地球的永續經營是二十一世紀最重要的議題之一，無論是企業或個人在原料及能源的消費上都必須多加考慮，因此舊產品在廢棄前的價值萃取是勢在必行的。在所有舊產品的回收方法中，成為二手產品直接再使用，是對環境最有利的策略。另一方面，目前高科技創新產品的生命週期明顯縮短，新產品的購買往往與舊產品的折價貼換相連，造就了市場上許多狀況仍相當良好的舊產品。但二手產品的品質無法由外觀得知，消費者對二手產品品質的疑慮阻礙了二手產品市場的發展。因此本研究主要是針對二手產品，分別站在製造商與個別消費者的立場，提出品質策略。所謂品質可以劃分成消費者趨動品質及工程品質兩類，本研究採用保固及產品品質升級(或預防保養)分別做為改善兩種品質的方法。對依照法律規定負責所有舊產品回收的製造商，本研究提出利潤模式，將銷售二手產品的收入及成本(包括購買舊產品、產品品質升級、表面磨光、保固期間產品失效時的修理、不堪用產品的廢棄處理等相關費用)加入模式，同時決定出最佳的保固期間及產品品質升級的年齡門檻數值，以獲得所有回收產品的期望利潤最高為目的。對二手產品的單一消費者，為降低失效次數，本研究發展出兩個週期性預防保養模式，以供消費者根據執行的困難度做選擇。目的在決定最佳預防保養次數及保養程度，以在預定的產品使用期間內，相關的預防保養及產品失效時修理的總費用最低為目標。無論是生產者的利潤模式或消費者的費用模式，本研究皆以數學分析探討模式結構；對特殊例題證明最佳解的存在，並列出尋求最佳解的演算法。 更以實際應用例題說明各模式的可行性及優勢；對重要參數的敏感度分析亦藉由許多數值例題來展現。

For the sustainability of this globe we all live in, effective end-of-life value realization is essential. Reuse is considered the most environmentally beneficial way of product recovery. On the other hand, the rapidly changing technologies and fierce competition characters of modern manufacturing results in the market with a lot of younger and better used products. However, the concerns over the quality of the second-hand products hinder the development of second-hand product market. Quality can be classified into two types: customer-driven quality and engineered quality. This study uses warranty and upgrade action (or preventive maintenance) as the way to improve customer-driven and engineered quality respectively. For the manufacturers, considering the age at the end of first life as stochastic, this study develops a profit model. Relevant costs like purchase of the used item, surface polish, upgrade and the minimal repair during the warranty period are included. Optimal upgrade threshold value and warranty length are jointly derived so that the expected profit per recovered item can be maximized. For individual consumer, this research develops two periodical age reduction preventive maintenance cost models for practitioners to choose based on the easiness of the implementation. The objective is to determine the optimal number and degree of preventive maintenance, so that the expected cost (including preventive maintenance and minimal repair) for a pre-determined usage period can be minimized. Structural properties are investigated for both manufacturer’s and individual consumer’s models; algorithms are provided to search for the optimal solutions of some special cases. To demonstrate the feasibility and the advantages of the proposed approach, practical application is illustrated. Sensitivity analyses regarding the important parameters are also conducted through various numerical examples.

Content	I
List of figures	III
List of tables	IV
Chapter 1 Introduction	1
1.1 BACKGROUND AND MOTIVATION	1
1.2 RESEARCH PROBLEM AND OBJECTIVES	4
1.3 RESEARCH SCOPE AND LIMITATION	4
Chapter 2 Literature review	7
2.1 PRODUCT RECOVERY	7
2.2 WARRANTY	8
2.3 MAINTENANCE	12
2.4 WARRANTY AND MAINTENANCE FOR SECOND-HAND PRODUCT	15
Chapter 3 Quality policy from Manufacturer’s point of view	20
3.1 NOTATIONS FOR MANUFACTURER’S PROFIT MODEL	22
3.2 MATHEMATICAL FORMULATION FOR MANUFACTURER’S PROFIT MODEL	23
3.3 ANALYSIS OPTIMIZATION FOR MANUFACTURER’S PROFIT MODEL	26
3.3.1 General Case	26
3.3.2 Optimization for a special case	27
3.4 NUMERICAL EXAMPLES FOR MANUFACTURER’S PROFIT MODEL	32
3.4.1 Practical Application	32
3.4.2 Sensitivity analysis	33
3.5 CONCLUSIONS FOR MANUFACTURER’S PROFIT MODEL	38
Chapter 4 Maintenance policies from consumer’s point of view	39
4.1 NOTATIONS FOR THE INDIVIDUAL CONSUMER’S COST MODEL	41
4.2 MATHEMATICAL FORMULATION FOR INDIVIDUAL CONSUMER’S COST MODEL	41
4.3 OPTIMAL PM POLICY FOR INDIVIDUAL CONSUMER’S COST MODEL	44
4.3.1 General case	44
4.3.2 Special case for Weibull failure rate and linear maintenance cost	47
4.4 NUMERICAL EXAMPLES FOR INDIVIDUAL CONSUMER’S COST MODEL	52
4.4.1 Practical applications	52
4.4.2 Sensitivity analysis	53
4.4.3 Comparisons of two models	55
4.5 CONCLUSIONS FOR INDIVIDUAL CONSUMER’S COST MODEL	56
Chapter 5 Conclusions and suggestions	57
5.1 CONCLUSIONS	57
5.2 SUGGESTIONS FOR FUTURE RESEARCH	58
References	60

List of figures
Fig. 1.1 Research scheme........6
Fig. 3.1 Optimal value of upgrade threshold value for different values of k2 and cm ..37
Fig. 3.2 Optimal length of the warranty period for different values of k2 and cm . ..37
Fig. 4.1 The periodical PM scheme with fixed age reduction y . .................................42
Fig. 4.2 The periodical PM scheme with an age threshold value theta . ............................43
Fig. 4.3 The reduction of total expected cost under fixed age reduction.....................55
Fig. 4.4 The optimal number of PM actions under fixed age reduction ......................56

List of tables
Table 3.1 Optimal upgrade threshold value and warranty length for the special case.34
Table 3.2 Optimal upgrade threshold value and warranty length for general cases ....36
Table 3.3 Optimal upgrade threshold value and warranty length for different  (the age dependent factor) ..37
Table 4.1 Numerical results for model I and model II ...54

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