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121.
Giovana de Fátima Menegotto Paulo César Borges Eduardo Mauro do Nascimento Carlos Maurício Lepienski Elaine Cristina Azevedo 《Brazilian Journal of Physics》2011,41(4-6):223-228
The influence of hydrogen loading temperature on the mechanical strength of optical fibers is investigated. Fibers subjected to high-pressure hydrogen loading at different temperatures were submitted to bend tests, and the results compared with those for pristine fibers. The Weibull probability distribution function was used to analyze the data of the mechanical bending strength of the fibers. Fiber strength is reduced by the presence of hydrogen, and this decrease is greater for higher hydrogen loading temperatures. The mechanical properties of the polymers used to coat fibers are affected by the hydrogen loading process and also by the increase in temperature. However, there is no evidence of cracks formation that might allow water to penetrate to the surface of the glass. Observation using scanning electron microscopy revealed that the morphology of fractures in nonhydrogen-loaded fibers have distinct fracture characteristics to that of fibers that are hydrogen loaded at 90°C and 120°C. 相似文献
122.
Daciberg L. Gon?alves Mauro Spreafico Oziride Manzoli Neto 《Journal of Fixed Point Theory and Applications》2011,9(2):285-294
In this work, we show for which odd-dimensional homotopy spherical space forms the Borsuk–Ulam theorem holds. These spaces
are the quotient of a homotopy odd-dimensional sphere by a free action of a finite group. Also, the types of these spaces
which admit a free involution are characterized. The case of even-dimensional homotopy spherical space forms is basically
known. 相似文献
123.
Sfarra Stefano Regi Mauro Tortora Mariagrazia Casieri Cinzia Perilli Stefano Paoletti Domenica 《Journal of Thermal Analysis and Calorimetry》2018,132(2):1367-1387
Journal of Thermal Analysis and Calorimetry - The aim of this work is to evaluate the potentiality of a multi-technique nondestructive approach for characterizing the state of conservation of... 相似文献
124.
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126.
A recent analysis of the experimental data on some physical phenomena ruled by the four fundamental interactions (electromagnetic, weak, strong and gravitational) seems to show the possibility of describing such interactions in terms of a deformation of the usual Minkowski spacetime, with a metric whose coefficients do depend on the energy of the process considered. In this paper, we show that such results can be accounted for in terms of a Kaluza-Klein-like scheme, based on a five-dimensional Riemannian space in which energy plays the role of the fifth dimension. The corresponding five-dimensional Einstein equations in vacuum are solved in some cases of physical relevance and it is shown that all the phenomenological metrics describing the four fundamental forces are recovered as special cases of the classes of solutions found. Possible developments of the formalism are also briefly outlined. 相似文献
127.
Mauro Cerasoli 《Journal of Mathematical Analysis and Applications》1983,94(1):150-165
In occupancy problems we randomize the number of balls with a Poisson process of intensity α. Thus some classical formulas are very easily demonstrated and generalized with the aid of inclusion-exclusion principle. Then we give a general theorem to calculate the distributions and moments of particular random variables or waiting times when infinite balls are considered. This theorem can be applied to the well-known birthday and coupon collectors problems. 相似文献
128.
Vittadini A Casarin M Sambi M Selloni A 《The journal of physical chemistry. B》2005,109(46):21766-21771
Periodic density functional calculations have been used to investigate the structure and stability of epitaxial vanadium oxide films grown on the TiO(2)(001) anatase surface. The formation energy of films of V(2)O(5) stoichiometry, initially low, is found to rapidly increase with the film thickness, at variance to what is obtained for reduced pseudomorphic VO(2) films. This is in tune with results of oxygen-assisted molecular beam epitaxy. The oxidation of thick, viz. >2 monolayers (ML), VO(2) films yields a c(2 x 2) reconstructed surface, in agreement with low energy electron diffraction. These films are composed by partially reduced inner V atoms in a distorted-octahedral environment, and by isolated surface dioxovanadium centers exhibiting a distorted trigonal-bipyramidal coordination. Single scattering simulations of X-ray photoelectron diffraction patterns have also been performed, taking both 2- and 3-ML surface surface-oxidized films as models. Results are in fair agreement with experiments referring to films grown in oxidizing conditions, which suggests that coherent vanadia ultrathin films could be formed in vanadia-titania catalysts. The electronic structure of the films has been finally studied, finding that the terminal oxygens carried by the surface dioxovanadium species have a strong nucleophilic character, which makes them potential active centers for selective oxidation catalysis. 相似文献
129.
The phytochemical study of aerial parts of Viburnum sargenti Koehne, a species spontaneous in Mongolia and Northern China, led to the isolation of three iridoid glucosides of Valeriana-type: the novel 7,10,2'-triacetylsuspensolide F, 1, and the known viburtinoside IV and V. In addition, (+)-epicatechin was also isolated. 相似文献
130.
Two flavonoid glycosides containing acetylated allose, and two iridoid glucosides were obtained from a EtOH extract of Stachys corsica, an endemic plant of Sardinia and Corsica. All the compounds have previously been isolated from other species of Stachys. 相似文献