• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1407-1412
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• 2004

Impedance calculations of electric railway traction systems is essential to define characteristics and to design it. The self impedance is defined voltage drop rate per unit length, the mutual impedance is represented as a voltage induced to transmission line from transmission line. The self and the mutual impedance are influenced by ground return currents. The earth is considered as a semi-infinitely extended non-ideal conductor. The current of transmission line produces earth current induced magnetically and it flow through a path having minimum impedance. Carson proposed the impedance calculation formula using wave equations and magnetic field equations. Though the formula have an improper equation, that is still used as a standard impedance calculation method. This paper introduced an impedance calculation method that the complex depth of earth return method assumes that the current in conductor returns through an imagined earth depth path located directly under original conductor at a depth of. In this paper, we showed that this proposed method has a closed form and is easier than Carson's.

• Nuclear Engineering and Technology
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• 제37권2호
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• pp.151-158
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• 2005

Advanced nuclear power plants are generally large complex systems automated by computers. Whenever a rare plant emergency occurs the plant operators must cope with the emergency under severe mental stress without committing any fatal errors. Furthermore, The operators must train to improve and maintain their ability to cope with every conceivable situation, though it is almost impossible to be fully prepared for an infinite variety of situations. In view of the limited capability of operators in emergency situations, there has been a new approach to preventing the human error caused by improper human-machine interaction. The new approach has been triggered by the introduction of advanced information systems that help operators recognize and counteract plant emergencies. In this paper, the adverse effect of automation in human-machine systems is explained. The discussion then focuses on how to configure a joint human-machine system for ideal human-machine interaction. Finally, there is a new proposal on how to organize technologies that recognize the different states of such a joint human-machine system.

• 전자공학회논문지S
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• 제34S권3호
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• pp.33-45
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• 1997

In this paper, we propsoe a new method of th ecommunication system for cooperative behaviors and works in collective autonomous mobile robots. A communication function among the collective robots is essential to intelligent cooperative works. In genral, global communication is effective for small number of robots. However when the number of robot goes on increasing, this becomes difficult to be realized because of limited communication capacity and increasing amount of information to handle. And also the problems such as communciation interfeence and improper message transmission occur. So we propose local communication system based on infrared sensor to realize the cooperative behavior among robots as the solution of above problem. It is possible to prevent overflow of information and exchange of complex information by fusion sign board model which transmits the information to unspecified robots and message passing model which communicate a specific robot. And we formularize optimal communication range by analysis of information propagation mechanism from the proposed comunication system. At last we verify the effectiveness of the proposed communication system from example of cooperative works.

• 전산구조공학
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• 제7권4호
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• pp.137-144
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• 1994

기존 대형구조물의 안전진단에 관련하여 구조계의 동적계수를 실험적으로 추정하는 방법이 연구되었다. 시간영역방법인 순차적 예측오차방법과 주파수영역의 방법인 주파수응답함수 추정법이 비교검토되었다. 기법의 검증은 2 Bay 3층 구조물 모형에 대해서 수행되었는데, 각 실험적 방법에 의한 추정결과는 일관된 추정치를 보이었다. 그러나, 유한요소법에 의한 결과와는 차이를 보이었다. 이 차이는 구조해석시 절점조건에 대한 부적절한 모형화에 기인한 것으로 사료된다.

• 한국실내디자인학회논문집
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• 제29호
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• pp.94-102
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• 2001

The urban land is incapacitated to grow and correspond to demand the space in urban area. And recently, rapid increasing of population and complex of urban function on pushed to develop the underground space. In Korea, the underground space development in inefficient in aspect. because development of underground space have not consistent and systematic planning method in underground environment inclounding interion design, extererior design. Therefore this study is suggested the design element for comfortable underground living environment and assortment on utilization of underground space. The results of this study on utilization are security of space through land use efficiency, conservation of historical place, building and natural environment, and technological characteristics, mental image. Accordingly, this study is proposed design element that make comfortable underground space as aspect from stimulation and diversity, sapciousness and feeling of warmth and dryness to compensate improper image of underground space, spacial orientation and way finding.

• 한국태양에너지학회 논문집
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• 제32권spc3호
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• pp.185-193
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• 2012

Recently rapid urbanization facilitates development of high-rise building complex including apartment and office building in urban area. Many problems related with high -rise building are reported. Especially, unpleasant strong winds in pedestrian area are frequently encountered around the high-rise building. CFD simulation methods are used to analyze the wind environment of pedestrian level in high-rise building block. However, the results show differences between CFD and measurement. This difference is attributed to improper use of CFD. Conventional CFD simulation for wind environment around high-rise building does not describe the effect of trees, shrubs and plants near ground which affect the wind environment of pedestrian level. Canopy model can be used to reproduce the aerodynamic effects of trees, shrubs and plants near ground. In this paper, CFD simulation methods coupled with the tree canopy model to predict wind environment of pedestrian level in high-rise residential building block were suggested and the validity was analyzed by comparison between measurement and CFD results.

• Journal of Welding and Joining
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• 제14권6호
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• pp.58-67
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• 1996

The horizontal filet welding is prevalently used in heavy and ship building industries to join the parts. The phenomena occurring in the horizonal fillet welding process are very complex and highly non-linear, so that its analysis is relatively difficult. Furthermore, various kinds of weld defect such as undercut, overlap, porosity. excess weld metal and incomplete penetration can be induced due to improper welding conditions. Among these defects, undercut, overlap and excess weld metal appear frequently in horizontal filet welding. To achieve a satisfactory weld bead geometry without weld defects, it is necessary to study the effect of welding conditions in the weld bead geometry. For analyzing the weld bead geometry with and without weld defects in horizontal fillet welding, a mathematical model was proposed in conjunction with a two-dimensional heat flow analysis adopted for computing the melting tone in . base metal. The reliability of the proposed model was evaluated through experiments. which showed that the proposed model was very effective for predicting the weld bead shape with or without weld defects in horizontal fillet welding.

• 한국항공운항학회지
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• 제22권2호
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• pp.34-39
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• 2014

Airworthiness authorities specify the technical standards of airworthiness that propose minimum requirement of the commercial transport category and apply the rules in the certification process to ensure the safety of the aircraft. The Federal Aviation Administration and other national airworthiness authorities define the fatal accident risk levels for the safety assessment of the aircraft system and establish standard procedures to apply both qualitative and quantitative analysis techniques. However, an accident or incident may occur by the combination of various factors, although the aircraft is designed in accordance with the strict standards and approval by the Airworthiness Authorities. There are some key factors, such as human error, unpredictable complex system failures, degradation of the components reliability, improper maintenance task and intervals. Risk can be reduced by reflecting aircraft operational experience with similar types of aircraft in the process of aircraft development and safety assessment. Result of the root cause analysis for the Airbus A300-600 incident in which the aircraft engine reverser was deployed in the air have been introduced to reflect the design of system and related components. Also, this paper suggests to create a big-database in order to provide a feed-back to the FAR Part 25 transport category design and safety assessment of the operational experience.

• Journal of Astronomy and Space Sciences
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• 제15권2호
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• pp.459-473
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• 1998

인공위성이 더욱 복잡해 감에 따라 예측할 수 없는 실패의 발생은 설계의 부적당성, 경험 부족, 문제인식 부족, 빈약한 품질제어 능력, 부적당한 시험 또는 작업자의 실수 등 때문에 늘어나고 이들은 위성의 임무 수명을 단축시킬 수 있다. 본 고에서는 위성의 일반적인 실패유형과 임무수명 인자에 대해 검토하고, 지구 및 해양관측 임무를 갖고 있는 태양동기 저궤도위성인 다목적 실용위성에 대한 임무수명인자를 조사하고 실제 예상되는 위성의 임무수명을 예측하였다. 임무수명의 예측 시 랜덤하게 발생하는 실패에 의한 수명의 중단은 예측할 수 없는 것이기 때문에, 여기서는 주로 예측이 가능한 마모에 의한 대표적인 임무수명 인자 예를 들어, 전력 버짓, 추진제 버짓, 배터리 충 방전 사이클, 복사환경의 영향, 탑재체의 신뢰도, 단일 점 실패, 위성 여유 분을 등을 조사하고 개략적인 수명을 예측하였다.

• 한국화재소방학회논문지
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• 제4권2호
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• pp.15-26
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• 1990

Building become higher. larger and more complex than ever before, showing abrupt changes in building structures. forms and mechanical systems. Likewise hazads of fire and the scale of fire losses become more and more greater. Therefore. considerations for fire safety take up great portion of the building design process. In this study, problems of high-rise building fires and basic directions for fire safety of high-rise building design were studied through the statistical analysis of 138 fire cases. The results of this study are summarized as follows : ·Most of the fires in high-rise building occur on the low floors and the fire frequencies are very low on the upper floors. Fire casualties are liable to be more on the upper floors than on tile floor of fire origin. ·The important causes of evacuation failures were analyzed as being late in escape and lack of stairwell enclosures. ·The main cause of vertical fire spread is lack of stairwell enclosures. However, the fire spreads mainly through the enterior windows in apartment houses. The combustible materials in buildings act on as the major factors of horizontal fire spread and the improper fire doors play role of another the critical causes. ·The basic directions for fire safety of high-rise building design put much stress firstly on the compartmentation of the buildings effectively performing the provision of safe escape routes and the safe refuse places in buildings.