The present work is aimed at verifying the influence of high asymmetries in the variation of in-plane lead-lag stiffness of one blade on the ground resonance phenomenon in helicopters. The periodical equations of motions are analyzed by using Floquet’s Theory (FM) and the boundaries of instabilities predicted. The stability chart obtained as a function of asymmetry parameters and rotor speed re...

The scenarios of achieving effective ionospheric modification are summarized and the likely physical processes engaging linear and nonlinear mode conversions through plasma inhomogeneity and nonlinearity are revealed. Parametric instabilities, which are the directly relevant processes to achieve effective heating of the ionospheric F region, are formulated and analyzed. The threshold fields and...

We present an analytical study of four-wave mixing instabilities in tapered fibers and photonic crystal fibers. Our approach avoids the use of Taylor expansion for the linear susceptibility and the slowly-varying envelope approximation. This allows us to describe the generation of sidebands strongly detuned from the pump wave with simultaneous account for the entire dispersion characteristic of...