变曲率对称圆弧曲线及其在圆弧样条拟合中的应用

针对数控加工的需要，对圆弧样条拟合曲线的形状进行局部修改和优化，提出了一种新的圆弧样条曲线的基本形式－变曲率对称圆弧曲线，并给出了其计算方法和具体应用，该方法可满足不同运算字长数控系统对拟合后圆弧样条曲线最大曲率半径的要求，同时还可满足随动控制加工对拟合曲率变动量的要求。     

基于VB的优化双圆弧拟合误差分析及其算法改进

摘 要：针对数控加工的特点,分析了双圆弧拟合的方式,运用VB实现了双圆弧拟合算法并进行了误差分析;通过对误差分布的分析以及对影响误差因素的研究,探索了双圆弧曲线误差变化的规律,提出了基于步长规划来减小误差的改进拟合算法。     

平面列表点曲线的最优双圆弧拟合

本文利用相切的双圆弧拟合平面列表点曲线，最优原则取“应变能”与弧长加权之和为最小。这个方法克服了单圆弧样条拟合及其它优化原则方法的缺点，在数控加工中将得到很好的应用。     

一种简单的二次B样条曲线拟合算法

针对双圆弧拟合算法绘制一条B样条曲线,需要反复多次计算各坐标分量的3次多项式,计算量大,绘制拟合速度极慢,难以满足实际需要等情况,该算法提出了一种简单的二次B样条曲线拟合算法,该算法提高了B样条曲线的绘制速度,有效地解决了4个点以上控制点的拟合问题。     

基于遗传算法的以线段和圆弧为基元的曲线拟合

采用线段和圆弧作逼近基元是数字曲线拟合中的一个难点。文中给出一种基于改进遗传算法的拟合方法。通过对点列进行二进制编码，以拟合段数较少和拟合误差较小为优化目标，变异概率和交叉概率自适应生成，并根据相关知识控制分界点间隙，所得最优解中值为1的基因对应数字曲线的分界点，对线段与圆弧相交和相切以及具有噪声等多种情况进行检测，可同时提取尖点和切点，还可得到逼近基元及其之间关系。较好地解决了用线段和圆弧拟合曲线问题。     

基于最小均方误差的圆弧分段曲线拟合方法

提出了一种基于最小均方误差准则的圆弧分段拟合方法。该方法采用自适应高斯滤波器对原始曲线进行平滑处理以消除噪声影响,并提出了一种适合于圆弧曲线拟合的分段算法。在该算法的基础上根据最小均方意味着准则,以圆弧作为基元对曲线进行拟合。实验结果表明,该方法能够较好地消除噪声影响并保留曲线的局部特征。     

有向几何及平面参数曲线的圆弧样条拟合

51．引言考虑任意平面参数曲线：其中函数二＊和。山在区间［孔，乃1内至少两次连续可微．取二十1个节点马：马一（JK），y…儿J一风1，又…；n；（2）其中兀二t。＜h＜…＜Ln一万我们试图用一组逐次相切的圆弧，称之为圆弧样条，拟合曲线，通过节点且有相同的一阶导数，并达到给定的拟合精度．计算非线性样条函数已由Malcolm山论述．以局部坐标研究样条函数和圆弧样条函数由孙家路先生给出问．在＊中建立圆弧逼近和双圆弧逼近，并做出了误差分析．这些工作为圆弧样条逼近平面曲线奠定了基础．在则中，把问中的方法具体化，给出了计算程度…     

二次均匀B样条曲线的双圆弧逼近方法*

提出了一种用双圆弧对二次均匀B样条曲线的分段逼近方法。首先,对一条具有n 1个控制顶点的二次均匀B样条曲线按照相邻两节点界定的区间分成n-1段只有三个控制顶点的二次均匀B样条曲线段;然后对每一曲线段构造一条双圆弧进行逼近。所构造的双圆弧满足端点及端点切向量条件,即双圆弧的两个端点分别是所逼近的曲线段的端点,而且双圆弧在两个端点处的切向量是所逼近的曲线段在端点处的单位切向量。同时,双圆弧的连接点是双圆弧连接点轨迹圆与其所逼近的曲线段的交点。这些新构造出来的双圆弧连接在一起构成了一条圆弧样条曲线,即二次均匀B样条曲线的逼近曲线。另外给出了逼近误差分析和实例说明。     

二次Bézier曲线的双圆弧样条插值二分算法*

在数控加工领域,通常需要用尽量少段数的圆弧样条来对曲线进行拟合。采用二分查找算法,用G1连续的双圆弧样条对二次Bézier曲线进行拟合。该算法在给定误差范围内所需的圆弧段数较少。最后给出了具体的实例说明。     

三次有理双圆弧曲线与双圆弧直纹面

本文提出了由共面四点确定双圆弧曲线的方法，分析了它的几何性质，并建立了双圆弧曲线的三次有理参数形式的方程，它可在计算机上表示。作为应用，本文构造一类以双圆弧为横向截线的直纹曲面，包括其特殊情形双圆弧锥面与双圆弧柱面，这些算法对于计算机辅助形设计与数控技术是有益的。     

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