zones. This implies that the shape of the wave packet can change drastically with time in these zones.

Time-resolved X-ray scattering by electronic wave packets: analytic solutions to the hydrogen atom

DEFF Research Database (Denmark)

Simmermacher, Mats; Henriksen, Niels Engholm; Møller, Klaus Braagaard

2017-01-01

Modern pulsed X-ray sources permit time-dependent measurements of dynamical changes in atoms and molecules via non-resonant scattering. The planning, analysis, and interpretation of such experiments, however, require a firm and elaborated theoretical framework. This paper provides a detailed...... description of time-resolved X-ray scattering by non-stationary electronic wave packets in atomic systems. A consistent application of the Waller-Hartree approximation is discussed and different contributions to the total differential scattering signal are identified and interpreted. Moreover......, it is demonstrated how the scattering signal of wave packets in the hydrogen atom can be expressed analytically. This permits simulations without numerical integration and establishes a benchmark for both efficiency and accuracy. Based on that, scattering patterns of an exemplary wave packet in the hydrogen atom...

Kapitza–Dirac effect with traveling waves

International Nuclear Information System (INIS)

Hayrapetyan, Armen G; Götte, Jörg B; Grigoryan, Karen K; Petrosyan, Rubik G

2015-01-01

We report on the possibility of diffracting electrons from light waves traveling inside a dielectric medium. We show that, in the frame of reference which moves with the group velocity of light, the traveling wave acts as a stationary diffraction grating from which electrons can diffract, similar to the conventional Kapitza–Dirac effect. To characterize the Kapitza–Dirac effect with traveling light waves, we make use of the Hamiltonian Analogy between electron optics and quantum mechanics and apply the Helmholtz–Kirchhoff theory of diffraction. (fast track communication)

Generic short-time propagation of sharp-boundaries wave packets

Science.gov (United States)

Granot, E.; Marchewka, A.

2005-11-01

A general solution to the "shutter" problem is presented. The propagation of an arbitrary initially bounded wave function is investigated, and the general solution for any such function is formulated. It is shown that the exact solution can be written as an expression that depends only on the values of the function (and its derivatives) at the boundaries. In particular, it is shown that at short times (t << 2mx2/hbar, where x is the distance to the boundaries) the wave function propagation depends only on the wave function's values (or its derivatives) at the boundaries of the region. Finally, we generalize these findings to a non-singular wave function (i.e., for wave packets with finite-width boundaries) and suggest an experimental verification.

Nonlinear interactions of counter-travelling waves

International Nuclear Information System (INIS)

Matsuuchi, Kazuo

1980-01-01

Nonlinear interactions between two waves travelling in opposite directions are investigated. When a nonlinear Klein-Gordon equation is adopted as a model equation, it is shown that such a wave system is governed by a simple set of equations for their complex amplitudes. Steady progressive waves governed by this set are investigated for various cases classified according to the signs of the coefficients. It is then found that one wave travelling in one direction appears from a certain point and the other travelling in the opposite direction has a constant amplitude from that point. This phenomenon may be regarded as a sort of reflection in spite of no rigid boundary. (author)

Time-resolved dynamics of two-channel molecular systems in cw laser fields: Wave-packet construction in the Floquet formalism

International Nuclear Information System (INIS)

Nguyen-Dang, T.T.; Chateauneuf, F.; Atabek, O.; He, X.

1995-01-01

The description of the wave-packet time-resolved dynamics in a two-channel molecular system driven by a cw laser field is considered within the time-independent Floquet representation. It is shown that, at high field intensity, the wave-packet motions are governed solely by the pair of adiabatic dressed potential-energy surfaces (PES's) associated with a single Brillouin zone. The same expressions of the wave-packet motions in terms of the adiabatic PES's are obtained within a short-time approximation, thereby furnishing a new numerical algorithm for the wave-packet propagation in a laser-driven two-channel system at any intensity. Numerical tests of this algorithm are presented. The numerical results establish unambiguously the adiabaticity of nuclear motions at high field intensities

Study of the wave packet treatment of neutrino oscillation at Daya Bay

Science.gov (United States)

Daya Bay Collaboration

2017-09-01

The disappearance of reactor \\bar{ν }_e observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion σ _{rel}. Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of \\bar{ν }_e acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: 2.38 × 10^{-17}< σ _{rel} < 0.23. Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: 10^{-14} ≲ σ _ {rel} < 0.23, and an upper limit of σ _ {rel}<0.20 (which corresponds to σ _x ≳ 10^{-11} {cm }) is obtained. All limits correspond to a 95% C.L. Furthermore, the effect due to the wave packet nature of neutrino oscillation is found to be insignificant for reactor antineutrinos detected by the Daya Bay experiment thus ensuring an unbiased measurement of the oscillation parameters sin ^22θ _{13} and Δ m^2_{32} within the plane wave model.

Manipulating the Shape of Electronic Non-Dispersive Wave-Packets in the Hydrogen Atom: Numerical Tests in Realistic Experimental Conditions

International Nuclear Information System (INIS)

Delande, D.; Sacha, K.; Zakrzewski, J.

2002-01-01

We show that combination of a linearly polarized resonant microwave field and a parallel static electric field may be used to create a non-dispersive electronic wave packet in Rydberg atoms. The static electric field allows for manipulation of the shape of the elliptical trajectory the wave packet is propagating on. Exact quantum numerical calculations for realistic experimental parameters show that the wave packet evolving on a linear orbit can be very easily prepared in a laboratory either by a direct optical excitation or by preparing an atom in an extremal Stark state and then slowly switching on the micro wave field. The latter scheme seems to be very resistant to experimental imperfections. Once the wave packet on the linear orbit is excited, the static field may be used to manipulate the shape of the orbit. (author)

Parametric form of QCD travelling waves

OpenAIRE

Peschanski, R.

2005-01-01

We derive parametric travelling-wave solutions of non-linear QCD equations. They describe the evolution towards saturation in the geometric scaling region. The method, based on an expansion in the inverse of the wave velocity, leads to a solvable hierarchy of differential equations. A universal parametric form of travelling waves emerges from the first two orders of the expansion.

Wave packet dynamics and photofragmentation in time-dependent quadratic potentials

DEFF Research Database (Denmark)

Møller, Klaus Braagaard; Henriksen, Niels Engholm

1996-01-01

We study the dynamics of generalized harmonic oscillator states in time-dependent quadratic potentials and derive analytical expressions for the momentum space and the Wigner phase space representation of these wave packets. Using these results we consider a model for the rotational excitation...

Monte Carlo Wave Packet Theory of Dissociative Double Ionization

DEFF Research Database (Denmark)

Leth, Henriette Astrup; Madsen, Lars Bojer; Mølmer, Klaus

2009-01-01

Nuclear dynamics in strong-field double ionization processes is predicted using a stochastic Monte Carlo wave packet technique. Using input from electronic structure calculations and strong-field electron dynamics the description allows for field-dressed dynamics within a given molecule as well...

Nonlinear wave equation with intrinsic wave particle dualism

International Nuclear Information System (INIS)

Klein, J.J.

1976-01-01

A nonlinear wave equation derived from the sine-Gordon equation is shown to possess a variety of solutions, the most interesting of which is a solution that describes a wave packet travelling with velocity usub(e) modulating a carrier wave travelling with velocity usub(c). The envelop and carrier wave speeds agree precisely with the group and phase velocities found by de Broglie for matter waves. No spreading is exhibited by the soliton, so that it behaves exactly like a particle in classical mechanics. Moreover, the classically computed energy E of the disturbance turns out to be exactly equal to the frequency ω of the carrier wave, so that the Planck relation is automatically satisfied without postulating a particle-wave dualism. (author)

Quantum dynamics of solid Ne upon photo-excitation of a NO impurity: A Gaussian wave packet approach

International Nuclear Information System (INIS)

Unn-Toc, W.; Meier, C.; Halberstadt, N.; Uranga-Piña, Ll.; Rubayo-Soneira, J.

2012-01-01

A high-dimensional quantum wave packet approach based on Gaussian wave packets in Cartesian coordinates is presented. In this method, the high-dimensional wave packet is expressed as a product of time-dependent complex Gaussian functions, which describe the motion of individual atoms. It is applied to the ultrafast geometrical rearrangement dynamics of NO doped cryogenic Ne matrices after femtosecond laser pulse excitation. The static deformation of the solid due to the impurity as well as the dynamical response after femtosecond excitation are analyzed and compared to reduced dimensionality studies. The advantages and limitations of this method are analyzed in the perspective of future applications to other quantum solids.

Quantum dynamics of solid Ne upon photo-excitation of a NO impurity: A Gaussian wave packet approach

Energy Technology Data Exchange (ETDEWEB)

Unn-Toc, W.; Meier, C.; Halberstadt, N. [Laboratoire Collisions Agregats et Reactivite, IRSAMC, UMR CNRS 5589, Universite Paul Sabatier, 31062 Toulouse (France); Uranga-Pina, Ll. [Laboratoire Collisions Agregats et Reactivite, IRSAMC, UMR CNRS 5589, Universite Paul Sabatier, 31062 Toulouse (France); Facultad de Fisica, Universidad de la Habana, San Lazaro y L, Vedado, 10400 La Habana (Cuba); Rubayo-Soneira, J. [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), Ave. Salvador Allende y Luaces, Habana 10600, AP 6163 La Habana (Cuba)

2012-08-07

A high-dimensional quantum wave packet approach based on Gaussian wave packets in Cartesian coordinates is presented. In this method, the high-dimensional wave packet is expressed as a product of time-dependent complex Gaussian functions, which describe the motion of individual atoms. It is applied to the ultrafast geometrical rearrangement dynamics of NO doped cryogenic Ne matrices after femtosecond laser pulse excitation. The static deformation of the solid due to the impurity as well as the dynamical response after femtosecond excitation are analyzed and compared to reduced dimensionality studies. The advantages and limitations of this method are analyzed in the perspective of future applications to other quantum solids.

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

Energy Technology Data Exchange (ETDEWEB)

Buoninfante, Luca [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); University of Groningen, Van Swinderen Institute, Groningen (Netherlands); Lambiase, Gaetano [Universita di Salerno, Dipartimento di Fisica ' ' E.R. Caianiello' ' , Fisciano (Italy); INFN-Sezione di Napoli, Gruppo Collegato di Salerno, Fisciano (Italy); Mazumdar, Anupam [University of Groningen, Van Swinderen Institute, Groningen (Netherlands); University of Groningen, Kapteyn Astronomical Institute, Groningen (Netherlands)

2018-01-15

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1/r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future. (orig.)

Traveling-Wave Membrane Photomixers

Science.gov (United States)

Wyss, R. A.; Martin, S. C.; Nakamura, B. J.; Neto, A.; Pasqualini, D.; Siegel, P. H.; Kadow, C.; Gossard, A. C.

2001-01-01

Traveling-wave photomixers have superior performance when compared with lumped area photomixers in the 1 to 3 THz frequency range. Their large active area and distributed gain mechanism assure high thermal damage threshold and elimination of the capacitive frequency roll-off. However, the losses experienced by the radio frequency wave traveling along the coplanar strips waveguide (due to underlying semi-infinite GaAs substrate) were a serious drawback. In this paper we present device designs and an experimental setup that make possible the realization of photomixers on membranes which eliminate the losses.

Non-dispersive traveling waves in inclined shallow water channels

International Nuclear Information System (INIS)

Didenkulova, Ira; Pelinovsky, Efim

2009-01-01

Existence of traveling waves propagating without internal reflection in inclined water channels of arbitrary slope is demonstrated. It is shown that traveling non-monochromatic waves exist in both linear and nonlinear shallow water theories in the case of a uniformly inclined channel with a parabolic cross-section. The properties of these waves are studied. It is shown that linear traveling waves should have a sign-variable shape. The amplitude of linear traveling waves in a channel satisfies the same Green's law, which is usually derived from the energy flux conservation for smoothly inhomogeneous media. Amplitudes of nonlinear traveling waves deviate from the linear Green's law, and the behavior of positive and negative amplitudes are different. Negative amplitude grows faster than positive amplitude in shallow water. The phase of nonlinear waves (travel time) is described well by the linear WKB approach. It is shown that nonlinear traveling waves of any amplitude always break near the shoreline if the boundary condition of the full absorption is applied.

Travelling Wave Pulse Coupled Oscillator (TWPCO) Using a Self-Organizing Scheme for Energy-Efficient Wireless Sensor Networks.

Science.gov (United States)

Al-Mekhlafi, Zeyad Ghaleb; Hanapi, Zurina Mohd; Othman, Mohamed; Zukarnain, Zuriati Ahmad

2017-01-01

Recently, Pulse Coupled Oscillator (PCO)-based travelling waves have attracted substantial attention by researchers in wireless sensor network (WSN) synchronization. Because WSNs are generally artificial occurrences that mimic natural phenomena, the PCO utilizes firefly synchronization of attracting mating partners for modelling the WSN. However, given that sensor nodes are unable to receive messages while transmitting data packets (due to deafness), the PCO model may not be efficient for sensor network modelling. To overcome this limitation, this paper proposed a new scheme called the Travelling Wave Pulse Coupled Oscillator (TWPCO). For this, the study used a self-organizing scheme for energy-efficient WSNs that adopted travelling wave biologically inspired network systems based on phase locking of the PCO model to counteract deafness. From the simulation, it was found that the proposed TWPCO scheme attained a steady state after a number of cycles. It also showed superior performance compared to other mechanisms, with a reduction in the total energy consumption of 25%. The results showed that the performance improved by 13% in terms of data gathering. Based on the results, the proposed scheme avoids the deafness that occurs in the transmit state in WSNs and increases the data collection throughout the transmission states in WSNs.

Travelling Wave Pulse Coupled Oscillator (TWPCO) Using a Self-Organizing Scheme for Energy-Efficient Wireless Sensor Networks

Science.gov (United States)

Hanapi, Zurina Mohd; Othman, Mohamed; Zukarnain, Zuriati Ahmad

2017-01-01

Recently, Pulse Coupled Oscillator (PCO)-based travelling waves have attracted substantial attention by researchers in wireless sensor network (WSN) synchronization. Because WSNs are generally artificial occurrences that mimic natural phenomena, the PCO utilizes firefly synchronization of attracting mating partners for modelling the WSN. However, given that sensor nodes are unable to receive messages while transmitting data packets (due to deafness), the PCO model may not be efficient for sensor network modelling. To overcome this limitation, this paper proposed a new scheme called the Travelling Wave Pulse Coupled Oscillator (TWPCO). For this, the study used a self-organizing scheme for energy-efficient WSNs that adopted travelling wave biologically inspired network systems based on phase locking of the PCO model to counteract deafness. From the simulation, it was found that the proposed TWPCO scheme attained a steady state after a number of cycles. It also showed superior performance compared to other mechanisms, with a reduction in the total energy consumption of 25%. The results showed that the performance improved by 13% in terms of data gathering. Based on the results, the proposed scheme avoids the deafness that occurs in the transmit state in WSNs and increases the data collection throughout the transmission states in WSNs. PMID:28056020

Study of the wave packet treatment of neutrino oscillation at Daya Bay

Energy Technology Data Exchange (ETDEWEB)

An, F.P. [East China Univ. of Science and Technology, Shanghai (China). Inst. of Modern Physics; Balantekin, A.B. [Wisconsin Univ., Madison, WI (United States); Band, H.R. [Yale Univ., New Haven, CT (United States). Dept. of Physics; Collaboration: Daya Bay Collaboration; and others

2017-09-15

The disappearance of reactor anti ν{sub e} observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion σ{sub rel}. Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of anti ν{sub e} acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: 2.38 x 10{sup -17} < σ{sub rel} < 0.23. Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: 10{sup -14} or similar 10{sup -11} cm) is obtained. All limits correspond to a 95% C.L. Furthermore, the effect due to the wave packet nature of neutrino oscillation is found to be insignificant for reactor antineutrinos detected by the Daya Bay experiment thus ensuring an unbiased measurement of the oscillation parameters sin{sup 2}2θ{sub 13} and Δm{sup 2}{sub 32} within the plane wave model. (orig.)

Wave-packet revival for the Schroedinger equation with position-dependent mass

International Nuclear Information System (INIS)

Schmidt, Alexandre G.M.

2006-01-01

We study the temporal evolution of solutions of 1D Schroedinger equation with position-dependent mass inside an infinite well. Revival of wave-packet is shown to exist and partial revivals are different from the usual ones

Multiple pulse traveling wave excitation of neon-like germanium

International Nuclear Information System (INIS)

Moreno, J. C.; Nilsen, J.; Silva, L. B. da

1995-01-01

Traveling wave excitation has been shown to significantly increase the output intensity of the neon-like germanium x-ray laser. The driving laser pulse consisted of three 100 ps Gaussian laser pulses separated by 400 ps. Traveling wave excitation was employed by tilting the wave front of the driving laser by 45 degrees to match the propagation speed of the x-ray laser photons along the length of the target. We show results of experiments with the traveling wave, with no traveling wave, and against the traveling wave and comparisons to a numerical model. Gain was inferred from line intensity measurements at two lengths

Space-time evolution of Gaussian wave packets through superlattices containing left-handed layers

Energy Technology Data Exchange (ETDEWEB)

Pereyra, P; Romero-Serrano, M [Departamento de Ciencias Basicas, Universidad Autonoma Metropolitana-Azcapotzalco, Mexico DF (Mexico); Robledo-Martinez, A, E-mail: ppereyra@correo.azc.uam.m, E-mail: a.robledo@mailaps.or [Departamento de EnergIa, Universidad Autonoma Metropolitana-Azcapotzalco, Mexico DF (Mexico)

2009-05-01

We study the space-time evolution of Gaussian electromagnetic wave packets moving through (L/R){sup n} superlattices, containing alternating layers of left and right-handed materials. We show that the time spent by the wave packet moving through arbitrary (L/R){sup n} superlattices are well described by the phase time. We show that in the particular case where the thicknesses d{sub L,R} and indices n{sub l,r} of the layers satisfy the condition d{sub L}|n{sub L}| = d{sub R}n{sub R}, the usual band structure becomes a sequence of isolated and equidistant peaks with negative phase times.

Monte Carlo wave packet approach to dissociative multiple ionization in diatomic molecules

DEFF Research Database (Denmark)

Leth, Henriette Astrup; Madsen, Lars Bojer; Mølmer, Klaus

2010-01-01

A detailed description of the Monte Carlo wave packet technique applied to dissociative multiple ionization of diatomic molecules in short intense laser pulses is presented. The Monte Carlo wave packet technique relies on the Born-Oppenheimer separation of electronic and nuclear dynamics...... and provides a consistent theoretical framework for treating simultaneously both ionization and dissociation. By simulating the detection of continuum electrons and collapsing the system onto either the neutral, singly ionized or doubly ionized states in every time step the nuclear dynamics can be solved....... The computational effort is restricted and the model is applicable to any molecular system where electronic Born-Oppenheimer curves, dipole moment functions, and ionization rates as a function of nuclear coordinates can be determined....

Riemann zeta function from wave-packet dynamics

DEFF Research Database (Denmark)

Mack, R.; Dahl, Jens Peder; Moya-Cessa, H.

2010-01-01

We show that the time evolution of a thermal phase state of an anharmonic oscillator with logarithmic energy spectrum is intimately connected to the generalized Riemann zeta function zeta(s, a). Indeed, the autocorrelation function at a time t is determined by zeta (sigma + i tau, a), where sigma...... index of JWKB. We compare and contrast exact and approximate eigenvalues of purely logarithmic potentials. Moreover, we use a numerical method to find a potential which leads to exact logarithmic eigenvalues. We discuss possible realizations of Riemann zeta wave-packet dynamics using cold atoms...

Resonant tunneling of spin-wave packets via quantized states in potential wells.

Science.gov (United States)

Hansen, Ulf-Hendrik; Gatzen, Marius; Demidov, Vladislav E; Demokritov, Sergej O

2007-09-21

We have studied the tunneling of spin-wave pulses through a system of two closely situated potential barriers. The barriers represent two areas of inhomogeneity of the static magnetic field, where the existence of spin waves is forbidden. We show that for certain values of the spin-wave frequency corresponding to the quantized spin-wave states existing in the well formed between the barriers, the tunneling has a resonant character. As a result, transmission of spin-wave packets through the double-barrier structure is much more efficient than the sequent tunneling through two single barriers.

Global time asymmetry as a consequence of a wave packets theorem

International Nuclear Information System (INIS)

Castagnino, Mario A.; Gueron, Jorge; Ordonez, Adolfo R.

2002-01-01

When t→∞ any wave packet in the Liouvillian representation of the density matrices becomes a Hardy class function from below. This fact, in the global frame of the Reichenbach diagram, is used to explain the observed global time asymmetry of the universe

Nonlinear wave-packet dynamics for a generic one-dimensional time-independent system and its application to the hydrogen atom in a weak magnetic field

International Nuclear Information System (INIS)

Dupret, K.; Delande, D.

1996-01-01

We study the time propagation of an initially localized wave packet for a generic one-dimensional time-independent system, using the open-quote open-quote nonlinear wave-packet dynamics close-quote close-quote [S. Tomsovic and E. J. Heller, Phys. Rev. Lett. 67, 664 (1991)], a semiclassical approximation using a local linearization of the wave packet in the vicinity of classical reference trajectories. Several reference trajectories are needed to describe the behavior of the full wave packet. The introduction of action-angle variables allows us to obtain a simple analytic expression for the autocorrelation function, and to show that a universal behavior (quantum collapses, quantum revivals, etc.) is obtained via interferences between the reference trajectories. A connection with the standard WKB approach is established. Finally, we apply the nonlinear wave-packet dynamics to the case of the hydrogen atom in a weak magnetic field, and show that the semiclassical expressions obtained by nonlinear wave-packet dynamics are extremely accurate. copyright 1996 The American Physical Society

Optimal reflection-free complex absorbing potentials for quantum propagation of wave packets

International Nuclear Information System (INIS)

Shemer, Oded; Brisker, Daria; Moiseyev, Nimrod

2005-01-01

The conditions for optimal reflection-free complex-absorbing potentials (CAPs) are discussed. It is shown that the CAPs as derived from the smooth-exterior-scaling transformation of the Hamiltonian [J. Phys. B 31, 1431 (1998)] serve as optimal reflection-free CAPs (RF CAPs) in wave-packet propagation calculations of open systems. The initial wave packet, Φ(t=0), can be located in the interaction region (as in half collision experiments) where the CAPs have vanished or in the asymptote where V CAP ≠0. As we show, the optimal CAPs can be introduced also in the region where the physical potential has not vanished. The unavoided reflections due to the use of a finite number of grid points (or basis functions) are discussed. A simple way to reduce the 'edge-grid' reflection effect is described

New exact travelling wave solutions of nonlinear physical models

International Nuclear Information System (INIS)

Bekir, Ahmet; Cevikel, Adem C.

2009-01-01

In this work, we established abundant travelling wave solutions for some nonlinear evolution equations. This method was used to construct travelling wave solutions of nonlinear evolution equations. The travelling wave solutions are expressed by the hyperbolic functions, the trigonometric functions and the rational functions. The ((G ' )/G )-expansion method presents a wider applicability for handling nonlinear wave equations.

Traveling Theta Waves in the Human Hippocampus

Science.gov (United States)

Zhang, Honghui

2015-01-01

The hippocampal theta oscillation is strongly correlated with behaviors such as memory and spatial navigation, but we do not understand its specific functional role. One hint of theta's function came from the discovery in rodents that theta oscillations are traveling waves that allow parts of the hippocampus to simultaneously exhibit separate oscillatory phases. Because hippocampal theta oscillations in humans have different properties compared with rodents, we examined these signals directly using multielectrode recordings from neurosurgical patients. Our findings confirm that human hippocampal theta oscillations are traveling waves, but also show that these oscillations appear at a broader range of frequencies compared with rodents. Human traveling waves showed a distinctive pattern of spatial propagation such that there is a consistent phase spread across the hippocampus regardless of the oscillations' frequency. This suggests that traveling theta oscillations are important functionally in humans because they coordinate phase coding throughout the hippocampus in a consistent manner. SIGNIFICANCE STATEMENT We show for the first time in humans that hippocampal theta oscillations are traveling waves, moving along the length of the hippocampus in a posterior–anterior direction. The existence of these traveling theta waves is important for understanding hippocampal neural coding because they cause neurons at separate positions in the hippocampus to experience different theta phases simultaneously. The theta phase that a neuron measures is a key factor in how that cell represents behavioral information. Therefore, the existence of traveling theta waves indicates that, to fully understand how a hippocampal neuron represents information, it is vital to also account for that cell's location in addition to conventional measures of neural activity. PMID:26354915

Quantum Mechanics in the Gaussian wave-packet phase space representation: Dynamics

International Nuclear Information System (INIS)

Mizrahi, S.S.

1985-01-01

The Heisenberg and Liouville dynamical equations are mapped using the Wave-Packet Phase Space Representation. A semiclassical perturbative expansion is introduced - the Quasi-Causal Approximation - for the Green function and an expression for transition probabilities is derived up to the first order. (Author) [pt

Production and manipulation of wave packets from ultracold atoms in an optical lattice

DEFF Research Database (Denmark)

Pedersen, Poul Lindholm; Gajdacz, Miroslav; Winter, Nils

2013-01-01

of the system. The modulation technique also allows for a controllable transfer (deexcitation) of atoms from such wave packets to a state bound by the lattice. Thus, it acts as a beam splitter for matter waves that can selectively address different bands, enabling the preparation of atoms in localized states...

Effects of packet retransmission with finite packet lifetime on traffic capacity in scale-free networks

Science.gov (United States)

Jiang, Zhong-Yuan; Ma, Jian-Feng

Existing routing strategies such as the global dynamic routing [X. Ling, M. B. Hu, R. Jiang and Q. S. Wu, Phys. Rev. E 81, 016113 (2010)] can achieve very high traffic capacity at the cost of extremely long packet traveling delay. In many real complex networks, especially for real-time applications such as the instant communication software, extremely long packet traveling time is unacceptable. In this work, we propose to assign a finite Time-to-Live (TTL) parameter for each packet. To guarantee every packet to arrive at its destination within its TTL, we assume that a packet is retransmitted by its source once its TTL expires. We employ source routing mechanisms in the traffic model to avoid the routing-flaps induced by the global dynamic routing. We compose extensive simulations to verify our proposed mechanisms. With small TTL, the effects of packet retransmission on network traffic capacity are obvious, and the phase transition from flow free state to congested state occurs. For the purpose of reducing the computation frequency of the routing table, we employ a computing cycle Tc within which the routing table is recomputed once. The simulation results show that the traffic capacity decreases with increasing Tc. Our work provides a good insight into the understanding of effects of packet retransmission with finite packet lifetime on traffic capacity in scale-free networks.

Travelling wave solutions of generalized coupled Zakharov–Kuznetsov and dispersive long wave equations

Directory of Open Access Journals (Sweden)

M. Arshad

Full Text Available In this manuscript, we constructed different form of new exact solutions of generalized coupled Zakharov–Kuznetsov and dispersive long wave equations by utilizing the modified extended direct algebraic method. New exact traveling wave solutions for both equations are obtained in the form of soliton, periodic, bright, and dark solitary wave solutions. There are many applications of the present traveling wave solutions in physics and furthermore, a wide class of coupled nonlinear evolution equations can be solved by this method. Keywords: Traveling wave solutions, Elliptic solutions, Generalized coupled Zakharov–Kuznetsov equation, Dispersive long wave equation, Modified extended direct algebraic method

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules

Science.gov (United States)

Huang, Jiayu; Liu, Shu; Zhang, Dong H.; Krems, Roman V.

2018-04-01

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Travelling wave solutions in delayed cooperative systems

International Nuclear Information System (INIS)

Li, Bingtuan; Zhang, Liang

2011-01-01

We establish the existence of travelling wave solutions for delayed cooperative recursions that are allowed to have more than two equilibria. We define an important extended real number that is used to determine the speeds of travelling wave solutions. The results can be applied to a large class of delayed cooperative reaction–diffusion models. We show that for a delayed Lotka–Volterra reaction–diffusion competition model, there exists a finite positive number c * + that can be characterized as the slowest speed of travelling wave solutions connecting two mono-culture equilibria or connecting a mono-culture with the coexistence equilibrium

Mean flow generated by an internal wave packet impinging on the interface between two layers of fluid with continuous density

Energy Technology Data Exchange (ETDEWEB)

McHugh, John P. [The University of New Hampshire, Department of Mechanical Engineering, Kingsbury Hall, Durham, NH (United States)

2008-04-15

Internal waves propagating in an idealized two-layer atmosphere are studied numerically. The governing equations are the inviscid anelastic equations for a perfect gas atmosphere. The numerical formulation eliminates all variables in the linear terms except vertical velocity, which are then treated implicitly. Nonlinear terms are treated explicitly. The basic state is a two-layer flow with continuous density at the interface. Each layer has a unique constant for the Brunt-Vaeisaelae frequency. Waves are forced at the bottom of the domain, are periodic in the horizontal direction, and form a finite wave packet in the vertical. The results show that the wave packet forms a mean flow that is confined to the interface region that persists long after the wave packet has moved away. Large-amplitude waves are forced to break beneath the interface. (orig.)

Wave-packet continuum-discretization approach to ion-atom collisions including rearrangement: Application to differential ionization in proton-hydrogen scattering

Science.gov (United States)

Abdurakhmanov, I. B.; Bailey, J. J.; Kadyrov, A. S.; Bray, I.

2018-03-01

In this work, we develop a wave-packet continuum-discretization approach to ion-atom collisions that includes rearrangement processes. The total scattering wave function is expanded using a two-center basis built from wave-packet pseudostates. The exact three-body Schrödinger equation is converted into coupled-channel differential equations for time-dependent expansion coefficients. In the asymptotic region these time-dependent coefficients represent transition amplitudes for all processes including elastic scattering, excitation, ionization, and electron capture. The wave-packet continuum-discretization approach is ideal for differential ionization studies as it allows one to generate pseudostates with arbitrary energies and distribution. The approach is used to calculate the double differential cross section for ionization in proton collisions with atomic hydrogen. Overall good agreement with experiment is obtained for all considered cases.

Tracking nuclear wave-packet dynamics in molecular oxygen ions with few-cycle infrared laser pulses

International Nuclear Information System (INIS)

De, S.; Bocharova, I. A.; Magrakvelidze, M.; Ray, D.; Cao, W.; Thumm, U.; Cocke, C. L.; Bergues, B.; Kling, M. F.; Litvinyuk, I. V.

2010-01-01

We have tracked nuclear wave-packet dynamics in doubly charged states of molecular oxygen using few-cycle infrared laser pulses. Bound and dissociating wave packets were launched and subsequently probed via a pair of 8-fs pulses of 790 nm radiation. Ionic fragments from the dissociating molecules were monitored by velocity-map imaging. Pronounced oscillations in the delay-dependent kinetic energy release spectra were observed. The occurrence of vibrational revivals permits us to identify the potential curves of the O 2 dication which are most relevant to the molecular dynamics. These studies show the accessibility to the dynamics of such higher-charged molecules.

Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.

Science.gov (United States)

Krafft, C; Volokitin, A

2013-05-01

Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed.

Travelling Waves in Hybrid Chemotaxis Models

KAUST Repository

Franz, Benjamin

2013-12-18

Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant), which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybrid models shows good agreement in the case of weak chemotaxis and qualitative agreement for the strong chemotaxis case. In the case of slow cell adaptation, we detect oscillating behaviour of the wave, which cannot be explained by mean-field approximations. © 2013 Society for Mathematical Biology.

Quantum wave packet dynamics with trajectories: Implementation with distributed approximating functionals

International Nuclear Information System (INIS)

Wyatt, Robert E.; Kouri, Donald J.; Hoffman, David K.

2000-01-01

The quantum trajectory method (QTM) was recently developed to solve the hydrodynamic equations of motion in the Lagrangian, moving-with-the-fluid, picture. In this approach, trajectories are integrated for N fluid elements (particles) moving under the influence of both the force from the potential surface and from the quantum potential. In this study, distributed approximating functionals (DAFs) are used on a uniform grid to compute the necessary derivatives in the equations of motion. Transformations between the physical grid where the particle coordinates are defined and the uniform grid are handled through a Jacobian, which is also computed using DAFs. A difficult problem associated with computing derivatives on finite grids is the edge problem. This is handled effectively by using DAFs within a least squares approach to extrapolate from the known function region into the neighboring regions. The QTM-DAF is then applied to wave packet transmission through a one-dimensional Eckart potential. Emphasis is placed upon computation of the transmitted density and wave function. A problem that develops when part of the wave packet reflects back into the reactant region is avoided in this study by introducing a potential ramp to sweep the reflected particles away from the barrier region. (c) 2000 American Institute of Physics

Strong quantum violation of the gravitational weak equivalence principle by a non-Gaussian wave packet

International Nuclear Information System (INIS)

Chowdhury, P; Majumdar, A S; Sinha, S; Home, D; Mousavi, S V; Mozaffari, M R

2012-01-01

The weak equivalence principle of gravity is examined at the quantum level in two ways. First, the position detection probabilities of particles described by a non-Gaussian wave packet projected upwards against gravity around the classical turning point and also around the point of initial projection are calculated. These probabilities exhibit mass dependence at both these points, thereby reflecting the quantum violation of the weak equivalence principle. Second, the mean arrival time of freely falling particles is calculated using the quantum probability current, which also turns out to be mass dependent. Such a mass dependence is shown to be enhanced by increasing the non-Gaussianity parameter of the wave packet, thus signifying a stronger violation of the weak equivalence principle through a greater departure from Gaussianity of the initial wave packet. The mass dependence of both the position detection probabilities and the mean arrival time vanishes in the limit of large mass. Thus, compatibility between the weak equivalence principle and quantum mechanics is recovered in the macroscopic limit of the latter. A selection of Bohm trajectories is exhibited to illustrate these features in the free fall case. (paper)

Self-action of Bessel wave packets in a system of coupled light guides and formation of light bullets

Energy Technology Data Exchange (ETDEWEB)

Balakin, A. A., E-mail: balakin.alexey@yandex.ru; Mironov, V. A.; Skobelev, S. A., E-mail: sk.sa1981@gmail.com [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

2017-01-15

The self-action of two-dimensional and three-dimensional Bessel wave packets in a system of coupled light guides is considered using the discrete nonlinear Schrödinger equation. The features of the self-action of such wave fields are related to their initial strong spatial inhomogeneity. The numerical simulation shows that for the field amplitude exceeding a critical value, the development of an instability typical of a medium with the cubic nonlinearity is observed. Various regimes are studied: the self-channeling of a wave beam in one light guide at powers not strongly exceeding a critical value, the formation of the “kaleidoscopic” picture of a wave packet during the propagation of higher-power radiation along a stratified medium, the formation of light bullets during competition between self-focusing and modulation instabilities in the case of three-dimensional wave packets, etc. In the problem of laser pulse shortening, the situation is considered when the wave-field stratification in the transverse direction dominates. This process is accompanied by the self-compression of laser pulses in well enough separated light guides. The efficiency of conversion of the initial Bessel field distribution to two flying parallel light bullets is about 50%.

Frame properties of wave packet systes in L^2 (R^d)

DEFF Research Database (Denmark)

Christensen, Ole; Rahimi, Asghar

2008-01-01

Extending work by Hernandez, Labate and Weiss, we present a sufficent condition for a generalized shift-invariant system to be a Bessel sequence or even a frame forL(2)(R-d). In particular, this leads to a sufficient condition for a wave packet system to form a frame. On the other hand, we show...

New travelling wave solutions for nonlinear stochastic evolution ...

Indian Academy of Sciences (India)

expansion method to look for travelling wave solutions of nonlinear partial differential equations. It is interesting to mention that, in this method the sign of the parameters can be used to judge the numbers and types of travelling wave solutions.

Construction of localized atomic wave packets

International Nuclear Information System (INIS)

Ranjani, S Sree; Kapoor, A K; Panigrahi, P K

2010-01-01

It is shown that highly localized solitons can be created in lower dimensional Bose-Einstein condensates (BECs), trapped in a regular harmonic trap, by temporally varying the trap frequency. A BEC confined in such a trap can be effectively used to construct a pulsed atomic laser emitting coherent atomic wave packets. In addition to having a complete control over the spatio-temporal dynamics of the solitons, we can separate the equation governing the Kohn mode (centre of mass motion). We investigate the effect of the temporal modulation of the trap frequency on the spatio-temporal dynamics of the bright solitons and also on the Kohn mode. The dynamics of the solitons and the variations in the Kohn mode with time are compared with those in a BEC confined in a trap with unmodulated trap frequency.

Parsimonious wave-equation travel-time inversion for refraction waves

KAUST Repository

Fu, Lei; Hanafy, Sherif M.; Schuster, Gerard T.

2017-01-01

We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N

Study of diffusion of wave packets in a square lattice under external fields along the discrete nonlinear Schrödinger equation

International Nuclear Information System (INIS)

Brito, P.E. de; Nazareno, H.N.

2012-01-01

The object of the present work is to analyze the effect of nonlinearity on wave packet propagation in a square lattice subject to a magnetic and an electric field in the Hall configuration, by using the Discrete Nonlinear Schrödinger Equation (DNLSE). In previous works we have shown that without the nonlinear term, the presence of the magnetic field induces the formation of vortices that remain stationary, while a wave packet is introduced in the system. As for the effect of an applied electric field, it was shown that the vortices propagate in a direction perpendicular to the electric field, similar behavior as presented in the classical treatment, we provide a quantum mechanics explanation for that. We have performed the calculations considering first the action of the magnetic field as well as the nonlinearity. The results indicate that for low values of the nonlinear parameter U the vortices remain stationary while preserving the form. For greater values of the parameter the picture gets distorted, the more so, the greater the nonlinearity. As for the inclusion of the electric field, we note that for small U, the wave packet propagates perpendicular to the applied field, until for greater values of U the wave gets partially localized in a definite region of the lattice. That is, for strong nonlinearity the wave packet gets partially trapped, while the tail of it can propagate through the lattice. Note that this tail propagation is responsible for the over-diffusion for long times of the wave packet under the action of an electric field. We have produced short films that show clearly the time evolution of the wave packet, which can add to the understanding of the dynamics.

Persistence of travelling waves in a generalized Fisher equation

International Nuclear Information System (INIS)

Kyrychko, Yuliya N.; Blyuss, Konstantin B.

2009-01-01

Travelling waves of the Fisher equation with arbitrary power of nonlinearity are studied in the presence of long-range diffusion. Using analogy between travelling waves and heteroclinic solutions of corresponding ODEs, we employ the geometric singular perturbation theory to prove the persistence of these waves when the influence of long-range effects is small. When the long-range diffusion coefficient becomes larger, the behaviour of travelling waves can only be studied numerically. In this case we find that starting with some values, solutions of the model lose monotonicity and become oscillatory

Periodic travelling and non-travelling wave solutions of the nonlinear Klein-Gordon equation with imaginary mass

International Nuclear Information System (INIS)

Tang Xiaoyan; Shukla, Padma Kant

2008-01-01

Exact solutions, including the periodic travelling and non-travelling wave solutions, are presented for the nonlinear Klein-Gordon equation with imaginary mass. Some arbitrary functions are permitted in the periodic non-travelling wave solutions, which contribute to various high dimensional nonlinear structures

Review of inelastic losses of UCN and quantum mechanics of the de Broglie wave packet

International Nuclear Information System (INIS)

Ignatovich, V.K.; Utsuro, M.

1998-01-01

Different inelastic processes of ultracold neutrons (UCN) losses in traps are considered. A hypothesis of the de Broglie singular wave-packet description of the neutron wave-function to explain anomalous losses of UCN is proposed. An experiment to check the hypothesis and its results are discussed

Steering wave packet dynamics and population transfer between electronic states of the Na2 molecule by femtosecond laser pulses

International Nuclear Information System (INIS)

Yuan Kaijun; Sun Zhigang; Cong Shulin; Wang Senming; Yu Jie; Lou Nanquan

2005-01-01

An approach used for steering the wave packet dynamics and the population transfer between electronic states of the Na 2 molecule by a pair of femtosecond laser pulses is demonstrated. Four controlling schemes, i.e., four different combinations of time delays (intuitive and counterintuitive sequences) and frequency detunings (positive and negative detunings), are discussed in detail. The light-induced potentials are used to describe the wave packet dynamics and population transfer. The numerical results show that the wave packet excited by femtosecond laser pulses oscillates drastically on 2 1 Π g state with time. The efficiency of controlling population transfer from the X 1 Σ g + to2 1 Π g states of Na 2 is nearly 100% for the schemes of the counterintuitive sequence pulses with positive and negative detunings

Traveling waves in a free-electron laser with an electromagnetic wiggler

International Nuclear Information System (INIS)

Olumi, Mohsen; Maraghechi, B; Rouhani, M H

2011-01-01

The propagation of electromagnetic traveling wave in a free-electron laser (FEL) with an electromagnetic wiggler is investigated using the relativistic fluid-Maxwell formulation. By adapting the traveling-wave ansatz, three coupled, nonlinear ordinary differential equations are obtained describing the nonlinear propagation of the coupled wave. These equations may be used to study saturation in FELs. By linearizing the nonlinear equations dispersion relations for the traveling wave are obtained. Numerical solution of the small-signal traveling dispersion relation reveals the coupling of radiation to both slow and fast space-charge waves. It is shown that the traveling wave, which is not a normal mode in a laboratory frame, becomes a normal mode in terms of a transformed variable.

Theoretical prediction of a rotating magnon wave packet in ferromagnets.

Science.gov (United States)

Matsumoto, Ryo; Murakami, Shuichi

2011-05-13

We theoretically show that the magnon wave packet has a rotational motion in two ways: a self-rotation and a motion along the boundary of the sample (edge current). They are similar to the cyclotron motion of electrons, but unlike electrons the magnons have no charge and the rotation is not due to the Lorentz force. These rotational motions are caused by the Berry phase in momentum space from the magnon band structure. Furthermore, the rotational motion of the magnon gives an additional correction term to the magnon Hall effect. We also discuss the Berry curvature effect in the classical limit of long-wavelength magnetostatic spin waves having macroscopic coherence length.

Tunnel ionization of H2 in a low-frequency laser field: A wave-packet approach

International Nuclear Information System (INIS)

Nguyen-Dang, T.; Chateauneuf, F.; Manoli, S.; Atabek, O.; Keller, A.

1997-01-01

The dynamics of multielectron dissociative ionization (MEDI) of H 2 in an intense IR laser pulse are investigated using a wave-packet propagation scheme. The electron tunneling processes corresponding to the successive ionizations of H 2 are expressed in terms of field-free Born-Oppenheimer (BO) potential energy surfaces (PES) by transforming the tunnel shape resonance picture into a Feshbach resonance problem. This transformation is achieved by defining a new, time-dependent electronic basis in which the bound electrons are still described by field-free BO electronic states while the ionized ones are described by Airy functions. In the adiabatic, quasistatic approximation, these functions describe free electrons under the influence of the instantaneous electric field of the laser and such an ionized electron can have a negative total energy. As a consequence, when dressed by the continuous ejected electron energy, the BO PES of an ionic channel can be brought into resonance with states of the parent species. This construction gives a picture in which wave packets are to be propagated on a continuum of coupled electronic manifolds. A reduction of the wave-packet propagation scheme to an effective five-channel problem has been obtained for the description of the first dissociative ionization process in H 2 by using Fano's formalism [U. Fano, Phys. Rev. 124, 1866 (1961)] to analytically diagonalize the infinite, continuous interaction potential matrix and by using the properties of Fano's solutions. With this algorithm, the effect that continuous ionization of H 2 has on the dissociation dynamics of the H 2 + ion has been investigated. In comparison with results that would be obtained if the first ionization of H 2 was impulsive, the wave-packet dynamics of the H 2 + ion prepared continuously by tunnel ionization are markedly nonadiabatic. (Abstract Truncated)

QCD traveling waves beyond leading logarithms

International Nuclear Information System (INIS)

Peschanski, R.; Sapeta, S.

2006-01-01

We derive the asymptotic traveling-wave solutions of the nonlinear 1-dimensional Balitsky-Kovchegov QCD equation for rapidity evolution in momentum space, with 1-loop running coupling constant and equipped with the Balitsky-Kovchegov-Kuraev-Lipatov kernel at next-to-leading logarithmic accuracy, conveniently regularized by different resummation schemes. Traveling waves allow us to define ''universality classes'' of asymptotic solutions, i.e. independent of initial conditions and of the nonlinear damping. A dependence on the resummation scheme remains, which is analyzed in terms of geometric scaling properties

Traveling-wave synchronous coil gun

International Nuclear Information System (INIS)

Elliott, D.G.

1991-01-01

This paper reports on a traveling-wave synchronous coil gun which permits independent adjustment of the magnetic field and armature current for high velocity at low armature mass fraction. Magnetic field energy is transferred from the rear of the wave to the front without passing through the power supply. Elaborate switching is required

Spectro-spatial analysis of wave packet propagation in nonlinear acoustic metamaterials

Science.gov (United States)

Zhou, W. J.; Li, X. P.; Wang, Y. S.; Chen, W. Q.; Huang, G. L.

2018-01-01

The objective of this work is to analyze wave packet propagation in weakly nonlinear acoustic metamaterials and reveal the interior nonlinear wave mechanism through spectro-spatial analysis. The spectro-spatial analysis is based on full-scale transient analysis of the finite system, by which dispersion curves are generated from the transmitted waves and also verified by the perturbation method (the L-P method). We found that the spectro-spatial analysis can provide detailed information about the solitary wave in short-wavelength region which cannot be captured by the L-P method. It is also found that the optical wave modes in the nonlinear metamaterial are sensitive to the parameters of the nonlinear constitutive relation. Specifically, a significant frequency shift phenomenon is found in the middle-wavelength region of the optical wave branch, which makes this frequency region behave like a band gap for transient waves. This special frequency shift is then used to design a direction-biased waveguide device, and its efficiency is shown by numerical simulations.

Quantum spreading of a self-gravitating wave-packet in singularity free gravity

NARCIS (Netherlands)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein’s general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential – such

Revisiting the difference between traveling-wave and standing-wave thermoacoustic engines - A simple analytical model for the standing-wave one

Science.gov (United States)

Yasui, Kyuichi; Kozuka, Teruyuki; Yasuoka, Masaki; Kato, Kazumi

2015-11-01

There are two major categories in a thermoacoustic prime-mover. One is the traveling-wave type and the other is the standing-wave type. A simple analytical model of a standing-wave thermoacoustic prime-mover is proposed at relatively low heat-flux for a stack much shorter than the acoustic wavelength, which approximately describes the Brayton cycle. Numerical simulations of Rott's equations have revealed that the work flow (acoustic power) increases by increasing of the amplitude of the particle velocity (| U|) for the traveling-wave type and by increasing cosΦ for the standing-wave type, where Φ is the phase difference between the particle velocity and the acoustic pressure. In other words, the standing-wave type is a phase-dominant type while the traveling-wave type is an amplitude-dominant one. The ratio of the absolute value of the traveling-wave component (| U|cosΦ) to that of the standing-wave component (| U|sinΦ) of any thermoacoustic engine roughly equals the ratio of the absolute value of the increasing rate of | U| to that of cosΦ. The different mechanism between the traveling-wave and the standing-wave type is discussed regarding the dependence of the energy efficiency on the acoustic impedance of a stack as well as that on ωτα, where ω is the angular frequency of an acoustic wave and τα is the thermal relaxation time. While the energy efficiency of the traveling-wave type at the optimal ωτα is much higher than that of the standing-wave type, the energy efficiency of the standing-wave type is higher than that of the traveling-wave type at much higher ωτα under a fixed temperature difference between the cold and the hot ends of the stack.

Mechanism of travelling-wave transport of particles

International Nuclear Information System (INIS)

Kawamoto, Hiroyuki; Seki, Kyogo; Kuromiya, Naoyuki

2006-01-01

Numerical and experimental investigations have been carried out on transport of particles in an electrostatic travelling field. A three-dimensional hard-sphere model of the distinct element method was developed to simulate the dynamics of particles. Forces applied to particles in the model were the Coulomb force, the dielectrophoresis force on polarized dipole particles in a non-uniform field, the image force, gravity and the air drag. Friction and repulsion between particle-particle and particle-conveyer were included in the model to replace initial conditions after mechanical contacts. Two kinds of experiments were performed to confirm the model. One was the measurement of charge of particles that is indispensable to determine the Coulomb force. Charge distribution was measured from the locus of free-fallen particles in a parallel electrostatic field. The averaged charge of the bulk particle was confirmed by measurement with a Faraday cage. The other experiment was measurements of the differential dynamics of particles on a conveyer consisting of parallel electrodes to which a four-phase travelling electrostatic wave was applied. Calculated results agreed with measurements, and the following characteristics were clarified. (1) The Coulomb force is the predominant force to drive particles compared with the other kinds of forces, (2) the direction of particle transport did not always coincide with that of the travelling wave but changed partially. It depended on the frequency of the travelling wave, the particle diameter and the electric field, (3) although some particles overtook the travelling wave at a very low frequency, the motion of particles was almost synchronized with the wave at the low frequency and (4) the transport of some particles was delayed to the wave at medium frequency; the majority of particles were transported backwards at high frequency and particles were not transported but only vibrated at very high frequency

Bifurcations and new exact travelling wave solutions for the ...

Indian Academy of Sciences (India)

2016-10-17

Oct 17, 2016 ... Abstract. By using the method of dynamical system, the bidirectional wave equations are considered. Based on this method, all kinds of phase portraits of the reduced travelling wave system in the parametric space are given. All possible bounded travelling wave solutions such as dark soliton solutions, ...

Bifurcations and new exact travelling wave solutions for the ...

Indian Academy of Sciences (India)

By using the method of dynamical system, the bidirectional wave equations are considered. Based on this method, all kinds of phase portraits of the reduced travelling wave system in the parametric space are given. All possible bounded travelling wave solutions such as dark soliton solutions, bright soliton solutions and ...

Stability of post-fertilization traveling waves

Science.gov (United States)

Flores, Gilberto; Plaza, Ramón G.

This paper studies the stability of a family of traveling wave solutions to the system proposed by Lane et al. [D.C. Lane, J.D. Murray, V.S. Manoranjan, Analysis of wave phenomena in a morphogenetic mechanochemical model and an application to post-fertilization waves on eggs, IMA J. Math. Appl. Med. Biol. 4 (4) (1987) 309-331], to model a pair of mechanochemical phenomena known as post-fertilization waves on eggs. The waves consist of an elastic deformation pulse on the egg's surface, and a free calcium concentration front. The family is indexed by a coupling parameter measuring contraction stress effects on the calcium concentration. This work establishes the spectral, linear and nonlinear orbital stability of these post-fertilization waves for small values of the coupling parameter. The usual methods for the spectral and evolution equations cannot be applied because of the presence of mixed partial derivatives in the elastic equation. Nonetheless, exponential decay of the directly constructed semigroup on the complement of the zero eigenspace is established. We show that small perturbations of the waves yield solutions to the nonlinear equations decaying exponentially to a phase-modulated traveling wave.

Relative merits of travelling-wave and resonant operation of linac

International Nuclear Information System (INIS)

Shoffstall, D.R.; Gallagher, W.J.

1985-01-01

Discussion of the relative merits of so-called standing wave vis-a-vis travelling wave operation of linear accelerator waveguides is complicated by various considerations. In the first instance, standing wave should be distinguished from resonant operation. Standing wave operation is exactly the same as travelling wave, excepting that the waveguide is terminated by a total reflection of power instead of a matched load. In resonant operation a length of slow wave structure is terminated, theoretically at reflection planes of symmetry; the discrete modes of resonance consist of two oppositely directed travelling wave ensembles, one of which will provide a space harmonic of an intended phase velocity

Exact traveling wave solutions of the Boussinesq equation

International Nuclear Information System (INIS)

Ding Shuangshuang; Zhao Xiqiang

2006-01-01

The repeated homogeneous balance method is used to construct exact traveling wave solutions of the Boussinesq equation, in which the homogeneous balance method is applied to solve the Riccati equation and the reduced nonlinear ordinary differential equation, respectively. Many new exact traveling wave solutions of the Boussinesq equation are successfully obtained

Theoretical study of the influence of intense femtosecond laser field on the evolution of the wave packet and the population of NaRb molecule

International Nuclear Information System (INIS)

Ning, Ma; Mei-Shan, Wang; Chuan-Lu, Yang; Xiao-Guang, Ma; De-Hua, Wang

2010-01-01

Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6 1 σ + state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes. (atomic and molecular physics)

Bifurcations of traveling wave solutions for an integrable equation

International Nuclear Information System (INIS)

Li Jibin; Qiao Zhijun

2010-01-01

This paper deals with the following equation m t =(1/2)(1/m k ) xxx -(1/2)(1/m k ) x , which is proposed by Z. J. Qiao [J. Math. Phys. 48, 082701 (2007)] and Qiao and Liu [Chaos, Solitons Fractals 41, 587 (2009)]. By adopting the phase analysis method of planar dynamical systems and the theory of the singular traveling wave systems to the traveling wave solutions of the equation, it is shown that for different k, the equation may have infinitely many solitary wave solutions, periodic wave solutions, kink/antikink wave solutions, cusped solitary wave solutions, and breaking loop solutions. We discuss in a detail the cases of k=-2,-(1/2),(1/2),2, and parametric representations of all possible bounded traveling wave solutions are given in the different (c,g)-parameter regions.

Travelling-wave-sustained discharges

International Nuclear Information System (INIS)

Schlueter, Hans; Shivarova, Antonia

2007-01-01

This review is on discharges maintained by travelling waves: new plasma sources, discovered in 1974 and considered as a prototype of the gas discharges according to their definition as nonlinear systems which unify in a self-consistent manner plasmas and fields. In the presentation here of the fluid-plasma models of the diffusion-controlled regime of the travelling-wave-sustained discharges (TWSDs), the basic features of the discharge maintenance-the discharge self-consistency and the electron heating in the high-frequency field-are stressed. Operation of stationary and pulsed discharges, discharge maintenance without and in external magnetic fields as well as discharge production in different gases (argon, helium, helium-argon gas mixtures and hydrogen) are covered. Modulation instability of diffusion-controlled discharges and discharge filamentation at higher gas pressures are also included in the review. Experimental findings which motivate aspects of the reported modelling are pointed out

Traveling wave behavior for a generalized fisher equation

International Nuclear Information System (INIS)

Feng Zhaosheng

2008-01-01

There is the widespread existence of wave phenomena in physics, chemistry and biology. This clearly necessitates a study of traveling waves in depth and of the modeling and analysis involved. In the present paper, we study a nonlinear reaction-diffusion equation, which can be regarded as a generalized Fisher equation. Applying the Cole-Hopf transformation and the first integral method, we obtain a class of traveling solitary wave solutions for this generalized Fisher equation

Travelling waves in expanding spatially homogeneous space–times

International Nuclear Information System (INIS)

Alekseev, George

2015-01-01

Some classes of the so-called ‘travelling wave’ solutions of Einstein and Einstein–Maxwell equations in general relativity and of dynamical equations for massless bosonic fields in string gravity in four and higher dimensions are presented. Similarly to the well known plane-fronted waves with parallel rays (pp-waves), these travelling wave solutions may depend on arbitrary functions of a null coordinate which determine the arbitrary profiles and polarizations of the waves. However, in contrast with pp-waves, these waves do not admit the null Killing vector fields and can exist in some curved (expanding and spatially homogeneous) background space–times, where these waves propagate in certain directions without any scattering. Mathematically, some of these classes of solutions arise as the fixed points of Kramer–Neugebauer transformations for hyperbolic integrable reductions of the above mentioned field equations or, in other cases, after imposing the ansatz that these waves do not change the part of the spatial metric transverse to the direction of wave propagation. It is worth noting that the strikingly simple forms of all the solutions presented prospectively make possible the consideration of the nonlinear interaction of these waves with the background curvature and singularities, as well as the collision of such wave pulses with solitons or with each other in the backgrounds where such travelling waves may exist. (paper)

Traveling wave antenna for fast wave heating and current drive in tokamaks

International Nuclear Information System (INIS)

Ikezi, H.; Phelps, D.A.

1995-07-01

The traveling wave antenna for heating and current drive in the ion cyclotron range of frequencies is shown theoretically to have loading and wavenumber spectrum which are largely independent of plasma conditions. These characteristics have been demonstrated in low power experiments on the DIII-D tokamak, in which a standard four-strap antenna was converted to a traveling wave antenna through use of external coupling elements. The experiments indicate that the array maintains good impedance matching without dynamic tuning during abrupt changes in the plasma, such as during L- to H-mode transitions, edge localized mode activity, and disruptions. An analytic model was developed which exhibits the features observed in the experiments. Guidelines for the design of traveling wave antennas are derived from the validated model

Characterizing the astrophysical S factor for 12C+12C fusion with wave-packet dynamics

Science.gov (United States)

Diaz-Torres, Alexis; Wiescher, Michael

2018-05-01

A quantitative study of the astrophysically important subbarrier fusion of 12C+12C is presented. Low-energy collisions are described in the body-fixed reference frame using wave-packet dynamics within a nuclear molecular picture. A collective Hamiltonian drives the time propagation of the wave packet through the collective potential-energy landscape. The fusion imaginary potential for specific dinuclear configurations is crucial for understanding the appearance of resonances in the fusion cross section. The theoretical subbarrier fusion cross sections explain some observed resonant structures in the astrophysical S factor. These cross sections monotonically decline towards stellar energies. The structures in the data that are not explained are possibly due to cluster effects in the nuclear molecule, which need to be included in the present approach.

Traveling waves of the regularized short pulse equation

International Nuclear Information System (INIS)

Shen, Y; Horikis, T P; Kevrekidis, P G; Frantzeskakis, D J

2014-01-01

The properties of the so-called regularized short pulse equation (RSPE) are explored with a particular focus on the traveling wave solutions of this model. We theoretically analyze and numerically evolve two sets of such solutions. First, using a fixed point iteration scheme, we numerically integrate the equation to find solitary waves. It is found that these solutions are well approximated by a finite sum of hyperbolic secants powers. The dependence of the soliton's parameters (height, width, etc) to the parameters of the equation is also investigated. Second, by developing a multiple scale reduction of the RSPE to the nonlinear Schrödinger equation, we are able to construct (both standing and traveling) envelope wave breather type solutions of the former, based on the solitary wave structures of the latter. Both the regular and the breathing traveling wave solutions identified are found to be robust and should thus be amenable to observations in the form of few optical cycle pulses. (paper)

Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation

International Nuclear Information System (INIS)

Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.

2006-01-01

Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility

Traveling waves in twisted nematic liquid crystal cells

International Nuclear Information System (INIS)

Zakharov, A.V.; Vakulenko, A.A.

2007-01-01

We have described a novel reorientation mechanism in the form of the traveling waves, under influence of an external electric field, directed parallel to both glass plates, which occur in the twisted nematic cell (TNC). It is found that the slowest velocity of the traveling front is proportional to the field strength, and, approximately, in three times higher than the front velocity corresponding to the non-traveling solution. The value of the critical electric field E cr which may excite the traveling waves in the TNC in π times less than the value of the threshold electric field E th corresponding to the untwisted geometry

Evoked traveling alpha waves predict visual-semantic categorization-speed

Science.gov (United States)

Fellinger, Robert; Gruber, Walter; Zauner, Andrea; Freunberger, Roman; Klimesch, Wolfgang

2012-01-01

In the present study we have tested the hypothesis that evoked traveling alpha waves are behaviorally significant. The results of a visual-semantic categorization task show that three early ERP components including the P1–N1 complex had a dominant frequency characteristic in the alpha range and behaved like traveling waves do. They exhibited a traveling direction from midline occipital to right lateral parietal sites. Phase analyses revealed that this traveling behavior of ERP components could be explained by phase-delays in the alpha but not theta and beta frequency range. Most importantly, we found that the speed of the traveling alpha wave was significantly and negatively correlated with reaction time indicating that slow traveling speed was associated with fast picture-categorization. We conclude that evoked alpha oscillations are functionally associated with early access to visual-semantic information and generate – or at least modulate – the early waveforms of the visual ERP. PMID:22100769

Numerical study of the time evolution of a wave packet in quantum mechanics

International Nuclear Information System (INIS)

Segura, J.; Fernandez de Cordoba, P.

1993-01-01

We solve the Schrodinger equation in order to study the time evolution of a wave packet in different situations of physical interest. This work illustrates, with pedagogical aim, some quantum phenomena which shock our classical conception of the universe: propagation in classically forbidden regions, energy quantization. (Author)

Expansion of a quantum wave packet in a one-dimensional disordered potential in the presence of a uniform bias force

Science.gov (United States)

Crosnier de Bellaistre, C.; Trefzger, C.; Aspect, A.; Georges, A.; Sanchez-Palencia, L.

2018-01-01

We study numerically the expansion dynamics of an initially confined quantum wave packet in the presence of a disordered potential and a uniform bias force. For white-noise disorder, we find that the wave packet develops asymmetric algebraic tails for any ratio of the force to the disorder strength. The exponent of the algebraic tails decays smoothly with that ratio and no evidence of a critical behavior on the wave density profile is found. Algebraic localization features a series of critical values of the force-to-disorder strength where the m th position moment of the wave packet diverges. Below the critical value for the m th moment, we find fair agreement between the asymptotic long-time value of the m th moment and the predictions of diagrammatic calculations. Above it, we find that the m th moment grows algebraically in time. For correlated disorder, we find evidence of systematic delocalization, irrespective to the model of disorder. More precisely, we find a two-step dynamics, where both the center-of-mass position and the width of the wave packet show transient localization, similar to the white-noise case, at short time and delocalization at sufficiently long time. This correlation-induced delocalization is interpreted as due to the decrease of the effective de Broglie wavelength, which lowers the effective strength of the disorder in the presence of finite-range correlations.

Sequentially pulsed traveling wave accelerator

Science.gov (United States)

Caporaso, George J [Livermore, CA; Nelson, Scott D [Patterson, CA; Poole, Brian R [Tracy, CA

2009-08-18

A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

Determining the wavelength of Langmuir wave packets at the Earth's bow shock

Directory of Open Access Journals (Sweden)

V. V. Krasnoselskikh

2011-03-01

Full Text Available The propagation of Langmuir waves in plasmas is known to be sensitive to density fluctuations. Such fluctuations may lead to the coexistence of wave pairs that have almost opposite wave-numbers in the vicinity of their reflection points. Using high frequency electric field measurements from the WIND satellite, we determine for the first time the wavelength of intense Langmuir wave packets that are generated upstream of the Earth's electron foreshock by energetic electron beams. Surprisingly, the wavelength is found to be 2 to 3 times larger than the value expected from standard theory. These values are consistent with the presence of strong inhomogeneities in the solar wind plasma rather than with the effect of weak beam instabilities.

Anisotropy, propagation failure, and wave speedup in traveling waves of discretizations of a Nagumo PDE

International Nuclear Information System (INIS)

Elmer, Christopher E.; Vleck, Erik S. van

2003-01-01

This article is concerned with effect of spatial and temporal discretizations on traveling wave solutions to parabolic PDEs (Nagumo type) possessing piecewise linear bistable nonlinearities. Solution behavior is compared in terms of waveforms and in terms of the so-called (a,c) relationship where a is a parameter controlling the bistable nonlinearity by varying the potential energy difference of the two phases and c is the wave speed of the traveling wave. Uniform spatial discretizations and A(α) stable linear multistep methods in time are considered. Results obtained show that although the traveling wave solutions to parabolic PDEs are stationary for only one value of the parameter a,a 0 , spatial discretization of these PDEs produce traveling waves which are stationary for a nontrivial interval of a values which include a 0 , i.e., failure of the solution to propagate in the presence of a driving force. This is true no matter how wide the interface is with respect to the discretization. For temporal discretizations at large wave speeds the set of parameter a values for which there are traveling wave solutions is constrained. An analysis of a complete discretization points out the potential for nonuniqueness in the (a,c) relationship

Phase and group velocity tracing analysis of projected wave packet motion along oblique radar beams – qualitative analysis of QP echoes

Directory of Open Access Journals (Sweden)

F. S. Kuo

2007-02-01

Full Text Available The wave packets of atmospheric gravity waves were numerically generated, with a given characteristic wave period, horizontal wave length and projection mean wind along the horizontal wave vector. Their projection phase and group velocities along the oblique radar beam (vpr and vgr, with different zenith angle θ and azimuth angle φ, were analyzed by the method of phase- and group-velocity tracing. The results were consistent with the theoretical calculations derived by the dispersion relation, reconfirming the accuracy of the method of analysis. The RTI plot of the numerical wave packets were similar to the striation patterns of the QP echoes from the FAI irregularity region. We propose that the striation range rate of the QP echo is equal to the radial phase velocity vpr, and the slope of the energy line across the neighboring striations is equal to the radial group velocity vgr of the wave packet; the horizontal distance between two neighboring striations is equal to the characteristic wave period τ. Then, one can inversely calculate all the properties of the gravity wave responsible for the appearance of the QP echoes. We found that the possibility of some QP echoes being generated by the gravity waves originated from lower altitudes cannot be ruled out.

High-order-harmonic generation from solids: The contributions of the Bloch wave packets moving at the group and phase velocities

Science.gov (United States)

Du, Tao-Yuan; Huang, Xiao-Huan; Bian, Xue-Bin

2018-01-01

We study numerically the Bloch electron wave-packet dynamics in periodic potentials to simulate laser-solid interactions. We introduce an alternative perspective in the coordinate space combined with the motion of the Bloch electron wave packets moving at group and phase velocities under the laser fields. This model interprets the origins of the two contributions (intra- and interband transitions) in the high-order harmonic generation (HHG) processes by investigating the local and global behaviours of the wave packets. It also elucidates the underlying physical picture of the HHG intensity enhancement by means of carrier-envelope phase, chirp, and inhomogeneous fields. It provides a deep insight into the emission of high-order harmonics from solids. This model is instructive for experimental measurements and provides an alternative avenue to distinguish mechanisms of the HHG from solids in different laser fields.

Traveling-wave antenna for fast-wave heating and current drive in tokamaks

International Nuclear Information System (INIS)

Ikezi, H.; Phelps, D.A.

1997-01-01

The travelling-wave antenna for heating and current drive in the ion cyclotron range of frequencies is shown theoretically to have loading and wavenumber spectra that are largely independent of plasma conditions. These characteristics have been demonstrated in low-power experiments on the DIII-D tokamak, in which a standard four-strap antenna was converted to a traveling-wave antenna through use of external coupling elements. The experiments indicate that the array maintains good impedance matching without dynamic tuning during abrupt changes in the plasma, such as during L- to H-mode transitions, edge-localized mode activity, and disruptions. An analytic model was developed that exhibits the features observed in the experiments. Guidelines for the design of travelling-wave antennas are derived from the validated model. 11 refs., 14 figs

Travelling Wave Solutions to Stretched Beam's Equation: Phase Portraits Survey

International Nuclear Information System (INIS)

Betchewe, Gambo; Victor, Kuetche Kamgang; Thomas, Bouetou Bouetou; Kofane, Timoleon Crepin

2011-01-01

In this paper, following the phase portraits analysis, we investigate the integrability of a system which physically describes the transverse oscillation of an elastic beam under end-thrust. As a result, we find that this system actually comprises two families of travelling waves: the sub- and super-sonic periodic waves of positive- and negative-definite velocities, respectively, and the localized sub-sonic loop-shaped waves of positive-definite velocity. Expressing the energy-like of this system while depicting its phase portrait dynamics, we show that these multivalued localized travelling waves appear as the boundary solutions to which the periodic travelling waves tend asymptotically. (general)

Advantages of traveling wave resonant antennas for fast wave heating systems

International Nuclear Information System (INIS)

Phelps, D.A.; Callis, R.W.; Grassie, J.S. de

1997-04-01

The resilience of a maximally flat externally coupled traveling wave antenna (TWA) is contrasted with the sensitivity of a simple directly driven resonant loop array to vacuum and plasma conditions in DIII-D. We find a unique synergy between standing and traveling wave resonant TWA components. This synergy extends TWA operation to several passbands between 60 and 120 MHZ, provides 60 degrees- 120 degrees tunability between elements within a 1-2 MHZ bandwidth and permits efficient and continuous operation during ELMing H-mode

Theory analysis and simple calculation of travelling wave burnup scheme

International Nuclear Information System (INIS)

Zhang Jian; Yu Hong; Gang Zhi

2012-01-01

Travelling wave burnup scheme is a new burnup scheme that breeds fuel locally just before it burns. Based on the preliminary theory analysis, the physical imagine was found. Through the calculation of a R-z cylinder travelling wave reactor core with ERANOS code system, the basic physical characteristics of this new burnup scheme were concluded. The results show that travelling wave reactor is feasible in physics, and there are some good features in the reactor physics. (authors)

Vacillations induced by interference of stationary and traveling planetary waves

Science.gov (United States)

Salby, Murry L.; Garcia, Rolando R.

1987-01-01

The interference pattern produced when a traveling planetary wave propagates over a stationary forced wave is explored, examining the interference signature in a variety of diagnostics. The wave field is first restricted to a diatomic spectrum consisting of two components: a single stationary wave and a single monochromatic traveling wave. A simple barotropic normal mode propagating over a simple stationary plane wave is considered, and closed form solutions are obtained. The wave fields are then restricted spatially, providing more realistic structures without sacrificing the advantages of an analytical solution. Both stationary and traveling wave fields are calculated numerically with the linearized Primitive Equations in a realistic basic state. The mean flow reaction to the fluctuating eddy forcing which results from interference is derived. Synoptic geopotential behavior corresponding to the combined wave and mean flow fields is presented, and the synoptic signature in potential vorticity on isentropic surfaces is examined.

Engineering and manipulating exciton wave packets

Science.gov (United States)

Zang, Xiaoning; Montangero, Simone; Carr, Lincoln D.; Lusk, Mark T.

2017-05-01

When a semiconductor absorbs light, the resulting electron-hole superposition amounts to a uncontrolled quantum ripple that eventually degenerates into diffusion. If the conformation of these excitonic superpositions could be engineered, though, they would constitute a new means of transporting information and energy. We show that properly designed laser pulses can be used to create such excitonic wave packets. They can be formed with a prescribed speed, direction, and spectral make-up that allows them to be selectively passed, rejected, or even dissociated using superlattices. Their coherence also provides a handle for manipulation using active, external controls. Energy and information can be conveniently processed and subsequently removed at a distant site by reversing the original procedure to produce a stimulated emission. The ability to create, manage, and remove structured excitons comprises the foundation for optoexcitonic circuits with application to a wide range of quantum information, energy, and light-flow technologies. The paradigm is demonstrated using both tight-binding and time-domain density functional theory simulations.

The extended (G/G)-expansion method and travelling wave ...

Indian Academy of Sciences (India)

In this paper, we construct the travelling wave solutions to the perturbed nonlinear Schrödinger's equation (NLSE) with Kerr law non-linearity by the extended (′/)-expansion method. Based on this method, we obtain abundant exact travelling wave solutions of NLSE with Kerr law nonlinearity with arbitrary parameters.

Quantum wave packet study of D+OF reaction

International Nuclear Information System (INIS)

Kurban, M.; Karabulut, E.; Tutuk, R.; Goektas, F.

2010-01-01

The quantum dynamics of the D+OF reaction on the adiabatic potential energy surface of the ground 1 3 A ' state has been studied by using a time-dependent quantum real wave packet method. The state-to-state and state-to-all reaction probabilities for total angular momentum J = 0 have been calculated. The probabilities for J > 0 have been calculated by J-shifting the J = 0 results by means of capture model. Then, the integral cross sections and initial state selected rate constants have been calculated. The initial state-selected reaction probabilities and reaction cross section show threshold but not manifest any resonances and the initial state selected rate constants are sensitive to the temperature.

Traveling wave interferometry particularly for solar power satellites

International Nuclear Information System (INIS)

Ott, J.H.; Rice, J.S.

1983-01-01

A method and apparatus are described for use in scientific measurement analysis and control. Travelling interference fringes are generated by radiating at least two different periodic waves at two different frequencies, one from each of two different radiators. The waves are received, mixed and filtered to detect at least one beat signal from these waves which represents the travelling interference fringe. The phase of that beat signal is detected relative to a reference signal of the same frequency as the beat signal. The radiated waves may be received at a second antenna and the phase of the beat of the waves at the first antenna is compared to the phase of the beat as observed at the second antenna. A third wave may be radiated from the first antenna to provide a reference signal which is the beat generated by the third wave and the other wave from the same radiator

Traveling Wave Accelerating Structure for a Superconducting Accelerator

CERN Document Server

Kanareykin, Alex; Solyak, Nikolay

2005-01-01

We are presenting a superconducting traveling wave accelerating structure (STWA) concept, which may prove to be of crucial importance to the International Linear Collider. Compared to the existing design of a TESLA cavity, the traveling wave structure can provide ~20-40% higher accelerating gradient for the same aperture and the same peak surface magnetic RF field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ~50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by the two couplers with appropriate phase advance to excite a traveling wave inside the structure. The system requires two independent tuners to be able to adjust the cavity and feedback waveguide frequencies and hence to reduce the unwanted backward wave. In this presentation we discuss the structure design, optimization of the parameters, tuning requirements and plans for further development.

expansion method and travelling wave solutions for the perturbed ...

Indian Academy of Sciences (India)

Abstract. In this paper, we construct the travelling wave solutions to the perturbed nonlinear. Schrödinger's equation (NLSE) with Kerr law non-linearity by the extended (G /G)-expansion method. Based on this method, we obtain abundant exact travelling wave solutions of NLSE with. Kerr law nonlinearity with arbitrary ...

On the Quantum Potential and Pulsating Wave Packet in the Harmonic Oscillator

International Nuclear Information System (INIS)

Dubois, Daniel M.

2008-01-01

A fundamental mathematical formalism related to the Quantum Potential factor, Q, is presented in this paper. The Schroedinger equation can be transformed to two equations depending on a group velocity and a density of presence of the particle. A factor, in these equations, was called ''Quantum Potential'' by D. Bohm and B. Hiley. In 1999, I demonstrated that this Quantum Potential, Q, can be split in two Quantum Potentials, Q 1 , and Q 2 , for which the relation, Q=Q 1 +Q 2 , holds. These two Quantum Potentials depend on a fundamental new variable, what I called a phase velocity, u, directly related to the probability density of presence of the wave-particle, given by the modulus of the wave function. This paper gives some further developments for explaining the Quantum Potential for oscillating and pulsating Gaussian wave packets in the Harmonic Oscillator. It is shown that the two Quantum Potentials play a central role in the interpretation of quantum mechanics. A breakthrough in the formalism of the Quantum Mechanics could be provoked by the physical properties of these Quantum Potentials. The probability density of presence of the oscillating and pulsating Gaussian wave packets in the Harmonic Oscillator is directly depending on the ratio Q 2 /Q 1 of the two Quantum Potentials. In the general case, the energy of these Gaussian wave packets is not constant, but is oscillating. The energy is given by the sum of the kinetic energy, T, the potential energy, V, and the two Quantum Potentials: E=T+V+Q 1 +Q 2 . For some conditions, given in the paper, the energy can be a constant. The first remarkable result is the fact that the first Quantum Potential, Q 1 , is related to the ground state energy, E 0 , of the Quantum Harmonic Oscillator: Q 1 =h-bar ω/2=E 0 . The second result is related to the property of the second Quantum Potential, Q 2 , which plays the role of an anti-potential, Q 2 =-V(x), where V is the harmonic oscillator potential. This Quantum Potential

Numerical study of traveling-wave solutions for the Camassa-Holm equation

International Nuclear Information System (INIS)

Kalisch, Henrik; Lenells, Jonatan

2005-01-01

We explore numerically different aspects of periodic traveling-wave solutions of the Camassa-Holm equation. In particular, the time evolution of some recently found new traveling-wave solutions and the interaction of peaked and cusped waves is studied

Travelling Waves in Hyperbolic Chemotaxis Equations

KAUST Repository

Xue, Chuan; Hwang, Hyung Ju; Painter, Kevin J.; Erban, Radek

2010-01-01

Mathematical models of bacterial populations are often written as systems of partial differential equations for the densities of bacteria and concentrations of extracellular (signal) chemicals. This approach has been employed since the seminal work of Keller and Segel in the 1970s (Keller and Segel, J. Theor. Biol. 30:235-248, 1971). The system has been shown to permit travelling wave solutions which correspond to travelling band formation in bacterial colonies, yet only under specific criteria, such as a singularity in the chemotactic sensitivity function as the signal approaches zero. Such a singularity generates infinite macroscopic velocities which are biologically unrealistic. In this paper, we formulate a model that takes into consideration relevant details of the intracellular processes while avoiding the singularity in the chemotactic sensitivity. We prove the global existence of solutions and then show the existence of travelling wave solutions both numerically and analytically. © 2010 Society for Mathematical Biology.

Travelling Waves in Hyperbolic Chemotaxis Equations

KAUST Repository

Xue, Chuan

2010-10-16

Mathematical models of bacterial populations are often written as systems of partial differential equations for the densities of bacteria and concentrations of extracellular (signal) chemicals. This approach has been employed since the seminal work of Keller and Segel in the 1970s (Keller and Segel, J. Theor. Biol. 30:235-248, 1971). The system has been shown to permit travelling wave solutions which correspond to travelling band formation in bacterial colonies, yet only under specific criteria, such as a singularity in the chemotactic sensitivity function as the signal approaches zero. Such a singularity generates infinite macroscopic velocities which are biologically unrealistic. In this paper, we formulate a model that takes into consideration relevant details of the intracellular processes while avoiding the singularity in the chemotactic sensitivity. We prove the global existence of solutions and then show the existence of travelling wave solutions both numerically and analytically. © 2010 Society for Mathematical Biology.

Molecular orientation via a dynamically induced pulse-train: Wave packet dynamics of NaI in a static electric field

DEFF Research Database (Denmark)

Marquetand, P.; Materny, A.; Henriksen, Niels Engholm

2004-01-01

We regard the rovibrational wave packet dynamics of NaI in a static electric field after femtosecond excitation to its first electronically excited state. The following quasibound nuclear wave packet motion is accompanied by a bonding situation changing from covalent to ionic. At times when...... the charge separation is present, i.e., when the bond-length is large, a strong dipole moment exists and rotational excitation takes place. Upon bond contraction, the then covalently bound molecule does not experience the external field. This scenario repeats itself periodically. Thus, the vibrational...

Wave-packet approach to Rydberg resonances in dissociative recombination

International Nuclear Information System (INIS)

Morisset, Sabine; Pichl, Lukas; Orel, Ann E.; Schneider, Ioan F.

2007-01-01

We report the time-dependent approach to resonant electron capture into Rydberg states in collisions with molecular cations at low impact energy, as an alternative to the method based on multichannel quantum defect theory (MQDT), and present the results for the HD + ion. The propagation of the initial wave function on 13 Rydberg states (besides one valence state) correctly describes the indirect dissociative recombination mechanism in the time domain. Notably, the nonlocal coupling operator between the ionization and dissociation channels is accounted for in the indirect process, extending previous work on the case of direct coupling. The present approach compares to the MQDT framework with remarkable precision: resonant structures in the cross section correctly emerge from the wave-packet propagation; the time-dependent result also forms a cross section envelope for the dense series of ultrafine MQDT resonances corresponding to the quasicontinuous part of the Rydberg state manifold

Test particle modeling of wave-induced energetic electron precipitation

International Nuclear Information System (INIS)

Chang, H.C.; Inan, U.S.

1985-01-01

A test particle computer model of the precipitation of radiation belt electrons is extended to compute the dynamic energy spectrum of transient electron fluxes induced by short-duration VLF wave packets traveling along the geomagnetic field lines. The model is adapted to estimate the count rate and associated spectrum of precipitated electrons that would be observed by satellite-based particle detectors with given geometric factor and orientation with respect to the magnetic field. A constant-frequency wave pulse and a lightning-induced whistler wave packet are used as examples of the stimulating wave signals. The effects of asymmetry of particle mirror heights in the two hemispheres and the atmospheric backscatter of loss cone particles on the computed precipitated fluxes are discussed

Mean field effects for counterpropagating traveling wave solutions of reaction-diffusion systems

International Nuclear Information System (INIS)

Bernoff, A.J.; Kuske, R.; Matkowsky, B.J.; Volpert, V.

1995-01-01

In many problems, one observes traveling waves that propagate with constant velocity and shape in the χ direction, say, are independent of y, and z and describe transitions between two equilibrium states. As parameters of the system are varied, these traveling waves can become unstable and give rise to waves having additional structure, such as traveling waves in the y and z directions, which can themselves be subject to instabilities as parameters are further varied. To investigate this scenario the authors consider a system of reaction-diffusion equations with a traveling wave solution as a basic state. They determine solutions bifurcating from the basic state that describe counterpropagating traveling wave in directions orthogonal to the direction of propagation of the basic state and determine their stability. Specifically, they derive long wave modulation equations for the amplitudes of the counterpropagating traveling waves that are coupled to an equation for a mean field, generated by the translation of the basic state in the direction of its propagation. The modulation equations are then employed to determine stability boundaries to long wave perturbations for both unidirectional and counterpropagating traveling waves. The stability analysis is delicate because the results depend on the order in which transverse and longitudinal perturbation wavenumbers are taken to zero. For the unidirectional wave they demonstrate that it is sufficient to consider the cases of (1) purely transverse perturbations, (2) purely longitudinal perturbations, and (3) longitudinal perturbations with a small transverse component. These yield Eckhaus type, zigzag type, and skew type instabilities, respectively

New exact travelling wave solutions of bidirectional wave equations

Indian Academy of Sciences (India)

Department of Mathematics, Sungkyunkwan University, Suwon 440-746, Republic of Korea. ∗ ... exact travelling wave solutions of system (1) using the modified tanh–coth function method ... The ordinary differential equation is then integrated.

Topological horseshoes in travelling waves of discretized nonlinear wave equations

International Nuclear Information System (INIS)

Chen, Yi-Chiuan; Chen, Shyan-Shiou; Yuan, Juan-Ming

2014-01-01

Applying the concept of anti-integrable limit to coupled map lattices originated from space-time discretized nonlinear wave equations, we show that there exist topological horseshoes in the phase space formed by the initial states of travelling wave solutions. In particular, the coupled map lattices display spatio-temporal chaos on the horseshoes

Topological horseshoes in travelling waves of discretized nonlinear wave equations

Energy Technology Data Exchange (ETDEWEB)

Chen, Yi-Chiuan, E-mail: YCChen@math.sinica.edu.tw [Institute of Mathematics, Academia Sinica, Taipei 10617, Taiwan (China); Chen, Shyan-Shiou, E-mail: sschen@ntnu.edu.tw [Department of Mathematics, National Taiwan Normal University, Taipei 11677, Taiwan (China); Yuan, Juan-Ming, E-mail: jmyuan@pu.edu.tw [Department of Financial and Computational Mathematics, Providence University, Shalu, Taichung 43301, Taiwan (China)

2014-04-15

Applying the concept of anti-integrable limit to coupled map lattices originated from space-time discretized nonlinear wave equations, we show that there exist topological horseshoes in the phase space formed by the initial states of travelling wave solutions. In particular, the coupled map lattices display spatio-temporal chaos on the horseshoes.

Travelling wave solutions of the generalized Benjamin-Bona-Mahony equation

International Nuclear Information System (INIS)

Estevez, P.G.; Kuru, S.; Negro, J.; Nieto, L.M.

2009-01-01

A class of particular travelling wave solutions of the generalized Benjamin-Bona-Mahony equation is studied systematically using the factorization technique. Then, the general travelling wave solutions of Benjamin-Bona-Mahony equation, and of its modified version, are also recovered.

Algebraic Traveling Wave Solutions of a Non-local Hydrodynamic-type Model

International Nuclear Information System (INIS)

Chen, Aiyong; Zhu, Wenjing; Qiao, Zhijun; Huang, Wentao

2014-01-01

In this paper we consider the algebraic traveling wave solutions of a non-local hydrodynamic-type model. It is shown that algebraic traveling wave solutions exist if and only if an associated first order ordinary differential system has invariant algebraic curve. The dynamical behavior of the associated ordinary differential system is analyzed. Phase portraits of the associated ordinary differential system is provided under various parameter conditions. Moreover, we classify algebraic traveling wave solutions of the model. Some explicit formulas of smooth solitary wave and cuspon solutions are obtained

Absolute instabilities of travelling wave solutions in a Keller-Segel model

OpenAIRE

Davis, P. N.; van Heijster, P.; Marangell, R.

2016-01-01

We investigate the spectral stability of travelling wave solutions in a Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity function and a constant, sublinear, and linear consumption rate. Linearising around the travelling wave solutions, we locate the essential and absolute spectrum of the associated linear operators and find that all travelling wave solutions have essential spectrum in the right half plane. However, we show that in the case of constant or sublinea...

Traveling wave solutions for reaction-diffusion systems

DEFF Research Database (Denmark)

Lin, Zhigui; Pedersen, Michael; Tian, Canrong

2010-01-01

This paper is concerned with traveling waves of reaction–diffusion systems. The definition of coupled quasi-upper and quasi-lower solutions is introduced for systems with mixed quasimonotone functions, and the definition of ordered quasi-upper and quasi-lower solutions is also given for systems...... with quasimonotone nondecreasing functions. By the monotone iteration method, it is shown that if the system has a pair of coupled quasi-upper and quasi-lower solutions, then there exists at least a traveling wave solution. Moreover, if the system has a pair of ordered quasi-upper and quasi-lower solutions...

Existence and exponential stability of traveling waves for delayed reaction-diffusion systems

Science.gov (United States)

Hsu, Cheng-Hsiung; Yang, Tzi-Sheng; Yu, Zhixian

2018-03-01

The purpose of this work is to investigate the existence and exponential stability of traveling wave solutions for general delayed multi-component reaction-diffusion systems. Following the monotone iteration scheme via an explicit construction of a pair of upper and lower solutions, we first obtain the existence of monostable traveling wave solutions connecting two different equilibria. Then, applying the techniques of weighted energy method and comparison principle, we show that all solutions of the Cauchy problem for the considered systems converge exponentially to traveling wave solutions provided that the initial perturbations around the traveling wave fronts belong to a suitable weighted Sobolev space.

Hybrid Modelling of a Traveling Wave Piezoelectric Motor

DEFF Research Database (Denmark)

El, Ghouti N.

a theoretical model is derived. Since the dynamic characteristics of the real motor are difficult to capture in an analytical model, and the parameters of the motor are time varying and highly nonlinear, then some assumptions are required in order to simplify the modeling task and thus provide a suitable model......This thesis considers the modeling of the traveling wave piezoelectric motor (PEM). The rotary traveling wave ultrasonic motor "Shinsei type USR60" is the case study considered in this work. The traveling wave PEM has excellent performance and many useful features such as high holding torque, high....... Despite many attempts a lumped motor model of the PEM is unavailable so far. The dynamical characteristics of the PEM are complicated, highly nonlinear, and the motor parameters are time varying due to temperature rise and changes in motor drive operating conditions. Therefore it is difficult to predict...

Traveling waves in an optimal velocity model of freeway traffic

Science.gov (United States)

Berg, Peter; Woods, Andrew

2001-03-01

Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].

Traveling waves in a spring-block chain sliding down a slope

Science.gov (United States)

Morales, J. E.; James, G.; Tonnelier, A.

2017-07-01

Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.

Coupler tuning for constant gradient travelling wave accelerating structures

International Nuclear Information System (INIS)

Guo Xingkun; Ma Yanyun; Wang Xiulong

2013-01-01

The method of the coupler tuning for the constant gradient traveling wave accelerating structure was described and the formula of coupling coefficient p was deduced on the basis of analyzing the existing methods for the constant impedance traveling wave accelerating structures and coupling-cavity chain equivalent circuits. The method and formula were validated by the simulation result by CST and experiment data. (authors)

Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures

International Nuclear Information System (INIS)

Lipton, Robert; Polizzi, Anthony

2014-01-01

We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections is adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the size of the period cell.

Wave packets, Maslov indices, and semiclassical quantization

International Nuclear Information System (INIS)

Littlejohn, R.G.

1989-01-01

The Bohr-Sommerfeld quantization condition, as refined by Keller and Maslov, reads I=(n+m/4)h, where I is the classical action, n is the quantum number, and where m is the Maslov index, an even integer. The occurrence of the integers n and m in this formula is a reflection of underlying topological features of semiclassical quantization. In particular, the work of Arnold and others has shown that m/2 is a winding number of closed curves on the classical symplectic group manifold, Sp(2N). Wave packets provide a simple and elegant means of establishing the connection between semiclassical quantization and the homotopy classes of Sp(2N), as well as a practical way of calculating Maslov indices in complex problems. Topological methods can also be used to derive general formulas for the Maslov indices of invariant tori in the classical phase space corresponding to resonant motion. (orig.)

Dynamics of coupled plasmon polariton wave packets excited at a subwavelength slit in optically thin metal films

Science.gov (United States)

Wang, Lei-Ming; Zhang, Lingxiao; Seideman, Tamar; Petek, Hrvoje

2012-10-01

We study by numerical simulations the excitation and propagation dynamics of coupled surface plasmon polariton (SPP) wave packets (WPs) in optically thin Ag films and a bulk Ag/vacuum interface under the illumination of a subwavelength slit by 400 nm continuous wave (cw) and femtosecond pulsed light. The generated surface fields include contributions from both SPPs and quasicylindrical waves, which dominate in different regimes. We explore aspects of the coupled SPP modes in Ag thin films, including symmetry, propagation, attenuation, and the variation of coupling with incident angle and film thickness. Simulations of the electromagnetic transients initiated with femtosecond pulses reveal new features of coupled SPP WP generation and propagation in thin Ag films. Our results show that, under pulsed excitation, the SPP modes in an Ag thin film break up into two distinct bound surface wave packets characterized by marked differences in symmetries, group velocities, attenuation lengths, and dispersion properties. The nanometer spatial and femtosecond temporal scale excitation and propagation dynamics of the coupled SPP WPs are revealed in detail by movies recording the evolution of their transient field distributions.

Bifurcation analysis and the travelling wave solutions of the Klein

Indian Academy of Sciences (India)

In this paper, we investigate the bifurcations and dynamic behaviour of travelling wave solutions of the Klein–Gordon–Zakharov equations given in Shang et al, Comput. Math. Appl. 56, 1441 (2008). Under different parameter conditions, we obtain some exact explicit parametric representations of travelling wave solutions by ...

Design of traveling wave windows for the PEP-II RF coupling network

International Nuclear Information System (INIS)

Kroll, N.M.; Ng, C.K.; Judkins, J.; Neubauer, M.

1995-05-01

The waveguide windows in the PEP-II RF coupling network have to withstand high power of 500 kW. Traveling wave windows have lower power dissipation than conventional self-matched windows, thus rendering the possibility of less stringent mechanical design. The traveling wave behavior is achieved by providing a reflecting iris on each side of the window, and depending on the configuration of the irises, traveling wave windows are characterized as inductive or capacitive types. A numerical design procedure using MAFIA has been developed for traveling wave windows. The relative advantages of inductive and capacitive windows are discussed. Furthermore, the issues of bandwidth and multipactoring are also addressed

A note on poroacoustic traveling waves under Forchheimer's law

International Nuclear Information System (INIS)

Jordan, P.M.

2013-01-01

Acoustic traveling waves in a gas that saturates a rigid porous medium is investigated under the assumption that the drag experienced by the gas is modeled by Forchheimer's law. Exact traveling wave solutions (TWS)s, as well as approximate and asymptotic expressions, are obtained; decay rates are determined; and acceleration wave results are presented. In addition, special cases are considered, critical values of the wave variable and parameters are derived, and comparisons with predictions based on Darcy's law are performed. It is shown that, with respect to the Darcy case, most of the metrics that characterize such waveforms exhibit an increase in magnitude under Forchheimer's law

Massachusetts Bay - Internal wave packets digitized from SAR imagery and intersected with a bathymetrically derived slope surface

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — This feature class contains internal wave packets digitized from SAR imagery and intersected with a bathymetrically derived slope surface for Massachusetts Bay. The...

The coupled three-dimensional wave packet approach to reactive scattering

Science.gov (United States)

Marković, Nikola; Billing, Gert D.

1994-01-01

A recently developed scheme for time-dependent reactive scattering calculations using three-dimensional wave packets is applied to the D+H2 system. The present method is an extension of a previously published semiclassical formulation of the scattering problem and is based on the use of hyperspherical coordinates. The convergence requirements are investigated by detailed calculations for total angular momentum J equal to zero and the general applicability of the method is demonstrated by solving the J=1 problem. The inclusion of the geometric phase is also discussed and its effect on the reaction probability is demonstrated.

Dissociative double ionization of H2 and D2: Comparison between experiment and Monte Carlo wave packet calculations

DEFF Research Database (Denmark)

Leth, Henriette Astrup; Madsen, Lars Bojer; Mølmer, Klaus

2010-01-01

Theoretical calculations on dissociative double ionization of H2 and D2 in short intense laser pulses using the Monte Carlo wave packet technique are presented for several different field intensities, wavelengths, and pulse durations. We find convincing agreement between theory and experimental...... results for the kinetic energy release spectra of the nuclei. Besides the correctly predicted spectra the Monte Carlo wave packet method offers insight into the nuclear dynamics during the pulse and makes it possible to address the origin of different structures observed in the spectra. Three......-photon resonances in the singly ionized molecule and charge-resonance-enhanced ionization are shown to be the main processes responsible for the observed nuclear energy distributions....

Dispersion-Engineered Traveling Wave Kinetic Inductance Parametric Amplifier

Science.gov (United States)

Zmuidzinas, Jonas (Inventor); Day, Peter K. (Inventor)

2014-01-01

A traveling wave kinetic inductance parametric amplifier comprises a superconducting transmission line and a dispersion control element. The transmission line can include periodic variations of its dimension along its length. The superconducting material can include a high normal state resistivity material. In some instances the high normal state resistivity material includes nitrogen and a metal selected from the group consisting of titanium, niobium and vanadium. The traveling wave kinetic inductance parametric amplifier is expected to exhibit a noise temperature below 100 mK/GHz.

Apocrypha of standard scattering theory (SST) and quantum mechanics of the de Broglie wave packet

International Nuclear Information System (INIS)

Ignatovich, V.K.

2001-01-01

It is shown that the Standard Scattering Theory (SST) does not correspond to the principles of Standard Quantum Mechanics (SQM). A more consistent theory is formulated. Some new results are obtained. Reflection and transmission of the de Broglie wave packet by thin layers of matter is considered

Traveling-Wave Maser for 32 GHz

Science.gov (United States)

Shell, James; Clauss, Robert

2009-01-01

The figure depicts a traveling-wave ruby maser that has been designed (though not yet implemented in hardware) to serve as a low-noise amplifier for reception of weak radio signals in the frequency band of 31.8 to 32.3 GHz. The design offers significant improvements over previous designs of 32-GHz traveling-wave masers. In addition, relative to prior designs of 32-GHz amplifiers based on high-electron-mobility transistors, this design affords higher immunity to radio-frequency interference and lower equivalent input noise temperature. In addition to the basic frequency-band and low-noise requirements, the initial design problem included a requirement for capability of operation in a closed-cycle helium refrigerator at a temperature .4 K and a requirement that the design be mechanically simplified, relative to prior designs, in order to minimize the cost of fabrication and assembly. Previous attempts to build 32- GHz traveling-wave masers involved the use of metallic slow-wave structures comprising coupled transverse electromagnetic (TEM)-mode resonators that were subject to very tight tolerances and, hence, were expensive to fabricate and assemble. Impedance matching for coupling signals into and out of these earlier masers was very difficult. A key feature of the design is a slow-wave structure, the metallic portions of which would be mechanically relatively simple in that, unlike in prior slow-wave structures, there would be no internal metal steps, irises, or posts. The metallic portions of the slow-wave structure would consist only of two rectangular metal waveguide arms. The arms would contain sections filled with the active material (ruby) alternating with evanescent-wave sections. This structure would be transparent in both the signal-frequency band (the aforementioned range of 31.8 to 32.3 GHz) and the pump-frequency band (65.75 to 66.75 GHz), and would impose large slowing factors in both frequency bands. Resonant ferrite isolators would be placed in the

Existence, uniqueness, monotonicity and asymptotic behaviour of travelling waves for epidemic models

International Nuclear Information System (INIS)

Hsu, Cheng-Hsiung; Yang, Tzi-Sheng

2013-01-01

The purpose of this work is to investigate the existence, uniqueness, monotonicity and asymptotic behaviour of travelling wave solutions for a general epidemic model arising from the spread of an epidemic by oral–faecal transmission. First, we apply Schauder's fixed point theorem combining with a supersolution and subsolution pair to derive the existence of positive monotone monostable travelling wave solutions. Then, applying the Ikehara's theorem, we determine the exponential rates of travelling wave solutions which converge to two different equilibria as the moving coordinate tends to positive infinity and negative infinity, respectively. Finally, using the sliding method, we prove the uniqueness result provided the travelling wave solutions satisfy some boundedness conditions. (paper)

Wave packet revivals in a graphene quantum dot in a perpendicular magnetic field

International Nuclear Information System (INIS)

Torres, J. J.; Romera, E.

2010-01-01

We study the time evolution of localized wave packets in graphene quantum dots in a perpendicular magnetic field, focusing on the quasiclassical and revival periodicities, for different values of the magnetic field intensities in a theoretical framework. We have considered contributions of the two inequivalent points in the Brillouin zone. The revival time has been found as an observable that shows the break valley degeneracy.

Hanbury Brown–Twiss Effect with Wave Packets

Directory of Open Access Journals (Sweden)

Tabish Qureshi

2017-11-01

Full Text Available The Hanbury Brown–Twiss (HBT effect, at the quantum level, is essentially an interference of one particle with another, as opposed to interference of a particle with itself. Conventional treatments of identical particles encounter difficulties while dealing with entanglement. A recently introduced label-free approach to indistinguishable particles is described, and is used to analyze the HBT effect. Quantum wave-packets have been used to provide a better understanding of the quantum interpretation of the HBT effect. The effect is demonstrated for two independent particles governed by Bose–Einstein or Fermi–Dirac statistics. The HBT effect is also analyzed for pairs of entangled particles. Surprisingly, entanglement has almost no effect on the interference seen in the HBT effect. In the light of the results, an old quantum optics experiment is reanalyzed, and it is argued that the interference seen in that experiment is not a consequence of non-local correlations between the photons, as is commonly believed. Quanta 2017; 6: 61–69.

Geometric scaling as traveling waves

International Nuclear Information System (INIS)

Munier, S.; Peschanski, R.

2003-01-01

We show the relevance of the nonlinear Fisher and Kolmogorov-Petrovsky-Piscounov (KPP) equation to the problem of high energy evolution of the QCD amplitudes. We explain how the traveling wave solutions of this equation are related to geometric scaling, a phenomenon observed in deep-inelastic scattering experiments. Geometric scaling is for the first time shown to result from an exact solution of nonlinear QCD evolution equations. Using general results on the KPP equation, we compute the velocity of the wave front, which gives the full high energy dependence of the saturation scale

Bistable traveling waves for a competitive-cooperative system with nonlocal delays

Science.gov (United States)

Tian, Yanling; Zhao, Xiao-Qiang

2018-04-01

This paper is devoted to the study of bistable traveling waves for a competitive-cooperative reaction and diffusion system with nonlocal time delays. The existence of bistable waves is established by appealing to the theory of monotone semiflows and the finite-delay approximations. Then the global stability of such traveling waves is obtained via a squeezing technique and a dynamical systems approach.

Traveling waves in lattice differential equations with distributed maturation delay

Directory of Open Access Journals (Sweden)

Hui-Ling Niu

2013-07-01

Full Text Available In this paper we derive a lattice model with infinite distributed delay to describe the growth of a single-species population in a 2D patchy environment with infinite number of patches connected locally by diffusion and global interaction. We consider the existence of traveling wave solutions when the birth rate is large enough that each patch can sustain a positive equilibrium. When the birth function is monotone, we prove that there exists a traveling wave solution connecting two equilibria with wave speed $c>c^*(\\theta$ by using the monotone iterative method and super and subsolution technique, where $\\theta\\in [0,2\\pi]$ is any fixed direction of propagation. When the birth function is non-monotone, we prove the existence of non-trivial traveling wave solutions by constructing two auxiliary systems satisfying quasi-monotonicity.

Instability of traveling waves of the convective-diffusive Cahn-Hilliard equation

International Nuclear Information System (INIS)

Gao Hongjun; Liu Changchun

2004-01-01

In this paper we study the instability of the traveling waves of the convective-diffusive Cahn-Hilliard equation. We prove that it is nonlinearly unstable under H 2 perturbations, for some traveling wave solution that is asymptotic to a constant as x→∞

Travelling wave solutions to the Kuramoto-Sivashinsky equation

International Nuclear Information System (INIS)

Nickel, J.

2007-01-01

Combining the approaches given by Baldwin [Baldwin D et al. Symbolic computation of exact solutions expressible in hyperbolic and elliptic functions for nonlinear PDEs. J Symbol Comput 2004;37:669-705], Peng [Peng YZ. A polynomial expansion method and new general solitary wave solutions to KS equation. Comm Theor Phys 2003;39:641-2] and by Schuermann [Schuermann HW, Serov VS. Weierstrass' solutions to certain nonlinear wave and evolution equations. Proc progress electromagnetics research symposium, 28-31 March 2004, Pisa. p. 651-4; Schuermann HW. Traveling-wave solutions to the cubic-quintic nonlinear Schroedinger equation. Phys Rev E 1996;54:4312-20] leads to a method for finding exact travelling wave solutions of nonlinear wave and evolution equations (NLWEE). The first idea is to generalize ansaetze given by Baldwin and Peng to find elliptic solutions of NLWEEs. Secondly, conditions used by Schuermann to find physical (real and bounded) solutions and to discriminate between periodic and solitary wave solutions are used. The method is shown in detail by evaluating new solutions of the Kuramoto-Sivashinsky equation

Propagation of nonlinear ion acoustic wave with generation of long-wavelength waves

International Nuclear Information System (INIS)

Ohsawa, Yukiharu; Kamimura, Tetsuo

1978-01-01

The nonlinear propagation of the wave packet of an ion acoustic wave with wavenumber k 0 asymptotically equals k sub(De) (the electron Debye wavenumber) is investigated by computer simulations. From the wave packet of the ion acoustic wave, waves with long wavelengths are observed to be produced within a few periods for the amplitude oscillation of the original wave packet. These waves are generated in the region where the original wave packet exists. Their characteristic wavelength is of the order of the length of the wave packet, and their propagation velocity is almost equal to the ion acoustic speed. The long-wavelength waves thus produced strongly affect the nonlinear evolution of the original wave packet. (auth.)

Squeezing of Ion Populations and Peaks in Traveling Wave Ion Mobility Separations and Structures for Lossless Ion Manipulations using Compression Ratio Ion Mobility Programming

Energy Technology Data Exchange (ETDEWEB)

Garimella, Venkata BS; Hamid, Ahmed M.; Deng, Liulin; Ibrahim, Yehia M.; Webb, Ian K.; Baker, Erin M.; Prost, Spencer A.; Norheim, Randolph V.; Anderson, Gordon A.; Smith, Richard D.

2016-11-02

In this work, we report an approach for spatial and temporal gas phase ion population manipulation, and demonstrate its application for the collapse of the ion distributions in ion mobility (IM) separations into tighter packets providing higher sensitivity measurements in conjunction with mass spectrometry (MS). We do this for ions moving from a conventionally traveling wave (TW)-driven region to a region where the TW is intermittently halted or ‘stuttered’. This approach causes the ion packets spanning a number of TW-created traveling traps (TT) to be redistributed into fewer TT, resulting in spatial compression. The degree of spatial compression is controllable and determined by the ratio of stationary time of the TW in the second region to its moving time. This compression ratio ion mobility programming (CRIMP) approach has been implemented using Structures for Lossless Ion Manipulations (SLIM) in conjunction with MS. CRIMP with the SLIM-MS platform is shown to provide increased peak intensities, reduced peak widths, and improved S/N ratios with MS detection. CRIMP also provides a foundation for extremely long path length and multi-pass IM separations in SLIM providing greatly enhanced IM resolution by reducing the detrimental effects of diffusional peak broadening due to increasing peak widths.

Spreading speed and travelling waves for a spatially discrete SIS epidemic model

International Nuclear Information System (INIS)

Zhang, Kate Fang; Zhao Xiaoqiang

2008-01-01

This paper is devoted to the study of the asymptotic speed of spread and travelling waves for a spatially discrete SIS epidemic model. By appealing to the theory of spreading speeds and travelling waves for monotonic semiflows, we establish the existence of asymptotic speed of spread and show that it coincides with the minimal wave speed for monotonic travelling waves. This also gives an affirmative answer to an open problem presented by Rass and Radcliffe (2003 Spatial Deterministic Epidemics (Mathematical Surveys and Monographs vol 102) (Providence, RI: American Mathematical Society)) in the case of discrete spatial habitat

Longitudinal traveling waves bifurcating from Vlasov plasma equilibria

International Nuclear Information System (INIS)

Holloway, J.P.

1989-01-01

The kinetic equations governing longitudinal motion along a straight magnetic field in a multi-species collisionless plasma are investigated. A necessary condition for the existence of small amplitude spatially periodic equilibria and traveling waves near a given spatially uniform background equilibrium is derived, and the wavelengths which such solutions must approach as their amplitude decreases to zero are discussed. A sufficient condition for the existence of these small amplitude waves is also established. This is accomplished by studying the nonlinear ODE for the potential which arises when the distribution functions are represented in a BGK form; the arbitrary functions of energy that describe the BGK representation are tested as an infinite dimensional set of parameters in a bifurcation theory for the ODE. The positivity and zero current condition in the wave frame of the BGK distribution functions are maintained. The undamped small amplitude nonlinear waves so constructed can be made to satisfy the Vlasov dispersion relation exactly, but in general they need only satisfy it approximately. Numerical calculations reveal that even a thermal equilibrium electron-proton plasma with equal ion and electron temperatures will support undamped traveling waves with phase speeds greater than 1.3 times the electron velocity; the dispersion relation for this case exhibits both Langmuir and ion-acoustic branches as long wavelength limits, and shows how these branches are in fact connected by short wavelength waves of intermediate frequency. In apparent contradiction to the linear theory of Landau, these exact solutions of the kinetic equations do not damp; this contradiction is explained by observing that the linear theory is, in general, fundamentally incapable of describing undamped traveling waves

Existence and Stability of Traveling Waves for Degenerate Reaction-Diffusion Equation with Time Delay

Science.gov (United States)

Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue

2018-01-01

This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0 . Furthermore, we prove the global existence and uniqueness of C^{α ,β } -solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1 -space. The exponential convergence rate is also derived.

Existence and Stability of Traveling Waves for Degenerate Reaction-Diffusion Equation with Time Delay

Science.gov (United States)

Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue

2018-06-01

This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0. Furthermore, we prove the global existence and uniqueness of C^{α ,β }-solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1-space. The exponential convergence rate is also derived.

Absolute instabilities of travelling wave solutions in a Keller-Segel model

Science.gov (United States)

Davis, P. N.; van Heijster, P.; Marangell, R.

2017-11-01

We investigate the spectral stability of travelling wave solutions in a Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity function and a constant, sublinear, and linear consumption rate. Linearising around the travelling wave solutions, we locate the essential and absolute spectrum of the associated linear operators and find that all travelling wave solutions have parts of the essential spectrum in the right half plane. However, we show that in the case of constant or sublinear consumption there exists a range of parameters such that the absolute spectrum is contained in the open left half plane and the essential spectrum can thus be weighted into the open left half plane. For the constant and sublinear consumption rate models we also determine critical parameter values for which the absolute spectrum crosses into the right half plane, indicating the onset of an absolute instability of the travelling wave solution. We observe that this crossing always occurs off of the real axis.

Traveling wave fronts and the transition to saturation

International Nuclear Information System (INIS)

Munier, S.; Peschanski, R.

2004-01-01

We propose a general method to study the solutions to nonlinear QCD evolution equations, based on a deep analogy with the physics of traveling waves. In particular, we show that the transition to the saturation regime of high energy QCD is identical to the formation of the front of a traveling wave. Within this physical picture, we provide the expressions for the saturation scale and the gluon density profile as a function of the total rapidity and the transverse momentum. The application to the Balitskii-Kovchegov equation for both fixed and running coupling constants confirms the effectiveness of this method

Space-Qualified Traveling-Wave Tube

Science.gov (United States)

Wilson, Jeffrey D.; Krawczyk, Richard; Simons, Rainee N.; Williams, Wallace D.; Robbins, Neal R.; Dibb, Daniel R.; Menninger, William L.; Zhai, Xiaoling; Benton, Robert T.

2010-01-01

The L-3 Communications Electron Technologies, Inc. Model 999HA traveling-wave tube (TWT), was developed for use as a high-power microwave amplifier for high-rate transmission of data and video signals from deep space to Earth (see figure). The 999HA is a successor to the 999H a non-space qualified TWT described in High-Power, High-Efficiency Ka-Band Traveling-Wave Tube (LEW-17900-1), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 32. Operating in the 31.8-to-32.3 GHz frequency band, the 999HA has been shown to generate 252 W of continuous- wave output power at 62 percent overall power efficiency a 75-percent increase in output power over the 999H. The mass of the 999HA is 35 percent less than that of the 999H. Moreover, taking account of the elimination of a Faraday cage that is necessary for operation of the 999H but is obviated by a redesign of high-voltage feed-throughs for the 999HA, the overall reduction in mass becomes 57 percent with an 82 percent reduction in volume. Through a series of rigorous tests, the 999HA has been qualified for operation aboard spacecraft with a lifetime exceeding seven years. Offspring of the 999HA will fly on the Kepler and Lunar Reconnaissance Orbiter missions.

BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER

DEFF Research Database (Denmark)

2010-01-01

Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...

Coherent control of interfering wave packets in dissociating HD+ molecules: the role of phase and delay time

International Nuclear Information System (INIS)

Qin, Chaochao; Zhang, Lili; Zhang, Xianzhou; Liu, Yufang; Qiu, Xuejun

2016-01-01

The coherent control of interference between dissociating wave packets of the HD + molecules generated by a pair of time-delayed and phase-locked femtosecond laser pulses is theoretically studied by using the time-dependent quantum wave packet method. The density function in both coordinate and momentum representation are presented and discussed. It is demonstrated that the interference pattern is observed in both coordinate and momentum density functions. The interference undergoes a π-phase shift when the delay time between the two phase-locked femtosecond laser pulses is changed by half an optical period. In particular, the number of interference fringes, the fringe spacing in the R-dependent density distribution |ψ(R)| 2 , and the modulation period of the energy-dependent distribution of the fragments P(E) can be tuned by two phase-locked femtosecond pulses. (paper)

Wave packet autocorrelation functions for quantum hard-disk and hard-sphere billiards in the high-energy, diffraction regime.

Science.gov (United States)

Goussev, Arseni; Dorfman, J R

2006-07-01

We consider the time evolution of a wave packet representing a quantum particle moving in a geometrically open billiard that consists of a number of fixed hard-disk or hard-sphere scatterers. Using the technique of multiple collision expansions we provide a first-principle analytical calculation of the time-dependent autocorrelation function for the wave packet in the high-energy diffraction regime, in which the particle's de Broglie wavelength, while being small compared to the size of the scatterers, is large enough to prevent the formation of geometric shadow over distances of the order of the particle's free flight path. The hard-disk or hard-sphere scattering system must be sufficiently dilute in order for this high-energy diffraction regime to be achievable. Apart from the overall exponential decay, the autocorrelation function exhibits a generally complicated sequence of relatively strong peaks corresponding to partial revivals of the wave packet. Both the exponential decay (or escape) rate and the revival peak structure are predominantly determined by the underlying classical dynamics. A relation between the escape rate, and the Lyapunov exponents and Kolmogorov-Sinai entropy of the counterpart classical system, previously known for hard-disk billiards, is strengthened by generalization to three spatial dimensions. The results of the quantum mechanical calculation of the time-dependent autocorrelation function agree with predictions of the semiclassical periodic orbit theory.

Traveling waves in a magnetized Taylor-Couette flow

International Nuclear Information System (INIS)

Liu Wei; Ji Hantao; Goodman, Jeremy

2007-01-01

We investigate numerically a traveling wave pattern observed in experimental magnetized Taylor-Couette flow at low magnetic Reynolds number. By accurately modeling viscous and magnetic boundaries in all directions, we reproduce the experimentally measured wave patterns and their amplitudes. Contrary to previous claims, the waves are shown to be transiently amplified disturbances launched by viscous boundary layers, rather than globally unstable magnetorotational modes

Detuning effect in a traveling wave type linac

International Nuclear Information System (INIS)

Arai, Shigeaki.

1981-10-01

Detailed measurement of acceleration characteristics has been performed on a 15 MeV electron linac as the injector of the electron synchrotron at Institute for Nuclear Study, University of Tokyo. Remarkable feature of the results is that the energy gain as well as the energy spread of the output beam, are optimized when the linac is operated with the microwave whose frequency is higher than the resonant frequency of the accelerator waveguide. The difference of this operating frequency from the resonant frequency grows up as the beam intensity is increased, and amounts to 250 KHz when the beam intensity is 350 mA. In order to clarify the mechanism of the phenomena, the interaction of electron beam with the microwave in the accelerator structure of traveling wave type, is examined on the linac and also on a test accelerator structure. For the analysis of the experimental results, the normal mode method which has been used for standing wave cavities, is developed so as to be applied to the accelerator structure of traveling wave type. The results of analysis show that the observed phenomena at INS linac are caused by the resonant frequency shift, detuning, due to the reactive beam loading and this detuning effects are compensated by use of the microwave of higher frequency. Thus the detuning effects are significant even in the traveling wave type linac composed of buncher and regular sections as well as in the standing wave type accelerator structure. (author)

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.

Science.gov (United States)

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1).

Traveling-wave ion mobility mass spectrometry of protein complexes

DEFF Research Database (Denmark)

Salbo, Rune; Bush, Matthew F; Naver, Helle

2012-01-01

The collision cross-section (Ω) of a protein or protein complex ion can be measured using traveling-wave (T-wave) ion mobility (IM) mass spectrometry (MS) via calibration with compounds of known Ω. The T-wave Ω-values depend strongly on instrument parameters and calibrant selection. Optimization ...

EXACT TRAVELLING WAVE SOLUTIONS TO BBM EQUATION

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

Abundant new travelling wave solutions to the BBM (Benjamin-Bona-Mahoni) equation are obtained by the generalized Jacobian elliptic function method. This method can be applied to other nonlinear evolution equations.

Deltons, peakons and other traveling-wave solutions of a Camassa-Holm hierarchy

International Nuclear Information System (INIS)

Peng Xiaochun; Dai Huihui

2009-01-01

In this letter, we study an integrable Camassa-Holm hierarchy whose high-frequency limit is the Camassa-Holm equation. Phase plane analysis is employed to investigate bounded traveling wave solutions. An important feature is that there exists a singular line on the phase plane. By considering the properties of the equilibrium points and the relative position of the singular line, we find that there are in total three types of phase planes. Those paths in phase planes which represented bounded solutions are discussed one-by-one. Besides solitary, peaked and periodic waves, the equations are shown to admit a new type of traveling waves, which concentrate all their energy in one point, and we name them deltons as they can be expressed as some constant multiplied by a delta function. There also exists a type of traveling waves we name periodic deltons, which concentrate their energy in periodic points. The explicit expressions for them and all the other traveling waves are given.

Photo-induced travelling waves in condensed Langmuir monolayers

Energy Technology Data Exchange (ETDEWEB)

Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)

2003-06-01

We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.

Snakes mimic earthworms: propulsion using rectilinear travelling waves

Science.gov (United States)

Marvi, Hamidreza; Bridges, Jacob; Hu, David L.

2013-01-01

In rectilinear locomotion, snakes propel themselves using unidirectional travelling waves of muscular contraction, in a style similar to earthworms. In this combined experimental and theoretical study, we film rectilinear locomotion of three species of snakes, including red-tailed boa constrictors, Dumeril's boas and Gaboon vipers. The kinematics of a snake's extension–contraction travelling wave are characterized by wave frequency, amplitude and speed. We find wave frequency increases with increasing body size, an opposite trend than that for legged animals. We predict body speed with 73–97% accuracy using a mathematical model of a one-dimensional n-linked crawler that uses friction as the dominant propulsive force. We apply our model to show snakes have optimal wave frequencies: higher values increase Froude number causing the snake to slip; smaller values decrease thrust and so body speed. Other choices of kinematic variables, such as wave amplitude, are suboptimal and appear to be limited by anatomical constraints. Our model also shows that local body lifting increases a snake's speed by 31 per cent, demonstrating that rectilinear locomotion benefits from vertical motion similar to walking. PMID:23635494

The role of ro-vibrational coupling in the revival dynamics of diatomic molecular wave packets

International Nuclear Information System (INIS)

Banerji, J; Ghosh, Suranjana

2006-01-01

We study the revival and fractional revivals of a diatomic molecular wave packet of circular states whose weighing coefficients are peaked about a vibrational quantum number ν-bar and a rotational quantum number j-bar. Furthermore, we show that the interplay between the rotational and vibrational motion is determined by a parameter γ =√D/C, where D is the dissociation energy and C is inversely proportional to the reduced mass of the two nuclei. Using I 2 and H 2 as examples, we show, both analytically and visually (through animations), that for γ>>ν-bar, j-bar, the rotational and vibrational time scales are so far apart that the ro-vibrational motion gets decoupled and the revival dynamics depends essentially on one time scale. For γ∼ν-bar, j-bar, on the other hand, the evolution of the wave packet depends crucially on both the rotational and vibrational time scales of revival. In the latter case, an interesting rotational-vibrational fractional revival is predicted and explained

Fundamental investigation on electrostatic travelling-wave transport of a liquid drop

International Nuclear Information System (INIS)

Kawamoto, Hiroyuki; Hayashi, Satoshi

2006-01-01

Basic research has been carried out on the transport of a liquid drop and a soft body in an electrostatic travelling field. A conveyer consisting of parallel electrodes was constructed and a four-phase electrostatic travelling wave was applied to the electrodes to transport the drop on the conveyer. The following were clarified by the experiment. (1) Drops and soft bodies can be transported by virtue of the travelling wave in an insulative liquid that is insoluble to the drop, because the drop was charged on the conveyer by friction and driven by the Coulomb force. (2) A drop that covered less than three arrays of the parallel electrode can be transported in the travelling wave field. (3) A threshold voltage exists for the transport. (4) Although the transport was possible not only for insulative but also for conductive drops, the insulative drop can be transported efficiently. (5) The modes of transport can be classified into three categories, namely, a synchronous region where the motion of the liquid drop is in synchrony with the travelling wave, a delayed response regime, and a regime where transport does not occur. (6) Mixing of drops for a chemical reaction was demonstrated on the conveyer with scroll electrodes. A simple model was proposed to simulate the dynamics of the drop in the electrostatic travelling field

Neutronic design of a traveling wave reactor core

International Nuclear Information System (INIS)

Lopez S, R. C.; Francois L, J. L.

2010-10-01

The traveling wave reactor is an innovative kind of fast breeder reactor, capable of operate for decades without refueling and whose operation requires only a small amount of enriched fuel for the ignition. Also, one of its advantages is its versatility; it can be designed as small modules of about 100 M We or large scale units of 1000 M We. In this paper the behaviour of the traveling wave reactor core is studied in order to determine whether the traveling breeding/burning wave moves (as theoretically predicted) or not. To achieve this, we consider a two pieces cylinder, the first one, the ignition zone, containing highly enriched fuel and the second, the breeding zone, which is the larger, containing natural or depleted uranium or thorium. We consider that both zones are homogeneous mixtures of fuel, sodium as coolant and iron as structural material. We also include a reflector material outside the cylinder to reduce the neutron leakages. Simulations were run with MCNPX version 2.6 code. We observed that the wave does move as time passes as predicted by theory, and reactor remains supercritical in the time we have simulated (3000 days). Also, we found that thorium does not perform as well as uranium for breeding in this type of reactor. Further test with different reflectors are planned for both U-Pu and Th-U fuel cycles. (Author)

Travelling wave solutions for a surface wave equation in fluid mechanics

Directory of Open Access Journals (Sweden)

Tian Yi

2016-01-01

Full Text Available This paper considers a non-linear wave equation arising in fluid mechanics. The exact traveling wave solutions of this equation are given by using G'/G-expansion method. This process can be reduced to solve a system of determining equations, which is large and difficult. To reduce this process, we used Wu elimination method. Example shows that this method is effective.

Counting states of black strings with traveling waves

International Nuclear Information System (INIS)

Horowitz, G.T.; Marolf, D.

1997-01-01

We consider a family of solutions to string theory which depend on arbitrary functions and contain regular event horizons. They describe six-dimensional extremal black strings with traveling waves and have an inhomogeneous distribution of momentum along the string. The structure of these solutions near the horizon is studied and the horizon area computed. We also count the number of BPS string states at weak coupling whose macroscopic momentum distribution agrees with that of the black string. It is shown that the number of such states is given by the Bekenstein-Hawking entropy of the black string with traveling waves. copyright 1997 The American Physical Society

Control of Spiral Waves and Spatiotemporal Chaos by Exciting Travel Wave Trains

International Nuclear Information System (INIS)

Yuan Guoyong; Wang Guangrui; Chen Shigang

2005-01-01

Spiral waves and spatiotemporal chaos usually are harmful and need to be suppressed. In this paper, a method is proposed to control them. Travel wave trains can be generated by periodic excitations near left boundary, spiral waves and spatiotemporal chaos can be eliminated by the trains for some certain excitation periods. Obvious resonant behavior can be observed from the relation between the periods of the trains and excitation ones. The method is against noise.

Research on backward traveling wave electron linac

International Nuclear Information System (INIS)

Chen Huaibi; Zheng Shuxin; Ding Xiaodong; Lin Yuzheng

1999-01-01

Future electron linacs require high gradient acceleration. The studies on the high shunt impedance backward traveling wave electron linac accelerating structure (BTW) are presented. At first, the characteristics of BTW are researched. The option of mode and optimal design methods of accelerating cavity for BTW are studied. A physical design method for BTW accelerators, including longitudinal and transversal particle dynamics, is given. Based on above studies, a 9 MeV BTW accelerating tube at 3π/4 mode with frequency 2856 MHz for inspecting large container as radiation source at customs is designed, and a comparison with disk-loaded waveguide accelerating tube is made. The result of research leads to the conclusion that backward traveling wave accelerating structure is preferable. Because BTW has higher effective shunt impedance, shorter filling time and more stable operation

NIKHEF traveling wave monitor: user guide

International Nuclear Information System (INIS)

Sluijk, T.

1984-01-01

The NIKHEF Travelling Wave Monitor (TWM) is a sensitive, non intercepting device to measure beam displacement. The measurement is independent of the beam intensity. The TWM consists of a waveguide assembly and separate electronics assembly. Specifications are given, as well as instructions for use. (Auth./G.J.P.)

Travelling Solitary Wave Solutions for Generalized Time-delayed Burgers-Fisher Equation

International Nuclear Information System (INIS)

Deng Xijun; Han Libo; Li Xi

2009-01-01

In this paper, travelling wave solutions for the generalized time-delayed Burgers-Fisher equation are studied. By using the first-integral method, which is based on the ring theory of commutative algebra, we obtain a class of travelling solitary wave solutions for the generalized time-delayed Burgers-Fisher equation. A minor error in the previous article is clarified. (general)

Traveling wave tube and method of manufacture

Science.gov (United States)

Vancil, Bernard K. (Inventor)

2004-01-01

A traveling wave tube includes a glass or other insulating envelope having a plurality of substantially parallel glass rods supported therewithin which in turn support an electron gun, a collector and an intermediate slow wave structure. The slow wave structure itself provides electrostatic focussing of a central electron beam thereby eliminating the need for focussing magnetics and materially decreasing the cost of construction as well as enabling miniaturization. The slow wave structure advantageously includes cavities along the electron beam through which the r.f. energy is propagated, or a double, interleaved ring loop structure supported by dielectric fins within a ground plane cylinder disposed coaxially within the glass envelope.

Control and dynamics of attosecond electron wave packets in strong laser fields

International Nuclear Information System (INIS)

Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier; Lopez-Martens, R.; Valentin, C.; Balcou, P.; Kazamias, S.; Mauritsson, J.; Gaarde, M.B.; Schafer, K.J.; Mairess, Y.; Wabnitz, H.; Boutu, W.; Salieres, P.

2005-01-01

Full text: Trains of attosecond pulses, emerging from the phase-locking of high-order harmonics generated in a strong laser field are now being routinely produced and characterized in a few laser laboratories. Attosecond pulse trains (APTs) are flexible attosecond sources, since the amplitude and relative phase of the spectral components (the harmonics) can be tailored, allowing us to vary both the duration and the carrier frequency of the pulses. Attosecond pulses interacting with a gas of atoms generate electron wave packets (EWPs), which are temporally localized with approximately the same duration as the attosecond pulses. In contrast to the tunneling electron wave packets giving rise to processes such as high-order harmonic generation and above-threshold-ionization (ATI), the properties of these EWPs are inherited from the attosecond pulses through the single-photon ionization step. Thus the energy and temporal characteristics of the EWPs can be varied independently of the process under investigation, by controlling the properties of the attosecond pulses. This talk will describe two recent experiments done in Lund. First we report on the generation, compression and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. The APT is synthesized from the 13 th to 35 th harmonics of a 35 fs Ti:sapphire laser. The harmonics are generated by focusing the laser beam into a window-less gas cell, filled with argon. To achieve the required on-target attosecond pulses, the harmonics are filtered spatially, using a fixed aperture, and spectrally using aluminum filters. The aluminum filters also serve the purpose of compressing the attosecond pulses, using the negative group-delay dispersion of aluminum to compensate for the intrinsic positive chirp of the attosecond pulses. This experiment demonstrates a practical method for the synthesis and control of attosecond waveforms, and in this case the production of pulses

Magnetized Langmuir wave packets excited by a strong beam-plasma interaction

International Nuclear Information System (INIS)

Pelletier, G.; Sol, H.; Asseo, E.

1988-01-01

The physics of beam-plasma interaction, which has been investigated for a long time mostly in relation with solar bursts, is now more widely invoked in various astrophysical contexts such as pulsars, active galactic nuclei, close binaries, cataclysmic variables, γ bursters, and so on. In these situations the interaction is more likely in the spirit of strong Langmuir turbulence rather than in the spirit of quasilinear theory. Many investigations have been done for two opposite extremes, namely, in very weak and in very strong magnetic fields. Very few properties of the strong Langmuir turbulence are known in the most usual astrophysical situation where the magnetic field plays a significant role but is not strong enough to force the electrons into one-dimensional motion. For this case, we analyze the dynamics of Langmuir wave packets and provide new results about the stability of the solitons against transverse perturbations. It turns out that both the averaged Lagrangian method and the adiabatic perturbation method derived from the inverse scattering transform give exactly the same results (which is not obvious in soliton perturbation theory). In particular, they predict the stability of the solitons as long as the electron gyrofrequency is greater than the plasma frequency (strong magnetic field) and their instability against transverse self-modulation in the opposite case (weak magnetic field); moreover, they allow one to deduce the self-similar collapsing oblate cavitons in the latter case. The laws governing the collapse of the wave packets determine the relaxation of the beam in the surrounding medium and we derive a useful formula giving the power loss of the beam. We outline the astrophysical consequences of this investigation

The non-local Fisher–KPP equation: travelling waves and steady states

International Nuclear Information System (INIS)

Berestycki, Henri; Nadin, Grégoire; Perthame, Benoit; Ryzhik, Lenya

2009-01-01

We consider the Fisher–KPP equation with a non-local saturation effect defined through an interaction kernel φ(x) and investigate the possible differences with the standard Fisher–KPP equation. Our first concern is the existence of steady states. We prove that if the Fourier transform φ-circumflex(ξ) is positive or if the length σ of the non-local interaction is short enough, then the only steady states are u ≡ 0 and u ≡ 1. Next, we study existence of the travelling waves. We prove that this equation admits travelling wave solutions that connect u = 0 to an unknown positive steady state u ∞ (x), for all speeds c ≥ c * . The travelling wave connects to the standard state u ∞ (x) ≡ 1 under the aforementioned conditions: φ-circumflex(ξ) > 0 or σ is sufficiently small. However, the wave is not monotonic for σ large

Exact traveling wave solutions of modified KdV-Zakharov-Kuznetsov equation and viscous Burgers equation.

Science.gov (United States)

Islam, Md Hamidul; Khan, Kamruzzaman; Akbar, M Ali; Salam, Md Abdus

2014-01-01

Mathematical modeling of many physical systems leads to nonlinear evolution equations because most physical systems are inherently nonlinear in nature. The investigation of traveling wave solutions of nonlinear partial differential equations (NPDEs) plays a significant role in the study of nonlinear physical phenomena. In this article, we construct the traveling wave solutions of modified KDV-ZK equation and viscous Burgers equation by using an enhanced (G '/G) -expansion method. A number of traveling wave solutions in terms of unknown parameters are obtained. Derived traveling wave solutions exhibit solitary waves when special values are given to its unknown parameters. 35C07; 35C08; 35P99.

Traveling waves in the discrete fast buffered bistable system.

Science.gov (United States)

Tsai, Je-Chiang; Sneyd, James

2007-11-01

We study the existence and uniqueness of traveling wave solutions of the discrete buffered bistable equation. Buffered excitable systems are used to model, among other things, the propagation of waves of increased calcium concentration, and discrete models are often used to describe the propagation of such waves across multiple cells. We derive necessary conditions for the existence of waves, and, under some restrictive technical assumptions, we derive sufficient conditions. When the wave exists it is unique and stable.

Wave packets in quantum cosmology and the cosmological constant

International Nuclear Information System (INIS)

Kiefer, C.

1990-01-01

Wave packets are constructed explicitly in minisuperspace of quantum gravity corresponding to a Friedmann universe containing a conformally coupled scalar field with and without a cosmological constant. The construction is performed in close analogy to the case of constructing coherent states in quantum mechanics. Various examples are also depicted numerically. The corresponding lorentzian path integrals are evaluated for some cases. It is emphasized that the new concept of time in quantum gravity demands the imposition of a kind of boundary conditions not encountered in quantum gravity demands the imposition of a kind of boundary conditions not encountered in quantum mechanics. Connection is also made to recent investigations predicting a vanishing cosmological constant. It is shown that the fact of whether this result is generic or not depends on where the boundary conditions are imposed in the configuration space. (orig.)

Semiclassical wave packet treatment of scattering resonances: application to the delta zero-point energy effect in recombination reactions.

Science.gov (United States)

Vetoshkin, Evgeny; Babikov, Dmitri

2007-09-28

For the first time Feshbach-type resonances important in recombination reactions are characterized using the semiclassical wave packet method. This approximation allows us to determine the energies, lifetimes, and wave functions of the resonances and also to observe a very interesting correlation between them. Most important is that this approach permits description of a quantum delta-zero-point energy effect in recombination reactions and reproduces the anomalous rates of ozone formation.

K-Band Traveling-Wave Tube Amplifier

Science.gov (United States)

Force, Dale A.; Simons, Rainee N.; Peterson, Todd T.; Spitsen, Paul C.

2010-01-01

A new space-qualified, high-power, high-efficiency, K-band traveling-wave tube amplifier (TWTA) will provide high-rate, high-capacity, direct-to-Earth communications for science data and video gathered by the Lunar Reconnaissance Orbiter (LRO) during its mission. Several technological advances were responsible for the successful demonstration of the K-band TWTA.

Quantum wave packet revival in two-dimensional circular quantum wells with position-dependent mass

International Nuclear Information System (INIS)

Schmidt, Alexandre G.M.; Azeredo, Abel D.; Gusso, A.

2008-01-01

We study quantum wave packet revivals on two-dimensional infinite circular quantum wells (CQWs) and circular quantum dots with position-dependent mass (PDM) envisaging a possible experimental realization. We consider CQWs with radially varying mass, addressing particularly the cases where M(r)∝r w with w=1,2, or -2. The two PDM Hamiltonians currently allowed by theory were analyzed and we were able to construct a strong theoretical argument favoring one of them

Heat driven thermoacoustic cooler based on traveling-standing wave

International Nuclear Information System (INIS)

Kang Huifang; Zhou Gang; Li Qing

2010-01-01

This paper presents a heat driven thermoacoustic cooler system without any moving part. It consists of a thermoacoustic engine and a thermoacoustic cooler, and the former is the driving source of the latter. Both the engine and the cooler are located in one loop tube coupled with a resonator tube, and the acoustic power produced by the engine is used to drive the cooler directly. Both regenerators of the engine and the cooler are located in the near region of the pressure antinode, and operate in traveling-standing wave phase region. In the engine's regenerator, both components of the standing wave and the traveling wave realize the conversion from heat to acoustic energy. This improves the efficiency of the engine. In the cooler's regenerator, both components of the traveling wave and the standing wave pump heat from the cold end. This improves the efficiency of the cooler. At the operating point with a mean pressure of 22 bar, helium as working gas, a frequency of 234 Hz, and a heating power of 300 W, the experimental cooler provides a no-load temperature of -30 deg. C and a cooling power of 40 W at the cooling temperature of 0 deg. C. The total length of this cooler system is less than 1 m, which shows a good prospect for the domestic cooler system in room-temperature cooling such as food refrigeration and air-conditioning.

New Exact Travelling Wave and Periodic Solutions of Discrete Nonlinear Schroedinger Equation

International Nuclear Information System (INIS)

Yang Qin; Dai Chaoqing; Zhang Jiefang

2005-01-01

Some new exact travelling wave and period solutions of discrete nonlinear Schroedinger equation are found by using a hyperbolic tangent function approach, which was usually presented to find exact travelling wave solutions of certain nonlinear partial differential models. Now we can further extend the new algorithm to other nonlinear differential-different models.

Wave packet dynamics, time scales and phase diagram in the IBM-Lipkin-Meshkov-Glick model

Science.gov (United States)

Castaños, Octavio; de los Santos, Francisco; Yáñez, Rafael; Romera, Elvira

2018-02-01

We derive the phase diagram of a scalar two-level boson model by studying the equilibrium and stability properties of its energy surface. The plane of control parameters is enlarged with respect to previous studies. We then analyze the time evolution of wave packets centered around the ground state at various quantum phase transition boundary lines. In particular, classical and revival times are computed numerically.

Ultra-High-Speed Travelling Wave Protection of Transmission Line Using Polarity Comparison Principle Based on Empirical Mode Decomposition

Directory of Open Access Journals (Sweden)

Dong Wang

2015-01-01

Full Text Available The traditional polarity comparison based travelling wave protection, using the initial wave information, is affected by initial fault angle, bus structure, and external fault. And the relationship between the magnitude and polarity of travelling wave is ignored. Because of the protection tripping and malfunction, the further application of this protection principle is affected. Therefore, this paper presents an ultra-high-speed travelling wave protection using integral based polarity comparison principle. After empirical mode decomposition of the original travelling wave, the first-order intrinsic mode function is used as protection object. Based on the relationship between the magnitude and polarity of travelling wave, this paper demonstrates the feasibility of using travelling wave magnitude which contains polar information as direction criterion. And the paper integrates the direction criterion in a period after fault to avoid wave head detection failure. Through PSCAD simulation with the typical 500 kV transmission system, the reliability and sensitivity of travelling wave protection were verified under different factors’ affection.

Bifurcations of Exact Traveling Wave Solutions for (2+1)-Dimensional HNLS Equation

International Nuclear Information System (INIS)

Xu Yuanfen

2012-01-01

For the (2+1)-Dimensional HNLS equation, what are the dynamical behavior of its traveling wave solutions and how do they depend on the parameters of the systems? This paper will answer these questions by using the methods of dynamical systems. Ten exact explicit parametric representations of the traveling wave solutions are given. (general)

Fifth-order amplitude equation for traveling waves in isothermal double diffusive convection

International Nuclear Information System (INIS)

Mendoza, S.; Becerril, R.

2009-01-01

Third-order amplitude equations for isothermal double diffusive convection are known to hold the tricritical condition all along the oscillatory branch, predicting that stable traveling waves exist Only at the onset of the instability. In order to properly describe stable traveling waves, we perform a fifth-order calculation and present explicitly the corresponding amplitude equation.

Monostable traveling waves for a time-periodic and delayed nonlocal reaction-diffusion equation

Science.gov (United States)

Li, Panxiao; Wu, Shi-Liang

2018-04-01

This paper is concerned with a time-periodic and delayed nonlocal reaction-diffusion population model with monostable nonlinearity. Under quasi-monotone or non-quasi-monotone assumptions, it is known that there exists a critical wave speed c_*>0 such that a periodic traveling wave exists if and only if the wave speed is above c_*. In this paper, we first prove the uniqueness of non-critical periodic traveling waves regardless of whether the model is quasi-monotone or not. Further, in the quasi-monotone case, we establish the exponential stability of non-critical periodic traveling fronts. Finally, we illustrate the main results by discussing two types of death and birth functions arising from population biology.

Traveling waves in a diffusive predator-prey model with holling type-III functional response

International Nuclear Information System (INIS)

Li Wantong; Wu Shiliang

2008-01-01

We establish the existence of traveling wave solutions and small amplitude traveling wave train solutions for a reaction-diffusion system based on a predator-prey model with Holling type-III functional response. The analysis is in the three-dimensional phase space of the nonlinear ordinary differential equation system given by the diffusive predator-prey system in the traveling wave variable. The methods used to prove the results are the shooting argument, invariant manifold theory and the Hopf bifurcation theorem

Smooth and non-smooth travelling waves in a nonlinearly dispersive Boussinesq equation

International Nuclear Information System (INIS)

Shen Jianwei; Xu Wei; Lei Youming

2005-01-01

The dynamical behavior and special exact solutions of nonlinear dispersive Boussinesq equation (B(m,n) equation), u tt -u xx -a(u n ) xx +b(u m ) xxxx =0, is studied by using bifurcation theory of dynamical system. As a result, all possible phase portraits in the parametric space for the travelling wave system, solitary wave, kink and anti-kink wave solutions and uncountably infinite many smooth and non-smooth periodic wave solutions are obtained. It can be shown that the existence of singular straight line in the travelling wave system is the reason why smooth waves converge to cusp waves, finally. When parameter are varied, under different parametric conditions, various sufficient conditions guarantee the existence of the above solutions are given

Effect of switching-off of a plasma medium on a traveling wave

International Nuclear Information System (INIS)

Kalluri, D.K.

1989-01-01

It is known that a sudden creation of a plasma medium of plasma frequency ω ρ splits a traveling wave of frequency ω o into two new waves of frequencies. The negative value for the frequency here indicates a reflected wave. The effect of a sudden collapse of the plasma medium, on a travelling wave of frequency ω o is shown to be the creation of two new waves of frequencies. A numerical solution is obtained for the case of a gradual collapse of the plasma medium. For the case of a slow decay of the particle density an approximate WKB type solution is obtained. Several results are presented

Quantum wave packet revival in two-dimensional circular quantum wells with position-dependent mass

Energy Technology Data Exchange (ETDEWEB)

Schmidt, Alexandre G.M. [Departamento de Ciencias Exatas, Polo Universitario de Volta Redonda-Universidade Federal Fluminense, Av. dos Trabalhadores 420, Volta Redonda RJ, CEP 27255-125 (Brazil)], E-mail: agmschmidt@gmail.com; Azeredo, Abel D. [Departamento de Fisica-Universidade Federal de Roraima, Av. Cap. Ene Garcez 2413, Boa Vista RR, CEP 69304-000 (Brazil)], E-mail: aazeredo@gmail.com; Gusso, A. [Departamento de Ciencias Exatas e Tecnologicas-Universidade Estadual de Santa Cruz, km 16 Rodovia Ilheus-Itabuna, Ilheus BA, CEP 45662-000 (Brazil)], E-mail: agusso@uesc.br

2008-04-14

We study quantum wave packet revivals on two-dimensional infinite circular quantum wells (CQWs) and circular quantum dots with position-dependent mass (PDM) envisaging a possible experimental realization. We consider CQWs with radially varying mass, addressing particularly the cases where M(r){proportional_to}r{sup w} with w=1,2, or -2. The two PDM Hamiltonians currently allowed by theory were analyzed and we were able to construct a strong theoretical argument favoring one of them.

Development of Traveling Wave Actuators Using Waveguides of Different Geometrical Forms

Directory of Open Access Journals (Sweden)

Ramutis Bansevicius

2016-01-01

Full Text Available The paper covers the research and development of piezoelectric traveling wave actuators using different types of the waveguides. The introduced piezoelectric actuators can be characterized by specific areas of application, different resolution, and torque. All presented actuators are ultrasonic resonant devices and they were developed to increase amplitudes of the traveling wave oscillations of the contact surface. Three different waveguides are introduced, that is, symmetrical, asymmetrical, and cone type waveguide. A piezoelectric ring with the sectioned electrodes is used to excite traveling wave oscillations for all actuators. Operating principle, electrode pattern, and excitation regimes of piezoelectric actuators are described. A numerical modelling of the actuators was performed to validate the operating principle and to calculate trajectories of the contact points motion. Prototype actuators were made and experimental study was performed. The results of numerical and experimental analysis are discussed.

New traveling wave solutions to AKNS and SKdV equations

International Nuclear Information System (INIS)

Ozer, Teoman

2009-01-01

We analyze the traveling wave solutions of Ablowitz-Kaup-Newell-Segur (AKNS) and Schwarz-Korteweg-de Vries (SKdV) equations. As the solution method for differential equations we consider the improved tanh approach. This approach provides to transform the partial differential equation into the ordinary differential equation and then obtain the new families of exact solutions based on the solutions of the Riccati equation. The different values of the coefficients of the Riccati equation allow us to obtain new type of traveling wave solutions to AKNS and SKdV equations.

The motion of a Dirac wave packet in a gravitational field

International Nuclear Information System (INIS)

Pietropaolo, F.; Toller, M.

1983-01-01

It is studied the motion of a test particle provided with spin in a gravitational field with a nonvanishing torsion with the aim of clarifying the relationship between the approach based on the balance equations for energy, momentum and angular momentum and the approach based directly on a semiclassical approximation of the Dirac equation. The balance equations in the pole-dipole approximation are applied to a Dirac wave packet minimally coupled to the gravitational field and it is shown that, in this particular case, it is possible to compute the dipole moments of energy current, which are essential for a correct calculation of the motion of the centre of the particle and of the precession of its spin

Wave packet dynamics for a system with position and time-dependent effective mass in an infinite square well

Energy Technology Data Exchange (ETDEWEB)

Vubangsi, M.; Tchoffo, M.; Fai, L. C. [Mesoscopic and Multilayer Structures Laboratory, Physics Department, University of Dschang, P.O. Box 417 Dschang (Cameroon); Pisma’k, Yu. M. [Department of Theoretical Physics, Saint Petersburg State University, Saint Petersburg (Russian Federation)

2015-12-15

The problem of a particle with position and time-dependent effective mass in a one-dimensional infinite square well is treated by means of a quantum canonical formalism. The dynamics of a launched wave packet of the system reveals a peculiar revival pattern that is discussed. .

Travelling wave solutions in a class of generalized Korteweg-de Vries equation

International Nuclear Information System (INIS)

Shen Jianwei; Xu Wei

2007-01-01

In this paper, we consider a new generalization of KdV equation u t = u x u l-2 + α[2u xxx u p + 4pu p-1 u x u xx + p(p - 1)u p-2 (u x ) 3 ] and investigate its bifurcation of travelling wave solutions. From the above analysis, we know that there exists compacton and cusp waves in the system. We explain the reason that these non-smooth travelling wave solution arise by using the bifurcation theory

PZT Thin Film Piezoelectric Traveling Wave Motor

Science.gov (United States)

Shen, Dexin; Zhang, Baoan; Yang, Genqing; Jiao, Jiwei; Lu, Jianguo; Wang, Weiyuan

1995-01-01

With the development of micro-electro-mechanical systems (MEMS), its various applications are attracting more and more attention. Among MEMS, micro motors, electrostatic and electromagnetic, are the typical and important ones. As an alternative approach, the piezoelectric traveling wave micro motor, based on thin film material and integrated circuit technologies, circumvents many of the drawbacks of the above mentioned two types of motors and displays distinct advantages. In this paper we report on a lead-zirconate-titanate (PZT) piezoelectric thin film traveling wave motor. The PZT film with a thickness of 150 micrometers and a diameter of 8 mm was first deposited onto a metal substrate as the stator material. Then, eight sections were patterned to form the stator electrodes. The rotor had an 8 kHz frequency power supply. The rotation speed of the motor is 100 rpm. The relationship of the friction between the stator and the rotor and the structure of the rotor on rotation were also studied.

Probability distribution of wave packet delay time for strong overlapping of resonance levels

International Nuclear Information System (INIS)

Lyuboshits, V.L.

1983-01-01

Time behaviour of nuclear reactions in the case of high level densities is investigated basing on the theory of overlapping resonances. In the framework of a model of n equivalent channels an analytical expression is obtained for the probability distribution function for wave packet delay time at the compound nucleus production. It is shown that at strong overlapping of the resonance levels the relative fluctuation of the delay time is small at the stage of compound nucleus production. A possible increase in the duration of nuclear reactions with the excitation energy rise is discussed

Stability of a family of travelling wave solutions in a feedforward chain of phase oscillators

International Nuclear Information System (INIS)

Lanford, O E III; Mintchev, S M

2015-01-01

Travelling waves are an important class of signal propagation phenomena in extended systems with a preferred direction of information flow. We study the generation of travelling waves in unidirectional chains of coupled oscillators communicating via a phase-dependent pulse-response interaction borrowed from mathematical neuroscience. Within the context of such systems, we develop a widely applicable, jointly numerical and analytical methodology for deducing existence and stability of periodic travelling waves. We provide careful numerical studies that support the existence of a periodic travelling wave solution as well as the asymptotic relaxation of a single oscillator to the wave when it is forced with the wave profile. Using this evidence as an assumption, we analytically prove global stability of waves in the infinite chain, with respect to initial perturbations of downstream sites. This rigorous stability result suggests that asymptotic relaxation to the travelling wave occurs even when the forcing is perturbed from the wave profile, a property of the motivating system that is supported by previous work as well as the convergence of the more sophisticated numerical algorithm that we propose in order to compute a high-precision approximation to the solution. We provide additional numerical studies that show that the wave is part of a one-parameter family, and we illustrate the structural robustness of this family with respect to changes in the coupling strength. (paper)

New exact travelling wave solutions for two potential coupled KdV equations with symbolic computation

International Nuclear Information System (INIS)

Yang Zonghang

2007-01-01

We find new exact travelling wave solutions for two potential KdV equations which are presented by Foursov [Foursov MV. J Math Phys 2000;41:6173-85]. Compared with the extended tanh-function method, the algorithm used in our paper can obtain some new kinds of exact travelling wave solutions. With the aid of symbolic computation, some novel exact travelling wave solutions of the potential KdV equations are constructed

Plasma particle drifts due to traveling waves with cyclotron frequencies

International Nuclear Information System (INIS)

Hatakeyama, Rikizo; Sato, Naoyuki; Sato, Noriyoshi

1991-01-01

A particle orbit theory yields that traveling waves with cyclotron frequencies give rise to charged particle drifts perpendicular both to the wave propagation and external magnetic field lines. The result is applicable to particle-flux control of magnetized plasmas. (author)

Concentration field in traveling-wave and stationary convection in fluid mixtures

International Nuclear Information System (INIS)

Eaton, K.D.; Ohlsen, D.R.; Yamamoto, S.Y.; Surko, C.M.; Barten, W.; Luecke, M.; Kamps, M.; Kolodner, P.

1991-01-01

By comparison of measurements of shadowgraph images of convection in ethanol-water mixtures with the results of recent numerical calculations, we study the role of the concentration field in traveling-wave and stationary convection. The results confirm the existence of a large concentration contrast between adjacent traveling-wave convection rolls. This concentration modulation, which decreases as the Rayleigh number is increased and the transition to stationary convection is approached, is fundamental to the translation of the pattern

Traveling-wave piezoelectric linear motor part II: experiment and performance evaluation.

Science.gov (United States)

Ting, Yung; Li, Chun-Chung; Chen, Liang-Chiang; Yang, Chieh-Min

2007-04-01

This article continues the discussion of a traveling-wave piezoelectric linear motor. Part I of this article dealt with the design and analysis of the stator of a traveling-wave piezoelectric linear motor. In this part, the discussion focuses on the structure and modeling of the contact layer and the carriage. In addition, the performance analysis and evaluation of the linear motor also are dealt with in this study. The traveling wave is created by stator, which is constructed by a series of bimorph actuators arranged in a line and connected to form a meander-line structure. Analytical and experimental results of the performance are presented and shown to be almost in agreement. Power losses due to friction and transmission are studied and found to be significant. Compared with other types of linear motors, the motor in this study is capable of supporting heavier loads and provides a larger thrust force.

Travelling waves in heterogeneous media

OpenAIRE

Boden, Adam

2013-01-01

In this thesis we study the existence of travelling wave type solutions for a reaction diffusion equation in R2 with a nonlinearity which depends periodically on the spatial variable. Specifically we will consider a particular class of nonlinearities where we treat the coefficient of the linear term as a parameter. For this class of nonlinearities we formulate the problem as a spatial dynamical system and use a centre manifold reduction to find conditions on the parameter and nonlinearity for...

Friction Factor Correlation for Regenerator Working in a Travelling-Wave Thermoacoustic System

Directory of Open Access Journals (Sweden)

Fatimah A. Z. Mohd Saat

2017-03-01

Full Text Available Regenerator is a porous solid structure which is important in the travelling-wave thermoacoustic system. It provides the necessary contact surface and thermal capacity for the working gas to undergo a thermodynamic cycle under acoustic oscillatory flow conditions. However, it also creates a pressure drop that could degrade the overall system performance. Ideally, in a travelling-wave system, the phase angle between oscillating pressure and velocity in the regenerator should be zero, or as close to zero as possible. In this study, the hydrodynamic condition of a regenerator has been investigated both experimentally (in a purpose-built rig providing a travelling-wave phasing and numerically. A two-dimensional ANSYS FLUENT CFD model, capturing the important features of the experimental conditions, has been developed. The findings suggest that a steady-state correlation, commonly used in designing thermoacoustic systems, is applicable provided that the travelling-wave phase angle is maintained. However, for coarse mesh regenerators, the results show interesting “phase shifting” phenomena, which may limit the correlation validity. Current experimental and CFD studies are important for predicting the viscous losses in future models of thermoacoustic systems.

A tuning method for nonuniform traveling-wave accelerating structures

International Nuclear Information System (INIS)

Gong Cunkui; Zheng Shuxin; Shao Jiahang; Jia Xiaoyu; Chen Huaibi

2013-01-01

The tuning method of uniform traveling-wave structures based on non-resonant perturbation field distribution measurement has been widely used in tuning both constant-impedance and constant-gradient structures. In this paper, the method of tuning nonuniform structures is proposed on the basis of the above theory. The internal reflection coefficient of each cell is obtained from analyzing the normalized voltage distribution. A numerical simulation of tuning process according to the coupled cavity chain theory has been done and the result shows each cell is in right phase advance after tuning. The method will be used in the tuning of a disk-loaded traveling-wave structure being developed at the Accelerator Laboratory, Tsinghua University. (authors)

A traveling wave direct energy converter for a D-3He fusion reactor

International Nuclear Information System (INIS)

Sato, K.; Katayama, H.; Miyawaki, F.; Tajima, T.

1994-01-01

A concept of a traveling wave direct energy converter (TWDEC) is developed for 14.7-MeV fusion protons based on the principle of a backward wave oscillator. Separation of fusion protons from thermal ions is accomplished by using ExB ion drift. Energy conversion rate up to 0.87 is attained by applying three-stage modulation of the proton beam. A one-dimensional particle-circuit code is developed to examine self-excitation of the traveling wave and its stability under loading. Electrostatic wave with a fixed frequency is excited spontaneously, and stability of the wave is ensured under loading. (author)

On the development and evolution of nonlinear ion acoustic wave packets

Directory of Open Access Journals (Sweden)

A. M. Hamza

2005-09-01

Full Text Available A simple model of ion fluctuations (ion acoustic and ion cyclotron fluctuations for example driven by an electron current which leads to intermittent fluctuations when the linear growth rate exceeds the wave packet dispersion rate is analized. The normalized fluctuation amplitude eφ0/T can be much larger than the mass ratio (me/mi level predicted by the conventional quasilinear theory or Manheimer's theory (see references in this document, and where φ0 represents the amplitude of the main peak of the ion fluctuations. Although the ion motion is linear, intermittency is produced by the strong nonlinear electron response, which causes the electron momentum input to the ion fluctuations to be spatially localized. We treat the 1-D case because it is especially simple from an intuitive and analytical point of view, but it is readily apparent and one can put forward the conjecture that the effect occurs in a three dimensional magnetized plasma. The 1-D analysis, as shown in this manuscript will clearly help identify the subtle difference between turbulence as conventionally understood and intermittency as it occurs in space and laboratory plasmas. Keywords. Meteorology and atmospheric dynamics (Turbulence – Ionosphere (Wave-particles interactions – Space plasma physics (Waves and instabilities

Spike-like solitary waves in incompressible boundary layers driven by a travelling wave.

Science.gov (United States)

Feng, Peihua; Zhang, Jiazhong; Wang, Wei

2016-06-01

Nonlinear waves produced in an incompressible boundary layer driven by a travelling wave are investigated, with damping considered as well. As one of the typical nonlinear waves, the spike-like wave is governed by the driven-damped Benjamin-Ono equation. The wave field enters a completely irregular state beyond a critical time, increasing the amplitude of the driving wave continuously. On the other hand, the number of spikes of solitary waves increases through multiplication of the wave pattern. The wave energy grows in a sequence of sharp steps, and hysteresis loops are found in the system. The wave energy jumps to different levels with multiplication of the wave, which is described by winding number bifurcation of phase trajectories. Also, the phenomenon of multiplication and hysteresis steps is found when varying the speed of driving wave as well. Moreover, the nature of the change of wave pattern and its energy is the stability loss of the wave caused by saddle-node bifurcation.

Long-range traveling waves of activity triggered by local dichoptic stimulation in V1 of behaving monkeys

Science.gov (United States)

Yang, Zhiyong; Heeger, David J.; Blake, Randolph

2014-01-01

Traveling waves of cortical activity, in which local stimulation triggers lateral spread of activity to distal locations, have been hypothesized to play an important role in cortical function. However, there is conflicting physiological evidence for the existence of spreading traveling waves of neural activity triggered locally. Dichoptic stimulation, in which the two eyes view dissimilar monocular patterns, can lead to dynamic wave-like fluctuations in visual perception and therefore, provides a promising means for identifying and studying cortical traveling waves. Here, we used voltage-sensitive dye imaging to test for the existence of traveling waves of activity in the primary visual cortex of awake, fixating monkeys viewing dichoptic stimuli. We find clear traveling waves that are initiated by brief, localized contrast increments in one of the monocular patterns and then, propagate at speeds of ∼30 mm/s. These results demonstrate that under an appropriate visual context, circuitry in visual cortex in alert animals is capable of supporting long-range traveling waves triggered by local stimulation. PMID:25343785

Study of a high-order-mode gyrotron traveling-wave amplifier

International Nuclear Information System (INIS)

Chiu, C. C.; Tsai, C. Y.; Kao, S. H.; Chu, K. R.; Barnett, L. R.; Luhmann, N. C. Jr.

2010-01-01

Physics and performance issues of a TE 01 -mode gyrotron traveling-wave amplifier are studied in theory. For a high order mode, absolute instabilities on neighboring modes at the fundamental and higher cyclotron harmonic frequencies impose severe constraints to the device capability. Methods for their stabilization are outlined, on the basis of which the performance characteristics are examined in a multidimensional parameter space under the marginal stability criterion. The results demonstrate the viability of a high-order-mode traveling-wave amplifier and provide a roadmap for design tradeoffs among power, bandwidth, and efficiency. General trends are observed and illustrated with specific examples.

Detuning effect in a traveling wave type linac

International Nuclear Information System (INIS)

Arai, S.; Kobayashi, K.; Tojyo, E.; Yoshida, K.

1979-01-01

A 15-MeV traveling wave type electron linac is used as the injector for the 1.3-GeV electron synchrotron at the Institute for Nuclear Study, University of Tokyo. The resonant frequency of this accelerator waveguide is 2758.00 MHz at 30 0 C. The performance of the linac,however, is improved when it is operated with a frequency which is higher than the design value by 200 to 400 KHz. It is shown that the detuning due to the beam loading is serious in such an accelerator waveguide in which the buncher and regular sections are combined, and the detuning effect can approximately be compensated by changing the operating frequency. The detuning effect in the traveling wave-type accelerator waveguide was studied both from experimental and theoretical aspects by using a short test waveguide

Dynamics and bifurcations of travelling wave solutions of R (m, n ...

Indian Academy of Sciences (India)

The qualitative change in the physical structures of these waves is shown to depend on the systemic parameters. Under different regions of parametric spaces, various sufficient conditions to guarantee the existence of the above waves are given. Moreover, some explicit exact parametric representations of travelling wave ...

Theoretical investigation of a travelling-wave rf gun

International Nuclear Information System (INIS)

Gao, J.

1991-12-01

A travelling-wave type rf gun (TW gun) is investigated theoretically. Analytical formulae concerning energy gain, energy spread, and transverse emittance are derived. After showing the corresponding formulae for the standing-wave rf gun (SW gun), comparisons are made between the two types of rf gun. Finally, some numerical results are calculated to demonstrate further the behaviours of the TW gun, and to compare with those from analytical formulae. (author) 11 refs.; 27 figs

Exact travelling wave solutions of the (3+1)-dimensional mKdV-ZK ...

Indian Academy of Sciences (India)

In this paper, the new generalized (′/)-expansion method is executed to find the travelling wave solutions of the (3+1)-dimensional mKdV-ZK equation and the (1+1)-dimensional compound KdVB equation. The efficiency of this method for finding exact and travelling wave solutions has been demonstrated. It is shown ...

Development of a fishbone travelling wave antenna for LHD

International Nuclear Information System (INIS)

Takase, Y.; Ejiri, A.; Shiraiwa, S.

2002-10-01

A travelling wave antenna in the ion cyclotron range of frequencies (ICRF) is being developed for LHD, motivated by the need to provide a capability for rotational transform profile control by noninductively driven current. Stability calculations suggest that it is possible to increase the beta limit and obtain access to the second stability regime by controlling the rotational transform profile. Current drive by the ICRF fast wave (magnetosonic wave) can be used for such a purpose. (author)

Applications of exact traveling wave solutions of Modified Liouville and the Symmetric Regularized Long Wave equations via two new techniques

Science.gov (United States)

Lu, Dianchen; Seadawy, Aly R.; Ali, Asghar

2018-06-01

In this current work, we employ novel methods to find the exact travelling wave solutions of Modified Liouville equation and the Symmetric Regularized Long Wave equation, which are called extended simple equation and exp(-Ψ(ξ))-expansion methods. By assigning the different values to the parameters, different types of the solitary wave solutions are derived from the exact traveling wave solutions, which shows the efficiency and precision of our methods. Some solutions have been represented by graphical. The obtained results have several applications in physical science.

Classification of All Single Travelling Wave Solutions to Calogero-Degasperis-Focas Equation

International Nuclear Information System (INIS)

Liu Chengshi

2007-01-01

Under the travelling wave transformation, Calogero-Degasperis-Focas equation is reduced to an ordinary differential equation. Using a symmetry group of one parameter, this ODE is reduced to a second-order linear inhomogeneous ODE. Furthermore, we apply the change of the variable and complete discrimination system for polynomial to solve the corresponding integrals and obtained the classification of all single travelling wave solutions to Calogero-Degasperis-Focas equation.

Optimal Design of a Traveling-Wave Kinetic Inductance Amplifier Operated in Three-Wave Mixing Mode

Science.gov (United States)

Erickson, Robert; Bal, Mustafa; Ku, Ksiang-Sheng; Wu, Xian; Pappas, David

In the presence of a DC bias, an injected pump, of frequency fP, and a signal, of frequency fS, undergo parametric three-way mixing (3WM) within a traveling-wave kinetic inductance (KIT) amplifier, producing an idler product of frequency fI =fP -fS . Periodic frequency stops are engineered into the coplanar waveguide of the device to enhance signal amplification. With fP placed just above the first frequency stop gap, 3WM broadband signal gain is achieved with maximum gain at fS =fP / 2 . Within a theory of the dispersion of traveling waves in the presence of these engineered loadings, which accounts for this broadband signal gain, we show how an optimal frequency-stop design may be constructed to achieve maximum signal amplification. The optimization approach we describe can be applied to the design of other nonlinear traveling-wave parametric amplifiers. This work was supported by the Army Research Office and the Laboratory for Physical Sciences under EAO221146, EAO241777, and the NIST Quantum Initiative. RPE acknowledges Grant 60NANB14D024 from the US Department of Commerce, NIST.

High-frequency homogenization for travelling waves in periodic media.

Science.gov (United States)

Harutyunyan, Davit; Milton, Graeme W; Craster, Richard V

2016-07-01

We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 1 plus a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 2 . We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω 1 = ω 2 and [Formula: see text] where Λ =(λ 1 λ 2 …λ d ) is the periodicity cell of the medium and for any two vectors [Formula: see text] the product a ⊙ b is defined to be the vector ( a 1 b 1 , a 2 b 2 ,…, a d b d ). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

Chaotic operation and chaos control of travelling wave ultrasonic motor.

Science.gov (United States)

Shi, Jingzhuo; Zhao, Fujie; Shen, Xiaoxi; Wang, Xiaojie

2013-08-01

The travelling wave ultrasonic motor, which is a nonlinear dynamic system, has complex chaotic phenomenon with some certain choices of system parameters and external inputs, and its chaotic characteristics have not been studied until now. In this paper, the preliminary study of the chaos phenomenon in ultrasonic motor driving system has been done. The experiment of speed closed-loop control is designed to obtain several groups of time sampling data sequence of the amplitude of driving voltage, and phase-space reconstruction is used to analyze the chaos characteristics of these time sequences. The largest Lyapunov index is calculated and the result is positive, which shows that the travelling wave ultrasonic motor has chaotic characteristics in a certain working condition Then, the nonlinear characteristics of travelling wave ultrasonic motor are analyzed which includes Lyapunov exponent map, the bifurcation diagram and the locus of voltage relative to speed based on the nonlinear chaos model of a travelling wave ultrasonic motor. After that, two kinds of adaptive delay feedback controllers are designed in this paper to control and suppress chaos in USM speed control system. Simulation results show that the method can control unstable periodic orbits, suppress chaos in USM control system. Proportion-delayed feedback controller was designed following and arithmetic of fuzzy logic was used to adaptively adjust the delay time online. Simulation results show that this method could fast and effectively change the chaos movement into periodic or fixed-point movement and make the system enter into stable state from chaos state. Finally the chaos behavior was controlled. Copyright © 2013 Elsevier B.V. All rights reserved.

The origin of traveling waves in an emperor penguin huddle

International Nuclear Information System (INIS)

Gerum, R C; Fabry, B; Metzner, C; Zitterbart, D P; Beaulieu, M; Ancel, A

2013-01-01

Emperor penguins breed during the Antarctic winter and have to endure temperatures as low as −50 °C and wind speeds of up to 200 km h −1 . To conserve energy, they form densely packed huddles with a triangular lattice structure. Video recordings from previous studies revealed coordinated movements in regular wave-like patterns within these huddles. It is thought that these waves are triggered by individual penguins that locally disturb the huddle structure, and that the traveling wave serves to remove the lattice defects and restore order. The mechanisms that govern wave propagation are currently unknown, however. Moreover, it is unknown if the waves are always triggered by the same penguin in a huddle. Here, we present a model in which the observed wave patterns emerge from simple rules involving only the interactions between directly neighboring individuals, similar to the interaction rules found in other jammed systems, e.g. between cars in a traffic jam. Our model predicts that a traveling wave can be triggered by a forward step of any individual penguin located within a densely packed huddle. This prediction is confirmed by optical flow velocimetry of the video recordings of emperor penguins in their natural habitat. (paper)

Preparing isolated vibrational wave packets with light-induced molecular potentials by chirped laser pulses

Science.gov (United States)

Vatasescu, Mihaela

2012-05-01

We consider a specific wave packet preparation arising from the control of tunneling in the 0g-(6s,6p3/2) double well potential of a Cs2 cold molecule with chirped laser pulses. Such a possibility to manipulate the population dynamics in the 0g-(6s,6p3/2) potential appears in a pump-dump scheme designed to form cold molecules by photoassociation of two cold cesium atoms. The initial population in the 0g-(6s,6p3/2) double well is a wave packet prepared in the outer well at large interatomic distances (94 a0) by a photoassociation step with a first chirped pulse, being a superposition of several vibrational states whose energies surround the energy of a tunneling resonance. Our present work is focused on a second delayed chirped pulse, coupling the 0g-(6s,6p3/2) surface with the a3Σu+(6s,6s) one in the zone of the double well barrier (15 a0) and creating deeply bound cold molecules in the a3Σu+(6s,6s) state. We explore the parameters choice (intensity, duration, chirp rate and sign) for this second pulse, showing that picoseconds pulses with a negative chirp can lead to trapping of population in the inner well in strongly bound vibrational states, out of the resonant tunneling able to transfer it back to the outer well.

Study on monostable and bistable reaction-diffusion equations by iteration of travelling wave maps

Science.gov (United States)

Yi, Taishan; Chen, Yuming

2017-12-01

In this paper, based on the iterative properties of travelling wave maps, we develop a new method to obtain spreading speeds and asymptotic propagation for monostable and bistable reaction-diffusion equations. Precisely, for Dirichlet problems of monostable reaction-diffusion equations on the half line, by making links between travelling wave maps and integral operators associated with the Dirichlet diffusion kernel (the latter is NOT invariant under translation), we obtain some iteration properties of the Dirichlet diffusion and some a priori estimates on nontrivial solutions of Dirichlet problems under travelling wave transformation. We then provide the asymptotic behavior of nontrivial solutions in the space-time region for Dirichlet problems. These enable us to develop a unified method to obtain results on heterogeneous steady states, travelling waves, spreading speeds, and asymptotic spreading behavior for Dirichlet problem of monostable reaction-diffusion equations on R+ as well as of monostable/bistable reaction-diffusion equations on R.

Emergence of traveling wave endothermic reaction in a catalytic fixed bed under microwave heating

International Nuclear Information System (INIS)

Gerasev, Alexander P.

2017-01-01

This paper presents a new phenomenon in a packed bed catalytic reactor under microwave heating - traveling wave (moving reaction zones) endothermic chemical reaction. A two-phase model is developed to simulate the nonlinear dynamic behavior of the packed bed catalytic reactor with an irreversible first-order chemical reaction. The absorbed microwave power was obtained from Lambert's law. The structure of traveling wave endothermic chemical reaction was explored. The effects of the gas velocity and microwave power on performance of the packed bed catalytic reactor were presented. Finally, the effects of the change in the location of the microwave source at the packed bed reactor was demonstrated. - Highlights: • A new phenomenon - traveling waves of endothermic reaction - is predicted. • The physical and mathematical model of a packed bed catalytic reactor under microwave heating is presented. • The structure of the traveling waves is explored. • The configuration of heating the packed bed reactor via microwave plays a key role.

Quantum elastic net and the traveling salesman problem

International Nuclear Information System (INIS)

Kostenko, B.F.; Pribis, J.; Yur'ev, M.Z.

2009-01-01

Theory of computer calculations strongly depends on the nature of elements the computer is made of. Quantum interference allows one to formulate the Shor factorization algorithm turned out to be more effective than any one written for classical computers. Similarly, quantum wave packet reduction allows one to devise the Grover search algorithm which outperforms any classical one. In the present paper we argue that the quantum incoherent tunneling can be used for elaboration of new algorithms able to solve some NP-hard problems, such as the traveling Salesman Problem, considered to be intractable in the classical theory of computer computations

A traveling wave approach to plasma pumping for X-ray sources

International Nuclear Information System (INIS)

Jensen, R.J.

1989-01-01

Progress in high-brightness excimer lasers and in optical angular multiplexing of excimer lasers presents an opportunity to provide very intense pumping of X-ray sources, both in favorable geometry and in travelling waves, all at low cost. The traveling-wave strategy can be tailored to the parameters of the system to be pumped. This design option can be of great importance for systems lasing at wavelengths in the kilovolt regime where upper level lifetimes are short, and where mirror technology is presently tenuous. Features of several design strategies are explored. (author)

Attosecond ionization gating for isolated attosecond electron wave packet and broadband attosecond xuv pulses

International Nuclear Information System (INIS)

Lan Pengfei; Lu Peixiang; Cao Wei; Li Yuhua; Wang Xinlin

2007-01-01

An attosecond ionization gating is achieved using a few-cycle laser pulse in combination with its second harmonic. With this gating, the generation of the electron wave packet (EWP) is coherently controlled, and an isolated EWP of about 270 as is generated. An isolated broadband attosecond extreme ultraviolet pulse with a bandwidth of about 75 eV can also be generated using this gating, which can be used for EWP measurements as efficiently as a 50-as pulse, allowing one to measure a wide range of ultrafast dynamics not normally accessible before

New exact travelling wave solutions for the generalized nonlinear Schroedinger equation with a source

International Nuclear Information System (INIS)

Abdou, M.A.

2008-01-01

The generalized F-expansion method with a computerized symbolic computation is used for constructing a new exact travelling wave solutions for the generalized nonlinear Schrodinger equation with a source. As a result, many exact travelling wave solutions are obtained which include new periodic wave solution, trigonometric function solutions and rational solutions. The method is straightforward and concise, and it can also be applied to other nonlinear evolution equations in physics

Current generation by monochromatic electromagnetic waves

International Nuclear Information System (INIS)

Belikov, V.S.; Kolesnichenko, Ya.I.; Plotnik, I.S.

1983-01-01

The generation of longitudinal currents in a magnetically confined plasma with travelling monochromatic electromagnetic waves of finite amplitude propagating at some angle to the external magnetic field is considered. By averaging over the particle cyclotron gyration period, the kinetic equation for the distribution function of electrons interacting with an electromagnetic wave is derived. This equation is solved for the case of low-frequency waves, on the assumption that the bounce period of electrons trapped by the wave field is small compared to the typical times of Coulomb collisions (in which case, the driving current is largest). From the solution obtained, analytic expressions for the driving current and the absorbed power, which are valid for a wide range of wave phase velocities, are found. The current drive method considered and the method using the wave packet are compared. (author)

Traveling waves and conservation laws for highly nonlinear wave equations modeling Hertz chains

Science.gov (United States)

Przedborski, Michelle; Anco, Stephen C.

2017-09-01

A highly nonlinear, fourth-order wave equation that models the continuum theory of long wavelength pulses in weakly compressed, homogeneous, discrete chains with a general power-law contact interaction is studied. For this wave equation, all solitary wave solutions and all nonlinear periodic wave solutions, along with all conservation laws, are derived. The solutions are explicitly parameterized in terms of the asymptotic value of the wave amplitude in the case of solitary waves and the peak of the wave amplitude in the case of nonlinear periodic waves. All cases in which the solution expressions can be stated in an explicit analytic form using elementary functions are worked out. In these cases, explicit expressions for the total energy and total momentum for all solutions are obtained as well. The derivation of the solutions uses the conservation laws combined with an energy analysis argument to reduce the wave equation directly to a separable first-order differential equation that determines the wave amplitude in terms of the traveling wave variable. This method can be applied more generally to other highly nonlinear wave equations.

New travelling wave solutions for nonlinear stochastic evolution

Indian Academy of Sciences (India)

The nonlinear stochastic evolution equations have a wide range of applications in physics, chemistry, biology, economics and finance from various points of view. In this paper, the (′/)-expansion method is implemented for obtaining new travelling wave solutions of the nonlinear (2 + 1)-dimensional stochastic ...

Symbolic computation and abundant travelling wave solutions to ...

Indian Academy of Sciences (India)

The method is reliable and useful, and gives more general exact travelling wave solutions than the existing methods. The solutions obtained are in the form of hyperbolic, trigonometricand rational functions including solitary, singular and periodic solutions which have many potential applications in physical science and ...

Numerical study of radial stepwise fuel load reshuffling traveling wave reactor

International Nuclear Information System (INIS)

Zhang Dalin; Zheng Meiyin; Tian Wenxi; Qiu Suizheng; Su Guanghui

2015-01-01

Traveling wave reactor is a new conceptual fast breeder reactor, which can adopt natural uranium, depleted uranium and thorium directly to realize the self sustainable breeding and burning to achieve very high fuel utilization fraction. Based on the mechanism of traveling wave reactor, a concept of radial stepwise fuel load reshuffling traveling wave reactor was proposed for realistic application. It was combined with the typical design of sodium-cooled fast reactors, with which the asymptotic characteristics of the inwards stepwise fuel load reshuffling were studied numerically in two-dimension. The calculated results show that the asymptotic k_e_f_f parabolically varies with the reshuffling cycle length, while the burnup increases linearly. The highest burnup satisfying the reactor critical condition is 38%. The power peak shifts from the fuel discharging zone (core centre) to the fuel uploading zone (core periphery) and correspondingly the power peaking factor decreases along with the reshuffling cycle length. In addition, at the high burnup case the axial power distribution close to the core centre displays the M-shaped deformation. (authors)

Wave-particle interaction and Hamiltonian dynamics investigated in a traveling wave tube

International Nuclear Information System (INIS)

Doveil, Fabrice; Macor, Alessandro

2006-01-01

For wave-particle interaction studies, the one-dimensional (1-D) beam-plasma system can be advantageously replaced by a Traveling Wave Tube (TWT). This led us to a detailed experimental analysis of the self-consistent interaction between unstable waves and a small either cold or warm beam. More recently, a test electron beam has been used to observe its non-self-consistent interaction with externally excited wave(s). The velocity distribution function of the electron beam is investigated with a trochoidal energy analyzer that records the beam energy distribution at the output of the TWT. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4 m long helix) of the TWT. The nonlinear synchronization of particles by a single wave responsible for Landau damping is observed. The resonant velocity domain associated to a single wave is also observed, as well as the transition to large-scale chaos when the resonant domains of two waves and their secondary resonances overlap leading to a typical 'devil's staircase' behavior. A new strategy for the control of chaos is tested

Acoustic field characteristics and performance analysis of a looped travelling-wave thermoacoustic refrigerator

International Nuclear Information System (INIS)

Jin, T.; Yang, R.; Wang, Y.; Feng, Y.; Tang, K.

2016-01-01

Highlights: • Key issues for a highly efficient thermoacoustic conversion are analyzed. • A looped thermoacoustic refrigerator with one engine stage and one refrigerator stage is proposed. • Effective refrigeration powered by heat sources below 250 °C is demonstrated in the simulation. • Impact of cooling/heating temperatures on system performance is analyzed in view of acoustic field. - Abstract: This paper focuses on a looped travelling-wave thermoacoustic refrigerator powered by thermal energy. Based on a simplified model for the regenerator, key issues for a highly efficient thermoacoustic conversion, including both thermal-to-acoustic and heat-pumping processes, are summarized. A looped travelling-wave thermoacoustic refrigerator with one engine stage and one refrigerator stage is proposed, with emphasis on high normalized acoustic impedance, sufficient volumetric velocity and appropriate phase relation close to travelling wave in the regenerators of both engine and refrigerator. Simulation results indicate that for the ambient temperature of 30 °C, the looped travelling-wave thermoacoustic refrigerator can be powered by the heat at 210–250 °C to achieve the refrigeration at −3 °C with the overall coefficient of performance above 0.4 and the relative Carnot coefficient of performance over 13%. The characteristics of the acoustic field inside the loop configuration are analyzed in detail to reveal the operation mechanism of the looped travelling-wave thermoacoustic refrigerator. Additional analyses are conducted on the impact of the cooling and the heating temperatures, which are of great concern to the refrigeration applications and the utilization of low-grade thermal energy.

Characterization of a quantum phase transition in Dirac systems by means of the wave-packet dynamics

Directory of Open Access Journals (Sweden)

E. Romera

2012-12-01

Full Text Available We study the signatures of phase transitions in the time evolution of wave-packets by analyzing two simple model systems: a graphene quantum dot model in a magnetic field and a Dirac oscillator in a magnetic field. We have characterized the phase transitions using the autocorrelation function. Our work also reveals that the description in terms of Shannon entropy of the autocorrelation function is a clear phase transition indicator.

The (′/-Expansion Method for Abundant Traveling Wave Solutions of Caudrey-Dodd-Gibbon Equation

Directory of Open Access Journals (Sweden)

Hasibun Naher

2011-01-01

Full Text Available We construct the traveling wave solutions of the fifth-order Caudrey-Dodd-Gibbon (CDG equation by the (/-expansion method. Abundant traveling wave solutions with arbitrary parameters are successfully obtained by this method and the wave solutions are expressed in terms of the hyperbolic, the trigonometric, and the rational functions. It is shown that the (/-expansion method is a powerful and concise mathematical tool for solving nonlinear partial differential equations.

Traveling waves in a delayed SIR model with nonlocal dispersal and nonlinear incidence

Science.gov (United States)

Zhang, Shou-Peng; Yang, Yun-Rui; Zhou, Yong-Hui

2018-01-01

This paper is concerned with traveling waves of a delayed SIR model with nonlocal dispersal and a general nonlinear incidence. The existence and nonexistence of traveling waves of the system are established respectively by Schauder's fixed point theorem and two-sided Laplace transform. It is also shown that the spread speed c is influenced by the dispersal rate of the infected individuals and the delay τ.

The nuclear news interview. John Gilleland. On the traveling-wave reactor

International Nuclear Information System (INIS)

Michal, Rick; Blake, E. Michael

2010-01-01

The traveling-wave reactor, in concept, would use depleted uranium to produce vast amounts of energy without the need for enrichment plants and reprocessing facilities, which is why billionaire Bill Gates is interested in developing it. TerraPower LLC has been launched by the company Intellectual Ventures to design a traveling-wave nuclear reactor that could run for 100 years without refueling or removing spent fuel. So convincing is the science behind the concept that billionaire Bill Gates has gotten involved to help finance the project. Led by John Gilleland, TerraPower's chief executive officer, a team of researchers has run computer simulations and is doing engineering studies that have produced evidence that a wave of fission moving slowly through a fuel core could generate a billion watts of electricity continuously without refueling. Gilleland noted that these new reactors could reduce the amount of nuclear waste by using existing stockpiles of depleted uranium as fuel. ''By extracting centuries' worth of energy from waste at enrichment plants, these reactors would turn a social and financial liability into an asset,'' he said. Gilleland, a member of the American Nuclear Society, talked about the traveling-wave reactor with Nuclear News editors Rick Michal and E. Michael Blake. (orig.)

Traveling waves in a continuum model of 1D schools

Science.gov (United States)

Oza, Anand; Kanso, Eva; Shelley, Michael

2017-11-01

We construct and analyze a continuum model of a 1D school of flapping swimmers. Our starting point is a delay differential equation that models the interaction between a swimmer and its upstream neighbors' wakes, which is motivated by recent experiments in the Applied Math Lab at NYU. We coarse-grain the evolution equations and derive PDEs for the swimmer density and variables describing the upstream wake. We study the equations both analytically and numerically, and find that a uniform density of swimmers destabilizes into a traveling wave. Our model makes a number of predictions about the properties of such traveling waves, and sheds light on the role of hydrodynamics in mediating the structure of swimming schools.

On Traveling Waves in Lattices: The Case of Riccati Lattices

Science.gov (United States)

Dimitrova, Zlatinka

2012-09-01

The method of simplest equation is applied for analysis of a class of lattices described by differential-difference equations that admit traveling-wave solutions constructed on the basis of the solution of the Riccati equation. We denote such lattices as Riccati lattices. We search for Riccati lattices within two classes of lattices: generalized Lotka-Volterra lattices and generalized Holling lattices. We show that from the class of generalized Lotka-Volterra lattices only the Wadati lattice belongs to the class of Riccati lattices. Opposite to this many lattices from the Holling class are Riccati lattices. We construct exact traveling wave solutions on the basis of the solution of Riccati equation for three members of the class of generalized Holling lattices.

Traveling waves and their tails in locally resonant granular systems

International Nuclear Information System (INIS)

Xu, H.; Kevrekidis, P. G.; Stefanov, A.

2015-01-01

In the present study, we revisit the theme of wave propagation in locally resonant granular crystal systems, also referred to as mass-in-mass systems. We use three distinct approaches to identify relevant traveling waves. In addition, the first consists of a direct solution of the traveling wave problem. The second one consists of the solution of the Fourier tranformed variant of the problem, or, more precisely, of its convolution reformulation (upon an inverse Fourier transform) in real space. Finally, our third approach will restrict considerations to a finite domain, utilizing the notion of Fourier series for important technical reasons, namely the avoidance of resonances, which will be discussed in detail. All three approaches can be utilized in either the displacement or the strain formulation. Typical resulting computations in finite domains result in the solitary waves bearing symmetric non-vanishing tails at both ends of the computational domain. Importantly, however, a countably infinite set of anti-resonance conditions is identified for which solutions with genuinely rapidly decaying tails arise

Traveling Wave Modes of a Plane Layered Anelastic Earth

Science.gov (United States)

2016-05-20

grant, “Coupled Modes in Elastic Bottoms” (1) is the publication “Traveling wave modes of a plane layered anelastic earth ” accepted for...anelastic earth Robert I. Odom Applied Physics Laboratory and Department of Earth and Space Sciences University of Washington, 1013 NE 40th St., Seattle...contrast to a similar standing wave problem for the earth free oscillations (Tromp and Dahlen, 1990). Attenuation is commonly incorporated into synthetic

Design of hybrid electron linac with standing wave buncher and traveling wave structure

International Nuclear Information System (INIS)

Kutsaev, S.V.; Sobenin, N.P.; Smirnov, A.Yu.; Kamenschikov, D.S.; Gusarova, M.A.; Nikolskiy, K.I.; Zavadtsev, A.A.; Lalayan, M.V.

2011-01-01

A disk-loaded waveguide (DLW) is the most common structure for compact linear accelerators working in a traveling wave (TW) regime. Among its advantages are high shunt impedance and manufacturing simplicity. The other popular structure is an on-axis coupled bi-periodical accelerating structure (BAS) that works in standing wave (SW) regime. Both the standing and the traveling wave regimes have their own advantages and disadvantages. The design of the hybrid accelerator with SW buncher and TW accelerating section presented in this paper unites the advantages of both regimes. For example, the buncher in the hybrid accelerator is shorter than in a pure TW accelerator, and it requires no solenoid; this structure is more technologically convenient as it does not require a circulator. The other way to combine the advantages of DLW and BAS is to design a magnetic coupled disk-loaded waveguide (DLW-M). This paper also presents the results of a survey study that analyzed the electrodynamical parameters of such a structure and compared them with those of DLW. The experimental data is also presented. Higher order modes, multipacting discharge and thermal simulations show that DLW-M structure is more preferable to classical DLW.

A new auxiliary equation and exact travelling wave solutions of nonlinear equations

International Nuclear Information System (INIS)

Sirendaoreji

2006-01-01

A new auxiliary ordinary differential equation and its solutions are used for constructing exact travelling wave solutions of nonlinear partial differential equations in a unified way. The main idea of this method is to take full advantage of the auxiliary equation which has more new exact solutions. More new exact travelling wave solutions are obtained for the quadratic nonlinear Klein-Gordon equation, the combined KdV and mKdV equation, the sine-Gordon equation and the Whitham-Broer-Kaup equations

Diffraction of ultracold fermions by quantized light fields: Standing versus traveling waves

International Nuclear Information System (INIS)

Meiser, D.; Search, C.P.; Meystre, P.

2005-01-01

We study the diffraction of quantum-degenerate fermionic atoms off of quantized light fields in an optical cavity. We compare the case of a linear cavity with standing-wave modes to that of a ring cavity with two counterpropagating traveling wave modes. It is found that the dynamics of the atoms strongly depends on the quantization procedure for the cavity field. For standing waves, no correlations develop between the cavity field and the atoms. Consequently, standing-wave Fock states yield the same results as a classical standing wave field while coherent states give rise to a collapse and revivals in the scattering of the atoms. In contrast, for traveling waves the scattering results in quantum entanglement of the radiation field and the atoms. This leads to a collapse and revival of the scattering probability even for Fock states. The Pauli exclusion principle manifests itself as an additional dephasing of the scattering probability

A generic travelling wave solution in dissipative laser cavity

Indian Academy of Sciences (India)

2016-09-09

Sep 9, 2016 ... Abstract. A large family of cosh-Gaussian travelling wave solution of a complex Ginzburg–Landau equation ... pling, wherein the real part represents diffusive coupling ... knowledge, this is the first time that cosh-Gaussian pro-.

Pierce gain analysis for a sheet beam in a rippled waveguide traveling-wave tube

International Nuclear Information System (INIS)

Carlsten, Bruce E.

2001-01-01

A Pierce-type mode analysis is presented for a planar electron beam in a rippled planar waveguide. This analysis describes the gain of a traveling-wave tube consisting of that geometry. The dispersion relation is given by the determinant of a matrix based on the coupling of different free-space modes through the boundary conditions. For the case of high-frequency, low-power amplifiers, the dispersion relation reduces to a simple cubic expression for the Compton regime, leading to three roots analogous to the Pierce solution of a standard traveling-wave tube. The analysis shows that this type of traveling-wave tube is capable of very high gain at extremely high frequencies

Travelling waves in models of neural tissue: from localised structures to periodic waves

NARCIS (Netherlands)

Meijer, Hil Gaétan Ellart; Coombes, Stephen

2014-01-01

We consider travelling waves (fronts, pulses and periodics) in spatially extended one dimensional neural field models. We demonstrate for an excitatory field with linear adaptation that, in addition to an expected stable pulse solution, a stable anti-pulse can exist. Varying the adaptation strength

Exact travelling wave solutions for some important nonlinear

Indian Academy of Sciences (India)

The two-dimensional nonlinear physical models and coupled nonlinear systems such as Maccari equations, Higgs equations and Schrödinger–KdV equations have been widely applied in many branches of physics. So, finding exact travelling wave solutions of such equations are very helpful in the theories and numerical ...

Traveling wave accelerating structures with a large phase advance

International Nuclear Information System (INIS)

Paramonov, V.V.

2012-01-01

The cells RF parameters for the well known Disk Loaded Waveguide (DLW) are considered in higher pass bands of TM01 wave, providing operating phase advance between 180 o - 1230 o per cell. With an appropriate shape optimization and some additional elements proposed traveling wave structures with such large phase advance overlap the classical first band DLW in RF efficiency. Examples of proposed structures together with RF and dispersion properties are presented.

Traveling wave front solutions in lateral-excitatory neuronal networks

Directory of Open Access Journals (Sweden)

Sittipong Ruktamatakul

2008-05-01

Full Text Available In this paper, we discuss the shape of traveling wave front solutions to a neuronal model with the connection function to be of lateral excitation type. This means that close connecting cells have an inhibitory influence, while cells that aremore distant have an excitatory influence. We give results on the shape of the wave fronts solutions, which exhibit different shapes depend ing on the size of a threshold parameter.

Modeling traveling-wave Thomson scattering using PIConGPU

Energy Technology Data Exchange (ETDEWEB)

Debus, Alexander; Schramm, Ulrich; Cowan, Thomas; Bussmann, Michael [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Steiniger, Klaus; Pausch, Richard; Huebl, Axel [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Universitaet Dresden (Germany)

2016-07-01

Traveling-wave Thomson scattering (TWTS) laser pulses are pulse-front tilted and dispersion corrected beams that enable all-optical free-electron lasers (OFELs) up to the hard X-ray range. Electrons in such a side-scattering geometry experience the TWTS laser field as a continuous plane wave over centimeter to meter interaction lengths. After briefly discussing which OFEL scenarios are currently numerically accessible, we detail implementation and tests of TWTS beams within PIConGPU (3D-PIC code) and show how numerical dispersion and boundary effects are kept under control.

Neutrino wave function and oscillation suppression

International Nuclear Information System (INIS)

Dolgov, A.D.; Lychkovskiy, O.V.; Mamonov, A.A.; Okun, L.B.; Schepkin, M.G.

2005-01-01

We consider a thought experiment, in which a neutrino is produced by an electron on a nucleus in a crystal. The wave function of the oscillating neutrino is calculated assuming that the electron is described by a wave packet. If the electron is relativistic and the spatial size of its wave packet is much larger than the size of the crystal cell, then the wave packet of the produced neutrino has essentially the same size as the wave packet of the electron. We investigate the suppression of neutrino oscillations at large distances caused by two mechanisms: (1) spatial separation of wave packets corresponding to different neutrino masses; (2) neutrino energy dispersion for given neutrino mass eigenstates. We resolve the contributions of these two mechanisms. (orig.)

A new sub-equation method applied to obtain exact travelling wave solutions of some complex nonlinear equations

International Nuclear Information System (INIS)

Zhang Huiqun

2009-01-01

By using a new coupled Riccati equations, a direct algebraic method, which was applied to obtain exact travelling wave solutions of some complex nonlinear equations, is improved. And the exact travelling wave solutions of the complex KdV equation, Boussinesq equation and Klein-Gordon equation are investigated using the improved method. The method presented in this paper can also be applied to construct exact travelling wave solutions for other nonlinear complex equations.

On "new travelling wave solutions" of the KdV and the KdV-Burgers equations

NARCIS (Netherlands)

Kudryashov, Nikolai A.

The Korteweg-de Vries and the Korteweg-de Vries-Burgers equations are considered. Using the travelling wave the general solutions of these equations are presented. "New travelling wave solutions" of the KdV and the KdV-Burgers equations by Wazzan [Wazzan L Commun Nonlinear Sci Numer Simulat

Detecting strain wave propagation through quantum dots by pump-probe spectroscopy: A theoretical analysis

International Nuclear Information System (INIS)

Huneke, J; Kuhn, T; Axt, V M

2010-01-01

The influence of strain waves traveling across a quantum dot structure on its optical response is studied for two different situations: First, a strain wave is created by the optical excitation of a single quantum dot near a surface which, after reflection at the surface, reenters the dot; second, a phonon wave packet is emitted by the excitation of a nearby second dot and then travels across the quantum dot. Pump-probe type excitations are simulated for quantum dots in the strong confinement limit. We show that the optical signals allow us to monitor crossing strain waves for both structures in the real-time response as well as in the corresponding pump-probe spectra. In the time-derivative of the phase of the polarization a distinct trace reflects the instantaneous shifts of the transition energy during the passage while in the spectra pronounced oscillations reveal the passage of the strain waves.

Limiting Behavior of Travelling Waves for the Modified Degasperis-Procesi Equation

Directory of Open Access Journals (Sweden)

Jiuli Yin

2014-01-01

Full Text Available Using an improved qualitative method which combines characteristics of several methods, we classify all travelling wave solutions of the modified Degasperis-Procesi equation in specified regions of the parametric space. Besides some popular exotic solutions including peaked waves, and looped and cusped waves, this equation also admits some very particular waves, such as fractal-like waves, double stumpons, double kinked waves, and butterfly-like waves. The last three types of solutions have not been reported in the literature. Furthermore, we give the limiting behavior of all periodic solutions as the parameters trend to some special values.

On the maximal noise for stochastic and QCD travelling waves

International Nuclear Information System (INIS)

Peschanski, Robi

2008-01-01

Using the relation of a set of nonlinear Langevin equations to reaction-diffusion processes, we note the existence of a maximal strength of the noise for the stochastic travelling wave solutions of these equations. Its determination is obtained using the field-theoretical analysis of branching-annihilation random walks near the directed percolation transition. We study its consequence for the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation. For the related Langevin equation modeling the quantum chromodynamic nonlinear evolution of gluon density with rapidity, the physical maximal-noise limit may appear before the directed percolation transition, due to a shift in the travelling-wave speed. In this regime, an exact solution is known from a coalescence process. Universality and other open problems and applications are discussed in the outlook

Pn seismic wave travel time at the Semipalatinsk Test Site - Borovoe seismic station trace

International Nuclear Information System (INIS)

An, V.A.; Kaazik, P.B.; Ovchinnikov, V.M.

2001-01-01

This paper preparation involved 160 explosions at the Degelen Site conducted in 1961-1989 and 89 explosions at the Balapan Site conducted in 1968-1989. Pn wave travel time was tied to the sea level in accordance with velocity characteristics of the explosion hypocenter medium; and to average epicentral distance for every site basing on their local travel time curves of Pn wave relative to Borovoe station. Maximum amplitude of mean-year travel times variations is 0.3-0.5 s as at the Nevada Test Site - Borovoe trace and Mirniy (Antarctica). However, the linear trend in contrast to previous traces has negative sign (0.08 s for Degelen and 0.1 s for Balapan). Thus, Pn wave velocity increases with calendar time. (author)

On weakly singular and fully nonlinear travelling shallow capillary–gravity waves in the critical regime

Energy Technology Data Exchange (ETDEWEB)

Mitsotakis, Dimitrios, E-mail: dmitsot@gmail.com [Victoria University of Wellington, School of Mathematics, Statistics and Operations Research, PO Box 600, Wellington 6140 (New Zealand); Dutykh, Denys, E-mail: Denys.Dutykh@univ-savoie.fr [LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, F-73376 Le Bourget-du-Lac Cedex (France); Assylbekuly, Aydar, E-mail: asylbekuly@mail.ru [Khoja Akhmet Yassawi International Kazakh–Turkish University, Faculty of Natural Science, Department of Mathematics, 161200 Turkestan (Kazakhstan); Zhakebayev, Dauren, E-mail: daurjaz@mail.ru [Al-Farabi Kazakh National University, Faculty of Mechanics and Mathematics, Department of Mathematical and Computer Modelling, 050000 Almaty (Kazakhstan)

2017-05-25

In this Letter we consider long capillary–gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott–Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well. - Highlights: • A model for long capillary–gravity weakly dispersive and fully nonlinear water waves is derived. • Shallow capillary–gravity waves are classified using phase plane analysis. • Peaked travelling waves are found in the critical regime. • The dynamics of peakons in Serre–Green–Naghdi equations is studied numerically.

Atom-field interaction in the single-quantum limit in a two dimensional travelling-wave cavity

International Nuclear Information System (INIS)

Youn, Sun Hyun; Chough, Young Tak; An, Kyung Won

2003-01-01

We analyze the interaction of an atom with two dimensional travelling-wave cavity modes in the strong coupling region, with the quantized atomic center of mass motion taken into account. Analytic and numerical calculation shows that the atom in two independent pairs of travelling wave modes can be made to interact only with a particular travelling mode by matching the initial momentum and the detuning of the cavities. We also numerically investigate the atomic momentum deflection in the cavities

New binary travelling-wave periodic solutions for the modified KdV equation

International Nuclear Information System (INIS)

Yan Zhenya

2008-01-01

In this Letter, the modified Korteweg-de Vries (mKdV) equations with the focusing (+) and defocusing (-) branches are investigated, respectively. Many new types of binary travelling-wave periodic solutions are obtained for the mKdV equation in terms of Jacobi elliptic functions such as sn(ξ,m)cn(ξ,m)dn(ξ,m) and their extensions. Moreover, we analyze asymptotic properties of some solutions. In addition, with the aid of the Miura transformation, we also give the corresponding binary travelling-wave periodic solutions of KdV equation

Controlled Quantum Packets

Science.gov (United States)

DeMartino, Salvatore; DeSiena, Silvio

1996-01-01

We look at time evolution of a physical system from the point of view of dynamical control theory. Normally we solve motion equation with a given external potential and we obtain time evolution. Standard examples are the trajectories in classical mechanics or the wave functions in Quantum Mechanics. In the control theory, we have the configurational variables of a physical system, we choose a velocity field and with a suited strategy we force the physical system to have a well defined evolution. The evolution of the system is the 'premium' that the controller receives if he has adopted the right strategy. The strategy is given by well suited laboratory devices. The control mechanisms are in many cases non linear; it is necessary, namely, a feedback mechanism to retain in time the selected evolution. Our aim is to introduce a scheme to obtain Quantum wave packets by control theory. The program is to choose the characteristics of a packet, that is, the equation of evolution for its centre and a controlled dispersion, and to give a building scheme from some initial state (for example a solution of stationary Schroedinger equation). It seems natural in this view to use stochastic approach to Quantum Mechanics, that is, Stochastic Mechanics [S.M.]. It is a quantization scheme different from ordinary ones only formally. This approach introduces in quantum theory the whole mathematical apparatus of stochastic control theory. Stochastic Mechanics, in our view, is more intuitive when we want to study all the classical-like problems. We apply our scheme to build two classes of quantum packets both derived generalizing some properties of coherent states.

Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

Science.gov (United States)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.

Analytical structural optimization and experimental verifications for traveling wave generation in self-assembling swimming smart boxes

International Nuclear Information System (INIS)

Bani-Hani, M A; Karami, M A

2015-01-01

This paper presents vibration analysis and structural optimization of a swimming–morphing structure. The swimming of the structure is achieved by utilization of piezoelectric patches to generate traveling waves. The third mode shape of the structure in the longitudinal direction resembles the body waveform of a swimming eel. After swimming to its destination, the morphing structure changes shape from an open box to a cube using shape memory alloys (SMAs). The SMAs used for the configuration change of the box robot cannot be used for swimming since they fail to operate at high frequencies. Piezoelectric patches are actuated at the third natural frequency of the structure. We optimize the thickness of the panels and the stiffness of the springs at the joints to generate swimming waveforms that most closely resemble the body waveform of an eel. The traveling wave is generated using two piezoelectric sets of patches bonded to the first and last segments of the beams in the longitudinal direction. Excitation of the piezoelectric results in coupled system dynamics equations that can be translated into the generation of waves. Theoretical analysis based on the distributed parameter model is conducted in this paper. A scalar measure of the traveling to standing wave ratio is introduced using a 2-dimensional Fourier transform (2D-FFT) of the body deformation waveform. An optimization algorithm based on tuning the flexural transverse wave is established to obtain a higher traveling to standing wave ratio. The results are then compared to common methods in the literature for assessment of standing to traveling wave ratios. The analytical models are verified by the close agreement between the traveling waves predicted by the model and those measured in the experiments. (paper)

Concepts and limitations of macroparticle accelerators using travelling magnetic waves

International Nuclear Information System (INIS)

Wipf, S.L.

1980-01-01

The concept of an accelerator using a travelling magnetic wave acting on magnetized projectiles is discussed. Although superconductors have a high potential as projectile material, their low critical temperature makes them unsuitable. Among ferromagnetic materials dysprosium seems to be superior. For stable suspension and guidance a high conductivity, preferably superconducting, guide sheet is necessary. Magnetic field gradients of 10 9 A/m 2 travelling at 10 6 m/s should be achievable using present state-of-the-art components; resulting accelerations are greater than or equal to 500 km/s 2 . A linear accelerator for final speeds of 50 km/s needs a length of 2.5 km. Guidance forces sufficient to produce acceleration of 2 x 10 6 m/s 2 allow circular accelerators of reasonable size to achieve hypervelocities for small (50 to 100 mg) projectiles. An accelerator of 170 m diameter would surpass the best results from light gas guns. Travelling waves suitable for accelerations of the order of 10 4 m/s 2 can be produced without switching, by means of flux displacing rotors, easily adapted to circular accelerators

Simulation of Noise in a Traveling Wave Tube

Science.gov (United States)

Verboncoeur, J. P.; Christenson, P. J.; Smith, H. B.

1999-11-01

Low frequency noise, manifested as close-in sidebands, has long been a significant limit to the performance of many traveling wave tubes. In this study, we investigate oscillations in the gun region due to the presence of plasma formed by electron-impact ionization of a background gas. The gun region of a coupled-cavity traveling wave tube is modeled using the two-dimensional XOOPIC particle-in-cell Monte Carlo collision code (J. P. Verboncoeur et al. Comput. Phys. Comm.) 87, 199-211 (1995). (available via the web: http://ptsg.eecs.berkeley.edu). The beam is 20.5 kV, 2.8 A, in near-confined flow in a solenoidal magnetic field with peak axial value of 0.263 T. Beam scalloping leads to trapping of plasma generated via electron-impact ionization of a background gas. The trapped plasma periodically leaves the system rapidly, and the density begins regenerating at a slow rate, leading to characteristic sawtooth oscillations. Plasma electrons are observed to exit the system axially about 20 ns before the ions exit primarily radially.

Quantum solitonic wave-packet of a meso-scopic system in singularity free gravity

Science.gov (United States)

Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

2018-06-01

In this paper we will discuss how to localise a quantum wave-packet due to self-gravitating meso-scopic object by taking into account gravitational self-interaction in the Schrödinger equation beyond General Relativity. In particular, we will study soliton-like solutions in infinite derivative ghost free theories of gravity, which resolves the gravitational 1 / r singularity in the potential. We will show a unique feature that the quantum spread of such a gravitational system is larger than that of the Newtonian gravity, therefore enabling us a window of opportunity to test classical and quantum properties of such theories of gravity in the near future at a table-top experiment.

Symbolic computation and abundant travelling wave solutions to ...

Indian Academy of Sciences (India)

2016-12-09

Dec 9, 2016 ... Abstract. In this article, the novel (G /G)-expansion method is successfully applied to construct the abundant travelling wave solutions to the KdV–mKdV equation with the aid of symbolic computation. This equation is one of the most popular equation in soliton physics and appear in many practical scenarios ...

Benchmark on traveling wave fast reactor with negative reactivity feedback obtained with MCNPX code

International Nuclear Information System (INIS)

Gann, V.V.; Gann, A.V.

2012-01-01

This paper presents results of computer simulations of traveling wave fast reactor with negative reactivity feedback. The results were obtained using MCNPX code combined with CINDER90 subroutine for depletion calculations. We considered 1-D model of TWR containing 4 m long core made of mixture of 66 at. % 238 U and 34 at. % 10 B. Ignitor made of 235 U was located in the center of the core. Boron was included as imitator of structural in-core materials and coolant. Negative reactivity feedback was adjusted to reactor power of 500 MW. In this case two burning waves originated from the igniter and travel to the ends of the core during the following 40 years; coefficient of utilization of 238 U reached 80 %. Distribution of specific power in traveling wave, isotope concentration of fission products and actinides, neutron flux, fast neutron spectrum, specific activity were calculated. Data of the computer simulation is in qualitative agreement with theoretical results obtained in slow burning wave approximation

Ferruleless coupled-cavity traveling-wave tube cold-test characteristics simulated with micro-SOS

Science.gov (United States)

Schroeder, Dana L.; Wilson, Jeffrey D.

1993-01-01

The three-dimensional, electromagnetic circuit analysis code, Micro-SOS, can be used to reduce expensive and time consuming experimental 'cold-testing' of traveling-wave tube (TWT) circuits. The frequency-phase dispersion and beam interaction impedance characteristics of a ferruleless coupled-cavity traveling-wave tube slow-wave circuit were simulated using the code. Computer results agree closely with experimental data. Variations in the cavity geometry dimensions of period length and gap-to-period ratio were modeled. These variations can be used in velocity taper designs to reduce the radiofrequency (RF) phase velocity in synchronism with the decelerating electron beam. Such circuit designs can result in enhanced TWT power and efficiency.

Boundary mediated position control of traveling waves

Science.gov (United States)

Martens, Steffen; Ziepke, Alexander; Engel, Harald

Reaction control is an essential task in biological systems and chemical process industry. Often, the excitable medium supporting wave propagation exhibits an irregular shape and/or is limited in size. In particular, the analytic treatment of wave phenomena is notoriously difficult due to the spatial modulation of the domain's. Recently, we have provided a first systematic treatment by applying asymptotic perturbation analysis leading to an approximate description that involves a reduction of dimensionality; the 3D RD equation with spatially dependent NFBCs on the reactants reduces to a 1D reaction-diffusion-advection equation. Here, we present a novel method to control the position ϕ (t) of traveling waves in modulated domains according to a prespecified protocol of motion. Given this protocol, the ``optimal'' geometry of reactive domains Q (x) is found as the solution of the perturbatively derived equation of motion. Noteworthy, such a boundary control can be expressed in terms of the uncontrolled wave profile and its propagation velocity, rendering detailed knowledge of the reaction kinetics unnecessary. German Science Foundation DFG through the SFB 910 ''Control of Self-Organizing Nonlinear Systems''.

The Liouville equation for flavour evolution of neutrinos and neutrino wave packets

Energy Technology Data Exchange (ETDEWEB)

Hansen, Rasmus Sloth Lundkvist; Smirnov, Alexei Yu., E-mail: rasmus@mpi-hd.mpg.de, E-mail: smirnov@mpi-hd.mpg.de [Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

2016-12-01

We consider several aspects related to the form, derivation and applications of the Liouville equation (LE) for flavour evolution of neutrinos. To take into account the quantum nature of neutrinos we derive the evolution equation for the matrix of densities using wave packets instead of Wigner functions. The obtained equation differs from the standard LE by an additional term which is proportional to the difference of group velocities. We show that this term describes loss of the propagation coherence in the system. In absence of momentum changing collisions, the LE can be reduced to a single derivative equation over a trajectory coordinate. Additional time and spatial dependence may stem from initial (production) conditions. The transition from single neutrino evolution to the evolution of a neutrino gas is considered.

Variable coefficient Korteweg-de Vries equations and travelling waves in an inhomogeneous medium

International Nuclear Information System (INIS)

Baby, B.V.

1987-04-01

The well-known Korteweg-de Vries equations with the coefficients as two arbitrary functions of the time variable, is studied in this paper. The Painleve property analysis provides the conditions on the two variable coefficients, in order to form the Lax pairs associated with this equation. The similarity analysis shows the non-existence of travelling wave solutions when the equation has variable coefficients. These results are used to show the non-existence of travelling waves in an inhomogeneous medium. (author). 33 refs

Numerical simulation of single bubble dynamics under acoustic travelling waves.

Science.gov (United States)

Ma, Xiaojian; Huang, Biao; Li, Yikai; Chang, Qing; Qiu, Sicong; Su, Zheng; Fu, Xiaoying; Wang, Guoyu

2018-04-01

The objective of this paper is to apply CLSVOF method to investigate the single bubble dynamics in acoustic travelling waves. The Naiver-Stokes equation considering the acoustic radiation force is proposed and validated to capture the bubble behaviors. And the CLSVOF method, which can capture the continuous geometric properties and satisfies mass conservation, is applied in present work. Firstly, the regime map, depending on the dimensionless acoustic pressure amplitude and acoustic wave number, is constructed to present different bubble behaviors. Then, the time evolution of the bubble oscillation is investigated and analyzed. Finally, the effect of the direction and the damping coefficient of acoustic wave propagation on the bubble behavior are also considered. The numerical results show that the bubble presents distinct oscillation types in acoustic travelling waves, namely, volume oscillation, shape oscillation, and splitting oscillation. For the splitting oscillation, the formation of jet, splitting of bubble, and the rebound of sub-bubbles may lead to substantial increase in pressure fluctuations on the boundary. For the shape oscillation, the nodes and antinodes of the acoustic pressure wave contribute to the formation of the "cross shape" of the bubble. It should be noted that the direction of the bubble translation and bubble jet are always towards the direction of wave propagation. In addition, the damping coefficient causes bubble in shape oscillation to be of asymmetry in shape and inequality in size, and delays the splitting process. Copyright © 2017 Elsevier B.V. All rights reserved.

Travelling wave solutions to nonlinear physical models by means

Indian Academy of Sciences (India)

This paper presents the first integral method to carry out the integration of nonlinear partial differential equations in terms of travelling wave solutions. For illustration, three important equations of mathematical physics are analytically investigated. Through the established first integrals, exact solutions are successfully ...

Emergence of traveling density waves in cyclic multiparticle transport

NARCIS (Netherlands)

Kannellopoulos, G.; van der Meer, Roger M.; van der Weele, J.P.

2015-01-01

Multiparticle flow through a cyclic array of connected compartments with a preferential direction is found to be able to organize itself in traveling waves. This behavior is connected with the transition between uniform flow and cluster formation. When the bias in the system is large, the particles

Time-dependent wave-packet study of the direct low-energy dissociative recombination of HD+

International Nuclear Information System (INIS)

Orel, A. E.

2000-01-01

Wave-packet methods involving the numerical solution of the time-dependent Schroedinger equation have been used with great success in the calculation of cross sections for dissociative recombination of molecular ions by electron impact in the high energy region where the ''boomerang'' model [L. Dube and A. Herzenberg, Phys. Rev. A 11, 1314 (1975)] is valid. We extend this method to study low-energy dissociative recombination where this approximation is no longer appropriate. We apply the method to the ''direct'' low-energy dissociative recombination of HD + . Our results are in excellent agreement with calculations using the multichannel quantum defect method. (c) 2000 The American Physical Society

Radiation from nonlinear coupling of plasma waves

International Nuclear Information System (INIS)

Fung, S.F.

1986-01-01

The author examines the generation of electromagnetic radiation by nonlinear resonant interactions of plasma waves in a cold, uniformly magnetized plasma. In particular, he considers the up-conversion of two electrostatic wave packets colliding to produce high frequency electromagnetic radiation. Efficient conversion of electrostatic to electromagnetic wave energy occurs when the pump amplitudes approach and exceed the pump depletion threshold. Results from the inverse scattering transform analysis of the three-wave interaction equations are applied. When the wave packets are initially separated, the fully nonlinear set of coupling equations, which describe the evolution of the wave packets, can be reduced to three separate eigenvalue problems; each can be considered as a scattering problem, analogous to eh Schroedinger equation. In the scattering space, the wave packet profiles act as the scattering potentials. When the wavepacket areas approach (or exceed) π/2, the wave functions are localized (bound states) and the scattering potentials are said to contain solitons. Exchange of solitons occurs during the interaction. The transfer of solitons from the pump waves to the electromagnetic wave leads to pump depletion and the production of strong radiation. The emission of radio waves is considered by the coupling of two upper-hybrid branch wave packets, and an upper-hybrid and a lower hybrid branch wave packet

Tunnel pressure waves - A smartphone inquiry on rail travel

Science.gov (United States)

Müller, Andreas; Hirth, Michael; Kuhn, Jochen

2016-02-01

When traveling by rail, you might have experienced the following phenomenon: The train enters a tunnel, and after some seconds a noticeable pressure change occurs, as perceived by your ears or even by a rapid wobbling of the train windows. The basic physics is that pressure waves created by the train travel down the tunnel, are reflected at its other end, and travel back until they meet the train again. Here we will show (i) how this effect can be well understood as a kind of large-scale outdoor case of a textbook paradigm, and (ii) how, e.g., a prediction of the tunnel length from the inside of a moving train on the basis of this model can be validated by means of a mobile phone measurement.

Travelling wave solutions to the K-P-P equation at supercritical wave speeds: a parallel to Simon Harris' probabilistic analysis

NARCIS (Netherlands)

Kyprianou, A.E.

2000-01-01

Recently Harris using probabilistic methods alone has given new proofs for the known existence asymptotics and unique ness of travelling wave solutions to the KPP equation Following in this vein we outline alternative probabilistic proofs for wave speeds exceeding the critical minimal wave speed

Traveling Wave Solutions of ZK-BBM Equation Sine-Cosine Method

Directory of Open Access Journals (Sweden)

Sadaf Bibi

2014-03-01

Full Text Available Travelling wave solutions are obtained by using a relatively new technique which is called sine-cosine method for ZK-BBM equations. Solution procedure and obtained results re-confirm the efficiency of the proposed scheme.

Integrable, oblique travelling waves in quasi-charge-neutral two-fluid plasmas

Directory of Open Access Journals (Sweden)

G. M. Webb

2008-02-01

Full Text Available A Hamiltonian description of oblique travelling waves in a two-fluid, charge-neutral, electron-proton plasma reveals that the transverse momentum equations for the electron and proton fluids are exactly integrable in cases where the total transverse momentum flux integrals, P_y^(d and P_z^(d, are both zero in the de Hoffman Teller (dHT frame. In this frame, the transverse electric fields are zero, which simplifies the transverse momentum equations for the two fluids. The integrable travelling waves for the case P_y^(d=P_z^(d=0, are investigated based on the Hamiltonian trajectories in phase space, and also on the longitudinal structure equation for the common longitudinal fluid velocity component u_x of the electron and proton fluids. Numerical examples of a variety of travelling waves in a cold plasma, including oscillitons, are used to illustrate the physics. The transverse, electron and proton velocity components u_jy and u_jz (j=e, p of the waves exhibit complex, rosette type patterns over several periods for u_x. The role of separatrices in the phase space, the rotational integral and the longitudinal structure equation on the different wave forms are discussed.

The propagation of travelling waves for stochastic generalized KPP equations

International Nuclear Information System (INIS)

Elworthy, K.D.; Zhao, H.Z.

1993-09-01

We study the existence and propagation of approximate travelling waves of generalized KPP equations with seasonal multiplicative white noise perturbations of Ito type. Three regimes of perturbation are considered: weak, milk, and strong. We show that weak perturbations have little effect on the wave like solutions of the unperturbed equations while strong perturbations essentially destroy the wave and force the solutions to die down. For mild perturbations we show that there is a residual wave form but propagating at a different speed to that of the unperturbed equation. In the appendix J.G. Gaines illustrates these different regimes by computer simulations. (author). 27 refs, 13 figs

Conditions for sustaining low-pressure plasma columns by travelling electromagnetic UHF waves

International Nuclear Information System (INIS)

Benova, E.; Zhelyazkov, I.

1997-01-01

The paper considers the conditions for sustaining low-pressure plasma columns by travelling electromagnetic waves in symmetric and dipolar modes, respectively. The treatment is fully electrodynamic. It is shown that the wave energy flux along the plasma column determines the conditions for sustaining the discharge. In particular as the plasma is sustained by a symmetric wave whose flux depends mainly on the radial distribution of the wave electric field whilst for a dipolar wave sustained plasma the flux is specified by the magnitude of the axial wave field component at the plasma-dielectric interface. (orig.)

Travelling wave solutions for an infection-age structured epidemic model with external supplies

International Nuclear Information System (INIS)

Ducrot, Arnaud; Magal, Pierre

2011-01-01

The aim of this paper is to investigate the spatial invasion of some infectious disease. The contamination process is described by the age since infection. Compared with the classical Kermack and McKendrick's model, the vital dynamic is not omitted, and we allow some constant input flux into the population. This problem is rather natural in the context of epidemic problems and it has not been studied. Here we prove an existence and non-existence result for travelling wave solutions. We also describe the minimal wave speed. We are able to construct a suitable Lyapunov like functional decreasing along the travelling wave allowing to derive some qualitative properties, namely their convergence towards equilibrium points at x = ±∞

Theory of multiwave mixing within the superconducting kinetic-inductance traveling-wave amplifier

Science.gov (United States)

Erickson, R. P.; Pappas, D. P.

2017-03-01

We present a theory of parametric mixing within the coplanar waveguide (CPW) of a superconducting nonlinear kinetic-inductance traveling-wave (KIT) amplifier engineered with periodic dispersion loadings. This is done by first developing a metamaterial band theory of the dispersion-engineered KIT using a Floquet-Bloch construction and then applying it to the description of mixing of the nonlinear RF traveling waves. Our theory allows us to calculate signal gain versus signal frequency in the presence of a frequency stop gap, based solely on loading design. We present results for both three-wave mixing (3WM), with applied dc bias, and four-wave mixing (4WM), without dc. Our theory predicts an intrinsic and deterministic origin to undulations of 4WM signal gain with signal frequency, apart from extrinsic sources, such as impedance mismatch, and shows that such undulations are absent from 3WM signal gain achievable with dc. Our theory is extensible to amplifiers based on Josephson junctions in a lumped LC-ladder transmission line (TWPA).

Drag reduction by streamwise traveling wave-like Lorenz Force in channel flow

International Nuclear Information System (INIS)

Mamori, Hiroya; Fukagata, Koji

2011-01-01

Skin-friction drag reduction effect of traveling wave-like wall-normal Lorenz force in a fully developed turbulent channel flow is investigated by means of direct numerical simulation. A sinusoidal profile of the wall-normal body force is assumed as the Lorenz force. While upstream traveling waves reduce the drag in the case of blowing/suction, standing waves reduce it in the case of present forcing. Visualization of vortical structure under the standing wave-like wall-normal Lorenz force reveals that the near-wall streamwise vortices, which increase the skin-friction drag, disappear and spanwise roller-like vortices are generated instead. Three component decomposition of the Reynolds shear stress indicates that the spanwise roller-like vortices contribute to the negative Reynolds shear stress in the region near the wall, similarly to the case of laminar flows. While the analogy between the wall-normal and streamwise forcings can be expected, the statistics are found to exhibit different behaviors due to the difference in the energy flow.

Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

International Nuclear Information System (INIS)

Yu Tsvelodub, O

2016-01-01

The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically. (paper)

Kinetic Monte Carlo simulations of travelling pulses and spiral waves in the lattice Lotka-Volterra model.

Science.gov (United States)

Makeev, Alexei G; Kurkina, Elena S; Kevrekidis, Ioannis G

2012-06-01

Kinetic Monte Carlo simulations are used to study the stochastic two-species Lotka-Volterra model on a square lattice. For certain values of the model parameters, the system constitutes an excitable medium: travelling pulses and rotating spiral waves can be excited. Stable solitary pulses travel with constant (modulo stochastic fluctuations) shape and speed along a periodic lattice. The spiral waves observed persist sometimes for hundreds of rotations, but they are ultimately unstable and break-up (because of fluctuations and interactions between neighboring fronts) giving rise to complex dynamic behavior in which numerous small spiral waves rotate and interact with each other. It is interesting that travelling pulses and spiral waves can be exhibited by the model even for completely immobile species, due to the non-local reaction kinetics.

Electron detector with a traVelling wave

International Nuclear Information System (INIS)

Goncharov, A.S.; Kazakov, V.M.; Kozlov, O.V.

1979-01-01

Basic principles of operation of a travelling-wave detector designed to measure the shapes of nanosecond electron pulses are discussed. Propagation of electrons through the input window into the detector results in spreading of TEM waves to both sides. The energy of the wave propagating towards resistor R is absorbed by the latter, while the wave propagating in the opposite direction hits a register. Thus good matching of all the detector elements results in the absence of reflection and standing waves which provides extremely high time resolution and minimum distortion of the electron pulse shape. The detector constitutes a piece of a cylindrical coaxial line whose impedance is equal to the impedance of a transmission line. On one side the detector is loaded onto resistor R equal to the wave resistance of the detector. On the other side the detector is loaded onto the transmission line which connects the detector with a wide-range register. The design and calculation of a detector having a time resolution of about 0.1 ns are presented. The results of testing the coaxial detector When measuring electron pulses with a duration of 60 ns and frequency of 1818 MHz have shown that the developed detector (external diameter being 63 mm, internal diameter 18 mm, length 400 mm) provides the 0.2 ns time resolution

The extended (G/G)-expansion method and travelling wave ...

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 82; Issue 6. The extended (′/)-expansion method and travelling wave solutions for the perturbed nonlinear Schrödinger's equation with Kerr law nonlinearity. Zaiyun Zhang Jianhua Huang Juan Zhong Sha-Sha Dou Jiao Liu Dan Peng Ting Gao. Research Articles ...

Time-dependent wave packet simulations of transport through Aharanov-Bohm rings with an embedded quantum dot.

Science.gov (United States)

Kreisbeck, C; Kramer, T; Molina, R A

2017-04-20

We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin-Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations.

Traveling wave deflector design for femtosecond streak camera

International Nuclear Information System (INIS)

Pei, Chengquan; Wu, Shengli; Luo, Duan; Wen, Wenlong; Xu, Junkai; Tian, Jinshou; Zhang, Minrui; Chen, Pin; Chen, Jianzhong; Liu, Rong

2017-01-01

In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.

Nonlinear travelling waves in rotating Hagen–Poiseuille flow

Science.gov (United States)

Pier, Benoît; Govindarajan, Rama

2018-03-01

The dynamics of viscous flow through a rotating pipe is considered. Small-amplitude stability characteristics are obtained by linearizing the Navier–Stokes equations around the base flow and solving the resulting eigenvalue problems. For linearly unstable configurations, the dynamics leads to fully developed finite-amplitude perturbations that are computed by direct numerical simulations of the complete Navier–Stokes equations. By systematically investigating all linearly unstable combinations of streamwise wave number k and azimuthal mode number m, for streamwise Reynolds numbers {{Re}}z ≤slant 500 and rotational Reynolds numbers {{Re}}{{Ω }} ≤slant 500, the complete range of nonlinear travelling waves is obtained and the associated flow fields are characterized.

Traveling wave deflector design for femtosecond streak camera

Energy Technology Data Exchange (ETDEWEB)

Pei, Chengquan; Wu, Shengli [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Luo, Duan [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wen, Wenlong [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Xu, Junkai [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tian, Jinshou, E-mail: tianjs@opt.ac.cn [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Zhang, Minrui; Chen, Pin [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Jianzhong [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Liu, Rong [Xi' an Technological University, Xi' an 710021 (China)

2017-05-21

In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.

A novel traveling wave piezoelectric actuated tracked mobile robot utilizing friction effect

Science.gov (United States)

Wang, Liang; Shu, Chengyou; Jin, Jiamei; Zhang, Jianhui

2017-03-01

A novel traveling wave piezoelectric-actuated tracked mobile robot with potential application to robotic rovers was proposed and investigated in this study. The proposed tracked mobile robot is composed of a parallelogram-frame-structure piezoelectric transducer with four rings and a metal track. Utilizing the converse piezoelectric and friction effects, traveling waves were propagated in the rings and then the metal track was actuated by the piezoelectric transducer. Compared with traditional tracked mechanisms, the proposed tracked mobile robot has a simpler and more compact structure without lubricant, which eliminates the problem of lubricant volatilization and deflation, thus, it could be operated in the vacuum environment. Dynamic characteristics were simulated and measured to reveal the mechanism of actuating track of the piezoelectric transducer. Experimental investigations of the traveling wave piezoelectric-actuated tracked mobile robot were then carried out, and the results indicated that the robot prototype with a pair of exciting voltages of 460 Vpp is able to achieve a maximum velocity of 57 mm s-1 moving on the foam plate and possesses the obstacle crossing capability with a maximum height of 27 mm. The proposed tracked mobile robot exhibits potential to be the driving system of robotic rovers.

Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments

Science.gov (United States)

Tarditi, A. G.; George, J. A.; Miley, G. H.; Scott, J. H.

2013-01-01

Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.

The classification of the single travelling wave solutions to the ...

Indian Academy of Sciences (India)

The discrimination system for the polynomial method is applied to variant Boussinesq equations to classify single travelling wave solutions. In particular, we construct corresponding solutions to the concrete parameters to show that each solution in the classification can be realized.

Nonlinearly driven oscillations in the gyrotron traveling-wave amplifier

International Nuclear Information System (INIS)

Chiu, C. C.; Pao, K. F.; Yan, Y. C.; Chu, K. R.; Barnett, L. R.; Luhmann, N. C. Jr.

2008-01-01

By delivering unprecedented power and gain, the gyrotron traveling-wave amplifier (gyro-TWT) offers great promise for advanced millimeter wave radars. However, the underlying physics of this complex nonlinear system is yet to be fully elucidated. Here, we report a new phenomenon in the form of nonlinearly driven oscillations. A zero-drive stable gyro-TWT is shown to be susceptible to a considerably reduced dynamic range at the band edge, followed by a sudden transition into driven oscillations and then a hysteresis effect. An analysis of this unexpected behavior and its physical interpretation are presented.

Exact traveling wave solutions of the bbm and kdv equations using (G'/G)-expansion method

International Nuclear Information System (INIS)

Saddique, I.; Nazar, K.

2009-01-01

In this paper, we construct the traveling wave solutions involving parameters of the Benjamin Bona-Mahony (BBM) and KdV equations in terms of the hyperbolic, trigonometric and rational functions by using the (G'/G)-expansion method, where G = G(zeta) satisfies a second order linear ordinary differential equation. When the parameters are taken special values, the Solitary was are derived from the traveling waves. (author)

SPREADING SPEEDS AND TRAVELING WAVES FOR NON-COOPERATIVE INTEGRO-DIFFERENCE SYSTEMS

Science.gov (United States)

Wang, Haiyan; Castillo-Chavez, Carlos

2014-01-01

The study of spatially explicit integro-difference systems when the local population dynamics are given in terms of discrete-time generations models has gained considerable attention over the past two decades. These nonlinear systems arise naturally in the study of the spatial dispersal of organisms. The brunt of the mathematical research on these systems, particularly, when dealing with cooperative systems, has focused on the study of the existence of traveling wave solutions and the characterization of their spreading speed. Here, we characterize the minimum propagation (spreading) speed, via the convergence of initial data to wave solutions, for a large class of non cooperative nonlinear systems of integro-difference equations. The spreading speed turns out to be the slowest speed from a family of non-constant traveling wave solutions. The applicability of these theoretical results is illustrated through the explicit study of an integro-difference system with local population dynamics governed by Hassell and Comins’ non-cooperative competition model (1976). The corresponding integro-difference nonlinear systems that results from the redistribution of individuals via a dispersal kernel is shown to satisfy conditions that guarantee the existence of minimum speeds and traveling waves. This paper is dedicated to Avner Friedman as we celebrate his immense contributions to the fields of partial differential equations, integral equations, mathematical biology, industrial mathematics and applied mathematics in general. His leadership in the mathematical sciences and his mentorship of students and friends over several decades has made a huge difference in the personal and professional lives of many, including both of us. PMID:24899868

The Influence of Drift Gas Composition on the Separation Mechanism in Traveling Wave Ion Mobility Spectrometry: Insight from Electrodynamic Simulations.

Science.gov (United States)

May, Jody C; McLean, John A

2003-06-01

The influence of three different drift gases (helium, nitrogen, and argon) on the separation mechanism in traveling wave ion mobility spectrometry is explored through ion trajectory simulations which include considerations for ion diffusion based on kinetic theory and the electrodynamic traveling wave potential. The model developed for this work is an accurate depiction of a second-generation commercial traveling wave instrument. Three ion systems (cocaine, MDMA, and amphetamine) whose reduced mobility values have previously been measured in different drift gases are represented in the simulation model. The simulation results presented here provide a fundamental understanding of the separation mechanism in traveling wave, which is characterized by three regions of ion motion: (1) ions surfing on a single wave, (2) ions exhibiting intermittent roll-over onto subsequent waves, and (3) ions experiencing a steady state roll-over which repeats every few wave cycles. These regions of ion motion are accessed through changes in the gas pressure, wave amplitude, and wave velocity. Resolving power values extracted from simulated arrival times suggest that momentum transfer in helium gas is generally insufficient to access regions (2) and (3) where ion mobility separations occur. Ion mobility separations by traveling wave are predicted to be effectual for both nitrogen and argon, with slightly lower resolving power values observed for argon as a result of band-broadening due to collisional scattering. For the simulation conditions studied here, the resolving power in traveling wave plateaus between regions (2) and (3), with further increases in wave velocity contributing only minor improvements in separations.

Electron and VLF travel time differences for wave-particle interactions at L=4: Pt. 2

International Nuclear Information System (INIS)

Rash, J.P.S.; Scourfield, M.W.J.; Dougherty, M.K.

1984-01-01

The cyclotron resonance or gyroresonance interaction has been widely invoked as a generation mechanism for discrete VLF emissions and plasmaspheric hiss. This interaction involves electrons and VLF waves travelling in opposite directions along a geomagnetic field line. We examine, for an interaction region in the equatorial plane at L=4, the energy of the resonant electrons as a function of VLF wave frequency and ambient equatorial electron density. Then for two different spatial configurations of the interaction and two standard plasma distribution models we examine the difference in travel times to a ground-based observer in the Southern hemisphere for the electrons and waves taking part in the interaction. This difference in travel times is shown as a function of VLF wave frequency and equatorial electron density. The results, and their significance for observations of auroral electrons and VLF at Sanae, Antarctica, are discussed and compared with similar results for the Cerenkov interaction discussed in an earlier paper

Possibility to Probe Negative Values of a Wigner Function in Scattering of a Coherent Superposition of Electronic Wave Packets by Atoms.

Science.gov (United States)

Karlovets, Dmitry V; Serbo, Valeriy G

2017-10-27

Within a plane-wave approximation in scattering, an incoming wave packet's Wigner function stays positive everywhere, which obscures such purely quantum phenomena as nonlocality and entanglement. With the advent of the electron microscopes with subnanometer-sized beams, one can enter a genuinely quantum regime where the latter effects become only moderately attenuated. Here we show how to probe negative values of the Wigner function in scattering of a coherent superposition of two Gaussian packets with a nonvanishing impact parameter between them (a Schrödinger's cat state) by atomic targets. For hydrogen in the ground 1s state, a small parameter of the problem, a ratio a/σ_{⊥} of the Bohr radius a to the beam width σ_{⊥}, is no longer vanishing. We predict an azimuthal asymmetry of the scattered electrons, which is found to be up to 10%, and argue that it can be reliably detected. The production of beams with the not-everywhere-positive Wigner functions and the probing of such quantum effects can open new perspectives for noninvasive electron microscopy, quantum tomography, particle physics, and so forth.

The Direct Digital Modulation of Traveling Wave Tubes

Science.gov (United States)

Radhamohan, Ranjan S.

2004-01-01

Traveling wave tube (TWT) technology, first described by Rudolf Kompfner in the early 1940s, has been a key component of space missions from the earliest communication satellites in the 1960s to the Cassini probe today. TWTs are essentially signal amplifiers that have the special capability of operating at microwave frequencies. The microwave frequency range, which spans from approximately 500 MHz to 300 GHz, is shared by many technologies including cellular phones, satellite television, space communication, and radar. TWT devices are superior in reliability, weight, and efficiency to solid-state amplifiers at the high power and frequency levels required for most space missions. TWTs have three main components -an electron gun, slow wave structure, and collector. The electron gun generates an electron beam that moves along the length of the tube axis, inside of the slow wave circuit. At the same time, the inputted signal is slowed by its travel through the coils of the helical slow wave circuit. The interaction of the electron beam and this slowed signal produces a transfer of kinetic energy to the signal, and in turn, amplification. At the end of its travel, the spent electron beam moves into the collector where its remaining energy is dissipated as heat or harnessed for reuse. TWTs can easily produce gains in the tens of decibels, numbers that are suitable for space missions. To date, however, TWTs have typically operated at fixed levels of gain. This gain is determined by various, unchanging, physical factors of the tube. Traditionally, to achieve varying gain, an input signal s amplitude has had to first be modulated by a separate device before being fed into the TWT. This is not always desirable, as significant distortion can occur in certain situations. My mentor, Mr. Dale Force, has proposed an innovative solution to this problem called direct digital modulation . The testing and implementation of this solution is the focus of my summer internship. The

New exact travelling wave solutions of generalised sinh- Gordon and (2 + 1-dimensional ZK-BBM equations

Directory of Open Access Journals (Sweden)

Sachin Kumar

2012-10-01

Full Text Available Exact travelling wave solutions have been established for generalised sinh-Gordon andgeneralised (2+1 dimensional ZK-BBM equations by using GG      expansion method whereG  G( satisfies a second-order linear ordinary differential equation. The travelling wave solutionsare expressed by hyperbolic, trigonometric and rational functions.

Qualitative analysis and traveling wave solutions for the perturbed nonlinear Schroedinger's equation with Kerr law nonlinearity

International Nuclear Information System (INIS)

Zhang Zaiyun; Liu Zhenhai; Miao Xiujin; Chen Yuezhong

2011-01-01

In this Letter, we investigate the perturbed nonlinear Schroedinger's equation (NLSE) with Kerr law nonlinearity. All explicit expressions of the bounded traveling wave solutions for the equation are obtained by using the bifurcation method and qualitative theory of dynamical systems. These solutions contain bell-shaped solitary wave solutions, kink-shaped solitary wave solutions and Jacobi elliptic function periodic solutions. Moreover, we point out the region which these periodic wave solutions lie in. We present the relation between the bounded traveling wave solution and the energy level h. We find that these periodic wave solutions tend to the corresponding solitary wave solutions as h increases or decreases. Finally, for some special selections of the energy level h, it is shown that the exact periodic solutions evolute into solitary wave solution.

Investigating The Travelling Wave Solution For an SIR Endemic ...

African Journals Online (AJOL)

This paper presents the travelling wave solution for an SIR endemic disease model with no disease related death when the spatial spread of the susceptible is not negligible. In this case the disease is driven by both the susceptible and the infective classes. The population is open since the disease is habitually prevalent in ...

Phase defects and spatiotemporal disorder in traveling-wave convection patterns

International Nuclear Information System (INIS)

La Porta, A.; Surko, C.M.

1997-01-01

Spatiotemporal disorder is studied in traveling-wave convection in ethanol-water mixtures. Spectral measures of disorder, linear correlation functions, and mutual information are used to characterize the patterns, and are found to give a weak indication of the level of disorder. The calculation of the complex order parameter for experimental patterns is described. It is found that the ordering of the patterns is accompanied by a dramatic change in the topological structure of the order parameter. Specific arrangements of defects are found to be associated with the elements of traveling-wave patterns, and the net charge and total number of defects is introduced as a measure of disorder in the patterns. The coarsening of the patterns is marked by an accumulation of net charge and a dramatic decrease in the number of defects. The physical significance of the defects is discussed, and it is shown that the phase velocity of the waves is lower in the vicinity of the defects. The defect-defect correlation functions are calculated for the convection patterns. It is shown that the ordering of the patterns is closely related to the apparent defect-defect interactions. copyright 1997 The American Physical Society

The probability distribution of the delay time of a wave packet in strong overlap of resonance levels

International Nuclear Information System (INIS)

Lyuboshitz, V.L.

1982-01-01

The time development of nuclear reactions at a large density of levels is investigated using the theory of overlapping resonances. The analytical expression for the function describing the time delay probability distribution of a wave packet is obtained in the framework of the model of n equi - valent channels. It is shown that a relative fluctuation of the time delay at the stage of the compound nucleus is snall. The possibility is discussed of increasing the duration of nuclear raactions with rising excitation energy

The classification of the single travelling wave solutions to the ...

Indian Academy of Sciences (India)

a large number of methods for finding exact solutions have been established and devel ... Painleve method [1] and transformed rational function method for finding ... travelling wave transformation and integrating it, the nonlinear differential ...... The project is supported by Scientific Research Fund of Education Department of.

Pulsed Traveling-wave Quadrature Squeezing Using Quasi-phase Matched Lithium Niobate Crystals

Science.gov (United States)

Chen, Chao-Hsiang

Interests in generating higher quantum noise squeezing in order to develop methods to enhance optical measurement below the shot-noise limit in various applications has grown in recent years. The noise suppression from squeezing can improve the SNR in coherent optical systems when the returning signal power is weak, such as optical coherence tomography, LADAR, confocal microscopy and low-light coherent imaging. Unlike the generation of squeezing with a continuous wave, which is currently developed mainly for gravitational wave detection in LIGO project, the study of pulsed-traveling waves is focused on industrial, medical and other commercial interests. This dissertation presents the experimental results of pulsed traveling wave squeezing. The intention of the study is to explore the possibility of using quasi-phase matched crystals to generate the highest possible degree of quadrature squeezing. In order to achieve this goal, efforts to test the various effects from spatial Gaussian modes and relative beam waist placement for the second-harmonic pump were carried out in order to further the understanding of limiting factors to pulsed traveling wave squeezing. 20mm and 30mm-long periodically poled lithium noibate (PPLN) crystals were used in the experiment to generate a squeezed vacuum state. A maximum of 4.2+/-0.2dB quadrature squeezing has been observed, and the measured anti-squeezing exceeds 20dB.The phase sensitive amplification (PSA) gain and de-gain performance were also measured to compare the results of measured squeezing. The PPLN crystals can produce high conversion efficiency of second-harmonic generation (SHG) without a cavity. When a long PPLN crystal is used in a squeezer, the beam propagation in the nonlinear medium does not follow the characteristics in thin crystals. Instead, it is operated under the long-crystal criteria, which the crystal length is multiple times longer than the Rayleigh range of the injected beam i n the crystals. Quasi

Some Further Results on Traveling Wave Solutions for the ZK-BBM( Equations

Directory of Open Access Journals (Sweden)

Shaoyong Li

2013-01-01

Full Text Available We investigate the traveling wave solutions for the ZK-BBM( equations by using bifurcation method of dynamical systems. Firstly, for ZK-BBM(2, 2 equation, we obtain peakon wave, periodic peakon wave, and smooth periodic wave solutions and point out that the peakon wave is the limit form of the periodic peakon wave. Secondly, for ZK-BBM(3, 2 equation, we obtain some elliptic function solutions which include periodic blow-up and periodic wave. Furthermore, from the limit forms of the elliptic function solutions, we obtain some trigonometric and hyperbolic function solutions which include periodic blow-up, blow-up, and smooth solitary wave. We also show that our work extends some previous results.

Wave Packet Simulation of Nonadiabatic Dynamics in Highly Excited 1,3-Dibromopropane

DEFF Research Database (Denmark)

Brogaard, Rasmus Y.; Møller, Klaus Braagaard; Sølling, Theis Ivan

2008-01-01

]. In the experiment. DBP is excited to a Rydberg state 8 eV above the ground state. The interpretation of the results is that a torsional motion of the bromomethylene groups with a vibrational period of 680 is is activated upon excitation. The Rydberg state decays to a valence state, causing a dissociation of one...... of the carbon bromine bonds oil a time scale of 2.5 ps. Building the theoretical framework for the wave packet propagation around this model of the reaction dynamics, the Simulations reproduce, to a good extent, the time scales observed in the experiment. Furthermore. the Simulations provide insight into how...... the torsion motion influences the bond breakage, and C we can conclude that the mechanism that delays the dissociation is solely the electronic transition from the Rydberg state to the valence state and does not involve, for example, intramolecular vibrational energy redistribution (IVR)....

Whole body traveling wave magnetic resonance imaging at high field strength: homogeneity, efficiency, and energy deposition as compared with traditional excitation mechanisms.

Science.gov (United States)

Zhang, Bei; Sodickson, Daniel K; Lattanzi, Riccardo; Duan, Qi; Stoeckel, Bernd; Wiggins, Graham C

2012-04-01

In 7 T traveling wave imaging, waveguide modes supported by the scanner radiofrequency shield are used to excite an MR signal in samples or tissue which may be several meters away from the antenna used to drive radiofrequency power into the system. To explore the potential merits of traveling wave excitation for whole-body imaging at 7 T, we compare numerical simulations of traveling wave and TEM systems, and juxtapose full-wave electrodynamic simulations using a human body model with in vivo human traveling wave imaging at multiple stations covering the entire body. The simulated and in vivo traveling wave results correspond well, with strong signal at the periphery of the body and weak signal deep in the torso. These numerical results also illustrate the complicated wave behavior that emerges when a body is present. The TEM resonator simulation allowed comparison of traveling wave excitation with standard quadrature excitation, showing that while the traveling wave B +1 per unit drive voltage is much less than that of the TEM system, the square of the average B +1 compared to peak specific absorption rate (SAR) values can be comparable in certain imaging planes. Both systems produce highly inhomogeneous excitation of MR signal in the torso, suggesting that B(1) shimming or other parallel transmission methods are necessary for 7 T whole body imaging. Copyright © 2011 Wiley-Liss, Inc.

The classification of single travelling wave solutions to the Camassa ...

Indian Academy of Sciences (India)

Introduction. Classifications of single travelling wave solutions to some nonlinear differential equations have been obtained extensively by the complete discrimination system for polynomial method proposed by Liu [1–7]. Furthermore, Wang and Li [8] used Liu's method and factorization method proposed by Cornejo-Pérez ...

Travelling wave solutions for a singularly perturbed Burgers–KdV ...

Indian Academy of Sciences (India)

This paper concerns with the existence problem of travelling wave solutions to a singularly perturbed Burgers–KdV equation. For this, we use the dynamical systems approach, specifically, the geometric singular perturbation theory and centre manifold theory. We also numerically show approximations, in particular, for ...

Nonlinear self-modulation of ion-acoustic waves

International Nuclear Information System (INIS)

Ikezi, H.; Schwarzenegger, K.; Simons, A.L.; Ohsawa, Y.; Kamimura, T.

1978-01-01

The nonlinear evolution of an ion-acoustic wave packet is studied. Experimentally, it is found that (i) nonlinear phase modulation develops in the wave packet; (ii) the phase modulation, together with the dispersion effect, causes expansion and breaking of the wave packet; (iii) the ions trapped in the troughs of the wave potential introduce self-phase modulation; and (iv) the ion-acoustic wave is stable with respect to the modulational instability. Computer simulations have reproduced the experimental results. The physical picture and the model equation describing the wave evolution are discussed

First tests of a traveling-wave chopper for the ATLAS positive ion linac

International Nuclear Information System (INIS)

Pardo, R. C.

1998-01-01

A ten segment traveling-wave chopper has been constructed and successfully tested at 5% of the design 12 MHz repetition rate. The chopper must remove unbunched tails from a partially bunched heavy-ion beam in order to avoid undue emittance growth in the linac and the production of undesirable satellite beam bunches. When poorly bunched beams traverse the traditional sine-wave chopper, it produces unacceptable transverse emittance growth and unnecessary beam loss. These effects are expected to be much reduced in the traveling wave chopper. First tests have confirmed the validity of these claims, clearly showing much reduced transverse emittance growth as compared to the original sine wave chopper and excellent selectivity for the desired beam. Details of these tests will be presented and compared to calculations. Operation of the new chopper at the full 12 MHz rate is the next goal. Development of a driver power supply capable of full CW operation will also be described

Travelling water waves with compactly supported vorticity