• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1274-1277
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• 2004

최근 에너지 소비구조의 선진화에 따라 전력수요는 매년 10%이상 증가하고 있지만 철탑부지확보 및 환경 문제 둥에 의해 신규 송전선의 건설은 점차 어려워지고 있다. 이에 대한 대책으로 철탑의 교체 없이 송전선의 전류용량간 증가시키는 방안이 우선적으로 고려되어 적용되고 있다. 이미 국내에서도 기존 송전선인 ACSR 전선을 중용량 저이도의 특성을 가진 STACIR/AW(Super Thermal-resistant Aluminum alloy Conductors, aluminum-clad Invar-Reinforced)송전선으로 교체하여 전력 수송량을 증가시키고 있다. STACIR/AW전선은 도체의 내열성을 향상시켜 연속허용온도$(210^{\circ}C)$를 높임으로 전류용량을 증가시키고, ACSR에 사용되는 강심재료인 고탄소강선을 선팽창계수가 낮은 인바강선(INVAR)으로 대체함으로 고온환경에 따른 이도증가를 방지하고 있다. 그러나 STACIR/AW 송전선은 ACSR 송전선에 비하여 연속허용온도가 높고 경간의 거리가 멀기 때문에 열화에 의한 피로특성의 변화 가능성이 높다. 따라서 본 연구에서는 증용량저이도전선의 강심소재인 INVAR/AW강선을 소정의 온도에서 경년 열화하고, 열화시간에 따른 강도와 피로특성의 변화를 조사하여, STACIR/AW전선의 안정적 운전을 위한 재료물성적 관리인자를 도출하고자 하였다.

• Progress in Superconductivity
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• 제9권1호
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• pp.80-84
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• 2007

Charcoal was used as a carbon source for improving the critical current density of $MgB_2$ and the effect of annealing temperature on the $J_c$ of $MgB_2$ was investigated. The charcoal powder used in this study was $1{\sim}2$ microns in size and was prepared by wet attrition milling. $MgB_2$ bulk samples with a nominal composition of $Mg(B_{0.95}C_{0.05})_2$ were prepared by in situ process of Mg and B powders. The powder mixture was uniaxially compacted into pellets and heat treated at temperatures of $650^{\circ}C\;-\;1000^{\circ}C$ for 30 minutes in flowing Ar gas. It was found that superconducting transition temperature of $Mg(B_{0.95}C_{0.05})_2$ decreased by charcoal additions which indicates the carbon substitution for boron site. $J_c$ of $Mg(B_{0.95}C_{0.05})_2$ was lower than that of the undoped $MgB_2$ at the magnetic fields smaller than 4 Tesla, while it was higher than that of the undoped sample especially at the magnetic field higher than 4 T. High temperature annealing seems to be effective in increasing $J_c$ due to the enhanced carbon diffusion into boron sites.

• 청정기술
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• 제20권4호
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• pp.383-389
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• 2014

이산화탄소 흡수공정은 대규모의 이산화탄소를 처리하는데 유리하지만, 다량의 흡수액을 재생하는데 필요한 현열과 증발열로 인한 에너지 비용 상승이 단점으로 지적되고 있다. 이를 극복하기 위해 이산화탄소를 흡수한 탄산칼륨 흡수액을 냉각 결정화시켜, 다량의 물로부터 이산화탄소가 많이 포함된 중탄산칼륨 결정을 선택적으로 분리할 수 있다. 본 연구에서는 이산화탄소 분리효율을 높이기 위해 입체 장애 알카놀아민 첨가제를 도입하여, 이들이 중탄산칼륨 연속식 결정화에 미치는 영향에 대해 살펴보았다. 결정의 석출량은 2-아미노-2-메틸-1-프로판올(2-amino-2-methyl-1-propanol, AMP), 2-아미노-2-메틸-1,3-프로판디올(2-amino-2-methyl-1,3-propanediol, AMPD), 2-아미노-2-히드록시메틸-1,3-프로판디올(2-amino-2-hydroxymethyl-1,3-propanediol, AHPD)의 순서로 증가하였으며, 반용매로 작용하는 첨가제들의 히드록실기 개수와 관계가 있는 것으로 나타났다. 탄소 핵자기공명분광 분석 결과, 첨가제들은 입체 장애 효과에 의해 중탄산 이온의 생성을 유도하고 과포화도를 상승시킨 것으로 나타났다. 또한, 첨가제들은 과포화도 상승을 통해 평균 입도와 결정 성장 속도를 증가시키는 것으로 나타났다. 입체 장애 알카놀아민 첨가제는 중탄산칼륨 결정화를 촉진함으로써, 물로부터 이산화탄소의 분리효율을 향상시키고 재생에너지를 저감시킬 수 있을 것으로 기대된다.

• 대한기계학회논문집A
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• 제34권1호
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• pp.67-72
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• 2010

원전 배관의 LBB 해석을 위한 파괴인성(J-R곡선)은 일반적으로 ASTM E1820에 따라 시험을 수행하여 획득한다. 그러나 ASTM E1820에 제시되어 있는 파괴인성에 관한 식은 균질재의 물성 평가를 위한 것 이며, 협개선 용접부에 적용할 경우 실제와는 다른 파괴인성을 나타낼 수 있다. 따라서 본 연구에서는 ASTM에 제시되어 있는 균질재의 파괴인성식에 의한 결과와 협개선 용접재의 특성을 고려하여 제안된 소성 $\eta$계수 식에 의한 파괴인성의 차이를 비교 검토하기 위하여 협개선 용접이 적용된 배관에서 CT 시험편을 채취한 후 파괴인성 시험을 수행하였다.

• The Journal of Korean Physical Therapy
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• 제26권6호
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• pp.442-448
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• 2014

Purpose: The objective of this study is to evaluate the effect of neuro-feedback training and transcutaneous electrical nerve stimulation (TENS) on stress, quantitative sensory threshold and pain in patients suffering from tension type headache. Methods: 22 participants who passed the preliminary evaluation were enrolled in the study and 11 participants were randomly assigned to each group. The control group (n=11) was subject to the TENS treatment of which was composed of a 20-minute session for 5 times a week during 4 weeks, and the experimental group (n=11) was subject to both neuro feedback training and TENS treatment for 10 minutes a day and 5 days a week during 4 weeks. The Perceived Stress Scale (PSS) was used to measure a level of stress and the quantitative sensory testing (QST) was used for the measurement of cold pain threshold (CPT) and heat pain threshold (HPT); A degree of pain was evaluated through the headache impact test-6 (HIT-6). Results: In comparision of all dependent variables between the control and subject groups, there were significant differences in stress, quantitative sensory threshold and pain after the treatment (p<0.05), and the experimental group showed significant differences in stress, CPT, HPT and pain (p<0.05) and the control group showed only a significant difference in HPT (p<0.05). Conclusion: Findings of this study demonstrate that the concomitant administration of the TENS treatment and neuro feedback training is effective on alleviation of stress, quantitative sensory threshold and pain in patients with tension type headache.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.175-176
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• 2013

근래 우리나라 에서는 압화에 대한 관심이 증폭되고 있으며 그 예술성에 대한 지속적인 연구가 이뤄지고 있다. 실내디자인 압화는 압화의 예술적인 활동으로부터 실생활 용품으로 발전된 것이다. 실내 디자인이란 인간이 거주하는 실내공간을 목적에 맞게 기능적 조건과 정서적 조건을 모두 만족 시켜야 하는 종합디자인 활동이라 할 수 있다. 본 연구에서는 압화의 예술성을 실내 디자인에 적용 시키기 위해 기존 압화기법에 광매체와 빛 투과성이 우수한 양파 압화를 이용하여 감성적이고 세련된 광매체압화 조형물 제작 기법을 연구하고 이를 이용하여 실제 조형물을 제작 하였다. 여기에 사용된 무기전계 발광시크는 두께가 약 0.2mm의 얇은 발광판으로 저전력에서 고휘도의 빛을 발생시키면서도 열이 발성하지 않는 첨단 광매체로 압화와 무기전계발광시트의 접목으로 기존의 압화의 한계를 넘어서는 새로운 형태와 내러티브를 도입하는 것이 가능해 졌고, 이를 통해 절전형 조명 조형물을 만들 수 있게 되었다.

• 대한기계학회논문집A
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• 제21권6호
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• pp.961-970
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• 1997

A numerical method is presented to predict and analyze the shape of a growing billet produced from the "spray forming process" which is a fairly new near-net shape manufacturing process. It is important to understand the mechanism of billet growing because one can obtain a billet with the desired final shape without secondary operations by accurate control of the billet shape, and it can also serve as a base for heat transfer and deformation analysis. The shape of a growing billet is determined by the flow rate of the alloy melt, the mode of nozzle scanning which is due to cam profile, the initial positio of the spray nozzle, scanning angle, and the withdrawal speed of the substrate. In the present study, a theoretical model is first established to predict the shape of the billet and next the effects of the most dominent processing conditions, such as withdrawal speed of the substrate and the cam profile, on the shape of the growing billet are studied. Process conditions are obtained to produce a billet with uniform diameter and flat top surface, and an ASP30 high speed steel billet is manufactured using the same process conditions established from the simulation.imulation.

• 한국의류학회지
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• 제34권11호
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• pp.1767-1778
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• 2010

This study investigates applying $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via electrospinning for the development of UV-protective materials. To fabricate uniform nanocomposite fibers, three types of $TiO_2$ nanoparticles were applied: powder, colloid, and $TiO_2$ coated polymer pellets. $TiO_2$/polyurethane (PU) and $TiO_2$/poly(vinyl alcohol) (PVA) nanocomposite fibers were electrospun and the morphology was examined using a field-emission scanning electron microscope and a transmission electron microscope. Layered fabric systems with electrospun $TiO_2$ nanocomposite fiber webs were developed at various concentrations of $TiO_2$ in a range of the web area density. The effects of $TiO_2$ concentration and web area density on UV-protective properties were examined. When $TiO_2$ colloid was added into a PVA polymer solution, uniform nanocomposite fiber webs in which $TiO_2$ particles were evenly dispersed were produced. Water-soluble PVA nanofiber webs were given a heat treatment to stabilize the electrospun PVA fibrous structure against dissolution in water. $TiO_2$/PVA nanoeomposite fiber webs with 2wt% $TiO_2$ and 3.0g/$m^2$ web area density exhibited an ultraviolet protection factor of greater than 50, indicating excellent UV protection.

• 한국의류학회지
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• 제35권11호
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• pp.1297-1308
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• 2011

This research investigates the application of ZnO (zinc oxide) nanoparticles and $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via an electrospinning technique for the development of textile materials that can decompose harmful gases. To fabricate uniform ZnO nanocomposite fibers, two types of ZnO nanoparticles were applied. Colloidal $TiO_2$ nanoparticles were chosen to fabricate $TiO_2$ nano- composite fibers. ZnO/poly(vinyl alcohol) (PVA) and $TiO_2$/PVA nanocomposite fibers were electrospun under a variety of conditions that include various feed rates, electric voltages, and capillary diameters. The morphology of electrospun nanocomposite fibers was examined with a field-emission scanning electron micro- scope and a transmission electron microscope. Decomposition efficiency of gaseous materials (formaldehyde, ammonia, toluene, benzene, nitrogen dioxide, sulfur dioxide) by nanocomposite fiber webs with 3wt% nano-particles (ZnO or $TiO_2$) and 7$g/m^2$ web area density was assessed. This study shows that ZnO nanoparticles in colloid were more suitable for fabricating nanocomposite fibers in which nanoparticles are evenly dispersed than in powder. A heat treatment was applied to water-soluble PVA nanofiber webs in order to stabilize the electrospun nanocomposite fibrous structure against dissolution in water. ZnO/PVA and $TiO_2$/PVA nanofiber webs exhibited a range of degradation efficiency for different types of gases. For nitrogen dioxide, the degradation efficiency was 92.2% for ZnO nanocomposite fiber web and 87% for $TiO_2$ nanocomposite fiber web after 20 hours of UV light irradiation. The results indicate that ZnO/PVA and $TiO_2$/PVA nano- composite fiber webs have possible uses in functional textiles that can decompose harmful gases.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.241.1-241.1
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• 2011

Numerous possible applications for $ZrO_2$ nanotubes exist such as for catalyst support structures, for sensing or for applications as a solid state electrolyte. Especially, because of a large specific surface area, high efficiency for solid oxide fuel cell (SOFC) application at low temperature can be expected for nanotublar structures in even small size. A zirconium precursor, Tetrakis (ethylmethylamino) zirconium, TEMAZr and $H_2O$ oxidant were used to deposit$ZrO_2$ thin films on an anodized aluminum oxide (AAO) templates having sub-100nm cylindrical pores by atomic layer deposition (ALD) in the temperature range of 150~250$^{\circ}C$. The crystalline structures of as-prepared and post-annealed $ZrO_2$ nanotubes were characterized by x-ray diffraction and high-resolution transmission electron microscopy. The as-prepared samples at $150^{\circ}C$ and $200^{\circ}C$ were showed amorphous, whereas a mixed phase of tetragonal, monoclinic and amorphous polymorph was observed at $250^{\circ}C$. In the bulk, zirconia remains monoclinic phase up to $1,175^{\circ}C$, however, $ZrO_2$ nanotubes were showed tetragonal phase upon post thermal treatments merely at $400^{\circ}C$. This trend may be indicative of high-curvature surfaces of nanotubes and thereby the presence of intrinsic compressive strain. The amount of amorphous structures in the mixed phase as well as as-grown $ZrO_2$ nanotubes were also gradually decreased by subsequent heat treatment.