• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.119-127
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• 2008

The flow characteristics and the aspects of riverbed changes were analyzed for the upstream and downstream sections of Gongju Bridge. The upstream and downstream had complex topography, and the sections had the confluence of tributaries and several structures. In order to simulate the flow characteristics of the target sections, 1D HEC-RAS and 2D RMA2 were applied. As a result, the longitudinal water level of the target sections matched the results of simulated 1D and 2D samples. Also, 2D SED2D were applied to predict riverbed changes. As a result of the simulation, quantitative analysis was able to be performed for longitudinal riverbed changes from the sections of sudden change, bridges, the confluence of tributaries, and bends. Also, the distribution of riverbed changes on the main sections was in close relation to flow velocity. As a result of evaluating the sensitivity of SED2D, the concentration of suspended sediment, the thickness of sand beds, and the size of sand grains affected riverbed changes sensitively. These results will be used to apply the models of riverbed changes in the future.

• The Journal of the Korean dental association
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• v.13 no.3
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• pp.221-229
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• 1975

• The Journal of the Korean dental association
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• v.14 no.4
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• pp.367-376
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• 1976

• Journal of Rheumatic Diseases
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• v.26 no.4
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• pp.219-220
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• 2019

• Journal of the Korea Convergence Society
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• v.10 no.2
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• pp.217-225
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• 2019

The Latent Growth Modeling(LGM) is known as the typical analysis method of longitudinal data and it could be classified into unconditional model and conditional model. It is common to assume that the growth trajectory of unconditional model of LGM is linear. In the case of quasi-linear, the methodology for improving the model fitness using Sequential Pattern of Association Rule Mining is suggested. To do this, we divide longitudinal data into quintiles and extract periodic changes of the longitudinal data in each quintiles and make sequential pattern based on this periodic changes. To evaluate the effectiveness, the LGM module in SPSS AMOS was used and the dataset of the Youth Panel from 2001 to 2006 of Korea Employment Information Service. Our methodology was able to increase the fitness of the model compared to the simple linear growth trajectory.

• Journal of Preventive Medicine and Public Health
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• v.57 no.5
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• pp.443-450
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• 2024

Objectives: Lack of physical activity has a critical effect on the physical and mental health of adolescents. This study examined the influence of family adversities on the longitudinal changes in physical inactivity among adolescents during the coronavirus disease 2019 (COVID-19) pandemic. Methods: The study used multi-wave data from the Korean Children and Youth Panel Survey, including 2590 Korean adolescents aged 12-14 years. The longitudinal trajectory of physical inactivity among adolescents and the effects of related factors were estimated using a latent growth modeling method. Results: Our results revealed a significant increase in physical inactivity among adolescents over time. At the onset of the pandemic, approximately one-seventh of Korean middle schoolers reported a lack of physical activity. However, 3 years later, during the quarantine, nearly one-fifth of these adolescents reported a significant increase in their physical inactivity. Initially, low level parental education was predictive of adolescents' physical inactivity, but this effect diminished over time, becoming statistically insignificant by the end of the 3-year period. Moreover, the increase in physical inactivity over the 3 years was significantly influenced by parental rejection. Conclusions: These findings suggest that adolescents who experience parental rejection are more likely to report an increase in sedentary behaviors in contexts such as the COVID-19 pandemic.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.52-56
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• 2004

Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircraft by inputted program in advance or artificial intelligence. In this study Aileron and Elevator are used to control the movement of airplane for horizontal and vertical flights about its longitudinal and lateral axis. In an introduction, the drone was linearly modeled by extracting aerodynamic parameter through flight test and simulation, lift and drag coefficient corresponding to angle of attack, changes of pitching moment coefficient. In the main subject, the flight simulation was performed after constructing hardware using TMS320F2812 from TI company and PID with lateral and longitudinal controller for horizontal and vertical flights. Flying characteristics of two system were estimated and compared through real flight test with hardware equipped algorithm and adaptive algorithm that was applied to consider external factors such as turbulence. In conclusion the control performance of the controller with proposed algorithm was streamlined at lateral and longitudinal controller respectively, we will discuss guidance command to pass way point.

• Survey Research
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• v.18 no.4
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• pp.25-59
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• 2017

The current study investigated how elderly husbands and wives' marital satisfaction and depression change over time and examined how changes in marital satisfaction account for changes in depression between and within the dyads. The longitudinal dyadic data from the first wave(2006) to the fifth wave(2014) of the Korean Longitudinal Study of Aging(KLoSA), collected by the Korea Employment Information Service, were used for the analyses. Because husbands and wives are interdependent within couples, we applied statistical models for dyadic data. The dyadic growth model(DGM) was used to model the trajectories of marital satisfaction and depressive symptoms. In order to analyze the association of these growth factors, we proposed the dyadic growth actor-partner interdependence model(DG-APIM) and applied the model to the data. The results showed that on average the husbands' marital satisfaction was higher but decreased faster over the course of the study than the wives'. It also showed that the average depression of the husbands was lower than that of the wives but the husbands' depression increased faster than the wives' over the course of the study. The variance of the averages of husbands' (wives's) depression was accounted for by that of wives'(husbands') marital satisfaction, showing a partner effect. The variance of the slopes of husbands'(wives') depression was accounted for by that of marital satisfaction of themselves, showing an actor effect. The results showed that there is a longitudinal interdependence between husbands and wives' marital satisfaction and depression and supported the marital discord model of depression.

• Journal of Internet Computing and Services
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• v.13 no.2
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• pp.127-136
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• 2012

IT industry is rapidly changing technologies and trends are leading the field. Website also typical of these areas in the field of IT as a sector, technological advances faster, depending on the nature of the IT industry and the emergence of new services, changes in a variety of platforms, and is rapidly rising. In addition, a website containing information in accordance with the social situation changes and exposure of the agenda and vary greatly. Therefore, these changes in terms of B2C websites that can make a difference in the reliability factor looks. From this perspective, in this study to compare data before and after 10 years on the reliability factor by conducting longitudinal studies, most are not addressed in previous studies due to time differences website users to change the reliability of the analyzed factors.

• Journal of Science Education
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• v.38 no.1
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• pp.57-77
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• 2014

A longitudinal study traced changes in students' understanding of Nature Of science (NOS) through the public secondary science education in Ontario Canada. Although the concepts of NOS are complicated, and students' understandings are not easy to change, not many longitudinal studies have been done across the world. The current study tried to identify the changes of participating students' understandings of NOS for two and half years of public secondary science education in Ontario Canada. Pretest was administered using Views of Nature of Science (VNOS-C) when six participants graduated from a middle school of Toronto. Two and half years of secondary education, the posttest was carried out using the same instrument. After pre and posttest, probing interviews were performed. The analysis of the data was founded on the Standards and the conceptual framework for this study. The findings were that the initial views have little changed. Most examples and explanations the participants provided were from their science classes. Lab activities for confirming the existing laws and theories and observable photos in science textbooks made students regard the knowledge as a truth. Naturally, their knowledge has been expanded for 2 and 1/2 years, but this expansion of scientific knowledge led students toward Universalist views on science. On the other hand, when science was presented with a historical approach or was networked with other concepts, students acknowledged science and scientific knowledge had been induced from inferences as well as observations and experimental results. Based on the findings the authors of this research suggest that educating the knowledge of science should be historical and networked approaches rather than teaching the knowledge as concise and true statements of the nature.