• Journal of Korean Society of Environmental Engineers
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• v.37 no.10
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• pp.558-562
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• 2015

This study was tested to evaluate the effect of the six different combinations of microbubble, catalyst, and air as oxidant on the sludge and organic matter reduction. When all of microbubbles and catalyst, and an oxidizing agent (under Conditions 1) such as air were used, the sludge was removed more than 99%, and TCOD and SCOD removal was 58% and 13%, respectively. This result was the highest value of six conditions. In the following order, the sludge reduction of the microbubbles with air (Condition 2) and catalyst with air (condition 4) was 95% and 93.1%, respectively. TCOD removal was found to be each 53% and 47%. When the microbubbles were used with oxidant like air, the removal of sludge and organic matter was high. All of these values were higher than that of using only microbubbles and catalyst without air. In the microbubbles and catalyst react under air supply condition, OH-radicals were generated in the reaction process. These OH-radicals in the reaction process decomposed the pollutants by the strong oxidizing power. In all conditions with air, the sludge reduction was high removal rate more than 93% and TCOD removal was over 47%.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.133-141
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• 2011

The effect of payload on fuel consumption and emission of light duty freight truck during acceleration driving has been analyzed. Running tests were carried out with various payload conditions on chassis dynamometer. A typical driving pattern for urban cities was used. Real time emission measurement systems for gaseous and soot emission were utilized to investigate the real time dynamic of fuel use and exhaust emissions. It was observed that fuel use and pollutant emissions were increased as payload was increased. Under the same payload condition, the increased amount of acceleration driving is much higher than that of steady state driving. The results demonstrated the advantages of eco-driving, which is an environmentally friendly driving manner, could be emphasized in heavier payload condition. Inertial tractive power was introduced for considering the parameters affecting emission during acceleration driving, which are speed, acceleration and payload. Fuel use and emission in various driving conditions were expressed as functions of inertial tractive power. The estimated result by these functions well predicted measured result within 10 % deviation.

• Journal of Environmental Impact Assessment
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• v.19 no.6
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• pp.539-546
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• 2010

In nature, the overall effect of heavy metals on the biota can be influenced by a number of environmental factors like soil characteristics and air pollution by elevated $CO_2$. Pillbugs(Isopoda, Armadillium vulgare) take up heavy metals with their food and store them mainly in the vesicles of hepatopancreas. They accumulate certain metals, occuring in relatively large numbers, are easily collected and identified. Therefore, it has been suggested that total body concentration of metals in pillbugs could be positively correlated to the levels of environmental exposure and that pillbugs could be used as biological indicators of metal pollution and global change by $CO_2$. The aim of the study is to determine effects of heavy metal concentrations in soil and elevated $CO_2$ on pillbugs'body accumulation of heavy metal and growth rate. In this study, pillbugs were collected at five sites (N=287) May 2006. Cu and Zn concentrations in pillbugs were higher than in soils (1.39-41.70 times) than in control. The high bioconcentration of lead in Sangam may be partly associated with reclaimed land uses. Pillbugs in low $CO_2$ and Pb condition showed higher growth rate than in elevated $CO_2$ and Pb condition.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.101-108
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• 2000

Through numerical experiment using simplified OSU-1D PBL(Oregon State University One-Dimensional Planetary Boundary Layer) model and field measurement, we studied the impacts of vegetation canopy on heat island that was one of the characteristics of local climaate in urban area. it was found that if the fraction of vegetation was extended by 10 percent, the maximum air temperature and the maximum ground temperature can come down about 0.9${\circ}C$, 2.3${\circ}C$, respectively. Even though the field measurement was done under a little unstable atmospheric condition, the canopy air temperature was lower in the daytime, and higher at night than the air and ground temperature. This result suggests that the extention of vegetation canopy can bring about more pleasant local climate by causing the oasis, the shade and the blanket effect.

• Journal of Environmental Science International
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• v.21 no.2
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• pp.153-163
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• 2012

The seasonal variations of ozone ($O_3$) concentrations were investigated with regard to the relationship between $O_3$ and wind distributions at two different sites (Jung Ang (JA): a semi-closed topography and Seo Chang (SC): a closed topography) within a valley city (Yangsan) and their comparison between these sites (JA and SC) and two non-valley sites (Dae Jeo (DJ) and Sang Nam (SN)) located downwind from coastal cities (Busan and Ulsan). This analysis was performed using the data sets of hourly $O_3$ concentrations, meteorological factors (especially, wind speed and direction), and those on high $O_3$ days exceeding the 8-h standard (60 ppb) during 2008-2009. In summer and fall (especially in June and October), the monthly mean values of the daily maximum $O_3$ concentrations and the number of high $O_3$ days at JA (and SC) were relatively higher than those at DJ (and SN). The increase in daytime $O_3$ concentrations at JA in June was likely to be primarily impacted by the transport of $O_3$ and its precursors from the coastal emission sources in Busan along the dominant southwesterly winds (about 5 m/s) under the penetration of sea breeze condition, compared to other months and sites. Such a phenomenon at SC in October was likely to be mainly caused by the accumulation of $O_3$ and its precursors due to the relatively weak winds under the localized stagnant weather condition rather than the contribution of regional transport from the emission sources in Busan and Ulsan.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.528-536
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• 2016

The purpose of Total Pollution Load Control at Tributary is to obtain maximum improvement effect of water quality through finding the most impaired section of water-body and establishing the proper control measure of pollutant load. This study was implemented to determine the optimal management of reach, period, condition, watershed, and pollution source and propose appropriate reduction practices using the Load duration curve (LDC) and field monitoring data. With the data of measurement, LDC analysis shows that the most impaired condition is reach V (G4~G5), E group (flow exceedance percentile 90~100%) and winter season. For this reason, winter season and low flow condition should be preferentially considered to restore water quality. The result of pollution analysis for the priority reach and period shows that agricultural nonpoint source loads from onion and garlic culture are most polluting. Therefore, it is concluded that agricultural reuse of surface effluent (storm-water runoff with non-point sources) and low impact farming that includes reducing fertilization and controlling the height of drainage outlet are efficient water quality management for this study watershed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.283-288
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• 2018

Since the crack self-healing materials are activated according to the exposure environmental conditions from the time of crack occurrence, it is very important to clarify the relationship between the healing performance and the exposure environmental conditions of the crack surface. In this paper, the influence of the exposure environmental conditions on the crack healing performance of self-healing repair mortar was investigated through the water permeability test. The influence of temperature and humidity on the crack width of cracked specimens was evaluated. As a result of measuring the change of the crack width, the effect of curing temperature was negligible but it was confirmed that crack-closing occurred due to the change of dry-wet condition. The healing materials produced on the crack surface of the specimens was identified as calcite minerals. Since the minerals with high density are precipitated under the influence of gravity, the healing performance is somewhat different according to the direction of the crack surface, and the healing performance was significantly improved in the wet exposure condition than the air exposure condition.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.314-318
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• 2007

The feasibility of the employment of waste oyster shell as an adsorbent for fluoride ion has been tested by considering the effect ionic condition on the adsorption of fluoride ion on oyster shell. The adsorption capacity of oyster shell for fluoride ion was found not to be significantly influenced by the ionic strength of aqueous environment. The existence of complexing agent such as nitrilotriacetic acid in wastewater decreased the adsorbed amount of fluoride ion by forming a stable complex of $CaT^-$ and the adsorption reaction of fluoride ion on oyster shell was examined to be endothermic. The coexisting heavy metal ionic adsorbate in wastewater hindered the adsorption of fluoride ion, however, its adsorbed amount was increased as the particulate size of adsorbent was decreased. Finally, a serial adsorption column test has been conducted for a practical application of adsorption process and the breakthrough of the column adsorption was observed in 22 hours under the experimental condition.

• Journal of the Korean GEO-environmental Society
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• v.17 no.1
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• pp.29-37
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• 2016

This study examined the magnitude and distribution of earth pressure on the support system in a jointed rock mass due to the different joint spacing as well as varying the rock type and joint condition (joint shear strength and joint inclination angle). Based on a physical model test and its numerical simulation, a series of numerical parametric analyses were conducted using a discrete element method. The results showed that the magnitude and distribution of earth pressure were strongly affected by the different joint spacing as well as the rock type and joint condition. In addition, the study results were compared with Peck's earth pressure for soil ground, which indicated that the earth pressure in a jointed rock mass could be considerably different from that in soil ground. The study suggests that the joint spacing as well as the rock type and joint condition are important factors affecting the earth pressure in a jointed rock mass and they should be considered when designing a support system in a jointed rock mass.

• Water Engineering Research
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• v.5 no.1
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• pp.1-16
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• 2004

The purpose of this study is to understand the characteristics of hourly PET(Potential Evapo Transpiration) variation estimated using Penman ET model. The estimated PET using Penman model was compared with measured ET. For this study, two subwatersheds were selected, and fluxes, meteorological data and soil moisture data were measured during the summer and winter days. During the winter days, the aerodynamic term of Penman ET is much greater than that of energy term of Penman ET for dry soil condition. The opposite phenomena appeared fer wet soil condition. During the summer days, energy term is much more important factor for ET estimation compared with aerodynamic term regardless of soil moisture condition. Penman ET, measured ET, and energy term show the similar hourly variation pattern mainly because the influence of net radiation on the estimation of Penman ET is much more significant compared with other variables. Even though there are much more soil moisture in the soil during the wet days, the estimated hourly ET from Penman model and measured hourly ET have smaller values compared with those of dry days, indicating the effect of cloudy weather condition.