• 에너지공학
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• 제19권2호
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• pp.116-120
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• 2010

국내 집단에너지 사업의 대표적인 지역난방시스템은 전체 배관망이 약 3,000 km에 이르고 있다. 이러한 장거리 배관망을 통한 열수송에서는 마찰 저항으로 인해 많은 펌프동력이 필요하게 된다. 효율적인 장거리 열수송을 위한 연구로서 대표적인 방법 중 하나가 마찰저감제를 투입하는 것이다. 이러한 마찰저감제는 파이프내 표면의 마찰저항을 감소시킴으로써 유체의 유동을 향상시키게 되는 것이다. 본 연구에서는 친환경 계면활성제인 Amine Oxide $C_{18}$을 이용하여 $80{\sim}110^{\circ}C$의 온도범위에서 단기간 동안에 마찰저감 특성을 비교하고, 장기간 동안 퇴화현상을 비교 평가함으로써 향후 지역난방 시스템에서 적용 가능성을 평가하기 위하여 지역 난방시스템을 축소하여 실험장치를 제작하였다. 마찰저감제를 첨가하지 않은 파이프내의 차압과 마찰저감제를 첨가하였을때의 차압을 비교하여 마찰저감율을 측정하였다. 단기성능 실험결과 마찰저감제는 온도의 영향을 받아 유체의 온도가 높아질수록 마찰저감율이 낮게 나타났다. $80^{\circ}C$의 실험에서 최대 30%의 마찰저감율이 나타났으며, $100^{\circ}C$ 이상에서는 마찰저감율이 감소하여 약 15%의 마찰저감율을 보였다. 장기성능 실험결과 $80^{\circ}C$의 실험에서는 1000 ppm 0.8 m/s의 유속에서 마찰저감율의 지속시간이 155시간동안 유지되었으며 온도가 높아질수록 지속시간이 감소하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.314-321
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• 2000

Excessive torsional behavior of asymmetric building structures is observed to be the main cause of the poor seismic performance. Concepts of current design provisions for torsion are based on the assumption that the strength of the lateral load resisting elements can be adjusted without changing their stiffness. This paper investigates inelastic torsional effects of multi-story high rise residential building in Korea on increase of strength demand and ductility of members using some methods published in literature. The methods analyze the reduction of strength and member ductility resulting from torsional mechanisms. This study shows that use of these concepts control inelastic torsion during preliminary seismic design of multi-story building of irregular plans.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
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• pp.53-56
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• 1995

Despite the recent development of structural analysis programs for the CRCP pavements over Westergaard's equations and finite element techniques, the Winkler foundations which are modelled by series of vertical springs at the nodes are generally used for the computer modelling of subbases under the concrete slab. Herewith, two parameter of soil foundation model is adopted as the most convenient mathematical model to enable deflections outside the loaded area to be effected and to upgrade the Winkler foundations. This paper highlights the derivations of finite element method for the two-parameter soil foundation model in the concrete pavements.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.207-212
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• 2001

In this paper, dynamic stability and vibration characteristics of a flexible shoe in drum brake systems are investigated. The frictional force between the drum and the shoe is assumed as a distributed frictional force, while the shoe is modeled as an elastic beam supported by two translational springs at both ends and elastic foundations. Governing equations of motion are derived by energy expressions, and numerical results are calculated by finite element method. Through the numerical simulation, critical distributed frictional forces are calculated by changing the stiffness of two translational springs and elastic foundation parameters. It is also shown that the beam loses its stability by flutter and divergence depending on the stiffness of elastic supports and elastic foundation parameters. Finally, the time responses of the beam corresponding to their instability types are demonstrated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.452-455
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• 1995

Various physical limitations which intrinsically exist in the manipulator control system, for example kinematic limits and torque limit, cause some undesirable effects. Specifically, when one or more actuators are saturated the expected control performance can not be anticipated and in some cases it induces instability of the system. The effect of torque limit, especially for redundant manipulators, is studied in this article, and an analytic method to reconstruct the control input using the redundancy is proposed based on the kinematically decomposed modeling of redundant manipulators. It results to no degradation of the output motion closed-loop dynamics at the cost of the least degradation of the null motion closed-loop dynamics. Numerical simulations help to verify the advantages of the proposed scheme.

• Water Engineering Research
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• 제7권1호
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• pp.29-41
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• 2006

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. Sediment inflow from upland area has also deteriorated the water quality and caused negative effects on the aquatic ecosystem of the Imha reservoir. The Imha reservoir was affected by sediment-laden density currents during the typhoon 'Maemi' in 2003. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon 'Maemi'. The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon 'Maemi' were predicted as 3,450 tons/km2/year and 2,920 ton/km2/'Maemi', respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997. The trap efficiency of the Imha reservoir was calculated using the methods of Julien, Brown, Brune, and Churchill and ranges from 96% to 99%.

• KIEAE Journal
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• 제9권5호
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• pp.105-113
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• 2009

Daylighting provides the opportunity for both energy savings and improved visual comfort. An accurate estimation of the amount of daylight entering a building is the key step for daylight designing. This research aims to assess comparative daylighting performance of four different configurations of fenestration in case of unilateral windows and their variation under clear and overcast sky conditions. The selected window openings in this study were single punched, double punched, multiple punched and clerestory, and the area was same for each type of window. The experiment was designed for an office space using 1/10 scale model. Daylighting performance was evaluated by measuring the illuminance on work-plane height using Agilent data logger and photometric sensor Li-Cor. Thecomputer program ECOTECT was also used to simulate the pattern of interior illuminance distribution. Clerestory window showed the best performance in term of both illuminance level and distribution in the experiment. Multiple punched window provided more uniform illuminance distribution than single punched window. Lowest daylighting performance in the experiment was shown by double punched window.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3211-3217
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• 2013

대학생의 취업에 대한 부담과 불안감이 날로 심해지고 있는 가운데, 그들의 역기능적 태도가 취업불안에 어떤 영향을 미치는지에 대해 알아보았다. 본 연구 대상자는 수도권 소재 대학생 600명으로 하였다. 조사 기간은 2012. 5. 21.~6. 1까지 이루어졌다. 연구 결과 첫째, 역기능적 태도가 취업불안에 미치는 영향은 심리상태 27%, 유발상황 18%, 부모기대 10%로 나타났으며 특히 완벽성이 취업불안에 많은 영향을 미치는 것으로 분석되었다. 둘째, 역기능적 태도와 취업불안의 상관분석 결과, 역기능적 태도는 심리상태 유발상황 부모기대에 모두 정적인 영향력을 보이고 있었다. 대학생의 취업불안을 낮추고, 그들이 건강한 직장생활을 준비할 수 있도록 역기능적 태도에 관해 보다 면밀한 진단과 개입이 필요하다. 특히 완벽성의 역기능적인 면을 최소화하고 취업목표를 성취하는데 원동력으로 작용하도록 돕는 프로그램 등에 대한 개발과 연구가 필요하다.

• 대한간호학회지
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• 제36권8호
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• pp.1324-1330
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• 2006

Purpose. This study developed a web-based wound care course for undergraduate nursing students and evaluated the course's content, system, and student-satisfaction. Methods. This study was done in three stages, the development of the web-based wound care course, the implementation and evaluation of the course. The course was developed based on the ARCS model. 80 under-graduate nursing students to Y University in Korea used the web-based wound care program during four weeks. After that, they completed questionnaires, evaluating the contents, system, and their satisfaction. Results. Eighteen learning objectives were used to create the web-based wound care course and the course was developed with 7 chapters and 20 subsections. The analysis of the questionnaires showed a mean score for content and system-related items of 3.04 each, out of a possible 4 points. Student satisfaction items had a mean score of 2.89. Conclusions. The web-based course allowed students access to the course anytime and anywhere, and according to their own learning abilities. However this advantage would only be possible when nurse educators develop qualitative web-based course to meet the demand of a complex health care system as well as the needs of the students and the effectively incorporate it into traditional lectures.

• 한국문헌정보학회지
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• 제40권4호
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• pp.33-61
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• 2006

본 연구는 성균관대학교에서 교양과목으로 실시하고 있는 온라인 정보문해 2학점 과목의 교육 효과 및 만족도를 평가하고자 하였다. 이를 위해 쌍방향 온라인 튜토리얼 방식으로 정보문해 교수 학습안을 구안하였으며, 2006년 1학기 정보문해 과목의 수강생 284명 중 9개 계열 251명의 정보문해 교육 사전 사후 테스트 결과와 246명의 학기말 강의 평가결과를 분석하였다. 연구결과 5개의 일반적인 정보문해 능력이 모두 향상됨으로써 온라인 정보문해 과목의 교육 효과가 높은 것으로 나타났으나 계열에 따라 교육 효과에 차이가 있었다. 그리고 온라인 정보문해 과목의 교육 내용과 구성에 대해 비교적 높은 만족도를 나타내었다. 따라서 정규 교양과목으로서 온라인 정보문해 교육은 대학생에게 일반적인 정보문해를 가르치기 위한 매우 효과적인 방법임이 밝혀졌다.