• 열처리공학회지
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• 제29권3호
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• pp.124-131
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• 2016

GaN and InN epilayers with nucleation layer (LT-buffer) were grown on (0001) sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). As-grown and annealed GaN and InN nucleation layers grown at various growth condition were observed by reflection high-energy electron diffraction (RHEED). When temperature of effusion cell for III source was very low, diffraction pattern with cubic symmetry was observed and zincblende nucleation layer was flattened easily by annealing. As cell temperature increased, LT-GaN and LT-InN showed typical diffraction pattern from wurtzite structure, and FWHM of (10-12) plane decreased remarkably which means much improved crystalline quality. Diffraction pattern was changed to be from streaky to spotty when plasma power was raised from 160 to 220 W because higher plasma power makes more nitrogen adatoms on the surface and suppressed surface mobility of III species. Therefore, though wurtzite nucleation layer was a little hard to be flattened compared to zincblende, higher cell temperature led to easier movement of III surface adatoms and resulted in better crystalline quality of GaN and InN epilayers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.315-315
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• 2016

The hydrogenated amorphous silicon (a-Si:H) thin film solar cells using n/Al or n/Ag/Al back reflector have low short circuit current (Jsc) due to high absorption coefficients of Al or work function difference between n-layer and the metal. In this article, we utilized aluminum doped zinc oxide (AZO) to raise the internal reflectance for the improvement of short current density (Jsc) in a-Si:H thin film solar cells. It was found that there was a slight increase in the reflectance in the long wavelength range at the process temperature of 125oC due to improved crystalline quality of the AZO back reflector. The optical band gap (Eg) and work function were affected by the temperature and so did the internal reflectance. The increased internal reflectance within the solar cell resulted in Jsc of 14.94 mA/cm2 and the efficiency of 8.84%. Jsc for the cell without back reflector was 12.29 mA/cm2.

• 한국응용과학기술학회지
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• 제23권3호
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• pp.185-191
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• 2006

It is desirable to have an accurate expression on the temperature dependence of surface(or interfacial) tension ${\sigma}$, because most of the interfacial thermodynamic functions can be derived from it. There have been proposed several equations on the temperature dependence of the surface tension, ${\sigma}(T)$. Among them $E{\ddot{o}}tv{\ddot{o}}s$ equation and the one modified by Katayama, which is called Katayama equation, for improving accuracies of $E{\ddot{o}}tv{\ddot{o}}s$ equation close to critical points, have been most well-known. In this article Katayama equation is interpreted on the basis of the cell model to understand the nature of the equation. The cell model results in an expression very similar to Katayama equation. This implies that, although $E{\ddot{o}}tv{\ddot{o}}s$ and Katayama equations were obtained on the basis of experimental results, they have a sound theoretical background. The Katayama equation is also modified with the phase volume replaced with a critical scaling expression. The modified Katayama equation becomes a power-law equation with the exponent slightly different from the value obtained by critical-scaling theory. This implies that Katayama equation can be replaced by a critical-scaling equation which is proven to be accurate.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1902-1906
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• 2011

Sulfonated poly(fluorinated arylene ether)s (SDF-F)/poly[(N-vinylimidazole)-co-(3-methacryloxypropyl-trimethoxysilane)] (poly(VI-co-MPS))/poly(tetrafluoroethylene) (PTFE) is prepared for a high temperature proton exchange membrane fuel cell (PEMFC). The reaction of the membrane with phosphoric acid forms silicate phosphor, as a chemically bound proton carrier, in the membrane. Thus-formed silicate phosphor, nitrogen in the imidazole ring, and physically bound phosphoric acid act as proton carriers in the membrane. The physico-chemical and electrochemical properties of the membrane are investigated by various analytical tools. The phosphoric acid uptake and proton conductivity of the SDF-F/poly(VI-co-MPS)/PTFE membrane are higher than those of SDF-F/PVI/PTFE. The power densities of cells with SDF-F/poly(VI-co-MPS)/PTFE membranes at 0.6 V are 286, 302, and 320 mW $cm^{-2}$ at 150, 170, and 190 $^{\circ}C$, respectively. Overall, the SDFF/poly(VI-co-MPS)/PTFE membrane is one of the candidates for anhydrous HT-PEMFCs with enhanced mechanical strength and improved cell performance.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.96.1-96.1
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• 2011

Solid oxide fuel cells(SOFCs) can convert the chemical energy of fuel into electricity directly. With the rising fuel prices and stricter emission requirement, SOFCs have been widely recognized as a promising technology in the near future. In this study, lean premixed flame using the orifice swirl burner was analyzed numerically and experimentally. We used the program CHEMKIN and the GRI 3.0 chemical reaction mechanism for the calculation of burning velocity and adiabatic flame temperature to investigate the effects of equivalence ratio on the adiabatic flame temperature and burning velocity respectively. Burning velocity of hydrogen was calculated by CHEMKIN simulation was 325cm/s, which was faster than that of methane having 42 cm/s at the same equivalence ratio. Also Ansys Fluent was used so as to analysis the performance with alteration of swirl structure and orifice mixer structure. This experimental study focused on stability and emission characteristics and the influence of swirl and orifice mixer in Solid Oxide Fuel Cell Systme burner. The results show that the stable blue flame with different equivalence ratio. NOx was measured below 20 ppm from equivalence ratios 0.72 to 0.84 and CO which is a very important emission index in combustor was observed below 160 ppm under the same equivalence region.

• 한국세라믹학회지
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• 제44권12호
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• pp.733-739
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• 2007

NiO-YSZ anode-supported single cell was prepared by spin-coating YSZ and LSM slurries as electrolyte and cathode, respectively. Dense YSZ electrolyte film was successfully prepared on the porous NiO-YSZ anode substrate by tuning pre-sintering temperature of NiO-YSZ and co-firing temperature. The thickness of YSZ film was controlled by the solid content of slurry and coating cycles. The experimental conditions affecting on the thickness of YSZ film was discussed. Single cells with the active electrode area ${\sim}0.8\;cm^2$ were prepared by spin-coating the cathode layers of LSM-YSZ mixture and LSM consequently as well. The effects of the pre-sintering temperature and thus the microstructure of NiO-YSZ substrate on the current-voltage characteristics of co-fired cell were investigated.

• Journal of Information Display
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• 제1권1호
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• pp.14-19
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• 2000

Due to distinct properties of plastic substrates such as poor thermal resistance, non-rigidness and high thermal expansion, it is difficult to fabricate plastic film LCDs by conventional LCD processes. Poor thermal resistance and high thermal expansion of substrates induced deformation of substrates surface, mismatch of thermal expansion between ITO electrodes and substrates resulted in defects in the ITO electrodes during the high temperature process. Defects of ITO electrodes and non-uniform cell gap caused by non-rigid and flexible properties were also observed in the pressuring process. Based on in these observations, we used a newly developed material and fabrication process to prevent deformation of substrates, defects of electrodes and to maintain uniform cell gap. The maximum temperature of the process is limited up to $110^{\circ}C$ and pressure loaded during the process is five times less than conventional one. With these invented processes and materials, we obtained highly reliable Plastic Film STN LCDs whose electro-optical characteristics are better than or equivalent to those of typical glass LCDs.

• Journal of Magnetics
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• 제17권1호
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• pp.42-45
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• 2012

We have developed an alternating magnetic field stimulation system consisting of a switched-mode power supply and a digital control circuit which modulates a duty ratio to maintain a magnetic field intensity of a few mT even while the frequency increases up to 4 kHz with a controllable coil temperature below $30^{\circ}C$ in air. This duty ratio modulation and water circulation are advantageous for cell culture under ac-magnetic field stimulation by preventing the incubator from exceeding a cell-viable temperature of $37^{\circ}C$. Although the temperature of the coil when subjected to a sinusoidal voltage rapidly increased, that of our system modulated by the duty factor did not change. This is a potentially valuable method to investigate the effects of intermediate frequency magnetic field stimulation on biological entities such as cells, tissues and organs.

• 한국식품위생안전성학회지
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• 제4권1호
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• pp.29-36
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• 1989

In order to investigate the Storage time of chicken eggs, several physico-chemical tests from chicken eggs store at 5, 13 and 27$^{\circ}C$ were examined. Egg samples were collected from six poultry farms. Egg stored at 5$^{\circ}C$ based on the depth of air cell and specific gravity, were all acceptable until 17 days ; on the egg yolk coefficient and pH of the egg white and egg yolk until about 10 days. Egg stored at 13$^{\circ}C$, based on the depth of air cell. were acceptable by about 10 days of storage, but on the other physico-chemical tests by about 7 days. Egg samples stored at room temperature(about 27$^{\circ}C$) base on the depth of air cell, were acceptable by about 5 days of storage ; on the specific gravity by 4 days ; and on the egg yolk coefficient and pH of the egg yolk and egg white by 3 days. The results of this study showed that egg stored at 5$^{\circ}C$ were considered acceptable by 10 days of storage ; at 13$^{\circ}C$ by 7 days ; at room temperature (27$^{\circ}C$) by 3 days.

• Journal of Applied Biological Chemistry
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• 제44권2호
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• pp.84-86
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• 2001

Capsaicin synthesis by suspension cultured cells of Jalapeno pepper (Capcicum annuum L.) was assessed in vitro under various conditions including temperature (23 and $30^{\circ}C$), light intensity (with light and without light), and shaking speed (110 and 200 rpm). Capsaicin production increased, while the cell biomass growth decreased possibly due to the production of a secondary metabolite. Capsaicin synthesis was primarily affected by light condition. Cells cultivated at 110 rpm and $23^{\circ}C$ under light condition yielded the highest fresh weight, while those cultivated under the same condition, but without light resulted in the lowest cell mass. Capsaicin content in cells of 18-day-old pepper grown at 110 rpm and $23^{\circ}C$ under light was 0.125% of the cell mass. However, without light treatment, the capsaicin content in cells at the same shaking speed and temperature increased up to 169%, indicating no light is favored in the capsaicin synthesis by Jalapeno pepper. Increasing the shaking speed from 110 to 200 rpm without light enhanced the capsaicin synthesis. Results of this study demonstrate that light condition is the limiting factor in the synthesis of capsaicin in tissue-cultured Jalapeno pepper cells.