• Atmosphere
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• v.26 no.1
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• pp.19-33
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• 2016

Water vapor in the atmosphere is an important element that generates various meteorological phenomena and modifies a hydrological cycle. In general, the Yeongdong region has a lot of snow compared to the other regions in winter due to the complex topography and an adjacent East Sea. However, the phase change from water vapor to ice cloud and further snowfall has little been examined in detail. Therefore, in this study, we investigated phase change of liquid water in terms of a quantitative budget as well as time lag of water vapor conversion to snowfall in the ESSAY (Experiment on Snow Storms At Yeongdong) campaign that had been carried out from 2012 to 2015. First, we classified 3 distinctive synoptic patterns such as Low Crossing, Low Passing, and Stagnation. In general, the amount of water vapor of Low Crossing is highest, and Low Passing, Stagnation in order. The snowfall intensity of Stagnation is highest, whereas that of Low Crossing is the lowest, when a sharp increase in water vapor and accordingly a following increase in precipitation are shown with the remarkable time lag. Interestingly, the conversion rate of water vapor to snowfall seems to be higher (about 10%) in case of the Stagnation type in comparison with the other types at Bukgangneung, which appears to be attributable to significant cooling caused by cold surge in the lower atmosphere. Although the snowfall is generally preceded by an increase in water vapor, its amount converted into the snowfall is also controlled by the atmosphere condition such as temperature, super-saturation, etc. These results would be a fundamental resource for an improvement of snowfall forecast in the Yeongdong region and the successful experiment of weather modification in the near future.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.10
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• pp.933-940
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• 2009

To evaluate characteristics in spray flame, laminar counterflow is investigated on the effects of equivalence ratio and fuel by a two-dimensional DNS (direct numerical simulation). For the gaseous phase, Eulerian mass, momentum, energy, and species conservation equations are solved. For the disperse phase, all individual droplets are calculated by the Lagrangian method without the parcel model. n-Decane ($C_{10}H_{22}$) and n-heptane ($C_7H_{16}$) is used as a liquid spray fuel, and a one-step global reaction is employed for the combustion reaction model. As equivalence ratio increases, the fuel ignites early and the high temperature region spreads wider. The peak value of temperature, however, tends to once increase and then decreases with increasing equivalence ratio. The decrease in the peak value of temperature for the higher equivalence ratio condition is caused by the cooling effect associated with droplet group combustion. Since the evaporation of n-heptane is early, the high temperature region spreads wider than ndecane, but the peak values of temperature for both n-heptane and n-decane is almost same.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.267-279
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• 1990

The temporal and spatial distribution of the coastal cold waters which was formed due to winter colling in the South Sea of Korea was analyzed by IR images from satellite and in situ data from shipboard observations. The coastal waters are known to be consisted of the Yellow Sea Coastal Waters(YSCW) and the South Korean Coastal Waters(SKCW). The former is driven around the Chuja-do and drifted into the Cheju Strait by residual currents, while the latter expands toward offsea by southward wind forcing. The expansion patterns of the SKCW were observed as sinking expansion or drifting expansion such that both were strongly dependent on the surface heat flux conditions. Under the condition of positive heat flux(warmer sea surface) or when the sea surface heat is lost to the atmosphere, the surface water started sinking and eventually expanded toward the open sea causing the cooling of the water column. For the negative heat flux the surface water was just drifted horizontally and expanded seaward and in this case only the surface layer of water was cooled.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.101-109
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• 2013

Recently, it is certain that the increase of heating and cooling energy consumption by radical change in climate condition has caused serious problems related to environmental and energy concerns associated with increase of fossil fuel usage and carbon dioxide production as well as global warming. So, various actions to reduce greenhouse gas exhaustion and energy consumption have been prepared by world developed countries. Our government has also been trying to seek energy control methods for houses and buildings by proclaiming political polices on low-carbon green growth and construction and performance standards for environment-friendly housing. The energy consumption by buildings approximately reaches 25% of total korea energy consumption, and the increasing rate of energy consumption by buildings is stiffer than the rate by the other industries. The greatest part in the buildings of the energy consumption is building facade. While lots of research projects for reducing energy consumption of the facade have been conducted, but a few research projects on concrete comprising more than 70% of outsider of buildings has been tried. This research presents here a study to improve the insulation property of structural concrete formed by micro form admixture (MFA) with experimentally reviewing the physical, mechanical and thermal characteristics of the concrete. As the results of this experiment, in the case of concrete mixed with MFA, slump loss has been improved. As the mixing ratio of MFA increases, the compressive strength is decreased and thermal conductivity is increased. Also it was found that water-cement ratio increases, the compressive strength is decreased and thermal conductivity is increased. but, there was not big influence by the change of fine aggregate ratio.

• Korean Journal of Food Science and Technology
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• v.34 no.5
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• pp.931-934
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• 2002

To establish the optimal conditions for increasing oil yields from grape seed, extraction solvent, extraction time, and temperature were examined. Using grinding, grinding and roasting, grinding and steaming, and grinding, roasting, and steaming methods. Pressing extraction method resulted in 34.0% oil yield. Grinding and roasting, grinding and steaming, and grinding, roasting, and steaming gave 64.3, 63.0, and 65.6% yield, respectively. Ether solvent treatment resulted in 77.4 and 80.9% recoveries after 24 and 48 h static, respectively. The results of sensory evaluation revealed, oils extracted under optimal condition showed the best flavor, aroma, and whor, followed by grinding, grinding and roasting, grinding, roasting, and steaming, and grinding and steaming. Taking these results together, the optimal methods for oils extraction from grape seed were as follows: grape seed ${\rightarrow}$ washing ${\rightarrow}$ drying ${\rightarrow}$ roasting ($95{\sim}100^{\circ}C$ for 20 min) ${\rightarrow}$ cooling (room temperature) grinding ${\rightarrow}$ (0.5 mm>) ${\rightarrow}$ steaming ($0.8{\sim}0.9\;kg{\cdot}f/cm^2$ for 10 min) ${\rightarrow}$ pressing ($1st\;400\;kg/cm^2\;for\;2{\sim}3\;min,\;2^{nd}\;550{\sim}600\;/cm^2$ for 10 min, $3^{rd}\;700kg/cm^2$ for 60 min) ${\rightarrow}$ oils (yield $;85{\sim}90%$).

• Journal of Korea Foundry Society
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• v.35 no.6
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• pp.147-154
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• 2015

The effects of Sc and Sr elements on the modification of the eutectic $Mg_2Si$ phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic $Mg_2Si$ phase with additions of the Sr and Sc elements. Here, a fine eutectic $Mg_2Si$ phase and a decrease in the growth temperature of the eutectic $Mg_2Si$ phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic $Mg_2Si$ phase decreased and the effect on the modification of the eutectic $Mg_2Si$ phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic $Mg_2Si$ phase, and the resulting microstructure of the eutectic $Mg_2Si$ phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine ${\alpha}$-Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro-shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Journal of the Korean Solar Energy Society
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• v.35 no.2
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• pp.73-83
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• 2015

When it comes to these buildings for business use, cooling load during summertime was reported to have great importance which, as a result, impressively increased interest in Solar Heat Gain Coefficient (SHGC). Such SHGC is considered to be lowered with the help of colors and functions of glass itself, internal shading devices, insulation films and others but basically, these external shading devices for initial blocking that would not allow solar heat to come in from outside the buildings are determined to be most effective. Of many different external shading devices, this thesis conducted an analysis on Exterior Venetian Blind. As for vertical shading devices, previous researches already calculated SHGC conveniently using concepts of sky-opening ratios. However in terms of the Venetian Blind, such correlation is not possibly applied. In light of that, in order to extract a valid correlation, this study first introduced a concept called shape factor, which would use the breadth and a space of a shade, before carrying out the analysis. As a consequence, the concept helped this study to find a very similar correlation. Results of the analysis are summarized as follows. (1) Regarding SHGC depending on the surface reflectance of a shade, an average of 2% error is observed and yet, the figure can always be ignored when it comes to a simple calculation. (2) As for SHGC of each bearing, this study noticed deviations of 4% or less and in the end, it is confirmed that extraction can be achieved with no more than one correlation formula. (3) When only the shape factor and nothing else is used for finding a correlation formula, the formula with a deviation of approximately 5% or less is what one would expect. (4) Since the study observed slight differences in bearings depending on ranges of the shape factors, it needed to extract a weighted value of each bearing, and learned that the smaller the shape factor, the wider the range of a weighted value. The study now suggests that a follow-up research to extract a simple calculation formula by dealing with all these various inclined angles of shade, solar radiation conditions of each region (the ratio of diffuse radiation to direct radiation and others) as well as seasonal features should be carried out.

• Analytical Science and Technology
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• v.15 no.6
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• pp.514-520
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• 2002

The electrothermal vaporization (ETV) hollow cathode glow discharge atomic emission spectrometer for analysis of liquid sample has been developed and characterized. This system has improved the sample introduction method of electrothermal vaporization and the hollow cathode glow discharge. The sample introduction method was possible to provide high analyte transport efficiency to the plasma by helix coil made of tungsten material. In addition, small volume samples (<$30{\mu}{\ell}$) could be used. The system has glow discharge cell with special design for improvement of precision. The effect of discharge parameters such as discharge power, gas flow rate has been studied to find optimum condition. The emitted light was effectively carried into detector by fiber optic cable in UV region. The calibration curve of Pb, Cd were obtained with 3 samples.

• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.523-528
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• 2015

In this study, we investigated the effects of sulfuric acid on the synthesis of calcium borate in the artificial boron-containing brine (bittern) saturated with calcium hydroxide. For the study, we attempted to synthesize calcium borate under various conditions such as reaction temperature, reaction time, and cooling temperature after heating, and then to examine the recovery and purity of the calcium borate according to the presence or absence of sulfuric acid at each condition. The XRD analysis confirmed that, regardless of the presence of sulfuric acid, the calcium borate ($Ca_2B_2O_5{\cdot}H_2O$) was synthesized, while, in the presence of sulfuric acid, the calcium sulfate ($CaSO_4{\cdot}0.5H_2O$) was produced as a by-product. In all the experiments performed by varying the reaction temperature and time, the recovery and purity of the calcium borate without sulfuric acid were observed higher than those with it. The results indicated that the addition of sulfuric acid increased the solubility of the calcium hydroxide, but the calcium sulfate produced as a by-product could decrease the recovery and purity of the calcium borate by preventing the synthesis. In this study, the artificial boron-containing brine (bittern) (500 mg-B/L) was saturated with calcium hydroxide in the absence of sulfuric acid, and then the solution was heated at $80-105^{\circ}C$ for less than 10 minutes to synthesize the calcium borate. The recovery and purity of calcium borate were measured as high as 80 % and 96 %, respectively.