520 research outputs found
Nonlinear polaritons in Bose-Einstein condensates in optical lattices
We study the interaction of a Bose-Einstein condensate in an optical lattice
with additional electromagnetic fields under Raman resonance condition. System
of evolution equations describing ultra-short optical pulse propagation and
photo-induced transport of cold atoms in optical lattice is derived. The steady
state solution of these equations was found. There are new kinds of polaritonic
solitary waves propagating.Comment: pdf-file, Reported on "IX International Readings on Quantum Optics",
12-17 October, St-Peterburg, Russi
Propagation and interaction of ultrashort electromagnetic pulses in nonlinear media with a quadratic-cubic nonlinearity
Propagation of extremely short unipolar pulses of electromagnetic field
("videopulses") is considered in the framework of a model in which the material
medium is represented by anharmonic oscillators (approximating bound electrons)
with quadratic and cubic nonlinearities. Two families of exact analytical
solutions (with positive or negative polarity) are found for the moving
solitary pulses. Direct simulations demonstrate that the pulses are very robust
against perturbations. Two unipolar pulses collide nearly elastically, while
collisions between pulses with opposite polarities and a small relative
velocity are inelastic, leading to emission of radiation and generation of a
small-amplitude additional pulse.Comment: 12 pages, 10 figure
Solitary electromagnetic waves propagation in the asymmetric oppositely-directed coupler
We consider the electromagnetic waves propagating in the system of coupled
waveguides. One of the system components is a standard waveguide fabricated
from nonlinear medium having positive refraction and another component is a
waveguide produced from an artificial material having negative refraction. The
metamaterial constituting the second waveguide has linear characteristics and a
wave propagating in the waveguide of this type propagates in the direction
opposite to direction of energy flux. It is found that the coupled nonlinear
solitary waves propagating both in the same direction are exist in this
oppositely-directed coupler due to linear coupling between nonlinear positive
refractive waveguide and linear negative refractive waveguide. The
corresponding analytical solution is found and it is used for numerical
simulation to illustrate that the results of the solitary wave collisions are
sensible to the relative velocity of the colliding solitary waves.Comment: 9 pages,5 figure
Chemistry for engineering education
We will look at the practical implementation of the disciplines of chemistry intechnological orientation programs. It is shown that with the uniformrequirements of the GEF to the quality of training, volumes for disciplines ofchemistry differ significantly. These shortcomings inherent in the existingteaching methods and ways to improve the learning process are discussed. Notedthat the promising direction of the basic educational program is to build themin a modular fashion.Рассмотрена практика реализации дисциплин химии в программах технологической направленности. Показано, что при единых требованиях ФГОС к качеству подготовки специалистов объемы дисциплин химии существенно различаются. Указаны недостатки, присущие существующей методике обучения, и рассмотрены пути повышения эффективности учебного процесса. Отмечено, что перспективным направлением реализации ООП является построение их по модульному принципу
Non-linear determined methodology of professional-pedagogic education
The article describes the approach to professional-pedagogic education’s designing on the base of non-linear determined methodologyВ статье рассматривается подход к проектированию профессионально-педагогического образования на основе нелинейно-детерминированной методологи
Response evolution of a tetrachiral metamaterial unit cell under architectural transformations
This paper studies a mechanical metamaterial with tetrachiral topology by mathematical modeling. Chirality is the property of an object that makes the object distinguishable from its mirror image; chirality can be left‐ or right‐handed. The mechanical response of two metamaterial unit cells with different configurations (patterns A and B) is investigated. It is found that the cubic cell with a regular pattern A exhibits orthotropic mechanical behavior under loading along three coordinate axes. An irregular pattern B differs from pattern A in that the upper face of the unit cell has an opposite chirality. This architectural transformation is considered as a topological defect, which enhances the twisting effect in the loaded metamaterial. Analysis of displacements and stresses shows that the mechanical behavior of the pattern B cell is described by the model of a transversely isotropic material. The orthotropic and transversely isotropic behavior of the cells of given configurations is also confirmed by the values of the effective elastic constants. Microstructural geometry and mechanical deformation of metamaterials are shown to be closely related. It is shown that a topological defect in a unit cell of a tetrachiral metamaterial strongly determines its twisting behavior
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