分布式数据库存储子系统设计与实现

本文通过对分布式关系型数据库的分析研究,开发了利用价值较高的分布式关系数据库系统CRDB,该系统最大限度地利用网络和磁盘的I/O能力,提高用户体验,并利用Linux提供的API大大节约了系统开销。     

Asynchronous design methodologies: an overview

Asynchronous design has been an active area of research since at least the mid 1950's, but has yet to achieve widespread use. We examine the benefits and problems inherent in asynchronous computations, and in some of the more notable design methodologies. These include Huffman asynchronous circuits, burst-mode circuits, micropipelines, template-based and trace theory-based delay-insensitive circuits, signal transition graphs, change diagrams, and complication-based quasi-delay-insensitive circuits     

基于进化的电路自动设计方法

电路进化设计是可进化硬件(Evolvable:HardWare，简称EHW）研究的重要内容，即利用进化计算技术配置电路的内部结构以获得所需的电路功能。该方法的优点包括：可获得常规设计方法考虑范围以外的最佳设计；不依赖于先验知识，但仍可利用巳有的知识和经济来提高设计的频率；自动化程度高，便于实施：因此有希望替代常规设计方法，实现复杂和大规模电路的自动设计。本文简述EHW的基本概念，介绍电路进化设计的基本原理、关键技术和主要进展，讨论重要的开放问题及未来的研究方向。     

Modular design methodologies for image processing architectures

A methodology for the design of modular and optimized architectural blocks for the generation of local windows of pixels is presented. The proposed formalization and the related techniques follow a design approach derived from the window-based algorithmic decomposition of low- and medium-level image processing algorithms     

Simulation-based design optimization methodologies applied to CFD

Finding the optimal physical design for an electronic system is extremely time-consuming. In this paper, we describe a sequential global optimization methodology that can lead to better designs in less time, and illustrate its use by optimizing the design of a heat sink for a simple system. The results show the need for a global approach, the insights that can be gained through automated design optimization, and illustrate the efficiency of the reported methodology in finding the optimum design.     

Distributed query processing a multiple database system

Mermaid is a testbed system which provides integrated access to multiple databases. Two query optimization algorithms have been developed for Mermaid. The semijoin algorithm tends to reduce the data transmission cost, while the replicate algorithm reduces the processing cost. An algorithm that integrates the features of these two algorithms to optimize the processing cost as well as the transmission cost is presented. A dynamic network environment is considered where processing speeds at each site and transmission speeds at each link can be variable. Moreover, distributed processing of aggregates is considered based on the functional dependency among the fragment attribute, the aggregate attribute, and the group-by attribute. Semantic information is utilized to obtain efficient query processing     

Distributed database systems in high-speed wide-area networks

The issues involved in developing a distributed database system (DDBS) in a high-speed environment are discussed. The inadequacy of existing database protocols in utilizing the gigabit network is described. A concurrency control protocol that performs better than traditional DDBSs in high-speed networks is developed. Both analytical and simulation results are presented. The focus is on the concurrency control aspect of DDBS since this protocol is at the heart of the overall functioning of the distributed system     

System design methodologies: aiming at the 100 h design cycle

As methodologies and tools for chip-level design mature, design effort becomes focused on increasingly higher levels of abstraction. We present a tutorial on a design methodology for chip and system design and present a test case that justifies the future goal of a 100 h design cycle     

Hierarchical design methodologies and tools for VLSI chips

Hierarchical design methods are considered to be a means of managing the VLSI design problem. This paper will consider why this problem exists and discuss alternative means that can be used to arrive at a solution. The merits of design methodologies, with emphasis on hierarchical techniques, will be compared with those of automated design approaches. The discussion of hierarchy will lead to the conclusion that the method requires formal abstraction facilities in order to be effective. Hierarchical design methods permit the creation of a new generation of CAD programs that can both give a designer better support and can be much more efficient than the present generation of tools. An example of such a tool, VOILA, will be given.     

Low power design for DSP: methodologies and techniques

Power dissipation is becoming a limiting factor in the realization of VLSI systems. The principal reasons for this are maximum operating temperature and, for portable applications, battery life. Because of the relatively greater complexity, the power dissipation in digital signal processing (DSP) applications is of special significance, and low power design techniques are now emerging. This paper provides an overview of the techniques and methodologies that have emerged in the past few years for DSP system design. These include techniques for minimizing power at architectural and algorithmic levels including DSP programming issues. In addition, the paper indicates some potential design directions.     

Perturbation analytic methodologies for design and optimization ofcommunication networks

Perturbation analysis (PA) is a technique for estimating performance sensitivities of queuing networks from direct observation of a single stochastic realization. It is used here to address such problems for communication networks. For a G/G/1 link model, it is shown that efficient PA algorithms can be used to estimate online the marginal delay of messages due to incoming flow perturbations. This information is used in a minimum-delay distribution algorithm to optimize routing. PA algorithms are extended to estimate throughput and mean delay sensitivities with respect to link capacities, including blocking phenomena due to finite queues. A window-flow-control model is considered, and experimental results of PA estimates for throughput sensitivities are provided. these estimates are seen to be accurate under heavy-load conditions, but, in general, enhanced PA techniques are required to incorporate more-complicated dynamic flow control and routing policies     

Technology transfer between VLSI design and software engineering: CAD tools and design methodologies

Recent research on the explicit transfer of technology used in computer-aided design (CAD) tools and design methodologies is reported. First, several examples are given of applications of these technologies to software engineering. Then, three research projects are described which focused on applying software engineering principles to the VLSI design process. They are: a methodology, language, and assessment tool for multilevel mixed-mode VLSI designs; a research project that explored the potential for transfer of software design methodologies for managing VLSI design complexity; and a specification technique for "modules" in a VLSI design that localizes the impact of changes to the design. Next, a CAD tool and design methodology are described which consider the design of software and hardware together, and apply common techniques to both. Finally, some observations are made on the appropriateness of technology transfer between VLSI design and software engineering.     

网络考试系统中数据库的设计及架构

介绍了网络考试系统在高校教学中的必要性,对网上考试系统进行研究,其目的是为教学资源的共享提供一种途径,提高教师的工作效率,保证考试的公平性与公正性。而作为网络考试系统来说,如何构架数据库是整个网络考试系统的核心,文章通过对网络考试试题库的分析来搭建数据库设计,从而解决网络考试系统的核心模块。     

一种安全数据库体系结构的设计

较为详细地分析了安全数据库实现的模型和技术，重点论述了多级安全数据库中的强制访问控制和基于角色的访问控制模块的实现方案及其关键技术；并在此基础上设计出了一种安全级别至少为Bl的安全数据库体系结构。     

High-speed/high-bandwidth design methodologies for on-chip DRAMcore multimedia system LSI's

Recently, as multimedia large scale integrated devices (LSIs) have developed, there has been strongly increased demand for high-speed/high-bandwidth LSIs which integrate the DRAM core and logic elements (CPU etc.). However, the high-speed/high-bandwidth operation induces the large switching noise. This noise degrades the DRAM's operating margin, and especially its data retention characteristics. In this paper, we analyze the noise transmission model and propose DRAM and logic compatible design methodologies to maintain the reliability of high-speed/high-bandwidth system LSIs. We also show that good experimental results are obtained on the test device. Furthermore, we propose the most suitable V_DD/GND line scheme for on-chip DRAM system LSI     

数据库设计中E-R模型设计的探究

数据库设计中概念模型设计的核心是E-R模型设计。设计实践中,设计者感到更多的困惑是实体的选择、属性的确定及实体间联系的确定。在此提出了如何选择实体,如何确定实体的属性及如何确定实体间的联系。这就是文中要侧重探讨的问题。     

计算机软件数据库设计中存在的问题及设计原则

计算机软件数据库是计算机软件的底层基础和主要支撑,这一底层基础设计质量的好坏不仅直接关乎到用户对数据库相关数据信息的使用,同时还会对计算机软件系统运行的流畅性、稳定性及安全性产生巨大影响.在实际的设计过程中,受到不少设计人员对计算机软件数据库设计重要性认识不足、专业技能不足、对数据库设计原则及流程等掌握不足等因素的影响...     

分析数据库设计在网站开发中的应用

就目前情况而言,大部分编程人员在工作的过程中都会涉及到数据库技术的设计和编写.编程人员数据库技术水平的高低和编写出的程序质量有着直接联系,本文将针对数据库技术,简要说明数据库概念和数据库的主要内容、分析数据库设计中数据表字段、数据表设计时应注意的要点,以及数据库技术的设计原则.详细介绍数据库设计在网站开发中的应用.