• Journal of Biosystems Engineering
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• v.4 no.1
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• pp.24-34
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• 1979

현재 실용테라스 (Terrace) 축조비용의 추정은 단위 테라스장이나 이동토양의 단가에 근거하고 있다. 그런, 근래 l국의 옥수수 지대 (corn belt)에서 널리 이용되고 있는 평행형 테라스의 경우 각 지점마다 성토 및 절토양이 다르기 때문에 이들 방법은 적합하지 않다. 이들 테라스의 경우 테라스장을 따라 토양의 이동이 불가피하므로 차륜형 자적식 스크레이퍼(scraper)가 테라스 축조에 널리 사용되고 있다. 본연구의 목적은 테라스 축조기계의 운행거리에 근거하여 테라스 축조시의 토공비용을 추정하기 위한 새로운 방법을 개발하는데 있었다. 테라스 축조시 토공작업은 전적으로 스크레이퍼에 의해서 , 그리고 테라스 경호장의 마무리 작업은 모트그레이터 (motor grader )에 의하여 수행되는 것을 가정하였다. 이들 기계의 세부적인 수행동작은 테라스 각지점에서의 절토와 성토량 및 이들 토양의 처리를 디지털 컴퓨터(digital computer)를 이용하므로서 계산할 수 있었다. 또한 테라스 축조에 소요되는 토양은 전적으로 테라스 수로부문에서 절취하는 것으로 가정하였다. (즉, 테라스 전장의 총절토양 과 총성토양은 같음) 연구결과 다음과 같은 결론을 얻었다. 1. 성토 및 절토양이 균형된 테라스에 있어서는 스크레이퍼의 운행거리에 근거하여 토공비용을 추정할 수 있는 방법의 개발이 가능하다. 2. 스크레이퍼의 수행구간, 회수 및 토공비용을 결정하기 위해서는 컴퓨터 방법을 이용하는 것이 필요하다. 3. 새로운 컴퓨터 모델은 예시의 테라스에 적용한 결과 테라스 토공비용을 추정하는 데 적합함을 보여주었다. 4. 이 방법은 테라스 축조에 있어서 효율적인 스크레이퍼의 적용에 지침이 될 수 있다.

• School Mathematics
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• v.11 no.4
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• pp.607-623
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• 2009

This study aims to investigate a child's informal knowledge of carrying and borrowing in additive calculations. The additive word problems including three types of calculations are posed a child that is the first grader and has no lessons about carrying and borrowing. By analysing his answers, his informal knowledge, that is his methods and strategies for calculating the additive problems are revealed. As a result, conceptual aspects and procedural aspects of his informal knowledge are recognized, and the didactical implications are induced for connecting his informal knowledge and the formal knowledge about carrying and borrowing.

• The Mathematical Education
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• v.54 no.4
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• pp.299-315
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• 2015

The aim of this qualitative case study is twofold: 1) to analyze how an eleventh-grader, Min-Seon, conceive and represent a pattern of change between two varying quantities in a quadratic functional situation, and 2) further to help her form a concept of 'derivative' as a tool to express the relationship with employing a concept of 'rate of change.' The result indicates that Min-Seon was able to construct graphs of piecewise functions that take average rates of change as range of the functions, and managed to conjecture the derivative of a quadratic function, $y=x^2$. In conclusion, we argue that covariational approach could not only facilitate students' construction of an initial function concept, but also support their understanding of the concept of 'derivative.'

• The Mathematical Education
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• v.52 no.2
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• pp.149-161
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• 2013

This study was to focus on analyzing about the composition of storytelling in the first graders' math textbooks of the middle school, which were recently implemented. The textbooks published by three well known publishing companies were chosen and three graduate students had scored the frequency of the problems according to three types of storytelling. As the results, in areas of mathematics, Number & Operation(44.23%), Letters & Formula(44.53%), Function(46.53%), Probability(41.67%), Geometry(46.23%) showed to have storytelling in balance. The type of 'explosion of mathematical history(EMH)' was shown in geometry most, the type of 'connection to daily life(CDL)' in statistics most, and the type of integration of disciplines(ID)' in geometry most in 5 math areas. Among three types of storytelling, the type of EMH was shown fewer that other 2 types. If we develop more problems in this type, students would study mathematics in-depth according to Freudenthal's principle of historical reinvention.

• School Mathematics
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• v.9 no.3
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• pp.427-445
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• 2007

This study presents the results of a case study that investigated a seventh grader's fractional reasoning related to multiplicative reasoning. In addition, by employing domain analysis and taxonomic analysis for analyzing qualitative data, I show how a qualitative methodology was used for the data collected by teaching experiment methodology. The study identifies three distinct issues that emerged as the student engaged in solving fraction problems: a view of fractions as operations vs. results, the issue of units, and mixed numbers vs. improper fractions. These three issues have instructional implications in that each of them is critical in developing multiplicative reasoning and investigating how they relate to each other suggests a way to improve multiplicative reasoning in fractional contexts.

• The Mathematical Education
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• v.50 no.2
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• pp.185-212
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• 2011

The purpose of this study is to analyze whether spreadsheet-used instruction can improve statistical thinking ability and attitude and also to identify what characteristics of statistical thinking is constructed. For this study, a subject of 2 classes were randomly selected among the 12 classes of the 11th grader in D high school and designated one class as the experimental group and the other class as the control group. Eight hours of the spread sheet-used instruction and the traditional textbook-oriented instruction had been carried out in each class. The research findings are as follows. First, the spread sheet-used instruction is shown to be more effective in enhancing statistical thinking than the traditional textbook-oriented instruction. Second, the spread sheet-used instruction is shown to be more effective in improving statistical attitude than the traditional textbook-oriented instruction. Third, students have shown the various characteristics of statistical thinking in the data descriptive process, data arrange-summary process, data representing process, and data analying process through the spread sheet-used instructions. Hence, the spread sheet-used instruction is recommended in teaching statistics.

• Korean Journal of Community Nutrition
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• v.9 no.2
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• pp.135-141
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• 2004

Although many studies have focused on dietary habits and behaviors among children, few have looked at individual dietary behaviors and food preferences and their relationships with personality traits. This study examined the relationships between children's dietary behaviors, food preferences and personality traits using a random sample of 236 sixth graders in Chuncheon. Results showed a high prevalence of undesirable dietary behaviors among children: 42.8% of the children had skipped breakfast at least twice a week, 53% had overeaten, 45.8% had eaten irregularly, and 66.5% had eaten an unbalanced meal. These undesirable dietary behaviors were negatively associated with such personality traits as sociability, responsibility, emotional stability, activity, and superiority. When asked about food preference, fruits were most popular while vegetables were least desirable. Total food preference scores were positively correlated with emotional stability (r=.204), activeness (r=.247), sociability (r=.156), responsibility (r=.249), and superiority (r=.133). Preference for meats had negative correlations with responsibility (r=-.133), sociability (r=-.146), and superiority (r=-.132), while preference for vegetables was positively correlated with these personality traits (r=.292, .244, and .230, respectively). In conclusion, the more desirable dietary behaviors and the higher total food preference scores, the more positive the child's personality traits. In addition, preference for vegetables was associated with positive personality traits. The findings suggest the need for continuous attention and guidance on desirable dietary habits for school children both at home and at school.

• Journal of Korean Elementary Science Education
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• v.38 no.4
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• pp.510-521
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• 2019

This study investigated the effect of career education using female scientists role models on science-related attitude, science career awareness, gender stereotype of science-related career, and image of scientists. Interaction effect with students' gender were also investigated. The subjects of this study were 70 $5^{th}$ grader. The experimental group was introduced career education using female scientists role models with 7 cases of female scientists in the form of 10 minutes movies or cartoons, while the comparison group performed reading science books. The results showed that science-related attitudes and science career awareness of experimental group were significantly higher than control group, not only for girls but has for boys. Gender stereotype of science-related career has changed more neutrally in experimental group. After the career education using female scientists role models, more female scientists were presented in students' image of scientist in DAST. This results showed positive effects of the career education using female scientists role models and educational implications were discussed.

• Korean Journal of Childcare and Education
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• v.17 no.5
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• pp.43-61
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• 2021

Objective: This study aimed to examine the sequential mediating effects of children's perceived maternal acceptance and peer acceptance in the relationship between maternal warmth and first grade children's school adjustment. Methods: Participants in this study were 979 seven-year-old children(498 boys, 481 girls) recruited for the Korea Child Panel Study. Data were analyzed by analyzing descriptive statistics, correlations, and significance of serial mediation pathways using SPSS 18.0 and PROCESS Macro 3.4. Results: Maternal warmth at age five effected perception of maternal acceptance at age six. Perceived maternal acceptance at age six effected perceived peer acceptance at age six. Perceived peer acceptance at age six effected school adjustment at age seven. Lastly, perceived maternal acceptance and peer acceptance at age six had a serial mediation effect between maternal warmth at age five and school adjustment at age seven. Conclusion/Implications: Perceived social acceptance during preschool years should be emphasized in order to promote school adjustment for first grade children. Parent education for promoting better parent child relationships should be considered and teachers should encourage peer play interaction to help children perceive acceptance from their peers.

• Journal of Preventive Medicine and Public Health
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• v.56 no.1
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• pp.59-66
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• 2023

Objectives: The aim of this study was to evaluate the effect of body weight status and sleep duration on the discrete-time hazard of menarche in Korean schoolgirls using multiple-point prospective panel data. Methods: The study included 914 girls in the 2010 Korean Children and Youth Panel Study who were in the elementary first-grader panel from 2010 until 2016. We used a Gompertz regression model to estimate the effects of weight status based on age-specific and sex-specific body mass index (BMI) percentile and sleep duration on an early schoolchild's conditional probability of menarche during a given time interval using general health condition and annual household income as covariates. Results: Gompertz regression of time to menarche data collected from the Korean Children and Youth Panel Study 2010 suggested that being overweight or sleeping less than the recommended duration was related to an increased hazard of menarche compared to being average weight and sleeping 9 hours to 11 hours, by 1.63 times and 1.38 times, respectively, while other covariates were fixed. In contrast, being underweight was associated with a 66% lower discrete-time hazard of menarche. Conclusions: Weight status based on BMI percentiles and sleep duration in the early school years affect the hazard of menarche.