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Nyström, Kaj
Publications (10 of 11) Show all publications
Broman, D., Nyström, K. & Fritzson, P. (2006). Determining Over- and Under-Constrained Systems of Equations using Structural Constraint Delta. In: : . Paper presented at Proceedings of the 5th International Conference on Generative Programming and Component Engineering (pp. 151-160).
Open this publication in new window or tab >>Determining Over- and Under-Constrained Systems of Equations using Structural Constraint Delta
2006 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Computer aided modeling and simulation of complex physical systems, using components from multiple application domains, such as electrical, mechanical, and hydraulic, have in recent years witnessed a significant growth of interest. In the last decade, equation-based object-oriented (EOO) modeling languages, (e.g. Modelica, gPROMS, and VHDL-AMS) based on acausal modeling using Differential Algebraic Equations (DAEs), have appeared. With such languages, it is possible to model physical systems at a high level of abstraction by using reusable components.A model in an EOO language needs to have the same number of equations as unknowns. A previously unsolved problem concerning this property is the efficient detection of over- or under-constrained models in the case of separately compiled models.This paper describes a novel technique to determine over- and under-constrained systems of equations in models, based on a concept called structural constraint delta. In many cases it is also possible to locate the source of the constraint-problem. Our approach makes use of static type checking and consists of a type inference algorithm. We have implemented it for a subset of the Modelica language, and successfully validated it on several examples.

Keywords
equation-based, modeling, object-oriented, over-constrained, separate compilation, type checking, under-constrained, simulation languages, algorithms
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-12699 (URN)10.1145/1173706.1173729 (DOI)
Conference
Proceedings of the 5th International Conference on Generative Programming and Component Engineering
Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2014-10-08
Sydsjö, G., Selling, K., Nyström, K., Oscarsson, C. & Kjellberg, S. (2006). Knowledge of reproduction in teenagers and young adults in Sweden. European journal of contraception & reproductive health care, 11(2), 117-125
Open this publication in new window or tab >>Knowledge of reproduction in teenagers and young adults in Sweden
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2006 (English)In: European journal of contraception & reproductive health care, ISSN 1362-5187, E-ISSN 1473-0782, Vol. 11, no 2, p. 117-125Article in journal (Refereed) Published
Abstract [en]

Objective: To investigate the knowledge of reproductive physiology and anatomy among adolescents and young adults in Sweden, and to evaluate the education obtained on these issues. Methods: Two hundred and nine study specific questionnaires were distributed, of which 206 were answered by students in primary school, upper secondary school and at first year of university. A total knowledge score based on 21 out of the 35 questions in the questionnaire was calculated. As only 44 of the 206 respondents answered all the questions a revised score was also calculated, in which partial dropouts were interpreted as wrong answers. Results: The mean of the total knowledge score was 28.7 out of 54 among the 44 respondents answering all questions, and the revised knowledge score was 24.0. The level of knowledge tended to be higher in older age groups, among women, as well as among respondents who had visited a Youth clinic. The time of ovulation was known by 21.4% of men compared to 63.4% of women. Almost 50% of the students knew one mechanism whereby oral contraceptives act to protect against pregnancy. Of the respondents, 77.2% knew of Chlamydia trachomatis but the knowledge of other STIs, like condyloma, was poorer (16.5%). Reasons for infertility were relatively well known among the respondents. Of the respondents, 57.5% stated that they had not received enough information on reproductive issues. Conclusions: The students have not achieved sufficient knowledge concerning sexual and reproductive matters that they, according to the national curriculum, should have attained by the end of the 9th grade. An improvement of the quality of the education, adapted to the students' age and pre-existing knowledge, and a review of the contents of the education is therefore needed. © 2006 European Society of Contraception.

Keywords
Attitudes, Knowledge, Reproduction, Teenagers, Young adults
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-48022 (URN)10.1080/13625180600557589 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Fritzson, P., Pop, A. D., Lundvall, H., Aronsson, P., Nyström, K., Saldamli, L., . . . Sandholm, A. (2006). OpenModelica - A Free Open-Source Environment for System Modeling, Simulation, and Teaching. In: Proceedings of the2006 IEEE International Conference on Control Applications (CCA)2006 IEEE Conference on Computer-Aided Control Systems Design (CACSD)2006 IEEE International Symposium on Intelligent Control (ISIC): . Paper presented at IEEE International Conference on Control Applications, IEEE International Symposium on Computer-Aided, Control Systems Design, IEEE International Symposium on Intelligent Control, October 4-6, 2006, Munich, Germany (pp. 1588-1595). Munich, Germany: IEEE
Open this publication in new window or tab >>OpenModelica - A Free Open-Source Environment for System Modeling, Simulation, and Teaching
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2006 (English)In: Proceedings of the2006 IEEE International Conference on Control Applications (CCA)2006 IEEE Conference on Computer-Aided Control Systems Design (CACSD)2006 IEEE International Symposium on Intelligent Control (ISIC), Munich, Germany: IEEE , 2006, p. 1588-1595Conference paper, Published paper (Refereed)
Abstract [en]

Modelica is a modern, strongly typed, declarative, and object-oriented language for modeling and simulation of complex systems. This paper gives a quick overview of some aspects of the OpenModelica environment - an open-source environment for modeling, simulation, and development of Modelica applications. An introduction of the objectives of the environment is given, an overview of the architecture is outlined and a number of examples are illustrated.   

Place, publisher, year, edition, pages
Munich, Germany: IEEE, 2006
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-35788 (URN)10.1109/CACSD-CCA-ISIC.2006.4776878 (DOI)28586 (Local ID)0-7803-9797-5 (ISBN)0-7803-9797-5 (ISBN)28586 (Archive number)28586 (OAI)
Conference
IEEE International Conference on Control Applications, IEEE International Symposium on Computer-Aided, Control Systems Design, IEEE International Symposium on Intelligent Control, October 4-6, 2006, Munich, Germany
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-01-13
Nyström, K. & Fritzson, P. (2006). Parallel Simulation with Transmission Lines in Modelica. In: : . Paper presented at 5th International Modelica Conference Modelica2006..
Open this publication in new window or tab >>Parallel Simulation with Transmission Lines in Modelica
2006 (English)Conference paper, Published paper (Refereed)
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-37370 (URN)35068 (Local ID)35068 (Archive number)35068 (OAI)
Conference
5th International Modelica Conference Modelica2006.
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2018-01-13
Mattson, H., Kessler, C., Nyström, K. & Fritzson, P. (2005). GridModelica: Modeling and Simulating on the Grid. In: : . Paper presented at 6th Annual Workshop on Linux Cluster for Super Computing (LCSC), Linköping, October.
Open this publication in new window or tab >>GridModelica: Modeling and Simulating on the Grid
2005 (English)Conference paper, Published paper (Refereed)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-110206 (URN)
Conference
6th Annual Workshop on Linux Cluster for Super Computing (LCSC), Linköping, October
Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2014-10-14Bibliographically approved
Berg, K. & Nyström, K. (2005). Hydrological Modeling in Modelica. In: 4th International Modelica Conference, March 2005,2005.
Open this publication in new window or tab >>Hydrological Modeling in Modelica
2005 (English)In: 4th International Modelica Conference, March 2005,2005, 2005Conference paper, Published paper (Other academic)
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-23123 (URN)2520 (Local ID)2520 (Archive number)2520 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2018-01-13
Nyström, K., Aronsson, P. & Fritzson, P. (2005). Parallelization in Modelica. In: : . Paper presented at 4th International Modelica Conference March 2005..
Open this publication in new window or tab >>Parallelization in Modelica
2005 (English)Conference paper, Published paper (Other academic)
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-23122 (URN)2519 (Local ID)2519 (Archive number)2519 (OAI)
Conference
4th International Modelica Conference March 2005.
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2018-01-13
Fritzson, P., Aronsson, P., Lundvall, H., Nyström, K., Pop, A., Saldamli, L. & Broman, D. (2005). The OpenModelica Modeling, Simulation, and Development Environment. In: : . Paper presented at 46th Conference on Simulation and Modelling of the Scandinavian Simulation Society (SIMS2005), Trondheim, Norway, October 13-14, 2005.
Open this publication in new window or tab >>The OpenModelica Modeling, Simulation, and Development Environment
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2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Modelica is a modern, strongly typed, declarative, and object-oriented language for modeling and simulation of complex systems. This paper gives a quick overview of some aspects of the OpenModelica environment – an open-source environment for modeling, simulation, and development of Modelica applications. An introduction of the objectives of the environment is given, an overview of the architecture is outlined and a number of examples are illustrated.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-110211 (URN)
Conference
46th Conference on Simulation and Modelling of the Scandinavian Simulation Society (SIMS2005), Trondheim, Norway, October 13-14, 2005
Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2014-10-20Bibliographically approved
Nyström, K., Aronsson, P. & Fritzson, P. (2004). GridModelica- A Modeling and Simulation Framework for the Grid. In: : . Paper presented at SIMS 2004, the 45th Conference on Simulation and Modelling. September 2004,2004.
Open this publication in new window or tab >>GridModelica- A Modeling and Simulation Framework for the Grid
2004 (English)Conference paper, Published paper (Other academic)
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-23124 (URN)2521 (Local ID)2521 (Archive number)2521 (OAI)
Conference
SIMS 2004, the 45th Conference on Simulation and Modelling. September 2004,2004
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2018-01-13
Fritzson, P., Engelson, V., Idebrant, A., Aronsson, P., Lundvall, H., Bunus, P. & Nyström, K. (2004). Modelica - A Strongly Typed System Specification Language for Safe Engineering Practices. In: Proceedings of the SimSAFE Conference, Karlskoga, Sweden, June 15-17, 2004: . Paper presented at SIMSAFE 2004, June 17, Karlskoga, Sweden.
Open this publication in new window or tab >>Modelica - A Strongly Typed System Specification Language for Safe Engineering Practices
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2004 (English)In: Proceedings of the SimSAFE Conference, Karlskoga, Sweden, June 15-17, 2004, 2004Conference paper, Published paper (Other academic)
Abstract [en]

Recent years have witnessed a significant growth of interest in modeling and simulation of engineering application systems. A key factor in this growth has been the development of efficient equation-based simulation languages, with Modelica as one of the prime examples. Such languages have been designed to allow automatic generation of efficient simulation code from declarative specifications. A major objective is to facilitate reuse and exchange of models, model libraries, and simulation specifications.

The Modelica language and its associated support technologies have achieved considerable success through the development of domain libraries in a number of technical areas. By using domain-libraries complex simulation models can be built by aggregating and combining submodels and components from various physical domains.

The concept of safe engineering practices has been one of the most important guidelines when designing Modelica. This made it natural to make Modelica a statically strongly typed language, which allows the compiler to check the consistency of a design before it is executed, in contrast to dynamically typed languages such as Matlab.

The ability of static checking has also influenced the design of conditional equations and the ongoing the design of variant handling features in Modelica. Moreover, the language allows support for standardized physical units, thus enabling tools for unit checking of relationships and connections between interfaces. A third possible level of checking is through design rules within application-specific libraries, which can be enforced via assert statements. These properties taken together gives a good foundation for safe engineering practices, even though more work is needed to further increase the safety quality level.

National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-23103 (URN)2500 (Local ID)2500 (Archive number)2500 (OAI)
Conference
SIMSAFE 2004, June 17, Karlskoga, Sweden
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2018-01-13Bibliographically approved
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