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1.
A critical survey of approximate scattering wave theories from random rough surfaces 总被引:4,自引:0,他引:4
Tanos Mikhael Elfouhaily Charles-Antoine Gu rin 《Waves in Random and Complex Media》2004,14(4):R1-R40
This review is intended to provide a critical and up-to-date survey of the analytical approximate methods that are encountered in scattering from random rough surfaces. The underlying principles of the different methods are evidenced and the functional form of the corresponding scattering amplitude or cross-section is given. The reader is referred to the original papers in order to obtain the explicit expressions of the coefficients and kernels. We have tried to identify the main strengths and weaknesses of the various theories. We provide synthetic tables of their respective performances, according to a dozen important requirements a valuable method should meet. Both scalar acoustic and vector electromagnetic theories are equally addressed. 相似文献
2.
Mayra G. Álvarez Adriana Urdă Vicente Rives Silvia R.G. Carrazán Cristina Martín Didier Tichit Ioan-Cezar Marcu 《Comptes Rendus Chimie》2018,21(3-4):210-220
The catalytic properties of ZnAlVO mixed oxides derived from decavanadate-exchanged ZnAl–layered double hydroxide (LDH) precursors prepared by a sol–gel method (ZnAlVO–LDHx,y) were investigated in the oxidative dehydrogenation of propane and compared with those of supported catalysts obtained by conventional impregnation of NH4VO3 on ZnO (ZnVO-I,y) and ZnAlO mixed oxide (ZnAlVO-I,y) supports. The effects of composition and calcination time on the catalytic behavior were particularly examined. Higher propane conversions were achieved at higher vanadium content and calcination time of the precursors. The LDH-derived catalysts were the most active ones in all the temperature range studied (300–425 °C). The order of activity for propane conversion for the different catalyst families varies as ZnAlVO–LDHx,y > ZnAlVO-I > ZnVO-I and follows the strength of the Lewis and Brønsted acid sites determined by monitoring of pyridine adsorption by Fourier transform infrared spectroscopy, whereas the propene selectivities are close together in agreement with the similar densities of basic sites determined by CO2–temperature-programmed desorption measurements. It was indeed established that the acidity, rather than the nature of the crystalline phases, the reducibility, or the specific surface area of the samples, governs the catalytic activity. 相似文献
3.
Lavison G Bertoncini F Thiébaut D Beziau JF Carrazé B Valette P Duteurtre X 《Journal of chromatography. A》2007,1161(1-2):300-307
Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. Their total amount in the commercial lubricant varies from a few percents to 20-25%. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming as it should involve sample treatment and preparative scale separations in order to simplify the sample. The aim of this work is to determine the feasibility of the separation of low molecular weight lubricant additives using various packed columns with pure CO(2) as a mobile phase to enable implementation of flame ionisation detection as universal detector. This is part of a hypernated system including more sophisticated specific detectors, such as AED, FTIR or MS to obtain detailed structural information of compounds. This paper is devoted to the comparison of some stationary phases supposed to provide hydrocarbon group type separation (silica and normal phase) or separations on alkyl-bonded silica in non-aqueous mode of some selected classes of additives in test mixtures or in base stocks. Adsorption chromatography allows partial separation of additives from the base stocks while the direct elution of test additives can only be obtained on reversed phase supports having a very efficient silanol group protection so the interaction of the more polar compounds is much reduced. A two-dimensional scheme of analysis is also described. It combines adsorption chromatography to separate most of the polar additives from the base stock and alkyl-bonded silica for more detailed separation of the additives. However, overlapping between groups of compounds and the lack of resolution between some additives and the base stock should be addressed by the implementing of selective detectors. 相似文献
4.
In mathematical physics, one sometimes has to deal with averages of the type $$M\mu (T) = \frac{1}{{T^n }}\int\limits_{|\xi | \leqslant T} { d\xi |\hat \mu (\xi )|^2 , T > 0}$$ where $\hat \mu$ is the Fourier transform of some probability Borel measure μ. We show that the asymptotic behavior ofMμ is governed by the usual (upper and lower) correlation dimension of the measure μ. 相似文献
5.
Cobalt and bismuth molybdates catalysts prepared by three different methods (coprecipitation, mechanical mixing and dispersion in n-pentane), have been studied by Laser Raman spectroscopy before and after testing the catalysts in the selective oxidation of isobutene to methacrolein. Raman bands ascribed to the component phases are observed in the spectra before test, while a phase transformation is detected after test. 相似文献
6.
Charles-Antoine Guérin 《Journal of Fourier Analysis and Applications》2000,6(4):403-425
Processes with stationary n-increments are known to be characterized by the stationarity of their continuous wavelet coefficients.
We extend this result to the case of processes with stationary fractional increments and locally stationary processes. Then
we give two applications of these properties. First, we derive the explicit covariance structure of processes with stationary
n-increments. Second, for fractional Brownian motion, the stationarity of the fractional increments of order greater than
the Hurst exponent is recovered. 相似文献
7.
Bertoncini F Thiébaut D Caude M Gagean M Carrazé B Beurdouche P Duteurtre X 《Journal of chromatography. A》2001,910(1):127-135
Interfacing and evaluation of packed column supercritical fluid chromatography (SFC)-microwave-induced plasma atomic emission detection (AED) is described. Via a flow splitter and an integral restrictor, efficient transfer of solutes from column to detector without band broadening is obtained. Variation of CO2 flow-rate during pressure gradients has little influence on both AED signal and baseline drift while it provides similar sensitivity as in capillary SFC. Continuous introduction of CO2 in the plasma reduces the available range of emission domains; nevertheless the region of detection which is free of CO2 interferences allows selective detection of C1 and Br as reported in this paper. reserved. 相似文献
8.
James S. Fleming Karen L. V. Mann Charles-Antoine Carraz Elefteria Psillakis John C. Jeffery Jon A. McCleverty Michael D. Ward 《Angewandte Chemie (International ed. in English)》1998,37(9):1279-1281
The templating effect of the tetrafluoroborate ion leads to assembly of four CoII ions and six bridging ligands around this anion to give a tetrahedral complex with a bridging ligand along each edge and the anion trapped in the central cavity (shown below). Surprisingly under identical conditions but with NiII a simpler dinuclear complex forms. 相似文献
9.
C. Détraz D. Guillemaud G. Huber R. Klapisch M. Langevin F. Naulin C. Thibault L.C. Carraz F. Touchard 《Nuclear Physics A》1978,302(1):41-50
The 48K, 49K and 50K nuclides have been produced in high energy fragmentation and analyzed by mass spectroscopy techniques. Their half-lives have been measured as 6 ± 1 s, 1.1 ± 0.3 s and and 0.7 ± 0.3 s, respectively. The γ-rays from their radioactive decay have been observed and the corresponding γ-intensities measured. The nuclide 50K is shown to be a delayed neutron emitter. The antianalog states in the daughter Ca nuclei with a neutron configuration, preferentially populated in the β-decay, have been located. The corresponding neutron single-particle energy is found to remain approximately constant for these neutron-rich Ca isotopes. 相似文献
10.
J.M. DAuria L.C. Carraz P.G. Hansen B. Jonson S. Mattsson H.L. Ravn M. Skarestad L. Westgaard 《Physics letters. [Part B]》1977,66(3):233-235
Improved experimental techniques have permitted the observation of the new nuclide 74Rb with a half-life of 64.9 ± 0.5 ms, which represents the heaviest self-conjugate nucleus detected until now. The absenceof along-lived isomer indicates that the T = 0 state of 74Rb lies a bove the T = 1 state. An upper limit of 10?3 relative top 74Rb can be placed on the yield of the (unobserved) mirror nucleus 73Rb, and it appears likely that the limit of particle stability has been reached. The half-life of 75Rb is 17.0 ± 1.0 s. 相似文献