• Journal of the Korean Geotechnical Society
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• v.29 no.2
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• pp.15-21
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• 2013

The analysis of long-term performance of pavement sections under wheel loads is normally conducted in two separated steps. First the resilient behavior of the pavement is calculated assuming the pavement is a layered or discrete elastic medium, and then the permanent deformation is evaluated based on empirical permanent displacement equations. Material properties required in both steps can be obtained from cyclic triaxial tests, in other words, resilient and permanent deformation tests. While this analytical approach is simple and convenient, it does not consider the modulus degradation caused by cyclic loads, and some types of reinforcements such as geosynthetic cannot be modeled in this type of analysis. A model for degraded secant modulus is proposed and suggested to be used for the analysis of permanent behavior of unpaved roadway sections. The parameter for suggested model can be obtained from cyclic triaxial tests, regular practice in pavement engineering. Examples to estimate the model parameters are presented based on both laboratory permanent deformation test and large-scale plate load test.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.1
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• pp.91-99
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• 2008

A multilayer tower-type photoreactor, in which $TiO_2$-coated glass-tubes were installed, was used to measure the vapor-phase BTEX removal efficiencies by ozone oxidation ($O_3$/UV), photocatalytic oxidation ($TiO_2$/UV) and the combination of ozone and photocatalytic oxidation ($O_3/TiO_2$/UV) process, respectively. The experiments were conducted under various relative humidities, temperatures, ozone concentrations, gas flow rates and BTEX concentrations. As a result, the BTEX removal efficiency and the oxidation rate by $O_3/TiO_2$/UV system were highest, compared to $O_3$/UV and $TiO_2$/UV system. The $O_3/TiO_2$/UV system accelerated the low oxidation rate of low-concentration organic compounds and removed organic compounds to a large extent in a fixed volume of reactor in a short time. Therefore, $O_3/TiO_2$/UV system as a superimposed oxidation technology was developed to efficiently and economically treat refractory VOCs. Also, this study demonstrated feasibility of a technology to scale up a photoreactor from lab-scale to pilot-scale, which uses (i) a separated light-source chamber and a light distribution system, (ii) catalyst fixing to glass-tube media, and (iii) unit connection in series and/or parallel. The experimental results from $O_3/TiO_2$/UV system showed that (i) the highest BTEX removal efficiencies were obtained under relative humidity ranging from 50 to 55% and temperature ranging from 40 to $50^{\circ}C$, and (ii) the removal efficiencies linearly increased with ozone dosage and decreased with gas flow rate. When applying Langmuir-Hinshelwood model to $TiO_2$/UV and $O_3/TiO_2$/UV system, reaction rate constant for $O_3/TiO_2$/UV system was larger than that for $TiO_2$/UV system, however, it was found that adsorption constant for $O_3/TiO_2$/UV system was smaller than that for $TiO_2$/UV system due to competitive adsorption between organics and ozone.

• Environmental Mutagens and Carcinogens
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• v.26 no.4
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• pp.125-132
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• 2006

Previous studies showed that epigallocatechin gallate(EGCG) have substantial effects of suppressing the N-methyl-N'-nitro-N-nitrosoguanidine(MNNG)-initiated cell transformation process on the bases of foci formation frequency and loss of anchorage dependency. In this study we tried to clarify the molecular mechanism of suppressing the cell transformation process. Mouse cell line balb/c 3T3 A31-1-1 was exposed 2 days to MNNG followed by 15 days 12-O-tetradecanoylphorbol-13-acetate(TPA) treatment for our transformation process. EGCG was added after the time point of 24 hours exposure to TPA and incubated for 19 days. 2029 genes were selected in our transformation process that showed fold change value of 1.5 or more in the microarray gene expression analysis covering the mouse full genome. These genes were found to be involved mainly in the cell cycle pathway, focal adhesion, adherens junction, TGE-$\beta$ signaling, apoptosis, lysine degradation, insulin signaling, ECM-receptor interaction. Among the genes, we focused on the 631 genes(FC>0.5) reciprocally affected by EGCG treatment. Our study suggest that EGCG down-regulate the gene expressions of up stream signaling factors such as nemo like kinase with MAPK activity and PI3-Kinase, Ras GTPase and down stream factors such as cyclin D1, D2, H, T2, cdk6.

• Korean Journal of Environmental Agriculture
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• v.7 no.1
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• pp.14-20
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• 1988

The effect of polyethylene film(P.E.) mulching on the degradation of alachlor(N-methoxymethyl-2, 6-diethyl ${\alpha}-chloroacetoanilide$), pendimethalin(3, 4-dimethyl-2, 6-dinitro-N-l-ethylpropylanilide) and diphenamid(N,N-dimethyl-2, 2-diphenylacetamide) in red pepper, peanut, and sesame fields was investigated. In soils under the non-mulching condition the half-lives of alachlor, pendimethalin and diphenamid were 3, 37 and $24{\sim}46$ days, respectively. However, the half-lives of those under the P.E. mulching condition were longer than under the non-mulching condition. The differences in the half-lives between P.E. mulching and non-mulching conditions were about 30 days for pendimethalin and from 20 to 90 days for diphenamid. However, the half-life of alachlor was hardly affected by P.E. mulching. Pendimethalin and alachlor were not detected in the harvasted red peppers, peanuts and sesame under P.E. mulching and non-mulching conditions. But, the residue of diphenamid in peanuts was 0. 147 ppm under the P.E. mulching condition and 0.071 ppm under the non-mulching condition, and the residue of diphenamid in sesame was 0.022 ppm under the P.E. mulching condition and 0.129 ppm under the non-mulching condition. The amounts, however, were below the tolerance limits for pesticide residue.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.320-326
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• 1997

In order to elucidate the degradation characteristics of the herbicide imazapyr in soil, mineralization to $^{14}CO_2$and adsorption were investigated using eight types of soils with the different physico-chemical properties. The results obtained were as follows: 1. During the incubation period of 12 weeks after the treatment of imazapyr, the amounts of $^{14}CO_2$ evolved from 8 types of soils with different properties ranged from 1.5 to 4.9% of the originally applied $^{14}C$ activities. Soil C, G, and H with low pH and high organic matter showed low $^{14}CO_2$evolution, whereas soil B and D with high pH and low organic matter did high $^{14}CO_2$ evolution. 2. Time for reaching the equilibrium concentrations in the adsorption experiment of imazapyr in soils was about 3 hours at $25^{\circ}c$ in soil C, D, G, and H. Imazapyr was adsorbed in the range of 0.25${\sim}$28.32% in soils with different physico-chemical properties. Among the soil parameters, organic matter content was the most influential in imazapyr adsorption on soil. The Freundlich adsorption coefficient $(K_f)$ increased 5.5 to 25.6 times as organic matter content increased 2.0 to 21.3 times. Hence it seems that the extent to which soil organic matter contributes to imazapyr adsorption is greater than that of clay mineral. $K_f$ values for the soils tested were 0.44, 0.08, 0.65, and 2.05 in soil C, D, G, and H, respectively. In all the soils tested, $K_f$ values had a strong resemblance to K_$K_d$.

• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.62-69
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• 2005

Removal of 4-chlorophenol (4CP) by natural manganese dioxide (NMD) catalyzed reaction was investigated in this study. Tests were also carried out to evaluate the effects of pH and natural organic matter (NOM) on the degradative oxidation of 4CP. Experimental results proved that NMD was effective for the removal of 4CP. Extensive kinetic analysis suggests that overall oxidation of 4CP by NMD is second-order reaction, the first-order with respect to 4CP, and the first-order with respect to NMD, respectively. Also, 4CP oxidation rates on the Mn-oxide surfaces were highly dependent upon experimental conditions such as pH, initial concentration of 4CP or NMD, and existence of humic acid. As pH increased above PZC of NMD, the reaction rate of 4CP was decreased, due to the low affinity of 4CP on NMD at high pH. At pH lower than PZC of NMD, reaction rate of 4CP was also decreased. It was considered that humic acid was involved in the oxidative coupling reaction of 4CP by NMD, resulting in the enhanced degradation rate of 4CP. This study proved that natural manganese oxide can be effectively applied for the removal of chlorophenols in aqueous phase.

• Journal of Soil and Groundwater Environment
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• v.14 no.5
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• pp.10-17
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• 2009

Bioremediation has been applied as a proven technology in remediation of TPH contaminated soil. However, the efficiency of biodegradation is dependent on temperature as microbial activity is depressed at lower temperature ranges ($30^{\circ}C{\sim}80^{\circ}C$). The objective of this study was to develop microbes with enhanced activities at the stated temperature conditions and to evaluate the remediation effectiveness of these microbes in TPH contaminated soil. Experiments were conducted to isolate hydrocarbon degradable microbial consortia cultured under different temperature conditions. It was found that there were 5 strains of mesophilic ($30^{\circ}C$) and 3 strains of psychrophilic ($80^{\circ}C$) microbes. The TPH concentration was reduced from 4,044 mg/kg to 1,084 mg/kg, (73.2%) in 10 days by using mesophilic microbial consortia and from 5,427 mg/kg to 1,756 (67.6%) in 50 days with psychrophilic microbial consortia in laboratory cultures under controlled conditions. This rate determination excluded physical degradation such as venting and dilution. A field study was then performed to examine the feasibility of applying these microbes in the land-farming process. In this case, 87.1% of the 2,560 mg/kg TPH contaminated soil was degraded in 56 days. The biodegradation rate coefficient (k) was $0.0374\;day^{-1}$. Findings of this study provide viable options for applying microbes for bioremediation of TPH in lower temperature conditions.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.25-32
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• 2014

The amount of TPH contaminated soil treated at off-site remediation facilities is ever increasing. For the recycle of the treated-soil on farmlands, it is necessary to restore biological and physico-chemical soil characteristics and to remove residual TPH in the soil by an economic polishing treatment method such as phytoremediation. In this study, a series of experiments was performed to select suitable plant species and to devise a proper planting method for the phyto-restoration of TPH-treated soil. Rye (Secale cereale) was selected as test species through a germination test, among 5 other plants. Five 7-day-old rye seedlings were planted in a plastic pot, 20 cm in height and 15 cm in diameter. The pot was filled with TPH-treated soil (residual TPH of 1,118 mg/kg) up to 15 cm, and upper 5 cm was filled with horticulture soil to prevent TPH toxic effects and to act as root growth zone. The planted pot was cultivated in a greenhouse for 38 days along with the control that rye planted in a normal soil and the blank with no plants. After 38 days, the above-ground biomass of rye in the TPH-treated soil was 30.6% less than that in the control, however, the photosynthetic activity of the leaf remained equal on both treatments. Soil DHA (dehydrogenase activity) increased 186 times in the rye treatment compared to 10.8 times in the blank. The gross TPH removal (%) in the planted soil and the blank soil was 34.5% and 18.4%, respectively, resulting in 16.1% increase of net TPH removal. Promotion of microbial activity by root exudate, increase in soil permeability and air ventilation as well as direct uptake and degradation by planted rye may have contributed to the higher TPH removal rate. Therefore, planting rye on the TPH-treated soil with the root growth zone method showed both the potential of restoring biological soil properties and the possibility of residual TPH removal that may allow the recycle of the treated soil to farmlands.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.822-826
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• 2005

Colloidal Silica (CS)/methyltrimethoxysilane (MTMS) and CS/MTMS/epoxysilane (ES) sol solutions were prepared using various synthesizing parameters such as reaction time and types of CS and silane. In order to understand their physical and chemical properties, sol-gel coating films on glass were fabricated. In the case of the CS/MTMS sol, the coating films had high contact angle and more enhanced flat surface than the CS/MTMS/ES sol. In the case of thermal stability, thermal degradation of the CS/MTMS and CS/MTMS/ES coating films did not occur up to $550^{\circ}C$ and $440^{\circ}C$, respectively. The coating films prepared from the CS/MTMS sol were thicker than those of the CS/MTMS/ES sol. In addition, the coating films prepared from single CS were thicker than those of mixed CS. Hardness of the coating films prepared from CS/MTMS increased by adding ES. In case of the mixed CS, the hardness decreased by adding ES.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.2
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• pp.41-48
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• 2011

In this study, the soil remediation by landfarming was carried out using microbial activators. Feasibility studies and reduction capacity of TPH(Total Petroleum Hydrocarbons) were investigated in order to find out how fast and eco-friendly the contaminated soil can be recovered. The lab-test confirmed not only the performance and degradation efficiency of microbial activators but also the effect of TPH reduction in the contaminated soil. The optimum growth conditions for indigenous microorganisms were identified using microbial activators. Based on the results of TPH removal, although there had been a little of difference in between natural decomposition and microbial activators until 20 days, the sample groups of microbial activators were higher than the control ones after 20 days. Microbial activators were applied to the field experiments on landfarming. Based on the results of removal rate in each floor of soil, it was found that the removal rates were 85.8 % in the upper, 84.4 % in the middle, and 66.10 % in the bottom. Considering that the reduction rate of TPH for the control group averaged 71.1%, the microbial activators might not be fully transferred into the bottom, which resulted from the piles of soil. As the piles have already reached 1 m in the field experiments, the low piles of soil under 0.6 m may enhance the treatment efficiency of TPH.