Dynamics of liquid-filled spacecraft

A method is presented for simulating coupled liquid-solid dynamics. An important example of a coupled liquid-solid system is a satellite carrying fuel. The dynamics of the satellite and the onboard fuel influence each other, which may lead to satellite motion that is uncontrollable. For better understanding of the complex dynamics of coupled systems, a numerical model is developed. The model consists of two parts. The first part that solves the liquid motion is only briefly discussed here. The focus in this paper is on the way in which the dynamics of the liquid and the solid body are coupled. For this, the governing equations are presented in which terms appear that represent the force and torque on the solid body due to the sloshing liquid. The governing equations are rewritten such that the discrete approximation of these equations can be integrated in a stable manner for arbitrary liquid/solid mass ratios. Results are presented demonstrating the stability of the present model. A grid-refinement study and a time-step analysis are performed. Finally, the flat-spin motion of a satellite, partially filled with liquid, that flew in 1992 as part of the Wet Satellite Model experiment is studied. Results from the simulation are compared with the actual flight data.     

交通平衡分配下的公路桥收费策略

假定一个城市被一条河流分为两部分（如我国的武汉，重庆等市），河上至少架设了两座公路桥梁，本文研究在交通平衡状态下，怎样制定车辆过桥梁的收费水平，使获得的总收入最大，乘客的总行驶时间最少，对多车种问题，研究了等价的数学模型和算法。还对一个含两座桥梁与三种车型的简单算例，进行了计算与分析。     

Optimal H∞ general distance problem with degree constraint

In this paper the optimal H_∞, general distance problem, for continuous-time systems, with a prescribed degree on the solution is studied. The approach is based on designing the Hankel singular values using an imbedding idea. The problem is first imbedded into another problem with desirable characteristics on the Hankel singular values, then the solution to the original problem is retracted via a compression. The result is applicable to both the one-block and the four-block problems. A special case is given for illustration.     

二维多孔数控钻床加工路径的生成及优化

印刷电路板 PCB的加工是二维多孔数控钻的典型。实践表明加工同一零件不同的走刀路径其长度相差极大。为提高生产率 ,应使刀具的走刀路径尽量短 ,这其实是大型的 TSP问题。本文提出了几种路径的生成方法 ,分析了各自的适用场合。并用实例验证所提出的路径生成方法可极大地提高实际钻孔的加工效率。     

一种新的加权最小二乘测距定位方法

三站二维定位问题是最小定位问题，一般只利用几何关系就能获得定位估计，但由于未利用距离测量的统计信息，定位精度较差。该文先将点到点的距离测量转化为点到线的距离估计，再在此基础上推导出一种新的加权几休定位方法，其中加权的确定利用了距离测量的统计信息。仿真实验表明，在测距误差较小时新方法具有更高的定位精度。     

Modeling of Energy Density Distribution in Rock Mass on the Basis of Seismotectonic and Geodetic Data

Using the focal mechanisms of earthquakes taken place from 1950 to 1996, the type and direction of principal strains were established, which made it possible to determine the volume stress-strain state of the south-east flank of the Baikal rift zone on the basis of the inverse problem solution. The variations in the stress-strain fields and spatial distribution of the stored potential energy density were found by the displacements of the daylight surface points in Tunkinsk geodetic proving ground in 1975 - 1986.     

The solution of the inverse problem of gravitational potential using a set of measurements of different field elements

A numerical solution of the inverse problem of the gravitational field at a single point is obtained using six field elements for a point, a spherical cap, a differential spherical sector and a vertical segment. In the system of six equations obtained, the unknowns are the mass of the body, the depth of its center, and the second, third, and fourth degree moments. The accuracy of the solution of this system is ten times higher than when using three field elements. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2007.     

合理开发利用钨矿资源 促进钨矿业可持续发展

简述了我国钨矿业概况、现有采选技术水平及钨矿加工利用率 ;从资源配置出发 ,阐述了钨矿业发展存在的几个主要问题 ,并且针对性地提出了可持续发展的几点建议。     

Solution of a multidimensional inverse radiation problem by means of mode reduction

The Karhunen–Loève Galerkin procedure is employed to solve an inverse radiation problem of determining the time‐varying strength of a heat source, which mimics flames in a furnace, from temperature measurements in three‐dimensional participating media where radiation and conduction occur simultaneously. The inverse radiation problem is solved through the minimization of a performance function, which is expressed by the sum of square residuals between calculated and observed temperature, using a conjugate gradient method. Through the Karhunen–Loève Galerkin procedure, one can represent the system dynamics with a minimum degree of freedom, and consequently the amount of computation required in the solution of the inverse problem is reduced drastically when the present technique is adopted. Copyright © 2004 John Wiley & Sons, Ltd.     

LW15-252型SF_6断路器存在的问题和对策

国产SF6断路器已在电力系统中得到了广泛的应用,随着时间的推移,这种断路器存在的问题也逐渐地暴露出来。笔者介绍了LW15-252型SF6断路器在实际运用中存在的问题和采取的对策。