Robotic assembly of printed circuit boards with component feeder location consideration

The use of industrial robots for the assembly of printed circuit boards (PCB) is fast gaining popularity. Minimization of the time required for board assembly while maintaining production quality is the process planner's main task. This task involves the specification of the insertion sequence of components in their respective locations and the assignment of component types to feeders or dispensing magazine slots. The time taken by a robot to fetch a component for insertion is dependent on the location of the feeder that holds the component type. Similarly, board assembly lime is dependent on the order of component insertion on the board and the fetch time of components between insertions. In this paper, models to minimize the total assembly time for a board are developed and studied. Factors considered in the analysis of the assembly time are the component assignment to magazine     

中国农村金融体制改革的最优路径选择

从系统论的观点出发,并利用“樊、胡福利指数模型”对我国农村金融体制改革路径进行了分析、验证。研究表明:我国现行农村金融体制所遵循的“循序渐进”改革路径造成了农村金融体制内部不协调发展。受“不协调成本”的影响,我国农村金融的功能非但没有在改革中更趋完善,反而出现了萎缩。建议我国农村金融体制选择“平行推进”的改革路径。     

On the Contingent Valuation of Safety and the Safety of Contingent Valuation: Part 2 - The CV/SG "Chained" Approach

This article reports the results of a study aimed at estimating a willingness-to-pay based value of statistical life for road risks using a multi-stage approach which involves "chaining together" responses to contingent valuation and standard gamble questions.The rationale for employing a multi-stage approach is to break the wealth/risk of death trade-off down into a number of conceptually manageable steps, thereby trying to attenuate the various biases that appear to be pervasive in responses to more direct contingent valuation questions in the health and safety field.     

Policy Sequencing and the Development of Rice Value Chains in Senegal

In response to the world food crisis in 2008, Senegal developed a productivist national food self‐sufficiency programme. However, the critical question is not whether the programme can meet its ambitious target of self‐sufficiency in rice production by 2015, but, if it does, how will domestic rice reach urban markets, where consumers generally prefer imported rice for its superior grain quality. Information collected through interviews and a stakeholder workshop advances the argument that policy sequencing will be crucial in order to upgrade Senegalese rice value chains progressively. Any large‐scale investments in productivity will need to be preceded by investments in post‐harvest grain‐quality infrastructure before sector‐wide marketing strategies can be adopted that enhance the chain competitiveness of domestic relative to imported rice.     

Beta approximation of ratio distribution and its application to next generation sequencing read counts

Paired sequencing data are commonly collected in genomic studies to control biological variation. However, existing data processing strategies suffer at low coverage regions, which are unavoidable due to the limitation of current sequencing technology. Furthermore, information contained in the absolute values of the read counts is commonly ignored. We propose a read count ratio processing/modification method, to not only incorporate information contained in the absolute values of paired counts into one variable, but also mitigate the discrete artifact, especially when both counts are small. Simulation shows that the processed variable fits well with a Beta distribution, thus providing an easy tool for down-stream inference analysis.     

下料问题与运输问题联合优化建模

本文研究了考虑子材运输的标准一维下料问题。建立了由生产商负责运输时,标准一维下料与运输协调优化整数规划模型,最小化母材使用成本,子材库存成本及子材运输成本。采用拉格朗日松弛技术对有关约束进行松弛和模型分解,设计基于序列规则和FFD规则的混合启发式算法求解模型。该算法由两部分组成,分别用于求解标准一维下料子问题和卖方运输子问题。通过随机产生的1800个算例,验证模型合理性与算法的有效性。与基于列生成法的两阶段算法解进行比较,平均总成本降低了17.57%,表明集成算法优于两阶段算法。     

Sequencing heuristics for dependent setups in a continuous process industry

In this paper we address the scheduling of Biaxially Oriented Polypropylene (BOPP) film production, which belongs to the plastics industry and is a continuous process. Scheduling problems in BOPP film production involve processing different thickness settings of films on a common facility. Customer orders of the same thickness setting are usually grouped together as a production batch and a setup time is incurred whenever the batch is switched. However, there is usually more than one batch for the same thickness setting because of the due date constraints of the orders. Therefore, there is a need to develop a batching and sequencing scheme that minimizes the total setup time, or equivalently the makespan, under the due date constraint. In this paper heuristics are developed to generate a near-optimal solution for the problem. The heuristics are evaluated by an optimal solution procedure and are tested by using the actual data from a plant making the BOPP film. Comparison of the heuristics with the results of the current system has demonstrated a significant reduction in total setup time.     

A note on the complexity of the problem of two-agent scheduling on a single machine

We consider a two-agent scheduling problem on a single machine, where the objective is to minimize the total completion time of the first agent with the restriction that the number of tardy jobs of the second agent cannot exceed a given number. It is reported in the literature that the complexity of this problem is still open. We show in this paper that this problem is NP-hard under high multiplicity encoding and can be solved in pseudo-polynomial time under binary encoding. When the first agent's objective is to minimize the total weighted completion time, we show that the problem is strongly NP-hard even when the number of tardy jobs of the second agent is restricted to be zero.     

Dynamic Policies for Optimal LEO Satellite Launches

Low‐earth orbit satellite (LEO) systems continue to provide mobile communication services. The issue of cost containment in system maintenance is a critical factor for continued operation. Satellite finite life‐times follow a stochastic process, and since satellite replenishment cost is the most significant on‐going cost of operation, finding optimal launch policies is of paramount importance. This paper formulates the satellite launch problem as a Markovian decision model that can be solved using dynamic programming. The policy space of the system is enormous and traditional action space dominance rules do not apply. In order to solve the dynamic program for realistic problem sizes, a novel procedure for limiting the state space considered in the dynamic program is developed. The viability of the proposed solution procedure is demonstrated in example problems using realistic system data. The policies derived by the proposed solution procedure are superior to those currently considered by LEO system operators, and result in substantial annual cost savings.     

基于JIT装配模式的网上超市订单分拣优化模型

订单分拣是大型网上超市生存和发展的关键环节，如何在数百万种商品中将订单要求的商品高效、准确地进行拣选并包装，是亟待解决的难题。本文以提高大型网上超市订单分拣方法的科学性为目标，针对订单拣选、集货复核、包装这一作业流程，基于JIT装配流水线思想，建立大型网上超市订单成组分拣的优化模型与求解方法。在构建订单分拣流程中各工序作业时间计算模型的基础上，建立了订单分批与排序的联合优化模型。围绕缩减求解空间的思想提出两阶段启发式优化方法。通过应用实例分析和灵敏度分析证明了算法的有效性。结果表明，本文提出的网上超市订单成组分拣方法相较于传统方法可较大幅度提高订单分拣的效率，为网上零售企业的订单拣选和包装作业流程的优化提供了理论指导。