| 1. |
- Axsäter, Sven, et al.
(författare)
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Approximating general multi-echelon inventory systems by Poisson models
- 1994
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Ingår i: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 35:1-3, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- We consider a continuous review two-level inventory system with a central warehouse and a number of retailers. The demand processes at the retailers are different compound Poisson processes. We present and evaluate an approximate optimization technique, where the real demand is replaced by "equivalent" Poisson demand such that the ratio between mean and standard deviation is the same as for the real distribution. The solution of the Poisson model is then scaled back to the original problem.
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| 2. |
- Segerstedt, Anders
(författare)
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Inventory control with variation in lead times, especially when demand is intermittent
- 1994
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 35:1-3, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a model for inventory control where variation in lead times is allowed. No reorder point is computed. The mean value and the variance for the time between withdrawals, the order size and the lead time are measured by exponential smoothing. These variables are assumed to be Gamma distributed. Together with the constants: the inventory on hand plus on-order, passed time since the last withdrawal and time to the next inspection; the probability for a shortage is calculated. If the probability is greater than the service level requires then a replenishment order must be placed.
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| 3. |
- Wikner, Joakim, et al.
(författare)
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Smoothing Supply Chain Dynamics
- 1991
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 22:3, s. 231-248
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Tidskriftsartikel (refereegranskat)abstract
- A three-echelon Forrester production distribution system is used as a supply chain reference model for comparing various methods of improving total dynamic performance. Many authors have exploited the original simulation results for the nominal system, especially when describing problems associated with supply chain behaviour. However, few of these authors have attempted to produce a dynamically superior supply chain as distinct from offering detailed organisational and attitudinal changes needed to achieve any improvement. As the starting point of this paper, the production-distribution system has been transformed into a block diagram representation capable of considerable simplification. A combination of analysis and simulation can then be used to gain a far deeper understanding of the system dynamics than has so far been published. Thus, although the Forrester model is far from optimal, it does provide a well established benchmark against which proposals may be evaluated. For the purpose of illustration, five different approaches are then used to improve the supply chain dynamics. These are-“fine tuning” the existing ordering policy parameters;-reducing system delays;-removal of the distribution echelon;-changing the individual echelon decision rules;-better use of information flow throughout the supply chain.It is shown that by better utilisation of the information flow, significant reductions in the demand amplification can be achieved without substantial expenditure. This is because it is only necessary to separate out the flow of “real” orders from “system” orders as they are passed up the chain. Such collaboration does, however, correspond to the establishment of an integrated supply chain in which the concept of “total system stocks” is accepted.
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