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111.
112.
Vijay Kumar 《Bulletin of Materials Science》1996,19(6):1047-1058
With the discovery of solid C60, efforts are being made to develop new clusters and molecules which could be assembled to form new materials. Here we present
some recent developments in this direction and discuss bonding in such materials. 相似文献
113.
114.
S Kasiviswanathan P S Asoka Kumar B K Mathur K L Chopra 《Bulletin of Materials Science》1996,19(2):411-416
Surface structure of thin silver films (200 Å) on two technologically important films, indium tin oxide (ITO) and aluminium oxide, has been studied using scanning tunneling microscope. ITO films were prepared by reactive electron beam evaporation. Aluminium oxide films were prepared by oxidizing 2000 Å thick aluminium films evaporated on to H2 terminated single crystal silicon substrates. The surface structure of silver on ITO and aluminium oxide appeared to be same and was characteristic of Stranski-Krastanov type. The observed asymmetry in the island shape was attributed to the anisotropic nature of the strain fields surrounding the nucleation centres. 相似文献
115.
Erythrocyte ghosts were exposed to various levels of oxyradical shock in order to identify the extent of accumulation of peroxidative intermediates. Malondialdehyde reacting end products were the same in all different models. But, the accumulation of dienyl radical species increased with higher intensity of oxyradical shock. These dienyl radicals may rearrange to create a homogeneous smectic multilamellar microenvironment which may be more fluid in terms of the molecular dynamics. 相似文献
116.
117.
Summary The three-dimensional Poisson-Voronoi model, which is topologically equivalent to the microstructure of real ceramics and metals, has been used to study the stress distribution within a simulated polycrystalline aggregate having 200 grains. Micro-stresses such as the maximum principal stress, maximum shear stress, first invariant of stress, and Von-Mises stress are found to vary systematically with the anisotropy of single crystal. 相似文献
118.
Vendrame L. Zabotto E. Dal Fabbro A. Zanini A. Verzellesi G. Zanoni E. Chantre A. Pavan P. 《Electron Devices, IEEE Transactions on》1995,42(9):1636-1646
In this paper we describe a set of measurements representing a complete characterization of impact-ionization effects in bipolar transistors. We demonstrate that impact-ionization significantly influences the dependence of base resistance on current and voltages applied to the device. A dc method for the simultaneous extraction of all parasitic resistances in bipolar transistors is presented. The method can separate the influence of current-crowding on the base resistance from that of base width and conductivity modulation; the collector parasitic resistance is measured in the active region. Starting from the parameters extracted by means of these techniques, a complete and accurate circuit-model of impact-ionization effects can be defined 相似文献
119.
J Barrette R Bellwied P Braun-Munzinger WE Cleland T Cormier G Dadusc G David J Dee O Dietzsch M Fatyga SV Greene JV Germani JR Hall TK Hemmick N Herrmann RW Hogue B Hong K Jayananda D Kraus BS Kumar R Lacasse D Lissauer WJ Llope TW Ludlam R Majka SK Mark JT Mitchell M Muthuswamy E O'Brien C Pruneau FS Rotondo da Silva NC J Simon-Gillo U Sonnadara J Stachel H Takai EM Takagui TG Throwe L Waters C Winter D Wolfe CL Woody N Xu Y Zhang Z Zhang C Zou 《Canadian Metallurgical Quarterly》1995,52(5):2679-2683
120.
The kinetics and mechanism of oligomerization of cardanol over acid catalysts were studied. GPC results showed the formation of a mixture of oligomers such as dimer, trimer, tetramer, etc. IR spectra of the products of oligomerization showed a decrease in the intensity of the double bond absorption band at 1630 cm?1 and the disappearance of terminal vinyl bands at 895 cm?1 and 907 cm?1. 1H NMR spectra showed drastic changes in the unsaturated proton resonance signals at 5.5δ with respect to saturated protons at 0.2–2.5δ. The ratio of resonance integrals of unsaturated to saturated protons decreased from 1 : 6.5 to 1 : 20 after oligomerization. GPC studies showed that the rate of formation of the dimer, trimer, tetramer, etc. follow an identical path and that the individual oligomers are formed in the same weight percentage at any time during the reaction. A kinetic scheme is proposed to explain this phenomenon. Kinetic studies showed that the oligomerization reaction follows first order kinetics with respect to the monomer concentration and the rate constant is K = 6.6 × 10?5s?1. A probable mechanism for the oligomerization of cardanol is proposed. 相似文献