• Journal for History of Mathematics
• /
• v.21 no.1
• /
• pp.139-156
• /
• 2008

We investigate the inducing method of irrational numbers in junior high school, under algebraic as well as geometric point of view. Also we study the treatment of irrational numbers in the 7th national curriculum. In fact, we discover that i) incommensurability as essential factor of concept of irrational numbers is not treated, and ii) the concept of irrational numbers is not smoothly interconnected to that of rational numbers. In order to understand relationally the incommensurability, we suggest the method for inducing irrational numbers using construction in junior high school.

• Structural Engineering and Mechanics
• /
• v.69 no.4
• /
• pp.371-381
• /
• 2019

A hybrid prestressed segmental concrete (HPSC) girder utilizing low carbon materials was developed in this paper. This paper introduces the hybrid prestressing concept of pre-tensioning the center segment and assembling all segments by post-tensioning, as well as the development process of the low carbon HPSC girder. First, an optimized mix proportion of 60 MPa high strength concrete containing high volume blast furnace slag was developed, then its mechanical properties and durability characteristics were evaluated. Second, the mechanical properties of 2,400 MPa high strength prestressing strands and the transfer length characteristics in pre-tensioned prestressed concrete beams were evaluated. Third, using those low carbon materials and the hybrid prestressing concept, the HPSC girders were manufactured, and their structural performance was evaluated. A 30-m long HPSC girder for highway bridges and a 35-m long HPSC girder for railway bridges were designed, manufactured, and structurally confirmed as having sufficient strength and safety. Finally, five 35-m long HPSC girders were successfully applied to an actual railway bridge for the first time.

• Transactions of the Korean hydrogen and new energy society
• /
• v.16 no.3
• /
• pp.229-237
• /
• 2005

A new burner configuration for a compact fuel-cell reformer with a high-temperature air combustion concept was numerically studied. The burner was designed for a 40 $Nm^3/hr$ hydrogen-generated reformer using natural gas-steam reforming method. In order to satisfy the primary requirements for designing a reformer burner (uniform distribution of temperature along the fuel processor walls and minimum heat losses from the reformer), the features of the present burner configuration included 1) a self-regenerative burner for an exhaust-gas-recirculation to apply for the high-temperature air combustion concept, and 2) an annular-type shield for protecting direct contact of flame with the processor walls. For the injection velocities of the recirculated gas of 0.6-2.4 m/s, the recirculated gas temperature of 1000 K, and the recirculated oxygen mole fraction of 4%, the temperature distributions along the processor walls were found uniform within 100 K variation. Thus, the present burner configuration satisfied the requirement for reducing temperature gradients along the processor walls, and consequently demonstrated that the high-temperature air combustion concept could be applied to the practical fuel reformers for use of fuel cells. The uniformity of temperature distribution is enhanced as the amount of the recirculated gas increases.

• Journal of the Korean Chemical Society
• /
• v.64 no.1
• /
• pp.30-37
• /
• 2020

The purpose of this study was to identify the problems faced by students in sub-microscopic representation of acid-base reactions. Herein, we selected 30 students of 12^th grade science classes, who had studied various acid-base models. In order to investigate the sub-microscopic representation ability of the students, we developed nine items related to various contexts, such as one type of solute and solvent, two types of solutes and solvent, cases with water as solvent or with nonaqueous solvents. For all items, we consistently observed lack of concept of chemical change. In context of aqueous and nonaqueous solutions, the frequency of lack of concept of chemical bonding was high if ammonia was the solute or solvent. Moreover, the frequency of lack of concept related to the degree of electrolytic dissociation was high. Therefore, chemistry teachers should understand that students' ability to sub-microscopic representation of acid-base reactions can be enhanced by analyzing the difficulties faced by the students in solving diverse acid-base problems.

• Journal of Digital Convergence
• /
• v.9 no.6
• /
• pp.13-25
• /
• 2011

The purpose of this study is to explore a characteristic for raising the percentage of employment of the special high-school. And consider the specialization concept appearing on the stage as these means and analysis the actual operation condition. There are various of the major cause factors of the special high-school and these factors were judged on having a negative effect of raising the percentage of employment of the special high-school. Also, the study were suggested various improvement plan for minimizing negative effect of these factors. Based on the findings, the study showed that grasp the situation of the special high-school and improving plan and present the political plan.

• Korean Journal of Health Education and Promotion
• /
• v.23 no.2
• /
• pp.91-107
• /
• 2006

Objectives: The school adjustment problems of the adolescence groups become more aggravated and are on the increase. The objective of this study is to identify the causal relationship of intra-family conflicts, self-concept and school adjustment as health protection behavior. Methods: The study setting is the adolescence groups. Data were collected by self-administered questionnaires from the middle and high school students in Seoul. The study sample consisted of 268 students. Structural Equation Modeling(SEM) analysis was conducted to find the causal relationship of intra-family conflicts, self-concept and school adjustment. Results: This study shows that firstly, the total effects of intra-family conflicts have a negative effect on self-concept(path coefficients=-0.080) and school adjustment(path coefficients=-0.107). And the self-concept factor as an intervening variable are affecting positively on school adjustment(path coefficients=0.411). Secondly, the economic conflicts, personaliy conflicts and social activity conflicts of father and mother among various family conflicts are more highly affecting on self-concept and school adjustment(p<0.01) Conclusions: These results imply that first, communication between parents and students is essential to solve the problems of school adjustment. Especially economic conflicts should be solved to improve the self-concept and school adjustment. second, a variety of programs are available for schools to employ in an effort to provide interventions for students who demonstrate school adjustment. Finally, it is necessary for family, school and all the society members to comprehensively cooperate to solve family conflicts and school adjustment.

• Journal of Korean Academy of Nursing
• /
• v.14 no.2
• /
• pp.63-74
• /
• 1984

This study attempted to analyze and confirm the correlation between self-concept and the degree of satisfaction on clinical practice. The subjects of the survey were 194 junior and senior students selected from S universities by questionaire from Nov. 1 to Nov. 30, 1983 in Seoul. The collected data was analyzed by t-test, AN-OVA, Pearson correlation according to purpose of study. The results were as follows: 1. Self-concept by religion was significant (F = 4.51, df=4/185, p= .002). 2. In the motives of selecting the nursing, most of students chose the nursing depending on their altruism(62.9%), ability and aptitude(57.7%) and better opportunity of studying abroad and Setting a job(49.5％） respectively. 3. The degree of clinical practice satisfaction was low as 2.80 of a total score 4.0. The degree of satisfaction of contents(3.33) revealed to be high. Compared with the degree of satisfaction on instruction(2.77), practice hours(2.83), practice environment (3.65), and clinical evaluation(2.60) revealed to be low. Religion and choice order of the admission were not significant in satisfaction of clinical practice(t=.37, p=.715). The main hypothesis that“The more positive self concept will be, the higher the degree of satisfaction on clinical practice will be”was not supported (r= .0509, p=.240). The first sub-hypothesis that“The more positive the cognitive self-concept will be, the higher the degree of satisfaction will be”was partially supported. Because favorite-isolated self-concept was significantly correlated with the satisfaction (r=.1189, P=.005). The second sub·hypothesis that“The more positive the evaluational self-concept will be, the higher the degree of satisfaction on clinical practice will be”was not supported. As a above results, self-concept was not influenced to the degree of satisfaction on clinical practice, therefore it is required that environment, instruction method and evaluation for clinical practice should be refined and improved by clinical administrators and nursing faculties for nor-sing student's satisfaction on clinical practice.

• Journal of Gifted/Talented Education
• /
• v.5 no.2
• /
• pp.37-54
• /
• 1995

The radical development of modern mathematics is due to the appearance of Collection Theory by George Cantor. The Set Theory is independent as an area and also closely interrelated with other areas. So its content becomes a common sense and a basic part across the whole area of modern mathematics. Accordingly, the basic element of modern mathematics is helping young children get familiar with set as early as possible. The thinking of set by which children can categorize, make partial sets and correspondences, understand the general characteristic, and conceptualize the discovered relationships is very important for young children. At this point where the Math education for young children is emphasized under the influence of the modernization movement of Math education, the systematic education for building up the set concept as the basic background of number concept during the early childhood is required. On current mathematics education for young children, graphs, the foundation of geometry, time, and patterns have been included in the traditional and practical content related to numbers. However, the education on collection which is the foundation of number concept is insufficient. A study shows that the level of young children's understanding on set is quite high, but the set concept isn't reflected in current Math curriculum for young children. And basic activities neccesary on building up the set concept, such as categorization, comparison, etc. are conducted in kindergardens but unsatisfactory because of those kindergarden teachers' premature understanding on the set concept. In conclusion, the curriculum for young children should be reorganized based on the set concept as the kernel concept. Also, the reappraisal of the training curriculum and the supplementary efucation for kindergarden teachers are urgent for raising the teaching ability of those kindergarden teachers.

• Journal of the Korean Home Economics Association
• /
• v.31 no.1
• /
• pp.181-192
• /
• 1993

This study was undertaken to investigate the factorial structure of clothing purchase motives, and to examine the relationship between clothing purchase motives, self-concept, and post-purchase clothing satisfaction of males. Questionnaire was comprised of three sections: 25 Likert type statements of clothing purchase motive measure; post-purchase clothing satisfaction measure; and three self-concepts measure(physical, personal, and social self-concept). For the measurement of self-concepts, a portion of‘Self-Concept Scale’by Wonshik Chung was used. Samples were 312 male white collar workers in Seoul, whose age were ranged from 20 to 39. the data were analyzed using factor analysis, Cronbach's alpha reliability coefficient, Pearson's correlation coefficient, and multiple regression analysis. The results of the study were the followings: 1. Six factors of clothing purchase motives derived by factor analysis. 21 items having a factor loading of ± .40 or higher were given consideration in the interpretation of each factor: F.1‘clothing dsign’; F.2‘fashion and impulsive buying’, F.3‘clothing utility’; F.4‘others influence’: F.5‘financial margin’; F.6‘clothing’2. Male consumers perceived the purchase motive of‘clothing design’to be the most important,‘clothing deficiency’the second important, and‘others influence’the least important. 3. Physical, personal, and social self-concept had positive relations to the purchase motive of‘clothing design’and negative relations to the‘clothing deficiency’. Physical self-concept had negative relation to the motive of‘others influence’. 4. Male consumers high in physical, personal, and social self-concept had more positive attitude in the evaluation of post-purchase clothing satisfaction. 5. Post-purchase clothing satisfaction was influenced most by the purchase motive of‘clothing design’, and next by physical self-concept, and age. Age of subjects had negative relation to post-purchase clothing satisfaction. The explanatory power of the 3 variables was 19.9%.

• Journal of Ocean Engineering and Technology
• /
• v.32 no.6
• /
• pp.502-510
• /
• 2018

In order to accumulate data to lower the friction coefficient of a press mold, tribological tests were performed before and after coating SM45C with a PVC/PO film and plasma coating (CrN, concept). The ultrasonic nanocrystal surface modification (UNSM)-treated material had a nano-size surface texture, high surface hardness, and large and deep compressive residual stress formation. Even when the load was doubled, the small amount of abrasion, small weight of the abrasion, and width and depth of the abrasion did not increase as much as those of untreated materials. A comparison of the weight change before and after the tribological test with the CrN and the concept coating material and that of the untreated material showed that the wear loss of the concept coating material and P-UNSM treated material (that is, the UNSM treated material treated with the concept coating) showed a tendency to decrease by approximately 55-75%. Concept 100N had a lower friction coefficient of about 0.6, and P-UNSM-30-100N showed almost the same curve as concept 100N and had a low coefficient of friction of about 0.6. The concept multilayer coating had a thickness of $5.32{\mu}m$. In the beginning, the coefficient of friction decreased because of the plasma coating, but it started to increase from about 250-300 s. After about 350 s, the coefficient of friction tended to approach the friction coefficient of the SM45C base metal. The SGV-280F film-attached test specimen was slightly pushed back and forth, but the SM45C base material was not exposed due to abrasion. The friction coefficient was 0.22, which was the lowest, and the tribological property was the best in this study.