基于本体论的产品拆卸信息建模

拆卸序列规划生成是虚拟维修的核心之一,直接关系到虚拟维修的可行性及成本。以最优拆卸树的方法研究拆卸序列规划是拆卸序列生成最行之有效的途径。从虚拟维修中产品拆卸模型的基本特点入手,应用本体论的思想和方法,构建了影响拆卸相关的本体,包括几何本体、关系本体、物理本体、化学本体,并综合考虑各本体之间的相互联系,建立了比较完整的产品拆卸信息模型,同时依据成熟的拆卸树算法生成最优拆卸树,以便后期进行拆卸序列规划的研究。并应用于某产品的拆卸模型建立。     

虚拟维修拆卸路径规划关键技术研究

如何进行合理的拆卸路径规划是虚拟维修技术必须解决的难题之一。在对虚拟维修中拆卸路径规划基本流程分析的基础上,得出虚拟维修拆卸路径规划的关键技术,并提出了基于vgPicker类的拾取方法、基于鼠标运动与虚拟实体运动关联的拖曳方法和一种快速而精确的碰撞检测方法。相关算法在某型装备虚拟维修训练系统VMTS中得到应用,并对其他复杂装备的拆卸维修训练有指导意义。     

支持复杂产品并行拆卸序列规划的遗传算法

为高效求解复杂产品的并行拆卸序列规划问题,提出基于遗传算法的复杂产品并行拆卸序列规划方法.针对并行拆卸序列规划问题中拆卸序列长度和每步拆卸零部件个数不确定的特点,提出并行序列染色体编码方法,分别将拆卸单元序列和拆卸步长作为染色体的前段和后段,以此表示一个拆卸序列.基于该染色体编码,采用拆卸混合图描述产品零部件间装配约束关系和拆卸优先级,并导出拆卸约束矩阵和邻接矩阵,由矩阵随机获取可行的初始染色体种群;将基本拆卸时间和不可行拆卸惩罚因子作为优化目标来构建适应度函数,确保最优解的可行性;在初始染色体种群的基础上,适应度函数最小为优化目标,通过遗传、交叉和变异遗传算子实现并行拆卸序列的优化.最后通过实例验证了该方法的可行性和实用性.     

一种基于混沌迁移的伪并行遗传算法及其应用

为了解决遗传算法寻优过程中的早熟收敛问题 ,本文提出了一种基于混沌迁移策略的伪并行遗传算法 ,该算法针对实时性要求不高的优化问题采用串行的算法结构实现分解型并行遗传算法的“独立进化、信息交换”思想 .在并行进化的个体异步迁移过程中 ,引入了混沌迁移序列引导个体迁移过程 ,利用其遍历性和随机性 ,保证了子种群之间能够进行充分高效的信息交换 .仿真研究和在库存优化方面的应用研究表明 ,这种算法具有很强的全局搜索能力 ,寻优效率高 ,有效克服了标准遗传算法的早熟收敛问题 .     

基于改进蚁群算法的维修拆卸序列规划

维修拆卸序列规划是整个维修性设计的重要内容。为了能够以较高的效率求解出产品中零件的拆卸方案,依据产品的基本信息和零件之间的约束关系,建立拆卸Petri网可达图,将拆卸序列规划问题转化为对Petri网可达图最优路径的搜索和寻优问题。同时利用蚁群优化算法对组合优化具有高强适应性的特征,改进基本蚁群算法,对可达图模型进行路径寻优,得到最优或次优的拆卸序列。最后通过实例验证了该方法的有效性。     

混沌遗传算法用于求解混合整数规划问题

针对遗传算法的早熟收敛问题,提出了一种混沌遗传算法（CGA）用于解决混合整数规划问题（MIPP）。该算法的基本思想是把混沌变量加载于初始个体的混沌生成和最优个体的混沌搜索过程中。研究结果表明：混沌遗传算法能够有效地解决混合整数规划问题,改善了遗传算法的早熟问题。该算法效果显著,明显提高了解决混合整数规划问题的计算效率,在收敛速度、解的精度和稳定性方面也都优于遗传算法。     

混沌时间序列预测模型的应用与研究

混沌时间序列预测模型的参数对预测结果起着关键作用,传统上参数优化单独进行,忽略参数之间的联系,导致预测的精度比较低.为了提高混沌时间序列预测精度,提出一种基于遗传算法的混沌时间序列预测模型参数优化方法.参数优化方法的核心思想是相空间重构和支持向量机参数寻优同时进行,通过遗传算法算法的选择、交叉和变异操作达到参数优化求解问题.以经典混沌时间序列Mackey-Glass为例进行了验证性实验.实验结果表明,相对传统的参数寻优方法和分开优化的方法,方法时间复杂度低、预测精度高,是一种有效性的混沌时间序列预测模型参数优化算法.     

超混沌遗传算法在多约束QoS组播路由中的应用研究

针对多约束QoS组播路由的优化问题,提出了一种超混沌遗传混沌算法.该算法利用遗传算法中的改进的适应度函数,通过结合超混沌映射优越性的搜索能力,对遗传算法选出的个体进行混沌优化,以改善遗传算法过早陷入早熟的情况.通过仿真实验表明,该算法有效地改进了搜索效率,且收敛速度更快更稳定,是一种解决多约束QoS路由问题可行和有效的方法.     

旋转约束的船舶装配拆卸路径规划算法

研究船舶装配拆卸路径规划优化问题,设备在安装维修过程中时会受到各种约束的限制,对快速有效地规划可行的装配拆卸路径-直都是船舶虚拟原型设计中的难点之-.针对装配拆卸路径规划中的旋转约束问题,提出一种基于快速探索随机树(RRT)算法的新的旋转约束路径规划算法.算法针对RRT算法中基于欧拉角的三维空间旋转分量随机采样函数分布不均匀的问题,设计了一种新的欧拉角均匀分布随机采样函数来生成随机位姿点,将欧拉角距离引入到C空间距离度量函数中,对路径中的旋转变化量进行控制,并引导路径规划方向.进行仿真的结果证明,算法能够对高维空间中刚体的旋转范围进行有效控制,具有较高的装配效率.     

面向产品装配序列规划的智能优化算法库

针对复杂产品装配规划的组合爆炸和盲目搜索难题,以及单个智能优化算法各自存在的缺点,提出一种用装配序列智能优化算法库解决装配序列规划问题的方法.装配序列规划智能优化算法库主要由算法顾问和算法池构成,算法顾问依据装配规划问题的描述、算法可量化性能的主要参考指标和经验公式,向装配规划人员推荐解决规划任务的最合适算法;算法池包括改进的遗传算法、蚁群算法和模拟退火算法等3种智能优化算法.建立了统一的装配序列规划优化模型和智能算法评价指标体系,并给出了装配序列规划智能优化算法库的具体操作流程.最后结合瓶塞开启机实例,验证了该算法库为装配规划人员推荐的智能优化算法是合理的.     

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。     

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.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).