rational functions are of great interest to engineers and geoscientists. the rational polynomial coefficient (rpc) model as a generalized sensor model has been introduced as an alternative for the rigorous sensor model of the satellite imaging. numerical instability of normal equations is the only single obstacle to the implementation of these functions. practically, estimating rational functio...

We describe the first analytically tractable example of an instability of a nonorientable minimal surface under parametric variation of its boundary. A one-parameter family of incomplete Meeks Möbius surfaces is defined and shown to exhibit an instability threshold as the bounding curve is opened up from a double-covering of the circle. Numerical and analytical methods are used to determine the...

This work presents recent results of ongoing investigations into rotating spoke instabilities in Hall thrusters. Recent work by the authors demonstrated large amounts of electron current carried by spokes in the nearanode region in the H6 6-kW laboratory model Hall thruster, and raises the question of whether spokes may play a larger role in electron transport throughout the Hall thruster plume...

Internal gravity wave beams are time-harmonic plane waves with general spatial profile that arise in continuously stratified fluids owing to the anisotropy of this wave motion. In the last decade, these wave disturbances have been at the forefront of research, both from a fundamental perspective and in connection with various geophysical flow processes. Oceanic internal wave beams, in particula...

A dynamic system of the three resonantly coupled waves, two of which are parametrically excited, is investigated. It is shown that when the pump amplitude is increased in this system, a strange attractor (analogous to the known Lorentz attractor) is produced and corresponds to stochastic self-oscillations of the wave amplitudes, yet the phases are always fully correlated. A concrete realization...

Known schemes of coherent X-ray and gamma-ray sources are basically connected with the creation of the conditions, when resonant transitions of MSssbauer nuclei or the internal electron shell of heavy atoms have an inverse population. It was shown in refs. [1,2] that these conditions were realized for a relatively small threshold current (j ~ 10 2 A/cm2), when parametric X-rays [2,3] from the m...

Knowledge of the diffraction losses in higher-order modes of large optical cavities is essential for predicting three-mode parametric photon-phonon scattering, which can lead to mechanical instabilities in long-baseline gravitational wave detectors. We explore different numerical methods in order to determine the diffraction losses of the higher-order optical modes. Diffraction losses not only ...

Explosive particle production due to parametric resonance is a crucial feature of reheating in in ationary cosmology. Coherent oscillations of the in aton eld act as a periodically varying mass in the evolution equation for matter elds which couple to the in aton. This in turn results in the parametric resonance instability. Thermal and quantum noise will lead to a nonperiodic perturbation in t...