• Wind and Structures
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• 제16권2호
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• pp.193-211
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• 2013

This paper presents results from a wind tunnel study that examined the drag coefficient and wind flow over an asymmetric wave train immersed in turbulent boundary layer flow. The modeled wavy surface consisted of eight replicas of a statistically-valid hurricane-generated wave, located near the coast in the shoaling wave region. For an aerodynamically rough model surface, the air flow remained attached and a pronounced speed-up region was evident over the wave crest. A wavelength-averaged drag coefficient was determined using the wind profile method, common to both field and laboratory settings. It was found that the drag coefficient was approximately 50% higher than values obtained in deep water hurricane conditions. This study suggests that nearshore wave drag is markedly higher than over deep water waves of similar size, and provides the groundwork for assessing the impact of nearshore wave conditions on storm surge modeling and coastal wind engineering.

• 한국가시화정보학회지
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• 제21권1호
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• pp.26-30
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• 2023

Interaction of a droplet and substrate is important to determine the coating and final deposition pattern in inkjet printing system. In particular, an accurate deposition of the droplet should be guaranteed for high-resolution patterning. In this study, we performed high-speed shadowgraph experiments on droplet train impact in inkjet system. From the high-speed images, we observed an unexpected bouncing phenomenon. We have found two factors affecting bouncing regime; the Weber number and the curvature of deposited droplet. Experimental results indicate that there is a critical curvature diameter of deposited droplet, which splits into bouncing and merging regime. From this result, we obtained a power-law behavior between the Weber number and the curvature. The understanding of bouncing phenomena helps to improve the accuracy and productivity of inkjet printing.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1916-1932
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• 2008

철도사고의 발생 확률은 적지만 한 번의 사고로 인하여 피해가 막대하고 빠르게 확산되는 특징이 있다. 이러한 예상치 못한 철도사고 예방을 위하여 열차안전운행의 최일선 접점에 있는 기관사의 역할은 무엇보다 큰 비중을 차지하고 있다 할 것이다. 철도안전법 시행 이전 기관사 양성은 각 철도운영기관에서 자체적으로 정한 자격기준, 교육기간, 실무수습을 거쳐 양성하였으며 동일차종을 운전하는 기관사 양성에 있어 철도운영기관 별로 각기 다른 기준으로 선발 교육함에 따라 철도차량운전자에 대한 양성 관리가 체계적으로 이루어 지지 않았다. 철도안전법 시행으로 철도차량 종류에 따라 면허의 종류를 분류하고 전문교육훈련기관을 지정하여 일정한 교육을 이수한 후 제3의 평가기관을 지정, 평가토록 함으로써 일정 수준이상 득점을 해야만 면허가 발급되는 체제를 갖추게 되었으며 교육훈련기관과 평가기관을 분리하여 운전자에 대한 능력을 객관적으로 검증할 수 있도록 하였다. 교육대상자에 따라 과목별 이론교육 시간을 달리 배정하고 실기교육의 대부분을 차지하고 있는 운전시뮬레이터의 취급시간을 최대한 확보하여 철도차량운전자의 자질을 극대화하는 교육프로그램이 되도록 설계하여야 한다. 본 논문을 통하여 면허취득을 위한 교육훈련의 효과를 극대화 하고 실용적인 교육을 위하여 필요한 제반 여건에 대하여 국내외 면허 교육훈련을 비교분석을 통하여 현행 제도의 문제점 및 개선방안에 대하여 연구하고자 한다.

• Journal of KIEE
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• 제11권1호
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• pp.62-68
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• 2001

In this paper it is proposed an advanced modified sliding mode control of a rotor field oriented control of induction motor. The application of this unconventional control has very good results, such as disturbance rejection and nice dynamic properties. Stability can be guaranteed even in the worst situation. A conventional "sliding mode" controller is characterised by fast switching control signal, which causes the chattering of the drive system. To overcome this problem, a modified law is used, by introducing a hysteresis band and a continuous control, which modifies the conventional law. The control is accomplished with dual TMS320C44 floating-point digital signal processor. The validity of the proposed method was verified by experiment on the propulsion system simulator, used for the development of Korean High-Speed Railway Train(KHSRT).in(KHSRT).

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.322-328
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• 2001

In the electric railway systems, it is very important that we should design the system configuration, location and power capacity of substation. This paper presents the results of system configuration and system design of the DC traction power supply for the test line of Light Rail Vehicle. The voltage fluctuation of train and the power capacity of substation are calculated by computer simulation using the nodal equation, K.C.L／K.V.L, Ohm's law and superposition theory.

• 한국항만학회지
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• 제13권1호
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• pp.101-112
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• 1999

Traffic accidents increase with the increase of the vehicles in operation on the street. Especially big traffic accidents composed of over 3 killed or 20 injured accidents with the property damage become one of the serious problems to be solved in most of the cities. The purpose of this study is to build the discrimination model on big traffic accidents using the Quantification II theory for establishing the countermeasures to reduce the big traffic accidents. The results are summarized as follows. 1)The existing traffic accident related model could not explain the phenomena of the current traffic accident appropriately. 2) Based on the big traffic accident types vehicle-vehicle, vehicle-alone, vehicle-pedestrian and vehicle-train accident rates 73%, 20.5% 5.6% and two cases respectively. Based on the law violation types safety driving non-fulfillment center line invasion excess speed and signal disobedience were 48.8%, 38.1% 2.8% and 2.8% respectively. 3) Based on the law violation types major factors in big traffic accidents were road and environment, human, and vehicle in order. Those factors were vehicle, road and environment, and human in order based on types of injured driver’s death. 4) Based on the law violation types total hitting and correlation rates of the model were 53.57% and 0.97853. Based on the types of injured driver’s death total hitting and correlation rates of the model were also 71.4% and 0.59583.

• 한국벤처창업학회:학술대회논문집
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• 한국벤처창업학회 2017년도 춘계학술대회
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• pp.42-42
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• 2017

There are lots of specialized graduate schools such as law school, medical school, business school. These specialized graduate schools has been designed to train the special experts practically from 1990s in Korea. For all that, there are no specialized graduate schools supported by the Small and Medium Business Administration(SMBA). So we will research the establishment plan of SME(Small and Medium Enterprise) specialized school for the development of SMEs. Recently, the SMBA supports the 2 types of graduate school such as the entrepreneurship graduate school and consulting graduate school. However, it is clear that these 2 types of schools are yet insufficient in terms of efficiency and redundancy. As the representative specialized graduate schools are law school and MOT(Management of Technology) in Korea, we do the comparative study with law school and MOT school. Through the comparative study, we can find some implication for SME specialized graduate school. As a result, the SME school has to need the training system such as the special master's and doctor's degree, over 3 year course work, daytime class, many practical professors, specialized programs with industry like the MOT school. In conclusion, we suggest that : First, the SME specialized graduate school has to be designed for potential SME consultants. Second, the entrepreneurship graduate school and the consulting graduate school can be integrated into the SME specialized school easily. Third, the SME specialized graduate school can have new educational models.

• 한국전산유체공학회지
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• 제16권2호
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• pp.17-23
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• 2011

The turbulent flow and vortex shedding phenomena around pantograph panhead of high speed train were investigated and compared with available experimental data and other simulations. The pantograph head was simplified to be a square-cross-section pillar and assumed to be no interference with other bodies. The Reynolds number (Re) was 22,000. The LES(large eddy simulation) of FDS code was applied to solve the momentum equations and the Wener-Wengle wall model was employed to solve the near wall turbulent flow. Smagorinsky model($C_s$=0.2) was used as SGS(subgrid scale) model. The total grid numbers were about 9 millions and the analyzed domain was divided into 12 multi blocks which were communicated with each other by MPI. The time-averaged mainstream flows were calculated and well compared with experimental data. The phased-averaged quantities had also a good agreement with experimental data. The near-wall turbulence should be carefully treated by wall function or direct resolution to get successful application of LES methods.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2439-2449
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• 2011

Existing grade crossings between railway and roadway area gradually changed to grade separation systems by the law. In the case of new roadway construction which crosses railways, it shall be grade separation system in principle. With the railway underground crossing method, many practices have been developed which can minimize rail displacements and avoid rail release. With these methods, the effects to the train can be reduced. The underground crossing methods can be identified as open-cut methods and non open-cut methods. The open-cut methods include temporary support methods and special rail construction methods. Also the non open-cut methods includes pipe roof methods, front jacking methods, messer shield methods, NTR methods and JES methods. Among these, the most suitable method is applied considering safety, economy, class of each rail system (train passing frequency and velocity), etc. In the non open-cut methods, the cost and duration shall be increased to keep existing rail system during construction. In the open-cut methods which use plate girders, the rail speed shall be restricted due to the displacement and vibration of the girder. In this study new grade separation methods were developed. With this method, the safety during construction can be increased. This method refines temporary support methods, but pc slab girder with huge stiffness is applied instead of plate girders. With this method, the rail displacement can be reduced and higher safety can be obtained during construction. Also construction cost and duration can be minimized because the temporary work and the overburden soil depth can be reduced.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.699-704
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• 2005

In the station of the railway and the subway various illumination equipment and a general power equipment for a passenger convenience, the signal equipment and the communication equipment which is necessary to the train operation provided. At the all of like this equipment from the electric room which is established in each station by changing from high voltage to low voltage and it supplies from the illumination transformer, the power transformer and the signal transformer. If it supplies to the equipment from the high voltage to the low voltage, it must be established to contact protection device in between the high voltage coil and the low voltage coil. Also it must do the grounding faulting device at the low voltage lines, the earthing devices at apparatus for the protection of an electric shock and an electric fire by the electric relation law. Compared the related regulations between the facilities which require protective functions such as grounding fault or earthing in public utilities like subway stations, and the facilities which do not require line earthing or protective functions such as electricity supplied for signalling the train. Also, will describe a countermeasure for the accident from a grounding fault.