scholarly journals Фазово-модулированный двухкомпонентный импульс в диспергирующей среде

2019 ◽  
Vol 127 (11) ◽  
pp. 798
Author(s):  
Г.Т. Адамашвили
Keyword(s):  
Dispersive Medium ◽  
Expansion Method ◽  
Perturbative Expansion ◽  
Carrier Wave ◽  
Two Component ◽  
Component Pulse ◽  
Material Equations ◽  
Formation Conditions ◽  
Induced Transparency ◽  
Analytical Expressions

Abstract A theory of optical two-component pulse of self-induced transparency in a dispersive medium has been developed. Using the generalized version of the perturbative expansion method, the system of material equations for an ensemble of two-level atoms and the wave equation in a dispersive medium are reduced to coupled nonlinear Schrödinger equations. A solution in the form of a phase-modulated two-component $$0\pi $$  pulse is obtained. The pulse components oscillate at the sum and difference frequencies in the vicinity of the carrier-wave frequency. Explicit analytical expressions for the parameters and formation conditions of a nonlinear wave, which depend on the dispersive properties of the medium, are presented. Known results are obtained for a particular case.

scholarly journals ANISOTROPIC NULL STRING COSMOLOGIES

1998 ◽  
Vol 13 (39) ◽  
pp. 3169-3177 ◽  
Author(s):  
IOANNIS GIANNAKIS ◽  
K. KLEIDIS ◽  
A. KUIROUKIDIS ◽  
D. PAPADOPOULOS
Keyword(s):  
Equations Of Motion ◽  
String Tension ◽  
Perturbative Expansion ◽  
Speed Of Light ◽  
Zeroth Order ◽  
First Order ◽  
Cosmological Background ◽  
String Propagation ◽  
Analytical Expressions ◽  
Null String

We study string propagation in an anisotropic, cosmological background. We solve the equations of motion and the constraints by performing a perturbative expansion of the string coordinates in powers if c2 — the worldsheet speed of light. To zeroth order the string is approximated by a tensionless string (since c is proportional to the string tension T). We obtain exact, analytical expressions for the zeroth- and first-order solutions and we discuss some cosmological implications.

scholarly journals Самоиндуцированная прозрачность в монослое черного фосфора

2018 ◽  
Vol 44 (8) ◽  
pp. 77
Author(s):  
Г.Т. Адамашвили
Keyword(s):  
Surface Wave ◽  
Pulse Propagation ◽  
Optical Soliton ◽  
Black Phosphorus ◽  
Two Dimensional ◽  
Two Dimensional Materials ◽  
Soliton Amplitude ◽  
Induced Transparency ◽  
Analytical Expressions ◽  
Armchair Direction

AbstractA theory of the optical soliton of self-induced transparency (SIT) in a black phosphorus monolayer (phosphorene) has been developed. Explicit analytical expressions describing the surface soliton in phosphorene and other anisotropic two-dimensional materials are obtained. It is shown that the anisotropic phosphorene conductivity leads to exponential damping of the amplitude of the soliton of the surface wave, which strongly depends on the direction of pulse propagation. The maximum damping of the SIT soliton amplitude takes place in the “armchair” direction of phosphorene.

scholarly journals ACHROMATIZATION OF THE VOLUME HOLOGRAPHIC OPTICAL ELEMENS

2020 ◽  
Vol 8 (1) ◽  
pp. 139-145
Author(s):  
Yury Ts. Batomunkuev
Keyword(s):  
Spectral Range ◽  
Optical System ◽  
Optical Element ◽  
Chromatic Aberration ◽  
Lens Model ◽  
Base Element ◽  
First Approximation ◽  
Two Component ◽  
Diffraction Structure ◽  
Analytical Expressions

The work considers a two-component holographic optical system having a base element in the form of a thick (volume) hologram optical element and intended for use in a given spectral range. The calculation of a two-component holographic system is carried out using formulas obtained from the mirror-lens model of the thick hologram element proposed by the author. It is indicated that according to the mirror model a thick hologram optical element is achromatic in a first approximation. For this the local period of the volume diffraction structure of the hologram element must be many times greater than the working wavelength, and the transverse dimensions of the element must be less than its thickness. Analytical expressions are given for the mutual correction of the chromatic aberration of the position of a thick hologram optical element and a relief kinoform element. The condition for achromatization of this two-component holographic system is formulated.

Forced and Free Flow in a Vertical Annular Duct Under Nonaxisymmetric Conditions

2005 ◽  
Vol 127 (6) ◽  
pp. 606-613 ◽  
Author(s):  
A. Barletta ◽  
S. Lazzari
Keyword(s):  
Expansion Method ◽  
Axial Direction ◽  
Boussinesq Approximation ◽  
Free Flow ◽  
Fourier Series Expansion ◽  
Dimensionless Temperature ◽  
Thermal Boundary Conditions ◽  
Annular Duct ◽  
Fanning Friction Factor ◽  
Analytical Expressions

The combined forced and free flow in a vertical annular duct is studied under the hypothesis of steady-state parallel laminar flow. The Boussinesq approximation is invoked and the viscous dissipation is considered as negligible. The thermal boundary conditions are such that axial symmetry does not occur and temperature does not change in the axial direction. The dimensionless local balance equations are solved analytically by means of the Fourier series expansion method. The analytical expressions of the dimensionless temperature field, of the dimensionless velocity field, and of the Fanning friction factor are obtained.

Elastic Wave Propagation from Point Excitations on Thin-Walled Cylindrical Shells

1990 ◽  
Vol 112 (3) ◽  
pp. 399-406 ◽  
Author(s):  
A. D. Pierce ◽  
Hyun-Gwon Kil
Keyword(s):  
Wave Propagation ◽  
Dispersive Medium ◽  
Circular Cylindrical Shell ◽  
Exciting Force ◽  
Cylinder Surface ◽  
Two Dimensional ◽  
Phase Velocities ◽  
Unbounded Medium ◽  
Thin Walled ◽  
Analytical Expressions

The circular cylindrical shell is described by equations that govern wave propagation in a two-dimensional homogeneous, but anisotropic and dispersive, medium. The idealization of an unbounded medium is applicable if the source is replaced by a periodic array of forces, the repetition distance being the cylinder circumference. Analytical expressions and calculations are presented for wavefront patterns, amplitude distributions, polarizations, and phase velocities for waves on the cylinder surface. The analysis includes all three possible directions of the exciting force and gives fundamental results that can be superimposed to predict vibration fields resulting from arbitrary excitations.

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