Browsing by Subject "Inventory control"
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Item A profit-based lot-sized model for the N-job, M-machine job shop: incorporating quality, capacity, and cycle time(Texas Tech University, 1997-12) Kenyon, George N.Existing economic order quantity models base their calculations upon operations management principles established in the early 1900's. These principles focused primarily upon the control and reduction of the firm's variable costs. Total Quality Management has shifted this focus from costs and local optimization to quality and systems optimization. The marketplace also has changed. It has expanded from being primarily domestic into a globally competitive marketplace. In this new business environment, quality, market share, and profits must be primary elements in all of the firm's operating policies. Recent operations management theories, such as Goldratt's (1980) Theory of Constraints, not only address these concerns but redefine how operations management should think about the production system. This research proposal evaluates the classical economic order quantity model and proposes a new model that addresses the lot sizing decision for shop floor operations. A profit maximizing (rather than a cost minimizing) perspective is taken. In this research, a theorized model is derived that considers cycle time and quality issues in addition to the traditional cost issues of production, holding and setup. To validate this model, empirical data and a simulation model are developed to parameterize and collaborate the findings of the theorized model.Item An analysis of the effects of unbalancing in a just-in-time production system with variable operation times(Texas Tech University, 1985-08) Villeda Rodriguez, RamiroA significant amount of research has been conducted aimed at providing industrial engineers and production managers with effective flow-line design, inventory control, and work design principles that are applicable to production systems operating under a push type production order system. However, the validity of some of these principles under a pull type production order system has not been fully verified. One of these principles is related to the line-balancing problem. There was no information about the allocation of work elements to work stations of Just-in-Time (JIT) production systems , when these elements have a great variability or when equal allocation of work to stations may be prevented by precedence and/or technological constraints. A perfectly balanced production system was used in this research as a control in order to analyze and evaluate the effects of unbalancing on this type of production system. This system (control) was compared with systems that were unbalanced with different strategies (high-low-high, low-medium-high, high-low-low and high-medium-low). The JIT production system studied (three lines with three work stations each, and a final assembly) was simulated with GPSS/H and executed under the effect of four independent variables: buffer stock allowed between each pair of work stations (three levels); line variability (three levels), and degree of imbalance (sixteen levels). The statistical analysis of the results showed that the output of all the configurations unbalanced with the high-medium-low strategy (at the two lower levels of buffer stock) was significantly higher than that of its balanced counterparts. The increase in production was in the 0.25% to 8.72% range. Furthermore, the analysis showed that there is a statistically significant reduction in work-i-process (WIP) for those configurations (between 2.65% and 15.1%. Additional experimentation confirmed that inequality of variability of operation times have the same general effect on output rate as inequality of operation times but little effect on the number of units (WIP) in the system.Item Common due date scheduling with batch delivery(Texas Tech University, 2001-05) Ongsakul, ViputNot availableItem Essays in financial propagation and corporate inventory investment behavior(2006) Yang, Xiaolou, 1973-; Cooper, Russell W., 1955-Item Integrated inventory problem and vehicle routing problem in one warehouse and multi-retailer distribution system(Texas Tech University, 1998-12) Prutsakul, AnchaleeThe objective of the one warehouse multi-retailer distribution problem is to find replenishment policies that specify delivery quantities, delivery intervals and vehicle routes that minimize inventory and transportation costs. Since each retailer has a different demand, the warehouse has to supply each retailer with different order quantities and replenishment periods. In addition, the warehouse has to decide which retailers can be served by the same route. Thus, to solve this distribution system, we must include both the inventory problem and the vehicle routing problem. This chapter is organized as follows. The inventory problem, which is the EOQ model, will be described first and the classical VRP model will be discussed next. Finally, we present the single warehouse and many retailers distribution system including some general assumptions.Item Item Integrating hierarchically significant part numbers to bill of materials processing(Texas Tech University, 1985-12) Kini, Ranjan BailurThe Bill of Materials is the front-end information required in the material planning function of an organization. Processing of the Bills of Materials in an organization is usually computerized. Products can be exploded and requirements for the production schedule can be planned in an efficient and timely manner. Currently, bill processing is performed by maintaining two separate direct access files--Item Master File and Product Structure File. By linking these two files through pointers product explosion or implosion is accomplished. This method, as it incurs a large number of disk accesses, slows down Master Production Schedule explosion in material planning. Most major commercial software are using basically the same logic in their bill processing applications. Although part numbers are not related to bill processing other than to uniquely identify a part, a new part numbering scheme indicated an opportunity to use it in bill processing. This Hierarchically Significant Part Numbering (HSPN) scheme through its unique encoding/ decoding part numbering algorithm generates a numerator/denominator part number embedding the parent-child linkage information in it. This information about the structure is used in developing the HSPN approach to bill processing. This approach not only identifies a part uniquely but also helps out substantially in the data processing function of bill processing by exploding and imploding a product much faster. The HSPN approach is compared to the current link listing approach for its performance in explosion/implosion queries. The testing is conducted by simulating both the approaches and actually counting instruction operations for each query. For data, a set of complex product structures used in several other research is used. The results have indicated the HSPN approach to be far superior to the current link listing approach. When the tables of part numbers used in the HSPN approach are kept in entirety in the main memory the HSPN approach performed significantly better by a factor of 150 in all explosion and implosion queries, where as when only the partial segments of tables are brought into the main memory the HSPN performed moderately better than the current approach. Regardless, the HSPN approach has shown a new way of processing the bills and an approach to process the bill significantly faster than with the traditional approach.Item Joint economic lot size problem with pipeline inventory cost(Texas Tech University, 1998-12) Ongsakul, ViputIn this thesis, we study the buyer-vendor problems of supply chain management. In particular, we focus on the joint order quantity model, which can reduce the total cost of both the buyer and the vendor. The Joint order quantity is an order quantity that is optimal between the buyer and the vendor. Banerjee's Joint Economic Lot Size (JELS) model is one of the models we will focus on and then propose an extension. The extension that we add to the model is the pipeluie inventory cost. In the JELS model, the holding cost, which occurs while a product is beuig transported, is not explicitly considered. Therefore, this causes the model to be unrealistic. The pipeline uiventory cost is the holduig cost incurred duruig the delivery period. We add this pipeline inventory cost to the model and caU it the Joint economic lot size with the pipeline inventory cost. In this model, we classify the pipeline inventory into two cases: the buyer is responsible for the pipeline cost or the vendor is responsible for the pipeline cost.