• 한국농공학회지
• /
• 제44권5호
• /
• pp.54-66
• /
• 2002

A grid-based hydrological model, CELTHYM, capable of estimating base flow and surface runoff using only readily available data, was used to assess hydrologic impacts caused by land use change on Little Eagle Creek (LEC) in Central Indiana. Using time periods when land use data are available, the model was calibrated with two years of observed stream flow data, 1983-1984, and verified by comparison of model predictions with observed stream flow data for 1972-1974 and 1990-1992. Stream flow data were separated into direct runoff and base flow using HYSEP (USGS) to estimate the impacts of urbanization on each hydrologic component. Analysis of the ratio between direct runoff and total runoff from simulation results, and the change in these ratios with land use change, shows that the ratio of direct runoff increases proportionally with increasing urban area. The ratio of direct runoff also varies with annual rainfall, with dry year ratios larger than those for wet years shows that urbanization might be more harmful during dry years than abundant rainfall years in terms of water yield and water quality management.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
• /
• pp.324-327
• /
• 2005

지하수와 지표수를 연계하여 flow와 transport를 모의하는 프로그램인 HydroSphere를 Canada Ontario주의 Canadian Forces Base Borden에서의 실험 (Abdul ,1985) 자료를 이용하여 평가해 보았고, 유성지역 소유역에서의 강수, 지표수, 지하수의 수소동위원소 모니터링 (박준형, 고용권, 박경우, 정형재, 김교원, 2003) 자료를 이용하여 평가해 볼 예정이다.

• Wind and Structures
• /
• 제6권5호
• /
• pp.347-356
• /
• 2003

Experimental studies on drag reduction of a circular cylinder of diameter D were conducted in the subcritical flow regime at Reynolds numbers in the range $4{\times}10^4{\leq}Re{\leq}10^5$. To shield the cylinder rear surface from the pressure deficit of the unsteady vortex generation in the near wake, two shield plates were attached downstream of the separation points to form a cavity at the base region. The chord of the shield plates, L, ranged from 0.22 to 1.52 D and the cavity width, G, was in the range from 0 to 0.96 D. It is concluded that significant drag reductions from that of a plain cylinder may be achieved by proper sizing of the shield plates and the base cavity. The study shows that using a pair of shield plates at G/D of 0.86 and angular position ${\theta}$ of ${\pm}121^{\circ}$ results in a configuration with percentage drag reduction of 40% for L/D of 0.5, and 55% for L/D of 1.0.

• 전자공학회논문지B
• /
• 제31B권10호
• /
• pp.53-66
• /
• 1994

In this paper, a fuzzy expert system is developed for fault diagnoisis of a drum-type boiler system in fossil power plants. The develped fuzzy espert system is composed of knowledge base, fuzzification module, knowledge base process module, knowledge base management module, inference module, and linguistic approximation module. The main objective of the fuzzy expert system is to check the states of the system including the drum level and detect faults such as the feedwater flow sensor fault, feedwater flow control valve fault, and water wall bube rupture. The fuzzy expert system diagnoses faults using process values, manipulated values, and knowledge base which is built via interviews and questionaries with the experts on the plant operations. Finally, the validity of the developed fuzzy expert system is shown via experiments using the digital simulator for boiler system is Seoul Power Plant Unit 4.

• 대한기계학회논문집
• /
• 제18권10호
• /
• pp.2664-2674
• /
• 1994

Drag, lift, and pitching moment measurements have been made on a range of slanted-base ogive cylinders, using the KANOMAX wind tunnel and balance system. Test Reynolds numbers(based on model maximum diameter) varied from $0.54{\times}10^{5}{\;}to{\;}1.56{\times}10^{5}$. Crossflow velocity maesurement was conducted by 5-hole pitot tube at $Re_{D}=1.46{\times}10^{5}$. For two base angle $({\theta}=30$ and 45 deg.), aerodynamic forces and moment were measured with increasing angle of attack(0~30 deg.). Two types of wake flow were observed, a quasisymetric turbulent closure or a longitudinal vortex flow. Aerodynamic characteristics differ dramatically between the two wake types. It was found that the drag, lift and pitching moment coefficients increased with increasing angle of attack.

• 대한교통학회지
• /
• 제27권1호
• /
• pp.117-127
• /
• 2009

본 논문에서는 우리나라의 도로교통사업의 타당성 평가시 활용되는 국가교통DB 기종점 자료를 이용하여, 통행량 변화에 따른 추정 링크 교통량의 불확실성을 분석하였다. 분석 결과, 평균적으로 기종점 통행량의 확률변동으로 변화될 수 있는 전체 국가교통DB 네트워크의 교통량 불확실성 정도는 15.4%로, 혼잡한 구간의 교통량에 대한 불확실성이 그렇지 않은 구간의 불확실성보다 매우 큰 것으로 나타났다. 특히, 본 논문에서는 교통량 추정치에 대한 분산추정치를 계산하고 이를 토대로, 주어진 신뢰수준에서 구간추정 치를 제시하여 교통투자를 결정하는 의사결정가나 분석가들에게 다양한 정보를 제공할 수 있는 기틀을 마련하였으며 도로부문 투자에 대한 불확실성을 정량적으로 평가할 수 있는 토대를 마련하였다.

• 대한기계학회논문집B
• /
• 제32권10호
• /
• pp.776-783
• /
• 2008

The object of this paper is to study on the thermal performance of a micro channel water block for computer CPU cooling. The effects of liquid flow rate, micro channel width and height on the thermal performances of water block are investigated experimentally. The water block was fabricated Al and machined with a micro milling. The water block consisted of rectangular micro channels 0.5 to 0.9 mm width and 1.5 to 4.5 mm height. The experiments were conducted using deionized water, over a liquid flow rate ranging from 0.2 to 2.0 kg/min. The base temperature and thermal resistance decrease with increasing of liquid flow rate. The increase of a channel height is more effective on the thermal resistance than the decrease of a channel width. At the flow rate of 0.7 kg/min, input power of 100 W, the base temperature and thermal resistance of sample 6 is $33^{\circ}C$ and $0.13\;^{\circ}C/W$ respectively.

• 한국추진공학회지
• /
• 제16권2호
• /
• pp.51-57
• /
• 2012

고속의 제트에서 기저압력은 유체역학 및 실용적 공학 적용의 관점으로 매우 중요한 분야중의 하나로 다루어져 왔다. 현재까지 비압축성 유동의 기저압력 특성들은 비교적 상세하게 알려져 있다. 하지만 천음속 혹은 초음속에서의 기저압력은 압축성 효과 및 충격파 발생으로 인해 매우 다르게 나타난다. 본 연구에서는 이러한 천음속 혹은 초음속에서의 기저압력특성에 관한 이해를 위해 선행된 실험 연구 결과를 바탕으로 수치해석적 연구를 수행하였다. 간단한 오리피스를 사용하여 기저 압력 조절하는 것에 주안점을 두었다. 기저 압력에 영향을 미치는 유동변수의 적용으로 여러 형태의 초음속 제트 플룸을 분석하였다. 선행된 실험결과를 모사하여 수치해석 기법의 타당성을 조사하였으며, 계산된 기저압력과 오리피스의 유출계수에 관하여 논의하였다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
• /
• pp.285-287
• /
• 2006

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 학술대회
• /
• pp.327-333
• /
• 2008

The cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has developed a base code for simulating cavitating flows past cylinders and hydrofoils. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with spherical, 1- and 0-caliber forebody and hydrofoil of ALE and NACA cross-section and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. The present base code has shown the feasibility to solve the cavitating flow past supercavitating torpedo after the improvement for compressibility effects and interactions with hot exhaust gas of propulsive rocket.