• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.117-129
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• 2009

Evaporation over the world is expected to increase owing to increase in temperature by global warming. However, pan evaporation around the world has decreased in the past few decades. This study, which has been conducted in 18 meteorological gauging stations in Korean peninsula, investigates the changes in pan evaporation and climate variables such as precipitation, temperature, relative humidity, wind speed, sunshine hours, and percentage of sunshine, which can affect evaporation processes; the changes in these variables have been recorded between 1960 and 2007. At most gauging stations, pan evaporation shows statistically significant downward trends. The relative humidity, wind speed, sunshine hours, and percentage of sunshine also show downward trends. On the other hand, precipitation and temperature show upward trends. The spatial distribution of the downward trend in sunshine hours and percentage of sunshine correspond to that of the downward trend in pan evaporation. Scatter plots imply that pan evaporation has a strong positive correlation with the sunshine hours and percentage of sunshine, while it has a negative correlation with precipitation. At the Gangneung gauging station, the open water evaporation estimated using the Penman equation does not show the significant downward trend shown by pan evaporation. This result implies that pan evaporation is not a good indicator of potential or open water evaporations during the investigation of their long-term variability. Finally, this study explains the complementary relationship between pan and actual evaporations. Decreases in the pan evaporation can act as an evidence for the ever-increasing actual evaporation.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.1
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• pp.161-167
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• 2001

The purpose of this study is to find out the difference of Zoysia matrella's evaporation in between 100 percent soil and mixed soil with 50 percent of perlite to create green spaces on the artificial ground. It is believed that the weight against the artificial ground will be reduced, provided the vegetation is possible in the circumstance of the mixed sol with 50 percent of perlite. The study employed a modified Makkink's model by Iwasa who had developed the model for estimating Zoysia matrella's evaporation in the natural ground using the Makkink's formula in 1997 at Chiba University, Japan. The parameter of Makkink's formula is the solar radiation. For that reason, the Makkink's formula is simple and easy to measure the parameter and has a high utility. If the outcomes from mixed soil are close to modified Makkinks formula, the modified Makkink's formula will be applied to estimate in the artificial ground with mixed soil with 50 percent of perlite. Weather observation and actual amount of evaporation of Zoysia matrella have been measured, and the relation between weather condition and actual amount of evaporation had been also investigated. In line with this, we found out that there is a relevant relationship between daily average temperature, the modified Makkink's model by Iwasa, and the actual amount of evaporation. As the results of the experiment, the outcomes from mixed soil with 50 percent of perlite have very high relation to 100 percent soil. In addition, mixed soil has more adhesion with water than natural soil. However, it needs to be adequately maintained in terms of fertilization and damage from disease and harmful insects until the gras fastens its roots into the soil. By using mixed soil with 50 percent of perlite, the load from soil on the artificial ground can be reduced. The study on the growth of the grass throughout the plant vegetation and the actual amount of evaporation in the mixed soil with 50 percent of perlite should be performed in the future.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.4
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• pp.484-491
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• 2012

The hydrological components of a sandy loam soil of nearly level in Chuncheon over 30 years were computed using the E-DiGOR model. Daily simulations were carried out for each year during the period of 1980 to 2009 using standard climate data. Reference evapotranspiration and potential soil evaporation based on Penman-Montheith model were higher during May to August because of the higher atmospheric evaporative demand. Actual soil evaporation was mainly found to be a function of the amount and timing of rainfall, and presumably soil wetness in addition to atmospheric demand. Drainage was affected by rainfall and increased with a higher amount of precipitation and soil water content. Excess drainage occurred throughout rainy months (from July to September), with a peak in July. Therefore, leaching may be a serious problem in the soils all through these months. The 30-year average annual reference evapotranspiration and potential soil evaporation were 951.5 mm and 714.2 mm, respectively. The actual evaporation from bare soil varied between 396.9-528.4 mm and showed comparatively lesser inter-annual variations than drainage. Annual drainage rates below 120 cm soil depth ranged from 477.8 to 1565.9 mm. The long-term mean annual drainage-loss was approximately two times higher than actual soil evaporation.

• Water for future
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• v.5 no.2
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• pp.44-48
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• 1972

This article includes hydrometeorological analysis of evapotranspiration and precipitation, which are used available basic data for a certain basin water budget. Evapotranspiration on water surface, bare soil and rice fields is directly measured by Thornthwaite's type Lysimeter and on water surface and vegetables computed using the Penman's equation. Areal precipitation is analized through the Thiessen method and arithmatic mean method. It is interested fact that the correlation coefficient for Class A Pan's evaporation vs. the actual evapotranspiration is the highest value among the coefficients for different type evaporimeter and Penman equation, and evaporation ratio on rice field's evapotranspiration vs. Class A Pan's evaporation is 1. 5-2. 3.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.5
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• pp.373-380
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• 2009

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.75-81
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• 2008

The water shortage in mega cities in Asia, which face a rapid growth in urban population, is an outstanding problem. It is important, therefore, to accurately estimate the water balance in each city in order to use the limited water resources effectively. In this study, we estimated the potential water resources in し sixteen mega cities in Asia. The target cities were Delhi and Calcutta, India; Colombo, Sri Lanka; Dhaka, Bangladesh; Yangon, Myanmar; Bangkok, Thailand; Kuala Lumpur, Malaysia; Singapore; Jakarta, Indonesia; Hanoi, Vietnam; Beijing and Hong Kong, the People's Republic of China; Seoul, the People's Republic of Korea; Manila, the Philippines, and Sapporo and Tokyo, Japan. The potential water resources were estimated by subtracting the actual evaporation from the amount of rainfall. The actual evaporation was estimated using the potential evaporation obtained by Hamon's equation which requires the air temperature and the possible hours of sunshine. When the results of Hamon's and Penman's evaporation equations were compared, a considerable error appeared in the low latitude region. The estimation using Hamon's equation was corrected with the linear regression line of Hamon's and Penman's equations. A classification of the land cover was carried out based on satellite photographs of the target cities, and the volume of surface runoff for each city was obtained using the runoff ratios which depended on the land cover. As a result, the potential water resources in the above mega cities in Asia were found to be greater than the world average. However, the actual water resources which are available for one person to use are probably very limited.

• Magazine of the Korean Society of Agricultural Engineers
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• v.19 no.3
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• pp.4472-4482
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• 1977

In order to estimate furture consumtive use, some statistical characteristics of 22-year pan evaporation data at four selected stations were calculated in this study. Districal distribution, trend analysis and time-series, statistical and periodic analysis for annual, monethly and ten-day values were performed in the statistical analysis. The stations are Seoul, Taeku, Jeonju and Mokpo for monthly data, and Suweon data are compared to the reported Penman values. The results are as followed: 1. Annual evaporation ranged to 990-1,375mm varying with the locations of the stations. The Districal distribution of evaporation in the Republic is shown in Fig. 1. 2. The trend analysis for annual evaporation resulted in detail in Table 2 and Fig. 2, through simple moving average methods. The results show relatively short-period data of about 10 years would be acceptable for field use. 3. The means and dispersions of monthly evaporation at four stations are detailed in Table 3. 4. The monthly evaporation approached to the trend of normal distribution Fig. 3 showed the examples of normal distribution for each typical monthly data. 5. The correlograms detailed in Fig. 4, shows the time-series characteristics of monthly evaporation, whose periodic term should be twelve months. 6. The periodic analysis for monthly evapolation results in Table 4. Fig. 5 shows the comparison of estimated values to actual and the trend approaches Shuster's periodic trend. 7. A periodic description of days after March 1 for irrigation periods was developed to predict ten-day evaporation in Fig. 6. The ten-day etraporation is different in the distribution form and occurence period of maximum values from the reported Penman's man's evapotranspiration.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.36-43
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• 1999

Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.3
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• pp.244-252
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• 2007

A long-term change in the evaporation rate have an influence on the hydrologic processes at the interface between the land surface-air and crop yield. Several previous studies have reported declines in pan evaporation rate, while actual evaporation rate is expected to increase due to anthropogenic global change in the future. The decreasing trend of pan evaporation rate might be involved with global warming and accordingly the trend of annual pan evaporation rate also needs to be checked here in Korea. In this study, 14 points of pan evaporation observation are intensively studied to investigate the trend of pan evaporation for the time period of 1970-2000. Annual pan evaporation is decreasing at the rate of 1.6mm/yr, which corresponds to approximately 50mm for 30 years. Annual pan evaporation rate is larger by $\sim10%$ at the coastal area and decreasing rate is faster as -2.46 mm/yr per year, while that is -0.82 mm/yr per year at the in-land area. The results of the Mann-Kendall trend test shows 4 points are decreasing and 10 points are unchanged with 95% confidence interval. But national annual average values show the decreasing trend of pan evaporation rate as a whole, which corresponds to general trend all over the world. This study will contribute to a variety of studies on water resources, hydrology, agricultural engineering, meteorology, and coastal engineering in association with future global climate change.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.533-542
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• 2013

In this study, estimation methods for actual evapotranspiration have been studied using the concept of potential and actual evapotranspiration. Among the diverse estimation methods, SWAT-K application is chosen for hydrological modeling. For Jeju island we have characterized annual and monthly evapotranspiration using SWAT-K. In the results, simulated potential evapotranspiration reached to the 91% of small pan evaporation. With respect to the temperature lapse rate($-6^{\circ}C/km$) depending on the altitude of Halla mountain, evapotranspiration rate decreased by 7.5% compared to the status when the temperature data from the Jeju weather station were applied to the watershed. As the average of annual rainfall increased, potential evapotranspiration was increased, actual evapotranspiration was, however, decreased.