Symmetric normal wave spectrum in an orthotropic layer

A solution is constructed for an orthotropic layer with free plane faces, that corresponds to the plane elastic waves symmetric over the thickness. The dynamical reconstruction of the normal wave spectrum during rotation of the wave vector from one to another elastically equivalent direction is investigated on the basis of a numerical analysis of the dispersion equation.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 116–121, 1988.     

Ultrashort electron beam and volume high-current discharge in air under the atmospheric pressure

Conditions are studied under which an electron beam and a volume discharge with a subnanosecond rise time of a voltage pulse are produced in air under atmospheric pressure. It is shown that the electron beam appears in a gas-filled diode at the front of the voltage pulse in ∼0.5 ns, has a half-intensity duration of ≤0.4 ns and an average electron energy of ∼0.6 of the voltage across the gas-filled diode, and terminates when the voltage across the gap reaches its maximum value. The electron beam with an average electron energy of 60 to 80 keV and a current amplitude of ≥70 A is obtained. It is assumed that the electron beam is formed from electrons produced in the gap due to gas ionization by fast electrons when the intensity of the field between the front of the expanding plasma cloud and the anode reaches its critical value. A nanosecond volume discharge with a specific power input of ≥400 MW/cm³, a density of the discharge current at the anode of up to 3 kA/cm², and specific energy deposition of ∼1 J/cm³ over 3 to 5 ns is created.     

Low-temperature photochemical transformations of monobrominated naphthalene impurities in crystalline naphthalene

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 4, pp. 653–658, April, 1988.     

NMR determination of the composition of balsams from scotch pine resin

We have used ¹H and ¹³C NMR spectroscopy to study the composition of pine resin balsams from Scotch pines grown in different regions of the Republic of Belarus. We have established that their chemical composition does not depend very much on the region where they are grown or the level of contamination of the forests by radioactive and industrial emissions. Prolonged storage of the balsams leads to a substantial change in their compositions, due to isomerization of the resin acids. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 411–415, May–June, 2008.     

Compression of a Runaway Electron Flow in an Air Gap with a Nonuniform Magnetic Field

JETP Letters - The first results of study of the compression of a picosecond runaway electron flow in an air electrode gap by a pulsed guiding magnetic field increasing along the electron...     

Quasi-periodic relaxation to a steady flow regime after pulsed energy input into the incoming stream

Numerical simulation was used to analyze the quasi-periodic process induced against the steady flow pattern around a blunt forebody by a pulse from an external source located in the incoming stream.     

Bending normal waves in a crystal layer surrounded by a liquid

We obtain the dispersion relations that describe the spectrum of the “effluent” harmonic antisymmetric normal waves for an arbitrary direction in the plane of an orthotropic layer surrounded by a viscous or ideally compressible fluid. We present the results of computation of the lower branches of the dispersion spectrum for elastically equivalent directions of propagation in a layer of monocrystal Seignette salt in water. Four figures. Bibliography: 5 titles. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 28, 1998, pp. 123–131.     

Experimental observation of superradiance in the stimulated scattering of an intense microwave pump wave by a counterpropagating subnanosecond high-current relativistic electron bunch

The generation of ultrashort superradiant pulses in the stimulated scattering of an intense microwave (38 GHz) pump wave by a counterpropagating high-current relativistic electron bunch has been observed. Scattered radiation is a single ～200-ps pulse with a peak power of about 1 MW. Owing to the Doppler shift of the radiation frequency, frequencies up to 150 GHz are present in the spectrum of the scattered pulse.