• 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.

• Polymer(Korea)
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• v.35 no.3
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• pp.238-243
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• 2011

Organic/inorganic hybrid materials have a lot of interest in various areas due to their fascinating properties. To control the location and dispersion of inorganic nanoparticles within polymer matrix. thiol-terminated polymeric ligands have been widely used to tune the surface property of nanoparticles. However, the specific binding between the thiol functional group and metal is unstable with increasing temperature. To archive the thermally-stable Au nanoparticles, we previously synthesized various UV-crosslinkable polymeric ligands, which have different compositions of polar, UV-crosslinkable azide unit comparing to non-polar 스티렌 units. After crosslinking the Au nanoparticles, it was found that the nanoparticles had superb stability at high temperature (above $180^{\circ}C$). In this work, we used thermally-stable Au nanoparticles to control the location within the polymer matrix. By changing the amount of polar azide units in the polymeric ligands, we could precisely control the location of nanoparticles from one domain to the interface of block copolymer templates.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.19-26
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• 2017

Objectives: In the Lung, the VMAT rotates continuously and examines radiation. That increases the low doses to normal lung. Due to that, the incidence of radiation pneumonia among radiation side effects may increase. The cause of radiation pneumonia is the lower dose area of the lungs. The H-VMAT was applied to patients who applied to reduce radiation in the lower doses of the lungs. We wanted to assess the usefulness of the H-VMAT by comparing the radiation doses to the low dose areas of the lungs and the normal organs. Materials and Methods: A total of 26 patients who applied for a H-VMAT procedure were applied to the patient. The prescription dose applied to total dose 44 Gy from 22 divisions. For each patient, a plan was implemented with Conventional RT, VMAT and H-VMAT. Conventional RT was carried out in four to five fields each, considering the size, location, shape, and location of the PTV. In the case of a VMAT plan, the two Half ARC, three Half ARC method and the two Full ARC were planned. The H-VMAT was planned by adding two Static fields in the VMAT, taking into account the dose of the lung and the tolerance dose of the organs. Results: In the NSCLC, the lung doses $V_5$ and $V_{10}$ of the lungs except for the treatment plan volume were the lowest with $55.40{\pm}13.39%$ and $32.05{\pm}11.37%$ of H-VMAT. And, in the SCLC, the lung doses of V5 and V10 were the lowest at $64.32{\pm}16.15%$ and $35.50{\pm}9.91%$, respectively. The spinal dose of VMAT in NSCLC was $21.15{\pm}4.02Gy$, which was 7.94 Gy lower than other treatment methods. The lowest spinal dose was delivered at $19.72{\pm}1.82Gy$ for SCLC. The mean dose delivered to the esophagus was also $17.44{\pm}2.04Gy$ and $17.84{\pm}9.20Gy$ in SCLC and NSCLC, respectively. Conclusion: When comparing the value of the surrounding normal organ dose, the VMAT showed that less doses were transmitted from the heart, esophagus and spinal cord than the rest of the treatment plan. However, it was similar to VMAT in normal organs except for the spinal cord. VMAT has increased doses of some normal organs but did not exceed the tolerance dose. It showed a low value in $V_5$, $V_{10}$. When comparing Conventional RT, VMAT, and H-VMAT, If the dose to the heart, esophagus and spinal cord is lower than the tolerance dose, it is thought to reduce the incidence of radiation pneumonia by applying H-VMAT that show the benefits of low doses of the lungs.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.4
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• pp.510-517
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• 2015

Miscanthus has been considered as the most promising bioenergy crop for lignocellulosic biomass production. In Korea, M. sacchariflorus and M. sinensis can be found easily in all regions. It is a great advantage to utilize as important species with respect to genetic and cross-breeding programs materials for creation of novel hybrids. For successful breeding programs, it is important to precisely understand the variability of flowering traits among Miscanthus species as breeding parents materials. In this study, flowering traits were observed daily in 960 germplasms of two Miscanthus species (M. sacchariflorus and M. sinensis) for growing seasons over 2 years. The flowering process was divided into three stages. ST (sprouting time) was recorded when first leaf of the plant emerged on soil. FS1 (flowering stage 1) and FS2 (flowering stage 2) were recorded when flag leaf was firstly observed, and 1 cm of panicle was showing on at least one stem, respectively. For 2013 and 2014, the latest germplasms exerted flag leaf, i.e. September 30 (DOY of FS1 164.1) and September 4 (DOY of FS1 141.0) occurred M. sacchariflorus cv. Geodae 1 and M. sacchariflorus cv. Uram collected from Southern Korea (Jeollanam-do), while Miscanthus germplasms collected from northern Korea (Gyeonggi-do) which emerged the earliest flag leaf in July and August, significantly decreased DOY. For DOY from ST to FS2, M. sacchriflorus germplasms ranged from 140 to 190 days, and 110 to 170 days for 2013 and 2014. The highest frequency showed to 160 days for 2013, and 150 days for 2014. In M. sinensis germplasms, the highest frequency showed to 180 days for 2013, and 170 days for 2014. In the results of correlation between the day of years from ST to FS2 for 2013 and 2014, M. sacchriflorus and M. sinensis showed high coefficient of correlation (0.70 and 0.89). It can be supposed that flowering characteristics of Miscanthus are largely affected by the unique phenotypic characteristic of native habitat than environmental factors of the current planted site. This study for flowering traits of Miscanthus may provides an important information in order to expedite the introduction as breeding materials for creation of new hybrid.