Efficient algorithms for flexible job shop scheduling with parallel machines

Job shop scheduling with a bank of machines in parallel is important from both theoretical and practical points of view. Herein we focus on the scheduling problem of minimizing the makespan in a flexible two-center job shop. The first center consists of one machine and the second has k parallel machines. An easy-to-perform approximate algorithm for minimizing the makespan with one-unit-time operations in the first center and k-unit-time operations in the second center is proposed. The algorithm has the absolute worst-case error bound of k − 1 , and thus for k = 1 it is optimal. Importantly, it runs in linear time and its error bound is independent of the number of jobs to be processed. Moreover, the algorithm can be modified to give an optimal schedule for k = 2 .     

基于开路分支线加载双模谐振器的微带带通滤波器设计

文章设计了一款基于开路分支线加载双模谐振器的微带带通滤波器。通过对开路分支线加载双模谐振器的奇偶模特性及固有传输零点分析,利用调节分支线的长度可以灵活地调整谐振器的固有传输零点位置这一特性,采用了两个具有不同分支线长度的谐振器实现了一个高选择性滤波器的设计与测试,测试结果与仿真结果基本一致。所设计的滤波器中心频率为2.45 GHz,通带宽度为150 MHz,通带内插损小于1.5 dB,具有两个位于2.27 GHz和2.57 GHz的传输零点,在2.0 GHz与2.95 GHz处的衰减分别达到41 dB和29.8 dB。此外,该滤波器尺寸小巧,设计加工方便,具有一定的实用价值。     

基于压力控制的常分离式双离合器膜片弹簧设计与仿真

为了保证干式双离合器在摩擦片磨损后仍能可靠传递扭矩,首先利用解析法对常分离式膜片弹簧载荷-变形特性进行理论分析,提出了基于压力控制的膜片弹簧磨损后压力保持方法,其次通过优化设计对膜片弹簧的结构参数进行了优化,并利用MSC.Patran/Marc软件对优化后常分离式离合器膜片弹簧工作过程进行了有限元接触仿真,最终得到了更符合实际工况的膜片弹簧载荷-变形特性曲线。结果表明：经过优化后的膜片弹簧,采用压力控制方法,摩擦片磨损后无需机械补偿,仍能保证扭矩的可靠传递。     

基于COM的开放式数控系统软件模块通信方法的研究

采用基于COM技术的软件设计方法 ,对数控系统软件进行模块化开发 ,模块间的通信问题是关键。应用COM技术中的“事件”和“事件槽”方式实现了客户组件模块与服务器之间、客户组件模块之间的通信。这为开放式数控系统软件设计中通信问题的解决提供了一种新的软件方法     

Scheduling and lot streaming in two‐machine open shops with no‐wait in process

We study the problem of minimizing the makespan in no‐wait two‐machine open shops producing multiple products using lot streaming. In no‐wait open shop scheduling, sublot sizes are necessarily consistent; i.e., they remain the same over all machines. This intractable problem requires finding sublot sizes, a product sequence for each machine, and a machine sequence for each product. We develop a dynamic programming algorithm to generate all the dominant schedule profiles for each product that are required to formulate the open shop problem as a generalized traveling salesman problem. This problem is equivalent to a classical traveling salesman problem with a pseudopolynomial number of cities. We develop and test a computationally efficient heuristic for the open shop problem. Our results indicate that solutions can quickly be found for two machine open shops with up to 50 products. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

Flow‐shop batch scheduling with identical processing‐time jobs

In many practical situations of production scheduling, it is either necessary or recommended to group a large number of jobs into a relatively small number of batches. A decision needs to be made regarding both the batching (i.e., determining the number and the size of the batches) and the sequencing (of batches and of jobs within batches). A setup cost is incurred whenever a batch begins processing on a given machine. This paper focuses on batch scheduling of identical processing‐time jobs, and machine‐ and sequence‐independent setup times on an m‐machine flow‐shop. The objective is to find an allocation to batches and their schedule in order to minimize flow‐time. We introduce a surprising and nonintuitive solution for the problem. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Scheduling recurrent construction

A problem we call recurrent construction involves manufacturing large, complex, expensive products such as airplanes, houses, and ships. Customers order configurations of these products well in advance of due dates for delivery. Early delivery may not be permitted. How should the manufacturer determine when to purchase and release materials before fabrication, assembly, and delivery? Major material expenses, significant penalties for deliveries beyond due dates, and long product makespans in recurrent construction motivate choosing a release timetable that maximizes the net present value of cash flows. Our heuristic first projects an initial schedule that dispatches worker teams to tasks for the backlogged products, and then solves a series of maximal closure problems to find material release times that maximize NPV. This method compares favorably with other well‐known work release heuristics in solution quality for large problems over a wide range of operating conditions, including order strength, cost structure, utilization level, batch policy, and uncertainty level. Computation times exhibit near linear growth in problem size. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Two‐machine flow shop no‐wait scheduling with a nonavailability interval

We study a two‐machine flow shop scheduling problem with no‐wait in process, in which one of the machines is not available during a specified time interval. We consider three scenarios of handing the operation affected by the nonavailability interval. Its processing may (i) start from scratch after the interval, or (ii) be resumed from the point of interruption, or (iii) be partially restarted after the interval. The objective is to minimize the makespan. We present an approximation algorithm that for all these scenarios delivers a worst‐case ratio of 3/2. For the second scenario, we offer a 4/3‐approximation algorithm. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

基于BIST的3D SRAM中TSV开路测试算法研究与实现

基于3D-IC技术实现的3D SRAM,其电路中使用了大量的TSV。目前TSV制造工艺尚未成熟,使得TSV容易出现开路或短路故障,从而给3D SRAM的测试带来新的挑战。现有的2D BIST测试方式能够探测到3D SRAM中存在的故障,但并不能判定是TSV故障还是存储器本身故障；TSV专用测试电路虽然能够探测出TSV的故障,但需要特定的测试电路来实现,这就增加了额外的面积开销,同时加大了电路设计复杂度。基于此,本文提出了一种使用测试算法来探测TSV开路故障的方法,在不使用TSV专用测试电路且不增加额外面积开销的情况下通过BIST电路解决3D SRAM中TSV的开路故障检测问题。结果显示该TSV测试算法功能正确,能够准确探测到TSV的开路故障,并快速定位TSV的开路位置。     

Using real options analysis to value reoptimization options in the shifting bottleneck heuristic

The reoptimization procedure within the shifting bottleneck (SB) involves reevaluation of all previously scheduled toolgroup subproblems at each iteration of the SB heuristic. A real options analysis (ROA) model is developed to value the option to reoptimize in the SB heuristic, such that reoptimization only occurs when it is most likely to lead to a schedule with a lower objective function. To date, all ROA models have sought to value options financially (i.e., in terms of monetary value). The ROA model developed in this paper is completely original in that it has absolutely no monetary basis. The ROA methodologies presented are shown to greatly outperform both full and no reoptimization approaches with respect to both computation time and total weighted tardiness. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006