• 디지털융복합연구
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• 제19권12호
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• pp.477-486
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• 2021

본 연구의 목적은 국민건강영양조사 2016-2019년 자료 중 성인을 대상으로 대사증후군의 위험요인 탐색하고, 성별에 따른 위험요인의 차이를 규명하여 대사증후군 예방 및 치료에 기초자료로 제공하기 위함이다. 다양한 선행연구를 통해 대사증후군 위험요인을 수집하고, 4개의 머신러닝(Logistic Regression, Decision Tree, Naïve Bayes, Random Forest)의 방법을 이용하여 분석하였다. 남성과 여성 모두에서 Random Forest의 대사증후군 예측 정확도가 높았다. 대사증후군 유병에 영향을 주는 상위 위험요인으로는 여성과 남성 모두에서 BMI, 식이(지방, 비타민 C, 비타민 A, 단백질, 에너지 섭취), 기저질환의 개수, 연령으로 나타났다. 여성의 경우 교육수준과 초경 연령, 폐경 여부가 추가적으로 주요 위험요인으로 나타났고, 남성에 비해 연령과 기저질환의 개수에서 영향력이 큰 것으로 나타났다. 대사증후군을 예방하기 위해선 BMI, 식이, 질환의 이환, 초경 및 폐경여부를 고려하여 접근해야하며 후속 연구를 통해 다양한 중재 전략을 수립하고 검증해야 할 것이다.

• 한국물환경학회지
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• 제35권5호
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• pp.432-438
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• 2019

The purpose of this study is to predict Trophic Diatom Index (TDI) in tributaries of the Han River watershed using the random forest algorithm. The one year (2017) and supplied aquatic ecology health data were used. The data includes water quality(BOD, T-N, $NH_3-N$, T-P, $PO_4-P$, water temperature, DO, pH, conductivity, turbidity), hydraulic factors(water width, average water depth, average velocity of water), and TDI score. Seven factors including water temperature, BOD, T-N, $NH_3-N$, T-P, $PO_4-P$, and average water depth are selected by the Correlation Feature Selection. A TDI prediction model was generated by random forest using the seven factors. To evaluate this model, 2017 data set was used first. As a result of the evaluation, $R^2$, % Difference, NSE(Nash-Sutcliffe Efficiency), RMSE(Root Mean Square Error) and accuracy rate show that this model is compatible with predicting TDI. To be more concrete, $R^2$ is 0.93, % Difference is -0.37, NSE is 0.89, RMSE is 8.22 and accuracy rate is 70.4%. Also, additional evaluation using data set more than 17 times the measured point was performed. The results were similar when the 2017 data set were used. The Wilcoxon Signed Ranks Test shows there was no statistically significant difference between actual and predicted data for the 2017 data set. These results can specify the elements which probably affect aquatic ecology health. Also, these will provide direction relative to water quality management for a watershed that must be continuously preserved.

• 한국ITS학회 논문지
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• 제16권1호
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• pp.26-37
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• 2017

본 연구는 random effects Tobit 회귀모형을 이용하여 도심지 교차로에 대한 교통사고모형을 개발하여 교통사고와 요인간의 상관관계를 파악하는 것이 목적이다. Random effects Tobit 회귀모형의 적용성을 비교 분석하기 위하여 fixed effect Tobit 회귀모형을 산정하였다. 산정결과, 교통량, 제한속도, 차로수, 토지이용, 우회전차로, 전방신호등이 유효한 변수로 나타났으며, 총 교통사고율에 대한 random effects 모형의 모형 적합도(결정계수: 0.418, 로그-우도함수값: -3210.103, 우도비: 0.056)와 모형 설명력(MAD: 19.533, MAPE: 75.725, RMSE: 26.886)은 fixed effects 모형의 모형 적합도 (결정계수: 0.298, 로그-우도함수값: -3276.138, 우도비: 0.037)와 모형 설명력(MAD: 20.725, MAPE: 82.473, RMSE: 27.267)보다 우수한 것으로 나타났으며, 부상교통사고율에 대한 교통사고모형에서도 총 교통사고율의 산정결과와 동일하게 나타나 두 모형에서 random effects Tobit 회귀모형이 다소 우수한 것으로 분석되었다.

• Ocean Systems Engineering
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• 제6권2호
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• pp.191-201
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• 2016

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권3호
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• pp.197-204
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• 2002

DRAM, SRAM, and FLASH memory are three major memory devices currently used in most electronic applications. But, they have very distinct attributes, therefore, each memory could be used only for limited applications. MRAM (Magneto-resistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. To be a commercially competitive memory device, scalability is an important factor as well. This paper is testing the actual electrical parameters and the scaling factors to limit MRAM technology in the semiconductor based memory device by an actual integration of MRAM core cell. Electrical tuning of MOS/MTJ, and control of resistance are important factors for data sensing, and control of magnetic switching for data writing.

• Journal of the Korean Data and Information Science Society
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• 제18권2호
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• pp.471-479
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• 2007

This paper discusses about how to build up mixed-effects model for analysing ordinal response data by using cumulative logits. Random factors are assumed to be coming from the designed sampling scheme for choosing observational units. Since the observed responses of individuals are ordinal, a proportional odds model with two random effects is suggested. Estimation procedure for the unknown parameters in a suggested model is also discussed by an illustrated example.

• 말소리와 음성과학
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• 제16권2호
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• pp.1-9
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• 2024

This study investigates the fixed and random factors affecting response patterns of wh-scope interpretations in Gyeongsang Korean. It employed logistic mixed-effects regression models to analyze responses from 24 participants who listened to 40 pre-recorded stimuli from 40 different speakers. The stimuli consisted of an embedded wh-phrase and an interrogative ending marker, "-nkiko," thereby forming a wh-question, specifically a matrix wh-scope. Participants repeated the test three times. The study found that the prominence level of a prosodic phrase composed of an embedded verb and a complementizer was inversely related to responses with wh-questions, as demonstrated through multiple regression analysis in Yun. The test trial significantly impacted the number of responses with wh-questions, increasing from 50.3% in the first trial to 58.8% and 61.2% in subsequent trials. Examination of random subject effects revealed two main factors influencing responses: morpho-syntactic constraints and prosodic structural integrity. These two factors demonstrated the potential to be inversely weighted. Analysis of random stimulus effects suggested that the prominence level had limited effects on response patterns with each stimulus primarily eliciting one type of responses across trials.

• 대한통합의학회지
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• 제12권2호
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• pp.155-166
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• 2024

Purpose : This study aims to identify key factors for predicting dropout risk at the university level and to provide a foundation for policy development aimed at dropout prevention. This study explores the optimal machine learning algorithm by comparing the performance of various algorithms using data on college students' dropout risks. Methods : We collected data on factors influencing dropout risk and propensity were collected from N University. The collected data were applied to several machine learning algorithms, including random forest, decision tree, artificial neural network, logistic regression, support vector machine (SVM), k-nearest neighbor (k-NN) classification, and Naive Bayes. The performance of these models was compared and evaluated, with a focus on predictive validity and the identification of significant dropout factors through the information gain index of machine learning. Results : The binary logistic regression analysis showed that the year of the program, department, grades, and year of entry had a statistically significant effect on the dropout risk. The performance of each machine learning algorithm showed that random forest performed the best. The results showed that the relative importance of the predictor variables was highest for department, age, grade, and residence, in the order of whether or not they matched the school location. Conclusion : Machine learning-based prediction of dropout risk focuses on the early identification of students at risk. The types and causes of dropout crises vary significantly among students. It is important to identify the types and causes of dropout crises so that appropriate actions and support can be taken to remove risk factors and increase protective factors. The relative importance of the factors affecting dropout risk found in this study will help guide educational prescriptions for preventing college student dropout.

• 인간식물환경학회지
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• 제24권6호
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• pp.651-662
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• 2021

Background and objective: This study identifies whether children's planning-organizing executive function can be significantly classified and predicted by home environment quality and wealth factors. Methods: For empirical analysis, we used the data collected from the 10th Panel Study on Korean Children in 2017. Using machine learning tools such as support vector machine (SVM) and random forest (RF), we evaluated the accuracy of the model in which home environment factors classify and predict children's planning-organizing executive functions, and extract the relative importance of variables that determine these executive functions by income group. Results: First, SVM analysis shows that home environment quality and wealth factors show high accuracy in classification and prediction in all three groups. Second, RF analysis shows that estate had the highest predictive power in the high-income group, followed by income, asset, learning, reinforcement, and emotional environment. In the middle-income group, emotional environment showed the highest score, followed by estate, asset, reinforcement, and income. In the low-income group, estate showed the highest score, followed by income, asset, learning, reinforcement, and emotional environment. Conclusion: This study confirmed that home environment quality and wealth factors are significant factors in predicting children's planning-organizing executive functions.

• Journal of the Korean Data and Information Science Society
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• 제22권2호
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• pp.287-296
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• 2011

36명의 여대생을 대상으로 체 지방 감소효과에 대한 실험을 실시하였다. 이 실험에서 처리는 매일 섭취하는 식사종류 및 양에 대한 식사일지 작성과 카메라 폰으로 찍어 실험관리자에게 전송하여 매주상담을 받는 것이다. 실험관리자는 체 지방 및 관련된 자료를 일주일마다 측정하여 8주간의 반복측정자료를 얻었다. 이 실험자료를 이용하여 혼합모형의 일종인 변량계수모형을 이용하여 추정 및 유의성 검정을 실시한 결과, 유의한 고정인자들은 처리 전체지방 값, 비만지수, 확장기 혈압, 총 콜레스테롤 및 시간이다. 처리 후 시간에 따른 체 지방 감소는 2차 함수의 관계가 성립된다. 변량인자인 개체효과와 개체와 시간과의 교호작용에서 1차 함수의 관계가 존재한다. 처리 후 시간이 지남에 따라 체 지방 량은 점점 감소하였으며, 실험실시 8주 후에는 평균 2.1kg 감소한 효과가 있음을 보여주었다.