关系数据库性能优化研究

效率是数据库开发中经常遇到的问题，数据库性能的优劣将直接关系到软件的运行效率。为了提高数据库产品的性能，对影响关系数据库性能的一些主要因素进行了阐述。结合实际给出了数据库性能优化的一些建议并用实验数据证明之。分析和比较了不同设计方案可能对数据库性能的影响，提出了目前关于数据库性能优化的问题是没有通用方案的观点。     

Oracle数据库性能优化技术

Oracle数据库足当前应用最广泛的大型数据库之一，而其性能优化直接关系到系统的正常运行效率。该以数据库性能优化的基本原则为出发点，阐述了在数据库设计阶段如何避免竞争和如何优化数据访问，在数据库运行阶段如何从操作系统和数据库实例级别上调整内存和I/O来达到数据库性能优化的各种技术。     

基于SQL数据库的性能优化问题分析

随着数据库应用系统中数据的增加,效率是将是数据库应用开发与管理过程中必须解决的主要问题。因此必须对数据库进行优化。其中既包括了对逻辑数据库设计的优化、物理数据库硬件的优化、服务器硬件平台性能的优化、以及SQL语句本身查询的优化。本文通过对SQL Server数据库应用中影响效率的主要问题进行相应的分析,给出了数据库的性能优化方法,从而提高了整个数据库的运行效率。     

数据库应用系统的性能优化

针对数据库应用系统中普遍存在的效率问题，提出了结合软件工程的分阶段的优化模型，介绍了各阶段可以采用的系统性能优化的具体方法。优化数据库应用系统是一个系统工程，若单纯注重某一方面的优化不易取得整体效果，应将效率意识贯穿应用开发的全部过程。     

Oralce数据库的SQL查询优化研究

Oracle数据库的性能优化问题一直是决策者及技术人员共同关注的焦点,影响数据库性能的一个重要因素就是SQL查询语句的低效率。阐述了几种常见的Oracle数据库的性能优化技术,如数据库设计的优化、I/O优化、数据库各种动态参数的调整,并着重讨论了SQL语句的查询优化。从查询优化的测试结果来看,系统的响应时间明显降低,系统运行效率得到提升。     

基于Oracle数据库性能优化技术研究

Oracle数据库性能直接影响到Oracle数据库应用系统的运行效率,文章首先简要介绍了Oracle数据库性能优化的目标,然后分析了影响Oracle数据库系统性能的因素,接着详细介绍了数据库的优化、内存优化、I/O优化和SQL语句优化技术,最后通过实验证明,经过优化后,Oracle数据库性能得到了改善和提高。     

数据库优化在海量数据下的研究与应用

基于云计算技术和海量数据的支撑,对数据库进行多方面的调整和优化能够最大程度地提高数据库系统的运行效率,降低系统运行的资源消耗,使得海量数据的响应效率大幅提高。以Oracle数据库为例,分析了影响数据库性能的各方面因素和数据库优化应遵循的方法,就数据库优化技术方法进行了探讨。通过数据库实施该优化方案前后的性能对比,得到数据库在运用此方法进行优化后性能明显提升的结果,这表明该方法有一定的使用价值。     

销售财务系统中数据库性能优化研究

随着数据库在各行各业中的广泛应用,销售财务系统中数据库性能的好坏直接影响到企业业务的正常运行以及企业的效率。为了提高企业效率,通过在设计阶段、运行阶段调优数据库,介绍了几点优化销售财务系统中数据库性能的方法,完成了数据库的优化,使数据库运行在高性能状态下。     

数据库应用系统性能与数据查询优化

数据库查询的效率是数据库应用系统性能的重要指标，本文好数据查询优化的几种方式，并以实例说明查询优化的过程及其在数据库应用系统中的应用。     

Oracle数据库性能优化技术研究

Oracle数据库应用的广泛性要求更加重视其性能的优化,以提高Oracle数据库的运行效率,发挥其最大应用价值。文章根据Oracle数据库性能评价指标,综合性的提出了Oracle数据库性能优化技术措施,可为相关数据库人员提供参考。     

Profibus-DP现场总线实时性的研究

作为底层的工业控制网络,Profibus总线信息传输的实时性直接影响着整个控制系统的性能,因此,对于实时性能的研究和计算显得尤为重要。测控周期是衡量Profibus系统实时性能的一个非常重要的指标。文章针对多主站系统,在分析目标令牌循环时间不同设置的基础上,通过工程应用实例分析计算测控周期的方法。     

基于分辨函数的科研项目评估专家知识获取研究

为了解决省级科研项目评估中专家知识难以获取的问题,提出了一种基于分辨函数的知识获取方法。该方法以粗糙集理论为基础,对预选评审指标,采集专家意见,构建决策表,生成分辨函数求解核和约简,从中发现隐含规则,提取专家共识,构建知识库。以甘肃省自然科学研究基金项目评估进行了仿真案例计算,计算表明该方法能够客观反映专家意见,适用于立项评估、中期评估、绩效评估等科研项目管理全过程,也可应用于其它科研项目评估决策中。     

AB SLC500与Modbus网络通信的实现

AB SLC500不支持Modbus协议,所以不能直接与Modbus网络通信。为了实现两者快速准确的通信,深入研究了Modbus协议,并在AB SLC500 BASIC-T模块中开发了Modbus应用程序,实现了SIE500与Modbus网络的通信。应用SIE500编写梯形图程序来控制其他设备和网络,由于程序冗长,增加了信息传输的延迟,不利于实时传送。BASIC-T模块的应用,与过去直接应用SIE500控制其他设备和网络相比,提高了控制的效率和响应速度,即提高了控制系统整体的实时性。实验测试结果表明,此方案能保证数据传输的准确性、可靠性和高效性。     

宽带数字信号精确时延实现

数字信号的精确时延在信号处理领域有着广泛的应用,特别是实序列时延的实现,在工程实践中有着重要的意义。提出了基于线性移不变系统实现精确延时的方法并进行了性能分析,并指出了工程设计要点;根据信号的时延与其频谱的对应关系,给出了基于线性相位加权的频域实现方法。通过时延误差、系统的频率响应和引入总体平均误差参数对不同方法的性能进行了比较。实验结果表明,这两类方法具有延时精度高,实现方便等优点。     

Effect of project characteristics on project performance in construction projects based on structural equation model

Most past studies that analyze project performance and the characteristics that affect such performance consist of a simple form, in which they present the brief relationship between project performance and a few characteristics that affect it. Furthermore, due to the limitations of the research methodologies used in these studies, important characteristics were often not considered in developing the relationship between project performance and project characteristics. This study aims to analyze the overall relationship between project performance and a project’s characteristics. This study deduced (i) the overall causal relationship and (ii) the degree of influence between 17 project characteristics and five project performance indices. In order to achieve this goal, this study employed the factor analysis method and a structural equation model (SEM). In addition, this study established a SEM based on quantitative data from actual case studies as opposed to previous SEM studies that mainly use qualitative data.The SEM developed in this study can identify the project characteristics that affect the level of project performance required by owner in the planning stage, and is thus expected to help facilitate the decision-making process in the early planning stage of a project.     

Investing in project management certification: Do organisations get their money’s worth?

The professionalisation of project management has been a contentious topic for some time. Project management certification is seen as a step towards the professionalisation of the discipline. Certifications were developed as a means to provide individuals with the appropriate knowledge and skills required to deliver projects successfully. Although project management certification programmes are now commonplace across the globe, research is yet to fully investigate the true influence certifications have on project performance. This paper revealed that South African IT project performance is not influenced by project management certification. Moreover, it was established that certifications need to be redesigned to ensure that the professionalisation of project management remains on track.     

高冲击载荷下磁流变阻尼器的控制系统设计

针对工程领域中高冲击环境下的阻尼特点,采用了一种能够缓冲高冲击载荷的磁流变阻尼器,并设计了延时模糊PID的控制算法,通入实时改变阻尼器中电磁线圈的控制电流,实现了对高冲击载荷的有效缓冲控制.整个控制方法是基于TMS320F2812来实现的.实验结果表明,通过延时模糊PID控制算法的实时精确控制,能够明显提高阻尼器控制系...     

Managing OO projects better

The author reveals that estimation of effort is key to managing OO development projects, then documents a few rules of thumb for doing this. One lesson he's learned from using these rules is that estimates for a whole project are not reliable if estimates for subcomponents are simply added up. As the project size increases, so does the overhead for communication and general interaction. He goes beyond effort metrics and recommends that one collects metrics throughout the project and uses them for continuous revalidation of assumptions and project performance. If one accepts that “what you can't measure, you can't manage”, this is good advice     

Interactive and diagnostic uses of management control systems in IS projects: Antecedents and their impact on performance

We attempted to determine how formal management control systems (MCS) are used by project managers in IS development (ISD) contexts. This involved investigating the antecedents of two types of project MCS use (interactive and diagnostic), and their direct and moderated impact on project performance. PLS analysis of data collected in a survey of 93 projects indicated that project managers’ level of discretion positively affected their level of interactive use of project MCS but did not influence their diagnostic use. Our findings also showed that interactive use of MCS enhanced performance when task uncertainty (task novelty and complexity) of an ISD was high, but worsened it when task uncertainty was low. Finally, diagnostic use of MCS apparently increased project performance when an ISD task uncertainty was low, but did not reduce it when task uncertainty was high. Overall, these results were stable across different size projects.