• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.920-924
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• 2011

ZnO crystals with belt and comb shapes were synthesized without any catalysts through a simple thermal oxidation of ZnS powder in alumina crucible under air atmosphere. X-ray diffraction (XRD) pattern revealed that the ZnO crystals had wurtzite structure of hexagonal phase. Energy dispersive x-ray (EDX) spectra showed that the ZnO was of high purity. In the cathodoluminescece spectra obtained for the ZnO crystals with belt and comb shapes, a strong ultraviolet emission centered at 380nm was observed, which indicates the ZnO crystal has high crystalline quality.

• Journal of Life Science
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• v.10 no.1
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• pp.61-67
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• 2000

An experiment was conducted for extension of shelf-life of cooked squid (Todarodes pacificus) using modified atmosphere packaging. The products were packed in a Ny/PE/LLDPE (0.015/0.045/0.040 mm) laminated film with air, vacuum, CO2 gas, and N2 gas, respectively, and then stored at 5$^{\circ}C$ and 2$0^{\circ}C$. Keeping qualities of the products were investigated by measuring moisture content, H, volatile basic nitrogen (VBN), viable cell count, thiobarbituric acid (TBA) value, peroxide value (POV) and color value. Good qualities of the products stored at 5$^{\circ}C$were maintained at least 9 days, 11 days, more than 35 days and 24 days in air, vacuum, CO2 gas and N2 gas packaging products, respectively. In cases of 2$0^{\circ}C$ storage, however, the shelf-lives of all the products were only one day. The shelf-life extension of the products were observed in CO2 ga>N2 gas>vacuum>air packaging in order.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.256-260
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• 2011

ZnO nanostructures with tetrapod, needle and multipod shapes were synthesized without catalysts through a simple thermal oxidation of metallic Zn powder in alumina crucible under air atmosphere. X-ray diffraction data revealed that the ZnO nanostructures had wurtzite structure of hexagonal phase. Energy dispersive X-ray (EDX) spectra showed that the ZnO was of high purity. After the oxidation of Zn powder, white colored product was mainly observed and yellow colored product was observed only a very little on the surface of the oxidized source materials. The white product consisted of tetrapods, while yellow product was composed of needles and multipods. Cathodoluminescece spectra showed that the crystalline quality of tetrapods was better that those of needles and multipods.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.215-222
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• 1995

Nb doped strontium titanate single crystals were grown by the floating zone method. The doping amount of $Nb_2O_5$ was 0.2 wt %. Those crystals were grown in air and N z atmosphere and the growth rate was 5 mmlhr and rotation speed of upper and lower shaft was 30 rpm. The shapes of melt - feed rod interface depending on sintering temperatures were observed. In air atmosphere, the flow rate of air was 1.5 ${\ell}/min$ and in $N_2$ atmosphere, that of $N_2$ gas was 0.5 ${\ell}/min$. As grown crystals were analyseQ by XRD, Laue back - reflection and chemical etching. After annealing in $N_2$ atmosphere, resistivities of crystals were measured and the activation energies of each samples were calculated.

• 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.

• Food Science and Preservation
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• v.4 no.3
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• pp.265-270
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• 1997

Effect of modified atmosphere packaging conditions on quality changes of dry jujube was investigated. Dry jujubes with moisture content of 26.7% were packaged in PET/Al/PE film pouches with modified atmospheres. The tested packages include those with normal air, vacuum, CO2 flushing, N2 flushing and O2 scavenger. Packages were stored at 25$^{\circ}C$ for 6 months, during which ascorbic acid concentration, browning level, titratable acidity and surface color were measured. Generally modified atmosphere packages could improve quality retention of dry jujubes except that vacuum package resulted in large surface color change. CO2-flushed package showed the best quality retention of high ascorbic acid content and low browning during 112 days, but caused high amounts of ascorbic acid destruction and browning in longer storage. In all the modified atmosphere packages titratable acidity reached a maximum followed by decline and subsequent rise, while it increased linearly with time in normal air package. Considering ascorbic acid retention browning level and surface color changes during 112 days, the packages of CO2 flushing and N2 flushing were better than others.

• Preventive Nutrition and Food Science
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• v.6 no.4
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• pp.240-243
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• 2001

Fresh pasta was packaged in a modified atmosphere of 22% $CO_2$/78% $N_2$ and compared with a control air package for its quality changes during storage at 8$^{\circ}C$. The modified atmosphere packaging suppressed the microbial growth of total aerobic bacteria and yeasts/molds with a concomitant reduction in the rates of physical and chemical quality changes, and thus successfully extended the shelf life of fresh packs from 20 days of air packs to 40 days based on microbial criterion of 10$^{6}$ cfu/g. The shelf life extension was greater when the initial microbial quality of the product was better.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.71-76
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• 1997

A lot of experiments and analyses have been done to determine the aging mechanism of mica-epoxy composite material used for large generator stator windings in order to estimate remaining life of the generator for last decades. After degrading artificially the mica-epoxy composite material, the surface analysis is performed to analyze breakdown mechanism of insulation in air and hydrogen atmosphere; i) In the case of air atmosphere, it is observed that an aging propagation from conductor to core by partial discharge effect and the formation of cracks between layers is widely carbonized surface. ii) In case of hydrogen atmosphere, the partial discharge effect is reduced by the hydrogen pressure (4kg/$\textrm{cm}^2$). Potassium ions forming a sheet of mica is replaced by hydrogen ions, which can lead to microcracks. It is confirmed that the sizes of crack by SEM analysis are 10∼20[$\mu\textrm{m}$] in length under air, and 1∼5[$\mu\textrm{m}$] in diameter, 10∼50[$\mu\textrm{m}$] in length under hydrogen atmosphere respectively. The breakdown mechanism of sttor winding insulation materials which are composed of mica-epoxy is analyzed by the component of materials with EDS, SEM techniques. We concluded that the postassium ions of mica components are replaced by H\ulcorner, H$_3$O\ulcorner at boundary area of mica-epoxy and/or mica-mica. It is proposed that through these phenomena, the conductive layers of potassium enable creation of voids and cracks due to thermal, mechanical, electrical and environmental stresses.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.04a
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• pp.670-671
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• 2008

• Transactions of the KSME C: Technology and Education
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• v.2 no.2
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• pp.105-111
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• 2014

Generally the lower part of the Earth's atmosphere, which is 20km above the ground, is called "air." The composition of this area is almost consistent consisting of nitrogen, oxygen, and other gases. Air density refers to the mass per unit volume of earth atmosphere. Though air is made of the mixed gases in a constant composition, the water vapor is one of the very changeable components. The density of moist air is lower than the dry one at the same temperature and pressure. As the density varies according to the pressure and temperature, this paper attempts to explore the main factors in the air quantity calculation by examining first the density calculation process according to the air property, and second the relation between the actual and standard air flow.