• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.279-284
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• 2000

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 60m/min using the high speed ball screw. Also, a lot of problems have happened the feed drive system. It is necessary to study about the character of positioning accuracy, heat generation and high speed control for feed drive system of high speed. in this study, we make use of the feed drive system with a high lead ball screw. We'll develop the feed drive system at the speed of 60m/min. Using the design of the mechanical element and the high speed control, the basic design concept can be established. After manufacturing one-shaft feed drive system and then conducting the performance test, It'll be analyzed properties of the high speed feed drive system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.363-368
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• 2004

Due to various advantages over the conventional linear motion device such as ball-screw, linear motors have been used in wide variety of industrial applications for years. Driven by increased demand for precision machine tools, the importance of high positioning accuracy, high stiffness and high thrust are greatly increasing. The merits of linear motor are high speed, high acceleration and good positioning accurcy. In addition, Linear motor for high quality machine tool call for high thrust, high stiffness. In this paper, thrust ripple, detent force and thermal behavior are considered for the development of high performance linear motor whose thrust is up to 10,000N. This paper presents a comprehensive study for an iron core type linear motor characteristics that include the influence of PM position on thrust, thrust ripple by detent force and motor dynamics as well.

• The Bulletin of The Korean Astronomical Society
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• v.34 no.1
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• pp.188.2-188.2
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• 2009

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.1-4
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• 2007

Because reinforced concrete structures were being high more and more in recent year, concrete was being demanded high performance of high strength and high fluidity. But various characteristics must be confirmed besides guarantee of demand strength in ultra-high strength concrete. In ultra-high strength concrete, autogenous shrinkage and drying shrinkage grow big because of a low water cement ratio and much quantity of binder. So dangerousness of crack generation grow big in early ages. And ultra-high strength concrete is influenced by use materials more than ordinary strength concrete. In this study we were examined mix design, atuogenous shrinkage and pumpability of ultra-high strength concrete to apply on the ground.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.423-428
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• 2002

Due to various advantages over the conventional linear motion device such as ball-screw, linear motors have been used in wide variety of industrial applications for years. Driven by increased demand for precision machine tools, the importance of high positioning accuracy, high stiffness and high thrust are greatly increasing. The merits of linear motor are high speed, high acceleration and good positioning accurcy. In addition, Linear motor for high quality machine tool call for high thrust, high stiffness. In this paper, thrust ripple, detent force and thermal behavior are considered for the development of high performance linear motor whose thrust is up to 4,000N. This paper presents a comprehensive study for an iron core type linear motor characteristics that include the influence of PM position on thrust, thrust ripple by detent force and motor dynamics as well.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.137-144
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• 2004

Recently, as steel structures become higher and more long-spanned, application of high-strength steels is increasing gradually. However, criteria and example for design of high-strength steel are not built up. exiting criteria for structural steels is not proper for economical design of high-strength steel. Moreover, exiting criteria will be decrease the fatigue performance of steel bridge using high-strength steel. Therefore, criterion for application of high-strength steel must be established. In this paper, the behavior of plate girder using high-strength vertical stiffeners was clarified by carrying out layer elastic-plastic finite element analysis using finite deformation theory. In order to optimize the design and construction of plate girder using high-strength vertical stiffener, criterion for application of high-strength vertical stiffener is proposed.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.155-159
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• 2005

High speed presses with high resolution in semiconductor lead frame manufacturing process are needed . But high speed operation accompanies mechanical vibration. therefore optimized kinematic structure to minimize vibration is required for a high speed press. And the growing competition in the industry asks a press with low cost, high speed, high resolution, and high pressing force, For this purpose a high speed press was modeled with 3D CAD solid modeling system and dynamic analysis were performed with CAE S/W for multibody dynamic analysis, Through these analyses a motor appropriate to a high speed press was selected and link structure for feeding system of the press was modified to reduce vibration. To perform this analysis working Model which is 2D kinematics and dynamic analysis software was used.

• The Journal of Korean Society for School & Community Health Education
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• v.2 no.2
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• pp.89-99
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• 2001

This paper is based on the assumption that the sexual awareness and sexual behaviour of high school students would show the difference between an academic high school and a vocational high school. The main purpose of this paper is to provide basic information on establishing the direction of a realistic and efficient education, which leads to the desirable sex ethics eventually. To do this, a comparative study was carried out to figure out the difference between academic high school students and vocational high school students in terms of their actual awareness and behaviour of sex. I put the following two questions in order to achieve the goal of this study. First, what is the difference in sexual awareness between academic high school students and vocational high school students? Second, what is the difference in sexual behaviour between academic high school students and vocational high school students? The subjects of the survey conducted were 595 high school students in Kyunggi Province and I made the questionnaires referencing pre-studies. The SPSS program was used to get a frequency and a percentage from the results of the survey and then, by applying t-text, $x^2$ verification and interrelation, the following results were obtained. First, regarding sexual awareness, there wasn't much difference in their idea of keeping virginity before marriage between academic high school students and vocational high school students. From the results obtained by analyzing the interrelation between students and their parents and friends in terms of a will to keep virginity, it is found that there was a relevance in both academic high school and vocational high school. When they have a sex problem, it was friends that they are looking for consulting and both groups showed thesame result. But pertaining to an experience of a sex education, the comparative analysis indicated an meaningful difference. Second, as for sex behaviour, it was shown that there was a difference in the experience of going out with the other sex between academic high school students and vocational high school students as well as in the degree of physical touch. However, not much difference was shown in controlling a sex desire between the two groups. As a results of the comparative analysis of the sex experience between the two groups, there was a meaningful difference. In terms of the object of their sex experience, the majority of students in the two groups chose a friend as their first answer and there was little difference. From these results I can draw some conclusions that most of the students in both groups have a link with friends and parents in keeping their virginity. Furthermore, a meaningful difference in experiencing a sex education is presented between the two groups. With regard to the sex behaviour of high school students, a meaningful difference is shown in dating the other sex, a physical touch and a sex experience between the two groups. Consequently, we realize that there is a meaningful difference in some variants on the sexual awareness and sexual behaviour of high school students between academic high school and vocational high school.

• Steel and Composite Structures
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• v.18 no.4
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• pp.873-887
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• 2015

The continuous composite I-girder should have a sufficient rotation capacity (or ductility) to redistribute the negative bending moment into an adjacent positive bending moment region. However, it is generally known that the ductility of the high strength steel is smaller than that of conventional steel, and application of high strength steel can cause ductility problems in a negative moment region of the I-girder. In this study, moment redistribution of the continuous composite I-girder with high strength steel was studied, where high strength steel with yield stress of 690 MPa was considered (the ultimate stress of the steel was 800 MPa). The available and required rotation capacity of the continuous composite I-girder with high strength steel was firstly derived based on the stress-strain curve of high strength steel and plastic analysis, respectively. A large scale test and a series of non-linear finite element analysis for the continuous composite I-girder with high strength steel were then conducted to examine the effectiveness of proposed models and to investigate the effect of high strength steel on the inelastic behavior of the negative bending moment region of the continuous composite I-girder with high strength steel. Finally, it can be found that the proposed equations provided good estimation of the requited and available rotation capacity of the continuous composite I-girder with high strength steel.

• Korean Journal of Human Ecology
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• v.5 no.1
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• pp.99-111
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• 1996

The purpose of this study is to find some directions to enhance high school students' recognitions for the necessity of Home Economics(HE) education. 309 respondents were sampled from boys', girls' and co-ed high schools in Chongju. The questionnaire consisted of some items about the respondents' interest, necessity, and the required level for HE. The results are as follows : 1) Students from girls' high school and co-ed high school showed more interest in HE than did the students from boys' high school. 2) The recognition of the necessity for learning HE in high school was significantly differed according to the school systems. 3) The demand level on HE was 52.8 out of 100 point, which is fairly low. Girls from co-ed high school showed higher demand on HE than did the girls' high school. 4) The highest demand level of students in the detailed domains of HE was on consumption. And the students showed a comparatively high demand on health, job, and consumption, while showing low demand on clothing. 5) Students from boys' high school and co-ed high school favored practice-oriented HE education.