| 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. |
- Ari, E. Aysen, et al.
(författare)
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Disaggregation under uncertainty in hierarchical production planning
- 1988
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Ingår i: European Journal of Operational Research. - : Elsevier BV. - 0377-2217 .- 1872-6860. ; 35:2, s. 182-186
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with a hierarchical planning system that is used for planning of a single-stage manufacturing system. We consider two decision levels, aggregate and detailed planning, and formulate a model for evaluation of aggregate plans and optimal disaggregation in case of independent stochastic demand. It is shown how the optimal solution can be obtained with the aid of a dynamic programming algorithm. Furthermore, we give conditions that will guarantee optimality of a simple intuitive disaggregation rule
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| 6. |
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| 7. |
- 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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| 8. |
- Axsäter, Sven, et al.
(författare)
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Combining items for lot sizing in multi-level assembly systems
- 1987
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 25:6, s. 795-807
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Tidskriftsartikel (refereegranskat)abstract
- Many manufacturing firms are faced with the problem of planning the production/purchase quantities for items in single product, multi-level assembly production/inventory systems. Such systems are characterized by a single product, or end item, used to satisfy customer demand, which is assembled from a number of component items which, in turn, may be assembled from one or more other component items, etc. Component items may be either fabricated or purchased. This paper identifies conditions on the cost parameters which, when applicable, allow items to be combined for purpose of optimization, thereby reducing the size of the problem.
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| 9. |
- 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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| 10. |
- Axsäter, Sven
(författare)
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Control theory concepts in production and inventory control
- 1985
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Ingår i: International Journal of Systems Science. - : Informa UK Limited. - 0020-7721 .- 1464-5319. ; 16:2, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- The use of efficient production and inventory control systems is of great importance for industry. Therefore this area could be expected to provide many fruitful applications of control theory techniques. However, control theory has traditionally been aimed at applications in other fields, and results have only limited applicability in production and inventory control. This paper gives an overview of earlier research concerning control theory applications in production and inventory control. Areas given special emphasis are those in which control theory seems to have a stronger potential for practical application
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