• Journal of the Korean Solar Energy Society
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• v.22 no.3
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• pp.57-65
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• 2002

The photocatalytic degradation of TCE using solar energy in POFR was studied. The use of solar energy was investigated in plastic optica fiber photocatalytic reactor (POFR). In POFR, the main parameters of photocatalytic degradation of TCE were lihgt intensity, thickness of $TiO_2$-coated film on plastic fiber core, the same of total $TiO_2$-coated surface area with changed length. We studied the apparent photonic efficiency and photocatalytic degradation rate of TCE in POFR. The apparent photonic efficiency of various light intensities was decreased by an incresed intensities. The photocatalytic activities of $TiO_2$-coated optical fiber reactor system depended on the coating thickness, and total clad-stripped surface area of POF. Photocatalytic degradation of trichloroethylene ($C_2HCl_3$, TCE) in the gas-phase was elucidated by using $TiO_2$-coated plastic optical fiber reactor. In TCE degradation, in-situ FTIR measurement resulted in mineralization into $CO_2$.

• Solar Energy
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• v.10 no.3
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• pp.53-59
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• 1990

[ $CdSe_xTe_{1-x}$ ] ($0{\le}x{\le}1$) thin films were deposited cathodically on Ti substrates in aqueous sulfric acid solution containing 1M $CdSO_4$ and 1mM$(TeO_2+SeO_2)$. The limiting current was observed in deposition potential ranging from -0.20 to -0.65 vs.Ag/AgCl ; although its value has changed a little depending on the mole ratio x, the limiting current was almost constant in deposition potential of -0.45V in spite of the change of mole ratio x. The crystal structure of the $CdSe_xTe_{1-x}$ thin films was cubic zinc-blonde in the range of mole ratio $x=0{\sim}0.8$, and hexagonal wurtzite in the mole ratio x=1 When the mole ratio changed from x=0 to x=0.8, diffraction peaks was shifted to the larger diffraction angle.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.47-54
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• 2006

Activated carbon fibers (ACFs) with high surface area and pore volume were modified with metal Ni impregnation and fluorination and investigated hydrogen storage properties by volumetric method. Micropore volume values of ACFs obtained from surface modification with Ni impregnation and fluorination were decreased 9 and 35 %, respectively. Hydrogen storage capacities of fluorinated ACFs were slightly changed, on the other hand, that of Ni impregnated ACF was considerably increased. It means that hydrogen was not only adsorbed on ACF surface, but also on Ni metal surface by means of dissociation. Although the microphone volume of ACF modified with fluorination was decreased, its hydrogen storage were found not to be changed compared with fresh ACF. These results indicated that the surface of ACF after fluorination modification may be strongly attracted hydrogen due to high electronegativity of fluorine. Therefore, it was proven that hydrogen storage capacity was related with micropore volume and surface property of carbon materials as well as specific surface area.

• Nuclear Engineering and Technology
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• v.31 no.3
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• pp.287-293
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• 1999

To assess the effects of gamma-ray (Co-60) on radiation sensitivity and genetic similarity of the basidiospore and mycelium in oyster mushroom, Pleurotus ostreatus, the D$_{10}$ values and RAPD patterns were analysed. Three strains were isolated from basidiospores (PO-Bl, -B2, and - B3 from 2 kGy irradiation group) and five strains from mycelia (PO-Ml, -M2 from 1 key, PO-M3 from 2 kGy, and PO-M4 and -M5 from 2+1 key irradiation group). The D$_{10}$ values of basidiospore and mycelium of P. Preurotus ostreatus were 1,250 Gy and 500 Gy, respectively. The growth rates of the eight strains on the five media were various and the activities of extracellular chitinases of them were generally higher than those of the control. By the gamma-ray radiation, 22-25% of genetic similarities were changed in the basidiospore strains and 23-36% of them in the mycelium strains. From these results, it seems that the basidiospore could be more radio-resistant than the mycelium of P. ostreatus and that the genetic similarity of the mycelium of P ostrentus could be changed easier than that of the basidiospore by the gamma-ray radiation.ion.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.5
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• pp.617-625
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• 2018

Since FERC order 755 was published, each frequency regulation market rules of the North American ISO/RTO have been revised in many parts. In 2016, the domestic CBP market has also changed its market rules to allow ESS to participate in the frequency regulation reserve services(Governor Free and Automatic Generation Control). This paper compares and analyzes the changed North American ISP/RTO market and domestic CBP market rules. In particular, we compare PJM and CAISO frequency regulation market pricing mechanism and settlement rules with the settlement rules of the domestic CBP market and compare the factors of each market used to compensate the participating resources in terms of resource dependency and accuracy.

• Journal of Powder Materials
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• v.6 no.4
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• pp.307-313
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• 1999

The effect of carbon content on the shape of WC grains dispersed in the Co-rich matrix during liquid phase sintering of WC-35%Co hard metals has been determined. The shape of WC grains was observed using SEM stereography after removing cobalt matrix with boiling hydrochloric acid solution. The WC grains changed from hexagonal to trigonal prism as the carbon content increased in the two-phase region of(WC + $\beta$ - Co), while the morphology of WC grains changed from trigonal to hexagonal shape as the carbon content decreased. The morphology of WC grains changes reversibly along with carbon loss or carbon pick-up. Morphology change of WC grains is attributed to crystal structure of WC, which has an asymmetric array of carbon atoms. There are two types of prismatic planes having different numbers of broken W-C bonds in WC grains. It is scrutinized that as the carbon content increases, the high energy prism planes grow fast and the crystals change from hexagonal to trigonal shape. On the other hand, when the carbon content decreases, the high energy prism planes are dissolved accompanying split of (100) plane into (101) and (101) planes.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.424-431
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• 2009

Treatment for water repellency on the carbon supports of GDL which composed a part of MEA has been suggested as a solution to prevent flooding. PTFE is a fluoropolymer that has hydrophobic property and a PTFE emulsion was selected as waterproof agent in this investigation. Carbon paper was coated by PTFE emulsion with different particle size of 5~500 nm and 3~$5\;{\mu}m$ as various concentration. PTFE coated carbon paper has difference in weight variation changed proportionally at PTFE concentration and coating times. Then gas permeability of the coated carbon paper with emulsion of 3~$5\;{\mu}m$ PTFE was changed vastly. Characteristics of carbon paper coated with different PTFE emulsion were analyzed by FE-SEM, FT-IR spcetroscopy and were evaluated by weight variations, gas permeability and water contact angle.

• Journal of Power Electronics
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• v.13 no.5
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• pp.829-840
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• 2013

The modified sinusoidal pulse-width modulation (SPWM) is one of the PWM techniques used in three-phase AC-DC buck converters. The modified SPWM works without the current sensor (the converter is current sensorless), improves production of sinusoidal AC current, enables obtainment of near-unity power factor, and controls output voltage through modulation gain (ranging from 0 to 1). The main problem of the modified SPWM is the huge starting current and voltage (during transient) that results from a large step change from the reference voltage. When the load changes, the output voltage significantly drops (through switching losses and non-ideal converter elements). The single-input single-output (SISO) approach with minor-loop voltage feedback controller presented here overcomes this problem. This approach is created on a theoretical linear model and verified by discrete-model simulation on MATLAB/Simulink. The capability and effectiveness of the SISO approach in compensating start-up current/voltage and in achieving zero steady-state error were tested for transient cases with step-changed load and step-changed reference voltage for linear and non-linear loads. Tests were done to analyze the transient performance against various controller gains. An experiment prototype was also developed for verification.

• Solar Energy
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• v.17 no.1
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• pp.35-46
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• 1997

In this study comparison of experiment results with the computed results of linear theory and nonlinear theory using singularity method was obtainable. Specially singularity points like sources and vortexes on hydrofoil and freestreamline were distributed to analyze two dimensional flow field of supercavitating cascade using nonlinear theory, and governing equations of flow field were derived and hydraulic characteristics of cascade were calculated by numerical analysis of the governing equations. The results compared linear theory and nonlinear theory with the experiment results of the study are as follows: The tolerances of nonlinear theory were larger than those of linear theory in case of ${\alpha}<10^{\circ}$. Moreover the computational range of attack angles could be expanded from ${\alpha}=10^{\circ}$ to ${\alpha}=25^{\circ}$, the flow field of supercavitating cascade could be analyzed in the condition which the wake thickness and the length of cavity are a variable. The shapes of cavity were changed sensitively according to various variable such as attack angles, pitches and wake thickness, and the pressure distribution of hydrofoil surface was identical almost disregarding wake thickness but changed largely according to attack angle and the length of cavity. Lift coefficient and drag coefficient were reduced according to increasing of wake thickness but the influences of wake thickness were very little in the situation of small pitch and long cavity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.5
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• pp.452-458
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• 2005

In Korea, pumping pipe using gravity way by water is most popular method in drainage system. But, it is difficult to repair a drainpipe in this method because the drain pipe diameter is increased as using this method. In this research, we propose a new drainage system. The system aim for an adaptedness with buildings, freedom of plan, construction and renewal in water pipe equipments, etc. The new system is not need of incline of piping, and it uses drainage power that is changed potential energy by high velocity flow as making Siphonage at vertical pipe. Therefore, the diameter of piping can decreased than existing piping system established in the ceiling. Also because connecting position will be located at the lower part, it is changed the potential energy of drainage to the high velocity flow. In addition, drainage will be smooth because the fixture drain is linked by each drain pipes.