412 research outputs found
Automation of obtaining initial estimates of reservoir parameters when processing the pressure change curve
This paper proposes the use of artificial neural network for the identification of the modes of filtration that will help to set the initial estimates of the parameters of the reservoir in accordance with the established nature of fluid flow in porous media. The evaluation procedures with the degree of accumulation, permeability, skin factor, coefficient of compressibility of formation and transmittance are described. The results of the experiment on a set of real data of well testing are used to assess the effectiveness of the proposed approach
The definition of productive reservoirs by the method of fuzzy inference
The lithological classification and allocation of reservoirs are based on the difference of physical and geophysical parameters of rocks. Finding the values of physical and geophysical parameters in some ranges makes it possible to predict the lithology of the formation. The class of information systems based on fuzzy logic provides an effective use of existing knowledge about a certain object. This allows to apply fuzzy logic in intelligent systems of interpretation of well geophysical research materials
Construction of the publication and patent clusters produced by the arbitrary terms with the use of the specialized Google tools
There has been developed the analytical technique of construction of the publication and patent clusters produced by the arbitrary terms with the use of the specialized Google tools. Different names of types of the computer calculations and devices were selected as the scienfific terms for testing with the use of Google Scholar, Google Books and Google Patents beginning with the words: Quantum, Bacterial, Cognitive, Cellular, Cloud, Ubiquitou
Crystal structure of mixed fluorites Ca(1-x)Sr(x)F(2) and Sr(1-x)Ba(x)F(2) and luminescence of Eu(2+) in the crystals
Within the framework of the virtual crystal method implemented in the shell
model and pair potential approximation the crystal structure of mixed fluorites
Ca(1-x)Sr(x)F(2) and Sr(1-x)Ba(x)F(2) has been calculated. The impurity center
Eu(2+) and the distance Eu(2+)-F in this crystals have been also calculated.
The low level position of excited 4f65d configuration of the Eu(2+) ion has
been expressed using phenomenological dependence on distance E(2+)-F. The
dependences of Stokes shift and Huang-Rhys factor on concentration x have been
received for yellow luminescence in Sr(1-x)Ba(x)F(2):Eu(2+). The value x, for
which the eg -level of Eu(2+) ion will be in conduction band in
Sr(1-x)Ba(x)F(2):Eu(2+) has been calculated.Comment: 8 pages, 3 figures. The manuscript is sent to journal 'Physics of the
solid state'. The results will be submitted on inernational conference
SCINTMAT'2002 in oral session (june,20-22,2002,Ekaterinburg,Russia).
Corresponding author e-mail: [email protected]
Rapid Mass Spectrometric Study of a Supercritical CO2-extract from Woody Liana Schisandra chinensis by HPLC-SPD-ESI-MS/MS
Woody liana Schisandra chinensis contains valuable lignans, which are phenylpropanoids with valuable biological activity. Among green and selective extraction methods, supercritical carbon dioxide (SC-CO2) was shown to be the method of choice for the recovery of these naturally occurring compounds. Carbon dioxide (CO2) was the solvent with the flow rate (10−25 g/min) with 2% ethanol as co-solvent. In this piece of work operative parameters and working conditions were optimized by experimenting with different pressures (200–400 bars) and temperatures (40–60 °C). The extraction time varied from 60 to 120 min. HPLC-SPD-ESI -MS/MS techniques were applied to detect target analytes. Twenty-six different lignans were identified in the S. chinensis SC-CO2 extracts
Lifetime of Gapped Excitations in a Collinear Quantum Antiferromagnet
We demonstrate that local modulations of magnetic couplings have a profound
effect on the temperature dependence of the relaxation rate of optical magnons
in a wide class of antiferromagnets in which gapped excitations coexist with
acoustic spin waves. In a two-dimensional collinear antiferromagnet with an
easy-plane anisotropy, the disorder-induced relaxation rate of the gapped mode,
Gamma_imp=Gamma_0+A(TlnT)^2, greatly exceeds the magnon-magnon damping,
Gamma_m-m=BT^5, negligible at low temperatures. We measure the lifetime of
gapped magnons in a prototype XY antiferromagnet BaNi2(PO4)2 using a
high-resolution neutron-resonance spin-echo technique and find experimental
data in close accord with the theoretical prediction. Similarly strong effects
of disorder in the three-dimensional case and in noncollinear antiferromagnets
are discussed.Comment: 4.5 pages + 2.5 pages supplementary material, published versio
Vibrational spectroscopy of GdCr3(BO3)4: Quantitative separation of crystalline phases
This work is devoted to the investigation of GdCr3(BO3)4 crystals by the method of infrared spectroscopy. Incongruently melting borate GdCr3(BO3)4 was obtained as a result of spontaneous crystallization. Crystal structures were identified by the method of infrared spectroscopy. Ab initio calculations in the frame of density functional theory enabled us to separate modes belonging to the R32 and C2/c phases and to estimate the ratio of these phases in GdCr3(BO3)4 crystals. We have found that the content of the rhombohedral R32 (non- centrosymmetric) modification is about 85%. © Published under licence by IOP Publishing Ltd
Spin Diffusion in Double-Exchange Manganites
The theoretical study of spin diffusion in double-exchange magnets by means
of dynamical mean-field theory is presented. We demonstrate that the
spin-diffusion coefficient becomes independent of the Hund's coupling JH in the
range of parameters JH*S >> W >> T, W being the bandwidth, relevant to colossal
magnetoresistive manganites in the metallic part of their phase diagram. Our
study reveals a close correspondence as well as some counterintuitive
differences between the results on Bethe and hypercubic lattices. Our results
are in accord with neutron scattering data and with previous theoretical work
for high temperatures.Comment: 4.0 pages, 3 figures, RevTeX 4, replaced with the published versio
Quantum vs. Geometric Disorder in a Two-Dimensional Heisenberg Antiferromagnet
We present a numerical study of the spin-1/2 bilayer Heisenberg
antiferromagnet with random interlayer dimer dilution. From the temperature
dependence of the uniform susceptibility and a scaling analysis of the spin
correlation length we deduce the ground state phase diagram as a function of
nonmagnetic impurity concentration p and bilayer coupling g. At the site
percolation threshold, there exists a multicritical point at small but nonzero
bilayer coupling g_m = 0.15(3). The magnetic properties of the single-layer
material La_2Cu_{1-p}(Zn,Mg)_pO_4 near the percolation threshold appear to be
controlled by the proximity to this new quantum critical point.Comment: minor changes, updated figure
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