| 21. |
- Dufek, Jan, 1978
(författare)
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Building the nodal nuclear data dependences in a many-dimensional state-variable space
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:7, s. 1569-1577
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Tidskriftsartikel (refereegranskat)abstract
- We present new methods for building the polynomial-regression based nodal nuclear data models. Thedata models can reflect dependences on a large number of state variables, and they can consider varioushistory effects. Suitable multivariate polynomials that approximate the nodal data dependences are identifiedefficiently in an iterative manner. The history effects are analysed using a new sampling scheme forlattice calculations where the traditional base burnup and branch calculations are replaced by a largenumber of diverse burnup histories. The total number of lattice calculations is controlled so that the datamodels are built to a required accuracy.
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| 22. |
- Dufek, Jan, 1978-
(författare)
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Complex models of nodal nuclear data
- 2011
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Ingår i: International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2011). - 9788563688002
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Konferensbidrag (refereegranskat)abstract
- During the core simulations, nuclear data are required at various nodal thermal-hydraulic and fuel burnup conditions. The nodal data are also partially affected by thermal-hydraulic and fuel burnup conditions in surrounding nodes as these change the neutron energy spectrum in the node. Therefore, the nodal data are functions of many parameters (state variables), and the more state variables are considered by the nodal data models the more accurate and flexible the models get. The existing table and polynomial regressionmodels, however, cannot reflect the data dependences on many state variables. As for the table models, the number of mesh points (and necessary lattice calculations) grows exponentially with the number of variables. As for the polynomial regression models, the number of possible multivariate polynomials exceeds the limits of existing selection algorithms that should identify a few dozens of the most important polynomials. Also, the standard scheme of lattice calculations is not convenient for modelling the data dependences on various burnup conditions since it performs only a single or few burnup calculations at fixed nominal conditions. We suggest a new efficient algorithm for selecting the most important multivariate polynomials for the polynomial regression models so that dependences on many state variables can be considered. We also present a new scheme for lattice calculations where a large number of burnup histories are accomplished at varied nodal conditions. The number of lattice calculations being performed and the number of polynomials being analysed are controlled and minimised while building the nodal data models of a required accuracy.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Engström, Tomas, 1950, et al.
(författare)
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Alternativ montering
- 2008
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Ingår i: Chukyo Keiei Kenkyu (academic japanese journal). ; 18:1, s. 73 - 153
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Tidskriftsartikel (refereegranskat)abstract
- A translation into Japanese of the three authors’’ book written for and financed by the Swedish Metal Workers Union (IF Metall is Swedish). Namely, “Alternativ montering. Principer och erfarenheter från fordonsindustrin”, Engström, Jonnsson and Medbo 2005). Which was financed by this organization (i.e. Metall), and which summarizes the authors’’ insights and experiences in more popular terms (used for this organization’s education, as well as made available on their website) (see other publications registered in Chalmers Public library CPL).
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| 29. |
- Engström, Tomas, 1950, et al.
(författare)
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Alternatives to Line Assembly: Some Swedish examples
- 1996
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Ingår i: International Journal of Industrial Ergonomics. - 1872-8219 .- 0169-8141. ; 17:3, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, some criticism of Lean production has occurred, focusing among other things on the working conditions and the susceptibility of traditional assembly work in a society upgrading the demands for a more humanized work. Recently, this criticism has also concerned the technical aspects of this type of manufacturing. Because of this, alternatives to line assembly merit some attention. Experiences from some innovative production systems operated in the Swedish automotive industry during the last two decades are of particular interest. These unconventional production systems feature autonomous work groups and extended work cycles. These types of production systems are elucidated in detail by means of e.g nuance the concept of utilising buffers, i.e. there are different types of buffers (or buffer functions) as is classified (or clarified) in this publications.
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| 30. |
- Engström, Tomas, 1950
(författare)
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Avrapportering av projekt ”Dokumentation av Volvo Personvagnars slutmonteringsfabrik i Uddevalla”
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This publication reports on some of a research foundation's (Arbetsmiljöfonden) financed parts of Engström’s and his colleagues' (researchers a well as other individuals) participation in the design, development, starting-up and full-scale production phases of the Volvo Automobile assembly plant in Uddevalla. This particular initiative (for the publication now treated here) resulted on in the fact that all of the documents from this assembly plant was collected (thereafter sorted on site in order to eliminate redundancies), and finally were each and every binder of documents etc. sent to the basement at of Engström’s final experimental workshop located at Chalmers University of Technology (such workshops are nowadays utopian, see below). There these documents were harboured at this premise for several years until totally new building facilities were provided for a number of different departments. At this moment were rents accelerated (bewildering costs was claimed on individual scientists) (an experimental workshop proved to be utopian). Engström’s research group was therefore forced to let this documentation to be sent to external store rented outside of Chalmers. Moreover, this documentation included (in a similar manner but much better prepared from our side), all of the documents from the Volvo Kalmar assembly plant which was closed approximately a year after the Volvo Uddevalla assembly plant (see some of the other publications registered in Chalmers Public Library CPL). Later on (more than approximately two decades), was this totally unique documentation transferred to Volvo’s Historical Archive (organised under the Volvo Museum) who in all respects mistreated this material and also unfortunately neglected a written agreement (contract) with Chalmers and Engström. In fact, it was by no means a professional treatment of the material in question. In fact, they gradually proved to neglect it. as a part of a protracted process, i.e. this Volvo organisation dragged for years to do anything at all with it (they changed manager and proved to not be able to deal with these two documentations in any professional manner, among other things due to lack of space and must probably for other reasons as well). On the other hand, interest and help from Chalmers side were almost non-existing, at the very end of Engström’s employment were some rather lame efforts to carried out. Individuals at Chalmers were afraid to create conflicts Volvo by asserting the contract due to ongoing financing and the fact that Engström had to retire anyway. Consequently, were no help available from Chalmers side to claim the agreement with the previous manager of Volvo Museum etc. As a result, this material from the two unique/pioneering assembly plants was forever lost to the scientist, or lest severely mutilated (see comment below) (sadly, we never got time to gain any academic merits of this material, it just cost money drawn from Engström's donation granted from Volvo Uddevalla assembly plant). And believe the author here, it was an enormous (almost frightening) amount of binders, books etc. each of them scrupulous registered by Engström and his research colleagues as well as by local Volvo personnel that also kindly helped us out. Note, two written agreement with the top manager of each of these two assembly plants were both predating the contract with the Volvo archive by decades. Among other things, the material was partly used once again by local Volvo personnel than the Autonova plant later was constructed, i.e. some years after the closing down, i.e. the rebirth of the Volvo Uddevalla plant. However, to be frank, here, some of the material was just thrown in pallets at the very end, due to time restraints during our documentation processes. But generally speaking, were most of the material fully organised and saved in bookshelves at the basement of our final experimental workshop at Chalmers (and each binder etc, was assigned a sequence number that corresponded to our register sequence number, denotation, finding-place etc. (in accordance with the written agreements with the two top managers). It was in many respects a bewildering work carried out during several years (e.g. it was not easy for us to figure out exactly how) besides during the period of closing down were not Volvo personnel keen to let the central Volvo organisation get hold of anything (no other would probably have managed to carry through such documentation for a number of different reasons). A comment and important: The documentation work from our side was organised in accordance with the process and organisation of each of the two assembly plants. Thus, was it not following the Swedish Archive Standard usually supported by rather unmanageable PC-based systems (which Volvo’s Historical Archive practised). This archive standard would, in fact, have fragmented et the two documentations, and thereby not enhanced a deeper understanding of each assembly plant (such standards are used for saving of single/individual documents or series thereof) (interrelation between binders and documents are thereby entirely lost). This fact was clear to us and also considered by the earlier manager at the Volvo archive and thus dealt with in the agreement between Chalmers and the historical archive. Among other things was Engström from the beginning supposed to help Volvo out by means of packing up the material. However, this was not considered by the new manager (who, as said before, neglected the registering and work carried out by Engström's research group).
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