Browsing by Subject "Production scheduling"
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Item A procedure to integrate aggregate production planning and master scheduling(Texas Tech University, 1980-05) Adams, MarkNot availableItem A review and analysis of changed work schedules in hospitals, vol 1 and 2(Texas Tech University, 1975-05) Johnson, William ClintNot availableItem A single machine sequencing problem with multiple criteria.(Texas Tech University, 1974-08) Tilak, Avinash G.Not availableItem An analysis of inter-relationships of multiple criteria in a flowshop with set-up sesquence dependence(Texas Tech University, 1976-08) Pulle, Christopher VNot availableItem An investigation of parts flow in the flexible manufacturing system(Texas Tech University, 1983-05) Napierala, ElzbietaA certain Flexible Manufacturing System was investigated. The line of the system consists of four machines, a queueing area, and a material handling system represented by a cart. The main objective of this study was to investigate the effects of different levels of cart utilization, local storages, and the size and design of the queueing area on the FMS performance. Additionally, the examination of different scheduling rules was conducted in order to see their impact on the FMS performance. Simulation was the chosen methodology for investigating the above stated issues. The GPSS/H simulation language was used to simulate the model of the examined FMS and to investigate the stated problems. Cart utilization was defined as the ratio of the total time that the cart was in use to the total time of the system operation. Different levels of cart utilization were obtained by changing the processing times of the part mixes manufactured in the system. The main criteria for the FMS examined were the number of parts and operations completed, as well as the machine utilization. The experimental results showed that the FMS was strongly affected by increasing cart, or generally speaking, material handling utilization. When a high level of cart utilization was experienced, this caused machine utilization and therefore, system productivity to decline. Cart utilization is a dependent variable in any FMS, an effect of several factors in the FMS design. The major components of material handling utilization are travel times, number of machines in the system, and part processing times. A ratio factor R, taking into account the above factors was proposed and the curve between the ratio R and cart utilization was developed. The FMS proposed by the General Dynamics in Fort Worth, Texas was used to test the ability of the developed curve to predict the material handling utilization for a different system. The theoretical cart utilization based on the ratio R and the developed curve, was very close to the material handling utilization obtained through the simulation. Adding local storages to the system configuration reduced the machine idleness due to the lack of cart service. The highest improvement in the system productivity after installing local storages was observed for the FMS operating with a cart utilization of 75% - 97%. The experimental results showed that the system was very sensitive to any changes in the configuration which caused cart utilization to increase. Providing more queueing stations by expanding the line length, and therefore increasing cart utilization, resulted in poorer performance of the FMS. The effects of the number of parts in process on the system productivity was examined by changing the size of the queueing area. The experimental results indicated that a given FMS provided the best performance with a certain number of parts in process. Expanding the queueing area above this level did not produce the better system output; on the other hand too few parts in process led to lower machine utilization. The experimental results showed that for the FMS examined, such rules as SPT, SPT*TOT or FCFS to system, provided the most balanced demands for all machines and therefore the highest system output. It was noted that the scheduling problem in the FMS should be carefully investigated for any system developed in terms of the production and configuration characteristics.Item An investigation of the job-type performance of priority scheduling in manufacturing cells(Texas Tech University, 1991-12) Gunal, Ali KamilIn traditional job-shop studies, it is usually assumed that jobs arrive randomly, they have random processing requirements, and measures of performance are taken over all jobs completed within a time period. There are many instances in practice, however, where a group of machines is formed to process a certain set of similar job types. A number of flexible manufacturing systems and group technology cells are examples of such manufacturing environments. In these types of manufacturing environments, the performance by job type is as important as the performance over all jobs. Problems may arise when jobs of a certain type are delayed more than the other job types. Such a situation is more likely to be seen when priorities are assigned based on information that is dependent on the type of a job. This study is an investigation of such variation in the job-type performance of the scheduling rules. It may be looked upon as an exploratory study since there is a lack of published results in this field of scheduling literature. Some fundamental questions regarding the job-type performance of a typical manufacturing cell are answered through a large-scale simulation experiment.Item An investigation of the mixed-model assembly line sequencing problem(Texas Tech University, 1981-08) Kao, Chung ChiungNot availableItem Application of system methodologies to scheduling(Texas Tech University, 1979-05) Ulgen, Onur M.This research investigates the application of a set of new techniques (system methodologies) to dynamic job shop scheduling problems. These techniques are applied in combination with the heuristic procedures and primarily used to increase the effectiveness of heuristic procedures. The system methodologies considered relate the interactions in a dynamic job shop to the problem of coordination among the decision-making units (i.e., sales department, inventory department, etc.) of the production system. The application of the system methodologies may provide help to resolve the complexity in a dynamic job shop hy increasing the coordination among decisionmaking units that monitor different aspects of the shop. An increase in coordination among the decision-making units will also reduce the outside intrusions (i.e., expediting) to the scheduling activities. In testing the application of different system methodologies, the research also considers a new set of conditions in scheduling environment.Item Architectures and algorithms for high performance switching(2004) Prakash, Amit; Aziz, AdnanSwitches are ubiquitous in modern computing, appearing in wide-area networks, multiprocessor servers, and data storage systems. With the the advent of high-speed link technology, switches have become the bottleneck in moving data in the network. Existing switch architectures either require the interconnection network and packet buffers to work at a very high speed or require complex scheduling problems to be solved quickly. In this dissertation we investigate whether there are switch architectures that can support high-speed links that are simultaneously easy to schedule, and can be built out of inexpensive components. The approach we take is using parallelism to solve complex scheduling problems. We choose switching architectures such that the corresponding scheduling problem can be efficiently solved with a reasonable amount of hardware. In particular, we present two switch architectures for which we have developed efficient scheduling algorithms. The first switch achieves optimum throughput and optimum average latency while the second switch guarantees optimum throughput only but uses considerably less hardware.Item Assignment models for the machine interference problem(Texas Tech University, 1983-08) Koulamas, Christos PNot availableItem Coordination of distributed schedules in a heterogeneous environment : identification of conflicts using schedule mappings(2008-08) Siddiqui, Mohsin Khalid, 1976-; O'Brien, William J.Construction Projects involve a large number of participants with often overlapping activities. Schedules play a key role in coordination of these activities. A general contractor or a construction manager is usually responsible for coordination and has a master schedule that covers the scope of the entire project. The individual participants have different project management objectives and build schedules for their scope of work using different breakdown structures, different levels of detail, different scheduling software and different naming conventions. Existing scheduling techniques and software provide a robust set of constructs to generate these individual schedules. However, coordination of these schedules is a manual iterative task not adequately supported by existing theories and software tools. The primary aim of this research was to provide a framework to enable analysis across distributed heterogeneous schedules. The framework presented in this dissertation, schedule mappings, provides a set of constructs to dynamically link individual participant schedules to the master schedule. The schedule mappings approach uses the linked schedules to facilitate schedule coordination by rapid identification of scheduling conflicts. This identification enables rapid initial coordination of schedules and supports assessment of scheduling alternatives in response to a schedule change. A software tool was developed using Microsoft Visual Basic[trademark] programming language as a Shared Addin for Microsoft Project[trademark]. This dissertation contributes to state of the art of scheduling by providing a framework for reasoning across multiple schedules. From an industry perspective, this research makes a contribution by formalizing identification of scheduling conflicts. The formalisms and the tool should help industry professionals in rapid assessment of scheduling alternatives. The tool enabled the use of the schedule mappings approach by industry professionals and was used for validation. The approach was validated in a two step process and was shown to be beneficial.Item Critical arc strategies for the reentrant job shop scheduling problem with setups(2002) Zoghby, Jeriad Marcus; Hasenbein, John J.; Barnes, J. Wesley.Item Disruption managment for project scheduling problem(2005) Zhu, Guidong; Yu, Gang; Bard, Jonathan F.Item Dynamic scheduling system based on changes in job characteristics(Texas Tech University, 1997-12) Buraparate, VirojDynamic Scheduling System (DSS) Based on Changes in Job Characteristics is a system that provides adjustability to a current schedule as a consequence of unpredictable or predictable changes. Changes in manufacturing systems are those that occur during production and cause the systems to behave unpredictably. The understanding of the relationship between these changes and their effects can be used to lessen such manufacturing problems. The main concept of this scheduling system is to continuously monitor and predict a manufacturing system's status so that as soon as a change is detected or able to be predicted, this scheduling system will react by offering new production schedules to lessen the effects of this change. This system will integrate several techniques (e.g., control chart, forecasting model, linear regression, and statistical analysis) to provide a scheduling system that can be used in a dynamic manufacturing system. This dissertation shows in detail how to develop and test a DSS prototype. Simulation modeling and statistical analysis are used as a basis to select appropriate variables in this prototype. A hypothetical sk-machine dynamic job shop is developed by using GPSS/H simulation language to compare three performance measures, which are weighted mean flow time, weighted mean tardiness, and weighted mean lateness obtained from DSS prototype versus four dispatching rules (SPT, S/OPN, FIFO, and EDD). By comparing results from 300 random test cases, it is found that generally DSS can produce resuhs as good as the best results obtained among SPT, S/OPN, FIFO, and EDD 84% ofthe time. However, in weighted mean flow time and weighted mean lateness performance measures, DSS has matched up to 95% ofthe best results. Thus, based on these sunulations, this prototype of DSS has shown that by incorporating the abilities to monitor, forecast, and adjust the current schedules in a dynamic manufacturing system, undesirable results can be avoided.Item Economic aspects of scheduling theory.(Texas Tech University, 1969-12) Gupta, Jatinder Nath DassNot availableItem Effects of job file and study parameters on the performance of a dynamic job shop.(Texas Tech University, 1975-05) Ulgen, Onur M.Not availableItem Evolution of expert systems(Texas Tech University, 1993-12) Culebro, JoaquĆn Marcos PalaciosExpert systems are computer programs for providing expertise emulative of that which might be expected from human experts in solving complex problems for which analytical solutions are not available. Evolution of an expert system refers to the initial development of the system and its continuing modification in order to improve its performance. Any modifications made to an expert system have the potential of producing undesirable logical errors and side-effects that are difficult to find or prevent. Although much research has focused on facilitating the evolution of expert systems, most of the limitations still exist. This dissertation proposes an approach for structuring and evolving expert systems for applications in which the provision of the desired expertise is beyond the reach of either analytical or traditional heuristic approaches, but in which the knowledge domain is causally connected and the relevant causality can be expressed in procedural form. The research vehicle used is that of a hypothetical manufacturing system in which products of different types use some of the same workstations, and some of the product types loop back to workstations that they have previously used. The expertise sought is that of scheduling starts of products into the first stage of production so as to yield a stream of output that satisfies a user-specified balance among a variety of business performance measures including timeliness of production output.Item Heuristics for flexible flowshop scheduling problems(Texas Tech University, 1993-08) Leung, Cherng-yeeA flexible flowshop consists of a number of work centers, each having one or more parallel machines. A set of immediately available jobs has to be processed through the ordered work centers. A job is processed on any and only one of the parallel machines at each of the work centers?) Structurally, a flexible flowshop represents a generalization of the simple flowshop and the identical parallel machine shop. For the case of having the same number of identical parallel machines at every work center, two approaches are developed: the para-flow approach and the flow-para approach. Two situations regarding the job route are examined. These are the partially flexible job route situation and the completely flexible job route situation. (The objective of this research is to find heuristics that minimize the makespan of the problem in reasonable computation time. A computer experiment verifies that the para-flow approach and the flow-para approach outperform published algorithms. Problem size includes three elements: the number of jobs, the number of work centers, and the number of parallel machines at each work center. By fixing any two of the three elements, the trend caused by the third element can be analyzed. A trend analysis of the proposed algorithms has been conducted.Item Highway bridge construction production rates for time estimation(2004-05) Huh, Youngki, 1969-; O'Connor, James ThomasItem Highway earthwork and pavement production rates for construction time estimation(2004) Kuo, Yao-chen; O'Connor, James ThomasIn recent decades, the complexity and size of highway construction projects have increased dramatically. Because of this change, Contract Time estimates for most construction projects have been based on the critical path method (CPM). However, with the use of the CPM, many problems associated with unrealistic contract timing are encountered. In order to solve these problems, many transportation agencies have attempted to establish a standard process to estimate Contract Time with the belief that reasonable Contract Time estimation should rely on realistic Production Rates. Personal experience, historical records, and existing standards are usually used for Production Rates estimation. These sources are often unreliable because they do not include the effects of important drivers on Production Rates. Many studies on construction productivity have been conducted. However, most of them focus on cost management rather than construction time estimation. Little information is available on Production Rates for construction time estimation. This study is intended to be a reference tool for the highway construction industry to schedule and plan construction time. The purpose of this research study was to investigate the Production Rates of seven major Work Items in Earthwork- and Pavement-related construction. In addition, drivers that are known at the design stage and have a significant impact on Production Rates were identified and the effects of those drivers were quantified.