Average-Case Analysis for a Simple Compression Algorithm

In this paper we treat the static dictionary problem , very well known in computer science. It consists in storing a set S of m elements in the range [1 . . . n ] so that membership queries on S 's elements can be handled in O(1) time. It can be approached as a table compression problem in which a size n table has m ones and the other elements are zeros. We focus our attention on sparse case (m n ). We use a simple algorithm to solve the problem and make an average-case analysis of the total space required when the input derives from uniform probability distribution. We also find some conditions able to minimize storage requirements. We then propose and analyze a new algorithm able to reduce storage requirements drastically to O(m ^4/3 ) . Received December 1, 1997; revised March 1, 1998.     

0LAP中多维数组的一种改进压缩算法

基于多维数组MOLAP技术,针对目前使用较多的多维数组线性化压缩存储方法在处理维内部层次的聚集查询方面效率比较低的问题,本文提出了一种新的压缩存储方法,即采用二进制编码存储维方法,能有效提高存储和查询效率。     

基于论域压缩的启发式属性约简算法

论证在简化的信息系统上进行属性约简的可行性,指出某信息系统属性约简快速算法的计算结果可能含冗余属性,且在时间复杂度计算上存在错误。在此基础上,提出一种基于论域压缩的启发式属性约简算法,将相对支持度作为启发信息,缩小搜索空间,加入二次约简过程以消除冗余属性。实例分析表明,该算法具有较好的约简效果。     

一种密集相机阵列的低复杂度视频压缩方法

为了降低多视点视频压缩的复杂度，根据密集相机阵列系统与Wyner—Ziv编码的特点，提出了基于Wyner—Ziv编码的密集相机阵列低复杂度视频压缩算法。该算法首先在各相机之间相互独立地采用基于感兴趣区提取的低复杂度来进行Wyner—ziv编码，然后在中心解码端利用各视点间的相关性进行联合解码。该算法是通过对DCT量化系数进行相似性判断来提取感兴趣区，以有效地避免对背景和平坦等区域进行编码，从而降低了编码复杂度。实验证明，该算法具有极低的编码复杂度特性和良好的率失真性能，编码复杂度仅为H．264帧间预测编码的1／22。     

Development of a State-Space Water-Level Control for an Array of Cells to be Employed as Compensator in Radiotherapy

This paperdeals with the problem of water-level control for an array ofcells by means of an hydraulic circuit. An on-off valve fillsall the cells, while each cell is drained by a single on-offvalve, so the control is intrinsically coupled. An optimal controlwith PWM (pulse width modulation) valves is carried out. At theend, simulation and experimental results are presented. The arrayof cells may find application as compensator for radiotherapy(Total Body Irradiation), by interposing the cells between thex-ray source and the patient: on-line water-level variationsin the cells allow local radiation dose control.     

浅析C语言中指针与数组

数组和指针是C语言学习的重点与难点,就数组与指针的密切关系,分别对指针、数组元素的引用、数组指针和指针数组等知识点进行归纳总结,探讨了不同类型指针在数组中的使用方法,并通过实例进行说明.     

Entropy and Compression: A Simple Proof of an Inequality of Khinchin-Ornstein-Shields

Problems of Information Transmission - This paper concerns the folklore statement that “entropy is a lower bound for compression.” More precisely, we derive from the entropy theorem a...     

Average Case Analyses of List Update Algorithms, with Applications to Data Compression

We study the performance of the Timestamp (0) (TS(0)) algorithm for self-organizing sequential search on discrete memoryless sources. We demonstrate that TS(0) is better than Move-to-front on such sources, and determine performance ratios for TS(0) against the optimal off-line and static adversaries in this situation. Previous work on such sources compared on-line algorithms only with static adversaries. One practical motivation for our work is the use of the Move-to-front heuristic in various compression algorithms. Our theoretical results suggest that in many cases using TS(0) in place of Move-to-front in schemes that use the latter should improve compression. Tests using implementations on a standard corpus of test documents demonstrate that TS(0) leads to improved compression. Received December 3, 1995; revised April 5, 1997.     

Analysis of a Heuristic for Code Partitioning

In this paper, we analyze the time complexity and performance of a heuristic for code partitioning for Distributed Memory Multiprocessors (DMMs). The partitioning method is data-flow based where all levels of parallelism are exploited. Given a weighted Directed Acyclic Graph (DAG) representation of the program, our algorithm automatically determines the granularity of parallelism by partitioning the graph into tasks to be scheduled on the DMM. The granularity of parallelism depends only on the program to be executed and on the target machine parameters. The output of our algorithm is passed on as input to the scheduling phase. Finding an optimal solution to this problem is NP-complete. Due to the high cost of graph algorithms, it is nearly impossible to come up with close to optimal solutions that do not have very high cost (higher order polynomial). Our proposed heuristic gives good performance and has relatively low cost.     

基于稀疏表示的阵列声波测井仪数据无损压缩传输方法

交叉多极子阵列声波测井仪在井下信号采集的同时,采用无损压缩提升单位时间内上传数据量,是目前主流的仪器上传带宽增加方式。针对传统压缩方法压缩率较低,导致仪器在单位深度地层工作时长过长的问题,从信号稀疏表示的角度出发,对采集的多路声波波列采用预先构建的稀疏变换矩阵进行稀疏变换,将求解的稀疏表示系数和其重构信号与原始信号的误差进行压缩编码上传;地面系统通过相同的稀疏变换矩阵进行信号重构,实现解码;其中,稀疏变换矩阵采用K-SVD算法进行预训练,提升稀疏变换系数的稀疏度与重构信号精度,进一步降低上传的压缩编码长度。在HB油田3口井实际测井资料的实验中,本方法与目前主流的测井数据压缩方法相比,压缩率平均提升约17.3%;在4口井的阵列声波实际测井作业的应用测试中,作业效率平均提升约20.2%。结果表明,数据压缩传输算法极大地提升了阵列声波测井时效,在保证数据采集质量的同时,实现了阵列声波仪器的高速测量。     

Heuristic Scheduling of Job Orders in a Build-to-Order Manufacturing System

With the continuous development of technology, traditional manual work has been becoming more and more automated. Most large or medium-sized companies have applied Enterprise Resource Planning (ERP) software into their business and production activities. However, since many small firms cannot afford ERP because of its expensive cost, they often still employ manual work for the same tasks this software resolves, especially for scheduling. This paper aims to provide a possible solution for small businesses to try automated scheduling and discover whether it can help much. There are two main ways to make this determination: a mathematical model and a heuristic model, which are suitable for assessing low- and medium-sized workloads, respectively. This case study was carried out in a small domestic interior furniture company, particularly in scheduling for their customized products in two-stage flow shop. Normally, they produce according to the sequence of customers’ orders. However, when we applied these supportive tools with batch-processing machines, they experienced enhanced production performance due to diminishing setup time for distinctive items and a more streamlined arrangement of job sequences. These changes were implemented for some small companies that do not use many production stages and have a suitable number of jobs and customers. If this method were applied to larger demands, it would need further improvement and development to become a complete tool that can perform like a part of an ERP system.     

Heuristic approach to allocation of trucks in a transportation system

This paper considers the problem of how luggages should be assign to each truck for the transportation system consists of a depot, a fixed area and two types of luggages, called schedule problem. The main purpose of this paper is to propose a procedure for the problem subject to keep the balance of work loads among truck drivers. The procedure is based on 3 (heuristic) rules for replacing the addresses of each luggage with the ‘conventional address,’ converting size of each luggage into ‘weight’ and introducing a measure to keep the balance of work loads. The procedure consists of three stages according to ‘priority’ of the types of luggages. A case study is presented that demonstrate the practical usefulness of the procedure.     

极低码速率下工业视频图象的压缩技术与特点分析

文章讨论儿分析工业视频图象的特点以及适用于极低码速度下的工业运动视频图压缩编码方法。     

Heuristic Methods for Dynamic Load Balancing in a Message-Passing Multicomputer

In this paper, a new adaptive scheme is presented for dynamic load balancing in a message-passing multicomputer. The scheme is based on using easy-to-implement heuristics and adaptive threshold in balancing the system load among dispersed nodes. It uses a distributed control over all computer nodes as coordinated by an information collector. Four heuristic methods are presented here, which are distinguished by the ranges for location and threshold update policies and by the disciplines used for determining the load transfer destination. A parallel simulator with distributed load balancers is developed on an iPSC/2 hypercube multi-computer. The load balancing scheme is evaluated on the basis of the effects of system utilization, load imbalance, communication and migration overhead, and multicomputer size. Relative merits of the four methods are revealed under various physical configurations of the multicomputer. The application potentials are discussed for parallel execution of AI-oriented programs and distributed semantic network data bases.     

求图符号控制数的启发式算法

针对具有NP难度的图符号控制数问题，沿着拟人的途径，制定了若干求解策略，给出了一个启发式算法即Local-Search-SDN算法。通过与完全算法的比较，实验结果表明Local－Search－SDN算法能快速找到问题的高质量解。     

Exact inferences in a neural implementation of a hidden Markov model

From first principles, we derive a quadratic nonlinear, first-order dynamical system capable of performing exact Bayes-Markov inferences for a wide class of biologically plausible stimulus-dependent patterns of activity while simultaneously providing an online estimate of model performance. This is accomplished by constructing a dynamical system that has solutions proportional to the probability distribution over the stimulus space, but with a constant of proportionality adjusted to provide a local estimate of the probability of the recent observations of stimulus-dependent activity-given model parameters. Next, we transform this exact equation to generate nonlinear equations for the exact evolution of log likelihood and log-likelihood ratios and show that when the input has low amplitude, linear rate models for both the likelihood and the log-likelihood functions follow naturally from these equations. We use these four explicit representations of the probability distribution to argue that, in contrast to the arguments of previous work, the dynamical system for the exact evolution of the likelihood (as opposed to the log likelihood or log-likelihood ratios) not only can be mapped onto a biologically plausible network but is also more consistent with physiological observations.     

验证平台的可重用性分析

传统的验证方法学已经不能满足SoC验证的需求,现在通常使用验证平台来提高验证的质量.SoC的设计实际上是IP的集成设计,因此需要建立两个验证平台IP单独验证平台和SoC系统验证平台.为了减少验证时间,提高验证质量,最有效的办法是使这两个验证平台统一,即IP单独验证平台的部分元件甚至全部元件可以直接被SoC系统验证平台重用.本文对验证平台的元件,如激励、驱动、监视器、脚本等的可重用性进行了分析,并提出了达到最大可重用的验证平台的设计方法,按该方法设计的验证平台的可重用率至少可达到60%.     

一种启发式反病毒技术的研究

本文主要讨论了反病毒技术的一般原理和技术,并针对常用反病毒方法存在的问题,提出了启发式反病毒的基本原理与实现方法。