Well-posedness and generalized plane waves simulations of a 2D mode conversion model
Imbert-Gérard, Lise-Marie
2015-01-01
Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.
Simulations and cold-test results of a prototype plane wave transformer linac structure
Directory of Open Access Journals (Sweden)
Arvind Kumar
2002-03-01
Full Text Available We have built a 4-cell prototype plane wave transformer (PWT linac structure. We discuss here details of the design and fabrication of the PWT linac structure. We present results from superfish and gdfidl simulations as well as cold tests, which are in good agreement with each other. We also present detailed tolerance maps for the PWT structure. We discuss beam dynamics simulation studies performed using parmela.
Ring-plane traveling-wave tube slow-wave circuit design simulations at V-Band frequencies
Kory, Carol L.; Wilson, Jeffrey D.
1995-01-01
The V-Band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for intersatellite communications. As a first effort to develop a high-efficiency V-band TWT, variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite the high-power capabilities of the ring-plane TWT, disadvantages of low bandwidth and high voltage requirements have until now prevented its acceptance outside the laboratory. In this paper, we use the three-dimensional electromagnetic simulation code MAFIA to investigate methods of increasing the bandwidth and lowering the operating voltage. Dispersion, impedance, and attenuation calculations for various geometric variations and loading distributions were performed. Based on the results of the variations, a circuit termed the finned-ladder TWT slowwave circuit was designed and is compared here to the scaled ring-plane prototype and the conventional ferruled coupled-cavity TWT circuit over the V-band frequency range.
Statistics for long irregular wave run-up on a plane beach from direct numerical simulations
Didenkulova, Ira; Senichev, Dmitry; Dutykh, Denys
2017-04-01
Very often for global and transoceanic events, due to the initial wave transformation, refraction, diffraction and multiple reflections from coastal topography and underwater bathymetry, the tsunami approaches the beach as a very long wave train, which can be considered as an irregular wave field. The prediction of possible flooding and properties of the water flow on the coast in this case should be done statistically taking into account the formation of extreme (rogue) tsunami wave on a beach. When it comes to tsunami run-up on a beach, the most used mathematical model is the nonlinear shallow water model. For a beach of constant slope, the nonlinear shallow water equations have rigorous analytical solution, which substantially simplifies the mathematical formulation. In (Didenkulova et al. 2011) we used this solution to study statistical characteristics of the vertical displacement of the moving shoreline and its horizontal velocity. The influence of the wave nonlinearity was approached by considering modifications of probability distribution of the moving shoreline and its horizontal velocity for waves of different amplitudes. It was shown that wave nonlinearity did not affect the probability distribution of the velocity of the moving shoreline, while the vertical displacement of the moving shoreline was affected substantially demonstrating the longer duration of coastal floods with an increase in the wave nonlinearity. However, this analysis did not take into account the actual transformation of irregular wave field offshore to oscillations of the moving shoreline on a slopping beach. In this study we would like to cover this gap by means of extensive numerical simulations. The modeling is performed in the framework of nonlinear shallow water equations, which are solved using a modern shock-capturing finite volume method. Although the shallow water model does not pursue the wave breaking and bore formation in a general sense (including the water surface
From plane waves to local Gaussians for the simulation of correlated periodic systems
Booth, George H.; Tsatsoulis, Theodoros; Chan, Garnet Kin-Lic; Grüneis, Andreas
2016-08-01
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.
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...
Forgács, Péter; Romańczukiewicz, Tomasz
2013-01-01
It is shown that in a large class of systems plane waves can act as tractor beams: i.e., an incident plane wave can exert a pulling force on the scatterer. The underlying physical mechanism for the pulling force is due to the sufficiently strong scattering of the incoming wave into another mode having a larger wave number, in which case excess momentum is created behind the scatterer. Such a tractor beam or negative radiation pressure effect arises naturally in systems where the coupling between the scattering channels is due to Aharonov-Bohm (AB) gauge potentials. It is demonstrated that this effect is also present if the AB potential is an induced, ("artificial") gauge potential such as the one found in J. March-Russell, J. Preskill, F. Wilczek, Phys. Rev. Lett. 58 2567 (1992).
Singularities from colliding plane gravitational waves
Tipler, Frank J.
1980-12-01
A simple geometrical argument is given which shows that a collision between two plane gravitational waves must result in singularities. The argument suggests that these singularities are a peculiar feature of plane waves, because singularities are also a consequence of a collision between self-gravitating plane waves of other fields with arbitrarily small energy density.
Singularities from colliding plane gravitational waves
Energy Technology Data Exchange (ETDEWEB)
Tipler, F.J.
1980-12-15
A simple geometrical argument is given which shows that a collision between two plane gravitational waves must result in singularities. The argument suggests that these singularities are a peculiar feature of plane waves, because singularities are also a consequence of a collision between self-gravitating plane waves of other fields with arbitrarily small energy density.
Homogeneity and plane-wave limits
Figueroa-O'Farrill, J M; Philip, S; Farrill, Jos\\'e Figueroa-O'; Meessen, Patrick; Philip, Simon
2005-01-01
We explore the plane-wave limit of homogeneous spacetimes. For plane-wave limits along homogeneous geodesics the limit is known to be homogeneous and we exhibit the limiting metric in terms of Lie algebraic data. This simplifies many calculations and we illustrate this with several examples. We also investigate the behaviour of (reductive) homogeneous structures under the plane-wave limit.
DEFF Research Database (Denmark)
Udesen, Jesper; Gran, Fredrik; Hansen, Kristoffer Lindskov;
2008-01-01
Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1......) The ultrasound is not focused during the transmissions of the ultrasound signals; 2) A 13-bit Barker code is transmitted simultaneously from each transducer element; and 3) The 2-D vector velocity of the blood is estimated using 2-D cross-correlation. A parameter study was performed using the Field II program......, and performance of the method was investigated when a virtual blood vessel was scanned by a linear array transducer. An improved parameter set for the method was identified from the parameter study, and a flow rig measurement was performed using the same improved setup as in the simulations. Finally, the common...
Directory of Open Access Journals (Sweden)
Larry W. Burggraf
2013-07-01
Full Text Available To find low energy SinCn structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA. We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each SinCn cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to SinCn (n = 4–12 clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each SinCn cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region.
Causal inheritence in plane wave quotients
Energy Technology Data Exchange (ETDEWEB)
Hubeny, Veronika E.; Rangamani, Mukund; Ross, Simon F.
2003-11-24
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.
Horizons and plane waves: A review
Hubeny, V E; Hubeny, Veronika E.; Rangamani, Mukund
2003-01-01
We review the attempts to construct black hole/string solutions in asymptotically plane wave spacetimes. First, we demonstrate that geometries admitting a covariantly constant null Killing vector cannot admit event horizons, which implies that pp-waves can't describe black holes. However, relaxing the symmetry requirements allows us to generate solutions which do possess regular event horizons while retaining the requisite asymptotic properties. In particular, we present two solution generating techniques and use them to construct asymptotically plane wave black string/brane geometries.
Aperture domain model image reconstruction (ADMIRE) with plane wave synthesis
Dei, Kazuyuki; Tierney, Jaime; Byram, Brett
2017-03-01
In our previous studies, we demonstrated that our aperture domain model-based clutter suppression algorithm improved image quality of in vivo B-mode data obtained from focused transmit beam sequences. Our approach suppresses off-axis clutter and reverberation and tackles limitations of related algorithms because it preserves RF channel signals and speckle statistics. We call the algorithm aperture domain model image reconstruction (ADMIRE). We previously focused on reverberation suppression, but ADMIRE is also effective at suppressing off-axis clutter. We are interested in how ADMIRE performs on plane wave sequences and the impact of AD- MIRE applied before and after synthetic beamforming of steered plane wave sequences. We employed simulated phantoms using Field II and tissue-mimicking phantoms to evaluate ADMIRE applied to plane wave sequencing. We generated images acquired from plane waves with and without synthetic aperture synthesis and measured contrast and contrast-to-noise ratio (CNR). For simulated cyst images formed from single plane waves, the contrast for delay-and-sum (DAS) and ADMIRE are 15.64 dB and 28.34 dB, respectively, while the CNR are 1.76 dB and 3.90 dB, respectively. Based on these findings, ADMIRE improves plane wave image quality. We also applied ADMIRE to resolution phantoms having a point target at 3 cm depth on-axis, simulating the point spread functions from data obtained from 1 and 75 steered plane waves, along with linear scan at focus of 3 and 4 cm depth. We then examined the outcome of applying ADMIRE before and after synthetic aperture processing. Finally, we applied this to an in vivo carotid artery.
In-plane propagation of electromagnetic waves in planar metamaterials
Yi, Changhyun; Rhee, Joo Yull; Kim, Ki Won; Lee, YoungPak
2016-08-01
Some planar metamaterials (MMs) or subwavelength antenna/hole arrays have a considerable amount of in-plane propagation when certain conditions are met. In this paper, the in-plane propagation caused by a wave incident on a MM absorber was studied by using a finite-difference time-domain (FDTD) technique. By using a FDTD simulation, we were able to observe a nonnegligible amount of in-plane propagation after the incident wave had arrived at the surface of the planar structure and gradually decreased propagation of the electromagnetic wave in the planar direction gradually decreased. We performed the FDTD simulation carefully to reproduce valid results and to verify the existence of in-plane propagation. For verification of the in-plane propagation explicitly, Poynting vectors were calculated and visualized inside the dielectric substrate between the metallic back-plate and an array of square patches. We also investigated several different structures with resonators of various shapes and found that the amount of facing edges of adjacent metallic patches critically determined the strength of the in-plane propagation. Through this study, we could establish the basis for the existence of in-plane propagation in MMs.
Exact plane gravitational waves and electromagnetic fields
Enrico MontanariUniversity of Ferrara and INFN sezione di Ferrara, Italy; Mirco Calura(University of Ferrara and INFN sezione di Ferrara, Italy)
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exact gravitational plane wave is investigated in the framework of Einstein's general relativity. We have expressed the general solution to the de Rham equations as a Fourier-like integral. In the general case we have reduced the problem to a set of ordinary differential equations and have explicitly written the solution in the case of linear polarization of the gravitational wave. We have expressed our ...
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....
Fang, Changming; Li, Wun-Fan; Koster, Rik S; Klimeš, Jiří; van Blaaderen, Alfons; van Huis, Marijn A
2015-01-07
Knowledge about the intrinsic electronic properties of water is imperative for understanding the behaviour of aqueous solutions that are used throughout biology, chemistry, physics, and industry. The calculation of the electronic band gap of liquids is challenging, because the most accurate ab initio approaches can be applied only to small numbers of atoms, while large numbers of atoms are required for having configurations that are representative of a liquid. Here we show that a high-accuracy value for the electronic band gap of water can be obtained by combining beyond-DFT methods and statistical time-averaging. Liquid water is simulated at 300 K using a plane-wave density functional theory molecular dynamics (PW-DFT-MD) simulation and a van der Waals density functional (optB88-vdW). After applying a self-consistent GW correction the band gap of liquid water at 300 K is calculated as 7.3 eV, in good agreement with recent experimental observations in the literature (6.9 eV). For simulations of phase transformations and chemical reactions in water or aqueous solutions whereby an accurate description of the electronic structure is required, we suggest to use these advanced GW corrections in combination with the statistical analysis of quantum mechanical MD simulations.
Exact plane gravitational waves and electromagnetic fields
Montanari, E; Montanari, Enrico; Calura, Mirco
2000-01-01
The behaviour of a "test" electromagnetic field in the background of an exactgravitational plane wave is investigated in the framework of Einstein's generalrelativity. We have expressed the general solution to the de Rham equations asa Fourier-like integral. In the general case we have reduced the problem to aset of ordinary differential equations and have explicitly written the solutionin the case of linear polarization of the gravitational wave. We have expressedour results by means of Fermi Normal Coordinates (FNC), which define the properreference frame of the laboratory. Moreover we have provided some "gedankenexperiments", showing that an external gravitational wave induces measurableeffects of non tidal nature via electromagnetic interaction. Consequently it isnot possible to eliminate gravitational effects on electromagnetic field, evenin an arbitrarily small spatial region around an observer freely falling in thefield of a gravitational wave. This is opposite to the case of mechanicalinteraction invo...
Optics in a nonlinear gravitational plane wave
Harte, Abraham I.
2015-09-01
Gravitational waves can act like gravitational lenses, affecting the observed positions, brightnesses, and redshifts of distant objects. Exact expressions for such effects are derived here in general relativity, allowing for arbitrarily-moving sources and observers in the presence of plane-symmetric gravitational waves. At least for freely falling sources and observers, it is shown that the commonly-used predictions of linear perturbation theory can be generically overshadowed by nonlinear effects; even for very weak gravitational waves, higher-order perturbative corrections involve secularly-growing terms which cannot necessarily be neglected when considering observations of sufficiently distant sources. Even on more moderate scales where linear effects remain at least marginally dominant, nonlinear corrections are qualitatively different from their linear counterparts. There is a sense in which they can, for example, mimic the existence of a third type of gravitational wave polarization.
The memory effect for plane gravitational waves
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.
Free string evolution across plane wave singularities
Craps, Ben; Evnin, Oleg
2009-01-01
In these proceedings, we summarize our studies of free string propagation in (near-)singular scale-invariant plane wave geometries. We analyze the singular limit of the evolution for the center-of-mass motion and all excited string modes. The requirement that the entire excitation energy of the string should be finite excludes consistent propagation across the singularity, in case no dimensionful scales are introduced at the singular locus (in an otherwise scale-invariant space-time).
Generalized plane gravitational waves of non-symmetric unified field theories in plane symmetry
Directory of Open Access Journals (Sweden)
Sanjiv R. Bhoyar
2012-12-01
Full Text Available In this paper we investigated the plane wave solutions of both the weak and strong non-symmetric unified field equations of Einstein and Bonner in a generalized plane symmetric space-time in the sense of Taub [Ann. Math. 53, 472 (1951] for plane gravitational waves. We show that the plane wave solutions of Einstein and Bonner field equations exist in plane symmetry.
Blackfolds, Plane Waves and Minimal Surfaces
Armas, Jay
2015-01-01
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...
Blackfolds, plane waves and minimal surfaces
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.
Colliding Plane Waves in String Theory
Chen, B; Furuta, K; Lin, F L; Chen, Bin; Chu, Chong-Sun; Furuta, Ko; Lin, Feng-Li
2004-01-01
We construct colliding plane wave solutions in higher dimensional gravity theory with dilaton and higher form flux, which appears naturally in the low energy theory of string theory. Especially, the role of the junction condition in constructing the solutions is emphasized. Our results not only include the previously known CPW solutions, but also provide a wide class of new solutions that is not known in the literature before. We find that late time curvature singularity is always developed for the solutions we obtained in this paper. This supports the generalized version of Tipler's theorem in higher dimensional supergravity.
Blackfolds, plane waves and minimal surfaces
Armas, Jay; Blau, Matthias
2015-01-01
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 comp...
On General Plane Fronted Waves. Geodesics
Candela, A M; Sánchez, M; Sanchez, Miguel
2003-01-01
A general class of Lorentzian metrics, $M_0 x R^2$, $ds^2 = + 2 du dv + H(x,u) du^2$, with $(M_0, $ any Riemannian manifold, is introduced in order to generalize classical exact plane fronted waves. Here, we start a systematic study of their main geodesic properties: geodesic completeness, geodesic connectedness and multiplicity, causal character of connecting geodesics. These results are independent of the possibility of a full integration of geodesic equations. Variational and geometrical techniques are applied systematically. In particular, we prove that the asymptotic behavior of $H(x,u)$ with $x$ at infinity determines many properties of geodesics. Essentially, a subquadratic growth of $H$ ensures geodesic completeness and connectedness, while the critical situation appears when $H(x,u)$ behaves in some direction as $|x|^2$, as in the classical model of exact gravitational waves
Institute of Scientific and Technical Information of China (English)
赵立强; 柯亮
2013-01-01
利用M atlab数值模拟复色平面光波与复色发散球面光波相遇发生复杂干涉现象时的光强度分布，由数值模拟直观地看到：对于同一级次的干涉圆环形条纹，波长短的光波形成的干涉圆环处于内侧，波长长的光波形成的干涉圆环处于外侧，且它们都是同心圆；波长长的光波形成的圆环形干涉条纹相邻条纹之间的距离比波长短的形成的圆环形干涉条纹相邻条纹之间的距离大。%Making use of Matlab numerical software ,the intensity distribution of the interference between polychromatic plane light wave and divergent spherical light wave was simulated .The results of the numerical simulation were as follows :for the same interference order ,the inner interference ring corresponded to long-wavelength ,while the outer ring corresponded to short-wavelength ,and they were all concentric circles ;the distance of the adjacent stripes formed by light of long-wavelength was greater than that of the adjacent stripes formed by light of short-wavelength .
On the plane-wave cubic vertex
Lucietti, J; Sinha, A K; Lucietti, James; Schäfer-Nameki, Sakura; Sinha, Aninda
2004-01-01
The exact bosonic Neumann matrices of the cubic vertex in plane-wave light-cone string field theory are derived using the contour integration techniques developed in our earlier paper. This simplifies the original derivation of the vertex. In particular, the Neumann matrices are written in terms of \\mu-deformed Gamma-functions, thus casting them into a form that elegantly generalizes the well-known flat-space solution. The asymptotics of the \\mu-deformed Gamma-functions allow one to determine the large-\\mu behaviour of the Neumann matrices including exponential corrections. We provide an explicit expression for the first exponential correction and make a conjecture for the subsequent exponential correction terms.
The plane wave spectrum representation of electromagnetic fields
Clemmow, P C
1966-01-01
The Plane Wave Spectrum Representation of Electromagnetic Fields presents the theory of the electromagnetic field with emphasis to the plane wave. This book explains how fundamental electromagnetic fields can be represented by the superstition of plane waves traveling in different directions. Organized into two parts encompassing eight chapters, this book starts with an overview of the methods whereby plane wave spectrum representation can be used in attacking different characteristic problems belonging to the theories of radiation, diffraction, and propagation. This book then discusses the co
Plane-wave least-squares reverse-time migration
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.
Plane waves in a thermally conducting viscous liquid
Indian Academy of Sciences (India)
Baljeet Singh
2004-02-01
The aim of this paper is to investigate plane waves in a thermally conducting viscous liquid half-space with thermal relaxation times. There exist three basic waves, namely; thermal wave, longitudinal wave and transverse wave in a thermally conducting viscous liquid half-space. Reﬂection of plane waves from the free surface of a thermally conducting viscous liquid half-space is studied. The results are obtained in terms of amplitude ratios and are compared with those without viscosity and thermal disturbances.
Loads and responses for planing craft in waves
2004-01-01
Experimental and numerical analysis of loads and responses for planing craft in waves is considered. Extensive experiments have been performed on a planing craft, in full-scale as well as in model scale. The test set-ups and significant results are reviewed. The required resolution in experiments on planing craft in waves, concerning sampling frequencies, filtering and pressure transducer areas, is investigated. The aspects of peak identification in transient signals, fitting of analytical cu...
Plane wave method for elastic wave scattering by a heterogeneous fracture
Energy Technology Data Exchange (ETDEWEB)
Nakagawa, Seiji; Nihei, Kurt T.; Myer, Larry R.
2003-02-21
A plane-wave method for computing the three-dimensional scattering of propagating elastic waves by a planar fracture with heterogeneous fracture compliance distribution is presented. This method is based upon the spatial Fourier transform of the seismic displacement-discontinuity (SDD) boundary conditions (also called linear slip interface conditions), and therefore, called the wave-number-domain SDD method (wd-SDD method). The resulting boundary conditions explicitly show the coupling between plane waves with an incident wave number component (specular component) and scattered waves which do not follow Snell's law (nonspecular components) if the fracture is viewed as a planar boundary. For a spatially periodic fracture compliance distribution, these boundary conditions can be cast into a linear system of equations that can be solved for the amplitudes of individual wave modes and wave numbers. We demonstrate the developed technique for a simulated fracture with a stochastic (correlated) surface compliance distribution. Low- and high-frequency solutions of the method are also compared to the predictions by low-order Born series in the weak and strong scattering limit.
3D plane-wave least-squares Kirchhoff migration
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.
Plane Waves in a Transparent Isotropic Chiral Medium
Fisanov, V. V.
2015-04-01
A homogeneous isotropic transparent chiral medium supports two normal plane waves with left and right circular polarization and differently valued positive wave numbers. The presence or absence of forward and backward Beltrami waves and their helicity are regulated by the signs of the permittivity and permeability and the strength of the chirality. The ray refractive index is a universal parameter whose sign differentiates the forward and backward waves.
Regularized plane-wave least-squares Kirchhoff migration
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.
Simulation Exploration through Immersive Parallel Planes: Preprint
Energy Technology Data Exchange (ETDEWEB)
Brunhart-Lupo, Nicholas; Bush, Brian W.; Gruchalla, Kenny; Smith, Steve
2016-03-01
We present a visualization-driven simulation system that tightly couples systems dynamics simulations with an immersive virtual environment to allow analysts to rapidly develop and test hypotheses in a high-dimensional parameter space. To accomplish this, we generalize the two-dimensional parallel-coordinates statistical graphic as an immersive 'parallel-planes' visualization for multivariate time series emitted by simulations running in parallel with the visualization. In contrast to traditional parallel coordinate's mapping the multivariate dimensions onto coordinate axes represented by a series of parallel lines, we map pairs of the multivariate dimensions onto a series of parallel rectangles. As in the case of parallel coordinates, each individual observation in the dataset is mapped to a polyline whose vertices coincide with its coordinate values. Regions of the rectangles can be 'brushed' to highlight and select observations of interest: a 'slider' control allows the user to filter the observations by their time coordinate. In an immersive virtual environment, users interact with the parallel planes using a joystick that can select regions on the planes, manipulate selection, and filter time. The brushing and selection actions are used to both explore existing data as well as to launch additional simulations corresponding to the visually selected portions of the input parameter space. As soon as the new simulations complete, their resulting observations are displayed in the virtual environment. This tight feedback loop between simulation and immersive analytics accelerates users' realization of insights about the simulation and its output.
Simulation Exploration through Immersive Parallel Planes
Energy Technology Data Exchange (ETDEWEB)
Brunhart-Lupo, Nicholas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bush, Brian W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gruchalla, Kenny M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Smith, Steve [Los Alamos Visualization Associates
2017-05-25
We present a visualization-driven simulation system that tightly couples systems dynamics simulations with an immersive virtual environment to allow analysts to rapidly develop and test hypotheses in a high-dimensional parameter space. To accomplish this, we generalize the two-dimensional parallel-coordinates statistical graphic as an immersive 'parallel-planes' visualization for multivariate time series emitted by simulations running in parallel with the visualization. In contrast to traditional parallel coordinate's mapping the multivariate dimensions onto coordinate axes represented by a series of parallel lines, we map pairs of the multivariate dimensions onto a series of parallel rectangles. As in the case of parallel coordinates, each individual observation in the dataset is mapped to a polyline whose vertices coincide with its coordinate values. Regions of the rectangles can be 'brushed' to highlight and select observations of interest: a 'slider' control allows the user to filter the observations by their time coordinate. In an immersive virtual environment, users interact with the parallel planes using a joystick that can select regions on the planes, manipulate selection, and filter time. The brushing and selection actions are used to both explore existing data as well as to launch additional simulations corresponding to the visually selected portions of the input parameter space. As soon as the new simulations complete, their resulting observations are displayed in the virtual environment. This tight feedback loop between simulation and immersive analytics accelerates users' realization of insights about the simulation and its output.
Large eddy simulation of breaking waves
DEFF Research Database (Denmark)
Christensen, Erik Damgaard; Deigaard, Rolf
2001-01-01
is described by large eddy simulation where the larger turbulent features are simulated by solving the flow equations, and the small scale turbulence that is not resolved by the flow model is represented by a sub-grid model. A simple Smagorinsky sub-grid model has been used for the present simulations......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...
Solitary plane waves in an isotropic hexagonal lattice
DEFF Research Database (Denmark)
Zolotaryuk, Yaroslav; Savin, A.V.; Christiansen, Peter Leth
1998-01-01
Solitary plane-wave solutions in a two-dimensional hexagonal lattice which can propagate in different directions on the plane are found by using the pseudospectral method. The main point of our studies is that the lattice model is isotropic and we show that the sound velocity is the same for diff...
Exact Nonlinear Internal Equatorial Waves in the f-plane
Hsu, Hung-Chu
2016-07-01
We present an explicit exact solution of the nonlinear governing equations for internal geophysical water waves propagating westward above the thermocline in the f-plane approximation near the equator. Moreover, the mass transport velocity induced by this internal equatorial wave is eastward and a westward current occurs in the transition zone between the great depth where the water is still and the thermocline.
An Apparatus for Constructing an Electromagnetic Plane Wave Model
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…
An Apparatus for Constructing an Electromagnetic Plane Wave Model
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…
DEFF Research Database (Denmark)
Hansen, Hendrik H.G.; Stuart, Matthias Bo; Villagómez Hoyos, Carlos Armando
2014-01-01
using linear array ultrasound data of a pulsating concentric homogeneous artery simulated using Field II . The transducer ( f c = 9 MHz, pitch = 197.9 μ m, 192 elements, f s = 180 MHz) transmitted plane waves at 3 sequentially alternating angles (0°, + θ , - θ ) at a PRF of 2 kHz. Simulations were...
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....
Wave-equation Migration Velocity Analysis Using Plane-wave Common Image Gathers
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.
Strings On Plane-waves And Spin Chains On Orbifolds
Sadri, D
2005-01-01
This thesis covers a number of topics in string theory focusing on various aspects of the AdS/CFT duality in various guises and regimes. In the first chapter we present a self-contained review of the Plane- wave/super-Yang-Mills duality. This duality is a specification of the usual AdS/CFT correspondence in the “Penrose limit”. In chapter two we study the most general parallelizable pp-wave backgrounds which are non-dilatonic solutions in the NS-NS sector of type IIA and IIB string theories. We demonstrate that parallelizable pp-wave backgrounds are necessarily homogeneous plane-waves, and that a large class of homogeneous plane-waves are parallelizable, stating the necessary conditions. Quantization of string modes, their compactification and behaviour under T- duality are also studied, as are BPS Dp- branes on such backgrounds. In chapter three we consider giant gravitons on the maximally supersymmetric plane-wave background. We deduce the low energy effective light-cone Hamiltonian of ...
AdS plane waves, entanglement and mutual information
Mukherjee, Debangshu
2014-01-01
$AdS$ plane wave backgrounds are dual to CFT excited states with energy momentum density $T_{++}=Q$. Building on previous work on entanglement entropy in these and nonconformal brane plane wave backgrounds, we first describe a phenomenological scaling picture for entanglement in terms of "entangling partons". We then study aspects of holographic mutual information in these backgrounds for two strip shaped subsystems, aligned parallel or orthogonal to the flux. We focus on the wide ($Ql^d\\gg 1$) and narrow ($Ql^d\\ll 1$) strip regimes. In the wide strip regime, mutual information exhibits growth with the individual strip sizes and a disentangling transition as the separation between the strips increases, whose behaviour is distinct from the ground and thermal states. In the narrow strip case, our calculations have parallels with "entanglement thermodynamics" for these $AdS$ plane wave deformations. We also discuss some numerical analysis.
Plane-Wave Imaging Challenge in Medical Ultrasound
DEFF Research Database (Denmark)
Liebgott, Herve; Molares, Alfonso Rodriguez; Cervenansky, F.
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...
Thermally-induced vacuum instability in a single plane wave
King, B; Di Piazza, A
2012-01-01
Ever since Schwinger published his influential paper [J. Schwinger, Phys. Rev. \\textbf{82}, 664 (1951)], it has been unanimously accepted that the vacuum is stable in the presence of an electromagnetic plane wave. However, we advance an analysis that indicates this statement is not rigorously valid in a real situation, where thermal effects are present. We show that the thermal vacuum, in the presence of a single plane-wave field, even in the limit of zero frequency (a constant crossed field), decays into electron-positron pairs. Interestingly, the pair-production rate is found to depend nonperturbatively on both the amplitude of the constant crossed field and on the temperature.
Polarization operator for plane-wave background fields
Meuren, S; Di Piazza, A
2013-01-01
We derive an alternative representation of the leading-order contribution to the polarization operator in strong-field QED with a plane-wave electromagnetic background field, which is manifestly symmetric with respect to the external photon momenta. Our derivation is based on a direct evaluation of the corresponding Feynman diagram, using the Volkov-representation of the dressed fermion propagator. Furthermore, the validity of the Ward-Takahashi identity is shown for general loop diagrams in an external plane-wave background field.
Metaphysics of colliding self-gravitating plane waves
Energy Technology Data Exchange (ETDEWEB)
Matzner, R.A.; Tipler, F.J.
1984-04-15
We discuss certain global features of colliding plane-wave solutions to Einstein's equations. In particular, we show that the apparently local curvature singularities both in the Khan-Penrose solution and in the Bell-Szekeres solution are actually global. These global singularities are associated with the breakdown of nondegenerate planar symmetry in the characteristic initial data sets.
Metaphysics of colliding self-gravitating plane waves
Matzner, Richard A.; Tipler, Frank J.
1984-04-01
We discuss certain global features of colliding plane-wave solutions to Einstein's equations. In particular, we show that the apparently local curvature singularities both in the Khan-Penrose solution and in the Bell-Szekeres solution are actually global. These global singularities are associated with the breakdown of nondegenerate planar symmetry in the characteristic initial data sets.
Supersymmetry and Branes in M-theory Plane-waves
Kim, N; Kim, Nakwoo; Yee, Jung-Tay
2003-01-01
We study brane embeddings in M-theory plane-waves and their supersymmetry. The relation with branes in AdS backgrounds via the Penrose limit is also explored. Longitudinal planar branes are originated from AdS branes while giant gravitons of AdS spaces become spherical branes which are realized as fuzzy spheres in the massive matrix theory.
Plane-Wave Propagation in Extreme Magnetoelectric (EME) Media
Lindell, I V; Favaro, A
2016-01-01
The extreme magnetoelectric medium (EME medium) is defined in terms of two medium dyadics, $\\alpha$, producing electric polarization by the magnetic field and $\\beta$, producing magnetic polarization by the electric field. Plane-wave propagation of time-harmonic fields of fixed finite frequency in the EME medium is studied. It is shown that (if $\\omega\
Exact near-wall traveling waves of plane Poiseuille flow
Gibson, John; Brand, Evan
2013-11-01
We present several spatially-localized equilibrium and traveling-wave solutions of plane Couette and plane Poiseuille flow. The solutions consist of highly concentrated and spanwise-localized alternating streamwise rolls, centered over low-speed streamwise streaks and flanked on either side by high-speed streaks. For large Reynolds numbers the solutions develop critical layers that are concentrated at isolated points on the critical surface u = c . For several traveling-wave solutions of plane Poiseuille flow, the rolls are concentrated near one wall, producing streaks near the wall and larger reduction of the bulk flow in the core. These solutions form particularly isolated and elemental versions of near-wall coherent structures in shear flows and capture, as precise time-independent solutions of Navier-Stokes, the process by which near-wall rolls exchange momentum between the wall and core regions and thereby increase drag.
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...
Radiation of Electron in the Field of Plane Light Wave
Energy Technology Data Exchange (ETDEWEB)
Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; /Kharkov, KIPT; Tatchyn, R.; /SLAC
2006-02-24
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.
Focal plane wave-front sensing algorithm for high-contrast imaging
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system.We derive an algorithm for the wave-front measurement directly from 3 focal plane images.The 3 images are achieved through a deformable mirror to provide specific phases for the optics system.We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front sensing.The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.
Focal plane wave-front sensin8 algorithm for high-contrast imaging
Institute of Scientific and Technical Information of China (English)
DOU JiangPei; REN DeQing; ZHU YongTian; ZHANG Xi
2009-01-01
High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star. A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system. We derive an algorithm for the wave-front measurement directly from 3 focal plane images. The 3 images are achieved through a deformable mirror to provide specific phases for the optics system. We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front, which is a critical procedure for wave-front sensing. The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically, which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.
Back Radiation Suppression through a Semitransparent Ground Plane for a mm-Wave Patch Antenna
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.
Plane waves and spherical means applied to partial differential equations
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
Study of simple plane wave generator with an air-metal barrier
Directory of Open Access Journals (Sweden)
Wei Xiong
2014-06-01
Full Text Available Plane wave generators (PWGs are used to accelerate flyer plates to high velocities with their generated plane waves, which are widely used in the test of dynamic properties of materials. The traditional PWG is composed of two explosives with different detonation velocities. It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures. A simple plane wave generator is presented in this paper, which is composed of two identical cylindrical high explosive (HE charges and an air-metal barrier. A theoretical model was established based on two different paths of the propagation of detonation waves, based on which the size of air-metal barrier was calculated for a given charge. The corresponding numerical simulations were also carried out by AUTODYN-2D® based on the calculated results, which were used to compare with the theoretical calculations. A detonation wave with a flatness of 0.039 μs within the range of 70-percent diameter of the main charge was obtained through the simulations.
Study of simple plane wave generator with an air-metal barrier
Institute of Scientific and Technical Information of China (English)
Wei XIONG; Xian-feng ZHANG; Zhong-wei GUAN; Yong HE; Liang QIAO; Li-li GUO
2014-01-01
Plane wave generators (PWGs) are used to accelerate flyer plates to high velocities with their generated plane waves, which are widely used in the test of dynamic properties of materials. The traditional PWG is composed of two explosives with different detonation velocities. It is difficult to implement the related fabrication processes and control the generated waves due to its complicated structures. A simple plane wave generator is presented in this paper, which is composed of two identical cylindrical high explosive (HE) charges and an air-metal barrier. A theoretical model was established based on two different paths of the propagation of detonation waves, based on which the size of air-metal barrier was calculated for a given charge. The corresponding numerical simulations were also carried out by AUTODYN-2D® based on the calculated results, which were used to compare with the theoretical calculations. A detonation wave with a flatness of 0.039 ms within the range of 70-percent diameter of the main charge was obtained through the simulations.
CMS-Wave Model: Part 5. Full-plane Wave Transformation and Grid Nesting
2012-04-01
are available in previous reports and CHETNs (Lin et al. 2006; Demirbilek et al. 2007). CMS -Wave is part of the Coastal Modeling System ( CMS ...the U.S. Army Corps of Engineers’ (USACE) Surface-water Modeling System (SMS). The CMS -Wave FP option is available in SMS Version 11.1 and higher...ERDC/CHL CHETN-IV-81 April 2012 Approved for public release; distribution is unlimited. CMS -Wave Model: Part 5. Full-plane Wave Transformation
Reichert, R, S.; Biringen, S.; Howard, J. E.
1999-01-01
LINER is a system of Fortran 77 codes which performs a 2D analysis of acoustic wave propagation and noise suppression in a rectangular channel with a continuous liner at the top wall. This new implementation is designed to streamline the usage of the several codes making up LINER, resulting in a useful design tool. Major input parameters are placed in two main data files, input.inc and nurn.prm. Output data appear in the form of ASCII files as well as a choice of GNUPLOT graphs. Section 2 briefly describes the physical model. Section 3 discusses the numerical methods; Section 4 gives a detailed account of program usage, including input formats and graphical options. A sample run is also provided. Finally, Section 5 briefly describes the individual program files.
Gravitational scattering of zero-rest-mass plane waves
De Logi, W. K.; Kovacs, S. J., Jr.
1977-01-01
The Feyman-diagram technique is used to calculate the differential cross sections for the scattering of zero-rest-mass plane waves of spin 0, 1, and 2 by linearized Schwarzschild and Kerr geometries in the long-wavelength weak-field limit. It is found that the polarization of right (or left) circularly polarized electromagnetic waves is unaffected by the scattering process (i.e., helicity is conserved) and that the two helicity (polarization) states of the photon are scattered differently by the Kerr geometry. This coupling between the photon helicity and the angular momentum of the scatterer also leads to a partial polarization of unpolarized incident light. For gravitational waves, on the other hand, there is neither helicity conservation nor helicity-dependent scattering; the angular momentum of the scatterer has no polarizing effect on incident unpolarized gravitational waves.
Scattering of Plane Guided Waves Obliquely Incident on Straight Features
Wilcox, P. D.; Velichko, A.; Drinkwater, B. W.; Croxford, A. J.; Todd, M. D.
2011-06-01
A semi-analytical finite element model is developed to study the scattering of plane guided waves obliquely incident on a straight geometric feature. The model is first used to investigate the reflection of the S0 mode from a free edge and the results are compared to those of bulk waves reflecting from a free boundary. The model is then used to predict the transmission of the S0 mode past an adhesively-bonded stiffener. The results obtained are in excellent agreement with experimental measurements.
Scattering of a CW plane wave by a pulse
Trivett, D. H.; Rogers, P. H.
1982-05-01
A procedure similar to the CW crossed-beam calculation of Ingard and Pridmore-Brown (1956) is used to calculate the far field scattered sound pressure of a pulse interacting with a plane wave. The scattered sound is found to be at neither the sum nor the difference frequency. It is suggested that this type of interaction is ideal for investigating the scattering of sound by sound, and a numerical solution is used to discuss the general features of the nearfield waveform.
Two-Flux Colliding Plane Waves in String Theory
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
We construct the two-flux colliding plane wave solutions in higher-dimensional gravity theory with dilaton,and two complementary fluxes. Two kinds of solutions have been obtained: Bell-Szekeres (BS) type and homogeneous type. After imposing the junction condition, we find that only the BS type solution is physically well-defined. Furthermore, we show that the future curvature singularity is always developed for our solutions.
The worldline approach to helicity flip in plane waves
Ilderton, Anton
2016-01-01
We apply worldline methods to the study of vacuum polarisation effects in plane wave backgrounds, in both scalar and spinor QED. We calculate helicity-flip probabilities to one loop order and treated exactly in the background field, and provide a toolkit of methods for use in investigations of higher-order processes. We also discuss the connections between the worldline, S-matrix, and lightfront approaches to vacuum polarisation effects.
Plane-wave Least-squares Reverse Time Migration
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.
Stolt's f-k migration for plane wave ultrasound imaging.
Garcia, Damien; Le Tarnec, Louis; Muth, Stéphan; Montagnon, Emmanuel; Porée, Jonathan; Cloutier, Guy
2013-09-01
Ultrafast ultrasound is an emerging modality that offers new perspectives and opportunities in medical imaging. Plane wave imaging (PWI) allows one to attain very high frame rates by transmission of planar ultrasound wave-fronts. As a plane wave reaches a given scatterer, the latter becomes a secondary source emitting upward spherical waves and creating a diffraction hyperbola in the received RF signals. To produce an image of the scatterers, all the hyperbolas must be migrated back to their apexes. To perform beamforming of plane wave echo RFs and return high-quality images at high frame rates, we propose a new migration method carried out in the frequency-wavenumber (f-k) domain. The f-k migration for PWI has been adapted from the Stolt migration for seismic imaging. This migration technique is based on the exploding reflector model (ERM), which consists in assuming that all the scatterers explode in concert and become acoustic sources. The classical ERM model, however, is not appropriate for PWI. We showed that the ERM can be made suitable for PWI by a spatial transformation of the hyperbolic traces present in the RF data. In vitro experiments were performed to outline the advantages of PWI with Stolt's f-k migration over the conventional delay-and-sum (DAS) approach. The Stolt's f-k migration was also compared with the Fourier-based method developed by J.-Y. Lu. Our findings show that multi-angle compounded f-k migrated images are of quality similar to those obtained with a stateof- the-art dynamic focusing mode. This remained true even with a very small number of steering angles, thus ensuring a highly competitive frame rate. In addition, the new FFT-based f-k migration provides comparable or better contrast-to-noise ratio and lateral resolution than the Lu's and DAS migration schemes. Matlab codes for the Stolt's f-k migration for PWI are provided.
Numerical Study of Submerged Vertical Plane Jets Under Progressive Water Surface Waves
Institute of Scientific and Technical Information of China (English)
DAI Hui-chao; WANG Ling-ling
2005-01-01
When wastewater is discharged into a coastal area through an outfall system, it will always be subjected to the action of waves. It is important to study and quantify the mixing of the discharge with the ambient water so that accurate environmental impact assessment can be made for such discharge conditions. The present work aims to study the phenomenon of a plane jet discharged into water environment with regular waves. A 3D numerical model based on the full Navier-Stokes equations (NSE) in the σ-coordinate is developed to study the present problem. Turbulence effects are modeled by a subgrid-scale (SGS) model using the concept of large eddy simulation (LES). The operator splitting method is used to solve the modified NSE. The model has been applied to the simulation of three different cases of submerged plane jets with surface waves: jet with strong waves, jet with weak waves and jet without waves. Numerical results show that the waves enhance the mixing of the jet with the ambient fluid, and cause a periodic deflection of the jet. The size of the re-circulation is about 1.5～2.4 depth of water. The velocity profile of the jet is self-similar in the zone of established flow for both the pure jet and jet in wave circumstances. The spreading characteristic constant α is 0.100 and 0.105 for pure momentum jets with Re numbers 1025 and 2050. The value of α increases from 0.130 to 0.147 for a jet in weak and strong wave circumstances, showing that waves have an obvious effect on the mixing and dilution properties of jets. Numerical results are in good agreement with the experimental data for the cases of pure jets and jets with waves.
On the local plane wave methods for in situ measurement of acoustic absorption
Wijnant, Y.H.
2015-01-01
In this paper we address a series of so-called local plane wave methods (LPW) to measure acoustic absorption. As opposed to other methods, these methods do not rely on assumptions of the global sound field, like e.g. a plane wave or diffuse field, but are based on a local plane wave assumption. Ther
Waveguide characteristics of coupled in-plane waves.
Pan, Jie; Lu, Jing; Qiu, Xiaojun
2012-06-01
In-plane waves in a waveguide made from a thin plate are described by a superposition of a set of orthogonal functions that satisfy the edge conditions of the waveguide. Due to the Poisson and shear effects, the displacement components of the in-plane waves along the two in-plane orthogonal coordinates are coupled and this coupling affects the propagation and spatial properties of the waveguide modes. The orthogonal functions and their associated wavenumbers represent the characteristics of the uncoupled modes of the waveguide where the above mentioned couplings are ignored. This study demonstrates that the characteristics of the waveguide modes are determined by the couplings of the uncoupled mode pairs, which become significant when the pairs satisfy the conditions of spatial coincidence. At some frequencies, certain waveguide modes can be determined by a single pair of uncoupled modes. For this case, the analytical solution for the waveguide modes exists and provides both a qualitative and quantitative interpretation of the characteristics of the waveguide mode.
Ye, Qian; Jiang, Yikun; Lin, Haoze
2017-03-01
In most textbooks, after discussing the partial transmission and reflection of a plane wave at a planar interface, the power (energy) reflection and transmission coefficients are introduced by calculating the normal-to-interface components of the Poynting vectors for the incident, reflected and transmitted waves, separately. Ambiguity arises among students since, for the Poynting vector to be interpreted as the energy flux density, on the incident (reflected) side, the electric and magnetic fields involved must be the total fields, namely, the sum of incident and reflected fields, instead of the partial fields which are just the incident (reflected) fields. The interpretation of the cross product of partial fields as energy flux has not been obviously justified in most textbooks. Besides, the plane wave is actually an idealisation that is only ever found in textbooks, then what do the reflection and transmission coefficients evaluated for a plane wave really mean for a real beam of limited extent? To provide a clearer physical picture, we exemplify a light beam of finite transverse extent by a fundamental Gaussian beam and simulate its reflection and transmission at a planar interface. Due to its finite transverse extent, we can then insert the incident fields or reflected fields as total fields into the expression of the Poynting vector to evaluate the energy flux and then power reflection and transmission coefficients. We demonstrate that the power reflection and transmission coefficients of a beam of finite extent turn out to be the weighted sum of the corresponding coefficients for all constituent plane wave components that form the beam. The power reflection and transmission coefficients of a single plane wave serve, in turn, as the asymptotes for the corresponding coefficients of a light beam as its width expands infinitely.
Directory of Open Access Journals (Sweden)
A. A. Lubchich
2005-07-01
Full Text Available Characteristics of small amplitude plane waves within the medium separated by the plane discontinuity into two half spaces are analysed. The approximation of the ideal one-fluid magnetohydrodynamics (MHD is used. The discontinuities with the nonzero mass flux across them are mainly examined. These are fast or slow shock waves and rotational discontinuities. The dispersion equation for MHD waves within each of half space is obtained in the reference frame connected with the discontinuity surface. The solution of this equation permits one to determine the wave vectors versus the parameter c_{p}, which is the phase velocity of surface discontinuity oscillations. This value of c_{p} is common for all MHD waves and determined by an incident wave or by spontaneous oscillations of the discontinuity surface. The main purpose of the study is a detailed analysis of the dispersion equation solution. This analysis let us draw the following conclusions. (I For a given c_{p}, ahead or behind a discontinuity at most, one diverging wave can transform to a surface wave damping when moving away from the discontinuity. The surface wave can be a fast one or, in rare cases, a slow, magnetoacoustic one. The entropy and Alfvén waves always remain in a usual homogeneous mode. (II For certain values of c_{p} and parameters of the discontinuity behind the front of the fast shock wave, there can be four slow magnetoacoustic waves, satisfying the dispersion equation, and none of the fast magnetoacoustic waves. In this case, one of the four slow magnetoacoustic waves is incident on the fast shock wave from the side of a compressed medium. It is shown that its existence does not contradict the conditions of the evolutionarity of MHD shock waves. The four slow magnetoacoustic waves, satisfying the dispersion equation, can also exist from either side of a slow shock wave or rotational discontinuity. (III The
Simulation study of plane motion of air cushion vehicle
Institute of Scientific and Technical Information of China (English)
ZHAO Shu-qin; SHI Xiao-cheng; SHI Yi-long; BIAN Xin-qian
2003-01-01
This research is on horizontal plane motion equations of Air Cushion Vehicle (ACV) and its simulation. To investigate this, a lot of simulation study including ACV's voyage and turning performance has been done. It was found that the voyage simulation results were accorded with ACV own characteristic and turning simulation results were accorded with USA ACV's movement characteristic basically.
Simulation study of plane motion of air cushion vehicle
Zhao, Shu-Qin; Shi, Xiao-Cheng; Shi, Yi-Long; Bian, Xin-Qian
2003-12-01
This research is on horizontal plane motion equations of Air Cushion Vehicle (ACV) and its simulation. To investigate this, a lot of simulation study including ACV’s voyage and turning performance has been done. It was found that the voyage simulation results were accorded with ACV own characteristic and turning simulation results were accorded with USA ACV’s movement characteristic basically.
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...... Field H and a 7 MHz, 128-elements, linear array transducer with lambda/2-spacing. MV is compared to the conventional delay-and-sum (DS) beamformer with Boxcar and Hanning weights. Furthermore, the PW images are compared to the a conventional ultrasound image, obtained from a linear scan sequence...
Plane-Wave Propagation in Electromagnetic PQ Medium
Lindell, Ismo V
2015-01-01
Two basic classes of electromagnetic media, recently defined and labeled as those of P media and Q media, are generalized to define the class of PQ media. Plane wave propagation in the general PQ medium is studied and the quartic dispersion equation is derived in analytic form applying four-dimensional dyadic formalism. The result is verified by considering various special cases of PQ media for which the dispersion equation is known to decompose to two quadratic equations or be identically satisfied (media with no dispersion equation). As a numerical example, the dispersion surface of a PQ medium with non-decomposable dispersion equation is considered.
Plane shock wave structure in a dilute granular gas
Reddy, M. H. Lakshminarayana; Alam, Meheboob
2016-11-01
We analyse the early time evolution of the Riemann problem of planar shock wave structures for a dilute granular gas by solving Navier-Stokes equations numerically. The one-dimensional reduced Navier-Stokes equations for plane shock wave problem are solved numerically using a relaxation-type numerical scheme. The results on the shock structures in granular gases are presented for different Mach numbers and restitution coefficients. Based on our analysis on early time shock dynamics we conclude that the density and temperature profiles are "asymmetric"; the density maximum and the temperature maximum occur within the shock layer; the absolute magnitudes of longitudinal stress and heat flux which are initially zero at both end states attain maxima in a very short time and thereafter decrease with time.
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
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......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...... calibration, carried out in plane wave couplers, is the most extended. Here plane wave propagation is assumed. While this assumption is valid at low and mid frequencies, it fails at higher frequencies because the membrane of the microphones is not moving uniformly, and there are viscous losses. An existing...
Fisanov, V. V.
2017-09-01
Analytical expressions for complex values of the wave number, refractive index, and the characteristic wave impedance of homogeneous electromagnetic plane waves propagating in a linear, homogeneous, isotropic medium with losses and gain are derived. Formulas for determining the type of normal wave as a function of the values of the real and imaginary parts of the permittivity and permeability are obtained, and conditions for the appearance of positive and negative refraction at the interface of two isotropic media are indicated. In the approach applied here, the concept of a negative refractive index is not used.
Travelling-wave solutions bifurcating from relative periodic orbits in plane Poiseuille flow
Rawat, Subhendu; Rincon, François
2016-01-01
Travelling-wave solutions are shown to bifurcate from relative periodic orbits in plane Poiseuille flow at Re = 2000 in a saddle-node infinite period bifurcation. These solutions consist in self-sustaining sinuous quasi-streamwise streaks and quasi- streamwise vortices located in the bulk of the flow. The lower branch travelling-wave solutions evolve into spanwise localized states when the spanwise size Lz of the domain in which they are computed is increased. On the contrary, upper branch of travelling-wave solutions develop multiple streaks when Lz is increased. Upper branch travelling-wave solutions can be continued into coherent solutions of the filtered equations used in large-eddy simulations where they represent turbulent coherent large-scale motions.
A physical solution for plane SH waves in anelastic media
Ursin, Bjorn; Carcione, José M.; Gei, Davide
2017-05-01
In a lossy medium with complex frequency-dependent wave speed both rays and plane waves at an interface should satisfy the dispersion relation (that is, the wave equation), the radiation condition (the amplitude should go to zero at infinity) and the horizontal complex slowness should be continuous (Snell's law). It is known that this may lead to a transmitted wave which violates the radiation condition and which also causes problems with the phase of the reflection coefficient. In fact, ray-tracing algorithms and analytical evaluations of the reflection and transmission coefficients in anelastic media may lead to non-physical solutions related to the complex square roots of the vertical slowness and polarizations. The steepest-descent approximation with complex horizontal slowness involves non-physical complex horizontal distances, and in some cases also a non-physical vertical slowness that violates the radiation condition. Similarly, the reflection and transmission coefficients and ray-tracing codes obtained with this approach yields wrong results. In order to tackle this problem, we choose the stationary-phase approximation with real horizontal slowness. This gives real horizontal distances, the radiation condition is always satisfied and the reflection and transmission coefficients are correct. This is shown by comparison to full-wave space-time modelling results by computing the reflection and transmission coefficients and respective phase angles from synthetic seismograms. This numerical evaluation is based on a 2-D wavenumber-frequency Fourier transform. The results indicate that the stationary-phase method with a real horizontal slowness provides the correct physical solution.
Yong, Peng; Huang, Jianping; Li, Zhenchun; Liao, Wenyuan; Qu, Luping; Li, Qingyang; Liu, Peijun
2017-02-01
In finite-difference (FD) method, numerical dispersion is the dominant factor influencing the accuracy of seismic modelling. Various optimized FD schemes for scalar wave modelling have been proposed to reduce grid dispersion, while the optimized time-space domain FD schemes for elastic wave modelling have not been fully investigated yet. In this paper, an optimized FD scheme with Equivalent Staggered Grid (ESG) for elastic modelling has been developed. We start from the constant P- and S-wave speed elastic wave equations and then deduce analytical plane wave solutions in the wavenumber domain with eigenvalue decomposition method. Based on the elastic plane wave solutions, three new time-space domain dispersion relations of ESG elastic modelling are obtained, which are represented by three equations corresponding to P-, S- and converted-wave terms in the elastic equations, respectively. By using these new relations, we can study the dispersion errors of different spatial FD terms independently. The dispersion analysis showed that different spatial FD terms have different errors. It is therefore suggested that different FD coefficients to be used to approximate the three spatial derivative terms. In addition, the relative dispersion error in L2-norm is minimized through optimizing FD coefficients using Newton's method. Synthetic examples have demonstrated that this new optimal FD schemes have superior accuracy for elastic wave modelling compared to Taylor-series expansion and optimized space domain FD schemes.
On the types and number of plane waves in hypoelastic materials
Rushchitsky, J. J.
2005-11-01
General principles are formulated for modeling the elastic deformation of materials and analyzing plane waves in nonlinearly elastic materials such as hyperelastic, hypoelastic, and those governed by the general law of elasticity. The results of studying the propagation of plane waves in hypoelastic materials are further outlined. The influence of initial stresses and initial velocities on the types and number of plane waves is studied. Wave effects characteristic of hypoelastic materials are predicted theoretically. One of such effects is blocking of certain types of plane waves by initial stresses
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
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...
Improved beamforming performance using pulsed plane wave decomposition
DEFF Research Database (Denmark)
Munk, Peter; Jensen, Jørgen Arendt
2000-01-01
A tool for calculating the beamformer setup associated with a specified pulsed acoustic field is presented. The method is named Pulsed Plane Wave Decomposition (PPWD) and is based on the decomposition of a pulsed acoustic field into a set of PPWs at a given depth. Each PPW can be propagated...... to the location of the elements of an array transducer by a time delay. The contribution of each propagated PPW is summed to form one time function for each array element (the BMF matrix). This approach gives the beamformer setup needed to obtain a close approximation to the desired bounded pulsed acoustic field...... without involving any optimization scheme. The approximation arises due to the limited size of the acoustic aperture and the spatial sampling property of the array transducer. Thus, the acoustical field can be designed according to the imaging needs. The method is demonstrated by examples in the 2D space...
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.
Rossby wave radiation by an eddy on the polar beta-plane
Zhang, Yang
2015-01-01
Results from the laboratory experiments on the evolution of vortices (eddies) generated in a rotating tank with topographic beta-effect are presented. The surface elevation and velocity fields are measured by the Altimetric Imaging Velocimetry. The experiments are supplemented by shallow water numerical simulations as well as a linear theory which describes the Rossby wave radiation by travelling vortices. The cyclonic vortices observed in the experiments travel to the northwest and continuously radiate Rossby waves. Measurements show that initially axisymmetric vortices develop a dipolar component which enables them to perform translational motion. A pattern of alternating zonal jets to the west of the vortex is created by Rossby waves with approximately zonal crests. Energy spectra of the flows in the wavenumber space indicate that a wavenumber similar to that introduced by Rhines for turbulent flows on the beta-plane can be introduced here. The wavenumber is based on the translational speed of a vortex rat...
Effects of a covering layer in a circular-arc canyon on incident plane SV waves
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
An analytical solution for scattering of incident plane SV waves by a circular-arc canyon with a covering layer was derived by Fourier-Bessel series expansion technique, and the solution was utilized to analyze the effects of the covering layer on incident plane SV waves. It was shown that the covering layer in a canyon, even if it is very thin, amplifies incident plane SV waves tremendously, and the amplification can be two and half times more than that for a simple canyon; the stiffness and thickness of the covering layer also have great effects on incident plane SV waves.
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...
Ciliary beating plane and wave propagation in the bovine oviduct.
Schätz, G; Schneiter, M; Rička, J; Kühni-Boghenbor, K; Tschanz, S A; Doherr, M G; Frenz, M; Stoffel, M H
2013-01-01
The uterine tube is an essential conduit for the gametes and zygote during reproduction. The necessary bidirectional conveyance occurs through peristalsis and ciliary activity, but unlike in respiratory tract, little is known about mucociliary transport in the uterine tube, and the direction of transport and the alignment of oviductal cilia have not been conclusively characterized. This study aimed to determine the uniformity in the axonemal orientation of motile cilia in the bovine uterine tube, to identify the direction of mucociliary transport and to relate the presumptive beating plane and the mucociliary transport direction to the long axis of the uterine tube. The angular spread of oviductal motile cilia was determined by electron microscopy, and by maintaining the accurate alignment of the samples throughout the processing steps, axonemal orientation was determined relative to the long axis of the oviduct. The direction of the effective mucociliary transport was determined by the analysis of video microscopic data recorded on explants. Vector-based analysis of electron micrographs yielded the mean angle of deviation between the 'effective ciliary stroke', as derived from axonemal orientation, and the tubal longitudinal axis pointing towards the uterus to be 0.8°, with a standard deviation of 35.2°. The corresponding angular deviation of the short-wave propagation was -6.8° (SD 34.6°). These results show that oviductal motile cilia are rigorously aligned, that the beating plane of the cilia is parallel to the long axis of the uterine tube and that the 'effective stroke' and mucociliary transport are directed towards the uterus. © 2014 S. Karger AG, Basel.
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.
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.
The Lukash Plane-Wave Attractor and Relative Energy
Korunur, M; Salti, M; Aydogdu, Oktay; Korunur, Murat; Salti, Mustafa
2006-01-01
We study energy distribution in the context of teleparallel theory of gravity, due to matter and fields including gravitation, of the universe based on the plane-wave Bianchi VII$_{\\delta}$ spacetimes described by the Lukash metric. In order to make this calculation we consider the teleparallel gravity analogs of the energy-momentum formulations of Einstein, Bergmann-Thomson and Landau-Lifshitz. We find that Einstein and Bergmann-Thomson prescriptions agree with each other and give the same results for the energy distribution in a given spacetime, but the Landau-Lifshitz complex does not. Energy density turns out to be non-vanishing in all of these prescriptions. It is interesting to mention that the results can be reduced to the already available results for the Milne universe when we write $\\omega=1$ and $\\Xi^2=1$ in the metric of the Lukash spacetime, and for this special case, we get the same relation among the energy-momentum formulations of Einstein, Bergmann-Thomson and Landau-Lifshitz as obtained for ...
Exact exchange plane-wave-pseudopotential calculations for slabs.
Engel, Eberhard
2014-05-14
The exact exchange of density functional theory is applied to both free-standing graphene and a Si(111) slab, using the plane-wave pseudopotential (PWPP) approach and a periodic repetition of the supercell containing the slab. It is shown that (i) PWPP calculations with exact exchange for slabs in supercell geometry are basically feasible, (ii) the width of the vacuum required for a decoupling of the slabs is only moderately larger than in the case of the local-density approximation, and (iii) the resulting exchange potential vx shows an extended region, both far outside the surface of the slab and far from the middle of the vacuum region between the slabs, in which vx behaves as -e(2)/z, provided the width of the vacuum is chosen sufficiently large. This last result is corroborated by an analytical analysis of periodically repeated jellium slabs. The intermediate -e(2)/z behavior of vx can be used for an absolute normalization of vx and the total Kohn-Sham potential, which, in turn, allows the determination of the work function.
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...
Reflection of semi-guided plane waves at angled thin-film transitions
Çivitci, Fehmi; Hammer, Manfred; Hoekstra, Hugo J.W.M.
2013-01-01
The propagation of thin-film guided, in-plane unguided plane optical waves, and their partial or total reflection at transitions between regions with different film thickness, is considered. The properties of reflected and refracted waves can be predicted reasonably by readily available Helmholtz- a
Sánchez, N G
2003-01-01
Key issues of classical and quantum strings in gravitational plane waves, shock waves and spacetime singularities are synthetically understood. This includes the string mass and mode number excitations, energy-momentum tensor, scattering amplitudes, vacuum polarization and wave-string polarization effect. The role of the real pole singularities characteristic of the tree level string spectrum (real mass resonances) and that of spacetime singularities is clearly exhibited. This throws light on the issue of singularities in string theory which can be thus classified and fully physically characterized in two different sets: strong singularities (poles of order equal or larger than 2, and black holes), where the string motion is collective and non oscillating in time, outgoing and scattering states do not appear, the string does not cross the singularities, and weak singularities (poles of order smaller than 2, Dirac delta, and conic/orbifold singularities) where the whole string motion is oscillatory in time, ou...
Parallel 3-dim fast Fourier transforms with load balancing of the plane waves
Gao, Xingyu; Fang, Jun; Wang, Han
2016-01-01
The plane wave method is most widely used for solving the Kohn-Sham equations in first-principles materials science computations. In this procedure, the three-dimensional (3-dim) trial wave functions' fast Fourier transform (FFT) is a regular operation and one of the most demanding algorithms in terms of the scalability on a parallel machine. We propose a new partitioning algorithm for the 3-dim FFT grid to accomplish the trade-off between the communication overhead and load balancing of the plane waves. It is shown by qualitative analysis and numerical results that our approach could scale the plane wave first-principles calculations up to more nodes.
Experimental evidence of a triadic resonance of plane inertial waves in a rotating fluid
Bordes, Guilhem; Dauxois, Thierry; Cortet, Pierre-Philippe
2011-01-01
Plane inertial waves are generated using a wavemaker, made of oscillating stacked plates, in a rotating water tank. Using particle image velocimetry, we observe that, after a transient, the primary plane wave is subject to a subharmonic instability and excites two secondary plane waves. The measured frequencies and wavevectors of these secondary waves are in quantitative agreement with the predictions of the triadic resonance mechanism. The secondary wavevectors are found systematically more normal to the rotation axis than the primary wavevector: this feature illustrates the basic mechanism at the origin of the energy transfers towards slow, quasi two-dimensional, motions in rotating turbulence.
Plane-wave decomposition by spherical-convolution microphone array
Rafaely, Boaz; Park, Munhum
2001-05-01
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.
Plane-wave decomposition by spherical-convolution microphone array
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.
Inertial effects on thin-film wave structures with imposed surface shear on an inclined plane
Sivapuratharasu, M.; Hibberd, S.; Hubbard, M. E.; Power, H.
2016-06-01
This study provides an extended approach to the mathematical simulation of thin-film flow on a flat inclined plane relevant to flows subject to high surface shear. Motivated by modelling thin-film structures within an industrial context, wave structures are investigated for flows with moderate inertial effects and small film depth aspect ratio ε. Approximations are made assuming a Reynolds number, Re ∼ O(ε-1) and depth-averaging used to simplify the governing Navier-Stokes equations. A parallel Stokes flow is expected in the absence of any wave disturbance and a generalisation for the flow is based on a local quadratic profile. This approach provides a more general system which includes inertial effects and is solved numerically. Flow structures are compared with studies for Stokes flow in the limit of negligible inertial effects. Both two-tier and three-tier wave disturbances are used to study film profile evolution. A parametric study is provided for wave disturbances with increasing film Reynolds number. An evaluation of standing wave and transient film profiles is undertaken and identifies new profiles not previously predicted when inertial effects are neglected.
Lamb waves in phononic crystal slabs: truncated plane parallels to the axis of periodicity.
Chen, Jiujiu; Xia, Yunjia; Han, Xu; Zhang, Hongbo
2012-09-01
A theoretical study is presented on the propagation properties of Lamb wave modes in phononic crystal slabs consisting of a row or more of parallel square cylinders placed periodically in the host material. The surfaces of the slabs are parallel to the axis of periodicity. The dispersion curves of Lamb wave modes are calculated based on the supercell method. The finite element method is employed to calculate the band structures and the transmission power spectra, which are in good agreement with the results by the supercell method. We also have found that the dispersion curves of Lamb waves are strongly dependent on the crystal termination, which is the position of the cut plane through the square cylinders. There exist complete or incomplete (truncated) layers of square cylinders with the change of the crystal termination. The influence of the crystal termination on the band gaps of Lamb wave modes is analyzed by numerical simulations. The variation of the crystal termination leads to obvious changes in the dispersion curves of the Lamb waves and the widths of the band gaps. Copyright © 2012 Elsevier B.V. All rights reserved.
Longshore Currents of Random Waves on Different Plane Beaches
Institute of Scientific and Technical Information of China (English)
邹志利; 王淑平; 邱大洪; 王艳; 王风龙; 董国海
2003-01-01
Model tests and numerical calculation of longshore currents and wave heights produced by irregular waves on two beaches with slopes of 1:100 and 1:40 are studied. The cross-shore distributions of longshore current velocities and wave heights are given and the influences of wave heights, wave periods, and beach slopes on longshore currents are discussed. The discussion is also made on the influences of different eddy viscosity coefficients on the numerical results of longshore current velocities.
Wang, Yu; Jiang, Jingfeng
2017-07-01
Shear wave elastography (SWE) has been used to measure viscoelastic properties for characterization of fibrotic livers. In this technique, external mechanical vibrations or acoustic radiation forces are first transmitted to the tissue being imaged to induce shear waves. Ultrasonically measured displacement/velocity is then utilized to obtain elastographic measurements related to shear wave propagation. Using an open-source wave simulator, k-Wave, we conducted a case study of the relationship between plane shear wave measurements and the microstructure of fibrotic liver tissues. Particularly, three different virtual tissue models (i.e., a histology-based model, a statistics-based model, and a simple inclusion model) were used to represent underlying microstructures of fibrotic liver tissues. We found underlying microstructures affected the estimated mean group shear wave speed (SWS) under the plane shear wave assumption by as much as 56%. Also, the elastic shear wave scattering resulted in frequency-dependent attenuation coefficients and introduced changes in the estimated group SWS. Similarly, the slope of group SWS changes with respect to the excitation frequency differed as much as 78% among three models investigated. This new finding may motivate further studies examining how elastic scattering may contribute to frequency-dependent shear wave dispersion and attenuation in biological tissues.
Plane wave holonomies in quantum gravity. II. A sine wave solution
Neville, Donald E.
2015-08-01
This paper constructs an approximate sinusoidal wave packet solution to the equations of canonical gravity. The theory uses holonomy-flux variables with support on a lattice (LHF =lattice-holonomy flux ). There is an SU(2) holonomy on each edge of the LHF simplex, and the goal is to study the behavior of these holonomies under the influence of a passing gravitational wave. The equations are solved in a small sine approximation: holonomies are expanded in powers of sines and terms beyond sin2 are dropped; also, fields vary slowly from vertex to vertex. The wave is unidirectional and linearly polarized. The Hilbert space is spanned by a set of coherent states tailored to the symmetry of the plane wave case. Fixing the spatial diffeomorphisms is equivalent to fixing the spatial interval between vertices of the loop quantum gravity lattice. This spacing can be chosen such that the eigenvalues of the triad operators are large, as required in the small sine limit, even though the holonomies are not large. Appendices compute the energy of the wave, estimate the lifetime of the coherent state packet, discuss circular polarization and coarse-graining, and determine the behavior of the spinors used in the U(N) SHO realization of LQG.
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...
No pair production of open strings in a plane-wave background
Sakaguchi, Makoto; Yoshida, Kentaroh
2014-01-01
We consider whether an external electric field may cause the pair production of open strings in a type IIA plane-wave background. The boundary states of D-branes with condensates are constructed in the Green-Schwarz formulation of superstring with the light-cone gauge. The cylinder diagrams are computed with massive theta functions. Although the value of the electric field is bounded by the upper value as usual, there is no pole in the amplitudes and it indicates that no pair production occurs in the plane-wave background. This result would be universal for a class of plane-wave backgrounds.
On the Hagedorn Behaviour of Singular Scale-Invariant Plane Waves
Blau, Matthias; O'Loughlin, M; Blau, Matthias; Borunda, Monica; Loughlin, Martin O'
2005-01-01
As a step towards understanding the properties of string theory in time-dependent and singular spacetimes, we study the divergence of density operators for string ensembles in singular scale-invariant plane waves, i.e. those plane waves that arise as the Penrose limits of generic spacetime singularities. We show that the scale invariance implies that the Hagedorn behaviour of bosonic and supersymmetric strings in these backgrounds, even with the inclusion of RR or NS fields, is the same as that of strings in flat space. This is in marked contrast to the behaviour of strings in the BFHP plane wave which exhibit quantitatively and qualitatively different thermodynamic properties.
Scaling of plane-wave functions in statistically optimized near-field acoustic holography.
Hald, Jørgen
2014-11-01
Statistically Optimized Near-field Acoustic Holography (SONAH) is a Patch Holography method, meaning that it can be applied in cases where the measurement area covers only part of the source surface. The method performs projections directly in the spatial domain, avoiding the use of spatial discrete Fourier transforms and the associated errors. First, an inverse problem is solved using regularization. For each calculation point a multiplication must then be performed with two transfer vectors--one to get the sound pressure and the other to get the particle velocity. Considering SONAH based on sound pressure measurements, existing derivations consider only pressure reconstruction when setting up the inverse problem, so the evanescent wave amplification associated with the calculation of particle velocity is not taken into account in the regularized solution of the inverse problem. The present paper introduces a scaling of the applied plane wave functions that takes the amplification into account, and it is shown that the previously published virtual source-plane retraction has almost the same effect. The effectiveness of the different solutions is verified through a set of simulated measurements.
Zhang, Xiao-Zheng; Thomas, Jean-Hugh; Bi, Chuan-Xing; Pascal, Jean-Claude
2012-10-01
A time-domain plane wave superposition method is proposed to reconstruct nonstationary sound fields. In this method, the sound field is expressed as a superposition of time convolutions between the estimated time-wavenumber spectrum of the sound pressure on a virtual source plane and the time-domain propagation kernel at each wavenumber. By discretizing the time convolutions directly, the reconstruction can be carried out iteratively in the time domain, thus providing the advantage of continuously reconstructing time-dependent pressure signals. In the reconstruction process, the Tikhonov regularization is introduced at each time step to obtain a relevant estimate of the time-wavenumber spectrum on the virtual source plane. Because the double infinite integral of the two-dimensional spatial Fourier transform is discretized directly in the wavenumber domain in the proposed method, it does not need to perform the two-dimensional spatial fast Fourier transform that is generally used in time domain holography and real-time near-field acoustic holography, and therefore it avoids some errors associated with the two-dimensional spatial fast Fourier transform in theory and makes possible to use an irregular microphone array. The feasibility of the proposed method is demonstrated by numerical simulations and an experiment with two speakers.
Geometry of magnetosonic shocks and plane-polarized waves: Coplanarity Variance Analysis (CVA)
Scudder, J. D.
2005-02-01
Minimum Variance Analysis (MVA) is frequently used for the geometrical organization of a time series of vectors. The Coplanarity Variance Analysis (CVA) developed in this paper reproduces the layer geometry involving coplanar magnetosonic shocks or plane-polarized wave trains (including normals and coplanarity directions) 300 times more precisely (CVA technique exploits the eigenvalue degeneracy of the covariance matrix present at planar structures to find a consistent normal to the coplanarity plane of the fluctuations. Although Tangential Discontinuities (TDs) have a coplanarity plane, the eigenvalues of their covariance matrix are usually not degenerate; accordingly, CVA does not misdiagnose TDs as shocks or plane-polarized waves. Together CVA and MVA may be used to sort between the hypotheses that the time series is caused by a one-dimensional current layer that has magnetic disturbances that are (1) coplanar, linearly polarized (shocks/plane waves), (2) intrinsically helical (rotational/tangential discontinuities), or (3) neither 1 nor 2.
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...
Contributions of Higgs bosons in anomalous momentum of electron in plane-wave field
Klimenko, E Y
2002-01-01
The Higgs bosons contribution to the anomalous magnetic momentum of the electron, moving in the field representing the superposition of the constant crossed field and plane electromagnetic wave of the elliptical polarization are considered in this work
Shepherd, James J.; Grüneis, Andreas; Booth, George H.; Kresse, Georg; Alavi, Ali
2012-07-01
Using the finite simulation-cell homogeneous electron gas (HEG) as a model, we investigate the convergence of the correlation energy to the complete-basis-set (CBS) limit in methods utilizing plane-wave wave-function expansions. Simple analytic and numerical results from second-order Møller-Plesset theory (MP2) suggest a 1/M decay of the basis-set incompleteness error where M is the number of plane waves used in the calculation, allowing for straightforward extrapolation to the CBS limit. As we shall show, the choice of basis-set truncation when constructing many-electron wave functions is far from obvious, and here we propose several alternatives based on the momentum transfer vector, which greatly improve the rate of convergence. This is demonstrated for a variety of wave-function methods, from MP2 to coupled-cluster doubles theory and the random-phase approximation plus second-order screened exchange. Finite basis-set energies are presented for these methods and compared with exact benchmarks. A transformation can map the orbitals of a general solid state system onto the HEG plane-wave basis and thereby allow application of these methods to more realistic physical problems. We demonstrate this explicitly for solid and molecular lithium hydride.
Numerical Simulation of a Planing Vessel at High Speed
Institute of Scientific and Technical Information of China (English)
Yumin Su; Qingtong Chen; Hailong Shen; Wei Lu
2012-01-01
Planing vessels are applied widely in civil and military situations.Due to their high speed,the motion of planning vessels is complex.In order to predict the motion of planning vessels,it is important to analyze the hydrodynamic performance of planning vessels at high speeds.The computational fluid dynamic method (CFD) has been proposed to calculate hydrodynamic performance of planning vessels.However,in most traditional CFD approaches,model tests or empirical formulas are needed to obtain the running attitude of the planing vessels before calculation.This paper presents a new CFD method to calculate hydrodynamic forces of planing vessels.The numerical method was based on Reynolds-Averaged Navier-Stokes (RANS)equations.The volume of fluid (VOF) method and the six-degrees-of-freedom equation were applied.An effective process was introduced to solve the numerical divergence problem in numerical simulation.Compared with experimental results,numerical simulation results indicate that both the running attitude and hydrodynamic performance can be predicted well at high speeds.
Matrix basis for plane and modal waves in a Timoshenko beam.
Claeyssen, Julio Cesar Ruiz; Tolfo, Daniela de Rosso; Tonetto, Leticia
2016-11-01
Plane waves and modal waves of the Timoshenko beam model are characterized in closed form by introducing robust matrix basis that behave according to the nature of frequency and wave or modal numbers. These new characterizations are given in terms of a finite number of coupling matrices and closed form generating scalar functions. Through Liouville's technique, these latter are well behaved at critical or static situations. Eigenanalysis is formulated for exponential and modal waves. Modal waves are superposition of four plane waves, but there are plane waves that cannot be modal waves. Reflected and transmitted waves at an interface point are formulated in matrix terms, regardless of having a conservative or a dissipative situation. The matrix representation of modal waves is used in a crack problem for determining the reflected and transmitted matrices. Their euclidean norms are seen to be dominated by certain components at low and high frequencies. The matrix basis technique is also used with a non-local Timoshenko model and with the wave interaction with a boundary. The matrix basis allows to characterize reflected and transmitted waves in spectral and non-spectral form.
Matrix basis for plane and modal waves in a Timoshenko beam
Claeyssen, Julio Cesar Ruiz; Tolfo, Daniela de Rosso; Tonetto, Leticia
2016-11-01
Plane waves and modal waves of the Timoshenko beam model are characterized in closed form by introducing robust matrix basis that behave according to the nature of frequency and wave or modal numbers. These new characterizations are given in terms of a finite number of coupling matrices and closed form generating scalar functions. Through Liouville's technique, these latter are well behaved at critical or static situations. Eigenanalysis is formulated for exponential and modal waves. Modal waves are superposition of four plane waves, but there are plane waves that cannot be modal waves. Reflected and transmitted waves at an interface point are formulated in matrix terms, regardless of having a conservative or a dissipative situation. The matrix representation of modal waves is used in a crack problem for determining the reflected and transmitted matrices. Their euclidean norms are seen to be dominated by certain components at low and high frequencies. The matrix basis technique is also used with a non-local Timoshenko model and with the wave interaction with a boundary. The matrix basis allows to characterize reflected and transmitted waves in spectral and non-spectral form.
Application of Plane Wave Method to the Calculation of Electronic States of Nano-Structures
Institute of Scientific and Technical Information of China (English)
LI Shu-Shen; XIA Jian-Bai
2006-01-01
@@ The electronic states of nano-structures are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The barrier width and the number of plane waves are proposed to be 2.5 times the effective Bohr radius and 15n, respectively, for n-dimensional nano-structures (n = 1, 2, 3). Our proposals can be widely applied in the design of various nano-structure devices.
LOBSTER: A tool to extract chemical bonding from plane-wave based DFT.
Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard
2016-04-30
The computer program LOBSTER (Local Orbital Basis Suite Towards Electronic-Structure Reconstruction) enables chemical-bonding analysis based on periodic plane-wave (PAW) density-functional theory (DFT) output and is applicable to a wide range of first-principles simulations in solid-state and materials chemistry. LOBSTER incorporates analytic projection routines described previously in this very journal [J. Comput. Chem. 2013, 34, 2557] and offers improved functionality. It calculates, among others, atom-projected densities of states (pDOS), projected crystal orbital Hamilton population (pCOHP) curves, and the recently introduced bond-weighted distribution function (BWDF). The software is offered free-of-charge for non-commercial research. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
Traveling Wave Modes of a Plane Layered Anelastic Earth
2016-05-20
variable in the standing wave free oscillation problem is the frequency , which makes the eigenvalue problem nonlinear. The choice of the wavenumber as...38) By making the assignment Irn = κn Iqn, (39) the quadratic generalized eigenvalue problem Eq. (34) can be converted to a linear generalized...elastic eigenfunctions and the complex frequency dependent elastic moduli. The lateral standing-wave nature of the earth free oscillation problem leads to
Propagation of plane waves in poroviscoelastic anisotropic media
Institute of Scientific and Technical Information of China (English)
A.K.Vashishth,M.D.Sharma
2008-01-01
This study discusses wave propagation in perhaps the most general model of a poroelastic medium.The medium is considered as a viscoelastic,anisotropic and porous solid frame such that its pores of anisotropic permeability are filled with a viscous fluid.The anisotropy considered is of general type,and the attenuating waves in the medium are treated as the inhomogeneous waves.The complex slowness vector is resolved to define the phase velocity,homogeneous attenuation,inhomogeneous attenuation,and angle of attenuation for each of the four attenuating waves in the medium.A non-dimensional parameter measures the deviation of an inhomogeneous wave from its homogeneous version.An numerical model of a North-Sea sandstone is used to analyze the effects of the propagation direction,inhomogeneity parameter,frequency regime,anisotropy symmetry,anelasticity of the frame,and viscosity of the pore-fluid on the propagation characteristics of waves in such a medium.
Response of a Doppler canceling system to plane gravitational waves
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 a 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-cancelled 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.
Direct numerical simulation of turbulent plane Couette flow
Lee, Moon Joo
1991-01-01
Turbulent plane Couette flow was numerically simulated at a Reynolds number (U(sub w)h/nu) of 6000, where U(sub w) is the relative wall speed and h is half the channel-height. Unlike in Poiseuille flow, where the mean shear rate changes its sign at the centerline, the sign of mean shear rate in plane Couette flow remains the same across the whole channel. This difference is expected to yield several differences between the two flows, especially in the core region. The most significant and dramatic difference observed was the existence of large-scale structures in the core region of the plane Couette flow. The large eddies are extremely long in the flow direction and fill the entire channel (i.e., their vertical extent is 2h). The large-scale structures have the largest contribution from the wavenumber (k(sub x)h,k(sub z)h) = (0, plus or minus 1.5), corresponding to a wavelength lambda(sub z)/h is approximately equal to 4. The secondary motion associated with the k(sub x)h = 0 mode consists of the large-scale vortices. The large eddies contribute about 30 percent of turbulent kinetic energy.
The Relativistic Transformation for an Electromagnetic Plane Wave with General Time Dependence
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…
An experimental study on runup of two solitary waves on plane beaches
Institute of Scientific and Technical Information of China (English)
XUAN Rui-tao; WU Wei; LIU Hua
2013-01-01
Experiments of the runup of two solitary waves on a plane beach are carried out in a wave flume.The two solitary waves with the same amplitude and the crest separating distances are generated by using an improved wave generation method.It is found that,with regard to the two solitary waves with same wave amplitude,the runup amplification of the second wave is less than that of the first wave if the relative crest separating distance is reduced to a certain threshold value.The rundown of the first solitary wave depresses the maximum runup of the second wave.If the leading solitary wave is of relatively smaller amplitude for the two solitary waves,the runup amplification is affected by the overtaking process of two solitary waves.It turns out that the runup amplification of the second wave is larger than that of the first wave if the similarity factor is approximately larger than 15,which means the larger wave overtakes the smaller one before the waves runup on a beach.
A phase-plane analysis of localized frictional waves
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.
Characteristics of Plane Wave Propagation in Biaxially Anisotropic Gyrotropic Media
Institute of Scientific and Technical Information of China (English)
PAN Wei-Tao; LIU Song-Hua; QIU Zhi-Liang
2012-01-01
Propagation characteristics of electromagnetic waves at the interface between an isotropic regular medium and a biaxially anisotropic gyrotropic medium are investigated.The results indicate that the reflection and refract ionproperties of electromagnetic waves are closely dependent on the dispersion relation of the gyrotropic media,and that anomalous total reflection and negative refraction may occur.The existence conditions of total transmission are also considered.It is found that total transmission arises when the TE-polarized incident waves are normal to the interface and the physical parameters of the two media are chosen properly,which are quite different from the existence conditions of total transmission at the anisotropic left-handed material interface.Numerical resul tsare given to validate our theoretical analysis.
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.
Numerical simulations of heat transfer in plane channel flow
Gharbi, Najla El; Benzaoui, Ahmed
2010-01-01
Reynolds-averaged Navier-Stokes (RANS) turbulence models (such as k-{\\epsilon} models) are still widely used for engineering applications because of their relatively simplicity and robustness. In fully developed plane channel flow (i.e. the flow between two infinitely large plates), even if available models and near-wall treatments provide adequate mean flow velocities, they fail to predict suitable turbulent kinetic energy "TKE" profiles near walls. TKE is involved in determination of eddy viscosity/diffusivity and could therefore provide inaccurate concentrations and temperatures. In order to improve TKE a User Define Function "UDF" based on an analytical profile for TKE was developed and implemented in Fluent. Mean streamwise velocity and turbulent kinetic energy "TKE" profiles were compared to DNS data for friction Reynolds number $Re_{\\tau}$ = 150. Simulation results for TKE show accurate profiles. Simulation results for horizontal heated channel flows obtained with Fluent are presented. Numerical result...
Planckian energy scattering, colliding plane gravitational waves and black hole creation
Viswanathan, K S; Viswanathan, K S; Volovich, I V
1994-01-01
In a series of papers Amati, Ciafaloni and Veneziano and 't Hooft conjectured that black holes occur in the collision of two light particles at planckian energies. In this paper we discuss a possible scenario for such a process by using the Chandrasekhar-Ferrari-Xanthopoulos duality between the Kerr black hole solution and colliding plane gravitational waves. We clarify issues arising in the definition of transition amplitude from a quantum state containing only usual matter without black holes to a state containing black holes. Collision of two plane gravitational waves producing a space-time region which is locally isometric to an interior of black hole solution is considered. The phase of the transition amplitude from plane waves to white and black hole is calculated by using the Fabbrichesi, Pettorino, Veneziano and Vilkovisky approach. An alternative extension beyond the horizon in which the space-time again splits into two separating gravitational waves is also discussed. Such a process is interpreted a...
Propagation of plane waves in thermoelastic cubic crystal material with two relaxation times
Institute of Scientific and Technical Information of China (English)
Rajneesh Kumar; Manjeet Singh
2007-01-01
A problem concerned with the reflection and refraction of thermoelastic plane waves an imperfect interface between two generalized thermally conducting cutimes has been investigated.The generalized thermoelastic theory with two relaxation of retiected and refracted waves to the amplitude of incident waves are obtained for an imperfect boundary and deduced for normal stiffness,transverse stiffness,themlal contact conductance,slip and welded boundaries. Amplitude ratios of different reflected and graphically for different incident waves.It is observed that the amplitude ratios of reflected and refracted waves are affected by the stiffness and thermal properties of the media.
Finite-amplitude steady waves in plane viscous shear flows
Milinazzo, F. A.; Saffman, P. G.
1985-01-01
Computations of two-dimensional solutions of the Navier-Stokes equations are carried out for finite-amplitude waves on steady unidirectional flow. Several cases are considered. The numerical method employs pseudospectral techniques in the streamwise direction and finite differences on a stretched grid in the transverse direction, with matching to asymptotic solutions when unbounded. Earlier results for Poiseuille flow in a channel are re-obtained, except that attention is drawn to the dependence of the minimum Reynolds number on the physical constraint of constant flux or constant pressure gradient. Attempts to calculate waves in Couette flow by continuation in the velocity of a channel wall fail. The asymptotic suction boundary layer is shown to possess finite-amplitude waves at Reynolds numbers orders of magnitude less than the critical Reynolds number for linear instability. Waves in the Blasius boundary layer and unsteady Rayleigh profile are calculated by employing the artifice of adding a body force to cancel the spatial or temporal growth. The results are verified by comparison with perturbation analysis in the vicinity of the linear-instability critical Reynolds numbers.
Numerical Simulation of Breaking Wave Based on Higher-Order Mild Slope Equation
Institute of Scientific and Technical Information of China (English)
陶建华; 韩光
2001-01-01
The "surface roller" to simulate wave energy dissipation of wave breaking is introduced into the random wave model based on approximate parabolic mild slope equation in this paper to simulate the random wave transportation including diffraction, refraction and breaking in nearshore areas. The roller breaking random wave higher-order approximate parabolic equation model has been verified by the existing experimental data for a plane slope beach and a circularshoal, and the numerical results of random wave breaking model agree with the experimental data very well. This modelcan be applied to calculate random wave propagation from deep to shallow water in large areas near the shore over natural topography.
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.
Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets
Miceli, Giacomo; Pasquarello, Alfredo
2016-01-01
We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.
Parallel Multi-Focusing Using Plane Wave Decomposition
DEFF Research Database (Denmark)
Misaridis, Thanassis; Munk, Peter; Jensen, Jørgen Arendt
2003-01-01
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...... 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......In conventional phased-array imaging, identical short single-carrier pulses are emitted from the entire aperture, and focusing is done in one direction at a time by applying simple geometric delays. This is a sequential and not optimal transmission scheme, which limits the frame rate and makes 3D...
THE USE OF PLANE WAVES TO APPROXIMATE WAVE PROPAGATION IN ANISOTROPIC MEDIA
Institute of Scientific and Technical Information of China (English)
Tomi Huttunen; Peter Monk
2007-01-01
In this paper we extend the standard Ultra Weak Variational Formulation (UWVF) of Maxwell's equations in an isotropic medium to the case of an anisotropic medium. We verify that the underlying theoretical framework carries over to anisotropic media (however error estimates are not yet available) and completely describe the new scheme. We then consider TM mode scattering, show how this results in a Helmholtz equation in two dimensions with an anisotropic coefficient and demonstrate how to formulate the UWVF for it. In one special case, convergence can be proved. We then show some numerical results that suggest that the UWVF can successfully simulate wave propagation in anisotropic media.
Modelling and Simulation of Wave Loads
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
A simple model of the wave load on slender members of offshore structures is described. The wave elevation of the sea state is modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...... velocity can be approximated by a Gaussian Markov process. Known approximate results for the first-passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results...
Modelling and Simulation of Wave Loads
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1985-01-01
A simple model of the wave load on stender members of offshore structures is described . The wave elevation of the sea stateis modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...... velocity can be approximated by a Gaussian Markov process. Known approximate results for the first passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results...
Effects of Non-Elevation-Focalized Linear Array Transducer on Ultrasound Plane-Wave Imaging
Directory of Open Access Journals (Sweden)
Congzhi Wang
2016-11-01
Full Text Available Plane-wave ultrasound imaging (PWUS has become an important method of ultrasound imaging in recent years as its frame rate has exceeded 10,000 frames per second, allowing ultrasound to be used for two-dimensional shear wave detection and functional brain imaging. However, compared to the traditional focusing and scanning method, PWUS images always suffer from a degradation of lateral resolution and contrast. To improve the image quality of PWUS, many different beamforming algorithms have been proposed and verified. Yet the influence of transducer structure is rarely studied. For this paper, the influence of using an acoustic lens for PWUS was evaluated. Two linear array transducers were fabricated. One was not self-focalized in the elevation direction (non-elevation-focalized transducer, NEFT; the other one was a traditional elevation-focalized transducer (EFT. An initial simulation was conducted to show the influence of elevation focusing. Then the images obtained with NEFT on a standard ultrasound imaging phantom were compared with those obtained with EFT. It was demonstrated that, in a relatively deep region, the contrast of an NEFT image is better than that of an EFT image. These results indicate that a more sophisticated design of ultrasound transducer would further improve the image quality of PWUS.
Continuous-wave terahertz multi-plane in-line digital holography
Huang, Haochong; Wang, Dayong; Li, Weihua; Rong, Lu; Taylor, Zachary D.; Deng, Qinghua; Li, Bin; Wang, Yunxin; Wu, Weidong; Panezai, Spozmai
2017-07-01
Terahertz digital holography is a non-scanning and real time method for reconstructing the absorption and phase distributions of the wave-front diffracted by a given sample simultaneously in the terahertz region. A continuous-wave terahertz in-line digital holographic multi-plane imaging method is presented here for achieving a three-dimensional shape of a specific portion of a sample with the best possible focus. The three enhancement techniques of synthetic aperture, autofocusing and phase retrieval are applied to the single plane recordings for achieving a high resolution, good quality and optimally focused reconstructed image. Later, multi-plane reconstructed images are processed with the threshold mask and a three dimensional profile of the sample is obtained. Experimental verification confirms that the proposed method is a valid tool for acquiring multi-plane information of a target in the terahertz range.
Planck 2015 results. XII. Full Focal Plane simulations
Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Bartolo, N; Battaner, E; Benabed, K; Beno\\^\\it, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bock, J J; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Castex, G; Catalano, A; Challinor, A; Chamballu, A; Chiang, H C; Christensen, P R; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Delouis, J -M; Désert, F -X; Dickinson, C; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Karakci, A; Keihänen, E; Keskitalo, R; Kiiveri, K; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; Lindholm, V; López-Caniego, M; Lubin, P M; Mac\\'\\ias-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Mart\\'\\inez-González, E; Masi, S; Matarrese, S; McGehee, P; Meinhold, P R; Melchiorri, A; Melin, J -B; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Pearson, T J; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Roman, M; Rosset, C; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Welikala, N; Yvon, D; Zacchei, A; Zonca, A
2015-01-01
We present the 8th Full Focal Plane simulation set (FFP8), deployed in support of the Planck 2015 results. FFP8 consists of 10 fiducial mission realizations reduced to 18144 maps, together with the most massive suite of Monte Carlo realizations of instrument noise and CMB ever generated, comprising $10^4$ mission realizations reduced to about $10^6$ maps. The resulting maps incorporate the dominant instrumental, scanning, and data analysis effects; remaining subdominant effects will be included in future updates. Generated at a cost of some 25 million CPU-hours spread across multiple high-performance-computing (HPC) platforms, FFP8 is used for the validation and verification of analysis algorithms, as well as their implementations, and for removing biases from and quantifying uncertainties in the results of analyses of the real data.
Planck 2015 results. XII. Full focal plane simulations
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Castex, G.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Karakci, A.; Keihänen, E.; Keskitalo, R.; Kiiveri, K.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; Lindholm, V.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Roman, M.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.
2016-09-01
We present the 8th full focal plane simulation set (FFP8), deployed in support of the Planck 2015 results. FFP8 consists of 10 fiducial mission realizations reduced to 18 144 maps, together with the most massive suite of Monte Carlo realizations of instrument noise and CMB ever generated, comprising 104 mission realizations reduced to about 106 maps. The resulting maps incorporate the dominant instrumental, scanning, and data analysis effects, and the remaining subdominant effects will be included in future updates. Generated at a cost of some 25 million CPU-hours spread across multiple high-performance-computing (HPC) platforms, FFP8 is used to validate and verify analysis algorithms and their implementations, and to remove biases from and quantify uncertainties in the results of analyses of the real data.
Two- and three-dimensional computation of solitary wave runup on non-plane beach
Directory of Open Access Journals (Sweden)
B. H. Choi
2008-06-01
Full Text Available Solitary wave runup on a non-plane beach is studied analytically and numerically. For the theoretical approach, nonlinear shallow-water theory is applied to obtain the analytical solution for the simplified bottom geometry, such as an inclined channel whose cross-slope shape is parabolic. It generalizes Carrier-Greenspan approach for long wave runup on the inclined plane beach that is currently used now. For the numerical study, the Reynolds Averaged Navier-Stokes (RANS system is applied to study soliton runup on an inclined beach and the detailed characteristics of the wave processes (water displacement, velocity field, turbulent kinetic energy, energy dissipation are analyzed. In this study, it is theoretically and numerically proved that the existence of a parabolic cross-slope channel on the plane beach causes runup intensification, which is often observed in post-tsunami field surveys.
Efficient computation of GW energy level corrections for molecules described in a plane wave basis
Rousseau, Bruno; Laflamme Janssen, Jonathan; Côté, Michel
2013-03-01
An efficient computational approach is presented to compute the ionisation energy and quasiparticle band gap at the level of the GW approximation when the Hilbert space is described in terms of plane waves. The method relies on ab initio calculations as a starting point. Then, the use of the Sternheimer equation eliminates slowly convergent sums on conduction states. Further, the Lanczos method is used to efficiently extract the most important eigenstates of the dielectric operator. This approach avoids the explicit computation of matrix elements of the dielectric operator in the plane wave basis, a crippling bottleneck of the brute force approach. The method is initially applied to organic molecules of current interest in the field of organic photovoltaics. Given the completeness of the plane wave basis, systematic convergence studies can be conducted. Furthermore, the method can readily be extended to describe polymers, which are also of interest for photovoltaic applications, but remain a significant computational challenge for methods based on localized basis sets.
Reflection of plane waves from free surface of a microstretch elastic solid
Indian Academy of Sciences (India)
Baljeet Singh
2002-03-01
In the present investigation, it is shown that there exists five basic waves in a microstretch elastic solid half-space. The problem of reflection of plane waves from free surface of a microstretch elastic solid half-space is studied. The energy ratios for various reflected waves are obtained for aluminium- epoxy composite as a microstretch elastic solid half-space. The variations of the energy ratios with the angle of incidence are shown graphically. The microstretch effect is shown on various reflected waves.
Directory of Open Access Journals (Sweden)
Zhang Rong
2013-01-01
Full Text Available This paper analyzes the reflection and refraction of plane wave incidences at the interface between magnetoelectroelastic (MEE and liquid media. The MEE medium is assumed to be transversely isotropic and the liquid medium to be nonviscous. Three cases, i.e., the coupled quasipressure wave incidence from the MEE medium, the coupled quasi-shear vertical wave incidence from the MEE medium, and the pressure wave incidence from the liquid medium, are discussed. The expressions of reflection and transmission coefficients varying with the incident angle are obtained. This investigation would be useful to the MEE acoustic device field.
Institute of Scientific and Technical Information of China (English)
Song Falun; Cao Jinxiang; Wang Ge
2005-01-01
The purpose of the present work is to present a full-wave analysis of scattering from the weakly ionized plasma in the plane geometry. We have yielded an approximate solution in an analytic form to the electromagnetic wave scattering from the weakly ionizsd plasma. In the normal and oblique incidence, the analytic solution works well, as compared with the exact solution and the solution based on the Wenzell-Kramers-Brillouin-Jeffreys (WKBJ) approximation to the uniform density profile.
Yum, H N; Jang, Y J; Liu, X; Shahriar, M S
2012-08-13
In a white light cavity (WLC), the group velocity is superluminal over a finite bandwidth. For a WLC-based data buffering system we recently proposed, it is important to visualize the behavior of pulses inside such a cavity. The conventional plane wave transfer functions, valid only over space that is translationally invariant, cannot be used for the space inside WLC or any cavity, which is translationally variant. Here, we develop the plane wave spatio temporal transfer function (PWSTTF) method to solve this problem, and produce visual representations of a Gaussian input pulse incident on a WLC, for all times and positions.
Plane-wave transverse oscillation for high-frame-rate 2-D vector flow imaging.
Lenge, Matteo; Ramalli, Alessandro; Tortoli, Piero; Cachard, Christian; Liebgott, Hervé
2015-12-01
Transverse oscillation (TO) methods introduce oscillations in the pulse-echo field (PEF) along the direction transverse to the ultrasound propagation direction. This may be exploited to extend flow investigations toward multidimensional estimates. In this paper, the TOs are coupled with the transmission of plane waves (PWs) to reconstruct high-framerate RF images with bidirectional oscillations in the pulse-echo field. Such RF images are then processed by a 2-D phase-based displacement estimator to produce 2-D vector flow maps at thousands of frames per second. First, the capability of generating TOs after PW transmissions was thoroughly investigated by varying the lateral wavelength, the burst length, and the transmission frequency. Over the entire region of interest, the generated lateral wavelengths, compared with the designed ones, presented bias and standard deviation of -3.3 ± 5.7% and 10.6 ± 7.4% in simulations and experiments, respectively. The performance of the ultrafast vector flow mapping method was also assessed by evaluating the differences between the estimated velocities and the expected ones. Both simulations and experiments show overall biases lower than 20% when varying the beam-to-flow angle, the peak velocity, and the depth of interest. In vivo applications of the method on the common carotid and the brachial arteries are also presented.
A time domain energy theorem for scattering of plane electromagnetic waves
de Hoop, A. T.
1984-10-01
A time domain analysis of the scattering problem reveals the more general conditions under which the relevant theorems in the theory of the scattering of electromagnetic waves by an obstacle of bounded extent may also hold in the time domain. The present investigation is concerned with the energy theorem for plane wave scattering. Three different kinds of time behavior are considered, taking into account transient fields, time-periodic fields, and perpetuating fields. The derived energy theorem relates the energy which is both absorbed and scattered by the object to the spherical-wave amplitude of the scattered field in the far-field region, when observed in the direction of propagation of the incident plane wave.
Uphill diffusion, zero-flux planes and transient chemical solitary waves in garnet
Vielzeuf, D.; Saúl, A.
2011-05-01
Diffusion profiles in minerals are increasingly used to determine the duration of geological events. For this purpose, the distinction between growth and diffusion zoning is critical; it requires the understanding of complex features associated with multicomponent diffusion. Seed-overgrowth interdiffusion experiments carried out in the range 1,050-1,250°C at 1.3 GPa have been designed to quantify and better understand Fe-Mg-Ca interdiffusion in garnet. Some of the diffusion profiles measured by analytical transmission electron microscope show characteristic features of multicomponent diffusion such as uphill diffusion, chemical solitary waves, zero-flux planes and complex diffusion paths. We implemented three different methods to calculate the interdiffusion coefficients of the D matrix from the experimental penetration curves and determined that with Ca as the dependent component, the crossed coefficients of the D matrix are negative. Experiments and numerical simulations indicate that: (1) uphill diffusion in garnet can be observed indifferently on the three components Fe, Mg and Ca, (2) it takes the form of complementary depletion/repletion waves and (3) chemical waves occur preferentially on initially flat concentration profiles. Derived D matrices are used to simulate the fate of chemical waves in time, in finite crystals. These examples show that the flow of atoms in multicomponent systems is not necessarily unidirectional for all components; it can change both in space along the diffusion profile and in time. Moving zero-flux planes in finite crystals are transitory features that allow flux reversals of atoms in the diffusion zone. Interdiffusion coefficients of the D matrices are also analyzed in terms of eigenvalues and eigenvectors. This analysis and the experimental results show that depending on the composition of the diffusion couple, (1) the shape of chemical waves and diffusion paths changes; (2) the width of the diffusion zone for each component
Causality and conjugate points in general plane waves
Energy Technology Data Exchange (ETDEWEB)
Flores, J L; Sanchez, M [Departamento de Geometria y Topologia, Facultad de Ciencias, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada (Spain)
2003-06-07
Let M = M{sub 0} x R{sup 2} be a pp-wave-type spacetime endowed with the metric ({center_dot}, {center_dot}){sub z} = ({center_dot}, {center_dot}){sub x} + 2 du dv + H(x, u) du{sup 2}, where (M{sub 0}, ({center_dot}, {center_dot}){sub x}) is any Riemannian manifold and H(x, u) is an arbitrary function. We show that the behaviour of H(x, u) at spatial infinity determines the causality of M, say: (a) if -H(x, u) behaves subquadratically (i.e, essentially -H(x, u) {<=} R{sub 1}(u)|x|{sup 2-{epsilon}} for some {epsilon} > 0 and large distance |x| to a fixed point) and the spatial part (M{sub 0}, ({center_dot}, {center_dot}){sub x}) is complete, then the spacetime M is globally hyperbolic, (b) if -H(x, u) grows at most quadratically (i.e, -H(x, u) {<=} R{sub 1}(u)|x|{sup 2} for large |x|) then it is strongly causal and (c) M is always causal, but there are non-distinguishing examples (and thus, not strongly causal), even when -H(x, u) {<=} R{sub 1}(u)|x|{sup 2+{epsilon}}, for small {epsilon} > 0. Therefore, the classical model M{sub 0} = R{sup 2}, H(x, u) = {sigma}{sub i,j} h{sub ij}(u)x{sub i}x{sub j} {ne} 0), which is known to be strongly causal but not globally hyperbolic, lies in the critical quadratic situation with complete M{sub 0}. This must be taken into account for realistic applications. In fact, we argue that -H will be subquadratic (and the spacetime globally hyperbolic) if M is asymptotically flat. The relation of these results with the notion of astigmatic conjugacy and the existence of conjugate points is also discussed.
Band structure of thin films by the linear augmented-plane-wave method
DEFF Research Database (Denmark)
Jepsen, O.; Madsen, J.; Andersen, Ole Krogh
1978-01-01
We present a linear augmented-plane-wave method for solving the band-structure problem in thin crystalline films. The potential is separated into a muffin-tin potential inside the film, a potential depending exclusively on the normal coordinate outside the film, and corrections in both regions...
Linear GPR Imaging Based on Electromagnetic Plane-Wave Spectra and Diffraction Tomography
DEFF Research Database (Denmark)
Meincke, Peter
2004-01-01
in the forward model. The two inversion schemes include an accurate electromagnetic description of the GPR antennas through their plane-wave transmitting and receiving spectra. The performance of the FTM is investigated through a numerical example involving a 2.5-dimensional configuration in which the GPR...
Optimized Plane Wave Imaging for Fast and High-Quality Ultrasound Imaging
DEFF Research Database (Denmark)
Jensen, Jonas; Stuart, Matthias Bo; Jensen, Jørgen Arendt
2016-01-01
This paper presents a method for optimizing parameters affecting the image quality in plane wave imaging. More specifically, the number of emissions and steering angles is optimized to attain the best images with the highest frame rate possible. The method is applied to a specific problem, where ...
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 curv...
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...
Z sup 0 -boson contribution in anomalous electron momenta in plane-wave electromagnetic field
Klimenko, E Y
2002-01-01
The Z sup 0 -boson contribution to the mass of electron moving in plane-wave field is considered. The dependence of the Z sup 0 -boson contribution to electron anomalous magnetic momentum and anomalous electric momentum on the external field parameters is studied within the frames of the Weinberg-Salam-Glashow standard model
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...
Fast color flow mode imaging using plane wave excitation and temporal encoding
DEFF Research Database (Denmark)
Udesen, Jesper; Gran, Fredrik; Jensen, Jørgen Arendt
2005-01-01
velocity image is presented. The method is based on using a plane wave excitation with temporal encoding to compensate for the decreased SNR, resulting from the lack of focusing. The temporal encoding is done with a linear frequency modulated signal. To decrease lateral sidelobes, a Tukey window is used...
LDA+DMFT implemented with the pseudopotential plane-wave approach
Energy Technology Data Exchange (ETDEWEB)
Trimarchi, G; Leonov, I; Binggeli, N [Abdus Salam International Centre for Theoretical Physics, Trieste 34014 (Italy); Korotin, Dm; Anisimov, V I [Institute of Metal Physics, Russian Academy of Sciences, Ural Division, 620219 Yekaterinburg GSP-170 (Russian Federation)], E-mail: binggeli@ictp.it
2008-04-02
We present a joint implementation of dynamical-mean-field theory (DMFT) with the pseudopotential plane-wave approach, via Wannier functions, for the determination of the electronic properties of strongly correlated materials. The scheme uses, as input for the DMFT calculations, a tight-binding Hamiltonian obtained from the plane-wave calculations by projection onto atomic-centered symmetry-constrained Wannier functions for the correlated orbitals. We apply this scheme to two prototype systems: a paramagnetic correlated metal, SrVO{sub 3}, and a paramagnetic correlated system, V{sub 2}O{sub 3}, which exhibits a metal-insulator transition. Comparisons with available linear-muffin-tin-orbital (LMTO) plus DMFT calculations demonstrate the suitability of the joint DMFT pseudopotential plane-wave approach to describe the electronic properties of strongly correlated materials. This opens the way to future developments using the pseudopotential plane-wave DMFT approach to address total-energy properties, such as structural properties.
The motion of charged particles in strong plane waves including radiation reaction
Leinemann, R.; Herold, H.; Ruder, H.; Kegel, W. H.
The Lorentz-Dirac equation in the Landau approximation is used to study the motion of charged particles in strong plane vacuum waves. It is shown that integration for circularly polarized waves can be used to determine analytically the curves of the particle trajectories. The solution is used to investigate the particle trajectories and energy evolution for various strong waves. The initial conditions for the motion are chosen so that the particles start from a radiation-free path and the growing effect of the radiation reaction on the particle trajectory is highlighted.
Indian Academy of Sciences (India)
Baljeet Singh; Anand Kumar Yadav
2013-08-01
Reflection of plane waves is studied at a free surface of a perfectly conducting transversely isotropic elastic solid half-space with initial stress. The governing equations are solved to obtain the velocity equation which indicates the existence of two quasi planar waves in the medium. Reflection coefficients and energy ratios for reflected qP and qSV waves are derived and computed numerically for a particular material. Effects of the initial stress and magnetic field are shown graphically on these reflection coefficients and energy ratios.
Schaeffer, Marshall; Ruzzene, Massimo
2016-01-01
We report on a Digital Image Correlation-based technique for the detection of in-plane elastic waves propagating in structural lattices. The experimental characterization of wave motion in lattice structures is currently of great interest due its relevance to the design of novel mechanical metamaterials with unique/unusual properties such as strongly directional behavior, negative refractive indexes and topologically protected wave motion. Assessment of these functionalities often requires the detection of highly spatially resolved in-plane wavefields, which for reticulated or porous structural assemblies is an open challenge. A Digital Image Correlation approach is implemented that tracks small displacements of the lattice nodes by centering image subsets about the lattice intersections. A high speed camera records the motion of the points by properly interleaving subsequent frames thus artificially enhancing the available sampling rate. This, along with an imaging stitching procedure, enables the capturing ...
Radiation of de-excited electrons at large times in a strong electromagnetic plane wave
Kazinski, P O
2013-01-01
The late time asymptotics of the physical solutions to the Lorentz-Dirac equation in the electromagnetic external fields of simple configurations -- the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave -- are found. The solutions to the Landau-Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. General properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half of the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late ti...
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The reflection of plane electromagnetic waves (TE wave and TM wave) from a perfect conductor which moves in an arbitrary direction is investigated. Based on Maxwell's equations and the boundary conditions for moving boundary, the relation between the field vectors of reflected and incident waves, and the reflection coefficient are derived. The energy balance between incident and reflected waves, the force exerted by electromagnetic waves to the moving conductor are also discussed and some new conclusions are suggested for notice.
Schwab, Hans-Martin; Beckmann, Martin F; Schmitz, Georg
2016-04-01
Photoacoustic imaging aims to visualize light absorption properties of biological tissue by receiving a sound wave that is generated inside the observed object as a result of the photoacoustic effect. In clinical applications, the strong light absorption in human skin is a major problem. When high amplitude photoacoustic waves that originate from skin absorption propagate into the tissue, they are reflected back by acoustical scatterers and the reflections contribute to the received signal. The artifacts associated with these reflected waves are referred to as clutter or skin echo and limit the applicability of photoacoustic imaging for medical applications severely. This study seeks to exploit the acoustic tissue information gained by plane wave ultrasound measurements with a linear array in order to correct for reflections in the photoacoustic image. By deriving a theory for clutter waves in k-space and a matching inversion approach, photoacoustic measurements compensated for clutter are shown to be recovered.
Possible second-order nonlinear interactions of plane waves in an elastic solid.
Korneev, V A; Demčenko, A
2014-02-01
There exist ten possible nonlinear elastic wave interactions for an isotropic solid described by three constants of the third order. All other possible interactions out of 54 combinations (triplets) of interacting and resulting waves are prohibited, because of restrictions of various kinds. The considered waves include longitudinal and two shear waves polarized in the interacting plane and orthogonal to it. The amplitudes of scattered waves have simple analytical forms, which can be used for experimental setup and design. The analytic results are verified by comparison with numerical solutions of initial equations. Amplitude coefficients for all ten interactions are computed as functions of frequency for polyvinyl chloride, together with interaction and scattering angles. The nonlinear equation of motion is put into a general vector form and can be used for any coordinate system.
Matda, Y.; Crawford, F. W.
1974-01-01
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.
Fresnel spatial filtering of quasihomogeneous sources for wave optics simulations
Hyde, Milo W.; Bose-Pillai, Santasri R.
2017-08-01
High-spatial-frequency optical fields or sources are often encountered when simulating directed energy, active imaging, or remote sensing systems and scenarios. These spatially broadband fields are a challenge in wave optics simulations because the sampling required to represent and then propagate these fields without aliasing is often impractical. To address this, two spatial filtering techniques are presented. The first, called Fresnel spatial filtering, finds a spatially band-limited source that, after propagation, produces the exact observation plane field as the broadband source over a user-specified region of interest. The second, called statistical or quasihomogeneous spatial filtering, finds a spatially band-limited source that, after propagation and over a specified region of interest, yields an observation plane field that is statistically representative of that produced by the original broadband source. The pros and cons of both approaches are discussed in detail. A wave optics simulation of light transiting a ground glass diffuser and then propagating to an observation plane in the near-zone is performed to validate the two filtering approaches.
Sum, K S; Pan, J
2007-07-01
Distributions of sound pressure and intensity on the surface of a flat impedance strip flush-mounted on a rigid baffle are studied for a grazing incident plane wave. The distributions are obtained by superimposing the unperturbed wave (the specularly reflected wave as if the strip is rigid plus the incident wave) with the radiated wave from the surface vibration of the strip excited by the unperturbed pressure. The radiated pressure interferes with the unperturbed pressure and distorts the propagating plane wave. When the plane wave propagates in the baffle-strip-baffle direction, it encounters discontinuities in acoustical impedance at the baffle-strip and strip-baffle interfaces. The radiated pressure is highest around the baffle-strip interface, but decreases toward the strip-baffle interface where the plane wave distortion reduces accordingly. As the unperturbed and radiated waves have different magnitudes and superimpose out of phase, the surface pressure and intensity increase across the strip in the plane wave propagation direction. Therefore, the surface absorption of the strip is nonzero and nonuniform. This paper provides an understanding of the surface pressure and intensity behaviors of a finite impedance strip for a grazing incident plane wave, and of how the distributed intensity determines the sound absorption coefficient of the strip.
LARGE EDDY SIMULATION FOR PLUNGING BREAKER WAVE
Institute of Scientific and Technical Information of China (English)
Bai Yu-chuan; Wang Zhao-yin
2003-01-01
As wave propagates into shallow water, the shoaling effect leads to increase of wave height, and at a certain position, the wave will be breaking. The breaking wave is powerful agents for generating turbulence, which plays an important role in most of the fluid dynamical processes in the surf zone, so a proper numerical model for describing the turbulent effect is needed urgently. A numerical model is set up to simulate the wave breaking process, which consists of a free surface model using the surface marker method and the vertical two-dimensional model that solves the flow equations. The turbulence is described by Large Eddy Simulation (LES) method where the larger turbulent features are simulated by solving the flow equations, and the small-scale turbulence that is represented by a sub-grid model. A dynamic eddy viscosity sub-grid scale stress model has been used for the present simulation. The large eddy simulation model, which we presented in this paper, can be used to study the propagation of a solitary wave in constant water depth and the shoaling of a non-breaking solitary wave on a beach. To track free-surface movements, The TUMMAC method is employed. By applying the model to wave breaking problem in the surf zone, we found that these model results compared very well with experimental data. In addition, this model is able to reproduce the complicated flow phenomena, especially the plunging breaker.
Nemeth, A.A.; Hulscher, S.J.M.H.; Damme, van R.M.J.
2003-01-01
Sand waves form a prominent regular pattern in the offshore seabeds of sandy shallow seas. A two dimensional vertical (2DV) flow and morphological numerical model describing the behaviour of these sand waves has been developed. The model contains the 2DV shallow water equations, with a free water su
Superresolution Imaging Using Resonant Multiples and Plane-wave Migration Velocity Analysis
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
On the exact open-closed vertex in plane-wave light-cone string field theory
Lucietti, J; Sinha, A K; Lucietti, James; Schafer-Nameki, Sakura; Sinha, Aninda
2003-01-01
The open-closed vertex in the maximally supersymmetric type IIB plane-wave light-cone string field theory is considered and an explicit solution for the bosonic part of the vertex is derived, valid for all values of the mass parameter, \\mu. This vertex is of relevance to IIB plane-wave orientifolds, as well as IIB plane-wave strings in the presence of D-branes, and their gauge theory duals. Methods of complex analysis are used to develop a systematic procedure for obtaining the solution. This procedure is first applied to the vertex in flat space, and then extended to the plane-wave case. The plane-wave solution for the vertex requires introducing certain ``\\mu-deformed Gamma functions'', which are generalizations of the ordinary Gamma function. The behaviour of the Neumann matrices is graphically illustrated and their large-\\mu asymptotics are analysed.
Multi-view horizon-driven sea plane estimation for stereo wave imaging on moving vessels
Bergamasco, Filippo; Benetazzo, Alvise; Barbariol, Francesco; Carniel, Sandro; Sclavo, Mauro
2016-10-01
In the last few years we faced an increased popularity of stereo imaging as an effective tool to investigate wind sea waves at short and medium scales. Given the advances of computer vision techniques, the recovery of a scattered point-cloud from a sea surface area is nowadays a well consolidated technique producing excellent results both in terms of wave data resolution and accuracy. Nevertheless, almost all the subsequent analyses tasks, from the recovery of directional wave spectra to the estimation of significant wave height, are bound to two limiting conditions. First, wave data are required to be aligned to the mean sea plane. Second, a uniform distribution of 3D point samples is assumed. Since the stereo-camera rig is placed tilted with respect to the sea surface, perspective distortion do not allow these conditions to be met. Errors due to this problem are even more challenging if the optical instrumentation is mounted on a moving vessel, so that the mean sea plane cannot be simply obtained by averaging data from multiple subsequent frames. We address the first problem with two main contributions. First, we propose a novel horizon estimation technique to recover the attitude of a moving stereo rig with respect to the sea plane. Second, an effective weighting scheme is described to account for the non-uniform sampling of the scattered data in the estimation of the sea-plane distance. The interplay of the two allows us to provide a precise point cloud alignment without any external positioning sensor or rig viewpoint pre-calibration. The advantages of the proposed technique are evaluated throughout an experimental section spanning both synthetic and real-world scenarios.
Fan, Xiaofeng; Baek, Yonggeun; Ha, Kanglyeol; Kim, Moojoon; Kim, Jungsoon; Kim, Duckjong; Kang, Hyun Wook; Oh, Junghwan
2017-07-01
An optoacoustic transducer made of light-absorbing and elastomeric materials can generate high-pressure wide-band ultrasound waves in water when it is illuminated by a pulse laser. To generate such waves with high efficiency, carbon nanotubes (CNTs) and poly(dimethylsiloxane) (PDMS) are widely used as the light-absorbing and elastomeric materials, respectively. It was previously reported that an optoacoustic concave transducer made of these materials can produce strong shock waves, namely, blast waves, within its focal zone. In this study, we have shown that these waves can also be generated by a plane optoacoustic transducer fabricated by coating CNTs-PDMS on a poly(methyl methacrylate) (PMMA) plate. Some propagation characteristics of the blast wave generated were measured and compared with the calculated results. It was found that the propagation speed and attenuation of the wave are different from those of usual sounds. From the comparison of the measured and the calculated acoustic fields, it is assumed that every point on the transducer surface produces almost the same blast wave.
Cavity-based linear polarizer immune to the polarization direction of an incident plane wave.
Wang, Jiang; Shen, Zhongxiang; Gao, Xiang; Wu, Wen
2016-01-15
We herein report a linear polarizer based on a 2D array of substrate integrated waveguide cavities, which can convert an arbitrary linearly polarized (LP) incident wave into an outgoing LP wave in a specified polarization direction with constant transmittance. Two orthogonal slots etched on the front surface of the cavity are utilized to couple a wave of arbitrary polarization into the cavity, while another slot on the back side helps to couple the field out along a desired polarization direction. Microwave experiments are performed as a proof of concept. The proposed polarizer exhibits very good performance with stable transmittance as 50% and a polarization extinction ratio over 45 dB. The new polarizer is potentially useful in novel polarization-selective devices that are immune to the polarization direction of an incident plane wave.
Radiation of a Plane Shear Wave from an Elastic Waveguide to a Composite Elastic Space
Directory of Open Access Journals (Sweden)
Grigoryan E.Kh.
2007-09-01
Full Text Available The radiation of a plane shear wave from an elastic strip (waveguide to an elastic space is investigated in this paper. The strip is embedded into a space and is partially bonded with it. A given plane shear wave propagates from the free part of the strip and radiates into the composite space. The problem’s solution is led to a system of two uncoupled functional Wiener-Hopf type equations which are solved via the method of factorization. Closed form expressions are obtained which determine the wavefield in all the parts of the strip and space. Asymptotic expressions are provided which represent the wavefield in the far field and in the neighborhood of the contact zones. From these formulas it follows that: a in the cases of several values of the ratio of the wave numbers of the strip and space the order of vanishing of the volume wave in the strip becomes less and equal to the one in the case of a homogeneous material, b the radiated volume wave in the strip has a velocity of propagation equal to the volume wave’s velocity in the space.
A Michelson Interferometer in the Field of a Plane Gravitational Wave
Poplawski, N J
2006-01-01
In this paper we treat the problem of a Michelson interferometer in the field of a weak, monochromatic, plane gravitational wave in the framework of the general theory of relativity. The arms of the interferometer are regarded as world lines, whose motion is determined by the equations of geodesics in the Hamilton-Jacobi formalism. We find that interference appears in the second approximation. Moreover, the measurement of the light beam delay between both arms can be used for determining the wavelength of such a wave.
SCATTERING OF PLANE SH-WAVE BY A CYLINDRICAL HILL OF ARBITRARY SHAPE
Institute of Scientific and Technical Information of China (English)
曹欣荣; 宋天舒; 刘殿魁
2001-01-01
The problems of scattering of plane SH-wave by a cylindrical hill of arbitrary shape is studied based on the methods of conjunction and division of solution zone. The scattering wave function is given by using the complex variable and conformal mapping methods. The conjunction boundary conditions are satisfied. Furthermore appling orthogonal function expanding technique, the problems can finally be summarized into the solution of a series of infinite algebraic equations. At last, numerical results of surface displacements of a cylindrical arc hill and of a semi-ellipse hill are obtained. And those computational results are compared with the results of finite element method (FEM).
Reﬂection of plane micropolar viscoelastic waves at a loosely bonded solid-solid interface
Indian Academy of Sciences (India)
Baljeet Singh
2002-10-01
A solution of the ﬁeld equations governing small motions of a micropolar viscoelastic solid half-space is employed to study the reﬂection and transmission of plane waves at a loosely bonded interface between two dissimilar micropolar viscoelastic solid half-spaces. The amplitude ratios for various reﬂected and refracted waves are computed for a particular model for different values of bonding parameter. The variations of these amplitude ratios with the angle of incidence are shown graphically. Effects of bonding parameter and viscosity on the amplitude ratios are shown.
Relativistic two-boson system in presence of electromagnetic plane waves
Droz-Vincent, Philippe
2015-01-01
The relativistic two-body problem is considered for spinless particles subject to an external macroscopic electromagnetic field. When this field is made of the monochromatic superposition of two conter-propagating plane waves (and provided the mutual interaction between particles is known), it is possible to write down explicitly a pair of coupled wave equations (corresponding to a pair of mass-shell constraints) which takes into account also the field contribution. These equations are manifestly covariant; constants of the motion are exhibited, so one ends up with a reduced problem concerning five degrees of freedom.
Abramov, Arnold; Kostikov, Alexander
2017-03-01
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.
Flach, S
1995-01-01
We study tangent bifurcation of band edge plane waves in nonlinear Hamiltonian lattices. The lattice is translationally invariant. We argue for the breaking of permutational symmetry by the new bifurcated periodic orbits. The case of two coupled oscillators is considered as an example for the perturbation analysis, where the symmetry breaking can be traced using Poincare maps. Next we consider a lattice and derive the dependence of the bifurcation energy on the parameters of the Hamiltonian function in the limit of large system sizes. A necessary condition for the occurence of the bifurcation is the repelling of the band edge plane wave's frequency from the linear spectrum with increasing energy. We conclude that the bifurcated orbits will consequently exponentially localize in the configurational space.
Dynamics of a spiral pair source and its interaction with plane waves.
Rabinovitch, A; Biton, Y; Gutman, M; Aviram, I
2009-05-01
Spiral pair creation and dynamics is a widely occurring phenomenon in nature. It can appear in the heart tissue, causing severe arrhythmia, known as a figure-eight reentry. We consider the appearance of a spiral pair source, its minimal strength for survival, and the possible results of its interaction with a plane wave. In particular, its ability to outlast such an encounter is of interest. We also consider the question of exposing the source to a train of pulses, in terms of the frequency and angle of encounter. Results show different regimes of behavior, e.g. source annihilation, motion of the source away from, or towards the origin of the plane waves, its breaking and multiplication. Relevance of these results to heart arrhythmia and their possible cancellation by external pacing are briefly discussed.
Tiny graviton matrix theory: DLCQ of IIB plane-wave string theory, a conjecture
Energy Technology Data Exchange (ETDEWEB)
Sheikh-Jabbari, Mohammad M. [Department of Physics, Stanford University, 382 via Pueblo Mall, Stanford CA 94305-4060 (United States)]. E-mail: jabbari@itp.stanford.edu
2004-09-01
We conjecture that the discrete light-cone quantization (DLCQ) of strings on the maximally supersymmetric type IIB plane-wave background in the sector with J units of light-cone momentum is a supersymmetric 0+1 dimensional U(J) gauge theory (quantum mechanics) with PSU(2|2) x PSU(2|2) x U(1) superalgebra. The conjectured hamiltonian for the plane-wave matrix (string) theory, the tiny graviton matrix theory, is the quantized (regularized) three brane action on the same background. We present some pieces of evidence for this conjecture through analysis of the hamiltonian , its vacua, spectrum and coupling constant. Moreover, we discuss an extension of our conjecture to the DLCQ of type IIB strings on AdS{sub 5} x S{sup 5} geometry. (author)
The Fermionic Signature Operator and Hadamard States in the Presence of a Plane Electromagnetic Wave
Finster, Felix
2016-01-01
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.
Institute of Scientific and Technical Information of China (English)
宋海斌; 马在田; 张关泉
1996-01-01
A layer-stripping method is presented for simultaneous inversion of compressional velocity and shear velocity in layered medium from single precritical-incident-angle data of P-P and P-SV plane wave seismogram. A finite bandwidth algorithm is provided and results obviously better than previous research work are obtained by the numerical experiments for band-limited seismogram and synthetic data including noise.
Contributions in anomalous fermion momenta of neutral vector boson in plane-wave field
Klimenko, E Y
2002-01-01
The contributions of the neutral vector boson to the anomalous magnetic and electric momenta of the polarized fermion moving in the plane-wave electromagnetic field are considered in this paper. The contributions are divided by the fermion spin polarization states, which makes it possible to investigate the important problem on the contributions to the fermion anomalous momenta, coming from the the fermion transition to the intermediate state spin-nonflip or spin flip of fermion
Mahillo-Isla, R; Gonźalez-Morales, M J; Dehesa-Martínez, C
2011-06-01
The slowly varying envelope approximation is applied to the radiation problems of the Helmholtz equation with a planar single-layer and dipolar sources. The analyses of such problems provide procedures to recover solutions of the Helmholtz equation based on the evaluation of solutions of the parabolic wave equation at a given plane. Furthermore, the conditions that must be fulfilled to apply each procedure are also discussed. The relations to previous work are given as well.
Multiple-scattering corrections in diluted magnetic semiconductors: A plane-wave expansion
Scalbert, D.; Ghazali, A.; Benoit à la Guillaume, C.
1993-12-01
Energy levels of band edges in diluted magnetic semiconductors are calculated in the effective-mass approximation, retaining off-diagonal terms in the exchange interaction and using a plane-wave expansion. This model accounts qualitatively for the observed asymmetry in the splitting of the A exciton in a magnetic field in Cd1-xMnxS for which multiple-scattering corrections are expected to be important.
Candela, Anna Maria; Sánchez, Miguel
2013-01-01
Recently, classical results on completeness of trajectories of Hamiltonian systems obtained at the beginning of the seventies, have been revisited, improved and applied to Lorentzian Geometry. Our aim here is threefold: to give explicit proofs of some technicalities in the background of the specialists, to show that the introduced tools allow to obtain more results for the completeness of the trajectories, and to apply these results to the completeness of spacetimes that generalize classical plane and pp-waves.
Li, Chuang; Huang, Jian-Ping; Li, Zhen-Chun; Wang, Rong-Rong
2017-03-01
Least squares migration can eliminate the artifacts introduced by the direct imaging of irregular seismic data but is computationally costly and of slow convergence. In order to suppress the migration noise, we propose the preconditioned prestack plane-wave least squares reverse time migration (PLSRTM) method with singular spectrum constraint. Singular spectrum analysis (SSA) is used in the preconditioning of the take-offangle-domain common-image gathers (TADCIGs). In addition, we adopt randomized singular value decomposition (RSVD) to calculate the singular values. RSVD reduces the computational cost of SSA by replacing the singular value decomposition (SVD) of one large matrix with the SVD of two small matrices. We incorporate a regularization term into the preconditioned PLSRTM method that penalizes misfits between the migration images from the plane waves with adjacent angles to reduce the migration noise because the stacking of the migration results cannot effectively suppress the migration noise when the migration velocity contains errors. The regularization imposes smoothness constraints on the TADCIGs that favor differential semblance optimization constraints. Numerical analysis of synthetic data using the Marmousi model suggests that the proposed method can efficiently suppress the artifacts introduced by plane-wave gathers or irregular seismic data and improve the imaging quality of PLSRTM. Furthermore, it produces better images with less noise and more continuous structures even for inaccurate migration velocities.
On the integrability of large N plane-wave matrix theory
Energy Technology Data Exchange (ETDEWEB)
Klose, Thomas E-mail: thklose@aei.mpg.de; Plefka, Jan E-mail: plefka@aei.mpg.de
2004-02-16
We show the three-loop integrability of large N plane-wave matrix theory in a subsector of states comprised of two complex light scalar fields. This is done by diagonalizing the theory's Hamiltonian in perturbation theory and taking the large N limit. At one-loop level the result is known to be equal to the Heisenberg spin-1/2 chain, which is a well-known integrable system. Here, integrability implies the existence of hidden conserved charges and results in a degeneracy of parity pairs in the spectrum. In order to confirm integrability at higher loops, we show that this degeneracy is not lifted and that (corrected) conserved charges exist. Plane-wave matrix theory is intricately connected to N=4 super-Yang-Mills, as it arises as a consistent reduction of the gauge theory on a three-sphere. We find that after appropriately renormalizing the mass parameter of the plane-wave matrix theory the effective Hamiltonian is identical to the dilatation operator of N=4 super-Yang-Mills theory in the considered subsector. Our results therefore represent a strong support for the conjectured three-loop integrability of planar N=4 SYM and are in disagreement with a recent dual string theory finding. Finally, we study the stability of the large N integrability against nonsupersymmetric deformations of the model.
Institute of Scientific and Technical Information of China (English)
Mehran Vahdani Moghaddam; Zeynab Chenari; Hamid Latifi; Vladimir Vladimirovich Shuvalov; Konestantin Valentinovich Rudenko
2008-01-01
@@ We deal with computer simulation of a transient process in a self-pumped phase conjugate plane-curve loop mirror based on BaTiO3. In optimal circumstances the nonlinear reflectivity and fidelity of such a mirror respectively achieve 0.80-0.90 and 0.95-0.98. The generation of conjugate wave-front occurs due to scattering from the dynamic hologram which is produced in the region of self-intersection of forward and backward beams. In such a model the scenario of passing to unstable generation regimes is similar to the self-pumped phase conjugate plane-plane loop mirror and substantially differs from a single-crystal double phase conjugate mirror.
Bogdanov, O. V.; Kazinski, P. O.
2015-02-01
The problem of scattering of ultrarelativistic electrons by a strong plane electromagnetic wave of a low (optical) frequency and linear polarization is solved in the semiclassical approximation, when the electron wave packet size is much smaller than the wavelength of electromagnetic wave. The exit momenta of ultrarelativistic electrons scattered are found using the exact solutions to the equations of motion with radiation reaction included (the Landau-Lifshitz equation). It is found that the momentum components of electrons traversed the electromagnetic wave depend weakly on the initial values of momenta. These electrons are mostly scattered at small angles to the propagation direction of the electromagnetic wave. The maximum Lorentz factor of electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momentum. The momentum component parallel to the electric field vector of the electromagnetic wave is determined solely by the laser beam diameter measured in the units of the classical electron radius. As for the reflected electrons, they for the most part lose the energy, but remain relativistic. A reflection law that relates the incident and reflection angles and is independent of any parameters is found.
Destructive tests with the wave overtopping simulator
Trung, L.H.
2011-01-01
Report on destructive overtopping tests executed with the wave overtopping simulator along the coast of Vietnam to investigate the strength of the inner slopes of grass dikes. This report presents measurement and observation results obtained during destructive tests with the simulator in Do Son, Thi
Fast color flow mode imaging using plane wave excitation and temporal encoding
Udesen, Jesper; Gran, Fredrik; Jensen, Jorgen A.
2005-04-01
In conventional ultrasound color flow mode imaging, a large number (~500) of pulses have to be emitted in order to form a complete velocity map. This lowers the frame-rate and temporal resolution. A method for color flow imaging in which a few (~10) pulses have to be emitted to form a complete velocity image is presented. The method is based on using a plane wave excitation with temporal encoding to compensate for the decreased SNR, resulting from the lack of focusing. The temporal encoding is done with a linear frequency modulated signal. To decrease lateral sidelobes, a Tukey window is used as apodization on the transmitting aperture. The data are beamformed along the direction of the flow, and the velocity is found by 1-D cross correlation of these data. First the method is evaluated in simulations using the Field II program. Secondly, the method is evaluated using the experimental scanner RASMUS and a 7 MHz linear array transducer, which scans a circulating flowrig. The velocity of the blood mimicking fluid in the flowrig is constant and parabolic, and the center of the scanned area is situated at a depth of 40 mm. A CFM image of the blood flow in the flowrig is estimated from two pulse emissions. At the axial center line of the CFM image, the velocity is estimated over the vessel with a mean relative standard deviation of 2.64% and a mean relative bias of 6.91%. At an axial line 5 mm to the right of the center of the CFM image, the velocity is estimated over the vessel with a relative standard deviation of 0.84% and a relative bias of 5.74%. Finally the method is tested on the common carotid artery of a healthy 33-year-old male.
Optical Measurement of In-plane Waves in Mechanical Metamaterials Through Digital Image Correlation
Schaeffer, Marshall; Trainiti, Giuseppe; Ruzzene, Massimo
2017-02-01
We report on a Digital Image Correlation-based technique for the detection of in-plane elastic waves propagating in structural lattices. The experimental characterization of wave motion in lattice structures is currently of great interest due its relevance to the design of novel mechanical metamaterials with unique/unusual properties such as strongly directional behaviour, negative refractive indexes and topologically protected wave motion. Assessment of these functionalities often requires the detection of highly spatially resolved in-plane wavefields, which for reticulated or porous structural assemblies is an open challenge. A Digital Image Correlation approach is implemented that tracks small displacements of the lattice nodes by centring image subsets about the lattice intersections. A high speed camera records the motion of the points by properly interleaving subse- quent frames thus artificially enhancing the available sampling rate. This, along with an imaging stitching procedure, enables the capturing of a field of view that is sufficiently large for subsequent processing. The transient response is recorded in the form of the full wavefields, which are processed to unveil features of wave motion in a hexagonal lattice. Time snapshots and frequency contours in the spatial Fourier domain are compared with numerical predictions to illustrate the accuracy of the recorded wavefields.
Borzdov
2000-04-01
Vector plane-wave superpositions defined by a given set of orthonormal scalar functions on a two- or three-dimensional manifold-beam manifold-are treated. We present a technique for composing orthonormal beams and some other specific types of fields such as three-dimensional standing waves, moving and evolving whirls. It can be used for any linear fields, in particular, electromagnetic fields in complex media and elastic fields in crystals. For electromagnetic waves in an isotropic medium or free space, unique families of exact solutions of Maxwell's equations are obtained. The solutions are illustrated by calculating fields, energy densities, and energy fluxes of beams defined by the spherical harmonics. It is shown that the obtained results can be used for a transition from the plane-wave approximation to more accurate models of real incident beams in free-space techniques for characterizing complex media. A mathematical formalism convenient for the treatment of various beams defined by the spherical harmonics is presented.
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.
Probing phase of a scattering amplitude beyond the plane-wave approximation
Karlovets, Dmitry V
2016-01-01
Within a plane-wave approach, a number of scattering events in a generic collision process is insensitive to an overall complex phase of a transition amplitude, although this phase is extremely important for a number of problems, especially in hadronic physics at the LHC energies. In reality, however, the particles are better described as localized wave packets with the mean momenta $p$, their uncertainties $\\sigma$, and here we show that the observables grow dependent upon this phase if one lays aside the simplified plane-wave model. A relative contribution of the phase to the cross section is generally attenuated by a small factor $\\sigma^2/p^2 \\ll 1$, making its experimental measurement a rather challenging task. We discuss two methods for probing how this phase changes with the transferred momentum $t$, either by colliding two beams at a non-zero impact-parameter (say, $pp \\rightarrow X$) or by employing the states with the non-trivial wave functions, for instance, vortex particles carrying orbital angula...
Optical Measurement of In-plane Waves in Mechanical Metamaterials Through Digital Image Correlation
Schaeffer, Marshall; Trainiti, Giuseppe; Ruzzene, Massimo
2017-01-01
We report on a Digital Image Correlation-based technique for the detection of in-plane elastic waves propagating in structural lattices. The experimental characterization of wave motion in lattice structures is currently of great interest due its relevance to the design of novel mechanical metamaterials with unique/unusual properties such as strongly directional behaviour, negative refractive indexes and topologically protected wave motion. Assessment of these functionalities often requires the detection of highly spatially resolved in-plane wavefields, which for reticulated or porous structural assemblies is an open challenge. A Digital Image Correlation approach is implemented that tracks small displacements of the lattice nodes by centring image subsets about the lattice intersections. A high speed camera records the motion of the points by properly interleaving subse- quent frames thus artificially enhancing the available sampling rate. This, along with an imaging stitching procedure, enables the capturing of a field of view that is sufficiently large for subsequent processing. The transient response is recorded in the form of the full wavefields, which are processed to unveil features of wave motion in a hexagonal lattice. Time snapshots and frequency contours in the spatial Fourier domain are compared with numerical predictions to illustrate the accuracy of the recorded wavefields. PMID:28205589
NUMERICAL SIMULATION OF SHOCK WAVE REFRACTION ON INCLINED CONTACT DISCONTINUITY
Directory of Open Access Journals (Sweden)
P. V. Bulat
2016-05-01
Full Text Available We consider numerical simulation of shock wave refraction on plane contact discontinuity, separating two gases with different density. Discretization of Euler equations is based on finite volume method and WENO finite difference schemes, implemented on unstructured meshes. Integration over time is performed with the use of the third-order Runge–Kutta stepping procedure. The procedure of identification and classification of gas dynamic discontinuities based on conditions of dynamic consistency and image processing methods is applied to visualize and interpret the results of numerical calculations. The flow structure and its quantitative characteristics are defined. The results of numerical and experimental visualization (shadowgraphs, schlieren images, and interferograms are compared.
45∘ Relative Orientations of Planes of Polarizations States of Gravitational Waves and the Graviton
Manoukian, E. B.
2016-11-01
The recent detection of gravitational waves calls for, not just in words or by plausible arguments, of an explicit derivation of polarization aspects of gravitational waves with emphasis, especially, on the non-trivial aspect of the relative 45∘ orientations of the planes of polarization states of gravitation in the same way as has been done over the years for the far simpler case involving electromagnetic wave propagation with the well known relative 90∘ between its polarization states. The purpose of this communication is to carry out in a covariant description as well as by giving special attention to the underlying gauge problem these polarization aspects via a direct consideration of the graviton propagator in a quantum field theory setting from which fundamental properties of polarizations are readily extracted.
Nonlinear dynamics and band transport in a superlattice driven by a plane wave
Apostolakis, A.; Awodele, M. K.; Alekseev, K. N.; Kusmartsev, F. V.; Balanov, A. G.
2017-06-01
A quantum particle transport induced in a spatially periodic potential by a propagating plane wave has a number of important implications in a range of topical physical systems. Examples include acoustically driven semiconductor superlattices and cold atoms in an optical crystal. Here we apply a kinetic description of the directed transport in a superlattice beyond standard linear approximation, and utilize exact path-integral solutions of the semiclassical transport equation. We show that the particle drift and average velocities have nonmonotonic dependence on the wave amplitude with several prominent extrema. Such nontrivial kinetic behavior is related to global bifurcations developing with an increase of the wave amplitude. They cause dramatic transformations of the system phase space and lead to changes of the transport regime. We describe different types of phase trajectories contributing to the directed transport and analyze their spectral content.
45∘ Relative Orientations of Planes of Polarizations States of Gravitational Waves and the Graviton
Manoukian, E. B.
2016-07-01
The recent detection of gravitational waves calls for, not just in words or by plausible arguments, of an explicit derivation of polarization aspects of gravitational waves with emphasis, especially, on the non-trivial aspect of the relative 45∘ orientations of the planes of polarization states of gravitation in the same way as has been done over the years for the far simpler case involving electromagnetic wave propagation with the well known relative 90∘ between its polarization states. The purpose of this communication is to carry out in a covariant description as well as by giving special attention to the underlying gauge problem these polarization aspects via a direct consideration of the graviton propagator in a quantum field theory setting from which fundamental properties of polarizations are readily extracted.
Institute of Scientific and Technical Information of China (English)
魏培君; 章梓茂; 汪越胜
2002-01-01
The interaction of a general plane P wave and an elastic cylindrical inclusion of infinite length partially debonded from its surrounding viscoelastic matrix of infinite extension is investigated. The debonded region is modeled as an arc-shaped interface crack between inclusion and matrix with non-contacting faces. With wave functions expansion and singular integral equation technique, the interaction problem is reduced to a set of simultaneous singular integral equations of crack dislocation density function. By analysis of the fundamental solution of the singular integral equation, it is found that dynamic stress field at the crack tip is oscillatory singular,which is related to the frequency of incident wave. The singular integral equations are solved numerically, and the crack open displacement and dynamic stress intensity factor are evaluated for various incident angles and frequencies.
Numerical simulation for explosion wave propagation of combustible mixture gas
Institute of Scientific and Technical Information of China (English)
WANG Cheng; NING Jian-guo; MA Tian-bao
2008-01-01
A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code, Young's technique was employed to track the interface between the explosion products and air, and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct, for point initiation, the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall, multi-peak values appear on pressure-time curve, and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct, explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products, and indicate that the ignition model and multi-material interface treatment method are feasible.
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...
Stress Waves in Composite Laminates Excited by Transverse Plane Shock Waves
Directory of Open Access Journals (Sweden)
G.R. Liu
1996-01-01
Full Text Available A simple 1-dimensional model is presented to investigate elastic stress waves in composite laminates excited by underwater explosion shocks. The focus is on the elastic dynamic stress fields in the composite laminate immediately after the action of the shock wave. In this model, the interaction between the laminate and the water is taken into account, and the effects of the laminate-water interaction on the stress wave fields in the laminate are investigated. In the formulation of the model, wave fields in the laminate and the water are the first obtained in the frequency domain and then transferred into the time domain using the Fourier transform techniques. A quadrature technique is used to deal with the Fourier transform integrals in which the integrands have very sharp peaks on the integral axis. Numerical examples for stress waves in a steel plate and a glass reinforced plastic sandwich laminate are presented. The technique and the results presented in this article may be used in the design of ship hull structures subjected to underwater explosions.
SAR IMAGING SIMULATION OF HORIZONTAL FULLY TWO-DIMENSIONAL INTERNAL WAVES
Institute of Scientific and Technical Information of China (English)
SHEN Hui; HE Yi-Jun
2006-01-01
Based on the research of Lynett and Liu, a new horizontal fully two-dimensional internal wave propagation model with rotation effect was deduced, which can be used to simulate the characteristics of internal waves in a horizontal fully two-dimensional plane. By combining the imaging mechanism of Synthetic Aperture Radar(SAR), a simulation procedure was fatherly acquired, which can simulate the propagation characteristics of oceanic internal waves into SAR images. In order to evaluate the validity of the proposed simulation procedure, case studies are performed in South China Sea and results from simulation procedure are analyzed in detail. A very good consistency was found between the simulation results and satellite images. The proposed simulation procedure will be a possible foundation for the quantitative interpretation of internal waves from fully two-dimensional satellite images.
On plane-wave relativistic electrodynamics in plasmas and in vacuum
Fiore, Gaetano
2016-01-01
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. Because of this penetration the el...
N=4 Supersymmetric Yang-Mills on S^3 in Plane Wave Matrix Model at Finite Temperature
Kitazawa, Yoshihisa
2008-01-01
We investigate the large N reduced model of gauge theory on a curved spacetime through the plane wave matrix model. We formally derive the action of the N=4 supersymmetric Yang-Mills theory on R \\times S^3 from the plane wave matrix model in the large N limit. Furthermore, we evaluate the effective action of the plane wave matrix model up to the two-loop level at finite temperature. We find that the effective action is consistent with the free energy of the N=4 supersymmetric Yang-Mills theory on S^3 at high temperature limit where the planar contributions dominate. We conclude that the plane wave matrix model can be used as a large N reduced model to investigate nonperturbative aspects of the N=4 supersymmetric Yang-Mills theory on R \\times S^3.
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,...
Voss, D. E.; Koslover, R. A.; Cremer, C. D.; Silvestro, J.; Miner, L. M.
1990-05-01
The High Power Microwaves (HPM) susceptibility testing often requires irradiating test objects at the highest fluences possible. For aperture antennas, the highest fluences are generally found in the radiating near field region. For valid effects testing, the energy coupled to the object interior must accurately replicate that which would occur in a true weapon environment (plane wave illumination). Some believe that valid testing requires object placement at distances from the aperture exceeding 2 D squared/lambda (D=antenna effective diameter). Many also believe testing at farther away than 2 D squared/lambda guarantees plane wave-like coupling conditions. Neither view is correct. Testing in the reactive field region (less than lambda from the aperture) is generally invalid due to dominance of reactive coupling. For testing in the radiating near field, determination of validity is less trivial. An investigation was performed quantifying deviations from plane wave coupling. The measurements, using an instrumented Maverick missile in an anechoic chamber, and supported by theory, indicate conditions for which testing the Maverick missile accurately simulates plane wave coupling.
Long-Wave Runup on a Plane Beach: An Experimental and Numerical Investigation
Vater, Stefan; Drähne, Ulrike; Goseberg, Nils; Beisiegel, Nicole; Behrens, Jörn
2016-04-01
In this study the runup generated by leading depression single sinusoidal waves as a very basic representation of a tsunami is investigated through physical and numerical experiments. The results are compared against existing analytical expressions for the long-wave runup of periodic sinusoidal waves. It can be shown that shallow water theory is applicable for the investigated type of waves. Furthermore, we demonstrate how such a comparative, inter-methodological work contributes to the understanding of shoreline motion of long waves. The produced data set may serve as a novel benchmark for leading depression sinusoidal waves. The experimental study was conducted using an innovative pump-driven wave generator that is capable of generating arbitrarily long waves which might even exceed the length of the wave flume. Due to the complex control problem for the chosen type of wave generator, spurious over-riding small-scale waves were unavoidable in some of the experiments. The numerical simulations were carried out with a one-dimensional Runge-Kutta discontinuous Galerkin (RKDG) non-linear shallow water model. It incorporates a high fidelity wetting and drying scheme. The sinusoidal waves are generated in a constant depth section attached to a linearly sloping beach, have periods between 20 and 100 seconds and surf similarity parameters between 4.4 and 15.6. In a first qualitative analysis the evolution of the runup elevation and velocity is compared. In order to quantify analytical, numerical and experimental data, the wave similarity measured by the Brier score, maximum run-up and run-down height, as well as run-up/run-down velocities are utilized as metrics. As a starting point, periodic and non-periodic clean sinusoidal waves are compared numerically to rule out differences due to the single sinusoidal wave generation in the wave flume. On further analysis, significant differences in experimental and analytically expected values are observed. However, with the
Plane-Wave Least-Squares Reverse Time Migration for Rugged Topography
Institute of Scientific and Technical Information of China (English)
Jianping Huang; Chuang Li; Rongrong Wang; Qingyang Li
2015-01-01
We present a method based on least-squares reverse time migration with plane-wave encod-ing (P-LSRTM) for rugged topography. Instead of modifying the wave field before migration, we modify the plane-wave encoding function and fill constant velocity to the area above rugged topography in the model so that P-LSRTM can be directly performed from rugged surface in the way same to shot domain reverse time migration. In order to improve efficiency and reduce I/O (input/output) cost, the dynamic en-coding strategy and hybrid encoding strategy are implemented. Numerical test on SEG rugged topography model show that P-LSRTM can suppress migration artifacts in the migration image, and compensate am-plitude in the middle-deep part efficiently. Without data correction, P-LSRTM can produce a satisfying image of near-surface if we could get an accurate near-surface velocity model. Moreover, the pre-stack P-LSRTM is more robust than conventional RTM in the presence of migration velocity errors.
Radiation of de-excited electrons at large times in a strong electromagnetic plane wave
Kazinski, P. O.
2013-12-01
The late time asymptotics of the physical solutions to the Lorentz-Dirac equation in the electromagnetic external fields of simple configurations-the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave-are found. The solutions to the Landau-Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. Some general properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above. This provides a simple method to verify experimentally that the charged particle has reached the asymptotic regime.
The radiation of sound by the instability waves of a compressible plane turbulent shear layer
Tam, C. K. W.; Morris, P. J.
1980-01-01
The problem of acoustic radiation generated by instability waves of a compressible plane turbulent shear layer is solved. The solution provided is valid up to the acoustic far-field region. It represents a significant improvement over the solution obtained by classical hydrodynamic-stability theory which is essentially a local solution with the acoustic radiation suppressed. The basic instability-wave solution which is valid in the shear layer and the near-field region is constructed in terms of an asymptotic expansion using the method of multiple scales. This solution accounts for the effects of the slightly divergent mean flow. It is shown that the multiple-scales asymptotic expansion is not uniformly valid far from the shear layer. Continuation of this solution into the entire upper half-plane is described. The extended solution enables the near- and far-field pressure fluctuations associated with the instability wave to be determined. Numerical results show that the directivity pattern of acoustic radiation into the stationary medium peaks at 20 degrees to the axis of the shear layer in the downstream direction for supersonic flows. This agrees qualitatively with the observed noise-directivity patterns of supersonic jets.
Trail-Needs pseudopotentials in quantum Monte Carlo calculations with plane-wave/blip basis sets
Drummond, N. D.; Trail, J. R.; Needs, R. J.
2016-10-01
We report a systematic analysis of the performance of a widely used set of Dirac-Fock pseudopotentials for quantum Monte Carlo (QMC) calculations. We study each atom in the periodic table from hydrogen (Z =1 ) to mercury (Z =80 ), with the exception of the 4 f elements (57 ≤Z ≤70 ). We demonstrate that ghost states are a potentially serious problem when plane-wave basis sets are used in density functional theory (DFT) orbital-generation calculations, but that this problem can be almost entirely eliminated by choosing the s channel to be local in the DFT calculation; the d channel can then be chosen to be local in subsequent QMC calculations, which generally leads to more accurate results. We investigate the achievable energy variance per electron with different levels of trial wave function and we determine appropriate plane-wave cutoff energies for DFT calculations for each pseudopotential. We demonstrate that the so-called "T-move" scheme in diffusion Monte Carlo is essential for many elements. We investigate the optimal choice of spherical integration rule for pseudopotential projectors in QMC calculations. The information reported here will prove crucial in the planning and execution of QMC projects involving beyond-first-row elements.
Directory of Open Access Journals (Sweden)
Davtyan A.V.
2014-09-01
Full Text Available In present paper is considered the problem of penetration of the pressure in an isotropic elastic half-plane, boundary of which has the rigid support moving with arbitrary velocity. Solution of the plane problem is sought by method of integral transforms Laplace, Fourier and by method of the convolutions. Partial problems about a shock wave propagating along the boundary half-plane are solved. The stress intensity factors, stress on the line of contact is calculated.
Stamnes, J J; Sithambaranathan, G S
2001-12-01
Exact solutions are obtained for the reflected and transmitted fields resulting when an arbitrary electromagnetic field is incident on a plane interface separating an isotropic medium and a biaxially anisotropic medium in which one of the principal axes is along the interface normal. From our exact solutions for the reflected fields resulting when a plane TE or TM wave is incident on the plane interface, it can be inferred that the reflected field contains both a TE and a TM component. This gives a change in polarization that can be utilized to determine the properties of the biaxial medium. The time-harmonic solution for the reflected field is in the form of two quadruple integrals, one of which is a superposition of plane waves polarized perpendicular to the plane of incidence and the other a superposition of plane waves polarized parallel to the plane of incidence. The time-harmonic solution for the transmitted field is also in the form of two quadruple integrals. Each of these is a superposition of extraordinary plane waves with displacement vectors that are perpendicular to the direction of phase propagation.
Ding, Chaoliang; Cai, Yangjian; Zhang, Yongtao; Pan, Liuzhan
2012-06-01
The scattering of a stochastic electromagnetic plane-wave pulse on a deterministic spherical medium is investigated. An analytical formula for the degree of polarization (DOP) of the scattered field in the far zone is derived. Letting pulse duration T(0) → ∞, our formula can be applied to study the scattering of a stationary stochastic electromagnetic light wave. Numerical results show that the DOP of the far zone field is closely determined by the size of the spherical medium when the incident field is a stochastic electromagnetic plane-wave pulse. This is much different from the case when the incident field is a stationary stochastic electromagnetic light wave, where the DOP of the far zone field is independent of the size of the medium. One may obtain the information of the spherical medium by measuring the scattering-induced changes in the DOP of a stochastic electromagnetic plane-wave pulse.
An Exact Transfer Matrix Formulation of Plane Sound Wave Transmission in Inhomogeneous Ducts
Dockumaci, E.
1998-11-01
The impedance, or the reflection coefficient, of plane sound waves in inhomogeneous ducts satisfies a Riccati equation. The present paper shows that the duct impedance matrix, or the scattering matrix, can be related explicitly to the solutions of the associated linear equation of the Riccati equation for duct impedance, or reflection coefficient, respectively. New exact analytical scattering matrix solutions, which follow as consequences of this connection, are given for two significant duct acoustics problems, namely, the sound transmission in non-uniform ducts carrying an incompressible subsonic low Mach number mean flow transmission of sound in uniform ducts with a full quadratic axial mean temperature gradient.
Nonlocal Effects on D-branes in Plane-Wave Backgrounds
Ganor, O J; Ganor, Ori J.; Varadarajan, Uday
2002-01-01
We argue that the effective field theory on D3-branes in a plane-wave background with 3-form flux is a nonlocal deformation of Yang-Mills theory. In the case of NSNS flux, it is a dipole field theory with lightlike dipole vectors. For an RR 3-form flux the dipole theory is strongly coupled. We propose a weakly coupled S-dual description for it. The S-dual description is local at any finite order in string perturbation theory but becomes nonlocal when all perturbation theory orders are summed together.
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...
NC plane waves, Casimir effect and flux tube potential with L\\"uscher terms
Kováčik, Samuel
2016-01-01
We analyze plane waves in a model of quantum mechanics in a three dimensional noncommutative (NC) space $R^3_{\\lambda}$. Signature features of NC models are impossibility of probing distances smaller than a certain length scale {\\lambda} and a presence of natural energetic cut-off at energy scale of order $1/{\\lambda}^2$ (in convenient units). We analyze consequences of such restrictions on a 1 dimensional Casimir effect. The result shows resemblance to flux tube potential for quark-antiquark pairs and to effective bosonic string theories with L\\"uscher terms. Such behavior might effect the radius of possible compact (fuzzy) dimensions.
Plane wave matrix theory vs. N=4 D=4 super Yang-Mills
Energy Technology Data Exchange (ETDEWEB)
Kim, N. [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, 14476 Golm (Germany)
2004-06-01
A mass deformed, supersymmetric, Yang-Mills quantum mechanics has been introduced recently as the matrix model of M-theory on plane-wave backgrounds. Here we point out that the massive matrix model can be obtained as a dimensional reduction of N=4, D=4 Super Yang-Mills theory on S{sup 3}. The hamiltonian of the matrix model can be matched with the dilatation operator of the conformal field theory, and we discuss how they behave in the perturbative computations. (Abstract Copyright [2004], Wiley Periodicals, Inc.)
Electromagnetic plane-wave pulse transmission into a Lorentz half-space.
Cartwright, Natalie A
2011-12-01
The propagation of an electromagnetic plane-wave signal obliquely incident upon a Lorentz half-space is studied analytically. Time-domain asymptotic expressions that increase in accuracy with propagation distance are derived by application of uniform saddle point methods on the Fourier-Laplace integral representation of the transmitted field. The results are shown to be continuous in time and comparable with numerical calculations of the field. Arrival times and angles of refraction are given for prominent transient pulse features and the steady-state signal.
Simulation of wave interactions with MHD
Energy Technology Data Exchange (ETDEWEB)
Batchelor, D; Bernholdt, D; Berry, L; Elwasif, W; Jaeger, E; Keyes, D; Klasky, S [Oak Ridge National Laboratory, Oak Ridge, TN 37331 (United States); Alba, C; Choi, M [General Atomics, San Diego, CA 92186 (United States); Bateman, G [Lehigh University, Bethlehem, PA 18015 (United States); Bonoli, P [Plasma Science and Fusion Center, MTT, Cambridge, MA 02139 (United States); Bramley, R [Indiana University, Bloomington, IN 47405 (United States); Breslau, J; Chance, M; Chen, J; Fu, G; Jardin, S [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Harvey, R [CompX, Del Mar, CA 92014 (United States); Jenkins, T [University of Wisconsin, Madison, WI 53706 (United States); Kruger, S [Tech-X, Boulder, CO 80303 (United States)], E-mail: batchelordb@ornl.gov (and others)
2008-07-15
The broad scientific objectives of the SWIM (Simulation 01 Wave Interaction with MHD) project are twofold: (1) improve our understanding of interactions that both radio frequency (RF) wave and particle sources have on extended-MHD phenomena, and to substantially improve our capability for predicting and optimizing the performance of burning plasmas in devices such as ITER: and (2) develop an integrated computational system for treating multiphysics phenomena with the required flexibility and extensibility to serve as a prototype for the Fusion Simulation Project. The Integrated Plasma Simulator (IPS) has been implemented. Presented here are initial physics results on RP effects on MHD instabilities in tokamaks as well as simulation results for tokamak discharge evolution using the IPS.
Simulation of wave interactions with MHD
Energy Technology Data Exchange (ETDEWEB)
Batchelor, Donald B [ORNL; Abla, G [General Atomics, San Diego; Bateman, Glenn [Lehigh University, Bethlehem, PA; Bernholdt, David E [ORNL; Berry, Lee A [ORNL; Bonoli, P. [Massachusetts Institute of Technology (MIT); Bramley, R [Indiana University; Breslau, J. [Princeton Plasma Physics Laboratory (PPPL); Chance, M. [Princeton Plasma Physics Laboratory (PPPL); Chen, J. [Princeton Plasma Physics Laboratory (PPPL); Choi, M. [General Atomics; Elwasif, Wael R [ORNL; Fu, GuoYong [Princeton Plasma Physics Laboratory (PPPL); Harvey, R. W. [CompX, Del Mar, CA; Jaeger, Erwin Frederick [ORNL; Jardin, S. C. [Princeton Plasma Physics Laboratory (PPPL); Jenkins, T [University of Wisconsin; Keyes, David E [Columbia University; Klasky, Scott A [ORNL; Kruger, Scott [Tech-X Corporation; Ku, Long-Poe [Princeton Plasma Physics Laboratory (PPPL); Lynch, Vickie E [ORNL; McCune, Douglas [Princeton Plasma Physics Laboratory (PPPL); Ramos, J. [Massachusetts Institute of Technology (MIT); Schissel, D. [General Atomics; Schnack, [University of Wisconsin; Wright, J. [Massachusetts Institute of Technology (MIT)
2008-07-01
The broad scientific objectives of the SWIM (Simulation of Wave Interaction with MHD) project are twofold: (1) improve our understanding of interactions that both radio frequency (RF) wave and particle sources have on extended-MHD phenomena, and to substantially improve our capability for predicting and optimizing the performance of burning plasmas in devices such as ITER: and (2) develop an integrated computational system for treating multiphysics phenomena with the required flexibility and extensibility to serve as a prototype for the Fusion Simulation Project. The Integrated Plasma Simulator (IPS) has been implemented. Presented here are initial physics results on RF effects on MHD instabilities in tokamaks as well as simulation results for tokamak discharge evolution using the IPS.
Liu, Xu; Greenhalgh, Stewart
2014-09-01
Using Biot's poroelasticity theory, we derive expressions for the reflection and transmission coefficients for a plane shear wave incident on an interface separating two different poroelastic solids. The coefficients are formulated as a function of the wave incidence angle, frequency and rock properties. Specific cases calculated include the boundary between water-saturated sand and water-saturated sandstone and the gas-water interface in sand. The results show a very different interface response to that of an incident P wave. Plane SV wave incidence does not significantly excite the Biot slow P wave if the frequency of the wave is below the transition frequency. Above this frequency, an incident plane SV wave can generate a mode-converted slow Biot P wave which is actually a normal propagating wave and not highly attenuating as in the usual (diffusive) case. For an incident SV wave onto a gas-water interface, even at very high frequency, there is no significant Biot second P wave produced. For small incident angles, the gas-water interface is essentially transparent. With increasing angles, there can arise an unusual "definitive angle" in the reflection/transmission coefficient curves which is related to the change of fluid viscosity on both sides of the interface and provides a possible new means for underground fluid assessment.
Wave optics approach for incoherent imaging simulation through distributed turbulence
Underwood, Thomas A.; Voelz, David G.
2013-09-01
An approach is presented for numerically simulating incoherent imaging using coherent wave optics propagation methods. The approach employs averaging of irradiance from uncorrelated coherent waves to produce incoherent results. Novel aspects of the method include 1) the exploitation of a spatial windowing feature in the wave optics numerical propagator to limit the angular spread of the light and 2) a simple propagation scaling concept to avoid aliased field components after the focusing element. Classical linear systems theory is commonly used to simulate incoherent imaging when it is possible to incorporate aberrations and/or propagation medium characteristics into an optical transfer function (OTF). However, the technique presented here is useful for investigating situations such as "instantaneous" short-exposure imaging through distributed turbulence and phenomena like anisoplanatism that are not easily modeled with the typical linear systems theory. The relationships between simulation variables such as spatial sampling, source and aperture support, and intermediate focal plane are discussed and the requirement or benefits of choosing these in certain ways are demonstrated.
The physical simulation of wave groups and their variations in a wave flume
Institute of Scientific and Technical Information of China (English)
LIU Si; ZHANG Yongliang; LIU Shuxue; LI Jinxuan; XIA Zhisheng
2013-01-01
The physical simulation method of wave groups in a wave flume is proposed and verified by the exper-iments. The experimental results demonstrate that random waves with desired wave groupiness, which simultaneously includes the wave group height and length, can be generated satisfactorily at the specified position in a wave flume using the proposed method. Furthermore, the transformation properties of the wave groupiness along the flat-bottomed wave flume are investigated based on the physically simulated waves. Associated proposals with the physical simulation of wave groups are given.
Directional dependence of nonlinear surface acoustic waves in the (001) plane of cubic crystals.
Kumon, R E; Hamilton, M F
2002-05-01
Spectral evolution equations are used to perform analytical and numerical studies of nonlinear surface acoustic waves in the (001) plane of a variety of nonpiezoelectric cubic crystals. The basic theory underlying the model equations is outlined, and quasilinear solutions of the equations are presented. Expressions are also developed for a characteristic length scale for nonlinear distortion and a nonlinearity coefficient. A time-domain equation corresponding to the spectral equations is derived. Numerical calculations based on measured second- and third-order elastic constants taken from the literature are performed to predict the evolution of initially monofrequency surface waves. Nonlinearity matrix elements that indicate the coupling strength of harmonic interactions are shown to provide a useful tool for characterizing waveform distortion. The formation of compression or rarefaction shocks can be strongly dependent on the direction of propagation, and harmonic generation is suppressed or increased in certain directions.
An efficient algorithm for time propagation as applied to linearized augmented plane wave method
Dewhurst, J. K.; Krieger, K.; Sharma, S.; Gross, E. K. U.
2016-12-01
An algorithm for time propagation of the time-dependent Kohn-Sham equations is presented. The algorithm is based on dividing the Hamiltonian into small time steps and assuming that it is constant over these steps. This allows for the time-propagating Kohn-Sham wave function to be expanded in the instantaneous eigenstates of the Hamiltonian. The method is particularly efficient for basis sets which allow for a full diagonalization of the Hamiltonian matrix. One such basis is the linearized augmented plane waves. In this case we find it is sufficient to perform the evolution as a second-variational step alone, so long as sufficient number of first variational states are used. The algorithm is tested not just for non-magnetic but also for fully non-collinear magnetic systems. We show that even for delicate properties, like the magnetization density, fairly large time-step sizes can be used demonstrating the stability and efficiency of the algorithm.
PARTICLE DISPLACEMENTS ON THE WALL OF A BOREHOLE FROM INCIDENT PLANE WAVES.
Lee, M.W.
1987-01-01
Particle displacements from incident plane waves at the wall of a fluid-filled borehole are formulated by applying the seismic reciprocity theorem to far-field displacement fields. Such displacement fields are due to point forces acting on a fluid-filled borehole under the assumption of long wavelengths. The displacement fields are analyzed to examine the effect of the borehole on seismic wave propagation, particularly for vertical seismic profiling (VSP) measurements. When the shortest wavelength of interest is approximately 25 times longer than the borehole's diameter, the scattered displacements are proportional to the first power of incident frequency and borehole diameter. When the shortest wavelength of interest is about 40 times longer than the borehole's diameter, borehole effects on VSP measurements using a wall-locking geophone are negligible.
Diffraction of a Shear Plane Wave in Elastic Medium with Piecewise Homogeneous Infinite Inclusion
Directory of Open Access Journals (Sweden)
Voskanyan A. R.
2007-06-01
Full Text Available Diffraction of shear plane wave incident from infinity at arbitrary angle on infinite inclusion is considered. The infinite inclusion consists of two semi-infinite parts made of different materials. The problem’s solution is presented in the form of sum of its even and odd problems. The case of long waves is considered and these problems (the even and odd ones are modelled in a corresponding way after which each of them is reduced to the solution of Wiener-Hopf functional equation. Asymptotic formulas are obtained for displacement’s amplitude and contacts stresses in the far field. The behaviors of contact stresses in the neighborhood of the bonding line of the semi-infinite parts of the inclusion are also obtained.
Reflection for three-dimensional plane waves in triclinic crystalline medium
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The propagation of three-dimensional plane waves at a traction free boundary of a half-space composed of triclinic crystalline material is discussed. A method has been developed to find the analytical expressions of all the three phase velocities of quasi-P (qP), quasi-SV (qSV) and quasi-SH (qSH) in three dimensions. Closed form expressions in three dimensions for the amplitude ratios of reflection coefficients of qP, qSV and qSH waves in a triclinic medium are obtained. These expressions are used for numerically studying the variation of the reflection coefficients with the angle of incidence. The graphs are drawn for different polar angle and azimuth. Numerical results presented indicate that the anisotropy affect the reflection coefficients significantly in the three dimensional case compared to the two-dimensional case.
A comparison of exact TM plane wave diffraction by coated wedges and impedance wedges
DEFF Research Database (Denmark)
Andersen, Lars S.; Breinbjerg, Olav; Moore, John T.
1996-01-01
without interference from direct fields or reflected fields. Results have been obtained in the case of illumination by a transverse magnetic (TM) uniform plane wave. The analysis of the coated wedge is based on an integral equation formulation combined with a hybrid technique, while the analysis......The purpose of this work is to numerically investigate the accuracy of the standard impedance boundary condition (SIBC) approximation for edge diffraction. To this end, we compare the scattering by coated wedges and SIBC wedges for which the diffracted field from a single edge can be observed...... of the SIBC wedge is based on Maliuzhinets' solution. Comparisons have been carried out for a series of configurations including lossy coatings as well as lossless coatings permitting unattenuated propagation of surface waves. The results show that the presence of an edge in a coated structure does...
Spatial-Spectral Hamiltonian Boussinesq Wave Simulations
Kurnia, Ruddy; van Groesen, Embrecht W.C.
2014-01-01
This contribution concerns a specific simulation method for coastal wave engineering applications. As is common to reduce computational costs the flow is assumed to be irrotational so that a Boussinesq-type of model in horizontal variables only can be used. Here we advocate the use of such a model t
RANSE Simulation of High-speed Planning Craft in Regular Waves
Institute of Scientific and Technical Information of China (English)
Shuo Wang; Yumin Su; Xi Zhang; Jinglei Yang
2012-01-01
This paper presents a study on the numerical simulation of planing crafts sailing in regular waves.This allows an accurate estimate of the seas keeping performance of the high speed craft.The simulation set in six-degree of freedom motions is based on the Reynolds averaged Navier Stokes equations volume of fluid (RANSE VOF) solver.The trimming mesh technique and integral dynamic mesh method are used to guarantee the good accuracy of the hydrodynamic force and high efficiency of the numerical simulation.Incident head waves,oblique waves and beam waves are generated in the simulation with three different velocities (Fn =1.0,1.5,2.0).The motions and sea keeping performance of the planing craft with waves coming from different directions are indicated in the flow solver.The ship designer placed an emphasis on the effects of waves on sailing amplitude and pressure distribution of planing craft in the configuration of building high speed crafts.
Energy Technology Data Exchange (ETDEWEB)
Caballero, J.A. [Univ. de Sevilla (Spain). Dept. de Fisica Atomica, Molecular y Nucl.]|[Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, Madrid 28006 (Spain); Donnelly, T.W. [Centre for Theoretical Physics, Laboratory for Nuclear Science and Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States); Moya de Guerra, E. [Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, Madrid 28006 (Spain); Udias, J.M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Avda. Complutense s/n, Madrid 28040 (Spain)
1998-03-23
The issue of factorization within the context of coincidence quasi-elastic electron scattering is revisited. Using a relativistic formalism for the entire reaction mechanism and restricting ourselves to the case of plane waves for the outgoing proton, we discuss the role of the negative-energy components of the bound nucleon wave function. (orig.). 30 refs.
Numerical simulations of aerodynamic contribution of flows about a space-plane-type configuration
Matsushima, Kisa; Takanashi, Susume; Fujii, Kozo; Obayashi, Shigeru
1987-01-01
The slightly supersonic viscous flow about the space-plane under development at the National Aerospace Laboratory (NAL) in Japan was simulated numerically using the LU-ADI algorithm. The wind-tunnel testing for the same plane also was conducted with the computations in parallel. The main purpose of the simulation is to capture the phenomena which have a great deal of influence to the aerodynamic force and efficiency but is difficult to capture by experiments. It includes more accurate representation of vortical flows with high angles of attack of an aircraft. The space-plane shape geometry simulated is the simplified model of the real space-plane, which is a combination of a flat and slender body and a double-delta type wing. The comparison between experimental results and numerical ones will be done in the near future. It could be said that numerical results show the qualitatively reliable phenomena.
Tremblay-Darveau, Charles; Williams, Ross; Milot, Laurent; Bruce, Matthew; Burns, Peter N
2014-12-01
Plane-wave imaging offers image acquisition rates at the pulse repetition frequency, effectively increasing the imaging frame rates by up to two orders of magnitude over conventional line-by-line imaging. This form of acquisition can be used to achieve very long ensemble lengths in nonlinear modes such as pulse inversion Doppler, which enables new imaging trade-offs that were previously unattainable. We first demonstrate in this paper that the coherence of microbubble signals under repeated exposure to acoustic pulses of low mechanical index can be as high as 204 ± 5 pulses, which is long enough to allow an accurate power Doppler measurement. We then show that external factors, such as tissue acceleration, restrict the detection of perfusion at the capillary level with linear Doppler, even if long Doppler ensembles are considered. Hence, perfusion at the capillary level can only be detected with ultrasound through combined microbubbles and Doppler imaging. Finally, plane-wave contrast-enhanced power and color Doppler are performed on a rabbit kidney in vivo as a proof of principle. We establish that long pulse-inversion Doppler sequences and conventional wall-filters can create an image that simultaneously resolves both the vascular morphology of veins and arteries, and perfusion at the capillary level with frame rates above 100 Hz.
Concepts and Tradeoffs in Velocity Estimation With Plane-Wave Contrast-Enhanced Doppler.
Tremblay-Darveau, Charles; Williams, Ross; Sheeran, Paul S; Milot, Laurent; Bruce, Matthew; Burns, Peter N
2016-11-01
While long Doppler ensembles are, in principle, beneficial for velocity estimates, short acoustic pulses must be used in microbubble contrast-enhanced (CE) Doppler to mitigate microbubble destruction. This introduces inherent tradeoffs in velocity estimates with autocorrelators, which are studied here. A model of the autocorrelation function adapted to the microbubble Doppler signal accounting for transit time, the echo frequency uncertainty, and contrast-agent destruction is derived and validated in vitro. It is further demonstrated that a local measurement of the center frequency of the microbubble echo is essential in order to avoid significant bias in velocity estimates arising from the linear and nonlinear frequency-dependent scattering of microbubbles and compensate for the inherent speckle nature of the received echo frequency. For these reasons, broadband Doppler estimators (2-D autocorrelator and Radon projection) are better suited than simpler narrow-band estimators (1-D autocorrelator and 1-D Fourier transform) for CE flow assessment. A case study of perfusion in a VX-2 carcinoma using CE plane-wave Doppler is also shown. We demonstrate that even when considering all uncertainties associated with microbubble-related decorrelation (destruction, pulse bandwidth, transit time, and flow gradient) and the need for real-time imaging, a coefficient of variation of 4% on the axial velocity is achievable with plane-wave imaging.
Lectures on the Plane-Wave String/Gauge Theory Duality
Plefka, J
2004-01-01
These lectures give an introduction to the novel duality relating type IIB string theory in a maximally supersymmetric plane-wave background to N=4, d=4, U(N) Super Yang-Mills theory in a particular large N and large R-charge limit due to Berenstein, Maldacena and Nastase. In the first part of these lectures the duality is derived from the AdS/CFT correspondence by taking a Penrose limit of the AdS_5 x S^5 geometry and studying the corresponding double-scaling limit on the gauge theory side. The resulting free plane-wave superstring is then quantized in light-cone gauge. On the gauge theory side of the correspondence the composite Super Yang-Mills operators dual to string excitations are identified, and it is shown how the string spectrum can be mapped to the planar scaling dimensions of these operators. In the second part of these lectures we study the correspondence at the interacting respectively non-planar level. On the gauge theory side it is demonstrated that the large N large R-charge limit in question...
2, Pulse-mode expansions and refractive indices in plane-wave propagation
Energy Technology Data Exchange (ETDEWEB)
Shore, B.W.; Sacks, R.; Karr, T.; Morris, J.; Paisner, J.A.
1987-06-20
This memo presents basic background theory for treating simultaneous propagation of electromagnetic pulses of various colors, directed along a common ray, through a molecular vapor. The memo discusses some techniques for expanding the positive frequency part of the transverse electric field into pulse modes, characterized by carrier frequencies within a modulated envelope. We discuss, in the approximation of plane waves with slowly varying envelopes, a set of uncoupled envelope equations in which a polarization mode-envelope acts as a source for an electric-field envelope. These equations, when taken with a prescription for the polarization field, are the basic equations of plane-wave pulse propagation through a molecular medium. We discuss two ways of treating dispersive media, one based upon expansions in the frequency domain and the other based in the time domain. In both cases we find envelope equations that involve group velocities. This memo represents a portion of a more extensive treatment of propagation to be presented separately. Many of the equations presented here have been described in various books and articles. They are collected and described here as a summary and review of contemporary theory.
Fast solution of elliptic partial differential equations using linear combinations of plane waves
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 A x =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 (N logN ) memory and executing an iteration in O (N log2N ) 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.
Plane Wave Imaging for ultrasonic non-destructive testing: Generalization to multimodal imaging.
Le Jeune, Léonard; Robert, Sébastien; Lopez Villaverde, Eduardo; Prada, Claire
2016-01-01
This paper describes a new ultrasonic array imaging method for Non-Destructive Testing (NDT) which is derived from the medical Plane Wave Imaging (PWI) technique. The objective is to perform fast ultrasound imaging with high image quality. The approach is to transmit plane waves at several angles and to record the back-scattered signals with all the array elements. Focusing in receive is then achieved by coherent summations of the signals in every point of a region of interest. The medical PWI is generalized to immersion setups where water acts as a coupling medium and to multimodal (direct, half-skip modes) imaging in order to detect different types of defects (inclusions, porosities, cracks). This method is compared to the Total Focusing Method (TFM) which is the reference imaging technique in NDT. First, the two post-processing algorithms are described. Then experimental results with the array probe either in contact or in immersion are presented. A good agreement between the TFM and the PWI is observed, with three to ten times less transmissions required for the PWI.
Planar plane-wave matrix theory at the four loop order: integrability without BMN scaling
Energy Technology Data Exchange (ETDEWEB)
Fischbacher, Thomas [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany); Physique Theorique et Mathematique and International Solvay Institutes, Universite Libre de Bruxelles, Campus Plaine C.P. 231, B-1050 Brussels (Belgium); Klose, Thomas; Plefka, Jan [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany)]. E-mail: jan.plefka@aei.mpg.de
2005-02-01
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)
Mcaninch, G. L.; Myers, M. K.
1980-01-01
The parabolic approximation for the acoustic equations of motion is applied to the study of the sound field generated by a plane wave at or near grazing incidence to a finite impedance boundary. It is shown how this approximation accounts for effects neglected in the usual plane wave reflection analysis which, at grazing incidence, erroneously predicts complete cancellation of the incident field by the reflected field. Examples are presented which illustrate that the solution obtained by the parabolic approximation contains several of the physical phenomena known to occur in wave propagation near an absorbing boundary.
Numerical simulation of lowest-order short-crested wave instabilities
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.; Bingham, Harry
2006-01-01
A numerical study of doubly periodic deep-water short-crested wave instabilities, arising from various quartet resonant interactions, is conducted using a high-order Boussinesq-type model. The model is first verified through a series of simulations involving classical class I plane wave...... demonstrates a reasonably similar evolution. These simulations consider the simplest physical situations involving three-dimensional instabilities of genuinely three-dimensional progressive waves, revealing qualitative differences from classical two-dimensional descriptions. This study is therefore...
Reconstruction of wave front and object for inline holography from a set of detection planes.
Hagemann, J; Robisch, A-L; Luke, D R; Homann, C; Hohage, T; Cloetens, P; Suhonen, H; Salditt, T
2014-05-19
We illustrate the errors inherent in the conventional empty beam correction of full field X-ray propagation imaging, i.e. the division of intensities in the detection plane measured with an object in the beam by the intensity pattern measured without the object, i.e. the empty beam intensity pattern. The error of this conventional approximation is controlled by the ratio of the source size to the smallest feature in the object, as is shown by numerical simulation. In a second step, we investigate how to overcome the flawed empty beam division by simultaneous reconstruction of the probing wavefront (probe) and of the object, based on measurements in several detection planes (multi-projection approach). The algorithmic scheme is demonstrated numerically and experimentally, using the defocus wavefront of the hard X-ray nanoprobe setup at the European Synchrotron Radiation Facility (ESRF).
Large eddy simulation of vertical turbulent jets under JONSWAP waves
Institute of Scientific and Technical Information of China (English)
Jun Lu; Ling-Ling Wang; Hong-Wu Tang; Hui-Chao Dai
2011-01-01
The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier-Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.
Gillet, N; Knebe, A; Libeskind, N; Yepes, G; Gottlober, S; Hoffman, Y
2014-01-01
We search for vast planes of satellites (VPoS) in a high resolution simulation of the Local Group performed by the CLUES project, which improves significantly the resolution of former similar studies. We use a simple method for detecting planar configurations of satellites, and validate it on the known plane of M31. We implement a range of prescriptions for modelling the satellite populations, roughly reproducing the variety of recipes used in the literature, and investigate the occurence and properties of planar structures in these populations. The structure of the simulated satellite systems is strongly non-random and contains planes of satellites, predominantly co-rotating, with, in some cases, sizes comparable to the plane observed in M31 by Ibata et al.. However the latter is slightly richer in satellites, slightly thinner and has stronger co-rotation, which makes it stand out as overall more exceptional than the simulated planes, when compared to a random population. Although the simulated planes we fin...
Simulation Analysis of Wave Effect on Exceeding Water Gesture and Load of Submarine Launched Missile
Directory of Open Access Journals (Sweden)
Ke Zhao
2014-02-01
Full Text Available In this study, we have a research on wave action on the submarine launched missile water trajectory and gesture angles during the process between launch and exit from water. Infinite water depth plane wave was used as the wave model, mathematics models of missile exceeding water under different wave conditions were established based on ideal potential flow theory. The flow field velocity potential was obtained by solving the Laplace equation, thus can obtain missile surface pressure. Considering free surface effects, simple Green’s function was introduced to solve boundary value problems. Three-dimensional Fortran program and finite software ABAQUS were combined to complete the fluid-structure interaction simulation. The rules that wave level and phases effects on submarine-launched missile were finally obtained, which shows wave affect cannot be neglected. Simulation methods and results of this study have a certain reference value for the submarine-launched missile launching.
Terahertz/mm wave imaging simulation software
Fetterman, M. R.; Dougherty, J.; Kiser, W. L., Jr.
2006-10-01
We have developed a mm wave/terahertz imaging simulation package from COTS graphic software and custom MATLAB code. In this scheme, a commercial ray-tracing package was used to simulate the emission and reflections of radiation from scenes incorporating highly realistic imagery. Accurate material properties were assigned to objects in the scenes, with values obtained from the literature, and from our own terahertz spectroscopy measurements. The images were then post-processed with custom Matlab code to include the blur introduced by the imaging system and noise levels arising from system electronics and detector noise. The Matlab code was also used to simulate the effect of fog, an important aspect for mm wave imaging systems. Several types of image scenes were evaluated, including bar targets, contrast detail targets, a person in a portal screening situation, and a sailboat on the open ocean. The images produced by this simulation are currently being used as guidance for a 94 GHz passive mm wave imaging system, but have broad applicability for frequencies extending into the terahertz region.
Mathematical simulation of steep waves at a focus point
Institute of Scientific and Technical Information of China (English)
XU Li; ZHANG Min; WANG Yan-ying
2007-01-01
Mathematical models simulating steep waves at a focus point are presented in this paper. Simulations of extreme waves in a model basin were used to determine the loads on floating structures induced by the waves. Based on a new wave theory, numerical test results show that the simulation procedure is effective and the induced motion of water particles in the front of waves is an important factor influencing impact loads on floating bodies.
The strain in the array is mainly in the plane (waves below ~1 Hz)
Gomberg, J.; Pavlis, G.; Bodin, P.
1999-01-01
We compare geodetic and single-station methods of measuring dynamic deformations and characterize their causes in the frequency bands 0.5-1.0 Hz and 4.0-8.0 Hz. The geodetic approach utilizes data from small-aperture seismic arrays, applying techniques from geodesy. It requires relatively few assumptions and a priori information. The single-station method uses ground velocities recorded at isolated or single stations and assumes all the deformation is due to plane-wave propagation. It also requires knowledge of the azimuth and horizontal velocity of waves arriving at the recording station. Data employed come from a small-aperture, dense seismic array deployed in Geyokcha, Turkmenistan, and include seismograms recorded by broadband STS2 and short-period L28 sensors. Poor agreement between geodetic and single-station estimates in the 4.0-8.0 Hz passband indicates that the displacement field may vary nonlinearly with distance over distances of ~50 m. STS2 geodetic estimates provide a robust standard in the 0.5-1.0 Hz passband because they appear to be computationally stable and require fewer assumptions than single-station estimates. The agreement between STS2 geodetic estimates and single-station L28 estimates is surprisingly good for the S-wave and early surface waves, suggesting that the single-station analysis should be useful with commonly available data. These results indicate that, in the 0.5 to 1.0 Hz passband, the primary source of dynamic deformation is plane-wave propagation along great-circle source-receiver paths. For later arriving energy, the effects of scattering become important. The local structure beneath the array exerts a strong control on the geometry of the dynamic deformation, implying that it may be difficult to infer source characteristics of modern or paleoearthquakes from indicators of dynamic deformations. However, strong site control also suggests that the dynamic deformations may be predictable, which would be useful for engineering
Majhi, S.; Pal, P. C.; Kumar, S.
2017-01-01
This study investigates the reflection and transmission of plane SH-waves in two semi-infinite anisotropic magnetoelastic media. The lower half-space is considered as initially stressed and inhomogeneous. The density of lower half-space is taken exponentially varying with depth. The solutions for half-spaces are obtained analytically. The expressions for reflection and transmission coefficient are obtained in the closed form subject to continuity conditions at the interfaces of anisotropic magnetoelastic half-spaces and the Snell's law. It is found that these coefficients depend on the initial stress, inhomogeneity parameter, the magnetoelastic coupling parameter, and the angle at which wave crosses the magnetic field of the half-spaces. Numerical computations are performed for these coefficients for a specific model of two different anisotropic magnetoelastic half-spaces. The numerical results are illustrated by the graph of reflection and transmission coefficient versus the angle of incidence. In general, as the initial stress increases the reflection and transmission coefficient increases, the affect is more prominent for more than 10 GPa. Inhomogeneity in the density of the material also increases the reflection and transmission coefficient. The anisotropic magnetoelastic parameter and the angle at which the wave crosses the magnetic field for both the half-spaces have a quite significant effect on the reflection and transmission coefficient.
Majhi, S.; Pal, P. C.; Kumar, S.
2016-06-01
This study investigates the reflection and transmission of plane SH-waves in two semi-infinite anisotropic magnetoelastic media. The lower half-space is considered as initially stressed and inhomogeneous. The density of lower half-space is taken exponentially varying with depth. The solutions for half-spaces are obtained analytically. The expressions for reflection and transmission coefficient are obtained in the closed form subject to continuity conditions at the interfaces of anisotropic magnetoelastic half-spaces and the Snell's law. It is found that these coefficients depend on the initial stress, inhomogeneity parameter, the magnetoelastic coupling parameter, and the angle at which wave crosses the magnetic field of the half-spaces. Numerical computations are performed for these coefficients for a specific model of two different anisotropic magnetoelastic half-spaces. The numerical results are illustrated by the graph of reflection and transmission coefficient versus the angle of incidence. In general, as the initial stress increases the reflection and transmission coefficient increases, the affect is more prominent for more than 10 GPa. Inhomogeneity in the density of the material also increases the reflection and transmission coefficient. The anisotropic magnetoelastic parameter and the angle at which the wave crosses the magnetic field for both the half-spaces have a quite significant effect on the reflection and transmission coefficient.
Kusakabe, T.; Kame, N.
2015-12-01
We develop an extended boundary integral equation method (XBIEM) to analyse dynamic behavior of rupture crossing a medium interface in 2D. Many faults often lie near medium interfaces in the Earth's heterogeneous crust consisting of various types of rocks. Some faults cross the interfaces, and the theoretical analysis of their dynamic behavior has been awaited. In the development, we focus on the extended parts of XBIEM in comparison to the conventional BIEM, and derive all the 2D displacement and stress kernels in response to a unit boundary traction in explicit discretized forms, which are the ingredients in the extension of BIEM. The final forms of kernels are compact and easy to evaluate numerically. They are implemented in simulating dynamic anti-plane rupture propagation across a bimaterial interface allowing secondary interfacial rupture. Our analysis shows a significant effect of an interfacial medium contrast on the control of dynamic rupture propagation.
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 of a piezoele......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...
Developing Serpent-Type Wave Generators to Create Solitary Wave Simulations with BEM
Institute of Scientific and Technical Information of China (English)
Wen-Kai WENG; Ruey-Syan SHIH; Chung-Ren CHOU
2013-01-01
Developing serpent-type wave generators to generate solitary waves in a 3D-basin was investigated in this study. Based on the Lagrangian description with time-marching procedures and finite differences of the time derivative, a 3D multiple directional wave basin with multidirectional piston wave generators was developed to simulate ocean waves by using BEM with quadrilateral elements, and to simulate wave-caused problems with fully nonlinear water surface conditions. The simulations of perpendicular solitary waves were conducted in the first instance to verify this scheme. Furthermore, the comparison of the waveform variations confirms that the estimation of 3D solitary waves is a feasible scheme.
Collision of plane thermonuclear detonation waves in a preliminarily compressed DT mixture
Khishchenko, K. V.; Charakhch'yan, A. A.
2015-03-01
The paper deals with a one-dimensional problem on symmetric irradiation of a plane DT fuel layer with a thickness 2 H and density ρ0 ⩽ 100ρ s (where ρ s is the density of the DT fuel in the solid state at atmospheric pressure and a temperature of 4 K) by two identical monoenergetic proton beams with a kinetic energy of 1 MeV, an intensity of 1019 W/cm2, and a duration of 50 ps. The problem is solved in the framework of one-fluid two-temperature hydrodynamic model that takes into account the equation of state for hydrogen, electron and ion heat conductivities, kinetics of the DT reaction, plasma self-radiation, and plasma heating by α-particles. The irradiation of the fuel results in the appearance of two counterpropagating detonation waves to the fronts of which rarefaction waves are adjacent. The efficiency of the DT reaction after the collision (reflection from the plane of symmetry) of the detonation waves depends on the spatial homogeneity of thermodynamic functions between the fronts of the reflected detonation waves. At Hρ0 ≈ 1 g/cm2, the gain factor is G ≈ 200, whereas at Hρ0 ≈ 5 g/cm2, it is G > 2000. As applied to a cylindrical target that is ignited from ends and in which the cylinder with the fuel is surrounded by a heavy magnetized shell, the obtained values of the burn-up and gain factors are maximum possible. To estimate the ignition energy E ig of a cylindrical target by using solutions to the one-dimensional problem, a quasi-one-dimensional model is developed. The model assumes that the main mechanism of target ignition is fuel heating by α-particles. The trajectories of α-particles are limited by a cylindrical surface with a given radius, which is a parameter of the model and is identified with the fuel radius in the target and the radii of the irradiating proton beams. This model reproduces the well-known theoretical dependence E ig ˜ ρ{0/-2} and yields E ig = 160 kJ as a lower estimate of the ignition energy for ρ0 = 100ρ s
Cheng, Qiang; Cui, Tie Jun
2006-12-01
We have investigated the reflection and refraction properties of plane waves incident from free space into a uniaxially anisotropic chiral medium, where the chirality appears only in one direction and the host medium can be either an isotropic dielectric or an anisotropic electric plasma. We show that the reflection and refraction properties are closely related to the dispersion relation of the chiral medium and that negative phase refractions and/or negative group refractions may occur. We further demonstrate that the two eigenwaves within the uniaxially anisotropic chiral medium behave differently with respect to the incident angle, and in some cases only one of them can be supported and transmitted. We have studied the critical angle and Brewster's angle with some special properties. We have also discussed the potential application of the uniaxially anisotropic chiral medium for the polarization beam splitter. Numerical results are given to validate our analysis.
Resonant plane waves in metamaterials with dipoles and quadrupoles coupled with quantum system
Chipouline, A; Pertsch, T
2013-01-01
Here the multipole approach [13], in combination with the density matrix formalism is used for establishing of the model for MMs with gain. This approach allows us to investigate analytically or semi-analytically the interplay between gain and magnetic properties of the MMs, the influence of internally unstable operation mode for spasers (MAs coupled with emitters, which the MMs consist of) on the propagation characteristics, and finally to optimize MM design. Moreover, the presented model is in line with the previously presented approach [16] (actually is its natural extension on the problem of plane wave propagation) and from the other side pretty clear and observable. The results presented in this paper resolve the discussion excited by [12] followed by [35-38].
Institute of Scientific and Technical Information of China (English)
Lu Ke-Qing; Zhao Wei; Yang Yan-Long; Zhu Xiang-Ping; Li Jin-Ping; Zhang Yan-Peng
2004-01-01
We investigate the modulation instability of quasi-plane-wave optical beams in biased photorefractive-photovoltaic crystals by globally treating the space-charge field. The modulation instability growth rate is obtained, which depends on the external bias field, on the bulk photovoltaic effect, and on the ratio of the optical beam's intensity to that of the dark irradiance. Our analysis indicates that this modulation instability growth rate is identical to the modulation instability growth rate studied previously in biased photorefractive-nonphotovoltaic crystals when the bulk photovoltaic effect is negligible for shorted circuits, and predicts the modulation instability growth rate in open- and closed-circuit photorefractive-photovoltaic crystals when the external bias field is absent.
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.)
Integrable Open Spin Chain in Super Yang-Mills and the Plane-wave/SYM duality
Chen, B; Wu, Y S; Chen, Bin; Wang, Xiao-Jun; Wu, Yong-Shi
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.
Progress in parallel implementation of the multilevel plane wave time domain algorithm
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.
Integrable open spin chain in super Yang-Mills and the plane-wave/SYM duality
Chen, Bin; Wang, Xiao-Jun; Wu, Yong-Shi
2004-02-01
We investigate the integrable structures in an Script N = 2 superconformal 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, Script N = 4 SYM. For the open string sector, the planar one-loop mixing matrix for gauge invariant holomorphic scalar 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.
Implementation of LDA+DMFT with the pseudo-potential-plane-wave method
Institute of Scientific and Technical Information of China (English)
Zhao Jian-Zhou; Zhuang Jia-Ning; Deng Xiao-Yu; Bi Yan; Cai Ling-Cang; Fang Zhong; Dai Xi
2012-01-01
We propose an efficient implementation of combining dynamical mean field theory(DMFT)with electronic structural calculation based on the local density approximation(LDA).The pseudo-potential-plane-wave method is used in the LDA part,which enables it to be applied to large systems.The full loop self consistency of the charge density has been reached in our implementation,which allows us to compute the total energy related properties.The procedure of LDA+DMFT is introduced in detail with a complete flow chart.We have also applied our code to study the electronic structure of several typical strong correlated materials,including cerium,americium and NiO.Our results fit quite well with both the experimental data and previous studies.
Fully converged plane-wave-based self-consistent G W calculations of periodic solids
Cao, Huawei; Yu, Zhongyuan; Lu, Pengfei; Wang, Lin-Wang
2017-01-01
The G W approximation is a well-known method to obtain the quasiparticle and spectral properties of systems ranging from molecules to solids. In practice, G W calculations are often employed with many different approximations and truncations. In this work, we describe the implementation of a fully self-consistent G W approach based on the solution of the Dyson equation using a plane wave basis set. Algorithmic, numerical, and technical details of the self-consistent G W approach are presented. The fully self-consistent G W calculations are performed for GaAs, ZnO, and CdS including semicores in the pseudopotentials. No further approximations and truncations apart from the truncation on the plane wave basis set are made in our implementation of the G W calculation. After adopting a special potential technique, a ˜100 Ry energy cutoff can be used without the loss of accuracy. We found that the self-consistent G W (sc-G W ) significantly overestimates the bulk band gaps, and this overestimation is likely due to the underestimation of the macroscopic dielectric constants. On the other hand, the sc-G W accurately predicts the d -state positions, most likely because the d -state screening does not sensitively depend on the macroscopic dielectric constant. Our work indicates the need to include the high-order vertex term in order for the many-body perturbation theory to accurately predict the semiconductor band gaps. It also sheds some light on why, in some cases, the G0W0 bulk calculation is more accurate than the fully self-consistent G W calculation, because the initial density-functional theory has a better dielectric constant compared to experiments.
Radiation of de-excited electrons at large times in a strong electromagnetic plane wave
Energy Technology Data Exchange (ETDEWEB)
Kazinski, P.O., E-mail: kpo@phys.tsu.ru
2013-12-15
The late time asymptotics of the physical solutions to the Lorentz–Dirac equation in the electromagnetic external fields of simple configurations–the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave–are found. The solutions to the Landau–Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. Some general properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above. This provides a simple method to verify experimentally that the charged particle has reached the asymptotic regime. -- Highlights: •Late time asymptotics of the solutions to the Lorentz–Dirac equation are studied. •General properties of the total radiation power of electrons are established. •The total radiation power equals a half the rest energy divided by the proper-time. •Spectral densities of radiation formed on the late time asymptotics are derived. •Possible experimental verification of the results is proposed.
Dispersion of circumferential waves in cylindrically anisotropic layered pipes in plane strain.
Vasudeva, R Y; Sudheer, G; Vema, Anu Radha
2008-06-01
Dispersion spectra of circumferential waves along the periphery of circular pipes made of layered anisotropic materials do not seem to be available in literature. This note attempts to partially fill this gap by providing the dispersion spectra in two and three layered cylindrically anisotropic pipes in plane strain motion. The spectra for pipes executing time harmonic vibrations in plane strain condition are obtained as roots of a numerical characteristic equation derived extending a weighted residual method of solution of the governing equations for a single layer pipe [Towfighi et al., J. Appl. Mech. 69, 283-291 (2002)] to a general N layered pipe. The anisotropic elastic coefficients are considered to be independent of position coordinates and the bond condition at interfaces of the layers is assumed to be perfect. Numerical illustrations are presented for two and three layered pipes with anisotropy directions differing in adjacent layers. Increase in curvature of the pipe and inclination of the fiber orientation in the outermost layers to propagation direction are factors that seem to influence the mode number and pattern within the limited examples worked out.
Monte Carlo simulations of in-plane stacking disorder in hard-sphere crystals.
Miedema, P S; de Villeneuve, V W A; Petukhov, A V
2008-01-01
On-lattice Monte Carlo simulations of colloidal random-stacking hard-sphere colloidal crystals are presented. The model yields close-packed crystals with random-stacking hexagonal structure. We find a significant amount of in-plane stacking disorder, which slowly anneals in the course of the simulation. The in-plane stacking disorder leads to lateral broadening of the stacking-disorder-induced Bragg rods. It is found that not only the scattering intensity, but also the width is modulated along the Bragg rods.
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.
Scattering and diffraction of plane SH-waves by periodically distributed canyons
Ba, Zhenning; Liang, Jianwen; Zhang, Yanju
2016-06-01
A new method is presented to study the scattering and diffraction of plane SH-waves by periodically distributed canyons in a layered half-space. This method uses the indirect boundary element method combined with Green's functions of uniformly distributed loads acting on periodically distributed inclined lines. The periodicity feature of the canyons is exploited to limit the discretization effort to a single canyon, which avoids errors induced by the truncation of the infinite boundary, and the computational complexity and the demand on memory can be significantly reduced. Furthermore, the total wave fields are decomposed into the free field and scattered field in the process of calculation, which means that the method has definite physical meaning. The implementation of the method is described in detail and its accuracy is verified. Parametric studies are performed in the frequency domain by taking periodically distributed canyons of semi-circular and semi-elliptic cross-sections as examples. Numerical results show that the dynamic responses of periodically distributed canyons can be quite different from those for a single canyon and significant dynamic interactions exist between the canyons.
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.
The Fundamental Plane of star formation in galaxies revealed by the EAGLE hydrodynamical simulations
Lagos, Claudia del P.; Theuns, Tom; Schaye, Joop; Furlong, Michelle; Bower, Richard G.; Schaller, Matthieu; Crain, Robert A.; Trayford, James W.; Matthee, Jorryt
2016-07-01
We investigate correlations between different physical properties of star-forming galaxies in the `Evolution and Assembly of GaLaxies and their Environments' (EAGLE) cosmological hydrodynamical simulation suite over the redshift range 0 ≤ z ≤ 4.5. A principal component analysis reveals that neutral gas fraction (fgas,neutral), stellar mass (Mstellar) and star formation rate (SFR) account for most of the variance seen in the population, with galaxies tracing a two-dimensional, nearly flat, surface in the three-dimensional space of fgas, neutral-Mstellar-SFR with little scatter. The location of this plane varies little with redshift, whereas galaxies themselves move along the plane as their fgas, neutral and SFR drop with redshift. The positions of galaxies along the plane are highly correlated with gas metallicity. The metallicity can therefore be robustly predicted from fgas, neutral, or from the Mstellar and SFR. We argue that the appearance of this `Fundamental Plane of star formation' is a consequence of self-regulation, with the plane's curvature set by the dependence of the SFR on gas density and metallicity. We analyse a large compilation of observations spanning the redshift range 0 ≲ z ≲ 3, and find that such a plane is also present in the data. The properties of the observed Fundamental Plane of star formation are in good agreement with EAGLE's predictions.
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.
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.
Numerical Simulation of Solitary Kinetic Alfven Waves
Institute of Scientific and Technical Information of China (English)
DING Jian; LI Yi; WANG Shui
2008-01-01
Using the two-fluid model in the case of α1 (α=β/2Q, β is the ratio of thermal pressure to magnetic pressure, and Q=m,e/m,I), we numerically investigate the interactions between two solitary kinetic Alfven waves (SKAWs) and between an SKAW and a density discontinuity. The results show that the two SKAWs would remain in their original shapes and propagate at their initiating speeds, which indicates that SKAWs behave just like standard solitons. The simulation also shows that SKAWs will reflect and refract when crossing a discontinuity and propagating into a higher density region. The transmission wave is an SKAW with increasing density, and the reverberation is a disturbance with lower amplitude.
Slamming Simulations in a Conditional Wave
DEFF Research Database (Denmark)
Seng, Sopheak; Jensen, Jørgen Juncher
2012-01-01
A study of slamming events in conditional waves is presented in this paper. The ship is sailing in head sea and the motion is solved for under the assumption of rigid body motion constrained to two degree-of-freedom i.e. heave and pitch. Based on a time domain non-linear strip theory most probable...... surface NS/VOF CFD simulations under the same wave conditions. In moderate seas and no occurrence of slamming the structural responses predicted by the methods agree well. When slamming occurs the strip theory overpredicts VBM but the peak values of VBM occurs at approximately the same time as predicted...... by the CFD method implying the possibility to use the more accurate CFD results to improve the estimation of slamming loads in the strip theory through a rational correction coefficient....
Directory of Open Access Journals (Sweden)
C. Zorammuana
2015-01-01
Full Text Available The problem of reflection and refraction of SH-waves at a plane interface between the homogeneous and inhomogeneous fibre-reinforced elastic half-spaces has been investigated. Amplitude and energy ratios corresponding to the reflected and refracted SH-waves are derived using appropriate boundary conditions. These ratios are computed numerically for a particular model and the results are depicted graphically.
A Plane-Parallel Wind Solution For Testing Numerical Simulations of Photoevaporation
Hutchison, Mark A
2016-01-01
Here we derive a Parker-wind like solution for a stratified, plane-parallel atmosphere undergoing photoionisation. The difference compared to the standard Parker solar wind is that the sonic point is crossed only at infinity. The simplicity of the analytic solution makes it a convenient test problem for numerical simulations of photoevaporation in protoplanetary discs.
Monte Carlo simulations of in-plane stacking disorder in hard-sphere crystals
Miedema, P.S.; de Villeneuve, V.W.A.; Petukhov, A.V.
2008-01-01
On-lattice Monte Carlo simulations of colloidal random-stacking hard-sphere colloidal crystals are presented. The model yields close-packed crystals with random-stacking hexagonal structure. We find a significant amount of in-plane stacking disorder, which slowly anneals in the course of the simulat
Direct numerical simulation of three-dimensional coherent structure in plane mixing layer
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The three-dimensional temporally evolving plane mixing layer is sinulated by directly solying the Navier-Stokes equations using pseudo-spectral method. The process of loss of stability, and the formation paring, and development of vortex are presented. The simulated result shows that the evolving characteristics of coherent structure are important mechanism of growing and entrainment of mixing layer.
Shear Creep Simulation of Structural Plane of Rock Mass Based on Discontinuous Deformation Analysis
Directory of Open Access Journals (Sweden)
Guoxin Zhang
2017-01-01
Full Text Available Numerical simulations of the creep characteristics of the structural plane of rock mass are very useful. However, most existing simulation methods are based on continuum mechanics and hence are unsuitable in the case of large displacements and deformations. The discontinuous deformation analysis method proposed by Genhua is a discrete one and has a significant advantage when simulating the contacting problem of blocks. In this study, we combined the viscoelastic rheological model of Burgers with the discontinuous deformation analysis (DDA method. We also derived the recurrence formula for the creep deformation increment with the time step during numerical simulations. Based on the minimum potential energy principle, the general equilibrium equation was derived, and the shear creep deformation in the structural plane was considered. A numerical program was also developed and its effectiveness was confirmed based on the curves obtained by the creep test of the structural plane of a rock mass under different stress levels. Finally, the program was used to analyze the mechanism responsible for the creep features of the structural plane in the case of the toppling deformation of the rock slope. The results showed that the extended DDA method is an effective one.
Filippov, A. I.; Akhmetova, O. V.; Koval‧skii, A. A.
2016-11-01
The filtration-wave process in the central layer of a three-layer anisotropic medium is described as an equivalent plane wave with a modified asymptotic method accurate in the mean. The initial problem is parametrized and broken down into simpler problems for the coefficients of expansion in an asymptotic parameter. The zero expansion coefficient describes the sought plane wave, whereas the first coefficient ensures refinement of the wave-front geometry. The exact solution of the parametrized problem is obtained on the basis of the Fourier sine transformation. The correctness of the developed method is confirmed by comparing the obtained asymptotic solutions and the coefficients of Maclaurin-series expansion of the exact solution of the parametrized problem in a formal parameter.
Terada, Takahide; Yamanaka, Kazuhiro; Suzuki, Atsuro; Tsubota, Yushi; Wu, Wenjing; Kawabata, Ken-ichi
2017-07-01
Ultrasound computed tomography (USCT) is promising for a non-invasive, painless, operator-independent and quantitative system for breast-cancer screening. Assembly error, production tolerance, and aging-degradation variations of the hardwire components, particularly of plane-wave-based USCT systems, may hamper cost effectiveness, precise imaging, and robust operation. The plane wave is transmitted from a ring-shaped transducer array for receiving the signal at a high signal-to-noise-ratio and fast aperture synthesis. There are four signal-delay components: response delays in the transmitters and receivers and propagation delays depending on the positions of the transducer elements and their directivity. We developed a highly precise calibration method for calibrating these delay components and evaluated it with our prototype plane-wave-based USCT system. Our calibration method was found to be effective in reducing delay errors. Gaps and curves were eliminated from the plane wave, and echo images of wires were sharpened in the entire imaging area.
Plane-wave matrix theory from N=4 super-Yang-Mills on RxS{sup 3}
Energy Technology Data Exchange (ETDEWEB)
Kim, Nakwoo E-mail: kim@aei.mpg.de; Klose, Thomas E-mail: thklose@aei.mpg.de; Plefka, Jan E-mail: plefka@aei.mpg.de
2003-11-03
Recently a mass deformation of the maximally supersymmetric Yang-Mills quantum mechanics has been constructed from the supermembrane action in eleven-dimensional plane-wave backgrounds. However, the origin of this plane-wave matrix theory in terms of a compactification of a higher-dimensional super-Yang-Mills model has remained obscure. In this paper we study the Kaluza-Klein reduction of D=4, N=4 super-Yang-Mills theory on a round three-sphere, and demonstrate that the plane-wave matrix theory arises through a consistent truncation to the lowest lying modes. We further explore the relation between the dilatation operator of the conformal field theory and the Hamiltonian of the quantum mechanics through perturbative calculations up to two-loop order. In particular, we find that the one-loop anomalous dimensions of pure scalar operators are completely captured by the plane-wave matrix theory. At two-loop level this property ceases to exist.
Ould-Lahoucine, H. K.; Chetouani, L.
2012-07-01
Exact Green function for a Dirac particle subject to a couple of orthogonal plane wave fields is obtained throughout a path integral approach. In addition, a suitable representation of the Dirac matrices is deduced so that the initial problem becomes the one of a free particle.
Pechereau, Francois; Jansky, Jaroslav; Bourdon, Anne
2012-10-01
In recent years, experimental studies on flue gas treatment have demonstrated the efficiency of plasma assisted catalysis for the treatment of a wide range of pollutants at a low energetic cost. In plasma reactors, usual catalyst supports are pellets, monoliths or porous media, and then atmospheric pressure discharges have to interact with many obstacles and to propagate in microcavities and pores. As a first step to better understand atmospheric pressure discharge dynamics in these complex geometries, in this work, we have carried out numerical simulations using a 2D-axisymmetric fluid model for a point-to-plane discharge with a dielectric plane obstacle placed in the path of the discharge. First, we have simulated the discharge ignition at the point electrode, its propagation in the gap and its impact and expansion on the dielectric plane. Depending on the applied voltage, the dielectric plane geometry and permittivity, we have identified conditions for the reignition of a second discharge behind the plane obstacle. These conditions will be discussed and compared with recent experimental results on the same configuration.
Simulating acoustic waves in spotted stars
Papini, Emanuele; Gizon, Laurent; Hanasoge, Shravan M
2015-01-01
Acoustic modes of oscillation are affected by stellar activity, however it is unclear how starspots contribute to these changes. Here we investigate the non-magnetic effects of starspots on global modes with angular degree $\\ell \\leq 2$ in highly active stars, and characterize the spot seismic signature on synthetic light curves. We perform 3D time-domain simulations of linear acoustic waves to study their interaction with a model starspot. We model the spot as a 3D change in the sound speed stratification with respect to a convectively stable stellar background, built from solar Model S. We perform a parametric study by considering different depths and perturbation amplitudes. Exact numerical simulations allow investigation of the wavefield-spot interaction beyond first order perturbation theory. The interaction of the axisymmetric modes with the starspot is strongly nonlinear. As mode frequency increases, the frequency shifts for radial modes exceed the value predicted by linear theory, while the shifts for...
Kawashima, Yukio; Hirao, Kimihiko
2017-02-24
We introduced two methods to correct the singularity in the calculation of long-range Hartree-Fock (HF) exchange for long-range-corrected density functional theory (LC-DFT) calculations in plane-wave basis sets. The first method introduces an auxiliary function to cancel out the singularity. The second method introduces a truncated long-range Coulomb potential, which has no singularity. We assessed the introduced methods using the LC-BLYP functional by applying it to isolated systems of naphthalene and pyridine. We first compared the total energies and the HOMO energies of the singularity-corrected and uncorrected calculations and confirmed that singularity correction is essential for LC-DFT calculations using plane-wave basis sets. The LC-DFT calculation results converged rapidly with respect to the cell size as the other functionals, and their results were in good agreement with the calculated results obtained using Gaussian basis sets. LC-DFT succeeded in obtaining accurate orbital energies and excitation energies. We next applied LC-DFT with singularity correction methods to the electronic structure calculations of the extended systems, Si and SiC. We confirmed that singularity correction is important for calculations of extended systems as well. The calculation results of the valence and conduction bands by LC-BLYP showed good convergence with respect to the number of k points sampled. The introduced methods succeeded in overcoming the singularity problem in HF exchange calculation. We investigated the effect of the singularity correction on the excitation state calculation and found that careful treatment of the singularities is required compared to ground-state calculations. We finally examined the excitonic effect on the band gap of the extended systems. We calculated the excitation energies to the first excited state of the extended systems using a supercell model at the Γ point and found that the excitonic binding energy, supposed to be small for
Sondergaard, R.; Cantwell, B.; Mansour, N.
1997-01-01
Direct numerical simulations have been used to examine the effect of the initial disturbance field on the development of three-dimensionality and the transition to turbulence in the incompressible plane wake. The simulations were performed using a new numerical method for solving the time-dependent, three-dimensional, incompressible Navier-Stokes equations in flows with one infinite and two periodic directions. The method uses standard Fast Fourier Transforms and is applicable to cases where the vorticity field is compact in the infinite direction. Initial disturbances fields examined were combinations of two-dimensional waves and symmetric pairs of 60 deg oblique waves at the fundamental, subharmonic, and sub-subharmonic wavelengths. The results of these simulations indicate that the presence of 60 deg disturbances at the subharmonic streamwise wavelength results in the development of strong coherent three-dimensional structures. The resulting strong three-dimensional rate-of-strain triggers the growth of intense fine scale motions. Wakes initiated with 60 deg disturbances at the fundamental streamwise wavelength develop weak coherent streamwise structures, and do not develop significant fine scale motions, even at high Reynolds numbers. The wakes which develop strong three-dimensional structures exhibit growth rates on par with experimentally observed turbulent plane wakes. Wakes which develop only weak three-dimensional structures exhibit significantly lower late time growth rates. Preliminary studies of wakes initiated with an oblique fundamental and a two-dimensional subharmonic, which develop asymmetric coherent oblique structures at the subharmonic wavelength, indicate that significant fine scale motions only develop if the resulting oblique structures are above an angle of approximately 45 deg.
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
Self-consistent theory for a plane wave in a moving medium and light-momentum criterion
Wang, Changbiao
2014-01-01
A self-consistent theory is developed based on the principle of relativity for a plane wave in a moving non-dispersive, lossless, non-conducting, isotropic uniform medium. Light-momentum criterion is set up for the first time, which states that the momentum of light in a medium is parallel to the wave vector in all inertial frames of reference. By rigorous analysis, novel basic properties of the plane wave are exposed: (1) Poynting vector does not necessarily represent the electromagnetic (EM) power flow when a medium moves, (2) Minkowski light momentum and energy constitute a Lorentz four-vector in a form of single EM-field cell or single photon, and Planck constant is a Lorentz invariant, (3) there is no momentum transfer taking place between the plane wave and the uniform medium, and the EM momentum conservation equation cannot be uniquely determined without resort to the principle of relativity, and (4) the moving medium behaves as a so-called "negative index medium" when it moves opposite to the wave vec...
Simulation of Flapping-wing Unmanned Aerial Vehicle using X-plane and Matlab/Simulink
Directory of Open Access Journals (Sweden)
A. Kaviyarasu
2014-07-01
Full Text Available This paper presents the simulation of flapping-wing unmanned aerial vehicle model using X-plane and Matlab/ Simulink. The flapping-wing ornithopter model (i.e. an aircraft that flies by flapping its wings has been developed in plane maker software and executed in the X-plane environment. The key idea of flapping-wing mechanism in X-plane software is by varying its dihedral angle sinusoidally. This sinusoidally varying dihedral angle of wing creates upward and downward stroke moments inturn this creates a lift and a forward thrust for flying the flapping-wing model. Here pitch, roll, yaw and throttle (flapping rate is fed as reference input through the user datagram protocol (UDP port. The difference between the reference inputs, the simulated outputs are again fed back to simulator through UDP port and the gains are observed for the responses of flapping-wing unmanned aerial vehicle in Matlab/Simulink environment. Here various gains are used to monitor the optimized flying of flapping-wing model.Defence Science Journal, Vol. 64, No. 4, July 2014, pp.327-331, DOI:http://dx.doi.org/10.14429/dsj.64.4933
Large eddy simulation of a particle-laden turbulent plane jet
Institute of Scientific and Technical Information of China (English)
金晗辉; 罗坤; 樊建人; 岑可法
2003-01-01
Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems. To predict the particle dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems. A large eddy simulation of the two-phase plane jet was conducted to investigate the particle dispersion patterns. The particles with Stokes numbers equal to 0.0028, 0.3, 2.5, 28 (corresponding to particle diameter 1 μm, 10 μm, 30 μm, 100 μm, respectively) in Re=11 300 gas flow were studied. The simulation results of gas phase motion agreed well with previous experimental results. And the simulation results of the solid particles motion showed that particles with different Stokes number have different spatial dispersion; and that particles with intermediate Stokes number have the largest dispersion ratio.
Large eddy simulation of a particle-laden turbulent plane jet.
Jin, Han-Hui; Luo, Kun; Fan, Jian-Ren; Cen, Ke-Fa
2003-01-01
Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems. To predict the particle dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems. A large eddy simulation of the two-phase plane jet was conducted to investigate the particle dispersion patterns. The particles with Stokes numbers equal to 0.0028, 0.3, 2.5, 28 (corresponding to particle diameter 1 microm, 10 microm, 30 microm, 100 microm, respectively) in Re = 11 300 gas flow were studied. The simulation results of gas phase motion agreed well with previous experimental results. And the simulation results of the solid particles motion showed that particles with different Stokes number have different spatial dispersion; and that particles with intermediate Stokes number have the largest dispersion ratio.
Large eddy simulation of a particle—laden turbulent plane jet
Institute of Scientific and Technical Information of China (English)
金含辉; 罗坤; 樊建人; 岑可法
2003-01-01
Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems.To predict the particle dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems.A large eddy simulation of the two-phase plane jet eas conducted to in-vestigate the particle dispersion patterns.The particles with Stokes numbers equal to 0.0028,0.3,2.5,28(corresponding to particle diamster 1μm,10μm,30μm,100μm,respectively)in Re=11300 gas flow were strudied.The simulation results of gas phase motion agreed well with previous experimental results.And the simulation results of the solid particles motion showed that particles with different Stokes number have dif-ferent spatial dispersion;and that particles with intermediate Stokes number have the largest dispersion ratio.
Reﬂection of plane waves at the free surface of a ﬁbre-reinforced elastic half-space
Indian Academy of Sciences (India)
Baljeet Singh; Sarva Jit Singh
2004-06-01
The propagation of plane waves in ﬁbre-reinforced, anisotropic, elastic media is discussed. The expressions for the phase velocity of quasi-$P(qP)$ and quasi-$SV(qSV)$ waves propagating in a plane containing the reinforcement direction are obtained as functions of the angle between the propagation and reinforcement directions. Closed form expressions for the amplitude ratios for qP and qSV waves reﬂected at the free surface of a ﬁbre-reinforced, anisotropic, homogeneous, elastic half-space are obtained. These expressions are used to study the variation of amplitude ratios with angle of incidence. It is found that reinforcement has a signiﬁcant effect on the amplitude ratios and critical angle.
Maity, Narottam; Barik, S. P.; Chaudhuri, P. K.
2016-09-01
In this paper, plane wave propagation in a rotating anisotropic material of general nature under the action of a magnetic field of constant magnitude has been investigated. The material is supposed to be porous in nature and contains voids. Following the concept of [Cowin S. C. and Nunziato, J. W. [1983] “Linear elastic materials with voids,” J. Elasticity 13, 125-147.] the governing equations of motion have been written in tensor notation taking account of rotation, magnetic field effect and presence of voids in the medium and the possibility of plane wave propagation has been examined. A number of particular cases have been derived from our general results to match with previously obtained results in this area. Effects of various parameters on the velocity of wave propagation have been presented graphically.
Hospital-Bravo, Raúl; Sarrate, Josep; Díez, Pedro
2016-05-01
A new 2D numerical model to predict the underwater acoustic propagation is obtained by exploring the potential of the Partition of Unity Method (PUM) enriched with plane waves. The aim of the work is to obtain sound pressure level distributions when multiple operational noise sources are present, in order to assess the acoustic impact over the marine fauna. The model takes advantage of the suitability of the PUM for solving the Helmholtz equation, especially for the practical case of large domains and medium frequencies. The seawater acoustic absorption and the acoustic reflectance of the sea surface and sea bottom are explicitly considered, and perfectly matched layers (PML) are placed at the lateral artificial boundaries to avoid spurious reflexions. The model includes semi-analytical integration rules which are adapted to highly oscillatory integrands with the aim of reducing the computational cost of the integration step. In addition, we develop a novel strategy to mitigate the ill-conditioning of the elemental and global system matrices. Specifically, we compute a low-rank approximation of the local space of solutions, which in turn reduces the number of degrees of freedom, the CPU time and the memory footprint. Numerical examples are presented to illustrate the capabilities of the model and to assess its accuracy.
The decay of plane wave pulses with complex structure in a nonlinear dissipative medium
Gurbatov, S N; Pasmanik, G V; Gurbatov, Sergei N.; Enflo, Bengt O.; Pasmanik, Galina V.
2000-01-01
Nonlinear plane acoustic waves propagating through a fluid are studied using Burgers' equation with finite viscosity. The evolution of a simple N-pulse with regular and random initial amplitude and of pulses with monochromatic and noise carrier is considered. In the latter case the initial pulses are characterized by two length scales. The length scale of the modulation function is much greater than the period or the length scale of the carrier. With increasing time the initial pulses are deformed and shocks appear. The finite viscosity leads to a finite shock width, which does not depend on the fine structure of the initial pulse and is fully determined by the shock position in the zero viscosity limit. The other effect of nonzero viscosity is the shift of the shock position from the position at zero viscosity. This shift, as well as the linear time, at which the nonlinear stage of evolution changes to the linear stage, depends on the fine structure of the initial pulse. It is also shown that the nonlinearit...
Ab initio Sternheimer-GW method for quasiparticle calculations using plane waves
Lambert, Henry; Giustino, Feliciano
2013-08-01
We report on the extension and implementation of the Sternheimer-GW method introduced by Giustino [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.115105 81, 115105 (2010)] to the case of first-principles pseudopotential calculations based on a plane-waves basis. The Sternheimer-GW method consists of calculating the GW self-energy operator without resorting to the standard expansion over unoccupied Kohn-Sham electronic states. The Green's function is calculated by solving linear systems for frequencies along the real axis. The screened Coulomb interaction is calculated for frequencies along the imaginary axis by using the Sternheimer equation. Analytic continuation to the real axis is performed using Padé approximants. The generalized plasmon-pole approximation is avoided by performing explicit calculations at multiple frequencies using Frommer's multishift solver. We demonstrate our methodology by reporting tests on common insulators and semiconductors, including Si, diamond, LiCl, and SiC. Our calculated quasiparticle energies are in agreement with the results of fully converged calculations based on the sum-over-states approach. As the Sternheimer-GW method yields the complete self-energy Σ(r,r',ω) and not only its expectation values on Kohn-Sham states, this work opens the way to nonperturbative GW calculations and to direct calculations of spectral functions for angle-resolved photoemission spectroscopy. As an example of the capabilities of the method we calculate the G0W0 spectral functions of silicon and diamond.
Quartic scaling MP2 for solids: A highly parallelized algorithm in the plane-wave basis
Schäfer, Tobias; Kresse, Georg
2016-01-01
We present a low-complexity algorithm to calculate the correlation energy of periodic systems in second-order M{\\o}ller-Plesset perturbation theory (MP2). In contrast to previous approximation-free MP2 codes, our implementation possesses a quartic scaling, $\\mathcal O(N^4$), 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 solved by an internal basis set extrapolation. The key concept to reduce the scaling of the algorithm is to eliminate all summations over virtual bands which can be elegantly achieved in the Laplace transformed MP2 (LTMP2) formulation using plane-wave basis sets. Analogously, this approach could allow to calculate second order screened exchange (SOSEX) 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.
Quantum Larmor radiation from a moving charge in an electromagnetic plane wave background
Nakamura, Gen; 10.1142/S0217751X12501424
2012-01-01
We extend our previous work [Phys. Rev. D83 045030 (2011)], which investigated the first-order quantum effect in the Larmor radiation from a moving charge in a spatially homogeneous time-dependent electric field. Specifically, we investigate the quantum Larmor radiation from a moving charge in a monochromatic electromagnetic plane wave background based on the scalar quantum electrodynamics at the lowest order of the perturbation theory. Using the in-in formalism, we derive the theoretical formula of the total radiation energy from a charged particle in the initial states being at rest and being in a relativistic motion. Expanding the theoretical formula in terms of the Planck constant \\hbar, we obtain the first-order quantum effect on the Larmor radiation. The quantum effect generally suppresses the total radiation energy compared with the prediction of the classical Larmor formula, which is a contrast to the previous work. The reason is explained by the fact that the radiation from a moving charge in a monoc...
On the formation of shocks of electromagnetic plane waves in non-linear crystals
Christodoulou, Demetrios
2015-01-01
An influential result of F. John states that no genuinely non-linear strictly hyperbolic quasi-linear first order system of partial differential equations in two variables has a global $C^2$-solution for small enough initial data. Inspired by recent work of D. Christodoulou, we revisit John's original proof and extract a more precise description of the behaviour of solutions at the time of shock. We show that John's singular first order quantity, when expressed in characteristic coordinates, remains bounded until the final time, which is then characterised by an inverse density of characteristics tending to zero in one point. Moreover, we study the derivatives of second order, showing again their boundedness when expressed in appropriate coordinates. We also recover John's upper bound for the time of shock formation and complement it with a lower bound. Finally, we apply these results to electromagnetic plane waves in a crystal with no magnetic properties and cubic electric non-linearity in the energy density...
On the formation of shocks of electromagnetic plane waves in non-linear crystals
Christodoulou, Demetrios; Perez, Daniel Raoul
2016-08-01
An influential result of F. John states that no genuinely non-linear strictly hyperbolic quasi-linear first order system of partial differential equations in two variables has a global C2-solution for small enough initial data. Inspired by recent work of D. Christodoulou, we revisit John's original proof and extract a more precise description of the behaviour of solutions at the time of shock. We show that John's singular first order quantity, when expressed in characteristic coordinates, remains bounded until the final time, which is then characterised by an inverse density of characteristics tending to zero in one point. Moreover, we study the derivatives of second order, showing again their boundedness when expressed in appropriate coordinates. We also recover John's upper bound for the time of shock formation and complement it with a lower bound. Finally, we apply these results to electromagnetic plane waves in a crystal with no magnetic properties and cubic electric non-linearity in the energy density, assuming no dispersion.
Towards a generalized iso-density continuum model for molecular solvents in plane-wave DFT
Gunceler, Deniz; Arias, T. A.
2017-01-01
Implicit electron-density solvation models offer a computationally efficient solution to the problem of calculating thermodynamic quantities of solvated systems from first-principles quantum mechanics. However, despite much recent interest in such models, to date the applicability of such models in the plane-wave context to non-aqueous solvents has been limited because the determination of the model parameters requires fitting to a large database of experimental solvation energies for each new solvent considered. This work presents a simple approach to quickly find approximations to the non-electrostatic contributions to the solvation energy, allowing for development of new iso-density models for a large class of protic and aprotic solvents from only simple, single-molecule ab initio calculations and readily available bulk thermodynamic data. Finally, to illustrate the capabilities of the resulting theory, we also calculate the surface solvation energies of crystalline LiF in various different non-aqueous solvents, and discuss the observed trends and their relevance to lithium battery technology.
Noise characteristics analysis of short wave infrared InGaAs focal plane arrays
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.
Bakker, J F; Paulides, M M; Christ, A; Kuster, N; van Rhoon, G C
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(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.
Bakker, J. F.; Paulides, M. M.; Christ, A.; Kuster, N.; van Rhoon, G. C.
2010-06-01
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 (SARwb) and the peak 10 g spatial-averaged SAR (SAR10g). 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% (SARwb) and 58% (SAR10g) due to variations in simulation settings and tissue properties. In this study, we found that the basic restriction on the SARwb is occasionally exceeded for children, up to a maximum of 45% in small children. The maximum SAR10g 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.
Institute of Scientific and Technical Information of China (English)
Jianwen Liang; Zhongxian Liu
2009-01-01
This paper presents an indirect boundary integration equation method for diffraction of plane P waves by a two-dimensional canyon of arbitrary shape in poroelastic half-space. The Green's functions of compressional and shear wave sources in poroelastic half-space are derived based on Biot's theory. The scattered waves are constructed using the fictitious wave sources close to the boundary of the canyon, and magnitude of the fictitious wave sources are determined by the boundary conditions. The precision of the method is verified by the satisfaction extent of boundary conditions, the comparison between the degenerated solutions of single-phased half-space and the well-known solutions, and the numerical stability of the method.
Simulation research on the process of large scale ship plane segmentation intelligent workshop
Xu, Peng; Liao, Liangchuang; Zhou, Chao; Xue, Rui; Fu, Wei
2017-04-01
Large scale ship plane segmentation intelligent workshop is a new thing, and there is no research work in related fields at home and abroad. The mode of production should be transformed by the existing industry 2.0 or part of industry 3.0, also transformed from "human brain analysis and judgment + machine manufacturing" to "machine analysis and judgment + machine manufacturing". In this transforming process, there are a great deal of tasks need to be determined on the aspects of management and technology, such as workshop structure evolution, development of intelligent equipment and changes in business model. Along with them is the reformation of the whole workshop. Process simulation in this project would verify general layout and process flow of large scale ship plane section intelligent workshop, also would analyze intelligent workshop working efficiency, which is significant to the next step of the transformation of plane segmentation intelligent workshop.
Directory of Open Access Journals (Sweden)
Fontara I.-K.
2015-03-01
Full Text Available This work addresses the evaluation of the seismic wave field in a graded half-plane with free-surface and/or sub-surface relief subjected to shear horizontally (SH-polarized wave, radiating from an embedded seismic source. The considered boundary value problem is transformed into a system of boundary integral equations (BIEs along the boundaries of the free-surface and of any sub-surface relief, using an analytically derived frequency-dependent Green’s function for a quadratically inhomogeneous in depth half-plane. The numerical solution yields synthetic seismic signals at any point of the half-plane in both frequency and time domain following application of Fast Fourier Transform (FFT. Finally, in the companion paper, the verification and numerical simulation studies demonstrate the accuracy and efficiency of the present computational approach. The proposed BIE tool possesses the potential to reveal the sensitivity of the seismic signal to the type and properties of the seismic source, to the existence and type of the material gradient and to the lateral inhomogeneity, due to the free-surface and/or sub-surface relief peculiarities.
Wind turbine wakes in forest and neutral plane wall boundary layer large-eddy simulations
Schröttle, Josef; Piotrowski, Zbigniew; Gerz, Thomas; Englberger, Antonia; Dörnbrack, Andreas
2016-09-01
Wind turbine wake flow characteristics are studied in a strongly sheared and turbulent forest boundary layer and a neutral plane wall boundary layer flow. The reference simulations without wind turbine yield similar results as earlier large-eddy simulations by Shaw and Schumann (1992) and Porte-Agel et al. (2000). To use the fields from the homogeneous turbulent boundary layers on the fly as inflow fields for the wind turbine wake simulations, a new and efficient methodology was developed for the multiscale geophysical flow solver EULAG. With this method fully developed turbulent flow fields can be achieved upstream of the wind turbine which are independent of the wake flow. The large-eddy simulations reproduce known boundary-layer statistics as mean wind profile, momentum flux profile, and eddy dissipation rate of the plane wall and the forest boundary layer. The wake velocity deficit is more asymmetric above the forest and recovers faster downstream compared to the velocity deficit in the plane wall boundary layer. This is due to the inflection point in the mean streamwise velocity profile with corresponding turbulent coherent structures of high turbulence intensity in the strong shear flow above the forest.
Bahar, Ezekiel
2010-09-01
The common definition of the Brewster angles for dielectric and magnetic achiral materials are the angles at which the vertically and horizontally polarized reflection coefficients vanish. We examine broader definitions of the Brewster conditions for waves that are incident on a free-space-chiral interface. Besides the common definition, the Brewster angles have been defined as the angles at which the polarizations of the reflected waves are independent of the polarizations of the incident waves. We consider total transmission of incident plane waves that satisfy the Brewster conditions at a free-space-chiral medium planar interface. In this case we determine the polarization of the incident wave for which the reflected vertically and horizontally polarized waves vanish simultaneously. Thus with this definition of the Brewster conditions the polarization of the reflected wave is undefined. The conditions for the excitation of surface waves are considered. The characteristic polarizations that are the same for the reflected and incident waves are also examined subject to the Brewster conditions. Potential applications of this analysis are to experimentally determine the chiral or geotropic measure of the medium and to identify and characterize biological and chemical materials through their optical activity in real time. Several independent measurements can be taken with the same polarimetric instrument to avoid false identifications. Since measurements can be conducted in the reflection mode they can be nonintrusive.
Compression Waves and Phase Plots: Simulations
Orlikowski, Daniel
2011-01-01
Compression wave analysis started nearly 50 years ago with Fowles.[1] Coperthwaite and Williams [2] gave a method that helps identify simple and steady waves. We have been developing a method that gives describes the non-isentropic character of compression waves, in general.[3] One result of that work is a simple analysis tool. Our method helps clearly identify when a compression wave is a simple wave, a steady wave (shock), and when the compression wave is in transition. This affects the analysis of compression wave experiments and the resulting extraction of the high-pressure equation of state.
Three-dimensional, prestack, plane wave migration of teleseismic P-to-S converted phases: 1. Theory
Poppeliers, Christian; Pavlis, Gary L.
2003-02-01
We present the theoretical foundations for a prestack migration technique to image teleseismic P-to-S converted phases. The method builds on teleseismic P wave deconvolution, pseudostation stacking [, 1999] and on the idea of using a plane wave decomposition for imaging as introduced by [1982]. Deconvolution operators are constructed by pseudostation stacking of the array aligned to the incident P wave arrival times to produce a space-variable deconvolution operator. The resulting data are then muted to remove the deconvolved direct P wave pulse and pseudostation stacked over a grid of feasible slowness vectors. The pseudostation stack interpolates the wave field onto a regular grid along Earth's surface producing a series (one per slowness vector) of uniformly sampled three-dimensional data cubes (two space variables and time). The plane wave components can be propagated downward using a form of approximate ray tracing with a three-dimensional Earth model. This yields a series of distorted cubes topologically equivalent to the original uniformly sampled data cubes. These data volumes are summed as a weighted stack with the weights derived from an integration formula for inverse scattering based on the generalized Radon transform. This allows an image of the subsurface to be constructed on an event by event basis beneath the array. We apply this technique to data from the Lodore array that was deployed in northwestern Colorado. The results suggest the presence of a major lithospheric-scale discontinuity defined by a south dipping boundary.
Energy Technology Data Exchange (ETDEWEB)
Alshits, V.I.; Darinskii, A.N. [Russian Academy of Sciences, Moscow (Russian Federation); Radovich, A. [Kielce Technological Univ., Kielce (Poland)
1995-05-01
The specific features of acoustic wave reflection are analyzed at the interface between two hexagonal crystals with a sliding contact between them. Attention is focused on the angles of incidence corresponding to excitation of the leaky wave. The conditions supporting the existence of leaky waves are found. The expressions illustrating the behavior of plane wave transformation coefficients for reflection, refraction, and excitation of interfacial oscillations are found in analytic form. In addition, the features of nonmirror reflection are studied for a slightly diverging acoustic beam having initially a rectangular profile. The study deals with the case when the tangential projection of the {open_quotes}mean{close_quotes} wavevector for the beam is close to or coincides with the real part of the wavevector of the leaky wave. 9 refs., 10 figs.
Chefranov, Sergey; Chefranov, Alexander
2016-04-01
Linear hydrodynamic stability theory for the Hagen-Poiseuille (HP) flow yields a conclusion of infinitely large threshold Reynolds number, Re, value. This contradiction to the observation data is bypassed using assumption of the HP flow instability having hard type and possible for sufficiently high-amplitude disturbances. HP flow disturbance evolution is considered by nonlinear hydrodynamic stability theory. Similar is the case of the plane Couette (PC) flow. For the plane Poiseuille (PP) flow, linear theory just quantitatively does not agree with experimental data defining the threshold Reynolds number Re= 5772 ( S. A. Orszag, 1971), more than five-fold exceeding however the value observed, Re=1080 (S. J. Davies, C. M. White, 1928). In the present work, we show that the linear stability theory conclusions for the HP and PC on stability for any Reynolds number and evidently too high threshold Reynolds number estimate for the PP flow are related with the traditional use of the disturbance representation assuming the possibility of separation of the longitudinal (along the flow direction) variable from the other spatial variables. We show that if to refuse from this traditional form, conclusions on the linear instability for the HP and PC flows may be obtained for finite Reynolds numbers (for the HP flow, for Re>704, and for the PC flow, for Re>139). Also, we fit the linear stability theory conclusion on the PP flow to the experimental data by getting an estimate of the minimal threshold Reynolds number as Re=1040. We also get agreement of the minimal threshold Reynolds number estimate for PC with the experimental data of S. Bottin, et.al., 1997, where the laminar PC flow stability threshold is Re = 150. Rogue waves excitation mechanism in oppositely directed currents due to the PC flow linear instability is discussed. Results of the new linear hydrodynamic stability theory for the HP, PP, and PC flows are published in the following papers: 1. S.G. Chefranov, A
Ovsiyuk, E M; Red'kov, V M
2010-01-01
The aim of the article to clarify the status of Shapiro plane wave solutions of the Schr\\"odinger's equation in the frames of the well-known general method of separation of variables. To solve this task, we use the well-known cylindrical coordinates in Riemann and Lobachevsky spaces, naturally related with Euler angle-parameters. Conclusion may be drawn: the general method of separation of variables embraces the all plane wave solutions; the plane waves in Lobachevsky and Riemann space consist of a small part of the whole set of basis wave functions of Schr\\"odinger equation. In space of constant positive curvature $S_{3}$, a complex analog of horospherical coordinates of Lobachevsky space $H_{3}$ is introduced. To parameterize real space $S_{3}$, two complex coordinates $(r,z)$ must obey additional restriction in the form of the equation $r^{2} = e^{z-z^{*}} - e^{2z} $. The metrical tensor of space $S_{3}$ is expressed in terms of $(r,z)$ with additional constraint, or through pairs of conjugate variables $(...
Directory of Open Access Journals (Sweden)
T. D. Karamanos
2012-11-01
Full Text Available In this paper, a polarizability matrix retrieval method for bianisotropic metamaterials is presented. Assuming that scatterers can be modeled by electric and magnetic pointdipoles located at their centers, the induced dipole moments are analytically related to the normally incident fields, while the scattered fields are also analytically obtained for two individual cases of normal wave incidence. The latter can be combined with the incident fields, to express the desired polarizabilities, with regard to the measured or simulated scattering parameters. In this way, the polarizability matrix can be extracted by solving the resulting non-linear system of equations. The proposed technique is applied to two different split-ring resonator structures and reveals very good agreement with previously reported techniques.
Use of an adjustable hand plate in studying the perceived horizontal plane during simulated flight.
Tribukait, Arne; Eiken, Ola; Lemming, Dag; Levin, Britta
2013-07-01
Quantitative data on spatial orientation would be valuable not only in assessing the fidelity of flight simulators, but also in evaluation of spatial orientation training. In this study a manual indicator was used for recording the subjective horizontal plane during simulated flight. In a six-degrees-of-freedom hexapod hydraulic motion platform simulator, simulating an F-16 aircraft, seven fixed-wing student pilots were passively exposed to two flight sequences. The first consisted in a number of coordinated turns with visual contact with the landscape below. The visually presented roll tilt was up to a maximum 670. The second was a takeoff with a cabin pitch up of 100, whereupon external visual references were lost. The subjects continuously indicated, with the left hand on an adjustable plate, what they perceived as horizontal in roll and pitch. There were two test occasions separated by a 3-d course on spatial disorientation. Responses to changes in simulated roll were, in general, instantaneous. The indicated roll tilt was approximately 30% of the visually presented roll. There was a considerable interindividual variability. However, for the roll response there was a correlation between the two occasions. The amplitude of the response to the pitch up of the cabin was approximately 75%; the response decayed much more slowly than the stimulus. With a manual indicator for recording the subjective horizontal plane, individual characteristics in the response to visual tilt stimuli may be detected, suggesting a potential for evaluation of simulation algorithms or training programs.
Park, D H; Pagán, V R; Murphy, T E; Luo, J; Jen, A K-Y; Herman, W N
2015-04-06
We report in-plane slotted patch antenna-coupled electro-optic phase modulators with a carrier-to-sideband ratio (CSR) of 22 dB under an RF power density of 120 W/m(2) and a figure of merit of 2.0 W(-1/2) at the millimeter wave frequencies of 36-37 GHz based on guest-host type of second-order nonlinear polymer SEO125. CSR was improved more than 20 dB by using a SiO(2) protection layer. We demonstrate detection of 3 GHz modulation of the RF carrier. We also derive closed-form expressions for the modulated phase of optical wave and carrier-to-sideband ratio. Design, simulation, fabrication, and experimental results are discussed.
NUMERICAL SIMULATION OF SOLITARY WAVE RUN-UP AND OVERTOPPING USING BOUSSINESQ-TYPE MODEL
Institute of Scientific and Technical Information of China (English)
TSUNG Wen-Shuo; HSIAO Shih-Chun; LIN Ting-Chieh
2012-01-01
In this article,the use of a high-order Boussinesq-type model and sets of laboratory experiments in a large scale flume of breaking solitary waves climbing up slopes with two inclinations are presented to study the shoreline behavior of breaking and non-breaking solitary waves on plane slopes.The scale effect on run-up height is briefly discussed.The model simulation capability is well validated against the available laboratory data and present experiments.Then,serial numerical tests are conducted to study the shoreline motion correlated with the effects of beach slope and wave nonlinearity for breaking and non-breaking waves.The empirical formula proposed by Hsiao et al.for predicting the maximum run-up height of a breaking solitary wave on plane slopes with a wide range of slope inclinations is confirmed to be cautious.Furthermore,solitary waves impacting and overtopping an impermeable sloping seawall at various water depths are investigated.Laboratory data of run-up height,shoreline motion,free surface elevation and overtopping discharge are presented.Comparisons of run-up,run-down,shoreline trajectory and wave overtopping discharge are made.A fairly good agreement is seen between numerical results and experimental data.It elucidates that the present depth-integrated model can be used as an efficient tool for predicting a wide spectrum of coastal problems.
Kinetic Monte Carlo simulations of GaN homoepitaxy on c- and m-plane surfaces
Xu, Dongwei; Zapol, Peter; Stephenson, G. Brian; Thompson, Carol
2017-04-01
The surface orientation can have profound effects on the atomic-scale processes of crystal growth and is essential to such technologies as GaN-based light-emitting diodes and high-power electronics. We investigate the dependence of homoepitaxial growth mechanisms on the surface orientation of a hexagonal crystal using kinetic Monte Carlo simulations. To model GaN metal-organic vapor phase epitaxy, in which N species are supplied in excess, only Ga atoms on a hexagonal close-packed (HCP) lattice are considered. The results are thus potentially applicable to any HCP material. Growth behaviors on c-plane (0001) and m-plane (01 1 ¯ 0 ) surfaces are compared. We present a reciprocal space analysis of the surface morphology, which allows extraction of growth mode boundaries and direct comparison with surface X-ray diffraction experiments. For each orientation, we map the boundaries between 3-dimensional, layer-by-layer, and step flow growth modes as a function of temperature and growth rate. Two models for surface diffusion are used, which produce different effective Ehrlich-Schwoebel step-edge barriers and different adatom diffusion anisotropies on m-plane surfaces. Simulation results in agreement with observed GaN island morphologies and growth mode boundaries are obtained. These indicate that anisotropy of step edge energy, rather than adatom diffusion, is responsible for the elongated islands observed on m-plane surfaces. Island nucleation spacing obeys a power-law dependence on growth rate, with exponents of -0.24 and -0.29 for the m- and c-plane, respectively.
Wagner, L. S.; Forsyth, D. W.; Fouch, M. J.; James, D. E.
2009-12-01
The High Lava Plains (HLP) of eastern Oregon represent an unusual track of bimodal volcanism extending from the southeastern-most corner of the state to its current position beneath the Newberry Volcano on the eastern margin of the Cascades. The silicic volcanism is time progressive along this track, beginning some 15 Ma near the Owyhee plateau and then trending to the north east. The timing and location of the start of the HLP coincides with that of the initial volcanism associated with the Yellowstone/Snake River Plain track (YSRP). While the YSRP has often been interpreted as the classic intra-continental hot spot track, the HLP, which trends almost normal to absolute plate motion, is harder to explain. This study uses the 100+ stations associated with the HLP seismic deployment together with another ~100 Earthscope Transportable Array stations (TA) to perform a high resolution inversion for Rayleigh wave phase velocities using the 2-plane-wave methodology of Forsyth and Li (2004). Because of the comparatively small grid spacing of this study, we are able to discern much finer scale structures than studies looking at the entire western U.S. with only TA stations. Preliminary results indicate very low velocities across the study area, especially at upper mantle depths. Especially low velocities are seen beneath the Owyhee plateau and along both the HLP and YSRP tracks. Final details about the exact geometries of these features will help constrain possible scenarios for the formation of the HLP volcanic sequence.
Gao, Jing Kun; Qin, Yu Liang; Deng, Bin; Wang, Hong Qiang; Li, Jin; Li, Xiang
2016-04-01
This paper presents two parts of work around terahertz imaging applications. The first part aims at solving the problems occurred with the increasing of the rotation angle. To compensate for the nonlinearity of terahertz radar systems, a calibration signal acquired from a bright target is always used. Generally, this compensation inserts an extra linear phase term in the intermediate frequency (IF) echo signal which is not expected in large-rotation angle imaging applications. We carried out a detailed theoretical analysis on this problem, and a minimum entropy criterion was employed to estimate and compensate for the linear-phase errors. In the second part, the effects of spherical wave on terahertz inverse synthetic aperture imaging are analyzed. Analytic criteria of plane-wave approximation were derived in the cases of different rotation angles. Experimental results of corner reflectors and an aircraft model based on a 330-GHz linear frequency-modulated continuous wave (LFMCW) radar system validated the necessity and effectiveness of the proposed compensation. By comparing the experimental images obtained under plane-wave assumption and spherical-wave correction, it also showed to be highly consistent with the analytic criteria we derived.
Zhang, Baile; Wu, Bae-Ian; Chen, Hongsheng; Kong, Jin Au
2008-08-08
We demonstrate some interesting phenomena associated with a nonmonochromatic plane wave passing through a spherical invisibility cloak whose radial permittivity and permeability are of Drude and Lorentz types. We observe that the frequency center of a quasimonochromatic incident wave will suffer a blueshift in the forward scattering direction. Different frequency components have different depths of penetration, causing a rainbowlike effect within the cloak. The concept of group velocity at the inner boundary of the cloak needs to be revisited. Extremely low scattering can still be achieved within a narrow band.
Institute of Scientific and Technical Information of China (English)
FengYangde; WangYuesheng; ZhangZimao; CuiJunzhi
2003-01-01
A 2D time domain boundary element method (BEM) is developed to solve the transient scattering of plane waves by a unilaterally frictionally constrained inclusion. Coulomb friction is assumed along the contact interface. The incident wave is assumed strong enough so that localized slip and separation take place along the interface. The present problem is in effect a nonlinear boundary value problem since the mixed boundary conditions involve unknown intervals (slip, separation and stick regions). In order to determine the unknown intervals, an iterative technique is developed. As an example, we consider the scattering of a circular cylinder embeddedin an infinite solid.
Li, Xiang-Guo; Zhang, X -G; Cheng, Hai-Ping
2015-01-01
Electron transport in graphene is along the sheet but junction devices are often made by stacking different sheets together in a "side-contact" geometry which causes the current to flow perpendicular to the sheets within the device. Such geometry presents a challenge to first-principles transport methods. We solve this problem by implementing a plane-wave based multiple scattering theory for electron transport. This implementation improves the computational efficiency over the existing plane-wave transport code, scales better for parallelization over large number of nodes, and does not require the current direction to be along a lattice axis. As a first application, we calculate the tunneling current through a side-contact graphene junction formed by two separate graphene sheets with the edges overlapping each other. We find that transport properties of this junction depend strongly on the AA or AB stacking within the overlapping region as well as the vacuum gap between two graphene sheets. Such transport beh...
Hu, Min; Wang, Hailong; Gong, Qian; Wang, Shumin
2017-04-01
A comparison is made between the plane wave basis and variational method. Within the framework of effective-mass approximation theory, the variational and plane wave basis method are used to calculate ground state energy and ground state binding energy in low-dimensional nano-structures under the external electric field. Comparing calculation results, the donor binding energies of ground state display the consistent trend, both of them are strongly dependent on the quantum size, impurity position and external electric field. However, the impurity ground state energy calculated using variational method may be larger than the real value and it results in the smaller binding energy for variational method. In addition, the binding energy is more sensitive to the external electric field for the variational method, which can be seen more clearly from Stark shift.
Numerical simulation and mechanism analysis of freak waves
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A numerical wave model based on the modified fourth-order nonlinear Schroe dinger equation (mNLSE) in deep water was developed to simulate the formation of freak waves and a standard split-step, pseudo-spectral method was used to solve the equation. The validation of the model is firstly verified, then the simulation of freak waves was performed by changing sideband conditions, and the variation of wave energy was also analyzed in the evolution. The results indicate that Benjamin-Feir instability (sideband instability) is an important mechanism for freak wave formation.
Institute of Scientific and Technical Information of China (English)
Li Ying-Le; Huang Ji-Ying
2006-01-01
The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications.
Determination of the in-plane components of motion in a Lamb wave from single-axis laser vibrometry.
Rajic, Nik; Rosalie, Cedric; Norman, Patrick; Davis, Claire
2014-06-01
A method is proposed for determining in-plane components of motion in a Lamb wave from laser vibrometer measurements of surface motion out of plane. The approach relies on a frequency domain transformation that assumes knowledge only of the plate thickness and the bulk wave speeds. An outline of the relevant theory is followed by several validation case studies that generally affirm a useful level of accuracy and robust performance across a relatively wide frequency-thickness product range. In a comparison to the two-angle vibrometry approach, the proposed method is shown to be simpler to implement and to yield estimates with a consistently higher signal to noise ratio. The approach is then used to furnish estimates of the in-plane strains in Lamb waves propagating in an aluminum plate at frequencies below the first cut-off. These estimates are compared to strain measurements obtained from an adhesively bonded fiber Bragg grating. The agreement is shown to be excellent overall with an average discrepancy of less than 6%; however, systematic errors of twice that amount were recorded in the low-frequency-thickness product regime. These low-frequency discrepancies are not consistent with known sources of experimental error and cannot be explained by shear-lag theory.
Charakhch'yan, Alexander A
2014-01-01
The one-dimensional (1D) problem on bilatiral irradiation by proton beams of the plane layer of condensed DT mixture with length $2H$ and density $\\rho_0 \\leqslant 100\\rho_s$, where $\\rho_s$ is the fuel solid-state density at atmospheric pressure and temperature of 4 K, is considered. The proton kinetic energy is 1 MeV, the beam intensity is $10^{19}$ W/cm$^2$ and duration is 50 ps. A mathematical model is based on the one-fluid two-temperature hydrodynamics with a wide-range equation of state of the fuel, electron and ion heat conduction, DT fusion reaction kinetics, self-radiation of plasma and plasma heating by alpha-particles. If the ignition occurs, a plane detonation wave, which is adjacent to the front of the rarefaction wave, appears. Upon reflection of this detonation wave from the symmetry plane, the flow with the linear velocity profile along the spatial variable $x$ and with a weak dependence of the thermodynamic functions of $x$ occurs. An appropriate solution of the equations of hydrodynamics is...
Mei, Jun; Liu, Zhengyou; Qiu, Chunyin
2005-06-29
We extend the multiple-scattering theory (MST) to out-of-plane propagating elastic waves in 2D periodical composites by taking into account the full vector character. The formalism for both the band structure calculation and the reflection and transmission coefficient calculation for finite slabs is presented. The latter is based on a double-layer scheme, which obtains the reflection and transmission matrix elements for the multilayer slab from those of a single layer. Being more rapid in both the band structure and the transmission coefficient calculations for out-of-plane propagating elastic waves, our approach especially shows great advantages in handling the systems with mixed solid and fluid components, for which the conventional plane wave approach fails. As the applications of the formalism, we calculate the band structure as well as the transmission coefficients through finite slabs for systems with lead rods in an epoxy host, steel rods in a water host and water rods in a PMMA host.
Three-Dimensional Simulations of Deep-Water Breaking Waves
Brucker, Kyle A; Dommermuth, Douglas G; Adams, Paul
2014-01-01
The formulation of a canonical deep-water breaking wave problem is introduced, and the results of a set of three-dimensional numerical simulations for deep-water breaking waves are presented. In this paper fully nonlinear progressive waves are generated by applying a normal stress to the free surface. Precise control of the forcing allows for a systematic study of four types of deep-water breaking waves, characterized herein as weak plunging, plunging, strong plunging, and very strong plunging.
An IBEM solution to the scattering of plane SH-waves by a lined tunnel in elastic wedge space
Institute of Scientific and Technical Information of China (English)
Zhongxian Liu; Lei Liu
2015-01-01
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.
Computational simulation of wave propagation problems in infinite domains
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper deals with the computational simulation of both scalar wave and vector wave propagation problems in infinite domains. Due to its advantages in simulating complicated geometry and complex material properties, the finite element method is used to simulate the near field of a wave propagation problem involving an infinite domain. To avoid wave reflection and refraction at the common boundary between the near field and the far field of an infinite domain, we have to use some special treatments to this boundary. For a wave radiation problem, a wave absorbing boundary can be applied to the common boundary between the near field and the far field of an infinite domain, while for a wave scattering problem, the dynamic infinite element can be used to propagate the incident wave from the near field to the far field of the infinite domain. For the sake of illustrating how these two different approaches are used to simulate the effect of the far field, a mathematical expression for a wave absorbing boundary of high-order accuracy is derived from a two-dimensional scalar wave radiation problem in an infinite domain, while the detailed mathematical formulation of the dynamic infinite element is derived from a two-dimensional vector wave scattering problem in an infinite domain. Finally, the coupled method of finite elements and dynamic infinite elements is used to investigate the effects of topographical conditions on the free field motion along the surface of a canyon.
Energy Technology Data Exchange (ETDEWEB)
Gillet, N.; Ocvirk, P.; Aubert, D. [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de lUniversité, F-67000 Strasbourg (France); Knebe, A.; Yepes, G. [Departamento de Física Teórica, Módulo, Universidad Autónomade Madrid, Cantoblanco E-28049 (Spain); Libeskind, N.; Gottlöber, S. [Leibniz-Institute für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Hoffman, Y. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)
2015-02-10
We search for vast planes of satellites (VPoS) in a high-resolution simulation of the Local Group performed by the CLUES project, which improves significantly the resolution of previous similar studies. We use a simple method for detecting planar configurations of satellites, and validate it on the known plane of M31. We implement a range of prescriptions for modeling the satellite populations, roughly reproducing the variety of recipes used in the literature, and investigate the occurrence and properties of planar structures in these populations. The structure of the simulated satellite systems is strongly non-random and contains planes of satellites, predominantly co-rotating, with, in some cases, sizes comparable to the plane observed in M31 by Ibata et al. However, the latter is slightly richer in satellites, slightly thinner, and has stronger co-rotation, which makes it stand out as overall more exceptional than the simulated planes, when compared to a random population. Although the simulated planes we find are generally dominated by one real structure forming its backbone, they are also partly fortuitous and are thus not kinematically coherent structures as a whole. Provided that the simulated and observed planes of satellites are indeed of the same nature, our results suggest that the VPoS of M31 is not a coherent disk and that one-third to one-half of its satellites must have large proper motions perpendicular to the plane.
Explaining Electromagnetic Plane Waves in a Vacuum at the Introductory Level
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…
Stress wave velocity patterns in the longitudinal-radial plane of trees for defect diagnosis
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 longitudinalâ...
Explaining Electromagnetic Plane Waves in a Vacuum at the Introductory Level
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…
Theoretical and Experimental Study of Scattering of a Plane Wave by an Inhomogeneous Plasma Sphere
Institute of Scientific and Technical Information of China (English)
SONG Fa-Lun; CAO Jin-Xiang; WANG Ge; WANG Yan; ZHU Ying; ZHU Jian; WANG Liang; NIU Tian-Ye
2006-01-01
@@ Scattering of electromagnetic waves by an inhomogeneous plasma sphere has been studied theoretically and experimentally. The offset angles of electromagnetic waves caused by the plasma sphere have been observed experimentally. The effects of the electromagnetic wave frequency and plasma density on the offset angle are discussed. The plasma density is estimated with the offset angle.
Research on fast rise time EMP radiating-wave simulator
Fan, Lisi; Liu, Haitao; Wang, Yun
2013-03-01
This paper presents an antenna of High altitude electromagnetic pulse (HEMP) radiating-wave simulator which expands the testing zone larger than the traditional transmission line simulator. The numerical results show that traverse electramagnetic (TEM) antenna can be used to radiate HEMP simulation radiating wave, but in low frequency band the emissive capability is poor. The experiment proves the numerical model is valid. The results of this paper show that TEM antenna can be used to HEMP radiating-wave simulator, and can prove the low frequency radiation capability through resistance loaded method.
Global Simulation of Electromagnetic Ion Cyclotron Waves
Khazanov, George V.; Gallagher, D. L.; Kozyra, J. U.
2007-01-01
It is very well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis of modern
Multiple scattering of polarized light in turbid infinite planes: Monte Carlo simulations.
Otsuki, Soichi
2016-05-01
Monte Carlo simulations were performed for infinite plane media containing spherical particles of different sizes. Most of the features of the surface plots for the elements of the effective scattering Mueller matrices are explained by the azimuthal dependence of the matrix predicted according to the theory of Raković et al. [Appl. Opt.38, 3399 (1999)10.1364/AO.38.003399APOPAI1559-128X]. The reduced effective scattering Mueller matrices calculated according to the theory have eight nonzero elements, which are only dependent on the distance from the illumination point. The reduced matrices are factorized approximately into products of a depolarizer and retarding diattenuators. The turbid infinite plane media nearly behave as a pure depolarizer at long distances and become more diattenuating and birefringent with decreasing distance.
Numerical Simulation of Wave Height and Wave Set-Up in Nearshore Regions
Institute of Scientific and Technical Information of China (English)
郑永红; 沈永明; 邱大洪
2001-01-01
Based on the time dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation, and then a practical method for the simulation of wave height and wave set-up in nearshore regions is presented. The variation of the complex wave amplitude is numerically simulated by use of the parabolic mild slope equation including the effect of wave energy dissipation due to wave breaking. The components of wave radiation stress are calculated subsequently by new expressions for them according to the obtained complex wave amplitude, and then the depth-averaged equation is applied to the calculation of wave set-up due to wave breaking. Numerical results are in good agreement with experimental data,showing that the expression for the energy dissipation factor is reasonable and that the new method is effective for the simulation of wave set-up due to wave breaking in nearshore regions.
Numerical Simulation of a Negative Impulsive Wave
Institute of Scientific and Technical Information of China (English)
ToshiakiSETOGUCHI; ShenYU; 等
1996-01-01
A compression wave discharged from an open end of a tube causes positive impulsive noise,Active noise cancellation which is the cancelling of the noise by the addition of an inverse wave is a useful technique for reducing impulsive noise,The main objective of this study is to present the design for a negative impulsive wave generator utilizing unsteady mass influx.In this paper,in order to clarify the relationship between the unsteady mass influx and the negative impulsive wave,numerical and aeroacoustic analyses have been carried out using an unsteady expansion wave discharged from an open end of a shock tube.As a result,the effect of an unsteady expansion wave on a negative impulsive wave was charified.
Olano, C. A.
2009-11-01
Context: Using certain simplifications, Kompaneets derived a partial differential equation that states the local geometrical and kinematical conditions that each surface element of a shock wave, created by a point blast in a stratified gaseous medium, must satisfy. Kompaneets could solve his equation analytically for the case of a wave propagating in an exponentially stratified medium, obtaining the form of the shock front at progressive evolutionary stages. Complete analytical solutions of the Kompaneets equation for shock wave motion in further plane-parallel stratified media were not found, except for radially stratified media. Aims: We aim to analytically solve the Kompaneets equation for the motion of a shock wave in different plane-parallel stratified media that can reflect a wide variety of astrophysical contexts. We were particularly interested in solving the Kompaneets equation for a strong explosion in the interstellar medium of the Galactic disk, in which, due to intense winds and explosions of stars, gigantic gaseous structures known as superbubbles and supershells are formed. Methods: Using the Kompaneets approximation, we derived a pair of equations that we call adapted Kompaneets equations, that govern the propagation of a shock wave in a stratified medium and that permit us to obtain solutions in parametric form. The solutions provided by the system of adapted Kompaneets equations are equivalent to those of the Kompaneets equation. We solved the adapted Kompaneets equations for shock wave propagation in a generic stratified medium by means of a power-series method. Results: Using the series solution for a shock wave in a generic medium, we obtained the series solutions for four specific media whose respective density distributions in the direction perpendicular to the stratification plane are of an exponential, power-law type (one with exponent k=-1 and the other with k =-2) and a quadratic hyperbolic-secant. From these series solutions, we deduced
Blanco, Joaquín. E.; Nolan, David S.; Tulich, Stefan N.
2016-10-01
Convectively coupled Kelvin waves (CCKWs) represent a significant contribution to the total variability of the Intertropical Convergence Zone (ITCZ). This study analyzes the structure and propagation of CCKWs simulated by the Weather Research and Forecasting (WRF) model using two types of idealized domains. These are the "aquachannel," a flat rectangle on a beta plane with zonally periodic boundary conditions and length equal to the Earth's circumference at the equator, and the "aquapatch," a square domain with zonal extent equal to one third of the aquachannel's length. A series of simulations are performed, including a doubly nested aquapatch, in which convection is solved explicitly along the equator. The model intercomparison is carried out throughout the use of several techniques such as power spectra, filtering, wave tracking, and compositing, and it is extended to some simulations from the Aquaplanet Experiment (APE). Results show that despite the equatorial superrotation bias produced by the WRF simulations, the CCKWs simulated with this model propagate with similar phase speeds (relative to the low-level mean flow) as the corresponding waves from the APE simulations. Horizontal and vertical structures of the CCKWs simulated with aquachannels are also in overall good agreement with those from aquaplanet simulations and observations, although there is a distortion of the zonal extent of anomalies when the shorter aquapatch is used.
A 1D time-domain method for in-plane wave motions in a layered half-space
Institute of Scientific and Technical Information of China (English)
Jingbo Liu; Yan Wang
2007-01-01
A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the layered half-space is discretized on the basis of the propagation cha-racteristic of elastic wave according to the Snell law. Then, the finite element method with lumped mass and the cen-tral difference method are incorporated to establish 2D wave motion equations, which can be transformed into 1D equa-tions by discretization principle and explicit finite element method. By solving the 1D equations, the displacements of nodes in any vertical line can be obtained, and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave. Both the theoretical ana-lysis and the numerical results demonstrate that the proposed method has high accuracy and good stability.
Shepherd, James J; Booth, George H; Kresse, Georg; Alavi, Ali
2012-01-01
Using the finite simulation-cell homogeneous electron gas (HEG) as a model, we investigate the convergence of the correlation energy to the complete basis set (CBS) limit in methods utilising plane-wave wavefunction expansions. Simple analytic and numerical results from second-order M{\\o}ller-Plesset theory (MP2) suggest a 1/M decay of the basis-set incompleteness error where M is the number of plane waves used in the calculation, allowing for straightforward extrapolation to the CBS limit. As we shall show, the choice of basis set truncation when constructing many-electron wavefunctions is far from obvious, and here we propose several alternatives based on the momentum transfer vector, which greatly improve the rate of convergence. This is demonstrated for a variety of wavefunction methods, from MP2 to coupled-cluster doubles theory (CCD) and the random-phase approximation plus second-order screened exchange (RPA+SOSEX). Finite basis-set energies are presented for these methods and compared with exact benchm...
Simulation of Wave Overtopping of Maritime Structures in a Numerical Wave Flume
Directory of Open Access Journals (Sweden)
Tiago C. A. Oliveira
2012-01-01
Full Text Available A numerical wave flume based on the particle finite element method (PFEM is applied to simulate wave overtopping for impermeable maritime structures. An assessment of the performance and robustness of the numerical wave flume is carried out for two different cases comparing numerical results with experimental data. In the first case, a well-defined benchmark test of a simple low-crested structure overtopped by regular nonbreaking waves is presented, tested in the lab, and simulated in the numerical wave flume. In the second case, state-of-the-art physical experiments of a trapezoidal structure placed on a sloping beach overtopped by regular breaking waves are simulated in the numerical wave flume. For both cases, main overtopping events are well detected by the numerical wave flume. However, nonlinear processes controlling the tests proposed, such as nonlinear wave generation, energy losses along the wave propagation track, wave reflection, and overtopping events, are reproduced with more accuracy in the first case. Results indicate that a numerical wave flume based on the PFEM can be applied as an efficient tool to supplement physical models, semiempirical formulations, and other numerical techniques to deal with overtopping of maritime structures.
Stochastic stresses in granular matter simulated by dripping identical ellipses into plane silo
DEFF Research Database (Denmark)
Berntsen, Kasper Nikolaj; Ditlevsen, Ove Dalager
2000-01-01
A two-dimensional silo pressure model-problem is investigated by molecular dynamics simulations. A plane silo container is filled by a granular matter consisting of congruent elliptic particles dropped one by one into the silo. A suitable energy absorbing contact force mechanism is activatedduring...... the granular matter in the silo are compared to thesolution of a stochastic equilibrium differential equation. In this equation the stochasticity source is a homogeneouswhite noise gamma-distributed side pressure factor field along the walls. This is a generalization of the deterministic side pressure factor...
Monte Carlo simulations of fluid vesicles with in-plane orientational ordering.
Ramakrishnan, N; Sunil Kumar, P B; Ipsen, John H
2010-04-01
We present a method for simulating fluid vesicles with in-plane orientational ordering. The method involves computation of local curvature tensor and parallel transport of the orientational field on a randomly triangulated surface. It is shown that the model reproduces the known equilibrium conformation of fluid membranes and work well for a large range of bending rigidities. Introduction of nematic ordering leads to stiffening of the membrane. Nematic ordering can also result in anisotropic rigidity on the surface leading to formation of membrane tubes.
Corrected Formula of Bed Resistance Coefficient for Plane Numerical Simulation of Tidal Current
Institute of Scientific and Technical Information of China (English)
宋志尧; 刘一凡
2000-01-01
By means of a logarithm law for the velocity profile, a corrected formula of bed resistance coefficient, which involves many factors such as gradient of still water depth, variation of surface elevation, flow direction, and so on, is derived from the 3D governing equations of tidal current by averaging over the whole water depth. Theoretical analysis and application have shown that the 2D plane tidal current numerical model would be more reasonable and could be applied to steep bottom topography when the corrected bed resistance coefficient is used, therefore the results of reproduction simulation and engineering calculation would be more scientific and reasonable.
Monte Carlo simulations of fluid vesicles with in plane orientational ordering
Ramakrishnan, N; Ipsen, John H
2010-01-01
We present a method for simulating fluid vesicles with in-plane orientational ordering. The method involves computation of local curvature tensor and parallel transport of the orientational field on a randomly triangulated surface. It is shown that the model reproduces the known equilibrium conformation of fluid membranes and work well for a large range of bending rigidities. Introduction of nematic ordering leads to stiffening of the membrane. Nematic ordering can also result in anisotropic rigidity on the surface leading to formation of membrane tubes.
Coupling atmospheric and ocean wave models for storm simulation
DEFF Research Database (Denmark)
Du, Jianting
This thesis studies the wind-wave interactions through the coupling between the atmospheric model and ocean surface wave models. Special attention is put on storm simulations in the North Sea for wind energy applications in the coastal zones. The two aspects, namely storm conditions and coastal...... areas, are challenging for the wind-wave coupling system because: in storm cases, the wave field is constantly modified by the fast varying wind field; in coastal zones, the wave field is strongly influenced by the bathymetry and currents. Both conditions have complex, unsteady sea state varying...... with time and space that challenge the current coupled modeling system. The conventional approach of estimating the momentum exchange is through parameterizing the aerodynamic roughness length (z0) with wave parameters such as wave age, steepness, significant wave height, etc. However, it is found in storm...
Barbosa, Filipe J.; Skews, Beric W.
1997-05-01
Double exposure holographic interferometry and high speed laser shadowgraph photography and videography are used to investigate the mutual reflection of two plane shock waves. Normally research on the transition from regular to Mach reflection is undertaken by allowing a plane shock wave to impinge on a wedge. However due to the boundary layer growth on the wedge, regular reflection persists at wedge angles higher than that allowed for by inviscid shock wave theory. Several bifurcated shock tubes have been constructed, wherein an initially planar shock wave is split symmetrically into two and then recombined at the trailing edge of a wedge. The plane of symmetry acts as an ideal rigid wall eliminating thermal and viscous boundary layer effects. The flow visualization system used needs to provide high resolution information on the shockwave, slipstream, triple point and vortex positions and angles. Initially shadowgraph and schlieren methods, with a Xenon light source, were used. These results, while proving useful, are not of a sufficient resolution to measure the Mach stem and slipstream lengths accurately enough in order to determine the transition point between regular and Mach reflection. To obtain the required image resolution a 2 joule double pulse ruby laser, with a 30 ns pulse duration, was used to make holographic interferograms. The combined advantages of holographic interferometry and the 30 ns pulse laser allows one to obtain much sharper definition, and more qualitative as well as quantitative information on the flow field. The disadvantages of this system are: the long time taken to develop holograms, the difficulty of aligning the pulse laser and the fact that only one image per test is obtained. Direct contact shadowgraphs were also obtained using the pulse ruby laser to help determine triple point trajectory angles. In order to provide further information a one million frames per second CCD camera, which can take up to 10 superimposed images, was
The fundamental plane of star formation in galaxies revealed by the EAGLE hydrodynamical simulations
Lagos, Claudia del P; Schaye, Joop; Furlong, Michelle; Bower, Richard G; Schaller, Matthieu; Crain, Robert A; Trayford, James W; Matthee, Jorryt
2015-01-01
We investigate correlations between different physical properties of star-forming galaxies in the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) cosmological hydrodynamical simulation suite over the redshift range $0\\le z\\le 4.5$. A principal component analysis reveals that neutral gas fraction ($f_{\\rm gas, neutral}$), stellar mass ($M_{\\rm stellar}$) and star formation rate (SFR) account for most of the variance seen in the population, with galaxies tracing a two-dimensional, nearly flat, surface in the three-dimensional space of $f_{\\rm gas, neutral}-M_{\\rm stellar}-\\rm SFR$ with little scatter. The location of this plane varies little with redshift, whereas galaxies themselves move along the plane as their $f_{\\rm gas, neutral}$ and SFR drop with redshift. The positions of galaxies along the plane are highly correlated with gas metallicity. The metallicity can therefore be robustly predicted from $f_{\\rm gas, neutral}$, or from the $M_{\\rm stellar}$ and SFR. We argue that the appearan...
Westerveld, W.J.; Urbach, H.P.; Yousefi, M.
2011-01-01
We present an accurate and fast 3-D simulation scheme for out-of-plane grating couplers, based on 2-D rigorous [finite difference time domain (FDTD)] grating simulations, the effective index method, and the RayleighSommerfeld diffraction formula. In comparison with full 3-D FDTD simulations, the rms
NUMERICAL SIMULATIONS OF NONLINEAR WAVE TRANSFORMATION AROUND WAVE-PERMEABLE STRUCTURE
Institute of Scientific and Technical Information of China (English)
Li Xi; YAN Yi-xin
2005-01-01
The problem of wave partial/full reflection and transmission by wave-permeable structure is approached by solving the shape-related function with focus on the understanding of wave attenuation.2D depth-averaged Boussinesq type wave equations are given with new damping item in simulating the nonlinear wave transmission through wave-permeable structure.1D wave equation is examined to give the analytical expression of the absorbing coefficient, and is compared with laboratory data in flume to calibrate the coefficients, and the expression is applied directly in modified Boussinesq type equations.Compared with wave basin data for various incident wave conditions,the accurate predictions of combined diffraction-refraction effects in simulating nonlinear wave going through wave-permeable breakwater in the engineering application can be obtained.It shows that wave-permeable breakwaters with proper absorbing effects can be used as an effective alternative to massive gravity breakwaters in reduction of wave transmission in shallow water.
Energy Technology Data Exchange (ETDEWEB)
Hou Zhilin [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)], E-mail: zhilin.hou@lpmi.uhp-nancy.fr; Assouar, Badreddine M. [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)
2008-03-17
We show that the conversional three-dimensional plane wave expansion method can be revised to investigate the lamb wave propagation in the plate with two-dimensional phononic crystal layer coated on uniform substrate. We find that an imaginary three-dimensional periodic system can be constructed by stacking the studied plates and vacuum layers alternately, and then the Fourier series expansion can be performed. The difference between our imaginary periodic system and the true three-dimensional one is that, in our system, the Bloch feature of the wave along the thickness direction is broken. Three different systems are investigated by the proposed method as examples. The principle and reliability of the method are also discussed.
Numerical Simulation of Waves Generated by Seafloor Movements
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Waves generated by vertical seafloor movements are simulated by use of a fully nonlinear two-dimensional numerical wave tank. In the source region, the seafloor lifts to a designated height by a generation function. The numerical tests show that the linear theory is only valid for estimating the wave behaviors induced by the seafloor movements with a small amplitude, and the fully nonlinear numerical model should be adopted in the simulation of the wave generation by the large amplitude seafloor movements. Without the background surface waves, many numerical tests on the stable maximum elevations ηmax0 are carried out by both the linear theory and the fully nonlinear model. The results of two models are compared and analyzed. For the fully nonlinear model, the influences of the amplitudes and the horizontal lengths on ηmax0 are stronger than that of the characteristic duration times. Furthermore, results reveal that there are significant differences between the linear theory and the fully nonlinear model. When the influences of the background surface waves are considered, the corresponding numerical analyses reveal that with the fully nonlinear model the ηmax0 near-linearly varies with the wave amplitudes of the surface waves, and the ηmax0 has significant depndences on the wave lengths and the wave phases of the surface waves. In addition, the differences between the linear theory and the fully nonlinear model are still obvious, and these differences are significantly affected by the wave parameters of the background surface waves, such as the wave amplitude, the wave length and the wave phase.
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 Θ_{c} 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 Θ_{c}~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.
Khurana, Aarti; Tomar, S. K.
2008-04-01
Reflection and transmission phenomena of a plane longitudinal displacement wave impinging obliquely at a plane interface between a micropolar elastic solid half-space and a chiral elastic solid half-space are investigated. The incident wave is assumed to be striking at the plane interface after propagating through the micropolar elastic solid half-space. The reflection and transmission coefficients are obtained by utilizing two possible sets of boundary conditions, for a specific model and there values corresponding to two boundary conditions are also compared graphically. The effect of chirality parameter on various reflection and transmission coefficients have been noticed and shown graphically. Results of Lakhtakia et al. [Reflection of elastic plane waves at a planar achiral-chiral interface, Journal of the Acoustical Society of America 87 (1990) 2314-2318] and Miklowitz [The Theory of Elastic Waves and Waveguides, North-Holland, New York, 1978] have also been reduced as special cases from the present formulation.
Hsu, Jin-Chen; Wu, Tsung-Tsong
2008-02-01
Based on Mindlin's piezoelectric plate theory and the plane wave expansion method, a formulation is proposed to study the frequency band gaps and dispersion relations of the lower-order Lamb waves in two-dimensional piezoelectric phononic plates. The method is applied to analyze the phononic plates composed of solid-solid and airsolid constituents with square and triangular lattices, respectively. Factors that influence the opening and width of the complete Lamb wave gaps are identified and discussed. For solid/solid phononic plates, it is suggested that the filling material be chosen with larger mass density, proper stiffness, and weak anisotropic factor embedded in a soft matrix in order to obtain wider complete band gaps of the lower-order Lamb waves. By comparing to the calculated results without considering the piezoelectricity, the influences of piezoelectric effect on Lamb waves are analyzed as well. On the other hand, for air/solid phononic plates, a background material itself with proper anisotropy and a high filling fraction of air may favor the opening of the complete Lamb wave gaps.
Numerical simulation of converging shock waves
Yee, Seokjune; Abe, Kanji
We can achieve the high pressure and high temperature state of gas if the shock wave converges stably. In order to check the stability of the converging shock wave, we introduce two kinds of perturbed initial conditions. The Euler equations of conservation form are integrated by using explicit Non-Muscl TVD finite difference scheme.
Numerical modeling of extended short wave infrared InGaAs focal plane arrays
Glasmann, Andreu; Wen, Hanqing; Bellotti, Enrico
2016-05-01
Indium gallium arsenide (In1-xGaxAs) is an ideal material choice for short wave infrared (SWIR) imaging due to its low dark current and excellent collection efficiency. By increasing the indium composition from 53% to 83%, it is possible to decrease the energy gap from 0.74 eV to 0.47 eV and consequently increase the cutoff wavelength from 1.7 μm to 2.63 μm for extended short wavelength (ESWIR) sensing. In this work, we apply our well-established numerical modeling methodology to the ESWIR InGaAs system to determine the intrinsic performance of pixel detectors. Furthermore, we investigate the effects of different buffer/cap materials. To accomplish this, we have developed composition-dependent models for In1-xGaxAs, In1-xAlxAs, and InAs1-y Py. Using a Green's function formalism, we calculate the intrinsic recombination coefficients (Auger, radiative) to model the diffusion-limited behavior of the absorbing layer under ideal conditions. Our simulations indicate that, for a given total thickness of the buffer and absorbing layer, structures utilizing a linearly graded small-gap InGaAs buffer will produce two orders of magnitude more dark current than those with a wide gap, such as InAlAs or InAsP. Furthermore, when compared with experimental results for ESWIR photodiodes and arrays, we estimate that there is still a 1.5x magnitude of reduction in dark current before reaching diffusion-limited behavior.
Simulation of Typhoon-Driven Waves in the Yangtze Estuary with Multiple-Nested Wave Models
Institute of Scientific and Technical Information of China (English)
XU Fu-min; Will Perrie; ZHANG Jun-lun; SONG Zhi-yao; Bechara Toulany
2005-01-01
Typhoon-generated waves are simulated with two numerical wave models, the SWAN model for the coastal and Yangtze Estuary domain, nested within the WAVEWATCHIII (WW3) for the basin-scale East China Sea domain. Typhoon No. 8114 is chosen because it was very strong, and generated high waves in the Estuary. WW3 was implemented for the East China Sea coarse-resolution computational domain, to simulate the waves over a large spatial scale and provide boundary conditions for SWAN model simulations, implemented on a fine-resolution nested domain for the Yangtze Estuary area. The Takahashi wind model is applied to the simulation of the East China Sea scale (3-hourly) and Yangtze Estuary scale (1-hourly) winds. Simulations of significant wave heights in the East China Sea show that the highest waves are on the right side of the storm track, and maxima tend to occur at the eastern deep-water open boundary of the Yangtze Estuary. In the Yangtze Estuary, incoming swell is dominant over locally generated waves before the typhoon approaches the Estuary. As the typhoon approaches the Estuary, wind waves and swell coexist, and the wave direction is mainly influenced by the swell direction and the complex topography.
Possible second-order nonlinear interactions of plane waves in an elastic solid
Korneev, V.A.; Demcenko, A.
2014-01-01
There exist ten possible nonlinear elastic wave interactions for an isotropic solid described by three constants of the third order. All other possible interactions out of 54 combinations (triplets) of interacting and resulting waves are prohibited, because of restrictions of various kinds. The cons
Bogdanov, O V
2014-01-01
The relations among the components of the exit momenta of ultrarelativistic electrons scattered on a strong electromagnetic wave of a low (optical) frequency and linear polarization are established using the exact solutions to the equations of motion with radiation reaction included (the Landau-Lifshitz equation). It is found that the momentum components of the electrons traversed the electromagnetic wave depend weakly on the initial values of the momenta. These electrons are mostly scattered at the small angles to the direction of propagation of the electromagnetic wave. The maximum Lorentz factor of the electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momenta. The momentum component parallel to the electric field strength vector of the electromagnetic wave is determined only by the diameter of the laser beam measured in the units of the classical electron radius. As for the reflected electrons, they for the most part l...
A Unified Computational Method for Simulating Dynamic Behavior of Planing Vessels
Institute of Scientific and Technical Information of China (English)
Mohammad Saeed SEIF; Ebrahim JAHANBAKHSH; Roozbeh PANAHI; Mohammad Hossein KARIMI
2009-01-01
High speed planing hulls have complex hydrodynamic behaviors. The trim angle and drafts are very sensitive to speed and location of the center of gravity. Therefore, motion simulation for such vessels needs a strong coupling between rigid body motions and hydrodynamic analysis. In addition, free surface shoald be predicted with good accuracy for each time step. In this paper, velocity and pressure fields are coupled by use of the fractional step method. On the basis of in- tegration of the two-phase viscous flow induced stresses over the hull, acting loads (forces and moments) are calculated. With the strategy of boundary-fitted body-attached mesh and calculation of 6-DoF motions in each time step, time history of ship motions including displacements, speeds and accelerations are evaluated. For the demonstration of the software capabilities, circular cylinder slamming is simulated as a simple type of water slamming. Then, a high-speed planing catamaran is investigated in the case of steady forward motion. All of the results are in good concordance with experimen-tal data. The present toothed can be widely implemented in design as well as in the performance prediction of high-speed vessels.
Mathematical model of small water-plane area twin-hull and application in marine simulator
Zhang, Xiufeng; Lyu, Zhenwang; Yin, Yong; Jin, Yicheng
2013-09-01
Small water-plane area twin-hull (SWATH) has drawn the attention of many researchers due to its good sea-keeping ability. In this paper, MMG's idea of separation was used to perform SWATH movement modeling and simulation; respectively the forces and moment of SWATH were divided into bare hull, propeller, rudder at the fluid hydrodynamics, etc. Wake coefficient at the propellers which reduces thrust coefficient, and rudder mutual interference forces among the hull and propeller, for the calculation of SWATH, were all considered. The fourth-order Runge-Kutta method of integration was used by solving differential equations, in order to get SWATH's movement states. As an example, a turning test at full speed and full starboard rudder of `Seagull' craft is shown. The simulation results show the SWATH's regular pattern and trend of motion. It verifies the correctness of the mathematical model of the turning movement. The SWATH's mathematical model is applied to marine simulator in order to train the pilots or seamen, or safety assessment for ocean engineering project. Lastly, the full mission navigation simulating system (FMNSS) was determined to be a successful virtual reality technology application sample in the field of navigation simulation.
An Experimental and Numerical Study of Long Wave Run-Up on a Plane Beach
Directory of Open Access Journals (Sweden)
Ulrike Drähne
2015-12-01
Full Text Available This research is to facilitate the current understanding of long wave dynamics at coasts and during on-land propagation; experimental and numerical approaches are compared against existing analytical expressions for the long wave run-up. Leading depression sinusoidal waves are chosen to model these dynamics. The experimental study was conducted using a new pump-driven wave generator and the numerical experiments were carried out with a one-dimensional discontinuous Galerkin non-linear shallow water model. The numerical model is able to accurately reproduce the run-up elevation and velocities predicted by the theoretical expressions. Depending on the surf similarity of the generated waves and due to imperfections of the experimental wave generation, riding waves are observed in the experimental results. These artifacts can also be confirmed in the numerical study when the data from the physical experiments is assimilated. Qualitatively, scale effects associated with the experimental setting are discussed. Finally, shoreline velocities, run-up and run-down are determined and shown to largely agree with analytical predictions.
Stress Wave Propagation in Larch Plantation Trees-Numerical Simulation
Fenglu Liu; Fang Jiang; Xiping Wang; Houjiang Zhang; Wenhua Yu
2015-01-01
In this paper, we attempted to simulate stress wave propagation in virtual tree trunks and construct two dimensional (2D) wave-front maps in the longitudinal-radial section of the trunk. A tree trunk was modeled as an orthotropic cylinder in which wood properties along the fiber and in each of the two perpendicular directions were different. We used the COMSOL...
Evarestov, Robert A.; Blokhin, Evgeny; Gryaznov, Denis; Kotomin, Eugene A.; Maier, Joachim
2010-01-01
The atomic, electronic structure and phonon frequencies have been calculated in a cubic and low-temperature tetragonal SrTiO3 phases at the ab initio level. We demonstrate that the use of hybrid exchange-correlation PBE0 functional gives the best agreement with experimental data. The results for the standard PBE and hybrid PBE0 are compared for the two types of basis sets: a linear combination of atomic orbitals (LCAO, CRYSTAL09 computer code) and plane waves (PW, VASP 5.2 code). Relation bet...
Wilson, Chick C.; Morrison, Carole A.
2002-08-01
Low temperature neutron diffraction and high level computational methods have been applied to investigate the short hydrogen bond in urea-phosphoric acid. It is found that isolated molecule calculations predict a `normal' O-H⋯O hydrogen bond, in strong disagreement with the very short, 3 c-4 e hydrogen bond found from the neutron diffraction. Extending these calculations into a periodic environment using plane-wave DFT methods give much improved agreement with experiment, with a much shorter, stronger hydrogen bond, and significant elongation of the O-H `covalent' bond.
Institute of Scientific and Technical Information of China (English)
SUN Yu-guo; WU Lin-zhi
2005-01-01
The dynamic behavior of two collinear cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied using the Schmidt method for the permeable crack surface conditions. By using the Fourier transform, the problem can be solved with a set of triple integral equations in which the unknown variable is the jump of the displacements across the crack surfaces. In solving the triple integral equations, the jump of the displacements across the crack surface is expanded in a series of Jacobi polynomials. It can be obtained that the stress field is independent of the electric field and the magnetic flux.
Numerical simulation of the resonantly excited capillary-gravity waves
Hanazaki, Hideshi; Hirata, Motonori; Okino, Shinya
2015-11-01
Capillary gravity waves excited by an obstacle are investigated by a direct numerical simulation. In the flow without capillary effects, it is well known that large-amplitude upstream advancing solitary waves are generated periodically under the resonant condition, i.e., when the phase velocity of the long surface waves and the mean flow velocity agrees. With capillary effects, solutions of the Euler equations show the generation of very short waves further upstream of the solitary waves and also in the depression region downstream of the obstacle. The overall characteristics of these waves agree with the solutions of the forced fifth-order KdV equation, while the weakly nonlinear theory generally overestimates the wavelength of the short waves.
Nonlinear numerical simulation on extreme-wave kinematics
Institute of Scientific and Technical Information of China (English)
NING Dezhi; TENG Bin; LIU Shuxue
2009-01-01
A fully nonlinear numerical model based on a time-domain higher-order boundary element method (HOBEM) is founded to simulate the kinematics of extreme waves. In the model, the fully nonlinear free surface boundary conditions are satisfied and a semi-mixed Euler-Lagrange method is used to track free surface; a fourth-order Runga-Kutta technique is "adopted to refresh the wave elevation and velocity potential on the free surface at each time step; an image Green function is used in the numerical wave tank so that the integrations on the lateral surfaces and bottom are excluded. The extreme waves are generated by the method of wave focusing. The physical experiments are carried out in a wave flume. On the horizontal velocity of the measured point, numerical solutions agree well with experimental results. The characteristics of the nonlinear extreme-wave kinematics and the velocity distribution are studied here.
Wave energy power take off system control and simulation
Energy Technology Data Exchange (ETDEWEB)
Zhoul, Z.; Holland, P.M.; Igic, P. [Swansea Univ., Swansea, Wales (United Kingdom). School of Engineering; Knapp, W. [Technische Univ. Muenchen, Munich (Germany); MacEnri, J. [ESB International, Dublin (Ireland); Srensen, H.Ch.; Friis-Madsen, E. [Wave Dragon APS and LTD, Copenhagen (Denmark)
2008-07-01
The generation of electric power from wave energy using an offshore wave energy take-off system has received global interest. Several different wave energy take off techniques have been suggested. Among these, the Wave Dragon is one of the most efficient wave energy conversion systems. This paper presented a wave energy power take off system control and simulation scheme. The characteristics of low pressure hydro turbine were described. A variable speed control scheme using IGBT alternating current/direct current converter for low-head hydro-turbine was described in order to achieve maximum efficiency. The electrical system configuration, operation and grid connection issues were presented. Last, in order to investigate the long electro-mechanical process, a simulation model was developed for simulating the generator-turbine starting-stop process. The simulated parameters included the effects of the water head on the torque, speed and output power. Simulation results were presented and discussed. It was concluded that the proposed model is suitable for investigating the overall performance of a wave energy power take off system. 12 refs., 14 figs.
Numerical simulation of sediment transport in coastal waves and wave-induced currents
Institute of Scientific and Technical Information of China (English)
TANG Jun; LYU Yigang; SHEN Yongming
2016-01-01
Prediction of coastal sediment transport is of particularly importance for analyzing coast erosion accurately and solving the corresponding coast protection engineering problems. The present study provided a numerical scheme for sediment transport in coastal waves and wave-induced currents. In the scheme, the sand transport model was implemented with wave refraction-diffraction model and near-shore current model. Coastal water wave was simulated by using the parabolic mild-slope equation in which wave refraction, diffraction and breaking effects are considered. Wave-induced current was simulated by using the nonlinear shallow water equations in which wave provides radiation stresses for driving current. Then, sediment transport in waves and wave-induced currents was simulated by using the two-dimensional suspended sediment transport equations for suspended sediment and the bed-load transport equation for bed load. The numerical scheme was validated by experiment results from the Large-scale Sediment Transport Facility at the US Army Corps of Engineer Research and Development Center in Vicksburg. The numerical results showed that the present scheme is an effective tool for modeling coastal sediment transport in waves and near-shore currents.
Institute of Scientific and Technical Information of China (English)
LI Lin; ZHOU Zhen-gong; WANG Biao
2006-01-01
The scattering problem of anti-plane shear waves in a functionally graded material strip with an off-center crack is investigated by use of Schmidt method. The crack is vertically to the edge of the strip. By using the Fourier transform, the problem can be solved with the help of a pair of dual integral equations that the unknown variable is the jump of the displacement across the crack surfaces. To solve the dual integral equations, the jump of the displacement across the crack surfaces was expanded in a series of Jacobi polynomials. Numerical examples were provided to show the effects of the parameter describing the functionally graded materials, the position of the crack and the frequency of the incident waves upon the stress intensity factors of the crack.
Anti-plane (SH) waves diffraction by an underground semi-circular cavity: analytical solution
Institute of Scientific and Technical Information of China (English)
Luo Hao; Vincent W. Lee; Liang Jianwen
2010-01-01
Diffraction of a two-dimensional (2D) semi-circular cavity in a half-space under incident SH-waves is studied using the classic wave function expansion method with a new de-coupling technique. This so-called "improved cosine half-range expansion" algorithm exhibits an excellent performance in reducing displacement residual errors at two rim points of concern. The governing equations are developed in a manner that minimizes the residues of the boundary conditions. Detailed derivation and analysis procedures as well as truncation of infinite linear governing equations are presented. The semi-circular cavity model presented in this paper, due to its simple profile, is expected to be used in seismic wave propagation studies as a benchmark for examining the accuracies of various analytical or numerical methods for mixed-boundary wave propagation problems.
Directory of Open Access Journals (Sweden)
Adam Martowicz
2015-01-01
Full Text Available The paper addresses the problem of numerical dispersion in simulations of wave propagation in solids. This characteristic of numerical models results from both spatial discretization and temporal discretization applied to carry out transient analyses. A denser mesh of degrees of freedom could be a straightforward solution to mitigate numerical dispersion, since it provides more advantageous relation between the model length scale and considered wavelengths. However, this approach also leads to higher computational effort. An alternative approach is the application of nonlocal discretization schemes, which employ a relatively sparse spatial distribution of nodes. Numerical analysis carried out to study the propagation of elastic waves in isotropic solid materials is demonstrated. Fourier-based nonlocal discretization for continuum mechanics is introduced for a two-dimensional model undergoing out-of-plane wave propagation. The results show gradual increase of the effectiveness of this approach while expanding the region of nonlocal interactions in the numerical model. A challenging case of high ratio between the model length scale and wavelength is investigated to present capability of the proposed approach. The elaborated discretization method also provides the perspective of accurate representation of any arbitrarily shaped dispersion relation based on physical properties of modelled materials.
3-D NUMERICAL SIMULATION OF CONVOY-GENERATED WAVES IN A RESTRICTED WATERWAY
Institute of Scientific and Technical Information of China (English)
JI Sheng Cheng; OUAHSINE Abdellatif; SMAOUI Hassan; SERGENT Philippe
2012-01-01
We consider waves generated by the passing of convoys in a restricted waterway.The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy,such as the speed and the hull geometry.The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown.Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-ε model for turbulent processes.The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rh(o)ne (CNR).
Electromagnetic Characteristics of Microstrip Circuits Under Plane Wave Illumination%平面波照射下微带电路的电磁特性
Institute of Scientific and Technical Information of China (English)
李守荣; 李莹; 孙震; 王帆
2013-01-01
基于十字结微带结构的等效电路,建立了平面波照射下不连续微带电路的电磁敏感性模型.利用场耦合理论计算入射平面波在微带电路终端产生的等效源表达式,并分别对十字结微带结构和单级放大器等电路的电磁敏感性模型进行计算和仿真验证.结果显示,仿真结果与测量结果具有很好的一致性,且仿真时间短,有助于设计者更加快速准确地预测电磁干扰对不连续微带电路的影响.%Based on the equivalent circuit of the microstrip cross bend, the electromagnetic sensitivity model of discontinuous microstrip circuits with the presence of a uniform plane incident wave is estab-lished,.First,the analytical expressions are modeled as equivalent voltage and current sources for discussing the global effect of the incident plane wave on the associated interconnects. Then,these field-induced equiv alent source expressions are incorporated into ADS circuit solver,and a fast model is established for analy zing the output responses of microstrip circuits,such as the cross bend and the single-stage amplifier. The corresponding simulated results from the proposed model are also validated by comparing the results from the measurements. With the merit of short simulation time, the proposed approach would be an efficient method to solve the electromagnetic susceptibility problems associated with the discontinuous microstrip circuits.
Continuity waves in fully resolved simulations of settling particles
Willen, Daniel; Sierakowski, Adam; Prosperetti, Andrea
2016-11-01
Fully resolved simulations of 500 to 2,000 particles settling in a fluid have been conducted with the Physalis method. A new approach to the reconstruction of pseudo-continuum fields is described and is used to examine the results with the purpose of identifying concentration waves. The velocity of concentration waves is successfully deduced from the simulations. A comparison of the results with continuity wave theory shows good agreement. Several new insights about the particle microstructure conditionally averaged on volume fraction and velocity are also described. This work is supported by NSF award CBET1335965.
Institute of Scientific and Technical Information of China (English)
Ni Zhen; Feng-Lian Li; Yue-Sheng Wang; Chuan-Zeng Zhang
2012-01-01
In this paper,a method based on the Dirichletto-Neumann map is developed for bandgap calculation of mixed in-plane waves propagating in 2D phononic crystals with square and triangular lattices.The method expresses the scattered fields in a unit cell as the cylindrical wave expansions and imposes the Bloch condition on the boundary of the unit cell.The Dirichlet-to-Neumann (DtN) map is applied to obtain a linear eigenvalue equation,from which the Bloch wave vectors along the irreducible Brillouin zone are calculated for a given frequency.Compared with other methods,the present method is memory-saving and time-saving.It can yield accurate results with fast convergence for various material combinations including those with large acoustic mismatch without extra computational cost.The method is also efficient for mixed fluid-solid systems because it considers the different wave modes in the fluid and solid as well as the proper fluid-solid interface condition.
Liu, Zhongxian; Wang, Yirui; Liang, Jianwen
2016-06-01
The scattering of plane harmonic P and SV waves by a pair of vertically overlapping lined tunnels buried in an elastic half space is solved using a semi-analytic indirect boundary integration equation method. Then the effect of the distance between the two tunnels, the stiffness and density of the lining material, and the incident frequency on the seismic response of the tunnels is investigated. Numerical results demonstrate that the dynamic interaction between the twin tunnels cannot be ignored and the lower tunnel has a significant shielding effect on the upper tunnel for high-frequency incident waves, resulting in great decrease of the dynamic hoop stress in the upper tunnel; for the low-frequency incident waves, in contrast, the lower tunnel can lead to amplification effect on the upper tunnel. It also reveals that the frequency-spectrum characteristics of dynamic stress of the lower tunnel are significantly different from those of the upper tunnel. In addition, for incident P waves in low-frequency region, the soft lining tunnels have significant amplification effect on the surface displacement amplitude, which is slightly larger than that of the corresponding single tunnel.
Energy Technology Data Exchange (ETDEWEB)
Boudjedaa, T. [Ecole Normale Superieure, Jijel (Algeria). Dept. de Physique; Chetouani, L. [Dept. de Physique Theorique, Inst. de Physique, Univ. de Constantine (Algeria); Guechi, L. [Dept. de Physique Theorique, Inst. de Physique, Univ. de Constantine (Algeria); Hammann, T.F. [Lab. de Mathematiques et Physique Mathematique, Faculte des Sciences et Techniques, 68 Mulhouse (France)
1995-07-01
The Green`s functions for charged particles of spin zero and 1/2, subjected to the action of a Redmond field which is the combination of an electromagnetic plane wave plus a parallel constant magnetic field, are calculated via the Schwinger action principle. The Heisenberg equations are then exactly solved. The spectrum and the waves are deduced in both cases. (orig.).
Surface wave modelling and simulation for wave tanks and coastal areas
Groesen, van, E.; Bunnik, T.; Andonowati
2011-01-01
For testing ships and offshore structures in hydrodynamic laboratories, the sea and ocean states should be represented as realistic as possible in the wave tanks in which the scaled experiments are executed. To support efficient testing, accurate software that determines and translates the required wave maker motion into the downstream waves is very helpful. This paper describes an efficient hybrid spatial-spectral code that can deal with simulations above flat and varying bottom. The accurac...
PIC simulation of a thermal anisotropy-driven Weibel instability in a circular rarefaction wave
Dieckmann, M E; Murphy, G C; Bret, A; Romagnani, L; Kourakis, I; Borghesi, M; Ynnerman, A; Drury, L O'C; 10.1088/1367-2630/14/2/023007
2012-01-01
The expansion of an initially unmagnetized planar rarefaction wave has recently been shown to trigger a thermal anisotropy-driven Weibel instability (TAWI), which can generate magnetic fields from noise levels. It is examined here if the TAWI can also grow in a curved rarefaction wave. The expansion of an initially unmagnetized circular plasma cloud, which consists of protons and hot electrons, into a vacuum is modelled for this purpose with a two-dimensional particle-in-cell (PIC) simulation. It is shown that the momentum transfer from the electrons to the radially accelerating protons can indeed trigger a TAWI. Radial current channels form and the aperiodic growth of a magnetowave is observed, which has a magnetic field that is oriented orthogonal to the simulation plane. The induced electric field implies that the electron density gradient is no longer parallel to the electric field. Evidence is presented here for that this electric field modification triggers a second magnetic instability, which results i...
3D Ultrasonic Wave Simulations for Structural Health Monitoring
Campbell, Leckey Cara A/; Miler, Corey A.; Hinders, Mark K.
2011-01-01
Structural health monitoring (SHM) for the detection of damage in aerospace materials is an important area of research at NASA. Ultrasonic guided Lamb waves are a promising SHM damage detection technique since the waves can propagate long distances. For complicated flaw geometries experimental signals can be difficult to interpret. High performance computing can now handle full 3-dimensional (3D) simulations of elastic wave propagation in materials. We have developed and implemented parallel 3D elastodynamic finite integration technique (3D EFIT) code to investigate ultrasound scattering from flaws in materials. EFIT results have been compared to experimental data and the simulations provide unique insight into details of the wave behavior. This type of insight is useful for developing optimized experimental SHM techniques. 3D EFIT can also be expanded to model wave propagation and scattering in anisotropic composite materials.
Laboratory simulation of magnetospheric chorus wave generation
Van Compernolle, B.; An, X.; Bortnik, J.; Thorne, R. M.; Pribyl, P.; Gekelman, W.
2017-01-01
Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. A laboratory experiment (Van Compernolle et al 2015 Phys. Rev. Lett. 114 245002, An et al 2016 Geophys. Res. Lett.) in the large plasma device at UCLA was designed to closely mimic the scaled plasma parameters observed in the inner magnetosphere, and shed light on the excitation of discrete frequency whistler waves. It was observed that a rich variety of whistler wave emissions is excited by a gyrating electron beam. The properties of the whistler emissions depend strongly on plasma density, beam density and magnetic field profiles.
Do, V. Nam; Le, H. Anh; Vu, V. Thieu
2017-04-01
We propose a computational approach to combining the plane-wave method and the real-space treatment to describe the periodic variation in the material plane and the decay of wave functions from the material surfaces. The proposed approach is natural for two-dimensional material systems and thus may circumvent some intrinsic limitations involving the artificial replication of material layers in traditional supercell methods. In particular, we show that the proposed method is easy to implement and, especially, computationally effective since low-cost computational algorithms, such as iterative and recursive techniques, can be used to treat matrices with block tridiagonal structure. Using this approach we show first-principles features that supplement the current knowledge of some fundamental issues in bilayer graphene systems, including the coupling between the two graphene layers, the preservation of the σ band of monolayer graphene in the electronic structure of the bilayer system, and the differences in low-energy band structure between the AA- and AB-stacked configurations.
Nikolaev, A. V.; Lamoen, D.; Partoens, B.
2016-07-01
In order to increase the accuracy of the linearized augmented plane wave (LAPW) method, we present a new approach where the plane wave basis function is augmented by two different atomic radial components constructed at two different linearization energies corresponding to two different electron bands (or energy windows). We demonstrate that this case can be reduced to the standard treatment within the LAPW paradigm where the usual basis set is enriched by the basis functions of the tight binding type, which go to zero with zero derivative at the sphere boundary. We show that the task is closely related with the problem of extended core states which is currently solved by applying the LAPW method with local orbitals (LAPW+LO). In comparison with LAPW+LO, the number of supplemented basis functions in our approach is doubled, which opens up a new channel for the extension of the LAPW and LAPW+LO basis sets. The appearance of new supplemented basis functions absent in the LAPW+LO treatment is closely related with the existence of the u ˙ l -component in the canonical LAPW method. We discuss properties of additional tight binding basis functions and apply the extended basis set for computation of electron energy bands of lanthanum (face and body centered structures) and hexagonal close packed lattice of cadmium. We demonstrate that the new treatment gives lower total energies in comparison with both canonical LAPW and LAPW+LO, with the energy difference more pronounced for intermediate and poor LAPW basis sets.
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.
Torres, Ana M; Lopez, Jose J; Pueo, Basilio; Cobos, Maximo
2013-04-01
Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.
Implicit large eddy simulation of unsteady cloud cavitation around a plane- convex hydrofoil
Institute of Scientific and Technical Information of China (English)
罗先武; 季斌
2015-01-01
The present paper focuses on the erosive cavitation behavior around a plane convex hydrofoil. The Zwart-Gerber-Belamri cavitation model is implemented in a library form to be used with the OpenFOAM. The implicit large eddy simulation (ILES) is app- lied to analyze the three dimensional unsteady cavitating flow around a plane convex hydrofoil. The numerical results in the cases under the hydrodynamic-conditions, which were experimentally tested at the high speed cavitation tunnel of the École Polytechnique Fédérale de Lausanne (EPFL), clearly show the sheet cavitation development, the shedding and the collapse of vapor clouds. It is noted that the cavitation evolutions including the maximum vapor length, the detachment and the oscillation frequency, are captured fairly well. Furthermore, the pressure pulses due to the cavitation development as well as the complex vortex structures are reasona- bly well predicted. Consequently, it may be concluded that the present numerical method can be used to investigate the unsteady cavitation around hydrofoils with a satisfactory accuracy.
Nonuniform fast Fourier transform method for numerical diffraction simulation on tilted planes.
Xiao, Yu; Tang, Xiahui; Qin, Yingxiong; Peng, Hao; Wang, Wei; Zhong, Lijing
2016-10-01
The method, based on the rotation of the angular spectrum in the frequency domain, is generally used for the diffraction simulation between the tilted planes. Due to the rotation of the angular spectrum, the interval between the sampling points in the Fourier domain is not even. For the conventional fast Fourier transform (FFT)-based methods, a spectrum interpolation is needed to get the approximate sampling value on the equidistant sampling points. However, due to the numerical error caused by the spectrum interpolation, the calculation accuracy degrades very quickly as the rotation angle increases. Here, the diffraction propagation between the tilted planes is transformed into a problem about the discrete Fourier transform on the uneven sampling points, which can be evaluated effectively and precisely through the nonuniform fast Fourier transform method (NUFFT). The most important advantage of this method is that the conventional spectrum interpolation is avoided and the high calculation accuracy can be guaranteed for different rotation angles, even when the rotation angle is close to π/2. Also, its calculation efficiency is comparable with that of the conventional FFT-based methods. Numerical examples as well as a discussion about the calculation accuracy and the sampling method are presented.
Roll waves numerical simulation in closed channels
2013-01-01
Resumo: Utilizando um método numérico especializado em problemas hiperbólicos chamado Riemann Solver, é feito um estudo para avaliar o processo de evolução de roll waves em canais fechados. Todo o estudo se baseia em fenômenos de propagação de ondas hiperbólicas do tipo ondas de gravidade. Foi utilizado um modelo unidimensional para representar a dinâmica das roll waves. Inicialmente foi feita uma análise das velocidades características envolvidas, a qual indicou, para o arranjo estratificado...
Takahashi, Yukio; Nishino, Yoshinori; Tsutsumi, Ryosuke; Kubo, Hideto; Furukawa, Hayato; Mimura, Hidekazu; MATSUYAMA, Satoshi; Zettsu, Nobuyuki; Matsubara, Eiichiro; Ishikawa, Tetsuya; Yamauchi, Kazuto
2009-01-01
X-ray waves in the center of the beam waist of nearly diffraction limited focused x-ray beams can be considered to have amplitude and phase that are both almost uniform, i.e., they are x-ray plane waves. Here we report the results of an experimental demonstration of high-resolution diffraction microscopy using the x-ray plane wave of the synchrotron x-ray beam focused using Kirkpatrik-Baez mirrors. A silver nanocube with an edge length of ∼100 nm is illuminated with the x-ray beam focused to ...
Large Eddy Simulation for Wave Breaking in the Surf Zone
Institute of Scientific and Technical Information of China (English)
白玉川; 蒋昌波; 沈焕庭
2001-01-01
In this paper, the large eddy simulation method is used combined with the marker and cell method to study the wave propagation or shoaling and breaking process. As wave propagates into shallow water, the shoaling leads to the increase of wave height, and then at a certain position, the wave will be breaking. The breaking wave is a powerful agent for generating turbulence, which plays an important role in most of the fluid dynamic processes throughout the sarf zone, such as transformation of wave energy, generation of near-shore current and diffusion of materials. So a proper numerical model for describing the turbulence effect is needed. In this paper, a revised Smagorinsky subgrid-scale model is used to describe the turbulence effect. The present study reveals that the coefficient of the Smagorinsky model for wave propagation or breaking simulation may be taken as a varying function of the water depth and distance away from the wave breaking point. The large eddy simulation model presented in this paper has been used to study the propagation of the solitary wave in constant water depth and the shoaling of the non-breaking solitary wave on a beach. The model is based on large eddy simulation, and to track free-surface movements, the Tokyo University Modified Marker and Cell (TUMMAC) method is employed. In order to ensure the accuracy of each component of this wave mathematical model,several steps have been taken to verify calculated solutions with either analytical solutions or experimental data. For non-breaking waves, very accurate results are obtained for a solitary wave propagating over a constant depth and on a beach. Application of the model to cnoidal wave breaking in the surf zone shows that the model results are in good agreement with analytical solution and experimental data. From the present model results, it can be seen that the turbulent eddy viscosity increases from the bottom to the water surface in surf zone. In the eddy viscosity curve, there is a
Directory of Open Access Journals (Sweden)
Narottam Maity
2016-01-01
Full Text Available Reflection of longitudinal displacement waves in a generalized thermoelastic half space under the action of uniform magnetic field has been investigated. The magnetic field is applied in such a direction that the problem can be considered as a two-dimensional one. The discussion is based on the three theories of generalized thermoelasticity: Lord-Shulman (L-S, Green-Lindsay (G-L, and Green-Naghdi (G-N with energy dissipation. We compute the possible wave velocities for different models. Amplitude ratios have been presented. The effects of magnetic field on various subjects of interest are discussed and shown graphically.
Energy Technology Data Exchange (ETDEWEB)
Hoffmann, T.; Strawinska, J. [Politechnika Poznanska, Poznan (Poland)
1993-12-31
The present considerations are devoted to the description of an electromagnetic field in deformable body within the framework of the conceptional extended electrodynamics. The formal tool used is the classical field theory based on methods of analytical mechanics. The deformation is described by applying the relativistic kinematics of a medium which makes it possible to obtain, as a particular case, three dimensional laws with simple physical interpretation. The dynamics of bodies interacting with an electromagnetic field has been expressed by Lagrange`s equation of motion with a view to obtaining linear field equations. In the domain of wave problems one-dimensional volume waves have been analysed. (author). 19 refs.
Molecular dynamics simulation of surface melting behaviours of the V (110) plane
Institute of Scientific and Technical Information of China (English)
Yang Xi-Yuan; Hu Wang-Yu; Yuan Xiao-Jian; Cai Xin-Hua
2008-01-01
The modified analytic embedded-atom method and molecular dynamics simulations are applied to the investigation of the surface premelting and melting behaviours of the V (110) plane by calculating the interlayer relaxation, the layer structure factor and atomic snapshots in this paper. The results obtained indicate that the premelting phenomenon occurs on the V(110) surface at about 1800K and then a liquid-like layer, which approximately keeps the same thickness up to 2020K, emerges on it. We discover that the temperature 2020K the V(110) surface starts to melt and is in a completely disordered state at the temperature of 2140K under the melting point for the bulk vanadium.
Fabrication of simulated plate fuel elements: Defining role of out-of-plane residual shear stress
Rakesh, R.; Kohli, D.; Sinha, V. P.; Prasad, G. J.; Samajdar, I.
2014-02-01
Bond strength and microstructural developments were investigated during fabrication of simulated plate fuel elements. The study involved roll bonding of aluminum-aluminum (case A) and aluminum-aluminum + yttria (Y2O3) dispersion (case B). Case B approximated aluminum-uranium silicide (U3Si2) 'fuel-meat' in an actual plate fuel. Samples after different stages of fabrication, hot and cold rolling, were investigated through peel and pull tests, micro-hardness, residual stresses, electron and micro-focus X-ray diffraction. Measurements revealed a clear drop in bond strength during cold rolling: an observation unique to case B. This was related to significant increase in 'out-of-plane' residual shear stresses near the clad/dispersion interface, and not from visible signatures of microstructural heterogeneities.
Simulation of the interaction of tsunami waves with underwater barriers
Boshenyatov, B. V.; Zhiltsov, K. N.
2016-10-01
This article examines the experimental and numerical simulation of the processes of distribution and interaction of tsunami-type gravitational waves with one barrier and a complex of two barriers. Experiments were conducted in a hydrodynamic channel using high-precision sensors for the measurement of the wave processes. Mathematical modelling was carried out using two-dimensional non-stationary Navier-Stokes equations for an incompressible fluid using the freely available software package OpenFOAM. It is shown that for small-amplitude waves, when their advance speed is described by the linear theory of shallow water, the interaction with the underwater barriers has important non-linear and viscous effects. Our results explain why a complex of two barriers spaced at a definite distance from each other has a significant impact on the power of the transmitted wave. The energy of the waves passing through the two barriers can be reduced to 35% of the incident wave.
Efficient Simulation of Freak Waves in Random Oceanic Sea States
Institute of Scientific and Technical Information of China (English)
ZHANG Yun-qiu; HU Jin-peng; ZHANG Ning-chuan
2009-01-01
Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum.The evolution of initial random wave trains is numerically carried out within the framework of the modified fourorder nonlinear Schruedinger equation (mNLSE),and some involved influence factors are also discussed.Results show that if the sideband instability is satisfied,a random wave train may evolve into a freak wave train,and simultaneously the setting of the Phillips parameter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves.The way to increase the generation efficiency of freak waves thsough changing the involved parameters is also presented.
Design and Control of Full Scale Wave Energy Simulator System
DEFF Research Database (Denmark)
Pedersen, Henrik C.; Hansen, Anders Hedegaard; Hansen, Rico Hjerm
2012-01-01
For wave energy to become feasible it is a requirement that the efficiency and reliability of the power take-off (PTO) systems are significantly improved. The cost of installing and testing PTO-systems at sea are however very high, and the focus of the current paper is therefore on the design...... of a full scale wave simulator for testing PTO-systems for point absorbers. The main challenge is here to design a system, which mimics the behavior of a wave when interacting with a given PTO-system. The paper includes a description of the developed system, located at Aalborg University......, and the considerations behind the design. Based on the description a model of the system is presented, which, along with a description of the wave theory applied, makes the foundation for the control strategy. The objective of the control strategy is to emulate not only the wave behavior, but also the dynamic wave...
Ibata, Rodrigo A; Lewis, Geraint F; Martin, Nicolas F; Conn, Anthony; Elahi, Pascal; Arias, Veronica; Fernando, Nuwanthika
2014-01-01
In a recent contribution, Bahl \\& Baumgardt investigated the incidence of planar alignments of satellite galaxies in the Millennium-II simulation, and concluded that vast thin planes of dwarf galaxies, similar to that observed in the Andromeda galaxy (M31), occur frequently by chance in $\\Lambda$-Cold Dark Matter cosmology. However, their analysis did not capture the essential fact that the observed alignment is simultaneously radially extended, yet thin, and kinematically unusual. With the caveat that the Millennium-II simulation may not have sufficient mass resolution to identify confidently simulacra of low-luminosity dwarf galaxies, we re-examine that simulation for planar structures, using the same method as employed by Ibata et al. (2013) on the real M31 satellites. We find that 0.04\\% of host galaxies display satellite alignments that are at least as extreme as the observations, when we consider their extent, thickness and number of members rotating in the same sense. We further investigate the ang...
Wave overtopping simulator tests in Vietnam
Trung, L.H.; Van der Meer, J.M.; Schiereck, G.J.; Cat, V.M.; Van der Meer, G.
2010-01-01
Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm
Wave overtopping simulator tests in Vietnam
Trung, L.H.; Van der Meer, J.M.; Schiereck, G.J.; Cat, V.M.; Van der Meer, G.
2010-01-01
Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm surg
Variational approaches to water wave simulations
Gagarina, Elena Vitalyevna
2014-01-01
This thesis starts with the study the theoretical aspects of water wave modelling using a variational framework, which is directly associated with phase space and energy conservation laws. In particular, we focus on a new variational model based on the work of Cotter and Bokhove. The new model inclu
Winjum, B. J.; Banks, J. W.; Berger, R. L.; Cohen, B. I.; Chapman, T.; Hittinger, J. A. F.; Rozmus, W.; Strozzi, D. J.; Brunner, S.
2012-10-01
We present results on the kinetic filamentation of finite-width nonlinear electron plasma waves (EPW). Using 2D simulations with the PIC code BEPS, we excite a traveling EPW with a Gaussian transverse profile and a wavenumber k0λDe= 1/3. The transverse wavenumber spectrum broadens during transverse EPW localization for small width (but sufficiently large amplitude) waves, while the spectrum narrows to a dominant k as the initial EPW width increases to the plane-wave limit. For large EPW widths, filaments can grow and destroy the wave coherence before transverse localization destroys the wave; the filaments in turn evolve individually as self-focusing EPWs. Additionally, a transverse electric field develops that affects trapped electrons, and a beam-like distribution of untrapped electrons develops between filaments and on the sides of a localizing EPW. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD-061. Supported also under Grants DE-FG52-09NA29552 and NSF-Phy-0904039. Simulations were performed on UCLA's Hoffman2 and NERSC's Hopper.
Numerical Simulation of Sediment Transport due to Plunging Breaking Waves
DEFF Research Database (Denmark)
Pedersen, Claus
A numerical model simulating the sediment transport due to plunging breaking waves has been developed. The model is two-dimensional, assuming conditions in the long-shore direction invariable. A plunging breaker is simulated by superimposing a non-breaking wave with a jet. Based on the description...... of the sediment transport rates, a simple model describing the morphological changes has been applied to simulate the evolution of a plunge point generated vorticity included, the bottom topography from the experiments by Dette & Uliczka was not in equilibrium according to the model....
Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard
2013-11-05
Quantum-chemical computations of solids benefit enormously from numerically efficient plane-wave (PW) basis sets, and together with the projector augmented-wave (PAW) method, the latter have risen to one of the predominant standards in computational solid-state sciences. Despite their advantages, plane waves lack local information, which makes the interpretation of local densities-of-states (DOS) difficult and precludes the direct use of atom-resolved chemical bonding indicators such as the crystal orbital overlap population (COOP) and the crystal orbital Hamilton population (COHP) techniques. Recently, a number of methods have been proposed to overcome this fundamental issue, built around the concept of basis-set projection onto a local auxiliary basis. In this work, we propose a novel computational technique toward this goal by transferring the PW/PAW wavefunctions to a properly chosen local basis using analytically derived expressions. In particular, we describe a general approach to project both PW and PAW eigenstates onto given custom orbitals, which we then exemplify at the hand of contracted multiple-ζ Slater-type orbitals. The validity of the method presented here is illustrated by applications to chemical textbook examples-diamond, gallium arsenide, the transition-metal titanium-as well as nanoscale allotropes of carbon: a nanotube and the C60 fullerene. Remarkably, the analytical approach not only recovers the total and projected electronic DOS with a high degree of confidence, but it also yields a realistic chemical-bonding picture in the framework of the projected COHP method.
Energy Technology Data Exchange (ETDEWEB)
Moll, J; Schulte, R T; Fritzen, C-P [Institute of Mechanics and Control Engineering - Mechatronics, University of Siegen (Germany); Rezk-Salama, C [Mediadesign University of Applied Science Duesseldorf (Germany); Klinkert, T; Kolb, A, E-mail: moll@imr.mb.uni-siegen.de [Computer Graphics and Multimedia Systems, University of Siegen (Germany)
2011-07-19
Structural health monitoring systems allow a continuous surveillance of the structural integrity of operational systems. As a result, it is possible to reduce time and costs for maintenance without decreasing the level of safety. In this paper, an integrated simulation and visualization environment is presented that enables a detailed study of Lamb wave propagation in isotropic and anisotropic materials. Thus, valuable information about the nature of Lamb wave propagation and its interaction with structural defects become available. The well-known spectral finite element method is implemented to enable a time-efficient calculation of the wave propagation problem. The results are displayed in an interactive visualization framework accounting for the human perception that is much more sensitive to motion than to changes in color. In addition, measurements have been conducted experimentally to record the full out-of-plane wave-field using a Laser-Doppler vibrometry setup. An aluminum structure with two synthetic cuts has been investigated, where the elongated defects have a different orientation with respect to the piezoelectric actuator. The resulting wave-field is also displayed interactively showing that the scattered wave-field at the defect is highly directional.
Producing Acoustic 'Frozen Waves': Simulated experiments
Prego, Jose' L; Recami, Erasmo; Hernandez-Figueroa, Hugo E
2012-01-01
In this paper we show how appropriate superpositions of Bessel beams can be successfully used to obtain arbitrary longitudinal intensity patterns of nondiffracting ultrasonic wavefields with very high transverse localization. More precisely, the method here described allows generating longitudinal acoustic pressure fields, whose longitudinal intensity patterns can assume, in principle, any desired shape within a freely chosen interval 0
Shock Mechanism Analysis and Simulation of High-Power Hydraulic Shock Wave Simulator
Directory of Open Access Journals (Sweden)
Xiaoqiu Xu
2017-01-01
Full Text Available The simulation of regular shock wave (e.g., half-sine can be achieved by the traditional rubber shock simulator, but the practical high-power shock wave characterized by steep prepeak and gentle postpeak is hard to be realized by the same. To tackle this disadvantage, a novel high-power hydraulic shock wave simulator based on the live firing muzzle shock principle was proposed in the current work. The influence of the typical shock characteristic parameters on the shock force wave was investigated via both theoretical deduction and software simulation. According to the obtained data compared with the results, in fact, it can be concluded that the developed hydraulic shock wave simulator can be applied to simulate the real condition of the shocking system. Further, the similarity evaluation of shock wave simulation was achieved based on the curvature distance, and the results stated that the simulation method was reasonable and the structural optimization based on software simulation is also beneficial to the increase of efficiency. Finally, the combination of theoretical analysis and simulation for the development of artillery recoil tester is a comprehensive approach in the design and structure optimization of the recoil system.
LES/FDF simulation of particle dispersion in a gas-particle two phase plane wake flow
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
A filtered density function (FDF) transport equation was derived for the fluid velocity seen by the particles in gas-particle two-phase flow. An LES/FDF simulation of a two-phase plane wake flow was carried out. The simulation results were compared with both the experimental photograph and the simulation results without using the FDF model, and proved that the LES/FDF model can clearly improve the spatial dispersion of the particle phase.
Plane Wave-Perturbative Method for Evaluating the Effective Speed of Sound in 1D Phononic Crystals
Directory of Open Access Journals (Sweden)
J. Flores Méndez
2016-01-01
Full Text Available A method for calculating the effective sound velocities for a 1D phononic crystal is presented; it is valid when the lattice constant is much smaller than the acoustic wave length; therefore, the periodic medium could be regarded as a homogeneous one. The method is based on the expansion of the displacements field into plane waves, satisfying the Bloch theorem. The expansion allows us to obtain a wave equation for the amplitude of the macroscopic displacements field. From the form of this equation we identify the effective parameters, namely, the effective sound velocities for the transverse and longitudinal macroscopic displacements in the homogenized 1D phononic crystal. As a result, the explicit expressions for the effective sound velocities in terms of the parameters of isotropic inclusions in the unit cell are obtained: mass density and elastic moduli. These expressions are used for studying the dependence of the effective, transverse and longitudinal, sound velocities for a binary 1D phononic crystal upon the inclusion filling fraction. A particular case is presented for 1D phononic crystals composed of W-Al and Polyethylene-Si, extending for a case solid-fluid.
Prediction of Vertical-Plane Wave Loading and Ship Responses in High Seas
DEFF Research Database (Denmark)
Wang, Zhaohui; Xia, Jinzhu; 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.......From the rather extensive computations and comparisons, it is found that non-linear effects are significant in head and bow waes in the motion-wave resonant region for both heave and pitch motions, bow accelerations and vertical bending moments for two container ships considered, whereas not significant...... for a VLCC. The non-linearities in motions and structural loads of conventional monohull ships seem well predicted by the present non-linear strip theory....
A plane wave analysis of coherent holographic image reconstruction by phase transfer
Field, Jeffrey J; Bartels, Randy A
2015-01-01
Fluorescent imaging plays a critical role in a myriad of scientific endeavors, particularly in the biological sciences. Three-dimensional imaging of fluorescent intensity often requires serial data acquisition, that is voxel-by-voxel collection of fluorescent light emitted throughout the specimen with a non-imaging single-element detector. While non-imaging fluorescence detection offers some measure of scattering robustness, the rate at which dynamic specimens can be imaged is severely limited. Other fluorescent imaging techniques utilize imaging detection to enhance collection rates. A notable example is light-sheet fluorescence microscopy, also known as selective-plane illumination microscopy (SPIM), which illuminates a large region within the specimen and collects emitted fluorescent light at an angle either perpendicular or oblique to the illumination light sheet. Unfortunately, scattering of the emitted fluorescent light can cause blurring of the collected images in highly turbid biological media. We rec...
Numerical simulation of landslide-generated impulse wave
Institute of Scientific and Technical Information of China (English)
赵兰浩; 毛佳; 刘晓青; 李同春
2014-01-01
A numerical model is proposed for the simulation of impulse waves generated by landslides. The fluid-like landslide is modeled as a generalized non-Newtonian visco-plastic fluid. The conservative level set method is extended to the n-phase flow and applied to capture the interfaces of air, water and landslide. Numerical results show an excellent performance of the current model to capture the whole process of the landslide and the impulse wave generation.
SIMULATION OF ANALYTICAL TRANSIENT WAVE DUE TO DOWNWARD BOTTOM THRUST
Directory of Open Access Journals (Sweden)
Sugih Sudharma Tjandra
2015-11-01
Full Text Available Generation process is an important part of understanding waves, especially tsunami. Large earthquake under the sea is one major cause of tsunamis. The sea surface deforms as a response from the sea bottom motion caused by the earthquake. Analytical description of surface wave generated by bottom motion can be obtained from the linearized dispersive model. For a bottom motion in the form of a downward motion, the result is expressed in terms of improper integral. Here, we focus on analyzing the convergence of this integral, and then the improper integral is approximated into a finite integral so that the integral can be evaluated numerically. Further, we simulate free surface elevation for three different type of bottom motions, classified as impulsive, intermediate, and slow movements. We demonstrate that the wave propagating to the right, with a depression as the leading wave, followed with subsequent wave crests. This phenomena is often observed in most tsunami events.
Simulation of Fully Nonlinear 3-D Numerical Wave Tank
Institute of Scientific and Technical Information of China (English)
张晓兔; 滕斌; 宁德志
2004-01-01
A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.
Directory of Open Access Journals (Sweden)
Naděžda Bartošová
2015-01-01
Full Text Available This article examines options for applying expert systems for the needs of identification of conflict situations between planes in flight simulations, which are applied during basic training of air traffic controllers. It focuses on the conditions for basic training of military air traffic controllers and presents the use of rule systems to automatic detection of conflict between planes within a basic training polygon. The system of rules is a part of the expert system, consisting of realisation of tasks for identifying optimum resolution of conflict situations in selected types of simulations.
A Numerical Simulation of a Plunging Breaking Wave
Adams, Paul; Stephens, Mike; Brucker, Kyle A; O'Shea, Thomas; Dommermuth, Douglas
2009-01-01
This article describes the fluid dynamics video, "A Numerical Simulation of a Plunging Breaking Wave", which was submitted to the gallery of fluid motion at the 2009 APS/DFD conference. The simulation was of a deep-water plunging breaking wave. It was a two-phase calculation which used a Volume of Fluid (VOF) method to simulate the interface between the two immiscible fluids. Surface tension and viscous effects were not considered. The initial wave was generated by applying a spatio-temporal pressure forcing on the free surface. The video shows the 50% isocontour of the volume fraction from several different perspectives. Significant air entrainment is observed as well as the presence of stream-wise vortex structures.
Scattering of plane SH waves by a circular-arc hill with a circular tunnel
Institute of Scientific and Technical Information of China (English)
LIANG Jian-wen(梁建文); LUO Hao(罗昊); Vincent W. Lee
2004-01-01
An analytical solution for scattering of incident SH waves by a circular-arc hill with a concentric circular tunnel was derived by Fourier-Bessel series expansion and auxiliary functions technique. The solution is reduced to solving a set of infinite linear algebraic equations finally. The accuracies of the numerical results are checked by the residual errors of boundary conditions with the truncation order increasing. The numerical results show that the existence and dimension of the tunnel have great effect on motion of the ground surface nearby and dynamic stress concentration of the tunnel.
Fraternale, Federico; Staffilani, Gigliola; Tordella, Daniela
2016-01-01
By deriving conditions for no transient enstrophy growth for two-dimensional small perturbations in the plane Couette and Poiseuille flows, we show that transient kinetic energy growth for small traveling waves is not a sufficient condition for the enstrophy growth. It should be recalled that the vorticity perturbation problem in wall parallel flows was addressed at the beginning of the 20th century by J. L. Synge in an original way and as an alternative and equivalent way of determining flow stability with respect to the classical kinetic energy analysis. However, mathematical difficulties related to the vorticity boundary conditions left the problem open since then. Historically, the discovery of nonmodal perturbation growth and its link to the subcritical transition to turbulence lead to a preferential energy-based analysis. Here, we follow Synge's procedure and extend its work to the nonmodal approach and thus to the initial value problem capable to describe possible transient vorticity growth. Our calcul...
Kim, V T; Pivovarov, G B; Vary, J P; Kim, Victor T.; Matveev, Victor A.; Pivovarov, Grigorii B.; Vary, James P.
2001-01-01
Without a gauge fixing, canonical variables for the light-front SU(2) gluodynamics are determined. The Gauss law is written in terms of the canonical variables. The system is qualified as a generalized dynamical system with first class constraints. Abeliazation is a specific feature of the formulation (most of the canonical variables transform nontrivially only under the action of an Abelian subgroup of the gauge transformations). At finite volume, a discrete spectrum of the light-front Hamiltonian $P_+$ is obtained in the sector of vanishing $P_-$. We obtain, therefore, a quantized form of the classical solutions previously known as non-Abelian plane waves. Then, considering the infinite volume limit, we find that the presence of the mass gap depends on the way the infinite volume limit is taken, which may suggest the presence of different ``phases'' of the infinite volume theory.
Energy Technology Data Exchange (ETDEWEB)
D`yachkov, P.N. [Kurnakov Institute of General and Inorganic Chemistry, Moscow (Russian Federation); Nikolaev, A.V. [Institute of Physcial Chemistry, Moscow (Russian Federation)
1995-10-01
The advent of carbon nanotubes, which are graphite layers convoluted in cylinders several nanometers in diameter and several micrometers in length, as well as the experiments on implanting metal atoms in such tubes open the way to producing nanoconductors and other materials with unique properties. For theorists, the basic challenge is interpreting and predicting the structure and properties of these systems. The linearized augmented-plane-wave method (LAPW) is one of the most accurate methods in the theory of the electronic structure of solids. A generalization of this method for quasi-two-dimensional systems, surface electronic states, and layered crystals is known. The LAPW theory for quasi-unidimensional systems, which exhibit translational symmetry in one direction, has been absent thus far. In this paper, the authors suggest a version of such a theory and use this method to calculate the electronic structure of carbyne (a linear chain of carbon atoms) and carbon nanotube with implanted Sc atoms.
Directory of Open Access Journals (Sweden)
C. H. Schmidt
2009-05-01
Full Text Available The radiation of large antennas and those operating at low frequencies can be determined efficiently by near-field measurement techniques and a subsequent near-field far-field transformation. Various approaches and algorithms have been researched but for electrically large antennas and irregular measurement contours advanced algorithms with low computation complexity are required. In this paper an algorithm employing plane waves as equivalent sources and utilising efficient diagonal translation operators is presented. The efficiency is further enhanced using simple far-field translations in combination with the expensive near-field translations. In this way a low complexity near-field transformation is achieved, which works for arbitrary sample point distributions and incorporates a full probe correction without increasing the complexity.
Mobile Ultrasound Plane Wave Beamforming on iPhone or iPad using Metal- based GPU Processing
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.
Scattering and Absorption of Gravitational Plane Waves by Rotating Black Holes
Dolan, Sam R
2008-01-01
In this study, we investigate scattering and absorption of planar gravitational waves by a Kerr black hole in vacuum. We compute cross sections for radiation incident along the rotation axis, and consider both co- and counter-rotating circular polarizations. We show that, if a novel series reduction method is employed, the partial wave approach developed by Matzner and coworkers yields accurate results. Phase shifts are computed via a Sasaki-Nakamura transformation, and spheroidal harmonics via a spectral decomposition method. A catalogue of cross sections is presented for a range of parameters ($M\\omega \\le 4$ and $a \\le 0.99M$). In the long- and short-wavelength regimes we find good agreement with perturbative and semi-classical approximations. We confirm that helicity is not conserved: flux scattered in the backward direction has the opposite polarization to the incident radiation. At low frequencies, fast-rotating holes generate superradiance in the $l = 2$, $m = 2$ mode which enhances the back-scattered ...
Plane wave excitation-detection of non-resonant plasmons along finite-width graphene strips.
Gómez-Díaz, J S; Esquius-Morote, M; Perruisseau-Carrier, J
2013-10-21
An approach to couple free-space waves and non-resonant plasmons propagating along graphene strips is proposed based on the periodic modulation of the graphene strip width. The solution is technologically very simple, scalable in frequency, and provides customized coupling angle and intensity. Moreover, the coupling properties can be dynamically controlled at a fixed frequency via the graphene electrical field effect, enabling advanced and flexible plasmon excitation-detection strategies. We combine a previously derived scaling law for graphene strips with leaky-wave theory borrowed from microwaves to achieve rigorous and efficient modeling and design of the structure. In particular we analytically derive its dispersion, predict its coupling efficiency and radiated field structure, and design strip configurations able to fulfill specific coupling requirements. The proposed approach and developed methods are essential to the recent and fundamental problem of the excitation-detection of non-resonant plasmons propagating along a continuous graphene strip, and could pave the way to smart all-graphene sensors and transceivers.
Institute of Scientific and Technical Information of China (English)
Chang-Jun Zheng; Hai-Bo Chen; Lei-Lei Chen
2013-01-01
This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave problems.The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only.Moreover,a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived,and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating,translating and saving the multipole/local expansion coefficients of the image domain.The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems.As for exterior acoustic problems,the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method.Details on the implementation of the present method are described,and numerical examples are given to demonstrate its accuracy and efficiency.
Mita, Akifumi; Okamoto, Atsushi; Funakoshi, Hisatoshi
2004-06-01
We have proposed an all-optical authentic memory with the two-wave encryption method. In the recording process, the image data are encrypted to a white noise by the random phase masks added on the input beam with the image data and the reference beam. Only reading beam with the phase-conjugated distribution of the reference beam can decrypt the encrypted data. If the encrypted data are read out with an incorrect phase distribution, the output data are transformed into a white noise. Moreover, during read out, reconstructions of the encrypted data interfere destructively resulting in zero intensity. Therefore our memory has a merit that we can detect unlawful accesses easily by measuring the output beam intensity. In our encryption method, the random phase mask on the input plane plays important roles in transforming the input image into a white noise and prohibiting to decrypt a white noise to the input image by the blind deconvolution method. Without this mask, when unauthorized users observe the output beam by using CCD in the readout with the plane wave, the completely same intensity distribution as that of Fourier transform of the input image is obtained. Therefore the encrypted image will be decrypted easily by using the blind deconvolution method. However in using this mask, even if unauthorized users observe the output beam using the same method, the encrypted image cannot be decrypted because the observed intensity distribution is dispersed at random by this mask. Thus it can be said the robustness is increased by this mask. In this report, we compare two correlation coefficients, which represents the degree of a white noise of the output image, between the output image and the input image in using this mask or not. We show that the robustness of this encryption method is increased as the correlation coefficient is improved from 0.3 to 0.1 by using this mask.
Dorn, H
2003-01-01
Projecting on a suitable subset of coordinates, a picture is constructed in which the conformal boundary of AdS sub 5 xS sup 5 and that of the plane wave resulting in the Penrose limit are located at the same line. In a second line of arguments all AdS sub 5 xS sup 5 and plane wave geodesics are constructed in their integrated form. Performing the Penrose limit, the approach of null geodesics reaching the conformal boundary of AdS sub 5 xS sup 5 to that of the plane wave is studied in detail. At each point these null geodesics of AdS sub 5 xS sup 5 form a cone which degenerates in the limit. (author)
DEFF Research Database (Denmark)
Celestinos, Adrian; Nielsen, Sofus Birkedal
2008-01-01
When low frequency sound is radiated inside small listening spaces by loudspeakers, large uniformities occur over the sound field. This is due to the multiple reflection and diffraction of sound on the walls and different objects in the room. A developed system named Controlled Acoustically Bass...... evaluated by using a computer simulation program based on the Finite Difference Time Domain Method (FDTD). CABS has been simulated in a small car cabin and in an irregular room. Non-ideal placement of loudspeakers in CABS have been evaluated. The influence of utilizing CABS with different types...
Tunnel effect of fractal fault and transient S-wave velocity rupture (TSVR) of in-plane shear fault
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
Transient S-wave velocity rupture (TSVR) means the velocity of fault rupture propagation is between S-wave velocity βand P-wave velocity α. Its existing in the rupture of in-plane (i.e. strike-slip) fault has been proved, but in 2-dimensional classical model, there are two difficulties in transient S-wave velocity rupture, i.e., initialization difficulty and divergence difficulty in interpreting the realization of TSVR. The initialization difficulty means, when v↑vR (Rayleigh wave velocity), the dynamic stress strength factor K2(t)→+0, and changes from positive into negative in the interval (vR,β). How v transit the forbidden of (vR,β)? The divergence difficulty means K2(t)→+ when v↓. Here we introduce the concept of fractal and tunnel effect that exist everywhere in fault. The structure of all the faults is fractal with multiple cracks. The velocity of fault rupture is differentiate of the length of the fault respect to time, so the rupture velocity is also fractal. The tunnel effect means the dynamic rupture crosses over the interval of the cracks, and the coalescence of the intervals is slower than the propagation of disturbance. Suppose the area of earthquake nucleation is critical or sub-critical propagation everywhere, the arriving of disturbance triggers or accelerates the propagation of cracks tip at once, and the observation system cannot distinguish the front of disturbance and the tip of fracture. Then the speed of disturbance may be identified as fracture velocity, and the phenomenon of TSVR appears, which is an apparent velocity. The real reason of apparent velocity is that the mathematics model of shear rupture is simplified of complex process originally. The dual character of rupture velocity means that the apparent velocity of fault and the real velocity of micro-crack extending, which are different in physics, but are unified in rupture criterion. Introducing the above-mentioned concept to the calculation of K2 (t), the difficulty of
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
Multiscale Simulation of Breaking Wave Impacts
DEFF Research Database (Denmark)
Lindberg, Ole
-distance based adaptivity method and redistributed via a point position filtering method. The incompressible and inviscid ALE-WLS model is applied to the following standard validation test cases: deforming elliptical drop, small amplitude standing waves and the dam break problem. The deforming elliptical drop...... and mass conservation is satisfied through a pressure-corrector type calculation of the pressure. The weighted least squares method (WLS) is combined with approximate Riemann solvers to introduce numerical smoothing of the solution around steep gradients in the velocity and pressure fields. The Poisson...... equation is solved and the pressure boundary conditions are satisfied by a generalized finite pointset method (GFPM); This provides a geometrically flexible and stable solution for the fluid pressure. The numerical approximations of these equations are performed on unstructured point distributions...
Simulation of Random Waves and Associated Laminar Bottom Shear Stresses
Institute of Scientific and Technical Information of China (English)
Mao-Lin SHEN; Ching-Jer HUANG
2008-01-01
This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundary conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves are determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the numerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug's model (1995). The transfer function method is also employed to determine the maximum shear stress, and is proved accurate.
Bryan, Sean; Che, George; Doyle, Simon; Flanigan, Daniel; Groppi, Christopher; Johnson, Bradley; Jones, Glenn; Mauskopf, Philip; McCarrick, Heather; Monfardini, Alessandro; Mroczkowski, Tony
2015-01-01
Imaging and spectroscopy at (sub-)millimeter wavelengths are key frontiers in astronomy and cosmology. Large area spectral surveys with moderate spectral resolution (R=50-200) will be used to characterize large scale structure and star formation through intensity mapping surveys in emission lines such as the CO rotational transitions. Such surveys will also be used to study the SZ effect, and will detect the emission lines and continuum spectrum of individual objects. WSPEC is an instrument proposed to target these science goals. It is a channelizing spectrometer realized in rectangular waveguide, fabricated using conventional high-precision metal machining. Each spectrometer is coupled to free space with a machined feed horn, and the devices are tiled into a 2D array to fill the focal plane of the telescope. The detectors will be aluminum Lumped-Element Kinetic Inductance Detectors (LEKIDs). To target the CO lines and SZ effect, we will have bands at 135-175 GHz and 190-250 GHz, each Nyquist-sampled at R~200...
Bryan, Sean; Aguirre, James; Che, George; Doyle, Simon; Flanigan, Daniel; Groppi, Christopher; Johnson, Bradley; Jones, Glenn; Mauskopf, Philip; McCarrick, Heather; Monfardini, Alessandro; Mroczkowski, Tony
2016-07-01
Imaging and spectroscopy at (sub-)millimeter wavelengths are key frontiers in astronomy and cosmology. Large area spectral surveys with moderate spectral resolution (R=50-200) will be used to characterize large-scale structure and star formation through intensity mapping surveys in emission lines such as the CO rotational transitions. Such surveys will also be used to study the the Sunyaev Zeldovich (SZ) effect, and will detect the emission lines and continuum spectrum of individual objects. WSPEC is an instrument proposed to target these science goals. It is a channelizing spectrometer realized in rectangular waveguide, fabricated using conventional high-precision metal machining. Each spectrometer is coupled to free space with a machined feed horn, and the devices are tiled into a 2D array to fill the focal plane of the telescope. The detectors will be aluminum lumped-element kinetic inductance detectors (LEKIDs). To target the CO lines and SZ effect, we will have bands at 135-175 and 190-250 GHz, each Nyquist-sampled at R≈ 200 resolution. Here, we discuss the instrument concept and design, and successful initial testing of a WR10 (i.e., 90 GHz) prototype spectrometer. We recently tested a WR5 (180 GHz) prototype to verify that the concept works at higher frequencies, and also designed a resonant backshort structure that may further increase the optical efficiency. We are making progress towards integrating a spectrometer with a LEKID array and deploying a prototype device to a telescope for first light.
Wave climate of the Adriatic Sea: a future scenario simulation
Directory of Open Access Journals (Sweden)
A. Benetazzo
2012-06-01
Full Text Available We present a study on expected wind wave severity changes in the Adriatic Sea for the period 2070–2099 and their impact on extremes. To do so, the phase-averaged spectral wave model SWAN is forced using wind fields computed by the high-resolution regional climate model COSMO-CLM, the climate version of the COSMO meteorological model downscaled from a global climate model running under the IPCC-A1B emission scenario. Namely, the adopted wind fields are given with a horizontal resolution of 14 km and 40 vertical levels, and they are prepared by the Italian Aerospace Research Centre (CIRA. Firstly, in order to infer the wave model accuracy in predicting seasonal variability and extreme events, SWAN results are validated against a control simulation, which covers the period 1965–1994. In particular, numerical predictions of the significant wave height H_{s} are compared against available in-situ data. Further, a statistical analysis is carried out to estimate changes on wave storms and extremes during the simulated periods (control and future scenario simulations. In particular, the generalized Pareto distribution is used to predict changes of storm peak H_{s} for frequent and rare storms in the Adriatic Sea. Finally, Borgman's theory is applied to estimate the spatial pattern of the expected maximum wave height H_{max} during a storm, both for the present climate and that of the future scenario. Results show a future wave climate in the Adriatic Sea milder than the present climate, even though increases of wave severity can occur locally.
Reliable Damping of Free Surface Waves in Numerical Simulations
Peric, Robinson
2015-01-01
This paper generalizes existing approaches for free-surface wave damping via momentum sinks for flow simulations based on the Navier-Stokes equations. It is shown in 2D flow simulations that, to obtain reliable wave damping, the coefficients in the damping functions must be adjusted to the wave parameters. A scaling law for selecting these damping coefficients is presented, which enables similarity of the damping in model- and full-scale. The influence of the thickness of the damping layer, the wave steepness, the mesh fineness and the choice of the damping coefficients are examined. An efficient approach for estimating the optimal damping setup is presented. Results of 3D ship resistance computations show that the scaling laws apply to such simulations as well, so the damping coefficients should be adjusted for every simulation to ensure convergence of the solution in both model and full scale. Finally, practical recommendations for the setup of reliable damping in flow simulations with regular and irregular...
Calculation technique for simulation of wave and fracture dynamics in a reinforced sheet
Ayzenberg-Stepanenko, M; Osharovich, G
2011-01-01
Mathematical models and computer algorithms are developed to calculate dynamic stress concentration and fracture wave propagation in a reinforced composite sheet. The composite consists of a regular system alternating extensible fibers and pliable adhesive layers. In computer simulations, we derive difference algorithms preventing or minimizing the parasite distortions caused by the mesh dispersion and obtain precise numerical solutions in the plane fracture problem of a pre-stretched sheet along the fibers. Interactive effects of microscale dynamic deformation and multiple damage in fibers and adhesive are studied. Two engineering models of the composite are considered: the first assumes that adhesive can be represented by inertionless bonds of constant stiffness, while in the second one an adhesive is described by inertial medium perceived shear stresses. Comparison of results allows the evaluation of facilities of models in wave and fracture patterns analysis.
Numerical simulation of pressure waves in the cochlea induced by a microwave pulse.
Yitzhak, Nir M; Ruppin, Raphael; Hareuveny, Ronen
2014-10-01
The pressure waves developing at the cochlea by the irradiation of the body with a plane wave microwave pulse are obtained by numerical simulation, employing a two-step finite-difference time-domain (FDTD) algorithm. First, the specific absorption rate (SAR) distribution is obtained by solving the Maxwell equations on a FDTD grid. Second, the temperature rise due to this SAR distribution is used to formulate the thermoelastic equations of motion, which are discretized and solved by the FDTD method. The calculations are performed for anatomically based full body human models, as well as for a head model. The dependence of the pressure amplitude at the cochlea on the frequency, the direction of propagation, and the polarization of the incident electromagnetic radiation, as well as on the pulse width, was investigated.
Design of full scale wave simulator for testing Power Take Off systems for wave energy converters
DEFF Research Database (Denmark)
Pedersen, H. C.; Hansen, R. H.; Hansen, Anders Hedegaard
2016-01-01
For wave energy to become a major future contributor of renewable energy it is a requirement that the efficiency and reliability of the Power Take-Off (PTO) systems is significantly improved. However, the cost of installing and testing PTO-systems at sea is very high. The focus of the current paper...... is therefore on the design and commissioning of a full scale wave simulator for testing PTO-systems for point absorbers. The challenge is to be able to design a system, which mimics the behavior of a wave when interacting with a given PTO-system – especially when considering discrete type PTO......-systems. The paper presents the designed system, including the major design considerations. A model of the complete system is presented and controllers for the system are developed. These enable the system to emulate the wave behavior and the wave–float interaction. Finally both simulation and experimental results...
Yaakob, M. K.; Taib, M. F. M.; Lu, L.; Hassan, O. H.; Yahya, M. Z. A.
2015-11-01
The structural, electronic, elastic, and optical properties of BiFeO3 were investigated using the first-principles calculation based on the local density approximation plus U (LDA + U) method in the frame of plane-wave pseudopotential density functional theory. The application of self-interaction corrected LDA + U method improved the accuracy of the calculated properties. Results of structural, electronic, elastic, and optical properties of BiFeO3, calculated using the LDA + U method were in good agreement with other calculation and experimental data; the optimized choice of on-site Coulomb repulsion U was 3 eV for the treatment of strong electronic localized Fe 3d electrons. Based on the calculated band structure and density of states, the on-site Coulomb repulsion U had a significant effect on the hybridized O 2p and Fe 3d states at the valence and the conduction band. Moreover, the elastic stiffness tensor, the longitudinal and shear wave velocities, bulk modulus, Poisson’s ratio, and the Debye temperature were calculated for U = 0, 3, and 6 eV. The elastic stiffness tensor, bulk modulus, sound velocities, and Debye temperature of BiFeO3 consistently decreased with the increase of the U value.
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.)
Characteristics of gravity waves generated in a baroclinic instability simulation
Directory of Open Access Journals (Sweden)
Y.-H. Kim
2015-11-01
Full Text Available An idealized baroclinic instability case is simulated using a ~ 10 km resolution global model to investigate the characteristics of gravity waves (GWs generated in the baroclinic life cycle. Three groups of GWs (W1–W3 appear around the high-latitude surface trough at the mature stage of the baroclinic wave. They have horizontal and vertical wavelengths of 40–400 and 2.9–9.8 km, respectively, in the upper troposphere. The two-dimensional phase-velocity spectrum of the waves is arc-shaped with a peak at 17 m s−1 eastward, which is difficult for the waves to propagate upward through the tropospheric westerly jet. At the breaking stage of the baroclinic wave, a midlatitude surface low is isolated from the higher-latitude trough, and two groups of quasi-stationary GWs (W4 and W5 appear near the surface low. These waves have horizontal and vertical wavelengths of 60–400 and 4.9–14 km, respectively, and are able to propagate vertically for long distances. The generation mechanism of the simulated GWs is discussed.
A family of nonlinear Schrödinger equations admitting q-plane wave solutions
Nobre, F. D.; Plastino, A. R.
2017-08-01
Nonlinear Schrödinger equations with power-law nonlinearities have attracted considerable attention recently. Two previous proposals for these types of equations, corresponding respectively to the Gross-Pitaievsky equation and to the one associated with nonextensive statistical mechanics, are here unified into a single, parameterized family of nonlinear Schrödinger equations. Power-law nonlinear terms characterized by exponents depending on a real index q, typical of nonextensive statistical mechanics, are considered in such a way that the Gross-Pitaievsky equation is recovered in the limit q → 1. A classical field theory shows that, due to these nonlinearities, an extra field Φ (x → , t) (besides the usual one Ψ (x → , t)) must be introduced for consistency. The new field can be identified with Ψ* (x → , t) only when q → 1. For q ≠ 1 one has a pair of coupled nonlinear wave equations governing the joint evolution of the complex valued fields Ψ (x → , t) and Φ (x → , t). These equations reduce to the usual pair of complex-conjugate ones only in the q → 1 limit. Interestingly, the nonlinear equations obeyed by Ψ (x → , t) and Φ (x → , t) exhibit a common, soliton-like, traveling solution, which is expressible in terms of the q-exponential function that naturally emerges within nonextensive statistical mechanics.
PIC simulations of wave-mode conversion on the plasmapause
Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej
2017-04-01
We study a conversion process from the electron Bernstein modes to electromagnetic free space modes using a 2D-3V electromagnetic PIC code with predefined particle density irregularities. We use a Gaussian profile of the particle density irregularity along the external magnetic field. Our results show the electron Bernstein modes generated by the ring-beam instability in the dense plasma region as well as their conversion into the electromagnetic waves. The resulting free space mode waves propagate out of the dense region perpendicular to magnetic field with the corresponding energy flux. Our simulation results are compared with measured data from Cluster and Van Allen Probes spacecraft. This wave mode conversion process might help us to explain generation of electromagnetic waves over the plasmapause density gradient.
Numerical Simulation of Cylindrical Solitary Waves in Periodic Media
Quezada de Luna, Manuel
2013-07-14
We study the behavior of nonlinear waves in a two-dimensional medium with density and stress relation that vary periodically in space. Efficient approximate Riemann solvers are developed for the corresponding variable-coefficient first-order hyperbolic system. We present direct numerical simulations of this multiscale problem, focused on the propagation of a single localized perturbation in media with strongly varying impedance. For the conditions studied, we find little evidence of shock formation. Instead, solutions consist primarily of solitary waves. These solitary waves are observed to be stable over long times and to interact in a manner approximately like solitons. The system considered has no dispersive terms; these solitary waves arise due to the material heterogeneity, which leads to strong reflections and effective dispersion.
Simulation of Wave-Plus-Current Scour beneath Submarine Pipelines
DEFF Research Database (Denmark)
Eltard-Larsen, Bjarke; Fuhrman, David R.; Sumer, B. Mutlu
2016-01-01
A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier–Stokes equations, coupled with k-ω turbulence closure, with additional bed and suspen......A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier–Stokes equations, coupled with k-ω turbulence closure, with additional bed...... and suspended load descriptions forming the basis for seabed morphology. The model was successfully validated against experimental measurements involving scour development and eventual equilibrium in pure-current flows over a range of Shields parameters characteristic of both clear-water and live-bed regimes....... This validation complements previously demonstrated accuracy for the same model in simulating pipeline scour processes in pure-wave environments. The model was subsequently utilized to simulate combined wave-plus-current scour over a wide range of combined Keulegan–Carpenter numbers and relative current strengths...
Simulation of guided wave propagation near numerical Brillouin zones
Kijanka, Piotr; Staszewski, Wieslaw J.; Packo, Pawel
2016-04-01
Attractive properties of guided waves provides very unique potential for characterization of incipient damage, particularly in plate-like structures. Among other properties, guided waves can propagate over long distances and can be used to monitor hidden structural features and components. On the other hand, guided propagation brings substantial challenges for data analysis. Signal processing techniques are frequently supported by numerical simulations in order to facilitate problem solution. When employing numerical models additional sources of errors are introduced. These can play significant role for design and development of a wave-based monitoring strategy. Hence, the paper presents an investigation of numerical models for guided waves generation, propagation and sensing. Numerical dispersion analysis, for guided waves in plates, based on the LISA approach is presented and discussed in the paper. Both dispersion and modal amplitudes characteristics are analysed. It is shown that wave propagation in a numerical model resembles propagation in a periodic medium. Consequently, Lamb wave propagation close to numerical Brillouin zone is investigated and characterized.
Simulating and understanding sand wave variation: A case study of the Golden Gate sand waves
Sterlini, F.; Hulscher, S.J.M.H.; Hanes, D.M.
2009-01-01
In this paper we present a detailed comparison between measured features of the Golden Gate sand wave field and the results of a nonlinear sand wave model. Because the Golden Gate sand waves exhibit large variation in their characteristics and in their environmental physics, this area gives us the opportunity to study sand wave variation between locations, within one well-measured, large area. The nonlinear model used in this paper is presently the only tool that provides information on the nonlinear evolution of large-amplitude sand waves. The model is used to increase our understanding of the coupling between the variability in environmental conditions and the sand wave characteristics. Results show that the model is able to describe the variation in the Golden Gate sand waves well when both the local oscillating tidal current and the residual current are taken into account. Current and water depth seem to be the most important factors influencing sand wave characteristics. The simulation results give further confidence in the underlying model hypothesis and assumptions. Copyright 2009 by the American Geophysical Union.
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
Several techniques can estimate the 2-D velocity vector in ultrasound. Directional beamforming (DB) estimates blood flow velocities with a higher precision and accuracy than transverse oscillation (TO), but at the cost of a high beamforming load when estimating the flow angle. In this paper......, it is proposed to use TO to estimate an initial flow angle, which is then refined in a DB step. Velocity magnitude is estimated along the flow direction using cross-correlation. It is shown that the suggested TO-DB method can improve the performance of velocity estimates compared to TO, and with a beamforming...... but within 4% for TO-DB. The same trends are observed in measurements although with a slightly larger bias. Simulations of realistic flow in a carotid bifurcation model provide visualization of complex flow, and the spread of velocity magnitude estimates is 7.1 cm/s for TO-DB, while it is 11.8 cm/s using...
Energy Technology Data Exchange (ETDEWEB)
Preston, M.F. [Lund University, SE-221 00 Lund (Sweden); Myers, L.S. [Duke University, Durham, NC 27708 (United States); Annand, J.R.M. [University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom); Fissum, K.G., E-mail: kevin.fissum@nuclear.lu.se [Lund University, SE-221 00 Lund (Sweden); Hansen, K.; Isaksson, L. [MAX IV Laboratory, Lund University, SE-221 00 Lund (Sweden); Jebali, R. [Arktis Radiation Detectors Limited, 8045 Zürich (Switzerland); Lundin, M. [MAX IV Laboratory, Lund University, SE-221 00 Lund (Sweden)
2014-04-21
Rate-dependent effects in the electronics used to instrument the tagger focal plane at the MAX IV Laboratory were recently investigated using the novel approach of Monte Carlo simulation to allow for normalization of high-rate experimental data acquired with single-hit time-to-digital converters (TDCs). The instrumentation of the tagger focal plane has now been expanded to include multi-hit TDCs. The agreement between results obtained from data taken using single-hit and multi-hit TDCs demonstrate a thorough understanding of the behavior of the detector system.
Guzatov, D. V.; Gaida, L. S.; Afanas'ev, Anatolii A.
2008-12-01
The light pressure force acting on a spherical dielectric particle in the interference field of two plane monochromatic electromagnetic waves is studied in detail for different particle radii and angles of incidence of waves.
Ba, Zhenning; Yin, Xiao
2016-06-01
A multidomain indirect boundary element method (IBEM) is proposed to study the wave scattering of plane SH waves by complex local site in a layered half-space. The new method, using both the full-space and layered half-space Green's functions as its fundamental solutions can also be regarded as a coupled method of the full-space IBEM and half-space IBEM. First, the whole model is decomposed into independent closed regions and an opened layered half-space region with all of the irregular interfaces; then, fictitious uniformly distributed loads are applied separately on the boundaries of each region, and scattered fields of the closed regions and the opened layered half-space region are constructed by calculating the full-space and layered half-space Green's functions, respectively; finally, all of the regions are assembled to establish the linear algebraic system that arises from discretization. The densities of the distributed loads are determined directly by solving the algebraic system. The accuracy and capability of the new approach are verified extensively by comparing its results with those of published approaches for a class of hills, valleys and embedded inclusions. And the capability of the new method is further displayed when it is used to investigate a hill-triple layered valley-hill coupled topography in a multilayered half-space. All of the numerical calculations presented in this paper demonstrate that the new method is very suitable for solving multidomain coupled multilayered wave scattering problems with the merits of high accuracy and representing the scattered fields in different kinds of regions more reasonably and flexibly.
Simulation of Surface Wave with Large Eddy Simulation in σ-Coordinate System
Institute of Scientific and Technical Information of China (English)
王玲玲
2004-01-01
A three-dimensional numerical model in the σ-coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgrid-scale (SGS) model with the concept of large eddy simulation (LES). The σ-coordinate transformation is introduced to map the irregular physical domain of the wavy free surface and uneven bottom onto the regular computational domain of the shape of rectangular prism. The operator splitting method, which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified Navier-Stokes Equation.The model is used to simulate the propagation of solitary wave and wave passing over a submerged breakwater. Numerical results are compared with available analytical solutions and experimental data in terms of velocity profiles, free surface displacement, and energy conservation. Good agreement is obtained. The method is proved to be of high accuracy and efficiency in simulating surface wave propagation and wave-structure interaction. It is suitable for the large and irregular physical domain, and requiring the non-uniform grid system. The present work provides a foundation for further studies of random waves, wave-structure interaction, wave-discharge interaction,etc.
Device for Underwater Laboratory Simulation of Unconfined Blast Waves
Courtney, Elijah; Courtney, Michael
2015-01-01
Shock tubes simulate blast waves to study their effects in air under laboratory conditions; however, few experimental models exist for simulating underwater blast waves that are needed for facilitating experiments in underwater blast transmission, determining injury thresholds in marine animals, validating numerical models, and exploring mitigation strategies for explosive well removals. This method incorporates an oxy-acetylene driven underwater blast simulator which creates peak blast pressures of about 1860 kPa. Shot-to-shot consistency was fair, with an average standard deviation near 150 kPa. Results suggest peak blast pressures from 460 kPa to 1860 kPa are available by adjusting the distance from the source.
Simulated Obstructive Sleep Apnea Increases P-Wave Duration and P-Wave Dispersion
Wons, Annette M.; Rossi, Valentina; Bratton, Daniel J.; Schlatzer, Christian; Schwarz, Esther I.; Camen, Giovanni; Kohler, Malcolm
2016-01-01
Background A high P-wave duration and dispersion (Pd) have been reported to be a prognostic factor for the occurrence of paroxysmal atrial fibrillation (PAF), a condition linked to obstructive sleep apnea (OSA). We tested the hypothesis of whether a short-term increase of P-wave duration and Pd can be induced by respiratory manoeuvres simulating OSA in healthy subjects and in patients with PAF. Methods 12-lead-electrocardiography (ECG) was recorded continuously in 24 healthy subjects and 33 patients with PAF, while simulating obstructive apnea (Mueller manoeuvre, MM), obstructive hypopnea (inspiration through a threshold load, ITH), central apnea (AP), and during normal breathing (BL) in randomized order. The P-wave duration and Pd was calculated by using dedicated software for ECG-analysis. Results P-wave duration and Pd significantly increased during MM and ITH compared to BL in all subjects (+13.1ms and +13.8ms during MM; +11.7ms and +12.9ms during ITH; p<0.001 for all comparisons). In MM, the increase was larger in healthy subjects when compared to patients with PAF (p<0.05). Conclusion Intrathoracic pressure swings through simulated obstructive sleep apnea increase P-wave duration and Pd in healthy subjects and in patients with PAF. Our findings imply that intrathoracic pressure swings prolong the intra-atrial and inter-atrial conduction time and therefore may represent an independent trigger factor for the development for PAF. PMID:27071039
Compressive spectral method for the simulation of the water waves
Bayindir, Cihan
2015-01-01
In this paper an approach for decreasing the computational effort required for the spectral simulations of the water waves is introduced. Signals with majority of the components zero, are known as the sparse signals. Like majority of the signals in the nature it can be realized that water waves are sparse either in time or in the frequency domain. Using the sparsity property of the water waves in the time or in the frequency domain, the compressive sampling algorithm can be used as a tool for improving the performance of the spectral simulation of the water waves. The methodology offered in this paper depends on the idea of using a smaller number of spectral components compared to the classical spectral method with a high number of components. After performing the time integration with a smaller number of spectral components and using the compressive sampling technique, it is shown that the water wave field can be reconstructed with a significantly better efficiency compared to the classical spectral method w...
FEM Simulations of Leaky Lamb Wave in Ultrasonic Waveguide Sensor
Energy Technology Data Exchange (ETDEWEB)
Bae, Jin Ho; Joo, Young Sang; Kim, Jong Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-05-15
As the sodium coolant of a sodium-cooled fast reactor (SFR) is opaque to light, a conventional visual inspection cannot be used for carrying out an in-service inspection of the internal structures under a sodium level. An ultrasonic wave should be applied for an under-sodium viewing of the internal structures in a reactor vessel. Recently, a noble plate-type ultrasonic waveguide sensor has been developed for versatile applications in an under-sodium viewing application. The beam profile of a A{sub 0}-mode leaky Lamb wave of the waveguide sensor affects the resolution of visualization image in under-sodium viewing. In the design and manufacture of the waveguide sensor, the finite element method (FEM) modeling and simulation of the propagation of a leaky Lamb wave is required for the estimation and optimization of the waveguide sensor design parameters. In the previous research, the simple 2D modeling and simulation of the waveguide sensor had been carried out. In this work, FEM simulation of the propagation and radiation of the leaky Lamb wave in the waveguide sensor is performed for the vertical and lateral beam profile analysis using the pseudo 3D modeling including the wedge
Westerveld, W J; Yousefi, M
2015-01-01
We present an accurate and fast 3D simulation scheme for out-of-plane grating couplers, based on two dimensional rigorous (finite difference time domain) grating simulations, the effective index method (EIM), and the Rayleigh-Sommerfeld diffraction formula. In comparison with full 3D FDTD simulations, the rms difference in electric field is below 5% and the difference in power flux is below 3%. A grating coupler for coupling from a silicon-on-insulator photonic integrated circuit to an optical fiber positioned 0.1 mm above the circuit is designed as example.
Kinetic simulations of ladder climbing by electron plasma waves
Hara, Kentaro; Barth, Ido; Kaminski, Erez; Dodin, I. Y.; Fisch, N. J.
2017-05-01
The energy of plasma waves can be moved up and down the spectrum using chirped modulations of plasma parameters, which can be driven by external fields. Depending on whether the wave spectrum is discrete (bounded plasma) or continuous (boundless plasma), this phenomenon is called ladder climbing (LC) or autoresonant acceleration of plasmons. It was first proposed by Barth et al. [Phys. Rev. Lett. 115, 075001 (2015), 10.1103/PhysRevLett.115.075001] based on a linear fluid model. In this paper, LC of electron plasma waves is investigated using fully nonlinear Vlasov-Poisson simulations of collisionless bounded plasma. It is shown that, in agreement with the basic theory, plasmons survive substantial transformations of the spectrum and are destroyed only when their wave numbers become large enough to trigger Landau damping. Since nonlinear effects decrease the damping rate, LC is even more efficient when practiced on structures like quasiperiodic Bernstein-Greene-Kruskal (BGK) waves rather than on Langmuir waves per se.
Numerical Simulation of Wave Interaction with Moving Net Structures
DEFF Research Database (Denmark)
Chen, Hao; Christensen, Erik Damgaard
2015-01-01
Fluid structure interaction is an important issue in designof many engineering systems including offshore fish cages. As a first step to develop a coupled CFD/FEM model, in the present study a moving porous media model has been developed in the open source library Open FOAM. The net structure...... was described as a sheet of porous media with prescribed rigid body motion and mesh motion was incorporated to conform the motion of the net. Free surface wave generation and absorption framework was also introduced to simulate wave interaction with moving net structures. The results showed that mesh motion...... with moving net structures....
Large Eddy Simulation of the ventilated wave boundary layer
DEFF Research Database (Denmark)
Lohmann, Iris P.; Fredsøe, Jørgen; Sumer, B. Mutlu
2006-01-01
A Large Eddy Simulation (LES) of (1) a fully developed turbulent wave boundary layer and (2) case 1 subject to ventilation (i.e., suction and injection varying alternately in phase) has been performed, using the Smagorinsky subgrid-scale model to express the subgrid viscosity. The model was found...... size. The results indicate that the large eddies develop in the resolved scale, corresponding to fluid with an effective viscosity decided by the sum of the kinematic and subgrid viscosity. Regarding case 2, the results are qualitatively in accordance with experimental findings. Injection generally...... significantly. Ventilation therefore results in a net current, even in symmetric waves....
Wide-band slow-wave systems simulation and applications
Staras, Stanislovas
2012-01-01
The field of electromagnetics has seen considerable advances in recent years, based on the wide applications of numerical methods for investigating electromagnetic fields, microwaves, and other devices. Wide-Band Slow-Wave Systems: Simulation and Applications presents new technical solutions and research results for the analysis, synthesis, and design of slow-wave structures for modern electronic devices with super-wide pass-bands. It makes available, for the first time in English, significant research from the past 20 years that was previously published only in Russian and Lithuanian. The aut
Simulations of shock wave propagation in heterogeneous solids
Hertzsch, Jan-Martin; Ivanov, Boris A.; Kenkmann, Thomas
2002-11-01
Studies of shock wave propagation in heterogeneous materials are important for the interpretation of impact deformation and impact metamorphism of natural rocks. Reflection, refraction, and interference of shock waves caused by inhomogeneities lead to localised concentrations of pressure, temperature, and deformation rate, and in some cases to phase transitions. We have simulated numerically the shock compression of complex media in selected geometries with the aim of modelling shock recovery experiments and have observed reversible phase transitions in the target, shock heating alone may not be sufficient for the formation of impact melt, but localised shear at material boundaries results in considerable temperature increase which makes partial melting possible.