• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.138-145
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• 2013

In order to develop the efficient control algorithm of the two-fluid fogging system, cooling experiments for the many different types of fogging cycles were conducted in tomato greenhouses. It showed that the cooling effect was 1.2 to $4.0^{\circ}C$ and the cooling efficiency was 8.2 to 32.9% on average. The cooling efficiency with fogging interval was highest in the case of the fogging cycle of 90 seconds. The cooling efficiency showed a tendency to increase as the fogging time increased and the stopping time decreased. As the spray rate of fog in the two-fluid fogging system increased, there was a tendency for the cooling efficiency to improve. However, as the inside air approaches its saturation level, even though the spray rate of fog increases, it does not lead to further evaporation. Thus, it can be inferred that increasing the spray rate of fog before the inside air reaches the saturation level could make higher the cooling efficiency. As cooling efficiency increases, the saturation deficit of inside air decreased and the difference between absolute humidity of inside and outside air increased. The more fog evaporated, the difference between absolute humidity of inside and outside air tended to increase and as the result, the discharge of vapor due to ventilation occurs more easily, which again lead to an increase in the evaporation rate and ultimately increase in the cooling efficiency. Regression analysis result on the saturation deficit of inside air showed that the fogging time needed to change of saturation deficit of $10g{\cdot}kg^{-1}$ was 120 seconds and stopping time was 60 seconds. But in order to decrease the amplitude of temperature and to increase the cooling efficiency, the fluctuation range of saturation deficit was set to $5g{\cdot}kg^{-1}$ and we decided that the fogging-stopping time of 60-30 seconds was more appropriate. Control types of two-fluid fogging systems were classified as computer control or simple control, and their control algorithms were derived. We recommend that if the two-fluid fogging system is controlled by manipulating only the set point of temperature, humidity, and on-off time, it would be best to set up the on-off time at 60-30 seconds in time control, the lower limit of air temperature at 30 to $32^{\circ}C$ and the upper limit of relative humidity at 85 to 90%.

• Korean Journal of Environmental Agriculture
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• v.24 no.1
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• pp.24-28
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• 2005

Waste of the hydroponic solution from the plastic film house cultivation was recycled to grow the red pepper(Capsicum annum L.) in upland fields as supplement for plant nutrients and irrigation sources. Application of hydroponic waste solution increased the pH and EC of the soils, coupled with the increases in the concentrations of exchangeable cations(Ca, Mg, and K), total nitrogen, $NH_4-N,\;and\;NO_3-N$. Growth and yield of red pepper were highest when the treatment of chemical fertilizer(70%) was combined with hydroponic waste solution(30%). Amounts of the daily producing hydroponic waste solution were 2,880 L $ha^{-1}\;day^{-1}$ from the experimental facilities and this could irrigate $409.86m^2$ of area to compensate for the amount of water loss by evapotranspiration(3%). The overall results demonstrated that hydroponic waste solution could be recycled as plant nutrients and irrigation water resources for enhancing soil fertility and environmental quality.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.748-754
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• 2010

The contents of soil organic matter (SOM) and $Al_o+1/2Fe_o$ in soils are important criteria for the classification of new Andisols in Soil Taxonomy system. There are many soil types in Jeju Island with various soil forming environments. This paper was conducted to estimate the contents of soil organic matter and the content of ammonium oxalate extracted Al and Fe ($Al_o+1/2Fe_o$) using various environmental variables and to make soil property maps using a statistical analyses. The soil samples were collected from 321 locations and analyzed to measure the contents of SOM and $Al_o+1/2Fe_o$. It was analyzed the relationships among them and various environmental variables such as temperature, precipitation, net primary product, radiation, evapotranspiration, altitude, soil forming energy, topographic wetness index, elevation, difference surrounded area, and distances from the shore and the peak. We can exclude multi-collinearity among environmental variables with principal component analysis and reduce all the variables to 3 principal components. The contents of SOM and $Al_o+1/2Fe_o$ were estimated by multiple regression models and maps of them were made using the models.

• Journal of Bio-Environment Control
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• v.3 no.1
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• pp.58-65
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• 1994

It is necessary to effective temperature and humidity management for normal growth of crops in protected cultivation during the summer season. Because the highest temperature of vinyl house inhibit normal growth of crop and decrease of crop production or marketability in summer season. Finally, the vinyl house was impossible some crop cultivation in summer season. This study was conducted to investigate effective and economic method for temperature drop in protected cultivation during the summer season. 1. In medium size vinyl house(5$\times$13$\times$3m), the effect of temperature drop appeared the highest in treatment of shading with aluminium thermal curtain＋fog system＋ventilation with fan. The effect of temperature drop was about 1$0^{\circ}C$ lower than outer air temperature and about 4$^{\circ}C$ lower than outer soil temperature. 2. The effect of temperature drop according to shading with aluminium thermal curtain＋fog system＋ventilation with fan during the highest temperature of summer season Jul., 20 to Aug., 21 was appeared about 8$^{\circ}C$ lower than outdoor above ground(1.2m) and about 7$^{\circ}C$ lower than outdoor surface ground. 3. The changes of solar radiation during a day according to shading with aluminium thermal curtain＋ventilation with fan and shading with black curtain＋ventilation with fan treatments was appeared respectively about 29.3%, 32.5% of outdoor solar radiation a fine day and respectively about 27.4%, 31.8% of outdoor solar radiation a cloudy day.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.191-200
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• 2016

The ventilation effect of a ventilation system, which is classified as the forced ventilation and natural ventilation, is predominantly dependent on the combination of air supply and discharge. Perhaps the simplest ventilation is merely supplying the air as it is. However, to improve the indoor working environment during the summer, an air supply that is cooled to some extent has been widely adopted. Recently, a cooling method utilizing the vaporization of water was introduced. In this study, the performance of an evaporation-type air supply unit that was produced by Japan K-company and was installed in a shoe-manufacturing plant in Busan was investigated. The purpose of the experiment was to measure how much the supplied air could be cooled. From this experimental study, we confirmed that the evaporation-type air supply system is efficient, capable of improving the working environment during the summer while minimizing the energy cost.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.2
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• pp.146-154
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• 2014

In the result of effect on freezing damage reduction by the shade net colors and the shade rate to tea trees during wintering period, the high shade ratio decreased tea trees growth and increased freezing damage and 55% of shade ratio based on non treatment developed new leafs and green leaf productivity. By the shade net colors, colorless shade net (55% of shade type) treatment and green shade net treatment increased green leaf productivity and decreased damaged area compare to non treatment shade net and black shade net treatment. Colorless net shade treatment reduced over 50% of freezing damage and increased (10a) 68 kg for green leaf productivity compare to non treatment shade net. The colors of shade net treatments for reduction freezing damaged in order of Black < Green < Colorless but reduction of freezing damage was so high. In the relative microclimates, treatment shade nets were $0.7^{\circ}C$ lower, average relatively humidity 14.9% higher, soil temperature $0.6^{\circ}C$ lower and soil moisture 4.6% higher than non treatment shade net. And treatment shade nets decreased average wind speed 0.7 m/s and it showed us treatment net shades effected to excessive evapotranspiration and soil dry by wind and considered one of good solution for freezing damages.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.1
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• pp.14-20
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• 1986

Responses of three different crops to soil water status were investigated in a Bonryang Sandy loam for 5 years. The changes in soil water potential, water and nutrient uptakes, growth pattern, water use efficiency and yield were analyzed under different irrigation conditions. Chinses cabbage showed more water stress than radish and red pepper in the non-irrigatedcultivation. The higher soil water potential, the more nutrient and water uptake, and evapotranspiration were observed. Water use efficiency was increased with the increase of evapotranspiration up to the optimum amount, whereas the efficiency was decreased when evapotranspiration was exceeded the optimum lebel. Little growth of chinese cabbage was observed when the soil water potential was lower than -1.7 bar at 20-30 cm depth in spring cultivation. The optimum soil water potential for irrigation was -0.2 bar, -0.5 bar and -0.2 - -0.5 bar for chinese cabbage, radish and red pepper, respectively. Optimum irrigation markedly improved the crop quality and yield in comparison to non irrigation condition.

• Journal of Environmental Policy
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• v.13 no.3
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• pp.43-73
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• 2014

Cities in Korea have rapidly urbanized and they are not well prepared for natural disasters which have been increased by climate change. In particular, they often struggle with urban flooding. Recently, green infrastructure has been emphasized as a critical strategy for flood mitigation in developed countries due to its capability to infiltrate water into the ground, provide the ability to absorb and store rainfall, and contribute to mitigating floods. However, in Korea, green infrastructure planning only focuses on esthetic functions or accessibility, and does not think how other functions such as flood mitigation, can be effectively realized. Based on this, we address this critical gap by suggesting the new green infrastructure planning framework for improving urban water cycle and maximizing flood mitigation capacity. This framework includes flood vulnerability assessment for identifying flood risk area and deciding suitable locations for green infrastructure. We propose the use of the combination of frequency ratio model and GIS for flood vulnerability assessment. The framework also includes the selection process of green infrastructure practices under local conditions such as geography, flood experience and finance. Finally, we applied this planning framework to the case study area, namely YeonJe-gu an Nam-gu in Busan. We expect this framework will be incorporated into green infrastructure spatial planning to provide effective decision making process regarding location and design of green infrastructure.

• Fire Science and Engineering
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• v.15 no.4
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• pp.41-48
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• 2001

Halogen-based fire suppressing agents have been the most effective fire suppressants and widely used for flammable liquid and electric fire. However they have environmental problems causing stratospheric ozone depletion and globe warming. As a substitution of halon, fire suppression system using fine water mist is one of an effective fire suppressant. Suffocating and cooling effects of water mist are increased by the evaporation characteristics because it has droplet size less than 1,000 $\mu{m}$ and very large surface area. In this study, the extinguishing characteristics of fire was measured with changing of water mist droplet size, flow density; discharge pressure, and fire size. As a result, the extinguishing time of pool fire was shortened with the increase of flow density and in case of low flow density less than 0.5$\pm$0.05 ml/$\textrm{cm}^2$ . min, the extinguishing time was shortened with the increase of droplet size. The cycling discharge was effective for $\eta$-heptane pool fire, and total amount of water mist required to extinguish fire was reduced to a quarter compare with continuous discharge.

• Plant Journal
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• v.16 no.3
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• pp.42-46
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• 2020

In the large LNG process in FLNG or FSRU, sudden temperature drops of the steel in the event of LNG leaks may cause brittle fracture of the structure. In this paper, we investigate the principle and process of forming a cryogenic fluid on a steel plate through a cryogenic spillage experiment, and analyze the correlation of the temperature distribution of the steel plate according to the distance from the nozzle and exposure time. Two types of cryogenic fluids were used: LN2 and LNG. The cyogenic liquid was released on the steel plate at 1.6L/min for LN2 and 1.5L/min for LNG. For the steel, DH was used and the temperature was measured at 10 points in total. The Leidenfrost effect was observed on the steel plate, and the temperature distribution of the steel was varied according the flow path and the heat of evaporation of the fluid.