The Experts below are selected from a list of 1125 Experts worldwide ranked by ideXlab platform
Hyunjoo Kim - One of the best experts on this subject based on the ideXlab platform.
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nonstationary markovian replication process causing diverse diffusions
Physical Review E, 2017Co-Authors: Yichul Choi, Hyunjoo KimAbstract:We introduce a single generative mechanism that can be used to describe diverse nonstationary diffusions. A nonstationary Markovian replication process for steps is considered for which we derive analytically the time evolution of the probability distribution of the walker's displacement and the generalized Telegrapher equation with time-varying coefficients, and we find that diffusivity can be determined by temporal changes of replication of an immediate step. By controlling the replications, we realize diverse diffusions such as alternating diffusion, superdiffusion, subdiffusion, and marginal diffusion, which originate from oscillating, increasing, decreasing, and slowly increasing or decreasing replications with time, respectively.
Sergey Tkachenko - One of the best experts on this subject based on the ideXlab platform.
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High-Frequency Multiconductor Transmission-Line Theory
2020Co-Authors: Jurgen Nitsch, Sergey TkachenkoAbstract:Abstract This work presents a thorough derivation of the full-wave transmission-line equations on the basis of Maxwell's theory. The multiconductor system is assumed to be composed of nonuniform thin wires. It is shown that the mixed potential integral equations are equivalent to generalized Telegrapher equations. Novel, exact, and compact expressions for the multiconductor transmission-line parameters are derived, and it is shown how they are connected to radiation effects. Iteration and perturbation procedures are proposed for the solution of the generalized transmission-line equations
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High-Frequency Multiconductor Transmission-Line Theory
Foundations of Physics, 2010Co-Authors: Jurgen Nitsch, Sergey TkachenkoAbstract:This work presents a thorough derivation of the full-wave transmission-line equations on the basis of Maxwell’s theory. The multiconductor system is assumed to be composed of nonuniform thin wires. It is shown that the mixed potential integral equations are equivalent to generalized Telegrapher equations. Novel, exact, and compact expressions for the multiconductor transmission-line parameters are derived, and their connection to radiation effects is shown. Iteration and perturbation procedures are proposed for the solution of the generalized transmission-line equations.
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generalized form of Telegrapher s equations for the electromagnetic field coupling to buried wires of finite length
IEEE Transactions on Electromagnetic Compatibility, 2009Co-Authors: Dragan Poljak, Sergey Tkachenko, Vicko Doric, Farhad Rachidi, Khalil El Khamlichi Drissi, Kamal Kerroum, Silvestar SesnicAbstract:In this paper, a generalized form of Telegrapher's equations for electromagnetic field coupling to buried wires is derived. The presented approach is based on thin-wire antenna theory. The effect of a dissipative half-space is taken into account via the reflection/transmission coefficient approximation. The conductor losses can be taken into account via the surface impedance per unit length. The derived equations are treated numerically via the Galerkin-Bubnov indirect boundary element method. Numerical results are presented for induced current along the wire, and compared with transmission-line (TL) and modified TL (MTL) approximations, respectively, for the case of perfectly conducting electrode buried in a lossy medium. It is shown that the TL and MTL approximations can result in an inaccurate induced current distribution along the conductor at HFs and for shorter electrode lengths, respectively.
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generalized form of Telegrapher s equations for the electromagnetic field coupling to finite length lines above a lossy ground
IEEE Transactions on Electromagnetic Compatibility, 2007Co-Authors: Dragan Poljak, Farhad Rachidi, Sergey TkachenkoAbstract:In this paper, a generalized form of the Telegrapher's equations for electromagnetic field coupling to finite-length transmission lines above a lossy ground is derived. The approach is fully based on the thin-wire antenna theory. The effect of a lossy half-space is taken into account by means of the reflection coefficient approximation. The conductor losses can also be taken into account via surface impedance per unit length. The resulting equations are handled numerically via the Galerkin--Bubnov indirect boundary element method. Numerical results are presented for induced current along the line, and compared with transmission line (TL) approximation, for the case of lossless conductor. It is shown that the TL approximation can result in a significant underestimation of the induced currents.
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Telegrapher equations for arbitrary frequencies and modes radiation of an infinite lossless transmission line
Radio Science, 2004Co-Authors: J Nitsch, Sergey TkachenkoAbstract:[1] Maxwell's equations for an infinite, lossless transmission line above a perfectly conducting ground are transformed into Telegrapher equations with new generalized per-unit-length parameters of the conductor. These new line parameters are complex-valued, frequency-dependent, and contain the radiation resistance. Their explicit expressions depend on the chosen gauge, but there is also a gauge-independent representation for them. In the quasi-static approach of the Maxwell-Telegrapher equations the line parameters become real-valued, and radiation is absent. A Poynting vector analysis leads to a deeper physical understanding and interpretation of the new parameters.
Kh E Kaghashvili - One of the best experts on this subject based on the ideXlab platform.
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compound perpendicular diffusion of cosmic rays and field line random walk with drift
Particle Acceleration and Transport in the Heliosphere and Beyond: 7th Annual International AstroPhysics Conference, 2008Co-Authors: G M Webb, G P Zank, J Le A Roux, Kh E KaghashviliAbstract:A Chapman‐Kolmogorov equation describing compound transport of cosmic rays across the magnetic field, due to random walk of the field lines is investigated. The probability distribution (pdf) for the particle transport across the field P⊥, is given as a convolution of the pdf for random walk of the magnetic field, PFRW, with the pdf Pp, for particle transport relative to the random walking field. The model generalizes the previous work of Webb et al. [1], by including the effects of advection, drift and local perpendicular diffusion of the particles. At late times, it is found that the effective cross‐field diffusion coefficient κ⊥eff = κ⊥+κF where κ⊥ is the local perpendicular diffusion coefficent, and κF is the perpendicular diffusion coefficient due to field line random walk and due to advection and drift of the particles. At early times the particles undergo compound diffusion across the field. A Telegrapher model for Pp indicates that at the earliest times, the particles diffuse across the field due to field line random walk.A Chapman‐Kolmogorov equation describing compound transport of cosmic rays across the magnetic field, due to random walk of the field lines is investigated. The probability distribution (pdf) for the particle transport across the field P⊥, is given as a convolution of the pdf for random walk of the magnetic field, PFRW, with the pdf Pp, for particle transport relative to the random walking field. The model generalizes the previous work of Webb et al. [1], by including the effects of advection, drift and local perpendicular diffusion of the particles. At late times, it is found that the effective cross‐field diffusion coefficient κ⊥eff = κ⊥+κF where κ⊥ is the local perpendicular diffusion coefficent, and κF is the perpendicular diffusion coefficient due to field line random walk and due to advection and drift of the particles. At early times the particles undergo compound diffusion across the field. A Telegrapher model for Pp indicates that at the earliest times, the particles diffuse across the field due ...
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compound and perpendicular diffusion of cosmic rays and random walk of the field lines i parallel particle transport models
The Astrophysical Journal, 2006Co-Authors: G M Webb, G P Zank, Kh E Kaghashvili, J Le A RouxAbstract:A Chapman-Kolmogorov equation description of compound transport of cosmic rays due to random walk of the magnetic field lines, and for a range of models for particle transport along the field, is developed. The probability distribution, Pp, for the particle propagation along the field corresponds to either (1) a ballistic or scatter-free model, (2) a parallel diffusion model, or (3) a Telegrapher equation model. The probability distribution function (pdf) describing the magnetic field statistics, PFRW, is assumed to be Gaussian. These models are used to discuss features of the dropout events in the low-energy, solar cosmic-ray intensity observed by Mazur et al. We show that the Chuvilgin andPtuskintransportequationforcompounddiffusion,atsufficientlylatetimes,canbewrittenasafractionalFokkerPlanck equation, involving ordinary diffusion parallel to the mean magnetic field and compound diffusion of the particles normal to thefield. The Green’s function solution of the equation and the corresponding spatial moments of the particle transport, both parallel and perpendicular to the field, are obtained. The two-dimensional pdf for compound diffusion across the field is obtained as an inverse Laplace transform, or as a real integral. Subject headingg cosmic rays — diffusion — turbulence Online material: color figure
J Le A Roux - One of the best experts on this subject based on the ideXlab platform.
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compound perpendicular diffusion of cosmic rays and field line random walk with drift
Particle Acceleration and Transport in the Heliosphere and Beyond: 7th Annual International AstroPhysics Conference, 2008Co-Authors: G M Webb, G P Zank, J Le A Roux, Kh E KaghashviliAbstract:A Chapman‐Kolmogorov equation describing compound transport of cosmic rays across the magnetic field, due to random walk of the field lines is investigated. The probability distribution (pdf) for the particle transport across the field P⊥, is given as a convolution of the pdf for random walk of the magnetic field, PFRW, with the pdf Pp, for particle transport relative to the random walking field. The model generalizes the previous work of Webb et al. [1], by including the effects of advection, drift and local perpendicular diffusion of the particles. At late times, it is found that the effective cross‐field diffusion coefficient κ⊥eff = κ⊥+κF where κ⊥ is the local perpendicular diffusion coefficent, and κF is the perpendicular diffusion coefficient due to field line random walk and due to advection and drift of the particles. At early times the particles undergo compound diffusion across the field. A Telegrapher model for Pp indicates that at the earliest times, the particles diffuse across the field due to field line random walk.A Chapman‐Kolmogorov equation describing compound transport of cosmic rays across the magnetic field, due to random walk of the field lines is investigated. The probability distribution (pdf) for the particle transport across the field P⊥, is given as a convolution of the pdf for random walk of the magnetic field, PFRW, with the pdf Pp, for particle transport relative to the random walking field. The model generalizes the previous work of Webb et al. [1], by including the effects of advection, drift and local perpendicular diffusion of the particles. At late times, it is found that the effective cross‐field diffusion coefficient κ⊥eff = κ⊥+κF where κ⊥ is the local perpendicular diffusion coefficent, and κF is the perpendicular diffusion coefficient due to field line random walk and due to advection and drift of the particles. At early times the particles undergo compound diffusion across the field. A Telegrapher model for Pp indicates that at the earliest times, the particles diffuse across the field due ...
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compound and perpendicular diffusion of cosmic rays and random walk of the field lines i parallel particle transport models
The Astrophysical Journal, 2006Co-Authors: G M Webb, G P Zank, Kh E Kaghashvili, J Le A RouxAbstract:A Chapman-Kolmogorov equation description of compound transport of cosmic rays due to random walk of the magnetic field lines, and for a range of models for particle transport along the field, is developed. The probability distribution, Pp, for the particle propagation along the field corresponds to either (1) a ballistic or scatter-free model, (2) a parallel diffusion model, or (3) a Telegrapher equation model. The probability distribution function (pdf) describing the magnetic field statistics, PFRW, is assumed to be Gaussian. These models are used to discuss features of the dropout events in the low-energy, solar cosmic-ray intensity observed by Mazur et al. We show that the Chuvilgin andPtuskintransportequationforcompounddiffusion,atsufficientlylatetimes,canbewrittenasafractionalFokkerPlanck equation, involving ordinary diffusion parallel to the mean magnetic field and compound diffusion of the particles normal to thefield. The Green’s function solution of the equation and the corresponding spatial moments of the particle transport, both parallel and perpendicular to the field, are obtained. The two-dimensional pdf for compound diffusion across the field is obtained as an inverse Laplace transform, or as a real integral. Subject headingg cosmic rays — diffusion — turbulence Online material: color figure
Yichul Choi - One of the best experts on this subject based on the ideXlab platform.
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nonstationary markovian replication process causing diverse diffusions
Physical Review E, 2017Co-Authors: Yichul Choi, Hyunjoo KimAbstract:We introduce a single generative mechanism that can be used to describe diverse nonstationary diffusions. A nonstationary Markovian replication process for steps is considered for which we derive analytically the time evolution of the probability distribution of the walker's displacement and the generalized Telegrapher equation with time-varying coefficients, and we find that diffusivity can be determined by temporal changes of replication of an immediate step. By controlling the replications, we realize diverse diffusions such as alternating diffusion, superdiffusion, subdiffusion, and marginal diffusion, which originate from oscillating, increasing, decreasing, and slowly increasing or decreasing replications with time, respectively.
