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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 350–354, November, 1992. 相似文献
972.
Evolution of the capillary network in a reactive powder concrete during hydration process 总被引:7,自引:0,他引:7
V. Morin F. Cohen-Tenoudji A. Feylessoufi P. Richard 《Cement and Concrete Research》2002,32(12):1907-1914
Ultrasonic waves in echographic mode, combined with autogenous shrinkage measurements, were used to study the evolution of the capillary network of reactive powder concrete (RPC) from the time after the mixing. Two characteristic porous classes have been identified: the first, between 10 and 20 nm, begins when the material reaches its solid hyperstatic state, and the second about 1 or 2 nm. The first class is associated with the porous space between the C-S-H hydrate clusters and the second with the internal porosity of the hydrate. The evolution of the active capillary radius as a function of the degree of hydration allows us to understand the strong interaction between the capillary network size and the chemical activity given by the dissipated calorimetric power curve. Indeed, the maximum point of the chemical activity marks the transition of the first class of pores to the second one. Finally, measurements of electrical conductivity through RPC samples show that after the maximum of the dissipated power, the curve of this electrical conductivity presents the same evolution as the capillary radius. As the electrical conductivity clearly depends on the evolution of the capillary network, the similarity between the results confirms our analysis in pore classes. 相似文献
973.
974.
The method of layer-by-layer physicochemical analysis is used to study phase transformations in chromium-nickel steels of martensitic class after high-cycle fatigue tests and after thermal exposure at similar temperature and time conditions. The Laves phase is shown to be distributed nonuniformly over the cross section of specimens tested for fatigue resistance. The results of the tests are used to correct phase compositions. 相似文献
975.
V. I. Dubovik V. A. Bogdanova N. A. Davletkil’deev N. A. Semikolenova O. A. Shutyak 《Semiconductors》1998,32(1):31-32
The influence of gg irradiation (60Co) of various intensities (P
γ≈1.7−7.5kGR/h) on the photoluminescence of GaAs:Te single crystals [n
0=(1.2–2.3×1018 cm−3] is investigated. Together with the known photoluminescence impurity bands (hν
max≈1.2 eV and/or hν
max≈1.35 eV) and edge band (hν
max≈1.51 eV), new bands are also observed in the spectra at hν
max≈1.3 eV and hν
max≈1.48 eV. The observed effects are attributed to radiation-stimulated ordering of the donor impurity and deep impurity centers.
Fiz. Tekh. Poluprovodn. 32, 38–39 (January 1998) 相似文献
976.
A response to criticism of threshold plates for the study of color vision developed at the Mendeleev All-Russia Research Institute
of Metrology and published in 1994 is presented. The critics base their conclusions on colorimetric testing and the examination
of the plates.
In response to the article by M. V. Danilova and J. D. Mollon [4].
__________
Translated from Izmeritel’naya Tekhnika, No. 1, pp. 37–39, January, 2007. 相似文献
977.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
978.
979.
An analytical model for electroluminescence in SrS:Ce AC thin-film electroluminescent display devices is presented. The model incorporates an exact calculation of the electric field and the effect of activator ionization and bulk traps. Activator ionization is needed to explain several features of luminescence behavior in SrS:Ce devices. These features include the second luminescence peak at the trailing edge of the voltage pulse and the time lag between the luminescence and the applied voltage when the applied voltage consists of bipolar trapezoidal pulses and rectangular pulses of low voltage amplitudes. As a mechanism for the ionization of activators, field-assisted tunneling is shown to be more likely than impact ionization by hot electrons. Physical processes are described in terms of rate equations, and field, current, and luminescence waveforms are calculated for one set of device parameters. The calculated and experimental luminescence waveforms agree 相似文献
980.