• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.366-369
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• 2002

Subsurface biobarrier technology has potential applications to contain contaminated groundwater and/or to degrade toxic pollutants in groundwater. Most biobarrier studies were conducted under aerobic condition, however there were several obstacles to make aerobic condition. Thus, In this study, we examined biobarrier formation under denitrifying condition by using nitrate as an electron acceptor. Experiments were performed with a sand column inoculated with activated sludge from the nearby WWTP. The substrate medium was pumped to the sand column in an upflow mode. During the low substrate loading rate period, the extent of reduction rate in hydraulic conductivity was found similar throughout the column, and permeability became relatively stable after couple of days. However, during the high substrate loading rate period, the column demonstrated a gradient of permeability reduction, with the greatest reduction in sections nearest the column inlet. Rapid growth of microorganisms near the column inlet resulted in the unbalanced reduction of hydraulic conductivity throughout the sand column. As a result, at this denitrifying condition the thickness of biobarrier could be controlled by adjusting the medium conditions of microbial growth.

• 한국환경과학회지
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• 제11권3호
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• pp.209-214
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• 2002

The lab-scale anaerobic continuous reactor which was filled with the sludge of anaerobic digestion from Suyoung wastewater treatment plant was operated by feeding of various concentrations and flow rates. This experiment indicated that more than 6,870 mgCOD/L of substrate concentration was required to promote good metabolism and growth of anaerobic biomass. And increasing loading rate slowly was also required in order to treat substrate of higher concentration and higher loading rate. The substrate concentration of about 10,000 mgCOD/L was adequate to generate biogas efficiently. The pH was sharply decreased at the onset of higher leading rate, but the pH was restabilized soon at 8. During the experiment, the amount of the attached biomass was kept constant.

• 한국재료학회지
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• 제14권3호
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• pp.163-167
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• 2004

TiAl(La)N thin films were oxidized in vacuum of about 7 Pa to reduce the oxidation of WC-Co as a substrate. The oxidation rate constants of the thin films were quantified by an assumption of parabolic oxidation. Increasing AI content significantly decreased the parabolic oxidation rate constant. A simultaneous addition of AI and La was more effective to reduce the oxidation rate. The parabolic oxidation rate constant of $Ti_{0.66}$ $Al_{0.32}$ $La_{ 0.02}$N thin film at 1273 K showed about ten times lower than that of TiN. The addition of a small amount of La with Al induced the preferential formation of dense $\alpha$ $-Al_2$$O_3$ film in oxide film, leading to the abrupt reduction of oxidation rate.

• 한국결정성장학회지
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• 제11권4호
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• pp.166-169
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• 2001

6H-SiC bulk crystals were grown by sublimation method with different conditions in term of gaseous pressures ad source temperatures. In order to optimize the growth rate, pressure at growth period and source and substrate temperatures were investigated as experimental variables. the results were compared with each other and finally the optimum growth conditions were discussed. Furthermore the relation of the growth steps and defects formation was evaluates in the point of reducing the micropipes. Subsequently the growth steps and defects formation was evaluated in the point of reducing the micropipes. Subsequently the growth steps were observed leading to the lower step height with the lower growth rate.

• 접착 및 계면
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• 제4권2호
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• pp.1-9
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• 2003

Epoxy-amine liquid prepolymers are extensively applied onto metallic substrates and cured to obtain painted materials or bonded joint structures. Overall performances of such systems depend on the created interphase between the organic layer and the substrate. When epoxy-amine liquid mixtures are applied onto more or less hydrated metallic oxide layer, concomitant amine chemical sorption and hydroxide dissolution appear lending to the chelate formation. As soon as the chelate concentration is higher than the solubility product, these species crystallize as sharp needles. Moreover, intrinsic and thermal residual stresses are developed within painted or bonded systems. When residual stresses are higher than the organic layer/substrate adhesion, buckling, blistering, debonding may occur leading to a catastrophic drop of system performances. Practical adhesion can be evaluated with either ultimate parameters (Fmax or Dmax) or the critical strain energy release rate, using the three point flexure test (ISO 14679-1997). We observe that, for the same system, the ultimate load decreases while residual stresses increase when the liquid/solid time increases. Ultimate loads and residual stresses depend on the metallic surface treatment. For these systems, the critical strain energy release rate which takes into account the residual stress profile and the Young's modulus gradient remains quite constant whatever the metallic surface treatment was. These variations will be discussed and correlate to the formation mechanisms of the interphase.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• Journal of Welding and Joining
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• 제25권1호
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• pp.30-36
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• 2007

A joining of dissimilar metal combination faces significant problems such as poor strength and cracking associated with brittle intermetallic compounds(IMC) formed. An application of laser allows low heat input; leading to less dilution and smaller heat affected zone. The $CO_2$ laser overlay was conducted on an AC2B alloy with feeding Fe-based powders. The overlay area was significantly influenced from the travel velocity rather than the powder feeding rate. The interface between the overlay and substrate consisted of the hard and brittle IMC($FeAl_3,\;Fe_3Al,\;Fe_2Al_5$), which initiating and propagating the crack. The reciprocating test for the slide wear was conducted on a multi-pass overlay experiment. Comparing with the multi-pass overlay with no overlap, the overlay with 50% overlap showed better wear resistance.

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.96-99
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• 2019

Atomic layer etching (ALE) is one of the most promising techniques in the semiconductor industry. Since ALE has to be precisely controlled on the angstrom scale to achieve ideal results, an in-situ analysis of the processes is highly required. In this regard, we found during ALE experiments with in-situ monitoring with an ellipsometer that changes in the substrate temperature affected the refractive index of a material, leading to changes in measured film thickness. In addition, more ideal ALE results could be achieved by keeping the substrate temperature constant.

• 한국산업융합학회 논문집
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• 제26권1호
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• pp.105-112
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• 2023

We analyze the global market for flexible electronic circuits, technical considerations, and analyze the market for application areas and regions. In the market analysis of the application field, the display field has the greatest influence in terms of market size and annual growth rate, and the OLE D lighting market size is expected to grow by nearly 50% in 2026. The multilayer flexible electronics, which dependently requires the semiconductor technology, has a larger market size than other structures and its growth rate is relatively large, leading the market and will be further analyzed in depth. The market size of multilayer flexible electronics applied to display field is expected to show an annual growth rate of 21.1% from $2.7 billion in 2017 to $9.8 billion in 2026, and the OLED market is expected to grow by 75.2% during the same periods. Recently, as electronic products have been miniaturized and advanced, and robust installation in a small space is required, companies that preoccupy multilayer structure or rigid flexible electronic circuit technology have an advantage in competitiveness, so many companies are trying to obtain this technology. These efforts are systematically supported by many countries because they can achieve mutual growth by strengthening the competitiveness of the application field and the same industry. In the case of Korea, a support system is established, but it is required to expand and activate it, and to localize manufacturing equipment and materials.

• Journal of electromagnetic engineering and science
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• 제14권3호
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• pp.314-316
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• 2014

This letter presents two types of metamaterial-inspired absorbers adopting resistive trumpet structures at the X band. The unit cell of the first type is composed of a trumpet-shaped resonator loading a chip resistor, a metallic back plane, and a FR4 (${\varepsilon}_r=4.4-j0.02$) substrate between them (single-layer). The absorption rate is 99.5% at 13.3 GHz. The full width at half maximum (FWHM) is 95 % at 11.2 GHz (from 5.9 to 16.5 GHz). The size of unit cell is $5.6{\times}5.6{\times}2.4mm^3$. The second type has been optimized with a $7{\Omega}$/square uniform resistive coating, removing the chip resistors but leading to results comparable to the first type. The proposed absorbers are almost insensitive to polarizations of incident waves due to symmetric geometry.