• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.892-898
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• 2013

A field emission projection microscope was constructed to investigate the atomic and chemical-bonding structure of molecules using electron in-line holography. Fringes of carbon nanotube images were found to be interferograms equivalent to those created by the electron biprism in conventional electron microscopy. By exploiting carbon nanotubes as the filament of the electron biprism, we measured the transverse coherence length of the electron beam from tungsten field emitters. The measurements revealed that a partially coherent electron-beam was emitted from a finite area.

• Advances in materials Research
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• 제3권2호
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• pp.77-89
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• 2014

In the present article, the thermal buckling of zigzag single-walled carbon nanotubes (SWCNTs) is studied using a nonlocal refined shear deformation beam theory and Von-Karman geometric nonlinearity. The model developed simulates both small scale effects and higher-order variation of transverse shear strain through the depth of the nanobeam. Furthermore the present formulation also accommodates stress-free boundary conditions on the top and bottom surfaces of the nanobeam. A shear correction factor, therefore, is not required. The equivalent Young's modulus and shear modulus for zigzag SWCNTs are derived using an energy-equivalent model. The present study illustrates that the thermal buckling properties of SWCNTs are strongly dependent on the scale effect and additionally on the chirality of zigzag carbon nanotube. Some illustrative examples are also presented to verify the present formulation and solutions. Good agreement is observed.

• 자원리싸이클링
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• 제7권3호
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• pp.27-35
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• 1998

전기로 제강업체에서 생성되는 분진을 매립할 경우 토양 및 수질오염등의 심각한 환경문제를 야기시킬 수 있지만 적절한 처리공정을 거치게 되면 고부가가치를 얻을 수 있는 Fe, Zn, Pb, Cd 등의 원소들이 함유되어 있다. 이에 국내외 제강업체에서는 폐자원의 재자원화 측면 뿐만 아니라 환경오염 억제 차원에서 이러한 전기로 분진중 유가금속의 회수를 위한 처리공정의 개발이 시급히 요구되고 있으나, 현재 전기로 분진의 대부분은 재활용 처리되지 않고 매립되고 있는 실정이다. 따라서, 본 연구에서는 전기로 분진에 함유된 산화철을 Fe로 회수하기 위한 기초자료를 얻고자 실제 전기로 분진의 화학적 조성과 유사한 시료를 제조하여 $1500^{\circ}C$ Ar 분위기 하에서 탄소첨가량 및 연기도의 변화가 슬래그내의 $Fe_2O$ 회수율에 미치는 영향을 조사하였으며 그 결과는 다음과 같다. 합성시료의 고온용융특성 조사에서 탄소환원당량 대비 탄소첨가량이 증가함에 따라 연화점 및 용융점이 증가하였으며 슬래그중 $Fe_2O$의 환원속도는 탄소환원당량대비 탄소첨가량이 100%, 염기도 1.7에서 가장 높았다. 또한 $Fe_2O$의 환원반응차수는 거의 1차반응임을 알 수 있었다.

• 한국산업융합학회 논문집
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• 제11권4호
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• pp.195-199
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• 2008

The carbon fiber has low x-ray absorption property and high stiffness. This is the reason why many CT(Computed Tomography) manufacturer use carbon fiber in couch tabletop for CT scanner. In this paper, we design and make the couch tabletop made of carbon fiber composite, and verify the validity in CT scanner. In designing the couch tabletop, to determine the aluminum equivalent thickness of couch tabletop, we evaluate X-ray the transmissivity of aluminum and carbon plate in 80-120kVp X-ray energy range. And we perform structural analysis and mechanical design using determined thickness of carbon sheet. In conclusion, it was evaluated that manufactured couch tabletop satisfies X-ray transmissivity and mechanical requirements in CT scanner.

• 한국환경보건학회지
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• 제21권4호
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• pp.24-31
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• 1995

Gas sensing element, $\alpha-Fe_2O_3$ was synthesized by dehydration, reduction, and oxidation of $\alpha-FeOOH$, which was synthesized with $FeSO_4\cdot 7H_2O$ and NaOH. They were produced as a bulk-type, a thick film-type. Then, their responses and mechanisms of response to the gas of carbon monoxide were studied. The qualities of gas sefising elements are decided by the structure and the relative surface area. In the process of $\alpha-FeOOH$ synthesis, the effects of reaction conditions as the equivalent ratio, on the structure and the relative surface area of gas sensing element were observed. The changes of the structure were measured with XRD, SEM,TG-DTA and BET. The resistance changes of the synthesized gas sensor in the air were measured. The response ratio were also measured for the changes of working temperature and gas concentration. As a result of analysis with XRD, it was confirmed that the the best conditions for the synthesis of $\alpha-FeOOH$ were equivalent ratio 0.65. The thick film-type element of $\gamma-Fe_2O_3$ responded more quickly than the bulk-type did. The structure and the relative surface area of the $\rho-FeOOH$ were confirmed as the important factors deciding gas response charcteristics.

• 한국가스학회지
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• 제2권2호
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• pp.40-47
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• 1998

이산화탄소를 분해할 목적으로 황산철과 수산화나트륨을 이용하여 $Fe_3O_4$를 합성하였다. 합성조건은 황산철과 수산화나트륨의 혼합당량비를 0.50${\~}$l.50까지로 반응온도는 $40^{\circ}C$, 반응시간은 20시간으로 하였다. 또한 혼합당량비를 1.00으로 고정하고, 여기에 $NiCl_2,\;RhCl_3$를 mole$\%$로 첨가하여 합성하였다. 이 합성된 $Fe_3O_4$의 구조변화에 미치는 Ni과 Rh의 영향을 XRD, SEM으로 비교 검토하였다.

• Advances in Computational Design
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• 제7권3호
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• pp.173-188
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• 2022

In modern buildings, glass is considered a structurally unsafe material due to its brittleness and unpredictable failure behavior. The possible use of structural glass elements (i.e., floors, beams and columns) is generally prevented by its poor tensile strength and a frequent occurrence of brittle failures. In this study an innovative modelling based on an equivalent thickness concept of laminated glass beam reinforced with FRP (Fiber Reinforced Polymer) composite material and of glass plates punched is presented. In particular, the novel numerical modelling applied to an embedding Carbon FRP-rod in the interlayer of a laminated structural glass beam is considered in order to increase both its failure strength, together with its post-failure strength and ductility. The proposed equivalent modelling of different specimens enables us to carefully evaluate the effects of this reinforcement. Both the responses of the reinforced beam and un-reinforced one are evaluated, and the corresponding results are compared and discussed. A novel equivalent modelling for reinforced glass beams using FRP composites is presented for FEM analyses in modern material components and proved estimations of the expected performance are provided. Moreover, the new suggested numerical analysis is also applied to laminated glass plates with wide holes at both ends for the technological reasons necessary to connect a glass beam to a structure. Obtained results are compared with an integer specimen. Experimental considerations are reported.

• 한국가스학회지
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• 제15권1호
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• pp.35-39
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• 2011

본 논문에서는 FEV 차량용 복합소재 연료탱크의 탄소섬유 적층두께에 따라 달라지는 강도안전성에 미치는 기여율의 영향을 해석하고자 한다. 기여율에 의한 영향을 FEM 모델링으로 고찰하기 위해, 복합소재 연료탱크의 알루미늄 라이너와 탄소섬유 적층에 작용하는 von Mises 등가응력을 후프방향과 헤리컬방향에 대하여 각각 계산 하였다. FEM 해석결과에 따르면, 알루미늄 라이너에 작용하는 등가응력 기여율은 후프방향으로는 77.5%, $70^{\circ}C$ 경사진 헤리컬방향으로는 18.11%, $12^{\circ}C$ 경사진 헤리컬방향으로는 4.39%로 각각 작용하는 것으로 나타났다. $12^{\circ}C$ 경사진 탄소섬유의 적층 두께비가 후프방향 적층 두께비의 42% 정도로 높게 유지됨에도 불구하고 알루미늄 라이너 소재에서 보여준 기여율 경향은 탄소섬유 적층의 강도안전성에 대해서도 유사한 것으로 나타났다. 결과적으로, 탄소섬유 연료탱크의 강도안전성은 탄소섬유 적층의 두께보다 와인딩 각도에 의해 더 많은 영향을 받는다는 계산결과를 보여주고 있다.

• Journal of Forest and Environmental Science
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• 제39권3호
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• pp.119-127
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• 2023

In this study, quantitative models were applied to case parks to estimate the carbon reduction by trees, which was compared and analyzed at the tree and park levels. At the tree level, quantitative models of carbon storage and uptake differed by up to 7.9 times, even for the same species and size. At the park level, the carbon reduction from quantitative models varied by up to 3.7 times for the same park. In other words, carbon reduction by quantitative models exhibited considerable variation at the tree and park levels. These differences are likely due to the use of different growth environment coefficients and annual diameter at breast height growth rates and the overestimation of carbon reduction due to the substitution of the same genus and group model for each tree species. Extending the annual carbon uptake per unit area of the case park to the total park area of Chuncheon a carbon uptake ranging from a minimum of 370.4 t/yr and a maximum of 929.3 t/yr, and the difference can reach up to 558.9 t/yr. This is equivalent to the carbon emissions from the annual household electricity consumption of approximately 2,430 people. These results suggest that the indiscriminate application of quantitative models to estimate carbon reduction in urban trees can lead to significant errors and deviations in estimating carbon storage and uptake in urban greenspaces. The findings of this study can serve as a basis for estimating carbon reduction in urban greening research, projects, and policies.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.1-16
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• 2017

The compression or tension-controlled failure mode of concrete beams prestressed with unbonded FRP tendons is governed by the relative amount of prestressing tendon to the balanced one. Explicit assessment to determine the balanced reinforcement ratio of a beam with unbonded tendons (${\rho}^U_{pfb}$) is difficult because it requires a priori knowledge of the deformed beam geometry in order to evaluate the unbonded tendon strain. In this study, a theoretical evaluation of ${\rho}^U_{pfb}$ is presented based on a concept of three equivalent rectangular curvature blocks for simply supported concrete beams internally prestressed with unbonded carbon-fiber-reinforced polymer (CFRP) tendons. The equivalent curvature blocks were iteratively refined to closely simulate beam rotations at the supports, mid-span beam deflection, and member-dependent strain of the unbonded tendon at the ultimate state. The model was verified by comparing its predictions with the test results. Parametric studies were performed to examine the effects of various parameters on ${\rho}^U_{pfb}$.