一种对位图文件的有效压缩算法

目前广泛使用位图文件作为图像文件类型。使用游程编码方法可对位图文件进行较高效的压缩。本文讨论了Windows位图文件的结构和游程编码的算法 ,并利用C语言实现了位图文件的压缩和解压缩。     

Querying Compressed Data in Data Warehouses

The large size of most data warehouses (typically hundreds of gigabytes to terabytes) results in non-trivial storage costs and makes compression techniques attractive. For the most part, page-level compression (as opposed to attribute or record level schemes) has been shown to achieve the greatest reductions in storage size for databases. A key issue with such schemes is how to quickly access the data to answer queries, since individual tuple boundaries are lost. In this paper we introduce an approach that aims to maintain the benefits of page-level compression (i.e., large reductions in storage size), while at the same time improving query performance through an efficient signature file indexing scheme. The approach uses an attribute-level signature generation method that exploits the value distribution of each attribute in a data warehouse. We provide an extensive theoretical analysis of this approach in which we compare our approach with a recently proposed indexing technique, encoded bitmapped indexing, along a number of important metrics including query processing, insertion, and storage costs. Results show that our approach is preferred in many situations that are likely to occur in practice. We have also implemented a prototype system which validates our analytical findings.     

落凼矿区地质构造特征及矿床成因分析

通过采矿区揭露的地质构造,结合整个拉拉基底形式和特征,对拉拉地区地质构造进行了重新认识。河口复背斜的南翼是由一系列的次级背斜、向斜组成,并存在近东西向和一系列北西向、近南北向的断裂组合,矿区矿体的分布受近东西向同斜倒转背、向斜控制,被各组断裂切割;并从矿体与构造、地层、变质、热液的关系,分析了落凼矿区矿床的成因,总结出矿床可能的成矿模式,构造-热液复合成因铜多金属矿床。     

基于Web的无组件多文件上传方案的研究与实现

基于Web的多文件上传是网络应用中存在的一个普遍问题。该文介绍了目前常见的通过浏览器上传多文件的方案，并提出了一个利用Java技术和J2EE规范实现基于Web的无组件多文件上传的实现方案。     

INVARIANT SLIDING SECTOR FOR VARIABLE STRUCTURE CONTROL

A sliding sector has been defined as a subset of the state space, inside which a norm of state decreases with zero control input [1]. In this paper, an invariant sliding sector is defined to be such a kind of sliding sector inside which with a suitable control law, the norm keeps decreasing and the system state stays there since then after entering the sector, i.e. the sector defined in the paper is an invariant subset of the state space. Design algorithms of the invariant sliding sector and the Variable Structure (VS) controller with the sector are given. The proposed VS controller with the invariant sliding sector ensures that the system state moves from the outside to the inside of the sector in a finite time and stays inside it forever after being moved into it, and that the norm of state keeps decreasing in the state space. The resulted VS control system is quadratically stable with a smooth VS control law. The experimental results with the inverted pendulum show the invariance of the sector and the robustness of the proposed VS control system with the invariant sliding sector.     

Mathematical modeling of elastic inverted pendulum control system

Inverted pendulums are important objects of theoretical investigation and experiment in the area of control theory and engineering. The researches concentrate on the rigid finite dimensional models which are described by ordinary differential equations(ODEs) .Complete rigidity is the approximation of practical models; Elasticity should be introduced into mathematical models in the analysis of system dynamics and integration of highly precise controller. A new kind of inverted pendulum, elastic inverted pendulum was proposed, and elasticity was considered. Mathematical model was derived from Hamiltonian principle and variational methods, which were formulated by the coupling of partial differential equations (PDE) and ODE. Becausse of infinite dimensional, system analysis and control of elastic inverted pendulum is more sophisticated than the rigid one.     

基于LQR最优调节器的倒立摆控制系统

倒立摆控制系统是一个典型的高阶次、不稳定、多变量、非线性和强藕合控制系统。本文研究分析了单节倒立摆控制系统的数学模型，介绍了线性二次型最优调节器(LQR)的基本原理，并用该方法实现对单节倒立摆的最优控制，MATLAB仿真结果和实验结果表明了该方法的有效性。     

二级倒立摆的半物理仿真模型研究与实现

本文在MATLAB环境下建立了二级倒立摆的半物理实时仿真模型，并应用线性二次型最优控制策略．设计了一个二级倒立摆LQR控制器。在实验中，运行该半实物仿真模型，成功的使倒立摆稳定地平衡在“倒立”状态。     

用PB编程配置ODBC数据源访问Excel文件

ODBC(Open Database Connectivity)是一个用于访问数据库的统一界面标准，应用程序通过ODBC驱动程序支持．可以访问不同数据源。PowerBuilder作为功能强大的数据库前端开发工具，可以访问大量的ODBC数据源。本文介绍使用PB编程配置Excel数据源来动态存取不同的Excel文件的方法。     

四级倒立摆的状态变量合成模糊神经网络控制

文章给出了四级倒立摆系统的硬件组成，分析了四级倒立摆的系统结构、建立了数学模型。分析了系统的可控性、可观测性，给出了一种基于状态变量合成的模糊神经网络控制控制方法。在实践中证明该方法可行，成功地立起四级倒立摆。