• Clean Technology
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• v.28 no.4
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• pp.285-292
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• 2022

Adsorption tower systems based on activated carbon adsorption towers have mainly been employed to reduce the emission of volatile organic compounds (VOCs), a major cause of air pollution. However, the activated carbon currently used in these systems has a short lifespan and thus requires frequent replacement. An approach to overcome this shortcoming could be to develop metal oxide photocatalysis-activated carbon composites capable of degrading VOCs by simultaneously utilizing photocatalytic activation and powerful adsorption by activated carbon. TiO₂ has primarily been used as a metal oxide photocatalyst, but it has low economic efficiency due to its high cost. In this study, ZnO particles were synthesized as a photocatalyst due to their relatively low cost. Silver nanoparticles (Ag NPs) were deposited on the ZnO surface to compensate for the photocatalytic deactivation that arises from the wide band gap of ZnO. A microfluidic process was used to synthesize ZnO particles and Ag NPs in separate reactors and the solutions were continuously supplied with a pack bed reactor loaded with activated carbon powder. This microfluidic-assisted pack bed reactor efficiently prepared a Ag-ZnO-activated carbon composite for VOC removal. Analysis confirmed that Ag-ZnO photocatalytic particles were successfully deposited on the surface of the activated carbon. Conducting a toluene gasbag test and adsorption breakpoint test demonstrated that the composite had a more efficient removal performance than pure activated carbon. The process proposed in this study efficiently produces photocatalysis-activated carbon composites and may offer the potential for scalable production of VOC removal composites.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.379-384
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• 2015

Electrospinning has recently been used for micropatterning. The electrospinning method as a patterning tool has the advantage of a rapid patterning speed because it is based on a continuous printing mode rather than a drop-on-demand mode. To obtain stable continuous printing, a high molecular weight polymer must be mixed with functional materials for patterning. In this paper, polyethylene oxide (PEO) was used. The effect of polymer on viscosity and formation of a Taylor cone jet from the electrospinning nozzle was investigated. Finally, the electrospinning patterning results of a silver paste ink on a glass substrate were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.662-662
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• 2013

Over the last several decades, innovative light-harvesting devices have evolved to achieve high efficiency in solar energy transfer. Research on the mechanisms for plasmon resonance is very desirable to overcome the conventional efficiency limits of photovoltaics. The influence of localized surface plasmon resonance on hot electron flow at a metal-semiconductor interface was observed with a Schottky diode composed of a thin silver layer on $TiO_2$. The photocurrent is generated by absorption of photons when electrons have enough energy to travel over the Schottky barrier and into the titanium oxide conduction band. The correlation between the hot electrons and the surface plasmon is confirmed by matching the range of peaks between the incident photons to current conversion efficiency (IPCE, flux of collected electrons per flux of incident photons) and UV-Vis spectra. The photocurrent measured on Ag/$TiO_2$ exhibited surface plasmon peaks; whereas, in contrast to the Au/$TiO_2$, a continuous Au thin film doesn't exhibit surface plasmon peaks. We modified the thickness and morphology of a continuous Ag layer by electron beam evaporation deposition and heating under gas conditions and found that the morphological change and thickness of the Ag film are key factors in controlling the peak position of light absorption.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.53-53
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• 2010

The development of synthetic pathway to produce a highly yield nanoparticles is an important aspect of industrial technology. Herein, we report a simple, rapid approach to synthesize organic-soluble Cu and Ag nanoparticles in colloidal method for the application in a conductive pattern using inkjet printing. The silver nanoparticles have been synthesized in highly concentrated organic phase. The Cu nanoparticles have been synthesized by the reducing of the copper oxide materials using acid molecules in high concentrated organic phase. Their sintering and electric conductivity properties were investigated by melting process between $200^{\circ}C$ and $250^{\circ}C$ for application to printed electronics.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.427-431
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• 2001

In this research, porous materials were made from mine's waste slime. As a temperature changes, a phase changes, a porosity, and a mechanical strength of porous materials were observed and measured. The process of pore-formation was observed by SEM according to the change of heat-treatment temperature and time. It fumed out that the foaming reaction of mine's waste slime was resulted from liquid phase by decomposition of the sanidine and the muscovite-3T. When heat- treated at over 120$0^{\circ}C$, it appeared high porosity. And, to activate the foaming reaction, an alkaline oxide concerned with liquid formation was added and its effects were examined.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.409-412
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• 2003

Total extraction of stream sediments in the Kwangyang mine area shows their significant pollution with most trace metals such as Cr, Co, Fe, Pb, Cu, Ni, Zn and Cd, due to sulfide oxidation in waste dumps. Calculations of enrichment factor shows that Chonam-ri creek sediments are more severely contaminated than Sagok-ri sediments. Using the weak acid (0.1N HCl) extraction and sequential extraction techniques, the transport and sediment-water partitioning of heavy metals in mine drainage were examined for contaminated sediments in the Chonam-ri and Sagok-ri creeks of the Kwangyang Au-Ag mine area. Calculated distribution coefficient (Kd) generally decreases in the order of Pb $\geq$Al > Cu > Mn > Zn > Co > Ni $\geq$ Cd. Sequential extraction of Chonam-ri creek sediments shows that among non-residual fractions the Fe-Mn oxide fraction is most abundant for most of the metals. This indicates that precipitation of Fe hydroxides plays an important role in regulating heavy metal concentrations in water, as shown by field observations.

• IMMUNE NETWORK
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• v.10 no.6
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• pp.230-238
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• 2010

Background: The MK1 strain, a novel bacterial isolate from soft-rotten tissue of the Neungee mushroom, produces copious amounts of exopolysaccharide (EPS) in a dextrose minimal medium. This study examined the molecular characteristics and immunomodulatory activity of MK1 EPS. Methods: The EPS in the culture supernatant was purified by cold ethanol precipitation, and characterized by SDS- PAGE/silver staining and Bio-HPLC. The immunomodulatory activities of the EPS were examined using the mouse monocytic cell line, RAW 264.7 cells. Results: The molecular weights of the purified EPS were rather heterogeneous, ranging from 10.6 to 55 kDa. The EPS was composed of glucose, rhamnose, mannose, galactose, and glucosamine at an approximate molar ratio of 1.00 : 0.8 : 0.71 : 0.29 : 0.21. EPS activated the RAW cells to produce cytokines, such as TNF-${\alpha}$ and IL-$1{\beta}$, and nitric oxide (NO). EPS also induced the expression of co-stimulatory molecules, such as B7-1, B7-2 and ICAM-1, and increased the phagocytic activity. The macrophage-activating activity of EPS was not due to endotoxin contamination because the treatment of EPS with polymyin B did not reduce the macrophage-activating activity. Conclusion: The EPS produced from the MK1 strain exerts macrophage-activating activity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.27.2-27.2
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• 2010

In recent years, there is a strong requirement of low cost, stable microelectro mechanical systems (MEMS) for resonators, microswitches and sensors. Most of these devices consist of freely suspended microcantilevers, which are usually made by the etching of some sacrificial materials. Herein, we have attempted to use Si nanowires, inherited from the parent Si wafer, as a sacrificial material due to its porosity, low cost and ease of fabrication. Prior to the fabrication of the Si nanowires silver nanoparticles were continuously formed on the surface of Si wafer. Vertically aligned Si nanowires were fabricated from the parent Si wafers by aqueous chemical route at $50^{\circ}C$. Afterwards, the morphological and structural characteristics of the Si nanowires were investigated. The morphology of nanowires was strongly modulated by the resistivity of the parent wafer. The 3-step etching of nanowires in diluted KOH solution was carried out at room temperature in order to control the fast etching. A layer of $Si_3N_4$ (300 nm) was used for the selective fabrication of nanowires. Finally, a freely suspended bridge of zinc oxide (ZnO) was fabricated after the removal of nanowires from the parent wafer. At present, we believe that this technique may provide a platform for the inexpensive fabrication of futuristic MEMS.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.24-33
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• 2013

Renewable energy industries, including sola cell plants, has been ever increasing ones for reducing fossil fuel consumption and strengthening national energy policy. In this paper we tried to identify occupational health hazards in solar cell-related industries operated in Korea. Poly silicon, silicon ingot and wafer, solar cell and module are major processes for producing solar cells. Poly silicon operations may cause hazards to workers from metal silicon, silanes, silicon, hydro fluoric acid and nitric acid. Solar cells could not be constructed without using metals such as aluminum and silver, acids such as hydrofluoric acid and nitric acid, bases such as sodium hydroxide and potassium hydroxide, and solvent and phosphorus chloride oxide. Workers in module assembly process may exposed to isopropanol, flux, solders that contain lead, tin and/or copper. To prevent occupational exposure to these hazards, it is essential to identify the hazards in each process and educate workers in industries with proper engineering and administrative control measures.

• ETRI Journal
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• v.35 no.4
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• pp.587-593
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• 2013

We demonstrate semitransparent organic photovoltaics (OPVs) based on thin metal electrodes and polymer photoactive layers consisting of poly(3-hexylthiophene) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester. The power conversion efficiency of a semitransparent OPV device comprising a 15-nm silver (Ag) rear electrode is 1.98% under AM 1.5-G illumination through the indium-tin-oxide side of the front anode at 100 $mW/cm^2$ with 15.6% average transmittance of the entire cell in the visible wavelength range. As its thickness increases, a thin Ag electrode mainly influences the enhancement of the short circuit current density and fill factor. Its relatively low absorption intensity makes a Ag thin film a viable option for semitransparent electrodes compatible with organic layers.