| 1. |
- Larsson, Torbjörn, et al.
(författare)
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One-parametric analysis of column-oriented linear programs
- 2023
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Ingår i: Oncoscience. - : ELSEVIER. - 0255-0156 .- 2214-7160. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- A linear optimization problem which is amenable to column generation and contains a single parameter in the objective function is considered. We extend and adapt the standard linear programming column generation scheme to effectively and efficiently solve this problem for all values of the parameter. As a potential application we consider bi-objective discrete optimization and describe how the one-parametric column generation scheme can be used to form an outer approximation of the Pareto frontier for such a problem.
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| 2. |
- Aleman, Alexandru, et al.
(författare)
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A Quantitative Estimate for Bounded Point Evaluations in P-t(mu)-spaces
- 2010
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Ingår i: Topics In Operator Theory: Operators, Matrices And Analytic Functions, Vol 1. - 0255-0156. ; 202, s. 1-10
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Konferensbidrag (refereegranskat)abstract
- In this note we explain how X. Tolsa's work on analytic capacity and an adaptation of Thomson's coloring scheme can be used to obtain a quantitative version of J. Thomson's theorem on bounded point evaluations for P-t(mu)-spaces.
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| 3. |
- Bennewitz, C., et al.
(författare)
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The spectral problem for the dispersionless camassa-holm equation
- 2016
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Ingår i: Operator Theory: Advances and Applications. - 0255-0156. ; 255, s. 67-90
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Tidskriftsartikel (refereegranskat)abstract
- We present a spectral and inverse spectral theory for the zero dispersion spectral problem associated with the Camassa-Holm equation. This is an alternative approach to that in [10] by Eckhardt and Teschl.
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| 4. |
- Carling, Kenneth, et al.
(författare)
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Testing the gravity p-median model empirically
- 2015
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Ingår i: Operations Research Perspectives. - : Elsevier. - 2214-7160. ; 2:124
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Tidskriftsartikel (refereegranskat)abstract
- Regarding the location of a facility, the presumption in the widely used p-median model is that the customer opts for the shortest route to the nearest facility. However, this assumption is problematic on free markets since the customer is presumed to gravitate to a facility by the distance to and the attractiveness of it. The recently introduced gravity p-median model offers an extension to the p-median model that account for this. The model is therefore potentially interesting, although it has not yet been implemented and tested empirically. In this paper, we have implemented the model in an empirical problem of locating vehicle inspections, locksmiths, and retail stores of vehicle spare-parts for the purpose of investigating its superiority to the p-median model. We found, however, the gravity p-median model to be of limited use for the problem of locating facilities as it either gives solutions similar to the p-median model, or it gives unstable solutions due to a non-concave objective function.
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| 5. |
- Christiansen, Jacob Stordal, et al.
(författare)
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Asymptotics of Chebyshev Polynomials, III. Sets saturating Szegö, Schiefermayr, and Totik-Widom Bounds
- 2020
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Ingår i: Analysis as a Tool in Mathematical Physics. - Cham : Springer International Publishing. - 0255-0156 .- 2296-4878. - 9783030315306 - 9783030315313 ; 276, s. 231-246
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Bokkapitel (refereegranskat)abstract
- We determine which sets saturate the Szegő and Schiefermayr lower bounds on the norms of Chebyshev Polynomials. We also discuss sets that saturate our optimal Totik–Widom upper bound.
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| 6. |
- Dencker, Nils
(författare)
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Solvability and complex limit bicharacteristics
- 2020
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Ingår i: Operator Theory : Advances and Applications - Advances and Applications. - Cham : Springer International Publishing. - 0255-0156 .- 2296-4878. ; 276, s. 247-276
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Bokkapitel (refereegranskat)abstract
- We shall study the solvability of pseudodifferential operators which are not of principal type. The operator will have complex principal symbol satisfying condition (Ψ) and we shall consider the limits of semibicharacteristics at the set where the principal symbol vanishes of at least second order. The convergence shall be as smooth curves, and we shall assume that the normalized complex Hamilton vector field of the principal symbol over the semicharacteristics converges to a real vector field. Also, we shall assume that the linearization of the real part of the normalized Hamilton vector field at the semibicharacteristic is tangent to and bounded on the tangent space of a Lagrangean submanifold at the semibicharacteristics, which we call a grazing Lagrangean space. Under these conditions one can invariantly define the imaginary part of the subprincipal symbol. If the quotient of the imaginary part of the subprincipal symbol with the norm of the Hamilton vector field switches sign from − to + on the bicharacteristics and becomes unbounded as they converge to the limit, then the operator is not solvable at the limit bicharacteristic.
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| 7. |
- Dijksma, Aad, et al.
(författare)
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Approximation of N∞ κ -functions I : Models and regularization
- 2008
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Ingår i: Spectral Theory in Inner Product Spaces and Applications - 6th Workshop on Operator Theory in Krein Spaces and Operator Polynomials, 2006. - 0255-0156 .- 2296-4878. - 9783764389109 ; 188, s. 87-112
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Konferensbidrag (refereegranskat)abstract
- The class N∞ κ consists of all generalized Nevanlinna functions N with κ negative squares for which the root space at ∞ of the self-adjoint relation in the minimal model (short for self-adjoint operator realization) of N contains a κ-dimensional non-positive subspace. In this paper we discuss two specific models for the function N ∈ N∞ κ: one associated with the irreducible representation of N and one associated with a regularized version of this representation which need not be irreducible. The state space in each of these models is a reproducing kernel Pontryagin space whose reproducing kernel is a matrix function constructed from the data in the representation.
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| 8. |
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| 9. |
- Langer, Matthias, et al.
(författare)
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On norms in indefinite inner product spaces
- 2010
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Ingår i: Recent Advances in Operator Theory in Hilbert and Krein Spaces. - 2296-4878 .- 0255-0156. - 9783034601795 ; 198, s. 259-264
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Konferensbidrag (refereegranskat)abstract
- In a Krein space various norms can be defined by choosing different underlying fundamental decompositions. In this note we consider this dependence explicitly and draw the conclusion that - even in a Pontryagin space - there does not exist a natural choice motivated by minimizing properties.
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| 10. |
- Rozenblioum, Grigori, 1948
(författare)
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Nikolai’s spaces
- 2020
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Ingår i: Operator Theory: Advances and Applications. - Cham : Springer International Publishing. - 0255-0156 .- 2296-4878. - 9783030446512 ; 279, s. 25-26
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Oh, it is a hard job to write an article for a jubilee of such a great person. Surely, it is not his first jubilee, and all the nice words have been already said, and all the proper jokes are already laughed at. Thus, about Nikolai, there are two excellent detailed reports [1, 2].
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| 11. |
- Rozenblioum, Grigori, 1948, et al.
(författare)
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Toeplitz operators via sesquilinear forms
- 2018
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Ingår i: Operator Theory: Advances and Applications. - Cham : Springer International Publishing. - 0255-0156 .- 2296-4878. ; 262, s. 287-304
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The classical theory of Toeplitz operators in spaces of analytic functions deals usually with symbols that are bounded measurable functions on the domain in question. A further extension of the theory was made for symbols being unbounded functions, measures, and compactly supported distributions, all of them subject to some restrictions. In the context of a reproducing kernel Hilbert space we propose a certain common framework, based upon the extensive use of the language of sesquilinear form, for definition of Toeplitz operators for a ‘maximally wide’ class of ‘highly singular’ symbols. Besides covering all previously considered cases, such an approach permits us to introduce a further substantial extension of the class of admissible symbols that generate bounded Toeplitz operators. Although our approach is unified for all reproducing kernel Hilbert spaces, concrete operator consideration are given for Toeplitz operators acting on the standard Fock space, on the standard Bergman space on the unit disk (two leading examples in the classical theory of Toeplitz operators), and on the so-called Herglotz space consisting of the solutions of the Helmholtz equation.
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| 12. |
- Rozenblioum, Grigori, 1948, et al.
(författare)
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Toeplitz operators with singular symbols in polyanalytic Bergman spaces on the half-plane
- 2020
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Ingår i: Operator Theory: Advances and Applications. - Cham : Springer International Publishing. - 0255-0156 .- 2296-4878. - 9783030446512 ; 279, s. 403-421
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Using the approach based on sesquilinear forms, we introduce Toeplitz operators in the analytic Bergman space on the upper half-plane with strongly singular symbols, derivatives of measures. Conditions for boundedness and compactness of such operators are found. A procedure of reduction of Toeplitz operators in Bergman spaces of polyanalytic functions to operators with singular symbols in the analytic Bergman space by means of the creation-annihilation structure is elaborated, which leads to the description of the properties of the former operators.
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| 13. |
- Saari, Juhamatti, et al.
(författare)
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Detecting operation regimes using unsupervised clustering with infected group labelling to improve machine diagnostics and prognostics
- 2018
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Ingår i: Operations Research Perspectives. - : Elsevier. - 2214-7160. ; 5, s. 232-244
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Tidskriftsartikel (refereegranskat)abstract
- Estimating the stress level of components while operation modes are varying is a key issue for many prognostic models in condition monitoring. The identification of operation profiles during production is therefore important. Clustering condition monitoring data with regard to operation regimes will provide more detailed information about the variation of stress levels during production. The distribution of the operation regimes can then support prognostics by revealing the cause-and-effect relationship between the operation regimes and the wear level of components.In this study unsupervised clustering technique was used for detecting operation regimes for an underground LHD (load-haul-dump machine) by using features extracted from vibration signals measured on the front axle and the speed of the Cardan axle. The clusters were also infected with a small portion of the data to obtain the corresponding labels for each cluster. Promising results were obtained where each sought-for operation regime was detected in a sensible manner using vibration RMS values together with speed.
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