• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.181.2-181.2
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• 2014

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly (methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. We found that the gas species of mass/charge (m/e) ratio of 15 ($CH_3{^+}$) was mainly originated from the thermal decomposition of PMMA, indicating that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for dominantly vaporizing hydrocarbon molecules from PMMA and the length of time, the gaseous hydrocarbon atmosphere is maintained, are dependent on both the heating temperature profile and the amount of a solid carbon feedstock. From those results, we strongly suggest that the heating rate and the amount of solid carbon are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ${\sim}2,700cm^2V^{-1}s^{-1}$ at room temperature, which is superior to common graphene converted from solid carbon.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2342-2354
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• 2002

The present study has numerically predicted both the flow -induced and thermally-induced residual stresses and birefringence in injection o. injection/compression molded center -gated disks. Analysis system for entire molding process was developed based on an ap propriate physical modeling including a nonlinear viscoelastic fluid model, stress-optical law, a linear viscoelastic solid model, free volume theory for density relaxation phenomena and a photoviscoelasticity and so on. Part I presents physical modeling a nd typical numerical analysis results of residual stresses and birefringence in the injection molded center-gated disk. Thermal residual stress was found to be extensional near the center, compressive near the surface and tend to become toward tensional at the surface. A double-hump profile was obtained across the thickness in birefringence distribution: nonzero birefringence is found to be thermally induced, the outer peak is due to the shear flow and subsequent stress relaxation during the filling stage a nd the inner peak is due to the additional shear flow and stress relaxation during the packing stage. Predicted birefringence including both the flow -induced and thermally-induced one becomes quite similar to the experimental one.

• Asian Journal of Atmospheric Environment
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• 제11권3호
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• pp.176-183
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• 2017

Although it is well known that rain plays an important role in capturing air pollutants, its quantitative evaluation has not been done enough. In this study, the effect of raindrop size on pollutant scavenging was investigated by clarifying the chemical nature of individual size-resolved raindrops and their residual particles. Raindrops as a function of their size were collected using the raindrop collector devised by our oneself in previous study (Ma et al., 2000) during high atmospheric loading for $PM_{2.5}$. Elemental analyses of solid residues and individual residual particles in raindrops were subsequently analyzed by Particle Induced X-ray Emission (PIXE) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX), respectively. The raindrop number concentration ($m^{-2}h^{-1}$) tended to drastically decrease as the drop size goes up. Particle scavenging rate, $R_{sca.}$ (%), based on the actual measurement values were 38.7, 69.5, and 80.8% for the particles with 0.3-0.5, 0.5-1.0, and $1.0-2.0{\mu}m$ diameter, respectively. S, Ca, Si, and Al ranked relatively high concentration in raindrops, especially small ones. Most of the element showed a continuous decrease in concentration with increasing raindrop diameter. The source profile by factor analysis for the components of residual particles indicated that the rainfall plays a valuable role in scavenging natural as well as artificial particles from the dirty atmosphere.

• 유기물자원화
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• 제9권2호
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• pp.87-92
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• 2001

발암성 물질 내지는 내분비계장애물질로 인식되고 있는 농약에 대한 관심이 날로 증가함에 따라 잔류농약제거에 관한 연구의 중요성이 증대되고 있다. 본 연구에서는 과산화수소가 첨가된 광산화공정을 이용한 고체상의 표면에 잔류하는 농약의 분해에 관한 실험을 수행하였다. 카바메이트계인 베노밀과 유기염소계인 클로로타로닐을 대상으로 실험을 한 결과 파장은 350nm에서, 과산화수소의 공급은 20%에서 최적처리효율을 나타냈으며 과산화수소 또는 UV 조사를 단독적으로 적용하였을 때 그 제거효과는 미미하였으나 UV와 과산화수소를 병행하여 처리하였을 때 처리효율은 가속화되었다. 최적조건에서 20분간 반응하였을 때 고체상 표면에 잔류하는 베노밀은 약 $2{\mu}g/cm^2$이 제거되었으며, 클로로타로닐은 약$1.88{\mu}g/cm^2$이 제거되었다.

• 한국토양비료학회지
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• 제50권4호
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• pp.285-292
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• 2017

Antibiotics have been used for treating human and animal disease and enhancing growth of cattle, swine, and poultries. However, overused antibiotics can be released into the environment and produce antibiotic resistance genes (ARGs) in the environment. Main objective of this research was to monitor residual of antibiotics in solid matrix such as manure, wastewater sludge, soil and sediment. Total of six antibiotics, Chlortetracycline (CTC), Oxytetracycline (OTC), Tetracycline (TC), Sulfamethazine (SMT), Sulfamethoxazole (SMX), Sulfathiazole (STZ), used for both human and animal was monitored. Result showed that the detection frequency of 6 antibiotics was ordered SMT (100%) > TC = CTC (75%) > OTC (38%) > STZ (13%) > SMZ (0%) and the highest concentration ($309.83{\mu}g\;kg^{-1}$, SMT) was observed in manure. Comparing residual concentration of antibiotics (TC, CTC, and OTC) in soil and sediment, higher concentration was observed in sediment indicating that dissolved forms of antibiotics are released into river and sorbed into sediment particle. In conclusion, monitoring for residual of antibiotics in the environment is necessary and more research should be conducted to verify the source of antibiotic release.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.236-244
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• 2017

In this study, the high-velocity impact penetration behavior of $[45/0/-45/90]_{ns}$ carbon/epoxy composite laminates was studied. The considered configuration includes a spherical steel ball impacting clamped circular laminates with various thicknesses and diameters. First, the impact experiment was performed to measure residual velocity and extent of damage. Next, the impact experiment was numerically simulated through finite element analysis using LS-dyna. Three-dimensional solid elements were used to model each ply of the laminates discretely, and progressive material failure was modeled using MAT162. The result indicated that the finite element simulation yielded residual velocities and damage modes well-matched with those obtained from the experiment. It was found that fiber damage was localized near the impactor penetration path, while matrix and delamination damage were much more spread out with the damage mode showing a dependency on the orientation angles and ply locations. The ballistic-limit velocities obtained by fitting the residual velocities increased almost linearly versus the laminate diameter, but the amount of increase was small, showing that the impact energy was absorbed mostly by the localized impact damage and that the influence of the laminate size was not significant at high-velocity impact.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.173-180
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• 2004

The tread pattern of a tire has an important effect on tire performances such as handling, wear, noise, hydroplaning and so on. However, a finite element analysis of a patterned tire with detailed tread blocks has been limited owing to the complexity of making meshes for tread blocks and the huge computation time. The computation time has been shortened due to the advance in the computer technology. The modeling of tread blocks usually requires creating a solid model using a CAD software. Therefore it is a very complicated and time-consuming job to generate meshes of a patterned tire using a CAD model. A new efficient and convenient method for generating meshes of a patterned tire has been developed. In this method, 3-D meshes of tread pattern are created by mapping 2-D meshes of tread geometry onto 3-D tread surfaces and extruding them through tread depth. Then, the tread pattern meshes are assembled with the tire body meshes by the tie contact constraint. Residual aligning torque and frictional energy are calculated by using a patterned tire model and compared to the experimental results. It is shown that the calculated results of a patterned tire model are in a good agreement with the experimental ones.

• 생약학회지
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• 제32권3호통권126호
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• pp.200-211
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• 2001

This study was carried out to determine the 11 organochlorine, 7 organophosphorus residual pesticides in 251 crude drugs. These residual pesticides in herbal drugs were extracted with acetonitrile and the extracts were cleaned up via LC-florisil solid phase extraction column. The prepared samples were assayed for pesticide residues using GC-ECD, NPD with capillary column and identified by GC-MSD. Recoveries were $63.9{\sim}111.5%$ in the organochlorine pesticides and $69.8{\sim}92.4%$ in the organophosphorus pesticides, and detection limits were $0.001{\sim}0.65\;ppm$ in the organochlorine pesticides and $0.0009{\sim}0.0074\;ppm$ in the organophosphorus pesticides. Pesticide residues were detected in 9 cases.

• 소성∙가공
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• 제31권6호
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• pp.394-403
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• 2022

In the automotive industry, cold-drawn austenitic stainless steel is commonly used to handle high fuel pressures in gasoline direct injection (GDI) engines. In this study, we analyzed the effects of main process variables such as cross-sectional shape, drawing speed and friction coefficient on the microstructure, hardness and residual stress of the drawn material in the two-step cold drawing process. By changing the cross-sectional shape in the first-step cold drawing, the possibility of improving the shape accuracy or physical properties of the finally cold-drawn fuel rail pressure sensor product was investigated.

• 한국식품저장유통학회지
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• 제8권3호
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• pp.302-307
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• 2001

파쇄한 재료와 젖산균 스타터를 사용하여 김치를 숙성시킨 후 열풍건조 (HAD) 및 동결건조 (FD)를 행하고, 성형압력 (100, 150, 200 kg/cm2)과 성형시간별 (0, 1, 2, 3, 4분)로 제조한 김치타블궷 (KT)의 붕해성과 여백의 특성, 텍스쳐, 객도, 흡습성 및 관능적 품질을 조사하였다. FD-KT의 성형압력의 증가에 따른 붕해성은 큰 차이를 보이지 않았으나 HAD-KT는 크게 감소하였으며, FD-KT는 HAD-KT에 비하여 붕해성이 높았다. KT 수용액의 pH는 건조방법과 성형압력에 따른 차이를 보이지 않았으나 산도와 총당은 HAD-KT가 FD-KT에 비하여 낮았다. KT의 max, yield, strength 및 hardness는 HAD-KT가 FD-KT에 비하여 높았다. FD-KT는 HAD-KT에 비하여 다소 낮은 적색도를 보였으나 백색도는 높았다. KT의 색상, 촉감, 향미, 씹는 맛 및 기호도는 전반적으로 FD-KT가 높은 값을 나타내었다. 흡습성은 FD-KT가 HAD-KT에 비하여 성형압력에 관계없이 높았다. HAD-KT는 성형압력과 성형시간이 증가함에 따라 흡습량이 감소하였으나 FD-KT는 흡습량이 증가되었다. 품질특성을 종합한 결과 FD-KT, HAD-KT 다같이 성형 압력은 200kg$\textrm{cm}^2$에서 우수하였으며 성형시간은 3분이 적합하였다.