• Computers and Concrete
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• 제18권6호
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• pp.1083-1096
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• 2016

Beam-column joints are recognized as the weak points of reinforcement concrete frames. The ductility of reinforced concrete (RC) frames during severe earthquakes can be measured through the dissipation of large energy in beam-column joint. Retrofitting and rehabilitating structures through proper methods, such as carbon fiber reinforced polymer (CFRP), are required to prevent casualties that result from the collapse of earthquake-damaged structures. The main challenge of this issue is identifying the effect of CFRP on the occurrence of failure in the joint of a cross section with normal ductility. The present study evaluates the retrofitting method for a normal ductile beam-column joint using CFRP under monotonic and cyclic loads. Thus, the finite element model of a cross section with normal ductility and made of RC is developed, and CFRP is used to retrofit the joints. This study considers three beam-column joints: one with partial CFRP wrapping, one with full CFRP wrapping, and one with normal ductility. The two cases with partial and full CFRP wrapping in the beam-column joints are used to determine the effect of retrofitting with CFRP wrapping sheets on the behavior of the beam-column joint confined by such sheets. All the models are subjected to monotonic and cyclic loading. The final capacity and hysteretic results of the dynamic analysis are investigated. A comparison of the dissipation energy graphs of the three connections shows significant enhancement in the models with partial and full CFRP wrapping. An analysis of the load-displacement curves indicates that the stiffness of the specimens is enhanced by CFRP sheets. However, the models with both partial and full CFRP wrapping exhibited no considerable improvement in terms of energy dissipation and stiffness.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.257.1-257.1
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• 2014

We investigated characteristics of ITO/Ag-Pd-Cu (APC)/ITO multilayer electrodes prepared by direct current magnetron sputtering for use as an anode in organic solar cells (OSCs). To optimize electrical properties of ITO/APC/ITO multilayer, we fabricated the ITO/APC/ITO multilayer at a fixed ITO thickness of 30 nm as a function of APC thickness. Compare to the surface of Ag layer on ITO, the APC had a smooth surface morphology. At optimized APC thickness of 12 nm, the ITO/APC/ITO multilayer exhibited a sheet resistance of $6{\Omega}/square$ and optical transmittance of 84.15% at a wavelength of 550 nm which is comparable to conventional ITO/Ag/ITO multilayer. However, the APC-based ITO multilayer showed a higher average transmittance in a visible region than the Ag-based ITO multilayer. The higher average transmittance of ITO/APC/ITO multilayer indicated the multilayer is suitable anode for organic solar cells with P3HT:PCBM active layer. OSCs fabricated on the optimized ITO/ACP/ITO multilayer exhibited a better performance with a fill factor of 64.815%, a short circuit current of $8.107mA/cm^2$, an open circuit voltage of 0.59 V, and power conversion efficiency (3.101%) than OSC with ITO/Ag/ITO multilayer (2.8%).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.473.1-473.1
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• 2014

We report on the characteristics of Zr-doped $In_2O_3$ (IZrO) films prepared by DC-RF magnetron cosputtering of $In_2O_3$ and $ZrO_2$ targets for use as a transparent electrode for high efficient organic solar cells (OSCs). The effect of $ZrO_2$ doping power on electrical, optical, structural, and surface morphology of the IZrO film was investigated in detail. At optimized $ZrO_2$ RF power of 50 W, the IZrO film exhibited a low sheet resistance of 20.71 Ohm/square, and a high optical transmittance of 83.9 %. Furthermore, the OSC with the IZrO anode showed a good cell-performance: fill factor of 61.71 %, short circuit current (Jsc) of $8.484mA/cm^2$, open circuit voltage (Voc) of 0.593 V, and power conversion efficiency (PCE) of 3.106 %. In particular, the overall OSC characteristics of the cell with the IZrO anode were comparable to those of the OSC with the conventional Sn-doped $In_2O_3$ (FF of 65.03 %, Jsc of $8.833mA/cm^2$, Voc of 0.608 V, PCE of 3.495 %), demonstrating that the IZrO anode is a promising alternative to ITO anode in OSCs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.394.2-394.2
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• 2014

We fabricated highly transparent and flexible Ti doped In2O3 (TIO)/Ag nanowire(NW)/TIO (TAT) multilayer electrodes by linear facing target sputtering (LFTS) and brush-painting for used as flexible for anode organic solar cells(FOSCs). The characteristics of TAT transparent anode as a function of number of brush-painting cycles was also investigated. At optimized conditions we achieved highly flexible TAT multilayer electrodes with a low sheet resistance of $9.01{\Omega}/square$ and a high diffusive transmittance more than 80% in visible region as well as superior mechanical stability. The effective embedment of the Ag NW network between top and bottom TIO films led to a metallic conductivity, high transparency. Based on FE-SEM HRTEM, and XRD analysis, we can find that the Ag NW network was effectively embedded between top and bottom TIO layers due to good flexibility of Ag NW, the TAT multilayer showed superior flexibility than single TIO layer. Successful operation of FOSCs with high power conversion efficiency of 3.01% indicates that TAT hybrid electrode is a promising alternative to conventional ITO electrode for high performance FOSCs.

• 한국의류산업학회지
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• 제22권2호
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• pp.233-239
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• 2020

We proposed a simple process of fabricating electroconductive textiles by coating conductive polymer PEDOT:PSS (Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) on biocompatible PLA (Poly Lactic Acid) nanofiber web for application to smart healthcare. Electroconductive textiles were obtained by a drop-coating process using different amounts of PEDOT:PSS solutions., DMSO (dimethyl sulfoxide) was then used as an additive in the post-treatment process to improve conductivity. The surface morphology of the specimens was observed by FE-SEM. The chemical structures of the specimens were characterized using FTIR. The electrical properties (linear and sheet resistance) of the specimens were measured. The effect of the bending angles on the electrical properties was also investigated to confirm their applicability as wearable smart textiles. FE-SEM and FTIR analysis confirmed that the deposition of PEDOT:PSS on the PLA nanofiber web surface was successful. The conductivity of the PEDOT:PSS/PLA nanofiber web was enhanced up to 1.5 ml with an increasing amount of PEDOT:PSS solutions, but there was no significant difference at 2.0 ml. The optimum condition of PEDOT:PSS deposition was established to 1.5 ml. Even when the specimen coated with 1.5 ml was bent every 30°, the change in the electrical resistance values was still low within 3.7 Ω. It confirmed that stable electrical performance was maintained and proved the applicability as a flexible textile sensor.

• 한국표면공학회지
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• 제48권4호
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• pp.158-162
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• 2015

To substitute indium tin oxide (ITO), many substituents have been studied such as metal nanowires, carbon based materials, 2D materials, and conducting polymers. These materials are not good enough to apply to an electrode because theses exhibit relatively high resistance. So metal grids are required as an additionalelectrode to improve the conductivities of substituents. The metal grids were printed by electrohydrodynamic printing system using Ag nanoparticle based ink. The Ag grids showed high uniformity and the line width was about $10{\mu}m$. The Ag nanoparticles are surrounded by dispersants such as unimolecular and polymer to prevent aggregation between Ag nanoparticles. The dispersants lead to low conductivity of Ag grids. Thus, the sintering process of Ag nanoparticles is strongly recommended to remove dispersants and connect each nanoparticles. For sintering process, the interface and microstructure of the Ag grid were controlled in 1.0 torr Ar atmosphere at aound $400^{\circ}C$ of temperature. From the sintering process, the uniformity of the Ag grid was improved and the defects on the Ag grids were reduced. As a result, the resistivity of Ag grid was greatly reduced up to $5.03({\pm}0.10){\times}10^{-6}{\Omega}{\cdot}cm$. The metal grids embedded substrates containing low pressure Ar sintered Ag grids showed 90.4% of transmittance in visible range with $0.43{\Omega}/{\square}$ of sheet resistance.

• 한국구조물진단유지관리공학회 논문집
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• 제12권3호
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• pp.71-83
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• 2008

본 논문에서는 비접촉 손상검출기법으로 관심의 대상이 되고 있는 열화상 기법의 기본 원리, 활용 예, 제한 사항 등을 국내외 주요 연구성과를 분석하고 정리하였다. 콘크리트 구조물의 내부 결함 진단, 내부 철근 부식 측정과 콘크리트 구조물 표면과 섬유 보강 시트 사이의 비부착 검출, 포장도로의 표면 결함 검출, 오래된 건물의 표면 누수 측정, 철도 트랙 자갈의 상태 측정 등을 최근 연구결과 중심으로 광범위하게 검토하였고 최근에 보고된 실험결과도 제시하였다. 검토 결과, 열화상 기법은 광범위한 형태의 토목 구조물의 넓은 표면을 빠르게 정성적으로 검사할 수 있는 장점을 가지고 있는 것으로 확인되었다. 반면, 정량적 기법은 주변 온도 등 환경 요인에 민감하게 영향을 받는 것으로 판단되었으며, 다른 정밀계측장비와 혼용시 좋은 성과를 기대할 수 있을 것으로 예측된다.

• 콘크리트학회논문집
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• 제23권1호
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• pp.31-38
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• 2011

이 연구에서는 FRP와 강섬유로 보강한 콘크리트 시편의 충격하중과 정적하중에서의 거동을 보기 위해 휨 실험과 펀칭 실험을 수행하였다. 1방향 휨 실험과 2방향 펀칭 실험에서 콘크리트 시편은 각각 $50{\times}100{\times}350$ mm와 $50{\times}350{\times}350$ mm의 크기로 제작하였다. 0.75% 혼입률의 강섬유 보강 콘크리트는 2방향 충격하중 및 정적하중에서 높은 저항 성능을 보였다. 일반 콘크리트와 강섬유 보강 콘크리트에서 FRP 보강은 높은 성능 증가를 보였다. 초고성능 콘크리트는 콘크리트 자체가 가지고 있는 높은 인장강도와 인성으로 인해, CFRP로 보강한 경우 강도와 에너지 소산 능력이 크게 증가하지 않았다.

• Steel and Composite Structures
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• 제34권1호
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• pp.91-105
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• 2020

Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.1216-1221
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• 2014

PEIT는 옥수수와 같은 재생 가능한 자원에서 유래한 isosorbide monomer를 이용하여 bio-contents를 함유하고 있는 PET이다. 하지만 isosorbide contents가 향상될수록 기계적물성이 감소하는 단점이 있다. 본 연구에서는 우수한 기계적 물성을 가지고 있는 polycarbonate를 이용하여 PEIT의 단점을 보완하고, 또한 PEIT를 이용하여 PC의 인장신율 향상을 통해 성형가공성을 개선하고자 하였다. 이축압출기를 통해 제조한 PEIT/PC 블렌드에서 polycarbonate가 모폴로지, 유리전이온도거동, 열적안정성 및 기계적 물성에 미치는 영향을 확인하기 위해 FE-SEM, DMA, TGA, UTM 및 Izod impact tester를 통하여 분석을 수행하였다. 이로써 우수한 기계적 물성을 가진 polycarbonate는 PEIT와 상용성이 있음을 확인하였으며, 특히 PEIT25PC75 조성에서 열적 안정성 및 기계적 특성의 향상이 뛰어난 것을 알 수 있었다.