• 전자공학회논문지B
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• 제32B권12호
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• pp.1680-1686
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• 1995

GAs, effective stochastic search algorithms based on the model of natural evolution and genetics, have been successfully applied to various optimization problems. When population size is not large, GAs often suffer from the phenomenon of premature convergence in which all chromosomes in the population lose the diversity of genes before they find the optimal solution. In this paper, we propose that a new heuristic that maintains the diversity of genes by adding some chromosomes with random mutation and selective mutation into population during evolution. And population size changes dynamically with supplement of new chromosomes. Experimental results for several test functions show that when population size is rather small and the length of chromosome is not long, this method is effective.

• 한국대기환경학회지
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• 제22권6호
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• pp.912-921
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• 2006

This study examines greenhouse gas reduction potentials in cement manufacturing industry of Korea. An energy system model in the MARKAL (MARKet ALlocation) modeling framework was used in order to identify appropriate energy technologies and to quantify their possible implications In terms of greenhouse gas reduction. The model is characterized as mathematical tool for the long term energy system analysis provides an useful informations on technical assessment. Four scenarios are developed that covers the ti me span from 2000 to 2020. Being technology as a fundamental driving factor of the evolution of energy systems, it is essential to study the basic mechanisms of technological change and its role in developing more efficient, productive and clean energy systems. For this reasons, the learning curves on technologies for greenhouse gas reduction is specially considered. The analysis in this study shows that it is not easy to mitigate greenhouse gas with low cost in cement manufacturing industry under the current cap and trade method of Kyoto protocol.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.101-107
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• 2008

We introduce an optimization of fuzzy set-fuzzy systems based on IG (Information Granules). The proposed fuzzy model implements system structure and parameter identification by means of IG and GAs. The concept of information granulation was coped with to enhance the abilities of structural optimization of the fuzzy model. Granulation of information realized with C-Means clustering helps determine the initial parameters of the fuzzy model such as the initial apexes of the membership functions in the premise part and the initial values of polynomial functions in the consequence part of the fuzzy rules. The initial parameters are adjusted effectively with the help of the GAs and the standard least square method. To optimally identify the structure and the parameters of the fuzzy model we exploit GAs with successive tuning method to simultaneously search the structure and the parameters within one individual. We also consider the variant generation-based evolution to adjust the rate of identification of the structure and the parameters in successive tuning method. The proposed model is evaluated with the performance of the conventional fuzzy model.

• 천문학회보
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• 제38권1호
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• pp.31.1-31.1
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• 2013

Barred-spiral galaxies possess double patterns: a bar and spiral arms. While their angular speeds play an important role in governing gas dynamical evolution of barred spiral galaxies, there is no direct way to observe them. The Tremaine-Weinberg (TW) method has been one of the most reliable indirect methods to estimate pattern speeds, although it requires a few strict assumptions, notably one that the gas tracer is in a quasi-steady state. In barred-spiral galaxies, however, non-steady gas flows are significant especially when the double patterns have different angular speeds. Using numerical models, we explore the effect of non-steady gas motions on the determination of double pattern speeds based on the TW method. We find that the TW method is accurate within 15% when there is only a single pattern or when double patterns have the same angular speed. When double patterns have different speeds, on the other hand, neglecting the non-steady flows leads to quite large errors (> 30%) in the derived pattern speeds, and severely underestimate the real values for the viewing angle parallel to the bar minor axis. This suggests that one should be cautious when applying the TW method to galaxies with double patterns with different speeds.

• 한국해양공학회지
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• 제16권4호
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• pp.25-31
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• 2002

This paper is to find optimum design of plane framed structures with discrete variables. Global search algorithms for this problem are Genetic Algorithms(GAs), Simulated Annealing(SA) and Shuffled Complex Evolution(SCE), and hybrid methods (GAs-SA, GAs-SCE). GAs and SA are heuristic search algorithms and effective tools which is finding global solution for discrete optimization. In particular, GAs is known as the search method to find global optimum or near global optimum. In this paper, reinforced concrete plane frames with rectangular section and steel plane frames with W-sections are used for the design of discrete optimization. These structures are designed for stress constraints. The robust and effectiveness of Genetic Algorithms are demonstrated through several examples.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.714-716
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• 1996

This paper presents an optimization method for optimal reactive power dispatch which minimizes real power loss and improves voltage profile of power systems using evolutionary computation such as genetic algorithms(GAs), evolutionary programming(EP). and evolution strategy(ES). Many conventional methods to this problem have been proposed in the past, but most these approaches have the common defect of being caught to a local minimum solution. Recently, global search methods such as GAs, EP, and ES are introduced. The proposed methods were applied to the IEEE 30-bus system. Each simulation result, compared with that obtained by using a conventional gradient-based optimization method, Sequential Quadratic Programming (SQP), shows the possibility of applications of evolutionary computation to large scale power systems.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2000년도 춘계학술대회 학술발표 논문집
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• pp.134-137
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• 2000

Genetic algorithms(GAs) have been widely used as a method to solve optimization problems. This is because GAs have simple and elegant tools with reproduction, crossover, and mutation to rapidly discover good solutions for difficult high-dimensional problems. They, however, do not guarantee the convergence of global optima in GA-hard problems such as deceptive problems. Therefore we proposed a Schema Co-Evolutionary Algorithm(SCEA) and derived extended schema 76988theorem from it. Using co-evolution between the first population made up of the candidates of solution and the second population consisting of a set of schemata, the SCEA works better and converges on global optima more rapidly than GAs. In this paper, we show advantages and efficiency of the SCEA by applying it to some problems.

• 천문학회보
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• 제36권2호
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• pp.57.2-57.2
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• 2011

To study the formation and evolution of sub-galactic scale structures, we have added SPH (Smoothed Particle Hydrodynamics) method into an existing cosmological PMTree code, GOTPM. To follow the evolution of gas particles, we consider heating/cooling processes, star formation, and energy & metal feedback by supernova explosion. We have performed various tests for the new code and found that the results reproduce observed quantities or follow the known analytic solutions. We present a test simulation of isolated disk galaxy with a focus on whether the star formation reproduces the observed features.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.260-268
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• 2019

The pyrolysis characteristics of pulverized coal particle was numerically analyzed with the drop tube furnace. Based on the simulated gas flow field in the drop tube furnace, the particle velocity, temperature and volatile evolution were calculated with the fourth order Runge-Kutta method. The effects of changes in reactor wall temperature and particle diameter on the pyrolysis behavior of coal particle were investigated. The particle heating rate was very sensitive to the reactor wall temperature and particle size, that is, the higher wall temperature and the smaller particle size resulted in the higher heating rate and the consequent quicker volatile evolution.

• 천문학회지
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• 제33권1호
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• pp.1-17
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• 2000

We have performed extensive simulations of response of gaseous disk in barred galaxies using SPH method. The gravitational potential is assumed to be generated by disk, bulge, halo, and bar. The mass of gaseous disk in SPH simulation is assumed to be negligible compared to the stellar and dark mass component, and the gravitational potential generated by other components is fixed in time. The self-gravity of the gas is not considered in most simulations, but we have made a small set of simulations including the self-gravity of the gas. Non-circular component of velocity generated by the rotating, non-axisymmetric potential causes many interesting features. In most cases, there is a strong tendency of concentration of gas toward the central parts of the galaxy. The morphology of the gas becomes quite complex, but the general behavior can be understood in terms of simple linear approximations: the locations and number of Lindblad resonances play critical role in determining the general distribution of the gas. We present our results in the form of 'atlas' of artificial galaxies. We also make a brief comment on the observational implications of our calculations. Since the gaseous component show interesting features while the stellar component behaves more smoothly, high resolution mapping using molecular emission line for barred galaxies would be desirable.