• 한국습지학회지
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• 제5권1호
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• pp.41-52
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• 2003

The flood damage reduction studies have been performed by the channel improvement plan and the levee has mainly constructed with the freeboard concept. However, the freeboard concept might be an inappropriate choice as a safety factor of the levee because many uncertainties are involved in the procedure of the channel improvement plan studies. So, we considered the uncertainties In the discharge-probability, stage-discharge, and stage-damage functions and estimate the expected annual damage. The Monte Carlo technique for uncertainty analysis is used. As our results, the expected annual damage with uncertainty shows the larger value than without uncertainty. Since the expected annual damage with uncertainty already considers the safety factor it is the proper result. However, the expected annual damage without uncertainty does not consider the safety factor yet. Thus, if the expected annual damage without uncertainty considers the freeboard concept, it could be compared with the expected annual damage with uncertainty for the evaluation of the overestimation or underestimation of the levee construction.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.161-161
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• 2011

The design methodology of the sluice caisson structure is one of important factor that is closely related to the efficiency in tidal power generation. When the sluice caisson is designed to maximize the water discharge capability, it is possible to minimize the number of sluice caissons for attaining the water amount required for achieving the target power generation, which results in reduction of the construction cost for the sluice caisson structure. The discharge capability of sluice caisson is dependent on the geometrical conditions of an apron structure which is placed in both sides of the sluice caisson. In this study, we investigated numerically the variation of water discharge capability of sluice caisson according to the geometrical conditions of apron. Flow fields are simulated with FLOW-3D software using VOF method.

• 한국수자원학회논문집
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• 제49권7호
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• pp.615-623
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• 2016

본 연구에서는 개량형 공압식 가동보를 대상으로 가동보의 기립 각도변화에 따른 잠김흐름 특성을 분석하고 유량계수를 산정하였다. 실험결과, 위어마루에서 하류수면까지의 높이와 위어마루에서 상류 수면고 높이의 비($h_t/H$)에 대한 유량감소계수($Q_s/Q_1$)의 변화는 ($h_t/H$가 1에 가까울수록 감소하였다. 따라서 보 하류에서의 수심은 상류보다 작지만 보를 통과하는 흐름으로 인해 하류 유속이 빠르게 나타났으며, 유량이 증가할수록 상 하류 수위차는 감소하는 것으로 나타났다. 또한 같은 유량조건인 경우 하류수두는 L/W가 클수록 크게 증가하였다. 개량형 공압식 가동보의 잠김흐름 유량계수는 가동보의 물리적 제원보다는 상류 접근흐름수두와 상 하류 흐름조건에 의하여 결정되었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.795-798
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• 2003

Inside of working PDP, there exist highly reactive conditions in the gap between two glass panels. MgO layer and phosphor have been investigated as a function of discharge and temperature. A drastic reduction in carbon impurity was observed on the surfaces after discharging and heat treatment. Carbon composition on the MgO and phosphor is a dominant factor for their instability

• 한국수자원학회논문집
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• 제48권8호
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• pp.625-634
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• 2015

합류부에서의 지류의 합류각, 지류와 본류의 유량비에 추가하여, 본류 준설에 의한 하상고 불일치에 따른 다양한 양상의 분리구역의 특성을 CCHE2D 모형을 사용하여 분석하였다. 분리구역은 지류가 합류되어진 직후 단면에서의 유속이 0(영)인 경계로 정의하였다. 합류각 $30^{\circ}$ 이하에서는 분리구역이 형성되지 않았다. 유량비와 합류각 증가에 따른 분리구역의 크기는 일반적으로 증가하는 양상으로 나타났다. 준설 깊이비 증가에 따른 분리구역의 크기는 합류부 수용체의 증가에 기인한 지류에서의 상대적인 운동량의 감소로 인하여 감소되었다. 유량비와 합류각의 변화에 따른 분리구역의 수축지수를 규명하였고, 통수기능의 저하에 따른 배수영향을 확인하였다. 합류각, 유량비, 준설 깊이비에 따른 분리구역의 형상지수의 관계식을 제안하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.389-395
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• 2006

In the single-phase switched reluctance motor (SRM) drive, the required DC source is generally supplied by the circuit consisting of bridge rectifier with diodes and many filter capacitances connected with AC source. Although the peak torque ripple of SRM is small because of large capacity of the capacitance, the charge and discharge time swhich the AC source acts on the capacitance are small and the peak current will pass on the side of source, so power factor and system efficiency decrease. Therefore a novel SRM drive system is presented in this paper, which includes drive circuit realizing reduction of torque ripple and improvement of power factor and switching topology. The proposed drive circuit consists of one switching part and diodes which can separate the output of AC/DC rectifier from the large capacitance and supply power to SRM alternately in order to realize reduction of torque ripple and improvement of power factor through the turn on and turn off of switching part. In addition, the validity of method is tested by simulation and experiment.

• 한국수자원학회논문집
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• 제48권11호
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• pp.879-889
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• 2015

본 연구는 지류의 합류각, 지류와 본류의 유량비, 준설 깊이비의 변화에 따른 지류에서의 두부침식 양상과 합류부 이동상 하도에서의 분리구역의 특성을 분석하였다. 분리구역은 지류가 합류되어진 직후 단면에서의 유속이 0(영)인 구간으로 정의하였다. 준설 깊이에 따른 두부침식이 발생치 않은 범위를 제시하였다. 합류각, 유량비, 준설 깊이비 증가에 따른 두부침식 깊이비 및 천급점의 이동거리비는 전반적으로 증가하였으며, 천급점의 이동거리비의 관계식을 제시하였다. 이동상 하도에서의 유량비와 합류각 증가에 따른 분리구역의 길이비 및 폭비는 고정상 하도에서와 같은 양상으로 증가하였다. 준설 깊이비 증가에 따른 분리구역의 길이비는 감소하고 폭비은 증가하여 형상지수는 크게 증가하여 통수단면의 감소로 배수위 현상이 기대된다. 고정상 하도와 이동상하도에서의 합류각, 유량비, 준설 깊이비에 따른 형상지수 관계식을 제안하였다.

• 한국정밀공학회지
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• 제15권1호
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• pp.87-93
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• 1998

Pressure ripples of hydraulic vane pump results from flow ripples due to pump geometry and reverse flow through the discharge port due to compressibility of fluid and result in vibration and noise of connected hydraulic elements. In a balanced type vane pump, cam ring curve is important factor to influence the flow ripples. Therefore, to reduce the flow ripple, it has been required that optimal selection of seal region by proper design of cam ring and each port position, and notches for preventing the excessive reverse flow. This paper has been performed analytical study of compression characteristics with major design parameter in side plate and cam ring. and examined into the role of notch and radius reduction ratio.

• 한국수소및신에너지학회논문집
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• 제25권5호
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• pp.516-524
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• 2014

Proper discharge of nitrogen gas and water condensate is required in a conventional fuel cell system for performance, stability and durability of fuel cell stacks. Present study covers the development of integrated unit and its functioning logic for simultaneous nitrogen gas purge and water condensate drainage in a fuel cell vehicle system. Configuration of condensate drainage pipe, purge valve and level sensor is considered and optimized in physical integration. As a key factor, discharge time is considered and optimized based on the test result of constant-current operation with various operating temperature in logic development. Consequently, derived optimal values are applied and verified in actual vehicle drive mode test. Increase of system design flexibility, weight reduction and cost reduction are anticipated with this study. Additional study for physical and logical improvement is currently being implemented.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1799-1805
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• 2014

In this article, we described about the preparation and electrochemical properties of a flexible energy storage system based on a plastic polyethylene terephthalate (PET) substrate. The PET treated with UV/ozone was fabricated with multilayer films composed of 30 polyaniline (PANi)/graphene oxide (GO) bilayers using layer-by-layer assembly of positively charged PANi and negatively charged GO. The conversion of GO to the reduced graphene oxide (RGO) in the multilayer film was achieved using hydroiodic acid vapor at $100^{\circ}C$, whereby PANi structure remained nearly unchanged except a little reduction of doping state. Cyclic voltammetry and charge/discharge curves of 30 PANi/RGO bilayers on PET substrate (shorten to PANi-$RGO_{30}$/PET) exhibited an excellent volumetric capacitance, good cycling stability, and rapid charge/discharge rates despite no use of any metal current collectors. The specific capacitance from charge/discharge curve of the PANi-$RGO_{30}$/PET electrode was found to be $529F/cm^3$ at a current density of $3A/cm^3$, which is one of the best values yet achieved among carbon-based materials including conducting polymers. Furthermore, the intrinsic electrical resistance of the PANi-$RGO_{30}$/PET electrodes varied within 20% range during 200 bending cycles at a fixed bend radius of 2.2 mm, indicating the increase in their flexibility by a factor of 225 compared with the ITO/PET electrode.