• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.113-124
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• 1998

Numerical study using nonlinear finite element analysis is done for investigating behavior of isolated reinforced concrete walls subject to combined in-plane and out-of-plane bending moments and axial force. A method for estimating the ultimate strength of wall is developed, based on the analytical results. For the nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities is developed. An existing unified method combining plasticity theory and damage model is used for material model of reinforced concrete. By numerical studies, the internal force distribution in the cross section is idealized, and a new method for estimating the ultimate strength of wall is developed. According to the proposed method, variation of the interaction curve of in-plane bending moment and axial force depends on the range of the permissible axial force per unit length that is determined by the given amount of out-of-plane bending moment. As the out-of-plane bending moment increases, the interaction curve shrinks, which indicates a decrease in the ultimate strength. The proposed method is compared with an existing method using the general assumption that strain shall be directly proportional to the distance from the neutral axis. Compared with the proposed method, the existing method overestimates the ultimate strength for walls subject to low out-of-plane bending moments, and it underestimates the ultimate strength for walls subject to high out-of-plane bending moments.

• Science of Emotion and Sensibility
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• v.27 no.1
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• pp.59-68
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• 2024

This study aimed to develop a soft fabric-based elbow-bending angle sensor that can replace conventional hard-type inertial sensors and a system for estimating bending angles using it. To enhance comfort during exercise, this study treated four fabrics (Bergamo, E-band, span cushion, and polyester) by single-walled carbon nanotube dip coating to create conductive textiles. Subsequently, one fabric was selected based on performance evaluations, and an elbow flexion angle sensor was fabricated. Gauge factor, hysteresis, and sensing range were employed as performance evaluation metrics. The data obtained using the fabricated sensor showed different trends in sensor values for the changes in the angle during bending and extending movements. Because of this divergence, the two movements were separated, and this constituted the one-step process. In the two-step process, multilayer perceptron (MLP) was employed to handle the complex nonlinear relationships and achieve high data accuracy. Based on the results of this study, we anticipate effective utilization in various smart wearable and healthcare domains. Consequently, a soft- fabric bending angle sensor was developed, and using MLP, nonlinear relationships can be addressed, enabling angle estimation. Based on the results of this study, we anticipate the effective utilization of the developed system in smart wearables and healthcare.

• Geotechnical Engineering
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• v.12 no.6
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• pp.87-100
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• 1996

This paper verifies the accuracy and efficiency of the implicit stress integration algorithm for an anisotropic hardening constitutive model developed in a companion paper[Oh & Lee (1996)3. Simulation of undrained triaxial test results shows the accuracy of the method through an error estimation, and analyses of accuracy and convergence were performed for a numerical excavation problem. As a result, the stress was accurately integrated by the algorithm and the nonlinear solution was converged to be asymptotically quadratic. Furthermore nonlinear FE analysis of a real excavation problem was by performed considering the initial soil conditions and the in-situ construction sequences. The displacements of wall induced by excavation were more accurately estimated by the anisotropic hardening model than by the Cam-clay model.

• Computational Structural Engineering
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• v.1 no.1
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• pp.103-112
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• 1988

In this study, the earthquake response of building structures with foundation uplift was investigated. The Winkler foundation model and two-spring model are widely used to represent the interaction between foundation mat and soil. While the analysis using the Winkler foundation model results in more accurate prediction, it requires a complex procedure and longer computation time. In this study, an equivalent two-spring model(S model) is proposed. The S model can represent the Winkler foundation model more accurately and the analysis using the S model is simpler and more effective. The S model is derived by simplifying the nonlinear moment-rotation relationship of foundation mat. The dynamic responses predicted by the S model gave a good agreement to those of the Winkler foundation model.

• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1361-1371
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• 2016

Quantile regression provides a variety of useful statistical information to examine how covariates influence the conditional quantile functions of a response variable. However, traditional quantile regression (which assume a linear model) is not appropriate when the relationship between the response and the covariates is a nonlinear. It is also necessary to conduct variable selection for high dimensional data or strongly correlated covariates. In this paper, we propose a penalized quantile regression tree model. The split rule of the proposed method is based on residual analysis, which has a negligible bias to select a split variable and reasonable computational cost. A simulation study and real data analysis are presented to demonstrate the satisfactory performance and usefulness of the proposed method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.9-11
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• 2016

최근 UHDTV(ultra high definition television) 등의 고해상도 디스플레이가 시장에 등장하면서, 기존의 저해상도 FHD(full high definition) 영상을 고해상도 영상으로 변환할 수 있는 초해상화(super-resolution, SR) 기법들이 각광을 받고 있다. 그 중, 선형 매핑(linear mapping)을 사용하여 저해상도 패치(patch)로부터 고해상도 패치를 복원하는 초해상화 기법은 상대적으로 낮은 복잡도로 좋은 품질의 고해상도 영상을 생성한다. 그러나 이러한 기법은 단순한 선형 매핑을 기반으로 하기 때문에 복잡한 비선형적(nonlinear) 저해상도-고해상도 관계를 예측하기 힘든 단점이 있다. 최근 각광받는 딥러닝(deep learning) 기술은 다층(multi-layer) 네트워크를 쌓아 입력과 출력 간의 복잡한 비선형 관계를 훈련시켜 좋은 성능을 보이는데, 이를 바탕으로 본 논문에서는 다중의 레이어로 구성된 다층 선형 매핑(multi-layer linear mappings, MLLM)을 기반으로 하는 초해상화 기법을 새롭게 제안한다. 제안하는 다층 선형 매핑은 기존 선형 매핑보다 비선형적 관계를 더 잘 예측하여 높은 품질의 고해상도 영상을 생성할 수 있게 한다. 제안된 초해상화 기법은 딥러닝 기반 초해상화 기법과 필적하는 품질의 고해상도 영상을 생성하면서도 더 낮은 복잡도를 지니는 것을 확인하였다.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.475-481
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• 2015

We use polynomial regression instead of linear regression if there is a nonlinear relation between a dependent variable and independent variables in a regression analysis. The performance of polynomial regression, however, may deteriorate because of the correlation caused by the power terms of independent variables. We present a polynomial regression model for the numerical inversion of PGF and show that polynomial regression results in the deterioration of the estimation of the coefficients. We apply principal components regression to the polynomial regression model and show that principal components regression dramatically improves the performance of the parameter estimation.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.564-564
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• 2016

개념적 수문 모형은 탱크의 개수, 탱크 간 관계구조, 그리고 저류량과 유출량 간 선형/비선형 관계 정의 방식 등에 따라 다양한 형태로 개발되어왔으며, 각 모형마다 매개변수 수 및 입력 자료가 상이하다. 모형의 매개변수가 많아지면 결과가 좋게 나타날 수 있으나, 늘어난 매개변수에 대해 물리적 의미를 부여하고 해석하기가 쉽지 않다. 단순한 모형은 보정이 용이하고 그 특성상 실무에서 널리 이용되고 있으나, 물순환 구조가 복잡한 유역에 대해서는 적용성이 떨어질 수 있다. 하지만 매개변수의 수가 많은 모형이 적은 모형에 비해 항상 결과가 좋은 것은 아니다. 복잡한 모형은 부족한 안정성에 의해 보정 기간에서는 결과가 좋았으나, 검정 기간 대해 결과가 안 좋을 수도 있으며 이에 대한 평가가 필요하다. 본 연구에서는 국내에서 주로 이용되는 개념적 모형을 대상으로 모형의 복잡성과의 정확도의 관계를 비교 평가하고자 한다. 대상 모형으로는 수정 3단 Tank 모형, Im's Tank 모형, Two-Parametric Hyperbolic Model (TPHM), 그리고 Daily Watershed Streamflow Model (DAWAST)을 선정하였고, 대상유역으로는 이동저수지 상류에 위치한 2개 유역을 선정하였다. 모형 간 비교를 위한 정량적 통계적 지표로 $R^2$, Nash-Sutcliffe efficiency (NSE), root mean square error-observations standard deviation ratio (RSR), 그리고 percent bias (PBIAS)를 이용하였다. 본 연구 결과는 개념적 수문 모형에 대한 이해를 증진하고, 장기유출 해석을 위한 수문 모형의 선택 시 모형의 복잡도 및 정확도의 관점에서 도움을 줄 수 있는 기초자료로 이용될 수 있을 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.213-220
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• 2015

CFT column has a lot of structural advantages due to the composite behavior between in-filled concrete and steel tube. This paper deals with the development of an effective numerical model which can consider the bond-slip behavior between both components of concrete matrix and steel tube without taking double nodes. Since the applied axial load to in-filled concrete matrix is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatability conditions. In advance, the force and displacement relations between adjacent two nodes make it possible to express the slip behavior with the concrete nodes only. This model results in significant savings in the numerical modeling of CFT columns to take into account the effect of bond-slip. Finally, correlation studies between numerical results and experimental data are conducted to verifying the efficiency of the introduced numerical model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.253-263
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• 2018

This paper examined the U-shape curvilinear relationship between team level conflict management and individual level turnover intention by using exit-voice theory, bandwagon effect, and social loafing theory. In addition to the non-linear relationship between team-level conflict management and individual-level turnover intentions, we also examined how trust in leaders has a moderating effect on this relationship. The samples were collected from a South Korean manufacturing company with 331 team members from 48 teams and items were measured twice to avoid common method biases. The intercepts-as-outcomes model of hierarchical linear modelling was conducted to verify the hypothesis. Results supported the cross-level curvilinear hypothesis which indicated that employees' turnover intention sharply decreased if the activeness of group conflict management was small and increases slightly, but this tendency moderated as activeness increases. After passing the lowest point, their turnover intention increased in the end. However, the moderation effect of trust in leader on this relationship was not statistically significant and hypothesis 2 was rejected. This paper explained the effects of group dynamics of conflict management on individual turnover intention. Such evidence may elucidate the importance of managing the social loafing behavior on conflict management process. This paper examined the sequential, multi-level, and curvilinear relationship between conflict management and turnover intention. Organizations and managers will benefit from avoiding the human resource loss by managing the conflict management process.