• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.623-628
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• 2004

Zeolite SUZ-4 was successfully synthesized with TEAOH (Tetraethyl ammonium hydroxide) as structure directing agent under a vigorous stirring condition. Well-defined zeolite SUZ-4 structure was only obtained under stirring of 250 rpm or more. The results imply that stirring plays a pivotal role for reproducible synthesis. Morphology of SUZ-4 crystal was controlled by adjustment of water concentrations. The physicochemical characterization of SUZ-4 and its hydrothermal stability using a steam treatment were investigated by using XRD, BET, and $NH_3-TPD$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.669-675
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• 2008

The objectives of this paper are to examine the effect of nano-particles on the pool type absorption heat transfer enhancement and to find the optimal conditions to design a highly effective compact absorber for ammonia/water absorption system. The effect of $Al_2O_3$ nano-particles and carbon nanotube(CNT) on the absorption performance is studied experimentally. The experimental ranges of the key parameters are 20% of ammonia concentration, $0{\sim}0.08\;vol%$ (volume fraction) of CNT particles, and $0{\sim}0.06 \;vol%$ of $Al_2O_3$ nano-particles. For the ammonia/water nanofluids, the heat transfer rate and absorption rate with 0.02 vol% $Al_2O_3$ nano-particles were found to be 29% and 18% higher than those without nano-particles, respectively. It is recommended that the concentration of 0.02 vol% of $Al_2O_3$ nano-particles be the best candidate for ammonia/water absorption performance enhancement.

• Water for future
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• v.19 no.4
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• pp.321-328
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• 1986

Bottom sediment-river water samples were studied to determine the extent of biodegradable matter and to examine the reduction of COD, TKN and TOC by using of warburg and aerated batch reactor. Warburg studies were conducted to study the Oxygen Uptake Rates, Reaction Rate Constants and CBOD. Bacth reator studies were conducted to determine the reduction of COD, TKN and TOC. Results from the batch recator study indicate high concentration of COD in samples. Less than 10 precent of the Organic Carbon was found to be biodegradable in 48 hours of Warburg experiment. Appreciable Immediate Oxygen Demand of sediments suggests that dredging of the river bottom is likely to deplete dissolved significantly in the river water.

• Membrane Journal
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• v.8 no.4
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• pp.220-227
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• 1998

Recent data from Environmental department show that some out of 2,000 places surveyed are contaminated by nitrate, ammonia, fluoride, chloride and so forth in excess of the environmental standard-including purification plants, water taps, small water supply systems. In this study, some items which exceed drinking water standard were chosen and their concentrations were made varying from around standard level to around detected maximum concentration. After they permeated through the membrane module sold in the domestic market and made for household water-purifier, the most suitable membranes were selected according to individual water quality of various regions. In addition, the bacterial growth after storage for various days and under various temperatures was examined for the purpose of the effect of the time and temperature on bacterial growth.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.255-255
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• 2013

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 박막(nanosheet)이나 붕소 탄화질화물(boron caronitride; BCN) 박막과 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 박막으로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 폴리스틸렌(polystyrene, PS)과 보레인 암모니아(borane ammonia)를 고체 소스로 이용하여 열화학 기상증착법을 이용하여 BCN 박막를 SiO2 기판 위에 직접 합성하였다. SEM과 AFM 관측을 통해 합성된 BCN 박막을 확인하였으며, RMS roughness가 0.5~2.6 nm로 매우 낮은 것을 확인하였다. 합성과정에서 PS의 양을 조절하여 BCN 박막의 탄소의 밀도를 성공적으로 제어하였으며, 이에 따라 전기적인 특성이 제어되는 양상을 확인하였다. 또한 합성온도 변화에 따른 BCN 박막의 전기적인 특성이 제어되는 양상을 확인하였다. 추가적으로 같은 방법을 이용하여 BCN 박막을 Ni 위에서 합성하여 SiO2 기판위에 전사 하였다. 합성된 BCN 박막의 구조적 특징과 화학적 조성 및 결합 상태를 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy)을 통해 조사하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1117-1125
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• 2004

In this study, in order to utilize the waste heat of industrial wastewater in the range of the relatively low temperature of 40～5$0^{\circ}C$ as a heat source, a hybrid heat pump system was considered by computer simulation method. In the simulation, an absorber, desorber and solution heat exchanger were modelled by UA values while a compressor and pump performance were specified by an isentropic efficiency. Simulation results show that the performance of hybrid heat pump can be up to 80% higher than that of conventional R134a heat pump when it makes a process hot water of 9$0^{\circ}C$ while the wastewater is cooled down to 2$0^{\circ}C$. As the absorber pressure increases, the system performance and deserter pressure increase with a favorable effect of a compressor discharge gas temperature drop.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.102-111
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• 2000

A numerical model which simulates the simultaneous heat and mass transfer within a vertical tube GAX absorber was developed. The ammonia vapor and the solution liquid are in counter-current flow, and the hydronic fluid flows counter to the solution liquid. The film thickness and the velocity distribution of the liquid film were obtained by matching the shear stress at the liquid-vapor interface. Two-dimensional diffusion and energy equations were solved in the liquid film to give the temperature and concentration, and a modified Colburn-Drew analysis was used for the vapor phase to determine the heat and mass fluxes at the liquid-vapor interface. The model was applied to a GAX absorber to investigate the absorption rates, temperature and concentration profiles, and mass flow rates of liquid and vapor phases. It was shown that the mass flux of water was negligible compared with that of ammonia except the region near the liquid inlet. Ammonia absorption rate increases rapidly near the liquid inlet and decrease slowly. Both the absorption rate of ammonia vapor and the desorption rate of water near the liquid inlet increase as the vapor mass flow rate increases, but the mass fluxes of the ammonia and the water near the liquid outlet decrease as the mass flow rate of the vapor increases.

• Nuclear Engineering and Technology
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• v.7 no.2
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• pp.127-133
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• 1975

For isotopic exchange labelling of 3,5,3'-triiodothyronine (T$_3$) and thyroxine (T$_4$) with radioiodide in the presence of molecular iodine, T$_3$:I$_2$ or T$_4$:I$_2$ molar ratios, pH, and reaction time are. considered to be important factors. A modified labelling and separation method is proposed in present paper, by which T$_3$-$^{125}$ I and T$_4$-$^{125}$ I can be obtained with the mean labelling yields of 45%, and 50%, respectively. The whole reaction products can be separated by adoption of thin-layer chromatography technique using silica gel plate and the solvent system composd of chloroform, methanol and ammonia.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.395-399
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• 2011

In this study, micro gas sensors for ammonia gas were prepared by adopting MEMS technology and using a sol-gel process. Three types of sensors were prepared via different synthesis routes starting with W sol and Ru sol mixture. This mixture was deposited on a MEMS platform and the platform was subsegueny heated to a temperature of $350^{\circ}C$. The topography and crystal structure of the sensing film were studied using FE-SEM and XRD. The response of the gas sensor to $NH_3$ gas was examined at various operating temperatures and gas concentrations. The sensor response increased almost linearly with gas concentration and the best sensing response was obtained at $333^{\circ}C$ for 5.0 ppm $NH_3$ for the specimen prepared by coating $WO_3$ powders with the Ru sol mixture.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.38-49
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• 2010

The technology of anaerobic digestion of organic wastes has been researched for the production of biogas in various purposes. Biogas comes from anaerobic digestion and landfill in which that of main components are methane and carbon dioxide containing small amount of hydrogen sulfide and ammonia. Biogas can either be used directly on the site where it is generated after proper upgrading or distributed to external customer via separate pipelines like natural gas. There are four basic ways biogas can be utilized such as production of heat and steam, electricity production, vehicle fuel and production of chemicals. There is no international technical standard for biogas use but some countries have developed national standards and procedures for biogas use. In this paper, technical standards of biogas depending on purpose have reviewed for the several countries.