• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.227-235
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• 2012

The void distribution in concrete materials strongly affects its material properties. Therefore, the identification of spatial distribution of void is important to understand and estimate material behavior. To examine and quantify the void distribution inside lightweight aggregates, CT(computed tomography) image is used. 3D lightweight aggregate images are generated by stacking of cross-sectional images from CT. Spatial distribution of void of aggregate along the direction is visualized on the sphere using probability distribution function. Stiffness of lightweight aggregate for the directions is also examined. It is confirmed that direction-based probability distribution and stiffness from CT images are effective in characterizing void distributions of aggregates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.39-46
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• 2020

Carbonation is a deterioration which degrades structural and material performance by permitting CO₂ and corrosion of embedded steel. Service life evaluation through deterministic method is conventional, however the researches with probabilistic approach on service life considering loading and cold joint effect on carbonation have been performed very limitedly. In this study, probabilistic service life evaluation was carried out through MCS (Monte Carlo Simulation) which adopted random variables such as cover depth, CO₂ diffusion coefficient, exterior CO₂ concentration, and internal carbonatable materials. Probabilistic service life was derived by changing mean value and COV (Coefficient of variation) from 100 % to 300 % and 0.1 ~ 0.2, respectively. From the analysis, maximum reduction ratio (47.7%) and minimum reduction ratio (11.4%) of service life were obtained in cover depth and diffusion coefficient, respectively. In the loading conditions of 30~60% for compressive and tensile stress, GGBFS concrete was effective to reduce cold joint effect on carbonation. In the tensile condition, service life decreased linearly regardless of material types. Additionally service life rapidly decreased due to micro crack propagation in the all cases when 60% loading was considered in compressive condition.

• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.77-82
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• 2019

The purpose of this study is to analyze the relationship between the controlling shareholding ratio and the business diversification of savings banks The difference in this study is the analysis of the relationship between the controlling shareholding ratio of the savings bank and the business diversification using panel data. In this study, the semi-annual financial statements for the period 2014-2018 were used on the basis of a sample of 79 saving banks. The research model is analyzed using random effects generalized linear square (GLS) model considering the autocorrelation problem. As a result of the empirical analysis, it is estimated that the relationship between the controlling shareholding ratio of the savings bank and the business diversification is significant (+). This is the result of supporting the hedging hypothesis.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.115-119
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• 2008

본 연구는 휴대용 게임기에서 가상현실(Virtual Reality)을 구현한 비행기 시뮬레이션 게임을 대상으로 상황인식(Situation Awareness), 수행도(Performance), 현실감(Presence)을 측정하여 세 측정 지표의 상관관계를 분석하였다. 상황인식 측정은 SAGAT (Situation Awareness Global Assessment Technique)을 이용하였고, 수행도는 분당 격추 시킨 적기 수를 기준으로 측정하였다. 현실감은 Presence Questionnaire (Version 3.0) 기법을 통해 측정하였다. 실험 결과 상황인식 2 단계와 3 단계의 능력이 좋을수록 현실감이 증가하는 경향을 보여 상황인식 능력과 현실감에 밀접한 연관이 있다는 기존 연구와 동일한 결과가 휴대용 게임기에서도 일어남을 밝혀냈다. 또한 상황인식 2 단계와 3 단계의 능력이 증가할수록 수행도도 같이 증가하는 경향이 있어 좋은 상황인식 능력이 높은 수행도를 가질 확률을 증가시킨다는 기존의 연구 결과를 뒷받침할 수 있었다. 현실감과 수행도의 관계는 본 실험 결과에서 서로 연관이 있는지 결정하기 어려웠다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06c
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• pp.517-521
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• 2008

HMM의 약점인 상태 지속 분포를 개선하는 새로운 개념의 확률적 전역+지역 시간 지속 분포 segment 모델(GL-STDM)을 제안한다. 즉, 시계열 신호의 전역적 시간 정보를 표현하고, 각 상태 별 duration 모델과 각 상태의 duration 정보 사이의 상관관계를 표현하는 global pattern (shape 또는 long-term dependency)을 제안한다. 그러나 제안 모델은, Markov 가정을 깨뜨리기 때문에 dynamic programming이 자랑하는 단순함, 효율성을 유지하지는 못한다. 하지만 최근 부각되는 방법인 Monte Carlo 표본 기법을 이용하여 효과적으로 문제를 해결하는 방법을 제시하였다. 본 논문에서는 제안 모델 GL-STDM의 개념과 정의, 그리고 추론 방법과 모델 평가 방법을 기술하였다.

• Korea Trade Review
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• v.42 no.2
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• pp.277-296
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• 2017

More than 95% of imports and exports in the World are being transported by vessels. In other words, marine transportation accounts for a large portion of share in the world trade. The purpose of this study is to analyze factors of seaborne trade volume according to items affecting on the world economy. This study conducted a linear regression analysis between seaborne trade volume and the world economy (world GDP) to estimate the correlation between them. Panel data analysis and random effects model analysis have been applied to examine the effect of seaborne trade volume. For this study, the seaborne trade volume is categorized into 10 items, and estimated how much global GDP will be affected when the trade volume changes. In addition, the granger causality test was conducted to verify the relationship between seaborne trade volume and the world GDP. As a result, seaborne trade volume and the world GDP were mutually influenced each other. However, seaborne trade volume affects the world economy more significantly. The items affecting world economic growth include petroleum products, crude oil, chemical products, and so on. The estimated value of the coefficients of petroleum products, crude oil and chemical products were 1.014, 1.013 and 1.010, respectively. The estimated value 1.014 of petroleum products means that the growth rate is 1.014 times higher than the current world GDP growth rate when the seaborne trade volume of petroleum products increased by one unit Lastly, this study examines the seaborne trade volume of 10 categories and then verifies whether the growth rate of world GDP will increase when the volume of seaborne trade increased. This study is expected to provide policy-makers with useful information about formulating policies related to international trade.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1217-1225
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• 2015

Survey research, data is commonly collected through a sample design with complex design features that allow the relative efficiency on the precision of an estimator to be measured using the concept of the design effect compared to simple random sampling as a reference design. This concept is most useful when the design effect can be expressed as a function of various design features. We propose a design effect formula suitable under a stratified multistage sampling by generalizing Gabler et al. (1999, 2006)'s approaches for multistage sampling. Its use can either guide improvement in the design efficiency when in design stage or enable the evaluation of the adopted design features afterwards.

• Korean Journal of Family Social Work
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• no.23
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• pp.153-182
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• 2008

This study performed a meta-analysis on 45 research studies conducted in Korea on the relationship between domestic violence experience and juvenile delinquency. The meta-analysis calculated 125 effect sizes. The study then analyzed the effect of exposure to domestic violence on juvenile delinquency and evaluated the relationship according to research variables. The probabilities of juvenile delinquency by children who witnessed domestic violence, experienced violence directly, or experienced child abuse were 14%, 17.8% and 17.2% higher than that of children otherwise, respectively. However, the difference in experience types or child abuse types on mean effect sizes was not statistically significant. Cross effect between the type of domestic violence and the type of juvenile delinquency did not significantly impact the mean effect size of juvenile delinquency. The effect of domestic violence experience on delinquency was highest for junior high students, followed by elementary students and high school students, Difference in the effect size among groups was statistically significant. The effect size with respect to publication year was shown to have a minor static correlation, but the publication type was not meaningful. The study confirmed the effect of domestic violence on juvenile delinquency and emphasized that the responsibility of social environment in juvenile delinquency increase has been overlooked.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.5 no.3 s.11
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• pp.13-23
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• 2006

The system using UWB is processing brisk study with Bluetooth among the wireless access that is major technology in Telematics. The low complexity and cost for realization is advantage of UWB have communication of high speed. Mamy papers have published on the timing jitter effect on system performance except for the UWB system. In this paper, we analyze the effect of timing jitter on M-ary UWB system using orthogonal Hermite pulse and perform the simulation to show symbol error rate performance. For theoretical analysis, we derive correlation function of orthogonal Hermits pulse with closed form, and as well upper bound of Symbol Error Probability for M-ary orthogonal Hermite pulse system mathematically. It is found that numerical analysis is accurate enough through simulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.293-293
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• 2021

자연유량이란 인위적 행위에 의한 하천의 유량 변화가 없는 개발되지 않은 상태의 하천유량을 말하며, 실제 유량을 측정하거나 관측자료를 활용한 장기유출모형을 통해 산정할 수 있다. 미계측 유역에 대한 강우-유출 모형 구축시, 무엇보다 실제 미계측유역에 적용시 나타날 수 있는 문제점을 최소화할 수 있는 방향으로 모형 개발이 이루어지는 것이 필요하다. 강우-유출 모형 매개변수의 수가 많아질수록 과적합(over-fitting)의 발생 소지가 증가하게 되며, 지역화 모형 구축시 불확실성을 더욱 가중시키게 된다. 이러한 이유로, 모형의 검정보다는 검증에 초점이 맞춰져 있어야 하며, 더불어 사용되는 강우-유출 모형의 매개변수가 적어야 한다. 본 연구에서는 대표 강우-유출모형의 선정시 여러 평가 기준 중 예측의 정확성 측면에서 통계적 지표를 통해 모형의 수행능력에 중점을 두었으며, 적은 개수의 매개변수를 갖음에도 불구하고 상대적 우수한 모의결과를 제공하는 GR4J(Ge'nie Rural a 4 parame tres Journalier)모형을 최적 유출모형으로 선정하여 댐 상류유역에 대한 자연유량 재현성능을 평가하였다. 최종적으로 강우-유출모형의 최적매개변수와 유역특성인자 사이의 상호연관성을 고려해 매개변수를 지역화하기 위하여, 본 연구에서는 두 가지 이상의 변량에 대한 상관성을 효과적으로 재현하는데 효과적이며, 자유로운 주변확률분포 선택과 결합확률분포의 추정이 용이한 장점이 있는 Copula 함수를 활용하였다. 제시된 방법론에 대한 적합성을 평가하기 위해 교차검증 관점에서 지역화된 매개변수의 적합성을 검토하였으며, 본 연구에서 도출된 결과는 유역특성에 따른 미계측유역의 자연유량 산정시 지역 매개변수를 강우-유출모형에 활용함으로써 신뢰성 있는 자연유량 산정 결과를 제공할 수 있을 것으로 판단된다.