• Journal of Sensor Science and Technology
• /
• v.23 no.1
• /
• pp.51-57
• /
• 2014

The evaporating materials for $MgGa_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MgGa_2Se_4$ compounded polycrystal powder was deposited on thoroughly etched semi-insulated GaAs(100) substrate by the hot wall epitaxy (HWE) method system. The source and substrate temperatures of optimized growth conditions, were $610^{\circ}C$ and $400^{\circ}C$, respectively.The source and substrate temperatures were $610^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MgGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.34\;eV-(8.81{\times}10^{-4}\;eV/K)T^2/(T+251\;K)$. After the as-grown $MgGa_2Se_4$ single crystal thin films was annealed in Mg-, Se-, and Ga-atmospheres, the origin of point defects of $MgGa_2Se_4$ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Mg}$, $V_{Se}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted $MgGa_2Se_4$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $MgGa_2Se_4$/GaAs did not form the native defects because Ga in $MgGa_2Se_4$ single crystal thin films existed in the form of stable bonds.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.2
• /
• pp.117-126
• /
• 2005

A stoichiometric mixture of evaporating materials for $AgGaS_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $AgGaS_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $590^{\circ}C\;and\;440^{\circ}C$, respectively The temperature dependence of the energy band gap of the $AgGaS_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.7284 eV-(8.695{\times}10^{-4}eV/K)T^2/T(T+332K)$. After the as-grown $AgGaS_2$, single crystal thin films was annealed in Ag-, S-, and Ga-atmospheres, the origin of point defects of $AgGaS_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10K. The native defects of $V_{Ag},\;V_s,\;Ag_{int},\;and\;S_{int}$, obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted $AgGaS_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $AgGaS_2$ crystal thin films did not form the native defects because Ga in $AgGaS_2$ single crystal thin films existed in the form of stable bonds.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.24 no.2
• /
• pp.130-136
• /
• 1991

In present paper, we investigated the changes in lipid components of skipjack and Alaska pollack meat by thermal processing at high temperature. TBA values and peroxide values of both fish meats decreased markedly by heat treatment; decreasing range of TBA and peroxide values in skipjack meat was larger than those of Alaska pollack meat. Also carbonyl value of skipjack meat was decreased by thermal processing, contrary, that of Alaska pollack meat was increased. Total lipid(TL) of skipjack and Alaska pollack meat consisted of $61.9\%,\;49.6\%$ non-polar lipid(NL), $38.1\%,\;50.4\%$ polar lipid(PL), respectively. When the samples were heated at the Fo values of 5 or higher, contents of NL were increased, while that of PL were decreased. In fatty acid composition of NL and PL in both fishes, NL revealed higher contents in saturates and monoenes such as 16:0, 18:1, while PL showed higher contents in polyenes such as 20:5, 22:6; percentages of polyenes such as 22:6 especially in both fishes decreased with increasing of Fo values. The remaining ratio of PUFA(20:5+22:6/16:0) of Fo 20 samples in skipjack and Alaska pollack meat were $73\%$ and $65\%$, respectively. However, when the samples were heated at $98^{\circ}C$ for 30 minutes, no appreciable changes occured in fatty acid composition of TL, NL and PL in both fish meats examined.

• Korean Journal of Materials Research
• /
• v.8 no.9
• /
• pp.831-836
• /
• 1998

The B1914 Ni-base superalloy was manufactured according to crystal structures of poly-, directionally solidified- and single crystals. We observe deformation as type of different crystal structure from room to high temperature. Specimens are controled by cooling rate and thermal gradient and then heat treatment in vacuum and then cooling with Ar gas. Different crystal structure has different stress-strain characteristic. At $600^{\circ}C$, yield strength and ultimate strength is increased single-, directionally solidified- and poly crystals in order.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.352-356
• /
• 2003

A stoichiometric mixture of evaporating materials for $CuGaSe_2$ single crystal am films was prepared from horizontal electric furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.615\;{\AA}\;and\;11.025\;{\AA}$, respectively. To obtain the single crystal thin films, $CuGaSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $450^{\circ}C$, respectively, The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuGaSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}$ and $295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;:\;1.7998\;eV\;-\;(8.7489\;{\times}\;10^{-4}\;eV/K)T^2(T\;+\;335\;K)$. After the as-grown $CuGaSe_2$ single crystal thin films was annealed in Cu-, Se-, and Ga-atmospheres, the origin of point defects of $CuGaSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{CU}$, $V_{Se}$, $CU_{int}$, and $Se_{int}$, obtained by PL measurements were classified as a donors or accepters type. And we concluded that the heat-treatment in the Cu-atmosphere converted $CuGaSe_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $CuGaSe_2/GaAs$ did not form the native defects because Ga in $CuGaSe_2$ single crystal thin films existed in the form of stable bonds.

• KSBB Journal
• /
• v.20 no.6
• /
• pp.425-430
• /
• 2005

Thermophilic $H_2$ was produced for 1 year using a bench-scale continuous stirred tank reactor(CSTR). The CSTR was inoculated with anaerobically digested sludge after heat treatment and fed with a glucose-based medium. The reactor showed relatively short start-up period(30 days) and high maximal $H_2$ yield(2.4 mol $H_2/mol$ glucose). Keeping pH 5.0 or less suppressed methanogenic activity. Bacteria affiliated with Thermoanaerobacterium thermosaccharolyticum kept being dominant from approximately 40 days as determined by DGGE. Environmental perturbation(pH or temperature) caused the decrease of biomass concentration in the reactor and the instability of reactor performance, $H_2$ production rate and $H_2$ yield. The unstable performance was accompanied with high concentration of lactate in the effluent. Taken together, the poor recovery of CSTR after perturbations could be partly explained by low biomass concentration and/or metabolic shift of the major population in the CSTR.

• Resources Recycling
• /
• v.17 no.5
• /
• pp.52-59
• /
• 2008

Sol-gel process applied in this study was carried out by chelation of metal ions and citric acid. From the results of thermal gravimetric analysis and XRD analysis of gel powder obtained through sol-gel and heat treatment, gel powders are mostly amorphous, and crystallize completely at $900^{\circ}C$, and the crystalline structure of YAG increases with increasing calcinations temperature. Since YAG prepared by sol-gel & calcinations process was porous, and the sape and size was irregular and nonuniform, the shape and size of YAG powder had to be controlled. Therefore the effects of organic materials such as ethylene glycol and surfactant on the crystalline structure of YAG powder were investigated. Polyesterification of ethylene glycol and citric acid separated reaction area of metal ions in the solution and decreased the size of YAG primary particles. The addition of Igepal 630 as surfactant formed the droplet in the solution, and increased the size of primary particles which forms the aggregate of YAG In order to obtain monodispersed YAG particles of uniform size, gel powder prepared with organic materials had to be milled before calcination. And milling process was very important for obtaining YAG of uniform size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.111-112
• /
• 2005

To obtain the single crystal thin films, $CuInSe_2$, mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wail epitaxy (HWE) system. The source and substrate temperatures were 620$^{\circ}C$ and 410$^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobilily of $CuInSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.62\times10^{16}$ $cm^{-3}$ and $296cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the CulnSe$_2$ obtained from the absorption spectra was well described by the Varshni's relation E$_g$(T) = 1.1851 eV - ($8.99\times10^{-4}$ ev/K)T$_2$/(T + 153K). After the as-grown $CuInSe_2$ single crystal thin films was annealed in Cu-, Se-, and In-atmospheres the origin of point defects of $CuInSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The nat ive defects of V$_{Cu}$, $V_{Se}$, Cu$_{int}$, and $Se_{int}$ obtained by PL measurements were classified as a donors or accepters type. And we concluded that the heat-treatment in the Cu-atmosphere converted $CuInSe_2$ single crystal thin films to an optical n-type. Also, we confirmed that In in $CuInSe_2$/GaAs did not form the native defects because In in $CuInSe_2$ single crystal thin films existed in the form of stable bonds.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.34 no.9
• /
• pp.1485-1489
• /
• 2005

The dropwort was fermented by steeping with brown sugar, fructose syrup or oligosaccharide at room temperature for 2 month, and then stored at cold room for 6 months. The dropwort extracts prepared with three different sugars showed more than $50^{\circ}$Brix, below pH 4.0 and about $0.7\%$ titratable acidity. The dropwort extract with brown sugar showed $1.6{\times}10^6$ viable cell counts and $21.2\%$ reducing sugar. Formation of $CO_2$ gas was superior to the dropwort fermented with brown sugar or oligosaccharide. The dropwort extract with fructose syrup indicated $9.0{\times}10^3$ viable cell counts and $50.1\%$ reducing sugar. Microorganism present in fermented dropwort extract was effectively pasteurized by the addition of $3\%$ citric acid and heat-treatment at $85^{\circ}C$ for 15 min, resulting in the less production of $CO_2$ gas. The dropwort extracts prepared with brownsugar, fructose syrup or oligosaccharide was suitable for the standardization that required for plant extract in Korea Food Codex.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.13 no.4
• /
• pp.397-402
• /
• 1984

As a basic research for inhibition of enzymatic browning of apple wine, polyphenol oxidase (EC 1.10.3.1) from apple (Jonathan) was extracted, partially purified, and some properties of the enzyme and changes o( active bands by heat treatment were investigated. Optimum conditions for the enzyme reaction were pH6.5 and temperature of $30^{\circ}C$, and o-diphenol was the main substrate for the enzyme. Approximately 35% and 15% of initia lpolyphenol oxidase activity remained after heating at $60^{\circ}C$ and $70^{\circ}C$ for 1 hour, respectively. About 0.5mM of the inhibitor such as sodium metabisulfite, cysteine and ascorbic acid was required for effective inhibition of the enzyme reaction. However, EDTA was found to be a very poor inhibitor. Ethanol did not affect the enzyme activity. The number of active bands of polyphenol oxidase from apple(Jonathan) was found to be four, but two bands and one band were observed after heating at $60^{\circ}C$ and $70^{\circ}C$ for 1 hour, respectively, which showed a significant difference in thermal stability among active bands.