Nonlinear oscillations in marine hydroids

Irregular oscillations in a colony of marine hydroids Podocoryne carnea were investigated. Quantitative characteristics were obtained as a result of long term (10-12 h) monitoring of oscillations at arbitrary sites. The sliding window spectra as well as the pulse-to-pulse dynamics argue the transient chaotic behavior of hydroid colony. The significant change of amplitudes and frequencies in intact colony oscillations after feeding and long sustained oscillations of stolons separated from colony suggest that the irregular activity could be determined by the network of pacemakers residing in stolon wall cells. These are influenced mechanically by the amount of digesting food and/or by chemical action of nutrients inside the stolon lumen. The possible correlation of these oscillations which can evoke Ca(2+) waves in stolon wall cells is discussed.     

Nonlinear nonaxisymmetric oscillations of a space-charged jet

The problem of nonlinear nonaxisymmetric oscillations of a jet of a space-charged dielectric (zeroconductivity) liquid is solved asymptotically. The solution is accurate up to second-order terms in initial deformation amplitude. It is shown that the difference between the amplitude values of second-order corrections to the solutions for perfectly conducting and perfectly dielectric liquids depends on the permittivity of the latter and may amount to several tens of percent. The permittivity of the liquid also governs the positions of internal resonances, in the vicinity of which nonlinear energy transfer between modes takes place.     

Nonlinear oscillations and chaos in n-InSb

We present evidence for chaotic behavior in n-InSb. The Hall voltage exhibits a period-doubling route to chaos as the (non-ohmic) dc current is increased. The nonlinear oscillation and bifurcation processes are strongly influenced by irradiation with CO₂ laser radiation.     

Nonlinear torsional oscillations in rotating systems

Torsional oscillations, temporal variations in the differential rotation in rotating systems, are a well-established phenomenon in the fluid regions of convective stars and planets. We show for the first time that nonlinear torsional oscillations can be generated and maintained by convective instabilities in rotating systems.     

Nonlinear dynamics in an electrical circuit containing a ferroelectric

Nonlinear effects in a series oscillator circuit containing a ferroelectric capacitor are investigated as a function of the temperature and the amplitude of the applied field. A relation is established between the circuit parameters and the resonance shift in samples of a pure triglycine sulfate crystal and in samples containing chromium impurity ions. The observed effects are explained on the basis of a feature in the domain structure of the samples and the influence of point defects on it. Fiz. Tverd. Tela (St. Petersburg) 39, 918–919 (May 1997)     

Subharmonic oscillations of a mixing layer-wedge system associated with free surface effects

An unstable mixing layer, in conjunction with free surface wave effects, can give rise to well-defined subharmonic oscillations of the vortex shedding frequency provided certain streamwise phase conditions are satisfied. Visualization of these oscillations, forces acting on the impingement edge, and streamwise evolution of velocity spectra are addressed.     

Nonlinear oscillations of a charged drop accelerated in an electrostatic field

An analytical asymptotic solution to the problem of nonlinear oscillations of a charged drop moving with acceleration through a vacuum in a uniform electrostatic field is found. The solution is based on a quadratic approximation in two small parameters: the eccentricity of the equilibrium spheroidal shape of the drop and the amplitude of the initial deformation of the equilibrium shape. In the calculations carried out in an inertial frame of reference with the origin at the center of mass of the drop, expansions in fractional powers of the small parameter are used. Corrections to the vibration frequencies are always negative and appear even in the second order of smallness. They depend on the stationary deformation of the drop in the electric field and nonlinearly reduce the surface charge critical for development of the drops’s instability. It is found that the evolutions of the shapes of nonlinearly vibrating unlike-charged drops differ slightly owing to inertial forces.     

Plasma oscillations in oxide free Al clusters

Plasma oscillations in oxide free Al clusters with radii of the order 10 Å are excited by 50 keV electrons. Only surface plasma oscillations are observed. Results are in excellent agreement with the hydrodynamic theory put forward by Fujimoto and Komaki. This theory is for the first time quantitatively confirmed.     

Nonlinear oscillations of circular membranes of a low-frequency acoustic radiator

We study the features of oscillations of an acoustic radiator in the form of a rigid cylinder with elastic circular membranes fixed at the cylinder ends. For different membrane models and different vibration modes, the spectra of linear and nonlinear free and forced oscillations are found. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 199–215, March 2008.