59 research outputs found
Spectral and polarization effects in deterministically nonperiodic multilayers containing optically anisotropic and gyrotropic materials
Influence of material anisotropy and gyrotropy on optical properties of
fractal multilayer nanostructures is theoretically investigated. Gyrotropy is
found to uniformly rotate the output polarization for bi-isotropic multilayers
of arbitrary geometrical structure without any changes in transmission spectra.
When introduced in a polarization splitter based on a birefringent fractal
multilayer, isotropic gyrotropy is found to resonantly alter output
polarizations without shifting of transmission peak frequencies. The design of
frequency-selective absorptionless polarizers for polarization-sensitive
integrated optics is outlined
Microwave Properties of Ba(0.6)K(0.4)BiO(3) Crystals
We report on field-induced variations of the microwave surface resistance at
9.6 GHz of Ba(0.6)K(0.4)BiO(3) crystals. Energy losses have been investigated
as a function of the static magnetic field in the range of temperatures 4.2 K -
Tc. By analyzing the experimental results in the framework of the Coffey and
Clem model we determine the temperature dependence of the first-penetration
field, upper critical field and depinning frequency. The results show that the
pinning energy of this bismuthate superconductor is weaker than those of
cuprates.Comment: 6 pages, 8 embedded figure
Dielectric multilayer waveguides for TE and TM mode matching
We analyse theoretically for the first time to our knowledge the perfect
phase matching of guided TE and TM modes with a multilayer waveguide composed
of linear isotropic dielectric materials. Alongside strict investigation into
dispersion relations for multilayer systems, we give an explicit qualitative
explanation for the phenomenon of mode matching on the basis of the standard
one-dimensional homogenization technique, and discuss the minimum number of
layers and the refractive index profile for the proposed device scheme. Direct
applications of the scheme include polarization-insensitive, intermodal
dispersion-free planar propagation, efficient fibre-to-planar waveguide
coupling and, potentially, mode filtering. As a self-sufficient result, we
present compact analytical expressions for the mode dispersion in a finite,
N-period, three-layer dielectric superlattice.Comment: 13 pages with figure
Full-size core epoh at laboratory research of EOR technologies
The article analyzes influence of core sample size on authenticity of data, obtained in laboratory simulation of reservoir stimulation technologies depending on reservoir type.
It is found that in contrast to composite models, a full-size core reflects relationship of pore systems of complex reservoirs to the full extend. That allows making more correct conclusions about the effectiveness of technologies. In particular determination of adsorption and mechanical destruction of polymer compositions, strength of created water-proof barrier, dynamics of pressure during mixture injection etc. In order to improve authenticity of results obtained in laboratory simulation at the stage of selection of full-size core samples rock anisotropy, which is common for carbonate reservoirs and are usually connected to rocks fracture system, have to be taken into account.
On the basis of ideas about improved efficiency of modeling technologies for enhanced oil recovery (EOR) for the conditions of complex carbonate reservoirs laboratory study is performed. The study used core samples with thermo reversible polymer composition МЕТКА, developed by the Institute of Petroleum Chemistry of Siberian Branch of the Russian Academy of Science. Use of a full-size core allowed evaluating the effectiveness of МЕТКА technology. The technology allowed to involve in the development low-permeability reservoirs and reservoirs that were not flooded. Study showed that results of standard-size core models are not informative to evaluate flooding efficiency.
For the conditions of complex carbonate reservoirs due to low representation of standard samples the need to use core samples of maximal diameter is determined. Results obtained have practical importance in correct determination of parameters for EOR application during field development
Non-cubic layered structure of Ba(1-x)K(x)BiO3 superconductor
Bismuthate superconductor Ba(1-x)K(x)BiO3 (x=0.27-0.49, Tc=25-32K) grown by
an electrolysis technique was studied by electron diffraction and
high-resolution electron microscopy. The crystalline structure thereof has been
found to be non-cubic, of the layered nature, and non-centrosymmetric, with the
lattice parameters a ~ ap, c ~ 2ap (ap is a simple cubic perovskite cell
parameter) containing an ordered arrangement of barium and potassium. The
evidence for the layered nature of the bismuthate superconductor removes the
principal crystallographic contradiction between bismuthate and cuprate high-Tc
superconductors.Comment: 4 pages, 3 figures, to be published in Physical Review B as a Rapid
Communicatio
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