• Communications for Statistical Applications and Methods
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• 제21권2호
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• pp.169-181
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• 2014

Marginalized random effects models (MREM) are commonly used to analyze longitudinal categorical data when the population-averaged effects is of interest. In these models, random effects are used to explain both subject and time variations. The estimation of the random effects covariance matrix is not simple in MREM because of the high dimension and the positive definiteness. A relatively simple structure for the correlation is assumed such as a homogeneous AR(1) structure; however, it is too strong of an assumption. In consequence, the estimates of the fixed effects can be biased. To avoid this problem, we introduce one approach to explain a heterogenous random effects covariance matrix using a modified Cholesky decomposition. The approach results in parameters that can be easily modeled without concern that the resulting estimator will not be positive definite. The interpretation of the parameters is sensible. We analyze metabolic syndrome data from a Korean Genomic Epidemiology Study using this method.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2003년도 춘계 학술발표회 논문집
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• pp.69-74
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• 2003

The estimation of pest density is a prime concern of Integrated Pest Management (IPM) because the success of artificial intervention such as spraying pestcides or natural enemies depends on pest density. Also, the spatial pattern of pest population within plants or plots has been studies in various ways. In this study, we applied generalized linear mixed model to Tetranychus urticae Koch , two-spotted spider mite count in glasshouse grown roses. For this analysis, the subject-specific as well as pupulation-averaged approaches are used.

• 한국조경학회지
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• 제26권3호
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• pp.104-117
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• 1998

Rising concern about climate change has evoked interest in the potential for urban vegetation to help reduce the level of atmospheric CO\sub 2\, a major heat-trapping gas. This study quantified the functio of home energy savings and carbon emission reduction by shading, evapotranspiration and windspeed reduction of urban vegetatioin in Chuncheon. Tree and shrub cover averaged approximately 13% in residential land. The effects of shading, evapotranspiration and windspeed reduction annually saved heating energy by 2.2% and cooling energy by 8.8%. The heating and cooling energy savings reduced carbon emissions by 3.0% annually. These avoided emissions equaled the amount of carbon emitted annually from fossil fuel consumption by a population of about 1,230. Carbon emission reduction per residential building was 55kg for detached buildings and 872 kg for multifamily buildings. Urban vegetation annually decreased heating and cooling energy cost by ￦1.1 billions, which were equivalent to annual savings of ￦10,000 savings and carbon emission reduction due to tree plantings in the wrong locations, while windspeed reduction had a great effect. Plantings fo large trees close to the west and east wall of buildings, full tree plantings on the north, and avoidance of shade-tree plantings or selection of solar-friendlytrees on the south were recommended to improve the function of building energy savings and carbon emission reduction by urban vegetation.

• 한국운동역학회지
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• 제22권2호
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• pp.219-228
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• 2012

The purpose of this study was to investigate how induced fatigue of the ankle joint muscles affects the capability and recovery of postural control during single-leg stance in healthy adults. The study population included 22 randomly recruited men and women. Postural control was performed on single-leg stance with eyes open. Ankle joint muscle was fatigued by repeated heel raises. According to the results of this study, for the anteroposterior variables, both men and women showed significantly increased center of mass velocity and decreased center of pressure 95% edge frequency immediately after fatigue. For the mediolateral variables, both men and women showed significantly increased center of mass velocity and decreased center of pressure 95% edge frequency immediately after fatigue. For the total variables, both men and women showed significantly increased center of mass averaged-velocity immediately after fatigue, and also, the center of pressure 95% confidence ellipse area significantly increased in women. Postural control variables were not significantly different for men and women at any time (Pre, P0, P10, and P20). In conclusion, the gender does not affect the capability and recovery after induced fatigue of ankle joint muscles. The effect of fatigue found for the anteroposterior and the mediolateral variables in both men and women. Furthermore ankle joint muscle fatigue led to change of postural control strategy from an ankle joint strategy towards a hip joint strategy. These changes are believed to damage postural control. The ankle joint muscle recovered from fatigue within 20 min during single-leg stance.

• Ocean and Polar Research
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• 제30권3호
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• pp.261-275
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• 2008

The profile of a fixed site at station M ($34.77^{\circ}N,\;129.13^{\circ}E$) in the Korea Strait was studied from March 2006 to February 2007. The aim was to understand the relationship between the annual thermal stratification pattern and seasonal variation in phytoplankton community structure. Physicochemical factors including temperature, salinity and nutrient concentrations, which strongly influence the proliferation and diversity of phytoplankton, were measured. The study period was divided into three due to the characteristic of thermohaline structures; mixed I (March-May 2006), stratified (June-November 2006) and mixed II(December 2006-Feburuary 2007). Diatoms dominated during the mixed I (89%) and II (48%) periods, while nanoplankton group occupied over 83% of total population during the stratified period. The dominant species during the mixed I and II was Chaetoceros socialis (47% and 29%, respectively), while during the stratified period Gyrodinium sp.(4%) was the most dominant. Averaged total chl a concentrations during the mixed I and II periods were 0.61 mg $m^{-3}$ and 0.72 mg $m^{-3}$, respectively, which were at least two-fold higher than that during the stratified period (0.30 mg $m^{-3}$). The vertical mixing and convection process of the water column induced nutrient supply from the bottom layer to the euphotic zone. It also led to the dominance of diatoms during the mixed periods, whereas small phytoplankton prevailed over large phytoplankton as stratification blocked the upward movement of nutrients to subsurface during the stratified period. During the mixed I and II periods, microplanktonic chl a dominated concentrations (50% and 48%, respectively), while picoplanktonic chl a occupied over 37% of total chl a during the stratified period.

• Journal of Radiation Protection and Research
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• 제42권2호
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• pp.130-140
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• 2017

Background: With the need for a domestic level 3 probabilistic safety assessment (PSA), it is essential to develop a Korea-specific code. Health effect assessments study radiation-induced impacts; in particular, long-term health effects are evaluated in terms of cancer risk. The objective of this study was to analyze the latest cancer risk models developed by foreign organizations and to compare the methodology of how they were developed. This paper also provides suggestions regarding the development of Korean cancer risk models. Materials and Methods: A review of cancer risk models was carried out targeting the latest models: the NUREG model (1993), the BEIR VII model (2006), the UNSCEAR model (2006), the ICRP 103 model (2007), and the U.S. EPA model (2011). The methodology of how each model was developed is explained, and the cancer sites, dose and dose rate effectiveness factor (DDREF) and mathematical models are also described in the sections presenting differences among the models. Results and Discussion: The NUREG model was developed by assuming that the risk was proportional to the risk coefficient and dose, while the BEIR VII, UNSCEAR, ICRP, and U.S. EPA models were derived from epidemiological data, principally from Japanese atomic bomb survivors. The risk coefficient does not consider individual characteristics, as the values were calculated in terms of population-averaged cancer risk per unit dose. However, the models derived by epidemiological data are a function of sex, exposure age, and attained age of the exposed individual. Moreover, the methodologies can be used to apply the latest epidemiological data. Therefore, methodologies using epidemiological data should be considered first for developing a Korean cancer risk model, and the cancer sites and DDREF should also be determined based on Korea-specific studies.

• 대한치위생과학회지
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• 제6권2호
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• pp.129-139
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• 2023

연구배경: 우리나라 65세 이상 고령 인구는 2023년 18.4%로, 향후 계속 증가하여 2025년에는 20.6%로 초고령사회로 진입 전망이다. 임상에서 치과위생사의 노인차별주의는 고령화에 따른 노인 환자의 증가로 인하여 치위생 처치 시 어려움을 경험할 수 있고 이는 업무 부적응과 이직으로도 이어질 수 있기 때문에 예비 치과위생사인 치위생학과 학생을 대상으로 노인의 이해에 대한 교육이 반드시 필요하고 사료된다. 이에 노인차별주의와 노인의 지식 및 태도의 관련성 연구를 통해 초고령화 사회를 대비하고 대학의 교육과정 변화 및 노인관련 프로그램 개발을 위해 연구를 실시하였다. 연구방법: D지역 치위생학과 재학생 204명을 대상으로 SPSS/WIN 25.0 프로그램을 이용하여 분석하였다. 대상자의 노인차별주의, 노인에 대한 지식, 노인에 대한 태도는 평균과 표준편차로 구하였다. 대상자의 일반적 특성에 따른 노인차별주의 차이를 검증하기 위해 t-test, one-way ANOVA를 실시하였으며, 사후검증은 Scheffe' test를 실시하였다. 대상자의 노인차별주의, 노인에 대한 지식, 노인에 대한 태도는 상관관계분석을 실시하였다. 결과: 노인차별주의는 4점 만점에 2.03±0.36점이었다. 노인에 대한 지식은 신체적 영역 0.57±0.15, 사회적 영역 0.36±0.17, 심리적 영역 0.35±0.20 순이었다. 노인에 대한 태도는 3.86±0.27로 나타났다. 노인에 대한 지식은 25점 만점에 평균 11.27±3.30점이었다. 노인에 대한 지식 정답률이 가장 높은 문항은 '체력은 나이가 들면서 감소하는 경향이 있다'로 93.1%였다. 연구대상자의 일반적 특성에 따른 노인에 대한 태도는 연령(p=0.009)에서 노인 차별주의는 성별(p=0.040), 연령(p=0.026), 조부모와 생활경험(p=0.001)유의한 차이를 보였다. 연구 대상자의 노인 차별주의는 노인에 대한 태도와 지식 모두 음의 상관관계를 보였으며, 노인 차별주의 중에서도 정서회피(r=.892, p<0.001)와 관련하여 높은 양의 상관관계를 보였다. 결론: 대학생들은 노인 부양의 주도적 역할자이자 고령화 사회문제에 직접적인 영향을 받게 된다. 그러므로 노인들에 대한 긍정적인 사고 형성과 노인차별을 야기 시키는 부정적 편견을 지양할 수 있도록 국가와 사회, 교육기관에서 다양한 프로그램의 적용이 필요할 것으로 사료된다.