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    Wyświetlanie 1-10 z 10
    Tytuł:
    Improving Population-Based Algorithms with Fitness Deterioration
    Autorzy:
    Wolny, A.
    Schaefer, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/308437.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    basin of attraction
    clustering
    fitness deterioration
    genetic algorithm
    optics
    sequential niching
    Opis:
    This work presents a new hybrid approach for supporting sequential niching strategies called Cluster Supported Fitness Deterioration (CSFD). Sequential niching is one of the most promising evolutionary strategies for analyzing multimodal global optimization problems in the continuous domains embedded in the vector metric spaces. In each iteration CSFD performs the clustering of the random sample by OPTICS algorithm and then deteriorates the fitness on the area occupied by clusters. The selection pressure pushes away the next-step sample (population) from the basins of attraction of minimizers already recognized, speeding up finding the new ones. The main advantages of CSFD are low memory an computational complexity even in case of large dimensional problems and high accuracy of deterioration obtained by the flexible cluster definition delivered by OPTICS. The paper contains the broad discussion of niching strategies, detailed definition of CSFD and the series of the simple comparative tests.
    Źródło:
    Journal of Telecommunications and Information Technology; 2011, 4; 31-44
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The island model as a Markov dynamic system
    Autorzy:
    Schaefer, R.
    Byrski, A.
    Smołka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/331253.pdf
    Data publikacji:
    2012
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    algorytm genetyczny
    analiza asymptotyczna
    optymalizacja globalna
    algorytm ewolucyjny równoległy
    łańcuch Markova
    genetic algorithms
    asymptotic analysis
    global optimization
    parallel evolutionary algorithms
    Markov chain modeling
    Opis:
    Parallel multi-deme genetic algorithms are especially advantageous because they allow reducing the time of computations and can perform a much broader search than single-population ones. However, their formal analysis does not seem to have been studied exhaustively enough. In this paper we propose a mathematical framework describing a wide class of island-like strategies as a stationary Markov chain. Our approach uses extensively the modeling principles introduced by Vose, Rudolph and their collaborators. An original and crucial feature of the framework we propose is the mechanism of inter-deme agent operation synchronization. It is important from both a practical and a theoretical point of view. We show that under a mild assumption the resulting Markov chain is ergodic and the sequence of the related sampling measures converges to some invariant measure. The asymptotic guarantee of success is also obtained as a simple issue of ergodicity. Moreover, if the cardinality of each island population grows to infinity, then the sequence of the limit invariant measures contains a weakly convergent subsequence. The formal description of the island model obtained for the case of solving a single-objective problem can also be extended to the multi-objective case.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2012, 22, 4; 971-984
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hierarchical genetic computation in optimal design
    Hierarchiczne obliczenia genetyczne w projektowaniu optymalnym
    Autorzy:
    Kołodziej, J.
    Schaefer, R.
    Paszyńska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/281989.pdf
    Data publikacji:
    2004
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    hierarchical genetic optimization
    graph encoding
    shape optimization
    Opis:
    The paper presents two examples of genetic hierarchic global optimization methods. They are two different goals of introducing hierarchy into the computational model: to perform the multi-scale search with the adapted accuracy and to better express the structure geometry in the optimal shape design. Results of the formal analysis and simple computational examples are also attached.
    Praca przedstawia dwa przykłady hierarchicznych, genetycznych metod optymalizacji. Sklasyfikowano dwa główne powody wprowadzenia hierarchii do modelu obliczeniowego: dla uzyskania wieloskalowego przeszukania z adaptowaną dokładnością oraz dla lepszego odwzorowania kształtu konstrukcji w zadaniach optymalnego projektowania kształtu. Zamieszczono rezultaty formalnej analizy proponowanych strategii oraz proste przykłady obliczeniowe.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2004, 42, 3; 519-538
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the computational cost and complexity of stochastic inverse solvers
    Autorzy:
    Faliszewski, P.
    Smołka, M.
    Schaefer, R.
    Paszyński, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/305383.pdf
    Data publikacji:
    2016
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    hierarchic genetic strategy
    inverse problem
    hybrid method
    Opis:
    The goal of this paper is to provide a starting point for investigations into a mainly underdeveloped area of research regarding the computational cost analysis of complex stochastic strategies for solving parametric inverse problems. This area has two main components: solving global optimization problems and solving forward problems (to evaluate the misfit function that we try to minimize). For the first component, we pay particular attention to genetic algorithms with heuristics and to multi-deme algorithms that can be modeled as ergodic Markov chains. We recall a simple method for evaluating the first hitting time for the single-deme algorithm and we extend it to the case of HGS, a multi-deme hierarchic strategy. We focus on the case in which at least the demes in the leaves are well tuned. Finally, we also express the problems of finding local and global optima in terms of a classic complexity theory. We formulate the natural result that finding a local optimum of a function is an NP-complete task, and we argue that finding a global optimum is a much harder, DP-complete, task. Furthermore, we argue that finding all global optima is, possibly, even harder (#P-hard) task. Regarding the second component of solving parametric inverse problems (i.e., regarding the forward problem solvers), we discuss the computational cost of hp-adaptive Finite Element solvers and their rates of convergence with respect to the increasing number of degrees of freedom. The presented results provide a useful taxonomy of problems and methods of studying the computational cost and complexity of various strategies for solving inverse parametric problems. Yet, we stress that our goal was not to deliver detailed evaluations for particular algorithms applied to particular inverse problems, but rather to try to identify possible ways of obtaining such results.
    Źródło:
    Computer Science; 2016, 17 (2); 225-264
    1508-2806
    2300-7036
    Pojawia się w:
    Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Misfit landforms imposed by ill-conditioned inverse parametric problems
    Autorzy:
    Łoś, M.
    Smołka, M.
    Schaefer, R.
    Sawicki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/305739.pdf
    Data publikacji:
    2018
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    taxonomy of ill-conditioned problems
    ill-posed global optimization problems
    fitness landscapes
    Opis:
    In this paper, we put forward a new topological taxonomy that allows us to distinguish and separate multiple solutions to ill-conditioned parametric inverse problems appearing in engineering, geophysics, medicine, etc. This taxonomy distinguishes the areas of insensitivity to parameters called the landforms of the misfit landscape, be it around minima (lowlands), maxima (uplands), or stationary points (shelves). We have proven their important separability and completeness conditions. In particular, lowlands, uplands, and shelves are pairwise disjoint, and there are no other subsets of the positive measure in the admissible domain on which the misfit function takes a constant value. The topological taxonomy is related to the second, “local” one, which characterizes the types of ill-conditioning of the particular solutions. We hope that the proposed results will be helpful for a better and more precise formulation of ill-conditioned inverse problems and for selecting and profiling complex optimization strategies used in solving these problems.
    Źródło:
    Computer Science; 2018, 19 (2); 157-178
    1508-2806
    2300-7036
    Pojawia się w:
    Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Asymptotic guarantee of success for multi-agent memetic systems
    Autorzy:
    Byrski, A.
    Schaefer, R.
    Smołka, M.
    Cotta, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/201942.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    computational multi-agent systems
    asymptotic analysis
    global optimization
    parallel evolutionary algorithms
    Markov chain modeling
    Opis:
    The paper introduces a stochastic model for a class of population-based global optimization meta-heuristics, that generalizes existing models in the following ways. First of all, an individual becomes an active software agent characterized by the constant genotype and the meme that may change during the optimization process. Second, the model embraces the asynchronous processing of agent’s actions. Third, we consider a vast variety of possible actions that include the conventional mixing operations (e.g. mutation, cloning, crossover) as well as migrations among demes and local optimization methods. Despite the fact that the model fits many popular algorithms and strategies (e.g. genetic algorithms with tournament selection) it is mainly devoted to study memetic algorithms. The model is composed of two parts: EMAS architecture (data structures and management strategies) allowing to define the space of states and the framework for stochastic agent actions and the stationary Markov chain described in terms of this architecture. The probability transition function has been obtained and the Markov kernels for sample actions have been computed. The obtained theoretical results are helpful for studying metaheuristics conforming to the EMAS architecture. The designed synchronization allows the safe, coarse-grained parallel implementation and its effective, sub-optimal scheduling in a distributed computer environment. The proved strong ergodicity of the finite state Markov chain results in the asymptotic stochastic guarantee of success, which in turn imposes the liveness of a studied metaheuristic. The Markov chain delivers the sampling measure at an arbitrary step of computations, which allows further asymptotic studies, e.g. on various kinds of the stochastic convergence.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2013, 61, 1; 257-278
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    HP-HGS strategy for inverse AC/DC resistivity logging measurement simulations
    Autorzy:
    Gajda-Zagórska, E.
    Paszyński, M
    Schaefer, R.
    Pardo, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/305666.pdf
    Data publikacji:
    2013
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    resistivity logging simulations
    adaptive finite element method
    hierarchical genetic search
    inverse problems
    Opis:
    In this paper, we present resistivity-logging-measurement simulation with the use of two types of borehole logging devices: those which operate with zero frequency (direct current, DC) and those with higher frequencies (alternate current, AC). We perform simulations of 3D resistivity measurements in deviated wells, with a sharp angle between the borehole and formation layers. We introduce a hierarchical adaptive genetic strategy hp−HGS interfaced with an adaptive finite element method. We apply a strategy for the solution of the inverse problem, where we identify the resistivities of the formation layers based on a given measurement. We test the strategy on both direct and alternate current cases.
    Źródło:
    Computer Science; 2013, 14 (4); 629-644
    1508-2806
    2300-7036
    Pojawia się w:
    Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An agent-oriented hierarchic strategy for solving inverse problems
    Autorzy:
    Smołka, M.
    Schaefer, R.
    Paszyński, M.
    Pardo, D.
    Álvarez-Aramberri, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/329764.pdf
    Data publikacji:
    2015
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    inverse problem
    hybrid optimization method
    memetic algorithm
    multi-agent system
    magnetotelluric data inversion
    zadanie odwrotne
    optymalizacja hybrydowa
    algorytm memetyczny
    system wieloagentowy
    Opis:
    The paper discusses the complex, agent-oriented hierarchic memetic strategy (HMS) dedicated to solving inverse parametric problems. The strategy goes beyond the idea of two-phase global optimization algorithms. The global search performed by a tree of dependent demes is dynamically alternated with local, steepest descent searches. The strategy offers exceptionally low computational costs, mainly because the direct solver accuracy (performed by the hp-adaptive finite element method) is dynamically adjusted for each inverse search step. The computational cost is further decreased by the strategy employed for solution inter-processing and fitness deterioration. The HMS efficiency is compared with the results of a standard evolutionary technique, as well as with the multi-start strategy on benchmarks that exhibit typical inverse problems’ difficulties. Finally, an HMS application to a real-life engineering problem leading to the identification of oil deposits by inverting magnetotelluric measurements is presented. The HMS applicability to the inversion of magnetotelluric data is also mathematically verified.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2015, 25, 3; 483-498
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A hybrid algorithm for solving inverse problems in elasticity
    Autorzy:
    Barabasz, B.
    Gajda-Zagórska, E.
    Migórski, S.
    Paszyński, M.
    Schaefer, R.
    Smołka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/331427.pdf
    Data publikacji:
    2014
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    inverse problem
    hierarchic genetic strategy
    hybrid optimization
    automatic hp adaptive finite element method
    zagadnienie odwrotne
    strategia genetyczna
    optymalizacja hybrydowa
    metoda elementów skończonych
    Opis:
    The paper offers a new approach to handling difficult parametric inverse problems in elasticity and thermo-elasticity, formulated as global optimization ones. The proposed strategy is composed of two phases. In the first, global phase, the stochastic hp-HGS algorithm recognizes the basins of attraction of various objective minima. In the second phase, the local objective minimizers are closer approached by steepest descent processes executed singly in each basin of attraction. The proposed complex strategy is especially dedicated to ill-posed problems with multimodal objective functionals. The strategy offers comparatively low computational and memory costs resulting from a double-adaptive technique in both forward and inverse problem domains. We provide a result on the Lipschitz continuity of the objective functional composed of the elastic energy and the boundary displacement misfits with respect to the unknown constitutive parameters. It allows common scaling of the accuracy of solving forward and inverse problems, which is the core of the introduced double-adaptive technique. The capability of the proposed method of finding multiple solutions is illustrated by a computational example which consists in restoring all feasible Young modulus distributions minimizing an objective functional in a 3D domain of a photo polymer template obtained during step and flash imprint lithography.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2014, 24, 4; 865-886
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Jak zapobiec odległym następstwom choroby nerek z okresu dzieciństwa?
    Averting the legacy of kidney disease – focus on childhood
    Autorzy:
    Ingelfinger, Julie R.
    Kalantar-Zadeh, Kamyar
    Schaefer, Franz
    Powiązania:
    https://bibliotekanauki.pl/articles/1034090.pdf
    Data publikacji:
    2016
    Wydawca:
    Medical Communications
    Tematy:
    chronic kidney disease
    congenital anomalies of the kidney and urinary tract (CAKUT)
    developmental origins of health and disease (DoHAD)
    paediatric nephrology
    paediatrics
    przewlekła choroba nerek
    nefrologia dziecięca
    pediatria
    wady wrodzone nerek i dróg moczowych
    (cakut)
    koncepcja zdrowia i rozwoju chorób
    Opis:
    World Kidney Day 2016 focuses on kidney disease in childhood and the antecedents of adult kidney disease that can begin in earliest childhood. Chronic kidney disease in childhood differs from that in adults, as the largest diagnostic group among children includes congenital anomalies and inherited disorders, with glomerulopathies and kidney disease in the setting of diabetes being relatively uncommon. In addition, many children with acute kidney injury will ultimately develop sequelae that may lead to hypertension and chronic kidney disease in later childhood or in adult life. Children born early or who are small-for date newborns have relatively increased risk for the development of chronic kidney disease later in life. Persons with a high-risk birth and early childhood history should be watched closely in order to help detect early signs of kidney disease in time to provide effective prevention or treatment. Successful therapy is feasible for advanced chronic kidney disease in childhood; there is evidence that children fare better than adults, if they receive kidney replacement therapy including dialysis and transplantation, while only a minority of children may require this ultimate intervention. Because there are disparities in access to care, effort is needed so that those children with kidney disease, wherever they live, may be treated effectively, irrespective of their geographic or economic circumstances. Our hope is that World Kidney Day will inform the general public, policy makers and caregivers about the needs and possibilities surrounding kidney disease in childhood.
    W 2016 roku obchody Światowego Dnia Nerek koncentrują się na chorobach występujących u dzieci i zdarzeniach nawet z najwcześniejszego dzieciństwa, które mogą stać się podłożem przewlekłego schorzenia u dorosłych. U dzieci choroba nerek przybiera nieco inną formę niż u dorosłych – dużą grupę najmłodszych pacjentów stanowią ci z wadami wrodzonymi i genetycznymi układu moczowego, glomerulopatiami oraz (rzadziej) chorobami nerek na podłożu cukrzycy. U wielu dzieci z ostrym uszkodzeniem nerek pojawiają się następstwa w postaci nadciśnienia tętniczego i przewlekłej choroby nerek w późniejszym dzieciństwie albo wieku dorosłym. Wcześniaki i stosunkowo małe noworodki cechują się podwyższonym ryzykiem wystąpienia przewlekłej choroby nerek w późniejszym życiu. Pacjentów z obciążonym wywiadem okołoporodowym i dotyczącym wczesnego dzieciństwa należy ściśle monitorować w celu rozpoznania pierwszych oznak choroby i wdrożenia efektywnej profilaktyki lub leczenia. Możliwa jest skuteczna terapia przewlekłej choroby nerek u dzieci, które – jak wskazują badania – znacznie lepiej niż dorośli radzą sobie z uciążliwością leczenia nerkozastępczego, w tym programu dializ i przeszczepienia. Ponieważ dostęp do specjalistycznej opieki nefrologicznej nie jest jednolity, należy wdrożyć odpowiednie działania, aby zapewnić skuteczne leczenie wszystkim chorym dzieciom, bez względu na ich miejsce zamieszkania czy status ekonomiczny. Żywimy nadzieję, że Światowy Dzień Nerek pomoże w edukacji opinii publicznej, ustawodawców i pracowników służby zdrowia w zakresie potrzeb związanych z chorobą nerek występującą w dzieciństwie.
    Źródło:
    Pediatria i Medycyna Rodzinna; 2016, 12, 1; 10-19
    1734-1531
    2451-0742
    Pojawia się w:
    Pediatria i Medycyna Rodzinna
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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