• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.405-406
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• 2006

Raw materials from different sources, produced by a given process and having equal chemical composition, are supposed to be equivalent. The differences in sintering behavior have been investigated on P/M steels obtained from four diffusion-bonded powders (Fe + Ni + Cu + Mo) on atomized iron base, at the same alloy contents. Two levels of carbon and two sintering conditions have been investigated. Dimensional changes, C content, hardness, microhardness pattern, universal hardness, fractal analysis, pore features, microstructure features, and rupture strength have been compared to characterize different raw materials. The results show that the claimed equivalence is not confirmed by experimental data.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 춘계 학술발표회 논문집
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• pp.95-100
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• 1999

One of the unsolved problems of the natural gas dual fuel engine is that there is too much exhaust of Total Hydrogen Carbon(THC) at a low equivalent mixture ratio. To fix it, a natural gas mixed with hydrohen was applied to engine test. The results showed that the higher the mixture ratio of hydrogen to natural gas, the higher the combustion efficiency. And when the amount of the intake air is reached to 90% of WOT, the combustion efficiency was promoted. But, like a case making the injection timing earlier, the equivalent mixture ratio for the nocking limit decreases and the produce of NOx increases.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.481-481
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• 2007

This work describes the effect of the number of roll pressing and the composition of carbon black on the electric and mechanical properties of carbon-PTFE electrode, in which composition is MSP 20 : carbon black: PTFE = 95-x : x : 5 wt.%. It was found that the best electric and mechanical properties were obtained in sheet electrode roll-pressed for about 15 times and in sheet electrode, in which composition is MSP 20 : carbon black: PTFE = 80 : 15 : 5 wt.%. These behaviors could be explained by the network structure of PTFE fibrils and conducting paths linked with carbon blacks, respectively. On the other hand, cell capacitor using the sheet electrode with 15 wt.% of carbon black attached on aluminum current collector with the electric conductive adhesive, in composition is carbon black : CMC = 70 : 30 wt.%, has exhibited the best rate capability in the current range of $0.5mA/cm^2$ $100mA/cm^2$ and the lowest equivalent series resistance.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.570-576
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• 2018

철근콘크리트 구조물에서 철근의 이음은 철근을 겹쳐서 결속선으로 결속한 겹침이음과 커플러에 의한 기계적 이음이 일반적이다. 국내 설계기준(콘크리트구조기준)에서는 일반철근(비용접 철근)에 대해 용접 겹침이음을 제한하고 있으나, 해외기준(AWS D1.4)에서는 예열을 통한 일반철근의 용접 겹침이음을 허용하고 있다. 본 연구에서는 국내외 규격 및 설계기준을 조사하고, 건설현장에서 가장 많이 사용되는 SD400 강종의 일반철근을 대상으로 용접 겹침이음 인장실험을 수행하여 인장강도를 평가하였다. 용접 겹침이음 시험체의 용접길이는 KS규격(KS B ISO 17660-1)에 제시된 최소용접길이인 8d를 적용하고, 예열온도는 AWS D1.4에 따라 D19이하는 $150^{\circ}C$, D22이상은 $260^{\circ}C$로 설정하였다. 인장실험 결과, 용접 겹침이음된 일반철근은 콘크리트구조기준에서 요구하는 인장강도(항복강도의 125%)를 발현하였으며, 모두 철근 모재에서 파단이 발생되었다. 예열 유무에 따른 영향을 검토하기 위해, 일반철근을 예열한 후 용접한 것과 예열 등의 열처리하지 않은 것을 비교한 결과, 인장강도는 큰 차이를 보이지 않았다. 실험시 사용한 일반철근을 대상으로 화학성분을 분석하여 탄소당량(Ceq)을 확인한 결과, 0.45% 이하로 낮았다. AWS D1.4에 따르면, 탄소당량이 0.45% 이하면 예열이 필요하지 않은 조건이다. 결과적으로 예열의 영향이 미비한 것은 일반철근의 탄소당량이 낮았기 때문인 것으로 확인되었다.

• 자원리싸이클링
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• 제23권1호
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• pp.40-47
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• 2014

폐자원으로 분류되는 석탄재의 미연탄소를 경제적으로 재활용하기 위한 방안을 모색하기 위하여, 서천화력발전소 매립 석탄재로부터 미연탄소를 분리한 후 활성탄소 제조가능성을 평가하였다. 정선부선을 4단계 실시하여 얻어진 미연탄소 정광의 고정탄소 품위는 87%로 얻어졌다. 미연탄소 정광에 포함된 결정질 불순물로는 주로 석영과 뮬라이트가 존재하였다. 화학적 활성화 전 미연탄소의 비표면적은 $10m^2/g$로 매우 낮았으며, 이는 국내 무연탄의 높은 탄화도와 관련되는 것으로 추측되었다. 또한 미연탄소는 대체로 다공성이며 결정학적으로는 터보스트래틱 구조를 갖고 있었다. 미연탄소 1 g과 KOH 6 g 을 혼합하여 활성화시킨 경우 얻어진 비표면적값이 $670m^2/g$로 가장 높았으며 미세공이 발달된 것을 확인하였다. KOH 용액을 사용한 경우 질소흡착량이 분말상 활성화 시료보다 낮게 나타난 것은 탄소입자의 젖음성 및 함침성이 낮은 때문으로 추측되었다. 본 실험에서 제조한 활성탄소는 미세공 분포가 높은 기능성 활성탄소의 세공특성을 보이며, 범용의 활성탄소에 준하는 비표면적값을 나타내 기존의 석탄계 활성탄소보다 우수하며 회분 함량도 적정 수준이었다. 따라서 공정의 경제성과 미연탄소 자체의 특성을 고려하여, 정수용 활성탄소 대체재나 혹은 카본블랙 대체용으로 재활용하는 것이 가능할 것으로 판단된다.

• Advances in nano research
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• 제16권3호
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• pp.289-301
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• 2024

In this work, an analytical model employing a new higher-order shear deformation beam theory is utilized to investigate the bending behavior of axially randomly oriented functionally graded carbon nanotubes reinforced composite nanobeams. A modified continuum nonlocal strain gradient theory is employed to incorporate both microstructural effects and geometric nano-scale length scales. The extended rule of mixture, along with molecular dynamics simulations, is used to assess the equivalent mechanical properties of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) beams. Carbon nanotube reinforcements are randomly distributed axially along the length of the beam. The equilibrium equations, accompanied by nonclassical boundary conditions, are formulated, and Navier's procedure is used to solve the resulting differential equation, yielding the response of the nanobeam under various mechanical loadings, including uniform, linear, and sinusoidal loads. Numerical analysis is conducted to examine the influence of inhomogeneity parameters, geometric parameters, types of loading, as well as nonlocal and length scale parameters on the deflections and stresses of axially functionally graded carbon nanotubes reinforced composite (AFG CNTRC) nanobeams. The results indicate that, in contrast to the nonlocal parameter, the beam stiffness is increased by both the CNTs volume fraction and the length-scale parameter. The presented model is applicable for designing and analyzing microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) constructed from carbon nanotubes reinforced composite nanobeams.

• 한국정밀공학회지
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• 제16권12호
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• pp.198-203
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• 1999

In this study, chip-tool friction and shear characteristics of cold drawn free machining steels in turning were assessed. To do this, a newly developed equivalent oblique cutting model was adopted. And for comparison with those of free machining steels, chip-tool friction and shear characteristics of conventional carbon steels were also investigated. The Pb-S free machining steel shows superior machinability to others. In case of the Bi-S free machining steel, the shear stress and the specific friction energy are relatively lower than those of conventional carbon steels, but its shear strain is relatively high, so it does not show any remarkable improvement of machinability.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.724-729
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• 2004

The purpose of this study is to investigate the strength and ductility improvement of columns retrofitted with Fiber-Steel Composite Plate, compared with Steel Plate, and Carbon Fiber Sheet. Test specimens strengthened with 3 different materials--- carbon fiber sheet, steel plate and fiber-steel composite plate --- were tested under cyclic lateral force and a constant axial load equal to $20\%$ of the column's axial load capacity. The hypothetical equivalent value of the strengthening among three materials is introduced to evaluate.

• 한국생산제조학회지
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• 제22권6호
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• pp.963-968
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• 2013

In this study, we carried out a structural analysis for determining the stresses acting on the tempered glass of a freely falling cellular phone using ANSYS 13.0, commercial finite element code. We designed a phone heavier than any contemporary cellular phone and performed finite element analysis using the falling speed at a height of 104 cm, which is equal to of the average leg length of Koreans. By determining the maximum stress acting on the phone's tempered glass and frame, we identified the location of large deformation. Furthermore, we evaluated the maximum/minimum equivalent stress and deformation of the reinforced glass and frame as functions of time.

• Computers and Concrete
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• 제17권5호
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• pp.567-578
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• 2016

As concrete is most usable material in construction industry it's been required to improve its quality. Nowadays, nanotechnology offers the possibility of great advances in construction. For the first time, the nonlinear buckling of straight concrete columns armed with single-walled carbon nanotubes (SWCNTs) resting on foundation is investigated in the present study. The column is modelled with Euler-Bernoulli and Timoshenko beam theories. The characteristics of the equivalent composite being determined using mixture rule. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of SWCNTs, geometrical parameters, elastic foundation and boundary conditions on the buckling of column are investigated. Numerical results indicate that reinforcing the concrete column with SWCNTs, the structure becomes stiffer and the buckling load increases with respect to concrete column armed with steel.