元动作单元故障树建模在复杂机电产品可靠性优化中的应用

针对传统的可靠性建模方法难以建立复杂机电产品的可靠性数学模型,提出一种结合功能分解(FMA,function-motion-action)和故障树(FTA,fault tree analysis)的建模方法,降低了复杂机电产品的可靠性优化模型的构造难度。针对遗传算法(GA,genetic algorithm)和粒子群算法(PSO,particle swarm optimization)在模型求解时存在的不足,提出构建混合GA-PSO算法来改善GA算法易陷入局部最优或全局搜索能力弱的现象。通过数控磨齿机的实例分析,验证了用混合GA-PSO算法构造优化模型的可行性,以及采用混合粒子群算法优化求解的有效性。     

基于遗传和粒子群结合的文化算法

针对粒子群优化(PSO)算法的"早熟"现象,给出了基于遗传和粒子群结合的文化演化算法.该算法将PSO/GA纳入文化算法框架,形成PSO的主群体空间和GA的信仰群体空间,两群体空间可以独立并行演化,并在适当的时机实现信仰群体空间对主群体空间的引导,达到改善粒子群优化算法全局搜索能力、提高计算精度的目的.仿真表明,该算法的优化性能和效率优于PSO算法、GA算法和GA-PSO混合算法.     

带时间窗的物流配送区域划分模型及其算法

针对烟草行业存在客户点大规模、客户需求量不固定、配送车辆最大行驶距离限制以及客户点送货时间不固定等特点,综合考虑配送的多产品、多客户、时间限制等影响因素,通过聚类方法划分不同的配送单元,应用整数规划选择中转站不固定配送单元,以物流配送网络构建的总成本最小化为目标函数,建立了基于配送单元的固定成本和变动成本以及带时间窗的时滞成本的数学规划模型,并提出了一种改进粒子群-遗传混合算法进行直接求解.该算法在评价函数中隐含加入了距离和时间等约束条件,并设计了算法间选择性赋予方法,具有较高的全局和局部搜索能力.实例仿真表明,该混合算法的优化性能和效率优于PSO算法、GA算法、GA-PSO算法和MPSO算法,因此能够更有效地解决大规模配送点的物流配送区域划分问题.     

一种新的优化神经网络权值算法及其应用

为克服和改进BP算法的不足,文章在分析遗传算法(GA)和粒子群优化(PSO)算法优越性与不足的基础上,提出了一种基于GA和PSO结合的算法——GA-PSO算法,用于训练神经网络权值.算法产生下一代个体时,不仅采用交叉和变异算子,而且在重新定义局部最优粒子的基础上,引入粒子群优化算法,有效地结合了遗传算法的全局收敛性能和粒子群优化算法的局部搜索能力.通过对异或问题和IRIS模式分类问题的学习,仿真结果明显好于单纯地用GA或PSO进行前向神经网络训练,能有效避免早熟收敛的同时,提高搜索精度.     

基于GAs/PSO组合算法的水轮机调速系统PID参数寻优

提出了一种基于GA s/PSO组合算法的P ID控制器参数自整定方法,这种方法兼有遗传算法(GA s)和粒子群算法(PSO)的优点。组合算法种群由GA s和PSO的最佳个体迁移形成,其中GA s采用了实数编码和变异概率自适应,PSO算法采用了带指数衰减的惯性因子的速度更新算法,以加快收敛速度。通过对水轮机调速系统P ID控制器参数寻优仿真比较表明,该组合算法寻优性能比单独的GA s和PSO表现更为优异,且所得系统具有更好的动态性能。     

机器人路径规划：一个改进的粒子群灰狼混合算法

为提高自主移动机器人路径规划器的快速性和最优性，提出一种改进的基于粒子群优化（PSO）算法和灰狼优化（GWO）算法的混合算法，简称H-PSO-GWO算法。首先，利用Tent混沌映射初始化种群，提高种群多样性；然后，采用改进的控制参数和新的个体位置更新策略来加快算法的收敛速度和增强种群个体趋于全局最优的能力。通过与其他算法进行数值对比实验和路径规划对比试验，验证了所提出算法的有效性和优越性。最后，使用贝塞尔曲线将所生成的路径平滑化，使得路径更适合移动机器人移动。     

基于PSO-DE混合算法的结构可靠性优化设计

为提高结构可靠性优化设计的效率,利用粒子群优化(PSO)和差分进化(DE)算法的搜索特性,构造一种PSO-DE混合算法,以克服基本PSO算法的早熟问题.将PSO-DE混合算法与结构可靠性优化理论相结合,建立了结构系统失效概率约束下以结构质量最小化为目标的优化模型.算例结果表明:与基本PSO算法相比,文中提出的PSO-DE混合算法提高了收敛速度和计算精度;该算法易于实现,鲁棒性好.     

融合粒子群优化算法与蚁群算法的随机搜索算法

针对PSO算法与蚁群算法的优缺点,提出一种融合PSO算法与蚁群算法的混合随机搜索算法.该算法充分利用PSO算法的快速、全局收敛性和蚁群算法的信息素正反馈机制,达到优势互补,将这种优化方法拓展到求解连续空间问题,并通过实例来验证该算法对于单峰、多峰函数都能取得较好的优化效果.     

求解一类Minimax分式优化问题的几何规划方法

研究了一类Minimax分式规划问题(MFP).首先通过引进变量，将问题(MFP)等价转化为问题(EP1),其次，再将问题(EP1)中的约束函数整理成正项式的形式，然后，利用特殊不等式的性质将问题(EP1)转化为易于求解的几何规划问题(GP),通过求解一系列(GP)问题获得原问题的最优解，最后，给出求解问题(MFP)的迭代算法以及算法的收敛性分析，数值结果表明了算法的有效性.     

基于GA-PSO的多目标混流装配线排序研究

为求解生产调度中的多目标混流装配线排序问题,提出一种将遗传算法与粒子群算法相结合的混合算法——GA-PSO算法.为更好地评价个体,提出一种引入个体的Pareto分级和拥挤距离的适应度函数.针对标准PSO算法求解排序问题的不足,提出了一种将实数映射成离散值的方法.在算法的历次迭代中,早期通过遗传算法全局搜索优势扩大搜索范...     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。