• Environmental Engineering Research
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• 제19권4호
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• pp.339-344
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• 2014

Different types of polyethersulfone (PES) support layer for a thin film composite (TFC) membrane were synthesized under various synthesis conditions using the phase inversion method to study the combined effects of substrate, adhesive, and pore former. The permeability, selectivity, pore structure, and morphology of the prepared membranes were analyzed to evaluate the membrane performance. The combined use of substrate, adhesive, and pore former produced a thinner dense top layer, with more straight finger-like pores. The pure water permeation (PWP) of the optimized PES membrane was $27.42L/m^2hr$ (LMH), whereas that of bare PES membrane was 3.24 LMH. Moreover, membrane selectivity, represented as divalent ion ($CaSO_4$) rejection, was not sacrificed under the synthesis conditions, which produced the dramatically enhanced PWP. The high permeability and selectivity of the PES membrane produced under the optimized synthesis conditions suggest that it can be utilized as a potential support layer for TFC membranes.

• 대한기계학회논문집
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• 제19권4호
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• pp.1033-1040
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• 1995

To simulate strength reliability and durability of ceramic parts under gas turbine application environments, particle impact damage behaviors in silicon carbide oxidized at 1673 K and 1523 K for 200 hours in atmosphere were investigated. The long-term oxidation produced a slight increase in the static fracture strength. Particle impact caused a spalling of oxide layer. The patterns of spalling and damage induced were dependent upon the property and impact velocity of the particle. Especially, the difference in spalling behaviors induced could be explained by introducing the formation mechanism of lateral crack and elastic-plastic deformation behavior at impact sit. At the low impact velocity regions, the oxidized SiC showed a little increase in the residual strength due to the cushion effect of oxide layer, as compared with the as-received SiC without oxide layer.

• 한국지반공학회논문집
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• 제35권8호
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• pp.5-15
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• 2019

이 연구는 오염원 유출을 방지하기 위한 해상폐기물매립장 차수시스템에 요구되는 적절한 기준을 제안하기 위해 수행되었다. 차수시스템은 바닥층과 연직벽으로 구성된다. 바닥층은 불투수 점토층으로 연직벽은 이중벽체로 외곽벽체는 강관쉬트파일로 외력에 대한 저항을 담당하고 연직내부벽체가 차수를 담당하는 것으로 가정하였다. SEEP/W와 CTRAN/W 프로그램을 이용하여 침투-이류-분산 해석을 정상류 및 비정상류 조건에서 실시하였다. 해석결과, 정상류 조건에서 비정상류 조건 보다 오염원 이동이 크게 나타나 설계관점에서 차수기준은 정상류조건에서 산정된 값을 적용하는 것이 타당한 것으로 나타났다. 바닥층의 점토지반이 균질하고 연직차수시스템의 시공에 문제가 없다는 전제하에 정상류조건에서 오염원 이동의 차수에 요구되는 점토층 및 연직차수벽의 투수계수, 두께, 근입깊이 등이 제안되었다.

• Geomechanics and Engineering
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• 제28권3호
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• pp.209-224
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• 2022

In this study, the numerical analysis model of π-beam explosion is established to compare and analyze the failure modes of the π-beam under the action of explosive loads, thus verifying the accuracy of the numerical model. Then, based on the numerical analysis of different protection forms of π beams under explosive loads, the peak pressure of π beam under different protection conditions, the law of structural energy consumption, the damage pattern of the π beam after protection, and the protection efficiency of different protective layers was studied. The testing results indicate that the pressure peak of π beam is relatively small under the combined protection of steel plate and aluminum foam, and the peak value of pressure decays quickly along the beam longitudinal. Besides, as the longitudinal distance increases, the pressure peak attenuates most heavily on the roof's explosion-facing surface. Meanwhile, the combined protective layer has a strong energy consumption capacity, the energy consumed accounts for 90% of the three parts of the π beam (concrete, steel, and protective layer). The damaged area of π beam is relatively small under the combined protection of steel plate and aluminum foam. We also calculate the protection efficiency of π beams under different protection conditions using the maximum spalling area of concrete. The results show that the protective efficiency of the combined protective layer is 45%, demonstrating a relatively good protective ability.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.83-88
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• 1994

Recently, the equipments of the structure are increasing remarkably. It is very important to evaluate the stability of the domes under concentrated loading such as a large-scale illuminating, visional, and sound equipment. The paper is aimed at investigating the buckling characteristics of single-layer latticed domes with triangular network under the uniformly distributed vertical-loading and the partially concentrated equipment-loading. The results show that the effects of the equipment-loading on the buckling strength is much more sensitive in domes of overall buckling than in domes of member buckling.

• ETRI Journal
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• 제35권6호
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• pp.1068-1074
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• 2013

This paper proposes an additional forward error correction (FEC) layer to compensate for the defectiveness inherent in the conventional FEC layer in the Long Term Evolution specifications. The proposed additional layer is called a graceful degradation (GD)-FEC layer and maintains desirable service quality even under burst data loss conditions of a few seconds. This paper also proposes a non-delayed decoding (NDD)-GD-FEC layer that is inherent in the decoding process. Computer simulations and device-based tests show a better loss recovery performance with a negligible increase in CPU utilization and occupied memory size.

• 한국지반신소재학회논문집
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• 제18권4호
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• pp.97-106
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• 2019

본 연구는 오염원 유출을 방지하기 위한 경사식호안 해상폐기물매립장 차수시스템에 요구되는 적절한 기준을 제안하기 위하여 해석을 수행하였다. 차수시스템은 바닥과 측면으로 구성하였다. 바닥차수시스템은 불투수 점토층이 측면차수시스템은 HDPE 차수시트가 주 역할을 하고 부수적으로 중간보호층이 차수를 담당한다. SEEP/W와 CTRAN/W 프로그램을 이용하여 침투·이류 분산 해석을 실시하였다. 해석결과, 바닥차수시스템인 점토층에 대하여 요구되는 투수계수와 두께가 제안되었다. 측면차수시스템인 HDPE 차수시트에 대해서는 설치길이와 중간보호층에 대해서는 요구되는 투수계수가 제안되었다.

• 한국표면공학회지
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• 제29권6호
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• pp.615-620
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• 1996

Chromium-Molybdenum steel was plasma-nitrided at 823 K for 10.8 ks in an atmosphere of 30% $N_2$-70% $H_2$ gas under 665 Pa without and with a subsidiary cathode of $MoS_2$ to compare ion-nitriding and plasma-sulfnitriding using subsidiary cathode. When the steel was ion-nitrided without $MoS_2$, iron nitride layer of 4$\mu\textrm{m}$ and nitrogen diffusion layer of 400mm were formed on the steel. A compound layer of 15$\mu\textrm{m}$ and nitrogen diffusion layer of 400$\mu\textrm{m}$ were formed on the surface of the steel plasma-sulfnitrided with subsidiary cathode of $MoS_2$. The compound layer consisted of FeS containing Mo and iron nitrides. The nitrides of $\varepsilon$-$Fe_2$, $_3N$ and $\gamma$-$Fe_4N$ formed under the FeS. The thicker compound layer was formed by plasma-sulfnitriding than ion-nitriding. In plasma-sulfnitriding, the surface hardness was about 730 Hv. The surface hardness of the steel plasma-sulfnitrided with $MoS_2$ was lower than that of ion-nitrided without $MoS_2$. This may be due to the soft FeS layer formed on the surface of the plasma-sulfnitrided steel.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.252-253
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• 2011

ZnO-based thin film transistors (TFTs) are of great interest for application in next generation flat panel displays. Most research has been based on amorphous indium-gallium-zinc-oxide (IGZO) TFTs, rather than single binary oxides, such as ZnO, due to the reproducibility, uniformity, and surface smoothness of the IGZO active channel layer. However, recently, intrinsic ZnO-TFTs have been investigated, and TFT- arrayss have been demonstrated as prototypes of flat-panel displays and electronic circuits. However, ZnO thin films have some significant problems for application as an active channel layer of TFTs; it was easy to change the electrical properties of the i-ZnO thin films under external conditions. The variable electrical properties lead to unstable TFTs device characteristics under bias stress and/or temperature. In order to obtain higher performance and more stable ZnO-based TFTs, HZO thin film was used as an active channel layer. It was expected that HZO-TFTs would have more stable electrical characteristics under gate bias stress conditions because the binding energy of Hf-O is greater than that of Zn-O. For deposition of HZO thin films, Hf would be substituted with Zn, and then Hf could be suppressed to generate oxygen vacancies. In this study, the fabrication of the oxide-based TFTs with HZO active channel layer was reported with excellent stability. Application of HZO thin films as an active channel layer improved the TFT device performance and bias stability, as compared to i-ZnO TFTs. The excellent negative bias temperature stress (NBTS) stability of the device was analyzed using the HZO and i-ZnO TFTs transfer curves acquired at a high temperature (473 K).

• 한국재료학회지
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• 제33권2호
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• pp.77-86
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• 2023

High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ' precipitate free zone) accompanied by Cr carbide of Cr₂₃C₆ and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several ㎛ depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or µ phase of TCP precipitation with the high-Cr component resulting in material brittleness.