• Food Science and Preservation
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• v.23 no.6
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• pp.772-777
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• 2016

Activity of the noncontacted low temperature atmospheric pressure surface discharged plasma (LASDP) converts stable gas to ionized gas known as discharge or plasma. This ionized gas exhibits the antimicrobial activity. We examined the effects of 3 different storage treatments for 80 days on 'Setoka' : ambient storage (AS), low-tempperature storage (LTS), and low-temperature atmospheric pressure plasma+low-tempperature storage (PLTS). Total soluble solids showed no the significant differences between the 3 treatments. Acidity gradually decreased, and was 0.5% under AS after 30 days of storage. Fruit firmness increased by a few percent until 40 days of storage. Weight loss in AS was higher than for other treatments. After 80 days of storage, the decay ratio was significantly low in PLTS treatment: (AS, 50.5%; LTS, 5.6%; PLTS, 1.9%). In AS treatment, 73% of the rotten fruits were infected particularly with green and blue mold; however, only 1% of the rotten fruits were infected in case of PLTS treatment. In conclusion, LASDP treatment can prevent postharvest decay caused by fungi and is an efficacious alternative extending the shelf-life of citrus fruits.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.1-8
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• 2009

Hydrophilic Surface modification of Polysarene (PS) was performed by Atmospheric Pressure Plasma (APP). Air or 0, gases were used for carrier gases and RF power was changed from 150 to 350 W. We controlled the treatment time as 1 time to 4 time passing through the plasma region. when the carrier gas was air, the water contact angle on the PS surface was decreased from $91^{\circ}$ to $20^{\circ}$. And the surface energy increased from 45.74 dyne/cm to 68.48 dyne/cm. In case of the $O_2$ plasma treatment, at 300 W of RF power and 4 times treatment, the water contact angle on the PS. Surface was decreased from $91^{\circ}$ to $17^{\circ}$ and the surface energy was increased from 45.74 dyne/cm to 69.73 dyne/cm. The surface energy was increased by polar force not by dispersion force. Improvement of surface properties can be explained by the formation of new hydrophilic groups which is identified as C-O, C=O by XPS analysis. The contact angle of APP treated PS surface kept in air was increased with time elapse, but maintained same value when it was kept in water. We treated the PS surface by APP and deposited Cu as $4,000\;{\AA}$ and $8,000\;{\AA}$ by thermal evaporation. The adhesion between sample and Cu thin film improvement of treated PS surface against untreated sample. could be verifiable by Tape test (ASTM D3359)

• Journal of Welding and Joining
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• v.21 no.4
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• pp.46-55
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• 2003

TiO$_2$-WO$_3$(8.2wt%) coatings were prepared by the APS (Atmospheric Plasma Spraying) process to clarify the relationship between the process parameters(H$_2$ gas flow rate of plasma 2nd gas and spraying distance) of the APS coating and photo-decomposition efficiency kinetics of the MB(methylene blue) aqueous solution decomposition and to understand the effect of addition of WO$_3$ on photocatalytic properties of TiO$_2$ sprayed coating. Further, the temperature and velocity of flying particles were measured by DPV-2000 to investigate the relationship between microstructure of coatings and process parameters. Properties of coatins were investigated by XRD, SEM, XPS, RAMAN, UV/VIS spectrometer. In case of the TiO$_2$-WO$_3$(8.2wt%) coating, it had a lower anatase fraction than that of pure-TiO$_2$ coatings because of flying in the higher temperature plasma plume by the heavy weight of TiO$_2$, WO$_3$. And, when WO$_3$ added powders were spayed, the doping effects of W ions substituted into the Ti ion sites was not occured during melting and solidification cycles of spraying. It was found that the addition of WO$_3$ was ineffective effective on increasing photo-decomposition efficiency of TiO$_2$ sprayed coating.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E3
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• pp.91-99
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• 2001

Plasma reactor was used to generate a high potential difference between two surfaces of concentric pyrex tubes by electrical current. The annular gap of the reactor was calculated by trial and error from the breakdown voltage equation and set at 0.45 cm. The overall objective of this research was to know the effects of the frequency, humidity, and residence time on the formation of nitrogen oxides in a plasma reactor. The primary voltage varied from 50 to 90 volts and the frequency was varied in increments of 10 Hz from 60 to 650 Hz at the primary voltage of 90. The increase in the secondary voltage was not linear but exponential at high frequencies. At a maximum concentration of about 745 ppm, the frequency and secondary voltage was 600 Hz and 4,200 volts, respectively. All tests for the effects of humidity on NO$_{x}$ production were performed at the optimal setting of 90 colts and 600 Hz frequency. Since the NO$_{x}$ production was not an one dimensional phenomenon, competing reactions were assumed to occur in the discharge chamber. The sharp peak concentration of 1,810 ppm was observed at 38% of relative humidity, The enhanced production was choked off, and the production rate rapidly dropped to 3 ppm at above 40% of relative humidity. It is assumed that the corona attacks the most vulnerable molecules in the reaction chamber before attacking other more lightly bonded molecules, possibly at humidities above 38% and the optimized 90 volt setting. Thus, there was not enough energy left after attacking all water molecules to decompose an appreciable amount of $N_2$. If nitrogen breakdown does not occur, then oxides of nitrogen are not likely to be produced.ced.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.653-657
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• 2011

Conversion characteristics of $CH_4$ and $CO_2$ was studied using an atmospheric pressure plasma for the preparation of synthesis gas composed of $H_2$ and CO. The effects of delivered power, total gas flow rate, and gas residence time in the reactor on the conversion of $CH_4$ and $CO_2$ were evaluated in a plasma reactor with the type of dielectric barrier discharge. The increase of reactor temperature did not affect on the increase of conversion if the temperature does not reach to the appropriate level. The conversion of $CH_4$ and $CO_2$ largely increased with increasing the delivered power. As the $CH_4/CO_2$ ratio increased, the $CH_4$ conversion decreased, whereas the $CO_2$ conversion increased. Generally, the $CH_4$ convesion was higher than the $CO_2$ conversion through the variation of the process parameters.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.106-110
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• 2011

A high thermal conductive AlN composite coating is attractive in thermal management applications. In this study, AlN-YAG composite coatings were manufactured by atmospheric plasma spraying from two different powders: spray-dried and plasma-treated. The mixture of both AlN and YAG was first mechanically alloyed and then spray-dried to obtain an agglomerated powder. The spray-dried powder was primarily spherical in shape and composed of an agglomerate of primary particles. The decomposition of AlN was pronounced at elevated temperatures due to the porous nature of the spray-dried powder, and was completely eliminated in nitrogen environment. A highly spherical, dense AlN-YAG composite powder was synthesized by plasma alloying and spheroidization (PAS) in an inert gas environment. The AlN-YAG coatings consisted of irregular-shaped, crystalline AlN particles embedded in amorphous YAG phase, indicating solid deposition of AlN and liquid deposition of YAG. The PAS-processed powder produced a lower-porosity and higher-hardness AlN-YAG coating due to a greater degree of melting in the plasma jet, compared to that of the spray-dried powder. The amorphization of the YAG matrix was evidence of melting degree of feedstock powder in flight because a fully molten YAG droplet formed an amorphous phase during splat quenching.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.905-907
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• 2014

The plasma and microwave surface treatments of carbon nanotubes that loaded on plastic substrates were carried out with expecting a change of carbon nanotube dispersion by increasing treatment time. The microwave treatment process was undergone by commercial microwave oven (800 W). The electrical property was measured by hall measurement and resistance was increased by increasing $O_2$ flow rate of plasma, suggesting an improvement of carbon nanotube dispersion and a possibility of controlling the resistances of carbon nanotubes by plasma surface treatment. The resistance was increased in both polyethylene terephthalate and polyimide substrates by increasing $O_2$ flow rate. Resistance changes only slightly with different $O_2$ flow treatment in measure rho for all polyimide samples. Sheet resistance is lowest in polyimide substrate not due to high carbon nanotube loading but due to tendency to remain in elongated structure. $O_2$ or $N_2$ plasma treatments on both polyethylene terephthalate and polyimide substrates lead to increase in sheet resistance.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.501-510
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• 2008

The stealth technology to conceal an aircraft from the vision of a radar have been accomplished by coating the surface with special paints absorbing the electromagnetic wave. Nowadays, researches to utilize characteristics of the plasma-wave interaction for realizing the stealth technology are actively progressed. In this paper, to investigate the physical feasibility of the plasma stealth, calculation results for the required conditions of the plasma cloaking on the aircraft flying in the air for showing the stealth function, using a flat non-magnetized non-uniform plasma model, are reported and discussed.

• Journal of Korean Society for Atmospheric Environment
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• v.5 no.2
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• pp.21-29
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• 1989

The metals present in atmospheric particulate come from various sources; natural or anthropogenic. Among various metals Fe, Zn, Pb, Cu, and Mn are of particular concern in as much as they are not only present in large quantity, but toxic to human body. A simple, fast, and non-destructive analytical method for these metals in atmospheric particulate was developed and the analytical details were described herein. The method involves the measurements of X-ray fluorescence of sample contained in filters and comparing it with those for standards. The standard filters were prepared by applicating premeasured standard solution to the filters and then drying. The accuracy of the method was tested by analyzing standard reference materials and by independently analyzing samples using a different, previously accuracy-proven method, inductively coupled plasma atomic emission spectrometry, and comparing the results obtained. Analytical sensitivities and detection limits of the present method were 62.9, 178.2, 82.9, 146.1, 37.2, 120.3 cps/$\mug/cm^2$ and 39.0 35.6, 137.5, 125.9, 182.6, 72.8 $ng/cm^2$ for Fe, Zn, Pb, Cu, Mn, and Ni respectively. The method was applied to Seoul atmospheric particulate and some results were reported.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.708-718
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• 2020

Offensive odor is recognized as a social environmental problem due to its olfactory effects. Ammonia(NH₃), hydrogen sulfide(H₂S) and benzene(C₆H₆) are produced from various petrochemical plants, public sewage treatment plants, public livestock wastes, and food waste disposal facilities in large quantities. Therefore efficient decomposition of offensive odor is needed. In this study, the removal efficiency of atmospheric-pressure plasma operating at an ambient condition was investigated by evaluating the concentrations at upflow and downflow between the plasma reactor. The decomposition of offensive odor using plasma is based on the mechanism of photochemical oxidation of offensive odor using free radical and ozone(O₃) generated when discharging plasma, which enables the decomposition of offensive odor at ordinary temperature and has the advantage of no secondary pollutants. As a result, all three odor substances were completely decontaminated within 1 minute as soon as discharging the plasma up to 500 W. This result confirms that high concentration odors or mixed odor materials can be reduced using atmospheric-pressure plasma.