Change search
Refine search result
1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    CASSCF second-order perturbation theory (CASPT2)1998In: Encyclopedia of Computational Chemistry / [ed] P. von Ragué Schleyer, Chichester, England: John Wiley & Sons , 1998Chapter in book (Refereed)
  • 2.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cellular Automata2003Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Properties and behavior of cellular automata are considered. Cellular automata can simply be described as lattices of cells, where the cells can be in a finite number of states. By using simple rules the states of the cells are updated at discrete time steps. The evolution of cellular automata can be used for computations. Some cellular automata display universality meaning that there is no limit to the sophistication of the computations they can perform.

  • 3.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cellular Automata2004In: Promote IT 2004: proceedings of the fourth Conference for the Promotion of Research in IT at New Universities and University Colleges in Sweden : 5-7 May, 2004, Karlstad University, Sweden. P. 1 / [ed] Bubenko, Janis, Karlstad: Karlstad University Press , 2004, Vol. 2004:26, p. 598-608Conference paper (Refereed)
    Abstract [en]

    In this paper properties and behavior of cellular automata are considered. Cellular automata can simply be described as lattices of cells, where the cells can be in a finite number of states. By using simple rules the states of the cells are updated in parallel at discrete time steps. Depending on the rule and, to a certain degree, the initial states of the cells, the evolution of a cellular automaton is restricted to a small number a ways. Some cellular automata evolve uniformly, meaning that all cells end up in the same state, while others evolve randomly, meaning that the states of the cells appear to be totally randomized during evolution. Intermediate behavior, displaying repetitiveness or nesting, also occurs.Properties of cellular automata that are discussed in the paper are, for instance, sensitivity to initial conditions, randomness, reversibility, entropy, and conservation. These properties also appear in the physical world and cellular automata provide good examples in the understanding of these properties.The evolution of cellular automata can be used for computations. Some cellular automata even display the property of universality, a term well known from the universal Turing machine, meaning that there is no limit to the sophistication of the computations they can perform.

  • 4.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cellular Automata2005In: Promote IT 2005: proceedings of the fifth Conference for the Promotion of Research in IT at New Universities and University Colleges in Sweden : Borlänge, Sweden 11-13 May, 2005 / [ed] Bubenko, Janis, Lund: Studentlitteratur , 2005, p. 21-30Conference paper (Refereed)
    Abstract [en]

    Cellular automata have a widespread use in the description of complex phenomena in disciplines as disparate as for example physics and economics. They are described by a lattice of cells, states of the cells, and rules for updating the states of the cells. One characteristics of a cellular automaton is the simplicity of the rules that determine how the cellular automaton evolves in time. These rules are local, are applied in parallel to all the cells and despite their simplicity they may give rise to a complex macroscopic behaviour. In this paper this is illustrated by examples from hydrodynamics and it is shown that cellular automata might provide powerful alternatives to partial differential equations

  • 5.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Cellular Automata in Science2005Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Cellular automata have a widespread use in the description of complex phenomena in disciplines as disparate as, for example, physics and economics. A cellular automaton is a lattice of cells, and the cells can be in a finite number of states. By using simple local rules the states of the cells are updated in parallel at discrete time steps. In short, a cellular automaton can be characterised by the three words - simple, local, and parallel. These three words are one of the reasons for the attractiveness of cellular automata. They are simple to implement and they are well suited for parallel computers (computations). Another reason for using cellular automata are for their spatio-temporal properties. The lattice may represent space and the updating of the cells gives a

    dimension of time.



    In spite of the simplicity of cellular automata they may give rise to a complex macroscopic behaviour. This is illustrated, in this thesis, by an hydrodynamic example, namely the creation of vortices in flow behind a cylinder.



    Although cellular automata have the ability to describe complex phenomena it is sometimes hard to find the proper rules for a given macroscopic behaviour. One approach which has been successfully employed is to let cellular automata rules evolve (for example, through genetic algorithms) when finding the desired properties. In this thesis this is demonstrated for two-dimensional cellular automata with two possible states of the cells. A genetic algorithm is used to find rules that evolve a given initial configuration of the cells to another given configuration.

  • 6.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Different forms of the zeroth-order Hamiltonian in second-order perturbation theory with a complete active space self-consistent field reference function1995In: Theoretica Chimica Acta, 91:31Article in journal (Refereed)
  • 7.
    Andersson, Kerstin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Exact Probability Distribution versus Entropy2014In: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 16, no 10, p. 5198-5210Article in journal (Refereed)
    Abstract [en]

    The problem addressed concerns the determination of the average numberof successive attempts of guessing a word of a certain length consisting of letters withgiven probabilities of occurrence. Both first- and second-order approximations to a naturallanguage are considered. The guessing strategy used is guessing words in decreasing orderof probability. When word and alphabet sizes are large, approximations are necessary inorder to estimate the number of guesses. Several kinds of approximations are discusseddemonstrating moderate requirements regarding both memory and central processing unit(CPU) time. When considering realistic sizes of alphabets and words (100), the numberof guesses can be estimated within minutes with reasonable accuracy (a few percent) andmay therefore constitute an alternative to, e.g., various entropy expressions. For manyprobability distributions, the density of the logarithm of probability products is close to anormal distribution. For those cases, it is possible to derive an analytical expression for theaverage number of guesses. The proportion of guesses needed on average compared to thetotal number decreases almost exponentially with the word length. The leading term in anasymptotic expansion can be used to estimate the number of guesses for large word lengths.Comparisons with analytical lower bounds and entropy expressions are also provided.

  • 8.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Multiconfigurational perturbation theory1992Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The aim of the thesis is to analyze a method which describes the electron correlation in atoms and molecules. The method is based on Rayleigh-Schrödinger perturbation theory with a partitioning of the Hamiltonian into a fairly simple zeroth-order operator and a perturbation operator. The zeroth-order Hamiltonian is founded on a one-electron Fock-type operator and two different operators have been tested. The zeroth-order wave function is constructed from a complete active space self-consistent field (CASSCF) calculation. This means that the zeroth-order wave function for open-shell systems and systems with strong configurational mixing (near degeneracy) can be obtained on an equal level as closed-shell (single determinant) states. The theory is formulated in such a way that the Möller-Plesset perturbation theory is obtained for the closed-shell (single determinant) state. The flexibility of the CASSCF method makes it possible, in principle, to construct the zeroth-order wave function (and the zeroth-order Hamiltonian) to any desired accuracy. The perturbation expansion of the energy is therefore expected to converge fast and only up to the second-order contribution has been implemented leading to fairly fast and accurate calculations. The aim of the computer implementation is to describe the electron correlation in small and medium-sized molecules (up to 20 atoms) accurately. The application of the perturbation method to a number of problems in chemistry is demonstrated in the thesis: (1) the calculation of electronic properties and harmonic vibrational frequencies of the ozone molecule; (2) the calculation of electric dipole polarizabilities of excited valence states of several first- and second-row atoms; (3) the calculation of excited states of the nickel atom, the benzene molecule, and the azabenzenes pyridine, pyrazine, pyridazine, and s-triazine

  • 9.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Numerical Evaluation of the Average Number of Successive Guesses2012In: Unconventional Computation and Natural Computation: 11th International Conference, UCNC 2012, Orléans, France, September 3-7, 2012, Proceedings / [ed] Jérôme Durand-Lose, Natasa Jonoska, Berlin Heidelberg: Springer , 2012, p. 234-234Conference paper (Refereed)
  • 10.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    The electronic spectrum of Cr21995In: Chemical Physics Letters, 237:212Article in journal (Refereed)
  • 11.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    The electronic spectrum of VCr2003In: Theoretical Chemistry Accounts, volume 110, number 3Article in journal (Refereed)
    Abstract [en]

    The electronic spectrum of VCr has been studied using the complete-active-space self-consistent field complete-active-space second-order perturbation theory approach. Potential energy curves for 12 electronic states have been computed. Transition energies, with respect to the X^2Delta ground state, for some of the calculated electronic states are (with possible experimental values within parentheses): 0.53 eV (0.56) for A^2Sigma+, 1.03 eV (1.14) for A^4Delta, 1.20 eV (1.14) for B^2Delta, 1.45 eV (1.51) for B^4Delta, 1.60 eV (1.51, 1.78) for C^2Delta, and 1.61 eV (1.63) for A^4Sigma^-.

  • 12.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Vad är det för kunskap som värderas?2000In: Universitetsläraren, nummer 7Article in journal (Other (popular science, discussion, etc.))
  • 13.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Vad är kunskap?2006In: Kapet, nummer 1, Vol. 1Article in journal (Other (popular science, discussion, etc.))
  • 14.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Bauschlicher Jr., C. W.
    Persson, B. J.
    Roos, B. O.
    The structure of dichromium tetraformate1996In: Chemical Physics Letters, 257:238Article in journal (Refereed)
  • 15.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Borowski, P.
    Fowler, P. W.
    Malmqvist, P.-Å.
    Roos, B. O.
    Sadlej, A. J.
    Electric properties of the ozone molecule1992In: Chemical Physics Letters, 190:367Article in journal (Refereed)
  • 16.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fulscher, M. P.
    Lindh, R.
    Malmqvist, P.-Å.
    Olsen, J.
    Roos, B. O.
    Widmark, P.-O.
    MOLCAS: A general purpose quantum chemistry program system for correlated wavefunctions1994In: Methods and Techniques in Computational Chemistry: METECC-94, chapter 7, page 275 / [ed] Enrico Clementi, Cagliari, Italy: STEF , 1994Chapter in book (Refereed)
  • 17.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Malmqvist, P.-Å.
    Roos, B. O.
    Second-order perturbation theory with a complete active space self-consistent field reference function1992In: Journal of Chemical Physics, 96:1218Article in journal (Refereed)
  • 18.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Malmqvist, P.-Å.
    Roos, B. O.
    Sadlej, A. J.
    Wolinski, K.
    Second-order perturbation theory with a CASSCF reference function1990In: Journal of Physical Chemistry, 94:5483Article in journal (Refereed)
  • 19.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Roos, B. O.
    Excitation energies in the nickel atom studied with the complete active space SCF method and second-order perturbation theory1992In: Chemical Physics Letters, 191:507Article in journal (Refereed)
  • 20.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Roos, B. O.
    Multiconfigurational second-order perturbation theory1995In: Modern electronic structure theory, volume 1 / [ed] D. R. Yarkony, New York: World Scientific Publishing , 1995Chapter in book (Refereed)
  • 21.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Roos, B. O.
    Multiconfigurational second-order perturbation theory: A test of geometries and binding energies1993In: International Journal of Quantum Chemistry, 45:591Article in journal (Refereed)
  • 22.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Roos, B. O.
    Malmqvist, P.-Å.
    Widmark, P.-O.
    The Cr2 potential energy curve studied with multiconfigurational second-order perturbation theory1994In: Chemical Physics Letters, 230:391Article in journal (Refereed)
  • 23.
    Andersson, Kerstin
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Sadlej, A. J.
    Electric dipole polarizabilities of atomic valence states1992In: Physical Review A, 46:2356Article in journal (Refereed)
  • 24. Borowski, P.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Malmqvist, P.-Å.
    Roos, B. O.
    The vibrational frequencies of ozone: A multiconfigurational approach1992In: Journal of Chemical Physics, 97:5568Article in journal (Refereed)
  • 25. Fulscher, M. P.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Roos, B. O.
    Towards an accurate molecular orbital theory for excited states: The azabenzenes1992In: Journal of Physical Chemistry, 96:9204Article in journal (Refereed)
  • 26. Roos, B. O.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Multiconfigurational perturbation theory with level shift - the Cr2 potential revisited1995In: Chemical Physics Letters, 245:215Article in journal (Refereed)
  • 27. Roos, B. O.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fulscher, M. P.
    Towards an accurate molecular orbital theory for excited states: The benzene molecule1992In: Chemical Physics Letters, 192:5Article in journal (Refereed)
  • 28. Roos, B. O.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fulscher, M. P.
    Malmqvist, P.-Å.
    Serrano-Andrés, L.
    Pierloot, K.
    Merchán, M.
    Multiconfigurational perturbation theory: Applications in electronic spectroscopy1996In: Advances in Chemical Physics: New Methods in Computational Quantum Mechanics, volume XCIII:219 / [ed] S. A. Rice, New York: John Wiley & Sons , 1996Chapter in book (Refereed)
  • 29. Roos, B. O.
    et al.
    Andersson, Kerstin
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Fulscher, M. P.
    Serrano-Andrés, L.
    Pierloot, K.
    Merchán, M.
    Molina, V.
    Applications of level shift corrected perturbation theory in electronic spectroscopy1996In: Journal of Molecular Structure, number 388Article in journal (Refereed)
1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf