• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.369-373
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• 2005

High quality CdTe single crystal for the solar cell fabrication was grown by vertical Bridgman method. The etch pits patterns of (111) surfaces of CdTe etched by Nakagawa solution was observed the (111)A compesed of Cd atoms with typical triangle etch pits of pyramid mode. From the photoluminescence measurement on (111)A, we observed free exciton ($E_{x}$) existing only high quality crystal and neutal acceptor bound exciton ($A^{0}$,X) having very strong peak intensity. Then, the full width at half maximum and binding energy of neutral acceptor bound exciton were 7 meV and 5.9 meV, respectively. By Haynes rule, an activation enery of impurity was 59 meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.

• Applied Science and Convergence Technology
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• v.27 no.5
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• pp.109-112
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• 2018

Optical properties of InAs/GaAs submonolayer-quantum dot (SML-QD) have been investigated using excitation intensity ($I_{ex}$)- and temperature-dependent photoluminescence (PL). At a low temperature (13 K) strong PL was observed at 1.420 eV with a very narrow full-width at half maximum, of 7.09 meV. The results of the $I_{ex}$ dependence show that the PL intensities increase with increasing $I_{ex}$. The enhancement factors (k) of PL increment as a function of $I_{ex}$ are 3.3 and 1.22 at low and high $I_{ex}$ regime, respectively. The high k value at low $I_{ex}$, implies that the activation energy of the SML-QDs is low. The calculated activation energy of the SML-QDs from temperature dependence is 30 meV.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.604-610
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• 2007

Characteristics of steam gasification and combustion of naphtha tar pitch, which is the bottom product of naphtha cracking process, were investigated by using the thermo gravimetric analyzer to develop the technology for obtaining syngas by using the naphtha tar pitch as a carbon source. Friedman's and Ozawa-Flynn-Wall method were used to calculate activation energy, reaction order and frequency factor of reaction rate constant for both of steam gasification and combustion. The activation energy of combustion of naphtha tar pitch based on the fractional conversion by Friedman's method was in the range of 41.58 ~ 68.14 kJ/g-mol when the fractional conversion level was in the range of 0.2~0.6, but 183.07~191.17 kJ/g-mol when the conversion level was 0.9~1.0, respectively. In case of steam gasification of naphtha tar pitch, the activation energy was in the range of 31.87~44.87 kJ/g-mol in the relatively lower conversion level (0.2~0.6), but 70.63~87.79 kJ/g-mol in the relatively higher conversion level (0.8~0.95), respectively. Those results exhibited that the steam gasification as well as combustion would occur by means of two steps such as devolitilization followed by combustion or gasification.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.205-210
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• 1983

Extracellular $\beta$-galactosidase was prepared from a culture of Lactobacillus sporogenes, a spore-forming lactic acid bacterium. The enzyme functioned optimally at pH 6.8 and at 6$0^{\circ}C$ o-nitrophenyl-$\beta$-D-galactopyranoside (ONPG) in 0.05M sodium phosphate buffer. The activation energy of the enzymatic hydrolysis of ONPG was about 16,000 cal/mole below $50^{\circ}C$ and 11,300 cal/mole above the temperature. It was fairly stable over a pH range from 4.0 to 8.0 losing only less than 30% of its activity after hearting at 6$0^{\circ}C$ and pH 6.8 for 3 hours. Metal ions showed no significant effect on the enzyme activity, whereas L-cysteine exerted a slight stimulatory effect at the concentration of 10mM. The km values were 1.48mM for ONPG and 64.5mM for lactose. Hydrolysis of ONPG by the enzyme was product-inhibited by galactose (Ki=13.3mM, competitive inhibition) and by glucose(Ki= 11.4mM, uncompetitive type). The enzyme activity was also noncompetitively inhibited in the presence of lactose (Ki= 17.8mM).