| 1. |
- Eriksson, Håkan, et al.
(författare)
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A robust correlation receiver for distance estimation
- 1994
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - New York : Institute of Electrical and Electronics Engineers (IEEE). - 0885-3010 .- 1525-8955. ; 41:5, s. 596-603
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Tidskriftsartikel (refereegranskat)abstract
- Many methods for distance estimation, such as the ultrasonic pulse-echo method, involve the estimation of a time-of-flight (TOF). In this paper, a signal model is developed that, apart from the TOF, accounts for an unknown, linear frequency dependent distortion as well as for additive noise. We derive a TOF estimator for this model based on the criteria of maximum likelihood. The resulting receiver can be seen as an extension or generalization of the well known cross-correlation, or "matched filter", estimator described, e.g., by Nilsson. The novel receiver is found to be more robust against unknown pulse shape distortion than the cross-correlation estimator, giving less biased TOF estimates. Also, bias versus noise sensitivity can be controlled by proper model order selection
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| 2. |
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| 3. |
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| 4. |
- Sandell, A., et al.
(författare)
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THE INNER VALENCE REGION OF CO ADSORBED ON PD(100)
- 1994
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 26:19, s. 10659-10668
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Tidskriftsartikel (refereegranskat)abstract
- The inner valence region of CO/Pd(100) p(2square-root2 x square-root2)R45-degrees has been studied by angular resolved photoemission at the Pd 4d Cooper minimum, and with resonant Auger spectroscopy at photon energies corresponding to the C 1s and O 1s x-ray absorption (XA) maxima of the unoccupied parts of the 2pi*-Pd 4d hybrid (2pi(un)). Previously unobserved inner valence states are revealed in the direct photoemission and are compared with resonant Auger results. The interpretation and assignment of the different spectral features to different main final state configurations are based on energy, symmetry and intensity arguments, as well as comparisons with previous results.
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| 5. |
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| 6. |
- 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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| 7. |
- Axsäter, Sven
(författare)
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Continuous review policies for multi-level inventory systems with stochastic demand
- 1993
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Ingår i: Handbooks in Operations Research and Management Science. - 0927-0507 .- 2212-1323. ; 4, s. 175-197
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Tidskriftsartikel (refereegranskat)abstract
- This chapter deals with continuous review policies. This means that the inventory levels are followed continuously and that replenishments may be ordered at any time. If the demand is Poisson (or compound Poisson) it is easy to realize that it is sufficient to consider those moments of time when demands occur. In case of low demand, there are relatively few such events, and it is usually suitable to apply continuous review policies. On the other hand, in case of very high demand, continuous review can lead to high information costs and it may be more practical to review the inventory system periodically. This means that continuous review policies are of special interest for inventory items that naturally have a low demand like—for example, spare parts. The chapter also discusses available models dealing with continuous review policies for multi-level inventory systems and emphasizes the main characteristics of different approaches. Furthermore, two-level systems and consumable items are also discussed in the chapter.
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| 8. |
- Axsäter, Sven, et al.
(författare)
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Evaluation of a new type of sequential lot sizing techniques
- 1990
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Ingår i: Engineering Costs and Production Economics. - 0167-188X .- 1878-4011. ; 19:1-3, s. 281-286
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Tidskriftsartikel (refereegranskat)abstract
- The classical dynamic lot size problem without backlogging is usually solved with the aid of various heuristics. Most heuristics are sequential, i.e. the demand is considered period for period, and a decision whether to include the demand in a certain period in the preceding batch is taken without regarding the future demand. Recently, it has been shown how to design a sequential lot sizing rule that will optimize the average performance, provided that a typical demand looks like a sequence of independent and identically distributed random numbers. The purpose of this paper is to evaluate if and how this methodology can be implemented in practice. The new lot sizing techniques are evaluated in a simulation study for different types of demand.
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| 9. |
- Axsäter, Sven
(författare)
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Exact and approximate evaluation of batch-ordering policies for two-level inventory systems
- 1993
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Ingår i: Operations Research. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0030-364X .- 1526-5463. ; 41:4, s. 777-785
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Tidskriftsartikel (refereegranskat)abstract
- We consider a two-level inventory system with one warehouse and N identical retailers. Lead times (transportation times) are constant and the retailers face independent Poisson demand. In a previous paper, we derived a recursive procedure for determining the policy costs for an average item in case of one-for-one replenishment policies. In this paper, we show how these results can be used for the exact or approximate evaluation of more general policies where both the retailers and the warehouse order in batches. We compare our methods to the method recently suggested by A. Svoronos and P. Zipkin.
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| 10. |
- Axsäter, Sven
(författare)
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Optimization of order-up-to-S policies in two-echelon inventory systems with periodic review
- 1993
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Ingår i: Naval Research Logistics. - 0894-069X .- 1520-6750. ; 40:2, s. 245-253
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Tidskriftsartikel (refereegranskat)abstract
- We consider an inventory system with one warehouse and N retailers. Transportation times are constant and the retailers face independent Poisson demand. Each facility applies a periodic review order-up-to-S policy. In case of shortages at the warehouse, orders for individual units are filled in the same order as the original demand at the retailers, i.e., according to a so-called virtual allocation scheme. Using that the considered policy is very similar to a continuous review one-for-one ordering policy, we are able to provide simple recursive procedures for exact evaluation of holding and shortage costs
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