• 공업화학
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• 제31권3호
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• pp.317-322
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• 2020

수산화암모늄나이트레이트(HAN; NH₃OHNO₃)는 낮은 용융점과 증기압의 특성을 가지고 있고, 상대적으로 높은 산소균형을 이루고 있는 이온성 화합물이다. 본 연구에서는 높은 함량의 액상추진제를 제조하기 위한 산화제로 활용하기 위하여 이중용매를 적용하여 고체입자상으로 얻었다. 감압 하에서 액상의 HAN으로부터 수분을 증발시킨 후, 반용매로서 아세톤과 에탄올을 적용하여 추출한 입자상의 HAN에는 13.8 wt%의 수분이 포함되어 있었다. 아세톤을 단독으로 적용하였을 때, 합성수율은 질량기준으로 최대 88%이었고, TGA로 측정된 최대 함량은 86.2%, 분해온도는 160~205℃ 범위로 나타났다.

• 한국지열·수열에너지학회논문집
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• 제11권4호
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• pp.1-6
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• 2015

In this study, energy performance of two types of food dryers which are electric heater and heat pump is studied experimentally. With drying chamber temperatures controlled at 45, 50 and $55^{\circ}C$, sliced radish is dried from an initial mass of 90 to final 7 kg. Moisture content, drying time, total power consumption, MER (moisture extraction rate, kg/h) and SMER (specific moisture extraction rate, kg/kWh) are measured and analyzed. As the drying chamber temperature is increased, drying time is shortened but energy efficiency is reduced for both types. For an electric heater dryer, the effect of chamber temperature on drying time is significant but less significant on energy efficiency. For a heat pump dryer, the dependence of chamber temperature on drying time is weak but strong on energy efficiency. Temperature levels have little effect on electric heater dryer performance but strong effect on heat pump dryer which operates on a vapor compression refrigeration cycle. The energy performance of the heat pump dryer is superior with an average SMER of 2.175 kg/kWh which is 2.22 times greater than that of the electric heater dryer with SMER of 1.224 kg/kWh.

• 한국환경과학회지
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• 제17권1호
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• pp.97-105
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• 2008

This study examined the contaminated soils with an indicator of TPH using SVE (Soil Vapor Extraction) and biological treatments. Their results are as follows. Water content in the polluted soils slowly decreased from 15% during the initial experimental condition to 10% during the final condition. Purification of polluted soils by Bioventing system is likely to hinder the microbial activity due to decrease of water content. Removal rate of TPH in the upper reaction chamber was a half of initial removal rate at the 25th day of the experiment. The removal rate in the lower reaction chamber was 45% with concentration of 995.4 mg/kg. When the Bioventing is used the removal rate at the 14th day of the experiment was 53%, showing 7 day shortenting. Since the Bioventing method control the microbial activity due to dewatering of the polluted soil, SVE method is likely to be preferable to remove in-situ TPH. The reactor that included microbes and nutrients showed somewhat higher removal rate of TPH than the reactor that included nurtients only during experimental period. In general, the concentration showed two times peaks and then decreased, followed by slight variation of the concentration in low concentration levels. Hence, in contrast to SVE treatment, the biological treatment tend to show continuous repetitive peaks of concentration followed by concentration decrease.

• Transactions on Electrical and Electronic Materials
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• 제14권6호
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• pp.329-333
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• 2013

SiOC films were prepared by capacitively coupled plasma chemical vapor deposition, and the correlation between the binding energy by X-ray photoelectron spectroscopy and Arrhenius equation for ionization energy was studied. The ionization energy decreased with increase of the potential barrier, and then the dielectric constant also decreased. The binding energy decreased with increase of the potential barrier. The dielectric constant and electrical characteristic of SiOC film was obtained by Arrhenius equation. The dielectric constant of SiOC film was decreased by lowering the polarization, which was made from the recombination between opposite polar sites, and the dissociation energy during the deposition. The SiOC film with the lowest dielectric constant had a flat surface, which depended on how carbocations recombined with other broken bonds of precursor molecules, and it became a fine cross-linked structure with low ionization energy, which contributed to decreasing the binding energy by Si 2p, C 1s electron orbital spectra and O 1s electron orbital spectra. The dielectric constant after annealing decreased, owing to the extraction of the $H_2O$ group, and lowering of the polarity.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.301-304
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• 2006

For the purpose of investigating the contributions of various gases to climate change, the thermal radiation associated with greenhouse gases are extracted from AIRS (Atmospheric Infrared Sounder) infrared radiances over the tropical pacific region. AIRS instrument which was launched on the EOS-Aqua satellite in May 2002 covers the spectral range from 650 cm-1 to 2700 cm-1 with a spectral resolution of between 0.4 cm-1 and 1 cm-1. In order to extract the thermal radiation absorbed by individual gases, the interfering background radiances at the top of the atmosphere are simulated using the radiative transfer code MODTRAN (MODerate spectral resolution atmospheric TRANsmittance). The simulations incorporated the temperature and water vapor profiles taken from NCEP (National Centers for Environmental Prediction) reanalyses. The differences between the simulated background radiance and AIRS-measured radiance result in the absorption of upward longwave radiation by atmospheric gases (i.e. greenhouse effect). The extracted absorption bands of individual gases will allow us to quantify the radiative forcing of individual greenhouse gases and thus those data will be useful for climate change studies and for the validation of radiative transfer codes used in general circulation models.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2002년도 춘계 국제 학술대회
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• pp.9-12
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• 2002

Diffusive transport of volatile organic compounds(VOCs) and their degradation by bacteria in unsaturated soils are couple by poorly understood mass transfer kinetics at the gas/water interface. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interaction in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations form diffusion experiments using toluene as a representative VOC in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas Putida, as the sole active microbial species. The coefficient for gas-liquid mass-transfer, K$\sub$LA/, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.

• 환경위생공학
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• 제19권4호
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• pp.19-24
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• 2004

The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOCs transport, microbial activity, and sorptive interactions in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOCs transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations from diffusion experiments using toluene as a representative VOCs in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas putida G7 md Fl, as the sole active microbial species. The gas-liquid mass-transfer was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils. Therefore we found that Pseudomonas putida G7 and Fl were very effective to remove of refractory pollutants such as toluene in soil by Bio-filter

• 한국미생물·생명공학회지
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• 제41권1호
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• pp.1-7
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• 2013

비휘발성, 비폭발성, 열적 안정성의 특성을 가지고 있는 이온성액체는 환경친화적인 용매이고, 또한 양이온과 음이온의 다양한 조합을 통해 사용 목적에 부합하는 이온성액체를 용이하게 합성할 수 있어 용매로서의 다양성으로 인해 청정 용매, 촉매, 추출 및 분리, 전해질 등의 분야에서 다양하게 응용되고 있다. 이에 본 논문에서는 이온성액체에 대한 기본 지식와 함께 현재 미생물생명화학공정에서 이온성액체가 용매로서 효과적으로 응용되고 있는 효소반응 분야, 단백질 재접힘 분야, 바이오매스 용해 및 활용분야에서의 최근 연구동향을 기술하였다.

• Fisheries and Aquatic Sciences
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• 제15권1호
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• pp.9-14
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• 2012

The objectives of this research were to improve the film-forming properties of Channel Catfish Ictalurus punctatus skin gelatin (CSG) by cross-linking with transglutaminase (TG), determine and optimize the TG reaction time, and characterize the mechanical and barrier properties of CSG edible film. Cross-linking of CSG was performed by TG for 0, 10, 20, 30, and 40 min at $50^{\circ}C$, and the reaction was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The color and mechanical and barrier properties of edible films fabricated with CSG cross-linked with TG were characterized. Gelatin yields from the extraction ranged from 18.2% to 23.3%. SDS-PAGE exhibited dark bands at 120 and 250 kDa, indicating successful TG-mediated cross-linking. The color of CSG film was not affected by TG cross-linking. The tensile strength of CSG films cross-linked with TG decreased from 42.59 to 21.73 MPa and the percent elongation increased from 42.92% to 76.96% as reaction times increased from 0 to 40 min. There was no significant difference in water vapor permeability of CSG films.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.684-689
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• 2012

Poly(acrylic acid) (PAA) 구형 입자는 바이오 분야의 소재에서부터 전자 재료에 이르기까지 다양한 분야에 사용되는 고분자 물질이다. 이를 생산하기 위해서는, 분산제(surfactant)를 이용한 중합 방법으로 합성을 한 후, 사용한 분산제를 제거하기 위한 별도의 Purification 과정을 거치게 된다. 일반 유기 용매를 사용하면 막대한 폐수 발생, 별도의 분리 공정 추가, 잔류 용매의 가능성 등의 문제점이 발생한다. 이에 이러한 문제를 해결하고자, 액체 이산화탄소를 용매로 하여, high-pressure Soxhlet extraction 방법을 개발하였다. 본 연구에서는 compressed liquid dimethyl ether (DME) 상에서 PAA 분산 중합에 사용된 pyrrolidene carboxylic acid-g-poly (siloxane) 계열의 분산제, Monasil PCA 제거하는 연구를 진행하였다. 추출된 PAA 입자의 모양은 field emission scanning electron microscopy (FE-SEM)으로 확인을 하였고, Monasil PCA의 농도는 Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES)로 분석하였다. 용매의 효과를 비교하기 위해서, 액체 이산화탄소와 n-hexane과 liquid DME를 대상으로 추출 실험을 하였다. 그 결과 n-hexane의 경우 일부 정제된 PAA 구형 입자를 얻을 수 있었지만, 일부는 n-hexane 증기의 높은 열에 의해서 변형된 형태의 입자를 얻었다. Liquid DME의 경우엔, 추출이 잘 되지 않았다. 액체 $CO_2$를 이용하는 경우에 구형의 형태는 유지하면서 분산제가 제거된 입자를 얻을 수 있었다. 그리고 최적 운전 조건을 알기 위해서 8시간 동안 재비기와 응축기의 온도를 달리하면서 실험을 실시하였다. 그 결과 추출기의 온도가 $19.6{\pm}0.2^{\circ}C$, 압력이 $51.5{\pm}0.5$ bar일 때, 가장 좋은 제거 효율을 보였다.