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Wyszukujesz frazę "optimization algorithms" wg kryterium: Temat


Wyświetlanie 1-7 z 7
Tytuł:
Application of SVR with improved ant colony optimization algorithms in exchange rate forecasting
Autorzy:
Hung, W. M.
Hong, W. C.
Powiązania:
https://bibliotekanauki.pl/articles/969706.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
support vector regression (SVR)
continuous ant colony optimization algorithms (CACO)
exchange rates
financial forecasting
Opis:
Traditional time series forecasting models, like ARIMA and regression models, can hardly capture nonlinear patterns. Support vector regression (SVR), a novel neural network technique, has been successfully used to solve nonlinear regression and time series problems. The SVR model applies the structural risk minimization principle to minimize the upper bound of the generalization error, instead of minimizing the training error, employed by most conventional neural network models. Thus, parameter determination for an SVR model is appropriate for achieving high forecasting accuracy. Several evolutionary algorithms, such as genetic algorithms and simulated annealing algorithms have been used in parameter selection, but these algorithms often suffer from the possibility of being trapped in local optimum. This study used an improved ant colony optimization algorithm in an SVR model, called SVRCACO, for selecting suitable parameters, with encouraging local search in areas where forecasting accuracy improvement continues to be made, then, autocatalytically converge to promising regions. Numerical examples of exchange rate forecasting from the existing literature are employed to assess the performance of the proposed model. Experimental results show that the proposed model outperforms other approaches from the literature.
Źródło:
Control and Cybernetics; 2009, 38, 3; 863-891
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New evaluations of ant colony optimization start nodes
Autorzy:
Fidanova, S.
Marinov, P.
Atanassov, K.
Powiązania:
https://bibliotekanauki.pl/articles/206546.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
combinatorial optimization
ant algorithms
start nodes evaluation
semi random start
Opis:
Ant Colony Optimization (ACO) is a stochastic search method that mimics the social behavior of real ant colonies, managing to establish the shortest route to the feeding sources and back. Such algorithms have been developed to arrive at near-optimal solutions to large-scale optimization problems, for which traditional mathematical techniques may fail. In this paper, the semi-random start procedure is applied. A new kind of evaluation of start nodes of the ants is developed and several starting strategies are prepared and combined. The idea of semi-random start is related to a better management of the ants. This new technique is tested on the Multiple Knapsack Problem (MKP). A Comparison among the strategies applied is presented in terms of quality of the results. A comparison is also carried out between the new evaluation and the existing one. Based on this comparative analysis, the performance of the algorithm is discussed. The study presents the idea that should be beneficial to both practitioners and researchers involved in solving optimization problems.
Źródło:
Control and Cybernetics; 2014, 43, 3; 471-485
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solving Markov decision processes by d-graph algorithms
Autorzy:
Kátai, Z.
Powiązania:
https://bibliotekanauki.pl/articles/205688.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
Markov decision processes
dynamic programming
graph representation
graph algorithms
optimization problems
Opis:
Markov decision processes (MDPs) provide a mathematical model for sequential decisionmaking (sMDP/dMDP: stochastic/ deterministic MDP). We introduce the concept of generalized dMDP (g-dMDP) where each action may result in more than one next (parallel or clone) state. The common tools to represent dMDPs are digraphs, but these are inadequate for sMDPs and g-dMDPs. We introduce d-graphs as general tools to represent all the above mentioned processes (stationary versions). We also present a combined d-graph algorithm that implements dynamic programming strategies to find optimal policies for the finite/infinite horizon versions of these Markov processes. (The preliminary version of this paper was presented at the Conference MACRo 2011.)
Źródło:
Control and Cybernetics; 2012, 41, 3; 577-593
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An optimized soft computing-based passage retrieval system
Autorzy:
Ortiz-Arroyo, D.
Christensen, H. U.
Powiązania:
https://bibliotekanauki.pl/articles/970939.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
information retrieval
question answering systems
passage retrieval
fuzzy logic
optimization
genetic algorithms
Opis:
In this paper we propose and evaluate a soft computing-based passage retrieval system for Question Answering Systems (QAS). Fuzzy PR, our base-line passage retrieval system, employs a similarity measure that attempts to model accurately the question reformulation intuition. The similarity measure includes fuzzy logic-based models that evaluate efficiently the proximity of question terms and detect term variations occurring within a passage. Our experimental results using FuzzyPR on the TREC and CLEF corpora show that our novel passage retrieval system achieves better performance compared to other similar systems. Finally, we describe the performance results of OptFuzzyPR, an optimized version of FuzzyPR, created by optimizing the values of FuzzyPR system parameters using genetic algorithms.
Źródło:
Control and Cybernetics; 2009, 38, 2; 457-479
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heuristic algorithms for the optimization of total weighted completion time for asynchronous transmission in a packet data transmission system
Autorzy:
Piórkowski, A.
Werewka, J.
Bielecka, M.
Powiązania:
https://bibliotekanauki.pl/articles/206673.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
total weighted completion time
total cost factor
optimization
heuristic algorithms
packet transmission
Opis:
In this paper, the minimization of total weighted completion time (total cost) for asynchronous transmission in distributed systems is discussed. Special attention has been paid to the problem of message scheduling on the sender side. Messages to be sent form a queue, therefore the order in which they are to be sent has to be set. Scheduling algorithms can be chosen to optimize scheduling criteria such as total completion time or total weighted completion time. The message scheduling problem becomes complicated considerably when the transmitted data stream between the sender and the receiver is formed into packets. TheWSPT (Weighted Shortest Processing Time) scheduling rule, which orders messages according to non-decreasing length and weight ratios has been proven to be non-optimal. It has been demonstrated that the problem of minimizing the total weighted completion time is NP-hard. Here, we propose heuristic algorithms for scheduling messages and experimentally evaluate the performance of these scheduling algorithms.
Źródło:
Control and Cybernetics; 2014, 43, 4; 507-529
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimization of urban MV multi-loop electric power distribution networks structure using Artificial Intelligence methods
Autorzy:
Parol, M.
Baczyński, D.
Brożek, J.
Powiązania:
https://bibliotekanauki.pl/articles/205678.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
electric power distribution networks
optimization of network structure
evolutionary algorithms
artificial neural networks
Opis:
Urban medium voltage (MV) electric power distribution networks are supplied with primary (HV/MV) substations. These networks supply secondary (MV/LV) transformer substations and are often built as closed structures - loop arrangements. The design problem of optimal urban MV distribution network structure consists of determining the number of primary substations, establishing the number of MV loops supplied with the primary substations, and assigning the secondary MV/LV transformer substations to the MV loops. The optimization task becomes especially complex when the number of the primary substations is greater than one. The minimum of total annual costs is sought. The total annual costs include: fixed (investment) costs, variable (operating) costs and supply-interruption costs. Typical constraints are also accounted for. The so defined optimization problem is a complicated mathematical problem in respect of computational effort. In order to resolve the mathematical model of the optimization problem, evolutionary algorithms and artificial neural networks have been used. Exemplary computational experiments have been executed on the model of urban MV multi-loop electric power distribution networks. The results from the evolutionary algorithm and the artificial neural network calculations have been compared.
Źródło:
Control and Cybernetics; 2012, 41, 3; 667-689
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sub-gradient algorithms for computation of extreme eigenvalues of a real symmetric matrix
Autorzy:
Yassine, A.
Powiązania:
https://bibliotekanauki.pl/articles/205834.pdf
Data publikacji:
1998
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
problem wartości własnej
difference of convex functions
eigenvalue problems
Lagrangian duality
non-convex optimization
sub-gradient algorithms
Opis:
The computation of eigenvalues of a matrix is still of importance from both theoretical and practical points of view. This is a significant problem for numerous industrial and scientific situations, notably in dynamics of structures (e.g. Gerardin, 1984), physics (e.g. Rappaz, 1979), chemistry (e.g. Davidson, 1983), economy (e.g. Morishima, 1971; Neumann, 1946), mathematics (e.g. Golub, 1989; Chatelin, 1983, 1984, 1988). The study of eigenvalue problems remains a delicate task, which generally presents numerical difficulties in relation to its sensivity to roundoff errors that may lead to numerical unstabilities, particularly if the eigenvalues are not well separated. In this paper, new subgradient-algorithms for computation of extreme eigenvalues of a symmetric real matrix are presented. Those algorithms are based on stability of Lagrangian duality for non-convex optimization and on duality in the difference of convex functions. Some experimental results which prove the robustness and efficiency of our algorithms are provided.
Źródło:
Control and Cybernetics; 1998, 27, 3; 387-415
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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