• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.581-586
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1110-1118
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff' s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• 한국음향학회지
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• 제19권4호
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• pp.69-76
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• 2000

본 연구에서는 Class IV Flextensional 트랜스듀서의 여러 설계변수들에 따른 음압 변화 및 열 발생 경향성을 유한요소 해석법으로 해석하였다. 해석되어진 결과를 바탕으로 최대 음압을 구현하고, 열 발생이 최소인 중심 주파수 1 kHz를 가지는 Class IV extensional 트랜스듀서의 최적구조를 설정하였다. 본 연구에서 설정한 최적구조는 기본모델에 비해 음압이 2배 이상 크고 열 발생은 아주 작은 것으로 나타났다. 본 연구의 결과는 향후 다양한 중심 주파수 및 최대 음압을 구현하고 열 발생이 최소인 Class IV Flextensional 트랜스듀서를 설계함에 있어 유용한 자료로 활용될 수 있을 것이다.

• 한국강구조학회 논문집
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• 제21권4호
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• pp.361-373
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• 2009

유전자 알고리즘을 이용한 닐센아치교의 최적설계기법을 이 논문에서 제시하였다. 설계 매개변수로는 닐센아치교의 아치-라이즈비와 강중비에 대해서 최적화기법을 적용하여 각각의 거동을 분석하고, 적정성을 평가하여 최적의 매개변수 값을 결정하였다. 매개변수의 결정은 구조물의 안전성과 사용성 그리고 경제성에 중요한 설계인자로서 정형화가 요구된다. 이를 위해 최적화 기법으로 전역 최적해 탐색능력이 우수한 유전자 알고리즘을 사용하였으며, 설계 목적함수로는 구조물의 총 중량을 사용하였고, 제약조건으로는 변위, 응력, 시공성 제약조건을 두었다. 구조해석은 미소변위이론에 의한 탄성해석을 수행하여 유전자 알고리즘과 조합하여 병렬연산으로 수행시간을 단축시켰다. 이 연구에서 개발된 최적설계기법을 사용하여 최적의 아치-라이즈비와 강중비, 최적설계영역을 제시 하였으며 실무에 적용할 수 있도록 하였다.

• Earthquakes and Structures
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• 제9권5호
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• pp.1115-1132
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• 2015

The study considers earthquake shake table testing of bending-torsion coupled structures under multi-component stationary random earthquake excitations. An experimental procedure to arrive at the optimal excitation cross-power spectral density (psd) functions which maximize/minimize the steady state variance of a chosen response variable is proposed. These optimal functions are shown to be derivable in terms of a set of system frequency response functions which could be measured experimentally without necessitating an idealized mathematical model to be postulated for the structure under study. The relationship between these optimized cross-psd functions to the most favourable/least favourable angle of incidence of seismic waves on the structure is noted. The optimal functions are also shown to be system dependent, mathematically the sharpest, and correspond to neither fully correlated motions nor independent motions. The proposed experimental procedure is demonstrated through shake table studies on two laboratory scale building frame models.

• Structural Engineering and Mechanics
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• 제14권1호
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• pp.39-56
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• 2002

In order to trace a target in deep sky, a feed cabin 20 tons in weight used for a large radio telescope is drawn with six cables. To realize a smooth tracing all the time, optimal distribution of the cable tensions is explored. A set of cable-clog systems is utilized to control the wind-induced vibration of the cable-cabin structure. This is an attempt to apply the passive structural control strategy in the area of radio astronomy. Simulations of wind-induced vibration of the structure in both time and frequency domains offer a valuable reference for construction of the next generation large radio telescope.

• Journal of applied mathematics & informatics
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• 제24권1_2호
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• pp.49-64
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• 2007

In this paper, we investigate optimal policies for three age-dependent populations in a competition system, which is controlled by fertility. By using Dubovitskii-Milyutin's general theory, the maximum principles are obtained for problems with free terminal states, infinite horizon and target sets, respectively.

• 로봇학회논문지
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• 제17권4호
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• pp.493-499
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• 2022

This paper presents the design for the kinematic structure of a system for an automatically moored 6000 ton autonomous ship in a port, and the process and results of optimal design for the link cross-sectional shape. We propose an automatic mooring system with a PPP type serial manipulator structure capable of linear motion in the XYZ axis. The mooring force applied by the mooring system was derived with dynamics simulation tool "ADAMS". The design goal is the minimization of the cross-sectional area of the link. Constrains include compressive stress and shear stress. The optimization problems were solved by using the sequential quadratic programing method implemented in the fmincon package. The shape of the cross section was assumed to be rectangle. Through future research, we plan to manufacture automatic mooring system for 6000ton class autonomous ship.

• Earthquakes and Structures
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• 제14권1호
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• pp.1-10
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• 2018

Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

• 한국멀티미디어학회논문지
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• 제23권8호
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• pp.1040-1048
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• 2020

In this study, in order to improve the implantable bone conduction transducer of the prototype proposed by Shin et al., the effect of the element parameters of the transducer on the frequency characteristics was analyzed using electromagnetic and mechanical vibration analysis. Electromagnetic analysis was performed on the size of the permanent magnet and the distance between the metal plate and the coil to derive an optimal structure that generates the maximum Lorentz force. In addition, mechanical vibration analysis was performed on the cantilever structure of the vibrational membrane in order to minimize the distortion of the transducer and to have a frequency characteristic suitable for conductive hearing loss compensation. The frequency characteristics of the transducer of the optimal structure derived through finite element method were compared with the simulation results of the previous transducer. As a result, the output magnitude (displacement) of the transducer designed with the optimal structure generated an average 8.8 times higher than the previous transducer, and the resonance frequency was generated at 0.9 kHz.