• Earthquakes and Structures
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• 제19권5호
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• pp.347-359
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• 2020

The Mega-Sub Controlled Structure System (MSCSS), an innovative vibration passive control system for building structures, is improved by adding lead rubber bearings (LRBs) on top of the substructure. For the new system, a genetic algorithm is used to optimize the dynamic parameters and distributions of dampers and LRBs. The program uses various seismic performance indicators as optimization objectives, and corresponding results are compared. It is found that the optimization procedure for maximizing the energy dissipation ratio yields the best solutions, and optimized models have consistent seismic performances under different earthquakes. Seismic performances of optimized MSCSS models with and without LRBs, as well as the traditional Mega-Sub Structure model, are evaluated and compared under El Centro wave, Taft wave and 20 other artificial waves. In both elastic and plastic analysis, the model with LRBs shows significantly smaller story drift and horizontal acceleration than those of the other two models, and fewer plastic hinges are developed during severe earthquakes. Energy analysis also shows that LRBs installed in proper locations increase the deformation and energy dissipation of dampers, thereby significantly reduce the kinetic, potential, and hysteretic energy in the structure. However, LRBs do not have to be mounted on all the additional columns. It is also demonstrated that LRBs at unfavorable locations can decrease the energy dissipation for dampers. After LRBs are installed, the optimal damping coefficient and the optimal damping exponent of dampers are reduced to produce the best damping effect.

• 한국지리정보학회지
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• 제6권3호
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• pp.21-32
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• 2003

지역 분석 연구에서 접근성 분석은 오랜 연구 주제였으며, GIS에서 지리정보의 시각적 표현 및 지도화는 많은 장점과 이점을 제공하고 있다. 본 연구의 목적은 특정 지역의 접근성 결과를 해석하는데 있어, GIS의 3차원 시각화(visualization) 표현 기법들의 유용함을 사례지역의 분석을 통해서 보여 주고자 하는 것이다. 본 연구는, 기존 연구(Kim, 2002)의 후속 연구로써 영국 리즈시를 실험대상으로, 영국의 그리드 메쉬(British Nation Grid system) 위치 정보를 바탕으로 한 1991 년도 인구센서스를 이용하였다. 본 연구에서는 시설물에 이용 주민들간의 접근성을 분석하고 결과를 해석하는데 3차원 시각화 기법이 어떻게 이용될 수 있으며, 어떠한 장점들이 시설물 입지와 관련된 공간의사결정에 기여할 수 있는지를 고찰하였다. 본 연구의 결론은, 분석 지역마다 상이하게 나타나는 분석 결과의 효과적인 시각적 표현 방법은 GIS를 이용한 공간의사결정 및 대안 제시에 있어 중요할 뿐만 아니라, 향후 국내 지리정보 연구에 많은 기여를 할 수 있음을 제시하고자 하는 것이다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권4호
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• pp.750-769
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• 2015

The geometry of engineering systems affects their performances. For this reason, the shape of engineering systems needs to be optimized in the initial design stage. However, engineering system design problems consist of multi-objective optimization and the performance analysis using commercial code or numerical analysis is generally time-consuming. To solve these problems, many engineers perform the optimization using the approximation model (response surface). The Response Surface Method (RSM) is generally used to predict the system performance in engineering research field, but RSM presents some prediction errors for highly nonlinear systems. The major objective of this research is to establish an optimal design method for multi-objective problems and confirm its applicability. The proposed process is composed of three parts: definition of geometry, generation of response surface, and optimization process. To reduce the time for performance analysis and minimize the prediction errors, the approximation model is generated using the Backpropagation Artificial Neural Network (BPANN) which is considered as Neuro-Response Surface Method (NRSM). The optimization is done for the generated response surface by non-dominated sorting genetic algorithm-II (NSGA-II). Through case studies of marine system and ship structure (substructure of floating offshore wind turbine considering hydrodynamics performances and bulk carrier bottom stiffened panels considering structure performance), we have confirmed the applicability of the proposed method for multi-objective side constraint optimization problems.

• 한국전자파학회논문지
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• 제30권6호
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• pp.438-444
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• 2019

본 논문에서는 간섭 신호원의 방향을 정확히 탐지 및 식별하기 위해 상호결합특성을 고려한 16소자 배열안테나의 배열 형상 및 개별소자 구조에 대해 연구하였다. 제안된 배열 안테나는 상호결합특성, 능동소자패턴의 편차, 반전력빔폭을 고려하여 개별소자의 접지면간 이격거리를 도출하였다. 개별소자는 마이크로스트립 패치안테나로 구성되며, 광대역 특성 및 안테나의 소형화를 위해 접지면과 연결된 방사체 및 L 모양의 간접 급전 급전부로 구성된다. 제안된 안테나를 사용한 신호탐지 성능 평가 결과 제시된 시나리오 범위 내에서 낮은 RMS(root mean square) error의 성능을 갖는 것을 확인하였다.

• 한국해양공학회지
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• 제35권6호
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• pp.434-445
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• 2021

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle's horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle's rotation and maintaining its heading. However, for the numerical simulations, the vehicle's hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle's various final performances, including its ability to overcome strong current.

• 대한기계학회논문집
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• 제8권6호
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• pp.517-525
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• 1984

본 연구에서는 2개의 축적탱크와 외부 열교환기로 구성된 가정용 태양열 급탕 시스템을 시뮬레이션 모델로 이론적인 해석을 하고 설계인자들의 값들을 변화시킴으로 써 각각의 성능을 계산할 수 있었다. 또 이 성능 계산치에 의하여 최적설계 인자치 들을 구할 수 있었다. 또한 1983년 1년간 서울지방의 매 시간 일분량과 기온을 사용 하였다.

• 대한산업공학회지
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• 제34권4호
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• pp.481-488
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• 2008

This paper deals with a scheduling problem for two-machine flow shop, in which the preceding machine is a batch processing machine that can process a number of jobs simultaneously. To minimize makespan of the system, we present a mixed integer linear programming formulation for the problem, and using this formulation, it is shown that an optimal solution for small problem can be obtained by a commercial optimization software. However, since the problem is NP-hard and the size of a real problem is very large, we propose a number of heuristic algorithms including genetic algorithm to solve practical big-sized problems in a reasonable computational time. To verify performances of the algorithms, we compare them with lower bound for the problem. From the results of these computational experiments, some of the heuristic algorithms show very good performances for the problem.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.463-471
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• 2013

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.

• 한국항공우주학회지
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• 제33권8호
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• pp.26-33
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• 2005

틸트로터 비행체 개념인 스마트무인기는 수직이착륙, 장기체공, 그리고 고속비행성능을 동시에 요구한다. 이와 같은 세 가지의 상반된 비행체 성능의 구현을 위해서는 비행모드별로 최적의 공력성능을 갖도록 하는 플랩시스템의 운용이 불가피하다. 스마트무인기의 플래퍼론을 설계하는데 있어서 다양한 후보 형상을 생성하고, 이들 형상에 대해 전산유동해석을 수행하여 각 형상에 대한 공력성능을 분석하였다. 이와 같은 공력성능과 실제형상의 구조적인 단순성을 고려하여 스마트무인기의 최종 플래퍼론 형상을 선정하였으며, 40% 축소모델에 대한 풍동시험을 통해 선정된 플래퍼론에 대한 성능을 검증하였다.

• Journal of the Optical Society of Korea
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• 제9권1호
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• pp.26-31
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• 2005

We describe the design and the implementation of video-rate reflection confocal scanning microscopy (CSM) using an acousto-optical deflector (AOD) for the fast horizontal scan and a galvanometer mirror (GM) for the slow vertical scan. Design parameters of the optical system are determined for optimal resolution and contrast. The OSLO simulations show that the performances of CSM are not changed with deflection angle and the wavefront errors of the system are less than 0.012λ. To evaluate the performances of designed CSM, we do a series of tests, measuring lateral and axial resolution, real time image acquisition. Due to a higher axial resolution compared with conventional microscopy, CSM can detect the surface of sub-micrometer features. We detect 138㎚ line shape pattern with a video-rate (30 frm/sec). And 10㎚ axial resolution is archived. The lateral resolution of the topographic images will be further enhanced by differential confocal microscopy (DCM) method and computational algorithms.