• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.588-593
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• 2007

Fiber reinforced polymer(FRP) composite decks are new to bridge applications and hence not much literature exists on their structural mechanical behavior. As there are many differences between numerical displacements through static analysis of the primary model and experimental displacements through static load tests, system identification (SI)techniques such as Neural Networks (NN) and support vector machines (SVM) utilized in the optimization of the FE model. During the process of identification, displacements were used as input while stiffness as outputs. Through the comparison of numerical displacements after SI and experimental displacements, it can note that NN and SVM would be effective SI methods in modeling an FRP deck. Moreover, two methods such as response surface method and iteration were proposed to optimize the estimated stiffness. Finally, the results were compared through the mean square error (MSE) of the differences between numerical displacements and experimental displacements at 6 points.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.565-570
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• 2007

Fiber reinforced polymer(FRP) composite decks are new to bridge applications and hence not much literature exists on their structural mechanical behavior. As there are many differences between numerical displacements through static analysis of the primary model and experimental displacements through static load tests, system identification (SI)techniques such as Neural Networks (NN) and support vector machines (SVM) utilized in the optimization of the FE model. During the process of identification, displacements were used as input while stiffness as outputs. Through the comparison of numerical displacements after SI and experimental displacements, it can note that NN and SVM would be effective SI methods in modeling an FRP deck. Moreover, two methods such as response surface method and iteration were proposed to optimize the estimated stiffness. Finally, the results were compared through the mean square error (MSE) of the differences between numerical displacements and experimental displacements at 6 points.

• 대한토목학회논문집
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• 제28권2A호
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• pp.215-222
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• 2008

본 논문은 현수교 이중 행어 시스템에 대한 진동기반 SI 장력추정기법의 실험적 검증을 소개한다. 현수교 이중 행어 시스템을 모사한 실험 모델을 제작되었으며, 세가지 경우의 클램프 위치에 대한 세가지 경우의 행어장력에 대해서 총 9회의 진동실험이 반복 수행되었다. 각각의 계측된 가속도 응답 데이터에 대해서, 모달분석을 통한 고유진동수와 모드 형상이 추출되었다. 추출된 일련의 동특성치들에 대하여 기존의 장력추정 이론인 현이론과 선형회기법을 적용하여 장력을 추정하였다. 또한 진동기반 SI 장력추정기법을 적용하여 장력을 추정하였는데, 추정된 장력은 수치모델과 계측모델의 동적 특성치들이 동일하게 될 때, 수치모델의 케이블 장력을 인식함으로써 추정되었다. 추정결과, 클램프의 위치에 따라서 기존의 이론을 이용한 추정장력의 오차는 최대 53.1%까지 보이는 반면, 진동기반 SI기법을 이용한 추정장력기법의 장력추정 오차는 모든 경우에 대하여 3% 이내 이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.614-618
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• 2003

This paper presents a system identification (SI) scheme in time domain using measured acceleration data. The error function is defined as the time integral of the least square errors between the measured acceleration and the calculated acceleration by a mathmatical model. Damping parameters as well as stiffness properties of a structure are considered as system parameters. The structural damping is modeled by the Rayleigh damping. A new regularization function defined by the L$_1$-norm of the first derivative of system parameters with respect to time is proposed to alleviate the ill-posed characteristics of inverse problems and to accommodate discontinuities of system parameters in time. The time window concept is proposed to trace variation of system parameters in time.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.95-102
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• 2003

To define an analytical model for a structural system or to assess damage in the system, system identification(SI) methods have been developed and widely applied. The paper presents a method of determining optimal sensor location(OSL) based on the maximum likelihood approach, which is applicable to modal SI methods. To estimate unknown parameters reliably, it is necessary that the information provided by the experiment should be maximized. By applying the Cramer-Rao inequality, a Fisher information matrix in terms of the probability density function of measurements is obtained from a lower bound of the estimation error. The paper also proposes a scheme of determining of OSL on damaged structures by using maximum strain energy factor. Simulation studies have carried out to investigate the proposed OSL algorithm for both undamaged and damaged structures.

• 한국구조물진단유지관리공학회 논문집
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• 제3권1호
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• pp.179-184
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• 1999

In this study, a method for damage assessment of existing structures is suggested using system identification approach. The natural frequencies of damaged structures are utilized to determine the size of damage. The SUMT algorithm is used to minimize error of the criterion function. The structural analysis is performed by using finite element method. Numerical examples are carried out to verify the validity of the proposed method and its computational procedures. And damage estimation of PSC beam is performed to demonstrate the effectiveness of the proposed method. From the results, it is found that the proposed SI method can be applied to estimate damage in existing structures accurately and rapidly.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2572-2580
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• 2020

Emerging gamma ray detection applications that utilize neutron-based interrogation result in the prompt emission of high-energy (>2 MeV) gamma-rays. Rapid imaging is enabled by scintillators that possess high density, high atomic number, and excellent energy resolution. In this paper, we evaluate the bright (50,000 photons/MeV) oxide scintillator, cerium-doped Gd₂Al₂Ga₃O₁₂ (GAGG(Ce)). A silicon photomultiplier (SiPM) array is coupled to a GAGG(Ce) scintillator array (12 × 12 pixels) and integrated into a coded-aperture based gamma-ray imaging system. A resistor-based symmetric charge division circuit was used reduce the multiplicity of the analog outputs from 144 to 4. The developed system exhibits 9.1%, 8.3%, and 8.0% FWHM energy resolutions at 511 keV, 662 keV, and 1173.2 keV, respectively. In addition, a pixel-identification resolution of 602 ㎛ FWHM was obtained from the GAGG(Ce) scintillator array.

• 한국구조물진단유지관리공학회 논문집
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• 제9권2호
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• pp.217-224
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• 2005

모드자료를 이용한 SI기법을 효과적으로 적용하기 위하여 최적 모델을 선택하는 방법을 제안하였다. 축소된 유한요소 모델 대신 가능한 상세한 유한요소 모델을 정하고 SI기법으로 식별하였다. 다만 미지변수의 수를 조절하기 위하여 부재그룹 개념을 도입하였다. 최적 모델은 시도된 부재그룹 경우 중에서 최소의 통계적 오차를 갖는 것으로 선택하였다. 본 논문에서는 단경간 box-girder교에 대한 예제 수행을 통하여 제안된 방법을 검토하였다.

• Reproductive and Developmental Biology
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• 제32권4호
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• pp.229-235
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• 2008

Silencing of Dicer1 by siRNA did not inhibit development up to the blastocyst stage, but decreased expression of selected transcription factors, including Oct-4, Sox2 and Nanog, suggesting that Dicer1 gene expression is associated with differentiation processes at the blastocyst stage (Cui et al., 2007). In order to get insights into genes which may be linked with microRNA system, we compared gene expression profiles in Gapdh and Dicer1 siRNA-microinjected blastocysts using the Applied Biosystem microarray technology. Our data showed that 397 and 737 out of 16354 genes were up- and down-regulated, respectively, following siRNA microinjection (p<0.05), including 24 up- and 28 down-regulated transcription factors. Identification of genes that are preferentially expressed at particular Dicer1 knock down embryos provides insights into the complex gene regulatory networks that drive differentiation processes in embryos at blastocyst stage.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.430-433
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• 2003

This paper presents a system identification (SI) scheme in time domain using measured acceleration data. The error function is defined as the time integral of the least square errors between the measured acceleration and the calculated acceleration by a mathematical model. Damping parameters as well as stiffness properties of a structure are considered as system parameters. The structural damping is modeled by the Rayleigh damping in SI. The regularization technique is applied to alleviate the ill-posed characteristics of inverse problems. The validity of the proposed method is demonstrated by an experimental study on a shear building model.