435 research outputs found
Ultra-high energy cosmic ray investigations by means of EAS muon density measurements
A new approach to investigations of ultra-high energy cosmic rays based on
the ground-level measurements of the spectra of local density of EAS muons at
various zenith angles is considered. Basic features of the local muon density
phenomenology are illustrated using a simple semi-analytical model. It is shown
that muon density spectra are sensitive to the spectrum slope, primary
composition, and to the features of hadronic interaction. New experimental data
on muon bundles at zenith angles from 30 degrees to horizon obtained with the
coordinate detector DECOR are compared with CORSIKA-based simulations. It is
found that measurements of muon density spectra in inclined EAS give
possibility to study characteristics of primary cosmic ray flux in a very wide
energy range from 10^15 to 10^19 eV.Comment: 7 pages, 7 figures. Presented at CRIS-2006, Catania, Italy, May 29 -
June 2, 2006. Accepted for publication in Nucl. Phys. B (Proc. Suppl.
Characteristics of ADS target irradiated by 200…400 MeV proton beam
The problems of target choice for compact ADS with reactor thermal power 200…400 MW and 200…400 MeV proton beam are considered. Simulation results of neutron yield from fissile and non-fissile targets are presented and the optimal target sizes are calculated. The principal target design characteristics and its thermal condition are also considered.Рассмотрены вопросы выбора мишени для компактной электроядерной установки с мощностью реактора 200…400 МВт и энергией протонов 200…400 МэВ. Представлены результаты моделирования выходов нейтронов из размножающих и неразмножающих мишеней и определены оптимальные размеры мишени. Рассмотрены особенности конструкции мишени и вопросы ее температурного состояния.Розглянуто питання вибору мішені для компактної електроядерної установки з потужністю реактора 200…400 МВт і енергією протонів 200…400 МеВ. Представлено результати моделювання виходів нейтронів із розмножуючих і нерозмножуючих мішеней та визначені оптимальні розміри мішені. Розглянуто особли-вості конструкції мішені і питання її температурного стану
Excitation of surface plasmon waves with a nanoantenna: simple analytical solution and its numerical verification
В работе предлагается простой аналитический метод решения задачи о возбуждении поверхностных плазмон-поляритонов металлической наноантенной, расположенной вблизи поверхности металла. Метод основан на теореме взаимности и аналогичен нахождению амплитуд мод диэлектрических волноводов, возбуждаемых источниками тока. Для большей наглядности предлагаемый подход демонстрируется на примере наиболее простой двухмерной геометрии. Справедливость аналитического решения подтверждается результатами численного моделирования методами конечных разностей и конечных элементов.
In this work, we demonstrate a simple analytical approach to the problem of surface plasmon polaritons excitation with a metallic nanoantenna placed above a metal surface. The method uses the reciprocity theorem and is similar to the calculation of amplitudes of dielectric waveguide modes excited by a current distribution. To maximize clarity of the demonstration, we formulate the problem in a simple two-dimensional geometry. The analytical results are shown to agree well with the numerical solution obtained by finite elements in frequency domain and finite difference in time domain methods.Работа выполнена при поддержке Российского фонда фундаментальных исследований (грант №20-02-00556А)
From nonassociativity to solutions of the KP hierarchy
A recently observed relation between 'weakly nonassociative' algebras A (for
which the associator (A,A^2,A) vanishes) and the KP hierarchy (with dependent
variable in the middle nucleus A' of A) is recalled. For any such algebra there
is a nonassociative hierarchy of ODEs, the solutions of which determine
solutions of the KP hierarchy. In a special case, and with A' a matrix algebra,
this becomes a matrix Riccati hierarchy which is easily solved. The matrix
solution then leads to solutions of the scalar KP hierarchy. We discuss some
classes of solutions obtained in this way.Comment: 7 pages, 4 figures, International Colloquium 'Integrable Systems and
Quantum Symmetries', Prague, 15-17 June 200
Quasiparticle picture of high temperature superconductors in the frame of Fermi liquid with the fermion condensate
A model of a Fermi liquid with the fermion condensate (FC) is applied to the
consideration of quasiparticle excitations in high temperature superconductors,
in their superconducting and normal states. Within our model the appearance of
the fermion condensate presents a quantum phase transition, that separates the
regions of normal and strongly correlated electron liquids. Beyond the phase
transition point the quasiparticle system is divided into two subsystems, one
containing normal quasiparticles and the other --- fermion condensate localized
at the Fermi surface and characterized by almost dispersionless single-particle
excitations. In the superconducting state the quasiparticle dispersion in
systems with FC can be presented by two straight lines, characterized by
effective masses and , respectively, and intersecting near
the binding energy which is of the order of the superconducting gap. This same
quasiparticle picture persists in the normal state, thus manifesting itself
over a wide range of temperatures as new energy scales. Arguments are presented
that fermion systems with FC have features of a quantum protectorate.Comment: 12 pages, Late
Estimation of the Dihedral Angle Between Metal Nanoparticles During Their Coalescence
The process of coalescence of various metal nanoparticles has been studied by the Monte Carlo method.
The interaction of nanoparticles is described by a multiparticle Gupta type potential. An algorithm of recognizing
and estimating a dihedral angle at the neck is developed. The dihedral angle between metal nanoparticles
during their sintering is estimated
Structure optimization effects on the electronic properties of BiSrCaCuO
We present detailed first-principles calculations for the normal state
electronic properties of the high T superconductor
BiSrCaCuO, by means of the linearized augmented plane wave
(LAPW) method within the framework of density functional theory (DFT). As a
first step, the body centered tetragonal (BCT) cell has been adopted, and
optimized regarding its volume, ratio and internal atomic positions by
total energy and force minimizations. The full optimization of the BCT cell
leads to small but visible changes in the topology of the Fermi surface,
rounding the shape of CuO barrels, and causing both the BiO bands,
responsible for the pockets near the \textit{\=M} 2D symmetry point, to dip
below the Fermi level. We have then studied the influence of the distortions in
the BiO plane observed in nature by means of a
orthorhombic cell (AD-ORTH) with space group. Contrary to what has been
observed for the Bi-2201 compound, we find that for Bi-2212 the distortion does
not sensibly shift the BiO bands which retain their metallic character. As a
severe test for the considered structures we present Raman-active phonon
frequencies () and eigenvectors calculated within the frozen-phonon
approximation. Focussing on the totally symmetric A modes, we observe
that for a reliable attribution of the peaks observed in Raman experiments,
both - and a-axis vibrations must be taken into account, the latter being
activated by the in-plane orthorhombic distortion.Comment: 22 pages, 4 figure
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