The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Petr Bouř - One of the best experts on this subject based on the ideXlab platform.
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A Fourier Transform Method for Generation of Anharmonic Vibrational Molecular Spectra.
Journal of chemical theory and computation, 2010Co-Authors: Ivan Ivani, Vladimír Baumruk, Petr BouřAbstract:Accurate computations of vibrational energies and vibrational spectra of molecules require inclusion of the anharmonic forces. In standard computational protocols, this leads to a large vibrational Hamiltonian matrix that needs to be diagonalized. Spectral intensities are calculated for individual transitions separately. In this work, an alternate direct generation of the spectral curves is proposed, based on a temporal propagation of a trial vibrational wave function followed by the Fourier Transformation (FT). The Method was applied to model water dimer and fenchone molecules. Arbitrary resolutions could be achieved by longer-time propagations, although a smaller integration time step (∼0.02 fs) was needed for accurate peak frequencies than previously found for similar time-dependent applications within the harmonic approximation. Acceptably accurate relative vibrational spectra intensities were obtained when many random vectors used in the propagations were averaged. For a model fenchone Hamiltonian, simulated Raman and Raman optical activity (ROA) spectral shapes compared well with those obtained by the classical approach. The algorithm is amendable to parallelization. The lack of the lengthy and computer-memory-demanding diagonalization thus makes the FT procedure especially convenient for spectral simulations of larger molecules.
J.m. Jarem - One of the best experts on this subject based on the ideXlab platform.
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The Green's function of a four-parallel-wire antenna system using Fourier Transform Method
IEEE Transactions on Electromagnetic Compatibility, 1993Co-Authors: M.k. Mansour, J.m. JaremAbstract:The Green's function associated with a four-parallel-wire antenna system is calculated using the spatial Fourier Transform Method. The specification of the Green's function is an important intermediate step toward determining the amount of coupling that occurs between an actual object located in the target zone of the antenna system and the four wires of the antenna system. The currents induced on the four wires and the scattered electromagnetic (EM) fields associated with a dipole source are calculated. Comparison of Fourier Transform Method (FTM) solution with Method-of-moments (MOM) solution is made for infinite four-parallel-wire antenna system. >
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Analysis of a four parallel wire antenna system by the spatial Fourier Transform Method
IEEE Transactions on Electromagnetic Compatibility, 1991Co-Authors: J.m. JaremAbstract:The electromagnetic fields and currents associated with an infinite four parallel wire transmission line are analyzed through the use of the spatial Fourier Transform Method. The near and far electromagnetic fields and currents that are associated with frill and gap voltage excitations are analyzed by the Fourier Transform Method. Possible VHF compact range applications of a four parallel wire antenna system are discussed, including the possibility of simulating an off-axis EM plane wave by the appropriate adjustment of the exciting voltage phase on each of the four parallel wires. Comparisons of Fourier Transform Method solutions with Method-of-moments solutions and finite-difference-time-domain solutions are made for an infinite four parallel wire antenna system. >
Ivan Ivani - One of the best experts on this subject based on the ideXlab platform.
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A Fourier Transform Method for Generation of Anharmonic Vibrational Molecular Spectra.
Journal of chemical theory and computation, 2010Co-Authors: Ivan Ivani, Vladimír Baumruk, Petr BouřAbstract:Accurate computations of vibrational energies and vibrational spectra of molecules require inclusion of the anharmonic forces. In standard computational protocols, this leads to a large vibrational Hamiltonian matrix that needs to be diagonalized. Spectral intensities are calculated for individual transitions separately. In this work, an alternate direct generation of the spectral curves is proposed, based on a temporal propagation of a trial vibrational wave function followed by the Fourier Transformation (FT). The Method was applied to model water dimer and fenchone molecules. Arbitrary resolutions could be achieved by longer-time propagations, although a smaller integration time step (∼0.02 fs) was needed for accurate peak frequencies than previously found for similar time-dependent applications within the harmonic approximation. Acceptably accurate relative vibrational spectra intensities were obtained when many random vectors used in the propagations were averaged. For a model fenchone Hamiltonian, simulated Raman and Raman optical activity (ROA) spectral shapes compared well with those obtained by the classical approach. The algorithm is amendable to parallelization. The lack of the lengthy and computer-memory-demanding diagonalization thus makes the FT procedure especially convenient for spectral simulations of larger molecules.
Li Zhi-quan - One of the best experts on this subject based on the ideXlab platform.
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Study on the split-step Fourier Transform Method in soliton evolution
Journal of Applied Optics, 2007Co-Authors: Li Zhi-quanAbstract:The split-step Fourier Transform Method(SSFM) and its simulation process are presented in detail.Matlab was used to simulate the soliton propagation in the optical fiber.The influence of optical fiber attenuation on soliton propagation is discussed.It is pointed out that two optical solitons will strongly affect each other if they are very close,which makes the soliton shape aberrant.The EDFA was adopted to compensate the power of the soliton and its result was reviewed.It is concluded that dispersion is the major limitation in the optical soliton communication,980 nm laser is selected to pump the EDFA to obtain better result.
Vladimír Baumruk - One of the best experts on this subject based on the ideXlab platform.
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A Fourier Transform Method for Generation of Anharmonic Vibrational Molecular Spectra.
Journal of chemical theory and computation, 2010Co-Authors: Ivan Ivani, Vladimír Baumruk, Petr BouřAbstract:Accurate computations of vibrational energies and vibrational spectra of molecules require inclusion of the anharmonic forces. In standard computational protocols, this leads to a large vibrational Hamiltonian matrix that needs to be diagonalized. Spectral intensities are calculated for individual transitions separately. In this work, an alternate direct generation of the spectral curves is proposed, based on a temporal propagation of a trial vibrational wave function followed by the Fourier Transformation (FT). The Method was applied to model water dimer and fenchone molecules. Arbitrary resolutions could be achieved by longer-time propagations, although a smaller integration time step (∼0.02 fs) was needed for accurate peak frequencies than previously found for similar time-dependent applications within the harmonic approximation. Acceptably accurate relative vibrational spectra intensities were obtained when many random vectors used in the propagations were averaged. For a model fenchone Hamiltonian, simulated Raman and Raman optical activity (ROA) spectral shapes compared well with those obtained by the classical approach. The algorithm is amendable to parallelization. The lack of the lengthy and computer-memory-demanding diagonalization thus makes the FT procedure especially convenient for spectral simulations of larger molecules.