基于多重约束的飞机移动装配线作业调度优化

基于对飞机移动装配线作业多重约束的分析,建立了作业调度优化问题的整数规划模型,提出了组合优先规则WRST以及基于此规则的启发式算法.WRST综合考虑了最迟完成时间、资源以及空间稀缺度三个指标;而算法设计包括基于WRST规则的作业拓扑排序和作业资源分配两阶段.数值试验结果显示基于WRST规则的启发式算法求解质量高,求解速...     

集装箱码头岸吊作业调度建模及调度策略研究

岸吊作业调度对集装箱码头整体运营效率具有重要影响.综合考虑岸吊实际作业中的特有约束,包括预定义顺序约束、依赖于作业次序的设备调整时间、岸吊干涉约束,建立岸吊作业调度问题的混合整数规划模型.针对混合装卸模式,使用启发式算法生成预定义作业顺序,在此基础上采用基于连续贝作业策略的启发式算法对问题进行求解.数据实验结果显示基于SPT规则和连续贝作业的启发式算法能有效利用混合装卸带来的时间节省,减少设备调整时间,对实际岸吊作业调度具有指导意义.     

平行顺序移动的同顺序排序法研究

作业计划的排序方法是成组生产组织方式下生产作业计划的重要内容,本文分析了平行顺序移动方式下的同顺序排序问题的数模结构,提出了一个新的启发式算法,并将该启发式算法规则作为分枝限界条件,提出了该问题的分枝限界算法。该启发式算法优化程度高,作为分枝限界条件其剪枝速度快。该方法不但可以用于确定组内顺序,而且还可用于确定组间顺序。     

多资源作业车间的混合自适应GA优化调度

针对多资源约束的车间调度问题,将启发式算法和自适应GA优化方法结合起来,提出了混合自适应GA方法,建立了多资源约束的车间优化调度模型.根据启发式调度算法中优先规则对调度目标的影响,设计了新的编码规则.采用正弦函数作为自适应因子,使得交叉概率和变异概率随群体的适应度自动改变,提高了运算的效率,克服了启发式算法和普通GA的缺陷.通过实例仿真并与其他算法比较结果表明,混合自适应GA算法可以很好的解决作业车间在机床、刀具等多种生产资源约束下的优化调度,并在评价指标上较其他算法更优.     

带时间窗口的自动化混流生产线调度方法

研究了一类带时间窗口的自动化混流生产线调度问题,其中包括工件排序和机器人搬运作业排序两类问题.在对问题进行系统分析的基础上,考虑处理时间窗口约束、机器人搬运能力约束和工作站能力约束,使用混合整数规划方法建立了此类问题的通用数学模型,并采用CPLEX软件求解模型,以印刷电路板电镀生产线为实例并通过随机算例验证该方法的有效性.     

基于灰色机会约束规划的不确定条件下车间作业调度

针对不确定条件下job shop调度问题的约束条件中含有灰色变量,提出用灰色机会约束规划方法解决不确定条件下job shop调度问题,建立了灰色机会约束规划调度模型.同时,使用灰色模拟的方法和手段解决了灰色机会约束规划问题.给出了如何使用灰色模拟技术处理复杂的灰色机会约束以及基于遗传算法的求最优解的过程,并提出用灰色模拟技术结合遗传算法求解生产调度问题中的灰色不确定规划问题.计算仿真结果表明,这种基于灰色机会约束规划的方法处理不确定条件下车间作业调度问题的模型是可行而有效的.     

飞机移动装配线资源水平问题的建模研究

针对飞机总装移动装配线的资源水平问题,以最小化资源成本为目标,提出并建立了具有空间约束的资源水平问题的数学模型。针对问题特点,提出了非关键任务调度优先级规则,并以遗传算法为框架,优化非关键任务调度优先级。在解码中,提出利用区间细分的方式来确定非关键任务位置,以提高计算效率,提出并设计了当前任务调度对全局资源水平影响的评估公式,极大提高了未调度任务在后续调度过程中选择更佳调度位置的几率。针对空间约束,构建了包含当前关键任务的局部调整方法。最后通过数据实验验证了算法的有效性和优越性。     

基于产出速度的Job-shop型企业生产作业计划与控制方法

借鉴均衡生产思想以及约束理论,提出基于产出速度的Job-shop型企业生产作业计划与控制方法.为及时反映生产过程的瓶颈漂移现象,提出一种基于产出速度确认系统瓶颈的新方法.利用系统的最佳产出速度确定客户订单的投料顺序,并对可能产生的订单堆积提出推平方法.为较好解决存在的计划与调度相脱节问题,提出一种新的调度策略,即平衡产出法则,使作业计划与之相协调.仿真研究的结果证明了方法的有效性.     

面向柔性作业调度问题的启发性规则改进遗传算法

对柔性作业调度问题,提出了一种启发性规则的改进遗传求解方法,此方法从启发性规则出发产生初始调度解。通过对初始调度解进行比较而产生初始种群。对初始种群通过启发规则的改进遗传算法进行优化计算,对染色体进行交叉、变异、交换和选择操作,应用启发式规则搜索关键工序并提高关键工序的交换、变异操作概率,在变异操作中利用启发式规则对变异过程加以引导,从而得到优化解。将此方法运用于一系列典型柔性调度问题进行了实验求解,并将求解结果与其他的计算方法进行了比较,表明此方法能提高求解效率,适合复杂的柔性作业调度问题求解。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.