نتایج جستجو برای: moment equations
تعداد نتایج: 295805 فیلتر نتایج به سال:
Diffusive moment equations with an arbitrary number of moments are formally derived from the semiconductor Boltzmann equation employing a moment method and a Chapman-Enskog expansion. The moment equations are closed by employing a generalized Fermi-Dirac distribution function obtained from entropy maximization. The current densities allow for a drift-diffusion-type formulation or a “symmetrized...
We consider Bayesian estimation of state space models when the measurement density is not available but estimating equations for the parameters of the measurement density are available from moment conditions. The most common applications are partial equilibrium models involving moment conditions that depend on dynamic latent variables (e.g., timevarying parameters, stochastic volatility) and dy...
Numerical methods for linear kinetic equations based on moment expansions for a discretization in the velocity direction are examined. The moment equations are hyperbolic systems which can be shown to converge to the kinetic equation as the order of the expansion tends to innnity and to a drift-diiusion model as the Knudsen number tends to zero. A discretiza-tion of the moment equations with re...
This work discusses the application of the moment method to a generic form of kinetic equations, given by the Boltzmann equation, to simplify kinetic models of particle systems. Implicit to the method of moments is an approximation of moment closure relations to close the system of equations. The main aim is to explore the opportunities, pertaining to goal-oriented adaptive modeling, presented ...
In this paper, we propose a moment method to numerically solve the Vlasov equations using the framework of the NRxxmethod developed in [6, 8, 7] for the Boltzmann equation. Due to the same convection term of the Boltzmann equation and the Vlasov equation, it is very convenient to use the moment expansion in the NRxx method to approximate the distribution function in the Vlasov equations. The mo...
In order to overcome the disadvantages of time consuming and high computational cost in spatial moment, an improved sub-pixel edge detection algorithm based on spatial moment is proposed. Firstly, region of interest and Canny operator is used to reduce the number of edge points in the moment template operation. Then a constraint is set up by using the space moment characteristic of the edge to ...
The aim of this paper is to establish a connecting thread through the probabilistic concepts of pth-moment Lyapunov exponents, the integral averaging method, and Hale’s reduction approach for delay dynamical systems. We demonstrate this connection by studying the stability of perturbed deterministic and stochastic differential equations with fixed time delays in the displacement and derivative ...
We analyze a piecewise deterministic PDE consisting of the diffusion equation on a finite interval Ω with randomly switching boundary conditions and diffusion coefficient. We proceed by spatially discretizing the diffusion equation using finite differences and constructing the Chapman–Kolmogorov (CK) equation for the resulting finite-dimensional stochastic hybrid system. We show how the CK equa...
A complete set of boundary conditions for Grad’s 13 moment equations is derived from Maxwell’s boundary conditions for the Boltzmann equation. The equations are solved for plane Couette flow. The results exhibit temperature jump and slip, and agree well with DSMC calculations for Knudsen numbers Kn ≤ 0.1. Nonlinear effects lead to unphysical results at larger Knudsen numbers, and for very fast ...
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