• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.41-56
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• 2012

This study is focused on evaluation of the tensile properties of concrete exposed to acid rain environment. Acid rain environment was simulated by the mixture of sulfate and nitric acid in the laboratory. The dumbell-shaped concrete specimens were submerged in pure water and acid solution for accelerated conditioning. Weighing, tensile test, CT, SEM/EDS test and microanalysis were performed on the specimens. Tensile characteristics of the damaged concrete are obtained quantitatively. Evolution characteristics of the voids, micro cracks, chemical compounds, elemental distribution and contents in the concrete are examined. The deterioration mechanisms of concrete exposed to acid rain are well elucidated.

• Journal of the Mineralogical Society of Korea
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• v.22 no.1
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• pp.35-47
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• 2009

The deteriorations of stone monuments located in Gyeongju area are predicted in a modeling study. Artificial rain and accelerated weathering test are here applied to the Gyeongju Namsan granite and cement mortar. They are reacted with pH 4.0, pH 8.0 and pH 5.6 rain, respectively. The two former values are the limited acidity values in the Gyeongju (the acidity of rain of the Gyeongju were pH $4.93{\sim}6.39$ in 2005) and the latter is the limited acidity of acid rain. The rains of pH 5.6 and pH 8.0 reach close to a value of pH 7.0 after the reaction with the Gyeongju Namsan granite. After application of the artificial rain and weathering test, the weight of specimens were reduced and the contents of soluble ions in the specimens were increased. These results are attributable to solution of minerals in the specimens. At first, the microlithic have dissolved in ground from the reaction with acid rain. And then mainly quartz, plagioclase and orthoclase bound by the microlithic are disintegrated. The cement mortars are dissolved after the reaction with not only acid but alkali rain. The concentrations of ions in the dissolved cement mortar are higher than those in granite.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.227-235
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• 2018

In this study, we developed a relational formula for observing high - resolution rainfall using vehicle rain sensor. The vehicle rain sensor consists of eight channels. Each channel generates a sensor signal by detecting the amount of rainfall on the windshield of the vehicle when rainfall occurs. The higher the rainfall, the lower the sensor signal is. Using these characteristics of the sensor signal generated by the rain sensor, we developed a relational expression. In order to generate specific rainfall, an artificial rainfall generator was constructed and the change of the sensor signal according to the variation of the rainfall amount in the artificial rainfall generator was analyzed. Among them, the optimal sensor channel which reflects various rainfall amounts through the sensitivity analysis was selected. The sensor signal was generated in 5 minutes using the selected channel and the representative values of the generated 5 - minute sensor signals were set as the average, 25th, 50th, and 75th quartiles. The calculated rainfall values were applied to the actual rainfall data using the constructed relational equation and the calculated rainfall amount was compared with the rainfall values observed at the rainfall station. Although the reliability of the relational expression was somewhat lower than that of the data of the verification result data, it was judged that the experimental data of the residual range was insufficient. The rainfall value was calculated by applying the developed relation to the actual rainfall, and compared with the rainfall value generated by the ground rainfall observation instrument observed at the same time to verify the reliability. As a result, the rain sensor showed a fine rainfall of less than 0.5 mm And the average observation error was 0.36mm.

• Journal of Sensor Science and Technology
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• v.26 no.3
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• pp.149-154
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• 2017

Detection of rain is one of the essential weather factors that are monitored by automatic weather stations in Korea. In this work, we studied the operation standards required for impedance-based rain detectors in terms of surface temperature and sensitivity, in an effort to establish a qualification procedure for rain detectors. The surface temperature of rain detectors was measured at varying air temperatures from $-30^{\circ}C$ to $20^{\circ}C$, considering the hypothetical presence and absence of rain/snow. In addition, the sensitivity of rain detectors was studied generating artificial raindrops of regular size. The sensitivity was evaluated in terms of the critical number of droplets that triggers the activation of the rain detector. We found that the sensitivity is affected by stationary, horizontal, and vertical droplet deposition methods. The critical number of droplets for the stationary deposition is higher than that for both horizontal and vertical depositions, which provides the maximum limit of droplets required to activate the detector. Based on our experiments considering surface temperature measurements and sensitivity tests, we suggest a revised version of surface temperature and sensitivity requirements for the qualification of impedance-based rain detectors.

• Journal of Korean Society of Forest Science
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• v.83 no.3
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• pp.280-285
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• 1994

This study was conducted to investigate the effects of acid deposition on forest soil, major five Korean forest soils(Brown, Dark red, Gray brown, Red and Yellow, and Volcanic ash forest soils) The samples were subjected to receive 1200mm($100mm{\times}12$ times) of artificial acid rain adjusted to pH5.6, 4.0, 3.0 and 2.0. The results obtained of major importance are summarized as follow ; 1. Ca appeared mostly affected at pH treatment of 2.0, while less affected by other pH treatments. Leaching of Ca rapidly increased with increasing of artificial acid rain acidity and application times in Dark red forest soil. 2. In the cases of Mg, K and Na, they showed gradual increase with the addition of artificial acid rain. Mg and Na losses showed similar leaching patterns, but they didn't show difference among the five forest soils. 3. Exchangeable canon concentrations in the soil leachates, which looked slightly different among the five forest soils, were the highest in pH2.0 treatment. Hydrogen ion comsumption capability by exchangeable canon was the highest in Dark red forest soil followed by Volcanic ash, Red and Yellow, Gray brown and Brown forest soils when artificial acid rain were treated.

• Asian Journal of Atmospheric Environment
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• v.7 no.3
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• pp.161-168
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• 2013

In this study, an investigation was conducted to assess the washout mechanism of Asian dust particles through both laboratory-scale experiment and model calculation. To artificially simulate Asian dust particle, $CaCO_3$ particles were generated inside an experimental chamber. They were then scavenged by the artificial rain drops. The abundant $CaCO_3$ particles scavenged on a rain drop were successively identified by SEM observation. The concentrations of Ca in residual $CaCO_3$ particles on individual droplet were quantified by PIXE analysis. There was a tendency toward a high accumulation of Ca on a relatively small drop (e.g., <1.0 mm diameter). It is thus suggested that smaller rain drops can effectively scavenge a significant amount of Asian dust particles in ambient atmosphere. The numerical estimation can account for 92.1% and 83.2% of Ca that were measured in small (<1.0 mm diameter) and large (>2.0 mm diameter) size drops, respectively.

• The Korean Journal of Ecology
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• v.19 no.1
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• pp.71-80
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• 1996

The effects of simulated acid rain on the growth and interspecific competition of Echinochloa crus-galli and Digitaria sanguinalis were studied. Changes of growth in height and dry weight were examined and competition between the two species was investigated using the experimental model proposed by de Wit (1960). The experiments were carried out in the greenhouse, and test plants were germinated and grown for 4 weeks and then sprayed with simulated acid rain of pH 5.6, 4.2 and 2.8 for another 8 weeks. In de Wit replacement experiments, the variation of density and the treatment of simulated acid rain showed little effect on the interspecific competition between E. Crus-galli and D.sanguinalis. The ratio diagram, another method to reveal the interrelations between two competing species, always showed the predominance of E. crus-galli in competition, regardless of density and pH. The interspecific competition of the two species, represented by relative yield total (RYT), revealed that intraspecific competition was stronger than interspecific competition in both species.The treatment of simulated acid rain showed little effect on the growth of E. Crus-galli and D. sanguinalis. Height growth of both species did not differ from that of control (pH 5.6), but root/shoot ratio increased with the decrease in pH of simulated acid rain. Growth of tatal dry weight of E. crus-galli and D. sanguinalis was not influenced by the change of pH, except that D.sanguinalis showed a decrease in the total dry weight at pH 2.8 along with a visible sign of white spots on leaves. Physical environmental conditions can exert an effect on the interrelationships between the two species, but this experiment did not show the reversion of competition, and showed that E.crus-gilli was competitively dominant under any environmental conditions given in this study.

• Journal of Korean Society of Forest Science
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• v.76 no.1
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• pp.33-40
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• 1987

Simulated acid rain (pH 4.0, pH 2.0) containing sulfuric and nitric acid in the ratio of 60:40 (chemical equivalent basis) diluted with underground water, and underground water (pH 6.5) as control were treated on potted Pines koraiensis seeds during the growing season (May 1 to August 31) in 1985. The regime of artificial acid rain, in terms of spray frequency and amount per plot, was simulated on the basis of climatological data averaged for 30 years of records. The seedling growth, contents of chemical substances in needles and chemical properties of the tested soil were compared among the various pH levels of acid rain on October 31, 1985. Following results were obtained. 1. With decreasing pH levels of acid rain, S and $K_2O$ contents in leaf tissue were increased, but MgO and $P_2O_5$ contents were decreased. 2. Soil pH was dropped, and exchangeable aluminum content in the tested soil was dramatically increased as the pH levels of acid rain decreased. 3. Exchangeable calcium, magnesium, potassium contents, and base saturation degree of the soil were significantly decreased with decreasing pH levels of acid rain. 4. Sulfate concentrations in the soil were significantly increased as rain pH decreased, but total nitrogen and available phosphate contents were not influenced by acid rain.

• Journal of Soil and Groundwater Environment
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• v.16 no.5
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• pp.82-89
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• 2011

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are $52.5{\times}10^{-10}m^2$ and $75{\times}10^{-10}m^2$ for the artificial rain-on-snow experiments and observations of diel variation, respectively.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.63-71
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• 2010

The artificial rains having different pH and weathering simulation test were performed for Gyeongju Namsan granite and dacitic tuff to predict the role of acid rain in the deterioration of stone monuments located in Gyeongju area. The pH 4.0 rain reacted with the fresh granite showed near neutral pH at the early stage due to the hydrolysis of minerals in the rock surface. But the pH changed back to the initial pH in the later stage. On the other hand, the pH 5.6 rain showed the neutral pH for a longer time than the experiment with pH 4.0 rain, reflecting slower reaction of minerals due to the weaker acidity. When the pH 5.6 rain reacted with the weathered granite, the water showed neutral pH longer than the case of the fresh granite. The similar tendencies were observed in the experiment of dacitic tuff, except that the pH 4.0 rain reacted with dacitic tuff took a longer time to go back to the initial pH as compared with the case of granite. These results may due to the differences in mineral composition and texture of two rocks. Dacitic tuff contains more fine-grained or glassy groundmass than granite and is more reactive with weaker acid rain. It was predicted that the weight loss and strength decrease rate of dacitic tuff would be approximatetly twice relative to those of granite in the same experimental environment.