• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1636-1641
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• 2008

In this study, we introduce a new approach to Parallel Genetic Algorithms (PGA) which combines AHFCGA with crossover operator. As to crossover operators, we use three types of the crossover operators such as modified simple crossover(MSX), arithmetic crossover(AX), and Unimodal Normal Distribution Crossover(UNDX) for real coding. The AHFC model is given as an extended and adaptive version of HFC for parameter optimization. The migration topology of AHFC is composed of sub-populations(demes), the admission threshold levels, and admission buffer for the deme of each threshold level through succesive evolution process. In particular, UNDX is mean-centric crossover operator using multiple parents, and generates offsprings obeying a normal distribution around the center of parents. By using test functions having multimodality and/or epistasis, which are commonly used in the study of function parameter optimization, Experimental results show that AHFCGA can produce more preferable output performance result when compared to HFCGA and RCGA.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.320-320
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• 2006

The authors report the synthesis and radical ring-crossover polymerization of macrocycles with radically exchangeable dynamic covalent bonds. The macrocyclic compounds with alkoxyamine units were designed and synthesized by condensation from alkoxyamine-based diol and the corresponding acid chlorides in the presence of pyridine under high-dilution condition. The macrocycles can thermally polymerize by intermolecular radical crossover reaction. Furthermore, the poly(alkoxyamine)s depolymerized to the monomers principally by the intramolecular radical exchange process under high-dilution conditions.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2290-2295
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• 2018

An acceleration stress test (AST) was performed to evaluate the durability of a polymer membrane in a polymer electrolyte membrane fuel cell (PEMFC) for 500 hours. Previous studies have shown that hydrogen crossover measured by linear sweep voltammetry (LSV) increases when the polymer membrane deteriorates in the AST process. On the other hand, hydrogen crossover of the membrane often decreases in the early stages of the AST test. To investigate the cause of this phenomenon, we analyzed the MEA operated for 50 hours using the AST method (OCV, RH 30% and $90^{\circ}C$). Cyclic voltammetry and transmission electron showed that the electrochemical surface area (ECSA) decreased due to the growth of electrode catalyst particles and that the hydrogen crossover current density measured by LSV could be reduced. Fourier transform infrared spectroscopy and thermogravimetric/differential thermal analysis showed that -S-O-S- crosslinking occurred in the polymer after the 50 hour AST. Gas chromatography showed that the hydrogen permeability was decreased by -S-O-S- crosslinking. The reduction of the hydrogen crossover current density measured by LSV in the early stages of AST could be caused by both reduction of the electrochemical surface area of the electrode catalyst and -S-O-S- crosslinking.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.2
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• pp.227-232
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• 2015

Nowadays, there are many innovative products in the pro-audio market thanks to advanced IT technology, DSP is very important technology to process high quality audio signal in SR(Sound Reinforcement) system. Digital audio technology that converged with IT technology can give new user-experience. In this paper, we present a new digital crossover system for active speakers using DSP and network technology. The prototype of crossover module consists of various audio process module such as filters, delay, phase controls and also it provides user to remote monitoring and remote control features by internet connection.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.4
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• pp.67-72
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• 2012

In this paper a new method of handling linear constraints for the genetic algorithm is suggested. The method is designed to maintain the feasibility of offsprings during the evolution process of the genetic algorithm. In the genetic algorithm, the chromosomes are coded as the vectors in the real vector space constrained by the linear constraints. A method of handling the linear constraints already exists in which all the constraints of equalities are eliminated so that only the constraints of inequalities are considered in the process of the genetic algorithm. In this paper a new method is presented in which all the constraints of inequalities are eliminated so that only the constraints of equalities are considered. Several genetic operators such as arithmetic crossover, simplex crossover, simple crossover and random vector mutation are designed so that the resulting offspring vectors maintain the feasibility subject to the linear constraints in the framework of the new handling method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1809-1814
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• 2003

Differential evolution (DE) algorithm is presented and applied to global optimization in this research. DE suggested initially fur the solution to Chebychev polynomial fitting problem is similar to genetic algorithm(GA) including crossover, mutation and selection process. However, differential evolution algorithm is simpler than GA because it uses a vector concept in populating process. And DE turns out to be converged faster than CA, since it employs the difference information as pseudo-sensitivity In this paper, a trial vector and its control parameters of DE are examined and unconstrained optimization problems of highly nonlinear multimodal functions are demonstrated. To illustrate the efficiency of DE, convergence rates and robustness of global optimization algorithms are compared with those of simple GA.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.2
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• pp.69-80
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• 1999

A genetic algorithm to determine the optimal signal sequence and double cycle pattern is described. The signal sequence and double cycle pattern are used as the input for TRANSYT to find optimal signal timing at each junction in the area traffic networks, In the genetic process, the partially matched crossover and simple crossover operators are used for evolution of signal sequence and double cycle pattern respectively. A special conversion algorithm is devised to convert the signal sequence into the link-stage assignment for TRANSYT. Results from tests using data from an area traffic network in Leicester region R are given.

• Korean Journal of Social Welfare
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• v.60 no.3
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• pp.253-274
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• 2008

The link between work life and family life is an essential subject matter in understanding the lives of dual-earner couples. Concepts of spillover and crossover explain the link between work and family. The present study examines both the positive and negative aspects in these processes. The data come from the Sloan Working Families Study conducted by the Alfred P. Sloan Center on Parents, Children, and Work and NORC at the University of Chicago. The Experience Sampling Method employed explores directly the daily life experiences of the participants. The data were analysed using t-test. Both spillover and crossover were found in the lives of dual-earner couples in this study. Men and women brought happy emotions at work to home, but the data provide limited support for spillover of negative emotions. Gender differences were more apparent in examining the process of crossover. Men appear responsive to the positive and negative emotional experiences their spouse brought home while women were found not to be responsive to their spouses' positive emotional experiences at work. Furthermore, the analysis revealed an interesting trend concerning the emotions of working couples in that they generally seem to recover to their average level of emotions once home. This suggests that home can be a respite from strong emotions, a comforting place. By looking closely into the emotions experienced by working parents in their daily lives, this study adds contextual understanding concerning the link between work and family life. The findings on the effects of positive experiences at work invite social work practitioners and researchers to further investigate the phenomena of spillover and crossover processed in greater detail, taking into account this contextual aspect of family life as well as the work life of dual-earner couples.

• Computers and Concrete
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• v.11 no.6
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• pp.541-569
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• 2013

There is a wide variety of existing Genetic Algorithms (GA) operators and parameters in the literature. However, there is no unique technique that shows the best performance for different classes of optimization problems. Hence, the evaluation of these operators and parameters, which influence the effectiveness of the search process, must be carried out on a problem basis. This paper presents a comparison for the influence of GA operators and parameters on the performance of the damage identification problem using the finite element model updating method (FEMU). The damage is defined as reduction in bending rigidity of the finite elements of a reinforced concrete beam. A certain damage scenario is adopted and identified using different GA operators by minimizing the differences between experimental and analytical modal parameters. In this study, different selection, crossover and mutation operators are compared with each other based on the reliability, accuracy and efficiency criteria. The exploration and exploitation capabilities of different operators are evaluated. Also a comparison is carried out for the parallel and sequential GAs with different population sizes and the effect of the multiple use of some crossover operators is investigated. The results show that the roulettewheel selection technique together with real valued encoding gives the best results. It is also apparent that the Non-uniform Mutation as well as Parent Centric Normal Crossover can be confidently used in the damage identification problem. Nevertheless the parallel GAs increases both computation speed and the efficiency of the method.