• The Korean Journal of Applied Statistics
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• v.29 no.1
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• pp.75-83
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• 2016

We propose methodology to analyze the dynamic mechanisms of financial market contagion under market integration using a biological contagion analytical approach. We employ U-statistic to measure market integration, and a dynamic model based on an error correction mechanism (single equation error correction model) and latent factor model to examine market contagion. We also use quantile regression and Wald-Wolfowitz runs test to test market contagion. This methodology is designed to effectively handle heteroscedasticity and correlated errors. Our simulation results show that the single equation error correction model fits well with the linear regression model with a stationary predictor and correlated errors.

• Korean Journal of Environment and Ecology
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• v.29 no.4
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• pp.636-644
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• 2015

In this paper, we examined factors that affect the success of a policy on trekking time restriction using questionnaire survey data collected from the visitors of seven national parks where the trekking time restriction policy is in force as of 2014. Results suggest that the trekking time restriction policy has been successfully publicized. In total, 60.7% of the survey respondents were aware of trekking time restrictions in the national parks they were visiting. Using exploratory factor analysis, we identified three latent factors (visitors' careless trekking, park rangers' insufficient management and visitors' unpreparedness) that the visitors perceived the causes of trekking accidents in the national parks. Multiple regression analysis on the three extracted factors and respondents' socioeconomic status shows that the respondents who read information signs in national parks and who judged visitors' careless trekking and visitors' unpreparedness as the causes of trekking accidents tended to agree more with restricting trekking time. These results indicate that visitors who do not agree with the trekking time restriction tend to attribute trekking accidents in national parks not to individual visitors, suggesting that educating visitors is more effective in preventing trekking accidents in national parks than installing and maintaining safety facilities by park rangers.

• Korean Journal of Social Welfare Studies
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• v.44 no.2
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• pp.327-358
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• 2013

This study aimed to analyze the trajectories of cognitive function and functional disability, and to identify the impacts of socio-demographic factors on the two variables. Based on the assumption that there are differences according to the progress of cognitive impairment, it focused on examining the differences in trajectories of cognitive function and functional disability between two groups: dementia conversion group and dementia non-conversion group among cognitively normal older adults. This study was conducted based on the data from a 3-wave panel study of a sample of 966 Yeoncheon elderly cohort aged 65 and over between 1997 and 2003. Latent growth curve model and multi-group structural equation modeling were used to examine the hypothesis. Results revealed that dementia conversion group exhibited faster rate of cognitive decline as well as lower initial cognitive level. Difference between two groups was not significant in the initial level of functional disability, yet dementia conversion group showed greater degree of deterioration in the functional disability over time than dementia non-conversion group did. In terms of the influence of socio-demographic factors on cognitive function and functional disability, the cognitive decline was more drastic in the female group, whereas functional decline was more apparent for the male group. The level of education in early life had a strong impact on the cognitive function in later life. Based on these findings, practical implication for high risk groups in cognitive function and functional disability were discussed.

• Management & Information Systems Review
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• v.33 no.2
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• pp.37-61
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• 2014

This research is to study presenteeism of members of a organization. It factually verifies how the job stress perceived by the members affect on presenteeism and examines factors to alleviate presenteeism, in addition, tests moderating effects based on the core self-evaluations and team climate. Research results reveal, first of all, that influencing relationship which job stress increases presenteeism exists. Second, core self-evaluations control the relationship between job stress and presenteeism, which means the stronger subconscious to oneself is the more it relieve the relationship between job stress and presenteeism. Third, team climate partially contolled the relationship between job stress and presenteeism. Atmosphere with clearer performance responsibility has better controlling effect to alleviate the relationship between job stress and presenteeism. Within the team climate, subordinate variables determine the effect on the presenteeism relationship. Significances and limitations of this research was discussed at the last.

• The Journal of Korean Association of Computer Education
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• v.7 no.5
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• pp.45-56
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• 2004

With recent surge of Internet use, many people become concerned with side effects of Internet. Especially Internet addiction has become a significant issue. As Internet users become much younger than before, Internet addiction is salient even among elementary school students. While much research has been conducted on adolescents' addiction, only a little research has been conducted on elementary students' Internet addiction. In addition, it is necessary to use a standardized and reliable evaluation tool that is designed to assess the level of children's and adolescents' Internet addiction. The purpose of this study is to grasp the realities of elementary students' Internet addiction using an evaluation tool developed for elementary and secondary students, and to analyze the factors affecting Internet addiction. A survey was conducted to 1,382 5th and 6th graders selected from nationwide schools. The results of this study shows that 5.5% of the sample students are in the stage of serious addiction, and 12.4% in the stage of early addiction. In addition, the degree of Internet addiction significantly differs by various variables such as demographic factors, the experience of Internet use, family-related traits, and social activities.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2060-2071
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• 1999

The complicate software failure system is defined to the superposition of the points of failure from several component point process. Because the likelihood function is difficulty in computing, we consider Gibbs sampler using iteration sampling based method. For each observed failure epoch, we applied to latent variables that indicates with component of the superposition mode. For model selection, we explored the posterior Bayesian criterion and the sum of relative errors for the comparison simple pattern with superposition model. A numerical example with NHPP simulated data set applies the thinning method proposed by Lewis and Shedler[25] is given, we consider Goel-Okumoto model and Weibull model with GOS, inference of parameter is studied. Using the posterior Bayesian criterion and the sum of relative errors, as we would expect, the superposition model is best on model under diffuse priors.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.3
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• pp.307-316
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• 2011

The majority of maritime accidents happened by human factor. For that reason, navigation experts want to an intelligent support system for navigation safety, without officer involvement. The expert system which is one of artificial intelligence skills for navigation support is an important tool that a machine can substitute for an expert through the design of a knowledge base and inference engine using the experience or knowledge of an expert. Further, in the real world, a complex situation requires synthetic estimation with the input of experts in various fields for the correct estimation of the situation, not any one expert. In particular, synthetic estimation is more important for navigation situations than in other cases, because of diverse potential threats. This paper presents the method of knowledge fusion pertaining to navigation safety knowledge from various expert systems, using a blackboard system. Then we will show the validity of the method via a design and implementation of test system effort.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.779-785
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• 2007

This study identifies visible/invisible factors and analyzes facilities, structure, and visible perceptive contents in the aspects of operation and efficiency with a focus on the interfaces between interior design of the subway and users. More specifically, it diagnoses the requirements and empirically presents improvements. As the interior design in the subway trains is fur the public reflecting the value, consciousness, and behaviors of users, it should be approached through the application of the concept of universal design that considers the potential needs and psychological satisfaction of users. In arranging the indoor of the vehicles, the conditions for the facilities should be specified through the interdisciplinary approach from professional fields including ergonomics and psychology, the path of flow should be induced through the use of space and the analysis of passengers' behaviors, an integrated planning should be re-established, and continuous evaluations of basic guidelines, manuals, and requirements should be made.

• Korean Journal of Remote Sensing
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• v.25 no.2
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• pp.95-105
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• 2009

Irregular temporal sampling is a common feature of geophysical and biological time series in remote sensing. This study proposes an on-line system for reconstructing observation image series including bad or missing observation that result from mechanical problems or sensing environmental condition. The surface parameters associated with the land are usually dependent on the climate, and many physical processes that are displayed in the image sensed from the land then exhibit temporal variation with seasonal periodicity. An adaptive feedback system proposed in this study reconstructs a sequence of images remotely sensed from the land surface having the physical processes with seasonal periodicity. The harmonic model is used to track seasonal variation through time, and a Gibbs random field (GRF) is used to represent the spatial dependency of digital image processes. In this study, the Normalized Difference Vegetation Index (NDVI) image was computed for one week composites of the Advanced Very High Resolution Radiometer (AVHRR) imagery over the Korean peninsula, and the adaptive reconstruction of harmonic model was then applied to the NDVI time series from 1996 to 2000 for tracking changes on the ground vegetation. The results show that the adaptive approach is potentially very effective for continuously monitoring changes on near-real time.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1003-1007
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• 2007

최근 기상이변, 불투수층의 증가와 배수체계개선 등의 요인으로 인한 홍수량의 증대로 하도방어 위주의 현재 홍수방어체제는 지속적인 치수사업의 시행에도 불구하고 오히려 하류에서의 홍수가 격심해지는 등 상당한 어려움에 직면하고 있다. 따라서 최근의 유역종합치수계획에서는 천변저류지 등에 의한 면적 개념의 2차원적 홍수량 분담을 통한 피해의 잠재성을 경감시키고자 하는 방안들이 제시되고 있다. 이러한 기술적 수요의 증가에 따라 낙동강유역종합치수계획, 삽교천유역종 합치수계획 등에서는 중규모 이상의 천변저류지가 검토되었지만 이러한 예는 대하천유역이므로 홍수피해가 빈발하는 농촌지역의 중소규모 하천에서는 계획된 적이 없다. 지금까지 지속적인 하천개수사업으로 2004년말 현재 하천연장 기준으로 전국의 하천 개수율은 78%에 이르고 있다. 이 중 국가하천과 지방1급하천은 약 15%로서 개수율이 약 90%이상으로 높고, 지방2급하천은 약 85%를 차지하나 대부분은 농촌지역에 위치하여 약 70% 미만의 낮은 개수율을 나타내고 있으므로 향후 중소규모유역의 지방2급하천에서 하천개수가 지속적으로 추진될 것이다. 현재 하천정비기본계획이 미수립된 하천구간에 대하여 하도계획시 제방축제에 의한 경제성이 미미한 일부 구간에 무제부의 소규모 아지늪을 조성하고, 홍수파의 전파속도를 저감하여 하류의 홍수집중을 경감시키고 유수 에너지를 감소시키며 아울러 본천의 유수환경과는 다른 습지로서의 정수환경을 창출하여 하천생태계의 다양성을 확보하는 방안도 있을 것이다. 본 연구에서는 경남 하동군에 위치하는 지방2급하천인 주교천에 약 $4000m^2$의 소형 습지(아지늪)를 2004년 3월에 조성하고 2006년 11월에 습지의 어류 및 수생식물에 대한 모니터링을 실시하여 아지늪의 하천생태의 다양성의 달성도를 평가하였다. 또한 주교천에서 홍수량의 증가에 따른 홍수류의 유속 변동과 그에 따른 에너지의 변화를 고찰하기 위하여 HEC-RAS를 적용하고 주교천 아지늪 주변의 수리학적 거동을 고찰하였다.