WorldWideScience

Sample records for nonmonochromatic plane wave

  1. Parametric instability of a large-amplitude nonmonochromatic Alfvacute en wave

    International Nuclear Information System (INIS)

    Malara, F.; Velli, M.

    1996-01-01

    The parametric instability of a finite-amplitude Alfvacute en wave is studied in a one-dimensional geometry. The pump wave is an exact solution of the nonlinear magnetohydrodynamic (MHD) equations, i.e., the magnetic field perturbation has a uniform intensity and rotates in the plane perpendicular to the propagation direction, but its Fourier spectrum contains several wavelengths. The weakly nonmonochromatic regime is first studied by an analytical approach. It is shown that the growth rate of the instability decreases quadratically with a parameter that measures the departure from the monochromatic case. The fully nonmonochromatic case is studied by numerically solving the instability equations, when the phase function of the pump wave has a power-law spectrum. Though the growth rate is maximum in the monochromatic case, it remains of the same order of magnitude also for wide spectrum pump waves. For quasimonochromatic waves the correction to the growth rate depends only on the spectral index of the phase function. copyright 1996 American Institute of Physics

  2. Colliding almost-plane gravitational waves: Colliding plane waves and general properties of almost-plane-wave spacetimes

    International Nuclear Information System (INIS)

    Yurtsever, U.

    1988-01-01

    It is well known that when two precisely plane-symmetric gravitational waves propagating in an otherwise flat background collide, they focus each other so strongly as to produce a curvature singularity. This paper is the first of several devoted to almost-plane gravitational waves and their collisions. Such waves are more realistic than plane waves in having a finite but very large transverse size. In this paper we review some crucial features of the well-known exact solutions for colliding plane waves and we argue that one of these features, the breakdown of ''local inextendibility'' can be regarded as nongeneric. We then introduce a new framework for analyzing general colliding plane-wave spacetimes; we give an alternative proof of a theorem due to Tipler implying the existence of singularities in all generic colliding plane-wave solutions; and we discuss the fact that the recently constructed Chandrasekhar-Xanthopoulos colliding plane-wave solutions are not strictly plane symmetric and thus do not satisfy the conditions and the conclusion of Tipler's theorem

  3. Effect of an external alternating electric field non-monochromaticity on parametric excitation of surface ion cyclotron X-modes

    International Nuclear Information System (INIS)

    Girka, V O; Puzyrkov, S Yu; Shpagina, V O; Shpagina, L O

    2012-01-01

    The application of an external alternating electric field in the range of ion cyclotron frequencies is a well-known method for the excitation of surface electromagnetic waves. The present paper is devoted to the development of a kinetic theory of parametric excitation of these eigenwaves propagating across an external steady magnetic field along the plasma boundary at the second harmonic of the ion cyclotron frequency. Unlike previous papers on this subject, parametric excitation of surface ion cyclotron X-modes is studied here under the condition of non-monochromaticity of an external alternating electric field. Non-monochromaticity of the external alternating electric field is modeled by the superposition of two uniform and monochromatic electric fields with different amplitudes and frequencies. The nonlinear boundary condition is formulated for a tangential magnetic field of the studied surface waves. An infinite set of equations for the harmonics of a tangential electric field is solved using the approximation of the wave packet consisting of the main harmonic and two nearest satellite harmonics. Two different regimes of instability have been considered. If one of the applied generators has an operation frequency that is close to the ion cyclotron frequency, then changing the amplitude of the second generator allows one to enhance the growth rate of the parametric instability or to diminish it. But if the operation frequencies of the both generators are not close to the ion cyclotron frequency, then changing the amplitudes of their fields allows one to decrease the growth rate of the instability and even to suppress its development. The problem is studied both analytically and numerically.

  4. Generating asymptotically plane wave spacetimes

    International Nuclear Information System (INIS)

    Hubeny, Veronika E.; Rangamani, Mukund

    2003-01-01

    In an attempt to study asymptotically plane wave spacetimes which admit an event horizon, we find solutions to vacuum Einstein's equations in arbitrary dimension which have a globally null Killing field and rotational symmetry. We show that while such solutions can be deformed to include ones which are asymptotically plane wave, they do not posses a regular event horizon. If we allow for additional matter, such as in supergravity theories, we show that it is possible to have extremal solutions with globally null Killing field, a regular horizon, and which, in addition, are asymptotically plane wave. In particular, we deform the extremal M2-brane solution in 11-dimensional supergravity so that it behaves asymptotically as a 10-dimensional vacuum plane wave times a real line. (author)

  5. Conceptual Design of Wave Plane

    DEFF Research Database (Denmark)

    Frigaard, Peter; Trewers, Andrew; Kofoed, Jens Peter

    The Wave Plane is a patented Wave Energy device of the overtopping type, designed to capture potential as well as kinetic energy. This is as such different to other overtopping devices, who usually only focus on potential energy. If Wave Plane A/S can deliver the turbine technology to utilize both...

  6. Plane-wave least-squares reverse-time migration

    KAUST Repository

    Dai, Wei

    2013-06-03

    A plane-wave least-squares reverse-time migration (LSRTM) is formulated with a new parameterization, where the migration image of each shot gather is updated separately and an ensemble of prestack images is produced along with common image gathers. The merits of plane-wave prestack LSRTM are the following: (1) plane-wave prestack LSRTM can sometimes offer stable convergence even when the migration velocity has bulk errors of up to 5%; (2) to significantly reduce computation cost, linear phase-shift encoding is applied to hundreds of shot gathers to produce dozens of plane waves. Unlike phase-shift encoding with random time shifts applied to each shot gather, plane-wave encoding can be effectively applied to data with a marine streamer geometry. (3) Plane-wave prestack LSRTM can provide higher-quality images than standard reverse-time migration. Numerical tests on the Marmousi2 model and a marine field data set are performed to illustrate the benefits of plane-wave LSRTM. Empirical results show that LSRTM in the plane-wave domain, compared to standard reversetime migration, produces images efficiently with fewer artifacts and better spatial resolution. Moreover, the prestack image ensemble accommodates more unknowns to makes it more robust than conventional least-squares migration in the presence of migration velocity errors. © 2013 Society of Exploration Geophysicists.

  7. Causal inheritance in plane wave quotients

    International Nuclear Information System (INIS)

    Hubeny, Veronika E.; Rangamani, Mukund; Ross, Simon F.

    2003-01-01

    We investigate the appearance of closed timelike curves in quotients of plane waves along spacelike isometries. First we formulate a necessary and sufficient condition for a quotient of a general spacetime to preserve stable causality. We explicitly show that the plane waves are stably causal; in passing, we observe that some pp-waves are not even distinguishing. We then consider the classification of all quotients of the maximally supersymmetric ten-dimensional plane wave under a spacelike isometry, and show that the quotient will lead to closed timelike curves iff the isometry involves a translation along the u direction. The appearance of these closed timelike curves is thus connected to the special properties of the light cones in plane wave spacetimes. We show that all other quotients preserve stable causality

  8. Causal inheritance in plane wave quotients

    Science.gov (United States)

    Hubeny, Veronika E.; Rangamani, Mukund; Ross, Simon F.

    2004-01-01

    We investigate the appearance of closed timelike curves in quotients of plane waves along spacelike isometries. First we formulate a necessary and sufficient condition for a quotient of a general space-time to preserve stable causality. We explicitly show that the plane waves are stably causal; in passing, we observe that some pp waves are not even distinguishing. We then consider the classification of all quotients of the maximally supersymmetric ten-dimensional plane wave under a spacelike isometry, and show that the quotient will lead to closed timelike curves iff the isometry involves a translation along the u direction. The appearance of these closed timelike curves is thus connected to the special properties of the light cones in plane wave space-times. We show that all other quotients preserve stable causality.

  9. Fast Plane Wave Imaging

    DEFF Research Database (Denmark)

    Jensen, Jonas

    This PhD project investigates and further develops methods for ultrasound plane wave imaging and blood flow estimation with the objective of overcoming some of the major limitations in conventional ultrasound systems, which are related to low frame rates and only estimation of velocities along...... the ultrasound beam. The first part of the contribution investigates the compromise between frame rate and plane wave image quality including the influence of grating lobes from a λ-pitch transducer. A method for optimizing the image quality is suggested, and it is shown that the frame rate can be increased...... healthy volunteers. Complex flow patterns were measured in an anthropomorphic flow phantom and showed good agreement with the velocity field simulated using computational fluid dynamics. The last part of the contribution investigates two clinical applications. Plane wave imaging was used for slow velocity...

  10. Wave-equation Migration Velocity Analysis Using Plane-wave Common Image Gathers

    KAUST Repository

    Guo, Bowen

    2017-06-01

    Wave-equation migration velocity analysis (WEMVA) based on subsurface-offset, angle domain or time-lag common image gathers (CIGs) requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, a WEMVA method using plane-wave CIGs is presented. Plane-wave CIGs reduce the computational cost and memory storage because they are directly calculated from prestack plane-wave migration, and the number of plane waves is often much smaller than the number of shots. In the case of an inaccurate migration velocity, the moveout of plane-wave CIGs is automatically picked by a semblance analysis method, which is then linked to the migration velocity update by a connective function. Numerical tests on two synthetic datasets and a field dataset validate the efficiency and effectiveness of this method.

  11. 3D plane-wave least-squares Kirchhoff migration

    KAUST Repository

    Wang, Xin

    2014-08-05

    A three dimensional least-squares Kirchhoff migration (LSM) is developed in the prestack plane-wave domain to increase the quality of migration images and the computational efficiency. Due to the limitation of current 3D marine acquisition geometries, a cylindrical-wave encoding is adopted for the narrow azimuth streamer data. To account for the mispositioning of reflectors due to errors in the velocity model, a regularized LSM is devised so that each plane-wave or cylindrical-wave gather gives rise to an individual migration image, and a regularization term is included to encourage the similarities between the migration images of similar encoding schemes. Both synthetic and field results show that: 1) plane-wave or cylindrical-wave encoding LSM can achieve both computational and IO saving, compared to shot-domain LSM, however, plane-wave LSM is still about 5 times more expensive than plane-wave migration; 2) the regularized LSM is more robust compared to LSM with one reflectivity model common for all the plane-wave or cylindrical-wave gathers.

  12. Full-wave solution of short impulses in inhomogeneous plasma

    International Nuclear Information System (INIS)

    Ferencz, Orsolya E.

    2005-01-01

    In this paper the problem of real impulse propagation in arbitrarily inhomogeneous media will be presented on a fundamentally new, general, theoretical way. The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened. The earlier theoretical models for spatial inhomogeneities have some errors regarding the structure of the resultant signal originated from backward and forward propagating parts. The application of the method of inhomogeneous basic modes (MIBM) and the complete full-wave solution of arbitrarily shaped non-monochromatic plane waves in plasmas made it possible to obtain a better description of the problem, on a fully analytical way, directly from Maxwell's equations. The model investigated in this paper is inhomogeneous of arbitrary order (while the wave pattern can exist), anisotropic (magnetized), linear, cold plasma, in which the gradient of the one-dimensional spatial inhomogeneity is parallel to the direction of propagation. (author)

  13. Instability of surface electron cyclotron TM-modes influenced by non-monochromatic alternating electric field

    International Nuclear Information System (INIS)

    Girka, I. O.; Girka, V. O.; Sydora, R. D.; Thumm, M.

    2016-01-01

    The influence of non-monochromaticity of an external alternating electric field on excitation of TM eigenmodes at harmonics of the electron cyclotron frequency is considered here. These TM-modes propagate along the plasma interface in a metal waveguide. An external static constant magnetic field is oriented perpendicularly to the plasma interface. The problem is solved theoretically using the kinetic Vlasov-Boltzmann equation for description of plasma particles motion and the Maxwell equations for description of the electromagnetic mode fields. The external alternating electric field is supposed to be a superposition of two waves, whose amplitudes are different and their frequencies correlate as 2:1. An infinite set of equations for electric field harmonics of these modes is derived with the aid of nonlinear boundary conditions. This set is solved using the wave packet approach consisting of the main harmonic frequency and two nearest satellite temporal harmonics. Analytical studies of the obtained set of equations allow one to find two different regimes of parametric instability, namely, enhancement and suppression of the instability. Numerical analysis of the instability is carried out for the three first electron cyclotron harmonics.

  14. Regularized plane-wave least-squares Kirchhoff migration

    KAUST Repository

    Wang, Xin

    2013-09-22

    A Kirchhoff least-squares migration (LSM) is developed in the prestack plane-wave domain to increase the quality of migration images. A regularization term is included that accounts for mispositioning of reflectors due to errors in the velocity model. Both synthetic and field results show that: 1) LSM with a reflectivity model common for all the plane-wave gathers provides the best image when the migration velocity model is accurate, but it is more sensitive to the velocity errors, 2) the regularized plane-wave LSM is more robust in the presence of velocity errors, and 3) LSM achieves both computational and IO saving by plane-wave encoding compared to shot-domain LSM for the models tested.

  15. Plane-wave scattering from half-wave dipole arrays

    DEFF Research Database (Denmark)

    Jensen, Niels E.

    1970-01-01

    A matrix equation for determination of plane-wave scattering from arrays of thin short-circuited dipoles of lengths about half a wavelength is derived. Numerical and experimental results are presented for linear, circular, and concentric circular arrays.......A matrix equation for determination of plane-wave scattering from arrays of thin short-circuited dipoles of lengths about half a wavelength is derived. Numerical and experimental results are presented for linear, circular, and concentric circular arrays....

  16. Topologically protected edge states for out-of-plane and in-plane bulk elastic waves

    Science.gov (United States)

    Huo, Shao-Yong; Chen, Jiu-Jiu; Huang, Hong-Bo

    2018-04-01

    Topological phononic insulators (TPnIs) show promise for application in the manipulation of acoustic waves for the design of low-loss transmission and perfectly integrated communication devices. Since solid phononic crystals exist as a transverse polarization mode and a mixed longitudinal-transverse polarization mode, the realization of topological edge states for both out-of-plane and in-plane bulk elastic waves is desirable to enhance the controllability of the edge waves in solid systems. In this paper, a two-dimensional (2D) solid/solid hexagonal-latticed phononic system that simultaneously supports the topologically protected edge states for out-of-plane and in-plane bulk elastic waves is investigated. Firstly, two pairs of two-fold Dirac cones, respectively corresponding to the out-of-plane and in-plane waves, are obtained at the same frequency by tuning the crystal parameters. Then, a strategy of zone folding is invoked to form double Dirac cones. By shrinking and expanding the steel scatterer, the lattice symmetry is broken, and band inversions induced, giving rise to an intriguing topological phase transition. Finally, the topologically protected edge states for both out-of-plane and in-plane bulk elastic waves, which can be simultaneously located at the frequency range from 1.223 to 1.251 MHz, are numerically observed. Robust pseudospin-dependent elastic edge wave propagation along arbitrary paths is further demonstrated. Our results will significantly broaden its practical application in the engineering field.

  17. Plane-wave least-squares reverse-time migration

    KAUST Repository

    Dai, Wei; Schuster, Gerard T.

    2013-01-01

    . The merits of plane-wave prestack LSRTM are the following: (1) plane-wave prestack LSRTM can sometimes offer stable convergence even when the migration velocity has bulk errors of up to 5%; (2) to significantly reduce computation cost, linear phase

  18. Interaction of gravitational plane waves

    International Nuclear Information System (INIS)

    Ferrari, V.

    1988-01-01

    The mathematical theory of colliding, infinite-fronted, plane gravitational waves is presented. The process of focusing, the creation of singularities and horizons, due to the interaction, and the lens effect due to a beam-like gravitational wave are discussed

  19. Plane wave limits and T-duality

    International Nuclear Information System (INIS)

    Guven, R.

    2000-04-01

    The Penrose limit is generalized to show that, any leading order solution of the low-energy field equations in any one of the five string theories has a plane wave solution as a limit. This limiting procedure takes into account all the massless fields that may arise and commutes with the T-duality so that any dual solution has again a plane wave limit. The scaling rules used in the limit are unique and stem from the scaling property of the D = 11 supergravity action. Although the leading order dual solutions need not be exact or supersymmetric, their plane wave limits always preserve some portion of the Poincare supersymmetry and solve the relevant field equations in all powers of the string tension parameter. Further properties of the limiting procedure are discussed. (author)

  20. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    Science.gov (United States)

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

  1. DLCQ and plane wave matrix Big Bang models

    Science.gov (United States)

    Blau, Matthias; O'Loughlin, Martin

    2008-09-01

    We study the generalisations of the Craps-Sethi-Verlinde matrix big bang model to curved, in particular plane wave, space-times, beginning with a careful discussion of the DLCQ procedure. Singular homogeneous plane waves are ideal toy-models of realistic space-time singularities since they have been shown to arise universally as their Penrose limits, and we emphasise the role played by the symmetries of these plane waves in implementing the flat space Seiberg-Sen DLCQ prescription for these curved backgrounds. We then analyse various aspects of the resulting matrix string Yang-Mills theories, such as the relation between strong coupling space-time singularities and world-sheet tachyonic mass terms. In order to have concrete examples at hand, in an appendix we determine and analyse the IIA singular homogeneous plane wave - null dilaton backgrounds.

  2. DLCQ and plane wave matrix Big Bang models

    International Nuclear Information System (INIS)

    Blau, Matthias; O'Loughlin, Martin

    2008-01-01

    We study the generalisations of the Craps-Sethi-Verlinde matrix big bang model to curved, in particular plane wave, space-times, beginning with a careful discussion of the DLCQ procedure. Singular homogeneous plane waves are ideal toy-models of realistic space-time singularities since they have been shown to arise universally as their Penrose limits, and we emphasise the role played by the symmetries of these plane waves in implementing the flat space Seiberg-Sen DLCQ prescription for these curved backgrounds. We then analyse various aspects of the resulting matrix string Yang-Mills theories, such as the relation between strong coupling space-time singularities and world-sheet tachyonic mass terms. In order to have concrete examples at hand, in an appendix we determine and analyse the IIA singular homogeneous plane wave - null dilaton backgrounds.

  3. Plane waves and spacelike infinity

    International Nuclear Information System (INIS)

    Marolf, Donald; Ross, Simon F

    2003-01-01

    In an earlier paper, we showed that the causal boundary of any homogeneous plane wave satisfying the null convergence condition consists of a single null curve. In Einstein-Hilbert gravity, this would include any homogeneous plane wave satisfying the weak null energy condition. For conformally flat plane waves such as the Penrose limit of AdS 5 x S 5 , all spacelike curves that reach infinity also end on this boundary and the completion is Hausdorff. However, the more generic case (including, e.g., the Penrose limits of AdS 4 x S 7 and AdS 7 x S 4 ) is more complicated. In one natural topology, not all spacelike curves have limit points in the causal completion, indicating the need to introduce additional points at 'spacelike infinity' - the endpoints of spacelike curves. We classify the distinct ways in which spacelike curves can approach infinity, finding a two-dimensional set of distinct limits. The dimensionality of the set of points at spacelike infinity is not, however, fixed from this argument. In an alternative topology, the causal completion is already compact, but the completion is non-Hausdorff

  4. A differentiated plane wave as an electromagnetic vortex

    International Nuclear Information System (INIS)

    Hannay, J H; Nye, J F

    2015-01-01

    Differentiating a complex scalar plane wave with respect to its direction produces an isolated straight vortex line and has a natural extension, described in earlier papers, to the vector waves of electromagnetism—a differentiated plane wave (DPW). It epitomizes destructive interference and will be shown to have the local structure of an electromagnetic vortex. In this paper its polarization structure and Poynting vector field are compared and contrasted with that of the family of linear polynomial waves, of which it is a special member. By definition this wider family has a general linear complex vector function of position multiplying a plane wave, but the function must be such that the combination satisfies Maxwell’s equations. This forces translational invariance of the function along the wavevector direction—in other words the wave is ‘non-diffracting’. In a natural sense all possible polarizations are exhibited once only. But the DPW has a distinctive polarization structure only partly explored previously. Both classes of waves share similar Poynting vector fields, which can be ‘elliptic’ (helix-like flow lines) or ‘hyperbolic’, of a repulsive nature, unexpected for a vortex. Both classes can be considered as a limit in the superposition of three closely parallel ordinary plane waves in destructive interference, and this derivation is supplied in full here. (paper)

  5. The geometry of plane waves in spaces of constant curvature

    International Nuclear Information System (INIS)

    Tran, H.V.

    1988-01-01

    We examined the geometry of possible plane wave fronts in spaces of constant curvature for three cases in which the cosmological constant is positive, zero, or negative. The cosmological constant and a second-order invariant determined by a congruence of null rays were used in the investigation. We embedded the spaces under investigation in a flat five-dimensional space, and studied the null hyperplanes passing through the origin of the flat five-dimensional space. The embedded spaces are represented by quadrics in the five-dimensional space. The plane wave fronts are represented by the intersection of the quadric with null hyperplanes passing through the origin of the five-dimensional space. We concluded that in Minkowski spaces (zero cosmological constant), the plane-fronted waves will intersect if and only if the second-order invariant mentioned above is non-zero. For deSitter spaces (positive cosmological constant), plane-fronted waves will always intersect. For anti-deSitter spaces (negative cosmological constant), plane-fronted waves may but need not intersect

  6. Plane-wave Least-squares Reverse Time Migration

    KAUST Repository

    Dai, Wei

    2012-11-04

    Least-squares reverse time migration is formulated with a new parameterization, where the migration image of each shot is updated separately and a prestack image is produced with common image gathers. The advantage is that it can offer stable convergence for least-squares migration even when the migration velocity is not completely accurate. To significantly reduce computation cost, linear phase shift encoding is applied to hundreds of shot gathers to produce dozens of planes waves. A regularization term which penalizes the image difference between nearby angles are used to keep the prestack image consistent through all the angles. Numerical tests on a marine dataset is performed to illustrate the advantages of least-squares reverse time migration in the plane-wave domain. Through iterations of least-squares migration, the migration artifacts are reduced and the image resolution is improved. Empirical results suggest that the LSRTM in plane wave domain is an efficient method to improve the image quality and produce common image gathers.

  7. Plane-Wave Imaging Challenge in Medical Ultrasound

    DEFF Research Database (Denmark)

    Liebgott, Herve; Molares, Alfonso Rodriguez; Jensen, Jørgen Arendt

    2016-01-01

    for this effect, but comparing the different methods is difficult due to the lack of appropriate tools. PICMUS, the Plane-Wave Imaging Challenge in Medical Ultrasound aims to provide these tools. This paper describes the PICMUS challenge, its motivation, implementation, and metrics.......Plane-Wave imaging enables very high frame rates, up to several thousand frames per second. Unfortunately the lack of transmit focusing leads to reduced image quality, both in terms of resolution and contrast. Recently, numerous beamforming techniques have been proposed to compensate...

  8. Goedel, Penrose, anti-Mach: extra supersymmetries of time-dependent plane waves

    International Nuclear Information System (INIS)

    Blau, Matthias; O'Loughlin, Martin; Meessen, Patrick

    2003-01-01

    We prove that M-theory plane waves with extra supersymmetries are necessarily homogeneous (but possibly time-dependent), and we show by explicit construction that such time-dependent plane waves can admit extra supersymmetries. To that end we study the Penrose limits of Goedel-like metrics, show that the Penrose limit of the M-theory Goedel metric (with 20 supercharges) is generically a time-dependent homogeneous plane wave of the anti-Mach type, and display the four extra Killings spinors in that case. We conclude with some general remarks on the Killing spinor equations for homogeneous plane waves. (author)

  9. Goedel, Penrose, anti-Mach: extra supersymmetries of time-dependent plane waves

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Matthias; O' Loughlin, Martin; Meessen, Patrick [SISSA/ISAS, Via Beirut 2-4, 34014 Trieste (Italy)]. E-mail: meessen@sissa.it

    2003-09-01

    We prove that M-theory plane waves with extra supersymmetries are necessarily homogeneous (but possibly time-dependent), and we show by explicit construction that such time-dependent plane waves can admit extra supersymmetries. To that end we study the Penrose limits of Goedel-like metrics, show that the Penrose limit of the M-theory Goedel metric (with 20 supercharges) is generically a time-dependent homogeneous plane wave of the anti-Mach type, and display the four extra Killings spinors in that case. We conclude with some general remarks on the Killing spinor equations for homogeneous plane waves. (author)

  10. Plane waves with weak singularities

    International Nuclear Information System (INIS)

    David, Justin R.

    2003-03-01

    We study a class of time dependent solutions of the vacuum Einstein equations which are plane waves with weak null singularities. This singularity is weak in the sense that though the tidal forces diverge at the singularity, the rate of divergence is such that the distortion suffered by a freely falling observer remains finite. Among such weak singular plane waves there is a sub-class which does not exhibit large back reaction in the presence of test scalar probes. String propagation in these backgrounds is smooth and there is a natural way to continue the metric beyond the singularity. This continued metric admits string propagation without the string becoming infinitely excited. We construct a one parameter family of smooth metrics which are at a finite distance in the space of metrics from the extended metric and a well defined operator in the string sigma model which resolves the singularity. (author)

  11. A plane-wave final-state theory of ATI

    International Nuclear Information System (INIS)

    Parker, J.S.; Clark, C.W.

    1993-01-01

    A Fermi Golden Rule calculation of ionization cross-sections provides us with the simplest example of a plane-wave final-state theory. In this method the final (unbound) state is modeled as a plane wave, an approximation that generally gives best results in the high energy limit in which the affect of the atomic potential on the final state can be neglected. A cross-section is then calculated from the matrix element connecting the bound initial state with the final state. The idea of generalizing this method to model transitions among unbound states is credited to L.V. Keldysh, and a number of related formalisms have been proposed that are consistent with the general features of experimental data. Here we describe a plane-wave final-state model of ATI that is in the spirit of these theories, but differs significantly in its implementation and predictions. We will present a comparison of the predictions of the plane-wave model with those of a full numerical integration of the time-dependent Schrodinger equation for atomic hydrogen in a radiation field. The theory and the numerical integration give good qualitative agreement in their predictions of photoelectron spectra over about 14 orders of magnitude

  12. New family of exact solutions for colliding plane gravitational waves

    International Nuclear Information System (INIS)

    Yurtsever, U.

    1988-01-01

    We construct an infinite-parameter family of exact solutions to the vacuum Einstein field equations describing colliding gravitational plane waves with parallel polarizations. The interaction regions of the solutions in this family are locally isometric to the interiors of those static axisymmetric (Weyl) black-hole solutions which admit both a nonsingular horizon, and an analytic extension of the exterior metric to the interior of the horizon. As a member of this family of solutions we also obtain, for the first time, a colliding plane-wave solution where both of the two incoming plane waves are purely anastigmatic, i.e., where both incoming waves have equal focal lengths

  13. Plane waves and structures in turbulent channel flow

    Science.gov (United States)

    Sirovich, L.; Ball, K. S.; Keefe, L. R.

    1990-01-01

    A direct simulation of turbulent flow in a channel is analyzed by the method of empirical eigenfunctions (Karhunen-Loeve procedure, proper orthogonal decomposition). This analysis reveals the presence of propagating plane waves in the turbulent flow. The velocity of propagation is determined by the flow velocity at the location of maximal Reynolds stress. The analysis further suggests that the interaction of these waves appears to be essential to the local production of turbulence via bursting or sweeping events in the turbulent boundary layer, with the additional suggestion that the fast acting plane waves act as triggers.

  14. Problems of the orthogonalized plane wave method. 1

    International Nuclear Information System (INIS)

    Farberovich, O.V.; Kurganskii, S.I.; Domashevskaya, E.P.

    1979-01-01

    The main problems of the orthogonalized plane wave method are discussed including (a) consideration of core states; (b) effect of overlap of wave functions of external core states upon the band structure; (c) calculation of d-type states. The modified orthogonal plane wave method (MOPW method) of Deegan and Twose is applied in a general form to solve the problems of the usual OPW method. For the first time the influence on the spectrum of the main parameters of the MOPW method is studied systematically by calculating the electronic energy spectrum in the transition metals Nb and V. (author)

  15. Tunnelling of plane waves through a square barrier

    Energy Technology Data Exchange (ETDEWEB)

    Julve, J [IMAFF, Consejo Superior de Investigaciones CientIficas, Serrano 113 bis, Madrid 28006 (Spain); UrrIes, F J de [Departamento de Fisica, Universidad de Alcala de Henares, Alcala de Henares, Madrid (Spain)], E-mail: julve@imaff.cfmac.csic.es, E-mail: fernando.urries@uah.es

    2008-08-01

    The time evolution of plane waves in the presence of a one-dimensional square quantum barrier is considered. Comparison is made between the cases of an infinite and a cut-off (shutter) initial plane wave. The difference is relevant when the results are applied to the analysis of the tunnelling regime. This work is focused on the analytical calculation of the time-evolved solution and highlights the contribution of the resonant (Gamow) states.

  16. Plane-wave electronic structure calculations on a parallel supercomputer

    International Nuclear Information System (INIS)

    Nelson, J.S.; Plimpton, S.J.; Sears, M.P.

    1993-01-01

    The development of iterative solutions of Schrodinger's equation in a plane-wave (pw) basis over the last several years has coincided with great advances in the computational power available for performing the calculations. These dual developments have enabled many new and interesting condensed matter phenomena to be studied from a first-principles approach. The authors present a detailed description of the implementation on a parallel supercomputer (hypercube) of the first-order equation-of-motion solution to Schrodinger's equation, using plane-wave basis functions and ab initio separable pseudopotentials. By distributing the plane-waves across the processors of the hypercube many of the computations can be performed in parallel, resulting in decreases in the overall computation time relative to conventional vector supercomputers. This partitioning also provides ample memory for large Fast Fourier Transform (FFT) meshes and the storage of plane-wave coefficients for many hundreds of energy bands. The usefulness of the parallel techniques is demonstrated by benchmark timings for both the FFT's and iterations of the self-consistent solution of Schrodinger's equation for different sized Si unit cells of up to 512 atoms

  17. A differentiated plane wave: its passage through a slab

    International Nuclear Information System (INIS)

    Hannay, J H; Nye, J F

    2013-01-01

    Differentiating a monochromatic uniform plane electromagnetic wavefield with respect to its direction produces, from a field that is completely lacking in localized specific features, one that contains a straight vortex-like line, a ‘C-line’ of defined circular polarization. There is also a second separate C-line of opposite handedness; indeed, in a sense, a straight line of every polarization is realized. Because of its primitive construction it is analytically simple to study the passage of a differentiated wave obliquely through a plane interface into a medium of different refractive index, to trace its C-line. This was done in an earlier paper. Here we extend the method to passage through a parallel-sided transparent slab. There are multiple reflections within the slab, as in a Fabry–Pérot interferometer. The exiting wave, as a single differentiated plane wave, has a straight oblique C-line. Inside the slab, and in front of it, there is wave interference. The result is a coiled, helix-like, C-line in front of the slab and another inside it. The two coils wrap around separate hyperboloids of one sheet, like cooling towers. The emerging straight C-line is shifted (with respect to a C-line in a notional undisturbed incident plane wave) both in the plane of incidence and transversely to it, and the second C-line behaves similarly. The analysis is exact and could be extended in a straightforward way to a general stratified medium. (paper)

  18. Ground penetrating radar antenna measurements based on plane-wave expansions

    DEFF Research Database (Denmark)

    Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

    2005-01-01

    The plane-wave transmitting spectrum of the system consisting of the ground penetrating radar (GPR) antenna and the air-soil interface is measured using a loop buried in the soil. The plane-wave spectrum is used to determine various parameters characterizing the radiation of the GPR antenna...

  19. Plane-Wave Characterization of Antennas Close to a Planar Interface

    DEFF Research Database (Denmark)

    Meincke, Peter; Hansen, Thorkild

    2004-01-01

    The plane-wave scattering matrix is used to characterize antennas that are located just above a planar interface that separates two media. The plane-wave transmitting spectrum for the field radiated downwards into the lower medium is expressed directly in terms of the current distribution of the ...

  20. Scattering on plane waves and the double copy

    Science.gov (United States)

    Adamo, Tim; Casali, Eduardo; Mason, Lionel; Nekovar, Stefan

    2018-01-01

    Perturbatively around flat space, the scattering amplitudes of gravity are related to those of Yang–Mills by colour-kinematic duality, under which gravitational amplitudes are obtained as the ‘double copy’ of the corresponding gauge theory amplitudes. We consider the question of how to extend this relationship to curved scattering backgrounds, focusing on certain ‘sandwich’ plane waves. We calculate the 3-point amplitudes on these backgrounds and find that a notion of double copy remains in the presence of background curvature: graviton amplitudes on a gravitational plane wave are the double copy of gluon amplitudes on a gauge field plane wave. This is non-trivial in that it requires a non-local replacement rule for the background fields and the momenta and polarization vectors of the fields scattering on the backgrounds. It must also account for new ‘tail’ terms arising from scattering off the background. These encode a memory effect in the scattering amplitudes, which naturally double copies as well.

  1. Parallel Multi-Focusing Using Plane Wave Decomposition

    DEFF Research Database (Denmark)

    Misaridis, Thanassis; Munk, Peter; Jensen, Jørgen Arendt

    2003-01-01

    of desired 2-D sensitivity functions is specified, for multi-focusing in a number of directions. The field along these directions is decomposed to a sufficiently large (for accurate specification) number of plane waves, which are then back-propagated to all transducer elements. The contributions of all plane...... waves result in one time function per element. The numerical solution is presented and discussed. It contains pulses with a variation in central frequency and time-varying apodization across the aperture (dynamic apodization). The RMS difference between the transmitted field using the calculated pulse...... of the transmitted pulses is based on the directivity spectrum method, a generalization of the angular spectrum method, a generalization of the angular spectrum method, containing no evanescent waves. The underlying theory is based on the Fourier slice theorem, and field reconstruction from projections. First a set...

  2. Quantum scattering beyond the plane-wave approximation

    Science.gov (United States)

    Karlovets, Dmitry

    2017-12-01

    While a plane-wave approximation in high-energy physics works well in a majority of practical cases, it becomes inapplicable for scattering of the vortex particles carrying orbital angular momentum, of Airy beams, of the so-called Schrödinger cat states, and their generalizations. Such quantum states of photons, electrons and neutrons have been generated experimentally in recent years, opening up new perspectives in quantum optics, electron microscopy, particle physics, and so forth. Here we discuss the non-plane-wave effects in scattering brought about by the novel quantum numbers of these wave packets. For the well-focused electrons of intermediate energies, already available at electron microscopes, the corresponding contribution can surpass that of the radiative corrections. Moreover, collisions of the cat-like superpositions of such focused beams with atoms allow one to probe effects of the quantum interference, which have never played any role in particle scattering.

  3. Soliton emission stimulated by sound wave or external field

    International Nuclear Information System (INIS)

    Malomed, B.A.

    1987-01-01

    Langmuir soliton interaction with ion-acoustic wave results in soliton radiative decay at the expence of emission by the soliton of linear langmuir waves. Intensity of this radiation in the ''subsonic'' regime as well as the rate of energy transfer from acoustic waves to langmuir ones and soliton decay rate are calculated. Three cases are considered: monochromatic acoustic wave, nonmonochromatic wave packet with a wide spectrum, random acoustic field, for which results appear to be qualitatively different. A related problem, concerning the radiation generation by soliton under external electromagnetic wave effect is also considered. Dissipation effect on radiation is investigated

  4. Blackfolds, plane waves and minimal surfaces

    Science.gov (United States)

    Armas, Jay; Blau, Matthias

    2015-07-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  5. Blackfolds, plane waves and minimal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Armas, Jay [Physique Théorique et Mathématique, Université Libre de Bruxelles and International Solvay Institutes, ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland); Blau, Matthias [Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland)

    2015-07-29

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  6. Diffraction of love waves by two parallel perfectly weak half planes

    International Nuclear Information System (INIS)

    Asghar, S.; Zaman, F.D.; Ayub, M.

    1986-04-01

    We consider the diffraction of Love waves by two parallel perfectly weak half planes in a layer overlying a half space. The problem is formulated in terms of the Wiener-Hopf equations in the transformed plane. The transmitted waves are then calculated using the Wiener-Hopf procedure and inverse transforms. (author)

  7. Plane-wave Least-squares Reverse Time Migration

    KAUST Repository

    Dai, Wei; Schuster, Gerard T.

    2012-01-01

    convergence for least-squares migration even when the migration velocity is not completely accurate. To significantly reduce computation cost, linear phase shift encoding is applied to hundreds of shot gathers to produce dozens of planes waves. A

  8. Regularized plane-wave least-squares Kirchhoff migration

    KAUST Repository

    Wang, Xin; Dai, Wei; Schuster, Gerard T.

    2013-01-01

    A Kirchhoff least-squares migration (LSM) is developed in the prestack plane-wave domain to increase the quality of migration images. A regularization term is included that accounts for mispositioning of reflectors due to errors in the velocity

  9. Dirac particle in a plane wave field and the semi-classical approximation

    Energy Technology Data Exchange (ETDEWEB)

    Bourouaine, S. [Department of Physics, Faculty of Sciences, Mentouri University, Constantine (Algeria)

    2005-04-01

    In this paper we investigate the influence of photon represented by plane wave field on Dirac particle in the context of path integral approach given by Fradkin and Gitman formalism. In our case, although the action relative to Dirac particle in plane wave field seems to be non quadratic, the result obtained by semi-classical approach is the same as that found by an exact calculation. Hence; when we add the plane wave field to any quadratic actions related to Fradkin and Gitman approach, the total action behaves like quadratic. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  10. Dirac particle in a plane wave field and the semi-classical approximation

    International Nuclear Information System (INIS)

    Bourouaine, S.

    2005-01-01

    In this paper we investigate the influence of photon represented by plane wave field on Dirac particle in the context of path integral approach given by Fradkin and Gitman formalism. In our case, although the action relative to Dirac particle in plane wave field seems to be non quadratic, the result obtained by semi-classical approach is the same as that found by an exact calculation. Hence; when we add the plane wave field to any quadratic actions related to Fradkin and Gitman approach, the total action behaves like quadratic. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  11. A new GTD slope diffraction coefficient for plane wave illumination of a wedge

    DEFF Research Database (Denmark)

    Lumholt, Michael; Breinbjerg, Olav

    1997-01-01

    Two wedge problems including slope diffraction are solved: one in which the incident field is a non-uniform plane wave, and one in which it is an inhomogeneous plane wave. The two solutions lead to the same GTD slope diffraction coefficient. This coefficient reveals the existence of a coupling...... effect between a transverse magnetic (or transverse electric) incident plane wave and the transverse electric (or transverse magnetic) slope-diffracted field. The coupling effect is not described by the existing GTD slope diffraction coefficient...

  12. Diffraction of love waves by two staggered perfectly weak half-planes

    International Nuclear Information System (INIS)

    Asghar, S.; Zaman, F.D.; Sajida Asghar

    1989-01-01

    Love wave travelling in a layer of uniform thickness overlying a half-space is assumed to be incident on two parallel but staggered perfectly weak half-planes lying in the upper layer. The diffracted fields is calculated using the modified Wiener-Hopf technique and contour integration method. The diffracted waves satisfy the dispersion relations appropriate to different regions formed by the perfectly weak half-planes

  13. Synchrotron-radiation plane-wave topography

    International Nuclear Information System (INIS)

    Riglet, P.; Sauvage, M.; Petroff, J.F.; Epelboin, Y.

    1980-01-01

    A computer program based on the Takagi-Taupin differential equations for X-ray propagation in distorted crystals has been developed in order to simulate dislocation images in the Bragg case. The program is valid both for thin and thick crystals. Simulated images of misfit dislocations formed either in a thin epilayer or in a thick substrate are compared with experimental images obtained by synchrotron-radiation plane-wave topography. The influence of the various strain components on the image features is discussed. (author)

  14. Superresolution Imaging Using Resonant Multiples and Plane-wave Migration Velocity Analysis

    KAUST Repository

    Guo, Bowen

    2017-08-28

    Seismic imaging is a technique that uses seismic echoes to map and detect underground geological structures. The conventional seismic image has the resolution limit of λ/2, where λ is the wavelength associated with the seismic waves propagating in the subsurface. To exceed this resolution limit, this thesis develops a new imaging method using resonant multiples, which produces superresolution images with twice or even more the spatial resolution compared to the conventional primary reflection image. A resonant multiple is defined as a seismic reflection that revisits the same subsurface location along coincident reflection raypath. This reverberated raypath is the reason for superresolution imaging because it increases the differences in reflection times associated with subtle changes in the spatial location of the reflector. For the practical implementation of superresolution imaging, I develop a post-stack migration technique that first enhances the signal-to-noise ratios (SNRs) of resonant multiples by a moveout-correction stacking method, and then migrates the post-stacked resonant multiples with the associated Kirchhoff or wave-equation migration formula. I show with synthetic and field data examples that the first-order resonant multiple image has about twice the spatial resolution compared to the primary reflection image. Besides resolution, the correct estimate of the subsurface velocity is crucial for determining the correct depth of reflectors. Towards this goal, wave-equation migration velocity analysis (WEMVA) is an image-domain method which inverts for the velocity model that maximizes the similarity of common image gathers (CIGs). Conventional WEMVA based on subsurface-offset, angle domain or time-lag CIGs requires significant computational and memory resources because it computes higher dimensional migration images in the extended image domain. To mitigate this problem, I present a new WEMVA method using plane-wave CIGs. Plane-wave CIGs reduce the

  15. 3D plane-wave least-squares Kirchhoff migration

    KAUST Repository

    Wang, Xin; Dai, Wei; Huang, Yunsong; Schuster, Gerard T.

    2014-01-01

    A three dimensional least-squares Kirchhoff migration (LSM) is developed in the prestack plane-wave domain to increase the quality of migration images and the computational efficiency. Due to the limitation of current 3D marine acquisition

  16. Helical waves in easy-plane antiferromagnets

    Science.gov (United States)

    Semenov, Yuriy G.; Li, Xi-Lai; Xu, Xinyi; Kim, Ki Wook

    2017-12-01

    Effective spin torques can generate the Néel vector oscillations in antiferromagnets (AFMs). Here, it is theoretically shown that these torques applied at one end of a normal AFM strip can excite a helical type of spin wave in the strip whose properties are drastically different from characteristic spin waves. An analysis based on both a Néel vector dynamical equation and the micromagnetic simulation identifies the direction of magnetic anisotropy and the damping factor as the two key parameters determining the dynamics. Helical wave propagation requires the hard axis of the easy-plane AFM to be aligned with the traveling direction, while the damping limits its spatial extent. If the damping is neglected, the calculation leads to a uniform periodic domain wall structure. On the other hand, finite damping decelerates the helical wave rotation around the hard axis, ultimately causing stoppage of its propagation along the strip. With the group velocity staying close to spin-wave velocity at the wave front, the wavelength becomes correspondingly longer away from the excitation point. In a sufficiently short strip, a steady-state oscillation can be established whose frequency is controlled by the waveguide length as well as the excitation energy or torque.

  17. Several localized waves induced by linear interference between a nonlinear plane wave and bright solitons

    Science.gov (United States)

    Qin, Yan-Hong; Zhao, Li-Chen; Yang, Zhan-Ying; Yang, Wen-Li

    2018-01-01

    We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.

  18. In-Vivo Synthetic Aperture and Plane Wave High Frame Rate Cardiac Imaging

    DEFF Research Database (Denmark)

    Stuart, Matthias Bo; Jensen, Jonas; Brandt, Andreas Hjelm

    2014-01-01

    A comparison of synthetic aperture imaging using spherical and plane waves with low number of emission events is presented. For both wave types, a 90 degree sector is insonified using 15 emission events giving a frame rate of 200 frames per second. Field II simulations of point targets show simil.......43 for spherical and 0.70 for plane waves. All measures are well within FDA limits for cardiac imaging. In-vivo images of the heart of a healthy 28-year old volunteer are shown....

  19. Trapped waves on the mid-latitude β-plane

    Science.gov (United States)

    Paldor, Nathan; Sigalov, Andrey

    2008-08-01

    A new type of approximate solutions of the Linearized Shallow Water Equations (LSWE) on the mid-latitude β-plane, zonally propagating trapped waves with Airy-like latitude-dependent amplitude, is constructed in this work, for sufficiently small radius of deformation. In contrast to harmonic Poincare and Rossby waves, these newly found trapped waves vanish fast in the positive half-axis, and their zonal phase speed is larger than that of the corresponding harmonic waves for sufficiently large meridional domains. Our analysis implies that due to the smaller radius of deformation in the ocean compared with that in the atmosphere, the trapped waves are relevant to observations in the ocean whereas harmonic waves typify atmospheric observations. The increase in the zonal phase speed of trapped Rossby waves compared with that of harmonic ones is consistent with recent observations that showed that Sea Surface Height features propagated westwards faster than the phase speed of harmonic Rossby waves.

  20. An Apparatus for Constructing an Electromagnetic Plane Wave Model

    Science.gov (United States)

    Kneubil, Fabiana Botelho; Loures, Marcus Vinicius Russo; Amado, William

    2015-01-01

    In this paper we report on an activity aimed at building an electromagnetic wave. This was part of a class on the concept of mass offered to a group of 20 pre-service Brazilian physics teachers. The activity consisted of building a plane wave using an apparatus in which it is possible to fit some rods representing electric and magnetic fields into…

  1. Plane Wave Medical Ultrasound Imaging Using Adaptive Beamforming

    DEFF Research Database (Denmark)

    Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt

    2008-01-01

    In this paper, the adaptive, minimum variance (MV) beamformer is applied to medical ultrasound imaging. The Significant resolution and contrast gain provided by the adaptive, minimum variance (MV) beamformer, introduces the possibility of plane wave (PW) ultrasound imaging. Data is obtained using...

  2. The Uniform geometrical Theory of Diffraction for elastodynamics: Plane wave scattering from a half-plane.

    Science.gov (United States)

    Djakou, Audrey Kamta; Darmon, Michel; Fradkin, Larissa; Potel, Catherine

    2015-11-01

    Diffraction phenomena studied in electromagnetism, acoustics, and elastodynamics are often modeled using integrals, such as the well-known Sommerfeld integral. The far field asymptotic evaluation of such integrals obtained using the method of steepest descent leads to the classical Geometrical Theory of Diffraction (GTD). It is well known that the method of steepest descent is inapplicable when the integrand's stationary phase point coalesces with its pole, explaining why GTD fails in zones where edge diffracted waves interfere with incident or reflected waves. To overcome this drawback, the Uniform geometrical Theory of Diffraction (UTD) has been developed previously in electromagnetism, based on a ray theory, which is particularly easy to implement. In this paper, UTD is developed for the canonical elastodynamic problem of the scattering of a plane wave by a half-plane. UTD is then compared to another uniform extension of GTD, the Uniform Asymptotic Theory (UAT) of diffraction, based on a more cumbersome ray theory. A good agreement between the two methods is obtained in the far field.

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

    International Nuclear Information System (INIS)

    Booth, George H.; Tsatsoulis, Theodoros; Grüneis, Andreas; Chan, Garnet Kin-Lic

    2016-01-01

    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 the 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Booth, George H., E-mail: george.booth@kcl.ac.uk [Department of Physics, King’s College London, Strand, London WC2R 2LS (United Kingdom); Tsatsoulis, Theodoros; Grüneis, Andreas, E-mail: a.grueneis@fkf.mpg.de [Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart (Germany); Chan, Garnet Kin-Lic [Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    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 the 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.

  5. The memory effect for plane gravitational waves

    Science.gov (United States)

    Zhang, P.-M.; Duval, C.; Gibbons, G. W.; Horvathy, P. A.

    2017-09-01

    We give an account of the gravitational memory effect in the presence of the exact plane wave solution of Einstein's vacuum equations. This allows an elementary but exact description of the soft gravitons and how their presence may be detected by observing the motion of freely falling particles. The theorem of Bondi and Pirani on caustics (for which we present a new proof) implies that the asymptotic relative velocity is constant but not zero, in contradiction with the permanent displacement claimed by Zel'dovich and Polnarev. A non-vanishing asymptotic relative velocity might be used to detect gravitational waves through the "velocity memory effect", considered by Braginsky, Thorne, Grishchuk, and Polnarev.

  6. Traveling Wave Modes of a Plane Layered Anelastic Earth

    Science.gov (United States)

    2016-05-20

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

  7. Multiphoton processes in the field of two-frequency circularly polarized plane electromagnetic waves

    International Nuclear Information System (INIS)

    Yu, An

    1997-01-01

    The authors solve Dirac's equation for an electron in the field of a two-frequency plane electromagnetic wave, deriving general formulae for the probabilities of radiation of a photon by the electron, and for the probabilities for pair production by a photon when the two-frequency wave is circularly polarized. In contrast to the case of a monochromatic-plane electromagnetic wave, when an electron is in the field of a two-frequency circularly polarized wave, besides the absorption of multiphotons and emission of simple harmonics of the individual waves, stimulated multiphoton emission processes and various composite harmonic-photon emission processes are occurred: when a high-energy photon is in a such a field, multiphoton processes also follow the pair production processes

  8. Scattering of spinning test particles by gravitational plane waves

    International Nuclear Information System (INIS)

    Bini, D.; Gemelli, G.

    1997-01-01

    The authors study the motion of spinning particles in the gravitational plane-wave background and discuss particular solutions under a suitable choice of supplementary conditions. An analysis of the discontinuity of the motion across the wavefront is presented too

  9. Technique for measurements of plane waves of uniaxial strain

    International Nuclear Information System (INIS)

    Graham, R.A.

    1977-01-01

    The measurement of plane waves in uniaxial strain, in which large surface areas are loaded and the measurements are restricted to a central region that is not influenced by lateral boundaries, is discussed. Measuring techniques are covered and instruments are discussed

  10. Soft Gravitons & the Memory Effect for Plane Gravitational Waves

    OpenAIRE

    Zhang, P. -M.; Duval, C.; Gibbons, G. W.; Horvathy, P. A.

    2017-01-01

    The "gravitational memory effect" due to an exact plane wave provides us with an elementary description of the diffeomorphisms associated with soft gravitons. It is explained how the presence of the latter may be detected by observing the motion of freely falling particles or other forms of gravitational wave detection. Numerical calculations confirm the relevance of the first, second and third time integrals of the Riemann tensor pointed out earlier. Solutions for various profiles are constr...

  11. ULF/ELF Waves in Near-Moon Space

    Science.gov (United States)

    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.

  12. Phase function of a spherical particle when scattering an inhomogeneous electromagnetic plane wave

    DEFF Research Database (Denmark)

    Frisvad, Jeppe Revall

    2018-01-01

    of the complex hypergeometric function 2F1 for every term of a series expansion. In this work, I develop a simpler solution based on associated Legendre functions with argument zero. It is similar to the solution for homogeneous plane waves but with new explicit expressions for the angular dependency of the far......In absorbing media, electromagnetic plane waves are most often inhomogeneous. Existing solutions for the scattering of an inhomogeneous plane wave by a spherical particle provide no explicit expressions for the scattering components. In addition, current analytical solutions require evaluation......-field scattering components, that is, the phase function. I include recurrence formulae for practical evaluation and provide numerical examples to evaluate how well the new expressions match previous work in some limiting cases. The predicted difference in the scattering phase function due to inhomogeneity...

  13. Scattering of three-dimensional plane waves in a self-reinforced half-space lying over a triclinic half-space

    Science.gov (United States)

    Gupta, Shishir; Pramanik, Abhijit; Smita; Pramanik, Snehamoy

    2018-06-01

    The phenomenon of plane waves at the intersecting plane of a triclinic half-space and a self-reinforced half-space is discussed with possible applications during wave propagation. Analytical expressions of the phase velocities of reflection and refraction for quasi-compressional and quasi-shear waves under initial stress are discussed carefully. The closest form of amplitude proportions on reflection and refraction factors of three quasi-plane waves are developed mathematically by applying appropriate boundary conditions. Graphics are sketched to exhibit the consequences of initial stress in the three-dimensional plane wave on reflection and refraction coefficients. Some special cases that coincide with the fundamental properties of several layers are designed to express the reflection and refraction coefficients.

  14. Energy Relations for Plane Waves Reflected from Moving Media

    DEFF Research Database (Denmark)

    Daly, P.; Gruenberg, Harry

    1967-01-01

    When a plane wave is obliquely incident from vacuum on a semi-infinite moving medium, the energy flow carried by the incident wave, is in general, not carried away by the reflected and transmitted waves. This is only the case when the medium velocity is parallel to its vacuum interface. Otherwise...... there is a net inflow or outflow of electromagnetic energy, which can be accounted for by the change of stored energy in the system, and the work done by the mechanical forces acting on the medium. A detailed energy balance is drawn up for two different media moving normal to their vacuum interfaces: (a...

  15. Geometrical optics in the near field: local plane-interface approach with evanescent waves.

    Science.gov (United States)

    Bose, Gaurav; Hyvärinen, Heikki J; Tervo, Jani; Turunen, Jari

    2015-01-12

    We show that geometrical models may provide useful information on light propagation in wavelength-scale structures even if evanescent fields are present. We apply a so-called local plane-wave and local plane-interface methods to study a geometry that resembles a scanning near-field microscope. We show that fair agreement between the geometrical approach and rigorous electromagnetic theory can be achieved in the case where evanescent waves are required to predict any transmission through the structure.

  16. Far-field divergence of a vectorial plane wave diffracted by a circular aperture from the vectorial structure

    International Nuclear Information System (INIS)

    Zhou Guo-Quan

    2011-01-01

    Based on the vectorial structure of an electromagnetic wave, the analytical and concise expressions for the TE and TM terms of a vectorial plane wave diffracted by a circular aperture are derived in the far-field. The expressions of the energy flux distributions of the TE term, the TM term and the diffracted plane wave are also presented. The ratios of the power of the TE and TM terms to that of the diffracted plane wave are examined in the far-field. In addition, the far-field divergence angles of the TE term, the TM term and the diffracted plane wave, which are related to the energy flux distribution, are investigated. The different energy flux distributions of the TE and TM terms result in the discrepancy of their divergence angles. The influences of the linearly polarized angle and the radius of the circular aperture on the far-field divergence angles of the TE term, the TM term and the diffracted plane wave are discussed in detail. This research may promote the recognition of the optical propagation through a circular aperture. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  17. Simulation of Guided Wave Interaction with In-Plane Fiber Waviness

    Science.gov (United States)

    Leckey, Cara A. C.; Juarez, Peter D.

    2016-01-01

    Reducing the timeline for certification of composite materials and enabling the expanded use of advanced composite materials for aerospace applications are two primary goals of NASA's Advanced Composites Project (ACP). A key a technical challenge area for accomplishing these goals is the development of rapid composite inspection methods with improved defect characterization capabilities. Ongoing work at NASA Langley is focused on expanding ultrasonic simulation capabilities for composite materials. Simulation tools can be used to guide the development of optimal inspection methods. Custom code based on elastodynamic finite integration technique is currently being developed and implemented to study ultrasonic wave interaction with manufacturing defects, such as in-plane fiber waviness (marcelling). This paper describes details of validation comparisons performed to enable simulation of guided wave propagation in composites containing fiber waviness. Simulation results for guided wave interaction with in-plane fiber waviness are also discussed. The results show that the wavefield is affected by the presence of waviness on both the surface containing fiber waviness, as well as the opposite surface to the location of waviness.

  18. Spin waves in two-dimensional ferromagnet with large easy-plane anisotropy

    International Nuclear Information System (INIS)

    Fridman, Yu.A.; Spirin, D.V.

    2002-01-01

    Spin waves in easy-plane two-dimensional ferromagnet when anisotropy is much stronger than exchange are investigated. The spectra of magnons, the spin-spin and quadrupolar correlation functions have been derived. It is shown that in such a system there exist spin waves at low temperatures. Some properties of the quadrupolar ordering in ferromagnets are discussed

  19. Quadrupole mass detector in the field of weak plane gravitational waves

    International Nuclear Information System (INIS)

    Borisova, L.B.

    1978-01-01

    Studied is the behaviour of the system which consists of two test particles connected by a string (quadrupole mass detector) and placed in the field of weak plane monochromatic gravitational waves. It is shown that at cross orientation of the detector the gravitational wave effecting such a system excites oscillations in it with the frequency equal to that of the gravitational wave source. The role of the driving force is played by the periodical change with the time of the equilibrium position. The gravitational wave does not influence the detector at its longitudinal orientation

  20. A projection-free method for representing plane-wave DFT results in an atom-centered basis

    International Nuclear Information System (INIS)

    Dunnington, Benjamin D.; Schmidt, J. R.

    2015-01-01

    Plane wave density functional theory (DFT) is a powerful tool for gaining accurate, atomic level insight into bulk and surface structures. Yet, the delocalized nature of the plane wave basis set hinders the application of many powerful post-computation analysis approaches, many of which rely on localized atom-centered basis sets. Traditionally, this gap has been bridged via projection-based techniques from a plane wave to atom-centered basis. We instead propose an alternative projection-free approach utilizing direct calculation of matrix elements of the converged plane wave DFT Hamiltonian in an atom-centered basis. This projection-free approach yields a number of compelling advantages, including strict orthonormality of the resulting bands without artificial band mixing and access to the Hamiltonian matrix elements, while faithfully preserving the underlying DFT band structure. The resulting atomic orbital representation of the Kohn-Sham wavefunction and Hamiltonian provides a gateway to a wide variety of analysis approaches. We demonstrate the utility of the approach for a diverse set of chemical systems and example analysis approaches

  1. A parallel orbital-updating based plane-wave basis method for electronic structure calculations

    International Nuclear Information System (INIS)

    Pan, Yan; Dai, Xiaoying; Gironcoli, Stefano de; Gong, Xin-Gao; Rignanese, Gian-Marco; Zhou, Aihui

    2017-01-01

    Highlights: • Propose three parallel orbital-updating based plane-wave basis methods for electronic structure calculations. • These new methods can avoid the generating of large scale eigenvalue problems and then reduce the computational cost. • These new methods allow for two-level parallelization which is particularly interesting for large scale parallelization. • Numerical experiments show that these new methods are reliable and efficient for large scale calculations on modern supercomputers. - Abstract: Motivated by the recently proposed parallel orbital-updating approach in real space method , we propose a parallel orbital-updating based plane-wave basis method for electronic structure calculations, for solving the corresponding eigenvalue problems. In addition, we propose two new modified parallel orbital-updating methods. Compared to the traditional plane-wave methods, our methods allow for two-level parallelization, which is particularly interesting for large scale parallelization. Numerical experiments show that these new methods are more reliable and efficient for large scale calculations on modern supercomputers.

  2. Non-dispersive traveling waves in inclined shallow water channels

    International Nuclear Information System (INIS)

    Didenkulova, Ira; Pelinovsky, Efim

    2009-01-01

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

  3. Lectures on strings in flat space and plane waves from N = 4 super Yang Mills

    International Nuclear Information System (INIS)

    Maldacena, J.

    2003-01-01

    In these lecture notes we explain how the string spectrum in flat space and plane waves arises from the large N limit of U(N) N = 4 super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We also describe some other aspects of string propagation on plane wave backgrounds. (author)

  4. Path integral for Dirac particle in plane wave field

    International Nuclear Information System (INIS)

    Zeggari, S.; Boudjedaa, T.; Chetouani, L.

    2001-01-01

    The problem of a relativistic spinning particle in interaction with an electromagnetic plane wave field is treated via path integrals. The dynamics of the spin of the particle is described using the supersymmetric action proposed by Fradkin and Gitman. The problem has been solved by using two identities, one bosonic and the other fermionic, which are related directly to the classical equations of motion. The exact expression of the relative Green's function is given and the result agrees with those of the literature. Further, the suitably normalized wave functions are also extracted. (orig.)

  5. Path integral for Dirac particle in plane wave field

    Energy Technology Data Exchange (ETDEWEB)

    Zeggari, S.; Boudjedaa, T.; Chetouani, L. [Mentouri Univ., Constantine (Algeria). Dept. of Physique

    2001-10-01

    The problem of a relativistic spinning particle in interaction with an electromagnetic plane wave field is treated via path integrals. The dynamics of the spin of the particle is described using the supersymmetric action proposed by Fradkin and Gitman. The problem has been solved by using two identities, one bosonic and the other fermionic, which are related directly to the classical equations of motion. The exact expression of the relative Green's function is given and the result agrees with those of the literature. Further, the suitably normalized wave functions are also extracted. (orig.)

  6. On the comparsion of the Spherical Wave Expansion-to-Plane Wave Expansion and the Sources Reconstruction Method for Antenna Diagnostics

    DEFF Research Database (Denmark)

    Alvarez, Yuri; Cappellin, Cecilia; Las-Heras, Fernando

    2008-01-01

    A comparison between two recently developed methods for antenna diagnostics is presented. On one hand, the Spherical Wave Expansion-to-Plane Wave Expansion (SWE-PWE), based on the relationship between spherical and planar wave modes. On the other hand, the Sources Reconstruction Method (SRM), based...

  7. Can plane wave modes be physical modes in soliton models?

    International Nuclear Information System (INIS)

    Aldabe, F.

    1995-08-01

    I show that plane waves may not be used as asymptotic states in soliton models because they describe unphysical states. When asymptotic states are taken to the physical there is not T-matrix of O(1). (author). 9 refs

  8. Effect of weak nonlinearities on the plane waves in a plasma stream

    International Nuclear Information System (INIS)

    Seshadri, S.R.

    1976-01-01

    The effect of weak nonlinearities on the monochromatic plane waves in a cold infinite plasma stream is investigated for the case in which the waves are progressing parallel to the drift velocity. The fast and the slow space-charge waves undergo amplitude-dependent frequency and wave number shifts. There is a long time slow modulation of the amplitude of the electromagnetic mode which becomes unstable to this nonlinear wave modulation. The importance of using the relativistically correct equation of motion for predicting correctly the modulational stability of the electromagnetic mode is pointed out. (author)

  9. Plane waves and spherical means applied to partial differential equations

    CERN Document Server

    John, Fritz

    2004-01-01

    Elementary and self-contained, this heterogeneous collection of results on partial differential equations employs certain elementary identities for plane and spherical integrals of an arbitrary function, showing how a variety of results on fairly general differential equations follow from those identities. The first chapter deals with the decomposition of arbitrary functions into functions of the type of plane waves. Succeeding chapters introduce the first application of the Radon transformation and examine the solution of the initial value problem for homogeneous hyperbolic equations with con

  10. Simplified description of out-of-plane waves in thin annular elastic plates

    DEFF Research Database (Denmark)

    Zadeh, Maziyar Nesari; Sorokin, Sergey

    2013-01-01

    Dispersion relations are derived for the out-of-plane wave propagation in planar elastic plates with constant curvature using the classical Kirchhoff thin plate theory. The dispersion diagrams and the mode shapes are compared with their counterparts for a straight plate strip and the role...... of curvature is assessed for plates with unconstrained edges. Elementary Bernoulli–Euler theory for a beam of rectangular cross-section with the circular shape of its axis is also employed to analyze the wave guide properties of this structure in its out-of-plane deformation. The applicability range...... of the elementary beam theory is validated. The wave finite element method in the formulation of the three-dimensional elasticity theory is used to ensure that the comparison of dispersion diagrams is performed in the frequency range, where the classical thin plate theory is valid. Thus, the paper summarizes...

  11. Augmented-plane-wave calculations on small molecules

    International Nuclear Information System (INIS)

    Serena, P.A.; Baratoff, A.; Soler, J.M.

    1993-01-01

    We have performed ab initio calculations on a wide range of small molecules, demonstrating the accuracy and flexibility of an alternative method for calculating the electronic structure of molecules, solids, and surfaces. It is based on the local-density approximation (LDA) for exchange and correlation and the nonlinear augmented-plane-wave method. Very accurate atomic forces are obtained directly. This allows for implementation of Car-Parrinello-like techniques to determine simultaneously the self-consistent electron wave functions and the equilibrium atomic positions within an iterative scheme. We find excellent agreement with the best existing LDA-based calculations and remarkable agreement with experiment for the equilibrium geometries, vibrational frequencies, and dipole moments of a wide variety of molecules, including strongly bound homopolar and polar molecules, hydrogen-bound and electron-deficient molecules, and weakly bound alkali and noble-metal dimers, although binding energies are overestimated

  12. Theory of steady-state plane tunneling-assisted impact ionization waves

    International Nuclear Information System (INIS)

    Kyuregyan, A. S.

    2013-01-01

    The effect of band-to-band and trap-assisted tunneling on the properties of steady-state plane ionization waves in p + -n-n + structures is theoretically analyzed. It is shown that such tunneling-assisted impact ionization waves do not differ in a qualitative sense from ordinary impact ionization waves propagating due to the avalanche multiplication of uniformly distributed seed electrons and holes. The quantitative differences of tunneling-assisted impact ionization waves from impact ionization waves are reduced to a slightly different relation between the wave velocity u and the maximum field strength E M at the front. It is shown that disregarding impact ionization does not exclude the possibility of the existence of tunneling-assisted ionization waves; however, their structure radically changes, and their velocity strongly decreases for the same E M . A comparison of the dependences u(E M ) for various ionization-wave types makes it possible to determine the conditions under which one of them is dominant. In conclusion, unresolved problems concerning the theory of tunneling-assisted impact ionization waves are discussed and the directions of further studies are outlined

  13. Invertible propagator for plane wave illumination of forward-scattering structures.

    Science.gov (United States)

    Samelsohn, Gregory

    2017-05-10

    Propagation of directed waves in forward-scattering media is considered. It is assumed that the evolution of the wave field is governed by the standard parabolic wave equation. An efficient one-step momentum-space propagator, suitable for a tilted plane wave illumination of extended objects, is derived. It is expressed in terms of a propagation operator that transforms (the complex exponential of) a linogram of the illuminated object into a set of its diffraction patterns. The invertibility of the propagator is demonstrated, which permits a multiple-shot scatter correction to be performed, and makes the solution especially attractive for either projective or tomographic imaging. As an example, high-resolution tomograms are obtained in numerical simulations implemented for a synthetic phantom, with both refractive and absorptive inclusions.

  14. Phase function of a spherical particle when scattering an inhomogeneous electromagnetic plane wave.

    Science.gov (United States)

    Frisvad, Jeppe Revall

    2018-04-01

    In absorbing media, electromagnetic plane waves are most often inhomogeneous. Existing solutions for the scattering of an inhomogeneous plane wave by a spherical particle provide no explicit expressions for the scattering components. In addition, current analytical solutions require evaluation of the complex hypergeometric function F 1 2 for every term of a series expansion. In this work, I develop a simpler solution based on associated Legendre functions with argument zero. It is similar to the solution for homogeneous plane waves but with new explicit expressions for the angular dependency of the far-field scattering components, that is, the phase function. I include recurrence formulas for practical evaluation and provide numerical examples to evaluate how well the new expressions match previous work in some limiting cases. The predicted difference in the scattering phase function due to inhomogeneity is not negligible for light entering an absorbing medium at an oblique angle. The presented theory could thus be useful for predicting scattering behavior in dye-based random lasing and in solar cell absorption enhancement.

  15. REFLECT: a program to integrate the wave equation through a plane stratified plasma

    International Nuclear Information System (INIS)

    Greene, J.W.

    1975-01-01

    A program was developed to integrate the wave equation through a plane stratified plasma with a general density distribution. The reflection and transmission of a plane wave are computed as a function of the angle of incidence. The polarization of the electric vector is assumed to be perpendicular to the plane of incidence. The model for absorption by classical inverse bremsstrahlung avoids the improper extrapolation of underdense formulae that are singular at the plasma critical surface. Surprisingly good agreement with the geometric-optics analysis of a linear layer was found. The system of ordinary differential equations is integrated by the variable-step, variable-order Adams method in the Lawrence Livermore Laboratory Gear package. Parametric studies of the absorption are summarized, and some possibilities for further development of the code are discussed. (auth)

  16. Plane-wave spectrum approach for the calculation of electromagnetic absorption under near-field exposure conditions

    International Nuclear Information System (INIS)

    Chatterjee, I.; Gandhi, O.P.; Hagmann, M.J.; Riazi, A.

    1980-01-01

    The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researcher. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to the resulting from plane-wave exposed

  17. The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence

    Science.gov (United States)

    Smith, Glenn S.

    2012-01-01

    In special relativity, the transformation between inertial frames for an electromagnetic plane wave is usually derived for the time-harmonic case (the field is a sinusoid of infinite duration), even though all practical waves are of finite duration and may not even contain a dominant sinusoid. This paper presents an alternative derivation in which…

  18. Excitation of plane Lamb wave in plate-like structures under applied surface loading

    Science.gov (United States)

    Zhou, Kai; Xu, Xinsheng; Zhao, Zhen; Yang, Zhengyan; Zhou, Zhenhuan; Wu, Zhanjun

    2018-02-01

    Lamb waves play an important role in structure health monitoring (SHM) systems. The excitation of Lamb waves has been discussed for a long time with absorbing results. However, little effort has been made towards the precise characterization of Lamb wave excitation by various transducer models with mathematical foundation. In this paper, the excitation of plane Lamb waves with plane strain assumption in isotropic plate structures under applied surface loading is solved with the Hamiltonian system. The response of the Lamb modes excited by applied loading is expressed analytically. The effect of applied loading is divided into the product of two parts as the effect of direction and the effect of distribution, which can be changed by selecting different types of transducer and the corresponding transducer configurations. The direction of loading determines the corresponding displacement of each mode. The effect of applied loading on the in-plane and normal directions depends on the in-plane and normal displacements at the surface respectively. The effect of the surface loading distribution on the Lamb mode amplitudes is mainly reflected by amplitude versus frequency or wavenumber. The frequencies at which the maxima and minima of the S0 or A0 mode response occur depend on the distribution of surface loading. The numerical results of simulations conducted on an infinite aluminum plate verify the theoretical prediction of not only the direction but also the distribution of applied loading. A pure S0 or A0 mode can be excited by selecting the appropriate direction and distribution at the corresponding frequency.

  19. Imaging off-plane shear waves with a two-dimensional phononic crystal lens

    International Nuclear Information System (INIS)

    Chiang Chenyu; Luan Pigang

    2010-01-01

    A two-dimensional flat phononic crystal (PC) lens for focusing off-plane shear waves is proposed. The lens consists of a triangular lattice hole-array, embedded in a solid matrix. The self-collimation effect is employed to guide the shear waves propagating through the lens along specific directions. The Dirichlet-to-Neumann maps (DtN) method is employed to calculate the band structure of the PC, which can avoid the problems of bad convergence and fake bands automatically in the void-solid PC structure. When the lens is illuminated by the off-plane shear waves emanating from a point source, a subwavelength image appears in the far-field zone. The imaging characteristics are investigated by calculating the displacement fields explicitly using the multiple scattering method, and the results are in good agreement with the ray-trace predictions. Our results may provide insights for designing new phononic devices.

  20. Photonic band structures solved by a plane-wave-based transfer-matrix method.

    Science.gov (United States)

    Li, Zhi-Yuan; Lin, Lan-Lan

    2003-04-01

    Transfer-matrix methods adopting a plane-wave basis have been routinely used to calculate the scattering of electromagnetic waves by general multilayer gratings and photonic crystal slabs. In this paper we show that this technique, when combined with Bloch's theorem, can be extended to solve the photonic band structure for 2D and 3D photonic crystal structures. Three different eigensolution schemes to solve the traditional band diagrams along high-symmetry lines in the first Brillouin zone of the crystal are discussed. Optimal rules for the Fourier expansion over the dielectric function and electromagnetic fields with discontinuities occurring at the boundary of different material domains have been employed to accelerate the convergence of numerical computation. Application of this method to an important class of 3D layer-by-layer photonic crystals reveals the superior convergency of this different approach over the conventional plane-wave expansion method.

  1. Photonic band structures solved by a plane-wave-based transfer-matrix method

    International Nuclear Information System (INIS)

    Li Zhiyuan; Lin Lanlan

    2003-01-01

    Transfer-matrix methods adopting a plane-wave basis have been routinely used to calculate the scattering of electromagnetic waves by general multilayer gratings and photonic crystal slabs. In this paper we show that this technique, when combined with Bloch's theorem, can be extended to solve the photonic band structure for 2D and 3D photonic crystal structures. Three different eigensolution schemes to solve the traditional band diagrams along high-symmetry lines in the first Brillouin zone of the crystal are discussed. Optimal rules for the Fourier expansion over the dielectric function and electromagnetic fields with discontinuities occurring at the boundary of different material domains have been employed to accelerate the convergence of numerical computation. Application of this method to an important class of 3D layer-by-layer photonic crystals reveals the superior convergency of this different approach over the conventional plane-wave expansion method

  2. Measurement of Plane-Wave Spectra of Ground Penetrating Radar Antennas

    DEFF Research Database (Denmark)

    Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

    2005-01-01

    The plane-wave transmitting spectrum of a ground penetrating radar (GPR) loop antenna close to the air-soil interface is measured by means of a probe buried in soil. Probe correction is implemented based upon knowledge about the complex permittivity of the soil and the current distribution...

  3. Tissue elasticity of in vivo skeletal muscles measured in the transverse and longitudinal planes using shear wave elastography.

    Science.gov (United States)

    Chino, Kentaro; Kawakami, Yasuo; Takahashi, Hideyuki

    2017-07-01

    The aim of the present study was to measure in vivo skeletal muscle elasticity in the transverse and longitudinal planes using shear wave elastography and then to compare the image stability, measurement values and measurement repeatability between these imaging planes. Thirty-one healthy males participated in this study. Tissue elasticity (shear wave velocity) of the medial gastrocnemius, rectus femoris, biceps brachii and rectus abdominis was measured in both the transverse and longitudinal planes using shear wave elastography. Image stability was evaluated by the standard deviation of the colour distribution in the shear wave elastography image. Measurement repeatability was assessed by the coefficient of variance obtained from three measurement values. Image stability of all tested muscles was significantly higher in the longitudinal plane (Pplanes (P>0·05), except in the biceps brachii (P = 0·001). Measurement values of the medial gastrocnemius, rectus femoris and biceps brachii were significantly different between the imaging planes (Pplane, which indicates that imaging plane should be considered when measuring skeletal muscle tissue elasticity by shear wave elastography. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  4. Existence and Stability of Spatial Plane Waves for the Incompressible Navier-Stokes in R^3

    Science.gov (United States)

    Correia, Simão; Figueira, Mário

    2018-03-01

    We consider the three-dimensional incompressible Navier-Stokes equation on the whole space. We observe that this system admits a L^∞ family of global spatial plane wave solutions, which are connected with the two-dimensional equation. We then proceed to prove local well-posedness over a space which includes L^3(R^3) and these solutions. Finally, we prove L^3-stability of spatial plane waves, with no condition on their size.

  5. An Analytical Method of Auxiliary Sources Solution for Plane Wave Scattering by Impedance Cylinders

    DEFF Research Database (Denmark)

    Larsen, Niels Vesterdal; Breinbjerg, Olav

    2004-01-01

    Analytical Method of Auxiliary Sources solutions for plane wave scattering by circular impedance cylinders are derived by transformation of the exact eigenfunction series solutions employing the Hankel function wave transformation. The analytical Method of Auxiliary Sources solution thus obtained...

  6. Ion Acceleration in Plasmas with Alfven Waves

    International Nuclear Information System (INIS)

    Kolesnychenko, O.Ya.; Lutsenko, V.V.; White, R.B.

    2005-01-01

    Effects of elliptically polarized Alfven waves on thermal ions are investigated. Both regular oscillations and stochastic motion of the particles are observed. It is found that during regular oscillations the energy of the thermal ions can reach magnitudes well exceeding the plasma temperature, the effect being largest in low-beta plasmas (beta is the ratio of the plasma pressure to the magnetic field pressure). Conditions of a low stochasticity threshold are obtained. It is shown that stochasticity can arise even for waves propagating along the magnetic field provided that the frequency spectrum is non-monochromatic. The analysis carried out is based on equations derived by using a Lagrangian formalism. A code solving these equations is developed. Steady-state perturbations and perturbations with the amplitude slowly varying in time are considered

  7. Quantum fields interacting with colliding plane waves: the stress-energy tensor and backreaction

    International Nuclear Information System (INIS)

    Dorca, M.; Verdaguer, E.

    1997-01-01

    Following a previous work on the quantization of a massless scalar field in a space-time representing the head on collision of two plane waves which focus into a Killing-Cauchy horizon, we compute the renormalized expectation value of the stress-energy tensor of the quantum field near that horizon in the physical state which corresponds to the Minkowski vacuum before the collision of the waves. It is found that for minimally coupled and conformally coupled scalar fields the respective stress-energy tensors are unbounded in the horizon. The specific form of the divergences suggests that when the semiclassical Einstein equations describing the backreaction of the quantum fields on the space-time geometry are taken into account, the horizon will acquire a curvature singularity. Thus the Killing-Cauchy horizon which is known to be unstable under ''generic'' classical perturbations is also unstable by vacuum polarization. The calculation is done following the point-splitting regularization technique. The dynamical colliding wave space-time has four quite distinct space-time regions, namely, one flat region, two single plane wave regions, and one interaction region. Exact mode solutions of the quantum field equation cannot be found exactly, but the blueshift suffered by the initial modes in the plane wave and interaction regions makes the use of the WKB expansion a suitable method of solution. To ensure the correct regularization of the stress-energy tensor, the initial flat modes propagated into the interaction region must be given to a rather high adiabatic order of approximation. (orig.)

  8. Radiation of Electron in the Field of Plane Light Wave

    International Nuclear Information System (INIS)

    Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; Tatchyn, R.

    2006-01-01

    Results of integration of a Lorentz equation for a relativistic electron moving in the field of running, plane, linear polarized electromagnetic wave are presented in the paper. It is shown that electron velocities in the field of the wave are almost periodic functions of time. For calculations of angular spectrum of electron radiation intensity expansion of the electromagnetic field in a wave zone into generalized Fourier series was used. Expressions for the radiation intensity spectrum are presented in the paper. Derived results are illustrated for electron and laser beam parameters of NSC KIPT X-ray generator NESTOR. It is shown that for low intensity of the interacting electromagnetic wave the results of energy and angular spectrum calculations in the frame of classical electrodynamics completely coincide with calculation results produced using quantum electrodynamics. Simultaneously, derived expressions give possibilities to investigate dependence of energy and angular Compton radiation spectrum on phase of interaction and the interacting wave intensity

  9. On plane-wave relativistic electrodynamics in plasmas and in vacuum

    International Nuclear Information System (INIS)

    Fiore, Gaetano

    2014-01-01

    We revisit the exact microscopic equations (in differential, and equivalent integral form) ruling a relativistic cold plasma after the plane-wave Ansatz, without customary approximations. We show that in the Eulerian description the motion of a very diluted plasma initially at rest and excited by an arbitrary transverse plane electromagnetic travelling-wave has a very simple and explicit dependence on the transverse electromagnetic potential; for a non-zero density plasma the above motion is a good approximation of the real one as long as the back-reaction of the charges on the electromagnetic field can be neglected, i.e. for a time lapse decreasing with the plasma density, and can be used as initial step in an iterative resolution scheme. As one of many possible applications, we use these results to describe how the ponderomotive force of a very intense and short plane laser pulse hitting normally the surface of a plasma boosts the surface electrons into the ion background. In response to this penetration, the electrons are pulled back by the electric force exerted by the ions and the other displaced electrons and may leave the plasma with high energy in the direction opposite to that of propagation of the pulse ‘slingshot effect’ (Fiore G et al 2013 arXiv:1309.1400). (paper)

  10. A ''quadratized'' augmented plane wave method

    International Nuclear Information System (INIS)

    Smrcka, L.

    1982-02-01

    The exact radial solution inside the muffin-tin sphere is replaced by its Taylor expansion with respect to the energy, truncated after the quadratic term. Making use of it the energy independent augmented plane waves are formed which lead to the secular equations linear in energy. The method resembles the currently used linearized APW method but yields higher accuracy. The analysis of solution inside one muffin-tin sphere shows that the eigenvalue error is proportional to (E-E 0 ) 6 as compared with (E-E 0 ) 4 for LAPW. The error of eigenfunctions is (E-E 0 ) 3 ((E-E 0 ) 2 for LAPW). These conclusions are confirmed by direct numerical calculation of band structure of Cu and Al. (author)

  11. Back radiation suppression through a semi-transparent round ground plane for a mm-Wave monopole antenna

    KAUST Repository

    Klionovski, Kirill; Farooqui, Muhammad Fahad; Shamim, Atif

    2017-01-01

    Omnidirectional radiation pattern with minimum backward radiation is highly desirable for millimeter-wave telecommunication antennas. In this work, we propose a round, semitransparent ground plane of radius 0.8λ with uniform impedance distribution that can reduce the back radiation of a monopole antenna by 8.8 dB as compared with a similar sized metallic ground plane. The value of uniform impedance is obtained through analytical optimization by using asymptotic expressions in the Kirchhoff approximation of the radiation pattern of a toroidal wave scattered by a round semitransparent ground plane. The semitransparent ground plane has been realized using a low-cost carbon paste on a Kapton film. Experimental results match closely with those of simulations and validate the overall concept.

  12. Back radiation suppression through a semi-transparent round ground plane for a mm-Wave monopole antenna

    KAUST Repository

    Klionovski, Kirill

    2017-10-25

    Omnidirectional radiation pattern with minimum backward radiation is highly desirable for millimeter-wave telecommunication antennas. In this work, we propose a round, semitransparent ground plane of radius 0.8λ with uniform impedance distribution that can reduce the back radiation of a monopole antenna by 8.8 dB as compared with a similar sized metallic ground plane. The value of uniform impedance is obtained through analytical optimization by using asymptotic expressions in the Kirchhoff approximation of the radiation pattern of a toroidal wave scattered by a round semitransparent ground plane. The semitransparent ground plane has been realized using a low-cost carbon paste on a Kapton film. Experimental results match closely with those of simulations and validate the overall concept.

  13. Propagation of magnetostatic spin waves in an yttrium iron garnet film for out-of-plane magnetic fields

    Science.gov (United States)

    Bang, Wonbae; Lim, Jinho; Trossman, Jonathan; Tsai, C. C.; Ketterson, John B.

    2018-06-01

    We have observed the propagation of spin waves across a thin yttrium iron garnet film on (1 1 1) gadolinium gallium garnet for magnetic fields inclined with respect to the film plane. Two principle planes were studied: that for H in the plane defined by the wave vector k and the plane normal, n, with limiting forms corresponding to the Backward Volume and Forward Volume modes, and that for H in the plane perpendicular to k, with limiting forms corresponding to the Damon-Eshbach and Forward Volume modes. By exciting the wave at one edge of the film and observing the field dependence of the phase of the received signal at the opposing edge we determined the frequency vs. wavevector relation, ω = ω (k), of various propagating modes in the film. Avoided crossings are observed in the Damon-Eshbach and Forward Volume regimes when the propagating mode intersects the higher, exchange split, volume modes, leading to an extinction of the propagating mode; analysis of the resulting behavior allows a determination of the exchange parameter. The experimental results are compared with theoretical simulations.

  14. Plane wave fast color flow mode imaging

    DEFF Research Database (Denmark)

    Bolic, Ibrahim; Udesen, Jesper; Gran, Fredrik

    2006-01-01

    A new Plane wave fast color flow imaging method (PWM) has been investigated, and performance evaluation of the PWM based on experimental measurements has been made. The results show that it is possible to obtain a CFM image using only 8 echo-pulse emissions for beam to flow angles between 45...... degrees and 75 degrees. Compared to the conventional ultrasound imaging the frame rate is similar to 30 - 60 times higher. The bias, B-est of the velocity profile estimate, based on 8 pulse-echo emissions, is between 3.3% and 6.1% for beam to flow angles between 45 degrees and 75 degrees, and the standard...

  15. Progress in parallel implementation of the multilevel plane wave time domain algorithm

    KAUST Repository

    Liu, Yang; Bagci, Hakan; Michielssen, Eric

    2013-01-01

    The computational complexity and memory requirements of classical schemes for evaluating transient electromagnetic fields produced by Ns dipoles active for Nt time steps scale as O(NtN s 2) and O(Ns 2), respectively. The multilevel plane wave time

  16. Localized orbitals vs. pseudopotential-plane waves basis sets: performances and accuracy for molecular magnetic systems

    CERN Document Server

    Massobrio, C

    2003-01-01

    Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbital, has become the method of choice for calculating the exchange-couplings in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50-300 cm sup - sup 1). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm sup - sup 1 to -300 cm sup - sup 1. The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably employed to predict and r...

  17. Localized orbitals vs. pseudopotential-plane waves basis sets: performances and accuracy for molecular magnetic systems

    International Nuclear Information System (INIS)

    Massobrio, C.; Ruiz, E.

    2003-01-01

    Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbital, has become the method of choice for calculating the exchange-couplings in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50-300 cm -1 ). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm -1 to -300 cm -1 . The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably employed to predict and rationalize the magnetic properties of molecular-based materials. (author)

  18. Proposal of coherent Cherenkov radiation matched to circular plane wave for intense terahertz light source

    International Nuclear Information System (INIS)

    Sei, Norihiro; Sakai, Takeshi; Hayakawa, Ken; Tanaka, Toshinari; Hayakawa, Yasushi; Nakao, Keisuke; Nogami, Kyoko; Inagaki, Manabu

    2015-01-01

    Highlights: • We proposed a new intense terahertz-wave source based on coherent Cherenkov radiation (CCR). • A hollow conical dielectric is used to generate the CCR beam. • The wave front of the CCR beam can be matched to the basal plane. • The peak-power of the CCR beam is above 1 MW per micropulse with a short interval of 350 ps. - Abstract: We propose a high-peak-power terahertz-wave source based on an electron accelerator. By passing an electron beam through a hollow conical dielectric with apex facing the incident electron beam, the wave front of coherent Cherenkov radiation generated on the inner surface of the hollow conical dielectric matches the basal plane. Using the electron beam generated at the Laboratory for Electron Beam Research and Application at Nihon University, the calculated power of coherent Cherenkov radiation that matched the circular plane (CCR-MCP) was above 1 MW per micropulse with a short interval of 350 ps, for wavelengths ranging from 0.5 to 5 mm. The electron beam is not lost for generating the CCR-MCP beam by using the hollow conical dielectric. It is possible to combine the CCR-MCP beams with other light sources based on an accelerator

  19. Propagation of plane waves in a rotating magneto-thermoelastic fiber-reinforced medium under G-N theory

    Directory of Open Access Journals (Sweden)

    Maity N.

    2017-06-01

    Full Text Available The article is concernedwith the possibility of plane wave propagation in a rotating elastic medium under the action of magnetic and thermal fields. The material is assumed to be fibre-reinforced with increased stiffness, strength and load bearing capacity. Green and Nagdhi’s concepts of generalized thermoelastic models II and III have been followed in the governing equations expressed in tensor notation. The effects of various parameters of the applied fields on the plane wave velocity have been shown graphically.

  20. Plane-wave scattering by self-complementary metasurfaces in terms of electromagnetic duality and Babinet's principle

    Science.gov (United States)

    Nakata, Yosuke; Urade, Yoshiro; Nakanishi, Toshihiro; Kitano, Masao

    2013-11-01

    We investigate theoretically electromagnetic plane-wave scattering by self-complementary metasurfaces. By using Babinet's principle extended to metasurfaces with resistive elements, we show that the frequency-independent transmission and reflection are realized for normal incidence of a circularly polarized plane wave onto a self-complementary metasurface, even if there is diffraction. Next, we consider two special classes of self-complementary metasurfaces. We show that self-complementary metasurfaces with rotational symmetry can act as coherent perfect absorbers, and those with translational symmetry compatible with their self-complementarity can split the incident power equally, even for oblique incidences.

  1. [A new method to orthodontically correct dental occlusal plane canting: wave-shaped arch].

    Science.gov (United States)

    Zheng, X; Hu, X X; Ma, N; Chen, X H

    2017-02-18

    To introduce a technique of second order wave-shaped arch wire to orthodontically treat dental occlusal plane canting (DOPC) with left-right interactive anchorage, and to test its clinical efficacy. Among the permanent dentition malocclusion patients who showed no obvious facial asymmetry, we screened for patients who showed anterior occlusal plane canting (AOPC) after routine orthodontic examination, treatment planning, MBT fixed appliance installation and serial arch wires alignment. Each patient had been clinically appraised in frontal view by 2 orthodontists and the patient him/herself; if all 3 agreed that the AOPC was obvious, the patient was included. By this means, we included 37 patients, including 10 males and 27 females; the average age was (21.9±5.2) years. To correct AOPC, opposite direction equal curvature second order rocking-chair curve was bent on each side of 0.46 mm×0.56 mm stainless steel edgewise wire. With reference to normal occlusal plane, a curve toward the occlusal surface was made to extrude under-erupted teeth on one side while a curve toward the gingiva was made to intrude over-erupted teeth on the other side, so that the arch wire was made into a wave shape in vertical dimension. Before and after application of wave-shaped arch wire, frontal facial photographs were taken when the patient's mouth was open slightly with lips retracted to show anterior occlusal plane (AOP) clearly. An AOP was constructed by connecting the center of the slot in the medial edge of canine bracket on each side in the photograph. The angles between the bipupillary plane(BPP) and the constructed AOP were measured in ImageJ1-48v software and the angle differences before and after treatment were compared with paired Wilcoxon test in SPSS 10.0 software. The wave-shaped arch could correct AOPC effectively in 3 to 10 months time with an average of 5.5±1.7 months; the angles between AOP and BBP before treatment ranged from 2.90° to 6.12° with a median of 4.01

  2. ONETEP: linear-scaling density-functional theory with plane-waves

    International Nuclear Information System (INIS)

    Haynes, P D; Mostof, A A; Skylaris, C-K; Payne, M C

    2006-01-01

    This paper provides a general overview of the methodology implemented in onetep (Order-N Electronic Total Energy Package), a parallel density-functional theory code for largescale first-principles quantum-mechanical calculations. The distinctive features of onetep are linear-scaling in both computational effort and resources, obtained by making well-controlled approximations which enable simulations to be performed with plane-wave accuracy. Titanium dioxide clusters of increasing size designed to mimic surfaces are studied to demonstrate the accuracy and scaling of onetep

  3. An extended Fourier modal method for plane-wave scattering from finite structures

    NARCIS (Netherlands)

    Pisarenco, M.; Maubach, J.M.L.; Setija, I.D.; Mattheij, R.M.M.

    2010-01-01

    This paper extends the area of application of the Fourier modal method from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating

  4. Formation of whispering gallery modes by scattering of an electromagnetic plane wave by two cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Abramov, Arnold, E-mail: qulaser@gmail.com [Kuang-Chi Institute of Advanced Technology, Shenzhen, 518057 (China); Kostikov, Alexander [Donbass State Engineering Academy, 84303, Kramatorsk, Donetsk (Ukraine)

    2017-03-26

    We report the effect of scattering of electromagnetic plane waves by two cylinders on whispering gallery mode (WGM) formation in a cylinder. WGM can occur because of the presence of additional cylinder scatterers at specific location, while WGMs can only form in a single cylinder for specific cylinder radius and/or wavelength values, the matching accuracy required would be much greater than that required in our model for the additional cylinders locations. Analysis of the general solution to the problem showed that the effect can be explained by the interference of waves scattered by additional cylinders and incident on the main cylinder. - Highlights: • We consider scattering of electromagnetic plane waves by two cylinders. • WGMs occur because of the presence of additional cylinder at specific location. • The accuracy for the locations is much less than required for specific values of single cylinder. • The interference of waves scattered by additional cylinders and incident on the main is responsible for the effect.

  5. Plane shock wave studies of geologic media

    International Nuclear Information System (INIS)

    Anderson, G.D.; Larson, D.B.

    1977-01-01

    Plane shock wave experiments have been conducted on eight geologic materials in an effort to determine the importance of time-dependent mechanical behavior. Of the eight rocks studied, only Westerly granite and nugget sandstone appear to show time independence. In the slightly porous materials (1-5 percent), Blair dolomite and sodium chloride, and in the highly porous (15 to 40 percent) rock, Mt. Helen tuff and Indiana limestone, time-dependent behavior is associated with the time required to close the available porosity. In water-saturated rocks the time dependence arises because the water that is present shows no indication of transformation to the higher pressure ice phases, thus suggesting the possibility that a metastable form of water exists under dynamic conditions

  6. The influence of air-filled structures on wave propagation and beam formation of a pygmy sperm whale (Kogia breviceps) in horizontal and vertical planes.

    Science.gov (United States)

    Song, Zhongchang; Zhang, Yu; Thornton, Steven W; Li, Songhai; Dong, Jianchen

    2017-10-01

    The wave propagation, sound field, and transmission beam pattern of a pygmy sperm whale (Kogia breviceps) were investigated in both the horizontal and vertical planes. Results suggested that the signals obtained at both planes were similarly characterized with a high peak frequency and a relatively narrow bandwidth, close to the ones recorded from live animals. The sound beam measured outside the head in the vertical plane was narrower than that of the horizontal one. Cases with different combinations of air-filled structures in both planes were used to study the respective roles in controlling wave propagation and beam formation. The wave propagations and beam patterns in the horizontal and vertical planes elucidated the important reflection effect of the spermaceti and vocal chambers on sound waves, which was highly significant in forming intensive forward sound beams. The air-filled structures, the forehead soft tissues and skull structures formed wave guides in these two planes for emitted sounds to propagate forward.

  7. Acoustic backscattering and radiation force on a rigid elliptical cylinder in plane progressive waves.

    Science.gov (United States)

    Mitri, F G

    2016-03-01

    This work proposes a formal analytical theory using the partial-wave series expansion (PWSE) method in cylindrical coordinates, to calculate the acoustic backscattering form function as well as the radiation force-per-length on an infinitely long elliptical (non-circular) cylinder in plane progressive waves. The major (or minor) semi-axis of the ellipse coincides with the direction of the incident waves. The scattering coefficients for the rigid elliptical cylinder are determined by imposing the Neumann boundary condition for an immovable surface and solving a resulting system of linear equations by matrix inversion. The present method, which utilizes standard cylindrical (Bessel and Hankel) wave functions, presents an advantage over the solution for the scattering that is ordinarily expressed in a basis of elliptical Mathieu functions (which are generally non-orthogonal). Furthermore, an integral equation showing the direct connection of the radiation force function with the square of the scattering form function in the far-field from the scatterer (applicable for plane waves only), is noted and discussed. An important application of this integral equation is the adequate evaluation of the radiation force function from a bistatic measurement (i.e., in the polar plane) of the far-field scattering from any 2D object of arbitrary shape. Numerical predictions are evaluated for the acoustic backscattering form function and the radiation force function, which is the radiation force per unit length, per characteristic energy density, and per unit cross-sectional surface of the ellipse, with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes, as well as the dimensionless size parameter kb, without the restriction to a particular range of frequencies. The results are particularly relevant in acoustic levitation, acousto-fluidics and particle dynamics applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Quantum mechanics of lattice gas automata: One-particle plane waves and potentials

    International Nuclear Information System (INIS)

    Meyer, D.A.

    1997-01-01

    Classical lattice gas automata effectively simulate physical processes, such as diffusion and fluid flow (in certain parameter regimes), despite their simplicity at the microscale. Motivated by current interest in quantum computation we recently defined quantum lattice gas automata; in this paper we initiate a project to analyze which physical processes these models can effectively simulate. Studying the single particle sector of a one-dimensional quantum lattice gas we find discrete analogs of plane waves and wave packets, and then investigate their behavior in the presence of inhomogeneous potentials. copyright 1997 The American Physical Society

  9. On the energy-momentum density of gravitational plane waves

    International Nuclear Information System (INIS)

    Dereli, T; Tucker, R W

    2004-01-01

    By embedding Einstein's original formulation of general relativity into a broader context, we show that a dynamic covariant description of gravitational stress-energy emerges naturally from a variational principle. A tensor T G is constructed from a contraction of the Bel tensor with a symmetric covariant second degree tensor field Φ and has a form analogous to the stress-energy tensor of the Maxwell field in an arbitrary spacetime. For plane-fronted gravitational waves helicity-2 polarized (graviton) states can be identified carrying non-zero energy and momentum

  10. String interactions in a plane-fronted parallel-wave spacetime

    International Nuclear Information System (INIS)

    Gopakumar, Rajesh

    2002-01-01

    We argue that string interactions in a plane-fronted parallel-wave spacetime are governed by an effective coupling g eff =g s (μp + α ' )f(μp + α ' ) where f(μp + α ' ) is proportional to the light-cone energy of the string states involved in the interaction. This simply follows from generalities of a matrix string description of this background. g eff nicely interpolates between the expected result (g s ) for flat space (small μp + α ' ) and a recently conjectured expression from the perturbative gauge theory side (large μp + α ' )

  11. On completeness and orthogonality of solutions of relativistic wave equations on zero plane

    International Nuclear Information System (INIS)

    Gitman, D.M.; Shakhmatov, V.M.; Shvartsman, Sh.M.

    1975-01-01

    The work considers the possible redeterminations of the scalar product for the relativistic wave fields, such as the Klein-Gordon and Dirac ones. It has been shown that a whole class of new exact solutions, for which the usual scalar product on the plane x 0 =const. could not be previously determinated, allows a correct scalar product on the zero plane x 0 -x 3 =const. The relations of orthogonality and completeness with respect to the above scalar product have been proved. Possible applications of the obtained results are discussed

  12. Back Radiation Suppression through a Semitransparent Ground Plane for a mm-Wave Patch Antenna

    KAUST Repository

    Klionovski, Kirill

    2017-06-21

    Omnidirectional radiation pattern with minimum backward radiation is highly desirable for base station antennas to minimize the multipath effects. Semitransparent ground planes have been used to reduce the backward radiation, but mostly with complicated non-uniform impedance distribution. In this work, we propose, for the first time, a round semitransparent ground plane of radius 0.8 λ with uniform impedance distribution that can improve the front-to-back ratio of a wideband patch antenna by 11.6 dB as compared to a similar sized metallic ground plane. The value of uniform impedance is obtained through analytical optimization by using asymptotic expressions in the Kirchhoff approximation of the radiation pattern of a toroidal wave scattered by a round semitransparent ground plane. The semitransparent ground plane has been realized using a low-cost carbon paste on a Kapton film. Experimental results match closely with those of simulations and validate the overall concept.

  13. A wavenumber approach to analysing the active control of plane waves with arrays of secondary sources

    Science.gov (United States)

    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.

  14. Observation of proton chorus waves close to the equatorial plane by Cluster

    Science.gov (United States)

    Grison, B.; Pickett, J. S.; Santolik, O.; Robert, P.; Cornilleau-Wehrlin, N.; Engebretson, M. J.; Constantinescu, D. O.

    2009-12-01

    Whistler mode chorus waves are a widely studied phenomena. They are present in numerous regions of the magnetosphere and are presumed to originate in the magnetic equatorial region. In a spectrogram they are characterized by narrowband features with rise (or fall) in frequency over short periods of time. Being whistler mode waves around a few tenths of the electron cyclotron frequency they interact mainly with electrons. In the present study we report observations by the Cluster spacecraft of what we call proton chorus waves. They have spectral features with rising frequency, similar to the electron chorus waves, but they are detected in a frequency range that starts roughly at 0.50fH+ up to fH+ (the local proton gyro-frequency). The lower part of their spectrum seems to originate from monochromatic Pc 1 waves (1.5 Hz). Proton chorus waves are detected close to the magnetic equatorial plane in both hemispheres during the same event. Our interpretation of these waves as proton chorus is supported by polarization analysis with the Roproc procedures and the Prassadco software using both the magnetic (STAFF-SC) and electric (EFW) parts of the fluctuations spectrum.

  15. Solution of the Bethe-Salpeter equation in the field of a plane electromagnetic wave

    International Nuclear Information System (INIS)

    Starostin, V.S.

    1988-01-01

    A solution is obtained of the Bethe--Salpeter equation for positronium in the field of linearly and circularly polarized plane electromagnetic waves at frequencies much higher than atomic. It is not assumed that the field is weak

  16. Initial value problem for colliding gravitational plane waves. III

    International Nuclear Information System (INIS)

    Hauser, I.; Ernst, F.J.

    1990-01-01

    The development of a homogeneous Hilbert problem (HHP) approach to the initial value problem (IVP) for colliding gravitational plane waves with noncollinear polarization that began in two earlier papers [I. Hauser and F. J. Ernst, J. Math. Phys. 30, 872 (1989) and 30, 2322 (1989)] is continued. After formulating the HHP, the description of how one can apply it to generate a new family of solutions of the colliding wave problem that generalizes a three-parameter family constructed by Ernst, Garcia, and Hauser [J. Math. Phys. 29, 681 (1988)] using a double-Harrison transformation is given. Then the proof that the solution of the new HHP indeed solves the IVP that is posed is presented. A matrix Fredholm equation of the second kind that is equivalent to the HHP is also deduced. This will be used in a sequel to complete the proof of existence of solutions of the HHP and the proof that certain assumed differentiability hypotheses are in fact valid

  17. Path integral for spinning particle in the plane wave field: Global and local projections

    International Nuclear Information System (INIS)

    Boudiaf, N.; Boudjedaa, T.; Chetouani, L.

    2001-01-01

    The Green function related to the problem of a Dirac particle interacting with a plane wave is calculated via the path integral formalism proposed recently by Alexandrou et al. according to the two so-called global and local projections. With the help of the incorporation of two simple identities, it is shown that the contribution to the calculation of the integrals comes essentially from classical solutions projected along the direction of wave propagation. (orig.)

  18. Computational dosimetry in embryos exposed to electromagnetic plane waves over the frequency range of 10 MHz-1.5 GHz

    International Nuclear Information System (INIS)

    Kawai, Hiroki; Nagaoka, Tomoaki; Watanabe, Soichi; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi

    2010-01-01

    This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg -1 when the incident power density is at the reference level of ICNIRP guideline for general public environment. (note)

  19. Diffraction of an inhomogeneous plane wave by an impedance wedge in a lossy medium

    CSIR Research Space (South Africa)

    Manara, G

    1998-11-01

    Full Text Available The diffraction of an inhomogeneous plane wave by an impedance wedge embedded in a lossy medium is analyzed. The rigorous integral representation for the field is asymptotically evaluated in the context of the uniform geometrical theory...

  20. Stability of plane wave solutions of the two-space-dimensional nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Martin, D.U.; Yuen, H.C.; Saffman, P.G.

    1980-01-01

    The stability of plane, periodic solutions of the two-dimensional nonlinear Schroedinger equation to infinitesimal, two-dimensional perturbation has been calculated and verified numerically. For standing wave disturbances, instability is found for both odd and even modes; as the period of the unperturbed solution increases, the instability associated with the odd modes remains but that associated with the even mode disappears, which is consistent with the results of Zakharov and Rubenchik, Saffman and Yuen and Ablowitz and Segur on the stability of solitons. In addition, we have identified travelling wave instabilities for the even mode perturbations which are absent in the long-wave limit. Extrapolation to the case of an unperturbed solution with infinite period suggests that these instabilities may also be present for the soliton. In other words, the soliton is unstable to odd, standing-wave perturbations, and very likely also to even, travelling-wave perturbations. (orig.)

  1. Optimization of exit-plane waves restored from HRTEM through-focal series

    International Nuclear Information System (INIS)

    Erni, Rolf; Rossell, Marta D.; Nakashima, Philip N.H.

    2010-01-01

    Atomic-resolution transmission electron microscopy has largely benefited from the implementation of aberration correctors in the imaging part of the microscope. Though the dominant geometrical axial aberrations can in principle be corrected or suitably adjusted, the impact of higher-order aberrations, which are mainly due to the implementation of non-round electron optical elements, on the imaging process remains unclear. Based on a semi-empirical criterion, we analyze the impact of residual aperture aberrations on the quality of exit-plane waves that are retrieved from through-focal series recorded using an aberration-corrected and monochromated instrument which was operated at 300 kV and enabled for an information transfer of ∼0.05 nm. We show that the impact of some of the higher-order aberrations in retrieved exit-plane waves can be balanced by a suitable adjustment of symmetry equivalent lower-order aberrations. We find that proper compensation and correction of 1st and 2nd order aberrations is critical, and that the required accuracy is difficult to achieve. This results in an apparent insensitivity towards residual higher-order aberrations. We also investigate the influence of the detector characteristics on the image contrast. We find that correction for the modulation transfer function results in a contrast gain of up to 40%.

  2. Improved Plane-Wave Ultrasound Beamforming by Incorporating Angular Weighting and Coherent Compounding in Fourier Domain.

    Science.gov (United States)

    Chen, Chuan; Hendriks, Gijs A G M; van Sloun, Ruud J G; Hansen, Hendrik H G; de Korte, Chris L

    2018-05-01

    In this paper, a novel processing framework is introduced for Fourier-domain beamforming of plane-wave ultrasound data, which incorporates coherent compounding and angular weighting in the Fourier domain. Angular weighting implies spectral weighting by a 2-D steering-angle-dependent filtering template. The design of this filter is also optimized as part of this paper. Two widely used Fourier-domain plane-wave ultrasound beamforming methods, i.e., Lu's f-k and Stolt's f-k methods, were integrated in the framework. To enable coherent compounding in Fourier domain for the Stolt's f-k method, the original Stolt's f-k method was modified to achieve alignment of the spectra for different steering angles in k-space. The performance of the framework was compared for both methods with and without angular weighting using experimentally obtained data sets (phantom and in vivo), and data sets (phantom) provided by the IEEE IUS 2016 plane-wave beamforming challenge. The addition of angular weighting enhanced the image contrast while preserving image resolution. This resulted in images of equal quality as those obtained by conventionally used delay-and-sum (DAS) beamforming with apodization and coherent compounding. Given the lower computational load of the proposed framework compared to DAS, to our knowledge it can, therefore, be concluded that it outperforms commonly used beamforming methods such as Stolt's f-k, Lu's f-k, and DAS.

  3. Worldline path integrals for a Dirac particle in a weak gravitational plane wave

    International Nuclear Information System (INIS)

    Haouat, S.; Chetouani, L.

    2008-01-01

    The problem of a relativistic spinning particle interacting with a weak gravitational plane wave in (3+1) dimensions is formulated in the frame work of covariant supersymmetric path integrals. The relative Green function is expressed through a functional integral over bosonic trajectories that describe the external motion and fermionic variables that describe the spin degrees of freedom. The (3+1) dimensional problem is reduced to the (1+1) dimensional one by using an identity. Next, the relative propagator is exactly calculated and the wave functions are extracted. (orig.)

  4. X-ray Laue diffraction with allowance for second derivatives of amplitudes in dynamical diffraction equations

    International Nuclear Information System (INIS)

    Balyan, M.K.

    2014-01-01

    Asymmetrical Laue diffraction in a perfect crystal with a plane entrance surface is considered. The second derivatives of amplitudes in the direction, perpendicular to diffraction plane in the dynamical diffraction equations are taken into account. Using the corresponding Green function a general form for the amplitude of diffracted wave in the crystal is derived. The sizes of the source in both directions as well as the source of crystal distance and non-monochromaticity of the radiation incident on the crystal are taken into account. On the basis of obtained expression the coherent properties of the field depending on the sizes of the source and on the width of the spectrum of the incident radiation are analyzed. Taking into account the second derivatives of amplitudes with respect to the direction, perpendicular to the diffraction plane, the time dependent propagation equations for an X-ray pulse in a perfect crystal are given

  5. A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes.

    Science.gov (United States)

    Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

    2015-03-01

    A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm(3)) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

  6. Multiple projection optical diffusion tomography with plane wave illumination

    International Nuclear Information System (INIS)

    Markel, Vadim A; Schotland, John C

    2005-01-01

    We describe a new data collection scheme for optical diffusion tomography in which plane wave illumination is combined with multiple projections in the slab imaging geometry. Multiple projection measurements are performed by rotating the slab around the sample. The advantage of the proposed method is that the measured data are more compatible with the dynamic range of most commonly used detectors. At the same time, multiple projections improve image quality by mutually interchanging the depth and transverse directions, and the scanned (detection) and integrated (illumination) surfaces. Inversion methods are derived for image reconstructions with extremely large data sets. Numerical simulations are performed for fixed and rotated slabs

  7. Plane wave diffraction by a finite plate with impedance boundary conditions.

    Science.gov (United States)

    Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

    2014-01-01

    In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in.

  8. Acoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves.

    Science.gov (United States)

    Badiey, Mohsen; Katsnelson, Boris G; Lin, Ying-Tsong; Lynch, James F

    2011-04-01

    Simultaneous measurements of acoustic wave transmissions and a nonlinear internal wave packet approaching an along-shelf acoustic path during the Shallow Water 2006 experiment are reported. The incoming internal wave packet acts as a moving frontal layer reflecting (or refracting) sound in the horizontal plane. Received acoustic signals are filtered into acoustic normal mode arrivals. It is shown that a horizontal multipath interference is produced. This has previously been called a horizontal Lloyd's mirror. The interference between the direct path and the refracted path depends on the mode number and frequency of the acoustic signal. A mechanism for the multipath interference is shown. Preliminary modeling results of this dynamic interaction using vertical modes and horizontal parabolic equation models are in good agreement with the observed data.

  9. Application of structural symmetries in the plane-wave-based transfer-matrix method for three-dimensional photonic crystal waveguides

    International Nuclear Information System (INIS)

    Li Zhiyuan; Ho Kaiming

    2003-01-01

    The plane-wave-based transfer-matrix method (TMM) exhibits a peculiar advantage of being capable of solving eigenmodes involved in an infinite photonic crystal and electromagnetic (EM) wave propagation in finite photonic crystal slabs or even semi-infinite photonic crystal structures within the same theoretical framework. In addition, this theoretical approach can achieve much improved numerical convergency in solution of photonic band structures than the conventional plane-wave expansion method. In this paper we employ this TMM in combination with a supercell technique to handle two important kinds of three-dimensional (3D) photonic crystal waveguide structures. The first one is waveguides created in a 3D layer-by-layer photonic crystal that possesses a complete band gap, the other more popular one is waveguides built in a two-dimensional photonic crystal slab. These waveguides usually have mirror-reflection symmetries in one or two directions perpendicular to their axis. We have taken advantage of these structural symmetries to reduce the numerical burden of the TMM solution of the guided modes. The solution to the EM problems under these mirror-reflection symmetries in both the real space and the plane-wave space is discussed in a systematic way and in great detail. Both the periodic boundary condition and the absorbing boundary condition are employed to investigate structures with or without complete 3D optical confinement. The fact that the EM field components investigated in the TMM are collinear with the symmetric axes of the waveguide brings great convenience and clarity in exploring the eigenmode symmetry in both the real space and the plane-wave space. The classification of symmetry involved in the guided modes can help people to better understand the coupling of the photonic crystal waveguides with external channels such as dielectric slab or wire waveguides

  10. Extending the precision and efficiency of the all-electron full-potential linearized augmented plane-wave density-functional theory method

    International Nuclear Information System (INIS)

    Michalicek, Gregor

    2015-01-01

    Density functional theory (DFT) is the most widely-used first-principles theory for analyzing, describing and predicting the properties of solids based on the fundamental laws of quantum mechanics. The success of the theory is a consequence of powerful approximations to the unknown exchange and correlation energy of the interacting electrons and of sophisticated electronic structure methods that enable the computation of the density functional equations on a computer. A widely used electronic structure method is the full-potential linearized augmented plane-wave (FLAPW) method, that is considered to be one of the most precise methods of its kind and often referred to as a standard. Challenged by the demand of treating chemically and structurally increasingly more complex solids, in this thesis this method is revisited and extended along two different directions: (i) precision and (ii) efficiency. In the full-potential linearized augmented plane-wave method the space of a solid is partitioned into nearly touching spheres, centered at each atom, and the remaining interstitial region between the spheres. The Kohn-Sham orbitals, which are used to construct the electron density, the essential quantity in DFT, are expanded into a linearized augmented plane-wave basis, which consists of plane waves in the interstitial region and angular momentum dependent radial functions in the spheres. In this thesis it is shown that for certain types of materials, e.g., materials with very broad electron bands or large band gaps, or materials that allow the usage of large space-filling spheres, the variational freedom of the basis in the spheres has to be extended in order to represent the Kohn-Sham orbitals with high precision over a large energy spread. Two kinds of additional radial functions confined to the spheres, so-called local orbitals, are evaluated and found to successfully eliminate this error. A new efficient basis set is developed, named linearized augmented lattice

  11. Plane wave diffraction by a finite plate with impedance boundary conditions.

    Directory of Open Access Journals (Sweden)

    Rab Nawaz

    Full Text Available In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in.

  12. Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange

    International Nuclear Information System (INIS)

    Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

    2011-01-01

    One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

  13. Measurement Verification of Plane Wave Synthesis Technique Based on Multi-probe MIMO-OTA Setup

    DEFF Research Database (Denmark)

    Fan, Wei; Carreño, Xavier; Nielsen, Jesper Ødum

    2012-01-01

    Standardization work for MIMO OTA testing methods is currently ongoing, where a multi-probe anechoic chamber based solution is an important candidate. In this paper, the probes located on an OTA ring are used to synthesize a plane wave field in the center of the OTA ring. This paper investigates...

  14. Diffraction of a plane electromagnetic wave on a dielectric plate of variable density. [Field equatios, diffracted-wave angular distributions

    Energy Technology Data Exchange (ETDEWEB)

    Aivazyan, Yu M; Mergelyan, O S; Poulatov, M P

    1974-01-01

    Aproblem for the diffraction of a plane electromagnetic wave on a dielectric plate between two other dielectrics is solved. The dielectric constant of the plate depends periodically on three coordinates. From this solution it is possible to obtain the equations for fields and the angular distribution of diffracted waves for the particular cases of a crystal plate and a dielectric surface fluted in all directions. If the expansion is made in the variable of the electron density in crystals, the results will correspond to the problem for the X-ray diffraction on a crystal lattice, the values of the coefficient ..cap alpha -->..sub(tau) being determined by the lattice parameters.

  15. Trajectories of electrons with large longitudinal momenta in the phase plane during surfatron acceleration by an electromagnetic wave

    Energy Technology Data Exchange (ETDEWEB)

    Mkrtichyan, G. S., E-mail: hay-13@mail.ru [Peoples’ Friendship University of Russia (Russian Federation)

    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 trajectory 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.

  16. Fast solution of elliptic partial differential equations using linear combinations of plane waves.

    Science.gov (United States)

    Pérez-Jordá, José M

    2016-02-01

    Given an arbitrary elliptic partial differential equation (PDE), a procedure for obtaining its solution is proposed based on the method of Ritz: the solution is written as a linear combination of plane waves and the coefficients are obtained by variational minimization. The PDE to be solved is cast as a system of linear equations Ax=b, where the matrix A is not sparse, which prevents the straightforward application of standard iterative methods in order to solve it. This sparseness problem can be circumvented by means of a recursive bisection approach based on the fast Fourier transform, which makes it possible to implement fast versions of some stationary iterative methods (such as Gauss-Seidel) consuming O(NlogN) memory and executing an iteration in O(Nlog(2)N) time, N being the number of plane waves used. In a similar way, fast versions of Krylov subspace methods and multigrid methods can also be implemented. These procedures are tested on Poisson's equation expressed in adaptive coordinates. It is found that the best results are obtained with the GMRES method using a multigrid preconditioner with Gauss-Seidel relaxation steps.

  17. Generating gravity waves with matter and electromagnetic waves

    International Nuclear Information System (INIS)

    Barrabes, C.; Hogan, P A.

    2008-01-01

    If a homogeneous plane lightlike shell collides head on with a homogeneous plane electromagnetic shock wave having a step-function profile then no backscattered gravitational waves are produced. We demonstrate, by explicit calculation, that if the matter is accompanied by a homogeneous plane electromagnetic shock wave with a step-function profile then backscattered gravitational waves appear after the collision

  18. Linear augmented plane wave method for self-consistent calculations

    International Nuclear Information System (INIS)

    Takeda, T.; Kuebler, J.

    1979-01-01

    O.K. Andersen has recently introduced a linear augmented plane wave method (LAPW) for the calculation of electronic structure that was shown to be computationally fast. A more general formulation of an LAPW method is presented here. It makes use of a freely disposable number of eigenfunctions of the radial Schroedinger equation. These eigenfunctions can be selected in a self-consistent way. The present formulation also results in a computationally fast method. It is shown that Andersen's LAPW is obtained in a special limit from the present formulation. Self-consistent test calculations for copper show the present method to be remarkably accurate. As an application, scalar-relativistic self-consistent calculations are presented for the band structure of FCC lanthanum. (author)

  19. Electromagnetic forces and torques in nanoparticles irradiated by plane waves

    International Nuclear Information System (INIS)

    Garcia de Abajo, F.J.

    2004-01-01

    Optical tweezers and optical lattices are making it possible to control small particles by means of electromagnetic forces and torques. In this context, a method is presented in this work to calculate electromagnetic forces and torques for arbitrarily-shaped objects in the presence of other objects illuminated by a plane wave. The method is based upon an expansion of the electromagnetic field in terms of multipoles around each object, which are in turn used to derive forces and torques analytically. The calculation of multipole coefficients are obtained numerically by means of the boundary element method. Results are presented for both spherical and non-spherical objects

  20. Explicit formulas for Neumann coefficients in the plane-wave geometry

    International Nuclear Information System (INIS)

    He Yanghui; Schwarz, John H.; Spradlin, Marcus; Volovich, Anastasia

    2003-01-01

    We obtain explicit formulas for the Neumann coefficients and associated quantities that appear in the three-string vertex for type IIB string theory in a plane-wave background, for any value of the mass parameter μ. The derivation involves constructing the inverse of a certain infinite-dimensional matrix, in terms of which the Neumann coefficients previously had been written only implicitly. We derive asymptotic expansions for large μ and find unexpectedly simple results, which are valid to all orders in 1/μ. Using BMN duality, these give predictions for certain gauge theory quantities to all orders in the modified 't Hooft coupling λ ' . A specific example is presented

  1. Surface effects on anti-plane shear waves propagating in magneto-electro-elastic nanoplates

    International Nuclear Information System (INIS)

    Wu, Bin; Zhang, Chunli; Chen, Weiqiu; Zhang, Chuanzeng

    2015-01-01

    Material surfaces may have a remarkable effect on the mechanical behavior of magneto-electro-elastic (or multiferroic) structures at nanoscale. In this paper, a surface magneto-electro-elasticity theory (or effective boundary condition formulation), which governs the motion of the material surface of magneto-electro-elastic nanoplates, is established by employing the state-space formalism. The properties of anti-plane shear (SH) waves propagating in a transversely isotropic magneto-electro-elastic plate with nanothickness are investigated by taking surface effects into account. The size-dependent dispersion relations of both antisymmetric and symmetric SH waves are presented. The thickness-shear frequencies and the asymptotic characteristics of the dispersion relations considering surface effects are determined analytically as well. Numerical results show that surface effects play a very pronounced role in elastic wave propagation in magneto-electro-elastic nanoplates, and the dispersion properties depend strongly on the chosen surface material parameters of magneto-electro-elastic nanoplates. As a consequence, it is possible to modulate the waves in magneto-electro-elastic nanoplates through surface engineering. (paper)

  2. Can continuous scans in orthogonal planes improve diagnostic performance of shear wave elastography for breast lesions?

    Science.gov (United States)

    Yang, Pan; Peng, Yulan; Zhao, Haina; Luo, Honghao; Jin, Ya; He, Yushuang

    2015-01-01

    Static shear wave elastography (SWE) is used to detect breast lesions, but slice and plane selections result in discrepancies. To evaluate the intraobserver reproducibility of continuous SWE, and whether quantitative elasticities in orthogonal planes perform better in the differential diagnosis of breast lesions. One hundred and twenty-two breast lesions scheduled for ultrasound-guided biopsy were recruited. Continuous SWE scans were conducted in orthogonal planes separately. Quantitative elasticities and histopathology results were collected. Reproducibility in the same plane and diagnostic performance in different planes were evaluated. The maximum and mean elasticities of the hardest portion, and standard deviation of whole lesion, had high inter-class correlation coefficients (0.87 to 0.95) and large areas under receiver operation characteristic curve (0.887 to 0.899). Without loss of accuracy, sensitivities had increased in orthogonal planes compared with single plane (from 73.17% up to 82.93% at most). Mean elasticity of whole lesion and lesion-to-parenchyma ratio were significantly less reproducible and less accurate. Continuous SWE is highly reproducible for the same observer. The maximum and mean elasticities of the hardest portion and standard deviation of whole lesion are most reliable. Furthermore, the sensitivities of the three parameters are improved in orthogonal planes without loss of accuracies.

  3. Analytical Time-Domain Solution of Plane Wave Propagation Across a Viscoelastic Rock Joint

    Science.gov (United States)

    Zou, Yang; Li, Jianchun; Laloui, Lyesse; Zhao, Jian

    2017-10-01

    The effects of viscoelastic filled rock joints on wave propagation are of great significance in rock engineering. The solutions in time domain for plane longitudinal ( P-) and transverse ( S-) waves propagation across a viscoelastic rock joint are derived based on Maxwell and Kelvin models which are, respectively, applied to describe the viscoelastic deformational behaviour of the rock joint and incorporated into the displacement discontinuity model (DDM). The proposed solutions are verified by comparing with the previous studies on harmonic waves, which are simulated by sinusoidal incident P- and S-waves. Comparison between the predicted transmitted waves and the experimental data for P-wave propagation across a joint filled with clay is conducted. The Maxwell is found to be more appropriate to describe the filled joint. The parametric studies show that wave propagation is affected by many factors, such as the stiffness and the viscosity of joints, the incident angle and the duration of incident waves. Furthermore, the dependences of the transmission and reflection coefficients on the specific joint stiffness and viscosity are different for the joints with Maxwell and Kelvin behaviours. The alternation of the reflected and transmitted waveforms is discussed, and the application scope of this study is demonstrated by an illustration of the effects of the joint thickness. The solutions are also extended for multiple parallel joints with the virtual wave source method and the time-domain recursive method. For an incident wave with arbitrary waveform, it is convenient to adopt the present approach to directly calculate wave propagation across a viscoelastic rock joint without additional mathematical methods such as the Fourier and inverse Fourier transforms.

  4. Accuracy and Precision of Plane Wave Vector Flow Imaging for Laminar and Complex Flow In Vivo

    DEFF Research Database (Denmark)

    Jensen, Jonas; Traberg, Marie Sand; Villagómez Hoyos, Carlos Armando

    2017-01-01

    In this study, a comparison between velocity fields for a plane wave 2-D vector flow imaging (VFI) method and a computational fluid dynamics (CFD) simulation is made. VFI estimates are obtained from the scan of a flow phantom, which mimics the complex flow conditions in the carotid artery....... Furthermore, the precision of the VFI method is investigated under laminar and complex flow conditions in vivo. The carotid bifurcation of a healthy volunteer was scanned using both fast plane wave ultrasound and magnetic resonance imaging (MRI). The acquired MRI geometry of the bifurcation was used...... difference within 15 %, however, it was 23 % in the external branch. For the in vivo scan, the precision in terms of mean standard deviation (SD) of estimates aligned to the cardiac cycle was highest in the center of the common carotid artery (SD 4.7◦ for angles) and lowest in the external branch and close...

  5. ABINIT: Plane-Wave-Based Density-Functional Theory on High Performance Computers

    Science.gov (United States)

    Torrent, Marc

    2014-03-01

    For several years, a continuous effort has been produced to adapt electronic structure codes based on Density-Functional Theory to the future computing architectures. Among these codes, ABINIT is based on a plane-wave description of the wave functions which allows to treat systems of any kind. Porting such a code on petascale architectures pose difficulties related to the many-body nature of the DFT equations. To improve the performances of ABINIT - especially for what concerns standard LDA/GGA ground-state and response-function calculations - several strategies have been followed: A full multi-level parallelisation MPI scheme has been implemented, exploiting all possible levels and distributing both computation and memory. It allows to increase the number of distributed processes and could not be achieved without a strong restructuring of the code. The core algorithm used to solve the eigen problem (``Locally Optimal Blocked Congugate Gradient''), a Blocked-Davidson-like algorithm, is based on a distribution of processes combining plane-waves and bands. In addition to the distributed memory parallelization, a full hybrid scheme has been implemented, using standard shared-memory directives (openMP/openACC) or porting some comsuming code sections to Graphics Processing Units (GPU). As no simple performance model exists, the complexity of use has been increased; the code efficiency strongly depends on the distribution of processes among the numerous levels. ABINIT is able to predict the performances of several process distributions and automatically choose the most favourable one. On the other hand, a big effort has been carried out to analyse the performances of the code on petascale architectures, showing which sections of codes have to be improved; they all are related to Matrix Algebra (diagonalisation, orthogonalisation). The different strategies employed to improve the code scalability will be described. They are based on an exploration of new diagonalization

  6. Useful Solutions for Plane Wave Diffraction by Dielectric Slabs and Wedges

    Directory of Open Access Journals (Sweden)

    Gianluca Gennarelli

    2012-01-01

    Full Text Available This work presents an overview of available uniform asymptotic physical optics solutions for evaluating the plane wave diffraction by some canonical geometries of large interest: dielectric slabs and wedges. Such solutions are based on a physical optics approximation of the electric and magnetic equivalent surface currents in the involved scattering integrals. The resulting diffraction coefficients are expressed in terms of the geometrical optics response of the considered structure and the standard transition function of the Uniform Geometrical Theory of Diffraction. Numerical tests and comparisons make evident the effectiveness and reliability of the presented solutions.

  7. Dispersive photonic crystals from the plane wave method

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Cabrera, E.; Palomino-Ovando, M.A. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Flores-Desirena, B., E-mail: bflores@fcfm.buap.mx [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Gaspar-Armenta, J.A. [Departamento de Investigación en Física de la Universidad de Sonora Apdo, Post 5-088, Hermosillo Sonora 83190, México (Mexico)

    2016-03-01

    Nowadays photonic crystals are widely used in many different applications. One of the most used methods to compute their band structure is the plane wave method (PWM). However, it can only be applied directly to non-dispersive media and be extended to systems with a few model dielectric functions. We explore an extension of the PWM to photonic crystals containing dispersive materials, that solves an eigenvalue equation for the Bloch wave vectors. First we compare our calculation with analytical results for one dimensional photonic crystals containing Si using experimental values of its optical parameters, and obtainig very well agreement, even for the spectrum region with strong absorption. Then, using the same method, we computed the band structure for a two dimensional photonic crystal without absorption, formed by an square array of MgO cylinders in air. The optical parameters for MgO were modeled with the Lorentz dielectric function. Finally, we studied an array of MgO cylinders in a metal, using Drude model without absorption, for the metal dielectric function. For this last case, we study the gap–midgap ratio as a function of the filling fraction for both the square and triangular lattice. The gap–midgap ratio is larger for the triangular lattice, with a maximum value of 10% for a filling fraction of 0.6. Our results show that the method can be applied to dispersive materials, and then to a wide range of applications where photonic crystals can be used.

  8. Flow features that arise due to the interaction of a plane shock wave with concave profiles

    CSIR Research Space (South Africa)

    MacLucas, David A

    2012-10-01

    Full Text Available The focus of the author's thesis was the aerodynamic flow field that develops as a result of the interaction of a moving plane shock wave with concave profiles. In this presentation, he discusses some of the interesting flow phenomena that arise...

  9. Increased Frame Rate for Plane Wave Imaging Without Loss of Image Quality

    DEFF Research Database (Denmark)

    Jensen, Jonas; Stuart, Matthias Bo; Jensen, Jørgen Arendt

    2015-01-01

    Clinical applications of plane wave imaging necessitate the creation of high-quality images with the highest possible frame rate for improved blood flow tracking and anatomical imaging. However, linear array transducers create grating lobe artefacts, which degrade the image quality especially...... in the near field for λ-pitch transducers. Artefacts can only partly be suppressed by increasing the number of emissions, and this paper demonstrates how the frame rate can be increased without loss of image quality by using λ/2-pitch transducers. The number of emissions and steering angles are optimized...

  10. Acoustic radiation force on cylindrical shells in a plane standing wave

    International Nuclear Information System (INIS)

    Mitri, F G

    2005-01-01

    In this paper, the radiation force per length resulting from a plane standing wave incident on an infinitely long cylindrical shell is computed. The cases of elastic and viscoelastic shells immersed in ideal (non-viscous) fluids are considered with particular emphasis on their thickness and the content of their interior hollow spaces. Numerical calculations of the radiation force function Y st are performed. The fluid-loading effect on the radiation force function curves is analysed as well. The results show several features quite different when the interior hollow space is changed from air to water. Moreover, the theory developed here is more general since it includes the results on cylinders

  11. On the determination of general plane stress states in orthotropic materials from ultrasonic velocity data in non symmetry planes

    International Nuclear Information System (INIS)

    Goncalves Filho, Orlando J.A.

    2015-01-01

    This work reports the progress in the development of a new experimental protocol for plane stress determination in orthotropic materials based on the ultrasonic velocity of bulk waves propagating in non symmetry planes with oblique incidence. The presence of stress-induced deformation introduces an acoustic anisotropy in the material in addition to that defined by its texture. Orthotropic materials under general plane stress states become acoustically monoclic and its orthotropic planes orthogonal to the stress plane become non symmetry planes. The inverse solution of the generalized Christoffel equation for ultrasonic bulk waves propagating in non symmetry planes of anisotropic bodies is known to be numerically unstable. The suggested protocol deals with this numerical instability without recourse to bulk wave propagation in the stress plane as proposed in the literature. Hence, it should be useful for plane stress analysis of thin wall pressure vessels where ultrasonic measurements in the direction of the wall plane are not possible. For the initial validation of the suggested protocol and verification of the stability of the inversion algorithm, computer simulation of stress determination have been performed from synthetic sets of velocity data obtained by the forward solution of the generalized Christoffel equation. Preliminary results for slightly orthotropic aluminium highlight the potential of the suggested protocol. (author)

  12. A numerical method for determining the radial wave motion correction in plane wave couplers

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Barrera Figueroa, Salvador; Torras Rosell, Antoni

    2016-01-01

    Microphones are used for realising the unit of sound pressure level, the pascal (Pa). Electro-acoustic reciprocity is the preferred method for the absolute determination of the sensitivity. This method can be applied in different sound fields: uniform pressure, free field or diffuse field. Pressure...... solution is an analytical expression that estimates the difference between the ideal plane wave sound field and a more complex lossless sound field created by a non-planar movement of the microphone’s membranes. Alternatively, a correction may be calculated numerically by introducing a full model...... of the microphone-coupler system in a Boundary Element formulation. In order to obtain a realistic representation of the sound field, viscous losses must be introduced in the model. This paper presents such a model, and the results of the simulations for different combinations of microphones and couplers...

  13. Efficient evaluation of Coulomb integrals in a mixed Gaussian and plane-wave basis

    Czech Academy of Sciences Publication Activity Database

    Čársky, Petr

    2007-01-01

    Roč. 107, č. 1 (2007), s. 56-62 ISSN 0020-7608 R&D Projects: GA AV ČR IAA100400501; GA AV ČR 1ET400400413 Grant - others:European Science Foundation (EIPAM)(XE) PESC7-20; U.S. National Science Foundation(US) OISE-0532040 Institutional research plan: CEZ:AV0Z40400503 Keywords : two- electron integrals * mixed plane-wave and Gaussian basis sets * Coulomb integrals Subject RIV: CF - Physical ; The oretical Chemistry Impact factor: 1.368, year: 2007

  14. Cylindrical and spherical space equivalents to the plane wave expansion technique of Maxwell's wave equations

    Science.gov (United States)

    Gauthier, Robert C.; Alzahrani, Mohammed A.; Jafari, Seyed Hamed

    2015-02-01

    The plane wave expansion (PWM) technique applied to Maxwell's wave equations provides researchers with a supply of information regarding the optical properties of dielectric structures. The technique is well suited for structures that display a linear periodicity. When the focus is directed towards optical resonators and structures that lack linear periodicity the eigen-process can easily exceed computational resources and time constraints. In the case of dielectric structures which display cylindrical or spherical symmetry, a coordinate system specific set of basis functions have been employed to cast Maxwell's wave equations into an eigen-matrix formulation from which the resonator states associated with the dielectric profile can be obtained. As for PWM, the inverse of the dielectric and field components are expanded in the basis functions (Fourier-Fourier-Bessel, FFB, in cylindrical and Fourier- Bessel-Legendre, BLF, in spherical) and orthogonality is employed to form the matrix expressions. The theoretical development details will be presented indicating how certain mathematical complications in the process have been overcome and how the eigen-matrix can be tuned to a specific mode type. The similarities and differences in PWM, FFB and BLF are presented. In the case of structures possessing axial cylindrical symmetry, the inclusion of the z axis component of propagation constant makes the technique applicable to photonic crystal fibers and other waveguide structures. Computational results will be presented for a number of different dielectric geometries including Bragg ring resonators, cylindrical space slot channel waveguides and bottle resonators. Steps to further enhance the computation process will be reported.

  15. Shape optimization of solid-air porous phononic crystal slabs with widest full 3D bandgap for in-plane acoustic waves

    Science.gov (United States)

    D'Alessandro, Luca; Bahr, Bichoy; Daniel, Luca; Weinstein, Dana; Ardito, Raffaele

    2017-09-01

    The use of Phononic Crystals (PnCs) as smart materials in structures and microstructures is growing due to their tunable dynamical properties and to the wide range of possible applications. PnCs are periodic structures that exhibit elastic wave scattering for a certain band of frequencies (called bandgap), depending on the geometric and material properties of the fundamental unit cell of the crystal. PnCs slabs can be represented by plane-extruded structures composed of a single material with periodic perforations. Such a configuration is very interesting, especially in Micro Electro-Mechanical Systems industry, due to the easy fabrication procedure. A lot of topologies can be found in the literature for PnCs with square-symmetric unit cell that exhibit complete 2D bandgaps; however, due to the application demand, it is desirable to find the best topologies in order to guarantee full bandgaps referred to in-plane wave propagation in the complete 3D structure. In this work, by means of a novel and fast implementation of the Bidirectional Evolutionary Structural Optimization technique, shape optimization is conducted on the hole shape obtaining several topologies, also with non-square-symmetric unit cell, endowed with complete 3D full bandgaps for in-plane waves. Model order reduction technique is adopted to reduce the computational time in the wave dispersion analysis. The 3D features of the PnC unit cell endowed with the widest full bandgap are then completely analyzed, paying attention to engineering design issues.

  16. Necessary conditions for the initiation and propagation of nuclear-detonation waves in plane atmospheres

    International Nuclear Information System (INIS)

    Weaver, T.A.; Wood, L.

    1979-01-01

    The basic conditions for the initiation of a nuclear-detonation wave in an atmosphere having plane symmetry (e.g., a thin, layered fluid envelope on a planet or star) are developed. Two classes of such a detonation are identified: those in which the temperature of the plasma is comparable to that of the electromagnetic radiation permeating it, and those in which the temperature of the plasma is much higher. Necessary conditions are developed for the propagation of such detonation waves for an arbitrarily great distance. The contribution of fusion chain reactions to these processes is evaluated. By means of these considerations, it is shown that neither the atmosphere nor oceans of the Earth may be made to undergo propagating nuclear detonation under any circumstances

  17. Photonic antenna enhanced middle wave and longwave infrared focal plane array with low noise and high operating temperature, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Photodetectors and focal plane arrays (FPAs) covering the middle-wave and longwave infrared (MWIR/LWIR) are of great importance in numerous NASA applications,...

  18. Validation of the k-filtering technique for a signal composed of random-phase plane waves and non-random coherent structures

    Directory of Open Access Journals (Sweden)

    O. W. Roberts

    2014-12-01

    Full Text Available Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame and those described as being structure-like (advected by the plasma bulk velocity. Typically with single-spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed for temporal and spatial changes to be resolved, using techniques such as k filtering. While this technique does not assume Taylor's hypothesis it requires both weak stationarity of the time series and that the fluctuations can be described by a superposition of plane waves with random phases. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random-phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.

  19. The effect of sources on horizons that may develop when plane gravitational waves collide

    International Nuclear Information System (INIS)

    Chandrasekhar, Subrahmanyan; Xanthopoulos, B.C.

    1987-01-01

    Colliding plane gravitational waves that lead to the development of a horizon and a subsequent time-like singularity are coupled with an electromagnetic field, a perfect fluid, and null dust (consisting of massless particles). The coupling of the gravitational waves with an electromagnetic field does not affect, in any essential way, the development of the horizon or the time-like singularity if the polarizations of the colliding gravitational waves are not parallel. If the polarizations are parallel, the space-like singularity which occurs in the vacuum is transformed into a horizon followed by a three-dimensional time-like singularity by the merest presence of the electromagnetic field. The coupling of the gravitational waves with a perfect fluid and null dust affect the development of horizons and singularities in radically different ways: the perfect fluid affects the development decisively in all cases but qualitatively in the same way, while null dust prevents the development of horizons and allows only the development of space-like singularities. The contrasting behaviours of a perfect fluid and of null dust in the framework of general relativity is compared with the behaviours one may expect, under similar circumstances, in the framework of special relativity. (author)

  20. Connection between in-plane upper critical field Hc 2 and gap symmetry in layered d -wave superconductors

    Science.gov (United States)

    Wang, Jing-Rong; Liu, Guo-Zhu; Zhang, Chang-Jin

    2016-07-01

    Angle-resolved upper critical field Hc 2 provides an efficient tool to probe the gap symmetry of unconventional superconductors. We revisit the behavior of in-plane Hc 2 in d -wave superconductors by considering both the orbital effect and Pauli paramagnetic effect. After carrying out systematic analysis, we show that the maxima of Hc 2 could be along either nodal or antinodal directions of a d -wave superconducting gap, depending on the specific values of a number of tuning parameters. This behavior is in contrast to the common belief that the maxima of in-plane Hc 2 are along the direction where the superconducting gap takes its maximal value. Therefore, identifying the precise d -wave gap symmetry through fitting experiments results of angle-resolved Hc 2 with model calculations at a fixed temperature, as widely used in previous studies, is difficult and practically unreliable. However, our extensive analysis of angle-resolved Hc 2 show that there is a critical temperature T*: in-plane Hc 2 exhibits its maxima along nodal directions at T change as other parameters vary, but the existence of π /4 shift of Hc 2 at T* appears to be a general feature. Thus a better method to identify the precise d -wave gap symmetry is to measure Hc 2 at a number of different temperatures, and examine whether there is a π /4 shift in its angular dependence at certain T*. We further show that Landau level mixing does not change this general feature. However, in the presence of Fulde-Ferrell-Larkin-Ovchinnikov state, the angular dependence of Hc 2 becomes quite complicated, which makes it more difficult to determine the gap symmetry by measuring Hc 2. Our results indicate that some previous studies on the gap symmetry of CeCu2Si2 are unreliable and need to be reexamined, and also provide a candidate solution to an experimental discrepancy in the angle-resolved Hc 2 in CeCoIn5.

  1. Correction of the near threshold behavior of electron collisional excitation cross-sections in the plane-wave Born approximation

    Science.gov (United States)

    Kilcrease, D. P.; Brookes, S.

    2013-12-01

    The modeling of NLTE plasmas requires the solution of population rate equations to determine the populations of the various atomic levels relevant to a particular problem. The equations require many cross sections for excitation, de-excitation, ionization and recombination. A simple and computational fast way to calculate electron collisional excitation cross-sections for ions is by using the plane-wave Born approximation. This is essentially a high-energy approximation and the cross section suffers from the unphysical problem of going to zero near threshold. Various remedies for this problem have been employed with varying degrees of success. We present a correction procedure for the Born cross-sections that employs the Elwert-Sommerfeld factor to correct for the use of plane waves instead of Coulomb waves in an attempt to produce a cross-section similar to that from using the more time consuming Coulomb Born approximation. We compare this new approximation with other, often employed correction procedures. We also look at some further modifications to our Born Elwert procedure and its combination with Y.K. Kim's correction of the Coulomb Born approximation for singly charged ions that more accurately approximate convergent close coupling calculations.

  2. C-plane Reconstructions from Sheaf Acquisition for Ultrasound Electrode Vibration Elastography.

    Science.gov (United States)

    Ingle, Atul; Varghese, Tomy

    2014-09-03

    This paper presents a novel algorithm for reconstructing and visualizing ablated volumes using radiofrequency ultrasound echo data acquired with the electrode vibration elastography approach. The ablation needle is vibrated using an actuator to generate shear wave pulses that are tracked in the ultrasound image plane at different locations away from the needle. This data is used for reconstructing shear wave velocity maps for each imaging plane. A C-plane reconstruction algorithm is proposed which estimates shear wave velocity values on a collection of transverse planes that are perpendicular to the imaging planes. The algorithm utilizes shear wave velocity maps from different imaging planes that share a common axis of intersection. These C-planes can be used to generate a 3D visualization of the ablated region. Experimental validation of this approach was carried out using data from a tissue mimicking phantom. The shear wave velocity estimates were within 20% of those obtained from a clinical scanner, and a contrast of over 4 dB was obtained between the stiff and soft regions of the phantom.

  3. The Fermionic Signature Operator and Hadamard States in the Presence of a Plane Electromagnetic Wave

    Science.gov (United States)

    Finster, Felix; Reintjes, Moritz

    2017-05-01

    We give a non-perturbative construction of a distinguished state for the quantized Dirac field in Minkowski space in the presence of a time-dependent external field of the form of a plane electromagnetic wave. By explicit computation of the fermionic signature operator, it is shown that the Dirac operator has the strong mass oscillation property. We prove that the resulting fermionic projector state is a Hadamard state.

  4. Perturbation theory for the Bethe-Salpeter equation in the field of a plane electromagnetic wave

    International Nuclear Information System (INIS)

    Starostin, V.S.; Litskevich, I.K.

    1990-01-01

    The completeness and orthogonality of the solutions of the Bethe-Salpeter equation is proven. A correct derivation of perturbation-theory equations is given. A generalization that includes the field of a plane electromagnetic wave is proposed. The rate of one-photon annihilation of positronium in this field is calculated. If the one-photon decay is allowed, the stationary states of the system are found (states of light-positronium)

  5. Spin-wave logic devices based on isotropic forward volume magnetostatic waves

    International Nuclear Information System (INIS)

    Klingler, S.; Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V.

    2015-01-01

    We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves

  6. Spin-wave logic devices based on isotropic forward volume magnetostatic waves

    Energy Technology Data Exchange (ETDEWEB)

    Klingler, S., E-mail: stefan.klingler@wmi.badw-muenchen.de; Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany)

    2015-05-25

    We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves.

  7. Plane-wave diffraction by periodic structures with artificial anisotropic dielectrics

    International Nuclear Information System (INIS)

    Kazerooni, Azadeh Semsar; Shahabadi, Mahmoud

    2010-01-01

    Periodic structures with artificial anisotropic dielectrics are studied. The artificial anisotropic dielectric material in this work is made of two alternating isotropic dielectric layers. By a proper choice of the dielectric constant of the layers, we can realize a uniaxial anisotropic medium with controllable anisotropy. The artificial anisotropic dielectric is then used in periodic structures. For these structures, the optical axis of the artificial dielectric is assumed to be parallel or perpendicular to the period of the structure. Diffraction of plane waves by these structures is analyzed by a fully vectorial rigorous matrix method based on a generalized transmission line (TL) formulation. The propagation constants and field distributions are computed and diffraction properties of such structures are studied to show that, by a proper choice of structural parameters, these periodic structures with artificial anisotropic dielectrics can be used as polarizers or polarizing mirrors

  8. A semi-analytical approach towards plane wave analysis of local resonance metamaterials using a multiscale enriched continuum description

    NARCIS (Netherlands)

    Sridhar, A.; Kouznetsova, V.; Geers, M.G.D.

    2017-01-01

    This work presents a novel multiscale semi-analytical technique for the acoustic plane wave analysis of (negative) dynamic mass density type local resonance metamaterials with complex micro-structural geometry. A two step solution strategy is adopted, in which the unit cell problem at the

  9. Propagation of plane waves at the interface of an elastic solid half-space and a microstretch thermoelastic diffusion solid half-space

    Directory of Open Access Journals (Sweden)

    Rajneesh Kumar

    Full Text Available The problem of reflection and refraction phenomenon due to plane waves incident obliquely at a plane interface between uniform elastic solid half-space and microstretch thermoelastic diffusion solid half-space has been studied. It is found that the amplitude ratios of various reflected and refracted waves are functions of angle of incidence, frequency of incident wave and are influenced by the microstretch thermoelastic diffusion properties of the media. The expressions of amplitude ratios and energy ratios are obtained in closed form. The energy ratios have been computed numerically for a particular model. The variations of energy ratios with angle of incidence are shown for thermoelastic diffusion media in the context of Lord-Shulman (L-S (1967 and Green-Lindsay (G-L (1972 theories. The conservation of energy at the interface is verified. Some particular cases are also deduced from the present investigation.

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

    Science.gov (United States)

    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.

  11. Magnetism of hexagonal close-packed nickel calculated by full-potential linearized augmented plane wave method

    International Nuclear Information System (INIS)

    Tian, F.; Tian, H.; Whitmore, L.; Ye, L.Y.

    2015-01-01

    The energy dependent on volume of hexagonal close-packed (hcp) nickel with different magnetism is calculated by full-potential linearized augmented plane wave method. Based on the calculation ferromagnetic state is found to be the most stable state. The magnetic moment of hcp Ni is calculated and compared to those calculated by different pseudo-potential methods. Furthermore, it is also compared to that of face-centered cubic (fcc) one with the reason discussed

  12. Propagation properties of Rossby waves for latitudinal β-plane variations of f and zonal variations of the shallow water speed

    Directory of Open Access Journals (Sweden)

    C. T. Duba

    2012-05-01

    Full Text Available Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude Rossby wave on a β-plane is a circle in wave number (ky,kx space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f, combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.

  13. Phase Plane Analysis Method of Nonlinear Traffic Phenomena

    Directory of Open Access Journals (Sweden)

    Wenhuan Ai

    2015-01-01

    Full Text Available A new phase plane analysis method for analyzing the complex nonlinear traffic phenomena is presented in this paper. This method makes use of variable substitution to transform a traditional traffic flow model into a new model which is suitable for the analysis in phase plane. According to the new model, various traffic phenomena, such as the well-known shock waves, rarefaction waves, and stop-and-go waves, are analyzed in the phase plane. From the phase plane diagrams, we can see the relationship between traffic jams and system instability. So the problem of traffic flow could be converted into that of system stability. The results show that the traffic phenomena described by the new method is consistent with that described by traditional methods. Moreover, the phase plane analysis highlights the unstable traffic phenomena we are chiefly concerned about and describes the variation of density or velocity with time or sections more clearly.

  14. Controlling the position of a stabilized detonation wave in a supersonic gas mixture flow in a plane channel

    Science.gov (United States)

    Levin, V. A.; Zhuravskaya, T. A.

    2017-03-01

    Stabilization of a detonation wave in a stoichiometric hydrogen-air mixture flowing at a supersonic velocity into a plane symmetric channel with constriction has been studied in the framework of a detailed kinetic mechanism of the chemical interaction. Conditions ensuring the formation of a thrust-producing f low with a stabilized detonation wave in the channel are determined. The inf luence of the inf low Mach number, dustiness of the combustible gas mixture supplied to the channel, and output cross-section size on the position of a stabilized detonation wave in the f low has been analyzed with a view to increasing the efficiency of detonation combustion of the gas mixture. It is established that thrust-producing flow with a stabilized detonation wave can be formed in the channel without any energy consumption.

  15. Spin effects in nonlinear Compton scattering in a plane-wave laser pulse

    International Nuclear Information System (INIS)

    Boca, Madalina; Dinu, Victor; Florescu, Viorica

    2012-01-01

    We study theoretically the electron angular and energy distribution in the non-linear Compton effect in a finite plane-wave laser pulse. We first present analytical and numerical results for unpolarized electrons (described by a Volkov solution of the Dirac equation), in comparison with those corresponding to a spinless particle (obeying the Klein–Gordon equation). Then, in the spin 1/2 case, we include results for the spin flip probability. The regime in which the spin effects are negligible, i.e. the results for the unpolarized spin 1/2 particle coincide practically with those for the spinless particle, is the same as the regime in which the emitted radiation is well described by classical electrodynamics.

  16. Planar plane-wave matrix theory at the four loop order: integrability without BMN scaling

    International Nuclear Information System (INIS)

    Fischbacher, Thomas; Klose, Thomas; Plefka, Jan

    2005-01-01

    We study SU(N) plane-wave matrix theory up to fourth perturbative order in its large N planar limit. The effective hamiltonian in the closed su(2) subsector of the model is explicitly computed through a specially tailored computer program to perform large scale distributed symbolic algebra and generation of planar graphs. The number of graphs here was in the deep billions. The outcome of our computation establishes the four-loop integrability of the planar plane-wave matrix model. To elucidate the integrable structure we apply the recent technology of the perturbative asymptotic Bethe ansatz to our model. The resulting S-matrix turns out to be structurally similar but nevertheless distinct to the so far considered long-range spin-chain S-matrices of Inozemtsev, Beisert-Dippel-Staudacher and Arutyunov-Frolov-Staudacher in the AdS/CFT context. In particular our result displays a breakdown of BMN scaling at the four-loop order. That is, while there exists an appropriate identification of the matrix theory mass parameter with the coupling constant of the N=4 superconformal Yang-Mills theory which yields an eighth order lattice derivative for well separated impurities (naively implying BMN scaling) the detailed impurity contact interactions ruin this scaling property at the four-loop order. Moreover we study the issue of 'wrapping' interactions, which show up for the first time at this loop-order through a Konishi descendant length four operator. (author)

  17. Excited state nuclear forces from the Tamm-Dancoff approximation to time-dependent density functional theory within the plane wave basis set framework

    Science.gov (United States)

    Hutter, Jürg

    2003-03-01

    An efficient formulation of time-dependent linear response density functional theory for the use within the plane wave basis set framework is presented. The method avoids the transformation of the Kohn-Sham matrix into the canonical basis and references virtual orbitals only through a projection operator. Using a Lagrangian formulation nuclear derivatives of excited state energies within the Tamm-Dancoff approximation are derived. The algorithms were implemented into a pseudo potential/plane wave code and applied to the calculation of adiabatic excitation energies, optimized geometries and vibrational frequencies of three low lying states of formaldehyde. An overall good agreement with other time-dependent density functional calculations, multireference configuration interaction calculations and experimental data was found.

  18. In-plane confinement and waveguiding of surface acoustic waves through line defects in pillars-based phononic crystal

    Directory of Open Access Journals (Sweden)

    Abdelkrim Khelif

    2011-12-01

    Full Text Available We present a theoretical analysis of an in-plane confinement and a waveguiding of surface acoustic waves in pillars-based phononic crystal. The artificial crystal is made up of cylindrical pillars placed on a semi-infinite medium and arranged in a square array. With a well-chosen of the geometrical parameters, this pillars-based system can display two kinds of complete band gaps for guided waves propagating near the surface, a low frequency gap based on locally resonant mode of pillars as well as a higher frequency gap appearing at Bragg scattering regime. In addition, we demonstrate a waveguiding of surface acoustic wave inside an extended linear defect created by removing rows of pillars in the perfect crystal. We discuss the transmission and the polarization of such confined mode appearing in the higher frequency band gap. We highlight the strong similarity of such defect mode and the Rayleigh wave of free surface medium. An efficient finite element analysis is used to simulate the propagation of guided waves through silicon pillars on a silicon substrate.

  19. Simulation of angle-resolved photoemission spectra by approximating the final state by a plane wave: From graphene to polycyclic aromatic hydrocarbon molecules

    Energy Technology Data Exchange (ETDEWEB)

    Puschnig, Peter, E-mail: peter.puschnig@uni-graz.at; Lüftner, Daniel

    2015-04-15

    Highlights: • Computational study on angular dependent photoemission spectroscopy. • Graphene and polycyclic aromatic hydrocarbon molecules. • Plane wave final state approximation accounts for experimental findings. - Abstract: We present a computational study on the angular-resolved photoemission spectra (ARPES) from a number of polycyclic aromatic hydrocarbons and graphene. Our theoretical approach is based on ab-initio density functional theory and the one-step model where we greatly simplify the evaluation of the matrix element by assuming a plane wave for the final state. Before comparing our ARPES simulations with available experimental data, we discuss how typical approximations for the exchange-correlation energy affect orbital energies. In particular, we show that by employing a hybrid functional, considerable improvement can be obtained over semi-local functionals in terms of band widths and relative energies of π and σ states. Our ARPES simulations for graphene show that the plane wave final state approximation provides indeed an excellent description when compared to experimental band maps and constant binding energy maps. Furthermore, our ARPES simulations for a number of polycyclic aromatic molecules from the oligo-acene, oligo-phenylene, phen-anthrene families as well as for disc-shaped molecules nicely illustrate the evolution of the electronic structure from molecules with increasing size towards graphene.

  20. Stability of the Superconducting d-Wave Pairing Toward the Intersite Coulomb Repulsion in CuO_2 Plane

    Science.gov (United States)

    Val'kov, V. V.; Dzebisashvili, D. M.; Korovushkin, M. M.; Barabanov, A. F.

    2018-06-01

    Taking into account the real crystalline structure of the CuO_2 plane and the strong spin-fermion coupling, we study the influence of the intersite Coulomb repulsion between holes on the Cooper instability of the spin-polaron quasiparticles in cuprate superconductors. The analysis shows that only the superconducting d-wave pairing is implemented in the whole region of doping, whereas the solutions of the self-consistent equations for the s-wave pairing are absent. It is shown that intersite Coulomb interaction V_1 between the holes located at the nearest oxygen ions does not affect the d-wave pairing, because its Fourier transform V_q vanishes in the kernel of the corresponding integral equation. The intersite Coulomb interaction V_2 of quasiparticles located at the next-nearest oxygen ions does not vanish in the integral equations, however, but it is also shown that the d-wave pairing is robust toward this interaction for physically reasonable values of V_2.

  1. FDTD analysis of reflection of electromagnetic wave from a conductive plane covered with inhomogeneous time-varying plasma

    International Nuclear Information System (INIS)

    Liu Shaobin; Mo Jinjun; Yuan Naichang

    2003-01-01

    A finite-difference time-domain (FDTD) algorithm is applied to study the electro-magnetic reflection of conduction plane covered with inhomogeneous time-varying plasma, homogeneous plasma and inhomogeneous plasma. The collisions frequency of plasma is a function of electron density and plasma temperature. The number density profile follows a parabolic function. A discussion on the effect of various plasma parameters on the reflection coefficient is presented. Under the one-dimensional case, transient electromagnetic propagation through various plasmas has been obtained, and the reflection coefficients of EM wave through various plasma are calculated under different conditions. The results illustrate that a plasma cloaking system can successfully absorb the incident EM wave

  2. DFT LCAO and plane wave calculations of SrZrO3

    International Nuclear Information System (INIS)

    Evarestov, R.A.; Bandura, A.V.; Alexandrov, V.E.; Kotomin, E.A.

    2005-01-01

    The results of the density functional (DFT) LCAO and plane wave (PW) calculations of the electronic and structural properties of four known SrZrO 3 phases (Pm3m, I4/mcm, Cmcm and Pbnm) are presented and discussed. The calculated unit cell energies and relative stability of these phases agree well with the experimental sequence of SrZrO 3 phases as the temperature increases. The lattice structure parameters optimized in the PW calculations for all four phases are in good agreement with the experimental neutron diffraction data. The LCAO and PW results for the electronic structure, density of states and chemical bonding in the cubic phase (Pm3m) are discussed in detail and compared with the results of previous PW calculations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Electromagnetic waves in gravitational wave spacetimes

    International Nuclear Information System (INIS)

    Haney, M.; Bini, D.; Ortolan, A.; Fortini, P.

    2013-01-01

    We have considered the propagation of electromagnetic waves in a space-time representing an exact gravitational plane wave and calculated the induced changes on the four-potential field Aμ of a plane electromagnetic wave. By choosing a suitable photon round-trip in a Michelson interferometer, we have been able to identify the physical effects of the exact gravitational wave on the electromagnetic field, i.e. phase shift, change of the polarization vector, angular deflection and delay. These results have been exploited to study the response of an interferometric gravitational wave detector beyond the linear approximation of the general theory of relativity. A much more detailed examination of this problem can be found in our paper recently published in Classical and Quantum Gravity (28 (2011) 235007).

  4. Singularities and horizons in the collisions of gravitational waves

    International Nuclear Information System (INIS)

    Yurtsever, U.H.

    1989-01-01

    This thesis presents a study of the dynamical, nonlinear interaction of colliding gravitational waves, as described by classical general relativity. In the work on the collisions of exactly-plane waves, it is shown that Killing horizons in any plane-symmetric spacetime are unstable against small plane-symmetric perturbations. It is thus concluded that the Killing-Cauchy horizons produced by the collisions of some exactly plane gravitational waves are nongeneric, and the generic initial data for the colliding plane waves always produce pure spacetime singularities without such horizons. This conclusion is later proved rigorously (using the full nonlinear theory rather than perturbation theory), in connection with an analysis of the asymptotic singularity structure of a general colliding plane-wave spacetime. This analysis also proves that asymptotically the singularities created by colliding plane waves are of inhomogeneous-Kasner type; the asymptotic Kasner axes and exponents of these singularities in general depend on the spatial coordinate that runs tangentially to the singularity in the non-plane-symmetric direction. In the work on collisions of almost-plane gravitational waves, first some general properties of single almost-plane gravitational-wave spacetimes are explored. It is shown that, by contrast with an exact plane wave, an almost-plane gravitational wave cannot have a propagation direction that is Killing; i.e., it must diffract and disperse as it propagates. It is also shown that an almost-plane wave cannot be precisely sandwiched between two null wave-fronts; i.e., it must leave behind tails in the spacetime region through which is passes

  5. Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves

    Science.gov (United States)

    Mitri, F. G.

    2015-12-01

    The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.

  6. Projecting non-diffracting waves with intermediate-plane holography.

    Science.gov (United States)

    Mondal, Argha; Yevick, Aaron; Blackburn, Lauren C; Kanellakopoulos, Nikitas; Grier, David G

    2018-02-19

    We introduce intermediate-plane holography, which substantially improves the ability of holographic trapping systems to project propagation-invariant modes of light using phase-only diffractive optical elements. Translating the mode-forming hologram to an intermediate plane in the optical train can reduce the need to encode amplitude variations in the field, and therefore complements well-established techniques for encoding complex-valued transfer functions into phase-only holograms. Compared to standard holographic trapping implementations, intermediate-plane holograms greatly improve diffraction efficiency and mode purity of propagation-invariant modes, and so increase their useful non-diffracting range. We demonstrate this technique through experimental realizations of accelerating modes and long-range tractor beams.

  7. A singularity extraction technique for computation of antenna aperture fields from singular plane wave spectra

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel

    2008-01-01

    An effective technique for extracting the singularity of plane wave spectra in the computation of antenna aperture fields is proposed. The singular spectrum is first factorized into a product of a finite function and a singular function. The finite function is inverse Fourier transformed...... numerically using the Inverse Fast Fourier Transform, while the singular function is inverse Fourier transformed analytically, using the Weyl-identity, and the two resulting spatial functions are then convolved to produce the antenna aperture field. This article formulates the theory of the singularity...

  8. Three-dimensional stability of solitary kinetic Alfven waves and ion-acoustic waves

    International Nuclear Information System (INIS)

    Ghosh, G.; Das, K.P.

    1994-01-01

    Starting from a set of equations that lead to a linear dispersion relation coupling kinetic Alfven waves and ion-acoustic waves, three-dimensional KdV equations are derived for these waves. These equations are then used to investigate the three-dimensional stability of solitary kinetic Alfven waves and ion-acoustic waves by the small-k perturbation expansion method of Rowlands and Infeld. For kinetic Alfven waves it is found that there is instability if the direction of the plane-wave perturbation lies inside a cone, and the growth rate of the instability attains a maximum when the direction of the perturbation lies in the plane containing the external magnetic field and the direction of propagation of the solitary wave. For ion-acoustic waves the growth rate of instability attains a maximum when the direction of the perturbation lies in a plane perpendicular to the direction of propagation of the solitary wave. (Author)

  9. Next generation sub-millimeter wave focal plane array coupling concepts: an ESA TRP project to develop multichroic focal plane pixels for future CMB polarization experiments

    Science.gov (United States)

    Trappe, N.; Bucher, M.; De Bernardis, P.; Delabrouille, J.; Deo, P.; DePetris, M.; Doherty, S.; Ghribi, A.; Gradziel, M.; Kuzmin, L.; Maffei, B.; Mahashabde, S.; Masi, S.; Murphy, J. A.; Noviello, F.; O'Sullivan, C.; Pagano, L.; Piacentini, F.; Piat, M.; Pisano, G.; Robinson, M.; Stompor, R.; Tartari, A.; van der Vorst, M.; Verhoeve, P.

    2016-07-01

    The main objective of this activity is to develop new focal plane coupling array concepts and technologies that optimise the coupling from reflector optics to the large number of detectors for next generation sub millimetre wave telescopes particularly targeting measurement of the polarization of the cosmic microwave background (CMB). In this 18 month TRP programme the consortium are tasked with developing, manufacturing and experimentally verifying a prototype multichroic pixel which would be suitable for the large focal plane arrays which will be demanded to reach the required sensitivity of future CMB polarization missions. One major development was to have multichroic operation to potentially reduce the required focal plane size of a CMB mission. After research in the optimum telescope design and definition of requirements based on a stringent science case review, a number of compact focal plane architecture concepts were investigated before a pixel demonstrator consisting of a planar mesh lens feeding a backend Resonant Cold Electron Bolometer RCEB for filtering and detection of the dual frequency signal was planned for manufacture and test. In this demonstrator the frequencies of the channels was chosen to be 75 and 105 GHz in the w band close to the peak CMB signal. In the next year the prototype breadboards will be developed to test the beams produced by the manufactured flat lenses fed by a variety of antenna configurations and the spectral response of the RCEBs will also be verified.

  10. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  11. Coherent quantum states of a relativistic particle in an electromagnetic plane wave and a parallel magnetic field

    International Nuclear Information System (INIS)

    Colavita, E.; Hacyan, S.

    2014-01-01

    We analyze the solutions of the Klein–Gordon and Dirac equations describing a charged particle in an electromagnetic plane wave combined with a magnetic field parallel to the direction of propagation of the wave. It is shown that the Klein–Gordon equation admits coherent states as solutions, while the corresponding solutions of the Dirac equation are superpositions of coherent and displaced-number states. Particular attention is paid to the resonant case in which the motion of the particle is unbounded. -- Highlights: •We study a relativistic electron in a particular electromagnetic field configuration. •New exact solutions of the Klein–Gordon and Dirac equations are obtained. •Coherent and displaced number states can describe a relativistic particle

  12. Fourier plane imaging microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez, Daniel, E-mail: daniel.dominguez@ttu.edu; Peralta, Luis Grave de [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Alharbi, Nouf; Alhusain, Mdhaoui [Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Bernussi, Ayrton A. [Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States); Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-09-14

    We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonic crystals.

  13. An IBEM solution to the scattering of plane SH-waves by a lined tunnel in elastic wedge space

    Science.gov (United States)

    Liu, Zhongxian; Liu, Lei

    2015-02-01

    The indirect boundary element method (IBEM) is developed to solve the scattering of plane SH-waves by a lined tunnel in elastic wedge space. According to the theory of single-layer potential, the scattered-wave field can be constructed by applying virtual uniform loads on the surface of lined tunnel and the nearby wedge surface. The densities of virtual loads can be solved by establishing equations through the continuity conditions on the interface and zero-traction conditions on free surfaces. The total wave field is obtained by the superposition of free field and scattered-wave field in elastic wedge space. Numerical results indicate that the IBEM can solve the diffraction of elastic wave in elastic wedge space accurately and efficiently. The wave motion feature strongly depends on the wedge angle, the angle of incidence, incident frequency, the location of lined tunnel, and material parameters. The waves interference and amplification effect around the tunnel in wedge space is more significant, causing the dynamic stress concentration factor on rigid tunnel and the displacement amplitude of flexible tunnel up to 50.0 and 17.0, respectively, more than double that of the case of half-space. Hence, considerable attention should be paid to seismic resistant or anti-explosion design of the tunnel built on a slope or hillside.

  14. Dynamics of plane-symmetric thin walls in general relativity

    International Nuclear Information System (INIS)

    Wang, A.

    1992-01-01

    Plane walls (including plane domain walls) without reflection symmetry are studied in the framework of Einstein's general relativity. Using the distribution theory, all the Einstein field equations and Bianchi identities are split into two groups: one holding in the regions outside of the wall and the other holding at the wall. The Einstein field equations at the wall are found to take a very simple form, and given explicitly in terms of the discontinuities of the metric coefficients and their derivatives. The Bianchi identities at the wall are also given explicitly. Using the latter, the interaction of a plane wall with gravitational waves and some specific matter fields is studied. In particular, it is found that, when a gravitational plane wave passes through a wall, if the wall has no reflection symmetry, the phenomena, such as reflection, stimulation, or absorption, in general, occur. It is also found that, unlike for gravitational waves, a massless scalar wave or an electromagnetic wave continuously passes through a wall without any reflection. The repulsion and attraction of a plane wall are also studied. It is found that the acceleration of an observer who is at rest relative to the wall usually consists of three parts: one is due to the force produced by the wall, the second is due to the force produced by the space-time curvature, which is zero if the wall has reflection symmetry, and the last is due to the accelerated motion of the wall. As a result, a repulsive (attractive) plane wall may not be repulsive (attractive) at all. Finally, the collision and interaction among the walls are studied

  15. Temperature elevation in the eye of anatomically based human head models for plane-wave exposures

    International Nuclear Information System (INIS)

    Hirata, A; Watanabe, S; Fujiwara, O; Kojima, M; Sasaki, K; Shiozawa, T

    2007-01-01

    This study investigated the temperature elevation in the eye of anatomically based human head models for plane-wave exposures. The finite-difference time-domain method is used for analyzing electromagnetic absorption and temperature elevation. The eyes in the anatomic models have average dimensions and weight. Computational results show that the ratio of maximum temperature in the lens to the eye-average SAR (named 'heating factor for the lens') is almost uniform (0.112-0.147 deg. C kg W -1 ) in the frequency region below 3 GHz. Above 3 GHz, this ratio increases gradually with an increase of frequency, which is attributed to the penetration depth of an electromagnetic wave. Particular attention is paid to the difference in the heating factor for the lens between this study and earlier works. Considering causes clarified in this study, compensated heating factors in all these studies are found to be in good agreement

  16. Four-dimensional parameter estimation of plane waves using swarming intelligence

    International Nuclear Information System (INIS)

    Zaman Fawad; Munir Fahad; Khan Zafar Ullah; Qureshi Ijaz Mansoor

    2014-01-01

    This paper proposes an efficient approach for four-dimensional (4D) parameter estimation of plane waves impinging on a 2-L shape array. The 4D parameters include amplitude, frequency and the two-dimensional (2D) direction of arrival, namely, azimuth and elevation angles. The proposed approach is based on memetic computation, in which the global optimizer, particle swarm optimization is hybridized with a rapid local search technique, pattern search. For this purpose, a new multi-objective fitness function is used. This fitness function is the combination of mean square error and the correlation between the normalized desired and estimated vectors. The proposed hybrid scheme is not only compared with individual performances of particle swarm optimization and pattern search, but also with the performance of the hybrid genetic algorithm and that of the traditional approach. A large number of Monte—Carlo simulations are carried out to validate the performance of the proposed scheme. It gives promising results in terms of estimation accuracy, convergence rate, proximity effect and robustness against noise. (interdisciplinary physics and related areas of science and technology)

  17. Scattering of electromagnetic plane waves by a buried vertical dike

    Directory of Open Access Journals (Sweden)

    Batista Lurimar S.

    2003-01-01

    Full Text Available The complete and exact solution of the scattering of a TE mode frequency domain electromagnetic plane wave by a vertical dike under a conductive overburden has been established. An integral representation composed of one-sided Fourier transforms describes the scattered electric field components in each one of the five media: air, overburden, dike, and the country rocks on both sides of the dike. The determination of the terms of the series that represents the spectral components of the Fourier integrals requires the numerical inversion of a sparse matrix, and the method of successive approaches. The zero-order term of the series representation for the spectral components of the overburden, for given values of the electrical and geometrical parameters of the model, has been computed. This result allowed to determine an approximate value of the variation of the electric field on the top of the overburden in the direction perpendicular to the strike of the dike. The results demonstrate the efficiency of this forward electromagnetic modeling, and are fundamental for the interpretation of VLF and Magnetotelluric data.

  18. Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves

    International Nuclear Information System (INIS)

    Mitri, F. G.

    2015-01-01

    The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries

  19. Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves

    Energy Technology Data Exchange (ETDEWEB)

    Mitri, F. G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology–ETC, Santa Fe, New Mexico 87508 (United States)

    2015-12-07

    The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.

  20. Mobile ultrasound plane wave beamforming on iPhone or iPad using metal-based GPU processing

    OpenAIRE

    Hewener, H.; Tretbar, S.

    2015-01-01

    Mobile and cost effective ultrasound devices are being used in point of care scenarios or the drama room. To reduce the costs of such devices we already presented the possibilities of consumer devices like Apple iPad for full signal processing of raw data for ultraound image generation. Using technologies like plane wave imaging to generate a full image with only one excitation/reception event the acquisition times and power consumption of ultrasound imaging can be reduced for low power mobil...

  1. Comparison of the projector augmented-wave, pseudopotential, and linearized augmented-plane-wave formalisms for density-functional calculations of solids

    International Nuclear Information System (INIS)

    Holzwarth, N.A.; Matthews, G.E.; Dunning, R.B.; Tackett, A.R.; Zeng, Y.

    1997-01-01

    The projector augmented-wave (PAW) method was developed by Bloechl as a method to accurately and efficiently calculate the electronic structure of materials within the framework of density-functional theory. It contains the numerical advantages of pseudopotential calculations while retaining the physics of all-electron calculations, including the correct nodal behavior of the valence-electron wave functions and the ability to include upper core states in addition to valence states in the self-consistent iterations. It uses many of the same ideas developed by Vanderbilt in his open-quotes soft pseudopotentialclose quotes formalism and in earlier work by Bloechl in his open-quotes generalized separable potentials,close quotes and has been successfully demonstrated for several interesting materials. We have developed a version of the PAW formalism for general use in structural and dynamical studies of materials. In the present paper, we investigate the accuracy of this implementation in comparison with corresponding results obtained using pseudopotential and linearized augmented-plane-wave (LAPW) codes. We present results of calculations for the cohesive energy, equilibrium lattice constant, and bulk modulus for several representative covalent, ionic, and metallic materials including diamond, silicon, SiC, CaF 2 , fcc Ca, and bcc V. With the exception of CaF 2 , for which core-electron polarization effects are important, the structural properties of these materials are represented equally well by the PAW, LAPW, and pseudopotential formalisms. copyright 1997 The American Physical Society

  2. Three-dimensional shear wave elastography for differentiation of breast lesions: An initial study with quantitative analysis using three orthogonal planes.

    Science.gov (United States)

    Wang, Qiao

    2018-05-25

    To prospectively evaluate the diagnostic performance of three-dimensional (3D) shear wave elastography (SWE) for breast lesions with quantitative stiffness information from transverse, sagittal and coronal planes. Conventional ultrasound (US), two-dimensional (2D)-SWE and 3D-SWE were performed for 122 consecutive patients with 122 breast lesions before biopsy or surgical excision. Maximum elasticity values of Young's modulus (Emax) were recorded on 2D-SWE and three planes of 3D-SWE. Area under the receiver operating characteristic curve (AUC), sensitivity and specificity of US, 2D-SWE and 3D-SWE were evaluated. Two combined sets (i.e., BI-RADS and 2D-SWE; BI-RADS and 3D-SWE) were compared in AUC. Observer consistency was also evaluated. On 3D-SWE, the AUC and sensitivity of sagittal plane were significantly higher than those of transverse and coronal planes (both P 0.05). However, the combined set of BI-RADS and sagittal plane of 3D-SWE had significantly higher sensitivity than the combined set of BI-RADS and 2D-SWE. The sagittal plane shows the best diagnostic performance among 3D-SWE. The combination of BI-RADS and 3D-SWE is a useful tool for predicting breast malignant lesions in comparison with BI-RADS alone.

  3. DFT LCAO and plane wave calculations of SrZrO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Evarestov, R.A.; Bandura, A.V.; Alexandrov, V.E. [Department of Quantum Chemistry, St. Petersburg State University, 26 Universitetskiy Prospekt, Stary Peterhof 198504 (Russian Federation); Kotomin, E.A. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr. 1, 70569, Stuttgart (Germany)

    2005-02-01

    The results of the density functional (DFT) LCAO and plane wave (PW) calculations of the electronic and structural properties of four known SrZrO{sub 3} phases (Pm3m, I4/mcm, Cmcm and Pbnm) are presented and discussed. The calculated unit cell energies and relative stability of these phases agree well with the experimental sequence of SrZrO{sub 3} phases as the temperature increases. The lattice structure parameters optimized in the PW calculations for all four phases are in good agreement with the experimental neutron diffraction data. The LCAO and PW results for the electronic structure, density of states and chemical bonding in the cubic phase (Pm3m) are discussed in detail and compared with the results of previous PW calculations. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Progress in parallel implementation of the multilevel plane wave time domain algorithm

    KAUST Repository

    Liu, Yang

    2013-07-01

    The computational complexity and memory requirements of classical schemes for evaluating transient electromagnetic fields produced by Ns dipoles active for Nt time steps scale as O(NtN s 2) and O(Ns 2), respectively. The multilevel plane wave time domain (PWTD) algorithm [A.A. Ergin et al., Antennas and Propagation Magazine, IEEE, vol. 41, pp. 39-52, 1999], viz. the extension of the frequency domain fast multipole method (FMM) to the time domain, reduces the above costs to O(NtNslog2Ns) and O(Ns α) with α = 1.5 for surface current distributions and α = 4/3 for volumetric ones. Its favorable computational and memory costs notwithstanding, serial implementations of the PWTD scheme unfortunately remain somewhat limited in scope and ill-suited to tackle complex real-world scattering problems, and parallel implementations are called for. © 2013 IEEE.

  5. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  6. Propagation of sound waves in ducts

    DEFF Research Database (Denmark)

    Jacobsen, Finn

    2000-01-01

    Plane wave propagation in ducts with rigid walls, radiation from ducts, classical four-pole theory for composite duct systems, and three-dimentional waves in wave guides of various cross-sectional shape are described.......Plane wave propagation in ducts with rigid walls, radiation from ducts, classical four-pole theory for composite duct systems, and three-dimentional waves in wave guides of various cross-sectional shape are described....

  7. Evaluation of the Electromagnetic Power Absorption in Humans Exposed to Plane Waves: The Effect of Breathing Activity

    Directory of Open Access Journals (Sweden)

    Marta Cavagnaro

    2013-01-01

    Full Text Available The safety aspects of the exposure of people to uniform plane waves in the frequency range from 900 MHz to 5 GHz are analyzed. Starting from a human body model available in the literature, representing a man in resting state, two new anatomical models are considered, representing different phases of the respiratory activity: tidal breath and deep breath. These models have been used to evaluate the whole body Specific Absorption Rate (SAR and the 10-g averaged and 1-g averaged SAR. The analysis is performed using a parallel implementation of the finite difference time domain method. A uniform plane wave, with vertical polarization, is used as an incident field since this is the canonical exposure situation used in safety guidelines. Results show that if the incident electromagnetic field is compliant with the reference levels promulgated by the International Commission on Non-Ionizing Radiation Protection and by IEEE, the computed SAR values are lower than the corresponding basic restrictions, as expected. On the other side, when the Federal Communications Commission reference levels are considered, 1-g SAR values exceeding the basic restrictions for exposure at 4 GHz and above are obtained. Furthermore, results show that the whole body SAR values increase passing from the resting state model to the deep breath model, for all the considered frequencies.

  8. Fast Plane Wave 2-D Vector Flow Imaging Using Transverse Oscillation and Directional Beamforming

    DEFF Research Database (Denmark)

    Jensen, Jonas; Villagómez Hoyos, Carlos Armando; Stuart, Matthias Bo

    2017-01-01

    load, which is 4.6 times larger than for TO and seven times smaller than for conventional DB. Steered plane wave transmissions are employed for high frame rate imaging, and parabolic flow with a peak velocity of 0.5 m/s is simulated in straight vessels at beamto- flow angles from 45 to 90. The TO......-DB method estimates the angle with a bias and standard deviation (SD) less than 2, and the SD of the velocity magnitude is less than 2%. When using only TO, the SD of the angle ranges from 2 to 17 and for the velocity magnitude up to 7%. Bias of the velocity magnitude is within 2% for TO and slightly larger...

  9. Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

    International Nuclear Information System (INIS)

    Angus, J. R.; Krasheninnikov, S. I.; Smolyakov, A. I.

    2010-01-01

    The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth δ a when δ a a >>L, the heating is shown to decay with 1/δ a 3 . The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

  10. Fast plane wave density functional theory molecular dynamics calculations on multi-GPU machines

    International Nuclear Information System (INIS)

    Jia, Weile; Fu, Jiyun; Cao, Zongyan; Wang, Long; Chi, Xuebin; Gao, Weiguo; Wang, Lin-Wang

    2013-01-01

    Plane wave pseudopotential (PWP) density functional theory (DFT) calculation is the most widely used method for material simulations, but its absolute speed stagnated due to the inability to use large scale CPU based computers. By a drastic redesign of the algorithm, and moving all the major computation parts into GPU, we have reached a speed of 12 s per molecular dynamics (MD) step for a 512 atom system using 256 GPU cards. This is about 20 times faster than the CPU version of the code regardless of the number of CPU cores used. Our tests and analysis on different GPU platforms and configurations shed lights on the optimal GPU deployments for PWP-DFT calculations. An 1800 step MD simulation is used to study the liquid phase properties of GaInP

  11. CMS-Wave

    Science.gov (United States)

    2015-10-30

    Coastal Inlets Research Program CMS -Wave CMS -Wave is a two-dimensional spectral wind-wave generation and transformation model that employs a forward...marching, finite-difference method to solve the wave action conservation equation. Capabilities of CMS -Wave include wave shoaling, refraction... CMS -Wave can be used in either on a half- or full-plane mode, with primary waves propagating from the seaward boundary toward shore. It can

  12. Applicability of geometrical optics to in-plane liquid-crystal configurations.

    Science.gov (United States)

    Sluijter, M; Xu, M; Urbach, H P; de Boer, D K G

    2010-02-15

    We study the applicability of geometrical optics to inhomogeneous dielectric nongyrotropic optically anisotropic media typically found in in-plane liquid-crystal configurations with refractive indices n(o)=1.5 and n(e)=1.7. To this end, we compare the results of advanced ray- and wave-optics simulations of the propagation of an incident plane wave to a special anisotropic configuration. Based on the results, we conclude that for a good agreement between ray and wave optics, a maximum change in optical properties should occur over a distance of at least 20 wavelengths.

  13. Plane-wave and common-translation-factor treatments of He2++H collisions at high velocities

    International Nuclear Information System (INIS)

    Errea, L.F.; Harel, C.; Jouin, H.; Maidagan, J.M.; Mendez, L.; Pons, B.; Riera, A.

    1992-01-01

    We complement previous work that showed that the molecular approach, modified with plane-wave translation factors, is able to reproduce the fall of charge-exchange cross sections in He 2+ +H collisions, by presenting the molecular data, and studying the corresponding mechanism. We test the accuracy of simplifications of the method that have been employed in the literature, and that lead to very simple calculations. We show that the common-translation-factor method is also successful at high nuclear velocities, provided that sufficiently excited states are included in the basis; moreover, it yields a simple picture of the mechanism and a description of ionization processes at high velocities

  14. Density fitting for derivatives of Coulomb integrals in ab initio calculations using mixed Gaussian and plane-wave basis

    Czech Academy of Sciences Publication Activity Database

    Čársky, Petr

    2009-01-01

    Roč. 109, č. 620 (2009), s. 1237-1242 ISSN 0020-7608 R&D Projects: GA ČR GA203/07/0070; GA ČR GA202/08/0631; GA AV ČR 1ET400400413; GA AV ČR IAA100400501 Institutional research plan: CEZ:AV0Z40400503 Keywords : Derivatives of Coulomb integrals * mixed Gaussian and plane-wave basis sets * electron scattering * computer time saving Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.315, year: 2009

  15. Magnetoelastic plane waves in rotating media in thermoelasticity of type II (G-N model

    Directory of Open Access Journals (Sweden)

    S. K. Roychoudhuri

    2004-01-01

    Full Text Available A study is made of the propagation of time-harmonic plane waves in an infinite, conducting, thermoelastic solid permeated by a uniform primary external magnetic field when the entire medium is rotating with a uniform angular velocity. The thermoelasticity theory of type II (G-N model (1993 is used to study the propagation of waves. A more general dispersion equation is derived to determine the effects of rotation, thermal parameters, characteristic of the medium, and the external magnetic field. If the primary magnetic field has a transverse component, it is observed that the longitudinal and transverse motions are linked together. For low frequency (χ≪1, χ being the ratio of the wave frequency to some standard frequency ω∗, the rotation and the thermal field have no effect on the phase velocity to the first order of χ and then this corresponds to only one slow wave influenced by the electromagnetic field only. But to the second order of χ, the phase velocity, attenuation coefficient, and the specific energy loss are affected by rotation and depend on the thermal parameters cT, cT being the nondimensional thermal wave speed of G-N theory, and the thermoelastic coupling εT, the electromagnetic parameters εH, and the transverse magnetic field RH. Also for large frequency, rotation and thermal field have no effect on the phase velocity, which is independent of primary magnetic field to the first order of (1/χ (χ≫1, and the specific energy loss is a constant, independent of any field parameter. However, to the second order of (1/χ, rotation does exert influence on both the phase velocity and the attenuation factor, and the specific energy loss is affected by rotation and depends on the thermal parameters cT and εT, electromagnetic parameter εH, and the transverse magnetic field RH, whereas the specific energy loss is independent of any field parameters to the first order of (1/χ.

  16. The effect of lower-hybrid waves on the propagation of hydromagnetic waves

    International Nuclear Information System (INIS)

    Hamabata, Hiromitsu; Namikawa, Tomikazu; Mori, Kazuhiro

    1988-01-01

    Propagation characteristics of hydromagnetic waves in a magnetic plasma are investigated using the two-plasma fluid equations including the effect of lower-hybrid waves propagating perpendicularly to the magnetic field. The effect of lower-hybrid waves on the propagation of hydromagnetic waves is analysed in terms of phase speed, growth rate, refractive index, polarization and the amplitude relation between the density perturbation and the magnetic-field perturbation for the cases when hydromagnetic waves propagate in the plane whose normal is perpendicular to both the magnetic field and the propagation direction of lower-hybrid waves and in the plane perpendicular to the propagation direction of lower-hybrid waves. It is shown that hydromagnetic waves propagating at small angles to the propagation direction of lower-hybrid waves can be excited by the effect of lower-hybrid waves and the energy of excited waves propagates nearly parallel to the propagation direction of lower-hybrid waves. (author)

  17. Coherent field propagation between tilted planes.

    Science.gov (United States)

    Stock, Johannes; Worku, Norman Girma; Gross, Herbert

    2017-10-01

    Propagating electromagnetic light fields between nonparallel planes is of special importance, e.g., within the design of novel computer-generated holograms or the simulation of optical systems. In contrast to the extensively discussed evaluation between parallel planes, the diffraction-based propagation of light onto a tilted plane is more burdensome, since discrete fast Fourier transforms cannot be applied directly. In this work, we propose a quasi-fast algorithm (O(N 3  log N)) that deals with this problem. Based on a proper decomposition into three rotations, the vectorial field distribution is calculated on a tilted plane using the spectrum of plane waves. The algorithm works on equidistant grids, so neither nonuniform Fourier transforms nor an explicit complex interpolation is necessary. The proposed algorithm is discussed in detail and applied to several examples of practical interest.

  18. Neoclassical Solution of Transient Interaction of Plane Acoustic Waves with a Spherical Elastic Shell

    Directory of Open Access Journals (Sweden)

    Hanson Huang

    1996-01-01

    Full Text Available A detailed solution to the transient interaction of plane acoustic waves with a spherical elastic shell was obtained more than a quarter of a century ago based on the classical separation of variables, series expansion, and Laplace transform techniques. An eight-term summation of the time history series was sufficient for the convergence of the shell deflection and strain, and to a lesser degree, the shell velocity. Since then, the results have been used routinely for validation of solution techniques and computer methods for the evaluation of underwater explosion response of submerged structures. By utilizing modern algorithms and exploiting recent advances of computer capacities and floating point mathematics, sufficient terms of the inverse Laplace transform series solution can now be accurately computed. Together with the application of the Cesaro summation using up to 70 terms of the series, two primary deficiencies of the previous solution are now remedied: meaningful time histories of higher time derivative data such as acceleration and pressure are now generated using a sufficient number of terms in the series; and uniform convergence around the discontinuous step wave front is now obtained, completely eradicating spurious oscillations due to the Gibbs' phenomenon. New results of time histories of response items of interest are presented.

  19. Covariant quantum mechanics on a null plane

    International Nuclear Information System (INIS)

    Leutwyler, H.; Stern, J.

    1977-03-01

    Lorentz invariance implies that the null plane wave functions factorize into a kinematical part describing the motion of the system as a whole and an inner wave function that involves the specific dynamical properties of the system - in complete correspondence with the non-relativistic situation. Covariance is equivalent to an angular condition which admits non-trivial solutions

  20. Reflection and Transmission of Plane Electromagnetic Waves by a Geologic Layer.

    Energy Technology Data Exchange (ETDEWEB)

    Aldridge, David F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-04-01

    Electric field and magnetic field reflection and transmission responses generated by a plane wave normally incident onto a finite - thickness geologic layer are mathematically derived and numerically evaluated. A thin layer with enhanced electric current conductivity and/or magnetic permeability is a reasonable geophysical representation of a hydraulic fracture inject ed with a high - contrast proppant pack. Both theory and numerics indicate that backward - and forward - scattered electromagnetic wavefields are potentially observable in a field experiment, despite the extreme thinness of a fracture compared to a typical low - frequency electromagnetic wavelength. The First Born Approximation (FBA) representation of layer scattering, significant for inversion studies, is shown to be accurate for a thin layer with mild medium parameter (i.e., conductivity, permeability, and per mittivity) contrasts with the surrounding homogeneous wholespace. However, FBA scattering theory breaks down for thick layers and strong parameter contrasts. ACKNOWLEDGEMENTS Sandia National Laboratories is a multi - mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000. This research is conducted under the auspices of CRADA (Cooperative Research and Development Agreement) SC11/01780.00 between Carbo Ceramics Inc. and Sandia National Laboratories. The author acknowledges former Carbo R&D Vic e - President Mr. Chad Cannan and former SNL Geophysics Department manage r Ms. Amy Halloran for their interest i n and support of this work. Technical discussions with Project Manager and Principal Investigator Dr. Chester J. Weiss of the SNL Geophysics Department greatly benefited this work. Dr. Lewis C. Bartel, formerly with S NL and presently a consultant to Carbo Ceramics, provided many useful and intuitive insights, and

  1. Wave phenomena

    CERN Document Server

    Towne, Dudley H

    1988-01-01

    This excellent undergraduate-level text emphasizes optics and acoustics, covering inductive derivation of the equation for transverse waves on a string, acoustic plane waves, boundary-value problems, polarization, three-dimensional waves and more. With numerous problems (solutions for about half). ""The material is superbly chosen and brilliantly written"" - Physics Today. Problems. Appendices.

  2. In-plane angular dependence of the spin-wave nonreciprocity of an ultrathin film with Dzyaloshinskii-Moriya interaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Vanessa Li; Di, Kai; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau, E-mail: phykmh@nus.edu.sg [Department of Physics, National University of Singapore, Singapore 117551 (Singapore); Yu, Jiawei; Yoon, Jungbum; Qiu, Xuepeng; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2015-07-13

    The nonreciprocal propagation of spin waves in an ultrathin Pt/Co/Ni film has been measured by Brillouin light scattering. The frequency nonreciprocity, due to the interfacial Dzyaloshinskii-Moriya interaction (DMI), has a sinusoidal dependence on the in-plane angle between the magnon wavevector and the applied magnetic field. The results, which are in good agreement with analytical predictions reported earlier, yield a value of the DMI constant which is the same as that obtained previously from a study of the magnon dispersion relations. We have demonstrated that our magnon-dynamics based method can experimentally ascertain the DMI constant of multilayer thin films.

  3. The plain truth about forming a plane wave of neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Wagh, Apoorva G., E-mail: nintsspd@barc.gov.i [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Abbas, Sohrab [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Treimer, Wolfgang [Helmholtz Zentrum Berlin, Glienicker Str. 100, D-14109 Berlin (Germany)

    2011-04-01

    We have attained the first sub-arcsecond collimation of a monochromatic neutron beam by diffracting neutrons from a Bragg prism, viz. a single crystal prism operating in the vicinity of Bragg incidence. Analytical as well numerical computations based on the dynamical diffraction theory, led to the optimised collimator configuration of a silicon {l_brace}1 1 1{r_brace} Bragg prism for 5.26 A neutrons. We fabricated a Bragg prism to these specifications, tested and operated it at the double diffractometer setup in Helmholtz Zentrum Berlin to produce a 0.58 arcsec wide monochromatic neutron beam. With a similarly optimised Bragg prism analyser of opposite asymmetry, we recorded a 0.62 arcsec wide virgin rocking curve for this ultra-parallel beam. With this nearly plane-wave neutron beam, we have recorded the first ever USANS spectrum in Q{approx}10{sup -6} A{sup -1} range with a hydroxyapatite casein protein sample and demonstrated the instrument capability to characterise agglomerates up to 150 {mu}m in size. The super-collimated monochromatic beam has also enabled us to record the first neutron diffraction pattern from a macroscopic grating of 200 {mu}m period. The transverse coherence length of 175 {mu}m (FWHM) of the ultra-parallel beam derived from the analysis of this pattern, is the greatest achieved to date for A wavelength neutrons.

  4. A phase-plane analysis of localized frictional waves

    Science.gov (United States)

    Putelat, T.; Dawes, J. H. P.; Champneys, A. R.

    2017-07-01

    Sliding frictional interfaces at a range of length scales are observed to generate travelling waves; these are considered relevant, for example, to both earthquake ground surface movements and the performance of mechanical brakes and dampers. We propose an explanation of the origins of these waves through the study of an idealized mechanical model: a thin elastic plate subject to uniform shear stress held in frictional contact with a rigid flat surface. We construct a nonlinear wave equation for the deformation of the plate, and couple it to a spinodal rate-and-state friction law which leads to a mathematically well-posed problem that is capable of capturing many effects not accessible in a Coulomb friction model. Our model sustains a rich variety of solutions, including periodic stick-slip wave trains, isolated slip and stick pulses, and detachment and attachment fronts. Analytical and numerical bifurcation analysis is used to show how these states are organized in a two-parameter state diagram. We discuss briefly the possible physical interpretation of each of these states, and remark also that our spinodal friction law, though more complicated than other classical rate-and-state laws, is required in order to capture the full richness of wave types.

  5. Experimental and numerical study of guided wave propagation in a thin metamaterial plate

    International Nuclear Information System (INIS)

    Zhu, R.; Huang, G.L.; Huang, H.H.; Sun, C.T.

    2011-01-01

    In this Letter, both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. Through the numerical simulation, a new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. Experiments were conducted to validate the numerical design. In the experiment, piezoelectric transducers were used to generate and receive guided wave signals. The results show that the numerical predictions are in very good agreement with the experimental measurements. Specifically, the connection between the local resonance in the thin plate and its wave attenuation mechanism was discussed. -- Highlights: → Both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. → A new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. → Experiments were conducted to validate the numerical design. → The connection between the local resonance in the thin plate and its wave attenuation mechanism was investigated.

  6. Rayleigh-wave phase-velocity maps and three-dimensional shear velocity structure of the western US from local non-plane surface wave tomography

    Science.gov (United States)

    Pollitz, F.F.; Snoke, J. Arthur

    2010-01-01

    We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the first step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by defining a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local fits to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images confirm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat flow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high

  7. Generation and Propagation of Finite-Amplitude Waves in Flexible Tubes (A)

    DEFF Research Database (Denmark)

    Jensen, Leif Bjørnø

    1972-01-01

    Highly reproducible finite-amplitude waves, generated by a modified electromagnetic plane-wave generator, characterized by a rise time......Highly reproducible finite-amplitude waves, generated by a modified electromagnetic plane-wave generator, characterized by a rise time...

  8. Statistics for long irregular wave run-up on a plane beach from direct numerical simulations

    Science.gov (United States)

    Didenkulova, Ira; Senichev, Dmitry; Dutykh, Denys

    2017-04-01

    -975 (2011). [2] P. Denissenko, I. Didenkulova, A. Rodin, M. Listak, E. Pelinovsky. Experimental statistics of long wave runup on a plane beach. Journal of Coastal Research 65, 195-200 (2013). [3] I. Didenkulova, E. Pelinovsky, A. Sergeeva. Statistical characteristics of long waves nearshore. Coastal Engineering 58, 94-102 (2011). [4] D. Dutykh, T. Katsaounis, D. Mitsotakis. Finite volume schemes for dispersive wave propagation and runup. J. Comput. Phys. 230 (8), 3035-3061 (2011a). [5] D. Dutykh, C. Labart, D. Mitsotakis. Long wave run-up on random beaches. Phys. Rev. Lett. 107, 184504 (2011b).

  9. Designing broad phononic band gaps for in-plane modes

    Science.gov (United States)

    Li, Yang Fan; Meng, Fei; Li, Shuo; Jia, Baohua; Zhou, Shiwei; Huang, Xiaodong

    2018-03-01

    Phononic crystals are known as artificial materials that can manipulate the propagation of elastic waves, and one essential feature of phononic crystals is the existence of forbidden frequency range of traveling waves called band gaps. In this paper, we have proposed an easy way to design phononic crystals with large in-plane band gaps. We demonstrated that the gap between two arbitrarily appointed bands of in-plane mode can be formed by employing a certain number of solid or hollow circular rods embedded in a matrix material. Topology optimization has been applied to find the best material distributions within the primitive unit cell with maximal band gap width. Our results reveal that the centroids of optimized rods coincide with the point positions generated by Lloyd's algorithm, which deepens our understandings on the formation mechanism of phononic in-plane band gaps.

  10. Time-domain analytic Solutions of two-wire transmission line excited by a plane-wave field

    Institute of Scientific and Technical Information of China (English)

    Ni Gu-Yan; Yan Li; Yuan Nai-Chang

    2008-01-01

    This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain.By the frequency-domain Baum-Liu-Tesche(BLT)equation,the time-domain analytic solutions are obtained and expressed in an infinite geometric series.Moreover,it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval.In other word.the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval.The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform,and the agreement is excellent.

  11. Three-dimensional sheaf of ultrasound planes reconstruction (SOUPR) of ablated volumes.

    Science.gov (United States)

    Ingle, Atul; Varghese, Tomy

    2014-08-01

    This paper presents an algorithm for 3-D reconstruction of tumor ablations using ultrasound shear wave imaging with electrode vibration elastography. Radio-frequency ultrasound data frames are acquired over imaging planes that form a subset of a sheaf of planes sharing a common axis of intersection. Shear wave velocity is estimated separately on each imaging plane using a piecewise linear function fitting technique with a fast optimization routine. An interpolation algorithm then computes velocity maps on a fine grid over a set of C-planes that are perpendicular to the axis of the sheaf. A full 3-D rendering of the ablation can then be created from this stack of C-planes; hence the name "Sheaf Of Ultrasound Planes Reconstruction" or SOUPR. The algorithm is evaluated through numerical simulations and also using data acquired from a tissue mimicking phantom. Reconstruction quality is gauged using contrast and contrast-to-noise ratio measurements and changes in quality from using increasing number of planes in the sheaf are quantified. The highest contrast of 5 dB is seen between the stiffest and softest regions of the phantom. Under certain idealizing assumptions on the true shape of the ablation, good reconstruction quality while maintaining fast processing rate can be obtained with as few as six imaging planes suggesting that the method is suited for parsimonious data acquisitions with very few sparsely chosen imaging planes.

  12. Curvature collineations for the field of gravitational waves

    International Nuclear Information System (INIS)

    Singh, K.P.; Singh, Gulab

    1981-01-01

    It has been shown that the space-times formed from a plane-fronted gravity wave and from a plane sandwich wave with constant polarisation admit proper curvature collineation in general. The curvature collineation vectors have been determined explicitly. (author)

  13. Time-domain analytic solutions of two-wire transmission line excited by a plane-wave field

    International Nuclear Information System (INIS)

    Ni Guyan; Yan Li; Yuan Naichang

    2008-01-01

    This paper reports that an analytic method is used to calculate the load responses of the two-wire transmission line excited by a plane-wave directly in the time domain. By the frequency-domain Baum–Liu–Tesche (BLT) equation, the time-domain analytic solutions are obtained and expressed in an infinite geometric series. Moreover, it is shown that there exist only finite nonzero terms in the infinite geometric series if the time variate is at a finite interval. In other word, the time-domain analytic solutions are expanded in a finite geometric series indeed if the time variate is at a finite interval. The computed results are subsequently compared with transient responses obtained by using the frequency-domain BLT equation via a fast Fourier transform, and the agreement is excellent. (the physics of elementary particles and fields)

  14. Integrable open spin chain in Super Yang-Mills and the plane-wave/SYM duality

    International Nuclear Information System (INIS)

    Chen Bin; Wang Xiaojun; Wu Yongshi

    2004-01-01

    We investigate the integrable structures in an N = 2 superconfomal Sp(N) Yang-Mills theory with matter, which is dual to an open+closed string system. We restrict ourselves to the BMN operators that correspond to free string states. In the closed string sector, an integrable structure is inherited from its parent theory, N = 4 SYM. For the open string sector, the planar one-loop mixing matrix for gauge invariant holomorphic operators is identified with the Hamiltonian of an integrable SU(3) open spin chain. Using the K-matrix formalism we identify the integrable open-chain boundary conditions that correspond to string boundary conditions. The solutions to the algebraic Bethe ansatz equations (ABAE) with a few impurities are shown to recover the anomalous dimensions that exactly match the spectrum of free open string in the plane-wave background. We also discuss the properties of the solutions of ABAE beyond the BMN regime. (author)

  15. Three Dimensional Sheaf of Ultrasound Planes Reconstruction (SOUPR) of Ablated Volumes

    Science.gov (United States)

    Ingle, Atul; Varghese, Tomy

    2014-01-01

    This paper presents an algorithm for three dimensional reconstruction of tumor ablations using ultrasound shear wave imaging with electrode vibration elastography. Radiofrequency ultrasound data frames are acquired over imaging planes that form a subset of a sheaf of planes sharing a common axis of intersection. Shear wave velocity is estimated separately on each imaging plane using a piecewise linear function fitting technique with a fast optimization routine. An interpolation algorithm then computes velocity maps on a fine grid over a set of C-planes that are perpendicular to the axis of the sheaf. A full three dimensional rendering of the ablation can then be created from this stack of C-planes; hence the name “Sheaf Of Ultrasound Planes Reconstruction” or SOUPR. The algorithm is evaluated through numerical simulations and also using data acquired from a tissue mimicking phantom. Reconstruction quality is gauged using contrast and contrast-to-noise ratio measurements and changes in quality from using increasing number of planes in the sheaf are quantified. The highest contrast of 5 dB is seen between the stiffest and softest regions of the phantom. Under certain idealizing assumptions on the true shape of the ablation, good reconstruction quality while maintaining fast processing rate can be obtained with as few as 6 imaging planes suggesting that the method is suited for parsimonious data acquisitions with very few sparsely chosen imaging planes. PMID:24808405

  16. Radiation and propagation of electromagnetic waves

    CERN Document Server

    Tyras, George; Declaris, Nicholas

    1969-01-01

    Radiation and Propagation of Electromagnetic Waves serves as a text in electrical engineering or electrophysics. The book discusses the electromagnetic theory; plane electromagnetic waves in homogenous isotropic and anisotropic media; and plane electromagnetic waves in inhomogenous stratified media. The text also describes the spectral representation of elementary electromagnetic sources; the field of a dipole in a stratified medium; and radiation in anisotropic plasma. The properties and the procedures of Green's function method of solution, axial currents, as well as cylindrical boundaries a

  17. Precursor Wave Emission Enhanced by Weibel Instability in Relativistic Shocks

    Science.gov (United States)

    Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro; Matsumoto, Yosuke

    2018-05-01

    We investigated the precursor wave emission efficiency in magnetized purely perpendicular relativistic shocks in pair plasmas. We extended our previous study to include the dependence of upstream magnetic field orientations. We performed two-dimensional particle-in-cell simulations and focused on two magnetic field orientations: the magnetic field in the simulation plane (i.e., in-plane configuration) and that perpendicular to the simulation plane (i.e., out-of-plane configuration). Our simulations in the in-plane configuration demonstrated that not only extraordinary but also ordinary mode waves are excited. We quantified the emission efficiency as a function of the magnetization parameter σ e and found that the large-amplitude precursor waves are emitted for a wide range of σ e . We found that especially at low σ e , the magnetic field generated by Weibel instability amplifies the ordinary mode wave power. The amplitude is large enough to perturb the upstream plasma, and transverse density filaments are generated as in the case of the out-of-plane configuration investigated in the previous study. We confirmed that our previous conclusion holds regardless of upstream magnetic field orientations with respect to the two-dimensional simulation plane. We discuss the precursor wave emission in three dimensions and the feasibility of wakefield acceleration in relativistic shocks based on our results.

  18. Pixel-size-maintained image reconstruction of digital holograms on arbitrarily tilted planes by the angular spectrum method.

    Science.gov (United States)

    Jeong, Seung Jun; Hong, Chung Ki

    2008-06-01

    We present an effective method for the pixel-size-maintained reconstruction of images on arbitrarily tilted planes in digital holography. The method is based on the plane wave expansion of the diffraction wave fields and the three-axis rotation of the wave vectors. The images on the tilted planes are reconstructed without loss of the frequency contents of the hologram and have the same pixel sizes. Our method shows good results in the extreme cases of large tilting angles and in the region closer than the paraxial case. The effectiveness of the method is demonstrated by both simulation and experiment.

  19. Wave-equation Migration Velocity Analysis Using Plane-wave Common Image Gathers

    KAUST Repository

    Guo, Bowen; Schuster, Gerard T.

    2017-01-01

    Wave-equation migration velocity analysis (WEMVA) based on subsurface-offset, angle domain or time-lag common image gathers (CIGs) requires significant computational and memory resources because it computes higher dimensional migration images

  20. Characteristic wave fronts in magnetohydrodynamics

    International Nuclear Information System (INIS)

    Menon, V.V.; Sharma, V.D.

    1981-01-01

    The influence of magnetic field on the process of steepening or flattening of the characteristic wave fronts in a plane and cylindrically symmetric motion of an ideal plasma is investigated. This aspect of the problem has not been considered until now. Remarkable differences between plane, cylindrical diverging, and cylindrical converging waves are discovered. The discontinuity in the velocity gradient at the wave front is shown to satisfy a Bernoulli-type equation. The discussion of the solutions of such equations reported in the literature is shown to be incomplete, and three general theorems are established. 18 refs

  1. Response of a Doppler canceling system to plane gravitational waves

    International Nuclear Information System (INIS)

    Caporali, A.

    1982-01-01

    This paper discusses the interaction of long periodic gravitational waves with a three-link microwave system known as the Doppler canceling system. This system, which was developed for gravitational red-shift experiment, uses one-way and two-way Doppler information to construct the beat signal of two reference oscillators moving with respect to each other. The geometric-optics approximation is used to derive the frequency shift produced on a light signal propagating in a gravitational-wave space-time. The signature left on the Doppler-canceled beat by bursts and continuous gravitational waves is analyzed. A comparison is made between the response to gravitational waves of the Doppler canceling system and that of a (NASA) Doppler tracking system which employs two-way, round-trip radio waves. A threefold repetition of the gravitational wave form is found to be a common feature of the response functions of both systems. These two functions otherwise exhibit interesting differences

  2. Infragravity Waves Produced by Wave Groups on Beaches

    Institute of Scientific and Technical Information of China (English)

    邹志利; 常梅

    2003-01-01

    The generation of low frequency waves by a single or double wave groups incident upon two plane beaches with the slope of 1/40 and 1/100 is investigated experimentally and numerically. A new type of wave maker signal is used to generate the groups, allowing the bound long wave (set-down) to be included in the group. The experiments show that the low frequency wave is generated during breaking and propagation to the shoreline of the wave group. This process of generation and propagation of low frequency waves is simulated numerically by solving the short-wave averaged mass and momentum conservation equations. The computed and measured results are in good agreement. The mechanism of generation of low frequency waves in the surf zone is examined and discussed.

  3. Energy flow analysis of out-of-plane vibration in coplanar coupled finite Mindlin plates

    Directory of Open Access Journals (Sweden)

    Young-Ho Park

    2015-01-01

    Full Text Available : In this paper, an Energy Flow Analysis (EFA for coplanar coupled Mindlin plates was performed to estimate their dynamic responses at high frequencies. Mindlin plate theory can consider the effects of shear distortion and rotatory inertia, which are very important at high frequencies. For EFA for coplanar coupled Mindlin plates, the wave transmission and reflection relationship for progressing out-of-plane waves (out-of-plane shear wave, bending dominant flexural wave, and shear dominant flexural wave in coplanar coupled Mindlin plates was newly derived. To verify the validity of the EFA results, numerical analyses were performed for various cases where coplanar coupled Mindlin plates are excited by a harmonic point force, and the energy flow solutions for coplanar coupled Mindlin plates were compared with the classical solutions in the various conditions.

  4. Helicons in uniform fields. I. Wave diagnostics with hodograms

    Science.gov (United States)

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

    2018-03-01

    The wave equation for whistler waves is well known and has been solved in Cartesian and cylindrical coordinates, yielding plane waves and cylindrical waves. In space plasmas, waves are usually assumed to be plane waves; in small laboratory plasmas, they are often assumed to be cylindrical "helicon" eigenmodes. Experimental observations fall in between both models. Real waves are usually bounded and may rotate like helicons. Such helicons are studied experimentally in a large laboratory plasma which is essentially a uniform, unbounded plasma. The waves are excited by loop antennas whose properties determine the field rotation and transverse dimensions. Both m = 0 and m = 1 helicon modes are produced and analyzed by measuring the wave magnetic field in three dimensional space and time. From Ampère's law and Ohm's law, the current density and electric field vectors are obtained. Hodograms for these vectors are produced. The sign ambiguity of the hodogram normal with respect to the direction of wave propagation is demonstrated. In general, electric and magnetic hodograms differ but both together yield the wave vector direction unambiguously. Vector fields of the hodogram normal yield the phase flow including phase rotation for helicons. Some helicons can have locally a linear polarization which is identified by the hodogram ellipticity. Alternatively the amplitude oscillation in time yields a measure for the wave polarization. It is shown that wave interference produces linear polarization. These observations emphasize that single point hodogram measurements are inadequate to determine the wave topology unless assuming plane waves. Observations of linear polarization indicate wave packets but not plane waves. A simple qualitative diagnostics for the wave polarization is the measurement of the magnetic field magnitude in time. Circular polarization has a constant amplitude; linear polarization results in amplitude modulations.

  5. Evaluation of uterine peristalsis using cine MRI on the coronal plane in comparison with the sagittal plane.

    Science.gov (United States)

    Shitano, Fuki; Kido, Aki; Kataoka, Masako; Fujimoto, Koji; Kiguchi, Kayo; Fushimi, Yasutaka; Togashi, Kaori

    2016-01-01

    Uterine peristalsis is supposed to be closely related to the early stages of reproduction. Sperms are preferentially transported from the uterine cervix to the side of the tube with the dominant follicle. However, with respect to magnetic resonance imaging (MRI), uterine peristalsis has only been evaluated at the sagittal plane of cine MRI. To evaluate and compare uterine peristalsis both on sagittal and coronal planes using cine MRI. Internal ethics committee approval was obtained, and subjects provided informed written consent. Thirty-one women underwent MRI scans in the periovulatory phase of the menstrual cycle. Cine MR images obtained by fast advanced spin echo sequence at 3-T field strength magnet (Toshiba Medical Systems) were visually evaluated by two independent radiologists. The frequency and the direction of peristalsis, and the presence of outer myometrium conduction of signal intensities (OMC), were evaluated. The laterality of the dominant follicle was determined on axial images and compared with the peristaltic direction in fundus. The subjects in which peristaltic directions were more clearly recognized were significantly frequent in coronal planes than in sagittal planes (P < 0.05). There was no significant difference in the peristaltic frequency between the sagittal and the coronal plane. However, the OMC was more recognized in the coronal plane than in the sagittal plane (P < 0.05). Peristaltic waves conducted toward the possible ovulation side were observed in only three of the 10 subjects. OMC of uterine peristalsis was better demonstrated in the coronal plane compared to the sagittal plane. © The Foundation Acta Radiologica 2015.

  6. Propagation of Quasi-plane Nonlinear Waves in Tubes

    Directory of Open Access Journals (Sweden)

    P. Koníček

    2002-01-01

    Full Text Available This paper deals with possibilities of using the generalized Burgers equation and the KZK equation to describe nonlinear waves in circular ducts. A new method for calculating of diffraction effects taking into account boundary layer effects is described. The results of numerical solutions of the model equations are compared. Finally, the limits of validity of the used model equations are discussed with respect to boundary conditions and the radius of the circular duct. The limits of applicability of the KZK equation and the GBE equation for describing nonlinear waves in tubes are discussed.

  7. Plane-Wave Implementation and Performance of à-la-Carte Coulomb-Attenuated Exchange-Correlation Functionals for Predicting Optical Excitation Energies in Some Notorious Cases.

    Science.gov (United States)

    Bircher, Martin P; Rothlisberger, Ursula

    2018-06-12

    Linear-response time-dependent density functional theory (LR-TD-DFT) has become a valuable tool in the calculation of excited states of molecules of various sizes. However, standard generalized-gradient approximation and hybrid exchange-correlation (xc) functionals often fail to correctly predict charge-transfer (CT) excitations with low orbital overlap, thus limiting the scope of the method. The Coulomb-attenuation method (CAM) in the form of the CAM-B3LYP functional has been shown to reliably remedy this problem in many CT systems, making accurate predictions possible. However, in spite of a rather consistent performance across different orbital overlap regimes, some pitfalls remain. Here, we present a fully flexible and adaptable implementation of the CAM for Γ-point calculations within the plane-wave pseudopotential molecular dynamics package CPMD and explore how customized xc functionals can improve the optical spectra of some notorious cases. We find that results obtained using plane waves agree well with those from all-electron calculations employing atom-centered bases, and that it is possible to construct a new Coulomb-attenuated xc functional based on simple considerations. We show that such a functional is able to outperform CAM-B3LYP in some cases, while retaining similar accuracy in systems where CAM-B3LYP performs well.

  8. Noise characteristics analysis of short wave infrared InGaAs focal plane arrays

    Science.gov (United States)

    Yu, Chunlei; Li, Xue; Yang, Bo; Huang, Songlei; Shao, Xiumei; Zhang, Yaguang; Gong, Haimei

    2017-09-01

    The increasing application of InGaAs short wave infrared (SWIR) focal plane arrays (FPAs) in low light level imaging requires ultra-low noise FPAs. This paper presents the theoretical analysis of FPA noise, and point out that both dark current and detector capacitance strongly affect the FPA noise. The impact of dark current and detector capacitance on FPA noise is compared in different situations. In order to obtain low noise performance FPAs, the demand for reducing detector capacitance is higher especially when pixel pitch is smaller, integration time is shorter, and integration capacitance is larger. Several InGaAs FPAs were measured and analyzed, the experiments' results could be well fitted to the calculated results. The study found that the major contributor of FPA noise is coupled noise with shorter integration time. The influence of detector capacitance on FPA noise is more significant than that of dark current. To investigate the effect of detector performance on FPA noise, two kinds of photodiodes with different concentration of the absorption layer were fabricated. The detectors' performance and noise characteristics were measured and analyzed, the results are consistent with that of theoretical analysis.

  9. Beam Dynamics a Integrated Plane Wave Transformer Photoinjector at S- and X- band

    Science.gov (United States)

    Rosenzweig, J. B.; Ding, X.; Pellegrini, X.; Serafini, L.; Yu, D.

    1997-05-01

    The beam dynamics of an integrated S-band rf photoinjector based on the plane wave transformer concept, proposed as part of an SBIR collaboration between UCLA and DULY Research, are studied. The intial design, which calls for an 11.5 cell structure run at a peak on-axis accelerating field of 60 MV/m, and has a compact solenoid around the intial 2.5 cells, is based on the recently developed theory of emittance compensation(L.Serafini, and J.B. Rosenzweig, submitted to Physical Review E.). It calls for matching the beam onto an envelope which is a generalized Brillouin flow, producing a beam which diminishes in transverse size as the square root of the accelerating beam energy. This condition produces a minimized emittance, which for the S-band case is 1 mm-rad at at charge of 1 nC. This design is also scaled to produce nearly identical performance at X-band, giving an injector appropriate to running an FEL at the SLAC NLCTA. It is noted that these designs are insensitive to rf emittance increase, allowign a choice of injection phase, and the option to compress the emitted pulse.

  10. Quartic scaling MP2 for solids: A highly parallelized algorithm in the plane wave basis

    Science.gov (United States)

    Schäfer, Tobias; Ramberger, Benjamin; Kresse, Georg

    2017-03-01

    We present a low-complexity algorithm to calculate the correlation energy of periodic systems in second-order Møller-Plesset (MP2) perturbation theory. In contrast to previous approximation-free MP2 codes, our implementation possesses a quartic scaling, O ( N 4 ) , with respect to the system size N and offers an almost ideal parallelization efficiency. The general issue that the correlation energy converges slowly with the number of basis functions is eased by an internal basis set extrapolation. The key concept to reduce the scaling is to eliminate all summations over virtual orbitals which can be elegantly achieved in the Laplace transformed MP2 formulation using plane wave basis sets and fast Fourier transforms. Analogously, this approach could allow us to calculate second order screened exchange as well as particle-hole ladder diagrams with a similar low complexity. Hence, the presented method can be considered as a step towards systematically improved correlation energies.

  11. Acoustically mediated long-range interaction among multiple spherical particles exposed to a plane standing wave

    International Nuclear Information System (INIS)

    Zhang, Shenwei; Qiu, Chunyin; Wang, Mudi; Ke, Manzhu; Liu, Zhengyou

    2016-01-01

    In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n  = −1 or −2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction. (paper)

  12. On AdS/CFT correspondence beyond SUGRA: plane waves, free CFTs and double-trace deformations

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Vazquez, D.E.

    2007-09-13

    This thesis deals with three corners of the AdS/CFT Correspondence that lie one step beyond the classical supergravity (SUGRA) approximation. We first explore the BMN limit of the duality and study, in particular, the behavior of field theoretic propagators in the corresponding Penrose limit. We unravel the semiclassical (WKB-) exactness of the propagators in the resulting plane wave background metric. Then, we address the limit of vanishing coupling of the conformal field theory (CFT) at large N. In the simplified scenario of Higher Spin/O(N) Vector Model duality, the conformal partial wave (CPW) expansion of scalar four-point functions are reorganized to make them suggestive of a bulk interpretation in term of a consistent truncated massless higher spin theory and their corresponding exchange Witten graphs. We also explore the connection to the interacting O(N) Vector Model at its infra-red fixed point, at leading large N. Finally, coming back to the gauge theory, we study the effect of a relevant double-trace deformations of the boundary CFT on the partition function and its dual bulk interpretation. We show how the one-loop computation in the Anti-de Sitter (AdS) space correctly reproduces the partition function and conformal anomaly of the boundary theory. In all, we get a clean test of the duality beyond the classical SUGRA approximation in the AdS bulk and at the corresponding next-to-leading 1/N order of the CFT at the conformal boundary. (orig.)

  13. On AdS/CFT correspondence beyond SUGRA: plane waves, free CFTs and double-trace deformations

    International Nuclear Information System (INIS)

    Diaz Vazquez, D.E.

    2007-01-01

    This thesis deals with three corners of the AdS/CFT Correspondence that lie one step beyond the classical supergravity (SUGRA) approximation. We first explore the BMN limit of the duality and study, in particular, the behavior of field theoretic propagators in the corresponding Penrose limit. We unravel the semiclassical (WKB-) exactness of the propagators in the resulting plane wave background metric. Then, we address the limit of vanishing coupling of the conformal field theory (CFT) at large N. In the simplified scenario of Higher Spin/O(N) Vector Model duality, the conformal partial wave (CPW) expansion of scalar four-point functions are reorganized to make them suggestive of a bulk interpretation in term of a consistent truncated massless higher spin theory and their corresponding exchange Witten graphs. We also explore the connection to the interacting O(N) Vector Model at its infra-red fixed point, at leading large N. Finally, coming back to the gauge theory, we study the effect of a relevant double-trace deformations of the boundary CFT on the partition function and its dual bulk interpretation. We show how the one-loop computation in the Anti-de Sitter (AdS) space correctly reproduces the partition function and conformal anomaly of the boundary theory. In all, we get a clean test of the duality beyond the classical SUGRA approximation in the AdS bulk and at the corresponding next-to-leading 1/N order of the CFT at the conformal boundary. (orig.)

  14. FDTD method for computing the off-plane band structure in a two-dimensional photonic crystal consisting of nearly free-electron metals

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Sanshui; He Sailing

    2002-12-01

    An FDTD numerical method for computing the off-plane band structure of a two-dimensional photonic crystal consisting of nearly free-electron metals is presented. The method requires only a two-dimensional discretization mesh for a given off-plane wave number k{sub z} although the off-plane propagation is a three-dimensional problem. The off-plane band structures of a square lattice of metallic rods with the high-frequency metallic model in the air are studied, and a complete band gap for some nonzero off-plane wave number k{sub z} is founded.

  15. FDTD method for computing the off-plane band structure in a two-dimensional photonic crystal consisting of nearly free-electron metals

    International Nuclear Information System (INIS)

    Xiao Sanshui; He Sailing

    2002-01-01

    An FDTD numerical method for computing the off-plane band structure of a two-dimensional photonic crystal consisting of nearly free-electron metals is presented. The method requires only a two-dimensional discretization mesh for a given off-plane wave number k z although the off-plane propagation is a three-dimensional problem. The off-plane band structures of a square lattice of metallic rods with the high-frequency metallic model in the air are studied, and a complete band gap for some nonzero off-plane wave number k z is founded

  16. Large eddy simulation of breaking waves

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Deigaard, Rolf

    2001-01-01

    A numerical model is used to simulate wave breaking, the large scale water motions and turbulence induced by the breaking process. The model consists of a free surface model using the surface markers method combined with a three-dimensional model that solves the flow equations. The turbulence....... The incoming waves are specified by a flux boundary condition. The waves are approaching in the shore-normal direction and are breaking on a plane, constant slope beach. The first few wave periods are simulated by a two-dimensional model in the vertical plane normal to the beach line. The model describes...... the steepening and the overturning of the wave. At a given instant, the model domain is extended to three dimensions, and the two-dimensional flow field develops spontaneously three-dimensional flow features with turbulent eddies. After a few wave periods, stationary (periodic) conditions are achieved...

  17. Three-wave interaction in two-component quadratic nonlinear lattices

    DEFF Research Database (Denmark)

    Konotop, V. V.; Cunha, M. D.; Christiansen, Peter Leth

    1999-01-01

    We investigate a two-component lattice with a quadratic nonlinearity and find with the multiple scale technique that integrable three-wave interaction takes place between plane wave solutions when these fulfill resonance conditions. We demonstrate that. energy conversion and pulse propagation known...... from three-wave interaction is reproduced in the lattice and that exact phase matching of parametric processes can be obtained in non-phase-matched lattices by tilting the interacting plane waves with respect to each other. [S1063-651X(99)15110-9]....

  18. The effect of finite-difference time-domain resolution and power-loss computation method on SAR values in plane-wave exposure of Zubal phantom

    International Nuclear Information System (INIS)

    Uusitupa, T M; Ilvonen, S A; Laakso, I M; Nikoskinen, K I

    2008-01-01

    In this paper, the anatomically realistic body model Zubal is exposed to a plane wave. A finite-difference time-domain (FDTD) method is used to obtain field data for specific-absorption-rate (SAR) computation. It is investigated how the FDTD resolution, power-loss computation method and positioning of the material voxels in the FDTD grid affect the SAR results. The results enable one to estimate the effects due to certain fundamental choices made in the SAR simulation

  19. Performance evaluation of compounding and directional beamforming techniques for carotid strain imaging using plane wave transmissions

    DEFF Research Database (Denmark)

    Hansen, Hendrik H.G.; Stuart, Matthias Bo; Villagómez Hoyos, Carlos Armando

    2014-01-01

    Carotid strain imaging in 3D is not possible with conventional focused imaging, because the frame rate is too low. Plane wave ultrasound provides sufficiently high frame rates, albeit at t he cost of image quality, especially in the off - axis direction due to the lack of focusing . Multiple...... techniques have been developed to cope with the low off - axis image quality when performing 2D (and in future 3D) motion estimation: cross correlation with directional beamforming (with or without RF (coherent) compounding) and displacement compounding. This study compares the precision of these techniques...... with RF compounding and 2D displacement compounding with θ = ~20 ° per formed equally and best with a relative root - mean - squared error of ~2% with respect to the analytical solution . The mean and standard deviation of the estimated motion direction for 2D displacement compounding with θ = 20 ° was 0...

  20. Acceleration waves in non-ideal magnetogasdynamics

    Directory of Open Access Journals (Sweden)

    R. Singh

    2014-03-01

    Full Text Available The problem of propagation of acceleration waves in an unsteady inviscid non-ideal gas under the influence of magnetic field is investigated. The characteristic solution to the problem in the neighbourhood of leading characteristics has been determined. An evolution equation governing the behaviour of acceleration waves has been derived. It is shown that a linear solution in the characteristic plane exhibits non-linear behaviour in physical plane. The effect of magnetic field on the formation of shock in non-ideal gas flow with planar and cylindrical symmetry is analysed. It is noticed that all compressive waves terminate into a shock wave. Further, we also compare/contrast the nature of solution in ideal and non-ideal magnetogasdynamic regime.

  1. Correlations in quantum systems and branch points in the complex plane

    OpenAIRE

    Rotter, I.

    2001-01-01

    Branch points in the complex plane are responsible for avoided level crossings in closed and open quantum systems. They create not only an exchange of the wave functions but also a mixing of the states of a quantum system at high level density. The influence of branch points in the complex plane on the low-lying states of the system is small.

  2. Kinematics and dynamics of green water on a fixed platform in a large wave basin in focusing wave and random wave conditions

    Science.gov (United States)

    Chuang, Wei-Liang; Chang, Kuang-An; Mercier, Richard

    2018-06-01

    Green water kinematics and dynamics due to wave impingements on a simplified geometry, fixed platform were experimentally investigated in a large, deep-water wave basin. Both plane focusing waves and random waves were employed in the generation of green water. The focusing wave condition was designed to create two consecutive plunging breaking waves with one impinging on the frontal vertical wall of the fixed platform, referred as wall impingement, and the other directly impinging on the deck surface, referred as deck impingement. The random wave condition was generated using the JONSWAP spectrum with a significant wave height approximately equal to the freeboard. A total of 179 green water events were collected in the random wave condition. By examining the green water events in random waves, three different flow types are categorized: collapse of overtopping wave, fall of bulk water, and breaking wave crest. The aerated flow velocity was measured using bubble image velocimetry, while the void fraction was measured using fiber optic reflectometry. For the plane focusing wave condition, measurements of impact pressure were synchronized with the flow velocity and void fraction measurements. The relationship between the peak pressures and the pressure rise times is examined. For the high-intensity impact in the deck impingement events, the peak pressures are observed to be proportional to the aeration levels. The maximum horizontal velocities in the green water events in random waves are well represented by the lognormal distribution. Ritter's solution is shown to quantitatively describe the green water velocity distributions under both the focusing wave condition and the random wave condition. A prediction equation for green water velocity distribution under random waves is proposed.

  3. High Intensity Compton Scattering in a strong plane wave field of general form

    International Nuclear Information System (INIS)

    Hartin, A.; Moortgat-Pick, G.; Hamburg Univ.

    2011-06-01

    Photon emission by an electron embedded in a strong external field of general form is studied theoretically. The external field considered is a plane wave electromagnetic field of any number of components, period and polarisation. Exact, Volkov solutions of the Dirac equation with the 4-potential of the general external field are obtained. The photon emission is considered in the usual perturbation theory using the Volkov solutions to represent the electron. An expression for the transition probability of this process is obtained after the usual spin and polarisation sums, trace calculation and phase space integration. The final transition probability in the general case contains a single sum over contributions from external field photons, an integration over one of the phase space components and the Fourier transforms of the Volkov phases. The validity of the general expression is established by considering specific external fields. Known specific analytic forms of the transition probability are obtained after substitution of the 4-potential for a circularly polarised and constant crossed external field. As an example usage of the general result for the transition probability, the case of two circularly polarised external fields separated by a phase difference is studied both analytically and numerically. (orig.)

  4. High Intensity Compton Scattering in a strong plane wave field of general form

    Energy Technology Data Exchange (ETDEWEB)

    Hartin, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Moortgat-Pick, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

    2011-06-15

    Photon emission by an electron embedded in a strong external field of general form is studied theoretically. The external field considered is a plane wave electromagnetic field of any number of components, period and polarisation. Exact, Volkov solutions of the Dirac equation with the 4-potential of the general external field are obtained. The photon emission is considered in the usual perturbation theory using the Volkov solutions to represent the electron. An expression for the transition probability of this process is obtained after the usual spin and polarisation sums, trace calculation and phase space integration. The final transition probability in the general case contains a single sum over contributions from external field photons, an integration over one of the phase space components and the Fourier transforms of the Volkov phases. The validity of the general expression is established by considering specific external fields. Known specific analytic forms of the transition probability are obtained after substitution of the 4-potential for a circularly polarised and constant crossed external field. As an example usage of the general result for the transition probability, the case of two circularly polarised external fields separated by a phase difference is studied both analytically and numerically. (orig.)

  5. Explaining Electromagnetic Plane Waves in a Vacuum at the Introductory Level

    Science.gov (United States)

    Allred, Clark L.; Della-Rose, Devin J.; Flusche, Brian M.; Kiziah, Rex R.; Lee, David J.

    2010-01-01

    A typical introduction to electromagnetic waves in vacuum is illustrated by the following quote from an introductory physics text: "Maxwell's equations predict that an electromagnetic wave consists of oscillating electric and magnetic fields. The changing fields induce each other, which maintains the propagation of the wave; a changing electric…

  6. The application of digital image plane holography technology to identify Chinese herbal medicine

    Science.gov (United States)

    Wang, Huaying; Guo, Zhongjia; Liao, Wei; Zhang, Zhihui

    2012-03-01

    In this paper, the imaging technology of digital image plane holography to identify the Chinese herbal medicine is studied. The optical experiment system of digital image plane holography which is the special case of pre-magnification digital holography was built. In the record system, one is an object light by using plane waves which illuminates the object, and the other one is recording hologram by using spherical light wave as reference light. There is a Micro objective lens behind the object. The second phase factor which caus ed by the Micro objective lens can be eliminated by choosing the proper position of the reference point source when digital image plane holography is recorded by spherical light. In this experiment, we use the Lygodium cells and Onion cells as the object. The experiment results with Lygodium cells and Onion cells show that digital image plane holography avoid the process of finding recording distance by using auto-focusing approach, and the phase information of the object can be reconstructed more accurately. The digital image plane holography is applied to the microscopic imaging of cells more effectively, and it is suit to apply for the identify of Chinese Herbal Medicine. And it promotes the application of digital holographic in practice.

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

    International Nuclear Information System (INIS)

    Peng Xiaochun; Dai Huihui

    2009-01-01

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

  8. Mobile Ultrasound Plane Wave Beamforming on iPhone or iPad using Metal- based GPU Processing

    Science.gov (United States)

    Hewener, Holger J.; Tretbar, Steffen H.

    Mobile and cost effective ultrasound devices are being used in point of care scenarios or the drama room. To reduce the costs of such devices we already presented the possibilities of consumer devices like the Apple iPad for full signal processing of raw data for ultrasound image generation. Using technologies like plane wave imaging to generate a full image with only one excitation/reception event the acquisition times and power consumption of ultrasound imaging can be reduced for low power mobile devices based on consumer electronics realizing the transition from FPGA or ASIC based beamforming into more flexible software beamforming. The massive parallel beamforming processing can be done with the Apple framework "Metal" for advanced graphics and general purpose GPU processing for the iOS platform. We were able to integrate the beamforming reconstruction into our mobile ultrasound processing application with imaging rates up to 70 Hz on iPad Air 2 hardware.

  9. Accuracy and Precision of a Plane Wave Vector Flow Imaging Method in the Healthy Carotid Artery

    DEFF Research Database (Denmark)

    Jensen, Jonas; Villagómez Hoyos, Carlos Armando; Traberg, Marie Sand

    2018-01-01

    The objective of the study described here was to investigate the accuracy and precision of a plane wave 2-D vector flow imaging (VFI) method in laminar and complex blood flow conditions in the healthy carotid artery. The approach was to study (i) the accuracy for complex flow by comparing...... of laminar flow in vivo. The precision in vivo was calculated as the mean standard deviation (SD) of estimates aligned to the heart cycle and was highest in the center of the common carotid artery (SD = 3.6% for velocity magnitudes and 4.5° for angles) and lowest in the external branch and for vortices (SD...... the velocity field from a computational fluid dynamics (CFD) simulation to VFI estimates obtained from the scan of an anthropomorphic flow phantom and from an in vivo scan; (ii) the accuracy for laminar unidirectional flow in vivo by comparing peak systolic velocities from VFI with magnetic resonance...

  10. Absolute parametric instability in a nonuniform plane plasma

    Indian Academy of Sciences (India)

    The paper reports an analysis of the effect of spatial plasma nonuniformity on absolute parametric instability (API) of electrostatic waves in magnetized plane waveguides subjected to an intense high-frequency (HF) electric field using the separation method. In this case the effect of strong static magnetic field is considered.

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

    Science.gov (United States)

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

    2017-11-01

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

  12. Absolute parametric instability in a nonuniform plane plasma ...

    Indian Academy of Sciences (India)

    Abstract. The paper reports an analysis of the effect of spatial plasma nonuniformity on absolute parametric instability (API) of electrostatic waves in magnetized plane waveguides subjected to an intense high-frequency (HF) electric field using the separation method. In this case the effect of strong static magnetic field is ...

  13. Characteristics of phase-averaged equations for modulated wave groups

    NARCIS (Netherlands)

    Klopman, G.; Petit, H.A.H.; Battjes, J.A.

    2000-01-01

    The project concerns the influence of long waves on coastal morphology. The modelling of the combined motion of the long waves and short waves in the horizontal plane is done by phase-averaging over the short wave motion and using intra-wave modelling for the long waves, see e.g. Roelvink (1993).

  14. Geometric characteristics of aberrations of plane-symmetric optical systems

    International Nuclear Information System (INIS)

    Lu Lijun; Deng Zhiyong

    2009-01-01

    The geometric characteristics of aberrations of plane-symmetric optical systems are studied in detail with a wave-aberration theory. It is dealt with as an extension of the Seidel aberrations to realize a consistent aberration theory from axially symmetric to plane-symmetric systems. The aberration distribution is analyzed with the spot diagram of a ray and an aberration curve. Moreover, the root-mean-square value and the centroid of aberration distribution are discussed. The numerical results are obtained with the focusing optics of a toroidal mirror at grazing incidence.

  15. Japanese space gravitational wave antenna DECIGO and DPF

    Science.gov (United States)

    Musha, Mitsuru

    2017-11-01

    The gravitational wave detection will open a new gravitational wave astronomy, which gives a fruitful insight about early universe or birth and death of stars. In order to detect gravitational wave, we planed a space gravitational wave detector, DECIGO (DECi-heltz Interferometer Gravitational wave Observatory), which consists of three drag-free satellites forming triangle shaped Fabry-Perot laser interferometer with the arm length of 1000 km, and whose strain sensitivity is designed to be 2x10-24 /√Hz around 0.1 Hz. Before launching DECIGO around 2030, a milestone mission named DECIGO pathfinder (DPF) is planed to be launched whose main purpose is the feasibility test of the key technologies for DECIGO. In the present paper, the conceptual design and current status of DECIGO and DPF are reviewed.

  16. Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging

    International Nuclear Information System (INIS)

    Tiran, Elodie; Deffieux, Thomas; Correia, Mafalda; Maresca, David; Osmanski, Bruno-Felix; Pernot, Mathieu; Tanter, Mickael; Sieu, Lim-Anna; Bergel, Antoine; Cohen, Ivan

    2015-01-01

    Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable.Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients.The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8  ±  0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz −1 cm −1 ). In shear wave elastography, the same multiplane wave configuration yields a 2.07  ±  0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in

  17. Back Radiation Suppression through a Semitransparent Ground Plane for a mm-Wave Patch Antenna

    KAUST Repository

    Klionovski, Kirill; Shamim, Atif

    2017-01-01

    by a round semitransparent ground plane. The semitransparent ground plane has been realized using a low-cost carbon paste on a Kapton film. Experimental results match closely with those of simulations and validate the overall concept.

  18. Features of propagation and recordingof the stress waves in plates of finite thickness

    Directory of Open Access Journals (Sweden)

    Cherednichenko Rostislav Andreevich

    2014-02-01

    Full Text Available This work was carried out to study at the same time the dynamics of wave propagation in plane and axisymmetric plates by finite-difference numerical calculation and by the method of dynamic photoelasticity.In many cases it is possible to carry out the investigation of the dynamic stressed state of solid structures under the impact of seismic waves in plane statement, observing the foundation and the building itself in the conditions of plane deformation. Such problems in structural mechanics are usually investigated on plates providing the conditions of generalized plane stressed condition and accounting for the necessity of the known substitution of elastic constants. In case of applying the model of generalized plane stressed state for investigating two-dimensional waves’ propagation in three-dimensional elastic medium it may be necessary to observe certain additional conditions, which for example limit the class of external impacts of high frequencies (short waves. The use of candling for wave recording in plane models explored with the method of dynamic photoelasticity in the observed cases of impulse loading of the plates with finite thickness gives satisfactory results.

  19. Contribution to study of interfaces instabilities in plane, cylindrical and spherical geometry

    Science.gov (United States)

    Toque, Nathalie

    1996-12-01

    This thesis proposes several experiments of hydrodynamical instabilities which are studied, numerically and theoretically. The experiments are in plane and cylindrical geometry. Their X-ray radiographies show the evolution of an interface between two solid media crossed by a detonation wave. These materials are initially solid. They become liquide under shock wave or stay between two phases, solid and liquid. The numerical study aims at simulating with the codes EAD and Ouranos, the interfaces instabilities which appear in the experiments. The experimental radiographies and the numerical pictures are in quite good agreement. The theoretical study suggests to modelise a spatio-temporal part of the experiments to obtain the quantitative development of perturbations at the interfaces and in the flows. The models are linear and in plane, cylindrical and spherical geometry. They preceed the inoming study of transition between linear and non linear development of instabilities in multifluids flows crossed by shock waves.

  20. Extended application of Kohn-Sham first-principles molecular dynamics method with plane wave approximation at high energy—From cold materials to hot dense plasmas

    International Nuclear Information System (INIS)

    Zhang, Shen; Kang, Wei; Wang, Hongwei; Zhang, Ping; He, X. T.

    2016-01-01

    An extended first-principles molecular dynamics (FPMD) method based on Kohn-Sham scheme is proposed to elevate the temperature limit of the FPMD method in the calculation of dense plasmas. The extended method treats the wave functions of high energy electrons as plane waves analytically and thus expands the application of the FPMD method to the region of hot dense plasmas without suffering from the formidable computational costs. In addition, the extended method inherits the high accuracy of the Kohn-Sham scheme and keeps the information of electronic structures. This gives an edge to the extended method in the calculation of mixtures of plasmas composed of heterogeneous ions, high-Z dense plasmas, lowering of ionization potentials, X-ray absorption/emission spectra, and opacities, which are of particular interest to astrophysics, inertial confinement fusion engineering, and laboratory astrophysics.

  1. Extended application of Kohn-Sham first-principles molecular dynamics method with plane wave approximation at high energy—From cold materials to hot dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shen; Kang, Wei, E-mail: weikang@pku.edu.cn [Center for Applied Physics and Technology, HEDPS, Peking University, Beijing 100871 (China); College of Engineering, Peking University, Beijing 100871 (China); Wang, Hongwei [College of Engineering, Peking University, Beijing 100871 (China); Zhang, Ping, E-mail: zhang-ping@iapcm.ac.cn [Center for Applied Physics and Technology, HEDPS, Peking University, Beijing 100871 (China); LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); He, X. T., E-mail: xthe@iapcm.ac.cn [Center for Applied Physics and Technology, HEDPS, and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2016-04-15

    An extended first-principles molecular dynamics (FPMD) method based on Kohn-Sham scheme is proposed to elevate the temperature limit of the FPMD method in the calculation of dense plasmas. The extended method treats the wave functions of high energy electrons as plane waves analytically and thus expands the application of the FPMD method to the region of hot dense plasmas without suffering from the formidable computational costs. In addition, the extended method inherits the high accuracy of the Kohn-Sham scheme and keeps the information of electronic structures. This gives an edge to the extended method in the calculation of mixtures of plasmas composed of heterogeneous ions, high-Z dense plasmas, lowering of ionization potentials, X-ray absorption/emission spectra, and opacities, which are of particular interest to astrophysics, inertial confinement fusion engineering, and laboratory astrophysics.

  2. Frequency tunable surface magneto elastic waves

    NARCIS (Netherlands)

    Janusonis, J.; Chang, C. L.; van Loosdrecht, P. H. M.; Tobey, R. I.

    2015-01-01

    We use the transient grating technique to generate narrow-band, widely tunable, in-plane surface magnetoelastic waves in a nickel film. We monitor both the structural deformation of the acoustic wave and the accompanying magnetic precession and witness their intimate coupling in the time domain.

  3. Nonlinear differential equations for the wavefront surface at arbitrary Hartmann-plane distances.

    Science.gov (United States)

    Téllez-Quiñones, Alejandro; Malacara-Doblado, Daniel; Flores-Hernández, Ricardo; Gutiérrez-Hernández, David A; León-Rodríguez, Miguel

    2016-03-20

    In the Hartmann test, a wave aberration function W is estimated from the information of the spot diagram drawn in an observation plane. The distance from a reference plane to the observation plane, the Hartmann-plane distance, is typically chosen as z=f, where f is the radius of a reference sphere. The function W and the transversal aberrations {X,Y} calculated at the plane z=f are related by two well-known linear differential equations. Here, we propose two nonlinear differential equations to denote a more general relation between W and the transversal aberrations {U,V} calculated at any arbitrary Hartmann-plane distance z=r. We also show how to directly estimate the wavefront surface w from the information of {U,V}. The use of arbitrary r values could improve the reliability of the measurements of W, or w, when finding difficulties in adequate ray identification at z=f.

  4. Model test study on propagation law of plane stress wave in jointed rock mass under different in-situ stresses

    Science.gov (United States)

    Dong, Qian

    2017-12-01

    The study of propagation law of plane stress wave in jointed rock mass under in-situ stress has important significance for safety excavation of underground rock mass engineering. A model test of the blasting stress waves propagating in the intact rock and jointed rock mass under different in-situ stresses was carried out, and the influencing factors on the propagation law, such as the scale of static loads and the number of joints were studied respectively. The results show that the transmission coefficient of intact rock is larger than that of jointed rock mass under the same loading condition. With the increase of confining pressure, the transmission coefficients of intact rock and jointed rock mass both show an trend of increasing first and then decreasing, and the variation of transmission coefficients in intact rock is smaller than that of jointed rock mass. Transmission coefficient of jointed rock mass decreases with the increase of the number of joints under the same loading condition, when the confining pressure is relatively small, the reduction of transmission coefficients decreases with the increasing of the number of joints, and the variation law of the reduction of transmission coefficients is contrary when the confining pressure is large.

  5. Scattering in a spherical potential: Motion of complex-plane poles and zeros

    International Nuclear Information System (INIS)

    Arndt, R.A.; Roper, L.D.

    1989-01-01

    Scattering of spinless nucleons in a spherical potential is examined with the use of a computer graphics simulation VSCAT. The potential is defined stepwise and the Schroedinger equation is solved to obtain wavefunctions, scattering phases, partial-wave total cross sections, and differential cross sections, which are then displayed graphically. For the particular case of a square well, partial-wave amplitudes are displayed over the complex momentum plane in a three-dimensional plot. The well depth is then varied to follow the motion of poles in the complex momentum plane as they become resonances and then are bound states. Also displayed are the partial-wave zeros, which are required to satisfy Levinson's theorem for multiple states. The requirement on well depth is developed to produce a specified number of bound states and enumerate the energies which, at a given well depth, create equal scattering phases in adjoining partial waves δ/sub l//sub -1/ = δ/sub l/ = δ/sub l//sub +1/. This symmetry of scattering phases exists for both repulsive and attractive square potentials. A square repulsive core is also studied, which has the same triple-point symmetry as the square well

  6. Electromagnetic waves in stratified media

    CERN Document Server

    Wait, James R; Fock, V A; Wait, J R

    2013-01-01

    International Series of Monographs in Electromagnetic Waves, Volume 3: Electromagnetic Waves in Stratified Media provides information pertinent to the electromagnetic waves in media whose properties differ in one particular direction. This book discusses the important feature of the waves that enables communications at global distances. Organized into 13 chapters, this volume begins with an overview of the general analysis for the electromagnetic response of a plane stratified medium comprising of any number of parallel homogeneous layers. This text then explains the reflection of electromagne

  7. Orbital effects of a monochromatic plane gravitational wave with ultra-low frequency incident on a gravitationally bound two-body system

    Directory of Open Access Journals (Sweden)

    Lorenzo Iorio

    2014-09-01

    Full Text Available We analytically compute the long-term orbital variations of a test particle orbiting a central body acted upon by an incident monochromatic plane gravitational wave. We assume that the characteristic size of the perturbed two-body system is much smaller than the wavelength of the wave. Moreover, we also suppose that the wave's frequency νg is much smaller than the particle's orbital one nb. We make neither a priori assumptions about the direction of the wavevector kˆ nor on the orbital configuration of the particle. While the semi-major axis a is left unaffected, the eccentricity e, the inclination I, the longitude of the ascending node Ω, the longitude of pericenter ϖ and the mean anomaly ℳ undergo non-vanishing long-term changes of the form dΨ/dt=F(Kij;e,I,Ω,ω,Ψ=e,I,Ω,ϖ,M, where Kij, i,j=1,2,3 are the coefficients of the tidal matrix K. Thus, in addition to the variations of its orientation in space, the shape of the orbit would be altered as well. Strictly speaking, such effects are not secular trends because of the slow modulation introduced by K and by the orbital elements themselves: they exhibit peculiar long-term temporal patterns which would be potentially of help for their detection in multidecadal analyses of extended data records of planetary observations of various kinds. In particular, they could be useful in performing independent tests of the inflation-driven ultra-low gravitational waves whose imprint may have been indirectly detected in the Cosmic Microwave Background by the Earth-based experiment BICEP2. Our calculation holds, in general, for any gravitationally bound two-body system whose orbital frequency nb is much larger than the frequency νg of the external wave, like, e.g., extrasolar planets and the stars orbiting the Galactic black hole. It is also valid for a generic perturbation of tidal type with constant coefficients over timescales of the order of the orbital period of the perturbed particle.

  8. The light wave flow effect in a plane-parallel layer with a quasi-zero refractive index under the action of bounded light beams

    International Nuclear Information System (INIS)

    Gadomsky, O. N.; Shchukarev, I. A.

    2016-01-01

    It is shown that external optical radiation in the 450–1200 nm range can be efficiently transformed under the action of bounded light beams to a surface wave that propagates along the external and internal boundaries of a plane-parallel layer with a quasi-zero refractive index. Reflection regimes with complex and real angles of refraction in the layer are considered. The layer with a quasi-zero refractive index in this boundary problem is located on a highly reflective metal substrate; it is shown that the uniform low reflection of light is achieved in the wavelength range under study.

  9. Non-Linear Langmuir Wave Modulation in Collisionless Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Pécseli, Hans

    1977-01-01

    in the expressions concerning the modulation instability of a plane Langmuir wave. When the Vlasov equation for the ions is applied, a Langmuir wave is modulationally unstable for arbitrary perturbations independent of the unperturbed wave amplitude, in contrast to what is found for fluid ions. A simple analogy...

  10. Study on crack scattering in aluminum plates with Lamb wave frequency–wavenumber analysis

    International Nuclear Information System (INIS)

    Yu, Lingyu; Tian, Zhenhua; Leckey, Cara A C

    2013-01-01

    The multimodal characteristic of Lamb waves makes the interpretation of Lamb wave signals difficult in either the time or frequency domain. In this work, we present our study of Lamb wave propagation characterization and crack scattering using frequency–wavenumber analysis. The aim is to investigate three dimensional (3D) Lamb wave behavior in the presence of crack damage via the application of frequency–wavenumber analysis. The analysis techniques are demonstrated using simulation examples of an aluminum plate with a through-thickness crack. Both in-plane and out-of-plane components are acquired through a 3D elastodynamic finite integration technique (EFIT), while the out-of-plane component is also experimentally obtained using a scanning laser Doppler vibrometer for verification purposes. The time–space wavefield is then transformed to the frequency–wavenumber domain by a two dimensional (2D) Fourier transform and the out-of-plane EFIT results are compared to experimental measurements. The experimental and simulated results are found to be in close agreement. The frequency–wavenumber representation of in-plane and out-of-plane components shows clear distinction among various Lamb wave modes that are present. However, spatial information is lost during this 2D transformation. A short space 2D Fourier transform is therefore adopted to obtain the frequency–wavenumber spectra at various spatial locations, resulting in a space–frequency–wavenumber representation of the signal. The space–frequency–wavenumber analysis has shown its potential for indicating crack presence. (paper)

  11. The two-wave X-ray field calculated by means of integral-equation methods

    International Nuclear Information System (INIS)

    Bremer, J.

    1984-01-01

    The problem of calculating the two-wave X-ray field on the basis of the Takagi-Taupin equations is discussed for the general case of curved lattice planes. A two-dimensional integral equation which incorporates the nature of the incoming radiation, the form of the crystal/vacuum boundary, and the curvature of the structure, is deduced. Analytical solutions for the symmetrical Laue case with incoming plane waves are obtained directly for perfect crystals by means of iteration. The same method permits a simple derivation of the narrow-wave Laue and Bragg cases. Modulated wave fronts are discussed, and it is shown that a cut-off in the width of an incoming plane wave leads to lateral oscillations which are superimposed on the Pendelloesung fringes. Bragg and Laue shadow fields are obtained. The influence of a non-zero kernel is discussed and a numerical procedure for calculating wave amplitudes in curved crystals is presented. (Auth.)

  12. On the role of lateral waves in the radiation from the dielectric wedge

    DEFF Research Database (Denmark)

    Balling, Peter

    1973-01-01

    The field on the dielectric wedge is approximated by a plane-wave expansion as in [1]. Contributions from this solution to both the surface field and the radiation field are examined. Finally, an experimental radiation field is compared with the plane-wave solution and with a geometric-optical...

  13. Applicability of geometrical optics to in-plane liquid-crystal configurations

    NARCIS (Netherlands)

    Sluijter, M.; Xu, M.; Urbach, H.P.; De Boer, D.K.G.

    2010-01-01

    We study the applicability of geometrical optics to inhomogeneous dielectric nongyrotropic optically anisotropic media typically found in in-plane liquid-crystal configurations with refractive indices no=1.5 and ne=1.7. To this end, we compare the results of advanced ray- and wave-optics simulations

  14. Forward volume and surface magnetostatic modes in an yttrium iron garnet film for out-of-plane magnetic fields: Theory and experiment

    Science.gov (United States)

    Lim, Jinho; Bang, Wonbae; Trossman, Jonathan; Amanov, Dovran; Ketterson, John B.

    2018-05-01

    We present experimental and theoretical results on the propagation of magnetostatic spin waves in a film of yttrium iron garnet (YIG) for out-of-plane magnetic fields for which propagation in opposite directions is nonreciprocal in the presence of a metal layer. The plane studied is defined by the film normal n and n × k where k is the wave vector of the mode. Spin waves in this setting are classified as forward volume waves or surface waves and display non-reciprocity in the presence of an adjacent metal layer except for when H//n. The measurements are carried out in a transmission geometry, and a microwave mixer is used to measure the change of phase, and with it the evolution of wavevector, of the arriving spin wave with external magnetic field.

  15. Gravitational Couplings for Gop-Planes and y-Op-Planes

    OpenAIRE

    Giraldo, Juan Fernando Ospina

    2000-01-01

    The Wess-Zumino actions for generalized orientifold planes (GOp-planes) and y-deformed orientifold planes (yOp-planes) are presented and two series power expantions are realized from whiches processes that involves GOp-planes,yOp-planes, RR-forms, gravitons and gaugeons, are obtained. Finally non-standard GOp-planes and y-Op-planes are showed.

  16. The D-instanton and other supersymmetric D-branes in IIB plane-wave string theory

    International Nuclear Information System (INIS)

    Gaberdiel, Matthias R.; Green, Michael B.

    2003-01-01

    A class of D-branes for the type IIB plane-wave background is considered that preserve half the dynamical supersymmetries of the light-cone gauge. The D-branes of this type are the Euclidean (or instantonic) (0,0), (0,4), and (4,0) branes (where (r,s) denotes a brane oriented with r axes in the first four directions transverse to the +, - light-cone, and s axes in the second four directions). Corresponding Lorentzian D-branes are (+,-;0,0), (+,-;0,4), and (+,-;4,0). These are constructed in two ways. The first uses a boundary state formalism which implements appropriate fermionic gluing conditions and the second is based on a direct quantization of the open strings ending on the branes. In distinction to the D-branes considered earlier these have massless world-volume fermions but do not possess kinematical supersymmetries. Cylinder diagrams describing the overlap between a pair of boundary states displaced by some distance are evaluated. The open-string description of this system involves mode frequencies that are, in general, given by irrational solutions to transcendental equations. The closed-string and open-string descriptions are shown to be equivalent by a nontrivial implementation of the S modular transformation. A classical description of the D-instanton (the (0,0) case) in light-cone gauge is also given

  17. Modeling stress wave propagation in rocks by distinct lattice spring model

    Directory of Open Access Journals (Sweden)

    Gaofeng Zhao

    2014-08-01

    Full Text Available In this paper, the ability of the distinct lattice spring model (DLSM for modeling stress wave propagation in rocks was fully investigated. The influence of particle size on simulation of different types of stress waves (e.g. one-dimensional (1D P-wave, 1D S-wave and two-dimensional (2D cylindrical wave was studied through comparing results predicted by the DLSM with different mesh ratios (lr and those obtained from the corresponding analytical solutions. Suggested values of lr were obtained for modeling these stress waves accurately. Moreover, the weak material layer method and virtual joint plane method were used to model P-wave and S-wave propagating through a single discontinuity. The results were compared with the classical analytical solutions, indicating that the virtual joint plane method can give better results and is recommended. Finally, some remarks of the DLSM on modeling of stress wave propagation in rocks were provided.

  18. Realistic full wave modeling of focal plane array pixels.

    Energy Technology Data Exchange (ETDEWEB)

    Campione, Salvatore [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Electromagnetic Theory Dept.; Warne, Larry K. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Electromagnetic Theory Dept.; Jorgenson, Roy E. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Electromagnetic Theory Dept.; Davids, Paul [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Applied Photonic Microsystems Dept.; Peters, David W. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States). Applied Photonic Microsystems Dept.

    2017-11-01

    Here, we investigate full-wave simulations of realistic implementations of multifunctional nanoantenna enabled detectors (NEDs). We focus on a 2x2 pixelated array structure that supports two wavelengths of operation. We design each resonating structure independently using full-wave simulations with periodic boundary conditions mimicking the whole infinite array. We then construct a supercell made of a 2x2 pixelated array with periodic boundary conditions mimicking the full NED; in this case, however, each pixel comprises 10-20 antennas per side. In this way, the cross-talk between contiguous pixels is accounted for in our simulations. We observe that, even though there are finite extent effects, the pixels work as designed, each responding at the respective wavelength of operation. This allows us to stress that realistic simulations of multifunctional NEDs need to be performed to verify the design functionality by taking into account finite extent and cross-talk effects.

  19. Stresses in a submarine topography under ocean waves

    Energy Technology Data Exchange (ETDEWEB)

    Mei, C.C.; McTigue, D.F.

    1984-09-01

    The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular, the dynamic pore pressure and the combined static and dynamic effective stresses are presented.

  20. An Enhanced Plane Wave Expansion Method to Solve Piezoelectric Phononic Crystal with Resonant Shunting Circuits

    Directory of Open Access Journals (Sweden)

    Ziyang Lian

    2016-01-01

    Full Text Available An enhanced plane wave expansion (PWE method is proposed to solve piezoelectric phononic crystal (PPC connected with resonant shunting circuits (PPC-C, which is named as PWE-PPC-C. The resonant shunting circuits can not only bring about the locally resonant (LR band gap for the PPC-C but also conveniently tune frequency and bandwidth of band gaps through adjusting circuit parameters. However, thus far, more than one-dimensional PPC-C has been studied just by Finite Element method. Compared with other methods, the PWE has great advantages in solving more than one-dimensional PC as well as various lattice types. Nevertheless, the conventional PWE cannot accurately solve coupling between the structure and resonant shunting circuits of the PPC-C since only taking one-way coupling from displacements to electrical parameters into consideration. A two-dimensional PPC-C model of orthorhombic lattice is established to demonstrate the whole solving process of PWE-PPC-C. The PWE-PPC-C method is validated by Transfer Matrix method as well as Finite Element method. The dependence of band gaps on circuit parameters has been investigated in detail by PWE-PPC-C. Its advantage in solving various lattice types is further illustrated by calculating the PPC-C of triangular and hexagonal lattices, respectively.

  1. Acoustic plane waves normally incident on a clamped panel in a rectangular duct. [to explain noise reduction curves for reducing interior noise in aircraft

    Science.gov (United States)

    Unz, H.; Roskam, J.

    1979-01-01

    The theory of acoustic plane wave normally incident on a clamped panel in a rectangular duct is developed. The coupling theory between the elastic vibrations of the panel (plate) and the acoustic wave propagation in infinite space and in the rectangular duct is considered. The partial differential equation which governs the vibration of the panel (plate) is modified by adding to its stiffness (spring) forces and damping forces, and the fundamental resonance frequency and the attenuation factor are discussed. The noise reduction expression based on the theory is found to agree well with the corresponding experimental data of a sample aluminum panel in the mass controlled region, the damping controlled region, and the stiffness controlled region. All the frequency positions of the upward and downward resonance spikes in the sample experimental data are identified theoretically as resulting from four cross interacting major resonance phenomena: the cavity resonance, the acoustic resonance, the plate resonance, and the wooden back panel resonance.

  2. Modelling the optical response of human retinal photoreceptors to plane wave illumination with the finite integration technique

    Science.gov (United States)

    Akhlagh Moayed, Alireza; Dang, Shannon; Ramahi, Omar M.; Bizheva, Kostadinka K.

    2009-02-01

    The early stages of ocular diseases such as Diabetic Retinopathy are manifested by morphological changes in retinal tissue occurring on cellular level. Therefore, a number of ophthalmic diseases can be diagnosed at an early stage by detecting spatial and temporal variations in the scattering profile of retinal tissue. It was recently demonstrated that, OCT can be used to probe the functional response of retinal photoreceptors to external light stimulation [1]-[3]. fUHROCT measures localized differential changes in the retina reflectivity over time resulting from external light stimulation of the retina. Currently the origins of the observed reflectivity changes are not well understood. However, due to the complex nature of retinal physiology using purely experimental approaches in this case is problematic. For example fUHROCT is sensitive to small changes in the refractive index of biological tissue which as demonstrated previously, can result from a number of processes such as membrane hyperpolarization, osmotic swelling, metabolic changes, etc. In this paper, we present a computational model of interaction between photoreceptor cells and optical plane wave based on the Finite Integration Technique (FIT).

  3. Benney's long wave equations

    International Nuclear Information System (INIS)

    Lebedev, D.R.

    1979-01-01

    Benney's equations of motion of incompressible nonviscous fluid with free surface in the approximation of long waves are analyzed. The connection between the Lie algebra of Hamilton plane vector fields and the Benney's momentum equations is shown

  4. Modulational instability, solitons and periodic waves in a model of quantum degenerate boson-fermion mixtures

    International Nuclear Information System (INIS)

    Belmonte-Beitia, Juan; Perez-Garcia, Victor M.; Vekslerchik, Vadym

    2007-01-01

    In this paper, we study a system of coupled nonlinear Schroedinger equations modelling a quantum degenerate mixture of bosons and fermions. We analyze the stability of plane waves, give precise conditions for the existence of solitons and write explicit solutions in the form of periodic waves. We also check that the solitons observed previously in numerical simulations of the model correspond exactly to our explicit solutions and see how plane waves destabilize to form periodic waves

  5. RCS Diversity of Electromagnetic Wave Carrying Orbital Angular Momentum.

    Science.gov (United States)

    Zhang, Chao; Chen, Dong; Jiang, Xuefeng

    2017-11-13

    An electromagnetic (EM) wave with orbital angular momentum (OAM) has a helical wave front, which is different from that of the plane wave. The phase gradient can be found perpendicular to the direction of propagation and proportional to the number of OAM modes. Herein, we study the backscattering property of the EM wave with different OAM modes, i.e., the radar cross section (RCS) of the target is measured and evaluated with different OAM waves. As indicated by the experimental results, different OAM waves have the same RCS fluctuation for the simple target, e.g., a small metal ball as the target. However, for complicated targets, e.g., two transverse-deployed small metal balls, different RCSs can be identified from the same incident angle. This valuable fact helps to obtain RCS diversity, e.g., equal gain or selective combining of different OAM wave scattering. The majority of the targets are complicated targets or expanded targets; the RCS diversity can be utilized to detect a weak target traditionally measured by the plane wave, which is very helpful for anti-stealth radar to detect the traditional stealth target by increasing the RCS with OAM waves.

  6. Model-based internal wave processing

    Energy Technology Data Exchange (ETDEWEB)

    Candy, J.V.; Chambers, D.H.

    1995-06-09

    A model-based approach is proposed to solve the oceanic internal wave signal processing problem that is based on state-space representations of the normal-mode vertical velocity and plane wave horizontal velocity propagation models. It is shown that these representations can be utilized to spatially propagate the modal (dept) vertical velocity functions given the basic parameters (wave numbers, Brunt-Vaisala frequency profile etc.) developed from the solution of the associated boundary value problem as well as the horizontal velocity components. Based on this framework, investigations are made of model-based solutions to the signal enhancement problem for internal waves.

  7. Nonlinear modulation of ionization waves

    International Nuclear Information System (INIS)

    Bekki, Naoaki

    1981-01-01

    In order to investigate the nonlinear characteristics of ionization waves (moving-striations) in the positive column of glow discharge, a nonlinear modulation of ionization waves in the region of the Pupp critical current is analysed by means of the reductive perturbation method. The modulation of ionization waves is described by a nonlinear Schroedinger type equation. The coefficients of the equation are evaluated using the data of the low pressure Argon-discharge, and the simple solutions (plane wave and envelope soliton type solutions) are presented. Under a certain condition an envelope soliton is propagated through the positive column. (author)

  8. Propagation of Quasi-plane Nonlinear Waves in Tubes

    OpenAIRE

    P. Koníček; M. Bednařík; M. Červenka

    2002-01-01

    This paper deals with possibilities of using the generalized Burgers equation and the KZK equation to describe nonlinear waves in circular ducts. A new method for calculating of diffraction effects taking into account boundary layer effects is described. The results of numerical solutions of the model equations are compared. Finally, the limits of validity of the used model equations are discussed with respect to boundary conditions and the radius of the circular duct. The limits of applicabi...

  9. Reflection of P and SV waves at the free surface of a monoclinic ...

    Indian Academy of Sciences (India)

    The propagation of plane waves in an anisotropic elastic medium possessing monoclinic symmetry is discussed. The expressions for the phase velocity of qP and qSV waves propagating in the plane of elastic symmetry are obtained in terms of the direction cosines of the propagation vector. It is shown that, in general, ...

  10. Continuous contour phase plates for tailoring the focal plane irradiance profile

    International Nuclear Information System (INIS)

    Dixit, S.N.; Rushford, M.C.; Thomas, I.M.; Perry, M.D.

    1995-01-01

    We present fully continuous phase screens for producing super-Gaussian focal-plane irradiance profiles. Such phase screens are constructed with the assumption of either circular symmetric near-field and far-field profiles or a separable phase screen in Cartesian co-ordinates. In each case, the phase screen is only a few waves deep. Under illumination by coherent light, such phase screens produce high order super-Gaussian profiles in the focal plane with high energy content effects of beam aberrations on the focal profiles and their energy content are also discussed

  11. Resonance of Superconducting Microstrip Antenna with Aperture in the Ground Plane

    Directory of Open Access Journals (Sweden)

    S. Benkouda

    2013-08-01

    Full Text Available This paper presents a rigorous full-wave analysis of a high Tc superconducting rectangular microstrip antenna with a rectangular aperture in the ground plane. To include the effect of the superconductivity of the microstrip patch in the full-wave analysis, a complex surface impedance is considered. The proposed approach is validated by comparing the computed results with previously published data. Results showing the effect of the aperture on the resonance of the superconducting microstrip antenna are given.

  12. Wakefield radiation from the open end of an internally coated metallic tube

    Directory of Open Access Journals (Sweden)

    M. Ivanyan

    2014-07-01

    Full Text Available In this paper the problem of radiation from the open end of a semi-infinite circular metallic waveguide with perfectly conducting walls and a thin internal low-conducting metal coating is considered. Electromagnetic fields are generated by the ultrarelativistic point charge moving along the axis of the waveguide. The far fields of radiation are obtained using the near-field to far-field recovery technique. The technique is extended for the nonmonochromatic waves. It is shown that the radiation has a narrow-band and narrow-directional character.

  13. Alfven wave resonances and flow induced by nonlinear Alfven waves in a stratified atmosphere

    International Nuclear Information System (INIS)

    Stark, B. A.; Musielak, Z. E.; Suess, S. T.

    1996-01-01

    A nonlinear, time-dependent, ideal MHD code has been developed and used to compute the flow induced by nonlinear Alfven waves propagating in an isothermal, stratified, plane-parallel atmosphere. The code is based on characteristic equations solved in a Lagrangian frame. Results show that resonance behavior of Alfven waves exists in the presence of a continuous density gradient and that the waves with periods corresponding to resonant peaks exert considerably more force on the medium than off-resonance periods. If only off-peak periods are considered, the relationship between the wave period and induced longitudinal velocity shows that short period WKB waves push more on the background medium than longer period, non-WKB, waves. The results also show the development of the longitudinal waves induced by finite amplitude Alfven waves. Wave energy transferred to the longitudinal mode may provide a source of localized heating

  14. ARBITRARY INTERACTION OF PLANE SUPERSONIC FLOWS

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2015-11-01

    Full Text Available Subject of study.We consider the Riemann problem for parameters at collision of two plane flows at a certain angle. The problem is solved in the exact statement. Most cases of interference, both stationary and non-stationary gas-dynamic discontinuities, followed by supersonic flows can be reduced to the problem of random interaction of two supersonic flows. Depending on the ratio of the parameters in the flows, outgoing discontinuities turn out to be shock waves, or rarefactionwaves. In some cases, there is no solution at all. It is important to know how to find the domain of existence for the relevant decisions, as the type of shock-wave structures in these domains is known in advance. The Riemann problem is used in numerical methods such as the method of Godunov. As a rule, approximate solution is used, known as the Osher solution, but for a number of problems with a high precision required, solution of this problem needs to be in the exact statement. Main results.Domains of existence for solutions with different types of shock-wave structure have been considered. Boundaries of existence for solutions with two outgoing shock waves are analytically defined, as well as with the outgoing shock wave and rarefaction wave. We identify the area of Mach numbers and angles at which the flows interact and there is no solution. Specific flows with two outgoing rarefaction waves are not considered. Practical significance. The results supplement interference theory of stationary gas-dynamic discontinuities and can be used to develop new methods of numerical calculation with extraction of discontinuities.

  15. Stresses in a submarine topography under ocean waves

    Energy Technology Data Exchange (ETDEWEB)

    Mei, C.C.; McTigue, D.F.

    1984-01-01

    The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, to obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular the dynamic pore pressure and the combined static and dynamic effective stresses are presented. 10 references, 11 figures.

  16. Three-dimensional instability of standing waves

    Science.gov (United States)

    Zhu, Qiang; Liu, Yuming; Yue, Dick K. P.

    2003-12-01

    We investigate the three-dimensional instability of finite-amplitude standing surface waves under the influence of gravity. The analysis employs the transition matrix (TM) approach and uses a new high-order spectral element (HOSE) method for computation of the nonlinear wave dynamics. HOSE is an extension of the original high-order spectral method (HOS) wherein nonlinear wave wave and wave body interactions are retained up to high order in wave steepness. Instead of global basis functions in HOS, however, HOSE employs spectral elements to allow for complex free-surface geometries and surface-piercing bodies. Exponential convergence of HOS with respect to the total number of spectral modes (for a fixed number of elements) and interaction order is retained in HOSE. In this study, we use TM-HOSE to obtain the stability of general three-dimensional perturbations (on a two-dimensional surface) on two classes of standing waves: plane standing waves in a rectangular tank; and radial/azimuthal standing waves in a circular basin. For plane standing waves, we confirm the known result of two-dimensional side-bandlike instability. In addition, we find a novel three-dimensional instability for base flow of any amplitude. The dominant component of the unstable disturbance is an oblique (standing) wave oriented at an arbitrary angle whose frequency is close to the (nonlinear) frequency of the original standing wave. This finding is confirmed by direct long-time simulations using HOSE which show that the nonlinear evolution leads to classical Fermi Pasta Ulam recurrence. For the circular basin, we find that, beyond a threshold wave steepness, a standing wave (of nonlinear frequency Omega) is unstable to three-dimensional perturbations. The unstable perturbation contains two dominant (standing-wave) components, the sum of whose frequencies is close to 2Omega. From the cases we consider, the critical wave steepness is found to generally decrease/increase with increasing radial

  17. Experimental Study on Corrosion Detection of Aluminum Alloy Using Lamb Wave Mixing Technique

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Heeung; Lee, Jaesun; Cho, Younho [Pusan Nat’l Univ., Busan (Korea, Republic of)

    2016-11-15

    In this study, the Lamb wave mixing technique, which is basised on advanced research on the nonlinear bulk wave mixing technique, is applied for corrosion detection. To demonstrate the validity of the Lamb wave mixing technique, an experiment was performed with normal and corroded specimens. Comparison group in an experimentation are selected to mode and frequency with dominant in-plane displacement and out-of-plane displacement of Lamb waves. The results showed that the Lamb wave mixing technique can monitor corrosion defects, and it has a trend similar to that of the conventional Lamb wave technique. It was confirmed that the dominant displacement and mode matching the theory were generated. Flaw detectability is determined depending on displacement ratio instead of using the measurement method and mode selection.

  18. Nonlinear elastic waves in materials

    CERN Document Server

    Rushchitsky, Jeremiah J

    2014-01-01

    The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...

  19. Penetration of an ordinary wave into a weakly inhomogeneous magnetoplasma at oblique incidence

    International Nuclear Information System (INIS)

    Preinhaelter, J.

    1973-12-01

    The propagation was studied of high-frequency electromagnetic waves in a plane-stratified weakly inhomogeneous plasma. The density gradient was assumed to be perpendicular to the external magnetic field and the wave vector was not considered to be generally parallel to the plane given by the two former vectors. The analysis shows that an ordinary wave may penetrate the plasma resonance region if the orientation of the vacuum wave vector is appropriately chosen. Analytical expressions for the reflexion and transmission coefficients were obtained and their dependence on the direction cosines of the wave vector of the incident wave was studied. It is also briefly shown that after the transmission through plasma resonance the ordinary wave was transformed into an extraordinary wave and the latter was reflected back to the region of hybrid resonance. In this region the extraordinary wave was fully transformed into the Bernstein modes. (author)

  20. Effects of Medium Characteristics on Laser RCS of Airplane with E-Wave Polarization

    Directory of Open Access Journals (Sweden)

    Hosam El-Ocla

    2015-01-01

    Full Text Available Plane wave incidence should be postulated to have an authentic target detection. Practically, the plane wave is incapable usually of keeping its power in the far field especially when propagating through an inhomogeneous medium. Consequently, we assume an incident beam wave with a finite width around the target. In this work, we calculate numerically a laser radar cross section (LRCS of conducting targets having smooth cross sections with inflection points such as airplane in random media. Effects of fluctuations intensity of random media on the LRCS performance are studied in this paper. E-wave polarization (E-wave incidence is considered while the mean target size is approximately twice the wavelength.

  1. Damage detection in composite panels based on mode-converted Lamb waves sensed using 3D laser scanning vibrometer

    Science.gov (United States)

    Pieczonka, Łukasz; Ambroziński, Łukasz; Staszewski, Wiesław J.; Barnoncel, David; Pérès, Patrick

    2017-12-01

    This paper introduces damage identification approach based on guided ultrasonic waves and 3D laser Doppler vibrometry. The method is based on the fact that the symmetric and antisymmetric Lamb wave modes differ in amplitude of the in-plane and out-of-plane vibrations. Moreover, the modes differ also in group velocities and normally they are well separated in time. For a given time window both modes can occur simultaneously only close to the wave source or to a defect that leads to mode conversion. By making the comparison between the in-plane and out-of-plane wave vector components the detection of mode conversion is possible, allowing for superior and reliable damage detection. Experimental verification of the proposed damage identification procedure is performed on fuel tank elements of Reusable Launch Vehicles designed for space exploration. Lamb waves are excited using low-profile, surface-bonded piezoceramic transducers and 3D scanning laser Doppler vibrometer is used to characterize the Lamb wave propagation field. The paper presents theoretical background of the proposed damage identification technique as well as experimental arrangements and results.

  2. Analysis of a plane stress wave by the moving least squares method

    Directory of Open Access Journals (Sweden)

    Wojciech Dornowski

    2014-08-01

    Full Text Available A meshless method based on the moving least squares approximation is applied to stress wave propagation analysis. Two kinds of node meshes, the randomly generated mesh and the regular mesh are used. The nearest neighbours’ problem is developed from a triangulation that satisfies minimum edges length conditions. It is found that this method of neighbours’ choice significantly improves the solution accuracy. The reflection of stress waves from the free edge is modelled using fictitious nodes (outside the plate. The comparison with the finite difference results also demonstrated the accuracy of the proposed approach.[b]Keywords[/b]: civil engineering, meshless method, moving least squares method, elastic waves

  3. Spin waves in terbium. III. Magnetic anisotropy at zero wave vector

    DEFF Research Database (Denmark)

    Houmann, Jens Christian Gylden; Jensen, J.; Touborg, P.

    1975-01-01

    The energy gap at zero wave vector in the spin-wave dispersion relation of ferromagnetic. Tb has been studied by inelastic neutron scattering. The energy was measured as a function of temperature and applied magnetic field, and the dynamic anisotropy parameters were deduced from the results...... the effects of zero-point deviations from the fully aligned ground state, and we tentatively propose polarization-dependent two-ion couplings as their origin........ The axial anisotropy is found to depend sensitively on the orientation of the magnetic moments in the basal plane. This behavior is shown to be a convincing indication of considerable two-ion contributions to the magnetic anisotropy at zero wave vector. With the exception of the sixfold basal...

  4. Optimal Control Of Nonlinear Wave Energy Point Converters

    DEFF Research Database (Denmark)

    Nielsen, Søren R.K.; Zhou, Qiang; Kramer, Morten

    2013-01-01

    idea behind the control strategy is to enforce the stationary velocity response of the absorber into phase with the wave excitation force at any time. The controller is optimal under monochromatic wave excitation. It is demonstrated that the devised causal controller, in plane irregular sea states...

  5. Polarisations of quasi-waves in a general anisotropic porous solid ...

    Indian Academy of Sciences (India)

    in fluid-saturated porous media was developed by. Biot (1956). ... anisotropic permeability controlling the flow of vis- cous fluid in its pores. ..... solid: III reflection of plane waves at a free plane boundary (general case); Bull. Seism. Soc. Am. 52.

  6. Inertia–gravity wave radiation from the elliptical vortex in the f -plane shallow water system

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Research and Education Center for Natural Sciences, Department of Physics, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)

    2017-04-15

    Inertia–gravity wave (IGW) radiation from the elliptical vortex is investigated in the f -plane shallow water system. The far field of IGW is analytically derived for the case of an almost circular Kirchhoff vortex with a small aspect ratio. Cyclone–anticyclone asymmetry appears at finite values of the Rossby number (Ro) caused by the source originating in the Coriolis acceleration. While the intensity of IGWs from the cyclone monotonically decreases as f increases, that from the anticyclone increases as f increases for relatively smaller f and has a local maximum at intermediate f . A numerical experiment is conducted on a model using a spectral method in an unbounded domain. The numerical results agree quite well with the analytical ones for elliptical vortices with small aspect ratios, implying that the derived analytical forms are useful for the verification of the numerical model. For elliptical vortices with larger aspect ratios, however, significant deviation from the analytical estimates appears. The intensity of IGWs radiated in the numerical simulation is larger than that estimated analytically. The reason is that the source of IGWs is amplified during the time evolution because the shape of the vortex changes from ideal ellipse to elongated with filaments. Nevertheless, cyclone–anticyclone asymmetry similar to the analytical estimate appears in all the range of aspect ratios, suggesting that this asymmetry is a robust feature. (paper)

  7. 3D synthetic aperture imaging using a virtual source element in the elevation plane

    DEFF Research Database (Denmark)

    Nikolov, Svetoslav; Jensen, Jørgen Arendt

    2000-01-01

    . However, the resolution in the elevation plane is determined by the fixed mechanical elevation focus. This paper suggests to post-focus the RF lines from several adjacent planes in the elevation direction using the elevation focal point of the transducer as a virtual source element, in order to obtain...... dynamic focusing in the elevation plane. A 0.1 mm point scatterer was mounted in an agar block and scanned in a water bath. The transducer is a 64 elements linear array with a pitch of 209 μm. The transducer height is 4 mm in the elevation plane and it is focused at 20 mm giving a F-number of 5. The point...... are passed through a second beamformer, in which the fixed focal points in the elevation plane are treated as virtual sources of spherical waves. Synthetic aperture focusing is applied on them. The -6 dB resolution in the elevation plane is increased from 7 mm to 2 mm. This gives a uniform point spread...

  8. 2D full-wave simulation of waves in space and tokamak plasmas

    Directory of Open Access Journals (Sweden)

    Kim Eun-Hwa

    2017-01-01

    Full Text Available Simulation results using a 2D full-wave code (FW2D for space and NSTX fusion plasmas are presented. The FW2D code solves the cold plasma wave equations using the finite element method. The wave code has been successfully applied to describe low frequency waves in planetary magnetospheres (i.e., dipole geometry and the results include generation and propagation of externally driven ultra-low frequency waves via mode conversion at Mercury and mode coupling, refraction and reflection of internally driven field-aligned propagating left-handed electromagnetic ion cyclotron (EMIC waves at Earth. In this paper, global structure of linearly polarized EMIC waves is examined and the result shows such resonant wave modes can be localized near the equatorial plane. We also adopt the FW2D code to tokamak geometry and examine radio frequency (RF waves in the scape-off layer (SOL of tokamaks. By adopting the rectangular and limiter boundary, we compare the results with existing AORSA simulations. The FW2D code results for the high harmonic fast wave heating case on NSTX with a rectangular vessel boundary shows excellent agreement with the AORSA code.

  9. 2D full-wave simulation of waves in space and tokamak plasmas

    Science.gov (United States)

    Kim, Eun-Hwa; Bertelli, Nicola; Johnson, Jay; Valeo, Ernest; Hosea, Joel

    2017-10-01

    Simulation results using a 2D full-wave code (FW2D) for space and NSTX fusion plasmas are presented. The FW2D code solves the cold plasma wave equations using the finite element method. The wave code has been successfully applied to describe low frequency waves in planetary magnetospheres (i.e., dipole geometry) and the results include generation and propagation of externally driven ultra-low frequency waves via mode conversion at Mercury and mode coupling, refraction and reflection of internally driven field-aligned propagating left-handed electromagnetic ion cyclotron (EMIC) waves at Earth. In this paper, global structure of linearly polarized EMIC waves is examined and the result shows such resonant wave modes can be localized near the equatorial plane. We also adopt the FW2D code to tokamak geometry and examine radio frequency (RF) waves in the scape-off layer (SOL) of tokamaks. By adopting the rectangular and limiter boundary, we compare the results with existing AORSA simulations. The FW2D code results for the high harmonic fast wave heating case on NSTX with a rectangular vessel boundary shows excellent agreement with the AORSA code.

  10. Measurements of electromagnetic waves in Phaedrus-B: Bench-mark test of ANTENA wave field calculations

    International Nuclear Information System (INIS)

    Intrator, T.; Meassick, S.; Browning, J.; Majeski, R.; Ferron, J.R.; Hershkowitz, N.

    1989-01-01

    It is shown that the predictions of a numerical code (ANTENA) and the data of wave field measurements in the Phaedrus-B tandem mirror are consistent (±25%) for right-handed (B-vector - ) wave fields and less so (±40%) for left-handed (B-vector + ) wave fields in the plasma core, and that they disagree for B-vector + fields near the column edge. Shorting out or reduction of the wave azimuthal electric fields by limiters is the probable cause of this discrepancy. The ICRF fluctuating wave B-vector fields are shown as |B-vector| contour maps in the r-z plane, where the B-vector + data peak at a smaller radius than predicted. The waves are characterized by different dominant axial wave numbers for the left- and right-handed circularly polarized fields. (author). 28 refs, 20 figs, 1 tab

  11. Fault plane solutions as related to known geological faults in and near India

    Directory of Open Access Journals (Sweden)

    N. SRIVASTAVA

    1975-05-01

    Full Text Available Based on the focal mechanism solutions of newly determined solutions, and other recent workers the correlation between one of the nodal planes and the geological faults has been discussed for three regions namely Kashmir, Central Himalayas and northeast India including Assam. The variability between multiple solutions reported for some earthquakes and the limitations in the choice of the nodal plane from /'-wave solutions have been brought out. It is seen that no standard criteria either on the basis of isoseismals or of aftershocks can be used to distinguish the fault plane from the auxiliary plane. It has been found that in general there is good agreement between one of the nodal planes and the geological faults in Kashmir and the Central Himalayas. In northeast India, the strike directions obtained from the mechanism solutions generally agree with the trends of the main thrusts but the dip direction for shocks originating in the India-Burma border

  12. Does the source energy change when gravitaion waves are emitted in the einstein's gravitation theory

    International Nuclear Information System (INIS)

    Logunov, A.A.; Folomeshkin, V.N.

    1977-01-01

    It is shown that in the Einstein's gravitation theory the total ''energy'' of a plane gravitational wave calculated with any pseudotensor is equal to zero. The known Einstein's result, according to which the energy of a sourceis decreased when plane weak gravitational waves are emitted, have no place in the Einstein's gravitational theory. The examples are given of exact wave solutions for which the pseudotensor is strictly equal to zero. The energy-momentum of any weak gravitational waves is always equal to zero in the Einstein's gravitation theory. When such waves are emitted the energy of the source cannot change, although these waves are real curvature waves. By the means in the Einstein's gravitation theory the energy, e, is in essenc generated from nothing

  13. Ionic wave propagation and collision in an excitable circuit model of microtubules

    Science.gov (United States)

    Guemkam Ghomsi, P.; Tameh Berinyoh, J. T.; Moukam Kakmeni, F. M.

    2018-02-01

    In this paper, we report the propensity to excitability of the internal structure of cellular microtubules, modelled as a relatively large one-dimensional spatial array of electrical units with nonlinear resistive features. We propose a model mimicking the dynamics of a large set of such intracellular dynamical entities as an excitable medium. We show that the behavior of such lattices can be described by a complex Ginzburg-Landau equation, which admits several wave solutions, including the plane waves paradigm. A stability analysis of the plane waves solutions of our dynamical system is conducted both analytically and numerically. It is observed that perturbed plane waves will always evolve toward promoting the generation of localized periodic waves trains. These modes include both stationary and travelling spatial excitations. They encompass, on one hand, localized structures such as solitary waves embracing bright solitons, dark solitons, and bisolitonic impulses with head-on collisions phenomena, and on the other hand, the appearance of both spatially homogeneous and spatially inhomogeneous stationary patterns. This ability exhibited by our array of proteinic elements to display several states of excitability exposes their stunning biological and physical complexity and is of high relevance in the description of the developmental and informative processes occurring on the subcellular scale.

  14. Quasiparticle conductance-voltage characteristics for break junctions involving d-wave superconductors: charge-density-wave effects.

    Science.gov (United States)

    Ekino, T; Gabovich, A M; Suan Li, Mai; Szymczak, H; Voitenko, A I

    2017-12-20

    Quasiparticle tunnel conductance-voltage characteristics (CVCs), [Formula: see text], were calculated for break junctions (BJs) made up of layered d-wave superconductors partially gapped by charge-density waves (CDWs). The current is assumed to flow in the ab-plane of electrodes. The influence of CDWs is analyzed by comparing the resulting CVCs with CVCs calculated for BJs made up of pure d-wave superconductors with relevant parameters. The main CDW-effects were found to be the appearance of new CVC peculiarities and the loss of CVC symmetry with respect to the V-sign. Tunnel directionality was shown to be one of the key factors in the formation of [Formula: see text] dependences. In particular, the orientation of electrodes with respect to the current channel becomes very important. As a result, [Formula: see text] can acquire a large variety of forms similar to those for tunnel junctions between superconductors with s-wave, d-wave, and mixed symmetry of their order parameters. The diversity of peculiarities is especially striking at finite temperatures. In the case of BJs made up of pure d-wave superconductors, the resulting CVC can include a two-peak gap-driven structure. The results were compared with the experimental BJ data for a number of high-T c oxides. It was shown that the large variety of the observed current-voltage characteristics can be interpreted in the framework of our approach. Thus, quasiparticle tunnel currents in the ab-plane can be used as an additional mean to detect CDWs competing with superconductivity in cuprates or other layered superconductors.

  15. Capture of charged particles by transverse electromagnetic waves

    Energy Technology Data Exchange (ETDEWEB)

    Davydovskii, V Ya; Sapogin, V G; Ukolov, A S

    1975-01-01

    An estimate is made of the maximum possible number of resonance particles interacting with a plane, transverse electromagnetic wave. The estimate is obtained by means of a distribution function, which is expressed in terms of the integrals of motion of the particles in the wave. Values of proton fluxes accelerated by an amplitude-modulated wave in the solar corona coincide with those observed during bursts of sporadic radioemission. (SJR)

  16. Higher-order rogue wave solutions of the three-wave resonant interaction equation via the generalized Darboux transformation

    International Nuclear Information System (INIS)

    Wang, Xin; Chen, Yong; Cao, Jianli

    2015-01-01

    In this paper, we utilize generalized Darboux transformation to study higher-order rogue wave solutions of the three-wave resonant interaction equation, which describes the propagation and mixing of waves with different frequencies in weakly nonlinear dispersive media. A general Nth-order rogue wave solution with two characteristic velocities structural parameters and 3N independent parameters under a determined plane-wave background and a specific parameter condition is derived. As an application, we show that four fundamental rogue waves with fundamental, two kinds of line and quadrilateral patterns, or six fundamental rogue waves with fundamental, triangular, two kinds of quadrilateral and circular patterns can emerge in the second-order rogue waves. Moreover, several important wave characteristics including the maximum values, the corresponding coordinate positions of the humps, and the stability problem for some special higher-order rogue wave solutions such as the fundamental and quadrilateral cases are discussed. (paper)

  17. Soft modes in the easy plane pyrochlore antiferromagnet

    International Nuclear Information System (INIS)

    Champion, J D M; Holdsworth, P C W

    2004-01-01

    Thermal fluctuations lift the high ground state degeneracy of the classical nearest neighbour pyrochlore antiferromagnet, with easy plane anisotropy, giving a first-order phase transition to a long range ordered state. We show, from spin wave analysis and numerical simulation, that even below this transition a continuous manifold of states, of dimension N 2/3 , exist (N is the number of degrees of freedom). As the temperature goes to zero a further 'order by disorder' selection is made from this manifold. The pyrochlore antiferromagnet Er 2 Ti 2 O 7 is believed to have an easy plane anisotropy and is reported to have the same magnetic structure. This is perhaps surprising, given that the dipole interaction lifts the degeneracy of the classical model in favour of a different structure. We interpret our results in the light of these facts

  18. On scattering of electromagnetic waves by a wormhole

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, A.A., E-mail: ka98@mail.ru [Dubna International University of Nature, Society and Man, Universitetskaya Str. 19, Dubna, 141980 (Russian Federation); Savelova, E.P. [Dubna International University of Nature, Society and Man, Universitetskaya Str. 19, Dubna, 141980 (Russian Federation)

    2012-04-20

    We consider scattering of a plane electromagnetic wave by a wormhole. It is found that the scattered wave is depolarized and has a specific interference picture depending on parameters of the wormhole and the distance to the observer. It is proposed that such features can be important in the direct search of wormholes.

  19. On scattering of electromagnetic waves by a wormhole

    International Nuclear Information System (INIS)

    Kirillov, A.A.; Savelova, E.P.

    2012-01-01

    We consider scattering of a plane electromagnetic wave by a wormhole. It is found that the scattered wave is depolarized and has a specific interference picture depending on parameters of the wormhole and the distance to the observer. It is proposed that such features can be important in the direct search of wormholes.

  20. A Study on Elastic Guided Wave Modal Characteristics in Multi-Layered Structures

    International Nuclear Information System (INIS)

    Cho, Youn Ho; Lee, Chong Myoung

    2008-01-01

    In this study, we have developed a program which can calculate phase and group velocities, attenuation and wave structures of each mode in multi-layered plates. The wave structures of each mode are obtained, varying material properties and number of layers. The key in the success of guided wave NDE is how to optimize the mode selection scheme by minimizing energy loss when a structure is in contact with liquid. In this study, the normalized out-of-plane displacements at the surface of a free plate are used to predict the variation of modal attenuation and verily the correlation between attenuation and wave structure. It turns out that the guided wave attenuation can be efficiently obtain from the out-of-plane displacement variation of a free wave guide alleviating such mathematical difficulties in extracting complex roots for the eigenvalue problem of a liquid loaded wave guide. Through this study, the concert to optimize guided wave mode selection is accomplished to enhance sensitivity and efficiency in nondestructive evaluation for multi-layered structures.

  1. Quantum fluctuations of some gravitational waves

    OpenAIRE

    Enginer, Y.; Hortacsu, M.; Kaya, R.; Ozdemir, N.; Ulker, K.; Yapiskan, B.

    1998-01-01

    We review our previous work on the the calculation of the stress-energy tensor for a scalar particle in the background metric of different types of spherical impulsive, spherical shock and plane impulsive gravitational waves.

  2. Computational study of nonlinear plasma waves. I. Simulation model and monochromatic wave propagtion

    International Nuclear Information System (INIS)

    Matda, Y.; Crawford, F.W.

    1974-12-01

    An economical low noise plasma simulation model is applied to a series of problems associated with electrostatic wave propagation in a one-dimensional, collisionless, Maxwellian plasma, in the absence of magnetic field. The model is described and tested, first in the absence of an applied signal, and then with a small amplitude perturbation, to establish the low noise features and to verify the theoretical linear dispersion relation at wave energy levels as low as 0.000,001 of the plasma thermal energy. The method is then used to study propagation of an essentially monochromatic plane wave. Results on amplitude oscillation and nonlinear frequency shift are compared with available theories. The additional phenomena of sideband instability and satellite growth, stimulated by large amplitude wave propagation and the resulting particle trapping, are described. (auth)

  3. Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT

    Directory of Open Access Journals (Sweden)

    Subir Patra

    2018-01-01

    Full Text Available Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM of plate-like structures and nondestructive evaluation (NDE of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

  4. Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT.

    Science.gov (United States)

    Patra, Subir; Ahmed, Hossain; Banerjee, Sourav

    2018-01-18

    Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D) Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS) and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT) transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D) in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM) of plate-like structures and nondestructive evaluation (NDE) of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

  5. In-plane and cross-plane thermal conductivities of molybdenum disulfide

    International Nuclear Information System (INIS)

    Ding, Zhiwei; Pei, Qing-Xiang; Zhang, Yong-Wei; Jiang, Jin-Wu

    2015-01-01

    We investigate the in-plane and cross-plane thermal conductivities of molybdenum disulfide (MoS 2 ) using non-equilibrium molecular dynamics simulations. We find that the in-plane thermal conductivity of monolayer MoS 2 is about 19.76 W mK −1 . Interestingly, the in-plane thermal conductivity of multilayer MoS 2 is insensitive to the number of layers, which is in strong contrast to the in-plane thermal conductivity of graphene where the interlayer interaction strongly affects the in-plane thermal conductivity. This layer number insensitivity is attributable to the finite energy gap in the phonon spectrum of MoS 2 , which makes the phonon–phonon scattering channel almost unchanged with increasing layer number. For the cross-plane thermal transport, we find that the cross-plane thermal conductivity of multilayer MoS 2 can be effectively tuned by applying cross-plane strain. More specifically, a 10% cross-plane compressive strain can enhance the thermal conductivity by a factor of 10, while a 5% cross-plane tensile strain can reduce the thermal conductivity by 90%. Our findings are important for thermal management in MoS 2 based nanodevices and for thermoelectric applications of MoS 2 . (paper)

  6. Radiation of planar electromagnetic waves by a line source in anisotropic metamaterials

    International Nuclear Information System (INIS)

    Cheng Qiang; Jiang Weixiang; Cui Tiejun

    2010-01-01

    We show experimentally that a line source in an anisotropic metamaterial directly radiates planar electromagnetic waves instead of cylindrical waves, when one component of the permeability tensor approaches zero. The impedance of this material can be perfectly matched to that of free space, which can significantly reduce the reflections between the source and the superstrate, as in traditional highly directive antennas based on zero index metamaterials. Such a unique property determines the two-way propagation of electromagnetic waves excited by a line source, instead of all-way propagation. From this feature, a highly directive emission of electromagnetic waves is achieved using the anisotropic metamaterial with arbitrary shape. We have designed and fabricated the anisotropic metamaterial in the microwave region, and observed the generation of plane waves and their highly directive emission. The proposed plane-wave emission is independent of the shape variance of the anisotropic metamaterial, which can be utilized in the design of conformal antennas.

  7. Simulation of in-plane distribution of beam irradiation amount in ion implantation

    International Nuclear Information System (INIS)

    Sone, Yuki; Sato, Masataka; Yamamoto, Yasuhiro

    1994-01-01

    In the ion implantation process which is one of the important technologies for making devices, the good controllability and the implantation in a short time aiming at high through put have been demanded. Therefore, the increase of current in implantation beam is planned, but such short time implantation is to worsen the uniformity of dose in wafer plane. The method of quantitatively determining this in-plane uniformity by computer simulation has been established, therefore, it is reported. In the simulation, the method of beam scan was made into raster scan, and the in-plane uniformity of dose was determined when the time of implantation, the with of overscan, and the band width of beam scanning waveform were taken as the parameters. As the result, in the case of assuming the scan waveform being ideal triangular wave, under the supposed condition, by taking the time of implantation as longer than 30s, the in-plane uniformity within 1% was able to be attained. It was found that the scanning device having 175 kHz band must be used for the above conditions. The simulation and as the results, the relation of the time of implantation with the in-plane uniformity, the scanning waveform and the in-plane uniformity and so on are reported. (K.I.)

  8. Generation of neutrons in a plane system by explosive implosion of a variable-density liner

    International Nuclear Information System (INIS)

    Kaliski, S.

    1978-01-01

    The neutron yield has been calculated in a plane system at explosive implosion of a variable density liner into the explosive region. Due to high speed of implosion effected with the aid of a cumulative cone the neutron yield has already been obtained for the plane wave incident and reflected in deuterium gas. This has permitted an analytical approximate estimation of the neutron yield. This yield may be enhanced in a further phase of compression. (author)

  9. Seismic shear waves as Foucault pendulum

    Science.gov (United States)

    Snieder, Roel; Sens-Schönfelder, Christoph; Ruigrok, Elmer; Shiomi, Katsuhiko

    2016-03-01

    Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of ScS and ScS2 waves, we show that the Foucault-like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed SKS splitting.

  10. Coulomb Final State Interactions for Gaussian Wave Packets

    CERN Document Server

    Wiedemann, Urs Achim; Heinz, Ulrich W

    1999-01-01

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

  11. Wave fields in real media wave propagation in anisotropic, anelastic, porous and electromagnetic media

    CERN Document Server

    Carcione, José M

    2014-01-01

    Authored by the internationally renowned José M. Carcione, Wave Fields in Real Media: Wave Propagation in Anisotropic, Anelastic, Porous and Electromagnetic Media examines the differences between an ideal and a real description of wave propagation, starting with the introduction of relevant stress-strain relations. The combination of this relation and the equations of momentum conservation lead to the equation of motion. The differential formulation is written in terms of memory variables, and Biot's theory is used to describe wave propagation in porous media. For each rheology, a plane-wave analysis is performed in order to understand the physics of wave propagation. This book contains a review of the main direct numerical methods for solving the equation of motion in the time and space domains. The emphasis is on geophysical applications for seismic exploration, but researchers in the fields of earthquake seismology, rock acoustics, and material science - including many branches of acoustics of fluids and ...

  12. Nearaffine planes

    NARCIS (Netherlands)

    Wilbrink, H.A.

    1982-01-01

    In this paper we develop a theory for nearaffine planes analogous to the theory of ordinary affine translation planes. In a subsequent paper we shall use this theory to give a characterization of a certain class of Minkowski planes.

  13. Out-of-plane superfluid density of a layered organic superconductor: The coherent Josephson tunneling

    International Nuclear Information System (INIS)

    Tomic, S.; Prester, M.; Drobac, D.; Milat, O.; Maki, K.; Schweitzer, D.

    1999-01-01

    Measurements of AC magnetic susceptibility in κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br show that the b-axis penetration depth below T c exhibits behaviour different from that observed in the ac plane, which exhibits the T-linear dependence. In agreement with earlier measurements, a leading quadratic temperature dependence is found at low temperatures. The temperature dependence of the out-of-plane superfluid density is shown to best agree with a model of d-wave superconducting layers coupled by coherent Josephson tunneling. (orig.)

  14. Reconstruction of Interfering Waves from Three Dimensional Analysis of Their Interference Pattern

    Directory of Open Access Journals (Sweden)

    M. T. Tavassoli

    1997-04-01

    Full Text Available   Optical interferometry is being used as an efficient tool to analyse smooth surfaces for more than a century. Although, due to introduction of novel computer assisted analyzing techniques and array detectors, like CCD, the speed and the precision of processing have been increased tremendously, but the main equation involved is not changed. The main equation is the intensity distribution in the interference pattern of a plane reference wave and the required wave.   In the paper it is shown that by analysis of the interference pattern of two unknown waves in three dimension (which is possible for coherent waves it is possible to reconstruct each wave separately. This approach has several useful applications, namely, on can do without reference plane wave in the interferometric surface analysis and, it is possible to reconstruct an unknown wave by making it to interfere with itself. This is very useful in determining the profile of laser beams and erasing the effect of atmospheric disturbances on observing astronomical objects.

  15. Reflection of Lamb waves obliquely incident on the free edge of a plate.

    Science.gov (United States)

    Santhanam, Sridhar; Demirli, Ramazan

    2013-01-01

    The reflection of obliquely incident symmetric and anti-symmetric Lamb wave modes at the edge of a plate is studied. Both in-plane and Shear-Horizontal (SH) reflected wave modes are spawned by an obliquely incident in-plane Lamb wave mode. Energy reflection coefficients are calculated for the reflected wave modes as a function of frequency and angle of incidence. This is done by using the method of orthogonal mode decomposition and by enforcing traction free conditions at the plate edge using the method of collocation. A PZT sensor network, affixed to an Aluminum plate, is used to experimentally verify the predictions of the analysis. Experimental results provide support for the analytically determined results. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Assessment of induced SAR in children exposed to electromagnetic plane waves between 10 MHz and 5.6 GHz

    International Nuclear Information System (INIS)

    Bakker, J F; Paulides, M M; Van Rhoon, G C; Christ, A; Kuster, N

    2010-01-01

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SAR wb ) and the peak 10 g spatial-averaged SAR (SAR 10g ). The objective of this study is to assess if the SAR in children remains below the basic restrictions upon exposure at the reference levels. Finite difference time domain (FDTD) modeling was used to calculate the SAR in six children and two adults when exposed to all 12 orthogonal plane wave configurations. A sensitivity study showed an expanded uncertainty of 53% (SAR wb ) and 58% (SAR 10g ) due to variations in simulation settings and tissue properties. In this study, we found that the basic restriction on the SAR wb is occasionally exceeded for children, up to a maximum of 45% in small children. The maximum SAR 10g values, usually found at body protrusions, remain under the limit for all scenarios studied. Our results are in good agreement with the literature, suggesting that the recommended ICNIRP reference levels may need fine tuning.

  17. Assessment of induced SAR in children exposed to electromagnetic plane waves between 10 MHz and 5.6 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Bakker, J F; Paulides, M M; Van Rhoon, G C [Erasmus MC-Daniel den Hoed Cancer Center, Department of Radiation Oncology, Section Hyperthermia, PO box 5201, NL-3008 AE, Rotterdam (Netherlands); Christ, A; Kuster, N, E-mail: j.bakker@erasmusmc.n [Foundation for Research on Information Technologies in Society (IT' IS) (Switzerland)

    2010-06-07

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels from the basic restrictions on the induced whole-body-averaged specific absorption rate (SAR{sub wb}) and the peak 10 g spatial-averaged SAR (SAR{sub 10g}). The objective of this study is to assess if the SAR in children remains below the basic restrictions upon exposure at the reference levels. Finite difference time domain (FDTD) modeling was used to calculate the SAR in six children and two adults when exposed to all 12 orthogonal plane wave configurations. A sensitivity study showed an expanded uncertainty of 53% (SAR{sub wb}) and 58% (SAR{sub 10g}) due to variations in simulation settings and tissue properties. In this study, we found that the basic restriction on the SAR{sub wb} is occasionally exceeded for children, up to a maximum of 45% in small children. The maximum SAR{sub 10g} values, usually found at body protrusions, remain under the limit for all scenarios studied. Our results are in good agreement with the literature, suggesting that the recommended ICNIRP reference levels may need fine tuning.

  18. Excitation of surface waves of ultracold neutrons on absorbing trap walls as anomalous loss factor

    International Nuclear Information System (INIS)

    Bokun, R.Ch.

    2006-01-01

    One analyzed probability of excitation of surface waves of ultracold neutrons in terms of a plane model consisting of three media: vacuum, a finite depth neutron absorbing substance layer and a neutron reflecting substrate. One demonstrated the absence of the mentioned surface waves in terms of the generally accepted model of two media: vacuum contiguous to the plane surface of a substance filled half-space. One pointed out the effect of the excited surface waves of ultracold neutrons on the increase of their anomalous losses in traps [ru

  19. Formulation of the rotational transformation of wave fields and their application to digital holography.

    Science.gov (United States)

    Matsushima, Kyoji

    2008-07-01

    Rotational transformation based on coordinate rotation in Fourier space is a useful technique for simulating wave field propagation between nonparallel planes. This technique is characterized by fast computation because the transformation only requires executing a fast Fourier transform twice and a single interpolation. It is proved that the formula of the rotational transformation mathematically satisfies the Helmholtz equation. Moreover, to verify the formulation and its usefulness in wave optics, it is also demonstrated that the transformation makes it possible to reconstruct an image on arbitrarily tilted planes from a wave field captured experimentally by using digital holography.

  20. Reconstruction of an Non-Monochromatically Illuminated Object Imaged through an Electron Microscope with a Fluctuating Electromagnetic Field

    NARCIS (Netherlands)

    Hoenders, B.J.

    1975-01-01

    It is shown that a weak phase object imaged by an electron microscope within the presence of instabilities of the lense currents and the acceleration voltage, fluctuating electromagnetic field, can be reconstructed from the intensity distribution in the image plane. Perfectly incoherent illumination

  1. Oblique Modulation of Ion-Acoustic Waves in a Warm Plasma

    International Nuclear Information System (INIS)

    Xue Jukui; Tang Rongan

    2003-01-01

    The stability of oblique modulation of ion-acoustic waves in an unmagnetized warm plasma is studied. A nonlinear Schroedinger equation governing the slow modulation of the wave amplitude is derived. The effect of temperature on the oblique modulational instability of the ion-acoustic wave is investigated. It is found that the ion temperature significantly changes the domain of the modulational instability in the k-θ plane

  2. Asymmetric rogue waves, breather-to-soliton conversion, and nonlinear wave interactions in the Hirota–Maxwell–Bloch system

    International Nuclear Information System (INIS)

    Wang Lei; Zhu Yujie; Wang Ziqi; Xu Tao; Qi Fenghua; Xue Yushan

    2016-01-01

    We study the nonlinear localized waves on constant backgrounds of the Hirota–Maxwell–Bloch (HMB) system arising from the erbium doped fibers. We derive the asymmetric breather, rogue wave (RW) and semirational solutions of the HMB system. We show that the breather and RW solutions can be converted into various soliton solutions. Under different conditions of parameters, we calculate the locus of the eigenvalues on the complex plane which converts the breathers or RWs into solitons. Based on the second-order solutions, we investigate the interactions among different types of nonlinear waves including the breathers, RWs and solitons. (author)

  3. Asymmetric Rogue Waves, Breather-to-Soliton Conversion, and Nonlinear Wave Interactions in the Hirota-Maxwell-Bloch System

    Science.gov (United States)

    Wang, Lei; Zhu, Yu-Jie; Wang, Zi-Qi; Xu, Tao; Qi, Feng-Hua; Xue, Yu-Shan

    2016-02-01

    We study the nonlinear localized waves on constant backgrounds of the Hirota-Maxwell-Bloch (HMB) system arising from the erbium doped fibers. We derive the asymmetric breather, rogue wave (RW) and semirational solutions of the HMB system. We show that the breather and RW solutions can be converted into various soliton solutions. Under different conditions of parameters, we calculate the locus of the eigenvalues on the complex plane which converts the breathers or RWs into solitons. Based on the second-order solutions, we investigate the interactions among different types of nonlinear waves including the breathers, RWs and solitons.

  4. Traveling wave tube and method of manufacture

    Science.gov (United States)

    Vancil, Bernard K. (Inventor)

    2004-01-01

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

  5. Nonreciprocal acoustics and dynamics in the in-plane oscillations of a geometrically nonlinear lattice.

    Science.gov (United States)

    Zhang, Zhen; Koroleva, I; Manevitch, L I; Bergman, L A; Vakakis, A F

    2016-09-01

    We study the dynamics and acoustics of a nonlinear lattice with fixed boundary conditions composed of a finite number of particles coupled by linear springs, undergoing in-plane oscillations. The source of the strongly nonlinearity of this lattice is geometric effects generated by the in-plane stretching of the coupling linear springs. It has been shown that in the limit of low energy the lattice gives rise to a strongly nonlinear acoustic vacuum, which is a medium with zero speed of sound as defined in classical acoustics. The acoustic vacuum possesses strongly nonlocal coupling effects and an orthogonal set of nonlinear standing waves [or nonlinear normal modes (NNMs)] with mode shapes identical to those of the corresponding linear lattice; in contrast to the linear case, however, all NNMs except the one with the highest wavelength are unstable. In addition, the lattice supports two types of waves, namely, nearly linear sound waves (termed "L waves") corresponding to predominantly axial oscillations of the particles and strongly nonlinear localized propagating pulses (termed "NL pulses") corresponding to predominantly transverse oscillating wave packets of the particles with localized envelopes. We show the existence of nonlinear nonreciprocity phenomena in the dynamics and acoustics of the lattice. Two opposite cases are examined in the limit of low energy. The first gives rise to nonreciprocal dynamics and corresponds to collective, spatially extended transverse loading of the lattice leading to the excitation of individual, predominantly transverse NNMs, whereas the second case gives rise to nonreciprocal acoutics by considering the response of the lattice to spatially localized, transverse impulse or displacement excitations. We demonstrate intense and recurring energy exchanges between a directly excited NNM and other NNMs with higher wave numbers, so that nonreciprocal energy exchanges from small-to-large wave numbers are established. Moreover, we show the

  6. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans

    1975-01-01

    with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results......, which are corrected for the effect of the direct coupling between the magnons and the phonons, and for the field dependence of the relative magnetization at finite temperatures. A large q⃗-dependent difference between the two energy components is observed, showing that the anisotropy of the two...

  7. On quantum motion of particle in linear potential bounded by perfectly reflecting plane and parabolic surfaces

    International Nuclear Information System (INIS)

    Pokotilovskij, Yu.N.

    1999-01-01

    The motion of a particle in the linear potential bounded by an inclined plane or parabolic surfaces is considered. The quantization of energy and wave functions is obtained numerically by the separation of the variables method

  8. Lamb Wave Assessment of Fiber Volume Fraction in Composites

    Science.gov (United States)

    Seale, Michael D.; Smith, Barry T.; Prosser, W. H.; Zalameda, Joseph N.

    1998-01-01

    Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.

  9. Superresolution Imaging Using Resonant Multiples and Plane-wave Migration Velocity Analysis

    KAUST Repository

    Guo, Bowen

    2017-01-01

    Seismic imaging is a technique that uses seismic echoes to map and detect underground geological structures. The conventional seismic image has the resolution limit of λ/2, where λ is the wavelength associated with the seismic waves propagating

  10. Spin wave absorber generated by artificial surface anisotropy for spin wave device network

    Directory of Open Access Journals (Sweden)

    Naoki Kanazawa

    2016-09-01

    Full Text Available Spin waves (SWs have the potential to reduce the electric energy loss in signal processing networks. The SWs called magnetostatic forward volume waves (MSFVWs are advantageous for networking due to their isotropic dispersion in the plane of a device. To control the MSFVW flow in a processing network based on yttrium iron garnet, we developed a SW absorber using artificial structures. The mechanical surface polishing method presented in this work can well control extrinsic damping without changing the SW dispersion of the host material. Furthermore, enhancement of the ferromagnetic resonance linewidth over 3 Oe was demonstrated.

  11. Twisted electron-acoustic waves in plasmas

    International Nuclear Information System (INIS)

    Aman-ur-Rehman; Ali, S.; Khan, S. A.; Shahzad, K.

    2016-01-01

    In the paraxial limit, a twisted electron-acoustic (EA) wave is studied in a collisionless unmagnetized plasma, whose constituents are the dynamical cold electrons and Boltzmannian hot electrons in the background of static positive ions. The analytical and numerical solutions of the plasma kinetic equation suggest that EA waves with finite amount of orbital angular momentum exhibit a twist in its behavior. The twisted wave particle resonance is also taken into consideration that has been appeared through the effective wave number q_e_f_f accounting for Laguerre-Gaussian mode profiles attributed to helical phase structures. Consequently, the dispersion relation and the damping rate of the EA waves are significantly modified with the twisted parameter η, and for η → ∞, the results coincide with the straight propagating plane EA waves. Numerically, new features of twisted EA waves are identified by considering various regimes of wavelength and the results might be useful for transport and trapping of plasma particles in a two-electron component plasma.

  12. Relative merits of travelling-wave and resonant operation of linac

    International Nuclear Information System (INIS)

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

    1985-01-01

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

  13. Proof-of-Concept of a Millimeter-Wave Integrated Heterogeneous Network for 5G Cellular.

    Science.gov (United States)

    Okasaka, Shozo; Weiler, Richard J; Keusgen, Wilhelm; Pudeyev, Andrey; Maltsev, Alexander; Karls, Ingolf; Sakaguchi, Kei

    2016-08-25

    The fifth-generation mobile networks (5G) will not only enhance mobile broadband services, but also enable connectivity for a massive number of Internet-of-Things devices, such as wireless sensors, meters or actuators. Thus, 5G is expected to achieve a 1000-fold or more increase in capacity over 4G. The use of the millimeter-wave (mmWave) spectrum is a key enabler to allowing 5G to achieve such enhancement in capacity. To fully utilize the mmWave spectrum, 5G is expected to adopt a heterogeneous network (HetNet) architecture, wherein mmWave small cells are overlaid onto a conventional macro-cellular network. In the mmWave-integrated HetNet, splitting of the control plane (CP) and user plane (UP) will allow continuous connectivity and increase the capacity of the mmWave small cells. mmWave communication can be used not only for access linking, but also for wireless backhaul linking, which will facilitate the installation of mmWave small cells. In this study, a proof-of-concept (PoC) was conducted to demonstrate the practicality of a prototype mmWave-integrated HetNet, using mmWave technologies for both backhaul and access.

  14. 17O NMR Study of Undoped and Lightly Hole Doped CuO2 Planes

    International Nuclear Information System (INIS)

    Thurber, K.R.; Hunt, A.W.; Imai, T.; Chou, F.C.; Lee, Y.S.

    1997-01-01

    Using 17 O NMR, we probed the short wavelength excitations in the CuO 2 planes of insulating and weakly metallic high T c cuprates. We measured the spin wave damping for an S=1/2 2D quantum Heisenberg antiferromagnet for the first time. The results establish the nearly free behavior (asymptotic freedom) of the high energy spin waves, even without long range magnetic order. Light hole doping dramatically enhances the low energy excitation spectrum below 300K. copyright 1997 The American Physical Society

  15. Reflection of plane waves from free surface of a microstretch elastic ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Department of Mathematics, Jat College, Rohtak 124 001, Haryana, India. e-mail: baljeet−gill@hotmail.com. In the present investigation, it is shown that there exists five basic waves in a ..... in layered media, (New York: McGraw-Hill). Gauthier ...

  16. Classical wave experiments on chaotic scattering

    International Nuclear Information System (INIS)

    Kuhl, U; Stoeckmann, H-J; Weaver, R

    2005-01-01

    We review recent research on the transport properties of classical waves through chaotic systems with special emphasis on microwaves and sound waves. Inasmuch as these experiments use antennas or transducers to couple waves into or out of the systems, scattering theory has to be applied for a quantitative interpretation of the measurements. Most experiments concentrate on tests of predictions from random matrix theory and the random plane wave approximation. In all studied examples a quantitative agreement between experiment and theory is achieved. To this end it is necessary, however, to take absorption and imperfect coupling into account, concepts that were ignored in most previous theoretical investigations. Classical phase space signatures of scattering are being examined in a small number of experiments

  17. Exact exchange plane-wave-pseudopotential calculations for slabs: Extending the width of the vacuum

    Science.gov (United States)

    Engel, Eberhard

    2018-04-01

    Standard plane-wave pseudopotential (PWPP) calculations for slabs such as graphene become extremely demanding, as soon as the exact exchange (EXX) of density functional theory is applied. Even if the Krieger-Li-Iafrate (KLI) approximation for the EXX potential is utilized, such EXX-PWPP calculations suffer from the fact that an accurate representation of the occupied states throughout the complete vacuum between the replicas of the slab is required. In this contribution, a robust and efficient extension scheme for the PWPP states is introduced, which ensures the correct exponential decay of the slab states in the vacuum for standard cutoff energies and therefore facilitates EXX-PWPP calculations for very wide vacua and rather thick slabs. Using this scheme, it is explicitly verified that the Slater component of the EXX/KLI potential decays as -1 /z over an extended region sufficiently far from the surface (assumed to be perpendicular to the z direction) and from the middle of the vacuum, thus reproducing the asymptotic behavior of the exact EXX potential of a single slab. The calculations also reveal that the orbital-shift component of the EXX/KLI potential is quite sizable in the asymptotic region. In spite of the long-range exchange potential, the replicas of the slab decouple rather quickly with increasing width of the vacuum. Relying on the identity of the work function with the Fermi energy obtained with a suitably normalized total potential, the present EXX/KLI calculations predict work functions for both graphene and the Si(111) surface which are substantially larger than the corresponding experimental data. Together with the size of the orbital-shift potential in the asymptotic region, the very large EXX/KLI work functions indicate a failure of the KLI approximation for nonmetallic slabs.

  18. Fundamental structure of steady plastic shock waves in metals

    OpenAIRE

    Molinari, A.; Ravichandran, G.

    2004-01-01

    The propagation of steady plane shock waves in metallic materials is considered. Following the constitutive framework adopted by R. J. Clifton [Shock Waves and the Mechanical Properties of Solids, edited by J. J. Burke and V. Weiss (Syracuse University Press, Syracuse, N.Y., 1971), p. 73] for analyzing elastic–plastic transient waves, an analytical solution of the steady state propagation of plastic shocks is proposed. The problem is formulated in a Lagrangian setting appropriate for large de...

  19. Instability of combined gravity-inertial-Rossby waves in atmospheres and oceans

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2011-06-01

    Full Text Available The properties of the instability of combined gravity-inertial-Rossby waves on a β-plane are investigated. The wave-energy exchange equation shows that there is an exchange of energy with the background stratified medium. The energy source driving the instability lies in the background enthalpy released by the gravitational buoyancy force. It is shown that if the phase speed of the westward propagating low frequency-long wavelength Rossby wave exceeds the Poincaré-Kelvin (or "equivalent" shallow water wave speed, instability arises from the merging of Rossby and Poincaré modes. There are two key parameters in this instability condition; namely, the equatorial/rotational Mach (or Froude number M and the latitude θ0 of the β-plane. In general waves equatorward of a critical latitude for given M can be driven unstable, with corresponding growth rates of the order of a day or so. Although these conclusions may only be safely drawn for short wavelengths corresponding to a JWKB wave packet propagating internally and located far from boundaries, nevertheless such a local instability may play a significant role in atmosphere-ocean dynamics.

  20. Out-of-plane reflections - are they evidence for deep subducted lithosphere?

    Science.gov (United States)

    Schumacher, Lina; Thomas, Christine

    2015-04-01

    Subduction zones form dominant tectonic features on the Earth and have complex three-dimensional structures. Tomographic inversions for P- and S-wave seismic velocities in the Earth's mantle give impressive images of slabs descending into the deep Earth. However, direct observations of deep slabs are scarce but necessary to make statements concerning physical parameters, structural differences within the slab and its behavior with depth. The main objective of this study is to investigate the geometry, physical parameters and structural differences of subducted lithosphere by investigating seismic P-wave arrivals that reflect off the base of the slab using seismic array techniques. The great circle paths of the source-receiver combinations used do not intersect the slab and serve as reference. We focus on the North pacific region by using earthquakes from Japan, the Philippines and the Hindukush recorded at North American networks (e.g. USArray, Alaska and Canada). The data cover a period from 2000-2012 with a minimum magnitude of 5.6 Mw and depths below 100 km. We are looking for reflections from the slab region that would arrive at the stations with deviating backazimuths. Information on slowness, backazimuth and travel time of the observed out-of-plane arrivals is used to backtrace the wave to its scattering location and to map seismic heterogeneities associated with subduction zones. The reflection points give an idea for the 3D structures within the mantle. Assuming only single scattering in the backtracing algorithm, most out-of-plane signals have to travel as P*P and only a few as S*P phases, due to their timing. Taking into account the radiation pattern of each event in direction of the great circle path and towards the calculated reflection point, it is possible to compare the polarities of the out-of-plane signals with P and/or PP. Furthermore, we analyze the out-of-plane waveforms in the beam trace of the observed slowness and backazimuth by cross

  1. Some Considerations Regarding Plane to Plane Parallelism Error Effects in Robotic Systems

    Directory of Open Access Journals (Sweden)

    Stelian Alaci

    2015-06-01

    Full Text Available The paper shows that by imposing the parallelism constraint between the measured plane and the reference plane, the position of the current plane is not univocal specified and is impossible to specify the way to attain the parallelism errors imposed by accuracy constrains. The parameters involved in the calculus of plane to plane parallelism error can be used to set univocal the relative position between the two planes.

  2. Computation of nonlinear water waves with a high-order Boussinesq model

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Madsen, Per A.; Bingham, Harry

    2005-01-01

    Computational highlights from a recently developed high-order Boussinesq model are shown. The model is capable of treating fully nonlinear waves (up to the breaking point) out to dimensionless depths of (wavenumber times depth) kh \\approx 25. Cases considered include the study of short......-crested waves in shallow/deep water, resulting in hexagonal/rectangular surface patterns; crescent waves, resulting from unstable perturbations of plane progressive waves; and highly-nonlinear wave-structure interactions. The emphasis is on physically demanding problems, and in eachcase qualitative and (when...

  3. Stress wave velocity patterns in the longitudinal-radial plane of trees for defect diagnosis

    Science.gov (United States)

    Guanghui Li; Xiang Weng; Xiaocheng Du; Xiping Wang; Hailin Feng

    2016-01-01

    Acoustic tomography for urban tree inspection typically uses stress wave data to reconstruct tomographic images for the trunk cross section using interpolation algorithm. This traditional technique does not take into account the stress wave velocity patterns along tree height. In this study, we proposed an analytical model for the wave velocity in the longitudinal–...

  4. Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

    Science.gov (United States)

    Mohseni, S. Morteza; Yazdi, H. F.; Hamdi, M.; Brächer, T.; Mohseni, S. Majid

    2018-03-01

    Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.

  5. Empty substrate integrated waveguide technology for E plane high-frequency and high-performance circuits

    Science.gov (United States)

    Belenguer, Angel; Cano, Juan Luis; Esteban, Héctor; Artal, Eduardo; Boria, Vicente E.

    2017-01-01

    Substrate integrated circuits (SIC) have attracted much attention in the last years because of their great potential of low cost, easy manufacturing, integration in a circuit board, and higher-quality factor than planar circuits. A first suite of SIC where the waves propagate through dielectric have been first developed, based on the well-known substrate integrated waveguide (SIW) and related technological implementations. One step further has been made with a new suite of empty substrate integrated waveguides, where the waves propagate through air, thus reducing the associated losses. This is the case of the empty substrate integrated waveguide (ESIW) or the air-filled substrate integrated waveguide (air-filled SIW). However, all these SIC are H plane structures, so classical H plane solutions in rectangular waveguides have already been mapped to most of these new SIC. In this paper a novel E plane empty substrate integrated waveguide (ESIW-E) is presented. This structure allows to easily map classical E plane solutions in rectangular waveguide to this new substrate integrated solution. It is similar to the ESIW, although more layers are needed to build the structure. A wideband transition (covering the frequency range between 33 GHz and 50 GHz) from microstrip to ESIW-E is designed and manufactured. Measurements are successfully compared with simulation, proving the validity of this new SIC. A broadband high-frequency phase shifter (for operation from 35 GHz to 47 GHz) is successfully implemented in ESIW-E, thus proving the good performance of this new SIC in a practical application.

  6. Transformada fraccional de Fourier en el caso de un plano imagen inclinado Fraccional Fourier transform in the case of an inclined image plane

    Directory of Open Access Journals (Sweden)

    Y Torres

    2010-12-01

    Full Text Available La conocida fórmula de difracción de Fresnel relaciona la distribución de amplitud compleja de una onda en el plano objeto (campo ondulatorio de entrada con la distribución de amplitud compleja de la onda en el plano imagen(campo ondulatorio de salida cuando se trata de propagación en el espaciolibre; esto significa que si los planos objeto e imagen son paralelos entre sí, el sistema imagen correspondiente se dice que es un sistema lineal invariantea desplazamiento (LSI. Esta propiedad ventajosa es esencial para el desarrollo de técnicas de imagen sensitivas a fase; sin embargo, si el plano imagen está inclinado con respecto al haz incidente, la distancia efectiva de propagación cambiará sobre el plano imagen, consecuentemente el sistema imagen será no invariante a desplazamiento. En este artículo es propuesta una extensión del formalismo de la difracción de Fresnel al caso de un plano imageninclinado utilizando la transformada de Fourier de orden fraccional.The well-known Fresnel integral relates a known complex wave defined in the object plane (the input wave field to the observable complex wave (the output wave field defined in the image plane after free-space propagation; this means that if the object and image plane are parallel to each other, corresponding imaging system is said to be linear-shift-invariant (LSI. This advantageous property was essential for the development of phase sensitive imaging techniques; however, if the image plane is inclined with respect to the incident beam, the effective propagation distance will vary over the image plane, consequently, the imaging system is not shiftinvariant. In this paper an extension of the theoretical formalism of Fresnel diffraction to the case of an inclined image plane is proposed using the fractional Fourier transform.

  7. Treatment of Ion-Atom Collisions Using a Partial-Wave Expansion of the Projectile Wavefunction

    Science.gov (United States)

    Wong, T. G.; Foster, M.; Colgan, J.; Madison, D. H.

    2009-01-01

    We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge…

  8. Scattering of elastic waves by thin inclusions

    International Nuclear Information System (INIS)

    Simons, D.A.

    1980-01-01

    A solution is derived for the elastic waves scattered by a thin inclusion. The solution is asymptotically valid as inclusion thickness tends to zero with the other dimensions and the frequency fixed. The method entails first approximating the total field in the inclusion in terms of the incident wave by enforcing the appropriate continuity conditions on traction and displacement across the interface, then using these displacements and strains in the volume integral that gives the scattered field. Expressions are derived for the far-field angular distributions of P and S waves due to an incident plane P wave, and plots are given for normalized differential cross sections of an oblate spheroidal tungsten carbide inclusion in a titanium matrix

  9. High-order integral equation methods for problems of scattering by bumps and cavities on half-planes.

    Science.gov (United States)

    Pérez-Arancibia, Carlos; Bruno, Oscar P

    2014-08-01

    This paper presents high-order integral equation methods for the evaluation of electromagnetic wave scattering by dielectric bumps and dielectric cavities on perfectly conducting or dielectric half-planes. In detail, the algorithms introduced in this paper apply to eight classical scattering problems, namely, scattering by a dielectric bump on a perfectly conducting or a dielectric half-plane, and scattering by a filled, overfilled, or void dielectric cavity on a perfectly conducting or a dielectric half-plane. In all cases field representations based on single-layer potentials for appropriately chosen Green functions are used. The numerical far fields and near fields exhibit excellent convergence as discretizations are refined-even at and around points where singular fields and infinite currents exist.

  10. Dynamics of the spatial structure of pulsed discharges in dense gases in point cathode−plane anode gaps and their erosion effect on the plane electrode surface

    International Nuclear Information System (INIS)

    Baksht, E. Kh.; Blinova, O. M.; Erofeev, M. V.; Karelin, V. I.; Ripenko, V. S.; Tarasenko, V. F.; Trenkin, A. A.; Shibitov, Yu. M.; Shulepov, M. A.

    2016-01-01

    The dynamics of the spatial structure of the plasma of pulsed discharges in air and nitrogen in a nonuniform electric field and their erosion effect on the plane anode surface were studied experimentally. It is established that, at a nanosecond front of the voltage pulse, a diffuse discharge forms in the point cathode–plane anode gap due to the ionization wave propagating from the cathode. As the gap length decreases, the diffuse discharge transforms into a spark. A bright spot on the anode appears during the diffuse discharge, while the spark channel forms in the later discharge stage. The microstructure of autographs of anode spots and spark channels in discharges with durations of several nanoseconds is revealed. The autographs consist of up to 100 and more microcraters 5–100 μm in diameter. It is shown that, due to the short duration of the voltage pulse, a diffuse discharge can be implemented, several pulses of which do not produce appreciable erosion on the plane anode or the soot coating deposited on it.

  11. MHD Wave Propagation at the Interface Between Solar Chromosphere and Corona

    Science.gov (United States)

    Huang, Y.; Song, P.; Vasyliunas, V. M.

    2017-12-01

    We study the electromagnetic and momentum constraints at the solar transition region which is a sharp layer interfacing between the solar chromosphere and corona. When mass transfer between the two domains is neglected, the transition region can be treated as a contact discontinuity across which the magnetic flux is conserved and the total forces are balanced. We consider an Alfvénic perturbation that propagates along the magnetic field incident onto the interface from one side. In order to satisfy the boundary conditions at the transition region, only part of the incident energy flux is transmitted through and the rest is reflected. Taking into account the highly anisotropic propagation of waves in magnetized plasmas, we generalize the law of reflection and specify Snell's law for each of the three wave MHD modes: incompressible Alfvén mode and compressible fast and slow modes. Unlike conventional optical systems, the interface between two magnetized plasmas is not rigid but can be deformed by the waves, allowing momentum and energy to be transferred by compression. With compressible modes included, the Fresnel conditions need substantial modification. We derive Fresnel conditions, reflectivities and transmittances, and mode conversion for incident waves propagating along the background magnetic field. The results are well organized when the incident perturbation is decomposed into components in and normal to the incident plane (containing the background magnetic field and the normal direction of the interface). For a perturbation normal to the incident plane, both transmitted and reflected perturbations are incompressible Alfvén mode waves. For a perturbation in the incident plane, they can be compressible slow and fast mode waves which may produce ripples on the transition region.

  12. Diffraction of a plane wave on two-dimensional conductive structures and a surface wave

    Science.gov (United States)

    Davidovich, Mikhael V.

    2018-04-01

    We consider the structures type of two-dimensional electron gas in the form of a thin conductive, in particular, graphene films described by tensor conductivity, which are isolated or located on the dielectric layers. The dispersion equation for hybrid modes, as well as scattering parameters. We show that free wave (eigenwaves) problem follow from the problem of diffraction when linking the amplitude of the current of the linear equations are unsolvable, i.e., the determinant of this system is zero. As a particular case the dispersion equation follow from the conditions of matching (with zero reflection coefficient).

  13. Focusing optical waves with a rotationally symmetric sharp-edge aperture

    Science.gov (United States)

    Hu, Yanwen; Fu, Shenhe; Li, Zhen; Yin, Hao; Zhou, Jianying; Chen, Zhenqiang

    2018-04-01

    While there has been various kinds of patterned structures proposed for wave focusing, these patterned structures usually involve complicated lithographic techniques since the element size of the patterned structures should be precisely controlled in microscale or even nanoscale. Here we propose a new and straightforward method for focusing an optical plane wave in free space with a rotationally symmetric sharp-edge aperture. The focusing phenomenon of wave is realized by superposition of a portion of the higher-order symmetric plane waves generated from the sharp edges of the apertures, in contrast to previously focusing techniques which usually depend on a curved phase. We demonstrate both experimentally and theoretically the focusing effect with a series of apertures having different rotational symmetry, and find that the intensity of the hotspots could be controlled by the symmetric strength of the sharp-edge apertures. The presented results would advance the conventional wisdom that light would diffract in all directions and become expanding when it propagates through an aperture. The proposed method is easy to be processed, and might open potential applications in interferometry, image, and superresolution.

  14. Iterative calculation of reflected and transmitted acoustic waves at a rough interface

    NARCIS (Netherlands)

    Berkhoff, Arthur P.; van den Berg, P.M.; Thijssen, J.M.

    A rigorous iterative technique is described for calculating the acoustic wave reflection and transmission at an irregular interface between two different media. The method is based upon a plane-wave expansion technique in which the acoustic field equations and the radiation condition are satisfied

  15. Two-body Schrödinger wave functions in a plane-wave basis via separation of dimensions

    Science.gov (United States)

    Jerke, Jonathan; Poirier, Bill

    2018-03-01

    Using a combination of ideas, the ground and several excited electronic states of the helium atom and the hydrogen molecule are computed to chemical accuracy—i.e., to within 1-2 mhartree or better. The basic strategy is very different from the standard electronic structure approach in that the full two-electron six-dimensional (6D) problem is tackled directly, rather than starting from a single-electron Hartree-Fock approximation. Electron correlation is thus treated exactly, even though computational requirements remain modest. The method also allows for exact wave functions to be computed, as well as energy levels. From the full-dimensional 6D wave functions computed here, radial distribution functions and radial correlation functions are extracted—as well as a 2D probability density function exhibiting antisymmetry for a single Cartesian component. These calculations support a more recent interpretation of Hund's rule, which states that the lower energy of the higher spin-multiplicity states is actually due to reduced screening, rather than reduced electron-electron repulsion. Prospects for larger systems and/or electron dynamics applications appear promising.

  16. Spin-waves in Antiferromagnetic Single-crystal LiFePO4

    International Nuclear Information System (INIS)

    Li, Jiying; Garlea, Vasile O.; Zarestky, Jarel; Vaknin, D.

    2006-01-01

    Spin-wave dispersions in the antiferromagnetic state of single-crystal LiFePO 4 were determined by inelastic neutron scattering measurements. The dispersion curves measured from the (0,1,0) reflection along both a* and b* reciprocal-space directions reflect the anisotropic coupling of the layered Fe 2+ (S=2) spin system. The spin-wave dispersion curves were theoretically modeled using linear spin-wave theory by including in the spin Hamiltonian in-plane nearest- and next-nearest-neighbor interactions (J 1 and J 2 ), inter-plane nearest-neighbor interactions (J(perpendicular)) and a single-ion anisotropy (D). A weak (0,1,0) magnetic peak was observed in elastic neutron scattering studies of the same crystal indicating that the ground state of the staggered iron moments is not along the (0,1,0) direction, as previously reported from polycrystalline samples studies, but slightly rotated away from this axis.

  17. Observation of the in-plane spin-dephasing anisotropy in [111]-grown GaAs/AlGaAs quantum well

    International Nuclear Information System (INIS)

    Zhao, Chunbo; Li, Junbin; Yu, Ying; Ni, Haiqiao; Niu, Zhichuan; Zhang, Xinhui

    2014-01-01

    The electron density and temperature dependent in-plane spin-dephasing anisotropy in [111]-grown GaAs quantum well (QW) has been investigated by time-resolved magneto-Kerr rotation technique. Due to the specific symmetry of [111]-grown quantum well, the in-plane Rashba and linear Dresselhaus effective spin-orbit magnetic field is parallel to each other for electron wave vectors in all directions. However, an obvious in-plane spin-dephasing anisotropy comparing [2 ¯ 11] with [01 ¯ 1] crystalline orientations has been observed and discussed in this work. Our results demonstrate the innegligible spin dephasing channel through inhomogeneous broadening induced by the out-of-plane non-linear Dresselhaus field, which arises naturally from the C 3 symmetry of [111]-grown GaAs QW

  18. Time-dependent radiation transfer with rayleigh scattering in finite plane-parallel media using pomraning-eddington approximation

    International Nuclear Information System (INIS)

    El-Wakil, S.A.; Sallah, M.; Degheidy, A.R.

    2005-01-01

    The time-dependent radiation transfer equation in plane geometry with Rayleigh scattering is studied. The traveling wave transformation is used to obtain the corresponding stationary-like equation. Pomraning-Eddington approximation is then used to calculate the radiation intensity in finite plane-parallel media. Numerical results and shielding calculations are shown for reflectivity and transmissivity at different times. The medium is assumed to have specular-reflecting boundaries. For the sake of comparison, two different weight functions are introduced and to force the boundary conditions to be fulfilled

  19. First-order reflection/transmission coefficients for unconverted plane P waves in weakly anisotropic media

    Czech Academy of Sciences Publication Activity Database

    Farra, V.; Pšenčík, Ivan

    2010-01-01

    Roč. 183, č. 3 (2010), s. 1443-1454 ISSN 0956-540X R&D Projects: GA ČR GA205/08/0332 Institutional research plan: CEZ:AV0Z30120515 Keywords : body waves * seismic anisotropy * wave propagation Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.411, year: 2010

  20. Plane-wave decomposition by spherical-convolution microphone array

    Science.gov (United States)

    Rafaely, Boaz; Park, Munhum

    2004-05-01

    Reverberant sound fields are widely studied, as they have a significant influence on the acoustic performance of enclosures in a variety of applications. For example, the intelligibility of speech in lecture rooms, the quality of music in auditoria, the noise level in offices, and the production of 3D sound in living rooms are all affected by the enclosed sound field. These sound fields are typically studied through frequency response measurements or statistical measures such as reverberation time, which do not provide detailed spatial information. The aim of the work presented in this seminar is the detailed analysis of reverberant sound fields. A measurement and analysis system based on acoustic theory and signal processing, designed around a spherical microphone array, is presented. Detailed analysis is achieved by decomposition of the sound field into waves, using spherical Fourier transform and spherical convolution. The presentation will include theoretical review, simulation studies, and initial experimental results.

  1. Anisotropic effects of background fields on Born-Infeld electromagnetic waves

    International Nuclear Information System (INIS)

    Aiello, Matias; Bengochea, Gabriel R.; Ferraro, Rafael

    2007-01-01

    We show exact solutions of the Born-Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of the Born-Infeld equations generates an interaction between the background and the wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction-a behavior resembling the one of a wave in an anisotropic medium. This feature could open up a way to experimental tests of the Born-Infeld theory

  2. Anisotropic effects of background fields on Born-Infeld electromagnetic waves

    Energy Technology Data Exchange (ETDEWEB)

    Aiello, Matias [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina) and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)]. E-mail: aiello@iafe.uba.ar; Bengochea, Gabriel R. [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina) and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)]. E-mail: gabriel@iafe.uba.ar; Ferraro, Rafael [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina) and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)]. E-mail: ferraro@iafe.uba.ar

    2007-01-22

    We show exact solutions of the Born-Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of the Born-Infeld equations generates an interaction between the background and the wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction-a behavior resembling the one of a wave in an anisotropic medium. This feature could open up a way to experimental tests of the Born-Infeld theory.

  3. Transverse spin and transverse momentum in scattering of plane waves

    OpenAIRE

    Saha, Sudipta; Singh, Ankit K.; Ray, Subir K.; Banerjee, Ayan; Gupta, Subhasish Dutta; Ghosh, Nirmalya

    2016-01-01

    We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demon...

  4. Instability of in-plane vortices in two-dimensional easy-plane ferromagnets

    International Nuclear Information System (INIS)

    Wysin, G.M.

    1994-01-01

    An analysis of the core region of an in-plane vortex in the two-dimensional Heisenberg model with easy-plane anisotropy λ=J z /J xy leads to a clear understanding of the instability towards transformation into an out-of-plane vortex as a function of anisotropy. The anisotropy parameter λ c at which the in-plane vortex becomes unstable and develops into an out-of-plane vortex is determined with an accuracy comparable to computer simulations for square, hexagonal, and triangular lattices. For λ c , the in-plane vortex is stable but exhibits a normal mode whose frequency goes to zero as ω∝(λ c -λ) 1/2 as λ approaches λ c . For λ>λ c , the static nonzero out-of-plane spin components grow as (λ-λ c ) 1/2 . The lattice dependence of λ c is determined strongly by the number of spins in the core plaquette, is fundamentally a discreteness effect, and cannot be obtained in a continuum theory

  5. Pulsed discharges produced by high-power surface waves

    Science.gov (United States)

    Böhle, A.; Ivanov, O.; Kolisko, A.; Kortshagen, U.; Schlüter, H.; Vikharev, A.

    1996-02-01

    The mechanisms of the ionization front advance in surface-wave-produced discharges are investigated using two experimental set-ups. The high-power surface waves are excited in a 3 cm wavelength band by a surfaguide and a novel type of launcher (an E-plane junction). The ionization front velocity of the surface wave is measured for a wide range of gas pressures, incident microwave power and initial pre-ionization. The experimental results are compared with theoretical ones based on three different models. The comparison between theory and experiment allows one to suggest a new interpretation of the ionization front's advance. The ionization front velocity is determined by a breakdown wave or an ionization wave in the electric field of a high-power surface wave in the zone near the ionization front.

  6. The acoustic field of a point source in a uniform boundary layer over an impedance plane

    Science.gov (United States)

    Zorumski, W. E.; Willshire, W. L., Jr.

    1986-01-01

    The acoustic field of a point source in a boundary layer above an impedance plane is investigated anatytically using Obukhov quasi-potential functions, extending the normal-mode theory of Chunchuzov (1984) to account for the effects of finite ground-plane impedance and source height. The solution is found to be asymptotic to the surface-wave term studies by Wenzel (1974) in the limit of vanishing wind speed, suggesting that normal-mode theory can be used to model the effects of an atmospheric boundary layer on infrasonic sound radiation. Model predictions are derived for noise-generation data obtained by Willshire (1985) at the Medicine Bow wind-turbine facility. Long-range downwind propagation is found to behave as a cylindrical wave, with attention proportional to the wind speed, the boundary-layer displacement thickness, the real part of the ground admittance, and the square of the frequency.

  7. Proof-of-Concept of a Millimeter-Wave Integrated Heterogeneous Network for 5G Cellular

    Directory of Open Access Journals (Sweden)

    Shozo Okasaka

    2016-08-01

    Full Text Available The fifth-generation mobile networks (5G will not only enhance mobile broadband services, but also enable connectivity for a massive number of Internet-of-Things devices, such as wireless sensors, meters or actuators. Thus, 5G is expected to achieve a 1000-fold or more increase in capacity over 4G. The use of the millimeter-wave (mmWave spectrum is a key enabler to allowing 5G to achieve such enhancement in capacity. To fully utilize the mmWave spectrum, 5G is expected to adopt a heterogeneous network (HetNet architecture, wherein mmWave small cells are overlaid onto a conventional macro-cellular network. In the mmWave-integrated HetNet, splitting of the control plane (CP and user plane (UP will allow continuous connectivity and increase the capacity of the mmWave small cells. mmWave communication can be used not only for access linking, but also for wireless backhaul linking, which will facilitate the installation of mmWave small cells. In this study, a proof-of-concept (PoC was conducted to demonstrate the practicality of a prototype mmWave-integrated HetNet, using mmWave technologies for both backhaul and access.

  8. Spin-waves in antiferromagnetic single crystal LiFePO$_4$

    OpenAIRE

    Li, Jiying; Garlea, Vasile O.; Zarestky, Jerel L.; Vaknin, David

    2005-01-01

    Spin-wave dispersions in the antiferromagnetic state of single crystal LiFePO$_4$ were determined by inelastic neutron scattering measurements. The dispersion curves measured from the (010) reflection along both {\\it a}$^\\ast$ and {\\it b}$^\\ast$ reciprocal-space directions reflect the anisotropic coupling of the layered Fe$^{2+}$ (S = 2) spin-system. The spin-wave dispersion curves were theoretically modeled using linear spin-wave theory by including in the spin-Hamiltonian in-plane nearest- ...

  9. Scalar fields nonminimally coupled to pp waves

    International Nuclear Information System (INIS)

    Ayon-Beato, Eloy; Hassaiene, Mokhtar

    2005-01-01

    Here, we report pp waves configurations of three-dimensional gravity for which a scalar field nonminimally coupled to them acts as a source. In absence of self-interaction the solutions are gravitational plane waves with a profile fixed in terms of the scalar wave. In the self-interacting case, only power-law potentials parameterized by the nonminimal coupling constant are allowed by the field equations. In contrast with the free case the self-interacting scalar field does not behave like a wave since it depends only on the wave-front coordinate. We address the same problem when gravitation is governed by topologically massive gravity and the source is a free scalar field. From the pp waves derived in this case, we obtain at the zero topological mass limit, new pp waves solutions of conformal gravity for any arbitrary value of the nonminimal coupling parameter. Finally, we extend these solutions to the self-interacting case of conformal gravity

  10. Boundary attenuation angles for inhomogeneous plane waves in anisotropic dissipative media

    Czech Academy of Sciences Publication Activity Database

    Červený, V.; Pšenčík, Ivan

    2011-01-01

    Roč. 76, č. 3 (2011), WA51-WA62 ISSN 0016-8033 R&D Projects: GA ČR(CZ) GAP210/11/0117 Institutional research plan: CEZ:AV0Z30120515 Keywords : attenuation angles * seismic waves * seismic anisotropy Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.418, year: 2011

  11. Heteroepitaxial growth of basal plane stacking fault free a-plane GaN

    Energy Technology Data Exchange (ETDEWEB)

    Wieneke, Matthias; Hempel, Thomas; Noltemeyer, Martin; Witte, Hartmut; Dadgar, Armin; Blaesing, Juergen; Christen, Juergen; Krost, Alois [Otto-von-Guericke Universitaet Magdeburg, FNW/IEP, Magdeburg (Germany)

    2010-07-01

    Growth of light emitting quantum-wells based on a-plane GaN is a possibility to reduce or even to avoid polarization correlated luminescence red shift and reduction of radiative recombination efficiency. But until now heteroepitaxially grown a-plane GaN films are characterized by a poor crystalline quality expressed by a high density of basal plane stacking faults (BSF) and partial dislocations. We present Si doped a-plane GaN films grown on r-plane sapphire substrates by metal organic vapor phase epitaxy using high temperature AlGaN nucleation layers. FE-SEM images revealed three dimensionally grown GaN crystallites sized up to tenth micrometer in the basal plane and a few tenth micrometers along the c-axes. Though, the full width at half maxima of the X-ray diffraction {omega}-scans of the in-plane GaN(1 anti 100) and GaN(0002) Bragg reflections exhibited a very high crystal quality. Furthermore, luminescence spectra were dominated by near band gap emission, while there was no separated peak of the basal plane stacking fault. In summary we present heteroepitaxially grown a-plane GaN without an evidence of basal plane stacking faults in X-ray diffraction measurements and luminescence spectra.

  12. Unified formulation of radiation conditions for the wave equation

    DEFF Research Database (Denmark)

    Krenk, Steen

    2002-01-01

    A family of radiation conditions for the wave equation is derived by truncating a rational function approxiamtion of the corresponding plane wave representation, and it is demonstrated how these boundary conditions can be formulated in terms of fictitious surface densities, governed by second......-order wave equations on the radiating surface. Several well-established radiation boundary conditions appear as special cases, corresponding to different choice of the coefficients in the rational approximation. The relation between these choices is established, and an explicit formulation in terms...

  13. (211) oriented ZnTe growth on m-plane sapphire by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Nakasu, Taizo [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Tokyo 169-0051 (Japan); Togo, Hiroyoshi [NTT Microsystem Integration Laboratories, Atugi-shi 243-0198 (Japan); Asahi, Toshiaki [Technology Development Center, JX Nippon Mining and Metals Corporation, Hitachi-shi 317-0056 (Japan)

    2013-11-15

    Single-crystalline and single domain ZnTe thin films are sought for high-performance terahertz wave detectors, and ZnTe/sapphire heterostructures were considered since the Electro-Optical (EO) effect could be obtained only from epilayers. ZnTe epilayers were grown on m-plane sapphire substrates by molecular beam epitaxy, and the potential of single domain epilayers was explored. Through the X-ray diffraction pole figure measurement it was confirmed that one (100) oriented ZnTe domain along with two kinds of (211) oriented domains were formed on the m-plane sapphire when the layer was grown at 340 C. When the layer was grown at 350 C, the (211) oriented domain dominated the film. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Monrelativistic particle in a magnetic field in two-dimensional Lobachevsky space, the cylindrical coordinates and the Poincare half-plane

    International Nuclear Information System (INIS)

    Ovsiyu, E.M.

    2012-01-01

    Exact solutions of the Schrodinger equation in the two-dimensional Riemannian space of negative curvature, the hyperbolic Lobachevsky plane, in the presence of an external magnetic field, which is an analog of a uniform magnetic field in the Minkowski space, are constructed. The description uses the cylindrical and quasi-Cartesian coordinates. The quasi-Cartesian coordinates determine the Poincare half-plane. In the both coordinate systems, the Schrodinger equation is solved exactly, the wave functions are constructed. A generalized formula for energy levels is found, which describes the quantized motion of a particle in a magnetic field in the Lobachevsky plane. (authors)

  15. Scattering of wave packets with phases

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-03-09

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

  16. Computational study of nonlinear plasma waves. I. Simulation model and monochromatic wave propagation

    International Nuclear Information System (INIS)

    Matsuda, Y.; Crawford, F.W.

    1975-01-01

    An economical low-noise plasma simulation model originated by Denavit is applied to a series of problems associated with electrostatic wave propagation in a one-dimensional, collisionless, Maxwellian plasma, in the absence of magnetic field. The model is described and tested, first in the absence of an applied signal, and then with a small amplitude perturbation. These tests serve to establish the low-noise features of the model, and to verify the theoretical linear dispersion relation at wave energy levels as low as 10 -6 of the plasma thermal energy: Better quantitative results are obtained, for comparable computing time, than can be obtained by conventional particle simulation models, or direct solution of the Vlasov equation. The method is then used to study propagation of an essentially monochromatic plane wave. Results on amplitude oscillation and nonlinear frequency shift are compared with available theories

  17. Nanoscale measurement of Nernst effect in two-dimensional charge density wave material 1T-TaS2

    Science.gov (United States)

    Wu, Stephen M.; Luican-Mayer, Adina; Bhattacharya, Anand

    2017-11-01

    Advances in nanoscale material characterization on two-dimensional van der Waals layered materials primarily involve their optical and electronic properties. The thermal properties of these materials are harder to access due to the difficulty of thermal measurements at the nanoscale. In this work, we create a nanoscale magnetothermal device platform to access the basic out-of-plane magnetothermal transport properties of ultrathin van der Waals materials. Specifically, the Nernst effect in the charge density wave transition metal dichalcogenide 1T-TaS2 is examined on nano-thin flakes in a patterned device structure. It is revealed that near the commensurate charge density wave (CCDW) to nearly commensurate charge density wave (NCCDW) phase transition, the polarity of the Nernst effect changes. Since the Nernst effect is especially sensitive to changes in the Fermi surface, this suggests that large changes are occurring in the out-of-plane electronic structure of 1T-TaS2, which are otherwise unresolved in just in-plane electronic transport measurements. This may signal a coherent evolution of out-of-plane stacking in the CCDW → NCCDW transition.

  18. Triple differential cross-sections of Ne (2s2) in coplanar to perpendicular plane geometry

    Science.gov (United States)

    Chen, L. Q.; Khajuria, Y.; Chen, X. J.; Xu, K. Z.

    2003-10-01

    The distorted wave Born approximation (DWBA) with the spin averaged static exchange potential has been used to calculate the triple differential cross-sections (TDCSs) for Ne (2s^2) ionization by electron impact in coplanar to perpendicular plane symmetric geometry at 110.5 eV incident electron energy. The present theoretical results at gun angles Psi = 0^circ (coplanar symmetric geometry) and Psi = 90^circ (perpendicular plane geometry) are in satisfactory agreement with the available experimental data. A deep interference minimum appears in the TDCS in the coplanar symmetric geometry and a strong peak at scattering angle xi = 90^circ caused by the single collision mechanism has been observed in the perpendicular plane geometry. The TDCSs at the gun angles Psi = 30^circ, and Psi = 60^circ are predicted.

  19. Wave fields in real media wave propagation in anisotropic, anelastic, porous and electromagnetic media

    CERN Document Server

    Carcione, José M

    2007-01-01

    This book examines the differences between an ideal and a real description of wave propagation, where ideal means an elastic (lossless), isotropic and single-phase medium, and real means an anelastic, anisotropic and multi-phase medium. The analysis starts by introducing the relevant stress-strain relation. This relation and the equations of momentum conservation are combined to give the equation of motion. The differential formulation is written in terms of memory variables, and Biot's theory is used to describe wave propagation in porous media. For each rheology, a plane-wave analysis is performed in order to understand the physics of wave propagation. The book contains a review of the main direct numerical methods for solving the equation of motion in the time and space domains. The emphasis is on geophysical applications for seismic exploration, but researchers in the fields of earthquake seismology, rock acoustics, and material science - including many branches of acoustics of fluids and solids - may als...

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

    OpenAIRE

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

    2016-01-01

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

  1. The focusing effect of electromagnetic waves in two-dimensional photonic crystals with gradually varying lattice constant

    Directory of Open Access Journals (Sweden)

    F Bakhshi Garmi

    2016-02-01

    Full Text Available In this paper we studied the focusing effect of electromagnetic wave in the two-dimensional graded photonic crystal consisting of Silicon rods in the air background with gradually varying lattice constant. The results showed that graded photonic crystal can focus wide beams on a narrow area at frequencies near the lower edge of the band gap, where equal frequency contours are not concave. For calculation of photonic band structure and equal frequency contours, we have used plane wave expansion method and revised plane wave expansion method, respectively. The calculation of the electric and magnetic fields was performed by finite difference time domain method.

  2. Probing the CuO planes with positrons in high Tc cuprates: theoretical predictions

    International Nuclear Information System (INIS)

    Barbiellini, B.; Jarlborg, T.; Massidda, S.; Peter, M.

    1995-01-01

    Positron annihilation spectroscopy is a useful tool to investigate the Fermi surface in high T c superconductors. To study the physics of the copper-oxygen subsystem that forms the Cu-O layers, it is important to provide theoretical predictions, on materials where there is a large overlap between the positron and the interesting Cu-O planes. We have performed first-principle electronic structure calculations obtained using the linear muffin-tin orbital and the full-potential linearized augmented plane wave methods. The positron charge distributions and their sensitivity to different potentials are calculated. Secondly, we have computed the annihilation rates and the electron-positron momentum density in order to give predictions of the Fermi surface signals. (orig.)

  3. Kubo-Greenwood electrical conductivity formulation and implementation for projector augmented wave datasets

    Science.gov (United States)

    Calderín, L.; Karasiev, V. V.; Trickey, S. B.

    2017-12-01

    As the foundation for a new computational implementation, we survey the calculation of the complex electrical conductivity tensor based on the Kubo-Greenwood (KG) formalism (Kubo, 1957; Greenwood, 1958), with emphasis on derivations and technical aspects pertinent to use of projector augmented wave datasets with plane wave basis sets (Blöchl, 1994). New analytical results and a full implementation of the KG approach in an open-source Fortran 90 post-processing code for use with Quantum Espresso (Giannozzi et al., 2009) are presented. Named KGEC ([K]ubo [G]reenwood [E]lectronic [C]onductivity), the code calculates the full complex conductivity tensor (not just the average trace). It supports use of either the original KG formula or the popular one approximated in terms of a Dirac delta function. It provides both Gaussian and Lorentzian representations of the Dirac delta function (though the Lorentzian is preferable on basic grounds). KGEC provides decomposition of the conductivity into intra- and inter-band contributions as well as degenerate state contributions. It calculates the dc conductivity tensor directly. It is MPI parallelized over k-points, bands, and plane waves, with an option to recover the plane wave processes for their use in band parallelization as well. It is designed to provide rapid convergence with respect to k-point density. Examples of its use are given.

  4. Certain Solutions Of Shock-Waves In Non-Ideal Gases

    Directory of Open Access Journals (Sweden)

    Kanti Pandey

    2016-05-01

    Full Text Available In present paper non similar solutions for plane, cylindrical and spherical unsteady flows of non-ideal gas behind shock wave of arbitrary strength initiated by the instantaneous release of finite energy and propagating in a non-ideal gas is investigated. Asymptotic analysis is applied to obtain a solution up to second order. Solution for numerical calculation Runga-Kutta method of fourth order is applied and is concluded that for non-ideal case there is a decrease in velocity, pressure and density for 0th and IInd order in comparison to ideal gas but a increasing tendency in velocity, pressure and density for Ist order in comparison to ideal gas. The energy of explosion J0 for ideal gas is greater in comparison to non-ideal gas for plane, cylindrical and spherical waves.

  5. Subharmonic edge waves on a large, shallow island

    Science.gov (United States)

    Foda, Mostafa A.

    1988-08-01

    Subharmonic resonance of edge waves by incident and reflected waves has been studied thus far for the case of a plane infinite beach. The analysis will be extended here to the case of a curved coastline, with a large radius of curvature and slowly varying beach slope in the longshore direction. It will be shown that the effects of such slow beach slope changes on a propagating edge wave are similar to the familiar shoaling effects on incident waves. The case of subharmonic edge wave generation on large shallow islands will be discussed in detail. The nonlinear analysis will show that within a certain range of island sizes, the generation mechanism can produce a stable standing edge wave around the island. For larger islands the solution disintegrates into two out-of-phase envelopes of opposite-going edge waves. For still larger islands, the generated progressive edge waves become unstable to sideband modulations.

  6. A NEXT GENERATION MULTI-BEAM FOCAL PLANE ARRAY RECEIVER OF TRAO FOR 86-115 GHZ BAND

    Directory of Open Access Journals (Sweden)

    Moon-Hee Chung

    2006-03-01

    Full Text Available The noise temperature of existing millimeter-wave receivers is already within two or three times quantum noise limit. One of practical ways to increase the observation speed of single dish radio telescope without longer integration time is use of multi-beam focal plane array receiver as demonstrated in several large single dish radio telescopes. In this context the TRAO (Taeduk Radio Astronomy Observatory, which operates a 143n Cassegrain radio telescope, is planning to develop a 4 x 4 beams focal plane array SIS receiver system for 86-115 GHz band. Even though millimeter-wave HEMT LNA-based receivers approach the noise temperature comparable to the SIS receiver at W-band, it is believed that the receiver based on SIS mixer seems to offer a bit more advantages. The critical part of the multi-beam array receiver will be sideband separating SIS mixers. Employing such a type of SIS mixer makes it possible to simplify the quasi-optics of receiver. Otherwise, an SSB filter should be used in front of the mixer or some sophisticated post-processing of observation data is needed. In this paper we will present a preliminary design concept and components needed for the development of a new 3 mm band multi-beam focal plane array receiver.

  7. Design of high-speed planing hulls for the improvement of resistance and seakeeping performance

    Directory of Open Access Journals (Sweden)

    Dong Jin Kim

    2013-03-01

    Full Text Available High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No. 2 and no. 3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences ‘fly over’ phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.

  8. Ion-acoustic cnoidal waves in a quantum plasma

    International Nuclear Information System (INIS)

    Mahmood, S.; Haas, F.

    2014-01-01

    Nonlinear ion-acoustic cnoidal wave structures are studied in an unmagnetized quantum plasma. Using the reductive perturbation method, a Korteweg-de Vries equation is derived for appropriate boundary conditions and nonlinear periodic wave solutions are obtained. The corresponding analytical solution and numerical plots of the ion-acoustic cnoidal waves and solitons in the phase plane are presented using the Sagdeev pseudo-potential approach. The variations in the nonlinear potential of the ion-acoustic cnoidal waves are studied at different values of quantum parameter H e which is the ratio of electron plasmon energy to electron Fermi energy defined for degenerate electrons. It is found that both compressive and rarefactive ion-acoustic cnoidal wave structures are formed depending on the value of the quantum parameter. The dependence of the wavelength and frequency on nonlinear wave amplitude is also presented

  9. Transition operators in electromagnetic-wave diffraction theory - General theory

    Science.gov (United States)

    Hahne, G. E.

    1992-01-01

    A formal theory is developed for the scattering of time-harmonic electromagnetic waves from impenetrable immobile obstacles with given linear, homogeneous, and generally nonlocal boundary conditions of Leontovich (impedance) type for the wave of the obstacle's surface. The theory is modeled on the complete Green's function and the transition (T) operator in time-independent formal scattering theory of nonrelativistic quantum mechanics. An expression for the differential scattering cross section for plane electromagnetic waves is derived in terms of certain matrix elements of the T operator for the obstacle.

  10. Parametric transformation of weak gravitational wave into electromagnetic one in a three-level system

    International Nuclear Information System (INIS)

    Tagirov, Eh.A.

    1985-01-01

    A model of resonance parametric transformation of a gravitational wave to electromagnetic one is considered. Two plane monochromatic waves: a strong electromagnetic and weak gravitational - interacting in a medium generate at difference and sum frequencies an electromagnetic wave in a direction determined with the condition of spatial wave synchronism. Rarefied cold gas or beam of elementary emitters (''molecules'') serve as a medium model. Coefficients of parametric transformation have been determined

  11. Vibration isolation design for periodically stiffened shells by the wave finite element method

    Science.gov (United States)

    Hong, Jie; He, Xueqing; Zhang, Dayi; Zhang, Bing; Ma, Yanhong

    2018-04-01

    Periodically stiffened shell structures are widely used due to their excellent specific strength, in particular for aeronautical and astronautical components. This paper presents an improved Wave Finite Element Method (FEM) that can be employed to predict the band-gap characteristics of stiffened shell structures efficiently. An aero-engine casing, which is a typical periodically stiffened shell structure, was employed to verify the validation and efficiency of the Wave FEM. Good agreement has been found between the Wave FEM and the classical FEM for different boundary conditions. One effective wave selection method based on the Wave FEM has thus been put forward to filter the radial modes of a shell structure. Furthermore, an optimisation strategy by the combination of the Wave FEM and genetic algorithm was presented for periodically stiffened shell structures. The optimal out-of-plane band gap and the mass of the whole structure can be achieved by the optimisation strategy under an aerodynamic load. Results also indicate that geometric parameters of stiffeners can be properly selected that the out-of-plane vibration attenuates significantly in the frequency band of interest. This study can provide valuable references for designing the band gaps of vibration isolation.

  12. Efficient Multivariable Generalized Predictive Control for Autonomous Underwater Vehicle in Vertical Plane

    OpenAIRE

    Yao, Xuliang; Yang, Guangyi

    2016-01-01

    This paper presents the design and simulation validation of a multivariable GPC (generalized predictive control) for AUV (autonomous underwater vehicle) in vertical plane. This control approach has been designed in the case of AUV navigating with low speed near water surface, in order to restrain wave disturbance effectively and improve pitch and heave motion stability. The proposed controller guarantees compliance with rudder manipulation, AUV output constraints, and driving energy consumpti...

  13. Large band gaps of water waves through two-dimensional periodic topography

    International Nuclear Information System (INIS)

    Yang Shaohua; Wu Fugen; Zhong Huilin; Zhong Lanhua

    2006-01-01

    In this Letter, the band structures and band gaps of liquid surface waves propagating over two-dimensional periodic topography was investigated by plane-waves expansion method. The periodic topography drilled by square hollows with square lattice was considered. And the effects of the filling fraction and the orientation of bottom-hollows on the band gaps are investigated in detail

  14. Electromagnetic waves in a layer of hot plasma with negligible collisions

    International Nuclear Information System (INIS)

    Vacca, J.

    1975-01-01

    The propagation of electromagnetic waves in a plane plasma layer in a uniform magnetic field has been studied, following the hypothesis of immoble ions and negligible ion-electron interactions. Waves dependent on one spatial coordinate are considered and all the parameters of the problems are considered. The cases of perpendicular and parallel magnetic field are treated

  15. Spin wave vortex from the scattering on Bloch point solitons

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho-Santos, V.L., E-mail: vagson.carvalho@usach.cl [Instituto Federal de Educação, Ciência e Tecnologia Baiano - Campus Senhor do Bonfim, Km 04 Estrada da Igara, 48970-000 Senhor do Bonfim, Bahia (Brazil); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Elías, R.G., E-mail: gabriel.elias@usach.cl [Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Nunez, A.S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile)

    2015-12-15

    The interaction of a spin wave with a stationary Bloch point is studied. The topological non-trivial structure of the Bloch point manifests in the propagation of spin waves endowing them with a gauge potential that resembles the one associated with the interaction of a magnetic monopole and an electron. By pursuing this analogy, we are led to the conclusion that the scattering of spin waves and Bloch points is accompanied by the creation of a magnon vortex. Interference between such a vortex and a plane wave leads to dislocations in the interference pattern that can be measurable by means of magnon holography.

  16. An accelerated hologram calculation using the wavefront recording plane method and wavelet transform

    Science.gov (United States)

    Arai, Daisuke; Shimobaba, Tomoyoshi; Nishitsuji, Takashi; Kakue, Takashi; Masuda, Nobuyuki; Ito, Tomoyoshi

    2017-06-01

    Fast hologram calculation methods are critical in real-time holography applications such as three-dimensional (3D) displays. We recently proposed a wavelet transform-based hologram calculation called WASABI. Even though WASABI can decrease the calculation time of a hologram from a point cloud, it increases the calculation time with increasing propagation distance. We also proposed a wavefront recoding plane (WRP) method. This is a two-step fast hologram calculation in which the first step calculates the superposition of light waves emitted from a point cloud in a virtual plane, and the second step performs a diffraction calculation from the virtual plane to the hologram plane. A drawback of the WRP method is in the first step when the point cloud has a large number of object points and/or a long distribution in the depth direction. In this paper, we propose a method combining WASABI and the WRP method in which the drawbacks of each can be complementarily solved. Using a consumer CPU, the proposed method succeeded in performing a hologram calculation with 2048 × 2048 pixels from a 3D object with one million points in approximately 0.4 s.

  17. Observation of self-excited acoustic vortices in defect-mediated dust acoustic wave turbulence.

    Science.gov (United States)

    Tsai, Ya-Yi; I, Lin

    2014-07-01

    Using the self-excited dust acoustic wave as a platform, we demonstrate experimental observation of self-excited fluctuating acoustic vortex pairs with ± 1 topological charges through spontaneous waveform undulation in defect-mediated turbulence for three-dimensional traveling nonlinear longitudinal waves. The acoustic vortex pair has helical waveforms with opposite chirality around the low-density hole filament pair in xyt space (the xy plane is the plane normal to the wave propagation direction). It is generated through ruptures of sequential crest surfaces and reconnections with their trailing ruptured crest surfaces. The initial rupture is originated from the amplitude reduction induced by the formation of the kinked wave crest strip with strong stretching through the undulation instability. Increasing rupture causes the separation of the acoustic vortex pair after generation. A similar reverse process is followed for the acoustic vortex annihilating with the opposite-charged acoustic vortex from the same or another pair generation.

  18. Chiral retrieval method based on right circularly polarized and left circularly polarized waves

    International Nuclear Information System (INIS)

    Martín, Ernesto; Muñoz, Juan; Margineda, José; Molina-Cuberos, Gregorio J; García-Collado, Ángel J

    2014-01-01

    The free-wave characterization of metamaterials is usually carried out by illuminating a sample with a linearly polarized plane electromagnetic wave. At points before and after the sample, sensors are introduced to measure the transverse components of the field, in order to compute the reflection and transmission coefficients related with the co- and cross-polar field components. Based on this information, retrieval algorithms allow parameters like rotation angle, effective chirality and refraction index to be calculated. Here we propose to use the transmission signals under illumination with plane circularly polarized waves, without sensing the reflection signal, to calculate the chirality parameter and the rotation angle due to the electromagnetic activity of the material. This new method, which allows a simpler characterization of a chiral slab, is applied to the study of metamaterials composed of both periodic and random distributions of metallic structures with chiral symmetry. The experimental results are contrasted with simulations and alternative measurements obtained using linearly polarized waves. (paper)

  19. On Maximally Dissipative Shock Waves in Nonlinear Elasticity

    OpenAIRE

    Knowles, James K.

    2010-01-01

    Shock waves in nonlinearly elastic solids are, in general, dissipative. We study the following question: among all plane shock waves that can propagate with a given speed in a given one-dimensional nonlinearly elastic bar, which one—if any—maximizes the rate of dissipation? We find that the answer to this question depends strongly on the qualitative nature of the stress-strain relation characteristic of the given material. When maximally dissipative shocks do occur, they propagate according t...

  20. Investigation of the spin-1 honeycomb antiferromagnet BaNi2V2O8 with easy-plane anisotropy

    Science.gov (United States)

    Klyushina, E. S.; Lake, B.; Islam, A. T. M. N.; Park, J. T.; Schneidewind, A.; Guidi, T.; Goremychkin, E. A.; Klemke, B.; Mânsson, M.

    2017-12-01

    The magnetic properties of the two-dimensional, S =1 honeycomb antiferromagnet BaNi2V2O8 have been comprehensively studied using dc susceptibility measurements and inelastic neutron scattering techniques. The magnetic excitation spectrum is found to be dispersionless within experimental resolution between the honeycomb layers, while it disperses strongly within the honeycomb plane where it consists of two gapped spin-wave modes. The magnetic excitations are compared to linear spin-wave theory allowing the Hamiltonian to be determined. The first- and second-neighbor magnetic exchange interactions are antiferromagnetic and lie within the ranges 10.90 meV ≤Jn≤13.35 meV and 0.85 meV ≤Jn n≤1.65 meV, respectively. The interplane coupling Jout is four orders of magnitude weaker than the intraplane interactions, confirming the highly two-dimensional magnetic behavior of this compound. The sizes of the energy gaps are used to extract the magnetic anisotropies and reveal substantial easy-plane anisotropy and a very weak in-plane easy-axis anisotropy. Together these results reveal that BaNi2V2O8 is a candidate compound for the investigation of vortex excitations and Berezinsky-Kosterliz-Thouless phenomenon.

  1. WKB solution 4×4 for electromagnetic waves in a planar magnetically anisotropic inhomogeneous layer

    Science.gov (United States)

    Moiseeva, Natalya Michailovna; Moiseev, Anton Vladimirovich

    2018-04-01

    In the paper, an oblique incidence of a plane electromagnetic wave on a planar magnetically anisotropic inhomogeneous layer is considered. We consider the case when all the components of the magnetic permeability tensor are non zero and vary with distance from the interface of media. The WKB method gives a matrix 4 × 4 solution for the projections of the electromagnetic wave fields during its propagation. The dependence of the cross-polarized components on the orientation of the anisotropic medium relative to the plane of incidence of the medium is analyzed.

  2. Reflection of P and SV waves at the free surface of a monoclinic ...

    Indian Academy of Sciences (India)

    R.Narasimhan(krishtel emaging)1461 1996 Oct 15 13:05:22

    The propagation of plane waves in an anisotropic elastic medium possessing monoclinic symmetry is discussed. The expressions for ... Keywords. Anisotropic medium; elastic waves; monoclinic half-space; reflection coefficients. Proc. Indian Acad. Sci. ...... In contrast, for C < 0, the angle of reflec- tion is less than the angle of ...

  3. Propagation of inertial-gravity waves on an island shelf

    Science.gov (United States)

    Bondur, V. G.; Sabinin, K. D.; Grebenyuk, Yu. V.

    2015-09-01

    The propagation of inertial-gravity waves (IGV) at the boundary of the Pacific shelf near the island of Oahu (Hawaii), whose generation was studied in the first part of this work [1], is analyzed. It is shown that a significant role there is played by the plane oblique waves; whose characteristics were identified by the method of estimating 3D wave parameters for the cases when the measurements are available only for two verticals. It is established that along with the descending propagation of energy that is typical of IGVs, wave packets ascend from the bottom to the upper layers, which is caused by the emission of waves from intense jets of discharged waters flowing out of a diffusor located at the bottom.

  4. Electron waves and resonances in bounded plasmas

    CERN Document Server

    Vandenplas, Paul E

    1968-01-01

    General theoretical methods and experimental techniques ; the uniform plasma slab-condenser system ; the hollow cylindrical plasma ; scattering of a plane electromagnetic wave by a plasma column in steady magnetic fields (cold plasma approximation) ; hot non-uniform plasma column ; metallic and dielectric resonance probes, plasma-dielectric coated antenna, general considerations.

  5. (2+1)-dimensional dissipation nonlinear Schrödinger equation for envelope Rossby solitary waves and chirp effect

    International Nuclear Information System (INIS)

    Li Jin-Yuan; Fang Nian-Qiao; Yuan Xiao-Bo; Zhang Ji; Xue Yu-Long; Wang Xue-Mu

    2016-01-01

    In the past few decades, the (1+1)-dimensional nonlinear Schrödinger (NLS) equation had been derived for envelope Rossby solitary waves in a line by employing the perturbation expansion method. But, with the development of theory, we note that the (1+1)-dimensional model cannot reflect the evolution of envelope Rossby solitary waves in a plane. In this paper, by constructing a new (2+1)-dimensional multiscale transform, we derive the (2+1)-dimensional dissipation nonlinear Schrödinger equation (DNLS) to describe envelope Rossby solitary waves under the influence of dissipation which propagate in a plane. Especially, the previous researches about envelope Rossby solitary waves were established in the zonal area and could not be applied directly to the spherical earth, while we adopt the plane polar coordinate and overcome the problem. By theoretical analyses, the conservation laws of (2+1)-dimensional envelope Rossby solitary waves as well as their variation under the influence of dissipation are studied. Finally, the one-soliton and two-soliton solutions of the (2+1)-dimensional NLS equation are obtained with the Hirota method. Based on these solutions, by virtue of the chirp concept from fiber soliton communication, the chirp effect of envelope Rossby solitary waves is discussed, and the related impact factors of the chirp effect are given. (paper)

  6. Dynamic Interaction of Interfacial Point Source Loading and Cylinder in an Elastic Quarter with Anti-plane Shear

    Science.gov (United States)

    Chun, Gao; Hui, Qi; Nan, Pan Xiang; Bo, Zhao Yuan

    2017-07-01

    Theoretical steady state solution of a semi-circular cylinder impacted by an anti-plane point loading in a vertical bound of an elastic quarter is formulated in this paper through using image method and wave function expansion series. The elastic quarter is extended as a half space, and the semi-circular interfacial cylinder is extended as a circular cylinder. Displacement field is constructed as series of Fourier-Hankel and Fourier-Bessel wave functions. At last, circular boundary is expanded as Fourier series to determine coefficients of wave function. Numerical results show that material parameters have two widely divergent effects on the radial and circumferential dynamic stress distribution.

  7. Affine planes, ternary rings, and examples of non-Desarguesian planes

    OpenAIRE

    Ivanov, Nikolai V.

    2016-01-01

    The paper is devoted to a detailed self-contained exposition of a part of the theory of affine planes leading to a construction of affine (or, equivalently, projective) planes not satisfying the Desarques axiom. It is intended to complement the introductory expositions of the theory of affine and projective planes. A novelty of our exposition is a new notation for the ternary operation in a ternary ring, much more suggestive than the standard one.

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

    Science.gov (United States)

    Berk, N. F.

    2014-03-01

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

  9. Submillimeter wave ESR of copper-oxides

    International Nuclear Information System (INIS)

    Ohta, Hitoshi; Motokawa, Mitsuhiro

    1993-01-01

    Since the discovery of high T c superconductors the magnetism of various copper-oxides has attracted much interest. Especially the magnetism of strong spin correlation systems in various CuO 4 networks is of great interest because it is well known that the superconductivity is occurring in the CuO 2 plane of the high T c superconductors. Here the authors will show some of their work done on copper-oxides by submillimeter wave ESR. The submillimeter wave ESR can provide the frequency region of 90 ∼ 3,100 GHz and the pulse magnetic field up to 30T

  10. The Interaction between the Plane Wave and the Plate with Limited Height in Soil

    Directory of Open Access Journals (Sweden)

    N.A. Lokteva

    2017-03-01

    Full Text Available A solution of the two-dimensional task on interaction between the harmonic wave and the plate with the limited height in soil has been provided. The plate surrounded on both sides with the half-spaces filled with soil medium has been used as a vibro-absorbing obstacle. The mechanical behavior of the plate has been described by S.P. Timoshenko's shift model and the mechanical behavior of soil by a linear elasticity theory equation. The main purpose of the paper is to determine the total acceleration vector field inducted by the penetrated and radiated waves in the second half-space. The mathematical formulation of the task includes a model of upcoming wave, soil medium and plate movement equation, infinity conditions, and conditions of soil contact with obstacle. Conditions of free slip have been taken as the contact conditions between the soil and the obstacle. We have considered a closed system of equations, which includes wave equations for scalar and vector potentials, elasticity theory equations for soil mediums, Koshi's relations, physical law, and plate movement equation. The boundary conditions for the plate correspond to a hinged support. To solve this task, all functions have been expanded in trigonometric series that allowed to obtain potential values in the coefficients of the series. To define the integrations constants, the contact conditions between the obstacle and soil have been used. On the basis of the revealed potentials, we have defined displacements on the boundary between the plate and soil and in other points of the second half-space. The vibro-absorbing properties of the plate have been investigated depending on the frequency of the harmonic wave falling on the plate. From the practical point of view, this task is related to protection of buildings from vibrations formed at a distance from underground railways.

  11. Noncommuting limits of oscillator wave functions

    International Nuclear Information System (INIS)

    Daboul, J.; Pogosyan, G. S.; Wolf, K. B.

    2007-01-01

    Quantum harmonic oscillators with spring constants k > 0 plus constant forces f exhibit rescaled and displaced Hermite-Gaussian wave functions, and discrete, lower bound spectra. We examine their limits when (k, f) → (0, 0) along two different paths. When f → 0 and then k → 0, the contraction is standard: the system becomes free with a double continuous, positive spectrum, and the wave functions limit to plane waves of definite parity. On the other hand, when k → 0 first, the contraction path passes through the free-fall system, with a continuous, nondegenerate, unbounded spectrum and displaced Airy wave functions, while parity is lost. The subsequent f → 0 limit of the nonstandard path shows the dc hysteresis phenomenon of noncommuting contractions: the lost parity reappears as an infinitely oscillating superposition of the two limiting solutions that are related by the symmetry

  12. Parallel ferromagnetic resonance and spin-wave excitation in exchange-biased NiFe/IrMn bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, Marcos Antonio de, E-mail: marcossharp@gmail.com [Instituto de Física, Universidade Federal de Goiás, Goiânia, 74001-970 (Brazil); Pelegrini, Fernando [Instituto de Física, Universidade Federal de Goiás, Goiânia, 74001-970 (Brazil); Alayo, Willian [Departamento de Física, Universidade Federal de Pelotas, Pelotas, 96010-900 (Brazil); Quispe-Marcatoma, Justiniano; Baggio-Saitovitch, Elisa [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, 22290-180 (Brazil)

    2014-10-01

    Ferromagnetic Resonance study of sputtered Ru(7 nm)/NiFe(t{sub FM})/IrMn(6 nm)/Ru(5 nm) exchange-biased bilayers at X and Q-band microwave frequencies reveals the excitation of spin-wave and NiFe resonance modes. Angular variations of the in-plane resonance fields of spin-wave and NiFe resonance modes show the effect of the unidirectional anisotropy, which is about twice larger for the spin-wave mode due to spin pinning at the NiFe/IrMn interface. At Q-band frequency the angular variations of in-plane resonance fields also reveal the symmetry of a uniaxial anisotropy. A modified theoretical model which also includes the contribution of a rotatable anisotropy provides a good description of the experimental results.

  13. Spatial mode structures of electrostatic drift waves in a collisional cylindrical helicon plasma

    DEFF Research Database (Denmark)

    Schröder, C.; Grulke, O.; Klinger, T.

    2004-01-01

    In a cylindrical helicon plasma, mode structures of coherent drift waves are studied in the poloidal plane, the plane perpendicular to the ambient magnetic field. The mode structures rotate with a constant angular velocity in the direction of the electron diamagnetic drift and show significant...... radial bending. The experimental observations are compared with numerical solutions of a linear nonlocal cylindrical model for drift waves [ Ellis , Plasma Phys. 22, 113 (1980) ]. In the numerical model, a transition to bended mode structures is found if the plasma collisionality is increased....... This finding proves that the experimentally observed bended mode structures are the result of high electron collisionality. (C) 2004 American Institute of Physics....

  14. Vacillations induced by interference of stationary and traveling planetary waves

    Science.gov (United States)

    Salby, Murry L.; Garcia, Rolando R.

    1987-01-01

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

  15. Modeling of steady motion and vertical-plane dynamics of a tunnel hull

    Directory of Open Access Journals (Sweden)

    Chaney Christopher S.

    2014-06-01

    Full Text Available High-speed marine vehicles can take advantage of aerodynamically supported platforms or air wings to increase maximum speed or transportation efficiency. However, this also results in increased complexity of boat dynamics, especially in the presence of waves and wind gusts. In this study, a mathematical model based on the fully unsteady aerodynamic extreme-ground-effect theory and the hydrodynamic added-mass strip theory is applied for simulating vertical-plane motions of a tunnel hull in a disturbed environment, as well as determining its steady states in calm conditions. Calculated responses of the boat to wind gusts and surface waves are demonstrated. The present model can be used as a supplementary method for preliminary estimations of performance of aerodynamically assisted marine craft.

  16. Prediction of Vertical-Plane Wave Loading and Ship Responses in High Seas

    DEFF Research Database (Denmark)

    Wang, Z.; Xia, J.; Jensen, Jørgen Juncher

    2000-01-01

    The non-linearities in wave- and slamming-induced rigid-body motions and structural responses of ships such as heave, pitch and vertical bending moments are consistently investigated based on a rational time-domain strip method. A hydrodynamic model for predicting sectional green water force is a...

  17. Bloch Surface Waves Using Graphene Layers: An Approach toward In-Plane Photodetectors

    Directory of Open Access Journals (Sweden)

    Richa Dubey

    2018-03-01

    Full Text Available A dielectric multilayer platform was investigated as a foundation for two-dimensional optics. In this paper, we present, to the best of our knowledge, the first experimental demonstration of absorption of Bloch surface waves in the presence of graphene layers. Graphene is initially grown on a Cu foil via Chemical Vapor Deposition and transferred layer by layer by a wet-transfer method using poly(methyl methacrylate, (PMMA. We exploit total internal reflection configuration and multi-heterodyne scanning near-field optical microscopy as a far-field coupling method and near-field characterization tool, respectively. The absorption is quantified in terms of propagation lengths of Bloch surface waves. A significant drop in the propagation length of the BSWs is observed in the presence of graphene layers. The propagation length of BSWs in bare multilayer is reduced to 17 times shorter in presence of graphene monolayer, and 23 times shorter for graphene bilayer.

  18. Simulation and Optimization of Surface Acoustic Wave Devises

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    2007-01-01

    In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model...... in effective refractive index introduced in the Mach-Zehnder interferometer arms by the stresses from the surface acoustic wave is calculated. It is shown that the effective refractive index of the fundamental optical mode increases at a surface acoustic wave crest and decreases at a trough. The height...... of a piezoelectric, inhomogeneous material and reflections from the boundaries are avoided by applying perfectly matched layers. The optical modes in the waveguides are modeled by the time-harmonic wave equation for the magnetic field. The two models are coupled using the stress-optical relation and the change...

  19. Frequency selective tunable spin wave channeling in the magnonic network

    Energy Technology Data Exchange (ETDEWEB)

    Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Kotel' nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009 (Russian Federation); Beginin, E. N.; Odincov, S. A.; Sheshukova, S. E.; Sharaevskii, Yu. P. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Stognij, A. I. [Scientific-Practical Materials Research Center, National Academy of Sciences of Belarus, 220072 Minsk (Belarus)

    2016-04-25

    Using the space-resolved Brillouin light scattering spectroscopy, we study the frequency and wavenumber selective spin-wave channeling. We demonstrate the frequency selective collimation of spin-wave in an array of magnonic waveguides, formed between the adjacent magnonic crystals on the surface of yttrium iron garnet film. We show the control over spin-wave propagation length by the orientation of an in-plane bias magnetic field. Fabricated array of magnonic crystal can be used as a magnonic platform for multidirectional frequency selective signal processing applications in magnonic networks.

  20. An Algorithm for constructing Hjelmslev planes

    OpenAIRE

    Hall, Joanne L.; Rao, Asha

    2013-01-01

    Projective Hjelmslev planes and Affine Hjelmselv planes are generalisations of projective planes and affine planes. We present an algorithm for constructing a projective Hjelmslev planes and affine Hjelsmelv planes using projective planes, affine planes and orthogonal arrays. We show that all 2-uniform projective Hjelmslev planes, and all 2-uniform affine Hjelsmelv planes can be constructed in this way. As a corollary it is shown that all 2-uniform Affine Hjelmselv planes are sub-geometries o...

  1. Estimation of spin contamination error in dissociative adsorption of Au2 onto MgO(0 0 1) surface: First application of approximate spin projection (AP) method to plane wave basis

    Science.gov (United States)

    Tada, Kohei; Koga, Hiroaki; Okumura, Mitsutaka; Tanaka, Shingo

    2018-06-01

    Spin contamination error in the total energy of the Au2/MgO system was estimated using the density functional theory/plane-wave scheme and approximate spin projection methods. This is the first investigation in which the errors in chemical phenomena on a periodic surface are estimated. The spin contamination error of the system was 0.06 eV. This value is smaller than that of the dissociation of Au2 in the gas phase (0.10 eV). This is because of the destabilization of the singlet spin state due to the weakening of the Au-Au interaction caused by the Au-MgO interaction.

  2. Wave-optics description of self-healing mechanism in Bessel beams.

    Science.gov (United States)

    Aiello, Andrea; Agarwal, Girish S

    2014-12-15

    Bessel beams' great importance in optics lies in that these propagate without spreading and can reconstruct themselves behind an obstruction placed across their path. However, a rigorous wave-optics explanation of the latter property is missing. In this work, we study the reconstruction mechanism by means of a wave-optics description. We obtain expressions for the minimum distance beyond the obstruction at which the beam reconstructs itself, which are in close agreement with the traditional one determined from geometrical optics. Our results show that the physics underlying the self-healing mechanism can be entirely explained in terms of the propagation of plane waves with radial wave vectors lying on a ring.

  3. Ultrasound-Guided Out-of-Plane vs. In-Plane Interscalene Catheters: A Randomized, Prospective Study.

    Science.gov (United States)

    Schwenk, Eric S; Gandhi, Kishor; Baratta, Jaime L; Torjman, Marc; Epstein, Richard H; Chung, Jaeyoon; Vaghari, Benjamin A; Beausang, David; Bojaxhi, Elird; Grady, Bernadette

    2015-12-01

    Continuous interscalene blocks provide excellent analgesia after shoulder surgery. Although the safety of the ultrasound-guided in-plane approach has been touted, technical and patient factors can limit this approach. We developed a caudad-to-cephalad out-of-plane approach and hypothesized that it would decrease pain ratings due to better catheter alignment with the brachial plexus compared to the in-plane technique in a randomized, controlled study. To compare an out-of-plane interscalene catheter technique to the in-plane technique in a randomized clinical trial. Eighty-four patients undergoing open shoulder surgery were randomized to either the in-plane or out-of-plane ultrasound-guided continuous interscalene technique. The primary outcome was VAS pain rating at 24 hours. Secondary outcomes included pain ratings in the recovery room and at 48 hours, morphine consumption, the incidence of catheter dislodgments, procedure time, and block difficulty. Procedural data and all pain ratings were collected by blinded observers. There were no differences in the primary outcome of median VAS pain rating at 24 hours between the out-of-plane and in-plane groups (1.50; IQR, [0 - 4.38] vs. 1.25; IQR, [0 - 3.75]; P = 0.57). There were also no differences, respectively, between out-of-plane and in-plane median PACU pain ratings (1.0; IQR, [0 - 3.5] vs. 0.25; IQR, [0 - 2.5]; P = 0.08) and median 48-hour pain ratings (1.25; IQR, [1.25 - 2.63] vs. 0.50; IQR, [0 - 1.88]; P = 0.30). There were no differences in any other secondary endpoint. Our out-of-plane technique did not provide superior analgesia to the in-plane technique. It did not increase the number of complications. Our technique is an acceptable alternative in situations where the in-plane technique is difficult to perform.

  4. Numerical tests of evolution systems, gauge conditions, and boundary conditions for 1D colliding gravitational plane waves

    International Nuclear Information System (INIS)

    Bardeen, J.M.; Buchman, L.T.

    2002-01-01

    We investigate how the accuracy and stability of numerical relativity simulations of 1D colliding plane waves depends on choices of equation formulations, gauge conditions, boundary conditions, and numerical methods, all in the context of a first-order 3+1 approach to the Einstein equations, with basic variables some combination of first derivatives of the spatial metric and components of the extrinsic curvature tensor. Hyperbolic schemes, specifically variations on schemes proposed by Bona and Masso and Anderson and York, are compared with variations of the Arnowitt-Deser-Misner formulation. Modifications of the three basic schemes include raising one index in the metric derivative and extrinsic curvature variables and adding a multiple of the energy constraint to the extrinsic curvature evolution equations. Redundant variables in the Bona-Masso formulation may be reset frequently or allowed to evolve freely. Gauge conditions which simplify the dynamical structure of the system are imposed during each time step, but the lapse and shift are reset periodically to control the evolution of the spacetime slicing and the longitudinal part of the metric. We show that physically correct boundary conditions, satisfying the energy and momentum constraint equations, generically require the presence of some ingoing eigenmodes of the characteristic matrix. Numerical methods are developed for the hyperbolic systems based on decomposing flux differences into linear combinations of eigenvectors of the characteristic matrix. These methods are shown to be second-order accurate, and in practice second-order convergent, for smooth solutions, even when the eigenvectors and eigenvalues of the characteristic matrix are spatially varying

  5. METHOD FOR DETERMINATION OF FOCAL PLANE LOCATION OF FOCUSING COMPONENTS

    Directory of Open Access Journals (Sweden)

    A. I. Ivashko

    2017-01-01

    Full Text Available Mass-production of different laser systems often requires utilization of the focal spot size method for determination of output laser beam spatial characteristics. The main challenge of this method is high accuracy maintenance of a CCD camera beam profiler in the collecting lens focal plane. The aim of our work is development of new method for placing of photodetector array in the collecting lens focal plane with high accuracy.Proposed technique is based on focusing of several parallel laser beams. Determination of the focal plane position requires only longitudinal translation of the CCD-camera to find a point of laser beams intersection. Continuous-wave (CW diode-pumped laser emitting in the spectral region near 1μm was created to satisfy the requirements of the developed technique. Designed microchip laser generates two stigmatic Gaussian beams with automatically parallel beam axes due to independent pumping of different areas of the one microchip crystal having the same cavity mirrors.It was theoretically demonstrated that developed method provides possibility of the lenses focal plane determination with 1 % accuracy. The microchip laser generates two parallel Gaussian beams with divergence of about 10 mrad. Laser output power can be varied in the range of 0.1–1.5 W by changing the pumping laser diode electrical current. The distance between two beam axes can be changed in the range of 0.5–5.0 mm.We have proposed method for determination of positive lens focal plane location by using of CCDcamera and two laser beams with parallel axes without utilization of additional optical devices. We have developed CW longitudinally diode pumped microchip laser emitting in the 1-μm spectral region that can be used in the measuring instrument that doesn’t require precision mechanical components for determination of focal plane location with 1 % accuracy. The overall dimensions of laser head was 70 × 40 × 40 mm3 and maximum power consumption was

  6. SCALAR AND VECTOR NONLINEAR DECAYS OF LOW-FREQUENCY ALFVÉN WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Voitenko, Y.; De Keyser, J., E-mail: js_zhao@pmo.ac.cn [Solar-Terrestrial Centre of Excellence, Space Physics Division, Belgian Institute for Space Aeronomy, Ringlaan 3 Avenue Circulaire, B-1180 Brussels (Belgium)

    2015-02-01

    We found several efficient nonlinear decays for Alfvén waves in the solar wind conditions. Depending on the wavelength, the dominant decay is controlled by the nonlinearities proportional to either scalar or vector products of wavevectors. The two-mode decays of the pump MHD Alfvén wave into co- and counter-propagating product Alfvén and slow waves are controlled by the scalar nonlinearities at long wavelengths ρ{sub i}{sup 2}k{sub 0⊥}{sup 2}<ω{sub 0}/ω{sub ci} (k {sub 0} is wavenumber perpendicular to the background magnetic field, ω{sub 0} is frequency of the pump Alfvén wave, ρ {sub i} is ion gyroradius, and ω {sub ci} is ion-cyclotron frequency). The scalar decays exhibit both local and nonlocal properties and can generate not only MHD-scale but also kinetic-scale Alfvén and slow waves, which can strongly accelerate spectral transport. All waves in the scalar decays propagate in the same plane, hence these decays are two-dimensional. At shorter wavelengths, ρ{sub i}{sup 2}k{sub 0⊥}{sup 2}>ω{sub 0}/ω{sub ci}, three-dimensional vector decays dominate generating out-of-plane product waves. The two-mode decays dominate from MHD up to ion scales ρ {sub i} k {sub 0} ≅ 0.3; at shorter scales the one-mode vector decays become stronger and generate only Alfvén product waves. In the solar wind the two-mode decays have high growth rates >0.1ω{sub 0} and can explain the origin of slow waves observed at kinetic scales.

  7. Undamped electrostatic plasma waves

    Energy Technology Data Exchange (ETDEWEB)

    Valentini, F.; Perrone, D.; Veltri, P. [Dipartimento di Fisica and CNISM, Universita della Calabria, 87036 Rende (CS) (Italy); Califano, F.; Pegoraro, F. [Dipartimento di Fisica and CNISM, Universita di Pisa, 56127 Pisa (Italy); Morrison, P. J. [Institute for Fusion Studies and Department of Physics, University of Texas at Austin, Austin, Texas 78712-1060 (United States); O' Neil, T. M. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States)

    2012-09-15

    Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named corner modes. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the (k,{omega}{sub R}) plane ({omega}{sub R} being the real part of the wave frequency and k the wavenumber), away from the well-known 'thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower k-values and chopping the tail shifts them toward higher k-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.

  8. Undamped electrostatic plasma waves

    International Nuclear Information System (INIS)

    Valentini, F.; Perrone, D.; Veltri, P.; Califano, F.; Pegoraro, F.; Morrison, P. J.; O'Neil, T. M.

    2012-01-01

    Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named corner modes. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the (k,ω R ) plane (ω R being the real part of the wave frequency and k the wavenumber), away from the well-known “thumb curve” for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower k-values and chopping the tail shifts them toward higher k-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.

  9. Torsional Alfvén Waves in a Dipolar Magnetic Field

    Science.gov (United States)

    Nataf, H. C.; Tigrine, Z.; Cardin, P.; Schaeffer, N.

    2017-12-01

    The discovery of torsional Alfvén waves in the Earth's core (Gillet et al, 2010) is a strong motivation for investigating the properties of these waves. Here, we report on the first experimental study of such waves. Alfvén waves are difficult to excite and observe in liquid metals because of their high magnetic diffusivity. Nevertheless, we obtained clear signatures of such diffusive waves in our DTS experiment. In this setup, some 40 liters of liquid sodium are contained between a ro = 210 mm-radius stainless steel outer shell, and a ri = 74 mm-radius copper inner sphere. Both spherical boundaries can rotate independently around a common vertical axis. The inner sphere shells a strong permanent magnet, which produces a nearly dipolar magnetic field whose intensity falls from 175 mT at ri to 8 mT at ro in the equatorial plane. We excite Alfvén waves in the liquid sodium by applying a sudden jerk of the inner sphere. To study the effect of global rotation, which leads to the formation of geostrophic torsional Alfvén waves, we spin the experiment at rotation rates fo = fi up to 15 Hz. The Alfvén wave produces a clear azimuthal magnetic signal on magnetometers installed in a sleeve inside the fluid. We also probe the associated azimuthal velocity field using ultrasound Doppler velocimetry. Electric potentials at the surface of the outer sphere turn out to be very revealing as well. In parallel, we use the XSHELLS magnetohydrodynamics spherical code to model torsional Alfvén waves in the experimental conditions, and beyond. We explore both linear and non-linear regimes. We observe a strong excitation of inertial waves in the equatorial plane, where the wave transits from a region of strong magnetic field to a region dominated by rotation (see figure of meridian map of azimuthal velocity). These novel observations should help deciphering the dynamics of Alfvén waves in planetary cores.

  10. Three-dimensional manipulation of single cells using surface acoustic waves.

    Science.gov (United States)

    Guo, Feng; Mao, Zhangming; Chen, Yuchao; Xie, Zhiwei; Lata, James P; Li, Peng; Ren, Liqiang; Liu, Jiayang; Yang, Jian; Dao, Ming; Suresh, Subra; Huang, Tony Jun

    2016-02-09

    The ability of surface acoustic waves to trap and manipulate micrometer-scale particles and biological cells has led to many applications involving "acoustic tweezers" in biology, chemistry, engineering, and medicine. Here, we present 3D acoustic tweezers, which use surface acoustic waves to create 3D trapping nodes for the capture and manipulation of microparticles and cells along three mutually orthogonal axes. In this method, we use standing-wave phase shifts to move particles or cells in-plane, whereas the amplitude of acoustic vibrations is used to control particle motion along an orthogonal plane. We demonstrate, through controlled experiments guided by simulations, how acoustic vibrations result in micromanipulations in a microfluidic chamber by invoking physical principles that underlie the formation and regulation of complex, volumetric trapping nodes of particles and biological cells. We further show how 3D acoustic tweezers can be used to pick up, translate, and print single cells and cell assemblies to create 2D and 3D structures in a precise, noninvasive, label-free, and contact-free manner.

  11. Teaching the Common Aspects in Mechanical, Electromagnetic and Quantum Waves at Interfaces and Waveguides

    Science.gov (United States)

    Rojas, R.; Robles, P.

    2011-01-01

    We discuss common features in mechanical, electromagnetic and quantum systems, supporting identical results for the transmission and reflection coefficients of waves arriving perpendicularly at a plane interface. Also, we briefly discuss the origin of special notions such as refractive index in quantum mechanics, massive photons in wave guides and…

  12. Coherent states of an electron in a quantized electromagnetic wave

    International Nuclear Information System (INIS)

    Bagrov, V.G.; Bukhbinder, I.L.; Gitman, D.M.; Lavrov, P.M.

    1977-01-01

    Coherent states for interacting electrons and photons in a plane elecmagnetic wave are found. Trajectories of the electron and the characteristics of the electromagnetic field are investigated. Limiting transition to the given external field is studied

  13. Radiative cooling and broadband phenomenon in low-frequency waves

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, we analyze the effects of radiative cooling on the pure baroclinic low-frequency waves under the approximation of equatorial -plane and semi-geostrophic condition. The results show that radiative cooling does not, exclusively, provide the damping effects on the development of low-frequency waves. Under the delicate radiative-convective equilibrium, radiative effects will alter the phase speed and wave period, and bring about the broadband of phase velocity and wave period by adjusting the vertical profiles of diabatic heating. when the intensity of diabatic heating is moderate and appropriate, it is conductive to the development and sustaining of the low-frequency waves and their broadband phenomena, not the larger, the better. The radiative cooling cannot be neglected in order to reach the moderate and appropriate intensity of diabatic heating.

  14. On the use of a variational technique based on integral equations for plane acoustic and vibro-acoustic problems

    DEFF Research Database (Denmark)

    Brunskog, Jonas; Richard, Antoine Philippe André

    2016-01-01

    Problems such as sound insulation and absorption of plane structures in laboratory conditions can theoretically be described as an integral or integral-differential equation. This equation contains the Green’s function integrated over the surface, which describes the radiation from the surface....... A variational technique, well described by Morse and Ingard, has successfully been used for both absorption and sound insulation for a plane incident wave. The resulting formulas are surprisingly simple, accurate and robust. Moreover, they capture the physics of sound radiation of a finite surface well. However...

  15. Surface wave photonic device based on porous silicon multilayers

    International Nuclear Information System (INIS)

    Guillermain, E.; Lysenko, V.; Benyattou, T.

    2006-01-01

    Porous silicon is widely studied in the field of photonics due to its interesting optical properties. In this work, we present theoretical and first experimental studies of a new kind of porous silicon photonic device based on optical surface wave. A theoretical analysis of the device is presented using plane-wave approximation. The porous silicon multilayered structures are realized using electrochemical etching of p + -type silicon. Morphological and optical characterizations of the realized structures are reported

  16. Evolution of a Directional Wave Spectrum in a 3D Marginal Ice Zone with Random Floe Size Distribution

    Science.gov (United States)

    Montiel, F.; Squire, V. A.

    2013-12-01

    A new ocean wave/sea-ice interaction model is proposed that simulates how a directional wave spectrum evolves as it travels through a realistic marginal ice zone (MIZ), where wave/ice dynamics are entirely governed by coherent conservative wave scattering effects. Field experiments conducted by Wadhams et al. (1986) in the Greenland Sea generated important data on wave attenuation in the MIZ and, particularly, on whether the wave spectrum spreads directionally or collimates with distance from the ice edge. The data suggest that angular isotropy, arising from multiple scattering by ice floes, occurs close to the edge and thenceforth dominates wave propagation throughout the MIZ. Although several attempts have been made to replicate this finding theoretically, including by the use of numerical models, none have confronted this problem in a 3D MIZ with fully randomised floe distribution properties. We construct such a model by subdividing the discontinuous ice cover into adjacent infinite slabs of finite width parallel to the ice edge. Each slab contains an arbitrary (but finite) number of circular ice floes with randomly distributed properties. Ice floes are modeled as thin elastic plates with uniform thickness and finite draught. We consider a directional wave spectrum with harmonic time dependence incident on the MIZ from the open ocean, defined as a continuous superposition of plane waves traveling at different angles. The scattering problem within each slab is then solved using Graf's interaction theory for an arbitrary incident directional plane wave spectrum. Using an appropriate integral representation of the Hankel function of the first kind (see Cincotti et al., 1993), we map the outgoing circular wave field from each floe on the slab boundaries into a directional spectrum of plane waves, which characterizes the slab reflected and transmitted fields. Discretizing the angular spectrum, we can obtain a scattering matrix for each slab. Standard recursive

  17. Solitary impulse wave run-up and overland flow

    International Nuclear Information System (INIS)

    Fuchs, H.

    2013-04-01

    Impulse waves are generated by landslides, rockfalls or avalanches impacting a reservoir or natural lake. These long waves generated by the impulse transferred to the water body in combination with the usually short propagation distance within a lake lead to a large damage potential due to wave run-up or dam overtopping. Damages are then caused by (1) direct wave load on structures, (2) driftwood and float impact and (3) their deposits after water retreat. Major historic events occurred at Lituya Bay, Alaska, in 1958, or at the Vaiont Reservoir, Italy, in 1963. Recent events were observed at Lake Chehalis, Canada, or Lake Lucerne, Switzerland, both in 2007, or at the Lower Grindelwald proglacial lake, Switzerland, in 2009. Whereas previous VAW research aimed at the generation phase of landslide-generated impulse waves with a special focus on the wave characteristics, the current research concentrates on the opposite wave-shore interaction. A particular focus is given to the transition point from the shore slope to the horizontal plane where the orbital wave motion is transformed into a shore-parallel flow. As most literature relates only to plain wave run-up on a linearly-inclined plane and the few studies focussing on wave-induced overland flow are case studies considering only a specific bathymetry, currently no general conclusions on wave-induced overland flow can be drawn. The present study therefore intends to fill in this gap by physical modeling. Testing involved a new test-setup including a piston-type wave maker to generate solitary waves, and a smooth impermeable PVC shore of height w = 0.25 m with a connected horizontal overland flow portion. By varying the shore slope tanβ = 1/1.5, 1/2.5 and 1/5.0, the still water depth h = 0.16 - 0.24 m, and the relative wave height H/h = 0.1 -0.7, a wide range of basic parameters was covered. Overland flow depths and front velocities were measured along the shore using Ultrasonic Distance Sensors. Further, flow

  18. Landsat 9 OLI 2 focal plane subsystem: design, performance, and status

    Science.gov (United States)

    Malone, Kevin J.; Schrein, Ronald J.; Bradley, M. Scott; Irwin, Ronda; Berdanier, Barry; Donley, Eric

    2017-09-01

    The Landsat 9 mission will continue the legacy of Earth remote sensing that started in 1972. The Operational Land Imager 2 (OLI 2) is one of two instruments on the Landsat 9 satellite. The OLI 2 instrument is essentially a copy of the OLI instrument flying on Landsat 8. A key element of the OLI 2 instrument is the focal plane subsystem, or FPS, which consists of the focal plane array (FPA), the focal plane electronics (FPE) box, and low-thermal conductivity cables. This paper presents design details of the OLI 2 FPS. The FPA contains 14 critically-aligned focal plane modules (FPM). Each module contains 6 visible/near-IR (VNIR) detector arrays and three short-wave infrared (SWIR) arrays. A complex multi-spectral optical filter is contained in each module. Redundant pixels for each array provide exceptional operability. Spare detector modules from OLI were recharacterized after six years of storage. Radiometric test results are presented and compared with data recorded in 2010. Thermal, optical, mechanical and structural features of the FPA will be described. Special attention is paid to the thermal design of the FPA since thermal stability is crucial to ensuring low-noise and low-drift operation of the detectors which operate at -63°C. The OLI 2 FPE provides power, timing, and control to the focal plane modules. It also digitizes the video data and formats it for the solid-state recorder. Design improvements to the FPA-FPE cables will be discussed and characterization data will be presented. The paper will conclude with the status of the flight hardware assembly and testing.

  19. Surface electrostatic waves in bounded high temperature superconductors

    International Nuclear Information System (INIS)

    Averkov, Yu.O.; Yakovenko, V.M.

    2008-01-01

    The dispersion relations of surface electrostatic waves propagating along the surface of semi bounded layered superconductor and in the slab of layered superconductor are theoretically investigated. An arbitrary inclination of superconductor layers to the interface of a vacuum - crystal and an arbitrary direction of propagation of surface waves in the plane of the interface are taking into account. The possibility of initiation of an absolute instability during the propagation of a non-relativistic plasma stream above the surface of the layered superconductor is shown

  20. Cross plane scattering correction

    International Nuclear Information System (INIS)

    Shao, L.; Karp, J.S.

    1990-01-01

    Most previous scattering correction techniques for PET are based on assumptions made for a single transaxial plane and are independent of axial variations. These techniques will incorrectly estimate the scattering fraction for volumetric PET imaging systems since they do not take the cross-plane scattering into account. In this paper, the authors propose a new point source scattering deconvolution method (2-D). The cross-plane scattering is incorporated into the algorithm by modeling a scattering point source function. In the model, the scattering dependence both on axial and transaxial directions is reflected in the exponential fitting parameters and these parameters are directly estimated from a limited number of measured point response functions. The authors' results comparing the standard in-plane point source deconvolution to the authors' cross-plane source deconvolution show that for a small source, the former technique overestimates the scatter fraction in the plane of the source and underestimate the scatter fraction in adjacent planes. In addition, the authors also propose a simple approximation technique for deconvolution