• Spatial Information Research
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• 제16권3호
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• pp.279-290
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• 2008

자연재해로 인한 수많은 피해 중 특히 산사태 등 사면붕괴로 인한 피해는 인간에게 많은 인적/물적 자원의 손실을 가져왔다. 이런 사면붕괴로 인한 피해를 줄이고자 사면붕괴 예방을 위해 다양한 계측장비를 이용하여 사면붕괴 예 경보 시스템을 구축하였다. 하지만 대상사면에 접근성 문제를 해결하고 위험 사면 전체에 대한 안전성 평가를 실시할 수 있는 효율적인 계측장비는 많지 않은 실정이다. 이에 사면붕괴예방을 위한 효율적인 계측장비로서 측량학적인 접근 방법으로 사면거동의 정확한 계측을 위해 지상라이다시스템을 이용하여 사면붕괴 예방을 위한 시스템의 활용가능성 판단을 위한 실험을 실시하였다. 본 연구에서는 인공으로 조성되어 사면안정화 공법이 적용된 토사사면에 사면상부에서 단계별로 실물 하중을 가하여 하중에 따른 사면의 거동을 Total Station과 지상라이다시스템을 이용하여 계측하였다. 두 시스템을 이용하여 계측한 성과의 정확한 비교 분석을 위해 두 시스템의 계측 결과를 동일한 좌표계로 일치시키는 3D Similarity Transformation을 통해 서로 다른 좌표계를 가지고 있는 두 좌표계를 하나의 좌표계로 통일시켜 사면이 실물하중에 어떤 거동이 일어나는지를 분석하였다. 타켓중심의 사면거동 분석결과, 지상라이다 시스템은 Total Station과 비교해 X축으로는 1cm이내의 차이가, Y축으로는 규칙적이지 않는 거동의 경향이 발생하고, Z축으로는 서로 유사한 경향을 보였다. 연속된 점에 대한 사면지동 분석결과, Y축의 위치에 따라 사면 하부에서 상부의 방향으로 사면거동의 경향이 다르게 나타나 Total Station에서 분석하기 어려웠던 사면의 연속적인 변화를 관찰할 수 있었다. 따라서 지상라이다 시스템은 Total Station에 버금가는 측량성과를 획득하여 효율적인 사면모니터링을 위한 계측장비로 판단되었으며 기존의 사면모니터링기법의 한계를 대체 할 수 있는 측량학적 분석방법으로 많은 활용이 기대된다.

• 소성∙가공
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• 제18권7호
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• pp.565-571
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• 2009

This paper is concerned with the analysis on the surface stress profiles of perfectly plastic material in backward extrusion process. Due to heavy surface expansion appeared usually in the backward extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the analyses have focused to reveal the surface conditions at the contact boundary for various punch shapes in terms of surface expansion, contact pressure, and relative movement between punch and workpiece which consists of sliding velocity and distance, respectively. Punch geometries adopted in the analysis include concave, hemispherical, pointed and ICFG recommended shapes. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward extrusion process under different punch geometries. The simulation results are summarized in terms of surface expansion, contact pressure, sliding velocity and sliding distance at different reduction in height, deformation patterns, and load-stroke relationship, respectively.

• Spatial Information Research
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• 제11권4호
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• pp.509-518
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• 2003

토양의 포장은 도시의 기후나 홍수 그리고 수질오염 등에 영향을 미친다. 토양의 포장률이 높아질수록 건물과 도로의 열 저장능력이 커져 대기의 온도가 상승하며, 유출수가 증가하여 집중호우시 홍수를 유발한다. 아울러 비점오염의 부하량이 늘어나서 수질오염을 가중시킨다. 이와 같이 도시의 생태, 재해 그리고 오염에 영향을 미치는 토양의 포장현황을 파악하고 모니터링하는 것은 매우 중요하다. 그러나 도시지역의 토양포장 상태는 복잡하며, 이를 조사하는데 시간과 비용이 많이 소요되기 때문에 자료를 얻기가 매우 어려운 실정이다. 이와 같은 문제인식 하에서, 이 연구에서는 효과적으로 불투수지표면을 조사하는 방법의 하나로서 인공위성영상자료를 이용하는 방법을 모색하였다. 이 연구에서는 실제로 IKONOS 영상을 이용하여 안양시의 불투수지표면(不透水地表面)의 현황을 조사 분석하고, 이 방법의 유용성과 한계를 살펴보았다.

• Environmental Engineering Research
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• 제15권3호
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• pp.167-172
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• 2010

The effects of low impact development (LID) techniques, such as green roofs and porous pavements, on the runoff and pollutant load from an apartment complex were simulated using the Site Evaluation Tool (SET). The study site was the Olympic Village, a preexisting apartment complex in Seoul, South Korea, which has a high percentage of impervious surfaces (approximately 72% of the total area). Using the SET, the effects of replacing parking lots, sidewalks and driveways (37.5% of the total area) having porous pavements and rooftops (14.5% of the total area) with green roofs were simulated. The simulation results indicated that LID techniques reduced the surface runoff, and peak flow and pollutant load, and increased the evapotranspiration and soil infiltration of precipitation. Per unit area, the green roofs were better than the porous pavements at reducing the surface runoff and pollutant loads, while the porous pavements were better than green roofs at enhancing the infiltration to soil. This study showed that LID methods can be useful for urban stormwater management and that the SET is a useful tool for evaluating the effects of LID on urban hydrology and pollutant loads from various land covers.

• 대한조선학회논문집
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• 제47권5호
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• pp.697-702
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• 2010

A WIG(Wing-In-Ground effect) craft flies close to the water surface by utilizing a cushion of relatively high pressurized air between its wing and water surface. This implies that when one designs such craft it is important to have lightweight structures with adequate strength to resist external loads with some margins. To investigate this requirement, this paper deals with the structural analysis of the bottom plate of small WIG craft having a design landing weight of 1.2-ton. As building materials for the WIG craft, pre-preg carbon/epoxy composites are considered. The strength information of the bottom plate is obtained using the first-ply-failure analysis in conjunction with a mid-plane symmetric laminated plate theory. As a result, the first-ply-failure location, load and deflection of the bottom plate are obtained. The calculated strength information is compared with the water reaction load for the bottom plate of seaplanes considered when they land on the water surface -the same fluid-structure interaction mechanism as that of WIG craft. In the calculation of seaplane water reaction load information, the rules shown in FAR(Federal Aviation Regulations) Part 25 are used. Through the comparison, the structural integrity of the bottom plate for the WIG craft is checked.

• 콘크리트학회논문집
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• 제11권6호
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• pp.79-88
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• 1999

In this paper, the electro-deposition method for the rehabilitation of cracked concrete, based on the electro-chemical technique, is presented. The main purpose of this paper is to apply this technique to reinforced concrete members on land. After cracking with a specified load(crack width 0.5mm), 10$\times$10$\times$20cm concrete specimens with embedded steel bars were immersed in several solutions, then a constant current density between the embedded steel in concrete and an electrode in the solution was applied for 4~20 weeks. The results indicate that electro-deposits formed in this process are able to close concrete cracks and to coat the concrete surface and that formation of these electro-deposits is confirmed to have an effect of protection against detrimental materials. Therefore, it is demonstrated that the electro-deposition method can be usefully applied for the rehabilitation technique of concrete.

• 소성∙가공
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• 제16권7호
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• pp.521-529
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• 2007

This paper is concerned with the analysis on the surface expansion of AA 2024 and AA 1100 aluminum alloys in backward extrusion process. Due to heavy surface expansion appeared usually in the backward can extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the surface expansion is analyzed especially under various process conditions. The main goal of this study is to investigate the influence of degree of reduction in height, geometries of punch nose, friction and hardening characteristics of different aluminum alloys on the material flow and thus on the surface expansion on the working material. Two different materials are selected for investigation as model materials and they are AA 2024 and AA 1100 aluminum alloys. The geometrical parameters employed in analysis include punch corner radius and punch nose angle. The geometry of punch follows basically the recommendation of ICFG and some variations of punch geometry are adopted to obtain quantitative information on the effect of geometrical parameters on material flow. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward can extrusion process under different geometrical, material, and interface conditions. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including pressure distributions along the interface between workpiece and punch, comparison of surface expansion between two model materials, geometrical and interfacial parametric effects on surface expansion, and load-stroke relationships.

• 한국기계가공학회지
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• 제18권11호
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• pp.9-17
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• 2019

Interest in renewable energy is rapidly growing around the world. One of the most popular renewable energy sources is solar power, and photovoltaic (PV) systems are the most representative route for generating solar energy. However, with the growing adoption of solar power systems, the demand for land on which to install these systems has increased, which has caused environmental degradation. Recently, floating PV systems have been designed to utilize idle water surface areas of dams, rivers, and oceans. Because floating PV systems will be exposed to harsh environmental stresses, the safety of such systems should be secured before installation. In this study, the structural robustness of a floating PV system was analyzed by conducting numerical simulation to investigate whether the system can withstand harsh environmental stresses, such as wind and wave loads. Additionally, conventional wind and wave load predictions based on the design method and the simulation results were compared. The comparison revealed that the design method overestimated wind and wave loads. The total drag of the PV system was significantly overestimated by the conventional design criteria, which would increase the cost of the mooring system. The simulation offers additional advantages in terms of identifying the robustness of the floating PV system because it considers real-world environmental factors.

• 전기학회논문지P
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• 제58권4호
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• pp.568-573
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• 2009

Because of environmental crisis, researchers are seeking and developing a new, clean, safe and renewable energy. Solar cell energy and fuel cell energy have inestimable development potential. The paper introduces hybrid photovoltaic-fuel cell generation systems supplying a remote power load and hybrid system of solar cell and fuel cell considering the advantages of stable and sustainable energy from the economic point of view. Fuel cell power system has been proven a viable technology to back up severe PV power fluctuations under inclement weather conditions. Fuel cell power generation, containing small land us, is able to alleviate the heavy burden for large surface requirement of PV power plants. In addition, the PV-fuel cell hybrid power system shows a very little potential for lifetime $CO_2$ emissions. In this paper shows the I-V characteristics of the solar module which are dependent on the power of the halogen lamp and the I-V characteristics of fuel cells which are connected in parallel. Also, it shows efficiency of the hybrid system.

• 한국태양에너지학회 논문집
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• 제30권6호
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• pp.59-65
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• 2010

Analysis on turbulence intensity profile depending on wind speed is an important process to set up design condition of wind turbine in terms of fatigue load. This paper tests goodness of fit of turbulence intensity empirical equations suggested by the IEC 61400 Standards with Jejudo Gimnyeong met-tower measurement, which is erected at a seashore. Therefore sea breeze and land breeze coexist. Sea breeze case showed apparent increasing trend of turbulence intensity in a high wind speed regime due to increase of sea surface roughness. However, neither inland wind turbine standard IEC 61400-1 nor offshore wind turbine standard IEC 61400-3 fit such a trend adequately. On the other hand, the modified empirical equation of turbulence intensity of IEC 61400-3 derived from Germany FINO1 application study by considering turbulence intensity behavior in a high wind speed regime showed good agreement with the measurement. Therefore, we can reconfirm and conclude that IEC 61400-3 Ed.1 legislated in 2009 needs to be modified.