• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.339-348
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• 2002

The study developed an automatic design method of steel frames which uses nonlinear analysis. The geometric nonlinearity was considered using stability functions. Likewise, the transverse shear deformation effect in a beam-column was explained. A direct search method was used as an automatic design technique. The unit value of each part was evaluated using LRFD interaction equation. The member with the largest unit value was replaced one by one with an adjacent larger member selected from the database. The weight of the steel frame was considered as an objective function. On the other hand, load-carrying capacities, deflections, inter-story drifts, and ductility requirement were used as constraint functions. Case studies of a two-dimensional and a three-dimensional two-story frames were presented.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.3
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• pp.191-199
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• 2001

This paper presents a new genetic algorithm for job-shop scheduling problems. When we design a genetic algorithm for difficult ordering problems such as job-shop scheduling problems, it is important to design encoding/crossover that is excellent in characteristic preservation and to maintain a diversity of population. We used Job-based order crossover(JOX). Since the schedules generated by JOX are not always active-schedule, we proposed a method to transform them into active schedulesby using the GT method with c)laracteristic preservation. We introduce strategies for maintaining a diversity of the population by eliminating same individuals in the population. Furthermore, we are not used mutation. Experiments have been done on two examples: Fisher s and Thompson s $lO\timeslO and 20\times5$ benchmark problem.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.120-129
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• 2023

Hanger cable tension is a major response that can determine the integrity and safety of suspension bridges. In general, the vibration method is used to estimate hanger cable tension on operational suspension bridges. It measures natural frequencies from hanger cables and indirectly estimates tension using the geometry conditions of the hanger cables. This study estimated the hanger cable tension of the Palyeong Bridge using a vision-based system. The vision-based system used digital camcorders and tripods considering the convenience and economic efficiency of measurement. Measuring the natural frequencies for high-order modes required for the vibration method is difficult because the hanger cable response measured using the vision-based system is displacement-based. Therefore, this study proposed a back analysis technique for estimating tension using the natural frequencies of low-order modes. Optimization for the back analysis technique was performed by defining the difference between the natural frequencies of hanger cables measured in the field and those calculated using finite element analysis as the objective function. The direct search method that does not require the partial derivatives of the objective function was applied as the optimization method. The reliability and accuracy of the back analysis technique were verified by comparing the tension calculated using the method with that estimated using the vibration method. Tension was accurately estimated using the natural frequencies of low-order modes by applying the back analysis technique.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1590-1595
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• 2003

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1719-1726
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• 2004

Direct drive servovalve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the DC motor. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• The Journal of the Acoustical Society of Korea
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• v.17 no.7
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• pp.36-41
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• 1998

본 논문에서는 부분파수적분법과 유전자알고리즘기법의 조합을 통한 광대역 신호로 부터 직접적인 해저지질특성치의 역산기법을 제시하였다. 광대역주파수신호의 시간영역 모 의는 부분파수적분법을 사용하여 계산시간을 단축하였고, 다수의 국부최소점이 존재하는 역 산문제에 유전자알고리즘기법을 적용한 전역되적점에 대한 탐색을 수행하였다. 본 방법을 사용하여 해저퇴적층의 지질특성 요소에 대한 역산을 수행하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.165-179
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• 2007

For the purpose of optimum design of reinforced concrete structures, pre-determined section database of column and beam are constructed and arranged in order of the resisting capacity. Then, regression equations representing the relation between section number and section resisting capacity are derived. In advance, effective optimization algorithms which search optimized solution quickly using direct search method from these database are proposed. In practice, from the fact that engineers conduct member design close to capacity optimization rather than cost optimization, both capacity and cost optimization using proposed algorithms are performed, and the review for the obtained results are followed. Moreover, the investigation for the applicability and effectiveness of the Introduced design procedure is conducted through correlation study for example structures. Because of no restriction in constructing objective functions with very simple optimization processes and fast convergence, the introduced method can effectively be used in the preliminary design stage. Especially, selected solutions from database are directly applicable in practice because these sections already satisfy all the requirements in design codes and practical restrictions.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.109-111
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• 2010

Recent studies have described various microorganisms that can degrade PAH, however, there are currently limited methods available to screen for PAH-degrading microorganisms. To screen for PAH-degrading microorganisms, a sublimation method (Alley, Jeremy F. and Lewis R. Brown. 2000. Appl. Environ. Microbiol. 66, 439-442) was modified to produce a simple screening system. In our results, there were several bacterial species capable of pyrene degradation including genera, Coryenbacterium, Gordonia, Rhodococcus, and Streptomyces, which have been screened from 350 bacterial isolates of commercial gasoline and oil-spilled sediment by the sublimation method. The main advantage of this method is that it (i) safely deposits an even, thin and visible layer of PAH onto the agar surface without the use of solvents and (ii) the quantity of PAH sublimed onto the agar can be easily controlled. Overall, this sublimation method may be an effective and simple technique to screen for PAH-degrading microorganisms.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.4
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• pp.1-8
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• 2004

The optimum design parameters of several hydraulic systems are obtained using the complex method that is one kind of constrained direct search method. First, the parameters of lead-lag controller of the direct drive servovalve is designed using the complex method to satisfy the steady-state error requirement. Second, the optimum locating point of hydraulic cylinder Is determined to minimize the cylinder force in the operation range of rotational sluice gate. For the third application case, the optimum piston area of hydraulic cylinder is determined to minimize the man power to elevate the manually operated sluice gate.

• Proceedings of the Korea Water Resources Association Conference
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• 1991.07a
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• pp.88-101
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• 1991

충주댐 및 소양강댐 유역에 대해 현재 한국수자원공사에서 개발 사용되고 있는 저류함수 유출모형에 최적화 기법을 적용하여 모형을 효율적으로 자동보정 하기위함이 본 연구의 목적이다. 최적화 기법으로는 다양한 조건하에서도 해의 안정성이 Gradient-Based 방법보다 우수한 직접 탐색법(Direct Search Method)의 하나인 Pattern-Search법으로 선정하였으며 목적함수로는 산정된 유출과 관측치의 편차의 제곱에 대한 누계치로 정의하였다. 합성유입량(Synthetic Inflow)을 이용한 민감도 분석에 의해 매개변수 5개(유역 저류상수 및 지체시간, 포화우량, 하도의 지체시간)를 결정변수로 선정하였다. 또한 실시간 모형의 보정을 위하여 최적화 모형의 수렴조건을 분석한 결과 P-S 법의 증분 감소횟수 2회가 합리적으로 나타났다. 본 모형을 충주댐 및 소양강댐의 과거 홍수사상에 대해 적용하였으며 댐지점에서 전체유역을 일괄 보정하는 방법과 댐 상류 수위국을 기준으로 나눈 중유역별로 일괄 보정하는 방법을 채택하여 분석하였다. 실시간 보정된 모형의 예측기능을 시험한 결과 상당한 오차발생의 여지가 충분하며 중유역별 매개변수의 보정은 대유역 일괄보정에 비해 예측에 따른 오차를 줄일 수 있는 방법의 하나이다. 또한 최적화 기법에 의한 매개변수의 자동 보정은 시행착오에 의한 수동보정의 경우보다 시간 및 노력면에서 효율적이며 보다 신뢰성 있는 보정을 실시 할 수 있다.