• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.799-809
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• 2020

In this study, the supercavitating flow of a high-velocity moving body near air-water surface is calculated and analyzed based on a commercial CFD software ANSYS Fluent. The effect of regular wave parameters including both wave height and wavelength on the cavitating flow and force characteristics of a body at different velocities is investigated. It is found that the cavity shape, lift coefficient and drag coefficient of the body vary periodically with wave fluctuation, and the variation period is basically consistent with wave period. When the wavelength is much greater than the cavity length, the effect of wave on supercavitation is the alternating effect of axial compression and radial compression. However, when the wavelength varies around the cavity length, the cavity often crosses two adjacent troughs and is compressed periodically by the two wave troughs. With the variation of wavelength, the average area of cavity shows a different trend with the change of wave height.

• 한국항공운항학회지
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• 제23권4호
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• pp.36-41
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• 2015

The cyclone separator is a simple device, which causes the centrifugal separation of materials such as droplets or particles in a fluid stream. The cyclone separator utilizes the energy obtained from fluid pressure and linear motion to create rotational fluid motion. This rotational motion leads the materials suspended in the fluid to separate from the fluid quickly due to the centrifugal force. The rotation is produced by the tangential or involuted introduction of fluid into the vessel. These materials may be droplets of fuel in blow-by gas through an engine. Droplets suspended in the feed liquid may separate according to size, shape, or density. And the change of part dimension in a cyclone separator can yield the its performance variation. The current study shows the influence of design parameters on the performance of a cyclone separator for blow-by gas.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.57-60
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• 2002

Developed power off automatic stanch that keep floodgate upper stream water level changelessly for curtailment of operation by manpower and electricity lead-in equal early investment expense that manual system floodgate and electric motion floodgate have. Human strength does not need in floodgate operation as that power off automatic floodgate open and close floodgate automatically by buoyancy and also, another thing power does not need. Before establish floodgate, effect that get to waterway when behaves repair calculation of correct waterway and decide size of floodgate accordingly and establish floodgate must do examination analysis fussily. power off automatic floodgate night soil that get between countermeasure is the urgentest low-down in reply because can do mistake in operation by phenomenon and so on about water resources by different plate shape change through a model experiment examine closely need to.

• 한국조경학회지
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• 제28권2호
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• pp.108-121
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• 2000

This study seeks what kind of factors influence to locate dwellings and to establish scenic spots in nature by a case study focused on a meandering stream. The study specially concentrates on the interrelationship between both residences and beautiful sceneries and a meander cut-off-area that reveals a special topographical characteristics, located at Samji village in Youngyang-eup, Youngyang-gun, Koungsangbuk-do. The meander cut-off area, developed at the middle or upper reaches of a river, often makes up specific landscapes such as precipitous cliffs, sheer cliffs and caves. And the area where is specially created by sudden change of flow due to erosion ;perceived by the cut surface to be the most beautiful scenic spot. These beautiful landscapes were used to be called as Dae, Dam or Gul and managed by Confucian scholars who enjoy refined taste and devote themselves to the study in nature. Moreover, the Ku-Hado-literary means the area of ex-flow-made the scholars' lving with a well prepared basis for agriculture where supplied a cornucopia of organic matters and water. The merit of agriculture made it possible that the scholars became economically independent, and the fact might be the essential point why the meander cut-off area took noticed. Actually, Cho-family has been in Smaji Village for generations, producing a large number of scholars and keeping the actual power of the region. The physical shape of the meander cut-off area, cozily surrounded by mountains, is considered as a good place for the dwelling due to the influence of traditional sight of view for location and P'ungsuchiri which is known as Feng Shui in China and geomancy in the western world. It is a fruit in it own way that we could find the ancestors' discernment and wisdom from this study, who have lived their lives adapting themselves to the given natural environment and also utilizing the nature wisely. But this is a current-argued study on the meander cut-off area. Follow-up studies have to be continued about the landscapes of the meander streams and the meander cut-off areas scattered all over the country except Samji Village and draw the characteristics from the comparative analysis.

• 한국태양에너지학회 논문집
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• 제21권2호
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• pp.69-78
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• 2001

This paper introduces the physical phenomena involved in Direct Contact Heat Exchangers (DCHXs) and also investigates the possibility of applying of EIT(Electrical Impedance Tomography) technique for capturing the images of dispersed phases as they stream through a stagnant body of water. A number of cases are studied where two dimensional cross-sectional static images are given for fictitious and actual masses present in a column of water(saline solution). In most direct contact liquid-liquid heat exchangers, oil or hydrocarbon with a density different(lighter or heavier) from water is normally used as dispersed working fluid. The main difficulty that arises with this arrangement lies in the elucidation of complicated flow field where the dispersed phase fluid tends to change its shape and size constantly during its journey through the other phase(water). This paper presents a number of results with different types of dispersed phases that are immiscible with water. The EIT technique has been employed in this context to test its applicability in capturing the dynamic images of dispersed phases. It shows static images of dispersed phases where dynamic images could be obtained by simply extending the algorithms and strategies employed in the present analysis.

• 대한공간정보학회지
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• 제21권4호
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• pp.37-44
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• 2013

최근 기상 이변에 따라 단시간에 집중되는 돌발홍수에 의해 해마다 막대한 인적, 물적 피해를 입고 있다. 이러한 국지성호우에 의한 산지하천이나 미소하천에서 첨두유출량을 예측하기 위한 도구로서 GIS를 적용하고 있는 추세이다. 하지만 수문학적 접근이 주를 이루고 있으며 GIS를 이용한 지형분석으로의 접근은 매우 미비한 실정이다. 본 연구에서는 돌발홍수를 발생시키는 강우량을 GIS기법과 GcIUH의 모형을 연계하여 산정하였고, 유역별 GcIUH 매개변수를 추출하여 한계유량에 따른 GcIUH 매개변수간의 상관관계를 분석하였다.

• 한국농공학회논문집
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• 제61권4호
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• pp.33-42
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• 2019

In this study, the channel and floodplain widths are indirectly measured for three different watersheds using satellite images to reflect the shape of Korean channels in the Soil and Water Assessment Tool (SWAT) model. For measuring the channel and floodplain widths, multiple satellite images were referred to ensure the widest width of certain points. In the single channel, the widths at the multiple points were measured. Based on the measured data, the regression equations were derived to estimate the channel and floodplain widths according to watershed areas. Applying these developed equations, this study evaluated the effect of the change of channel and floodplain widths on the SWAT simulation by comparing to the measured streamflow data. The developed equations estimated larger channel width and smaller floodplain compared with those calculated in the current SWAT model. As shown in the results, there was no considerable changes in the predicted streamflow using the current and developed equations. However, the flow velocity and channel depth calculated from the developed equations were smaller than those of the current equations. The differences were caused by the effect of different channel geometries used for calculating the hydraulic characteristics. The channel geometries also affected the water quality simulation in channels because the hydraulic characteristics calculated by the channel geometries are directly related to the water quality simulation. Therefore, application of the river cross-sectional regression equation reflecting the domestic stream shape is necessary for accurate water quantity / quality and water ecosystem simulation using hydrological model.

• 대한전자공학회논문지SP
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• 제43권2호
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• pp.57-64
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• 2006

본 논문에서는 해마신경망(HCNN:HippoCampal Neural Network)을 이용하여 사용자 친화적인 객체 기반 멀티미디어 검색시스템을 제안한다. 내용 기반 검색(Content-based Retrieval)에 관한 대부분의 기존의 질의 방법은 입력 영상에 의한 질의 또는 컬러(color), 형태(shape), 질감(texture)등과 같은 low-level의 특징을 사용한다. 본 논문에서 제안하는 방법은 MPEG 기반의 압축 비디오 스트림으로부터 장면 전환 검출을 수행하여 샷을 검출한다. 이 샷 프레임에서 컬러 객체의 자동 추출을 위하여 similar colorization과 ACE(Adaptive Circular filter and Edge) 알고리즘을 사용한다. 그리고 이렇게 추출된 특징을 해마 신경망을 통하여 학습한 후 멀티미디어 검색 시스템을 구성한다. 제안하는 해마 신경망은 호감도 조정에 의해서 입력되는 영상패턴의 특징들을 흥분학습과 억제학습을 이용하여 불필요한 특징은 억제시키고 중요한 특징은 흥분학습을 통해 장기기억 시켜서 적응성 있는 실시간 검색 시스템을 구현한다.

• 한국수자원학회논문집
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• 제51권8호
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• pp.655-664
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• 2018

하상재료 조사는 유사량 계산 및 하상변동과 같은 하도 계획에 필요한 기초 자료로서 입도분포, 비중, 다공성 등을 조사하는 것이다. 원칙적으로, 조사 지점은 하천 종단 방향으로 1 km 간격이고 하나의 횡단면에 3 개 이상이다. 따라서 조사 대상 하천의 종단 길이에 따라 조사 지점이 아주 많아지기 때문에 조사에 소요되는 시간과 비용이 상당히 증가한다. 본 연구는 입도분석법인 체적법과 화상해석법의 작업 효율성과 비용을 비교하고, 화상해석법의 적용 가능성을 검토하였다. 화상해석법에 의하여 환산된 등가원의 직경이 하상재료 입도분석에 적용될 수 있음을 확인하였다. 또한, 체적법과 화상해석법의 작업효율성과 비용을 분석한 결과 약 80%의 절감효과가 있음을 입증하였다.

• 한국방재학회 논문집
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• 제6권1호
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• pp.59-68
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• 2006

합류부는 유량의 변화, 흐름방향의 전환으로 순환흐름의 분리구역의 발생에 의한 통수단면의 축소에 의한 통수능의 저하와 이에 따른 배수의 영향이 야기된다. 지류와 본류와의 유량비와 합류각을 달리하면서 실험한 결과를 이용하여 분리구역의 특성을 규명하였다. 분리구역의 정의는 유함수를 이용하여 그 값이 0(영)인 유선을 분리구역으로 정의하여 그 길이와 폭을 본류 하천폭으로 나눈 무차원 길이비와 무차원 폭비로 하였고, 유선에 의한 분리구역의 연구결과가 기존의 실험들과 비교적 잘 맞는 것으로 나타났다. 작은 유량비와 합류각 30도에서는 분리구역이 나타나지 않아서 유량비와 합류각에 의한 분리구역의 출현경계식을 만들었다. 분리구역에 대한 고찰로 합류각, 유량비, 그리고 본류 하류에서의 Froude수에 의한 분리구역의 무차원 길이비와 폭비에 대한 기존의 실험식을 수정하였고, 수굴계수와 형상지수의 수리적 특성을 분석하였다. 일반적으로 유량비와 합류각이 커질수록 분리구역이 크게 나타났다. 합류부를 전후한 상하류 구간에서 수면의 추적에서 유량비와 합류각이 커질수록 배수위의 영향이 크게 나타났고, 합류부가 접하는 내측보다 외측의 배수영향이 크게 나타났다. 하류부 유량에 의해 등류수심을 산정하여 합류가 시작되는 점에서부터 하류의 등류수심에 이르는 곳까지의 거리를 $X_l$로 보고 합류각과 유량비와 단면폭 및 수축계수간의 상관관계식을 산출하였다. 유량비와 합류각에 따른 수로내의 배수위에 의한 최대수위와 분리구역에서의 최소수심과의 비를 분석하였다.