Nonequilibrium Ionization by Vibrationally Excited Molecules in Supersonic Flows

The results of experimental investigations on thermal nonequilibrium ionization in CO₂: N₂: He mixtures are presented. Measurements of electron density, n_e, in vibrationally excited nitrogen were made in a supersonic flow with different CO₂ contents as well as in a CO₂: N₂: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N₂ and CO₂ + He was used in some experiments. The measured values of n_e in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser-active medium are discussed.     

To the ray tomography problem for creeping waves

This paper justifies the necessity of introducing corrections for the ray curvature into the standard procedure of the tomographic inversion in the case of using traveltime data for the creeping waves. The results of relevant numerical experiments are presented. Bibliography: 3 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 218, 1994, pp 67–71. This work was supported by the Russian Foundation of Fundamental Research (Grant 93-05-9961). Translated by A. P. Krauklis.     

Evaluation of fluid-filled fractures during acoustic measurements on tube waves

The problem of reflection, transmission, and conversion of the tube wave on a fracture intersecting a borehole is investigated. We consider the case where an acoustic sonde is placed inside a borehole and the fracture separates two different elastic half-spaces and is filled with a porous material. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 324, 2005, pp. 121–128.     

The Interference Slow Wave in a Poroacoustic Biot Layer

It is shown that in a poroacoustic Biot layer placed inside an elastic medium, for any parameters of the model an interference slow wave exists. For low frequencies, the wave has very weak attenuation and the polarization of it coincides with the direction of the layer. This is evidence for the possibility of mapping subtle collectors inside an elastic medium in crosshole measurements. Bibliography: 7 titles.     

Comparative characteristics of a tryptophan molecule in the gas phase and water

The L and D isomers of the tryptophan (Trp) molecule and the (Trp)⁺ cation in the gas phase and water are calculated at the DFT level to reveal the effect of water considered in the dielectric continuum approximation on the electronic characteristics of the molecule. The distribution of effective atomic charges and bond lengths enables the prediction of the most probable parts of the chemical bond cleavage during the fragmentation of the molecule under the ionizing particle flux. These data are supplemented with a calculation of fragmentation energies. Zwitterionic structures characterized by the appearance of considerable dipole moments and a change in their orientation with respect to the ground state are distinguished among the possible isomeric forms in water.     

Attenuation of the interference slow wave in a cracked layer

The attenuation of the interference slow wave propagating in a cracked fluid-filled layer sandwiched between two elastic half-spaces is evaluated. It is proposed that the attenuation is induced by the inelasticity of the fluid. It is shown that the attenuation of the wave may be very small if the thickness of the layer is much less than the wavelength. This explains the possibility of observing the slow wave in real field seismic experiments. Bibliography: 8 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 250, 1998, pp. 153–160. Translated by P. V. Krauklis.     

A slow wave in a fluid layer simulating an oil-saturated seam

A simple model of an oil-saturated layer is proposed. A slow wave propagating in a fluid layer sandwiched between two elastic half-spaces is studied. For this wave the phase and group velocities and also the horizontal and vertical components of the displacement are presented. The theoretical results are in good agreement with the experimental data obtained. Bibliography:4 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 203, 1992, pp. 101–112. Translated by P. V. Krauklis.     

The tube wave generated by a point source located outside a borehole

The excitation of the tube wave by a point source situated inside an elastic medium is considered. The amplitude of the tube wave as a function of the radial distance is given for media with high and low velocies. Two models of sources are considered: a point vertical source and a point horizontal source. It is shown that the radial source is an efficient tool for excitation of a tube wave in high-and low-velocity media. Bibliography: 17 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 332, 2006, pp. 99–122.     

Influence of a Weak Boundary on the Wave Field of an Approaching Source

The response of a weak interface inside an isotropic elastic medium to an approaching source is considered. It is shown that a strong shear wave arises in the wave field reflected at an angle greater than a critical one. Properties of this wave are studied, and theoretical seismograms describing the contribution of all reflected waves to the total field are presented. Bibliography: 19 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 308, 2004, pp. 89–100.