• The Transactions of the Korea Information Processing Society
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• v.2 no.5
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• pp.807-813
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• 1995

This paper proposes a method to determine the optimal utilizations of the UNIX systems. This method is developed using the definition-the optimal utilization is the maximum allowable utilization. In other words, the optimal utilization is the maximum utilization that can be allowed by users while providing tolerable response time. As the tolerable response time increases, the optimal utilization increases. Therefore, the optimal utilization is obtained at the maximal value of tolerable response time. Our analysis shows tolerable response time is achieved when the average of the trivial response time is less than 0.24 seconds for a given service objective. It also shows the optimal utilization consists of three components-%wio, and %usr. By way of example, the optimal utilizations of a machine (IBM 3081) running under the UNIX operating system are computed are computed using the proposed method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.277-286
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• 2001

Among the ULSAB methods for the lightweight automobile body, Tailor Welded Blank(TWB) is adopted and the design process is developed for the existing component. Topology optimization conducted to find the distribution of the variable thickness. The number of parts and the welding lines are determined from it. In the detail design, size optimization is carried out to find the optimum thickness of each part and then, the final parting lines are tuned by shape optimization. A commercial optimization software GENESIS is utilized for the optimization processes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.619-627
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• 1999

다분야 통합 시스템의 설계문제는 다량의 설계변수와 구속조건으로 구성되며 다수의 공학적 현상으로 연관되어 있다. 다분야 통합 최적설계 문제를 효과적으로 다루기 위해서는 다양한 해석분야의 공학적 설계원리를 동시에 고려하여 균형 있고 유기적인 방법으로 최적의 설계를 결정하는 체계적인 설계자동화기술이 요구된다. 다분야 통합 설계문제를 위한 효율적인 설계방법론으로 분리기반 최적화 기법이 적용되는데 이 방법은 한 단위의 대규모 설계문제를 여러 개의 하부시스템으로 분리하여 독립적으로 최적화를 수행하고 각 하부 시스템으로부터의 설계해 사이의 중재 및 통합화를 거쳐 최종적으로 수렴된 최적설계를 찾는 방법이다. 본 논문에서는 분리기반 최적화기법을 다분야 통합최적 설계문제에 적용하는데 필요한 시스템분리기법을 유전알고리즘 및 다층 역전 파 신경회로망을 이용하여 정립하였다. 시스템분리기법을 검증하기 위해 최근 미국 Boeing사에서 개발중인 고속 민간항공기인 HSCT의 시뮬레이션기반 설계문제를 이용하였다. 대규모 설계시스템의 분리결과는 전체 설계문제의 특성을 파악하기 위한 자료로 활용되며 향후, 분리기반 최적화과정에서 최종적으로 통합된 최적설계를 탐색하는데 필요한 기반구조를 제공한다.

• The Korean Journal of Financial Management
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• v.16 no.1
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• pp.223-243
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• 1999

포트폴리오의 위험을 통제하거나 감소시키기 위해서 헤저들은 최적헤지비율을 추정하여야 하는데, 최적헤지비율의 추정치는 사용하는 모형에 따라 많은 차이를 보인다. 전통적인 회귀분석모형에 의하여 추정된 최적헤지비율은 시계열자료의 불안정성(nonstationary) 등으로 인하여 잘못될 가능성이 많으며, 잘못 추정된 헤지비율을 그대로 이용할 경우 현물포트폴리오의 시장위험을 최소화시키지 못하고 헤징비용을 증가시키는 결과를 초래한다. 시계열자료의 불안정성으로 말미암아 야기되는 문제점들을 개선할 수 있는 모형으로서 오차 수정모형(Error Correction Model : ECM)이 널리 이용되고 있다. 본 연구는 ECM을 사용하여 추정된 최적헤지비율과 전통적 회귀분석모형을 사용하여 추정한 최적헤지비율을 비교하여 어떤 모형으로 추정한 헤지비율이 더 정확한지를 평가하는데 목적을 두고 있다. 즉, 본 연구는 KOSPI 200 현 선물지수 자료를 대상으로 ECM과 전통적 회귀분석모형에 의한 최적헤지비율을 추정하고 각 모형의 설명력과 예측력을 비교하고자 한다. 실증분석 결과, KOSPI 200 현물지수와 KOSPI 200 선물지수간에는 공적분 관계가 존재하며, ECM과 전통적 회귀분석모형을 이용하여 추정한 최적헤지비율의 크기는 서로 다르며, ECM을 이용할 때 모형의 설명력이 조금 더 높게 나타났으며, 예측력도 ECM이 좀더 우월한 것으로 나타났다.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.170-177
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• 2014

Genetic Algorithms are robust search and optimization techniques but have some problems such as premature convergence and convergence to local extremum. As population diversity converges to low value, the search ability decreases and converges to local extremum but population diversity converges to high value, then the search ability increases and converges to global optimum or genetic algorithm may diverge. To guarantee that genetic algorithms converge to the global optima, the genetic operators should be chosen properly. In this paper, we propose the genetic operators with the hybrid function of the average Hamming distance and the fitness value to maintain the diversity of the GA's population for escaping from the premature convergence. Results of simulation studies verified the effects of the mutation operator for maintaining diversity and the other operators for improving convergence properties as well as the feasibility of using proposed genetic operators on convergence properties to avoid premature convergence and convergence to local extremum.

• The Korean Journal of Applied Statistics
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• v.13 no.2
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• pp.393-405
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• 2000

Box and Draper( 19(5) listed some properties of a design that should be considered in design selection. But it is impossible that one design criterion from optimal experimental design theory reflects many potential objectives of an experiment, because the theory was originally based on the underlying model and its strict assumption about the error structure. Therefore, when it is neces::;ary to implement multi-objective experimental design. it is common practice to balance out the several optimal design criteria so that each design criterion involved benefits in terms of its relative "high" efficiency. In this study, we proposed several composite design criteria taking the case of heteroscedastic model. WVhen the heteroscedasticity is present in the model. the well known equivalence theorem between 1)- and C-optimality no longer exists and furthermore their design characteristics are sometimes drastically different. We introduced three different design criteria for this purpose: constrained design, combined design, and minimax design criteria. While the first two methods do reflect the prior belief of experimenter, the last one does not take it into account. which is sometimes desirable. Also we extended this method to the case when there are uncertainties concerning the error structure in the model. A simple algorithm and concluslOn follow.On follow.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.361-373
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• 2009

Using the genetic algorithm, the optimal-design technique of the Nielsen arch bridge was proposed in this paper. The design parameters were the arch-rise ratio and the steel weight ratio of the Nielsen arch bridge, and optimal-design techniques were utilized to analyze the behavior of the bridge. The optimal parameter values were determined for the estimated optimal level. The parameter determination requires the standardization of the safety, utility, and economic concepts as the critical factors of a structure. For this, a genetic algorithm was used, whose global-optimal-solution search ability is superior to the optimization technique, and whose object function in the optimal design is the total weight of the structure. The constraints for the optimization were displacement, internal stress, and time and space. The structural analysis was a combination of the small displacement theory and the genetic algorithm, and the runtime was reduced for parallel processing. The optimal-design technique that was developed in this study was employed and deduced using the optimal arch-rise ratio, steel weight ratio, and optimal-design domain. The optimal-design technique was presented so it could be applied in the industry.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.1001-1013
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• 2011

Development of an optimal water supply system considering water quantity, quality, and economical efficiency is needed to decide optimal available area by combine water supply systems in overlapped area where are more than 2 water sources. The EPAnet and the KModSim were coupled to develop optimal network model. The developed network model was calibrated by measured data from water supply system in Geoje City, Korea in 2007 which have three water sources such as Sadeong booster pumping station, Guchun dam reservoir and Yoncho dam reservoir. The optimum network model was validated by operating results of 2011 to assess the economically optimized service area and optimal pump combination under the given hydraulic operating rules developed in this study. The developed model can be applied into designing water supply systems and operating rules for the conjunctive operation since the model can give the optimal solution satisfied with water quantity, economical efficiency and quality.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.138-144
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• 2020

The Army's engineers are carrying out a range of operations using various equipment, of which, artillery unit support is the representative engineering operation field. The main task of the artillery unit is to attack the enemy's center with firepower from the rear of a friendly force. The artillery must move its original position after firing several times to prevent exposure of the shooting position. This paper proposed a mathematical model and heuristic algorithm that can be used to determine the optimal allocation among engineer equipment, the team (work), and position while reflecting the constraints of the construction of an artillery position. The model proposed in this paper derived the optimal solution for the small size problems, but it takes a long time to derive the optimal solution for the problem of equipment placement of the engineer battalion and brigade scale. Although the heuristic suggested in this study does not guarantee the optimal solution, the solution could be obtained in a reasonable amount of time.

• The KIPS Transactions:PartB
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• v.10B no.3
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• pp.311-320
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• 2003

The Optimal filter yielding optimal texture feature separation is a most effective technique for extracting the texture objects from multiple textures images. But, most optimal filter design approaches are restricted to the issue of supervised problems. No full-unsupervised method is based on the recognition of texture objects in image. We propose a novel approach that uses unsupervised learning schemes for efficient texture image analysis, and the band-pass feature of Gabor-filter is used for the optimal filter design. In our approach, the self-organizing neural network for multiple texture image identification is based on block-based clustering. The optimal frequency of Gabor-filter is turned to the optimal frequency of the distinct texture in frequency domain by analyzing the spatial frequency. In order to show the performance of the designed filters, after we have attempted to build a various texture images. The texture objects extraction is achieved by using the designed Gabor-filter. Our experimental results show that the performance of the system is very successful.