• 한국해양공학회지
• /
• 제6권2호
• /
• pp.35-40
• /
• 1992

A recently developed new technique for measuring the fraction of wetted area has applied to pool boiling of water. The basis of the new applied technique of ultrasonic makes use of the reflection of ultrasonic from the vapour surface to measure the fraction of wetted area values. The results are the measured fraction of wetted area values in nucleate and transition boiling and the pool boiling curve for water under steady state conditions. The measurement of this paper shows a fraction of wetted areaf around 0.98 at the critical heat flux for water.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2004년도 학술발표회
• /
• pp.1331-1334
• /
• 2004

Wet/Dry phenomena typically incorporate a number of complex flow mechanism. These include a momentum transfer and turbulent mixing caused by the delivery of water. However currently available one dimensional schemes applicable to wet/dry process cannot effectively simulate such process. Two dimensional finite element model, SU/PG, is used to simulate complex flow in this study. The Wetted Area Method in SU/PG allows elements to transition gradually between wet and dry states. The model is applicable to a straight river reach with irregular bathymetry. Wet/dry calculation using the wetted area method can simulate simple numerical test. The computed results of velocity vectors and water depth agree with those of observed. The methodology Presented in this study will contributed to two-dimensional wet/dry analysis in a river in this country.

• 한국농공학회지
• /
• 제24권2호
• /
• pp.56-66
• /
• 1982

This study was carried out in order to estimate water losses in irrigation canals, which may be used to evaluate the water requirement for irrigation projects. The conveyance losses were measured by the inflow-outflow method, the seepage losses were measured by the ponding method, and the operation losses in the course of irrigation were calculated by comparing the two kinds of losses. The results obtained in this experiment were as follows; 1. Conveyance losses per unit area of wetted perimeter by the main irrigation canal, the secondary irrigation canal and the tributary irrigation canal, were 1.399${\times}10^{-5}m^3/sec/m^2$, 5.154${\times}10^{-5}m^3/sec/m^2$, and 2.67${\times}10^{-5}m^3/sec/m^2$ respectively in the Goong-sa area. And they were 1.934${\times}10^{-5}m^3/sec/m^2$, 2.149${\times}10^{-5}m^3/sec/m^2$, and 4.558${\times}10^{-5}m^3/sec/m^2$ respectively in the Seong-dug area. 2. Seepage losses per unit area of wetted perimeter by the secondary irrigation canal and the tributary irrigation canal, were 2.180${\times}10^{-6}m^3/sec/m^2$ and 2.168${\times}10^{-6}m^3/sec/m^2$ in the Goong-sa area, 1.150${\times}10^{-6}m^3/sec/m^2$ and 1.084${\times}10^{-6}m^3/sec/m^2$ in the Seong-dug area respectively. 3. Operation losses per unit area of wetted perimeter by the secondary irrigation canal and the tributary irrigation canal, were 4.936${\times}10^{-5}m^3/sec/m^2$ and 2.453${\times}10^{-5}m^3/sec/m^2$ in the Goong-sa area, 2.034${\times}10^{-5}m^3/sec/m^2$ and 4.450${\times}10^{-5}m^3/sec/m^2$ in the Seong-dug area respectively. 4. Conveyance, seepage and operation losses in the Goong-sa area were 6.7%, 94.6%, and 14.0% more than those in the Seong-dug area. Operation losses amount to about 17 times as much as seepage losses in the Goong-sa area and about 29 times in the Seong-dug area. 5. The seepage losses depend much on the soil texture, ranging from 7.437${\times}10^{-7}m^3/sec/m^2$ to 2.430${\times}10^{-6}m^3/sec/m^2$. 6. Water loss rates in the main irrigatin canal, the secondary irrigation canal and the tributary irrigation canal, were estimated as 8.49%, 37.27% and 9.81% respectively in the Goong-sa area. And they were estimated as 15.10%, 32.67% and 13.78% respectively in the Seong-dug area.

• 한국항해항만학회지
• /
• 제31권10호
• /
• pp.813-818
• /
• 2007

선박의 선형시험설비로는 회류수조, 예인수조 등이 있으나, 소형 고속선박은 실선 대응 모형선의 축적비가 대형선에 비해 매우 작고 수조의 유속과 예인전차의 속도제한으로 고속선의 설계선속까지의 성능검증에는 한계로 작용하였다. 이에, 고속 활주형선의 선형시험 검증을 위해 실 해상모형시험기법을 정립하였다. 한편, 고속 Stepped Hull선형은 일체형 활주형 선저선형에 비하여 고속 주행시 공기공급에 따른 접수면 감소로 인하여 저항감소에 따른 속도향상과 연비절감 효과가 있으나, 선미 좌우측의 접수면 감소에 따른 횡동요 안정성이 감소되는 경향이 있다. 이에, 본 논문에서는 고속 선형시험이 가능한 해상모형시험을 이용하여 선미 보조동체 장착 유무에 따른 고속 Stepped Hull 선형의 횡동요 및 저항특성을 비교, 분석한 것이다.

• 환경영향평가
• /
• 제20권1호
• /
• pp.1-11
• /
• 2011

This study was carried out to suggest the baseline data necessary for vegetation restoration at riverine wetland within stream corridor. We used the prevalence index for wetland assessment by applying the method of weighted averages with index values based on five hydrophyte indicator status as defined by estimated probability occurred in wetland. We selected near nature and urbanized reach of Gap and Yanghwa streams as experimental site. Although two sites have some different disturbance and characteristics of watershed, they showed that similarity of vegetation community including three dominant species - Salix koreensis, Phragmites communis, Miscanthus sacchariflorus - was very high. But in case of Yanghwa stream, various kinds of emergent plants along wetted condition were distinctly occurred, resulted from difference of hydrological regime and substrate, etc. Degree of naturalness of vegetation at the sampled areas indicated that near nature area of Gap stream and all area of Yanghwa stream were fitted as riverine wetland, while urbanized area of Gap stream has changed into upland condition. In conclusion assessment system using prevalence index would be considered an effective method for evaluating of natural states of riverine wetland, but further integrated consideration of physical, hydrological, and biological factors of stream process, and also with considering the difference between those qualitative data of vegetation community.

• 대한조선학회지
• /
• 제24권2호
• /
• pp.11-19
• /
• 1987

A Series 60, $C_b=0.60$ model was tested in the towing tank of Seoul National University. Total resistance, hull attitude, wake distributions and wave measured at FR condition(free trim and sinkage) and FX condition(fixed trim and sinkage). From the measured data, residual, viscous and wave pattern resistance components were evaluated and compared. It is found that the changes in wetted surface area should be considered in predictions of frictional resistances, and can be easily found from hydrostatic data and measured mean sinkages without additional tests. Applications of the concept to the geosim tests of Series 60, Wigley, Lucy Ashton models show that the conventional extrapolation method can be improved considerably.

• 대한설비공학회지:설비저널
• /
• 제15권2호
• /
• pp.188-195
• /
• 1986

Condensation heat transfer can be classified in dropwise condensation and filmwise condensation, and for the industrial purpose, the former is more useful than the latter because of the higher heat transfer rate. But it is difficult to maintain the dropwise condensation continuously since most of the metal surfaces become wetted after exposure to a condensing vapor over an extended period of time. To maintain dropwise condensation continuously , various surface coatings and promoters have been used recently, but these methods must be reconsidered about the durability of condensing surface. Therefore, in this study, evaporating method of various pure metals on the condensing surface has been performed to maintain dropwise condensation. The results have showed that the heat transfer rate of silver evaporating surface is higher than any other metal evaporating in dropwise area. Transition temperature and filmwise condensation curves are uniform regardless of kinds of evaporating metals.

• 마이크로전자및패키징학회지
• /
• 제22권1호
• /
• pp.35-41
• /
• 2015

In this study, in order to improve the reliability of ACF interconnections, solder ACF joints were investigated interms of solder joint morphology and solder wetting areas, and evaluated the electrical properties of Flex-on-Board (FOB) interconncections. Solder ACF joints with the ultrasonic bonding method showed excellent solder wetting by broken solder oxide layers on solder surfaces compared with solder joints with remaining solder oxide layer bonded by the conventional thermo-compression (TC) bonding method. When higher target temperature was used, Sn58Bi solder joints showed concave shape due to lower degree of cure of resin at solder MP by higher heating rate. ACFs with epoxy resins and SAC305 solders showed lower degree of resin cure at solder MP due to the slow curing rate resulting in concave shaped solder joints. In terms of solder wetting area, solder ACFs with $25-32{\mu}m$ diameters and 30-40 wt% showed highest wetted solder areas. Solder ACF joints with the concave shape and the highest wetting area showed lower contact resistances and higher reliability in PCT results than conventional ACF joints. These results indicate that solder morphologies and wetting areas of solder ACF joints can be controlled by adjustment of bonding conditions and material properties of solder and polymer resin to improve reliability of ACF joints.

• 한국항해항만학회지
• /
• 제32권8호
• /
• pp.583-588
• /
• 2008

활주형선은 고속 운항시 선저에 동적압력을 발생시켜 선체를 부상시킴으로서 저항이 감소하게 되어 고속의 항주가 가능하게 된다. 일반적으로 선저에 스텝을 적용한 선형은 일체형 활주형선에 비하여 고속 주행시 선저 공기공급에 따른 접수면 감소로 인하여 전체저항 감소에 따른 속도향상과 연비절감 효과가 있다. 본 논문에서는 고속 선형시험이 가능한 실 해역모형시험을 이용하여 선저 스텝개수에 따른 고속 Stepped Hull 선형의 저항성능을 비교, 분석하였다. 시험결과, 2개의 스텝을 가지는 선형이 최소저항 선형임을 확인할 수 있었다.

• Journal of Welding and Joining
• /
• 제23권5호
• /
• pp.25-29
• /
• 2005

Steel has been mainly used in the automotive industry, because of good mechanical properties, weldability and so on. However, there has been increase in using aluminum to reduce the weight of vehicle. This leads to improve fuel efficiency and to reduce air pollution. A steel-aluminum hybrid body structure is recently used not only to reduce the weight of vehicle but also to increase safety. In this paper, the laser beam joining method is suggested to join steel and aluminum. To avoid making brittle intermetallic compounds(IMC) that reduce mechanical properties of the joint area, only aluminum is melted by laser irradiation and wetted on the steel surface. The brittle IMC layer is formed with small thickness at the interface between steel and aluminum. By controlling the process parameters, brittle IMC layer thickness is suppressed under 10 micrometers which is a criterion to maintain good mechanical properties.