• Journal of Preventive Medicine and Public Health
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• v.40 no.6
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• pp.495-504
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• 2007

Objectives : This study attempts to show how studies using non-experimental data can strengthen causal inferences by applying propensity score and instrumental variable methods based on the counterfactual framework. For illustrative purposes, we examine the effect of having private health insurance on the probability of experiencing at least one hospital admission in the previous year. Methods : Using data from the 4th wave of the Korea Labor and Income Panel Study, we compared the results obtained using propensity score and instrumental variable methods with those from conventional logistic and linear regression models, respectively. Results : While conventional multiple regression analyses fail to identify the effect, the results estimated using propensity score and instrumental variable methods suggest that having private health insurance has positive and statistically significant effects on hospital admission. Conclusions : This study demonstrates that propensity score and instrumental variable methods provide potentially useful alternatives to conventional regression approaches in making causal inferences using non-experimental data.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.1
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• pp.23-35
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• 2012

Due to the convenience, RMR has been widely applied in civil engineering works such as tunnel, slope, and so on. Many researchers have studied to suggest more simple and trustable RMR by modifying its parameters. However, those researches have just focused on looking for easy modified-RMRs by reducing number of parameters using various statistical analyses. Therefore, this research studied questions of modified-RMRs and gaps between RMR and its parameters. Approximately 2,000 parameters of 400 RMRs from various tunnel sites were normalized respectively and compared with one another to study their relations and divergences. The comparison results showed that there were common patterns among RMR and parameters. Data of uniaxial compressive strength and RQD, qualitative parameters, were located in upper side of RMR line. Discontinuity condition and ground water, quantitative oriented parameters, were opposite to them. It means if both qualitative and quantitative parameters can be properly combined then it can be easy to make simple and easy modified-RMRs without using difficult statistics. This results also show that the majority of field engineers used to estimate RMR conservatively when they did quantitative oriented parameters.

• The Korean Journal of Financial Management
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• v.18 no.1
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• pp.43-66
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• 2001

본 연구는 투자자 집단에 따라 그 매매에 있어서 주가와의 관련성을 분석하고자 하였다. 투자자 집단의 매매 성향은 월별 순매매율로 측정하였으며 주가의 대용변수는 한국종합주가지수(KOSPI)의 월별 수익률로서 분석에 사용된 기간은 1992년 1월부터 1999년 12월까지이다. 분석을 위한 방법론으로 상관분석과 회귀분석을 이용하였다. 상관분석은 스피어만 순위상관분석을 이용하여 KOSPI와 각 투자자 집단의 순매매 비중의 상관계수를 도출하였으며 그 결과 KOSPI와 개인투자자의 순매매와는 음의 유의적 상관관계를, KOSPI와 외국인 투자자의 순매매율과는 양(+)의 유의적 상관관계를 알 수 있었다. 그러나 기관투자자의 경우 기관투자자 전체 범주로 볼 때 유의적 상관관계가 없었으나 세분화된 기관투자자 일부는 유의적 상관관계를 보였다. 또한 본 연구는 KOSPI와 각 투자자 집단의 매매에 대한 인과관계를 추론한 바 외국인 투자자의 매매는 KOSPI에 영향을 주며 개인투자자의 매매는 오히려 KOSPI에 영향을 받는 것으로 보였다. 그러나 기관투자자의 경우 세부기관마다 그 매매의 성격을 달리하는 것으로 보였다. 이러한 분석결과를 바탕으로 회귀분석을 실시하였으며 그 분석결과 외국인 투자자와 기관투자가 가운데 증권사와 투신사의 경우, 순매수가 늘어날수록 주가는 상승하고 순매도가 늘어날수록 주가는 하락하는 것을 확인할 수 있었으며 반면 개인투자자의 매매는 KOSPI 주가에 따라 영향을 받는 것으로 나타났다. 즉 주가가 상승할수록 매도에 치중하고 주가가 하락할수록 매수에 치중하는 것으로 분석되었다. 기관투자자 가운데 보험사의 매매 역시 주가에 영향을 받는 것으로 나타났다. 본 연구의 성과로는 특정 투자자 집단이 주가의 움직임에 따라 매매를 하는 수동적 전략의 의미보다는 적극적으로 주가를 움직이는 주체로서 외국인투자자와 일부 기관투자자의 존재를 확인할 수 있었다는 점이며, 주가 움직임에 따른 개인투자자와 일부 기관 투자자의 수동적 매매 스타일과 기관투자자 사이의 투자스타일의 이질성을 통계적으로 확인할 수 있었다는 데에 있다.

• Journal of Digital Contents Society
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• v.9 no.4
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• pp.697-705
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• 2008

The recent web technology has been developed by three mainsprings which include integration, virtualization, and socialization. The web technology provides the increment of the social networking ability. However it deepens the exposure of privacy about personal information as more complicating and difficult problems. Representatively, it is impossible to define and manage the specific relation, so the personal information and interest can be inferred from collecting and summarizing the contents. Also, there are some problems that it is hard to construct the information owner's own social network. Thus this paper proposes the RCBAC(Relationship-Content based Access Control) Model which applies both the concepts of Relationship and Content Semantic to the existing access control methods to protect the user's own digital contents in web 2.0 environment. This method prevents privacy such as personal inclination from being exposed and enables to define and manage the specific relation. By doing this the information owners can construct their social network. This social network can be applied and extended to web contents.

• Journal of the HCI Society of Korea
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• v.12 no.2
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• pp.13-19
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• 2017

Various life-logging based on cloud service have developed social network according to the advanced technology of smartphone and wearable device. Daily digital life on social networks has been shared information and emotion and developed new social relationships. Recent life-logging has required social relationships beyond extension of personal memory and anonymity for privacy protection. This study is to determine social network group by using life-logging data obtained in daily lives and to categorize emotion behavior with anonymity guarantee. Social network group was defined by grouping similar representative emotional behavior. The public's patterns and trends was able to be inferred by analyzing representative emotion and behavior of the social groups network.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.945-956
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• 2020

The publication of data is essential in order to receive high quality services from many applications. However, if the original data is published as it is, there is a risk that sensitive information (political tendency, disease, ets.) may reveal. Therefore, many research have been proposed, not the original data but the synthetic data generating and publishing to privacy preserve. but, there is a risk of privacy leakage still even if simply generate and publish the synthetic data by various attacks (linkage attack, inference attack, etc.). In this paper, we propose a synthetic data generation algorithm in which privacy preserved by applying differential privacy the latest privacy protection technique to GAN, which is drawing attention as a synthetic data generative model in order to prevent the leakage of such sensitive information. The generative model used CGAN for efficient learning of labeled data, and applied Rényi differential privacy, which is relaxation of differential privacy, considering the utility aspects of the data. And validation of the utility of the generated data is conducted and compared through various classifiers.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.6
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• pp.1069-1086
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• 2013

Nowadays, web defacement becomes the utmost threat which can harm the target organization's image and reputation. These defacement activities reflect the hacker's political motivation or his tendency. Therefore, the analysis of the hacker's activities can give the decisive clue to pursue criminals. A specific message or photo or music on the defaced web site and the outcome of analysis will be supplying some decisive clues to track down criminals. The encoding method or used fonts of the remained hacker's messages, and hacker's SNS ID such as Twitter or Facebook ID also can help for tracking hackers information. In this paper, we implemented the web defacement analysis system by applying CBR algorithm. The implemented system extracts the features from the web defacement cases on zone-h.org. This paper will be useful to understand the hacker's purpose and to plan countermeasures as a IDSS(Investigation Detection Support System).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.141-148
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• 2015

This paper proposes the BDAS(Big Data analysis Scheme) design that extracts the real time shared information from SNS and Web, analyzes the extracted data rapidly for customers, and makes an on-line marketing strategy efficiently. First, the BDAS collects the data shared in SNS and Web. Second, it provides the result of visualization by analyzing the semantics of the collected data as positive or negative. Therefore, because the BDAS ensures an average 90% accuracy in judging the semantics about the shared SNA and Web data, it can judge customer's propensity accurately and be used for on-line marketing strategy efficiently.

• Knowledge Management Research
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• v.22 no.1
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• pp.155-181
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• 2021

The purpose of this study is to verify the correlation between leader's machiavellianism and turnover intention. To this end, we tried to investigate the overall mechanism of the research model through the mediating effect of hindsight bias. To verify the hypothesis, surveys were conducted twice with 335 employees working at companies with more than 300 employees in various occupations. As a result of the study, first, it was found that the machiavellianism of the leader had a positive significant effect on the employee turnover intention. Second, it was found that hindsight bias had a positive significant mediating effect between the leader's machiavellianism and employee turnover intention. It can be inferred that the higher the machiavellianism tendency of the leader, the higher the hindsight bias is experienced and the negative impact on the effectiveness of the organization, the higher the employee turnover intention. Therefore, this study in-depth verifies the mechanism between the leader's machiavellianism, hindsight bias, and employee turnover intentions, suggesting new implications from a perspective different from the existing research flow, and suggesting future research tasks and limitations on the role of leaders.

• Journal of Digital Convergence
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• v.19 no.2
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• pp.397-402
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• 2021

The purpose of this study is to measure the satisfaction level of user experience of athlesure brand community by generation through surveys, and to derive satisfaction level according to consumption taste by generation. As a tool for measuring brand community, a questionnaire written Creating Pleasurable Interfaces Model of Stephen P. Anderson was used and was conducted focusing on women in their 10s-40s, which are the main consumers. As a result of the survey, the community participation rate and satisfaction level are significantly different depending on the consumption tendency of each generation. In addition, focused on task satisfaction was high, but focused on experience satisfaction was relatively low. It was found that there is a need for a plan to improve satisfaction based on experience for revitalization of online and offline communities in the future. Through this study, we expect the use of consumer-centered brand communities and brand communities according to the satisfaction level of consumption demand by generation and consumption preference by demand.