• 한국자동차공학회논문집
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• 제16권3호
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• pp.166-171
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• 2008

In this paper, the optimization design module for the brake system of a vehicle is developed. As using this module, design variables, that minimize an object function and satisfy nonlinear constraint conditions, can be found easily. Before an optimization is operated, Plackett-Burman design, one of the factorial design methods, is used to choose the design variables which affect a response function significantly. Using the response surface analysis, second order recursive model function, which informs a relation between design variables and response function, is estimated. In order to verify the reliability of the model function, analysis of variances(ANOVA) table is used. The value of design variables which minimize the model function and satisfy the constraint conditions is predicted through Sequential Quadratic-Programming (SQP) method. As applying the above procedure to a real vehicle simulation model and comparing the values of object functions of a current and optimized system, the optimization results are verified.

• 한국정보통신학회논문지
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• 제14권10호
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• pp.2310-2316
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• 2010

이 논문에서는 형식 검증(formal verification)의 한 분야인 모델 검증(model checking)에 재타이밍(retiming) 기법을 적용하는 방법에서 대해 연구하였다. 재타이밍은 주어진 회로의 레지스터들을 재배치함으로써, 입출력 동작을 바꾸지 않으면서 전이 관계(transition relation)을 변환할 수 있는 기법이다. 이러한 재타이밍을 이용하면 모델 검증을 더 효율적으로 수행하도록 회로를 바꿀 수 있다. 이 논문에서는, 레지스터의 개수와 전이 관계의 특성을 반영한 cost 함수를 제안하고, 재타이밍으로 얻을 수 있는 회로 구조들을 효율적으로 탐색하는 heuristic annealing 알고리즘을 개발한다. 제안된 방법이 모델 검증의 성능을 향상시킬 수 있음을 실험 결과를 통해 보여주었다.

• 한국자동차공학회논문집
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• 제7권5호
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• pp.154-161
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• 1999

An elastomeric bushing is a device used in automotive suspension systems to cushion the force transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid metal shaft at its inner surface and a metal sleeve at its outer suface. The relation between the force applied to the shaft or sleeve and their relative deformation is nolinear and exhibits features of viscoelasticity. Numerical solutions of the boundary value problem represent the exact bushing response for use in the method for determining the force relaxation function of the bushing. The new nonlinear viscoelastic bushing model, which is called Pipkin-Rogers model, is proposed and it is shown that the predictions of the proposed force-displacement relation are in very good agreement with the exact results. This new bushing model is thus very suitable for use in multi-body dynamics codes. The success of the present study for axial mode response suggests that the same approach be applied to other modes, such as torsional or radial modes.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.415-419
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• 2003

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data for the elastomeric bushing material was obtained and this data was used to derive the new load-displacement for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

• Communications for Statistical Applications and Methods
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• 제5권1호
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• pp.77-84
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• 1998

ARES plot (Cook and Weisberg, 1987) idea is applied to a multiple regression model in which the relation between a response variable and some independent variable is nonlinear. This method is expected to show the impact on the function to which and independent variable should be transformed, as a variable is smoothly added to the model.

• Industrial Engineering and Management Systems
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• 제1권1호
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• pp.79-86
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• 2002

This paper proposes a new algorithm for estimating ARMA model parameters. In estimating ARMA model parameters, several methods such as generalized least square method, instrumental variable method have been developed. Among these methods, the utilization of a bootstrap type algorithm is known as one of the effective approach for the estimation, but there are cases that it does not converge. Hence, in this paper, making use of a cross correlation function and utilizing the relation of structural a priori knowledge, a new bootstrap algorithm is developed. By introducing theoretical relations, it became possible to remove terms, which is liable to include much noise. Therefore, this leads to robust parameter estimation. It is shown by numerical examples that using this algorithm, all simulation cases converge while only half cases succeeded with the previous one. As for the calculation time, judging from the fact that we got converged solutions, our proposed method is said to be superior as a whole.

• 한국수자원학회논문집
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• 제37권12호
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• pp.1055-1063
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• 2004

공간적 위치 및 유량 값에 따라 각 계산점마다 조도계수의 값이 달리 주어질 수 있도록 하는 가변 조도변수 부정류 계산모형을 수립하였다. 유량과 조도계수의 관계식으로는 계단함수 또는 멱함수를 적용할 수 있도록 하였다. 수립된 모형을 충주댐부터 팔당댐까지의 남한강 구간에 적용하여 최적화에 의한 매개변수의 추정을 수행하였다. 가변 매개변수 모형의 보정 결과, 계단함수 도형 및 멱함수 모형 모두 유량이 커질수록 조도계수가 감소하는 경향이 일관되게 나타났다. 이러한 경향은 여주 지점 상류구간의 경우에 더욱 현저한 것으로 나타났다. 가변 조도계수 모형의 매개변수 추정에 따른 오차가 고정 조도계수 모형의 경우보다 작아짐을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.125-128
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• 1999

A linear time-invariant model can be described either by a parametric model or by a nonparametric model. Nonparametric models, for which a priori information is not necessary, are basically the response of the dynamic system such as impulse response model and frequency models. Parametric models, such as transfer function models, can be easily described by a small number of parameters. In this paper aiming to take benefit from both types of models, we will use linear-combination of basis fuctions in an impulse response using a few parameters. We will expand and generalize the Kautz functions as basis functions for dynamical system representations and we will consider estimation problem of transfer functions using Kautz function. And so we will present the influences of poles settings of Kautz function on the identification accuracy.

• 해양정책연구
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• 제34권2호
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• pp.1-28
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• 2019

The purpose of this study is to analyze the substitution among production factors of Korean distant water longline fisheries in IATTC waters. In the analysis, the translog function which have one output variable of total cost and input variables of labor, fuel, fishing gear, and capital was established and it was transformed into simultaneous equations by each cost. Then, variables of equations were estimated by SUR (seemingly unrelated regression) model. Since distant water longline fisheries is a fishing type with high fuel usage, substitution of fuel with other factors was mainly analyzed. Results showed a substitute relation between fuel and labor as well as fuel and fishing gear, while a complementary relation between fuel and capital. In addition, it was analyzed that magnitude of fuel elasticity with other factors would be inelastic.

• 정보처리학회논문지D
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• 제10D권7호
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• pp.1137-1144
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• 2003

소프트웨어 규모를 측정하기 위한 기존의 기능점수 기법은 관리정보 시스템에 적합하도록 구성되어 있으나 최근의 실시간 및 내장형 시스템의 적용성 확장에 따라 완전기능점수(FFP, Full Function Point) 기법이 제안되었다. 그러나, FFP 기반의 소프트웨어 규모 측정 방법에 관한 많은 연구는 이루어지고 있으나, FFP로 측정된 소프트웨어 규모에 대한 개발비용을 추정할 수 있는 모델 연구는 미흡한 실정이다. 본 논문은 FFP로 실제 개발된 소프트웨어의 완전기능점수를 기반으로 소프트웨어 개발에 투입될 노력을 추정하는 선형 회귀분석 모델과 거듭제곱 회귀분석 모델을 평가하여 가장 적합한 모델로써 거듭제곱 모델을 선정하였다. 선정된 거듭제곱 모델을 적용할 경우 가장 근사치의 소프트웨어 개발비용을 추정할 수 있음을 보였다.