• Elastomers and Composites
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• v.34 no.3
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• pp.199-211
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• 1999

In this work, the effects of the addition of epoxy on the properties of PVC-sol sealants were investigated. PVC-sol was plasticized with dioctyl phthalates(DOP). Two kinds of epoxy resins having different epoxy equivalent weight (E.E.W.) were used. It was found that the properties of the PVC-sol sealants were significantly affected by the contents and types of the added epoxy resins. The viscosity behaviors of the epoxy-modified sealants, in the case of epoxy A addition, the viscosity was decreased with increasing the epoxy contents, but In the case of $CaCO_3$ addition, the viscosity was increased with increasing the $CaCO_3$ contents. The viscosity of epoxy modified sealants aged at $45^{\circ}C$ waterbath was decreased with increasing epoxy contents, since the epoxy acted on the sealants as a stabilizer. The thermal stability of the PVC-sol sealants was slightly improved by adding epoxy. The tensile strength and elongation of sealants modified with epoxy A(two functionalities of epoxy) were increased with increasing the epoxy contents up to a certain epoxy contents but was decreased with further increasing the epoxy contents. In the case of $CaCO_3$ addition, the tensile strength of sealants were decreased with increasing the $CaCO_3$ contents. In view of the electrical properties, such as tan ${\delta}$($0.1{\pm}0.04$) and ${\epsilon}_r$($0.5{\pm}0.04$), it was found that the epoxy modified sealants were as good as insulators.

• Polymer(Korea)
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• v.36 no.3
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• pp.251-261
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• 2012

The nanocomposites containing graphene oxide flakes were prepared in order to improve the mechanical properties of artificial marbles based on poly(methyl methacrylate)(PMMA) matrix. Graphene oxide flakes were prepared from graphite by oxidation with Hummers method followed by exfoliation with thermal treatment. Surface of graphene oxide flakes were modified with oxyfluorination in various oxygene:fluorine compositions to improve the interfacial compatibility. The nanocomposites containing graphenes modified with oxyfluorination in the oxygen content of 50% and higher showed the significant increase in flexural strength, flexural modulus, Rockwell hardness, Barcol hardness, and Izod impact strength. The morphology of fractured surface showed the improved interfacial adhesion between PMMA matrix and the graphenes which were properly treated with oxyfluorination. The mechanical properties of nanocomposite were deteriorated by increasing the content of graphene above 0.07 phr due to the nonuniform dispersion of graphenes.

• Journal of the Korea Institute of Building Construction
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• v.16 no.1
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• pp.1-7
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• 2016

In this research, it used cement powder and reduction slag, which generates high hydration heat in hydration reaction without heat cure below $-5^{\circ}C$ degree. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature due to own heat of concrete. and it is the result of physical characteristic and thermal property evaluation of reduction slag. Because reduction slag generates high hydration heat, compressive strength development is excellent. By generating highly hydration heat by $C_{12}A_7$ and $C_3A$ in reduction slag, compressive strength is developed in low temperature. In case of displacing only reduction slag without $SO_3$, it is indicated that quick-setting occurs by shortage of $SO_3$. For preventing quick-setting, gypsum is used essentially. According to this research result, in case of using reduction slag and gypsum as a ternary system, compressive strength developed 5MPa in 3 days below zero temperature. It is identified to prevent early frost damage of concrete below zero temperature.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.3
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• pp.246-252
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• 2016

Since thermal power plant (TPP) equipment is operated under very high pressure and temperature, failures of the equipment give rise to severe losses of life and property. To prevent the losses, fault detection method is, therefore, absolutely necessary to identify abnormal operating conditions of the equipment in advance. In this paper, we present Mahalanobis distance (MD) based fault detection method for steam boiler tube in TPP. In the MD-based method, it is supposed that abnormal data samples are far away from normal samples. Using multivariate samples collected from normal target system, mean vector and covariance matrix are calculated and threshold value of MD is decided. In a test phase, after calculating the MDs between the mean vector and test samples, alarm signals occur if the MDs exceed the predefined threshold. To demonstrate the performance, a failure case due to boiler tube leakage in 200MW TPP is employed. The experimental results show that the presented method can perform early detection of boiler tube leakage successfully.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.6
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• pp.1074-1079
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• 1996

Physicochemical characteristics of pigment separated from cockle shell were studied. Pigment on the cockle shell was peeled with distilled water, and soaked in 4% TCA solution for 30 minutes and filtered. Filtrate was washed 3 times with distilled water and Iyophilized. Dried pigment was dissolved with 2N NaOH solution and preparative TLC with 2N NaOH : acetone(1 : 1). UV/vis spectrum of pigment separated from cockle shell and melanin as standard was same one peak at UV area and λ$_{max}$was 226nm. Dissolved property of pigment was same as that of melanin. Pigment was not ommochrome but like melanin, because it was insoluble in formic acid, whitening in $H_2O_2, $ and pattern of UV-spectrum was same as melanin. Pigment separated from cockle shell was stable at high temperatures. In thermal treatment at $70^{\circ}C, $ $80^{\circ}C, $ $90^{\circ}C$ and $100^{\circ}C$ for 8 hours, retention ratio of pigment separated from cockle shell were 95.0%, 93.3%, 90.8% and 87.6%, respectively.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.216-224
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• 1997

Porous silica ceramics were prepared(with HCI catalyst) using H2O/TEOS molar ratios of 2.6~59.0, with the EtOH/TEOS ratio fixed. After preparing 9 kinds of sol, the followings were investigated; measurement of the gelation time, thermal analyses by TG/DTA, property analyses of the intermediates by FT-IR and X-ray diffractometry with dried samples, analyses of SiO2 polymer by FT-IR, the investigation of specific sur-face area and pore size distribution by N2-adsorption isotherm, and structural change of SiO2 polymer and pore morphology by TEM observation, with samples heat-treated to 50$0^{\circ}C$. In the concentrations of in-vestigated compositions and catalyst, gelation time showed a minimum at ca. 11 moles of water per one mole of TEOS, the highest degree of polymerization at ca. 8-18 moles, and the largest specific surface area at ca. 11 moles, which means that the polymerization proceeded fastest at ca. 11 moles of water. In con-clusion, the more water used, the faster the polymerization reaction up to ca. 11 moles, but more than ca. 11 moles of water caused retardation of gelation and resultant reduction of specific surface area.

• BMB Reports
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• v.40 no.6
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• pp.911-920
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• 2007

Tuberculosis, caused by Mycobacterium tuberculosis, continues to be one of the leading infectious diseases to humans. It is urgent to discover novel drug targets for the development of antitubercular agents. The 2-C-methyl-Derythritol-4-phosphate (MEP) pathway for isoprenoid biosynthesis has been considered as an attractive target for the discovery of novel antibiotics for its essentiality in bacteria and absence in mammals. MEP cytidyltransferase (IspD), the third-step enzyme of the pathway, catalyzes MEP and CTP to form 4-diphosphocytidyl-2-C-methylerythritol (CDP-ME) and PPi. In the work, ispD gene from M. tuberculosis H37Rv (MtIspD) was cloned and expressed. With N-terminal fusion of a histidine-tagged sequence, MtIspD could be purified to homogeneity by one-step nickel affinity chromatography. MtIspD exists as a homodimer with an apparent molecular mass of 52 kDa. Enzyme property analysis revealed that MtIspD has high specificity for pyrimidine bases and narrow divalent cation requirements, with maximal activity found in the presence of CTP and $Mg^{2+}$. The turnover number of MtIspD is $3.4 s^{-1}$. The Km for MEP and CTP are 43 and $92{\mu}M$, respectively. Furthermore, MtIspD shows thermal instable above $50^{\circ}C$. Circular dichroism spectra revealed that the alteration of tertiary conformation is closely related with sharp loss of enzyme activity at higher temperature. This study is expected to help better understand the features of IspD and provide useful information for the development of novel antibiotics to treat M. tuberculosis.

• Composites Research
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• v.32 no.6
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• pp.335-341
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• 2019

In this study, an acrylic acid (AAc) was grafted on a polypropylene (PP) nonwoven fabric using electron beam irradiation. Electron beam grafting was carried out under various conditions to produce AAc grafted PP (PP-g-AAc) nonwoven fabric having a grafting yield of about 50% at radiation dose of 100 kGy and a monomer concentration of 60%. The physical and chemical properties of PP-g-AAc nonwoven fabric were evaluated by SEM, ATR-FTIR, thermal analysis and tensile strength. The morphology of PP and PP-g-AAc nonwoven fabric confirmed by SEM showed no significant change, and it was judged that AAc was introduced into PP nonwoven fabric from ATR-FTIR. PP-g-AAc nonwoven fabric showed an increase in tensile strength and a decrease in tensile strain compared to PP nonwoven fabric. However, since change of value is not significant, it is considered that there is no significant influence on the physical characterization. Adsorption experiments of PP-g-AAc nonwoven fabric on various ions showed selective adsorption behavior for lead ion. In conclusion, the electron beam radiation-induced PP-g-AAc nonwoven fabric is expected to be applied as an effective adsorbent for the adsorption of lead ions.

• Membrane and Water Treatment
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• v.6 no.5
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• pp.365-378
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• 2015

Herein, the preparation of anion exchange membrane (AEM) from brominated poly(2,6-dimethyl 1,6-phenylene oxide) BPPO and dimethylaniline (DMA) by phase-inversion process is reported. Anion exchange membranes (AEMs) are prepared by varying the DMA contents. Prepared AEMs show high thermal stability, water uptake (WR) around 202% to 226%, dimensional change ratios of 1.5% to 2.6% and ion exchange capacities (IECs) of 0.34 mmol/g to 0.82 mmol/g with contact angle of $59.18^{\circ}$ to $65.15^{\circ}$. These membranes are porous in nature as confirmed by SEM observation. The porous property of membranes are important as it could reduce the resistance of transportation of ions across the membranes. They have been used in diffusion dialysis (DD) process for recovery of hydrochloric acid (HCl) from the mixture of HCl and ferrous chloride ($FeCl_2$). Presence of $-N+(CH_3)_2C_6H_5Br^-$ as a functional group in membrane matrix facilitates its applications in DD process. The dialysis coefficients of hydrochloric acid ($U_H$) of the membranes are in range of 0.0016 m/h to 0.14 m/h and the separation factors (S) are in range of 2.09 to 7.32 in the $HCl/FeCl_2$ system at room temperature. The porous membrane structure and presence of amine functional group are responsible for the mechanism of diffusion dialysis (DD).

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.1-5
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• 2006

We prepared 80 nm-thick TiSix on each 70 nm-thick amorphous silicon and polysilicon substrate using an RF sputtering with $TiSi_2$ target. TiSix composite silicide layers were stabilized by rapid thermal annealing(RTA) of $800^{\circ}C$ for 20 seconds. Line width of $0.5{\mu}m$ patterns were embodied by photolithography and dry etching process, then each additional annealing process at $750^{\circ}C\;and\;850^{\circ}C$ for 3 hours was executed. We investigated the change of sheet resistance with a four-point probe, and cross sectional microstructure with a field emission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM), respectively. We observe an abrupt change of resistivity and voids at the silicide surface due to interdiffusion of silicide and composite titanium silicide in the amorphous substrates with additional $850^{\circ}C$ annealing. Our result implies that the electrical resistance of composite titanium silicide may be tunned by employing appropriate substrates and annealing condition.