• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.346-349
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• 2004

Surfactant-enhanced electrokinetic (EK) process was investigated to remove polycyclic aromatic hydrocarbons (PAHs) from low-permeable soils. Phenanthrene and kaolinite were selected as a representative PAH and a model soil, respectively. A nonionic surfactant Tergitol 15-S-12 was applied to improve the solubility of phenanthrene and sodium chloride was used as an electrolyte at the various concentrations from 0.001 to 0.1M. The addition of electrolyte affected both the removal efficiency and operation cost. When electrolyte was introduced, the electrical potential gradient became low and thus power consumption was reduced. However, as electrolyte concentration increased, the electroosmotic flow also decreased, so the removal efficiency of contaminant decreased. Therefore, the removal efficiency and power consumption should be considered simultaneously to determine the iptimum surfactant concentration, so a relatively lower concentration of electrolyte than certain value is desired.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.861-871
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• 2014

This study analyzes the characteristics of ozone weekend effect(OWE) in Busan. $O_3$ concentration on Sunday was over 10% higher than that on weekdays in all areas except for Kwangbokdong, Taejongdae, and Joadong. Such a difference was higher in the industrial area than in the residential area. $O_3$ generation was facilitated by the decrease in $NO_X$ emission on Sunday in VOC-limited regime where the VOC/$NO_X$ ratio is low. Low NO concentration in the Sunday morning decreased inhibition of $O_3$. NO-$O_3$ crossover time on Sunday was shorter than that on weekdays which in turn extended the accumulated duration of $O_3$. Future studies can include whether the entire Busan is VOCS-limited or the coastal area is VOCS-limited while the inland area is $NO_X$-limited.

• Journal of ILASS-Korea
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• v.18 no.2
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• pp.81-86
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• 2013

To comply with the regulation of the reinforcing Clean Air Conservation Act, it is necessary for the semiconductor manufacturers to develop effective low-concentration acid gas abatement system to treat the flue gas. The low-concentration acid gas was found to be harder to deal with than the high-concentration one. In this study, the effect of various potential treatments such as air-assist nozzle spraying, magnetizing the scrubbing water, and adding surfactants to spraying and scrubbing water were investigate through the application of the statistical ANCOVA method, which was proved to be very useful tool when the inlet concentration of acid gas could not be controlled precisely and it affected the removal efficiency of the abatement system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.5
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• pp.487-495
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• 2005

Recently, due to the airtightness of buildings or the misuse of building materials, we have been witness SHS (Sick House Syndrome) which can have bad influences on the resident in an existing apartment house as well as newly constructed apartment house start to attract public attention. As a result of this situation, we went to restrict the TVOC (Total Volatile Organic Compound) and formaldehyde. But these guidelines concentrated on only TVOC although TVOC are consist of many individual VOC. Therefore, in this study, we will look about concentration change of VOCs (Volatile Organic Compounds) by using Mock-up test. As result of test, the concentration of four individual VOC (Benzene, Toluene, Ethylbenzene, Styrene) showed quitely low level after 7 days. On the other hand the concentration of Xylene and formaldehyde showed low level after 14 days.

• Journal of the Semiconductor & Display Technology
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• v.3 no.2
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• pp.17-21
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• 2004

Aluminum nitride(AlN) thin films were deposited on silicon substrate by reactive RF magnetron sputtering without substrate heating. We investigated the dependence of some properties for AlN thin film on sputtering conditions such as working pressure, $N_2$ concentration and RF power. XRD, Ellipsometer and AES has been measured to find out structural properties and preferred orientation of AlN thin films. Deposition rate of AlN thin film was increased with an increase of RF power and decreased with an increase of $N_2$ concentration. AES in-depth measurements showed that stoichiometry of Aluminium and Nitrogen elements were not affected by $N_2$ concentration. It has shown that low working pressure, low $N_2$ concentration and high RF power should be maintained to deposit AlN thin film with a high degree of (0002) preferred orientation.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.637-647
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• 1997

The purpose of this study was to evaluate the effect of concentration and pH of lactic acid on the formation of artificial root caries lesions formation in bovine teeth. The characterictics of artificially produced early root lesions were observed with polarized light microscope and the depth of lesions were mearsured with measuring microscope The results were as follows: 1. In the group of low pH and high concentration of lactic acid, the progress of lesion formation was faster than that of high pH and low concentration lactic acid group. 2. In the same group, initial lesion progress faster, but progression rate was reduced as time goes by. 3. In the development of initial root caries, cementum was act as a barrier to protect dentin from lesion progression.

• Economic and Environmental Geology
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• v.18 no.2
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• pp.135-138
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• 1985

The radioautographing of U-bearing cloaly slate samples were initiated in order to clarify the uranium distribution patterns in the samples of Ogcheon system. Moreover, x-ray powder diffraction and x-ray single crystal analysis studies were undertaken to identify the uranium mineral which was extracted from U-bearing coaly slate. The handspecimens were collected from the Boseong mine, located in Deokpyeong area, Goesan-gun, Chungcheongbug-do. According to the experimental studies, it has been found the following facts: (1) fixed carbon has close relation with uranium contents, (2) quartz veins developed in U-bearing coaly slate are diveded into two groups based on mode of occurrence, formation stage and uranium distribution pattern; early quartz vein ($QV_1$) with low uranium concentration and late quartz vein ($QV_2$) with high uranium concentration, (3) matrixes around $QV_1$ are displayed homogeneous and high uranium concentration, while matrixes around $QV_2$ are low uranium concentration, (4) uranium mineral is identified as a variety of autunite.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.577-582
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• 2002

Selective catalytic reduction and selective non-catalytic reduction processes are mainly used to treat nitrogen oxidants generated from fossil-fuel combustion. Especially, the selective non-catalytic reduction process can be operated more economical and designed more simply than the selective catalytic reduction. For this reason, many researchers carried out to increase the removal efficiency of nitrogen oxidants in the condition of low oxygen concentration by using the selective non-catalytic reduction process. However, this study was flue gas contained high oxygen concentration of 20(v/v%) with ammonia as a reducing agent. Moreover, it carried out experiment with many factors that are reaction temperature, retention time, initial NO concentration, NSR(normalized stoichiometric ratio). It was determined optimal operating conditions to improve NO removal efficiency with SNCR process. The De-NOx efficiency was increased with NSR, initial NO concentration and retention time increasement. This study has NO removal efficiency over 80% in the high oxygen concentration as well as low oxygen concentration. The injection of reducing agent may be considered for SNCR process and facility operation in 850$\^{C}$ of optimal condition.

• KSBB Journal
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• v.6 no.1
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• pp.35-43
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• 1991

The production of poly-$\beta$-hydroxybutyrate(PHB) from methanol by batch and fed-batch cultivations of Methylobacterium sp. GL-10 was studied. PHB accumulation was stimulated by the nutrients deficiency including, NH4+, SO42-, and K+. The nitrogen deficiency was the most critical factor for PHB accumulation. In batch cultivation, the maximum cell concentration and PHB content were 1.86g/l and 0.62g/l, respectively, with 1.0%(v/v) of methanol and 0.5g/1 of ammonium sulfate. The mass doubling time of Methylobacterum sp. GL-10 was in the range of 4-5 hrs. The cell growth and PHB accumulation were severely inhibited at the methanol concentration over than 2% (v/v). To overcome methanol Inhibition, constant feeding and intermittent feedillg fed-batch cultivations were adopted, using C/N molar ratio as a control factor. In constant feeding fed-batch process, cell concentration was increased up to 2.67g/1, and PHB yield was enhanced from 0.33 of batch culture to 0.53. The relatively low cell concentration was caused by methanol accumulated in culture broth at late growth phase. To prevent methanol accumulation and to maximize PHB production, DO-state intermittent fed-batch cultivation was attempted. The cell and PHB concentration was reached up to 4.55g/1 and 1.80g/1, respectively. It was possible to maintain methanol concentration low and also to feed nutrient of desired C/N molar ratio.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.857-862
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• 2014

Mechanical alloying under various gas atmospheres such as Ar, an Ar-$H_2$ mixture, and He gases were carried out, and its effects on the powder properties, microstructure and mechanical properties of ODS ferritic steels were investigated. Hot isostatic pressing and hot rolling processes were employed to consolidate the ODS steel plates. While the mechanical alloyed powder in He had a high oxygen concentration, a milling in Ar showed fine particle diameters with comparably low oxygen concentration. The microstructural observation revealed that low oxygen concentration contributed to the formation of fine grains and homogeneous oxide particle distribution by the Y-Ti-O complex oxides. A milling in Ar was sufficient to lower the oxygen concentration, and this led a high tensile strength and fracture elongation at a high temperature. It is concluded that the mechanical alloying atmosphere affects oxygen concentration as well as powder particle properties. This leads to a homogeneous grain and oxide particle distribution with excellent creep strength at high temperature.