Tham khảo tài liệu 'supply chain 2012 part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Transshipment Problems in Supply Chain Systems Review and Extensions 441 model. Various substitution models are also analyzed in . Pasternack Drezner 1991 Bitran Dasu 1992 Gerchak et al. 1996 Hsu Bassok 1999 . 4. Methodology The methodologies adopted for investigating transshipment models can be divided into two classes analytical and simulation. Analytical approach In Wong et al. 2005a considering the transshipment problem with waiting time constraints the system behavior with respect to an item i is independent of all other items and may be described by a two-dimensional Markov process. This problem is appropriate to be analyzed by Lagrange relaxation which was applied to general constrained optimization problems. Kukreja Schmidt 2005 analyzed a model for lumpy demand parts in a multi-location inventory system with transshipment by using analytical and simulation techniques. They derived analytical results for the mean and variance of the lead-time demand at various locations and then use simulation methodology to determine inventory control policies for such a system. In particular when the demand can not be met fully from the location s on-hand stock a dynamic programming recursion was used to and the lowest transshipment cost solution for satisfying demand at the location. In Wong et al. 2006 an integer-programming problem with a nonlinear objective function and non-linear constraints was structured for multi-item multi-location spare parts systems with lateral transshipment and waiting time constraints. Four different heuristics were developed and evaluated in terms of their total costs and computation times. The results showed that the greedy-type heuristic has the best performance. In Archibald 2006 for a given replenishment decision the problem of minimizing the long run average cost per period was modeled as a Markov decision process. The state of the system is the stock level in each of the locations at a review epoch. The decision is the number .