343 research outputs found

    A Novel Genetic Algorithm using Helper Objectives for the 0-1 Knapsack Problem

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    The 0-1 knapsack problem is a well-known combinatorial optimisation problem. Approximation algorithms have been designed for solving it and they return provably good solutions within polynomial time. On the other hand, genetic algorithms are well suited for solving the knapsack problem and they find reasonably good solutions quickly. A naturally arising question is whether genetic algorithms are able to find solutions as good as approximation algorithms do. This paper presents a novel multi-objective optimisation genetic algorithm for solving the 0-1 knapsack problem. Experiment results show that the new algorithm outperforms its rivals, the greedy algorithm, mixed strategy genetic algorithm, and greedy algorithm + mixed strategy genetic algorithm

    Mixed strategy may outperform pure strategy: An initial study

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    In pure strategy meta-heuristics, only one search strategy is applied for all time. In mixed strategy meta-heuristics, each time one search strategy is chosen from a strategy pool with a probability and then is applied. An example is classical genetic algorithms, where either a mutation or crossover operator is chosen with a probability each time. The aim of this paper is to compare the performance between mixed strategy and pure strategy meta-heuristic algorithms. First an experimental study is implemented and results demonstrate that mixed strategy evolutionary algorithms may outperform pure strategy evolutionary algorithms on the 0-1 knapsack problem in up to 77.8% instances. Then Complementary Strategy Theorem is rigorously proven for applying mixed strategy at the population level. The theorem asserts that given two meta-heuristic algorithms where one uses pure strategy 1 and another uses pure strategy 2, the condition of pure strategy 2 being complementary to pure strategy 1 is sufficient and necessary if there exists a mixed strategy meta-heuristics derived from these two pure strategies and its expected number of generations to find an optimal solution is no more than that of using pure strategy 1 for any initial population, and less than that of using pure strategy 1 for some initial population

    Analisa Perhitungan dan Pengaturan Relai Arus Lebih dan Relai Gangguan Tanah pada Kubikel Cakra 20 KV di PT XYZ

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    Gangguan hubung singkat fasa ke tanah dan fasa-fasa merupakan salah satu permasalahan yang mungkin timbul dalam pengoperasian transformator daya dalam sebuah Gardu Induk. Gangguan yang disebabkan oleh adanya hubung singkat menimbulkan banyak kerugian, kerugian pada sistem transmisi kelistrikan maupun kerugian di pihak konsumen energi listrik. Salah satu cara untuk mengatasi gangguan ini adalah dengan memasang peralatan pengaman pada transformator. Relai arus lebih merupakan relai proteksi yang bekerja dengan Pemutus Tenaga (Circuit Breaker). Pada tulisan ini diberikan perhitungan setting relay arus lebih dan relay tanah pada pada penyulang keluar dari kubikel Cakra 20 kV di sebuah Perusahaan, yang karena alasan privacy disebutkan sebagai PT XYZ. Analisa yang dilakukan menunjukkan bahwa setting relay arus lebih dan relay tanah eksisting telah sesuai dengan standar yang berlaku

    First Satellite-detected Perturbations of Outgoing Longwave Radiation Associated with Blowing Snow Events over Antarctica

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    We present the first satellite-detected perturbations of the outgoing longwave radiation (OLR) associated with blowing snow events over the Antarctic ice sheet using data from Cloud-Aerosol Lidar with Orthogonal Polarization and Clouds and the Earth's Radiant Energy System. Significant cloud-free OLR differences are observed between the clear and blowing snow sky, with the sign andmagnitude depending on season and time of the day. During nighttime, OLRs are usually larger when blowing snow is present; the average difference in OLRs between without and with blowing snow over the East Antarctic Ice Sheet is about 5.2 W/m2 for the winter months of 2009. During daytime, in contrast, the OLR perturbation is usually smaller or even has the opposite sign. The observed seasonal variations and day-night differences in the OLR perturbation are consistent with theoretical calculations of the influence of blowing snow on OLR. Detailed atmospheric profiles are needed to quantify the radiative effect of blowing snow from the satellite observations