A NEW METHOD FOR SEPARATING LONGITUDINAL WAVES IN A LARGE DIAMETER HOPKINSON BAR

This paper outlines various methods for separating fundamental longitudinal waves propagating along a Hopkinson pressure bar. Advantages and disadvantages of the different methods are presented and discussed in detail. A new method is then proposed for separating the fundamental waves in the frequency domain. This new method is based on the assumption that wave propagation can be adequately described by the first mode of the Pochhammer-Chree theory. The method requires two-point strain gauge measurements on the pressure bar. Fourier components of the positive wave at one gauge location are determined either from the corresponding Fourier components of the measured strain histories or from their derivatives. The method also makes use of the derivative of the wave number with respect to the circular frequency of the pressure bar. Important points of the implementation of the technique are described. Numerical accuracy of the proposed method is verified by considering a simple example with analytical solution and by comparing measured data derived from a large diameter Hopkinson pressure bar. The proposed method will find application in dynamic material tests using the split Hopkinson pressure bar technique.     

Simulation of time-resolved vibronic spectra and the possibility of analyzing molecules with similar spectral properties

The possibility of using time-resolved vibronic spectroscopy for spectral analysis of mixtures of chemical compounds with similar optical properties, when traditional methods (based on stedy-state spectra) are inefficient, is demonstrated by using the method of computer simulation. The analysis is carried out by the example of molecules of a series of polyenes (butadiene, hexadiene, octatetraene, decapentaene, and decatetraene), their various cis-and trans-rotational isomers, and phenyl-substituted polyenes. Ranges of relative concentrations of molecules similar in their spectral properties, where reliable interpretation of time-resolved spectra of mixtures and both qualitative and quantitative analyses are possible, are determined. The use of computer simulation methods for optimizing full-scale experiments in femtosecond spectroscopy is shown to hold much promise.     

A microeconomic simulation model of reproduction

Translated from Programmnoe Oborudovanie i Voprosy Prinyatiya Reshenii, pp. 152–184, 1989.     

Symmetries and conservation laws of Navier-Stokes equations

All the symmetries and conservation laws of Navier-Stokes equations are calculated.     

Behavior of massless feynman integrals near singular points

Nizhnetagil' State Pedagogical Institute. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 372–380, September, 1989.