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Title: Modeling and analysis of loading strategies for outbound logistics with RFID technology
Other Titles: Li yong wu xian she pin shi bie ji shu de chu ku guan li de zhuang zai ce lüe zhi jian mo yu fen xi
Authors: Wei, Jie (魏潔)
Department: Department of Management Sciences
Degree: Master of Philosophy
Issue Date: 2009
Publisher: City University of Hong Kong
Subjects: Business logistics -- Data processing.
Radio frequency identification systems.
Notes: CityU Call Number: HD38.5 .W444 2009
xiv, 135 leaves : ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves 94-97)
Type: thesis
Abstract: Logistics planning has become a major concern for most enterprises in recent years since logistics/distribution-related costs comprise a significant part of the total cost. In outbound logistics, loading activities play an important role and represent a major portion of logistics costs since they can impact the lead time to delivery of products to the final customers. In this study, we conduct a case study on a giant printing and paper bags manufacturer which has some problems with its current FIFO (first in, first out) loading strategy. When trucks arrive at the production plant for loading finished goods, some products have not yet been finished, with some percent still on the production line. This makes the trucks wait in the loading bay for unbearably long time and trucks which arrive early but have to await loading block other trucks ready for loading. Consequently, the average time trucks spend in the plant increases, while throughput, i.e. the number of trucks loaded decreases. Moreover, many trucks fail to leave the plant by the predefined time and miss their due date, which seriously impacts delivery performance. In this study, we reengineer the current loading processes and design some alternative strategies for loading operations. Some of these alternative strategies are dynamic, which make use of real-time production information provided by RFID technology. There are some literatures about applications of RFID in logistics and supply chain management but there have been few studies about its applications in loading for outbound logistics. Our study can fill this gap and give some practical guidelines for real logistics operations in production plants. In the first chapter, we briefly introduce the concept of logistics management and outbound logistics, RFID technology, and literature review of RFID's applications in logistics and supply chain management, as well as literature on simulation studies. Following these is the description of current loading operations process and problems associated with it. Chapter 2 introduces the methodology we use. We begin with an introduction of discrete event simulation, which is the main methodology we adopt. Then data collection procedures are discussed, followed by the experimental design illustration, which includes independent and decision variables, dependent variables, and inputs of different parameters. The function of simulation tool ProModel is introduced in the following section. One way ANOVA test and 95% confidence interval are used to test whether there are any significant differences among different loading strategies with respect to average operations time in system. If there is significant difference among different loading strategies, we use fisher's least significance test to identify which sets of strategies perform differently from each other. In the last section of Chapter 2, we introduce the methodology of model validation. Model validation is the process of determining whether the model is a meaningful and accurate representation of the real system, and it's usually the tool for decision making. We introduce Naylor and Finger's three-step approach for model validation and compare the model input-output transformation through a turing test since most of our model's output is based on the new configuration, in which statistical testing is almost impossible. Chapter 3 focuses on the reengineered loading operations process with RFID adoption in the loading bay. When a truck is scheduled for loading, its products are transported from the warehouse to the loading bay at the same time when the truck undertakes local travel within the plant, for empty weighing and delivery note submission operations. This reengineering reduces trucks' waiting time for loading, and, therefore, reduces the total average time trucks spend in system, i.e. in completing loading operations. Simulation results under the two scenarios verify this hypothesis. In Chapter 4, we first introduce deployment of RFID in the production line, and then illustrate four different product loading strategies. Simulation models of operations of these strategies are built for comparison. The results indicate that when finished percentage is in normal distribution, there are no significant differences between most strategies in terms of average operations time, except between the shortest remaining time ( SRT) and the earliest due date ( EDD) strategy. However, in the sensitivity analysis, in which products' finished percentage is lower, there are significant differences between FIFO and SRT, SRT and EDD, and EDD and S/RPTi , in terms of the time measure. Among these strategies, with respect to average operations time in system, SRT performs best in both the original experiment and sensitivity analysis. FIFO has the second best performance in the original experiment while S/RPT performs second best in sensitivity analysis. The sequence of performance in terms of throughput (total number of trucks loaded) is the same as in case of average operations time. With regard to percentage of tardy trucks, two RFID-enabled dynamic strategies, SRT and S/RPT , rank first and second, respectively, followed by EDD and FIFO. In Chapter 5, we improve the single product loading and extend it to mixed products loading strategies. Strategies FIFO and EDD perform the same as in single product loading. However, SRT and S/RPT must be changed since there are several different remaining production times for the same truck also, as several kinds of products are to be loaded on the same truck. Therefore, we choose the maximum remaining production time as a truck's remaining time, and change the two models accordingly. Original and sensitivity analysis simulation results suggest that with respect to average operations time in system, SRT has the best performance, especially when finished percentage is lower. S/RPT and FIFO have similar performances while EDD has the worst performance. Tardiness related measure has the same performance sequence as that of single product loading. In conclusion, our simulation study indicates that a combination of well-designed strategies and advanced RFID technology can greatly improve the performance of outbound logistics. It is expected that more and more research into RFID's applications will be conducted for performance improvement in outbound logistics.
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