Shielded distribution approximation for a wall-bounded classical fluid

We investigate lower order distribution functions in classical fluids in the presence of large-scale inhomogeneities, in particular those imposed by wall contacts. The consequences of the effective shielding of a wall by the nearest particle of the set being considered are determined in the context of two distribution function hierarchies, kinematic and dynamic in origin. The effects of both flat and spherical, hard and soft walls are considered, as well as those of curved and double walls. A few correction sequences to the basic shielding approximation are discussed.Supported in part by the Department of Energy under contract DE-AC02-76 ERO 3077.     

三维高频声波的矩阵压缩边界节点法模拟

本文采用边界节点法(Boundary Knot Method, BKM)求解三维高频声场．由于高频赫姆霍兹方程的解是振荡的，极大影响了数值求解的精确度，需要在计算区域增加离散点，这会增加计算量．同时对于大规模声学问题，依靠边界节点法形成的插值矩阵为满秩，导致计算量过高和存储量过大．所以本文采用矩阵压缩技术(Matrix Compression, MC)，在有效继承边界节点法高精确度的基础上减少计算内存需求和时间，从而提高计算效率．数值实验表明，MC-BKM 求解精度高、收敛速度快、计算时间少，在高频大规模声波问题中应用前景广泛．     

An enhanced decomposition algorithm for multistage stochastic hydroelectric scheduling

Handling uncertainty in natural inflow is an important part of a hydroelectric scheduling model. In a stochastic programming formulation, natural inflow may be modeled as a random vector with known distribution, but the size of the resulting mathematical program can be formidable. Decomposition-based algorithms take advantage of special structure and provide an attractive approach to such problems. We develop an enhanced Benders decomposition algorithm for solving multistage stochastic linear programs. The enhancements include warm start basis selection, preliminary cut generation, the multicut procedure, and decision tree traversing strategies. Computational results are presented for a collection of stochastic hydroelectric scheduling problems.     

A new result in the theory and computation of the least-norm solution of a linear program

By perturbing properly a linear program to a separable quadratic program, it is possible to solve the latter in its dual variable space by iterative techniques such as sparsity-preserving SOR (successive overrelaxation) algorithms. The main result of this paper gives an effective computational criterion to check whether the solutions of the perturbed quadratic programs provide the least-norm solution of the original linear program.This research was sponsored by the United States Army under Contract No. DAAG29-80-C-0041. This material is based upon work supported by the National Science Foundation, Grant Nos. DCR-84-20963 and DMS-82-109050, and by the Italian National Research Council (CNR).The author wishes to thank Professor O. L. Mangasarian for his helpful comments which helped to improve the paper.     

Method of large-scale system and analysis of three-axis stability of system partially filled with liquid

In the paper the method of large-scale system is investigated. The criteria of three-axis stability of a partially liquid-filled system are obtained by means of the method of large-scale system. Numerical results are given for a liquid-filled system with three-flywheels.     

Auxiliary problem principle and decomposition of optimization problems

The auxiliary problem principle allows one to find the solution of a problem (minimization problem, saddle-point problem, etc.) by solving a sequence of auxiliary problems. There is a wide range of possible choices for these problems, so that one can give special features to them in order to make them easier to solve. We introduced this principle in Ref. 1 and showed its relevance to decomposing a problem into subproblems and to coordinating the subproblems. Here, we derive several basic or abstract algorithms, already given in Ref. 1, and we study their convergence properties in the framework of i infinite-dimensional convex programming.     

基于块系构造的大规模地下爆炸不可逆位移计算方法

岩体是复杂的等级构造地质体,本文中假设岩体构造符合Sadovsky院士块系构造等级学说,即岩体中存在稳定的不变量λ和μ_△,从而采用简化的分析模型研究构成岩体的岩块在爆炸地冲击扰动作用下的平动和转动,指出Kocharyan激活块体尺度计算式中忽略的条件,重新推导给出了大规模地下爆炸诱发远区局部不可逆位移计算公式。

     

基于大规模并行计算的三维多群中子扩散方程有限差分方法

三维多群中子扩散方程的精确、高效求解是核动力堆芯设计及燃料管理的基础。应用有限差分方法求解该方程具有简便、精确、成熟的优点;然而,该方法的计算量和存储量均较大,极大地限制了它的计算规模和应用范围。本文基于大规模并行计算,研究三维多群中子扩散方程有限差分方法：采用中心有限差分格式离散中子扩散方程;基于MPI并行编程模型,采用空间区域分解的方式实现大规模并行计算;采用多群多区域耦合PGMRES算法进行并行加速。在集群服务器上开发了ParaFiDi程序,并采用IAEA3D,PHWR等多个基准题对该程序进行验证。数值结果表明,ParaFiDi程序具有较高的计算精度和计算效率。     

Development of a rapid and sensitive HPLC method for the identification and quantification of cavoxin and cavoxone in Phoma cava culture filtrates

Cavoxin is a tetrasubstituted phytotoxic chalcone and cavoxone is the corresponding chroman-4-one, both produced in vitro by Phoma cava, a fungus isolated from chestnut. Cavoxin showed biofungicide potential against fungal species responsible for food moulding. Therefore, cavoxin has potential to be incorporated into biopolymer to generate ‘intelligent food packaging’. To reach this objective, large-scale production of cavoxin by P. cava fermentation needs to be optimized. A rapid and efficient method for cavoxin analysis, as well as of cavoxone, in the fungal culture filtrates and the corresponding organic extracts is the first experimental step. Thus, a HPLC method was developed and applied to quantify cavoxin and cavoxone production in two different fungal culture conditions. The analysis proved that cavoxin production in stirred culture filtrates is significantly higher than in static ones.