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Population size reduction for the differential evolution algorithm
Janez Brest, Mirjam Sepesy Maučec, 2008, original scientific article

Abstract: This paper studies the efficiency of a recently defined population-based direct global optimization method called Differential Evolution with self-adaptive control parameters. The original version uses fixed population size but a method for gradually reducing population size is proposed in this paper. It improves the efficiency and robustness of the algorithm and can be applied to any variant of a Differential Evolution algorithm. The proposed modification is tested on commonly used benchmark problems for unconstrained optimization and compared with other optimization methods such as Evolutionary Algorithms and Evolution Strategies.
Keywords: differential evolution, control parameter, fitness function, global function optimization, self-adaptation, population size
Published: 01.06.2012; Views: 1197; Downloads: 64
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Performance comparison of self-adaptive and adaptive differential evolution algorithms
Janez Brest, Borko Bošković, Sašo Greiner, Viljem Žumer, Mirjam Sepesy Maučec, 2007, original scientific article

Abstract: Differential evolution (DE) has been shown to be a simple, yet powerful, evolutionary algorithm for global optimization. for many real problems. Adaptation, especially self-adaptation, has been found to be highly beneficial for adjusting control parameters, especially when done without any user interaction. This paper presents differential evolution algorithms, whichuse different adaptive or self-adaptive mechanisms applied to the control parameters. Detailed performance comparisons of these algorithms on the benchmark functions are outlined.
Keywords: differential evolution, control parameter, fitness function, optimization, self-adaption
Published: 01.06.2012; Views: 1253; Downloads: 54
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Flaw acceptability assessment detected in HSLA steel weld joints
Inoslav Rak, 1999, original scientific article

Abstract: The flow size in weld joint can be determined by non destructive examination (NDE). Because of different mateials, and loading as well as because of the possible effect of corrosive environment the question arises how to assess reliably the allowable falw size in different weld joint parts. The presence of flaws is obvious but the possibilities of their revealing are limited and not always posssible. The flaw size and distribution are the essential parameters for the structure capacity of bearing under high loading the weld joint. The larger is the allowable flaw size anticipated, the safer is the welded structure, and the easiest is the detection of the flaw size by NDE methods. Thus for assessing the safety of complex loaded welded structure, machine parts or equipment life time, it is obligatory to consider the requirements of different "Fitness for Purpose" systems. The article presents the possibility of assessing the detected flaw by means of NDE if the material fracture toughness of the area where the fatigue crack tip located is known. The fatigue crack represents the severest discontinuity that can occur in a welded joint. The principles of IIW Guidance on Assessment of The Fitness for Purpose of Welded Structures - IIW/IIS-SST-1157-90 and BS PD 6493 and separately ETM that treats mis-matched weld joints are shown and used.
Keywords: zvarni spoji, dopustna velikost napake, lomna žilavost, trdnostna heterogenost, primernost za uporabo, weld joint, allowable flaw size, fracture toughness, strength mis-match, fitness for purpose
Published: 10.07.2015; Views: 627; Downloads: 7
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The relationship between children's physical fitness and gender, age and environmental factors
Črtomir Matejek, Gregor Starc, 2013, original scientific article

Abstract: The main aim of the research was to determine how children’s physical fitness development is related to age, gender, and certain environmental factors at the onset of puberty. The research was carried out on a representative sample of 897 children (47.9 % females and 52.1 % males) aged eleven and fourteen. Twelve tests were used to assess their physical fitness. Based on the duration of the physical activities, the children were divided into four categories: inactive, occasionally active, active and highly active. In the case of paternal education and maternal education, the children were classified into three categories: low, average and high. Considering their school grades in mathematics, the children were divided into three groups: less successful, successful and very successful. In the case of their place of residence, the children were divided into three groups: urban, suburban and rural. A component model of factor analysis was used to identify their basic coordinate system of physical fitness. To solve the problem of the integration of physical fitness into environmental factors, age and gender, a factorial analysis of variance was used. The results show that most of the differences in physical fitness can mainly be explained through age and gender. We can conclude that the significant factors to physical fitness development are growth, development and the maturation rate of individuals, which are predominantly hereditarily determined. Place of residence, physical activity, school grades and parental education have less influence on physical fitness development and serve only as an additional impulse to further stimulate or inhibit the physical development of children.
Keywords: physical fitness development, environment, factorial analysis, effect size
Published: 21.07.2017; Views: 396; Downloads: 59
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Aerobic games and playful exercises in 9-year-old boys
Gunnar E Mathisen, Rein M Jensen, Svein A Pettersen, 2016, original scientific article

Abstract: Previous research on exercise for pre-adolescents with the purpose of improving aerobic fitness levels has yielded contradictory results. Sufficient training intensity, frequency and duration are the crucial factors in achieving this goal; the question, however, is whether it is possible to reach sufficient intensity levels using aerobic games and playful exercises. Variety and fun are the important factors in motivating children to participate in physical exercises and sports. Therefore, the aim of the study was to investigate the effect of high intensity exercises in pre-adolescent boys, using programs consisting of fun activities and aerobic games. The findings show that the participants achieved intensity levels above 80 % of HRpeak on average in about 60 % of the total exercise time, resulting in significantly improved aerobic fitness.
Keywords: physical fitness, children, exercise, aerobic games
Published: 19.09.2017; Views: 371; Downloads: 72
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