改进元胞遗传算法的转塔式贴片机贴装优化

研究了转塔式贴片机的贴装过程优化问题,将其分解为元件贴装顺序和供料器布置,建立以组装时间最短为目标的贴装过程优化模型,然后采用元胞遗传算法对模型进行求解,基于问题的特点提出二维分段式的十进制编码方式,在遗传操作过程中运用改进的顺序交叉和自适应的变异操作,并在算法中结合局部搜索策略,实现了贴装顺序和供料槽布置的同时优化.实例求解和对比结果表明本算法在求解效率和求解结果上都优于传统遗传算法,从而证明了该算法的有效性.     

基于遗传算法的复合式贴片机贴装过程优化

针对复合式贴片机的贴装过程优化问题,将其分解为元件分配、供料器布置和元件取贴顺序3个子问题.在分析实际工程应用的基础上,以动臂的负荷平衡和最小移动距离为目标,建立了双动臂转塔式贴片机的贴装过程集成优化模型,采用遗传算法和元件分配启发式方法相结合的方式实现了贴装过程的优化.算法中提出了一种分段二元实数编码方法,在一条染色体中同时描述了元件分配、供料器布置和元件取贴顺序.针对提出的编码方式,采用改进的顺序交叉和自适应的变异操作,结合轮盘赌选择和精英选择策略以及适应度函数的设计,在满足贴片机运动机构约束条件的情况下,使得遗传搜索能够快速地进入有效解空间进行搜索.实例计算结果表明,该算法能实现多动臂转塔式贴片机贴装过程的优化,从而提高印刷电路板的装配效率.     

拱架式贴片机贴装路径优化

贴片机工作时贴装头需在喂料器与印刷电路板之间频繁移动，缩短贴装头移动距离是提高贴装效率的重要途径。对多头拱架式贴片机贴装路径优化问题进行研究，分析贴装头沿喂料器移动取料时贴装路径变化，建立贴装头移动距离表达式。以贴装头移动距离最小为目标建立贴装路径优化模型，以贴装位置编号对取贴顺序编码，利用遗传算法对取贴顺序和取料方向进行优化。分析不同取料方式下贴装路径差异和结构特点，结果表明：双向取料与近侧取料在贴装点位置分布偏于PCB单侧较多时出现结构性差异，采用双向取料可获得比近侧取料更短的贴装路径，更利于提高贴装效率。     

基于RLS的用于贴片机贴装顺序优化的禁忌搜索算法

对元器件的拾取与贴装顺序进行优化是提高电子组装生产线上贴片机贴装效率的主要方法.在给定喂料器位置的前提下,寻求好的元器件拾取与贴装顺序,可以缩短贴装路径,提高贴装效率.为此,文中建立了数学规划模型,提出了一种基于参考解局部搜索(RLS)的改进禁忌搜索算法.在算法中,采用了双禁忌表来避免迂回搜索,设计了基于取贴循环插入移动的参考解局部搜索策略以提高算法跳出局部最优的能力.对20个印刷电路板贴装数据的仿真实验表明,文中所提算法的求解效果优于现有方法.     

基于机器视觉的印刷电路板误差校正方法

利用贴片机视觉系统,首先通过示教的方法消除第1块印刷电路板(PCB)的定位误差,然后利用对PCB板基准点的图像识别与计算,消除其余PCB板的定位误差和制造误差,从而保证了贴片机的重复贴装精度.本文提出的PCB板误差校正方法和步骤用于所研制的全视觉贴片机样机上,对细间距表面元件的贴装精度可以控制在±50μm以内.     

浅析贴片机国产化的关键技术

表面贴装技术(Surface Mount System)是评估电子加工行业技术水平的重要依据。贴片机是一种高精度的机电一体化设备,是靠机械运动将电子元器件从供料器中吸取出来并经过校准检测机构对中调整后贴装到电路板(PCB)上的。由于贴装元器件微型化和差异化及贴装技术对速度和精度的要求,必须采取多种精密而高端的机电一体化技术,才能达到机器生产和使用要求。作为SMT生产线的关键设备,外国生产商一直垄断着贴片机市场,价格相当高昂,因此贴片机实现国产化是我国发展的终极目标。当前我国的贴片机技术发展日趋成熟,该文将围绕贴片机的关键技术进行研究。     

贴片机贴装印刷电路板中供料器的分配问题

供料器分配问题是贴片机贴装印刷电路板(PCB)中的一个关键问题，它直接影响贴片机生产效率的高低．针对该问题提出其优化模型，规定一种元器件只能装在一个供料器上，将各个取贴循环中的元器件集合看成一个整体，追求贴片头沿着供料槽从供料器上吸取元器件的移动时间最短．同时基于该模型给出了一种启发式的解决方法，首先将元器件分配组合成各个取贴循环的元器件集合，然后根据这些集合里元器件的贴装位置来分配供料器的位置，使贴片头同时取料的次数尽可能的多，在一台4头贴片机上的相关实验表明，该模型和方法能大幅度地降低生产时间。     

表面贴装器件图像处理关键技术研究

针对贴片机中表面贴装器件(Surface Mount Device,SMD)的视觉测量问题,研究了SMD的图像识别和测量算法.基于视觉飞行对中技术获取SMD图像.根据SMD的几何特征,提出了用于其图像处理流程的高斯滤波、迭代算法和最小面积外接矩形算法,并分别在Halcon和OpenCV两大机器视觉平台上进行对比分析与验证.     

一种基于矩形拟合的LED贴片机元件定位算法

针对LED贴片机中元件的视觉定位问题,提出了一种基于矩形拟合的元件定位算法。利用大部分LED贴片灯珠为矩形的几何特征,首先根据背景灰度对采集图像进行全局阈值分割;然后以顶点为界将元件轮廓坐标分为四组并做等间隔采样;最后根据矩形相邻两边正交的特性对采样坐标进行矩形拟合实现元件定位的目的。实验表明,该方法具有较高的准确性和较强的鲁棒性,符合高精度贴片机的贴装要求。     

一种扩充的面向对象Petri网

在面向对象的Ｐｅｔｒｉ网基础上，引入依赖消息，提出了一种扩充的面向对象Ｐｅｔｒｉ网（ＥＯＰＮ）模型，并以企业中的一项生产活动－－ＰＣＢ元件贴装为实例，建立了描述这一活动系统的完整的ＥＯＰＮ模型，据此实现了物料分配的优化调度，构成了ＣＡＤ／ＣＡＭ集成系统中重要的一环。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

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.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to