Eigenoscillations of three- and two-element flexible systems

Eigenfrequencies and eigenmodes of composite mechanical systems consisting of a thin-walled cylindrical shell and elastic beams [beam–shell–beam (BSB), beam–beam–beam (BBB), etc. systems] are described by using semi-analytical methods. The methods are less universal comparing with the Finite Element Method, but they are very accurate and CPU-efficient, and they could have advantages in studying multicomponent structures. A comparative analysis of eigenfrequencies and eigenmodes of the considered composite systems versus characteristic geometric dimensions is presented.     

Generalized vorticity for bubbly liquidand dispersive shallow water equations

Received April 1, 2001 / Published online August 31, 2001     

Conversions of ethanol in thermolysis of dyes adsorbed on a silica surface

Using thermal desorption measurements with mass spectrometric analysis of the gas phase, we have studied the characteristics of the interaction of ethanol molecules with the silica surface under conditions when some of the adsorption centers are occupied by molecules of a heteroaromatic dye. The characteristics of the thermal conversions of ethanol on the surface are described in terms of ideas concerning the nature of the active centers on a surface of dispersed silicon dioxide. We observed occurrence of the reaction of ethoxylation of the surface with an increase in temperature. The interaction between the ethanol molecules and the dye molecules occurs with formation of a complex in an excited state upon UV irradiation, which stimulates adsorption of the solvent in strongly bound forms with decomposition of the complex in the surface layer.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 87–91, January–February, 1992.     

Sol-Gel Porous Glass as Holographic Medium

Experiments on hologram recording in porous structure obtained by the sol-gel technology were performed. It was shown that holograms with a diffraction efficiency close to 100% can be obtained with the exposure of about 0.1 J/cm. A pronounced birefringence was observed in dry samples, but it diminished upon immersion in liquids. To explain this effect, a theoretical model was developed. it was shown that even a low asymmetry in pore structure leads to a pronounced birefringence.     

X-ray diffraction investigation of the structure of propolis films

The structure of films of a biological organic material (propolis) on inorganic substrates is investigated for the first time. It is established that, despite the complex chemical composition (involving more than 300 different components), the propolis films prepared from an alcohol solution on amorphous glass substrates and on semiconductor substrates with a small number of dangling bonds have a crystal structure.     

An algorithmic representation of fractional powers of positive operators

We are concerned with a new representation of fractional powers of operators by a series using exclusively contractive operators or operators with uniformly bounded powers. This representation is suitable for the construction of efficient approximations for which the error estimates are given and the convergence is investigated. The rate of convergence turns out to be exponential for bounded operators and polynomial for unbounded operators