径向基/超限插值结构网格运动方法中的变形一致性问题

针对径向基函数插值和超限插值的结构网格运动方法(RBF_TFI)中变形一致性问题引起的空间网格棱线扭曲和网格单元交叉现象进行深入分析,并依据分析结果提出一种改进的RBF_TFI结构网格运动方`法.首先基于HIRENASD机翼模型计算网格绕y轴旋转30°的算例,从变形网格质量、棱线交叉点位移误差与空间棱线扭曲等方面分析了不同基点选择方案中变形一致性问题产生的原因;然后将与物面相连的空间棱线定义为边界棱线,并采用三次样条插值的方式更新边界棱线上网格点的坐标.使用HIRENASD算例对文中方法的效果进行了验证,结果表明,该方法能够消除变形一致性问题引起的棱线扭曲现象,有效地避免变形网格出现交叉和产生负体积单元.     

基于能量统一格式的多尺度有限元法

为分析简单晶体多尺度有限元计算的能量构成,利用能量最小原理得到在统一理论框架下多尺度有限元计算的统一格式,表明有限元计算可以在微观原子尺度下和在宏观连续介质尺度下进行多尺度有限元计算.基于简单晶体变形的特点说明过渡单元设计应遵守的原则,并指出理想过渡单元应该是类似于晶体结构的单元,对于较复杂的晶体,则应该利用空间群方法充分研究具有230种空间群的过渡单元的性质.引用EIDEL等的纳米压痕计算结果作为算例,表明在计算中无虚拟插值点,多级晶胞单元具有与原单胞相同的点群操作且位移场插值受晶体中原子间键长的约束.     

空间三次PH曲线的定弧长四元数插值

针对已知两端点处位矢和切矢的空间曲线定弧长插值问题,构造了C1连续的三次PH曲线。通过四元数运算描述空间曲线切矢的变化,将曲线分成两段进行插值。利用PH曲线可以精确计算弧长的优势,实现了给定曲线弧长,简单快速地插值出空间曲线,并且论证了所提曲线插值方法的控制方程解的存在性。最后,通过算例验证了该方法在实现空间曲线定弧长插值方面的有效性和实用性。     

基于空间网格表面距离的插值曲面

主要讨论基于空间网格表面距离的插值曲面.定义了一种空间网格表面距离,基于空间网格表 面距离,给出了两种定义在空间网格上的插值曲面：基于网格表面距离的径向基函数插值曲 面和基于网格表面距离的Kriging插值曲面,讨论了曲面的无穷阶光滑性,给出了一种计算网 格表面距离的折线跟踪算法.作为整体曲面,此类插值曲面与网格表面形状较为相符,比较适 合于局部插值与参数估计,如梯度、法方向的估计等计算.     

交互式棱柱网格生成方法

针对流动数值模拟中边界层区域棱柱网格生成与修改困难的问题,提出一种基于物面边界约束的交互式棱柱网格生成方法.该方法交互生成物面边界点的空间推进面网格;将边界点空间推进面网格的每层网格点看成边界网格点运动得到,计算对应的边界网格点位移;利用径向基函数插值将边界网格点位移光滑传递给内部网格点,获得内部网格点的空间推进网格;建立所有网格点之间的连接关系,构造棱柱网格单元.基于V型槽、飞机机头等外形对文中方法进行测试,并对该方法存在的一些问题进行了讨论;利用该方法生成一个大展弦比翼身组合体模型的棱柱/四面体混合计算网格,并在PHENGLEI计算平台上进行了数值模拟,结果表明,该方法能够生成高质量的粘性棱柱网格.     

基于Hermite插值的网格拼接和融合-CIDE2013

网格模型的拼接和融合是3维形状编辑和造型中的一个重要方面。基于Hermite插值技术,提出了一种适用于具有一般边界点空间分布的三角网格模型之间无缝光滑拼接和融合方法。首先查找网格模型待拼接区域的边缘点集,并利用二次B样条曲线插值边缘点集分别得到边缘曲线;然后对边缘曲线进行Hermite插值得到拼接区域连续曲面;最后对拼接曲面分别进行三角网格化和Laplacian光顺平滑处理以实现网格模型的光滑拼接和融合。由于利用B样条曲线插值待拼接模型边界,本文方法适用于具有各种不同边界情形的网格模型拼接和融合,它不仅仅可以处理平面边界曲线情形也可以处理空间边界曲线情形。结合Hermite曲面插值拼接过渡区域,使得产生的拼接网格能光滑地衔接待拼接模型。实验结果表明,本文方法能够有效地实现三角网格模型的光滑拼接、模型修复和模型融合。     

含复杂插值曲面实体六面体网格优化方法

复杂插值曲面的几何形态由散乱数据点控制,优化含这类曲面实体的六面体网格难以保证边界一致.借鉴Balendran提出的直接法,建立正四边形结点的空间几何关系方程,并作为优化约束,以移动结点使每个六面体的各个侧面趋近于正四边形,实现网格优化.将原始采样点及其它控制插值曲面几何形态的数据转化为控制点约束,以保证边界一致性.结合优化约束与控制点约束,作为离散光滑插值(DSI)方程的约束项,实现网格优化与曲面插值的耦合.实例表明,该方法能够在保证复杂插值曲面边界一致性的前提下实现六面体网格优化.     

基于Hermite插值的网格拼接和融合

网格模型的拼接和融合是3维形状编辑和造型中的一个重要方面。基于Hermite插值技术,提出一种适用于具有一般边界点空间分布的三角网格模型之间无缝光滑拼接和融合方法。首先查找网格模型待拼接区域的边缘点集,并利用二次B样条曲线插值边缘点集分别得到边缘曲线;然后对边缘曲线进行Hermite插值得到拼接区域连续曲面;最后对拼接曲面分别进行三角网格化和Laplacian光顺平滑处理以实现网格模型的光滑拼接和融合。由于利用B样条曲线插值待拼接模型边界,本文方法适用于具有各种不同边界情形的网格模型拼接和融合,它不仅仅可以处理平面边界曲线情形也可以处理空间边界曲线情形。结合Hermite曲面插值拼接过渡区域,使得产生的拼接网格能光滑地衔接待拼接模型。实验结果表明,本文方法能够有效地实现三角网格模型的光滑拼接、模型修复和模型融合。     

一个结构网格并行CFD程序的单机性能优化

从单机性能优化角度对一个高阶精度结构网格CFI)并行程序进行了优化。通过识别关键变量并对其进行 常量参数化优化,使编译器能够实现更高级别的针对性优化;根据程序数据结构特点及访问模式,设计了分级数据缓 存技术,使程序主要计算代码能够以更优的方式访问主要数据结构,提高了访存空间局部性;进行了各种循环变换,以 优化访存性能。在国家超算长沙中心“`Tianhe—lA',并行机上的测试结果表明,相对于采用Intel编译器最高优化级别 的版本,其对10。万网格点二维翼型算例,串行程序性能提高约22.2%-28.9%;对1. 12亿网格点三角翼算例,并行 程序性能提高约13.9%-20.2%。     

一种基于网格延展法的等值线生成算法

已有等值线生成算法研究存在算法复杂、不健壮,实现难度大,或与应用系统集成难度大,应用不灵活等问题,以雨量等值线生成算法为例,介绍一种基于网格延展法的等值线生成算法。基于网格延展法的等值线生成算法,通过网格延展法实现等值面的提取,并使用一种简单的方法实现等值线平滑计算,整体等值线生成算法简单、易于实现;基于规则网格进行空间插值计算,对研究区域数据点分布具有很强的适应性,算法表现出较好的健壮性;无须进行等值线边界裁剪计算,也无须考虑等值线追踪时出现的分叉、连通域等问题,可大大减少等值线生成的计算量,降低等值线算法的实现难度;同时计算过程多数是对二维数组的操作,可以使用多种计算机语言实现,具有较好的生产应用价值。     

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