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- 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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- Axsäter, Sven
(författare)
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Performance bounds for lot sizing heuristics
- 1985
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Ingår i: Management science. - : Institute for Operations Research and the Management Sciences (INFORMS). - 0025-1909 .- 1526-5501. ; 31:5, s. 634-640
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the classical dynamic lot size problem without backlogging and capacity limitation. The author derives worst case performance bounds for a class of lot sizing heuristics. When the considered methods are applied a decision whether to have a set-up or not in a certain period is taken without regarding the future demands. It is shown that 2 is a lower bound for the worst case performance ratio for such heuristics. The results illustrate circumstances under which the approximate techniques fail
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- Axsäter, Sven, et al.
(författare)
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The impact of capacity investments on work-in-process and inventories
- 1985
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Ingår i: Engineering Costs and Production Economics. - 0167-188X .- 1878-4011. ; 9:1-3, s. 119-124
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain higher productivity, investments in the production system are needed. Such investments may lead to improvements of two kinds: (i) increased unit production rate and (ii) reduced set-up times. In this paper the impact of capacity investments on capital tied up in work-in-process and inventories is analyzed. Increased production capacity will usually mean that planning parameters, such as lot sizes, have to be changed. For example, if set-up times are reduced an optimal policy will use smaller order quantities. This will then indirectly lead to lower holding costs. The purpose of this study is to evaluate and compare such consequences.
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- Jonsson, Mikael, et al.
(författare)
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Deformations and stresses in butt-welding of large plates with special reference to the mechanical material properties
- 1985
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Ingår i: Journal of engineering materials and technology. - : ASME International. - 0094-4289 .- 1528-8889. ; 107:4, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- Simulation of automatic butt-welding of large plates was investigated. Two different steels were considered. The plates were tack-welded before the butt-welding. The simulation includes the tack-welding, the butt-welding and the cooling to room temperature. The simulations should lead to an understanding of the mechanics behind the change in gap width in front of the moving arc, which is of importance in automatic welding production. The residual stresses due to the butt-welding were also studied. The magnitude and the distribution of the residual stress are important in design of welded structures.
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- Jonsson, Mikael, et al.
(författare)
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Plate motion and thermal stresses in root-bead butt-welding of plates
- 1985
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Ingår i: Numerical methods in thermal problems. - Swansea : Pineridge Press. - 0906674441 ; , s. 1092-1102
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Konferensbidrag (refereegranskat)abstract
- In this paper root-bead welding of plates of two different sizes was experimentally and theoretically analysed. The material of the plates was a fine-grain steel with yield limit 360 MPa. The finite element method was used for both the thermal analyses and the mechanical analyses. Temperature-dependent material properties and volume changes due to phase transformations were considered. Plane stress conditions were assumed. Good agreement between calculated and measured values were obtained.
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- Jonsson, Mikael, et al.
(författare)
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Simulation of tack welding procedures in butt joint welding of plates
- 1985
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Ingår i: Welding Journal. - 0043-2296. ; 64:10, s. 296-301
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Tidskriftsartikel (refereegranskat)abstract
- The influence of tack welding procedure on change in root opening was investigated. This change during the first part of welding depends on the order in which the tack welds are made. It is also affected by the starting position of the welding arc. These effects were studied in seven theoretical analyses - three cases where the tack welding procedures differed and four cases where the temperature fields at the beginning of the butt joint welding differed. The material investigated was a fine-grain steel with a yield stress of 360 MPa (52,200 psi) at room temperature. The filler material was ESAB 1. 2/12. 51 (AWS ER70S-6).
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