• 제목/요약/키워드: Longitudinal data analysis

검색결과 834건 처리시간 0.029초

유동방향의 열전도가 전열면의 성능에 미치는 영향 (Effects of longitudinal conduction on the performance of heat transfer surfaces)

  • 박병규;홍택;박상희
    • 설비공학논문집
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    • 제11권5호
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    • pp.561-569
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    • 1999
  • The effects of longitudinal heat conduction on the performance of heat transfer surfaces are investigated by using a single-blow method. In the transient testing method for determining the heat transfer characteristics, exponential inlet temperature variations are made by using screen-mesh heater with small time constant and low frontal velocities of the test section, and the experimentally determined inlet temperature profile is used as the inlet fluid temperature condition. The effects of longitudinal heat conduction are negligible only if $\gamma^\act<0.05\;and \;N_{tu}\le3$ and should be considered if $N_{tu}\le3$ The test results ate compared with the existing theoretical and experimental data and the validity of this technique is confirmed by the good agreement.

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Deconstructing Opinion Survey: A Case Study

  • Alanazi, Entesar
    • International Journal of Computer Science & Network Security
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    • 제21권4호
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    • pp.52-58
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    • 2021
  • Questionnaires and surveys are increasingly being used to collect information from participants of empirical software engineering studies. Usually, such data is analyzed using statistical methods to show an overall picture of participants' agreement or disagreement. In general, the whole survey population is considered as one group with some methods to extract varieties. Sometimes, there are different opinions in the same group, but they are not well discovered. In some cases of the analysis, the population may be divided into subgroups according to some data. The opinions of different segments of the population may be the same. Even though the existing approach can capture the general trends, there is a risk that the opinions of different sub-groups are lost. The problem becomes more complex in longitudinal studies where minority opinions might fade over time. Longitudinal survey data may include several interesting patterns that can be extracted using a clustering process. It can discover new information and give attention to different opinions. We suggest using a data mining approach to finding the diversity among the different groups in longitudinal studies. Our study shows that diversity can be revealed and tracked over time using the clustering approach, and the minorities have an opportunity to be heard.

청소년패널자료 분석에서의 반복측정분산분석을 활용한 잠재성장모형 (Analysis of latent growth model using repeated measures ANOVA in the data from KYPS)

  • 이화정;강석복
    • Journal of the Korean Data and Information Science Society
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    • 제24권6호
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    • pp.1409-1419
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    • 2013
  • 최근 종단자료 분석방법으로 많이 연구되는 잠재성장모형으로 청소년 패널자료를 분석하였다. 본 연구에서 잠재성장모형 분석에서 비조건적 모형을 좀 더 빠르게 찾기 위해 비조건적 모형에 반복측정 분산분석의 결과를 활용하였다. 또한, 비조건적 모형을 결정하기 위해 기존에 주로 사용된 6개 유형, 2차모형과 반복측정분산분석의 결과를 적용한 모형들을 비교하였다.

청소년의 휴대전화의존도, 우울의 변화 궤적 및 자기조절학습 능력 간의 구조적 관계 (The structural relationships among adolescents'mobile phone dependency, trajectories of depression, and self-regulated learning abilities)

  • 홍예지
    • Human Ecology Research
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    • 제59권3호
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    • pp.341-351
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    • 2021
  • The purpose of this study was to examine the longitudinal relationships between Korean adolescents'mobile phone dependency, trajectories of depression, and self-regulated learning abilities. To achieve these goals, structural equation modeling analysis was conducted, using the 3rd, 5th and 7th wave of the data on 4th graders taken from the Korean Children and Youth Panel Survey. The results can be summarized as follows. First, growth-curve longitudinal analysis indicates that depression in 6th through 10th grade has increased. Second, mobile phone dependency among adolescents at 6th grade has a significant effect on both the initial value and the rate of change in depression. Also, the initial value and the rate of change in depression have significant relationships with mobile phone dependency at 10th grade. Moreover, both increased levels of mobile phone dependency and the rate of change in depression significantly influence adolescents'self-regulated learning abilities at 10th grade. Based on a longitudinal data set, these findings demonstrate the causal relationships between Korean adolescents'trajectories of depression and their mobile phone dependency. The findings also provide a comprehensive framework with implications for adolescents'development through an understanding of the relationships between adolescents'depression and mobile phone dependency, which impact their self-regulated learning abilities.

Semiparametric Kernel Poisson Regression for Longitudinal Count Data

  • Hwang, Chang-Ha;Shim, Joo-Yong
    • Communications for Statistical Applications and Methods
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    • 제15권6호
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    • pp.1003-1011
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    • 2008
  • Mixed-effect Poisson regression models are widely used for analysis of correlated count data such as those found in longitudinal studies. In this paper, we consider kernel extensions with semiparametric fixed effects and parametric random effects. The estimation is through the penalized likelihood method based on kernel trick and our focus is on the efficient computation and the effective hyperparameter selection. For the selection of hyperparameters, cross-validation techniques are employed. Examples illustrating usage and features of the proposed method are provided.

Longitudinal Cut 파형해석의 응용을 위한 특성연구 (Study on th Wave-Pattern Analysis by Longitudinal Cut Method)

  • 강신형;이영길
    • 대한조선학회지
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    • 제18권1호
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    • pp.9-18
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    • 1981
  • The wave-pattern analysis has been one of important research tools in the towing tank, and applied for hull form design. The longitudinal-cut method of Newman and Sharma is adopted in KRIS deep towing tank. Instrumentations and data acquisition systems are developed for that. Local effects and truncation effects are estimated by using calculated wave patterns of simple source distributions. Wigley model of 2m is used to check the accuracy of the whole system. Cut positions and truncation points are changed to investigate characteristics of the wave-pattern analysis. Coefficients of wave-pattern resistance are low-estimated in comparison with those of Maruo and Ikehata. The general quality of the system is very good, but some more efforts to increase the accuracy are required. Two full-form models(one basic form, the other with bulbous bow) are tested to show high application-possibilities of the wave-pattern analysis for the hull form design.

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여성의 이혼선택 요인에 관한 종단 연구: 생존분석을 중심으로 (Longitudinal Study on the Major Factors Affecting Divorce Choices among Women: Focused on Survival Analysis)

  • 박수선;박태영
    • 가족자원경영과 정책
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    • 제26권3호
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    • pp.65-85
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    • 2022
  • 본 연구는 결혼생활에서 시간경과에 따라 여성이 이혼을 선택하게 만드는 영향 요인을 파악하여, 여성의 결혼과 이혼양상을 가족전환의 관점으로 이해하고 두 집단 모두 의미 있는 선택이 될 수 있도록 실천에 기반한 생활복지 차원의 성장에 기여하는데 목적이 있다. 이를 위해 본 연구는 여성가족패널 자료를 사용하여 생존분석 방법을 이용한 종단 연구를 시행하였다. 여성의 결혼생활에서 각 요인들이 이혼 선택에 어떤 영향을 미치는지 콕스회귀분석을 실시하여 세 가지 분석모형을 통해 파악한 결과 모든 모형이 분석에 적합한 것으로 나타났다.

미국 청소년의 비만에 관한 종단적 분석 (Longitudinal Data Analysis for School-aged Adolescents' Obesity Rates across the States)

  • 김태응;김종호;황선환
    • 한국콘텐츠학회논문지
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    • 제16권8호
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    • pp.743-755
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    • 2016
  • 이 연구의 목적은 미국 취학 아동-청소년의 BMI 변화율이 어떻게 달라지고 있는지, 그리고 청소년 발달 상태에 따른 비만을 유발하는 해로운 행동들이 청소년들의 비만 현상에 어떻게 영향을 미치는지 종단적으로 밝히는데 있다. 1999-2011 미국 청소년 위험 행동 조사 데이터를 사용하였으며, 총 연구 대상은 260,293명이다(9-12학년). 미국 취학 청소년들의 비만율에 미치는 종단적 시간의 효과를 검증하기 위해 인구통계학적 특성, 영양 및 신체활동 관련 행위들을 공변량으로 통제한 최소자승법 회귀분석과 위계적 선형 모델링이 활용되었다. 취학 청소년들의 BMI 퍼센티지는 시간과 유의미한 관련이 있는 것으로 나타났으며 특히 종단적 시간은 아이들의 BMI 퍼센티지에 상당히 긍정적인 효과가 있는 것으로 나타났다. 따라서 지난 10년 동안의 미국 아동 비만을 줄이기 위한 신체 활동 및 영양 정책은 미국 아동들의 비만 유지 및 감소를 위한 매우 효과적인 정책이었으며, 향후 청소년의 비만 요인 감소와 장애요소를 극복을 위한 정책을 강화하는데 더욱 많은 관심을 기울여야 할 것이다.

유아-교사 관계의 잠재프로파일 집단이 유아의 또래 상호작용에 미치는 영향에 관한 종단 연구 (Longitudinal Study of Child-Teacher Relationship and Peer Interactions Based on Latent Profile Analysis)

  • 이예진;신유림
    • Human Ecology Research
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    • 제54권3호
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    • pp.321-332
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    • 2016
  • This study clarified the maintenance of relationship between children and teachers based on longitudinal data and explored the latent classes. It clarified the latent classes connection with the children's peer play interaction. The subjects of this study were 194 children (aged 3) who attended 11 different kindergartens and daycare centers. We collected data three times (once every 6 months) until they reached age 4. The results of this study were: first, closeness, conflict, and dependence of child-teacher relationship that showed a continuous short-term connection. Second, we classified the child-teacher relationship into three groups according to longitudinal data. Those groups were, 'low level maintenance group' which had the lowest conflict and dependence compared to the highest closeness with teacher, 'middle level maintenance group' which had the teacher relationship in the middle level of the sub element area, and 'high level maintenance group' which showed high conflict and dependence compared to low closeness with the teacher. Third, the group which maintains a longitudinal high conflict.dependence showed more interruption and disruption behavior than the group which maintained a low conflict and dependence. In conclusion, the child-teacher relationship seemed to be the steady characteristic because it showed the early formation of a stable relationship. It was possible to predict the child's peer interaction through an early child-teacher relationship. Teachers need to be educated by the kindergarten and daily care center because the early formation of a child-teacher relationship can be the foundation of child's later peer and teacher relationships.

실험적 연구를 통한 비정형롤판재성형 예측 모델 개발 (Development of Prediction Model for Flexibly-reconfigurable Roll Forming based on Experimental Study)

  • 박지우;길민규;윤준석;강범수;이경훈
    • 소성∙가공
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    • 제26권6호
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    • pp.341-347
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    • 2017
  • Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.