• Journal of Microbiology
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• 제43권1호
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• pp.49-53
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• 2005

Putative genes for a two-component signal transduction system (akbS and akbT) were detected near the alkylbenzene-degrading operon of Rhodococcus sp. DK17. Sequence analysis indicates that AkbS possesses potential ATP-binding and histidine autophosphorylation sites in the N- and C-terminal regions, respectively, and that AkbT has a typical response regulator domain. Mutant analysis combined with RT-PCR experiments further shows that AkbS is required to induce the expression of o-xylene dioxygenase in DK17.

• Journal of Environmental Science International
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• 제8권4호
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• pp.473-477
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• 1999

The purpose of this study was to investigate the characteristics of removal efficiency for aromatic hydrocarbons using a high-temperature fiber filter on a laboratory scale. The main elemental compositions of a high-temperaure fiber filter are aluminium and silica, which can act as the catalysts. Benzene, toluene and o-xylene among aromatic hydrocarbons were used in this experiment. For 3cm thickness of fiber filter, these compounds were removed more than 90% at the face velocities of 3cm/sec and 5cm/sec above 45$0^{\circ}C$. For 4cm thickness of it, the removal efficiencies of these compounds were almost 90% from 40$0^{\circ}C$ at the same face velocities, suggesting that it may be due to increasing the contact time between the fiber filter and aromatic hydrocarbons. The pressure droop ranged from 22 to 48mmH2O for 3cm thickness of fiber filter. However, for 4cm thickness of it, it was about two times(41~89mm$H_2O$) higher than that for 3cm fiber thickness.

• Journal of ILASS-Korea
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• 제23권4호
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• pp.185-191
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• 2018

Benzene, toluene, ethylbenzene and xylene (BTEX) were well known as ozone precursors from photochemical reactions and contribute to the formation of photochemical smog which pose health hazards. Also, some of these compounds directly affect the human health due to their toxicity such as benzene. In this study, BTEX ratios and correlation of $C_2$-benzenes (xylenes, ethylbenzene) in vehicle exhaust from recreational vehicle (RV) and multi-purpose vehicle (MPV) were characterized using a chassis dynamometer. VOCs were collected by tedlar bag and a GC/MS system was used for their quantification. Among all of the BTEX, toluene has the highest concentration(more than 30% in composition of BTEX). The average ratio of toluene to benzene emissions (T/B ratio=2.2) was found in vehicle exhaust. The average m,p-xylene/ethylbenzene and m,p-xylene/o-xylene ratios were 1.0 and 3.0 respectively. As a result, it showed a good correlation between the $C_2$-benzenes ($R^2=0.98{\sim}0.99$). In the future, it can be used as a marker for effect evaluation to atmospheric environment by vehicle exhaust.

• Applied Chemistry for Engineering
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• 제18권6호
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• pp.552-556
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• 2007

In this study, noble metals (Pd, Ru, Ir) were supported to $TiO_2$ catalyst. In order to distribute metals uniformly, $H_2O-H_2$ pretreatment technique was used. Xylene, toluene, and MEK were used as reactants. The monometallic or bimetallic catalysts were prepared by the excess wetness impregnation method and were characterized by XRD, and XPS analysis. Pd-Ru, Pd-Ir bimetallic catalysts had multipoint active sites which improved the range of Pd metal state. Bimetallic catalysts had a higher conversion of VOCs than that of monometallic one. The effect of $H_2O-H_2$ pretreatment technique was the enhancement of uniform distribution of Pd particles and promotion of catalytic efficiency. In this study, addition of Ru and Ir metals to Pd promoted oxidation conversion of VOCs. In addition, $H_2O-H_2$ pretreatment promoted removal efficiency of VOCs on the $TiO_2$ support.

• Bulletin of the Korean Chemical Society
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• 제16권3호
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• pp.281-284
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• 1995

The visible emission spectra of the o-xylyl radical in the gas phase have been obtained using a Fourier transform spectrometer coupled with a technique of supersonic expansion. The o-xylyl radical was generated in a jet by expansion with an inert buffer gas He from a high voltage dc discharge of the precursor o-xylene. The spectra were analyzed on the basis of the rotational contours of the vibronic bands as well as the known vibrational frequencies by a matrix isolation method.

• Journal of Korean Society for Atmospheric Environment
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• 제23권1호
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• pp.84-96
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• 2007

We performed the experiments to manufacture the hydrophobic $200cells/in^2$-zeolite honeycomb using HY-type zeolite of Si/Al ratio of 80 for separating and removing the VOCs emitted from small and medium size-plants by adsorption and to determine the drying method for the honeycomb at $105^{\circ}C$ without cracking, then measured performances of the honeycomb to adsorb the benzene, o-xylene, and MEK and to desorb the benzene and MEK saturated on the honeycomb by the nitrogen gas as the desorption gas. As a results, the good honeycomb was formed and the honeycomb was not cracked when the mixing ratio of the zeolite to bentonite to methyl cellulose to polyvinyl alcohol to glycerine to water is 100 : 8.73 : 2.18 : 4.19 : 1.38 : 126 and dried the honeycomb at $105^{\circ}C$ for 24 hours in the drying oven. The shape of the dried honeycomb was not changed after calcination, and the compressive strengths of the honeycomb after drying and calcination were 6.7 and $0.69kg/cm^2$, respectively. The adsorption efficiencies of the honeycomb for benzene, o-xylene, and MEK were $92{\sim}96%$ at the room temperature. The desorption efficiency at $180^{\circ}C$ was higher than that at $150^{\circ}C\;by\;1.5{\sim}13.8%$ depending on the flow rate of the nitrogen gas, and it was found that desorption efficiency is higher than 85% at $180^{\circ}C$ and 1.0L/min of the nitrogen gas. At $180^{\circ}C$ and 0.2 L/min, the concentration of the benzene and MEK in the used desorption gas are higher than 40,000 and 50,000ppm, respectively, so it be used as the fuel for preheating the desorption gas fed into the column in desorption cycle.

• Membrane Journal
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• 제1권1호
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• pp.65-77
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• 1991

The perstraction of ethanol and acetic acid were performed for three systems of xylene-acetic acid-water, MIBK-ethanol-water, and TBP-ethanol-water, The operating variables were pressure difference between aqueous and organic phase, and superfial velocities of aqueous and organic phases. The tortuosities of PP hollow fiber membrane of Celgard X10-400 and PTFE hollow fober membrane of Tex TA001 were found to be 1.82 and 1.43 respectively, They were obtained from mass tranfer coeffidents in membrane phase for xylene-acetic acid-water systems. The permeation flux and overall mass transfer coefficient for MIBK-ethanol-water system are larger than those for TBP-ethanol-water system. This tendency is magnified with increasing the superficial velocity of organic phase. Overall mass transfer coefficient($K_o$) increases nonlinearly with the increase of superficial velocity of organic phase($V_{or}$), and the relationship between $K_o$ and $V_{or}$ is that $K_o {\propto} V_{or}^{-0.35}$. For ethanol perstraetion using the hollow fiber membrane of Gore Tex TA001, the mass transfer in membrane phase is the rate-limiting step.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• 제19권4호
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• pp.403-411
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• 2009

This study was performed to propose appropriate conditions suited to the analysis of naphthalene by comparing desorption efficiencies under various conditions. 1. As to influence by adsorbing media and desorbing solvent on desorption efficiency of naphthalene, when adsorbed by CCT, o-xylene gave the highest desorption efficiency of $73.96{\pm}0.53%$ while the lowest of $1.14{\pm}0.03%$ desorbed by ether. Both XAD-2 and Chromosorb 106 showed around 90% of desorption efficiencies for each solvent, especially desorption efficiencies more than 95% were achieved when adsorbed by Chromosorb 106 and desorbed by $CS_2$ or o-xylene. 2. Desorption efficiencies descended over the storage period in any condition(p<0.05). For all three adsorbing media, while desorption efficiencies showed no significant difference(p>0.05) between room temperature and refrigeration a day of loading, samples kept in room temperature had higher desorption efficiencies than refrigerated ones in 7 and 14 days with significant difference(p<0.05).Also, desorption efficiencies dropped drastically in 7 days, from that point the decreasing tendency went mild. 3. When respective 1 TLV and 0.1 TLV of naphthalene were spiked on CCT and desorbed by CS2($46.45{\pm}0.59%$ vs. $30.15{\pm}0.81%$), o-xylene($73.96{\pm}0.53%$ vs. $67.51{\pm}1.34%$), and ether($1.14{\pm}0.03%$ vs. N.D.) desorption efficiencies increased as the amount of loading increased(p<0.05).On the other hand, naphthalene spiked on XAD-2 and Chromosorb 106 indicated no significant difference(p>0.05) in desorption efficiencies between 1 TLV and 0.1 TLV. In conclusion, in order for favorable desorption efficiencies of naphthalene it is important to select appropriate adsorbing media and desorbing solvent accordingly. The result revealed that adsorbing media of XAD-2 and Chromosorb 106 outperformed CCT and desorbing solvents of $CS_2$ and o-xylene achieved over 90% of desorption efficiencies when adsorbed on XAD-2 and Chromosorb 106. Also, considering the tendency that desorption efficiencies of naphthalene decrease with time, the samples should be analyzed as soon as possible.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.240-240
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• 2003

SiC 섬유의 고온강도를 향상시키기 위한 소결조제로 boron, aluminum 등을 사용할 수 있다. 본 연구에서는 폴리카보실란에 aluminum precursor를 첨가한 후 중합반응을 거쳐 Al-contained polycarbosilane을 합성하였다. 합성된 Al-contained polycarbosilane을 용융방사하여 섬유화 하고 열분해 공정을 통해 Si-Al-C-O 나노복합 섬유를 제조하였다. 먼저 aluminum butoxide와 polycarbosilane(commercial)을 200m1 xylene에 용해시켜 14$0^{\circ}C$에서 1시간 동안 reflux하였다. evaporator를 이용하여 xylene를 제거한 후 autoclave에서 25$0^{\circ}C$/30$0^{\circ}C$ 중합과정을 통해 가교결합 시켰다 이와 같이 합성된 시료는 ICP분석을 통해 aluminum 함량을 확인하였고 FT-IR(Fig.1) 및 GPC분석(Fig.2)으로부터 화학구조 및 분자량변화를 확인하였다. aluminum 첨가량이 증가함에 따라 Si-H/Si-$CH_3$의 결합크기의 비가 감소하였으며 이로부터 aluminum butoxide와 polycarbosilane의 가교결합이 이루어진 것으로 보이며 중합 후 분자량의 증가 또한 가교결합에 의한 결과로 사료된다 열무게감량(TGA) 측정 결과는 40$0^{\circ}C$부터 유기리간드의 분해가 일어나며 80$0^{\circ}C$이상에서 세라믹화 과정이 완료되었음을 알 수 있었다 또한 aluminum 첨가량이 증가함에 따라 세라믹 수율도 증가하였음을 확인하였다. 합성된 aluminum-contained polycarbosilane은 20$0^{\circ}C$에서 1시간 동안 불융화과정을 거쳐 환원 및 진공 분위기에서 고온 열처리하였으며 이로부터 얻어진 시료에 대해 XRD분석을 수행하였다. SEM과 TEM을 이용하여 미세구조를 관찰하였다.

• Advances in environmental research
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• 제2권2호
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• pp.143-153
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• 2013

This study investigated the concentrations of odourous compounds in air, leachate, stream and well in and around Taju-Bello dumpsite. Meteorological parameters (temperature, relative humidity, wind velocity) and six odour families comprising sulphur ($H_2S$), ammonia ($NH_3$), aromatic (benzene, toluene, ethylbenzene, styrene, p-xylene, m-xylene), aliphatic (hexane), oxygenated (formaldehyde, acetaldehyde) and halogenated (tetrachloroethene, trichloroethene, carbontetrachloride) compounds were measured. Meteorological parameters suggested low dispersal of pollutants at L1 with possible perspiration and suffocation from exposure to high temperature, relative humidity and low wind velocity. The trend of abundance of odourous compounds at studied locations is of the order dumpsite (L1) > leachate (L4) > 100 m away from dumpsite (L2) > 200 m away from dumpsite (L3) > stream (L5) > well (L6). $H_2S$, Oxygenated and aromatic compounds were the major contributors to odour strength in these locations. Correlation, factor and cluster analyses of the data revealed similarities of sources as biogenics and xenobiotics inherent in the wastes as the main sources of these odourous compounds.