• Structural Engineering and Mechanics
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• v.52 no.5
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• pp.857-873
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• 2014

Structural behaviors of a sustainable hybrid column with the ultra high performance cementitious composites (UHPCC) permanent form under compression and flexure were studied. Critical state and failure stage characters are analyzed for large and small eccentricity cases. A simplified theoretical model is proposed for engineering designs and unified formulas for loading capacity of the hybrid column under compression and flexure loads are derived, including axial force and moment. Non-linear numerical analysis is carried out to verify the theoretical predictions. The theoretical predictions agree well with the numerical results which are verified by the short hybrid column tests recursively. Compared with the traditional reinforced concrete (RC) column, the loading capacity of the sustainable hybrid column is improved significantly due to UHPCC confinements.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.583-598
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• 2022

The Compaction effect is important for evaluating the subgrade construction. However, there is little research exploring the compaction quality of deep soil using hydraulic compaction. According to reinforcement effect analysis, dimensional analysis is adopted in this work to analyze subgrade compactness within the effective reinforcement depth, and a prediction model is obtained. A hydraulic compactor is then employed to carry out an in-situ reinforcement test on gravel soil subgrade, and the subgrade parameters before and after reinforcement are analyzed. Results show that a reinforcement difference exists inside the subgrade, and the effective reinforcement depth is defined as increasing compactness to 90% in the depth direction. Layered compactness within the effective reinforcement depth is expressed by parameters including the drop distance of the rammer, peak acceleration, tamping times, subgrade settlement, and properties of rammer and filler. Finally, a field test is conducted to verify the results.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.161-167
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• 2010

In this study, we implemented an experimental approach of ecological model development in order to emphasize the importance of input variable selection with respect to time-delayed arrangement between input and output variables. Time-series modeling requires relevant input variable selection for the prediction of a specific output variable (e.g. density of a species). Inadequate variable utility for input often causes increase of model construction time and low efficiency of developed model when applied to real world representation. Therefore, for future prediction, researchers have to decide number of time-delay (e.g. months, weeks or days; t-n) to predict a certain phenomenon at current time t. We prepared a total of 3,900 equation models produced by Time-Series Optimized Genetic Programming (TSOGP) algorithm, for the prediction of monthly averaged density of a potamic phytoplankton species Stephanodiscus hantzschii, considering future prediction from 0- (no future prediction) to 12-months ahead (interval by 1 month; 300 equations per each month-delay). From the investigation of model structure, input variable selectivity was obviously affected by the time-delay arrangement, and the model predictability was related with the type of input variables. From the results, we can conclude that, although Machine Learning (ML) algorithms which have popularly been used in Ecological Informatics (EI) provide high performance in future prediction of ecological entities, the efficiency of models would be lowered unless relevant input variables are selectively used.

• Journal of The Korean Association of Information Education
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• v.18 no.2
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• pp.345-356
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• 2014

Modern internet service is characterized as opening, sharing and participation based on Web2.0 so that users might actively participate in the internet environment. In this study, we suggested an instructional model based on precedent model of robot programming to promote positive interaction in Web2.0 environment. First, we figured out implications of precedent research through review the environmental features of Web2.0 and educational tools, robot programming learning model. Also, we suggest an instructional model using Web2.0 tools(cyworld, prezi, Mindmeister) for promoting interaction and applied it to learners. As a result, we have acquired positive results of robot programming education using Web2.0 tools. Most participants were evaluated that Web2.0 tool would be helpful to the overall robot programming course.

• Korean Journal of Community Nutrition
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• v.20 no.1
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• pp.1-10
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• 2015

Objectives: This study was conducted to develop and validate Eating Behaviors Test form (EBT) for infants and young children, including eating behaviors of their parents and parental feeding practices. Methods: Draft version of EBT form was developed after a pretest on 83 mothers. It was consisted of 42 questions including 3 components; eating behavior of children, eating behavior of parents, and parental feeding practices. Using these questionnaires, the first survey was conducted on 320 infants and children, 1 to 6 year old, for exploratory factor analysis, and the second survey was collected on 731 infants and children for confirmatory factor analysis. Results: Exploratory factor analysis on 42 questions of EBT form resulted in 3 factor model for children's eating behavior, 3 factor model for parents' eating behavior, and 1 factor model for parental feeding practices. Three factors for children's eating behavior could be explained as follows; factor 1, pickiness (reliability ${\alpha}=0.89$; explanation of variance=27.79), factor 2, over activity (${\alpha}=0.80$, explanation of variance=16.51), and factor 3, irregularity (${\alpha}=0.59$, explanation of variance=10.01). Three factors for mother's eating behavior could be explained as follows; factor 1,irregularities (${\alpha}=0.73$, explanation of variance=21.73), factor 2, pickiness (${\alpha}=0.65$, explanation of variance= 20.16), and factor 3, permissiveness (${\alpha}=0.60$, explanation of variance=19.13). Confirmatory factor analysis confirmed an acceptance fit for these models. Internal consistencies for these factors were above 0.6. Conclusions: Our results indicated that EBT form is a valid tool to measure comprehensive eating and feeding behaviors for infants and young children.

• Journal of Korean Association for Spatial Structures
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• v.16 no.1
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• pp.53-64
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• 2016

Solar power is being spotlighted recently as a new energy source due to environmental problems and applications of solar power to curved structures are increasing. Solar panels installed on curved surfaces have different efficiencies depending on its position and the efficient positioning of solar panels plays a critical role in the design of solar power generation systems. In this study, the changing characteristics of solar irradiance were analyzed for hemispherical dome with a large curvature and the positioning of solar panels that can efficiently utilize solar energy was investigated. With an icosahedron-based hemispherical dome consisting of triangular elements as target model, a program for calculating solar irradiance using a normal vector of the solar module on each face was developed. Furthermore, the change of solar irradiance according to the sun's path was analyzed by time and season, and its effects on shades were also examined. From the analysis results, the effective positioning could be determined on the basis of the efficiency of the solar panels installed on the dome surfaces on solar irradiance.

• The Journal of Korean Society for School & Community Health Education
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• v.18 no.2
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• pp.1-25
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• 2017

Objectives: There is higher rates of experience of suicide ideation and suicide attempt of adolescents in the Lima and Callao region compared with the results of the epidemiological study (2013) conducted by Peru National Institute of Mental Health and the Global School-based Student Health Survey (2010) which is was conducted among adolescents across all regions of Peru. Based on the PRECEDE model, this study analyzed the prevalence and the factor associated with the suicide attempt among the adolescent in a poor urban area in Peru. Methods: A stratified random sampling was used for the survey to select study participants from the 6 secondary schools based in Comas or Callao. The survey was conducted November 25th and December 4th in 2015 and a total of 738 individuals included in the analysis. In order to analyze factors influencing suicide attempt, comparison of predisposing factor, reinforcing factor, enabling factor, behavioral factor, environmental factor, psychological factors by suicide attempt and suicide risk group were identified through the chi-square test and hierarchical logistic regression. Results: Results showed that those who reported having less parental understanding, less time spent with parents, and 'almost none/none' for parental affection had more experience of suicide attempt and were more likely to sort into the high suicide risk group. Also, a greater proportion of those with the experience of suicide attempt had more experience of smoking and alcohol consumption, and experience of physical abuse and feeling insulted and depression in comparison to that of those without experience of suicide attempt. Variables that had a significant effect on suicide attempt included depression, subjective happiness, smoking experience, sexual intercourse, involvement in fight, parental affection, and gender (male). Conclusions: The results of the current study can serve as grounds for the necessity of acknowledging that adolescent suicide does not simply depend on a couple of factors, but arises from situations in which individual, home, school, social factors influence one another, and therefore adolescent suicide should be prevented and addressed through a multi-dimensional and integrated approach.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.8
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• pp.465-473
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• 2021

This study is the application of a choice experiment to assess Mekong Delta urban households' preferences and motivations for ecosystem conservation in the U Minh forest. The study applied a choice modeling approach to estimate the economic values of the proposed ecosystem conservation program in the U Minh forest by accessing urban consumer preferences and their willingness to pay for the project. Discrete choice experimental data was collected from 450 residents in the cities of the Vietnamese Mekong Delta. The multinomial logit model was employed to identify consumer's stated preferences for the environmental and sustainability attributes of the conservation project. The results showed that Mekong Delta urban residents paid much attention to the proposed project to protect and develop the U Minh forest. In addition, the results showed that higher education, income, and knowledge of the U Minh forest revealed a higher likelihood of selecting the project, while the older residents would select the status quo more than the younger ones. The study also proved that the effect of participation had a strong impact on the willingness to pay for the project. The findings could be useful for policymakers to take action to raise resident's awareness and willingness to pay for the U Minh forest project.

• Journal of the Economic Geographical Society of Korea
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• v.12 no.4
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• pp.627-644
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• 2009

In the knowledge-based economy highlighting the importance of human capital, there has been a growing interest in human capital externalities as a fundamental engine of growth and development of a region. The purpose of this study is to analyze human capital externalities using 3-level hierarchical linear model(3-HLM), decomposing determinants of wages into three levels involving workers(level-1) nested within firms(level-2) nested within regions(level-3). This study separately estimates the effect of the average education level on the wages by three different schooling groups on the assumption that the intensity of knowledge spillovers varies with each group's schooling level. The main results are as follows; First, the coefficient of the average education level of a region shows 0.044, indicating that one-year increase in the average level of schooling could increase average individual earnings by 4.4%. Secondly, the external effects of human capital on three different schooling groups are considerably different, raising less than high school graduates' wages by 3.0%, college graduates' wages by 4.7%, and graduate schools' wages by 11.8%, respectively. Thirdly, well educated workers are much more sensitive to the variation of the regional education level than less educated ones when we apply the shares of each schooling group as alternative measures for the average level of education. Such findings of this study draw an implication that local governments could speed up regional economic growth in the knowledge-based economy by not only raising total human capital stock in a region but building the close networks that promote productivity-enhancing human capital external effects.

• Journal of Korean Elementary Science Education
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• v.43 no.1
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• pp.108-121
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• 2024

In this study, we developed a sustainability education program employing a project-based learning strategy for prospective teachers and investigated its effectiveness. A total of 23 senior students from a university of education participated in the study. The investigation involved a pretest on their pro-environmental behavior and attitudes, followed by a five-week implementation of the program, during which students individually engaged in energy-saving projects. Following the program, a post-test, which used the same questionnaire as the pretest, was administered. In addition, we conducted individual interviews with nine students who actively engaged in the projects. We analyzed the interview contents, portfolios, and reports; identified sub-concepts related to the program's effectiveness and its causes; and then organized them into subcategories. Then, we extracted recurring relationships among the subcategories to formulate a tentative explanatory model. The results indicate that the program positively impacted students' pro-environmental behavior and values/attitudes. Notably, the students' "sense of achievement gained through success" emerged as a significant factor influencing their pro-environmental behavior. Furthermore, some causes were found to indirectly affect pro-environmental behavior through pro-environmental values and attitudes.