• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.21-27
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• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Tuberculosis and Respiratory Diseases
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• v.51 no.2
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• pp.166-172
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• 2001

Silicone fluid is a biomaterial widely used in modern cosmetic procedures because there are few side effects, considerable chemical stability and predictable physical properties. However, many local and systemic adverse reactions have reported. In particular some serious pulmonary complications have been reported such as pulmonary thromboembolism, acute respiratory distress syndrome with some cases leading to mortality. Most of the serious complicated cases were induced by an illegal silicone fluid injection. We experienced two cases of acute respiratory distress syndrome with pulmonary hemorrhage induced by an illegal silicone fluid injection. The patients were 41 & 51 year old women, who complained of dyspnea. The chest X-ray and HRCT scan findings showed a bilateral ground glass attenuation on the bilateral dependent portion of the upper and middle lung zone. The patients clinical symptoms and the radiologic and other laboratory findings were compatible with acute respiratory distress syndrome induced by the silicon fluid injection. Here we report two cases of acute respiratory distress syndrome with pulmonary hemorrhage induced by an illegal silicone injection with a review of the relevant literature.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.37-42
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• 2018

In order to increase the compatibility of polypropylene (PP) and kenaf fiber (KF) felt, PP/KF and PP/KF/polyurethane (PU) felt composites were prepared by treating KF with three kinds of silane coupling agents. The concentration of silane coupling agents was fixed at 1 wt%. The chemical reaction between KF and silane coupling agents was confirmed by the existence of Si-O-Si and Si-O-C functional group bands appeared on FT-IR and X-ray photoelectron spectra (XPS). Thermal properties of PP/KF composites were investigated by DSC and TGA, and the thermal stability of PP/KF composites with treated KF increased. Based on tensile, flexural and impact properties of PP/KF and PP/KF/PU composites, 1-2 wt% of (3-aminopropyl)triethoxysilane (APS) contents were the optimum formulation as a compatibilizer. The tensile and flexural strength of the felt composites treated with the silane coupling agents were improved. This is mainly due to the improvement in the compatibility between PP and KF, which was confirmed by SEM images of the fractured surfaces after tension tests.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.533-540
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• 2018

Graphene has been reported to be an excellent lubricant additive that reduces friction and wear when coated on the surface of various materials or when dispersed in lubricants as an atomic thin material with the low surface energy. In this study, alkyl functionalized graphene oxide (FGO) nanosheets for oil-based lubricant additives were prepared by using three types of alkyl chloride chemicals (butyl chloride, octyl chloride, and tetradecyl chloride). The chemical and structural properties of the synthesized FGOs were analyzed by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and transmission electron microscope (TEM). The synthesized FGOs were dispersed at 0.02 wt% in PAO-0W40 oil and its tribological characteristics were investigated using a high frequency friction/wear tester. The friction coefficient and the wear track width of poly alpha olefin (PAO) oil added with FGO-14 were tested by a ball-on-disk method, and the measured results were reduced by ~5.88 and ~3.8%, respectively compared with those of the conventional PAO oil. Thus, it was found that the wear resistance of PAO oil was improved. In this study, we demonstrated the successful functionalization of GO as well as the improvement of dispersion stability and tribological characteristics of FGOs based on various alkyl chain lengths.

• Journal of Korea Spatial Information System Society
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• v.10 no.2
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• pp.81-93
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• 2008

Current re-arrangement of river and waterway has been made uniformly ignoring characteristics of individual rivers thereby aggravating artificial river restructuring. Subsequently this severely affects the rivers' physical, chemical, and biological phenomenon. On the contrary, quantitative techniques to evaluate the aftermath of artificial river disturbance such as uprising of river bed, intrusion of foreign fisheries, and changes of ecological habitats are not available. To establish such quantitative techniques, analysis of river changes to evaluate the major causes of the river disturbance and its impacts is essential. Therefore, this study mainly focused on proposing a method which can be applied for the development of techniques to investigate river disturbance according to the major factors for the domestic rivers using airphotos and GIS techniques. For the analysis, the study area on the downstream of the river was selected and airphotos of the area were converted into GIS format to generate 'shape' files to secure waterways, river banks, and auxiliary data required for analyzing river disturbance. Trend analysis of the waterway sinuosity and changes of the flow path leaded to detailed verification of the river disturbance for specific location or time period, and this enabled to relatively accurate numbers representing sinuosity of the waterway and relevant changes. As the major results from the analysis, the relocation of waterways and the level of river sinuosity were quantified and used to verify the impacts on the stability of the waterways especially in the downstream of the dam. The results from this study enabled effective establishing proper measures against waterways' unstability, and emphasized subsequent researches for identifying better alternatives against river disturbances.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.720-725
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• 2017

M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm) catalysts were prepared for the partial oxidation of methane (POM) to syngas. The catalysts were characterized by BET, TEM, and XPS. The BET-specific surface area and average pore size for M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm) were 538.8, 504.3, and $447.3m^2/g$ and 6.4, 6.8, and 7.1 nm, respectively. TEM results showed that the mesoporous hexagonol structure was formed for SBA-15, while the homogeneous dispersion of Ni and Ce particles on the surface was formed for Ce(10)-Ni(5)/SBA-15 caused by the confinment effect of SBA-15. XPS data confirmed that $Ce^{4+}$ and $Ce^{3+}$ on the surface catalyst have two oxidation states due to the lattice oxygen species ($O^{2-}$, $O^-$). The yields of POM to syngas over Ce(10)-Ni(5)/SBA-15 were 52.9% $H_2$ and 21.7% CO at 1 atm, 973 K, $CH_4/O_2=2$, $GHSV=1.08{\times}10^5mL/g_{cat.}{\cdot}h$, and these values were kept constant even after 75 h on streams. The same tendency of syngas yields was observed for M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm). These results confirm that the redox reaction of promoters including Ce, Nd, and Sm enhanced the stability and yield of catalysts.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.187-196
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• 2007

The Dalseong acid mine drainage were studied focused on the characters of schwertmannite that controls geochemistry of the stream. Besides chemical analysis of stream water, particle size analysis, XRD SEM and TEM were performed on precipitates of streams and on wasted metalliferous ores. The AMD discharged from the abandoned mine reveals a decrease of pH and EC downward stream. Euhedral sulfur occurs as equigranular aggregates on the altered pyrite while fine acicula goethite coalesces to form cross, star, or starfish-like shapes. Water chemistry plotted on the Eh-pH diagram shows that schwertmannite and ferrihydrite are stable phases. Reddish brown precipitates consist of mostly schwertmannite with less goethite, whereas yellowish brown precipitates are composed of geothite with less schwertmannite. The particle size of precipitates ranges $d(0.1)\;0.861{\mu}m{\sim}3.769{\mu}m,\;d(0.5)\;3.984{\mu}m{\sim}15.255{\mu}m,\;and\;d(0.9)\;9.875{\mu}m{\sim}56.726{\mu}m$. Schwertmannite is characterized by equigranular spheric form. Pincushion or spicule with 100nm width and $200{\sim}300nm$length form on schwertmannite sphere with radial growth patterns. It is highly probable that reddish or yellowish brown precipitates formed in many AMDs may contain schwerhnannite. Because it can serve as sink for removing heavy elements by adsorption in AMD system, there is a need to correctly identify schwertmannite in precipitates and to characterize its phase stability.

• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.368-373
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• 1998

As device dimensions approach submicrometer size in ULSI, the demand for interlayer dielectric materials with very low dielectric constant is increased to solve problems of RC delay caused by increase in parasitic resistance and capacitance in multilevel interconnectins. Fluorinated amorphous carbon in one of the promising materials in ULSI for the interlayer dielectric films with low dielectric constant. However, poor thermal stability and adhesion with Si substrates have inhibited its use. Recently, amorphous hydrogenated carbon (a-C:H) film as a buffer layer between the Si substrate and a-C:F has been introduced because it improves the adhesion with Si substrate. In this study, therfore, a-C:F/a-C:H films were deposited on p-type Si(100) by ECRCVD from $C_2F_6, CH_4$and $H_2$gas source and investigated the effect of forward power and composition on the thickness, chemical bonding state, dielectric constant, surface morphology and roughness of a-C:F films as an interlayer dielectric for ULSI. SEM, FT-IR, XPS, C-V meter and AFM were used for determination of each properties. The dielectric constant in the a-C:F/a-C:H films were found to decrease with increasing fluorine content. However, the dielectric constant increased after furnace annealing in $N_2$atomosphere at $400^{\circ}C$ for 1hour due to decreasing of flurorine content. However, the dielectric constant increased after furnace annealing in $N_2$atmosphere at $400^{\circ}C$ for 1hour due to decreasing of fluorine concentration.

• Tuberculosis and Respiratory Diseases
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• v.40 no.5
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• pp.610-615
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• 1993

Silicone (polydimethylsiloxane) has widely been used in breast augmentation and other cosmetic procedures. Despite the stability of its chemical nature, local and systemic adverse reactions associated with silicone have been reported. There were several patients who suffered from pulmonary embolism associated with injection of silicone. Silicone-induced pneumonitis and sudden death after subcutaneous injection of silicone has been also described. However, there is no case in the literature of clinically diagnosed silicone-induced pulmonary embolism in Korea. We experienced 2 women who developed respiratory symptoms after illicit subcutaneous injection of silicone for the purpose of colporrhaphy. One patient was admitted because of dyspnea, chest pain, hemoptysis and bilateral pulmonary infiltration after repeated injection of silicone. Pulmonary function test initially showed severe restrictive pattern and transbronchial lung biopsy disclosed numerous oil-like material filling the alveolar septal capillaries and macrophages. High resolution C. T., bronchoalveolar lavage, transbronchial lung biopsy and pulmonary angiogram disclosed abnormalities compatible with silicone fluid-induced pulmonary embolism. The other patient expired shortly after arrival in the emergency room. It is suggested that illicit injecion of silicone fluid carries serious respiratory problems and can induce pulmonary embolism followed by acute respiratory failure.

• Composites Research
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• v.23 no.4
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• pp.44-51
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• 2010

Recently, to solve the problems associated with the neutralization and corrosion of reinforced concrete compression members, the structural configurations such as CFFT (Concrete Filled GFRP Tube) and RCFFT (Reinforced Concrete Filled GFRR Tube) have been developed and applied to main members of civil engineering structure. These members can increase structural performance in terms of structural stability, ductility as well as chemical resistance compared with conventional concrete structural members. Many researches in numerous institutions to predict the load carrying capacity of the concrete compression member strengthened with FRP materials have been conducted and they have been suggested an equation for the prediction of the load carrying capacity of the members. Through the review of the research results, it was found that their results are similar each other. Moreover, it was also found that the results are not directly applicable to our specimens since the results are largely depended upon the member configurations. Also, since the accurate design criteria for the RC members strengthened with FRP such as RCFFT have not been established properly, relevant theoretical and experimental investigations must be conducted for the application to the practical structures. In this study, structural behavior of RCFFT was evaluated through compressive and quasi-static flexural tests in order to formulate design criteria for the structural design. In addition, the RCFFT members were also investigated to examine their confinement effect and the equations capable of estimating the compressive ultimate strength and flexural stiffness of the RCFFT members were proposed.