一般中子输运方程的随机模拟方法

中子输运方程的随机摸拟方法在许多著作中部有研究,但它们所考虑的中子输运方程都与时间t无关,在所述的随机模拟法中都未给出具体的使用方案。本文将考虑更一般的中子输运方程     

二维柱坐标系辐射输运方程保球对称的离散纵标格式

 离散纵标格式是计算辐射输运方程的常用格式之一. 但是, 传统的离散纵标格式求解二维柱坐标系辐射输运方程模拟一维球对称问题时, 会出现明显的非对称现象, 球对称性被破坏. 针对该问题, 本文分析了传统离散纵标格式不能够保持球对称性的原因, 提出了空间基于柱坐标系、方向基于球坐标系的辐射输运方程, 并对该方程设计了新的离散纵标格式, 从理论上证明了当空间网格取球对称剖分时该离散格式能够保持一维球对称性的充分必要条件. 通过对真空球区域辐射输运、与物质耦合辐射输运等球对称算例的数值模拟, 验证了该格式的保球对称性, 球对称误差能够达到机器精度. 非对称辐射驱动模型以及非对称网格剖分条件下的数值模拟等算例也取得了较好的结果.     

锥形微通道内液滴自输运特性及力学驱动机制研究

针对液体在微通道内的自输运特性,采用数值仿真与能量解析相结合的方法研究了液滴在锥形微通道内的自输运特性及力学驱动机制,得到微通道的锥形角、液滴与微通道内壁的接触角及微通道的润湿性对液滴自输运特性的影响关系.分析表明,微通道的锥形角、液滴与微通道内壁的接触角均能影响液滴的自输运方向及驱动力大小.对于亲水性微通道,微通道的锥形角、液滴与微通道内壁的接触角其作用效果呈现整体形态;对于疏水性微通道,微通道的锥形角、液滴与微通道内壁的接触角其作用效果呈现局域形态.这可为研究液体在微通道内的自输运机理及界面内液体细观流动机制奠定理论基础.     

半导体材料科学中的能量输运模型

这是一篇关于半导体材料科学中能量输运模型的综述性章。该在这两个方面讨论了具有绝缘边值的两种典型能量输运模型的初边值问题，一方面得到了一种强解的存在性，另一方面得到了光滑解全局存在性和大时间行为。     

求解中子输运方程的粗网格再平衡方法

针对已知中子输运方程的标量通量P1近似值和网格边界通量模型情况下,我们提出了一种求解中子输运方程新的粗网格再平衡方法.方法将再平衡系统的稀疏矩阵变成对角占优矩阵,同时矩阵的逆是非负的.     

量子输运理论与非平衡手征凝聚

讨论量子输运理论以及反常手征凝聚 (DCC)的产生和演化 .建立了手征Nambu Jona Lasinio模型的量子输运方程和约束方程 .发现非平衡的夸克自旋分布是产生DCC的主要物理起因 ,而量子离壳效应可能导致长寿命的DCC .     

离散纵标方法与广义解

§1 中子,γ光子及其它粒子输运方程和计算方法的研究是核工程、技术领域内的一个重要内容.对粒子输运方程各种问题解的理论与数值研究具有重要意义.对这方面的研究有许多工作.本文的目的是用离散纵标(DSN)方法来作二维粒子输运方程:     

La0.5Sr0.5CoO3薄膜的外延生长及其电性能的研究

系统研究了在LaAlO3,SrTiO3和MgO衬底上、在不同的温度条件下利用脉冲激光法制备的La0.5Sr0.5CoO3薄膜的外延生长和电输运特性,测定了薄膜的电阻-温度关系.研究表明薄膜的电输运性质对其外延结构具有密切的依赖性,外延生长的薄膜具有低的电阻率和金属性导电特征;在LaAlO3衬底上在700℃左右外延生长的薄膜具有最佳的性能;探讨了这一薄膜的外延生长与其电输运性能的关系及其机理.     

非线性中子输运方程的Galerkin有限元解

§1.引言在核反应系统中,当中子数目足够多时,中子间的相互作用必须考虑,这就导致非线性中子输运方程。在这方面,已出现了一些研究工作,文献[1]对一类非线性中子输运方程,在一定的假定下,用半群方法证明了它的初边值问题解的存在性和唯一性。本文试图用[2]中的方法考察非线性中子输运方程的Galerkin有限元解。在§2中,给出了解的先验估计。在§3中,利用解的先验估计给出了广义解的存在性,构造了Galer-     

超临界系统自发启动概率计算

引言 我们曾求解过死绝方程,这种计算问题的核心是用Monte Carlo方法解非定常中子输运方程,同时还要解高次代数方程组。由于用Monte Carlo方法解非定常中子输运问题已有了介绍(见[1],[2]及[3]),于是本文重点在于求高次代数方程组的解,对     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

On a class of self-similar processes with stationary increments in higher order Wiener chaoses

We study a class of self-similar processes with stationary increments belonging to higher order Wiener chaoses which are similar to Hermite processes. We obtain an almost sure wavelet-like expansion of these processes. This allows us to compute the pointwise and local Hölder regularity of sample paths and to analyse their behaviour at infinity. We also provide some results on the Hausdorff dimension of the range and graphs of multidimensional anisotropic self-similar processes with stationary increments defined by multiple Wiener–Itô integrals.     

On a class of Riemann surfaces

It is considered the class of Riemann surfaces with dimT1 = 0, where T1 is a subclass of exact harmonic forms which is one of the factors in the orthogonal decomposition of the spaceΩH of harmonic forms of the surface, namely The surfaces in the class OHD and the class of planar surfaces satisfy dimT1 = 0. A.Pfluger posed the question whether there might exist other surfaces outside those two classes. Here it is shown that in the case of finite genus g, we should look for a surface S with dimT1 = 0 among the surfaces of the form Sg\K , where Sg is a closed surface of genus g and K a compact set of positive harmonic measure with perfect components and very irregular boundary.     

A REPRESENTATION FORMULA RELATED TO SCHR(O)DINGER OPERATORS

Schr(o)dinger operator is a central subject in the mathematical study of quantum mechanics.Consider the Schrodinger operator H = -△ V on R, where △ = d2/dx2 and the potential function V is real valued. In Fourier analysis, it is well-known that a square integrable function admits an expansion with exponentials as eigenfunctions of -△. A natural conjecture is that an L2 function admits a similar expansion in terms of "eigenfunctions" of H, a perturbation of the Laplacian (see [7], Ch. Ⅺ and the notes), under certain condition on V.     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.     

A unified approach to certain problems of best local approximation

In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms.     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Towards Excellence in Science Chinese Academy of Sciences

<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by