Wave front transformation of optical vortices with multiwave interactions in resonant media

The transformation of singular light beams is analyzed theoretically for multiwave interactions on amplitude and phase dynamic holograms in media with a resonant nonlinearity. The possibility of multiplying topological charge using different diffraction orders is demonstrated and optimal conditions for parametric energy exchange are determined which ensure retention of the structure of the wave front of optical vortices. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 395–402, May–June, 2009.     

Model of colossal magnetostriction in the martensite phase of Ni-Mn-Ga alloys

A model is proposed for describing the experimentally observed martensite and magnetic domain structures in Heusler ferromagnetic alloys Ni_2+x Mn_1?x Ga. On the basis of this model, the field dependences of magnetization and deformation of the alloys are calculated numerically and an expression for the maximum attainable strains induced by external magnetic fields in these alloys is derived. It is shown that for small values of the effective elastic modulus and demagnetizing factor of alloys, the strains induced by the magnetic field may attain maximum possible values of approximately 5%, which are determined by lattice distortions as a result of the martensite transition in fields of about 1 kOe.     

A method of determining the extraneous unknowns in problems of the stability and vibrations of rods

An approximate method of determining the critical loads in problems of the stability of compressed rods has been extended to statically indeterminate systems. For this purpose, a method has been developed for solving stability problems when there are extraneous unknowns defined by the stationarity condition for the potential energy of the system. It is shown that, combined with Grammel's method and Hamilton's variational principle, the method described for determining the extraneous unknowns in statically indeterminate systems can also be used in problems of finding the natural frequencies of vibrations of rods.     

Representations of elastic fields of circular dislocation and disclination loops in terms of spherical harmonics and their application to various problems of the theory of defects

Elastic fields of circular dislocation and disclination loops are represented in explicit form in terms of spherical harmonics, i.e. via series with Legendre and associated Legendre polynomials. Representations are obtained by expanding Lipschitz-Hankel integrals with two Bessel functions into Legendre series. Found representations are then applied to the solutions of elasticity boundary-value problems of the theory of defects and to the calculation of elastic fields of segmented spherical inclusions. In the framework of virtual circular dislocation–disclination loops technique, a general scheme to solving axisymmetric elasticity problems with boundary conditions specified on a sphere is given. New solutions for elastic fields of a twist disclination loop in a spherical particle and near a spherical pore are demonstrated. The easy and straightforward way for calculations of elastic fields of segmented spherical inclusion with uniaxial eigenstrain is shown.     

KCl crystals with a silver impurity: From point defects to oriented AgCl microcrystals in a crystalline host

This paper presents the first unambiguous optically detected magnetic-resonance (ODMR) evidence that AgCl crystals embedded in the KCl lattice and retaining the host orientation are formed in KCl crystals grown with a 2–3 mol % silver impurity. ODMR spectra were obtained of self-trapped holes, shallow electronic centers, and self-trapped excitons, which are typical of AgCl, and a number of substantially different ODMR spectra were also obtained. The differences between the ODMR spectra observed in samples cleaved from different parts of a KCl: AgCl crystal are probably accounted for by embedded AgCl crystals varying in size from large micro-to nanocrystals.     

The physical basics of structure formation in electroexplosive coatings

It is shown that, under an electroexplosive spraying of coatings of various systems, the dynamic rotation of the particles deposited is the basis for forming a vortex hierarchically organized structure in both the coating and upper layers of the substrate, including their interface. This causes dispersion of all the structural elements of the cover, their mutual penetration into each other, and the absence of a sharp interface between the coating and the substrate. The impact of multiple shocks on the deposited coating by a highenergy plasma jet from the discharge of a plasma accelerator creates the forged structure in the material, which is characterized by high strength, wear resistance, and relaxation capability.     

The synthesis of clusters of iron oxides in mesopores of monodisperse spherical silica particles

The method of obtaining nanoclusters α-Fe₂O₃ in the pores of monodisperse spherical particles of mesoporous silica (mSiO₂) by a single impregnation of the pores with a melt of crystalline hydrate of ferric nitrate and its subsequent thermal destruction has been proposed. Fe₃O₄ nanoclusters are synthesized from α-Fe₂O₃ in the pores by reducing in thermodynamically equilibrium conditions. Then particles containing Fe₃O₄ were annealed in oxygen for the conversion of Fe₃O₄ back to α-Fe₂O₃. In the result, the particles with the structure of the core-shell mSiO₂/Fe₃O₄@mSiO₂/α-Fe₂O₃ are obtained. The composition and structure of synthesized materials as well as the field dependence of the magnetic moment on the magnetic field strength have been investigated.

     

Parameters of defect mode of 1D microwave waveguide photonic crystal with metal inclusions in the element that disturbs periodicity

Amplitude–frequency characteristics of the transmission coefficient of microwave waveguide photonic crystal with violation of periodicity are studied in the presence of a plane conducting small-size inclusion that occupies a part of the transverse cross section of the waveguide inside a disturbed layer located at different positions. The conducting small-size inclusion in the disturbed layer of photonic crystal causes the low-frequency shift of the defect mode in the band gap, and the maximum shift is observed when the metal inclusion is located at the interface or center of disturbance depending on the thickness of the disturbed layer.     

Existence and Uniqueness Theorems for the Two-Dimensional Ericksen–Leslie System

In this paper we study the two dimensional Ericksen–Leslie equations for the nematodynamics of liquid crystals if the moment of inertia of the molecules does not vanish. We prove short time existence and uniqueness of strong solutions for the initial value problem in two situations: the space-periodic problem and the case of a bounded domain with spatial Dirichlet boundary conditions on the Eulerian velocity and the cross product of the director field with its time derivative. We also show that the speed of propagation of the director field is finite and give an upper bound for it.     

Investigation of changes in the spherical shell shape under the action of pulsed loading due to contact interaction with a rigid block

An axisymmetric problem of high strains in a spherical lead shell enclosed into an aluminum “spacesuit” under the action of pulsed loading is considered. The shell straining is described with the use of equations of mechanics of elastoviscoplastic media in Lagrangian variables, and the kinematic relations are determined in the current state metrics. Equations of state are taken in the form of equations of the flow theory with isotropic hardening. The problem is solved numerically by using the variational difference method and the “cross” explicit scheme of integration with respect to time. The influence of the yield stress as a function of the strain rate on changes in the shell shape is studied for different values of loading. The calculated final shape and residual strains are demonstrated to be in good agreement with experimental data.