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Al Shee/CFRP 다적층 하이브리드 복합재료의 굴곡강도에 미치는 카본섬유 체적률 및 배열방향 영향
유재환,Yoo Jae-hwan 한국안전학회 2004 한국안전학회지 Vol.19 No.4
The A17075/CFRP multi-layered hybrid laminate material consists of the alternating A17075-T6 sheets and carbon/epoxy prepregs of M40 fade. The influence of volume fraction and fiber orientation of A17075/CFRP layer on flexural properties of A17075/CFRP laminate alternating A17075-T6 and carbon/epoxy prepreg was investigated. The results obtained from the experimental analysis are as follows: 1. In the $0^{\circ}$ fiber orientation, the mont of increase of the flexural rigidity was $20.5\%$ at the $26.5\%$ volume fraction and $38.0\%\;at\;the\;35.7\%$ volume fraction compared with the flexural rigidity level(20.0GPa) of the $10\%$ volume fraction of CFRP. 2. In the $\pm45^{\circ}$ fiber orientation the amount of decrease of the flexural rigidity was $23.5\%\;at\;the\;20.0\%$ volume fraction and $31.5\%\;at\;the\;33.3\%$ volume fraction compared with the flexural rigidity level of the $10\%$ volume fraction of CFRP. 3. In the $0^{\circ}$ fiber orientation, the flexural strength was 481.5MPa at the $10\%$ volume fraction of CFRP and 583.8MPa at the $26.5\%$ volume fraction and 653.7MPa at the $35.7\%$ volume faction. 4. In the $\pm45^{\circ}$ fiber orientation, the flexural strength was 354.0MPa at the $20.0\%$ volume fraction of CFRP and 340.5MPa at the $33.3\%$ volume fraction.
다양한 형상에 따른 타원형 핀-튜브 열교환기의 열전달 특성에 관한 수치해석
유재환(Jae Hwan Yoo),윤준규(Jun Kyu Yoon) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.4
본 연구는 타원형 핀-튜브 열교환기에 대해 AR, 피치, 와류발생기의 위치, 튜브 표면의 돌기형상에 따른 열전달계수 및 압력강하 특성을 수치해석으로 분석하였다. CFD해석시 경계조건으로는 튜브표면의 온도는 348 K이고, 입구공기속도는 1~5 m/s 범위로 가정하였고, 수치해석시 사용된 모델로는 민감도를 고려하여 RSM 7차 난류모델을 하였다. 해석결과로는 AR 및 세로피치가 작을수록 열전달률이 향상되는 것으로 나타났으며 가로피치에 대한 영향은 근소한 차이를 나타냈으며, 와류발생기의 설치는 튜브 전방에 위치할수록 열전달특성상 양호한 것으로 나타났다. 또한 튜브표면의 돌기형상은 톱니형보다 원형이 압력강하나 열전달특성이 유리한 것으로 나타났다. In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (AR), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CFD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1?5 m/s. RSM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the AR and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type.
유재환(Yoo, Jae-Hwan),김학열(Kim, Hag-Yeol) 한국도시행정학회 2011 도시 행정 학보 Vol.24 No.4
This paper presents a method to evaluate redundancy in 33 Air Pollution Monitoring Stations (APMS) during 2007 and 2008 at Seoul Metropolitan Area by comparing daily average concentrations of one station to the other among APMS for the cases of air pollutant NO₂, SO₂, and O₃. The criteria to be tested for redundancy are as follows: 1) to check if two stations are within 3㎞ distance, 2) by one-way ANOVA, to test whether the air pollution levels from the different station are statistically different, 3) by paired comparisons, to test whether the mean difference is significantly different from zero, 4) by estimating a simple linear regression model, to figure out whether the concentration level of one station is considered as being statistically equal to that of the other at any day. The results show that no redundancy has been detected in daily average concentrations of both NO₂ and SO₂ during the two years. However, in the case of concentrations, Beon-dong and Banghak-dong station are identified to be possibly redundant since the test result gives the following conditions: 1) distance criterion is met between the two stations, 2) there is a statistical indication that the means of the concentrations at the two stations are equal, and 3) there is a strong evidence that the concentration of one station is able to be predicted by the other. Therefore, the two stations can be recommended to remove one station or to move one station to a new location so that they may cover two exclusive areas.
유재환(Yoo Jae Hwan) 전북대학교 교육문제연구소 2014 교육문제연구 Vol.20 No.1
학교장은 단위 학교의 최고 경영자로서 교육과정을 운영하고 학교 조직, 시설 및 예산을 나아가 지역과의 협력 교육, 교육개혁의 실현 등에 까지 많은 직무를 수행한다. 이 연구에서는 학교장의 핵심 직무 역량을 사전 연구들을 통해 규정하고, 현재 전라북도 교육청 중등교사의 승진 구조를 분석하였으며, 학교장의 핵심 직무 역량과 현행 승진구조 간의 연계성을 알아보고 다음과 같은 결과를 도출하였다. 첫째, 교장의 주요 역할을 교육자, 교육 행정가, 조직 관리자로 나누고 이에 필요한 핵심 직무 역량을ㆍ교육과정 개발 및 관리 역량ㆍ교수 학습 지원 및 학생 생활지도 역량ㆍ수업 전문성 신장 역량ㆍ교육법 및 교육정책 집행 역량ㆍ행ㆍ재정 관리 역량ㆍ 전문성과 책무성, 변혁 지향성ㆍ학교 시설 관리 역량ㆍ정보통신 기술 활용 역량ㆍ학교 비전 제시 및 목표 관리 역량ㆍ조직 및 인사관리 역량ㆍ학부모 및 지역사회와 협력 역량ㆍ갈등 해결 및 의사결정 역량ㆍ윤리의식과 공정성 역량ㆍ신뢰감과 배려의 리더십 역량의 14가지로 규정하였다. 둘째, 현재 전라북도 중등교사의 승진 구조는 경력평정 70점, 근무성적평정 100점, 연수성적 평정 30점(교장 승진 후보자는 18점), 가산점 13.366점의 총합 213.366점(교장 승진 후보자는 201.336점)으로 이루어져 있다. 셋째, 근무 경력 기간의 여러 업무 등을 점수화하여 점수가 높은 사람이 승진이 되는 현재의 제도는 교장으로서 역할에 필요한 직무 역량과는 거리가 멀다. 초ㆍ중등 교육법제21조 1항에 교감 또는 교장은 자격증 소유 여부, 교감 또는 교사로서의 근무 기간, 교육 이수 여부 등의 일정한 자격 기준 만을 정하고 있을 뿐 가져야 할 역량에 대해서는 정해진 바가 없기 때문이다. The Principal executes the critical job of managing the school curriculum, organization, and budget as the core indicator of the school’s quality. This study examines the principal’s job competence through prior investigation, the promotion system of Jeon-buk secondary school teachers and analyze through the comparison the between principal’s core job competency and current teacher promotion system. The results of this study are as follows. First, the core abilities of Principals are composed of 14 competencies indicated as the educator, the educational administrator, the organization administrator, etc. Second, the current promotion system of Jeon-buk secondary school teachers is composed of the career valuation, the performance score rating, training score rating and extra points. Third, the current teacher promotion system has limitations by the core role of Principals competencies. There is no criteria for the necessary competencies of Principals and by principals, there is just the certain criteria for Principles qualification in No.1 Article 21 Elementary and Secondary Education Act.