• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1252-1260
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• 2020

(R)-2-(4-hydroxyphenoxy)propionic acid (HPOPA) is a key intermediate for the preparation of aryloxyphenoxypropionic acid herbicides (R-isomer). In order to improve the HPOPA production from the substrate (R)-2-phenoxypropionic acid (POPA) with Beauveria bassiana CCN-A7, static cultivation and H₂O₂ addition were attempted and found to be conducive to the task at hand. This is the first report on HPOPA production under static cultivation and reactive oxygen species (ROS) induction. On this premise, the cultivation conditions and fermentation medium compositions were optimized. As a result, the optimal carbon source, organic nitrogen source, and inorganic nitrogen source were determined to be glucose, peptone, and ammonium sulfate, respectively. The optimal inoculum size and fermentation temperature were 13.3% and 28℃, respectively. The significant factors including glucose, peptone, and H₂O₂, identified based on Plackett-Burman design, were further optimized through Central Composite Design (CCD). The optimal concentrations were as follows: glucose 38.81 g/l, peptone 7.28 g/l, and H₂O₂ 1.08 g/l/100 ml. Under the optimized conditions, HPOPA titer was improved from 9.60 g/l to 19.53 g/l, representing an increase of 2.03-fold. The results obtained in this work will provide novel strategies for improving the biosynthesis of hydroxy aromatics.

• Composites Research
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• v.32 no.6
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• pp.388-394
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• 2019

Inherited the excellent electrical and mechanical properties based on the low dimensional structure of graphene, three-dimensional graphene nanostructures have gathered great attention as electrochemical energy storage electrodes owing to their high porosity and large specific surface area. Also, having the catecholamine structure, dopamine has been regarded as a multifunctional material to possess high affinity to various organic/inorganic materials and to modify a hydrophobic surface to a hydrophilic one. In this work, through coating dopamine on the three-dimensional graphene nanostructure, we tried to increase the specific capacitance by enhancing the wettability with electrolyte and to improve the mechanical compressive property by strengthening the nano-architecture. As a result, the dopamine-coated nanostructure exhibited significant improvement on the specific capacitance (51.5% increase) and compressive stress (59.6% increase).

• Journal of Photoscience
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• v.5 no.3
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• pp.105-109
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• 1998

By using the liquid -phase-deposition (LPD) process, which has a potetnial of preparing organic inorganic composite materials, samples doped with benzo[f]quinoline (BfQ)into silica thia films wre prepared. We observed the fluorescene and fluorescene excitation spectra of the samples, as well as the fluorescence lifetimes and time-resoluved fluorescence spectra. The comparison of thefluorescence spectra in pH-controlled buffer solutions yields the results that the dominant species of BfQ in the LPD silica films is a protonated one. The fluorescence band assigned to a hydrogen-bonded species was observed on the samples prepared from the dipping solutions of 3 and 2 M hexafluorosilicic acid. The band assignment was confirmed by the fluorescence lifetime measurement. The FT-IR M hexaflurosilicic acid. The band assignment was confirmed by the flurescence lifetime meausurement. The FT-IR data proved the existence of included water in silica films prepared from the LPD process. The appearance of the band corresponding to the hydrogen-bonded species within LPD silica phases was explained by the proesence of included water. Depending on the preparation conditions of LPD silica films, the band assigned to protonated species shows bad shifts in a wavenumber region between the peak of hydrogen-bonded and typical protonated species. This implies that there is some distribution of steric conformation of protonated species of BfQ interacting with adsorbing sites of LPD silica. The time -resolved fluorescence spectra suggest that some relaxation process is involved in the conformation of BfQ doped into the solid phase of LPD silica.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.974-980
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• 2015

Arc thermal spray coating using Al-3%Mg thermal spray wire was carried out to prevent steel from corrosion damage under the marine environment. Post-sealing was applied to Al-3%Mg spray coating treatment using organic/inorganic composite ceramics in order to improve the corrosion resistance of the as-sprayed coating. The results of various electrochemical experiments with sealing treatment indicated that the improvement in corrosion resistance was observed due to low current density in all applied potential range during anodic and cathodic polarization experiments. Futhermore, the natural potential measurement exhibited severe potential fluctuation due to influence of micro-crack presence on the surface of sealed thermal spray coating layer. In addition, the sealed layer was easily eliminated during anodic polarization. Nevertheless, Al-3%Mg spray coating layer improved corrosion resistance by sealing treatment because the sealed coating efficiency was determined to be 92.11%, indicating the exterior environment barrier effect which is based on the Tafel analysis.

• Conservation Science in Museum
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• v.26
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• pp.35-66
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• 2021

This study conducted scientific analysis and conservation treatment on four suits of armor and two helmets from the collection of the National Museum of Korea. Based on the findings, it identified structural characteristics of armor from the middle and late Joseon Dynasty. Since a suit of armor is made of composite materials consisting of both organic and inorganic elements, conservation treatment was conducted to the extent that the stable condition of each material remained unaffected by the other materials. The process took place in the sequence of investigation and analysis, removal of contamination, stabilization and reinforcement, repair of damaged parts, and storage. The armor and helmets had suffered severe damage, but were safely repaired and partially restored through the conservation treatment. The findings from the conservation treatment revealed the materials used and structural characteristics of the armored skirt from a two-piece set of armor from the middle Joseon period and for the two suits of overcoat-style armor, suit of vest-style armor, and helmets from the late Joseon era. It also allowed the investigation of the production methods of the armor and helmets.

• Applied Microscopy
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• v.40 no.3
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• pp.155-162
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• 2010

Bone is a hierarchically structured composite material which has been well studied by the materials engineering community because of its unique structure and mechanical properties. Bone is a laminated organic-inorganic composite composed of primarily hydroxyapatite, collagen and water. The main mineral that gives bone's hardness is calcium phosphate, which is also known as hydroxyapatite. Light microscopy (LM) and transmission electron microscopy (TEM) were used to study the structure of femurs from chicken and rabbit. The elemental analysis was used to search variation in the distribution of calcium, potassium and oxygen in the femur. Current investigation focused on two structural scales: micro scale (arrangement of compact bone) and nano scale (collagen fibril and apatite crystals). At micro scale, distinct difference was found in microstructures of chicken femur and rabbit femur. At nano scale, we analyzed the shape and size of apatite crystals and the arrangement of collagen fibril. Consequently, femurs of chicken and rabbit had very similar chemical property and structures at nano scale despite of their different species.

• Membrane Journal
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• v.32 no.5
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• pp.292-303
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• 2022

An eco-friendly energy conversion device without the emission of pollutants has gained much attention due to the rapid use of fossil fuels inducing carbon dioxide emissions ever since the first industrial revolution in the 18th century. Polymer electrolyte membrane fuel cells (PEMFCs) that can produce water during the reaction without the emission of carbon dioxide are promising devices for automotive and residential applications. As a key component of PEMFCs, polymer electrolyte membranes (PEMs) need to have high proton conductivity and physicochemical stability during the operation. Currently, perfluorinated sulfonic acid-based PEMs (PFSA-PEMs) have been commercialized and utilized in PEMFC systems. Although the PFSA-PEMs are found to meet these criteria, there is an ongoing need to improve these further, to be useful in practical PEMFC operation. In addition, the well-known drawbacks of PFSA-PEMs including low glass transition temperature and high gas crossover need to be improved. Therefore, this review focused on recent trends in the development of high-performance PFSA-PEMs in three different ways. First, control of the side chain of PFSA copolymers can effectively improve the proton conductivity and thermal stability by increasing the ion exchange capacity and polymer crystallinity. Second, the development of composite-type PFSA-PEMs is an effective way to improve proton conductivity and physical stability by incorporating organic/inorganic additives. Finally, the incorporation of porous substrates is also a promising way to develop a thin pore-filling membrane showing low membrane resistance and outstanding durability.

• Membrane Journal
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• v.33 no.6
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• pp.325-343
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• 2023

Direct methanol fuel cells (DMFCs) have been attracting attention as energy conversion devices that can directly supply methanol liquid fuel without a fuel reforming process. The commercial polymer electrolyte membranes (PEMs) currently applied to DMFC are perfluorosulfonic acid ionomer-based PEMs, which exhibit high proton conductivity and physicochemical stability during the operation. However, problems such as high methanol permeability and environmental pollutants generated during decomposition require the development of PEMs for DMFCs using novel ionomers. Recently, studies have been reported to develop PEMs using hydrocarbon-based ionomers that exhibit low fuel permeability and high physicochemical stability. This review introduces the following studies on hydrocarbon-based PEMs for DMFC applications: 1) synthesis of grafting copolymers that exhibit distinct hydrophilic/hydrophobic phase-separated structure to improve both proton conductivity and methanol selectivity, 2) introduction of cross-linked structure during PEM fabrication to reduce the methanol permeability and improve dimensional stability, and 3) incorporation of organic/inorganic composites or reinforcing substrates to develop reinforced composite membranes showing improved PEM performances and durability.

• Korean Journal of Microbiology
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• v.12 no.4
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• pp.159-179
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• 1974

In order to investigate morphological and cultural characteristics of strains in species, Flammulina velutipes, the author collected isolates of Flammultina velutipes at 49 locations in Korea and cultivated these isolates on the various kinds of solid media. After investigating the cultural characteristics, appeared on the various media, he obtained the following results : 1. The variation of colors in the fruit bodies is connected with the variation of climatic environments(composite effects between mean temperature in January and number of rain days of 1mm and over precipitation). The author, therfore, can find out the trend that brown type is distributed in the midland climatic region and yellow type in the southern climatic regoin. 2. Two types can be classified into several strains respectively : the strain of abundant or insufficient productivity, and strain of selectivity or non-selectivity of media. 3. According to the results of mutual comparison of soluble mycelial proteins by disc electrophoresis using polyacrylamide gels, each type has special common protein fractions(brown type : band located at 26..5mm position from surface of gel, yellow type : band located at 24.5mm position from surface of gel), and each strain has special protein fractions too. Therefore this phenomenon seems to support the results obtained by the above-stated morphological and cultural studies. 4. In the adaptability of strains to the temperature, every strain has the nature of growing in lower temperature(the optimum temperature of 20.deg.C to 25.deg.C) except that YI-1 strain has the optimum temperatue of $25^{\circ}C$-26^{\circ}C. And mycelial growth of every strain is discontinued at $35^{\circ}C.$ 5. In the adaptability of strains to the H-ion concentration, every strain has wide adaptable range of H-ion concentration, and has optimum range of pH 5.5 to 6.6 in mycelial growth excepting YA01, BI-2 and YI-1. 6. In the utility of carbon sources, the mycelial growth of every strain is very poor on the media containing xylose(average diameter of mycelial growth : 18mm), and most strains utilize favorably sucrose(39mm), maltose(37mm) and dextrose(35mm) in mycelial growth. In the utility of nitrogen sources, every strain utilizes favorably organic nitrogens(36 mm)more than inorganic nitrogens (25 mm), and utilizes fully peptone nad asparagine in organic nitrogens. Especially BA-1, BIK-2 and YA-1 strains grow vigorously on each media containing various carbon and nitrogen sources. 7. The characteristic tests of the number of days required for mycelial growth, the number of days requried for sprout of young bodies, the length of stipe and the number of fruit bodies formation seem to be useful methods in the early selection of the strain of the abundant productivity.

• Corrosion Science and Technology
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• v.9 no.4
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• pp.147-152
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• 2010

Conventional paints for conversion coating applications in steel production derived mainly from water-based polymer dispersions containing several additives actually show good general performance, but suffer from poor scratch and abrasion resistance during use. The reason for this is because the relatively soft organic binder matrix dominates the mechanical surface properties. In order to maintain the high quality and decorative function of coated steel sheets, the mechanical performance of the surface needs to be improved significantly. In fact the wear resistance should be enhanced without affecting the optical appearance of the coatings by using appropriate nanoparticulate additives. In this direction, nanocomposite coating compositions (Nanomer$^{(R)}$) have been derived from water-based polymer dispersions with an increasing amount of surface-modified nanoparticles in aqueous dispersion in order to monitor the effect of degree of filling with rigid nanoparticles. The surface of nanoparticles has been modified for optimum compatibility with the polymer matrix in order to achieve homogeneous nanoparticle dispersion over the matrix. This approach has been extended in such a way that a more expanded hybrid network has been condensed on the nanoparticle surface by a hydrolytic condensation reaction in addition to the quasi-monolayer type small molecular surface modification. It was expected that this additional modification will lead to more intensive cross-linking in coating systems resulting in further improved scratch-resistance compared to simple addition of nanoparticles with quasi-monolayer surface modification. The resulting compositions have been coated on zinc-galvanized steel and cured. The wear resistance and the corrosion protection of the modified coating systems have been tested in dependence on the compositional change, the type of surface modification as well as the mixing conditions with different shear forces. It has been found out that for loading levels up to 50 wt.-% nanoparticles, the mechanical wear resistance remains almost unaffected compared to the unmodified resin. In addition, the corrosion resistance remained unaffected even after $180^{\circ}$ bending test showing that the flexibility of coating was not decreased by nanoparticle addition. Electron microscopy showed that the inorganic nanoparticles do not penetrate into the organic resin droplets during the mixing process but rather formed agglomerates outside the polymer droplet phase resulting in quite moderate cross linking while curing, because of viscosity. The proposed mechanisms of composite formation and cross linking could explain the poor effect regarding improvement of mechanical wear resistance and help to set up new synthesis strategies for improved nanocomposite morphologies, which should provide increased wear resistance.