Balancing Stochastic Assembly Lines

This paper is concerned with balancing continuous assembly lines with stochastic work elements, The primary problem is defined as follows: “Given an initial balance, a cycle time, normally distributed work element times with given means and variances, and a precedence graph, rearrange the work elements such that the probability of one or more stations exceeding the cycle time is minimized.” Four solution procedures, Trade and Transfer, Branch and Bound, Heuristic Branch and Bound and BABTAT are evaluated.     

Stochastic Leadtimes in Two-Level Assembly Systems

Shortages of assembly parts often arise from late arrivals of one or more batches of components. We address the problem of determining planned leadtimes in two-level assembly systems with stochastic leadtimes, with the objective of minimizing the sum of inventory holding costs and tardiness costs. An algorithm is developed which exploits properties of the objective function to find optimal solutions. Computational results indicate that optimal solutions often have negative safety times for at least one of the components, as well as substantial safety times for the assembly stage.     

Deterministic Equivalents for Stochastic Assembly Line Balancing

Two methods for considering variations in task completion times in the assembly line balancing problem are (1) assign tasks to stations such that the sum of the completion times is less than a fixed proportion of the cycle time and (2) assign tasks to stations such that the probability for completing all tasks within the cycle time is greater than a fixed value. In this paper, we show that for certain classes of distributions of task completion times, the first method, which is basically a deterministic approach to the problem, is equivalent to the second, which requires a stochastic formulation. The nature of the relationship is also demonstrated.     

随机型双边装配线平衡问题的一种启发式算法

为有效求解随机型双边装配线第Ⅰ类平衡问题(STALBP 1),在分析双边装配线平衡特点的基础上,考虑各任务操作时间的随机性,提出了一种启发式算法。在该启发式算法中,假定各任务的操作时间服从正态分布,运用具有操作方位约束的任务优先分配等规则来进行任务的选择和分配,通过改变预设超限概率,在不同生产节拍下,分别得到不同的平衡方案。实例验证了算法的有效性。     

矿渣微晶玻璃专家系统经验设计

分析了矿渣微晶玻璃材料设计知识的特点,确定了合适的知识表示方法.模拟了材料设计专家进行材料设计的思路,建立了矿渣微晶玻璃材料设计专家系统的经验设计模块,并由实例验证其具有很好的设计效果.     

基于UG OPEN的3D-CAAP装配模块的设计与实现

设计了基于UG的三维装配工艺规划与管理系统（3D-CAAP）的构架，着重研究了运用MFC实现CAAP与UG的集成开发，可视化装配工艺规划环境设置、装配顺序、路径规划与编辑、工艺数据的数据库存储与动态连接库调用等关键技术，介绍了实现一种较实用的3D-CAAP系统的解决方案，实现了可视化装配规划、实时纪录装配顺序、装配知识查找、装配顺序、路径编辑修改、装配工艺文件管理的系统整合。     

深潜浮力材料的结构分析与设计

本文详细分析了空心微球填充的树脂类材料的结构,讨论了轻质填充物（空心微球）的结构与力学性能,计算分析了空心微球的结构与性能对复合材料性能的影响。以普通玻璃微珠填充的环氧树脂材料为例,分析了玻璃微球填充的最大比例与可能得到的浮力材料的最高性能。总结了浮力材料的设计原则和和发展方向。     

随机混合装配线的启发式平衡设计方法

把某个型号产品的数量占整个批次的比重作为它的权重,加权合并混合装配线上各个型号产品的同类型工作单元的时间.运用随机启发式方法对合并后的工作单元进行平衡排序,通过改变预设超限概率的值,获得一组排序方案.采用工作站总数、装配线效率、平滑指数和成本四个指标对这组排序方案进行综合评价,挑选出最佳的排序方案,并且用系统仿真来检验该最佳方案的实际运作效果.实证研究表明,各个工作站的平均等待时间和空闲率都有明显的下降.     

Assembly planning with an ordering genetic algorithm

The goal of assembly planning consists in generating feasible sequences to assemble a product and selecting an efficient assembly sequence from amongst these. This paper describes an original ordering genetic algorithm (OGA) developed to solve this problem. The developed approach permits the generation of assembly trees for a mechanical product. The algorithm is based on three main ideas. First, a mapping transforms any studied assembly plan into a valid one using 'precedence values' changing through the sequence, so that an invalid sequence will never be proposed. Secondly, to identify subsets, trace is kept all along the sequence of the components membership to a set of parts. Finally, the individuals of the OGA are compared with each other using a multi-criteria decision aided method called PROMETHEE II. The use of this method avoids aggregating several technical criteria into a unique fitness value. The proposed algorithm, illustrated through the simple example of a mouse device, has been applied on an industrial signalling relay made of 34 parts.     

Research of Dynamic Material Handling in an Automobile General Assembly Line Based on Real-time Information

The status of material delivery of an automobile general assembly line is analyzed,and the technique to achieve the real-time tracking of assembly statas information is proposed based on RFID( Radio Frequency Identification) . Thus the consumption of line-side buffer is obtained dynamically,then the type and quantity of needed material are fed back to the subsystem of material handling; the algorithm for determining the best time departure time of delivery driver based on minimizing of total time penalty function is proposed. This approach makes the ma- terial amount of a single delivery trip maximized and improves the efficiency of delivery drivers significantly in the case of does not affect the assembly line normal throughput. Additionally,although this dynamic material handling method is developed for the automobile assembly plant,it should be pointed out that this method is also applicable to other mixed model assembly plants such as electronics,semiconductor and aerospace industry.     

管子组件成形工艺分析

管子组件加工过程中经常出现漏气和扩口裂纹问题,为了解决此类问题,对不锈钢细管扩口工艺进行研究,通过管端壁厚计算、扩口力的计算及扩口应力的理论分析,为管子组件扩口工艺提供理论依据;有效避免了管子组件压力试验漏气及零件扩口裂纹问题,不锈钢管材供应状态及平管嘴口部转角对管子组件的成形影响较大。     

AI-Based Process Planning for Electronic Assembly

Diversity of electronic products, lack of human expertise, and inconsistency among manually generated process plans increase the necessity of developing Computer Aided Process Planning (CAPP) systems for electronic assembly. Artificial Intelligence (AI) offers a few techniques to develop CAPP systems which would behave in a 'knowledgeable' manner. Two rule-based CAPP systems, a backward-chaining system developed in M. 1 shell and a forward-chaining system developed in OPS 5, and an object-oriented system developed in Objective-C are discussed. The CAPP systems generate processes and select a set of machines to perform the generated processes for a given product. In the rule-based CAPP systems, product characteristics and bill of components are stored in working memory and capabilities of the available machines are stored as rules. In the object-oriented CAPP system, product as well as the available machines are represented as objects. A central decision module which does pattern matching and sends messages to appropriate machines (objects) is developed     

带时间窗的汽车总装线物料配送路径规划

分析了现阶段汽车总装线物料配送中存在的问题,建立了适用于汽车总装线物料配送路径规划的混合时间窗模型,提出了解决带时间窗的汽车总装线物料配送路径优化问题的改进遗传算法,使用了一种新的染色体编码方式和与之对应的交叉算子。针对传统轮盘赌随机操作选择误差比较大的弊端,提出改进的轮盘赌选择算子,加大随机数的产生次数并加入排序选择的思想,融合了最佳个体保存选择策略,提高算子的选优性能。实验表明该算法用于求解带时间窗的汽车总装线物料配送路径问题的有效性。     

支持复杂装配线物料配送的BOM映射技术研究

在复杂装配线生产过程中,如何实现物料的按时有序配送和关键零部件的齐套控制是物料配送管理的主要难题.在分析产品装配结构、装配工艺流程以及物料配送规则的基础上,通过梳理“制造BOM—作业BOM—配送BOM”之间的转换映射关系,建立基于装配工艺流程的作业BOM生成方法和基于工位结构分解的配送BOM生成方法,实现对复杂装配生产线物料配送信息的一致性映射和完整性控制,为物料配送的精细化管理提供能够反映装配作业过程特征的数据描述模型.最后通过应用实例验证说明上述BOM转换映射技术的合理性和可行性.     

Material Characterization of Photo-Fabrication Process

The characterization of photopolymerization for the rapid prototyping process has been studied using a laser stereolithography machine. The cross sections of the cured layers and lines were examined using an optical microscope. Perkin-Elmer differential scanning calorimeter (DSC)-7 was employed to investigate the degree of curing after laser scanning. It was observed that the profile of the cross section of a cured line and/or part determined by the laser exposure density is a function of laser power and scanning speed. DSC analysis shows the retained resin to be governed by laser exposure intensity and laser scanning pattern. By increasing the laser exposure or the overlapping area of two adjacent scanning lines, retained and uncured resin could be minimized. However, the efficiency of photopolymerization is lowered. The most efficient operating parameters for part building can be determined by a T factor.     

泡沫材料冰蓄冷板融化过程的研究

建立了填充泡沫材料冰蓄冷板内冰融化过程的数学物理模型,该模型考虑了融化液态水自然对流的影响。分别数值模拟了填充开孔聚氨酯泡沫、泡沫铜的冰蓄冷板的融化过程,研究了泡沫材料冰蓄冷板融化过程的速率、温度分布、相界面移动等规律。进行了实验对比,验证分析了泡沫材料的孔隙参数对融化速率的影响。结果表明,填充低导热系数泡沫材料可有效延长冰蓄冷板的释冷时间,该时间随泡沫孔密度的减小而增加、随孔隙率的增大而略减。填充高导热系数泡沫材料可有效改善冰蓄冷板温度分布,可加快冰融化速率,该速率随着泡沫孔隙率的减少而增加、随孔密度的减少而略增。     

Guided Molecular Assembly on a Locally Reactive 2D Material

Atomically precise engineering of the position of molecular adsorbates on surfaces of 2D materials is key to their development in applications ranging from catalysis to single‐molecule spintronics. Here, stable room‐temperature templating of individual molecules with localized electronic states on the surface of a locally reactive 2D material, silicene grown on ZrB₂, is demonstrated. Using a combination of scanning tunneling microscopy and density functional theory, it is shown that the binding of iron phthalocyanine (FePc) molecules is mediated via the strong chemisorption of the central Fe atom to the sp³‐like dangling bond of Si atoms in the linear silicene domain boundaries. Since the planar Pc ligand couples to the Fe atom mostly through the in‐plane d orbitals, localized electronic states resembling those of the free molecule can be resolved. Furthermore, rotation of the molecule is restrained because of charge rearrangement induced by the bonding. These results highlight how nanoscale changes can induce reactivity in 2D materials, which can provide unique surface interactions for enabling novel forms of guided molecular assembly.     

介孔材料的制备、表征、组装及其应用

介孔材料因具有一系列独特性质而成为近年来材料研究的热点.对介孔材料的制备技术进行了简要介绍并分析了其影响因素,概括了常用的表征方法,进一步系统阐述了介孔材料的组装及应用,并展望了介孔材料研究的发展前景.     

随机动力学响应的高斯相关过程模拟

动力学响应是描述系统振动状态、评估其性能、用于控制等的重要变量,复杂系统的不确定性、随机激励样本的不可测量性等导致传统随机响应时程与统计分析的计算困难,因此需要发展基于系统响应观测的、直接的随机过程概率模型与评估新方法。近年来,人工智能与数据处理技术等领域发展的无确定性系统模型的、直接随机过程概率模型,及其概率评估、系统状态预测等方法为动力学响应的概率分析提供了新思路,特别是具有很好普适性与可分析性的高斯相关过程已具有较完整的理论方法。鉴于此,本文提出针对动力学系统响应的、直接的随机过程概率模型与评估方法,并作探索性研究。先基于高斯白噪声激励动力学系统响应的统计特性分析,说明系统响应的高斯随机过程特性、响应在时间维度上的相关性、及其协方差随时间差的指数衰减特性等;再给出该系统响应的高斯相关过程概率建模与评估方法,包括由响应协方差计算,高斯过程协方差或核函数的拟合,到高斯相关过程概率模型的确定,响应样本过程的直接生成,及其统计评估等,并给出高斯相关过程的贝叶斯更新与系统状态预测有关基本公式。数值结果表明该高斯相关过程的概率建模与响应评估方法的可行性与有效性。     

多孔陶瓷材料制备方法

多孔陶瓷是一种新型材料，由于其具有较低的热传导等优良性能，而被广泛地应用于众多科学领域。综述了多孔陶瓷的类型、制备工艺、性能及应用，特别是详尽的讨论了制备工艺及各种工艺的优缺点，最后展望了多孔陶瓷的发展前景及今后的发展方向。