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81.
We study the transverse or off-axis localization of electromagnetic waves for several different random dielectric systems which are periodic on average. Unlike previous scalar wave treatments of transverse localization, in the present work we present results based on a full vector treatment of the electromagnetic fields based on Maxwell's equations. In a first system, we consider a random semi-infinite array of slabs with plane waves or finite beams of electromagnetic waves obliquely incident on the slab surfaces. The localization of the fields in a region near the surface of illumination is studied as a function of the oblique angle of incidence. In a second system, an array of semi-infinite slabs with random thickness is considered with an incident finite beam of electromagnetic waves initially directed parallel to the slab surfaces. The spreading of the beam width is computed as it propagates through the array of semi-infinite slabs. In a final system, we consider a semi-infinite array of random dielectric rods (2D system) with obliquely incident plane waves. The localization length of the plane-wave fields is computed as a function of the oblique angle of incidence and as a function of the strength of the disorder of the dielectric medium. All the random media we consider, when averaged over their randomness, are periodic on average. The above systems are studied for both p- and s-polarizations of incident electromagnetic waves, and the difference in the transverse localization of the electromagnetic field for these two polarizations is determined. 相似文献
82.
Processing effects of nanometric rare earth-doped tin oxides on the synthesis of methyl vinyl ketone 总被引:1,自引:0,他引:1
Adeilton Pereira Maciel Neftalí Lenin Villarreal Carre?o Poty Rodrigues de Lucena Edson Roberto Leite Elson Longo Humberto Vieira Fajardo Antoninho Valentini Luiz Fernando Dias Probst 《Reaction Kinetics and Catalysis Letters》2004,81(2):211-217
Nanoparticle catalysts based on SnO2 were processed by two different methods, víz.the polymeric precursor and high-energy mechanical milling. The sample morphology and catalytic performance in the aldol condensation
between methanol and acetone were modified by the processing and rare earth doping.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
83.
Alexandre Z. Simões Laecio Santos Cavalcante Carla Santos Riccardi José A. Varela Elson Longo 《Journal of Sol-Gel Science and Technology》2007,44(3):269-273
Bi0.92La0.08FeO3 (BLFO) thin films were grown on platine substrates by the soft chemical route. Ferroelectric and dielectric behaviors of
BLFO films deposited by spin-coating technique and annealed at 773 K for 2 h in air atmosphere were explained. BLFO thin films
obtained presents a rhombohedral structure. The BLFO films present dielectric and ferroelectric behaviors with dielectric
permittivity and dielectric loss of approximately 81 and 0.0144 at 1 kHz. The Au/BLFO/Pt capacitor shows a hysteresis loop
with remnant polarization of 20.6 μC/cm2 and coercive field of 53.88 kV/cm. The polarization switching and the fatigue behavior of the BLFO films were significantly
enhanced. 相似文献
84.
Methyl-methine linkages of Novolac, a commercially available t-butylphenol acetylene condensed (TBPA) resin, have been identified by recognition of pyrolysis pathways using pyrolysis-gas chromatography/mass spectrometry (Py-GC/mS) in vulcanized rubber. The diagnostic mass spectrum of t-butylphenol with methyl-methine linkages between phenolic rings was observed at m/z 192, corresponding to 4-t-butyl-2-ethyl-6-methylphenol. Other molecular ions were observed at m/z 178, 164, and 150 in the characteristic pyrolyzates. The ion at m/z 192 in the TBPA resin was observed to be characteristic for methyl-methine linkages between the phenolic groups, and the analytical pyrolysis-GC/mS method was thus able to identify the resin at low levels in vulcanized rubber. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
85.
The pipe flow drag-reducing properties of mixtures of alkyltrimethylammonium halides with 1-naphthol in aqueous solution have been investigated. The effects of solution concentration, soap-naphthol ratio, soap molecular weight and solution temperature upon drag reduction and swirl decay time are reported. The critical wall shear stresses above which the drag-reducing properties cease correlate well with swirl decay time. At low soap concentrations greater than equimolar proportions of 1-naphthol with the soap are required for maximum drag reduction. The drag-reducing properties of these solutions are greatest at and around the Krafft point of the pure soap. A phenomenon similar to onset for polymer solution drag reduction is reported for these soap solutions. 相似文献
86.
It is the purpose of this paper to give an analytical expression for the damping rate of a long-wavelength plasma wave in terms of the optical constants of the medium which supports the wave. This expression is a generalization of that given in the literature for a free electron gas. The expression is derived by two different methods below. 相似文献
87.
Rosa IL Marques AP Tanaka MT Melo DM Leite ER Longo E Varela JA 《Journal of fluorescence》2008,18(2):239-245
In this work Ba0.99Eu0.01MoO4 (BEMO) powders were prepared by the first time by the Complex Polymerization Method. The structural and optical properties
of the BEMO powders were characterized by Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), Raman Spectra, High-Resolution
Scanning Electron Microscopy (HR-SEM) and Photoluminescent Measurements. XRD show a crystalline scheelite-type phase after
the heat treatment at temperatures greater than 400 °C. The ionic radius of Eu3+ (0.109 nm) is lower than the Ba2+ (0.149 nm) one. This difference is responsible for the decrease in the lattice parameters of the BEMO compared to the pure
BaMoO4 matrix. This little difference in the lattice parameters show that Eu3+ is expected to occupy the Ba2+ site at different temperatures, stayed the tetragonal (S4) symmetry characteristic of scheelite-type crystalline structures of BaMoO4. The emission spectra of the samples, when excited at 394 nm, presented the 5D1→7F0, 1 and 2 and 5D0→7F0, 1, 2, 3 and 4 Eu3+ transitions at 523, 533, 554, 578, 589, 614, 652 and 699 nm, respectively. The emission spectra of the powders heat-treated
at 800 and 900 °C showed a marked increase in its intensities compared to the materials heat-treated from 400 to 700 °C. The
decay times for the sample were evaluated and all of them presented the average value of 0.61 ms. Eu3+ luminescence decay time follows one exponential curve indicating the presence of only one type of Eu3+ symmetry site. 相似文献
88.
Siegel J Elson DS Webb SE Parsons-Karavassilis D Lévêque-Fort S Cole MJ Lever MJ French PM Neil MA Juskaitis R Sucharov LO Wilson T 《Optics letters》2001,26(17):1338-1340
We report a novel whole-field three-dimensional fluorescence lifetime imaging microscope that incoporates multispectral imaging to provide five-dimensional (5-D) fluorescence microscopy. This instrument, which can acquire a 5-D data set in less than a minute, is based on potentially compact and inexpensive diode-pumped solid-state laser technology. We demonstrate that spectral discrimination as well as optical sectioning minimize artifacts in lifetime determination and illustrate how spectral discrimination improves the lifetime contrast of biological tissue. 相似文献
89.
Jo o B.L. Martins Vicent Moliner Juan Andr s Elson Longo Carlton A. Taft 《Journal of Molecular Structure》1995,330(1-3):347-351
The adsorption of water molecule and hydroxyl ions on the (10-10) and (0001) ZnO surfaces has been studied for (ZnO)4, (ZnO)5 and (ZnO)6 cluster models. Different representations for the atomic basis sets and the effective core potential (ECP) approximations have been employed and the effects of cluster size, conformation and basis sets are analyzed and discussed. 相似文献
90.
In this article, we report the formation of dispersed anisotropic nanostructures by the oriented attachment mechanism, under hydrothermal conditions and in a system that all other growth processes are improbable. The comparison of dilute and agglomerated experimental conditions indicate that oriented attachment is an effective mechanism for the formation of anisotropic nanocrystals, and the conclusions can be extended to other nanometric systems. 相似文献