264,896 research outputs found
Reflection and transmission coefficients of a thin bed
The study of thin-bed seismic response is an important part in lithologic and methane reservoir modeling, critical for predicting their physical attributes and/or elastic parameters. The complex propagator matrix for the exact reflections and transmissions of thin beds limits their application in thin-bed inversion. Therefore, approximation formulas with a high accuracy and a relatively simple form are needed for thin-bed seismic analysis and inversion. We have derived thin-bed reflection and transmission coefficients, defined in terms of displacements, and approximated them to be in a quasi-Zoeppritz matrix form under the assumption that the middle layer has a very thin thickness. We have verified the approximation accuracy through numerical calculation and concluded that the errors in PP-wave reflection coefficients RPP are generally smaller than 10% when the thin-bed thicknesses are smaller than one-eighth of the PP-wavelength. The PS-wave reflection coefficients RPS have lower approximation accuracy than RPP for the same ratios of thicknesses to their respective wavelengths, and the RPS approximation is not acceptable for incident angles approaching the critical angles (when they exist) except in the case of extremely strong impedance difference. Errors in phase for the RPP and RPS approximation are less than 10% for the cases of thicknesses less than one-tenth of the wavelengths. As expected, a thinner middle layer and a weaker impedance difference would result in higher approximation accuracy
Evolutionary computation in dynamic and uncertain environments
This book can be accessed from the link below - Copyright @ 2007 Springer-Verla
Editorial to special issue on evolutionary computation in dynamic and uncertain environments
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Maximally Flexible Assignment of Orthogonal Variable Spreading Factor Codes for Multi-Rate Traffic
In universal terrestrial radio access (UTRA) systems, orthogonal variable spreading factor (OVSF) codes are used to support different transmission rates for different users. In this paper, we first define the flexibility index to measure the capability of an assignable code set in supporting multirate traffic classes. Based on this index, two single-code assignment schemes, nonrearrangeable and rearrangeable compact assignments, are proposed. Both schemes can offer maximal flexibility for the resulting code tree after each code assignment. We then present an analytical model and derive the call blocking probability, system throughput and fairness index. Analytical and simulation results show that the proposed schemes are efficient, stable and fair
Optimal asymptotic cloning machines
We pose the question whether the asymptotic equivalence between quantum
cloning and quantum state estimation, valid at the single-clone level, still
holds when all clones are examined globally. We conjecture that the answer is
affirmative and present a large amount of evidence supporting our conjecture,
developing techniques to derive optimal asymptotic cloners and proving their
equivalence with estimation in virtually all scenarios considered in the
literature. Our analysis covers the case of arbitrary finite sets of states,
arbitrary families of coherent states, arbitrary phase- and
multiphase-covariant sets of states, and two-qubit maximally entangled states.
In all these examples we observe that the optimal asymptotic fidelity enjoys a
universality property, as its scaling does not depend on the specific details
of the set of input states, but only on the number of parameters needed to
specify them.Comment: 27 + 9 pages, corrected one observation about cloning of maximally
entangled state
On deformed double current algebras for simple Lie algebras
We prove the equivalence of two presentations of deformed double current
algebras associated to a complex simple Lie algebra, the first one obtained via
a degeneration of affine Yangians while the other one naturally appeared in the
construction of the elliptic Casimir connection. We also construct a specific
central element of these algebras and, in type A, show that they contain a very
large center for certain values of their parameters.Comment: 40 page
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