二维非结构网格Hamilton-Jacobi方程的一种简化的加权ENO格式

考虑标量Hamilton-Jacobi方程,对二维非结构网格给出了一种简化的三阶精度加权ENO格式.方法的主要思想是时间和空间分开处理,时间离散用三阶TVD Runge-Kutta 方法.对空间,在每一个三角形单元上构造一个三次多项式,该多项式是一些三次多项式的加权,并给出了加权因子的构造方法.最后用该格式对一些典型算例进行了数值试验,并分析了方法的精度,结果表明该格式是成功的.     

二维非线性反应扩散方程的局部间断Galerkin谱元法

本文提出了二维非线性反应扩散方程的局部间断Galerkin谱元法.在空间方向上采用了Legendre-Galerkin Chebyshev谱配置法,即在每个子区域上,该格式按Legendre-G alerkin谱方法形成,子区域交界面处的跳跃项利用数值流量进行处理,非线性项采用在Chebyshev-GaussLobatto点上的插值进行计算.时间方向上采用四阶低存储Runge-Kutta方法.文中给出了半离散格式下的稳定性和收敛性分析,以及单区域和多区域算法的数值算例,并与间断Galerkin有限元方法进行比较.     

径向基函数及移动网格在Euler方程数值计算中的应用

基于二维Euler方程,在利用弹簧技术的移动非结构三角形网格上给出了一种基于紧支径向基函数重构的ENO型有限体积格式,方法的主要思想是先对每一个三角形单元构造插值径向基函数,而在计算交界面的流通量采用两点高斯积分公式以保证格式的整体精度,时间离散采用三阶TVD Runge-Kutta方法。最后用该格式对一些典型算例进行了数值模拟,结果表明该方法计算速度快,对间断有很好的分辨能力。     

具有间断系数热传导方程的局部间断Galerkin方法

本文给出了求解具有间断系数热传导方程稳定的局部间断Galerkin方法.理论表明,当采用k阶多项式有限元空间逼近时,该方法连续时间的L~2模误差估计阶为O(h~(k+1/2)).文中分别应用显式和隐式时间离散求解局部间断Galerkin格式,数值算例验证了方法的有效性和理论结果.     

基于空间非迭代Oseen格式的时间解耦局部并行方法

基于空间非迭代的Oseen格式,以软件FreeFem++的MPI功能为平台,提出时间解耦的局部并行方法来求解Navier-Stokes/Navier-Stokes耦合方程.通过解耦复杂区域,将耦合方程的求解转换为并行区域上单一非定常Navier-Stokes方程的求解.在空间上利用Oseen格式一步线性校正,时间上按照步长直接推进.数值实验表明,与空间非迭代Oseen格式的欧拉时间推进方法相比,该方法在保证精度的情况下,运行时间较短,显现了耦合方程求解的高效性.     

虚拟单元有限体积WENO5格式及其应用

本文在笛卡尔网格上给出一种五阶有限体积加权基本无振荡格式首先在二十五个单元构成的空间大模板上构造五次不完全多项式;将此大模板划分为九个子模板,并在其上构造三次不完全多项式;计算线性权,光滑指示器和非线性权;利用三阶TVD Runge-Kutta时间离散方法得到时空一致高精度格式.虽然该格式具有较高数值精度但不能直接应用于具有复杂拓扑结构物体的可压缩绕流问题.为降低该格式对网格的要求,本文采用ST和GBCM两种浸入边界虚拟单元方法处理物面边界条件,将有限体积高精度格式同虚拟单元方法相结合,能有效降低格式构造和网格生成的复杂性.文中给出的多个经典复杂物体绕流问题的数值计算充分表明了本方法的可靠性和有效性.     

Klein-Gordon方程的紧致辛中点格式

本文利用紧致算子和修正的辛中点格式构造了Klein-Gordon方程初值问题的保结构算法.该紧致辛中点格式在时间方向具有二阶精度,在空间方向具有六阶精度,保持离散的辛结构,是线性稳定的算法.另外,该算法保持线性系统的离散能量,而对非线性系统,该算法满足一个离散能量的转移公式.数值算例验证了理论分析.     

一类二维粘性波动方程的交替方向有限体积元方法

针对二维粘性波动方程模型问题,提出了一类基于双线性插值的交替方向有限体积元方法,并给出了两种具体计算格式,一是基于有限差分方法中Douglas思想的格式,二是一类推广型的局部一维格式.分析证明了该方法按照L~2范数在时间和空间方向均有二阶收敛精度.最后,数值算例验证了算法的有效性和精确性.     

求解非线性Schroedinger方程的一个线性化紧致差分格式

通过对非线性项的局部外推,对非线性Schroedinger方程给出了一个线性化紧致差分格式,运用不动点定理和能量方法证明了格式的唯一可解性,文章还运用能量方法和数学归纳法,避开困难的先验估计,证明格式在空间方向和时间方向分别具有四阶和二阶精度,数值算例验证了格式的精度和数值稳定性．     

粘性Burgers方程的高阶隐式WCNS格式

JFNK (Jacobian-free Newton-Krylov)方法是由外层Newton迭代法和内层Krylov子空间迭代法构成的嵌套迭代方法.本文提出了一种基于JFNK方法的高阶隐式WCNS (weighted compact nonlinear scheme)格式,并用于求解一维、二维粘性Burgers方程.外层迭代法采用含参数的多步Newton迭代法,给出了收敛性分析,内层迭代法采用无矩阵GMRES迭代法.粘性Burgers方程的非线性对流项采用五阶WCNS格式计算.为提高方法精度和计算效率,时间离散采用三阶隐式的DIRK (diagonal implicit Runge-Kutta)方法.数值结果表明基于JFNK方法的隐式WCNS格式在时间上能达到三阶精度,与显式TVD Runge-Kutta WCNS方法相比,计算效率更高.此外,基于JFNK方法的隐式WCNS格式稳定性好,且具有良好的激波捕捉能力.     

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.     

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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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