Characterization of circadian blood pressure patterns using non-linear mixed effects modeling

채동우,김유경,박경수 대한임상약리학회 2019 Translational and Clinical Pharmacology Vol.27 No.1

Characterizing the time course of baseline or pre-drug blood pressure is important in acquiring unbiased estimates of antihypertensive drug effect. In this study, we recruited 23 healthy malevolunteers and measured systolic (SBP) and diastolic blood pressure (DBP) over 24 hours on anhourly basis. Using a non-linear mixed effects model, circadian rhythm observed in blood pressuremeasurements was described by incorporating two cosine functions with periods 24 and 12 hours. A mixture model was applied to identify subgroups exhibiting qualitatively different circadianrhythms. Our results suggested that 78% of the study population, defined as ‘dippers’, demonstrateda typical circadian profile with a morning rise and a nocturnal dip. The remaining 22% of the subjects defined as ‘non-dippers’, however, were not adequately described using the typical profile anddemonstrated an elevation of blood pressure during night-time. Covariate search identified weightas being positively correlated with mesor of SBP. Visual predictive checks using 1,000 simulated datasets were performed for model validation. Observations were in agreement with predicted valuesin ‘dippers’, but deviated slightly in ‘non-dippers’. Our work is expected to serve as a useful referencein assessing systematic intra-day blood pressure fluctuations and antihypertensive effects as well asassessing drug safety of incrementally modified drugs.

대학 정보공시 데이터베이스(DB)를 활용한 자율개선대학선정 예측에 관한 실증연구

채동우,전병훈,정군오,Chae, Dong Woo,Jeon, Byung Hoon,Jung, Kun Oh 한국데이터전략학회 2021 Journal of information technology applications & m Vol.28 No.6

Due to the decrease in the school-age population and government regulations, universities have made great efforts to secure their own competitiveness. In particular, the selection of universities with financial support based on the recent evaluation of the Ministry of Education has become a major concern enough to affect the existence of the university itself. This paper extracts three-year data from 124 major private universities nationwide, and quantitatively analyzes the variables of major universities selected as self-improvement universities, competency reinforcement universities, and universities with limited financial support. As a result of estimating the selection of self-powered universities using the ordered logit model by hierarchically inputting 12 variables, student competitiveness in the metropolitan area (1.318^**), Educational Restitution Rate (4.078^***), University operation expenditure index rate (1.088^***) values were found. Significant positive coefficient values were found in the admission enrollment rate (45.98^***) and the enrollment rate (13.25^***). As a result of analyzing the marginal effects, the increase in the rate of reduction of education costs has always been positive in the selection of self-powered universities, but it was observed that the rate of increase decreases in areas of increase of 150% or more. On the contrary, the probability of becoming a Em-powered university was negative in all sectors, but on the contrary, it was analyzed that marginal effects increased at the same time point. On the other hand, the employment rate of graduates was not able to find direct significance with the result of the selection of Self powered universities. Through this paper, it is expected that each university will analyze the possibility and shortcomings of the selection of Self powered universities in policy making, and in particular, the risk of dropout of selection for the vulnerable field can be predicted using marginal effects. It can be used as major research data for both university evaluators, university officials and students.

데이터 마이닝을 활용한 사립대학 교육비 환원요인 분석 : 패널 고정효과모형과 비모수회귀추정을 중심으로

채동우,이문범,정군오 한국정보기술응용학회 2020 Journal of information technology applications & m Vol.27 No.6

The Educational Restitution Rate is an important parameter that determines the quality of university education. This paper analyzed data from 148 private universities over the 10 years from 2009 to 2018 using data mining techniques in Korea. A significant causal relationship is detected in the fixed effect model as a result of the panel estimation. And the scale of faculty expansion and fund management, which are the university evaluation indicators, and the size of basic funds, respectively, have a positive effect on the ERR, which is within the confidence interval. In the analysis, the more private universities improve the tuition dependence rate, the more decisively positive affecting ERR. As a result of nonparametric regression estimation, when the faculty expansion ratio is reinforced, the effect of economies of scale is detected in some sections, the improvement of the tuition dependence rate, and the result value is generated through the improvement that results are derived at a certain point in time. We hope that the university based on this study can be a basic Indicators for the diagnosis of basic competencies and policy of student-centered education.

다층 필름구조를 이용한 광특성 기반 수동 복사냉각

채동우,정필훈,손수민,LIU YUTING,허대홍,김관,이주형,이헌 한국표면공학회 2019 한국표면공학회 학술발표회 초록집 Vol.2019 No.5

수도권과 지방대학 간의 입학경쟁률 격차에 관한 연구 - 경쟁 구조의 비대칭성과 패널모형적용을 중심으로 -

채동우,박현식 한국지역사회학회 2022 지역사회연구 Vol.30 No.4

본 연구는 급변하는 학령인구 감소의 귀로에 서있는 한국의 현실에 직면하여, 학생들의 수도권과 비수도권의 입학경쟁력 격차에 대한 계량적 연구를 시도하였다. 이를 위해 2010~2020년까지의 수도권과 지방권의 대학정보공시자료를 추출하여 이분화 하여 분석하였다. 변수의 변화율을 측정하기 위해 로그모형을 적극 활용하였고, 표준오차의 강건성을 확보하여 추정치의 신뢰도를 높였다. 브레슈 페이건(Breusch–Pagan) 및 하우스만 검정(Hausman Test)테스트를 통하여 패널 고정효과 모형을 적용 하였다. 주된 분석 결과는 첫째, 수도권과 지방의 입학경쟁률 구조는 커널밀도 확인결과 수도권대학을 중심으로 높은 경쟁률이 넓은 스팩트럼을 먼저 형성 하고, 지원하지 못한 나머지 입학자원이 지방으로 쓸려오는 경향이 나타났다. 둘째, 대학의 연구 환경과 등록금 수준에 있어 수도권은 지방권에 비해 크게 우위에 있는 현실이 확인되었다. 셋째, 대학의 재정지원규모는 경쟁률과 직결되었으며, 중도탈락률은 지방권이 훨씬 위험성 있는 구도를 형성하고 있음이 관측되었다. 이는 학생들의 수도권 과 지방간 학생의 경쟁 선호편차가 갈수록 심각하게 커지고 있다는 상식적 논증을 통계적으로 지지한다. 본 연구를 토대로 서울경기와 기타지방에 대한 학생 선호 격차를 해소하는 연구자료로 활용하기를 기대한다. 특히, 이를 통해 지역 간 교육격차 해소 정책에 일조되기를 기대한다. This study attempted a quantitative study on the gap in the entrance competitiveness of students in the metropolitan area and non-metropolitan area due to the rapidly changing school-age population decline. For this purpose, university information disclosure data for the metropolitan area and local area from 2010 to 2020 were extracted and bifurcated and analyzed. The main analysis results are: First, the structure of the admission competition rate in the metropolitan area and provincial areas was formed by forming a broad spectrum with high competition rate centering on the metropolitan universities as a result of checking the kernel density, and the remaining admission resources tended to apply to the provincial areas. Second, in the research environment and tuition level of universities, it was confirmed that the metropolitan area had a superior coefficient value compared to the local area, confirming that there was a substantial gap. Third, it was found that there was a significant difference in the size of university financial support and dropout rate between groups. This supports the argument that students' competitive preferences and resilience of students between metropolitan areas and regions are different.

UV 나노임프린트 공정을 이용한 SiC 나노입자 기반 마이크로-나노급 패턴 제작

채동우,정진희,류우정,정필훈,이헌 한국표면공학회 2018 한국표면공학회 학술발표회 초록집 Vol.2018 No.11

새마을 가꾸기 성공사례 : 우리는 이렇게 새 마을을 가꾸었다 - 부산시 영도구 청학 2 동 ; 경기파주군아동면맥 금 2 리 상곡동 ; 충북 보은군 보은면 강산리 ; 전남함평군손불면 양재 2 리 -

채동우,이상춘,한규석,모종국 대한지방행정공제회 1971 地方行政 Vol.20 No.215

Introduction to dynamical systems analysis in quantitative systems pharmacology: basic concepts and applications

채동우 대한임상약리학회 2020 Translational and Clinical Pharmacology Vol.28 No.3

Quantitative systems pharmacology (QSP) can be regarded as a hybrid of pharmacometricsand systems biology. Here, we introduce the basic concepts related to dynamical systemstheory that are fundamental to the analysis of systems biology models. Determination ofthe fixed points and their local stabilities constitute the most important step. Illustrationof a phase portrait further helps investigate multistability and bifurcation behavior. As amotivating example, we examine a cell circuit model that deals with tissue inflammationand fibrosis. We show how increasing the severity and duration of inflammatory stimulidivert the system trajectories towards pathological fibrosis. Simulations that involvedifferent parameter values offer important insights into the potential bifurcations andthe development of efficient therapeutic strategies. We expect that this tutorial serves asa good starting point for pharmacometricians striving to widen their scope to QSP andphysiologically-oriented modeling.

An imputation-based method to reduce bias in model parameter estimates due to non-random censoring in oncology trials

채동우,박경수 대한임상약리학회 2016 Translational and Clinical Pharmacology Vol.24 No.4

In oncology trials, patients are withdrawn from study at the time when progressive disease (PD) is diagnosed, which is defined as 20% increase of tumor size from the minimum. Such informative censoring can lead to biased parameter estimates when nonlinear mixed effects models are fitted using NONMEM. In this work, we investigated how empirical Bayes estimates (EBE) could be exploited to impute missing tumor size observations and partially correct biases in the parameter estimates. 50 simulated datasets, each consisting of 100 patients, were generated based on the pub¬lished model. From the simulated dataset, censoring due to PD diagnosis has been implemented. Using the post-hoc EBEs acquired from fitting the censored datasets using NONMEM, imputed values were generated from the tumor size model. Model fitting was carried out using censored and imputed datasets. Parameter estimates using both datasets were compared with true values. Tumor growth rate and cell kill rate were approximately 28% and 16% underestimated when fitted using the censored dataset, respectively. With the imputed datasets, relative biases of tumor growth rate and cell kill rate decreased to about 6% and 0%, respectively. Our work demonstrates that using EBEs acquired from fitting the model to the censored dataset and imputing the unknown tumor size observations with individual predictions beyond the PD time point is a viable option to solve the bias associated with structural parameter estimates. This approach, however, would not be help¬ful in getting better estimates of variance parameters.

중국의 주택수급요인 변화성에 관한 연구

채동우,진국화,김시용 한국중국문화학회 2021 中國學論叢 Vol.- No.72

Since 2000, China has rapidly become the world's second largest economy through rapid economic growth. Like other developing countries, China has promoted the process of urbanization through a government-led economic growth method, which has contributed to the increase in housing demand and housing prices, and this has caused various social problems such as the growing gap between the rich and the poor. . This research mainly analyzes China's housing ecosystem that affects China's housing supply. The analysis results of the Markov chain model and the effect model from 2001 to 2019 show that there are significant and significant differences in factors related to housing supply and demand, such as the degree of urbanization development and changes in income in different regions. Especially in the areas with the highest population density and income, most of them have not changed under the influence of 20 years of continuous urbanization and income disparity, and most of them have moved within the cluster. Taking into account the factors of housing urbanization and income changes, the elasticity of changes in investment supply and demand prices in 20 years is about 0.628, and the elasticity of changes in sales demand prices is about 0.748. In other words, housing in China is also a commodity with financial attributes. Based on this argument, if the Chinese government implements a housing supply policy that conforms to the relationship between housing supply and demand, the gap between the rich and the poor can be narrowed, and the two goals of income redistribution and economic growth can be achieved. 중국은 2000년 이후 고도성장을 통해 세계의 G2로 급부상하였다. 다른 개발도상국과 마찬가지로 정부주도하의 성장은 도시화와 빈부격차라는 근본적인 문제와 함께 주택수요증가와 이에 따른 수요가격상승을 부추겼다. 본 연구는 주택수급 요인에 영향을 미치는 중국 주택 생태계에 대한 분석이 주를 이룬다. 2001년에서 2019년의 마르코프 체인 모형과 패널 모형을 활용하여 분석한 결과, 지역 자치구별로 도시화정도, 소득변화정도 등과 함께 주택 수급요인에 유의적 차이가 확인되었다. 특히, 최상위 인구밀도와 소득지역은 20년 동안 지속 도시화와 소득 격차가 바뀌지 않고, 해당 클러스터(Cluster) 내에서 대부분 움직이는 것으로 확인되었다. 주택 도시화 변화요인과 소득변화 요인을 감안하였을 때, 20여 년간 수요에 대한 투자공급의 가격변화 탄력성은 약 0.628, 판매수요가격변화 측면에서 탄력성은 약 0.748로 관측되었다. 즉 중국에서도 주택은 필수적 재화 성격을 지니는 상품임이 재확인되었다. 본 논고를 근거로 중국정부가 빈부격차를 줄이고 주택 수급에 맞는 주택수급정책을 펼친다면, 소득재분배와 경제성장의 두 목적을 달성할 수 있을 것이다.