• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.1-5
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• 2000

Cathodoluminescence(CL) properties of ZnO:Zn green phosphor were investigated. ZnO:Zn phosphor was synthesized by varying reducing agents and firing temperatures. ZnS, charcoal and 5% H2 gas mixed with 95% N2 gas(5H2-95N2) were used as the reducing agent and atmosphere. The highest CL intensity of ZnO:Zn phosphor was observed under the condition of 5H2-95N2 atmosphere and firing temperature of 90$0^{\circ}C$ for 1h. Charocal and ZnO as reducing agents in the syntehsis of ZnO:Zn phosphor exhibited about 60% and 40%, respectively, of the CL intensity obtained with 5H2-95N2 atmosphere.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.1-6
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• 1997

In case of using the electrical apparatus in the hazardous atmosphere which exist flammable gas mixtures, There is a dangerosity of gas explosion accident by the electrical spark. The most general method to prevent the explosion by the spark is to use the flame-proof type electrical apparatus to isolate the ignition source. from the flammable atmosphere. But actualy it is impossible to isolate the ignition sources from the atmosphere. So it was needed to find the safe gap which prevent ignition of flammable atmosphere by transmission of flame or heat when a flammable gas mixture exploded inside the apparatus. In this study we tried to find the maximum experimental safe gap(MESG) of $H_2$-air, and $CH_4$-air mixtures by using the 8 litre spherical vessel with 25mm flange. The experiment parameter were ignition position, concentration and initial pressure before explosion. From the experiment the ignition position was affected to the MESG. MESG value was minimum near the stoichiometric concentration of gas mixtures, and according to the increase of initial pressure MESG was decreased.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.1-15
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• 2011

Korea Global Atmosphere Watch Center (KGAWC), which is located in Anmyeondo and, belongs to the Korea Meteorological Administration (KMA), measures sulfur hexafluoride ($SF_6$) in every hour since 2007. In this study, $SF_6$ observed in 2007 are discussed. A gas chromatograph-electron capture detector (GC-ECD) with pre-cooled device is applied during the observation, and produced data are qualified by means of periodic calibration with $SF_6$ standard gas made by Korea Research Institute of Standard and Science (KRISS). $SF_6$ has been greatly paid attention since Kyoto protocol because of its high global warming potential(GWP) with 22,200 times of $CO_2$ in the period of 100 years. It is a man-made compound and has been usually used for gas insulation since 1970s and for etching process in the information technology-based industry since 1990. Average mixing ratio of $SF_6$ in 2007 was 6.65 pmol/mol at Anmyeondo. According to the GAW report published in 2008, average mixing ratio of $SF_6$ in the atmosphere is continuously growing. At present, the average mixing ratio of $SF_6$ in the atmosphere is known to be approximately 6.25 pmol/mol at global observatory. $SF_6$ value in Anmyeondo shows 0.40 pmol/mol greater than that of the Mauna Loa observatory in 2007.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.19 no.2
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• pp.61-65
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• 2013

Modified atmosphere (MA) of reduced $O_2$ and elevated $CO_2$ concentrations has been used for keeping the quality of fresh produce and extending the shelf life. As a way to attain the beneficial MA package around the produce, a gas diffusion tube or perforation can be attached onto the container and controlled on real time in its opening/closing responding to $O_2$ and $CO_2$ concentrations measured by gas sensors. The timely-controlled opening of the gas diffusion tube can work in harmony with the produce respiration and help to create the desired MA. By use of the mathematical modeling, the effect of tube dimension on the controlled container atmosphere was figured out in this study. Spinach and king oyster mushroom were used as typical commodities for designing the model container system (0.35 and 0.9 kg in 13 L, respectively) because of their respiration characteristics and the optimal MA condition ($O_2$ 7~10%/$CO_2$ 5~10% for spinach; $O_2$ 2~5%/$CO_2$ 10~15% for mushroom). With a control logic for the gas composition to stay as close as possible to optimum MA window without invading injurious low $O_2$ and/or high $CO_2$ concentrations, the atmosphere of the sensor-controlled container could stay at its lower $O_2$ boundary or upper $CO_2$ limit under certain tube dimensional conditions. There were found to be the ranges of the tube diameter and length allowing the beneficial MA. The desired range of the tube dimension for spinach consisted of combinations of larger diameter and shorter length in the window of 0.3~2 cm diameter and 0.2~10 cm length. Similarly, that for king oyster mushroom was combinations of larger diameter and shorter length in the window of 0.9~2 cm diameter and 0.2~3 cm in length. Clear picture on generally affordable tube dimension range may be formulated by further study on a wide variety of commodity and pack conditions.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.270-275
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• 2009

Lotus-type porous nickel with cylindrical pores was fabricated by unidirectional solidification under an Ar gas atmosphere using the thermal decomposition method of the compounds such as sodium hydroxide, calcium hydroxide, calcium carbonate, and titanium hydride. The decomposed gas does form the pores in liquid nickel, and then, the pores become the cylindrical pores during unidirectional solidification. The decomposed particles from the compounds do play a rule on nucleation sites of the pores. The behavior of pore growth was controlled by atmosphere pressure, which can be explained by Boyle's law. The porosity and pore size decreased with increasing Ar gas pressure when the pores contain hydrogen gas decomposed from calcium and sodium hydroxide and titanium hydride, ; however it they did not change when the pores contain containing carbon dioxide decomposed from calcium carbonate. These results indicate that nickel does not have the solubility of carbon dioxide. Lotus-type porous metals can be easily fabricated by the thermal decomposition method, which is superior to the conventional fabrication method used to pressurized gas atmospheres.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.77-83
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• 2013

In this study, we aimed to determine the optical properties of the plasma used for the dry cleaning method. The optical properties of the atmospheric pressure plasma device were measured through the degree of ionization of hydrogen or nitrogen gas by ionized atmospheric gas. The degree of ionization of hydrogen or nitrogen is closely associated with surface modification. We observed through our experiments that argon gas, an atmospheric gas, caused an increase in the ionization of nitrogen gas, which has similar ionization energy. This type of increase in nitrogen gas ions is believed to affect surface modification. The results of our study show that the pressure of argon gas and the partial pressure of argon and nitrogen gases lead to different results. This important result shows that argon ions can affect the ionization of nitrogen gas.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.279-285
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• 1998

The $UO_2$ pellets are usually sintered under hydrogen gas atmosphere. Hydrogen gas may cause unexpected early failure of the refractory bricks in the sintering furnace. In this work, nitrogen was mixed with hydrogen to investigate the effect of nitrogen gas on a failure machanism of the refractory bricks and on the microstructure of the $UO_2$ pellet. The hydrogen-nitrogen mixed gas experiments show that the larger nitrogen the mixed gas contains, the less the refractory materials are reduced by hydrogen. The weight loss measurements at $1400^{\circ}C$ for fire clay and chamotte refractories containing high content of $SiO_2$ indicate that the weight loss rate for the mixed gas is about half of that for the hydrogen gas. Based on the thermochemical analyses, it is proposed that the weight loss is caused by hydrogen-induced reduction of free $SiO_2$ and/or $SiO_2$ bonded to $Al_2O_3$ in the fire clay and chamotte refractories. However, the retardation of the hydrogen-induced $SiO_2$ reduction rate under the mixed gas atmosphere may be due to the reduction of the surface reaction rate between hydrogen gas and refractory materials in proportion to volume fraction of nitrogen gas in the mixed gas. On the other hand, the mixed gas experiments show that the test data for $UO_2$ pellet still meet the related specification values, even if there exists a slight difference in the pellet microstructural parameters between the cases of the mixed gas and the hydrogen gas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.105-105
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• 2009

The composites were fabricated by adding 30, 35, 40, 45[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. $SiC-ZrB_2$ composites were sintered by Spark Plasma Sintering(hereafter, SPS) in vacuum or argon gas atmosphere. The relative density of SiC+40[vol.%]$ZrB_2$ composites reveal high 99.57[%] in argon gas atmosphere and pressure 50MPa.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.53-60
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• 1991

This study has been performed to investigate into the internal oxidation characteristics of low carbon steel with respect to the added amount of air in nitrogen-propane atmosphere after gas carburizing for various times at $930^{\circ}C$. The results obtained from the experiment are as follows ; (1) Optical micrographs have shown that the internal oxidation is unlikely to occur in the gas atmosphere without air and that oxidized zone in the outer surface layer is formed in the gas atmosphere with air revealing that the depth of oxidized zone increases with increasing the added amount of air. (2) The formation of internally oxidized zone in the outer surface layer has been found to be inhibited as Ni content increases, i. e, the amount of alloying element increases. (3) The depth of oxidation has been measured to increase with almost parabolically gas carburizing time of up to 6 hours.

• 연구논문집
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• s.30
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• pp.33-42
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• 2000

We must stabilize quickly increasing waste matters in urban life and livestock industry. Biogas including landfill gas and digester gas is byproduct of anaerobic decomposition of organic waste matter and contains 40%-70% methane, which can be used for energy purposes. Utilization of biogas reduce the emission of methane into the atmosphere to minimize greenhouse effect and the carbon dioxide (CO2) emitted when biogas is converted to energy has been taken out of the atmosphere by growing plant. Recently, bioenergy is world-widely noticeable as all contributing to the greenhouse effect. This paper presents development process of a biogas engine for cogeneration system and results of application to digester gas and landfill gas in site. The biogas engine is a dual fuel engine operated on biogas with a diesel pilot. At present, the engine can substitute biogas for diesel fuel up to 85%. but it can be said that there is a possibility of improvement in performance.