Revivals of Rydberg wave packets
International Nuclear Information System (INIS)
Bluhm, R.; Kostelecky, V.A.; Tudose, B.
1998-01-01
We examine the revival structure of Rydberg wave packets. These wave packets exhibit initial classical periodic motion followed by a sequence of collapse, fractional (or full) revivals, and fractional (or full) superrevivals. The effects of quantum defects on wave packets in alkali-metal atoms and a squeezed-state description of the initial wave packets are also considered. We then examine the revival structure of Rydberg wave packets in the presence of an external electric field - that is, the revival structure of Stark wave packets. These wave packets have energies that depend on two quantum numbers and exhibit new types of interference behavior
International Nuclear Information System (INIS)
Robinett, R.W.
2004-01-01
The numerical prediction, theoretical analysis, and experimental verification of the phenomenon of wave packet revivals in quantum systems has flourished over the last decade and a half. Quantum revivals are characterized by initially localized quantum states which have a short-term, quasi-classical time evolution, which then can spread significantly over several orbits, only to reform later in the form of a quantum revival in which the spreading reverses itself, the wave packet relocalizes, and the semi-classical periodicity is once again evident. Relocalization of the initial wave packet into a number of smaller copies of the initial packet ('minipackets' or 'clones') is also possible, giving rise to fractional revivals. Systems exhibiting such behavior are a fundamental realization of time-dependent interference phenomena for bound states with quantized energies in quantum mechanics and are therefore of wide interest in the physics and chemistry communities. We review the theoretical machinery of quantum wave packet construction leading to the existence of revivals and fractional revivals, in systems with one (or more) quantum number(s), as well as discussing how information on the classical period and revival time is encoded in the energy eigenvalue spectrum. We discuss a number of one-dimensional model systems which exhibit revival behavior, including the infinite well, the quantum bouncer, and others, as well as several two-dimensional integrable quantum billiard systems. Finally, we briefly review the experimental evidence for wave packet revivals in atomic, molecular, and other systems, and related revival phenomena in condensed matter and optical systems
revivals of Rydberg wave packets
International Nuclear Information System (INIS)
Bluhm, R.; Kostelecky, V.A.; Tudose, B.
1998-01-01
We examine the revival structure of Rydberg wave packets. The effects of quantum defects on wave packets in alkali-metal atoms and a squeezed-state description of the initial wave packets are also described. We then examine the revival structure of Rydberg wave packets in the presence of an external electric field, i.e., the revival structure of Stark wave packets. These wave packets have energies that depend on two quantum numbers and exhibit new types of interference behaviour
Shaarawi, Amr Mohamed
In this work, nondispersive wavepacket solutions to linear partial differential equations are investigated. These solutions are characterized by infinite energy content; otherwise they are continuous, nonsingular and propagate in free space without spreading out. Examples of such solutions are Berry and Balazs' Airy packet, MacKinnon's wave packet and Brittingham's Focus Wave Mode (FWM). It is demonstrated in this thesis that the infinite energy content is not a basic problem per se and that it can be dealt with in two distinct ways. First these wave packets can be used as bases to construct highly localized, slowly decaying, time-limited pulsed solutions. In the case of the FWMs, this path leads to the formulation of the bidirectional representation, a technique that provides the most natural basis for synthesizing Brittingham-like solutions. This representation is used to derive new exact solutions to the 3-D scalar wave equation. It is also applied to problems involving boundaries, in particular to the propagation of a localized pulse in a infinite acoustic waveguide and to the launchability of such a pulse from the opening of a semi-infinite waveguide. The second approach in dealing with the infinite energy content utilizes the bump-like structure of nondispersive solutions. With an appropriate choice of parameters, these bump fields have very large amplitudes around the centers, in comparison to their tails. In particular, the FWM solutions are used to model massless particles and are capable of providing an interesting interpretation to the results of Young's two slit experiment and to the wave-particle duality of light. The bidirectional representation provides, also, a systematic way of deriving packet solutions to the Klein-Gordon, the Schrodinger and the Dirac equations. Nondispersive solutions of the former two equations are compared to previously derived ones, e.g., the Airy packet and MacKinnon's wave packet.
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
Revivals of Quantum Wave Packets
Bluhm, Robert; Kostelecky, Alan; Porter, James; Tudose, Bogdan
1997-01-01
We present a generic treatment of wave-packet revivals for quantum-mechanical systems. This treatment permits a classification of certain ideal revival types. For example, wave packets for a particle in a one-dimensional box are shown to exhibit perfect revivals. We also examine the revival structure of wave packets for quantum systems with energies that depend on two quantum numbers. Wave packets in these systems exhibit quantum beats in the initial motion as well as new types of long-term r...
Scattering of accelerated wave packets
Longhi, S.; Horsley, S. A. R.; Della Valle, G.
2018-03-01
Wave-packet scattering from a stationary potential is significantly modified when the wave packet is subject to an external time-dependent force during the interaction. In the semiclassical limit, wave-packet motion is simply described by Newtonian equations, and the external force can, for example, cancel the potential force, making a potential barrier transparent. Here we consider wave-packet scattering from reflectionless potentials, where in general the potential becomes reflective when probed by an accelerated wave packet. In the particular case of the recently introduced class of complex Kramers-Kronig potentials we show that a broad class of time-dependent forces can be applied without inducing any scattering, while there is a breakdown of the reflectionless property when there is a broadband distribution of initial particle momentum, involving both positive and negative components.
Attosecond electron wave packet interferometry
International Nuclear Information System (INIS)
Remetter, T.; Ruchon, T.; Johnsson, P.; Varju, K.; Gustafsson, E.
2006-01-01
Complete test of publication follows. The well controlled generation and characterization of attosecond XUV light pulses provide an unprecedented tool to study electron wave packets (EWPs). Here a train of attosecond pulses is used to create and study the phase of an EWP in momentum space. There is a clear analogy between electronic wave functions and optical fields. In optics, methods like SPIDER or wave front shearing interferometry, allow to measure the spectral or spatial phase of a light wave. These two methods are based on the same principle: an interferogram is produced when recombining two sheared replica of a light pulse, spectrally (SPIDER) or spatially (wave front shearing interferometry). This enables the comparison of two neighbouring different spectral or spatial slices of the original wave packet. In the experiment, a train of attosecond pulses is focused in an Argon atomic gas jet. EWPs are produced from the single XUV photon ionization of Argon atoms. If an IR beam is synchronized to the EWPs, it is possible to introduce a shear in momentum space between two consecutive s wave packets. A Velocity Map Imaging Spectrometer (VMIS) enables us to detect the interference pattern. An analysis of the interferograms will be presented leading to a conclusion about the symmetry of the studied wave packet.
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.
Dynamics of quantum wave packets
International Nuclear Information System (INIS)
Gosnell, T.R.; Taylor, A.J.; Rodriguez, G.; Clement, T.S.
1998-01-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to develop ultrafast laser techniques for the creation and measurement of quantum vibrational wave packets in gas phase diatomic molecules. Moreover, the authors sought to manipulate the constitution of these wave packets in terms of harmonic-oscillator basis wavefunctions by manipulating the time-dependent amplitude and phase of the incident ultrashort laser pulse. They specifically investigated gaseous diatomic potassium (K 2 ), and discovered variations in the shape of the wave packets as a result of changing the linear chirp in the ultrashort preparation pulse. In particular, they found evidence for wave-packet compression for a specific degree of chirp. Important ancillary results include development of new techniques for denoising and deconvolution of femtosecond time traces and techniques for diagnosing the phase and amplitude of the electric field of femtosecond laser pulses
Spreading of a relativistic wave packet
International Nuclear Information System (INIS)
Almeida, C.; Jabs, A.
1983-01-01
A simple general proof that the spreading velocity of a relativistic free wave packet of the Broglie waves is limited is presented. For a wide class of packets it is confirmed that the limit is the velocity of light, and it is shown how this limit is approached when the width Δp of the wave packet in momentum space tends to infinity and the minimum width σ(t=o) in ordinary space tends to zero. (Author) [pt
Time evolution of wave packets on nanostructures
International Nuclear Information System (INIS)
Prunele, E de
2005-01-01
Time evolution of wave packets on nanostructures is studied on the basis of a three-dimensional solvable model with singular interactions (de Prunele 1997 J. Phys. A: Math. Gen. 30 7831). In particular, methods and tools are provided to determine time independent upper bounds for the overlap of the normalized time-dependent wave packet with the time independent normalized wave packet concentrated at an arbitrarily chosen vertex of the nanosystem. The set of upper bounds referring to all initial positions of the wave packet and all overlaps are summarized in a matrix. The analytical formulation allows a detailed study for arbitrary geometrical configurations. Time evolution on truncated quasicrystalline systems has been found to be site selective, depending on the position of the initial wave packet
International Nuclear Information System (INIS)
Naumov, D.V.
2013-01-01
In this paper we discuss some aspects of the theory of wave packets. We consider a popular non-covariant Gaussian model used in various applications and show that it predicts too slow a longitudinal dispersion rate for relativistic particles. We revise this approach by considering a covariant model of Gaussian wave packets, and examine our results by inspecting a wave packet of an arbitrary form. A general formula for the time dependence of the dispersion of a wave packet of an arbitrary form is found. Finally, we give a transparent interpretation of the disappearance of the wave function over time due to the dispersion - a feature often considered undesirable, but which is unavoidable for wave packets. We find, starting with simple examples, proceeding with their generalizations and finally by considering the continuity equation, that the integral over time of both the flux and probability densities is asymptotically proportional to the factor 1/|x| 2 in the rest frame of the wave packet, just as in the case of an ensemble of classical particles
Revivals of quantum wave packets in graphene
International Nuclear Information System (INIS)
Krueckl, Viktor; Kramer, Tobias
2009-01-01
We investigate the propagation of wave packets on graphene in a perpendicular magnetic field and the appearance of collapses and revivals in the time evolution of an initially localized wave packet. The wave-packet evolution in graphene differs drastically from the one in an electron gas and shows a rich revival structure similar to the dynamics of highly excited Rydberg states. We present a novel numerical wave-packet propagation scheme in order to solve the effective single-particle Dirac-Hamiltonian of graphene and show how the collapse and revival dynamics is affected by the presence of disorder. Our effective numerical method is of general interest for the solution of the Dirac equation in the presence of potentials and magnetic fields.
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.
High Angular Momentum Rydberg Wave Packets
Wyker, Brendan
2011-12-01
High angular momentum Rydberg wave packets are studied. Application of carefully tailored electric fields to low angular momentum, high- n (n ˜ 300) Rydberg atoms creates coherent superpositions of Stark states with near extreme values of angular momentum, ℓ. Wave packet components orbit the parent nucleus at rates that depend on their energy, leading to periods of localization and delocalization as the components come into and go out of phase with each other. Monitoring survival probability signals in the presence of position dependent probing leads to observation of characteristic oscillations based on the composition of the wave packet. The discrete nature of electron energy levels is observed through the measurement of quantum revivals in the wave packet localization signal. Time-domain spectroscopy of these signals allows determination of both the population and phase of individual superposition components. Precise manipulation of wave packets is achieved through further application of pulsed electric fields. Decoherence effects due to background gas collisions and electrical noise are also detailed. Quantized classical trajectory Monte-Carlo simulations are introduced and agree remarkably well with experimental results.
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
Gabor Wave Packet Method to Solve Plasma Wave Equations
International Nuclear Information System (INIS)
Pletzer, A.; Phillips, C.K.; Smithe, D.N.
2003-01-01
A numerical method for solving plasma wave equations arising in the context of mode conversion between the fast magnetosonic and the slow (e.g ion Bernstein) wave is presented. The numerical algorithm relies on the expansion of the solution in Gaussian wave packets known as Gabor functions, which have good resolution properties in both real and Fourier space. The wave packets are ideally suited to capture both the large and small wavelength features that characterize mode conversion problems. The accuracy of the scheme is compared with a standard finite element approach
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.)
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 Evolution and Revival Structure of Localized Quantum Wave Packets
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...
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
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
Massachusetts Bay - Internal wave packets digitized from SAR imagery
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...
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
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.
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
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.
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.
Do Free Quantum-Mechanical Wave Packets Always Spread?
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.…
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...
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 ...
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.
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.)
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.
International Nuclear Information System (INIS)
Graham, D. B.; Robinson, P. A.; Cairns, Iver H.; Skjaeraasen, O.
2011-01-01
Large-scale simulations of wave packet collapse are performed by numerically solving the three-dimensional (3D) electromagnetic Zakharov equations, focusing on individual wave packet collapses and on wave packets that form in continuously driven strong turbulence. The collapse threshold is shown to decrease as the electron thermal speed ν e /c increases and as the temperature ratio T i /T e of ions to electrons decreases. Energy lost during wave packet collapse and dissipation is shown to depend on ν e /c. The dynamics of density perturbations after collapse are studied in 3D electromagnetic strong turbulence for a range of T i /T e . The structures of the Langmuir, transverse, and total electric field components of wave packets during strong turbulence are investigated over a range of ν e /c. For ν e /c e /c > or approx. 0.17, transverse modes become trapped in density wells and contribute significantly to the structure of the total electric field. At all ν e /c, the Langmuir energy density contours of wave packets are predominantly oblate (pancake shaped). The transverse energy density contours of wave packets are predominantly prolate (sausage shaped), with the major axis being perpendicular to the major axes of the Langmuir component. This results in the wave packet becoming more nearly spherical as ν e /c increases, and in turn generates more spherical density wells during collapse. The results obtained are compared with previous 3D electrostatic results and 2D electromagnetic results.
Coulomb Final State Interactions for Gaussian Wave Packets
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.
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
Engineering and manipulating exciton wave packets
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.
Transfer of a wave packet in double-well potential
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.
Resonance-assisted decay of nondispersive wave packets
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.
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....
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.
Airy Wave Packets Accelerating in Space-Time
Kondakci, H. Esat; Abouraddy, Ayman F.
2018-04-01
Although diffractive spreading is an unavoidable feature of all wave phenomena, certain waveforms can attain propagation invariance. A lesser-explored strategy for achieving optical self-similar propagation exploits the modification of the spatiotemporal field structure when observed in reference frames moving at relativistic speeds. For such an observer, it is predicted that the associated Lorentz boost can bring to a halt the axial dynamics of a wave packet of an arbitrary profile. This phenomenon is particularly striking in the case of a self-accelerating beam—such as an Airy beam—whose peak normally undergoes a transverse displacement upon free propagation. Here we synthesize an acceleration-free Airy wave packet that travels in a straight line by deforming its spatiotemporal spectrum to reproduce the impact of a Lorentz boost. The roles of the axial spatial coordinate and time are swapped, leading to "time diffraction" manifested in self-acceleration observed in the propagating Airy wave-packet frame.
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.
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
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
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
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
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.
Angular momentum transport with twisted exciton wave packets
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.
State reconstruction of one-dimensional wave packets
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.
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
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.))
Cherenkov Radiation Control via Self-accelerating Wave-packets.
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.
Strongly nonlinear evolution of low-frequency wave packets in a dispersive plasma
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.
Nonlinear Evolution of Alfvenic Wave Packets
Buti, B.; Jayanti, V.; Vinas, A. F.; Ghosh, S.; Goldstein, M. L.; Roberts, D. A.; Lakhina, G. S.; Tsurutani, B. T.
1998-01-01
Alfven waves are a ubiquitous feature of the solar wind. One approach to studying the evolution of such waves has been to study exact solutions to approximate evolution equations. Here we compare soliton solutions of the Derivative Nonlinear Schrodinger evolution equation (DNLS) to solutions of the compressible MHD equations.
Pump-dump iterative squeezing of vibrational wave packets.
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.
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
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
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^...
Geometrical aspects in optical wave-packet dynamics.
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.
Nonlocality of a free atomic wave packet
International Nuclear Information System (INIS)
Haug, F.; Freyberger, M.; Wodkiewicz, K.
2004-01-01
A simple model allows us to study the nonclassical behavior of slowly moving atoms interacting with a quantized field. Atom and field become entangled and their joint state can be identified as a mesoscopic 'Schroedinger cat'. By introducing appropriate observables for atom and field and by analyzing correlations between them based on a Bell-type inequality we can show the corresponding nonclassical behavior
Energy and Information Transfer Via Coherent Exciton Wave Packets
Zang, Xiaoning
Electronic excitons are bound electron-hole states that are generated when light interacts with matter. Such excitations typically entangle with phonons and rapidly decohere; the resulting electronic state dynamics become diffusive as a result. However, if the exciton-phonon coupling can be reduced, it may be possible to construct excitonic wave packets that offer a means of efficiently transmitting information and energy. This thesis is a combined theory/computation investigation to design condensed matter systems which support the requisite coherent transport. Under the idealizing assumption that exciton-phonon entanglement could be completely suppressed, the majority of this thesis focuses on the creation and manipulation of exciton wave packets in quasi-one-dimensional systems. While each site could be a silicon quantum dot, the actual implementation focused on organic molecular assemblies for the sake of computational simplicity, ease of experimental implementation, potential for coherent transport, and promise because of reduced structural uncertainty. A laser design was derived to create exciton wave packets with tunable shape and speed. Quantum interference was then exploited to manipulate these packets to block, pass, and even dissociate excitons based on their energies. These developments allow exciton packets to be considered within the arena of quantum information science. The concept of controllable excitonic wave packets was subsequently extended to consider molecular designs that allow photons with orbital angular momentum to be absorbed to create excitons with a quasi-angular momentum of their own. It was shown that a well-defined measure of topological charge is conserved in such light-matter interactions. Significantly, it was also discovered that such molecules allow photon angular momenta to be combined and later emitted. This amounts to a new way of up/down converting photonic angular momentum without relying on nonlinear optical materials. The
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
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
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.
Theoretical prediction of a rotating magnon wave packet in ferromagnets.
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.
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
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...
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
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
Cho, Jungyeon
2011-05-13
Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.
International Nuclear Information System (INIS)
Cho, Jungyeon
2011-01-01
Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.
Aeroacoustic directivity via wave-packet analysis of mean or base flows
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 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.)
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.
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
Coherent wave packet dynamics in a double-well potential in cavity
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.
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
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
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.
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.
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
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
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...
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)
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)
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.)
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.)
Localization of Waves in Fractals : Spatial Behavior
Vries, Pedro de; Raedt, Hans De; Lagendijk, Ad
1989-01-01
Localization of a quantum particle on two-dimensional percolating networks is investigated numerically. Solving the time-dependent Schrödinger equation for particular initial wave packets we study the spatial behavior of eigenstates for two tight-binding models: the quantum percolation model and the
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...
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
Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.
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.
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
Extended wave-packet model to calculate energy-loss moments of protons in matter
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.
Steering dissociation of Br2 molecules with two femtosecond pulses via wave packet interference.
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.
Isolated drops from capillary jets by means of Gaussian wave packets
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.
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
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....
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
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
Resonant tunneling of spin-wave packets via quantized states in potential wells.
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.
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.
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
Quantum spreading of a self-gravitating wave-packet in singularity free gravity
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
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)
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...
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
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
Initial Dynamics of The Norrish Type I Reaction in Acetone: Probing Wave Packet Motion
DEFF Research Database (Denmark)
Brogaard, Rasmus Y.; Sølling, Theis I.; Møller, Klaus Braagaard
2011-01-01
The Norrish Type I reaction in the S1 (nπ*) state of acetone is a prototype case of ketone photochemistry. On the basis of results from time-resolved mass spectrometry (TRMS) and photoelectron spectroscopy (TRPES) experiments, it was recently suggested that after excitation the wave packet travels...
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...
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...
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.)
Understanding the spreading of a Gaussian wave packet using the ...
Indian Academy of Sciences (India)
ploiting the machinery of the Bohmian model of quantum mechanics, the way the wave ... inexactness of quantum theory seems to be eliminated by ensuring a ... In this paper, keeping aside the subtle conceptual debates concerning the.
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.
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.
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}
Study of the wave packet treatment of neutrino oscillation at Daya Bay
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.
A Wave-guide Model for Packetized Media Streaming in Lossless Networks
Konstantas, D.; Widya, I.A.
2002-01-01
Optimal operation of network based multimedia applications requires a precise specification of the network parameters. Different models have been used in the past in calculating the behavior of the network and defining parameters like throughput and delays of packets, using among others fluid
On reduction of the wave-packet, decoherence, irreversibility and the second law of thermodynamics
International Nuclear Information System (INIS)
Narnhofer, H.; Wreszinski, W.F.
2014-01-01
We prove a quantum version of the second law of thermodynamics: the (quantum) Boltzmann entropy increases if the initial (zero time) density matrix decoheres, a condition generally satisfied in Nature. It is illustrated by a model of wave-packet reduction, the Coleman–Hepp model, along the framework introduced by Sewell (2005) in his approach to the quantum measurement problem. Further models illustrate the monotonic-versus-non-monotonic behavior of the quantum Boltzmann entropy in time. As a last closely related topic, decoherence, which was shown by Narnhofer and Thirring (1999) to enforce macroscopic purity in the case of quantum K systems, is analyzed within a different class of quantum chaotic systems, viz. the quantum Anosov models as defined by Emch, Narnhofer, Sewell and Thirring (1994). A review of the concept of quantum Boltzmann entropy, as well as of some of the rigorous approaches to the quantum measurement problem within the framework of Schrödinger dynamics, is given, together with an overview of the C* algebra approach, which encompasses the relevant notions and definitions in a comprehensive way
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.)
Quantum spreading of a self-gravitating wave-packet in singularity free gravity
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.
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.
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
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....
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.
Characterizing the astrophysical S factor for 12C+12C fusion with wave-packet dynamics
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.
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.
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.
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
Wave packet dynamics, time scales and phase diagram in the IBM-Lipkin-Meshkov-Glick model
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.
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...
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
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.
Delocalization of charge and current in a chiral quasiparticle wave packet
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.
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)
Initial dynamics of the Norrish Type I reaction in acetone: probing wave packet motion.
Brogaard, Rasmus Y; Sølling, Theis I; Møller, Klaus B
2011-02-10
The Norrish Type I reaction in the S(1) (nπ*) state of acetone is a prototype case of ketone photochemistry. On the basis of results from time-resolved mass spectrometry (TRMS) and photoelectron spectroscopy (TRPES) experiments, it was recently suggested that after excitation the wave packet travels toward the S(1) minimum in less than 30 fs and stays there for more than 100 picoseconds [Chem. Phys. Lett.2008, 461, 193]. In this work we present simulated TRMS and TRPES signals based on ab initio multiple spawning simulations of the dynamics during the first 200 fs after excitation, getting quite good agreement with the experimental signals. We can explain the ultrafast decay of the experimental signals in the following manner: the wave packet simply travels, mainly along the deplanarization coordinate, out of the detection window of the ionizing probe. This window is so narrow that subsequent revival of the signal due to the coherent deplanarization vibration is not observed, meaning that from the point of view of the experiment the wave packets travels directly to the S(1) minimum. This result stresses the importance of pursuing a closer link to the experimental signal when using molecular dynamics simulations in interpreting experimental results.
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.
Generic short-time propagation of sharp-boundaries wave packets
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.
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.)
Experimental study of turbulent-jet wave packets and their acoustic efficiency
Breakey, David E. S.; Jordan, Peter; Cavalieri, André V. G.; Nogueira, Petrônio A.; Léon, Olivier; Colonius, Tim; Rodríguez, Daniel
2017-12-01
This paper details the statistical and time-resolved analysis of the relationship between the near-field pressure fluctuations of unforced, subsonic free jets (0.4 ≤M ≤0.6 ) and their far-field sound emissions. Near-field and far-field microphone measurements were taken on a conical array close to the jets and an azimuthal ring at 20∘ to the jet axis, respectively. Recent velocity and pressure measurements indicate the presence of linear wave packets in the near field by closely matching predictions from the linear homogenous parabolized stability equations, but the agreement breaks down both beyond the end of the potential core and when considering higher order statistical moments, such as the two-point coherence. Proper orthogonal decomposition (POD), interpreted in terms of inhomogeneous linear models using the resolvent framework allows us to understand these discrepancies. A new technique is developed for projecting time-domain pressure measurements onto a statistically obtained POD basis, yielding the time-resolved activity of each POD mode and its correlation with the far field. A single POD mode, interpreted as an optimal high-gain structure that arises due to turbulent forcing, captures the salient near-field-far-field correlation signature; further, the signatures of the next two modes, understood as suboptimally forced structures, suggest that these POD modes represent higher order, acoustically important near-field behavior. An existing Green's-function-based technique is used to make far-field predictions, and results are interpreted in terms of POD/resolvent modes, indicating the acoustic importance of this higher order behavior. The technique is extended to provide time-domain far-field predictions.
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.
Energy Technology Data Exchange (ETDEWEB)
Sanz, A.S., E-mail: asanz@iff.csic.es [Instituto de Física Fundamental (IFF-CSIC), Serrano 123, 28006 Madrid (Spain); Martínez-Casado, R. [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Peñate-Rodríguez, H.C.; Rojas-Lorenzo, G. [Instituto Superior de Tecnologías y Ciencias Aplicadas, Ave. Salvador Allende y Luaces, Quinta de Los Molinos, Plaza, La Habana 10600 (Cuba); Miret-Artés, S. [Instituto de Física Fundamental (IFF-CSIC), Serrano 123, 28006 Madrid (Spain)
2014-08-15
Classical viscid media are quite common in our everyday life. However, we are not used to find such media in quantum mechanics, and much less to analyze their effects on the dynamics of quantum systems. In this regard, the Caldirola–Kanai time-dependent Hamiltonian constitutes an appealing model, accounting for friction without including environmental fluctuations (as it happens, for example, with quantum Brownian motion). Here, a Bohmian analysis of the associated friction dynamics is provided in order to understand how a hypothetical, purely quantum viscid medium would act on a wave packet from a (quantum) hydrodynamic viewpoint. To this purpose, a series of paradigmatic contexts have been chosen, such as the free particle, the motion under the action of a linear potential, the harmonic oscillator, or the superposition of two coherent wave packets. Apart from their analyticity, these examples illustrate interesting emerging behaviors, such as localization by “quantum freezing” or a particular type of quantum–classical correspondence. The reliability of the results analytically determined has been checked by means of numerical simulations, which has served to investigate other problems lacking of such analyticity (e.g., the coherent superpositions). - Highlights: • A dissipative Bohmian approach is developed within the Caldirola–Kanai model. • Some simple yet physically insightful systems are then studied analytically. • Dissipation leads to spatial localization in free-force regimes. • Under the action of linear forces, dissipation leads to uniform motion. • In harmonic potentials, the system decays unavoidable to the well minimum.
International Nuclear Information System (INIS)
Sanz, A.S.; Martínez-Casado, R.; Peñate-Rodríguez, H.C.; Rojas-Lorenzo, G.; Miret-Artés, S.
2014-01-01
Classical viscid media are quite common in our everyday life. However, we are not used to find such media in quantum mechanics, and much less to analyze their effects on the dynamics of quantum systems. In this regard, the Caldirola–Kanai time-dependent Hamiltonian constitutes an appealing model, accounting for friction without including environmental fluctuations (as it happens, for example, with quantum Brownian motion). Here, a Bohmian analysis of the associated friction dynamics is provided in order to understand how a hypothetical, purely quantum viscid medium would act on a wave packet from a (quantum) hydrodynamic viewpoint. To this purpose, a series of paradigmatic contexts have been chosen, such as the free particle, the motion under the action of a linear potential, the harmonic oscillator, or the superposition of two coherent wave packets. Apart from their analyticity, these examples illustrate interesting emerging behaviors, such as localization by “quantum freezing” or a particular type of quantum–classical correspondence. The reliability of the results analytically determined has been checked by means of numerical simulations, which has served to investigate other problems lacking of such analyticity (e.g., the coherent superpositions). - Highlights: • A dissipative Bohmian approach is developed within the Caldirola–Kanai model. • Some simple yet physically insightful systems are then studied analytically. • Dissipation leads to spatial localization in free-force regimes. • Under the action of linear forces, dissipation leads to uniform motion. • In harmonic potentials, the system decays unavoidable to the well minimum
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
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.
Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.
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.
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
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
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
The coupled three-dimensional wave packet approach to reactive scattering
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.
Spectro-spatial analysis of wave packet propagation in nonlinear acoustic metamaterials
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.
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
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
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.
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
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
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...
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.
Quantum solitonic wave-packet of a meso-scopic system in singularity free gravity
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.
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
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.
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)....
Wave packet methods for the direct calculation of energy-transfer moments in molecular collisions
International Nuclear Information System (INIS)
Bradley, K.S.; Schatz, G.C.; Balint-Kurti, G.G.
1999-01-01
The authors present a new wave packet based theory for the direct calculation of energy-transfer moments in molecular collision processes. This theory does not contain any explicit reference to final state information associated with the collision dynamics, thereby avoiding the need for determining vibration-rotation bound states (other than the initial state) for the molecules undergoing collision and also avoiding the calculation of state-to-state transition probabilities. The theory applies to energy-transfer moments of any order, and it generates moments for a wide range of translational energies in a single calculation. Two applications of the theory are made that demonstrate its viability; one is to collinear He + H 2 and the other to collinear He + CS 2 (with two active vibrational modes in CS 2 ). The results of these applications agree well with earlier results based on explicit calculation of transition probabilities
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
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
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. .
Energy Technology Data Exchange (ETDEWEB)
Jakob, B.
2006-10-10
In this work the wave packet molecular dynamics (WPMD) is presented and applied to dense hydrogen. In the WPMD method the electrons are described by a slater determinant of periodic Gaussian wave packets. Each single particle wave function can parametrised through 8 coordinates which can be interpreted as the position and momentum, the width and its conjugate momentum. The equation of motion for these coordinates can be derived from a time depended variational principle. Properties of the equilibrium can be ascertained by a Monte Carlo simulation. With the now completely implemented antisymmetrisation the simulation yields a fundamental different behavior for dense hydrogen compare to earlier simplified models. The results show a phase transition to metallic hydrogen with a higher density than in the molecular phase. This behavior has e.g. a large implication to the physics of giant planets. This work describes the used model and explains in particular the calculation of the energy and forces. The periodicity of the wave function leads to a description in the Fourier space. The antisymmetrisation is done by Matrix operations. Moreover the numerical implementation is described in detail to allow the further development of the code. The results provided in this work show the equation of state in the temperature range 300K - 50000K an density 10{sup 23}-10{sup 24} cm{sup -3}, according a pressure 1 GPa-1000 GPa. In a phase diagram the phase transition to metallic hydrogen can be red off. The electrical conductivity of both phases is destined. (orig.)
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
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.
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%.
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)
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)
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....
Energy Technology Data Exchange (ETDEWEB)
Sindona, A. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy) and Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy)]. E-mail: sindona@fis.unical.it; Riccardi, P. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy); Maletta, S. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Rudi, S.A. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy); Falcone, G. [Dipartimento di Fisica, Universita della Calabria, Via P. Bucci 31C, 87036 Rende (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Gruppo collegato di Cosenza, Via P. Bucci 31C, 87036 Rende (Italy)
2007-05-15
Secondary emission of Ag{sup -} and Au{sup -} particles, following the sputtering of clean Ag(1 0 0) and Au(1 0 0) targets, respectively, is studied with a Crank-Nicholson wave-packet propagation method. A one-electron pseudo-potential is used to describe the plane metal surface, with a projected band gap, the ejected ion, whose charge state is investigated, and its nearest-neighbor substrate ion, put in motion by the collision cascade generated by the primary ion beam. Time-dependent Schroedinger equation is solved backwards in time to determine the evolution of the affinity orbital of the negative particles from an instant when they are unperturbed, at distances of the order of {approx}10{sup 2} a.u. from the surface, to the instant of ejection. The probability that a band electron will be eventually detected in affinity state of the ejected particle is, thus, calculated and compared with the result of another method based on the spectral decomposition of the one-electron Hamiltonian.
Kroh, Tim; Ahlrichs, Andreas; Sprenger, Benjamin; Benson, Oliver
2017-09-01
Future quantum networks require a hybrid platform of dissimilar quantum systems. Within the platform, joint quantum states have to be mediated either by single photons, photon pairs or entangled photon pairs. The photon wavelength has to lie within the telecommunication band to enable long-distance fibre transmission. In addition, the temporal shape of the photons needs to be tailored to efficiently match the involved quantum systems. Altogether, this requires the efficient coherent wavelength-conversion of arbitrarily shaped single-photon wave packets. Here, we demonstrate the heralded temporal filtering of single photons as well as the synchronisation of state manipulation and detection as key elements in a typical experiment, besides of delaying a photon in a long fibre. All three are realised by utilising commercial telecommunication fibre-optical components which will permit the transition of quantum networks from the lab to real-world applications. The combination of these renders a temporally filtering single-photon storage in a fast switchable fibre loop possible.
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.
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)
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)
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
‘Superluminal paradox’ in wave packet propagation and its quantum mechanical resolution
Energy Technology Data Exchange (ETDEWEB)
Sokolovski, D., E-mail: dgsokol15@gmail.com [Department of Physical Chemistry, University of the Basque Country, Leioa, Bizkaia (Spain); IKERBASQUE, Basque Foundation for Science, 48011, Bilbao (Spain); Akhmatskaya, E. [Basque Center for Applied Mathematics (BCAM), Alameda de Mazarredo, 14 48009, Bilbao Bizkaia (Spain)
2013-12-15
We analyse in detail the reshaping mechanism leading to apparently ‘superluminal’ advancement of a wave packet traversing a classically forbidden region. In the coordinate representation, a barrier is shown to act as an effective beamsplitter, recombining envelopes of the freely propagating pulse with various spacial shifts. Causality ensures that none of the constituent envelopes are advanced with respect to free propagation, yet the resulting pulse is advanced due to a peculiar interference effect, similar to the one responsible for ‘anomalous’ values which occur in Aharonov’s ‘weak measurements’. In the momentum space, the effect is understood as a bandwidth phenomenon, where the incident pulse probes local, rather than global, analytical properties of the transmission amplitude T(p). The advancement is achieved when T(p) mimics locally an exponential behaviour, similar to the one occurring in Berry’s ‘superoscillations’. Seen in a broader quantum mechanical context, the ‘paradox’ is but a consequence of an attempt to obtain ‘which way?’ information without destroying the interference between the pathways of interest. This explains, to a large extent, the failure to adequately describe tunnelling in terms of a single ‘tunnelling time’. -- Highlights: •Apparent superluminality is described in the language of quantum measurements. •A barrier acts as a beamsplitter delaying copies of the initial pulse. •In the coordinate space the effect is similar to what occurs in ‘weak measurements’. •In the momentum space it relies on superoscillations in the transmission amplitude. •It is an interference effect, unlikely to be explained in simpler physical terms.
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.
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
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.
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
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.
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.
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.
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...
Finite-measuring approximation of operators of scattering theory in representation of wave packets
International Nuclear Information System (INIS)
Kukulin, V.I.; Rubtsova, O.A.
2004-01-01
Several types of the packet quantization of the continuos spectrum in the scattering theory quantum problems are considered. Such a quantization leads to the convenient finite-measuring (i.e. matrix) approximation of the integral operators in the scattering theory and it makes it possible to reduce the solution of the singular integral equations, complying with the scattering theory, to the convenient purely algebraic equations on the analytical basis, whereby all the singularities are separated in the obvious form. The main attention is paid to the problems of the method practical realization [ru
International Nuclear Information System (INIS)
Brito, P E de; Nazareno, H N
2007-01-01
In the present work we treat the problem of a particle in a uniform magnetic field along the symmetric gauge, so chosen since the wavefunctions present the required cylindrical symmetry. It is our understanding that by means of this work we can make a contribution to the teaching of the present subject, as well as encourage students to use computer algebra systems in solving problems of quantum mechanics. We obtained the degeneracy of the spectrum of eigenvalues in a very clear way. Through the use of a computer algebra system we show graphs of the probability density associated with different eigenvalues as well as compare such functions for some degenerate states, which helps us to visualize the physics of the problem. We also present a semiclassical model which gives a physical insight regarding the paradoxical fact that eigenfunctions associated with opposite angular momenta and different energy eigenvalues have the same probability density. Finally, by solving the time-dependent Schroedinger equation we obtain the time evolution of a wave packet that at time zero was considered to be localized in a definite region of the lattice. The centroid of such a packet performs an orbit similar to that obtained in the classical treatment of a particle in a magnetic field
International Nuclear Information System (INIS)
Judson, R.S.; McGarrah, D.B.; Sharafeddin, O.A.; Kouri, D.J.; Hoffman, D.K.
1991-01-01
We compare three time-dependent wave packet methods for performing elastic scattering calculations from screened Coulomb potentials. The three methods are the time-dependent amplitude density method (TDADM), what we term a Cayley-transform method (CTM), and the Chebyshev propagation method of Tal-Ezer and Kosloff. Both the TDADM and the CTM are based on a time-dependent integral equation for the wave function. In the first, we propagate the time-dependent amplitude density, |ζ(t)right-angle=U|ψ(t)right-angle, where U is the interaction potential and |ψ(t)right-angle is the usual time-dependent wave function. In the other two, the wave function is propagated. As a numerical example, we calculate phase shifts and cross sections using a screened Coulomb, Yukawa type potential over the range 200--1000 eV. One of the major advantages of time-dependent methods such as these is that we get scattering information over this entire range of energies from one propagation. We find that in most cases, all three methods yield comparable accuracy and are about equally efficient computationally. However for l=0, where the Coulomb well is not screened by the centrifugal potential, the TDADM requires smaller grid spacings to maintain accuracy
Femtosecond Electron Wave Packet Propagation and Diffraction: Towards Making the ``Molecular Movie"
Miller, R. J. Dwayne
2003-03-01
Time-resolved electron diffraction harbors great promise for achieving atomic resolution of the fastest chemical processes. The generation of sufficiently short electron pulses to achieve this real time view of a chemical reaction has been limited by problems in maintaining short electron pulses with realistic electron densities to the sample. The propagation dynamics of femtosecond electron packets in the drift region of a photoelectron gun are investigated with an N-body numerical simulation and mean-field model. This analyis shows that the redistribution of electrons inside the packet, arising from space-charge and dispersion contributions, changes the pulse envelope and leads to the development of a spatially linear axial velocity distribution. These results have been used in the design of femtosecond photoelectron guns with higher time resolution and novel electron-optical methods of pulse characterization that are approaching 100 fs timescales. Time-resolved diffraction studies with electron pulses of approximately 500 femtoseconds have focused on solid-liquid phase transitions under far from equilibrium conditions. This work gives a microscopic description of the melting process and illustrates the promise of atomically resolving transition state processes.
Bhaumik, Swagata; Sengupta, Tapan K.
2017-12-01
Here, we present the impulse response of the canonical zero pressure gradient boundary layer from the dynamical system approach. The fundamental physical mechanism of the impulse response is in creation of a spatio-temporal wave-front (STWF) by a localized, time-impulsive wall excitation of the boundary layer. The present research is undertaken to explain the unit process of diverse phenomena in geophysical fluid flows and basic hydrodynamics. Creation of a tsunami has been attributed to localized events in the ocean-bed caused by earthquakes, landslides, or volcanic eruptions, whose manifestation is in the run up to the coast by surface waves of massive amplitude but of very finite fetch. Similarly rogue waves have often been noted; a coherent account of the same is yet to appear, although some explanations have been proposed. Our studies in both two- and three-dimensional frameworks in Sengupta and Bhaumik ["Onset of turbulence from the receptivity stage of fluid flows," Phys. Rev. Lett. 107(15), 154501 (2011)] and Bhaumik and Sengupta ["Precursor of transition to turbulence: Spatiotemporal wave front," Phys. Rev. E 89(4), 043018 (2014)] have shown that the STWF provides the central role for causing transition to turbulence by reproducing carefully conducted transition experiments. Here, we furthermore relax the condition of time behavior and use a Dirac-delta wall excitation for the impulse response. The present approach is not based on any simplification of the governing Navier-Stokes equation (NSE), which is unlike solving a nonlinear shallow water equation and/or nonlinear Schrödinger equation. The full nonlinear Navier-Stokes equation (NSE) is solved here using high accuracy dispersion relation preserving numerical schemes and using appropriate formulation of the NSE which minimizes error. The adopted numerical methods and formulation have been extensively validated with respect to various external and internal 2D and 3D flow problems. We also present
Energy Technology Data Exchange (ETDEWEB)
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)
Langmuir wave-packet generation from an electron beam propagating in the inhomogeneous solar wind
International Nuclear Information System (INIS)
Zaslavsky, A.; Maksimovic, M.; Volokitin, A. S.; Krasnoselskikh, V. V.; Bale, S. D.
2010-01-01
Recent in-situ observations by the TDS instrument equipping the STEREO spacecraft revealed that large amplitude spatially localized Langmuir waves are frequent in the solar wind, and correlated with the presence of suprathermal electron beams during type III events or close to the electron foreshock. We briefly present the new theoretical model used to perform the study of these localized electrostatic waves, and show first results of simulations of the destabilization of Langmuir waves by a beam propagating in the inhomogeneous solar wind. The main results are that the destabilized waves are mainly focalized near the minima of the density profiles, and that the nonlinear interaction of the waves with the resonant particles enhances this focalization compared to a situation in which the only propagation effects are taken into account.
Dynamics of wave packets in two-dimensional random systems with anisotropic disorder.
Samelsohn, Gregory; Gruzdev, Eugene
2008-09-01
A theoretical model is proposed to describe narrowband pulse dynamics in two-dimensional systems with arbitrary correlated disorder. In anisotropic systems with elongated cigarlike inhomogeneities, fast propagation is predicted in the direction across the structure where the wave is exponentially localized and tunneling of evanescent modes plays a dominant role in typical realizations. Along the structure, where the wave is channeled as in a waveguide, the motion of the wave energy is relatively slow. Numerical simulations performed for ultra-wide-band pulses show that even at the initial stage of wave evolution, the radiation diffuses predominantly in the direction along the major axis of the correlation ellipse. Spectral analysis of the results relates the long tail of the wave observed in the transverse direction to a number of frequency domain "lucky shots" associated with the long-living resonant modes localized inside the sample.
Energy Technology Data Exchange (ETDEWEB)
El-Labany, S. K., E-mail: skellabany@hotmail.com; Zedan, N. A., E-mail: nesreenplasma@yahoo.com [Department of Physics, Faculty of Science, Damietta University, New Damietta, P.O. 34517 (Egypt); El-Taibany, W. F., E-mail: eltaibany@hotmail.com, E-mail: eltaibany@du.edu.eg [Department of Physics, Faculty of Science, Damietta University, New Damietta, P.O. 34517 (Egypt); Department of Physics, College of Science for Girls in Abha, King Khalid University, P.O. 960 Abha (Saudi Arabia)
2015-07-15
Cylindrical and spherical amplitude modulations of dust acoustic (DA) solitary wave envelopes in a strongly coupled dusty plasma containing nonthermal distributed ions are studied. Employing a reductive perturbation technique, a modified nonlinear Schrödinger equation including the geometrical effect is derived. The influences of nonthermal ions, polarization force, and the geometries on the modulational instability conditions are analyzed and the possible rogue wave structures are discussed in detail. It is found that the spherical DA waves are more structurally stable to perturbations than the cylindrical ones. Possible applications of these theoretical findings are briefly discussed.
Similon, Philippe L.; Sudan, R. N.
1989-01-01
The importance of field line geometry for shear Alfven wave dissipation in coronal arches is demonstrated. An eikonal formulation makes it possible to account for the complicated magnetic geometry typical in coronal loops. An interpretation of Alfven wave resonance is given in terms of gradient steepening, and dissipation efficiencies are studied for two configurations: the well-known slab model with a straight magnetic field, and a new model with stochastic field lines. It is shown that a large fraction of the Alfven wave energy flux can be effectively dissipated in the corona.
Delay-time distribution in the scattering of time-narrow wave packets (II)—quantum graphs
Smilansky, Uzy; Schanz, Holger
2018-02-01
We apply the framework developed in the preceding paper in this series (Smilansky 2017 J. Phys. A: Math. Theor. 50 215301) to compute the time-delay distribution in the scattering of ultra short radio frequency pulses on complex networks of transmission lines which are modeled by metric (quantum) graphs. We consider wave packets which are centered at high wave number and comprise many energy levels. In the limit of pulses of very short duration we compute upper and lower bounds to the actual time-delay distribution of the radiation emerging from the network using a simplified problem where time is replaced by the discrete count of vertex-scattering events. The classical limit of the time-delay distribution is also discussed and we show that for finite networks it decays exponentially, with a decay constant which depends on the graph connectivity and the distribution of its edge lengths. We illustrate and apply our theory to a simple model graph where an algebraic decay of the quantum time-delay distribution is established.
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.
International Nuclear Information System (INIS)
Chwiej, T; Szafran, B
2013-01-01
We study electron transfer across a two-terminal quantum ring using a time-dependent description of the scattering process. For the considered scattering event the quantum ring is initially charged with one or two electrons, with another electron incident to the ring from the input channel. We study the electron transfer probability (T) as a function of the external magnetic field. We determine the periodicity of T for a varied number of electrons confined within the ring. For that purpose we develop a method to describe the wave packet dynamics for a few electrons participating in the scattering process, taking into full account the electron–electron correlations. We find that electron transfer across the quantum ring initially charged by a single electron acquires a distinct periodicity of half of the magnetic flux quantum (Φ 0 /2), corresponding to the formation of a transient two-electron state inside the ring. In the case of a three-electron scattering problem with two electrons initially occupying the ring, a period of Φ 0 /3 for T is formed in the limit of thin channels. The effect of disorder present in the confinement potential of the ring is also discussed. (paper)
Chwiej, T; Szafran, B
2013-04-17
We study electron transfer across a two-terminal quantum ring using a time-dependent description of the scattering process. For the considered scattering event the quantum ring is initially charged with one or two electrons, with another electron incident to the ring from the input channel. We study the electron transfer probability (T) as a function of the external magnetic field. We determine the periodicity of T for a varied number of electrons confined within the ring. For that purpose we develop a method to describe the wave packet dynamics for a few electrons participating in the scattering process, taking into full account the electron-electron correlations. We find that electron transfer across the quantum ring initially charged by a single electron acquires a distinct periodicity of half of the magnetic flux quantum (Φ0/2), corresponding to the formation of a transient two-electron state inside the ring. In the case of a three-electron scattering problem with two electrons initially occupying the ring, a period of Φ0/3 for T is formed in the limit of thin channels. The effect of disorder present in the confinement potential of the ring is also discussed.
Maurer, J.; Willenberg, B.; Daněk, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Klaiber, M.; Hatsagortsyan, K. Z.; Keitel, C. H.; Keller, U.
2018-01-01
We explore ionization and rescattering in strong mid-infrared laser fields in the nondipole regime over the full range of polarization ellipticity. In three-dimensional photoelectron momentum distributions (3D PMDs) measured with velocity map imaging spectroscopy, we observe the appearance of a sharp ridge structure along the major polarization axis. Within a certain range of ellipticity, the electrons in this ridge are clearly separated from the two lobes that commonly appear in the PMD with elliptically polarized laser fields. In contrast to the well-known lobes of direct electrons, the sharp ridge is created by Coulomb focusing of the softly recolliding electrons. These ridge electrons are directly related to a counterintuitive shift of the PMD peak opposite to the laser beam propagation direction when the dipole approximation breaks down. The ellipticity-dependent 3D PMDs give access to different ionization and recollision dynamics with appropriate filters in the momentum space. For example, we can extract information about the spread of the initial wave packet and the Coulomb momentum transfer of the rescattering electrons.
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.
Distortion of gravitational-wave packets due to their self-gravity
International Nuclear Information System (INIS)
Kocsis, Bence; Loeb, Abraham
2007-01-01
When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released ε and the duration of the emission τ, scaled by the total binary mass M. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of 2 M. For characteristic emission parameters at the final plunge between binary black holes of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of 10 -3 . Accounting for the wave distortion would significantly decrease the waveform extraction errors in numerical simulations
Third Wave of Cognitive Behavioral Therapies
Directory of Open Access Journals (Sweden)
Sevginar Vatan
Full Text Available The psychological functioning of an individual includes well-being, cognitions, emotions and behaviors as a whole. In the current models of psychopathologies, as similar to well-being, reciprocal interaction between emotions, behaviors and cognitions is emphasized. Notwithstanding that the effects of these three components on cognitive behavior therapies can be mentioned too, it can be claimed that emotions were remained in the background by the behaviors and cognitions until the third wave of cognitive behavior therapies. Emotions have became prominent with the third wave approaches in the field of cognitive behavior therapy. In this review article, similarities and differences of third wave of cognitive behavior therapy with other waves, the constructs of emotion and emotion regulation in the third wave and the impacts of these on treatment were included. Additionally, throughout this perspective, treatment processes focusing on emotion regulation skills were discussed. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2016; 8(3.000: 190-203
Rotating quantum Gaussian packets
International Nuclear Information System (INIS)
Dodonov, V V
2015-01-01
We study two-dimensional quantum Gaussian packets with a fixed value of mean angular momentum. This value is the sum of two independent parts: the ‘external’ momentum related to the motion of the packet center and the ‘internal’ momentum due to quantum fluctuations. The packets minimizing the mean energy of an isotropic oscillator with the fixed mean angular momentum are found. They exist for ‘co-rotating’ external and internal motions, and they have nonzero correlation coefficients between coordinates and momenta, together with some (moderate) amount of quadrature squeezing. Variances of angular momentum and energy are calculated, too. Differences in the behavior of ‘co-rotating’ and ‘anti-rotating’ packets are shown. The time evolution of rotating Gaussian packets is analyzed, including the cases of a charge in a homogeneous magnetic field and a free particle. In the latter case, the effect of initial shrinking of packets with big enough coordinate-momentum correlation coefficients (followed by the well known expansion) is discovered. This happens due to a competition of ‘focusing’ and ‘de-focusing’ in the orthogonal directions. (paper)
Spontaneous wave packet reduction
International Nuclear Information System (INIS)
Ghirardi, G.C.
1994-06-01
There are taken into account the main conceptual difficulties met by standard quantum mechanics in dealing with physical processes involving macroscopic system. It is stressed how J.A.Wheeler's remarks and lucid analysis have been relevant to pinpoint and to bring to its extreme consequences the puzzling aspects of quantum phenomena. It is shown how the recently proposed models of spontaneous dynamical reduction represent a consistent way to overcome the conceptual difficulties of the standard theory. Obviously, many nontrivial problems remain open, the first and more relevant one being that of generalizing the model theories considered to the relativistic case. This is the challenge of the dynamical reduction program. 43 refs, 2 figs
Packet reversed packet combining scheme
International Nuclear Information System (INIS)
Bhunia, C.T.
2006-07-01
The packet combining scheme is a well defined simple error correction scheme with erroneous copies at the receiver. It offers higher throughput combined with ARQ protocols in networks than that of basic ARQ protocols. But packet combining scheme fails to correct errors when the errors occur in the same bit locations of two erroneous copies. In the present work, we propose a scheme that will correct error if the errors occur at the same bit location of the erroneous copies. The proposed scheme when combined with ARQ protocol will offer higher throughput. (author)
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.
Masuda, Shumpei; Nakamura, Katsuhiro; Nakahara, Mikio
2018-02-01
We study phase imprinting on Bose-Einstein condensates (BECs) with the fast-forward scaling theory revealing a nontrivial scaling property in quantum dynamics. We introduce a wave packet with uniform momentum density (WPUM) which has peculiar properties but is short-lived. The fast-forward scaling theory is applied to derive the driving potential for creation of the WPUMs in a predetermined time. Fast manipulation is essential for the creation of WPUMs because of the instability of the state. We also study loading of a BEC into a predetermined Bloch state in the lowest band from the ground state of a periodic potential. Controlled linear potential is not sufficient for creation of the Bloch state with large wavenumber because the change in the amplitude of the order parameter is not negligible. We derive the exact driving potential for creation of predetermined Bloch states using the obtained theory.
Extensible packet processing architecture
Robertson, Perry J.; Hamlet, Jason R.; Pierson, Lyndon G.; Olsberg, Ronald R.; Chun, Guy D.
2013-08-20
A technique for distributed packet processing includes sequentially passing packets associated with packet flows between a plurality of processing engines along a flow through data bus linking the plurality of processing engines in series. At least one packet within a given packet flow is marked by a given processing engine to signify by the given processing engine to the other processing engines that the given processing engine has claimed the given packet flow for processing. A processing function is applied to each of the packet flows within the processing engines and the processed packets are output on a time-shared, arbitered data bus coupled to the plurality of processing engines.
van Harrevelt, Rob; van Hemert, Marc C.
2000-04-01
A complete three-dimensional quantum mechanical description of the photodissociation of water in the B˜ band, starting from its rotational ground state, is presented. In order to include B˜-X˜ vibronic coupling and the B˜-Ã Renner-Teller coupling, diabatic electronic states have been constructed from adiabatic electronic states and matrix elements of the electronic angular momentum operators, following the procedure developed by A. J. Dobbyn and P. J. Knowles [Mol. Phys. 91, 1107 (1997)], using the ab initio results discussed in the preceding paper. The dynamics is studied using wave packet methods, and the evolution of the time-dependent wave function is discussed in detail. Results for the H2O and D2O absorption spectra, OH(A)/OH(X) and OD(A)/OD(X) branching ratios, and rovibrational distributions of the OH and OD fragments are presented and compared with available experimental data. The present theoretical results agree at least qualitatively with the experiments. The calculations show that the absorption spectrum and the product state distributions are strongly influenced by long-lived resonances on the adiabatic B˜ state. It is also shown that molecular rotation plays an important role in the photofragmentation process, due to both the Renner-Teller B˜-X˜ mixing, and the strong effect of out-of-plane molecular rotations (K>0) on the dynamics at near linear HOH and HHO geometries.
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.
Jing, Qingli; Bello, Roger Y.; Martín, Fernando; Palacios, Alicia; Madsen, Lars Bojer
2018-04-01
Recent research interests have been raised in uncovering and controlling ultrafast dynamics in excited neutral molecules. In this work we generalize the Monte Carlo wave packet (MCWP) approach to XUV-pump-IR-probe schemes to simulate the process of dissociative double ionization of H2 where singly excited states in H2 are involved. The XUV pulse is chosen to resonantly excite the initial ground state of H2 to the lowest excited electronic state of 1Σu + symmetry in H2 within the Franck-Condon region. The delayed intense IR pulse couples the excited states of 1Σu + symmetry with the nearby excited states of 1Σg + symmetry. It also induces the first ionization from H2 to H2 + and the second ionization from H2 + to H++H+. To reduce the computational costs in the MCWP approach, a sampling method is proposed to determine in time the dominant ionization events from H2 to H2+. By conducting a trajectory analysis, which is a unique possibility within the MCWP approach, the origins of the characteristic features in the nuclear kinetic energy release spectra are identified for delays ranging from 0 to 140 fs and the nuclear dynamics in the singly excited states in H2 is mapped out.
Czech Academy of Sciences Publication Activity Database
Feygin, F. Z.; Prikner, Karel; Nekrasov, A. K.
2003-01-01
Roč. 43, č. 6 (2003), s. 701-707 ISSN 0016-7932 R&D Projects: GA AV ČR KSK3012103 Grant - others:INTAS(XE) 99-0335; RFFR(RU) 02-05-64610; RFFR(RU) 02-05-64612 Institutional research plan: CEZ:AV0Z3012916 Keywords : Pc1 bounce effect * inosphere reflection coefficient * EMIC-wave Poynting vector Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.342, year: 2003
Non-Hermitian wave packet approximation for coupled two-level systems in weak and intense fields
Energy Technology Data Exchange (ETDEWEB)
Puthumpally-Joseph, Raiju; Charron, Eric [Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay (France); Sukharev, Maxim [Science and Mathematics Faculty, College of Letters and Sciences, Arizona State University, Mesa, Arizona 85212 (United States)
2016-04-21
We introduce a non-Hermitian Schrödinger-type approximation of optical Bloch equations for two-level systems. This approximation provides a complete and accurate description of the coherence and decoherence dynamics in both weak and strong laser fields at the cost of losing accuracy in the description of populations. In this approach, it is sufficient to propagate the wave function of the quantum system instead of the density matrix, providing that relaxation and dephasing are taken into account via automatically adjusted time-dependent gain and decay rates. The developed formalism is applied to the problem of scattering and absorption of electromagnetic radiation by a thin layer comprised of interacting two-level emitters.
International Nuclear Information System (INIS)
Zhang, Zhaojun; Zhang, Dong H.
2014-01-01
Seven-dimensional time-dependent wave packet calculations have been carried out for the title reaction to obtain reaction probabilities and cross sections for CHD 3 in J 0 = 1, 2 rotationally excited initial states with k 0 = 0 − J 0 (the projection of CHD 3 rotational angular momentum on its C 3 axis). Under the centrifugal sudden (CS) approximation, the initial states with the projection of the total angular momentum on the body fixed axis (K 0 ) equal to k 0 are found to be much more reactive, indicating strong dependence of reactivity on the orientation of the reagent CHD 3 with respect to the relative velocity between the reagents H and CHD 3 . However, at the coupled-channel (CC) level this dependence becomes much weak although in general the K 0 specified cross sections for the K 0 = k 0 initial states remain primary to the overall cross sections, implying the Coriolis coupling is important to the dynamics of the reaction. The calculated CS and CC integral cross sections obtained after K 0 averaging for the J 0 = 1, 2 initial states with all different k 0 are essentially identical to the corresponding CS and CC results for the J 0 = 0 initial state, meaning that the initial rotational excitation of CHD 3 up to J 0 = 2, regardless of its initial k 0 , does not have any effect on the total cross sections for the title reaction, and the errors introduced by the CS approximation on integral cross sections for the rotationally excited J 0 = 1, 2 initial states are the same as those for the J 0 = 0 initial state
He, Haixiang; Zhu, Weimin; Su, Wenli; Dong, Lihui; Li, Bin
2018-03-08
The H + + H 2 reaction and its isotopic variants as the simplest triatomic ion-molecule reactive system have been attracting much interests, however there are few studies on the titled reaction at state-to-state level until recent years. In this work, accurate state-to-state quantum dynamics studies of the titled reaction have been carried out by a reactant Jacobi coordinate-based time-dependent wave packet approach on diabatic potential energy surfaces constructed by Kamisaka et al. Product ro-vibrational state-resolved information has been calculated for collision energies up to 0.2 eV with maximal total angular momentum J = 40. The necessity of including all K-component for accounting the Coriolis coupling for the reaction has been illuminated. Competitions between the two product channels, (D + + HD' → D' + + HD and D + + HD' → H + + DD') were investigated. Total integral cross sections suggest that resonances enhance the reactivity of channel D + + HD'→ H + + DD', however, resonances depress the reactivity of the another channel D + + HD' → D' + + HD. The structures of the differential cross sections are complicated and depend strongly on collision energies of the two channels and also on the product rotational states. All of the product ro-vibrational state-resolved differential cross sections for this reaction do not exhibit rigorous backward-forward symmetry which may indicate that the lifetimes of the intermediate resonance complexes should not be that long. The dynamical observables of this deuterated isotopic reaction are quite different from the reaction of H + + H 2 → H 2 + H + reported previously.
Rivero Santamaría, Alejandro; Dayou, Fabrice; Rubayo-Soneira, Jesus; Monnerville, Maurice
2017-03-02
The dynamics of the Si( 3 P) + OH(X 2 Π) → SiO(X 1 Σ + ) + H( 2 S) reaction is investigated by means of the time-dependent wave packet (TDWP) approach using an ab initio potential energy surface recently developed by Dayou et al. ( J. Chem. Phys. 2013 , 139 , 204305 ) for the ground X 2 A' electronic state. Total reaction probabilities have been calculated for the first 15 rotational states j = 0-14 of OH(v=0,j) at a total angular momentum J = 0 up to a collision energy of 1 eV. Integral cross sections and state-selected rate constants for the temperature range 10-500 K were obtained within the J-shifting approximation. The reaction probabilities display highly oscillatory structures indicating the contribution of long-lived quasibound states supported by the deep SiOH/HSiO wells. The cross sections behave with collision energies as expected for a barrierless reaction and are slightly sensitive to the initial rotational excitation of OH. The thermal rate constants show a marked temperature dependence below 200 K with a maximum value around 15 K. The TDWP results globally agree with the results of earlier quasi-classical trajectory (QCT) calculations carried out by Rivero-Santamaria et al. ( Chem. Phys. Lett. 2014 , 610-611 , 335 - 340 ) with the same potential energy surface. In particular, the thermal rate constants display a similar temperature dependence, with TDWP values smaller than the QCT ones over the whole temperature range.
Copepod Behavior Response in an Internal Wave Apparatus
Webster, D. R.; Jung, S.; Haas, K. A.
2017-11-01
This study is motivated to understand the bio-physical forcing in zooplankton transport in and near internal waves, where high levels of zooplankton densities have been observed in situ. A laboratory-scale internal wave apparatus was designed to create a standing internal wave for various physical arrangements that mimic conditions observed in the field. A theoretical analysis of a standing internal wave inside a two-layer stratification system including non-linear wave effects was conducted to derive the expressions for the independent variables controlling the wave motion. Focusing on a case with a density jump of 1.0 σt, a standing internal wave was generated with a clean interface and minimal mixing across the pycnocline. Spatial and frequency domain measurements of the internal wave were evaluated in the context of the theoretical analysis. Behavioral assays with a mixed population of three marine copepods were conducted in control (stagnant homogeneous fluid), stagnant density jump interface, and internal wave flow configurations. In the internal wave treatment, the copepods showed an acrobatic, orbital-like motion in and around the internal wave region (bounded by the crests and the troughs of the waves). Trajectories of passive, neutrally-buoyant particles in the internal wave flow reveal that they generally oscillate back-and-forth along fixed paths. Thus, we conclude that the looping, orbital trajectories of copepods in the region near the internal wave interface are due to animal behavior rather than passive transport.
Energy Technology Data Exchange (ETDEWEB)
Mouret, L
2002-11-01
The thesis concerns the development and implementation of numerical methods for solving the time-dependent Schroedinger equation. We first considered the case of electron-hydrogen scattering. The originality of our method is the use of a non-uniform radial grid defined by a Schwarz interpolation based on a Coulomb reference function. This grid allows many hydrogen bound states and associated matrix elements of various operators to be reproduced to machine accuracy. The wave function is propagated in time using a Split-Operator method. The efficiency of our method allows the wave function to be propagated out to large distances for all partial waves. We obtain excitation and ionization cross sections in excellent agreement with the best experimental and theoretical data. We subsequently adapted the method and the program package to study reactive atom-dihydrogen scattering. The wave packet is described using product Jacobi coordinates on a regular grid of radial coordinates combined with a basis of Legendre polynomials for the angular part (partial wave S). The wave function is analysed using a time-to-energy Fourier transform, which provides results over the energy range covered by the initial wave packet in one calculation. The method was first tested on the quasi-direct (F,H2) reaction and then applied to the indirect (C(1D),H2)reaction. The state-to-state reaction probabilities are in good agreement with those obtained by a time-independent approach. In particular, the strongly resonant structure of the (C(1D),H2) reaction probabilities is well reproduced. (author)
Energy Technology Data Exchange (ETDEWEB)
Mouret, L
2002-11-01
The thesis concerns the development and implementation of numerical methods for solving the time-dependent Schroedinger equation. We first considered the case of electron-hydrogen scattering. The originality of our method is the use of a non-uniform radial grid defined by a Schwarz interpolation based on a Coulomb reference function. This grid allows many hydrogen bound states and associated matrix elements of various operators to be reproduced to machine accuracy. The wave function is propagated in time using a Split-Operator method. The efficiency of our method allows the wave function to be propagated out to large distances for all partial waves. We obtain excitation and ionization cross sections in excellent agreement with the best experimental and theoretical data. We subsequently adapted the method and the program package to study reactive atom-dihydrogen scattering. The wave packet is described using product Jacobi coordinates on a regular grid of radial coordinates combined with a basis of Legendre polynomials for the angular part (partial wave S). The wave function is analysed using a time-to-energy Fourier transform, which provides results over the energy range covered by the initial wave packet in one calculation. The method was first tested on the quasi-direct (F,H2) reaction and then applied to the indirect (C(1D),H2)reaction. The state-to-state reaction probabilities are in good agreement with those obtained by a time-independent approach. In particular, the strongly resonant structure of the (C(1D),H2) reaction probabilities is well reproduced. (author)
Packet Tracer network simulator
Jesin, A
2014-01-01
A practical, fast-paced guide that gives you all the information you need to successfully create networks and simulate them using Packet Tracer.Packet Tracer Network Simulator is aimed at students, instructors, and network administrators who wish to use this simulator to learn how to perform networking instead of investing in expensive, specialized hardware. This book assumes that you have a good amount of Cisco networking knowledge, and it will focus more on Packet Tracer rather than networking.
Optical packet switched networks
DEFF Research Database (Denmark)
Hansen, Peter Bukhave
1999-01-01
Optical packet switched networks are investigated with emphasis on the performance of the packet switch blocks. Initially, the network context of the optical packet switched network is described showing that a packet network will provide transparency, flexibility and bridge the granularity gap...... in interferometric wavelength converters is investigated showing that a 10 Gbit/s 19 4x4 swich blocks can be cascaded at a BER of 10-14. An analytical traffic model enables the calculation of the traffice performance of a WDM packet network. Hereby the importance of WDM and wavelegth conversion in the switch blocks...... is established as a flexible means to reduce the optical buffer, e.g., the number of fibre delay lines for a 16x16 switch block is reduced from 23 to 6 by going from 2 to 8 wavelength channels pr. inlet. Additionally, a component count analysis is carried out to illustrate the trade-offs in the switch block...
Shear-wave dynamic behavior using two different orientations
International Nuclear Information System (INIS)
Ghassem Alaskari, M. K.; Hashemi, S. J.
2007-01-01
For laterally complex media, it may be more suitable to take a different orientation of the displacement vector of Shear-waves. This may change the sign of several imaginary reflections and conversion coefficients to be used in reservoir characterization and Amplitude Versus Offset analysis or modeling. In this new convention the positive direction of the displacement vector of reflected Shear-waves is chosen to the left of ray tangent (in the direction of wave propagation). Therefore, the definition of the displacement vector of shear-waves can be used properly even for very complicated media. Finally the shear-wave dynamic behavior of a reservoir zone can be illustrated for laterally varying structures in terms of the amplitude variation and phase behavior using this new orientation
Waveform and packet structure of lion roars
Directory of Open Access Journals (Sweden)
W. Baumjohann
Full Text Available The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5^{°}.
Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence
Waveform and packet structure of lion roars
Directory of Open Access Journals (Sweden)
W. Baumjohann
1999-12-01
Full Text Available The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5°.Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence
Wind Wave Behavior in Fetch and Depth Limited Estuaries
Karimpour, Arash; Chen, Qin; Twilley, Robert R.
2017-01-01
Wetland dominated estuaries serve as one of the most productive natural ecosystems through their ecological, economic and cultural services, such as nursery grounds for fisheries, nutrient sequestration, and ecotourism. The ongoing deterioration of wetland ecosystems in many shallow estuaries raises concerns about the contributing erosive processes and their roles in restraining coastal restoration efforts. Given the combination of wetlands and shallow bays as landscape components that determine the function of estuaries, successful restoration strategies require knowledge of wind wave behavior in fetch and depth limited water as a critical design feature. We experimentally evaluate physics of wind wave growth in fetch and depth limited estuaries. We demonstrate that wave growth rate in shallow estuaries is a function of wind fetch to water depth ratio, which helps to develop a new set of parametric wave growth equations. We find that the final stage of wave growth in shallow estuaries can be presented by a product of water depth and wave number, whereby their product approaches 1.363 as either depth or wave energy increases. Suggested wave growth equations and their asymptotic constraints establish the magnitude of wave forces acting on wetland erosion that must be included in ecosystem restoration design.
Fair packet scheduling in Wireless Mesh Networks
Nawab, Faisal
2014-02-01
In this paper we study the interactions of TCP and IEEE 802.11 MAC in Wireless Mesh Networks (WMNs). We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput due to the effect of queue utilization and packet relaying. A closed form solution is derived to numerically determine the throughput. Based on the developed model, we propose a distributed MAC protocol called Timestamp-ordered MAC (TMAC), aiming to alleviate the unfairness problem in WMNs. TMAC extends CSMA/CA by scheduling data packets based on their age. Prior to transmitting a data packet, a transmitter broadcasts a request control message appended with a timestamp to a selected list of neighbors. It can proceed with the transmission only if it receives a sufficient number of grant control messages from these neighbors. A grant message indicates that the associated data packet has the lowest timestamp of all the packets pending transmission at the local transmit queue. We demonstrate that a loose ordering of timestamps among neighboring nodes is sufficient for enforcing local fairness, subsequently leading to flow rate fairness in a multi-hop WMN. We show that TMAC can be implemented using the control frames in IEEE 802.11, and thus can be easily integrated in existing 802.11-based WMNs. Our simulation results show that TMAC achieves excellent resource allocation fairness while maintaining over 90% of maximum link capacity across a large number of topologies.
Bader, Ahmed
2014-01-01
A multihop network transmits a packet including a RACH area and a hop number. The RACH area includes a list of subcarriers. A source node in the network dynamically determines the size of the RACH area. A node in the network performs an open-loop transmit power control.
North Carolina State Dept. of Public Instruction, Raleigh. Div. of Social Studies Education.
This materials packet contains information on teaching about the electoral process and the elections of 1988, and on participation in a mock election for students whose schools would take part in the 1988 North Carolina Mock Election. Suggestions for teachers' preparations are given, including a classroom skit and a mock candidates' election…
Bader, Ahmed
2014-05-22
A multihop network transmits a packet including a RACH area and a hop number. The RACH area includes a list of subcarriers. A source node in the network dynamically determines the size of the RACH area. A node in the network performs an open-loop transmit power control.
Modified Aggressive Packet Combining Scheme
International Nuclear Information System (INIS)
Bhunia, C.T.
2010-06-01
In this letter, a few schemes are presented to improve the performance of aggressive packet combining scheme (APC). To combat error in computer/data communication networks, ARQ (Automatic Repeat Request) techniques are used. Several modifications to improve the performance of ARQ are suggested by recent research and are found in literature. The important modifications are majority packet combining scheme (MjPC proposed by Wicker), packet combining scheme (PC proposed by Chakraborty), modified packet combining scheme (MPC proposed by Bhunia), and packet reversed packet combining (PRPC proposed by Bhunia) scheme. These modifications are appropriate for improving throughput of conventional ARQ protocols. Leung proposed an idea of APC for error control in wireless networks with the basic objective of error control in uplink wireless data network. We suggest a few modifications of APC to improve its performance in terms of higher throughput, lower delay and higher error correction capability. (author)
Ando, Koji
2018-03-01
A model of localized electron wave packets (EWPs), floating and breathing Gaussians with non-orthogonal valence-bond spin-coupling, is applied to compute the high-harmonic generation (HHG) spectrum from a LiH molecule induced by an intense laser pulse. The characteristic features of the spectrum, a plateau up to 50 harmonic-order and a cutoff, agreed well with those from the previous time-dependent complete active-space self-consistent-field calculation [T. Sato and K. L. Ishikawa, Phys. Rev. A 91, 023417 (2015)]. In contrast to the conventional molecular orbital picture in which the Li 2s and H 1s atomic orbitals are strongly mixed, the present calculation indicates that an incoherent sum of responses of single electrons reproduces the HHG spectrum, in which the contribution from the H 1s electron dominates the plateau and cutoff, whereas the Li 2s electron contributes to the lower frequency response. The results are comprehensive in terms of the shapes of single-electron potential energy curves constructed from the localized EWP model.
Technology Corner: Internet Packet Sniffers
Directory of Open Access Journals (Sweden)
Nick Flor
2011-03-01
Full Text Available A packet sniffer is a piece of software that allows a person to eavesdrop on computer communications over the internet.Â A packet sniffer can be used as a diagnostic tool by network administrators or as a spying tool by hackers who can use it to steal passwords and other private information from computer users.Â Whether you are a network administrator or information assurance specialist, it helps to have a detailed understanding of how packet sniffers work. Â And one of the best ways to acquire such an understanding is to build and modify an actual packet sniffer.
Tropical Animal Tour Packet. Metro.
Metro Washington Park Zoo, Portland, OR. Educational Services Div.
This packet is designed to assist teachers in creating a tropical animals lesson plan that centers around a visit to the zoo. A teacher packet is divided into eight parts: (1) goals and objectives; (2) what to expect at the zoo; (3) student activities (preparatory activities, on-site activities, and follow-up activities); (4) background…
Ghosh, Sandip; Mukherjee, Saikat; Mukherjee, Bijit; Mandal, Souvik; Sharma, Rahul; Chaudhury, Pinaki; Adhikari, Satrajit
2017-08-21
The workability of beyond Born-Oppenheimer theory to construct diabatic potential energy surfaces (PESs) of a charge transfer atom-diatom collision process has been explored by performing scattering calculations to extract accurate integral cross sections (ICSs) and rate constants for comparison with most recent experimental quantities. We calculate non-adiabatic coupling terms among the lowest three singlet states of H 3 + system (1 1 A ' , 2 1 A ' , and 3 1 A ' ) using MRCI level of calculation and solve the adiabatic-diabatic transformation equation to formulate the diabatic Hamiltonian matrix of the same process [S. Mukherjee et al., J. Chem. Phys. 141, 204306 (2014)] for the entire region of nuclear configuration space. The nonadiabatic effects in the D + + H 2 reaction has been studied by implementing the coupled 3D time-dependent wave packet formalism in hyperspherical coordinates [S. Adhikari and A. J. C. Varandas, Comput. Phys. Commun. 184, 270 (2013)] with zero and non-zero total angular momentum (J) on such newly constructed accurate (ab initio) diabatic PESs of H 3 + . We have depicted the convergence profiles of reaction probabilities for the reactive non-charge transfer, non-reactive charge transfer, and reactive charge transfer processes for different collisional energies with respect to the helicity (K) and total angular momentum (J) quantum numbers. Finally, total and state-to-state ICSs are calculated as a function of collision energy for the initial rovibrational state (v = 0, j = 0) of the H 2 molecule, and consequently, those quantities are compared with previous theoretical and experimental results.
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.)
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.
Nonlinear density waves in a marginally stable gravitating disk
International Nuclear Information System (INIS)
Korchagin, V.I.
1986-01-01
The evolution of short nonlinear density waves in a disk at the stability limit is studied for arbitrary values of the radial wave number k/sub r/. For waves with wave numbers that do not lie at the minimum of the dispersion curve, the behavior of the amplitude is described by a nonlinear parabolic equation; however, stationary soliton solutions cannot exist in such a system since there is no dispersion spreading of a packet. For wave numbers lying at the minimum of the dispersion curve, soliton structures with determined amplitude are possible. In stable gravitating disks and in a disk at the stability limit, two physically different types of soliton can exist
Wave-packet dynamics in quantum wells
DEFF Research Database (Denmark)
Kuznetsov, A. V.; Sanders, G. D.; Stanton, C. J.
1995-01-01
It has been recently recognized that in bulk semiconductors the displacement current caused by ultrafast optical generation of ''polarized pairs'' in the applied de field is an important mechanism of charge transport in addition to the usual transport current. In quantum-well systems, this polari......It has been recently recognized that in bulk semiconductors the displacement current caused by ultrafast optical generation of ''polarized pairs'' in the applied de field is an important mechanism of charge transport in addition to the usual transport current. In quantum-well systems...... that the carriers in a quantum well can behave as an ensemble of classical particles and produce a transport like photocurrent....
Angularly resolved electron wave packet interferences
International Nuclear Information System (INIS)
Varju, K; Johnsson, P; Mauritsson, J; Remetter, T; Ruchon, T; Ni, Y; Lepine, F; Kling, M; Khan, J; Schafer, K J; Vrakking, M J J; L'Huillier, A
2006-01-01
We study experimentally the ionization of argon atoms by a train of attosecond pulses in the presence of a strong infrared laser field, using a velocity map imaging technique. The recorded momentum distribution strongly depends on the delay between the attosecond pulses and the laser field. We interpret the interference patterns observed for different delays using numerical and analytical calculations within the strong field approximation
Angularly resolved electron wave packet interferences
Energy Technology Data Exchange (ETDEWEB)
Varju, K [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Johnsson, P [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Mauritsson, J [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Remetter, T [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Ruchon, T [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Ni, Y [FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Lepine, F [FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Kling, M [FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Khan, J [FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); Schafer, K J [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Vrakking, M J J [FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam (Netherlands); L' Huillier, A [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden)
2006-09-28
We study experimentally the ionization of argon atoms by a train of attosecond pulses in the presence of a strong infrared laser field, using a velocity map imaging technique. The recorded momentum distribution strongly depends on the delay between the attosecond pulses and the laser field. We interpret the interference patterns observed for different delays using numerical and analytical calculations within the strong field approximation.
Nonlinear approximation with general wave packets
DEFF Research Database (Denmark)
Borup, Lasse; Nielsen, Morten
2005-01-01
We study nonlinear approximation in the Triebel-Lizorkin spaces with dictionaries formed by dilating and translating one single function g. A general Jackson inequality is derived for best m-term approximation with such dictionaries. In some special cases where g has a special structure, a complete...
Dynamic Behavior of Fault Slip Induced by Stress Waves
Directory of Open Access Journals (Sweden)
Guang-an Zhu
2016-01-01
Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.
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
Disk Operating System--DOS. Teacher Packet. Learning Activity Packets.
Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.
The Learning Activity Packets (LAPs) contained in this manual are designed to assist the beginning user in understanding DOS (Disk Operating System). LAPs will not work with any version below DOS Version 3.0 and do not address the enhanced features of versions 4.0 or higher. These elementary activities cover only the DOS commands necessary to…
Hunger and Development [Issue Packet].
American Freedom from Hunger Foundation, Washington, DC.
A variety of informational materials is compiled in this issue packet concentrating on hunger and development. They have been assembled to understand the issues associated with the facts of world hunger and to try to invent new forms of action and thought necessary to find the possibilities hidden in the hunger issue. Items include: (1) a fact and…
Trade Related Reading Packets for Disabled Readers.
Davis, Beverly; Woodruff, Nancy S.
Six trade-related reading packets for disabled readers are provided for these trades: assemblers, baking, building maintenance, data entry, interior landscaping, and warehousing. Each packet stresses from 9 to 14 skills. Those skills common to most packets include context clues, fact or opinion, details, following directions, main idea,…
Asymptotic Behavior of Periodic Wave Solution to the Hirota—Satsuma Equation
International Nuclear Information System (INIS)
Wu Yong-Qi
2011-01-01
The one- and two-periodic wave solutions for the Hirota—Satsuma (HS) equation are presented by using the Hirota derivative and Riemann theta function. The rigorous proofs on asymptotic behaviors of these two solutions are given such that soliton solution can be obtained from the periodic wave solution in an appropriate limiting procedure. (general)
Oblique propagation of nonlinear hydromagnetic waves: One- and two-dimensional behavior
International Nuclear Information System (INIS)
Malara, F.; Elaoufir, J.
1991-01-01
The one- and two-dimensional behavior of obliquely propagating hydromagnetic waves is analyzed by means of analytical theory and numerical simulations. It is shown that the nonlinear evolution of a one-dimensional MHD wave leads to the formation of a rotational discontinuity and a compressive steepened quasi-linearly polarized pulse whose structure is similar to that of a finite amplitude magnetosonic simple wave. For small propagation angles, the pulse mode (fast or slow) depends on the value of β with respect to unity while for large propagation angles the wave mode is fixed by the sign of the initial density-field correlation. The two-dimensional evolution shows that an MHD wave is unstable against a small-amplitude long-wavelength modulation in the direction transverse to the wave propagation direction. A two-dimensional magnetosonic wave solution is found, in which the density fluctuation is driven by the corresponding total pressure fluctuation, exactly as in the one-dimensional simple wave. Along with the steepening effect, the wave experiences both wave front deformation and a self-focusing effect which may eventually lead to the collapse of the wave. The results compare well with observations of MHD waves in the Earth's foreshock and at comets
Directory of Open Access Journals (Sweden)
K. Sigsbee
2004-07-01
Full Text Available We present the statistics of Langmuir wave amplitudes in the Earth's foreshock using Cluster Wideband Data (WBD Plasma Wave Receiver electric field waveforms from spacecraft 2, 3 and 4 on 26 March 2002. The largest amplitude Langmuir waves were observed by Cluster near the boundary between the foreshock and solar wind, in agreement with earlier studies. The characteristics of the waves were similar for all three spacecraft, suggesting that variations in foreshock structure must occur on scales greater than the 50-100km spacecraft separations. The electric field amplitude probability distributions constructed using waveforms from the Cluster WBD Plasma Wave Receiver generally followed the log-normal statistics predicted by stochastic growth theory for the event studied. Comparison with WBD receiver data from 17 February 2002, when spacecraft 4 was set in a special manual gain mode, suggests non-optimal auto-ranging of the instrument may have had some influence on the statistics.
Directory of Open Access Journals (Sweden)
K. Sigsbee
2004-07-01
Full Text Available We present the statistics of Langmuir wave amplitudes in the Earth's foreshock using Cluster Wideband Data (WBD Plasma Wave Receiver electric field waveforms from spacecraft 2, 3 and 4 on 26 March 2002. The largest amplitude Langmuir waves were observed by Cluster near the boundary between the foreshock and solar wind, in agreement with earlier studies. The characteristics of the waves were similar for all three spacecraft, suggesting that variations in foreshock structure must occur on scales greater than the 50-100km spacecraft separations. The electric field amplitude probability distributions constructed using waveforms from the Cluster WBD Plasma Wave Receiver generally followed the log-normal statistics predicted by stochastic growth theory for the event studied. Comparison with WBD receiver data from 17 February 2002, when spacecraft 4 was set in a special manual gain mode, suggests non-optimal auto-ranging of the instrument may have had some influence on the statistics.
Generation of attosecond electron packets via conical surface plasmon electron acceleration
Greig, S. R.; Elezzabi, A. Y.
2016-01-01
We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129
Multiwavelet packets and frame packets of L2( d)
Indian Academy of Sciences (India)
Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45
For a nice exposition of wavelet packets of L2( ) with dilation 2, see [11]. ..... p∈ d hr lm(ξ)cjp. {. ∑ q∈ d. ˆϕm(ξ + 2qπ) ˆϕj (ξ + 2qπ). } ·e−i〈k,Bξ〉 e i〈p, ξ〉 dξ ...... [14] Rudin W, Fourier Analysis on Groups (New York: John Wiley and Sons) (1962).
Unsupervised Ensemble Anomaly Detection Using Time-Periodic Packet Sampling
Uchida, Masato; Nawata, Shuichi; Gu, Yu; Tsuru, Masato; Oie, Yuji
We propose an anomaly detection method for finding patterns in network traffic that do not conform to legitimate (i.e., normal) behavior. The proposed method trains a baseline model describing the normal behavior of network traffic without using manually labeled traffic data. The trained baseline model is used as the basis for comparison with the audit network traffic. This anomaly detection works in an unsupervised manner through the use of time-periodic packet sampling, which is used in a manner that differs from its intended purpose — the lossy nature of packet sampling is used to extract normal packets from the unlabeled original traffic data. Evaluation using actual traffic traces showed that the proposed method has false positive and false negative rates in the detection of anomalies regarding TCP SYN packets comparable to those of a conventional method that uses manually labeled traffic data to train the baseline model. Performance variation due to the probabilistic nature of sampled traffic data is mitigated by using ensemble anomaly detection that collectively exploits multiple baseline models in parallel. Alarm sensitivity is adjusted for the intended use by using maximum- and minimum-based anomaly detection that effectively take advantage of the performance variations among the multiple baseline models. Testing using actual traffic traces showed that the proposed anomaly detection method performs as well as one using manually labeled traffic data and better than one using randomly sampled (unlabeled) traffic data.
Endogenous Crisis Waves: Stochastic Model with Synchronized Collective Behavior
Gualdi, Stanislao; Bouchaud, Jean-Philippe; Cencetti, Giulia; Tarzia, Marco; Zamponi, Francesco
2015-02-01
We propose a simple framework to understand commonly observed crisis waves in macroeconomic agent-based models, which is also relevant to a variety of other physical or biological situations where synchronization occurs. We compute exactly the phase diagram of the model and the location of the synchronization transition in parameter space. Many modifications and extensions can be studied, confirming that the synchronization transition is extremely robust against various sources of noise or imperfections.
Ising model for packet routing control
International Nuclear Information System (INIS)
Horiguchi, Tsuyoshi; Takahashi, Hideyuki; Hayashi, Keisuke; Yamaguchi, Chiaki
2004-01-01
For packet routing control in computer networks, we propose an Ising model which is defined in order to express competition among a queue length and a distance from a node with a packet to its destination node. By introducing a dynamics for a mean-field value of an Ising spin, we show by computer simulations that effective control of packet routing through priority links is possible
Packet telemetry and packet telecommand - The new generation of spacecraft data handling techniques
Hooke, A. J.
1983-01-01
Because of rising costs and reduced reliability of spacecraft and ground network hardware and software customization, standardization Packet Telemetry and Packet Telecommand concepts are emerging as viable alternatives. Autonomous packets of data, within each concept, which are created within ground and space application processes through the use of formatting techniques, are switched end-to-end through the space data network to their destination application processes through the use of standard transfer protocols. This process may result in facilitating a high degree of automation and interoperability because of completely mission-independent-designed intermediate data networks. The adoption of an international guideline for future space telemetry formatting of the Packet Telemetry concept, and the advancement of the NASA-ESA Working Group's Packet Telecommand concept to a level of maturity parallel to the of Packet Telemetry are the goals of the Consultative Committee for Space Data Systems. Both the Packet Telemetry and Packet Telecommand concepts are reviewed.
Nonstationary behavior in a delayed feedback traveling wave tube folded waveguide oscillator
International Nuclear Information System (INIS)
Ryskin, N.M.; Titov, V.N.; Han, S.T.; So, J.K.; Jang, K.H.; Kang, Y.B.; Park, G.S.
2004-01-01
Folded waveguide traveling-wave tubes (FW TWT) are among the most promising candidates for powerful compact amplifiers and oscillators in millimeter and submillimeter wave bands. In this paper, the nonstationary behavior of a FW TWT oscillator with delayed feedback is investigated. Starting conditions of the oscillations are derived analytically. Results of numerical simulation of single-frequency, self-modulation (multifrequency) and chaotic generation regimes are presented. Mode competition phenomena, multistability and hysteresis are discussed
Alagoz, Celal; Guez, Allon; Cohen, Andrew; Bullinga, John R
2015-08-01
Analysis of electrical activation patterns such as re-entries during atrial fibrillation (Afib) is crucial in understanding arrhythmic mechanisms and assessment of diagnostic measures. Spiral waves are a phenomena that provide intuitive basis for re-entries occurring in cardiac tissue. Distinct spiral wave behaviors such as stable spiral waves, meandering spiral waves, and spiral wave break-up may have distinct electrogram manifestations on a mapping catheter. Hence, it is desirable to have an automated classification of spiral wave behavior based on catheter recordings for a qualitative characterization of spatiotemporal electrophysiological activity on atrial tissue. In this study, we propose a method for classification of spatiotemporal characteristics of simulated atrial activation patterns in terms of distinct spiral wave behaviors during Afib using two different techniques: normalized compressed distance (NCD) and normalized FFT (NFFTD). We use a phenomenological model for cardiac electrical propagation to produce various simulated spiral wave behaviors on a 2D grid and labeled them as stable, meandering, or breakup. By mimicking commonly used catheter types, a star shaped and a circular shaped both of which do the local readings from atrial wall, monopolar and bipolar intracardiac electrograms are simulated. Virtual catheters are positioned at different locations on the grid. The classification performance for different catheter locations, types and for monopolar or bipolar readings were also compared. We observed that the performance for each case differed slightly. However, we found that NCD performance is superior to NFFTD. Through the simulation study, we showed the theoretical validation of the proposed method. Our findings suggest that a qualitative wavefront activation pattern can be assessed during Afib without the need for highly invasive mapping techniques such as multisite simultaneous electrogram recordings.
Complex dynamical behaviors of compact solitary waves in the perturbed mKdV equation
International Nuclear Information System (INIS)
Yin Jiu-Li; Xing Qian-Qian; Tian Li-Xin
2014-01-01
In this paper, we give a detailed discussion about the dynamical behaviors of compact solitary waves subjected to the periodic perturbation. By using the phase portrait theory, we find one of the nonsmooth solitary waves of the mKdV equation, namely, a compact solitary wave, to be a weak solution, which can be proved. It is shown that the compact solitary wave easily turns chaotic from the Melnikov theory. We focus on the sufficient conditions by keeping the system stable through selecting a suitable controller. Furthermore, we discuss the chaotic threshold for a perturbed system. Numerical simulations including chaotic thresholds, bifurcation diagrams, the maximum Lyapunov exponents, and phase portraits demonstrate that there exists a special frequency which has a great influence on our system; with the increase of the controller strength, chaos disappears in the perturbed system. But if the controller strength is sufficiently large, the solitary wave vibrates violently. (general)
Nie, Guoquan; Liu, Jinxi; Liu, Xianglin
2017-10-01
Propagation of transverse surface waves in a three-layer system consisting of a piezoelectric/piezomagnetic (PE/PM) bi-layer bonded on an elastic half-space is theoretically investigated in this paper. Dispersion relations and mode shapes for transverse surface waves are obtained in closed form under electrically open and shorted boundary conditions at the upper surface. Two transverse surface waves related both to Love-type wave and Bleustein-Gulyaev (B-G) type wave propagating in corresponding three-layer structure are discussed through numerically solving the derived dispersion equation. The results show that Love-type wave possesses the property of multiple modes, it can exist all of the values of wavenumber for every selected thickness ratios regardless of the electrical boundary conditions. The presence of PM interlayer makes the phase velocity of Love-type wave decrease. There exist two modes allowing the propagation of B-G type wave under electrically shorted circuit, while only one mode appears in the case of electrically open circuit. The modes of B-G type wave are combinations of partly normal dispersion and partly anomalous dispersion whether the electrically open or shorted. The existence range of mode for electrically open case is greatly related to the thickness ratios, with the thickness of PM interlayer increasing the wavenumber range for existence of B-G type wave quickly shortened. When the thickness ratio is large enough, the wavenumber range of the second mode for electrically shorted circuit is extremely narrow which can be used to remove as an undesired mode. The propagation behaviors and mode shapes of transverse surface waves can be regulated by the modification of the thickness of PM interlayer. The obtained results provide a theoretical prediction and basis for applications of PE-PM composites and acoustic wave devices.
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.)
Effect of transient wave forcing on the behavior of arsenic in a sandy nearshore aquifer
Rakhimbekova, S.; O'Carroll, D. M.; Robinson, C. E.
2016-12-01
Waves cause large quantities of coastal water to recirculate across the groundwater-coastal water interface in addition to inducing complex groundwater flows in the nearshore aquifer. Due to the distinct chemical composition of recirculating coastal water compared with discharging terrestrial groundwater, wave-induced recirculations and flows can alter geochemical gradients in the nearshore aquifer which may subsequently affect the mobilization and transport of reactive pollutants (e.g., arsenic). The impact of seasonal geochemical and hydrological variability on the occurrence and mobility of arsenic near the groundwater-surface water interface has been shown previously in riverine settings, however, the impact of high frequency geochemical variations (e.g., varying wave conditions) on arsenic mobility in groundwater-surface water environments is unclear. The objective of the study was to assess the impact of intensified wave conditions on the behavior of arsenic in a nearshore aquifer to determine the factors regulating its mobility and transport to receiving coastal waters. Field investigations were conducted at a permeable beach on the Great Lakes during a period of intensified wave conditions (wave event). High spatial resolution pore water sampling captured the geochemical conditions in the nearshore aquifer prior to the wave event, immediately after the wave event and over a recovery period of 3 weeks following the wave event. Shifts in pH and redox potential (ORP) gradients in response to varying wave conditions caused shifts in the iron and arsenic distributions in the aquifer. Sediment analysis was combined with the pore water distributions to assess the release of sediment-bound arsenic in response to the varying wave conditions. Insight into the effect of transient forcing on arsenic mobility and transport in groundwater-surface water environments is important for evaluating the potential risks associated with this toxic metalloid. The findings of this
Dynamic behaviors of a Zr-based bulk metallic glass under ramp wave and shock wave loading
Directory of Open Access Journals (Sweden)
Binqiang Luo
2015-06-01
Full Text Available Dynamic behaviors of Zr51Ti5Ni10Cu25Al9 bulk metallic glass were investigated using electric gun and magnetically driven isentropic compression device which provide shock and ramp wave loading respectively. Double-wave structure was observed under shock compression while three-wave structure was observed under ramp compression in 0 ∼ 18GPa. The HEL of Zr51Ti5Ni10Cu25Al9 is 8.97 ± 0.61GPa and IEL is 8.8 ± 0.3GPa, respectively. Strength of Zr51Ti5Ni10Cu25Al9 estimated from HEL is 5.0 ± 0.3GPa while the strength estimated from IEL is 3.6 ± 0.1GPa. Shock wave velocity versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under shock compression appears to be bilinear and a kink appears at about 18GPa. The Lagrangian sound speed versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under ramp wave compression exhibits two discontinuances and are divided to three regions: elastic, plastic-I and plastic-II. The first jump-down occurs at elastic-plastic transition and the second appears at about 17GPa. In elastic and plastic-I regions, Lagrangian sound speed increases linearly with particle velocity, respectively. Characteristic response of sound speed in plastic-I region disagree with shock result in the same pressure region(7GPa ∼ 18GPa, but is consistent with shock result at higher pressure(18-110GPa.
Liu, Tao; Xu, Yan Jun; Zhang, Yong Hui; Yan, Qing Hua; Song, Xiu Ling; Xie, Hui Yan; Luo, Yuan; Rutherford, Shannon; Chu, Cordia; Lin, Hua Liang; Ma, Wen Jun
2013-10-02
In many parts of the world, including in China, extreme heat events or heat waves are likely to increase in intensity, frequency, and duration in light of climate change in the next decades. Risk perception and adaptation behaviors are two important components in reducing the health impacts of heat waves, but little is known about their relationships in China. This study aimed to examine the associations between risk perception to heat waves, adaptation behaviors, and heatstroke among the public in Guangdong province, China. A total of 2,183 adult participants were selected using a four-stage sampling method in Guangdong province. From September to November of 2010 each subject was interviewed at home by a well-trained investigator using a structured questionnaire. The information collected included socio-demographic characteristics, risk perception and spontaneous adaptation behaviors during heat wave periods, and heatstroke experience in the last year. Chi-square tests and unconditional logistic regression models were employed to analyze the data. This study found that 14.8%, 65.3% and 19.9% of participants perceived heat waves as a low, moderate or high health risk, respectively. About 99.1% participants employed at least one spontaneous adaptation behavior, and 26.2%, 51.2% and 22.6% respondents employed 7 adaptation behaviors during heat waves, respectively. Individuals with moderate (OR=2.93, 95% CI: 1.38-6.22) or high (OR=10.58, 95% CI: 4.74-23.63) risk perception experienced more heatstroke in the past year than others. Drinking more water and wearing light clothes in urban areas, while decreasing activity as well as wearing light clothes in rural areas were negatively associated with heatstroke. Individuals with high risk perception and employing risks of heatstroke (OR=47.46, 95% CI: 12.82-175.73). There is a large room for improving health risk perception and adaptation capacity to heat waves among the public of Guangdong province. People with higher
2013-01-01
Background In many parts of the world, including in China, extreme heat events or heat waves are likely to increase in intensity, frequency, and duration in light of climate change in the next decades. Risk perception and adaptation behaviors are two important components in reducing the health impacts of heat waves, but little is known about their relationships in China. This study aimed to examine the associations between risk perception to heat waves, adaptation behaviors, and heatstroke among the public in Guangdong province, China. Methods A total of 2,183 adult participants were selected using a four-stage sampling method in Guangdong province. From September to November of 2010 each subject was interviewed at home by a well-trained investigator using a structured questionnaire. The information collected included socio-demographic characteristics, risk perception and spontaneous adaptation behaviors during heat wave periods, and heatstroke experience in the last year. Chi-square tests and unconditional logistic regression models were employed to analyze the data. Results This study found that 14.8%, 65.3% and 19.9% of participants perceived heat waves as a low, moderate or high health risk, respectively. About 99.1% participants employed at least one spontaneous adaptation behavior, and 26.2%, 51.2% and 22.6% respondents employed 7 adaptation behaviors during heat waves, respectively. Individuals with moderate (OR=2.93, 95% CI: 1.38-6.22) or high (OR=10.58, 95% CI: 4.74-23.63) risk perception experienced more heatstroke in the past year than others. Drinking more water and wearing light clothes in urban areas, while decreasing activity as well as wearing light clothes in rural areas were negatively associated with heatstroke. Individuals with high risk perception and employing risks of heatstroke (OR=47.46, 95% CI: 12.82-175.73). Conclusions There is a large room for improving health risk perception and adaptation capacity to heat waves among the public of
Oral Hygiene. Instructor's Packet. Learning Activity Package.
Hime, Kirsten
This instructor's packet accompanies the learning activity package (LAP) on oral hygiene. Contents included in the packet are a time sheet, suggested uses for the LAP, an instruction sheet, final LAP reviews, a final LAP review answer key, suggested activities, additional resources (student handouts), student performance checklists for both…
German Cultural Packets 13 and 14.
Atlanta Public Schools, GA.
These German culture packets are designed to accompany A-LM Level II and include a statement of the rationale behind the unit, the objectives of the packet, the activities themselves, and a brief evaluation by the student. The activities involve the use of the basic text, the student workbook, corresponding tapes, and fellow students as partners…
Grooming. Instructor's Packet. Learning Activity Package.
Stark, Pamela
This instructor's packet accompanies the learning activity package (LAP) on grooming. Contents included in the packet are a time sheet, suggested uses for the LAP, an instruction sheet, final LAP reviews, a final LAP review answer key, suggested activities, an additional resources list, and student completion cards to issue to students as an…
Certain problems concerning wavelets and wavelets packets
International Nuclear Information System (INIS)
Siddiqi, A.H.
1995-09-01
Wavelets is the outcome of the synthesis of ideas that have emerged in different branches of science and technology, mainly in the last decade. The concept of wavelet packets, which are superpositions of wavelets, has been introduced a couple of years ago. They form bases which retain many properties of wavelets like orthogonality, smoothness and localization. The Walsh orthornomal system is a special case of wavelet packet. The wavelet packets provide at our disposal a library of orthonormal bases, each of which can be used to analyze a given signal of finite energy. The optimal choice is decided by the entropy criterion. In the present paper we discuss results concerning convergence, coefficients, and approximation of wavelet packets series in general and wavelets series in particular. Wavelet packet techniques for solutions of differential equations are also mentioned. (author). 117 refs
Certain problems concerning wavelets and wavelets packets
Energy Technology Data Exchange (ETDEWEB)
Siddiqi, A H
1995-09-01
Wavelets is the outcome of the synthesis of ideas that have emerged in different branches of science and technology, mainly in the last decade. The concept of wavelet packets, which are superpositions of wavelets, has been introduced a couple of years ago. They form bases which retain many properties of wavelets like orthogonality, smoothness and localization. The Walsh orthornomal system is a special case of wavelet packet. The wavelet packets provide at our disposal a library of orthonormal bases, each of which can be used to analyze a given signal of finite energy. The optimal choice is decided by the entropy criterion. In the present paper we discuss results concerning convergence, coefficients, and approximation of wavelet packets series in general and wavelets series in particular. Wavelet packet techniques for solutions of differential equations are also mentioned. (author). 117 refs.
Deep Packet/Flow Analysis using GPUs
Energy Technology Data Exchange (ETDEWEB)
Gong, Qian [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wu, Wenji [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); DeMar, Phil [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
2017-11-12
Deep packet inspection (DPI) faces severe performance challenges in high-speed networks (40/100 GE) as it requires a large amount of raw computing power and high I/O throughputs. Recently, researchers have tentatively used GPUs to address the above issues and boost the performance of DPI. Typically, DPI applications involve highly complex operations in both per-packet and per-flow data level, often in real-time. The parallel architecture of GPUs fits exceptionally well for per-packet network traffic processing. However, for stateful network protocols such as TCP, their data stream need to be reconstructed in a per-flow level to deliver a consistent content analysis. Since the flow-centric operations are naturally antiparallel and often require large memory space for buffering out-of-sequence packets, they can be problematic for GPUs, whose memory is normally limited to several gigabytes. In this work, we present a highly efficient GPU-based deep packet/flow analysis framework. The proposed design includes a purely GPU-implemented flow tracking and TCP stream reassembly. Instead of buffering and waiting for TCP packets to become in sequence, our framework process the packets in batch and uses a deterministic finite automaton (DFA) with prefix-/suffix- tree method to detect patterns across out-of-sequence packets that happen to be located in different batches. In conclusion, evaluation shows that our code can reassemble and forward tens of millions of packets per second and conduct a stateful signature-based deep packet inspection at 55 Gbit/s using an NVIDIA K40 GPU.
Multidimensional signaling via wavelet packets
Lindsey, Alan R.
1995-04-01
This work presents a generalized signaling strategy for orthogonally multiplexed communication. Wavelet packet modulation (WPM) employs the basis functions from an arbitrary pruning of a full dyadic tree structured filter bank as orthogonal pulse shapes for conventional QAM symbols. The multi-scale modulation (MSM) and M-band wavelet modulation (MWM) schemes which have been recently introduced are handled as special cases, with the added benefit of an entire library of potentially superior sets of basis functions. The figures of merit are derived and it is shown that the power spectral density is equivalent to that for QAM (in fact, QAM is another special case) and hence directly applicable in existing systems employing this standard modulation. Two key advantages of this method are increased flexibility in time-frequency partitioning and an efficient all-digital filter bank implementation, making the WPM scheme more robust to a larger set of interferences (both temporal and sinusoidal) and computationally attractive as well.
Downlink Transmission of Short Packets
DEFF Research Database (Denmark)
Trillingsgaard, Kasper Fløe; Popovski, Petar
2017-01-01
Cellular wireless systems rely on frame-based transmissions. The frame design is conventionally based on heuristics, consisting of a frame header and a data part. The frame header contains control information that provides pointers to the messages within the data part. In this paper, we revisit...... the principles of frame design and show the impact of the new design in scenarios that feature short data packets, which are central to various 5G and Internet of Things applications. We~treat framing for downlink transmission in an AWGN broadcast channel with $K$ users, where the sizes of the messages....... This requires changes in the way control information is sent, and it requires that the users need to spend power decoding other messages, thereby increasing the average power consumption. We~show that the common heuristic design is only one point on a curve that represents the tradeoff between latency and power...
International Nuclear Information System (INIS)
Bhunia, C.T.
2007-07-01
Packet combining scheme is a well defined simple error correction scheme for the detection and correction of errors at the receiver. Although it permits a higher throughput when compared to other basic ARQ protocols, packet combining (PC) scheme fails to correct errors when errors occur in the same bit locations of copies. In a previous work, a scheme known as Packet Reversed Packet Combining (PRPC) Scheme that will correct errors which occur at the same bit location of erroneous copies, was studied however PRPC does not handle a situation where a packet has more than 1 error bit. The Modified Packet Combining (MPC) Scheme that can correct double or higher bit errors was studied elsewhere. Both PRPC and MPC schemes are believed to offer higher throughput in previous studies, however neither adequate investigation nor exact analysis was done to substantiate this claim of higher throughput. In this work, an exact analysis of both PRPC and MPC is carried out and the results reported. A combined protocol (PRPC and MPC) is proposed and the analysis shows that it is capable of offering even higher throughput and better error correction capability at high bit error rate (BER) and larger packet size. (author)
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
International Nuclear Information System (INIS)
Serbeto, A.; Alves, M.V.
1993-01-01
Using a nonlinear set of equations which describes the excitation of a purely transverse slow electromagnetic wave by a relativistic electron beam, it is shown that the system runs from chaotic behavior to a regular stable state due to crisis phenomenon and from stabilized soliton and repeated stabilized explosive solutions to a temporal chaos. These behaviors suggest that the primary mechanism for the saturation of the explosive instability is not only the cubic nonlinear frequency shift as pointed out by many authors until now. The inclusion of the velocity perturbation in the beam charge initial equilibrium state leads the system to these strange behaviors. (author)
Youth WAVE Screener: addressing weight-related behaviors with school-age children.
Isasi, Carmen R; Soroudi, Nafisseh; Wylie-Rosett, Judith
2006-01-01
This study evaluated the feasibility of using the youth Weight, Activity, Variety, and Excess (WAVE) screener in a classroom setting for assessing student weight control intentions and the extent to which they used the WAVE strategies to control their weight. The Youth WAVE Screener was administered to fifth-grade students in an inner-city school located in the Bronx, New York. The study was conducted in part to increase student awareness of snack foods and sugary beverages in relation to weight. Of the 169 students who completed the survey, 45.5% (n = 77) were trying to lose weight. Students who were trying to lose weight were more likely to have low-fat dairy products, less likely to have sugary beverages, and less likely to eat junk foods than those who were not trying to lose weight. Students who reported exercising 3 times weekly were more likely to report healthier dietary patterns and less sedentary behaviors than were students who exercise less often. Feedback and dialogue with fifth graders addressed the relationship between TV viewing and eating behavior, advertisement, availability, and preferences of fruits and vegetables. The Youth WAVE Screener can be used to quickly identify children who are concerned about their weight as well as those with dietary and physical activity patterns that may increase the risk of obesity. Diabetes educators can use this screener to start a dialogue with children about their weight-related behaviors.
Drop behavior in acoustic standing waves; Teizaihachu ni okeru ekiteki no kyodo
Energy Technology Data Exchange (ETDEWEB)
Kamimura, H. [National Aerospace Laboratory, Tokyo (Japan); Yamanaka, T. [Yokohama National University, Yokohama (Japan)
1997-10-01
When new materials, such as those for space shuttles, are developed, it is necessary to hold then in a non-contacting manner. Described herein is behavior of drops in a holding device which utilizes acoustic radiation pressure. When an object sufficiently small as compared with wavelength of a sound wave is placed in acoustic standing waves, it is subjected to acoustic radiation pressure. Chandrasekahr developed the theory on the stability of a rotating drop by equating the entire mechanical energy of a drop with its surface energy. This theory, based on the assumption of symmetric surface energy, is incapable of theoretically dealing with multi-lobed waves evolved by surface tension. In this study, multi-lobed waves excited by sound waves in a rotating drop are analytically found without assuming symmetry of drop surface energy. The multi-lobe waves are first found on the assumption that the acoustic radiation pressure around a drop is constant. Then, the effects of the deformed drop on the radiation pressure around the drop are considered. In addition, the equation for the relationship between the radiation pressure and a drop that becomes oblate due to the radiation pressure is obtained. The theoretically derived results by this equation are in good agreement with the observed results by the ground and flight tests. 17 refs., 18 figs.
Packet Guide to Routing and Switching
Hartpence, Bruce
2011-01-01
Go beyond layer 2 broadcast domains with this in-depth tour of advanced link and internetwork layer protocols, and learn how they enable you to expand to larger topologies. An ideal follow-up to Packet Guide to Core Network Protocols, this concise guide dissects several of these protocols to explain their structure and operation. This isn't a book on packet theory. Author Bruce Hartpence built topologies in a lab as he wrote this guide, and each chapter includes several packet captures. You'll learn about protocol classification, static vs. dynamic topologies, and reasons for installing a pa
Q FUNCTION AWARE OPTICAL PACKET SWITCH WITH LOW PACKET LOSS RATE
Directory of Open Access Journals (Sweden)
OMPAL SINGH
2017-03-01
Full Text Available Optical packet switching (OPS is a very promising technology for the next generation data transfer due to the very large bandwidth of the optical fiber. The success of the OPS relies heavily on design of the node architecture which supports comparatively larger buffering capacity without detiorating signal quality too much and it should provide very low packet loss probability with reasonably low average delay. In this paper, a design analysis of low complexity OPS node architecture is discussed along-with its advantages. The presented architecture support both fixed and variable length packets. The packets are stored in a single piece of fiber using the WDM technology. Physical layer analysis presented in this paper is to obtain the Q function (Bit Error Rate. Finally, the Monte Carlo simulation is done to obtain the packet loss. The average delay performance of the switch and effect of Q values on packet loss rates are discussed.
Data Aggregation and Packet Bundling of Uplink Small Packets for Monitoring Applications in LTE
DEFF Research Database (Denmark)
Kim, Dong Min; Sørensen, René Brandborg; Mahmood, Kashif
2017-01-01
topic. In this article we analyze the deployment scenarios in which aggregators can perform cellular access on behalf of multiple MTC devices. We study the effect of packet bundling at the aggregator, which alleviates overhead and resource waste when sending small packets. The aggregators give rise...... of aggregators and packet bundle size. Our results show that, in general, data aggregation can benefit the uplink massive MTC in LTE by reducing the signaling overhead....
Sparsely-Packetized Predictive Control by Orthogonal Matching Pursuit
DEFF Research Database (Denmark)
Nagahara, Masaaki; Quevedo, Daniel; Østergaard, Jan
2012-01-01
We study packetized predictive control, known to be robust against packet dropouts in networked systems. To obtain sparse packets for rate-limited networks, we design control packets via an ℓ0 optimization, which can be eectively solved by orthogonal matching pursuit. Our formulation ensures...
Satcom access in the Evolved Packet Core
Cano Soveri, M.D.; Norp, A.H.J.; Popova, M.P.
2011-01-01
Satellite communications (Satcom) networks are increasingly integrating with terrestrial communications networks, namely Next Generation Networks (NGN). In the area of NGN the Evolved Packet Core (EPC) is a new network architecture that can support multiple access technologies. When Satcom is
Satcom access in the evolved packet core
Cano, M.D.; Norp, A.H.J.; Popova, M.P.
2012-01-01
Satellite communications (Satcom) networks are increasingly integrating with terrestrial communications networks, namely Next Generation Networks (NGN). In the area of NGN the Evolved Packet Core (EPC) is a new network architecture that can support multiple access technologies. When Satcom is
Thermal-hydraulic behaviors of vapor-liquid interface due to arrival of a pressure wave
Energy Technology Data Exchange (ETDEWEB)
Inoue, Akira; Fujii, Yoshifumi; Matsuzaki, Mitsuo [Tokyo Institute of Technology (Japan)
1995-09-01
In the vapor explosion, a pressure wave (shock wave) plays a fundamental role for triggering, propagation and enhancement of the explosion. Energy of the explosion is related to the magnitude of heat transfer rate from hot liquid to cold volatile one. This is related to an increasing rate of interface area and to an amount of transient heat flux between the liquids. In this study, the characteristics of transient heat transfer and behaviors of vapor film both on the platinum tube and on the hot melt tin drop, under same boundary conditions have been investigated. It is considered that there exists a fundamental mechanism of the explosion in the initial expansion process of the hot liquid drop immediately after arrival of pressure wave. The growth rate of the vapor film is much faster on the hot liquid than that on the solid surface. Two kinds of roughness were observed, one due to the Taylor instability, by rapid growth of the explosion bubble, and another, nucleation sites were observed at the vapor-liquid interface. Based on detailed observation of early stage interface behaviors after arrival of a pressure wave, the thermal fragmentation mechanism is proposed.
Dynamic behavior of microscale particles controlled by standing bulk acoustic waves
Energy Technology Data Exchange (ETDEWEB)
Greenhall, J.; Raeymaekers, B., E-mail: bart.raeymaekers@utah.edu [Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Guevara Vasquez, F. [Department of Mathematics, University of Utah, Salt Lake City, Utah 84112 (United States)
2014-10-06
We analyze the dynamic behavior of a spherical microparticle submerged in a fluid medium, driven to the node of a standing bulk acoustic wave created by two opposing transducers. We derive the dynamics of the fluid-particle system taking into account the acoustic radiation force and the time-dependent and time-independent drag force acting on the particle. Using this dynamic model, we characterize the transient and steady-state behavior of the fluid-particle system as a function of the particle and fluid properties and the transducer operating parameters. The results show that the settling time and percent overshoot of the particle trajectory are dependent on the ratio of the acoustic radiation force and time-independent damping force. In addition, we show that the particle oscillates around the node of the standing wave with an amplitude that depends on the ratio of the time-dependent drag forces and the particle inertia.
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
Comparison of Ring-Buffer-Based Packet Capture Solutions
Energy Technology Data Exchange (ETDEWEB)
Barker, Steven Andrew [Sandia National Lab. (SNL-CA), Livermore, CA (United States)
2015-10-01
Traditional packet-capture solutions using commodity hardware incur a large amount of overhead as packets are copied multiple times by the operating system. This overhead slows sensor systems to a point where they are unable to keep up with high bandwidth traffic, resulting in dropped packets. Incomplete packet capture files hinder network monitoring and incident response efforts. While costly commercial hardware exists to capture high bandwidth traffic, several software-based approaches exist to improve packet capture performance using commodity hardware.
DEFF Research Database (Denmark)
Fjelde, Tina; Hansen, Peter Bukhave; Kloch, Allan
1999-01-01
We show that complex packet synchronisation may be avoided in optical packetswitched networks. Detailed traffic analysis demonstrates that packet lossratios of 1e-10 are feasible under bursty traffic conditions for a highcapacity network consisting of asynchronously operated add-drop switch...
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.
DEFF Research Database (Denmark)
Ibsen, Lars Bo
2008-01-01
Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many...... times smaller it remains very high. For example, whilst there is enough potential wave power off the UK to supply the electricity demands several times over, the economically recoverable resource for the UK is estimated at 25% of current demand; a lot less, but a very substantial amount nonetheless....
Quezada-Casasola, Andrés; Avendaño-Reyes, Leonel; Macías-Cruz, Ulises; Ramírez-Godínez, José Alejandro; Correa-Calderón, Abelardo
2014-04-01
In beef and dairy cattle, the number of follicular waves affects endocrine, ovarian, and behavioral events during a normal estrous cycle. However, in Mexican-native Criollo cattle, a shortly and recently domesticated breed, the association between wave patterns and follicular development has not been studied. The objective of this study was to evaluate the effect of number of follicular waves in an estrous cycle on development of anovulatory and ovulatory follicles, corpus luteum (CL) development and functionality, as well as estrual behavior in Criollo cows. Ovarian follicular activities of 22 cycling multiparous Criollo cows were recorded daily by transrectal ultrasound examinations during a complete estrous cycle. Additionally, blood samples were collected daily to determine serum progesterone concentrations. Only two- (n = 17, 77.3%) and three-wave follicular (n = 5, 22.7%) patterns were observed. Duration of estrus, length of estrous cycle, and length of follicular and luteal phases were similar (P > 0.05) between cycles of two and three waves. Two-wave cows ovulated earlier (P 0.05) by number of waves. Growth rate of first dominant follicle was higher (P 0.05) between two- and three-wave patterns. In conclusion, Criollo cows have two or three follicular waves per estrous cycle, which alters partially ovulatory follicle development and ovulation time after detection of estrus. Length of estrous cycle, as well as CL development and functionality, was not affected by number of follicular waves.
The wave function behavior of the open topological string partition function on the conifold
International Nuclear Information System (INIS)
Kashani-Poor, Amir-Kian
2007-01-01
We calculate the topological string partition function to all genus on the conifold, in the presence of branes. We demonstrate that the partition functions for different brane backgrounds (smoothly connected along a quantum corrected moduli space) can be interpreted as the same wave function in different polarizations. This behavior has a natural interpretation in the Chern-Simons target space description of the topological theory. Our detailed analysis however indicates that non-perturbatively, a modification of real Chern-Simons theory is required to capture the correct target space theory of the topological string. We perform our calculations in the framework of a free fermion representation of the open topological string, demonstrating that this framework extends beyond the simple C 3 geometry. The notion of a fermionic brane creation operator arises in this setting, and we study to what extent the wave function properties of the partition function can be extended to this operator
Digital transceiver implementation for wavelet packet modulation
Lindsey, Alan R.; Dill, Jeffrey C.
1998-03-01
Current transceiver designs for wavelet-based communication systems are typically reliant on analog waveform synthesis, however, digital processing is an important part of the eventual success of these techniques. In this paper, a transceiver implementation is introduced for the recently introduced wavelet packet modulation scheme which moves the analog processing as far as possible toward the antenna. The transceiver is based on the discrete wavelet packet transform which incorporates level and node parameters for generalized computation of wavelet packets. In this transform no particular structure is imposed on the filter bank save dyadic branching, and a maximum level which is specified a priori and dependent mainly on speed and/or cost considerations. The transmitter/receiver structure takes a binary sequence as input and, based on the desired time- frequency partitioning, processes the signal through demultiplexing, synthesis, analysis, multiplexing and data determination completely in the digital domain - with exception of conversion in and out of the analog domain for transmission.
Dimidjian, Sona; Arch, Joanna J; Schneider, Rebecca L; Desormeau, Philip; Felder, Jennifer N; Segal, Zindel V
2016-11-01
In this review, we examine common usage of the term "third wave" in the scientific literature, systematically review published meta-analyses of identified "third wave" therapies, and consider the implications and options for the use of "third wave" as a metaphor to describe the nature of and relationships among cognitive and behavioral therapies. We demonstrate that the "third wave" term has grown in its use over time, that it is commonly linked with specific therapies, and that the majority of such therapies have amassed a compelling evidence base attesting to their clinical and public health value. We also consider the extent to which the "third wave" designation is an effective guide for the future, and we encourage scientific inquiry and self-reflection among those concerned with cognitive and behavioral therapies and the scientific basis of psychotherapy more broadly. Copyright © 2016. Published by Elsevier Ltd.
SIMULASI JARINGAN KOMPUTER MENGGUNAKAN CISCO PACKET TRACER
Directory of Open Access Journals (Sweden)
M Mufadhol
2012-01-01
Full Text Available Perkembangan jaringan komputer saat ini begitu pesat, monitoring jaringan komputer akan menjadi suatu hal yang sulit dan rumit. Koneksi jaringan komputer merupakan suatu hal yang mendasar dalam suatu jaringan, karena bila koneksi itu bermasalah maka semua jenis aplikasi yang dijalankan melalui jaringan komputer tidak dapat digunakan. Cisco packet tracer dapat digunakan untuk simulasi yang mencerminkan arsitektur dan juga model dari jaringan komputer pada sistem jaringan yang digunakan. Dengan menggunakan aplikasi cisco packet tracer, simulasi mengenai jaringan dapat dimanfaatkan menjadi informasi tentang keadaan koneksi komputer dalam suatu jaringan.
Design of Packet-Based Block Codes with Shift Operators
Directory of Open Access Journals (Sweden)
Jacek Ilow
2010-01-01
Full Text Available This paper introduces packet-oriented block codes for the recovery of lost packets and the correction of an erroneous single packet. Specifically, a family of systematic codes is proposed, based on a Vandermonde matrix applied to a group of k information packets to construct r redundant packets, where the elements of the Vandermonde matrix are bit-level right arithmetic shift operators. The code design is applicable to packets of any size, provided that the packets within a block of k information packets are of uniform length. In order to decrease the overhead associated with packet padding using shift operators, non-Vandermonde matrices are also proposed for designing packet-oriented block codes. An efficient matrix inversion procedure for the off-line design of the decoding algorithm is presented to recover lost packets. The error correction capability of the design is investigated as well. The decoding algorithm, based on syndrome decoding, to correct a single erroneous packet in a group of n=k+r received packets is presented. The paper is equipped with examples of codes using different parameters. The code designs and their performance are tested using Monte Carlo simulations; the results obtained exhibit good agreement with the corresponding theoretical results.
Design of Packet-Based Block Codes with Shift Operators
Directory of Open Access Journals (Sweden)
Ilow Jacek
2010-01-01
Full Text Available This paper introduces packet-oriented block codes for the recovery of lost packets and the correction of an erroneous single packet. Specifically, a family of systematic codes is proposed, based on a Vandermonde matrix applied to a group of information packets to construct redundant packets, where the elements of the Vandermonde matrix are bit-level right arithmetic shift operators. The code design is applicable to packets of any size, provided that the packets within a block of information packets are of uniform length. In order to decrease the overhead associated with packet padding using shift operators, non-Vandermonde matrices are also proposed for designing packet-oriented block codes. An efficient matrix inversion procedure for the off-line design of the decoding algorithm is presented to recover lost packets. The error correction capability of the design is investigated as well. The decoding algorithm, based on syndrome decoding, to correct a single erroneous packet in a group of received packets is presented. The paper is equipped with examples of codes using different parameters. The code designs and their performance are tested using Monte Carlo simulations; the results obtained exhibit good agreement with the corresponding theoretical results.
Electronic Transport Behaviors due to Charge Density Waves in Ni-Nb-Zr-H Glassy Alloys
Fukuhara, Mikio; Umemori, Yoshimasa
2013-11-01
The amorphous Ni-Nb-Zr-H glassy alloy containing subnanometer-sized icosahedral Zr5 Nb5Ni3 clusters exhibited four types of electronic phenomena: a metal/insulator transition, an electric current-induced voltage oscillation (Coulomb oscillation), giant capacitor behavior and an electron avalanche with superior resistivity. These findings could be excluded by charge density waves that the low-dimensional component of clusters, in which the atoms are lined up in chains along the [130] direction, plays important roles in various electron transport phenomena.
Ebrahimi, Farzad; Dabbagh, Ali
2017-02-01
Main object of the present research is an exact investigation of wave propagation responses of smart rotating magneto-electro-elastic (MEE) graded nanoscale plates. In addition, effective material properties of functionally graded (FG) nanoplate are presumed to be calculated using the power-law formulations. Also, it has been tried to cover both softening and stiffness-hardening behaviors of nanostructures by the means of employing nonlocal strain gradient theory (NSGT). Due to increasing the accuracy of the presented model in predicting shear deformation effects, a refined higher-order plate theory is introduced. In order to cover the most enormous circumstances, maximum amount of load generated by plate’s rotation is considered. Furthermore, utilizing a developed form of Hamilton’s principle, containing magneto-electric effects, the nonlocal governing equations of MEE-FG rotating nanoplates are derived. An analytical solution is obtained to solve the governing equations and validity of the solution method is proven by comparing results from present method with those of former attempts. At last, outcomes are plotted in the framework of some figures to show the influences of various parameters such as wave number, nonlocality, length scale parameter, magnetic potential, electric voltage, gradient index and angular velocity on wave frequency, phase velocity and escape frequency of the examined nanoplate.
Rayleigh wave behavior in functionally graded magneto-electro-elastic material
Ezzin, Hamdi; Mkaoir, Mohamed; Amor, Morched Ben
2017-12-01
Piezoelectric-piezomagnetic functionally graded materials, with a gradual change of the mechanical and electromagnetic properties have greatly applying promises. Based on the ordinary differential equation and stiffness matrix methods, a dynamic solution is presented for the propagation of the wave on a semi-infinite piezomagnetic substrate covered with a functionally graded piezoelectric material (FGPM) layer. The materials properties are assumed to vary in the direction of the thickness according to a known variation law. The phase and group velocity of the Rayleigh wave is numerically calculated for the magneto-electrically open and short cases, respectively. The effect of gradient coefficients on the phase velocity, group velocity, coupled magneto-electromechanical factor, on the stress fields, the magnetic potential and the mechanical displacement are discussed, respectively. Illustration is achieved on the hetero-structure PZT-5A/CoFe2O4; the obtained results are especially useful in the design of high-performance acoustic surface devices and accurately prediction of the Rayleigh wave propagation behavior.
Solid Waste Activity Packet for Teachers.
Illinois Univ., Urbana. Cooperative Extension Service.
This solid waste activity packet introduces students to the solid waste problem in Illinois. Topics explore consumer practices in the market place, packaging, individual and community garbage generation, and disposal practices. The activities provide an integrated approach to incorporating solid waste management issues into subject areas. The…
Impact of Packet Sampling on Link Dimensioning
Schmidt, R.D.O.; Sadre, R.; Sperotto, A.; Berg, H. van den; Pras, A.
2015-01-01
Link dimensioning is used by network operators to properly provision the capacity of their network links. Proposed methods for link dimensioning often require statistics, such as traffic variance, that need to be calculated from packet-level measurements. In practice, due to increasing traffic
Impact of packet sampling on link dimensioning
de Oliveira Schmidt, R.; Stadler, R.; Sadre, R.; Sperotto, Anna; van den Berg, Hans Leo; Pras, Aiko
Link dimensioning is used by network operators to properly provision the capacity of their network links. Proposed methods for link dimensioning often require statistics, such as traffic variance, that need to be calculated from packet-level measurements. In practice, due to increasing traffic
Peninsula Humane Society Teacher's Packet. Secondary Level.
Peninsula Humane Society, San Mateo, CA.
Activities in this teacher's packet are designed to familiarize secondary school students with the responsibilities involved in pet ownership. Teaching plans are provided for a total of 12 lessons grouped under social studies, language arts, math, and health sciences. Activities focus on pet overpopulation, expressions of social responses in…
Packet models revisited: tandem and priority systems
M.R.H. Mandjes (Michel)
2004-01-01
textabstractWe examine two extensions of traditional single-node packet-scale queueing models: tandem networks and (strict) priority systems. Two generic input processes are considered: periodic and Poisson arrivals. For the two-node tandem, an exact expression is derived for the joint distribution
Biological Diversity. Global Issues Education Packet.
Holm, Amy E.
Biological diversity, also commonly called genetic diversity, refers to the variety of organisms on Earth. Scientists are concerned that many species will become extinct because of extensive development in the tropical regions. This packet is designed to increase student's awareness about direct and indirect causes of extinction, endangered…
Analysis of the packet formation process in packet-switched networks
Meditch, J. S.
Two new queueing system models for the packet formation process in packet-switched telecommunication networks are developed, and their applications in process stability, performance analysis, and optimization studies are illustrated. The first, an M/M/1 queueing system characterization of the process, is a highly aggregated model which is useful for preliminary studies. The second, a marked extension of an earlier M/G/1 model, permits one to investigate stability, performance characteristics, and design of the packet formation process in terms of the details of processor architecture, and hardware and software implementations with processor structure and as many parameters as desired as variables. The two new models together with the earlier M/G/1 characterization span the spectrum of modeling complexity for the packet formation process from basic to advanced.
The influence of different auto-ignition modes on the behavior of pressure waves
International Nuclear Information System (INIS)
Xu, Han; Yao, Anren; Yao, Chunde
2015-01-01
Highlights: • Modes of pressure oscillations in knocking, HCCI and super knock are recognized. • Three representative auto-ignition modes in engines are proposed. • A new method of “Energy Injected” is brought into understanding pressure wave. • Simulation results revealed the decisive factors for these three auto-ignition modes. • Different modes lead to different pressure wave behaviors damaging engines. - Abstract: For internal combustion engines, the knock of Homogeneous Charge Compression Ignition engines, the conventional knock of gasoline engines and the super knock are all caused by the auto-ignition of unburned mixture which leads to the oscillation burning, but their Maximal Pressure Oscillation Amplitude (MPOA) and Maximum Pressure Rising Rate (MPRR) are totally different. In order to explore the reason, we propose three typical auto-ignition modes and then bring up the method of “Energy Injected” (EI) which is based on the experiment measured heat release rate. Through changing the heat source term in the energy equation for different auto-ignition modes, we conducted a series of numerical simulations for these three modes. After that, the following pressure oscillations can be compared and analyzed. The numerical simulation results show that different combustion pressure waves with different oscillation characteristics come from different auto-ignition modes, thus the macroscopic MPRR and MPOA are totally different. Furthermore, the method of “EI” based on the experiment measured heat release rate can accurately and rapidly help to research the formation and propagation of pressure waves in the engine combustion chamber.
Influence of material selection on the structural behavior of a wave energy converter
Directory of Open Access Journals (Sweden)
Cândida M. S. P. Malça
2014-09-01
Full Text Available In the last decades, the world energy demand has raised significantly. Concerning this fact, wave energy should be considered as a valid alternative for electricity production. Devices suitable to harness this kind of renewable energy source and convert it into electricity are not yet commercially competitive. This paper is focused on the selection and analysis of different types of elastic materials and their influence on the structural behavior of a wave energy converter (WEC. After a brief characterization of the device, a tridimensional computer aided design (3D CAD numerical model was built and several finite element analyses (FEA were performed through a commercial finite element code. The main components of the WEC, namely the buoy, supporting cables and hydraulic cylinder were simulated assuming different materials. The software used needs, among other parameters, the magnitude of the resultant hydrodynamic forces acting upon the floating buoy obtained from a WEC time domain simulator (TDS which was built based on the WEC dynamic model previously developed. The Von Mises stress gradients and displacement fields determined by the FEA demonstrated that, regardless of the WEC component, the materials with low Young's modulus seems to be unsuitable for this kind of application. The same is valid for the material yield strength since materials with a higher yield strength lead to a better structural behavior of WEC components because lower stress and displacement values were obtained. The developed 3D CAD numerical model showed to be suitable to analyze different combinations of structural conditions. They could depend of different combinations of buoy position and resultant hydrodynamic forces acting upon the buoy, function of the specific sea wave parameters found on the deployment site.
Random linear network coding for streams with unequally sized packets
DEFF Research Database (Denmark)
Taghouti, Maroua; Roetter, Daniel Enrique Lucani; Pedersen, Morten Videbæk
2016-01-01
State of the art Random Linear Network Coding (RLNC) schemes assume that data streams generate packets with equal sizes. This is an assumption that results in the highest efficiency gains for RLNC. A typical solution for managing unequal packet sizes is to zero-pad the smallest packets. However, ...
All-optical signal processing for optical packet switching networks
Liu, Y.; Hill, M.T.; Calabretta, N.; Tangdiongga, E.; Geldenhuys, R.; Zhang, S.; Li, Z.; Waardt, de H.; Khoe, G.D.; Dorren, H.J.S.; Iftekharuddin, K.M.; awwal, A.A.S.
2005-01-01
We discuss how all-optical signal processing might play a role in future all-optical packet switched networks. We introduce a concept of optical packet switches that employ entirely all-optical signal processing technology. The optical packet switch is made out of three functional blocks: the
Short-distance behavior of the Bethe--Salpeter wave function in the ladder approximation
International Nuclear Information System (INIS)
Guth, A.H.; Soper, D.E.
1975-01-01
We investigate the short-distance behavior of the (Wick-rotated) Bethe--Salpeter wave function for the two spin-1/2 quarks bound by the exchange of a massive vector meson. We use the ladder-model kernel, which has the same p -4 scaling behavior as the true kernel in a theory with a fixed point of the renormalization group at g not equal to 0. For a bound state with the quantum numbers of the pion, the leading asymptotic behavior is chi (q/sup μ/) approx. cq/sup -4 + epsilon(g)/γ 5 , where epsilon (g) =1- (1-g 2 /π 2 ) 1 / 2 . Our method also provides the full asymptotic series, although it should be noted that the nonleading terms will depend on the nonleading behavior of the ladder-model kernel. A general term has the form cq - /sup a/(lnq)/sup n/phi (q/sup μ/), where c is an unknown constant, a may be integral or nonintegral, n is an integer, and phi (q/sup μ/) is a representation function of the rotation group in four dimensions
International Nuclear Information System (INIS)
Ren Changhong; Gao Yan; Wu Yonghong; Xu Zhiwei; Zhang Chenggang; Yuan Guangjiang; Xu Shouxi; Su Yinong; Liu Pukun
2010-01-01
C. elegans were exposed to high power millimeter waves (MMWs) with different mean power densities, to investigate their behavioral response and cell morphology changes under MMW irradiation. The time-course photomicrography system was used to record the behavioral changes of C. elegans. The behavioral response and cell morphology changes were further observed by stereoscopic microscopes. The results show that freely moving C. elegans will escape from the MMW irradiation region quickly. After the exposure to MMWs with output mean power of 10 W and 12 W, the bending speed of C. elegans increases significantly at first, while the movement gradually slows down until the bodies get rigid. However, exposed to 5 W MMW, C. elegans show a distinctive tolerant reaction because of the thermal effect. In addition, cell morphological observations show that the nuclear structure of the eggs are abnormal after abnormal after MMW irradiation. High power MMW significantly affects the behaviors and cell morphology of C. elegans, which suggests the C. elegans could be used as a typical model species to study the biological effects of MMW irradiation. (authors)
Bursts of electron waves modulated by oblique ion waves
International Nuclear Information System (INIS)
Boswell, R.W.
1984-01-01
Experimental evidence is presented which shows small packets of electron plasma waves modulated by large amplitude obliquely propagating non-linear ion plasma waves. Very often the whole system is modulated by an oscillation near the ion gyro frequency or its harmonics. The ion waves seem to be similar to those measured in the current carrying auroral plasma. These results suggest that the generation of ion and electron waves in the auroral plasma may be correlated
Kodama, Tetsuya; Tomita, Yukio; Koshiyama, Ken-Ichiro; Blomley, Martin J K
2006-06-01
The combination of ultrasound and ultrasound contrast agents (UCAs) is able to induce transient membrane permeability leading to direct delivery of exogenous molecules into cells. Cavitation bubbles are believed to be involved in the membrane permeability; however, the detailed mechanism is still unknown. In the present study, the effects of ultrasound and the UCAs, Optison on transfection in vitro for different medium heights and the related dynamic behaviors of cavitation bubbles were investigated. Cultured CHO-E cells mixed with reporter genes (luciferase or beta-gal plasmid DNA) and UCAs were exposed to 1 MHz ultrasound in 24-well plates. Ultrasound was applied from the bottom of the well and reflected at the free surface of the medium, resulting in the superposition of ultrasound waves within the well. Cells cultured on the bottom of 24-well plates were located near the first node (displacement node) of the incident ultrasound downstream. Transfection activity was a function determined with the height of the medium (wave traveling distance), as well as the concentration of UCAs and the exposure time was also determined with the concentration of UCAs and the exposure duration. Survival fraction was determined by MTT assay, also changes with these values in the reverse pattern compared with luciferase activity. With shallow medium height, high transfection efficacy and high survival fraction were obtained at a low concentration of UCAs. In addition, capillary waves and subsequent atomized particles became significant as the medium height decreased. These phenomena suggested cavitation bubbles were being generated in the medium. To determine the effect of UCAs on bubble generation, we repeated the experiments using crushed heat-treated Optison solution instead of the standard microbubble preparation. The transfection ratio and survival fraction showed no additional benefit when ultrasound was used. These results suggested that cavitation bubbles created by the
Wave properties of the neutron
International Nuclear Information System (INIS)
Shull, C.G.
1983-01-01
The wave properties of neutrons have been studied and exploited in many areas of physics almost from the time of Chadwick's discovery. Illustrations of these will be provided showing the extreme range of energy and de Broglie wavelength over which they have been observed. Attention will be directed to some of the characteristics associated with wave packet propagation. (author)
Quantum mechanics of lattice gas automata: One-particle plane waves and potentials
International Nuclear Information System (INIS)
Meyer, D.A.
1997-01-01
Classical lattice gas automata effectively simulate physical processes, such as diffusion and fluid flow (in certain parameter regimes), despite their simplicity at the microscale. Motivated by current interest in quantum computation we recently defined quantum lattice gas automata; in this paper we initiate a project to analyze which physical processes these models can effectively simulate. Studying the single particle sector of a one-dimensional quantum lattice gas we find discrete analogs of plane waves and wave packets, and then investigate their behavior in the presence of inhomogeneous potentials. copyright 1997 The American Physical Society
Experimental and analytical study on cesium iodide behavior in piping in wave experiment
Energy Technology Data Exchange (ETDEWEB)
Hidaka, A; Igarashi, M; Hashimoto, K; Sugimoto, J [Japan Atomic Energy Research Inst., Dep. of Reactor Safety Research, Tokai-mura (Japan); Yoshino, T [Toshiba Advanced System Corp., Isago Kawasaki-ku (Japan)
1996-12-01
The WAVE (Wide range Aerosol model VErification) experiments have been performed at JAERI to investigate cesium iodide (CsI) deposition onto an inner surface of piping wall under typical severe accident conditions. The test facility consists of a dish containing CsI powder, electrical heaters and a straight pipe of 1.5 m in length with diameter of 0.042m. Nitrogen gas and superheated steam were injected into the pipe to carry the vaporized CsI and to simulate the thermohydraulic condition for the PWR hot-leg inlet. Analyses of the experiments have been conducted with a three-dimensional thermohydraulic code, SPRAC and the radionuclide behavior analysis codes, ART and VICTORIA. A clear difference was found in the deposition behavior between nitrogen and steam conditions as carrier gases. For nitrogen gas, the analyses well reproduced the experimental results by closely coupling the CsI behavior and the detailed thermohydraulic analyses. For steam carrier gas, on the contrary, the experimental results could not be well reproduced without the use of larger aerosol size. Since the observed enhancement of aerosol size in superheated steam cannot be explained by existing models, it is necessary to further investigate this mechanisms by experiment and analysis. (author) 34 figs., 23 refs.
Modification of boundary plasma behavior by Ion Bernstein Wave heating on the HT-7 tokamak
International Nuclear Information System (INIS)
Xu, G.S.; Wan, B.N.; Song, M.; Ling, B.L.; Li, C.F.; Li, J.
2003-01-01
The boundary plasma behavior during Ion Bernstein Wave heating was investigated using Langmuir probe arrays on the HT-7 tokamak. A distinct weak turbulence regime was reproducibly observed in the 30 MHz IBW heated plasmas with RF power larger than 120 kW, which resulted in a particle confinement improvement of a factor of 2. The strong suppression and decorrelation effect of fluctuations resulted in the turbulent particle flux dropping by more than an order of magnitude in the plasma boundary region. An additional inward radial electric field and associated poloidal ExB flows were produced, which could account for the additional poloidal velocity in the electron diamagnetic direction at some radial locations of the boundary plasma. The electrostatic fluctuations were nearly completely decorrelated in the high frequency region and only low frequency fluctuations remained. The poloidal correlation was considerably reduced in the high poloidal wave number region and only the fluctuations with long poloidal wavelength remained. Three-wave nonlinear phase coupling between the whole frequency domain and the very low frequency region increased significantly in both the plasma edge and the SOL. Quite low frequency fluctuations (about 5 kHz) were generated, which dominated the boundary turbulence during IBW heating. Detailed analyses suggested that, when an IBW with a frequency of 30 MHz was launched into a plasma with the toroidal magnetic field between 1.75 T and 2.0 T, the ion cyclotron resonant layer of 5/2.D was located in the plasma edge region. The poloidal ExB sheared flows generated by IBW near this layer due to a ponderomotive interaction were found to be the mechanism underlying these phenomena. (author)
Effect of Vertically Propagating Shear Waves on Seismic Behavior of Circular Tunnels
Directory of Open Access Journals (Sweden)
Tohid Akhlaghi
2014-01-01
Full Text Available Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.
Modification of boundary plasma behavior by Ion Bernstein Wave heating on HT-7 tokamak
International Nuclear Information System (INIS)
Xu Guoshen
2002-01-01
Cooperated with Fusion Research Center, the University of Texas at Austin, U.S.A. The boundary plasma behavior during Ion Bernstein Wave (IBW) heating was investigated using Langmuir probe arrays on HT-7 tokamak. The particle confinement improvement of over a factor of 2 was observed in 30 MHz IBW heated plasma with RF power > 120 kW. The strong de-correlation effect of fluctuations resulted in that the turbulent particle flux dropped more than an order of magnitude. In IBW heated plasma, an additional inward E r and associated poloidal ExB flows were produced, which could account for the additional poloidal velocity in the electron diamagnetic direction in the scrape-of layer (SOL). Three-wave nonlinear phase coupling increased evidently and low frequency fluctuations (about 5 kHz) were generated, which dominated the boundary turbulence during IBW heating. The 5/2-D resonant layer was located in the plasma edge region, which is found to be the mechanism underlying these phenomena. (author)
Fiber fuse behavior in kW-level continuous-wave double-clad field laser
International Nuclear Information System (INIS)
Sun Jun-Yi; Xiao Qi-Rong; Li Dan; Wang Xue-Jiao; Zhang Hai-Tao; Gong Ma-Li; Yan Ping
2016-01-01
In this study, original experimental data for fiber fuse in kW-level continuous-wave (CW) high power double-clad fiber (DCF) laser are reported. The propagating velocity of the fuse is 9.68 m/s in a 3.1-kW Yb-doped DCF laser. Three other cases in Yb-doped DCF are also observed. We think that the ignition of fiber fuse is caused by thermal mechanism, and the formation of bullet-shaped tracks is attributed to the optical discharge and temperature gradient. The inducements of initial fuse and formation of bullet-shaped voids are analyzed. This investigation of fiber fuse helps better understand the fiber fuse behavior, in order to avoid the catastrophic destruction caused by fiber fuse in high power fiber laser. (paper)
A packet switched communications system for GRO
Husain, Shabu; Yang, Wen-Hsing; Vadlamudi, Rani; Valenti, Joseph
1993-11-01
This paper describes the packet switched Instrumenters Communication System (ICS) that was developed for the Command Management Facility at GSFC to support the Gamma Ray Observatory (GRO) spacecraft. The GRO ICS serves as a vital science data acquisition link to the GRO scientists to initiate commands for their spacecraft instruments. The system is ready to send and receive messages at any time, 24 hours a day and seven days a week. The system is based on X.25 and the International Standard Organization's (ISO) 7-layer Open Systems Interconnection (OSI) protocol model and has client and server components. The components of the GRO ICS are discussed along with how the Communications Subsystem for Interconnection (CSFI) and Network Control Program Packet Switching Interface (NPSI) software are used in the system.
Scalable Packet Classification with Hash Tables
Wang, Pi-Chung
In the last decade, the technique of packet classification has been widely deployed in various network devices, including routers, firewalls and network intrusion detection systems. In this work, we improve the performance of packet classification by using multiple hash tables. The existing hash-based algorithms have superior scalability with respect to the required space; however, their search performance may not be comparable to other algorithms. To improve the search performance, we propose a tuple reordering algorithm to minimize the number of accessed hash tables with the aid of bitmaps. We also use pre-computation to ensure the accuracy of our search procedure. Performance evaluation based on both real and synthetic filter databases shows that our scheme is effective and scalable and the pre-computation cost is moderate.
Quantum teleportation of nonclassical wave packets: An effective multimode theory
Energy Technology Data Exchange (ETDEWEB)
Benichi, Hugo; Takeda, Shuntaro; Lee, Noriyuki; Furusawa, Akira [Department of Applied Physics, University of Tokyo, Tokyo (Japan)
2011-07-15
We develop a simple and efficient theoretical model to understand the quantum properties of broadband continuous variable quantum teleportation. We show that, if stated properly, the problem of multimode teleportation can be simplified to teleportation of a single effective mode that describes the input state temporal characteristic. Using that model, we show how the finite bandwidth of squeezing and external noise in the classical channel affect the output teleported quantum field. We choose an approach that is especially relevant for the case of non-Gaussian nonclassical quantum states and we finally back-test our model with recent experimental results.
Non-linear wave packet dynamics of coherent states
Indian Academy of Sciences (India)
In recent years, the non-linear quantum dynamics of these states have revealed some striking features. It was found that under the action of a Hamil- tonian which is a non-linear function of the photon operator(s) only, an initial coherent state loses its coherent structure quickly due to quantum dephasing induced by the non-.
Wave packet construction in three-dimensional quantum billiards ...
Indian Academy of Sciences (India)
E-mail: mannu_711@yahoo.co.in. MS received 14 ... The motivation to extend the study to a three-dimensional (3D) system is .... with a GWP centred around the central value of the principle quantum number n0 instead of a GWP ...... Cubical and parallelepiped billiards are the potential candidates for the creation of arti-.
Fine structure of large amplitude chorus wave packets
Czech Academy of Sciences Publication Activity Database
Santolík, Ondřej; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.
2014-01-01
Roč. 41, č. 2 (2014), s. 293-299 ISSN 0094-8276 R&D Projects: GA MŠk 7E12026; GA ČR GAP205/10/2279 Institutional support: RVO:68378289 Keywords : whistler-mode chorus * waveform measurements * nonlinear phenomena Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.456, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013GL058889/abstract
Wave Packet Based Statistical Approach to Complex-Forming Reactions
Energy Technology Data Exchange (ETDEWEB)
Guo, Hua [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry and Chemical Biology
2017-12-06
Combustion represents a key chemical process in energy consumption in modern societies and a clear and comprehensive understanding of the elemental reactions in combustion is of great importance to a number of challenging areas such as engine efficiency and environmental protection. In this award, we proposed to develop new theoretical tools to understand elemental chemical processes in combustion environments. With the support of this DOE grant, we have made significant advances in developing new and more efficient and accurate algorithms to characterize reaction dynamics.
A microcomputer for a packet switched network
International Nuclear Information System (INIS)
Seller, P.; Bairstow, R.; Barlow, J.; Waters, M.
1982-12-01
The Bubble Chamber Research Group of the Rutherford and Appleton Laboratory has a large film analysis facility. This comprises 16 digitising tables used for the measurement of bubble chamber film. Each of these tables has an associated microcomputer. These microcomputers are linked by a star structured packet switched local area network (LAN) to a VAX 11/780. The LAN, and in particular a microcomputer of novel architecture designed to act as the central switch of the network, is described. (author)
Stochastic generation of continuous wave spectra
DEFF Research Database (Denmark)
Trulsen, J.; Dysthe, K. B.; Pécseli, Hans
1983-01-01
Wave packets of electromagnetic or Langmuir waves trapped in a well between oscillating reflectors are considered. An equation for the temporal evolution of the probability distribution for the carrier wave number is derived, and solved analytically in terms of moments in the limits of long...
Saha, Asit; Pal, Nikhil; Chatterjee, Prasanta
2014-10-01
The dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons has been investigated in the framework of perturbed and non-perturbed Kadomtsev-Petviashili (KP) equations. Applying the reductive perturbation technique, we have derived the KP equation in electron-positron-ion magnetoplasma with kappa distributed electrons and positrons. Bifurcations of ion acoustic traveling waves of the KP equation are presented. Using the bifurcation theory of planar dynamical systems, the existence of the solitary wave solutions and the periodic traveling wave solutions has been established. Two exact solutions of these waves have been derived depending on the system parameters. Then, using the Hirota's direct method, we have obtained two-soliton and three-soliton solutions of the KP equation. The effect of the spectral index κ on propagations of the two-soliton and the three-soliton has been shown. Considering an external periodic perturbation, we have presented the quasi periodic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas.
Energy Technology Data Exchange (ETDEWEB)
Saha, Asit, E-mail: asit-saha123@rediffmail.com, E-mail: prasantachatterjee1@rediffmail.com [Department of Mathematics, Sikkim Manipal Institute of Technology, Majitar, Rangpo, East-Sikkim 737136 (India); Department of Mathematics, Siksha Bhavana, Visva Bharati University, Santiniketan-731235 (India); Pal, Nikhil; Chatterjee, Prasanta, E-mail: asit-saha123@rediffmail.com, E-mail: prasantachatterjee1@rediffmail.com [Department of Mathematics, Siksha Bhavana, Visva Bharati University, Santiniketan-731235 (India)
2014-10-15
The dynamic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas with superthermal electrons and positrons has been investigated in the framework of perturbed and non-perturbed Kadomtsev-Petviashili (KP) equations. Applying the reductive perturbation technique, we have derived the KP equation in electron-positron-ion magnetoplasma with kappa distributed electrons and positrons. Bifurcations of ion acoustic traveling waves of the KP equation are presented. Using the bifurcation theory of planar dynamical systems, the existence of the solitary wave solutions and the periodic traveling wave solutions has been established. Two exact solutions of these waves have been derived depending on the system parameters. Then, using the Hirota's direct method, we have obtained two-soliton and three-soliton solutions of the KP equation. The effect of the spectral index κ on propagations of the two-soliton and the three-soliton has been shown. Considering an external periodic perturbation, we have presented the quasi periodic behavior of ion acoustic waves in electron-positron-ion magnetoplasmas.
Striegel-Moore, Ruth H; Rosselli, Francine; Holtzman, Niki; Dierker, Lisa; Becker, Anne E; Swaney, Gyda
2011-09-01
To examine prevalence and correlates (gender, Body Mass Index) of disordered eating in American Indian/Native American (AI/NA) and white young adults. We examined data from the 10,334 participants (mean age 21.93 years, SD = 1.8) of the National Longitudinal Study of Adolescent Health (ADD Health) Wave III for gender differences among AI/NA participants (236 women, 253 men) and ethnic group differences on measures of eating pathology. Among AI/NA groups, women were significantly more likely than men to report loss of control and embarrassment due to overeating. In gender-stratified analyses, a significantly higher prevalence of AI/NA women reported disordered eating behaviors compared with white women; there were no between group differences in prevalence for breakfast skipping or having been diagnosed with an eating disorder. Among men, disordered eating behaviors were uncommon and no comparison was statistically significant. Our study offers a first glimpse into the problem of eating pathology among AI/NA individuals. Gender differences among AI/NA participants are similar to results reported in white samples. That AI/NA women were as likely as white women to have been diagnosed with an eating disorder is striking in light of well documented under-utilization of mental health care among AI/NA individuals. Copyright © 2010 Wiley Periodicals, Inc.
Wang, Rui; Hu, Zhiping; Zhang, Dan; Wang, Qiyao
2017-12-01
The dynamic behavior of filled joints is mostly controlled by the filled medium. In addition to nonlinear elastic behavior, viscoelastic behavior of filled joints is also of great significance. Here, a theoretical study of stress wave propagation through a filled rock joint with linear viscoelastic deformation behavior has been carried out using a modified time-domain recursive method (TDRM). A displacement discontinuity model was extended to form a displacement and stress discontinuity model, and the differential constitutive relationship of viscoelastic model was adopted to introduce the mass and viscoelastic behavior of filled medium. A standard linear solid model, which can be degenerated into the Kelvin and Maxwell models, was adopted in deriving this method. Transmission and reflection coefficients were adopted to verify this method. Besides, the effects of some parameters on wave propagation across a filled rock joint with linear viscoelastic deformation behavior were discussed. Then, a comparison of the time-history curves calculated by the present method with those by frequency-domain method (FDM) was performed. The results indicated that change tendencies of the transmission and reflection coefficients for these viscoelastic models versus incident angle were the same as each other but not frequency. The mass and viscosity coupling of filled medium did not fundamentally change wave propagation. The modified TDRM was found to be more efficient than the FDM.
International Nuclear Information System (INIS)
Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Goossens, Marcel
2013-01-01
Magnetohydrodynamic (MHD) waves are ubiquitously observed in the solar atmosphere. Kink waves are a type of transverse MHD waves in magnetic flux tubes that are damped due to resonant absorption. The theoretical study of kink MHD waves in solar flux tubes is usually based on the simplification that the transverse variation of density is confined to a nonuniform layer much thinner than the radius of the tube, i.e., the so-called thin boundary approximation. Here, we develop a general analytic method to compute the dispersion relation and the eigenfunctions of ideal MHD waves in pressureless flux tubes with transversely nonuniform layers of arbitrary thickness. Results for kink waves are produced and compared with fully numerical resistive MHD eigenvalue computations in the limit of small resistivity. We find that the frequency and resonant damping rate are the same in both ideal and resistive cases. The actual results for thick nonuniform layers deviate from the behavior predicted in the thin boundary approximation and strongly depend on the shape of the nonuniform layer. The eigenfunctions in ideal MHD are very different from those in resistive MHD. The ideal eigenfunctions display a global character regardless of the thickness of the nonuniform layer, while the resistive eigenfunctions are localized around the resonance and are indistinguishable from those of ordinary resistive Alfvén modes. Consequently, the spatial distribution of wave energy in the ideal and resistive cases is dramatically different. This poses a fundamental theoretical problem with clear observational consequences
Xylella fastidiosa (Xf) is a foregut-borne bacterium that is inoculated into xylem cells of a healthy plant during feeding by sharpshooter vectors. Inoculation occurs during salivation and egestion behaviors that are likely represented by the sharpshooter X wave. The objective of this study was to t...
Papale, Andrew E; Zielinski, Mark C; Frank, Loren M; Jadhav, Shantanu P; Redish, A David
2016-12-07
Current theories posit that memories encoded during experiences are subsequently consolidated into longer-term storage. Hippocampal sharp-wave-ripple (SWR) events have been linked to this consolidation process during sleep, but SWRs also occur during awake immobility, where their role remains unclear. We report that awake SWR rates at the reward site are inversely related to the prevalence of vicarious trial and error (VTE) behaviors, thought to be involved in deliberation processes. SWR rates were diminished immediately after VTE behaviors and an increase in the rate of SWR events at the reward site predicted a decrease in subsequent VTE behaviors at the choice point. Furthermore, SWR disruptions increased VTE behaviors. These results suggest an inverse relationship between SWRs and VTE behaviors and suggest that awake SWRs and associated planning and memory consolidation mechanisms are engaged specifically in the context of higher levels of behavioral certainty. Copyright Â© 2016 Elsevier Inc. All rights reserved.
A meta-analysis of third wave mindfulness-based cognitive behavioral therapies for older people.
Kishita, Naoko; Takei, Yuko; Stewart, Ian
2017-12-01
The aim of this study is to review the effectiveness of third wave mindfulness-based cognitive behavioral therapies (CBTs) for depressive or anxiety symptomatology in older adults across a wide range of physical and psychological conditions. Electronic literature databases were searched for articles, and random-effects meta-analysis was conducted. Ten studies met the inclusion criteria, of which nine reported the efficacy of interventions on depressive symptoms and seven on anxiety symptoms. Effect-size estimates suggested that mindfulness-based CBT is moderately effective on depressive symptoms in older adults (g = 0.55). The results demonstrated a similar level of overall effect size for anxiety symptoms (g = 0.58). However, there was a large heterogeneity, and publication bias was evident in studies reporting outcomes on anxiety symptoms, and thus, this observed efficacy for late-life anxiety may not be robust. The quality of the included studies varied. Only one study used an active psychological control condition. There were a limited number of studies that used an intent-to-treat (last observation carried forward method) analysis and reported appropriate methods for clinical trials (e.g., treatment-integrity reporting). Third wave mindfulness-based CBT may be robust in particular for depressive symptoms in older adults. We recommend that future studies (i) conduct randomized controlled trials with intent-to-treat to compare mindfulness-based CBT with other types of psychotherapy in older people and (ii) improve study quality by using appropriate methods for checking treatment adherence, randomization, and blinding of assessors. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Plasma acceleration in a wave with varying frequency
International Nuclear Information System (INIS)
Petrzilka, V.A.
1978-01-01
The averaged velocity of a test particle and the averaged velocity of a plasma in an electromagnetic wave packet with varying frequency (e.g., a radiation pulse from pulsar) is derived. The total momentum left by the wave packet in regions of plasma inhomogeneity is found. In case the plasma concentration is changing due to ionization the plasma may be accelerated parallelly or antiparallelly to the direction of the wave packet propagation which is relevant for a laser induced breakdown in gas. (author)
Compressed Domain Packet Loss Concealment of Sinusoidally Coded Speech
DEFF Research Database (Denmark)
Rødbro, Christoffer A.; Christensen, Mads Græsbøll; Andersen, Søren Vang
2003-01-01
We consider the problem of packet loss concealment for voice over IP (VoIP). The speech signal is compressed at the transmitter using a sinusoidal coding scheme working at 8 kbit/s. At the receiver, packet loss concealment is carried out working directly on the quantized sinusoidal parameters......, based on time-scaling of the packets surrounding the missing ones. Subjective listening tests show promising results indicating the potential of sinusoidal speech coding for VoIP....
Development of optical packet and circuit integrated ring network testbed.
Furukawa, Hideaki; Harai, Hiroaki; Miyazawa, Takaya; Shinada, Satoshi; Kawasaki, Wataru; Wada, Naoya
2011-12-12
We developed novel integrated optical packet and circuit switch-node equipment. Compared with our previous equipment, a polarization-independent 4 × 4 semiconductor optical amplifier switch subsystem, gain-controlled optical amplifiers, and one 100 Gbps optical packet transponder and seven 10 Gbps optical path transponders with 10 Gigabit Ethernet (10GbE) client-interfaces were newly installed in the present system. The switch and amplifiers can provide more stable operation without equipment adjustments for the frequent polarization-rotations and dynamic packet-rate changes of optical packets. We constructed an optical packet and circuit integrated ring network testbed consisting of two switch nodes for accelerating network development, and we demonstrated 66 km fiber transmission and switching operation of multiplexed 14-wavelength 10 Gbps optical paths and 100 Gbps optical packets encapsulating 10GbE frames. Error-free (frame error rate optical packets of various packet lengths and packet rates, and stable operation of the network testbed was confirmed. In addition, 4K uncompressed video streaming over OPS links was successfully demonstrated. © 2011 Optical Society of America
Multiple descriptions for packetized predictive control
DEFF Research Database (Denmark)
Østergaard, Jan; Quevedo, Daniel
2016-01-01
be reliably reconstructed at the plant side. For the particular case of LTI plant models and i.i.d. channels, we show that the overall system forms a Markov jump linear system. We provide conditions for mean square stability and derive upper bounds on the operational bit rate of the quantizer to guarantee......In this paper, we propose to use multiple descriptions (MDs) to achieve a high degree of robustness towards random packet delays and erasures in networked control systems. In particular, we consider the scenario, where a data-rate limited channel is located between the controller and the plant...
Impurity behavior during ion-Bernstein wave heating in PBX-M
Isler, R. C.; Post-Zwicker, A. P.; Paul, S. F.; Tighe, W.; Ono, M.; Leblanc, B. P.; Bell, R.; Kugel, H. W.; Kaita, R.
1994-07-01
Ion-Bernstein-wave heating (IBWH) has been tested in several tokamaks. In some cases the results have been quite positive, producing temperature increases and also improving both energy and particle confinement times, whereas in others, no distinctive changes were observed. Most recently, IBWH has been utilized in the Princeton Beta Experiment-Modified (PBX-M) where the long-range goal is the achievement of operation in the second stable region by current and pressure profile control. Investigations have been performed in this machine using IBWH as the sole source of auxiliary power or using IBWH in conjunction with neutral-beam injection (NBI) or with lower-hybrid current drive (LHCD). Impurity studies seem particularly important for IBWH since not only have influxes often been observed to increase, but the global impurity confinement time has also been shown to lengthen as the confinement of the working gas improved. The authors present here a set of characteristic experimental results regarding the impurity behavior in PBX-M; in general, these are consonant with previous observations in other tokamaks.
Influence of Shock Wave on the Flutter Behavior of Fan Blades Investigated
Srivastava, Rakesh; Bakhle, Milind A.; Stefko, George L.
2003-01-01
Modern fan designs have blades with forward sweep; a lean, thin cross section; and a wide chord to improve performance and reduce noise. These geometric features coupled with the presence of a shock wave can lead to flutter instability. Flutter is a self-excited dynamic instability arising because of fluid-structure interaction, which causes the energy from the surrounding fluid to be extracted by the vibrating structure. An in-flight occurrence of flutter could be catastrophic and is a significant design issue for rotor blades in gas turbines. Understanding the flutter behavior and the influence of flow features on flutter will lead to a better and safer design. An aeroelastic analysis code, TURBO, has been developed and validated for flutter calculations at the NASA Glenn Research Center. The code has been used to understand the occurrence of flutter in a forward-swept fan design. The forward-swept fan, which consists of 22 inserted blades, encountered flutter during wind tunnel tests at part speed conditions.
Computer simulations on the nonlinear frequency shift and nonlinear modulation of ion-acoustic waves
International Nuclear Information System (INIS)
Ohsawa, Yukiharu; Kamimura, Tetsuo.
1976-11-01
The nonlinear behavior of ion-acoustic waves with rather short wave-length, k lambda sub(De) asymptotically equals 1, is investigated by computer sumulations. It is observed that the nonlinear frequency shift is negative and is proportional to square root of the initial wave amplitude when the amplitude is not too large. This proportionality breaks down and the frequency shift can become positive (for large Te/Ti), when (n tilde sub(i)/n 0 )sup(1/2)>0.25, where n tilde sub(i) is the ion density perturbation and n 0 the average plasma density. Nonlinear modulation of the wave-packet is clearly seen; however, modulational instability was not observed. The importance of the effects of trapped ions to these phenomena is emphasized. (auth.)
A study of artificial speech quality assessors of VoIP calls subject to limited bursty packet losses
Directory of Open Access Journals (Sweden)
Jelassi Sofiene
2011-01-01
Full Text Available Abstract A revolutionary feature of emerging media services over the Internet is their ability to account for human perception during service delivery processes, which surely increases their popularity and incomes. In such a situation, it is necessary to understand the users' perception, what should obviously be done using standardized subjective experiences. However, it is also important to develop artificial quality assessors that enable to automatically quantify the perceived quality. This efficiently helps performing optimal network and service management at the core and edges of the delivery systems. In our article, we explore the behavior rating of new emerging artificial speech quality assessors of VoIP calls subject to moderately bursty packet loss processes. The examined Speech Quality Assessment (SQA algorithms are able to estimate speech quality of live VoIP calls at run-time using control information extracted from header content of received packets. They are especially designed to be sensitive to packet loss burstiness. The performance evaluation study is performed using a dedicated set-up software-based SQA framework. It offers a specialized packet killer and includes the implementation of four SQA algorithms. A speech quality database, which covers a wide range of bursty packet loss conditions, has been created and then thoroughly analyzed. Our main findings are the following: (1 all examined automatic bursty-loss aware speech quality assessors achieve a satisfactory correlation under upper (> 20% and lower (< 10% ranges of packet loss processes; (2 they exhibit a clear weakness to assess speech quality under a moderated packet loss process; (3 the accuracy of sequence-by-sequence basis of examined SQA algorithms should be addressed in detail for further precision.
41 CFR 101-39.306 - Operator's packet.
2010-07-01
...-INTERAGENCY FLEET MANAGEMENT SYSTEMS 39.3-Use and Care of GSA Interagency Fleet Management System Vehicles § 101-39.306 Operator's packet. The GSA Interagency Fleet Management System (IFMS) will provide each... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Operator's packet. 101-39...
Label-controlled optical packet routing technologies and applications
DEFF Research Database (Denmark)
Koonen, A.M.J.; Yan, N.; Vegas Olmos, Juan José
2007-01-01
An overview is given of various optical packet labeling techniques. The architecture and technologies are discussed for optical packet routing nodes using orthogonal labeling with optoelectronic label processing, and for nodes using time-serial labeling with all-optical time-serial label processing...
MODELLING AND VERIFICATION OF KITSAT PACKET COMMUNICATION PROTOCOLS
Directory of Open Access Journals (Sweden)
Young-Ro Lee
1996-06-01
Full Text Available In this paper, in order to verify KITSAT 1/2 packet communication protocols, we model the AX.25 protocol and PACSAT protocol by using an extended Petri net and then verify the correctness, boundedness, liveness and deadlock freeness of packet protocols by utilizing reachability trees.
Dance Theatre of Harlem--Theater Activity Packet.
New York City Board of Education, Brooklyn, NY. Div. of Curriculum and Instruction.
Intended to complement the New York City communication arts curriculum, this packet introduces young students, guided by the classroom teacher, to a dress rehearsal performance of the Dance Theatre of Harlem ballet company. The packet is one of a series in the "Early Stages" program, a joint effort of the Mayor's Office of Film, Theater…
Packet throughput performance of multiservice, multirate OCDMA in elastic networks
DEFF Research Database (Denmark)
Raddo, Thiago R.; Sanches, Anderson L.; Tafur Monroy, Idelfonso
2016-01-01
the multiple-access interference (MAI) as binomially distributed. The packet throughput expression, by its turn, is derived considering a Poisson distribution for the composite packet arrivals. Numerical results show that the multicode technique is a good candidate for future multiservice, multirate OCDMA...
Langston Hughes Curriculum Packet: Dig and Be Dug in Return.
Danielson, Susan
Designed in a flexible format for use by college instructors, high school teachers, and community education workers, this curriculum packet serves as an introduction to the life and works of black poet Langston Hughes. The major component of the packet is a critical essay that explores the thematic highlights of Hughes's career. The remaining…
SDRAM-based packet buffer model for high speed switches
DEFF Research Database (Denmark)
Rasmussen, Anders; Ruepp, Sarah Renée; Berger, Michael Stübert
2011-01-01
based on the specifications of a real-life DDR3-SDRAM chip. Based on this model the performance of different schemes for optimizing the performance of such a packet buffer can be evaluated. The purpose of this study is to find efficient schemes for memory mapping of the packet queues and I/O traffic...
Systematic Sampling and Cluster Sampling of Packet Delays
Lindh, Thomas
2006-01-01
Based on experiences of a traffic flow performance meter this papersuggests and evaluates cluster sampling and systematic sampling as methods toestimate average packet delays. Systematic sampling facilitates for exampletime analysis, frequency analysis and jitter measurements. Cluster samplingwith repeated trains of periodically spaced sampling units separated by randomstarting periods, and systematic sampling are evaluated with respect to accuracyand precision. Packet delay traces have been ...
All-optical devices for ultrafast packet switching
DEFF Research Database (Denmark)
Dorren, H.J.S.; HerreraDorren, J.; Raz, O.
2007-01-01
We discuss integrated devices for all-optical packet switching. We focus on monolithically integrated all-optical flip-flops, ultra-fast semiconductor based wavelength converters and explain the operation principles. Finally, a 160 Gb/s all-optical packet switching experiment over 110 km of field...
Node design in optical packet switched networks
DEFF Research Database (Denmark)
Nord, Martin
2006-01-01
The thesis discusses motivation, realisation and performance of the Optical Packet Switching (OPS) network paradigm. The work includes proposals for designs and methods to efficiently use both the wavelength- and time domain for contention resolution in asynchronous operation. The project has also......S parameter. Finally, the thesis includes a proposal for a node design and associated MAC protocol for an OPS ring topology metropolitan area network with high throughput and fairness, also for unbalanced traffic....... proposed parallel designs to overcome scalability constraints and to support migration scenarios. Furthermore, it has proposed and demonstrated optical input processing schemes for hybrids networks to simultaneously support OPS and Optical Circuit Switching. Quality of Service (QoS) differentiation enables...
Nonlinear Raman scattering behavior with Langmuir and sound waves coupling in a homogeneous plasma
International Nuclear Information System (INIS)
Bonnaud, G.; Pesme, D.; Pellat, R.
1990-01-01
By means of wave-coupling simulations, the typical nonlinear evolution of stimulated Raman scattering (SRS) is investigated in a homogeneous sub-quarter-critical plasma for present-day low laser irradiances and kilo-electron-volt electron temperatures. The decrease of the Langmuir energy observed after the SRS growth is found to be basically the result of the electrostatic decay instability (EDI) onset, which generates a high-amplitude ion-acoustic wave. The resulting strong modulation of the plasma density causes a conversion process that transforms the initial one-wave-vector Langmuir wave driven by SRS into a Bloch wave and induces SRS detuning and larger damping. The conditions involved herein have allowed isolation of these processes from the modulational instability; in addition, the Langmuir collapse is found not to occur owing to the high electron temperature
The Absence of Stokes Drift in Waves
Chafin, Clifford
2015-01-01
Stokes drift has been as central to the history of wave theory as it has been distressingly absent from experiment. Neither wave tanks nor experiments in open bodies detect this without nearly canceling "eulerian flows." Acoustic waves have an analogous problem that is particularly problematic in the vorticity production at the edges of beams. Here we demonstrate that the explanation for this arises from subtle end-of-packet and wavetrain gradient effects such as microbreaking events and wave...
Multidimensional behavior of an electrostatic ion wave in a magnetized plasma
International Nuclear Information System (INIS)
Nishinari, K.; Abe, K.; Satsuma, J.
1994-01-01
Three-dimensional nonlinear evolution equations of an electrostatic ion wave in the short wave region in a magnetized plasma are derived by means of the reductive perturbation method. It is shown that, in some cases, the evolution equations reduce to the Davey--Stewartson 1 equations, which are known to admit solutions with localized structure in higher dimension. It is also shown that there is a possibility of collapse of localized structure in the case of wave propagation parallel to a magnetic field
A novel lost packets recovery scheme based on visual secret sharing
Lu, Kun; Shan, Hong; Li, Zhi; Niu, Zhao
2017-08-01
In this paper, a novel lost packets recovery scheme which encrypts the effective parts of an original packet into two shadow packets based on (2, 2)-threshold XOR-based visual Secret Sharing (VSS) is proposed. The two shadow packets used as watermarks would be embedded into two normal data packets with digital watermarking embedding technology and then sent from one sensor node to another. Each shadow packet would reveal no information of the original packet, which can improve the security of original packet delivery greatly. The two shadow packets which can be extracted from the received two normal data packets delivered from a sensor node can recover the original packet lossless based on XOR-based VSS. The Performance analysis present that the proposed scheme provides essential services as long as possible in the presence of selective forwarding attack. The proposed scheme would not increase the amount of additional traffic, namely, lower energy consumption, which is suitable for Wireless Sensor Network (WSN).
Directory of Open Access Journals (Sweden)
Gabriel Arquelau Pimenta Rodrigues
2017-10-01
Full Text Available Any network connected to the Internet is subject to cyber attacks. Strong security measures, forensic tools, and investigators contribute together to detect and mitigate those attacks, reducing the damages and enabling reestablishing the network to its normal operation, thus increasing the cybersecurity of the networked environment. This paper addresses the use of a forensic approach with Deep Packet Inspection to detect anomalies in the network traffic. As cyber attacks may occur on any layer of the TCP/IP networking model, Deep Packet Inspection is an effective way to reveal suspicious content in the headers or the payloads in any packet processing layer, excepting of course situations where the payload is encrypted. Although being efficient, this technique still faces big challenges. The contributions of this paper rely on the association of Deep Packet Inspection with forensics analysis to evaluate different attacks towards a Honeynet operating in a network laboratory at the University of Brasilia. In this perspective, this work could identify and map the content and behavior of attacks such as the Mirai botnet and brute-force attacks targeting various different network services. Obtained results demonstrate the behavior of automated attacks (such as worms and bots and non-automated attacks (brute-force conducted with different tools. The data collected and analyzed is then used to generate statistics of used usernames and passwords, IP and services distribution, among other elements. This paper also discusses the importance of network forensics and Chain of Custody procedures to conduct investigations and shows the effectiveness of the mentioned techniques in evaluating different attacks in networks.
Hydrodynamic Behavior of Overtopping Wave Energy Converters Built in Sea Defense Structures
DEFF Research Database (Denmark)
Victor, Lander; Kofoed, Jens Peter; Troch, Peter
2010-01-01
Many sea defense structures need to be adapted to the rising sea water level and changing wave climate due to global warming. The accordingly required investment opens perspectives for wave energy converters (WECs) – that are built as part of the sea defense structures – to become economically...... viable. In this paper the average overtopping discharges q of overtopping wave energy devices built in sea defense structures are studied. Physical model tests with this type of devices have been carried out in a wave flume leading to experimental q - values. The experimental q -values are compared...... with predicted average overtopping discharges by existing empirical formulae from literature. Overtopping converters have low relative crest freeboards and smooth slope characteristics to maximize overtopping, which is contradictive to the basic role of sea defense structures. As a consequence, the achieved...
Said-Houari, Belkacem
2012-03-01
In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.
Said-Houari, Belkacem
2012-01-01
In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.
Juretzek, C.; Perleth, M.; Hadziioannou, C.
2015-12-01
Ambient seismic noise has become an important source of signal for tomography and monitoring purposes. Better understanding of the noise field characteristics is crucial to further improve noise applications. Our knowledge about the common and different origins of Love and Rayleigh waves in the microseism bands is still limited. This applies in particular to constraints on source locations and source mechanisms of Love waves. Here, 3-component beamforming is used to distinguish between the differently polarized wave types present in the noise field recorded at several arrays across Europe. The focus lies on frequencies around the primary and secondary microseismic bands. We compare characteristics of Love and Rayleigh wave noise, such as source directions and frequency content. Further, Love to Rayleigh wave ratios are measured at each array, and a dependence on direction is observed. We constrain the corresponding source regions of both wave types by backprojection. By using a full year of data in 2013, we are able to track the seasonal changes in our observations of Love-to-Rayleigh ratio and source locations.
The energy density of a Landau damped plasma wave
Best, R. W. B.
1999-01-01
In this paper some theories about the energy of a Landau damped plasma wave are discussed and new initial conditions are proposed. Analysis of a wave packet, rather than an infinite wave, gives a clear picture of the energy transport from field to particles. Initial conditions are found which excite
Yang, Cen; Zhang, Yong-liang
2018-04-01
In this paper we propose a two-buoy wave energy converter composed of a heaving semi-submerged cylindrical buoy, a fixed submerged cylindrical buoy and a power take-off (PTO) system, and investigate the effect of the fixed submerged buoy on the hydrodynamics of the heaving semi-submerged buoy based on the three-dimensional potential theory. And the dynamic response of the semi-submerged buoy and the wave energy conversion efficiency of the converter are analyzed. The difference of the hydrodynamics and the wave energy conversion efficiency of a semi-submerged buoy converter with and without a fixed submerged buoy is discussed. It is revealed that the influence of the fixed submerged buoy on the exciting wave force, the added mass, the radiation damping coefficient and the wave energy conversion efficiency can be significant with a considerable variation, depending on the vertical distance between the heaving semi-submerged buoy and the fixed submerged buoy, the diameter ratio of the fixed submerged buoy to the heaving semi-submerged buoy and the water depth.
Green partial packet recovery in wireless sensor networks
Daghistani, Anas; Ben Khalifa, Abderrahman; Showail, Ahmad; Shihada, Basem
2015-01-01
wireless sensor motes. We propose Green-Frag, a novel adaptive partial packet recovery mechanism that is energy friendly. It can help prolonging the battery life of wireless sensor motes that are usually resource constrained. It dynamically partitions
Efficient incremental relaying for packet transmission over fading channels
Fareed, Muhammad Mehboob; Alouini, Mohamed-Slim; Yang, Hongchuan
2014-01-01
In this paper, we propose a novel relaying scheme for packet transmission over fading channels, which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from the destination. Our scheme capitalizes
Further Results on Extended Delivery Time for Secondary Packet Transmission
Usman, Muneer; Yang, Hong-Chuan; Alouini, Mohamed-Slim
2017-01-01
with non-work-preserving strategy, where interrupted packets must be repeated. We also analyze the effect of imperfect periodic sensing, i.e., the secondary user periodically senses the spectrum for availability, with a chance of missing an available
High-speed packet filtering utilizing stream processors
Hummel, Richard J.; Fulp, Errin W.
2009-04-01
Parallel firewalls offer a scalable architecture for the next generation of high-speed networks. While these parallel systems can be implemented using multiple firewalls, the latest generation of stream processors can provide similar benefits with a significantly reduced latency due to locality. This paper describes how the Cell Broadband Engine (CBE), a popular stream processor, can be used as a high-speed packet filter. Results show the CBE can potentially process packets arriving at a rate of 1 Gbps with a latency less than 82 μ-seconds. Performance depends on how well the packet filtering process is translated to the unique stream processor architecture. For example the method used for transmitting data and control messages among the pseudo-independent processor cores has a significant impact on performance. Experimental results will also show the current limitations of a CBE operating system when used to process packets. Possible solutions to these issues will be discussed.
Packet-Based Control Algorithms for Cooperative Surveillance and Reconnaissance
National Research Council Canada - National Science Library
Murray, Richard M
2007-01-01
..., and repeated transmissions. Results include analysis and design of estimation and control algorithms in the presence of packet loss and across multi-hop data networks, distributed estimation and sensor fusion algorithms...
Further Results on Extended Delivery Time for Secondary Packet Transmission
Usman, Muneer
2017-07-10
Cognitive radio transceiver can opportunistically access the underutilized spectrum resource of primary systems for new wireless services. With interweave cognitive implementation, secondary transmission may be interrupted by primary transmission. To facilitate the packet delay analysis of such secondary transmission, we study the extended delivery time of secondary packet transmission. In particular, we derive the exact distribution function of extended delivery time of a fixed-size secondary packet with non-work-preserving strategy, where interrupted packets must be repeated. We also analyze the effect of imperfect periodic sensing, i.e., the secondary user periodically senses the spectrum for availability, with a chance of missing an available channel on a certain sensing attempt. These results complement previous work on work-preserving strategy with perfect sensing. Selected numerical and simulation results are presented for verifying the mathematical formulation.
Packet-aware transport for video distribution [Invited
Aguirre-Torres, Luis; Rosenfeld, Gady; Bruckman, Leon; O'Connor, Mannix
2006-05-01
We describe a solution based on resilient packet rings (RPR) for the distribution of broadcast video and video-on-demand (VoD) content over a packet-aware transport network. The proposed solution is based on our experience in the design and deployment of nationwide Triple Play networks and relies on technologies such as RPR, multiprotocol label switching (MPLS), and virtual private LAN service (VPLS) to provide the most efficient solution in terms of utilization, scalability, and availability.
Packetized Media Streaming with Comprehensive Exploitation of Feedback Information
De Vleeschouwer, C.; Frossard, P.
2005-01-01
This paper addresses the problem of streaming packetized media over a lossy packet network, with sender-driven (re)transmission using acknowledgement feedback. The different transmission scenarios associated to a group of interdependent media data units are abstracted in terms of a finite alphabet of policies, for each single data unit. A rate-distortion optimized markovian framework is proposed, which supports the use of comprehensive feedback information. Contrarily to previous works in rat...
Performance evaluation of packet video transfer over local area networks
Lu, Jie
1993-01-01
This research investigates the implementation and performance of packet video transfer over local area networks. A network architecture is defined for packet video such that most of the processing is performed by the higher layers of the Open Systems Interconnection (OSI) reference model, while the lower layers provide real-time services. Implementation methods are discussed for coding schemes, including data compression, the network interface unit, and the underlying local are...
Optical packet networks - conclusions from the IST DAVID project
DEFF Research Database (Denmark)
Dittmann, Lars
2004-01-01
This work outlines the result from the European research project DAVID working with optical packet switch solutions for both WAN and MAN. The project started July 2000 and has been completed successfully by the end of 2003.......This work outlines the result from the European research project DAVID working with optical packet switch solutions for both WAN and MAN. The project started July 2000 and has been completed successfully by the end of 2003....
On zero-point energy, stability and Hagedorn behavior of Type IIB strings on pp-waves
International Nuclear Information System (INIS)
Bigazzi, F.; Cotrone, A.L.
2003-06-01
Type IIB strings on many pp-wave backgrounds, supported either by 5-form or 3-form fluxes, have negative light-cone zero-point energy. This raises the question of their stability and poses possible problems in the definition of their thermodynamic properties. After having pointed out the correct way of calculating the zero-point energy, an issue not fully discussed in literature, we show that these Type IIB strings are classically stable and have well defined thermal properties, exhibiting a Hagedorn behavior. (author)
TCP Packet Trace Analysis. M.S. Thesis
Shepard, Timothy J.
1991-01-01
Examination of a trace of packets collected from the network is often the only method available for diagnosing protocol performance problems in computer networks. This thesis explores the use of packet traces to diagnose performance problems of the transport protocol TCP. Unfortunately, manual examination of these traces can be so tedious that effective analysis is not possible. The primary contribution of this thesis is a graphical method of displaying the packet trace which greatly reduce, the tediousness of examining a packet trace. The graphical method is demonstrated by the examination of some packet traces of typical TCP connections. The performance of two different implementations of TCP sending data across a particular network path is compared. Traces many thousands of packets long are used to demonstrate how effectively the graphical method simplifies examination of long complicated traces. In the comparison of the two TCP implementations, the burstiness of the TCP transmitter appeared to be related to the achieved throughput. A method of quantifying this burstiness is presented and its possible relevance to understanding the performance of TCP is discussed.
Acoustic evaluation of wood quality in standing trees. Part I, Acoustic wave behavior
Xiping Wang; Robert J. Ross; Peter Carter
2007-01-01
Acoustic wave velocities in standing trees or live softwood species were measured by the time-of-flight (TOF) method. Tree velocities were compared with acoustic velocities measured in corresponding butt logs through a resonance acoustic method. The experimental data showed a skewed relationship between tree and log acoustic measurements. For most trees tested,...
Dynamic behavior of zirconium alloy E110 under submicrosecond shock-wave loading
Directory of Open Access Journals (Sweden)
Kazakov D.N.
2015-01-01
Full Text Available Stress waves have been measured under shock wave loading of zirconium alloy E110 samples with the 0.5 – 8 mm thickness at normal and elevated temperatures. Duration of shock loading pulses varied from ∼0.05 up to 1μs with the amplitude varying from 3.4 up to 23 GPa. Free-surface velocity profiles have been registered using VISAR and PDV interferometers with nanosecond resolution. Attenuation of the elastic precursor has been measured to determine plastic strain rate behind the elastic precursor front. The plastic strain rate was observed to decrease with propagation from 106 s−1 at the 0.46-mm distance down to 2 ⋅ 104 s−1 at the 8-mm distance. Spall strength has been measured under normal and elevated temperatures. Spall strength versus strain rate relationships have been constructed in the 105 s−1 – 106s−1 range. Under shock compression higher than 10.6 GPa, the three-wave configuration of the shock wave has been registered and the polymorphous α → ω transition is considered to be the reason of this phenomenon. This work was supported by State Atomic Energy Corporation “Rosatom” within State Contract # H.4x.44.90.13.1111
Dynamic behavior of zirconium alloy E110 under submicrosecond shock-wave loading
Kazakov, D. N.; Kozelkov, O. E.; Mayorova, A. S.; Malyugina, S. N.; Mokrushin, S. S.; Pavlenko, A. V.
2015-09-01
Stress waves have been measured under shock wave loading of zirconium alloy E110 samples with the 0.5 - 8 mm thickness at normal and elevated temperatures. Duration of shock loading pulses varied from ˜0.05 up to 1μs with the amplitude varying from 3.4 up to 23 GPa. Free-surface velocity profiles have been registered using VISAR and PDV interferometers with nanosecond resolution. Attenuation of the elastic precursor has been measured to determine plastic strain rate behind the elastic precursor front. The plastic strain rate was observed to decrease with propagation from 106 s-1 at the 0.46-mm distance down to 2 ṡ 104 s-1 at the 8-mm distance. Spall strength has been measured under normal and elevated temperatures. Spall strength versus strain rate relationships have been constructed in the 105 s-1 - 106s-1 range. Under shock compression higher than 10.6 GPa, the three-wave configuration of the shock wave has been registered and the polymorphous α → ω transition is considered to be the reason of this phenomenon. This work was supported by State Atomic Energy Corporation "Rosatom" within State Contract # H.4x.44.90.13.1111
Nonlinear behavior of a monochromatic wave in a one-dimensional Vlasov plasma
International Nuclear Information System (INIS)
Shoucri, M.M.; Gagne, R.R.J.
1978-01-01
The nonlinear evolution of a monochromatic wave in a one-dimensional Vlasov plasma is studied numerically. The numerical results are carried out far enough in time for phase mixing to dominate the asymptotic state of the system. A qualitative comparison with previously reported simulations is given
Colosi, John A
2008-09-01
While many results have been intuited from numerical simulation studies, the precise connections between shallow-water acoustic variability and the space-time scales of nonlinear internal waves (NLIWs) as well as the background environmental conditions have not been clearly established analytically. Two-dimensional coupled mode propagation through NLIWs is examined using a perturbation series solution in which each order n is associated with nth-order multiple scattering. Importantly, the perturbation solution gives resonance conditions that pick out specific NLIW scales that cause coupling, and seabed attenuation is demonstrated to broaden these resonances, fundamentally changing the coupling behavior at low frequency. Sound-speed inhomogeneities caused by internal solitary waves (ISWs) are primarily considered and the dependence of mode coupling on ISW amplitude, range width, depth structure, location relative to the source, and packet characteristics are delineated as a function of acoustic frequency. In addition, it is seen that significant energy transfer to modes with initially low or zero energy involves at least a second order scattering process. Under moderate scattering conditions, comparisons of first order, single scattering theoretical predictions to direct numerical simulation demonstrate the accuracy of the approach for acoustic frequencies upto 400 Hz and for single as well as multiple ISW wave packets.
Directory of Open Access Journals (Sweden)
Yuan Zhao
2017-01-01
Full Text Available A cognitive radio network with classified Secondary Users (SUs is considered. There are two types of SU packets, namely, SU1 packets and SU2 packets, in the system. The SU1 packets have higher priority than the SU2 packets. Considering the diversity of the SU packets and the real-time need of the interrupted SU packets, a novel spectrum allocation strategy with classified SUs and impatient packets is proposed. Based on the number of PU packets, SU1 packets, and SU2 packets in the system, by modeling the queue dynamics of the networks users as a three-dimensional discrete-time Markov chain, the transition probability matrix of the Markov chain is given. Then with the steady-state analysis, some important performance measures of the SU2 packets are derived to show the system performance with numerical results. Specially, in order to optimize the system actions of the SU2 packets, the individually optimal strategy and the socially optimal strategy for the SU2 packets are demonstrated. Finally, a pricing mechanism is provided to oblige the SU2 packets to follow the socially optimal strategy.
Nonlinear evolution of astrophysical Alfven waves
Spangler, S. R.
1984-01-01
Nonlinear Alfven waves were studied using the derivative nonlinear Schrodinger equation as a model. The evolution of initial conditions, such as envelope solitons, amplitude-modulated waves, and band-limited noise was investigated. The last two furnish models for naturally occurring Alfven waves in an astrophysical plasma. A collapse instability in which a wave packet becomes more intense and of smaller spatial extent was analyzed. It is argued that this instability leads to enhanced plasma heating. In studies in which the waves are amplified by an electron beam, the instability tends to modestly inhibit wave growth.
Nonlinear lattice waves in heterogeneous media
International Nuclear Information System (INIS)
Laptyeva, T V; Ivanchenko, M V; Flach, S
2014-01-01
We discuss recent advances in the understanding of the dynamics of nonlinear lattice waves in heterogeneous media, which enforce complete wave localization in the linear wave equation limit, especially Anderson localization for random potentials, and Aubry–André localization for quasiperiodic potentials. Additional nonlinear terms in the wave equations can either preserve the phase-coherent localization of waves, or destroy it through nonintegrability and deterministic chaos. Spreading wave packets are observed to show universal features in their dynamics which are related to properties of nonlinear diffusion equations. (topical review)
Stavinoha, Macy; Cooley, Joya A.; Minasian, Stefan G.; McQueen, Tyrel M.; Kauzlarich, Susan M.; Huang, C.-L.; Morosan, E.
2018-05-01
The solid solution Eu (Ga1-xAlx) 4 was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds EuGa4 and EuAl4, despite the similar covalent radii and electronic configurations of Ga and Al. Here we report the onset of magnetic spin reorientation and metamagnetic transitions for x =0 -1 evidenced by magnetization and temperature-dependent specific heat measurements. TN changes nonmonotonously with x , and it reaches a maximum around 20 K for x =0.50 , where the a lattice parameter also shows an extreme (minimum) value. Anomalies in the temperature-dependent resistivity consistent with charge density wave behavior exist only for x =0.50 and 1. Density functional theory calculations show increased polarization between the Ga-Al covalent bonds in the x =0.50 structure compared to the end compounds, such that crystallographic order and chemical pressure are proposed as the causes of the charge density wave behavior.
On the self-trapping of an electromagnetic wave in magnetized plasma
International Nuclear Information System (INIS)
El-Ashry, M.Y.; Berezhiani, V.I.; Pichkhadze, Sh.D.
1987-06-01
The possibility of relativistic self-trapping of an electromagnetic wave in magnetized plasma is studied. It is shown that in the case of propagation of fast wave packet of electromagnetic wave in plasma, self-trapping is possible due to the effect of relativistic non-linearity, which is effective even for small amplitudes of the pumping wave. (author). 7 refs
Ebrahimi, Farzad; Dabbagh, Ali
2018-03-01
In this paper, a three-variable plate model is utilized to explore the wave propagation problem of smart sandwich nanoplates made of a magnetostrictive core and ceramic face sheets while subjected to thermo-magnetic loading. Herein, the magnetostriction effect is considered and controlled via a feedback control system. The nanoplate is supposed to be embedded on a visco-Pasternak elastic substrate. The kinematic relations are derived based on the Kirchhoff plate theory; also, combining these obtained equations with Hamilton's principle, the local equations of motion are achieved. According to a nonlocal strain gradient theory (NSGT), the small-scale influences are covered precisely by introducing two scale coefficients. Afterwards, the nonlocal governing equations are derived coupling the local equations with those of the NSGT. Applying an analytical solution, the wave frequency and phase velocity of the propagated waves can be gathered solving an eigenvalue problem. On the other hand, accuracy and efficiency of the presented model are verified by setting a comparison between the obtained results with those of previous published researches. Effects of different variants are plotted in some figures and the highlights are discussed in detail.
Online Gaming Traffic Generator for Reproducing Gamer Behavior
Shin , Kwangsik; Kim , Jinhyuk; Sohn , Kangmin; Park , Changjoon; Choi , Sangbang
2010-01-01
International audience; In this paper, we proposed an online gaming traffic generator reflecting user behavior patterns. We analyzed the packet size and inter departure time distributions of a popular FPS game (Left4Dead) and MMORPG (World of Warcraft) for regenerating gaming traffic. The proposed traffic generator generates an inter departure time and gaming packetbased on analytical model of the gamer behaviors, then transmits the packet according to the inter departure time. Packet generat...
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)
SECURE SERVICE DISCOVERY BASED ON PROBE PACKET MECHANISM FOR MANETS
Directory of Open Access Journals (Sweden)
S. Pariselvam
2015-03-01
Full Text Available In MANETs, Service discovery process is always considered to be crucial since they do not possess a centralized infrastructure for communication. Moreover, different services available through the network necessitate varying categories. Hence, a need arises for devising a secure probe based service discovery mechanism to reduce the complexity in providing the services to the network users. In this paper, we propose a Secure Service Discovery Based on Probe Packet Mechanism (SSDPPM for identifying the DoS attack in MANETs, which depicts a new approach for estimating the level of trust present in each and every routing path of a mobile ad hoc network by using probe packets. Probing based service discovery mechanisms mainly identifies a mobile node’s genuineness using a test packet called probe that travels the entire network for the sake of computing the degree of trust maintained between the mobile nodes and it’s attributed impact towards the network performance. The performance of SSDPPM is investigated through a wide range of network related parameters like packet delivery, throughput, Control overhead and total overhead using the version ns-2.26 network simulator. This mechanism SSDPPM, improves the performance of the network in an average by 23% and 19% in terms of packet delivery ratio and throughput than the existing service discovery mechanisms available in the literature.
Cao, Xiaoshan; Shi, Junping; Jin, Feng
2012-06-01
The propagation behavior of Love waves in a layered structure that includes a functionally graded material (FGM) substrate carrying a piezoelectric thin film is investigated. Analytical solutions are obtained for both constant and gradient dielectric coefficients in the FGM substrate. Numerical results show that the gradient dielectric coefficient decreases phase velocity in any mode, and the electromechanical coupling factor significantly increases in the first- and secondorder modes. In some modes, the difference in Love waves' phase velocity between these two types of structure might be more than 1%, resulting in significant differences in frequency of the surface acoustic wave devices.
Optimization and Assessment of Wavelet Packet Decompositions with Evolutionary Computation
Directory of Open Access Journals (Sweden)
Schell Thomas
2003-01-01
Full Text Available In image compression, the wavelet transformation is a state-of-the-art component. Recently, wavelet packet decomposition has received quite an interest. A popular approach for wavelet packet decomposition is the near-best-basis algorithm using nonadditive cost functions. In contrast to additive cost functions, the wavelet packet decomposition of the near-best-basis algorithm is only suboptimal. We apply methods from the field of evolutionary computation (EC to test the quality of the near-best-basis results. We observe a phenomenon: the results of the near-best-basis algorithm are inferior in terms of cost-function optimization but are superior in terms of rate/distortion performance compared to EC methods.
Foreign Material in the Gastrointestinal Tract: Cocaine Packets
Directory of Open Access Journals (Sweden)
Nurten Turkel Kucukmetin
2014-01-01
Full Text Available Smuggling drugs by swallowing or inserting into a body cavity is not only a serious and growing international crime, but can also lead to lethal medical complications. The most common cause of death in ‘body packers', people transporting drugs by ingesting a packet into the gastrointestinal tract, is acute drug toxicity from a ruptured packet. However, more than 30 years after the initial report of body packing, there is still no definitive treatment protocol for the management of this patient group. The treatment strategy is determined according to the particular condition of the patient and the clinical experience of the treatment center. Surgical intervention is also less common now, due to both the use of improved packaging materials among smugglers and a shift towards a more conservative medical approach. Herein, we report a case of toxicity from ingested packets of cocaine that leaked and, despite surgery, resulted in exitus of the patient.
Packet Header Compression for the Internet of Things
Directory of Open Access Journals (Sweden)
Pekka KOSKELA
2016-01-01
Full Text Available Due to the extensive growth of Internet of Things (IoT, the number of wireless devices connected to the Internet is forecasted to grow to 26 billion units installed in 2020. This will challenge both the energy efficiency of wireless battery powered devices and the bandwidth of wireless networks. One solution for both challenges could be to utilize packet header compression. This paper reviews different packet compression, and especially packet header compression, methods and studies the performance of Robust Header Compression (ROHC in low speed radio networks such as XBEE, and in high speed radio networks such as LTE and WLAN. In all networks, the compressing and decompressing processing causes extra delay and power consumption, but in low speed networks, energy can still be saved due to the shorter transmission time.
Acceptance and commitment therapy: the new wave of cognitive behavior therapy
Directory of Open Access Journals (Sweden)
Wahyu Nanda Eka Saputra
2016-12-01
Full Text Available Cognitive behavior therapy (CBT is one of the major counseling theories today. However, reliability of this theory has received criticism from other theories, which claim to cognitive interventions do not provide added value on behavioral interventions. The theory criticized and showed dissatisfaction with the practice of CBT is the theory of Acceptance and Commitment Therapy (ACT. Furthermore, ACT is known to a new generation of CBT.ACT is one of the new counseling approach that can be applied to school counselors to deal with the issues of students in the school.
International Nuclear Information System (INIS)
Zhang, Jinzhao; Giot, M.
1992-01-01
A series of experiments has been performed on air-water countercurrent flow through short multi-tube geometries (tube number n = 3, diameter d = 36mm, length I = 2d, 10d and 20d). The time-varying thicknesses of the liquid films trickling down the individual tubes are measured by means of conductance probes mounted flush at different locations of the inner wall surfaces. Detailed time series analyses of the measured film thicknesses provide some useful information about the film flow behavior as well as the interfacial wave characteristics in individual tubes, which can be used as some guidelines for developing more general predictive flooding models. 18 refs., 18 figs., 1 tabs
Sornette, Didier
1993-05-01
A mean-field (MF) model of the critical behavior of charge-density waves below the threshold for sliding is proposed, which replaces the combined effect of the pinning force and of the forces exerted by the neighbors on a given particle n by an effective force threshold Xn. It allows one to rationalize the numerical results of Middleton and Fisher [Phys. Rev. Lett. 66 (1991) 92] on the divergence of the polarization and of the largest correlation length and of Pla and Nori [Phys. Rev. Lett. 67 (1991) 919] on the distribution D( d) of sliding bursts of size d, measured in narrow intervals of driving fields E at a finite distance below the threshold Ec.
A first packet processing subdomain cluster model based on SDN
Chen, Mingyong; Wu, Weimin
2017-08-01
For the current controller cluster packet processing performance bottlenecks and controller downtime problems. An SDN controller is proposed to allocate the priority of each device in the SDN (Software Defined Network) network, and the domain contains several network devices and Controller, the controller is responsible for managing the network equipment within the domain, the switch performs data delivery based on the load of the controller, processing network equipment data. The experimental results show that the model can effectively solve the risk of single point failure of the controller, and can solve the performance bottleneck of the first packet processing.
Existence and asymptotic behavior of the wave equation with dynamic boundary conditions
Graber, Philip Jameson; Said-Houari, Belkacem
2012-01-01
The goal of this work is to study a model of the strongly damped wave equation with dynamic boundary conditions and nonlinear boundary/interior sources and nonlinear boundary/interior damping. First, applying the nonlinear semigroup theory, we show the existence and uniqueness of local in time solutions. In addition, we show that in the strongly damped case solutions gain additional regularity for positive times t>0. Second, we show that under some restrictions on the initial data and if the interior source dominates the interior damping term and if the boundary source dominates the boundary damping, then the solution grows as an exponential function. Moreover, in the absence of the strong damping term, we prove that the solution ceases to exists and blows up in finite time. © 2012 Springer Science+Business Media, LLC.
Noise behavior of the Garching 30-meter prototype gravitational-wave detector
International Nuclear Information System (INIS)
Shoemaker, D.; Schilling, R.; Schnupp, L.; Winkler, W.; Maischberger, K.; Ruediger, A.
1988-01-01
The prototype gravitational-wave detector at Garching is described: in a laser-illuminated Michelson interferometer having arms 30 m in length, a folded optical path of 3 km is realized. The origin, action, and magnitude of possible noise sources are given. The agreement between the expected and measured noise is good. For a band of astrophysical interest, extending from 1 to 6 kHz, the quantum shot noise corresponding to a light power of P = 0.23 W is dominant. In terms of the dimensionless strain h the best sensitivity in a 1-kHz bandwidth is h = 3 x 10/sup -18/, comparable to the most sensitive Weber-bar-type antennas
Existence and asymptotic behavior of the wave equation with dynamic boundary conditions
Graber, Philip Jameson
2012-03-07
The goal of this work is to study a model of the strongly damped wave equation with dynamic boundary conditions and nonlinear boundary/interior sources and nonlinear boundary/interior damping. First, applying the nonlinear semigroup theory, we show the existence and uniqueness of local in time solutions. In addition, we show that in the strongly damped case solutions gain additional regularity for positive times t>0. Second, we show that under some restrictions on the initial data and if the interior source dominates the interior damping term and if the boundary source dominates the boundary damping, then the solution grows as an exponential function. Moreover, in the absence of the strong damping term, we prove that the solution ceases to exists and blows up in finite time. © 2012 Springer Science+Business Media, LLC.
Scattering of matter waves in spatially inhomogeneous environments
International Nuclear Information System (INIS)
Tsitoura, F.; Krüger, P.; Kevrekidis, P. G.; Frantzeskakis, D. J.
2015-01-01
In this article, we study scattering of quasi-one-dimensional matter waves at an interface of two spatial domains, one with repulsive and one with attractive interatomic interactions. It is shown that the incidence of a Gaussian wave packet from the repulsive to the attractive region gives rise to generation of a soliton train. More specifically, the number of emergent solitons can be controlled, e.g., by the variation of the amplitude or the width of the incoming wave packet. Furthermore, we study the reflectivity of a soliton incident from the attractive region to the repulsive one. We find the reflection coefficient numerically and employ analytical methods, which treat the soliton as a particle (for moderate and large amplitudes) or a quasilinear wave packet (for small amplitudes), to determine the critical soliton momentum (as a function of the soliton amplitude) for which total reflection is observed
Directory of Open Access Journals (Sweden)
Ümmihan Taşkoparan Yilmaz
2018-01-01
Full Text Available A new, fast, sensitive and simple voltammetric method is established for the direct determination of carnosic acid (CA. And the electroreduction of carnosic acid (CA was studied using electrochemical methods. The number of electrons transferred in electrode mechanisms were calculated for reversible and adsorption-controlled electrochemical reduction of CA at 17 mV versus Ag/AgCl at pH 7.0 in Britton–Robinson buffer (BR on a hanging mercury drop electrode. Square-wave voltammetry was developed and validated for direct determination of CA. Square-wave parameters were optimized as accumulation potential = 0.0 mV, accumulation time = 5 s, frequency = 50 Hz, pulse amplitude = 50 mV, and staircase step potential = 5 mV. The developed method displays three linear responses from 2 to 9 μM, 10 to 30 and 40 to 90 μM for carnosic acid with a correlation coefficient of 0.996, 0.999 and 0.999. The detection limits were found to be 1.5 μM, 4.0 μM and 40.1 μM, respectively. The interference effect of most common organic and inorganic species was investigated. Proposed method was successfully applied for determination of CA in natural extract of rosemary and the average content was determined as 11.9 ± 1.0 (μg CA/1 g rosemary. The results were in agreement with that obtained by HPLC-UV comparison method. The developed method can be widely used in routine quality control of herbal materials as well as other in foods, medicinal, pharmaceutical and environmental analysis.
Delta function excitation of waves in the earth's ionosphere
Vidmar, R. J.; Crawford, F. W.; Harker, K. J.
1983-01-01
Excitation of the earth's ionosphere by delta function current sheets is considered, and the temporal and spatial evolution of wave packets is analyzed for a two-component collisional F2 layer. Approximations of an inverse Fourier-Laplace transform via saddle point methods provide plots of typical wave packets. These illustrate cold plasma wave theory and may be used as a diagnostic tool since it is possible to relate specific features, e.g., the frequency of a modulation envelope, to plasma parameters such as the electron cyclotron frequency. It is also possible to deduce the propagation path length and orientation of a remote radio beacon.
Skripnyak, Vladimir
2011-06-01
Features of mechanical behavior of nanostructured (NS) and ultrafine grained (UFG) metal and ceramic materials under quasistatic and shock wave loadings are discussed in this report. Multilevel models developed within the approach of computational mechanics of materials were used for simulation mechanical behavior of UFG and NS metals and ceramics. Comparisons of simulation results with experimental data are presented. Models of mechanical behavior of nanostructured metal alloys takes into account a several structural factors influencing on the mechanical behavior of materials (type of a crystal lattice, density of dislocations, a size of dislocation substructures, concentration and size of phase precipitation, and distribution of grains sizes). Results show the strain rate sensitivity of the yield stress of UFG and polycrystalline alloys is various in a range from 103 up to 106 1/s. But the difference of the Hugoniot elastic limits of a UFG and coarse-grained alloys may be not considerable. The spall strength, the yield stress of UFG and NS alloys are depend not only on grains size, but a number of factors such as a distribution of grains sizes, a concentration and sizes of voids and cracks, a concentration and sizes of phase precipitation. Some titanium alloys with grain sizes from 300 to 500 nm have the quasi-static yield strength and the tensile strength twice higher than that of coarse grained counterparts. But the spall strength of the UFG titanium alloys is only 10 percents above than that of coarse grained alloys. At the same time it was found the spall strength of the bulk UFG aluminium and magnesium alloys with precipitation strengthening is essentially higher in comparison of coarse-grained counterparts. The considerable decreasing of the strain before failure of UFG alloys was predicted at high strain rates. The Hugoniot elastic limits of oxide nanoceramics depend not only on the porosity, but also on sizes and volume distribution of voids.
Nesi, Jacqueline; Miller, Adam B; Prinstein, Mitchell J
2017-07-01
This study examined the longitudinal effects of adolescents' depressive symptoms on engagement in technology-based social comparison and feedback seeking (SCFS) behaviors. A total of 816 adolescents (54.7% girls; M age =14.1 at Time 1) participated at three times points, each one year apart. Adolescents reported technology-based SCFS, depressive symptoms, and frequencies of technology use (cell phones, Facebook, and Instagram). Multiple group (by gender) latent growth curve models examined concurrent and lagged effects of depressive symptoms on SCFS, controlling for adolescent's underlying trajectories of SCFS and overall frequencies of technology use. Results indicated that higher levels of depressive symptoms were concurrently associated with greater SCFS after accounting for adolescents' typical patterns of SCFS. For boys only, higher depressive symptoms were prospectively associated with later increases in SCFS. Results highlight the importance of social media as a unique context in which depressed adolescents may be at risk for maladaptive interpersonal behavior.
Wang, Guiji; Luo, Binqiang; Zhang, Xuping; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Chong, Tao; Mo, Jianjun; Wu, Gang; Tao, Yanhui
2013-01-01
A pulsed power generator CQ-4 was developed to characterize dynamic behaviors of materials under ramp wave loading, and to launch high velocity flyer plates for shock compression and hypervelocity impact experiments of materials and structures at Institute of Fluid Physics, China Academy of Engineering Physics. CQ-4 is composed of twenty capacitor and primary discharge switch modules with total capacitance of 32 μF and rated charging voltage of 100 kV, and the storage energy is transmitted by two top and bottom parallel aluminum plates insulated by twelve layers of polyester film with total thickness of 1.2 mm. Between capacitor bank and chamber, there are 72 peaking capacitors with total capacitance of 7.2 μF and rated voltage of 120 kV in parallel, which are connected with the capacitor bank in parallel. Before the load, there is a group of seven secondary self-breaking down switches connected with the total circuit in series. The peaking capacitors and secondary switches are used to shape the discharging current waveforms. For short-circuit, the peak current of discharging can be up to 3 ~ 4 MA and rise time varies from 470 ns to 600 ns when the charging voltages of the generator are from 75 kV to 85 kV. With CQ-4 generator, some quasi-isentropic compression experiments under ramp wave loadings are done to demonstrate the ability of CQ-4 generator. And some experiments of launching high velocity flyer plates are also done on CQ-4. The experimental results show that ramp wave loading pressure of several tens of GPa on copper and aluminum samples can be realized and the velocity of aluminum flyer plate with size of 10 mm × 6 mm × 0.35 mm can be accelerated to about 11 km/s and the velocity of aluminum flyer plate with size of 10 mm × 6 mm × 0.6 mm can be up to about 9 km/s, which show that CQ-4 is a good and versatile tool to realize ramp wave loading and shock compression for shock physics.
DEFF Research Database (Denmark)
Hu, Hao; Laguardia Areal, Janaina; Mulvad, Hans Christian Hansen
2011-01-01
An asynchronous 10G Ethernet packet is synchronized and retimed to a master clock using a time lens. The NRZ packet is converted into an RZ packet and multiplexed with a serial 1.28 Tb/s signal.......An asynchronous 10G Ethernet packet is synchronized and retimed to a master clock using a time lens. The NRZ packet is converted into an RZ packet and multiplexed with a serial 1.28 Tb/s signal....
A multi-ring optical packet and circuit integrated network with optical buffering.
Furukawa, Hideaki; Shinada, Satoshi; Miyazawa, Takaya; Harai, Hiroaki; Kawasaki, Wataru; Saito, Tatsuhiko; Matsunaga, Koji; Toyozumi, Tatuya; Wada, Naoya
2012-12-17
We newly developed a 3 × 3 integrated optical packet and circuit switch-node. Optical buffers and burst-mode erbium-doped fiber amplifiers with the gain flatness are installed in the 3 × 3 switch-node. The optical buffer can prevent packet collisions and decrease packet loss. We constructed a multi-ring optical packet and circuit integrated network testbed connecting two single-ring networks and a client network by the 3 × 3 switch-node. For the first time, we demonstrated 244 km fiber transmission and 5-node hopping of multiplexed 14-wavelength 10 Gbps optical paths and 100 Gbps optical packets encapsulating 10 Gigabit Ethernet frames on the testbed. Error-free (frame error rate optical packets of various packet lengths. In addition, successful avoidance of packet collisions by optical buffers was confirmed.
Thermal effect on the thermomechanical behavior of contacts in a Traveling Wave Tube
Directory of Open Access Journals (Sweden)
Chbiki Mounir
2016-01-01
Full Text Available A new elasto-plastic study of the contact between the helix and the rods of the delay line of Traveling Waves Tubes (TWT was realized. Our study is focused on the analysis of the hot lines shrinking phenomenon. In the studied case, unlike brazed configuration, the contact areas are not perfect, resulting in a diminution of the heat transfer process. In order to maximize the contact area and to homogenize the contact pressure, a soft thermal conductive material is coated on the helix: copper was chosen for this study. In the present work, an analytical model is used to identify the properties of the copper coating at a given temperature. We focused on the mechanical properties in order to improve the assembly process with a better numerical study. Experimental method have been made to validate the proposed model. The first comparison results seem to indicate that the model represents the reality with a good agreement. It is very clearly shown that the temperature decreases the mechanical properties. (Young’s modulus, yield strength, tensile strength…. And the thickness of the coating increases the contact area. This last point is less important at room temperature (6% of increase than at 140°C (22%.
Elastic-Plastic Behavior of U6Nb Under Ramp Wave Loading
Hayes, D. B.; Hall, C.; Hixson, R. S.
2005-07-01
Prior shock experiments on the alloy uranium-niobium-6 wt.% (U6Nb) were absent an elastic precursor when one was expected (A. K. Zurek, et. al., Journal de Physique IV, 10 (#9) p677-682). This was later explained as a consequence of shear stress relaxation from time-dependent twinning that prevented sufficient shear stress for plastic yielding. (D. B. Hayes, et. al., Shock Compression of Condensed Matter-2003, p1177, American Institute of Physics 2004) Pressure was ramped to 13 GPa in 150-ns on eight U6Nb specimens with thicknesses from 0.5 -- 1.1-mm and the back surface velocities were measured with laser interferometry. This pressure load produces a stress wave with sufficiently fast rise time so that, according to the prior work, twins do not have time to form. Four of the U6Nb specimens had been cold-rolled which increased the yield stress. Each velocity history was analyzed with a backward integration analysis to give the stress-strain response of the U6Nb. Comparison of these results with prior Hugoniot measurements shows that the U6Nb in the present experiments responds as an elastic-plastic material and the deduced yield strength of the baseline and of the cold-rolled material agree with static results.
Guda Vishnu, Karthik; Strachan, Alejandro
2017-06-01
SWED materials play a crucial role in protecting both personnel and structures in close proximity to blasts or ballistic impact. Exposure to shock waves with intensities as low as 1 MPa can cause brain injury in personnel and, hence, it is extremely important to understand the mechanisms operating in SWED materials and help design improved formulations. Recent experimental studies show that NILs containing di-ammonium cations and citrate anions with glass transition temperatures (Tg) below room temperature exhibit shockwave absorption characteristics that outperform polyurea (PU), a benchmark SWED assessment material. The experimentalists further hypothesized that the increased SWED ability in NILs with longer side chains (in di-ammonium cation) is due to a permanent structural ordering and nano-scale segregation. We use molecular dynamics simulations with the Dreiding force field to study shock propagation mechanisms in NILs. Shock propagation mechanisms in these materials are explored by performing both Hugoniostat and large scale non-equilibrium molecular dynamics (NEMD) simulations at 300 K. The simulation results show that the NIL 5-6 (5 C atoms (back bone) and 6 C atoms (side chain)) attenuates shocks better than NIL 5-3 (3 C atoms (side chain) and higher Tg) and PMMA in agreement with experimental observation. The simulations show that under shock loading the structures lose long range order; we find no evidence of nano-segregation nor or permanent structural changes.
Elastic-Plastic Behavior of U6Nb under Ramp Wave Loading
International Nuclear Information System (INIS)
Hayes, D. B.; Gray, G. T. III; Hixson, R. S.; Hall, C. A.
2006-01-01
When uranium-niobium (6 wt.%) alloy is shock loaded, the expected elastic precursor is absent. A prior model attributed this absence to shear-induced twinning and the concomitant shear stress reduction that prevented the shocked material from reaching the plastic yield point. In the present study, carefully prepared U6Nb was subjected to shock loading to verify the adequacy of the prior model. Other samples were loaded with a ramp pressure pulse with strain rate large enough so that significant twinning would not occur during the experiment. Backward integration analyses of these latter experiments' back surface motion give stress-strain loading paths in U6Nb that suggest ordinary elastic-plastic flow. Some of the U6Nb was pre-strained by cold rolling in an effort to further ensure that twinning did not affect wave propagation. Shock and ramp loadings yielded similar results to the baseline material except, as expected, they are consistent with a higher yield stress and twinning shear stress threshold
Optical frame synchronizer for 10 G Ethernet packets aiming at 1 Tb/s OTDM Ethernet
DEFF Research Database (Denmark)
Hu, Hao; Palushani, Evarist; Laguardia Areal, Janaina
2010-01-01
Synchronization of 10 G Ethernet packets to a local clock was demonstrated using a phase modulator and a SMF as retiming elements. Error free performances for the synchronized packets with different lengths were achieved.......Synchronization of 10 G Ethernet packets to a local clock was demonstrated using a phase modulator and a SMF as retiming elements. Error free performances for the synchronized packets with different lengths were achieved....
Standard services for the capture, processing, and distribution of packetized telemetry data
Stallings, William H.
1989-01-01
Standard functional services for the capture, processing, and distribution of packetized data are discussed with particular reference to the future implementation of packet processing systems, such as those for the Space Station Freedom. The major functions are listed under the following major categories: input processing, packet processing, and output processing. A functional block diagram of a packet data processing facility is presented, showing the distribution of the various processing functions as well as the primary data flow through the facility.
160 Gbit/s optical packet switching using a silicon chip
DEFF Research Database (Denmark)
Hu, Hao; Ji, Hua; Galili, Michael
2012-01-01
We have successfully demonstrated 160 Gbit/s all-optical packet switching based on cross-phase modulation using a silicon chip. Error free performance is achieved for the 4-to-1 switched 160 Gbit/s packet.......We have successfully demonstrated 160 Gbit/s all-optical packet switching based on cross-phase modulation using a silicon chip. Error free performance is achieved for the 4-to-1 switched 160 Gbit/s packet....
H-Infinity Control Design Considering Packet Loss as a Disturbance for Networked Control Systems
OGURA, Takashi; KOBAYASHI, Kentaro; OKADA, Hiraku; KATAYAMA, Masaaki
2017-01-01
This paper studies H∞ control for networked control systems with packet loss. In networked control systems, packet loss is one of major weakness because the control performance deteriorates due to packet loss. H∞ control, which is one of robust control, can design a controller to reduce the influence of disturbances acting on the controlled object. This paper proposes an H∞ control design that considers packet loss as a disturbance. Numerical examples show that the proposed H∞ control design ...
Optical packet switching in HPC : an analysis of applications performance
Meyer, Hugo; Sancho, Jose Carlos; Mrdakovic, Milica; Miao, Wang; Calabretta, Nicola
2018-01-01
Optical Packet Switches (OPS) could provide the needed low latency transmissions in today large data centers. OPS can deliver lower latency and higher bandwidth than traditional electrical switches. These features are needed for parallel High Performance Computing (HPC) applications. For this
The Sphinx and the Pyramids at Giza. Educational Packet.
Gagliano, Sara; Rapport, Wendy
This packet of materials was created to accompany the exhibit "The Sphinx and the Pyramids: 100 Years of American Archaeology at Giza" at the Semitic Museum of Harvard University. The lessons and teacher's guide focus on the following: (1) "The Mystery of the Secret Tomb" where students take on the role of an archaeologist by…
Comparison of Deep Packet Inspection (DPI) Tools for Traffic Classification
DEFF Research Database (Denmark)
Bujlow, Tomasz; Carela-Español, Valentín; Barlet-Ros, Pere
the researchers do not only have the full payloads, but also they are provided the information which application created the flow. Therefore, the dataset is useful for testing Deep Packet Inspection (DPI) tools, as well as statistical, and port-based classifiers. The dataset was created in a fully manual way...
Customized lifting multiwavelet packet information entropy for equipment condition identification
International Nuclear Information System (INIS)
Chen, Jinglong; Zi, Yanyang; He, Zhengjia; Chen, Xuefeng; Zuo, Ming J; Yuan, Jing
2013-01-01
Condition identification of mechanical equipment from vibration measurement data is significant to avoid economic loss caused by unscheduled breakdowns and catastrophic accidents. However, this task still faces challenges due to the complexity of equipment and the harsh environment. This paper provides a possibility for equipment condition identification by proposing a method called customized lifting multiwavelet packet information entropy. Benefiting from the properties of multi-resolution analysis and multiple wavelet basis functions, the multiwavelet method has advantages in characterizing non-stationary vibration signals. In order to realize the accurate detection and identification of the condition features, a customized lifting multiwavelet packet is constructed via a multiwavelet lifting scheme. Then the vibration signal from the mechanical equipment is processed by the customized lifting multiwavelet packet transform. The relative energy in each frequency band of the multiwavelet packet transform coefficients that equals a percentage of the whole signal energy is taken as the probability. The normalized information entropy is obtained based on the relative energy to describe the condition of a mechanical system. The proposed method is applied to the condition identification of a rolling mill and a demountable disk–drum aero-engine. The results support the feasibility of the proposed method in equipment condition identification. (paper)
Production of a tracer packet of heavier rare earth elements
International Nuclear Information System (INIS)
Lahiri, S.; Nayak, D.; Maji, S.
2004-01-01
Production of a tracer packet of heavier rare earth elements containing carrier-free radionuclides of 153,155 Tb, 153,155,157 Dy, 159 Ho, 159,161 Er, 161 Tm produced by medium energy 7 Li and 12 C irradiation on an europium oxide target and the subsequent separation of bulk europium from the carrier-free products is described. (author)
Hardware packet pacing using a DMA in a parallel computer
Chen, Dong; Heidelberger, Phillip; Vranas, Pavlos
2013-08-13
Method and system for hardware packet pacing using a direct memory access controller in a parallel computer which, in one aspect, keeps track of a total number of bytes put on the network as a result of a remote get operation, using a hardware token counter.
a pyramid algorithm for the haar discrete wavelet packet transform
African Journals Online (AJOL)
PROF EKWUEME
computer-aided signal processing of non-stationary signals, this paper develops a pyramid algorithm for the discrete wavelet packet ... Edith T. Luhanga, School of Computational and Communication Sciences and Engineering, Nelson Mandela African. Institute of ..... Mathematics, Washington University. 134. EDITH T.
Green partial packet recovery in wireless sensor networks
Daghistani, Anas
2015-08-18
Partial packet recovery is well known for increasing network throughput and reducing frame retransmissions. However, partial packet recovery methods in the literature are not energy-aware and hence they are not suitable for the battery powered wireless sensor motes. We propose Green-Frag, a novel adaptive partial packet recovery mechanism that is energy friendly. It can help prolonging the battery life of wireless sensor motes that are usually resource constrained. It dynamically partitions the frame into smaller blocks to avoid dropping the whole frame due to a single bit error. Also, Green-Frag is able to tolerate high interference and save energy by varying the transmit power based on channel quality and interference pattern. We experimentally evaluate the energy efficiency as well as goodput and delay of Green-Frag using our TelosB sensor mote testbed. We find that Green-Frag reduces energy consumption by 33% on average compared to the state of the art partial packet recovery scheme in the literature in the presence of Wi-Fi interference. In the worst case, this reduction in energy consumption comes at the cost of 10% reduction in goodput. Finally, Green-Frag reduces the latency by 22% on average compared to other static frame fragmentation schemes.
A CURRICULUM FOR ENGLISH, STUDENT PACKET, GRADE 9.
Nebraska Univ., Lincoln. Curriculum Development Center.
THE FIRST UNIT OF THE STUDENT PACKET FOR GRADE NINE OF THE NEBRASKA ENGLISH CURRICULUM IS A STUDY OF THE RELATIONSHIPS WHICH EXIST BETWEEN AUTHOR AND AUDIENCE, AND AN EXAMINATION OF THE EPIGRAM, LIMERICK, PARABLE, FABLE, AND ODE. WITH THIS BACKGROUND, STUDENTS CONSIDER "ON AVARICE" AND "ANIMAL FARM" AS EXAMPLES OF FORMAL AND…
Hardware Realization of an Ethernet Packet Analyzer Search Engine
2000-06-30
specific for the home automation industry. This analyzer will be at the gateway of a network and analyze Ethernet packets as they go by. It will keep... home automation and not the computer network. This system is a stand-alone real-time network analyzer capable of decoding Ethernet protocols. The
Self-Management of Hybrid Optical and Packet Switching Networks
Fioreze, Tiago; Pras, Aiko
Hybrid optical and packet switching networks enable data to be forwarded at multiple levels. Large IP flows at the IP level may be therefore moved to the optical level bypassing the per hop routing decisions of the IP level. Such move could be beneficial since congested IP networks could be
Self-Management of Hybrid Optical and Packet Switching Networks
Fioreze, Tiago
2010-01-01
Hybrid optical and packet switching networks are composed of multi-service hybrid devices that enable forwarding of data at multiple levels. Large IP flows at the IP level may be therefore moved to the optical level bypassing therefore the per hop routing decisions of the IP level. Such move could
On the Effects of Heterogeneous Packet Lengths on Network Coding
DEFF Research Database (Denmark)
Compta, Pol Torres; Fitzek, Frank; Roetter, Daniel Enrique Lucani
2014-01-01
Random linear network coding (RLNC) has been shown to provide increased throughput, security and robustness for the transmission of data through the network. Most of the analysis and the demonstrators have focused on the study of data packets with the same size (number of bytes). This constitutes...
Opportunistic Nonorthogonal Packet Scheduling in Fixed Broadband Wireless Access Networks
Directory of Open Access Journals (Sweden)
Ahmed Mohamed H
2006-01-01
Full Text Available In order to mitigate high cochannel interference resulting from dense channel reuse, the interference management issues are often considered as essential part of scheduling schemes in fixed broadband wireless access (FBWA networks. To that end, a series of literature has been published recently, in which a group of base stations forms an interferer group (downlink transmissions from each base station become dominant interference for the users in other in-group base stations, and the scheduling scheme deployed in the group allows only one base station to transmit at a time. As a result of time orthogonality in transmissions, the dominant cochannel interferers are prevented, and hence the packet error rate can be improved. However, prohibiting concurrent transmissions in these orthogonal schemes introduces throughput penalty as well as higher end-to-end packet delay which might not be desirable for real-time services. In this paper, we utilize opportunistic nonorthogonality among the in-group transmissions whenever possible and propose a novel transmission scheduling scheme for FBWA networks. The proposed scheme, in contrast to the proactive interference avoidance techniques, strives for the improvements in delay and throughput efficiency. To facilitate opportunistic nonorthogonal transmissions in the interferer group, estimation of signal-to-interference-plus-noise ratio (SINR is required at the scheduler. We have observed from simulations that the proposed scheme outperforms the reference orthogonal scheme in terms of spectral efficiency, mean packet delay, and packet dropping rate.
Analysis Of Packets Delay In Wireless Data Networks
Directory of Open Access Journals (Sweden)
Krivchenkov Aleksandr
2015-12-01
Full Text Available The networks with wireless links for automation control applications traffic transmission when packets have small size and application payload is predictable are under consideration. Analytical model for packets delay on their propagation path through the network is proposed. Estimations for network architectures based on WiFi and Bluetooth wireless technologies are made. The specifications for physical layer 802.11 a/b/g/n and 802.15.1 are under consideration. Analytical and experimental results for delivered network bandwidth for different network architecture, traffic structure and wireless technologies were compared to validate that basic mechanisms are correctly taken into account in the model. It is shown that basic effects are taken into account and further accuracy “improvement” of the model will give not more than 5%. As a result that is important for automation control applications we have reliably received the lowest possible level for packets delay in one wireless link. For 802.11 it is of order of 0.2 ms, for 802.15.1 it is 1.25 ms and is true when application packet can be transferred by one data frame.
An integrated circuit/packet switched video conferencing system
International Nuclear Information System (INIS)
Kippenhan Junior, H.A.; Lidinsky, W.P.; Roediger, G.A.; Waits, T.A.
1996-01-01
The HEP Network Resource Center (HEPNRC) at Fermilab and the Collider Detector Facility (CDF) collaboration have evolved a flexible, cost-effective, widely accessible video conferencing system for use by high energy physics collaborations and others wishing to use video conferencing. No current systems seemed to fully meet the needs of high energy physics collaborations. However, two classes of video conferencing technology: circuit-switched and packet-switched, if integrated, might encompass most of HEPS's needs. It was also realized that, even with this integration, some additional functions were needed and some of the existing functions were not always wanted. HEPNRC with the help of members of the CDF collaboration set out to develop such an integrated system using as many existing subsystems and components as possible. This system is called VUPAC (Video conferencing Using Packets and Circuits). This paper begins with brief descriptions of the circuit-switched and packet-switched video conferencing systems. Following this, issues and limitations of these systems are considered. Next the VUPAC system is described. Integration is accomplished primarily by a circuit/packet video conferencing interface. Augmentation is centered in another subsystem called MSB (Multiport MultiSession Bridge). Finally, there is a discussion of the future work needed in the evolution of this system. (author)
INTERNET TRAFFIC AND PACKET ROUND TRIP DELAY SELF ...
African Journals Online (AJOL)
object of our interest)- is preserved with respect to scaling in space and/or ... models and the standard models for packet traffic considered in the ... tlle structure of the Internet, but failed to exhaustively ... the vehicle of Sel.fSimilar processes ...
An integrated circuit/packet switched video conferencing system
Energy Technology Data Exchange (ETDEWEB)
Kippenhan Junior, H.A.; Lidinsky, W.P.; Roediger, G.A. [Fermi National Accelerator Lab., Batavia, IL (United States). HEP Network Resource Center; Waits, T.A. [Rutgers Univ., Piscataway, NJ (United States). Dept. of Physics and Astronomy
1996-07-01
The HEP Network Resource Center (HEPNRC) at Fermilab and the Collider Detector Facility (CDF) collaboration have evolved a flexible, cost-effective, widely accessible video conferencing system for use by high energy physics collaborations and others wishing to use video conferencing. No current systems seemed to fully meet the needs of high energy physics collaborations. However, two classes of video conferencing technology: circuit-switched and packet-switched, if integrated, might encompass most of HEPS's needs. It was also realized that, even with this integration, some additional functions were needed and some of the existing functions were not always wanted. HEPNRC with the help of members of the CDF collaboration set out to develop such an integrated system using as many existing subsystems and components as possible. This system is called VUPAC (Video conferencing Using Packets and Circuits). This paper begins with brief descriptions of the circuit-switched and packet-switched video conferencing systems. Following this, issues and limitations of these systems are considered. Next the VUPAC system is described. Integration is accomplished primarily by a circuit/packet video conferencing interface. Augmentation is centered in another subsystem called MSB (Multiport MultiSession Bridge). Finally, there is a discussion of the future work needed in the evolution of this system. (author)
Application of Cellular Automata to Detection of Malicious Network Packets
Brown, Robert L.
2014-01-01
A problem in computer security is identification of attack signatures in network packets. An attack signature is a pattern of bits that characterizes a particular attack. Because there are many kinds of attacks, there are potentially many attack signatures. Furthermore, attackers may seek to avoid detection by altering the attack mechanism so that…
Analysis and implementation of packet preemption for Time Sensitive Networks
DEFF Research Database (Denmark)
Zhou, Zifan; Yan, Ying; Ruepp, Sarah Renée
2017-01-01
level simulation in Riverbed Modeler. The simulation is complemented by numerical analysis which provides the average queuing delay for both types of traffic (preemptable and express). Furthermore, the paper describes an approach to implement the packet preemption solution on an FPGA in VHDL, which...... illustrates the complexity of hardware implementation....
General writing-information packet for the environmental impact project
International Nuclear Information System (INIS)
Raaen, H.P.
1975-02-01
The information packet was prepared primarily for internal use at Holifield National Laboratory. The contents include suggestions to authors of environmental statements; format of environmental statements; formats of references given in environmental statements; preparation of SELECTED BIBLIOGRAPHY; troublesome words; glossary; abbreviations, initialisms, and symbols; and MT/ST taping procedure. (U.S.)
Solar Energy Education Packet for Elementary & Secondary Students.
Center for Renewable Resources, Washington, DC.
The arrangement of this packet is essentially evolutionary, with a conscious effort to alternate reading assignments, activities and experiments. It begins with solar energy facts and terminology as background to introduce the reader to basic concepts. It progresses into a discussion of passive solar systems. This is followed by several projects…
Solar Energy Education Packet for Elementary & Secondary Students. Revised Edition.
Center for Renewable Resources, Washington, DC.
The arrangement of this packet is essentially evolutionary, with a conscious effort to alternate reading assignments, activities and experiments. It begins with solar energy facts and terminology as background to introduce the reader to basic concepts. It progresses into a discussion of passive solar systems. This is followed by several projects…
Event-triggered control systems under packet losses
Dolk, V.S.; Heemels, W.P.M.H.
2017-01-01
Networked control systems (NCSs) offer many benefits in terms of increased flexibility and maintainability but might also suffer from inevitable imperfections such as packet dropouts and limited communications resources. In this paper, (static and dynamic) event-triggered control (ETC) strategies
Fast Packet forwarding Engine Based on Software Circuits
Makkes, M.X.; Varabanescu, A.; Laat, C. de; Meijer, R.J.
2015-01-01
Forwarding packets is part of the performance critical path of routing devices, and affects the network performance at any scale. This operation is typically performed by dedicated routing boxes, which are fast, but expensive and inflexible. Recent work has shown that in many cases commodity
Performance analysis of multi-hop wireless packet networks
Directory of Open Access Journals (Sweden)
Lim J.-T.
1997-01-01
Full Text Available In this paper, a unified analytical framework for performance analysis of multi-hop wireless packet networks is developed. The effect of coupling between the hops on the degradation of the delay-throughput characteristics and the probability of blocking is investigated. The issue of hop decoupling is addressed.
Random access with adaptive packet aggregation in LTE/LTE-A.
Zhou, Kaijie; Nikaein, Navid
While random access presents a promising solution for efficient uplink channel access, the preamble collision rate can significantly increase when massive number of devices simultaneously access the channel. To address this issue and improve the reliability of the random access, an adaptive packet aggregation method is proposed. With the proposed method, a device does not trigger a random access for every single packet. Instead, it starts a random access when the number of aggregated packets reaches a given threshold. This method reduces the packet collision rate at the expense of an extra latency, which is used to accumulate multiple packets into a single transmission unit. Therefore, the tradeoff between packet loss rate and channel access latency has to be carefully selected. We use semi-Markov model to derive the packet loss rate and channel access latency as functions of packet aggregation number. Hence, the optimal amount of aggregated packets can be found, which keeps the loss rate below the desired value while minimizing the access latency. We also apply for the idea of packet aggregation for power saving, where a device aggregates as many packets as possible until the latency constraint is reached. Simulations are carried out to evaluate our methods. We find that the packet loss rate and/or power consumption are significantly reduced with the proposed method.
Joint Connection and Packet level Analysis in W-CDMA Radio Interface
DEFF Research Database (Denmark)
Benetis, Vilius; Popova, Larissa; Iversen, Villy Bæk
2007-01-01
algorithm which defines the feasible state space at packet level. At packet level we take into consideration wireless interference (soft blocking). The traffic is modeled as multi-rate Binomial-Poisson-Pascal (BPP-) traffic at connection level and on-off traffic at packet level. We obtain individual...
Frustrated Brownian Motion of Nonlocal Solitary Waves
International Nuclear Information System (INIS)
Folli, V.; Conti, C.
2010-01-01
We investigate the evolution of solitary waves in a nonlocal medium in the presence of disorder. By using a perturbational approach, we show that an increasing degree of nonlocality may largely hamper the Brownian motion of self-trapped wave packets. The result is valid for any kind of nonlocality and in the presence of nonparaxial effects. Analytical predictions are compared with numerical simulations based on stochastic partial differential equations.
Weyns, Tessa; Verschueren, Karine; Leflot, Geertje; Onghena, Patrick; Wouters, Sofie; Colpin, Hilde
2017-10-01
The present article examined the development of relational aggression in middle childhood and the effects of observed teacher behavior on this development. Relying on social learning theory, we expected that teacher praise would slow down the increase of relational aggression, whereas teacher reprimands would promote the increase of relational aggression. A sample of 570 children (49% boys, M age =7years and 5months, >95% Belgian) was followed from second to fourth grade. Teacher praise and reprimands were observed at the beginning of second grade. Child relational aggression was assessed using teacher and peer reports, collected at five points in time: at the beginning and end of the second grade, at the beginning and end of the third grade, and at the end of the fourth grade. Multilevel modeling showed that relational aggression generally increased from second to fourth grade. Moreover, when teachers displayed more praise, students' relational aggression increased at a slower rate; when teachers displayed more reprimands, students' relational aggression increased at a faster rate. Overall, the results stress the importance of supporting teachers to reduce reprimands and increase praise when interacting with children. Copyright © 2017 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Medhin, Ashenafi Kiros; Kamchevska, Valerija; Galili, Michael
2014-01-01
We experimentally perform 1×4 optical packet switching of variable length 640 Gbit/s OTDM data packets using in-band notch-filter labeling with only 2.7-dB penalty. Up to 8 notches are employed to demonstrate scalability of the labeling scheme to 1×256 switching operation.......We experimentally perform 1×4 optical packet switching of variable length 640 Gbit/s OTDM data packets using in-band notch-filter labeling with only 2.7-dB penalty. Up to 8 notches are employed to demonstrate scalability of the labeling scheme to 1×256 switching operation....
Krahé, Barbara; Busching, Robert
2014-01-01
In a longitudinal study with N = 1,854 adolescents from Germany, we investigated patterns of change and gender differences in physical and relational aggression in relation to normative beliefs about these two forms of aggression. Participants, whose mean age was 13 years at T1, completed self-report measures of physically and relationally aggressive behavior and indicated their normative approval of both forms of aggression at four data waves separated by 12-month intervals. Boys scored higher than did girls on both forms of aggression, but the gender difference was more pronounced for physical aggression. Physical aggression decreased and relational aggression increased over the four data waves in both gender groups. The normative acceptance of both forms of aggression decreased over time, with a greater decrease for the approval of physical aggression. In both gender groups, normative approval of relational aggression prospectively predicted relational aggression across all data waves, and the normative approval of physical aggression predicted physically aggressive behavior at the second and third data waves. A reciprocal reinforcement of aggressive norms and behavior was found for both forms of aggression. The findings are discussed as supporting a social information processing perspective on developmental patterns of change in physical and relational aggression in adolescence.
Directory of Open Access Journals (Sweden)
Barbara eKrahé
2014-10-01
Full Text Available A longitudinal study with N = 1,854 adolescents from Germany investigated patterns of change and gender differences in physical and relational aggression in relation to normative beliefs about aggression. Participants, whose mean age was 13 years at T1, completed self-report measures of physically and relationally aggressive behavior and indicated their normative approval about both forms of aggression at four data waves separated by 12-month intervals. Boys scored higher than did girls on both forms of aggression, but the gender difference was more pronounced for physical aggression. Physical aggression decreased and relational aggression increased over the four data waves in both gender groups. The normative acceptance of both forms of aggression decreased over time, with a greater decrease for the approval of physical aggression. In both gender groups, normative approval of relational aggression prospectively predicted relational aggression across all data waves, and the normative approval of physical aggression predicted physically aggressive behavior at the second and third data waves. A reciprocal reinforcement of aggressive norms and behavior was found for both forms of aggression. The findings are discussed as supporting a social information processing perspective on developmental patterns of change in physical and relational aggression in adolescence.
Transmission Delay Modeling of Packet Communication over Digital Subscriber Line
Directory of Open Access Journals (Sweden)
Jiri Vodrazka
2013-01-01
Full Text Available Certain multimedia and voice services, such as VoIP, IPTV, etc., are significantly delay sensitive and their performance is influenced by the overall transmission delay and its variance. One of the most common solutions used in access networks are xDSL lines, especially ADSL2+ or VDSL2. Although these subscriber lines also use packet communication, there are several differences and mechanisms, which influence their resulting delay. Their delay characteristics are also dependent on the individual settings of each xDSL provider, therefore we decided to investigate this area for typical commercially available lines in Czech Republic. Based on the measured values and experiments with real ADSL2+ lines we also developed a potential modeling method, which is presented in this article as well. The parameters for packet jitter based on the generalized Pareto distribution were modeled.
Very low bit rate voice for packetized mobile applications
International Nuclear Information System (INIS)
Knittle, C.D.; Malone, K.T.
1991-01-01
This paper reports that transmitting digital voice via packetized mobile communications systems that employ relatively short packet lengths and narrow bandwidths often necessitates very low bit rate coding of the voice data. Sandia National Laboratories is currently developing an efficient voice coding system operating at 800 bits per second (bps). The coding scheme is a modified version of the 2400 bps NSA LPC-10e standard. The most significant modification to the LPC-10e scheme is the vector quantization of the line spectrum frequencies associated with the synthesis filters. An outline of a hardware implementation for the 800 bps coder is presented. The speech quality of the coder is generally good, although speaker recognition is not possible. Further research is being conducted to reduce the memory requirements and complexity of the vector quantizer, and to increase the quality of the reconstructed speech. This work may be of use dealing with nuclear materials
Service Time Analysis for Secondary Packet Transmission with Adaptive Modulation
Wang, Wen-Jing; Usman, Muneer; Yang, Hong-Chuan; Alouini, Mohamed-Slim
2017-01-01
Cognitive radio communications can opportunistically access underutilized spectrum for emerging wireless applications. With interweave cognitive implementation, secondary user transmits only if primary user does not occupy the channel and waits for transmission otherwise. Therefore, secondary packet transmission involves both transmission time and waiting time. The resulting extended delivery time (EDT) is critical to the throughput analysis of secondary system. In this paper, we study the EDT of secondary packet transmission with adaptive modulation under interweave implementation to facilitate the delay and throughput analysis of such cognitive radio system. In particular, we propose an analytical framework to derive the probability density functions of EDT considering random-length transmission and waiting slots. We also present selected numerical results to illustrate the mathematical formulations and to verify our analytical approach.
Traffic analysis and signal processing in optical packet switched networks
DEFF Research Database (Denmark)
Fjelde, Tina
2002-01-01
/s optical packet switched network exploiting the best of optics and electronics, is used as a thread throughout the thesis. An overview of the DAVID network architecture is given, focussing on the MAN and WAN architecture as well as the MPLS-based network hierarchy. Subsequently, the traffic performance...... of the DAVID core optical packet router, which exploits wavelength conversion and fibre delay-line buffers for contention resolution, is analysed using a numerical model developed for that purpose. The robustness of the shared recirculating loop buffer with respect to´bursty traffic is demonstrated...... the injection of an additional clock signal into the IWC is presented. Results show very good transmission capabilities combined with a high-speed response. It is argued that signal regeneration is an inherent attribute of the IWC employed as a wavelength converter due to the sinusoidal transfer function...
Service Time Analysis for Secondary Packet Transmission with Adaptive Modulation
Wang, Wen-Jing
2017-05-12
Cognitive radio communications can opportunistically access underutilized spectrum for emerging wireless applications. With interweave cognitive implementation, secondary user transmits only if primary user does not occupy the channel and waits for transmission otherwise. Therefore, secondary packet transmission involves both transmission time and waiting time. The resulting extended delivery time (EDT) is critical to the throughput analysis of secondary system. In this paper, we study the EDT of secondary packet transmission with adaptive modulation under interweave implementation to facilitate the delay and throughput analysis of such cognitive radio system. In particular, we propose an analytical framework to derive the probability density functions of EDT considering random-length transmission and waiting slots. We also present selected numerical results to illustrate the mathematical formulations and to verify our analytical approach.
Binary Systematic Network Coding for Progressive Packet Decoding
Jones, Andrew L.; Chatzigeorgiou, Ioannis; Tassi, Andrea
2015-01-01
We consider binary systematic network codes and investigate their capability of decoding a source message either in full or in part. We carry out a probability analysis, derive closed-form expressions for the decoding probability and show that systematic network coding outperforms conventional net- work coding. We also develop an algorithm based on Gaussian elimination that allows progressive decoding of source packets. Simulation results show that the proposed decoding algorithm can achieve ...
Uplink Packet-Data Scheduling in DS-CDMA Systems
Choi, Young Woo; Kim, Seong-Lyun
In this letter, we consider the uplink packet scheduling for non-real-time data users in a DS-CDMA system. As an effort to jointly optimize throughput and fairness, we formulate a time-span minimization problem incorporating the time-multiplexing of different simultaneous transmission schemes. Based on simple rules, we propose efficient scheduling algorithms and compare them with the optimal solution obtained by linear programming.
IP- -: A Reduced Internet Protocol for Optical Packet Networking
Ohta, Masataka; Fujikawa, Kenji
IP- - is proposed as an Internet Protocol suitable for optical packet networking. As optical routers require much faster control than electric ones and lack of optical buffers other than those by fiber delay lines requires fixed time control, Internet Protocols must be at least as simple as IPv4 and much simpler than IPv6. IP- - also addresses issues of IP address space exhaustion and IP routing table explosion.
Information Processing Techniques Program. Volume I. Packet Speech Systems Technology
1980-09-30
Itindsign has litt-rn vt-tntit-r aliti sill dI- ditiibuted trrni cparat- tintr aisa ithnnin ITtc-i A. Packet Vttice Terminal As Iprt- iouisik rtrtteti tin...September 1980. FO1M 1473 EDITION OF I NOV 65 IS OBSOLETEDD I JAN 73 UNCLA.SSI F[IF ) SECURITY CLASSIFICATION OF THIS PAGE (Ibmn Data fntew-d)
Effect of latency and packet loss on achievable bandwidth
CERN. Geneva
2015-01-01
Following an incident with a slow database replication between CERN's data centers, we discovered that even a very low rate packet loss in the network can induce significant penalties to long distance single stream TCP transfers. We explore the behaviour of multiple congestion control algorithms in a controlled loss environment in order to understand what is the achievable throughput of TCP data transfers between the Meyrin and Wigner data centres.
On Maximizing the Throughput of Packet Transmission under Energy Constraints.
Wu, Weiwei; Dai, Guangli; Li, Yan; Shan, Feng
2018-06-23
More and more Internet of Things (IoT) wireless devices have been providing ubiquitous services over the recent years. Since most of these devices are powered by batteries, a fundamental trade-off to be addressed is the depleted energy and the achieved data throughput in wireless data transmission. By exploiting the rate-adaptive capacities of wireless devices, most existing works on energy-efficient data transmission try to design rate-adaptive transmission policies to maximize the amount of transmitted data bits under the energy constraints of devices. Such solutions, however, cannot apply to scenarios where data packets have respective deadlines and only integrally transmitted data packets contribute. Thus, this paper introduces a notion of weighted throughput, which measures how much total value of data packets are successfully and integrally transmitted before their own deadlines. By designing efficient rate-adaptive transmission policies, this paper aims to make the best use of the energy and maximize the weighted throughput. What is more challenging but with practical significance, we consider the fading effect of wireless channels in both offline and online scenarios. In the offline scenario, we develop an optimal algorithm that computes the optimal solution in pseudo-polynomial time, which is the best possible solution as the problem undertaken is NP-hard. In the online scenario, we propose an efficient heuristic algorithm based on optimal properties derived for the optimal offline solution. Simulation results validate the efficiency of the proposed algorithm.
The performance analysis of linux networking - packet receiving
Energy Technology Data Exchange (ETDEWEB)
Wu, Wenji; Crawford, Matt; Bowden, Mark; /Fermilab
2006-11-01
The computing models for High-Energy Physics experiments are becoming ever more globally distributed and grid-based, both for technical reasons (e.g., to place computational and data resources near each other and the demand) and for strategic reasons (e.g., to leverage equipment investments). To support such computing models, the network and end systems, computing and storage, face unprecedented challenges. One of the biggest challenges is to transfer scientific data sets--now in the multi-petabyte (10{sup 15} bytes) range and expected to grow to exabytes within a decade--reliably and efficiently among facilities and computation centers scattered around the world. Both the network and end systems should be able to provide the capabilities to support high bandwidth, sustained, end-to-end data transmission. Recent trends in technology are showing that although the raw transmission speeds used in networks are increasing rapidly, the rate of advancement of microprocessor technology has slowed down. Therefore, network protocol-processing overheads have risen sharply in comparison with the time spent in packet transmission, resulting in degraded throughput for networked applications. More and more, it is the network end system, instead of the network, that is responsible for degraded performance of network applications. In this paper, the Linux system's packet receive process is studied from NIC to application. We develop a mathematical model to characterize the Linux packet receiving process. Key factors that affect Linux systems network performance are analyzed.
Modelling Packet Departure Times using a Known PDF
Directory of Open Access Journals (Sweden)
Stanislav Klucik
2014-01-01
Full Text Available This paper deals with IPTV traffic source modelling and describes a packet generator based on a known probability density function which is measured and formed from a histogram. Histogram based probability density functions destroy an amount of information, because classes used to form the histogram often cover significantly more events than one. In this work, we propose an algorithm to generate far more output states of random variable X than the input probability distribution function is made from. In this generator is assumed that all IPTV packets of the same video stream are the same length. Therefore, only packet times are generated. These times are generated using the measured normalized histogram that is converted to a cumulative distribution function which acts as a finite number of states that can be addressed. To address these states we use an ON/OFF model that is driven by an uniform random number generator in (0, 1. When a state is chosen then the resulting value is equal to a histogram class. To raise the number of possible output states of the random variable X, we propose to use an uniform random number generator that generates numbers within the range of the chosen histogram class. This second uniform random number generator assures that the number of output states is far more larger than the number of histogram classes.
Efficient incremental relaying for packet transmission over fading channels
Fareed, Muhammad Mehboob
2014-07-01
In this paper, we propose a novel relaying scheme for packet transmission over fading channels, which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from the destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying (EIR) scheme with both amplify and forward and decode and forward relaying. We compare the performance of the EIR scheme with the threshold-based incremental relaying (TIR) scheme. It is shown that the efficiency of the TIR scheme is better for lower values of the threshold. However, the efficiency of the TIR scheme for higher values of threshold is outperformed by the EIR. In addition, three new threshold-based adaptive EIR are devised to further improve the efficiency of the EIR scheme. We calculate the packet error rate and the efficiency of these new schemes to provide the analytical insight. © 2014 IEEE.
Hardware Accelerators Targeting a Novel Group Based Packet Classification Algorithm
Directory of Open Access Journals (Sweden)
O. Ahmed
2013-01-01
Full Text Available Packet classification is a ubiquitous and key building block for many critical network devices. However, it remains as one of the main bottlenecks faced when designing fast network devices. In this paper, we propose a novel Group Based Search packet classification Algorithm (GBSA that is scalable, fast, and efficient. GBSA consumes an average of 0.4 megabytes of memory for a 10 k rule set. The worst-case classification time per packet is 2 microseconds, and the preprocessing speed is 3 M rules/second based on an Xeon processor operating at 3.4 GHz. When compared with other state-of-the-art classification techniques, the results showed that GBSA outperforms the competition with respect to speed, memory usage, and processing time. Moreover, GBSA is amenable to implementation in hardware. Three different hardware implementations are also presented in this paper including an Application Specific Instruction Set Processor (ASIP implementation and two pure Register-Transfer Level (RTL implementations based on Impulse-C and Handel-C flows, respectively. Speedups achieved with these hardware accelerators ranged from 9x to 18x compared with a pure software implementation running on an Xeon processor.
Multifocal ERG wavelet packet decomposition applied to glaucoma diagnosis
Directory of Open Access Journals (Sweden)
Rodríguez-Ascariz José M
2011-05-01
Full Text Available Abstract Background Glaucoma is the second-leading cause of blindness worldwide and early diagnosis is essential to its treatment. Current clinical methods based on multifocal electroretinography (mfERG essentially involve measurement of amplitudes and latencies and assume standard signal morphology. This paper presents a new method based on wavelet packet analysis of global-flash multifocal electroretinogram signals. Methods This study comprised twenty-five patients diagnosed with OAG and twenty-five control subjects. Their mfERG recordings data were used to develop the algorithm method based on wavelet packet analysis. By reconstructing the third wavelet packet contained in the fourth decomposition level (ADAA4 of the mfERG recording, it is possible to obtain a signal from which to extract a marker in the 60-80 ms time interval. Results The marker found comprises oscillatory potentials with a negative-slope basal line in the case of glaucomatous recordings and a positive-slope basal line in the case of normal signals. Application of the optimal threshold calculated in the validation cases showed that the technique proposed achieved a sensitivity of 0.81 and validation specificity of 0.73. Conclusions This new method based on mfERG analysis may be reliable enough to detect functional deficits that are not apparent using current automated perimetry tests. As new stimulation and analysis protocols develop, mfERG has the potential to become a useful tool in early detection of glaucoma-related functional deficits.
Directory of Open Access Journals (Sweden)
Leandro Jose Guerra
1998-06-01
Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.
Soliton emission stimulated by sound wave or external field
International Nuclear Information System (INIS)
Malomed, B.A.
1987-01-01
Langmuir soliton interaction with ion-acoustic wave results in soliton radiative decay at the expence of emission by the soliton of linear langmuir waves. Intensity of this radiation in the ''subsonic'' regime as well as the rate of energy transfer from acoustic waves to langmuir ones and soliton decay rate are calculated. Three cases are considered: monochromatic acoustic wave, nonmonochromatic wave packet with a wide spectrum, random acoustic field, for which results appear to be qualitatively different. A related problem, concerning the radiation generation by soliton under external electromagnetic wave effect is also considered. Dissipation effect on radiation is investigated
Self-accelerating parabolic cylinder waves in 1-D
Energy Technology Data Exchange (ETDEWEB)
Yuce, C., E-mail: cyuce@anadolu.edu.tr
2016-11-25
Highlights: • We find a new class of self-accelerating waves. • We show that parabolic cylinder waves self-accelerates in a parabolic potential. • We discuss that truncated parabolic cylinder waves propagates large distance without almost being non-diffracted in free space. - Abstract: We introduce a new self-accelerating wave packet solution of the Schrodinger equation in one dimension. We obtain an exact analytical parabolic cylinder wave for the inverted harmonic potential. We show that truncated parabolic cylinder waves exhibits their accelerating feature.
Langmuir field structures favored in wave collapse
International Nuclear Information System (INIS)
Robinson, P.A.; Wouters, M.J.; Broderick, N.G.
1996-01-01
Study of Langmuir collapse thresholds shows that they have little polarization dependence and that moving packets have the lowest thresholds in the undamped case. However, incorporation of damping into the density response inhibits collapse of packets moving at more than a small fraction of the sound speed. Investigation of energy transfer to packets localized in density wells emdash the nucleation process emdash shows that at most a few trapped states can exist and that energy transfer is most effective when there is a single barely-trapped state. Coupled with an argument that closely packed wave packets have lower collapse thresholds, this argument yields an estimate of the number density of localized nucleating states in a turbulent plasma. It also leads to a simple and direct semiquantitative estimate of the collapse threshold. All these results are in accord with previous numerical simulations incorporating ion-sound damping, which show a preponderance of slow-moving or stationary packets with little or no intrinsic polarization dependence of thresholds. Likewise, the number densities obtained are in good agreement with simulation values, and the simple estimate of the threshold is semiquantitatively correct. The extent of the agreement supports the nucleation scenario with close-packed nucleation sites in the turbulent state. copyright 1996 American Institute of Physics
Sampled-Data Consensus of Linear Multi-agent Systems With Packet Losses.
Zhang, Wenbing; Tang, Yang; Huang, Tingwen; Kurths, Jurgen
In this paper, the consensus problem is studied for a class of multi-agent systems with sampled data and packet losses, where random and deterministic packet losses are considered, respectively. For random packet losses, a Bernoulli-distributed white sequence is used to describe packet dropouts among agents in a stochastic way. For deterministic packet losses, a switched system with stable and unstable subsystems is employed to model packet dropouts in a deterministic way. The purpose of this paper is to derive consensus criteria, such that linear multi-agent systems with sampled-data and packet losses can reach consensus. By means of the Lyapunov function approach and the decomposition method, the design problem of a distributed controller is solved in terms of convex optimization. The interplay among the allowable bound of the sampling interval, the probability of random packet losses, and the rate of deterministic packet losses are explicitly derived to characterize consensus conditions. The obtained criteria are closely related to the maximum eigenvalue of the Laplacian matrix versus the second minimum eigenvalue of the Laplacian matrix, which reveals the intrinsic effect of communication topologies on consensus performance. Finally, simulations are given to show the effectiveness of the proposed results.In this paper, the consensus problem is studied for a class of multi-agent systems with sampled data and packet losses, where random and deterministic packet losses are considered, respectively. For random packet losses, a Bernoulli-distributed white sequence is used to describe packet dropouts among agents in a stochastic way. For deterministic packet losses, a switched system with stable and unstable subsystems is employed to model packet dropouts in a deterministic way. The purpose of this paper is to derive consensus criteria, such that linear multi-agent systems with sampled-data and packet losses can reach consensus. By means of the Lyapunov function
Packet loss replacement in voip using a recursive low-order autoregressive modelbased speech
International Nuclear Information System (INIS)
Miralavi, Seyed Reza; Ghorshi, Seyed; Mortazavi, Mohammad; Choupan, Jeiran
2011-01-01
In real-time packet-based communication systems one major problem is misrouted or delayed packets which results in degraded perceived voice quality. When some speech packets are not available on time, the packet is known as lost packet in real-time communication systems. The easiest task of a network terminal receiver is to replace silence for the duration of lost speech segments. In a high quality communication system in order to avoid quality reduction due to packet loss a suitable method and/or algorithm is needed to replace the missing segments of speech. In this paper, we introduce a recursive low order autoregressive (AR) model for replacement of lost speech segment. The evaluation results show that this method has a lower mean square error (MSE) and low complexity compared to the other efficient methods like high-order AR model without any substantial degradation in perceived voice quality.
Physical Watermarking for Securing Cyber-Physical Systems via Packet Drop Injections
Energy Technology Data Exchange (ETDEWEB)
Ozel, Omur [Carnegie Mellon Univ., Pittsburgh, PA (United States); Weekrakkody, Sean [Carnegie Mellon Univ., Pittsburgh, PA (United States); Sinopoli, Bruno [Carnegie Mellon Univ., Pittsburgh, PA (United States)
2017-10-23
Physical watermarking is a well known solution for detecting integrity attacks on Cyber-Physical Systems (CPSs) such as the smart grid. Here, a random control input is injected into the system in order to authenticate physical dynamics and sensors which may have been corrupted by adversaries. Packet drops may naturally occur in a CPS due to network imperfections. To our knowledge, previous work has not considered the role of packet drops in detecting integrity attacks. In this paper, we investigate the merit of injecting Bernoulli packet drops into the control inputs sent to actuators as a new physical watermarking scheme. With the classical linear quadratic objective function and an independent and identically distributed packet drop injection sequence, we study the effect of packet drops on meeting security and control objectives. Our results indicate that the packet drops could act as a potential physical watermark for attack detection in CPSs.
Relation between the behaviors of P-wave and QT dispersions in elderly patients with heart failure
Directory of Open Access Journals (Sweden)
Szlejf Cláudia
2002-01-01
Full Text Available OBJECTIVE: To assess the relation between P-wave and QT dispersions in elderly patients with heart failure. METHODS: Forty-seven elderly patients (75.6±6 years with stable heart failure in NYHA functional classes II or III and with ejection fractions of 37±6% underwent body surface mapping to analyze P-wave and QT dispersions. The degree of correlation between P-wave and QT dispersions was assessed, and P-wave dispersion values in patients with QT dispersion greater than and smaller than 100 ms were compared. RESULTS: The mean values of P-wave and QT dispersions were 54±14 ms and 68±27 ms, respectively. The correlation between the 2 variables was R=0.41 (p=0.04. In patients with QT dispersion values > 100 ms, P-wave dispersion was significantly greater than in those with QT dispersion values < 100 ms (58±16 vs 53±12 ms, p=0.04 . CONCLUSION: Our results suggest that, in elderly patients with heart failure, a correlation between the values of P-wave and QT dispersions exists. These findings may have etiopathogenic, pathophysiologic, prognostic, and therapeutic implications, which should be investigated in other studies.
DEFF Research Database (Denmark)
Giacobello, Daniele; Murthi, Manohar N.; Christensen, Mads Græsbøll
2010-01-01
In this paper, we describe a new approach to cope with packet loss in speech coders. The idea is to split the information present in each speech packet into two components, one to independently decode the given speech frame and one to enhance it by exploiting interframe dependencies. The scheme...... is based on sparse linear prediction and a redeﬁnition of the analysis-by-synthesis process. We present Mean Opinion Scores for the presented coder with different degrees of packet loss and show that it performs similarly to frame dependent coders for low packet loss probability and similarly to frame...
Effects of wireless packet loss in industrial process control systems.
Liu, Yongkang; Candell, Richard; Moayeri, Nader
2017-05-01
Timely and reliable sensing and actuation control are essential in networked control. This depends on not only the precision/quality of the sensors and actuators used but also on how well the communications links between the field instruments and the controller have been designed. Wireless networking offers simple deployment, reconfigurability, scalability, and reduced operational expenditure, and is easier to upgrade than wired solutions. However, the adoption of wireless networking has been slow in industrial process control due to the stochastic and less than 100% reliable nature of wireless communications and lack of a model to evaluate the effects of such communications imperfections on the overall control performance. In this paper, we study how control performance is affected by wireless link quality, which in turn is adversely affected by severe propagation loss in harsh industrial environments, co-channel interference, and unintended interference from other devices. We select the Tennessee Eastman Challenge Model (TE) for our study. A decentralized process control system, first proposed by N. Ricker, is adopted that employs 41 sensors and 12 actuators to manage the production process in the TE plant. We consider the scenario where wireless links are used to periodically transmit essential sensor measurement data, such as pressure, temperature and chemical composition to the controller as well as control commands to manipulate the actuators according to predetermined setpoints. We consider two models for packet loss in the wireless links, namely, an independent and identically distributed (IID) packet loss model and the two-state Gilbert-Elliot (GE) channel model. While the former is a random loss model, the latter can model bursty losses. With each channel model, the performance of the simulated decentralized controller using wireless links is compared with the one using wired links providing instant and 100% reliable communications. The sensitivity of the
A Time-Frequency Auditory Model Using Wavelet Packets
DEFF Research Database (Denmark)
Agerkvist, Finn
1996-01-01
A time-frequency auditory model is presented. The model uses the wavelet packet analysis as the preprocessor. The auditory filters are modelled by the rounded exponential filters, and the excitation is smoothed by a window function. By comparing time-frequency excitation patterns it is shown...... that the change in the time-frequency excitation pattern introduced when a test tone at masked threshold is added to the masker is approximately equal to 7 dB for all types of maskers. The classic detection ratio therefore overrates the detection efficiency of the auditory system....
Memory of AMR coded speech distorted by packet loss
Nykänen, Arne; Lindegren, David; Wruck, Louisa; Ljung, Robert; Odelius, Johan; Möller, Sebastian
2014-01-01
Previous studies have shown that free recall of spoken word lists is impaired if the speech is presented in background noise, even if the signal-to-noise ratio is kept at a level allowing full word identification. The objective of this study was to examine recall rates for word lists presented in noise and word lists coded by an AMR (Adaptive Multi Rate) telephone codec distorted by packet loss. Twenty subjects performed a word recall test. Word lists consisting of ten words were played to th...
Integrated Fractional Load and Packet Scheduling for OFDMA Systems
DEFF Research Database (Denmark)
Monghal, Guillaume Damien; Kumar, S.; Pedersen, Klaus I.
2009-01-01
This paper study the performance of an orthogonal frequency division multiple access (OFDMA) system under fractional load based in long term evolution (LTE) downlink. Fractional load is defined by a situation where only a fraction of the bandwidth is used for transmission due to lack of traffic....... This type of situation should result in a global increase of signal to interference and noise ratio (SINR) conditions in the network. We propose different methods integrating the transmission pattern selection to the packet scheduling functionality of the enode-B depending only on the channel quality...
Directory of Open Access Journals (Sweden)
Gerald Kastberger
Full Text Available Shimmering is a collective defence behaviour in Giant honeybees (Apis dorsata whereby individual bees flip their abdomen upwards, producing Mexican wave-like patterns on the nest surface. Bucket bridging has been used to explain the spread of information in a chain of members including three testable concepts: first, linearity assumes that individual "agent bees" that participate in the wave will be affected preferentially from the side of wave origin. The directed-trigger hypothesis addresses the coincidence of the individual property of trigger direction with the collective property of wave direction. Second, continuity describes the transfer of information without being stopped, delayed or re-routed. The active-neighbours hypothesis assumes coincidence between the direction of the majority of shimmering-active neighbours and the trigger direction of the agents. Third, the graduality hypothesis refers to the interaction between an agent and her active neighbours, assuming a proportional relationship in the strength of abdomen flipping of the agent and her previously active neighbours. Shimmering waves provoked by dummy wasps were recorded with high-resolution video cameras. Individual bees were identified by 3D-image analysis, and their strength of abdominal flipping was assessed by pixel-based luminance changes in sequential frames. For each agent, the directedness of wave propagation was based on wave direction, trigger direction, and the direction of the majority of shimmering-active neighbours. The data supported the bucket bridging hypothesis, but only for a small proportion of agents: linearity was confirmed for 2.5%, continuity for 11.3% and graduality for 0.4% of surface bees (but in 2.6% of those agents with high wave-strength levels. The complimentary part of 90% of surface bees did not conform to bucket bridging. This fuzziness is discussed in terms of self-organisation and evolutionary adaptedness in Giant honeybee colonies to
Kastberger, Gerald; Weihmann, Frank; Hoetzl, Thomas; Weiss, Sara E; Maurer, Michael; Kranner, Ilse
2012-01-01
Shimmering is a collective defence behaviour in Giant honeybees (Apis dorsata) whereby individual bees flip their abdomen upwards, producing Mexican wave-like patterns on the nest surface. Bucket bridging has been used to explain the spread of information in a chain of members including three testable concepts: first, linearity assumes that individual "agent bees" that participate in the wave will be affected preferentially from the side of wave origin. The directed-trigger hypothesis addresses the coincidence of the individual property of trigger direction with the collective property of wave direction. Second, continuity describes the transfer of information without being stopped, delayed or re-routed. The active-neighbours hypothesis assumes coincidence between the direction of the majority of shimmering-active neighbours and the trigger direction of the agents. Third, the graduality hypothesis refers to the interaction between an agent and her active neighbours, assuming a proportional relationship in the strength of abdomen flipping of the agent and her previously active neighbours. Shimmering waves provoked by dummy wasps were recorded with high-resolution video cameras. Individual bees were identified by 3D-image analysis, and their strength of abdominal flipping was assessed by pixel-based luminance changes in sequential frames. For each agent, the directedness of wave propagation was based on wave direction, trigger direction, and the direction of the majority of shimmering-active neighbours. The data supported the bucket bridging hypothesis, but only for a small proportion of agents: linearity was confirmed for 2.5%, continuity for 11.3% and graduality for 0.4% of surface bees (but in 2.6% of those agents with high wave-strength levels). The complimentary part of 90% of surface bees did not conform to bucket bridging. This fuzziness is discussed in terms of self-organisation and evolutionary adaptedness in Giant honeybee colonies to respond to rapidly
International Nuclear Information System (INIS)
Torosyan, O.S.; Mkrtchyan, A.R.
2003-01-01
The amplification of acoustic waves due to the transfer of thermal energy from electrons to the neutral component of a glow discharge plasma is studied theoretically. It is shown that, in order for acoustic instability (sound amplification) to occur, the amount of energy transferred should exceed the threshold energy, which depends on the plasma parameters and the acoustic wave frequency. The energy balance equation for an electron gas in the positive column of a glow discharge is analyzed for conditions typical of experiments in which acoustic wave amplification has been observed. Based on this analysis, one can affirm that, first, the energy transferred to neutral gas in elastic electron-atom collisions is substantially lower than the threshold energy for acoustic wave amplification and, second, that the energy transferred from electrons to neutral gas in inelastic collisions is much higher than that transferred in elastic collisions and thus may exceed the threshold energy. It is also shown that, for amplification to occur, there should exist some heat dissipation mechanism more efficient than gas heat conduction. It is suggested that this may be convective radial mixing within a positive column due to acoustic streaming in the field of an acoustic wave. The features of the phase velocity of sound waves in the presence of acoustic instability are investigated
Parametric packet-based audiovisual quality model for IPTV services
Garcia, Marie-Neige
2014-01-01
This volume presents a parametric packet-based audiovisual quality model for Internet Protocol TeleVision (IPTV) services. The model is composed of three quality modules for the respective audio, video and audiovisual components. The audio and video quality modules take as input a parametric description of the audiovisual processing path, and deliver an estimate of the audio and video quality. These outputs are sent to the audiovisual quality module which provides an estimate of the audiovisual quality. Estimates of perceived quality are typically used both in the network planning phase and as part of the quality monitoring. The same audio quality model is used for both these phases, while two variants of the video quality model have been developed for addressing the two application scenarios. The addressed packetization scheme is MPEG2 Transport Stream over Real-time Transport Protocol over Internet Protocol. In the case of quality monitoring, that is the case for which the network is already set-up, the aud...
International Nuclear Information System (INIS)
Khelashvili, A.A.; Nadareishvili, T.P.
2015-01-01
Singular behavior of the Laplace operator in spherical coordinates is investigated. It is shown that in course of transition to the reduced radial wave function in the Schreodinger equation there appears additional term including the Dirac delta function, which was unnoted during the full history of physics and mathematics. The possibility of avoiding this contribution from the reduced radial equation is discussed. It is demonstrated that for this aim the necessary and sufficient condition is the requirement of the fast enough falling of the wave function at the origin. The result does not depend on character of potential - whether it is regular or singular. The various manifestations and consequences of this observation are considered as well. The cornerstone in our approach is the natural requirement that the solution of the radial equation at the same time must obey the full equation. [ru
In- and outbound spreading of a free-particle s-wave
DEFF Research Database (Denmark)
Bialynicki-Birula, i.; Cirone, M. A.; Dahl, Jens Peder
2002-01-01
We show that a free quantum particle in two dimensions with zero angular momentum (s wave) in the form of a ring-shaped wave packet feels an attraction towards the center of the ring, leading first to a contraction followed by an expansion. An experiment to demonstrate this effect is also outlined....
MMS Observations of Harmonic Electromagnetic Cyclotron Waves
Usanova, M.; Ahmadi, N.; Ergun, R.; Trattner, K. J.; Fuselier, S. A.; Torbert, R. B.; Mauk, B.; Le Contel, O.; Giles, B. L.; Russell, C. T.; Burch, J.; Strangeway, R. J.
2017-12-01
Harmonically related electromagnetic ion cyclotron waves with the fundamental frequency near the O+ cyclotron frequency were observed by the four MMS spacecraft on May 20, 2016. The wave activity was detected by the spacecraft on their inbound passage through the Earth's morning magnetosphere during generally quiet geomagnetic conditions but enhanced solar wind dynamic pressure. It was also associated with an enhancement of energetic H+ and O+ ions. The waves are seen in both magnetic and electric fields, formed by over ten higher order harmonics, most pronounced in the electric field. The wave activity lasted for about an hour with some wave packets giving rise to short-lived structures extending from Hz to kHz range. These observations are particularly interesting since they suggest cross-frequency coupling between the lower and higher frequency modes. Further work will focus on examining the nature and role of these waves in the energetic particle dynamics from a theoretical perspective.
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)