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91.
Manuel Amann 《Topology and its Applications》2011,158(2):183-189
Positive Quaternion Kähler Manifolds are Riemannian manifolds with holonomy contained in Sp(n)Sp(1) and with positive scalar curvature. Conjecturally, they are symmetric spaces. In this article we are mainly concerned with Positive Quaternion Kähler Manifolds M satisfying b4(M)=1. Generalising a result of Galicki and Salamon we prove that M4n in this case is homothetic to a quaternionic projective space if 2≠n?6. 相似文献
92.
93.
Y.I. Latyshev B. Pannetier P. Monceau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(4):421-426
We demonstrate for the first time that a periodic array of submicrometer holes (antidots) can be patterned into thin single
NbSe3 crystals. We report on the study of Charge Density Wave (CDW) transport of the network of mesoscopic units between antidots.
Size of the elementary unit can be as small as 0.5 μm along the chain axis and in cross-section. We observe size effects for Ohmic residual resistance and in CDW transport current-voltage characteristics
in submicronic networks.
Received: 25 November 1997 / Received in final form: 30 March 1998 / Accepted: 6 April 1998 相似文献
94.
Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations 总被引:2,自引:0,他引:2
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Monochromatic aberrations in post laser in-situ keratomileusis (LASIK) eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function (MTF) of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations. 相似文献
95.
The relaxation processes (α, β, and γ) in UHMW PE fibres drawn to different draw ratios λ have been studied by dynamic-mechanical and nuclear magnetic resonance methods. The temperature dependences of tensile loss
moduli E″ and spin-lattice relaxation times T
1 have been analyzed assuming distribution of correlation times τ according to the Davidson—Cole function. The activation energies E
a and parameters ε characterizing widths of distribution, and asymptotic value τ
0 for correlation times have been determined from experimental data for low-temperature γ-process and for high-temperature α-process. A weak β-process has been found by dynamic-mechanical method and quantitative analysis was made only for fibres with λ = 9. The temperature dependences of second moment M
2 of the broad-line NMR spectra have been analyzed according to the Gutowsky—Pake formula, which includes only a single correlation
time τ
c without distribution. In this case the activation energies E
a and values of τ
0 have been determined. 相似文献
96.
97.
Joachim Toft 《Bulletin des Sciences Mathématiques》2002,126(2):115-142
We study continuity properties for a family {sp}p?1 of increasing Banach algebras under the twisted convolution, which also satisfies that a∈sp, if and only if the Weyl operator aw(x,D) is a Schatten-von Neumann operator of order p on L2. We discuss inclusion relations between the sp-spaces, Besov spaces and Sobolev spaces. We prove also a Young type result on sp for dilated convolution. As an application we prove that f(a)∈s1, when a∈s1 and f is an entire odd function. We finally apply the results on Toeplitz operators and prove that we may extend the definition for such operators. 相似文献
98.
Martino Prizzi 《Journal of Differential Equations》2005,210(2):429-451
We study a non-autonomous parabolic equation with almost-periodic, rapidly oscillating principal part and nonlinear interactions. We associate to the equation a skew-product semiflow and, for a special class of nonlinearities, we define the Conley index of isolated compact invariant sets. As the frequency of the oscillations tends to infinity, we prove that every isolated compact invariant set of the averaged autonomous equation can be continued to an isolated compact invariant set of the skew-product semiflow associated to the non-autonomous equation. Finally, we illustrate some examples in which the Conley index can be explicitly computed and can be exploited to detect the existence of recurrent dynamics in the equation. 相似文献
99.
We study the Jordan structures and geometry of bounded matrix-valued harmonic functions on a homogeneous space and their analogue, the harmonic functionals, in the setting of Fourier algebras of homogeneous spaces.Supported by EPSRC grant GR/G91182 and NSERC grant 7679. 相似文献
100.
P. Foury-Leylekian J.P. Pouget M. Greenblatt E. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):157-167
We present a structural investigation of the family of quasi-one-dimensional (quasi-1D) conductors, which exhibit intriguing charge transport properties where, for x small, the conductivity exhibits a crossover from a semiconducting to a metallic like regime when the temperature decreases.
In these materials the double zig-zag chains, together with the diphosphate groups, delimit channels which are partially filled with the ions. It is found, from an X-ray diffuse scattering investigation, that at room temperature the ions are locally ordered on a lattice of well-defined sites in the channel direction and not ordered between neighboring
channels. These ions form 1D incommensurate concentration waves whose periodicity depends on the stoichiometry. In upon cooling, the intrachannel order increases significantly, and an interchannel order between the 1D concentration waves develops. But, probably because of kinetic effects, no tridimensional (3D) long range order of the ions is achieved at low temperature. The 3D low-temperature local order has been determined and it is found that the phase
shift between the concentration waves minimizes their Coulomb repulsions. This local order is increasingly reduced as the Cs concentration
diminishes. We interpret the intriguing features of the electrical conductivity in relationship with the thermal evolution
of the Cs ordering effects. We suggest that in , for x small, a localization-delocalization transition of the Anderson type occurs due to the thermal variation of the Cs disorder.
When x increases, the enhancement of the disorder leads to a localization of the electronic wave function in the whole temperature
range measured. Finally, and probably because of the disorder, no charge density wave instability is revealed by our X-ray
diffuse scattering investigation.
Received: 10 October 1997 / Received in final form: 11 December 1997 /
Accepted: 16 December 1997 相似文献