• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2953-2966
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• 2018

Housing prices are closely related to various variables that indicate macroeconomic conditions. In this paper, empirical analysis based on data is performed referring to previous studies. Focusing on the policy interest rate among the factors affecting the housing price, the non-linear impulse responses of other variables to the interest rate shock are analyzed. Using the random forest algorithm, the variable importance scores of the macroeconomic variables presented in the previous studies are calculated. After selecting the variables through this process, the impulse responses are calculated using a model that can capture non-linearity. According to the model, the responses of housing prices to the policy rate is only significant when the rate is raised. Especially, the impulse response is amplified when the shock increases due to the non-linear characteristics that can not be captured by the traditional VAR methodology. The analysis results suggest that the interest rate as a policy instrument should be approached from a more cautious perspective.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1703-1706
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• 2009

빗물관리시설은 강우, 증발량 등 기상조건과 집수면의 토지이용 및 토양 특성에 영향을 받으므로 대상지역의 조건에 따라 설치가능 여부, 시설 규모 등에 차이가 있다. 따라서 빗물관리시설의 계획 수립 시에는 대상지역의 기상, 지형특성을 종합적으로 검토할 필요가 있으며, 이는 시설의 효율적인 활용을 위해 필수적이다. 본 연구에서는 GIS 공간분석 기능을 통해 대상 지역의 강우-유출특성, 지형 공간 특성을 고려하여 빗물관리 포텐셜을 분석하였다. 빗물관리 포텐셜은 저류시설을 통해 확보하거나 침투시설로 침투시킬 수 있는 잠재적인 능력을 말한다. 저류 포텐셜은 잠재 지표면 유출량(Runoff potential)으로 산정하였으며, 침투 포텐셜은 일반화된 Green-Ampt 모델에 따라 산정하였다. 산정한 저류 및 침투 포텐셜의 크기, 제약조건인 경사도 등급에 따라 빗물관리 적합도(Suitability map)을 도출하였다. 향후 본 연구의 물리적 변수뿐만 아니라 사회 경제적 인자, 빗물관리가 어려운 제약조건들을 추가로 고려한다면 빗물관리시설의 적지 선정에 활용도가 높을 것으로 기대된다.

• The Korean Journal of Financial Studies
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• v.11 no.1
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• pp.243-273
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• 2005

본 연구는 국내기업의 자사주매입결정에 영향을 미치는 매입동기와 매입동기들의 상호관련성, 시간에 따른 매입동기의 변화를 분석하였다. 분석에 이용된 자료는 1994년 1월에서 2002년 12월까지 자사주매입을 실시한 기업의 실제 매입규모이며, t검정과 토빗모형의 추정을 통해 다음과 같은 사실들을 발견할 수 있었다. 첫째, 정보비대칭의 지표인 기업규모변수는 대부분의 기간에서 자사주매입결정에 양(+)의 영향을 미치는 것으로 나타났다. 이것은 정보비대칭수준이 낮을 것으로 예상되는 대기업이 자사주매입에 적극적이라는 것을 의미한다. 또한, 잠재적 저평가의 지표인 시장가치대장부가치변수는 연도별로 양(+)과 음(-)의 계수가 혼재되어 있어 일관성 있는 결과를 도출할 수 없었다. 이러한 결과는 자사주매입이 저평가를 시장에 신호하기 위한 것이라는 저평가가설을 기각하는 것으로 볼 수 있다. 둘째, 기업의 지불수준을 측정하는 지표인 여유현금흐름변수들은 대부분의 기간에서 자사주매입결정에 양(+)의 영향을 미쳤으며, 추정된 회귀계수들의 비교를 가능하게 하는 부분효과평균도 상대적으로 높게 나타났다. 이러한 결과는 기업의 여유현금흐름증가가 자사주매입결정에 강한 영향력을 미치는 요인이라는 것을 의미한다. 셋째, 기업의 레버리지수준을 측정하는 변수도 대부분의 기간에서 자사주매입결정에 음(-)의 영향을 미치는 것으로 나타났다. 이것은 자사주매입이 기업의 자본구조를 변경하기 위한 동기에서 결정된다는 것으로 해석될 수 있다.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.467-474
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• 2014

Preliminary design in chemical process furnishes economic feasibility through calculation of both mass balance and energy balance and makes it possible to produce a desired product under the given conditions. Through this design stage, the process possesses unchangeable characteristics, since the materials, reactions, unit configuration, and operating conditions were determined. Unique characteristics could be very economic, but it also implies various potential risk factors as well. Therefore, it becomes extremely important to design process considering both economics and safety by integrating process simulation and quantitative risk analysis during preliminary design stage. The target of this study is LNG liquefaction process. By the simulation using Aspen HYSYS and quantitative risk analysis, the design variables of the process were determined in the way to minimize the inherent explosion risks and operating cost. Instead of the optimization tool of Aspen HYSYS, the optimization was performed by using stochastic optimization algorithm (Covariance Matrix Adaptation-Evolution Strategy, CMA-ES) which was implemented through automation between Aspen HYSYS and Matlab. The research obtained that the important variable to enhance inherent safety was the operation pressure of mixed refrigerant. The inherent risk was able to be reduced about 4~18% by increasing the operating cost about 0.5~10%. As the operating cost increases, the absolute value of risk was decreased as expected, but cost-effectiveness of risk reduction had decreased. Integration of process simulation and quantitative risk analysis made it possible to design inherently safe process, and it is expected to be useful in designing the less risky process since risk factors in the process can be numerically monitored during preliminary process design stage.

• Informatization Policy
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• v.24 no.1
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• pp.79-99
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• 2017

Despite the early success story, the pan-industry diffusion of big data has been slow mostly due to lack of confidence of the value creation and privacy-related concerns. The problem leads us to the need to a stakeholder analysis on the adoption process of big data. The present study combines technology acceptance model, task-technology fit theory, and privacy calculus theory to integrate the positive and negative factors on the big data adoption. The empirical analysis was performed based on the survey from the current and potential big data users. Results revealed perceived usefulness, task-technology fit, and privacy concern are significant antecedents to the intention to use big data. Furthermore, there are significant differences in the perceptions of each constructs among groups divided by the types of big data use, with several exceptions. And the control effect was found in the magnitude of the relation between independent variables and dependent variable. The theoretical and politic implications of the analysis are discussed as to the promotion of big data industry.

• The Korean Journal of Applied Statistics
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• v.31 no.4
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• pp.463-473
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• 2018

Variable selection algorithms for linear regression models of large data are considered. Many algorithms are proposed focusing on the speed and the robustness of algorithms. Among them variance inflation factor (VIF) regression is fast and accurate due to the use of a streamwise regression approach. But a VIF regression is susceptible to outliers because it estimates a model by a least-square method. A robust criterion using a weighted estimator has been proposed for the robustness of algorithm; in addition, a robust VIF regression has also been proposed for the same purpose. In this article a fast and robust variable selection method is suggested via a VIF regression with detecting and removing potential outliers. A simulation study and an analysis of a dataset are conducted to compare the suggested method with other methods.

• 한국벤처창업학회:학술대회논문집
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• 2021.11a
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• pp.35-39
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• 2021

청소년 기업가정신에 관한 관심과 기업가정신 교육의 필요성이 중요시됨에 따라 초·중·고등학교 교육과정부터 체계적인 기업가 정신 교육이 강조되고 있으며, 이와 관련한 연구의 필요성이 대두되고 있다. 본 연구는 청소년을 대상으로 기업가정신, 긍정심리자본이 창업의지에 미치는 영향과 기업가 정신교육의 만족도가 조절효과를 갖는지 여부를 확인하고자 하였다. 이를 위해, 성별과 부모 창업의 여부를 통제한 상태에서 기업가정신의 주요 구성요소 '진취성', '위험 감수성', '혁신성'과 긍정심리자본의 '희망', '자기효능감', '회복 탄력성', '낙관주의'를 독립변수로 하였는데, 기업가정신 교육 프로그램에 참여한 청소년(중학생) 총 204명의 응답을 회수 후 실증분석을 시도 했다. 또한 기업가정신 교육의 만족도를 조절변수로 하는 연구 모형을 상정하였는데, 이는 기업가정신 및 긍정심리자본과 창업 의지의 관계에서 기업가정신 교육의 만족도가 조절 효과 여부를 확인하여 기업가정신 교육의 중요성을 밝히고 활성화를 목적으로 하고 있다. 이를 통해 잠재적 창업가가 될 수 있는 청소년의 기업가정신 영향요인을 검증하고 연구자료에 다양하게 비교할 수 있는 참고자료로서 도움이 되고자 한다.

• Korea Journal of Hospital Management
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• v.23 no.1
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• pp.87-106
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• 2018

Objective: The objective of this study is to examine the association between process quality of inpatient care and risk-adjusted, thirty-day potentially preventable hospital readmission (PPR) rates. Data Sources/Study Setting: This was an observational cross-sectional study of nonfederal acute-care hospitals located in two states California and Florida, discharging Medicare patients with a principal discharge diagnosis of heart failure, acute myocardial infarction, or pneumonia January through December 31, 2007. Data were obtained from the Healthcare Cost and Utilization Project State Inpatient Database of the Agency for Healthcare Research and Quality, Centers for Medicare and Medicaid Services Hospital Compare database, and the American Hospital Association Annual Survey of Hospitals. Study Design: The dependent variable of this study is condition-specific, risk-adjusted, thirty-day potentially preventable hospital readmission (PPR). 3M's PPR software was utilized to determine whether a readmission was potentially preventable. The independent variable of this study is hospital performance for process quality of inpatient care, measured by hospital adherence to recommended processes of care. We used multivariate hierarchical logistic models, clustered by hospitals, to examine the relationship between condition-specific, risk-adjusted, thirty-day PPR rates and process quality of inpatient care, after taking clinical and socio-demographic characteristics of patients and structural and operational characteristics of hospitals into account. Findings: Better performance on the process quality metrics was associated with better patient outcome (i.e., low thirty-day PPR rates) in pneumonia, but not generally in two cardiovascular conditions (i.e., heart failure and acute myocardial infarction). Practical Implication: Adherence to the process quality metrics currently in use by CMS is associated with risk-adjusted, thirty-day PPR rates for patients with pneumonia, but not with cardiovascular conditions. More evidence-based process quality metrics closely linked to 30-day PPR rates, particularly for cardiovascular conditions, need to be developed to serve as a guideline to reduce potentially preventable readmissions.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.505-518
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• 2023

The key to invasive pest management lies in preemptive action. However, most current research using species distribution models is conducted after an invasion has occurred. This study modeled the potential distribution of the globally notorious sweet potato pest, the sweet potato weevil(Cylas formicarius), that has not yet invaded Korea using MaxEnt. Using global occurrence data, bioclimatic variables, and topsoil characteristics, MaxEnt showed high explanatory power as both the training and test areas under the curve exceeded 0.9. Among the environmental variables used in this study, minimum temperature in the coldest month (BIO06), precipitation in the driest month (BIO14), mean diurnal range (BIO02), and bulk density (BDOD) were identified as key variables. The predicted global distribution showed high values in most countries where the species is currently present, with a significant potential invasion risk in most South American countries where C. formicarius is not yet present. In Korea, Jeju Island and the southwestern coasts of Jeollanam-do showed very high probabilities. The impact of climate change under shared socioeconomic pathway (SSP) scenarios indicated an expansion along coasts as climate change progresses. By applying the 10th percentile minimum training presence rule, the potential area of occurrence was estimated at 1,439 km² under current climate conditions and could expand up to 9,485 km² under the SSP585 scenario. However, the model predicted that an inland invasion would not be serious. The results of this study suggest a need to focus on the risk of invasion in islands and coastal areas.

• Korean Journal of Environment and Ecology
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• v.13 no.2
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• pp.167-175
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• 1999

본 연구의 목적은 자연지향적 집단의 생태관광 행동특성을 파악하는 데 있다. 이를 위해 서울지역의 5개 지역 지향적 집단을 중심으로 설문조사를 실시하였다. 설문조사는 여행객의 행동특성, 행동특성에 미치는 영향요소들, 그리고 행동특성에 영향을 주는 변수와의 차이를 분석하는데 중점을 두었는데, 이를 위해서 행동특성에 대한 요인분석과 독립변수들과의 차이를 알아보기 위해 일원배치 분산분석을 실시하였다. 연구결과 절대환경론자 및 정태형 생활양식을 가진 사람들은 계절과 방문빈도에 민감했으며 조화론자 및 모험형의 사람들은 동기부여에 영향을 주는 요소들과 장애요소들에 민감하게 반응하는 것으로 나타났다. 본 연구의 결과는 국내의 잠재적인 생태관광 시장의 효과적인 홍보 및 마케팅 전략수립에 기초적인 자료로서 제공할 수 있을 것으로 판단되며, 자료의 이용효율성 증대를 위해서는 생활양식적 차이와 다양성 요구에 의한 심리적 유형의 차이 및 개인의 환경관 등이 행동에 작용하는 범주와 영향의 구체적 원인에 대한 세부적인 연구가 향후 계속 되어야 할 것으로 판단된다.