• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.194-197
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• 2007

Polyacrylonitrile (PAN)/$Fe_2O_3$ nanocomposite membranes with a thickness of 0.02 mm were electrospun by adding 0 to 5 wt% of $Fe_2O_3$ into PAN. The surface tension, density, kinematic viscosity and dynamic viscosity of the PAN solution were determined to be $33.8{\pm}1mN/m$, 0.9794 g/ml, $1548.6mm^2/sec$ and 1516.7 cP, respectively. The average diameters of PAN fibers containing 0, 1 2, 3, and 4 wt% $Fe_2O_3$ particles were 300, 260, 210, 130, and 90 nm, respectively. Fourier-transform infrared spectroscopy results showed that the addition of $Fe_2O_3$ nanoparticles to the PAN mat reduced the absorption peak intensity at $2242cm^{-1}$ ($C{\equiv}N$ bond) while it caused a sharp increase in the peak intensity at $2356cm^{-1}$(C=O bond). Thus, it appears that an appropriate amount of $Fe_2O_3$ nanoparticles in the PAN backbone leads to an improvement of the performance of the $CO_2$ gas sensor, most likely due to the change of functional groups in the membrane.

• Journal of KIISE:Software and Applications
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• v.34 no.8
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• pp.689-696
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• 2007

It is important issue for software architects to estimate performance of software in the early phase of the development process due to the need to verify non-functional requirements and estimation of performance in various stages of architectural design. In order to analyze performance of software, there are many approaches to translate software architecture represented by Unified Modeling Language, into analytical models. However, in the development of agent-based systems, these approaches ignore or simplify the crucial details of the underlying performance of the agent platform. In this paper, we propose performance prediction methodology for agent based system using formal semantic descriptions, and then, we transform the descriptions into queuing network model which model reflects performance of hardware and software platform. We prove the accuracy of proposed methodology using prototype implementation. The accuracy is summarized at 80%.

• Microbiology and Biotechnology Letters
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• v.41 no.1
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• pp.60-69
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• 2013

Purified melanin pigment from Klebsiella sp. GSK was characterized by thermogravimetric, differential thermal, X-ray diffraction and elemental analysis. This melanin pigment is structurally amorphous in nature. It is thermally stable up to $300^{\circ}C$ and emits a strong exothermic peak at $700^{\circ}C$. Its carbon, hydrogen and nitrogen composition is 47.9%, 6.9% and 12.0%, respectively. It was used to scavenge metal ions and free radicals. After immobilizing the pigment and using it to adsorb copper and lead ions, the metal ion adsorption capacity was evaluated by atomic absorption spectroscopy (AAS) and the identity of melanin functional groups involved in the binding of metal ions was determined by Fourier transform infrared (FT-IR) spectroscopy. Batch adsorption studies showed that 169 mg/g of copper and 280 mg/g of lead were adsorbed onto melanin-alginate beads. The metal ion adsorption capacity of the melanin-alginate beads was relatively significant compared to alginate beads. The metal ion desorption capacity of HCl was greater (81.5% and 99% for copper and lead, respectively) than that of EDTA (80% and 71% for copper and lead, respectively). The ability of the melanin pigment to scavenge free radicals was evaluated by inhibition of the oxidation of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and was shown to be about 74% and 98%, respectively, compared with standard antioxidants.

• Korean Journal of Medicinal Crop Science
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• v.26 no.5
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• pp.417-429
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• 2018

Background: The objective of this study was to make colloidal dispersions of the active compounds of radix of Angelica gigas Nakai that could be charaterized as nano-composites using hot melt extrusion (HME). Food grade hydrophilic polymer matrices were used to disperse these compound in aqueous media. Methods and Results: Extrudate solid formulations (ESFs) mediated by various HPMCs (hydroxypropyl methylcelluloses) and Na-Alg polymers made from ultrafine powder of the radix of Angelica gigas Nakai were developed through a physical crosslink method (HME) using an ionization agent (treatment with acetic acid) and different food grade polymers [HPMCs, such as HP55, CN40H, AN6 and sodium alignate (Na-Alg)]. X-ray powder diffraction (XRD) analysis confirmed the amorphization of crystal compounds in the HP55-mediated extrudate solid formulation (HP55-ESF). Differential scanning calorimetry (DSC) analysis indicated a lower enthalpy (${\Delta}H=10.62J/g$) of glass transition temperature (Tg) in the HP55-ESF than in the other formulations. Infrared fourier transform spectroscopy (FT-IR) revealed that new functional groups were produced in the HP55-ESF. The content of phenolic compounds, flavonoid (including decursin and decursinol angelate) content, and antioxidant activity increased by 5, 10, and 2 times in the HP55-ESF, respectively. The production of water soluble (61.5%) nano-sized (323 nm) particles was achieved in the HP55-ESF. Conclusions: Nano-composites were developed herein utilizing melt-extruded solid dispersion technology, including food grade polymer enhanced nano dispersion (< 500 nm) of active compounds from the radix of Angelica gigas Nakai with enhanced solubility and bioavailability. These nano-composites of the radix of Angelica gigas Nakai can be developed and marketed as products with high therapeutic performance.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.433-438
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• 2012

A chemical process involves polymerization within microspheres, whereas a physical process involves the dispersion of polymer in a nonsolvent. Nano-sized monodisperse microspheres are usually prepared by chemical processes such as water-based emulsions, seed suspension polymerization, nonaqueous dispersion polymerization, and precipitation polymerizations. Polymerization was performed in a four-necked, separate-type flask equipped with a stirrer, a condenser, a nitrogen inlet, and a rubber stopper for adding the initiator with a syringe. Nitrogen was bubbled through the mixture of reagents for 1 hr. before elevating the temperature. Functional silane (3-mercaptopropyl)trimethoxysilane (MPTMS) was used for the modification of silica nanoparticles and the self-assembled monolayers obtained were characterized by X-ray photoelectron spectroscopy (XPS), laser scattering system (LSS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental analysis (EA), and thermogravimetric analysis (TGA). In addition, polymer microspheres were polymerized by radical polymerization of ${\gamma}$-mercaptopropyl modified silica nanoparticles (MPSN) and acrylamide monomer via precipitation polymerization; then, their characteristics were investigated. From the elemental analysis results, it can be concluded that the conversion rate of acrylamide monomer was 93% and that polyacrylamide grafted to MPSN nanospheres via the radical precipitation polymerization with AAm in ethanol solvent. The microspheres were successfully polymerized by the 'graft from' method.

• Carbon letters
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• v.6 no.2
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• pp.106-110
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• 2005

In this work, the effects of atmospheric oxygen plasma treatment of carbon fibers on mechanical interfacial properties of carbon fibers-reinforced epoxy matrix composites was studied. The surface properties of the carbon fibers were determined by acid/base values, Fourier-transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses. Also, the crack resistance properties of the composites were investigated in critical stress intensity factor ($K_{IC}$), and critical strain energy release rate mode II ($G_{IIC}$) measurements. As experimental results, FT-IR of the carbon fibers showed that the carboxyl/ester groups (C=O) at 1632 $cm^{-1}$ and hydroxyl group (O-H) at 3450 $cm^{-1}$ were observed for the plasma treated carbon fibers, and the treated carbon fibers had the higher O-H peak intensity than that of the untreated ones. The XPS results also indicated that the $O_{1S}/C_{1S}$ ratio of the carbon fiber surfaces treated by the oxygen plasma led to development of oxygen-containing functional groups. The mechanical interfacial properties of the composites, including $K_{IC}$ (critical stress intensity factor) and $G_{IIC}$ (critical strain energy release rate mode II), were also improved for the oxygen plasma-treated carbon fibersreinforced composites. These results could be explained that the oxygen plasma treatment played an important role to increase interfacial adhesions between carbon fibers and epoxy matrix resins in our composite system.

• Clean Technology
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• v.11 no.4
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• pp.189-194
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• 2005

Carboxymethylcellulose(CMC) which is water-soluble fiber was manufactured by mercerization and etherification in the earlier study. Experimental parameters were conversion time for each step, concentration of reagent and temperature. To know the presence of functional group, CMC was analyzed by FT-IR(Fourier Transform Infrared) spectroscopy. Ethanol was recovered using evaporator and purity of ethanol analyzed by GC-MASS was 97% and 83% after mercerization and etherification respectively. For the pilot plant, if CMC is folded by 40 times it showed maximum efficiency. Maximum solubility was obtained when the ratio of NaOH and MCA is 3 : 4.5.

• Polymer(Korea)
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• v.39 no.2
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• pp.219-224
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• 2015

In this work, the effect of fiber array direction including $0^{\circ}$, $0^{\circ}/90^{\circ}$, $0^{\circ}/45^{\circ}/-45^{\circ}$ was investigated for mechanical properties of basalt fiber-reinforced composites. Mechanical properties of the composites were studied using interlaminar shear strength (ILSS) and critical stress intensity factor ($K_{IC}$) measurements. The cross-section morphologies of basalt fiber-reinforced epoxy composites were observed by scanning electron microscope (SEM). Also, the surface properties of basalt fibers were determined by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). From the results, it was observed that acid treated basalt fiber-reinforced composites showed significantly higher mechanical interfacial properties than those of untreated basalt fiber-reinforced composites. These results indicated that the hydroxyl functional groups of basalt fibers lead to the improvement of the mechanical interfacial properties of basalt fibers/epoxy composites in the all array direction.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.2
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• pp.17-26
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• 2014

In this study, the adsorption efficiency of mixed heavy metals from an aqueous solution was examined using bentonite. The physical and chemical properties of bentonite was analyzed via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), Further, heavy metal adsorption was characterized using Freundlich and Langmuir equations. Equilibrium adsorption data were fitted well to the Langmuir model for bentonite. The adsorption uptake of heavy metals was high and followed the order $Pb^{2+}$ > $Cu^{2+}$ > $Cd^{2+}$ > $$Zn^{2+}{\sim_=}Ni^{2+}$$. The results also showed that adsorption uptake slightly increased as increasing pH from 6 to 10. The bentonite surface was observed viay SEM and FT-IR; Si-O and Si-O-Al were found to be the main functional groups by FT-IR analysis. From these results, the adsorption mechanisms of heavy metal were not only surface adsorption and ion exchange, but also surface precipitation. Thus, bentonite could be a useful adsorbent for treating heavy metal in aqueous solution.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1233-1241
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• 2017

The ginsenoside Rh2 has strong anti-cancer, anti-inflammatory, and anti-diabetic effects. However, the application of ginsenoside Rh2 is restricted because of the small amounts found in Korean white and red ginsengs. To enhance the production of ginsenoside Rh2-MIX (comprising 20(S)-Rh2, 20(R)-Rh2, Rk2, and Rh3 as a 10-g unit) with high specificity, yield, and purity, a new combination of enzymatic conversion using the commercial enzyme Viscozyme L followed by acid treatment was developed. Viscozyme L treatment at pH 5.0 and $50^{\circ}C$ was used initially to transform the major ginsenosides Rb1, Rb2, Rc, and Rd into ginsenoside F2, followed by acid-heat treatment using citric acid 2% (w/v) at pH 2.0 and $121^{\circ}C$ for 15 min. Scale-up production in a 10-L jar fermenter, using 60 g of the protopanaxadiol-type ginsenoside mixture from ginseng roots, produced 24 g of ginsenoside Rh2-MIX. Using 2 g of Rh2-MIX, 131 mg of 20(S)-Rh2, 58 mg of 20(R)-Rh2, 47 mg of Rk2, and 26 mg of Rh3 were obtained at over 98% chromatographic purity. Then, the anti-cancer effect of the four purified ginsenosides was investigated on B16F10, MDA-MB-231, and HuH-7 cell lines. As a result, these four rare ginsenosides markedly inhibited the growth of the cancer cell lines. These results suggested that rare ginsenoside Rh2-MIX could be exploited to prepare an anti-cancer supplement in the functional food and pharmaceutical industries.