• 한국수자원학회논문집
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• 제46권7호
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• pp.767-781
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• 2013

본 연구에서는 수로가 비대칭으로 연결되어 있는 합류부 및 합류부 주위에서의 홍수흐름특성에 대해 수리모형실험 및 수치모의를 통해 분석을 수행하였다. 본 연구에서 적용된 수치모형은 상업용 3차원 CFD 모형인 ANSYS CFX(ver. 14)이다. 수로 내로 유입되는 유량변화에 따른 수리모형실험과 수치모의에 의한 합류부 및 합류부 주위에서의 수심분포에 대한 측정된 결과와 모의된 결과를 비교한 결과 비교적 잘 일치하는 것으로 나타났다. 합류부와 연결된 네 개의 수로중 물이 유입되는 두개 수로 방향에 따라 합류부 및 합류부 주위에서의 수심분포의 양상은 달라지며, 수로내로 유입되는 유량의 증가에 따라서도 많은 차이가 발생된다는 것을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.329-336
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• 2010

The paper describes the electrical and optical properties of underwater discharges in highly inhomogeneous electric fields caused by 1.2/50 ${\mu}s$ impulse voltages as functions of the polarity and amplitude of the applied voltage, and various water conductivities. The electric fields are formed by a point-to-plane electrode system. The formation of air bubbles is associated with a thermal process of the water located at the tip of the needle electrode, and streamer coronas can be initiated in the air bubbles and propagated through the test gap with stepped leaders. The fastest streamer channel experiences the final jump across the test gap. The negative streamer channels not only have more branches but are also more widely spread out than the positive streamer channels. The propagation velocity of the positive streamer is much faster than that of the negative one and, in fact, both these velocities are independent of the water conductivity; in addition the time-lag to breakdown is insensitive to water conductivity. The higher the water conductivity the larger the pre-breakdown energy, therefore, the ionic currents do not contribute to the initiation and propagation of the underwater discharges in the test conditions considered.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1338-1348
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• 2016

A novel fully passive small modular superheated water reactor (SWR) for underwater deployment is designed to produce 160 MWe with steam at $500^{\circ}C$ to increase the thermodynamic efficiency compared with standard light water reactors. The SWR design is based on a conceptual 400-MWe integral SWR using the internally and externally cooled annular fuel (IXAF). The coolant boils in the external channels throughout the core to approximately the same quality as a conventional boiling water reactor and then the steam, instead of exiting the reactor pressure vessel, turns around and flows downward in the central channel of some IXAF fuel rods within each assembly and then flows upward through the rest of the IXAF pins in the assembly and exits the reactor pressure vessel as superheated steam. In this study, new cladding material to withstand high temperature steam in addition to the fuel mechanical and safety behavior is investigated. The steam temperature was found to depend on the thermal and mechanical characteristics of the fuel. The SWR showed a very different transient behavior compared with a boiling water reactor. The inter-play between the inner and outer channels of the IXAF was mainly beneficial except in the case of sudden reactivity insertion transients where additional control consideration is required.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.149-152
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• 2007

The detection of yellow sand dust using satellite has been utilized from various bands from ultraviolet to infrared channels. Among them, Infrared channels have an advantage of detecting aerosols over high reflecting surface as well as during nighttime. Especially, brightness temperature difference between 11 and 12{\mu}m(BTD) was often used to distinguish between water cloud and yellow sand, because Ice and liquid water particles preferentially absorb longer wavelengths while aerosol particles preferentially absorb shorter wavelengths. We have found that the BTD significantly depends on surface temperature, emissivity, and zenith angle and thereby the threshold of BTD. In order to overcome these problems, we have constructed the background brightness temperature threshold of BTD and then subtracted it from BTD. Along with this, we utilized high temporal coverage of geostationary satellite, MTSAT-1R, to verify the reliability of the retrieved signal in conjunction with forecasted wind information. The statistical score test illustrated that this newly developed algorithm showed a promising result for detecting mineral dust by reducing the errors in the current BTD method.

• 물과 미래
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• 제29권1호
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• pp.181-190
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• 1996

충적수로에서 유사량의 정량적인 산정은 초기운동개념이나 유사이송개념에 의한 방법에 기초하여 구하고 있다. 본는 연구에서는 유사이송개념에 의한 결정방법중의 하나인 회귀분석법에 의해 총유사량을 산정할 수 있는 유사농도에 관한 관계식을 유도하였다. 관계식의 유도에는 135개의 현장자료와 225개의 실험자료가 포함된 360개의 실측자료가 이용되었다. 또한 다중회귀분석법에 의한 관계식은 수심, 평균유속, 수로경사, Froude 수 및 하상재료의 중앙입경을 독립변수로 하여 유도되었다.

• 한국수산과학회지
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• 제18권2호
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• pp.157-165
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• 1985

어장환경관리의 기본자료를 얻기 위하여 1984년 6월중에 가막만에서 실시한 해양관측자료를 가지고 상기만의 밀물과 썰물시 해황분포를 알아보고 그 특성이 지형적 요인에 의해 크게 좌우됨을 살폈다. 가막만은 두개의 만구와 돌출한 도서 및 지세 등 그 지형적 여건에 의해 4개의 특징적 수괴가 나타난다. 내만수는 내륙의 영향이 강한 정체성을, 여수항수는 섬진강 영향이 큰 저염의 외해성을, 만외수는 해저난류 또는 와류발생으로 수직균질한 외해성을, 중간수는 만외수와 내만수의 중간성격이다. 밀물때 양만구로 유입한 해수는 대략 소경도와 항대를 연결하는 선에서 만난다. 군내리근에서는 지형성 와류 혹은 해저난류가 발생하는 것으로 추정되는데, 밀물때는 해수의 침강이, 썰물때는 저층수의 특성치가 보여지며 그 크기는 약 3 km 까지 뻗친다.

• Geomechanics and Engineering
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• 제28권6호
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• pp.613-624
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• 2022

A study of the evolution of overburden fractures under the solid-fluid coupling state was conducted based on the geological and mining characteristics of the coal seam depth, weak strata cementation, and high-intensity mining in the mining areas of West China. These mining characteristics are key to achieving water conservation during mining or establishing groundwater reservoirs in coal mines. Based on the engineering background of the Daliuta Coal Mine, a non-hydrophilic simulation material suitable for simulating the weakly cemented rock masses in this area was developed, and a physical simulation test was carried out using a water-sand gushing test system. The study explored the spatial distribution and dynamic evolution of the fractured zone in the mining overburden under the coupling of stress and seepage. The experimental results show that the mining overburden can be vertically divided into the overall migration zone, the fracture extension zone and the collapse zone; additionally, in the horizontal direction, the mining overburden can be divided into the primary fracture zone, periodic fracture zone, and stop-fracture zone. The scope of groundwater flow in the overburden gradually expands with the mining of coal seams. When a stable water inrush channel is formed, other areas no longer generate new channels, and the unstable water inrush channels gradually close. Finally, the primary fracture area becomes the main water inrush channel for coal mines. The numerical simulation results indicate that the overlying rock breaking above the middle of the mined-out area allows the formation of the water-conducting channel. The water body will flow into the fracture extension zone with the shortest path, resulting in the occurrence of water bursting accidents in the mining face. The experimental research results provide a theoretical basis for the implementation of water conservation mining or the establishment of groundwater reservoirs in western mining areas, and this theoretical basis has considerable application and promotion value.

• Korean Journal of Hydrosciences
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• 제1권
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• pp.49-60
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• 1990

Manning's roughness factor to flow in sand-bed channels may be divided into the grain roughness factor nd the form roughness factor. The grain roughness factor may be dedermined by using Keulegan's formula. By using available experimental data, it was found there is a unique relationship between the form roughness and the hydraulic radius to sediment particle size ratio for a given value of the Froude number. The form roughness and the bed form may be determined by using this unique relationship. The technique for engineering applications of the results appears to be quite simple.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1993년도 정기학술강연회 발표논문 초록집
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• pp.9-13
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• 1993

Modernization of a port requires a considerable port facility expansion through grading up the cargo handling efficiency, increasing water depth of channels and basins to accomodate Large ships, etc. In many ports in the world, the needs of bigger ship calls in excess of conventional capacity of channels and basins demand for capital dredging as well as maintenance dredging resulting from siltation, and those activities are incurring heavy annual expenditure of the ports. (omitted)

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.778-779
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• 2005