P-code位矩阵方法与扩展研究

以磁盘冗余阵列(Redundant Array of Inexpensive Disks, RAID)技术中新出现的Pcode编码为主要对象,进行了其构造方法、编码及译码算法的详细分析,并首次运用位矩阵(Binary Distribution Matrix, I3DM)的方法分析和研究了P-code码。在此基础上,对当前主要RAII}6编码的扩展即更多磁盘数量的容错问题进行了总结与探讨,提出了P-code等垂直最大距离可分码(Maximum Distance Separable, MDS)的扩展将是该领域未来研究的新方向和难点。     

基于V码的高可靠性磁盘阵列容错模型

在磁盘阵列模型中，关键是如何实现容许多个磁盘阵列故障使得系统性能达到最优。该文提出了一类新的纠双错编码――V码，使用该编码的磁盘阵列数据布局，阵列的盘数可以为偶数，校验信息均匀分散在阵列每个盘中，容许任意2个磁盘故障。与其它纠双码的磁盘阵列布局进行比较，当阵列盘数为偶数时，V码阵列布局具有最优性能，编译码复杂度、冗余率达到最低以及小写性能最优，利于解决磁盘阵列I/O问题。     

RS类纠删码的译码方法

RS(Reed-Solomon)码可以根据应用环境构造出任意容错能力的码字,有很好的灵活性,且使用RS纠删码作为容错方法的存储系统能达到理论最优的存储效率.但是,与异或(exclusive-OR,XOR)类纠删码相比,RS类纠删码译码计算的时间开销过大,这又很大程度上阻碍了它在分布式存储系统中的使用.针对这一问题,提出了一类RS纠删码的译码方法,该方法完全抛弃了当前大多RS类纠删码译码方法中普遍使用的矩阵求逆运算,仅使用计算复杂度更小的加法和乘法,通过构造译码变换矩阵并在此矩阵上执行相应的简单的矩阵变换,能够直接得出失效码元由有效码元组成的线性组合关系,从而降低译码计算复杂度.最后,通过理论证明了该方法的正确性,并且针对每种不同大小的文件,进行3种不同大小文件块的划分,将划分得到的数据块进行实验,实验结果表明:在不同的文件分块大小情况下,该新译码方法较其他方法的译码时间开销更低.     

RS柯西码编码算法改进研究

针对RS(Reed-Solomon)算法编码过程涉及有限域运算,复杂度高,效率低,运算代价难以被大规模分布式存储系统所接受等问题,提出了一种RS柯西码编码改进算法。该算法用贪心算法选取局部最优柯西矩阵,减少柯西码的计算量。同时,引入二进制矩阵替换柯西矩阵中的有限域元素进行阵列化,将有限域运算转换为异或运算,并对阵列进行运算优化,进一步减少计算量,增加柯西码的编码效率。根据仿真实验表明,改进后RS柯西码与通过遍历得到的最优柯西矩阵的柯西码相比,计算量更小,与编码效率著称的阵列码中的EVENODD码和STAR码相比,编码效率更高。并且具有类似阵列码性质,能够选择更简单高效的译码方法,在一定程度上提高解码效率。     

Lamda码:一种新的纠双删阵列码

为了解决集成存储系统或者分布式存储系统中的数据安全问题,提出了一种新的阵列码,名为Lamda码。Lamda码可以同时恢复最多两个删除错,或者纠正一个突发错误。该码是极大距离可分码(MDS),因此理论上具有最优的空间效率,并附有相应的证明。详细描述了编码算法与解码算法,同时讨论了相应算法的复杂度问题。结论表明,Lamda码也是一种有效的数据冗余方案。     

一种基于3容错阵列码的RAID数据布局

在EVENODD码的基础上,提出一种新的基于EEOD码的RAID数据布局,只需要3个额外的磁盘保存校验信息,能容许任意3个磁盘同时故障,并给出了EEOD的代数定义,理论上证明了EEOD码的MDS性质.从一种新的途径讨论了EEOD码的译码过程:用图的回路表示通过"异或"运算得到的校验方程组,把译码过程归结为图回路的叠加,进而校验方程组图中度为偶数的顶点逐步消除.讨论了基于EEOD码阵列布局的性能,与其它RAID结构相比,容灾能力大幅度提高,编码和译码过程只需要简单的异或运算,但是空间利用率影响非常小,并且EEOD具有很好的性能,具有很好的应用前景.     

纠错码和秩距离码的一些新的构造方法

给出一般纠错码和秩距离码的一些新的构造方法,求出了构造的各种码的生成矩阵。指出了最大秩距离Reed-Solomon码和最大秩距离BCH码为新构造的秩距离码的特殊情况。     

一种整体较优的RCPT码删除矩阵新算法

由于无线信道的时变、高误码等特性，要求信道编码方式不仅具有较强的抗误码能力，而且能够自适应的调整码率来适应无线信道状态的变化．码率可变的RCPT码能够实现这样的编码要求，但是RCPT码的编译码性能取决于其删除矩阵的选取．针对这一问题综合国内外的研究现状，提出了一种整体较优的求取RCPT码删除矩阵的新算法．这种算法利用不同删除矩阵求取算法的不同适用性，达到了在高、低码率下都能够取得较好编译码效果的目的．     

低编译复杂度的双容错阵列码

纠删码技术是独立磁盘冗余阵列-6(RAID-6)的双容错能力的底层实现技术，它的性能是左右RAID-6性能的重要因素。针对RAID-6中常用阵列纠删码的I/O不平衡和数据恢复速度慢的问题，提出一种基于异或（XOR）的混合阵列码——J码（J-code）。J-code采用新的校验生成规则，首先，利用原始数据构造的二维阵列计算出对角校验位并构造新的阵列；然后，利用新阵列中数据块之间的位置关系计算得到反对角校验位。此外，J-code将原始数据与部分校验位存储于同一磁盘，能减少编译码过程中的异或（XOR）操作次数和单盘恢复过程中读取数据块的个数，从而降低编译码复杂度和单盘故障修复的I/O成本，缓解磁盘热点集中现象。仿真实验结果表明，相较于RDP(RowDiagonal Parity)、EaR(Endurance-aware RAID-6)等阵列码，J-code的编码时间减少了0.30%～28.70%，单磁盘故障和双磁盘故障的修复用时分别减少了2.23%～31.62%和0.39%～36.00%。     

用于体全息存储系统的调制-阵列码的设计与实现

为克服传统体全息存储系统在读出数据的处理过程中信息利用低的问题，提出了一种具有新的编码结构的改进调制码：调制－阵列码，它是一种调制码与纠错码紧密结合的编码技术。同时采用了与其相适应的软判度量方法。在此基础之上综合调制码探测，软判决，阵列码纠错和Turbo码译码原理，形成了一种新的迭代译码算法。初步实验结果表明：在信道信噪比较低且有起伏。信道噪声参数不好统计的情况下，它能充分利用输入信号所包含的信息，获得较好的解码结果。     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

法律信息库系统

本文分析了法律数据库的结构和特点，介绍了采用面向对象设计方法和超文本数据库技术开发和实现法律信息库系统将作为重要网络资源之一为不同用户进行法律咨询服务。     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

International Journal of Automation and Computing Table of Contents

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Information for authors

正SCIENCE CHINA Information Sciences(Sci China Inf Sci),cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press,is committed to publishing highquality,original results of both basic and applied research in all areas of information sciences,including computer science and technology;systems science,control science and engineering(published in Issues with odd numbers);information and communication engineering;electronic science and technology(published in Issues with even numbers).Sci China Inf Sci is published monthly in both print and electronic forms.It is indexed by Academic OneFile,Astrophysics Data System(ADS),CSA,Cabells,Current Contents/Engineering,Computing and Technology,DBLP,Digital Mathematics Registry,Earthquake Engineering Abstracts,Engineering Index,Engineered Materials Abstracts,Gale,Google,INSPEC,Journal Citation Reports/Science Edition,Mathematical Reviews,OCLC,ProQuest,SCOPUS,Science Citation Index Expanded,Summon by Serial Solutions,VINITI,Zentralblatt MATH.     

Erratum to: Fast global kernel fuzzy c-means clustering algorithm for consonant/vowel segmentation of speech signal

正Erratum to:J Zhejiang Univ-Sci C(ComputElectron)2014 15(7):551-563doi:10.1631/jzus.C1300320The original version of this article unfortunately contained mistakes.Algorithm 6 should be as follows:Algorithm 6 FGKFCM-F clustering Input:(1)X={x_1,x_2,…,x_N},,x_iR~d,i=1,2,…,N,the dataset;(2)C,1C≤N,the number of clusters;(3)ε0,the stopping criterion;     

Journal of Zhejiang University-SCIENCE C (Computers & Electronics) Total contents

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A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.