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Nilsson, Bertil
Publications (10 of 11) Show all publications
Gåård, A., Löfgren, H., Nilsson, B. & Hallbäck, N. (2017). Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar. In: : . Paper presented at 6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 november – 23 november 2017.
Open this publication in new window or tab >>Införandet av Computer Based Mathematics (CBM) i ingenjörsutbildningar
2017 (Swedish)Conference paper, Published paper (Other (popular science, discussion, etc.))
Abstract [sv]

CBM är ett koncept som innebär användning av datorn och matematikprogramvaror som huvudverktyg i under-visningen. Istället för att som i traditionell undervisning kombinera handräkning med datorlabbar ligger tyngdpunkten i en CBM-kurs på datoriserade beräkningsverktyg. Härav för-flyttas fokus mot konceptförtåelse, modellering och tolkning av resultat. Vid Högskolan i Halmstad och Karlstads Universitet finns idag flera kurser baserat på CBM. Kvantitativt har införandet lett till ökad studentgenomströmning samtidigt som innehållet i kurser har ökat. Kvalitativa markörer, såsom studentens egen uppfattning om konceptuell förståelse och nyfikenhet inom ämnet, har baserat på kursvärderingar också ökat. 

National Category
Pedagogy
Identifiers
urn:nbn:se:hh:diva-38041 (URN)
Conference
6:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 november – 23 november 2017
Available from: 2018-09-23 Created: 2018-09-23 Last updated: 2018-10-31Bibliographically approved
Andersen, E., Nilsson, B. & Sahlén, G. (2016). Survival possibilities of the dragonfly Aeshna viridis (Insecta, Odonata) in southern Sweden predicted from dispersal possibilities. Journal of Insect Conservation, 20(2), 179-188
Open this publication in new window or tab >>Survival possibilities of the dragonfly Aeshna viridis (Insecta, Odonata) in southern Sweden predicted from dispersal possibilities
2016 (English)In: Journal of Insect Conservation, ISSN 1366-638X, E-ISSN 1572-9753, Vol. 20, no 2, p. 179-188Article in journal (Refereed) Published
Abstract [en]

We use public records from 1980 to 2014 to analyse survival of the EU Annex IV species Aeshna viridis in Sweden, a dragonfly strongly associated with the plant Stratiotes aloides. We clustered localities with S. aloides based on assumed dispersal abilities of A. viridis, using a dispersing radius of 2–100 km, calculating the proportion of sites with S. aloides that A. viridis is able to reach. If mean dispersal capability is high (40 km or above) 92.6 % or more of the localities are connected. For a good disperser, the probability of long-time survival is good. We further analysed the species richness of other Odonata and aquatic plants at 98 localities from the dataset. A. viridis co-occurred with more Odonata in the presence of S. aloides and running water but not in lakes. S. aloides sites had a higher number of other aquatic plants. Area had no impact on the occurrence of the species. For the present situation we surveyed 32 localities with known occurrence of the species. Only half of the sites for S. aloides contained any specimens while A. viridis occurred in the same number of sites. The species co-occurred in only 8 of 32 sites. In four sites A. viridis larvae appeared among Menyanthes trifoliata, Phragmites australis, Potamogeton natans and Sphagnum spp., indicating that at high latitudes A. viridis breeds among other species. Indirect monitoring based only on S. aloides would underestimate the number of populations of the dragonfly. © 2016 Springer International Publishing Switzerland

Place, publisher, year, edition, pages
Dordrecht: Springer Netherlands, 2016
Keywords
Annex IV, egg laying habitat, habitat preferences, metapopulation, monitoring, public database
National Category
Zoology
Identifiers
urn:nbn:se:hh:diva-30794 (URN)10.1007/s10841-016-9850-5 (DOI)000376022300002 ()2-s2.0-84957663314 (Scopus ID)
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. & Hansbo, P. (2011). A Stokes model with cavitation for the numerical simulation of hydrodynamic lubrication. International Journal for Numerical Methods in Fluids, 67(12), 2015-2025
Open this publication in new window or tab >>A Stokes model with cavitation for the numerical simulation of hydrodynamic lubrication
2011 (English)In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 67, no 12, p. 2015-2025Article in journal (Refereed) Published
Abstract [en]

We present a cavitation model based on the Stokes equation and formulate adaptive finite element methods for its numerical solution. A posteriori error estimates and adaptive algorithms are derived, and numerical examples illustrating the theory are supplied, in particular with comparison to the simplified Reynolds model of lubrication.

Place, publisher, year, edition, pages
Chichester, Sussex: John Wiley & Sons, 2011
Keywords
Stokes problem, cavitation, variational inequality, finite element method, adaptivity, error estimate
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-16334 (URN)10.1002/fld.2479 (DOI)000297736100014 ()2-s2.0-83255185872 (Scopus ID)
Available from: 2011-09-25 Created: 2011-09-25 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. & Hansbo, P. (2011). Weak coupling of a Reynolds model and a Stokes model for hydrodynamic lubrication. International Journal for Numerical Methods in Fluids, 66(6), 730-741
Open this publication in new window or tab >>Weak coupling of a Reynolds model and a Stokes model for hydrodynamic lubrication
2011 (English)In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 66, no 6, p. 730-741Article in journal (Refereed) Published
Abstract [en]

The Reynolds model is a reduced Stokes model, valid for narrow lubrication regions. In order to be able to handle locally non-narrow regions such as pits or grooves, often displaying rapid geometrical variations, there is a need to be able to transit to the more accurate Stokes model. A fundamental problem is how to couple the two models in a numerical simulation, preferably allowing for different meshes in the different domains. In this paper, we present a weak coupling method for Reynolds and Stokes models for lubrication computations, including the possibility of cavitation in the different regions. The paper concludes with a numerical example.

Place, publisher, year, edition, pages
Chichester, Sussex: John Wiley & Sons, 2011
Keywords
Reynolds problem, Stokes problem, interface coupling, cavitation, variational inequality, finite element method
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-16332 (URN)10.1002/fld.2281 (DOI)000291097500005 ()2-s2.0-77958550318 (Scopus ID)
Available from: 2011-09-25 Created: 2011-09-25 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. (2009). Finite element procedures for virtual tribology. (Doctoral dissertation). Göteborg: Chalmers
Open this publication in new window or tab >>Finite element procedures for virtual tribology
2009 (English)Doctoral thesis, monograph (Other academic)
Place, publisher, year, edition, pages
Göteborg: Chalmers, 2009. p. 134
Series
Doktorsavhandlingar vid Chalmers tekniska högskola, ISSN 0346-718X ; 2984
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-16333 (URN)
Public defence
2009-06-12, Chalmers, lokal Euler, Chalmers Tvärgata 3, Göteborg, 13:00 (English)
Opponent
Supervisors
Available from: 2011-09-27 Created: 2011-09-25 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. & Hansbo, P. (2007). Adaptive finite element methods for hydrodynamic lubrication with cavitation. International Journal for Numerical Methods in Engineering, 72(13), 1584-1604
Open this publication in new window or tab >>Adaptive finite element methods for hydrodynamic lubrication with cavitation
2007 (English)In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 72, no 13, p. 1584-1604Article in journal (Refereed) Published
Abstract [en]

We present an adaptive finite element method for a cavitation model based on Reynolds' equation. A posteriori error estimates and adaptive algorithms are discussed, and numerical examples illustrating the theory are supplied.

Place, publisher, year, edition, pages
Chichester: John Wiley & Sons, 2007
Keywords
cavitation, finite element, lubrication, Reynolds' equation, penalty
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-2017 (URN)10.1002/nme.2051 (DOI)000251908200005 ()2-s2.0-37249019079 (Scopus ID)2082/2412 (Local ID)2082/2412 (Archive number)2082/2412 (OAI)
Available from: 2008-10-06 Created: 2008-10-06 Last updated: 2018-03-23Bibliographically approved
Wiklund, D., Nilsson, L., Nilsson, B., Andersson, A., Rosén, B. G. & Gunnarsson, L. (2006). On the Implementation and Evaluation of a Roughness Based Friction Model in FE Simulations of Sheet Metal Forming. In: Proceedings of The 12th Nordic Symposium on Tribology: . Paper presented at Nordtrib 2006 - 12th Nordic symposium on Tribology,Helsingör, Denmark, June 7-9, 2006. Lyngby: DTU Mechanical Engineering
Open this publication in new window or tab >>On the Implementation and Evaluation of a Roughness Based Friction Model in FE Simulations of Sheet Metal Forming
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2006 (English)In: Proceedings of The 12th Nordic Symposium on Tribology, Lyngby: DTU Mechanical Engineering , 2006Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Lyngby: DTU Mechanical Engineering, 2006
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:hh:diva-16316 (URN)87-90416-19-8 (ISBN)
Conference
Nordtrib 2006 - 12th Nordic symposium on Tribology,Helsingör, Denmark, June 7-9, 2006
Available from: 2011-09-23 Created: 2011-09-23 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. (2005). Adaptive Finite Element Methods for the Reynolds Thin Film Model with Cavitation. (Licentiate dissertation). Göteborg: Chalmers University of Technology
Open this publication in new window or tab >>Adaptive Finite Element Methods for the Reynolds Thin Film Model with Cavitation
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The main purpose of this thesis is to use modern goal-oriented adaptive finite element techniques in order to improve the numerical simulation of tribology. Two novel adaptive finite element methods for the Reynolds thin film model including cavitation are presented and their different strategies are compared. The algorithms are inspired by an analogy with the obstacle problem and the cavitation problem that we consider is written as a variational inequality considering in the formulation the fact that the lubricant can not stand negative stresses induced by sub-atmospheric pressure. A posteriori, error estimates and adaptive algorithms are derived, and numerical examples illustrating the theory are supplied. The cavitation problem and calculations is introduced and put into historical and modern perspective. Modern thoughts and techniques around the oil-pocket idea in sheet metal forming are presented. The influence of oil pockets on the contact regime is assessed, and in particular the likely effect of oil-pocket-induced cavitation in order to produce lift, is discussed. The ultimate goal with the numerical simulation is to be able to optimize the surface structure so as to take advantage of cavitation effects in the lubricant.

Place, publisher, year, edition, pages
Göteborg: Chalmers University of Technology, 2005. p. 21
Series
Technical report, ISSN 1652-8565 ; 2005:6
Keywords
tribology, Reynolds equation, cavitation, FEM, adaptivity, variational inequality, penalty formulation, error estimation, residual, duality
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-1359 (URN)2082/1738 (Local ID)2082/1738 (Archive number)2082/1738 (OAI)
Presentation
(English)
Available from: 2008-04-25 Created: 2008-04-25 Last updated: 2018-03-23Bibliographically approved
Rosén, B.-G., Nilsson, B., Thomas, T. R., Wiklund, D. & Xiao, L. (2004). Oil pockets and surface topography: Mechanisms of friction reduction. In: : . Paper presented at The XI. International Colloquium on Surfaces, February 2-3, 2004, Chemnitz, Germany.
Open this publication in new window or tab >>Oil pockets and surface topography: Mechanisms of friction reduction
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2004 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Oil pockets reduce friction in two ways: by providing lift themselves by a cavitation mechanism, and also by acting as a reservoir of lubricant which will leak out around their boundaries to minimise direct metallic contact in the surrounding region. The relative importance of these mechanisms is estimated in particular tribological environments. The general cavitation conditions for oil pockets are defined and the cavitation models of Etsion and Kato are compared. Both these models require knowledge of the size and distribution of oil pockets, and an attempt is made to relate these to measurable surface topography parameters. Mechanisms for leakage of lubricant from oil pockets are also discussed. Advantages and disadvantages of the Wihiborg-Crafoord index are presented. The effect of oil pockets on the contact regime in gears is assessed, and in particular the likely effect of oil-pocket-induced cavitation on gear noise, and its relation to existing work on gear roughness, is discussed. Problems of oil pocket measurement on reaÌ surfaces are outlined and the advantages of 3D measurement are identified.

National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-30572 (URN)
Conference
The XI. International Colloquium on Surfaces, February 2-3, 2004, Chemnitz, Germany
Available from: 2016-03-23 Created: 2016-03-23 Last updated: 2018-03-22Bibliographically approved
Nilsson, B. & Hansbo, P.A goal oriented adaptive finite element method for hydrodynamic lubrication.
Open this publication in new window or tab >>A goal oriented adaptive finite element method for hydrodynamic lubrication
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We present a goal-oriented adaptive finite element method for a cavitation model based on Reynolds' equation. A posteriori error estimates and adaptive algorithms are derived, and numerical examples illustrating the theory are supplied.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hh:diva-30578 (URN)
Note

Som manuskript i avhandling. As manuscript in dissertation. Omfång: sid. C1 – C12 i avhandlingen

Available from: 2016-03-23 Created: 2016-03-23 Last updated: 2018-03-22Bibliographically approved
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