• Earthquakes and Structures
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• 제18권1호
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• pp.45-56
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• 2020

The application of critical excitation method with displacement-based objective function for multi degree of freedom (MDOF) systems is investigated. To this end, a new critical excitation method is developed to find the critical input motion of a MDOF system as a synthetic accelerogram. The upper bound of earthquake input energy per unit mass is considered as a new constraint for the problem, and its advantages are discussed. Considering this constraint, the critical excitation method is then used to generate synthetic accelerograms for MDOF models corresponding to three shear buildings of 10, 16, and 22 stories. In order to demonstrate the reliability of generated accelerograms to estimate dynamic response of the structures, three target ground motions with considerable level of energy contents are selected to represent "real critical excitation" of each model, and the method is used to re-generate these ground motions. Afterwards, linear dynamic analyses are conducted using these accelerograms along with the generated critical excitations, to investigate the key parameters of response including maximum displacement, maximum interstory drift, and maximum absolute acceleration of stories. The results show that the generated critical excitations can make an acceptable estimate of the structural behavior compared to the target ground motions. Therefore, the method can be reliably implemented to generate critical excitation of the structure when real one is not available.

• 지능정보연구
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• 제7권1호
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• pp.149-159
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• 2001

최근 전자상거래에는 일대일 마케팅이나 협력적 정보여과기법등을 이용한 다양한 추천서비스가 도입되고 있다. 이러한 추천 서비스의 형태는 다양한 제약 조건을 갖고 계산 복잡도가 높은 제품의 경우에는 고객을 만족시킬 만큼 적절한 추천서비스가 이루어지기 어려울 것으로 본다. 본 논문에서는 Clancey의 Classification Problem Solving 방법과 제약조건 기반 Configuration기술을 통합하여, 이러한 문제를 해결할 수 있는 방법을 제시하였다. 이 방법은 Clancey의 이론에 따라 구성 복잡도가 높은 제품의 해집합 도메인을 분할하여 문제의 복잡도를 줄일 수 있도록 하였으며, 여기에서 선택된 도메인을 제약조건 기반 Configuration기술에 적용시킴으로써, 구매자와 제품 컴포넌트 사이에 존재하는 제약조건을 처리할 수 있도록 하였다. 제약조건기반 Configuration기술은 구매자에게 적합한 제품을 구성하기 위해서 제막 조건 판촉 문제(Constraint Satisfaction Problem; CSP)해결 기법을 이용한다. 또한 Clancey이론은 구매자의 만족도를 고려하기 위해서 정보검색 분야의 벡터공간 모델링 방법을 변형하여 적용하였다. 마지막으로 본 모델의 평가를 위해 전체 시스템의 수행시간 및 구매자 만족도를 비교 분석하였다

• 한국해양공학회지
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• 제24권1호
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• pp.20-33
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• 2010

The paper deals with strength design of a riser support installed on floating production storage and offloading (FPSO) vessel under various loading conditions - operation, extreme, damaged, one line failure case (OLFC) and installation. The design problem is formulated such that thickness sizing variables are determined by minimizing the weight of a riser support structure subject to stresses constraints. The initial design model is generated based on an actual FPSO riser support specification. The finite element analysis (FEA) is conducted using MSC/NASTRAN, and optimal solutions are obtained via moving least squares method (MLSM) in the context of response surface based approximate optimization. For the meta-modeling of inequality constraint functions of stresses, a constraint-feasible moving least squares method (CF-MLSM) is used in the present study. The method of CF-MLSM, compared to a conventional MLSM, has been shown to ensure the constraint feasibility in a case where the approximate optimization process is employed. The optimization results present improved design performances under various riser operating conditions.

• 전자공학회논문지B
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• 제31B권9호
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• pp.150-158
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• 1994

In this paepr, Fuzzy Constraint Line Clustering (FCLC) method for optical flow estimation is proposed. FCLC represents the spatical and temporal gradients as fuzzy sets. Based on these sets, several constraint lines with different membership values are generated for the poxed whose velocity is to be estimated. We describe the process for obtaining the membership values of the spatial and temporal gradients and that of the corresponding constraint line. We also show the process for deciding the tightest cluster of point formalated by intersection between constraint lines. For the synthetic and real images, the results of FCLC are compared with of CLC.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.122-130
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• 2013

Rail geometries such as cant, grade and curvature can be easily represented by means of a track coordinate system. In this analysis, in order to derive a dynamic and constraint equation of a wheelset, the track coordinate system is used as an intermediate stage. Dynamic and constraint equations of railway vehicle bodies except the wheelset are written in the Cartesian coordinate system as a conventional method. Therefore, whole dynamic equations of a railway vehicle are derived by combining wheelset dynamic equations and dynamic equations of railway vehicle bodies. Constraint equations and constraint Jacobians are newly derived for the track coordinate system. A process for numerical analysis is suggested for the derived dynamic and constraint equations of a railway vehicle. The proposed dynamic analysis of a railway vehicle is validated by comparison against results obtained from VI-RAIL analysis.

• 한국콘텐츠학회논문지
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• 제11권8호
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• pp.428-437
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• 2011

이 연구는 중국인 유학생의 여가제약, 여가제약 협상 및 여가참가의 관계를 규명하는데 목적이 있다. 2010년 10월 2일대전에서 개최된 한국 중국인 유학생 체육대회에 참가한 중국인을 대상으로 유의표집법을 활용하여 총 210명의 연구대상을 표집하였고, 본 연구에서는 총 194명의 자료가 분석에 이용되었다. 수집된 문항은 SPSS 18.0 프로그램을 통해 Cronbach's ${\alpha}$ 값을 이용한 설문 문항의 신뢰도를 분석하였으며 연구과제 분석을 위해 단순 및 중다회귀분석을 실행하여 다음과 같은 결과를 도출하였다. 첫째, 여가제약은 여가제약 협상에 정적인 영향을 미치고 있다. 구체적으로, 여가제약은 여가제약 협상 전략 중에서 '여가활동 동반자 탐색 노력'과 '여가활동 강도 조절 노력'에 영향을 미치고 있다. 둘째, 여가 제약은 여가 참가에 부적인 영향을 미치고 있다. 셋째, 여가제약 협상은 여가 참가에 유의한 영향을 미치지 못하고 있다.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1597-1604
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• 2001

Alternative computational scheme is presented fur reliability based optimal design using a modified advanced first order second moment (AFOSH) method. Both design variables and design parameters are considered as random variables about their nominal values. Each probability constraint is transformed into a sub -optimization problem and then is resolved with the modified Hasofer- Lind-Rackwitz-Fiessler (HL-RF) method for computational efficiency and convergence. A method of design sensitivity analysis for probability constraint is presented and tested through simple examples. The suggested method is examined by solving several examples and the results are compared with those of other methods.

• 제어로봇시스템학회논문지
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• 제5권1호
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• pp.62-68
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• 1999

The attitude of a vehicle can be precisely determined using GPS carrier phase measurements from more than two antennas attached to a vehicle and an efficient integer ambiguity resolution technique. Many methods utilizing the known baseline length as a constraint of independent elements of integer ambiguities are proposed to resolve integer ambiguity at real time. Three-dimensional search space is reduced to two-dimensional search space with this constraint. Thus the true integer ambiguity can be easily determined with less computational burden and fewer number of measurements. But there are still strong requirements for the real time integer ambiguity resolution, which uses single epoch measurement of long baseline. In this paper, a new constraint from the geometry of multiple baselines is derived. With this new constraint, two-dimensional search space is further reduced to one-dimensional search space. It makes possible to determine integer ambiguity with single epoch measurement. The proposed method is applied to real data to show its effectiveness.

• 소성∙가공
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• 제8권1호
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• pp.47-56
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• 1999

The governing functional in plastic deformation has to satisfy the incompressibility constraint. This incompressibility constraint imposed on velocity fields can be removed by introducing either Lagrange multiplier or the penalty constant into the functional. In this study, two-dimensional rigid plastic FEM programs using these schemes were developed. These two programs and DEFORM were applied in a cylinder upsetting and a closed die forging to compare the values of load, local mean stress and volume loss. As the results, the program using Lagrange multiplier obtained a more exact and stable solution, but it took more computational time than the program using the penalty constant. Therefore, according to user's need, one of these two programs can be chosen to simulate a metal forming processes.

• 대한기계학회논문집
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• 제18권9호
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• pp.2339-2348
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• 1994

The objective of this paper is to develop a solution method for the differential-algebraic equation(DAE) derived from constrained muti-body dynamic systems. Mechanical systems are often modeled as bodies and joints. Differential equations of motion are formulated for bodies. Since the bodies are connected by joint, the differential variables must satisfy the kinematic constraint equations that come from the joints. Difficulties are arised due to drift of the differential variables off the constraint equations. An optimization method is adopted to correct the drift of the differential variables. To demonstrate the efficiency of the proposed method a slider-crank mechanism is analyzed dynamically. Identical results are obtained as these from the commercial program DADS. Dynamic analysis of a High Mobility Multi-purpose Wheeled. Vehicle(HMMWV) is carried out to show the practicalism of the proposed method.