• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.82-88
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• 2011

The artificial increase in the solar intensity incident on solar cells using lenses or mirrors can allow solar cells to generate equivalent power with a lower cost. There are two types of concentration optics for solar energy conversion. One is to use mirrors, and the other is to use Fresnel lenses. The gains that can be achieved with a Fresnel lens or a parabolic mirror are compared. The result showed the gains are comparable and the two configurations were developed competitively. In application areas of Fresnel lenses as solar concentrators, several variations of design were devised and tested. Some PV systems still use commercially available flat Fresnel lenses as concentrators. A convex linear Fresnel lens to improve the concentration ratio and the efficiency is devised and flat linear Fresnel lens in thermal energy collection is utilized. In this study, we designed and optimized flat Fresnel lens and the 'light pipe' to develop 500X concentrated solar PV system. In the process, we compare the transmission efficiencies according to groove types. We performed rigorous ray tracing simulation of the flat Fresnel lenses. The computer aided simulation showed the 'grooves in case' has the better efficiency than that of 'grooves out case'. Based on the ray-trace results we designed and manufactured sample Fresnel lenses. The optical performance were measured and compared with ray-trace results. Finally, the optical efficiency was measured to be above 75%. All the design and manufacturing were performed based on that InGaP/InGaAs/Ge triple junction solar cell is used to convert the photon energy to electrical power. Field test will be made and analyzed in the near future.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.26-49
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• 2018

The purpose of this study was to verify the reliability of the solar radiation model and discuss its applicability to the urban area of Seoul for summer heat stress mitigation. We extended the study area closer to the city scale and enhanced the spatial resolution sufficiently to determine pedestrian-level urban radiance. The domain was a $4km^2$ residential area with high-rise building sites. Radiance modelling (SOLWEIG) was performed with LiDAR (Light Detection and Ranging)-based detailed geomorphological land cover shape. The radiance model was evaluated using surface energy balance (SEB) observations. The model showed the highest accuracy on a clear day in summer. When the mean radiation temperature (MRT) was simulated, the highest value was for a low-rise building area and road surface with a low shadow effect. On the other hand, for high-rise buildings and vegetated areas, the effect of shadows was large and showed a relatively low value of mean radiation temperature. The method proposed in this study exhibits high reliability for the management of heat stress in urban areas at pedestrian height. It is applicable for many urban micro-climate management functions related to natural and artificial urban settings; for example, when a new urban infrastructure is planned.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.29-35
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• 2022

This paper proposes a fuel cell education framework installed on a Metaverse environment, which is to reduce the burden of education costs and improve the effect of education or learning. This Meta-Fuel cell platform utilizes the Unity 3D Web and enables not only theoretical education but also hands-on training. The platform was designed and developed to accommodate a variety of unit education contents, such as ppt documents, videos, etc. The platform, therdore, integrates ppt and video demonstrations for theoretical education, as well as software content "STACK-Up" for hands-on training. Theoretical education section provides specialized liberal arts knowledge on hydrogen, including renewable energy, hydrogen economy, and fuel cells. The software "STACK-Up" provides a hands-on practice on assembling the stack parts. Stack is the very core component of fuel cells. The Meta-Fuelcell platform improves the limitations of face-to-face education. It provides educators with the opportunities of non-face-to-face education without restrictions such as educational place, time, and occupancy. On the other hand, learners can choose educational themes, order, etc. It provides educators and learners with interesting experiences to be active in the metaverse space. This platform is being applied experimentally to a education project which is to develop advanced manpower in the fuel cell industry. Its improvement is in progress.

• Membrane Journal
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• v.32 no.1
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• pp.43-49
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• 2022

Solid-state supercapacitors with high safety and robust mechanical properties are attracting global attention as next-generation energy storage devices. As an electrode of a supercapacitor, an economical carbon-based electrode is widely used. However, when an aqueous electrolyte is introduced, the charge transfer resistance increases because the interfacial contact between the hydrophobic electrode surface and aqueous electrolyte is not good. In this regard, we propose a method to obtain higher electrochemical performance based on improved interfacial properties by treating the electrode surface with oxygen plasma. The surface hydrophilization induced by the enriched oxygen functionalities was confirmed by the contact angle measurement. As a result, the degree of hydrophilization was easily adjusted by controlling the power and duration of the oxygen plasma treatment. As the electrolyte of the supercapacitor, PVA/H₃PO₄, which is a typical solid-state aqueous electrolyte, was used. Free-standing membranes of PVA/H₃PO₄ electrolyte were prepared and then pressed onto the electrode. The optimal condition was to perform oxygen plasma treatment for 5 seconds with a low power of 15 W, and the energy density of the supercapacitor increased by about 8%.

• Korean Journal of Construction Engineering and Management
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• v.15 no.1
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• pp.111-121
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• 2014

The Clean Development Mechanism (CDM) allows New & Renewable Energy projects to make additional income by selling CER's, which represent the amount of Green House Gases(GHG) that is reduced in the project. However, forward contracts used to hedge fluctuating market prices does not allow projects to sell CER's at a premium. As an alternate approach to maximize CER revenue, CER's are modeled as a 'real option', in which CER's are sold only above the desired sales price. Using the Binomial Option Pricing model, the resultant lattices are used to determine whether to sell, defer or abandon the option at individual nodes. Overlaying Pascal's Triangle on the lattices also enabled the calculation of the annual probabilities for deferring CER sales without incurring downside losses. Application to an actual Landfill Gas project showed increased overall NPV, and that CER sales could be deferred at a maximum of 2 years. The proposed framework allows transparency in the analysis and provides valuable and strategical information when making investment decisions related to CER sales of CDM projects.

• Journal of the Korea Institute of Building Construction
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• v.11 no.3
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• pp.301-309
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• 2011

Apartment housings that adopt a bearing wall structure design, which account for a majority of the housing units available in Korea, are not free from structural constraints that limit the extension of their service life. The resulting need for reconstruction from the ground up requires a massive consumption of resources and energy, and triggers environmental pollution resulting from construction wastes. As a solution to such issues, the government enforces incentive schemes to promote a remodeling-friendly rahmen structure design. Green Frame, which is a novel concept of composite precast concrete structure to support rahmen structure apartment housing buildings, can address the constraints of bearing wall structure and conventional rahmen structure designs that limit the potential for remodeling projects, while reducing the term of construction. Therefore, this study aims to analyze the characteristics of Green Frame and its absolute term of construction, and compare the terms of frame work construction in apartment housing projects adopting different structural design approaches to illuminate their differences. In the end, Green Frame is found to be capable of reducing the term of construction in apartment housing projects. As the term of construction is a very critical element of a construction project, Green Frame will ultimately prove to be one of the key enablers to ensure the success of apartment housing construction projects.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.3
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• pp.445-457
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• 2013

This paper is about the study to build a quantitative methodology to assess cyber threats and vulnerabilities on control systems. The SCADA system in power industry is one of the most representative and biggest control systems. The SCADA system was originally a local system but it has been extended to wide area as both ICT and power system technologies evolve. Smart Grid is a concept to integrate energy and IT systems, and therefore the existing cyber threats might be infectious to the power system in the integration process. Power system is operated on a real time basis and this could make the power system more vulnerable to the cyber threats. It is a unique characteristic of power systems different from ICT systems. For example, availability is the most critical factor while confidentiality is the one from the CIA triad of IT security. In this context, it is needed to reflect the different characteristics to assess cyber security risks in power systems. Generally, the risk(R) is defined as the multiplication of threat(T), vulnerability(V), and asset(A). This formula is also used for the quantification of the risk, and a conceptual methodology is proposed for the objective in this study.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.63-69
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• 2003

90년대부터 많은 ERP를 도입하여 회사의 전체 업무를 통합시키고 실시간으로 모든 업무를 동시에 처리함에 따라 경영환경과 정보기술의 급격한 변화에 대처하고 있다. 이러한 ERP 시스템을 도입하던 기존의 업무 수행절차와 방법대신 ERP 패키지가 제공하는 프로세스와 기능을 적용하여 기업 내 업무기능을 혁신한다는 특징을 가지고 있어 조직변화를 수반하게 된다. 따라서 효과적인 ERP 구면을 위해서는 기업의 환경에 적절한 구축방법을 정하고 변화관리 이행 프로그램을 필요로 하고 있다. 본 연구에서는 ERP를 구축하는데 어떠한 조직적 환경요인이 영향을 미지고. ERP 구축방법에 따라 변화관리의 특성이 어떻게 달라지며. 변화관리가 ERP 성과에 어떠한 영향을 미치는지 파악하기 위한 프레임워크를 제시하고 이틀 근간으로 하여 상이한 구축방법을 통하여 ERP틀 구면탄 두 기업을 대상으로 심도있게 비교 분석함으로써 ERP 구축환경의 특성과 ERP 구축방법에 따른 변화관리 특성 및 ERP성과를 살펴보았다. 연구결과 ERP 구축방법은 ERP 구축환경에 따라 차이를 보였으며, ERP 구축 방법에 따라서 변화기법이 달라진다는 사실을 알 수 있었다. 그러나 변화관리 방법 중에서도 최고 경영자의 리더십과 현업 직원의 적극적인 참여 및 전사적인 커뮤니케이션은 ERP 구축방법과 관계없이 중요한 요인으로 나타났다. 그리고 ERP 구축방법에 있어서 변화관리 활동은 ERP 성과에 긍정적인 영향을 미쳤다. 본 사례연구로 얻은 시사점은 ERP의 구현하고자 하는 국내 기업들이 ERP 구축방법을 선정하고 적합탄 변화관리 방법의 전개를 위하여 실질적인 도움을 줄 것이다.6 전문가 그룹을 통해 시범적으로 적응하는 것으로 시작해, 학교 및 연구소를 통한 정보지식 공유 그리고 기업 정보화 솔루션으로 활용 될 수 있다.을 제시한다. 이렇게 함으로써 최대한 고객 납기를 만족하도록 계획을 수립할 수 있게 된다. 본 논문에서 제시하는 계획 모델을 사용함으로써 고객 주문에 대한 대응력을 높일 수 있고, 계획의 투명성으로 인한 전체 공급망의Bullwhip effect를 감소시킬 수 있는 장점이 있다. 동시에 이것은 향후 e-Business 시스템 구축을 위한 기본 인프라 역할을 수행할 수 있게 된다. 많았고 년도에 따른 변화는 보이지 않았다. 스키손상의 발생빈도는 초기에 비하여 점차 감소하는 경향을 보였으며, 손상의 특성도 부위별, 연령별로 다양한 변화를 나타내었다.해가능성을 가진 균이 상당수 검출되므로 원료의 수송, 김치의 제조 및 유통과정에서 병원균에 대한 오염방지에 유의하여야 할 것이다. 확인할 수 있었다. 이상의 결과에 의하면 고농도의 유기물이 함유된 음식물쓰레기는 Hybrid Anaerobic Reactor (HAR)를 이용하여 HRT 30일 정도에서 충분히 직접 혐기성처리가 가능하며, 이때 발생된 $CH_{4}$를 회수하여 이용하면 대체에너지원으로 활용 가치가 높은 것으로 판단된다./207), $99.2\%$(238/240), $98.5\%$(133/135) 및 $100\%$ (313)였다. 각각 두 개의 요골동맥과 우내흉동맥에서 부분협착이나 경쟁혈류가 관찰되었다. 결론: 동맥 도관만을 이용한 Off pump CABG를 시행하여

• Journal of the Korea Institute of Building Construction
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• v.10 no.1
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• pp.57-63
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• 2010

The bearing wall apartments which occupy the majority of multi-residential apartment buildings built in Korea, are known for having limited architectural plan flexibility, posing challenges in terms of maintenance and remodeling. The economic losses and environmental issues resulting from the reconstruction of bearing wall apartments are now accumulating to the extent that they are becoming a national concern. Multi-residential apartment buildings, which are now the dominant form of residence in Korea, must accommodate diverse customer needs and changes in life style. A new concept of Rahmen structure with architectural flexibility is Green Frame. GF multi-residence housing is expected to reduce construction costs and shorten the construction schedule by overcoming the shortcomings of conventional bearing wall apartments. This goal is consistent with the national policies that target the reduction of resource and energy consumption. In addition, GF will be established as a core contributor to achieving a reduction in $CO_2$ emissions, which will enable the sustainable growth of domestic construction industry, and address the low-carbon green growth drive implemented by the government.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2000.11a
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• pp.407-416
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• 2000

국방 부문에 종사하는 관리자들은 국방정보시스템 사업관리에 있어서 최신정보기술에 대한 기본적인 사항은 알고있어야 효율적이고 효과적이며 성공적인 사업관리를 진행할 수 있을 것이다. 국방 부문에 종사하는 관리자들이 저비용 고효율의 국방정보시스템을 건설하고 운영 유지관리 하기 위하여 알아야 할 핵심 및 최신정보기술은 크게 인공지능기술, 멀티미디어 정보화 기술, 가상현실 기술, 시뮬레이션 기술, 텔레프레즌스 기술, 나노테크놀로지 기술, 데이터베이스 기술, 병렬처리 기술, 로봇공학 기술, 소프트웨어 공학에 관련된 기술 등이 있다. 그러나 국방부문에 종사하는 정보통신 전문 인력을 제외한 관리자들이 국방관련 사업관리를 수행하면서 정보기술에 대한 이해 수준이 비교적 낮기 때문에 효율적으로 국방사업을 준비, 계획, 추진하기 어려운 실정이다. 따라서 국방부문에 종사하는 관리자들이 정보기술을 알기 쉽게 이해할 수 있도록 국방부문 핵심지능형정보기술 발전 및 군 활용방안을 이해하기 쉽도록 작성하며 효율적인 사업관리가 이루어질 수 있는 방안을 연구하였다. 본 논문은 국방부문핵심 지능정보기술 식별 및 활용방안을 연구하여 핵심적으로 식별된 사항들을 우리 국방부문의 $C^4$I(지휘, 통제, 통신, 컴퓨터시스템)시스템, 내장형 무기시스템, 각종 교육훈련 정보시스템, 자원관리 정보시스템 등에 어떻게 적용할 것이며 적용시 기대효과는 무엇인가를 제시토록 하여 국방부문에 종사하는 관리자들이 각종 국방사업을 조정, 통제, 확인, 감독, 준비/계획하면서 참고하여 저비용 고효율의 국방관련 각층 사업을 관리할 수 있는 능력을 배양시키도록 연구를 수행하였다. 국방관련 각종 사업을 관리할 수 있는 능력을 배양시키도록 연구를 수행하였다. 국방부문 핵심지능정보기술 발전 및 활용 방안에 포함될 주요 내용을 요약하여 제시하였다.의 경향성을 나타내는 오차 주기(error cyc1e)를 이용함으로써 고객들의 수요의 경향성을 좀 더 세밀한 부분까지 파악할 수 있게 해 준다.ction, secondary electron microscopy, atomic force microscoy, $\alpha$-step, Raman scattering spectroscopu, Fourier transform infrared spectroscopy 및 micro hardness tester를 이용하여 기판 bias 전압이 DLC 박막의 특성에 미치는 영향을 조사하였다. 분석결과 본 연구에서 제작된 DLC 박막은 탄소와 수소만으로 구성되어 있으며, 비정질 상태임을 알 수 있었다. 기판 bias 전압의 증가에 따라 박막의 두께가 감소됨을 알 수 있었고, -150V에서는 박막이 거의 만들어지지 않았으며, -200V에서는 기판 표면이 식각되었다. 이것은 기판 bias 전압과 ECR 플라즈마에 의한 이온충돌 효과 때문으로 판단되며, 150V 이하에서는 증착되는 양보다 re-sputtering 되는 양이 더 많을 것으로 생각된다. 기판 bias 전압을 증가시킬수록 플라즈마에 의한 이온충돌 현상이 두드러져 탄소와 결합하고 있던 수소원자들이 떨어져 나가는 탈수소화 (dehydrogenation) 현상을 확인할 수 있었으며, 이것은 C-H 결합에너지가 C-C 결합이나 C=C 결합보다 약하여 수소 원자가 비교적 해리가 잘되므로 이러한 현상이 일어난다고 판단된다. 결합이 끊어진 탄소 원자들은 다른 탄소원자들과 결합하여 3차원적 cross-link를 형성시켜 나가면서 내부 압축응력을 증가시키는 것으로 알려져 있으며, hardness 시험 결과로 이것을 확인할 수 있었다. 그리고 표면거칠기는 기판 bias 전압을 증가시킬수록 더 smooth 해짐을 확인