Dependence of growth of the phases of multiphase binary systems on the diffusion parameters

A mathematical model of the diffusion interaction of a binary system with several phases on the equilibrium phase diagram is presented. The theoretical and calculated dependences of the layer thickness of each phase in the multiphase diffusion zone on the isothermal annealing time and the ratio of the diffusion parameters in the neighboring phases with an unlimited supply of both components were constructed. The phase formation and growth in the diffusion zone during “reactive” diffusion corresponds to the equilibrium state diagram for two components, and the order of their appearance in the diffusion zone depends only on the ratio of the diffusion parameters in the phases themselves and on the duration of the incubation periods. The dependence of phase appearance on the incubation periods, annealing time, and difference in the movement rates of the components across the interface boundaries was obtained. An example of the application of the model for processing the experimental data on phase growth in a two-component three-phase system was given.     

Optical Properties of Single-Crystal Germanium in the THz Range

Optics and Spectroscopy - The transmission of intrinsic, antimony-doped, and gallium-doped Ge single crystals in the THz spectral range have been experimentally investigated. It is shown that the...     

Matching of asymptotic models in scattering of a plane acoustic wave by an elastic cylindrical shell

Scattering of a plane harmonic acoustic wave by an elastic cylindrical shell is considered. The procedure based on matching of asymptotic models is developed. The long-wave models (the Kirchhoff-Love theory (or its refinement) and the long-wave high-frequency approximation) are exploited in the vicinities of zero frequency and thickness resonance frequencies, whilst the model of a fluid-loaded flat elastic layer is utilized outside the aforementioned vicinities. Comparison with the exact solution demonstrates that the proposed approach is highly efficient for total synthesis of the scattered pressure as well as for uniform approximation of the resonant curves associated with partial modes.     

Localized vibration in elastic structures with slowly varying thickness

High frequency localized vibration modes for linear isotropicelastic plates and rods of slowly varying thickness are shownto occur within the vicinity of maximal or minimal cross-sections.Long wave asymptotic integration close to the eigenmodes ofsuch cross-sections is provided. The cases of a one integerparameter of thickness resonances (for a plate in plane stress)and two integer parameters (for a rod of circular cross-section)are fully investigated. One-dimensional Hermite-type equationsfor the eigenmodes are derived and associated frequency shiftsfrom those of the thickness resonances of the maximal or minimalcross-section obtained. It is established that the existenceof this type of localization phenomena is strongly dependenton the sign of the group velocity of the associated uniformthickness structure this being the same as that of the localgroup velocity calculated at the maximal or minimal cross-section.It is confirmed that positive group velocity allows localizationfor elevated structures with negative group velocity allowinglocalization only for ligaments. In each case intervals of thePoisson's ratio providing localization are given for the firstfew modes.     

The Electroluminescence Spectra of Light-Emitting Devices Based on Zinc Complexes of Amino-Substituted Ligands

Exciplex bands in the electroluminescence (EL) spectra of electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and in the photoluminescence (PL) spectra of the blends of a zinc complex and the triphenylamine derivative are studied. For the EL spectra, it is found that the relation between the exciplex bands and the intrinsic bands of the zinc complex emission depends on the thickness of layers in the EL devices and on the applied voltage. For the PL spectra of blends, this relation strongly depends on the concentration of components.     

Fundamental absorption of calcium,magnesium, and lithium fluorides in the range of 8–12 μm

The fundamental absorption of calcium, magnesium, and lithium fluorides in the range of 8–12 μm has been studied experimentally by the spectrophotometric method. The known and experimentally obtained values of the absorption coefficients of these materials have been analyzed. It has been shown that the values experimentally measured in the range of 8–12 μm obey the Uhrbach rule and the multiphoton absorption determines the long-wavelength transmission cutoff of pure optical materials. The results presented make it possible to suggest that plates made of LiF and CaF₂ crystals and of optical ceramics based on MgF₂ can be used to fabricate calibrated radiation attenuators in the spectral range of 8–12 μm.     

Preparation of Anion Exchanger for High-Efficiency Purification of Halogen-substituted Hydrocarbon Solvents Used To Clean Metal Optics

Phenomenon of rising sorption capacity of AV-17-8 anion exchanger upon an increase in its humidity due to the superequivalent absorption of Cl^– ions was revealed and substantiated. The purification of halogensubstituted hydrocarbon solvents to remove acids under dynamic conditions by the ion-exchange method and the dynamics of sorption by anion exchangers of halogen-substituted solvents from model solutions were studied. It was shown that AV-17-8 anion exchanger is stable in halogen-substituted solvents and, when present in the OH–form, raises their stability against destruction, and the equilibrium sorption capacity of the anion exchanger is 2–3 times its exchange capacity.     

Structural defects in germanium single crystals

The origin and distribution of structural defects (dislocations, small angle grain boundaries, slip lines, polycrystalline inclusions) is studied in large single crystals of germanium applied in manufacturing optical elements.     

Low-Frequency Cutoffs for the Dispersion Spectrum of Elastic Waves in a Thin-Walled Anisotropic Cylinder

A thin-walled cylinder of unrestricted anisotropy is considered. Low-frequency cutoffs corresponding to bending and extension-shear motions of the cylinder mid-surface are investigated. Their explicit approximations are found by two different methods: truncating the Peano series in the exact dispersion relation and using the Kirchhoff-Love theory of shells adapted to a generally anisotropic cylinder.