| Summary: | 碩士 === 淡江大學 === 管理科學研究所碩士班 === 93 === The Japanese experience of using Just-In-Time (JIT) production shows that there are advantages and benefits associated with their efforts to control lead time. Japanese manufacturers are known for their strong and lasting partnership with their suppliers. This helps reduce lead time and is one of the sources of success of their JIT philosophy. The successful JIT is through the various effects and continuous improvements that efficient usage of resources the high quality products in the most economical manner, so as to gain the competitive advantages for business enterprise. Many activities, such as reducing the setup cost, shorting the lead time, and improving the quality of production processes and products, are recognized as the feasible and effective ways to achieve the goal of JIT. In other viewpoints, the factors (setup cost, lead time, and quality) mentioned above are often assumed as fixed constant and uncontrollable in the traditional inventory models, but are controllable in practice. On the other hand, in many practices, the stockout cost often includes intangible components such as loss of goodwill and potential delay to the other parts of the inventory system, and hence it is difficult to determine an exact value for the stockout cost.
In this thesis, we employ a service level constraint to replace the shortage cost in the objective function, and discuss the problem. In chapter 2, we discuss the problem the problem of investing capital in reducing setup cost, where the setup cost is treated as one of the decision variables in the model. In chapter 3, we further consider the possible relationship between quality and lot size, and investigate the quality improvement problem in which the quality level is viewed as a controllable factor and is one of the decision variables. In chapter 4, we assume lead time and ordering cost reductions act dependently, and discuss the same problem as in chapter 3. For all models proposed in this thesis, we utilize the numerical examples to illustrate the effects of inventory systems associated with investing capital in changing the values of parameters.
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