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排序方式: 共有1122条查询结果,搜索用时 15 毫秒
51.
52.
A. Vecchione R. Fittipaldi C. Cirillo M. Hesselberth J. Aarts S.L. Prischepa V.N. Kushnir M.Yu. Kupriyanov C. Attanasio 《Surface science》2011,605(19-20):1791-1796
Specular and diffuse X-ray scattering are used to study interfacial roughness in Nb/Pd0.81Ni0.19 multilayers deposited by dc UHV sputtering. The data are analyzed to extract information about the correlated behavior of interface roughness in both the lateral and vertical directions. X-ray reflectivity is treated quantitatively by computer-aided simulation and modelling in order to extract values also for the layers thickness. From the analysis of the diffusive spectra of the reflectivity maps the roughness correlation has been evaluated. 相似文献
53.
I. M. Sokolov D. V. Kupriyanov M. D. Havey 《Journal of Experimental and Theoretical Physics》2011,112(2):246-260
Based on the developed quantum microscopic theory, the interaction of weak electromagnetic radiation with dense ultracold
atomic clouds is described in detail. The differential and total cooperative scattering cross sections are calculated for
monochromatic radiation as particular examples of application of the general theory. The angular, spectral, and polarization
properties of scattered light are determined. The dependence of these quantities on the sample size and concentration of atoms
is studied and the influence of collective effects is analyzed. 相似文献
54.
The Young’s modulus and the internal friction of beryllium polycrystals (size grain from 6 to 60 μm) prepared by the powder
metallurgy method have been studied as functions of the amplitude and temperature in the range from 100 to 873 K. The measurements
have been performed using the composite piezoelectric vibrator method for longitudinal vibrations at frequencies about 100
kHz. Based on the acoustic measurements, the data have been obtained on the elastic and inelastic (microplastic) properties
as functions of vibration stress amplitudes within the limits from 0.2 to 30–60 MPa. The microplastic deformation diagram
is shown to become nonlinear at the amplitudes higher than 5 MPa. The beryllium mechanical characteristics (the yield strength
σ
0.2, the ultimate strength σ
u
, and the conventional microscopic yield strength σ
y
) obtained with various grain sizes are compared. At room temperature, all the parameters satisfactorily obey the Hall-Petch
relationship, although there is no complete similarity. The temperature dependences are quite different, namely: σ
0.2(T) and σ
u
(T) decrease monotonically during heating from room temperature to higher temperatures; however, σ
y
(T) behaves unusually, and it has a minimum near 400 K. The different levels of stresses and the absence of similarity indicate
that the scattering of the ultrasound energy and the formation of a level of the macroscopic flow stresses in beryllium occur
on dislocation motion obstacles of different origins. 相似文献
55.
Denis N. Bazhin Dmitry L. Chizhov Gerd-Volker Röschenthaler Yulia S. Kudyakova Yanina V. Burgart Pavel A. Slepukhin Victor I. Saloutin Valery N. Charushin 《Tetrahedron letters》2014
1,1,1-Trifluoro-4,5,5-trimethoxyhex-3-en-2-one and lithium (2Z)-1,1,1-trifluoro-5,5-dialkoxy-4-oxohex-2-en-2-olate were synthesized for the first time via direct trifluoroacetylation of 2,3-butanedione acetal derivatives. A simple and effective approach to acetal or acyl substituted CF3-pyrazoles, 5,5′-bis(trifluoromethyl)-3,3′-bipyrazole, and, to 5-trifluoromethylfuran-3-ones is presented. 相似文献
56.
An efficient and simple method for the synthesis of 2-unsubstituted 1-aryl-4- and 1-aryl-5-acylimidazoles has been developed. It consists in the condensation of α-diketone monooximes with aromatic amines and formaldehyde on the presence of boron trifluoride etherate, leading to the formation of stable boron trifluoride complexes of N-oxides. Further reduction of these complexes led to the corresponding imidazoles. This method permits broad variations of substituents in the aryl part of these compounds. 相似文献
57.
Valery Kukhar Vladimir Solodenko Vadim Soloshonok Tamara Kasheva 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):529-532
Abstract Synthesis of enantiomeric amino phosphonic acids APA is described by using chiral auxiliary reagent or enzymatic resolution of racemic mixtures of APA phenacyl derivatives. Peptides with APA residue were obtained by application of trimethylsilyl derivatives or condensation in the presence of enzyme-papain 相似文献
58.
Alexey Bobrovsky Valery Shibaev Věra Hamplová Miroslav Kašpar Vladimira Novotna Milada Glogarová 《Liquid crystals》2013,40(9):989-997
A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation P s was measured and it was found that UV irradiation induces a decrease in the values of P s. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases. 相似文献
59.
Evgeny Pozhidaev Valery Shibaev Galina Elyashevich Maxim Minchenko 《Liquid crystals》2013,40(5):517-525
Electro-optically active polymer–liquid crystal composites based on ferroelectric liquid crystals and stretched porous polyethylene films were developed. The alignment of ferroelectric liquid crystals incorporated into the porous polyethylene films with average porous diameter of around 200 nm was observed and studied. It was shown experimentally that these samples containing ferroelectric liquid crystals are flexible electro-optical films exhibiting a saturation electric field near 2·107 Vm?1 and a response time of about 30 μs under the action of the saturation field. A simple theoretical model of ferroelectric liquid crystal molecules' complete reorientation in electric fields inside pores of the films has been proposed and confirmed experimentally. 相似文献
60.