• Journal of Oral Medicine and Pain
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• v.18 no.2
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• pp.97-106
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• 1993

This study was performed to investigate the effects of infrared and visible light laser irradiation on cell viability of human gingival fibroblast. For the present study, the author used cultured fibroblast originated from sound gingiva which were fifth of sixth passage. Laser machine utilized here were stomalaser which irradiate infrared (GaAs diode) and red (HeNe) laser in turn with pulse wave pattern or continuous wave pattern, and the machine had several frequency mode presented by regeneration, relaxation and analgesic modalities. Cultured fibroblast samples were divided by this modalities of cell counts and laser exposure time which were 7-seconds of 150 seconds, respectively. 1 day after laser irradiation, each cell-well was treated with MTT and measured optical density with ELISA. The obtained results were as follows : 1. There was a tendency of increasing optical density in proportion to irradiation time in groups of $1\times10^4$ cell per well but in groups of $5\times10^3$ cell per well, reverse phenomena were observed. 2. The difference of optical density according to frequency modalities were not showed significantly except several cases in groups of $5\times10^3$ cell per well. 3. In general, cell viability of cultured human gingival fibroblast wer not showed consistent feature by low level laser irradiation.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.3
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• pp.355-360
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• 2012

The characteristics of power generation were investigated by changing the electrical conductivity from 10 to 40mS/cm using air-cathode microbial fuel cell, which had graphite fiber fabric(GFF) anode. There were three kinds of cathode used: one was carbon cloth cathode coated with Pt, another was carbon nanotube(CNT) cathode with non-precious catalyst of Fe-Cu-Mn, and the other was carbon nanotube(CNT) cathode without any catalyst. When it was operated in batch mode, power density of 1369.5mW/$m^2$ was achieved at conductivity of 20mS/cm. Power density from MFC with CNT cathode coated with multi-catalyst of Fe-Cu-Mn was shown about 985.55mW/$m^2$, which was 75.1% compared the power density of carbon cloth coated with Pt. This meant that CNT cathode coated with multi-catalyst of Fe-Cu-Mn could be an alternative of carbon cloth cathode.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.147-151
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• 2007

A serpentine channel geometry often used in a polymer electrolyte membrane fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with relatively high aspect ratio active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compression conditions. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds to that of dropwise condensation in cathode channels.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.9-18
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• 2011

In this study the optimal volume for non-point source control retention is estimated considering spatio-temporal variation of land surface. The 3-parameter mixed exponential probability density function is used to represent the statistical properties of rainfall events, and NRCS-CN method is applied as rainfall-runoff transformation. The catchment drainage area is divided into individual $30m{\times}30m$ cells, and runoff curve number is estimated at each cell. Using the derived probability density function theory, the stormwater probability density function at each cell is derived from the rainfall probability density function and NRCS-CN rainfall-runoff transformation. Considering the antecedent soil moisture condition at each cell and the spatial variation of CN value at the whole catchment drainage area, the ensemble stormwater capture curve is established to estimate the optimal volume for an non-point source control retention. The comparison between spatio-temporally varied land surface and constant land surface is presented as a case study for a urban drainage area.

• Anatomy and Cell Biology
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• v.57 no.1
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• pp.61-69
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• 2024

Hypogonadism is associated with an increased risk of coronary artery disease. This study sought to describe the histomorphology of the left coronary arteries of the adult male rabbit following orchiectomy and subsequent testosterone administration. We included 20 adult male rabbits, divided into a baseline group (n=2), an interventional group subjected to castration only (n=6), an intervention group subjected to castration followed by testosterone injection (n=6), and a control group (n=6). Key variables under investigation were serum testosterone levels, the intima-media thickness of coronary arteries, smooth muscle cell density, and adventitial collagen fiber density. The mean coronary arteries' intimal medial thickness was significantly higher in the castrated group than in controls (0.488 mm and 0.388 mm, respectively), while the testosterone-injected group had a mean of 0.440 mm. Mean smooth muscle cell density was significantly lower in the castrated rabbits vs. controls (26.96% and 47.80%, respectively), this observation being reversed with testosterone injection (47.53%). Mean adventitial collagen fiber density was significantly higher in the castrated group than in controls (66.6% and 36.1%, respectively), with a marginal difference after testosterone injection (65.2%). This study demonstrates that castrationinduced hypogonadism causes morphological changes in the coronary arteries that are partly reversible using testosterone injections. These findings provide a morphological basis for understanding the role of testosterone in coronary arteries.

• Journal of Oriental Neuropsychiatry
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• v.20 no.3
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• pp.1-13
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• 2009

Objectives : The glial cell, located in between the blood vessel and nerve cell, takes charge of the cell support, nutrition supply, elimination of body waste, and cell action. GagamSohabhwangwon(GGSH), a chinese traditional medicinal prescription has been used orally for the treatment of seizures, infantile, convulsion, stroke and so forth. This paper examines the effect of the GagamSohabhwangwon(GGSH) essential oil on cell activity and anti oxidation. Methods : MTT assay methods were employed to measure the cell activity based on the amount of the GagamSohabhwangwon(GGSH) essential oil by using primarily cultivated glial cell. In addition, this paper measured a viability of the glial cell after a protein active retarder control to confirm the multiplication of the cell and examined the cell extinction by the active oxygen, an extinction shielding effect with different amount of the GagamSohabhwangwon(GGSH) essential oil to observe anti oxidation. Furthermore, this paper measured a viability of the cell and phosphorylation(phosphorylation) of the protein which affects the multiplication of the glial cell. Results : When controlling the amount of the GagamSohabhwangwon(GGSH), there was a multiplication effect of the primary glial cell, the multiplication of the cell was dependent on the density of the GagamSohabhwangwon. The multiplication power of the primary glial cell was suppressed by PKA inhibiter (H89). In compliance with the active oxygen the extinction of the primary glial cell was dependent on the density of the GagamSohabhwangwon, there was a shielding effect of the cell extinction when GagamSohabhwangwon(GGSH) was preprocessed. When inducing the multiplication of the primary glial cell, phosphorylation of the Akt, BDNF, CREB, ERK and ERM were increased. Conclusions: Based on the results, GagamSohabhwangwon essential oil will have the effect which activates the nervous system cell and protects the cell through anti oxidation.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.321-325
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• 2010

We analyze the current density - voltage (J - V) curve of a Cu(In,Ga)$Se_2$ (CIGS) thin-film solar cell measured at different irradiation power densities. For the solar-cell sample investigated in this study, the fill factor and power conversion efficiency decreased as the irradiation power density (IPD) increased in the range of 2 to 5 sun. Characteristic parameters of solar cell including the series resistance ($r_s$), the shunt resistance ($r_{sh}$), the photocurrent density ($J_L$), the saturation current density ($J_s$) of an ideal diode, and the coefficient ($C_s$) of the diode current due to electron-hole recombination via ionized traps at the p-n interface are determined from a theoretical fit to the experimental data of the J - V curve using a two-diode model. As IPD increased, both $r_s$ and $r_{sh}$ decreased, but $C_s$ increased.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.639-643
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• 2011

Zinc oxide as an optoelectronic device material was studied to utilize its wide band gap of 3.37 eV and high exciton biding energy of 60 meV. Using anti-site nitrogen to generate p-type zinc oxide has shown a deep acceptor level and low solubility. To increase the nitrogen solubility in zinc oxide, group 13 elements (aluminum, gallium, and indium) was co-added to nitrogen. The effect of aluminum on nitrogen solubility in a $3{\times}3{\times}2$ zinc oxide super cell containing 72 atoms was investigated using density functional theory with hybrid functionals of Heyd, Scuseria, and Ernzerhof (HSE). Aluminum and nitrogen were substituted for zinc and oxygen sites in the super cell, respectively. The band gap of the undoped super cell was calculated to be 3.36 eV from the density of states, and was in good agreement with the experimentally obtained value. Formation energies of a nitrogen molecule and nitric oxide in the zinc oxide super cell in zinc-rich conditions were lower than those in oxygen-rich conditions. When the number of nitrogen molecules near the aluminum increased from one to four in the super cell, their formation energies decreased to approach the valence band maximum to some degree. However, the acceptor level of nitrogen in zinc oxide with the co-incorporation of aluminum was still deep.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.70-73
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• 2017

We investigated n-i-p type single junction hydrogenated amorphous silicon oxide solar cells. These cells were without front surface texture or back reflector. Maximum power point efficiency of these cells showed that an optimized device structure is needed to get the best device output. This depends on the thickness and defect density ($N_d$) of the active layer. A typical 10% photovoltaic device conversion efficiency was obtained with a $N_d=8.86{\times}10^{15}cm^{-3}$ defect density and 630 nm active layer thickness. Our investigation suggests a correlation between defect density and active layer thickness to device efficiency. We found that amorphous silicon solar cell efficiency can be improved to well above 10%.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.703-707
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• 2001

A performance analysis of a SOFC/MGT hybrid system has been carried out for concept design. Thermo-dynamic models for each component being able to describe electrochemical characteristics and heat and mate-rial balance are proposed. Estimated is the power capacity of a SOFC suitable for the hybrid operation with a 5kW class MGT. Effects of current density and operating pressure are also investigated. Electric efficiency showed weak dependence on operating pressure and current density. It is desirable that the SOFC operates at high current density in manufacturing cost's point of view though operating with high current density slightly decreases the electric efficiency find specific power.