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31.
The frequency dependence of the electron-paramagnon spectrumP() in Pd is calculated within the finite bandwidth model. It is found that for an almost full band, the magnitude, the range, and the position of the peak frequency inP() are dramatically reduced compared to their values in the usual paramagnon theory. Also, we find that the frequency dependence of the spin-fluctuation contribution to the electron self-energy is strongly affected by a close proximity of the Fermi level to the top of the band. We speculate that an unusually large value of the Coulomb pseudopotential is probably partially responsible for the absence of superconductivity in Pd. 相似文献
32.
33.
The formation of oxide phases in the system (1 -x) Fe2O3 +xGd2O3 was investigated for 0 x 1. On the basis of XRD measurements the distribution of oxide phases, -Fe2O3, Gd3Fe5O12, GdFeO3 and Gd2O3 was determined, as a function ofx. No solid solutions were observed with certainty even at the very ends of the concentration range. This was also confirmed by57Fe Mössbauer spectroscopy. New accurate crystallographic data for Gd3Fe5O12 are given. The formation of oxide phases in the system Fe2O3- Gd2O3 is compared with the data for analogous system Fe2O3-Eu2O3. 相似文献
34.
Dual approach to multiple authorship in the study of collaboration/scientific output relationship 总被引:3,自引:0,他引:3
This paper presents an empirical study of the relations between scientific output and collaboration performed on two scales: (1) an individual scale, for members of a study model, and (2) a group scale, for three samples varying in the level of productivity. The rank approach was applied in the preparation of the study model resulting in the selection of a set of the most prolific authors. In the course of that process, multiple authorship problem was solved by a dual approach, consisting of normal count and modified straight count procedures. As shown by the analysis of collaborative patterns, either on individual or on group scales, scientific output is highly dependent on the frequency of collaboration among the same authors. Expressed as the collaboration measure, it might serve as an indicator in comparative analyses of scientific productivity in a given field of science. 相似文献
35.
This paper studies the behavior of motions of large-scale (LS) semistate systems (SSS) governed byP
i
(t)x
i
=M
i
(t,x
i
)x
i
+f
i
(t)+h
i
(t, x), i=1,2,...,s, =(x
1
T
x
2
T
x
s
T
)T, where matricesP
i
(t) are singular. Using Lyapunov's approach and the tools for LS system analysis, a variant of attractivity and ultimate boundedness of appropriate time-variable sets are investigated. The results are based on a specific choice of the aggregate functions. It is assumed that the reduction of equations to a normal form of lower order is inconvenient. The aggregation-decomposition approach used in this paper reduces the dimensionality of an aggregate matrix of the system to the number of its systems. Motion properties of LS systems are deduced from the properties of its isolated subsystems, the character of interconnections, and the conditions imposed on the system aggregate matrix. Sufficient algebraic conditions for the above-mentioned motion properties are developed. 相似文献
36.
The magnetic structure of a vortex in the presence of an anisotropic inhomogeneity distribution is calculated within the London model. The anisotropic supercurrent pattern consists of closed current loops, superimposed on a backflow pattern. The nonvanishing current density at the vortex core gives rise to an intrinsic Lorentz force identical with the pinning force resulting from the spatial variation of the vortex self-energy. 相似文献
37.
38.
The main aim of this work was to study the effects of particle size, particle volume fraction, and matrix strength on the
long fatigue crack growth resistance of two different grades of Al alloys (Al2124-T1 and Al6061-T1) reinforced with SiC particles.
Basically, it was found that an increase in particle volume fraction and particle size increases the fatigue crack growth
resistance at near threshold and Paris regimen, with matrix strength having a smaller effect. Near final failure, the stronger
and more brittle composites are affected more by static modes of failure as the applied maximum stress intensity factor (K
max) approaches mode I plane strain fracture toughness (K
IC). 相似文献
39.
E. Di Todaro C. T. O. F. Ruckert M. T. Milan W. W. Bose Filho J. R. Tarpani D. Spinelli 《Journal of Materials Engineering and Performance》2006,15(5):608-613
The main goal of this work was to evaluate the effectiveness of Walker’s equation in collapsing the fatigue crack propagation
data of a SAE AMS 7475-T7351 aluminum alloy loaded either longitudinally (L-T) or transversely (T-L) to the rolling direction.
T-L orientation testpieces presented lower ductility and fracture toughness values than L-T orientation. As a consequence,
during the fatigue crack propagation tests, T-L testpieces exhibited a stronger influence of monotonic modes of fracture,
resulting in higher Paris exponent values,m. Walker’s model was able to collapse fatigue crack propagation data of L-T test pieces at different applied stress ratios,R. However, for the T-L orientation, due to theR ratio dependency onm andC, simply averaging ofm values for the calculations of Walker’s exponent proved to be inefficient. A simple analytical procedure was proposed by
the authors to modify Walker’s model to take into account such effect. For T-L test pieces, when Walker’s model is modified
by considering both Paris’s exponent as well the coefficient as a function of theR ratio, the fatigue crack growth data collapses within a narrow band, thus allowing predictions to be made satisfactorily.
The collapsed band is even narrower if the empirical relationm=a+blogC is used instead of simple polynomial equations due to a better correlation coefficient. 相似文献
40.
Petar R. Dvornic Milutin N. Govedarica Jelena D. Jovanović Vesna V. Gerov Mališa P. Antić 《Polymer Bulletin》1995,35(5):539-545
Summary A new general procedure for preparation of functionalized oligopolysiloxanes of predetermined molecular weight is described. It utilizes heterogeneously catalyzed siloxane equilibration polymerization reactions which do not require troublesome and sometimes difficult post-preparative work-up procedures usually encountered with the well known homogeneously catalyzed corresponding reactions. The method is described using as example the preparation of , -telechelic vinyldimethylsiloxy-oligopolydimethylsiloxanes from octamethylcyclotetrasiloxane and 1,3-divinyltetramethyldisiloxane, but reference to the preparations of trimethylsiloxy-, dimethylsiloxy-and carboxypropyldimethylsiloxyoligopolydimethylsiloxanes, oligopolymethylhydridosiloxanes or their copolymers is also made. 相似文献