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51.
R.J Hand 《Journal of Non》2003,315(3):276-287
Glass may be strengthened by epoxy coatings although the strengthening mechanisms remain unclear. Possible strengthening mechanisms are reviewed and are used to analyse strength data for both a solvent based and a water based coating system. The coatings either fill (solvent based coatings), or partially fill (water based coatings) surface cracks and it is shown that closure stresses arising from the thermal expansion mismatch of the coating within these cracks can account for the observed degrees of strengthening. It is also demonstrated that other suggested mechanisms such as flaw healing cannot fully account for the observed degree of strengthening. 相似文献
52.
Surface free energy of a solid surface gives a direct measure of intermolecular interactions at interfaces and has a strong influence on adsorption and adhesion behaviour. However few data are available for the surface free energies of electroless Ni–P based composition coatings. In this paper, the electroless Ni–P, Ni–P-surfactant, Ni–Cu–P, Ni–P–PTFE and Ni–Cu–P–PTFE composite coatings were prepared under various coating conditions. The chemical compositions, surface morphology and thickness of the coatings were measured using an energy dispersive X-ray microanalysis (EDX), a scanning electron microscope (SEM) and a digital micrometer respectively. The contact angles of water, diiodomethane and ethylene glycol on the coatings were measured automatically using dataphysics OCA-20 contact angle analyser. The surface free energy of the coatings and their components (e.g. dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the incorporation of surfactant or PTFE particles into Ni–P matrixes has a significant influence on the surface free energy of the coatings, while the incorporation of copper into Ni–P matrixes has no significant influence on the surface free energy of the coatings. 相似文献
53.
F.O. Borges G.H. Cavalcanti A.G. Trigueiros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2003,78(1):119-129
The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multi configuration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S IX and S X spectral lines. 相似文献
54.
55.
We studied the low speed fracture regime (10−4-10−9 m s−1) in different glassy materials (soda-lime glass, glass ceramics) with variable but controlled length scale of heterogeneity. The chosen mechanical system enabled us to work in pure mode I (tensile) and at a fixed load on double cleavage drilled compression specimen. The internal residual stresses of studied samples were carefully relaxed by appropriate thermal treatment. By means of optical and atomic force microscopy techniques fracture surfaces have been examined. We have shown for the first time that the crack front line underwent an out-of-plane oscillating behavior as a result of a reproducible sequence of instabilities. The wavelength of such a phenomenon is in the micrometer range and its amplitude in the nanometer range. These features were observed for different glassy materials providing that a typical length scale characterizing internal heterogeneities was lower than a threshold limit estimated to few nanometers. This effect is the first clear experimental evidence of crack path instabilities in the low speed regime in a uniaxial loading experiment. This phenomenon has been interpreted by referring to the stability criterion for a straight crack propagation as presented by Adda-Bedia et al. [Phys. Rev. Lett. 76 (1996) 1497]. 相似文献
56.
57.
58.
M. C. Crabb 《Journal of Fixed Point Theory and Applications》2007,2(2):171-193
We describe an equivariant version (for actions of a finite group G) of Dold’s index theory, [10], for iterated maps. Equivariant Dold indices are defined, in general, for a G-map U → X defined on an open G-subset of a G-ANR X (and satisfying a suitable compactness condition). A local index for isolated fixed-points is introduced, and the theorem
of Shub and Sullivan on the vanishing of all but finitely many Dold indices for a continuously differentiable map is extended
to the equivariant case. Homotopy Dold indices, arising from the equivariant Reidemeister trace, are also considered.
相似文献
59.
Ken Ono 《Mathematische Annalen》1998,312(2):251-260
60.
This paper presents an analytic approach to the construction cost of fringe-balanced binary search trees. In [7], Mahmoud used a bottom-up approach and an urn model of Pólya. The present method is top-down and uses differential equations and Hwang's quasi-power theorem to derive the asymptotic normality of the number of rotations needed to construct such afringe balanced search tree. We also obtain the exact expectation and variance with this method. Although Pólya's urn model is no longer needed, we also present an elegant analysis of it based on an operator calculus as in [4].This research was supported by the Austrian Research Society (FWF) under the project number P12599-MAT. 相似文献