The Experts below are selected from a list of 69807 Experts worldwide ranked by ideXlab platform
M. Hadjinicolaou - One of the best experts on this subject based on the ideXlab platform.
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Multipole expansions in Stokes flow
International Journal of Engineering Science, 2002Co-Authors: George Dassios, M. HadjinicolaouAbstract:Maxwell's theory of Multipoles is extended from potential theory to Stokes flow field, and from spherical to spheroidal geometry. The expansion is based on an exterior integral representation of the velocity and the pressure field of Stokes flow as well as the appropriate fundamental solution. It is shown that the velocity field is expandable in terms of five different Multipoles, four of which are weighted Multipoles. On the other hand, the pressure as well as the vorticity field, have multipole expansions that involve only the non-weighted Multipoles. In fact, a more general result is demonstrated according to which the pressure and the vorticity are given as the scalar and the vector invariants of the same harmonic dyadic field. The importance of the multipole expansion for the velocity and the pressure field is well known, and it refers both to the theoretical understanding of the flow, as well as to practical applications and numerical implementations.
Yoichi Haneda - One of the best experts on this subject based on the ideXlab platform.
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directivity synthesis with Multipoles comprising a cluster of focused sources using a linear loudspeaker array
International Conference on Acoustics Speech and Signal Processing, 2018Co-Authors: Kimitaka Tsutsumi, Yoichi Haneda, Kenichi Noguchil, Hideaki TakadaAbstract:A method to create Multipoles comprising a cluster of focused sources by using a linear loudspeaker array has recently been investigated. Directivities in a listening area were confirmed with examples of primitive Multipoles such as dipoles and quadrupoles. This paper describes a method to create a sound source having more complex directivity by using a superposition of Multipoles comprising a collection of focused sources. An analytical method is also described with which coefficients can be obtained for each multipole by circular harmonic expansion of a sound field created by a directional sound source and Taylor expansion of the corresponding sound field. Simulation results show that a superposition of Multipoles based on analytical conversion introduces desired directivities to the sound sources created in the listening area by a linear loudspeaker array.
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ICASSP - Design of multipole loudspeaker array based on spherical harmonic expansion
2011 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2011Co-Authors: Yoichi Haneda, Kenichi Furuya, Hiroaki ItouAbstract:We investigated the multipole loudspeaker array based on spherical harmonic expansion in the Cartesian coordinate system. The arrangement of the Multipoles with the least number of loudspeaker units has been studied for 2nd order of spherical harmonic expansion. The directivity of the multipole array does not achieve ideal directivity of the spherical functions due to the asymmetrical arrangement. The multipole array was also applied to an end-fire array because a multipole array uses less loudspeakers than the spherical array if the look-direction is fixed. We compared the performance of the conventional least-squares design method and multipole array method for an end-fire array. The least squares method had a higher directivity due to the large number of variable coefficients. Nevertheless, the multipole array based on spherical harmonic expansion has advantages of easy setup in the Cartesian coordinate system, analytical directivity, and small number of filter coefficients.
Lee G. Pedersen - One of the best experts on this subject based on the ideXlab platform.
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HPAM: Hirshfeld partitioned atomic Multipoles
Computer physics communications, 2012Co-Authors: Dennis M. Elking, Lalith Perera, Lee G. PedersenAbstract:An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic Multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank lmax on molecules of arbitrary shape and size. The HD and HD-I atomic charges/Multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/Multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/Multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from lmax = 0 (atomic charges) to lmax = 4 (atomic hexadecapoles). Both HD and HD-I atomic Multipoles up to rank lmax are shown to exactly reproduce ab initio molecular multipole moments of rank L for L ≤ lmax. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only (lmax = 0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used.
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Atomic forces for geometry‐dependent point multipole and Gaussian multipole models
Journal of computational chemistry, 2010Co-Authors: Dennis M. Elking, Lalith Perera, Robert E. Duke, Thomas A. Darden, Lee G. PedersenAbstract:In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise due to 1) the transfer of torque between neighboring atoms, and 2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In the current study, atomic force expressions for geometry-dependent Multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first
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Gaussian Multipole Model (GMM)
Journal of chemical theory and computation, 2009Co-Authors: Dennis M. Elking, Thomas A. Darden, G. Andrés Cisneros, Jean-philip Piquemal, Lee G. PedersenAbstract:An electrostatic model based on charge density is proposed as a model for future force fields. The model is composed of a nucleus and a single Slater-type contracted Gaussian multipole charge density on each atom. The Gaussian Multipoles are fit to the electrostatic potential calculated at the B3LYP/6-31G* and HF/aug-cc-pVTZ levels of theory and tested by comparing electrostatic dimer energies, intermolecular density overlap integrals, and permanent molecular multipole moments with their respective ab initio values. For the case of water, the atomic Gaussian multipole moments Qlm are shown to be a smooth function of internal geometry (bond length and angle), which can be approximated by a truncated linear Taylor series. In addition, results are given when the Gaussian multipole charge density is applied to a model for exchange−repulsion energy based on the intermolecular density overlap.
Hannam Mark - One of the best experts on this subject based on the ideXlab platform.
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Including higher order Multipoles in gravitational-wave models for precessing binary black holes
'American Physical Society (APS)', 2020Co-Authors: Khan Sebastian, Ohme Frank, Chatziioannou Katerina, Hannam MarkAbstract:Estimates of the source parameters of gravitational-wave (GW) events produced by compact binary mergers rely on theoretical models for the GW signal. We present the first frequency-domain model for the inspiral, merger, and ringdown of the GW signal from precessing binary black hole systems that also includes Multipoles beyond the leading-order quadrupole. Our model, PhenomPv3HM, is a combination of the higher-multipole nonprecessing model PhenomHM and the spin-precessing model PhenomPv3 that includes two-spin precession via a dynamical rotation of the GW Multipoles. We validate the new model by comparing to a large set of precessing numerical-relativity simulations and find excellent agreement across the majority of the parameter space they cover. For mass ratios
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Including higher order Multipoles in gravitational-wave models for precessing binary black holes
'American Physical Society (APS)', 2020Co-Authors: Khan Sebastian, Ohme Frank, Chatziioannou Katerina, Hannam MarkAbstract:Estimates of the source parameters of gravitational-wave (GW) events produced by compact binary mergers rely on theoretical models for the GW signal. We present the first frequency-domain model for inspiral, merger and ringdown of the GW signal from precessing binary-black-hole systems that also includes Multipoles beyond the leading-order quadrupole. Our model, {\tt PhenomPv3HM}, is a combination of the higher-multipole non-precessing model {\tt PhenomHM} and the spin-precessing model {\tt PhenomPv3} that includes two-spin precession via a dynamical rotation of the GW Multipoles. We validate the new model by comparing to a large set of precessing numerical-relativity simulations and find excellent agreement across the majority of the parameter space they cover. For mass ratios $
S. Hlavac - One of the best experts on this subject based on the ideXlab platform.
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Neutral pion photoproduction from the proton near threshold
Physics Letters B, 1996Co-Authors: Michael Fuchs, Ralf Peter Averbeck, A. R. Gabler, F. Härter, P.d. Harty, J. Ahrens, A. Bernstein, G. Anton, R Beck, S. HlavacAbstract:Abstract Differential and total cross sections for the photoproduction of neutral pions from the proton have been measured for incident photon energies from 140–270 MeV, using the photon spectrometer TAPS at the tagged photon beam of the 855 MeV Mainz Microtron. The energy dependence of the s- and p-wave Multipoles close to threshold was deduced from a multipole fit and a multipole analysis. The extracted s-wave amplitude E 0+ at threshold is found to be significantly smaller than the prediction of the classical low energy theorems, but is in reasonable agreement with the chiral perturbation theory.
