• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.571-578
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• 2009

Recently, micropiling techniques are increasingly applied in foundation rehabilitation/underpinning and seismic retrofitting projects where working space provides the limited access for conventional piling methods. Micropiling techniques provide environmental-friendly methods for minimizing disturbance to adjacent structures, ground, and the environment. Its installation is possible in restrictive area and general ground conditions. The cardinal features that the installation procedures cause minimal vibration and noise and require very low ceiling height make the micropiling methods to be commonly used for underpin existing structures. In the design point of view, the current practice obligates the bearing capacity of micropile to be obtained from skin friction of only rock-socketing area, in which it implies the frictional resistance of upper soil layer is ignored in the design process. In this paper, a new micropiling method and its verification studies via field installation are presented. The new method provides a specific way to grout bore-hole to increase frictional resistance between surrounding soil and pile-structure and it allows to consider the skin friction of micropiles for upper soil layer during design process.

• Elastomers and Composites
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• 제30권3호
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• pp.185-194
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• 1995

Membrane process has been employed to separate a specific substance from gas or liquid mixture, and treat wastewater. This is due to the fact that the substance of mixture can be permeated and separated selectively by membrane. Since Initial equipment and operation costs are not expensive, membrane process has been adopted in various fields such as petroleum Industry, chemistry, polymer, electronics, foods, biochemical industry and wastewater treatment. In this study, $CaCO_3$ particles impregnated in silicone rubber network were extracted by using supercritical carbon dioxide and pore distribution of silicone $rubber-CaCO_3$ was investigated with varying amount of extract. Silicone rubber has excellent mechanical properties such as heat-resistance, cold-resistance etc. and $CaCO_3$ has microporous structure. It is possible to make silicone $rubber-CaCO_3$ composite sheets via work-intensive kneading processes. In so doing $CaCO_3$ particles become distributed and impregnated in silicone rubber network. Supercritical carbon dioxide diffuse through composite sample, then sample is swollen. $CaCO_3$ in silicone rubber network Is dissolved in supercritical carbon dioxide, and its sites become pores. Pore distribution, pore shape and surface area are observed by SEM(scanning electron microscope) micrograph and BET surface area analyzer examination respectively. Pore characteristics of membrane suggest the possibilities that the membrane can be used for process of mixture separation and wastewater treatment.

• 열처리공학회지
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• 제34권4호
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• pp.159-164
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• 2021

The Improvement of thermal performance using heat treatment of carbon nanotubes coated on the copper heat sink to take the radiation energy from solar ray for the energy harvesting in earth orbit. Using the additive coating of purified CNT for the increase of specific area and development of thermal conductive capacity, the performance of heat transfer is improved about 0.181 K/W while applying the power of 22 W under temperature of 3.98℃. Coating of purified CNT shows increase of area and volume of thermal layer however it led the partial thermal resistance.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.29-30
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• 2023

Wood is a construction material that has the advantages of carbon dioxide storage ability, noise reflection, and eco-friendliness. In order to use wood for a long time, you must use wood-specific paint, which is called oil stain. Oil stain improves water resistance and moisture resistance, but has the disadvantage of being weak against fire. This is because the oil contained in the oil stain causes a chemical reaction, and this chemical reaction causes the oil stain to spontaneously ignite, igniting nearby combustible materials and causing frequent fires. To improve this, in this study, different flame retardants were mixed and added to oil stain to produce functional oil stain. In addition, we would like to apply it to wood to check glow time and carbonization area. As a result of the experiment, it shows the best performance when mixed at 30(15 + 15)(%) and added to oil stain. The remaining burn time is satisfied from 10% for all samples, and the carbonized area is satisfied when it is 30%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.83.2-83.2
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• 2010

평판형 고체산화물 연료전지(planar SOFC : Solid oxide Fuelcell)는 높은 전류 효율 및 출력밀도를 가지는 중,대형 발전용 전기소자이다. SOFC 스택을 600~800도에서 작동할 경우, 금속 분리판에서 휘발된 크롬에 의한 열화현상과 금속의 산화에 의한 표면 저항의 증가가 큰 문제점으로 알려져 있으며, 이를 개선하기 위한 많은 연구가 진행되고 있다. 본 연구에서는 금속 분리판의 열화를 억제하기 위한 여러 보호코팅의 특성을 밝히고, 특성차이의 원인을 분석하고자 하였다. 모재는 상용 STS444합금 (Nisshin steel 생산) 2.0mmt 박판을 사용하였으며, 표면 상태를 균일하게 하기 위하여 표면은 동일한 #1200 번 사포로 연마후 코팅하였다. 적용한 코팅은 전기도금 Ni 코팅, (MnCo)3O4 wet powder spray 코팅, (MnCo)3O4 ADM코팅 3종이었으며, 코팅층의 두께는 최적 공정조건에 따라 달리 하였다. 산화후 형성되는 표면 산화물의 전기적 특성을 평가하기 위하여 시험편의 비면적 저항 (ASR : area specific resistance)을 장시간 측정하였다. 측정편의 크기는 가로 4cm ${\times}$ 세로 4cm였으며, 100시간 공기중 산화후 측정하였다. 표면 접촉을 높이기 위하여 Pt paste를 40~50um도포하였으며, 1~0.1A인가된 전류에 대한 저항을 4전극법 (4-probe)으로 측정하였다. 표면 코팅층이 크롬 휘발을 억제하는 정도를 평가하기 위하여 크롬 휘발량을 측정하였다. 시편은 가로 1.5cm ${\times}$ 세로 1cm 였으며, 공급된 공기와 수분의 혼합가스와 응축기 표면에 흡착된 크롬의 양을 ICP-MASS법으로 측정하였다.

• 한국분말재료학회지
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• 제18권2호
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• pp.122-128
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• 2011

This study investigated the high temperature oxidation behavior of Ni-22.4%Fe-22%Cr-6%Al (wt.%) porous metal. Two types of open porous metals with different pore sizes of 30 PPI and 40 PPI (pore per inch) were used. A 24-hour TGA test was conducted at three different temperatures of $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. The results of the BET analysis revealed that the specific surface area increased as the pore size decreased from 30 PPI to 40 PPI. The oxidation resistance of porous metal decreased with decreasing pore size. As the temperature increased, the oxidation weight gain of the porous metal also increased. Porous metals mainly created oxides such as $Al_2O_3$, $Cr_2O_3$, $NiAl_2O_4$, and $NiCr_2O_4$. In the 40 PPI porous metal with small pore size and larger specific surface area, the depletion of stabilizing elements such as Al and Cr occurred more quickly during oxidation compared to the 30 PPI porous metal. Ni-Fe-Cr-Al porous metal's high-temperature oxidation micro-mechanism was also discussed.

• 신재생에너지
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• 제18권2호
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• pp.40-49
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• 2022

In this study, the phase and electrochemical properties of Co and Ti substituted layered perovskites SmBaCo_2-xTi_xO_5+d (x=0.5, 0.7, 1.0, 1.1, 1.3, and 1.5) were analyzed, and their application as electrodes in solid oxide fuel cells (SOFCs) were evaluated. After calcination at 1300℃ for 6 h, a single phase was observed for two compositions of the SmBaCo_2-xTi_xO_5+d oxide system, SmBaCoTiO_5+d (x=1.0) and SmBaCo_0.9Ti_1.1O_5+d (x=1.1). However, the phases of SmBaCoTiO_5+d (SBCTO) and SmTiO₃ coexisted for compositions with x≥1.3 (Ti content). In contrast, for compositions of x≤0.7, the SmBaCo₂O_5+d phase was observed instead of the SmTiO₃ phase. To evaluate the applicability of these materials as SOFC electrodes, the electrical conductivities were measured under various atmospheres (air, N₂, and H₂). SBCTO exhibited stable semi-conductor electrical conductivity behavior in an air and N₂ atmosphere. However, SBCTO showed insulator behavior at temperatures above 600℃ in a H₂ atmosphere. Therefore, SBCTO may only be used as cathode materials. Moreover, SBCTO had an area specific resistance (ASR) value of 0.140 Ω·cm² at 750℃.

• 한국응용과학기술학회지
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• 제22권1호
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• pp.43-49
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• 2005

OXI-PAN fibers, Kynol fibers and rayon fibers were used as precursorsfor the preparation of activated carbon fibers (ACFs) by chemical activation with KOH at $800^{\circ}C$. The effects of different precursorfibers and fiber/KOH ratios on the final ACFs are discussed. The precursor fibers used are appropriate for the ACFs in a single stage pyrolysis process. The OXI-PAN fibers which were activated with KOH of 2.0M showed a specific surface area of $2328m^2/g$ however, loosed the fiber shape because of low yields. The Kynol fibers and Rayon fibers showed the high yields but the lower specific surface area of $900m^2/g$ and $774m^2/g$, respectively, at KOH of 1.5M. The OXI-PAN fibers which were activated with KOH of 1.5M have a specific surface area of $1028m^2/g$ and higher micro-pore volumes and lower yields rather than Kynol-1.5 and Rayon-1.5 samples. This phenomenon is because of higher chemical resistance of the Kynol and Rayon fibers rather than OXI-PAN fibers. However, the Kynol fibers were the best precursors on KOH activation at $800^{\circ}C$ considered carbon yields, surface areas and micropore volumes.

• 센서학회지
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• 제19권5호
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• pp.385-390
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• 2010

CO sensing thick film gas sensors using $Co_3O_4$ powders prepared by hydrothermal reaction method, were fabricated, and their structural, electrical and CO gas sensing properties were investigated. The specific surface area of the $Co_3O_4$ powders obtained from BET analysis was about 79.0 $m^2/g$. XRD and SEM results show that the thick films heat-treated at $500^{\circ}C$ for 30 min after screen printing had the preferred orientation of (311) direction and the crystalline size was calculated to 221 $\AA$. The maximum activation energy obtained from the temperature-resistance characteristics was 3.11 eV in the temperature range of $290^{\circ}C$ to $310^{\circ}C$. The sensitivity to 1,000 ppm CO was about 150 %. The specific surface area, crystalline size, and maximum activation energy were increased significantly and the sensitivity for CO gas was improved largely.

• 대한약침학회지
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• 제19권1호
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• pp.7-15
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• 2016

Objectives: Malaria has been a major global health problem in recent times with increasing mortality. Current treatment methods include parasiticidal drugs and vaccinations. However, resistance among malarial parasites to the existing drugs has emerged as a significant area of concern in anti-malarial drug design. Researchers are now desperately looking for new targets to develop anti-malarials drug which is more target specific. Malarial parasites harbor a plastid-like organelle known as the 'apicoplast', which is thought to provide an exciting new outlook for the development of drugs to be used against the parasite. This review elaborates on the current state of development of novel compounds targeted againstemerging malaria parasites. Methods: The apicoplast, originates by an endosymbiotic process, contains a range of metabolic pathways and housekeeping processes that differ from the host body and thereby presents ideal strategies for anti-malarial drug therapy. Drugs are designed by targeting the unique mechanism of the apicoplasts genetic machinery. Several anabolic and catabolic processes, like fatty acid, isopenetyl diphosphate and heme synthess in this organelle, have also been targeted by drugs. Results: Apicoplasts offer exciting opportunities for the development of malarial treatment specific drugs have been found to act by disrupting this organelle's function, which wouldimpede the survival of the parasite. Conclusion: Recent advanced drugs, their modes of action, and their advantages in the treatment of malaria by using apicoplasts as a target are discussed in this review which thought to be very useful in desigining anti-malarial drugs. Targetting the genetic machinery of apicoplast shows a great advantange regarding anti-malarial drug design. Critical knowledge of these new drugs would give a healthier understanding for deciphering the mechanism of action of anti-malarial drugs when targeting apicoplasts to overcome drug resistance.