• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.183-188
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• 1998

Gas sensitizations of tin oxide film were investigated by measuring the change of film resistance in various gas atmospheres such as $N_2,\; O_2,\; H_2O$. The main test sample, polycrystalline $SnO_2$ film containing small Sb as a dopant was prepared by a sputtering technique and showed a long term stability in base resistance and thus, in gas sensitivity. The adsorption of oxygen on the film surface as a type of $(O_{ads})$ at the temperature of around $300^{\circ}C$ played important roles in sensor operating mechanism. The roles were ⅰ) the increase of base resistance in ambient air, which consequently lead to high sensitivity and ⅱ) the promotion of fast recovery. The reaction of hydrogen gas with the already adsorbed $(O_{ads})$ ions was considered as a decisive sensitization mechanism of tin oxide film. However, the dissociation of hydrogen molecules on film surface, by direct donation of electron to film also took a major part in the sensitization. The effect of humidity on gas sensitization was found to be negligible at the sensor operating temperature of around $300^{\circ}C$.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.32-39
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• 2004

This papers describes on the experimental consideration for the intrinsically-safe explosion-proof capability of rechargeable battery's body about main item rechargeable battery and cellular phone battery which is selling in domestic that IEC(International Electrotechnical Commission) recommend the measurement of ignition limit by short circuit of rechargeable battery and temperature increase test to use a explosion grade Group IIC type of explosion-proof type apparatus test an object of hydrogen gas. Because of that there are many different results for existence or nonexistence for ignition by different company and different types. It is concluded that the maximum of self temperature increasing by spark circuit of rechargeable battery is $180^{\circ}C$ in case of Nickel-Hydrogen and $110^{\circ}C$ in case of Nickel-Cadmium. The reaction of cellular battery for external temperature have following processes. It is confirmed that the temperature of reaction is rise slantly as the ambient temperature rising, then exterior shape of one is swell up and change when the temperature of ambient reach to about $130\~140^{\circ}C$, and when reach to about $160^{\circ}C$ the battery is blown up. Therefore, it is considered that have to be in considering selection of rechargeable battery using in itself due to different ignition limits of various rechargeable battery when the portable electric containing rechargeable battery are designed, produced and used, the characteristics and the proper safety factors of devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.321-322
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• 2009

Al doped ZnO films deposited on glass substrate using RF magnetron sputtering in Ar and $Ar+H_2$ gas ambient at $100^{\circ}C$. The films deposited in $Ar+H_2$ were hydrogen-annealed at the temperature of $150\sim300^{\circ}C$ for 1hr. The lowest resistivity of $4.25\times10^{-4}{\Omega}cm$ was obtained for the AZO film deposited in $Ar+H_2$ after hydrogen annealing at $300^{\circ}C$ for 1hr. The average transmittance is above 85% in the range of 400-1000 nm for all films. The absorption efficiency of solar cell was improved by using the optimized AZO films as a top electrode.

• Journal of the Semiconductor & Display Technology
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• v.16 no.1
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• pp.116-119
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• 2017

In this paper, natural convection around the ambient evaporator was numerically studied using commercial computational fluid dynamics software. From the simulations, temperature and velocity fields around the evaporator were found as a function of evaporator size and liquefied gas flow rate. The heat transfer coefficient at the external surface of the evaporator was also calculated from the simulation results. In order to give the heat transfer coefficient for various conditions, correlation between Rayleigh number and Nusselt number was proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.852-859
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• 2000

The emission in the exhaust gas from diesel engine is effected by the fuel spray characteristics. The spray of D.I. diesel engine impinges on a piston cavity and a cylinder wall. It is very important to know exactly the distribution and behavior of the spray inside cylinder. The objective of this study is to develop more accurate evaporation model. The EPISO code was used to analyze the flow characteristics in the engine. The Wakil model and the Faeth model are applied to the EPISO code to analyze the behavior of impinging spray. And also experimental and numerical analysis were carried out. The spray behavior characteristics were investigated by changing injection pressure, ambient pressure and temperature. The behavior of impinging spray was strongly effected by the change of ambient pressure and temperature. The effects of evaporation and rebounding droplet should be considered.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2995-3000
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• 2014

A sensitive concentration method utilising modified gas-purge microsyringe extraction (GP-MSE) was developed. Concentration (reduction in volume) to a microlitre volume was achieved. PAHs were utilised as semivolatile analytes to optimise the various parameters that affect the concentration efficiency. The injection rate and temperature were the key factors that affected the concentration efficiency. An efficient concentration (75.0-96.1%) of PAHs was obtained under the optimised conditions. The method exhibited good reproducibility (RSD values that ranged from 1.5 to 9.0%). The GP-MSE concentration method enhances the volume reduction (concentration factor), leading to a low method detection limit ($0.5-15ngL^{-1}$). Furthermore, this method offers the advantage of small-volume sampling, enabling even the detection of diurnal hourly changes in the concentration of PAHs in ambient air. Utilising this method in combination with GC-MS, the diurnal hourly flux of PAHs from the gas phase of ambient air was measured. Indeed, the proposed technique is a simple, fast, low-cost and environmentally friendly.

• Journal of Environmental Science International
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• v.19 no.4
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• pp.447-457
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• 2010

This study aims to monitor the variation of concentration of PCDD/DFs between the gaseous phase-particulate phases in the ambient air of urban area in Korea. This monitoring is evaluated by using the Junge-Pankow model and the Koa absorption model with the application of the Octanol-air partition coefficient. In this study, the ambient air samples were analyzed according to each congener group of the PCDD/DFs by HRGC/HRMS, which have been investigated for the past 5 years. In the results, the annual variation in the concentration level of $\Sigma$PCDD/DFs in TSP was increased from $1588\;fg/m^3$ in 1998 to $5123\;fg/m^3$ in 2002, and from 31 fg I-TEQ/$m^3$ to 94 fg I-TEQ/$m^3$ in the $\Sigma$I-TEQ. In the case of PUF of gaseous phase sample, their variation was increased from $1615\;fg/m^3$ in 1998 to $2237\;fg/m^3$ in 2002, and in the $\Sigma$I-TEQ from 12 fg I-TEQ/$m^3$ to 17 fg I-TEQ/$m^3$. The relative coefficient between the gas phase concentration of PCDD/DFs and the temperature was a value of 0.744; the contributive rate of the temperature to the gaseous phase concentration was 0.554. According to the results, the pattern of the coefficient of distribution based on log $p_L^0$ is similar to the ambient air of the urban areas.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.127-132
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• 2003

A study of high-pressure n-heptane droplet vaporization is conducted with emphasis placed on equilibrium at vapor-liquid interface. General frame of previous rigorous model[1] is retained but tailored for flash equilibrium calculation of vapor-liquid interfacial thermodynamics. The model is based on complete time-dependent conservation equations with a full account of variable properties and vapor-liquid interfacial thermodynamics. The influences of high-pressure phenomena, including ambient gas solubility, thermodynamic non-ideality, and property variation on the droplet evaporation are investigated. The governing equations and associated moving interfacial boundary conditions are solved numerically using a implicit scheme with the preconditioning method and the dual time integration technique. And a parametric study of entire droplet vaporization history as a function of ambient pressure, temperature has been conducted. Some computational results are compared with Sato's experimental data for the validation of calculations. For low ambient temperatures, the droplet lifetime first increases with pressures, then decreases for high pressures. For higher ambient temperatures, the droplet lifetime increase with less amplitude than that of low ambient temperatures, which then decreases with more amplitude than that of low temperatures. The solubility of nitrogen can not be neglected in the high pressure and it becomes higher as the pressure goes up.

• Journal of Power System Engineering
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• v.20 no.2
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• pp.32-42
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• 2016

Under part load condition of spark-ignition engine, pumping loss had great effect on engine efficiency. To reduce pumping loss, the study designed spark-ignited engines to make direct spray of gasoline to combustion chamber. In spark-ignited direct-injection engines, ignition probability is important for successful combustion and flame propagation characteristics are also different from pre-mixed combustion. This study designed a visualization testing device to study ignition probability of spark-ignited direct-injection LPG fuel and combustion flame characteristics. This visualization device consists of combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. Ambient pressure, ambient temperature and ambient air flow velocity are important parameters on ignition probability of LPG-air mixture and flame propagation characteristics, and the study also found that sprayed LPG fuel can be directly ignited by spark-plug under proper ambient conditions. To all successful cases of ignition, the study recorded flame propagation image in digital method through ICCD camera and its flame propagation characteristics were analyzed.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.231-236
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• 2016

Electrocatalytic reduction can produce useful chemicals and fuels such as carbon monoxide, methane, formate, aldehydes, and alcohols using carbon dioxide, the green house gas, as a reactant through the supply of electrical energy. In this study, tin-lead (Sn-Pb) alloy electrodes are fabricated by electrodeposition on a carbon paper with different alloy composition and used as cathode for electrocatalytic reduction of carbon dioxide into formate in an aqueous system. The prepared electrodes are measured by Faradaic efficiency and partial current density for formate production. Electrocatalytic reduction experiments are carried out at -1.8 V (vs. Ag/AgCl) using H-type cell under ambient temperature and pressure and the gas and liquid products are analyzed by gas chromatograph and liquid chromatograph, respectively. As results, the Sn-Pb electrodes show higher Faradaic efficiency and partial current density than the single metal electrode. The Sn-Pb alloy electrode which have Sn:Pb molar ratio=2:1, shows the highest Faradaic efficiency of 88.7%.