Should we try to measure software quality attributes directly?

Most external software quality attributes are conceptually subjective. For example, maintainability is an external software quality attribute, and it is subjective because interpersonally agreed definitions for the attribute include the phrase ‘the ease with which maintenance tasks can be performed’. Subjectivity clearly makes measurement of the attributes and validation of prediction systems for the attributes problematic. In fact, in spite of the definitions, few statistically valid attempts at determining the predictive capability of prediction systems for external quality attributes have been published. When validations have been attempted, one approach used is to ask experts to indicate if the values provided by the prediction system informally agree with the experts’ intuition. These attempts are undertaken without determining, independently of the prediction system, whether the experts are capable of direct consistent measurement of the attribute. Hence, a statistically valid and unbiased estimate of the predictive capability of the prediction system cannot be obtained (because the experts’ measurement process is not independent of the prediction system’s values). In this paper, it is argued that the problem of subjective measurement of quality attributes should not be ignored if quality is to be introduced into software in a controlled way. Further, it is argued that direct measurement of quality attributes should be encouraged and that in fact such measurement can be quantified to establish consistency using an existing approach. However, the approach needs to be made more accessible to promote its use. In so doing, it would be possible to decide whether consistent independent estimates of the true values of software quality attributes can be assigned and prediction systems for quality attributes developed.

Decentralized voltage control of distributed generation using a distribution system structural MIMO model

The voltage control problem in Low Voltage (LV) distribution systems is becoming increasingly important due to the presence of Distributed Generation (DG). Recently, DG units have been proposed to contribute to voltage control according to a Volt/Var law which does not realize regulation. Moreover, since the existing LV systems are operated in a decentralized way without communication links, the simultaneous response of the controllers of the DG units may result into operational conflicts and instability. To overcome these problems, the present paper illustrates a design methodology for decentralized voltage controllers that act on DG reactive power injections. The controllers are suitable for the LV systems since they ensure voltage regulation and stability by using only local measurements and without information exchanges. The design is based on a proposed structural MIMO model of the distribution system. Robust stability is also analyzed: changes in the operating conditions of the distribution system are modeled as unstructured additive uncertainties affecting the MIMO model. A case study gives evidence of the applicability of the proposed design; the performance of the controllers in terms of both stability and regulation of the nodal voltages of three DG units connected to a LV distribution feeder is tested by numerical simulations; finally, a comparison with a Volt/Var technique is performed.     

分布式频谱监测系统中间件技术研究

目前电磁环境日趋复杂、对抗异常激烈,如何实现区域无线电信号实时监测与分析及区域电磁态势的实时呈现显得尤为重要。首先对现有的频谱监测系统相关技术进行了研究,分析了其各自特点;其次,针对实际的需求提出了基于中间件的分布式频谱监测系统的设计思想,在执行多测试任务时,利用中间件实现测试任务的分发及结果数据的回传;最后,对中间件进行了设计与实现并对其性能和可靠性进行了测试。     

公钥基础设施在网络安全中的研究与应用

文章提出了一种基于ＰＫＩ的网络安全模型,旨在为网络服务提供有效认证、访问控制、授权、传输机密性、不可否认性等安全机制。该模型在 ＰＫＩ的基础上,结合了 Ｋｅｒｂｅｒｏｓ的优势,并扩展了其机制中服务票据的思想,提出了由授权服务器签名的授权证书的概念,以保证自治式与集中式访问控制相结合的安全管理模式。     

基于马尔可夫随机场的图像恢复方法

根据噪声的先验特点,建立了基于Ｍａｒｋｏｖ随机场的退化图像恢复模型,从而将图像的恢复问题转化为求解最大后验概率（ＭＡＰ）问题。该文以模拟退火算法的思想为基础,通过引入随机判据的方法代替退火过程来进行ＭＡＰ的估计,实验结果证明了这种方法的有效性。     

基于Chernoff上界的多类问题特征选择优化迭代算法

本文提出正态分布条件下面向不同分布的多类问题基于Chernoff上界的特征选择优化迭代算法.该算法由两重迭代组成首先在设定的原始空间和特征空间Chernoff参数s条件下,通过解矩阵方程的迭代算法求得变换矩阵的最优解;然后,在变换矩阵确定的特征空间中搜索最佳的参数s使错误概率上界最小;最后采用折半法修正设定的Chernoff参数s及其迭代步长.通过分析和实例可见基于Chernoff上界特征选择是面向不同分布的多类问题的最佳特征选择方法.     

基于企业服务总线的内容管理系统的研究应用*

针对当前企业信息化建设和电子政务发展的特点,有效地结合了企业服务总线技术,提出了一种在J2EE平台上构建的分布式内容管理构架.以构建内容管理系统为例,描述了不同类型的数据如何在分布式平台之间高效实时地传递,如何解决信息异构和数据整合的问题.介绍了一些必要的相关知识,描述了如何用J2EE架构建立单个节点上的内容管理系统.运用ESB技术将部署的多个系统连接起来,最终构成该管理模型.     

江西省土壤可溶态稀土元素含量和分布规律的研究

对江西 1 1种母质发育的有代表性的水稻土、旱作地、自然土壤 ,61个剖面 ,4 1 2个土样的可溶态稀土元素分析测定 ,统计结果表明 :江西土壤稀土元素的强度因素处于较高水平 ,平均值为 1 9 0mg/kg ,有 4 2 80 %的样点处于丰富级 ;有由南向北 ,由东向西逐渐降低的趋势 .其含量最高的地区是赣南由花岗岩、泥质岩、第四纪红粘土、酸性紫色土、碳质岩类风化物等母质发育的土壤 ,较低的为赣西北由石英岩 ,第三纪红砂岩、石灰岩、下蜀系黄土等母质发育的土壤 ;在土壤剖面分布中 ,旱作地表层低于底层 ,水稻土表层有生物富集作用高于底层 ;影响土壤中可溶态稀土元素含量的主要因子有 :成土母质 ,气候条件 (温度 ,降水量 ) ,土壤 pH ,土壤质地和耕作类型     

轨道交通系统票务清分算法

提出了一个实现轨道交通系统票务清分的算法。给出了清分的精确算法,在论证精确算法的不可实现性的基础上,演变出切实可行的票务清分的近似算法,并通过一个清分实例来进一步阐述如何实现清分。     

Sampling from binomial and poisson distributions: A method with bounded computation times

An accurate acceptance-rejection algorithm is devised and tested. The procedure requires an average of less than 3 uniform deviates whenever the standard deviation of the distribution is at least 4, and this number decreases monotonically to 2.63 as . Variable parameters are permitted, and no subroutines for sampling from other statistical distributions are needed.This research was supported by the Austrian Research Council (Fonds zur Förderung der wissenschaftlichen Forschung).