• 한국산업보건학회지
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• 제15권3호
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• pp.261-269
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• 2005

To investigate the field applicability of a diffusive sampler (3M OVM #3500, passive sampling method) authors conducted a simultaneous measurement of personal organic solvents exposure in the air of the workplaces by charcoal tube with low volume sampler (active sampling method) and diffusive sampler. Samples were collected and analyzed by NIOSH method ($NMAM^{(R)}$) from thirty-eight workers in 12 factories who work in 6 different processes. Geometric mean (GM) and geometric standard deviation (GSD) were used to describe the result. To compare the results of the two methods, paired t-test was used. According to the manual of the exposure assessment of the mixed organic solvents (Ministry of Labor, Korea), Em was calculated. Simple linear regression was used to evaluate the relationship between the two methods. Results were as follows; 1. Eight different solvents (ethyl acetate, n-hexane, toluene, xylene, acetone, isopropyl alcohol, methyl ethyl ketone (MEK), and methyl isobutyl ketone) were detected simultaneously in the two methods and the concentrations of the personal exposure were lower than 0.5 TLV level. The concentration of the charcoal tube method was higher than that of a diffusive sampler in n-hexane and MEK (p<0.05). 2. Em of the charcoal tube method was higher than that of diffusive sampler method but not significantly different and was lower than the OEL (Occupational Exposure Limit) in all 6 processes. 3. There was a significant correlation between the two methods in low concentrations of the 8 organic solvents (p<0.05). In conclusion, there was no difference in charcoal tube method and diffusive sampler method in low concentrations of some organic solvents, diffusive sampler can be applied to assess the personal monitoring in low level exposure.

• 공업화학
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• 제1권2호
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• pp.240-248
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• 1990

$C_9$ aromatics의 transakylation에 대한 금속담지 H-mordenite의 촉매활성 및 선택도에 관한 실험이 고압의 연속흐름 고정층 반응기에서 수행되었다. 니켈담지 H-mordenite(T-Ni) 촉매는 높은 활성을 나타내었으며, 이 활성의 감소속도가 느렸다. 몰리브덴 및 니켈이 담지된 H-mordenite(T-NiMo) 촉매도 높은 활성을 나타내었으며, 탄화수소의 탄화를 억제하였다. T-Ni 및 T-NiMo 촉매의 선택도는 실험범위 내에서 반응온도가 증가함에 따라 감소하였지만, 상업적으로 사용되는 T촉매의 선택도는 반응온도가 증가함에 따라 서서히 증가하였다. 촉매의 초기활성 및 활성감소 측면에서는 T-Ni 및 T-NiMo 촉매의 성능이 T촉매보다 우수하였으며, 몰리브덴의 첨가는 T-Ni 촉매의 안정성을 다소 개선하였다.

• 멤브레인
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• 제23권2호
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• pp.176-184
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• 2013

다성분계 휘발성 유기화합물(VOCs; Volatile Organic Compounds)의 분리를 위하여 상전이법을 이용하여 방사한 poly (ether imide) (PEI) 중공사 지지체에 poly (dimethylsiloxane) (PDMS)를 코팅하여 중공사 복합막을 제조하였다. VOCs 회수용 중공사막으로서 적합성을 알아보기 위해서 중공사막의 모폴로지, 질소 및 산소 기체 투과도를 측정하고, 벤젠, 톨루엔 그리고 자일렌에 대한 내구성을 조사하였다. 다성분계 휘발성 유기화합물의 효과적인 분리성능을 조사하기 위하여 Stage-cut과 feed 농도에 따른 다성분계 VOCs 투과 성능 변화를 관찰하였다. PEI 지지체 중공사막에 PDMS를 코팅시킴에 따라 산소와 질소 투과도는 각각 45,000 GPU와 49,450 GPU에서 63 GPU와 30 GPU로 감소하는 것을 확인하였다. VOCs 투과농도는 Stage-cut이 감소함에 따라 증가하나, 회수율은 감소하였다. 반면에 공급농도 증가에 따라 투과농도는 비례적으로 증가하였지만, 농축비나 회수율은 큰 변화가 없었다.

• 한국재료학회지
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• 제22권8호
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• pp.416-420
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• 2012

Recently nanoscience and nanotechnology have been studied intensively, and many plants, insects, and animals in nature have been found to have nanostructures in their bodies. Among them, lotus leaves have a unique nanostructure and microstructure in combination and show superhydrophobicity and a self-cleaning function to wipe and clean impurities on their surfaces. Coating films with combined nanostructures and microstructures resembling those of lotus leaves may also have superhydrophobicity and self-cleaning functions; as a result, they could be used in various applications, such as in outfits, tents, building walls, or exterior surfaces of transportation vehicles like cars, ships, or airplanes. In this study, coating films were prepared by dip coating method using polypropylene polymers dissolved in a mixture of solvent, xylene and non-solvent, methylethylketon, and ethanol. Additionally, attempts were made to prepare nanostructures on top of microstructures by coating with the same coating solution with an addition of carbon nanotubes, or by applying a carbon nanotube over-coat on polymer coating films. Coating films prepared without carbon nanotubes were found to have superhydrophobicity, with a water contact angle of $152^{\circ}$ and sliding angle less than $2^{\circ}$. Coating films prepared with carbon nanotubes were also found to have a similar degree of superhydrophobicity, with a water contact angle of 150 degrees and a sliding angle of 3 degrees.

• 한국대기환경학회지
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• 제22권6호
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• pp.767-778
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• 2006

This study was carried out to evaluate the temporal variations of VOCs at an urban site, and to compare the concentrations of VOCs at an urban site in Daegu with those at a suburban site in Gyeongsan. Three hourly VOC samples in the ambient air were collected using a sequential tube sampler (STS 25, Perkin Elmer) throughout two weeks during May and July representing spring and summer seasons, respectively. The VOC concentrations were determined by an automatic thermal desorption apparatus with GC/MS analysis. A total of 12 VOCs of environmental concern were determined, which are chloroform, benzene, trichloroethylene, toluene, tetra-chloroethylene, ethylbenzene, m+p-xylenes, o-xylene, styrene, 1,3,5- and 1,2,4-trimethylbenzenes. Among 12 target VOCs, the most abundant compound appeared to be toluene, being followed by xylenes. The mean concentrations at the urbn site were 1.2 pub for benzene and 20.4 ppb for toluene (n=221) while the mean levels at the suburban site were 0.9 ppb and 4.3 ppb for benzene and toluene (n=96), respectively. The urban site concentrations were typically several-fold higher than those measured at the suburban site. It was found that general trends of VOC levels were significantly dependent on traffic conditions at the sampling site since VOC concentrations were at their maximum during rush hours, i.e. $9{\sim}12a.m$ and $6{\sim}9p.m$. Statistical investigations were conducted to investigate any significant relationships between VOC concentrations and affecting factors. Calculated correlation coefficients among VOCs were positively significant at a level of 0.05 in most cases. Increased concentrations of toluene in the urban site were estimated to reflect the effect of large industrial sources, mainly from textile industry.

• 한국대기환경학회지
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• 제22권6호
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• pp.876-887
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• 2006

Recently, there have been a large number of remodeling (or renovation) works in old buildings in urban areas. Compared to new buildings, environmental risk might be more significant in such buildings where remodeling works are going on, since some parts of the building may still be in service for people. This study was carried out to investigate the impacts of remodeling works on the indoor air quality (IAQ) of a large building (a 22 stories university library). Indoor air monitoring was conducted during and after the remodeling works every two weeks for a one year period, and target compounds included BTEX, styrene, TVOC, carbonyl compounds such as formaldehyde and acetaldehyde. $CO,\;CO_2,\;PM_{10}$, and $PM_{2.5}$. Overall, the IAQ appeared to be recovered within two months after the remodeling works. However, in some places, concentrations of formaldehyde, toluene, xylene. and ethylbenzene showed higher levels even after works than those during the works. The results indicate that painting, glues and office furnitures are major sources of aromatic VOCs and formaldehyde. Therefore, in order to decrease the concentrations of toxic VOCs, the use of environmental-friendly building materials is strongly recommended during the remodeling works. In addition, IAQ control and management scheme (for example, baking the inside of the building) should be taken into consideration before reopening the buildings.

• 한국대기환경학회지
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• 제22권6호
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• pp.929-939
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• 2006

In this study, the concentrations of major odorous compounds including reduced sulfur compounds (DMS, $CS_2$, and DMDS) and aromatic VOC (benzene, toluene, xylene, etc.) were measured continuously using an on-line GC analytical system. Our measurements were made from a residential area of Ansan city during about two weeks period of October, 2004. The highest mean concentrations of reduced S and VOC were recorded as 56.9 ppt of DMS and 21.7 ppb of toluene, respectively. The results of this study generally show that the pollution levels for both types of chemicals are significant relative to previous measurement results reported from comparable sites, if the results are compared simply in terms of the magnitude of the measured concentration data. Moreover, when the relative importance of different compounds is compared in terms of the odor strength, it indicates that the contribution of reduced S compounds may be much more important than that of VOC in the study area.

• 센서학회지
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• 제24권3호
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• pp.151-154
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• 2015

The gas sensing characteristic of $MoS_2-MoO_2$ composite yolk-shell spheres were investigated. $MoO_3$-carbon composite spheres were prepared by ultrasonic spray pyrolysis of aqueous droplets containing Mo-source and sucrose in nitrogen, which were converted into $MoO_3$ yolk-shell spheres by heat treatment at $400^{\circ}C$ in air. Subsequently, $MoS_2-MoO_2$ composite yolk-shell spheres were prepared by the partial sulfidation of $MoO_3$. The $MoS_2-MoO_2$ composite yolk-shell spheres showed relatively low and irreversible gas sensing characteristics at < $200^{\circ}C$. In contrast, the sensor showed high and reversible response (S=resistance ratio) to 5 ppm $NO_2$ (S=14.8) at $250^{\circ}C$ with low cross-responses (S=1.17-2.13) to other interference gases such as ethanol, CO, xylene, toluene, trimethylamine, $NH_3$, $H_2$, and HCHO. The $MoS_2-MoO_2$ composite yolk-shell spheres can be used as reliable sensors to detect $NO_2$ in a selective manner.

• 공업화학
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• 제1권1호
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• pp.73-82
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• 1990

로진과 말레산무수물로부터 rosin-maleic anhydride adduct (RMA)를 합성하고 이를 방향족디이소시아네이트와 반응시켜서 폴리아미드이미드를 합성하였다. 반응촉매로는 Sodium methoxide ($CH_3ONa$)를 사용하였고 반응용제로는 N-메틸-2-피롤리돈 (이하 NMP)을 사용하였다. NMP는 방향족디이소시아네이트와 부반응을 하기 때문에 중합체의 수율과 점성도가 낮았다. 부반응을 줄이기 위하여 NMP에 방향족용제인 크실렌, 아세토페논, 벤조니트릴 및 니트로벤젠을 공용제로 혼합, 사용하였다. 극성이 비교적 작은 공용제의 혼합시 공용제 혼합비율이 60%인 경우 약 70%정도, 극성이 비교적 큰 공용제의 혼합계에서는 혼합비율이 40%인 경우 90% 이상의 수율로서 높은 수율을 얻을 수 있었다. 중합체는 무정형이거나 약간의 결정성을 갖는 구조였으며 고극성용제에서만 용해하였다. 중합체의 점성도는 0.12-0.26dl/g의 범위였다. 열분석 결과 중합체의 초기분해온도는 $330^{\circ}C$ 이상으로서 양호한 열안정성을 나타내었다.

• 공업화학
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• 제27권5호
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• pp.546-550
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• 2016

국내 토양오염의 60~70% 이상이 석유제품에 의한 오염이며, 석유제품에 의해 토양오염이 발생될 경우, 토양환경보전법 상 B T E X와 total petroleum hydrocarbon (TPH)를 분석하도록 명시하고 있다. 본 연구에서는 국내 유통 중인 석유제품에 대한 구간별 TPH 패턴을 분석하였다. 또한 $C_8{\sim}C_{40}$ 구간만을 분석하는 현행 토양오염공정시험기준의 문제점을 보완하여 석유제품 내 TPH를 정량분석 하였다. 분석결과, 토양오염공정시험기준 분석조건으로 분석한 결과값과 보완된 분석방법을 이용했을 시, 휘발유와 용제 1호 같은 저비점 유류의 경우, 최대 85%의 차이가 발생하는 것을 확인하였다.