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31.
Monika Backhaus-Ricoult Serge Hagège Aurélie Peyrot Patrick Moreau 《Journal of the American Ceramic Society》1994,77(2):423-430
(Al,Cr)2 O3 single crystals and polycrystals were internally reduced at 1873 K in an Al/Al2 O3 buffer for periods of time ranging from 1 to 100 h. The growth kinetics of the reduction scale were measured. The microstructure of the reduction scale was investigated by SEM and TEM. As a result of the reduction, two types of discrete chromium precipitates developed inside the alumina matrix (inside the single crystal or the polycrystalline grains), each one being characterized by a particular morphology (needle or spheroid) and a low-energy orientation relationship with respect to the alumina matrix. In addition, larger precipitates without special orientation relationship developed along the grain boundaries and at the triple junctions of the polycrystais. In the first part of this paper, the precipitate morphology and size are described in terms of the crystallography of the interface between the two crystal structures in relation to the reduction mechanism. In the second part, the global reduction scale growth is analyzed in terms of point defect fluxes across the reduction scale. 相似文献
32.
Patrick Saint-Dizier 《Computational Intelligence》1988,4(2):143-145
This short text introduces this special issue of Computational Intelligence on artificial intelligence in France. After a brief presentation of the structure and the research activities in artificial intelligence in France, we introduce the papers enclosed herein. 相似文献
33.
A series of novel pi (π) conjugated polymers, originating from the archetypical Polyphenylene vinylene, in which the phenyl units are successively replaced by the larger naphthyl and anthryl acene units, were previously found to have a well-defined relationship between their relative fluorescence yields and their vibrational characteristics, as determined by Raman spectroscopy. In this study the Strickler-Berg equation is used to probe the influence of continual substitution of higher order acene units into the conjugated backbone in terms of the variation of the radiative and non-radiative rates. The deconvolution of the radiative and non-radiative rates enables the correlation of the reduction of the Raman intensity and concomitant increase in the fluorescence yield with the reduction of the non-radiative rate. This confirms that the reduction of the non-radiative rate is the dominant process introduced by the vibrational confinement originating from systematic substitution of higher order acene units into the polymer backbone. 相似文献
34.
Patrick Musonda 《Computational statistics & data analysis》2008,52(4):1942-1957
Second-order expressions for the asymptotic bias and variance of the log relative incidence estimator are derived for the self-controlled case series model in a simplified scenario. The dependence of the bias and variance on factors such as the relative incidence and ratio of risk to observation period are studied. Small-sample performance of the estimator in realistic scenarios is investigated using simulations. It is found that, in scenarios likely to arise in practice, asymptotic methods are valid for numbers of cases in excess of 20-50 depending on the ratio of the risk period to the observation period and on the relative incidence. The application of Monte Carlo methods to self-controlled case series analyses is also discussed. 相似文献
35.
Matthew N. Ashby Patrick R. Errada Victor L. Boyartchuk Jasper Rine 《Yeast (Chichester, England)》1993,9(8):907-913
We isolated a mutant defective in C-terminal farnesyl cysteine:carboxyl methyltransferase activity from a screen for mutations causing a -specific sterility. A genomic fragment was cloned from a yeast multi-copy library that restored mating. Both the cloned gene and the sterile mutation were allelic to the STE14 gene. A ste14-complementing 2·17 kb BamHI fragment subclone was sequenced and found to encode a 239 amino acid protein with a molecular weight of 27,887 Daltons. The hydrophobicity profile of the methyltransferase reveals the presence of at least five potential transmembrane domains. In comparisons of the C-terminal methyltransferase amino acid sequence with those in the PIR and Swiss protein databases, no significantly similar sequences were found nor were conserved regions from other methyltransferases present. 相似文献
36.
37.
The parallel resources time and hardware and the complexity classes defined by them are studied using the aggregate model. The equivalence of complexity classes defined by sequential space and uniform aggregate hardware is established. Aggregate time is related to (bounded fanin) circuit depth and, similarly, aggregate hardware is related to circuit width. Interelationships between aggregate time and hardware follow as corollaries. Aggregate time is related to the sequential resource reversal. Simultaneous relationships from aggregate hardware and time to sequential space and reversal are shown (and conversely), and these are used as evidence for an “extended parallel computation thesis.” These simultaneous relationships provide new characterizations for the simultaneous parallel complexity class NC and for the complementary class SC. The evaluation of monotone planar circuits is shown to be in NC, in fact in LOGCFL. 相似文献
38.
A multiconfiguration Dirac-Fock (MCDF) technique has been used for computing the wavelengths and transition probabilities for lines in the X-ray spectra of the gallium-like ions from Yb XL to U LXII. Results are presented for the 4s24p-4s24d and 4s24p-4s4p2 allowed transitions (E1) as well as for the forbidden transitions (M1 and E2) within the ground configuration 4s24p. A comparison of the calculated wavelengths with the few experimental results available is also presented. 相似文献
39.
We compare, in this paper, the far field radiated by two fractal distributions of current. The first one is obtained by a fractal cut following the Cantor arrangement, the second one keeps the length of each previous current element, but modifies the distance between the elements which is now taken as a constant. We establish the analytical formulations of the far field at any step n of the Cantor set. Then, we extract the array factor and we analyse and compare the following properties : convergence of the radiation pattern, wide of the main lobe, side lobes level and directivity. 相似文献
40.
Patrick E. Mcsharry Paulo R. C. Ruffino 《Dynamical Systems: An International Journal》2003,18(3):191-200
The asymptotic angular stability of a dynamical system may be quantified by its rotation number or its winding number. These two quantities are shown to result from different assumptions, made about the flow generating the Poincaré map which results from the sequence of homeomorphisms in S l. An ergodic theorem of existence a.s. of the rotation number for non-linear systems is given. The advantages and disadvantages of both the rotation and winding numbers are discussed. Numerical calculations of the distribution of rotation number and winding number arising from different initial conditions are presented for three different chaotic maps. 相似文献