摘要:

An analysis of the Weighted Linear Moments-Weighted Linear Discontinuous scheme (WLM-WLD scheme) for the transport equation is presented for the plane geometry case. The WLM-WLD scheme is an analogy of the WDD scheme in the class of schemes that use the zeroth and first spatial flux moments. It combines the high accuracy of nodal schemes with the main advantages of the WDD scheme such as arithmetic simplicity of algorithm and applicability to general multidimensional curvilinear geometry. The WLM-WLD scheme with the adaptive fix-up algorithm that is needed to ensure the positivity of solution gives an essential computational gain both in accuracy and speed for deep penetration transport problems compared with the WDD scheme.

ISSN:0041-1450    

DOI:10.1080/00411459408203535

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Transport and relaxation phenomena far away from local thermodynamic equilibrium are studied in the very long mean-free-path regime. A multiple timescale analysis of plasma kinetic equations with an extended Landau collision operator is performed up to third order in a small Larmor radius expansion. Coulomb collisions are shown to cause transient processes such as anisotropy and energy relaxations in second order and cross-field transport in third order of the smallness parameter. Examples of anisotropic screw-pinch equilibria and of relaxation processes in a deuterium plasma with hot minority ions are presented. The radial particle flux subjected to the constraint of ambipolarity is calculated and shown to be substantially modified in size and direction by transient relaxation processes and anisotropy effects.

ISSN:0041-1450    

DOI:10.1080/00411459408203536

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Monte Carlo simulation is often used to solve radiative transfer problems where complex physical phenomena and geometries must be handled. Slow convergence is a well-known disadvantage of such methods. In this paper we demonstrate that a significant improvement in computation time can be achieved by using Quasi-Monte Carlo methods to simulate Rapid Thermal Processing, which is an important technique for the production of semiconductor wafers, as well as many other industrial processes. Several factors are considered including surface absorptivity, position of wafer surface to heat source, and choice of quasi-random sequence. A comparison of the fractional and discrete absorption methods is also made. Results show accelerated convergence and improved accuracy of QMC over the standard Monte Carlo approach, and indicate when the fractional and discrete absorption methods should be used to obtain optimal results.

ISSN:0041-1450    

DOI:10.1080/00411459408203537

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

It is proved that the solution to the Boltzmann equation for the Lebowitz stick model is close in theL∞ norm to a local “Maxwellian” whose “parameters” satisfy the hydrodynamical equations.

ISSN:0041-1450    

DOI:10.1080/00411459408203538

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We study the one-dimensional streaming operator in a slab domain with boundary conditions of Maxwell type. By using techniques of the theory of semigroups of linear operators in a L1space context, we prove that the streaming operator is the infinitesimal generator of a strongly continuos semigroup, even if the boundary is “particle multiplying”. This semigroup is positive, quasi-bounded and obviously not contractive.

ISSN:0041-1450    

DOI:10.1080/00411459408203539

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

While solving Cauchy type singular integral equation via collocation procedure, the principal value integrals need to be approximated by suitable quadratures. This note highlights the superiority of the hyperbolic tangent quadrature for this purpose vis-a-vis conventional Gauss or Tchebyshev type quadratures. In particular, the ability to handle end point singularities of the integrand, arbitrary choice of collocation nodes combined with easy generation of nodes and efficiency are brought out by application to four test problems. IMT quadrature has also been adopted for this task but with less economy in computation.

ISSN:0041-1450    

DOI:10.1080/00411459408203540

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The distribution function of the one-dimensional Brownian motion in a uniform force field with Dirichlet boundary conditions is found by reducing it to an integral equation.

ISSN:0041-1450    

DOI:10.1080/00411459408203541

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Three-dimensional motion of rigid-sphere molecules in a specularly reflecting box is examined by the molecular dynamics method. Since the total energy of the molecular system is kept constant, the system settles down into a microcanonical equilibrium, for which the one-particle velocity distribution function is already known from the theory of microcanonical ensemble. It is shown that the time average of the molecular dynamics data at equilibrium gives the same velocity distribution function, i.e., that the system is ergodic.

ISSN:0041-1450    

DOI:10.1080/00411459408203542

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor