• Interaction and multiscale mechanics
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• 제5권3호
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• pp.211-228
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• 2012

This paper reports the development of a generalized inverse analysis formulation for the parameter estimation of four-parameter Burger model. The analysis is carried out by formulating the problem as a mathematical programming formulation in terms of identification of the design vector, the objective function and the design constraints. Thereafter, the formulated constrained nonlinear multivariable problem is solved with the aid of fmincon: an in-built constrained optimization solver module available in MatLab. In order to gain experience, a synthetic case-study is considered wherein key issues such as the determination and setting up of variable bounds, global optimality of the solution and minimum number of data-points required for prediction of parameters is addressed. The results reveal that the developed technique is quite efficient in predicting the model parameters. The best result is obtained when the design variables are subjected to a lower bound without any upper bound. Global optimality of the solution is achieved using the developed technique. A minimum of 4-5 randomly selected data-points are required to achieve the optimal solution. The above technique has also been adopted for real-time settlement of four oil refineries with encouraging results.

• 환경영향평가
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• 제15권2호
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• pp.101-109
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• 2006

Water quality simulation models include the difference between the measured and estimated values as an inevitable consequence because they represent the complicated natural phenomena as simplified mathematical equations. The major reason of the difference occurrence is due to the use of the imprecise values of the model parameters, but the parameter values are currently determined by the try and error method directly performed by humans. However, the use of this method requires many time and endeavor of humans, and generally does not obtain the most suitable parameter values. A method for deciding model parameter values is, therefore, developed in this study. The method minimizes the difference between the measured and estimated values and also distributes uniformly the measured values on the upper and lower sides of the line representing the estimated values. A user interface based on this method is also developed by using the Visual Basic 6.0 of Microsoft, and it can be operated in the environment of Windows 98/2000. In this study, the method for deciding model parameter values is applied for estimating the water quality of the stream Ko-heung. The results of the application show that the method, including its computer program, can effectively obtain the most suitable parameter values and also save many working time in comparison with the existing method directly performed by humans.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.59-64
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• 2003

The parameter modification of the initial FEM model to match it with the experimental results needs the modal information and the modal sensitivity matrix to the parameter change. There are two cases this methodology is ill-equip to deal with; the deficiency of the necessary modal information and the ill-conditioning of the sensitivity matrix. In this research, a novel concept of the feedback exciter that uses the summation of the white noise and the signals from the measurement sensors multiplied with feedback gains as the reference signal is proposed. There are 2 advantages using this external feedback excitation. First, we can use the change of the system response such as modal data by the active energy Path from the sensor to the exciter. This change of the system response can be additional clues to the system dynamics that we want to know. Secondly, the external energy Path alternates the offset of the Parameter change to the system response. That means the modal sensitivity of the parameters becomes different from the original sensitivities by the feedback excitation. Through the feedback loop, we can change the similar modal sensitivities of some updating parameters and consequently discriminate the parameters using the closed-loop modal data. To demonstrate the discrimination performance, the parameter estimation of an indeterminate structure by use of the feedback method is introduced.

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.31-39
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• 2021

To investigate numerically the effect of all parameters on the outcome of an aircraft impact into robust engineering structures like nuclear power plant containments is a tedious task. In order to reduce the problem to a manageable size, we propose a single dimensionless parameter, the damage potential, to characterize the main features of the impact. The damage potential, which is the ratio of the initial kinetic energy of the aircraft to the work required to crush it, enables us to find the crucial parameter settings that need to be modelled numerically in detail. We show in this paper that the damage potential is indeed the most important parameter of the impact that determines the time-dependent reaction force when either finite element (FE) modelling or the Riera model is applied. We find that parameters that do not alter the damage potential, like elasticity of the target, are of secondary importance and if parameters are altered in a way that the damage potential remains the same then the course of the impact remains similar. We show, however, that the maximum value of the reaction force can be higher in case of elastic targets than in case of rigid targets due to the vibration of the target. The difference between the Riera and FE model results is also found to depend on the damage potential.

• Advances in concrete construction
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• 제13권6호
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• pp.471-479
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• 2022

In this paper, vibrational attributes of double-walled carbon nanotubes (CNTs) has been studied based upon nonlocal elastic shell theory. The implication of small scale is being perceived by establishing nonlocal Love shell model. The wave propagation approach has been operated to frame the governing equations as eigen value system. The comparison of local and nonlocal model has been overtly explored by means of scaling parameter. An appropriate selection of material properties and nonlocal parameter has been considered. The influence of changing mechanical parameter Young's modulus has been studied in detail. The dominance of end condition via nonlocal parameter is explained graphically. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.

• 한국방재학회 논문집
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• 제10권6호
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• pp.131-138
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• 2010

본 연구에서는 저류함수법의 매개변수 추정을 위해 개발한 범용모형을 토대로 관측수문자료를 보유하고 있는 16개 댐유역에 적용하여 그 적정성을 확인하였다. 저류함수법의 기존 매개변수 추정식은 대부분 한정된 조건에서 얻어졌고 다양한 유역특성을 고려할 때 물리적 의미가 없는 값이 얻어지는 경우가 많아 미계측유역에서 적용이 회피되어 왔다. 본 연구에서 개발된 매개변수 추정결과는 이러한 문제를 보이지 않으면서도 다양한 유역특성인자의 변화에 민감하게 반응할 수 있는 특성을 보여주고 있었다. CN방법에 의해 직접적으로 도출된 유효우량과 함께 범용모형을 이용한 매개변수 추정을 토대로 미계측유역에서 저류함수법의 활용성을 높일 수 있을 것으로 기대된다.

• 한국지반공학회논문집
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• 제20권2호
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• pp.125-130
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• 2004

본 논문에서는 수치적 구성방정식인 연속 탄소성 캡 모델의 정수추정에 관한 방법이 제시되었다. 캡 모델을 이용하여 실제 토질의 거동을 예측하기 위하여서는 캡 모델을 이루는 토질의 물성과 직접적으로 연관된 여덟개의 정수가 결정되어야 한다. 이를 위하여 첫 번째로, Ottawa 모래를 사용하여 표준압밀시험기를 이용한 일축압축시험 및 배수삼축압측 시험이 토질거동의 실제기준값으로서 수행되었고, 두 번째로 탄소성 캡 수치해석모델의 반응을 실내실험값에 일치시키기 위하여 추정된 정수들을 사용한 수치실험이 수행되었다. 두 실험 간의 오차를 최소화하기 위하여 최적화 기법이 사용되었으며, 최적화 후 결정된 8개의 정수는 실내실험결과와 비교되었다. 특히, 수치적 삼축압축시험시 응력계산에 따른 수평변위 측정에 특별한 주의가 필요하다.

• Journal of Power Electronics
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• 제17권2호
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• pp.398-410
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• 2017

This work presents the design of a dual extended Kalman filter (EKF) as a state/parameter estimator suitable for adaptive state-of-charge (SoC) estimation of an automotive lithium-iron-phosphate ($LiFePO_4$) cell. The design of both estimators is based on an experimentally identified, lumped-parameter equivalent battery electrical circuit model. In the proposed estimation scheme, the parameter estimator has been used to adapt the SoC EKF-based estimator, which may be sensitive to nonlinear map errors of battery parameters. A suitable weighting scheme has also been proposed to achieve a smooth transition between the parameter estimator-based adaptation and internal model within the SoC estimator. The effectiveness of the proposed SoC and parameter estimators, as well as the combined dual estimator, has been verified through computer simulations on the developed battery model subject to New European Driving Cycle (NEDC) related operating regimes.

• 대한전자공학회논문지SD
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• 제47권9호
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• pp.24-29
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• 2010

본 논문에서는 30 nm 채널 길이와 5 nm의 채널 반지름을 갖는 실리콘 기반의 나노와이어 MOSFET의 고주파 모델링을 다루고 있다. 3차원 소자 시뮬레이션을 이용하여 실리콘 나노와이어 MOSFET의 Y-parameter와 Z-parameter를 100 GHz까지 확보하였으며 이를 이용하여 모델 파라미터에 필요한 수식을 구하였다. 모델과 파라미터 추출 수식을 이용하여 회로 검증용 tool인 HSPICE에 의하여 검증이 이루어졌으며 quasi-static 기반의 고주파 모델이 100 GHz의 높은 주파수까지도 소자의 특성을 정확히 예측함을 확인하였다. 모델 검증은 MOSFET의 포화 영역 ($V_{gs}$ = $_{ds}$ = 1 V)과 선형 영역 ($V_{gs}$ = 1 V, $V_{ds}$ = 0.5 V)의 바이어스 조건에서 이루어졌으며 두 바이어스 조건에서의 Y-parameter에 대한 모델의 오차는 약 1 %로 매우 작은 값을 보여 준다.

• Structural Engineering and Mechanics
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• 제71권1호
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• pp.45-56
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• 2019

A modified mechanical model of pre-pressed spring self-centering energy dissipation (PS-SCED) brace is proposed, and the hysteresis band is distinguished by the indication of relevant state variables. The MDOF frame system equipped with the braces is formulated in an incremental form of linear acceleration method. A multi-objective genetic algorithm (GA) based brace parameter optimization method is developed to obtain an optimal solution from the primary design scheme. Parameter sensitivities derived by the direct differentiation method are used to modify the change rate of parameters in the GA operator. A case study is conducted on a steel braced frame to illustrate the effect of brace parameters on node displacements, and validate the feasibility of the modified mechanical model. The optimization results and computational process information are compared among three cases of different strategies of parameter change as well. The accuracy is also verified by the calculation results of finite element model. This work can help the applications of PS-SCED brace optimization related to parameter sensitivity, and fulfill the systematic design procedure of PS-SCED brace-structure system with completed and prospective consequences.