Contact electroelasticity problem for a nonplane elliptical die

The stress-strain state of an elastic piezoceramic halfspace under the action of a rigid elliptical die with a convex base is considered, in the case where the symmetry axis of the body is in the direction of the preliminary-polarization field. The contact area is within the isotropy plane. Attention is confined to the case of die translation. Expressions are obtained for the semimajor axis and eccentricity of the contact area and the translational points of the die base under different electric boundary conditions. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 6, pp. 17–26, June, 1999.     

Numerical modeling of gravity currents in inclined channels

The mixing and wave formation processes in gravity currents induced by the rupture of a vertical dam initially separating a heavy and a light liquid are studied for different channel inclination angles. The calculations are performed using the LES and RANS models. It is shown that when the heavy liquid moves down the channel slope, the longitudinal and transverse internal waves break and form turbulent mixing zones. When the heavy liquid ascends the slope, the wavy motion mode predominates.     

Interlayer photoinduced electron transfer in Langmuir-Blodgett films based on porphyrin and phthalocyanine derivatives

Vectorial photoinduced electron transfer was studied in Langmuir-Blodgett films. The monolayers of polythiophene and phthalocyanine were used as secondary electron donors in multilayers together with the monolayer of porphyrin-fullerene donor-acceptor dyad molecules mixed with octadecylamine (1:9). Simultaneous utilization of all the three compounds in the preparation of three-layer samples allowed us to widen the range of the visible light absorption by the structure. The relative sensitivity of the sample to the excitation laser light increased by about 350 times compared with that of a dyad monolayer.     

TMSCl-promoted isocyanide-based MCR of ethylenediamines: an efficient assembling of 2-aminopyrazine core

New trimethylchlorosilane (TMSCl) promoted multicomponent reaction (MCR) of ethylenediamine(s), diverse carbonyl compounds, and isocyanides is proposed for the synthesis of a variety of highly substituted 3,4,5,6-tetrahydropyrazin-2-amines including corresponding spirocyclic compounds.     

Influence of the processing method on the properties of a PVDF film

The main electrophysical properties of polyvinylidene fluoride (PVDF) films produced by two technologies: the solution casting method and the method of hot pressing from the melt are investigated. To analyze the PVDF films, methods of dielectric spectroscopy (DS), IR spectroscopy, TGA/DSC analysis, and x-ray diffraction (XRD) are used. It is demonstrated that the IR spectra of both PVDF films change weakly in comparison with the virgin PVDF film. The absorption bands characteristic for α-, β-, and γ-phases are observed for the virgin and both types of PVDF films. This testifies to the fact that the molecular structure of film samples is practically independent of their processing method. The only difference is that the new absorption band at 1723 cm^–1 arises in the IR spectra of the films produced by the method of hot pressing from the melt. The TGA/DSC analysis demonstrates that the beginning melting temperature, melting temperature, beginning decomposition temperature, and decomposition temperature for the film samples produced by the method of hot pressing from the melt decrease by 8, 2, 10, and 12°C, respectively, compared to the film samples produced by the solution casting method.     

Multichannel queueing system in a random environment

This paper is focused on a multichannel queueing system with heterogeneous servers and regenerative input flow operating in a random environment. The environment can destroy the whole system and the system is reconstructed after that. The necessary and sufficient ergodicity condition is obtained for the system.     

Selective Hydrogenation of Acetylene and Physicochemical Properties of Pd–Fe/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Bimetallic Catalysts

The selective hydrogenation of acetylene on Pd–Fe/Al₂O₃ catalysts prepared by decomposition of ferrocene on reduced Pd/Al₂O₃ was studied. The effect of the conditions of treatment of the Pd–ferrocene/ Al₂O₃ precursor on the catalyst activity and selectivity was investigated, and the optimum conditions were determined at which the Pd–Fe/Al₂O₃ catalyst has higher selectivity than Pd/Al₂O₃ without any loss of activity.