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21.
Finer lamellar spacing in the lamellar structure of a Ti–45Al–2Nb–2Mn + 0.8 vol.%TiB2 (45XD) alloy does improve the primary creep resistance. However, the unstable nature of the fine plate contributes largely to the degradation of the lamellar structure and a rapid increase in the tertiary creep rate, indicating that a fine lamellar structure has a detrimental effect on the long-term creep. 相似文献
22.
The curing behavior of an epoxy/clay nanocomposite system composed of a bifunctional epoxy resin with an aromatic amine curing agent and an organically modified clay was investigated. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the epoxy/clay nanocomposite system. The curing rate of the nanocomposite system increased with increasing clay content. A kinetic equation, considering an autocatalytic reaction mechanism, could describe fairly well the curing behavior of the epoxy/clay nanocomposite system. The reaction kinetic parameters of the kinetic equation were determined by fitting DSC conversion data to the kinetic equation, using a nonlinear numerical method. Dynamic mechanical analysis was used to investigate the thermomechanical properties of the epoxy/clay nanocomposite system. The glass transition temperature of the epoxy/clay nanocomposite system increased slightly with increasing clay content. The structure of the nanocomposite system was characterized by X‐ray diffraction analysis and transmission electron microscope imaging. The formation of intercalated structures was observed dominantly in the epoxy/clay nanocomposites, together with some exfoliated structures. POLYM. ENG. SCI., 46:1318–1325, 2006. © 2006 Society of Plastics Engineers 相似文献
23.
Kyoung Duck Seo Jang Min Park Hyeonsoo Jeong Dong Sung Kim 《Microsystem Technologies》2014,20(2):243-250
We develop a miniaturized batch-type screw mixer (BSM) for uniform mixing of polymer resin and nanoparticles, based on the stretching of material elements. This stretching is induced by the combination of recirculating cross-sectional flows in deep channels of the screw and high shear stress developed at flight regions. The BSM is used to produce a polymer nano-composite composed of multi-walled carbon nanotubes and polydimethylsiloxane resin. The mixing performance of the BSM is characterized quantitatively by estimating two different types of mixing efficiencies (i.e., dispersive mixing and distributive mixing) via transmitted light microscope images. The developed BSM highly improves the mixing performance rather than that of a conventional ultrasonic mixing device. 相似文献
24.
Eddy characteristics on mass transfer close to free interface 总被引:1,自引:0,他引:1
The velocity fluctuations in the immediate vicinity of a free interface were measured with a hot film anemometer. And mass
transfer rates and eddy exposure times were analyzed by using the method of deterministic approach. These mass transfer rates
were compared with the mass transfer rates by means of concentration measurements in the air-water system.
The eddy exposure time distributions obtained from velocity data were skewed toward the lower time value. The contribution
of eddies wi:h small exposure time was increased as the liquid became more turbulent. The mass transfer rates were mainly
contributed by the Prandtl size eddies and even larger eddies. The mass transfer predictions by the single eddy model employing
a deterministic method were in good agreement with the experimental results by independent measurements of concentration. 相似文献
25.
Jong-Ho Ryu Jong Hyun Seo Jae-Han Jeong Sung-Kap Kim Dong Nyung Lee 《Journal of Applied Electrochemistry》2004,34(9):879-884
A study has been made of the electrochemical etching of 99.99% aluminum foils at a current density of 50 mA cm–2in AlCl3–HCl solutions (1 m Cl–) at 80 °C. The solutions were made by dissolving metallic aluminum into 1m HCl solution, to give a Cl– concentration of 1 m. The number density of etch tunnels and the homogeneity of tunnel length decreased, and the mean pit size and its standard deviation increased with increasing Al3+ concentration. The results were discussed based on potential transients at a current density of 50 mA cm–2, current–potential curves at a scan rate of 10 m Vs–1 and electrochemical impedance spectra. 相似文献
26.
We prepared poly(p‐phenylene pyromellitimide) (PMDA–PDA), poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10?10 to 11.3 × 10?10 cm2/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in‐plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003 相似文献
27.
Yongwon Seo Sung-Ho Jo Ho-Jung Ryu Hee Dal Bae Chong Kul Ryu Chang-Keun Yi 《Korean Journal of Chemical Engineering》2007,24(3):457-460
A bubbling fluidized bed reactor was used to study CO2 capture from flue gas by using a potassium-based solid sorbent, sorbKX35 which was manufactured by the Korea Electric Power
Research Institute. A dry sorbent, sorbKX35, consists of K2CO3 for absorption and supporters for mechanical strength. To increase initial CO2 removal, some amount of H2O was absorbed in the sorbent before injecting simulated flue gas. It was possible to achieve 100% CO2 removal for more than 10 minutes at 60°C and a residence time of 2 s with H2O pretreatment. When H2O pretreatment time was long enough to convert K2CO3 of sorbKX35 into K2CO3 · 1.5H2O, CO2 removal was excellent. The results obtained in this study can be used as basic data for designing and operating a large scale
CO2 capture process with two fluidized bed reactors.
This work was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
28.
Theoretical work has been carried out to investigate the filtration of ultra fine aerosol particles in a membrane filter. The analysis was done using a finite element method with a Newtonian fluid model for the carrier medium. Both inertial filtration and diffusional filtration were considered. Prior to the main analysis, our numerical scheme was tested with the analytical results for the diffusion of particles in the cylinder and showed good agreement, which confirms the importance of axial diffusion occurring in a short cylinder like a very thin membrane filter. Particle size, porosity, pressure drop, and flow velocity are found to be main variables that determine the filter efficiency. Two important mechanisms of filtration have opposite effects on the efficiency, depending on the variables. Increases in particle size, pressure drop, and flow velocity cause increases in the efficiency for intertial deposition, while decreases in those variables cause increases in the diffusional efficiency. The existence of a minimum value of total filtration efficiency (sum of inertial efficiency and diffusional efficiency) was indicated for intermediate values of the variables. Lower porosity is found to favor inertial deposition more than diffusion. Some other effects of filtration conditions on the total efficiency are also discussed. 相似文献
29.
Aeree Seo 《Electrochimica acta》2006,52(4):1603-1611
Carbon-supported Pt-based ternary alloy electrocatalysts were prepared by incipient wetness method in order to elucidate the origin of the enhanced activity of oxygen reduction reaction in PEMFC. To measure the catalytic activity and stability of the cathode alloy catalysts (electrodes containing Pt loading of 0.3 mg/cm2, 20 wt.% Pt/C, E-TEK), the I-V polarization curves were obtained. All alloy catalysts showed higher performances than Pt/C. It can be concluded that as platinum formed alloys with transition metals, the electronic state of Pt and the nearest neighbor Pt-Pt distance changes, which significantly influence the electrocatalytic activity for oxygen reduction.Long-term stability test was performed with the Pt6Co1Cr1/C alloy catalyst for 500 h. According to XPS analysis, the lower oxide component with Pt6Co1Cr1/C electrocatalyst provides a large portion of platinum in metallic species in the electrocatalyst and it seems to be mainly responsible for its enhanced activity towards oxygen reduction. 相似文献
30.
We present an algorithm that stylizes an input video into a painterly animation without user intervention. In particular, we focus on pointillist animation with stable temporal coherence. Temporal coherence is an important problem in non-photorealistic rendering for videos. To realize pointillist animation, the various characters of pointillism should be considered in painting process to maintain temporal coherence. For this, weused the particle video algorithm which is a new approach to long-range motion estimation in video. Based on this method, we introduce a method to control the density of particles considering the features of frames and importance maps. Finally, the propagation methods of stroke to minimize flickering effects of brush strokes are introduced. 相似文献