机场场道道面结构层电磁特性反演的辨识方法

研究了基于系统辨识方法的机场场道道面介质层电磁特性的反演问题.在传统系统辨识法反演层状介质电磁特性的基础上,对电磁波在地下介质层中传输时传输模型的建立及回波时延的估计方法作了改进.新方法传输模型中考虑了发射带宽内各频率分量对介质层介电常数虚部的影响,同时引入超分辨率时延估计WRELAX算法估计回波信号的时延.实现了具有薄层的道面介质层电磁特性及其厚度的反演,并使道面下各介质层电磁特性的反演精度有所提高.     

基于Monte Carlo仿真的降低光谱散射方法比较研究

散射是影响光谱分析与检测技术精度的主要因素,使光谱分析的基本线性定律——朗伯比尔定律不再成立。基于Monte Carlo仿真对3种常用的降低光散射的方法进行比较分析,即偏振差法、附加吸收剂法和空间滤波法。3种方法都是通过提取出弱散射光,线性化光强衰减度与吸收系数关系。提出线性度可以由透射光的光程方差判断。弱散射光的光程更短,光程均值更接近介质厚度,光程方差更低,但是光强也更弱。对3种方法在不同散射系数的透射光时间响应、光强衰减度与吸收系数关系、光程方差以及光强进行比较,表明偏振差法相比其他两种方法效果更佳。     

基于改进扩展卡尔曼粒子滤波的目标跟踪算法*

针对扩展卡尔曼粒子滤波算法滤波精度较低和粒子退化的问题,将马尔可夫链蒙特卡罗（MCMC）方法和扩展卡尔曼粒子滤波相结合,应用于目标跟踪。该算法利用扩展卡尔曼滤波来构造粒子滤波的建议分布函数,使建议分布函数能够融入最新的观测信息,以便得到更符合真实状态的后验概率分布,同时引入MCMC方法对所选的建议分布进行优化处理,使抽样粒子更加多样性。仿真结果表明,该算法能有效地解决粒子贫化问题并提高滤波精度。     

一种扩展的基于角色的访问控制模型

美国国家标准与技术研究局（NIST）建立的RBAC2001技术的参考模型,只规定了最基本的概念需求,还有许多方面值得研究。为使RBAC适用于更广泛的范围,提出一种具有条件约束的权限清晰的基于角色的访问控制扩展模型（ERBAC）。不同于以往对角色集的划分,直接对权限集进行划分,降低了角色-权限授权的难度,为角色-权限的自动配置提供了支持。此ERBAC模型不仅继承了传统RBAC的所有优势,而且可以不作任何修改地嵌入到工作流系统中,在工作流系统中实现动态的访问控制。     

基于Sentence-LDA主题模型的短文本分类

短文本特征稀疏、上下文依赖性强的特点,导致传统长文本分类技术不能有效地被直接应用。为了解决短文本特征稀疏的问题,提出基于Sentence-LDA主题模型进行特征扩展的短文本分类方法。该主题模型是隐含狄利克雷分布模型（Latent Dirichlet Allocation, LDA）的扩展,假设一个句子只产生一个主题分布。利用训练好的Sentence-LDA主题模型预测原始短文本的主题分布,从而将得到的主题词扩展到原始短文本特征中,完成短文本特征扩展。对扩展后的短文本使用支持向量机（Support Vector Machine, SVM）进行最后的分类。实验显示,与传统的基于向量空间模型（Vector Space Model,VSM）直接表示短文本的方法比较,本文提出的方法可以有效地提高短文本分类的准确率。     

一种基于相关性和STRIPS系统的Chance Discovery模型

机会发现(CD)是近年提出的一个新的研究课题.扩展了CD相关性的概念,使之具有更丰富的内涵和更大的应用范围,并将CD相关性推理嵌入到STRIPS规划系统之中,从而构建一种更接近应用需要的CD过程模型.     

高端磁盘阵列马尔科夫过程可靠性模型研究

介绍了基于马尔科夫过程的磁盘阵列典型模型,分析了典型模型中存在的不足。依照海量存储系统中磁盘阵列工作的特点,结合蒙特卡罗方法,引入新的状态和参数,对基于马尔科夫过程的磁盘阵列可靠性计算模型进行改进,使可靠性数值更接近实际情况。     

DS-MSK数字化接收机的自适应抗干扰滤波仿真

为在直接序列扩频-最小频移键控（DS-MSK）数字化接收机中设计和实现抗干扰模块,分析了过采样条件下DS-MSK信号的最小均方误差（MMSE）最优滤波问题,考虑到最优滤波难于直接实现,讨论了用自适应抗干扰滤波（AAJF）来逼近MMSE最优滤波性能.传统的非线性滤波往往假设干扰估计误差功率远小于码片功率,这一条件在工程实现中很难满足,相应的抗干扰性能难以达到.为此,对非线性滤波加以改进,提出了部分解扩非线性滤波（PDNF）.蒙特卡罗仿真表明：PDNF滤波性能明显优于传统非线性滤波,接近MMSE最优滤波性能.     

基于扩展Petri网的文本分类模型

在扩展Petri网基础上提出了一种新的文本分类模型。基本思想是利用定性映射方法扩展Petri网系统,利用状态方程进行推理,使文本分类更接近于人类思维判断过程,并给出了分类算法。     

ProMiner:系统性质驱动的双向一致性检验框架

在模型驱动软件开发过程中,基于模型的测试方法往往用于检验软件代码针对软件模型的一致性以确保软件质量.然而,随着当今软件系统规模的不断扩大,相应的软件开发过程也变得越来越灵活,代码有时会先于模型被修改,以更忠实地体现系统功能和实现机制.传统的基于模型的测试方法只能检测代码之于模型的一致性而不能反作用于模型层面,模型的修改者只能人为地评估修改的正确性,大大降低了效率并增加了系统的潜在隐患.为此,对传统基于模型的测试方法的一致性检验进行了扩展,实现了一致性检验框架ProMiner,通过抽取表达模型与代码的不一致的系统性质来自动定位模型中与实际运行系统不匹配的部分,并将其表示为可直接用于模型检测的线性时序逻辑(LTL)表达式,以支持软件模型和代码间双向的一致性检验.实验结果表明,ProMiner可有效查找软件模型和代码间的不一致并生成可直接检测模型的系统性质,从而实现了自动化的模型与代码间的双向一致性检测,不仅提高了一致性检测的有效性,而且大大减少了人力开销.     

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.     

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.     

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.     

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.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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