• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.115-119
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• 1992

산업의 발전과 더불어 새로운 재료의 개발에 대한 요구가 날로 증가하고 있으며 이와 같은 요구에 부응하기위하여 각종의 신소재가 개발되고있다. 이들 신소재 중에서 섬유강화 복합재료는 높은 비탄성과 비강도특성 때문에 구조물의 경량화가 요구되는 우주선, 항공기 등에 주로 이용 되어 왔으며 최근에는 복합재료의 가격이 저렴해 지면서 이 재료의 높은 비탄성과 감쇠특성을 이용하고자 스포츠용품 및 기계 부품에도 섬유강화 복합재료의 이용이 증가 되고 있다. 항공기나 고속회전체의 부품을 복합재료로 제작하였을 경우 복합재료를 다른 금속이나 다른 복합재료부품에 접합(joining)시켜야 하는데 이 때문에구조물의 효율은 Joint에서 주로 죄우된다. Joint를 제작하기 위해서는 복합재료의 표면을 가공한 수 Adhesive를 이용하거나 Bolt로 체결하기 위해 구멍 뚫기 작업이 필요하여 드릴링을 하였을때 이 재료가 매우 연마성이 강하여 심한 공구마멸을 일으키며, 드릴의 입구와 출구쪽에서 각 ply들의 박리 현상이 발생하고, 드릴가공된 벽면으로부터 섬유 또는 레진의 탈락현상등이 발생하는 결점을 가지고 있다. 따라서 본 연구에서는 이러한 결점을 최소화하여 고정밀도의 높은 생산성을 얻기위한 가공기술에 대한 자료를 만들고 최적 절삭조건 및 복합재료가공용 드릴의 설계를 위한 지침을 제시하고자 고속도강 표준드릴을 사용하여 유리섬유 에폭시 복합재료및 탄소섬유 에폭시 복합재료의 드릴링 실험에서 절삭조건이 가공면 생성, 공구마멸, 절삭력에 미치는 영향에 대하여 조사하였다.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.2
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• pp.1-6
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• 2011

This study aims at predicting structural behaviors of RC (Reinforced Concrete) beams retrofitted with hybrid FRPs (Fiber Reinforced Polymers). Toward this goal, structural analysis for the RC beams retrofitted with hybrid FRPs are performed and validated using existing experimental data. For the analysis, failure models due to debonding of FRPs and concrete separation are implemented within FE (Finite Element) model, based on Smith and Teng, model, and Teng and Yao model, respectively. Nonlinear material and geometrical effects are also included in the analysis. The suggested modeling approaches are able to predict structural behaviors of RC beams retrofitted with hybrid FRPs similar to the experimental data, however, a numerical model needs to be developed in order to predict failure strength of RC beams retrofitted with hybrid FRPs accurately.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.128-137
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• 2014

Sprayed fire resistive materials are mainly used at steel structures to satisfy fireproof construction standard. However, the regulations on bond strength have been not considered with the exception of structures in the nuclear power plants, although it is an important factor showing material properties. Therefore, this paper suggested guidelines for bond strength of sprayed fire resistive materials used in the substation, by measuring bond strength according to aging of structures and impact loading considering environment of substations. It is judged that the bond strength suggested in this paper is the minimum value because it was measured from specimens widely used.

• Analytical Science and Technology
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• v.23 no.2
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• pp.205-215
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• 2010

The purpose of this study is to examine Hangul signature changes of writers under the influence of alcohol using Scale for Handwriting Identification (SHWI). It has been recognized that handwriting is influenced by alcohol. However, in Korea, there has been no study which examined the handwriting changes after drinking alcohol. This study confirmed the differences between signatures in sobriety at police station (SIS) and signatures under the influence of alcohol at sobriety checkpoint (S-UIA) by analyzing the Hangul signature of 30 persons. The comparative characteristics are size, space, omission, writing order, connection. The changes of more than one characteristic were observed among the 27 out of 30 persons. Three of 30 persons did not show any change between S-IS and S-UIA.

• 월간 기계설비
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• s.262
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• pp.48-52
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• 2012

기획재정부와 행정안전부는 계약 예규를 개정하고 지난 4월 2일부터 시행에 들어갔다. 기획재정부는 이번 계약예규 개정을 통해 등록기간 3년 미만 업체가 공동수급제에 참여할 경우 만점기준을 완화했고, 1억 이상 3억 미만 전문공사의 경우 만점기준이 발주금액에 대한 '3년 실적의 1/2배 이상'에서 '평가면제'로, 3억 이상 50억 미만 전문공사의 경우 '3년 실적의 2배 이상'에서 '1/2배 이상'으로 평가방법을 완화했다. 또한 발주기관에서 공공공사 예정가격을 산정할 경우 반드시 최신 표준품셈을 사용하도록 의무화했으며, 적정 노무비 보장 심사 강화 방안으로, 최저가낙찰제 공사에서 업체가 제출한 노무비가 발주기관에서 산정한 노무비의 80% 미만일 경우 탈락된다. 기획재정부는 이번 개정으로 시공경험이 부족하지만 기술력 등이 우수한 신설 중소 업체가 공공공사에 참여할 수 있는 기회가 늘어날 것으로 기대하고 있으며, 최저가낙찰 시 과다한 노무비 삭감 등으로 인한 건설 근로자 소득감소 및 내국인 건설업 기피 등을 막을 수 있을 것으로 기대하고 있다. 한편 행정안전부는 이번 계약예규 개정을 통해 지방자치단체 입찰 및 계약관련 예규를 현행 11개에서 2개로 통합했고, 지자체가 발주하는 50억원 이상~100억원 미만의 공사의 경우 참가자격 적격심사 항목 중 자산회전율 평가를 삭제했으며, 신용평가 등급을 완화해 지방 중소기업들의 입찰 참가 기회를 확대하기로 했다.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.466-474
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• 2016

Pre-reinforcement with umbrella arch grouting is conducted around a tunnel where a portion of the upper part of the tunnel is located in a sand and gravel layer. Surroundings of a first tunnel situated below groundwater table are reinforced with LW or SSM that is composed of ultra-fine cement and injected into multi-stages through large diameter steel pipes. With them, a first tunnel is safely excavated without both leaking of groundwater and fallings of sand and gravel from the arch. A second tunnel where groundwater is drained down to the bedrock is reinforced with jet grouting. The effect of the pre-grouting reinforcement is monitored by checking whether groundwater is dripping or sand or gravel is falling from the arch of the tunnels.

• Journal of Information Technology Applications and Management
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• v.28 no.4
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• pp.21-32
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• 2021

In this study, factors affecting undergraduate students' dropout intentions consisted of aptitude and career fit of student's major, employement prospects of student's major, and graduation attitude were presented in the structural equation model and the moderating effect of academic year on the path coefficeint presented in the research model was verified. Undergraduate students are grouped into senior year (3rd and 4th grades) and junior year(1st and 2nd year) by the year in the university, As a result of analyzing 454 undergraduate students (105 in the junior group and 349 in the senior group), it was found that graduation attitude had a negative (-) effect on the dropout intention in both junior and senior group. The effect of employment prospects, and major aptitude and career firt on graduation attitude was not found in the junior group. However, in senior group, the effect of employment prospects, and major aptitude and career firt on graduation attitude was found to have a positive (+) effect, indicating that moderating effect of academic year does exist.

• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.1
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• pp.109-115
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• 2021

The number of freshmen at universities is decreasing due to the recent decline in the school-age population, and the survival of many universities is threatened. To overcome this situation, universities are seeking ways to use big data within the school to improve the quality of education. A study on the prediction of dropout students is a representative case of using big data in universities. The dropout prediction can prepare a systematic management plan by identifying students who will drop out of school due to reasons such as dropout or expulsion. In the case of actual on-campus data, a large number of missing values are included because it is collected and managed by various departments. For this reason, it is necessary to construct a model by effectively reflecting the missing values. In this study, we propose a university student dropout prediction model based on eXtreme Gradient Boost that can be applied to data with many missing values and shows high performance. In order to examine the practical applicability of the proposed model, an experiment was performed using data from C University in Chungbuk. As a result of the experiment, the prediction performance of the proposed model was found to be excellent. The management strategy of dropout students can be established through the prediction results of the model proposed in this paper.

• Asia-Pacific Journal of Business
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• v.13 no.3
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• pp.361-373
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• 2022

Purpose - This paper analyzes the student determinants of college non-completion and estimates the effects of each determinant on college non-completion. Design/methodology/approach - We use student panel data from a large Korean university from 2011 to 2021. Our results are from estimation of fixed-effects logit model. Findings - The results show that grade point average, participation in extracurricular activities, the number of counseling sessions with teachers, and financial aid are the main determinants of college non-completion. Academic probation, which is defined as any person who has a cumulative grade point average below a one point seven five, increases the non-completion rate by 2.6 percentage points and an one-point rise in extracurricular activities index reduces the rate by 0.1 percentage points. The effects of each determinant are heterogeneous across student sub-groups which are separated by gender, nationality, and academic discipline. Research implications or Originality - Tailored support programs for academically discouraged students that incorporate student characteristics and backgrounds are necessary to increase college completion rates and degree attainment.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.275-285
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• 2022

Educational culture generally refers to learners' perceptions, attitudes, and behaviors related to education. Given that educational culture of the university is considered a major factor influencing students' college life, such as learning development, achievement, and dropout, identifying their perceptions of the educational culture is critical to establish the university's education goals and directions. Therefore, this study aimed to identify the educational culture recognized by K university's students and analyze differences in perception with professors to derive implications for future improvement.