• 동력기계공학회지
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• 제8권4호
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• pp.49-56
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• 2004

To design very large ships, such as very large drillships, we have to estimate the hydroelastic responses of the very large ships in waves. A numerical procedure is described for estimating the hydroelastic responses of very large ships advancing with slow speed in waves. The developed numerical approach is based on a combination of the three-dimensional source distribution method and the finite element method, including fluid-structure interaction by regarding a very large ship as many hull elements connected with elastic beam elements. Numerical results are compared with experimental and numerical ones obtained in the literature. The results of comparison confirmed the validity of the proposed approach.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.399-405
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• 2014

For stable integration of large-scale wind farms, integration standards (Grid codes) have been proposed by the system operator. In particular, voltage control of large-scale wind farms is gradually becoming important because of the increasing size of individual wind farms. Among the various voltage control methods, Secondary Voltage Control (SVC) is a method that can control the reactive power reserve of a control area uniformly. This paper proposes hybrid SVC when a large-scale wind farm is integrated into the power grid. Using SVC, the burden of a wind turbine converter for generating reactive power can be reduced. To prove the effectiveness of the proposed strategy, a simulation study is carried out for the Jeju system. The proposed strategy can improve the voltage conditions and reactive power reserve with this hybrid SVC.

• ETRI Journal
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• 제44권5호
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• pp.780-793
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• 2022

Large-scale ontology management is one of the main issues when using ontology data practically. Although many approaches have been proposed in relational database management systems (RDBMSs) or object-oriented DBMSs (OODBMSs) to develop large-scale ontology management systems, they have several limitations because ontology data structures are intrinsically different from traditional data structures in RDBMSs or OODBMSs. In addition, users have difficulty using ontology data because many terminologies (ontology nodes) in large-scale ontology data match with a given string keyword. Therefore, in this study, we propose a (graph database-based ontology management system (GOMS) to efficiently manage large-scale ontology data. GOMS uses a graph DBMS and provides new query templates to help users find key concepts or instances. Furthermore, to run queries with multiple joins and path conditions efficiently, we propose GOMS encoding as a filtering tool and develop hash-based join processing algorithms in the graph DBMS. Finally, we experimentally show that GOMS can process various types of queries efficiently.

• 시큐리티연구
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• 제61호
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• pp.203-234
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• 2019

최근 협력업체의 기술유출로 인하여 고객사인 대기업의 경영에 위험을 초래하고 나아가 이미지와 신뢰도가 추락하는 등 보안사고 피해가 지속적으로 증가하고 있다. 그러나 현대 산업구조는 대기업의 독자적인 기업형태는 현실적으로 불가능하고 협력업체와의 전략적 제휴가 필수적이라 할 수 있는데 이에 따른 정보의 교환이 증가되고 정보시스템의 사무의존도가 극대화됨은 물론 업무프로세스의 복잡화와 보안관련 법률의 강화에 따른 법적 요구와 이해관계자의 요구사항이 증대되고 있는 산업구조 형태로 변화되고 있다. 중소기업의 기술보호 실태를 보면 대기업에 비하여 상대적으로 열악한 환경과 재정적 어려움으로 인하여 보안체계를 갖추지 못하고 있는 실정인데 반하여 대기업과 중소 협력 업체간의 산업구조가 IT시스템 공유가 필수 불가결하여 중소협력업체의 보안수준 향상없이는 고객사인 대기업의 보안관리는 불가능한 현실을 감안하여 고객사인 대기업과 중소협력업체 간의 보안체계구축 인증제도를 도입하므로써 대기업에 비하여 열악한 보안수준을 향상하여야 하는 시점이다. 이에 그간의 대중소기업 동반성장을 위한 제도와 여러 기관의 정보보호 역량 평가 모형을 살펴보고, 중소협력업체 인증제도 도입 방안을 제시하고자 한다.

• 전력전자학회논문지
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• 제11권6호
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• pp.535-542
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• 2006

저궤도 인공위성 전력계 시스템의 설계 및 해석을 위한 태양전지 전력조절기의 대신호 안정도해석을 수행한다. 태양전지 전력조절기에서 제어가능한 모든 방법에 따른 태양전지에서 바라본 태양전지 전력조절기의 부하특성을 분류하고, 상태공간해석을 이용하여 태양전지 시스템의 대신호적 안정도를 해석한다. 또한, 본 논문에서는 태양전지 전력조절기의 부하특성을 정전력부하에서 정저항부하로 변환하여 대신호적인 안정도를 확보하는 비선형변환을 제안한다. 제안된 변환기법을 통해 최대전력점 추적제어나 배터리 충전제어 및 전류분배제어가 가능한 병렬 모듈 태양전지 레귤레이터에 적합한 단일 전류 제어기를 구성한다. 제안된 대신호 해석과 저항제어를 검증하기위해, 200W급 태양전지와 100W급 태양전지 전력조절기 두 모듈을 병렬로 구성하여 실험하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.588-591
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• 2009

Ground source heat pump system; GSHPs is close to most practical use for early stage investment cost and energy efficiency in new renewable energies, and currently considered utilizing to the heat and cooling system of a building. Particularly, the case to utilize 'Standing Column well heat source gathering method' in the open standards process to have the excellent capability of gathering geothermal source is increased. But the research for the optimal design technology and the assessment of a pollution level of the ground to utilize a single well for gathering geothermal is insignificant and the design is insufficient. The heating and cooling system and the equipment to utilize a large size residential development to have over 1000 households have not developed yet. Therefore, our company developed 'geothermal hybrid system' which can construct the heat and cooling system using geothermal energy for a large size residential development of over 1000 households and conducted the evaluation of economic feasibility. Moreover we developed automatic equipment for gathering geothermal source and PLC (Programmable logic controller) to have optimal efficiency and FCU (fan coil unit) considering the floors of large size apartments.

• 로봇학회논문지
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• 제13권1호
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• pp.38-44
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• 2018

In this paper, we propose Intelligent Driver Assistance System (I-DAS) for driver safety. The proposed system recognizes safety and danger status by analyzing blind spots that the driver cannot see because of a large angle of head movement from the front. Most studies use image pre-processing such as face detection for collecting information about the driver's head movement. This not only increases the computational complexity of the system, but also decreases the accuracy of the recognition because the image processing system dose not use the entire image of the driver's upper body while seated on the driver's seat and when the head moves at a large angle from the front. The proposed system uses a convolutional neural network to replace the face detection system and uses the entire image of the driver's upper body. Therefore, high accuracy can be maintained even when the driver performs head movement at a large angle from the frontal gaze position without image pre-processing. Experimental result shows that the proposed system can accurately recognize the dangerous conditions in the blind zone during operation and performs with 95% accuracy of recognition for five drivers.

• 설비공학논문집
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• 제21권6호
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• pp.355-366
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• 2009

In the present study, fuel cell driven ground source heat pump system is applied to a large community building and performance of the heat pump system is computationally analyzed. Conduction heat transfer between brine pipe and ground is analyzed by TEACH code to predict the performance of heat pump system. Predicted COP of the heat pump system and the energy cost were compared with variation of the location of the objective building the water saturation rate of soil and the driven powers of heat pump system. Significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system in comparison with the late-night electricity driven system. It is due to the low electricity production cost of fuel cell system and the application of recovered waste heat generated during electricity production process to the heating of large community building.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.28-31
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• 2002

Filmless full-PACS in korea has rapidly been growing, since government had supported collaborative PACS project between industry and university hospital in late of 1995. At the same time, a small company had started PACS business, while the Korea PACS society was being formed. In the beginning, PACS societies had focused on developing peripheral solutions such as DICOM gateway for image acquisition, x-ray film digitizer, and viewing software for research or management of personal image data, while Samsung Medical Center had started installing an imported partial PACS system which had recently upgraded with a new system. In similar time frame, a few hospitals had started developing and installing domestic large scale full-PACS system. Several years later, many hospitals have installed full-PACS system with national policy of reimbursement for PACS exams in November 1999. It is believed that Korea is the first country that adopted PACS reimbursement for filmless full-PACS as a national policy. Both experiences of full-PACS installation and national policy generated tremendous intellectual and technological expertise about PACS at all levels, clinical, hospital management, education, and industrial sectors. There are currently three types of PACS system which includes domestic, imported, and hybrid PACS system with imported solution for core system and domestic solution for peripheral system. There are more than 20 domestic PACS companies and they have now enough experiences so that they are capable of installing a truly full-PACS system for large-scale teaching hospitals. PACS societies in Korea understand how to design, implement, install, manage, sustain, and provide good services for large-scale full-PACS. PACS society has also strength for the highest integration technology of the Hospital Information. However, further understanding and timely implementation of continuously evolving international standard and integrated healthcare enterprise concepts may be necessary for international leading of PACS technologies for the future.

• 소음진동
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• 제4권3호
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• pp.327-335
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• 1994

In this paper, to identify the dynamic characteristics of antenna system, the antenna is divided into 4 components and those were analyzed with a conventional FEM package MSC/NASTRAN. Using a Component Mode Synthesis Method, dynamic characteristics of total system is also identified. The Coherence of each component to total system is evaluated by using strain and kinetic component to total system is evaluated by using strain and kinetic energy. The improving strategy of dynamic characteristics is suggested by changing mass and stiffness of large coherence components.