• Ocean Systems Engineering
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• 제4권3호
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• pp.215-241
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• 2014

Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• 한국지반환경공학회 논문집
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• 제18권1호
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• pp.37-47
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• 2017

The Mekong River plays an extremely important role in Southeast Asia. Flowing through six countries, including China, Myanmar, Thailand, Laos PDR, Cambodia, and Vietnam, it is a site of great biological and ecological diversity and the habitat of numerous species of fish. It also supports a very large population that lives along the river basin. Therefore, much attention has been focused on the giant Mekong River Basin, particularly, its soil erosion and sedimentation problems. In fact, many methods have been used to calculate and simulate these problems. However, in the case of the Mekong River Basin, the available data is limited because of the extreme size of the area (about $795,000km^2$) and lack of equipment systems in the countries through which the Mekong River flows. In this study, we applied the Universal Soil Loss Equation (USLE) model in a GIS (Geographic Information System) framework to calculate the amount of soil erosion and sediment load during the selected period, from 1951 to 2007. The result points out dangerous areas, such as the Upper Mekong River Basin and 3S Basin (containing the Sekong, Sesan, and Srepok Rivers) that are suffering the serious consequences of soil erosion problems. Moreover, the present model is also useful for supporting river basin management in the implementation of sustainable management practices in the Mekong River Basin and other basins.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.519-525
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• 2003

XML의 등장으로 기존의 EDI를 전자상거래 환경에 맞게 발전시킨 기술이 XML/EDI이다. DTD는 XML 문서에 표현될 자료의 의미를 정의한 메타 데이터라고 할 수 있다. 따라서 DTD 정보가 손상될 경우 이 정보를 기반으로 한 XML 문서의 보안은 심각한 문제점을 가지게 된다. 본 연구에서는 인터넷 쇼핑몰에서 암호화된 XML/EDI를 위하여 XML 문서에만 전자서명을 첨부하는 것이 아니라, DTD에 전자서명을 첨부하는 방법을 제안하였다. 전자서명 시 메시지 다이제스트 과정에서 바꿔 순서에 대해서는 검사하지 못하기 때문에 전혀 다른 다이제스트 값을 생성하는 문제가 발생되는데, 이것은 표준화된 구조와 문서에 대한 트리구조를 구현할 수 있는 DOM을 이용하여 DTD의 전자서명을 생성하는 방법으로 해결하였다.

• 전기학회논문지
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• 제59권5호
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• pp.847-853
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• 2010

This paper describes switching surge analysis for reclosing decision in 345kV combined transmission line with XLPE power cable. Reclosing operation should be decided based on the detailed technical analysis in combined transmission line because this line includes power cable section which is week on insulation. Insulation of power cable can be breakdown at the week point in case of reclosing moment. Therefore the detailed analysis has to be carried out by considering several conditions such as length ratio of power cable section, arrestor, inserting resistance, charging rate, grounding resistance, etc.. On the other hand sheath voltage on IJ(Insulated Joint) is analyzed to check dangerous condition on cable cover. Analysis is performed by EMTP/ATP. Analysis results show that reclosing can be operated as the single line-to-ground fault occurs on overhead line in 345kV combined transmission line, if the inserting resistance is considered before the operation of main circuit breaker.

• 한국터널지하공간학회 논문집
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• 제8권1호
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• pp.65-76
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• 2006

기존의 NATM과 같은 터널공법에서는 불착 직후 벽연은 숏크리트나 록볼트에 의하여 지지되기 때문에 재래공법과 비교하여 암반의 느슨함을 감소시킬 수 있으나, 막장은 통상 무지보 상태로 놓여있기 때문에 붕괴의 위험성을 항상 내포하고 있는 것이 현실이다 현재 국내 터널시공시에는 막장이 굴진방향에 직립합A로써 응력의 집중이 발생하며 또한 막장의 안정성을 우려하여 단연분할공법을 채택하는 것이 일반적 공법으로 되어왔다. 그러나 이러한 방법은 경제적우로 큰 부당이 되며 공사기간 연장의 한 원인이 된다. 따라서 곡연막장 굴착공법을 개발하여 적용한다면 보다 나은 응력상태를 유지할 수 있어 1회 불진장의 증대 및 분할공법을 피함으로써 공사비절감 및 공사기간 단측에 매우 유리할 것이라 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.2058-2063
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• 2010

United Nations Framework Convention on Climate Change(UNFCCC) is one of the international environmental convention with the goal of stabilizing Greenhouse Gas(GHG) concent in the atmosphere and preventing potentially dangerous change in the earth's climate. The purpose of this convention is to reduce fossil fuel consumption and to prevent GHG emission. The Republic of Korea was one of the Annex-II parties submitted its national communication to the UNFCCC. As a developing county, there is no GHG emission reduction commitments made by South Korea during first commitment period(2008~2012). On the contrary, South Korea' status as an OECD member, joining in 1996, ranks 6th in GHG emission. Furthermore the rate of increase of GHG is first among OECD countries in year 2005. As a result, Korea will probably be incorporated into Annex-I in second commitment period (after 2013). So, Korea government established and announced Voluntary GHG Reduction scheme to reduce emissions of 4%(accounting for 30% reduction base on Business As Usual) from the 2005 level by the year 2020 for mitigation of reduction duty impact. In specific case of Korea, transportation section occupied almost 21% of total energy consumption and nearly 17% of total GHG emission at 2005, so systematic emission management is required. To do so, in this research, we focus on systematic way of GHG management system to handle GHG reduction duties in Railroad section.

• 제어로봇시스템학회논문지
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• 제14권1호
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• pp.95-103
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• 2008

This paper deals with the problem of autolanding for aircraft under windshear environment for which the landing trajectory is given. It is well known that the landing maneuver in windshear turbulence is very dangerous and hard for the pilot to control because windshear is unpredictable in when and where it happens and its aerodynamic characteristics are complicated. In order to accomplish satisfactory autolanding maneuver in this environment, we propose a gain-scheduled controller. The proposed controller consists of three parts: PID controller, called baseline controller, which is designed to satisfy requirements of stability and performance without considering windshear, gain scheduler based on fuzzy logic, and safety decision logic, which decides if the current autolanding maneuver needs to be aborted or not. The controller is applied to a 6-DOF simulation model of the associated airplane in order to illustrate the effectiveness of the proposed control algorithm. It is noted that a cross wind in the lateral direction is included to the simulation model. From the simulation results it is observed that the proposed gain scheduled controller shows superior performance than the case of controller without gain scheduling even in severe downburst and tailwind region of windshear. In addition, touchdown along centerline of the runway is more precise for the proposed controller than for the controller without gain scheduling in the cross wind and the tailwind.

• 전기학회논문지
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• 제58권12호
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• pp.2303-2310
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• 2009

Defense systems are needed to prevent catastrophic failures of a power grid due to cascaded events. Cascaded events can be attributed to improper operations of protective relays. Especially, it is the most dangerous problem that trips of backup relays by overload. In this paper, a new algorithm of predicting Zone 3 acting time of distance relay is proposed using the real time synchronized data from PMUs on the transmission system when the power system is danger. In the proposed, some part of the power system are outage when some unexpected fault in the power system, the algorithm will monitor the impedance locus of distance relay. At this time, if there is a big change of Impedance locus, the algorithm will calculate the Zone 3 acting time of the distance relay by the over load. In the case studies, the estimation and simulation network have been testified and analysed in Matlab Simulink.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.436-438
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• 2007

As the sensors and communication technology get advance, the remote health diagnosis for patients and senior persons at home are possible now without visiting doctors in hospitals. A low-power ubiquitous health check device was developed adapting Real-Time Embedded Linux is developed. This ubiquitous device is consisted of three sensors. The wrist type health checking terminal acquires periodically the health data by using a blood pressure sensor, a pulse sensor and a body temperature sensor. It transmits the health data to the access point located at the home center through the ZigBee wireless communication modem. This health data collector or access point device sends the data again to the main server operated in a hospital or health care organization. The health server control continuously the input data and sends an alarm signal to the assigned. doctor and responsible persons using cellular SMS when any dangerous events occur. This wrist type health check device has an embedded linux OS using Intel PAX255 MPU. The developed U-Health system is applicable for checking patients health in remote at home. And their family or related persons in remote site can check the patients health status at any time. They can be assured by receiving SMS record and alarm of emergency case which is transmitted from the health server.