Нелинейное подавление сигналов в лампе бегущей волны

The results of an experimental and theoretical study of the passage of monochromatic and pulse-modulated microwave signal through a traveling wave tube operating in the nonlinear suppression mode are presented. It was found that the TWT can operate either as a saturable absorber or as a power limiter and these regimes depend on the magnitude of the accelerating voltage and beam current. In the first case, the maximum signal suppression level corresponding to the Kompfner dip is realized in the linear mode, and in the second case - in the nonlinear mode, at a certain input signal power. It is shown that in the case of maximum suppression, a short pulse is formed at the front of the radio pulses. In the nonlinear Kompfner dip mode, the duration of such pulse is decreased with an increase in the power of the input radio pulse. The simulation results obtained using the nonlinear nonstationary theory of a traveling wave tube are in good qualitative agreement with the experimental data.

Nonstationary Theory of the Thermal Explosion for Monomolecular Exothermic Reactions

A new approach to the consideration of the thermal explosion macrokinetic features for monomolecular reactions in homogeneous systems based on a strict accounting of burnout during the reaction process is proposed. It is established, that the qualitative changes of the phase trajectory structure (phase portrait) on the plane: heating rate-temperature determine the characteristic modes of reaction. This approach makes it possible to go beyond the Semenov theory and allows us to consider the variety of the reaction modes. From this point of view, the theory of Semenov is a special case which is valid only for reactions of zero order. The phase trajectories analyze on the parametrical plane Semenov criterion – Todes criterion gives an opportunity to define the regions of the thermal explosion degeneration, the transition regions and the region of the thermal explosion realization. With the use of such consideration, the necessary and sufficient conditions of the thermal explosion are found.