Supported MgO–V<Subscript>2</Subscript>O<Subscript>5</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for oxidative propane dehydration: Effect of the molar Mg : V ratio on the phase composition and catalytic properties of samples

The physicochemical properties of V₂O₅/Al₂O₃ and MgO–V₂O₅/Al₂O₃ supported catalysts (Mg : V = 1 : 1, 2 : 1, and 3 : 2) obtained by consecutive impregnation of the support with solutions of vanadium and magnesium precursors are studied using a complex of mutually complementary methods (XRD, Raman spectroscopy, UV–Vis spectrometry, and TPR-H₂). The effect of the formation of surface magnesium vanadates of various composition and structure on the catalytic properties of the supported vanadium oxide catalysts in the oxidative dehydrogenation of propane is studied. The introduction of magnesium in the samples and an increase in its content, accompanied by a change in the structure of the surface vanadium oxide phases from polymeric VO₆/VO₅ species to surface metavanadate species, magnesium metavanadate, and further to magnesium divanadate, significantly affects their catalytic properties in the reaction of the oxidative dehydrogenation of propane to propylene.     

Nonstationary deformation of an elastic plate with a notch under the action of a shock wave

The behavior of a thin elastic plate with a rectilinear notch under the action a weak shock wave in air is studied experimentally. A technique is developed for this purpose. The effect of the notch on the strain state of the plate is analyzed __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 11, pp. 99–104, November 2007.     

Numerical solution of an inverse initial boundary-value problem for the full time-dependent Maxwell's equations in the presence of imperfections of small volume

We consider the numerical solution, in a three-dimensional bounded domain, of the inverse problem for identifying the location of small electromagnetic imperfections in a medium with homogeneous background. Our numerical algorithm is based on the coupling of a discontinuous Galerkin method for the time-dependent Maxwell's equations, on the exact controllability method and on a Fourier inversion. Several numerical results are given with one and two imperfections and the robustness and accuracy of the numerical method used for the dynamic detection problem are shown.     

Experimental studies of the protective properties of flat shock-wave shields in water

An experimental method is presented and an experimental study is made of the protective properties of flat shields for a series of materials of specific thicknesses. The decay factors of the materials are determined, and the characteristics of shock-wave loads which have passed through the shield are examined. S. P. Timoshenko Institute of Mechnics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 3, pp. 99–102, March, 1999.     

Effect of quasi-total internal reflection of shock waves at an interface between two elastic media

The interaction of a spherical shock stress wave generated by a point explosion with a plane interface between two elastic media with different mechanical parameters is considered. Using the method of zero approximation of ray theory, it is shown that, after passage of a shock from a medium with smaller acoustic stiffness into a medium with greater acoustic stiffness, the stresses at the front of the refracted shock tend to infinity near the points of quasi-total internal reflection, and this can result in local failure of the media. An experiment with a two-component medium water-Plexiglas confirms the theoretically predicted phenomenon with sufficient accuracy. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev 252057. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 1, pp. 21–27, January–February, 2000.     

Experimental determination of the natural frequencies of complex-shaped shells

The natural frequencies of a complex-shaped thin elastic shell under loading of two types that cause nonstationary vibrations are experimentally determined. The strains in the shell are recorded with piezoelectric strain gages, followed by the Fourier analysis of the oscillograms