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61.
62.
D'Humières D Ginzburg I Krafczyk M Lallemand P Luo LS 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2002,360(1792):437-451
This article provides a concise exposition of the multiple-relaxation-time lattice Boltzmann equation, with examples of 15-velocity and 19-velocity models in three dimensions. Simulation of a diagonally lid-driven cavity flow in three dimensions at Re = 500 and 2000 is performed. The results clearly demonstrate the superior numerical stability of the multiple-relaxation-time lattice Boltzmann equation over the popular lattice Bhatnagar-Gross-Krook equation. 相似文献
63.
Teplenko Marina A. Podchernyaeva Irina A. Panasyuk Alla D. 《Powder Metallurgy and Metal Ceramics》2002,41(3-4):154-161
We have studied the process of electrospark alloying of titanium alloy VT6 and steels with a composite material based on AlN ZrB2 with ZrSi2 additive. We have established that Al2SiO5 and ZrSiO4 forming in the coating directly during its formation play the role of a solid lubricant. Under optimal conditions for electrospark alloying of the titanium alloy, the coefficient of friction is 0.13, the wear is 6 m/km for a sliding velocity of 14 m/sec and a load of 2.56 MPa. Ceramics based on AlN ZrB2 can be recommended for use as wear-resistant and corrosion-resistant coatings. 相似文献
64.
Poly(N-isopropylacrylamide), NIPA, thermoresponsive hydrogels with well-defined concentrations of an electroactive probe, 1,1'-ferrocenedimethanol, Fc(MeOH)2, were prepared. The discontinuous reversible volume phase transition of such gels occurs at 32 +/- 1 degrees C and results in a release of approximately 93% of the solution from the polymeric network. Transport of Fc(MeOH)2 in both swollen and collapsed gels was studied using steady-state voltammetry and chronoamperometry at platinum microelectrodes. The diffusion coefficient of Fc(MeOH)2 in collapsed gels was approximately 2 orders of magnitude smaller than that in swollen gels. UV/vis spectroscopic studies showed that for 3.0% NIPA gel, the concentration of Fc(MeOH)2 in the collapsed phase was approximately 6 times higher than that in released solution and 4.5 times higher than in the original swollen gel. 相似文献
65.
A problem of a modal P-regulator synthesis for a linear multivariable dynamical system with uncertain (interval) parameters in state space is considered. The designed regulator has to place all coefficients of the system characteristic polynomial within assigned intervals. We have developed the approach proposed earlier in Dugarova and Smagina (Avtomat. i Telemech. 11 (1990) 176) and proved a direct correlation between interval system controllability and existence of robust modal P-regulator. 相似文献
66.
67.
Sergei V. Kostjuk Alexei Yu. Dubovik Irina V. Vasilenkol Vyacheslav P. Mardykin Ludmila V. Gaponik Fyodor N. Kaputsky Lev M. Antipin 《Polymer Bulletin》2004,52(3-4):227-234
Summary
Quasiliving cationic polymerization of styrene was obtained in the system 2-phenyl-2-propano-/AlCl3·OBu2/Bu2O in a mixture of 1,2-dichloroethane and n-hexane (55:45 viv) at -15 °C. The molecular weights of the polymers (Mn) increased in direct proportion to the monomer conversion. However, the experimental Mns are essentially higher than theoretical ones, indicating that slow initiation relative to propagation takes place. The molecular weight distributions were broad (Mw/Mn2.5), probably due to the slow initiation and slow exchange between reversibly terminated and propagating species. 相似文献
68.
Perminova IV Frimmel FH Kudryavtsev AV Kulikova NA Abbt-Braun G Hesse S Petrosyant VS 《Environmental science & technology》2003,37(11):2477-2485
Recorded molecular weights (MWs) for humic substances (HS) range from a few hundred to millions of daltons. For purposes of defining HS as a specific class of chemical compounds, it is of particular importance to ascertain if this broad range of MWs can be attributed to actual variability in molecular properties or is simply an artifact of the analytical techniques used to characterize HS. The main objectives of this study were (1)to establish if a preferential range of MWs exists for HS and (2) to determine any consistent MW properties of HS. To reach the goal, we have undertaken an approach to measure under standardized conditions the MW characteristics of a large set of HS from different natural environments. Seventy-seven humic materials were isolated from freshwater, soil, peat, and coal, such that each possessed a different fractional composition: humic acid (HA), fulvic acid (FA), and a nonfractionated mixture of HA and FA (HF). Size exclusion chromatography (SEC) was used as the analytical technique to determine molecular weight characteristics. The MW distributions were characterized by number (Mn) and weight (Mw) average MW, and by polydispersity. The complete range of Mw values varied within 4.7-30.4 kDa. The maximum Mw values were observed for peat HF and soil HA, whereas the smallest weights were measured for river water HF. Maximum values of polydispersity (3.5-4.4) were seen for peat HF and soil HA, while much lower values (1.6-3.1) were found for all preparations isolated with XAD-resins. Statistical evaluation showed consistent Mw and Mn variations with the HS source, while polydispersity was mostly a function of the isolation procedure used. A conclusion was made that HS have a preferential range of MW values that could characterize them as a specific class of chemical compounds. 相似文献
69.
Podchernyaeva Irina A. Lavrenko Vladimir A. 《Powder Metallurgy and Metal Ceramics》2001,40(1-2):44-48
The formation of a surface layer on low-alloyed steel during light-thermal treatment with a composite material based on Si3N4 Al2O3 was investigated. The working surfaces were studied using metallographic, x-ray diffraction, and electron-probe microanalysis. It was found that the corrosion-resistant phases Al2SiO5, (Fe, Cr)2O3, (Cr, Al) 2O3, and NiCrO4 formed in the alloyed layer, increasing its microhardness by 2-5 times and its corrosion resistance in sea water by more than two orders of magnitude. 相似文献
70.