在當今競爭激烈的市場中，賣家通常會向買家提供允許延期的付款（即信用交易）。通常情況下，如果未償還的金額在允許期限內支付，則不存在利息。但是，如果付款未在允許的延期期限內全額支付，則利息按未償還金額計算。
給予允許期限不僅增加了賣方的機會成本，而且增加了賣方的違約風險，因為允許期限越長，機會成本越高以及違約風險越高。因此，經銷商發現最佳的信用交易是一個重要且相關的問題，使得信用交易引起的銷售增長可以顯著地克服機會成本和違約風險的成本增加。
一個眾所周知的學習事實是，新產品的生產成本在每次累積生產量加倍時都下降了10％到50％。另一方面，買方資本投資對減少訂單的影響成本顯著對數。因此，確定最佳的資本投資是買方降低總成本的重要策略。
在本論文中，我們提出了信用交易條件下的三個確定性存貨模型。在第二章中，當供應商提供上游信用交易M時，我們為製造商（或批發商）建立了具有缺陷物品的經濟生產量模型，同時向買方（或零售商）提供下游信用交易N。在第三章中，我們提出一個經濟生產量模型，從賣方的前景來確定他/她的最佳的信用交易期和生產批量同時，其中（i）信用交易不僅增加銷售，而且增加機會成本和違約風險，以及（ii）生產成本下降並服從學習曲線現象。在第四章中，我們建立賣方和買方的年度總利潤，然後在即時存貨系統中公式化非合作納許解和合作整合解，其中（1）給予信用交易不僅增加需求，也增加了機會成本和違約風險;（2）資本投資對降低訂貨成本的影響是對數的。最後，在第五章中，我們為本論文提供了一些結論和未來的研究課題。

In today’s competitive markets, sellers usually offer their buyers a permissible delay in payments (i.e., trade credit). Usually, there is no interest charge if the outstanding amount is paid within the permissible delay period. However, if the payment is not paid in full by the end of the permissible delay period, then interest is charged on the outstanding amount. 
Granting a permissible delay period increases not only the seller's opportunity cost but also the seller's default risk because the longer the permissible delay period, the higher the opportunity cost as well as the default risk. Consequently, it is an important and relevant issue for the seller to find an optimal trade credit such that the sales increase induced by trade credit can significantly overcome the cost increase of opportunity cost and default risk. 
It is a well-known fact of learning-by-doing that production cost of a new product declines by a factor of from 10 to 50 percent each time the accumulated production volume doubles. On the other hand, the impact of buyer’s capital investment in reducing ordering cost is significantly logarithmic. Therefore, finding the optimal capital investment is an important strategy for the buyer to reduce his/her total cost.
  In this thesis, we propose three deterministic inventory models under the trade credit conditions. In Chapter 2, we establish an economic production quantity model for a manufacturer (or wholesaler) with defective items when its supplier offers an up-stream trade credit M while it in turn provides its buyers (or 

retailers) a down-stream trade credit N. In Chapter 3, we propose an economic production quantity model from the seller's prospective to determine his/her optimal trade credit period and production lot size simultaneously in which (i) trade credit increases not only sales but also opportunity cost and default risk, and (ii) production cost declines and obeys a learning curve phenomenon. In Chapter 4, we establish seller’s and buyer’s annual total profits, and then formulate non-cooperative Nash solution and cooperative integrated solution in a just-in-time inventory system, in which (1) granting trade credit increases not only the demand but also the opportunity cost and default risk and (2) the impact of capital investment in reducing ordering cost is logarithmic. Finally, in Chapter 5, we provide some conclusions and future research topics for this thesis.

Chinese abstract……………………………………………………………………...I
English abstract..………………………………… …...…………..…......................Ⅱ
Contents…..……..………………………………… …...…………..……………...IV
List oftables…..……..………………………………… …………..…......................V
List of figures…..…………………………………..……………………………….VI
Chapter 1 Introduction……………………………………………………………….1
1.1Motivation ……………………….……………………...……......................1
1.2 Literature review ………………………….………………...………………..3
1.3 Summary ……………………..…………………………………………….10
Chapter 2 Optimal lot-sizing policy for a manufacturer with defective items in a supply chain with up-stream and down-stream     tradecredits……………………………………………….…....................11
2.1	Introduction	………….11
2.2 Mathematical formulation	…14
2.3 Optimal solution	24
2.4 Numerical examples	27
2.5 Concluding remarks	29
Chapter 3 Optimal trade credit and lot size policies in economic production quantity models with learning curve production costs	….31
3.1	Introduction	31
3.2 Notation and assumptions	34
3.3 Mathematical model and optimal solution	36
3.4 Numerical examples	41
3.5 Concluding remarks	44
Chapter 4 Nash and integrated solutions in a just-in-time seller–buyer supply chain with buyer's ordering cost reductions………………………………….............46
4.1Introduction……………….……...……………..……………….46
4.2 Notation and assumptions	………….……..……....49
4.3 Mathematical model and solution	52
4.4 Numerical Examples	60
4.5 Concluding remarks	63
Chapter 5 Conclusion……	……….65
References	..68



List of tables
Table 2.1. Sensitivity analysis on parameters for optimal lot-sizing policy……………………………………………………….29
Table 3.1. Sensitivity analysis on parameters for optimal trade credit 
and lot size policies…………………………….…………...43
Table 4.1. Sensitivity analysis on parameters for Nash and integrated solutions………………………………………………….....62


List of Figures
Figure 2.1 Cumulative revenue for good items on  …………….18
Figure 2.2 Cumulative revenue for good items on  ……….…...21
Figure 2.3 Cumulative revenue for good itemson  …..……….…….23
Figure 4.1. Both seller’s and buyer’s on-hand quantities ..………………..54

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