Dissipative quantum trajectories in complex space: Damped harmonic oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Dissipative quantum trajectories in complex space are investigated in the framework of the logarithmic nonlinear Schrödinger equation. The logarithmic nonlinear Schrödinger equation provides a phenomenological description for dissipative quantum systems. Substituting the wave function expressed in terms of the complex action into the complex-extended logarithmic nonlinear Schrödinger equation, we derive the complex quantum Hamilton–Jacobi equation including the dissipative potential. It is shown that dissipative quantum trajectories satisfy a quantum Newtonian equation of motion in complex space with a friction force. Exact dissipative complex quantum trajectories are analyzed for the wave and solitonlike solutions to the logarithmic nonlinear Schrödinger equation formore » the damped harmonic oscillator. These trajectories converge to the equilibrium position as time evolves. It is indicated that dissipative complex quantum trajectories for the wave and solitonlike solutions are identical to dissipative complex classical trajectories for the damped harmonic oscillator. This study develops a theoretical framework for dissipative quantum trajectories in complex space.« less

Wigner molecules in carbon-nanotube quantum dots

NASA Astrophysics Data System (ADS)

Secchi, Andrea; Rontani, Massimo

2010-07-01

We demonstrate that electrons in quantum dots defined by electrostatic gates in semiconductor nanotubes freeze orderly in space realizing a “Wigner molecule.” Our exact diagonalization calculations uncover the features of the electron molecule, which may be accessed by tunneling spectroscopy—indeed some of them have already been observed by Deshpande and Bockrath [Nat. Phys. 4, 314 (2008)]10.1038/nphys895. We show that numerical results are satisfactorily reproduced by a simple ansatz vibrational wave function: electrons have localized wave functions, like nuclei in an ordinary molecule, whereas low-energy excitations are collective vibrations of electrons around their equilibrium positions.

Rapid calculation of acoustic fields from arbitrary continuous-wave sources.

PubMed

Treeby, Bradley E; Budisky, Jakub; Wise, Elliott S; Jaros, Jiri; Cox, B T

2018-01-01

A Green's function solution is derived for calculating the acoustic field generated by phased array transducers of arbitrary shape when driven by a single frequency continuous wave excitation with spatially varying amplitude and phase. The solution is based on the Green's function for the homogeneous wave equation expressed in the spatial frequency domain or k-space. The temporal convolution integral is solved analytically, and the remaining integrals are expressed in the form of the spatial Fourier transform. This allows the acoustic pressure for all spatial positions to be calculated in a single step using two fast Fourier transforms. The model is demonstrated through several numerical examples, including single element rectangular and spherically focused bowl transducers, and multi-element linear and hemispherical arrays.

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions.

PubMed

West, Aaron C; Schmidt, Michael W; Gordon, Mark S; Ruedenberg, Klaus

2017-02-09

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the juxtaposed nonbonded quasi-atoms and a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions, and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. The theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.

Non-contact thickness measurement using UTG

NASA Technical Reports Server (NTRS)

Bui, Hoa T. (Inventor)

1996-01-01

A measurement structure for determining the thickness of a specimen without mechanical contact but instead employing ultrasonic waves including an ultrasonic transducer and an ultrasonic delay line connected to the transducer by a retainer or collar. The specimen, whose thickness is to be measured, is positioned below the delay line. On the upper surface of the specimen a medium such as a drop of water is disposed which functions to couple the ultrasonic waves from the delay line to the specimen. A receiver device, which may be an ultrasonic thickness gauge, receives reflected ultrasonic waves reflected from the upper and lower surface of the specimen and determines the thickness of the specimen based on the time spacing of the reflected waves.

Interferometers as probes of Planckian quantum geometry

NASA Astrophysics Data System (ADS)

Hogan, Craig J.

2012-03-01

A theory of position of massive bodies is proposed that results in an observable quantum behavior of geometry at the Planck scale, tP. Departures from classical world lines in flat spacetime are described by Planckian noncommuting operators for position in different directions, as defined by interactions with null waves. The resulting evolution of position wave functions in two dimensions displays a new kind of directionally coherent quantum noise of transverse position. The amplitude of the effect in physical units is predicted with no parameters, by equating the number of degrees of freedom of position wave functions on a 2D space-like surface with the entropy density of a black hole event horizon of the same area. In a region of size L, the effect resembles spatially and directionally coherent random transverse shear deformations on time scale ≈L/c with typical amplitude ≈ctPL. This quantum-geometrical “holographic noise” in position is not describable as fluctuations of a quantized metric, or as any kind of fluctuation, dispersion or propagation effect in quantum fields. In a Michelson interferometer the effect appears as noise that resembles a random Planckian walk of the beam splitter for durations up to the light-crossing time. Signal spectra and correlation functions in interferometers are derived, and predicted to be comparable with the sensitivities of current and planned experiments. It is proposed that nearly colocated Michelson interferometers of laboratory scale, cross-correlated at high frequency, can test the Planckian noise prediction with current technology.

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

DOE PAGES

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.; ...

2017-01-30

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

Computing the Dynamic Response of a Stratified Elastic Half Space Using Diffuse Field Theory

NASA Astrophysics Data System (ADS)

Sanchez-Sesma, F. J.; Perton, M.; Molina Villegas, J. C.

2015-12-01

The analytical solution for the dynamic response of an elastic half-space for a normal point load at the free surface is due to Lamb (1904). For a tangential force, we have Chaós (1960) formulae. For an arbitrary load at any depth within a stratified elastic half space, the resulting elastic field can be given in the same fashion, by using an integral representation in the radial wavenumber domain. Typically, computations use discrete wave number (DWN) formalism and Fourier analysis allows for solution in space and time domain. Experimentally, these elastic Greeńs functions might be retrieved from ambient vibrations correlations when assuming a diffuse field. In fact, the field could not be totally diffuse and only parts of the Green's functions, associated to surface or body waves, are retrieved. In this communication, we explore the computation of Green functions for a layered media on top of a half-space using a set of equipartitioned elastic plane waves. Our formalism includes body and surface waves (Rayleigh and Love waves). These latter waves correspond to the classical representations in terms of normal modes in the asymptotic case of large separation distance between source and receiver. This approach allows computing Green's functions faster than DWN and separating the surface and body wave contributions in order to better represent Green's function experimentally retrieved.

A phase space approach to wave propagation with dispersion.

PubMed

Ben-Benjamin, Jonathan S; Cohen, Leon; Loughlin, Patrick J

2015-08-01

A phase space approximation method for linear dispersive wave propagation with arbitrary initial conditions is developed. The results expand on a previous approximation in terms of the Wigner distribution of a single mode. In contrast to this previously considered single-mode case, the approximation presented here is for the full wave and is obtained by a different approach. This solution requires one to obtain (i) the initial modal functions from the given initial wave, and (ii) the initial cross-Wigner distribution between different modal functions. The full wave is the sum of modal functions. The approximation is obtained for general linear wave equations by transforming the equations to phase space, and then solving in the new domain. It is shown that each modal function of the wave satisfies a Schrödinger-type equation where the equivalent "Hamiltonian" operator is the dispersion relation corresponding to the mode and where the wavenumber is replaced by the wavenumber operator. Application to the beam equation is considered to illustrate the approach.

Numerical simulation of electromagnetic waves in Schwarzschild space-time by finite difference time domain method and Green function method

NASA Astrophysics Data System (ADS)

Jia, Shouqing; La, Dongsheng; Ma, Xuelian

2018-04-01

The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.

Towards anti-causal Green's function for three-dimensional sub-diffraction focusing

NASA Astrophysics Data System (ADS)

Ma, Guancong; Fan, Xiying; Ma, Fuyin; de Rosny, Julien; Sheng, Ping; Fink, Mathias

2018-06-01

In causal physics, the causal Green's function describes the radiation of a point source. Its counterpart, the anti-causal Green's function, depicts a spherically converging wave. However, in free space, any converging wave must be followed by a diverging one. Their interference gives rise to the diffraction limit that constrains the smallest possible dimension of a wave's focal spot in free space, which is half the wavelength. Here, we show with three-dimensional acoustic experiments that we can realize a stand-alone anti-causal Green's function in a large portion of space up to a subwavelength distance from the focus point by introducing a near-perfect absorber for spherical waves at the focus. We build this subwavelength absorber based on membrane-type acoustic metamaterial, and experimentally demonstrate focusing of spherical waves beyond the diffraction limit.

Real-time holographic surveillance system

DOEpatents

Collins, H. Dale; McMakin, Douglas L.; Hall, Thomas E.; Gribble, R. Parks

1995-01-01

A holographic surveillance system including means for generating electromagnetic waves; means for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; means for receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; means for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and means for displaying the processed information to determine nature of the target. The means for processing the electrical signals includes means for converting analog signals to digital signals followed by a computer means to apply a backward wave algorithm.

Real-time wideband holographic surveillance system

DOEpatents

Sheen, David M.; Collins, H. Dale; Hall, Thomas E.; McMakin, Douglas L.; Gribble, R. Parks; Severtsen, Ronald H.; Prince, James M.; Reid, Larry D.

1996-01-01

A wideband holographic surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply a three dimensional backward wave algorithm.

Real-time wideband holographic surveillance system

DOEpatents

Sheen, D.M.; Collins, H.D.; Hall, T.E.; McMakin, D.L.; Gribble, R.P.; Severtsen, R.H.; Prince, J.M.; Reid, L.D.

1996-09-17

A wideband holographic surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply a three dimensional backward wave algorithm. 28 figs.

Quantum mechanics of a photon

NASA Astrophysics Data System (ADS)

Babaei, Hassan; Mostafazadeh, Ali

2017-08-01

A first-quantized free photon is a complex massless vector field A =(Aμ ) whose field strength satisfies Maxwell's equations in vacuum. We construct the Hilbert space H of the photon by endowing the vector space of the fields A in the temporal-Coulomb gauge with a positive-definite and relativistically invariant inner product. We give an explicit expression for this inner product, identify the Hamiltonian for the photon with the generator of time translations in H , determine the operators representing the momentum and the helicity of the photon, and introduce a chirality operator whose eigenfunctions correspond to fields having a definite sign of energy. We also construct a position operator for the photon whose components commute with each other and with the chirality and helicity operators. This allows for the construction of the localized states of the photon with a definite sign of energy and helicity. We derive an explicit formula for the latter and compute the corresponding electric and magnetic fields. These turn out to diverge not just at the point where the photon is localized but on a plane containing this point. We identify the axis normal to this plane with an associated symmetry axis and show that each choice of this axis specifies a particular position operator, a corresponding position basis, and a position representation of the quantum mechanics of a photon. In particular, we examine the position wave functions determined by such a position basis, elucidate their relationship with the Riemann-Silberstein and Landau-Peierls wave functions, and give an explicit formula for the probability density of the spatial localization of the photon.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blaut, Arkadiusz

We present the results of the estimation of parameters with LISA for nearly monochromatic gravitational waves in the low and high frequency regimes for the time-delay interferometry response. Angular resolution of the detector and the estimation errors of the signal's parameters in the high frequency regimes are calculated as functions of the position in the sky and as functions of the frequency. For the long-wavelength domain we give compact formulas for the estimation errors valid on a wide range of the parameter space.

Nonlinear Network Description for Many-Body Quantum Systems in Continuous Space

NASA Astrophysics Data System (ADS)

Ruggeri, Michele; Moroni, Saverio; Holzmann, Markus

2018-05-01

We show that the recently introduced iterative backflow wave function can be interpreted as a general neural network in continuum space with nonlinear functions in the hidden units. Using this wave function in variational Monte Carlo simulations of liquid 4He in two and three dimensions, we typically find a tenfold increase in accuracy over currently used wave functions. Furthermore, subsequent stages of the iteration procedure define a set of increasingly good wave functions, each with its own variational energy and variance of the local energy: extrapolation to zero variance gives energies in close agreement with the exact values. For two dimensional 4He, we also show that the iterative backflow wave function can describe both the liquid and the solid phase with the same functional form—a feature shared with the shadow wave function, but now joined by much higher accuracy. We also achieve significant progress for liquid 3He in three dimensions, improving previous variational and fixed-node energies.

Improved surface-wave retrieval from ambient seismic noise by multi-dimensional deconvolution

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; Ruigrok, Elmer; van der Neut, Joost; Draganov, Deyan

2011-01-01

The methodology of surface-wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface-wave Green's function. A point-spread function, derived from the same ambient noise field, quantifies the smearing in space and time of the virtual source of the Green's function. By multidimensionally deconvolving the retrieved Green's function by the point-spread function, the virtual source becomes better focussed in space and time and hence the accuracy of the retrieved surface-wave Green's function may improve significantly. We illustrate this at the hand of a numerical example and discuss the advantages and limitations of this new methodology.

Real-time holographic surveillance system

DOEpatents

Collins, H.D.; McMakin, D.L.; Hall, T.E.; Gribble, R.P.

1995-10-03

A holographic surveillance system is disclosed including means for generating electromagnetic waves; means for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; means for receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; means for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and means for displaying the processed information to determine nature of the target. The means for processing the electrical signals includes means for converting analog signals to digital signals followed by a computer means to apply a backward wave algorithm. 21 figs.

On the transition from the quantum to the classical regime for massive scalar particles: A spatiotemporal approach

NASA Astrophysics Data System (ADS)

Lusanna, Luca; Pauri, Massimo

2014-08-01

If the classical structure of space-time is assumed to define an a priori scenario for the formulation of quantum theory (QT), the coordinate representation of the solutions of the Schroedinger equation of a quantum system containing one ( N) massive scalar particle has a preferred status. Let us consider all of the solutions admitting a multipolar expansion of the probability density function (and more generally of the Wigner function) around a space-time trajectory to be properly selected. For every normalized solution there is a privileged trajectory implying the vanishing of the dipole moment of the multipolar expansion: it is given by the expectation value of the position operator . Then, the special subset of solutions which satisfy Ehrenfest's Theorem (named thereby Ehrenfest monopole wave functions (EMWF)), have the important property that this privileged classical trajectory is determined by a closed Newtonian equation of motion where the effective force is the Newtonian force plus non-Newtonian terms (of order ħ 2 or higher) depending on the higher multipoles of the probability distribution ρ. Note that the superposition of two EMWFs is not an EMWF, a result to be strongly hoped for, given the possible unwanted implications concerning classical spatial perception. These results can be extended to N-particle systems in such a way that, when N classical trajectories with all the dipole moments vanishing and satisfying Ehrenfest theorem are associated with the normalized wave functions of the N-body system, we get a natural transition from the 3 N-dimensional configuration space to the space-time. Moreover, these results can be extended to relativistic quantum mechanics. Consequently, in suitable states of N quantum particle which are EMWF, we get the "emergence" of corresponding "classical particles" following Newton-like trajectories in space-time. Note that all this holds true in the standard framework of quantum mechanics, i.e. assuming, in particular, the validity of Born's rule and the individual system interpretation of the wave function (no ensemble interpretation). These results are valid without any approximation (like ħ → 0, big quantum numbers, etc.). Moreover, we do not commit ourselves to any specific ontological interpretation of quantum theory (such as, e.g., the Bohmian one). We will argue that, in substantial agreement with Bohr's viewpoint, the macroscopic description of the preparation, certain intermediate steps and the detection of the final outcome of experiments involving massive particles are dominated by these classical "effective" trajectories. This approach can be applied to the point of view of de-coherence in the case of a diagonal reduced density matrix ρ red (an improper mixture) depending on the position variables of a massive particle and of a pointer. When both the particle and the pointer wave functions appearing in ρ red are EMWF, the expectation value of the particle and pointer position variables becomes a statistical average on a classical ensemble. In these cases an improper quantum mixture becomes a classical statistical one, thus providing a particular answer to an open problem of de-coherence about the emergence of classicality.

Construction of CASCI-type wave functions for very large active spaces.

PubMed

Boguslawski, Katharina; Marti, Konrad H; Reiher, Markus

2011-06-14

We present a procedure to construct a configuration-interaction expansion containing arbitrary excitations from an underlying full-configuration-interaction-type wave function defined for a very large active space. Our procedure is based on the density-matrix renormalization group (DMRG) algorithm that provides the necessary information in terms of the eigenstates of the reduced density matrices to calculate the coefficient of any basis state in the many-particle Hilbert space. Since the dimension of the Hilbert space scales binomially with the size of the active space, a sophisticated Monte Carlo sampling routine is employed. This sampling algorithm can also construct such configuration-interaction-type wave functions from any other type of tensor network states. The configuration-interaction information obtained serves several purposes. It yields a qualitatively correct description of the molecule's electronic structure, it allows us to analyze DMRG wave functions converged for the same molecular system but with different parameter sets (e.g., different numbers of active-system (block) states), and it can be considered a balanced reference for the application of a subsequent standard multi-reference configuration-interaction method.

Asymptotic behavior and interpretation of virtual states: The effects of confinement and of basis sets

NASA Astrophysics Data System (ADS)

Boffi, Nicholas M.; Jain, Manish; Natan, Amir

2016-02-01

A real-space high order finite difference method is used to analyze the effect of spherical domain size on the Hartree-Fock (and density functional theory) virtual eigenstates. We show the domain size dependence of both positive and negative virtual eigenvalues of the Hartree-Fock equations for small molecules. We demonstrate that positive states behave like a particle in spherical well and show how they approach zero. For the negative eigenstates, we show that large domains are needed to get the correct eigenvalues. We compare our results to those of Gaussian basis sets and draw some conclusions for real-space, basis-sets, and plane-waves calculations.

Radiation from long pulse train electron beams in space plasmas

NASA Technical Reports Server (NTRS)

Harker, K. J.; Banks, P. M.

1985-01-01

A previous study of electromagnetic radiation from a finite train of electron pulses is extended to an infinite train of such pulses. The electrons are assumed to follow an idealized helical path through a space plasma in such a manner as to retain their respective position within the beam. This leads to radiation by coherent spontaneous emission. The waves of interest in this region are the whistler slow (compressional) and fast (torsional) Alfven waves. Although a general theory is developed, analysis is then restricted to two approximations, the short and long electron beam. Formulas for the radiation per unit solid angle from the short beam are presented as a function of both propagation and ray angles, electron beam pulse width and separation and beam current, voltage, and pitch angle. Similar formulas for the total power radiated from the long beam are derived as a function of frequency, propagation angle, and ray angle. Predictions of the power radiated are presented for representative examples as determined by the long beam theory.

Green’s functions for a volume source in an elastic half-space

PubMed Central

Zabolotskaya, Evgenia A.; Ilinskii, Yurii A.; Hay, Todd A.; Hamilton, Mark F.

2012-01-01

Green’s functions are derived for elastic waves generated by a volume source in a homogeneous isotropic half-space. The context is sources at shallow burial depths, for which surface (Rayleigh) and bulk waves, both longitudinal and transverse, can be generated with comparable magnitudes. Two approaches are followed. First, the Green’s function is expanded with respect to eigenmodes that correspond to Rayleigh waves. While bulk waves are thus ignored, this approximation is valid on the surface far from the source, where the Rayleigh wave modes dominate. The second approach employs an angular spectrum that accounts for the bulk waves and yields a solution that may be separated into two terms. One is associated with bulk waves, the other with Rayleigh waves. The latter is proved to be identical to the Green’s function obtained following the first approach. The Green’s function obtained via angular spectrum decomposition is analyzed numerically in the time domain for different burial depths and distances to the receiver, and for parameters relevant to seismo-acoustic detection of land mines and other buried objects. PMID:22423682

Quantum phase space with a basis of Wannier functions

NASA Astrophysics Data System (ADS)

Fang, Yuan; Wu, Fan; Wu, Biao

2018-02-01

A quantum phase space with Wannier basis is constructed: (i) classical phase space is divided into Planck cells; (ii) a complete set of Wannier functions are constructed with the combination of Kohn’s method and Löwdin method such that each Wannier function is localized at a Planck cell. With these Wannier functions one can map a wave function unitarily onto phase space. Various examples are used to illustrate our method and compare it to Wigner function. The advantage of our method is that it can smooth out the oscillations in wave functions without losing any information and is potentially a better tool in studying quantum-classical correspondence. In addition, we point out that our method can be used for time-frequency analysis of signals.

Alignment error of mirror modules of advanced telescope for high-energy astrophysics due to wavefront aberrations

NASA Astrophysics Data System (ADS)

Zocchi, Fabio E.

2017-10-01

One of the approaches that is being tested for the integration of the mirror modules of the advanced telescope for high-energy astrophysics x-ray mission of the European Space Agency consists in aligning each module on an optical bench operated at an ultraviolet wavelength. The mirror module is illuminated by a plane wave and, in order to overcome diffraction effects, the centroid of the image produced by the module is used as a reference to assess the accuracy of the optical alignment of the mirror module itself. Among other sources of uncertainty, the wave-front error of the plane wave also introduces an error in the position of the centroid, thus affecting the quality of the mirror module alignment. The power spectral density of the position of the point spread function centroid is here derived from the power spectral density of the wave-front error of the plane wave in the framework of the scalar theory of Fourier diffraction. This allows the defining of a specification on the collimator quality used for generating the plane wave starting from the contribution to the error budget allocated for the uncertainty of the centroid position. The theory generally applies whenever Fourier diffraction is a valid approximation, in which case the obtained result is identical to that derived by geometrical optics considerations.

Real-time wideband cylindrical holographic surveillance system

DOEpatents

Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.; Severtsen, Ronald H.

1999-01-01

A wideband holographic cylindrical surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply Fast Fourier Transforms and obtain a three dimensional cylindrical image.

A stochastic fault model. 2. Time-dependent case.

USGS Publications Warehouse

Andrews, D.J.

1981-01-01

A random model of fault motion in an earthquake is formulated by assuming that the slip velocity is a random function of position and time truncated at zero, so that it does not have negative values. This random function is chosen to be self-affine; that is, on change of length scale, the function is multiplied by a scale factor but is otherwise unchanged statistically. A snapshot of slip velocity at a given time resembles a cluster of islands with rough topography; the final slip function is a smoother island or cluster of islands. In the Fourier transform domain, shear traction on the fault equals the slip velocity times an impedance function. The fact that this impedance function has a pole at zero frequency implies that traction and slip velocity cannot have the same spectral dependence in space and time. To describe stress fluctuations of the order of 100 bars when smoothed over a length of kilometers and of the order of kilobars at the grain size, shear traction must have a one-dimensional power spectrum is space proportional to the reciprocal wave number. Then the one-dimensional power spectrum for the slip velocity is proportional to the reciprocal wave number squared and for slip to its cube. If slip velocity has the same power law spectrum in time as in space, then the spectrum of ground acceleration with be flat (white noise) both on the fault and in the far field.-Author

Inhibition of quantum transport due to 'scars' of unstable periodic orbits

NASA Technical Reports Server (NTRS)

Jensen, R. V.; Sanders, M. M.; Saraceno, M.; Sundaram, B.

1989-01-01

A new quantum mechanism for the suppression of chaotic ionization of highly excited hydrogen atoms explains the appearance of anomalously stable states in the microwave ionization experiments of Koch et al. A novel phase-space representation of the perturbed wave functions reveals that the inhibition of quantum transport is due to the selective excitation of wave functions that are highly localized near unstable periodic orbits in the chaotic classical phase space. The 'scarred' wave functions provide a new basis for the quantum description of a variety of classically chaotic systems.

Adaptive multiconfigurational wave functions.

PubMed

Evangelista, Francesco A

2014-03-28

A method is suggested to build simple multiconfigurational wave functions specified uniquely by an energy cutoff Λ. These are constructed from a model space containing determinants with energy relative to that of the most stable determinant no greater than Λ. The resulting Λ-CI wave function is adaptive, being able to represent both single-reference and multireference electronic states. We also consider a more compact wave function parameterization (Λ+SD-CI), which is based on a small Λ-CI reference and adds a selection of all the singly and doubly excited determinants generated from it. We report two heuristic algorithms to build Λ-CI wave functions. The first is based on an approximate prescreening of the full configuration interaction space, while the second performs a breadth-first search coupled with pruning. The Λ-CI and Λ+SD-CI approaches are used to compute the dissociation curve of N2 and the potential energy curves for the first three singlet states of C2. Special attention is paid to the issue of energy discontinuities caused by changes in the size of the Λ-CI wave function along the potential energy curve. This problem is shown to be solvable by smoothing the matrix elements of the Hamiltonian. Our last example, involving the Cu2O2(2+) core, illustrates an alternative use of the Λ-CI method: as a tool to both estimate the multireference character of a wave function and to create a compact model space to be used in subsequent high-level multireference coupled cluster computations.

Solution of two-body relativistic bound state equations with confining plus Coulomb interactions

NASA Technical Reports Server (NTRS)

Maung, Khin Maung; Kahana, David E.; Norbury, John W.

1992-01-01

Studies of meson spectroscopy have often employed a nonrelativistic Coulomb plus Linear Confining potential in position space. However, because the quarks in mesons move at an appreciable fraction of the speed of light, it is necessary to use a relativistic treatment of the bound state problem. Such a treatment is most easily carried out in momentum space. However, the position space Linear and Coulomb potentials lead to singular kernels in momentum space. Using a subtraction procedure we show how to remove these singularities exactly and thereby solve the Schroedinger equation in momentum space for all partial waves. Furthermore, we generalize the Linear and Coulomb potentials to relativistic kernels in four dimensional momentum space. Again we use a subtraction procedure to remove the relativistic singularities exactly for all partial waves. This enables us to solve three dimensional reductions of the Bethe-Salpeter equation. We solve six such equations for Coulomb plus Confining interactions for all partial waves.

A numerical wave-optical approach for the simulation of analyzer-based x-ray imaging

NASA Astrophysics Data System (ADS)

Bravin, A.; Mocella, V.; Coan, P.; Astolfo, A.; Ferrero, C.

2007-04-01

An advanced wave-optical approach for simulating a monochromator-analyzer set-up in Bragg geometry with high accuracy is presented. The polychromaticity of the incident wave on the monochromator is accounted for by using a distribution of incoherent point sources along the surface of the crystal. The resulting diffracted amplitude is modified by the sample and can be well represented by a scalar representation of the optical field where the limitations of the usual ‘weak object’ approximation are removed. The subsequent diffraction mechanism on the analyzer is described by the convolution of the incoming wave with the Green-Riemann function of the analyzer. The free space propagation up to the detector position is well reproduced by a classical Fresnel-Kirchhoff integral. The preliminary results of this innovative approach show an excellent agreement with experimental data.

Magnetosonic solitons in space plasmas: dark or bright solitons?

NASA Astrophysics Data System (ADS)

Pokhotelov, O. A.; Onishchenko, O. G.; Balikhin, M. A.; Stenflo, L.; Shukla, P. K.

2007-12-01

The nonlinear theory of large-amplitude magnetosonic (MS) waves in highβ space plasmas is revisited. It is shown that solitary waves can exist in the form of `bright' or `dark' solitons in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion, which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived.It takes into account general plasma equilibria, such as the Dory-Guest-Harris (DGH) or Kennel-Ashour-Abdalla (KA) loss-cone equilibria, as well as distributions with a power-law velocity dependence that can be modelled by κdistributions. It is shown that in a bi-Maxwellian plasma the dispersion is negative, i.e. the phase velocity decreases with an increase of the wavenumber. This means that the solitary solution in this case has the form of a `bright' soliton with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas, such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall-MHD equations are reviewed. The relevance of our theoretical results to existing satellite wave observations is outlined.

Magnetosonic Solitons in Non-Maxwellian Space Plasmas

NASA Astrophysics Data System (ADS)

Pokhotelov, O. A.; Balikhin, M.; Onishchenko, O. G.

2006-12-01

The nonlinear theory of large-amplitude magnetosonic (MS) waves in high-beta space plasmas is developed. It is shown that solitary waves can exist in the form of magnetic humps and holes in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion velocity distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived. It takes into account general plasma equilibria such as the Dory-Guest-Harris or Kennel- Ashour-Abdalla loss cone equilibria, as well as distributions with a power law velocity dependence that can be modelled by kappa-distributions. It is shown that in Maxwellian and bi-Maxwellian plasmas the dispersion is negative, i.e. the phase velocity decreases with an increase of the wave number. This means that the solitary solution in this case has the form of a magnetic hump with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall-MHD equations are reviewed. The relevance of our theoretical results to experimental observations is outlined

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis.

PubMed

Gustafsson, Alexander; Paulsson, Magnus

2017-12-20

We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Paulsson, Magnus

2017-12-01

We present a method used to intuitively interpret the scanning tunneling microscopy (STM) contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(1 1 1) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

Integrability and solitons for the higher-order nonlinear Schrödinger equation with space-dependent coefficients in an optical fiber

NASA Astrophysics Data System (ADS)

Su, Jing-Jing; Gao, Yi-Tian

2018-03-01

Under investigation in this paper is a higher-order nonlinear Schrödinger equation with space-dependent coefficients, related to an optical fiber. Based on the self-similarity transformation and Hirota method, related to the integrability, the N-th-order bright and dark soliton solutions are derived under certain constraints. It is revealed that the velocities and trajectories of the solitons are both affected by the coefficient of the sixth-order dispersion term while the amplitudes of the solitons are determined by the gain function. Amplitudes increase when the gain function is positive and decrease when the gain function is negative. Furthermore, we find that the intensities of dark solitons are presented as a superposition of the solitons and stationary waves.

Effect of turbulence on the dissipation of the space-charge wave in a bounded turbulent plasma column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588

The dispersion relation and the dissipation process of the space-charge wave propagating in a bounded plasma such as a cylindrical waveguide are investigated by employing the longitudinal dielectric permittivity that contains the diffusivity based on the Dupree theory of turbulent plasma. We derived the dispersion relation for space-charge wave in terms of the radius of cylindrical waveguide and the roots of the Bessel function of the first kind which appears as the boundary condition. We find that the wave frequency for a lower-order root of the Bessel function is higher than that of a higher-order root. We also find thatmore » the dissipation is greatest for the lowest-order root, but it is suppressed significantly as the order of the root increases. The wave frequency and the dissipation process are enhanced as the radius of cylindrical waveguide increases. However, they are always smaller than the case of bulk plasma. We find that the diffusivity of turbulent plasma would enhance the damping of space-charge waves, especially, in the range of small wave number. For a large wave number, the diffusivity has little effect on the damping.« less

Quantum-mechanical analysis of low-gain free-electron laser oscillators

NASA Astrophysics Data System (ADS)

Fares, H.; Yamada, M.; Chiadroni, E.; Ferrario, M.

2018-05-01

In the previous classical theory of the low-gain free-electron laser (FEL) oscillators, the electron is described as a point-like particle, a delta function in the spatial space. On the other hand, in the previous quantum treatments, the electron is described as a plane wave with a single momentum state, a delta function in the momentum space. In reality, an electron must have statistical uncertainties in the position and momentum domains. Then, the electron is neither a point-like charge nor a plane wave of a single momentum. In this paper, we rephrase the theory of the low-gain FEL where the interacting electron is represented quantum mechanically by a plane wave with a finite spreading length (i.e., a wave packet). Using the concepts of the transformation of reference frames and the statistical quantum mechanics, an expression for the single-pass radiation gain is derived. The spectral broadening of the radiation is expressed in terms of the spreading length of an electron, the relaxation time characterizing the energy spread of electrons, and the interaction time. We introduce a comparison between our results and those obtained in the already known classical analyses where a good agreement between both results is shown. While the correspondence between our results and the classical results are shown, novel insights into the electron dynamics and the interaction mechanism are presented.

The Mean Curvature of the Influence Surface of Wave Equation With Sources on a Moving Surface

NASA Technical Reports Server (NTRS)

Farassat, F.; Farris, Mark

1999-01-01

The mean curvature of the influence surface of the space-time point (x, t) appears in linear supersonic propeller noise theory and in the Kirchhoff formula for a supersonic surface. Both these problems are governed by the linear wave equation with sources on a moving surface. The influence surface is also called the Sigma - surface in the aeroacoustic literature. This surface is the locus, in a frame fixed to the quiescent medium, of all the points of a radiating surface f(x, t) = 0 whose acoustic signals arrive simultaneously to an observer at position x and at the time t. Mathematically, the Sigma- surface is produced by the intersection of the characteristic conoid of the space-time point (x, t) and the moving surface. In this paper, we derive the expression for the local mean curvature of the Sigma - space of the space-time point for a moving rigid or deformable surface f(x, t) = 0. This expression is a complicated function of the geometric and kinematic parameters of the surface f(x, t) = 0. Using the results of this paper, the solution of the governing wave equation of high speed propeller noise radiation as well as the Kirchhoff formula for a supersonic surface can be written as very compact analytic expression.

An exact solution for the Hawking effect in a dispersive fluid

NASA Astrophysics Data System (ADS)

Philbin, T. G.

2016-09-01

We consider the wave equation for sound in a moving fluid with a fourth-order anomalous dispersion relation. The velocity of the fluid is a linear function of position, giving two points in the flow where the fluid velocity matches the group velocity of low-frequency waves. We find the exact solution for wave propagation in the flow. The scattering shows amplification of classical waves, leading to spontaneous emission when the waves are quantized. In the dispersionless limit the system corresponds to a 1 +1 -dimensional black-hole or white-hole binary and there is a thermal spectrum of Hawking radiation from each horizon. Dispersion changes the scattering coefficients so that the quantum emission is no longer thermal. The scattering coefficients were previously obtained by Busch and Parentani in a study of dispersive fields in de Sitter space [Phys. Rev. D 86, 104033 (2012)]. Our results give further details of the wave propagation in this exactly solvable case, where our focus is on laboratory systems.

Analysis and measurement of the modulation transfer function of harmonic shear wave induced phase encoding imaging.

PubMed

McAleavey, Stephen A

2014-05-01

Shear wave induced phase encoding (SWIPE) imaging generates ultrasound backscatter images of tissue-like elastic materials by using traveling shear waves to encode the lateral position of the scatters in the phase of the received echo. In contrast to conventional ultrasound B-scan imaging, SWIPE offers the potential advantages of image formation without beam focusing or steering from a single transducer element, lateral resolution independent of aperture size, and the potential to achieve relatively high lateral resolution with low frequency ultrasound. Here a Fourier series description of the phase modulated echo signal is developed, demonstrating that echo harmonics at multiples of the shear wave frequency reveal target k-space data at identical multiples of the shear wavenumber. Modulation transfer functions of SWIPE imaging systems are calculated for maximum shear wave acceleration and maximum shear constraints, and compared with a conventionally focused aperture. The relative signal-to-noise ratio of the SWIPE method versus a conventionally focused aperture is found through these calculations. Reconstructions of wire targets in a gelatin phantom using 1 and 3.5 MHz ultrasound and a cylindrical shear wave source are presented, generated from the fundamental and second harmonic of the shear wave modulation frequency, demonstrating weak dependence of lateral resolution with ultrasound frequency.

Approximating SIR-B response characteristics and estimating wave height and wavelength for ocean imagery

NASA Technical Reports Server (NTRS)

Tilley, David G.

1987-01-01

NASA Space Shuttle Challenger SIR-B ocean scenes are used to derive directional wave spectra for which speckle noise is modeled as a function of Rayleigh random phase coherence downrange and Poisson random amplitude errors inherent in the Doppler measurement of along-track position. A Fourier filter that preserves SIR-B image phase relations is used to correct the stationary and dynamic response characteristics of the remote sensor and scene correlator, as well as to subtract an estimate of the speckle noise component. A two-dimensional map of sea surface elevation is obtained after the filtered image is corrected for both random and deterministic motions.

Real-time wideband cylindrical holographic surveillance system

DOEpatents

Sheen, D.M.; McMakin, D.L.; Hall, T.E.; Severtsen, R.H.

1999-01-12

A wideband holographic cylindrical surveillance system is disclosed including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply Fast Fourier Transforms and obtain a three dimensional cylindrical image. 13 figs.

Adaptive multiconfigurational wave functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evangelista, Francesco A., E-mail: francesco.evangelista@emory.edu

2014-03-28

A method is suggested to build simple multiconfigurational wave functions specified uniquely by an energy cutoff Λ. These are constructed from a model space containing determinants with energy relative to that of the most stable determinant no greater than Λ. The resulting Λ-CI wave function is adaptive, being able to represent both single-reference and multireference electronic states. We also consider a more compact wave function parameterization (Λ+SD-CI), which is based on a small Λ-CI reference and adds a selection of all the singly and doubly excited determinants generated from it. We report two heuristic algorithms to build Λ-CI wave functions.more » The first is based on an approximate prescreening of the full configuration interaction space, while the second performs a breadth-first search coupled with pruning. The Λ-CI and Λ+SD-CI approaches are used to compute the dissociation curve of N{sub 2} and the potential energy curves for the first three singlet states of C{sub 2}. Special attention is paid to the issue of energy discontinuities caused by changes in the size of the Λ-CI wave function along the potential energy curve. This problem is shown to be solvable by smoothing the matrix elements of the Hamiltonian. Our last example, involving the Cu{sub 2}O{sub 2}{sup 2+} core, illustrates an alternative use of the Λ-CI method: as a tool to both estimate the multireference character of a wave function and to create a compact model space to be used in subsequent high-level multireference coupled cluster computations.« less

Shannon entropies and Fisher information of K-shell electrons of neutral atoms

NASA Astrophysics Data System (ADS)

Sekh, Golam Ali; Saha, Aparna; Talukdar, Benoy

2018-02-01

We represent the two K-shell electrons of neutral atoms by Hylleraas-type wave function which fulfils the exact behavior at the electron-electron and electron-nucleus coalescence points and, derive a simple method to construct expressions for single-particle position- and momentum-space charge densities, ρ (r) and γ (p) respectively. We make use of the results for ρ (r) and γ (p) to critically examine the effect of correlation on bare (uncorrelated) values of Shannon information entropies (S) and of Fisher information (F) for the K-shell electrons of atoms from helium to neon. Due to inter-electronic repulsion the values of the uncorrelated Shannon position-space entropies are augmented while those of the momentum-space entropies are reduced. The corresponding Fisher information are found to exhibit opposite behavior in respect of this. Attempts are made to provide some plausible explanation for the observed response of S and F to electronic correlation.

Multiconfiguration Pair-Density Functional Theory: A New Way To Treat Strongly Correlated Systems.

PubMed

Gagliardi, Laura; Truhlar, Donald G; Li Manni, Giovanni; Carlson, Rebecca K; Hoyer, Chad E; Bao, Junwei Lucas

2017-01-17

The electronic energy of a system provides the Born-Oppenheimer potential energy for internuclear motion and thus determines molecular structure and spectra, bond energies, conformational energies, reaction barrier heights, and vibrational frequencies. The development of more efficient and more accurate ways to calculate the electronic energy of systems with inherently multiconfigurational electronic structure is essential for many applications, including transition metal and actinide chemistry, systems with partially broken bonds, many transition states, and most electronically excited states. Inherently multiconfigurational systems are called strongly correlated systems or multireference systems, where the latter name refers to the need for using more than one ("multiple") configuration state function to provide a good zero-order reference wave function. This Account describes multiconfiguration pair-density functional theory (MC-PDFT), which was developed as a way to combine the advantages of wave function theory (WFT) and density functional theory (DFT) to provide a better treatment of strongly correlated systems. First we review background material: the widely used Kohn-Sham DFT (which uses only a single Slater determinant as reference wave function), multiconfiguration WFT methods that treat inherently multiconfigurational systems based on an active space, and previous attempts to combine multiconfiguration WFT with DFT. Then we review the formulation of MC-PDFT. It is a generalization of Kohn-Sham DFT in that the electron kinetic energy and classical electrostatic energy are calculated from a reference wave function, while the rest of the energy is obtained from a density functional. However, there are two main differences with respent to Kohn-Sham DFT: (i) The reference wave function is multiconfigurational rather than being a single Slater determinant. (ii) The density functional is a function of the total density and the on-top pair density rather than being a function of the spin-up and spin-down densities. In work carried out so far, the multiconfigurational wave function is a multiconfiguration self-consistent-field wave function. The new formulation has the advantage that the reference wave function has the correct spatial and spin symmetry and can describe bond dissociation (of both single and multiple bonds) and electronic excitations in a formally and physically correct way. We then review the formulation of density functionals in terms of the on-top pair density. Finally we review successful applications of the theory to bond energies and bond dissociation potential energy curves of main-group and transition metal bonds, to barrier heights (including pericyclic reactions), to proton affinities, to the hydrogen bond energy of water dimer, to ground- and excited-state charge transfer, to valence and Rydberg excitations of molecules, and to singlet-triplet splittings of radicals. We find that that MC-PDFT can give accurate results not only with complete-active-space multiconfiguration wave functions but also with generalized-active-space multiconfiguration wave functions, which are practical for larger numbers of active electrons and active orbitals than are complete-active-space wave functions. The separated-pair approximation, which is a special case of generalized active space self-consistent-field theory, is especially promising. MC-PDFT, because it requires much less computer time and storage than pure WFT methods, has the potential to open larger and more complex strongly correlated systems to accurate simulation.

Quantum trajectory analysis of multimode subsystem-bath dynamics.

PubMed

Wyatt, Robert E; Na, Kyungsun

2002-01-01

The dynamics of a swarm of quantum trajectories is investigated for systems involving the interaction of an active mode (the subsystem) with an M-mode harmonic reservoir (the bath). Equations of motion for the position, velocity, and action function for elements of the probability fluid are integrated in the Lagrangian (moving with the fluid) picture of quantum hydrodynamics. These fluid elements are coupled through the Bohm quantum potential and as a result evolve as a correlated ensemble. Wave function synthesis along the trajectories permits an exact description of the quantum dynamics for the evolving probability fluid. The approach is fully quantum mechanical and does not involve classical or semiclassical approximations. Computational results are presented for three systems involving the interaction on an active mode with M=1, 10, and 15 bath modes. These results include configuration space trajectory evolution, flux analysis of the evolving ensemble, wave function synthesis along trajectories, and energy partitioning along specific trajectories. These results demonstrate the feasibility of using a small number of quantum trajectories to obtain accurate quantum results on some types of open quantum systems that are not amenable to standard quantum approaches involving basis set expansions or Eulerian space-fixed grids.

Distinguishing between evidence and its explanations in the steering of atomic clocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, John M., E-mail: myers@seas.harvard.edu; Hadi Madjid, F., E-mail: gmadjid@aol.com

2014-11-15

Quantum theory reflects within itself a separation of evidence from explanations. This separation leads to a known proof that: (1) no wave function can be determined uniquely by evidence, and (2) any chosen wave function requires a guess reaching beyond logic to things unforeseeable. Chosen wave functions are encoded into computer-mediated feedback essential to atomic clocks, including clocks that step computers through their phases of computation and clocks in space vehicles that supply evidence of signal propagation explained by hypotheses of spacetimes with metric tensor fields. The propagation of logical symbols from one computer to another requires a shared rhythm—likemore » a bucket brigade. Here we show how hypothesized metric tensors, dependent on guesswork, take part in the logical synchronization by which clocks are steered in rate and position toward aiming points that satisfy phase constraints, thereby linking the physics of signal propagation with the sharing of logical symbols among computers. Recognizing the dependence of the phasing of symbol arrivals on guesses about signal propagation transports logical synchronization from the engineering of digital communications to a discipline essential to physics. Within this discipline we begin to explore questions invisible under any concept of time that fails to acknowledge unforeseeable events. In particular, variation of spacetime curvature is shown to limit the bit rate of logical communication. - Highlights: • Atomic clocks are steered in frequency toward an aiming point. • The aiming point depends on a chosen wave function. • No evidence alone can determine the wave function. • The unknowability of the wave function has implications for spacetime curvature. • Variability in spacetime curvature limits the bit rate of communications.« less

Ion hole formation and nonlinear generation of electromagnetic ion cyclotron waves: THEMIS observations

NASA Astrophysics Data System (ADS)

Shoji, Masafumi; Miyoshi, Yoshizumi; Katoh, Yuto; Keika, Kunihiro; Angelopoulos, Vassilis; Kasahara, Satoshi; Asamura, Kazushi; Nakamura, Satoko; Omura, Yoshiharu

2017-09-01

Electromagnetic plasma waves are thought to be responsible for energy exchange between charged particles in space plasmas. Such an energy exchange process is evidenced by phase space holes identified in the ion distribution function and measurements of the dot product of the plasma wave electric field and the ion velocity. We develop a method to identify ion hole formation, taking into consideration the phase differences between the gyromotion of ions and the electromagnetic ion cyclotron (EMIC) waves. Using this method, we identify ion holes in the distribution function and the resulting nonlinear EMIC wave evolution from Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. These ion holes are key to wave growth and frequency drift by the ion currents through nonlinear wave-particle interactions, which are identified by a computer simulation in this study.

Theoretical information measurement in nonrelativistic time-dependent approach

NASA Astrophysics Data System (ADS)

Najafizade, S. A.; Hassanabadi, H.; Zarrinkamar, S.

2018-02-01

The information-theoretic measures of time-dependent Schrödinger equation are investigated via the Shannon information entropy, variance and local Fisher quantities. In our calculations, we consider the two first states n = 0,1 and obtain the position Sx (t) and momentum Sp (t) Shannon entropies as well as Fisher information Ix (t) in position and momentum Ip (t) spaces. Using the Fourier transformed wave function, we obtain the results in momentum space. Some interesting features of the information entropy densities ρs (x,t) and γs (p,t), as well as the probability densities ρ (x,t) and γ (p,t) for time-dependent states are demonstrated. We establish a general relation between variance and Fisher's information. The Bialynicki-Birula-Mycielski inequality is tested and verified for the states n = 0,1.

Using level set based inversion of arrival times to recover shear wave speed in transient elastography and supersonic imaging

NASA Astrophysics Data System (ADS)

McLaughlin, Joyce; Renzi, Daniel

2006-04-01

Transient elastography and supersonic imaging are promising new techniques for characterizing the elasticity of soft tissues. Using this method, an 'ultrafast imaging' system (up to 10 000 frames s-1) follows in real time the propagation of a low-frequency shear wave. The displacement of the propagating shear wave is measured as a function of time and space. Here we develop a fast level set based algorithm for finding the shear wave speed from the interior positions of the propagating front. We compare the performance of level curve methods developed here and our previously developed (McLaughlin J and Renzi D 2006 Shear wave speed recovery in transient elastography and supersonic imaging using propagating fronts Inverse Problems 22 681-706) distance methods. We give reconstruction examples from synthetic data and from data obtained from a phantom experiment accomplished by Mathias Fink's group (the Laboratoire Ondes et Acoustique, ESPCI, Université Paris VII).

Stability of transition waves and positive entire solutions of Fisher-KPP equations with time and space dependence

NASA Astrophysics Data System (ADS)

Shen, Wenxian

2017-09-01

This paper is concerned with the stability of transition waves and strictly positive entire solutions of random and nonlocal dispersal evolution equations of Fisher-KPP type with general time and space dependence, including time and space periodic or almost periodic dependence as special cases. We first show the existence, uniqueness, and stability of strictly positive entire solutions of such equations. Next, we show the stability of uniformly continuous transition waves connecting the unique strictly positive entire solution and the trivial solution zero and satisfying certain decay property at the end close to the trivial solution zero (if it exists). The existence of transition waves has been studied in Liang and Zhao (2010 J. Funct. Anal. 259 857-903), Nadin (2009 J. Math. Pures Appl. 92 232-62), Nolen et al (2005 Dyn. PDE 2 1-24), Nolen and Xin (2005 Discrete Contin. Dyn. Syst. 13 1217-34) and Weinberger (2002 J. Math. Biol. 45 511-48) for random dispersal Fisher-KPP equations with time and space periodic dependence, in Nadin and Rossi (2012 J. Math. Pures Appl. 98 633-53), Nadin and Rossi (2015 Anal. PDE 8 1351-77), Nadin and Rossi (2017 Arch. Ration. Mech. Anal. 223 1239-67), Shen (2010 Trans. Am. Math. Soc. 362 5125-68), Shen (2011 J. Dynam. Differ. Equ. 23 1-44), Shen (2011 J. Appl. Anal. Comput. 1 69-93), Tao et al (2014 Nonlinearity 27 2409-16) and Zlatoš (2012 J. Math. Pures Appl. 98 89-102) for random dispersal Fisher-KPP equations with quite general time and/or space dependence, and in Coville et al (2013 Ann. Inst. Henri Poincare 30 179-223), Rawal et al (2015 Discrete Contin. Dyn. Syst. 35 1609-40) and Shen and Zhang (2012 Comm. Appl. Nonlinear Anal. 19 73-101) for nonlocal dispersal Fisher-KPP equations with time and/or space periodic dependence. The stability result established in this paper implies that the transition waves obtained in many of the above mentioned papers are asymptotically stable for well-fitted perturbation. Up to the author’s knowledge, it is the first time that the stability of transition waves of Fisher-KPP equations with general time and space dependence is studied.

Monte Carlo wave-function description of losses in a one-dimensional Bose gas and cooling to the ground state by quantum feedback

NASA Astrophysics Data System (ADS)

Schemmer, M.; Johnson, A.; Photopoulos, R.; Bouchoule, I.

2017-04-01

The effect of atom losses on a homogeneous one-dimensional Bose gas lying within the quasicondensate regime is investigated using a Monte Carlo wave-function approach. The evolution of the system is calculated, conditioned by the loss sequence, namely, the times of individual losses and the position of the removed atoms. We describe the gas within the linearized Bogoliubov approach. For each mode, we find that, for a given quantum trajectory, the state of the system converges towards a coherent state, i.e., the ground state, displaced in phase space. We show that, provided losses are recorded with a temporal and spatially resolved detector, quantum feedback can be implemented and cooling to the ground state of one or several modes can be realized.

Self-consistent adjoint analysis for topology optimization of electromagnetic waves

NASA Astrophysics Data System (ADS)

Deng, Yongbo; Korvink, Jan G.

2018-05-01

In topology optimization of electromagnetic waves, the Gâteaux differentiability of the conjugate operator to the complex field variable results in the complexity of the adjoint sensitivity, which evolves the original real-valued design variable to be complex during the iterative solution procedure. Therefore, the self-inconsistency of the adjoint sensitivity is presented. To enforce the self-consistency, the real part operator has been used to extract the real part of the sensitivity to keep the real-value property of the design variable. However, this enforced self-consistency can cause the problem that the derived structural topology has unreasonable dependence on the phase of the incident wave. To solve this problem, this article focuses on the self-consistent adjoint analysis of the topology optimization problems for electromagnetic waves. This self-consistent adjoint analysis is implemented by splitting the complex variables of the wave equations into the corresponding real parts and imaginary parts, sequentially substituting the split complex variables into the wave equations with deriving the coupled equations equivalent to the original wave equations, where the infinite free space is truncated by the perfectly matched layers. Then, the topology optimization problems of electromagnetic waves are transformed into the forms defined on real functional spaces instead of complex functional spaces; the adjoint analysis of the topology optimization problems is implemented on real functional spaces with removing the variational of the conjugate operator; the self-consistent adjoint sensitivity is derived, and the phase-dependence problem is avoided for the derived structural topology. Several numerical examples are implemented to demonstrate the robustness of the derived self-consistent adjoint analysis.

Wave computation on the Poincaré dodecahedral space

NASA Astrophysics Data System (ADS)

Bachelot-Motet, Agnès

2013-12-01

We compute the waves propagating on a compact 3-manifold of constant positive curvature with a non-trivial topology: the Poincaré dodecahedral space that is a plausible model of multi-connected universe. We transform the Cauchy problem to a mixed problem posed on a fundamental domain determined by the quaternionic calculus. We adopt a variational approach using a space of finite elements that is invariant under the action of the binary icosahedral group. The computation of the transient waves is validated with their spectral analysis by computing a lot of eigenvalues of the Laplace-Beltrami operator.

Propulsion system ignition overpressure for the Space Shuttle

NASA Technical Reports Server (NTRS)

Ryan, R. S.; Jones, J. H.; Guest, S. H.; Struck, H. G.; Rheinfurth, M. H.; Verferaime, V. S.

1981-01-01

Liquid and solid rocket motor propulsion systems create an overpressure wave during ignition, caused by the accelerating gas particles pushing against or displacing the air contained in the launch pad or launch facility and by the afterburning of the fuel-rich gases. This wave behaves as a blast or shock wave characterized by a positive triangular-shaped first pulse and a negative half-sine wave second pulse. The pulse travels up the space vehicle and has the potential of either overloading individual elements or exciting overall vehicle dynamics. The latter effect results from the phasing difference of the wave from one side of the vehicle to the other. This overpressure phasing, or delta P environment, because of its frequency content as well as amplitude, becomes a design driver for certain panels (e.g., thermal shields) and payloads for the Space Shuttle. The history of overpressure effects on the Space Shuttle, the basic overpressure phenomenon, Space Shuttle overpressure environment, scale model overpressure testing, and techniques for suppressing the overpressure environments are considered.

Origins and demonstrations of electrons with orbital angular momentum

PubMed Central

Agrawal, Amit; Ercius, Peter A.; Grillo, Vincenzo; Herzing, Andrew A.; Harvey, Tyler R.; Linck, Martin; Pierce, Jordan S.

2017-01-01

The surprising message of Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)) was that photons could possess orbital angular momentum in free space, which subsequently launched advancements in optical manipulation, microscopy, quantum optics, communications, many more fields. It has recently been shown that this result also applies to quantum mechanical wave functions describing massive particles (matter waves). This article discusses how electron wave functions can be imprinted with quantized phase vortices in analogous ways to twisted light, demonstrating that charged particles with non-zero rest mass can possess orbital angular momentum in free space. With Allen et al. as a bridge, connections are made between this recent work in electron vortex wave functions and much earlier works, extending a 175 year old tradition in matter wave vortices. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069765

Trial wave functions for ring-trapped ions and neutral atoms: Microscopic description of the quantum space-time crystal

NASA Astrophysics Data System (ADS)

Yannouleas, Constantine; Landman, Uzi

2017-10-01

A constructive theoretical platform for the description of quantum space-time crystals uncovers for N interacting and ring-confined rotating particles the existence of low-lying states with proper space-time crystal behavior. The construction of the corresponding many-body trial wave functions proceeds first via symmetry breaking at the mean-field level followed by symmetry restoration using projection techniques. The ensuing correlated many-body wave functions are stationary states and preserve the rotational symmetries, and at the same time they reflect the point-group symmetries of the mean-field crystals. This behavior results in the emergence of sequences of select magic angular momenta Lm. For angular-momenta away from the magic values, the trial functions vanish. Symmetry breaking beyond the mean-field level can be induced by superpositions of such good-Lm many-body stationary states. We show that superposing a pair of adjacent magic angular momenta states leads to formation of special broken-symmetry states exhibiting quantum space-time-crystal behavior. In particular, the corresponding particle densities rotate around the ring, showing undamped and nondispersed periodic crystalline evolution in both space and time. The experimental synthesis of such quantum space-time-crystal wave packets is predicted to be favored in the vicinity of ground-state energy crossings of the Aharonov-Bohm-type spectra accessed via an externally applied, natural or synthetic, magnetic field. These results are illustrated here for Coulomb-repelling fermionic ions and for a lump of contact-interaction attracting bosons.

Virtual detector theory for strong-field atomic ionization

NASA Astrophysics Data System (ADS)

Wang, Xu; Tian, Justin; Eberly, J. H.

2018-04-01

A virtual detector (VD) is an imaginary device located at a fixed position in space that extracts information from the wave packet passing through it. By recording the particle momentum and the corresponding probability current at each time, the VDs can accumulate and build the differential momentum distribution of the particle, in a way that resembles real experiments. A mathematical proof is given for the equivalence of the differential momentum distribution obtained by the VD method and by Fourier transforming the wave function. In addition to being a tool for reducing the computational load, VDs have also been found useful in interpreting the ultrafast strong-field ionization process, especially the controversial quantum tunneling process.

Scattering of targets over layered half space using a semi-analytic method in conjunction with FDTD algorithm.

PubMed

Cao, Le; Wei, Bing

2014-08-25

Finite-difference time-domain (FDTD) algorithm with a new method of plane wave excitation is used to investigate the RCS (Radar Cross Section) characteristics of targets over layered half space. Compare with the traditional excitation plane wave method, the calculation memory and time requirement is greatly decreased. The FDTD calculation is performed with a plane wave incidence, and the RCS of far field is obtained by extrapolating the currently calculated data on the output boundary. However, methods available for extrapolating have to evaluate the half space Green function. In this paper, a new method which avoids using the complex and time-consuming half space Green function is proposed. Numerical results show that this method is in good agreement with classic algorithm and it can be used in the fast calculation of scattering and radiation of targets over layered half space.

Improving particle beam acceleration in plasmas

NASA Astrophysics Data System (ADS)

C. de Sousa, M.; L. Caldas, I.

2018-04-01

The dynamics of wave-particle interactions in magnetized plasmas restricts the wave amplitude to moderate values for particle beam acceleration from rest energy. We analyze how a perturbing invariant robust barrier modifies the phase space of the system and enlarges the wave amplitude interval for particle acceleration. For low values of the wave amplitude, the acceleration becomes effective for particles with initial energy close to the rest energy. For higher values of the wave amplitude, the robust barrier controls chaos in the system and restores the acceleration process. We also determine the best position for the perturbing barrier in phase space in order to increase the final energy of the particles.

A relativistically interacting exactly solvable multi-time model for two massless Dirac particles in 1 + 1 dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lienert, Matthias, E-mail: lienert@math.lmu.de

2015-04-15

The question how to Lorentz transform an N-particle wave function naturally leads to the concept of a so-called multi-time wave function, i.e., a map from (space-time){sup N} to a spin space. This concept was originally proposed by Dirac as the basis of relativistic quantum mechanics. In such a view, interaction potentials are mathematically inconsistent. This fact motivates the search for new mechanisms for relativistic interactions. In this paper, we explore the idea that relativistic interaction can be described by boundary conditions on the set of coincidence points of two particles in space-time. This extends ideas from zero-range physics to amore » relativistic setting. We illustrate the idea at the simplest model which still possesses essential physical properties like Lorentz invariance and a positive definite density: two-time equations for massless Dirac particles in 1 + 1 dimensions. In order to deal with a spatio-temporally non-trivial domain, a necessity in the multi-time picture, we develop a new method to prove existence and uniqueness of classical solutions: a generalized version of the method of characteristics. Both mathematical and physical considerations are combined to precisely formulate and answer the questions of probability conservation, Lorentz invariance, interaction, and antisymmetry.« less

Information transport in classical statistical systems

NASA Astrophysics Data System (ADS)

Wetterich, C.

2018-02-01

For "static memory materials" the bulk properties depend on boundary conditions. Such materials can be realized by classical statistical systems which admit no unique equilibrium state. We describe the propagation of information from the boundary to the bulk by classical wave functions. The dependence of wave functions on the location of hypersurfaces in the bulk is governed by a linear evolution equation that can be viewed as a generalized Schrödinger equation. Classical wave functions obey the superposition principle, with local probabilities realized as bilinears of wave functions. For static memory materials the evolution within a subsector is unitary, as characteristic for the time evolution in quantum mechanics. The space-dependence in static memory materials can be used as an analogue representation of the time evolution in quantum mechanics - such materials are "quantum simulators". For example, an asymmetric Ising model on a Euclidean two-dimensional lattice represents the time evolution of free relativistic fermions in two-dimensional Minkowski space.

Wave propagation through an inhomogeneous slab sandwiched by the piezoelectric and the piezomagnetic half spaces.

PubMed

Jiao, Fengyu; Wei, Peijun; Li, Li

2017-01-01

Wave propagation through a gradient slab sandwiched by the piezoelectric and the piezomagnetic half spaces are studied in this paper. First, the secular equations in the transverse isotropic piezoelectric/piezomagnetic half spaces are derived from the general dynamic equation. Then, the state vectors at piezoelectric and piezomagnetic half spaces are related to the amplitudes of various possible waves. The state transfer equation of the functionally graded slab is derived from the equations of motion by the reduction of order, and the transfer matrix of the functionally gradient slab is obtained by solving the state transfer equation with the spatial-varying coefficient. Finally, the continuous interface conditions are used to lead to the resultant algebraic equations. The algebraic equations are solved to obtain the amplitude ratios of various waves which are further used to obtain the energy reflection and transmission coefficients of various waves. The numerical results are shown graphically and are validated by the energy conservation law. Based on the numerical results on the fives of gradient profiles, the influences of the graded slab on the wave propagation are discussed. It is found that the reflection and transmission coefficients are obviously dependent upon the gradient profile. The various surface waves are more sensitive to the gradient profile than the bulk waves. Copyright © 2016 Elsevier B.V. All rights reserved.

Helicon waves in uniform plasmas. IV. Bessel beams, Gendrin beams, and helicons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urrutia, J. M.; Stenzel, R. L.

Electromagnetic waves in the low frequency whistler mode regime are investigated experimentally and by digital data superposition. The radiation from a novel circular antenna array is shown to produce highly collimated helicon beams in a uniform unbounded plasma. The differences to Bessel beams in free space are remarked upon. Low divergence beams arise from the parallel group velocity of whistlers with phase velocity either along the guide field or at the Gendrin angle. Waves with angular momentum are produced by phasing the array in the circular direction. The differences in the field topologies for positive and negative modes numbers aremore » shown. It is also shown that in uniform plasmas, the radial amplitude profile of the waves depends on the antenna field topology. Thus, there are no helicon “eigenmodes” with radial Bessel function profiles in uniform plasmas. It is pointed out that phase measurements in helicon devices indicate radial wave propagation which is inconsistent with helicon eigenmode theory based on paraxial wave propagation. Trivelpiece-Gould modes also exist in uniform unbounded plasmas.« less

Retina as Reciprocal Spatial Fourier Transform Space Implies ``Wave-transformation'' Functions, String Theory, the Inappropriate Uncertainty Principle, and Predicts ``Quarked'' Protons.

NASA Astrophysics Data System (ADS)

Mc Leod, Roger David; Mc Leod, David M.

2007-10-01

Vision, via transform space: ``Nature behaves in a reciprocal way;' also, Rect x pressure-input sense-reports as Sinc p, indicating brain interprets reciprocal ``p'' space as object space. Use Mott's and Sneddon's Wave Mechanics and Its Applications. Wave transformation functions are strings of positron, electron, proton, and neutron; uncertainty is a semantic artifact. Neutrino-string de Broglie-Schr"odinger wave-function models for electron, positron, suggest three-quark models for protons, neutrons. Variably vibrating neutrino-quills of this model, with appropriate mass-energy, can be a vertical proton string, quills leftward; thread string circumferentially, forming three interlinked circles with ``overpasses''. Diameters are 2:1:2, center circle has quills radially outward; call it a down quark, charge --1/3, charge 2/3 for outward quills, the up quarks of outer circles. String overlap summations are nodes; nodes also far left and right. Strong nuclear forces may be --px. ``Dislodging" positron with neutrino switches quark-circle configuration to 1:2:1, `downers' outside. Unstable neutron charge is 0. Atoms build. With scale factors, retinal/vision's, and quantum mechanics,' spatial Fourier transforms/inverses are equivalent.

Application of time dependent Green's function method to scattering of elastic waves in anisotropic solids

NASA Astrophysics Data System (ADS)

Tewary, Vinod K.; Fortunko, Christopher M.

The present, time-dependent 3D Green's function method resembles that used to study the propagation of elastic waves in a general, anisotropic half-space in the lattice dynamics of crystals. The method is used to calculate the scattering amplitude of elastic waves from a discontinuity in the half-space; exact results are obtained for 3D pulse propagation in a general, anisotropic half-space that contains either an interior point or a planar scatterer. The results thus obtained are applicable in the design of ultrasonic scattering experiments, especially as an aid in the definition of the spatial and time-domain transducer responses that can maximize detection reliability for specific categories of flaws in highly anisotropic materials.

Wave-filter-based approach for generation of a quiet space in a rectangular cavity

NASA Astrophysics Data System (ADS)

Iwamoto, Hiroyuki; Tanaka, Nobuo; Sanada, Akira

2018-02-01

This paper is concerned with the generation of a quiet space in a rectangular cavity using active wave control methodology. It is the purpose of this paper to present the wave filtering method for a rectangular cavity using multiple microphones and its application to an adaptive feedforward control system. Firstly, the transfer matrix method is introduced for describing the wave dynamics of the sound field, and then feedforward control laws for eliminating transmitted waves is derived. Furthermore, some numerical simulations are conducted that show the best possible result of active wave control. This is followed by the derivation of the wave filtering equations that indicates the structure of the wave filter. It is clarified that the wave filter consists of three portions; modal group filter, rearrangement filter and wave decomposition filter. Next, from a numerical point of view, the accuracy of the wave decomposition filter which is expressed as a function of frequency is investigated using condition numbers. Finally, an experiment on the adaptive feedforward control system using the wave filter is carried out, demonstrating that a quiet space is generated in the target space by the proposed method.

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun; Wang, Xueyi; Chen, Lunjin; Denton, Richard E.

2018-01-01

Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi-perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

Invariance of Topological Indices Under Hilbert Space Truncation

DOE PAGES

Huang, Zhoushen; Zhu, Wei; Arovas, Daniel P.; ...

2018-01-05

Here, we show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z 2 topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement. As a possiblemore » application, we propose a partial quantum tomography scheme from which the topological index of a generic multicomponent wave function can be extracted by measuring only a small subset of wave function components, equivalent to the measurement of a bulk entanglement topological index.« less

Invariance of Topological Indices Under Hilbert Space Truncation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhoushen; Zhu, Wei; Arovas, Daniel P.

Here, we show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z 2 topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement. As a possiblemore » application, we propose a partial quantum tomography scheme from which the topological index of a generic multicomponent wave function can be extracted by measuring only a small subset of wave function components, equivalent to the measurement of a bulk entanglement topological index.« less

Space Weather Research in the Equatorial Region: A Philosophical Reinforcement

NASA Astrophysics Data System (ADS)

Chukwuma, Victor; Odunaike, Rasaki; Laoye, John

Investigations using radio waves reflected from the ionosphere, at high-and mid-latitudes indicate that ionospheric absorption can strongly increase following geomagnetic storms; which appears to suggest some definite relationship between ionospheric radio wave absorption and geomagnetic storms at these latitudes. However, corresponding earlier studies in the equatorial region did not appear to show any explicit relationship between ionospheric radio wave absorption and geomagnetic storm activity. This position appeared acceptable to the existing scientific paradigm, until in an act of paradigm shift, by a change of storm selection criteria, some more recent space weather investigations in the low latitudes showed that ionospheric radio wave absorption in the equatorial region clearly increases after intense storms. Given that these results in the equatorial region stood against the earlier results, this paper presently attempts to highlight their philosophical underpinning and posit that they constitute a scientific statement.

Mapping of spin wave propagation in a one-dimensional magnonic crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ordóñez-Romero, César L., E-mail: cloro@fisica.unam.mx; Lazcano-Ortiz, Zorayda; Aguilar-Huerta, Melisa

2016-07-28

The formation and evolution of spin wave band gaps in the transmission spectrum of a magnonic crystal have been studied. A time and space resolved magneto inductive probing system has been used to map the spin wave propagation and evolution in a geometrically structured yttrium iron garnet film. Experiments have been carried out using (1) a chemically etched magnonic crystal supporting the propagation of magnetostatic surface spin waves, (2) a short microwave pulsed excitation of the spin waves, and (3) direct spin wave detection using a movable magneto inductive probe connected to a synchronized fast oscilloscope. The results show thatmore » the periodic structure not only modifies the spectra of the transmitted spin waves but also influences the distribution of the spin wave energy inside the magnonic crystal as a function of the position and the transmitted frequency. These results comprise an experimental confirmation of Bloch′s theorem in a spin wave system and demonstrate good agreement with theoretical observations in analogue phononic and photonic systems. Theoretical prediction of the structured transmission spectra is achieved using a simple model based on microwave transmission lines theory. Here, a spin wave system illustrates in detail the evolution of a much more general physical concept: the band gap.« less

Wave scattering of complex local site in a layered half-space by using a multidomain IBEM: incident plane SH waves

NASA Astrophysics Data System (ADS)

Ba, Zhenning; Yin, Xiao

2016-06-01

A multidomain indirect boundary element method (IBEM) is proposed to study the wave scattering of plane SH waves by complex local site in a layered half-space. The new method, using both the full-space and layered half-space Green's functions as its fundamental solutions can also be regarded as a coupled method of the full-space IBEM and half-space IBEM. First, the whole model is decomposed into independent closed regions and an opened layered half-space region with all of the irregular interfaces; then, fictitious uniformly distributed loads are applied separately on the boundaries of each region, and scattered fields of the closed regions and the opened layered half-space region are constructed by calculating the full-space and layered half-space Green's functions, respectively; finally, all of the regions are assembled to establish the linear algebraic system that arises from discretization. The densities of the distributed loads are determined directly by solving the algebraic system. The accuracy and capability of the new approach are verified extensively by comparing its results with those of published approaches for a class of hills, valleys and embedded inclusions. And the capability of the new method is further displayed when it is used to investigate a hill-triple layered valley-hill coupled topography in a multilayered half-space. All of the numerical calculations presented in this paper demonstrate that the new method is very suitable for solving multidomain coupled multilayered wave scattering problems with the merits of high accuracy and representing the scattered fields in different kinds of regions more reasonably and flexibly.

Ultrasound Pulsed-Wave Doppler Detects an Intrathecal Location of an Epidural Catheter Tip: A Case Report.

PubMed

Elsharkawy, Hesham; Saasouh, Wael; Patel, Bimal; Babazade, Rovnat

2018-04-01

Currently, no gold standard method exists for localization of an epidural catheter after placement. The technique described in this report uses pulsed-wave Doppler (PWD) ultrasound to identify intrathecal location of an epidural catheter. A thoracic epidural catheter was inserted after multiple trials with inconclusive aspiration and test dose. Ultrasound PWD confirmed no flow in the epidural space and positive flow in the intrathecal space. A fluid aspirate was positive for glucose, reconfirming intrathecal placement. PWD is a potential tool that can be used to locate the tip of an epidural catheter.

Spatially Resolved Measurement of the Stress Tensor in Thin Membranes Using Bending Waves

NASA Astrophysics Data System (ADS)

Waitz, Reimar; Lutz, Carolin; Nößner, Stephan; Hertkorn, Michael; Scheer, Elke

2015-04-01

The mode shape of bending waves in thin silicon and silicon-carbide membranes is measured as a function of space and time, using a phase-shift interferometer with stroboscopic light. The mode shapes hold information about all the relevant mechanical parameters of the samples, including the spatial distribution of static prestress. We present a simple algorithm to obtain a map of the lateral tensor components of the prestress, with a spatial resolution much better than the wavelength of the bending waves. The method is not limited to measuring the stress of bending waves. It is applicable in almost any situation, where the fields determining the state of the system can be measured as a function of space and time.

Immediate and Longer-Term Stressors and the Mental Health of Hurricane Ike Survivors

PubMed Central

Lowe, Sarah R.; Tracy, Melissa; Cerdá, Magdalena; Norris, Fran H.; Galea, Sandro

2014-01-01

Previous research has documented that individuals exposed to more stressors during disasters and their immediate aftermath (immediate stressors) are at risk of experiencing longer-term postdisaster stressors. Longer-term stressors, in turn, have been found to play a key role in shaping postdisaster psychological functioning. Few studies have simultaneously explored the links from immediate to longer-term stressors, and from longer-term stressors to psychological functioning, however. Additionally, studies have inadequately explored whether postdisaster psychological symptoms influence longer-term stressors. In the current study, we aimed to fill these gaps. Participants (N = 448) were from population-based study of Hurricane Ike survivors and completed assessments 2–5 months (Wave 1), 5–9 months (Wave 2) and 14–18 months (Wave 3) postdisaster. Through path analysis, we found that immediate stressors, assessed at Wave 1, were positively associated with Wave 2 and Wave 3 stressors, which in turn were positively associated with Wave 2 and Wave 3 posttraumatic stress and depressive symptoms. Wave 2 posttraumatic stress symptoms were positively associated with Wave 3 stressors, and Wave 1 depressive symptoms were positively associated with Wave 2 stressors. The findings suggest that policies and interventions can reduce the impact of disasters on mental health by preventing and alleviating both immediate and longer-term postdisaster stressors. PMID:24343752

Impact of interfacial imperfection on transverse wave in a functionally graded piezoelectric material structure with corrugated boundaries

NASA Astrophysics Data System (ADS)

Kumar Singh, Abhishek; Kumar, Santan; Kumari, Richa

2018-03-01

The propagation behavior of Love-type wave in a corrugated functionally graded piezoelectric material layered structure has been taken into account. Concretely, the layered structure incorporates a corrugated functionally graded piezoelectric material layer imperfectly bonded to a functionally graded piezoelectric material half-space. An analytical treatment has been employed to determine the dispersion relation for both cases of electrically open condition and electrically short condition. The phase velocity of the Love-type wave has been computed numerically and its dependence on the wave number has been depicted graphically for a specific type of corrugated boundary surfaces for both said conditions. The crux of the study lies in the fact that the imperfect bonding of the interface, the corrugated boundaries present in the layer, and the material properties of the layer and the half-space strongly influence the phase velocity of the Love-type wave. It can be remarkably noted that the imperfect bonding of the interface reduces the phase velocity of the Love-type wave significantly. As a special case of the problem, it is noticed that the procured dispersion relation for both cases of electrically open and electrically short conditions is in accordance with the classical Love wave equation.

On observation of position in quantum theory

NASA Astrophysics Data System (ADS)

Kryukov, A.

2018-05-01

Newtonian and Schrödinger dynamics can be formulated in a physically meaningful way within the same Hilbert space framework. This fact was recently used to discover an unexpected relation between classical and quantum motions that goes beyond the results provided by the Ehrenfest theorem. A formula relating the normal probability distribution and the Born rule was also found. Here the dynamical mechanism responsible for the latter formula is proposed and applied to measurements of macroscopic and microscopic systems. A relationship between the classical Brownian motion and the diffusion of state on the space of states is discovered. The role of measuring devices in quantum theory is investigated in the new framework. It is shown that the so-called collapse of the wave function is not measurement specific and does not require a "concentration" near the eigenstates of the measured observable. Instead, it is explained by the common diffusion of a state over the space of states under interaction with the apparatus and the environment. This in turn provides us with a basic reason for the definite position of macroscopic bodies in space.

Propagation of ultrasonic Love waves in nonhomogeneous elastic functionally graded materials.

PubMed

Kiełczyński, P; Szalewski, M; Balcerzak, A; Wieja, K

2016-02-01

This paper presents a theoretical study of the propagation behavior of ultrasonic Love waves in nonhomogeneous functionally graded elastic materials, which is a vital problem in the mechanics of solids. The elastic properties (shear modulus) of a semi-infinite elastic half-space vary monotonically with the depth (distance from the surface of the material). The Direct Sturm-Liouville Problem that describes the propagation of Love waves in nonhomogeneous elastic functionally graded materials is formulated and solved by using two methods: i.e., (1) Finite Difference Method, and (2) Haskell-Thompson Transfer Matrix Method. The dispersion curves of phase and group velocity of surface Love waves in inhomogeneous elastic graded materials are evaluated. The integral formula for the group velocity of Love waves in nonhomogeneous elastic graded materials has been established. The effect of elastic non-homogeneities on the dispersion curves of Love waves is discussed. Two Love wave waveguide structures are analyzed: (1) a nonhomogeneous elastic surface layer deposited on a homogeneous elastic substrate, and (2) a semi-infinite nonhomogeneous elastic half-space. Obtained in this work, the phase and group velocity dispersion curves of Love waves propagating in the considered nonhomogeneous elastic waveguides have not previously been reported in the scientific literature. The results of this paper may give a deeper insight into the nature of Love waves propagation in elastic nonhomogeneous functionally graded materials, and can provide theoretical guidance for the design and optimization of Love wave based devices. Copyright © 2015 Elsevier B.V. All rights reserved.

Bayesian extraction of the parton distribution amplitude from the Bethe-Salpeter wave function

NASA Astrophysics Data System (ADS)

Gao, Fei; Chang, Lei; Liu, Yu-xin

2017-07-01

We propose a new numerical method to compute the parton distribution amplitude (PDA) from the Euclidean Bethe-Salpeter wave function. The essential step is to extract the weight function in the Nakanishi representation of the Bethe-Salpeter wave function in Euclidean space, which is an ill-posed inversion problem, via the maximum entropy method (MEM). The Nakanishi weight function as well as the corresponding light-front parton distribution amplitude (PDA) can be well determined. We confirm prior work on PDA computations, which was based on different methods.

The "Fermi hole" and the correlation introduced by the symmetrization or the anti-symmetrization of the wave function.

PubMed

Giner, Emmanuel; Tenti, Lorenzo; Angeli, Celestino; Malrieu, Jean-Paul

2016-09-28

The impact of the antisymmetrization is often addressed as a local property of the many-electron wave function, namely that the wave function should vanish when two electrons with parallel spins are in the same position in space. In this paper, we emphasize that this presentation is unduly restrictive: we illustrate the strong non-local character of the antisymmetrization principle, together with the fact that it is a matter of spin symmetry rather than spin parallelism. To this aim, we focus our attention on the simplest representation of various states of two-electron systems, both in atomic (helium atom) and molecular (H 2 and the π system of the ethylene molecule) cases. We discuss the non-local property of the nodal structure of some two-electron wave functions, both using analytical derivations and graphical representations of cuttings of the nodal hypersurfaces. The attention is then focussed on the impact of the antisymmetrization on the maxima of the two-body density, and we show that it introduces strong correlation effects (radial and/or angular) with a non-local character. These correlation effects are analyzed in terms of inflation and depletion zones, which are easily identifiable, thanks to the nodes of the orbitals composing the wave function. Also, we show that the correlation effects induced by the antisymmetrization occur also for anti-parallel spins since all M s components of a given spin state have the same N-body densities. Finally, we illustrate that these correlation effects occur also for the singlet states, but they have strictly opposite impacts: the inflation zones in the triplet become depletion zones in the singlet and vice versa.

Ultrasound Monitoring of Jugular Venous Pulse during Space Missions: Proof of Concept.

PubMed

Zamboni, Paolo; Sisini, Francesco; Menegatti, Erica; Taibi, Angelo; Gadda, Giacomo; Tavoni, Valentina; Malagoni, Anna Maria; Tessari, Mirko; Gianesini, Sergio; Gambaccini, Mauro

2018-03-01

The jugular venous pulse (JVP) is one of the main parameters of cardiac function and is used by cardiologists in diagnosing heart failure. Its waveform comprises three positive waves (a, c and v) and two negative waves (x and y). Recently, it was found that JVP can be extrapolated from an ultrasound (US) video recording of the internal jugular vein (IJV), suggesting its application in space missions, on which US scanners are already widely used. To date, the feasibility of assessing JVP in microgravity (microG) has not been investigated. To verify the feasibility of JVP assessment in microG, we tested a protocol of self-performed B-mode ultrasound on the International Space Station (ISS). The protocol consisted of a video recording of IJV synchronized with electrocardiogram that produces a cross-sectional area time trace (JVP trace) (in cm 2 ). The scans were acquired in six experimental sessions; two pre-flight (BDC1 and -2), two in space (ISS1 and -2) and two post-flight (Houston PF1, Cologne PF2). We measured the mean and standard deviation of the JVP waves and the phase relationship between such waves and P and T waves on the electrocardiogram. We verified that such parameters had the same accuracy on Earth as they did under microG, and we compared their values. The sensitivity, specificity and accuracy of JVP trace in microgravity are higher than those on Earth. The sequence of (a, c, and v) ascents and (x and y) descents along the cardiac cycle in microG is the same as that on Earth. The cause-and-effect relationship between the P and T waves on the electrocardiogram and a and v waves, respectively, of JVP is also confirmed in microG. Our experiment indicated the feasibility of deriving a JVP trace from a B-mode US examination self-performed by an astronaut in microG. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Tunnel effect wave energy detection

NASA Technical Reports Server (NTRS)

Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

1995-01-01

Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Comparison of variational real-space representations of the kinetic energy operator

NASA Astrophysics Data System (ADS)

Skylaris, Chris-Kriton; Diéguez, Oswaldo; Haynes, Peter D.; Payne, Mike C.

2002-08-01

We present a comparison of real-space methods based on regular grids for electronic structure calculations that are designed to have basis set variational properties, using as a reference the conventional method of finite differences (a real-space method that is not variational) and the reciprocal-space plane-wave method which is fully variational. We find that a definition of the finite-difference method [P. Maragakis, J. Soler, and E. Kaxiras, Phys. Rev. B 64, 193101 (2001)] satisfies one of the two properties of variational behavior at the cost of larger errors than the conventional finite-difference method. On the other hand, a technique which represents functions in a number of plane waves which is independent of system size closely follows the plane-wave method and therefore also the criteria for variational behavior. Its application is only limited by the requirement of having functions strictly localized in regions of real space, but this is a characteristic of an increasing number of modern real-space methods, as they are designed to have a computational cost that scales linearly with system size.

Observation and Control of Hamiltonian Chaos in Wave-particle Interaction

NASA Astrophysics Data System (ADS)

Doveil, F.; Elskens, Y.; Ruzzon, A.

2010-11-01

Wave-particle interactions are central in plasma physics. The paradigm beam-plasma system can be advantageously replaced by a traveling wave tube (TWT) to allow their study in a much less noisy environment. This led to detailed analysis of the self-consistent interaction between unstable waves and an either cold or warm electron beam. More recently a test cold beam has been used to observe its interaction with externally excited wave(s). This allowed observing the main features of Hamiltonian chaos and testing a new method to efficiently channel chaotic transport in phase space. To simulate accurately and efficiently the particle dynamics in the TWT and other 1D particle-wave systems, a new symplectic, symmetric, second order numerical algorithm is developed, using particle position as the independent variable, with a fixed spatial step. This contribution reviews : presentation of the TWT and its connection to plasma physics, resonant interaction of a charged particle in electrostatic waves, observation of particle trapping and transition to chaos, test of control of chaos, and description of the simulation algorithm. The velocity distribution function of the electron beam is recorded with a trochoidal energy analyzer at the output of the TWT. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the 4m long helix of the TWT. The nonlinear synchronization of particles by a single wave, responsible for Landau damping, is observed. We explore the resonant velocity domain associated with a single wave as well as the transition to large scale chaos when the resonant domains of two waves and their secondary resonances overlap. This transition exhibits a devil's staircase behavior when increasing the excitation level in agreement with numerical simulation. A new strategy for control of chaos by building barriers of transport in phase space as well as its robustness is successfully tested. The underlying concepts extend far beyond the field of electron devices and plasma physics.

Corrigendum: First principles calculation of field emission from nanostructures using time-dependent density functional theory: A simplified approach

NASA Astrophysics Data System (ADS)

Tawfik, Sherif A.; El-Sheikh, S. M.; Salem, N. M.

2016-09-01

Recently we have become aware that the description of the quantum wave functions in Sec. 2.1 is incorrect. In the published version of the paper, we have stated that the states are expanded in terms of plane waves. However, the correct description of the quantum states in the context of the real space implementation (using the Octopus code) is that states are represented by discrete points in a real space grid.

Supersymmetric dS/CFT

NASA Astrophysics Data System (ADS)

Hertog, Thomas; Tartaglino-Mazzucchelli, Gabriele; Van Riet, Thomas; Venken, Gerben

2018-02-01

We put forward new explicit realisations of dS/CFT that relate N = 2 supersymmetric Euclidean vector models with reversed spin-statistics in three dimensions to specific supersymmetric Vasiliev theories in four-dimensional de Sitter space. The partition function of the free supersymmetric vector model deformed by a range of low spin deformations that preserve supersymmetry appears to specify a well-defined wave function with asymptotic de Sitter boundary conditions in the bulk. In particular we find the wave function is globally peaked at undeformed de Sitter space, with a low amplitude for strong deformations. This suggests that supersymmetric de Sitter space is stable in higher-spin gravity and in particular free from ghosts. We speculate this is a limiting case of the de Sitter realizations in exotic string theories.

Beach-cusp formation

USGS Publications Warehouse

Sallenger, A.H.

1979-01-01

Field experiments on beach-cusp formation were undertaken to document how the cuspate form develops and to test the edge-wave hypothesis on the uniform spacing of cusps. These involved observations of cusps forming from an initially plane foreshore. The cuspate form was observed to be a product of swash modification of an intertidal beach ridge as follows. A ridge, cut by a series of channels quasi-equally spaced along its length, was deposited onto the lower foreshore. The ridge migrated shoreward with flood tide, while the longshore positions of the channels remained fixed. On ebb tide, changes in swash circulation over the ridge allowed the upwash to flow shoreward through the channels and the channel mouths were eroded progressively wider until adjacent mouths met, effecting a cuspate shape. Measured spacings of cusps, ranging in size from less than 1 m to more than 12 m, agree well with computed spacings due to either zero-mode subharmonic or zero-mode synchronous edge waves. Edge-wave-induced longshore variations in run up will cause water ponded behind a ridge to converge at points of low swash and flow seaward as relatively narrow currents eroding channels spaced at one edge-wave wavelength for synchronous edge waves or one half wavelength for subharmonic edge waves. The channels are subsequently modified into cusp troughs as described above.

An exact solution to the relativistic equation of motion of a charged particle driven by a linearly polarized electromagnetic wave

NASA Technical Reports Server (NTRS)

Shebalin, John V.

1988-01-01

An exact analytic solution is found for a basic electromagnetic wave-charged particle interaction by solving the nonlinear equations of motion. The particle position, velocity, and corresponding time are found to be explicit functions of the total phase of the wave. Particle position and velocity are thus implicit functions of time. Applications include describing the motion of a free electron driven by an intense laser beam..

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nottale, Laurent; Célérier, Marie-Noëlle

One of the main results of scale relativity as regards the foundation of quantum mechanics is its explanation of the origin of the complex nature of the wave function. The scale relativity theory introduces an explicit dependence of physical quantities on scale variables, founding itself on the theorem according to which a continuous and non-differentiable space-time is fractal (i.e., scale-divergent). In the present paper, the nature of the scale variables and their relations to resolutions and differential elements are specified in the non-relativistic case (fractal space). We show that, owing to the scale-dependence which it induces, non-differentiability involves a fundamentalmore » two-valuedness of the mean derivatives. Since, in the scale relativity framework, the wave function is a manifestation of the velocity field of fractal space-time geodesics, the two-valuedness of velocities leads to write them in terms of complex numbers, and yields therefore the complex nature of the wave function, from which the usual expression of the Schrödinger equation can be derived.« less

A structure-preserving method for a class of nonlinear dissipative wave equations with Riesz space-fractional derivatives

NASA Astrophysics Data System (ADS)

Macías-Díaz, J. E.

2017-12-01

In this manuscript, we consider an initial-boundary-value problem governed by a (1 + 1)-dimensional hyperbolic partial differential equation with constant damping that generalizes many nonlinear wave equations from mathematical physics. The model considers the presence of a spatial Laplacian of fractional order which is defined in terms of Riesz fractional derivatives, as well as the inclusion of a generic continuously differentiable potential. It is known that the undamped regime has an associated positive energy functional, and we show here that it is preserved throughout time under suitable boundary conditions. To approximate the solutions of this model, we propose a finite-difference discretization based on fractional centered differences. Some discrete quantities are proposed in this work to estimate the energy functional, and we show that the numerical method is capable of conserving the discrete energy under the same boundary conditions for which the continuous model is conservative. Moreover, we establish suitable computational constraints under which the discrete energy of the system is positive. The method is consistent of second order, and is both stable and convergent. The numerical simulations shown here illustrate the most important features of our numerical methodology.

Analyzing inflammatory response as excitable media

NASA Astrophysics Data System (ADS)

Yde, Pernille; Høgh Jensen, Mogens; Trusina, Ala

2011-11-01

The regulatory system of the transcription factor NF-κB plays a great role in many cell functions, including inflammatory response. Interestingly, the NF-κB system is known to up-regulate production of its own triggering signal—namely, inflammatory cytokines such as TNF, IL-1, and IL-6. In this paper we investigate a previously presented model of the NF-κB, which includes both spatial effects and the positive feedback from cytokines. The model exhibits the properties of an excitable medium and has the ability to propagate waves of high cytokine concentration. These waves represent an optimal way of sending an inflammatory signal through the tissue as they create a chemotactic signal able to recruit neutrophils to the site of infection. The simple model displays three qualitatively different states; low stimuli leads to no or very little response. Intermediate stimuli leads to reoccurring waves of high cytokine concentration. Finally, high stimuli leads to a sustained high cytokine concentration, a scenario which is toxic for the tissue cells and corresponds to chronic inflammation. Due to the few variables of the simple model, we are able to perform a phase-space analysis leading to a detailed understanding of the functional form of the model and its limitations. The spatial effects of the model contribute to the robustness of the cytokine wave formation and propagation.

Elementary derivation of the quantum propagator for the harmonic oscillator

NASA Astrophysics Data System (ADS)

Shao, Jiushu

2016-10-01

Operator algebra techniques are employed to derive the quantum evolution operator for the harmonic oscillator. The derivation begins with the construction of the annihilation and creation operators and the determination of the wave function for the coherent state as well as its time-dependent evolution, and ends with the transformation of the propagator in a mixed position-coherent-state representation to the desired one in configuration space. Throughout the entire procedure, besides elementary operator manipulations, it is only necessary to solve linear differential equations and to calculate Gaussian integrals.

Probability function of breaking-limited surface elevation. [wind generated waves of ocean

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.; Yuan, Y.; Long, S. R.

1989-01-01

The effect of wave breaking on the probability function of surface elevation is examined. The surface elevation limited by wave breaking zeta sub b(t) is first related to the original wave elevation zeta(t) and its second derivative. An approximate, second-order, nonlinear, non-Gaussian model for zeta(t) of arbitrary but moderate bandwidth is presented, and an expression for the probability density function zeta sub b(t) is derived. The results show clearly that the effect of wave breaking on the probability density function of surface elevation is to introduce a secondary hump on the positive side of the probability density function, a phenomenon also observed in wind wave tank experiments.

Tsunamis generated by subaerial mass flows

USGS Publications Warehouse

Walder, S.J.; Watts, P.; Sorensen, O.E.; Janssen, K.

2003-01-01

Tsunamis generated in lakes and reservoirs by subaerial mass flows pose distinctive problems for hazards assessment because the domain of interest is commonly the "near field," beyond the zone of complex splashing but close enough to the source that wave propagation effects are not predominant. Scaling analysis of the equations governing water wave propagation shows that near-field wave amplitude and wavelength should depend on certain measures of mass flow dynamics and volume. The scaling analysis motivates a successful collapse (in dimensionless space) of data from two distinct sets of experiments with solid block "wave makers." To first order, wave amplitude/water depth is a simple function of the ratio of dimensionless wave maker travel time to dimensionless wave maker volume per unit width. Wave amplitude data from previous laboratory investigations with both rigid and deformable wave makers follow the same trend in dimensionless parameter space as our own data. The characteristic wavelength/water depth for all our experiments is simply proportional to dimensionless wave maker travel time, which is itself given approximately by a simple function of wave maker length/water depth. Wave maker shape and rigidity do not otherwise influence wave features. Application of the amplitude scaling relation to several historical events yields "predicted" near-field wave amplitudes in reasonable agreement with measurements and observations. Together, the scaling relations for near-field amplitude, wavelength, and submerged travel time provide key inputs necessary for computational wave propagation and hazards assessment.

Auxiliary-field-based trial wave functions in quantum Monte Carlo calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chia -Chen; Rubenstein, Brenda M.; Morales, Miguel A.

2016-12-19

Quantum Monte Carlo (QMC) algorithms have long relied on Jastrow factors to incorporate dynamic correlation into trial wave functions. While Jastrow-type wave functions have been widely employed in real-space algorithms, they have seen limited use in second-quantized QMC methods, particularly in projection methods that involve a stochastic evolution of the wave function in imaginary time. Here we propose a scheme for generating Jastrow-type correlated trial wave functions for auxiliary-field QMC methods. The method is based on decoupling the two-body Jastrow into one-body projectors coupled to auxiliary fields, which then operate on a single determinant to produce a multideterminant trial wavemore » function. We demonstrate that intelligent sampling of the most significant determinants in this expansion can produce compact trial wave functions that reduce errors in the calculated energies. Lastly, our technique may be readily generalized to accommodate a wide range of two-body Jastrow factors and applied to a variety of model and chemical systems.« less

From plane waves to local Gaussians for the simulation of correlated periodic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Booth, George H., E-mail: george.booth@kcl.ac.uk; Tsatsoulis, Theodoros; Grüneis, Andreas, E-mail: a.grueneis@fkf.mpg.de

2016-08-28

We present a simple, robust, and black-box approach to the implementation and use of local, periodic, atom-centered Gaussian basis functions within a plane wave code, in a computationally efficient manner. The procedure outlined is based on the representation of the Gaussians within a finite bandwidth by their underlying plane wave coefficients. The core region is handled within the projected augment wave framework, by pseudizing the Gaussian functions within a cutoff radius around each nucleus, smoothing the functions so that they are faithfully represented by a plane wave basis with only moderate kinetic energy cutoff. To mitigate the effects of themore » basis set superposition error and incompleteness at the mean-field level introduced by the Gaussian basis, we also propose a hybrid approach, whereby the complete occupied space is first converged within a large plane wave basis, and the Gaussian basis used to construct a complementary virtual space for the application of correlated methods. We demonstrate that these pseudized Gaussians yield compact and systematically improvable spaces with an accuracy comparable to their non-pseudized Gaussian counterparts. A key advantage of the described method is its ability to efficiently capture and describe electronic correlation effects of weakly bound and low-dimensional systems, where plane waves are not sufficiently compact or able to be truncated without unphysical artifacts. We investigate the accuracy of the pseudized Gaussians for the water dimer interaction, neon solid, and water adsorption on a LiH surface, at the level of second-order Møller–Plesset perturbation theory.« less

Distinguishing between evidence and its explanations in the steering of atomic clocks

NASA Astrophysics Data System (ADS)

Myers, John M.; Hadi Madjid, F.

2014-11-01

Quantum theory reflects within itself a separation of evidence from explanations. This separation leads to a known proof that: (1) no wave function can be determined uniquely by evidence, and (2) any chosen wave function requires a guess reaching beyond logic to things unforeseeable. Chosen wave functions are encoded into computer-mediated feedback essential to atomic clocks, including clocks that step computers through their phases of computation and clocks in space vehicles that supply evidence of signal propagation explained by hypotheses of spacetimes with metric tensor fields. The propagation of logical symbols from one computer to another requires a shared rhythm-like a bucket brigade. Here we show how hypothesized metric tensors, dependent on guesswork, take part in the logical synchronization by which clocks are steered in rate and position toward aiming points that satisfy phase constraints, thereby linking the physics of signal propagation with the sharing of logical symbols among computers. Recognizing the dependence of the phasing of symbol arrivals on guesses about signal propagation transports logical synchronization from the engineering of digital communications to a discipline essential to physics. Within this discipline we begin to explore questions invisible under any concept of time that fails to acknowledge unforeseeable events. In particular, variation of spacetime curvature is shown to limit the bit rate of logical communication.

Aerospace Medicine and Biology: A Continuing Bibliography with Indexes

DTIC Science & Technology

1987-09-01

drug against motion sickness more closely than any other medication. Author A87-35422 THE USE OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY IN AVIATORS A87...diagnosis and treatment Denmark) Aviation, Space, and Environmental Medicine (ISSN Extracorporeal shock wave lithotripsy (ESWL) has recently become 0095...and M. J. GRIFFIN ( Southampton , University, functional mechanisms are insufficient. Solutions are discussed England) Aviation, Space, and Environmental

Field patterns: A new type of wave with infinitely degenerate band structure

NASA Astrophysics Data System (ADS)

Mattei, Ornella; Milton, Graeme W.

2017-12-01

Field pattern materials (FP-materials) are space-time composites with PT-symmetry in which the one-dimensional-spatial distribution of the constituents changes in time in such a special manner to give rise to a new type of waves, which we call field pattern waves (FP-waves) (MILTON G. W. and MATTEI O., Proc. R. Soc. A, 473 (2017) 20160819; MATTEI O. and MILTON G. W., New J. Phys., 19 (2017) 093022). Specifically, due to the special periodic space-time geometry of these materials, when an instantaneous disturbance propagates through the system, the branching of the characteristic lines at the space-time interfaces between phases does not lead to a chaotic cascade of disturbances but concentrates on an orderly pattern of disturbances: this is the field pattern. In this letter, by applying Bloch-Floquet theory, we show that the dispersion diagrams associated with these FP-materials are infinitely degenerate: associated with each point on the dispersion diagram is an infinite space of Bloch functions. Each generalized function is concentrated on a specific field pattern, each parameterized by a variable that we call the launch parameter. The dynamics separates into independent dynamics on the different field patterns, each with the same dispersion relation.

The Strange (Hi)story of Particles and Waves

NASA Astrophysics Data System (ADS)

Zeh, H. Dieter

2016-03-01

This is an attempt of a non-technical but conceptually consistent presentation of quantum theory in a historical context. While the first part is written for a general readership, Section 5 may appear a bit provocative to some quantum physicists. I argue that the single-particle wave functions of quantum mechanics have to be correctly interpreted as field modes that are "occupied once" (i.e. first excited states of the corresponding quantum oscillators in the case of boson fields). Multiple excitations lead to apparent many-particle wave functions, while the quantum states proper are defined by wave function(al)s on the "configuration" space of fundamental fields, or on another, as yet elusive, fundamental local basis.

Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking

PubMed Central

Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

2016-01-01

One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking. PMID:27387438

Nonparaxial wave beams and packets with general astigmatism

NASA Astrophysics Data System (ADS)

Kiselev, A. P.; Plachenov, A. B.; Chamorro-Posada, P.

2012-04-01

We present exact solutions of the wave equation involving an arbitrary wave form with a phase closely similar to the general astigmatic phase of paraxial wave optics. Special choices of the wave form allow general astigmatic beamlike and pulselike waves with a Gaussian-type unrestricted localization in space and time. These solutions are generalizations of the known Bateman-type waves obtained from the connection existing between beamlike solutions of the paraxial parabolic equation and relatively undistorted wave solutions of the wave equation. As a technical tool, we present a full description of parametrizations of 2×2 symmetric matrices with positive imaginary part, which arise in the theory of Gaussian beams.

Degenerate RS perturbation theory. [Rayleigh-Schroedinger energies and wave functions

NASA Technical Reports Server (NTRS)

Hirschfelder, J. O.; Certain, P. R.

1974-01-01

A concise, systematic procedure is given for determining the Rayleigh-Schroedinger energies and wave functions of degenerate states to arbitrarily high orders even when the degeneracies of the various states are resolved in arbitrary orders. The procedure is expressed in terms of an iterative cycle in which the energy through the (2n + 1)-th order is expressed in terms of the partially determined wave function through the n-th order. Both a direct and an operator derivation are given. The two approaches are equivalent and can be transcribed into each other. The direct approach deals with the wave functions (without the use of formal operators) and has the advantage that it resembles the usual treatment of nondegenerate perturbations and maintains close contact with the basic physics. In the operator approach, the wave functions are expressed in terms of infinite-order operators which are determined by the successive resolution of the space of the zeroth-order functions.

Suppressing Ionic Terms with Number-Counting Jastrow Factors in Real Space

DOE PAGES

Goetz, Brett Van Der; Neuscamman, Eric

2017-04-06

Here, we demonstrate that four-body real-space Jastrow factors are, with the right type of Jastrow basis function, capable of performing successful wave function stenciling to remove unwanted ionic terms from an overabundant Fermionic reference without unduly modifying the remaining components. In addition to greatly improving size consistency (restoring it exactly in the case of a geminal power), real-space wave function stenciling is, unlike its Hilbert-space predecessors, immediately compatible with diffusion Monte Carlo, allowing it to be used in the pursuit of compact, strongly correlated trial functions with reliable nodal surfaces. Furthermore, we demonstrate the efficacy of this approach in themore » context of a double bond dissociation by using it to extract a qualitatively correct nodal surface despite being paired with a restricted Slater determinant, that, due to ionic term errors, produces a ground state with a qualitatively incorrect nodal surface when used in the absence of the Jastrow.« less

Suppressing Ionic Terms with Number-Counting Jastrow Factors in Real Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goetz, Brett Van Der; Neuscamman, Eric

Here, we demonstrate that four-body real-space Jastrow factors are, with the right type of Jastrow basis function, capable of performing successful wave function stenciling to remove unwanted ionic terms from an overabundant Fermionic reference without unduly modifying the remaining components. In addition to greatly improving size consistency (restoring it exactly in the case of a geminal power), real-space wave function stenciling is, unlike its Hilbert-space predecessors, immediately compatible with diffusion Monte Carlo, allowing it to be used in the pursuit of compact, strongly correlated trial functions with reliable nodal surfaces. Furthermore, we demonstrate the efficacy of this approach in themore » context of a double bond dissociation by using it to extract a qualitatively correct nodal surface despite being paired with a restricted Slater determinant, that, due to ionic term errors, produces a ground state with a qualitatively incorrect nodal surface when used in the absence of the Jastrow.« less

Response of the Shockley surface state to an external electrical field: A density-functional theory study of Cu(111)

NASA Astrophysics Data System (ADS)

Berland, K.; Einstein, T. L.; Hyldgaard, P.

2012-01-01

The response of the Cu(111) Shockley surface state to an external electrical field is characterized by combining a density-functional theory calculation for a slab geometry with an analysis of the Kohn-Sham wave functions. Our analysis is facilitated by a decoupling of the Kohn-Sham states via a rotation in Hilbert space. We find that the surface state displays isotropic dispersion, quadratic until the Fermi wave vector but with a significant quartic contribution beyond. We calculate the shift in energetic position and effective mass of the surface state for an electrical field perpendicular to the Cu(111) surface; the response is linear over a broad range of field strengths. We find that charge transfer occurs beyond the outermost copper atoms and that accumulation of electrons is responsible for a quarter of the screening of the electrical field. This allows us to provide well converged determinations of the field-induced changes in the surface state for a moderate number of layers in the slab geometry.

Tunnel effect measuring systems and particle detectors

NASA Technical Reports Server (NTRS)

Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

1994-01-01

Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Tunnel effect measuring systems and particle detectors

NASA Technical Reports Server (NTRS)

Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

1993-01-01

Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

Dispersion characteristics of anisotropic unmagnetized ultra-relativistic transverse plasma wave with arbitrary electron degeneracy

NASA Astrophysics Data System (ADS)

Sarfraz, M.; Farooq, H.; Abbas, G.; Noureen, S.; Iqbal, Z.; Rasheed, A.

2018-03-01

Thermal momentum space anisotropy is ubiquitous in many astrophysical and laboratory plasma environments. Using Vlasov-Maxwell's model equations, a generalized polarization tensor for a collisionless ultra-relativistic unmagnetized electron plasma is derived. In particular, the tensor is obtained by considering anisotropy in the momentum space. The integral of moments of Fermi-Dirac distribution function in terms of Polylog functions is used for describing the border line plasma systems (T/e TF e ≈1 ) comprising arbitrary electron degeneracy, where Te and TF e, are thermal and Fermi temperatures, respectively. Furthermore, the effects of variation in thermal momentum space anisotropy on the electron equilibrium number density and the spectrum of electromagnetic waves are analyzed.

Localized spatially nonlinear matter waves in atomic-molecular Bose-Einstein condensates with space-modulated nonlinearity

PubMed Central

Yao, Yu-Qin; Li, Ji; Han, Wei; Wang, Deng-Shan; Liu, Wu-Ming

2016-01-01

The intrinsic nonlinearity is the most remarkable characteristic of the Bose-Einstein condensates (BECs) systems. Many studies have been done on atomic BECs with time- and space- modulated nonlinearities, while there is few work considering the atomic-molecular BECs with space-modulated nonlinearities. Here, we obtain two kinds of Jacobi elliptic solutions and a family of rational solutions of the atomic-molecular BECs with trapping potential and space-modulated nonlinearity and consider the effect of three-body interaction on the localized matter wave solutions. The topological properties of the localized nonlinear matter wave for no coupling are analysed: the parity of nonlinear matter wave functions depends only on the principal quantum number n, and the numbers of the density packets for each quantum state depend on both the principal quantum number n and the secondary quantum number l. When the coupling is not zero, the localized nonlinear matter waves given by the rational function, their topological properties are independent of the principal quantum number n, only depend on the secondary quantum number l. The Raman detuning and the chemical potential can change the number and the shape of the density packets. The stability of the Jacobi elliptic solutions depends on the principal quantum number n, while the stability of the rational solutions depends on the chemical potential and Raman detuning. PMID:27403634

Primordial black holes and uncertainties in the choice of the window function

NASA Astrophysics Data System (ADS)

Ando, Kenta; Inomata, Keisuke; Kawasaki, Masahiro

2018-05-01

Primordial black holes (PBHs) can be produced by the perturbations that exit the horizon during the inflationary phase. While inflation models predict the power spectrum of the perturbations in Fourier space, the PBH abundance depends on the probability distribution function of density perturbations in real space. To estimate the PBH abundance in a given inflation model, we must relate the power spectrum in Fourier space to the probability density function in real space by coarse graining the perturbations with a window function. However, there are uncertainties on what window function should be used, which could change the relation between the PBH abundance and the power spectrum. This is particularly important in considering PBHs with mass 30 M⊙, which account for the LIGO events because the required power spectrum is severely constrained by the observations. In this paper, we investigate how large an influence the uncertainties on the choice of a window function has over the power spectrum required for LIGO PBHs. As a result, it is found that the uncertainties significantly affect the prediction for the stochastic gravitational waves induced by the second-order effect of the perturbations. In particular, the pulsar timing array constraints on the produced gravitational waves could disappear for the real-space top-hat window function.

Longitudinal Waves Drive the Solar Cycle

NASA Astrophysics Data System (ADS)

Wagner, Orvin

2000-05-01

In Physics Essays 12: 3-10 I explain the placement of the planets in terms of low velocity waves emitted by the sun. Evidence for the wave pulse generated near the center of the sun is indicated by the initial high latitude sunspots observed on the butterfly diagram. The wave pulse carries charge with it as observed for similar waves in plants (W-waves). For the first half cycle negative charge is carried to the surface of the sun where much of the wave pulse radiates a wave crest into space while the charge slowly redistributes itself. Meanwhile the next wave pulse carrying excess positive charge moves outward. Rotating charge determines the polarity of the sun's magnetic poles so they reverse as the pulse moves outward. The wave pulse, which interacts strongly with force fields, is guided by centripetal force and gravity so that the pulse comes out near the sun's equator. W-waves produce an automatic return wave in the vacuum so that standing waves are produced in the space around the sun providing a template for the formation and stabilization planets. W-waves are hypothesized to provide self organization for both the universe and life. See the

Huygens-Fresnel Acoustic Interference and the Development of Robust Time-Averaged Patterns from Traveling Surface Acoustic Waves

NASA Astrophysics Data System (ADS)

Devendran, Citsabehsan; Collins, David J.; Ai, Ye; Neild, Adrian

2017-04-01

Periodic pattern generation using time-averaged acoustic forces conventionally requires the intersection of counterpropagating wave fields, where suspended micro-objects in a microfluidic system collect along force potential minimizing nodal or antinodal lines. Whereas this effect typically requires either multiple transducer elements or whole channel resonance, we report the generation of scalable periodic patterning positions without either of these conditions. A single propagating surface acoustic wave interacts with the proximal channel wall to produce a knife-edge effect according to the Huygens-Fresnel principle, where these cylindrically propagating waves interfere with classical wave fronts emanating from the substrate. We simulate these conditions and describe a model that accurately predicts the lateral spacing of these positions in a robust and novel approach to acoustic patterning.

Surface Green's function of a piezoelectric half-space.

PubMed

Laude, Vincent; Jerez-Hanckes, Carlos F; Ballandras, Sylvain

2006-02-01

The computation of the two-dimensional harmonic spatial-domain Green's function at the surface of a piezoelectric half-space is discussed. Starting from the known form of the Green's function expressed in the spectral domain, the singular contributions are isolated and treated separately. It is found that the surface acoustic wave contributions (i.e., poles in the spectral Green's function) give rise to an anisotropic generalization of the Hankel function H0(2), the spatial Green's function for the scalar two-dimensional wave equation. The asymptotic behavior at infinity and at the origin (for the electrostatic contribution) also are explicitly treated. The remaining nonsingular part of the spectral Green's function is obtained numerically by a combination of fast Fourier transform and quadrature. Illustrations are given in the case of a substrate of Y-cut lithium niobate.

Forecasting and Hindcasting Waves In and Near the Marginal Ice Zone: Wave Modeling and the ONR Sea State Field Experiment

DTIC Science & Technology

2018-04-12

non-directional) wave spectra, but we consider the energy at high frequencies to be unreliable, so we only use significant waveheight Hs and dominant...spectral density, N=E/s), which is a function of wavenumber or frequency (k or s), direction (θ), space (x,y), and time (t), with spectral density...Elgar 1987). As the spectra are now co-located in time, space , and frequency , the inversion is simply a minimization process for |logVR(6jvH>w(9

Alfvén simple waves

NASA Astrophysics Data System (ADS)

Webb, G. M.; Zank, G. P.; Burrows, R. H.; Ratkiewicz, R. E.

2011-02-01

Multi-dimensional Alfvén simple waves in magnetohydrodynamics (MHD) are investigated using Boillat's formalism. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function ϕ, which is a function of the space and time variables. The simple wave ansatz requires that the wave normal and the normal speed of the wave front depend only on the phase function ϕ. This leads to an implicit equation for the phase function and a generalization of the concept of a plane wave. We obtain examples of Alfvén simple waves, based on the right eigenvector solutions for the Alfvén mode. The Alfvén mode solutions have six integrals, namely that the entropy, density, magnetic pressure, and the group velocity (the sum of the Alfvén and fluid velocity) are constant throughout the wave. The eigenequations require that the rate of change of the magnetic induction B with ϕ throughout the wave is perpendicular to both the wave normal n and B. Methods to construct simple wave solutions based on specifying either a solution ansatz for n(ϕ) or B(ϕ) are developed.

Alfven Simple Waves

NASA Astrophysics Data System (ADS)

Webb, G. M.; Zank, G. P.; Burrows, R.

2009-12-01

Multi-dimensional Alfvén simple waves in magnetohydrodynamics (MHD) are investigated using Boillat's formalism. For simple wave solutions, all physical variables (the gas density, pressure, fluid velocity, entropy, and magnetic field induction in the MHD case) depend on a single phase function ǎrphi which is a function of the space and time variables. The simple wave ansatz requires that the wave normal and the normal speed of the wave front depend only on the phase function ǎrphi. This leads to an implicit equation for the phase function, and a generalisation of the concept of a plane wave. We obtain examples of Alfvén simple waves, based on the right eigenvector solutions for the Alfvén mode. The Alfvén mode solutions have six integrals, namely that the entropy, density, magnetic pressure and the group velocity (the sum of the Alfvén and fluid velocity) are constant throughout the wave. The eigen-equations require that the rate of change of the magnetic induction B with ǎrphi throughout the wave is perpendicular to both the wave normal n and B. Methods to construct simple wave solutions based on specifying either a solution ansatz for n(ǎrphi) or B(ǎrphi) are developed.

Exact analytic solution of position-dependent mass Schrödinger equation

NASA Astrophysics Data System (ADS)

Rajbongshi, Hangshadhar

2018-03-01

Exact analytic solution of position-dependent mass Schrödinger equation is generated by using extended transformation, a method of mapping a known system into a new system equipped with energy eigenvalues and corresponding wave functions. First order transformation is performed on D-dimensional radial Schrödinger equation with constant mass by taking trigonometric Pöschl-Teller potential as known system. The exactly solvable potentials with position-dependent mass generated for different choices of mass functions through first order transformation are also taken as known systems in the second order transformation performed on D-dimensional radial position-dependent mass Schrödinger equation. The solutions are fitted for "Zhu and Kroemer" ordering of ambiguity. All the wave functions corresponding to nonzero energy eigenvalues are normalizable. The new findings are that the normalizability condition of the wave functions remains independent of mass functions, and some of the generated potentials show a family relationship among themselves where power law potentials also get related to non-power law potentials and vice versa through the transformation.

Bifurcation of space-charge wave in a plasma waveguide including the wake potential effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

The wake potential effects on the propagation of the space-charge dust ion-acoustic wave are investigated in a cylindrically bounded dusty plasma with the ion flow. The results show that the wake potential would generate the double frequency modes in a cylindrically bounded dusty plasma. It is found that the upper mode of the wave frequency with the root of higher-order is smaller than that with the root of lower-order in intermediate wave number domains. However, the lower mode of the scaled wave frequency with the root of higher-order is found to be greater than that with the root of lower-order.more » It is found that the influence in the order of the root of the Bessel function on the wave frequency of the space-charge dust-ion-acoustic wave in a cylindrically confined dusty plasma decreases with an increase in the propagation wave number. It is also found that the double frequency modes increase with increasing Mach number due to the ion flow in a cylindrical dusty plasma. In addition, it is found that the upper mode of the group velocity decreases with an increase in the scaled radius of the plasma cylinder. However, it is shown that the lower mode of the scaled group velocity of the space-charge dust ion acoustic wave increases with an increase in the radius of the plasma cylinder. The variation of the space-charge dust-ion-acoustic wave due to the wake potential and geometric effects is also discussed.« less

Where Should the Nuclei Be Located?

ERIC Educational Resources Information Center

Ying Liu; Yue Liu; Drew, Michael G. B.

2005-01-01

The approach of determining the nature of the electron wave function via orbital representations qualitatively and via numerical calculations quantitatively is demonstrated. The angular part of the wave function provides suitable representation of the positions of the nuclei.

Analysis of Real Ship Rolling Dynamics under Wave Excitement Force Composed of Sums of Cosine Functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y. S.; Cai, F.; Xu, W. M.

2011-09-28

The ship motion equation with a cosine wave excitement force describes the slip moments in regular waves. A new kind of wave excitement force model, with the form as sums of cosine functions was proposed to describe ship rolling in irregular waves. Ship rolling time series were obtained by solving the ship motion equation with the fourth-order-Runger-Kutta method. These rolling time series were synthetically analyzed with methods of phase-space track, power spectrum, primary component analysis, and the largest Lyapunove exponent. Simulation results show that ship rolling presents some chaotic characteristic when the wave excitement force was applied by sums ofmore » cosine functions. The result well explains the course of ship rolling's chaotic mechanism and is useful for ship hydrodynamic study.« less

Extended space expectation values in quantum dynamical system evolutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demiralp, Metin

2014-10-06

The time variant power series expansion for the expectation value of a given quantum dynamical operator is well-known and well-investigated issue in quantum dynamics. However, depending on the operator and Hamiltonian singularities this expansion either may not exist or may not converge for all time instances except the beginning of the evolution. This work focuses on this issue and seeks certain cures for the negativities. We work in the extended space obtained by adding all images of the initial wave function under the system Hamiltonian’s positive integer powers. This requires the introduction of certain appropriately defined weight operators. The resultingmore » better convergence in the temporal power series urges us to call the new defined entities “extended space expectation values” even though they are constructed over certain weight operators and are somehow pseudo expectation values.« less

The Microtremor H/V Spectral Ratio: The Physical Basis of the Diffuse Field Assumption

NASA Astrophysics Data System (ADS)

Sanchez-Sesma, F. J.

2016-12-01

The microtremor H/V spectral ratio (MHVSR) is popular to obtain the dominant frequency at a site. Despite the success of MHVSR some controversy arose regarding its physical basis. One approach is the Diffuse Field Assumption, DFA. It is then assumed that noise diffuse features come from multiple scattering within the medium. According to theory, the average of the autocorrelation is proportional to directional energy density (DED) and to the imaginary part of the Green's function for same source and receiver. Then, the square of MHVSR is a ratio of DEDs which, in a horizontally layered system, is 2xImG11/ImG33, where ImG11 and ImG33 are the imaginary parts of Green's functions for horizontal and vertical components. This has physical implications that emerge from the duality DED-force, implicit in the DFA. Consider a surface force at a half-space. The radiated energy is carried away by various wave types and the proportions of each one are precisely the fractions of the energy densities of a diffuse elastic wave field at the free surface. Thus, some properties of applied forces are also characteristics of DEDs. For example, consider a Poisson solid. For a normal point load, 67 per cent of energy is carried away by Rayleigh waves. For the tangential case, it is less well known that, 77 per cent of energy goes as shear waves. In a full space, 92 per cent of the energy is emitted as shear waves. The horizontal DED at the half-space surface implies significant emission of down-going shear waves that explains the curious stair-like resonance spectrum of ImG11. Both ImG11 and ImG33 grow linearly versus frequency and this represents wave emission. For a layered medium, besides wave emission, the ensuing variations correspond to reflected waves. For high frequencies, ImG33 depends on the properties of the top layer. Reflected body waves are very small and Rayleigh waves behave in the top layer as in a kind of mini half-space. From HVSR one can invert the velocity model using the DFA. It is possible to compute efficiently the imaginary part of the Green's functions from the integrals along the radial wavenumber k. This can be made using either the Bouchon DWN method or the Cauchy residue theorem to get the pole contributions of Rayleigh and Love surface waves in the k complex plane. This allows separating the contributions of each wave type.

Graded-index fibers, Wigner-distribution functions, and the fractional Fourier transform.

PubMed

Mendlovic, D; Ozaktas, H M; Lohmann, A W

1994-09-10

Two definitions of a fractional Fourier transform have been proposed previously. One is based on the propagation of a wave field through a graded-index medium, and the other is based on rotating a function's Wigner distribution. It is shown that both definitions are equivalent. An important result of this equivalency is that the Wigner distribution of a wave field rotates as the wave field propagates through a quadratic graded-index medium. The relation with ray-optics phase space is discussed.

Enhanced production of ψ (2 S ) mesons in heavy ion collisions

NASA Astrophysics Data System (ADS)

Cho, Sungtae

2015-05-01

I study the production of a ψ (2 S ) meson in heavy ion collisions. I evaluate Wigner functions for the ψ (2 S ) meson using both Gaussian and Coulomb wave functions, and investigate the wave function dependence in the ψ (2 S ) meson production by recombination of charm and anticharm quarks. The enhanced transverse momentum distribution of ψ (2 S ) mesons compared to that of J /ψ mesons, originated from wave function distributions of the ψ (2 S ) and J /ψ meson in momentum space, provides a plausible explanation for the recent measurement of the nuclear modification factor ratio between the ψ (2 S ) and J /ψ meson.

Instabilities in dynamic anti-plane sliding of an elastic layer on a dissimilar elastic half-space

NASA Astrophysics Data System (ADS)

Kunnath, R.

2012-12-01

The stability of dynamic anti-plane sliding at an interface between an elastic layer and an elastic half-space with dissimilar elastic properties is studied. Friction at the interface is assumed to follow a rate- and state-dependent law, with a positive instantaneous dependence on slip velocity and a rate weakening behavior in the steady state. The perturbations are of the form exp(ikx+pt), where k is the wavenumber, x is the coordinate along the interface, p is the time response to the perturbation and t is time. The results of the stability analysis are shown in Figs. 1 and 2 with the velocity weakening parameter b/a=5, shear wave speed ratio cs'/cs=1.2, shear modulus ratio μ'/μ=1.2 and non-dimensional layer thickness H=100. The normalized instability growth rate and normalized phase velocity are plotted as a function of wavenumber. Fig.1 is for a non-dimensional unperturbed slip velocity ɛ=5 (rapid sliding) while Fig. 2 is for ɛ=0.05 (slow sliding). The results show the destabilization of interfacial waves. For slow sliding, destabilization of interfacial waves is still seen, indicating that the quasi-static approximation to slow sliding is not valid. This is in agreement with the result of Ranjith (Int. J. Solids and Struct., 2009, 46, 3086-3092) who predicted an instability of long-wavelength Love waves in slow sliding.

A complete active space valence bond method with nonorthogonal orbitals

NASA Astrophysics Data System (ADS)

Hirao, Kimihiko; Nakano, Haruyuki; Nakayama, Kenichi

1997-12-01

A complete active space self-consistent field (SCF) wave function is transformed into a valence bond type representation built from nonorthogonal orbitals, each strongly localized on a single atom. Nonorthogonal complete active space SCF orbitals are constructed by Ruedenberg's projected localization procedure so that they have maximal overlaps with the corresponding minimum basis set of atomic orbitals of the free-atoms. The valence bond structures which are composed of such nonorthogonal quasiatomic orbitals constitute the wave function closest to the concept of the oldest and most simple valence bond method. The method is applied to benzene, butadiene, hydrogen, and methane molecules and compared to the previously proposed complete active space valence bond approach with orthogonal orbitals. The results demonstrate the validity of the method as a powerful tool for describing the electronic structure of various molecules.

Parameter-space metric of semicoherent searches for continuous gravitational waves

NASA Astrophysics Data System (ADS)

Pletsch, Holger J.

2010-08-01

Continuous gravitational-wave (CW) signals such as emitted by spinning neutron stars are an important target class for current detectors. However, the enormous computational demand prohibits fully coherent broadband all-sky searches for prior unknown CW sources over wide ranges of parameter space and for yearlong observation times. More efficient hierarchical “semicoherent” search strategies divide the data into segments much shorter than one year, which are analyzed coherently; then detection statistics from different segments are combined incoherently. To optimally perform the incoherent combination, understanding of the underlying parameter-space structure is requisite. This problem is addressed here by using new coordinates on the parameter space, which yield the first analytical parameter-space metric for the incoherent combination step. This semicoherent metric applies to broadband all-sky surveys (also embedding directed searches at fixed sky position) for isolated CW sources. Furthermore, the additional metric resolution attained through the combination of segments is studied. From the search parameters (sky position, frequency, and frequency derivatives), solely the metric resolution in the frequency derivatives is found to significantly increase with the number of segments.

GW/Bethe-Salpeter calculations for charged and model systems from real-space DFT

NASA Astrophysics Data System (ADS)

Strubbe, David A.

GW and Bethe-Salpeter (GW/BSE) calculations use mean-field input from density-functional theory (DFT) calculations to compute excited states of a condensed-matter system. Many parts of a GW/BSE calculation are efficiently performed in a plane-wave basis, and extensive effort has gone into optimizing and parallelizing plane-wave GW/BSE codes for large-scale computations. Most straightforwardly, plane-wave DFT can be used as a starting point, but real-space DFT is also an attractive starting point: it is systematically convergeable like plane waves, can take advantage of efficient domain parallelization for large systems, and is well suited physically for finite and especially charged systems. The flexibility of a real-space grid also allows convenient calculations on non-atomic model systems. I will discuss the interfacing of a real-space (TD)DFT code (Octopus, www.tddft.org/programs/octopus) with a plane-wave GW/BSE code (BerkeleyGW, www.berkeleygw.org), consider performance issues and accuracy, and present some applications to simple and paradigmatic systems that illuminate fundamental properties of these approximations in many-body perturbation theory.

Evolution of wave function in a dissipative system

NASA Technical Reports Server (NTRS)

Yu, Li-Hua; Sun, Chang-Pu

1994-01-01

For a dissipative system with Ohmic friction, we obtain a simple and exact solution for the wave function of the system plus the bath. It is described by the direct product in two independent Hilbert space. One of them is described by an effective Hamiltonian, the other represents the effect of the bath, i.e., the Brownian motion, thus clarifying the structure of the wave function of the system whose energy is dissipated by its interaction with the bath. No path integral technology is needed in this treatment. The derivation of the Weisskopf-Wigner line width theory follows easily.

Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

NASA Astrophysics Data System (ADS)

Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

2016-11-01

A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

Using ISS Telescopes for Electromagnetic Follow-up of Gravitational Wave Detections of NS-NS and NS-BH Mergers

NASA Technical Reports Server (NTRS)

Camp, J.; Barthelmy, S.; Blackburn, L.; Carpenter, K. G.; Gehrels, N.; Kanner, J.; Marshall, F. E.; Racusin, J. L.; Sakamoto, T.

2013-01-01

The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of ground-based gravitational wave detections of neutron star and black hole mergers. We describe this possibility for OpTIIX, an ISS technology demonstration of a 1.5 m diffraction limited optical telescope assembled in space, and ISS-Lobster, a wide-field imaging X-ray telescope now under study as a potential NASA mission. Both telescopes will be mounted on pointing platforms, allowing rapid positioning to the source of a gravitational wave event. Electromagnetic follow-up rates of several per year appear likely, offering a wealth of complementary science on the mergers of black holes and neutron stars.

Application of magnetoelastic materials in spatiotemporally modulated phononic crystals for nonreciprocal wave propagation

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Attarzadeh, M. A.; Nouh, M.; Karami, M. Amin

2018-01-01

In this paper, a physical platform is proposed to change the properties of phononic crystals in space and time in order to achieve nonreciprocal wave transmission. The utilization of magnetoelastic materials in elastic phononic systems is studied. Material properties of magnetoelastic materials change significantly with an external magnetic field. This property is used to design systems with a desired wave propagation pattern. The properties of the magnetoelastic medium are changed in a traveling wave pattern, which changes in both space and time. A phononic crystal with such a modulation exhibits one-way wave propagation behavior. An extended transfer matrix method (TMM) is developed to model a system with time varying properties. The stop band and the pass band of a reciprocal and a nonreciprocal bar are found using this method. The TMM is used to find the transfer function of a magnetoelastic bar. The obtained results match those obtained via the theoretical Floquet-Bloch approach and numerical simulations. It is shown that the stop band in the transfer function of a system with temporal varying property for the forward wave propagation is different from the same in the backward wave propagation. The proposed configuration enables the physical realization of a class of smart structures that incorporates nonreciprocal wave propagation.

Methods utilized in evaluating the profitability of commercial space processing

NASA Technical Reports Server (NTRS)

Bloom, H. L.; Schmitt, P. T.

1976-01-01

Profitability analysis is applied to commercial space processing on the basis of business concept definition and assessment and the relationship between ground and space functions. Throughput analysis is demonstrated by analysis of the space manufacturing of surface acoustic wave devices. The paper describes a financial analysis model for space processing and provides key profitability measures for space processed isoenzymes.

On Gravitational Effects in the Schrödinger Equation

NASA Astrophysics Data System (ADS)

Pollock, M. D.

2014-04-01

The Schrödinger equation for a particle of rest mass and electrical charge interacting with a four-vector potential can be derived as the non-relativistic limit of the Klein-Gordon equation for the wave function , where and , or equivalently from the one-dimensional action for the corresponding point particle in the semi-classical approximation , both methods yielding the equation in Minkowski space-time , where and . We show that these two methods generally yield equations that differ in a curved background space-time , although they coincide when if is replaced by the effective mass in both the Klein-Gordon action and , allowing for non-minimal coupling to the gravitational field, where is the Ricci scalar and is a constant. In this case , where and , the correctness of the gravitational contribution to the potential having been verified to linear order in the thermal-neutron beam interferometry experiment due to Colella et al. Setting and regarding as the quasi-particle wave function, or order parameter, we obtain the generalization of the fundamental macroscopic Ginzburg-Landau equation of superconductivity to curved space-time. Conservation of probability and electrical current requires both electromagnetic gauge and space-time coordinate conditions to be imposed, which exemplifies the gravito-electromagnetic analogy, particularly in the stationary case, when div, where and . The quantum-cosmological Schrödinger (Wheeler-DeWitt) equation is also discussed in the -dimensional mini-superspace idealization, with particular regard to the vacuum potential and the characteristics of the ground state, assuming a gravitational Lagrangian which contains higher-derivative terms up to order . For the heterotic superstring theory , consists of an infinite series in , where is the Regge slope parameter, and in the perturbative approximation , is positive semi-definite for . The maximally symmetric ground state satisfying the field equations is Minkowski space for and anti-de Sitter space for.

Longitudinal direct and indirect pathways linking older sibling competence to the development of younger sibling competence.

PubMed

Brody, Gene H; Kim, Sooyeon; Murry, Velma McBride; Brown, Anita C

2003-05-01

A 4-wave longitudinal model tested direct and indirect links between older sibling (OS; M = 11.7 years) and younger sibling (YS; M = 9.2 years) competence in 152 rural African American families. Data were collected at 1-year intervals. At each wave, different teachers assessed OS competence, YS competence, and YS self-regulation. Mothers reported their own psychological functioning; mothers and YSs reported parenting practices toward the YS. OS competence was stable across time and was linked with positive changes in mothers' psychological functioning from Wave 1 to Wave 2. Mothers' Wave 2 psychological functioning was associated with involved-supportive parenting of the YS at Wave 3. OS Wave 2 competence and Wave 3 parenting were indirectly linked with Wave 4 YS competence, through Wave 3 YS self-regulation. Structural equation modeling controlled for Wave 1 YS competence; thus, the model accounted for change in YS competence across 3 years.

Generalized-active-space pair-density functional theory: an efficient method to study large, strongly correlated, conjugated systems.

PubMed

Ghosh, Soumen; Cramer, Christopher J; Truhlar, Donald G; Gagliardi, Laura

2017-04-01

Predicting ground- and excited-state properties of open-shell organic molecules by electronic structure theory can be challenging because an accurate treatment has to correctly describe both static and dynamic electron correlation. Strongly correlated systems, i.e. , systems with near-degeneracy correlation effects, are particularly troublesome. Multiconfigurational wave function methods based on an active space are adequate in principle, but it is impractical to capture most of the dynamic correlation in these methods for systems characterized by many active electrons. We recently developed a new method called multiconfiguration pair-density functional theory (MC-PDFT), that combines the advantages of wave function theory and density functional theory to provide a more practical treatment of strongly correlated systems. Here we present calculations of the singlet-triplet gaps in oligoacenes ranging from naphthalene to dodecacene. Calculations were performed for unprecedently large orbitally optimized active spaces of 50 electrons in 50 orbitals, and we test a range of active spaces and active space partitions, including four kinds of frontier orbital partitions. We show that MC-PDFT can predict the singlet-triplet splittings for oligoacenes consistent with the best available and much more expensive methods, and indeed MC-PDFT may constitute the benchmark against which those other models should be compared, given the absence of experimental data.

Correlating Near-Source Rock Damage from Single-Hole Explosions to Seismic Waves (Postprint)

DTIC Science & Technology

2012-05-07

Technical Paper APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. AIR FORCE RESEARCH LABORATORY Space Vehicles Directorate...Space Vehicles Directorate 3550 Aberdeen Ave SE 3550 Aberdeen Ave SE 11. SPONSOR/MONITOR’S REPORT Kirtland AFB, NM 87117-5776...function of pressure, • Fluid permeability as a function of pressure, • Electrical resistivity as a function of pressure, and • Rock strength. The

Decoherence and Determinism in a One-Dimensional Cloud-Chamber Model

NASA Astrophysics Data System (ADS)

Sparenberg, Jean-Marc; Gaspard, David

2018-03-01

The hypothesis (Sparenberg et al. in EPJ Web Conf 58:01016, [1]. https://doi.org/10.1051/epjconf/20135801016) that the particular linear tracks appearing in the measurement of a spherically-emitting radioactive source in a cloud chamber are determined by the (random) positions of atoms or molecules inside the chamber is further explored in the framework of a recently established one-dimensional model (Carlone et al. Comm Comput Phys 18:247, [2]. https://doi.org/10.4208/cicp.270814.311214a). In this model, meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the spherical wave is replaced by a linear superposition of two wave packets moving from the origin to the left and to the right, evolving deterministically according to the Schrödinger equation. We first revisit these results using a time-dependent approach, where the wave packets impinge on a symmetric two-sided detector. We discuss the evolution of the wave function in the configuration space and stress the interest of a non-symmetric detector in a quantum-measurement perspective. Next we use a time-independent approach to study the scattering of a plane wave on a single-sided detector. Preliminary results are obtained, analytically for the single-spin case and numerically for up to 8 spins. They show that the spin-excitation probabilities are sometimes very sensitive to the parameters of the model, which corroborates the idea that the measurement result could be determined by the atom positions. The possible origin of decoherence and entropy increase in future models is finally discussed.

Unidirectional Wave Vector Manipulation in Two-Dimensional Space with an All Passive Acoustic Parity-Time-Symmetric Metamaterials Crystal

NASA Astrophysics Data System (ADS)

Liu, Tuo; Zhu, Xuefeng; Chen, Fei; Liang, Shanjun; Zhu, Jie

2018-03-01

Exploring the concept of non-Hermitian Hamiltonians respecting parity-time symmetry with classical wave systems is of great interest as it enables the experimental investigation of parity-time-symmetric systems through the quantum-classical analogue. Here, we demonstrate unidirectional wave vector manipulation in two-dimensional space, with an all passive acoustic parity-time-symmetric metamaterials crystal. The metamaterials crystal is constructed through interleaving groove- and holey-structured acoustic metamaterials to provide an intrinsic parity-time-symmetric potential that is two-dimensionally extended and curved, which allows the flexible manipulation of unpaired wave vectors. At the transition point from the unbroken to broken parity-time symmetry phase, the unidirectional sound focusing effect (along with reflectionless acoustic transparency in the opposite direction) is experimentally realized over the spectrum. This demonstration confirms the capability of passive acoustic systems to carry the experimental studies on general parity-time symmetry physics and further reveals the unique functionalities enabled by the judiciously tailored unidirectional wave vectors in space.

Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity

NASA Astrophysics Data System (ADS)

Das, S.; Sahoo, T.; Meylan, M. H.

2018-01-01

The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity.

PubMed

Das, S; Sahoo, T; Meylan, M H

2018-01-01

The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

Quantum Dynamics with Short-Time Trajectories and Minimal Adaptive Basis Sets.

PubMed

Saller, Maximilian A C; Habershon, Scott

2017-07-11

Methods for solving the time-dependent Schrödinger equation via basis set expansion of the wave function can generally be categorized as having either static (time-independent) or dynamic (time-dependent) basis functions. We have recently introduced an alternative simulation approach which represents a middle road between these two extremes, employing dynamic (classical-like) trajectories to create a static basis set of Gaussian wavepackets in regions of phase-space relevant to future propagation of the wave function [J. Chem. Theory Comput., 11, 8 (2015)]. Here, we propose and test a modification of our methodology which aims to reduce the size of basis sets generated in our original scheme. In particular, we employ short-time classical trajectories to continuously generate new basis functions for short-time quantum propagation of the wave function; to avoid the continued growth of the basis set describing the time-dependent wave function, we employ Matching Pursuit to periodically minimize the number of basis functions required to accurately describe the wave function. Overall, this approach generates a basis set which is adapted to evolution of the wave function while also being as small as possible. In applications to challenging benchmark problems, namely a 4-dimensional model of photoexcited pyrazine and three different double-well tunnelling problems, we find that our new scheme enables accurate wave function propagation with basis sets which are around an order-of-magnitude smaller than our original trajectory-guided basis set methodology, highlighting the benefits of adaptive strategies for wave function propagation.

A 6-year Longitudinal Study of Self-harm and Suicidal Behaviors among Chinese Adolescents in Hong Kong.

PubMed

Law, Ben M F; Shek, Daniel T L

2016-02-01

To examine the trajectories of self-harm and suicidal behaviors among Chinese adolescents in Hong Kong and to investigate the related predictors, including gender, family nonintactness, economic disadvantage, positive youth development, and family functioning. We used quantitative data from a large sample of adolescent participants. Participants initially joined this study when they were in grade 7 (wave 1), and they were followed from grade 8 (wave 2) to grade 12 (wave 6). The participants consisted of 2023 grade 12 students from 28 secondary schools in Hong Kong. A multistage cluster random sampling method was adopted. Self-harm and suicidal behaviors. The trajectories of self-harm and suicidal behaviors in general declined from grade 7 to grade 12. Regarding the effect of gender, whereas adolescent girls showed a higher prevalence for self-harm and suicidal behaviors at baseline and other waves, adolescent boys showed a pronounced decline in self-harm rates. Adolescents from nonintact families were more likely to self-harm or engage in suicidal behaviors at wave 6. Economic disadvantage at wave 4 predicted higher suicidal behavior among adolescents but not self-harm at wave 6. Regarding positive youth development, several protective factors that include cognitive-behavioral competencies, prosocial attributes, general positive youth development qualities, and positive identity could help reduce self-harm and suicidal behaviors at different time points. Regarding the role of family functioning, more family conflicts predicted higher suicidality in adolescence (self-harm and suicidal behaviors), and family communication affected self-harming behaviors at wave 6. The trajectories of self-harm and suicidal behaviors decline from early to late adolescence among Chinese adolescents. Positive youth development and constructive family functioning are critical to help reduce suicidal behaviors. Regarding increased risk, more attention should be paid to adolescent girls and adolescents from nonintact and economic disadvantaged families. Copyright © 2016 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

The externally corrected coupled cluster approach with four- and five-body clusters from the CASSCF wave function.

PubMed

Xu, Enhua; Li, Shuhua

2015-03-07

An externally corrected CCSDt (coupled cluster with singles, doubles, and active triples) approach employing four- and five-body clusters from the complete active space self-consistent field (CASSCF) wave function (denoted as ecCCSDt-CASSCF) is presented. The quadruple and quintuple excitation amplitudes within the active space are extracted from the CASSCF wave function and then fed into the CCSDt-like equations, which can be solved in an iterative way as the standard CCSDt equations. With a size-extensive CASSCF reference function, the ecCCSDt-CASSCF method is size-extensive. When the CASSCF wave function is readily available, the computational cost of the ecCCSDt-CASSCF method scales as the popular CCSD method (if the number of active orbitals is small compared to the total number of orbitals). The ecCCSDt-CASSCF approach has been applied to investigate the potential energy surface for the simultaneous dissociation of two O-H bonds in H2O, the equilibrium distances and spectroscopic constants of 4 diatomic molecules (F2(+), O2(+), Be2, and NiC), and the reaction barriers for the automerization reaction of cyclobutadiene and the Cl + O3 → ClO + O2 reaction. In most cases, the ecCCSDt-CASSCF approach can provide better results than the CASPT2 (second order perturbation theory with a CASSCF reference function) and CCSDT methods.

A universality in pp-waves

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Partha

2007-06-01

We discuss a universality property of any covariant field theory in space-time expanded around pp-wave backgrounds. According to this property the space-time lagrangian density evaluated on a restricted set of field configurations, called universal sector, turns out to be same around all the pp-waves, even off-shell, with same transverse space and same profiles for the background scalars. In this paper we restrict our discussion to tensorial fields only. In the context of bosonic string theory we consider on-shell pp-waves and argue that universality requires the existence of a universal sector of world-sheet operators whose correlation functions are insensitive to the pp-wave nature of the metric and the background gauge flux. Such results can also be reproduced using the world-sheet conformal field theory. We also study such pp-waves in non-polynomial closed string field theory (CSFT). In particular, we argue that for an off-shell pp-wave ansatz with flat transverse space and dilaton independent of transverse coordinates the field redefinition relating the low energy effective field theory and CSFT with all the massive modes integrated out is at most quadratic in fields. Because of this simplification it is expected that the off-shell pp-waves can be identified on the two sides. Furthermore, given the massless pp-wave field configurations, an iterative method for computing the higher massive modes using the CSFT equations of motion has been discussed. All our bosonic string theory analyses can be generalised to the common Neveu-Schwarz sector of superstrings.

ATS-5 millimeter wave propagation measurements

NASA Technical Reports Server (NTRS)

Ippolito, L. J.

1973-01-01

Long term experimental measurements to determine the propagation characteristics of 15 and 32 GHz earth-space links and to evaluate performance characteristics of operational millimeter wave systems are reported. The ATS 5 millimeter wave experimental link experienced attenuation and fading characteristics as a function of rainfall rate and other meteorological parameters. A method of site selection for the lowest attenuation rainfall rate improved reception tremendously.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanty, Soumya D.; Nayak, Rajesh K.

The space based gravitational wave detector LISA (Laser Interferometer Space Antenna) is expected to observe a large population of Galactic white dwarf binaries whose collective signal is likely to dominate instrumental noise at observational frequencies in the range 10{sup -4} to 10{sup -3} Hz. The motion of LISA modulates the signal of each binary in both frequency and amplitude--the exact modulation depending on the source direction and frequency. Starting with the observed response of one LISA interferometer and assuming only Doppler modulation due to the orbital motion of LISA, we show how the distribution of the entire binary population inmore » frequency and sky position can be reconstructed using a tomographic approach. The method is linear and the reconstruction of a delta-function distribution, corresponding to an isolated binary, yields a point spread function (psf). An arbitrary distribution and its reconstruction are related via smoothing with this psf. Exploratory results are reported demonstrating the recovery of binary sources, in the presence of white Gaussian noise.« less

Dirac electron in a chiral space-time crystal created by counterpropagating circularly polarized plane electromagnetic waves

NASA Astrophysics Data System (ADS)

Borzdov, G. N.

2017-10-01

The family of solutions to the Dirac equation for an electron moving in an electromagnetic lattice with the chiral structure created by counterpropagating circularly polarized plane electromagnetic waves is obtained. At any nonzero quasimomentum, the dispersion equation has two solutions which specify bispinor wave functions describing electron states with different energies and mean values of momentum and spin operators. The inversion of the quasimomentum results in two other linearly independent solutions. These four basic wave functions are uniquely defined by eight complex scalar functions (structural functions), which serve as convenient building blocks of the relations describing the electron properties. These properties are illustrated in graphical form over a wide range of quasimomenta. The superpositions of two basic wave functions describing different spin states and corresponding to (i) the same quasimomentum (unidirectional electron states with the spin precession) and (ii) the two equal-in-magnitude but oppositely directed quasimomenta (bidirectional electron states) are also treated.

Momentum-Space Entanglement and Loschmidt Echo in Luttinger Liquids after a Quantum Quench.

PubMed

Dóra, Balázs; Lundgren, Rex; Selover, Mark; Pollmann, Frank

2016-07-01

Luttinger liquids (LLs) arise by coupling left- and right-moving particles through interactions in one dimension. This most natural partitioning of LLs is investigated by the momentum-space entanglement after a quantum quench using analytical and numerical methods. We show that the momentum-space entanglement spectrum of a LL possesses many universal features both in equilibrium and after a quantum quench. The largest entanglement eigenvalue is identical to the Loschmidt echo, i.e., the overlap of the disentangled and final wave functions of the system. The second largest eigenvalue is the overlap of the first excited state of the disentangled system with zero total momentum and the final wave function. The entanglement gap is universal both in equilibrium and after a quantum quench. The momentum-space entanglement entropy is always extensive and saturates fast to a time independent value after the quench, in sharp contrast to a spatial bipartitioning.

A class of reduced-order models in the theory of waves and stability.

PubMed

Chapman, C J; Sorokin, S V

2016-02-01

This paper presents a class of approximations to a type of wave field for which the dispersion relation is transcendental. The approximations have two defining characteristics: (i) they give the field shape exactly when the frequency and wavenumber lie on a grid of points in the (frequency, wavenumber) plane and (ii) the approximate dispersion relations are polynomials that pass exactly through points on this grid. Thus, the method is interpolatory in nature, but the interpolation takes place in (frequency, wavenumber) space, rather than in physical space. Full details are presented for a non-trivial example, that of antisymmetric elastic waves in a layer. The method is related to partial fraction expansions and barycentric representations of functions. An asymptotic analysis is presented, involving Stirling's approximation to the psi function, and a logarithmic correction to the polynomial dispersion relation.

ULF/ELF Waves in Near-Moon Space

NASA Astrophysics Data System (ADS)

Nakagawa, Tomoko

2016-02-01

The reflection of the solar wind protons is equivalent to a beam injection against the solar wind flow. It is expected to produce a ring beam with a 3D distribution function in many cases. The reflected protons are responsible for the generation of ultra-low-frequency (ULF) waves at ˜0.01 Hz and narrowband waves at ˜1 Hz in the extremely low frequency (ELF) range through resonant interaction with magnetohydrodynamic waves and whistler mode waves in the solar wind, respectively. This chapter discusses these commonly observed waves in the near-Moon space. The sinusoidal waveforms and sharp spectra of the monochromatic ELF waves are impressive, but commonly observed are non-monochromatic waves in the ELF range ˜0.03-10 Hz. Some of the solar wind protons reflected by the dayside lunar surface or crustal magnetic field gyrate around the solar wind magnetic field and can access the center of the wake owing to the large Larmour radius.

Some Interaction Solutions of a Reduced Generalised (3+1)-Dimensional Shallow Water Wave Equation for Lump Solutions and a Pair of Resonance Solitons

NASA Astrophysics Data System (ADS)

Wang, Yao; Chen, Mei-Dan; Li, Xian; Li, Biao

2017-05-01

Through Hirota bilinear transformation and symbolic computation with Maple, a class of lump solutions, rationally localised in all directions in the space, to a reduced generalised (3+1)-dimensional shallow water wave (SWW) equation are prensented. The resulting lump solutions all contain six parameters, two of which are free due to the translation invariance of the SWW equation and the other four of which must satisfy a nonzero determinant condition guaranteeing analyticity and rational localisation of the solutions. Then we derived the interaction solutions for lump solutions and one stripe soliton and the result shows that the particular lump solutions with specific values of the involved parameters will be drowned or swallowed by the stripe soliton. Furthermore, we extend this method to a more general combination of positive quadratic function and hyperbolic functions. Especially, it is interesting that a rogue wave is found to be aroused by the interaction between lump solutions and a pair of resonance stripe solitons. By choosing the values of the parameters, the dynamic properties of lump solutions, interaction solutions for lump solutions and one stripe soliton and interaction solutions for lump solutions and a pair of resonance solitons, are shown by dynamic graphs.

A computational and theoretical analysis of falling frequency VLF emissions

NASA Astrophysics Data System (ADS)

Nunn, David; Omura, Yoshiharu

2012-08-01

Recently much progress has been made in the simulation and theoretical understanding of rising frequency triggered emissions and rising chorus. Both PIC and Vlasov VHS codes produce risers in the region downstream from the equator toward which the VLF waves are traveling. The VHS code only produces fallers or downward hooks with difficulty due to the coherent nature of wave particle interaction across the equator. With the VHS code we now confine the interaction region to be the region upstream from the equator, where inhomogeneity factor S is positive. This suppresses correlated wave particle interaction effects across the equator and the tendency of the code to trigger risers, and permits the formation of a proper falling tone generation region. The VHS code now easily and reproducibly triggers falling tones. The evolution of resonant particle current JE in space and time shows a generation point at -5224 km and the wavefield undergoes amplification of some 25 dB in traversing the nonlinear generation region. The current component parallel to wave magnetic field (JB) is positive, whereas it is negative for risers. The resonant particle trap shows an enhanced distribution function or `hill', whereas risers have a `hole'. According to recent theory (Omura et al., 2008, 2009) sweeping frequency is due primarily to the advective term. The nonlinear frequency shift term is now negative (˜-12 Hz) and the sweep rate of -800 Hz/s is approximately nonlinear frequency shift divided by TN, the transition time, of the order of a trapping time.

Degenerate R-S perturbation theory

NASA Technical Reports Server (NTRS)

Hirschfelder, J. O.; Certain, P. R.

1973-01-01

A concise, systematic procedure is given for determining the Rayleigh-Schrodinger energies and wave functions of degenerate states to arbitrarily high orders even when the degeneracies of the various states are resolved in arbitrary orders. The procedure is expressed in terms of an iterative cycle in which the energy through the (2n+1)st order is expressed in terms of the partially determined wave function through the n-th order. Both a direct and an operator derivation are given. The two approaches are equivalent and can be transcribed into each other. The direct approach deals with the wave functions (without the use of formal operators) and has the advantage that it resembles the usual treatment of nondegenerate perturbations and maintains close contact with the basic physics. In the operator approach, the wave functions are expressed in terms of infinite order operators which are determined by the successive resolution of the space of the zeroth order functions.

Nonlocality of the original Einstein-Podolsky-Rosen state

NASA Astrophysics Data System (ADS)

Cohen, O.

1997-11-01

We examine the properties and behavior of the original Einstein-Podolsky-Rosen (EPR) wave function [Phys. Rev. 47, 777 (1935)] and related Gaussian-correlated wave functions. We assess the degree of entanglement of these wave functions and consider an argument of Bell [Ann. (N.Y.) Acad. Sci. 480, 263 (1986)] based on the Wigner phase-space distribution [Phys. Rev. 40, 749 (1932)], which implies that the original EPR correlations can accommodate a local hidden-variable description. We extend Bell's analysis to the related Gaussian wave functions. We then show that it is possible to identify definite nonlocal aspects for the original EPR state and related states. We describe possible experiments that would demonstrate these nonlocal features through violations of Bell inequalities. The implications of our results, and in particular their relevance for the causal interpretation of quantum mechanics, are considered.

Negative values of quasidistributions and quantum wave and number statistics

NASA Astrophysics Data System (ADS)

Peřina, J.; Křepelka, J.

2018-04-01

We consider nonclassical wave and number quantum statistics, and perform a decomposition of quasidistributions for nonlinear optical down-conversion processes using Bessel functions. We show that negative values of the quasidistribution do not directly represent probabilities; however, they directly influence measurable number statistics. Negative terms in the decomposition related to the nonclassical behavior with negative amplitudes of probability can be interpreted as positive amplitudes of probability in the negative orthogonal Bessel basis, whereas positive amplitudes of probability in the positive basis describe classical cases. However, probabilities are positive in all cases, including negative values of quasidistributions. Negative and positive contributions of decompositions to quasidistributions are estimated. The approach can be adapted to quantum coherence functions.

Functional differentiability in time-dependent quantum mechanics.

PubMed

Penz, Markus; Ruggenthaler, Michael

2015-03-28

In this work, we investigate the functional differentiability of the time-dependent many-body wave function and of derived quantities with respect to time-dependent potentials. For properly chosen Banach spaces of potentials and wave functions, Fréchet differentiability is proven. From this follows an estimate for the difference of two solutions to the time-dependent Schrödinger equation that evolve under the influence of different potentials. Such results can be applied directly to the one-particle density and to bounded operators, and present a rigorous formulation of non-equilibrium linear-response theory where the usual Lehmann representation of the linear-response kernel is not valid. Further, the Fréchet differentiability of the wave function provides a new route towards proving basic properties of time-dependent density-functional theory.

Use of an Atrial Lead with Very Short Tip-To-Ring Spacing Avoids Oversensing of Far-Field R-Wave

PubMed Central

Kolb, Christof; Nölker, Georg; Lennerz, Carsten; Jetter, Hansmartin; Semmler, Verena; Pürner, Klaus; Gutleben, Klaus-Jürgen; Reents, Tilko; Lang, Klaus; Lotze, Ulrich

2012-01-01

Objective The AVOID-FFS (Avoidance of Far-Field R-wave Sensing) study aimed to investigate whether an atrial lead with a very short tip-to-ring spacing without optimization of pacemaker settings shows equally low incidence of far-field R-wave sensing (FFS) when compared to a conventional atrial lead in combination with optimization of the programming. Methods Patients receiving a dual chamber pacemaker were randomly assigned to receive an atrial lead with a tip-to-ring spacing of 1.1 mm or a lead with a conventional tip-to-ring spacing of 10 mm. Postventricular atrial blanking (PVAB) was programmed to the shortest possible value of 60 ms in the study group, and to an individually determined optimized value in the control group. Atrial sensing threshold was programmed to 0.3 mV in both groups. False positive mode switch caused by FFS was evaluated at one and three months post implantation. Results A total of 204 patients (121 male; age 73±10 years) were included in the study. False positive mode switch caused by FFS was detected in one (1%) patient of the study group and two (2%) patients of the control group (p = 0.62). Conclusion The use of an atrial electrode with a very short tip-to-ring spacing avoids inappropriate mode switch caused by FFS without the need for individual PVAB optimization. Trial Registration ClinicalTrials.gov NCT00512915 PMID:22745661

Use of an atrial lead with very short tip-to-ring spacing avoids oversensing of far-field R-wave.

PubMed

Kolb, Christof; Nölker, Georg; Lennerz, Carsten; Jetter, Hansmartin; Semmler, Verena; Pürner, Klaus; Gutleben, Klaus-Jürgen; Reents, Tilko; Lang, Klaus; Lotze, Ulrich

2012-01-01

The AVOID-FFS (Avoidance of Far-Field R-wave Sensing) study aimed to investigate whether an atrial lead with a very short tip-to-ring spacing without optimization of pacemaker settings shows equally low incidence of far-field R-wave sensing (FFS) when compared to a conventional atrial lead in combination with optimization of the programming. Patients receiving a dual chamber pacemaker were randomly assigned to receive an atrial lead with a tip-to-ring spacing of 1.1 mm or a lead with a conventional tip-to-ring spacing of 10 mm. Postventricular atrial blanking (PVAB) was programmed to the shortest possible value of 60 ms in the study group, and to an individually determined optimized value in the control group. Atrial sensing threshold was programmed to 0.3 mV in both groups. False positive mode switch caused by FFS was evaluated at one and three months post implantation. A total of 204 patients (121 male; age 73±10 years) were included in the study. False positive mode switch caused by FFS was detected in one (1%) patient of the study group and two (2%) patients of the control group (p = 0.62). The use of an atrial electrode with a very short tip-to-ring spacing avoids inappropriate mode switch caused by FFS without the need for individual PVAB optimization. ClinicalTrials.gov NCT00512915.

Wigner molecules in carbon-nanotube quantum dots

NASA Astrophysics Data System (ADS)

Rontani, Massimo; Secchi, Andrea

2010-03-01

The paradigm of few-electron complexes in quantum dots (QDs) relies on the ``particle-in-a-box'' idea that lowest-energy orbitals are filled according to Pauli's exclusion principle. If Coulomb repulsion is sufficiently strong to overcome the kinetic energy cost of localization, a different scenario is predicted: a ``Wigner'' molecule (WM) forms, made of electrons frozen in space according to a geometrical pattern. Despite considerable experimental effort, evidence of the WM in semiconductor QDs has been elusive so far. Here we demonstrate theoretically that WMs occur in gate-defined QDs embedded in typical semiconducting carbon nanotubes (CNTs). Their signatures must be searched ---and indeed have already been observed [Deshpande and Bockrath, Nature Phys. 4, 314 (2008)] --- in tunneling spectra. Through exact diagonalisation (ED) calculations, we unveil the inherent features of the electron molecular states. We show that, like nuclei in a usual molecule, electrons have localized wave functions and hence negligible exchange interactions. The molecular excitations are vibrations around the equilibrium positions of electrons. ED results are well reproduced by an ansatz vibrational wave function, which provides a simple theoretical model for transport experiments in ultraclean CNTs.

Asymptotic behavior of Nambu-Bethe-Salpeter wave functions for multiparticles in quantum field theories

NASA Astrophysics Data System (ADS)

Aoki, Sinya; Ishii, Noriyoshi; Doi, Takumi; Ikeda, Yoichi; Inoue, Takashi

2013-07-01

We derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave function at large space separations for systems with more than two particles in quantum field theories. To deal with n particles in the center-of-mass frame coherently, we introduce the Jacobi coordinates of n particles and then combine their 3(n-1) coordinates into the one spherical coordinate in D=3(n-1) dimensions. We parametrize the on-shell T matrix for n scalar particles at low energy using the unitarity constraint of the S matrix. We then express asymptotic behaviors of the NBS wave function for n particles at low energy in terms of parameters of the T matrix and show that the NBS wave function carries information of the T matrix such as phase shifts and mixing angles of the n-particle system in its own asymptotic behavior, so that the NBS wave function can be considered as the scattering wave of n particles in quantum mechanics. This property is one of the essential ingredients of the HAL QCD scheme to define “potential” from the NBS wave function in quantum field theories such as QCD. Our results, together with an extension to systems with spin 1/2 particles, justify the HAL QCD’s definition of potentials for three or more nucleons (or baryons) in terms of the NBS wave functions.

Ground-Based High-Power Microwave Decoy Discrimination System.

DTIC Science & Technology

1987-12-23

understanding of plasma instabilities, self-induced magnetic effects , space - charge considerations, production of ion currents, etc. 3.3.4 Cross-Field...breakdown, due to small potential differences. Interaction volumes can therefore be large, avoiding breakdown and space - charge effects (at the price...the interference of the incident and reflected wave, and by the electrostatic forces of the surface (positive) and space charge (negative) trapped in

Short-range density functional correlation within the restricted active space CI method

NASA Astrophysics Data System (ADS)

Casanova, David

2018-03-01

In the present work, I introduce a hybrid wave function-density functional theory electronic structure method based on the range separation of the electron-electron Coulomb operator in order to recover dynamic electron correlations missed in the restricted active space configuration interaction (RASCI) methodology. The working equations and the computational algorithm for the implementation of the new approach, i.e., RAS-srDFT, are presented, and the method is tested in the calculation of excitation energies of organic molecules. The good performance of the RASCI wave function in combination with different short-range exchange-correlation functionals in the computation of relative energies represents a quantitative improvement with respect to the RASCI results and paves the path for the development of RAS-srDFT as a promising scheme in the computation of the ground and excited states where nondynamic and dynamic electron correlations are important.

Analysis of STM images with pure and CO-functionalized tips: A first-principles and experimental study

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Okabayashi, Norio; Peronio, Angelo; Giessibl, Franz J.; Paulsson, Magnus

2017-08-01

We describe a first-principles method to calculate scanning tunneling microscopy (STM) images, and compare the results to well-characterized experiments combining STM with atomic force microscopy (AFM). The theory is based on density functional theory with a localized basis set, where the wave functions in the vacuum gap are computed by propagating the localized-basis wave functions into the gap using a real-space grid. Constant-height STM images are computed using Bardeen's approximation method, including averaging over the reciprocal space. We consider copper adatoms and single CO molecules adsorbed on Cu(111), scanned with a single-atom copper tip with and without CO functionalization. The calculated images agree with state-of-the-art experiments, where the atomic structure of the tip apex is determined by AFM. The comparison further allows for detailed interpretation of the STM images.

Data synthesis and display programs for wave distribution function analysis

NASA Technical Reports Server (NTRS)

Storey, L. R. O.; Yeh, K. J.

1992-01-01

At the National Space Science Data Center (NSSDC) software was written to synthesize and display artificial data for use in developing the methodology of wave distribution analysis. The software comprises two separate interactive programs, one for data synthesis and the other for data display.

Statistical properties and correlation functions for drift waves

NASA Technical Reports Server (NTRS)

Horton, W.

1986-01-01

The dissipative one-field drift wave equation is solved using the pseudospectral method to generate steady-state fluctuations. The fluctuations are analyzed in terms of space-time correlation functions and modal probability distributions. Nearly Gaussian statistics and exponential decay of the two-time correlation functions occur in the presence of electron dissipation, while in the absence of electron dissipation long-lived vortical structures occur. Formulas from renormalized, Markovianized statistical turbulence theory are given in a local approximation to interpret the dissipative turbulence.

Study of beach cusps via high resolution TLS acquisitions on the pocket beach of Porsmilin (Brittany)

NASA Astrophysics Data System (ADS)

Chabrol, C.; Jaud, M.; Delacourt, C.; Allemand, P.; Augereau, E.; Cuq, V.

2011-12-01

Beach cusps are rhythmic shoreline features made up of series of horns and embayments. Their build-up occurs in specific conditions (steep beachface, low-energy wave conditions...). These features can notably be characterized by the cusp spacing λ and their prominence ɛ (difference in beachface gradient between embayment and horn). At present, two main theories confront to explain the formation of such features on natural beaches : standing edge waves (special class of waves propagating longshore) and self-organisation hypothesis. - Standing edge wave theory proposes that the superimposition of incident waves and standing edge waves generates longshore variations of swash height linked with the position of edge wave nodes and anti-nodes. These variations of swash height result in regular zones of erosion. Depending on the context, different types of edge-waves may occur. The predicted beach cusp spacing is : λ = (g T^2 tanβ) / π for a sub-harmonic edge wave model λ = (g T^2 tanβ) / 2π for a synchronous edge wave model with : λ : beach cusp spacing (m) g : gravitational acceleration (9.81 m/s) T : incident wave period (s) tanβ : beach gradient - Self-organisation theory suggests that a combination of interactions and feedbacks between swash flow and beach topography leads to the growth of morphologic irregularities of a given wavelength (because of flow divergence or convergence), resulting in beach cusp formation and maintaining. The predicted beach cusp spacing is then : λ = f S with : λ : beach cusp spacing (m) S : horizontal extent of the swash flow (m) f : empirical constant (~1.5) Three multitemporal Terrestrial Laser Scan acquisitions have been carried out for three consecutive days on the sandy beach of Porsmilin (Brittany, France) with a spatial resolution varying from few centimetres to few metres. Moreover the hydrodynamic conditions have been obtained thanks to the Previmer project website (http://www.previmer.org/), notably based on WaveWatch3 and MARS-2D models. This study proposes to profit from the high resolution and accuracy of Terrestrial Laser data to measure the geometry and the spacing of beach cusps, to compare the measured parameters to the predicted ones (with both theories) and thus to attempt to identify the hydrodynamic process which sparks off their formation.

Current drive with combined electron cyclotron wave and high harmonic fast wave in tokamak plasmas

NASA Astrophysics Data System (ADS)

Li, J. C.; Gong, X. Y.; Dong, J. Q.; Wang, J.; Zhang, N.; Zheng, P. W.; Yin, C. Y.

2016-12-01

The current driven by combined electron cyclotron wave (ECW) and high harmonic fast wave is investigated using the GENRAY/CQL3D package. It is shown that no significant synergetic current is found in a range of cases with a combined ECW and fast wave (FW). This result is consistent with a previous study [Harvey et al., in Proceedings of IAEA TCM on Fast Wave Current Drive in Reactor Scale Tokamaks (Synergy and Complimentarily with LHCD and ECRH), Arles, France, IAEA, Vienna, 1991]. However, a positive synergy effect does appear with the FW in the lower hybrid range of frequencies. This positive synergy effect can be explained using a picture of the electron distribution function induced by the ECW and a very high harmonic fast wave (helicon). The dependence of the synergy effect on the radial position of the power deposition, the wave power, the wave frequency, and the parallel refractive index is also analyzed, both numerically and physically.

Time-Harmonic Gaussian Beams: Exact Solutions of the Helmhotz Equation in Free Space

NASA Astrophysics Data System (ADS)

Kiselev, A. P.

2017-12-01

An exact solution of the Helmholtz equation u xx + u yy + u zz + k 2 u = 0 is presented, which describes propagation of monochromatic waves in the free space. The solution has the form of a superposition of plane waves with a specific weight function dependent on a certain free parameter a. If ka→∞, the solution is localized in the Gaussian manner in a vicinity of a certain straight line and asymptotically coincides with the famous approximate solution known as the fundamental mode of a paraxial Gaussian beam. The asymptotics of the aforementioned exact solution does not include a backward wave.

A Fast Method of Deriving the Kirchhoff Formula for Moving Surfaces

NASA Technical Reports Server (NTRS)

Farassat, F.; Posey, Joe W.

2007-01-01

The Kirchhoff formula for a moving surface is very useful in many wave propagation problems, particularly in the prediction of noise from rotating machinery. Several publications in the last two decades have presented derivations of the Kirchhoff formula for moving surfaces in both time and frequency domains. Here we present a method originally developed by Farassat and Myers in time domain that is both simple and direct. It is based on generalized function theory and the useful concept of imbedding the problem in the unbounded three-dimensional space. We derive an inhomogeneous wave equation with the source terms that involve Dirac delta functions with their supports on the moving data surface. This wave equation is then solved using the simple free space Green's function of the wave equation resulting in the Kirchhoff formula. The algebraic manipulations are minimal and simple. We do not need the Green's theorem in four dimensions and there is no ambiguity in the interpretation of any terms in the final formulas. Furthermore, this method also gives the simplest derivation of the classical Kirchhoff formula which has a fairly lengthy derivation in physics and applied mathematics books. The Farassat-Myers method can be used easily in frequency domain.

Generalized Case ``Van Kampen theory for electromagnetic oscillations in a magnetized plasma

NASA Astrophysics Data System (ADS)

Bairaktaris, F.; Hizanidis, K.; Ram, A. K.

2017-10-01

The Case-Van Kampen theory is set up to describe electrostatic oscillations in an unmagnetized plasma. Our generalization to electromagnetic oscillations in magnetized plasma is formulated in the relativistic position-momentum phase space of the particles. The relativistic Vlasov equation includes the ambient, homogeneous, magnetic field, and space-time dependent electromagnetic fields that satisfy Maxwell's equations. The standard linearization technique leads to an equation for the perturbed distribution function in terms of the electromagnetic fields. The eigenvalues and eigenfunctions are obtained from three integrals `` each integral being over two different components of the momentum vector. Results connecting phase velocity, frequency, and wave vector will be presented. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium, and by DoE Grant DE-FG02-91ER-54109.

Experimental investigation on aero-optical aberration of shock wave/boundary layer interactions

NASA Astrophysics Data System (ADS)

Ding, Haolin; Yi, Shihe; Fu, Jia; He, Lin

2016-10-01

After streaming through the flow field which including the expansion, shock wave, boundary, etc., the optical wave would be distorted by fluctuations in the density field. Interactions between laminar/turbulent boundary layer and shock wave contain large number complex flow structures, which offer a condition for studying the influences that different flow structures of the complex flow field have on the aero-optical aberrations. Interactions between laminar/turbulent boundary layer and shock wave are investigated in a Mach 3.0 supersonic wind tunnel, based on nanoparticle-tracer planar laser scattering (NPLS) system. Boundary layer separation/attachment, induced suppression waves, induced shock wave, expansion fan and boundary layer are presented by NPLS images. Its spatial resolution is 44.15 μm/pixel. Time resolution is 6ns. Based on the NPLS images, the density fields with high spatial-temporal resolution are obtained by the flow image calibration, and then the optical path difference (OPD) fluctuations of the original 532nm planar wavefront are calculated using Ray-tracing theory. According to the different flow structures in the flow field, four parts are selected, (1) Y=692 600pixel; (2) Y=600 400pixel; (3) Y=400 268pixel; (4) Y=268 0pixel. The aerooptical effects of different flow structures are quantitatively analyzed, the results indicate that: the compressive waves such as incident shock wave, induced shock wave, etc. rise the density, and then uplift the OPD curve, but this kind of shock are fixed in space position and intensity, the aero-optics induced by it can be regarded as constant; The induced shock waves are induced by the coherent structure of large size vortex in the interaction between turbulent boundary layer, its unsteady characteristic decides the induced waves unsteady characteristic; The space position and intensity of the induced shock wave are fixed in the interaction between turbulent boundary layer; The boundary layer aero-optics are induced by the coherent structure of large size vortex, which result in the fluctuation of OPD.

A single-sided representation for the homogeneous Green's function of a unified scalar wave equation.

PubMed

Wapenaar, Kees

2017-06-01

A unified scalar wave equation is formulated, which covers three-dimensional (3D) acoustic waves, 2D horizontally-polarised shear waves, 2D transverse-electric EM waves, 2D transverse-magnetic EM waves, 3D quantum-mechanical waves and 2D flexural waves. The homogeneous Green's function of this wave equation is a combination of the causal Green's function and its time-reversal, such that their singularities at the source position cancel each other. A classical representation expresses this homogeneous Green's function as a closed boundary integral. This representation finds applications in holographic imaging, time-reversed wave propagation and Green's function retrieval by cross correlation. The main drawback of the classical representation in those applications is that it requires access to a closed boundary around the medium of interest, whereas in many practical situations the medium can be accessed from one side only. Therefore, a single-sided representation is derived for the homogeneous Green's function of the unified scalar wave equation. Like the classical representation, this single-sided representation fully accounts for multiple scattering. The single-sided representation has the same applications as the classical representation, but unlike the classical representation it is applicable in situations where the medium of interest is accessible from one side only.

Cyclotron Acceleration of Relativistic Electrons through Landau Resonance with Obliquely Propagating Whistler Mode Chorus Emissions

NASA Astrophysics Data System (ADS)

Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.

2017-12-01

A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear interactions with VLF chorus, J. Geophys. Res. Space Physics, 122, 324-339, doi:10.1002/2016JA023429.

Wave Geometry: a Plurality of Singularities

NASA Astrophysics Data System (ADS)

Berry, M. V.

Five interconnected wave singularities are discussed: phase monopoles, at eigenvalue degeneracies in parameter space, where the 2-form generating the geomeeic phase is singular, phase dislocations, at zeros of complex wavefunctions in position space, where different wavefronts (surfaces of constant phase) meet; caustics, that is envelopes (foci) of families of classical paths or geometrical rays, where real rays are born violently and which are complementary to dislocations; Stokes sets, at which a complex ray is born gently where it is maximally dominated by another ray; and complex degeneracies, which are the sources of adiabatic quantum transtions in analytic Hamiltonians.

Bidirectional Brush Seals

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Wilson, Jack; Wu, Tom; Flower, Ralph

1997-01-01

Presented is a study of the use of a set of I.D./O.D. bidirectional press seals to reduce the leakage losses in a wave rotor. Relative to the baseline configuration, data indicate the use of brush seals enhanced wave rotor efficiency from 36 to 45 percent at low leakages (small rotor endwall gap spacings) and from 15 to 33 percent at high leakages (larger endwall gap spacings). These brush seals are capable of sealing positive or negative pressure drops with respect to the axial direction. Surface tribology for these tests suggested little evidence of grooving although the bristles appeared polished.

Wave energy transfer in elastic half-spaces with soft interlayers.

PubMed

Glushkov, Evgeny; Glushkova, Natalia; Fomenko, Sergey

2015-04-01

The paper deals with guided waves generated by a surface load in a coated elastic half-space. The analysis is based on the explicit integral and asymptotic expressions derived in terms of Green's matrix and given loads for both laminate and functionally graded substrates. To perform the energy analysis, explicit expressions for the time-averaged amount of energy transferred in the time-harmonic wave field by every excited guided or body wave through horizontal planes and lateral cylindrical surfaces have been also derived. The study is focused on the peculiarities of wave energy transmission in substrates with soft interlayers that serve as internal channels for the excited guided waves. The notable features of the source energy partitioning in such media are the domination of a single emerging mode in each consecutive frequency subrange and the appearance of reverse energy fluxes at certain frequencies. These effects as well as modal and spatial distribution of the wave energy coming from the source into the substructure are numerically analyzed and discussed.

Excitation spectra of retinal by multiconfiguration pair-density functional theory.

PubMed

Dong, Sijia S; Gagliardi, Laura; Truhlar, Donald G

2018-03-07

Retinal is the chromophore in proteins responsible for vision. The absorption maximum of retinal is sensitive to mutations of the protein. However, it is not easy to predict the absorption spectrum of retinal accurately, and questions remain even after intensive investigation. Retinal poses a challenge for Kohn-Sham density functional theory (KS-DFT) because of the charge transfer character in its excitations, and it poses a challenge for wave function theory because the large size of the molecule makes multiconfigurational perturbation theory methods expensive. In this study, we demonstrate that multiconfiguration pair-density functional theory (MC-PDFT) provides an efficient way to predict the vertical excitation energies of 11-Z retinal, and it reproduces the experimentally determined absorption band widths and peak positions better than complete active space second-order perturbation theory (CASPT2). The consistency between complete active space self-consistent field (CASSCF) and KS-DFT dipole moments is demonstrated to be a useful criterion in selecting the active space. We also found that the nature of the terminal groups and the conformations of retinal play a significant role in the absorption spectrum. By considering a thermal distribution of conformations, we predict an absorption spectrum of retinal that is consistent with the experimental gas-phase spectrum. The location of the absorption peak and the spectral broadening based on MC-PDFT calculations agree better with experiments than those of CASPT2.

Radical O-O coupling reaction in diferrate-mediated water oxidation studied using multireference wave function theory.

PubMed

Kurashige, Yuki; Saitow, Masaaki; Chalupský, Jakub; Yanai, Takeshi

2014-06-28

The O-O (oxygen-oxygen) bond formation is widely recognized as a key step of the catalytic reaction of dioxygen evolution from water. Recently, the water oxidation catalyzed by potassium ferrate (K2FeO4) was investigated on the basis of experimental kinetic isotope effect analysis assisted by density functional calculations, revealing the intramolecular oxo-coupling mechanism within a di-iron(vi) intermediate, or diferrate [Sarma et al., J. Am. Chem. Soc., 2012, 134, 15371]. Here, we report a detailed examination of this diferrate-mediated O-O bond formation using scalable multireference electronic structure theory. High-dimensional correlated many-electron wave functions beyond the one-electron picture were computed using the ab initio density matrix renormalization group (DMRG) method along the O-O bond formation pathway. The necessity of using large active space arises from the description of complex electronic interactions and varying redox states both associated with two-center antiferromagnetic multivalent iron-oxo coupling. Dynamic correlation effects on top of the active space DMRG wave functions were additively accounted for by complete active space second-order perturbation (CASPT2) and multireference configuration interaction (MRCI) based methods, which were recently introduced by our group. These multireference methods were capable of handling the double shell effects in the extended active space treatment. The calculations with an active space of 36 electrons in 32 orbitals, which is far over conventional limitation, provide a quantitatively reliable prediction of potential energy profiles and confirmed the viability of the direct oxo coupling. The bonding nature of Fe-O and dual bonding character of O-O are discussed using natural orbitals.

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

NASA Astrophysics Data System (ADS)

Kumari, Nirmala; Chattopadhyay, Amares; Singh, Abhishek K.; Sahu, Sanjeev A.

2017-03-01

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker's asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot's gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

A first-order k-space model for elastic wave propagation in heterogeneous media.

PubMed

Firouzi, K; Cox, B T; Treeby, B E; Saffari, N

2012-09-01

A pseudospectral model of linear elastic wave propagation is described based on the first order stress-velocity equations of elastodynamics. k-space adjustments to the spectral gradient calculations are derived from the dyadic Green's function solution to the second-order elastic wave equation and used to (a) ensure the solution is exact for homogeneous wave propagation for timesteps of arbitrarily large size, and (b) also allows larger time steps without loss of accuracy in heterogeneous media. The formulation in k-space allows the wavefield to be split easily into compressional and shear parts. A perfectly matched layer (PML) absorbing boundary condition was developed to effectively impose a radiation condition on the wavefield. The staggered grid, which is essential for accurate simulations, is described, along with other practical details of the implementation. The model is verified through comparison with exact solutions for canonical examples and further examples are given to show the efficiency of the method for practical problems. The efficiency of the model is by virtue of the reduced point-per-wavelength requirement, the use of the fast Fourier transform (FFT) to calculate the gradients in k space, and larger time steps made possible by the k-space adjustments.

Transport of phase space densities through tetrahedral meshes using discrete flow mapping

NASA Astrophysics Data System (ADS)

Bajars, Janis; Chappell, David J.; Søndergaard, Niels; Tanner, Gregor

2017-01-01

Discrete flow mapping was recently introduced as an efficient ray based method determining wave energy distributions in complex built up structures. Wave energy densities are transported along ray trajectories through polygonal mesh elements using a finite dimensional approximation of a ray transfer operator. In this way the method can be viewed as a smoothed ray tracing method defined over meshed surfaces. Many applications require the resolution of wave energy distributions in three-dimensional domains, such as in room acoustics, underwater acoustics and for electromagnetic cavity problems. In this work we extend discrete flow mapping to three-dimensional domains by propagating wave energy densities through tetrahedral meshes. The geometric simplicity of the tetrahedral mesh elements is utilised to efficiently compute the ray transfer operator using a mixture of analytic and spectrally accurate numerical integration. The important issue of how to choose a suitable basis approximation in phase space whilst maintaining a reasonable computational cost is addressed via low order local approximations on tetrahedral faces in the position coordinate and high order orthogonal polynomial expansions in momentum space.

Three-wave electron vortex lattices for measuring nanofields.

PubMed

Dwyer, C; Boothroyd, C B; Chang, S L Y; Dunin-Borkowski, R E

2015-01-01

It is demonstrated how an electron-optical arrangement consisting of two electron biprisms can be used to generate three-wave vortex lattices with effective lattice spacings between 0.1 and 1 nm. The presence of vortices in these lattices was verified by using a third biprism to perform direct phase measurements via off-axis electron holography. The use of three-wave lattices for nanoscale electromagnetic field measurements via vortex interferometry is discussed, including the accuracy of vortex position measurements and the interpretation of three-wave vortex lattices in the presence of partial spatial coherence. Copyright © 2014 Elsevier B.V. All rights reserved.

Protective longitudinal paths linking child competence to behavioral problems among African American siblings.

PubMed

Brody, Gene H; Kim, Sooyeon; Murry, Velma McBride; Brown, Anita C

2004-01-01

A 4-wave longitudinal design was used to examine protective links from child competence to behavioral problems in first- (M=10.97 years) and second- (M=8.27 years) born rural African American children. At 1-year intervals, teachers assessed child behavioral problems, mothers reported their psychological functioning, and both mothers and children reported parenting practices. Structural equation modeling indicated that child competence was linked with residualized positive changes in mothers' psychological functioning from Wave 1 to Wave 2. Mothers' psychological functioning and child competence at Wave 2 forecast involved-supportive parenting at Wave 3, which was associated negatively with externalizing and internalizing problems at Wave 4. The importance of replicating processes leading to outcomes among children in the same study is discussed.

Landau damping in space plasmas

NASA Technical Reports Server (NTRS)

Thorne, Richard M.; Summers, Danny

1991-01-01

The Landau damping of electrostatic Langmuir waves and ion-acoustic waves in a hot, isotropic, nonmagnetized, generalized Lorentzian plasma is analyzed using the modified plasma dispersion function. Numerical solutions for the real and imaginary parts of the wave frequency omega sub 0 - (i)(gamma) have been obtained as a function of the normalized wave number (k)(lambda sub D), where lambda sub D is the electron Debye length. For both particle distributions the electrostatic modes are found to be strongly damped at short wavelengths. At long wavelengths, this damping becomes less severe, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. It is concluded that Landau damping of ion-acoustic waves is only slightly affected by the presence of a high energy tail, but is strongly dependent on the ion temperature.

Electron number probability distributions for correlated wave functions.

PubMed

Francisco, E; Martín Pendás, A; Blanco, M A

2007-03-07

Efficient formulas for computing the probability of finding exactly an integer number of electrons in an arbitrarily chosen volume are only known for single-determinant wave functions [E. Cances et al., Theor. Chem. Acc. 111, 373 (2004)]. In this article, an algebraic method is presented that extends these formulas to the case of multideterminant wave functions and any number of disjoint volumes. The derived expressions are applied to compute the probabilities within the atomic domains derived from the space partitioning based on the quantum theory of atoms in molecules. Results for a series of test molecules are presented, paying particular attention to the effects of electron correlation and of some numerical approximations on the computed probabilities.

Magnetosonic cnoidal waves and solitons in a magnetized dusty plasma

NASA Astrophysics Data System (ADS)

Kaur, Nimardeep; Singh, Manpreet; Saini, N. S.

2018-04-01

An investigation of magnetosonic nonlinear periodic (cnoidal) waves is presented in a magnetized electron-ion-dust ( e -i -d ) plasma having cold dust fluid with inertialess warm ions and electrons. The reductive perturbation method is employed to derive the Korteweg-de Vries equation. The dispersion relation for magnetosonic cnoidal waves is determined in the linear limit. The magnetosonic cnoidal wave solution is derived using the Sagdeev pseudopotential approach under the specific boundary conditions. There is the formation of only positive potential magnetosonic cnoidal waves and solitary structures in the high plasma-β limit. The effects of various plasma parameters, viz., plasma beta (β), σ (temperature ratio of electrons to ions), and μd (ratio of the number density of dust to electrons) on the characteristics of magnetosonic cnoidal waves are also studied numerically. The findings of the present investigation may be helpful in describing the characteristics of various nonlinear excitations in Earth's magnetosphere, solar wind, Saturn's magnetosphere, and space/astrophysical environments, where many space observations by various satellites confirm the existence of dust grains, highly energetic electrons, and high plasma-β.

The diffraction of Rayleigh waves by a fluid-saturated alluvial valley in a poroelastic half-space modeled by MFS

NASA Astrophysics Data System (ADS)

Liu, Zhongxian; Liang, Jianwen; Wu, Chengqing

2016-06-01

Two dimensional diffraction of Rayleigh waves by a fluid-saturated poroelastic alluvial valley of arbitrary shape in a poroelastic half-space is investigated using the method of fundamental solutions (MFS). To satisfy the free surface boundary conditions exactly, Green's functions of compressional (PI and PII) and shear (SV) wave sources buried in a fluid-saturated poroelastic half-space are adopted. Next, the procedure for solving the scattering wave field is presented. It is verified that the MFS is of excellent accuracy and numerical stability. Numerical results illustrate that the dynamic response strongly depends on such factors as the incident frequency, the porosity of alluvium, the boundary drainage condition, and the valley shape. There is a significant difference between the diffraction of Rayleigh waves for the saturated soil case and for the corresponding dry soil case. The wave focusing effect both on the displacement and pore pressure can be observed inside the alluvial valley and the amplification effect seems most obvious in the case of higher porosity and lower frequency. Additionally, special attention should also be paid to the concentration of pore pressure, which is closely related to the site liquefaction in earthquakes.

Detection and modelling of the ionospheric perturbation caused by a Space Shuttle launch using a network of ground-based Global Positioning System stations

NASA Astrophysics Data System (ADS)

Bowling, Timothy; Calais, Eric; Haase, Jennifer S.

2013-03-01

The exhaust plume of the Space Shuttle during its ascent triggers acoustic waves which propagate through the atmosphere and induce electron density changes at ionospheric heights which changes can be measured using ground-based Global Positioning System (GPS) phase data. Here, we use a network of GPS stations to study the acoustic wave generated by the STS-125 Space Shuttle launch on May 11, 2009. We detect the resulting changes in ionospheric electron density, with characteristics that are typical of acoustic waves triggered by explosions at or near the Earth's surface or in the atmosphere. We successfully reproduce the amplitude and timing of the observed signal using a ray-tracing model with a moving source whose amplitude is directly scaled by a physical model of the shuttle exhaust energy, acoustic propagation in a dispersive atmosphere and a simplified two-fluid model of collisions between neutral gas and free electrons in the ionosphere. The close match between observed and model waveforms validates the modelling approach. This raises the possibility of using ground-based GPS networks to estimate the acoustic energy release of explosive sources near the Earth's surface or in atmosphere, and to constrain some atmospheric acoustic parameters.

The spatial sensitivity of Sp converted waves—scattered-wave kernels and their applications to receiver-function migration and inversion

NASA Astrophysics Data System (ADS)

Mancinelli, N. J.; Fischer, K. M.

2018-03-01

We characterize the spatial sensitivity of Sp converted waves to improve constraints on lateral variations in uppermost-mantle velocity gradients, such as the lithosphere-asthenosphere boundary (LAB) and the mid-lithospheric discontinuities. We use SPECFEM2D to generate 2-D scattering kernels that relate perturbations from an elastic half-space to Sp waveforms. We then show that these kernels can be well approximated using ray theory, and develop an approach to calculating kernels for layered background models. As proof of concept, we show that lateral variations in uppermost-mantle discontinuity structure are retrieved by implementing these scattering kernels in the first iteration of a conjugate-directions inversion algorithm. We evaluate the performance of this technique on synthetic seismograms computed for 2-D models with undulations on the LAB of varying amplitude, wavelength and depth. The technique reliably images the position of discontinuities with dips <35° and horizontal wavelengths >100-200 km. In cases of mild topography on a shallow LAB, the relative brightness of the LAB and Moho converters approximately agrees with the ratio of velocity contrasts across the discontinuities. Amplitude retrieval degrades at deeper depths. For dominant periods of 4 s, the minimum station spacing required to produce unaliased results is 5 km, but the application of a Gaussian filter can improve discontinuity imaging where station spacing is greater.

Gouy phase for relativistic quantum particles

NASA Astrophysics Data System (ADS)

Ducharme, R.; da Paz, I. G.

2015-08-01

Exact Hermite-Gaussian solutions to the Klein-Gordon equation for particle beams are obtained here that depend on the 4-position of the beam waist. These are Bateman-Hillion solutions that are shown to include Gouy phase and preserve their forms under Lorentz transformations. As the wave function contains two time coordinates, the particle current must be interpreted in a constraint space to reduce the number of independent coordinates. The form of the constraint space is not certain except in the nonrelativistic limit, but a trial form is proposed, enabling the observable properties of the beam to be calculated for future comparison to experiment. These results can be relevant in the theoretical development of singular electron optics since it was shown that the Gouy phase is crucial in this field as well as to investigate a possible Gouy phase effect in Zitterbewegung phenomenon of spin-zero particles. Additionally, the traditional argument that beam solutions belong to a complex shifted spacetime is shown to necessitate a corresponding Born reciprocal shift in 4-momentum space.

Wigner functions defined with Laplace transform kernels.

PubMed

Oh, Se Baek; Petruccelli, Jonathan C; Tian, Lei; Barbastathis, George

2011-10-24

We propose a new Wigner-type phase-space function using Laplace transform kernels--Laplace kernel Wigner function. Whereas momentum variables are real in the traditional Wigner function, the Laplace kernel Wigner function may have complex momentum variables. Due to the property of the Laplace transform, a broader range of signals can be represented in complex phase-space. We show that the Laplace kernel Wigner function exhibits similar properties in the marginals as the traditional Wigner function. As an example, we use the Laplace kernel Wigner function to analyze evanescent waves supported by surface plasmon polariton. © 2011 Optical Society of America

Stochastic analysis of pitch angle scattering of charged particles by transverse magnetic waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemons, Don S.; Liu Kaijun; Winske, Dan

2009-11-15

This paper describes a theory of the velocity space scattering of charged particles in a static magnetic field composed of a uniform background field and a sum of transverse, circularly polarized, magnetic waves. When that sum has many terms the autocorrelation time required for particle orbits to become effectively randomized is small compared with the time required for the particle velocity distribution to change significantly. In this regime the deterministic equations of motion can be transformed into stochastic differential equations of motion. The resulting stochastic velocity space scattering is described, in part, by a pitch angle diffusion rate that ismore » a function of initial pitch angle and properties of the wave spectrum. Numerical solutions of the deterministic equations of motion agree with the theory at all pitch angles, for wave energy densities up to and above the energy density of the uniform field, and for different wave spectral shapes.« less

Whistler wave generation by electron temperature anisotropy during asymmetric magnetic reconnection in space

NASA Astrophysics Data System (ADS)

Swerdlow, Josh; Yoo, Jongsoo; Kim, Eun-Hwa; Yamada, Masaaki; Ji, Hantao

2017-10-01

Generation of whistler waves during asymmetric reconnection is studied by analyzing data from a MMS (Magnetospheric Multiscale) event. In particular, the possible role of electron temperature anisotropy in excitation of whistler waves on the magnetosphere side is discussed. The local electron distribution function is fitted into a sum of bi-Maxwellian distribution functions. Then, the dispersion relation solver, WHAMP (waves in homogeneous, anisotropic, multicomponent plasmas), is used to obtain the local dispersion relation and growth rate of the whistler waves. We compare the theoretical calculations with the measured dispersion relation. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.

Effects of various cavity designs on the performance of a CO2 TEA laser with an unstable resonator

NASA Technical Reports Server (NTRS)

Zhao, Yanzeng; Post, Madison J.; Lawrence, T. R.

1992-01-01

Unstable resonator modeling has been carried out for an injection-seeded CO2 transversely excited atmosphere (TEA) laser in the NOAA/ERL/Wave Propagation Laboratory (WPL) Doppler lidar to examine the effects of various cavity designs on the quality of the output beam. The results show the effects of an injection pinhole, electrode spacing, mirror tilt, and radial reflectivity function of the output coupler. The electrode spacing in this laser has negligible effect. The injection pinhole, however, produces complicated structures in the output patterns. If the pinhole is removed, the output pattern is much smoother, and the frequency jitter is smaller. Misalignment sensitivity is very closely related to the radial reflectivity function. The superparabolic function provides the highest coupling efficiency, largest beam size, and good collimation, but produces a slightly higher misalignment sensitivity compared with a parabolic function. The Gaussian function provides the lowest misalignment sensitivity, but it produces the smallest beam size and the largest beam divergence. Also, the coupling coefficient is 50 percent lower than the optimum value. Methods for using a flat diffraction grating in unstable resonators are also investigated. The best way is to use a flat grating/positive lens combination to replace the back concave mirror.

Changes of brain response induced by simulated weightlessness

NASA Astrophysics Data System (ADS)

Wei, Jinhe; Yan, Gongdong; Guan, Zhiqiang

The characteristics change of brain response was studied during 15° head-down tilt (HDT) comparing with 45° head-up tilt (HUT). The brain responses evaluated included the EEG power spectra change at rest and during mental arithmetic, and the event-related potentials (ERPs) of somatosensory, selective attention and mental arithmetic activities. The prominent feature of brain response change during HDT revealed that the brain function was inhibited to some extent. Such inhibition included that the significant increment of "40Hz" activity during HUT arithmetic almost disappeared during HDT arithmetic, and that the positive-potential effect induced by HDT presented in all kinds of ERPs measured, but the slow negative wave reflecting mental arithmetic and memory process was elongated. These data suggest that the brain function be affected profoundly by the simulated weightlessness, therefore, the brain function change during space flight should be studied systematically.

Localized nonlinear waves and dynamical stability in spinor Bose–Einstein condensates with time–space modulation

NASA Astrophysics Data System (ADS)

Yao, Yu-Qin; Han, Wei; Li, Ji; Liu, Wu-Ming

2018-05-01

Nonlinearity is one of the most remarkable characteristics of Bose–Einstein condensates (BECs). Much work has been done on one- and two-component BECs with time- or space-modulated nonlinearities, while there is little work on spinor BECs with space–time-modulated nonlinearities. In the present paper we investigate localized nonlinear waves and dynamical stability in spinor Bose–Einstein condensates with nonlinearities dependent on time and space. We solve the three coupled Gross–Pitaevskii equations by similarity transformation and obtain two families of exact matter wave solutions in terms of Jacobi elliptic functions and the Mathieu equation. The localized states of the spinor matter wave describe the dynamics of vector breathing solitons, moving breathing solitons, quasi-breathing solitons and resonant solitons. The results show that one-order vector breathing solitons, quasi-breathing solitons, resonant solitons and the moving breathing solitons ψ ±1 are all stable, but the moving breathing soliton ψ 0 is unstable. We also present the experimental parameters to realize these phenomena in future experiments.

Offshore remote sensing of the ocean by stereo vision systems

NASA Astrophysics Data System (ADS)

Gallego, Guillermo; Shih, Ping-Chang; Benetazzo, Alvise; Yezzi, Anthony; Fedele, Francesco

2014-05-01

In recent years, remote sensing imaging systems for the measurement of oceanic sea states have attracted renovated attention. Imaging technology is economical, non-invasive and enables a better understanding of the space-time dynamics of ocean waves over an area rather than at selected point locations of previous monitoring methods (buoys, wave gauges, etc.). We present recent progress in space-time measurement of ocean waves using stereo vision systems on offshore platforms, which focus on sea states with wavelengths in the range of 0.01 m to 1 m. Both traditional disparity-based systems and modern elevation-based ones are presented in a variational optimization framework: the main idea is to pose the stereoscopic reconstruction problem of the surface of the ocean in a variational setting and design an energy functional whose minimizer is the desired temporal sequence of wave heights. The functional combines photometric observations as well as spatial and temporal smoothness priors. Disparity methods estimate the disparity between images as an intermediate step toward retrieving the depth of the waves with respect to the cameras, whereas elevation methods estimate the ocean surface displacements directly in 3-D space. Both techniques are used to measure ocean waves from real data collected at offshore platforms in the Black Sea (Crimean Peninsula, Ukraine) and the Northern Adriatic Sea (Venice coast, Italy). Then, the statistical and spectral properties of the resulting oberved waves are analyzed. We show the advantages and disadvantages of the presented stereo vision systems and discuss furure lines of research to improve their performance in critical issues such as the robustness of the camera calibration in spite of undesired variations of the camera parameters or the processing time that it takes to retrieve ocean wave measurements from the stereo videos, which are very large datasets that need to be processed efficiently to be of practical usage. Multiresolution and short-time approaches would improve efficiency and scalability of the techniques so that wave displacements are obtained in feasible times.

Hawking radiation and classical tunneling: A ray phase space approach

NASA Astrophysics Data System (ADS)

Tracy, E. R.; Zhigunov, D.

2016-01-01

Acoustic waves in fluids undergoing the transition from sub- to supersonic flow satisfy governing equations similar to those for light waves in the immediate vicinity of a black hole event horizon. This acoustic analogy has been used by Unruh and others as a conceptual model for "Hawking radiation." Here, we use variational methods, originally introduced by Brizard for the study of linearized MHD, and ray phase space methods, to analyze linearized acoustics in the presence of background flows. The variational formulation endows the evolution equations with natural Hermitian and symplectic structures that prove useful for later analysis. We derive a 2 × 2 normal form governing the wave evolution in the vicinity of the "event horizon." This shows that the acoustic model can be reduced locally (in ray phase space) to a standard (scalar) tunneling process weakly coupled to a unidirectional non-dispersive wave (the "incoming wave"). Given the normal form, the Hawking "thermal spectrum" can be derived by invoking standard tunneling theory, but only by ignoring the coupling to the incoming wave. Deriving the normal form requires a novel extension of the modular ray-based theory used previously to study tunneling and mode conversion in plasmas. We also discuss how ray phase space methods can be used to change representation, which brings the problem into a form where the wave functions are less singular than in the usual formulation, a fact that might prove useful in numerical studies.

Comparison of Regression Analysis and Transfer Function in Estimating the Parameters of Central Pulse Waves from Brachial Pulse Wave.

PubMed

Chai, Rui; Xu, Li-Sheng; Yao, Yang; Hao, Li-Ling; Qi, Lin

2017-01-01

This study analyzed ascending branch slope (A_slope), dicrotic notch height (Hn), diastolic area (Ad) and systolic area (As) diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure (PP), subendocardial viability ratio (SEVR), waveform parameter (k), stroke volume (SV), cardiac output (CO), and peripheral resistance (RS) of central pulse wave invasively and non-invasively measured. Invasively measured parameters were compared with parameters measured from brachial pulse waves by regression model and transfer function model. Accuracy of parameters estimated by regression and transfer function model, was compared too. Findings showed that k value, central pulse wave and brachial pulse wave parameters invasively measured, correlated positively. Regression model parameters including A_slope, DBP, SEVR, and transfer function model parameters had good consistency with parameters invasively measured. They had same effect of consistency. SBP, PP, SV, and CO could be calculated through the regression model, but their accuracies were worse than that of transfer function model.

Covariant extension of the GPD overlap representation at low Fock states

DOE PAGES

Chouika, N.; Mezrag, C.; Moutarde, H.; ...

2017-12-26

Here, we present a novel approach to compute generalized parton distributions within the lightfront wave function overlap framework. We show how to systematically extend generalized parton distributions computed within the DGLAP region to the ERBL one, fulfilling at the same time both the polynomiality and positivity conditions. We exemplify our method using pion lightfront wave functions inspired by recent results of non-perturbative continuum techniques and algebraic nucleon lightfront wave functions. We also test the robustness of our algorithm on reggeized phenomenological parameterizations. This approach paves the way to a better understanding of the nucleon structure from non-perturbative techniques and tomore » a unification of generalized parton distributions and transverse momentum dependent parton distribution functions phenomenology through lightfront wave functions.« less

Instability of quantum equilibrium in Bohm's dynamics

PubMed Central

Colin, Samuel; Valentini, Antony

2014-01-01

We consider Bohm's second-order dynamics for arbitrary initial conditions in phase space. In principle, Bohm's dynamics allows for ‘extended’ non-equilibrium, with initial momenta not equal to the gradient of phase of the wave function (as well as initial positions whose distribution departs from the Born rule). We show that extended non-equilibrium does not relax in general and is in fact unstable. This is in sharp contrast with de Broglie's first-order dynamics, for which non-standard momenta are not allowed and which shows an efficient relaxation to the Born rule for positions. On this basis, we argue that, while de Broglie's dynamics is a tenable physical theory, Bohm's dynamics is not. In a world governed by Bohm's dynamics, there would be no reason to expect to see an effective quantum theory today (even approximately), in contradiction with observation. PMID:25383020

Semiclassical approximations in the coherent-state representation

NASA Technical Reports Server (NTRS)

Kurchan, J.; Leboeuf, P.; Saraceno, M.

1989-01-01

The semiclassical limit of the stationary Schroedinger equation in the coherent-state representation is analyzed simultaneously for the groups W1, SU(2), and SU(1,1). A simple expression for the first two orders for the wave function and the associated semiclassical quantization rule is obtained if a definite choice for the classical Hamiltonian and expansion parameter is made. The behavior of the modulus of the wave function, which is a distribution function in a curved phase space, is studied for the three groups. The results are applied to the quantum triaxial rotor.

Exploring the Alfven-Wave Acceleration of Auroral Electrons in the Laboratory

NASA Astrophysics Data System (ADS)

Schroeder, James William Ryan

Inertial Alfven waves occur in plasmas where the Alfven speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfven waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfven waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfven waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfven waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfven waves, the measured portion of the distribution function oscillates at the Alfven wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfven wave antennas. The oscillation of the distribution function is described by a purely Alfvenic model when the Alfven wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvenic and non-Alfvenic effects. Indications of a nonlinear interaction between electrons and inertial Alfven waves are present in recent data.

Gluon amplitudes as 2 d conformal correlators

NASA Astrophysics Data System (ADS)

Pasterski, Sabrina; Shao, Shu-Heng; Strominger, Andrew

2017-10-01

Recently, spin-one wave functions in four dimensions that are conformal primaries of the Lorentz group S L (2 ,C ) were constructed. We compute low-point, tree-level gluon scattering amplitudes in the space of these conformal primary wave functions. The answers have the same conformal covariance as correlators of spin-one primaries in a 2 d CFT. The Britto-Cachazo-Feng-Witten (BCFW) recursion relation between three- and four-point gluon amplitudes is recast into this conformal basis.

Application of the Physics of Wave-Particle Interactions in the Auroral Upward Current Region for Use in the VASIMR° Deep Space Electric Propulsion System

NASA Astrophysics Data System (ADS)

Bering, E. A.; Olsen, C.; Longmier, B.; Ballenger, M.; Giambusso, M.; Carter, M.; Cassady, L.; Chang Diaz, F.; Glover, T.; McCaskill, G.; Squire, J.

2011-12-01

This paper will describe the laboratory application of the lessons learned from the study of wave particle interactions in the auroral upward current region to the industrial development problem of electric spacecraft propulsion. The VAriable Specific Impulse Magnetoplasma Rocket (VASIMR°) has been developed by using the results of space plasma experiments in laboratory plasma studies that will ultimately enable further space exploration. VASIMR° is a high power electric spacecraft propulsion system, capable of Isp/thrust modulation at constant power. The VASIMR° uses a helicon discharge to generate plasma. The plasma is leaked though a strong magnetic mirror to the second stage. In this stage, this plasma is energized by an RF booster stage that uses left hand polarized slow mode waves launched from the high field side of the ion cyclotron resonance. In the experiments reported in this paper, the booster uses 0.5-0.7 MHz waves with up to 170 kW of power. The single pass ion cyclotron heating (ICH) produced a substantial increase in ion velocity. Pitch angle distribution studies showed that this increase took place in the resonance region where the ion cyclotron frequency was roughly equal to the frequency on the injected rf waves. Downstream of the resonance region the perpendicular velocity boost should be converted to axial flow velocity through the conservation of the first adiabatic invariant as the magnetic field decreases in the exhaust region of the VASIMR°. Results from high power Helicon only and Helicon with ICH experiments are presented from the VX-200 using argon propellant. A two-axis translation stage has been used to survey the spatial structure of plasma parameters, momentum flux and magnetic perturbations in the VX-200 exhaust plume. These recent measurements were made within a new 150 cubic meter cryo-pumped vacuum chamber and are presented in the context of plasma detachment. For the first time, the thruster efficiency and thrust of a high-power VASIMR° prototype have been measured with the thruster installed inside a vacuum chamber with sufficient volume and pumping to simulate the vacuum conditions of space. Using an ion flux probe array and a plasma momentum flux sensor (PMFS), the exhaust of the VX-200 engine was characterized as a function of the coupled RF power and as a function of the radial and axial position within the exhaust plume. The ionization cost of argon propellant was determined to be 87 eV for optimized values of RF power and propellant flow rate. Recent results at 200 kW coupled RF power have shown a thruster efficiency of 72% at a specific impulse of 5000 s and a thrust of 5.7 N.

Relativistic differential-difference momentum operators and noncommutative differential calculus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mir-Kasimov, R. M., E-mail: mirkr@theor.jinr.ru

2013-09-15

The relativistic kinetic momentum operators are introduced in the framework of the Quantum Mechanics (QM) in the Relativistic Configuration Space (RCS). These operators correspond to the half of the non-Euclidean distance in the Lobachevsky momentum space. In terms of kinetic momentum operators the relativistic kinetic energy is separated as the independent term of the total Hamiltonian. This relativistic kinetic energy term is not distinguishing in form from its nonrelativistic counterpart. The role of the plane wave (wave function of the motion with definite value of momentum and energy) plays the generating function for the matrix elements of the unitary irrepsmore » of Lorentz group (generalized Jacobi polynomials). The kinetic momentum operators are the interior derivatives in the framework of the noncommutative differential calculus over the commutative algebra generated by the coordinate functions over the RCS.« less

On the Identication of Wrinkles of Membrane by Traveling Elastic Wave

NASA Astrophysics Data System (ADS)

Akaike, Yusuke; Yokozeki, Tomhiro

2012-07-01

Wrinkling is one of the critical factors that degrade the performance of space membrane structures. This paper proposes the way to detect the size and the position of wrinkles by observing reflection of the elastic waves at the boundary between the wrinkled section and the flat section. A wrinkle is modeled as a part of an annulus, and the effects of thickness, material properties and curvature of the membrane on the reflection rates of elastic waves are investigated. Finally, the proposed identification method is experimentally demonstrated.

Liquid-assisted tunable metasurface for simultaneous manipulation of surface elastic and acoustic waves

NASA Astrophysics Data System (ADS)

Yuan, Si-Min; Ma, Tian-Xue; Chen, A.-Li; Wang, Yue-Sheng

2018-03-01

A tunable and multi-functional one-dimensional metasurface, which is formed by engraving periodic semi-ellipse grooves on the surface of an aluminum half-space, is proposed in this paper. One characteristic of the metasurface is the manipulation of multi-physical fields, i.e. it could be utilized to manipulate surface elastic and acoustic waves simultaneously. The dispersion curves of the elastic and acoustic waves can be effectively tuned by adding liquids into the grooves. Based on the tunability different applications can be realized by adding different volumes of different liquids into the grooves. As an example, simultaneous rainbow trapping of the surface elastic and acoustic waves is demonstrated in the metasurface. Moreover, a resonant cavity where the elastic and acoustic waves are highly confined is reported. The proposed metasurface paves the way to the design of multi-functional devices for simultaneous control of elastic and acoustic waves.

Rogue waves in space dusty plasmas

NASA Astrophysics Data System (ADS)

Chowdhury, N. A.; Mannan, A.; Mamun, A. A.

2017-11-01

The modulational instability of dust-acoustic (DA) waves (DAWs) and corresponding DA rogue waves (DARWs) in a realistic space dusty plasma system (containing inertial warm positively and negatively charged dust, isothermal ions, and super-thermal kappa distributed electrons) has been theoretically investigated. The nonlinear Schrödinger equation is derived by using a reductive perturbation method for this investigation. It is observed that the dusty plasma system under consideration supports two branches of modes, namely, fast and slow DA modes, and that both of these two modes can be stable or unstable depending on the sign of ratio of the dispersive and nonlinear coefficients. The numerical analysis has shown that the basic features (viz., stability/instability, growth rate, amplitude, and width of the rogue structures, etc.) of the DAWs associated with the fast DA modes are significantly modified by super-thermal parameter (κ) and other various plasma parameters. The results of our present investigation should be useful for understanding DARWs in space plasma systems, viz., mesosphere and ionosphere.

Generalized-active-space pair-density functional theory: an efficient method to study large, strongly correlated, conjugated systems

DOE PAGES

Ghosh, Soumen; Cramer, Christopher J.; Truhlar, Donald G.; ...

2017-01-19

Predicting ground- and excited-state properties of open-shell organic molecules by electronic structure theory can be challenging because an accurate treatment has to correctly describe both static and dynamic electron correlation. Strongly correlated systems, i.e., systems with near-degeneracy correlation effects, are particularly troublesome. Multiconfigurational wave function methods based on an active space are adequate in principle, but it is impractical to capture most of the dynamic correlation in these methods for systems characterized by many active electrons. Here, we recently developed a new method called multiconfiguration pair-density functional theory (MC-PDFT), that combines the advantages of wave function theory and density functionalmore » theory to provide a more practical treatment of strongly correlated systems. Here we present calculations of the singlet–triplet gaps in oligoacenes ranging from naphthalene to dodecacene. Calculations were performed for unprecedently large orbitally optimized active spaces of 50 electrons in 50 orbitals, and we test a range of active spaces and active space partitions, including four kinds of frontier orbital partitions. We show that MC-PDFT can predict the singlet–triplet splittings for oligoacenes consistent with the best available and much more expensive methods, and indeed MC-PDFT may constitute the benchmark against which those other models should be compared, given the absence of experimental data.« less

Generalized-active-space pair-density functional theory: an efficient method to study large, strongly correlated, conjugated systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Soumen; Cramer, Christopher J.; Truhlar, Donald G.

Predicting ground- and excited-state properties of open-shell organic molecules by electronic structure theory can be challenging because an accurate treatment has to correctly describe both static and dynamic electron correlation. Strongly correlated systems, i.e., systems with near-degeneracy correlation effects, are particularly troublesome. Multiconfigurational wave function methods based on an active space are adequate in principle, but it is impractical to capture most of the dynamic correlation in these methods for systems characterized by many active electrons. Here, we recently developed a new method called multiconfiguration pair-density functional theory (MC-PDFT), that combines the advantages of wave function theory and density functionalmore » theory to provide a more practical treatment of strongly correlated systems. Here we present calculations of the singlet–triplet gaps in oligoacenes ranging from naphthalene to dodecacene. Calculations were performed for unprecedently large orbitally optimized active spaces of 50 electrons in 50 orbitals, and we test a range of active spaces and active space partitions, including four kinds of frontier orbital partitions. We show that MC-PDFT can predict the singlet–triplet splittings for oligoacenes consistent with the best available and much more expensive methods, and indeed MC-PDFT may constitute the benchmark against which those other models should be compared, given the absence of experimental data.« less

Bounds on quantum collapse models from matter-wave interferometry: calculational details

NASA Astrophysics Data System (ADS)

Toroš, Marko; Bassi, Angelo

2018-03-01

We present a simple derivation of the interference pattern in matter-wave interferometry predicted by a class of quantum master equations. We apply the obtained formulae to the following collapse models: the Ghirardi-Rimini-Weber (GRW) model, the continuous spontaneous localization (CSL) model together with its dissipative (dCSL) and non-Markovian generalizations (cCSL), the quantum mechanics with universal position localization (QMUPL), and the Diósi-Penrose (DP) model. We discuss the separability of the dynamics of the collapse models along the three spatial directions, the validity of the paraxial approximation, and the amplification mechanism. We obtain analytical expressions both in the far field and near field limits. These results agree with those already derived in the Wigner function formalism. We compare the theoretical predictions with the experimental data from two recent matter-wave experiments: the 2012 far-field experiment of Juffmann T et al (2012 Nat. Nanotechnol. 7 297-300) and the 2013 Kapitza-Dirac-Talbot-Lau (KDTL) near-field experiment of Eibenberger et al (2013 Phys. Chem. Chem. Phys. 15 14696-700). We show the region of the parameter space for each collapse model that is excluded by these experiments. We show that matter-wave experiments provide model-insensitive bounds that are valid for a wide family of dissipative and non-Markovian generalizations.

Stochastic Growth of Ion Cyclotron And Mirror Waves In Earth's Magnetosheath

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Grubits, K. A.

2001-01-01

Electromagnetic ion cyclotron and mirror waves in Earth's magnetosheath are bursty, have widely variable fields, and are unexpectedly persistent, properties difficult to reconcile with uniform secular growth. Here it is shown for specific periods that stochastic growth theory (SGT) quantitatively accounts for the functional form of the wave statistics and qualitatively explains the wave properties. The wave statistics are inconsistent with uniform secular growth or self-organized criticality, but nonlinear processes sometimes play a role at high fields. The results show SGT's relevance near marginal stability and suggest that it is widely relevant to space and astrophysical plasmas.

Effect of normalized plasma frequency on electron phase-space orbits in a free-electron laser

NASA Astrophysics Data System (ADS)

Ji, Yu-Pin; Wang, Shi-Jian; Xu, Jing-Yue; Xu, Yong-Gen; Liu, Xiao-Xu; Lu, Hong; Huang, Xiao-Li; Zhang, Shi-Chang

2014-02-01

Irregular phase-space orbits of the electrons are harmful to the electron-beam transport quality and hence deteriorate the performance of a free-electron laser (FEL). In previous literature, it was demonstrated that the irregularity of the electron phase-space orbits could be caused in several ways, such as varying the wiggler amplitude and inducing sidebands. Based on a Hamiltonian model with a set of self-consistent differential equations, it is shown in this paper that the electron-beam normalized plasma frequency functions not only couple the electron motion with the FEL wave, which results in the evolution of the FEL wave field and a possible power saturation at a large beam current, but also cause the irregularity of the electron phase-space orbits when the normalized plasma frequency has a sufficiently large value, even if the initial energy of the electron is equal to the synchronous energy or the FEL wave does not reach power saturation.

Orbitally invariant internally contracted multireference unitary coupled cluster theory and its perturbative approximation: theory and test calculations of second order approximation.

PubMed

Chen, Zhenhua; Hoffmann, Mark R

2012-07-07

A unitary wave operator, exp (G), G(+) = -G, is considered to transform a multiconfigurational reference wave function Φ to the potentially exact, within basis set limit, wave function Ψ = exp (G)Φ. To obtain a useful approximation, the Hausdorff expansion of the similarity transformed effective Hamiltonian, exp (-G)Hexp (G), is truncated at second order and the excitation manifold is limited; an additional separate perturbation approximation can also be made. In the perturbation approximation, which we refer to as multireference unitary second-order perturbation theory (MRUPT2), the Hamiltonian operator in the highest order commutator is approximated by a Mo̸ller-Plesset-type one-body zero-order Hamiltonian. If a complete active space self-consistent field wave function is used as reference, then the energy is invariant under orbital rotations within the inactive, active, and virtual orbital subspaces for both the second-order unitary coupled cluster method and its perturbative approximation. Furthermore, the redundancies of the excitation operators are addressed in a novel way, which is potentially more efficient compared to the usual full diagonalization of the metric of the excited configurations. Despite the loss of rigorous size-extensivity possibly due to the use of a variational approach rather than a projective one in the solution of the amplitudes, test calculations show that the size-extensivity errors are very small. Compared to other internally contracted multireference perturbation theories, MRUPT2 only needs reduced density matrices up to three-body even with a non-complete active space reference wave function when two-body excitations within the active orbital subspace are involved in the wave operator, exp (G). Both the coupled cluster and perturbation theory variants are amenable to large, incomplete model spaces. Applications to some widely studied model systems that can be problematic because of geometry dependent quasidegeneracy, H4, P4, and BeH(2), are performed in order to test the new methods on problems where full configuration interaction results are available.

Quantum Metric of Classic Physics

NASA Astrophysics Data System (ADS)

Machusky, Eugene

2017-09-01

By methods of differential geometry and number theory the following has been established: All fundamental physical constants are the medians of quasi-harmonic functions of relative space and relative time. Basic quantum units are, in fact, the gradients of normal distribution of standing waves between the points of pulsating spherical spiral, which are determined only by functional bonds of transcendental numbers PI and E. Analytically obtained values of rotational speed, translational velocity, vibrational speed, background temperature and molar mass give the possibility to evaluate all basic quantum units with practically unlimited accuracy. Metric of quantum physics really is two-dimensional image of motion of waves in three-dimensional space. Standard physical model is correct, but SI metric system is insufficiently exact at submillimeter distances.

Frequency and Wavevector Dependence of the Atomic Level Stress-Stress Correlation Function in a Model Supercooled Liquid

NASA Astrophysics Data System (ADS)

Levashov, Valentin A.; Morris, James R.; Egami, Takeshi

2012-02-01

Temporal and spatial correlations among the local atomic level shear stresses were studied for a model liquid iron by molecular dynamics simulation [PRL 106,115703]. Integration over time and space of the shear stress correlation function F(r,t) yields viscosity via Green-Kubo relation. The stress correlation function in time and space F(r,t) was Fourier transformed to study the dependence on frequency, E, and wave vector, Q. The results, F(Q,E), showed damped shear stress waves propagating in the liquid for small Q at high and low temperatures. We also observed additional diffuse feature that appears as temperature is reduced below crossover temperature of potential energy landscape at relatively low frequencies at small Q. We suggest that this additional feature might be related to dynamic heterogeneity and boson peaks. We also discuss a relation between the time-scale of the stress-stress correlation function and the alpha-relaxation time of the intermediate self-scattering function S(Q,E).

Theoretical derivation of laser-dressed atomic states by using a fractal space

NASA Astrophysics Data System (ADS)

Duchateau, Guillaume

2018-05-01

The derivation of approximate wave functions for an electron submitted to both a Coulomb and a time-dependent laser electric fields, the so-called Coulomb-Volkov (CV) state, is addressed. Despite its derivation for continuum states does not exhibit any particular problem within the framework of the standard theory of quantum mechanics (QM), difficulties arise when considering an initially bound atomic state. Indeed the natural way of translating the unperturbed momentum by the laser vector potential is no longer possible since a bound state does not exhibit a plane wave form explicitly including a momentum. The use of a fractal space permits to naturally define a momentum for a bound wave function. Within this framework, it is shown how the derivation of laser-dressed bound states can be performed. Based on a generalized eikonal approach, a new expression for the laser-dressed states is also derived, fully symmetric relative to the continuum or bound nature of the initial unperturbed wave function. It includes an additional crossed term in the Volkov phase which was not obtained within the standard theory of quantum mechanics. The derivations within this fractal framework have highlighted other possible ways to derive approximate laser-dressed states in QM. After comparing the various obtained wave functions, an application to the prediction of the ionization probability of hydrogen targets by attosecond XUV pulses within the sudden approximation is provided. This approach allows to make predictions in various regimes depending on the laser intensity, going from the non-resonant multiphoton absorption to tunneling and barrier-suppression ionization.

Application of the wavenumber jump condition to the normal and oblique interaction of a plane acoustic wave and a plane shock

NASA Technical Reports Server (NTRS)

Kleinstein, G. G.; Gunzburger, M. D.

1977-01-01

The kinematics of normal and oblique interactions between a plane acoustic wave and a plane shock wave are investigated separately using an approach whereby the shock is considered as a sharp discontinuity surface separating two half-spaces, so that the dispersion relation on either side of the shock and the wavenumber jump condition across a discontinuity surface completely specify the kinematics of the problem in the whole space independently of the acoustic-field dynamics. The normal interaction is analyzed for a stationary shock, and the spectral change of the incident wave is investigated. The normal interaction is then examined for the case of a shock wave traveling into an ambient region where an acoustic disturbance is propagating in the opposite direction. Detailed attention is given to the consequences of the existence of a critical shock speed above which the frequency of the transmitted wave becomes negative. Finally, the oblique interaction with a fixed shock is considered, and the existence and nature of the transmitted wave is investigated, particularly as a function of the angle of incidence.

A three-microphone acoustic reflection technique using transmitted acoustic waves in the airway.

PubMed

Fujimoto, Yuki; Huang, Jyongsu; Fukunaga, Toshiharu; Kato, Ryo; Higashino, Mari; Shinomiya, Shohei; Kitadate, Shoko; Takahara, Yutaka; Yamaya, Atsuyo; Saito, Masatoshi; Kobayashi, Makoto; Kojima, Koji; Oikawa, Taku; Nakagawa, Ken; Tsuchihara, Katsuma; Iguchi, Masaharu; Takahashi, Masakatsu; Mizuno, Shiro; Osanai, Kazuhiro; Toga, Hirohisa

2013-10-15

The acoustic reflection technique noninvasively measures airway cross-sectional area vs. distance functions and uses a wave tube with a constant cross-sectional area to separate incidental and reflected waves introduced into the mouth or nostril. The accuracy of estimated cross-sectional areas gets worse in the deeper distances due to the nature of marching algorithms, i.e., errors of the estimated areas in the closer distances accumulate to those in the further distances. Here we present a new technique of acoustic reflection from measuring transmitted acoustic waves in the airway with three microphones and without employing a wave tube. Using miniaturized microphones mounted on a catheter, we estimated reflection coefficients among the microphones and separated incidental and reflected waves. A model study showed that the estimated cross-sectional area vs. distance function was coincident with the conventional two-microphone method, and it did not change with altered cross-sectional areas at the microphone position, although the estimated cross-sectional areas are relative values to that at the microphone position. The pharyngeal cross-sectional areas including retropalatal and retroglossal regions and the closing site during sleep was visualized in patients with obstructive sleep apnea. The method can be applicable to larger or smaller bronchi to evaluate the airspace and function in these localized airways.

Space-Time Characteristic Functions in Multivariate Logic and Possible Interpretation of Entanglement

NASA Astrophysics Data System (ADS)

Gaudeau de Gerlicz, Claude; Sechpine, Pierre; Bobola, Philippe; Antoine, Mathias

The knowledge about hidden variables in physics, (Bohr's-Schrödinger theories) and their developments, boundaries seem more and more fuzzy at physical scales. Also some other new theories give to both time and space as much fuzziness. The classical theory, (school of Copenhagen's) and also Heisenberg and Louis de Broglie give us the idea of a dual wave and particle parts such the way we observe. Thus, the Pondichery interpretation recently developed by Cramer and al. gives to the time part this duality. According Cramer, there could be a little more to this duality, some late or advanced waves of time that have been confirmed and admitted as possible solutions with the Maxwell's equations. We developed here a possible pattern that could matched in the sequence between Space and both retarded and advanced time wave in the "Cramer handshake" in locality of the present when the observation is made everything become local.

Positive phase evolution of waves propagating along a photonic crystal with negative index of refraction.

PubMed

Martínez, Alejandro; Martí, Javier

2006-10-16

We analyze propagation of electromagnetic waves in a photonic crystal at frequencies at which it behaves as an effective medium with a negative index in terms of refraction at its interface with free space. We show that the phase evolution along the propagation direction is positive, despite the fact that the photonic crystal displays negative refraction following Snell's law, and explain it in terms of the Fourier components of the Bloch wave. Two distinct behaviors are found at frequencies far and close to the band edge of the negative-index photonic band. These findings contrast with the negative phase evolution that occurs in left-handed materials, so care has to be taken when applying the term left-handed to photonic crystals.

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

NASA Astrophysics Data System (ADS)

John, Sajeev; Golubentsev, Andrey

1995-01-01

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

Spatial transport of electron quantum states with strong attosecond pulses

NASA Astrophysics Data System (ADS)

Chovancova, M.; Agueny, H.; Førre, M.; Kocbach, L.; Hansen, J. P.

2017-11-01

This work follows up the work of Dimitrovsky, Briggs and co-workers on translated electron atomic states by a strong field of an atto-second laser pulse, also described as creation of atoms without a nucleus. Here, we propose a new approach by analyzing the electron states in the Kramers-Henneberger moving frame in the dipole approximation. The wave function follows the displacement vector α (t). This allows arbitrarily shaped pulses, including the model delta-function potentials in the Dimitrovsky and Briggs approach. In the case of final-length single-cycle pulses, we apply both the Kramers-Henneberger moving frame analysis and a full numerical treatment of our 1D model. When the laser pulse frequency exceeds the frequency associated by the energy difference between initial and final states, the entire wavefunction is translated in space nearly without loss of coherence, to a well defined distance from the original position where the ionized core is left behind. This statement is demonstrated on the excited Rydberg states (n = 10, n = 15), where almost no distortion in the transported wave functions has been observed. However, the ground state (n = 1) is visibly distorted during the removal by pulses of reasonable frequencies, as also predicted by Dimitrovsky and Briggs analysis. Our approach allows us to analyze general pulses as well as the model delta-function potentials on the same footing in the Kramers-Henneberger frame.

Solitons on Noncommutative Torus as Elliptic Calogero-Gaudin Models, Branes and Laughlin Wave Functions

NASA Astrophysics Data System (ADS)

Hou, Bo-Yu; Peng, Dan-Tao; Shi, Kang-Jie; Yue, Rui-Hong

For the noncommutative torus T, in the case of the noncommutative parameter θ = (Z)/(n), we construct the basis of Hilbert space Hn in terms of θ functions of the positions zi of n solitons. The wrapping around the torus generates the algebra An, which is the Zn × Zn Heisenberg group on θ functions. We find the generators g of a local elliptic su(n), which transform covariantly by the global gauge transformation of An. By acting on Hn we establish the isomorphism of An and g. We embed this g into the L-matrix of the elliptic Gaudin and Calogero-Moser models to give the dynamics. The moment map of this twisted cotangent sunT) bundle is matched to the D-equation with the Fayet-Illiopoulos source term, so the dynamics of the noncommutative solitons become that of the brane. The geometric configuration (k, u) of the spectral curve det|L(u) - k| = 0 describes the brane configuration, with the dynamical variables zi of the noncommutative solitons as the moduli T⊗ n/Sn. Furthermore, in the noncommutative Chern-Simons theory for the quantum Hall effect, the constrain equation with quasiparticle source is identified also with the moment map equation of the noncommutative sunT cotangent bundle with marked points. The eigenfunction of the Gaudin differential L-operators as the Laughlin wave function is solved by Bethe ansatz.

High Energy Scattering in the AdS/CFT Correspondence

NASA Astrophysics Data System (ADS)

Penedones, Joao

2007-12-01

This work explores the celebrated AdS/CFT correspondence in the regime of high energy scattering in Anti--de Sitter (AdS) spacetime. In particular, we develop the eikonal approximation to high energy scattering in AdS and explore its consequences for the dual Conformal Field Theory (CFT). Using position space Feynman rules, we rederive the eikonal approximation for high energy scattering in flat space. Following this intuitive position space perspective, we then generalize the eikonal approximation for high energy scattering in AdS and other spacetimes. Remarkably, we are able to resum, in terms of a generalized phase shift, ladder and cross ladder Witten diagrams associated to the exchange of an AdS spin j field, to all orders in the coupling constant. By the AdS/CFT correspondence, the eikonal amplitude in AdS is related to the four point function of CFT primary operators in the regime of large 't Hooft coupling, including all terms of the 1/N expansion. We then show that the eikonal amplitude determines the behavior of the CFT four point function for small values of the cross ratios in a Lorentzian regime and that this controls its high spin and dimension conformal partial wave decomposition. These results allow us to determine the anomalous dimension of high spin and dimension double trace primary operators, by relating it to the AdS eikonal phase shift. Finally we find that, at large energies and large impact parameters in AdS, the gravitational interaction dominates all other interactions, as in flat space. Therefore, the anomalous dimension of double trace operators, associated to graviton exchange in AdS, yields a universal prediction for CFT's with AdS gravitational duals.

NMR and NQR parameters of ethanol crystal

NASA Astrophysics Data System (ADS)

Milinković, M.; Bilalbegović, G.

2012-04-01

Electric field gradients and chemical shielding tensors of the stable monoclinic crystal phase of ethanol are computed. The projector-augmented wave (PAW) and gauge-including projector-augmented wave (GIPAW) models in the periodic plane-wave density functional theory are used. The crystal data from X-ray measurements, as well as the structures where either all atomic, or only hydrogen atom positions are optimized in the density functional theory are analyzed. These structural models are also studied by including the semi-empirical van der Waals correction to the density functional theory. Infrared spectra of these five crystal models are calculated.

Coherent distributions for the rigid rotator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigorescu, Marius

2016-06-15

Coherent solutions of the classical Liouville equation for the rigid rotator are presented as positive phase-space distributions localized on the Lagrangian submanifolds of Hamilton-Jacobi theory. These solutions become Wigner-type quasiprobability distributions by a formal discretization of the left-invariant vector fields from their Fourier transform in angular momentum. The results are consistent with the usual quantization of the anisotropic rotator, but the expected value of the Hamiltonian contains a finite “zero point” energy term. It is shown that during the time when a quasiprobability distribution evolves according to the Liouville equation, the related quantum wave function should satisfy the time-dependent Schrödingermore » equation.« less

Whistler Waves With Electron Temperature Anisotropy And Non-Maxwellian Distribution Functions

NASA Astrophysics Data System (ADS)

Masood, W.

2017-12-01

Low frequency waves (˜ 100Hz), popularly known as Lion roars, are ubiquitously observed by satellites in terrestrial magnetosheath. By dint of both wave and electron data from the Cluster spacecraft and employing the linear kinetic theory for the electromagnetic waves, Masood et. al. (Ann. Geophysicae. 24, 1725-1735 (2006)) examined the conjecture made by Thorne and Tsurutani (Nature, 93, 384 (1981)) that whistler waves with electron temperature anisotropy are the progenitors of lion roars. It turned out that the study based upon the bi-Maxwellian distribution function did not come up with a satisfactory explanation of certain disagreements between theory and data. In this paper, we revisit the problem using the generalized (r, q) distribution to carry out the linear stability analysis. It is shown that good qualitative and quantitative agreements are found between theory and data using this distribution. Whistler waves with electron temperature anisotropy are also investigated with other non-Maxwellian distribution functions and general comparison is made in the end and differences in each case are highlighted. The possible applications in space plasmas are also pointed out.

Realistic interpretation of quantum mechanics and encounter-delayed-choice experiment

NASA Astrophysics Data System (ADS)

Long, GuiLu; Qin, Wei; Yang, Zhe; Li, Jun-Lin

2018-03-01

In this paper, a realistic interpretation (REIN) of the wave function in quantum mechanics is briefly presented. We demonstrate that in the REIN, the wave function of a microscopic object is its real existence rather than a mere mathematical description. Specifically, the quantum object can exist in disjointed regions of space just as the wave function is distributed, travels at a finite speed, and collapses instantly upon a measurement. Furthermore, we analyze the single-photon interference in a Mach-Zehnder interferometer (MZI) using the REIN. Based on this, we propose and experimentally implement a generalized delayed-choice experiment, called the encounter-delayed-choice experiment, where the second beam splitter is decided whether or not to insert at the encounter of two sub-waves along the arms of the MZI. In such an experiment, the parts of the sub-waves, which do not travel through the beam splitter, show a particle nature, whereas the remaining parts interfere and thus show a wave nature. The predicted phenomenon is clearly demonstrated in the experiment, thus supporting the REIN idea.

A model for wave propagation in a porous solid saturated by a three-phase fluid.

PubMed

Santos, Juan E; Savioli, Gabriela B

2016-02-01

This paper presents a model to describe the propagation of waves in a poroelastic medium saturated by a three-phase viscous, compressible fluid. Two capillary relations between the three fluid phases are included in the model by introducing Lagrange multipliers in the principle of virtual complementary work. This approach generalizes that of Biot for single-phase fluids and allows to determine the strain energy density, identify the generalized strains and stresses, and derive the constitutive relations of the system. The kinetic and dissipative energy density functions are obtained assuming that the relative flow within the pore space is of laminar type and obeys Darcy's law for three-phase flow in porous media. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted as type I, II, III, and IV waves, and one shear wave. Numerical examples showing the behavior of all waves as function of saturation and frequency are presented.

Variations in plasma wave intensity with distance along the electron foreshock boundary at Venus

NASA Technical Reports Server (NTRS)

Crawford, G. K.; Strangeway, R. J.; Russell, C. T.

1991-01-01

Plasma waves are observed in the solar wind upstream of the Venus bow shock by the Pioneer Venus Orbiter. These wave signatures occur during periods when the interplanetary magnetic field through the spacecraft position intersects the bow shock, thereby placing the spacecraft in the foreshock region. Wave intensity is analyzed as a function of distance along the electron foreshock boundary. It is found that the peak wave intensity may increase along the foreshock boundary from the tangent point to a maximum value at several Venus radii, then decrease in intensity with subsequent increase in distance. These observations could be associated with the instability process: the instability of the distribution function increasing with distance from the tangent point to saturation at the peak. Thermalization of the beam for distances beyond this point could reduce the distribution function instability resulting in weaker wave signatures.

Benchmark solution for vibrations from a moving point source in a tunnel embedded in a half-space

NASA Astrophysics Data System (ADS)

Yuan, Zonghao; Boström, Anders; Cai, Yuanqiang

2017-01-01

A closed-form semi-analytical solution for the vibrations due to a moving point load in a tunnel embedded in a half-space is given in this paper. The tunnel is modelled as an elastic hollow cylinder and the ground surrounding the tunnel as a linear viscoelastic material. The total wave field in the half-space with a cylindrical hole is represented by outgoing cylindrical waves and down-going plane waves. To apply the boundary conditions on the ground surface and at the tunnel-soil interface, the transformation properties between the plane and cylindrical wave functions are employed. The proposed solution can predict the ground vibration from an underground railway tunnel of circular cross-section with a reasonable computational effort and can serve as a benchmark solution for other computational methods. Numerical results for the ground vibrations on the free surface due to a moving constant load and a moving harmonic load applied at the tunnel invert are presented for different load velocities and excitation frequencies. It is found that Rayleigh waves play an important role in the ground vibrations from a shallow tunnel.

Full Wave Function Optimization with Quantum Monte Carlo and Its Effect on the Dissociation Energy of FeS.

PubMed

Haghighi Mood, Kaveh; Lüchow, Arne

2017-08-17

Diffusion quantum Monte Carlo calculations with partial and full optimization of the guide function are carried out for the dissociation of the FeS molecule. For the first time, quantum Monte Carlo orbital optimization for transition metal compounds is performed. It is demonstrated that energy optimization of the orbitals of a complete active space wave function in the presence of a Jastrow correlation function is required to obtain agreement with the experimental dissociation energy. Furthermore, it is shown that orbital optimization leads to a 5 Δ ground state, in agreement with experiments but in disagreement with other high-level ab initio wave function calculations which all predict a 5 Σ + ground state. The role of the Jastrow factor in DMC calculations with pseudopotentials is investigated. The results suggest that a large Jastrow factor may improve the DMC accuracy substantially at small additional cost.

Isotope-selective high-order interferometry with large organic molecules in free fall

NASA Astrophysics Data System (ADS)

Rodewald, Jonas; Dörre, Nadine; Grimaldi, Andrea; Geyer, Philipp; Felix, Lukas; Mayor, Marcel; Shayeghi, Armin; Arndt, Markus

2018-03-01

Interferometry in the time domain has proven valuable for matter-wave based measurements. This concept has recently been generalized to cold molecular clusters using short-pulse standing light waves which realized photo-depletion gratings, arranged in a time-domain Talbot–Lau interferometer (OTIMA). Here we extend this idea further to large organic molecules and demonstrate a new scheme to scan the emerging molecular interferogram in position space. The capability of analyzing different isotopes of the same monomer under identical conditions opens perspectives for studying the interference fringe shift as a function of time in gravitational free fall. The universality of OTIMA interferometry allows one to handle a large variety of particles. In our present work, quasi-continuous laser evaporation allows transferring fragile organic molecules into the gas phase, covering more than an order of magnitude in mass between 614 amu and 6509 amu, i.e. 300% more massive than in previous OTIMA experiments. For all masses, we find about 30% fringe visibility.

A numerical solution method for acoustic radiation from axisymmetric bodies

NASA Technical Reports Server (NTRS)

Caruthers, John E.; Raviprakash, G. K.

1995-01-01

A new and very efficient numerical method for solving equations of the Helmholtz type is specialized for problems having axisymmetric geometry. It is then demonstrated by application to the classical problem of acoustic radiation from a vibrating piston set in a stationary infinite plane. The method utilizes 'Green's Function Discretization', to obtain an accurate resolution of the waves using only 2-3 points per wave. Locally valid free space Green's functions, used in the discretization step, are obtained by quadrature. Results are computed for a range of grid spacing/piston radius ratios at a frequency parameter, omega R/c(sub 0), of 2 pi. In this case, the minimum required grid resolution appears to be fixed by the need to resolve a step boundary condition at the piston edge rather than by the length scale imposed by the wave length of the acoustic radiation. It is also demonstrated that a local near-field radiation boundary procedure allows the domain to be truncated very near the radiating source with little effect on the solution.

Phase Imaging: A Compressive Sensing Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Sebastian; Stevens, Andrew; Browning, Nigel D.

Since Wolfgang Pauli posed the question in 1933, whether the probability densities |Ψ(r)|² (real-space image) and |Ψ(q)|² (reciprocal space image) uniquely determine the wave function Ψ(r) [1], the so called Pauli Problem sparked numerous methods in all fields of microscopy [2, 3]. Reconstructing the complete wave function Ψ(r) = a(r)e-iφ(r) with the amplitude a(r) and the phase φ(r) from the recorded intensity enables the possibility to directly study the electric and magnetic properties of the sample through the phase. In transmission electron microscopy (TEM), electron holography is by far the most established method for phase reconstruction [4]. Requiring a highmore » stability of the microscope, next to the installation of a biprism in the TEM, holography cannot be applied to any microscope straightforwardly. Recently, a phase retrieval approach was proposed using conventional TEM electron diffractive imaging (EDI). Using the SAD aperture as reciprocal-space constraint, a localized sample structure can be reconstructed from its diffraction pattern and a real-space image using the hybrid input-output algorithm [5]. We present an alternative approach using compressive phase-retrieval [6]. Our approach does not require a real-space image. Instead, random complimentary pairs of checkerboard masks are cut into a 200 nm Pt foil covering a conventional TEM aperture (cf. Figure 1). Used as SAD aperture, subsequently diffraction patterns are recorded from the same sample area. Hereby every mask blocks different parts of gold particles on a carbon support (cf. Figure 2). The compressive sensing problem has the following formulation. First, we note that the complex-valued reciprocal-space wave-function is the Fourier transform of the (also complex-valued) real-space wave-function, Ψ(q) = F[Ψ(r)], and subsequently the diffraction pattern image is given by |Ψ(q)|2 = |F[Ψ(r)]|2. We want to find Ψ(r) given a few differently coded diffraction pattern measurements yn = |F[HnΨ(r)]|2, where the matrices Hn encode the mask structure of the aperture. This is a nonlinear inverse problem, but has been shown to be solvable even in the underdetermined case [6]. Since each diffraction pattern yn contains diffraction information from selected regions of the same sample, the differences in each pattern contain local phase information, which can be combined to form a full estimate of the real-space wave-function[7]. References: [1] W. Pauli in “Die allgemeinen Prinzipien der Wellenmechanik“, ed. H Geiger and W Scheel, (Julius Springer, Berlin). [2] A. Tonomura, Rev. Mod. Phys. 59 (1987), p. 639. [3] J. Miao et al, Nature 400 (1999), p. 342. [4] H. Lichte et al, Annu. Rev. Mater. Res. 37 (2007), p. 539. [5] J. Yamasaki et al, Appl. Phys. Lett. 101 (2012), 234105. [6] P Schniter and S Rangan. Signal Proc., IEEE Trans. on. 64(4), (2015), pp. 1043. [7] Supported by the Chemical Imaging, Signature Discovery, and Analytics in Motion initiatives at PNNL. PNNL is operated by Battelle Memorial Inst. for the US DOE; contract DE-AC05-76RL01830.« less

Multidimensional fractional Schrödinger equation

NASA Astrophysics Data System (ADS)

Rodrigues, M. M.; Vieira, N.

2012-11-01

This work is intended to investigate the multi-dimensional space-time fractional Schrödinger equation of the form (CDt0+αu)(t,x) = iħ/2m(C∇βu)(t,x), with ħ the Planck's constant divided by 2π, m is the mass and u(t,x) is a wave function of the particle. Here (CDt0+α,C∇β are operators of the Caputo fractional derivatives, where α ∈]0,1] and β ∈]1,2]. The wave function is obtained using Laplace and Fourier transforms methods and a symbolic operational form of solutions in terms of the Mittag-Leffler functions is exhibited. It is presented an expression for the wave function and for the quantum mechanical probability density. Using Banach fixed point theorem, the existence and uniqueness of solutions is studied for this kind of fractional differential equations.

Producing data-based sensitivity kernels from convolution and correlation in exploration geophysics.

NASA Astrophysics Data System (ADS)

Chmiel, M. J.; Roux, P.; Herrmann, P.; Rondeleux, B.

2016-12-01

Many studies have shown that seismic interferometry can be used to estimate surface wave arrivals by correlation of seismic signals recorded at a pair of locations. In the case of ambient noise sources, the convergence towards the surface wave Green's functions is obtained with the criterion of equipartitioned energy. However, seismic acquisition with active, controlled sources gives more possibilities when it comes to interferometry. The use of controlled sources makes it possible to recover the surface wave Green's function between two points using either correlation or convolution. We investigate the convolutional and correlational approaches using land active-seismic data from exploration geophysics. The data were recorded on 10,710 vertical receivers using 51,808 sources (seismic vibrator trucks). The sources spacing is the same in both X and Y directions (30 m) which is known as a "carpet shooting". The receivers are placed in parallel lines with a spacing 150 m in the X direction and 30 m in the Y direction. Invoking spatial reciprocity between sources and receivers, correlation and convolution functions can thus be constructed between either pairs of receivers or pairs of sources. Benefiting from the dense acquisition, we extract sensitivity kernels from correlation and convolution measurements of the seismic data. These sensitivity kernels are subsequently used to produce phase-velocity dispersion curves between two points and to separate the higher mode from the fundamental mode for surface waves. Potential application to surface wave cancellation is also envisaged.

Drop dynamics

NASA Technical Reports Server (NTRS)

Elleman, D. D.

1981-01-01

The drop dynamics module is a Spacelab-compatible acoustic positioning and control system for conducting drop dynamics experiments in space. It consists basically of a chamber, a drop injector system, an acoustic positioning system, and a data collection system. The principal means of collecting data is by a cinegraphic camera. The drop is positioned in the center of the chamber by forces created by standing acoustic waves generated in the nearly cubical chamber (about 12 cm on a side). The drop can be spun or oscillated up to fission by varying the phse and amplitude of the acoustic waves. The system is designed to perform its experiments unattended, except for start-up and shutdown events and other unique events that require the attention of the Spacelab payload specialist.

Recurrence approach and higher order polynomial algebras for superintegrable monopole systems

NASA Astrophysics Data System (ADS)

Hoque, Md Fazlul; Marquette, Ian; Zhang, Yao-Zhong

2018-05-01

We revisit the MIC-harmonic oscillator in flat space with monopole interaction and derive the polynomial algebra satisfied by the integrals of motion and its energy spectrum using the ad hoc recurrence approach. We introduce a superintegrable monopole system in a generalized Taub-Newman-Unti-Tamburino (NUT) space. The Schrödinger equation of this model is solved in spherical coordinates in the framework of Stäckel transformation. It is shown that wave functions of the quantum system can be expressed in terms of the product of Laguerre and Jacobi polynomials. We construct ladder and shift operators based on the corresponding wave functions and obtain the recurrence formulas. By applying these recurrence relations, we construct higher order algebraically independent integrals of motion. We show that the integrals form a polynomial algebra. We construct the structure functions of the polynomial algebra and obtain the degenerate energy spectra of the model.

First Vlasiator results on foreshock ULF wave activity

NASA Astrophysics Data System (ADS)

Palmroth, M.; Eastwood, J. P.; Pokhotelov, D.; Hietala, H.; Kempf, Y.; Hoilijoki, S.; von Alfthan, S.; Vainio, R. O.

2013-12-01

For decades, a certain type of ultra low frequency waves with a period of about 30 seconds have been observed in the Earth's quasi-parallel foreshock. These waves, with a wavelength of about an Earth radius, are compressive and propagate obliquely with respect to the interplanetary magnetic field (IMF). The latter property has caused trouble to scientists as the growth rate for the instability causing the waves is maximized along the magnetic field. So far, these waves have been characterized by single or multi-spacecraft methods and 2-dimensional hybrid-PIC simulations, which have not fully reproduced the wave properties. Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves ions in the six-dimensional phase space using the Vlasov equation and electrons using magnetohydrodynamics (MHD). The outcome of the simulation is a global reproduction of ion-scale physics in a holistic manner where the generation of physical features can be followed in time and their consequences can be quantitatively characterized. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global magnetospheric scale presently with a resolution of 0.13 RE in the ordinary space and 20 km/s in the velocity space. We run two simulations, where we use both a typical Parker-spiral and a radial IMF as an input to the code. The runs are carried out in the ecliptic 2-dimensional plane in the ordinary space, and with three dimensions in the velocity space. We observe the generation of the 30-second ULF waves, and characterize their evolution and physical properties in time, comparing to observations by Cluster spacecraft. We find that Vlasiator reproduces these waves in all reported observational aspects, i.e., they are of the observed size in wavelength and period, they are compressive and propagate obliquely to the IMF. In particular, we investigate the oblique propagation and discuss the issues related to the long-standing question of oblique propagation.

Qualitative numerical studies of the modification of the pitch angle distribution of test particles by alfvènic wave activity

NASA Astrophysics Data System (ADS)

Keilbach, D.; Drews, C.; Berger, L.; Marsch, E.; Wimmer-Schweingruber, R. F.

2017-12-01

Using a test particle approach we have investigated, how an oxygen pickup ion torus velocity distribution is modified by continuous and intermittent alfvènic waves on timescales, where the gyro trajectory of each particle can be traced.We have therefore exposed the test particles to mono frequent waves, which expanded through the whole simulation in time and space. The general behavior of the pitch angle distribution is found to be stationary and a nonlinear function of the wave frequency, amplitude and the initial angle between wave elongation and field-perpendicular particle velocity vector. The figure shows the time-averaged pitch angle distributions as a function of the Doppler shifted wave frequency (where the Doppler shift was calculated with respect to the particles initial velocity) for three different wave amplitudes (labeled in each panel). The background field is chosen to be 5 nT and the 500 test particles were initially distributed on a torus with 120° pitch angle at a solar wind velocity of 450 km/s. Each y-slice of the histogram (which has been normalized to it's respective maximum) represents an individual run of the simulation.The frequency-dependent behavior of the test particles is found to be classifiable into the regimes of very low/high frequencies and frequencies close to first order resonance. We have found, that only in the latter regime the particles interact strongly with the wave, where in the time averaged histograms a branch structure is found, which was identified as a trace of particles co-moving with the wave phase. The magnitude of pitch angle change of these particles is as well as the frequency margin, where the branch structure is found, an increasing function with the wave amplitude.We have also investigated the interaction with mono frequent intermittent waves. Exposed to such waves a torus distribution is scattered in pitch angle space, whereas the pitch angle distribution is broadened systematically over time similar to pitch angle diffusion.The framework of our simulations is a first step toward understanding wave particle interactions at the most basic level and is readily expandable to e.g. the inclusion of multiple wave frequencies, intermittent wave activity, gradients in the background magnetic field or collisions with solar wind particles.

Resonance controlled transport in phase space

NASA Astrophysics Data System (ADS)

Leoncini, Xavier; Vasiliev, Alexei; Artemyev, Anton

2018-02-01

We consider the mechanism of controlling particle transport in phase space by means of resonances in an adiabatic setting. Using a model problem describing nonlinear wave-particle interaction, we show that captures into resonances can be used to control transport in momentum space as well as in physical space. We design the model system to provide creation of a narrow peak in the distribution function, thus producing effective cooling of a sub-ensemble of the particles.

Non-cooperative Fisher-KPP systems: traveling waves and long-time behavior

NASA Astrophysics Data System (ADS)

Girardin, Léo

2018-01-01

This paper is concerned with non-cooperative parabolic reaction-diffusion systems which share structural similarities with the scalar Fisher-KPP equation. These similarities make it possible to prove, among other results, an extinction and persistence dichotomy and, when persistence occurs, the existence of a positive steady state, the existence of traveling waves with a half-line of possible speeds and a positive minimal speed and the equality between this minimal speed and the spreading speed for the Cauchy problem. Non-cooperative KPP systems can model various phenomena where the following three mechanisms occur: local diffusion in space, linear cooperation and superlinear competition.

A geometric theory of waves and its applications to plasma physics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruiz, Daniel

Waves play an essential role in many aspects of plasma dynamics. For example, they are indispensable in plasma manipulation and diagnostics. Although the physics of waves is well understood in the context of relatively simple problems, difficulties arise when studying waves that propagate in inhomogeneous or nonlinear media. This thesis presents a new systematic wave theory based on phase-space variational principles. In this dissertation, waves are treated as geometric objects of a variational theory rather than formal solutions of specific PDEs. This approach simplifies calculations, highlights the underlying wave symmetries, and leads to improved modeling of wave dynamics. Specifically, thismore » dissertation presents two important breakthroughs that were obtained in the general theory of waves. The first main contribution of the present dissertation is an extension of the theory of geometrical optics (GO) in order to include polarization effects. Even when diffraction is ignored, the GO ray equations are not entirely accurate. This occurs because GO treats wave rays as classical particles described by their position and momentum coordinates. However, vector waves have another degree of freedom, their polarization. As a result, wave rays can behave as particles with spin and show polarization dynamics, such as polarization precession and polarization-driven bending of ray trajectories. In this thesis, the theory of GO is reformulated as a first-principle Lagrangian wave theory that governs both mentioned polarization phenomena simultaneously. The theory was applied successfully to several systems of interest, such as relativistic spin-$1/2$ particles and radio-frequency waves propagating in magnetized plasmas. The second main contribution of this thesis is the development of a phase-space method to study basic properties of nonlinear wave--wave interactions. Specifically, a general theory is proposed that describes the ponderomotive refraction that a wave can experience when interacting with another wave. It is also shown that phase-space methods can be useful to study problems in the field of wave turbulence, such as the nonlinear interaction of high-frequency waves with large-scale structures. Overall, the results obtained can serve as a basis for future studies on more complex nonlinear wave--wave interactions, such as modulational instabilities in general wave ensembles or wave turbulence.« less

Asymptotics with a positive cosmological constant: I. Basic framework

NASA Astrophysics Data System (ADS)

Ashtekar, Abhay; Bonga, Béatrice; Kesavan, Aruna

2015-01-01

The asymptotic structure of the gravitational field of isolated systems has been analyzed in great detail in the case when the cosmological constant Λ is zero. The resulting framework lies at the foundation of research in diverse areas in gravitational science. Examples include: (i) positive energy theorems in geometric analysis; (ii) the coordinate invariant characterization of gravitational waves in full, nonlinear general relativity; (iii) computations of the energy-momentum emission in gravitational collapse and binary mergers in numerical relativity and relativistic astrophysics; and (iv) constructions of asymptotic Hilbert spaces to calculate S-matrices and analyze the issue of information loss in the quantum evaporation of black holes. However, by now observations have led to a strong consensus that Λ is positive in our universe. In this paper we show that, unfortunately, the standard framework does not extend from the Λ =0 case to the Λ \\gt 0 case in a physically useful manner. In particular, we do not have positive energy theorems, nor an invariant notion of gravitational waves in the nonlinear regime, nor asymptotic Hilbert spaces in dynamical situations of semi-classical gravity. A suitable framework to address these conceptual issues of direct physical importance is developed in subsequent papers.

Equatorial waves in a stratospheric GCM: Effects of vertical resolution. [GCM (general circulation model)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boville, B.A.; Randel, W.J.

1992-05-01

Equatorially trapped wave modes, such as Kelvin and mixed Rossby-gravity waves, are believed to play a crucial role in forcing the quasi-biennial oscillation (QBO) of the lower tropical stratosphere. This study examines the ability of a general circulation model (GCM) to simulate these waves and investigates the changes in the wave properties as a function of the vertical resolution of the model. The simulations produce a stratopause-level semiannual oscillation but not a QBO. An unfortunate property of the equatorially trapped waves is that they tend to have small vertical wavelengths ([le] 15 km). Some of the waves, believed to bemore » important in forcing the QBO, have wavelengths as short as 4 km. The short vertical wavelengths pose a stringent computational requirement for numerical models whose vertical grid spacing is typically chosen based on the requirements for simulating extratropical Rossby waves (which have much longer vertical wavelengths). This study examines the dependence of the equatorial wave simulation of vertical resolution using three experiments with vertical grid spacings of approximately 2.8, 1.4, and 0.7 km. Several Kelvin, mixed Rossby-gravity, and 0.7 km. Several Kelvin, mixed Rossby-gravity, and inertio-gravity waves are identified in the simulations. At high vertical resolution, the simulated waves are shown to correspond fairly well to the available observations. The properties of the relatively slow (and vertically short) waves believed to play a role in the QBO vary significantly with vertical resolution. Vertical grid spacings of about 1 km or less appear to be required to represent these waves adequately. The simulated wave amplitudes are at least as large as observed, and the waves are absorbed in the lower stratosphere, as required in order to force the QBO. However, the EP flux divergence associated with the waves is not sufficient to explain the zonal flow accelerations found in the QBO. 39 refs., 17 figs., 1 tab.« less

Observations of a free-energy source for intense electrostatic waves. [in upper atmosphere near upper hybrid resonance frequency

NASA Technical Reports Server (NTRS)

Kurth, W. S.; Frank, L. A.; Gurnett, D. A.; Burek, B. G.; Ashour-Abdalla, M.

1980-01-01

Significant progress has been made in understanding intense electrostatic waves near the upper hybrid resonance frequency in terms of the theory of multiharmonic cyclotron emission using a classical loss-cone distribution function as a model. Recent observations by Hawkeye 1 and GEOS 1 have verified the existence of loss-cone distributions in association with the intense electrostatic wave events, however, other observations by Hawkeye and ISEE have indicated that loss cones are not always observable during the wave events, and in fact other forms of free energy may also be responsible for the instability. Now, for the first time, a positively sloped feature in the perpendicular distribution function has been uniquely identified with intense electrostatic wave activity. Correspondingly, we suggest that the theory is flexible under substantial modifications of the model distribution function.

Particle Acceleration by Cme-driven Shock Waves

NASA Technical Reports Server (NTRS)

Reames, Donald V.

1999-01-01

In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

FFT-split-operator code for solving the Dirac equation in 2+1 dimensions

NASA Astrophysics Data System (ADS)

Mocken, Guido R.; Keitel, Christoph H.

2008-06-01

The main part of the code presented in this work represents an implementation of the split-operator method [J.A. Fleck, J.R. Morris, M.D. Feit, Appl. Phys. 10 (1976) 129-160; R. Heather, Comput. Phys. Comm. 63 (1991) 446] for calculating the time-evolution of Dirac wave functions. It allows to study the dynamics of electronic Dirac wave packets under the influence of any number of laser pulses and its interaction with any number of charged ion potentials. The initial wave function can be either a free Gaussian wave packet or an arbitrary discretized spinor function that is loaded from a file provided by the user. The latter option includes Dirac bound state wave functions. The code itself contains the necessary tools for constructing such wave functions for a single-electron ion. With the help of self-adaptive numerical grids, we are able to study the electron dynamics for various problems in 2+1 dimensions at high spatial and temporal resolutions that are otherwise unachievable. Along with the position and momentum space probability density distributions, various physical observables, such as the expectation values of position and momentum, can be recorded in a time-dependent way. The electromagnetic spectrum that is emitted by the evolving particle can also be calculated with this code. Finally, for planning and comparison purposes, both the time-evolution and the emission spectrum can also be treated in an entirely classical relativistic way. Besides the implementation of the above-mentioned algorithms, the program also contains a large C++ class library to model the geometric algebra representation of spinors that we use for representing the Dirac wave function. This is why the code is called "Dirac++". Program summaryProgram title: Dirac++ or (abbreviated) d++ Catalogue identifier: AEAS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 474 937 No. of bytes in distributed program, including test data, etc.: 4 128 347 Distribution format: tar.gz Programming language: C++ Computer: Any, but SMP systems are preferred Operating system: Linux and MacOS X are actively supported by the current version. Earlier versions were also tested successfully on IRIX and AIX Number of processors used: Generally unlimited, but best scaling with 2-4 processors for typical problems RAM: 160 Megabytes minimum for the examples given here Classification: 2.7 External routines: FFTW Library [3,4], Gnu Scientific Library [5], bzip2, bunzip2 Nature of problem: The relativistic time evolution of wave functions according to the Dirac equation is a challenging numerical task. Especially for an electron in the presence of high intensity laser beams and/or highly charged ions, this type of problem is of considerable interest to atomic physicists. Solution method: The code employs the split-operator method [1,2], combined with fast Fourier transforms (FFT) for calculating any occurring spatial derivatives, to solve the given problem. An autocorrelation spectral method [6] is provided to generate a bound state for use as the initial wave function of further dynamical studies. Restrictions: The code in its current form is restricted to problems in two spatial dimensions. Otherwise it is only limited by CPU time and memory that one can afford to spend on a particular problem. Unusual features: The code features dynamically adapting position and momentum space grids to keep execution time and memory requirements as small as possible. It employs an object-oriented approach, and it relies on a Clifford algebra class library to represent the mathematical objects of the Dirac formalism which we employ. Besides that it includes a feature (typically called "checkpointing") which allows the resumption of an interrupted calculation. Additional comments: Along with the program's source code, we provide several sample configuration files, a pre-calculated bound state wave function, and template files for the analysis of the results with both MatLab and Igor Pro. Running time: Running time ranges from a few minutes for simple tests up to several days, even weeks for real-world physical problems that require very large grids or very small time steps. References:J.A. Fleck, J.R. Morris, M.D. Feit, Time-dependent propagation of high energy laser beams through the atmosphere, Appl. Phys. 10 (1976) 129-160. R. Heather, An asymptotic wavefunction splitting procedure for propagating spatially extended wavefunctions: Application to intense field photodissociation of H +2, Comput. Phys. Comm. 63 (1991) 446. M. Frigo, S.G. Johnson, FFTW: An adaptive software architecture for the FFT, in: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing, vol. 3, IEEE, 1998, pp. 1381-1384. M. Frigo, S.G. Johnson, The design and implementation of FFTW3, in: Proceedings of the IEEE, vol. 93, IEEE, 2005, pp. 216-231. URL: http://www.fftw.org/. M. Galassi, J. Davies, J. Theiler, B. Gough, G. Jungman, M. Booth, F. Rossi, GNU Scientific Library Reference Manual, second ed., Network Theory Limited, 2006. URL: http://www.gnu.org/software/gsl/. M.D. Feit, J.A. Fleck, A. Steiger, Solution of the Schrödinger equation by a spectral method, J. Comput. Phys. 47 (1982) 412-433.

Variational Optimization of the Second-Order Density Matrix Corresponding to a Seniority-Zero Configuration Interaction Wave Function.

PubMed

Poelmans, Ward; Van Raemdonck, Mario; Verstichel, Brecht; De Baerdemacker, Stijn; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E; Alcoba, Diego R; Bultinck, Patrick; Van Neck, Dimitri

2015-09-08

We perform a direct variational determination of the second-order (two-particle) density matrix corresponding to a many-electron system, under a restricted set of the two-index N-representability P-, Q-, and G-conditions. In addition, we impose a set of necessary constraints that the two-particle density matrix must be derivable from a doubly occupied many-electron wave function, i.e., a singlet wave function for which the Slater determinant decomposition only contains determinants in which spatial orbitals are doubly occupied. We rederive the two-index N-representability conditions first found by Weinhold and Wilson and apply them to various benchmark systems (linear hydrogen chains, He, N2, and CN(-)). This work is motivated by the fact that a doubly occupied many-electron wave function captures in many cases the bulk of the static correlation. Compared to the general case, the structure of doubly occupied two-particle density matrices causes the associate semidefinite program to have a very favorable scaling as L(3), where L is the number of spatial orbitals. Since the doubly occupied Hilbert space depends on the choice of the orbitals, variational calculation steps of the two-particle density matrix are interspersed with orbital-optimization steps (based on Jacobi rotations in the space of the spatial orbitals). We also point to the importance of symmetry breaking of the orbitals when performing calculations in a doubly occupied framework.

Analysis of bubble plume spacing produced by regular breaking waves

NASA Astrophysics Data System (ADS)

Phaksopa, J.; Haller, M. C.

2012-12-01

The breaking wave process in the ocean is a significant mechanism for energy dissipation, splash, and entrainment of air. The relationship between breaking waves and bubble plume characteristics is still a mystery because of the complexity of the breaking wave mechanism. This study takes a unique approach to quantitatively analyze bubble plumes produced by regular breaking waves. Various previous studies have investigated the formation and the characteristics of bubble plumes using either field observations, laboratory experiments, or numerical modeling However, in most observational work the plume characteristics have been studied from the underneath the water surface. In addition, though numerical simulations are able to include much of the important physics, the computational costs are high and bubble plume events are only simulated for short times. Hence, bubble plume evolution and generation throughout the surf zone is not yet computationally feasible. In the present work we take a unique approach to analyzing bubble plumes. These data may be of use for model/data comparisons as numerical simulations become more tractable. The remotely sensed video data from freshwater breaking waves in the OSU Large Wave Flume (Catalan and Haller, 2008) are analyzed. The data set contains six different regular wave conditions and the video intensity data are used to estimate the spacing of plume events (wavenumber spectrum), to calculate the spectral width (i.e. the range of plume spacing), and to relate these with the wave conditions. The video intensity data capture the evolution of the wave passage over a fixed bed arranged in a bar-trough morphology. Bright regions represent the moving path or trajectory coincident with bubble plume of each wave. It also shows the bubble foam were generated and released from wave crest shown in the form of bubble tails with almost regular spacing for each wave. The bubble tails show that most bubbles did not move along with wave. For the estimation of wavenumber spectrum, the density is high at low wavenumber and it decreases toward high wavenumber. The average spectrum bandwidth was estimated and represented as the bubble event spacing for each run. It is found that its magnitude varies with wave conditions range from 8.81 - 11.82 and is related to the waveheight. Additionally, the calculated wavenumbers from power density function vary in the range of 0.80 - 1.58 meters-1. It is found that the bubble wavenumbers are mostly higher than the wavenumbers calculated from the linear wave theory between 0.2L-0.7L. In other words, the bubble plume length does not exceed the progressive wavelength.

Slosh wave excitation due to cryogenic liquid reorientation in space-based propulsion system

NASA Technical Reports Server (NTRS)

Hung, R. J.; Shyu, K. L.; Lee, C. C.

1991-01-01

The objective of the cryogenic fluid management of the spacecraft propulsion system is to develop the technology necessary for acquistion or positioning of liquid and vapor within a tank in reduced gravity to enable liquid outflow or vapor venting. In this study slosh wave excitation induced by the resettling flow field activated by 1.0 Hz medium frequency impulsive reverse gravity acceleration during the course of liquid fluid reorientation with the initiation of geyser for liquid filled levels of 30, 50, and 80 percent have been studied. Characteristics of slosh waves with various frequencies excited are discussed.

Millimeter wave propagation measurements using the ATS 5 satellite

NASA Technical Reports Server (NTRS)

Ippolito, L. J.

1972-01-01

The ATS 5 millimeter wave propagation experiment determines long- and short-term attenuation statistics of operational millimeter wavelength earthspace links as functions of defined meteorological conditions. A preliminary analysis of results with 15 GHz downlink and 32 GHz uplink frequency bands indicates that both frequency bands exhibit an excellent potential for utilization in reliable high data rate earth-space communications systems.

A Model for Lower Hybrid Wave Excitation Compared with Observations by Viking

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Liemohn, M. W.; Krivorutsky, E. N.; Horwitz, J. L.

1997-01-01

The mechanism of lower hybrid wave (LHW) excitation due to the O+ relative drift in a plasma subjected to low-frequency waves (LFWs) is used for analysis of Viking satellite data for events in the cusp/cleft region. In some cases, such a mechanism leads to LHW energy densities and ion distribution functions close to those observed, suggesting the proposed mechanism is a plausible candidate to explain certain classes of LHW generation events in space plasmas.

Regression analysis and transfer function in estimating the parameters of central pulse waves from brachial pulse wave.

PubMed

Chai Rui; Li Si-Man; Xu Li-Sheng; Yao Yang; Hao Li-Ling

2017-07-01

This study mainly analyzed the parameters such as ascending branch slope (A_slope), dicrotic notch height (Hn), diastolic area (Ad) and systolic area (As) diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure (PP), subendocardial viability ratio (SEVR), waveform parameter (k), stroke volume (SV), cardiac output (CO) and peripheral resistance (RS) of central pulse wave invasively and non-invasively measured. These parameters extracted from the central pulse wave invasively measured were compared with the parameters measured from the brachial pulse waves by a regression model and a transfer function model. The accuracy of the parameters which were estimated by the regression model and the transfer function model was compared too. Our findings showed that in addition to the k value, the above parameters of the central pulse wave and the brachial pulse wave invasively measured had positive correlation. Both the regression model parameters including A_slope, DBP, SEVR and the transfer function model parameters had good consistency with the parameters invasively measured, and they had the same effect of consistency. The regression equations of the three parameters were expressed by Y'=a+bx. The SBP, PP, SV, CO of central pulse wave could be calculated through the regression model, but their accuracies were worse than that of transfer function model.

Progress on the development of FullWave, a Hot and Cold Plasma Parallel Full Wave Code

NASA Astrophysics Data System (ADS)

Spencer, J. Andrew; Svidzinski, Vladimir; Zhao, Liangji; Kim, Jin-Soo

2017-10-01

FullWave is being developed at FAR-TECH, Inc. to simulate RF waves in hot inhomogeneous magnetized plasmas without making small orbit approximations. FullWave is based on a meshless formulation in configuration space on non-uniform clouds of computational points (CCP) adapted to better resolve plasma resonances, antenna structures and complex boundaries. The linear frequency domain wave equation is formulated using two approaches: for cold plasmas the local cold plasma dielectric tensor is used (resolving resonances by particle collisions), while for hot plasmas the conductivity kernel is calculated. The details of FullWave and some preliminary results will be presented, including: 1) a monitor function based on analytic solutions of the cold-plasma dispersion relation; 2) an adaptive CCP based on the monitor function; 3) construction of the finite differences for approximation of derivatives on adaptive CCP; 4) results of 2-D full wave simulations in the cold plasma model in tokamak geometry using the formulated approach for ECRH, ICRH and Lower Hybrid range of frequencies. Work is supported by the U.S. DOE SBIR program.

Emissivity of half-space random media. [in passive remote sensing

NASA Technical Reports Server (NTRS)

Tsang, L.; Kong, J. A.

1976-01-01

Scattering of electromagnetic waves by a half-space random medium with three-dimensional correlation functions is studied with the Born approximation. The emissivity is calculated from a simple integral and is illustrated for various cases. The results are valid over a wavelength range smaller or larger than the correlation lengths.

Evolution of initial discontinuities in the Riemann problem for the Kaup-Boussinesq equation with positive dispersion

NASA Astrophysics Data System (ADS)

Congy, T.; Ivanov, S. K.; Kamchatnov, A. M.; Pavloff, N.

2017-08-01

We consider the space-time evolution of initial discontinuities of depth and flow velocity for an integrable version of the shallow water Boussinesq system introduced by Kaup. We focus on a specific version of this "Kaup-Boussinesq model" for which a flat water surface is modulationally stable, we speak below of "positive dispersion" model. This model also appears as an approximation to the equations governing the dynamics of polarisation waves in two-component Bose-Einstein condensates. We describe its periodic solutions and the corresponding Whitham modulation equations. The self-similar, one-phase wave structures are composed of different building blocks, which are studied in detail. This makes it possible to establish a classification of all the possible wave configurations evolving from initial discontinuities. The analytic results are confirmed by numerical simulations.

Evolution of initial discontinuities in the Riemann problem for the Kaup-Boussinesq equation with positive dispersion.

PubMed

Congy, T; Ivanov, S K; Kamchatnov, A M; Pavloff, N

2017-08-01

We consider the space-time evolution of initial discontinuities of depth and flow velocity for an integrable version of the shallow water Boussinesq system introduced by Kaup. We focus on a specific version of this "Kaup-Boussinesq model" for which a flat water surface is modulationally stable, we speak below of "positive dispersion" model. This model also appears as an approximation to the equations governing the dynamics of polarisation waves in two-component Bose-Einstein condensates. We describe its periodic solutions and the corresponding Whitham modulation equations. The self-similar, one-phase wave structures are composed of different building blocks, which are studied in detail. This makes it possible to establish a classification of all the possible wave configurations evolving from initial discontinuities. The analytic results are confirmed by numerical simulations.

Spatio-temporal evolutions of non-orthogonal equatorial wave modes derived from observations

NASA Astrophysics Data System (ADS)

Barton, Cory

Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. Historically, their activity is diagnosed mainly in the wavenumber-frequency domain. Recently, many studies have projected observational data onto parabolic cylinder functions (PCFs), which represent the meridional structure of individual wave modes, to attain time-dependent spatial wave structures. The non-orthogonality of wave modes has yet posed a problem when attempting to separate data into wave fields where the waves project onto the same structure functions. We propose the development and application of a new methodology for equatorial wave expansion of instantaneous flows using the full equatorial wave spectrum. By creating a mapping from the meridional structure function amplitudes to the equatorial wave class amplitudes, we are able to diagnose instantaneous wave fields and determine their evolution. Because all meridional modes are shared by some subset of the wave classes, we require constraints on the wave class amplitudes to yield a closed system with a unique solution for all waves' spatial structures, including IG waves. A synthetic field is analyzed using this method to determine its accuracy for data of a single vertical mode. The wave class spectra diagnosed using this method successfully match the correct dispersion curves even if the incorrect depth is chosen for the spatial decomposition. In the case of more than one depth scale, waves with varying equivalent depth may be similarly identified using the dispersion curves. The primary vertical mode is the 200 m equivalent depth mode, which is that of the peak projection response. A distinct spectral power peak along the Kelvin wave dispersion curve for this value validates our choice of equivalent depth, although the possibility of depth varying with time and height is explored. The wave class spectra diagnosed assuming this depth scale mostly match their expected dispersion curves, showing that this method successfully partitions the wave spectra by calculating wave amplitudes in physical space. This is particularly striking because the time evolution, and therefore the frequency characteristics, is determined simply by a timeseries of independently-diagnosed instantaneous horizontal fields. We use the wave fields diagnosed by this method to study wave evolution in the context of the stratospheric QBO of zonal wind, confirming the continuous evolution of the selection mechanism for equatorial waves in the middle atmosphere. The amplitude cycle synchronized with the background zonal wind as predicted by QBO theory is present in the wave class fields even though the dynamics are not forced by the method itself. We have additionally identified a time-evolution of the zonal wavenumber spectrum responsible for the amplitude variability in physical space. Similar to the temporal characteristics, the vertical structures are also the result of a simple height cross-section through multiple independently-diagnosed levels.

Analytic Wave Functions for the Half-Filled Lowest Landau Level

NASA Astrophysics Data System (ADS)

Ciftja, Orion

We consider a two-dimensional strongly correlated electronic system in a strong perpendicular magnetic field at half-filling of the lowest Landau level (LLL). We seek to build a wave function that, by construction, lies entirely in the Hilbert space of the LLL. Quite generally, a wave function of this nature can be built as a linear combination of all possible Slater determinants formed by using the complete set of single-electron states that belong to the LLL. However, due to the vast number of Slater determinant states required to form such basis functions, the expansion is impractical for any but the smallest systems. Thus, in practice, the expansion must be truncated to a small number of Slater determinants. Among many possible LLL Slater determinant states, we note a particular special class of such wave functions in which electrons occupy either only even, or only odd angular momentum states. We focus on such a class of wave functions and obtain analytic expressions for various quantities of interest. Results seem to suggest that these special wave functions, while interesting and physically appealing, are unlikely to be a very good approximation for the exact ground state at half-filling factor. The overall quality of the description can be improved by including other additional LLL Slater determinant states. It is during this process that we identify another special family of suitable LLL Slater determinant states to be used in an enlarged expansion.

Reflection and interference of electromagnetic waves in inhomogeneous media

NASA Technical Reports Server (NTRS)

Geiger, F. E.; Kyle, H. L.

1973-01-01

Solutions were obtained of the wave equation for a plane horizontally polarized electro-magnetic wave incident on a semi infinite two dimensional inhomogeneous medium. Two problems were considered: An inhomogeneous half space, and an inhomogeneous layer of arbitrary thickness. Solutions of the wave equation were obtained in terms of Hankel functions with complex arguments. Numerical calculations were made of the reflection coefficient R at the interface of the homogeneous medium. The startling results show that the reflection coefficient for a complex dielectric constant with gradient, can be less than that of the same medium with zero gradient.

Assessment of the measurement performance of the in-vessel system of gap 6 of the ITER plasma position reflectometer using a finite-difference time-domain Maxwell full-wave code.

PubMed

da Silva, F; Heuraux, S; Ricardo, E; Quental, P; Ferreira, J

2016-11-01

We conducted a first assessment of the measurement performance of the in-vessel components at gap 6 of the ITER plasma position reflectometry with the aid of a synthetic Ordinary Mode (O-mode) broadband frequency-modulated continuous-wave reflectometer implemented with REFMUL, a 2D finite-difference time-domain full-wave Maxwell code. These simulations take into account the system location within the vacuum vessel as well as its access to the plasma. The plasma case considered is a baseline scenario from Fusion for Energy. We concluded that for the analyzed scenario, (i) the plasma curvature and non-equatorial position of the antenna have neglectable impact on the measurements; (ii) the cavity-like space surrounding the antenna can cause deflection and splitting of the probing beam; and (iii) multi-reflections on the blanket wall cause a substantial error preventing the system from operating within the required error margin.

The structure of ion-acoustic waves in a low-frequency three-component electron-ion space plasma with two-electron populations

NASA Astrophysics Data System (ADS)

Govender, G.; Moolla, S.

2018-07-01

Low-frequency ion-acoustic waves are analysed on the ion time-scale, in a three-component electron-ion space plasma. The solitary waves propagate in the positive x direction relative to an ambient magnetic field ěc {B}_0 which forms static background for a configuration consisting of cool fluid ions and both warm and hot Boltzmann-distributed electrons with temperatures T_{ic}, T_{ew} and T_{eh}, respectively. We derive linear dispersion relation for the waves by introducing first-order density, pressure and velocity perturbations into the ion fluid equations. Additionally, the variation in the nonlinear structure of the waves are investigated by carrying out a full parametric analysis utilising our numerical code. Our results reveal that ion-acoustic waves exhibit well-defined nonlinear spikes at speeds of M≥ 2.25 and an electric field amplitude of E_0=0.85. It is also shown that low wave speeds (M≤ 2), higher densities of the hot electrons, antiparallel drifting of the cool fluid ions, and increased ion temperatures all lead to significant dispersive effects. The ion-acoustic plasma waves featured in this paper have forms that are consistent with those classified as the type-A and type-B broadband electrostatic noise (BEN) observed in the data obtained from earlier satellite missions.

The relationship between African easterly waves and equatorial waves and the influence from the Southern Hemisphere

NASA Astrophysics Data System (ADS)

Methven, John; Guiying, Yang; Hodges, Kevin; Woolnough, Steve

2017-04-01

There is strong intraseasonal and interannual variability in African easterly waves (AEWs). AEWs are crucial to precipitation across West Africa, but also generate positive vorticity centres that sometimes develop into tropical storms which can in turn spin-up into hurricanes in the easterlies across the North Atlantic. In this paper we show that there are connections between African easterly waves (AEWs), equatorial Rossby (R1 and R2) waves and westward-moving mixed Rossby gravity (WMRG) waves and that the conditions for propagation of equatorial waves may have a major influence on AEW and hence tropical cyclone variability. Two analysis approaches are taken using ERA-Interim data from 1979-2010: i) positive vorticity centres within AEWs are tracked at 600 hPa over West Africa to the Atlantic region and ii) the re-analysis data is filtered using a broad frequency and zonal wavenumber band and the filtered meridional wind is projected onto the horizontal structure functions derived from equatorial wave theory. The tracked vorticity centres are part of AEWs and are found to move along with features in the meridional wind projecting onto R1 and R2 waves. In contrast, the structures projecting onto WMRG waves move westwards at a faster rate. The projection is calculated independently on each pressure level to create composite cross-sections of each wave mode in the zonal-height plane, shown relative to the 600 hPa vorticity centres. The R2 waves tilt in the sense necessary for baroclinic growth and amplify from east to west, indicating that R2 horizontal structure captures the baroclinic wave component of AEWs. The composites show that the R2 structures have a wavelength matching the spacing between vorticity centres, while R1 and WMRG waves are longer. Intriguingly, the WMRG component has very strong cross-equatorial flow immediately to the east of positive vorticity centres developing on the AEJ. Although the WMRG propagates faster to the west and gets ahead of the original vorticity centre, the next AEW vorticity centre to the east develops with cross-equatorial flow in the same phase. This flow brings moist air from the southern hemisphere at low levels on the eastern flank of the vorticity centre, while there is an upper tropospheric "return flow" into the southern hemisphere above. Thus, there is a strong cross-equatorial component to the developing tropical storm outflow. WMRG waves may aid the initiation and development of AEW vorticity centres. Over West Africa, regressions show that the eastward group propagation of a WMRG packet precedes the genesis of vorticity centres on the AEJ. In years with stronger AEW activity, the upper tropospheric easterlies are stronger at the equator and extend further into the southern hemisphere. It is shown that stronger easterlies provide a waveguide for SH westward-moving Rossby waves in the upper troposphere to penetrate into the tropics, exciting equatorial WMRG waves and hence stronger AEW activity via the lower tropospheric cross-equatorial flow associated with WMRG waves.

Cosmological gravitational waves

NASA Technical Reports Server (NTRS)

Linder, Eric V.

1988-01-01

A cosmological background of gravitational waves would alter the propagation of radiation, inducing redshift fluctuations, apparent source position deflections, and luminosity variations. By comparing these astrophysical effects with observations, it is possible to deduce upper limits on the energy density present in gravitational waves. Emphasis is placed on microwave background anisotropy from the redshift deviations and galaxy clustering correlation functions from the angular deviations. Many of the gravitational wave effects are shown to be generalizations of the gravitational lensing formalism.

In-plane dynamic Green's functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic half-space

NASA Astrophysics Data System (ADS)

Ba, Zhenning; Kang, Zeqing; Liang, Jianwen

2018-04-01

The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green's functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic (TI) half-space. The loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces, which are then applied to the total system with the opposite sign. By adding solutions restricted in the loaded layer to solutions from the reaction forces, the global solutions in the wavenumber domain are obtained, and the dynamic Green's functions in the space domain are recovered by the inverse Fourier transform. The presented formulations can be reduced to the isotropic case developed by Wolf (1985), and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI half-space subjected to horizontally distributed loads which are special cases of the more general problem addressed. The deduced Green's functions, in conjunction with boundary element methods, will lead to significant advances in the investigation of a variety of wave scattering, wave radiation and soil-structure interaction problems in a layered TI site. Selected numerical results are given to investigate the influence of material anisotropy, frequency of excitation, inclination angle and layered on the responses of displacement and stress, and some conclusions are drawn.

Dodecahedral space topology as an explanation for weak wide-angle temperature correlations in the cosmic microwave background.

PubMed

Luminet, Jean-Pierre; Weeks, Jeffrey R; Riazuelo, Alain; Lehoucq, Roland; Uzan, Jean-Philippe

2003-10-09

The current 'standard model' of cosmology posits an infinite flat universe forever expanding under the pressure of dark energy. First-year data from the Wilkinson Microwave Anisotropy Probe (WMAP) confirm this model to spectacular precision on all but the largest scales. Temperature correlations across the microwave sky match expectations on angular scales narrower than 60 degrees but, contrary to predictions, vanish on scales wider than 60 degrees. Several explanations have been proposed. One natural approach questions the underlying geometry of space--namely, its curvature and topology. In an infinite flat space, waves from the Big Bang would fill the universe on all length scales. The observed lack of temperature correlations on scales beyond 60 degrees means that the broadest waves are missing, perhaps because space itself is not big enough to support them. Here we present a simple geometrical model of a finite space--the Poincaré dodecahedral space--which accounts for WMAP's observations with no fine-tuning required. The predicted density is Omega(0) approximately 1.013 > 1, and the model also predicts temperature correlations in matching circles on the sky.

Scattering by multiple cylinders located on both sides of an interface

NASA Astrophysics Data System (ADS)

Lee, Siu-Chun

2018-07-01

The solution for scattering by multiple parallel infinite cylinders located in adjacent half spaces with dissimilar refractive index is presented in this paper. The incident radiation is an arbitrarily polarized plane wave propagating in the upper half space in the plane perpendicular to the axis of the cylinders. The formulation of the electromagnetic field vectors utilized Hertz potentials that are expressed in terms of an expansion of cylindrical wave functions. It accounts for the near-field multiple scattering, Fresnel effect at the interface, and interaction between cylinders in both half spaces. Analytical formulas are derived for the electromagnetic field and Poynting vector in the far-field. The present solution provides the theoretical framework for deducing the solutions for scattering by cylinders located on either side of an interface irradiated by a propagating or an evanescent incident wave. Deduction of these solutions from the present formulation is demonstrated. Numerical results are presented to illustrate the frustration of total internal reflection and scattering of light beyond the critical angle by nanocylinders located in either or both half spaces.

Imaging the wave functions of adsorbed molecules

PubMed Central

Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg; Soubatch, Serguei; Tautz, F. Stefan; Ramsey, Michael G.; Puschnig, Peter

2014-01-01

The basis for a quantum-mechanical description of matter is electron wave functions. For atoms and molecules, their spatial distributions and phases are known as orbitals. Although orbitals are very powerful concepts, experimentally only the electron densities and -energy levels are directly observable. Regardless whether orbitals are observed in real space with scanning probe experiments, or in reciprocal space by photoemission, the phase information of the orbital is lost. Here, we show that the experimental momentum maps of angle-resolved photoemission from molecular orbitals can be transformed to real-space orbitals via an iterative procedure which also retrieves the lost phase information. This is demonstrated with images obtained of a number of orbitals of the molecules pentacene (C22H14) and perylene-3,4,9,10-tetracarboxylic dianhydride (C24H8O6), adsorbed on silver, which are in excellent agreement with ab initio calculations. The procedure requires no a priori knowledge of the orbitals and is shown to be simple and robust. PMID:24344291

Containerless Ripple Turbulence

NASA Astrophysics Data System (ADS)

Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

2002-11-01

One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k5/3 which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear interaction. Furthermore, the steady state distribution of energy again follows a Kolmogorov scaling law; in this case the ripple energy is distributed according to 1/k 7/4. Again, in parallel with vortex turbulence ripple turbulence exhibits intermittency. The problem of ripple turbulence presents an experimental opportunity to generate data in a controlled, benchmarked system. In particular the surface of a sphere is an ideal environment to study ripple turbulence. Waves run around the sphere and interact with each other, and the effect of walls is eliminated. In microgravity this state can be realized for over 2 decades of frequency. Wave turbulence is a physically relevant problem in its own right. It has been studied on the surface of liquid hydrogen and its application to Alfven waves in space is a source of debate. Of course, application of wave turbulence perspectives to ocean waves has been a major success. The experiment which we plan to run in microgravity is conceptually straightforward. Ripples are excited on the surface of a spherical drop of fluid and then their amplitude is recorded with appropriate photography. A key challenge is posed by the need to stably position a 10cm diameter sphere of water in microgravity. Two methods are being developed. Orbitec is using controlled puffs of air from at least 6 independent directions to provided the positioning force. This approach has actually succeeded to position and stabilize a 4cm sphere during a KC 135 segment. Guigne International is using the radiation pressure of high frequency sound. These transducers have been organized into a device in the shape of a dodecahedron. This apparatus 'SPACE DRUMS' has already been approved for use for combustion synthesis experiments on the International Space Station. A key opportunity presented by the ripple turbulence data is its use in driving the development of codes to simulate its properties.

Containerless Ripple Turbulence

NASA Technical Reports Server (NTRS)

Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

2002-01-01

One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k(sup 5/3) which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M$ millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear interaction. Furthermore, the steady state distribution of energy again follows a Kolmogorov scaling law; in this case the ripple energy is distributed according to 1/k (sup 7/4). Again, in parallel with vortex turbulence ripple turbulence exhibits intermittency. The problem of ripple turbulence presents an experimental opportunity to generate data in a controlled, benchmarked system. In particular the surface of a sphere is an ideal environment to study ripple turbulence. Waves run around the sphere and interact with each other, and the effect of walls is eliminated. In microgravity this state can be realized for over 2 decades of frequency. Wave turbulence is a physically relevant problem in its own right. It has been studied on the surface of liquid hydrogen and its application to Alfven waves in space is a source of debate. Of course, application of wave turbulence perspectives to ocean waves has been a major success. The experiment which we plan to run in microgravity is conceptually straightforward. Ripples are excited on the surface of a spherical drop of fluid and then their amplitude is recorded with appropriate photography. A key challenge is posed by the need to stably position a 10cm diameter sphere of water in microgravity. Two methods are being developed. Orbitec is using controlled puffs of air from at least 6 independent directions to provided the positioning force. This approach has actually succeeded to position and stabilize a 4cm sphere during a KC 135 segment. Guigne International is using the radiation pressure of high frequency sound. These transducers have been organized into a device in the shape of a dodecahedron. This apparatus 'SPACE DRUMS' has already been approved for use for combustion synthesis experiments on the International Space Station. A key opportunity presented by the ripple turbulence data is its use in driving the development of codes to simulate its properties.

Geometrization of quantum physics

NASA Astrophysics Data System (ADS)

Ol'Khov, O. A.

2009-12-01

It is shown that the Dirac equation for free particle can be considered as a description of specific distortion of the space euclidean geometry (space topological defect). This approach is based on possibility of interpretation of the wave function as vector realizing representation of the fundamental group of the closed topological space-time 4-manifold. Mass and spin appear to be topological invariants. Such concept explains all so called “strange” properties of quantum formalism: probabilities, wave-particle duality, nonlocal instantaneous correlation between noninteracting particles (EPR-paradox) and so on. Acceptance of suggested geometrical concept means rejection of atomistic concept where all matter is considered as consisting of more and more small elementary particles. There is no any particles a priori, before measurement: the notions of particles appear as a result of classical interpretation of the contact of the region of the curved space with a device.

Cosmic clustering

DOE PAGES

Anninos, Dionysios; Denef, Frederik

2016-06-30

We show that the late time Hartle-Hawking wave function for a free massless scalar in a fixed de Sitter background encodes a sharp ultrametric structure for the standard Euclidean distance on the space of field configurations. This implies a hierarchical, tree-like organization of the state space, reflecting its genesis as a branched diffusion process. In conclusion, an equivalent mathematical structure organizes the state space of the Sherrington-Kirkpatrick model of a spin glass.

Analysis of the dependence of surfatron acceleration of electrons by an electromagnetic wave in space plasma on the particle momentum along the wave front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erokhin, A. N., E-mail: nerokhin@mx.iki.rssi.ru; Zol’nikova, N. N.; Erokhin, N. S.

Based on the numerical solution of the nonlinear nonstationary second-order equation for the wave phase on the particle trajectory, the dynamics of surfatron acceleration of electrons by an electromagnetic wave propagating across the external magnetic field in space plasma is analyzed as a function of the electron momentum along the wave front. Numerical calculations show that, for strongly relativistic initial values of the electron momentum component along the wave front g{sub y}(0) (the other parameters of the problem being the same), electrons are trapped into the regime of ultrarelativistic surfatron acceleration within a certain interval of the initial wave phasemore » Ψ(0) on the particle trajectory. It is assumed in the calculations that vertical bar Ψ(0) vertical bar ≤ π. For strongly relativistic values of g{sub y}(0), electrons are immediately trapped by the wave for 19% of the initial values of the phase Ψ(0) (favorable phases). For the rest of the values of Ψ(0), trapping does not occur even at long times. This circumstance substantially simplifies estimations of the wave damping due to particle acceleration in subsequent calculations. The dynamics of the relativistic factor and the components of the electron velocity and momentum under surfatron acceleration is also analyzed. The obtained results are of interest for the development of modern concepts of possible mechanisms of generation of ultrarelativistic particle fluxes in relatively calm space plasma, as well as for correct interpretation of observational data on the fluxes of such particles and explanation of possible reasons for the deviation of ultrarelativistic particle spectra detected in the heliosphere from the standard power-law scalings and the relation of these variations to space weather and large-scale atmospheric processes similar to tropical cyclones.« less

Three-dimensional coupled thermoelastodynamic stress and flux induced wave propagation for isotropic half-space with scalar potential functions

NASA Astrophysics Data System (ADS)

Hayati, Yazdan; Eskandari-Ghadi, Morteza

2018-02-01

An asymmetric three-dimensional thermoelastodynamic wave propagation with scalar potential functions is presented for an isotropic half-space, in such a way that the wave may be originated from an arbitrary either traction or heat flux applied on a patch at the free surface of the half-space. The displacements, stresses and temperature are presented within the framework of Biot's coupled thermoelasticity formulations. By employing a complete representation for the displacement and temperature fields in terms of two scalar potential functions, the governing equations of coupled thermoelasticity are uncoupled into a sixth- and a second-order partial differential equation in cylindrical coordinate system. By virtue of Fourier expansion and Hankel integral transforms, the angular and radial variables are suppressed respectively, and a 6{th}- and a 2{nd}-order ordinary differential equation in terms of depth are received, which are solved readily, from which the displacement, stresses and temperature fields are derived in transformed space by satisfying both the regularity and boundary conditions. By applying the inverse Hankel integral transforms, the displacements and temperature are numerically evaluated to determine the solutions in the real space. The numerical evaluations are done for three specific cases of vertical and horizontal time-harmonic patch traction and a constant heat flux passing through a circular disc on the surface of the half-space. It has been previously proved that the potential functions used in this paper are applicable from elastostatics to thermoelastodynamics. Thus, the analytical solutions presented in this paper are verified by comparing the results of this study with two specific problems reported in the literature, which are an elastodynamic problem and an axisymmetric quasi-static thermoelastic problem. To show the accuracy of numerical results, the solution of this study is also compared with the solution for elastodynamics exists in the literature for surface excitation, where a very good agreement is achieved. The formulations presented in this study may be used as benchmark for other related researches and it may be implemented in the related boundary integral equations.

Location identification of closed crack based on Duffing oscillator transient transition

NASA Astrophysics Data System (ADS)

Liu, Xiaofeng; Bo, Lin; Liu, Yaolu; Zhao, Youxuan; Zhang, Jun; Deng, Mingxi; Hu, Ning

2018-02-01

The existence of a closed micro-crack in plates can be detected by using the nonlinear harmonic characteristics of the Lamb wave. However, its location identification is difficult. By considering the transient nonlinear Lamb under the noise interference, we proposed a location identification method for the closed crack based on the quantitative measurement of Duffing oscillator transient transfer in the phase space. The sliding short-time window was used to create a window truncation of to-be-detected signal. And then, the periodic extension processing for transient nonlinear Lamb wave was performed to ensure that the Duffing oscillator has adequate response time to reach a steady state. The transient autocorrelation method was used to reduce the occurrence of missed harmonic detection due to the random variable phase of nonlinear Lamb wave. Moreover, to overcome the deficiency in the quantitative analysis of Duffing system state by phase trajectory diagram and eliminate the misjudgment caused by harmonic frequency component contained in broadband noise, logic operation method of oscillator state transition function based on circular zone partition was adopted to establish the mapping relation between the oscillator transition state and the nonlinear harmonic time domain information. Final state transition discriminant function of Duffing oscillator was used as basis for identifying the reflected and transmitted harmonics from the crack. Chirplet time-frequency analysis was conducted to identify the mode of generated harmonics and determine the propagation speed. Through these steps, accurate position identification of the closed crack was achieved.

Elastic-wave-mode separation in TTI media with inverse-distance weighted interpolation involving position shading

NASA Astrophysics Data System (ADS)

Wang, Jian; Meng, Xiaohong; Zheng, Wanqiu

2017-10-01

The elastic-wave reverse-time migration of inhomogeneous anisotropic media is becoming the hotspot of research today. In order to ensure the accuracy of the migration, it is necessary to separate the wave mode into P-wave and S-wave before migration. For inhomogeneous media, the Kelvin-Christoffel equation can be solved in the wave-number domain by using the anisotropic parameters of the mesh nodes, and the polarization vector of the P-wave and S-wave at each node can be calculated and transformed into the space domain to obtain the quasi-differential operators. However, this method is computationally expensive, especially for the process of quasi-differential operators. In order to reduce the computational complexity, the wave-mode separation of mixed domain can be realized on the basis of a reference model in the wave-number domain. But conventional interpolation methods and reference model selection methods reduce the separation accuracy. In order to further improve the separation effect, this paper introduces an inverse-distance interpolation method involving position shading and uses the reference model selection method of random points scheme. This method adds the spatial weight coefficient K, which reflects the orientation of the reference point on the conventional IDW algorithm, and the interpolation process takes into account the combined effects of the distance and azimuth of the reference points. Numerical simulation shows that the proposed method can separate the wave mode more accurately using fewer reference models and has better practical value.

Origin of Everything and the 21 Dimensions of the Universe

NASA Astrophysics Data System (ADS)

Loev, Mark

2009-03-01

The Dimensions of the Universe correspond with the Dimensions of the human body. The emotion that is a positive for every dimension is Love. The negative emotion that effects each dimension are listed. All seven negative emotions effect Peace, Love and Happiness. 21st Dimension: Happiness Groin & Heart 20th Dimension: Love Groin & Heart 19th Dimension: Peace Groin & heart 18th Dimension: Imagination Wave Eyes Anger 17th Dimension: Z Wave / Closed Birth 16th Dimension: Electromagnetic Wave Ears Anger 15th Dimension: Universal Wave Skin Worry 14th Dimension: Lover Wave Blood Hate 13th Dimension: Disposal Wave Buttocks Fear 12th Dimension: Builder Wave Hands Hate 11th Dimension: Energy Wave Arms Fear 10th Dimension: Time Wave Brain Pessimism 9th Dimension: Gravity Wave Legs Fear 8th Dimension: Sweet Wave Pancreas Fear 7th Dimension: File Wave Left Lung Fear 6th Dimension: Breathing Wave Right Lung Fear 5th Dimension: Digestive Wave Stomach Fear 4th Dimension: Swab Wave Liver Guilt 3rd Dimension: Space Wave Face Sadness 2nd Dimension: Line Wave Mouth Revenge 1st Dimension: Dot Wave Nose Sadness The seven deadly sins correspond: Anger Hate Sadness Fear Worry Pessimism Revenge Note: Guilt is fear

TM surface wave diffraction by a truncated dielectric slab recessed in a perfectly conducting surface. [considering flush mounted space shuttle antenna

NASA Technical Reports Server (NTRS)

Pathak, P. H.; Kouyoumjian, R. G.

1974-01-01

The diffraction of a TM sub o surface wave by a terminated dielectric slab which is flush mounted in a perfectly conducting surface is studied. The incident surface wave gives rise to waves reflected and diffracted by the termination; these reflected and diffracted fields may be expressed in terms of the geometrical theory of diffraction by introducing surface wave reflection and diffraction coefficients which are associated with the termination. In this investigation, the surface wave reflection and diffraction coefficients have been deduced from a formally exact solution to this canonical problem. The solution is obtained by a combination of the generalized scattering matrix technique and function theoretic methods.

Effect of EMIC Wave Normal Angle Distribution on Relativistic Electron Scattering Based on the Newly Developed Self-consistent RC/EMIC Waves Model by Khazanov et al. [2006

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gallagher, D. L.; Gamayunov, K.

2007-01-01

It is well known that the effects of EMIC waves on RC ion and RB electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. Therefore, realistic characteristics of EMIC waves should be properly determined by modeling the RC-EMIC waves evolution self-consistently. Such a selfconsistent model progressively has been developing by Khaznnov et al. [2002-2006]. It solves a system of two coupled kinetic equations: one equation describes the RC ion dynamics and another equation describes the energy density evolution of EMIC waves. Using this model, we present the effectiveness of relativistic electron scattering and compare our results with previous work in this area of research.

Scattering of SH wave by a semi-cylindrical salient near vertical interface in the bi-material half space

NASA Astrophysics Data System (ADS)

Qi, Hui; Zhang, Xi-meng

2017-10-01

With the aid of the Green function method and image method, the problem of scattering of SH-wave by a semi-cylindrical salient near vertical interface in bi-material half-space is considered to obtain its steady state response. Firstly, by the means of the image method, Green function which is the essential solution of displacement field is constructed to satisfy the stress-free condition on the horizontal boundary in a right-angle space including a semi-cylindrical salient and bearing a harmonic out-of-plane line source force at any point on the vertical boundary. Secondly, the bi-material is separated into two parts along the vertical interface, then unknown anti-plane forces are applied on the vertical interface, and according to the continuity condition, the first kind of Fredholm integral equations is established to determine unknown anti-plane forces by "the conjunction method", then the integral equations are reduced to the linear algebraic equations by effective truncation. Finally, the dynamic stress concentration factor (DSCF) around the edge of semi-cylindrical salient is calculated, and the influences of incident wave number, incident angle, effect of interface and different combination of material parameters, etc. on DSCF are discussed.

Precipitated Fluxes of Radiation Belt Electrons via Injection of Whistler-Mode Waves

NASA Astrophysics Data System (ADS)

Kulkarni, P.; Inan, U. S.; Bell, T. F.

2005-12-01

Inan et al. (U.S. Inan et al., Controlled precipitation of radiation belt electrons, Journal of Geophysical Research-Space Physics, 108 (A5), 1186, doi: 10.1029/2002JA009580, 2003.) suggested that the lifetime of energetic (a few MeV) electrons in the inner radiation belts may be moderated by in situ injection of whistler mode waves at frequencies of a few kHz. We use the Stanford 2D VLF raytracing program (along with an accurate estimation of the path-integrated Landau damping based on data from the HYDRA instrument on the POLAR spacecraft) to determine the distribution of wave energy throughout the inner radiation belts as a function of injection point, wave frequency and injection wave normal angle. To determine the total wave power injected and its initial distribution in k-space (i.e., wave-normal angle), we apply the formulation of Wang and Bell ( T.N.C. Wang and T.F. Bell, Radiation resistance of a short dipole immersed in a cold magnetoionic medium, Radio Science, 4 (2), 167-177, February 1969) for an electric dipole antenna placed at a variety of locations throughout the inner radiation belts. For many wave frequencies and wave normal angles the results establish that most of the radiated power is concentrated in waves whose wave normals are located near the resonance cone. The combined use of the radiation pattern and ray-tracing including Landau damping allows us to make quantitative estimates of the magnetospheric distribution of wave power density for different source injection points. We use these results to estimate the number of individual space-based transmitters needed to significantly impact the lifetimes of energetic electrons in the inner radiation belts. Using the wave power distribution, we finally determine the energetic electron pitch angle scattering and the precipitated flux signatures that would be detected.

A New Algorithm with Plane Waves and Wavelets for Random Velocity Fields with Many Spatial Scales

NASA Astrophysics Data System (ADS)

Elliott, Frank W.; Majda, Andrew J.

1995-03-01

A new Monte Carlo algorithm for constructing and sampling stationary isotropic Gaussian random fields with power-law energy spectrum, infrared divergence, and fractal self-similar scaling is developed here. The theoretical basis for this algorithm involves the fact that such a random field is well approximated by a superposition of random one-dimensional plane waves involving a fixed finite number of directions. In general each one-dimensional plane wave is the sum of a random shear layer and a random acoustical wave. These one-dimensional random plane waves are then simulated by a wavelet Monte Carlo method for a single space variable developed recently by the authors. The computational results reported in this paper demonstrate remarkable low variance and economical representation of such Gaussian random fields through this new algorithm. In particular, the velocity structure function for an imcorepressible isotropic Gaussian random field in two space dimensions with the Kolmogoroff spectrum can be simulated accurately over 12 decades with only 100 realizations of the algorithm with the scaling exponent accurate to 1.1% and the constant prefactor accurate to 6%; in fact, the exponent of the velocity structure function can be computed over 12 decades within 3.3% with only 10 realizations. Furthermore, only 46,592 active computational elements are utilized in each realization to achieve these results for 12 decades of scaling behavior.

Mode-Division-Multiplexing of Multiple Bessel-Gaussian Beams Carrying Orbital-Angular-Momentum for Obstruction-Tolerant Free-Space Optical and Millimetre-Wave Communication Links.

PubMed

Ahmed, Nisar; Zhao, Zhe; Li, Long; Huang, Hao; Lavery, Martin P J; Liao, Peicheng; Yan, Yan; Wang, Zhe; Xie, Guodong; Ren, Yongxiong; Almaiman, Ahmed; Willner, Asher J; Ashrafi, Solyman; Molisch, Andreas F; Tur, Moshe; Willner, Alan E

2016-03-01

We experimentally investigate the potential of using 'self-healing' Bessel-Gaussian beams carrying orbital-angular-momentum to overcome limitations in obstructed free-space optical and 28-GHz millimetre-wave communication links. We multiplex and transmit two beams (l = +1 and +3) over 1.4 metres in both the optical and millimetre-wave domains. Each optical beam carried 50-Gbaud quadrature-phase-shift-keyed data, and each millimetre-wave beam carried 1-Gbaud 16-quadrature-amplitude-modulated data. In both types of links, opaque disks of different sizes are used to obstruct the beams at different transverse positions. We observe self-healing after the obstructions, and assess crosstalk and power penalty when data is transmitted. Moreover, we show that Bessel-Gaussian orbital-angular-momentum beams are more tolerant to obstructions than non-Bessel orbital-angular-momentum beams. For example, when obstructions that are 1 and 0.44 the size of the l = +1 beam, are placed at beam centre, optical and millimetre-wave Bessel-Gaussian beams show ~6 dB and ~8 dB reduction in crosstalk, respectively.

Mode-Division-Multiplexing of Multiple Bessel-Gaussian Beams Carrying Orbital-Angular-Momentum for Obstruction-Tolerant Free-Space Optical and Millimetre-Wave Communication Links

PubMed Central

Ahmed, Nisar; Zhao, Zhe; Li, Long; Huang, Hao; Lavery, Martin P. J.; Liao, Peicheng; Yan, Yan; Wang, Zhe; Xie, Guodong; Ren, Yongxiong; Almaiman, Ahmed; Willner, Asher J.; Ashrafi, Solyman; Molisch, Andreas F.; Tur, Moshe; Willner, Alan E.

2016-01-01

We experimentally investigate the potential of using ‘self-healing’ Bessel-Gaussian beams carrying orbital-angular-momentum to overcome limitations in obstructed free-space optical and 28-GHz millimetre-wave communication links. We multiplex and transmit two beams (l = +1 and +3) over 1.4 metres in both the optical and millimetre-wave domains. Each optical beam carried 50-Gbaud quadrature-phase-shift-keyed data, and each millimetre-wave beam carried 1-Gbaud 16-quadrature-amplitude-modulated data. In both types of links, opaque disks of different sizes are used to obstruct the beams at different transverse positions. We observe self-healing after the obstructions, and assess crosstalk and power penalty when data is transmitted. Moreover, we show that Bessel-Gaussian orbital-angular-momentum beams are more tolerant to obstructions than non-Bessel orbital-angular-momentum beams. For example, when obstructions that are 1 and 0.44 the size of the l = +1 beam, are placed at beam centre, optical and millimetre-wave Bessel-Gaussian beams show ~6 dB and ~8 dB reduction in crosstalk, respectively. PMID:26926068

The alpha channeling effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisch, N. J.

2015-12-10

Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a waymore » that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.« less

The alpha channeling effect

NASA Astrophysics Data System (ADS)

Fisch, N. J.

2015-12-01

Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a way that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.

High Resolution Millimeter Wave Detection of Vertical Cracks in the Space Shuttle External Tank Spray-On-Foam Insulation (SOFI)

NASA Technical Reports Server (NTRS)

Kharkovsky, S.; Zoughi, R.; Hepburn, F.

2006-01-01

Space Shuttle Columbia s catastrophic failure, the separation of a piece of spray-on-foam insulation (SOFI) from the external tank (ET) in the Space Shuttle Discovery s flight in 2005 and crack detected in its ET foam prior to its successful launch in 2006 emphasize the need for effective nondestructive methods for inspecting the shuttle ET SOFI. Millimeter wave nondestructive testing methods have been considered as potential and effective inspection tools for evaluating the integrity of the SOFI. This paper presents recent results of an investigation for the purpose of detecting vertical cracks in SOFI panels using a focused millimeter wave (150 GHz) reflectometer. The presented images of the SOFI panels show the capability of this reflectometer for detecting tight vertical cracks (also as a function of crack opening dimension) in exposed SOFI panels and while covered by a piece of SOFI ramp simulating a more realistic and challenging situation.

Spectral properties of Langmuir and beam-mode waves observed inside terrestrial foreshock by Cluster spacecraf

NASA Astrophysics Data System (ADS)

Pisa, D.; Soucek, J.; Santolik, O.

2016-12-01

Electrostatic plasma waves are commonly observed in the upstream regions of planetary shocks. Solar wind electrons accelerated at the shock front are reflected back into the solar wind and form electron beams. The electron distribution becomes unstable and electrostatic waves are generated inside the foreshock region. The processes of generation and evolution of electrostatic waves significantly depend on the solar wind plasma conditions and generally exhibit complex behavior. Langmuir waves can be identified as intense narrowband emission at the local plasma frequency and weaker broadband beam-mode waves below and above the plasma frequency deeper in the downstream region. We present a long-term survey of Langmuir and beam-mode waves in the vicinity of the plasma frequency observed upstream of the terrestrial bow shock by the Cluster spacecraft. Using solar wind data and bow shock positions from OMNI, as well as in-situ measurements of interplanetary magnetic field, we have mapped all available spacecraft positions into foreshock coordinates. For a study of plasma waves, we have used spectra and local plasma frequencies obtained from a passive and active mode of the WHISPER instrument. We show a spatial distribution of wave frequencies and spectral widths as a function of foreshock positions and solar wind conditions.

Evaluation of cluster expansions and correlated one-body properties of nuclei

NASA Astrophysics Data System (ADS)

Moustakidis, Ch. C.; Massen, S. E.; Panos, C. P.; Grypeos, M. E.; Antonov, A. N.

2001-07-01

Three different cluster expansions for the evaluation of correlated one-body properties of s-p and s-d shell nuclei are compared. Harmonic oscillator wave functions and Jastrow-type correlations are used, while analytical expressions are obtained for the charge form factor, density distribution, and momentum distribution by truncating the expansions and using a standard Jastrow correlation function f. The harmonic oscillator parameter b and the correlation parameter β have been determined by a least-squares fit to the experimental charge form factors in each case. The information entropy of nuclei in position space (Sr) and momentum space (Sk) according to the three methods are also calculated. It is found that the larger the entropy sum, S=Sr+Sk (the net information content of the system), the smaller the values of χ2. This indicates that maximal S is a criterion of the quality of a given nuclear model, according to the maximum entropy principle. Only two exceptions to this rule, out of many cases examined, were found. Finally an analytic expression for the so-called ``healing'' or ``wound'' integrals is derived with the function f considered, for any state of the relative two-nucleon motion, and their values in certain cases are computed and compared.

Circumferential and functional re-entry of in vivo slow-wave activity in the porcine small intestine.

PubMed

Angeli, T R; O'Grady, G; Du, P; Paskaranandavadivel, N; Pullan, A J; Bissett, I P; Cheng, L K

2013-05-01

Slow-waves modulate the pattern of small intestine contractions. However, the large-scale spatial organization of intestinal slow-wave pacesetting remains uncertain because most previous studies have had limited resolution. This study applied high-resolution (HR) mapping to evaluate intestinal pacesetting mechanisms and propagation patterns in vivo. HR serosal mapping was performed in anesthetized pigs using flexible arrays (256 electrodes; 32 × 8; 4 mm spacing), applied along the jejunum. Slow-wave propagation patterns, frequencies, and velocities were calculated. Slow-wave initiation sources were identified and analyzed by animation and isochronal activation mapping. Analysis comprised 32 recordings from nine pigs (mean duration 5.1 ± 3.9 min). Slow-wave propagation was analyzed, and a total of 26 sources of slow-wave initiation were observed and classified as focal pacemakers (31%), sites of functional re-entry (23%) and circumferential re-entry (35%), or indeterminate sources (11%). The mean frequencies of circumferential and functional re-entry were similar (17.0 ± 0.3 vs 17.2 ± 0.4 cycle min(-1) ; P = 0.5), and greater than that of focal pacemakers (12.7 ± 0.8 cycle min(-1) ; P < 0.001). Velocity was anisotropic (12.9 ± 0.7 mm s(-1) circumferential vs 9.0 ± 0.7 mm s(-1) longitudinal; P < 0.05), contributing to the onset and maintenance of re-entry. This study has shown multiple patterns of slow-wave initiation in the jejunum of anesthetized pigs. These results constitute the first description and analysis of circumferential re-entry in the gastrointestinal tract and functional re-entry in the in vivo small intestine. Re-entry can control the direction, pattern, and frequency of slow-wave propagation, and its occurrence and functional significance merit further investigation. © 2013 Blackwell Publishing Ltd.

Gravitational Waves Propagation through the Stochastic Background of Gravitational Waves

NASA Astrophysics Data System (ADS)

Frajuca, C.; Bortoli, F. S.; Nakamoto, F. Y.; Santos, G. A.

2018-02-01

With the recent claim that gravitational waves were finally detected and with other efforts around the world for GWs detection, its is reasonable to imagine that the relic gravitational wave background could be detected in some time in the future and with such information gather some hints about the origin of the universe. But, it’s also be considered that gravity has self-interaction, with such assumption it’s reasonable to expect that these gravitational wave will interact with the relic or nonrelic GW background by scattering, for example. Such interaction should decrease the distance which such propagating waves could be detected The propagation of gravitational waves (GWs) is analyzed in an asymptotically de Sitter space by the perturbation expansion around Minkowski space using a scalar component. Using the case of de Sitter inflationary phase scenario, the perturbation propagates through a FRW background. The GW, using the actual value for the Hubble scale (Ho), has a damping factor with a very small valor for the size of the observational universe; the stochastic relic GW background is given by a dimensionless function of the frequency. In this work we analyze this same damping including the gravitational wave background due to astrophysical sources such background is 3 orders of magnitude bigger in some frequencies and produces a higher damping factor.

Investigating Stimulated Wave-Particle Interaction of Radiation Belt Particles with Space-Borne Whistler Mode Transmitters

DTIC Science & Technology

2009-03-30

presented. ii Figure 12. Arrival time of electrons during the positive phase of charge on the antenna. ........ 15 The distances...relativistic electrons in the radiation belt. The target electrons are in the energy range of 0.5~3.0 MeV in the region between L = 1.7~2.2, where L is the...waves to pitch-angle diffuse the electrons into the loss-cone, i.e., to precipitate the relativistic electrons into the neutral atmosphere. There are

Asympotics with positive cosmological constant

NASA Astrophysics Data System (ADS)

Bonga, Beatrice; Ashtekar, Abhay; Kesavan, Aruna

2014-03-01

Since observations to date imply that our universe has a positive cosmological constant, one needs an extension of the theory of isolated systems and gravitational radiation in full general relativity from the asymptotically flat to asymptotically de Sitter space-times. In current definitions, one mimics the boundary conditions used in asymptotically AdS context to conclude that the asymptotic symmetry group is the de Sitter group. However, these conditions severely restricts radiation and in fact rules out non-zero flux of energy, momentum and angular momentum carried by gravitational waves. Therefore, these formulations of asymptotically de Sitter space-times are uninteresting beyond non-radiative spacetimes. The situation is compared and contrasted with conserved charges and fluxes at null infinity in asymptotically flat space-times.

Wave field synthesis of a virtual source located in proximity to a loudspeaker array.

PubMed

Lee, Jung-Min; Choi, Jung-Woo; Kim, Yang-Hann

2013-09-01

For the derivation of 2.5-dimensional operator in wave field synthesis, a virtual source is assumed to be positioned far from a loudspeaker array. However, such far-field approximation inevitably results in a reproduction error when the virtual source is placed adjacent to an array. In this paper, a method is proposed to generate a virtual source close to and behind a continuous line array of loudspeakers. A driving function is derived by reducing a surface integral (Rayleigh integral) to a line integral based on the near-field assumption. The solution is then combined with the far-field formula of wave field synthesis by introducing a weighting function that can adjust the near- and far-field contribution of each driving function. This enables production of a virtual source anywhere in relation to the array. Simulations show the proposed method can reduce the reproduction error to below -18 dB, regardless of the virtual source position.

Acoustic radiation force control: Pulsating spherical carriers.

PubMed

Rajabi, Majid; Mojahed, Alireza

2018-02-01

The interaction between harmonic plane progressive acoustic beams and a pulsating spherical radiator is studied. The acoustic radiation force function exerted on the spherical body is derived as a function of the incident wave pressure and the monopole vibration characteristics (i.e., amplitude and phase) of the body. Two distinct strategies are presented in order to alter the radiation force effects (i.e., pushing and pulling states) by changing its magnitude and direction. In the first strategy, an incident wave field with known amplitude and phase is considered. It is analytically shown that the zero- radiation force state (i.e., radiation force function cancellation) is achievable for specific pulsation characteristics belong to a frequency-dependent straight line equation in the plane of real-imaginary components (i.e., Nyquist Plane) of prescribed surface displacement. It is illustrated that these characteristic lines divide the mentioned displacement plane into two regions of positive (i.e., pushing) and negative (i.e., pulling) radiation forces. In the second strategy, the zero, negative and positive states of radiation force are obtained through adjusting the incident wave field characteristics (i.e., amplitude and phase) which insonifies the radiator with prescribed pulsation characteristics. It is proved that zero radiation force state occurs for incident wave pressure characteristics belong to specific frequency-dependent circles in Nyquist plane of incident wave pressure. These characteristic circles divide the Nyquist plane into two distinct regions corresponding to positive (out of circles) and negative (in the circles) values of radiation force function. It is analytically shown that the maximum amplitude of negative radiation force is exactly equal to the amplitude of the (positive) radiation force exerted upon the sphere in the passive state, by the same incident field. The developed concepts are much more deepened by considering the required power supply for distinct cases of zero, negative and positive radiation force states along with the frequency dependent asymmetry index. In addition, considering the effect of phase difference between the incident wave field and the pulsating object, and its possible variation with respect to spatial position of object, some practical points about the spatial average of generated radiation force, the optimal state of operation, the stability of zero radiation force states and the possibly of precise motion control are discussed. This work would extend the novel concept of smart carriers to and may be helpful for robust single-beam acoustic handling techniques. Furthermore, the shown capability of precise motion control may be considered as a new way toward smart acoustic driven micro-mechanisms and micro-machines. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimentally determining the locations of two astigmatic images for an underwater light source

NASA Astrophysics Data System (ADS)

Yang, Pao-Keng; Liu, Jian-You; Ying, Shang-Ping

2015-05-01

Images formed by an underwater object from light rays refracted in the sagittal and tangential planes are located at different positions for an oblique viewing position. The overlapping of these two images from the observer's perspective will thus prevent the image-splitting astigmatism from being directly observable. In this work, we present a heuristic method to experimentally visualize the astigmatism. A point light source is used as an underwater object and the emerging wave front is recorded using a Shack-Hartmann wave-front sensor. The wave front is found to deform from a circular paraboloid to an elliptic paraboloid as the viewing position changes from normal to oblique. Using geometric optics, we derive an analytical expression for the image position as a function of the rotating angle of an arm used to carry the wave-front sensor in our experimental setup. The measured results are seen to be in good agreement with the theoretical predictions.

Composite fermion basis for two-component Bose gases

NASA Astrophysics Data System (ADS)

Meyer, Marius; Liabotro, Ola

The composite fermion (CF) construction is known to produce wave functions that are not necessarily orthogonal, or even linearly independent, after projection. While usually not a practical issue in the quantum Hall regime, we have previously shown that it presents a technical challenge for rotating Bose gases with low angular momentum. These are systems where the CF approach yield surprisingly good approximations to the exact eigenstates of weak short-range interactions, and so solving the problem of linearly dependent wave functions is of interest. It can also be useful for studying CF excitations for fermions. Here we present several ways of constructing a basis for the space of ``simple CF states'' for two-component rotating Bose gases in the lowest Landau level, and prove that they all give a basis. Using the basis, we study the structure of the lowest-lying state using so-called restricted wave functions. We also examine the scaling of the overlap between the exact and CF wave functions at the maximal possible angular momentum for simple states. This work was financially supported by the Research Council of Norway.

Seniority number description of potential energy surfaces: Symmetric dissociation of water, N{sub 2}, C{sub 2}, and Be{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bytautas, Laimutis; Scuseria, Gustavo E.; Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589

2015-09-07

The present study further explores the concept of the seniority number (Ω) by examining different configuration interaction (CI) truncation strategies in generating compact wave functions in a systematic way. While the role of Ω in addressing static (strong) correlation problem has been addressed in numerous previous studies, the usefulness of seniority number in describing weak (dynamic) correlation has not been investigated in a systematic way. Thus, the overall objective in the present work is to investigate the role of Ω in addressing also dynamic electron correlation in addition to the static correlation. Two systematic CI truncation strategies are compared beyondmore » minimal basis sets and full valence active spaces. One approach is based on the seniority number (defined as the total number of singly occupied orbitals in a determinant) and another is based on an excitation-level limitation. In addition, molecular orbitals are energy-optimized using multiconfigurational-self-consistent-field procedure for all these wave functions. The test cases include the symmetric dissociation of water (6-31G), N{sub 2} (6-31G), C{sub 2} (6-31G), and Be{sub 2} (cc-pVTZ). We find that the potential energy profile for H{sub 2}O dissociation can be reasonably well described using only the Ω = 0 sector of the CI wave function. For the Be{sub 2} case, we show that the full CI potential energy curve (cc-pVTZ) is almost exactly reproduced using either Ω-based (including configurations having up to Ω = 2 in the virtual-orbital-space) or excitation-based (up to single-plus-double-substitutions) selection methods, both out of a full-valence-reference function. Finally, in dissociation cases of N{sub 2} and C{sub 2}, we shall also consider novel hybrid wave functions obtained by a union of a set of CI configurations representing the full valence space and a set of CI configurations where seniority-number restriction is imposed for a complete set (full-valence-space and virtual) of correlated molecular orbitals, simultaneously. We discuss the usefulness of the seniority number concept in addressing both static and dynamic electron correlation problems along dissociation paths.« less

Dirac-Kähler particle in Riemann spherical space: boson interpretation

NASA Astrophysics Data System (ADS)

Ishkhanyan, A. M.; Florea, O.; Ovsiyuk, E. M.; Red'kov, V. M.

2015-11-01

In the context of the composite boson interpretation, we construct the exact general solution of the Dirac--K\\"ahler equation for the case of the spherical Riemann space of constant positive curvature, for which due to the geometry itself one may expect to have a discrete energy spectrum. In the case of the minimal value of the total angular momentum, $j=0$, the radial equations are reduced to second-order ordinary differential equations, which are straightforwardly solved in terms of the hypergeometric functions. For non-zero values of the total angular momentum, however, the radial equations are reduced to a pair of complicated fourth-order differential equations. Employing the factorization approach, we derive the general solution of these equations involving four independent fundamental solutions written in terms of combinations of the hypergeometric functions. The corresponding discrete energy spectrum is then determined via termination of the involved hypergeometric series, resulting in quasi-polynomial wave-functions. The constructed solutions lead to notable observations when compared with those for the ordinary Dirac particle. The energy spectrum for the Dirac-K\\"ahler particle in spherical space is much more complicated. Its structure substantially differs from that for the Dirac particle since it consists of two paralleled energy level series each of which is twofold degenerate. Besides, none of the two separate series coincides with the series for the Dirac particle. Thus, the Dirac--K\\"ahler field cannot be interpreted as a system of four Dirac fermions. Additional arguments supporting this conclusion are discussed.

Long-term Variability of Beach Cusps

NASA Astrophysics Data System (ADS)

Pianca, C.; Holman, R. A.; Siegle, E.

2016-02-01

The most curious morphological features observed on beaches are the cusps. Due to their rhythmic spacing, beach cusps have attracted many observers and many, often contradictory, theories as to their form. Moreover, most of the research about beach cusps has focused on their formation. Few had available long time series to study such things as the variability of alongshore and cross-shore position and spacing on the cusp field, the presence, longevity and interactions between higher and lower sets of cusps, and the processes by which cusp fields extend, shrink or change length scale. The purpose of this work is to use long-term data sets of video images from two study sites, an intermediate (Duck, USA, 26 years) and a reflective beach (Massaguaçu, Brazil, 3 years), to investigate the temporal and spatial changes of cusps conditions. Time-evolving shoreline data were first extracted using an algorithm called ASLIM (Pianca et al 2015). Cusps were then identified based on the band-passed variability of time exposure image data about this shoreline as a function of elevation relative to MSL. The identified beaches cusps will be analyzed for cusp spacing, positions (upper or lower cusps), alongshore variability, merging events, percentage of cusp events, patterns of the events and time scales of variability. Finally, the relationship of these characteristics to environmental conditions (wave, tides, beach conditions) will be studied.

Variation Process of Radiation Belt Electron Fluxes due to Interaction With Chorus and EMIC Rising-tone Emissions Localized in Longitude

NASA Astrophysics Data System (ADS)

Kubota, Y.; Omura, Y.

2017-12-01

Using results of test particle simulations of a large number of electrons interacting with a pair of chorus emissions, we create Green's functions to model the electron distribution function after all of the possible interactions with the waves [Omura et al., 2015]. Assuming that the waves are generated in a localized range of longitudes in the dawn side, we repeat taking the convolution integral of the Green's function with the distribution function of the electrons injected into the generation region of the localized waves. From numerical and theoretical analyses, we find that electron acceleration process only takes place efficiently below 4 MeV. Because extremely relativistic electrons go through the wave generation region rapidly due to grad-B0 and curvature drift, they don't have enough interaction time to be accelerated. In setting up the electrons after all interaction with chorus emissions as initial electron distribution function, we also compute the loss process of radiation belt electron fluxes due to interaction with EMIC rising-tone emissions generated in a localized range of longitudes in the dusk side [Kubota and Omura,2017]. References: (1) Omura, Y., Y. Miyashita, M. Yoshikawa, D. Summers, M. Hikishima, Y. Ebihara, and Y. Kubota (2015), Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere, J. Geophys. Res. Space Physics, 120, 9545-9562, doi:10.1002/2015JA021563. (2) Kubota, Y., and Y. Omura (2017), Rapid precipitation of radiation belt electrons induced by EMIC rising tone emissions localized in longitude inside and outside the plasmapause, J. Geophys. Res. Space Physics, 122, 293-309, doi:10.1002/2016JA023267.

GPS, Earthquakes, the Ionosphere, and the Space Shuttle

NASA Technical Reports Server (NTRS)

Calais, Eric; Minster, J. Bernard

1998-01-01

Sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce infrasonic pressure waves in the atmosphere. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these acoustic waves induce variations of the ionospheric electron density. The Global Positioning System provides a way of directly measuring the Total Electron Content in the ionosphere and, therefore. of detecting such perturbations in the upper atmosphere. In this work, we demonstrate the capabilities of the GPS technique to detect ionospheric perturbations caused by the January 17. 1994, M (sub w) =6.7, Northridge earthquake and the STS-58 Space Shuttle ascent. In both cases, we observe a perturbation of the ionospheric electron density lasting for about 30 m, with periods less than 10 m. The perturbation is complex and shows two sub-events separated by about 15 m. The phase velocities and waveform characteristics of the two sub-events lead us to interpret the first arrival as the direct propagation of 2 free wave, followed by oscillatory guided waves propagating along horizontal atmospheric interfaces at 120 km altitude and below.

Wave dispersion and propagation in state-based peridynamics

NASA Astrophysics Data System (ADS)

Butt, Sahir N.; Timothy, Jithender J.; Meschke, Günther

2017-11-01

Peridynamics is a nonlocal continuum model which offers benefits over classical continuum models in cases, where discontinuities, such as cracks, are present in the deformation field. However, the nonlocal characteristics of peridynamics leads to a dispersive dynamic response of the medium. In this study we focus on the dispersion properties of a state-based linear peridynamic solid model and specifically investigate the role of the peridynamic horizon. We derive the dispersion relation for one, two and three dimensional cases and investigate the effect of horizon size, mesh size (lattice spacing) and the influence function on the dispersion properties. We show how the influence function can be used to minimize wave dispersion at a fixed lattice spacing and demonstrate it qualitatively by wave propagation analysis in one- and two-dimensional models of elastic solids. As a main contribution of this paper, we propose to associate peridynamic non-locality expressed by the horizon with a characteristic length scale related to the material microstructure. To this end, the dispersion curves obtained from peridynamics are compared with experimental data for two kinds of sandstone.

Discretized energy minimization in a wave guide with point sources

NASA Technical Reports Server (NTRS)

Propst, G.

1994-01-01

An anti-noise problem on a finite time interval is solved by minimization of a quadratic functional on the Hilbert space of square integrable controls. To this end, the one-dimensional wave equation with point sources and pointwise reflecting boundary conditions is decomposed into a system for the two propagating components of waves. Wellposedness of this system is proved for a class of data that includes piecewise linear initial conditions and piecewise constant forcing functions. It is shown that for such data the optimal piecewise constant control is the solution of a sparse linear system. Methods for its computational treatment are presented as well as examples of their applicability. The convergence of discrete approximations to the general optimization problem is demonstrated by finite element methods.

The dielectric function of weakly ionized dusty plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; China Research Institute of Radio wave Propagation; Wu, Jian

2016-07-15

Using classical Boltzmann kinetic theory, the dielectric function of weakly ionized unmagnetized dusty plasma is derived. The elastic Coulomb collision and inelastic charging collision of electrons with charged dust particle as well as charge variation on dust surface are taken into account. The theoretical result is applied to analyze the propagation of electromagnetic wave in a dusty plasma. It is demonstrated that the additional collision mechanism provided by charged dust particle can significantly increase the absorbed power of electromagnetic wave. These increases are mainly determined by the dust radius, density, and the charge numbers on the dust surface. The obtainedmore » results will support an enhanced understanding of the wave propagation processes in space and laboratory dusty plasmas.« less

Beyond the Schr{umlt o}dinger Equation: Quantum Motion with Traversal Time Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokolovski, D.

1997-12-01

We study a quantum particle, for which the duration {tau} it spends in some region of space is controlled by a meter, e.g., a Larmor clock. The particle is described by a wave function {Psi}(x,t{vert_bar}{tau}) , with {vert_bar}{Psi}(x,t{vert_bar}{tau}){vert_bar}{sup 2} giving the distribution of the meter{close_quote}s readings at location x . The wave function satisfies the {open_quotes}clocked{close_quotes} Schr{umlt o}dinger equation, which we solve numerically for the cases of bound motion and wave packet scattering. The method is shown to be a natural extension of the conventional quantum mechanics. {copyright} {ital 1997} {ital The American Physical Society}

Rogue waves and entropy consumption

NASA Astrophysics Data System (ADS)

Hadjihoseini, Ali; Lind, Pedro G.; Mori, Nobuhito; Hoffmann, Norbert P.; Peinke, Joachim

2017-11-01

Based on data from the Sea of Japan and the North Sea the occurrence of rogue waves is analyzed by a scale-dependent stochastic approach, which interlinks fluctuations of waves for different spacings. With this approach we are able to determine a stochastic cascade process, which provides information of the general multipoint statistics. Furthermore the evolution of single trajectories in scale, which characterize wave height fluctuations in the surroundings of a chosen location, can be determined. The explicit knowledge of the stochastic process enables to assign entropy values to all wave events. We show that for these entropies the integral fluctuation theorem, a basic law of non-equilibrium thermodynamics, is valid. This implies that positive and negative entropy events must occur. Extreme events like rogue waves are characterized as negative entropy events. The statistics of these entropy fluctuations changes with the wave state, thus for the Sea of Japan the statistics of the entropies has a more pronounced tail for negative entropy values, indicating a higher probability of rogue waves.

Wigner functions for nonparaxial, arbitrarily polarized electromagnetic wave fields in free space.

PubMed

Alonso, Miguel A

2004-11-01

New representations are defined for describing electromagnetic wave fields in free space exactly in terms of rays for any wavelength, level of coherence or polarization, and numerical aperture, as long as there are no evanescent components. These representations correspond to tensors assigned to each ray such that the electric and magnetic energy densities, the Poynting vector, and the polarization properties of the field correspond to simple integrals involving these tensors for the rays that go through the specified point. For partially coherent fields, the ray-based approach provided by the new representations can reduce dramatically the computation times for the physical properties mentioned earlier.

Patterns in the Waves

NASA Astrophysics Data System (ADS)

Coco, G.; Guza, R. T.; Garnier, R.; Lomonaco, P.; Lopez De San Roman Blanco, B.; Dalrymple, R. A.; Xu, M.

2014-12-01

Edge waves, gravity waves trapped close to the shoreline by refraction, can in some cases form a standing wave pattern with alongshore periodic sequence of high and low runup. Nonlinear mechanisms for generation of edge waves by monochromatic waves incident on a planar beach from deep water have been elaborated theoretically and in the lab. Edge waves have been long considered a potential source for alongshore periodic morphological patterns in the swash (e.g., beach cusps), and edge-wave based predictions of cusp spacing compare qualitatively well with many field observations. We will discuss the extension of lab observations and numerical modeling to include incident waves with significant frequency and directional bandwidth. Laboratory experiments were performed at the Cantabria Coastal and Ocean Basin. The large rectangular basin (25 m cross-shore by 32 m alongshore) was heavily instrumented, had reflective sidewalls, and a steep concrete beach (slope 1:5) with a constant depth (1m) section between the wavemaker and beach. With monochromatic, normally incident waves we observed the expected, previously described subharmonic observations. Edge wave vertical heights at the shoreline reached 80cm, and edge wave uprushes exceeded the sloping beach freeboard. When frequency and frequency-directional spread are increased, the excited edge wave character changes substantially. In some cases, subharmonic excitation is suppressed completely. In other cases, edge waves are excited intermittently and unpredictably. The spatially and temporally steady forcing required for strong, persistent subharmonic instability is lacking with even modestly spread (direction and frequency) incident waves. An SPH numerical model is capable of reproducing aspects of the observations. It seems unlikely to us that subhamonic edge waves alone are responsible for most cusp formation on natural beaches. The steady incident wave forcing needed to initiate subharmonic growth, and to maintain subharmonics long enough to build cups, are abundantly present with an incident plane wave, but lacking in many natural settings. Although subharmonic edge waves can potentially start the initial spacing, positive feedback between flow and morphology are likely critical to cusp growth.

Wigner molecules: the strong-correlation limit of the three-electron harmonium.

PubMed

Cioslowski, Jerzy; Pernal, Katarzyna

2006-08-14

At the strong-correlation limit, electronic states of the three-electron harmonium atom are described by asymptotically exact wave functions given by products of distinct Slater determinants and a common Gaussian factor that involves interelectron distances and the center-of-mass position. The Slater determinants specify the angular dependence and the permutational symmetry of the wave functions. As the confinement strength becomes infinitesimally small, the states of different spin multiplicities become degenerate, their limiting energy reflecting harmonic vibrations of the electrons about their equilibrium positions. The corresponding electron densities are given by products of angular factors and a Gaussian function centered at the radius proportional to the interelectron distance at equilibrium. Thanks to the availability of both the energy and the electron density, the strong-correlation limit of the three-electron harmonium is well suited for testing of density functionals.

Nonlinear damping of oblique whistler mode waves through Landau resonance

NASA Astrophysics Data System (ADS)

Hsieh, Y.; Omura, Y.

2017-12-01

Nonlinear trapping of electrons through Landau resonance is a characteristic dynamics in oblique whistler-mode wave particle interactions. The resonance velocity of the Landau resonance at quasi-parallel propagation becomes very close to the parallel group velocity of whistler-mode wave at frequency around 0.5 Ωe, causing a long distance of resonant interaction and strong acceleration of resonant electrons [1]. We demonstrate these effective accelerations for electrons with high equatorial pitch angle ( > 60°) by test particle simulations with parameters for the Earth's inner magnetosphere at L=5. In the simulations, we focus on slightly oblique whistler mode waves with wave normal angle < 20°. Analyzing the wave electric field E and the resonant current J, which is composed of electrons undergoing the Landau resonance, we find that the J·E is mainly positive, which denotes the damping of the wave. Furthermore, we confirm that this positive J•E is dominated by transverse component Jperp·Eperp rather than by longitudinal component Jpara·Eperp. The simulation results reveal that the Landau resonance contributes to the nonlinear damping at 0.5 Ωe for whistler mode waves. Reference [1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, doi:10.1002/2016JA023255.

Application of Semi-Definite Programming for Many-Fermion Systems

NASA Astrophysics Data System (ADS)

Zhao, Zhengji; Braams, Bastiaan; Fukuda, Mituhiro; Overton, Michael

2003-03-01

The ground state energy and other important observables of a many-fermion system with one- and two-body interactions only can all be obtained from the first order and second order Reduced Density Matrices (RDM's) of the system. Using these density matrices and a family of associated representability conditions one may obtain an approximation method for electronic structure theory that is in the mathematical form of Semi-Definite Programming (SDP): minimize a linear matrix functional over a space of positive semidefinite matrices subject to linear constraints. The representability conditions are some known necessary conditions, starting with the well-known P, Q, and G conditions [Claude Garrod and Jerome K. Percus, Reducation of the N-Particle Variational Problem, J. Math. Phys. 5 (1964) 1756-1776]. The RDM method with SDP has great potential advantages over the wave function method when the particle number N is large. The dimension of the full configuration space increases exponentially with N, but in RDM method with SDP the dimension of the objective matrix (which includes RDM's) increases only polynomially with N. We will report on the effect of adding the generalized three-index conditions proposed in [R. M. Erdahl, Representability, Int. J. Quantum Chem. 13 (1978) 697-718].

Using PVDF to locate the debris cloud impact position

NASA Astrophysics Data System (ADS)

Pang, Baojun; Liu, Zhidong

2010-03-01

With the increase of space activities, space debris environment has deteriorated. Space debris impact shields of spacecraft creates debris cloud, the debris cloud is a threat to module wall. In order to conduct an assessment of spacecraft module wall damage impacted by debris cloud, the damage position must be known. In order to design a light weight location system, polyvinylidene fluoride (PVDF) has been studied. Hyper-velocity impact experiments were conducted using two-stage light gas gun, the experimental results indicate that: the virtual wave front location method can be extended to debris cloud impact location, PVDF can be used to locate the damage position effectively, the signals gathered by PVDF from debris cloud impact contain more high frequency components than the signals created by single projectile impact event. The results provide a reference for the development of the sensor systems to detect impacts on spacecraft.

Potential Energy Surface of the Chromium Dimer Re-re-revisited with Multiconfigurational Perturbation Theory.

PubMed

Vancoillie, Steven; Malmqvist, Per Åke; Veryazov, Valera

2016-04-12

The chromium dimer has long been a benchmark molecule to evaluate the performance of different computational methods ranging from density functional theory to wave function methods. Among the latter, multiconfigurational perturbation theory was shown to be able to reproduce the potential energy surface of the chromium dimer accurately. However, for modest active space sizes, it was later shown that different definitions of the zeroth-order Hamiltonian have a large impact on the results. In this work, we revisit the system for the third time with multiconfigurational perturbation theory, now in order to increase the active space of the reference wave function. This reduces the impact of the choice of zeroth-order Hamiltonian and improves the shape of the potential energy surface significantly. We conclude by comparing our results of the dissocation energy and vibrational spectrum to those obtained from several highly accurate multiconfigurational methods and experiment. For a meaningful comparison, we used the extrapolation to the complete basis set for all methods involved.

Imaging of the internal structure of comet 67P/Churyumov-Gerasimenko from radiotomography CONSERT Data (Rosetta Mission) through a full 3D regularized inversion of the Helmholtz equations on functional spaces

NASA Astrophysics Data System (ADS)

Barriot, Jean-Pierre; Serafini, Jonathan; Sichoix, Lydie; Benna, Mehdi; Kofman, Wlodek; Herique, Alain

We investigate the inverse problem of imaging the internal structure of comet 67P/ Churyumov-Gerasimenko from radiotomography CONSERT data by using a coupled regularized inversion of the Helmholtz equations. A first set of Helmholtz equations, written w.r.t a basis of 3D Hankel functions describes the wave propagation outside the comet at large distances, a second set of Helmholtz equations, written w.r.t. a basis of 3D Zernike functions describes the wave propagation throughout the comet with avariable permittivity. Both sets are connected by continuity equations over a sphere that surrounds the comet. This approach, derived from GPS water vapor tomography of the atmosphere,will permit a full 3D inversion of the internal structure of the comet, contrary to traditional approaches that use a discretization of space at a fraction of the radiowave wavelength.

Magnetic antenna excitation of whistler modes. IV. Receiving antennas and reciprocity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stenzel, R. L., E-mail: stenzel@physics.ucla.edu; Urrutia, J. M.

Antenna radiation patterns are an important property of antennas. Reciprocity holds in free space and the radiation patterns for exciting and receiving antennas are the same. In anisotropic plasmas, radiation patterns are complicated by the fact that group and phase velocities differ and certain wave properties like helicity depend on the direction of wave propagation with respect to the background magnetic field B{sub 0}. Interference and wave focusing effects are different than in free space. Reciprocity does not necessarily hold in a magnetized plasma. The present work considers the properties of various magnetic antennas used for receiving whistler modes. Itmore » is based on experimental data from exciting low frequency whistler modes in a large uniform laboratory plasma. By superposition of linear waves from different antennas, the radiation patterns of antenna arrays are derived. Plane waves are generated and used to determine receiving radiation patterns of different receiving antennas. Antenna arrays have radiation patterns with narrow lobes, whose angular position can be varied by physical rotation or electronic phase shifting. Reciprocity applies to broadside antenna arrays but not to end fire arrays which can have asymmetric lobes with respect to B{sub 0}. The effect of a relative motion between an antenna and the plasma has been modeled by the propagation of a short wave packet moving along a linear antenna array. An antenna moving across B{sub 0} has a radiation pattern characterized by an oscillatory “whistler wing.” A receiving antenna in motion can detect any plane wave within the group velocity resonance cone. The radiation pattern also depends on loop size relative to the wavelength. Motional effects prevent reciprocity. The concept of the radiation pattern loses its significance for wave packets since the received signal does not only depend on the antenna but also on the properties of the wave packet. The present results are of fundamental interest and of relevance to loop antennas in space.« less

Analysis of Saccular Function With Vestibular Evoked Myogenic Potential Test in Meniere's Disease.

PubMed

Dabiri, Sasan; Yazdani, Nasrin; Esfahani, Mahdis; Tari, Niloufar; Adil, Susan; Mahvi, Zahra; Rezazadeh, Nima

2017-02-01

Meniere's disease is the disorder of inner ear characterized by vertigo, tinnitus and sensorineural hearing loss. The vestibular evoked myogenic potential (VEMP) test could be useful in the analysis of saccular function, and diagnosis of Meniere's disease. In this study, we've analyzed the saccular function, using VEMP test in different groups of Meniere's disease. Patients were categorized as possible, probable or definite Meniere's disease groups according to the guideline of American Academy of Otolaryngology-Head and Neck Surgery. The exclusion criteria were neuromuscular system diseases, diseases of central nervous system, inner ear disorders, conductive hearing loss, a history of ototoxic drug consumption, being a drug abuser and a positive history of inner ear surgery or manipulations. The VEMP test is the recording of positive and negative waves from sternocleidomastoid muscle that is made by an auditory click to the ear. From the total of 100 patients, the waves of VEMP test was seen in 59 patients which 19 patients had abnormal amplitude, and latency and 40 patients were with normally recorded waves. There was a significant relationship between the severity of hearing loss and a VEMP test without any recorded waves. Most of the cases with 'no wave recorded' VEMP test, were patients with severe hearing loss. However, there wasn't any relation between the pattern of hearing loss and 'no wave recorded' VEMP test. VEMP test could be a valuable diagnostic clue especially in patients with definite Meniere's disease.

Diffusive Cosmic-Ray Acceleration at Shock Waves of Arbitrary Speed with Magnetostatic Turbulence. I. General Theory and Correct Nonrelativistic Speed Limit

NASA Astrophysics Data System (ADS)

Schlickeiser, R.; Oppotsch, J.

2017-12-01

The analytical theory of diffusive acceleration of cosmic rays at parallel stationary shock waves of arbitrary speed with magnetostatic turbulence is developed from first principles. The theory is based on the diffusion approximation to the gyrotropic cosmic-ray particle phase-space distribution functions in the respective rest frames of the up- and downstream medium. We derive the correct cosmic-ray jump conditions for the cosmic-ray current and density, and match the up- and downstream distribution functions at the position of the shock. It is essential to account for the different particle momentum coordinates in the up- and downstream media. Analytical expressions for the momentum spectra of shock-accelerated cosmic rays are calculated. These are valid for arbitrary shock speeds including relativistic shocks. The correctly taken limit for nonrelativistic shock speeds leads to a universal broken power-law momentum spectrum of accelerated particles with velocities well above the injection velocity threshold, where the universal power-law spectral index q≃ 2-{γ }1-4 is independent of the flow compression ratio r. For nonrelativistic shock speeds, we calculate for the first time the injection velocity threshold, settling the long-standing injection problem for nonrelativistic shock acceleration.

Determination of wave-function functionals: The constrained-search variational method

NASA Astrophysics Data System (ADS)

Pan, Xiao-Yin; Sahni, Viraht; Massa, Lou

2005-09-01

In a recent paper [Phys. Rev. Lett. 93, 130401 (2004)], we proposed the idea of expanding the space of variations in variational calculations of the energy by considering the approximate wave function ψ to be a functional of functions χ , ψ=ψ[χ] , rather than a function. A constrained search is first performed over all functions χ such that the wave-function functional ψ[χ] satisfies a physical constraint or leads to the known value of an observable. A rigorous upper bound to the energy is then obtained via the variational principle. In this paper we generalize the constrained-search variational method, applicable to both ground and excited states, to the determination of arbitrary Hermitian single-particle operators as applied to two-electron atomic and ionic systems. We construct analytical three-parameter ground-state functionals for the H- ion and the He atom through the constraint of normalization. We present the results for the total energy E , the expectations of the single-particle operators W=∑irin , n=-2,-1,1,2 , W=∑iδ(ri) , and W=∑iδ(ri-r) , the structure of the nonlocal Coulomb hole charge ρc(rr') , and the expectations of the two particle operators u2,u,1/u,1/u2 , where u=∣ri-rj∣ . The results for all the expectation values are remarkably accurate when compared with the 1078-parameter wave function of Pekeris, and other wave functions that are not functionals. We conclude by describing our current work on how the constrained-search variational method in conjunction with quantal density-functional theory is being applied to the many-electron case.

A heterodyne interferometer for high resolution translation and tilt measurement as optical readout for the LISA inertial sensor

NASA Astrophysics Data System (ADS)

Schuldt, Thilo; Kraus, Hans-Jürgen; Weise, Dennis; Braxmaier, Claus; Peters, Achim; Johann, Ulrich

2017-11-01

The space-based gravitational wave detector LISA (Laser Interferometer Space Antenna) requires a high performance position sensor in order to measure the translation and tilt of the free flying test mass with respect to the LISA optical bench. Here, we present a mechanically highly stable and compact setup of a heterodyne interferometer combined with differential wavefront sensing for the tilt measurement which serves as a demonstrator for an optical readout of the LISA test mass position. First results show noise levels below 1 nm/√Hz and 1 μrad/√Hz, respectively, for frequencies < 10-3 Hz.

Voyager 1: Three "Tsunami Waves" in Interstellar Space

NASA Image and Video Library

2017-03-22

Voyager 1: Three "Tsunami Waves" in Interstellar Space. The Voyager 1 spacecraft has experienced three "tsunami waves" in interstellar space. Listen to how these waves cause surrounding ionized matter to ring. More details on this sound can be found here: www.nasa.gov/jpl/nasa-voyager-t…nterstellar-space/

An analysis of Isgur-Wise function of heavy-light mesons within a higher dimensional potential model approach

NASA Astrophysics Data System (ADS)

Roy, Sabyasachi; Choudhury, D. K.

2014-03-01

Nambu-Goto action for bosonic string predicts the quark-antiquark potential to be V(r) = -γ/r + σr + μ0. The coefficient γ = π(d - 2)/24 is the Lüscher coefficient of the Lüscher term 7/r, which depends upon the space-time dimension 'd'. Very recently, we have developed meson wave functions in higher dimension with this potential from higher dimensional Schrodinger equation by applying quantum mechanical perturbation technique with both Lüscher term as parent and as perturbation. In this letter, we analyze Isgur-Wise function for heavy-light mesons using these wave functions in higher dimension and make a comparative study on the status of the perturbation technique in both the cases.

Diffraction of SH-waves by topographic features in a layered transversely isotropic half-space

NASA Astrophysics Data System (ADS)

Ba, Zhenning; Liang, Jianwen; Zhang, Yanju

2017-01-01

The scattering of plane SH-waves by topographic features in a layered transversely isotropic (TI) half-space is investigated by using an indirect boundary element method (IBEM). Firstly, the anti-plane dynamic stiffness matrix of the layered TI half-space is established and the free fields are solved by using the direct stiffness method. Then, Green's functions are derived for uniformly distributed loads acting on an inclined line in a layered TI half-space and the scattered fields are constructed with the deduced Green's functions. Finally, the free fields are added to the scattered ones to obtain the global dynamic responses. The method is verified by comparing results with the published isotropic ones. Both the steady-state and transient dynamic responses are evaluated and discussed. Numerical results in the frequency domain show that surface motions for the TI media can be significantly different from those for the isotropic case, which are strongly dependent on the anisotropy property, incident angle and incident frequency. Results in the time domain show that the material anisotropy has important effects on the maximum duration and maximum amplitudes of the time histories.

A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitating Fluxes

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.

2002-01-01

Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.

Asymptotic structure of space-time with a positive cosmological constant

NASA Astrophysics Data System (ADS)

Kesavan, Aruna

In general relativity a satisfactory framework for describing isolated systems exists when the cosmological constant Lambda is zero. The detailed analysis of the asymptotic structure of the gravitational field, which constitutes the framework of asymptotic flatness, lays the foundation for research in diverse areas in gravitational science. However, the framework is incomplete in two respects. First, asymptotic flatness provides well-defined expressions for physical observables such as energy and momentum as 'charges' of asymptotic symmetries at null infinity, [special character omitted] +. But the asymptotic symmetry group, called the Bondi-Metzner-Sachs group is infinite-dimensional and a tensorial expression for the 'charge' integral of an arbitrary BMS element is missing. We address this issue by providing a charge formula which is a 2-sphere integral over fields local to the 2-sphere and refers to no extraneous structure. The second, and more significant shortcoming is that observations have established that Lambda is not zero but positive in our universe. Can the framework describing isolated systems and their gravitational radiation be extended to incorporate this fact? In this dissertation we show that, unfortunately, the standard framework does not extend from the Lambda = 0 case to the Lambda > 0 case in a physically useful manner. In particular, we do not have an invariant notion of gravitational waves in the non-linear regime, nor an analog of the Bondi 'news tensor', nor positive energy theorems. In addition, we argue that the stronger boundary condition of conformal flatness of intrinsic metric on [special character omitted]+, which reduces the asymptotic symmetry group from Diff([special character omitted]) to the de Sitter group, is insufficient to characterize gravitational fluxes and is physically unreasonable. To obtain guidance for the full non-linear theory with Lambda > 0, linearized gravitational waves in de Sitter space-time are analyzed in detail. i) We show explicitly that conformal flatness of the boundary removes half the degrees of freedom of the gravitational field by hand and is not justified by physical considerations; ii) We obtain gauge invariant expressions of energy-momentum and angular momentum fluxes carried by gravitational waves in terms of fields defined at [special character omitted]+; iii) We demonstrate that the flux formulas reduce to the familiar ones in Minkowski spacetime in spite of the fact that the limit Lambda → 0 is discontinuous (since, in particular, [special character omitted]+ changes its space-like character to null in the limit); iv) We obtain a generalization of Einstein's 1918 quadrupole formula for power emission by a linearized source to include a positive Lambda; and, finally v) We show that, although energy of linearized gravitational waves can be arbitrarily negative in general, gravitational waves emitted by physically reasonable sources carry positive energy.

Charge-transfer excited states: Seeking a balanced and efficient wave function ansatz in variational Monte Carlo

DOE PAGES

Blunt, Nick S.; Neuscamman, Eric

2017-11-16

We present a simple and efficient wave function ansatz for the treatment of excited charge-transfer states in real-space quantum Monte Carlo methods. Using the recently-introduced variation-after-response method, this ansatz allows a crucial orbital optimization step to be performed beyond a configuration interaction singles expansion, while only requiring calculation of two Slater determinant objects. As a result, we demonstrate this ansatz for the illustrative example of the stretched LiF molecule, for a range of excited states of formaldehyde, and finally for the more challenging ethylene-tetrafluoroethylene molecule.

Wave Number Selection for Incompressible Parallel Jet Flows Periodic in Space

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

1997-01-01

The temporal instability of a spatially periodic parallel flow of an incompressible inviscid fluid for various jet velocity profiles is studied numerically using Floquet Analysis. The transition matrix at the end of a period is evaluated by direct numerical integration. For verification, a method based on approximating a continuous function by a series of step functions was used. Unstable solutions were found only over a limited range of wave numbers and have a band type structure. The results obtained are analogous to the behavior observed in systems exhibiting complexity at the edge of order and chaos.

Quantum mechanics of conformally and minimally coupled Friedmann-Robertson-Walker cosmology

NASA Astrophysics Data System (ADS)

Kim, Sang Pyo

1992-10-01

The expansion method by a time-dependent basis of the eigenfunctions for the space-coordinate-dependent sub-Hamiltonian is one of the most natural frameworks for quantum systems, relativistic as well as nonrelativistic. The complete set of wave functions is found in the product integral formulation, whose constants of integration are fixed by Cauchy initial data. The wave functions for the Friedmann-Robertson-Walker (FRW) cosmology conformally and minimally coupled to a scalar field with a power-law potential or a polynomial potential are expanded in terms of the eigenfunctions of the scalar field sub-Hamiltonian part. The resultant gravitational field part which is an ``intrinsic'' timelike variable-dependent matrix-valued differential equation is solved again in the product integral formulation. There are classically allowed regions for the ``intrinsic'' timelike variable depending on the scalar field quantum numbers and these regions increase accordingly as the quantum numbers increase. For a fixed large three-geometry the wave functions corresponding to the low excited (small quantum number) states of the scalar field are exponentially damped or diverging and the wave functions corresponding to the high excited (large quantum number) states are still oscillatory but become eventually exponential as the three-geometry becomes larger. Furthermore, a proposal is advanced that the wave functions exponentially damped for a large three-geometry may be interpreted as ``tunneling out'' wave functions into, and the wave functions exponentially diverging as ``tunneling in'' from, different universes with the same or different topologies, the former being interpreted as the recently proposed Hawking-Page wormhole wave functions. It is observed that there are complex as well as Euclidean actions depending on the quantum numbers of the scalar field part outside the classically allowed region both of the gravitational and scalar fields, suggesting the usefulness of complex geometry and complex trajectories. From the most general wave functions for the FRW cosmology conformally coupled to scalar field, the boundary conditions for the wormhole wave functions are modified so that the modulus of wave functions, instead of the wave functions themselves, should be exponentially damped for a large three-geometry and be regular up to some negative power of the three-geometry as the three-geometry collapses. The wave functions for the FRW cosmology minimally coupled to an inhomogeneous scalar field are similarly found in the product integral formulation. The role of a large number of the inhomogeneous modes of the scalar field is not only to increase the classically allowed regions for the gravitational part but also to provide a mechanism of the decoherence of quantum interferences between the different sizes of the universe.

Multiconfiguration pair-density functional theory: barrier heights and main group and transition metal energetics.

PubMed

Carlson, Rebecca K; Li Manni, Giovanni; Sonnenberger, Andrew L; Truhlar, Donald G; Gagliardi, Laura

2015-01-13

Kohn-Sham density functional theory, resting on the representation of the electronic density and kinetic energy by a single Slater determinant, has revolutionized chemistry, but for open-shell systems, the Kohn-Sham Slater determinant has the wrong symmetry properties as compared to an accurate wave function. We have recently proposed a theory, called multiconfiguration pair-density functional theory (MC-PDFT), in which the electronic kinetic energy and classical Coulomb energy are calculated from a multiconfiguration wave function with the correct symmetry properties, and the rest of the energy is calculated from a density functional, called the on-top density functional, that depends on the density and the on-top pair density calculated from this wave function. We also proposed a simple way to approximate the on-top density functional by translation of Kohn-Sham exchange-correlation functionals. The method is much less expensive than other post-SCF methods for calculating the dynamical correlation energy starting with a multiconfiguration self-consistent-field wave function as the reference wave function, and initial tests of the theory were quite encouraging. Here, we provide a broader test of the theory by applying it to bond energies of main-group molecules and transition metal complexes, barrier heights and reaction energies for diverse chemical reactions, proton affinities, and the water dimerization energy. Averaged over 56 data points, the mean unsigned error is 3.2 kcal/mol for MC-PDFT, as compared to 6.9 kcal/mol for Kohn-Sham theory with a comparable density functional. MC-PDFT is more accurate on average than complete active space second-order perturbation theory (CASPT2) for main-group small-molecule bond energies, alkyl bond dissociation energies, transition-metal-ligand bond energies, proton affinities, and the water dimerization energy.

Homogeneous quantum electrodynamic turbulence

NASA Technical Reports Server (NTRS)

Shebalin, John V.

1992-01-01

The electromagnetic field equations and Dirac equations for oppositely charged wave functions are numerically time-integrated using a spatial Fourier method. The numerical approach used, a spectral transform technique, is based on a continuum representation of physical space. The coupled classical field equations contain a dimensionless parameter which sets the strength of the nonlinear interaction (as the parameter increases, interaction volume decreases). For a parameter value of unity, highly nonlinear behavior in the time-evolution of an individual wave function, analogous to ideal fluid turbulence, is observed. In the truncated Fourier representation which is numerically implemented here, the quantum turbulence is homogeneous but anisotropic and manifests itself in the nonlinear evolution of equilibrium modal spatial spectra for the probability density of each particle and also for the electromagnetic energy density. The results show that nonlinearly interacting fermionic wave functions quickly approach a multi-mode, dynamic equilibrium state, and that this state can be determined by numerical means.

The Virtual Wave Observatory (VWO): A Portal to Heliophysics Wave Data

NASA Technical Reports Server (NTRS)

Fung, Shing F.

2010-01-01

The Virtual Wave Observatory (VWO) is one of the discipline-oriented virtual observatories that help form the nascent NASA Heliophysics Data environment to support heliophysics research. It focuses on supporting the searching and accessing of distributed heliophysics wave data and information that are available online. Since the occurrence of a natural wave phenomenon often depends on the underlying geophysical -- i.e., context -- conditions under which the waves are generated and propagate, and the observed wave characteristics can also depend on the location of observation, VWO will implement wave-data search-by-context conditions and location, in addition to searching by time and observing platforms (both space-based and ground-based). This paper describes the VWO goals, the basic design objectives, and the key VWO functionality to be expected. Members of the heliophysics community are invited to participate in VWO development in order to ensure its usefulness and success.

Donders is dead: cortical traveling waves and the limits of mental chronometry in cognitive neuroscience.

PubMed

Alexander, David M; Trengove, Chris; van Leeuwen, Cees

2015-11-01

An assumption nearly all researchers in cognitive neuroscience tacitly adhere to is that of space-time separability. Historically, it forms the basis of Donders' difference method, and to date, it underwrites all difference imaging and trial-averaging of cortical activity, including the customary techniques for analyzing fMRI and EEG/MEG data. We describe the assumption and how it licenses common methods in cognitive neuroscience; in particular, we show how it plays out in signal differencing and averaging, and how it misleads us into seeing the brain as a set of static activity sources. In fact, rather than being static, the domains of cortical activity change from moment to moment: Recent research has suggested the importance of traveling waves of activation in the cortex. Traveling waves have been described at a range of different spatial scales in the cortex; they explain a large proportion of the variance in phase measurements of EEG, MEG and ECoG, and are important for understanding cortical function. Critically, traveling waves are not space-time separable. Their prominence suggests that the correct frame of reference for analyzing cortical activity is the dynamical trajectory of the system, rather than the time and space coordinates of measurements. We illustrate what the failure of space-time separability implies for cortical activation, and what consequences this should have for cognitive neuroscience.

Discontinuity-free edge-diffraction model for characterization of focused wave fields.

PubMed

Sedukhin, Andrey G

2010-03-01

A model of discontinuity-free edge diffraction is proposed that is valid in the framework of the scalar Debye approximation and describes the formation process and approximate structure of the stationary diffracted field of a monochromatic converging spherical wave of limited angular opening throughout the whole space about the focus. The field is represented semianalytically in terms of the sum of a direct quasi-spherical wave and two edge quasi-conical waves of the zeroth and first order. The angular spectrum amplitudes of all these waves have smooth continuous variations of the real and imaginary parts in polar angle and radius, the separable nonanalytic functions defining the polar-angle variations of the amplitudes being found by optimization techniques.

Existence and numerical simulation of periodic traveling wave solutions to the Casimir equation for the Ito system

NASA Astrophysics Data System (ADS)

Abbasbandy, S.; Van Gorder, R. A.; Hajiketabi, M.; Mesrizadeh, M.

2015-10-01

We consider traveling wave solutions to the Casimir equation for the Ito system (a two-field extension of the KdV equation). These traveling waves are governed by a nonlinear initial value problem with an interesting nonlinearity (which actually amplifies in magnitude as the size of the solution becomes small). The nonlinear problem is parameterized by two initial constant values, and we demonstrate that the existence of solutions is strongly tied to these parameter values. For our interests, we are concerned with positive, bounded, periodic wave solutions. We are able to classify parameter regimes which admit such solutions in full generality, thereby obtaining a nice existence result. Using the existence result, we are then able to numerically simulate the positive, bounded, periodic solutions. We elect to employ a group preserving scheme in order to numerically study these solutions, and an outline of this approach is provided. The numerical simulations serve to illustrate the properties of these solutions predicted analytically through the existence result. Physically, these results demonstrate the existence of a type of space-periodic structure in the Casimir equation for the Ito model, which propagates as a traveling wave.

Imaging the dynamics of free-electron Landau states

PubMed Central

Schattschneider, P.; Schachinger, Th.; Stöger-Pollach, M.; Löffler, S.; Steiger-Thirsfeld, A.; Bliokh, K. Y.; Nori, Franco

2014-01-01

Landau levels and states of electrons in a magnetic field are fundamental quantum entities underlying the quantum Hall and related effects in condensed matter physics. However, the real-space properties and observation of Landau wave functions remain elusive. Here we report the real-space observation of Landau states and the internal rotational dynamics of free electrons. States with different quantum numbers are produced using nanometre-sized electron vortex beams, with a radius chosen to match the waist of the Landau states, in a quasi-uniform magnetic field. Scanning the beams along the propagation direction, we reconstruct the rotational dynamics of the Landau wave functions with angular frequency ~100 GHz. We observe that Landau modes with different azimuthal quantum numbers belong to three classes, which are characterized by rotations with zero, Larmor and cyclotron frequencies, respectively. This is in sharp contrast to the uniform cyclotron rotation of classical electrons, and in perfect agreement with recent theoretical predictions. PMID:25105563

Acoustical levitation for space processing. [weightless molten material manipulation

NASA Technical Reports Server (NTRS)

Wang, T. G.; Saffren, M. M.; Elleman, D. D.

1974-01-01

It is pointed out that many space-manufacturing processes will require the manipulation of weightless molten material within a container in such a way that the material does not touch the container wall. A description is given of an acoustical method which can be used for the positioning and shaping of any molten material including nonconductors such as glasses. The new approach makes use of an acoustical standing wave which is excited within an enclosure or resonator.

Computing the Evans function via solving a linear boundary value ODE

NASA Astrophysics Data System (ADS)

Wahl, Colin; Nguyen, Rose; Ventura, Nathaniel; Barker, Blake; Sandstede, Bjorn

2015-11-01

Determining the stability of traveling wave solutions to partial differential equations can oftentimes be computationally intensive but of great importance to understanding the effects of perturbations on the physical systems (chemical reactions, hydrodynamics, etc.) they model. For waves in one spatial dimension, one may linearize around the wave and form an Evans function - an analytic Wronskian-like function which has zeros that correspond in multiplicity to the eigenvalues of the linearized system. If eigenvalues with a positive real part do not exist, the traveling wave will be stable. Two methods exist for calculating the Evans function numerically: the exterior-product method and the method of continuous orthogonalization. The first is numerically expensive, and the second reformulates the originally linear system as a nonlinear system. We develop a new algorithm for computing the Evans function through appropriate linear boundary-value problems. This algorithm is cheaper than the previous methods, and we prove that it preserves analyticity of the Evans function. We also provide error estimates and implement it on some classical one- and two-dimensional systems, one being the Swift-Hohenberg equation in a channel, to show the advantages.

Nonlinear dust-acoustic structures in space plasmas with superthermal electrons, positrons, and ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saberian, E., E-mail: e.saberian@neyshabur.ac.ir; Esfandyari-Kalejahi, A.; Afsari-Ghazi, M.

Some features of nonlinear dust-acoustic (DA) structures are investigated in a space plasma consisting of superthermal electrons, positrons, and positive ions in the presence of negatively charged dust grains with finite-temperature by employing a pseudo-potential technique in a hydrodynamic model. For this purpose, it is assumed that the electrons, positrons, and ions obey a kappa-like (κ) distribution in the background of adiabatic dust population. In the linear analysis, it is found that the dispersion relation yield two positive DA branches, i.e., the slow and fast DA waves. The upper branch (fast DA waves) corresponds to the case in which bothmore » (negatively charged) dust particles and (positively charged) ion species oscillate in phase with electrons and positrons. On the other hand, the lower branch (slow DA waves) corresponds to the case in which only dust particles oscillate in phase with electrons and positrons, while ion species are in antiphase with them. On the other hand, the fully nonlinear analysis shows that the existence domain of solitons and their characteristics depend strongly on the dust charge, ion charge, dust temperature, and the spectral index κ. It is found that the minimum/maximum Mach number increases as the spectral index κ increases. Also, it is found that only solitons with negative polarity can propagate and that their amplitudes increase as the parameter κ increases. Furthermore, the domain of Mach number shifts to the lower values, when the value of the dust charge Z{sub d} increases. Moreover, it is found that the Mach number increases with an increase in the dust temperature. Our analysis confirms that, in space plasmas with highly charged dusts, the presence of superthermal particles (electrons, positrons, and ions) may facilitate the formation of DA solitary waves. Particularly, in two cases of hydrogen ions H{sup +} (Z{sub i} = 1) and doubly ionized Helium atoms He{sup 2+} (Z{sub i} = 2), the mentioned results are the same. Additionally, the mentioned dusty plasma does not support DA solitons with positive polarity (compressive solitons). Furthermore, our analysis confirms that DA double layers cannot exist in such a system. Moreover, the positron density has not a considerable effect on the behavior of DA solitons in our model.« less

Acceleration of ions and neutrals by a traveling electrostatic wave

NASA Astrophysics Data System (ADS)

Lee, K. H.; Lee, L. C.; Wong, A. Y.

2018-02-01

We propose a new scheme for accelerating a weakly ionized gas by externally imposing a sinusoidal electrostatic (ES) potential in a tubular system. The weakly ionized gas consists of three fluid components: neutral hydrogen fluid ( H ), positively charged fluid ( H + ), and negatively charged fluids ( H - and/or e - ), as an example. The sinusoidal ES potential is imposed on a series of conductive meshes in the tubular system, and its phase varies with time and space to mimic a traveling ES wave. The charged fluids are trapped and accelerated by the sinusoidal ES potential, while the neutral fluid is accelerated through neutral-ion collisions. The neutral fluid can be accelerated to the wave phase velocity in a few neutral-ion collision times. The whole device remains charge-neutral, and there is no build-up of space charge. The acceleration scheme can be applied to, for example, the propulsion of glider in the air, partially ionized plasma in a chamber, spacecraft, and wind tunnel.

Love and Rayleigh wave dispersion from regional Ambient Noise Tomography in the Eastern Alps of Europe

NASA Astrophysics Data System (ADS)

Behm, Michael; Nakata, Nori; Bianchi, Irene; Bokelmann, Götz

2014-05-01

ALPASS is an international passive seismic monitoring experiment aimed at understanding the upper mantle structure in the in the European Eastern Alps. Data were collected from May 2005 to June 2006 at about 50 locations with an average spacing of 20 km, and have been used for teleseismic travel time tomography and receiver function analysis in previous studies. We combine the ALPASS data from 23 broadband stations with additional data from the temporary CBP (Carpathian Basin Project) network (15 stations), and present results from ambient noise tomography applied to the region covering the easternmost part of the Alps and its transition to the adjacent tectonic provinces (Vienna Basin, Bohemian Massif, Dinarides). By turning each station into a virtual source, we are able to recover surface waves in the frequency range of 0.05 - 0.5 Hz, which are sensitive to depths of approximately 2 - 15 kilometers. The three-component recordings allow distinguishing between Rayleigh waves on the vertical/radial components and Love waves on the transverse component. On average, the Love waves have higher apparent velocity by about 15%. Owing to dense receiver spacing and high S/N ratio of the obtained interferograms, we are able to derive a large set of dispersion curves. The complicated 3D structure of the investigated region calls for a tomographic approach to transform these dispersion curves to be representative of local 1D structures. The results correlate well with surface geology and provide the input to inversion for the vertical shear-wave velocity distribution. Compared to data from active source experiments, we derive lower average shear wave velocities. This observation is comparable to receiver functions analysis which show a high Vp/Vs ratio for the area of the Molasse basin, where the shear wave velocities retrieved from the surface wave inversion are in particular low.

A Standing-Wave Experiment with a Guitar

NASA Astrophysics Data System (ADS)

Inman, Fred W.

2006-10-01

When teaching standing waves, one often uses as examples musical instruments with strings, e.g., pianos, violins, and guitars. In today's popular music culture, young people may be more familiar with guitars than any other string instrument. I was helping my 15-year-old granddaughter make some repairs and adjustments to her electric guitar, and the subject of the spacing between the frets on the fingerboard was raised. I told her that the physics of standing waves and the equal tempered musical scale dictate the location of the frets. The purpose of this paper is to suggest that students might be introduced to the physics of standing waves using a guitar and to the formula for the fret locations. By measuring the positions of the frets, this formula can be tested.

A reprogrammable multifunctional chalcogenide guided-wave lens.

PubMed

Cao, Tun; Wei, Chen-Wei; Cen, Meng-Jia; Guo, Bao; Kim, Yong-June; Zhang, Shuang; Qiu, Cheng-Wei

2018-06-05

The transformation optics (TO) technique, which establishes an equivalence between a curved space and a spatial distribution of inhomogeneous constitutive parameters, has enabled an extraordinary paradigm for manipulating wave propagation. However, extreme constitutive parameters, as well as a static nature, inherently limit the simultaneous achievement of broadband performance, ultrafast reconfigurability and versatile reprogrammable functions. Here, we integrate the TO technique with an active phase-change chalcogenide to achieve a reconfigurable multi-mode guided-wave lens. The lens is made of a Rinehart-shaped curved waveguide with an effective refractive index gradient profile through partially crystallizing Ge2Sb2Te5. Upon changing the bias time of the external voltage imparted to the Ge2Sb2Te5 segments, the refractive index gradient profile can be tuned with a transformative platform for various functions for visible light. The electrically reprogrammable multi-mode guided-wave lens is capable of dynamically acquiring various functionalities with an ultrafast response time. Our findings may offer a significant step forward by providing a universal method to obtain ultrafast and highly versatile guided-wave manipulation, such as in Einstein rings, cloaking, Maxwell fish-eye lenses and Luneburg lenses.

Effects of dust polarity and nonextensive electrons on the dust-ion acoustic solitons and double layers in earth atmosphere

NASA Astrophysics Data System (ADS)

Ghobakhloo, Marzieh; Zomorrodian, Mohammad Ebrahim; Javidan, Kurosh

2018-05-01

Propagation of dustion acoustic solitary waves (DIASWs) and double layers is discussed in earth atmosphere, using the Sagdeev potential method. The best model for distribution function of electrons in earth atmosphere is found by fitting available data on different distribution functions. The nonextensive function with parameter q = 0.58 provides the best fit on observations. Thus we analyze the propagation of localized waves in an unmagnetized plasma containing nonextensive electrons, inertial ions, and negatively/positively charged stationary dust. It is found that both compressive and rarefactive solitons as well as double layers exist depending on the sign (and the value) of dust polarity. Characters of propagated waves are described using the presented model.

Study of transionospheric signal scintillation: Quasi- particle approach

NASA Astrophysics Data System (ADS)

Lyle, Ruthie D.

1998-07-01

A quasi-particle approach is applied to study amplitude scintillation of transionospheric signals caused by Bottomside Sinusoidal (BSS) irregularities. The quasi- particle method exploits wave-particle duality, viewing the wave as a distribution of quasi-particles. This is accomplished by transforming the autocorrelation of the wave function into a Wigner distribution function, which serves as a distribution of quasi-particles in the (/vec r,/ /vec k) phase space. The quasi-particle distribution at any instant of time represents the instantaneous state of the wave. Scattering of the signal by the ionospheric irregularities is equivalent to the evolution of the quasi-particle distribution, due to the collision of the quasi-particles with objects arising from the presence of the BSS irregularities. Subsequently, the perturbed quasi-particle distribution facilitates the computation of average space time propagation properties of the wave. Thus, the scintillation index S4 is determined. Incorporation of essential BSS features in the analysis is accomplished by analytically modeling the power spectrum of the BSS irregularities measured in-situ by the low orbiting Atmosphere-E (AE - E) Satellite. The effect of BSS irregularities on transionospheric signals has been studied. The numerical results agree well with multi-satellite scintillation observations made at Huancayo Peru in close time correspondence with BSS irregularities observed by the AE - E satellite over a few nights (December 8-11, 1979). During this period, the severity of the scintillation varied from moderate to intense, S4 = 0.1-0.8.

Body and Surface Wave Modeling of Observed Seismic Events

DTIC Science & Technology

1981-04-30

are commonly used and the third is a modification of a test of the representation theorem. All three give similar results for explosions in an NTS...order to better understand the Ms-Yield relationship for underground nuclear explosions , we need to be able to predict quantitatively the effects of...half-space Green’s functions, previously obtained, to calculate far-field Rayleigh waves from explosions . Consider a point explosion at h. (Figure 1

Existence, regularity, and concentration phenomenon of nontrivial solitary waves for a class of generalized variable coefficient Kadomtsev-Petviashvili equation

NASA Astrophysics Data System (ADS)

Alves, Claudianor O.; Miyagaki, Olímpio H.

2017-08-01

In this paper, we establish some results concerning the existence, regularity, and concentration phenomenon of nontrivial solitary waves for a class of generalized variable coefficient Kadomtsev-Petviashvili equation. Variational methods are used to get an existence result, as well as, to study the concentration phenomenon, while the regularity is more delicate because we are leading with functions in an anisotropic Sobolev space.

Simultaneous Airy beam generation for both surface plasmon polaritons and transmitted wave based on metasurface.

PubMed

Wang, Sen; Wang, Xinke; Zhang, Yan

2017-10-02

Based on the amplitude and phase modulation of subwavelength slits, a metasurface which can simultaneously generate Airy beam for surface plasmon polaritons (SPPs) and transmitted wave is presented. Interestingly, by changing the handedness of circularly polarized light, the position of SPPs Airy beam can be switched to the left or right side of the metasurface, while the field distribution and the position of the Airy beam for transmitted wave are not affected. The nondiffracting, self-bending and self-healing properties of the generated Airy beams are analyzed as well. In addition, abruptly autofocusing of SPPs and transmitted wave are demonstrated by interfering two Airy beams. The dual functionality and chirality features of the metasurface can provide more freedoms in the potential applications of Airy beams.

MHD simulation of the shock wave event on October 24, 2003

NASA Astrophysics Data System (ADS)

Ogino, T.; Kajiwara, Y.; Nakao, M.; Park, K. S.; Fukazawa, K.; Yi, Y.

2007-11-01

A three-dimensional global MHD simulation of the interaction between the solar wind and the Earth's magnetosphere has been executed to study the shock wave event on space weather problem on October 24, 2003, when an abnormal operation happened in a satellite for Environment Observation Technology, ADEOS-II (Midori-II). Characteristic features of the event are the long duration of southward IMF, arrival of a strong shock wave, then large variation of IMF By from negative to positive for about 15 min duration. In the simulation, the shock wave compresses the magnetosphere for southward IMF and a hot plasma was injected around the geosynchronous orbit from plasma sheet. During the interval when IMF By changes from negative to positive, the magnitude of IMF extremely decreases to bring attenuation of magnetic reconnection. The open-closed boundary shrinks in the polar cap and the transient expansion of the magnetic field lines occurs to imply enhancement of particle precipitation. The reconnection site moves from dawn to dusk in the dayside magnetopause and a narrow cockscomb closed field region is formed in the high latitude tail.

Bohmian mechanics without wave function ontology

NASA Astrophysics Data System (ADS)

Solé, Albert

2013-11-01

In this paper, I critically assess different interpretations of Bohmian mechanics that are not committed to an ontology based on the wave function being an actual physical object that inhabits configuration space. More specifically, my aim is to explore the connection between the denial of configuration space realism and another interpretive debate that is specific to Bohmian mechanics: the quantum potential versus guidance approaches. Whereas defenders of the quantum potential approach to the theory claim that Bohmian mechanics is better formulated as quasi-Newtonian, via the postulation of forces proportional to acceleration; advocates of the guidance approach defend the notion that the theory is essentially first-order and incorporates some concepts akin to those of Aristotelian physics. Here I analyze whether the desideratum of an interpretation of Bohmian mechanics that is both explanatorily adequate and not committed to configuration space realism favors one of these two approaches to the theory over the other. Contrary to some recent claims in the literature, I argue that the quasi-Newtonian approach based on the idea of a quantum potential does not come out the winner.

Deterministic alternatives to the full configuration interaction quantum Monte Carlo method for strongly correlated systems

NASA Astrophysics Data System (ADS)

Tubman, Norm; Whaley, Birgitta

The development of exponential scaling methods has seen great progress in tackling larger systems than previously thought possible. One such technique, full configuration interaction quantum Monte Carlo, allows exact diagonalization through stochastically sampling of determinants. The method derives its utility from the information in the matrix elements of the Hamiltonian, together with a stochastic projected wave function, which are used to explore the important parts of Hilbert space. However, a stochastic representation of the wave function is not required to search Hilbert space efficiently and new deterministic approaches have recently been shown to efficiently find the important parts of determinant space. We shall discuss the technique of Adaptive Sampling Configuration Interaction (ASCI) and the related heat-bath Configuration Interaction approach for ground state and excited state simulations. We will present several applications for strongly correlated Hamiltonians. This work was supported through the Scientific Discovery through Advanced Computing (SciDAC) program funded by the U.S. Department of Energy, Office of Science, Advanced Scientific Computing Research and Basic Energy Sciences.

Husimi function and phase-space analysis of bilayer quantum Hall systems at ν = 2/λ

NASA Astrophysics Data System (ADS)

Calixto, M.; Peón-Nieto, C.

2018-05-01

We propose localization measures in phase space of the ground state of bilayer quantum Hall systems at fractional filling factors , to characterize the three quantum phases (shortly denoted by spin, canted and ppin) for arbitrary -isospin λ. We use a coherent state (Bargmann) representation of quantum states, as holomorphic functions in the 8-dimensional Grassmannian phase-space (a higher-dimensional generalization of the Haldane’s 2-dimensional sphere ). We quantify the localization (inverse volume) of the ground state wave function in phase-space throughout the phase diagram (i.e. as a function of Zeeman, tunneling, layer distance, etc, control parameters) with the Husimi function second moment, a kind of inverse participation ratio that behaves as an order parameter. Then we visualize the different ground state structure in phase space of the three quantum phases, the canted phase displaying a much higher delocalization (a Schrödinger cat structure) than the spin and ppin phases, where the ground state is highly coherent. We find a good agreement between analytic (variational) and numeric diagonalization results.

Vlasov Simulation of Electrostatic Solitary Structures in Multi-Component Plasmas

NASA Technical Reports Server (NTRS)

Umeda, Takayuki; Ashour-Abdalla, Maha; Pickett, Jolene S.; Goldstein, Melvyn L.

2012-01-01

Electrostatic solitary structures have been observed in the Earth's magnetosheath by the Cluster spacecraft. Recent theoretical work has suggested that these solitary structures are modeled by electron acoustic solitary waves existing in a four-component plasma system consisting of core electrons, two counter-streaming electron beams, and one species of background ions. In this paper, the excitation of electron acoustic waves and the formation of solitary structures are studied by means of a one-dimensional electrostatic Vlasov simulation. The present result first shows that either electron acoustic solitary waves with negative potential or electron phase-space holes with positive potential are excited in four-component plasma systems. However, these electrostatic solitary structures have longer duration times and higher wave amplitudes than the solitary structures observed in the magnetosheath. The result indicates that a high-speed and small free energy source may be needed as a fifth component. An additional simulation of a five-component plasma consisting of a stable four-component plasma and a weak electron beam shows the generation of small and fast electron phase-space holes by the bump-on-tail instability. The physical properties of the small and fast electron phase-space holes are very similar to those obtained by the previous theoretical analysis. The amplitude and duration time of solitary structures in the simulation are also in agreement with the Cluster observation.

A theoretical prediction of the acoustic pressure generated by turbulence-flame front interactions

NASA Technical Reports Server (NTRS)

Huff, R. G.

1984-01-01

The equations of momentum annd continuity are combined and linearized yielding the one dimensional nonhomogeneous acoustic wave equation. Three terms in the non-homogeneous equation act as acoustic sources and are taken to be forcing functions acting on the homogeneous wave equation. The three source terms are: fluctuating entropy, turbulence gradients, and turbulence-flame interactions. Each source term is discussed. The turbulence-flame interaction source is used as the basis for computing the source acoustic pressure from the Fourier transformed wave equation. Pressure fluctuations created in turbopump gas generators and turbines may act as a forcing function for turbine and propellant tube vibrations in Earth to orbit space propulsion systems and could reduce their life expectancy. A preliminary assessment of the acoustic pressure fluctuations in such systems is presented.

A theoretical prediction of the acoustic pressure generated by turbulence-flame front interactions

NASA Technical Reports Server (NTRS)

Huff, R. G.

1984-01-01

The equations of momentum and continuity are combined and linearized yielding the one dimensional nonhomogeneous acoustic wave equation. Three terms in the non-homogeneous equation act as acoustic sources and are taken to be forcing functions acting on the homogeneous wave equation. The three source terms are: fluctuating entropy, turbulence gradients, and turbulence-flame interactions. Each source term is discussed. The turbulence-flame interaction source is used as the basis for computing the source acoustic pressure from the Fourier transformed wave equation. Pressure fluctuations created in turbopump gas generators and turbines may act as a forcing function for turbine and propellant tube vibrations in earth to orbit space propulsion systems and could reduce their life expectancy. A preliminary assessment of the acoustic pressure fluctuations in such systems is presented.

Bad Colourmaps Can Hide Big Structures

NASA Astrophysics Data System (ADS)

Kovesi, Peter

2014-05-01

Colourmaps are often selected with little awareness of the perceptual distortions they might introduce. A colourmap can be thought of as a line or curve drawn through a three dimensional colour space. Individual data values are mapped to positions along this line which, in turn, allows them to be mapped to a colour. For a colourmap to be effective it is important that the perceptual contrast that occurs as one moves along the line in the colour space is close to uniform. Many colourmaps are designed as piecewise linear paths through RGB space. This is a poor colour space to use because it is not perceptually uniform. Accordingly many colourmaps supplied by vendors have uneven perceptual contrast over their range. They may include points of locally high colour contrast leading you to think there might be some anomaly in your data when there is none. Conversely, colourmaps may also have flat spots of low perceptual contrast that prevent you from seeing features in your data. In some cases it is possible for structures having a magnitude of 10% of the full data range to be completely hidden by a flat spot in the colourmap. The deficiencies of many colourmaps can be revealed using a simple test image consisting of a high frequency sine wave superimposed on a ramp function. The amplitude of the sine wave is modulated from a maximum value at the top of the image to zero at the bottom. Ideally the sine wave should be uniformly visible across the image at all points on the ramp. For many colourmaps this will not be the case. At the very bottom of the image, where the sine wave amplitude has been modulated to 0, we just have a linear ramp which simply reproduces the colourmap. Given that the underlying data is a featureless ramp the colourmap should not induce the perception of any features across the bottom of the test image. Good colourmaps are difficult to design. A greyscale colourmap is generally a safe choice but is not always what is desired. For non-greyscale colourmaps the perceptual colour contrast between adjacent entries of the map should be constant across the whole colourmap. In addition, and more importantly, the colour lightness change between successive entries in the colourmap should also be constant. These conditions, if observed, constrain the design of colourmaps considerably, and they exclude the construction of rainbow style colourmaps. It is shown that good colourmaps can be formed from smooth curves constructed in a perceptually uniform colour space such as CIELAB. Colour lightness values should be monotonically increasing at a constant rate while at the same time the colourmap curve should stay close to the boundary of the colour space gamut to ensure that the colours are vivid.

Method for determining size of inhomogeneity localization region based on analysis of secondary wave field of second harmonic

NASA Astrophysics Data System (ADS)

Chernov, N. N.; Zagray, N. P.; Laguta, M. V.; Varenikova, A. Yu

2018-05-01

The article describes the research of the method of localization and determining the size of heterogeneity in biological tissues. The equation for the acoustic harmonic wave, which propagates in the positive direction, is taken as the main one. A three-dimensional expression that describes the field of secondary sources at the observation point is obtained. The simulation of the change of the amplitude values of the vibrational velocity of the second harmonic of the acoustic wave at different coordinates of the inhomogeneity location in three-dimensional space is carried out. For the convenience of mathematical calculations, the area of heterogeneity is reduced to a point.

ISIS Topside-Sounder Plasma-Wave Investigations as Guides to Desired Virtual Wave Observatory (VWO) Data Search Capabilities

NASA Technical Reports Server (NTRS)

Benson, Robert F.; Fung, Shing F.

2008-01-01

Many plasma-wave phenomena, observed by space-borne radio sounders, cannot be properly explained in terms of wave propagation in a cold plasma consisting of mobile electrons and infinitely massive positive ions. These phenomena include signals known as plasma resonances. The principal resonances at the harmonics of the electron cyclotron frequency, the plasma frequency, and the upper-hybrid frequency are well explained by the warm-plasma propagation of sounder-generated electrostatic waves, Other resonances have been attributed to sounder-stimulated plasma instability and non-linear effects, eigenmodes of cylindrical electromagnetic plasma oscillations, and plasma memory processes. Data from the topside sounders of the International Satellites for Ionospheric Studies (ISIS) program played a major role in these interpretations. A data transformation and preservation effort at the Goddard Space Flight Center has produced digital ISIS topside ionograms and a metadata search program that has enabled some recent discoveries pertaining to the physics of these plasma resonances. For example, data records were obtained that enabled the long-standing question (several decades) of the origin of the plasma resonance at the fundamental electron cyclotron frequency to be explained [Muldrew, Radio Sci., 2006]. These data-search capabilities, and the science enabled by them, will be presented as a guide to desired data search capabilities to be included in the Virtual Wave Observatory (VWO).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tracy, Eugene R

Quadratic corrections to the metaplectic formulation of mode conversions. In this work we showed how to systematically deal with quadratic corrections beyond the usual linearization of the dispersion matrix at a conversion. The linearization leads to parabolic cylinder functions as the local approximation to the full-wave behavior, but these do not include the variation in amplitude associated with ray refraction in the neighborhood of the conversion. Hence, the region over which they give a good fit to the incoming and outgoing WKB solutions is small. By including higher order corrections it is possible to provide a much more robust matching.more » We also showed that it was possible, in principle, to extend these methods to arbitrary order. A new normal form for mode conversion. This is based upon our earlier NSF-DOE-funded work on ray helicity. We have begun efforts to apply these new ideas in practical ray tracing algorithms. Group theoretical foundation of path integrals and phase space representations of wave problems. Using the symbol theory of N. Zobin, we developed a new understanding of path integrals on phase space. The initial goal was to find practical computational tools for dealing with non-standard mode conversions. Along the way we uncovered a new way to represent wave functions directly on phase space without the intermediary of a Wigner function. We are exploring the use of these ideas for numerical studies of conversion, with the goal of eventually incorporating kinetic effects. Wave packet studies of gyroresonance crossing. In earlier work, Huanchun Ye and Allan Kaufman -- building upon ideas due to Lazar Friedland -- had shown that gyroresonance crossings could be treated as a double conversion. This perspective is one we have used for many of our papers since then. We are now performing a detailed numerical comparison between full-wave and ray tracing approaches in the study of minority-ion gyroresonance crossing. In this study, a fast magnetosonic wave -- supported by a majority-ion species such as deuterium -- crosses the resonance layer associated with a minority species, such as hydrogen. By using wave packets instead of harmonic solutions, it becomes easy to see the evolution in k-space of the minority-ion disturbance, and the time delay for emission of the reflected fast-wave packet. Iterated conversion in a cavity. When mode conversion occurs in a cavity where rays are trapped, multiple conversions will occur and the resulting absorption profile will typically have a complicated spatial dependence due to overlapping interference patterns. The goal of this work is to develop fast and efficient ray-based methods for computing the cavity response to external driving, and to compute the spatial absorption profile. We have introduced a new approach that allows us to visualize in great detail the underlying iterated ray geometry, and should lead to simpler methods for identifying parameter values where global changes occur in the qualitative response (e.g. global bifurcations).« less

Space-time properties of wind-waves: a new look at directional wave distributions

NASA Astrophysics Data System (ADS)

Leckler, Fabien; Ardhuin, Fabrice; Benetazzo, Alvise; Fedele, Francesco; Bergamasco, Filippo; Dulov, Vladimir

2014-05-01

Few accurate observed directional wave spectra are available in the literature at spatial scales ranging between 0.5 and 5.0 m. These intermediate wave scales, relevant for air-sea fluxes and remote sensing are also expected to feed back on the dominant wave properties through wave generation. These wave scales can be prolifically investigated using the well-known optical stereo methods that provides, from a couple of synchronized images, instantaneous representation of wave elevations over a given sea surface. Thus, two stereo systems (the so-called Wave Acquisition Stereo Systems, WASS) were deployed on top of the deep-water platform at Katsiveli, in the Black Sea, in September 2011 and 2013. From image pairs taken by the couple of synchronized high-resolution cameras, ocean surfaces have been reconstructed by stereo-triangulation. Here we analyze sea states corresponding to mean wind speeds of 11 to 14 m/s, and young wave ages of 0.35 to 0.42, associated to significant wave heights of 0.3 to 0.55m. As a result, four 12 Hz time evolutions of sea surface elevation maps with areas about 10 x 10 m2 have been obtained for sequence durations ranging between 15 and 30 minutes, and carefully validated with nearby capacitance wave gauges. The evolving free surfaces elevations were processed into frequency-wavenumber-direction 3D spectra. We found that wave energy chiefly follows the dispersion relation up to frequency of 1.6Hz and wavenumber of 10 rad/m, corresponding to wavelength of about 0.5 m. These spectra also depict well the energy contribution from non-linear waves, which is quantified and compared to theory. A strong bi-modality of the linear spectra was also observed, with the angle of the two maxima separated by about 160 degrees. Furthermore, spectra also exhibit the bimodality of the non-linear part. Integrated over positive frequencies to obtain wavenumber spectra unambiguous in direction, the bimodality of the spectra is partially hidden by the energy from second order waves, in particular from wave harmonics of the peak waves. However, the obtained spreading functions and integrals question the isotropy of the spectrum at high frequencies, generally assumed to explain deep water pressure measurement.

Configurational forces in electronic structure calculations using Kohn-Sham density functional theory

NASA Astrophysics Data System (ADS)

Motamarri, Phani; Gavini, Vikram

2018-04-01

We derive the expressions for configurational forces in Kohn-Sham density functional theory, which correspond to the generalized variational force computed as the derivative of the Kohn-Sham energy functional with respect to the position of a material point x . These configurational forces that result from the inner variations of the Kohn-Sham energy functional provide a unified framework to compute atomic forces as well as stress tensor for geometry optimization. Importantly, owing to the variational nature of the formulation, these configurational forces inherently account for the Pulay corrections. The formulation presented in this work treats both pseudopotential and all-electron calculations in a single framework, and employs a local variational real-space formulation of Kohn-Sham density functional theory (DFT) expressed in terms of the nonorthogonal wave functions that is amenable to reduced-order scaling techniques. We demonstrate the accuracy and performance of the proposed configurational force approach on benchmark all-electron and pseudopotential calculations conducted using higher-order finite-element discretization. To this end, we examine the rates of convergence of the finite-element discretization in the computed forces and stresses for various materials systems, and, further, verify the accuracy from finite differencing the energy. Wherever applicable, we also compare the forces and stresses with those obtained from Kohn-Sham DFT calculations employing plane-wave basis (pseudopotential calculations) and Gaussian basis (all-electron calculations). Finally, we verify the accuracy of the forces on large materials systems involving a metallic aluminum nanocluster containing 666 atoms and an alkane chain containing 902 atoms, where the Kohn-Sham electronic ground state is computed using a reduced-order scaling subspace projection technique [P. Motamarri and V. Gavini, Phys. Rev. B 90, 115127 (2014), 10.1103/PhysRevB.90.115127].

Localization of one-photon state in space and Einstein-Podolsky-Rosen paradox in spontaneous parametric down conversion

NASA Technical Reports Server (NTRS)

Penin, A. N.; Reutova, T. A.; Sergienko, A. V.

1992-01-01

An experiment on one-photon state localization in space using a correlation technique in Spontaneous Parametric Down Conversion (SPDC) process is discussed. Results of measurements demonstrate an idea of the Einstein-Podolsky-Rosen (EPR) paradox for coordinate and momentum variables of photon states. Results of the experiment can be explained with the help of an advanced wave technique. The experiment is based on the idea that two-photon states of optical electromagnetic fields arising in the nonlinear process of the spontaneous parametric down conversion (spontaneous parametric light scattering) can be explained by quantum mechanical theory with the help of a single wave function.

Localization of one-photon state in space and Einstein-Podolsky-Rosen paradox in spontaneous parametric down conversion

NASA Astrophysics Data System (ADS)

Penin, A. N.; Reutova, T. A.; Sergienko, A. V.

1992-02-01

An experiment on one-photon state localization in space using a correlation technique in Spontaneous Parametric Down Conversion (SPDC) process is discussed. Results of measurements demonstrate an idea of the Einstein-Podolsky-Rosen (EPR) paradox for coordinate and momentum variables of photon states. Results of the experiment can be explained with the help of an advanced wave technique. The experiment is based on the idea that two-photon states of optical electromagnetic fields arising in the nonlinear process of the spontaneous parametric down conversion (spontaneous parametric light scattering) can be explained by quantum mechanical theory with the help of a single wave function.

A time reversal algorithm in acoustic media with Dirac measure approximations

NASA Astrophysics Data System (ADS)

Bretin, Élie; Lucas, Carine; Privat, Yannick

2018-04-01

This article is devoted to the study of a photoacoustic tomography model, where one is led to consider the solution of the acoustic wave equation with a source term writing as a separated variables function in time and space, whose temporal component is in some sense close to the derivative of the Dirac distribution at t  =  0. This models a continuous wave laser illumination performed during a short interval of time. We introduce an algorithm for reconstructing the space component of the source term from the measure of the solution recorded by sensors during a time T all along the boundary of a connected bounded domain. It is based at the same time on the introduction of an auxiliary equivalent Cauchy problem allowing to derive explicit reconstruction formula and then to use of a deconvolution procedure. Numerical simulations illustrate our approach. Finally, this algorithm is also extended to elasticity wave systems.

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

PubMed

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.

Complex-valued derivative propagation method with approximate Bohmian trajectories: Application to electronic nonadiabatic dynamics

NASA Astrophysics Data System (ADS)

Wang, Yu; Chou, Chia-Chun

2018-05-01

The coupled complex quantum Hamilton-Jacobi equations for electronic nonadiabatic transitions are approximately solved by propagating individual quantum trajectories in real space. Equations of motion are derived through use of the derivative propagation method for the complex actions and their spatial derivatives for wave packets moving on each of the coupled electronic potential surfaces. These equations for two surfaces are converted into the moving frame with the same grid point velocities. Excellent wave functions can be obtained by making use of the superposition principle even when nodes develop in wave packet scattering.

Recent Advances in Remote Sensing of Natural Hazards-Induced Atmospheric and Ionospheric Perturbations

NASA Astrophysics Data System (ADS)

Yang, Y. M.; Komjathy, A.; Meng, X.; Verkhoglyadova, O. P.; Langley, R. B.; Mannucci, A. J.

2015-12-01

Traveling ionospheric disturbances (TIDs) induced by acoustic-gravity waves in the neutral atmosphere have significant impact on trans-ionospheric radio waves such as Global Navigation Satellite System (GNSS, including Global Position System (GPS)) measurements. Natural hazards and solid Earth events, such as earthquakes, tsunamis and volcanic eruptions are actual sources that may trigger acoustic and gravity waves resulting in traveling ionospheric disturbances (TIDs) in the upper atmosphere. Trans-ionospheric radio wave measurements sense the total electron content (TEC) along the signal propagation path. In this research, we introduce a novel GPS-based detection and estimation technique for remote sensing of atmospheric wave-induced TIDs including space weather phenomena induced by major natural hazard events, using TEC time series collected from worldwide ground-based dual-frequency GNSS (including GPS) receiver networks. We demonstrate the ability of using ground- and space-based dual-frequency GPS measurements to detect and monitor tsunami wave propagation from the 2011 Tohoku-Oki earthquake and tsunami. Major wave trains with different propagation speeds and wavelengths were identified through analysis of the GPS remote sensing observations. Dominant physical characteristics of atmospheric wave-induced TIDs are found to be associated with specific tsunami propagations and oceanic Rayleigh waves. In this research, we compared GPS-based observations, corresponding model simulations and tsunami wave propagation. Results are shown to lead to a better understanding of the tsunami-induced ionosphere responses. Based on current distribution of Plate Boundary Observatory GPS stations, the results indicate that tsunami-induced TIDs may be detected about 60 minutes prior to tsunamis arriving at the U.S. west coast. It is expected that this GNSS-based technology will become an integral part of future early-warning systems.

ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared

NASA Astrophysics Data System (ADS)

Palmroth, Minna; Rami, Vainio; Archer, Martin; Hietala, Heli; Afanasiev, Alexandr; Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian

2015-04-01

For decades, a certain type of ultra low frequency waves with a period of about 30 seconds have been observed in the Earth's quasi-parallel foreshock. These waves, with a wavelength of about an Earth radius, are compressive and propagate with an average angle of 20 degrees with respect of the interplanetary magnetic field (IMF). The latter property has caused trouble to scientists as the growth rate for the instability causing the waves is maximized along the magnetic field. So far, these waves have been characterized by single or multi-spacecraft methods and 2-dimensional hybrid-PIC simulations, which have not fully reproduced the wave properties. Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves the six-dimensional phase space utilising the Vlasov equation for protons, while electrons are a charge-neutralising fluid. The outcome of the simulation is a global reproduction of ion-scale physics in a holistic manner where the generation of physical features can be followed in time and their consequences can be quantitatively characterised. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global scale magnetospheric scale with a resolution of a couple of hundred kilometres in the ordinary space and 20 km/s in the velocity space. We run Vlasiator under a radial IMF in five dimensions consisting of the three-dimensional velocity space embedded in the ecliptic plane. We observe the generation of the 30-second ULF waves, and characterize their evolution and physical properties in time. We compare the results both to THEMIS observations and to the quasi-linear theory. We find that Vlasiator reproduces the foreshock ULF waves in all reported observational aspects, i.e., they are of the observed size in wavelength and period, they are compressive and propagate obliquely to the IMF. In particular, we discuss the issues related to the long-standing question of oblique propagation.

System providing limit switch function with simultaneous absolute position output

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

2006-01-01

A limit and position sensing system includes a sensor assembly and an emitter. The sensor assembly includes first and second electrical conductors arranged in opposing parallel planes. The first electrical conductor is coiled outwardly from either end thereof in a clockwise fashion to form a first coil region and a second coil region. The second electrical conductor forms a single coil with portions of the single coil's rings lying between the first end and second end of the first electrical conductor being parallel to an axis of the first electrical conductor's plane. Ferromagnetic material is aligned with the first and second electrical conductors and spans beyond (a) the first and second ends of the first electrical conductor, and (b) the portions of the rings of the second electrical conductor's single coil that lie between the first end and second end of the first electrical conductor. The emitter is spaced apart from the sensor assembly and transmits a periodic electromagnetic wave towards the sensor assembly.

Accurate B-spline-based 3-D interpolation scheme for digital volume correlation

NASA Astrophysics Data System (ADS)

Ren, Maodong; Liang, Jin; Wei, Bin

2016-12-01

An accurate and efficient 3-D interpolation scheme, based on sampling theorem and Fourier transform technique, is proposed to reduce the sub-voxel matching error caused by intensity interpolation bias in digital volume correlation. First, the influence factors of the interpolation bias are investigated theoretically using the transfer function of an interpolation filter (henceforth filter) in the Fourier domain. A law that the positional error of a filter can be expressed as a function of fractional position and wave number is found. Then, considering the above factors, an optimized B-spline-based recursive filter, combining B-spline transforms and least squares optimization method, is designed to virtually eliminate the interpolation bias in the process of sub-voxel matching. Besides, given each volumetric image containing different wave number ranges, a Gaussian weighting function is constructed to emphasize or suppress certain of wave number ranges based on the Fourier spectrum analysis. Finally, a novel software is developed and series of validation experiments were carried out to verify the proposed scheme. Experimental results show that the proposed scheme can reduce the interpolation bias to an acceptable level.

Re-evaluation of ``;The Propagation of Radiation in the Spherical Wave Form''

NASA Astrophysics Data System (ADS)

Joshi, Narahari V.

2012-03-01

It is well accepted that radiation propagates in the free space (without obstacles) in a spherical wave form as well as in a plane wave form. Almost all observed phenomena such as interference, diffraction etc are explained satisfactorily on the basis of spherical wave propagation with a slight alteration in the mathematical treatment. However, one of the fundamental aspects, namely the intensity of the radiation as a function of the distance still remains an unsolved problem as the intensity varies with 1/(distance)2 when one represents the propagation in terms of spherical waves while it is independent of the distance if it is considered as a plane wave. In order to understand this puzzle, the propagation by a spherical wave form is reexamined. It is found that conversion of fields into particle (vice versa), via the field quantization process, explains several dilemma related with the radiation propagation.

Position, scale, and rotation invariant holographic associative memory

NASA Astrophysics Data System (ADS)

Fielding, Kenneth H.; Rogers, Steven K.; Kabrisky, Matthew; Mills, James P.

1989-08-01

This paper describes the development and characterization of a holographic associative memory (HAM) system that is able to recall stored objects whose inputs were changed in position, scale, and rotation. The HAM is based on the single iteration model described by Owechko et al. (1987); however, the system described uses a self-pumped BaTiO3 phase conjugate mirror, rather than a degenerate four-wave mixing proposed by Owechko and his coworkers. The HAM system can store objects in a position, scale, and rotation invariant feature space. The angularly multiplexed diffuse Fourier transform holograms of the HAM feature space are characterized as the memory unit; distorted input objects are correlated with the hologram, and the nonlinear phase conjugate mirror reduces cross-correlation noise and provides object discrimination. Applications of the HAM system are presented.

Study of travelling wave solutions for some special-type nonlinear evolution equations

NASA Astrophysics Data System (ADS)

Song, Junquan; Hu, Lan; Shen, Shoufeng; Ma, Wen-Xiu

2018-07-01

The tanh-function expansion method has been improved and used to construct travelling wave solutions of the form U={\\sum }j=0n{a}j{\\tanh }jξ for some special-type nonlinear evolution equations, which have a variety of physical applications. The positive integer n can be determined by balancing the highest order linear term with the nonlinear term in the evolution equations. We improve the tanh-function expansion method with n = 0 by introducing a new transform U=-W\\prime (ξ )/{W}2. A nonlinear wave equation with source terms, and mKdV-type equations, are considered in order to show the effectiveness of the improved scheme. We also propose the tanh-function expansion method of implicit function form, and apply it to a Harry Dym-type equation as an example.

Orbital stability of periodic traveling wave solutions for the Kawahara equation

NASA Astrophysics Data System (ADS)

de Andrade, Thiago Pinguello; Cristófani, Fabrício; Natali, Fábio

2017-05-01

In this paper, we investigate the orbital stability of periodic traveling waves for the Kawahara equation. We prove that the periodic traveling wave, under certain conditions, minimizes a convenient functional by using an adaptation of the method developed by Grillakis et al. [J. Funct. Anal. 74, 160-197 (1987)]. The required spectral properties to ensure the orbital stability are obtained by knowing the positiveness of the Fourier transform of the associated periodic wave established by Angulo and Natali [SIAM J. Math. Anal. 40, 1123-1151 (2008)].

The two Faces of Equipartition

NASA Astrophysics Data System (ADS)

Sanchez-Sesma, F. J.; Perton, M.; Rodriguez-Castellanos, A.; Campillo, M.; Weaver, R. L.; Rodriguez, M.; Prieto, G.; Luzon, F.; McGarr, A.

2008-12-01

Equipartition is good. Beyond its philosophical implications, in many instances of statistical physics it implies that the available kinetic and potential elastic energy, in phase space, is distributed in the same fixed proportions among the possible "states". There are at least two distinct and complementary descriptions of such states in a diffuse elastic wave field u(r,t). One asserts that u may be represented as an incoherent isotropic superposition of incident plane waves of different polarizations. Each type of wave has an appropriate share of the available energy. This definition introduced by Weaver is similar to the room acoustics notion of a diffuse field, and it suffices to permit prediction of field correlations. The other description assumes that the degrees of freedom of the system, in this case, the kinetic energy densities, are all incoherently excited with equal expected amplitude. This definition, introduced by Maxwell, is also familiar from room acoustics using the normal modes of vibration within an arbitrarily large body. Usually, to establish if an elastic field is diffuse and equipartitioned only the first description has been applied, which requires the separation of dilatational and shear waves using carefully designed experiments. When the medium is bounded by an interface, waves of other modes, for example Rayleigh waves, complicate the measurement of these energies. As a consequence, it can be advantageous to use the second description. Moreover, each spatial component of the energy densities is linked, when an elastic field is diffuse and equipartitioned, to the component of the imaginary part of the Green function at the source. Accordingly, one can use the second description to retrieve the Green function and obtain more information about the medium. The equivalence between the two descriptions of equipartition are given for an infinite space and extended to the case of a half-space. These two descriptiosn are equivalent thanks to the relationship of average autocorrelations with the imaginary part of Green function at the source. Preliminary results are displayed in data sets from Chilpancingo, Mexico, and the Tautona Gold Mine, South Africa, that strongly suggest that equipartition, that guarantees the diffuse nature of seismic fields, has more than one face. Acknowledgements. Partial supports from DGAPA-UNAM, Project IN114706, Mexico; from Proyect MCyT CGL2005-05500-C02/BTE, Spain; from project DyETI of INSU-CNRS, France, and from the Instituto Mexicano del Petróleo are greatly appreciated.

Quantum mechanical reality according to Copenhagen 2.0

NASA Astrophysics Data System (ADS)

Din, Allan M.

2016-05-01

The long-standing conceptual controversies concerning the interpretation of nonrelativistic quantum mechanics are argued, on one hand, to be due to its incompleteness, as affirmed by Einstein. But on the other hand, it appears to be possible to complete it at least partially, as Bohr might have appreciated it, in the framework of its standard mathematical formalism with observables as appropriately defined self-adjoint operators. This completion of quantum mechanics is based on the requirement on laboratory physics to be effectively confined to a bounded space region and on the application of the von Neumann deficiency theorem to properly define a set of self-adjoint extensions of standard observables, e.g. the momenta and the Hamiltonian, in terms of certain isometries on the region boundary. This is formalized mathematically in the setting of a boundary ontology for the so-called Qbox in which the wave function acquires a supplementary dependence on a set of Additional Boundary Variables (ABV). It is argued that a certain geometric subset of the ABV parametrizing Quasi-Periodic Translational Isometries (QPTI) has a particular physical importance by allowing for the definition of an ontic wave function, which has the property of epitomizing the spatial wave function “collapse.” Concomitantly the standard wave function in an unbounded geometry is interpreted as an epistemic wave function, which together with the ontic QPTI wave function gives rise to the notion of two-wave duality, replacing the standard concept of wave-particle duality. More generally, this approach to quantum physics in a bounded geometry provides a novel analytical basis for a better understanding of several conceptual notions of quantum mechanics, including reality, nonlocality, entanglement and Heisenberg’s uncertainty relation. The scope of this analysis may be seen as a foundational update of the multiple versions 1.x of the Copenhagen interpretation of quantum mechanics, which is sufficiently incremental so as to be appropriately characterized as Copenhagen 2.0.

The first radial-mode Lorentzian Landau damping of dust acoustic space-charge waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588

2016-05-15

The dispersion properties and the first radial-mode Lorentzian Landau damping of a dust acoustic space-charge wave propagating in a cylindrical waveguide dusty plasma which contains nonthermal electrons and ions are investigated by employing the normal mode analysis and the method of separation of variables. It is found that the frequency of dust acoustic space-charge wave increases as the wave number increases as well as the radius of cylindrical plasma does. However, the nonthermal property of the Lorentzian plasma is found to suppress the wave frequency of the dust acoustic space-charge wave. The Landau damping rate of the dust acoustic space-chargemore » wave is derived in a cylindrical waveguide dusty plasma. The damping of the space-charge wave is found to be enhanced as the radius of cylindrical plasma and the nonthermal property increase. The maximum Lorentzian Landau damping rate is also found in a cylindrical waveguide dusty plasma. The variation of the wave frequency and the Landau damping rate due to the nonthermal character and geometric effects are also discussed.« less

Low-Frequency Waves in Space Plasmas

NASA Astrophysics Data System (ADS)

Keiling, Andreas; Lee, Dong-Hun; Nakariakov, Valery

2016-02-01

Low-frequency waves in space plasmas have been studied for several decades, and our knowledge gain has been incremental with several paradigm-changing leaps forward. In our solar system, such waves occur in the ionospheres and magnetospheres of planets, and around our Moon. They occur in the solar wind, and more recently, they have been confirmed in the Sun's atmosphere as well. The goal of wave research is to understand their generation, their propagation, and their interaction with the surrounding plasma. Low-frequency Waves in Space Plasmas presents a concise and authoritative up-to-date look on where wave research stands: What have we learned in the last decade? What are unanswered questions? While in the past waves in different astrophysical plasmas have been largely treated in separate books, the unique feature of this monograph is that it covers waves in many plasma regions, including: Waves in geospace, including ionosphere and magnetosphere Waves in planetary magnetospheres Waves at the Moon Waves in the solar wind Waves in the solar atmosphere Because of the breadth of topics covered, this volume should appeal to a broad community of space scientists and students, and it should also be of interest to astronomers/astrophysicists who are studying space plasmas beyond our Solar System.

Intensity Distribution of the Three-Wave Diffraction from Dislocation Epitaxial Layers in the Reciprocal Space

NASA Astrophysics Data System (ADS)

Kyutt, R. N.

2018-04-01

The three-wave X-ray diffraction in strongly disordered epitaxial layers of GaN and ZnO is experimentally investigated. The charts of the intensity distribution in the reciprocal space are plotted in coordinates q θ and q ϕ for the most intensive three-wave combination (1010)/(1011) by means of subsequent θ- and ϕ-scanning. A nontrivial shape of the θ-sections of these contours at a distance from the ϕ center of reflection is revealed; it is different for different samples. For the θ-curves at the center of reflection, we observed a common peak that may be approximated by the Voigt function with a power-low decrease in the intensity at the wings; the decrease law (from-4.5 to-5.0) is found to be considerably greater than that for the similar curves of two-wave diffraction and not depending on the dislocation density and distribution in layers. In some films we observed a coarse-block structure; in addition, it follows from the distribution in the reciprocal space that these blocks are turned with respect to each other around a normal to the surface, which allows us to suggest the existence of low-angle boundaries between them, consisting exclusively of edge dislocations.

Real-time 3-D space numerical shake prediction for earthquake early warning

NASA Astrophysics Data System (ADS)

Wang, Tianyun; Jin, Xing; Huang, Yandan; Wei, Yongxiang

2017-12-01

In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.

Modeling RF Fields in Hot Plasmas with Parallel Full Wave Code

NASA Astrophysics Data System (ADS)

Spencer, Andrew; Svidzinski, Vladimir; Zhao, Liangji; Galkin, Sergei; Kim, Jin-Soo

2016-10-01

FAR-TECH, Inc. is developing a suite of full wave RF plasma codes. It is based on a meshless formulation in configuration space with adapted cloud of computational points (CCP) capability and using the hot plasma conductivity kernel to model the nonlocal plasma dielectric response. The conductivity kernel is calculated by numerically integrating the linearized Vlasov equation along unperturbed particle trajectories. Work has been done on the following calculations: 1) the conductivity kernel in hot plasmas, 2) a monitor function based on analytic solutions of the cold-plasma dispersion relation, 3) an adaptive CCP based on the monitor function, 4) stencils to approximate the wave equations on the CCP, 5) the solution to the full wave equations in the cold-plasma model in tokamak geometry for ECRH and ICRH range of frequencies, and 6) the solution to the wave equations using the calculated hot plasma conductivity kernel. We will present results on using a meshless formulation on adaptive CCP to solve the wave equations and on implementing the non-local hot plasma dielectric response to the wave equations. The presentation will include numerical results of wave propagation and absorption in the cold and hot tokamak plasma RF models, using DIII-D geometry and plasma parameters. Work is supported by the U.S. DOE SBIR program.

How Body Orientation Affects Concepts of Space, Time and Valence: Functional Relevance of Integrating Sensorimotor Experiences during Word Processing

PubMed Central

Ruiz Fernandez, Susana; Bury, Nils-Alexander; Gerjets, Peter; Fischer, Martin H.; Bock, Otmar L.

2016-01-01

The aim of the present study was to test the functional relevance of the spatial concepts UP or DOWN for words that use these concepts either literally (space) or metaphorically (time, valence). A functional relevance would imply a symmetrical relationship between the spatial concepts and words related to these concepts, showing that processing words activate the related spatial concepts on one hand, but also that an activation of the concepts will ease the retrieval of a related word on the other. For the latter, the rotation angle of participant’s body position was manipulated either to an upright or a head-down tilted body position to activate the related spatial concept. Afterwards participants produced in a within-subject design previously memorized words of the concepts space, time and valence according to the pace of a metronome. All words were related either to the spatial concept UP or DOWN. The results including Bayesian analyses show (1) a significant interaction between body position and words using the concepts UP and DOWN literally, (2) a marginal significant interaction between body position and temporal words and (3) no effect between body position and valence words. However, post-hoc analyses suggest no difference between experiments. Thus, the authors concluded that integrating sensorimotor experiences is indeed of functional relevance for all three concepts of space, time and valence. However, the strength of this functional relevance depends on how close words are linked to mental concepts representing vertical space. PMID:27812155

Lump solutions to nonlinear partial differential equations via Hirota bilinear forms

NASA Astrophysics Data System (ADS)

Ma, Wen-Xiu; Zhou, Yuan

2018-02-01

Lump solutions are analytical rational function solutions localized in all directions in space. We analyze a class of lump solutions, generated from quadratic functions, to nonlinear partial differential equations. The basis of success is the Hirota bilinear formulation and the primary object is the class of positive multivariate quadratic functions. A complete determination of quadratic functions positive in space and time is given, and positive quadratic functions are characterized as sums of squares of linear functions. Necessary and sufficient conditions for positive quadratic functions to solve Hirota bilinear equations are presented, and such polynomial solutions yield lump solutions to nonlinear partial differential equations under the dependent variable transformations u = 2(ln ⁡ f) x and u = 2(ln ⁡ f) xx, where x is one spatial variable. Applications are made for a few generalized KP and BKP equations.

Study of Linear and Nonlinear Wave Excitation

NASA Astrophysics Data System (ADS)

Chu, Feng; Berumen, Jorge; Hood, Ryan; Mattingly, Sean; Skiff, Frederick

2013-10-01

We report an experimental study of externally excited low-frequency waves in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional. Wave excitation in the drift wave frequency range is accomplished by low-percentage amplitude modulation of the RF plasma source. Laser-induced fluorescence is adopted to study ion-density fluctuations in phase space. The laser is chopped to separate LIF from collisional fluorescence. A single negatively-biased Langmuir probe is used to detect ion-density fluctuations in the plasma. A ring array of Langmuir probes is also used to analyze the spatial and spectral structure of the excited waves. We apply coherent detection with respect to the wave frequency to obtain the ion distribution function associated with externally generated waves. Higher-order spectra are computed to evaluate the nonlinear coupling between fluctuations at various frequencies produced by the externally generated waves. Parametric decay of the waves is observed. This work is supported by U.S. DOE Grant No. DE-FG02-99ER54543.

Ring polymer dynamics in curved spaces

NASA Astrophysics Data System (ADS)

Wolf, S.; Curotto, E.

2012-07-01

We formulate an extension of the ring polymer dynamics approach to curved spaces using stereographic projection coordinates. We test the theory by simulating the particle in a ring, {T}^1, mapped by a stereographic projection using three potentials. Two of these are quadratic, and one is a nonconfining sinusoidal model. We propose a new class of algorithms for the integration of the ring polymer Hamilton equations in curved spaces. These are designed to improve the energy conservation of symplectic integrators based on the split operator approach. For manifolds, the position-position autocorrelation function can be formulated in numerous ways. We find that the position-position autocorrelation function computed from configurations in the Euclidean space {R}^2 that contains {T}^1 as a submanifold has the best statistical properties. The agreement with exact results obtained with vector space methods is excellent for all three potentials, for all values of time in the interval simulated, and for a relatively broad range of temperatures.

NASA's next generation all-digital deep space network breadboard receiver

NASA Technical Reports Server (NTRS)

Hinedi, Sami

1993-01-01

This paper describes the breadboard advanced receiver (ARX) that is currently being built for future use in NASA's deep space network (DSN). This receiver has unique requirements in having to operate with very weak signals from deep space probes and provide high quality telemetry and tracking data. The hybrid analog/digital receiver performs multiple functions including carrier, subcarrier and symbol synchronization. Tracking can be achieved for either residual, suppressed or hybrid carriers and for both sinusoidal and square wave subcarriers. System requirements are specified and a functional description of the ARX is presented. The various digital signal processing algorithms used are also discussed and illustrated with block diagrams. Other functions such as time tagged Doppler extraction and monitor/control are also discussed including acquisition algorithms and lock detection schemes.

Development of crawler type device using new measuring system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maruyama, T.; Sasaki, T.; Yagi, T.

1995-08-01

This paper reports the development and field application of a new device which examine shell to shell weld joints of RPV. In a BWR type nuclear power plant, there is narrow space around the Reactor Pressure Vessel (RPV) because RPV is enclosed by the Reactor Shield Wall (RSW) and thermal insulations. The developed device is characterized by a new position measuring system and magnet wheels for driving. The new position measuring system uses laser beam and ultrasonic wave. The magnet wheels make the device travel freely in the narrow space between RPV and insulation. This device is tested on mock-upsmore » and applied examination of RPVs to verify field applicability.« less

A staggered-grid finite-difference scheme optimized in the time–space domain for modeling scalar-wave propagation in geophysical problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Sirui, E-mail: siruitan@hotmail.com; Huang, Lianjie, E-mail: ljh@lanl.gov

For modeling scalar-wave propagation in geophysical problems using finite-difference schemes, optimizing the coefficients of the finite-difference operators can reduce numerical dispersion. Most optimized finite-difference schemes for modeling seismic-wave propagation suppress only spatial but not temporal dispersion errors. We develop a novel optimized finite-difference scheme for numerical scalar-wave modeling to control dispersion errors not only in space but also in time. Our optimized scheme is based on a new stencil that contains a few more grid points than the standard stencil. We design an objective function for minimizing relative errors of phase velocities of waves propagating in all directions within amore » given range of wavenumbers. Dispersion analysis and numerical examples demonstrate that our optimized finite-difference scheme is computationally up to 2.5 times faster than the optimized schemes using the standard stencil to achieve the similar modeling accuracy for a given 2D or 3D problem. Compared with the high-order finite-difference scheme using the same new stencil, our optimized scheme reduces 50 percent of the computational cost to achieve the similar modeling accuracy. This new optimized finite-difference scheme is particularly useful for large-scale 3D scalar-wave modeling and inversion.« less

Preferential Heating of Oxygen 5+ Ions by Finite-Amplitude Oblique Alfven Waves

NASA Technical Reports Server (NTRS)

Maneva, Yana G.; Vinas, Adolfo; Araneda, Jamie; Poedts, Stefaan

2016-01-01

Minor ions in the fast solar wind are known to have higher temperatures and to flow faster than protons in the interplanetary space. In this study we combine previous research on parametric instability theory and 2.5D hybrid simulations to study the onset of preferential heating of Oxygen 5+ ions by large-scale finite-amplitude Alfven waves in the collisionless fast solar wind. We consider initially non-drifting isotropic multi-species plasma, consisting of isothermal massless fluid electrons, kinetic protons and kinetic Oxygen 5+ ions. The external energy source for the plasma heating and energization are oblique monochromatic Alfven-cyclotron waves. The waves have been created by rotating the direction of initial parallel pump, which is a solution of the multi-fluid plasma dispersion relation. We consider propagation angles theta less than or equal to 30 deg. The obliquely propagating Alfven pump waves lead to strong diffusion in the ion phase space, resulting in highly anisotropic heavy ion velocity distribution functions and proton beams. We discuss the application of the model to the problems of preferential heating of minor ions in the solar corona and the fast solar wind.

Simulation of electromagnetic ion cyclotron triggered emissions in the Earth's inner magnetosphere

NASA Astrophysics Data System (ADS)

Shoji, Masafumi; Omura, Yoshiharu

2011-05-01

In a recent observation by the Cluster spacecraft, emissions triggered by electromagnetic ion cyclotron (EMIC) waves were discovered in the inner magnetosphere. We perform hybrid simulations to reproduce the EMIC triggered emissions. We develop a self-consistent one-dimensional hybrid code with a cylindrical geometry of the background magnetic field. We assume a parabolic magnetic field to model the dipole magnetic field in the equatorial region of the inner magnetosphere. Triggering EMIC waves are driven by a left-handed polarized external current assumed at the magnetic equator in the simulation model. Cold proton, helium, and oxygen ions, which form branches of the dispersion relation of the EMIC waves, are uniformly distributed in the simulation space. Energetic protons with a loss cone distribution function are also assumed as resonant particles. We reproduce rising tone emissions in the simulation space, finding a good agreement with the nonlinear wave growth theory. In the energetic proton velocity distribution we find formation of a proton hole, which is assumed in the nonlinear wave growth theory. A substantial amount of the energetic protons are scattered into the loss cone, while some of the resonant protons are accelerated to higher pitch angles, forming a pancake velocity distribution.

Identifying explosives using broadband millimeter-wave imaging

NASA Astrophysics Data System (ADS)

Weatherall, James C.; Yam, Kevin; Barber, Jeffrey; Smith, Barry T.; Smith, Peter R.; Greca, Joseph

2017-05-01

Millimeter wave imaging is employed in Advanced Technology Imaging (AIT) systems to screen personnel for concealed explosives and weapons. AIT systems deployed in airports auto-detect potential threats by highlighting their location on a generic outline of a person using imaging data collected over a range of frequency. We show how the spectral information from the imaging data can be used to identify the composition of an anomalous object, in particular if it is an explosive material. The discriminative value of the technique was illustrated on military sheet explosive using millimeter-wave reflection data at frequencies 18 - 40 GHz, and commercial explosives using 2 - 18 GHz, but the free-space measurement was limited to a single horn with a large-area sample. This work extends the method to imaging data collected at high resolution with a 18 - 40 GHz imaging system. The identification of explosives is accomplished by extracting the dielectric constant from the free-space, multifrequency data. The reflection coefficient is a function of frequency because of propagation effects associated with the material's complex dielectric constant, which include interference from multiple reflections and energy loss in the sample. The dielectric constant is obtained by numerically fitting the reflection coefficient as a function of frequency to an optical model. In principal, the implementation of this technique in standoff imaging systems would allow threat assessment to be accomplished within the scope of millimeter-wave screening.

Field Evaluation in Four NEEMO Divers of a Prototype In-suit Doppler Ultrasound Bubble Detector

NASA Technical Reports Server (NTRS)

Acock, K. E.; Gernhardt, M. L.; Conkin, J.; Powell, M. R.

2004-01-01

It is desirable to know if astronauts produce venous gas emboli (VGE) as a result of their exposure to 4.3 psia during space walks. The current prototype in-suit Doppler (ISD) ultrasound bubble detector provides an objective assessment of decompression stress by monitoring for VGE. The NOAA Aquarius habitat and NASA Extreme Environment Mission Operations (NEEMO) series of dives provided an opportunity to assess the ability of the prototype ISDs to record venous blood flow and possibly detect VGE in the pulmonary artery. From July 16 to 29,2003, four aquanauts (two males and two females) donned the ISD for a 4 hr automated recording session, following excursion dives (up to 6hrs and 29 MSW below storage depth) from air saturation at 17 MSW. Doppler recordings for 32 excursion dives were collected. The recordings consisted of approximately 150 digital wave files. Each wave file contained 24 sec of recording for each min. A 1 - 4 Doppler Quality Score (DQS) was assigned to each wave file in 17 of the 32 records evaluated to date. A DQS of 1 indicates a poor flow signal and a score of 4 indicates an optimum signal. Only 23% of all wave files had DQSs considered adequate to detect low grade VGE (Spencer I-II). The distribution of DQS in 2,356 wave files is as follows: DQS 1-56%, DQS 2-21%, DQS 3-18% and DQS 4-5%. Six of the 17 records had false positive VGE (Spencer I-IV) detected in one or more wave files per dive record. The false positive VGE recordings are attributable to air entrainment associated with drinking (verified by control tests), and this observation is important as astronauts drink water during space walks. The current ISD design provides quality recordings only over a narrow range of chest anatomy.

Terahertz waves radiated from two noncollinear femtosecond plasma filaments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Hai-Wei; Hoshina, Hiromichi; Otani, Chiko, E-mail: otani@riken.jp

2015-11-23

Terahertz (THz) waves radiated from two noncollinear femtosecond plasma filaments with a crossing angle of 25° are investigated. The irradiated THz waves from the crossing filaments show a small THz pulse after the main THz pulse, which was not observed in those from single-filament scheme. Since the position of the small THz pulse changes with the time-delay of two filaments, this phenomenon can be explained by a model in which the small THz pulse is from the second filament. The denser plasma in the overlap region of the filaments changes the movement of space charges in the plasma, thereby changingmore » the angular distribution of THz radiation. As a result, this schematic induces some THz wave from the second filament to propagate along the path of the THz wave from the first filament. Thus, this schematic alters the direction of the THz radiation from the filamentation, which can be used in THz wave remote sensing.« less

Ionizing gas breakdown waves in strong electric fields.

NASA Technical Reports Server (NTRS)

Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

1972-01-01

A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

NASA Astrophysics Data System (ADS)

Tsiklauri, D.

2014-12-01

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refaction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph=ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011) [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013) [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012) [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014) [5] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 21, 012903 (2014)

Experiments on the Expansion of a Dense Plasma into a Background Magnetoplasma

NASA Astrophysics Data System (ADS)

Gekelman, Walter; Vanzeeland, Mike; Vincena, Steve; Pribyl, Pat

2003-10-01

There are many situations, which occur in space (coronal mass ejections, or are man-made (upper atmospheric detonations) as well as the initial stages of a supernovae, in which a dense plasma expands into a background magnetized plasma, that can support Alfvèn waves. The upgraded LArge Plasma Device (LAPD) is a machine, at UCLA, in which Alfvèn wave propagation in homogeneous and inhomogeneous plasmas has been studied. We describe a series of experiments,which involve the expansion of a dense (initially, n_laser-plasma/n_0≫1) laser-produced plasma into an ambient highly magnetized background plasma capable of supporting Alfvèn waves will be presented. The 150 MW laser is pulsed at the same 1 Hz repetition rate as the plasma in a highly reproducible experiment. The interaction results in the production of intense shear Alfvèn waves, as well as large density perturbations. The waves propagate away from the target and are observed to become plasma column resonances. In the initial phase the background magnetic field is expelled from a plasma bubble. Currents in the main body of the plasma are generated to neutralize the positively charged bubble. The current system which results, becomes that of a spectrum of shear Alfvèn waves. Spatial patterns of the wave magnetic fields waves are measured at over 10^4 locations. As the dense plasma expands across the magnetic field it seeds the column with shear waves. Most of the Alfvèn wave energy is in shear waves, which become field line resonances after a machine transit time. The interplay between waves, currents, inductive electric fields and space charge is analyzed in great detail. Dramatic movies of the measured wave fields and their associated currents will be presented. Work supported by ONR, and DOE /NSF.

Quasi Sturmian basis for the two-electon continuum

NASA Astrophysics Data System (ADS)

Zaytsev, A. S.; Ancarani, L. U.; Zaytsev, S. A.

2016-02-01

A new type of basis functions is proposed to describe a two-electron continuum which arises as a final state in electron-impact ionization and double photoionization of atomic systems. We name these functions, which are calculated in terms of the recently introduced quasi Sturmian functions, Convoluted Quasi Sturmian functions (CQS); by construction, they look asymptotically like a six-dimensional spherical wave. The driven equation describing an ( e, 3 e) process on helium in the framework of the Temkin-Poet model is solved numerically in the entire space (rather than in a finite region of space) using expansions on CQS basis functions. We show that quite rapid convergence of the solution expansion can be achieved by multiplying the basis functions by the logarithmic phase factor corresponding to the Coulomb electron-electron interaction.

Low-cost blast wave generator for studies of hearing loss and brain injury: blast wave effects in closed spaces.

PubMed

Newman, Andrew J; Hayes, Sarah H; Rao, Abhiram S; Allman, Brian L; Manohar, Senthilvelan; Ding, Dalian; Stolzberg, Daniel; Lobarinas, Edward; Mollendorf, Joseph C; Salvi, Richard

2015-03-15

Military personnel and civilians living in areas of armed conflict have increased risk of exposure to blast overpressures that can cause significant hearing loss and/or brain injury. The equipment used to simulate comparable blast overpressures in animal models within laboratory settings is typically very large and prohibitively expensive. To overcome the fiscal and space limitations introduced by previously reported blast wave generators, we developed a compact, low-cost blast wave generator to investigate the effects of blast exposures on the auditory system and brain. The blast wave generator was constructed largely from off the shelf components, and reliably produced blasts with peak sound pressures of up to 198dB SPL (159.3kPa) that were qualitatively similar to those produced from muzzle blasts or explosions. Exposure of adult rats to 3 blasts of 188dB peak SPL (50.4kPa) resulted in significant loss of cochlear hair cells, reduced outer hair cell function and a decrease in neurogenesis in the hippocampus. Existing blast wave generators are typically large, expensive, and are not commercially available. The blast wave generator reported here provides a low-cost method of generating blast waves in a typical laboratory setting. This compact blast wave generator provides scientists with a low cost device for investigating the biological mechanisms involved in blast wave injury to the rodent cochlea and brain that may model many of the damaging effects sustained by military personnel and civilians exposed to intense blasts. Copyright © 2015 Elsevier B.V. All rights reserved.

Low-Cost Blast Wave Generator for Studies of Hearing Loss and Brain Injury: Blast Wave Effects in Closed Spaces

PubMed Central

Newman, Andrew J.; Hayes, Sarah H.; Rao, Abhiram S.; Allman, Brian L.; Manohar, Senthilvelan; Ding, Dalian; Stolzberg, Daniel; Lobarinas, Edward; Mollendorf, Joseph C.; Salvi, Richard

2015-01-01

Background Military personnel and civilians living in areas of armed conflict have increased risk of exposure to blast overpressures that can cause significant hearing loss and/or brain injury. The equipment used to simulate comparable blast overpressures in animal models within laboratory settings is typically very large and prohibitively expensive. New Method To overcome the fiscal and space limitations introduced by previously reported blast wave generators, we developed a compact, low-cost blast wave generator to investigate the effects of blast exposures on the auditory system and brain. Results The blast wave generator was constructed largely from off the shelf components, and reliably produced blasts with peak sound pressures of up to 198 dB SPL (159.3 kPa) that were qualitatively similar to those produced from muzzle blasts or explosions. Exposure of adult rats to 3 blasts of 188 dB peak SPL (50.4 kPa) resulted in significant loss of cochlear hair cells, reduced outer hair cell function and a decrease in neurogenesis in the hippocampus. Comparison to existing methods Existing blast wave generators are typically large, expensive, and are not commercially available. The blast wave generator reported here provides a low-cost method of generating blast waves in a typical laboratory setting. Conclusions This compact blast wave generator provides scientists with a low cost device for investigating the biological mechanisms involved in blast wave injury to the rodent cochlea and brain that may model many of the damaging effects sustained by military personnel and civilians exposed to intense blasts. PMID:25597910

Uncertainty relations for angular momentum eigenstates in two and three spatial dimensions

NASA Astrophysics Data System (ADS)

Bracher, Christian

2011-03-01

I reexamine Heisenberg's uncertainty relation for two- and three-dimensional wave packets with fixed angular momentum quantum numbers m or ℓ. A simple proof shows that the product of the average extent Δr and Δp of a two-dimensional wave packet in position and momentum space is bounded from below by ΔrΔp ≥ℏ(|m|+1). The minimum uncertainty is attained by modified Gaussian wave packets that are special eigenstates of the two-dimensional isotropic harmonic oscillator, which include the ground states of electrons in a uniform magnetic field. Similarly, the inequality ΔrΔp ≥ℏ(ℓ +3/2) holds for three-dimensional wave packets with fixed total angular momentum ℓ and the equality holds for a Gaussian radial profile. I also discuss some applications of these uncertainty relations.

Impaired positioning of the gape in whiplash-associated disorders.

PubMed

Zafar, Hamayun; Nordh, Erik; Eriksson, Per-Olof

2006-01-01

We have previously introduced a new concept for natural jaw function suggesting that "functional jaw movements" are the result of coordinated jaw and neck muscle activation, leading to simultaneous movements in the temporomandibular, atlanto-occipital and cervical spine joints. Thus, jaw function requires a healthy state of both the jaw and the neck motor systems. The aim of this study was to examine the positioning of the gape in space during maximal jaw opening at fast and slow speed in healthy as well as whiplash-associated disorders (WAD) individuals. A wireless optoelectronic technique for three-dimensional movement recording was used. Subjects were seated in an upright position, with back support up to the mid-scapular level without headrest. The position of the gape in space was defined as the vertical midpoint position of the gape at maximal jaw opening (MP). In healthy, the MP generally coincided with the reference position at the start of jaw opening. In the WAD group, the MP was significantly lower than the reference position. No sex or speed related differences were found. The results suggest that both the width and orientation of the gape in space relies on coordinated jaw and neck muscle activation and mandibular and head-neck movements. This study also suggests an association between neck pain and dysfunction following trauma, and reduced width and impaired positioning of the gape in space. Finally, the MP seems to be a useful marker in evaluation of the functional state of the jaw-neck motor system.

Dusty Pair Plasma—Wave Propagation and Diffusive Transition of Oscillations

NASA Astrophysics Data System (ADS)

Atamaniuk, Barbara; Turski, Andrzej J.

2011-11-01

The crucial point of the paper is the relation between equilibrium distributions of plasma species and the type of propagation or diffusive transition of plasma response to a disturbance. The paper contains a unified treatment of disturbance propagation (transport) in the linearized Vlasov electron-positron and fullerene pair plasmas containing charged dust impurities, based on the space-time convolution integral equations. Electron-positron-dust/ion (e-p-d/i) plasmas are rather widespread in nature. Space-time responses of multi-component linearized Vlasov plasmas on the basis of multiple integral equations are invoked. An initial-value problem for Vlasov-Poisson/Ampère equations is reduced to the one multiple integral equation and the solution is expressed in terms of forcing function and its space-time convolution with the resolvent kernel. The forcing function is responsible for the initial disturbance and the resolvent is responsible for the equilibrium velocity distributions of plasma species. By use of resolvent equations, time-reversibility, space-reflexivity and the other symmetries are revealed. The symmetries carry on physical properties of Vlasov pair plasmas, e.g., conservation laws. Properly choosing equilibrium distributions for dusty pair plasmas, we can reduce the resolvent equation to: (i) the undamped dispersive wave equations, (ii) and diffusive transport equations of oscillations.

Exploring graphene superlattices: Magneto-optical properties

NASA Astrophysics Data System (ADS)

Duque, C. A.; Hernández-Bertrán, M. A.; Morales, A. L.; de Dios-Leyva, M.

2017-02-01

We present a detailed study of magnetic subbands, wave functions, and transition strengths for graphene superlattices (SLs) subject to a perpendicular magnetic field. It is shown that, for a weak magnetic field, the flat subbands of a SL exhibiting extra Dirac points are grouped into subsets, each of which consists of a singlet subband and a nearly degenerate doublet subband, and one nearly degenerate triplet subband. It was found that the wave functions corresponding to a singlet or to a doublet are always located around the image in real space of the central or extra Dirac points in k-space. The latter properties were explained by assuming that the electron motion is quasi-classical. Our study revealed that, for an intermediate field, the general characteristics of the wave functions are very similar to those of the pristine graphene, while for weak field, their behavior is drastically different. The latter is characterized by rapid oscillations which were understood using the solutions provided by the formalism of Luttinger-Kohn. The study on transition strengths allows us to obtain, for SLs with extra Dirac points in a weak magnetic field and different polarizations, the conditions under which transitions between multiplets are approximately allowed. It was shown that these conditions correspond to an unusual selection rule that is broken when the magnetic field intensity increases from weak to an intermediate value.

Interaction of wave with a body submerged below an ice sheet with multiple arbitrarily spaced cracks

NASA Astrophysics Data System (ADS)

Li, Z. F.; Wu, G. X.; Ji, C. Y.

2018-05-01

The problem of wave interaction with a body submerged below an ice sheet with multiple arbitrarily spaced cracks is considered, based on the linearized velocity potential theory together with the boundary element method. The ice sheet is modeled as a thin elastic plate with uniform properties, and zero bending moment and shear force conditions are enforced at the cracks. The Green function satisfying all the boundary conditions including those at cracks, apart from that on the body surface, is derived and is expressed in an explicit integral form. The boundary integral equation for the velocity potential is constructed with an unknown source distribution over the body surface only. The wave/crack interaction problem without the body is first solved directly without the need for source. The convergence and comparison studies are undertaken to show the accuracy and reliability of the solution procedure. Detailed numerical results through the hydrodynamic coefficients and wave exciting forces are provided for a body submerged below double cracks and an array of cracks. Some unique features are observed, and their mechanisms are analyzed.

Multi-domain boundary element method for axi-symmetric layered linear acoustic systems

NASA Astrophysics Data System (ADS)

Reiter, Paul; Ziegelwanger, Harald

2017-12-01

Homogeneous porous materials like rock wool or synthetic foam are the main tool for acoustic absorption. The conventional absorbing structure for sound-proofing consists of one or multiple absorbers placed in front of a rigid wall, with or without air-gaps in between. Various models exist to describe these so called multi-layered acoustic systems mathematically for incoming plane waves. However, there is no efficient method to calculate the sound field in a half space above a multi layered acoustic system for an incoming spherical wave. In this work, an axi-symmetric multi-domain boundary element method (BEM) for absorbing multi layered acoustic systems and incoming spherical waves is introduced. In the proposed BEM formulation, a complex wave number is used to model absorbing materials as a fluid and a coordinate transformation is introduced which simplifies singular integrals of the conventional BEM to non-singular radial and angular integrals. The radial and angular part are integrated analytically and numerically, respectively. The output of the method can be interpreted as a numerical half space Green's function for grounds consisting of layered materials.

Rogue wave and a pair of resonance stripe solitons to a reduced (3+1)-dimensional Jimbo-Miwa equation

NASA Astrophysics Data System (ADS)

Zhang, Xiaoen; Chen, Yong

2017-11-01

In this paper, a combination of stripe soliton and lump soliton is discussed to a reduced (3+1)-dimensional Jimbo-Miwa equation, in which such solution gives rise to two different excitation phenomena: fusion and fission. Particularly, a new combination of positive quadratic functions and hyperbolic functions is considered, and then a novel nonlinear phenomenon is explored. Via this method, a pair of resonance kink stripe solitons and rogue wave is studied. Rogue wave is triggered by the interaction between lump soliton and a pair of resonance kink stripe solitons. It is exciting that rogue wave must be attached to the stripe solitons from its appearing to disappearing. The whole progress is completely symmetry, the rogue wave starts itself from one stripe soliton and lose itself in another stripe soliton. The dynamic properties of the interaction between one stripe soliton and lump soliton, rogue wave are discussed by choosing appropriate parameters.

Self-consistent construction of virialized wave dark matter halos

NASA Astrophysics Data System (ADS)

Lin, Shan-Chang; Schive, Hsi-Yu; Wong, Shing-Kwong; Chiueh, Tzihong

2018-05-01

Wave dark matter (ψ DM ), which satisfies the Schrödinger-Poisson equation, has recently attracted substantial attention as a possible dark matter candidate. Numerical simulations have, in the past, provided a powerful tool to explore this new territory of possibility. Despite their successes in revealing several key features of ψ DM , further progress in simulations is limited, in that cosmological simulations so far can only address formation of halos below ˜2 ×1011 M⊙ and substantially more massive halos have become computationally very challenging to obtain. For this reason, the present work adopts a different approach in assessing massive halos by constructing wave-halo solutions directly from the wave distribution function. This approach bears certain similarities with the analytical construction of the particle-halo (cold dark matter model). Instead of many collisionless particles, one deals with one single wave that has many noninteracting eigenstates. The key ingredient in the wave-halo construction is the distribution function of the wave power, and we use several halos produced by structure formation simulations as templates to determine the wave distribution function. Among different models, we find the fermionic King model presents the best fits and we use it for our wave-halo construction. We have devised an iteration method for constructing the nonlinear halo and demonstrate its stability by three-dimensional simulations. A Milky Way-sized halo has also been constructed, and the inner halo is found to be flatter than the NFW profile. These wave-halos have small-scale interferences both in space and time producing time-dependent granules. While the spatial scale of granules varies little, the correlation time is found to increase with radius by 1 order of magnitude across the halo.

Millimeter-Wave Generation Via Plasma Three-Wave Mixing

DTIC Science & Technology

1988-06-01

are coupled to a third space -charge wave with dispersion 2w W k -k k . (16) A plasma-loaded-waveguide mode is excited at the intersection of this...DISPERSION "FAST" W PLASMA WAVE Wc PLASMA WAVE A-lA oppositely directed EPWs with different phase velocities (wp/k., and wO/k. 2) are coupled to a third ... space -charge wave with dispersion 2w I- k k .(16) e 2 A plaama-loaded-waveguide mode is excited at the intersection of this coupled space-charge wave

On a canonical quantization of 3D Anti de Sitter pure gravity

NASA Astrophysics Data System (ADS)

Kim, Jihun; Porrati, Massimo

2015-10-01

We perform a canonical quantization of pure gravity on AdS 3 using as a technical tool its equivalence at the classical level with a Chern-Simons theory with gauge group SL(2,{R})× SL(2,{R}) . We first quantize the theory canonically on an asymptotically AdS space -which is topologically the real line times a Riemann surface with one connected boundary. Using the "constrain first" approach we reduce canonical quantization to quantization of orbits of the Virasoro group and Kähler quantization of Teichmüller space. After explicitly computing the Kähler form for the torus with one boundary component and after extending that result to higher genus, we recover known results, such as that wave functions of SL(2,{R}) Chern-Simons theory are conformal blocks. We find new restrictions on the Hilbert space of pure gravity by imposing invariance under large diffeomorphisms and normalizability of the wave function. The Hilbert space of pure gravity is shown to be the target space of Conformal Field Theories with continuous spectrum and a lower bound on operator dimensions. A projection defined by topology changing amplitudes in Euclidean gravity is proposed. It defines an invariant subspace that allows for a dual interpretation in terms of a Liouville CFT. Problems and features of the CFT dual are assessed and a new definition of the Hilbert space, exempt from those problems, is proposed in the case of highly-curved AdS 3.

A vector-free ECG interpretation with P, QRS & T waves as unbalanced transitions between stable configurations of the heart electric field during P-R, S-T & T-P segments

PubMed Central

2014-01-01

Since cell membranes are weak sources of electrostatic fields, this ECG interpretation relies on the analogy between cells and electrets. It is here assumed that cell-bound electric fields unite, reach the body surface and the surrounding space and form the thoracic electric field that consists from two concentric structures: the thoracic wall and the heart. If ECG leads measure differences in electric potentials between skin electrodes, they give scalar values that define position of the electric field center along each lead. Repolarised heart muscle acts as a stable positive electric source, while depolarized heart muscle produces much weaker negative electric field. During T-P, P-R and S-T segments electric field is stable, only subtle changes are detectable by skin electrodes. Diastolic electric field forms after ventricular depolarization (T-P segments in the ECG recording). Telediastolic electric field forms after the atria have been depolarized (P-Q segments in the ECG recording). Systolic electric field forms after the ventricular depolarization (S-T segments in the ECG recording). The three ECG waves (P, QRS and T) can then be described as unbalanced transitions of the heart electric field from one stable configuration to the next and in that process the electric field center is temporarily displaced. In the initial phase of QRS, the rapidly diminishing septal electric field makes measured potentials dependent only on positive charges of the corresponding parts of the left and the right heart that lie within the lead axes. If more positive charges are near the "DOWN" electrode than near the "UP" electrode, a Q wave will be seen, otherwise an R wave is expected. Repolarization of the ventricular muscle is dampened by the early septal muscle repolarization that reduces deflection of T waves. Since the "UP" electrode of most leads is near the usually larger left ventricle muscle, T waves are in these leads positive, although of smaller amplitude and longer duration than the QRS wave in the same lead. The proposed interpretation is applied to bundle branch blocks, fascicular (hemi-) blocks and changes during heart muscle ischemia. PMID:24506945

Phase 1 Validation Testing and Simulation for the WEC-Sim Open Source Code

NASA Astrophysics Data System (ADS)

Ruehl, K.; Michelen, C.; Gunawan, B.; Bosma, B.; Simmons, A.; Lomonaco, P.

2015-12-01

WEC-Sim is an open source code to model wave energy converters performance in operational waves, developed by Sandia and NREL and funded by the US DOE. The code is a time-domain modeling tool developed in MATLAB/SIMULINK using the multibody dynamics solver SimMechanics, and solves the WEC's governing equations of motion using the Cummins time-domain impulse response formulation in 6 degrees of freedom. The WEC-Sim code has undergone verification through code-to-code comparisons; however validation of the code has been limited to publicly available experimental data sets. While these data sets provide preliminary code validation, the experimental tests were not explicitly designed for code validation, and as a result are limited in their ability to validate the full functionality of the WEC-Sim code. Therefore, dedicated physical model tests for WEC-Sim validation have been performed. This presentation provides an overview of the WEC-Sim validation experimental wave tank tests performed at the Oregon State University's Directional Wave Basin at Hinsdale Wave Research Laboratory. Phase 1 of experimental testing was focused on device characterization and completed in Fall 2015. Phase 2 is focused on WEC performance and scheduled for Winter 2015/2016. These experimental tests were designed explicitly to validate the performance of WEC-Sim code, and its new feature additions. Upon completion, the WEC-Sim validation data set will be made publicly available to the wave energy community. For the physical model test, a controllable model of a floating wave energy converter has been designed and constructed. The instrumentation includes state-of-the-art devices to measure pressure fields, motions in 6 DOF, multi-axial load cells, torque transducers, position transducers, and encoders. The model also incorporates a fully programmable Power-Take-Off system which can be used to generate or absorb wave energy. Numerical simulations of the experiments using WEC-Sim will be presented. These simulations highlight the code features included in the latest release of WEC-Sim (v1.2), including: wave directionality, nonlinear hydrostatics and hydrodynamics, user-defined wave elevation time-series, state space radiation, and WEC-Sim compatibility with BEMIO (open source AQWA/WAMI/NEMOH coefficient parser).

Non-contact radio frequency shielding and wave guiding by multi-folded transformation optics method

PubMed Central

Madni, Hamza Ahmad; Zheng, Bin; Yang, Yihao; Wang, Huaping; Zhang, Xianmin; Yin, Wenyan; Li, Erping; Chen, Hongsheng

2016-01-01

Compared with conventional radio frequency (RF) shielding methods in which the conductive coating material encloses the circuits design and the leakage problem occurs due to the gap in such conductive material, non-contact RF shielding at a distance is very promising but still impossible to achieve so far. In this paper, a multi-folded transformation optics method is proposed to design a non-contact device for RF shielding. This “open-shielded” device can shield any object at a distance from the electromagnetic waves at the operating frequency, while the object is still physically open to the outer space. Based on this, an open-carpet cloak is proposed and the functionality of the open-carpet cloak is demonstrated. Furthermore, we investigate a scheme of non-contact wave guiding to remotely control the propagation of surface waves over any obstacles. The flexibilities of such multi-folded transformation optics method demonstrate the powerfulness of the method in the design of novel remote devices with impressive new functionalities. PMID:27841358

On propagation of axisymmetric waves in pressurized functionally graded elastomeric hollow cylinders

NASA Astrophysics Data System (ADS)

Wu, Bin; Su, Yipin; Liu, Dongying; Chen, Weiqiu; Zhang, Chuanzeng

2018-05-01

Soft materials can be designed with a functionally graded (FG) property for specific applications. Such material inhomogeneity can also be found in many soft biological tissues whose functionality is only partly understood to date. In this paper, we analyze the axisymmetric guided wave propagation in a pressurized FG elastomeric hollow cylinder. The cylinder is subjected to a combined action of axial pre-stretch and pressure difference applied to the inner and outer cylindrical surfaces. We consider both torsional waves and longitudinal waves propagating in the FG cylinder made of incompressible isotropic elastomer, which is characterized by the Mooney-Rivlin strain energy function but with the material parameters varying with the radial coordinate in an affine way. The pressure difference generates an inhomogeneous deformation field in the FG cylinder, which dramatically complicates the superimposed wave problem described by the small-on-large theory. A particularly efficient approach is hence employed which combines the state-space formalism for the incremental wave motion with the approximate laminate or multi-layer technique. Dispersion relations for the two types of axisymmetric guided waves are then derived analytically. The accuracy and convergence of the proposed approach is validated numerically. The effects of the pressure difference, material gradient, and axial pre-stretch on both the torsional and the longitudinal wave propagation characteristics are discussed in detail through numerical examples. It is found that the frequency of axisymmetric waves depends nonlinearly on the pressure difference and the material gradient, and an increase in the material gradient enhances the capability of the pressure difference to adjust the wave behavior in the FG cylinder. This work provides a theoretical guidance for characterizing FG soft materials by in-situ ultrasonic nondestructive evaluation and for designing tunable waveguides via material tailoring along with an adjustment of the pre-stretch and pressure difference.

Propagation of Electron Acoustic Soliton, Periodic and Shock Waves in Dissipative Plasma with a q-Nonextensive Electron Velocity Distribution

NASA Astrophysics Data System (ADS)

El-Hanbaly, A. M.; El-Shewy, E. K.; Elgarayhi, A.; Kassem, A. I.

2015-11-01

The nonlinear properties of small amplitude electron-acoustic (EA) solitary and shock waves in a homogeneous system of unmagnetized collisionless plasma with nonextensive distribution for hot electrons have been investigated. A reductive perturbation method used to obtain the Kadomstev-Petviashvili-Burgers equation. Bifurcation analysis has been discussed for non-dissipative system in the absence of Burgers term and reveals different classes of the traveling wave solutions. The obtained solutions are related to periodic and soliton waves and their behavior are shown graphically. In the presence of the Burgers term, the EXP-function method is used to solve the Kadomstev-Petviashvili-Burgers equation and the obtained solution is related to shock wave. The obtained results may be helpful in better conception of waves propagation in various space plasma environments as well as in inertial confinement fusion laboratory plasmas.

Lower Hybrid Oscillations in Multicomponent Space Plasmas Subjected to Ion Cyclotron Waves

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Krivorutsky, E. N.; Moore, T. E.; Liemohn, M. W.; Horwitz, J. L.

1997-01-01

It is found that in multicomponent plasmas subjected to Alfven or fast magnetosonic waves, such as are observed in regions of the outer plasmasphere and ring current-plasmapause overlap, lower hybrid oscillations are generated. The addition of a minor heavy ion component to a proton-electron plasma significantly lowers the low-frequency electric wave amplitude needed for lower hybrid wave excitation. It is found that the lower hybrid wave energy density level is determined by the nonlinear process of induced scattering by ions and electrons; hydrogen ions in the region of resonant velocities are accelerated; and nonresonant particles are weakly heated due to the induced scattering. For a given example, the light resonant ions have an energy gain factor of 20, leading to the development of a high-energy tail in the H(+) distribution function due to low-frequency waves.

Scattering of Internal Tides by Irregular Bathymetry of Large Extent

NASA Astrophysics Data System (ADS)

Mei, C.

2014-12-01

We present an analytic theory of scattering of tide-generated internal gravity waves in a continuously stratified ocean with a randomly rough seabed. Based on the linearized approximation, the idealized case of constant mean sea depth and Brunt-Vaisala frequency is considered. The depth fluctuation is assumed to be a stationary random function of space characterized by small amplitude and correlation length comparable to the typical wavelength. For both one- and two-dimensional topography the effects of scattering on wave phase over long distances are derived explicitly by the method of multiple scales. For one-dimensional topography, numerical results are compared with Buhler-& Holmes-Cerfon(2011) computed by the method of characteristics. For two-dimensional topography, new results are presented for both statistically isotropic and anisotropic cases. In thi talk we shall apply the perturbation technique of multiple scales to treat analytically the random scattering of internal tides by gently sloped bathymetric irregularities.The basic assumptions are: incompressible fluid, infinitestimal wave amplitudes, constant Brunt-Vaisala frequency, and constant mean depth. In addition, the depth disorder is assumed to be a stationary random function of space with zero mean and small root-mean-square amplitude. The correlation length can be comparable in order of magnitude as the dominant wavelength. Both one- and two-dimensional disorder will be considered. Physical effects of random scattering on the mean wave phase i.e., spatial attenuation and wavenumber shift will be calculated and discussed for one mode of incident wave. For two dimensional topographies, statistically isotropic and anisotropic examples will be presented.

Eulerian velocity reconstruction in ideal atmospheric dynamics using potential vorticity and potential temperature

NASA Astrophysics Data System (ADS)

Blender, R.

2009-04-01

An approach for the reconstruction of atmospheric flow is presented which uses space- and time-dependent fields of density ?, potential vorticity Q and potential temperature Î& cedil;[J. Phys. A, 38, 6419 (2005)]. The method is based on the fundamental equations without approximation. The basic idea is to consider the time-dependent continuity equation as a condition for zero divergence of momentum in four dimensions (time and space, with unit velocity in time). This continuity equation is solved by an ansatz for the four-dimensional momentum using three conserved stream functions, the potential vorticity, potential temperature and a third field, denoted as ?-potential. In zonal flows, the ?-potential identifies the initial longitude of particles, whereas potential vorticity and potential temperature identify mainly meridional and vertical positions. Since the Lagrangian tracers Q, Î&,cedil; and ? determine the Eulerian velocity field, the reconstruction combines the Eulerian and the Lagrangian view of hydrodynamics. In stationary flows, the ?-potential is related to the Bernoulli function. The approach requires that the gradients of the potential vorticity and potential temperature do not vanish when the velocity remains finite. This behavior indicates a possible interrelation with stability conditions. Examples with analytical solutions are presented for a Rossby wave and zonal and rotational shear flows.

Quantum dark soliton: Nonperturbative diffusion of phase and position

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dziarmaga, J.

2004-12-01

The dark soliton solution of the Gross-Pitaevskii equation in one dimension has two parameters that do not change the energy of the solution: the global phase of the condensate wave function and the position of the soliton. These degeneracies appear in the Bogoliubov theory as Bogoliubov modes with zero frequencies and zero norms. These 'zero modes' cannot be quantized as the usual Bogoliubov quasiparticle harmonic oscillators. They must be treated in a nonperturbative way. In this paper I develop a nonperturbative theory of zero modes. This theory provides a nonperturbative description of quantum phase diffusion and quantum diffusion of solitonmore » position. An initially well localized wave packet for soliton position is predicted to disperse beyond the width of the soliton.« less

The East Atlantic - West Russia Teleconnection in the North Atlantic: Climate Impact and Relation to Rossby Wave Propagation

NASA Technical Reports Server (NTRS)

Lim, Young-Kwon

2014-01-01

Large-scale winter teleconnection of the East Atlantic - West Russia (EA-WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function (REOF) analysis of the upper-tropospheric monthly height field captures successfully the EA-WR pattern and its interannual variation, with the North Atlantic Oscillation as the first mode. EA-WRs climate impact extends from eastern North America to Eurasia. The positive (negative) EA-WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around 60E, where lower-level cyclonic (anticyclonic) circulation anomaly is dominant. The eastern Canada and the western Europe are characterized by negative (positive) precipitation anomalies.The EA-WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (approximately 40N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA-WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate improvement in the simulation of the EA-WR when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40-60N.

Standing wave acoustic levitation on an annular plate

NASA Astrophysics Data System (ADS)

Kandemir, Mehmet Hakan; Çalışkan, Mehmet

2016-11-01

In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

Directional asymmetry of the nonlinear wave phenomena in a three-dimensional granular phononic crystal under gravity.

PubMed

Merkel, A; Tournat, V; Gusev, V

2014-08-01

We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption.

A Source Term for Wave Attenuation by Sea Ice in WAVEWATCH III(registered trademark): IC4

DTIC Science & Technology

2017-06-07

energy in the high frequency face of the spectrum, which highlights the fact that frequency dependent attenuation in necessary to replicate the low-pass... frequency space ; M6) and an expanded version of M5 with up to 10 steps. The remainder of this report is structured as follows: a note about the...function period, T = 1/f. Measurements have shown that ice preferentially damps high frequency waves and in this way ice acts as a low pass filter

A new single-particle basis for nuclear many-body calculations

NASA Astrophysics Data System (ADS)

Puddu, G.

2017-10-01

Predominantly, harmonic oscillator single-particle wave functions are the preferred choice for a basis in ab initio nuclear many-body calculations. These wave-functions, although very convenient in order to evaluate the matrix elements of the interaction in the laboratory frame, have too fast a fall-off at large distances. In the past, as an alternative to the harmonic oscillator, other single-particle wave functions have been proposed. In this work, we propose a new single-particle basis, directly linked to nucleon-nucleon interaction. This new basis is orthonormal and complete, has the proper asymptotic behavior at large distances and does not contain the continuum which would pose severe convergence problems in nuclear many body calculations. We consider the newly proposed NNLO-opt nucleon-nucleon interaction, without any renormalization. We show that, unlike other bases, this single-particle representation has a computational cost similar to the harmonic oscillator basis with the same space truncation and it gives lower energies for 6He and 6Li.

Positrons vs electrons channeling in silicon crystal: energy levels, wave functions and quantum chaos manifestations

NASA Astrophysics Data System (ADS)

Shul'ga, N. F.; Syshchenko, V. V.; Tarnovsky, A. I.; Solovyev, I. I.; Isupov, A. Yu.

2018-01-01

The motion of fast electrons through the crystal during axial channeling could be regular and chaotic. The dynamical chaos in quantum systems manifests itself in both statistical properties of energy spectra and morphology of wave functions of the individual stationary states. In this report, we investigate the axial channeling of high and low energy electrons and positrons near [100] direction of a silicon crystal. This case is particularly interesting because of the fact that the chaotic motion domain occupies only a small part of the phase space for the channeling electrons whereas the motion of the channeling positrons is substantially chaotic for the almost all initial conditions. The energy levels of transverse motion, as well as the wave functions of the stationary states, have been computed numerically. The group theory methods had been used for classification of the computed eigenfunctions and identification of the non-degenerate and doubly degenerate energy levels. The channeling radiation spectrum for the low energy electrons has been also computed.

Energy, momentum, and angular momentum of sound pulses.

PubMed

Lekner, John

2017-12-01

Pulse solutions of the wave equation can be expressed as superpositions of scalar monochromatic beam wavefunctions (solutions of the Helmholtz equation). This formulation leads to causal (unidirectional) propagation, in contrast to all currently known closed-form solutions of the wave equation. Application is made to the evaluation of the energy, momentum, and angular momentum of acoustic pulses, as integrals over the beam and pulse weight functions. Equivalence is established between integration over space of the energy, momentum, and angular momentum densities, and integration over the wavevector weight function. The inequality linking the total energy and the total momentum is made explicit in terms of the weight function formulation. It is shown that a general pulse can be viewed as a superposition of phonons, each with energy ℏck, z component of momentum ℏq, and z component of angular momentum ℏm. A closed-form solution of the wave equation is found, which is localized and causal, and its energy and momentum are evaluated explicitly.

Electron Beam Transport in Advanced Plasma Wave Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Ronald L

2013-01-31

The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams weremore » generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.« less

Capacitive acoustic wave detector and method of using same

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor)

1994-01-01

A capacitor having two substantially parallel conductive faces is acoustically coupled to a conductive sample end such that the sample face is one end of the capacitor. A non-contacting dielectric may serve as a spacer between the two conductive plates. The formed capacitor is connected to an LC oscillator circuit such as a Hartley oscillator circuit producing an output frequency which is a function of the capacitor spacing. This capacitance oscillates as the sample end coating is oscillated by an acoustic wave generated in the sample by a transmitting transducer. The electrical output can serve as an absolute indicator of acoustic wave displacement.

The Dynamic Relationship Between Cognitive Function and Positive Well-Being in Older People: A Prospective Study Using the English Longitudinal Study of Aging

PubMed Central

2014-01-01

There is evidence that having a stronger sense of positive well-being may be a potential resource for healthier aging as represented by slower physical decline, reduced risk of frailty and longer survival. However, it is unclear whether positive well-being is protective of another crucial component of healthy aging, cognitive function, or whether it has a bidirectional relationship with cognitive function. We use multilevel models with within-person centering to estimate the within- and between-person association between cognitive function and positive well-being in 4 waves of data from the English Longitudinal Study of Ageing (ELSA), (N = 10985, aged 50–90 years at wave 1). Our findings show that, although most variation in cognitive function was explained by age, and most variation in well-being was explained by depression, small but significant associations between cognition and well-being remained after variation in age and depression were controlled. In models where cognition was the outcome, the association was mainly because of variation in mean levels of well-being between persons. In models where well-being was the outcome, the association was mainly because of within-person fluctuation in cognitive test performance. Exercise and depression were the most important moderating influences on the association between cognition and positive well-being. Depression had greater effect upon this association for those with higher well-being, but exercise protected cognitive performance against the adverse effects of lower well-being. PMID:24955999

The Hem protein mediates neuronal migration by inhibiting WAVE degradation and functions opposite of Abelson tyrosine kinase

PubMed Central

Zhu, Zengrong; Bhat, Krishna Moorthi

2011-01-01

In the nervous system, neurons form in different regions, then they migrate and occupy specific positions. We have previously shown that RP2/sib, a well-studied neuronal pair in the Drosophila ventral nerve cord (VNC), has a complex migration route. Here, we show that the Hem protein, via the WAVE complex, regulates migration of GMC-1 and its progeny RP2 neuron. In Hem or WAVE mutants, RP2 neuron either abnormally migrates, crossing the midline from one hemisegment to the contralateral hemisegment, or does not migrate at al and fail to send out its axon projection. We report that Hem regulates neuronal migration through stabilizing WAVE. Since Hem and WAVE normally form a complex, our data argues that in the absence of Hem, WAVE, which is presumably no longer in a complex, becomes susceptible to degradation. We also find that Abelson Tyrosine kinase affects RP2 migration in a similar manner as Hem and WAVE, and appears to operate via WAVE. However, while Abl negatively regulates the levels of WAVE, it regulates migration via regulating the activity of WAVE. Our results also show that during the degradation of WAVE, Hem function is opposite to that of and downstream of Abl. PMID:21726548

Nonlinear Wave-Particle Interaction: Implications for Newborn Planetary and Backstreaming Proton Velocity Distribution Functions

NASA Astrophysics Data System (ADS)

Romanelli, N.; Mazelle, C.; Meziane, K.

2018-02-01

Seen from the solar wind (SW) reference frame, the presence of newborn planetary protons upstream from the Martian and Venusian bow shocks and SW protons reflected from each of them constitutes two sources of nonthermal proton populations. In both cases, the resulting proton velocity distribution function is highly unstable and capable of giving rise to ultralow frequency quasi-monochromatic electromagnetic plasma waves. When these instabilities take place, the resulting nonlinear waves are convected by the SW and interact with nonthermal protons located downstream from the wave generation region (upstream from the bow shock), playing a predominant role in their dynamics. To improve our understanding of these phenomena, we study the interaction between a charged particle and a large-amplitude monochromatic circularly polarized electromagnetic wave propagating parallel to a background magnetic field, from first principles. We determine the number of fix points in velocity space, their stability, and their dependence on different wave-particle parameters. Particularly, we determine the temporal evolution of a charged particle in the pitch angle-gyrophase velocity plane under nominal conditions expected for backstreaming protons in planetary foreshocks and for newborn planetary protons in the upstream regions of Venus and Mars. In addition, the inclusion of wave ellipticity effects provides an explanation for pitch angle distributions of suprathermal protons observed at the Earth's foreshock, reported in previous studies. These analyses constitute a mean to evaluate if nonthermal proton velocity distribution functions observed at these plasma environments present signatures that can be understood in terms of nonlinear wave-particle processes.

Ventricular Fibrillation Associated With Dynamic Changes in J-Point Elevation in a Patient With Silent Thyroiditis.

PubMed

Karashima, Shigehiro; Tsuda, Toyonobu; Wakabayashi, Yusuke; Kometani, Mitsuhiro; Demura, Masashi; Ichise, Taro; Kawashiri, Masa-Aki; Takeda, Yoshiyu; Hayashi, Kenshi; Yoneda, Takashi

2018-02-01

A J wave is a common electrocardiographic finding in the general population. Individuals with prominent J waves in multiple electrocardiogram (ECG) leads have a higher risk of lethal arrhythmias than those with low-amplitude J waves. There are few reports about the relationship between thyroid function and J-wave amplitude. We report the case of a 45-year-old man who had unexpected ventricular fibrillation (VF). He had dynamic J-point elevation in multiple ECG leads. Possible early repolarization syndrome was diagnosed. He also had thyrotoxicosis caused by silent thyroiditis, and his J-wave amplitude decreased according to changes in thyroid function because of spontaneous remission of silent thyroiditis. There was a positive correlation between serum triiodothyronine levels and J-wave amplitudes. The findings in case suggested silent thyroiditis may contribute to the occurrence of VF in a patient with dynamic changes in J-point elevation in multiple ECG leads. Thyrotoxicosis is a relatively common endocrine disease; therefore, clinicians should pay attention to J-wave amplitude in the ECG of patients with thyrotoxicosis.

Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves.

PubMed

Meissner, Matthias; Sojka, Falko; Matthes, Lars; Bechstedt, Friedhelm; Feng, Xinliang; Müllen, Klaus; Mannsfeld, Stefan C B; Forker, Roman; Fritz, Torsten

2016-07-26

The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate-substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule-substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect.

Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves

PubMed Central

2016-01-01

The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate–substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule–substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect. PMID:27014920

Calculation of the exchange coupling constants of copper binuclear systems based on spin-flip constricted variational density functional theory.

PubMed

Zhekova, Hristina R; Seth, Michael; Ziegler, Tom

2011-11-14

We have recently developed a methodology for the calculation of exchange coupling constants J in weakly interacting polynuclear metal clusters. The method is based on unrestricted and restricted second order spin-flip constricted variational density functional theory (SF-CV(2)-DFT) and is here applied to eight binuclear copper systems. Comparison of the SF-CV(2)-DFT results with experiment and with results obtained from other DFT and wave function based methods has been made. Restricted SF-CV(2)-DFT with the BH&HLYP functional yields consistently J values in excellent agreement with experiment. The results acquired from this scheme are comparable in quality to those obtained by accurate multi-reference wave function methodologies such as difference dedicated configuration interaction and the complete active space with second-order perturbation theory. © 2011 American Institute of Physics

Full-wave generalizations of the fundamental Gaussian beam.

PubMed

Seshadri, S R

2009-12-01

The basic full wave corresponding to the fundamental Gaussian beam was discovered for the outwardly propagating wave in a half-space by the introduction of a source in the complex space. There is a class of extended full waves all of which reduce to the same fundamental Gaussian beam in the appropriate limit. For the extended full Gaussian waves that include the basic full Gaussian wave as a special case, the sources are in the complex space on different planes transverse to the propagation direction. The sources are cylindrically symmetric Gaussian distributions centered at the origin of the transverse planes, the axis of symmetry being the propagation direction. For the special case of the basic full Gaussian wave, the source is a point source. The radiation intensity of the extended full Gaussian waves is determined and their characteristics are discussed and compared with those of the fundamental Gaussian beam. The extended full Gaussian waves are also obtained for the oppositely propagating outwardly directed waves in the second half-space. The radiation intensity distributions in the two half-spaces have reflection symmetry about the midplane. The radiation intensity distributions of the various extended full Gaussian waves are not significantly different. The power carried by the extended full Gaussian waves is evaluated and compared with that of the fundamental Gaussian beam.

Combined approach to the Hubble Space Telescope wave-front distortion analysis

NASA Astrophysics Data System (ADS)

Roddier, Claude; Roddier, Francois

1993-06-01

Stellar images taken by the HST at various focus positions have been analyzed to estimate wave-front distortion. Rather than using a single algorithm, we found that better results were obtained by combining the advantages of various algorithms. For the planetary camera, the most accurate algorithms consistently gave a spherical aberration of -0.290-micron rms with a maximum deviation of 0.005 micron. Evidence was found that the spherical aberration is essentially produced by the primary mirror. The illumination in the telescope pupil plane was reconstructed and evidence was found for a slight camera misalignment.

Thermoacoustic enhancements for nuclear fuel rods and other high temperature applications

DOEpatents

Garrett, Steven L.; Smith, James A.; Kotter, Dale K.

2017-05-09

A nuclear thermoacoustic device includes a housing defining an interior chamber and a portion of nuclear fuel disposed in the interior chamber. A stack is disposed in the interior chamber and has a hot end and a cold end. The stack is spaced from the portion of nuclear fuel with the hot end directed toward the portion of nuclear fuel. The stack and portion of nuclear fuel are positioned such that an acoustic standing wave is produced in the interior chamber. A frequency of the acoustic standing wave depends on a temperature in the interior chamber.

Multiplexed phase-space imaging for 3D fluorescence microscopy.

PubMed

Liu, Hsiou-Yuan; Zhong, Jingshan; Waller, Laura

2017-06-26

Optical phase-space functions describe spatial and angular information simultaneously; examples of optical phase-space functions include light fields in ray optics and Wigner functions in wave optics. Measurement of phase-space enables digital refocusing, aberration removal and 3D reconstruction. High-resolution capture of 4D phase-space datasets is, however, challenging. Previous scanning approaches are slow, light inefficient and do not achieve diffraction-limited resolution. Here, we propose a multiplexed method that solves these problems. We use a spatial light modulator (SLM) in the pupil plane of a microscope in order to sequentially pattern multiplexed coded apertures while capturing images in real space. Then, we reconstruct the 3D fluorescence distribution of our sample by solving an inverse problem via regularized least squares with a proximal accelerated gradient descent solver. We experimentally reconstruct a 101 Megavoxel 3D volume (1010×510×500µm with NA 0.4), demonstrating improved acquisition time, light throughput and resolution compared to scanning aperture methods. Our flexible patterning scheme further allows sparsity in the sample to be exploited for reduced data capture.

Reversible electron heating vs. wave-particle interactions in quasi-perpendicular shocks

NASA Technical Reports Server (NTRS)

Veltri, P.; Mangeney, A.; Scudder, J. D.

1992-01-01

The energy necessary to explain the electron heating in quasi-perpendicular collisionless shocks can be derived either from the electron acceleration in the d.c. cross shock electric potential, or by the interactions between the electrons and the waves existing in the shock. A Monte Carlo simulation has been performed to study the electron distribution function evolution through the shock structure, with and without particle diffusion on waves. This simulation has allowed us to clarify the relative importance of the two possible energy sources; in particular it has been shown that the electron parallel temperature is determined by the d.c. electromagnetic field and not by any wave-particle-induced heating. Wave particle interactions are effective in smoothing out the large gradients in phase space produced by the 'reversible' motion of the electrons, thus producing a 'cooling' of the electrons.

Quantum supersymmetric Bianchi IX cosmology

NASA Astrophysics Data System (ADS)

Damour, Thibault; Spindel, Philippe

2014-11-01

We study the quantum dynamics of a supersymmetric squashed three-sphere by dimensionally reducing (to one timelike dimension) the action of D =4 simple supergravity for a S U (2 ) -homogeneous (Bianchi IX) cosmological model. The quantization of the homogeneous gravitino field leads to a 64-dimensional fermionic Hilbert space. After imposition of the diffeomorphism constraints, the wave function of the Universe becomes a 64-component spinor of spin(8,4) depending on the three squashing parameters, which satisfies Dirac-like, and Klein-Gordon-like, wave equations describing the propagation of a "quantum spinning particle" reflecting off spin-dependent potential walls. The algebra of the supersymmetry constraints and of the Hamiltonian one is found to close. One finds that the quantum Hamiltonian is built from operators that generate a 64-dimensional representation of the (infinite-dimensional) maximally compact subalgebra of the rank-3 hyperbolic Kac-Moody algebra A E3 . The (quartic-in-fermions) squared-mass term μ^ 2 entering the Klein-Gordon-like equation has several remarkable properties: (i) it commutes with all the other (Kac-Moody-related) building blocks of the Hamiltonian; (ii) it is a quadratic function of the fermion number NF; and (iii) it is negative in most of the Hilbert space. The latter property leads to a possible quantum avoidance of the singularity ("cosmological bounce"), and suggests imposing the boundary condition that the wave function of the Universe vanish when the volume of space tends to zero (a type of boundary condition which looks like a final-state condition when considering the big crunch inside a black hole). The space of solutions is a mixture of "discrete-spectrum states" (parametrized by a few constant parameters, and known in explicit form) and of continuous-spectrum states (parametrized by arbitrary functions entering some initial-value problem). The predominantly negative values of the squared-mass term lead to a "bottle effect" between small-volume universes and large-volume ones, and to a possible reduction of the continuous spectrum to a discrete spectrum of quantum states looking like excited versions of the Planckian-size universes described by the discrete states at fermionic levels NF=0 and 1.

Angry Birds in Space

NASA Astrophysics Data System (ADS)

Halford, A. J.

2017-12-01

When space computers first started listening into space radio, they noticed that there were radio noises that happened on the morning side of the Earth. Because these waves sounded like noises birds make in the morning, we named these waves after them. These bird sounding waves can move around the Earth, flying up and down, and sometimes move into an area where there is more stuff. This area is also much colder than where these bird noises are first made. When the waves move into this cold area where there is more stuff, they start to sound like angry birds instead of happy birds. Both of these waves, the happy and angry bird sounding waves, are very important to our understanding of how the tiny things in space move and change. Sometimes the waves which sound like birds can push these tiniest of things into the sky. The happy bird sounding waves can push the tiniest things quickly while the angry bird sounding waves push the tinest of things more slowly. When the tiny things fall into the sky, they create beautiful space lights and light that burns which can hurt people in up goers and not so up goers as well as our things like phones, and space computers. We study these waves that sound like birds to better understand when and where the tiny things will fall. That way we can be prepared and enjoy watching the pretty space lights at night with no worries.

Topology of the distribution of zeros of the Husimi function in the LiNC/LiCN molecular system.

PubMed

Arranz, F J; Benito, R M; Borondo, F

2004-04-08

Phase space representations of quantum mechanics constitute useful tools to study vibrations in molecular systems. Among all possibilities, the Husimi function or coherent state representation is very widely used, its maxima indicating which regions of phase space are relevant in the dynamics of the system. The corresponding zeros are also a good indicator to investigate the characteristics of the eigenstates, and it has been shown how the corresponding distributions can discriminate between regular, irregular, and scarred wave functions. In this paper, we discuss how this result can be understood in terms of the overlap between coherent states and system eigenfunctions. (c) 2004 American Institute of Physics

A wavenumber approach to analysing the active control of plane waves with arrays of secondary sources

NASA Astrophysics Data System (ADS)

Elliott, Stephen J.; Cheer, Jordan; Bhan, Lam; Shi, Chuang; Gan, Woon-Seng

2018-04-01

The active control of an incident sound field with an array of secondary sources is a fundamental problem in active control. In this paper the optimal performance of an infinite array of secondary sources in controlling a plane incident sound wave is first considered in free space. An analytic solution for normal incidence plane waves is presented, indicating a clear cut-off frequency for good performance, when the separation distance between the uniformly-spaced sources is equal to a wavelength. The extent of the near field pressure close to the source array is also quantified, since this determines the positions of the error microphones in a practical arrangement. The theory is also extended to oblique incident waves. This result is then compared with numerical simulations of controlling the sound power radiated through an open aperture in a rigid wall, subject to an incident plane wave, using an array of secondary sources in the aperture. In this case the diffraction through the aperture becomes important when its size is compatible with the acoustic wavelength, in which case only a few sources are necessary for good control. When the size of the aperture is large compared to the wavelength, and diffraction is less important but more secondary sources need to be used for good control, the results then become similar to those for the free field problem with an infinite source array.

On the Mathematical Modeling of Single and Multiple Scattering of Ultrasonic Guided Waves by Small Scatterers: A Structural Health Monitoring Measurement Model

NASA Astrophysics Data System (ADS)

Strom, Brandon William

In an effort to assist in the paradigm shift from schedule based maintenance to conditioned based maintenance, we derive measurement models to be used within structural health monitoring algorithms. Our models are physics based, and use scattered Lamb waves to detect and quantify pitting corrosion. After covering the basics of Lamb waves and the reciprocity theorem, we develop a technique for the scattered wave solution. The first application is two-dimensional, and is employed in two different ways. The first approach integrates a traction distribution and replaces it by an equivalent force. The second approach is higher order and uses the actual traction distribution. We find that the equivalent force version of the solution technique holds well for small pits at low frequencies. The second application is three-dimensional. The equivalent force caused by the scattered wave of an arbitrary equivalent force is calculated. We obtain functions for the scattered wave displacements as a function of equivalent forces, equivalent forces as a function of incident wave, and scattered wave amplitudes as a function of incident amplitude. The third application uses self-consistency to derive governing equations for the scattered waves due to multiple corrosion pits. We decouple the implicit set of equations and solve explicitly by using a recursive series solution. Alternatively, we solve via an undetermined coefficient method which results in an interaction operator and solution via matrix inversion. The general solution is given for N pits including mode conversion. We show that the two approaches are equivalent, and give a solution for three pits. Various approximations are advanced to simplify the problem while retaining the leading order physics. As a final application, we use the multiple scattering model to investigate resonance of Lamb waves. We begin with a one-dimensional problem and progress to a three-dimensional problem. A directed graph enables interpretation of the interaction operator, and we show that a series solution converges due to loss of energy in the system. We see that there are four causes of resonance and plot the modulation depth as a function of spacing between the pits.

Principles of Space Plasma Wave Instrument Design

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.

1998-01-01

Space plasma waves span the frequency range from somewhat below the ion cyclotron frequency to well above the electron cyclotron frequency and plasma frequency. Because of the large frequency range involved, the design of space plasma wave instrumentation presents many interesting challenges. This chapter discusses the principles of space plasma wave instrument design. The topics covered include: performance requirements, electric antennas, magnetic antennas, and signal processing. Where appropriate, comments are made on the likely direction of future developments.

Space-Charge Waves and Instabilities in Intense Beams

NASA Astrophysics Data System (ADS)

Wang, J. G.

1997-11-01

Advancced accelerator applications, such as drivers for heavy ion inertial fusion, high-intensity synchrotrons for spallation neutron sources, high energy boosters, free electron lasers, high-power microwave generators, etc., require ever-increasing beam intensity. An important beam dynamics issue in such beams is the collective behavior of charged particles due to their space charge effects. This includes the phenomena of space-charge waves and instabilities excited on beams by external perturbations. It is very crucial to fully understand these phenomena in order to develop advanced accelerators for various applications. At the University of Maryland we have been conducting experimental programs to study space-charge waves and longitudinal instabilities by employing low-energy, high-current, space-charge dominated electron beams. Localized perturbations on the beams are generated from a gridded electron gun. In a conducting transport channel focused by short solenoids, these perturbations evolve into space-charge waves propagating on the beams. The wave speed is measured and many beam parameters are determined with this technique. The reflection of space-charge waves at the shoulder of an initially rectangular beam bunch is also observed. In a resistive-wall channel focused by a uniform long solenoid, the space-charge waves suffer longitudinal instability. The properties of the instabilities are studied in detail in the long wavelength range. In this talk we review our experimental results on the waves and instabilities and compare with theory.

Mathematics for Physics

NASA Astrophysics Data System (ADS)

Stone, Michael; Goldbart, Paul

2009-07-01

Preface; 1. Calculus of variations; 2. Function spaces; 3. Linear ordinary differential equations; 4. Linear differential operators; 5. Green functions; 6. Partial differential equations; 7. The mathematics of real waves; 8. Special functions; 9. Integral equations; 10. Vectors and tensors; 11. Differential calculus on manifolds; 12. Integration on manifolds; 13. An introduction to differential topology; 14. Group and group representations; 15. Lie groups; 16. The geometry of fibre bundles; 17. Complex analysis I; 18. Applications of complex variables; 19. Special functions and complex variables; Appendixes; Reference; Index.

A low-order model of the equatorial ocean-atmosphere system

NASA Astrophysics Data System (ADS)

Legnani, Roberto

A low order model of the equatorial ocean-atmosphere coupled system is presented. The model atmosphere includes a hydrological cycle with cloud-radiation interaction. The model ocean is based on mixed layer dynamics with a parameterization of entrainment processes. The coupling takes place via transfer to momentum, sensible heat, latent heat and short wave and long wave radiation through the ocean surface. The dynamical formulation is that of the primitive equations of an equatorial beta-plane, with zonally periodic and meridionally infinite geometry. The system is expanded into the set of normal modes pertinent to the linear problem and severly truncated to a few modes; 54 degrees of freedom are retained. Some nonlinear terms of the equations are evaluated in physical space and then projected onto the functional space; other terms are evaluated directly in the functional space. Sensitivity tests to variations of the parameters are performed, and some results from 10-year initial value simulations are presented. The model is capable of supporting oscillations of different time scales, ranging from a few days to a few years; it prefers a particular zonally asymmetric state, but temporarily switches to a different (opposite) zonally asymmetric state in an event-like fashion.

a Low-Order Model of the Equatorial Ocean-Atmosphere System.

NASA Astrophysics Data System (ADS)

Legnani, Roberto

A low order model of the equatorial ocean-atmosphere coupled system is presented. The model atmosphere includes a hydrological cycle with cloud-radiation interaction. The model ocean is based on mixed layer dynamics with a parameterization of entrainment processes. The coupling takes place via transfer to momentum, sensible heat, latent heat and short -wave and long-wave radiation through the ocean surface. The dynamical formulation is that of the primitive equations of an equatorial beta-plane, with zonally periodic and meridionally infinite geometry. The system is expanded into the set of normal modes pertinent to the linear problem and severely truncated to a few modes; 54 degrees of freedom are retained. Some nonlinear terms of the equations are evaluated in physical space and then projected onto the functional space; other terms are evaluated directly in the functional space. Sensitivity tests to variations of the parameters are performed, and some results from 10-year initial value simulations are presented. The model is capable of supporting oscillations of different time scales, ranging from a few days to a few years; it prefers a particular zonally asymmetric state, but temporarily switches to a different (opposite) zonally asymmetric state in an event-like fashion.

Viscoelastic representation of surface waves in patchy saturated poroelastic media

NASA Astrophysics Data System (ADS)

Zhang, Yu; Xu, Yixian; Xia, Jianghai; Ping, Ping; Zhang, Shuangxi

2014-08-01

Wave-induced flow is observed as the dominated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation in patchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range (0.1-1,000 Hz). The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent viscoelastic media. The simulation of surface wave propagation within mesoscopic patches requires solving Biot's differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Biot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase viscoelastic differential equations.

Poynting vector, energy densities, and pressure of collective transverse electromagnetic fluctuations in unmagnetized plasmas

NASA Astrophysics Data System (ADS)

Schlickeiser, R.

2012-01-01

A systematic calculation of the electromagnetic properties (Poynting vector, electromagnetic energy, and pressure) of the collective transverse fluctuations in unmagnetized plasmas with velocity-anisotropic plasma particle distributions functions is presented. Time-averaged electromagnetic properties for monochromatic weakly damped wave-like fluctuations and space-averaged electromagnetic properties for monochromatic weakly propagating and aperiodic fluctuations are calculated. For aperiodic fluctuations, the Poynting vector as well as the sum of the space-averaged electric and magnetic field energy densities vanish. However, aperiodic fluctuations possess a positive pressure given by its magnetic energy density. This finite pressure density pa of aperiodic fluctuations has important consequences for the dynamics of cosmic unmagnetized plasmas such as the intergalactic medium after reionization. Adopting the standard cosmological evolution model, we show that this additional pressure changes the expansion law of the universe leading to further deceleration. Negative vacuum pressure counterbalances this deceleration to an accelerating universe provided that the negative vacuum pressure is greater than 1.5pa, which we estimate to be of the order 2.1 . 10-16 dyn cm-2.

Photodetector with absorbing region having resonant periodic absorption between reflectors

DOEpatents

Bryan, R.P.; Olbright, G.R.; Brennan, T.M.; Tsao, J.Y.

1995-02-14

A photodetector is disclosed that is responsive to a wavelength or wavelengths of interest which have heretofore been unrealized. The photodetector includes a resonant cavity structure bounded by first and second reflectors, the resonant cavity structure being resonant at the wavelength or wavelengths of interest for containing a plurality of standing waves therein. The photodetector further includes a radiation absorbing region disposed within the resonant cavity structure, the radiation absorbing region including a plurality of radiation absorbing layers spaced apart from one another by a distance substantially equal to a distance between antinodes of adjacent ones of the standing waves. Each of radiation absorbing layers is spatially positioned at a location of one of the antinodes of one of the standing waves such that radiation absorption is enhanced. The radiation absorbing layers may be either bulk layers or quantum wells includes a plurality of layers, each of which is comprised of a strained layer of InGaAs. Individual ones of the InGaAs layers are spaced apart from one another by a GaAs barrier layer. 11 figs.

Photodetector with absorbing region having resonant periodic absorption between reflectors

DOEpatents

Bryan, Robert P.; Olbright, Gregory R.; Brennan, Thomas M.; Tsao, Jeffrey Y.

1995-02-14

A photodetector that is responsive to a wavelength or wavelengths of interest which have heretofore been unrealized. The photodetector includes a resonant cavity structure bounded by first and second reflectors, the resonant cavity structure being resonant at the wavelength or wavelengths of interest for containing a plurality of standing waves therein. The photodetector further includes a radiation absorbing region disposed within the resonant cavity structure, the radiation absorbing region including a plurality of radiation absorbing layers spaced apart from one another by a distance substantially equal to a distance between antinodes of adjacent ones of the standing waves. Each of radiation absorbing layers is spatially positioned at a location of one of the antinodes of one of the standing waves such that radiation absorption is enhanced. The radiation absorbing layers may be either bulk layers or quantum wells includes a plurality of layers, each of which is comprised of a strained layer of InGaAs. Individual ones of the InGaAs layers are spaced apart from one another by a GaAs barrier layer.

Transition operators in acoustic-wave diffraction theory. I - General theory. II - Short-wavelength behavior, dominant singularities of Zk0 and Zk0 exp -1

NASA Technical Reports Server (NTRS)

Hahne, G. E.

1991-01-01

A formal theory of the scattering of time-harmonic acoustic scalar waves from impenetrable, immobile obstacles is established. The time-independent formal scattering theory of nonrelativistic quantum mechanics, in particular the theory of the complete Green's function and the transition (T) operator, provides the model. The quantum-mechanical approach is modified to allow the treatment of acoustic-wave scattering with imposed boundary conditions of impedance type on the surface (delta-Omega) of an impenetrable obstacle. With k0 as the free-space wavenumber of the signal, a simplified expression is obtained for the k0-dependent T operator for a general case of homogeneous impedance boundary conditions for the acoustic wave on delta-Omega. All the nonelementary operators entering the expression for the T operator are formally simple rational algebraic functions of a certain invertible linear radiation impedance operator which maps any sufficiently well-behaved complex-valued function on delta-Omega into another such function on delta-Omega. In the subsequent study, the short-wavelength and the long-wavelength behavior of the radiation impedance operator and its inverse (the 'radiation admittance' operator) as two-point kernels on a smooth delta-Omega are studied for pairs of points that are close together.

A probabilistic approach for the estimation of earthquake source parameters from spectral inversion

NASA Astrophysics Data System (ADS)

Supino, M.; Festa, G.; Zollo, A.

2017-12-01

The amplitude spectrum of a seismic signal related to an earthquake source carries information about the size of the rupture, moment, stress and energy release. Furthermore, it can be used to characterize the Green's function of the medium crossed by the seismic waves. We describe the earthquake amplitude spectrum assuming a generalized Brune's (1970) source model, and direct P- and S-waves propagating in a layered velocity model, characterized by a frequency-independent Q attenuation factor. The observed displacement spectrum depends indeed on three source parameters, the seismic moment (through the low-frequency spectral level), the corner frequency (that is a proxy of the fault length) and the high-frequency decay parameter. These parameters are strongly correlated each other and with the quality factor Q; a rigorous estimation of the associated uncertainties and parameter resolution is thus needed to obtain reliable estimations.In this work, the uncertainties are characterized adopting a probabilistic approach for the parameter estimation. Assuming an L2-norm based misfit function, we perform a global exploration of the parameter space to find the absolute minimum of the cost function and then we explore the cost-function associated joint a-posteriori probability density function around such a minimum, to extract the correlation matrix of the parameters. The global exploration relies on building a Markov chain in the parameter space and on combining a deterministic minimization with a random exploration of the space (basin-hopping technique). The joint pdf is built from the misfit function using the maximum likelihood principle and assuming a Gaussian-like distribution of the parameters. It is then computed on a grid centered at the global minimum of the cost-function. The numerical integration of the pdf finally provides mean, variance and correlation matrix associated with the set of best-fit parameters describing the model. Synthetic tests are performed to investigate the robustness of the method and uncertainty propagation from the data-space to the parameter space. Finally, the method is applied to characterize the source parameters of the earthquakes occurring during the 2016-2017 Central Italy sequence, with the goal of investigating the source parameter scaling with magnitude.

Energy Dissipation of Rayleigh Waves due to Absorption Along the Path by the Use of Finite Element Method

DTIC Science & Technology

1979-07-31

3 x 3 t Strain vector a ij,j Space derivative of the stress tensor Fi Force vector per unit volume o Density x CHAPTER III F Total force K Stiffness...matrix 6Vector displacements M Mass matrix B Space operating matrix DO Matrix moduli 2 x 3 DZ Operating matrix in Z direction N Matrix of shape...dissipating medium the deformation of a solid is a function of time, temperature and space . Creep phenomenon is a deformation process in which there is

Point-ahead limitation on reciprocity tracking. [in earth-space optical link

NASA Technical Reports Server (NTRS)

Shapiro, J. H.

1975-01-01

The average power received at a spacecraft from a reciprocity-tracking transmitter is shown to be the free-space diffraction-limited result times a gain-reduction factor that is due to the point-ahead requirement. For a constant-power transmitter, the gain-reduction factor is approximately equal to the appropriate spherical-wave mutual-coherence function. For a constant-average-power transmitter, an exact expression is obtained for the gain-reduction factor.

Fission fragment charge and mass distributions in 239Pu(n ,f ) in the adiabatic nuclear energy density functional theory

NASA Astrophysics Data System (ADS)

Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.

2016-05-01

Background: Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. Purpose: In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear density functional theory (DFT). Methods: Our theoretical framework is the nuclear energy density functional (EDF) method, where large-amplitude collective motion is treated adiabatically by using the time-dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). In practice, the TDGCM is implemented in two steps. First, a series of constrained EDF calculations map the configuration and potential-energy landscape of the fissioning system for a small set of collective variables (in this work, the axial quadrupole and octupole moments of the nucleus). Then, nuclear dynamics is modeled by propagating a collective wave packet on the potential-energy surface. Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. Results: We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in two-dimensional collective spaces. Theory and experiment agree typically within two mass units for the position of the asymmetric peak. As expected, calculations are sensitive to the structure of the initial state and the prescription for the collective inertia. We emphasize that results are also sensitive to the continuity of the collective landscape near scission. Conclusions: Our analysis confirms that the adiabatic approximation provides an effective scheme to compute fission fragment yields. It also suggests that, at least in the framework of nuclear DFT, three-dimensional collective spaces may be a prerequisite to reach 10% accuracy in predicting pre-neutron emission fission fragment yields.

Rayleigh wave effects in an elastic half-space.

NASA Technical Reports Server (NTRS)

Aggarwal, H. R.

1972-01-01

Consideration of Rayleigh wave effects in a homogeneous isotropic linearly elastic half-space subject to an impulsive uniform disk pressure loading. An approximate formula is obtained for the Rayleigh wave effects. It is shown that the Rayleigh waves near the center of loading arise from the portion of the dilatational and shear waves moving toward the axis, after they originate at the edge of the load disk. A study is made of the vertical displacement due to Rayleigh waves at points on the axis near the surface of the elastic half-space.

Quantum Optics in Phase Space

NASA Astrophysics Data System (ADS)

Schleich, Wolfgang P.

2001-04-01

Quantum Optics in Phase Space provides a concise introduction to the rapidly moving field of quantum optics from the point of view of phase space. Modern in style and didactically skillful, Quantum Optics in Phase Space prepares students for their own research by presenting detailed derivations, many illustrations and a large set of workable problems at the end of each chapter. Often, the theoretical treatments are accompanied by the corresponding experiments. An exhaustive list of references provides a guide to the literature. Quantum Optics in Phase Space also serves advanced researchers as a comprehensive reference book. Starting with an extensive review of the experiments that define quantum optics and a brief summary of the foundations of quantum mechanics the author Wolfgang P. Schleich illustrates the properties of quantum states with the help of the Wigner phase space distribution function. His description of waves ala WKB connects semi-classical phase space with the Berry phase. These semi-classical techniques provide deeper insight into the timely topics of wave packet dynamics, fractional revivals and the Talbot effect. Whereas the first half of the book deals with mechanical oscillators such as ions in a trap or atoms in a standing wave the second half addresses problems where the quantization of the radiation field is of importance. Such topics extensively discussed include optical interferometry, the atom-field interaction, quantum state preparation and measurement, entanglement, decoherence, the one-atom maser and atom optics in quantized light fields. Quantum Optics in Phase Space presents the subject of quantum optics as transparently as possible. Giving wide-ranging references, it enables students to study and solve problems with modern scientific literature. The result is a remarkably concise yet comprehensive and accessible text- and reference book - an inspiring source of information and insight for students, teachers and researchers alike.

THz emission of donor and acceptor doped GaAs/AlGaAs quantum well structures with inserted thin AlAs monolayer

NASA Astrophysics Data System (ADS)

van Dommelen, Paphavee; Daengngam, Chalongrat; Kalasuwan, Pruet

2018-04-01

In this paper, we explore THz range optical intersubband transition energies in a donor doped quantum well of a GaAs/AlGaAs system as a function of the insertion position of an AlAs monolayer in the GaAs quantum well. In simulated models, the optical transition energies between electron subband levels 1 and 2 were higher in the doped structure than in the undoped structure. This may be because the envelope wave function of the second electron subband strongly overlapped the envelope wave function of the first electron subband and influenced the optical intersubband transition between the two levels in the THz range. At different levels of bias voltage at the Schottky barrier on the donor doped structure, the electric field in the growth direction of the structure linearly increased the further away the AlAs monolayer was placed from the reference position. We also simulated the optical transition energies between acceptor energy levels of the acceptor doped structure as a function of the insertion position of the AlAs monolayer. The acceptor doped structure induced THz range emission whereas the undoped structure induced mid-IR emission.

A Simulated Heat Wave Has Diverse Effects on Immune Function and Oxidative Physiology in the Corn Snake (Pantherophis guttatus).

PubMed

Stahlschmidt, Z R; French, S S; Ahn, A; Webb, A; Butler, M W

Animals will continue to encounter increasingly warm environments, including more frequent and intense heat waves. Yet the physiological consequences of heat waves remain equivocal, potentially because of variation in adaptive plasticity (reversible acclimation) and/or aspects of experimental design. Thus, we measured a suite of physiological variables in the corn snake (Pantherophis guttatus) after exposure to field-parameterized, fluctuating temperature regimes (moderate temperature and heat wave treatments) to address two hypotheses: (1) a heat wave causes physiological stress, and (2) thermal performance of immune function exhibits adaptive plasticity in response to a heat wave. We found little support for our first hypothesis because a simulated heat wave had a negative effect on body mass, but it also reduced oxidative damage and did not affect peak performance of three immune metrics. Likewise, we found only partial support for our second hypothesis. After exposure to a simulated heat wave, P. guttatus exhibited greater performance breadth and reduced temperature specialization (the standardized difference between peak performance and performance breadth) for only one of three immune metrics and did so in a sex-dependent manner. Further, a simulated heat wave did not elicit greater performance of any immune metric at higher temperatures. Yet a heat wave likely reduced innate immune function in P. guttatus because each metric of innate immune performance in this species (as in most vertebrates) was lower at elevated temperatures. Together with previous research, our study indicates that a heat wave may have complex, modest, and even positive physiological effects in some taxa.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vankerschaver, Joris; Liao, Cuicui; Leok, Melvin

The main goal of this paper is to derive an alternative characterization of the multisymplectic form formula for classical field theories using the geometry of the space of boundary values. We review the concept of Type-I/II generating functionals defined on the space of boundary data of a Lagrangian field theory. On the Lagrangian side, we define an analogue of Jacobi's solution to the Hamilton–Jacobi equation for field theories, and we show that by taking variational derivatives of this functional, we obtain an isotropic submanifold of the space of Cauchy data, described by the so-called multisymplectic form formula. As an examplemore » of the latter, we show that Lorentz's reciprocity principle in electromagnetism is a particular instance of the multisymplectic form formula. We also define a Hamiltonian analogue of Jacobi's solution, and we show that this functional is a Type-II generating functional. We finish the paper by defining a similar framework of generating functions for discrete field theories, and we show that for the linear wave equation, we recover the multisymplectic conservation law of Bridges.« less

Studying Biological Rhythms of Person's Skin-galvanic Reaction and Dynamics of Light Transmission by Isomeric Substance in Space Flight Conditions

NASA Technical Reports Server (NTRS)

Glushko, Vladimir

2004-01-01

Intensity and amplitude of human functional systems and human most important organs are wavelike, rhythmic by nature. These waves have constant periodicity, phase and amplitude. The mentioned characteristics can vary, however their variations have a pronounced reiteration in the course of time. This indicates a hashing of several wave processes and their interference. Stochastic changes in wave processes characteristics of a human organism are explained either by 'pulsations' associated with hashing (superposition) of several wave processes and their interference, or by single influence of environmental physical factors on a human organism. Human beings have respectively periods of higher and lower efficiency, state of health and so on, depending not only of environmental factors, but also of 'internal' rhythmic factor. Sometimes peaks and falls periodicity of some or other characteristics is broken. Disturbance of steady-state biological rhythms is usually accompanied by reduction of activity steadiness of the most important systems of a human organism. In its turn this has an effect on organism's adaptation to changing living conditions as well as on general condition and efficiency of a human being. The latter factor is very important for space medicine. Biological rhythmology is a special branch of biology and medicine, it studies rhythmic activity mechanisms of organs, their systems, individuals and species. Appropriate researches were also carried out in space medicine.

Chiral Domain Structure in Superfluid 3He-A Studied by Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Kasai, J.; Okamoto, Y.; Nishioka, K.; Takagi, T.; Sasaki, Y.

2018-05-01

The existence of a spatially varying texture in superfluid 3He is a direct manifestation of the complex macroscopic wave function. The real space shape of the texture, namely, a macroscopic wave function, has been studied extensively with the help of theoretical modeling but has never been directly observed experimentally with spatial resolution. We have succeeded in visualizing the texture by a specialized magnetic resonance imaging. With this new technology, we have discovered that the macroscopic chiral domains, of which sizes are as large as 1 mm, and corresponding chiral domain walls exist rather stably in 3He - A film at temperatures far below the transition temperature.

Trajectories of electrons with large longitudinal momenta in the phase plane during surfatron acceleration by an electromagnetic wave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mkrtichyan, G. S., E-mail: hay-13@mail.ru

2015-07-15

The trajectories of electrons with large longitudinal momenta in the phase plane in the course of their surfatron acceleration by an electromagnetic wave propagating in space plasma across the external magnetic field are analyzed. Electrons with large longitudinal momenta are trapped immediately if the initial wave phase Ψ(0) on the particle trajectory is positive. For negative values of Ψ(0), no electrons trapping by the wave is observed over the available computational times. According to numerical calculations, the trajectories of trapped particles in the phase plane have a singular point of the stable focus type and the behavior of the trajectorymore » corresponds to the motion in a complex nonstationary effective potential well. For some initial phases, electrons are confined in the region of the accelerating electric field for relatively short time, the energy gain being about 50–130% and more.« less

Evidence for Highly Inhomogeneous mm-Wave Sources During the Impulsive Flare of May 9, 1991

NASA Technical Reports Server (NTRS)

Hermann, R.; Magun, A.; Kaufmann, P.; Correia, E.; Costa, J. E. R.; Machado, M. E.; Fishman, G.

1997-01-01

In this paper multiwavelength observations of an impulsive flare of May 9, 1991 are presented. This event was observed with the 48 GHz multibeam focal array used at the Itapetinga radio telescope, the microwave patrol telescopes at Bem and the BATSE high time resolution hard X-ray spectrometer on board CGRO. While spatially unresolved low sensitivity observations show two major impulsive peaks, the mm-wave observations with the ability of spatially high resolved tracking of the emission centroids suggest a primarily bipolar source configuration. For the first time two mm-wave sources with a spacing below the HPBW could be separated with the multibeam technique. The general features of the observations are explained as emission of partially trapped electrons. Furthermore we present evidence for highly inhomogeneous substructures within one of the two mm-wave sources for which the positional scatter of the emission center, within 2s, is less than 2".

Majorana quasiparticles in semiconducting carbon nanotubes

NASA Astrophysics Data System (ADS)

Marganska, Magdalena; Milz, Lars; Izumida, Wataru; Strunk, Christoph; Grifoni, Milena

2018-02-01

Engineering effective p -wave superconductors hosting Majorana quasiparticles (MQPs) is nowadays of particular interest, also in view of the possible utilization of MQPs in fault-tolerant topological quantum computation. In quasi-one-dimensional systems, the parameter space for topological superconductivity is significantly reduced by the coupling between transverse modes. Together with the requirement of achieving the topological phase under experimentally feasible conditions, this strongly restricts in practice the choice of systems which can host MQPs. Here, we demonstrate that semiconducting carbon nanotubes (CNTs) in proximity with ultrathin s -wave superconductors, e.g., exfoliated NbSe2, satisfy these needs. By precise numerical tight-binding calculations in the real space, we show the emergence of localized zero-energy states at the CNT ends above a critical value of the applied magnetic field, of which we show the spatial evolution. Knowing the microscopic wave functions, we unequivocally demonstrate the Majorana nature of the localized states. An effective four-band model in the k -space, with parameters determined from the numerical spectrum, is used to calculate the topological phase diagram and its phase boundaries in analytic form. Finally, the impact of symmetry breaking contributions, like disorder and an axial component of the magnetic field, is investigated.

Space-Time Localization of Plasma Turbulence Using Multiple Spacecraft Radio Links

NASA Technical Reports Server (NTRS)

Armstrong, John W.; Estabrook, Frank B.

2011-01-01

Space weather is described as the variability of solar wind plasma that can disturb satellites and systems and affect human space exploration. Accurate prediction requires information of the heliosphere inside the orbit of the Earth. However, for predictions using remote sensing, one needs not only plane-of-sky position but also range information the third spatial dimension to show the distance to the plasma disturbances and thus when they might propagate or co-rotate to create disturbances at the orbit of the Earth. Appropriately processed radio signals from spacecraft having communications lines-of-sight passing through the inner heliosphere can be used for this spacetime localization of plasma disturbances. The solar plasma has an electron density- and radio-wavelength-dependent index of refraction. An approximately monochromatic wave propagating through a thin layer of plasma turbulence causes a geometrical-optics phase shift proportional to the electron density at the point of passage, the radio wavelength, and the thickness of the layer. This phase shift is the same for a wave propagating either up or down through the layer at the point of passage. This attribute can be used for space-time localization of plasma irregularities. The transfer function of plasma irregularities to the observed time series depends on the Doppler tracking mode. When spacecraft observations are in the two-way mode (downlink radio signal phase-locked to an uplink radio transmission), plasma fluctuations have a two-pulse response in the Doppler. In the two-way mode, the Doppler time series y2(t) is the difference between the frequency of the downlink signal received and the frequency of a ground reference oscillator. A plasma blob localized at a distance x along the line of sight perturbs the phase on both the up and down link, giving rise to two events in the two-way tracking time series separated by a time lag depending the blob s distance from the Earth: T2-2x/c, where T2 is the two-way time-of-flight of radio waves to/from the spacecraft and c is the speed of light. In some tracking situations, more information is available. For example, with the 5-link Cassini radio system, the plasma contribution to the up and down links, y(sub up)(t) and y(sub dn)(t), can be computed separately. The times series y(sub up)(t) and y(sub dn)(t) respond to a localized plasma blob with one event in each time series. These events are also separated in time by T2-2x/c. By cross-correlating the up and down link Doppler time series, the time separation of the plasma events can be measured and hence the plasma blob s distance from the Earth determined. Since the plane-of-sky position is known, this technique allows localization of plasma events in time and three space dimensions.

Solving the Vlasov equation in two spatial dimensions with the Schrödinger method

NASA Astrophysics Data System (ADS)

Kopp, Michael; Vattis, Kyriakos; Skordis, Constantinos

2017-12-01

We demonstrate that the Vlasov equation describing collisionless self-gravitating matter may be solved with the so-called Schrödinger method (ScM). With the ScM, one solves the Schrödinger-Poisson system of equations for a complex wave function in d dimensions, rather than the Vlasov equation for a 2 d -dimensional phase space density. The ScM also allows calculating the d -dimensional cumulants directly through quasilocal manipulations of the wave function, avoiding the complexity of 2 d -dimensional phase space. We perform for the first time a quantitative comparison of the ScM and a conventional Vlasov solver in d =2 dimensions. Our numerical tests were carried out using two types of cold cosmological initial conditions: the classic collapse of a sine wave and those of a Gaussian random field as commonly used in cosmological cold dark matter N-body simulations. We compare the first three cumulants, that is, the density, velocity and velocity dispersion, to those obtained by solving the Vlasov equation using the publicly available code ColDICE. We find excellent qualitative and quantitative agreement between these codes, demonstrating the feasibility and advantages of the ScM as an alternative to N-body simulations. We discuss, the emergence of effective vorticity in the ScM through the winding number around the points where the wave function vanishes. As an application we evaluate the background pressure induced by the non-linearity of large scale structure formation, thereby estimating the magnitude of cosmological backreaction. We find that it is negligibly small and has time dependence and magnitude compatible with expectations from the effective field theory of large scale structure.

Breathers, quasi-periodic and travelling waves for a generalized ?-dimensional Yu-Toda-Sasa-Fukayama equation in fluids

NASA Astrophysics Data System (ADS)

Hu, Wen-Qiang; Gao, Yi-Tian; Zhao, Chen; Jia, Shu-Liang; Lan, Zhong-Zhou

2017-07-01

Under investigation in this paper is a generalized ?-dimensional Yu-Toda-Sasa-Fukayama equation for the interfacial wave in a two-layer fluid or the elastic quasi-plane wave in a liquid lattice. By virtue of the binary Bell polynomials, bilinear form of this equation is obtained. With the help of the bilinear form, N-soliton solutions are obtained via the Hirota method, and a bilinear Bäcklund transformation is derived to verify the integrability. Homoclinic breather waves are obtained according to the homoclinic test approach, which is not only the space-periodic breather but also the time-periodic breather via the graphic analysis. Via the Riemann theta function, quasi one-periodic waves are constructed, which can be viewed as a superposition of the overlapping solitary waves, placed one period apart. Finally, soliton-like, periodical triangle-type, rational-type and solitary bell-type travelling waves are obtained by means of the polynomial expansion method.