• Korean Journal of Materials Research
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• v.15 no.10
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• pp.626-631
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• 2005

GaN-related compound semiconductors were grown on the corrugated interface substrate using a metalorganic chemical vapor deposition system to increase the optical power of white LEDs. The patterning of substrate for enhancing the extraction efficiency was processed using an inductively coupled plasma reactive ion etching system and the surface morphology of the etched sapphire wafer and that of the non-etched surface were investigated using an atomic force microscope. The structural and optical properties of GaN grown on the corrugated interface substrate were characterized by a high-resolution x-ray diffraction, transmission electron microscopy, atomic force microscope and photoluminescence. The roughness of the etched sapphire wafer was higher than that of the non-etched one. The surface of III-nitride films grown on the hemispherically patterned wafer showed the nano-sized pin-holes that were not grown partially. In this case, the leakage current of the LED chip at the reverse bias was abruptly increased. The reason is that the hemispherically patterned region doesn't have (0001) plane that is favor for GaN growth. The lateral growth of the GaN layer grown on (0001) plane located in between the patterns was enhanced by raising the growth temperature ana lowering the reactor pressure resulting in the smooth surface over the patterned region. The crystal quality of GaN on the patterned substrate was also similar with that of GaN on the conventional substrate and no defect was detected in the interface. The optical power of the LED on the patterned substrate was $14\%$ higher than that on the conventional substrate due to the increased extraction efficiency.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.18-24
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• 2013

This study was conducted to recycle fly ash containing an abundance of CaO generated from combustion in a circulating layer as a carbon storage medium. The study utilized XRD, TG-DTA and XRF analyses during the hydration of fly ash and identified calcium substances within fly ash that could be used in a carbonation process. $Ca^{2+}$ ions in the calcium substances were easily converted to hydrates. A carbonation experiment was done, which used the method of $CO_2$ gas injection to produce suspensions by mixing fly ash with distilled water. The results were analyzed using TG-DTA, XRD, and pH meter measurements. The study was able to verify that the reaction was completed at a $CO_2$ flow rate of 300cc/min approximately 30 minutes after an injection into a solution with a solid-liquid ratio of 1 : 10 of fly ash and distilled water. Moreover, the stirring time of the suspensions did not influence the reaction, and the reaction time was found to diminish as the portion of the fly ash became smaller. Thus, this study produced carbon storage fly ash having a $CO_2$ storage rate of about 71% through the utilization of the CaO content contained within fly ash.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.557-565
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• 2014

We report the effect of basal-plane stacking faults (BSFs) on X-ray diffraction (XRD) of non-polar (11$\underline{2}$0) a-plane GaN films with different $SiN_x$ interlayers. Complete $SiN_x$ coverage and increased three-dimensional (3D) to two-dimensional (2D) transition stages substantially reduce BSF density. It was revealed that the Si-doping profile in the Si-doped GaN layer was unaffected by the introduction of a $SiN_x$ interlayer. The smallest in-plane anisotropy of the (11$\underline{2}$0) XRD ${\omega}$-scan widths was found in the sample with multiple $SiN_x$ layers, and this finding can be attributed to the relatively isotropic GaN mosaic resulting from the increase in the 3D-2D growth step. Williamson-Hall (WH) analysis of the (h0$\underline{h}$0) series of diffractions was employed to determine the c-axis lateral coherence length (LCL) and to estimate the mosaic tilt. The c-axis LCLs obtained from WH analyses of the present study's representative a-plane GaN samples were well correlated with the BSF-related results from both the off-axis XRD ${\omega}$-scan and transmission electron microscopy (TEM). Based on WH and TEM analyses, the trends in BSF densities were very similar, even though the BSF densities extracted from LCLs indicated that the values were reduced by a factor of about twenty.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.467-468
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• 2009

For the manufacture of the $CuGaS_2$, Cu, Ga and S were vapor-deposited in the named order. Among them, Cu and Ga were vapor-deposited by using the Evaporation method in consideration of their adhesive force to the substrate so that the composition of Cu and Ga might be 1 : 1, while the surface temperature having an effect on the quality of the thin film was changed from R.T.[$^{\circ}C$] to $150[^{\circ}C$] at intervals of 50[$^{\circ}C$]. As a result, at 300[$^{\circ}C$]of the Annealing temperature, their chemical composition was measured in the proportion of 1 : 1 : 2. It could be known from this experimental result that it is the optimum condition to conduct Annealing on the $CuGaS_2$ thin film under a vacuum when the $CuGaS_2$ thin film as an optical absorption layer material for a solar cell is manufactured.

• Toxicological Research
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• v.32 no.2
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• pp.103-108
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• 2016

The purpose of this study was to determine the hair growth effects of lavender oil (LO) in female C57BL/6 mice. The experimental animals were divided into a normal group (N: saline), a vehicle control group (VC: jojoba oil), a positive control group (PC: 3% minoxidil), experimental group 1 (E1: 3% LO), and experimental group 2 (E2: 5% LO). Test compound solutions were topically applied to the backs of the mice ($100{\mu}L$ per application), once per day, 5 times a week, for 4 weeks. The changes in hair follicle number, dermal thickness, and hair follicle depth were observed in skin tissues stained with hematoxylin and eosin, and the number of mast cells was measured in the dermal and hypodermal layers stained with toluidine blue. PC, E1, and E2 groups showed a significantly increased number of hair follicles, deepened hair follicle depth, and thickened dermal layer, along with a significantly decreased number of mast cells compared to the N group. These results indicated that LO has a marked hair growth-promoting effect, as observed morphologically and histologically. There was no significant difference in the weight of the thymus among the groups. However, both absolute and relative weights of the spleen were significantly higher in the PC group than in the N, VC, E1, or E2 group at week 4. Thus, LO could be practically applied as a hair growth-promoting agent.

• Korean Journal of Materials Research
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• v.26 no.12
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• pp.681-687
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• 2016

Zirconium(Zr) nuclear fuel cladding tubes are made using a three-time pilgering and annealing process. In order to remove the oxidized layer and impurities on the surface of the tube, a pickling process is required. Zr is dissolved in HF and $HNO_3$ mixed acid during the process and pickling waste acid, including dissolved Zr, is totally discarded after being neutralized. In this study, the waste acid was recycled by adding $BaF_2$, which reacted with the Zr ion involved in the waste acid; $Ba_2ZrF_8$ was subsequently precipitated due to its low solubility in water. It is very difficult to extract zirconium from the as-recovered $Ba_2ZrF_8$ because its melting temperature is $1031^{\circ}C$. Hence, we tried to recover Zr using an electrowinning process with a low temperature molten salt compound that was fabricated by adding $ZrF_4$ to $Ba_2ZrF_8$ to decrease the melting point. Change of the Zr redox potential was observed using cyclic voltammetry; the voltage change of the cell was observed by polarization and chronopotentiometry. The structure of the electrodeposited Zr was analyzed and the electrodeposition characteristics were also evaluated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.32-32
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• 2009

Silicon carbide (SiC) is a wide-bandgap semiconductor that has materials properties necessary for the high-power, high-frequency, high-temperature, and radiation-hard condition applications, where silicon devices cannot perform. SiC is also the only compound semiconductor material. on which a silicon oxide layer can be thermally grown, and therefore may fabrication processes used in Si-based technology can be adapted to SiC. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, we investigated that the local oxide growth on SiC under various conditions and demonstrated that an increased (up to ~100 nN) tip loading force (LF) on highly-doped SiC can lead a direct oxide growth (up to few tens of nm) on 4H-SiC. In addition, the surface potential and topography distributions of nano-scale patterned structures on SiC were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the nano-scale patterned on SiC was higher than that of original SiC surface. The results confirm the concept of the work function and the barrier heights of oxide structures/SiC structures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.2
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• pp.193-197
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• 1997

Elevation of the activities of phase 2 enzymes such as quinone reductase(QR) provides protection against several types of neoplasia. In this study, we performed partial purification of QR inducer(s) from roasted and defatted perilla meal by solvent fractionation and thin layer chromatography. Cellular QR induction was most notable in chloroform fraction of roasted perilla extract, compared with other solvent fractions. QR inducer(s) was partially purified by TLC, with 0.8 of $R_f$ value in n-butanol : n-propanol : 2N-ammonium hydroxide(10 : 60 : 30). AHH-inducing activity in TLC fractions isolated from methanol extracts of roasted perilla comigrated with QR-inducing fraction, suggesting that QR and AHH are induced by the same compound. TLC fractions shown strong QR-inducing activity also had a potent antioxidative activity, suggesting that cellular QR enzyme is induced by antioxidant(s) present in roasted perilla.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.556-562
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• 2001

The antioxidative activity of marine microalgae, Phaeodactylum tricornutum (P. tricornutum) of Bacillariophyceae, was determined by measuring radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The chloroform fraction of P. tricornutum showed strong antioxidative activity, The potential antioxidative activity of factions extracted with mixture solution of organic solvents was detected in dichloromethane : methanol (2 : 1) fraction, This fraction was further purified by preparative thin layer chromatography (PTLC) and repeated reverse-phase HPLC. On the basis of chemical and spectoscopic evidence from results obtained by UV, FT-IR, EIMS and NMR, the compound purified from P. tricornutum was identified as zeaxanthin.

• Journal of the Korean Society of Costume
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• v.59 no.3
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• pp.82-95
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• 2009

The kind and the use of the fabrics for crown manufacture in the Baekje period has been studied by characterizing the imprinted fabrics on the crowns and the diadem ornaments from the old tomb. The contact region with the skin inside of the crown and the region between the bark of white birch and the gilt bronze openwork plates contained fabrics. The fabrics used in the gilt-bronze crown were all plain weave silk except that of Yongwonri tomb where loosely woven thin tabby was used. There have been 4-types of iron framed diadem of the Baekje, which comprise the inverted triangle-shaped diadem only with iron frame, the diadem with gold plate ornament in the iron frame, the diadem decorated with mica plate and gold plate, and the diadem with silver ornament in the iron frame. The fabrics used in the triangle shaped iron frame diadem include plain weave silk, irregular plain woven silk, thin tabby, complex silk gauze, twill weave on plain ground, and warp-faced compound weave. The iron frames were wrapped with the fabrics from one layer up to three layers, and the iron diadem was covered with one later of loosely woven textile such as irregular plain woven silk, thin tabby, and complex silk gauze. But in case of decorating the iron diadem with gold Plate ornaments, multiple layers of fabric were used to sustain the weight of the ornaments. The fabrics in the iron diadem frame were sewed with running stitch, overedge stitch or hemming stitch, diagonal hemming stitch, half back stitch), and overcast stitch.