基于误差控制的薄壁叶片椭圆弧形前后缘建模方法

针对基于测量数据的发动机薄壁叶片椭圆弧形前后缘建模问题,在最小二乘法椭圆拟合的基础上,提出一种基于误差控制的叶片椭圆弧形前后缘拟合重建方法.通过设定迭代控制误差对拟合过程进行控制,当拟合误差小于等于预先设定的迭代控制误差时迭代拟合终止,可有效地避免叶盆、叶背上的点参与拟合;提出一种考虑叶片纵向光顺要求的各截面椭圆参数调整方法,可实现前后缘椭圆参数的提取以及叶片前后缘区域光顺曲面的生成.在文中方法的基础上开发了叶片前后缘建模软件模块,并通过实测数据验证了该方法的有效性.     

基于坐标变换的圆柱体点云数据拟合方法

为了解决工程测量中圆柱体点云数据的拟合问题,论文通过迭代逼近法求解圆柱体中轴线方向向量,再将点云数据按照中轴线方向进行坐标变换到与竖直方向平行,最后通过拟合平面圆形得到圆柱体的模型参数,将三维的非线性拟合问题转换为二维的线性拟合问题,降低了处理的复杂度,也避免了非线性最小二乘拟合过程中初值选取的问题,同时也能处理任意方向的圆柱体拟合问题.另外通过计算拟合中误差进行噪声点剔除处理,通过迭代拟合提高了圆柱体的拟合精度.实验结果表明该算法能够满足实际工程测量中圆柱体拟合的精度需求.     

基于混合最小二乘支持向量机网络模型的非线性系统辨识

针对基于输入输出数据的非线性系统辨识问题,提出一种新的混合最小二乘支持向量机(LS-SVMs)网络模型及相应的学习算法.该算法将系统的辨识问题动态自适应的划分为若干子问题,将支持向量机(SVM)用于各子模块辨识;通过分析模型的统计学特性,给出基于整体框架优化的系统参数辨识方法.针对系统中参数相关联的特性,采用期望条件最大化(ECM)算法对其进行条件辨识,同时结合正则化理论和最小二乘法,保证各专家模块的结构风险最小化辨识原则.试验结果表明,该方法兼具良好的辨识精度和泛化性能.     

燃气轮机叶片360°轮廓高精度测量

为了寻找一种既能满足叶片测量精度要求,又能解决叶片高精度测量成本高、测量效率低的测量方法,通过搭建基于相位测量的三维轮廓测量系统,对叶片进行360°测量,由于采集的点云数据需要进行数据融合,设计了一种基于相位测量轮廓方法的多角度点云数据融合机械装置,提出了基于参考平面数据旋转的新算法,最终实现了旋转多角度叶片三维轮廓点云数据高精度的自动融合,得到了完整清晰的叶片三维表面轮廓。同时对叶片局部大曲率部位进行测量,为局部二次因素的详细实验测量提供了有利条件。实验结果证明相位测量轮廓术应用于叶片三维轮廓测量非常具有实际价值。     

基于最小一乘的系统辨识方法研究

针对系统参数辨识中最小二乘估计的稳健性较差,给出稳健性较强的最小一乘的系统辨识方法。推导出了最小一乘回归系数的估计式,使用逐次逼近迭代的方法,构造迭代序列给出最小一乘回归系数的迭代算法。并把该算法应用于控制系统参数辨识中,与最小二乘辨识相比较,当模型的观测数据有测量噪声时,最小一乘回归系数的收敛性及数值稳定性较好。仿真结果验证了理论,显示了最小一乘辨识的优越性。     

二维截面轮廓特征重建方法

针对目前轮廓特征识别算法存在识别结果易受噪声数据干扰、需对每一图形轮廓测量数据进行矢量化等问题,对二维截面轮廓特征重建方法进行研究,提出采用分步方式进行截面轮廓拟合的方法.首先,用平均增量法将测量数据进行直线段分段,并用最小二乘法对分段数据进行拟合,再把拟合结果存入链表内;然后,对于直线段链表内的相邻3条直线段,若相邻2条线段形成的半径满足给定阈值,则进行直线段圆弧拟合处理;最后,搜索拟合的圆弧段,如果存在2个或2个以上的连续圆弧,则将其重构为B样条曲线,得到二维截面轮廓特征的重构图形.该方法能有效减少拟合特征单元的数目,提高拟合精度.     

基于轮廓重心参数调整的Bezier曲线拟合方法

传统的3次Bezier曲线拟合方法在拟合汉字轮廓曲线时,迭代次数多,效率较低.针对拟合的效率,设计了一种基于3次Bezier曲线的汉字曲线轮廓拟合新方法.该方法的核心是简单高效的参数迭代算法.在3次Bezier曲线控制点的求取方法上,采用最小二乘法拟合;在参数的优化问题上,用过型值点重心的直线与拟合曲线间的交点求解参数,迭代优化参数取值.该迭代算法占用资源少,运算量小,计算简便.实验结果表明,针对一般型值点和汉字轮廓特征点的曲线拟合,在相同精度要求下,该算法迭代次数少,收敛速度快,能达到更好的拟合效果.     

含有色噪声的神经模糊Hammerstein模型分离辨识

针对实际工业过程中普遍存在的有色噪声,本文提出一种基于递推增广最小二乘算法的神经模糊Hammerstein模型辨识方法,突破了传统的Hammerstein模型迭代分离算法.首先,利用多信号源实现Hammerstein模型中静态非线性环节和动态线性环节的分离,大大简化了辨识过程,提高了串联环节参数的分离精度.其次,利用长除法将噪声模型用有限脉冲响应模型逼近,采用增广递推最小二乘法进行线性环节的参数估计.最后,采用神经模糊模型拟合静态非线性环节,同时设计了神经模糊模型参数的非迭代优化算法,改善了模型的使用范围.该方法保证了模型的预测精度,对含有色噪声的非线性系统具有较好的拟合效果.仿真结果验证了上述方法的有效性.     

双目机器人工具末端姿态自动测量算法研究

针对标定过程中工业机器人工具末端姿态测量精度低的问题,提出了一种基于改进最小二乘法的双目机器人工具末端姿态测量算法。为了减少噪声对拟合收敛性的影响,提高拟合的精度和速度,该算法融合“邻域加权平均法”的去噪原理,结合空间解析几何理论和最小二乘法,对双目相机测量得到的点云数据进行筛选和特征提取。利用拟合模型完成点云数据的轴线拟合,实现对末端姿态的自动测量。实验表明,该算法相比传统姿态标定算法的测量精度提高 0.2°,保证了工业机器人的标定精度,在工业上具有较强的应用价值。     

有理模型辨识的两类新方法-----混合迭代与柔性最小二乘法

针对有理模型提出两类辨识方法.首先提出基于递阶辨识思想的混合辨识方法,将模型分解为分子和分母两个子模型,分别用最小二乘法辨识分子参数,用粒子群算法和智能多步长梯度迭代算法辨识分母参数.由于降低了模型维数,且信息向量与噪声不相关,相对于传统的偏差补偿最小二乘算法,混合迭代法可以提高辨识精度并降低计算量.然后,为消除模型结构已知的假设,且充分利用最新数据更新系统参数,提出柔性递推最小二乘辨识方法,将有理模型转化为时变参数系统,进而辨识出时变系统的参数.仿真例子验证了所提出方法的有效性.     

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)

正~~