To Örebro University

oru.seÖrebro University Publications
Change search
Refine search result
1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • 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, Johan
    Department of Mathematics, Stockholm University, Stockholm, Sweden.
    Disproof of some conjectures of P. Turán2007In: Acta Mathematica Hungarica, ISSN 0236-5294, E-ISSN 1588-2632, Vol. 117, no 3, p. 245-250Article in journal (Refereed)
    Abstract [en]

    We disprove some power sum conjectures of Turan that would have implied the density hypothesis of the Riemann zeta-function if true.

  • 2.
    Andersson, Johan
    Stockholm University, Stockholm, Sweden.
    Explicit solutions to certain inf max problems from Turán power sum theory2007In: Indagationes mathematicae, ISSN 0019-3577, E-ISSN 1872-6100, Vol. 18, no 2, p. 189-194Article in journal (Refereed)
  • 3.
    Andersson, Johan
    Uppsala University, Uppsala, Sweden.
    Lavrent\cprime ev’s approximation theorem with nonvanishing polynomials and universality of zeta-functions2009In: New directions in value-distribution theory of zeta and L-functions / [ed] Rasa Steuding, Jörn Steuding, Aachen: Shaker Verlag , 2009, p. 7-10Chapter in book (Other academic)
  • 4.
    Andersson, Johan
    Department of Mathematics, Stockholm University, Stockholm, Sweden.
    Mergelyan's approximation theorem with nonvanishing polynomials and universality of zeta-functions2013In: Journal of Approximation Theory, ISSN 0021-9045, E-ISSN 1096-0430, Vol. 167, p. 201-210Article in journal (Refereed)
    Abstract [en]

    We prove a variant of the Mergelyan approximation theorem that allows us to approximate functions that are analytic and nonvanishing in the interior of a compact set K with connected complement, and whose interior is a Jordan domain, with nonvanishing polynomials. This result was proved earlier by the author in the case of a compact set K without interior points, and independently by Gauthier for this case and the case of strictly starlike compact sets. We apply this result on the Voronin universality theorem for compact sets K, where the usual condition that the function is nonvanishing on the boundary can be removed. We conjecture that this version of Mergelyan's theorem might be true for a general set K with connected complement and show that this conjecture is equivalent to a corresponding conjecture on Voronin Universality.

  • 5.
    Andersson, Johan
    Department of Mathematics, Stockholm University, Stockholm, Sweden.
    On some power sum problems of montgomery and Turán2008In: International mathematics research notices, ISSN 1073-7928, E-ISSN 1687-0247, Vol. 2008, no 1, article id rnn015Article in journal (Refereed)
    Abstract [en]

    We use an estimate for character sums over finite fields of Katz to solve open problems of Montgomery and Turan. Let h >= 2 be an integer. We prove that inf(vertical bar zk vertical bar=1) max(nu=1,...,n)(h) vertical bar Sigma(n)(k=1) Z(k)(nu)vertical bar <= (h - 1 + o(1)root n. This gives the right order of magnitude for the quantity and improves on a bound of Erdos-Renyi by a factor of the order root logn.

  • 6.
    Andersson, Johan
    Stockholm University, Stockholm, Sweden.
    On the solutions to a power sum problem2007In: Analytic and probabilistic methods in number theory / Analiziniai ir tikimybiniai metodai skaiči\polhk u teorijoje, Vilnius: TEV , 2007, p. 1-5Chapter in book (Other academic)
  • 7.
    Andersson, Johan
    Örebro University, School of Science and Technology.
    Voronin Universality in several complex variables2018Manuscript (preprint) (Other academic)
  • 8.
    Andersson, Johan
    et al.
    Department of Mathematics, Stockholm University, Stockholm, Sweden.
    Gauthier, Paul M.
    Département de mathématiques et de statistique, Université de Montréal, Montréal, Canada.
    Mergelyan’s theorem with polynomials non-vanishing on unions of sets2014In: Complex Variables and Elliptic Equations, ISSN 1747-6933, E-ISSN 1747-6941, Vol. 59, no 1, p. 99-109Article in journal (Refereed)
    Abstract [en]

    We consider the problem of approximating a function having no zeros on the interior of a set by polynomials having no zeros on the entire set.

  • 9.
    Andersson, Johan
    et al.
    Örebro University, School of Science and Technology.
    Rousu, Linnea
    Polynomial approximation avoiding values in countable sets2019Manuscript (preprint) (Other academic)
  • 10.
    Andersson, Johan
    et al.
    Örebro University, School of Science and Technology.
    Södergren, Anders
    Chalmers University of Technology and the University of Gothenburg, Gothenburg, Sweden; University of Copenhagen, Copenhagen, Denmark.
    On the universality of the Epstein zeta function2020In: Commentarii Mathematici Helvetici, ISSN 0010-2571, E-ISSN 1420-8946, Vol. 95, no 1, p. 183-209Article in journal (Refereed)
    Abstract [en]

    We study universality properties of the Epstein zeta function E-n(L,s) for lattices L of large dimension n and suitable regions of complex numbers s. Our main result is that, as n -> infinity, E-n(L,s) is universal in the right half of the critical strip as L varies over all n-dimensional lattices L. The proof uses a novel combination of an approximation result for Dirichlet polynomials, a recent result on the distribution of lengths of lattice vectors in a random lattice of large dimension and a strong uniform estimate for the error term in the generalized circle problem. Using the same approach we also prove that, as n -> infinity, E-n(L-1,s) - E-n(L-2,s) is universal in the full half-plane to the right of the critical line as E-n(L,s) varies over all pairs of n-dimensional lattices. Finally, we prove a more classical universality result for E-n(L,s) in the s-variable valid for almost all lattices L of dimension n. As part of the proof we obtain a strong bound of E-n(L,s) on the critical line that is subconvex for n >= 5 and almost all n-dimensional lattices L.

  • 11.
    Bergwall, Andreas
    Örebro University, School of Science and Technology.
    Students’ arguments about the growth of a two-variable function2023In: Proceedings of the Thirteenth Congress of the European Society for Research in Mathematics Education (CERME13) / [ed] Paul Drijvers; Csaba Csapodi; Hanna Palmér; Katalin Gosztonyi; Eszter Kónya, Alfréd Rényi Institute of Mathematics / ERME , 2023, p. 2275-2282Conference paper (Refereed)
    Abstract [en]

    Calculus is a central part of the curriculum for tertiary educations in mathematics, science, and technology. At its core lies the concept of derivative, which is known to be problematic for many students. As the corresponding multi-variable concepts of partial derivative, gradient, and directional derivative are not mathematically equivalent, it is essential for students to learn their relations and what they represent geometrically. In this paper, 20 students’ written solutions to an exam problem about the growth of a two-variable function are studied. The warrants they present for their claims are characterized in terms of which representations, concepts, connections, and calculations they use. The findings indicate that students who solve the problem by calculation of directional derivatives are less explicit with their warrants than students who rely on properties of the gradient vector. While the first group only uses algebraic representations, the second combines algebraic and graphical representations.

    Download full text (pdf)
    Students’ arguments about the growth of a two-variable function
  • 12.
    Dmytryshyn, Andrii
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Miniversal deformations of pairs of skew-symmetric matrices under congruence2016In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 506, p. 506-534Article in journal (Refereed)
    Abstract [en]

    Miniversal deformations for pairs of skew-symmetric matrices under congruence are constructed. To be precise, for each such a pair (A, B) we provide a normal form with a minimal number of independent parameters to which all pairs of skew-symmetric matrices ((A) over tilde (,) (B) over tilde), close to (A, B) can be reduced by congruence transformation which smoothly depends on the entries of the matrices in the pair ((A) over tilde (,) (B) over tilde). An upper bound on the distance from such a miniversal deformation to (A, B) is derived too. We also present an example of using miniversal deformations for analyzing changes in the canonical structure information (i.e. eigenvalues and minimal indices) of skew-symmetric matrix pairs under perturbations.

    Download full text (pdf)
    Miniversal deformations of pairs of skew-symmetric matrices under congruence
  • 13.
    Dmytryshyn, Andrii
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Miniversal deformations of pairs of symmetric matrices under congruence2019In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 568, p. 84-105Article in journal (Refereed)
    Abstract [en]

    For each pair of complex symmetric matrices (A, B) we provide a normal form with a minimal number of independent parameters, to which all pairs of complex symmetric matrices ((A) over tilde (B) over tilde), close to (A, B) can be reduced by congruence transformation that smoothly depends on the entries of (A ) over tilde and (B) over tilde. Such a normal form is called a miniversal deformation of (A, B) under congruence. A number of independent parameters in the miniversal deformation of a symmetric matrix pencil is equal to the codimension of the congruence orbit of this symmetric matrix pencil and is computed too. We also provide an upper bound on the distance from (A, B) to its miniversal deformation.

  • 14.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Klymchuk, Tetiana
    Universitat Politècnica de Catalunya, Barcelona, Spain; Taras Shevchenko National University, Kiev, Ukraine.
    Sergeichuk, Vladimir V.
    Institute of Mathematics, Kiev, Ukraine.
    Generalization of Roth's solvability criteria to systems of matrix equations2017In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 527, p. 294-302Article in journal (Refereed)
    Abstract [en]

    W.E. Roth (1952) proved that the matrix equation AX - XB = C has a solution if and only if the matrices [Graphics] and [Graphics] are similar. A. Dmytryshyn and B. Kagstrom (2015) extended Roth's criterion to systems of matrix equations A(i)X(i')M(i) - (NiXi"Bi)-B-sigma i = Ci (i = 1,..., s) with unknown matrices X1,, X-t, in which every X-sigma is X, X-T, or X*. We extend their criterion to systems of complex matrix equations that include the complex conjugation of unknown matrices. We also prove an analogous criterion for systems of quaternion matrix equations. (C) 2017 Elsevier Inc. All rights reserved.

  • 15.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Kågström, Bo
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Klimenko, Lena
    National Technical University of Ukraine “Kyiv Polytechnic Institute”, Kiev, Ukraine.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Change of the congruence canonical form of 2-by-2 and 3-by-3 matrices under perturbations and bundles of matrices under congruence2015In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 469, p. 305-334Article in journal (Refereed)
    Abstract [en]

    We construct the Hasse diagrams G2 and G3 for the closure ordering on the sets of congruence classes of 2 × 2 and 3 × 3 complex matrices. In other words, we construct two directed graphs whose vertices are 2 × 2 or, respectively, 3 × 3 canonical matrices under congruence, and there is a directed path from A to B if and only if A can be transformed by an arbitrarily small perturbation to a matrix that is congruent to B. A bundle of matrices under congruence is defined as a set of square matrices A for which the pencils A + λAT belong to the same bundle under strict equivalence. In support of this definition, we show that all matrices in a congruence bundle of 2 × 2 or 3 × 3 matrices have the same properties with respect to perturbations. We construct the Hasse diagrams G2 B and G3 B for the closure ordering on the sets of congruence bundles of 2 × 2 and, respectively, 3 × 3 matrices. We find the isometry groups of 2 × 2 and 3 × 3 congruence canonical matrices.

  • 16.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Miniversal deformations of matrices of bilinear forms2012In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 436, no 7, p. 2670-2700Article in journal (Refereed)
    Abstract [en]

    Arnold [V.I. Arnold, On matrices depending on parameters, Russian Math. Surveys 26 (2) (1971) 29–43] constructed miniversal deformations of square complex matrices under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it can be reduced by similarity transformations that smoothly depend on the entries of B. We construct miniversal deformations of matrices under congruence.

  • 17.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Miniversal deformations of matrices under *congruence and reducing transformations2014In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 446, no April, p. 388-420Article in journal (Refereed)
    Abstract [en]

    Arnold (1971) [1] constructed a miniversal deformation of a square complex matrix under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it can be reduced by similarity transformations that smoothly depend on the entries of B. We give miniversal deformations of matrices of sesquilinear forms; that is, of square complex matrices under *congruence, and construct an analytic reducing transformation to a miniversal deformation. Analogous results for matrices under congruence were obtained by Dmytryshyn, Futorny, and Sergeichuk (2012) [11].

  • 18.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Johansson, Stefan
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Kågström, Bo
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Canonical structure transitions of system pencils2017In: SIAM Journal on Matrix Analysis and Applications, ISSN 0895-4798, E-ISSN 1095-7162, Vol. 38, no 4, p. 1249-1267Article in journal (Refereed)
    Abstract [en]

    We investigate the changes of the canonical structure information under small perturbations for a system pencil associated with a (generalized) linear time-invariant state-space system. The equivalence class of the pencil is taken with respect to feedback-injection equivalence transformations. The results allow us to track possible changes of important linear system characteristics under small perturbations.

  • 19.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Kågström, Bo
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Coupled Sylvester-type Matrix Equations and Block Diagonalization2015In: SIAM Journal on Matrix Analysis and Applications, ISSN 0895-4798, E-ISSN 1095-7162, Vol. 36, no 2, p. 580-593Article in journal (Refereed)
    Abstract [en]

    We prove Roth-type theorems for systems of matrix equations including an arbitrary mix of Sylvester and $\star$-Sylvester equations, in which the transpose or conjugate transpose of the unknown matrices also appear. In full generality, we derive consistency conditions by proving that such a system has a solution if and only if the associated set of $2 \times 2$ block matrix representations of the equations are block diagonalizable by (linked) equivalence transformations. Various applications leading to several particular cases have already been investigated in the literature, some recently and some long ago. Solvability of these cases follow immediately from our general consistency theory. We also show how to apply our main result to systems of Stein-type matrix equations.

  • 20.
    Drin, Iryna
    et al.
    Chernivtsi Institute of Trade and Economics of Kyiv National University of Trade and economics, Ukraine.
    Drin, Svitlana
    National University of “Kyiv-Mohyla Academy", Ukraine.
    Drin, Yaroslav
    Yuriy Fedkovych Chernivtsi National University, Ukraine.
    About one problem for equation of fractal diffusion with argument deviation2017In: Proceedings of the Sixth International Conference on «INFORMATICS AND COMPUTER TECHNICS PROBLEMS» (PICT – 2017), 2017, p. 29-31Conference paper (Other academic)
  • 21.
    Drin, Iryna
    et al.
    Chernivtsi Institute of Trade and Economics of Kyiv National University of Trade and economics, Ukraine.
    Drin, Svitlana
    National University of “Kyiv-Mohyla Academy”, Ukraine.
    Drin, Yaroslav
    Yuriy Fedkovych Chernivtsi National University, Ukraine.
    The boundary problem by variable t for equation of fractal diffusion with argument deviation2017In: Наукові записки НаУКМА. Фізико-математичні науки., no 201, p. 5-7Article in journal (Other academic)
    Abstract [en]

    For a quasilinear pseudodifferential equation with fractional derivative by time variable t with order a e (0,1), the second derivative by space variable x and the argument deviation with the help o f the stepmethod we prove the solvability o f the boundary problem with two unknown functions by variable t.

  • 22.
    Drin, Ya.
    et al.
    Yuriy Fedkovych Chernivtsi National University, Ukraine.
    Drin, I.
    Chernivtsi Trade and Economic Institute of the State Trade University, Ukraine.
    Drin, Svitlana
    Örebro University, Örebro University School of Business. National University “Kyiv-Mohyla Academy”, Ukraine.
    The Cauchy problem for quasilinear equation with nonstationary diffusion coefficient2023In: XХXVIII International Conference PROBLEMS OF DECISION MAKING UNDER UNCERTAINTIES (PDMU-2023): September 11 – 15, 2023: ABSTRACTS, 2023, p. 36-37Conference paper (Other academic)
  • 23.
    Drin, Yaroslav M.
    et al.
    Department of Mathematical Problems of Management and Cybernetics, Institute of Physical, Technical and Computer Sciences, Yuriy Fedkovych Chernivtsi National University, Chernivtsi, Ukraine.
    Drin, Iryna I.
    Department of Finance, Accounting and Taxation, Chernivtsi Trade and Economic Institute of the State Trade University, Chernivtsi, Ukraine.
    Drin, Svitlana S.
    Örebro University, Örebro University School of Business. Department of Mathematics, National University of Kyiv-Mohyla Academy, Kyiv, Ukraine.
    The Analytical View of Solution of the First Boundary Value Problem for the Nonlinear Equation of Heat Conduction with Deviation of the Argument2023In: Journal of Optimization, Differential Equations and Their Applications, ISSN 2617-0108, Vol. 31, no 2, p. 115-124Article in journal (Refereed)
    Abstract [en]

    In this article, for the first time, the first boundary value problem for the equation of thermal conductivity with a variable diffusion coefficient and with a nonlinear term, which depends on the sought function with the deviation of the argument, is solved. For such equations, the initial condition is set on a certain interval. Physical and technical reasons for delays can be transport delays, delays in information transmission, delays in decision-making, etc. The most natural are delays when modeling objects in ecology, medicine, population dynamics, etc. Features of the dynamics of vehicles in different environments (water, land, air) can also be taken into account by introducing a delay. Other physical and technical interpretations are also possible, for example, the molecular distribution of thermal energy in various media (solid bodies, liquids, etc.) is modeled by heat conduction equations. The Green’s function of the first boundary value problem is constructed for the nonlinear equation of heat conduction with a deviation of the argument, its properties are investigated, and the formula for the solution is established.

  • 24.
    Edman, Rickard
    et al.
    Örebro University, School of Science and Technology.
    Östberg, Markus
    Örebro University, School of Science and Technology.
    Γ-funktionenEn kort introduktion2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 25.
    Fasi, Massimiliano
    et al.
    Örebro University, School of Science and Technology.
    Feng, Jishe
    School of Mathematics and Statistics, Longdong University, Qingyang, Gansu, People’s Republic of China.
    Porzio, Gian Maria Negri
    Department of Mathematics, University of Manchester, United Kingdom.
    CORRIGENDUM TO "DETERMINANTS OF NORMALIZED BOHEMIAN UPPER HESSENBERG MATRICES" [ELECTRON. J. OF LINEAR ALGEBRA 36 (2020) 352-366]2021In: The Electronic Journal of Linear Algebra, ISSN 1537-9582, E-ISSN 1081-3810, Vol. 37, p. 160-162Article in journal (Refereed)
    Abstract [en]

    An amended version of Proposition 3.6 of [Fasi and Negri Porzio, Electron. J. Linear Algebra 36:352{366, 2020] is presented. The result shows that the set of possible determinants of upper Hessenberg matrices with ones on the subdiagonal and elements in the upper triangular part drawn from the set {-1, 1} is {2k vertical bar k is an element of <-2(n-2), 2(n-2)>}, instead of {2k vertical bar k is an element of <-n + 1, n - 1 >} as previously stated. This does not affect the main results of the article being corrected and shows that Conjecture 20 in the Characteristic Polynomial Database is true.

  • 26.
    Flodén, L.
    et al.
    Department of Quality technology and management, mechanical engineering and mathematics, Mid Sweden University, Östersund, Sweden.
    Holmbom, A.
    Department of Quality technology and management, mechanical engineering and mathematics, Mid Sweden University, Östersund, Sweden.
    Lobkova, T.
    Department of Quality technology and management, mechanical engineering and mathematics, Mid Sweden University, Östersund, Sweden.
    Olsson Lindberg, M.
    Department of Quality technology and management, mechanical engineering and mathematics, Mid Sweden University, Östersund, Sweden.
    Zhang, Ye
    Örebro University, School of Science and Technology.
    A discussion of a homogenization procedure for a degenerate linear hyperbolic-parabolic problem2017In: ICNPAA 2016 World Congress: 11th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences, Melville, USA: American Institute of Physics (AIP), 2017, Vol. 1798, no 1, article id 020177Conference paper (Refereed)
    Abstract [en]

    We study the homogenization of a hyperbolic-parabolic PDE with oscillations in one fast spatial scale. Moreover, the first order time derivative has a degenerate coefficient passing to infinity when ε → 0.We obtain a local problem which is of elliptic type, while the homogenized problem is also in some sense an elliptic problem but with the limit for ε−1∂tuε as an undetermined extra source term in the right-hand side. The results are somewhat surprising and work remains to obtain a fully rigorous treatment. Hence the last section is devoted to a discussion of the reasonability of our conjecture including numerical experiments.

  • 27.
    Jafari, Raheleh
    et al.
    Agder University College, Grimstad, Norway.
    Razvarz, Sina
    National Polytechnic Institute, Mexico City, Mexico.
    Gegov, Alexander
    University of Portsmouth, Portsmouth, UK.
    Paul, Satyam
    National Polytechnic Institute, Mexico City, Mexico.
    Keshtkar, Sajjad
    Universidad Nacional Autonoma de Mexico (UNAM), Mexico City, Mexico.
    Fuzzy Sumudu Transform Approach to Solving Fuzzy Differential Equations With Z-Numbers2019In: Advanced Fuzzy Logic Approaches in Engineering Science / [ed] Mangey Ram, Hershey, PA, USA: IGI Global , 2019, p. 18-48Chapter in book (Other academic)
    Abstract [en]

    Uncertain nonlinear systems can be modeled with fuzzy differential equations (FDEs) and the solutions of these equations are applied to analyze many engineering problems. However, it is very difficult to obtain solutions of FDEs. In this book chapter, the solutions of FDEs are approximated by utilizing the fuzzy Sumudu transform (FST) method. Here, the uncertainties are in the sense of fuzzy numbers and Z-numbers. Important theorems are laid down to illustrate the properties of FST. This new technique is compared with Average Euler method and Max-Min Euler method. The theoretical analysis and simulation results show that the FST method is effective in estimating the solutions of FDEs.

  • 28.
    Yousefnezhad, Mohsen
    et al.
    School of Mathematics, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran.
    Mohammadi, Seyyed Abbas
    Department of Mathematics, College of Sciences, Yasouj University, Yasouj, Iran.
    Bozorgnia, Farid
    Örebro University, School of Science and Technology.
    A free boundary problem for a predator-prey model with nonlinear prey-taxix2018In: Applications of Mathematics, ISSN 0862-7940, E-ISSN 1572-9109, Vol. 63, no 2, p. 125-147Article in journal (Refereed)
    Abstract [en]

    This paper deals with a reaction-diffusion system modeling a free boundary problem of the predator-prey type with prey-taxis over a one-dimensional habitat. The free boundary represents the spreading front of the predator species. The global existence and uniqueness of classical solutions to this system are established by the contraction mapping principle. With an eye on the biological interpretations, numerical simulations are provided which give a real insight into the behavior of the free boundary and the stability of the solutions.

  • 29.
    Zhang, Ye
    et al.
    Örebro University, School of Science and Technology.
    Lukyanenko, Dmitry V.
    Department of Mathematics, Faculty of Physics, M. V. Lomonosov Moscow State University, Moscow, Russian Federation.
    Yagola, Anatoly G.
    Department of Mathematics, Faculty of Physics, M. V. Lomonosov Moscow State University, Moscow, Russian Federation.
    An optimal regularization method for convolution equations on the sourcewise represented set2015In: Journal of Inverse and Ill-Posed Problems, ISSN 0928-0219, E-ISSN 1569-3945, Vol. 23, no 5, p. 465-475Article in journal (Refereed)
    Abstract [en]

    In this article, we consider an inverse problem for the integral equation of the convolution typein a multidimensional case. This problem is severely ill-posed. To deal with this problem, using a prioriinformation (sourcewise representation) based on optimal recovery theory we propose a new method. Theregularization and optimization properties of this method are proved. An optimal minimal a priori error ofthe problem is found. Moreover, a so-called optimal regularized approximate solution and its correspondingerror estimation are considered. Eciency and applicability of this method are demonstrated in a numericalexample of the image deblurring problem with noisy data.

1 - 29 of 29
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • 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