• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1354-1358
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• 2005

Nano- and microstructured indium nitride crystals were synthesized by the reaction of indium oxide ($In_2O_3$) powder and its pellet with ammonia in the temperature range 580-700 ${^{\circ}C}$. The degree of nitridation of $In_2O_3$ to InN was very sensitive to the nitridation temperature. The formation of zero- to three-dimensional structured InN crystals demonstrated that $In_2O_3$ is nitridated to InN via two dominant parallel routes (solid ($In_2O_3$)-to-solid (InN) and gas ($In_2O$)-to-solid (InN)). The growth of InN crystals with such various morphologies was explained by the vapor-solid (VS) mechanism where the degree of supersaturation of In vapor determines the growth morphology and the vapor was mainly by the reaction of $In_2O$ with ammonia and partially by sublimation of solid InN. The pellet method was proven to be useful to obtain homogeneous InN nanowires.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.818-826
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• 2004

The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR(Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated Particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.323-332
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• 1988

The bacteria containing urease convert each molecule of urea into two molecules of ammonia and one molecule of carbon dioxide gas. Bacterial electrodes have been constructed by immobilizing the Proteus vulgaris on an ammonia and a carbon dioxide gas-sensors, and were investigated for the effects of pH, temperature, buffer solution, bacterial amounts and interferences, and life time. NH3-bacterial electrode based on ammonia gas-sensor had linearity in the range of $7.0{\times}10^{-4}\;-\;3.0{\times}10^{-2}$M urea in pH 7.4, 0.05M phosphate buffer at $25^{\circ}C$ with a slope of 116.7 mV/decade. While $CO_{2-}$bacterial electrode based on carbon dioxide gas-sensor bad linearity in the range of $7.0{\times}10^{-4}\;-\;5. 0{\times}10^{-2}$M urea in pH 7.0, 0.1M phosphate buffer at $30^{\circ}C$with a slope of $45.4{\times}45.7mV/decade$. As the clinical application, urea in urine was determined by these devices and this result was compared with spectrophotometric method. Consequently, these electrodes could be used for the analysis of many samples because of simplicity, rapidity and convenience of the experimental procedure.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.112-117
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• 2020

Xylene is a hazardous volatile organic compound that should be precisely measured to monitor indoor air quality. However, the selective and sensitive detection of ppm-level xylene using oxide-semiconductor gas sensors remains a challenge. In this study, pure and Cr-doped Co₃O₄ nanoparticles (NPs) were prepared using flame spray pyrolysis, and their gas-sensing characteristics to 5-ppm xylene at 250 ℃ were investigated. The 4 at% Cr-doped Co₃O₄ NPs exhibited a high gas response to 5-ppm xylene (resistance ratio to gas and air = 39.1) and negligible cross-responses to other representative and ubiquitous indoor pollutants such as ethanol, benzene, formaldehyde, carbon monoxide, and ammonia. In this paper, the enhancement of the gas response and selectivity of Co₃O₄ NPs to xylene by Cr doping was discussed in relation to the catalytic promotion of the gas-sensing reaction. This sensor can be used to monitor indoor xylene.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.424-429
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• 2004

$Cr_{2}O_{3}$ thick films were fabricated by screen printing method on alumina substrates and annealed at $700^{\circ}C$, $800^{\circ}C$, and $900^{\circ}C$ in air, respectively. Structural properties examined by XRD and SEM showed (116) dominant $Cr_{2}O_{3}$ peak and increased grain sizes with the annealing. The resistance of the films decreased with increasing the annealing temperature. Gas sensing characteristics to $NH_{3}$, CO, $C_{4}H_{10}$, and NO gases showed sensitivity only to $NH_{3}$ gas. $Cr_{2}O_{3}$ thick films annealed at $700^{\circ}C$ had the sensitivity of about 15 % for 100 ppm $NH_{3}$ gas at the working temperature of $300^{\circ}C$. The thick films had good selectivity to the $NH_{3}$ gas. The response time to $NH_{3}$ gas was about 10 seconds.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.20-26
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• 2006

This study investigated on the conversion of nitrogen component in ammonia gas to control fuel-NOx. Control conditions were found to suppress the production of NOx in the catalytic combustion of the gasified fuels. Also, the results would provide the basis of the theoretical study on fuel-NOx generation mechanism.

• Journal of Environmental Science International
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• v.21 no.1
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• pp.49-55
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• 2012

In this study, the characteristic of offensive major odorous compound from the Bon-San industrial complex in Gimhae were determined by analytical methods of Gas Chromatography, High Performance Liquid Chromatography and UV/VIS Spectrophotometer. The kind of major odorous compounds examined acetaldehyde, sulfur compounds, ammonia and styrene. The concentration of all odorous compounds at 3 sampling points of industrial complex were lower than those of regulation standard levels of the industrial complex in Korea. The mean concentration of hydrogen sulfide was 0.0235 ppm at sampling point 2, it was higher than other sampling point. Complex odors was lower than regulation standard levels of the industrial complex in Korea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.126-131
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• 2003

Convective instability driven by surface tension is analyzed in an initially quiescent water absorbing ammonia gas with heat transfer using the linear stability analysis. The propagation theory is adapted to find the critical conditions of the onset of Marangoni convection. In this theory, the solutal penetration depth is chosen as the length scale factor. The results show that the liquid layer becomes more stable with decreasing the Schmidt number and increasing the Lewis number. It is also found that there is a critical Biot number to make the liquid layer be most unstable, and there is a linear relationship between the thor-mal Marangoni number and the solutal Marangoni number.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.557-563
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• 2001

Small capacity gas absorption systems for cooling and heating have been favorably considered to reduce the seasonal imbalance of electrical loads and LNG consumption recently. A multifunctional plate-fin heat exchanger was adopted as an absorber and the performance was tested and analyzed to reduce the size and weight of the absorption heat pump. The test was performed using breadboard type ammonia absorption machine. The performance was compared with the plate type absorber and there was little difference in heat and mass transfer characteristics. The heat and mass transfer performance was a function of poor solution and vapor flow rates and the mass transfer was dependent on vapor flow rate more than heat transfer.

• Journal of Environmental Science International
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• v.16 no.1
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• pp.33-38
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• 2007

The concentrations of offensive odorous compounds emitted from the two chemical plants in Chongju and Yeosu industrial complex in Korea were determined by uv/vis spectroscopy, gas chromatography, and high performance liquid chromatography. The odorous compounds examined in this study are ammonia, trimethyl amine, formaldehyde, acetaldehyde, propion aldehyde, butyl aldehyde, n-valeric aldehyde, iso-valeric aldehyde, hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfide. The concentrations of those were determined from the 10 sampling points of the two plants, respectively. The emission concentrations of all odorous com-pounds examined in the two plants were lower than those of the regulation standard levels of industrial complex in Korea, respectively. The propion aldehyde, n-valeric aldehyde, methyl mercaptan and dimethyl disulfide in Chongju and Yeosu plants, and butyl aldehyde and iso-valeric aldehyde in Yeosu plant were not detected at any sampling points examined.