The linear theory of oscillations traditionally operates with frequency representaÂ tions based on the concepts of a transfer function and a frequency response. The universality of the critria of Nyquist and Mikhailov and the simplicity and obviÂ ousness of the application of frequency and amplitude - frequency characteristics in analysing forced linear oscillations greatly encouraged the development of practiÂ cally important nonlinear theories based on various forms of the harmonic balance hypothesis . Therefore mathematically rigorous frequency methods of investiÂ gating nonlinear systems, which appeared in the 60s, also began to influence many areas of nonlinear theory of oscillations. First in this sphere of influence was a wide range of problems connected with multidimensional analogues of the famous van der Pol equation describing autoÂ oscillations of generators of various radiotechnical devices. Such analogues have as a rule a unique unstable stationary point in the phase space and are Levinson disÂ sipative. One of the pioneering works in this field, which started the investigation of a three-dimensional analogue of the van der Pol equation, was K. O. Friedrichs's paper . The author suggested a scheme for constructing a positively invariant set homeomorphic to a torus, by means of which the existence of non-trivial periodic solutions was established. That scheme was then developed and improved for difÂ ferent classes of multidimensional dynamical systems [131, 132, 297, 317, 334, 357, 358]. The method of Poincare mapping [12, 13, 17] in piecewise linear systems was another intensively developed direction.
Tailored especially for the working health professional, Radio Frequency and ELF Electrogmagnetic Energies is a practical guide to understanding, evaluating, and controlling the human health effects of radio-frequency (RF) and extremely low frequency (ELF) electromagnetic fields. Providing a perfect blend of applied information and theory, you'll find all you need to know about radiation safety, from the basic physics to how to set up a safety program. This book brings you cutting-edge discussions of exposure limits, monitoring instrumentation, new measurements required by human exposure standards, induced currents and contact currents, and the latest data on biological effects.
Time-Frequency Signal Analysis and Processing (TFSAP) is a collection of theory and algorithms used for the analysis and processing of non-stationary signals, as found in a wide range of applications including telecommunications, radar, and biomedical engineering. This book gives the university researcher and R&D engineer insight into how to use TFSAP methods to develop the engineering application systems they are looking to implement.
Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single- djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro- physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre- tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientists to review the field and discuss these questions of interpretation. A broad concensus has emerged: the subtleties of the line-formation process are understood, and the conditions under which reliable in- formation can easily be extracted from the line measurements are known. It thus appears likely that the emphasis will shift increasingly from the study of the line phenomenon itself to further application in other areas of astrophysics, ranging from physical processes in plasmas (temperatures, densities, ionization structure), to the large-scale properties of our galaxy (abundances, kinematics, structure), and studies of extragalactic systems.
Proceedings of a NATO ARW on Developing a New Standardization Agreement (STANAG) for Radiofrequency Radiation held in Pomezia (Rome), Italy, May 17-21, 1993