Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Routing and Scheduling for Medication Distribution Plans(2008-09-18) Herrmann, Jeffrey W.; Lu, Sara; Schalliol, KristenThis paper presents a two-stage approach for solving the medication distribution problem. The problem addresses a critical issue in emergency preparedness. Public health officials must plan the logistics for distributing medication to points of dispensing (PODs), which will give medication to the public in case of a bioterrorist attack such as anthrax. We consider the problem at the state and local levels. Our approach separates the problem into two subproblems: (1) the “routing problem” assigns PODs to vehicles and creates routes for each vehicle, and (2) the “scheduling problem” determines when the vehicles should start these routes and how much material should be delivered on each trip. This paper presents the results of using this approach to construct solutions for a realistic three-county scenario. The results show that the routing and scheduling decisions greatly affect the quality of the solution.Item Using Aggregation to Reduce Response Time Variability in Cyclic Fair Sequences(2008-08-15) Herrmann, Jeffrey W.Fair sequences are useful in a variety of manufacturing and computer systems. This paper considers the generation of cyclic fair sequences for a given set of products, each of which must be produced multiple times in each cycle. The objective is to create a sequence so that, for each product, the variability of the time between consecutive completions is minimized. Because minimizing response time variability is known to be NP-hard and the performance of existing heuristics is poor for certain classes of problems, we present an aggregation approach that combines products with the same demand into groups, creates a sequence for those groups, and then disaggregates the sequence into a sequence for each product. Computational experiments show that using aggregation can reduce response time variability dramatically.Item Generating Cyclic Fair Sequences using Aggregation and Stride Scheduling(2007) Herrmann, Jeffrey W.Fair sequences are useful in a variety of manufacturing and computer systems. This paper considers the generation of cyclic fair sequences for a given set of products, each of which must be produced multiple times in each cycle. The objective is to create a sequence so that, for each product, the variability of the time between consecutive completions is minimized. Because the problem is known to be NP-hard, we present a heuristic that combines aggregation and parameterized stride scheduling. This novel algorithm combines products with the same demand into groups, creates a sequence for those groups, and then disaggregates the sequence into a sequence for each product.Item Sequencing Wafer Handler Moves to Improve the Performance of Hybrid Cluster Tools(2000) Nguyen, Manh-Quan T.; Herrmann, Jeffrey W.; ISRCluster tools are highly integrated machines that can perform a sequence of semiconductor manufacturing processes. The sequence of wafer handler moves affects the total time needed to process a set of wafers.Reducing this time can reduce cycle time, reduce tool utilization, and increase tool capacity. This paper introduces the cluster tool scheduling problem for hybrid cluster tools, which are multiple-stage tools that have at least one stage with two or more parallel chambers.
This paper presents algorithms that can find superior sequences of wafer handler moves. Experimental results show that the tool performance can be improved significantly if the wafer handler follows a cyclic sequence instead of using a dispatching rule.
Item Sequencing Wafer Handler Moves to Improve the Performance of Sequential Cluster Tools(2000) Herrmann, Jeffrey W.; Nguyen, Manh-Quan T.; ISRCluster tools are highly integrated machines that can perform a sequence of semiconductor manufacturing processes. The sequence of wafer handler moves affects the total time needed to process a set of wafers. Reducing this time can reduce cycle time, reduce tool utilization, and increase tool capacity. This paper introduces the cluster tool scheduling problem for sequential cluster tools and describes a branch-and-bound algorithm that can find an optimal sequence of wafer handler moves. In addition, we enumerate the set of 1-unit cyclic sequences for two- and three-stage sequential cluster tools. Experimental results show that the tool performance can be improved significantly if the wafer handler follows a cyclic sequence instead of using a dispatching rule.Item On Parallel-Machine Scheduling with Operator-Constrained Setups(1994) Herrmann, Jeffrey W.; Lee, Chung-Yee; ISRThe processing of a task on a machine often requires an operator to setup the job. In this paper we consider the problem of scheduling a finite set of jobs on a number of identical parallel machines. Each job has a setup that must be performed by an operator, who can perform only one setup at a time. We examine the problems of minimizing the schedule makespan. Out results include complexity proofs, special cases that can be solved in polynomial time, lower bounds, and approximation algorithms with error bounds.