• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.197-206
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• 2017

The microstructure of a high-carbon and high-chromium cast steel (HK700) for cold-work die inserts was analyzed by advanced scanning electron microscopy. A continuous network of primary $M_7C_3$ carbide was developed among austenitic matrix after casting. A small amount of $M_2C$ was added to the carbide network owing to the enrichment of Mo and W during the solidification. After quenching in which the austenitization was performed at $1030^{\circ}C$ and double tempering at $520^{\circ}C$, the network structure of $M_7C_3$ was preserved while most of the matrix was transformed to martensite because of additional carbide precipitation. The $M_2C$ in the as-cast microstructure was also transformed to $M_6C$ due to its instability. The continuous network of coarse carbides owing to the absence of hot-working had little influence on the hardness after quenching and tempering, whereas it resulted in severe brittleness upon flexural loading.

• Macromolecular Research
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• v.11 no.2
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• pp.104-109
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• 2003

A microcellular, which combines a rubber with the conventional formulation of styrene/divinylbenzene/sorbitan monooleate/water system, was prepared using high internal phase emulsion (HIPE) polymerization. Although the open microcellular foam with low density from the conventional HIPE polymerization shows highly porous characteristics with fine, regular and isotropic structure, the one having much smaller cell size is desirable for various applications. In this study, a polybutadiene was introduced to reduce the cell size with comparable properties. Major interests were focused on the effects of rubber concentration and agitation speed on the cell sizes and compression properties. Scanning electron microscopy was used to observe the microcellular morphology and compression tests were conducted to evaluate the stress-strain behaviors. It was found that the cell size decreased as rubber concentration increased, reflecting a competition between the higher viscosity of continuous phase and the lower viscosity ratio of dispersed to continuous phases due to the addition of high molecular weight rubber into the oil phase of emulsion. A correlation for the average cell size depending on agitation speed was attempted and the result was quite satisfactory.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.150-152
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• 2003

YBa$_2$Cu$_3$O$_{7-{\delta}}$(YBCO) coated conductors were deposited by pulsed laser deposition (PLD) on short buffered substrate in continuous PLD reel-to-reel system. The oxide multilayer buffered substrate of architectures of CeO$_2$/YSZ/Y$_2$O$_3$was fabricated by PLD at steady status. The degree of texture of each layer was investigated using X-ray diffraction including $\theta$-2$\theta$ scans, $\omega$-scans and $\Phi$-scans analysis. Their surface morphology was observed by scanning electron microscopy (SEM) The FWHM of the X-ray $\omega$-scans and $\Phi$-scans indicated that YBCO and buffer layers closely replicate the in-plane and out-of-plane texture of metal tape. Critical current at 77K self-field of 19A, critical temperature of 86K, and current density of 2MA/$\textrm{cm}^2$ were measured. The film also exhibits a homogeneous and dense surface morphology.e morphology.

• The Korean Journal of Food And Nutrition
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• v.10 no.2
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• pp.234-240
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• 1997

Agar has widely been used as medical aids and food ingredients due to its pecular physicochemical and rheological properties. In this paper, the effects of spray drying and extrusion drying on functional properties of agar were investigated to clarify the sol-gel transition mechanism at low temperature and microstructure of agar gel by measuring phase transition by differential scanning calorimetery, structural differences by light microscope and scanning electron microscope observation. The lowest endothermic onset(To), peak(Tp), conclusion(Tc) temperature and enthalpy($\Delta$H) using differential scanning calorimetery were showed in extrusion-dried agar wic were checked in 41.30, 61.72, 80.50 and 0.73cal/g. In cases of unmodified and spray-dried, the values were 81.20, 95.51, 112.14 and 3.22cal/g, and 60.11, 76.45, 89.54 and 1.53cal/g, respectively. When all samples were reheated using differential scanning calorimetery after gelling fully, no significant differences of endothermic To, Tp, Tc and $\Delta$H appeared. The surface structure of unmodified agar powder observed by light microscope and scanning electron microscope appeared a continuous surface without any indication of small pores, gaps or point of discontinuity. In cases of spray-dried agar, the unstable structures with pores was resulted. The microstructures of extrusion-dried agar, however, was solid with large gaps and areas of discontinuity in the surface. From the results above, it was suggested that significant differences in phase transition and surface microstructures were clearly related to the physicochemical changes and rheological properties, solubility and gelling ability of the types of agar gel.

• Journal of the Korean institute of surface engineering
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• v.48 no.2
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• pp.38-42
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• 2015

Atomic layer deposition (ALD) is essential for the fabrication of nanoscale electronic devices because it has excellent conformality, atomic scale thickness control, and large area uniformity. Metal thin films are one of the important material components for electronic devices as a conductor. As the size of electronic devices shrinks, the thickness of metal thin films is decreased down to few nanometers, and the metal films become non-continuous due to inherent island growth of metal below a critical thickness. So, fabrication of continuous metal thin films by ALD is fundamentally and practically important. Since ALD films are grown through self-saturated reactions between precursors on surface, initial growth characteristics significantly depend on the surface properties and the selection of precursors. In this work, we investigated ALD Pt on $TiO_2$ substrate by using trimethyl-methyl-cyclopentadienyl-Platinum ($MeCpPtMe_3$) precursor and $O_3$ reactant. By using $O_3$ instead of $O_2$, initial nucleation rate of ALD Pt was increased on $TiO_2$ surface, resulting in formation of continuous thin Pt films. Morphologies of ALD Pt on $TiO_2$ were characterized by using Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Crystallinity of ALD Pt on $TiO_2$ correlated with its growth characteristics was analyzed by X-Ray Diffraction (XRD).

• Preventive Nutrition and Food Science
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• v.4 no.1
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• pp.6-13
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• 1999

The quality of the buckwheat bread made with previously heated ($55^{\circ}C$) and cooled buckwheat flour 0dough with the addition of ascorbic acid(AA) or/and sodium stearoyl lactylate(SSL) was evaluated . With heat treatemtn , handling property of dough and grain of the bread crumb were markedly improved and stickiness of the dough decreased . The optimum resting time to produce the best loaf volume and grain was found to be 3hr for both unheated and heated doughs. Heat treated dough showed higher dough expansion rate during fermentation than unheated dough, even though heated dough had lower loaf volume, probably because of an improper oven spring. Increase in shortening of dough formula from 3% to 5% improved loaf volume without improvement of handling property. With the addition of 100 ppm AA or/and 0.5% SSL, loaf volume and crumb grain were improved for both unheated and heated doughs.Microscopic analysis of a mixed dough by scanning electron microscope (SEM) showed that heated dough had a continuous network whereas unheated dough was discontinuous. The addition of AA and SSL gave the dough a more continuous network whereas unheated dough was discontinuous . The addition of AA and SSL gave the dough a more continuous structure with strengthened strands or interactions between the starch granule and protein. Therefore, it appears that the presence of continuity in heated buckwheat breadwheat bread dough is related to the improved loaf volume and crumb grain without dough stickness.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.652-657
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• 2017

The use of continuous welded rail is increasing because of its many advantages, including vibration reduction, enhanced driving stability, and maintenance cost savings. In this work, two different types of continuous welded rails were examined to determine the influence of repeated wheel-rail contact on the crystal structure, microstructure and mechanical properties of the rails. The crystal structure was determined by x-ray diffraction, and the microstructure was examined using optical microscopy and scanning electron microscopy. Tensile and microhardness tests were conducted to examine the mechanical behaviors of prepared specimens taken from different positions in the cross section of both newly manufactured rail and worn rail. Analysis revealed that both the new and worn rail had a mixed microstructure consisting of ferrite and pearlite. The specimens from the top position of each rail exhibited decreased lamella spacing of the pearlite and increased yield strength, ultimate tensile strength and hardness, as compared with those from other positions of the rail. It is thought that the enhanced mechanical property on the top position of the worn rail might be explained by a mixed effect resulting from a directional microstructure, the decreased lamella spacing of pearlite, and work hardening by the repeated wheel-rail contact stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.253-253
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• 2009

Electrospinning is one of the simple, cost- efficient methods to produce long continuous semiconducting oxide nanofibers. Polyvinyl Alcohol (PVA) and zinc acetate were used. PVA/Zinc acetate aqueous solutions were electrospun into nonwoven webs. CCD camera, with a lens of long working distance and digital video board were used in capturing the drop and web deposition. The diameter and morphology of nanofibers were analyzed with a Field-emission scanning electron microscopy (FE-SEM). In this study, the average diameter and morphology of nanofibers have been explorered.

• Carbon letters
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• v.19
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• pp.47-56
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• 2016

In this study, the fracture behavior of a thermoplastic-modified epoxy resin reinforced with continuous carbon fibers for two levels of fiber-matrix adhesion was performed. A carbon fiber with commercial sizing was used and also treated with a known silane, (3-glycidoxy propyl trimethoxysilane) coupling agent. Toughness was determined using the double cantilever test, together with surface analysis after failure using scanning electron microscope. The presence of polysulfone particles improved the fracture behavior of the composite, but fiber-matrix adhesion seemed to play a very important role in the performance of the composite material. There appeared to be a synergy between the matrix modifier and the fiber-matrix adhesion coupling agent.

• Textile Coloration and Finishing
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• v.10 no.6
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• pp.27-32
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• 1998

도시 Traditionally, dyes extracted from onion shells have been used as natural pigments but dyeing methods with reproducibility have not been developed. In this study, the dyes were analyzed by high performance thin layer chromatography(HPTLC) to obtain the ratio of pigments in water and ethyl acetate extract. Furthermore, the present study was also carried out to obtain the information characteristic of wavelength which proportionally decrease for continuous dyeing reaction. Scanning of water extract showed 4 peaks by the mobile phase of benzene/ethyl acetate/acetic acid(40/10/5) and the peak 1 exhibited yellow color with the maximal absorption spectra of 306nm and 309nm while ethyl acetate extract showed 9 peaks in the same mobile phase. The water extract after ethyl acetate extraction was adjusted to 0.5 of O.D.(optical density) at 550nm by adding of water and compared wavelength of the pigments from 200 to 600nm to find the proportional decrease of wavelength. As the result, it showed that wavelength of 306nm could be the standard of dyeing monitoring points.