ER2MD：一种ER模型到多维模型的转换算法

多维模型是数据仓库概念设计不可缺少的工具,将传统数据库实体关系模型直接转换到多维模型,势必在很大程度上缩短数据仓库系统的开发周期.针对数据仓库概念设计需求,在传统数据库基础上,提出一种面向多维模型的转换算法ER2MD.该算法可将满足一定条件的实体关系模型转换到多维模型,产生的多维模型符合广义多维范式,能够确保多维数据库分析计算的有效性,进而有利于物理数据库的设计.     

Techniques for establishing ergodic and recurrence properties of continuous-valued markov chains

We present techniques for classifying Markov chains with a continuous state space as either ergodic or recurrent. These methods are analogous to those of Foster for countable space chains. The theory is presented in the first half of the paper, while the second half consists of examples illustrating these techniques. The technique for proving ergodicity involves, in practice, three steps: showing that the chain is irreducible in a suitable sense; verifying that the mean hitting times on certain (usually bounded) sets are bounded, by using a “mean drift” criterion analogous to that of Foster; and finally, checking that the chain is such that bounded mean hitting times for these sets does actually imply ergodicity. The examples comprise a number of known and new results: using our techniques we investigate random walks, queues with waiting-time-dependent service times, dams with general and random-release rules, the s-S inventory model, and feedback models.     

The distribution of recoverable inventory items from a repair center when the number of consumption centers is large

This paper considers real-time decision rules for an inventory system where items are repaired than “used up.” The problem is to decide which user in the system has the greatest need for the newly available inventory items coming out of repair. The main result shows that two published approahes, the Transportation Time Look Ahead policy and METRIC, are optimal when the number of users gets large. A useful byproduct of the proof is a lower bound on the average backorder rate for a repair-inventory system of any size.     

条形装药在岩体中爆炸成腔过程的数值分析

利用LS-DYNA非线性有限元程序,对不同药量等级的条形装药,进行了无 限域岩体介质中的爆炸成腔数值模拟计算,得到了爆炸成腔过程的基本图像及爆腔形成的 位移时程曲线,通过对爆腔半径的数据分析对比,得到条形装药的长径比值k与爆腔半径和 装药半径之比值ra/R0呈线性关系、条形装药比集团装药具更强爆扩能力的结论。     

A decomposition algorithm applied to planning the interdiction of stochastic networks

We describe the application of a decomposition based solution method to a class of network interdiction problems. The problem of maximizing the probability of sufficient disruption of the flow of information or goods in a network whose characteristics are not certain is shown to be solved effectively by applying a scenario decomposition method developed by Riis and Schultz [Comput Optim Appl 24 (2003), 267–287]. Computational results demonstrate the effectiveness of the algorithm and design decisions that result in speed improvements. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

一维金属-介质光子晶体的特性

利用特征矩阵法对一维金属-介质光子晶体的特性进行了计算,发现此种光子晶体具有可见光透明,微波、紫外高反的光谱特性,而且存在比一维介质光子晶体更宽、反射更强的全向带隙.     

钢管初应力对方钢管混凝土构件性能的影响研究

在14根方钢管混凝土构件试验的基础上,分析了初应力系数、荷载偏心率、混凝土强度、试件长细比等因素对承载力的影响,给出了钢管初应力对方钢管混凝土压弯构件承载力的影响系数,采用ANSYS有限元分析程序进行了非线性全过程分析.     

基于TMS320DM642的电视跟踪系统设计

结合某电视跟踪系统的设计,介绍了其内部集成的通用视频端口,研究了它与编码器/解码器的无缝连接的实现方法,包括其驱动程序的构成特点和在CCS开发环境下的封装形式,着重介绍了标准PAL视频信号的采集、处理和显示的一般实现方法。     

流动注射分析法测定成烟产物中的Zn^2＋

采用流动注射分析技术建立了Zn^2＋的FIA分析方法．谊分析方法可行、简便。其数据可靠,具有较好的选择性和重现性．样品测定频率大于30个／h;在1．0～5．0mg／L范围内呈良好的线性关系,γ=0．9999;回收率大于98%．实现了烟幕剂成烟产物中Zn^2＋的快速定量测定．