• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.1-13
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• 1994

Procedures for the development of a preswirl stator-propulsion system for a VLCC 300K are described in this paper. The preswirl stator-propulsion system is one of the compound propulsor systems, which is used for the purpose of recovering propeller slipstream rotational energy by locating a stator in front of the propeller. The preswirl stator-propulsion system can be considered as a most reliable energy saving device because of its simple mechanism. Five stators are designed for the existing hull form and propeller, and their effects are verified by model tests. Open-water test result of the preswirl stator-propulsion system at the cavitation tunnel show $4{\sim}6%$ increase of open-water efficiency compared to that of a propeller without stators. Maximum 6.5% decrease of delivered power at the design speed(15.5knots) is expected with the designed stator based on the analysis results of resistance and self-propulsion test at the towing tank.

• Journal of Energy Engineering
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• v.26 no.2
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• pp.80-92
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• 2017

This paper attempts to estimate the diesel fuel demand function in Korea using panel data panel data of 16 major cities or provinces which consist of diesel demands, diesel market prices and gross value added from the year 1998 to 2015. I apply panel GLS(generalized least square) model, fixed effect model, random effect model and dynamic panel model to estimating the parameters of the diesel fuel demand function. The results show that short-run price elasticities of the diesel fuel demand are estimated to be -0.2146(panel GLS), -0.2886(fixed effect), -0.2854(random effect), -0.1905(dynamic panel) respectively. And short-run income elasticities of the diesel fuel demand are estimated to be 0.7379(panel GLS), 0.4119(fixed effect), 0.7260(random effect), 0.4166(dynamic panel) respectively. The short-run price and income elasticities explain that demand for diesel fuel is price- and income-inelastic. The long-run price and income elasticities are estimated to be -0.4784, 1.0461 by dynamic panel model, which means that demand for diesel fuel is price-inelastic but income-elastic in the long run. In addition I apply dummy variable model to estimate the effect of 16 major cities or provinces on diesel demands. The results show that diesel demands is affected 10 regions on the basis of Seoul.

• Journal of Korean Society of Transportation
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• v.29 no.4
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• pp.95-101
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• 2011

This study proposes the accident estimation model developed based on the time-series cross-sectional data at 50 intersections in Cheongju. The data were collected repeatedly and accumulated from 2004 to 2007. This study focused on deriving the optimal among the various models including TSCSREG(Time Series Cross Section Regression). Four different models utilizing various elements affecting accidents were developed. Through a statistical test, it was found that the t values of independent variables of the fixed effect models were less than those of the random effect models. Two variables were then found to be positive to the accidents: the number of crosswalks at an intersection and the number of intersections.

• Korean Journal of Social Welfare
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• v.68 no.3
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• pp.105-125
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• 2016

School absenteeism is considered one of the early predictors of school drop-out and serious delinquency or criminal behavior. The primary goal of the current study was to explore the protective and risk factors related to changing school absenteeism over time based on the ecological-systemic perspective. The data was derived from the Korean Children and Youth Panel Survey (KCYPS) using the 2011 and 2012 survey waves collected from 2,378 elementary school students. Using this data, Panel Fixed Effects Analysis was conducted. Major findings indicated that daily computer usage, parental abuse, school activity attendance, and school grades had an effect on students missing school days over time. Specifically, high levels of computer usage and parental abuse were related to increased school absenteeism, while high levels of school activity attendance and school grades were associated with decreased school absenteeism. These findings emphasized the importance of predictive intervention for children and suggested the need to construct a school absenteeism monitoring system in South Korea.

• Journal of Korea Port Economic Association
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• v.27 no.3
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• pp.161-177
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• 2011

Nowadays, a capital flow and intimacy of financial system among countries have been increasing in global financial environment. So it is easily possible that the risk of some countries which are in financial crisis infects other countries in the world. A recent global financial crisis reminds countries in East Asia of advancing the financial cooperation as well as financial integration. Countries in East Asia agreed with the Chiang Mai Initiative to prevent a recurrence of financial crisis in East Asia. A bilateral swap arrangement of the CMI has several purposes in order to offer foreign currency liquidity against economic crisis, remove the opportunity cost of foreign exchange reserve, push ahead the financial integration, increase the export-import logistics and so on. This paper analyzes the effect of financial cooperation in East Asia on the export-import logistics with random effect estimation and fixed effect estimation. As a result, each of country in East Asia is able to increase almost 10.3% of the export-import logistics on average.

• Environmental and Resource Economics Review
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• v.20 no.4
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• pp.735-760
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• 2011

This study examines the effect of pollution abatement cost on net export of Korea's manufacturing industries based on Heckscher-Ohlin model. We used the panel data on manufacturing industries for 1993~2007. The main findings are as follows. First, it was found that the pollution abatement cost had a significant negative effect on net export of Korea's manufacturing industries. In particular, the effect was stood out after 1997 IMF crisis. Second,skill labor was found to be very important in determining trade pattern among variables related to factor intensities.

• Journal of the Korean Data and Information Science Society
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• v.27 no.1
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• pp.101-110
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• 2016

Depression is a mental symptoms that accompany psychological symptoms such as anxiety, gloom, a sense of failure, helplessness as well as a physical symptoms that shows in the adaption process of stress. Depression may result in cognitive, emotional, and behavioral disorders in accordance with individual experience. In particular, the depression when growing lowers the concentration on studies of children and adolescents and also increases the violence and interpersonal problems causes a serious loss to individuals and society. This study analyzed the longitudinal data using mixed models to investigate how depression affects girls who experienced violence in home or at school.

• Journal of Labour Economics
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• v.37 no.4
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• pp.59-88
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• 2014

I estimate the non-market effects of implementing five-day workweek controlling for the individual-job fixed effect. I find that the implementation of five-day workweek has improved an individual's subjective health status, increased the frequency of exercises, increased the probability to get education or training other than job training, improved subjective quality of life, increased spending for leisure and cultural activities, and improved an individual's satisfaction with the job and the employer. Much of the effects are due to reduction not of working hours but of working days.

• Journal of the Economic Geographical Society of Korea
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• v.20 no.1
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• pp.84-104
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• 2017

In this study, we divided Gyeonggi-do into Northern, Southern, Western, and Eastern Parts and found out fiscal variables which affected regional economic growth of each Part differentially. And we drew the strategy for economic growth of each Part. After we found out the variables which affected regional economic growth using fixed-effect model, we carried out causality test to determine whether a specific fiscal variable caused economic growth. In the Eastern Part, local tax revenues had a significant effect on the economic growth. Total expenditures, current expenditure in the Southern Part and social welfare expenditure, expenditure on industries, current expenditure in the Northern Part had noticeable effects on economic growth respectively. And we calculated multipliers of fiscal variables to compare the magnitudes of effects among these Parts.

• Environmental and Resource Economics Review
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• v.15 no.2
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• pp.247-267
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• 2006

This paper formulates a monopolistic competition model by incorporating Leontief product function into Dixit and Stigliz model to analyze and compare the effects of two environmental policy instruments-fuel efficiency regulation and environmental tax-on a market which reflects characteristics of international vehicle market. As expected, both policy instruments raise equilibrium market prices. The effect of fuel efficiency regulation on firm output, the number of firms, and industry output, however, depends on three determinants-the increasing rate of the ratio of consumer expenditure to the income, the increasing rate of fixed cost, and the increasing rate of marginal cost. On the other hand, the imposition of the specific environmental tax reduces the firm output, but does not influence the number of firms. If these two instruments are assumed to lead to the same increasing rate of marginal costs, the environmental tax reduces the firm output as well as the industry output more than the fuel efficiency regulation. And it will induce more firms to exit the market than the fuel efficiency regulation if the increasing rate of the ratio of consumer expenditure to the income is larger than the increasing rate of fixed cost.