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    Wyświetlanie 1-5 z 5
    Tytuł:
    Internet shopping optimization problem
    Autorzy:
    Błażewicz, J.
    Kovalyov, M. Y.
    Musiał, J.
    Urbański, A. P.
    Wojciechowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/907755.pdf
    Data publikacji:
    2010
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    algorytm
    złożoność obliczeniowa
    algorytm kombinatoryczny
    optymalizacja
    zakupy internetowe
    algorithm
    computational complexity
    combinatorial algorithms
    optimization
    Internet shopping
    Opis:
    A high number of Internet shops makes it difficult for a customer to review manually all the available offers and select optimal outlets for shopping. A partial solution to the problem is brought by price comparators which produce price rankings from collected offers. However, their possibilities are limited to a comparison of offers for a single product requested by the customer. The issue we investigate in this paper is a multiple-item multiple-shop optimization problem, in which total expenses of a customer to buy a given set of items should be minimized over all available offers. In this paper, the Internet Shopping Optimization Problem (ISOP) is defined in a formal way and a proof of its strong NP-hardness is provided. We also describe polynomial time algorithms for special cases of the problem.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2010, 20, 2; 385-390
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimisation of crop rotations : A case study for corn growing practices in forest-steppe of Ukraine
    Autorzy:
    Romashchenko, Mykhailo
    Bohaienko, Vsevolod
    Shatkovskyi, Andrij
    Saidak, Roman
    Matiash, Tetiana
    Kovalchuk, Volodymyr
    Powiązania:
    https://bibliotekanauki.pl/articles/2203553.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Technologiczno-Przyrodniczy
    Tematy:
    combinatorial optimisation
    corn
    crop rotation
    genetic algorithms
    Opis:
    The formation of optimal crop rotations is virtually unsolvable from the standpoint of the classical methodology of experimental research. Here, we deal with a mathematical model based on expert estimates of “predecessor-crop” pairs’ efficiency created for the conditions of irrigation in the forest-steppe of Ukraine. Solving the problem of incorporating uncertainty assessments into this model, we present new models of crop rotations’ economic efficiency taking into account irrigation, application of fertilisers, and the negative environmental effect of nitrogen fertilisers’ introduction into the soil. For the considered models we pose an optimisation problem and present an algorithm for its solution that combines a gradient method and a genetic algorithm. Using the proposed mathematical tools, for several possible scenarios of water, fertilisers, and purchase price variability, the efficiency of growing corn as a monoculture in Ukraine is simulated. The proposed models show a reduction of the profitability of such a practice when the purchase price of corn decreases below 0.81 EUR∙kg-1 and the price of irrigation water increases above 0.32 EUR∙m-3 and propose more flexible crop rotations. Mathematical tools developed in the paper can form a basis for the creation of decision support systems that recommend optimal crop rotation variations to farmers and help to achieve sustainable, profitable, and ecologically safe agricultural production. However, future works on the actualisation of the values of its parameters need to be performed to increase the accuracy.
    Źródło:
    Journal of Water and Land Development; 2023, 56; 194--202
    1429-7426
    2083-4535
    Pojawia się w:
    Journal of Water and Land Development
    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:
    A note on hardness of multiprocessor scheduling with scheduling solution space tree
    Autorzy:
    Dwibedy, Debasis
    Mohanty, Rakesh
    Powiązania:
    https://bibliotekanauki.pl/articles/27312879.pdf
    Data publikacji:
    2023
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    combinatorial structures
    computational complexity
    hardness
    makespan
    multiprocessor scheduling
    multiuser
    NP-completeness
    nondeterministic algorithms
    reduction
    scheduling solution space tree
    Opis:
    We study the hardness of the non-preemptive scheduling problem of a list of independent jobs on a set of identical parallel processors with a makespan minimization objective. We make a maiden attempt to explore the combinatorial structure of the problem by introducing a scheduling solution space tree (SSST) as a novel data structure. We formally define and characterize the properties of SSST through our analytical results. We show that the multiprocessor scheduling problem is N P-complete with an alternative technique using SSST and weighted scheduling solution space tree (WSSST) data structures. We propose a non-deterministic polynomial-time algorithm called magic scheduling (MS) based on the reduction framework. We also define a new variant of multiprocessor scheduling by including the user as an additional input parameter, which we called the multiuser multiprocessor scheduling problem (MUMPSP). We also show that MUMPSP is N P-complete. We conclude the article by exploring several non-trivial research challenges for future research investigations.
    Źródło:
    Computer Science; 2023, 24 (1); 53--74
    1508-2806
    2300-7036
    Pojawia się w:
    Computer Science
    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
      Wyświetlanie 1-5 z 5

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