• 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.

• Korean Journal of Social Welfare Studies
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• v.42 no.4
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• pp.263-293
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• 2011

There have been many studies on the relationship between welfare states and the poverty. Yet, only a few studies have been addressed the poverty alleviation effect of public pension using difference in difference(DID). This study aims to analyze poverty alleviation effect for the old aged of public pension in 10 OECD countries using DID considering welfare states regimes. The empirical analyses are based on panel data of individuals aged 50 and over from two sources: SHARE in Europe(wave I~II) and HRS in USA(2004~2006). As a result of simple DID, this study provides evidence that the poverty rate of the old aged who has not been received the pension is increased, while the poverty rate of pensioner is sharply decreased. The anti-poverty effect of public pension using DID is 45.6% which is bigger than that of pre/post approach. The policy impact used by pre/post approach in conservative welfare regime is underestimated while those in liberal and socialist regime are overestimated. In last, GDP growth rate has not significant while public pension contributes to poverty alleviation effects of the old aged. Poverty alleviation effects of public pension are also varied with welfare state regimes. The poverty alleviation effects of public pension in conservative welfare and social democratic welfare state regime are significantly bigger than that in liberal welfare state regime.

• Information Systems Review
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• v.23 no.4
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• pp.147-163
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• 2021

We investigate the effect of comment history disclosure on portal news comments. Specifically, based on the scraped news comments from Naver and Daum (two leading Korean news portals), we employ the difference-in-differences estimator to empirically tease out the impact of the comment history disclosure policy implemented in Naver on its news comments. Our result shows that the policy implementation significantly increased the length and the positiveness of online news comments but did not affect their quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.401-408
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• 2013

Dual-layer differential codebook using 8-PSK (phase shift keying) constellation as its codeword elements, is proposed for Long term evolution (LTE) and/or LTE-Advanced systems. Due to the temporal correlation of the adjacent channel matrices, the consecutive precoding matrices are likely to be similar. This approach quantize only the differential information of the channel instead of the whole channel subspace, which virtually increase the codebook size to realize more accurate quantization of the channel. Especially, the proposed codebook has the same properties of LTE release-8 codebook that is, constant modulus, complexity reduction, and nested property. The mobile station can be designed by using less expensive non-linear amplifier utilizing constant modulus property. Computer simulations show that the capacity of the proposed dual-layer codebook performs almost 1.2dB better than those of any other non-differential codebooks with the same amount of feedback information.

• Journal of Labour Economics
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• v.41 no.4
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• pp.1-30
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• 2018

The 1995 tax reform in Korea has brought adjustment to the tax bracket, marginal tax rate, and tax deduction system which resulted in significant decrease in the income tax progressivity. In this paper we study the causal effect of the tax reform on male labor supply using difference-in-differences method. Using the data from Economic Active Population Survey (EAPS) and Daewoo Panel Data, we find about 1.5% increase in the hours worked of male wage workers.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.25.2-25.2
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• 2011

저궤도위성의 정밀궤도결정은 GPS 위성과 수신기의 시계 공통오차를 제거하기 위해 이중 차분하는 방법으로 요구된 위치 정밀도를 충족시켜왔다. 그러나 빠른 속도로 지구를 회전하는 저궤도위성의 정밀궤도결정에 있어 이러한 이중 차분방법은 지구상에 광범위하게 분포된 지상 IGS 망 처리에 많은 계산 부담을 안고 있다. 그리고 지상 측지뿐만 아니라 저궤도위성을 이용한 기상관측 또는 긴급한 영상 처리 응용분야에서도 고정밀도 준실시간(Near Real Time-NRT) 처리가 요구되고 있다. 고정밀 준실시간 정밀궤도결정을 위한 대안은 이중주파수 GPS 수신기으로 IGS에서 제공되는 정밀궤도력을 갖고 고정밀 단독측위가 가능한 정밀단독측위(precise point positioning) 기법으로 상대측위와 버금가는 위치 정밀도를 얻을 수 있다. 다목적실용위성 5호는 고정밀 합성 레이더 영상 처리를 위해서 요구되는 20 cm 위성 위치 정밀도를 만족시키고, 대기 기상관측을 위해 GPS 전파 엄폐 측정값 수집을 목적으로 고정밀 이중주파수 GPS 수신기(Integrated GPS and Occultation Receiver, IGOR)를 탑재하고 있다. 이 논문에서는 IGOR의 이전 제품인 Blackjack 수신기를 탑재한 GRACE 위성의 실제 GPS 데이터를 사용하여 대략 3 ~ 5cm의 위치 정밀도를 얻었다. 준실시간 정밀궤도결정에서 정밀도 손실없이 궤도결정 처리 지연시간(latency)을 줄이는 것이 중요하다. 이 지연시간은 GPS 측정값의 양에 따라 크게 좌우되기에 GPS 측정값 샘플링 주기를 10초에서 640초까지 변화시켜가면서 정밀도를 분석한 결과, 위치 정밀도 손실없이도 궤도결정처리 지연시간을 단축시킬 수 있음을 제시하고 있다.

• 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.

• Journal of Technology Innovation
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• v.32 no.2
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• pp.1-21
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• 2024

This study aims to estimate policy effects that appear heterogeneously within the beneficiary group by matching the beneficiary and non-beneficiary groups based on propensity score quartiles and analyzing the effect of policy benefits on sales growth. To achieve this, 239 SMEs that participated in R&D support program for the manufacturing of materials, components, and equipment in 2020 were selected as the beneficiary group. The propensity scores of these companies were calculated and divided into eight quartiles for matching between the non-beneficiary and beneficiary groups. Subsequently, double difference analysis was used to calculate the sales growth rate attributable to policy support. The study found that the largest policy effect was observed in the lowest quartile group, and companies with high patent application rates and 3-year sales growth rates experienced significant policy effects. These findings suggest that propensity score quartile-based analysis can be effectively utilized to refine the criteria for selecting beneficiary companies and the scope of industrial policy support.

• The Journal of the Convergence on Culture Technology
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• v.4 no.4
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• pp.145-154
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• 2018

The aim of this study is to analyze the policy effects of child care leave focusing on the childbirth in South Korea. This instituion of child care leave orinignally seeks to harmonize the work and family. The instituion is increasingly fortified in the receipants and benefits. This study analyze the policy effect of the institution using difference-in-difference method and Korea Welfare Panel Data. The result of the analysis suggest that substantial expansion of child care leave and family-friendly labor environment rebuilding are important.