• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.395-403
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• 2006

It is known that $MgAl_2O_4$ has higher resistance to moisture than MgO, in humid ambient MgO is chemically unstable. It reacts very easily with moisture in the air. In this study, the characteristic of $MgAl_2O_4$ and $MgAl_2O_4/MgO$ layers as dielectric protection layers for AC- PDP (Plasma Display Panel) have been investigated and analysed in comparison for conventional MgO layers. MgO and $MgAl_2O_4$ films both with a thickness of $1000\AA$ and $MgAl_2O_4/MgO$ film with a thickness of $200/800\AA$ were grown on the Cu substrates using the electron beam evaporation. $1000\AA$ thick aluminium layers were deposited on the protective layers in order to avoid the charging effect of $Ga^+$ ion beam while the focused ion beam(FIB) is being used. We obtained sputtering yieds for the MgO, $MgAl_2O_4$ and $MgAl_2O_4/MgO$ films using the FIB system. $MgAl_2O_4/MgO$ protective layers have been found th show $24{\sim}30%$ lower sputtering yield values from 0.244 up to 0.357 than MgO layers with the values from 0.364 up to 0.449 for irradiated $Ga^+$ ion beam with energies ranged from 10 kV to 14 kV. And $MgAl_2O_4$ layers have been found to show lowest sputtering yield values from 0.88 up to 0.109. Secondary electron emission coefficient(g) using the ${\gamma}$- FIB. $MgAl_2O_4/MgO$ and MgO have been found to have similar g values from 0.09 up to 0.12 for indicated $Ne^+$ ion with energies ranged from 50 V to 200 V. Observed images for the surfaces of MgO and $MgAl_2O_4/MgO$ protective layers, after discharge degradation process for 72 hours by SEM and AFM. It is found that $MgAl_2O_4/MgO$ protective layer has superior hardness and degradation resistance properties to MgO protective layer.

• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.111-143
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• 1997

We have developed a spherical FCT code in order to simulate the interaction of supernova remnants with stellar wind bubbles. We assume that the density profile of the supernova ejecta follows the Chevalier mode1(1982) where the outer portion has a power-law density distribution($\rho{\propto}\gamma^{-n}$) and the SN ejecta has a kinetic energy of $10^{51}$ ergs. The structure of wind bubble has been calculated with the stellar mass loss rate $\dot{M}=5\times10^{-6}M_{\odot}/yr$ and the wind velocity $\upsilon=2\times10^3$ km/s We have simulated seven models with different initial conditions In the first two models we computed the evolution of SNRs with n=7 and n=14 in the uniform medium The numerical results agree with the Chevalier's similarity solution at early times. When all of the power-law portion of the ejecta is swept up by the reverse shock, the evolution slowly converges to the Sedov-Taylor stage. There is not much difference between the two cases with different n's The other five models simulate SNRs produced inside wind bubbles. In model III, we consider the SN ejecta of 1.4 $M_{\odot}$ and the radius of bubble ~2.76 pc so that ratio of the mass $\alpha(=M_{W.S}/M_{ej}$ is 2. We follow the complex hydrodynamic flows produced by the interaction of SN shocks with stellar shocks and with the contact discontinuities, In the model III, the time scale for the SN shock to cross the wind shell $\tau_{cross}$ is similar to the time scale for the reverse shock to sweep the power-law density profile $\tau_{bend}$. Hence the SN shock crosses the wind shell. At late times SN shock produces another shell in the ambient medium so that we have a SNR with double shell structure. From the numerical results of the remaining models, we have found that when $\tau_{cross}/\tau_{bend}\leq2$, or equivalently when $\alpha\leq50$, the SNRs produced inside wind bubbles have double shell structure. Otherwise, either the SN shock does not cross the wind shell or even if it crosses at one time, the reverse shock reflected at the center accelerates the wind shell to merge into the SN shock Our results confirm the conclusion of Tenorio-Tagle et a1(1990).

• Polymer(Korea)
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• v.38 no.1
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• pp.38-42
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• 2014

The poly[(9,9-bis((6'-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)-9-fluorene)) dibromide (WPF-6-oxy-F)] and graphene oxide (GO) was blended and irradiated with gamma ray under ambient condition. This WPF-6-oxy-F-GO composite was investigated as a hole-transporting layer (HTL) in organic solar cells (OSCs). Compared with the pristine GO, the sheet resistance ($R_{sheet}$) of irradiated WPF-6-oxy-F-GO was decreased about 2 orders of magnitude. The reason for the decrease of $R_{sheet}$ is the effect of efficient ${\pi}-{\pi}$ packing resulted from the formation of C-N bond between WPF6-oxy-F and GO. As a result, the efficiency of OSCs was dramatically enhanced ~ 6.10% by introducing irradiated WPF-6-oxy-F-GO as a HTL. WPF-6-oxy-F-GO is a sufficient candidate for HTL to facilitate the low-cost and high efficiency OSCs.

• Food Science and Preservation
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• v.15 no.5
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• pp.774-781
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• 2008

was performed and Staphylococcus sciuri, Bacillus cereus, Escherichia coli, Proteus mirabilis, and Enterococcus faecalis were identified. No Salmonella strain, a typical contaminant of eggs, was found. The radiation sensitivities of isolated bacteria and Salmonella typhimurium, in an inoculated model system, were expressed in $D_{10}$ values. The ranges of $D_{10}$ values shown by S. typhimurium, S. sciuri, B. cereus, E. coli, P. mirabilis, and E. faecalis were 0.365-0.399 kGy, 0.418-0.471 kGy, 1.075-1.119 kGy, 0.280-0.304 kGy, 1.132-1.330 kGy, and 0.993-1.290 kGy, respectively. The growth of all six test bacteria in eggs (inoculated at $10^6-10^7\;CFU/g$) during 3 days of post-irradiation storage at ambient conditions ($25^{\circ}C$) was recorded. S. typhimurium was eliminated by irradiation at 3 kGy, and E. coli and S. sciuri were eliminated by irradiation at 5 kGy. The viable cell counts of B. cereus, P. mirabilis, and E. faecalis in eggs showed 4-6 log reductions after irradiation with 5 kGy.

• Journal of Food Hygiene and Safety
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• v.8 no.3
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• pp.135-140
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• 1993

Dried fishes such as dried pollack, dried sliced squid, dried white bait, dried anchoy) and dried cod used to cook Korean traditional foods were airpacked in polyethylene tube and irradiated with 7 kGy of gamma-ray source. The effect of gamma irradiation on microbial growth in dried fishes was investigated during storage at ambient temperature for 12 months. The total aerobic bacteria in the control group were contaminated by $3.9{\times}10^{3}\;cells/g$ in dried pollack, $5.6{\times}10^{5}\;cells/g$ in dried sliced squid, $1.2{\times}10^{5}\;cells/g$ in dried white bait, $1.2{\times}10^{4}\;cells/g$ in dried anchovy and $1.2{\times}10^{4}\;cells/g$ in dried cod and 7 kGy irradiation could eliminate the bacteria and also reduce aerobic bacterial load to 1~3 log cycle and no apparent growth of microorganisms occurred during storage. Molds in the control group were contaminated by $4.0{\times}10^{2}\;cells/g$ in dried pollack, $$1.3{\times}10^{2}\;cells/g$ in dried sliced squid, $2.5{\times}10^{2}\;cells/g$ in dried white bait, 90 cells/g in dried anchovy and $2.0{\times}10^{2}\;cells/g$ in dried cod, respectively. 7 kGy irradiation could sterilize the molds and the growth of molds of nonirradiated samples were slightly decreased during storage. Yeasts in the control group were contaminated by $1.4{\times}10^{3}\;cells/g$ in dried poUack, 75 cells/g in dried sliced squid, $1.1{\times}10^{3}\;cells/g$ in dried white bait, 50 cells/g in dried anchovy, $1.6{\times}10^{2}\;cells/g$ in dried cod, respectively and irradiation could sterilize the yeasts and growth of yeasts was slightly decreased in dried pollack and dried white bait but increased in order of dried anchovy, dried cod and dried sliced squid. Coliforms in all sample were sterilized by irradiation and its growth was decreased during storage except dried anchovy.

• Journal of Radiation Industry
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• v.7 no.1
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• pp.15-21
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• 2013

The detection characteristics of irradiated spices were investigated depending on radiation sources and doses by photostimulated luminescence (PSL) and Thermoluminescence (TL). 6 kinds of spices (turmeric, onion powder, red pepper, basil, parsley, black pepper) were irradiated at 0 to 10 kGy under ambient conditions by both a $^{60}Co$ gamma irradiator and an electron beam (EB) accelerator, respectively. The PSL analysis showed negative results for non-irradiated spices, while irradiated spices gave intermediate and positive value, which presented the limited potential of PSL technique. In TL measurement, TL glow curves on non-irradiated samples appeared at about $300^{\circ}C$ with low intensity. All irradiated samples were easily distinguishable through radiation-specific strong TL glow curves with maximum peak in range of $150{\sim}200^{\circ}C$. TL ratio ($TL_1/TL_2$) obtained by a re-irradiation step could verify the detection result of $TL_1$ glow curves, showing ratios lower than 0.1 in the non-irradiated sample and higher than 0.1 in irradiated ones. Therefore, in PSL measurement, the identification of irradiated spices showed more clear results in electron beam irradiated samples. TL analysis showed obvious difference between non-irradiated and irradiated samples in gamma ray and electron beam irradiated samples.

• Clean Technology
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• v.29 no.2
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• pp.126-134
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• 2023

Direct catalytic decomposition is a promising method for controlling the emission of nitrous oxide (N₂O) from the semiconductor and display industries. In this study, a γ-Al₂O₃ catalyst was developed to reduce N₂O emissions by a catalytic decomposition reaction. The γ-Al₂O₃ catalyst was prepared by an extrusion method using boehmite powder, and a N₂O decomposition test was performed using a catalyst reactor that was approximately 25.4 mm (1 in) in diameter packed with approximately 5 mm of catalysts. The N₂O decomposition tests were carried out with approximately 1% N₂O at 550 to 750 ℃, an ambient pressure, and a GHSV=1800-2000 h^-1. To confirm the N₂O decomposition properties and the effect of O₂ and steam on the N₂O decomposition, nitrogen, air, and air and steam were used as atmospheric gases. The catalytic decomposition tests showed that the 1% N₂O had almost completely disappeared at 700 ℃ in an N₂ atmosphere. However, air and steam decreased the conversion rate drastically. The long term stability test carried out under an N₂ atmosphere at 700 ℃ for 350 h showed that the N₂O conversion rate remained very stable, confirming no catalytic activity changes. From the results of the N₂O decomposition tests and long-term stability test, it is expected that the prepared γ-Al₂O₃ catalyst can be used to reduce N₂O emissions from several industries including the semiconductor, display, and nitric acid manufacturing industry.