• 한국안전학회지
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• 제33권5호
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• pp.127-133
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• 2018

The Saemangeum master plan includes dredging and waterproofing materials, construction projects that can change the hydraulic characteristics of the Saemangeum and Mangyeong and Dongjin River basins. In this study, the river safety of 2030 when the Saemangeum master plan was completed for 100 year frequency, 500 year frequency and 100 year frequency applied RCP 8.5 scenario was examined using Delft3D. As a result of the analysis, it was confirmed that there was no overflowing point at the 100 year frequency, but the difference between the flood level and the river bank elevation was relatively small at the curved and river joint part. At the 100-year frequency with the 500-year frequency and the RCP 8.5 scenario, the possibility of overflowing at several locations was confirmed. The possibility of river bed loss due to fast velocity appears in the upstream part of Mankyung River and it is necessary to monitor the safety of hydraulic structures continuously. In addition, it is expected that the expansion of the area showing the characteristics of the lake due to dredging will affect the sediment mechanism and water quality, so detailed and diverse studies will be needed.

• 수산해양교육연구
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• 제3권1호
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• pp.9-20
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• 1991

The authors investigated the existing international fishery relationship in the sea around the Korean Peninsula, and prospected on the reformation of the fishery order which might be followed by mutation of the international political condition and by effectuation of the U.N. Convention on the Law of the Sea in the future. It can be explained that the existing international fishery order in this sea has been constituted on the basis of restricting Japanese indiscriminate fishery expansion. But. when the South Korea and China proclaim the 200-mile EEZ in the future, a considerable part of existing fishery agreements will forfeit the role as general norms of the international fishery relationship. Accordingly a counterplan against the revision or abrogation of the Korea-Japan Fishery Agreement must be considered. And also a rational fishery relationship between Korea and China, as confronting countries, must be organized. The South-North Korea fishery relationship must be settled on the basis of co-operation. trust, and common interest. For this purpose, a political discussion on the establishment of the joint fishery zone around the military demarcation line and on the conservation for the fishery resources must be begun in earnest.

• 한국강구조학회 논문집
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• 제23권3호
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• pp.283-294
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• 2011

강재 거더교의 다이아프램과 상 하부 플랜지에 부착된 온도게이지의 값을 측정하여, 온도 분포와 시간적 변화를 검토하고, 도로교 설계기준과 비교하였다. 또한 측정 자료를 기초로 하여 일일 기온, 일 최고기온, 일 최저기온에 대한 교량 부재온도와의 상관관계를 각각 분석하여 회귀분석식과 신뢰도를 나타내는 상관계수를 산정하였다. 구조해석에서는 대상교량을 3차원 전체모델링을 수행하고, 실제의 온도 측정 자료를 기반으로 한 온도 하중을 부과하여 계산된 온도 응력값과 시방 규정상의 온도하중에 의한 단면력을 서로 비교 분석한다. 본 연구에서 구해진 대기 온도분포와 강교량 부재 온도 상관관계로부터 상하 플랜지의 온도차를 예측할 수 있고 이 결과를 이용하면 설계 시 신뢰성 있는 부재의 온도하중을 산정할 수 있어, 추후 강합성교량의 온도 영향 평가에 있어서 기초적 자료가 될 것이라 기대한다.

• 한국공간구조학회논문집
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• 제8권4호
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• pp.65-71
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• 2008

본 논문은 유닛 모듈러를 구성하는 주구조체인 각형강관 기둥과 냉간성형 LEB C-형강 보가 볼트 접합된 접합부를 가진 모듈러 건물의 시공성을 평가하는 것이 연구의 목적이다. 모듈러 건축의 장점은 공사기간 단축, 경량성, 이동가능성 등으로 볼 수 있다. 반면에 유닛 또는 모듈의 운송비용이 공사비 절감 비용을 반감시킬 수 있고 많은 공장들이 외부 지역에 있으므로 이들을 도심지나 원하는 지역으로 이동하기 위해서는 비용이 추가된다. 그리고 유닛이나 모듈 설치에 크레인 등의 장비 사용으로 인해 시공비용이 증가될 수 있는 단점들이 존재한다. 본 연구에서는 앞서 연구한 모듈형상에 근거하여 해체조립이 용이한 모듈러 건축물의 시공사례를 통하여 공기, 비용 등 측면에서 기존 연구와 비교분석을 진행하여 모듈러 건물의 시공성을 평가하고자 한다.

• 대한지리학회지
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• 제49권3호
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• pp.357-370
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• 2014

이 연구는 미국의 기숙사 REITs 사례를 중심으로 대학생 기숙사의 확충을 위한 REITs의 활용 방안을 모색하는 것을 목적으로 한다. 이를 위해 첫째로, 미국의 기숙사 REITs의 사례를 분석하고, 둘째로, 이를 토대로 국내에서 대학생 기숙사 및 임대주택 확충을 위한 기숙사 REITs의 활용 가능성 및 활용 방안을 모색한다. 미국에서는 대학생 기숙사 투자와 운영에 REITs가 참여하고 있는데, 기숙사 REITs는 대학생 임대주택의 설계-개발-투자-관리운영-컨설팅을 복합적으로 담당하는 수직적으로 통합된 부동산 투자 운영회사로 역할하고 있다. 기숙사 REITs는 국내에서도 활용 가능성은 충분하지만, 투자전략과 자산관리전략이 수직적으로 결합된 전략을 모색해야 하고, 수익성을 보장하면서도 임대료 수준을 적정 수준 이하로 통제할 수 있는 방안들이 마련해야 한다. 이러한 맥락에서 REITs의 활용 방안으로 합작투자형 모델과 민간투자사업 연계형 모델을 제시한다.

• 대한기계학회논문집
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• 제13권6호
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• pp.1269-1281
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• 1989

본 연구에서는 H를 고정하고 L을 변화시켜가며 내부의 유동구조가 어떻게 변하는가를 살펴보고, 특히 재부착이 일어나는 경우에는 급확대 부분만 존재하는 기존 실험결과와 비교분석하여 하류의 급축소부분이 전체 유동구조에 어떤 영향을 미치는가를 살펴보고자 한다. 실험에서 사용된 작동유체는 공기이며, 입구관 직경은 110mm, 급확대점과 급축소점사이의 연결부 직경은 220mm, 연결부의 길이는 L=300, 600 그리고 900mm의 3가지를 선택하였으며 기준속도는 입구관의 중심속도로 9.71 m/s이다. 입구직경(110mm)을 기준으로 한 Reynolds 수는 $R_{e}$=73,000 이고 입구관반경과 연결부반경의 차이인 계단높이(H=55mm)를 기준으로 하면 $R_{e=36}$ ,500이다. 연결부 의 급확대부분에서 입구관반경을 기준으로 한 반경확대비는 2이고 급축소부분의 반경 축소비는 1/2이다. 측정항목은 유동방향의 벽면압력분포, 유동방향의 평균속도분포 및 난류강도 등이며, L=900mm인 경우는 반경방향과 원주방향의 난류강도, Reynolds 전단응력도 측정되었다.

• International Journal of CAD/CAM
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• 제3권1_2호
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• pp.19-29
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• 2003

Disassembly is a fundamental process needed for component reuse and material recycling in all assembled products. Integral attachments, also known as 'snap' fits, are favored fastening means in design for assembly (DFA) methodologies, but not necessarily a favored choice for design for disassembly. In this paper, design methods of a new class of integral attachments are proposed, where the snapped joints can be disengaged by the application of localized heat sources. The design problem of reversible integral attachments is posed as the design of compliant mechanisms actuated with localized thermal expansion of materials. Topology optimization technique is utilized to obtain conceptual layout of snap-fit mechanisms that realizes a desired deformation of snapped features for joint release. Two design approaches are attempted and design results of each approach are presented, where the geometrical configuration extracted from optimal topologies are simplified to enhance the manufacturability for the conventional injection molding technologies. To maximize the magnitude of deformation, a design scheme has been proposed to include boundary conditions as design variables. Final designs are verified using commercial software for finite element analysis.

• Computers and Concrete
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• 제21권4호
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• pp.441-449
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• 2018

FE models for complex or large-scaled structures that need detailed modeling of structural components are usually constructed using commercial analysis softwares. Updating of such FE model by conventional sensitivity-based methods is difficult since repeated computation for perturbed parameters and manual calculations are needed to obtain sensitivity matrix in each iteration. In this study, an FE model updating procedure avoiding such difficulties by using response surface (RS) method and a Pareto-based multiobjective optimization (MOO) was formulated and applied to FE models constructed with a commercial analysis package. The test building is a low-rise reinforced concrete building that has been seismically retrofitted. Dynamic properties of the building were extracted from vibration tests performed before and after the seismic retrofits, respectively. The elastic modulus of concrete and masonry, and spring constants for the expansion joint were updated. Two RS functions representing the errors in the natural frequencies and mode shape, respectively, were obtained and used as the objective functions for MOO. Among the Pareto solutions, the best compromise solution was determined using the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) procedure. A similar task was performed for retrofitted building by taking the updating parameters as the stiffness of modified or added members. Obtained parameters of the existing building were reasonably comparable with the current code provisions. However, the stiffness of added concrete shear walls and steel section jacketed members were considerably lower than expectation. Such low values are seemingly because the bond between new and existing concrete was not as good as the monolithically casted members, even though they were connected by the anchoring bars.

• 한국재료학회지
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• 제9권2호
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• pp.199-204
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• 1999

As the engine design change to get high efficiency and performance of commercial diesel engine, surface wear of the cam follower becomes an important issues as applied load increasing at the contact face between cam follower and cam. Purpose of this study is the developing of the ceramic cam follower made of silicon nitride ceramic which is more wear resistant than the cast iron and sintered cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel can follower body using active bracing alloy. Effect of joining condition on the interfacial phases and joining strength wer examined at bvarious joining temperatures, times, and cooling rates. Crowning resulted from the difference of thermal expansion coefficient after direct brazing without using any stress-relieving inter layer was measured. Interfacial phases are mainly titanium silicide and titanium nitride which are the products between active metal(Ti) in brazing alloy and silicon nitiride. Maximum joining strength of the ceramic metal joint, measured by DBS method, was 334MPa. Crowning(R) of the prototype ceramic cam follower was 1595mm. As machining for crowning is not necessary, production cost can be reduced.

• Journal of Welding and Joining
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• 제19권3호
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• pp.311-316
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• 2001

This paper presents that the affecting factors to the solderability and initial reliability. It is the factor that the coefficient of thermal expansion between package and PCB(Printed Circuit Board), the quantity of solder paste and reflow condition, and Au thickness of the solder ball pad on polyimide tape. As the reflow soldering condition for 48 ${\mu}BGA$ is changed, it is estimated that the quantity of Au diffusion at eutectic Sn-Pb solder surface and initial bonding strength of eutectic Sn-Pb solder and lead free solder. It is the result that quantitative measurement of Au diffusion quantity is difficult, but the shear strength of eutectic Sn-Pb solder joint is 842 mN at first reflow and increases 879 mN at third reflow. The major failure mode in solder is judged solder fracture. So, Au diffusion quantity is more affected by reflow temperature than by the reflow times.