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- Abdul-Jalbar, Beatriz, et al.
(författare)
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A new heuristic to solve the one-warehouse N-retailer problem
- 2010
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Ingår i: Computers & Operations Research. - : Elsevier BV. - 0305-0548 .- 1873-765X. ; 37:2, s. 265-272
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Tidskriftsartikel (refereegranskat)abstract
- We deal with a multi-echelon inventory system in which one warehouse supplies an item to multiple retailers. Customer demand arrives at each retailer at a constant rate. The retailers replenish their inventories from the warehouse that in turn orders from an outside supplier. It is assumed that shortages are not allowed and lead times are negligible. The goal is to determine replenishment policies that minimize the overall cost in the system. We develop a heuristic to compute efficient policies, which also can easily be used in a spreadsheet application. The main idea consists of finding a balance between the replenishment and the inventory holding costs at each installation. This new heuristic we compare with two other approaches proposed in the literature; the computational studies show that in most of the instances generated the new method provides lower costs.
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| 4. |
- Segerstedt, Anders, et al.
(författare)
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Reformulated Silver-Meal and Similar Lot Sizing Techniques
- 2023
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Ingår i: AXIOMS. - : MDPI. - 2075-1680. ; 12:7
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Tidskriftsartikel (refereegranskat)abstract
- Literature and most textbooks around the world describe Silver-Meal in such a way that periods with zero demand make Silver-Meal suggest a higher frequency of order replenishments than necessary and therefore higher total costs than necessary. Silver-Meal, still the best-known technique, is therefore inferior to other lesser-known techniques when the time interval in the calculations presently is days and not months. The purpose of this article is to show that another mathematical formulation of Silver-Meal avoids this trouble. We also point to characteristics such as Silver-Meal, Least Unit Cost, Part-Period Balancing, and lot-sizing techniques that are available in many textbooks for operations and supply chain management. We illustrate the techniques with different examples of periods without demand, declining demand, and varying demand. We point out possible problems with the different techniques. Literature mostly does not consider periods of zero demand, which was not so important before. Lot-sizing methods must cope with the important performance indicator “Days of inventory”. Numerous practical situations with zero demand periods exist where a lot of sizing techniques help for efficient operations. It is necessary knowledge and a tool for students (future users, performers, and managers). “Lägsta periodkostnad” is a restored and reformulated Silver-Meal, with Silver-Meal’s characteristics already presented in literature, except those difficulties with zero demand periods disappear.
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| 5. |
- van der Sluis, Erik, et al.
(författare)
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Economic lot scheduling problems with new and different cost approximations
- 2008
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Ingår i: Book of Abstracts, 15th International Symposium on Inventories, Budapest, Hungary, Aug. 2008.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper considers scheduling the production of several different items on a single machine with constrained capacity, commonly known as the Economic Lot Scheduling Problem (ELSP). Nilsson and Segerstedt (2008) show that even for ELSP problems with high utilisation it is possible to find a feasible solution (fulfilling feasibility conditions from Eilon (1962), Goyal (1975), Segerstedt (1999)), but the real inventory holding cost is often higher than the common used approximation. This is because the production of an item has to start before the inventory of the same item reaches zero, to avoid a future shortage of the same item. The common cycle solution always presents the "right" inventory holding cost; but diversifications of the frequencies may not accomplish what it promises. Most traditional approaches for the ELSP consider only the sum of the setup cost and inventory holding cost and provide cyclicschedules that minimize this sum. In practice, there are not only costs for setups and inventory holding, but also costs for operating the production facility due to e.g. electricity, service, maintenance, tools, operators etc, which depend on the number of hours the facilityis operating per working day (cf. Brander and Segerstedt (2008).Our investigations in this paper find a solution method that can evaluate different schedulesdue to different frequencies, and find the right inventory holding cost without the common approximation and combine it with a facility time variable cost as in this paper. We start from an idea from Cooke et al (2004) and van der Sluis (2006). A mixed integer programming (MIP) problem that from a common time period and integer number of frequencies for each item minimises costs and avoids shortages. But we try to avoid MIP and its long calculation times, when in our case to find the best solution several MIP calculations have to be done after each other.
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