• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.438-438
• /
• 2011

White light-emitting diodes (LEDs), the so-called next-generation solid-state lighting, offer benefits in terms of reliability, energy-saving, maintenance, safety, lead-free, and eco-friendly. Recently, rare-earth-doped oxynitride or nitride compounds have attracted a great deal of interest as a photoluminescent material because of their unique luminescent property, especially for white LEDs applications. Ce doped ${\beta}$-SiAlON has been studied as a wavelength conversion phosphor in white LEDs thanks to its high absorption rates, high quantum efficiency, and excellent thermal stability. Previously researches were not enough to understand the detail mechanism and characteristics of ${\beta}$-SiALON. The bandgap structures and electronic structures were not exact due to limitation of calculation methods. In this study, to elucidate the Ce doping effect on the SiAlON system, accurate band structures and electronic structure of the Ce doped ${\beta}$-SiAlON was intensively investigated using density functional theory calculations. In order to get a better description of the band gaps, MBJLDA method were used. We have found a single Ce atom site in ${\beta}$-SiAlON super cell. Furthermore, the density of state, band structure and lattice constant were intensively investigated.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.153-160
• /
• 2018

An environmentally favorable (chlorine-free) solid oxidizer, guanidinium dinitramide [GDN; $NH_2C(NH_2)NH_2N(NO_2)_2$], was newly synthesized from guanidine carbonate [$NH_2C(=NH)NH_2{\cdot}1/2H_2CO_3$]. Two different crystalline forms (${\alpha}-type$ and ${\beta}-type$) appeared according to the applied solvents and synthesis conditions. Moisture, during extraction, might become trapped in a crystal between inner molecules. Therefore, despite having the same chemical composition, Raman-IR and TGA-DSC revealed different physical characteristics of the two forms. Peaks of Raman shift near $1000cm^{-1}$ implied different chemical structures. Thermal analysis revealed an exothermic temperature $155.7^{\circ}C$ for ${\alpha}-type$ but one of $191.6^{\circ}C$ for ${\beta}-type$. The caloric value of ${\alpha}-type$ was 536.4 J/g, which was 2.5 times larger than that of the ${\beta}-type$, which was 1310 J/g. While the synthesized GDN of ${\alpha}-type$ showed a steep exothermic decomposition, the ${\beta}-type$ was slowly decomposed after melting through an endothermic process. This work implied that despite of the same molecular formula some different core thermal properties would appear depending on synthesis conditions.

• The Journal of Korean Medicine
• /
• v.34 no.3
• /
• pp.126-142
• /
• 2013

Objectives: Previous reports have shown that Bogijetong-Tang (BJT) is effective in peripheral neuropathy induced by taxol and crush injury. In this study, we researched the effects of BJT on diabetic neuropathy induced by STZ in the mouse. Methods: We performed both in vitro and in vivo experiments to verify the effects of BJT on diabetic neuropathy induced by STZ in mice. Changes in axonal recovery were observed with immunofluorescence staining using NF-200, Hoechst33258, $S100{\beta}$, caspase 3 and anti-cdc2. Proliferation and degeneration of Schwann cells were investigated by immunofluorescence staining and western blot analyses. Results: BJT showed considerable effects on neurite outgrowth and axonal regeneration in diabetic neuropathy. BJT contributed to the creation of NF-200, GAP-43, Cdc2, phospho-vimentin, ${\beta}1$, active ${\beta}1$, ${\beta}3$ integrin, phospho-Erk1/2 protein. Conclusions: Through this study, we found that BJT is effective for enhanced axonal regeneration via dynamic regulation of regeneration-associated proteins. Therefore, BJT had a pharmaceutical property enhancing recovery of peripheral nerves induced by diabetic neuropathy and could be a candidate for drug development after more research.

• Journal of Technologic Dentistry
• /
• v.28 no.1
• /
• pp.27-41
• /
• 2006

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

• Journal of the Korean Ceramic Society
• /
• v.34 no.8
• /
• pp.854-860
• /
• 1997

The tribological property of ceramics is very important for use in seal rings, pump parts, thread guides and mechanical seal, etc. In the present study, which RBSC/graphite composites were manufactured by adding graphite powders with different particle sizes to mixtures of SiC powder, metallic silicon, carbon black and alumina, effects on the tribological property of each RBSC/graphite composite was investigated in accordance with the particle size of the added graphite powder. The water absorption, the bending strength and the resistance for the friction and wear were measured, and the crystalline phase and the microstructure were respectively examined by using XRD and SEM. In case that the particle size of the graphite powder was fine(2${\mu}{\textrm}{m}$), the formation of $\beta$-SiC was accelerated, thereby making the increase of the bending strength and the decrease of the water absorption, but no improvement for the tribological properties. Furthermore, in case that the particle size of the graphite powder was some large(88~149${\mu}{\textrm}{m}$), the formation of $\beta$-SiC was not accelerated, to thereby make the decrease of the bending strength and the increase of the water absorption, but the improvement for the tribological property of only the composite having the graphite powder of 20 vol%. In addition, in case that the particle size distribution of the graphite powder was large (under 53 ${\mu}{\textrm}{m}$), there was no improvement for every properties. However, the composites, which the graphite powder with the particle size of 53~88 ${\mu}{\textrm}{m}$ was added in 10~15 vol%, had the most increased resistance for the friction and wear which show the worn out amount of 0.4~0.6$\times$10-3 $\textrm{cm}^2$, and the value of the bending strength is 380~520 kg/$\textrm{cm}^2$.

• Proceedings of the PSK Conference
• /
• 2003.10b
• /
• pp.82.2-83
• /
• 2003

Beta-amyloid peptide (A${\beta}$) is considered to be responsible for the pathogenesis of the Alzheimer's disease. Several lines of evidence support that A${\beta}$-amyloid-induced cytotoxicity is mediated through the generation of reactive oxygen species (ROS). Agents that are able to scavenge excess ROS may be useful as protecting or reducing agents for development or progress of AD. Green tea extract has been known to have antioxidant property. Our previous studies also demonstrate that green tea extract protected ischemia/reperfusion-induced brain injury by reduction of cell death through scavenging of oxidative damages of macromolecules. (omitted)

• Applied Chemistry for Engineering
• /
• v.32 no.5
• /
• pp.504-508
• /
• 2021

In this study, the effect of molecular features of guest molecules on the structure, property, and formation of poly(vinyl alcohol) (PVA)/beta-cyclodextrin (bCD) inclusion compound hybrid films was investigated using three types of guest molecules such as hydroquinone (HQ), arbutin (AB), and tranexamic acid (TA). First, the successful formation of inclusion compounds between bCD and the guest molecules, and polymer/inclusion compound hybrid were proved using Raman spectroscopy. The effect of bCD-based inclusion compounds on the structure and property of PVA matrix composites containing inclusion compounds was also studied using X-ray diffraction (XRD) and thermal analyses such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was notable that the effect of TA to the crystalline structure of the PVA was significantly different from that of using other guest molecules including HQ and AB. It was also supported by a simple molecular simulation result. This article will be a good example for demonstrating the effect of molecular characteristics on the inclusion compound formation in polymer films, which can provide important information for relevant future research.

• KSBB Journal
• /
• v.24 no.6
• /
• pp.563-569
• /
• 2009

Fibroin is an insoluble structural protein from Bombyx mori. It can be solubilized by dissolving in a hot $CaCl_2$ solution and subsequent dialysis. The aqueous solution is unstable and a transition from aqueous fibroin molecules rich in random coil is undergo to one rich in $\beta$-sheet content, resulting in hydrogelation. However, fibroin gel is so fragile and plastic that its mechanical property should be reformed for various applications. In this report, a semi-solid form of fibroin gel was prepared using glycerol and ethanol and was investigated to analyze their flow properties. A fibroin gel with 80% glycerol showed pseudoplastic and thixotropic properties. The square root of its yield stress varied linearly with fibroin concentration and it extrapolated to zero shear stress at 0.2% fibroin. A fibroin gel with 40% ethanol was shown to be highly thixotropic but its shear-thinning behavior was only observed above a certain level of shear rate. Its pseudoplasticity was restored by a high rate of shear stress.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.11
• /
• pp.1297-1306
• /
• 2015

The introduction of multimedia 119-notification service utilizing smart devices causes firefighters to be more exposed to emotional labor. The purpose of this study is to investigate the effect of increased emotional labor of firemen on job satisfaction. As a result, the higher the emotional labor of firefighters is, the higher job stress (${\beta}=0.166$, p=0.000) and social support(${\beta}=0.540$, p=0.000) are. But job satisfaction tends to be lower(${\beta}=-0.136$, p=0.000). As they play an important role to protect the safety and property of citizens. their job satisfaction becomes the driving force of their duty. Therefore, we think that some systematic and substantial prevention curriculum to manage their emotional labor is required.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.27 no.6
• /
• pp.795-801
• /
• 2013

The purpose of this study is to investigate effects of White Ginseng-Ejung-tang (EG) and Red Ginseng-Ejung-tang (ER) water extract on production of various cytokines such as interleukin (IL)-21, IL-25, IL-$28{\beta}$, erythropoietin (EPO), Exodus-2, monocyte chemotactic protein (MCP)-5, macrophage inflammatory protein (MIP)-$3{\alpha}$, MIP-$3{\beta}$, Fractalkine, and TARC in RAW 264.7 mouse macrophages stimulated by lipopolysaccharide (LPS). Levels of cytokines were measured by High-throughput multiplex bead array cytokine assay based on xMAP (multi-analyte profiling beads) technology. ER significantly decreased levels of IL-21, IL-25, IL-$28{\beta}$, EPO, Exodus-2, MCP-5, MIP-$3{\alpha}$, MIP-$3{\beta}$, TARC, and fractalkine for 24 h incubation at the oncentrations of 25 and 100 ${\mu}g/mL$ in LPS-induced RAW 264.7 (P < 0.05). But EG did not show any significant effect. These results suggest that ER has anti-inflammtory property related with its inhibition on the production of IL-21, IL-25, IL-$28{\beta}$, and chemokines such as EPO, MCP-5, MIP-$3{\alpha}$, MIP-$3{\beta}$, Fractalkine, Exodus-2, and TARC in LPS-induced macrophages.