Performance analysis of long-lived cooperative transactions in active DBMS

Active database management systems (ADBMS) are used in different application domains and especially for cooperative and long duration activity management. This paper deals with performance analysis of long-lived cooperative transaction processing in an ADBMS. We first briefly discuss NP-QuadLock – a concurrency control scheme for cooperative and long durational transactions in ADBMS. A restricted version of NP-QuadLock named 2L-QuadLock has been used for simulation. We have modeled such an ADBMS supporting 2L-QuadLock scheme by a queuing model. The failure of the transactions running in such systems has been modeled by a failure recovery model. We have simulated this model for a transaction processing system serving long-lived and cooperative transactions. We also discuss some important emerging application scenarios, where the proposed cooperative complex transaction mechanism can be used (e.g. 3G-service environment, ubiquitous computing environment, feature composition in intelligent network environment, multi-site and multi-domain web-services).

An important objective of our work is to analyze quantitatively (a) the performance penalty on the system due to the partial abort, the number of locks held by a transaction, the number of states of the transactions, and (b) the gain in the performance of the system with the cooperation semantics proposed in 2L-QuadLock concurrency control mechanism. We have analyzed the effect of various parameters such as partial abort rate, cooperation rate, number of locks held by a transaction, multiprogramming level, on the performance metrics such as average service time, average saga length and the degree of compensation. Later, we characterize the application scenarios based on some important simulation parameters, and discuss the application performance needs for each of the application scenarios. The required performance parameters that need to be used for these application scenarios and the corresponding performance results using 2L-QuadLock are also discussed.     

MMR: An algorithm for clustering categorical data using Rough Set Theory

A variety of cluster analysis techniques exist to group objects having similar characteristics. However, the implementation of many of these techniques is challenging due to the fact that much of the data contained in today’s databases is categorical in nature. While there have been recent advances in algorithms for clustering categorical data, some are unable to handle uncertainty in the clustering process while others have stability issues. This research proposes a new algorithm for clustering categorical data, termed Min–Min-Roughness (MMR), based on Rough Set Theory (RST), which has the ability to handle the uncertainty in the clustering process.     

基于危险理论的web文本挖掘研究

web挖掘是处理Internet环境下数据挖掘的一个重要方向,本文在比较研究传统web挖掘方法的基础上提出了一种基于危险理论的web挖掘新方法,该方法具有很强的自适应性和更新能力,为web挖掘领域提供了一种新的研究思路.     

Theory of planning behavior (TPB) and customer satisfaction in the continued use of e-service: An integrated model

This study has devoted much effort to developing an integrated model designed to predict and explain an individual’s continued use of online services based on the concepts of the expectation disconfirmation model and the theory of planned behavior. Empirical data was collected from a field survey of Cyber University System (CUS) users to verify the fit of the hypothetical model. The measurement model indicates the theoretical constructs have adequate reliability and validity while the structured equation model is illustrated as having a high model fit for empirical data. Study’s findings show that a customer’s behavioral intention towards e-service continuance is mainly determined by customer satisfaction and additionally affected by perceived usefulness and subjective norm. Generally speaking, the integrated model can fully reflect the spirit of the expectation disconfirmation model and take advantage of planned behavior theory. After consideration of the impact of systemic features, personal characteristics, and social influence on customer behavior, the integrated model had a better explanatory advantage than other EDM-based models proposed in prior research.     

基于数据分析方法的属性简约算法的实现

属性约简是粗集理论中的研究热点之一。文章通过数据分析方法讨论了属性约简问题,该算法直观,易于理解,能计算出所有的约简,克服了启发式算法的不完备性,以及基于区分矩阵的属性约简算法中出现时间和空间浪费的问题。实例表明,该法是行之有效的。     

浅议《单片机原理及接口技术》课程的教学方法

论述了《单片机原理及接口技术》课程教学中存在的问题,结合教学的实践与经验,根据课程的不同阶段,采取不同的教学方法,提高教学效果.     

非计算机专业《计算机应用基础》课程改革探索

高校的《计算机应用基础》课程是为非计算机专业学生开设的学习计算机知识和应用的课程.针对《计算机应用基础》教程的教学现状和存在问题,结合一些教学实践和经验,对《计算机应该基础》课程提出几点建议.     

高温奥氏体γ Fe C晶胞的价电子结构计算

 利用自建的高温奥氏体γ Fe C晶胞价电子结构计算模型，通过研究碳的质量分数为04%的奥氏体在900 ℃时的价电子结构，表明温度可以明显影响奥氏体价电子结构。随着温度的升高，晶格常数增大，Fe原子向较低杂阶迁移，各键的共价电子对数nα及价电子结构中的相结构因子(nA、Σnc、FDC)均出现了不同程度的下降。进一步研究表明，在高温下相结构因子(nA、Σnc、FDC)随碳含量增加呈指数下降。     

流程供应链工作流构建方法研究

以流程供应链工作流图构建为目的,给出供应链工作流形式化定义,并从供应链连接弧、链节体的结构特征角度,给出供应链工作流的图示化结构描述法。针对煤炭供应链过程,分析链节间关联属性,刻画了链节体的逻辑关系,运用集合论方法分析物流、资金流关系视图并运用定义的工作流方法构建煤炭供应链整体视图。     

企业理论之奠基三论的比较——兼评科斯的《企业的性质》

新古典经济学的厂商理论、科斯开创的企业契约理论及奈特开创的企业的企业家理论是企业理论发展中具有重要意义的三个理论。本文对此进行了比较研究 ,意在指出企业性质的非单一性 ,最后介绍两种关于企业性质双重性的理论的主要内容。