共查询到20条相似文献,搜索用时 8 毫秒
1.
S.A. El-WakilM.A. Abdou A. Elhanbaly 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,75(4):517-527
Two different techniques have been used to solve the Fokker-Planck equation for electron transport in infinite homogeneous medium namely, maximum entropy and flux-limited approach. The solutions obtained for the scalar flux function φ0(x,s) by both methods are numerically compared. 相似文献
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An eigenexpansion solution of the time-independent Brownian motion Fokker-Planck equation is given for a situation in which the external acceleration is a step function. The solution describes the heavy-species velocity distribution function in a binary mixture undergoing a shock wave, in the limit of high dilution of the heavy species and negligible width of the light-gas internal shock. The diffusion solution is part of the eigenexpansion. The coefficients of the series of eigenfunctions are obtained analytically with transcendentally small errors of order exp(–1/M), whereM 1 is the mass ratio. Comparison is made with results from a hypersonic approximation. 相似文献
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GAO Jie 《中国物理C(英文版)》2009,33(2):135-144
In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC Ⅱ. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations. 相似文献
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In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations. 相似文献
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Y. Petroff 《Zeitschrift für Physik B Condensed Matter》1985,61(4):477-481
In this paper we briefly describe the principle of the free electron laser in a storage ring and the results obtained recently at Orsay. We also discuss the expected performances of such a device in more modern storage rings. 相似文献
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Half-range completeness theorems are proved for eigenfunctions associated to the one-dimensional Fokker-Planck equation in a semi-infinite medium. Existence and uniqueness results for perfectly absorbing, partially absorbing, and purely specularly reflecting boundary conditions are deduced for the stationary and time-dependent problems. Similar results are obtained for a slab geometry. 相似文献
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It is shown that the Fokker-Planck equations with linear drift γx and nonlinear drift , i.e. the Rayleigh process, have exact symmetries on their own solution manifolds, the sl(2, R) ? Weyl algebra and the sl(2, R) ? I, respectively. The symmetries of these two types of processes for 1 + 2-dimensional cases are explicitly found out too. 相似文献
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B. Dubroca J.-L. Feugeas M. Frank 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):301-307
An accurate and rapid kinetic model describing the
collisional transport of particles is presented. It is derived from
the Fokker-Planck equation and involves an angular closure in the
phase space leading to a set of hyperbolic equations for the moments
of the distribution function evolving in time, space and
energy. This method provides an alternative to the prohibitive cost
of a direct solution to the full kinetic equation. Moreover, it is
exact for the cases of collimated beams and the quasi-isotropic
distributions. It can be approximated with the usual numerical
schemes of the non-linear hyperbolic analysis. This model has
features that are required to simulate the electron or ion transport
for the inertial confinement fusion and the dose deposition for
radiation therapy of cancers. 相似文献
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In this paper a theoretical framework to estimate the bunch transverse emittance growing in electron storage rings due to short range transverse wakefield of the machine is established. New equilibrium emittance equations are derived and applied to explain the experimentally obtained results in ATF damping ring. This equation will be useful for linear collider damping ring design. 相似文献
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GAO Jie 《中国物理C(英文版)》2009,33(7)
In this paper a theoretical framework to estimate the bunch transverse emittance growing in electron storage rings due to short range transverse wakefield of the machine is established. New equilibrium emittance equations are derived and applied to explain the experimentally obtained results in ATF damping ring. This equation will be useful for linear collider damping ring design. 相似文献
16.
Christian Beck 《Journal of statistical physics》1995,79(5-6):875-894
We show that for certain classes of deterministic dynamical systems the Perron-Frobenius equation reduces to the Fokker-Planck equation in an appropriate scaling limit. By perturbative expansion in a small time scale parameter, we also derive the equations that are obeyed by the first- and second-order correction terms to the Fokker-Planck limit case. In general, these equations describe non-Gaussian corrections to a Langevin dynamics due to an underlying deterministic chaotic dynamics. For double-symmetric maps, the first-order correction term turns out to satisfy a kind of inhomogeneous Fokker-Planck equation with a source term. For a special example, we are able solve the first- and second-order equations explicitly. 相似文献
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Tarasov VE 《Chaos (Woodbury, N.Y.)》2005,15(2):23102
We consider the fractional generalizations of equation that defines the medium mass. We prove that the fractional integrals can be used to describe the media with noninteger mass dimensions. Using fractional integrals, we derive the fractional generalization of the Chapman-Kolmogorov equation (Smolukhovski equation). In this paper fractional Fokker-Planck equation for fractal media is derived from the fractional Chapman-Kolmogorov equation. Using the Fourier transform, we get the Fokker-Planck-Zaslavsky equations that have fractional coordinate derivatives. The Fokker-Planck equation for the fractal media is an equation with fractional derivatives in the dual space. 相似文献
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The Fokker-Planck equation in one dimension has been solved for a system in a periodic potential and linearly perturbed by a time- and space- varying external electric field. The solution is not exact, but we believe it is less approximate than any attempted previously on this problem. We have calculated the frequency and wave-vector dependent mobility and discussed its behaviour in some limiting cases.The application of our model to various physical situations is discussed. 相似文献