• Journal of the Korean Ceramic Society
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• v.42 no.8 s.279
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• pp.537-541
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• 2005

Silicon nitride is one of the most successful engineering ceramics, owing to a favorable combination of properties, including high strength, high hardness, low thermal expansion coefficient, and high fracture toughness. However, the impact damage behavior of $Si_3N_4$ ceramics has not been widely characterized. In this study, sphere and explosive indentations were used to characterize the static and dynamic damage behavior of $Si_3N_4$ ceramics with different microstructures. Three grades of $Si_3N_4$ with different grain size and shape, fine-equiaxed, medium, and coarse-elongated, were prepared. In order to observe the subsurface damaged zone, a bonded-interface technique was adopted. Subsurface damage evolution of the specimens was then characterized extensively using optical and electron microscopy. It was found that the damage response depends strongly on the microstructure of the ceramics, particularly on the glassy grain boundary phase. In the case of static indentation, examination of subsurface damage revealed competition between brittle and ductile damage modes. In contrast to static indentation results, dynamic indentation induces a massive subsurface yield zone that contains severe micro-failures. In this study, it is suggested that the weak glassy grain boundary phase plays an important role in the resistance to dynamic fracture.

• Journal of Families and Better Life
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• v.31 no.5
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• pp.201-210
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• 2013

The purpose of this study was to investigate the possibility of discriminating a high level of school adjustment in low-income school-aged children using interpersonal-related variables(mother attachment, peer attachment) and self-related variables(ego-resiliency, self-control). The subjects were 335 children in fourth, fifth and sixth grades in 4 elementary schools in Daegu. Mean(SD), t-test, and stepwise discriminant analysis were used for data analysis. Base on the results of the discriminant analysis, the discriminant functions suggested that the best predictor for distinguishing between a high level of school adjustment in low-income school-aged children and a low level of school adjustment was ego-resiliency. Self-control, mother attachment and peer attachment reliably separated the groups. And using ego-resiliency, self-control, mother attachment and peer attachment as predictors, the discriminant analysis correctly classified 92.3% of the participants.

• Research in Mathematical Education
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• v.8 no.2
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• pp.107-114
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• 2004

University teachers of linear algebra often feel annoyed and disarmed when faced with the inability of their students to cope with concepts that they consider to be very simple. Usually, they lay the blame on the impossibility for the students to use geometrical intuition or the lack of practice in basic logic and set theory. J.-L. Dorier [(2002): Teaching Linear Algebra at University. In: T. Li (Ed.), Proceedings of the International Congress of Mathematicians (Beijing: August 20-28, 2002), Vol. III: Invited Lectures (pp. 875-884). Beijing: Higher Education Press] mentioned that the situation could not be improved substantially with the teaching of Cartesian geometry or/and logic and set theory prior to the linear algebra. In East Asian countries, science-orientated mathematics curricula of the high schools consist of calculus with many other materials. To understand differential and integral calculus efficiently or for other reasons, students have to learn a lot of content (and concepts) in linear algebra, such as ordered pairs, n-tuple numbers, planar and spatial coordinates, vectors, polynomials, matrices, etc., from an early age. The content of linear algebra is spread out from grades 7 to 12. When the high school teachers teach the content of linear algebra, however, they do not concern much about the concepts of content. With small effort, teachers can help the students to build concepts of vocabularies and languages of linear algebra.

• Journal of Families and Better Life
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• v.9 no.1 s.17
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• pp.13-26
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• 1991

The purpose of the study is to examine the realities of the high school students's aggressive behavior, and to analyze factors causing aggressive behavior. Subjects were 418 Humanity High School students of 2nd grades in pusan. Analysis methods were used to frequency, percentage, t-test, one way ANOVA, Pearson's correlation, and multiple regression of SPSS program. The results are as follows ; 1) Male students are more aggressive than female students. 2) The more verbal aggression is the more physical aggression. 3) Students with the experience of parent-child violence are more aggressive. 4) Students with observation of parents's violence are more aggressive. 5) Family's social economic status is not related to the aggressive behavior. 6) Male students not admitted by teacher are more aggressive in verbal and physical behavior. 7) Female students not admitted by friend are more aggressive in verbal and physical behavior. 8) Students with deliquent friends are more aggressive in verbal and physical behavior. 9) Students with Academic anxiety are more aggressive in verbal behavior. 10) the variables influential to verbal aggressive behavior are sex, a delinquent friends and academic anaxiety. These factors explain 23.5% of the total variance of verbal aggressive behavior variables. The variables influential to physical aggressive behavior are a delinquent friends, sex, experience of parent-child violence and teacher's denial attitude. These factors explain 29.6% of the total variance for physical aggressive behavior variables.

• Journal of the Korean Home Economics Association
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• v.48 no.8
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• pp.87-97
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• 2010

The purposes of this study were to explore the differences in maternal parenting behaviors and mothers' family stress by children's sex and parental divorce and to investigate the relationships of maternal parenting behaviors with mothers' family stress in low income families. Participants of this study were 166 children of 4 to 6 grades and their mothers from low income divorced and intact families. The data were analyzed by descriptive statistics, two-way ANOVAs, Pearson's correlations. The result were as follows: Girls perceived more maternal warmth than boys in divorce families, but boys perceived more maternal warmth than girls in intact families. Boys perceived more maternal supervision than girls in intact and divorced families. Mother of divorced families had more childrearing stress than mothers of intact familes. In divorced families, children whose mothers had high levels of childrearing stress perceived less maternal warmth and supervision, and children whose mothers had high levels of work-family conflicts perceived less maternal warmth. In intact families, children whose mothers had high levels of economic stress perceived less maternal supervision.

• Journal of Fashion Business
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• v.19 no.4
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• pp.21-36
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• 2015

The purpose of this study is to classify the stress into groups and analyze their differences in self-consciousness, and appearance management behavior. Questionnaires were administered to 377 middle and high school girls living in Deagu metropolitan City. Frequency, factor analysis, reliability analysis, cluster analysis, ANOVA, Duncant-test, and t-test are all used for data analysis. Our findings show that stress developed due to several reasons: the categories are as follows into grades-related low stress, exam-related high stress, and society-related high stress. For the purposes of our study, we labeled self-consciousness as a combination of being socially and privately self-consciousness and showing signs of social anxiety. Appearance management behavior deals with esthetic plastic surgery, clothing harmony, weight management, hair management, health care, skin care, and meal management. Stress shows a significant correlation with the sub-variable self-consciousness and appearance management behavior. The groups show a significant difference in the self-consciousness, and appearance management behavior. There is also a significant difference among stress, self-consciousness and appearance management behavior by grade. The students in seemed to recognize that their appearance can be improved by dressing up and managing their outwardly appearance. Teachers should educate students to have the variety of views on the meaning of beauty. In addition, schools need to develop programs to educate student about appearances, as the student's interests differ due to the stress type of the adolescent.

• The Journal of Korean Academic Society of Nursing Education
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• v.21 no.3
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• pp.406-416
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• 2015

Purpose: This study investigated sexual knowledge, its related factors, and the needs of sex education among elementary, middle, and high school students in order to develop a sex education program. Method: The participants comprised 721 students in grades 5 through 12, from Seoul and the Kyeonggi-do area, in South Korea. Data was collected from the end of August through the end of September 2014, using an anonymous self-administered questionnaire. SPSS Statistics 21.0 was used for the descriptive analysis, chi-square, t-test, ANOVA, and multiple regressions. Results: Higher-grade students had a higher level of sexual knowledge than lower-grade students, but the overall level of sexual knowledge was low. Multivariate analysis showed that gender, grade, school record, and experiences of sex education from family and school were significant predictors of sexual knowledge among adolescents. Coping skills related to sexual crisis situations was the most wanted content of sex education. Conclusion: The results of this study suggested that it is important to develop a sex education program that considers the needs of sex education among adolescents. Also, it is important to periodically perform a survey to identify the need of sex education among elementary, middle, and high school students.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.569-577
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• 2000

The position of tobacco leaves is affluence to the quality. To evaluate its quality, sample leaves was collected according to the position of attachment. In Korea, the position was divided into four classes such as high, middle, low and inside positioned leaves. Until now, the grade of standard sample was determined by human expert from korea ginseng and tobacco company. Many research were done by the chemical and spectrum analysis using NIR and computer vision. The grade of tobacco leaves mainly classified into 5 grades according to the attached position and its chemical composition. In high and low positioned leaves shows a low level grade under grade 3. Generally, inside and medium positioned leaf has a high level grade. This is the basic research to develop a real time tobacco leaves grading system combined with portable NIR spectrum analysis system. However, this research just deals with position recognition and grading using the color machine vision. The RGB color information was converted to HSI image format and the sample was all investigated using the bundle of tobacco leaves. Quality grade and position recognition was performed through well known general error back propagation neural network. Finally, the relationship about attached leaf position and its grade was analyzed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.5
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• pp.408-418
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• 1987

The quality of different grades of dried lavers obtained from three culture areas was evaluated and its changes during the storage at different levels of water activity were measured. Not much differences in general chemical composition between the locality was detected except some in the content of lipid and pigments. But the quality grades of dried lavers were mainly depended upon the content of protein and pigments including chlorophyll a, carotenoids, and biliproteins although there was little difference in amino acid composition of the proteins, and glutamic acid, aspartic acid and alanine were high in general. The lipid of dried lavers was composed of a high level of polyunsaturated fatty acids, particularly, of eicosapentaenoic acid which amounted to as much as a half of the total lipid, and of palmitic acid that reached a quarter depending on grades. The quality of dried layers was significantly changed by equilibrium moisture level when stored for three months at different water activities in range of 0.1 to 0.6. The loss of chlorophyll a, carotenoid, biliproteins, ascorbic acid, and browning were markedly retarded at aw 0.1 to 0.2. Oxidation of polyunsaturated fatty acids and the loss of free amino acids were also minimized at aw 0.2. Glutamic acid and methionine were reduced very fast during the storage.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.6
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• pp.50-61
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• 2017

This study devised a user-participatory design process for users to participate directly in the design process and was implemented at Daegu Padong Elementary School. Users of the school forest were divided into four groups: the lower grades, the upper grades, local residents(parents included), and faculty. The methods of this study were image survey, preference survey, card playing, and model playing. Researchers investigated the level of user satisfaction the following year. The specific design process is as follows: First of all, the concept of the school forest was established through audio-visual education for students and image research was conducted through drawing and painting activities entitled 'The School Forest I Want'. Second, in the image survey, a survey of areas and facilities with high frequency use was conducted in the study of the lower grades, the upper grades, local residents, and the faculty. Image cards of spaces and facilities that showed high preference were produced and the cards were placed in four groups on the school lot plan to check the location of place and facilities desired. Based on this, a model and a basic idea were created through consultation with future users. Lastly, the study design was completed. After 1 year from the completion of the school forest, users were again surveyed regarding their satisfaction with use. The importance of this study is as follows: 1) Treating all potential users of a school forest as the subject of design participation, 2) Reasoning out a plan created by the users themselves through consultation and discussion throughout all steps of the design process, 3) Grasping how users utilize a school forest and the type of spaces most preferred via preference survey after completion of the school forest and showing the importance of user participation by showing that spaces preferred by users were similar to those in which experts were also highly interested.