• 대한교통학회지
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• 제29권4호
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• pp.95-101
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• 2011

이 연구는 2004년부터 2007년까지 청주시 50개 교차로에 대한 패널자료를 이용한 교통사고 모형을 다루고 있다. 패널자료는 동일한 샘플을 이용하여 매년 반복적으로 수집된 자료를 의미한다. 연구의 목적은 위의 패널자료를 이용하여 교통사고 모형을 개발하는데 있다. 이를 위해 이 연구에서는 TSCSREG에 포함된 다양한 모형 중 최적의 모형을 도출하는데 중점을 두고 있다. 본 연구의 주요 결과는 다음과 같다. 첫째, 교통사고의 다양한 요인들을 설명하는 4개의 패널자료 모형이 개발되었다. 둘째, 고정효과모형의 독립변수 t값이 임의효과모형에 비하여 더 작은 것으로 분석되었다. 마지막으로 교차로의 횡단보도수와 총 교차로수가 사고에 정(+)의 효과를 보이는 것으로 분석되었다.

• 한국안전학회지
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• 제27권3호
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• pp.141-146
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• 2012

This study deals with the accident model using panel data which are composed of time series data of 2005 through 2007 and cross sectional data of link sections in Cheongju. Panel data are repeatedly collected over time from the same sample. The purpose of the study is to develop the traffic accident model using the above panel data. In pursuing the above, this study gives particular attentions to deriving the optimal models among various models including TSCSREG (Time Series Cross Section Regression). The main results are as follows. First, 8 panel data models which explained the various effects of accidents were developed. Second, $R^2$ values of fixed effect models were analyzed to be higher than those of random effect models. Finally, such the variables as the sum of the number of crosswalk on intersections and sum of the number of intersections were analyzed to be positive to the accidents.

• Journal of the Korean Data and Information Science Society
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• 제20권5호
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• pp.787-796
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• 2009

이 논문에서는 반복측정치에 대한 분석모형 중, 혼합모형의 일종인 변량계수모형에 대하여 이론적으로 고찰한다. 특히 혼합모형의 설정, 모수 추정에 대하여 통계적으로 고찰하고 변량계수모형에 대한 가능한 모형을 열거하며, 그에 따르는 추정과 검정을 논의한다. 사례연구로 식이요법자료를 대상으로 가능한 변량계수모형을 적용하여 추정 및 검정을 실시한 결과, 고정인자인 사전값, 처리, 키 및 시간들의 인자는 체중감소에 대단히 유의함을 보여주었지만, 나이와 혈압은 유의하지 않았다. 처리효과에 있어서는 식이요법과 운동을 병행했을 때의 처리가 식이요법만 실시했을 때의 처리보다 체중이 더 감소했음을 알 수 있으며, 시간에 따른 체중감소의 효과는 삼차함수의 관계가 성립된다. 변량인자로는 개체효과는 유의하며 개체별 시간에 대한 교호작용의 효과는 차수가 높아질수록 급속도로 감소하여 3차 함수 관계가 적절한 모형으로 최종 선택되었다.

• 전기학회논문지
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• 제59권4호
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• pp.686-692
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• 2010

This paper analyzes the effect of the STATCOM on the improvement of the Fault Ride Through (FRT) capability of the fixed speed wind turbines(FSWTs). The steady-state models of the wind farm components, such as induction generator, capacitor bank, and the STATCOM, are developed based on the simplified equivalent circuit. Especially, the STATCOM is modeled as a controllable current source and a method that analytically determines the magnitude of the injection current is developed. For the quasi-steady-state(QSS) analysis, the steady-state model of the generator and STATCOM are merged with the dynamic model of drive train. The QSS simulation with the STATCOM shows that the STATCOM can enhance the FRT performance by improving the $W_r-T_e$ characteristics of the FSWTs.

• 노동경제논집
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• 제32권3호
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• pp.1-26
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• 2009

본고는 한국노동패널조사 1~10차년도 자료를 이용하여 정규직과 비정규직의 임금격차를 분석한다. 근로자 개인의 관찰되지 않은 이질성을 통제한 고정효과모형(fixed effect model)의 추정 결과에 의하면 정규직과 비정규직의 임금격차는 단순 횡단면 분석에서 나타난 임금격차의 약 50% 수준이다. 노동조합이 임금격차를 축소하거나 비정규직의 임금수준을 향상시킨다는 실증적 증거는 발견되지 않으며, 기업규모는 고용형태보다 임금수준에 더 큰 영향을 미치는 것으로 나타난다.

• 보건행정학회지
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• 제32권1호
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• pp.29-44
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• 2022

Background: This study was conducted to analyze the impact of having a usual source of care on health behaviors of the middle aged and the elderly, in order to investigate the potential effect of enhancing primary health care in a Korean context. Methods: This study constructed a balanced panel of middle-aged and elderly samples using the Korea Health Panel 2016-2018, and fixed-effect models were used to analyze the data. Results: Among three sets of dependent variables (physical activity, smoking, drinking), statistically significant results were found only in physical activity. Subgroup analysis showed that this effect was not observed in the late elderly (aged 75 and older) and those without chronic diseases. Conclusion: Results of the study implied that enhancing primary health care among middle age and the elderly may have an effect on improving health behaviors. Moving forward to person-centered primary health care from disease-focused primary health care should be considered in high-risk groups such as the middle aged and the elderly with chronic diseases.

• Genomics & Informatics
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• 제20권3호
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• pp.34.1-34.11
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• 2022

Multilevel analysis is an appropriate and powerful tool for analyzing hierarchical structure data widely applied from public health to genomic data. In practice, however, we may lose the information on multiple nesting levels in the multilevel analysis since data may fail to capture all levels of hierarchy, or the top or intermediate levels of hierarchy are ignored in the analysis. In this study, we consider a multilevel linear mixed effect model (LMM) with single imputation that can involve all data hierarchy levels in the presence of missing top or intermediate-level clusters. We evaluate and compare the performance of a multilevel LMM with single imputation with other models ignoring the data hierarchy or missing intermediate-level clusters. To this end, we applied a multilevel LMM with single imputation and other models to hierarchically structured cohort data with some intermediate levels missing and to simulated data with various cluster sizes and missing rates of intermediate-level clusters. A thorough simulation study demonstrated that an LMM with single imputation estimates fixed coefficients and variance components of a multilevel model more accurately than other models ignoring data hierarchy or missing clusters in terms of mean squared error and coverage probability. In particular, when models ignoring data hierarchy or missing clusters were applied, the variance components of random effects were overestimated. We observed similar results from the analysis of hierarchically structured cohort data.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.377-384
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• 2020

Banking is very regulated by the government and even has to follow regulations issued by the Basel Committee on Banking Supervision, which regulates banking in the world. According to Basel III, banks must provide capital reserves called capital buffers. The purpose of this study is to examine the factors that determine capital buffer. Factors thought to affect the capital buffer studied consisted of profitability (ROA), credit risk (NPL), liquidity risk (LDR), capital adequacy in the previous period (CARt-1), management risk (NIM), and ratio of operating risk (OER). The population in this study is conventional banks listed on the Indonesia Stock Exchange, as many as 42 banks, with a sample of 40 banks taken by purposive sampling method with an observation period of four years with quarterly data (2016-2019). To test the hypotheses, regression panel data is used. After being tested, it turns out that the fixed effect model is better than the common effect and random effect. The results of the study with fixed effect models show that ROA, NPL, and OER significantly and negatively affect capital buffer. CAR_t-1 has a positive and significant effect on capital buffer, while LDR and NIM do not affect capital buffer.

• Animal Bioscience
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• 제34권2호
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• pp.163-171
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• 2021

Objective: Considering the importance of dairy farming and the negative effects of heat stress, more tolerant genotypes need to be identified. The objective of this study was to investigate the effect of heat stress via temperature-humidity index (THI) and diurnal temperature variation (DTV) in the genetic evaluations for daily milk yield of Holstein dairy cattle, using random regression models. Methods: The data comprised 94,549 test-day records of 11,294 first parity Holstein cows from Brazil, collected from 1997 to 2013, and bioclimatic data (THI and DTV) from 18 weather stations. Least square linear regression models were used to determine the THI and DTV thresholds for milk yield losses caused by heat stress. In addition to the standard model (SM, without bioclimatic variables), THI and DTV were combined in various ways and tested for different days, totaling 41 models. Results: The THI and DTV thresholds for milk yield losses was THI = 74 (-0.106 kg/d/THI) and DTV = 13 (-0.045 kg/d/DTV). The model that included THI and DTV as fixed effects, considering the two-day average, presented better fit (-2logL, Akaike information criterion, and Bayesian information criterion). The estimated breeding values (EBVs) and the reliabilities of the EBVs improved when using this model. Conclusion: Sires are re-ranking when heat stress indicators are included in the model. Genetic evaluation using the mean of two days of THI and DTV as fixed effect, improved EBVs and EBVs reliability.

• 한국경영과학회지
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• 제41권1호
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• pp.113-126
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• 2016

This study investigates the effect of power dynamics on R&D and market performances. Various types of relationships in a supply chain are considered. An R&D company offering new technology for product quality and a manufacturer responsible for both production and sales are utilized as subjects. The company with bargaining power differs with respect to the supply chain situation in practice, and no fixed single relationship and supply chain structure exist. However, only a few studies have considered the various relationships among players in a supply chain and their effects on performance. Therefore, we propose three models with different supply chain structures and power dynamics among players. This study contributes to the academia and supply chain practice by revealing the different characteristics of supply chain models.