• 한국환경과학회지
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• 제23권4호
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• pp.533-541
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• 2014

The streams in Jeju Island have very distinctive hydrological and geological properties and there are a lot of limits in applying the general flood estimation method. This study presented parameters dominant in the Hancheon stream of Jeju Island by analyzing the sensitivity of parameters of HEC-HMS model regarding rainfall events in the target basin, and extracted the optimal parameter(Time of Concentration of Clark Unit Hydrograph: Kraven II method, Storage Coefficient: Sabol method) by analyzing and comparing it with the flood runoff data observed in the site and Jeju Island's observation data.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.721-726
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• 2001

The vibrational transition probability expressions for the forced Morse oscillator have been derived using the commutation relations of the anharmonic Boson operators. The formulation is based on the collinear collision model with the exponential repulsive potential in the framework of semiclassical collision dynamics. The sample calculation results for H2+ He collision system, where the anharmonicity is large, are in excellent agreement with those from an exact, numerical quantum mechanical study by Clark and Dickinson, using the reactance matrix. Our results, however, are markedly different from those of Ree, Kim and Shin's in which they approximate the commutation operator I。 as unity, the harmonic oscillator limit. We have concluded that the quantum number dependence in I。 must be retained to get accurate vibrational transition probabilities for the Morse oscillator.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2008년도 학술발표회 논문집
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• pp.2258-2263
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• 2008

최근 이상기후로 인하여 국지성 집중호우의 형태를 띠는 강우가 많이 발생하고 있다. 이러한 강우는 돌발 홍수가 발생하는데 중요한 요소로 작용하게 된다. 이에 본 연구에서는 돌발홍수지수산정을 위한 강우-유출모형 적용시, 집중형모형과 분포형모형의 장단점을 비교하였다. 이를 위하여 안양천 유역을 대상으로 HEC-HMS모형의 Clark 및 ModClack방법을 이용하여 돌발홍수지수를 산정하여 보았다. 2003년, 2004년, 2005년 각 연도별로 하나씩의 호우를 선정하여 이들을 대상으로 분석을 하였다. 집중형 모형에 대해서는 유역면적평균강우량을, 준분포형 모형에 대해서는 Kriging 기법을 통하여 공간분포된 강우량을 이용하였다. 돌발홍수는 상대적으로 크기가 작은 유역에 많이 발생하므로 소유역 분할시 결정한 소유역의 크기가 돌발홍수 지수에 큰 영향을 줄 수 있다. 따라서 돌발홍수지수의 산정은 유역의 크기에 따라 집중형 모형, 준분포형 모형 모형을 적절하게 선택하여 강우-유출관계를 유도해야 할 것으로 판단된다. 또한 돌발홍수지수의 산정이 돌발홍수예보를 위한 기준이 되는 것을 감안할 때 준분포 모형이 강우레이더에 의한 강우예측자료를 활용하는 데에 유리할 것으로 생각된다.

• 한국전산유체공학회지
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• 제19권2호
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• pp.17-23
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• 2014

Cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency in devices, such as propellers, pump impellers, nozzles, injectors, torpedoes, etc. Thus, the cavitating flow simulation is of practical importance for many engineering systems. In the present work, a two-phase flow solver based on the homogeneous mixture model has been developed. The solver employs an implicit preconditioning, dual time stepping algorithm in curvilinear coordinates. The flow characteristics around Clark-Y hydrofoil were calculated and then validated by comparing with the experimental data. The lift and drag coefficients with changes of angle of attack and cavitation number were obtained. The results show that cavity length and lift, drag coefficient increase with increasing angle of attack.

• 한국농공학회논문집
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• 제65권1호
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• pp.41-49
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• 2023

To utilize the hydraulic and hydrological models when simulating floods in agricultural watersheds, it is necessary to consider agricultural reservoirs, farmland, and farmland drainage system, which are characteristics of agricultural watersheds. However, most of them are developed individually by different researchers, also, each model has a different simulation scope, so it is hard to use them integrally. As a result, there is a need to link each hydraulic and hydrological model. Therefore, this study established an integrated flood simulation system for the comprehensive flood simulation of agricultural reservoir watersheds. The system can be applied easily to various watersheds because historical weather data and the SSP (Shared Socio-economic Pathways) climate change scenario database of ninety weather stations were built-in. Individual hydraulic and hydrological models were coded and coupled through Python. The system consists of multiplicative random cascade model, Clark unit hydrograph model, frequency analysis model, HEC-5 (Hydrologic Engineering Center-5), HEC-RAS (Hydrologic Engineering Center-River Analysis System), and farmland drainage simulation model. In the case of external models with limitations in conceptualization, such as HEC-5 and HEC-RAS, the python interpreter approaches the operating system and gives commands to run the models. All models except two are built based on the logical concept.

• 한국수자원학회논문집
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• 제37권9호
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• pp.707-718
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• 2004

최근 빈번한 기상이변에 따라 발생되는 자연재해에 대한 방재대책의 중요함이 절실히 요청되는 시점에서 수공구조물들의 설계빈도를 상향조정하는 등의 대책이 마련되고 있는 실정을 고려하여 유역의 수문학적 안정성을 확보하기 위한 최적방안을 마련하는데 필요한 강우의 임계지속시간 결정에 대한 연구를 수행하였다. 특히 2002년 여름 강릉지역에 발생한 태풍 "루사"로 인한 집중호우는 기존 PMP 규모를 초과하는 사상 초유의 24시간 최대 강수량(880mm)을 기록하여 댐설계기준에 대한 재고가 불가피 하게 되었다. 홍수제어를 위한 수공구조물은 그 특성상 계획홍수량 결정에 최대치 개념이 도입되어야 하므로, 설계강우의 지속기간을 결정할 경우 강우로 인한 최대유출과 홍수총량이 최대가 되는 임계지속시간을 이용하여 검토하는 것이 필요하다 본 연구에서는 합성단위도(Clark방법, Nakayasu방법, SCS방법)등 각 수문요소에 따른 임계지속시간의 변동양상을 파악한 결과 24시간 강우지속시간시 총유출량 보다 임계지속시간개념으로 산정한 유출량이 크게 산출되었으며, PMP시 적용된 시간분포모형 (Huff 4분위법, IDF곡선 분포법, Mononobe방법)별 적합성을 기왕최대 실측치와 비교ㆍ평가함으로써 수문설계시 활용 할 수 있는 자료를 제시하고자 하였다.

• 한국전산유체공학회지
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• 제18권3호
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• pp.8-13
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• 2013

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.1078-1083
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• 2009

HEC-HMS(Hydrologic Modeling System)은 강우-유출 모의를 위한 차세대 소프트웨어이며 HEC-1에 포함되어 있는 단위도 및 수문학적 홍수추적 이외에도 격자형 강우자료(레이더 데이터)를 이용하여 적용할 수있는 유사분포 유출변화와 장기 연속모의에 적용할 수 있는 간단한 수분감소 등을 추가적으로 포함하고 있다. 또한 GUI(Graphical User Interface)환경, 통합 수문분석 성분, 자료 저장 및 관리 능력, 그래�d 처리 및리포트 출력기능으로 구성되어 있으며 여러 가지 프로그램 언어(C, C++, Fortran)를 이용하여 개발되었다. 본 연구에서는 낙동강 수계의 금호강에 위치한 동촌 지점을 유출구로 선정하고 5개의 소유역과 두 개의 하도로 구성하여 유출모의를 실시하였으며 수문자료 선정은 2007년$^{\sim}$2008년에 발생한 홍수사상과 유량조사 사업단에서 개발한 수위-유량관계곡선식을 활용하였다. 또한, HEC-GeoHMS 모형을 GIS와 연계하여 지형인자를 추출하고 추출된 지형인자를 이용하여 매개변수를 산정하였다. HEC-HMS 모형의 계산 조건에서 손실 우량은 SCS CN, 유출변환은 Clark 단위도법을 적용하였다. 또한 관측치와 계산치의 적합도 검증은 평균제곱 근오차(root mean squar error; RMSE)와 모형 효율성 계수(model efficiency; ME)를 산정하여 분석하였다

• 아태비즈니스연구
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• 제5권1호
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• pp.43-53
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• 2014

Social and economic changes in the world, along with changes in the culture of government and structural changes in the relationship between the state, the market and higher education institutions, have resulted in new approaches pursued by states towards higher education (Konstantinov & Philonovich, 2007; Peterka, 2011). Higher education institutions, in its turn, enjoy more freedom in choosing to focus on various tasks and goals to their academic activities. This contributes to the diversity of expectations when it comes to the various roles modern academic institutions take on with regard to their development. Among many existing concepts in the current academic environment, the concept of "entrepreneurial university" is becoming a critically important concept in Russia. In this article, we consider the concept of the Entrepreneurial University as developed in Clark and Etzkowitz's theories, and the ways the concept is being adjusted in the higher education system in Russia. We analyze comparatively both contemporary and prior historical [1990s-mid2000s] state policies pertaining to higher-education institutions in Russia in order to provide an insight into how the national market of knowledge intensive production is being established in the country. As a consequence of these analyses, we present a new model of how universities can take a more systemic and meaningful approach to creating research-based innovation entrepreneurial activities. This approach is also viewed as making universities' innovation activities more sustainable and thus less dependent on the state support.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.45-53
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• 2020

Past literatures have not studied the impact of real-world events or information on the return and volatility of virtual currencies, particularly on the COVID-19 event, day-of-the-week effect, daily high-low price spreads and information flow rate. The study uses the ARMA-GARCH model to capture Bitcoin's return and conditional volatility, and explores the impact of information flow rate on conditional volatility in the Bitcoin market based on the Mixture Distribution Hypothesis (Clark, 1973). There were 3,064 samples collected during the period from 1^st of January 2012 to 20^th April, 2020. Empirical results show that in the Bitcoin market, a daily high-low price spread has a significant inverse relationship for daily return, and information flow rate has a significant positive relationship for condition volatility. The study supports a significant negative relationship between information asymmetry and daily return, and there is a significant positive relationship between daily trading volume and condition volatility. When Bitcoin trades on Saturday & Sunday, there is a significant reverse relationship for conditional volatility and there exists a day-of-the-week volatility effect. Under the impact of COVID-19 event, Bitcoin's condition volatility has increased significantly, indicating the risk of price changes. Finally, the Bitcoin's return has no impact on COVID-19 events and holidays (Saturday & Sunday).