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941.
942.
We have used x-ray phase analysis to study the composition of the products of reaction between oxygen and nanocrystalline
powders with particle sizes 15, 40, 55, and 80 nm, and also specimens pressed (and sintered) from them. The powders were oxidized
in air at 100°C (400 h) to 500°C (5 min), while the sintered specimens were oxidized at 600–900°C for 15, 120, and 240 min.
In all cases, in the initial oxidation step the oxynitride Ti(OxNy) is formed, which over time is oxidized to TiO, Ti2O3, Ti3O5, TiO2 (anatase) and TiO2 (rutile). In the range 600–800°C, formation of a continuous oxide layer and conversion of anatase to rutile slows down diffusion
of oxygen in the scale. We have established that at 900°C, the growth rate of the scale thickness increases and so the reflections
from the oxynitride are barely noticeable on the diffraction patterns taken from the surface of the oxidized specimen. In
these diffraction patterns, along with strong reflections from the rutile, we also observed weak reflections from lower oxides
and anatase, which may be due to reaction between oxygen and the titanium ions diffused to the scale surface. We have concluded
that at T > 850°C, the mechanism for oxidation of TiN changes. This is due to superposition of counterdiffusion of titanium
ions on the diffusion of oxygen.
__________
Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 72–78, March–April, 2006. 相似文献
943.
P.U. Sharma K.B. Modi V.K. Lakhani K.B. Zankat H.H. Joshi 《Ceramics International》2007,33(8):1543-1546
Compositional dependence of hyperfine parameters, determined through Mössbauer spectral analysis has been studied for Y3−xFe5+xO12 (x = 0.0, 0.1, 0.3 and 0.5) garnet system at 300 K. The Mössbauer spectra have been fitted with three sextets in the ferrimagnetic state corresponding to Fe3+ ions at tetrahedral (d), octahedral (a) and dodecahedral (c) sites of the crystal structure. It is observed that isormershift, quadrupole shift and hyperfine field of d-site show no significant variation with Fe3+ concentration. The change in hyperfine fields of a- and c-sites with composition (x) has been explained on the basis of strength of exchange integrals, change in isomershift can be understood due to s-electron charge distribution and asymmetric displacement of oxygen ions surrounding the a- and c-sites seems to be responsible for observable quadrupole shift. The magneton number values obtained from magnetization and Mossbauer data are in agreement to those calculated using Neel's three sublattice model of ferrimagnetism. 相似文献
944.
945.
V. V. Teleshov 《Russian Metallurgy (Metally)》2007,(2):161-165
Experimental data are often approximated by two-parameter relations in the form of a power or an exponential function. When a number of similar objects are considered, the parameters of these relations are connected by a correlation dependence. The examples of empirical relations where this dependence is observed are considered. In all cases of this correlation dependence, the value of an approximating function changes by several orders of magnitude when its argument varies by several times, and the initial data for the calculation of the empirical-equation parameters are located in a relatively narrow band in the coordinate space. This behavior is always accompanied by a linear relationship between the empirical coefficients of the equations obtained for a number of similar objects. 相似文献
946.
S. A. Abramov A. A. Bogolyubskaya V. A. Rostovtsev V. F. Edneral 《Programming and Computer Software》2007,33(2):55-59
An annual report on meetings of the scientific research seminar on computer algebra is presented. 相似文献
947.
A systematic approach for product families formation in Reconfigurable Manufacturing Systems 总被引:2,自引:0,他引:2
The aim of this work is to establish a methodology for an effective working of Reconfigurable Manufacturing Systems (RMSs). These systems are the next step in manufacturing, allowing the production of any quantity of highly customised and complex products together with the benefits of mass production. In RMSs, products are grouped into families, each of which requires a system configuration. The system is configured to produce the first family of products. Once it is finished, the system is reconfigured in order to produce the second family, and so forth. Therefore, the effectiveness of a RMS depends on the formation of the best set of product families. Therefore, a methodology for grouping products into families, which takes into account the requirements of products in RMSs, is an issue of core importance. These requirements are modularity, commonality, compatibility, reusability, and product demand. The methodology starts by calculating, for each product requirement, a matrix that summarises the similarity between pairs of products. Then, through the use of the AHP methodology, a unique matrix that comprises the similarity values between products is obtained. The Average Linkage Clustering algorithm is applied to this matrix in order to obtain a dendogram that shows the diverse sets of product families that may be formed. 相似文献
948.
A compound concentrator guide has been investigated that provides uniform energy distribution over the receiver. The values of the focal parameters of the parabolas that form the quasi-parabolic guide curve have been determined. The parametric equations of the curve along which the parabolas foci travel have been set up. Arrangement variants of the guide curve branches have been considered, and the compound concentrators have been assessed. 相似文献
949.
I. V. Shcherbatenko E. P. Ivanova V. I. Surikov 《Chemical and Petroleum Engineering》2007,43(5-6):335-342
A method is proposed for calculating the optimum density of lattice of blades of screw pump impeller that ensures, for a given
cavitation margin (inlet pressure), the first critical condition on the partial cavitation characteristic of the pump. The
equations obtained can be used also to calculate the permissible cavitation margin of screw centrifugal and screw mixed-flow
pumps as well as of stand-alone screw impeller, provided the geometric and operating conditions of the screw are given.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 29–33, June, 2007. 相似文献
950.
M. Sh. Marasulov V. D. Markova D. N. Sabirova Kh. A. Aslanov N. V. Tverdikov 《Fibre Chemistry》1986,17(6):435-436
Conclusions An attempt has been made to use the KÉ-250-ShS machine for twisting acetate yarns.It has been found that in developing a new twisting machine it is advisable to use a checkerboard disposition of the spindles in its lower part with the objective of reducing the noise level, and also to use pedal braking to stop the spindles. This helps increase the productivity of twister labor, and mechanization and automation of operations associated with transfer in removing packages of weight not less than 3 kg.Translated from Khimicheskie Volokna, No. 6, pp. 40–41, November–December, 1985. 相似文献