The time dependent behaviour of high speed sequential files on cycling storage

The high speed file organization for sequential files on cycling storage units is recapitulated and its time dependent behaviour is studied as a stochastic process. The effective data rate for the one-buffer one-file situation is derived.The more usual situation with more than one buffer and two coupled files (master-in and master-out) is then studied as a Markov process. The interference between the two files and the effective data rate for the most usual situations are presented and it is shown that two buffers per file are not sufficient to smoothe the data rate.This work has been supported by SAAB-SCANIA AB and the Swedish Board for Technical development (72-408/U328, 74-6362).     

Dynamic hashing

A new file organisation called dynamic hashing is presented. The organisation is based on normal hashing, but the allocated storage space can easily be increased and decreased without reorganising the file, according to the number of records actually stored in the file. The expected storage utilisation is analysed and is shown to be approximately 69% all the time. Algorithms for inserting and deleting a record are presented and analysed. Retrieval of a record is fast, requiring only one access to secondary storage. There are no overflow records. The proposed scheme necessitates maintenance of a relatively small index structured as a forest of binary trees or slightly modified binary tries. The expected size of the index is analysed and a compact representation of the index is suggested.     

基于混合日志的内存数据库恢复子系统

介绍了一个基于混合日志（即逻辑日志与物理日志相结合）的内存数据库恢复子系统MDMRS的设计,MDMRS有效地减少了事务日志信息量,缩短了系统恢复时间。文中详细阐述了MDMRS的事务处理、日志管理、基于分区的检查点,以及数据库恢复处理,最后对MDMRS进行了性能分析。     

Mathematical model and numerical method for spontaneous potential log in heterogeneous formations

This paper introduces a new spontaneous potential log model for the case in which formation resistivity is not piecewise constant. The spontaneous potential satisfies an elliptic boundary value problem with jump conditions on the interfaces. It has beer/ shown that the elliptic interface problem has a unique weak solution. Furthermore, a jump condition capturing finite difference scheme is proposed and applied to solve such elliptic problems. Numerical results show validity and effectiveness of the proposed method.     

Partial regularity for minimizers of convex integrals with L log L-growth

We prove -partial regularity of minimizers with for a class of convex integral functionals with nearly linear growth whose model is In this way we extend to any dimension n a previous, analogous, result in [FS] valid only in the case Received December 1998     

A Re‐Examination of Sharpe's Ratio for Log‐Normal Prices

The purpose of this paper is to examine the exact properties of Sharpe's ratio when prices are log‐normal. Depending on the definition of returns, different expressions are formed for unbiased estimators of Sharpe's ratio.     

绘制等应力线的一种有效方法

本文提出了一种绘制受载结构等应力图的有效而简单的方法,这种方法是在开发PRSA-1专用有限元程序中逐渐改进和完善的,它能根据有限元的计算结果连续地在结构内搜索等应力点,也采用了适当的方法构造出一些等应力点。借助于AUTOCAD绘图软件包,结构的等应力图可以在计算机屏幕上自动生成,也可以用绘图仪绘出以便永久保留。     

温箱控制器的运行控制文件测试与研究

为了建立综合控制台对温度试验箱进行集中控制,需要对各独立的温控试验箱的运行文件进行分析和整合,形成可被温控试验箱执行的*.PRG程序文件。方法是首先通过原系统操作界面程序,设定温箱工作温度和时间,产生一个温箱控制器执行的*.PRG文件。然后,用Beyond Compare工具,对此(二进制)文件进行测试分析,得出文件的开始标志,温度阶梯步数,温度值单元,温度点切换时间单元,切换点行标志和文件结束标志等6个部分的位置关系,从而获得温箱控制器运行文件*.PRG的内部结构。根据文件内部数据结构关系,可以建立符合原*.PRG文件格式且可通用的可执行程序文件。在某型综合控制台的设计中采用该方法建立的*.PRG文件对各试验箱进行独立运行实验,实现了对温箱的综合控制。     

Monte Carlo exact goodness‐of‐fit tests for nonhomogeneous Poisson processes

Nonhomogeneous Poisson processes (NHPPs) are often used to model failure data from repairable systems, and there is thus a need to check model fit for such models. We study the problem of obtaining exact goodness‐of‐fit tests for parametric NHPPs. The idea is to use conditional tests given a sufficient statistic under the null hypothesis model. The tests are performed by simulating conditional samples given the sufficient statistic. Algorithms are presented for testing goodness‐of‐fit for the power law and the log‐linear law NHPP models. It is noted that while exact algorithms for the power law case are well known in the literature, the availability of such algorithms for the log‐linear case seems to be less known. A data example, as well as simulations, are considered. Copyright © 2010 John Wiley & Sons, Ltd.