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Wyświetlanie 1-15 z 39
Tytuł:
A computationally inexpensive algorithm for determining outer and inner enclosures of nonlinear mappings of ellipsoidal domains
Autorzy:
Rauh, Andreas
Jaulin, Luc
Powiązania:
https://bibliotekanauki.pl/articles/2055165.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
bounded uncertainty
guaranteed enclosures
ellipsoidal enclosures
inner approximations
outer approximations
nonlinear system
confidence interval
niepewność ograniczona
układ nieliniowy
przedział ufności
Opis:
A wide variety of approaches for set-valued simulation, parameter identification, state estimation as well as reachability, observability and stability analysis for nonlinear discrete-time systems involve the propagation of ellipsoids via nonlinear functions. It is well known that the corresponding image sets usually possess a complex shape and may even be nonconvex despite the convexity of the input data. For that reason, domain splitting procedures are often employed which help to reduce the phenomenon of overestimation that can be traced back to the well-known dependency and wrapping effects of interval analysis. In this paper, we propose a simple, yet efficient scheme for simultaneously determining outer and inner ellipsoidal range enclosures of the solution for the evaluation of multi-dimensional functions if the input domains are themselves described by ellipsoids. The Hausdorff distance between the computed enclosure and the exact solution set reduces at least linearly when decreasing the size of the input domains. In addition to algebraic function evaluations, the proposed technique is-for the first time, to our knowledge-employed for quantifying worst-case errors when extended Kalman filter-like, linearization-based techniques are used for forecasting confidence ellipsoids in a stochastic setting.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2021, 31, 3; 399--415
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A New Approach to Measurement of Frequency Shifts Using the Principle of Rational Approximations
Autorzy:
Murrieta-Rico, F. N.
Petranovskii, V.
Sergiyenko, O. Y.
Hernandez-Balbuena, D.
Lindner, L.
Powiązania:
https://bibliotekanauki.pl/articles/220851.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
frequency measurement
rational approximations
sensors
Opis:
When a frequency domain sensor is under the effect of an input stimulus, there is a frequency shift at its output. One of the most important advantages of such sensors is their converting a physical input parameter into time variations. In consequence, changes of an input stimulus can be quantified very precisely, provided that a proper frequency counter/meter is used. Unfortunately, it is well known in the time-frequency metrology that if a higher accuracy in measurements is needed, a longer time for measuring is required. The principle of rational approximations is a method to measure a signal frequency. One of its main properties is that the time required for measuring decreases when the order of an unknown frequency increases. In particular, this work shows a new measurement technique, which is devoted to measuring the frequency shifts that occur in frequency domain sensors. The presented research result is a modification of the principle of rational approximations. In this work a mathematical analysis is presented, and the theory of this new measurement method is analysed in detail. As a result, a new formalism for frequency measurement is proposed, which improves resolution and reduces the measurement time.
Źródło:
Metrology and Measurement Systems; 2017, 24, 1; 45-56
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Algorithms solving the Internet shopping optimization problem with price discounts
Autorzy:
Musial, J.
Pecero, J. E.
Lopez-Loces, M. C.
Fraire-Huacuja, H. J.
Bouvry, P.
Blazewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/200209.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
e-commerce
Internet shopping
applications of operations research
approximations
algorithms
heuristics
combinatorial optimization
zakupy przez Internet
wnioski z badań operacyjnych
aproksymacje
algorytmy
heurystyki
optymalizacja kombinatoryczna
Opis:
The Internet shopping optimization problem arises when a customer aims to purchase a list of goods from a set of web-stores with a minimum total cost. This problem is NP-hard in the strong sense. We are interested in solving the Internet shopping optimization problem with additional delivery costs associated to the web-stores where the goods are bought. It is of interest to extend the model including price discounts of goods. The aim of this paper is to present a set of optimization algorithms to solve the problem. Our purpose is to find a compromise solution between computational time and results close to the optimum value. The performance of the set of algorithms is evaluated through simulations using real world data collected from 32 web-stores. The quality of the results provided by the set of algorithms is compared to the optimal solutions for small-size instances of the problem. The optimization algorithms are also evaluated regarding scalability when the size of the instances increases. The set of results revealed that the algorithms are able to compute good quality solutions close to the optimum in a reasonable time with very good scalability demonstrating their practicability.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 3; 505-516
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An improved comparison of three rough set approaches to missing attribute values
Autorzy:
Grzymala-Busse, J. W.
Grzymala-Busse, W. J.
Hippe, Z. S.
Rząsa, W.
Powiązania:
https://bibliotekanauki.pl/articles/969797.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
incomplete data sets
missing attribute values
approximations for incomplete data
LERS data mining system
MLEM2 algorithm
Opis:
In a previous paper three types of missing attribute values: lost values, attribute-concept values and "do not care" conditions were compared using six data sets. Since previous experimental results were affected by large variances due to conducting experiments on different versions of a given data set, we conducted new experiments, using the same pattern of missing attribute values for all three types of missing attribute values and for both certain and possible rules. Additionally, in our new experiments, the process of incremental replacing specified values by missing attribute values was terminated when entire rows of the data sets were full of missing attribute values. Finally, we created new, incomplete data sets by replacing the specified values starting from 5% of all attribute values, instead of 10% as in the previous experiments, with an increment of 5% instead of the previous increment of 10%. As a result, it is becoming more clear that the best approach to missing attribute values is based on lost values, with small difference between certain and possible rules, and that the worst approach is based on "do not care" conditions, certain rules. With our improved experimental setup it is also more clear that for a given data set the type of the missing attribute values should be selected individually.
Źródło:
Control and Cybernetics; 2010, 39, 2; 469-486
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Approximation of the probability of insolvability of a portfolio
Autorzy:
Pusz, Robert
Rolski, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/747757.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Matematyczne
Tematy:
Finance, portfolios, investment
Approximations to distributions (nonasymptotic)
Opis:
The authors review and criticize different approaches for calculations of ruin probabilities in one or multiperiod life insurance portfolios. They claim that precise calculations are time-consuming and in some cases (especially in the multiperiod ones) are practically inaccessible even if theoretical formulae are available. The reviewer considers that, because parameters of any such model must be estimated somehow, then precision in calculations cannot be achieved. For example, the authors assume a constant interest rate, which is not precisely the best way of doing things for the multiperiod model, and the precision must be lost anyway. Particularly, the authors show that the use of the central limit theorem is not appropriate; errors are large. The precise recursive method is difficult to perform for a large portfolio. The authors propose the importance of the Monte Carlo sampling method instead of the crude one. Their estimations are based on some probabilistic inequalities such as a version of Chernoff's (saddle point), also analyzed by S. Asmussen [Stochastic simulation with a view toward stochastic processes, Univ. Aarhus, Aarhus, 1999; Zbl 0981.65013], and are related to the approximation from D. Blackwell and J. L. Hodges, Jr. [Ann. Math. Statist. 30 (1959), 1113–1120; MR0112197].
Źródło:
Mathematica Applicanda; 2005, 33, 47/06
1730-2668
2299-4009
Pojawia się w:
Mathematica Applicanda
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computational Methods for Stochastic Differential Equations and Stochastic Partial Differential Equations Involving Standard Brownian and Fractional Brownian Motion
Autorzy:
Shea, J.
Zachariou, I.
Pasik-Duncan, B.
Powiązania:
https://bibliotekanauki.pl/articles/115867.pdf
Data publikacji:
2011
Wydawca:
Fundacja na Rzecz Młodych Naukowców
Tematy:
Brownian Motion (BM)
fractional Brownian Motion (fBM)
SDEs
SPDEs
Numerical Approximations
Opis:
As more applied science researchers are attempting to use Stochastic Differential Equations (SDEs) as well as Stochastic Partial Differential Equations (SPDEs) in their modeling, especially when involving Fractional Brownian Motion (fBM), one common issue appears: an exact solution cannot always be found. For cases involving SPDEs, exact solutions commonly do not exist and approximation schemes for their solution are typically still in development. Therefore, in this paper, we test various Numerical methods in solving SDEs and SPDEs with standard BM that have non-linear coeffi cients. In addition we extend our results to problems with fBM.
Źródło:
Challenges of Modern Technology; 2011, 2, 2; 3-12
2082-2863
2353-4419
Pojawia się w:
Challenges of Modern Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Continuous selections and approximations in α-convex metric spaces
Autorzy:
Kowalska, A.
Powiązania:
https://bibliotekanauki.pl/articles/729415.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
generalized convexity
selections
relative selections
graph-approximations
Opis:
In the paper, the notion of a generalized convexity was defined and studied from the view-point of the selection and approximation theory of set-valued maps. We study the simultaneous existence of continuous relative selections and graph-approximations of lower semicontinuous and upper semicontinuous set-valued maps with α-convex values having nonempty intersection.
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2007, 27, 2; 265-294
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Difference melt model
Autorzy:
Kazhikenova, Saule Sh.
Shaltakov, Sagyndyk N.
Nussupbekov, Bekbolat R.
Powiązania:
https://bibliotekanauki.pl/articles/1845514.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Navier-Stokes equations
hydrodynamic
approximations
mathematical models
melt
Opis:
The basic objective of the research is to construct a difference model of the melt motion. The existence of a solution to the problem is proven in the paper. It is also proven the convergence of the difference problem solution to the original problem solution of the melt motion. The Rothe method is implemented to study the Navier-Stokes equations, which provides the study of the boundary value problems correctness for a viscous incompressible flow both numerically and analytically.
Źródło:
Archives of Control Sciences; 2021, 31, 3; 607-627
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Difference melt model
Autorzy:
Kazhikenova, Saule Sh.
Shaltakov, Sagyndyk N.
Nussupbekov, Bekbolat R.
Powiązania:
https://bibliotekanauki.pl/articles/1845525.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Navier-Stokes equations
hydrodynamic
approximations
mathematical models
melt
Opis:
The basic objective of the research is to construct a difference model of the melt motion. The existence of a solution to the problem is proven in the paper. It is also proven the convergence of the difference problem solution to the original problem solution of the melt motion. The Rothe method is implemented to study the Navier-Stokes equations, which provides the study of the boundary value problems correctness for a viscous incompressible flow both numerically and analytically.
Źródło:
Archives of Control Sciences; 2021, 31, 3; 607-627
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dimensional contact problem for the prestressed cylindrical punch and layer lying without friction on a rigid foundation
Przestrzenne zadanie brzegowe dla wstępnie napiętej cylindrycznej stempli i warstwy leżącej bez tarcia na sztywnej podstawie
Autorzy:
Iaretska, N.
Powiązania:
https://bibliotekanauki.pl/articles/136128.pdf
Data publikacji:
2014
Wydawca:
Wyższa Szkoła Techniczno-Ekonomiczna w Szczecinie
Tematy:
theory of linear elasticity
initial tension
Henkel integrals
Fredholm equation
method of consecutive approximations
liniowa teoria sprężystości
próbne naprężenia
całki Henkelego
równanie Fredholma
metoda kolejnych przybliżeń
Opis:
Introduction and aim: The article deals with the problem of the elastic cylindrical die pressure on the layer with initial stresses within the framework of linearized elasticity theory. In general, the research was carried out for the theory of great initial deformations and two variants of the theory of small initial deformations with arbitrary structure of elastic potential. Material and methods: The mode of deformation in the elastic layer with initial stresses is defined with the help of harmonic functions by way of Henkel integrals. It reduces the task to Fredholm equations and the method of consecutive approximations. Results: We obtained a correlation between the components of potential vector and tensor of deformations in the case of equal roots. The solutions are defined by way of lines with the help of infinitive system of constants, derivated from the regular and linear algebraic system. Conclusion: The research investigates the influence of initial stresses on the law of distribution of contact stresses in the layer and punch with initial stresses.
Wstęp i cel: W ramach liniowej teorii sprężystości, należy rozważyć zadania o ciśnieniu sprężystego cylindrycznego stempla na warstwę z początkowym napięciem. Badanie wykonane w sposób ogólny do teorii znacznych odkształceń i dwóch wariantów teorii początkowych małych odkształceń przy dowolnej strukturze sprężystego potencjału. Materiał i metody: Naprężenie-odkształcenie stan w elastyczne warstwie z początkowym napięciem określamy poprzez harmoniczne funkcje w postaci całki Henkelego, które pozwalają sprowadzić zadanie do całkowania równań typu Fredgolma i metody kolejnych przybliżeń. Wyniki: Otrzymano korelację pomiędzy współrzędnymi wektora przemieszczeń i tensora naprężeń w przypadku równych stopni. Rozwiązanie przedstawione w postaci szeregu przez nieskończony system stałych. Te stałe są zdefiniowane z układem regularnych równań liniowych. Wniosek: Zbadana kwestię wpływu naprężeń początkowych na prawo dystrybucji kontaktowych w warstwie i stempli z naprężeniami początkowymi.
Źródło:
Problemy Nauk Stosowanych; 2014, 2; 101-108
2300-6110
Pojawia się w:
Problemy Nauk Stosowanych
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discrete-time feedback stabilization
Autorzy:
Mitkowski, W.
Bauer, W.
Zagórowska, M.
Powiązania:
https://bibliotekanauki.pl/articles/229169.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
stabilization
feedback stabilization
finite dimensional stabilization
infinite dimensional systems
finite dimensional approximations
continuous-discrete system
Opis:
This paper presents an algorithm for designing dynamic compensator for infinitedimensional systems with bounded input and bounded output operators using finite dimensional approximation. The proposed method was then implemented in order to find the control function for thin rod heating process. The optimal sampling time was found depending on discrete output measurements.
Źródło:
Archives of Control Sciences; 2017, 27, 2; 309-322
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic and Viscoelastic Stresses of Nonlinear Rotating Functionally Graded Solid and Annular Disks with Gradually Varying Thickness
Autorzy:
Allam, M. N. M.
Tantawy, R.
Yousof, A.
Zenkour, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/139874.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nonlinear rotation
viscoelasticity
functionally graded materials
successive approximations method
solid and annular disks
gradually varying thickness
rotacja nieliniowa
lepkosprężystość
funkcjonalne materiały gradientowe
metoda kolejnych przybliżeń
dyski pierścieniowe i stałe
stopniowa zmiana grubości
Opis:
Analytical and numerical nonlinear solutions for rotating variable-thickness functionally graded solid and annular disks with viscoelastic orthotropic material properties are presented by using the method of successive approximations.Variable material properties such as Young’s moduli, density and thickness of the disk, are first introduced to obtain the governing equation. As a second step, the method of successive approximations is proposed to get the nonlinear solution of the problem. In the third step, the method of effective moduli is deduced to reduce the problem to the corresponding one of a homogeneous but anisotropic material. The results of viscoelastic stresses and radial displacement are obtained for annular and solid disks of different profiles and graphically illustrated. The calculated results are compared and the effects due to many parameters are discussed.
Źródło:
Archive of Mechanical Engineering; 2017, LXIV, 4; 423-440
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Error analysis of discrete approximations to bang-bang optimal control problems: the linear case
Autorzy:
Veliov, V. M.
Powiązania:
https://bibliotekanauki.pl/articles/970563.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
liniowy system sterowania
aproksymacja dyskretna
szacowanie błędów
linear control systems
discrete approximations
error estimates
Opis:
The paper presents an error estimate for Runge-Kutta direct discretizations of terminal optimal control problems for linear systems. The optimal control for such problems is typically discontinuous, and Lipschitz stability of the solution with respect to perturbations does not necessarily hold. The estimate (in terms of the optimal controls) is of first order if certain recently obtained sufficient conditions for structural stability hold, and of fractional order, otherwise. The main tool in the proof is the established relation between the local convexity index of the reachable set and the multiplicity of zeros of appropriate switching functions associated with the problem.
Źródło:
Control and Cybernetics; 2005, 34, 3; 967-982
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Error estimates for finite element approximations of elliptic control problems
Autorzy:
Alt, Walter
Bräutigam, Nils
Rösch, Arnd
Powiązania:
https://bibliotekanauki.pl/articles/729441.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Linear quadratic optimal control problems
elliptic equations
finite element approximations
error estimates
Opis:
We investigate finite element approximations of one-dimensional elliptic control problems. For semidiscretizations and full discretizations with piecewise constant controls we derive error estimates in the maximum norm.
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2007, 27, 1; 7-22
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evolution equations with parameter in the hyperbolic case
Autorzy:
Bochenek, Jan
Winiarska, Teresa
Powiązania:
https://bibliotekanauki.pl/articles/1311127.pdf
Data publikacji:
1996
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
evolution problem
stable family of operators
stable approximations of the evolution operator
evolution problem with parameter
hyperbolic case
Opis:
The purpose of this paper is to give theorems on continuity and differentiability with respect to (h,t) of the solution of the initial value problem du/dt = A(h,t)u + f(h,t), u(0) = u₀(h) with parameter $h ∈ Ω ⊂ ℝ^m$ in the "hyperbolic" case.
Źródło:
Annales Polonici Mathematici; 1996, 64, 1; 47-60
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 39

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