一种无需包围盒的自适应采样可见外壳生成算法

针对可见外壳的体构造方法需要事先知道包围盒和转成三角面表示时低曲率区域存在大量小三角面的问题,本文提出一种基于体素生长的自适应采样可见外壳构造方法.将物体三维表面视为等值面,用多目立体匹配的方法求得等值面附近的一个空间点;然后以该点为中心构造体素,将体素在等值面上生长直至遍历整个等值面;同时根据体素的曲率变化控制下一个生长体素的大小.实验结果表明本文方法在不知道物体包围盒大小的情况下能够计算出可见外壳,而自适应采样可解决过多小三角面的问题.     

自适应细分二次多项式响应面算法

复杂模型(或黑箱函数,black-box function)的全局近似方法广泛应用于模型简化、灵敏度分析和参数(或控制)优化中。现有的单一响应面存在着采样估值与近似精度之间的矛盾,因此提出自适应细分二次多项式响应面算法:在构造初始响应面基础上,对设计域进行递归分割,每步选择最粗糙单元,沿着最粗糙维度方向进行自适应细分。通过实验测试,该方法以多响应面来近似黑箱函数,从而达到采样点少而响应面精度高的目标。     

基于BP神经网络的隐式曲面构造方法

通过把BP神经网络与隐式曲面构造原理相结合,提出构造隐式曲面的新方法.用约束点来描述、控制曲面形状,构造BP网的输入与输出,通过智能学习、仿真模拟,最后从仿真超曲面抽取出的零等值面就是隐式曲面.同时,从理论上证明了此方法所构造的隐式曲面具有任意精度.实验表明该方法对约束点的个数、误差、内外点与边点的距离等不敏感,表现出很好的稳定性与可操作性.该构造方法不仅可用于构造隐式曲面,而且在图形理解、数据分类等领域也具有良好的应用前景.     

车身响应面模型参数的拉丁超立方采样仿真

针对传统汽车车身采样方法没有计算减薄率,导致方法存在精度低、耗时长等问题,提出一种基于车身响应面模型参数的拉丁超立方采样法.运用参数优化对车身的质量做综合评价,获得参数的最大减薄率,通过设计样品点建立响应面近似模型,同时根据确定性系数来反映模型的优化目标和设计变量之间的规律,采用拉丁超立方采样法将样品点在设计空间内合理划分,运算获得目标函数的最小值,通过均匀性评价参数来保证样品的高性能和均衡性.仿真结果表明,所提方法能够提高车身的质量与精度,相比其它方法具有较强适用性、准确性以及优质的鲁棒性.     

压缩感知在传感器节点信息采集中的应用

随着无线传感器网络的快速发展,海量数据的处理、存储与传输给传统的以高速ADC和存储通信设备带来了巨大的压力.由于传感器节点采集的感知数据具有时间相关性,本文提出基于压缩感知理论的采样压缩方法,其打破了传统奈奎斯特采样定理的限制,在前端只需远低于奈奎斯特采样频率采样信号就可以完成对原始信号的精确重构,并构造了基于压缩感知的模拟信息转换器(AIC)模型.最后通过以Matlab为平台进行实验仿真,结果表明:该模型可以用较少的观测值即可精确重构稀疏信号,并且其重构精度与观测数M、稀疏度K有关.     

基于奇异值分解的Toeplitz结构测量矩阵构造方法

在压缩感知CS(Compressed Sensing)理论中,测量矩阵的构造至关重要,其性能直接影响到数据压缩采样的效率及信号的重构质量。针对Toeplitz结构测量矩阵重构性能不高的问题,提出一种基于奇异值分解的Toeplitz结构测量矩阵构造方法。首先对Toeplitz矩阵进行奇异值分解,然后通过对该矩阵的非零奇异值进行优化来提高矩阵的列向量独立性,从而提高其重构性能。仿真结果表明,相比较未优化的Toeplitz结构测量矩阵以及当前常用的高斯随机矩阵,当采用优化后的Toeplitz结构测量矩阵对信号进行压缩感知时,信号的重构精度得到显著提高。     

一种基于矢量场结构的等值面构造方法

为得到非结构矢量场中的等值面图像,给出了一种基于矢量场曲线结构的等值面构造新方法.算法利用矢量可视化映射过程中获得的曲线结构来组织数据并计算等值点,采取自适应聚类划分方法获得各个等值面包含的数据点集合后利用曲面重建算法来构造等值面.在计算等值点时,不但利用了数据场中各个数据点处的空间位置与场值大小,而且充分考虑了数据点处的矢量方向信息.实验表明,该方法能够稳定、有效地构造出非结构矢量数据场中的等值面.与基于体元的传统等值面构造方法相比,可以有效加快计算进程,得到更为准确的计算结果.     

基于广义Ricci曲率及深度信息的图像采样方法

随着采样技术的提高、数据量的剧增,给数据的存储及传输造成了一定困难,因此对数据进行重采样,以压缩数据量是解决该问题的一个有效手段.针对灰度图像采样问题,利用密度流形的广义Ricci曲率提出一种采样点之间相关性的衡量方法.首先,将图像看做是对二维流形的着色,通过处理目标物的深度或构造其深度,保留需要着重采样区域的深度信息;其次,结合深度与灰度信息计算密度流形的Ricci曲率;最后,根据相关性原则筛选采样点并重建图像.此外,针对采样过程提出了全局采样及加速的局部采样2种方式,用于权衡速度与精度.采用大量的标准测试图进行实验结果表明,该方法可以有效地应用于灰度图像的压缩;与已有方法相比,该方法在灰度变化剧烈、复杂的边缘采样点分布更为密集,同时对灰度变化平缓的区域采样点也相对更少.     

混合响应面法对汽车吸能部件优化关键技术*

结合sequential和successful的响应面方法以及Kriging插值技术,针对高维优化问题,建立一种混合响应面优化方法.首先采用sequential响应面方法基于初始化变量进行优化,采用Kriging插值方法对样本点和优化过程中形成的优化点重新进行响应面构造,以确定优化范围内新的初始值并将约束减小到一定范围;随后采用successful响应面对更新的设计变量初始值和约束范围进行优化.如此循环,直至得到最优解.采用该方法对汽车前纵梁中板的厚度问题进行优化,取得了不错的效果.     

基于径向函数的响应面法在薄板装配夹具设计中的应用

薄板产品装配夹具的定位策略优化可以有效地减少柔性零件定位的法向变形,而定位点优化方法直接影响到夹具的设计效率.针对直接采用有限元模型的定位点优化方法效率低的问题,提出面向夹具定位点优化的基于径向函数的响应面建模方法.该方法根据均匀采样对定位点位置参数域进行离散,并借助有限元分析构造样本集合;采用Multi-quadric函数描述夹具定位参数与零件变形间的非线性关系;应用均匀设计法优化径向基参量,从而建立基于径向函数的响应面模型.最后通过实例阐述了文中方法的建模过程,结果表明其具有良好的模拟效果和较高的预测精度.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

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.     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

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.