• 설비공학논문집
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• 제2권1호
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• pp.37-48
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• 1990

The drag and heat transfer reduction phenomena and degradation effects of drag reducing polymer solutions which are known as the viscoelastic fluids are investigated experimentally for the turbulent circular tube flows. Two stainless steel tubes are used for the experimental flow loops. Aqueous solutions of Polyacrylamide Separan AP-273 with concentrations from 300 to 1000 wppm are used as working fluids. Flow loops are set up to measure the friction factors and heat transfer coefficients of test tubes in the once-through system and the recirculating flow system. Test tubes are heated by power supply directly to apply constant heat flux boundary conditions on the wall. Capillary tube viscometer and falling ball viscometer are used to measure the viscous characteristics of fluids and the characteristic relaxation time of a fluid is determined by the Powell-Eyring model. The order of magnidude of the thermal entrance length of a drag reducing polymer solution is close to the order of magnitude of the laminar entrance length of Newtonian fluids. Dimensionless heat transfer coefficients of the viscoelastic non-Newtonian fluids may be represented as a function of flow behavior index n and newly defined viscoelastic Graetz number. As degradation continues viscosity and the characteristic relaxation time of the testing fluids decrease and heat transfer coefficients increase. The characteristic relaxation time is used to define the Weissenberg number and variations of friction factors and heat transfer coefficients due to degradation are presented in terms of the Weissenberg number.

• 대한토목학회논문집
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• 제39권6호
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• pp.877-886
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• 2019

도시철도 출입구 규모는 이용자의 수요에 따라 산정되어야 하나, 우리나라는 일률적인 값을 적용, 출입구 위치에 따라 이용자의 편차가 많이 발생하여 불편을 겪는다. 최근 교통약자편의증진법에 의해 에스컬레이터, 엘리베이터 등의 이동편의시설의 설치가 의무화되고 있지만 기존 역의 경우 이용자 수요와 상관없이 설치 가능한 곳에 주로 배치가 되기 때문에 실질적으로 이용이 많이 불편하다. 이동편의시설 위치 및 규모가 역 설계 또는 건설시 반영될 수 있도록 본 연구에서는 역 출입구별 이용수요를 예측하여 출입구의 이동편의시설 규모 산정 모형을 정립하고자 한다. 이를 위해 역별 승하차 이용수요, 철도역 주변 용도별 건물 연상면적을 활용하여 1일 수요 예측을 위한 다중회귀모형식을 수립하였다. 추정된 모형의 검증을 위해 동대문역과 종각역의 실제 데이터를 이용하였으며, 추가적으로 국내외 에스컬레이터 산정식을 활용하여 출입구별 에스컬레이터 설치 규모를 비교/분석하였다. 그 결과 단일역을 대상으로 이용수요를 추정하는 것이 좀 더 정확하였으며, 종각역은 1번 출구에 상하행 에스컬레이터가 설치되어 있으나, 4번 출구에 설치하는 것이 타당한 것으로 분석되었다. 본 연구는 2018년 게재한 도시철도역 출입구 유출입 이용자 추정 모형 수립 논문의 발전된 형태로 향후 역 신설시 또는 이동편의시설물 설치 및 확장시 활용될 수 있을 것이라 판단된다. 더불어 현재 무분별하게 설치하는 에스컬레이터 설치 기준의 기초가 될 것으로 보인다.

• 한국콘텐츠학회논문지
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• 제16권9호
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• pp.185-197
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• 2016

본 연구는 고등학교 재학기간 중 고교-대학 연계 프로그램 참여에 따른 진로진학의 영향을 실증적으로 분석하고 공교육 정상화를 도모하는 고교-대학 연계 방법을 탐구하는데 목적이 있다. 연구를 위해 K대학교의 재학생 371명 및 고교 교사 62명을 대상으로 설문을 실시하였다. 연구 결과는 전반적인 고교-대학 연계 프로그램 참여율은 '입시설명회', '전공진로탐색' 프로그램 순으로, 남학생보다 여학생의 참여율이 높게 나타났고, 입학전형별 대학진학에 미친 영향을 비교한 결과 '입시상담' 프로그램은 학생부종합전형(입학사정관 전형)에서 높게 나타났다. 교사들은 고교교육 정상화 및 대학진학에 가장 효과적인 고교-대학 연계 방법으로 '전공진로탐색'으로 응답해 전공진로탐색 프로그램의 활성화가 필요함을 알 수 있었다. 이러한 연구 결과는 고교-대학 연계의 다각적인 방법과 개선을 통한 공교육 정상화 촉진 가능성을 보여주는 것이라 하겠다.

• 한국치위생학회지
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• 제6권2호
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• pp.103-113
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• 2006

The purpose of this study was to examine and analyze motivation of entrance into the college, knowledge prior to the entrance, satisfaction with their major, and a sense of employment after graduation among students majoring in dental hygiene at some colleges and subdivide them by grades for comparative analysis to determine the progress of changes in general characteristics, department satisfaction, and a sense of employment among students majoring in dental hygiene for the recent three years and provide basic data for improving dental hygienic education. Questionnaires were distributed to 520 students majoring in dental hygiene at some college in South Chungcheong, South Jeolla, and North Jeolla Provinces, followed by explanation of the purport of the research and the content of the questionnaire; after completion, 513 copies were used for analysis with exception of 7 copies with insincere responses. The analysis of the data examined resulted in the following conclusions: First, Changes in Department Satisfaction among Students Majoring in Dental Hygiene As for motivation of entrance into a college, less and less students chose the department of dental hygiene through recommendation by parents or seniors while more and more students chose their major due to easy employment. Less and less students obtained information on the department from a college application guidebook while more and more students obtained it through Internet. There was also a gradual increase in prior knowledge about the department and in satisfaction with their major. More and more students had no will to change their course. Second, Changes in a Sense of Employment among Students Majoring in Dental Hygiene There was a gradual decrease in the number of students who would follow friends' or their own decision in selecting workplace but an increase in the number of those who would follow their professors' opinion. There was a gradual increase in the number of students who wanted to be employed in workplace with good social perception; many students wanted to be employed in a personal dental clinic, a general hospital, or a public health center; and more and more students also wanted to be employed in a school dental health center or to become a government official or an educator.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.183-189
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• 2013

In this paper, we propose a capacity modeling method for Bluetooth based LBSs (Location Based Services) between Bluetooth APs(Access Points) and mobile phones. In order to do this, we consider the entrance and exit of the users to and from the AP. Using parameters such as the connection time, data transmission time and number of users in the AP zone, we analyze the capacity of a Bluetooth AP using an appropriate queuing model. The required number of APs in a certain zone is estimated from the number of users in the zone using the proposed queuing model. By performing simulations and experiments, the validity and applicability of the proposed method are verified.

• 설비공학논문집
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• 제11권3호
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• pp.414-421
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• 1999

Falling film rectification involves simultaneous heat and mass transfer between vapor and liquid interface. In the present work, the adiabatic rectification process of ammonia-water vapor on the vertical plate was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer in each phases were investigated. The stripping of water in vapor mixture occurred new the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer in falling film.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권2호
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• pp.69-79
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• 2000

Falling film rectification involves simultaneous heat and mass transfer between vapor and solution film. In the present work, the adiabatic rectification process of ammonia-water vapor by the falling solution film on the vertical plate was investigated. The continuity momentum, energy and diffusion equations for the solution film and the vapor mixture were formulated in integral forms and solved numerically, The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer coefficient in each phases were investigated. The stripping of water in vapor mixture occurred near the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer coefficient in falling film.

• 한국주거학회논문집
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• 제25권1호
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• pp.63-71
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• 2014

This research is aimed to analyze the basic characteristics of the 16 floor plans of 4 small-sized apartments in DaLian-City. Recently, there are increasing that a small-sized apartments for new younger generation in China. The younger ages intend to got a new floor plan types apartments according to own's life style. Also, a lot of construction company showed the many types of new residential space design during the last about 10 years, in DaLian City. The research results are summarized as follows: First, all of the floor plan types were '-' shape, 'L' shape. Second, there were several co-relational types of space plan between living room, kitchen and dining space. Those are LDK, L K, L DK, LD K. Third, the bedroom of the $30m^2$-floor plan size has an open-space design but over the size of $40m^2$-floor plan the space is closed design. Fourth, The number of bathrooms in all the floor plans is just 1 and it's placed beside the entrance except for B3, C4. The basic equipments of the lavatory was a toilet, a washbowl, a shower. A bathtub is installed in the floor plans greater than $60m^2$. Fifth, almost all of the characteristics of the spatial interrelation - each room position order - based on the location of the entrance. In particular, almost all of the bedrooms are furthest from the entrance for the most privacy.

• 대한공간정보학회지
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• 제15권1호통권39호
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• pp.9-16
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• 2007

대학 입학생의 수가 급격히 감소하면서 각 대학 당국에서는 많은 입학생 유치와 학교 운영의 문제를 개선하기 위하여 다양한 방안을 모색하고 있다. 특히 대학의 입시 및 입학현황 자료는 대학당국의 입학 및 홍보정책을 결정하고, 나아가 학교생활복지를 향상하는데 있어서 중요성이 매우 높은 자료이다. 따라서 다양한 입시 및 입학 관련 현황 자료와 대학 결정 요인을 고려한 효율적인 분석이 이루어질 수 있는 입학관리시스템의 도입이 절실히 요구된다. 본 연구에서는 기본지리정보 데이터를 바탕으로 대학입시 지원자, 합격자 및 등록자의 자료에 대하여 분석할 수 있는 대학입학관리시스템을 개발하였으며, 해당 시스템을 이용하여 지역별 지원자, 지역별 합격자, 지역별 등록자, 지원자 대비 합격률 및 최근3년간 지원자 변화율을 분석할 수 있었다. 또한 대학의 입학홍보정책 및 학교운영에 요구되는 합리적이고 적합한 자료를 제공할 것으로 판단된다.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.111-118
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• 2004

The work presented in this paper concerns the aerodynamic characteristics and compression wave generated in a tunnel when a high speed train enters it. A large number of solutions have been proposed to reduce the amplitude of the pressure gradient in tunnels and some of the most efficient solutions consist of (a) addition ofa blind hood, (b) addition of inclined part at the entrance, and (c) holes in the ceiling of the tunnel. These are numerically studied by using the three-dimensional unsteady compressible Euler equation solver with ALE, CFD code, based on FEM method. Computational results showed that the smaller inclined angle leads to the lower pressure gradient of compression wave front. This study indicated that the most efficient slant angle is in the range from $30^{\circ}$ to $50^{\circ}$. The maximum pressure gradient is reduced by $26.81\%$ for the inclined angle of $30^{\circ}$ as compared to vertical entry. Results also showed that maximum pressure gradient can be reduced by $15.94\%$ in blind hood entry as compared to $30^{\circ}$ inclined tunnel entry. Furthermore, the present analysis showed that inclined slant angle has little effect on aerodynamic drag. Comparison of the pressure gradient between the inclined tunnel hood and the vertical entry with air vent holes indicated that the optimum inclined tunnel hood is much more effective way in reducing pressure gradient and increasing the pressure rise time.