• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.315-320
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• 2009

A computational investigation is conducted on free convection from a thin plate having a surface heat source. The thermal configuration simulates the recently-proposed transparent film heater made of a single-walled carbon nanotube film on a glass substrate. The Navier-Stokes computations are carried out to study laminar free convection from the heater. Parallel numerical experiments are performed by using a simplified design analysis model which solve the conduction equation with the boundary conditions utilizing several existing correlations for convective heat transfer coefficient. Comparison leads to the most suitable boundary condition for the thermal model to evaluate the performance evaluation of a transparent thin-film heater.

• Biomolecules & Therapeutics
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• v.12 no.3
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• pp.133-137
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• 2004

Present review is built on base of research work on Ganoderma lucidum in our laboratory. A great deal of experimental evidence has suggested that the pharmacological activities of Ganoderma lucidum (Lingzhi) are related to anti-oxidative and free radical scavenging activity. The anti-oxidative and free radical scavenging effects of polysaccharides and triterpenoids isolated from Ganoderma lucidum in different oxidative injury models including tert-butylhydroperoxide (tBOOH)- damaged mice peritoneal macrophages, alloxan-induced diabetes, experimental liver injury models induced by carbon tetrachloride (CCl4), D-galactosamine (DGal) and Bacillus Calmette-Guerin (BCG) plus lipopolysaccharides (LPS) were investigated. It is also demonstrated that Lugu lingzhi, one of Ganoderma product, significantly inhibited LDL oxidation mediated by endothelial cells and decreased monocyte adhesion to endothelial cell (EC) induced by Oxidative low-density lipoprotein (ox-LDL) and advanced glycation endproducts (AGE). Lugulingzhi-treated serum could markedly inhibit the expression of intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-l) induced by ox-LDL and AGE.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2004.04a
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• pp.61-77
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• 2004

Present review is built on base of research work on Ganoderma lucidum in our laboratory. A great deal of experimental evidence has suggested that the pharmacological activities of Ganoderma lucidum(Lingzhi) are related to anti-oxidative and free radical scavenging activity. The anti-oxidative and free radical scavenging effects of polysaccharides and triterpenoids isolated from Ganoderma lucidum in different oxidative injury models including tert-butylhydroperoxide (tBOOH)- damaged mice peritoneal macrophages, alloxan-induced diabetes, experimental liver injury models induced by carbon tetrachloride (CC14), D-galactosamine (DGal) and Bacillus Calmette-Guerin(BCG) plus lipopolysaccharides(LPS) were investigated. It is also demonstrated that Lugu lingzhi, one of Ganoderma product, significantly inhibited LDL oxidation mediated by endothelial cells and decreased monocyte adhesion to endothelial cell (EC) induced by Oxidative low-density lipoprotein (ox-LDL) and advanced glycation endproducts(AGE). Lugulingzhi-treated serum could markedly inhibit the expression of intercellular cell adhesion molecule-l (ICAM-1) and vascular cell adhesion molecule-l (VCAM-1) induced by ox-LDL and AGE.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.1
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• pp.49-53
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• 1999

We have studied the field emission characteristics of diamond-like-carbon (DLC) films deposited by a layer-by-layer technique using plasma enhanced chemical vapor deposition, in which the deposition of a thin layer of DLC and a CH4 plasma exposure on its surface were carried out alternatively. The hydrogen-free DLC can be deposited by CH4 plasma exposure for 140 sec on a 5 nm DLC layer. N2 gas-phase doping in the CH4 plasma was also carried out to reduce the work function of the DLC. The optimum [N2]/[CH4] flow rate ratio was found to be 9% for the efficient electron emission, at which the onset-field was 7.2 V/$\mu\textrm{m}$. It was found that the hydrogen-free DLC has a stable electron emitting property.

• Progress in Medical Physics
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• v.27 no.4
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• pp.220-223
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• 2016

Generally, it is recommended that the dosimetric effect of carbon fiber couch should be considered especially for an intensity-modulated therapy with a large portion of monitor units from posterior angles. Even a flattening filter free (FFF) beam has been used for stereotactic body radiation therapy (SBRT), the effect of carbon fiber couch for FFF beam is not well known. This work is an effort to evaluate the dosimetric effect of carbon fiber couch for flattened and FFF beam of Elekta linac empirically. The absorbed doses were measured with Farmer type chamber and water-equivalent phantoms with and without couch. And differences of the absorbed doses between with and without couch defined as "couch effect". By comparing calculated dose in treatment planning system (TPS) with measured dose, the optimal density of couch was evaluated. Finally, differences on patient's skin dose and target dose by couch were evaluated in TPS. As a result, the couch effect for 6 and 10 MV flattened beam were -2.71% and -2.32%, respectively. These values were agreed with provided data by vendor within 0.5%. The couch effect for 6 and 10 MV FFF beam were -3.75% and -2.80%, respectively. The patient's skin dose was increased as 18.6% and target dose was decreased as 0.87%, respectively. It was realized that the couch effect of FFF beam was more severe than that of flattened beam. Patient's skin dose and target dose were changed by the couch effect.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.6
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• pp.559-569
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• 2018

Catalytic supports made of carbon have many advantages, such as high coking resistance, tailorable pore and surface structures, and ease of recycling of waste catalysts. Moreover, they do not require pre-reduction. In this study, ash-free coal (AFC) was obtained by the thermal extraction of carbonaceous components from raw coal and its performance as a carbon catalytic support was compared with that of well-known activated carbon (AC). Nickel was dispersed on the carbon supports and the resulting catalysts were applied to the steam reforming of toluene (SRT), a model compound of biomass tar. Interestingly, nickel catalysts dispersed on AFC, which has a very small surface area (${\sim}0.13m^2/g$), showed higher activity than those dispersed on AC, which has a large surface area ($1,173A/cm^2$). X-ray diffraction (XRD) analysis showed that the particle size of nickel deposited on AFC was smaller than that deposited on AC, with the average values on AFC ${\approx}11nm$ and on AC ${\approx}23nm$. This proved that heteroatomic functional groups in AFC, such as carboxyls, can provide ion-exchange or adsorption sites for the nano-scale dispersion of nickel. In addition, the pore structure, surface morphology, chemical composition, and chemical state of the prepared catalysts were analyzed using Brunauer-Emmett-Taylor (BET) analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and temperature-programmed reduction (TPR).

• Membrane Journal
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• v.32 no.4
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• pp.218-226
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• 2022

Hydrogen, a carrier of large-capacity chemical and clean energy, is an important industrial gas widely used in the petrochemical industry and fuel cells. In particular, hydrogen is mainly produced from fossil fuels through steam reforming and gasification, and carbon dioxide is generated as a by-product. Therefore, in order to obtain high-purity hydrogen, carbon dioxide should be removed. This review focused on free-standing polymeric membranes and mixed-matrix membranes (MMMs) that separate hydrogen from carbon dioxide reported in units of Barrer [1 Barrer = 10^-10 cm³ (STP) × cm / (cm² × s × cmHg)]. By analyzing various recently reported papers, the structure, morphology, interaction, and preparation method of the membranes are discussed, and the structure-property relationship is understood to help find better membrane materials in the future. Robeson's upper bound limits for hydrogen/carbon dioxide separation were presented through reviewing the performance and characteristics of various separation membranes, and various MMMs that improve separation properties using technologies such as crosslinking, blending and heat treatment were discussed.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.70-77
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• 2023

Air environment regulations have been strengthened due to increasing air pollutant emissions, the target of reducing emissions has increased and interest in gas measurement methods is also increasing. The sampling method is mainly used, but due to the spatial and temporal measurement limitations, the laser absorption spectroscopy which is a real-time and in-situ method is in the spotlight. In this study, we studied the wavelength modulation spectroscopy and described the calibration-free algorithm. The developed algorithm was modified to reflect 46 multi-absorption lines and was applied to light absorption signal analysis in visible and mid-infrared regions. In addition, the difference between the modulation parameters of laser was analyzed. As a result of reviewing the performance through O₂ and NO gas measurement experiments of various concentration conditions, the linearity was R²_O2=0.99999 and R²_NO=0.99967.

• Journal of Ecology and Environment
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• v.40 no.1
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• pp.12-19
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• 2016

Background: Direct impact of inorganic carbon (i.e., carbon dioxide ($CO_2$)) on the periphyton community is important to understand how and to what extent atmospheric conditions can affect the structure and dynamics of these communities in lotic systems. We investigated the influence of elevated $CO_2$ concentration on the periphyton community in the artificially constructed channels during the winter period. The channels made of acrylic paneling were continuously supplied with surface water discharged from a small reservoir, which was supported with ground water, at a flow rate of 5 L/min, and water temperature ranging $4-5^{\circ}C$. The effects of elevated $CO_2$ concentrations (790 ppm) were evaluated in comparison with the control (395 ppm $CO_2$) by analyzing pH, water carbon content and nutrients in water, periphyton composition and biomass, chlorophyll-a, ash-free dry-matter at 2-day intervals for 10 days. Results: After the addition of $CO_2$, significant decreases of pH, $NH_3-N$, and $PO_4-P$ (p < 0.05) and increases of chlorophyll-a, ash-free dry-matter, and the cell density of periphyton (p < 0.01) were observed, whereas the species composition of periphyton and water carbon content did not change. Conclusions: These results suggest that elevated $CO_2$ in flowing water system with low temperature could facilitate the growth of periphyton resulting in biomass increase, which could further influence water quality and the consumers throughout the food web.

• Polymer(Korea)
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• v.35 no.6
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• pp.615-618
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• 2011

Carbon nanotubes (CNTs) draw attention as promising materials due to their excellent electrical and mechanical properties. However, the intrinsic strong interaction between CNTs presents a challenge to their use in various applications. Here, we present a facile method to disperse single-walled carbon nanotubes (SWCNTs) in a polar solution using a graft copolymer, poly(vinyl chloride)-graft-poly(oxyethylene methacrylate), PVC-g-POEM. The graft copolymer was synthesized via atom transfer radical polymerization (ATRP), as confirmed by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The SWCNTs were uniformly dispersed in a polar solvent such as dimethylsiloxane (DMSO) using PVC-g-POEM as a dispersant, due to interaction between CNT and the graft copolymer, as revealed by transmission electron microscopy (TEM) analysis. Upon removal of the solvent, free standing nanocomposite films with good homogeneity were obtained.