تصميمات مكان‌يابي ـ تخصيص در يك شبكه‌ي زنجيره‌ي تامين چندسطحي با در نظرگيري ارزش خالص فعلي جريان نقدي

Location-Allocation Decisions in a Multi-Echelon Supply Chain Network with Net Present Value

در اين مطالعه يك مدل برنامه‌ريزي خطي عدد صحيح مختلط براي تصميمات مكان‌يابي ـ تخصيص در يك شبكه‌ي زنجيره‌ي تامين چهار‌سطحي بيان شده است. اولين سطح اين شبكه‌ي زنجيره‌ي تامين به تامين‌كنندگان، دومين سطح به كارخانه‌ها، سومين سطح به توزيع‌كنندگان و آخرين سطح آن به مناطق مشتريان اختصاص دارد. در اين مدل هدف بيشينه‌كردن ارزش خالص فعلي جريان نقدي شبكه‌ي زنجيره‌ي تامين است. در اين شبكه هزينه‌ي احداث كارخانه‌ها توسط سرمايه‌ي اوليه‌ي موجود يا با وام گرفتن از بانك به دست مي آيد. مدل رياضي مكان‌يابي ـ تخصيص شامل هزينه‌ي سرمايه-گذاري، هزينه‌ي تهيه‌ي ماده‌ي اوليه، هزينه‌ي توليد كالا، هزينه‌ي احداث، هزينه‌ي نگه‌داري موجودي و هزينه‌ي ارسال كالاهاست. در مدل ارايه‌ شده، ارزش خالص فعلي جريان نقدي بعد از كسر ماليات براي دوره‌هاي زماني مختلف بيشينه مي-شود. در نهايت، در اين مطالعه براي توضيح هرچه بهتر مدل ارايه شده يك مثال عددي با نرم افزار GAMS حل شده است.

Supply chain management is a key issue and practical for sustainable economy, where its economic advantages can be shown in many papers. In order to remain competitive in the market, a supply chain must be efficient. One way to improve the efficiency is to maximize the total profit in the system. In this study, a mix-integer linear programming model is presented for location-allocation decisions in a four-echelon supply chain network. The first to the fourth echelon of the supply chain network includes suppliers, production plants, distribution centers, and customer zones, respectively. This paper amis to select the appropriate amount of loan and to adopt proper location-allocation decisions in all echelons of the chain in several periods, while maximizing the net present value. the net present value. Location-allocation decisions include locating a number of plants among a finite set of potential sites and decisions relate to the flow of goods from suppliers to production plants, from plants to distribution centers and from distribution centers to customer zones in each period. The suppliers prepare a similar raw material and the production plants produce a similar product from the raw material. The mix-integer linear mathematical model of the location-allocation problem includes sale price, investment costs, raw material costs, production costs, setup costs, holding costs, shortage costs and transportation cost of goods. Setup costs of the factories involved in the network are obtained by an initial capital or funds borrowed from banks. Also, shortages are allowed and are considered to be lost sale. The proposed model maximizes the net present value of the profit after tax in different time periods using continuous compound interest rate. In order to demonstrate the applicability of the proposed formulation and to validate the results obtained, a numerical example is solved at the end using GAMS software. Finally, conclusion and future research recommendations come in the last section of paper.