• Journal of the Korean Geographical Society
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• v.48 no.5
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• pp.615-628
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• 2013

The waterfall can be formed by difference between the height of up and down part in new channel, is formed by channel avulsion that rapidly changing of river channel course. This study described types and processes of waterfalls by channel avulsion, and analyzed rates and factors of waterfall recession, on object to 7 waterfalls in South Korea. Bulyeong falls at Uljin-gun, Yongchu falls at Yeongdeok-gun, Jikyeon falls at Yanggu-gun and Gwangpum falls at Uljin-gun are formed by natural incised meander cutoff. Samhyeongje falls at Taebaek-si and Guryong falls are formed by river capture processes, and Palbong falls at Chungju-si is formed by artificial channel cutting for farm land secured. The locations of waterfalls gradually moved to upstream over time by head erosion. The recession rates were measured by 3~4m/ka on Bulyeong falls, Yongchu falls, Jikyeon falls and Samhyeongje falls, to estimate of formation age. Recession rates of these 4 waterfalls were analyzed that have clearly positive correlations with drainage area, precipitation, corrosion and weathering capability of bedrock, and initial height of waterfall.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.225-230
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• 1998

The purpose of this study is to contribute the development of an El Nino prediction model. The objectives of the study are to (1) extract sea surface height data from the TOPEI/Poseidon altimeter, and (2) compare the relations among the sea surface height, sea surface temperature and wind field. NOAA AVHRR Multi-channel data is used for sea surface temperature and wind data is derived from ERS 1, 2 AMI wind scatterometer. The results showed that sea surface height has increased significantly during the El Nino season. The sea surface height is positively related to sea surface temperature and negatively related to zonal wind.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.9
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• pp.819-827
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• 1991

In this study, the efficiency of spectrum utilization has compared in case of channel spacking 100 KHz and 200 KHz by application of technical specifications of domestic FM broadcasting varing with effective radiated power, terrain irregularity factor and effective height of thrnsmit antenna. The results show that if arranging by 100 KHz channel total number of available channel will increase twice and the efficiency of spectrum unilization will be better 1.36 to 2.0 times than that of 200 KHz channel spacing.

• ETRI Journal
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• v.10 no.4
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• pp.118-126
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• 1988

A numerical analysis was performed for the flow field in the vertical channels consist of dummy cards and active cards to define the hydrodynamic role of dummy card which is often installed in electronic equipment between active cards to control the cooling air distribution. For a given velocity profile at the inlet and a pressure-based boundary condition at the outlet of the computation domain, the percentage of the flow rate distribution through active channel and dummy channel formed by an active card and dummy card, respectively, were investigated. As a result of present analysis, the pecentage of flow rate through active channel increases quadraticaly with the increase of the ratio of the height of barrier to the width of the dummy channel.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.276-279
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• 2002

A problem formulation and solution for design optimization of laminated composite channel section beam is presented in this study. The objective of this study is the determination of optimum section dimensions of composite laminated channel section beam which has equivalent flexural rigidities to flexural rigidities of steel channel section beam. The analytical model is based on the laminate theory and accounts for the material coupling for arbitrary laminate stacking sequence configuration. The model is used to determine the optimal section dimensions of composite channel section beam. The web height, flange width and thickness of the beam are treated as design variables. The solutions described are found using a global search algorithm, Genetic Algorithms (GA).

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2432-2437
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• 2007

The demand of high speed and miniaturization of electronic devices results in increased power dissipation requirement for thermal management. In this work, the effects of microchannel width, height and liquid flowrate on the cooling performances of microchannel waterblock are investigated experimentally. The microchannel waterblock considered ranged in width from 0.5 to 0.9 mm, with the channel height being nominally 1.7 to 9 times the width in each case. The experiments were conducted using water, over a liquid flow rate ranging from 0.2 to 2.0 lpm. The base temperature, thermal resistance and pressure drop increase with increasing of liquid flow rate. The measured thermal resistances ranged from 0.10 to 0.23 $^{\circ}C$/W for the channel 5.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.721-727
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• 2003

Freezing of turbulent water flow between two horizontal cooled parallel plates with the separated region has been investigated experimentally. The flow separation was induced by vertical plates (two-dimensional plates) situated at the inlet of the rectangular channel. The degree of flow separation was varied by employing vertical thin plates with various heights. Three kinds of the vertical plates with 8.0, 9.8 and 12.5 mm in height were utilized. The Reynolds number and cooling temperature ratio were ranged from $3.45\times10^3 to 1.73\times10^4$ and 7.0 to 20.0 respectively, The measurements show that the flow separation influenced remarkably on the local ice formation characteristics. The location of the first ice layer and the average heat transfer at the ice surface were found be correlated as a function of the Reynolds number, the cooling temperature ratio, and the orifice height ratio.

• Journal of Power System Engineering
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• v.18 no.2
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• pp.12-18
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• 2014

The local heat transfer of developed turbulent flows in the stationary ribbed rectangular convergent channels has been investigated experimentally. The rectangular convergent channels with one ribbed surface only have the inclination of $0.72^{\circ}$ and $1.43^{\circ}$ at which the ribbed wall is manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (p) to height (e) =10. The measurement was conducted within the range of Reynolds numbers from 15,000 to 89,000. The local heat transfer characteristics of the rectangular convergent channels are quite different from those of the ribbed square straight channel.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3086-3091
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• 2007

When a molten corium is relocated in a lower head of a reactor vessel, the ERVC (External Reactor Vessel Cooling) system is actuated as coolant is supplied into a reactor cavity to remove a decay heat from the molten corium during a severe accident. To achieve this severe accident mitigation strategy, the two-phase natural circulation flow in the annular gap between the external reactor vessel and the insulation should be formed sufficiently by designing the coolant inlet/outlet area and gap size adequately on the insulation device. For this reason, one-dimensional natural circulation flow tests were conducted to estimate the natural circulation flow under the ERVC condition of APR1400. The experimental facility is one-dimensional and scaled-down as the half height and 1/238 rectangular channel area of the APR1400 reactor vessel. As the water inlet area increased, the natural circulation mass flow rate asymptotically increased, that is, it converged at a specific value. And the circulation mass flow rate also increased as the outlet area, injected air flow rate, and outlet height increased. But the circulation mass flow rate was not changed along with the external water level variation if the water level was higher than the outlet height.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.653-657
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• 2004

The average bit error rate (HER) performance of a Gray coded arbitrary rectangular quadrature amplitude modulation (AR-QAM) signal with maximal ratio combining (MRC) diversity in an arbitrarily correlated Nakagami-m fading channel is derived and analyzed. The derived two types of general solutions are a simple closed-form and an integral form, depending on the types of the values (integer and non-integer) of the fading parameter. Using the derived equations in this paper, we analyzed the HER performances numerically based on the practical base station antenna configuration. The results show that MRC reception is a very effective scheme so far even though the combined signals are not independent each other because of the correlation values. The antenna height and separation of the MRC system relate to the correlation coefficient value between antennas, and go a long way with the diversity advantage. In particular, it is needed to be determined the antenna height that is carefully do for the diversity advantage because the correlation coefficient and the antenna height gain are contrary to each other from the aspect of the system performance. The expressions presented here can offer a convenient way to evaluate the exact HER performance of an arbitrary rectangular QAM signal with MRC diversity reception for various cases of practical interest on a correlated Nakagami fading channel.