• 한국사회정책
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• v.23 no.1
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• pp.25-59
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• 2016

This paper analyses the policy effect of minimum housing standards, using the fact that Seoul set the minimum housing standards in 1998. Because the whole country except Seoul did not set the minimum housing standards in 1998, we could find this situation as a quasi-experiment. In order to identify the policy effect of minimum housing standards, I compare decreasing amounts in the number of households below the threshold between Seoul and comparison regions from 1995 to 2000, using Differences-in-Differences method. I draw estimate of one-to-one comparison, using Gyeonggi province as a comparison region, and OLS estimate, utilizing the whole nation except Seoul as a comparison region, respectively, and compare two estimates. The former and the latter suggest that the setting of Seoul minimum housing standard in 1998 account for decreasing the number of households under the minimum housing standard, by about 216,638 and 325,149, respectively. The latter is statistically significant at the 0.001 level and the former is in the 95% confidence level of the latter. Therefore we could conclude that the setting of minimum housing standards contributes significantly to achieve the policy objectives, a decrease in the number of households, which are below the threshold.

• Environmental and Resource Economics Review
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• v.31 no.3
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• pp.343-365
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• 2022

This paper tries to identify the effect of reducing PM2.5 concentration of the First Seasonal Management Policy implemented by Korean government by using statistical method. In particular, this paper tests the hypothesis that this policy effect may differ by region (west-coast, south-coast, and east-coast). To this end, this paper analyzed only pure policy effects by removing temporal abnormalities such as COVID-19, warm winter temperature during the policy implementation period (December 2019 to March 2020) by using the difference-in-difference method (DID). As a result of the analysis, this policy had the effect of reducing PM2.5, but the effect is not homogenous by region. In particular, PM2.5 reducing effect is the largest in west-coast region and south-coast region folllows, but its effect is not statistically significant in the east-cost region. In conclusion, this paper drew implications that the current Seasonal mamangement policy which is implemented regardless of the regional difference needs to be changed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.5
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• pp.421-427
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• 2013

In general, it can be assumed that the tropospheric effect are removed through double-differencing technique in short-baseline GPS data processing. This means that the high-accuracy positioning can be obtained because various error sources can be eliminated and the number of unknown can be decreased in the adjustment computation procedure. As a consequence, short-baseline data processing is widely used in the fields such as deformation monitoring which require precise positioning. However, short-baseline data processing is limited to achieve high positioning accuracy when the height difference between the reference and the rover station is significant. In this study, the effects of tropospheric delays on the determination of short-baseline is analyzed, which depends on the orientation of baseline. The GPS measurements which include tropospheric effect and measurement noises are generated by simulation, and then rover coordinates are computed by short-baseline data processing technique. The residuals of rover coordinates are analyzed to interpret the tropospheric effect on the positioning. The results show that the magnitudes of the biases in the coordinate residuals increase as the baseline length gets longer. The increasing rate is computed as 0.07cm per meter in baseline length. Therefore, the tropospheric effects should be carefully considered in short-baseline data processing when the significant height difference between the reference and rover is observed.

• 한국벤처창업학회:학술대회논문집
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• 2021.04a
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• pp.143-146
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• 2021

전자상거래는 긴 역사에도 불구하고, 최근의 기술적 발달과 함께 COVID-19로 촉발된 사회경제적 변화로 인해 다시 한번 급속한 성장과 더불어 많은 주목을 받고 있다. 이러한 과정에서 소상공인들을 비롯한 판매자들은 전자상거래에 참여하여 판매를 하고자 노력하고 있다. 하지만 오프라인 상거래와는 달리, 온라인에서의 판매는 디지털 데이터를 비롯하여 정보통신(IT)에 대한 이해가 수반되어야 용이한 특징을 지닌다. 이에, 본 연구는 판매자를 돕기 위해 개발된 판매 보조 도구가 실제로 온라인에서 판매자들의 실적을 돕는지 알아보고, 이에 따라 전자상거래 플랫폼 운영사는 판매자의 판매를 어떤 방식으로 도와 성공적으로 플랫폼을 운영할뿐만 아니라 사회 전체적인 경제 효익을 증대시킬 수 있는지에 관한 시사점을 주고자 한다. 본 연구에서는 전자상거래에서 판매자에게 의사결정에 도움이 되는 도구들이 제공되어 이를 사용할 경우에 판매액(매출)를 비롯한 다양한 성과 측정 척도에서 유의미한 개선이 이루어지는가를 실증적으로 분석하고자 한다. 엄밀한 분석을 위해 성향점수매칭법과 이중차분법을 활용하여 판매자들의 데이터를 분석할 것이다. 이를 통해 의사결정 지원 시스템이 전자상거래 판매자에게도 유효한지 실증적으로 알아보고, 나아가 전자상거래 플랫폼 운영사에게도 경영 측면에서의 시사점을 줄 수 있을 것이다.

• Journal of Labour Economics
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• v.38 no.3
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• pp.97-130
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• 2015

This paper examines effects of the Korean Student Human Rights Ordinance on student behavior. The ordinance was put into effect in some municipalities (Seoul, Kyongki, Kwanju, Jonbuk) from 2010. Since the ordinance prohibits corporal punishment and other authoritative treatments of students in school, the paper estimates effects of indulgent teaching on student behaviors. Our difference-in-differences estimates suggest that the ordinance has little effect on the students' propensity to behave, intimacy with classmates and teachers and overall satisfaction with school life. In contrast, the ordinance increases the likelihood of students, especially low-performing and mid-performing students suffering from problem behaviors of other students. This implies that some (probably low-performing and mid-performing) students tend to commit more problem behaviors after the ordinance has taken effect.

• Journal of Labour Economics
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• v.37 no.3
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• pp.75-99
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• 2014

This study analyzes the initial effect of meister high school policy on labor market by DID based on the fact that most of the meister high schools that had its first graduates in 2013 were not newly established but assigned by government. We estimated employment and real hourly wages as quantitative measures and intent to remain in labor market as qualitative one. The results shows that, the meister high school policy increased the employment rate but didn't do real hourly wages and intent to remain. Therefore, meister high school policy can be assessed to be successful in short-term only in quantitative aspects. The study has its contribution as the first study of estimating the net effect of the policy.

• Journal of Labour Economics
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• v.34 no.3
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• pp.81-117
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• 2011

This study examined how firms responded to the articles regarding the prohibition or correction of discrimination against fixed-term workers in the 'fixed-term worker protection law', which has been effective since July of 2007 in Korea. Data used cone from the Korean Workplace Survey, and a difference-in-differences method was employed for the identification of the causal effect, noting that the 'discrimination prohibition law' has been applied to firms over stages based on their sizes. The empirical results show no strong evidence that the law played a positive role in reducing differentials between permanent workers and fixed-term workers in the areas of wage and various employee benefits, including the provision of severance pay, annual leave, and 4 major social insurances for fixed-term workers. A more thorough future analysis on the causes of the insignificant impact of the law in some employee welfare benefits, along with supplemental policies, is needed to have the law achieve the desired goal of removing discrimination at the workplace.

• Journal of Labour Economics
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• v.36 no.2
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• pp.67-94
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• 2013

Using data from the Economically Active Population Survey: Supplement by Employment Type, This paper examines the effects of the 2007 Act on the Protection of Fixed-term and Part-time Employees on employment levels. Since the Act is applied to only individuals below 55 years of age, we restrict the analysis sample to men whose ages are close to 55 at the time of the survey. For such a sample, the empirical analysis combines regression discontinuity design with a difference-in-differences. The results suggest that the employment effect of the 2007 Act takes a U-shape. The results suggest that the employment effect of the 2007 Act takes a U-shape. The negative effect of the Act was largest around August 2008, a year after it took effect. The negative effects on employment faded away toward August 2009.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.670-679
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• 1986

본 논문은 내관 외벽에 나선형 인공조도가 있는 동심 이중관 사이의 유동특성 을 관찰하기 위해 일정 나선각에 대하여 피치비를 변화시키면서 선회속도, 축방향속도 압력을 측정하였으며, Han등의 연구에서 발표된 조도함수를 도입하여 유한차분법으로 수치계산을 수행하였다.

• Tunnel and Underground Space
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• v.30 no.5
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• pp.484-495
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• 2020

To numerically simulate the advance of EPB TBM, various type of numerical analysis methods have been adopted including discrete element method (DEM), finite element method (FEM), and finite difference method (FDM). In this paper, an EPB TBM driving model was proposed by using coupled DEM-FDM. In the numerical model, DEM was applied in the TBM excavation area, and contact properties of particles were calibrated by a series of triaxial tests. Since the ground around the excavation area was coupled with FDM, the horizontal stress considering the coefficient of earth pressure at rest could be applied. Also, the number of required particles was reduced and the efficiency of the analysis was increased. The proposed model can control the advance rate and rotational speed of the cutter head and screw conveyor, and derive the torque, thrust force, chamber pressure, and discharging during TBM tunnelling.