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
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.
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
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
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)
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 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...
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.
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
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.
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.
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
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.
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
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.
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...
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.
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.
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
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....
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
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.
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.
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
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.
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
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
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
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.
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
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.
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
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.
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
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
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...
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.
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.)
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
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.))
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.
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
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
of 160 as duration. In the second experiment, we use these pulses to create electron wave packets of duration 180 as in argon and 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. At the zero crossings of the laser field, a significant energy (∼ 20 eV) is transferred from the IR field to the electrons resulting in dramatically enhanced above-threshold-ionization in conditions where the IR field alone does not induce any significant ionization of the medium. Further, by increasing the pulse length of the individual attosecond pulses, using a different thickness of the aluminum filter, a clear effect is seen in the delay-dependence of the photoelectron spectrum. In conclusion, the manipulations of the XUV amplitudes and phases that we have performed are the first step towards the production of arbitrary attosecond waveforms, which will facilitate broadband coherent control in the XUV range. Using these pulses as the injection mechanism of electron wave packets through ionization, we have studied the interaction between the EWPs and a strong IR field. With the pulse parameters used, the ionization is dominated by the APT, and tunable ATI plateaus appear as an effect of the dressing field. The strong delay dependence seen for these ATI spectra, is a direct consequence of the temporal localization of the EWPs to a time range much shorter than the period of the IR field. Because both the energy and duration of the EWPs can be varied independent of the IR laser, they should be very useful for the study and control of strong field processes. Refs. 2 (author)
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.
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
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
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...
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
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)
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.
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.
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.
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.
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-.
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.)
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.
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
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
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.
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. .
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
Test particle modeling of wave-induced energetic electron precipitation
International Nuclear Information System (INIS)
Chang, H.C.; Inan, U.S.
1985-01-01
A test particle computer model of the precipitation of radiation belt electrons is extended to compute the dynamic energy spectrum of transient electron fluxes induced by short-duration VLF wave packets traveling along the geomagnetic field lines. The model is adapted to estimate the count rate and associated spectrum of precipitated electrons that would be observed by satellite-based particle detectors with given geometric factor and orientation with respect to the magnetic field. A constant-frequency wave pulse and a lightning-induced whistler wave packet are used as examples of the stimulating wave signals. The effects of asymmetry of particle mirror heights in the two hemispheres and the atmospheric backscatter of loss cone particles on the computed precipitated fluxes are discussed
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....
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
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
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
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.
‘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.
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
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
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.
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.
Cheng, W.; Luo, X.; Dongen, van M.E.H.
2010-01-01
Complex wave patterns caused by unsteady heat release due to cloud formation in confined compressible flows are discussed. Two detailed numerical studies of condensation-induced waves are carried out. First, the response of a flow of nitrogen in a slender Laval nozzle to a sudden addition of water
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.
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.
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.
On radio frequency wave induced radial transport and wave helicity
International Nuclear Information System (INIS)
Petrzilka, V.
1992-09-01
Expressions for wave induced radial transport are derived allowing simple estimates. The transport is enhanced due to the presence of poloidal magnetostatic field and in the vicinity of the ion cyclotron resonance. The direction of the wave induced transport depends also on the wave polarization. (author) 19 refs
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
On helicon wave induced radial plasma transport
International Nuclear Information System (INIS)
Petrzilka, V.
1993-04-01
Estimates of helicon wave induced radial plasma transport are presented. The wave induced transport grows or decreases in dependence on the sign of the azimuthal wave number; these changes in transport may play an important role in helicon wave plasma sources. (author) 5 figs., 18 refs
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
Gravity induced wave function collapse
Gasbarri, G.; Toroš, M.; Donadi, S.; Bassi, A.
2017-11-01
Starting from an idea of S. L. Adler [in Quantum Nonlocality and Reality: 50 Years of Bell's Theorem, edited by M. Bell and S. Gao (Cambridge University Press, Cambridge, England 2016)], we develop a novel model of gravity induced spontaneous wave function collapse. The collapse is driven by complex stochastic fluctuations of the spacetime metric. After deriving the fundamental equations, we prove the collapse and amplification mechanism, the two most important features of a consistent collapse model. Under reasonable simplifying assumptions, we constrain the strength ξ of the complex metric fluctuations with available experimental data. We show that ξ ≥10-26 in order for the model to guarantee classicality of macro-objects, and at the same time ξ ≤10-20 in order not to contradict experimental evidence. As a comparison, in the recent discovery of gravitational waves in the frequency range 35 to 250 Hz, the (real) metric fluctuations reach a peak of ξ ˜10-21.
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.)
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)
Wave Induced Loads on the LEANCON Wave Energy Converter
DEFF Research Database (Denmark)
Frigaard, Peter; Kofoed, Jens Peter; Beserra, Eliab Ricarte
This report is a product of the co-operation agreement between Aalborg University and LEANCON (by Kurt Due Rasmussen) on the evaluation and development of the LEANCON wave energy converter (WEC). The work reported here has focused on evaluation of the wave induced loads on the device, based...... in the laboratory, all under the supervision of the personnel of the Wave Energy Research Group at Department of Civil Engineering, Aalborg University....
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.
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.
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)
Ohtsuki, Yukiyoshi
2004-01-01
Possibility of fs-laser-pulse isotope separation is numerically investigated using optimal control theory. Optimal pulses that separate the 1:1 mixture of 79 Br 2 and 28 1 Br 2 are calculated. Quantum interferences induced by the optimally designed fs pulse efficiently enhance the isotope shifts through multiple electronic transitions, which results in a high enrichment factor. When utilizing vibrational multi-photon transitions (a virtual model), an optimal pulse can transfer the two isotopes to specified different vibrational states with almost 100% probability. In the presence of colored noises, the optimal pulse achieves the control with minimum loss of product yields within the bath correlation time. (author)
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.
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)
Modeling of Mud-Wave Interaction: Mud-Induced Wave Transport & Wave-Induced Mud Transport
National Research Council Canada - National Science Library
Winterwerp, Johan C
2007-01-01
.... Also a new rheological model has been proposed to describe liquefaction of soft mud by waves, and the subsequent strength recovery after the passage of the waves. A scheme is presented on how to implement these formulations in Delft3D.
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.
Alfven wave resonances and flow induced by nonlinear Alfven waves in a stratified atmosphere
International Nuclear Information System (INIS)
Stark, B. A.; Musielak, Z. E.; Suess, S. T.
1996-01-01
A nonlinear, time-dependent, ideal MHD code has been developed and used to compute the flow induced by nonlinear Alfven waves propagating in an isothermal, stratified, plane-parallel atmosphere. The code is based on characteristic equations solved in a Lagrangian frame. Results show that resonance behavior of Alfven waves exists in the presence of a continuous density gradient and that the waves with periods corresponding to resonant peaks exert considerably more force on the medium than off-resonance periods. If only off-peak periods are considered, the relationship between the wave period and induced longitudinal velocity shows that short period WKB waves push more on the background medium than longer period, non-WKB, waves. The results also show the development of the longitudinal waves induced by finite amplitude Alfven waves. Wave energy transferred to the longitudinal mode may provide a source of localized heating
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...
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.
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)
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
Wave Induced Saline Intrusion in Sea Outfalls
DEFF Research Database (Denmark)
Larsen, Torben; Burrows, Richard
1989-01-01
Experimental and numerical studies have shown that the influence of wave increases the tendency of saline intrusion in multi-riser sea outfalls. The flow field in the diffusor under such unsteady and inhomogeneous circumstances is in general very complex, but when sufficient wave energy is dissip...
Wave induced supersonic rotation in mirrors
Fetterman, Abraham
2010-11-01
Wave-particle interactions in ExB supersonically rotating plasmas feature an unusual effect: particles are diffused by waves in both potential energy and kinetic energy [1]. This wave-particle interaction generalizes the alpha channeling effect, in which radio frequency waves are used to remove alpha particles collisionlessly at low energy. In rotating plasmas, the alpha particles may be removed at low energy through the loss cone, and the energy lost may be transferred to the radial electric field. This eliminates the need for electrodes in the mirror throat, which have presented serious technical issues in past rotating plasma devices. A particularly simple way to achieve this effect is to use a high azimuthal mode number perturbation on the magnetic field [2]. In the rotating frame, this perturbation is seen as a wave near the alpha particle cyclotron harmonic, and can break the azimuthal symmetry and magnetic moment conservation without changing the particle's total energy. The particle may exit if it reduces its kinetic energy and becomes more trapped if it gains kinetic energy, leading to a steady state current that maintains the field. Simulations of single particles in rotating mirrors show that a stationary wave can extract enough energy from alpha particles for a reactor to be self-sustaining. Rotation can also be sustained by waves in plasmas without a kinetic energy source. This type of wave has been considered for plasma centrifuges used for isotope separation [3]. [4pt] [1] A. J. Fetterman and N. J. Fisch, Phys Rev Lett 101, 205003 (2008). [0pt] [2] A. J. Fetterman and N. J. Fisch, Phys. Plasmas 17, 042112 (2010). [0pt] [3] A. J. Fetterman and N. J. Fisch, Plasma Sources Sci. Tech. 18, 045003 (2009).
Time variations of hf induced plasma waves
International Nuclear Information System (INIS)
Showen, R.L.
1976-01-01
Intense plasma waves are generated by an HF pump wave in an ionospheric heating experiment at the Arecibo Observatory. These plasma waves can be observed as enhancements to the ion and plasma lines of the incoherent backscatter echo. The enhancements can be three or four orders of magnitude more intense than the unenhanced lines, and tend to fluctuate wildly. Both the purely growing and the decay mode parametric instabilities are present. When the pump wave is turned on abruptly the enhancements develop in time in a repeatable manner. A rather remarkable feature on time scales of seconds is an overshoot in instability power. These overshoots occur frequently but not universally and last for 1 to 6 seconds. They can have a magnitude from ten to hundreds of times the average instability level. Field aligned irregularities may be the cause of the overshoots. The overshoots appear definitely related to an unusually rapid rise in measured electron temperature that cannot be understood in terms of ohmic energy deposition. On time scales of milliseconds there is a ''mini-overshoot'' before the growth of the instability to a large value. The spectral details also change in a striking manner. The instabilities can first be detected 2 to 4 msec after the pump wave turn-on. The decay mode is present as well as a broad featureless ''noise bump'', which partially sharpens into a line as time progresses. These changes of the spectra in time seem to run counter to the currently accepted theories of plasma wave saturation
Wave Induced Stresses Measured at the Wave Dragon Nissum Bredning Prototype
DEFF Research Database (Denmark)
Corona, L.; Kofoed, Jens Peter
2006-01-01
The paper describes the wave induced loading on the overtopping based wave energy converter Wave Dragon. Focus is put on the junction between the main body and the reflector, also called the "shoulder part", where large cross sectional forces and bending moments acts. There are two main objectives...... for this paper, first to verify the FEM results obtained by Niras, Danish society in charge of the finite element modelling and structural design, and then to make a first experimental fatigue analysis of a particular part of the Wave Dragon. This last part shall be considered as an exercise for the further work...
Wave-induced Ship Hull Vibrations in Stochastic Seaways
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Dogliani, M.
1996-01-01
A theoretical Study is undertaken on the determination of wave-induced loads in flexible ship hulls. The calculations are performed within the framework of a non-linear, quadratic strip theory formulated in the frequency domain. Included are non-linear effects due to changes in added mass......, hydrodynamic damping and water line breadth with sectional immersion in waves. The study is limited to continuous excitations from the waves and thus transient so-called whipping vibrations due to slamming loads are not considered.Because of the non-linearities the ship hull responses become non...... to the large separation between dominating wave frequencies and the lowest two-node frequency of the hull beam. Both extreme value predictions and fatigue damage are considered.For a fast container ship the rigid body and two-node (springing) vertical wave-induced bending moments amidship are calculated...
Biological effects of laser-induced stress waves
International Nuclear Information System (INIS)
Doukas, A.; Lee, S.; McAuliffe, D.
1995-01-01
Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress
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.
Impact induced solitary wave propagation through a woodpile structure
International Nuclear Information System (INIS)
Kore, R; Waychal, A; Yadav, P; Shelke, A; Agarwal, S; Sahoo, N; Uddin, Ahsan
2016-01-01
In this paper, we investigate solitary wave propagation through a one-dimensional woodpile structure excited by low and high velocity impact. Woodpile structures are a sub-class of granular metamaterial, which supports propagation of nonlinear waves. Hertz contact law governs the behavior of the solitary wave propagation through the granular media. Towards an experimental study, a woodpile structure was fabricated by orthogonally stacking cylindrical rods. A shock tube facility has been developed to launch an impactor on the woodpile structure at a velocity of 30 m s −1 . Embedded granular chain sensors were fabricated to study the behavior of the solitary wave. The impact induced stress wave is studied to investigate solitary wave parameters, i.e. contact force, contact time, and solitary wave velocity. With the aid of the experimental setup, numerical simulations, and a theoretical solution based on the long wavelength approximation, formation of the solitary wave in the woodpile structure is validated to a reasonable degree of accuracy. The nondispersive and compact supported solitary waves traveling at sonic wave velocity offer unique properties that could be leveraged for application in nondestructive testing and structural health monitoring. (paper)
Effects of ship-induced waves on aquatic ecosystems.
Gabel, Friederike; Lorenz, Stefan; Stoll, Stefan
2017-12-01
Most larger water bodies worldwide are used for navigation, and the intensity of commercial and recreational navigation is expected to further increase. Navigation profoundly affects aquatic ecosystems. To facilitate navigation, rivers are trained and developed, and the direct effects of navigation include chemical and biological impacts (e.g., inputs of toxic substances and dispersal of non-native species, respectively). Furthermore, propagating ships create hydrodynamic alterations, often simply summarized as waves. Although ship-induced waves are recognized as influential stressors, knowledge on their effects is poorly synthesized. We present here a review on the effects of ship-induced waves on the structure, function and services of aquatic ecosystems based on more than 200 peer reviewed publications and technical reports. Ship-induced waves act at multiple organizational levels and different spatial and temporal scales. All the abiotic and biotic components of aquatic ecosystems are affected, from the sediment and nutrient budget to the planktonic, benthic and fish communities. We highlight how the effects of ship-induced waves cascade through ecosystems and how different effects interact and feed back into the ecosystem finally leading to altered ecosystem services and human health effects. Based on this synthesis of wave effects, we discuss strategies for mitigation. This may help to develop scientifically based and target-oriented management plans for navigational waters that optimize abiotic and biotic integrity and their ecosystem services and uses. Copyright © 2017 Elsevier B.V. All rights reserved.
Qin, Yan-Hong; Zhao, Li-Chen; Yang, Zhan-Ying; Yang, Wen-Li
2018-01-01
We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.
Wave-induced current considering wave-tide interaction in Haeundae
Lim, Hak Soo
2017-04-01
The Haeundae, located at the south eastern end of the Korean Peninsula, is a famous beach, which has an approximately 1.6 km long and 70 m wide coastline. The beach has been repeatedly eroded by the swell waves caused by typhoons in summer and high waves originating in the East Sea in winter. The Korean government conducted beach restoration projects including beach nourishment (620,000 m3) and construction of two submerged breakwaters near both ends of the beach. To prevent the beach erosion and to support the beach restoration project, the Korean government initiated a R&D project, the development of coastal erosion control technology since 2013. As a part of the project, we have been measuring waves and currents at a water depth of 22 m, 1.8 km away from the beach using an acoustic wave and current meter (AWAC) continuously for more than three years; we have also measured waves and currents intensively near the surf-zone in summer and winter. In this study, a numerical simulation using a wave and current coupled model (ROMS-SWAN) was conducted for determining the wave-induced current considering seasonal swell waves (Hs : 2.5 m, Tp: 12 s) and for better understanding of the coastal process near the surf-zone in Haeundae. By comparing the measured and simulated results, we found that cross-shore current during summer is mainly caused by the eddy produced by the wave-induced current near the beach, which in turn, is generated by the strong waves coming from the SSW and S directions. During other seasons, longshore wave-induced current is produced by the swell waves coming from the E and ESE directions. The longshore current heading west toward Dong-Back Island, west end of the beach, during all the seasons and eddy current toward Mipo-Port, east end of the beach, in summer which is well matched with the observed residual current. The wave-induced current with long-term measurement data is incorporated in simulation of sediment transport modeling for developing
Wave Induced Loading and Stability of Rubble Mound Breakwaters
DEFF Research Database (Denmark)
Hald, Tue
conducting model tests very large variability in e.g. the degree of stability is observed. This background motivated the investigations conducted in the present study. The objective was to investigate and clarify which wave parameters are important for the hydraulic stability of the armour layer on typical...... rubble mound breakwaters. Furthermore, it was intended to quantify the influence on the stability of each parameter. Focus was put on the wave induced loading on single armour stones and the relation to the stability. Based on existing literature the state of physical understanding of the processes...... and the stability were investigated. At Aalborg University model tests with an idealized model of a rubble mound breakwater were conducted and formed the basis for a detailed parametric investigation of the wave induced loading. Based on analyses of the experimental data wave-force models were derived containing...
Deep-water bedforms induced by refracting Internal Solitary Waves
Falcini, Federico; Droghei, Riccardo; Casalbore, Daniele; Martorelli, Eleonora; Mosetti, Renzo; Sannino, Gianmaria; Santoleri, Rosalia; Latino Chiocci, Francesco
2017-04-01
Subaqueous bedforms (or sand waves) are typically observed in those environments that are exposed to strong currents, characterized by a dominant unidirectional flow. However, sand-wave fields may be also observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs), induced by tides, can produce an effective, unidirectional boundary flow filed that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.
Impacts of wave-induced circulation in the surf zone on wave setup
Guérin, Thomas; Bertin, Xavier; Coulombier, Thibault; de Bakker, Anouk
2018-03-01
Wave setup corresponds to the increase in mean water level along the coast associated with the breaking of short-waves and is of key importance for coastal dynamics, as it contributes to storm surges and the generation of undertows. Although overall well explained by the divergence of the momentum flux associated with short waves in the surf zone, several studies reported substantial underestimations along the coastline. This paper investigates the impacts of the wave-induced circulation that takes place in the surf zone on wave setup, based on the analysis of 3D modelling results. A 3D phase-averaged modelling system using a vortex force formalism is applied to hindcast an unpublished field experiment, carried out at a dissipative beach under moderate to very energetic wave conditions (Hm 0 = 6m at breaking and Tp = 22s). When using an adaptive wave breaking parameterisation based on the beach slope, model predictions for water levels, short waves and undertows improved by about 30%, with errors reducing to 0.10 m, 0.10 m and 0.09 m/s, respectively. The analysis of model results suggests a very limited impact of the vertical circulation on wave setup at this dissipative beach. When extending this analysis to idealized simulations for different beach slopes ranging from 0.01 to 0.05, it shows that the contribution of the vertical circulation (horizontal and vertical advection and vertical viscosity terms) becomes more and more relevant as the beach slope increases. In contrast, for a given beach slope, the wave height at the breaking point has a limited impact on the relative contribution of the vertical circulation on the wave setup. For a slope of 0.05, the contribution of the terms associated with the vertical circulation accounts for up to 17% (i.e. a 20% increase) of the total setup at the shoreline, which provides a new explanation for the underestimations reported in previously published studies.
Particle transport model sensitivity on wave-induced processes
Staneva, Joanna; Ricker, Marcel; Krüger, Oliver; Breivik, Oyvind; Stanev, Emil; Schrum, Corinna
2017-04-01
Different effects of wind waves on the hydrodynamics in the North Sea are investigated using a coupled wave (WAM) and circulation (NEMO) model system. The terms accounting for the wave-current interaction are: the Stokes-Coriolis force, the sea-state dependent momentum and energy flux. The role of the different Stokes drift parameterizations is investigated using a particle-drift model. Those particles can be considered as simple representations of either oil fractions, or fish larvae. In the ocean circulation models the momentum flux from the atmosphere, which is related to the wind speed, is passed directly to the ocean and this is controlled by the drag coefficient. However, in the real ocean, the waves play also the role of a reservoir for momentum and energy because different amounts of the momentum flux from the atmosphere is taken up by the waves. In the coupled model system the momentum transferred into the ocean model is estimated as the fraction of the total flux that goes directly to the currents plus the momentum lost from wave dissipation. Additionally, we demonstrate that the wave-induced Stokes-Coriolis force leads to a deflection of the current. During the extreme events the Stokes velocity is comparable in magnitude to the current velocity. The resulting wave-induced drift is crucial for the transport of particles in the upper ocean. The performed sensitivity analyses demonstrate that the model skill depends on the chosen processes. The results are validated using surface drifters, ADCP, HF radar data and other in-situ measurements in different regions of the North Sea with a focus on the coastal areas. The using of a coupled model system reveals that the newly introduced wave effects are important for the drift-model performance, especially during extremes. Those effects cannot be neglected by search and rescue, oil-spill, transport of biological material, or larva drift modelling.
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)
Estimation of Impulsive Wave-induced Loads on a FPSO
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Mansour, Alaa E.
2005-01-01
) and for green water loads from the results of Buchner (1995) and Wang et al. (1998) are applied. The phase lag relative to the wave-induced peak and the decay rate are derived mainly from published experimental results, Sikora, (1998). The results are given in closed-form expressions and the required input...
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.
Development of a wave-induced forcing threshold for nearshore impact of Wave Energy Converter arrays
O'Dea, A.; Haller, M. C.; Ozkan-Haller, H. T.
2016-02-01
Wave-induced forcing is a function of spatial gradients in the wave radiation stresses and is the main driver of alongshore currents, rip currents, and nearshore sediment transport. The installation of nearshore Wave Energy Converter (WEC) arrays may cause significant changes in the surf zone radiation stresses and could therefore impact nearshore littoral processes. In the first part of this study, a new threshold for nearshore hydrodynamic impact due to the presence of WEC devices is established based on changes in the alongshore radiation stress gradients shoreward of WEC arrays. The threshold is defined based on the relationship between nearshore radiation stresses and alongshore currents as observed in field data. Next, we perform a parametric study of the nearshore impact of WEC arrays using the SWAN wave model. Trials are conducted on an idealized, alongshore-uniform beach with a range of WEC array configurations, locations, and incident wave conditions, and conditions that generate radiation stress gradients above the impact threshold are identified. Finally, the same methodology is applied to two wave energy test sites off the coast of Newport, OR with more complicated bathymetries. Although the trends at the field sites are similar to those seen in the parametric study, the location and extent of the changes in the alongshore radiation stress gradients appear to be heavily influenced by the local bathymetry.
Shock wave induced sonoporation and gene transfer
Miller, Douglas L.
2003-10-01
During shockwave (SW) treatment, cavitation activity can be applied for cell killing. A bonus is that some surviving cells appear to be briefly permeabilized, or sonoporated, allowing them to take up large molecules including DNA. In vitro research has indicated that as the number of SW increased, survival declined exponentially but the number of sonoporated cells increased to better than 50% of survivors for 1000 SW. In vivo tests have demonstrated SW-induced tumor ablation could indeed be accompanied by the transfection of marker plasmids into mouse B16 melanoma tumors in vivo. With intratumor injection of plasmid DNA and air bubbles, significant results were obtained for only 400 SW. In a trial of cancer therapy, the effects of 500 SW combined with interleukin-12 immuno-gene therapy was observed on the progression of two mouse tumors, B16 melanoma and RENCA renal carcinoma. The combination of SW and IL-12 plasmid injection provided a statistically significant inhibition of tumor growth relative to SW alone for both tumor models, demonstrating feasibility for this treatment method. In the future, the development of intravenous gene delivery and improved transfection, together with image-guided ultrasound treatment, should lead to the clinical application of ultrasound enhanced gene therapy. [Work supported by NIH Grant No. EB002782.
Shear wave induced resonance elastography of spherical masses with polarized torsional waves
Hadj Henni, Anis; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy
2012-03-01
Shear wave induced resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an invitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary invivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection.
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…
On the Chemical Mixing Induced by Internal Gravity Waves
Energy Technology Data Exchange (ETDEWEB)
Rogers, T. M. [School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne (United Kingdom); McElwaine, J. N. [Planetary Science Institute, Tucson, AZ 85721 (United States)
2017-10-10
Detailed modeling of stellar evolution requires a better understanding of the (magneto)hydrodynamic processes that mix chemical elements and transport angular momentum. Understanding these processes is crucial if we are to accurately interpret observations of chemical abundance anomalies, surface rotation measurements, and asteroseismic data. Here, we use two-dimensional hydrodynamic simulations of the generation and propagation of internal gravity waves in an intermediate-mass star to measure the chemical mixing induced by these waves. We show that such mixing can generally be treated as a diffusive process. We then show that the local diffusion coefficient does not depend on the local fluid velocity, but rather on the wave amplitude. We then use these findings to provide a simple parameterization for this diffusion, which can be incorporated into stellar evolution codes and tested against observations.
Photo-induced travelling waves in condensed Langmuir monolayers
Energy Technology Data Exchange (ETDEWEB)
Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)
2003-06-01
We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.
Neutrino induced vorticity, Alfven waves and the normal modes
Energy Technology Data Exchange (ETDEWEB)
Bhatt, Jitesh R. [Theory Division, Physical Research Laboratory, Ahmedabad (India); George, Manu [Theory Division, Physical Research Laboratory, Ahmedabad (India); Indian Institute of Technology, Department of Physics, Ahmedabad (India)
2017-08-15
We consider a plasma consisting of electrons and ions in the presence of a background neutrino gas and develop the magnetohydrodynamic equations for the system. We show that the electron neutrino interaction can induce vorticity in the plasma even in the absence of any electromagnetic perturbations if the background neutrino density is left-right asymmetric. This induced vorticity supports a new kind of Alfven wave whose velocity depends on both the external magnetic field and on the neutrino asymmetry. The normal mode analysis show that in the presence of neutrino background the Alfven waves can have different velocities. We also discuss our results in the context of dense astrophysical plasma such as magnetars and show that the difference in the Alfven velocities can be used to explain the observed pulsar kick. We discuss also the relativistic generalisation of the electron fluid in presence of an asymmetric neutrino background. (orig.)
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.)
Analysis of Wave Fields induced by Offshore Pile Driving
Ruhnau, M.; Heitmann, K.; Lippert, T.; Lippert, S.; von Estorff, O.
2015-12-01
Impact pile driving is the common technique to install foundations for offshore wind turbines. With each hammer strike the steel pile - often exceeding 6 m in diameter and 80 m in length - radiates energy into the surrounding water and soil, until reaching its targeted penetration depth. Several European authorities introduced limitations regarding hydroacoustic emissions during the construction process to protect marine wildlife. Satisfying these regulations made the development and application of sound mitigation systems (e.g. bubble curtains or insulation screens) inevitable, which are commonly installed within the water column surrounding the pile or even the complete construction site. Last years' advances have led to a point, where the seismic energy tunneling the sound mitigation systems through the soil and radiating back towards the water column gains importance, as it confines the maximum achievable sound mitigation. From an engineering point of view, the challenge of deciding on an effective noise mitigation layout arises, which especially requires a good understanding of the soil-dependent wave field. From a geophysical point of view, the pile acts like a very unique line source, generating a characteristic wave field dominated by inclined wave fronts, diving as well as head waves. Monitoring the seismic arrivals while the pile penetration steadily increases enables to perform quasi-vertical seismic profiling. This work is based on datasets that have been collected within the frame of three comprehensive offshore measurement campaigns during pile driving and demonstrates the potential of seismic arrivals induced by pile driving for further soil characterization.
Theory of ion Bernstein wave induced shear suppression of turbulence
Craddock, G. G.; Diamond, P. H.; Ono, M.; Biglari, H.
1994-06-01
The theory of radio frequency induced ion Bernstein wave- (IBW) driven shear flow in the edge is examined, with the goal of application of shear suppression of fluctuations. This work is motivated by the observed confinement improvement on IBW heated tokamaks [Phys. Fluids B 5, 241 (1993)], and by previous low-frequency work on RF-driven shear flows [Phys. Rev. Lett. 67, 1535 (1991)]. It is found that the poloidal shear flow is driven electrostatically by both Reynolds stress and a direct ion momentum source, analogous to the concepts of helicity injection and electron momentum input in current drive, respectively. Flow drive by the former does not necessarily require momentum input to the plasma to induce a shear flow. For IBW, the direct ion momentum can be represented by direct electron momentum input, and a charge separation induced stress that imparts little momentum to the plasma. The derived Er profile due to IBW predominantly points inward, with little possibility of direction change, unlike low-frequency Alfvénic RF drive. The profile scale is set by the edge density gradient and electron dissipation. Due to the electrostatic nature of ion Bernstein waves, the poloidal flow contribution dominates in Er. Finally, the necessary edge power absorbed for shear suppression on Princeton Beta Experiment-Modified (PBX-M) [9th Topical Conference on Radio Frequency Power in Plasmas, Charleston, SC, 1991 (American Institute of Physics, New York, 1991), p. 129] is estimated to be 100 kW distributed over 5 cm.
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...
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
Variations of helicon wave induced radial plasma transport in different experimental conditions
International Nuclear Information System (INIS)
Petrzilka, V.
1993-08-01
Variations of the helicon wave induced radial plasma transport are presented in dependence on values of the plasma radius, magnetostatic field, plasma density, frequency of the helicon wave and on the ion charge. 22 refs., 14 figs
Patterns induced by magnetic impurities in d-wave superconductors
International Nuclear Information System (INIS)
Zuo Xianjun; Gong Changde; Zhou Yuan
2010-01-01
We investigate the modulated patterns induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping based on the t-t ' -U-V model. Modulated checkerboard patterns with periodicity of eight or four lattice constants (8a or 4a) in the spin-, charge- and DSC orders are observed. Moreover, the checkerboard modulation in the spin order appear to be robust against parameter changes, which is consistent with neutron-scattering experiments. For the two-impurity case, a modulated stripe-like spin order with periodicity 8a is induced, which coexists with the DSC order. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.
Patterns induced by magnetic impurities in d-wave superconductors
Zuo, Xian-Jun; Gong, Chang-De; Zhou, Yuan
2010-07-01
We investigate the modulated patterns induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping based on the t-t-U-V model. Modulated checkerboard patterns with periodicity of eight or four lattice constants (8 a or 4 a) in the spin-, charge- and DSC orders are observed. Moreover, the checkerboard modulation in the spin order appear to be robust against parameter changes, which is consistent with neutron-scattering experiments. For the two-impurity case, a modulated stripe-like spin order with periodicity 8 a is induced, which coexists with the DSC order. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.
Wave aberrations in rhesus monkeys with vision-induced ametropias
Ramamirtham, Ramkumar; Kee, Chea-su; Hung, Li-Fang; Qiao-Grider, Ying; Huang, Juan; Roorda, Austin; Smith, Earl L.
2007-01-01
The purpose of this study was to investigate the relationship between refractive errors and high-order aberrations in infant rhesus monkeys. Specifically, we compared the monochromatic wave aberrations measured with a Shack-Hartman wavefront sensor between normal monkeys and monkeys with vision-induced refractive errors. Shortly after birth, both normal monkeys and treated monkeys reared with optically induced defocus or form deprivation showed a decrease in the magnitude of high-order aberrations with age. However, the decrease in aberrations was typically smaller in the treated animals. Thus, at the end of the lens-rearing period, higher than normal amounts of aberrations were observed in treated eyes, both hyperopic and myopic eyes and treated eyes that developed astigmatism, but not spherical ametropias. The total RMS wavefront error increased with the degree of spherical refractive error, but was not correlated with the degree of astigmatism. Both myopic and hyperopic treated eyes showed elevated amounts of coma and trefoil and the degree of trefoil increased with the degree of spherical ametropia. Myopic eyes also exhibited a much higher prevalence of positive spherical aberration than normal or treated hyperopic eyes. Following the onset of unrestricted vision, the amount of high-order aberrations decreased in the treated monkeys that also recovered from the experimentally induced refractive errors. Our results demonstrate that high-order aberrations are influenced by visual experience in young primates and that the increase in high-order aberrations in our treated monkeys appears to be an optical byproduct of the vision-induced alterations in ocular growth that underlie changes in refractive error. The results from our study suggest that the higher amounts of wave aberrations observed in ametropic humans are likely to be a consequence, rather than a cause, of abnormal refractive development. PMID:17825347
Herman, Agnieszka
2017-11-01
In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.
Particle dispersion and mixing induced by breaking internal gravity waves
Bouruet-Aubertot, Pascale; Koudella, C.; Staquet, C.; Winters, K. B.
2001-01-01
The purpose of this paper is to analyze diapycnal mixing induced by the breaking of an internal gravity wave — the primary wave — either standing or propagating. To achieve this aim we apply two different methods. The first method consists of a direct estimate of vertical eddy diffusion from particle dispersion while the second method relies upon potential energy budgets [Winters, K.B., Lombard, P.N., Riley, J.J., D'Asaro, E.A., 1995. J. Fluid Mech. 289, 115-128; Winters, K.B., D'Asaro, E.A., 1996. J. Fluid Mech. 317, 179-193]. The primary wave we consider is of small amplitude and is statically stable, a case for which the breaking process involves two-dimensional instabilities. The dynamics of the waves have been previously analyzed by means of two-dimensional direct numerical simulations [Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1995. J. Fluid Mech. 285, 265-301; Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1996. Dyn. Atmos. Oceans 29, 41-63; Koudella, C., Staquet, C., 1998. In: Davis, P. (Ed.), Proceedings of the IMA Conference on Mixing and Dispersion on Stably-stratified Flows, Dundee, September 1996. IMA Publication]. High resolution three-dimensional calculations of the same wave are also reported here [Koudella, C., 1999]. A local estimate of mixing is first inferred from the time evolution of sets of particles released in the flow during the breaking regime. We show that, after an early evolution dominated by shear effects, a diffusion law is reached and the dispersion coefficient is fairly independent of the initial seeding location of the particles in the flow. The eddy diffusion coefficient, K, is then estimated from the diapycnal diffusive flux. A good agreement with the value inferred from particle dispersion is obtained. This finding is of particular interest regarding the interpretation of in situ estimates of K inferred either from tracer dispersion or from microstructure measurements. Computation of the Cox number, equal to the
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…
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.
Intraluminal bubble dynamics induced by lithotripsy shock wave
Song, Jie; Bai, Jiaming; Zhou, Yufeng
2016-12-01
Extracorporeal shock wave lithotripsy (ESWL) has been the first option in the treatment of calculi in the upper urinary tract since its introduction. ESWL-induced renal injury is also found after treatment and is assumed to associate with intraluminal bubble dynamics. To further understand the interaction of bubble expansion and collapse with the vessel wall, the finite element method (FEM) was used to simulate intraluminal bubble dynamics and calculate the distribution of stress in the vessel wall and surrounding soft tissue during cavitation. The effects of peak pressure, vessel size, and stiffness of soft tissue were investigated. Significant dilation on the vessel wall occurs after contacting with rapid and large bubble expansion, and then vessel deformation propagates in the axial direction. During bubble collapse, large shear stress is found to be applied to the vessel wall at a clinical lithotripter setting (i.e. 40 MPa peak pressure), which may be the mechanism of ESWL-induced vessel rupture. The decrease of vessel size and viscosity of soft tissue would enhance vessel deformation and, consequently, increase the generated shear stress and normal stresses. Meanwhile, a significantly asymmetric bubble boundary is also found due to faster axial bubble expansion and shrinkage than in radial direction, and deformation of the vessel wall may result in the formation of microjets in the axial direction. Therefore, this numerical work would illustrate the mechanism of ESWL-induced tissue injury in order to develop appropriate counteractive strategies for reduced adverse effects.
Wave-induced stresses and pore pressures near a mudline
Directory of Open Access Journals (Sweden)
Andrzej Sawicki
2008-12-01
Full Text Available Conventional methods for the determination of water-wave induced stresses inseabeds composed of granular soils are based on Biot-type models, in which the soilskeleton is treated as an elastic medium. Such methods predict effective stressesin the soil that are unacceptable from the physical point of view, as they permittensile stresses to occur near the upper surface of the seabed. Therefore, in thispaper the granular soil is assumed to behave as an elastic-ideally plastic material,with the Coulomb-Mohr yield criterion adopted to bound admissible stress states inthe seabed. The governing equations are solved numerically by a~finite differencemethod. The results of simulations, carried out for the case of time-harmonicwater waves, illustrate the depth distributions of the excess pore pressures and theeffective stresses in the seabed, and show the shapes of zones of soil in the plastic state.~In particular, the effects on the seabed behaviour of suchparameters as the degree of pore water saturation, the soil permeability, and theearth pressure coefficient, are illustrated.
Renal tissue damage induced by focused shock waves
Ioritani, N.; Kuwahara, M.; Kambe, K.; Taguchi, K.; Saitoh, T.; Shirai, S.; Orikasa, S.; Takayama, K.; Lush, P. A.
1990-07-01
Biological evidence of renal arterial wall damage induced by the microjet due to shock wave-cavitation bubble interaction was demonstrated in living dog kidneys. We also intended to clarify the mechanism of renal tissue damage and the effects of different conditions of shock wave exposure (peak pressure of focused area, number of shots, exposure rate) on the renal tissue damage in comparison to stone disintegration. Disruption of arterial wall was the most remarkable histological change in the focused area of the kidneys. This lesion appeared as if the wall had been punctured by a needle. Large hematoma formation in the renal parenchym, and interstitial hemorrhage seemed to be the results of the arterial lesion. This arterial disorder also led to ischemic necrosis of the tubules surrounding the hematoma. Micro-angiographic examination of extracted kidneys also proved such arterial puncture lesions and ischemic lesions. The number of shots required for model stone disintegration was not inversely proportional to peak pressure. It decreased markedly when peak pressure was above 700 bar. Similarly thenumber of shots for hematoma formation was not inversely proportional to peak pressure, however, this decreased markedly above 500 bar. These results suggested that a hematoma could be formed under a lower peak pressure than that required for stone disintegration.
Wave induced extreme hull girder loads on containerships
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Pedersen, Preben Terndrup; Shi, Bill
2009-01-01
This paper provides simple but rational procedures for prediction of extreme wave – induced sectional hull girder forces with reasonable engineering accuracy. The procedures take into account main ship hull characteristics such as: length, breadth, draught, block coefficient, bow flare coefficient......, forward speed and hull flexibility. The vertical hull girder loads are evaluated for specific operational profiles. Firstly a quadratic strip theory is presented which can give separate predictions for the hogging and sagging bending moments and shear forces and for hull girder loads. Then this procedure...... is based on rational methods it can be applied for novel single hull ship types not presently covered by the rules of the classification societies or to account for specific operational profiles....
Shock-induced borehole waves and fracture effects
Fan, H.; Smeulders, D.M.J.
2012-01-01
We perform wave experiments using a vertical shock tube setup. Shock waves are generated by the rupture of a thin membrane. In the test section the incident pressure waves generate borehole-guided waves along water-saturated samples. The tube is equipped with side wall gages and a mobile pressure
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…
Experimental particle acceleration by water evaporation induced by shock waves
Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.
2010-12-01
Shock waves are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by shock wave propagation in the acceleration of ash particles. We used a shock tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting shock and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air shock wave. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air shock; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. In all experiments particles velocities following the initial
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,…
Vacillations induced by interference of stationary and traveling planetary waves
Salby, Murry L.; Garcia, Rolando R.
1987-01-01
The interference pattern produced when a traveling planetary wave propagates over a stationary forced wave is explored, examining the interference signature in a variety of diagnostics. The wave field is first restricted to a diatomic spectrum consisting of two components: a single stationary wave and a single monochromatic traveling wave. A simple barotropic normal mode propagating over a simple stationary plane wave is considered, and closed form solutions are obtained. The wave fields are then restricted spatially, providing more realistic structures without sacrificing the advantages of an analytical solution. Both stationary and traveling wave fields are calculated numerically with the linearized Primitive Equations in a realistic basic state. The mean flow reaction to the fluctuating eddy forcing which results from interference is derived. Synoptic geopotential behavior corresponding to the combined wave and mean flow fields is presented, and the synoptic signature in potential vorticity on isentropic surfaces is examined.
Electromagnetically Induced Transparency in Four Wave Mixing Process
International Nuclear Information System (INIS)
Kucukkara, I.
2008-01-01
We have theoretically studied Four Wave Mixing (FWM) process in VUV (Vacuum Ultraviolet) region enhanced by Electromagnetically Induced Transparency in Krypton gas medium at room temperature. One of the mixing fields, in the ultraviolet region at 212.5 nm was in two-photon resonance with the 4p 6 1 S 0 -4p 5 5p[0,1/2] transition of Krypton and the second field (coupling field) at 759 nm was resonant with the 4p 5 5p[0,1/2]-4p 5 5s[1,1/2] transition in scheme. This coupling field produced an electromagnetically induced transparency and thus the efficiency of the generation of the field at 123.6 nm on the 4p 5 5s[1,1/2] to 4p 6 1 S 0 transition is enhanced. We modified the computer program previously written by changing some variables like pressure, interaction region length, UV energy, IR energy. As demonstrated by the intensity generated VUV light versus Krypton pressure graphic, the most efficient intensity value, which was approximately 4.2x10 1 6 arbitrary units, was obtained while IR energy was 3x10 - 4 J and the pressure was 2x10 - 3 bar
Wave-induced release of methane : littoral zones as a source of methane in lakes
Hofmann, Hilmar; Federwisch, Luisa; Peeters, Frank
2010-01-01
This study investigates the role of surface waves and the associated disturbance of littoral sediments for the release and later distribution of dissolved methane in lakes. Surface wave field, wave-induced currents, acoustic backscatter strength, and the concentration and distribution of dissolved methane were measured simultaneously in Lake Constance, Germany. The data indicate that surface waves enhance the release of dissolved methane in the shallow littoral zone via burst-like releases of...
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.
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).
Wang, Feng; Ni, Binbin; Zhao, Zhengyu; Zhao, Shufan; Zhao, Guangxin; Wang, Min
2017-05-01
Electromagnetic extremely low frequency (ELF) waves play an important role in modulating the Earth's radiation belt electron dynamics. High-frequency (HF) modulated heating of the ionosphere acts as a viable means to generate artificial ELF waves. The artificial ELF waves can reside in two different plasma regions in geo-space by propagating in the ionosphere and penetrating into the magnetosphere. As a consequence, the entire trajectory of ELF wave propagation should be considered to carefully analyze the wave radiation properties resulting from modulated ionospheric heating. We adopt a model of full wave solution to evaluate the Poynting vector of the ELF radiation field in the ionosphere, which can reflect the propagation characteristics of the radiated ELF waves along the background magnetic field and provide the initial condition of waves for ray tracing in the magnetosphere. The results indicate that the induced ELF wave energy forms a collimated beam and the center of the ELF radiation shifts obviously with respect to the ambient magnetic field with the radiation power inversely proportional to the wave frequency. The intensity of ELF wave radiation also shows a weak correlation with the size of the radiation source or its geographical location. Furthermore, the combination of ELF propagation in the ionosphere and magnetosphere is proposed on basis of the characteristics of the ELF radiation field from the upper ionospheric boundary and ray tracing simulations are implemented to reasonably calculate magnetospheric ray paths of ELF waves induced by modulated ionospheric heating.
High-Frequency Gravitational Wave Induced Nuclear Fusion
International Nuclear Information System (INIS)
Fontana, Giorgio; Baker, Robert M. L. Jr.
2007-01-01
Nuclear fusion is a process in which nuclei, having a total initial mass, combine to produce a single nucleus, having a final mass less than the total initial mass. Below a given atomic number the process is exothermic; that is, since the final mass is less than the combined initial mass and the mass deficit is converted into energy by the nuclear fusion. On Earth nuclear fusion does not happen spontaneously because electrostatic barriers prevent the phenomenon. To induce controlled, industrial scale, nuclear fusion, only a few methods have been discovered that look promising, but net positive energy production is not yet possible because of low overall efficiency of the systems. In this paper we propose that an intense burst of High Frequency Gravitational Waves (HFGWs) could be focused or beamed to a target mass composed of appropriate fuel or target material to efficiently rearrange the atomic or nuclear structure of the target material with consequent nuclear fusion. Provided that efficient generation of HFGW can be technically achieved, the proposed fusion reactor could become a viable solution for the energy needs of mankind and alternatively a process for beaming energy to produce a source of fusion energy remotely - even inside solid materials
Simulation of Irregular Waves and Wave Induced Loads on Wind Power Plants in Shallow Water
Energy Technology Data Exchange (ETDEWEB)
Trumars, Jenny [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Water Environment Transport
2004-05-01
The essay gives a short introduction to waves and discusses the problem with non-linear waves in shallow water and how they effect an offshore wind energy converter. The focus is on the realisation of non-linear waves in the time domain from short-term statistics in the form of a variance density spectrum of the wave elevation. For this purpose the wave transformation from deep water to the near to shore site of a wind energy farm at Bockstigen has been calculated with the use of SWAN (Simulating Waves Near Shore). The result is a wave spectrum, which can be used as input to the realisation. The realisation of waves is done by perturbation theory to the first and second-order. The properties calculated are the wave elevation, water particle velocity and acceleration. The wave heights from the second order perturbation equations are higher than those from the first order perturbation equations. This is also the case for the water particle kinematics. The increase of variance is significant between the first order and the second order realisation. The calculated wave elevation exhibits non-linear features as the peaks become sharper and the troughs flatter. The resulting forces are calculated using Morison's equation. For second order force and base moment there is an increase in the maximum values. The force and base moment are largest approximately at the zero up and down crossing of the wave elevation. This indicates an inertia dominated wave load. So far the flexibility and the response of the structure have not been taken into account. They are, however, of vital importance. For verification of the wave model the results will later on be compared with measurements at Bockstigen off the coast of Gotland in the Baltic Sea.
Stochastic procedures for extreme wave induced responses in flexible ships
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Andersen, Ingrid Marie Vincent; Seng, Sopheak
2014-01-01
Different procedures for estimation of the extreme global wave hydroelastic responses in ships are discussed. Firstly, stochastic procedures for application in detailed numerical studies (CFD) are outlined. The use of the First Order Reliability Method (FORM) to generate critical wave episodes...
A typical wave wake from high-speed vessels: its group structure and run-up
Directory of Open Access Journals (Sweden)
I. Didenkulova
2013-02-01
Full Text Available High-amplitude water waves induced by high-speed vessels are regularly observed in Tallinn Bay, the Baltic Sea, causing intense beach erosion and disturbing marine habitants in the coastal zone. Such a strong impact on the coast may be a result of a certain group structure of the wave wake. In order to understand it, here we present an experimental study of the group structure of these wakes at Pikakari beach, Tallinn Bay. The most energetic vessel waves at this location (100 m from the coast at the water depth 2.7 m have amplitudes of about 1 m and periods of 8–10 s and cause maximum run-up heights on a beach up to 1.4 m. These waves represent frequency modulated packets where the largest and longest waves propagate ahead of other smaller amplitude and period waves. Sometimes the groups of different heights and periods can be separated even within one wave wake event. The wave heights within a wake are well described by the Weibull distribution, which has different parameters for wakes from different vessels. Wave run-up heights can also be described by Weibull distribution and its parameters can be connected to the parameters of the distribution of wave heights 100 m from the coast. Finally, the run-up of individual waves within a packet is studied. It is shown that the specific structure of frequency modulated wave packets, induced by high-speed vessels, leads to a sequence of high wave run-ups at the coast, even when the original wave heights are rather moderate. This feature can be a key to understanding the significant impact on coasts caused by fast vessels.
Interfacial instability induced by a shock wave in a gas-liquid horizontal stratified system
International Nuclear Information System (INIS)
Sutradhar, S.C.; Chang, J.S.; Yoshida, H.
1987-01-01
The experiments are performed in a rectangular lucite duct equipped with the facility of generating shock waves. Piezo-type pressure transducers are used to monitor the strength and propagation velocity of the shock wave. As the liquid phase has high sound velocity, a prepulse wave system of flow amplitude travels in this phase at a speed faster than the principal shock wave. The magnitude of the transmitted wave in the liquid phase is estimated using a transmission coefficient for gas-liquid system. From the initial pressure ratio of the shock wave, the amplitude of the prepulse as well as the induced interfacial fluid velocity are calculated. The wave length and height of the ripples during the passage of the shock wave are estimated for a specific strength of shock wave moving through the phases. From the high speed photographs, the wave length of the ripples can be assessed. The interfacial friction factor is calculated using colebrook's equation for high speed flow. At least five distinct phenomena are observed to exist during the propagation of a shock wave. These are - (1) the energy carried by the pre-pulse is utilized in perturbing the interface; (2) shock wave induces a mass velocity at the interface; (3) the wavelength of the ripples at the interface is the product of induced interfacial mass velocity and the time period of the prepulse; (4) a portion of the liquid mass of the perturbed interface is entrained in the gas phase may be due to the hydrodynamic lift in that phase; and finally (5) waves with long wavelength are established at the interface
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
Ship-induced solitary Riemann waves of depression in Venice Lagoon
International Nuclear Information System (INIS)
Parnell, Kevin E.; Soomere, Tarmo; Zaggia, Luca; Rodin, Artem; Lorenzetti, Giuliano; Rapaglia, John; Scarpa, Gian Marco
2015-01-01
We demonstrate that ships of moderate size, sailing at low depth Froude numbers (0.37–0.5) in a navigation channel surrounded by shallow banks, produce depressions with depths up to 2.5 m. These depressions (Bernoulli wakes) propagate as long-living strongly nonlinear solitary Riemann waves of depression substantial distances into Venice Lagoon. They gradually become strongly asymmetric with the rear of the depression becoming extremely steep, similar to a bore. As they are dynamically similar, air pressure fluctuations moving over variable-depth coastal areas could generate meteorological tsunamis with a leading depression wave followed by a devastating bore-like feature. - Highlights: • Unprecedently deep long-living ship-induced waves of depression detected. • Such waves are generated in channels with side banks under low Froude numbers. • The propagation of these waves is replicated using Riemann waves. • Long-living waves of depression form bore-like features at rear slope
Ship-induced solitary Riemann waves of depression in Venice Lagoon
Energy Technology Data Exchange (ETDEWEB)
Parnell, Kevin E. [College of Marine and Environmental Sciences and Centre for Tropical Environmental and Sustainability Sciences, James Cook University, Queensland 4811 (Australia); Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Soomere, Tarmo, E-mail: soomere@cs.ioc.ee [Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn (Estonia); Zaggia, Luca [Institute of Marine Sciences, National Research Council, Castello 2737/F, 30122 Venice (Italy); Rodin, Artem [Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Lorenzetti, Giuliano [Institute of Marine Sciences, National Research Council, Castello 2737/F, 30122 Venice (Italy); Rapaglia, John [Sacred Heart University Department of Biology, 5151 Park Avenue, Fairfield, CT 06825 (United States); Scarpa, Gian Marco [Università Ca' Foscari, Dorsoduro 3246, 30123 Venice (Italy)
2015-03-06
We demonstrate that ships of moderate size, sailing at low depth Froude numbers (0.37–0.5) in a navigation channel surrounded by shallow banks, produce depressions with depths up to 2.5 m. These depressions (Bernoulli wakes) propagate as long-living strongly nonlinear solitary Riemann waves of depression substantial distances into Venice Lagoon. They gradually become strongly asymmetric with the rear of the depression becoming extremely steep, similar to a bore. As they are dynamically similar, air pressure fluctuations moving over variable-depth coastal areas could generate meteorological tsunamis with a leading depression wave followed by a devastating bore-like feature. - Highlights: • Unprecedently deep long-living ship-induced waves of depression detected. • Such waves are generated in channels with side banks under low Froude numbers. • The propagation of these waves is replicated using Riemann waves. • Long-living waves of depression form bore-like features at rear slope.
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.
Dispersive waves induced by self-defocusing temporal solitons in a beta-barium-borate crystal
DEFF Research Database (Denmark)
Zhou, Binbin; Bache, Morten
2015-01-01
We experimentally observe dispersive waves in the anomalous dispersion regime of a beta-barium-borate (BBO) crystal, induced by a self-defocusing few-cycle temporal soliton. Together the soliton and dispersive waves form an energetic octave-spanning supercontinuum. The soliton was excited...
Vaucher, Romain; Pittet, Bernard; Humbert, Thomas; Ferry, Serge
2017-11-01
The Cap Ferret sand spit is situated along the wave-dominated, tidally modulated Atlantic coast of western France, characterized by a semidiurnal macrotidal range. It displays peculiar dome-like bedforms that can be observed at low tide across the intertidal zone. These bedforms exhibit a wavelength of ca. 1.2 m and an elevation of ca. 30 cm. They occur only when the incident wave heights reach 1.5-2 m. The internal stratifications are characterized by swaley-like, sub-planar, oblique-tangential, oblique-tabular, as well as hummocky-like stratifications. The tabular and tangential stratifications comprise prograding oblique sets (defined as foresets and backsets) that almost always show variations in their steepness. Downcutting into the bottomsets of the oblique-tangential stratifications is common. The sets of laminae observed in the bedforms share common characteristics with those formed by supercritical flows in flume experiments of earlier studies. These peculiar bedforms are observed at the surf-swash transition zone where the backwash flow reaches supercritical conditions. This type of flow can explain their internal architecture but not their general dome-like (three-dimensional) morphology. Wave-wave interference induced by the geomorphology (i.e. tidal channel) of the coastal environment is proposed as explanation for the localized formation of such bedforms. This study highlights that the combination of supercritical flows occurring in the surf-swash transition zone and wave-wave interferences can generate dome-like bedforms in intertidal zones.
Wave-induced nearshore circulation along the Calangute-Candolim beach, Goa, West coast of India
Digital Repository Service at National Institute of Oceanography (India)
Krishnakumar, V.; Murty, C.S.; Heblekar, A.K.
The wave-induced nearshore circulation model suggested by Noda has been modified and applied for three small segments along the coast of Goa. The present model incorporates the prevailing bottom topography and considers its variation along...
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.)
The instability of the spiral wave induced by the deformation of elastic excitable media
International Nuclear Information System (INIS)
Ma Jun; Jia Ya; Wang Chunni; Li Shirong
2008-01-01
There are some similarities between the spiral wave in excitable media and in cardiac tissue. Much evidence shows that the appearance and instability of the spiral wave in cardiac tissue can be linked to one kind of heart disease. There are many models that can be used to investigate the formation and instability of the spiral wave. Cardiac tissue is excitable and elastic, and it is interesting to simulate the transition and instability of the spiral wave induced by media deformation. For simplicity, a class of the modified Fitzhugh-Nagumo (MFHN) model, which can generate a stable rotating spiral wave, meandering spiral wave and turbulence within appropriate parameter regions, will be used to simulate the instability of the spiral wave induced by the periodical deformation of media. In the two-dimensional case, the total acreage of elastic media is supposed to be invariable in the presence of deformation, and the problem is described with L x x L y = N x ΔxN x Δy = L' x L' y = N x Δx'N x Δy'. In our studies, elastic media are decentralized into N x N sites and the space of the adjacent sites is changed to simulate the deformation of elastic media. Based on the nonlinear dynamics theory, the deformation effect on media is simplified and simulated by perturbing the diffusion coefficients D x and D y with different periodical signals, but the perturbed diffusion coefficients are compensatory. The snapshots of our numerical results find that the spiral wave can coexist with the spiral turbulence, instability of the spiral wave and weak deformation of the spiral wave in different conditions. The ratio parameter ε and the frequency of deformation forcing play a deterministic role in inducing instability of the spiral wave. Extensive studies confirm that the instability of the spiral wave can be induced and developed only if an appropriate frequency for deformation is used. We analyze the power spectrum for the time series of the mean activator of four sampled sites
The instability of the spiral wave induced by the deformation of elastic excitable media
Ma, Jun; Jia, Ya; Wang, Chun-Ni; Li, Shi-Rong
2008-09-01
There are some similarities between the spiral wave in excitable media and in cardiac tissue. Much evidence shows that the appearance and instability of the spiral wave in cardiac tissue can be linked to one kind of heart disease. There are many models that can be used to investigate the formation and instability of the spiral wave. Cardiac tissue is excitable and elastic, and it is interesting to simulate the transition and instability of the spiral wave induced by media deformation. For simplicity, a class of the modified Fitzhugh-Nagumo (MFHN) model, which can generate a stable rotating spiral wave, meandering spiral wave and turbulence within appropriate parameter regions, will be used to simulate the instability of the spiral wave induced by the periodical deformation of media. In the two-dimensional case, the total acreage of elastic media is supposed to be invariable in the presence of deformation, and the problem is described with Lx × Ly = N × ΔxN × Δy = L'xL'y = N × Δx'N × Δy'. In our studies, elastic media are decentralized into N × N sites and the space of the adjacent sites is changed to simulate the deformation of elastic media. Based on the nonlinear dynamics theory, the deformation effect on media is simplified and simulated by perturbing the diffusion coefficients Dx and Dy with different periodical signals, but the perturbed diffusion coefficients are compensatory. The snapshots of our numerical results find that the spiral wave can coexist with the spiral turbulence, instability of the spiral wave and weak deformation of the spiral wave in different conditions. The ratio parameter ɛ and the frequency of deformation forcing play a deterministic role in inducing instability of the spiral wave. Extensive studies confirm that the instability of the spiral wave can be induced and developed only if an appropriate frequency for deformation is used. We analyze the power spectrum for the time series of the mean activator of four sampled sites
Scalar field vacuum expectation value induced by gravitational wave background
Jones, Preston; McDougall, Patrick; Ragsdale, Michael; Singleton, Douglas
2018-06-01
We show that a massless scalar field in a gravitational wave background can develop a non-zero vacuum expectation value. We draw comparisons to the generation of a non-zero vacuum expectation value for a scalar field in the Higgs mechanism and with the dynamical Casimir vacuum. We propose that this vacuum expectation value, generated by a gravitational wave, can be connected with particle production from gravitational waves and may have consequences for the early Universe where scalar fields are thought to play an important role.
A hydrodynamic model of nearshore waves and wave-induced currents
Directory of Open Access Journals (Sweden)
Ahmed Khaled Seif
2011-09-01
Full Text Available In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995 and Larson and Kraus (2002. Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF basin and the Hazaki Oceanographical Research Station (HORS. Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.
DEFF Research Database (Denmark)
Pu, Minhao; Chen, Yaohui; Yvind, Kresten
2014-01-01
Influence of thermal effects induced by nonlinear absorption on four-wave mixing in silicon waveguides is investigated. A conversion bandwidth reduction up to 63% is observed in simulation due to the thermal effects.......Influence of thermal effects induced by nonlinear absorption on four-wave mixing in silicon waveguides is investigated. A conversion bandwidth reduction up to 63% is observed in simulation due to the thermal effects....
The sequence of sediment behaviour during wave-induced liquefaction
DEFF Research Database (Denmark)
Sumer, B. Mutlu; Hatipoglu, Figen; Fredsøe, Jørgen
2006-01-01
to be in agreement with recent centrifuge wave-tank experiments. As for the final stage of the sequence of processes (formation of ripples), the ripple steepness (normalized with the angle of repose) for sediment with liquefaction history is found to be the same as that in sediment with no liquefaction history.......This paper presents the results of an experimental investigation of the complete sequence of sediment behaviour beneath progressive waves. The sediment was silty with d(50) = 0.060 mm. Two kinds of measurements were carried out: pore-water pressure measurements (across the sediment depth...... of liquefaction and compaction fronts in the sediment and (iii) the characteristics of the orbital motion of the liquefied sediment including the motion of the interface between the water body and the sediment. The ranges of the various quantities in the tests were: wave height, H = 9-17 cm, wave period, T = 1...
Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse
Energy Technology Data Exchange (ETDEWEB)
Grishkov, V. E.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
2017-03-15
Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron–ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.
Poloidal rotation induced by injecting lower hybrid waves in tokamak plasma edge
International Nuclear Information System (INIS)
Jiao Yiming; Gao Qingdi; Shi Bingren
2001-01-01
The poloidal rotation of the magnetized edge plasma in tokamak driven by the ponderomotive force which is generated by injecting lower hybrid wave (LHW) electric field has been studied. The LHW is launched from a waveguide in the plasma edge, and by Brambilla's grill theory, analytic expressions for the wave electric field in the slab model of an inhomogeneous cold plasma have been derived. It is shown that a strong wave electric field will be generated in the plasma edge by injecting LH wave of the power in MW magnitude, and this electric field will induce a poloidal rotation with a sheared poloidal velocity
Charging-delay induced dust acoustic collisionless shock wave: Roles of negative ions
International Nuclear Information System (INIS)
Ghosh, Samiran; Bharuthram, R.; Khan, Manoranjan; Gupta, M. R.
2006-01-01
The effects of charging-delay and negative ions on nonlinear dust acoustic waves are investigated. It has been found that the charging-delay induced anomalous dissipation causes generation of dust acoustic collisionless shock waves in an electronegative dusty plasma. The small but finite amplitude wave is governed by a Korteweg-de Vries Burger equation in which the Burger term arises due to the charging-delay. Numerical investigations reveal that the charging-delay induced dissipation and shock strength decreases (increases) with the increase of negative ion concentration (temperature)
Estimation of Ship Long-term Wave-induced Bending Moment using Closed-Form Expressions
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Mansour, A. E.
2002-01-01
A semi-analytical approach is used to derive frequency response functions and standard deviations for the wave-induced bending moment amidships for mono-hull ships. The results are given as closed-form expressions and the required input information for the procedure is restricted to the main......-empirical closed-form expression for the skewness. The effect of whipping is included by assuming that whipping and wave-induced responses are conditionally independent given Hs. The procedure is simple and can be used to make quick estimates of the design wave bending moment at the conceptual design phase...
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.
International Nuclear Information System (INIS)
Shvets, G.; Tushentsov, M.; Tokman, M.D.; Kryachko, A.
2005-01-01
Propagation of electromagnetic waves in magnetized plasma near the electron cyclotron frequency can be strongly modified by adding a weak magnetic undulator. For example, both right- and left-hand circularly polarized waves can propagate along the magnetic field without experiencing resonant absorption. This effect of entirely eliminating electron cyclotron heating is referred to as the undulator-induced transparency (UIT) of the plasma, and is the classical equivalent of the well-known quantum mechanical effect of electromagnetically induced transparency. The basics of UIT are reviewed, and various ways in which UIT can be utilized to achieve exotic propagation properties of electromagnetic waves in plasmas are discussed. For example, UIT can dramatically slow down the waves' group velocity, resulting in the extreme compression of the wave energy in the plasma. Compressed waves are polarized along the propagation direction, and can be used for synchronous electron or ion acceleration. Strong coupling between the two wave helicities are explored to impart the waves with high group velocities ∂ω/∂k for vanishing wave numbers k. Cross-helicity coupling for realistic density and magnetic field profiles are examined using a linearized fluid code, particle-in-cell simulations, and ray-tracing WKB calculations
Extreme Wave-Induced Oscillation in Paradip Port Under the Resonance Conditions
Kumar, Prashant; Gulshan
2017-12-01
A mathematical model is constructed to analyze the long wave-induced oscillation in Paradip Port, Odisha, India under the resonance conditions to avert any extreme wave hazards. Boundary element method (BEM) with corner contribution is utilized to solve the Helmholtz equation under the partial reflection boundary conditions. Furthermore, convergence analysis is also performed for the boundary element scheme with uniform and non-uniform discretization of the boundary. The numerical scheme is also validated with analytic approximation and existing studies based on harbor resonance. Then, the amplification factor is estimated at six key record stations in the Paradip Port with multidirectional incident waves and resonance modes are also estimated at the boundary of the port. Ocean surface wave field is predicted in the interior of Paradip Port for the different directional incident wave at various resonance modes. Moreover, the safe locations in the port have been identified for loading and unloading of moored ship with different resonance modes and directional incident waves.
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.
Induced wave propagation from a vibrating containment envelope
International Nuclear Information System (INIS)
Stout, R.B.; Thigpen, L.; Rambo, J.T.
1985-09-01
Low frequency wave forms are observed in the particle velocity measurements around the cavity and containment envelope formed by an underground nuclear test. The vibration solution for a spherical shell is used to formulate a model for the low frequency wave that propagates outward from this region. In this model the containment envelope is the zone of material that is crushed by the compressive shock wave of the nuclear explosion. The containment envelope is approximated by a spherical shell of material. The material in the spherical shell is densified and is given a relatively high kinetic energy density because of the high compressive stress and particle velocity of the shock wave. After the shock wave has propagated through the spherical shell, the spherical shell vibrates in order to dissipate the kinetic energy acquired from the shock wave. Based on the model, the frequency of vibration depends on the dimensions and material properties of the spherical shell. The model can also be applied in an inverse mode to obtain global estimates of averaged materials properties. This requires using experimental data and semi-empirical relationships involving the material properties. A particular case of estimating a value for shear strength is described. Finally, the oscillation time period of the lowest frequency from five nuclear tests is correlated with the energy of the explosion. The correlation provides another diagnostic to estimate the energy of a nuclear explosion. Also, the longest oscillation time period measurement provides additional experimental data that can be used to assess and validate various computer models. 11 refs., 2 figs
Influence of clay content on wave-induced liquefaction
DEFF Research Database (Denmark)
Kirca, V.S. Ozgur; Sumer, B. Mutlu; Fredsøe, Jørgen
2014-01-01
of measurements were carried out: (1) pore-water pressure measurements across the soil depth and (2) water-surface elevation measurements. These measurements were synchronized with video recordings of the liquefaction process from the side. The ranges of the various quantities in the experiments were wave height...... of silt and clay was not liquefied. Sand may become prone to liquefaction with the introduction of clay, contrary to the general perception that this type of sediment is normally liquefaction-resistant under waves. For instance, sand with d50 50:4 mmwas liquefied with CC510:8%, whereas sand with d50 50...
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)
Gravity induced corrections to quantum mechanical wave functions
International Nuclear Information System (INIS)
Singh, T.P.
1990-03-01
We perform a semiclassical expansion in the Wheeler-DeWitt equation, in powers of the gravitational constant. We then show that quantum gravitational fluctuations can provide a correction to the wave-functions which are solutions of the Schroedinger equation for matter. This also implies a correction to the expectation values of quantum mechanical observables. (author). 6 refs
Flow and sediment transport induced by a plunging solitary wave
DEFF Research Database (Denmark)
Sumer, B. Mutlu; Sen, M.Berke; Karagali, Ioanna
2011-01-01
Two parallel experiments involving the evolution and runup of plunging solitary waves on a sloping bed were conducted: (1) a rigid-bed experiment, allowing direct (hot film) measurements of bed shear stresses, and (2) a sediment-bed experiment, allowing for the measurement of pore-water pressures...
Cell detachment method using shock wave induced cavitation
Junge, L.; Junge, L.; Ohl, C.D.; Wolfrum, B.; Arora, M.; Ikink, R.
2003-01-01
The detachment of adherent HeLa cells from a substrate after the interaction with a shock wave is analyzed. Cavitation bubbles are formed in the trailing, negative pressure cycle following the shock front. We find that the regions of cell detachment are strongly correlated with spatial presence of
On Current Drive and Wave Induced Bootstrap Current in Toroidal Plasmas
International Nuclear Information System (INIS)
Hellsten, T.; Johnson, T.
2008-01-01
A comprehensive treatment of wave-particle interactions in toroidal plasmas including collisional relaxation, applicable to heating or anomalous wave induced transport, has been obtained by using Monte Carlo operators satisfying quasi-neutrality. This approach enables a self-consistent treatment of wave-particle interactions applicable to the banana regime in the neoclassical theory. It allows an extension into a regime with large temperature and density gradients, losses and transport of particles by wave-particle interactions making the method applicable to transport barriers. It is found that at large gradients the relationship between radial electric field, parallel velocity, temperature and density gradient in the neoclassical theory is modified such that coefficient in front of the logarithmic ion temperature gradient, which in the standard neoclassical theory is small and counteracts the electric field caused by the density gradient, now changes sign and contributes to the built up of the radial electric field. The possibility to drive current by absorbing the waves on trapped particles has been studied and how the wave-particle interactions affect the bootstrap current. Two new current drive mechanisms are studied: current drive by wave induced bootstrap current and selective detrapping into passing orbits by directed waves.
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
Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon
Directory of Open Access Journals (Sweden)
A. Torres-Freyermuth
2012-12-01
Full Text Available Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon are investigated by means of a phase-resolving non-hydrostatic wave model (SWASH. This model solves the nonlinear shallow water equations including non-hydrostatic pressure. The one-dimensional version of the model is implemented in order to investigate wave transformation in fringing reefs. Firstly, the numerical model is validated with (i laboratory experiments conducted on a physical model (Demirbilek et al., 2007and (ii field observations (Coronado et al., 2007. Numerical results show good agreement with both experimental and field data. The comparison against the physical model results, for energetic wave conditions, indicates that high- and low-frequency wave transformation is well reproduced. Moreover, extreme water-level conditions measured during the passage of Hurricane Ivan in Puerto Morelos are also estimated by the numerical tool. Subsequently, the model is implemented at different along-reef locations in Puerto Morelos. Extreme water levels, wave-induced setup, and infragravity wave energy are estimated inside the reef lagoon for different storm wave conditions (H_{s} >2 m. The numerical results revealed a strong correlation between the offshore sea-swell wave energy and the setup. In contrast, infragravity waves are shown to be the result of a more complex pattern which heavily relies on the reef geometry. Indeed, the southern end of the reef lagoon provides evidence of resonance excitation, suggesting that the reef barrier may act as either a natural flood protection morphological feature, or as an inundation hazard enhancer depending on the incident wave conditions.
Mesoscale variations in acoustic signals induced by atmospheric gravity waves.
Chunchuzov, Igor; Kulichkov, Sergey; Perepelkin, Vitaly; Ziemann, Astrid; Arnold, Klaus; Kniffka, Anke
2009-02-01
The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal wave-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated. The capability of acoustic tomography in estimating wind shear near ground is shown. A possible mechanism describing the temporal modulation of the near-ground wind field by ducted internal waves in the troposphere is proposed.
Induced photoassociation in the field of a strong electomagnetic wave
International Nuclear Information System (INIS)
Zaretskij, D.F.; Lomonosov, V.V.; Lyul'ka, V.A.
1979-01-01
The quantum-mechanical problem of the stimulated transition of a system in the field of a strong electromagnetic wave from the continuous spectrum to a bound state possessing a finite lifetime is considered. The expressions obtained are employed to calculate stimulated production of mesic atoms and mesic molecules (ddμ). It is demonstrated that in an external electromagnetic field the probability for production of this type may considerably increase
Numerical simulation of wave-induced scour and backfilling processes beneath submarine pipelines
DEFF Research Database (Denmark)
Fuhrman, David R.; Baykal, Cüneyt; Sumer, B. Mutlu
2014-01-01
A fully-coupled hydrodynamic/morphodynamic numerical model is presented and utilized for the simulation of wave-induced scour and backfilling processes beneath submarine pipelines. The model is based on solutions to Reynolds-averaged Navier–Stokes equations, coupled with k−ω turbulence closure......≤30 demonstrate reasonable match with previous experiments, both in terms of the equilibrium scour depth as well as the scour time scale. Wave-induced backfilling processes are additionally studied by subjecting initial conditions taken from scour simulations with larger KC to new wave climates...... characterized by lower KC values. The simulations considered demonstrate the ability of the model to predict backfilling toward expected equilibrium scour depths based on the new wave climate, in line with experimental expectations. The simulated backfilling process is characterized by two stages: (1...
Roughness-induced streaming in turbulent wave boundary layers
DEFF Research Database (Denmark)
Fuhrman, David R.; Sumer, B. Mutlu; Fredsøe, Jørgen
2011-01-01
-averaged streaming characteristics induced by bottom roughness variations are systematically assessed. The effects of variable roughness ratio, gradual roughness transitions, as well as changing flow orientation in plan are all considered. As part of the latter, roughness-induced secondary flows are predicted...
Energization of helium ions by proton-induced hydromagnetic waves
International Nuclear Information System (INIS)
Gendrin, R.; Roux, A.
1980-01-01
We consider the diffusion of He + ions under the influence of ion cyclotron waves generated in a plasma consisting of three different ion populations: a thermal isotropic population containing both H + and He + ions and an energetic H + population, with a positive anisotropy A=T/sub perpendicular//T/sub parallel/-1. We compute, in the velocity space upsilon/sub parallel/, upsilon/sub perpendicular/, the diffusion curves that He + ions will follow in the presence of ion cyclotron waves propagating in such a medium. We show that for small concentrations of the He + ions, of the order of 1 to approx.10%, these ions can be energized by such a process up to and above suprathermal energies (E> or approx. =20 eV). On some occasions the He + ions may even reach energies of the order of the Alfven energy of the cold plasma population: E/sub a/approx. =m/sub p/V/sub a/ 2 approx. =5 keV. Characteristic diffusion times, in pitch angle and energy, for both ion species, are evaluated. They are of the order of 2 to 20 min. These theoretical results are discussed in the frame of recent observations by Geos experimenters showing the close association that exists between the occurrence of ion cyclotron ULF waves and the presence of thermal or supra-thermal He + ions in the equatorial region of the magnetosphere
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
Reduced Sodium Current in the Lateral Ventricular Wall Induces Inferolateral J-Waves.
Meijborg, Veronique M F; Potse, Mark; Conrath, Chantal E; Belterman, Charly N W; De Bakker, Jacques M T; Coronel, Ruben
2016-01-01
J-waves in inferolateral leads are associated with a higher risk for idiopathic ventricular fibrillation. We aimed to test potential mechanisms (depolarization or repolarization dependent) responsible for inferolateral J-waves. We hypothesized that inferolateral J-waves can be caused by regional delayed activation of myocardium that is activated late during normal conditions. Computer simulations were performed to evaluate how J-point elevation is influenced by reducing sodium current conductivity (GNa), increasing transient outward current conductivity (Gto), or cellular uncoupling in three predefined ventricular regions (lateral, anterior, or septal). Two pig hearts were Langendorff-perfused with selective perfusion with a sodium channel blocker of lateral or anterior/septal regions. Volume-conducted pseudo-electrocardiograms (ECG) were recorded to detect the presence of J-waves. Epicardial unipolar electrograms were simultaneously recorded to obtain activation times (AT). Simulation data showed that conduction slowing, caused by reduced sodium current, in lateral, but not in other regions induced inferolateral J-waves. An increase in transient outward potassium current or cellular uncoupling in the lateral zone elicited slight J-point elevations which did not meet J-wave criteria. Additional conduction slowing in the entire heart attenuated J-waves and J-point elevations on the ECG, because of masking by the QRS. Experimental data confirmed that conduction slowing attributed to sodium channel blockade in the left lateral but not in the anterior/septal ventricular region induced inferolateral J-waves. J-waves coincided with the delayed activation. Reduced sodium current in the left lateral ventricular myocardium can cause inferolateral J-waves on the ECG.
Secondary current properties generated by wind-induced water waves in experimental conditions
Directory of Open Access Journals (Sweden)
Michio Sanjou
2014-06-01
Full Text Available Secondary currents such as the Langmuir circulation are of high interest in natural rivers and the ocean because they have striking impacts on scour, sedimentation, and mass transport. Basic characteristics have been well-studied in straight open-channel flows. However, little is known regarding secondary circulation induced by wind waves. The presented study describes the generation properties of wind waves observed in the laboratory tank. Wind-induced water waves are known to produce large scale circulations. The phenomenon is observed together with high-speed and low-speed streaks, convergence and divergence zones, respectively. Therefore, it is important to determine the hydrodynamic properties of secondary currents for wind-induced water waves within rivers and lakes. In this study, using two high-speed CMOS cameras, stereoscopic particle image velocimetry (PIV measurements were conducted in order to reveal the distribution of all three components of velocity vectors. The experiments allowed us to investigate the three-dimensional turbulent structure under water waves and the generation mechanism of large-scale circulations. Additionally, a third CMOS camera was used to measure the spanwise profile of thefree-surface elevation. The time-series of velocity components and the free-surface were obtained simultaneously. From our experiments, free-surface variations were found to influence the instantaneous velocity distributions of the cross-sectional plane. We also considered thegeneration process by the phase analysis related to gravity waves and compared the contribution of the apparent stress.
Shock wave and flame front induced detonation in a rapid compression machine
Wang, Y.; Qi, Y.; Xiang, S.; Mével, R.; Wang, Z.
2018-05-01
The present study focuses on one mode of detonation initiation observed in a rapid compression machine (RCM). This mode is referred to as shock wave and flame front-induced detonation (SWFID). Experimental high-speed imaging and two-dimensional numerical simulations with skeletal chemistry are combined to unravel the dominant steps of detonation initiation under SWFID conditions. It is shown that the interaction between the shock wave generated by the end-gas auto-ignition and the spherical flame creates a region of high pressure and temperature which enables the acceleration of the flame front and the detonation onset. The experimental observation lacks adequate spatial and temporal resolution despite good reproducibility of the detonation onset. Based on the numerical results, phenomenological interpretation of the event within the framework of shock wave refraction indicates that the formation of a free-precursor shock wave at the transition between regular and irregular refraction may be responsible for detonation onset. The present results along with previous findings on shock wave reflection-induced detonation in the RCM indicate that super-knock occurs after the interaction of the shock wave generated by end-gas auto-ignition with the RCM walls, preignition flame, or another shock wave.
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.
Shock Induced Melting in Aluminum: Wave Profile Measurements
Energy Technology Data Exchange (ETDEWEB)
Chhabildas, Lalit C.; Furnish, Michael D.; Reinhart, William D.
1999-06-23
We have developed launch capabilities that can propel macroscopic plates to hypervelocities (8 to 16 km/s). This capability has been used to determine the first time-resolved wave profile measurements using velocity interferometry techniques at impact velocities of 10 km/s. These measurements show that alu- minum continues to exhibit normal release behavior to 161 GPa with complete loss of strength in the shocked state. Results of these experiments are discussed and compared with the results of lower pressure experi- ments conducted at lower impact velocities.
Measurement and modelling of bed shear induced by solitary waves
Digital Repository Service at National Institute of Oceanography (India)
JayaKumar, S.
kleiner reibung. Z. Math. Phys., 56: 1- 37. Burbidge, D. and Cummins, P., 2007. Assessing the threat to western australia from tsunami generated by earthquakes along the sunda arc. Natural Hazards, 43(3): 319-331. Christian, J.T., Taylor, P.K., Yen, J....E. and Bernard, E.N., 2006. Tsunami science before and beyond boxing day 2004. Philosophical Transactions - A Math Physics Engineering Science, 364(1845): 2231-2265. Tadepalli, S. and Synolakis, C.E., 1994. The run-up of n-waves on sloping beaches...
Chaos induced by breakup of waves in a spatial epidemic model with nonlinear incidence rate
International Nuclear Information System (INIS)
Sun, Gui-Quan; Jin, Zhen; Liu, Quan-Xing; Li, Li
2008-01-01
Spatial epidemiology is the study of spatial variation in disease risk or incidence, including the spatial patterns of the population. The spread of diseases in human populations can exhibit large scale patterns, underlining the need for spatially explicit approaches. In this paper, the spatiotemporal complexity of a spatial epidemic model with nonlinear incidence rate, which includes the behavioral changes and crowding effect of the infective individuals, is investigated. Based on both theoretical analysis and computer simulations, we find out when, under the parameters which can guarantee a stable limit cycle in the non-spatial model, spiral and target waves can emerge. Moreover, two different kinds of breakup of waves are shown. Specifically, the breakup of spiral waves is from the core and the breakup of target waves is from the far-field, and both kinds of waves become irregular patterns at last. Our results reveal that the spatiotemporal chaos is induced by the breakup of waves. The results obtained confirm that diffusion can form spiral waves, target waves or spatial chaos of high population density, which enrich the findings of spatiotemporal dynamics in the epidemic model
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
Effects of wave-induced forcing on a circulation model of the North Sea
Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian
2017-04-01
The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution NEMO model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force and the sea-state dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water level and current predictions.
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.
Bai, Zhengyang; Xu, Datang; Huang, Guoxiang
2017-01-23
We propose a scheme to realize the storage and retrieval of high-dimensional electromagnetic waves with orbital angular momentum (OAM) via plasmon-induced transparency (PIT) in a metamaterial, which consists of an array of meta-atoms constructed by a metallic structure loaded with two varactors. We show that due to PIT effect the system allows the existence of shape-preserving dark-mode plasmonic polaritons, which are mixture of electromagnetic-wave modes and dark oscillatory modes of the meta-atoms and may carry various OAMs. We demonstrate that the slowdown, storage and retrieval of multi-mode electromagnetic waves with OAMs can be achieved through the active manipulation of a control field. Our work raises the possibility for realizing PIT-based spatial multi-mode memory of electromagnetic waves and is promising for practical application of information processing with large capacity by using room-temperature metamaterials.
Body-wave seismic interferometry applied to earthquake- and storm-induced wavefield
Ruigrok, E.N.
2012-01-01
Seismology is the study of the vibration of the Earth. Seismologists pay much attention to the main source of Earth vibration: earthquakes. But also other seismic sources, like mining blasts, ocean storms and windmills, are studied. All these sources induce seismic waves, which can eventually be
Shock wave-induced evaporation of water droplets in a gas-droplet mixture 646
Goossens, H.W.J.; Cleijne, J.W.; Smolders, H.J.; Dongen, van M.E.H.
1988-01-01
A model is presented for the droplet evaporation process induced by a shock wave propagating in a fog. The model is based on the existence of a quasi-steady wet bulb state of the droplets during evaporation. It is shown that for moderate shock strength, Ma = <2,=" and=" droplet=" radii=" in=" the="
Wu, J. F.; Xue, X. H.; Hoffmann, L.; Dou, X. K.; Li, H. M.; Chen, T. D.
2015-01-01
Atmospheric gravity waves (GWs) significantly influence global circulation. Deep convection, particularly that associated with typhoons, is believed to be an important source of gravity waves. Stratospheric gravity waves induced by Typhoon Mindulle (2004) were detected by the Atmospheric Infrared Sounder (AIRS). Semicircular GWs with horizontal wavelengths of 100–400 km were found over Taiwan through an inspection of AIRS radiances at 4.3 μm. Characteristics of the stratospheric gravity waves...
Nonlinear mechanisms for drift wave saturation and induced particle transport
International Nuclear Information System (INIS)
Dimits, A.M.; Lee, W.W.
1989-12-01
A detailed theoretical study of the nonlinear dynamics of gyrokinetic particle simulations of electrostatic collisionless and weakly collisional drift waves is presented. In previous studies it was shown that, in the nonlinearly saturated phase of the evolution, the saturation levels and especially the particle fluxes have an unexpected dependence on collisionality. In this paper, the explanations for these collisionality dependences are found to be as follows: The saturation level is determined by a balance between the electron and ion fluxes. The ion flux is small for levels of the potential below an E x B-trapping threshold and increases sharply once this threshold is crossed. Due to the presence of resonant electrons, the electron flux has a much smoother dependence on the potential. In the 2-1/2-dimensional (''pseudo-3D'') geometry, the electrons are accelerated away from the resonance as they diffuse spatially, resulting in an inhibition of their diffusion. Collisions and three-dimensional effects can repopulate the resonance thereby increasing the value of the particle flux. 30 refs., 32 figs., 2 tabs
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...
Song, Zhongchang; Zhang, Yu; Wei, Chong; Wang, Xianyan
2016-01-01
Through numerically solving the appropriate wave equations, propagation of biosonar signals in a Chinese river dolphin (baiji) was studied. The interfacial waves along the rostrum-tissue interfaces, including both compressional (longitudinal) and shear (transverse) waves in the solid rostrum through fluid-solid coupling were examined. The baiji's rostrum was found to effect acoustic beam formation not only as an interfacial wave generator but also as a sound reflector. The wave propagation patterns in the solid rostrum were found to significantly change the wave movement through the bone. Vibrations in the rostrum, expressed in solid displacement, initially increased but eventually decreased from posterior to anterior sides, indicating a complex physical process. Furthermore, the comparisons among seven cases, including the combination of (1) the rostrum, melon, and air sacs; (2) rostrum-air sacs; (3) rostrum-melon; (4) only rostrum; (5) air sacs-melon; (6) only air sacs; and (7) only melon revealed that the cases including the rostrum were better able to approach the complete system by inducing rostrum-tissue interfacial waves and reducing the differences in main beam angle and -3 dB beam width. The interfacial waves in the rostrum were considered complementary with reflection to determine the obbligato role of the rostrum in the baiji's biosonar emission. The far-field beams formed from complete fluid-solid models and non-fluid-solid models were compared to reveal the effects brought by the consideration of shear waves of the solid structures of the baiji. The results may provide useful information for further understanding the role of the rostrum in this odontocete species.
Enhanced Chondrocyte Proliferation in a Prototyped Culture System with Wave-Induced Agitation
Directory of Open Access Journals (Sweden)
Pilarek Maciej
2017-06-01
Full Text Available One of the actual challenges in tissue engineering applications is to efficiently produce as high of number of cells as it is only possible, in the shortest time. In static cultures, the production of animal cell biomass in integrated forms (i.e. aggregates, inoculated scaffolds is limited due to inefficient diffusion of culture medium components observed in such non-mixed culture systems, especially in the case of cell-inoculated fiber-based dense 3D scaffolds, inside which the intensification of mass transfer is particularly important. The applicability of a prototyped, small-scale, continuously wave-induced agitated system for intensification of anchorage-dependent CP5 chondrocytes proliferation outside and inside three-dimensional poly(lactic acid (PLA scaffolds has been discussed. Fibrous PLA-based constructs have been inoculated with CP5 cells and then maintained in two independent incubation systems: (i non-agitated conditions and (ii culture with wave-induced agitation. Significantly higher values of the volumetric glucose consumption rate have been noted for the system with the wave-induced agitation. The advantage of the presented wave-induced agitation culture system has been confirmed by lower activity of lactate dehydrogenase (LDH released from the cells in the samples of culture medium harvested from the agitated cultures, in contrast to rather high values of LDH activity measured for static conditions. Results of the proceeded experiments and their analysis clearly exhibited the feasibility of the culture system supported with continuously wave-induced agitation for robust proliferation of the CP5 chondrocytes on PLA-based structures. Aside from the practicability of the prototyped system, we believe that it could also be applied as a standard method offering advantages for all types of the daily routine laboratory-scale animal cell cultures utilizing various fiber-based biomaterials, with the use of only regular laboratory
Numerical simulation of travelling wave induced electrothermal fluid flow
International Nuclear Information System (INIS)
Perch-Nielsen, Ivan R; Green, Nicolas G; Wolff, Anders
2004-01-01
Many microdevices for manipulating particles and cells use electric fields to produce a motive force on the particles. The movement of particles in non-uniform electric fields is called dielectrophoresis, and the usual method of applying this effect is to pass the particle suspension over a microelectrode structure. If the suspension has a noticeable conductivity, one important side effect is that the electric field drives a substantial conduction current through the fluid, causing localized Joule-heating. The resulting thermal gradient produces local conductivity and permittivity changes in the fluid. Dielectrophoretic forces acting upon these pockets of fluid will then produce motion of both the fluid and the particles. This paper presents a numerical solution of the electrical force and the resulting electrothermal driven fluid flow on a travelling wave structure. This common electrode geometry consists of interdigitated electrodes laid down in a long array, with the phase of the applied potential shifted by 90 0 on each subsequent electrode. The resulting travelling electric field was simulated and the thermal field and electrical body force on the fluid calculated, for devices constructed from two typical materials: silicon and glass. The electrothermal fluid flow in the electrolyte over the electrode array was then numerically simulated. The model predicts that the thermal field depends on the conductivity and applied voltage, but more importantly on the geometry of the system and the material used in the construction of the device. The velocity of the fluid flow depends critically on the same parameters, with slight differences in the thermal field for glass and silicon leading to diametrically opposite flow direction with respect to the travelling field for the two materials. In addition, the imposition of slight external temperature gradients is shown to have a large effect on the fluid flow in the device, under certain conditions leading to a reversal of
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....
A packet-based dual-rate PID control strategy for a slow-rate sensing Networked Control System.
Cuenca, A; Alcaina, J; Salt, J; Casanova, V; Pizá, R
2018-05-01
This paper introduces a packet-based dual-rate control strategy to face time-varying network-induced delays, packet dropouts and packet disorder in a Networked Control System. Slow-rate sensing enables to achieve energy saving and to avoid packet disorder. Fast-rate actuation makes reaching the desired control performance possible. The dual-rate PID controller is split into two parts: a slow-rate PI controller located at the remote side (with no permanent communication to the plant) and a fast-rate PD controller located at the local side. The remote side also includes a prediction stage in order to generate the packet of future, estimated slow-rate control actions. These actions are sent to the local side and converted to fast-rate ones to be used when a packet does not arrive at this side due to the network-induced delay or due to occurring dropouts. The proposed control solution is able to approximately reach the nominal (no-delay, no-dropout) performance despite the existence of time-varying delays and packet dropouts. Control system stability is ensured in terms of probabilistic Linear Matrix Inequalities (LMIs). Via real-time control for a Cartesian robot, results clearly reveal the superiority of the control solution compared to a previous proposal by authors. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.
Characteristics of laser-induced shock wave injury to the inner ear of rats
Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro
2014-12-01
Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.
Characteristics of laser-induced shock wave injury to the inner ear of rats.
Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro
2014-12-01
Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.
Confinement effects of shock waves on laser-induced plasma from a graphite target
Energy Technology Data Exchange (ETDEWEB)
Huang, Feiling; Liang, Peipei; Yang, Xu; Cai, Hua; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian, E-mail: jsun@fudan.edu.cn [Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China)
2015-06-15
The spatial confinement effects of shock waves on the laser-induced plasma (LIP) from a graphite target in air were studied by probe beam deflection (PBD) measurements and optical emission spectroscopy (OES). A clear relationship between the confinement of the LIP by the shock wave and the effects on the LIP emission was observed, and the underlying mechanisms are discussed. PBD monitoring revealed that the laser-ablation induced shock wave could be well analogized to the shock wave generated by a point explosion and would be reflected by a block. OES measurements indicated that the optical emission of the LIP exhibited significant variations with the block placement. A first enhancement and then a fast decay of CN molecular emission as well as a suppression of carbon atomic emission were observed in the presence of the block. The results revealed that the reflected shock wave spatially confined the expansion of the LIP and compressed the LIP after encountering it, pushing back the species of the LIP and changing the density of the LIP species including luminous carbon atoms and CN molecules. It is suggested that the change of the LIP emission is attributed to the density variation of the LIP species due to the compression of the LIP and the reactions occurring in the plasma.
Hickling, Susannah; Leger, Pierre; El Naqa, Issam
2016-02-11
Irradiating an object with a megavoltage photon beam generated by a clinical radiotherapy linear accelerator (linac) induces acoustic waves through the photoacoustic effect. The detection and characterization of such acoustic waves has potential applications in radiation therapy dosimetry. The purpose of this work was to gain insight into the properties of such acoustic waves by simulating and experimentally detecting them in a well-defined system consisting of a metal block suspended in a water tank. A novel simulation workflow was developed by combining radiotherapy Monte Carlo and acoustic wave transport simulation techniques. Different set-up parameters such as photon beam energy, metal block depth, metal block width, and metal block material were varied, and the simulated and experimental acoustic waveforms showed the same relative amplitude trends and frequency variations for such setup changes. The simulation platform developed in this work can easily be extended to other irradiation situations, and will be an invaluable tool for developing a radiotherapy dosimetry system based on the detection of the acoustic waves induced following linear accelerator irradiation.
Three-dimensional wave-induced current model equations and radiation stresses
Xia, Hua-yong
2017-08-01
After the approach by Mellor (2003, 2008), the present paper reports on a repeated effort to derive the equations for three-dimensional wave-induced current. Via the vertical momentum equation and a proper coordinate transformation, the phase-averaged wave dynamic pressure is well treated, and a continuous and depth-dependent radiation stress tensor, rather than the controversial delta Dirac function at the surface shown in Mellor (2008), is provided. Besides, a phase-averaged vertical momentum flux over a sloping bottom is introduced. All the inconsistencies in Mellor (2003, 2008), pointed out by Ardhuin et al. (2008) and Bennis and Ardhuin (2011), are overcome in the presently revised equations. In a test case with a sloping sea bed, as shown in Ardhuin et al. (2008), the wave-driving forces derived in the present equations are in good balance, and no spurious vertical circulation occurs outside the surf zone, indicating that Airy's wave theory and the approach of Mellor (2003, 2008) are applicable for the derivation of the wave-induced current model.
Surface solitons of four-wave mixing in an electromagnetically induced lattice
International Nuclear Information System (INIS)
Zhang, Yanpeng; Yuan, Chenzhi; Zhang, Yiqi; Zheng, Huaibin; Chen, Haixia; Li, Changbiao; Wang, Zhiguo; Xiao, Min
2013-01-01
By creating lattice states with two-dimensional spatial periodic atomic coherence, we report an experimental demonstration of generating two-dimensional surface solitons of a four-wave mixing signal in an electromagnetically induced lattice composed of two electromagnetically induced gratings with different orientations in an atomic medium, each of which can support a one-dimensional surface soliton. The surface solitons can be well controlled by different experimental parameters, such as probe frequency, pump power, and beam incident angles, and can be affected by coherent induced defect states. (letter)
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.
Forced wave induced by an atmospheric pressure disturbance moving towards shore
Chen, Yixiang; Niu, Xiaojing
2018-05-01
Atmospheric pressure disturbances moving over a vast expanse of water can induce different wave patterns, which can be determined by the Froude number Fr. Generally, Fr = 1 is a critical value for the transformation of the wave pattern and the well-known Proudman resonance happens when Fr = 1. In this study, the forced wave induced by an atmospheric pressure disturbance moving over a constant slope from deep sea to shore is numerically investigated. The wave pattern evolves from a concentric-circle type into a triangular type with the increase of the Froude number, as the local water depth decreases, which is in accord with the analysis in the unbounded flat-bottom cases. However, a hysteresis effect has been observed, which implies the obvious amplification of the forced wave induced by a pressure disturbance can not be simply predicted by Fr = 1. The effects of the characteristic parameters of pressure disturbances and slope gradient have been discussed. The results show that it is not always possible to observe significant peak of the maximum water elevation before the landing of pressure disturbances, and a significant peak can be generated by a pressure disturbance with small spatial scale and fast moving velocity over a milder slope. Besides, an extremely high run-up occurs when the forced wave hits the shore, which is an essential threat to coastal security. The results also show that the maximum run-up is not monotonously varying with the increase of disturbance moving speed and spatial scale. There exists a most dangerous speed and scale which may cause disastrous nearshore surge.
Study on THz wave generation from air plasma induced by quasi-square Airy beam
Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin
2018-01-01
Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.
Godin, Lindsay M; Suzuki, Sakiko; Jacobs, Christopher R; Donahue, Henry J; Donahue, Seth W
2007-11-01
An early response to mechanical stimulation of bone cells in vitro is an increase in intracellular calcium concentration ([Ca (2+)](i)). This study analyzed the [Ca (2+)](i) wave area, magnitude, duration, rise time, fall time, and time to onset in individual osteoblasts for two identical bouts of mechanical stimulation separated by a 30-min rest period. The area under the [Ca (2+)](i) wave increased in the second loading bout compared to the first. This suggests that rest periods may potentiate mechanically induced intracellular calcium signals. Furthermore, many of the [Ca (2+)](i) wave parameters were strongly, positively correlated between the two bouts of mechanical stimulation. For example, in individual primary osteoblasts, if a cell had a large [Ca (2+)](i) wave area in the first bout it was likely to have a large [Ca (2+)](i) wave area in the second bout (r (2) = 0.933). These findings support the idea that individual bone cells have "calcium fingerprints" (i.e., a unique [Ca (2+)](i) wave profile that is reproducible for repeated exposure to a given stimulus).
Rogue waves and W-shaped solitons in the multiple self-induced transparency system.
Wang, Xin; Liu, Chong; Wang, Lei
2017-09-01
We study localized nonlinear waves on a plane wave background in the multiple self-induced transparency (SIT) system, which describes an important enhancement of the amplification and control of optical waves compared to the single SIT system. A hierarchy of exact multiparametric rational solutions in a compact determinant representation is presented. We demonstrate that this family of solutions contain known rogue wave solutions and unusual W-shaped soliton solutions. State transitions between the fundamental rogue waves and W-shaped solitons as well as higher-order nonlinear superposition modes are revealed in the zero-frequency perturbation region by the suitable choice for the background wavenumber of the electric field component. Particularly, it is found that the multiple SIT system can admit both stationary and nonstationary W-shaped solitons in contrast to the stationary results in the single SIT system. Moreover, the W-shaped soliton complex which is formed by a certain number of fundamental W-shaped solitons with zero phase parameters and its decomposition mechanism in the case of the nonzero phase parameters are shown. Meanwhile, some important characteristics of the nonlinear waves including trajectories and spectrum are discussed through the numerical and analytical methods.
Shifts and widths of p-wave confinement induced resonances in atomic waveguides
International Nuclear Information System (INIS)
Saeidian, Shahpoor; Melezhik, Vladimir S; Schmelcher, Peter
2015-01-01
We develop and analyze a theoretical model to study p-wave Feshbach resonances of identical fermions in atomic waveguides by extending the two-channel model of Lange et al (2009 Phys. Rev. A 79 013622) and Saeidian et al (2012 Phys. Rev. A 86 062713). The experimentally known parameters of Feshbach resonances in free space are used as input of the model. We calculate the shifts and widths of p-wave magnetic Feshbach resonance of 40 K atoms emerging in harmonic waveguides as p-wave confinement induced resonance (CIR). Particularly, we show a possibility to control the width and shift of the p-wave CIR by the trap frequency and the applied magnetic field which could be used in corresponding experiments. Our analysis also demonstrates the importance of the inclusion of the effective range in the computational schemes for the description of the p-wave CIRs contrary to the case of s-wave CIRs where the influence of this term is negligible. (paper)
Ionospheric Bow Waves and Perturbations Induced by the 21 August 2017 Solar Eclipse
Zhang, Shun-Rong; Erickson, Philip J.; Goncharenko, Larisa P.; Coster, Anthea J.; Rideout, William; Vierinen, Juha
2017-12-01
During solar eclipses, the Moon's shadow causes a large reduction in atmospheric energy input, including not only the stratosphere but also the thermosphere and ionosphere. The eclipse shadow has a supersonic motion which is theoretically expected to generate atmospheric bow waves, similar to a fast-moving river boat, with waves starting in the lower atmosphere and propagating into the ionosphere. However, previous geographically limited observations have had difficulty detecting these weak waves within the natural background atmospheric variability, and the existence of eclipse-induced ionospheric waves and their evolution in a complex coupling system remain controversial. During the 21 August 2017 eclipse, high fidelity and wide coverage ionospheric observations provided for the first time an oversampled set of eclipse data, using a dense network of Global Navigation Satellite System receivers at ˜2,000 sites in North America. We show the first unambiguous evidence of ionospheric bow waves as electron content disturbances over central/eastern United States, with ˜1 h duration, 300-400 km wavelength and 280 m/s phase speed emanating from and tailing the totality region. We also identify large ionospheric perturbations moving at the supersonic speed of the maximum solar obscuration which are too fast to be associated with known gravity wave or large-scale traveling ionospheric disturbance processes. This study reveals complex interconnections between the Sun, Moon, and Earth's neutral atmosphere and ionosphere and demonstrates persistent coupling processes between different components of the Earth's atmosphere, a topic of significant community interest.
Birefringence induced by pp-wave modes in an electromagnetically active dynamic aether
International Nuclear Information System (INIS)
Alpin, Timur Yu.; Balakin, Alexander B.
2017-01-01
In the framework of the Einstein-Maxwell-aether theory we study the birefringence effect, which can occur in the pp-wave symmetric dynamic aether. The dynamic aether is considered to be a latently birefringent quasi-medium, which displays this hidden property if and only if the aether motion is non-uniform, i.e., when the aether flow is characterized by the non-vanishing expansion, shear, vorticity or acceleration. In accordance with the dynamo-optical scheme of description of the interaction between electromagnetic waves and the dynamic aether, we shall model the susceptibility tensors by the terms linear in the covariant derivative of the aether velocity four-vector. When the pp-wave modes appear in the dynamic aether, we deal with a gravitationally induced degeneracy removal with respect to hidden susceptibility parameters. As a consequence, the phase velocities of electromagnetic waves possessing orthogonal polarizations do not coincide, thus displaying the birefringence effect. Two electromagnetic field configurations are studied in detail: longitudinal and transversal with respect to the aether pp-wave front. For both cases the solutions are found, which reveal anomalies in the electromagnetic response on the action of the pp-wave aether mode. (orig.)
Birefringence induced by pp-wave modes in an electromagnetically active dynamic aether
Energy Technology Data Exchange (ETDEWEB)
Alpin, Timur Yu.; Balakin, Alexander B. [Kazan Federal University, Department of General Relativity and Gravitation, Institute of Physics, Kazan (Russian Federation)
2017-10-15
In the framework of the Einstein-Maxwell-aether theory we study the birefringence effect, which can occur in the pp-wave symmetric dynamic aether. The dynamic aether is considered to be a latently birefringent quasi-medium, which displays this hidden property if and only if the aether motion is non-uniform, i.e., when the aether flow is characterized by the non-vanishing expansion, shear, vorticity or acceleration. In accordance with the dynamo-optical scheme of description of the interaction between electromagnetic waves and the dynamic aether, we shall model the susceptibility tensors by the terms linear in the covariant derivative of the aether velocity four-vector. When the pp-wave modes appear in the dynamic aether, we deal with a gravitationally induced degeneracy removal with respect to hidden susceptibility parameters. As a consequence, the phase velocities of electromagnetic waves possessing orthogonal polarizations do not coincide, thus displaying the birefringence effect. Two electromagnetic field configurations are studied in detail: longitudinal and transversal with respect to the aether pp-wave front. For both cases the solutions are found, which reveal anomalies in the electromagnetic response on the action of the pp-wave aether mode. (orig.)
Striped morphologies induced by magnetic impurities in d-wave superconductors
International Nuclear Information System (INIS)
Zuo Xianjun
2011-01-01
Research Highlights: → We investigate striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs). → For the single-impurity and two-impurity cases, modulated checkerboard pattern and stripe-like structures are induced. → When more magnetic impurities are inserted, more complex modulated structures could be induced, including rectilinear and right-angled stripes and quantum-corral-like structures. → Impurities could induce complex striped morphologies in DSCs. - Abstract: We study striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping by self-consistently solving the Bogoliubov-de Gennes equations based on the t - t' - U - V model. For the single-impurity case, it is found that the stable ground state is a modulated checkerboard pattern. For the two-impurity case, the stripe-like structures in order parameters are induced due to the impurity-pinning effect. The modulations of DSC and charge orders share the same period of four lattice constants (4a), which is half the period of modulations in the coexisting spin order. Interestingly, when three or more impurities are inserted, the impurities could induce more complex striped morphologies due to quantum interference. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.
Numerical study of laser-induced blast wave coupled with unsteady ionization processes
International Nuclear Information System (INIS)
Ogino, Y; Ohnishi, N; Sawada, K
2008-01-01
We present the results of the numerical simulation of laser-induced blast wave coupled with rate equations to clarify the unsteady property of ionization processes during pulse heating. From comparison with quasi-steady computations, the plasma region expands more widely, which is sustained by the inverse-bremsstrahlung since an ionization equilibrium does not establish at the front of the plasma region. The delayed relaxation leads to the rapid expansion of the driving plasma and enhances the energy conversion efficiency from a pulse heating laser to the blast wave
Parametrically tunable soliton-induced resonant radiation by three-wave mixing
DEFF Research Database (Denmark)
Zhou, Binbin; Liu, Xing; Guo, Hairun
2017-01-01
We show that a temporal soliton can induce resonant radiation by three-wave mixing nonlinearities. This constitutes a new class of resonant radiation whose spectral positions are parametrically tunable. The experimental verification is done in a periodically poled lithium niobate crystal, where...... a femtosecond near-IR soliton is excited and resonant radiation waves are observed exactly at the calculated soliton phasematching wavelengths via the sum- and difference-frequency generation nonlinearities. This extends the supercontinuum bandwidth well into the mid IR to span 550–5000 nm, and the mid-IR edge...
S-wave kaon-nucleon phase shifts with instanton induced effects
International Nuclear Information System (INIS)
Lemaire, S.; Labarsouque, J.; Silvestre-Brac, B.
2003-01-01
The kaon-nucleon S-wave phase shifts have been calculated, for both isospin channels I=0 and I=1, in the framework of a semirelativistic quark potential model which includes an instanton induced force. The agreement with experimental phase shifts is poor essentially because of a dominant attraction coming from instantons. The low-energy behaviour of S-wave phase shifts, for I=0 and I=1 channels, obtained in the kaon-nucleon system is characteristic of a potential which can produce one loosely bound state
S-wave kaon-nucleon phase shifts with instanton induced effects
Energy Technology Data Exchange (ETDEWEB)
Lemaire, S. E-mail: lemaire@cenbg.in2p3.fr; Labarsouque, J.; Silvestre-Brac, B
2003-09-22
The kaon-nucleon S-wave phase shifts have been calculated, for both isospin channels I=0 and I=1, in the framework of a semirelativistic quark potential model which includes an instanton induced force. The agreement with experimental phase shifts is poor essentially because of a dominant attraction coming from instantons. The low-energy behaviour of S-wave phase shifts, for I=0 and I=1 channels, obtained in the kaon-nucleon system is characteristic of a potential which can produce one loosely bound state.
Phase separation and d-wave superconductivity induced by extended electron-exciton interaction
Energy Technology Data Exchange (ETDEWEB)
Cheng Ming [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)], E-mail: cheng896@hotmail.com; Su Wupei [Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Road, Houston, Texas 77204 (United States)
2008-12-15
Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling.
Phase separation and d-wave superconductivity induced by extended electron-exciton interaction
International Nuclear Information System (INIS)
Cheng Ming; Su Wupei
2008-01-01
Using an auxiliary-field quantum Monte Carlo (AFQMC) method, we have studied a two-dimensional tight-binding model in which the conduction electrons can polarize an adjacent layer of molecules through electron-electron repulsion. Calculated average conduction electron density as a function of chemical potential exhibits a clear break characteristic of phase separation. Compared to the noninteracting system, the d-wave pair-field correlation function shows significant enhancement. The simultaneous presence of phase separation and d-wave superconductivity suggests that an effective extended pairing force is induced by the electron-exciton coupling
Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water
Ge, Zhongfu; Whitman, Richard L.; Nevers, Meredith B.; Phanikumar, Mantha S.
2012-01-01
Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s–1). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731–6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.
Kuwahara, M.; Ioritani, N.; Kambe, K.; Taguchi, K.; Saito, T.; Igarashi, M.; Shirai, S.; Orikasa, S.; Takayama, K.
1990-07-01
On an ultrasonic imaging system a hyperechoic region was observed in a focal area of fucused shock waves in the dog kidney. This study was performed to learn whether cavitation bubbles are responsible for this hyperechoic region. The ultrasonic images in water of varying temperatures were not markedly different. In the flowing stream of distilled water, the stream was demonstrated as a hyperechoic region only with a mixture of air bubbles. Streams of 5%-50% glucose solutions were also demonstrated as a hyperechoic region. However, such concentration changes in living tissue, as well as thermal changes, are hardly thought to be induced. The holographic interferometry showed that the cavitation bubbles remained for more than 500 msec. in the focal area in water. This finding indicate that the bubble can remain for longer period than previously supposed. These results support the contentions that cavitation bubbles are responsible for the hyperechoic region in the kidney in situ.
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.
Dreier, Norman; Fröhle, Peter
2017-12-01
The knowledge of the wave-induced hydrodynamic loads on coastal dikes including their temporal and spatial resolution on the dike in combination with actual water levels is of crucial importance of any risk-based early warning system. As a basis for the assessment of the wave-induced hydrodynamic loads, an operational wave now- and forecast system is set up that consists of i) available field measurements from the federal and local authorities and ii) data from numerical simulation of waves in the German Bight using the SWAN wave model. In this study, results of the hindcast of deep water wave conditions during the winter storm on 5-6 December, 2013 (German name `Xaver') are shown and compared with available measurements. Moreover field measurements of wave run-up from the local authorities at a sea dike on the German North Sea Island of Pellworm are presented and compared against calculated wave run-up using the EurOtop (2016) approach.
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.
International Nuclear Information System (INIS)
Rizzato, F.B.
1992-01-01
A nonlinear emission mechanism of electromagnetic waves at the fundamental plasma frequency has been examined. This mechanism is based on the electromagnetic oscillating two-stream instability driven by two oppositely propagating Langmuir waves. The excitation of the electromagnetic oscillating two-stream instability is due to nonlinear wave-wave coupling involving Langmuir waves, low-frequency density waves and electromagnetic waves. The Chian and Alves model is improved using the generalized Zakharov equations. Attention is directed toward the influence of induced low-frequency and Langmuir waves on the properties of the electromagnetic oscillating two-stream instability. Presumably, the properties derived in the present context may be relevant to both space and laboratory plasmas. (author)
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.
Mathematical modeling of calcium waves induced by mechanical stimulation in keratinocytes.
Directory of Open Access Journals (Sweden)
Yasuaki Kobayashi
Full Text Available Recent studies have shown that the behavior of calcium in the epidermis is closely related to the conditions of the skin, especially the differentiation of the epidermal keratinocytes and the permeability barrier function, and therefore a correct understanding of the calcium dynamics is important in explaining epidermal homeostasis. Here we report on experimental observations of in vitro calcium waves in keratinocytes induced by mechanical stimulation, and present a mathematical model that can describe the experimentally observed wave behavior that includes finite-range wave propagation and a ring-shaped pattern. A mechanism of the ring formation hypothesized by our model may be related to similar calcium propagation patterns observed during the wound healing process in the epidermis. We discuss a possible extension of our model that may serve as a tool for investigating the mechanisms of various skin diseases.
Observation of Atom Wave Phase Shifts Induced by Van Der Waals Atom-Surface Interactions
International Nuclear Information System (INIS)
Perreault, John D.; Cronin, Alexander D.
2005-01-01
The development of nanotechnology and atom optics relies on understanding how atoms behave and interact with their environment. Isolated atoms can exhibit wavelike (coherent) behavior with a corresponding de Broglie wavelength and phase which can be affected by nearby surfaces. Here an atom interferometer is used to measure the phase shift of Na atom waves induced by the walls of a 50 nm wide cavity. To our knowledge this is the first direct measurement of the de Broglie wave phase shift caused by atom-surface interactions. The magnitude of the phase shift is in agreement with that predicted by Lifshitz theory for a nonretarded van der Waals interaction. This experiment also demonstrates that atom waves can retain their coherence even when atom-surface distances are as small as 10 nm
EEG slow-wave coherence changes in propofol-induced general anesthesia: Experiment and theory
Directory of Open Access Journals (Sweden)
Kaier eWang
2014-10-01
Full Text Available The electroencephalogram (EEG patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. [Physical Review X 3(2, 021005 (2013] proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing and time (Hopf, modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing--Hopf balance (wake to Hopf-dominated chaotic slow-waves (unconsciousness. Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05--1.5 Hz slow-wave coherence between frontal, occipital, and frontal-occipital electrode pairs, with the most pronounced wake-versus-unconscious coherence changes occurring at the frontal cortex.
International Nuclear Information System (INIS)
Zhu, Jinrong; Han, Zhaoyan; Su, Yuanchang; Hu, Jingguo
2014-01-01
The mechanism of the domain wall (DW) motions induced by spin wave in finite magnetic nanostripe is studied by micromagnetic simulations. We find that the spin-wave induced DM motions are always accompanied by an energy imbalance between two sides of the DW. The DW motion can be attributed to the expansion of the low-energy-density area and the contraction of the high-energy-density area. The energy imbalance strongly depends on whether the spin wave passes through the DW or is reflected by the DW. In the area of the spin wave propagation, the energy density increases with the time. However, in the superposition area of the incident spin wave and the reflected spin wave, the energy density decreases with the increasing of the time. It shows that this energy imbalance can be controlled by tuning the frequency of the spin wave. Finally, the effect of the damping parameter value is discussed. - Highlights: • The mechanism of the spin-wave induced DW motions is studied. • The spin-wave induced DW motions and the energy imbalance mechanism are given. • The DW motion with the same direction to that of SW is explained. • The DW motion with the opposite direction to that of SW is explained
Gojani, Ardian B.; Danehy, Paul M.; Alderfer, David W.; Saito, Tsutomu; Takayama, Kazuyoshi
2004-02-01
In Extracorporeal Shock Wave Lithotripsy (ESWL) underwater shock wave focusing generates high pressures at very short duration of time inside human body. However, it is not yet clear how high temperatures are enhanced at the spot where a shock wave is focused. The estimation of such dynamic temperature enhancements is critical for the evaluation of tissue damages upon shock loading. For this purpose in the Interdisciplinary Shock Wave Research Center a technique is developed which employs laser induced thermal acoustics or Laser Induced Grating Spectroscopy. Unlike most of gas-dynamic methods of measuring physical quantities this provides a non-invasive one having spatial and temporal resolutions of the order of magnitude of 1.0 mm 3 and 400 ns, respectively. Preliminary experiments in still water demonstrated that this method detected sound speed and hence temperature in water ranging 283 K to 333 K with errors of 0.5%. These results are used to empirically establish the equation of states of water, gelatin or agar cell which will work as alternatives of human tissues.
Vortex-Induced Waves in Two-Phase Liquid-Liquid Flows past Bluff Body
Zainal Abidin, M. I. I.; Park, Kyeong H.; Angeli, Panagiota; Xie, Zhihua; Kahouadji, Lyes; Matar, Omar K.
2017-11-01
Transverse cylinders of various sizes are used to generate vortex-induced interfacial waves in two-phase oil-water flows and to influence flow pattern transitions. The vortex shedding properties at different cylinder sizes and the resulting induced waves are studied experimentally with Particle Image Velocimetry (PIV) and high-speed imaging. The system consists of a 7 m long horizontal 37 mm ID acrylic pipe and different cylinders with diameters of 2, 5 and 8 mm, located in the water phase, 460 mm after the two phases come into contact. The cylinder generates waves with frequencies similar to the von Karman vortices and changes in vortex shedding properties at different cylinder size are reflected on the resulting interfacial wave characteristics. The presence of the transverse cylinder actuates the transition from stratified to dispersed flows; the boundary between the two patterns is shifted to lower mixture velocity with increasing cylinder size. Three-dimensional numerical simulation of the system is developed to assist in designing new system. Project funded by EPSRC UK and Memphis Grant.
Impact induced damage assessment by means of Lamb wave image processing
Kudela, Pawel; Radzienski, Maciej; Ostachowicz, Wieslaw
2018-03-01
The aim of this research is an analysis of full wavefield Lamb wave interaction with impact-induced damage at various impact energies in order to find out the limitation of the wavenumber adaptive image filtering method. In other words, the relation between impact energy and damage detectability will be shown. A numerical model based on the time domain spectral element method is used for modeling of Lamb wave propagation and interaction with barely visible impact damage in a carbon-epoxy laminate. Numerical studies are followed by experimental research on the same material with an impact damage induced by various energy and also a Teflon insert simulating delamination. Wavenumber adaptive image filtering and signal processing are used for damage visualization and assessment for both numerical and experimental full wavefield data. It is shown that it is possible to visualize and assess the impact damage location, size and to some extent severity by using the proposed technique.
Sheared electric field-induced suppression of edge turbulence using externally driven R.F. waves
International Nuclear Information System (INIS)
Craddock, G.G.; Diamond, P.H.
1991-01-01
Here the authors propose a novel method for active control and suppression of edge turbulence by sheared ExB flows driven by externally launched RF waves. The theory developed addresses the problem of open-quotes flow driveclose quotes, which is somewhat analogous to the problem of plasma current drive. As originally demonstrated for the case of spontaneously driven flows, a net difference in the gradient of the fluid and magnetic Reynolds' stresses produced by radially propagating waves can drive the plasma flow. For the prototypical case of the Alfven wave flow drive considered here, ρ 0 r v θ > - r B θ > is proportional to k perpendicular 2 ρ s 2 in the case of the kinetic Alfven wave, and [(ηk perpendicular 2 -vk perpendicular 2 )/ω] 2 in the case of resistive MHD. Both results reflect the dependence of flow drive on the net stress imbalance. The shear layer width is determined by the waves evanescence length (determined by dissipation) that sets the stress gradient scale length, while the direction of the flow is determined by the poloidal orientation of the launched waves. In particular, it should be noted that both positive and negative E r may be driven, so that enhanced confinement need not be accompanied by impurity accumulation, as commonly encountered in spontaneous H-modes. The efficiency is determined by the criterion that the radial electric field shear be large enough to suppress turbulence. For typical TEXT parameters, and unity efficiency, 300 kW of absorbed power is needed to suppress turbulence over 3 cm radially. For DIII-D, 300 kW over 4 cm is needed. Also, direct transport losses induced by RF have been shown to be small. Extensions of the theory to ICRF are underway and are discussed. They also discuss the analogous problem of current drive using kinetic Alfven waves. 2 refs
Delay-induced wave instabilities in single-species reaction-diffusion systems
Otto, Andereas; Wang, Jian; Radons, Günter
2017-11-01
The Turing (wave) instability is only possible in reaction-diffusion systems with more than one (two) components. Motivated by the fact that a time delay increases the dimension of a system, we investigate the presence of diffusion-driven instabilities in single-species reaction-diffusion systems with delay. The stability of arbitrary one-component systems with a single discrete delay, with distributed delay, or with a variable delay is systematically analyzed. We show that a wave instability can appear from an equilibrium of single-species reaction-diffusion systems with fluctuating or distributed delay, which is not possible in similar systems with constant discrete delay or without delay. More precisely, we show by basic analytic arguments and by numerical simulations that fast asymmetric delay fluctuations or asymmetrically distributed delays can lead to wave instabilities in these systems. Examples, for the resulting traveling waves are shown for a Fisher-KPP equation with distributed delay in the reaction term. In addition, we have studied diffusion-induced instabilities from homogeneous periodic orbits in the same systems with variable delay, where the homogeneous periodic orbits are attracting resonant periodic solutions of the system without diffusion, i.e., periodic orbits of the Hutchinson equation with time-varying delay. If diffusion is introduced, standing waves can emerge whose temporal period is equal to the period of the variable delay.
Acoustic streaming induced by two orthogonal ultrasound standing waves in a microfluidic channel.
Doinikov, Alexander A; Thibault, Pierre; Marmottant, Philippe
2018-07-01
A mathematical model is derived for acoustic streaming in a microfluidic channel confined between a solid wall and a rigid reflector. Acoustic streaming is produced by two orthogonal ultrasound standing waves of the same frequency that are created by two pairs of counter-propagating leaky surface waves induced in the solid wall. The magnitudes and phases of the standing waves are assumed to be different. Full analytical solutions are found for the equations of acoustic streaming. The obtained solutions are used in numerical simulations to reveal the structure of the acoustic streaming. It is shown that the interaction of two standing waves leads to the appearance of a cross term in the equations of acoustic streaming. If the phase lag between the standing waves is nonzero, the cross term brings about circular vortices with rotation axes perpendicular to the solid wall of the channel. The vortices make fluid particles rotate and move alternately up and down between the solid wall and the reflector. The obtained results are of immediate interest for acoustomicrofluidic applications such as the ultrasonic micromixing of fluids and the manipulation of microparticles. Copyright © 2018 Elsevier B.V. All rights reserved.
Contribution of wave-induced liquefaction in triggering hyperpycnal flows in Yellow River Estuary
Liu, X.; Jia, Y.
2017-12-01
Hyperpycnal flows, driven mainly by the gravity of near-bed negatively buoyant layers, are one of the most important processes for moving marine sediment across the earth. The issue of hyperpycnal flows existing in marine environment has drawn increasing scholars' attention since that was observed in situ off the Yellow River estuary in the 1980s. Most researches maintain that hyperpycnal flows in the Yellow River estuary are caused by the high-concentration sediments discharged from the Yellow River into sea, however, other mechanisms have been discounted since the sediment input from the river has been significantly changed due to climate and anthropogenic change. Here we demonstrate that wave-seabed interactions can generate hyperpycnal flows, without river input, by sediment flux convergence above an originally consolidated seabed. Using physical model experiments and multi-sensor field measurements, we characterize the composition-dependent liquefaction properties of the sediment due to wave-induced pore water pressure accumulation. This allows quantification of attenuation of sediment threshold velocity and critical shear stress (predominant variables in transport mechanics) during the liquefaction under waves. Parameterising the wave-seabed interactions in a new concept model shows that high waves propagating over the seabed sediment can act as a scarifier plough remoulding the seabed sediment. This contributes to marine hyperpycnal flows as the sediment is quickly resuspended under accumulating attenuation in strength. Therefore, the development of more integrative numerical models could supply realistic predictions of marine record in response to rising magnitude and frequency of storms.
Welding induced residual stress evaluation using laser-generated Rayleigh waves
Ye, Chong; Zhou, Yuanlai; Reddy, Vishnu V. B.; Mebane, Aaron; Ume, I. Charles
2018-04-01
Welding induced residual stress could affect the dimensional stability, fatigue life, and chemical resistance of the weld joints. Ultrasonic method serves as an important non-destructive tool for the residual stress evaluation due to its easy implementation, low cost and wide application to different materials. Residual stress would result in the ultrasonic wave velocity variation, which is the so called acoustoelastic effect. In this paper, Laser/EMAT ultrasonic technique was proposed to experimentally study the relative velocity variation ΔV/V of Rayleigh wave, which has the potential to evaluate surface/subsurface longitudinal residual stress developed during the Gas Metal Arc Welding process. Broad band ultrasonic waves were excited by pulsed Q-Switched Nd: YAG laser. An electromagnetic acoustic transducer (EMAT) attached to the welded plates was used to capture the Rayleigh wave signals propagating along the weld seam direction. Different time of flight measurements were conducted by varying the distance between the weld seam and Rayleigh wave propagating path in the range of 0 to 45 mm. The maximum relative velocity difference was found on the weld seam. With the increasing distance away from the weld seam, the relative velocity difference sharply decreased to negative value. With further increase in distance, the relative velocity difference slowly increased and approached zero. The distribution of relative velocity variations indicates that tensile stress appears in the melted zone as it becomes compressive near the heat-affected zone.
A study on early microstructural changes in the rabbit gallbladder induced by shock waves
Energy Technology Data Exchange (ETDEWEB)
Oh, Eun Oak [Hong-Sung Koryo Hospital, Hongsung (Korea, Republic of); Shim, Hyung Jin; Kim, Kun Sang; Ryo, Dae Sik; Choi, Yun Sun; Song, In Sup; Kim, Young Koo [College of Medicine, Chung Ang University, Seoul (Korea, Republic of)
1994-05-15
In order to evaluate microstructural changes after shock wave exposure, gross, light microscopic and transmission electron microscopic findings were analyzed with rabbit gallbladders. A preliminary study(2 rabbits) was performed to determine the dosage intensity of shock waves needed to inflict damage, using a EDAP LT 01 piezoelectric extracorporeal shock wave lothotriptor. The Gallbladders of three different groups of rabbits were given shock waves of various intensity. A storage value of 100, 50, 25 at rate of 20/sec under 80% power were given to group I (4 rabbits), group II (4 rabbits), and group III (3 rabbits), respectively. The rabbits were sacrificed 6-12 hours later. The observed pathologic changes in the transmission electron microscopy were vaculization of cytoplasm and swelling of epithelial cells with dilatation and structural alteration of intracellular organelles, especially endoplasmic reticulum. Cell membrane rupture and necrosis were observed at the markedly affected area. The structural changes of intracellular organelles were minimally found at a storage value of 25. However, above pathologic changes with dilatation and structural alterations of endoplasmic reticulums were more profound at value of 100. Early histologic changes induced by shocked waves are dose dependent and findings of cellular damage caused by ESWL might be explained as above.
Enhancement of four-wave mixing induced by interacting dark resonances
International Nuclear Information System (INIS)
Yang Weifeng; Gong Shangqing; Niu Yueping; Jin Shiqi; Xu Zhizhan
2005-01-01
We analyse a four-wave mixing (FWM) scheme in a five-level atomic system in which double-dark resonances are present. It is found that the enhancement of FWM in both electromagnetically induced transparency (EIT) windows can be obtained even without the condition of multiphoton resonance. Moreover, the conversion efficiency of FWM in one EIT window can be much larger than that in the other due to the presence of interacting dark resonances
Perirenal hematomas induced by extracorporeal shock wave lithotripsy (ESWL). Therapeutic management.
Labanaris, Apostolos P; Kühn, Reinhard; Schott, Günter E; Zugor, Vahudin
2007-09-17
Extracorporeal shock wave lithotripsy (ESWL) is nowadays accepted as the treatment of choice for the majority of patients with renal or proximal ureteral calculi. Although, a relatively noninvasive modality with low morbidity, minor or major complications can be noted. A relative severe complication for the patient and confusing for the treating physician is the perirenal hematoma. With review the literature and an example of perirenal hematoma induced by ESWL in a patient treated in our department, we describe its therapeutic management.
Internal swells in the tropics: Near-inertial wave energy fluxes and dissipation during CINDY
Soares, S. M.; Natarov, A.; Richards, K. J.
2016-05-01
A developing MJO event in the tropical Indian Ocean triggered wind disturbances that generated inertial oscillations in the surface mixed layer. Subsequent radiation of near-inertial waves below the mixed layer produced strong turbulence in the pycnocline. Linear plane wave dynamics and spectral analysis are used to explain these observations, with the ultimate goal of estimating the wave energy flux in relation to both the energy input by the wind and the dissipation by turbulence. The results indicate that the wave packets carry approximately 30-40% of the wind input of inertial kinetic energy, and propagate in an environment conducive to the occurrence of a critical level set up by a combination of vertical gradients in background relative vorticity and Doppler shifting of wave frequency. Turbulent kinetic energy dissipation measurements demonstrate that the waves lose energy as they propagate in the transition layer as well as in the pycnocline, where approaching this critical level may have dissipated approximately 20% of the wave packet energy in a single event. Our analysis, therefore, supports the notion that appreciable amounts of wind-induced inertial kinetic energy escape the surface boundary layer into the interior. However, a large fraction of wave energy is dissipated within the pycnocline, limiting its penetration into the abyssal ocean.
The instability of internal gravity waves to localised disturbances
Directory of Open Access Journals (Sweden)
J. Vanneste
1995-02-01
Full Text Available The instability of an internal gravity wave due to nonlinear wave-wave interaction is studied theoretically and numerically. Three different aspects of this phenomenon are examined. 1. The influence of dissipation on both the resonant and the nonresonant interactions is analysed using a normal mode expansion of the basic equations. In particular, the modifications induced in the interaction domain are calculated and as a result some modes are shown to be destabilised by dissipation. 2. The evolution of an initial unstable disturbance of finite vertical extent is described as the growth of two secondary wave packets travelling at the same group velocity. A quasi-linear correction to the basic primary wave is calculated, corresponding to a localised amplitude decrease due to the disturbance growth. 3. Numerical experiments are carried out to study the effect of a basic shear on wave instability. It appears that the growing secondary waves can have a frequency larger than that of the primary wave, provided that the shear is sufficient. The instability of waves with large amplitude and long period, such as tides or planetary waves, could therefore be invoked as a possible mechanism for the generation of gravity waves with shorter period in the middle atmosphere.
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…
Localization of the relative position of two atoms induced by spontaneous emission
International Nuclear Information System (INIS)
Zheng, L.; Li, C.; Li, Y.; Sun, C.P.
2005-01-01
We reexamine the back-action of emitted photons on the wave packet evolution about the relative position of two cold atoms. We show that photon recoil resulting from the spontaneous emission can induce the localization of the relative position of the two atoms through the entanglement between the spatial motion of individual atoms and their emitted photons. The obtained result provides a more realistic model for the analysis of the environment-induced localization of a macroscopic object
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.
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
Energy Technology Data Exchange (ETDEWEB)
Xiong, Yan [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Tan, Jun; Wang, Chengjie; Zhu, Ying [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Fang, Shenwen [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Wu, Jiayi; Wang, Qing [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Duan, Ming, E-mail: swpua124@126.com [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500 (China); School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China)
2016-11-15
In this work, a miniaturized sensor was integrated on fiber surface and developed for oxygen determination through evanescent-wave induced fluorescence quenching. The sensor was designed by using light emitting diode (LED) as light source and optical fiber as light transmission element. Tris(2,2′-bipyridyl) ruthenium ([Ru(bpy){sub 3}]{sup 2+}) fluorophore was immobilized in the organically modified silicates (ORMOSILs) film and coated onto the fiber surface. When light propagated by total internal reflection (TIR) in the fiber core, evanescent wave could be produced on the fiber surface and excite [Ru(bpy){sub 3}]{sup 2+} fluorophore to produce fluorescence emission. Then oxygen could be determinated by its quenching effect on the fluorescence and its concentration could be evaluated according to Stern–Volumer model. Through integrating evanescent wave excitation and fluorescence quenching on fiber surface, the sensor was successfully miniaturized and exhibit improved performances of high sensitivity (1.4), excellent repeatability (1.2%) and fast analysis (12 s) for oxygen determination. The sensor provided a newly portable method for in-situ and real-time measurement of oxygen and showed potential for practical oxygen analysis in different application fields. Furthermore, the fabrication of this sensor provides a miniaturized and portable detection platform for species monitoring by simple modular design. - Highlights: • ORMOSILs sensing film immobilized with [Ru(bpy){sub 3}]{sup 2+} fluorophore was coated on fiber surface. • Evanescent wave on the fiber surface was utilized as excitation source to produce fluorescence. • Oxygen was measured based on its quenching effect on evanescent wave-induce fluorescence. • Sensor fabrication was miniaturized by integrating detection and sensing elements on the fiber. • The modular design sensor provides a detection platform for other species monitoring.
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
Meijborg, Veronique M F; Chauveau, Samuel; Janse, Michiel J; Anyukhovsky, Evgeny P; Danilo, Peter R; Rosen, Michael R; Opthof, Tobias; Coronel, Ruben
BACKGROUND: Long QT2 (LQT2) syndrome is characterized by bifid (or notched) T waves, whose mechanism is not understood. OBJECTIVE: The purpose of this study was to test whether increased interventricular dispersion of repolarization induces bifid T waves. METHODS: We simultaneously recorded surface
Meijborg, Veronique M. F.; Chauveau, Samuel; Janse, Michiel J.; Anyukhovsky, Evgeny P.; Danilo, Peter R.; Rosen, Michael R.; Opthof, Tobias; Coronel, Ruben
2015-01-01
Long QT2 (LQT2) syndrome is characterized by bifid (or notched) T waves, whose mechanism is not understood. The purpose of this study was to test whether increased interventricular dispersion of repolarization induces bifid T waves. We simultaneously recorded surface ECG and unipolar electrograms at
Modification of the ionosphere by VLF wave-induced electron precipitation
International Nuclear Information System (INIS)
Doolittle, J.H.
1982-01-01
Very low frequency (VLF) waves propagating in the whistler mode in the magnetosphere are known to cause precipitation of energetic electrons at middle latitudes. The interactions between the waves and electrons trapped in the magnetic field are believed to occur through cyclotron resonance. As a monochromatic wave propagates along a field line, the condition for resonance can be satisfied by electrons of a minimum energy at the equator and higher energies at increasing latitudes. Resonant interactions occurring in a field aligned region extending several thousand kilometers on both sides of the equator can therefore result in a precipitation flux with a wide range of energies. Electrons which are scattered into the loss cone will collide with the constituents of the ionosphere, causing additional ionization optical emissions, x-rays and heating. A computational technique is introduced which allows the temporal shape of pulse of precipitation to be modeled. A realistic energy distribution is used to weigh the contribution to the total precipitation energy flux resulting from resonant interactions in each segment of the duct. Wave growth along the path is found to affect the shape of the pulse. In its simplest application, the model sets limits on the time window in which a precipitation event can occur. The model arrival times are shown to agree with experimental correlations of VLF waves and effects of precipitation occurring on three occasions, thus supporting the assumption, that the precipitation results from cyclotron resonant scattering. Various techniques that have been employed for detecting wave-induced precipitation are compared. A quantitative analysis of the use of an HF radar for this purpose is introduced, based on the changes in the phase and group paths of the radar signals that are reflected from the perturbed ionosphere
Effect of a transverse plasma jet on a shock wave induced by a ramp
Directory of Open Access Journals (Sweden)
Hongyu WANG
2017-12-01
Full Text Available We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24Â°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2â¯mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found: the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation (IDDES method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets. Keywords: Flow control, Improved delayed detached eddy simulation (IDDES method, Plasma synthetic jet, Shock wave/boundary layer interaction, Time resolved schlieren system
Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements
International Nuclear Information System (INIS)
Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton
2017-01-01
We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansion and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.
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)
Striped morphologies induced by magnetic impurities in d-wave superconductors
Zuo, Xian-Jun
2011-05-01
We study striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping by self-consistently solving the Bogoliubov-de Gennes equations based on the t - t‧ - U - V model. For the single-impurity case, it is found that the stable ground state is a modulated checkerboard pattern. For the two-impurity case, the stripe-like structures in order parameters are induced due to the impurity-pinning effect. The modulations of DSC and charge orders share the same period of four lattice constants (4 a), which is half the period of modulations in the coexisting spin order. Interestingly, when three or more impurities are inserted, the impurities could induce more complex striped morphologies due to quantum interference. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.
Spiral Waves and Multiple Spatial Coherence Resonances Induced by Colored Noise in Neuronal Network
International Nuclear Information System (INIS)
Tang Zhao; Li Yuye; Xi Lei; Jia Bing; Gu Huaguang
2012-01-01
Gaussian colored noise induced spatial patterns and spatial coherence resonances in a square lattice neuronal network composed of Morris-Lecar neurons are studied. Each neuron is at resting state near a saddle-node bifurcation on invariant circle, coupled to its nearest neighbors by electronic coupling. Spiral waves with different structures and disordered spatial structures can be alternately induced within a large range of noise intensity. By calculating spatial structure function and signal-to-noise ratio (SNR), it is found that SNR values are higher when the spiral structures are simple and are lower when the spatial patterns are complex or disordered, respectively. SNR manifest multiple local maximal peaks, indicating that the colored noise can induce multiple spatial coherence resonances. The maximal SNR values decrease as the correlation time of the noise increases. These results not only provide an example of multiple resonances, but also show that Gaussian colored noise play constructive roles in neuronal network. (general)
Evaluation of a shock wave induced cavitation activity both in vitro and in vivo
International Nuclear Information System (INIS)
Tu Juan; Matula, Thomas J; Bailey, Michael R; Crum, Lawrence A
2007-01-01
This study evaluated the cavitation activity induced by shock wave (SW) pulses, both in vitro and in vivo, based on the area measurements of echogenic regions observed in B-mode ultrasound images. Residual cavitation bubble clouds induced by SW pulses were detected as echogenic regions in B-mode images. The temporal evolution of residual bubble clouds, generated by SWs with varying lithotripter charging voltage and pulse repetition frequency (PRF), was analyzed by measuring the time-varying behaviors of the echogenic region areas recorded in B-mode images. The results showed that (1) the area of SW-induced echogenic regions enlarged with increased SW pulse number; (2) echogenic regions in the B-mode images dissipated gradually after ceasing the SWs, which indicated the dissolution of the cavitation bubbles; and (3) larger echogenic regions were generated with higher charging voltage or PRF
Measurements in a container ship of wave-induced hull girder stresses in excess of design values
DEFF Research Database (Denmark)
Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2014-01-01
This paper describes full-scale measurements of the wave-induced vertical bending moment amidships a 9400 TEU container carrier and focuses on the effect of the hydro-elastic high-frequency vibration on the extreme hogging wave bending moment. One extreme event, where the vertical wave-induced ho...... is quite significant. Finally, the hydro-elastic behaviour of the hull girder is assessed by simple approximations using the measured statistical properties and closed-form expressions and the agreement with the actual measurements is found to be good. © 2014 Elsevier Ltd....
International Nuclear Information System (INIS)
Li Yuye; Jia Bing; Gu Huaguang; An Shucheng
2012-01-01
Diversity in the neurons and noise are inevitable in the real neuronal network. In this paper, parameter diversity induced spiral waves and multiple spatial coherence resonances in a two-dimensional neuronal network without or with noise are simulated. The relationship between the multiple resonances and the multiple transitions between patterns of spiral waves are identified. The coherence degrees induced by the diversity are suppressed when noise is introduced and noise density is increased. The results suggest that natural nervous system might profit from both parameter diversity and noise, provided a possible approach to control formation and transition of spiral wave by the cooperation between the diversity and noise. (general)
International Nuclear Information System (INIS)
Assis, A.S. de; Silva, C.E. da; Dias Tavares, A. Jr.; Leubner, C.; Kuhn, S.
2001-07-01
We have studied the formation of auroral electron fluxes induced by a field aligned dc electric field in the presence of plasma wave turbulence. The effect of the wave spectral shape on the production rate has been considered. This acceleration scheme was modelled by the weak turbulence approach. The electron fluxes for narrow and broad band spectra, in the case of low and high phase velocities, are calculated, and it is found as a general feature, for all modes, that their enhancement is larger the weaker the background electric field, while for its absolute enhancement it is just the opposite. The electron fluxes are enhanced by many orders of magnitude over that without turbulence. It is also shown that the modes enhance the runaway production rate via their Cherenkov dissipation, and that a synergetic effect occurs in the enhancement when more than one mode turbulent is present in the acceleration region. (author)
International Nuclear Information System (INIS)
Monti, J.M.; Tachino, C.A.; Hanssen, J.; Fojón, O.A.; Galassi, M.E.; Champion, C.; Rivarola, R.D.
2014-01-01
Distorted wave models are employed to investigate the electron loss process induced by bare ions on biological targets. The two main reactions which contribute to this process, namely, the single electron ionization as well as the single electron capture are here studied. In order to further assess the validity of the theoretical descriptions used, the influence of particular mechanisms are studied, like dynamic screening for the case of electron ionization and energy deposition on the target by the impacting projectile for the electron capture one. Results are compared with existing experimental data. - Highlights: ► Distorted wave models are used to investigate ion-molecule collisions. ► Differential and total cross-sections for capture and ionization are evaluated. ► The influence of dynamic screening is determined. ► Capture reaction dominates the mean energy deposited by the projectile on the target
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.
Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave
Energy Technology Data Exchange (ETDEWEB)
Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)
2012-08-15
Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic ({lambda} = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ{center_dot}cm{sup -2}. Images of the spark emission were recorded for times between 30 ns and 100 {mu}s after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J{center_dot}cm{sup -2} fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov-Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: Black-Right-Pointing-Pointer We investigated shock wave evolution by Rayleigh scattering method. Black-Right-Pointing-Pointer 2D map of shockwave position for several times after plasma generation is presented. Black-Right-Pointing-Pointer Shock wave evolution is not satisfactorily described within self-similar models. Black-Right-Pointing-Pointer Evolution of shock position similar to theory taking into account counter pressure. Black-Right-Pointing-Pointer Density profile behind the shock similar to numerical solution of Euler equations.
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.
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)
Formation and damping of a shock wave induced by laser in a metallic target
International Nuclear Information System (INIS)
Cottet, F.
1981-01-01
In the first part of this work, a numerical simulation of the formation and of the damping of the shock wave induced in a solid target by a laser impulse is developed. It allows to interpret the experimental obtained in the second part of the study. Two series of experiments have been realized. An iron target metallographic study is intended to verify if laser shocks produce effects comparable with conventional shocks, particularly a deformation by albite twinning the existence of which is related to the shock amplitude and its evolution during the propagation in the target. Macles observation become a possible mean to estimate the value of the induced pressures. Another experiment series has been realized to determine more directly the shock parameters. Piezoelectric cermets have been used to detect a shock-wave passage and to measure the time taken to go through targets of variable thickness. The numerical solution allows, afterwards, to deduce the maximum pressure of the induced shock. The most part of the tests have been done on copper targets, the behaviour of which is well known in a large pressure domain. Some tests have been realized on aluminium and iron targets [fr
Modeling quiescent phase transport of air bubbles induced by breaking waves
Shi, Fengyan; Kirby, James T.; Ma, Gangfeng
Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ɛ turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear
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...
International Nuclear Information System (INIS)
Tanaka, K.
1983-01-01
Attention is called to a laboratory experiment of an optical-fiber interferometer which can show the gravitationally induced phase shift of optical waves. A phase shift of approx.10 -6 rad is anticipated for the Earth's gravitational potential difference of 1 m when a He-Ne laser and two multiple-turn optical-fiber loops of length 5 km are used. The phase shift can be varied by rotating the loops about an axis parallel to the Earth's surface. This order of phase shifts can be detected by current optical-fiber interferometric techniques
Fluorescence and Four-Wave Mixing in Electromagnetically Induced Transparency Windows
International Nuclear Information System (INIS)
Wang Zhi-Guo; Li Cheng; Zhang Zhao-Yang; Che Jun-Ling; Qin Meng-Zhe; He Jia-Nan; Zhang Yan-Peng
2013-01-01
We simultaneously compare the probe transmission, Four-Wave Mixing (FWM) and fluorescence signals with dressing effects in a four-level atomic system. The variation rules of three types of signals are exhibited by changing the frequency detuning and power of incident laser beams. The interplay between two ladder subsystems is investigated in the Y-type atomic system. In particular, the fluorescence signal with ultra-narrow linewidth is obtained due to being sheared twice by the electromagnetically induced transparency window. Such fluorescence with very high coherence and monochromaticity can be used for the quantum correlation and narrow linewidth laser
International Nuclear Information System (INIS)
Nagel, H.
1986-01-01
The flow induced valve operation is calculated for single and two-phase flow conditions by the fluid dynamic computer code DYVRO and results are compared to experimental data. The analysis show that the operational behaviour of the valves is not only dependent on the condition of the induced flow, but also the pipe flow can cause a feedback as a result of the induced pressure waves. For the calculation of pressure wave propagation in pipes of which the operation of flow induced valves has a considerable influence it is therefore necessary to have a coupled analysis of the pressure wave propagation and the operational behaviour of the valves. The analyses of the fast transient transfer from steam to two-phase flow show a good agreement with experimental data. Hence even these very high loads on pipes resulting from such fluid dynamic transients can be calculated realistically. (orig.)
Time-synchronized continuous wave laser-induced fluorescence on an oscillatory xenon discharge.
MacDonald, N A; Cappelli, M A; Hargus, W A
2012-11-01
A novel approach to time-synchronizing laser-induced fluorescence measurements to an oscillating current in a 60 Hz xenon discharge lamp using a continuous wave laser is presented. A sample-hold circuit is implemented to separate out signals at different phases along a current cycle, and is followed by a lock-in amplifier to pull out the resulting time-synchronized fluorescence trace from the large background signal. The time evolution of lower state population is derived from the changes in intensity of the fluorescence excitation line shape resulting from laser-induced fluorescence measurements of the 6s(')[1/2](1)(0)-6p(')[3/2](2) xenon atomic transition at λ = 834.68 nm. Results show that the lower state population oscillates at twice the frequency of the discharge current, 120 Hz.
Time-synchronized continuous wave laser-induced fluorescence on an oscillatory xenon discharge
Energy Technology Data Exchange (ETDEWEB)
MacDonald, N. A.; Cappelli, M. A. [Stanford Plasma Physics Laboratory, Stanford University, Stanford, California 94305 (United States); Hargus, W. A. Jr. [Air Force Research Laboratory, Edwards AFB, California 93524 (United States)
2012-11-15
A novel approach to time-synchronizing laser-induced fluorescence measurements to an oscillating current in a 60 Hz xenon discharge lamp using a continuous wave laser is presented. A sample-hold circuit is implemented to separate out signals at different phases along a current cycle, and is followed by a lock-in amplifier to pull out the resulting time-synchronized fluorescence trace from the large background signal. The time evolution of lower state population is derived from the changes in intensity of the fluorescence excitation line shape resulting from laser-induced fluorescence measurements of the 6s{sup Prime }[1/2]{sub 1}{sup 0}-6p{sup Prime }[3/2]{sub 2} xenon atomic transition at {lambda}= 834.68 nm. Results show that the lower state population oscillates at twice the frequency of the discharge current, 120 Hz.
Wave-mixing-induced transparency with zero phase shift in atomic vapors
Zhou, F.; Zhu, C. J.; Li, Y.
2017-12-01
We present a wave-mixing induced transparency that can lead to a hyper-Raman gain-clamping effect. This new type of transparency is originated from a dynamic gain cancellation effect in a multiphoton process where a highly efficient light field of new frequency is generated and amplified. We further show that this novel dynamic gain cancellation effect not only makes the medium transparent to a probe light field at appropriate frequency but also eliminates the probe field propagation phase shift. This gain-cancellation-based induced transparency holds for many potential applications on optical communication and may lead to effective suppression of parasitic Raman/hyper-Raman noise field generated in high intensity optical fiber transmissions.
Planetary-scale circulations in the presence of climatological and wave-induced heating
Salby, Murry L; Garcia, Rolando R.; Hendon, Harry H.
1994-01-01
Interaction between the large-scale circulation and the convective pattern is investigated in a coupled system governed by the linearized primitive equations. Convection is represented in terms of two components of heating: A 'climatological component' is prescribed stochastically to represent convection that is maintained by fixed distributions of land and sea and sea surface temperature (SST). An 'induced component' is defined in terms of the column-integrated moisture flux convergence to represent convection that is produced through feedback with the circulation. Each component describes the envelope organizing mesoscale convective activity. As SST on the equator is increased, induced heating amplifies in the gravest zonal wavenumbers at eastward frequencies, where positive feedback offsets dissipation. Under barotropic stratification, a critical SST of 29.5 C results in positive feedback exactly cancelling dissipation in wavenumber 1 for an eastward phase speed of 6 m/s. Sympathetic interaction between the circulation and the induced heating is the basis for 'frictional wave-Conditional Instability of the Second Kind (CISK)', which is distinguished from classical wave-CISK by rendering the gravest zonal dimensions most unstable. Under baroclinic stratification, the coupled system exhibits similar behavior. The critical SST is only 26.5 C for conditions representative of equinox, but in excess of 30 C for conditions representative of solstice. Having the form of an unsteady Walker circulation, the disturbance produced by frictional wave-CISK compares favorably with the observed life cycle of the Madden-Julian oscillation (MJO). SST above the critical value produces an amplifying disturbance in which enhanced convection coincides with upper-tropospheric westerlies and is positively correlated with temperature and surface convergence. Conversely, SST below the critical value produces a decaying disturbance in which enhanced convection coincides with upper
Experimental investigation of flow induced dust acoustic shock waves in a complex plasma
Energy Technology Data Exchange (ETDEWEB)
Jaiswal, S., E-mail: surabhijaiswal73@gmail.com; Bandyopadhyay, P.; Sen, A. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)
2016-08-15
We report on experimental observations of flow induced large amplitude dust-acoustic shock waves in a complex plasma. The experiments have been carried out in a Π shaped direct current glow discharge experimental device using kaolin particles as the dust component in a background of Argon plasma. A strong supersonic flow of the dust fluid is induced by adjusting the pumping speed and neutral gas flow into the device. An isolated copper wire mounted on the cathode acts as a potential barrier to the flow of dust particles. A sudden change in the gas flow rate is used to trigger the onset of high velocity dust acoustic shocks whose dynamics are captured by fast video pictures of the evolving structures. The physical characteristics of these shocks are delineated through a parametric scan of their dynamical properties over a range of flow speeds and potential hill heights. The observed evolution of the shock waves and their propagation characteristics are found to compare well with model numerical results based on a modified Korteweg-de-Vries-Burgers type equation.
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....
Energy Technology Data Exchange (ETDEWEB)
Oran, R. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139 (United States); Landi, E.; Holst, B. van der; Sokolov, I. V.; Gombosi, T. I., E-mail: roran@mit.edu [Atmospheric, Oceanic and Atmospheric Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI, 48109 (United States)
2017-08-20
We test the predictions of the Alfvén Wave Solar Model (AWSoM), a global wave-driven magnetohydrodynamic (MHD) model of the solar atmosphere, against high-resolution spectra emitted by the quiescent off-disk solar corona. AWSoM incorporates Alfvén wave propagation and dissipation in both closed and open magnetic field lines; turbulent dissipation is the only heating mechanism. We examine whether this mechanism is consistent with observations of coronal EUV emission by combining model results with the CHIANTI atomic database to create synthetic line-of-sight spectra, where spectral line widths depend on thermal and wave-related ion motions. This is the first time wave-induced line broadening is calculated from a global model with a realistic magnetic field. We used high-resolution SUMER observations above the solar west limb between 1.04 and 1.34 R {sub ⊙} at the equator, taken in 1996 November. We obtained an AWSoM steady-state solution for the corresponding period using a synoptic magnetogram. The 3D solution revealed a pseudo-streamer structure transversing the SUMER line of sight, which contributes significantly to the emission; the modeled electron temperature and density in the pseudo-streamer are consistent with those observed. The synthetic line widths and the total line fluxes are consistent with the observations for five different ions. Further, line widths that include the contribution from the wave-induced ion motions improve the correspondence with observed spectra for all ions. We conclude that the turbulent dissipation assumed in the AWSoM model is a viable candidate for explaining coronal heating, as it is consistent with several independent measured quantities.
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...
Energy Technology Data Exchange (ETDEWEB)
Chandra, B.P.; Parganiha, S.; Sonwane, V.D. [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492010, Chhattisgarh (India); Chandra, V.K. [Department of Electrical and Electronics Engineering, Chhatrapati Shivaji Institute of Technology, Shivaji Nagar, Kolihapuri, Durg 491001, Chhattisgarh (India); Jha, Piyush, E-mail: piyushjha22@rediffmail.com [Department of Applied Physics, Raipur Institute of Technology, Chhatauna, Mandir Hasuad, Raipur 492101, Chhattisgarh (India); Baghel, R.N. [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492010, Chhattisgarh (India)
2016-10-15
The impact of a projectile propelled to velocities in the range of 0.5–2.5 km/s on to a target (X-cut quartz crystal) produces shock waves travelling at velocity of nearly 10 km/s in target, in which intense mechanoluminescence (ML) pulses of microsecond duration are produced, both in compression and post-compression conditions. The piezoelectric field produced due to surface charges of fractured target, causes band bending and subsequently, the free charge carriers are generated in the respective bands and the emission of ML occurs. The ML appears after a delay time t{sub th} whose value decreases with increasing value of the shock pressure. Initially, the ML intensity increases with the shock pressure because of the creation of more surfaces; however, for higher values of the shock pressure, the ML intensity tends to attain a saturation value because of the hardening of the crystals due to the creation of small crystallites in which the creation of new surfaces becomes difficult. The ratio between peak ML intensity in the uncompressed region and the maximum ML intensity in the compressed region decreases with increasing shock pressure because more defects produced at high pressure generate higher barrier for the relaxation of blocked cracks under compression. The expressions derived for characteristics of shock-induced ML are able to explain satisfactorily the experimental results. Shock-wave velocity, shock pressure, transit time, lifetime of electrons in conduction band, etc. can be determined by the shock-induced ML.As such, the shock-induced ML provides a new optical technique for the studies of materials under shock pressure.
International Nuclear Information System (INIS)
Ecault, Romain; Touchard, Fabienne; Boustie, Michel; Berthe, Laurent; Lescoute, Emilien; Sollier, Arnaud; Voillaume, Hubert
2015-01-01
In this work, original shock experiments are presented. Laser-induced shock and shear wave propagations have been observed in an epoxy resin, in the case of femtosecond laser irradiation. A specific time-resolved shadowgraphy setup has been developed using the photoelasticimetry principle to enhance the shear wave observation. Shear waves have been observed in epoxy resin after laser irradiation. Their propagation has been quantified in comparison with the main shock propagation. A discussion, hinging on numerical results, is finally given to improve understanding of the phenomenon. (paper)
International Nuclear Information System (INIS)
Hendijanifard, Mohammad; Willis, David A
2011-01-01
Laser-matter interactions are frequently studied by measuring the propagation of shock waves caused by the rapid laser-induced material removal. An improved method for calculating the thermo-fluid parameters behind shock waves is introduced in this work. Shock waves in ambient air, induced by pulsed Nd : YAG laser ablation of aluminium films, are measured using a shadowgraph apparatus. Normal shock solutions are applied to experimental data for shock wave positions and used to calculate pressure, temperature, and velocity behind the shock wave. Non-dimensionalizing the pressure and temperature with respect to the ambient values, the dimensionless pressure and temperature are estimated to be as high as 90 and 16, respectively, at a time of 10 ns after the ablation pulse for a laser fluence of F = 14.5 J cm -2 . The results of the normal shock solution and the Taylor-Sedov similarity solution are compared to show that the Taylor-Sedov solution under-predicts pressure when the Mach number of the shock wave is small. At a fluence of 3.1 J cm -2 , the shock wave Mach number is less than 3, and the Taylor-Sedov solution under-predicts the non-dimensional pressure by as much as 45%.
International Nuclear Information System (INIS)
Kanno, Manabu; Kono, Hirohiko; Fujimura, Yuichi; Lin, Sheng H.
2010-01-01
We theoretically investigated the nonadiabatic couplings between optically induced π-electron rotations and molecular vibrations in a chiral aromatic molecule irradiated by a nonhelical, linearly polarized laser pulse. The results of wave packet dynamics simulation show that the vibrational amplitudes strongly depend on the initial rotation direction, clockwise or counterclockwise, which is controlled by the polarization direction of the incident pulse. This suggests that attosecond π-electron rotations can be observed by spectroscopic detection of femtosecond molecular vibrations.
Wave-current induced erosion of cohesive riverbanks in northern Manitoba, Canada
Kimiaghalam, N.; Clark, S.; Ahmari, H.; Hunt, J.
2015-03-01
The field of cohesive soil erosion is still not fully understood, in large part due to the many soil parameters that affect cohesive soil erodibility. This study is focused on two channels, 2-Mile and 8-Mile channels in northern Manitoba, Canada, that were built to connect Lake Winnipeg with Playgreen Lake and Playgreen Lake with Kiskikittogisu Lake, respectively. The banks of the channels consist of clay rich soils and alluvial deposits of layered clay, silts and sands. The study of erosion at the sites is further complicated because the flow-induced erosion is combined with the effects of significant wave action due to the large fetch length on the adjacent lakes, particularly Lake Winnipeg that is the seventh largest lake in North America. The study included three main components: field measurements, laboratory experiments and numerical modelling. Field measurements consisted of soil sampling from the banks and bed of the channels, current measurements and water sampling. Grab soil samples were used to measure the essential physical and electrochemical properties of the riverbanks, and standard ASTM Shelby tube samples were used to estimate the critical shear stress and erodibility of the soil samples using an erosion measurement device (EMD). Water samples were taken to estimate the sediment concentration profile and also to monitor changes in sediment concentration along the channels over time. An Acoustic Doppler Current Profiler (ADCP) was used to collect bathymetry and current data, and two water level gauges have been installed to record water levels at the entrance and outlet of the channels. The MIKE 21 NSW model was used to simulate waves using historical winds and measured bathymetry of the channels and lakes. Finally, results from the wave numerical model, laboratory tests and current measurement were used to estimate the effect of each component on erodibility of the cohesive banks.
Wave-current induced erosion of cohesive riverbanks in northern Manitoba, Canada
Directory of Open Access Journals (Sweden)
N. Kimiaghalam
2015-03-01
Full Text Available The field of cohesive soil erosion is still not fully understood, in large part due to the many soil parameters that affect cohesive soil erodibility. This study is focused on two channels, 2-Mile and 8-Mile channels in northern Manitoba, Canada, that were built to connect Lake Winnipeg with Playgreen Lake and Playgreen Lake with Kiskikittogisu Lake, respectively. The banks of the channels consist of clay rich soils and alluvial deposits of layered clay, silts and sands. The study of erosion at the sites is further complicated because the flow-induced erosion is combined with the effects of significant wave action due to the large fetch length on the adjacent lakes, particularly Lake Winnipeg that is the seventh largest lake in North America. The study included three main components: field measurements, laboratory experiments and numerical modelling. Field measurements consisted of soil sampling from the banks and bed of the channels, current measurements and water sampling. Grab soil samples were used to measure the essential physical and electrochemical properties of the riverbanks, and standard ASTM Shelby tube samples were used to estimate the critical shear stress and erodibility of the soil samples using an erosion measurement device (EMD. Water samples were taken to estimate the sediment concentration profile and also to monitor changes in sediment concentration along the channels over time. An Acoustic Doppler Current Profiler (ADCP was used to collect bathymetry and current data, and two water level gauges have been installed to record water levels at the entrance and outlet of the channels. The MIKE 21 NSW model was used to simulate waves using historical winds and measured bathymetry of the channels and lakes. Finally, results from the wave numerical model, laboratory tests and current measurement were used to estimate the effect of each component on erodibility of the cohesive banks.
Proxy records of Holocene storm events in coastal barrier systems: Storm-wave induced markers
Goslin, Jérôme; Clemmensen, Lars B.
2017-10-01
Extreme storm events in the coastal zone are one of the main forcing agents of short-term coastal system behavior. As such, storms represent a major threat to human activities concentrated along the coasts worldwide. In order to better understand the frequency of extreme events like storms, climate science must rely on longer-time records than the century-scale records of instrumental weather data. Proxy records of storm-wave or storm-wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia. This review provides a detailed state-of-the-art compilation of the proxies available from coastal barrier systems to reconstruct Holocene storm chronologies (paleotempestology). The present paper aims (I) to describe the erosional and depositional processes caused by storm-wave action in barrier and back-barrier systems (i.e. beach ridges, storm scarps and washover deposits), (ii) to understand how storm records can be extracted from barrier and back-barrier sedimentary bodies using stratigraphical, sedimentological, micro-paleontological and geochemical proxies and (iii) to show how to obtain chronological control on past storm events recorded in the sedimentary successions. The challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm-chronologies using these various proxies are discussed, and future research prospects are outlined.
Vortex shedding induced by a solitary wave propagating over a submerged vertical plate
International Nuclear Information System (INIS)
Lin Chang; Ho, T.-C.; Chang, S.-C.; Hsieh, S.-C.; Chang, K.-A.
2005-01-01
Experimental study was conducted on the vortex shedding process induced by the interaction between a solitary wave and a submerged vertical plate. Particle image velocimetry (PIV) was used for quantitative velocity measurement while a particle tracing technique was used for qualitative flow visualization. Vortices are generated at the tip of each side of the plate. The largest vortices at each side of the plate eventually grow to the size of the water depth. Although the fluid motion under the solitary wave is only translatory, vortices are shed in both the upstream and downstream directions due to the interaction of the generated vortices as well as the vortices with the plate and the bottom. The process can be divided into four phases: the formation of a separated shear layer, the generation and shedding of vortices, the formation of a vertical jet, and the impingement of the jet onto the free surface. Similarity velocity profiles were found both in the separated shear layer and in the vertical jet
Influences of Gravity Waves on Convectively Induced Turbulence (CIT): A Review
Sharman, Robert D.; Trier, S. B.
2018-03-01
Thunderstorms are known to produce turbulence. Such turbulence is commonly referred to as convectively induced turbulence or CIT, and can be hazardous to aviation. Although this turbulence can occur both within and outside the convection, out-of-cloud CIT is particularly hazardous, since it occurs in clear air and cannot be seen by eye or onboard radar. Furthermore, due to its small scale and its ties to the underlying convection, it is very difficult to forecast. Guidelines for out-of-cloud CIT avoidance are available, but they are oversimplified and can be misleading. In the search for more appropriate and physically based avoidance guidelines, considerable research has been conducted in recent years on the nature of the phenomenon, and in particular, its connection to gravity waves generated by the convection. This paper reviews the advances in our understanding of out-of-cloud CIT and its relation to convective gravity waves, and provides several detailed examples of observed cases to elucidate some of the underlying dynamics.
Direct measurement of density oscillation induced by a radio-frequency wave
International Nuclear Information System (INIS)
Yamada, T.; Ejiri, A.; Shimada, Y.; Oosako, T.; Tsujimura, J.; Takase, Y.; Kasahara, H.
2007-01-01
An O-mode reflectometer at a frequency of 25.85 GHz was applied to plasmas heated by the high harmonic fast wave (21 MHz) in the TST-2 spherical tokamak. An oscillation in the phase of the reflected microwave in the rf range was observed directly for the first time. In TST-2, the rf (250 kW) induced density oscillation depends mainly on the poloidal rf electric field, which is estimated to be about 0.2 kV/m rms by the reflectometer measurement. Sideband peaks separated in frequency by ion cyclotron harmonics from 21 MHz, and peaks at ion cyclotron harmonics which are suggested to be quasimodes generated by parametric decay, were detected
DC current in the collisionless limit induced by a travelling wave
International Nuclear Information System (INIS)
Midzuno, Yukio; Fukuda, Masaji.
1977-03-01
The DC current induced by a Travelling Wave is calculated on the basis of the assumption that the distribution function of electrons in the collisionless limit should be determined by a condition derived from the nature of the collision operator, as in the case of the calculation of the neoclassical transport in a torus. The resultant net current is found to have the same parameter dependence as the one derived in a previous analysis, in which we assumed the initial distribution of electrons to be uniform and isotropic Maxwellian. The numerical coefficient is found, however, to be a little different from the previous one. The importance of the accurate matching of the distribution function of untrapped particles to the Maxwellian one for large velocity is demonstrated. (auth.)
Extreme value prediction of the wave-induced vertical bending moment in large container ships
DEFF Research Database (Denmark)
Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2015-01-01
increase the extreme hull girder response significantly. Focus in the present paper is on the influence of the hull girder flexibility on the extreme response amidships, namely the wave-induced vertical bending moment (VBM) in hogging, and the prediction of the extreme value of the same. The analysis...... in the present paper is based on time series of full scale measurements from three large container ships of 8600, 9400 and 14000 TEU. When carrying out the extreme value estimation the peak-over-threshold (POT) method combined with an appropriate extreme value distribution is applied. The choice of a proper...... threshold level as well as the statistical correlation between clustered peaks influence the extreme value prediction and are taken into consideration in the present paper....
Lorenz, Pierre; Ehrhardt, Martin; Zimmer, Klaus
The defect-free laser-assisted structuring of thin films on flexible substrates is a challenge for laser methods. However, solving this problem exhibits an outstanding potential for a pioneering development of flexible electronics. Thereby, the laser-assisted delamination method has a great application potential. At the delamination process: the localized removal of the layer is induced by a shock wave which is produced by a laser ablation process on the rear side of the substrate. In this study, the thin-film patterning process is investigated for different polymer substrates dependent on the material and laser parameters using a KrF excimer laser. The resultant structures were studied by optical microscopy and white light interferometry (WLI). The delamination process was tested at different samples (indium tin oxide (ITO) on polyethylene terephthalate (PET), epoxy-based negative photoresist (SU8) on polyimide (PI) and indium tin oxide/copper indium gallium selenide/molybdenum (ITO/CIGS/Mo) on PI.
International Nuclear Information System (INIS)
Wang, Z G; Zhang, Z Y; Che, J L; Zhang, Y Z; Li, C B; Zheng, H B; Zhang, Y P
2013-01-01
We report the first observation of six-wave mixing (SWM) and fluorescence signals in an electromagnetically induced transparency (EIT) window. Several remarkable advantages are described. First, multiple bright and dark states are simultaneously observed due to enhancement or suppression of the SWM signal. Second, ultra-narrow fluorescence, much narrower than the EIT window, is experimentally obtained. Third, the ultra-narrow fluorescence can also generate Autler–Townes splitting on scanning the coupling beam. Fourth, a double-peak EIT window is obtained using the nest-dressing scheme. Such studies concerning SWM and fluorescence have applications in optical switching, multi-channel communication and narrowband and long-range quantum communication. (letter)
Shock wave emission from laser-induced cavitation bubbles in polymer solutions.
Brujan, Emil-Alexandru
2008-09-01
The role of extensional viscosity on the acoustic emission from laser-induced cavitation bubbles in polymer solutions and near a rigid boundary is investigated by acoustic measurements. The polymer solutions consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose (CMC) aqueous solution with a weak elastic component. A reduction of the maximum amplitude of the shock wave pressure and a prolongation of the oscillation period of the bubble were found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. In both polymer solutions, however, the shock pressure decays proportionally to r(-1) with increasing distance r from the emission centre.
von Kameke, A; Huhn, F; Fernández-García, G; Muñuzuri, A P; Pérez-Muñuzuri, V
2011-08-12
We report the experimental observation of Richardson dispersion and a double cascade in a thin horizontal fluid flow induced by Faraday waves. The energy spectra and the mean spectral energy flux obtained from particle image velocimetry data suggest an inverse energy cascade with Kolmogorov type scaling E(k) ∝ k(γ), γ ≈ -5/3 and an E(k) ∝ k(γ), γ ≈ -3 enstrophy cascade. Particle transport is studied analyzing absolute and relative dispersion as well as the finite size Lyapunov exponent (FSLE) via the direct tracking of real particles and numerical advection of virtual particles. Richardson dispersion with ∝ t(3) is observed and is also reflected in the slopes of the FSLE (Λ ∝ ΔR(-2/3)) for virtual and real particles.
A Numerical Study on the Screening of Blast-Induced Waves for Reducing Ground Vibration
Park, Dohyun; Jeon, Byungkyu; Jeon, Seokwon
2009-06-01
Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock, but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact, and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration. The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration, namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes, distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method of blast-induced waves was considerably effective under certain design conditions. The design details for field application have also been proposed.
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...
Directory of Open Access Journals (Sweden)
Gábor Fleit
2016-07-01
Full Text Available Waves induced by ship movement might be harmful for the habitat in the littoral zone of rivers due to the temporally increasing bed shear stress, the high-energy breaking waves and the consequently related detachment of benthic animals. In order to understand the complex hydrodynamic phenomena resulting from littoral waves, we present the testing of a novel methodology that incorporates field observations and numerical tools. The study is performed at a section of the Danube River in Hungary and analyzes the influence of different ship types. The field methods consist of parallel acoustic measurements (using Acoustic Doppler Velocimetry (ADV conducted at the riverbed and Large Scale Particle Image Velocimetry (LSPIV of the water surface. ADV measurements provided near-bed flow velocities based on which the wave induced currents and local bed shear stress could be estimated. The LSPIV was able to quantify the dynamics of the breaking waves along the bank. Furthermore, computational fluid dynamics (CFD modeling was successfully applied to simulate the propagation and the breaking of littoral waves. The used techniques complement each other well and their joint application provides an adequate tool to support the improvement of riverine habitats.
Directory of Open Access Journals (Sweden)
Xin-ling LI
2016-09-01
Full Text Available Objective To observe the characteristics of rat brain injury induced by shock wave propagation in solids resulting from underwater explosion and explore the related mechanism. Methods Explosion source outside the simulated ship cabin underwater was detonated for establishing a model of brain injury in rats by shock wave propagation in solid; 72 male SD rats were randomly divided into normal control group (n=8, injury group 1 (600mg RDX paper particle explosion source, n=32, injury group 2 (800mg RDX paper particle explosion source, n=32. The each injury group was randomly divided into 4 subgroups (n=8, 3, 6, 24 and 72h groups. The division plate as a whole and the head of 8 rats in each injury group were measured for the peak value of the solid shock wave, its rising time and the duration time of shock wave propagation in solid. To observe the physiological changes of animals after injury, plasma samples were collected for determination of brain damage markers, NSE and S-100β. All the animals were sacrificed, the right hemisphere of the brain was taken in each group of animals, weighting after baking, and the brain water content was calculated. Pathological examination was performed for left cerebral hemisphere in 24-h group. The normal pyramidal cells in the hippocampal CA1 region were counted. Results The peak value, rising time and duration time of shock wave propagation on the division plate and head were 1369.74±91.70g, 0.317±0.037ms and 24.85±2.53ms, 26.83±3.09g, 0.901±0.077ms and 104.21±6.26ms respectively in injury group 1, 1850.11±83.86g, 0.184±0.031ms and 35.61±2.66ms, 39.75±3.14g, 0.607±0.069ms and 132.44±7.17ms in injury group 2 (P<0.01. After the injury, there was no abnormality in the anatomy, and brain damage markers NSE, S-100β increased, reached the peak at 24 h, and they were highest in injury group 2 and lowest in control group with a statistically significant difference (P<0.05. The brain water content
Sun, Yang-Yi; Liu, Jann-Yenq; Lin, Charles Chien-Hung; Lin, Chi-Yen; Shen, Ming-Hsueh; Chen, Chieh-Hung; Chen, Chia-Hung; Chou, Min-Yang
2018-01-01
A moon shadow of the total solar eclipse swept through the continent of United States (CONUS) from west to east on 21 August 2017. Massive total electron content (integration of electron density from 0 km to 20,200 km altitude) observations from 2,255 ground-based Global Navigation Satellite System receivers show that the moon shadow ship generates a great ionospheric bow wave front which extends 1,500 km away from the totality path covering the entire CONUS. The bow wave front consists of the acoustic shock wave due to the supersonic/near-supersonic moon shadow ship and the significant plasma recombination due to the reduction in solar irradiation within the shadow area. The deep bow wave trough (-0.02 total electron content unit (1 TECU = 1016 el m-2) area) nearly coincides with the 100% obscuration moving along the totality path over the CONUS through the entire eclipse period. The supersonic moon shadow ship induces a bow wave crest in front of the ship ( 80% obscuration). It is the first time to find the acoustic shock wave-formed bow wave trough and crest near the totality.
Sakuraba, A.
2015-12-01
I made a linear analysis of flow-induced oscillations along an underground cylindrical conduit with an elliptical cross section on the basis of the hypothesis that volcanic tremor is a result of magma movement through a conduit. As a first step to understand how the self oscillation occurs because of magma flow, I investigated surface wave propagation and attenuation along an infinitely long fluid-filled elliptic cylinder in an elastic medium. The boundary element method is used to obtain the two-dimensional wave field around the ellipse in the frequency-wavenumber domain. When the major axis is much greater than the minor axis of the ellipse, we obtain the analytic form of the dispersion relation of both the crack-wave mode (Korneev 2008, Lipovsky & Dunham 2015) and the Rayleigh-wave mode with flexural deformation. The crack-wave mode generally has a slower phase speed and a higher attenuation than the Rayleigh-wave mode. In the long-wavelength limit, the crack-wave mode disappears because of fluid viscosity, but the Rayleigh-wave mode exists with a constant Q-value that depends on viscosity. When the aspect ratio of the ellipse is finite, the surface waves can basically be understood as those propagating along a fluid pipe. The flexural mode does exist even when the wavelength is much longer than the major axis, but its phase speed coincides with that of the surrounding S-wave (Randall 1991). As its attenuation is zero in the long-wavelength limit, the flexural mode differs in nature from surface wave. I also obtain a result on linear stability of viscous flow through an elliptic cylinder. In this analysis, I made an assumption that the fluid inertia is so small that the Stokes equation can be used. As suggested by the author's previous study (Sakuraba & Yamauchi 2014), the flexural (Rayleigh-wave) mode is destabilized at a critical flow speed that decreases with the wavelength. However, when the wavelength is much greater than the major axis of the ellipse, the
DEFF Research Database (Denmark)
Sayed, Karim El; Birkedal, Dan; Vadim, Lyssenko
1997-01-01
We present a theoretical investigation of ultrafast transient four-wave mixing (FWM) of GaAs quantum wells for coherent excitation of excitons and a large number of continuum states. It is shown that in this case the line shape of the FWM signal is drastically altered due to an interaction-induce...
Directory of Open Access Journals (Sweden)
Reto Huber
2007-03-01
Full Text Available Sleep slow wave activity (SWA is thought to reflect sleep need, increasing in proportion to the length of prior wakefulness and decreasing during sleep. However, the process responsible for SWA regulation is not known. We showed recently that SWA increases locally after a learning task involving a circumscribed brain region, suggesting that SWA may reflect plastic changes triggered by learning.To test this hypothesis directly, we used transcranial magnetic stimulation (TMS in conjunction with high-density EEG in humans. We show that 5-Hz TMS applied to motor cortex induces a localized potentiation of TMS-evoked cortical EEG responses. We then show that, in the sleep episode following 5-Hz TMS, SWA increases markedly (+39.1+/-17.4%, p<0.01, n = 10. Electrode coregistration with magnetic resonance images localized the increase in SWA to the same premotor site as the maximum TMS-induced potentiation during wakefulness. Moreover, the magnitude of potentiation during wakefulness predicts the local increase in SWA during sleep.These results provide direct evidence for a link between plastic changes and the local regulation of sleep need.