• 한국세라믹학회지
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• 제50권2호
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• pp.122-126
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• 2013

The surface roughness of the inner and outer surfaces of a tube is an important requirement for nuclear fuel cladding. When an inner SiC clad tube, which is considered as an advanced Pressurized Water Cooled Reactor (PWR) clad with a three-layered structure, is fabricated by Chemical Vapor Deposition (CVD), the surface roughness of the substrate, graphite, is an important process parameter. The surface character of the graphite substrate could directly affect the roughness of the inner surface of SiC deposits, which is in contact with a substrate. To evaluate the effects of the surface roughness changes of a substrate, SiC deposits were fabricated using different types of graphite substrates prepared by the following four polishing paths and heat-treatment for purification: (1) polishing with #220 abrasive paper (PP) without heat treatment (HT), (2) polishing with #220 PP with HT, (3) #2400 PP without HT, (4) polishing with #2400 PP with HT. The average surface roughnesses (Ra) of each deposited SiC layer are 4.273, 6.599, 3.069, and $6.401{\mu}m$, respectively. In the low pressure SiC CVD process with a graphite substrate, the removal of graphite particles on the graphite surface during the purification and the temperature increasing process for CVD seemed to affect the surface roughness of SiC deposits. For the lower surface roughness of the as-deposited interlayer of SiC on the graphite substrate, the fine controlled processing with the completed removal of rough scratches and cleaning at each polishing and heat treating step was important.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2008년도 추계학술대회 초록집
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• pp.34-35
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• 2008

We investigated the effects of Pt nano electrodeposits on the corrosion of carbon substrate in an acidic solution. The electrodes for experiments were prepared by electrodepositing Pt on carbon substrate in a solution of 5 mM $H_2PtCl_6$ and 0.5 M $H_2SO_4$ using pulse deposition technique. In cyclic voltammograms for the carbon electrodes with and without Pt nano electrodeposits, total anodic current including both currents from oxygen evolution reaction and carbon corrosion increased abruptly above a critical potential. In addition, the critical potential of the carbon electrodes with Pt nano electrodeposits was lower than that of bare carbon electrode. This phenomenon was more prominent at $75^{\circ}C$ than $25^{\circ}C$. In potentiostatic experiments, the current transients and the corresponding power spectral density increased with increasing the applied potential for the electrodes. Furthermore, the current transients for the carbon electrodes with Pt nano electrodeposits were much higher than those for the bare carbon substrate. This indicates that the corrosion of carbon substrate can be highly accelerated by Pt nano electrodeposits.

• 한국재료학회지
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• 제15권11호
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• pp.741-744
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• 2005

Atomic layer deposition (ALD) is a very promising deposition technique for ZnO thin films. However, there have been very few reports on ZnO grown by ALD. Effects of substrate temperature in both ALD and post annealing on the microstructure and PL properties of ZnO thin films were investigated using X-ray diffraction, photoluminescence, and scanning electron microscopy. The temperature window of ALD is found to be between $130-180^{\circ}C$. The growth rate of ZnO thin film increases as the substrate temperature increases in the temperature range except the temperature window. The crystal quality depends most strongly on the substrate temperature among all the growth parameters of ALD. The crystallinity of the film is improved by increasing the growth thine per ALD cycle or doing post-annealing treatment. The grain size of the film tends to increase and the grain shape tends to change from a worm-like longish shape to a round one as the annealing temperature increases from $600^{\circ}C\;to\;1,000^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1879-1881
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• 1999

(Ba,Sr)$TiO_3$[BST] thin films were fabricated on Pt/Ti/$SiO_2$/Si substrate by RF sputtering. We investigated the effects of substrate temperature on the structural and dielectric properties of BST thin films. Increasing the substrate temperature, barium multi titanate phases were decreased, and BST (100), (200) peaks were increased. The relative dielectric constant and dielectric loss of the BST thin films at the substrate temperature of $500^{\circ}C$ were 300 and 0.018, respectively at l[kHz]. In all films, the dielectric constants decreased. Dielectric losses increased as increasing the frequency. The switching voltage was 5V of the BST thin films at the substrate temperature of $500^{\circ}C$.

• 한국연소학회지
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• 제8권2호
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• pp.50-55
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• 2003

Synthesis of carbon nanofibers on a metal substrate by an ethylene fueled inverse diffusion flame was observed. Stainless steel plates were used for the catalytic metal substrate. The effects of radial distance and residence time of the substrate were investigated. The role of hydrocarbon composition in the fuel was also viewed. Nanofibers with a diameter range of 30-70nm were found on the substrate. The carbon nanofibers were formed and grown in the region from 4 to 5.5mm from the central axis of a flame outside of the visible flame front in the radial direction. The minimum residence time required for the formation of carbon nanofibers were about 20 seconds, and over 60 seconds were required for the full-scale growth. The characteristic time of the formation of carbon nanofibers was much shorter than that of the substrate temperature growth. In this study, the variation in hydrocarbon composition had no significant effect on the formation and growth of the carbon nanofibers.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.40-47
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• 2002

Because UV wavelength lights can activate photocatalysts, plasma is used as a light source of a photocatalytic reactor. Even though plasma has good intensity for photo reaction, substrate of catalyst coating was limited by the geometry of plasma generator. Usually bead type substrate was used for a pack bed type reactor. Honeycomb monolith type substrate was used with UV lamps instead plasma, due to the light penetration the honeycomb monolith length was too short to show good activity In this study a photocatalytic reactor, which is using a honeycomb monolith substrate, was investigated with plasma as an activation light source. As a parametric study the effects of 1311owing factors on plasma generation and power consumption are examined; supply voltage, substrate length, environment condition, catalyst loading and ratio. Using the test results, the practicability test was done with simulated synthetic gases representing bad smells and automotive exhaust gases.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.162-168
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• 1997

A theoretical model for the interaction of the moving heat source and a solid substrate when they are in contact is described. for purposes of the model the substrate is assumed to act as a continuum and the Fourier equation for transient. three-dimensional conduction is solved using Laplace and Fourier transformations. Unlike most previous models, this model shows the explicit relations between the properties of heat source and that of the substrate. Since the size, shape and speed of heat source impact the ignition of substrate, considerable attention is devoted to evaluating these parameters. Results are presented which show the effects of the size, shape and speed of heat source on the substrate.

• 전자공학회논문지
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• 제51권7호
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• pp.49-59
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• 2014

개구면 결합 마이크로스트립 패치 안테나(aperture coupled microstrip patch antenna; ACMPA)의 급전 기판의 유전상수와 두께가 안테나 대역폭과 방사특성에 미치는 영향에 대하여 연구하였다. 급전 기판의 두께가 같은 여러 가지 유전상수의 급전기판을 가지는 ACMPA의 최적화된 반사손실 대역폭은 방사특성의 저하 없이 급전기판의 유전상수가 감소할수록 대역폭이 증가한다. MMIC(monolithic microwave integrated circuit)와 집적화가 가능한 높은 유전상수(${\epsilon}_r=10$)를 가지는 급전 기판을 사용한 ACMPA의 최적화된 반사손실 대역폭은 방사특성의 저하 없이 급전 기판의 두께가 감소할수록 대역폭이 증가한다. 따라서 ACMPA는 MMIC와 집적화하기에 좋은 구조를 가진 패치 안테나이다.

• Mycobiology
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• 제43권4호
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• pp.423-434
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• 2015

The study was conducted to compare the effects of different agro-wastes on the growth, yield, and nutritional composition of oyster mushrooms Pleurotus ostreatus (PO) and Pleurotus cystidiosus (PC). Seven substrate formulas including sawdust (SD), corncob (CC), sugarcane bagasse (SB) alone and in combination of 80 : 20, 50 : 50 ratio between SD and CC, SD and SB were investigated. The results indicated that different substrate formulas gave a significant difference in total colonization period, characteristics of fruiting bodies, yield, biological efficiency (BE), nutritional composition and mineral contents of two oyster mushrooms PO and PC. The results showed that increasing CC and SB reduced C/N ratio, and enhanced some mineral contents (Ca, P, and Mg) of substrate formulas. The increased amount of CC and SB of substrate formulas enhanced protein, ash, mineral contents (Ca, K, Mg, Mn, and Zn) of fruiting bodies of both mushrooms. Substrates with 100% CC and 100% SB were the most suitable substrate formulas for cultivation of oyster mushrooms PO and PC in which they gave the highest values of cap diameter, stipe thickness, mushroom weight, yield, BE, protein, fiber, ash, mineral content (Ca, K, and Mg) and short stipe length. However, substrate formula 100% CC gave the slowest time for the first harvest of both mushrooms PO and PC (46.02 days and 64.24 days, respectively). It is also found that the C/N ratio of substrate formulas has close correlation with total colonization period, mushroom weight, yield, BE and protein content of mushroom PO and PC.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.4-4
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• 2011

Extensive research efforts are directed toward the development of highly sensitive gas sensors using novel nanostructured materials. Among the different strategies for producing sensor devices based on nanosized building blocks, polymeric fiber templating approach which is combined by chemical and physical synthesis routes was attracted much attention. This unique morphology increases the surface area and reduces the interfacial area between film and substrate. Consequently, the surface activity is markedly enhanced while deleterious interfacial effects between film and substrate are significantly reduced. Both effects are highly advantageous for gas sensing applications. In this presentation, facile synthesis of hollow and porous metal oxide nanostructures and their applications in chemical sensors will be discussed.