• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.371-380
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• 2013

Though MBR process has many advantages, the greatest risk factors in operating MBR process are occurrence of membrane fouling and decrease of flux. It is very difficult to find exact mechanism due to complex influence by many effects, although there have been recently many studies of membrane fouling. The purposes of this study are firstly evaluating bioreactor of lab-scale and micro-filtration hollow fiber membrane, secondly investigating correlation between foulants affecting membrane performance and membrane fouling, and lastly evaluating various parameters affecting fouling and applicability of membrane fouling reducer. This study found that TMP was increasing rapidly and showed 0.32 bar and the average of flux was 88 LMH. EPS concentration tends not to change much above MLSS concentration (6,000 mg/L). However, EPS concentration variation is wide below MLSS concentration (6,000 mg/L). Also, from results of membrane surface condition and element analysis using SEM/EDX, carbon and fluorine were founded to be the highest percentage in membrane because of characteristics of membrane material. In operating continuously, inorganic fouling was generated by increase of these inorganic substances such as $Al^{3+}$ and $Mg^{2+}$. Lastly, the best filtration performance was obtained for 0.03 mg MFR/mg MLSS by results of particle size, zeta potential, $SCOD_{cr}$, EPS and MLSS concentration.

• Analytical Science and Technology
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• v.20 no.4
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• pp.279-288
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• 2007

We have studied a method for the preparation of $ACF/TiO_2$ composites involving the penetrationof titanium n-butoxide (TNB) solution into activated carbon fiber. It was focused on the characterization of $TiO_2$ formed in prorous carbon was which increased with surface functional groups by hydrochloric acid treatment. The conversion of TNB to $TiO_2$ for the acid treatment effect must be important for the preparationof $ACF/TiO_2$ composites. From the characterization of surface properties, both the BET surface area and the total pore volume decreased as the distribution of $TiO_2$ on the activated carbon fiber surfaces after acid treatments.The changes in XRD pattern showed the typical anatase type on $ACF/TiO_2$ composite for the sample named FT, FT1 and FT2 treated with 0.05, 0.1 and 0.5 M, respectively. However, XRD patern of FT3 treated with 0.5M showed mixed amatase-rutile structure. According to the results of SEM micrographs, the titanium complexe particles were irregularly distributed around carbon. And some large clusters were found when an amount of acid treatment increased. The EDX results of $ACF/TiO_2$ composites showed the presence of C, O and P with strong Ti peaks. Finally, the excellent photocatalytic activity of the $ACF/TiO_2$ composites between relative concentration($c/c_o$) of MB (methylene blue) and UV irradiation time could be attributed to the both effects between photocatalysis of the formation of titania complexes and adsorptivity of the activated carbon fiber.

• Journal of dental hygiene science
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• v.16 no.3
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• pp.235-241
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• 2016

This study was conducted to provide basic understanding regarding possible enamel erosion by three kinds of fist-aid antipyretic and analgesic medicines over a period of time, with comparison and analysis of the resulting deciduous teeth surface and microhardness changes. The analysis was performed using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) to examine the surface erosion and changes. The Kruskal-Wallis test show differences in surface erosion and changes after 3, 5 and 8 days of treatment as well as before and after the treatment in each group. According to the results, there was no significant difference in the early deciduous teeth enamel surface microhardness (p>0.01). However there were signigicant changes after 3, 5, and 8 days (p<0.01). Calcim (Ca) and phosphorous (P) analysis using EDX showed significant differences in the enamel characteristics according to each tissue area after 8 days (p<0.05), but there was no significant difference in any of the areas for P content (p>0.05). In the surface observation with the SEM treatment with Children's Tylenol$^{(R)}$ tablet, which has the lowest pH, looked the roughest, followed by Brufen syrup for children and Children's Tylenol$^{(R)}$ suspension. Based on these results, it should be considered that antipyretic and analgesic medicines for children, which have lower pH values, may cause tooth erosion. Hence, it is necessary to give special attention to oral hygiene in young children or infants by brushing their teeth after such drugs are administered.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.8-12
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• 2000

The properties variation by deterioration of the 600V grade heat-resistant polyvinyl chloride insulated wire(HIV) was analyzed. The weight variation of the thermal deteriorated HIV was about 42% at 80$0^{\circ}C$ and over. From the analysis result of the metallurgical microscope photographs it shows that the sorface of normal wire showed the elongated structures. However the elongated structures did not appear at $900^{\circ} and over and we could observe that particles were grown. The grown oxidized substances in the thermally deteriorated electric wire were observed by SEM. The CuL, CuK, $CuK_b$, OK and CIK spectra of the thermally deteriorated HIV at $300^{\circ}C$ were uniform regardless of the scanning length, but the spectra of CIK could not found at above $700^{\circ}. At the DTA analysis, the endothermic reactions were occurred around $3006{\circ}C\; and\; 400^{\circ}C$ and the exothermic reactions were occurred around $470^{\circ}, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.502-505
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• 2003

The accidnet of breaking insulator rod leads to inturruption of moving the subway. We investigate the analysis of analysis of breaking accident of FRP insulator rod installed in dead section for catenary feeding system. To analysis of accident reason, SEM is used to analysis microscopic struture on surface of cross section of broken FRP insulator rod. At the same time, we examine the chage of atomic amount on solace of accident insulator through EDX analysis. Also, the test for tensional breaking load is condoled to check the mechanical strength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.53-56
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• 1999

The weight decreases of the thermal deteriorated IV were rapidly increased at 80$0^{\circ}C$ and over. At the results of the analysis of the metallurgical microscope photographs. the surface of the thermal deteriorated IV at 30$0^{\circ}C$ was mixed with the elongated and original structures of Cu. But the elongated structures could not detected at 90$0^{\circ}C$ and over. The surface structures of SEM were detected a lot of small rounded particles between crystallizations. The EDX spectra of the thermal deteriorated IV at 3$0^{\circ}C$ were uniformly detected CuL, CuK, OK, and CIK, regardless of the scanning length, but the spectra of CIK could not found at 90$0^{\circ}C$. At the DTA curves, the endothermic reactions were occurred at about 25$0^{\circ}C$ to 30$0^{\circ}C$ and 43$0^{\circ}C$, and the exothermic reactions were occurred at about 48$0^{\circ}C$ respectively.

• Proceedings of the KIEE Conference
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• 2005.11c
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• pp.60-63
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• 2005

In this paper, the accidents of 6.6kV CV cable using many analysis methods such as a pattern anlysis were analyzed; the inner structure analysis; cross section analysis; SEM; EDX, etc. With the analysis and the accident reconstruction, It was possible to analyze the accident causes. For more correct assessment, another accident reconstruction and simulation with a software were required.

• Fire Science and Engineering
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• v.16 no.1
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• pp.39-44
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• 2002

In this paper, we analysed the flame patterns and the electrical characteristics of the electric outlet which was fired at standby mode. The carbonized patterns indicated that the flame had spread about 50 cm to 70 cm. After the combustibles on wall started to burn, the temperature went up to about $300^{\circ}c$ in 150 sec. The flame formed ceiling jet and spread quickly. The tracking was generated at the shortest distance between two electrodes and the resistance was about 100$\Omega$ to 300$\Omega$ As the result of analysis using metallurgical microscope, the normal part of a blade holder showed amorphous structure, but the melted part of a blade holder damaged by tracking showed dendrite structure and void evenly. When the blade holder of damaged outlet was analyzed by SEM and EDX, we found that the structure and components of the normal part were different from those of melted part.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.345-350
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• 2010

For the present paper, we prepared MgO/MWCNT/$TiO_2$ photocatalyst by using multi-walled carbon nanotubes (MWCNTs) pre-oxidized by m-chlorperbenzoic acid (MCPBA) with magnesium acetate tetrahydrate $(Mg(CH_2COO)_2\cdot4H_2O)$ and titanium n-butoxide $(Ti\{OC(CH_3)_3\}_4)$ as magnesium and titanium precursors. The prepared photocatalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The decomposition of methylene blue (MB) solution was determined under irradiation of ultraviolet (UV) light. The XRD results show that the MgO/MWCNT/$TiO_2$ photocatalyst have cubic MgO structure and anatase $TiO_2$ structure. The porous structure and the $TiO_2$ agglomerate coated on the MgO/MWCNT composite can be observed in SEM images. The Mg, O, Ti and C elements can be also observed in MgO/MWCNT/$TiO_2$ photocatalyst from EDX results. The results of photodegradation of MB solution under UV light show that the concentration of MB solution decreased with an increase of UV irradiation time for all of the samples. Also, the MgO/MWCNT/$TiO_2$ photocatalyst has the best photocatalytic activity among these samples. It can be considered that the MgO/MWCNT/$TiO_2$ photocatalyst had a combined effect, the effect of MWCNT, which could absorb UV light to create photoinduced electrons $(e^-)$, and the electron trapping effect of MgO, which resulted in an increase of the photocatalytic activity of $TiO_2$.

• Asian Journal of Atmospheric Environment
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• v.9 no.3
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• pp.228-235
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• 2015

In order to clarify the thermal and hygroscopic properties of indoor particulate matter (PM) in a semiclosed subway space, which is critically important for understanding of the distinctive particle formation processes as well as the assessment of their health effects, the size-resolved PMs (i.e., $PM_{2.5}$ and $PM_{10-2.5}$) were intensively collected on the platform of Miasageori station on the Seoul Subway Line-4. The elemental concentrations in soluble and insoluble fractions were determined by PIXE from the bulkily pretreated $PM_{2.5}$. The thermal and hygroscopic characteristics of individual particles were investigated via a combination of the unique pretreatment techniques (i.e., the high-temperature rapid thermal process and the water dialysis) and SEM-EDX analysis. Iron and calcium were unequaled in insoluble and soluble $PM_{2.5}$ fractions, respectively, with overwhelming concentration. The SEM-EDX's elemental net-counts for the pre- and post-pyrolyzed PMs newly suggest that magnesium and several elements (i.e., silica, aluminum, and calcium) may be readily involved in the newly generated subway fine PM by a high-temperature thermal processing when trains are breaking and starting. Through the water dialysis technique, it turned out that calcium has meaningful amount of water soluble fraction. Furthermore, the concentrations of the counter-ions associated with the calcium in subway $PM_{10-2.5}$ were theoretically estimated.