• 한국환경과학회지
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• 제27권3호
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• pp.147-154
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• 2018

The purpose of this article is analyzing the impacts of seawater surface temperature rise on sea mustard yields of Goheung and Wando coast in Korea, with employing a panel data regression model. Our results show that there has been a negative impacts on sea mustard yields as seawater surface temperature continuously has been rising. Especially if the upward trend in seawater surface temperature since 2005 will be maintained in future, sea mustard yield is expected to decrease by 2.6% per year.

• 한국항해항만학회지
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• 제43권2호
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• pp.134-141
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• 2019

The objective of this study was to establish whether global macroeconomic indicators affect the profitability of Korean shipping companies by using panel regression analysis. OROA (operating return on assets) and ROA (ratio of net profit to assets) were selected as proxy variables for profitability. OROA and ROA were used as dependent variables. The world GDP growth rate, interest rate, exchange rate, stock index, bunker price, freight, demand and supply of the world shipping market were set as independent variables. The size of the firm was added to the control variable. For small-sized firms, OROA was not affect by macroeconomic indicators. However, ROA was affected by variables such as interest rates, bunker prices, and size of firms. For medium-sized firms, OROA was affected by demand, supply, GDP, freight, and asset variables. However, macroeconomic indicators did not affect ROA. For large-sized firms, freight, GDP, and stock index (SCI; Shanghai Composite Index) have an effect on OROA. ROA was analyzed to be influenced by bunker price and SCI.

• 융합경영연구
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• 제7권3호
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• pp.43-49
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• 2019

Purpose - This paper empirically investigates what factors contribute to management decisions by corporate governance in the Korean stock market. In the paper, dividends and investments were imployed as management decisions and major stockholders' shares and foreign investors' shares were used as corporate governance. Research design, data, and Methodolog - Samples are constructed by manufacturing firms listed on the stock market of Korea as well as those who settle accounts in December from 2001 to 2018. Financial institutions are excluded from the sample as their accounting procedures, governance and regulations differ. This study adopted the panel regression model to assess the sample construction including yearly and cross-sectional data. Results - This results support the literatures that major shareholders showed insignificance to dividends, positive significance to investment in financially unconstrained firms and negative significance to investment in financially constrained firms. Whereas foreign investors favor firms to increase dividends but they decrease investments only in financially constrained firms. Conclusion - This paper documented evidence that financial constrained firms use dividends for their investment and foreign investors decrease investments under financial constraints. But for dividends decisions, foreign investors give significant positive impacts irrespective of financial constraints.

• Journal of the Korean Statistical Society
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• 제30권3호
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• pp.511-527
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• 2001

This paper consider the testing problem of variance component for the unbalanced tow=-way error component model. We provide a conditional LM test statistic for testing zero individual(time) effects assuming that the other time-specific(individual)efefcts are present. This test is extension of Baltagi, Chang and Li(1998, 1992). Monte Carlo experiments are conducted to study the performance of this LM test.

• Communications for Statistical Applications and Methods
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• 제19권2호
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• pp.293-301
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• 2012

Quantile regression proposed by Koenker and Bassett (1978) is a statistical technique that estimates conditional quantiles. The advantage of using quantile regression is the robustness in response to large outliers compared to ordinary least squares(OLS) regression. A regression tree approach has been applied to OLS problems to fit flexible models. Loh (2002) proposed the GUIDE algorithm that has a negligible selection bias and relatively low computational cost. Quantile regression can be regarded as an analogue of OLS, therefore it can also be applied to GUIDE regression tree method. Chaudhuri and Loh (2002) proposed a nonparametric quantile regression method that blends key features of piecewise polynomial quantile regression and tree-structured regression based on adaptive recursive partitioning. Lee and Lee (2006) investigated wage determinants in the Korean labor market using the Korean Labor and Income Panel Study(KLIPS). Following Lee and Lee, we fit three kinds of quantile regression tree models to KLIPS data with respect to the quantiles, 0.05, 0.2, 0.5, 0.8, and 0.95. Among the three models, multiple linear piecewise quantile regression model forms the shortest tree structure, while the piecewise constant quantile regression model has a deeper tree structure with more terminal nodes in general. Age, gender, marriage status, and education seem to be the determinants of the wage level throughout the quantiles; in addition, education experience appears as the important determinant of the wage level in the highly paid group.

• 대한한의학회지
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• 제35권3호
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• pp.22-31
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• 2014

Objectives: The aim of this study was to identify the complementary and substitute relationships between the use of Korean medicine (KM) and that of Western medicine (WM) in the treatment of musculoskeletal disease. Methods: We analyzed the 2009 Korea Health Panel dataset. General characteristics and the medical utilization of respondents were analyzed descriptively. Logistic regression, negative binominal regression, and Tobit regression analysis were used to identify the relationships between the use of KM and the use, visit frequency, and expenses of WM, respectively. Results: In the treatment of musculoskeletal disease, KM use and non-herbal treatments with Korean medicine significantly reduced WM use. Herb medication use significantly increased WM visit frequency. There were no significant relationships between KM use and WM expenses. Conclusions: There are substitute relationships between WM use and KM use, especially non-herbal treatments in KM. Therefore we need to develop the clinical protocols of KM and WM treatments in the treatment of musculoskeletal disease for proper distribution medical resources.

• The Journal of Asian Finance, Economics and Business
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• 제7권7호
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• pp.139-147
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• 2020

This paper aims to explore the relationship between the quality of the audit and the level of stock return co-movement in the context of the Vietnamese emerging market. The empirical study is designed based on the quatitative method and deductive approach. The panel dataset includes 256 listed firms from different industries,with 1115 firm-year observations on Ho Chi Minh City Stock Exchange for the period from 2014 to 2018. In the research, we built the econometric regression model, using stock return synchronicity and audit quality as the dependent and independent variable, respectively. Some control variables are also added to the econometric regression models as they are well-documented in prior research to have an effect on stock price synchronicity. To improve the accuracy of the regression coefficients, beside the Ordinary Least Squares, we employ the Random Effects Model and the Fixed Effects Model for better statistical analysis of panel data set. The results show that the quality of the audit is positively correlated to stock price synchronicity. This finding suggests that stock returns of companies with higher quality of the audit are more synchronous with the market. Results for other control variables also support our reasoning for the main findings.

• The Journal of Asian Finance, Economics and Business
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• 제9권9호
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• pp.181-189
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• 2022

The current study examines the nexus between the capital structure (debt-equity) and firm value (Tobin's Q) by including profitability (alternatively Return on Assets (ROA) and Return on Equity (ROE)) as a moderator in the companies of Saudi Arabia. The study sample consists of 102 companies listed on Tadawul (the Saudi Arabian stock exchange) from different sectors of Saudi Arabia during the period 2013 to 2020. The study estimates pooled regression, panel regression with fixed and random effects, and dynamic panel regression models to report the results. The study results report that there is a negative and significant association between capital structure and firm value in model 1, while in models 2 and 3 there is a more negative and significant impact between the two study variables compared to model 1 after the inclusion of interaction variable, i.e. profitability in terms of ROA and ROE. The comparative result shows that the companies of Saudi Arabia hold more debt in their capital structure mix, hence evidencing a decrease in the firm value. The reported results also show that models 2 and 3 are better in explaining the impact of capital structure on firm value due to the interaction of profitability compared to model 1.

• Journal of Preventive Medicine and Public Health
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• 제56권6호
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• pp.515-522
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• 2023

Objectives: The pandemic caused by coronavirus disease 2019 (COVID-19) has exerted an unprecedented impact on the health of populations worldwide. However, the adverse health consequences of the pandemic in terms of infection and mortality rates have varied across countries. In this study, we investigate whether COVID-19 mortality rates across a group of developed nations are associated with characteristics of their healthcare systems, beyond the differential policy responses in those countries. Methods: To achieve the study objective, we distinguished healthcare systems based on the extent of healthcare decommodification. Using available daily data from 2020, 2021, and 2022, we applied quantile regression with non-additive fixed effects to estimate mortality rates across quantiles. Our analysis began prior to vaccine development (in 2020) and continued after the vaccines were introduced (throughout 2021 and part of 2022). Results: The findings indicate that higher testing rates, coupled with more stringent containment and public health measures, had a significant negative impact on the death rate in both pre-vaccination and post-vaccination models. The data from the post-vaccination model demonstrate that higher vaccination rates were associated with significant decreases in fatalities. Additionally, our research indicates that countries with healthcare systems characterized by high and medium levels of decommodification experienced lower mortality rates than those with healthcare systems involving low decommodification. Conclusions: The results of this study indicate that stronger public health infrastructure and more inclusive social protections have mitigated the severity of the pandemic's adverse health impacts, more so than emergency containment measures and social restrictions.

• 디지털융복합연구
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• 제14권2호
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• pp.197-208
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• 2016

본 연구에서는 데이터마이닝의 회귀분석 기법과 의사결정 나무분석 기법을 사용하여 중학생의 삶의 만족도에 영향을 끼치는 요인을 분석하였다. 이를 위해 청소년들을 대상으로 한 한국아동 청소년패널조사(KYCPS) 중1패널 데이터 3차 년도 자료를 활용하였다. 회귀분석을 통해 추출된 공통 영향요인은 자아 존중감, 우울, 전체 성적 만족도, 지역사회 인식, 진로 정체감, 연간 비행 피해 경험 유무, 형제자매 유무, 신뢰, 행동통제, 주의집중으로 나타났다. 이를 통해 중학생의 삶의 만족도는 개인의 정서문제, 자아인식, 또래 애착, 학습습관, 가정환경 요인 등이 복합적으로 영향을 미치는 것을 알 수 있다. 이 중에서 중학생의 삶의 만족도에 예측하기 위한 중요한 영향을 미치는 요인을 분석하기 위해서 의사결정 나무분석 기법을 사용하여 분석한 결과, 자아 존중감, 우울, 진로 정체감, 주의집중으로 나타났다.