| 1. |
- Göthe-Lundgren, Maud, et al.
(författare)
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An optimization model for refinery production scheduling
- 2002
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Ingår i: International Journal of Production Economics. - Amsterdam, Netherlands : Elsevier. - 0925-5273 .- 1873-7579. ; 78:3, s. 255-270
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe a production planning and scheduling problem in an oil refinery company. The problem concerns the planning and the utilization of a production process consisting of one distillation unit and two hydro-treatment units. In the process crude oil is transformed to bitumen and naphthenic special oils. The aim of the scheduling is to decide which mode of operation to use in each processing unit at each point in time, in order to satisfy the demand while minimizing the production cost and taking storage capacities into account. The production cost includes costs for changing mode and for holding inventory. We formulate a mixed integer linear programming model for the scheduling problem. The model can be regarded as a generalized lot-sizing problem, where inventory capacities are considered and more than one product is obtained for some modes of operation. A number of modifications and extensions of the model are also discussed. It is shown how the optimization model can be used as a viable tool for supporting production planning and scheduling at the refinery, and that it is possible to analyze scheduling scenarios of realistic sizes. It is also shown that the model can support shipment planning and strategic decisions concerning new products and investments in storage capacity. © 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Persson, Jan, 1972-, et al.
(författare)
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A Tabu Search Heuristic for Scheduling the Production Processes at an Oil Refinery
- 2004
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Ingår i: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 42:3, s. 445-471
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a tabu search heuristic which can be used for scheduling the production at an oil refinery. The scheduling problem is to decide which production modes to use at the different processing units at each point in time. The problem is a type of lot-sizing problem where costs of changeovers, inventories and production are considered. In the suggested tabu search heuristic we explore the use of variable neighbourhood, dynamic penalty and different tabu lists. Computational results are presented for different versions of the heuristic and the results are compared to the best-known lower bound for a set of scheduling scenarios.
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| 3. |
- Varenhorst, Eberhard, 1937-, et al.
(författare)
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The National Prostate Cancer Register in Sweden 1998-2002 : trends in incidence, treatment and survival
- 2005
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Ingår i: Scandinavian Journal of Urology and Nephrology. - : Informa UK Limited. - 0036-5599 .- 1651-2065. ; 39:2, s. 117-123
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To provide a descriptive review of the establishment of the National Prostate Cancer Register (NPCR) in Sweden, to present clinical characteristics at diagnosis and to calculate the relative survival of different risk groups after 5 years. MATERIAL AND METHODS: Since 1998, data on all newly diagnosed prostate cancers, including TNM classification, grade of malignancy, prostate-specific antigen (PSA) level and treatment, have been prospectively collected. For the 35,223 patients diagnosed between 1998 and 2002, relative survival in different risk groups has been calculated. RESULTS: Between 1998 and 2002, 96% of all prostate cancer cases diagnosed in Sweden were registered in the NPCR. The number of new cases increased from 6137 in 1998 to 7385 in 2002. The age-standardized rate rose in those aged < 70 years, while it was stable, or possibly declining from 1999, in the older age groups. The proportion of T1c tumours increased from 14% to 28% of all recorded cases. The age-adjusted incidence of advanced tumours (M1 or PSA > 100 ng/ml) decreased by 17%. The proportion of patients receiving curative treatment doubled. Patients with N1 or M1 disease or poorly differentiated tumours (G3 or Gleason score 8-10) had a markedly reduced relative 5-year survival rate. CONCLUSIONS: It is possible to establish a nationwide prostate cancer register including basic data for assessment of the disease in the whole of Sweden. The introduction of PSA screening has increased the detection of early prostate cancer in younger men and, to a lesser extent, decreased the incidence of advanced disease. The effect of these changes on mortality is obscure but the NPCR in Sweden will serve as an important tool in such evaluation.
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| 4. |
- Ahnberg, Elisabeth, et al.
(författare)
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Följeforskning som företeelse och följeforskarrollen som konkret praktik
- 2010
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Ingår i: Arbetsmarknad & Arbetsliv. - Karlstad : Karlstads universitet. - 1400-9692 .- 2002-343X. ; 16:3, s. 55-66
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Tidskriftsartikel (refereegranskat)abstract
- Med utgångspunkt i fyra följeforskningsprocesser, där vi själva medverkat, diskuterar vi följeforskning som företeelse och rollen som följeforskare. Vår artikel ska ses som ett empiriskt exempel i anslutning till den debatt som Göran Brulin, Karin Sjöberg och Lennart Svensson initierade genom artikeln ”Gemensam kunskapsbildning för regional tillväxt” (publicerad i Arbetsmarknad & Arbetsliv, årg 15, nr 1, våren 2009).
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| 5. |
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| 6. |
- Björklund, Patrik, et al.
(författare)
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Västerås slott : Slott och borgar
- 2000
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Rapport (populärvet., debatt m.m.)abstract
- En majoritet av dagens byggnadsuppgifter gäller att hantera det redan byggda. När vi står inför situationen att restaurera en befintlig byggnad är det viktigt att förstå olika tidsperioders stilideal liksom byggnadsteknik och material. Först då kan vi göra en väl avvägd analys, som tar tillvara och utvecklar de kvaliteter som byggnaderna själva besitter. Därför är utbildningen upplagd som ett växelspel mellan föreläsningar, seminarier, exkursioner och en för året vald studieuppgift.Slott och borgar har varit läsårets tema. Vi har valt att arbeta med Västerås och Örebro slott - två ganska bortglömda Vasaslott som är väl värda att lyfta fram. Särskilt har vi studerat de senaste 300 årens förändringar, som inte tidigare ägnats lika stora forskarmöda som medelitden och Vasatiden. I dessa två exempel finns en provkarta på estetiska, praktiska och tekniska ingrepp från Carl Hårlemans tid och fram till idag.Studierna har således omfattat både gestaltning, funktion och byggnadsteknik. Avsikten är att visa på kvaliteter i de omvandlingar och restaureringar som skett, men också att peka på problem och analysera olika möjligheter inför framtiden. Arbetet har skett i samarbete med Statens fastighetsverk och är tänkt att utgöra ett underlag till vårdprogram och framtida restaureringsinsatser.
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| 7. |
- Fobelets, Kristel, et al.
(författare)
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High-frequency capacitance of bipolar resonant tunneling diodes
- 1996
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 79:2, s. 905-910
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Tidskriftsartikel (refereegranskat)abstract
- The high-frequency characteristics of bipolar resonant tunneling diodes are experimentally investigated at room temperature. The electron accumulation and discharging in these resonant tunneling light-emitting diodes are studied at frequencies up to 35 GHz. The experiments show capacitance peaks due to electron charge disappearing from the quantum well. The measurements are found to be in agreement with our theoretical model for the calculation of the high-frequency characteristics of resonant tunneling devices. The high-frequency characteristics of the bipolar light-emitting resonant tunneling diode are compared to the unipolar resonant tunneling diode and the resonant interband tunneling diode. The comparison shows a similar discharging characteristic of the quantum well, but a different overall variation of the capacitance.
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| 8. |
- Lundgren, Anna Karin, et al.
(författare)
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Augmentation of skull bone using a bioresorbable barrier supported by autologous bone grafts. An intra-individual study in the rabbit.
- 1997
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Ingår i: Clinical oral implants research. - : Wiley. - 0905-7161. ; 8:2, s. 90-5
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this experimental investigation was to compare the effect of using autologous particulate bone grafts with and without a bioresorbable barrier covering for augmentation of the rabbit skull bone. For this purpose, bilateral, circular, 8 mm wide and 1 mm deep skull bone defects were prepared and overfilled with particulate bone grafts. The grafts placed in the test sites were covered with a bioresorbable barrier (Guidor Matrix Barrier). The grafts placed in the control sites were covered only by the repositioned, cutaneous flap. 12 weeks later, the animals were sacrificed, the experimental sites were defleshed and the height and volume of the augmented bone in the test and control sites were measured clinically. Histologically, morphometrical measurements of the bone tissue were performed in decalcified vertical cross-sections of the experimental sites. Statistically significant differences were found in favour of the coverage of the bone graft particles with the barrier, both with respect to the height and the volume of the augmented bone.
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| 9. |
- Lundgren, Anna Karin, et al.
(författare)
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Bone augmentation at titanium implants using autologous bone grafts and a bioresorbable barrier. An experimental study in the rabbit tibia.
- 1997
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Ingår i: Clinical oral implants research. - : Wiley. - 0905-7161. ; 8:2, s. 82-9
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present investigation was to compare the effect of using autologous bone particles covered with a bioresorbable matrix barrier with the use of bone particles alone on bone augmentation at titanium implants installed in the rabbit tibia. Two Brånemark System implants, one in each tibia, were inserted in each of 9 rabbits in such a way that 5 threads were not covered with bone. Autologous bone particles were harvested from the skull and placed over the exposed implant surfaces on each tibia. The bone graft on one tibia was covered with a Guidor Matrix Barrier, while the bone graft on the other tibia served as a control. After a healing period of 12 weeks, the animals were sacrificed and specimens taken for histomorphometrical analyses. The analyses showed that a significantly larger volume of augmented bone tissue had formed at the test sites. There were, however, no differences in the amount of mineralized bone. In fact, the difference in tissue volume was due to an increased amount of bone marrow at the test sites. The degree of mineralized bone to implant contact as well as the degree of mineralized bone within the threads at the test implants were similar to that at the controls. In conclusion, it was found that the coverage of particulate autologous bone grafts with a bioresorbable barrier resulted in a larger volume of augmented bone than the use of bone grafts not covered with a barrier.
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| 10. |
- Lundgren, Jonas, 1993-, et al.
(författare)
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Flow–heat topology optimization of internally cooled high temperature applications using a voxelization approach for domain initialization
- 2023
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Ingår i: Engineering optimization (Print). - : Taylor & Francis. - 0305-215X .- 1029-0273.
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Tidskriftsartikel (refereegranskat)abstract
- A method is presented for obtaining topology optimized designs for internally cooled high temperature applications, using a flexible geometry description, by means of a voxelization methodology and a novel boundary detection algorithm. A conjugate heat transfer approach is taken; the physics is described by a Stokes-Brinkman model for the flow, weakly coupled with a convection-diffusion model for the heat transfer. A practically relevant optimization formulation, consisting of a maximum temperature objective with a mass flow constraint, is used, and applied to an industrial-relevant non-trivial geometry resembling a guide vane in a gas turbine. Temperatures and velocities from the optimized design are compared with the response from a Stokes flow model with body-fitted mesh and a high-fidelity Reynolds-averaged Navier-Stokes model. A comparison of the performance from a mixed and a penalty approach for solving the flow problem is included. The voxelization approach shows good promise for handling complex design domains.
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