Self-oscillatory systems with high-frequency energy sources

1989 ◽  
Vol 32 (8) ◽  
pp. 723-731 ◽  
Author(s):  
Polina S Landa ◽  
Ya B Duboshinskiĭ
Keyword(s):  
High Frequency ◽  
Energy Sources ◽  
Oscillatory Systems

Self-oscillatory systems with high-frequency energy sources

1989 ◽  
Vol 158 (8) ◽  
pp. 729 ◽  
Author(s):  
Polina S. Landa ◽  
Ya.B. Duboshinskii
Keyword(s):  
High Frequency ◽  
Energy Sources ◽  
Oscillatory Systems

On representing noise by deterministic excitations for interpreting the stochastic resonance phenomenon

2021 ◽  
Vol 379 (2192) ◽  
pp. 20200229 ◽  
Author(s):  
V. Sorokin ◽  
I. Demidov
Keyword(s):  
Stochastic Resonance ◽  
High Frequency ◽  
Stochastic Systems ◽  
Signal To Noise Ratio ◽  
Nonlinear Damping ◽  
Resonance Phenomenon ◽  
Oscillatory Systems ◽  
Stochastic Excitations ◽  
Viable Approach ◽  
Stochastic Resonance Phenomenon

Adding noise to a system can ‘improve’ its dynamic behaviour, for example, it can increase its response or signal-to-noise ratio. The corresponding phenomenon, called stochastic resonance, has found numerous applications in physics, neuroscience, biology, medicine and mechanics. Replacing stochastic excitations with high-frequency ones was shown to be a viable approach to analysing several linear and nonlinear dynamic systems. For these systems, the influence of the stochastic and high-frequency excitations appears to be qualitatively similar. The present paper concerns the discussion of the applicability of this ‘deterministic’ approach to stochastic systems. First, the conventional nonlinear bi-stable system is briefly revisited. Then dynamical systems with multiplicative noise are considered and the validity of replacing stochastic excitations with deterministic ones for such systems is discussed. Finally, we study oscillatory systems with nonlinear damping and analyse the effects of stochastic and deterministic excitations on such systems. This article is part of the theme issue ‘Vibrational and stochastic resonance in driven nonlinear systems (part 1)’.

IMPROVEMENT OF A HIGH-FREQUENCY BROADBAND ENERGY-INTENSITY BOUNDARY ELEMENT METHOD TO INCLUDE HIGH RESOLUTION SPECULAR REFLECTION

2005 ◽  
Vol 13 (01) ◽  
pp. 99-125 ◽  
Author(s):  
JERRY ROUSE ◽  
LINDA FRANZONI
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
High Frequency ◽  
Fourier Expansion ◽  
Energy Intensity ◽  
Specular Reflection ◽  
Original Method ◽  
Energy Sources ◽  
Frequency Basis ◽  
Element Method

The prediction of the spatial mean-square pressure distribution within enclosed high-frequency broadband sound fields is computationally intensive if determined on a frequency-by-frequency basis. Recently an energy-intensity boundary element method (EIBEM) has been formally developed. This method employs uncorrelated broadband directional energy sources to expeditiously predict such pressure distributions. The source directivity accounts for local correlation effects and specular reflection. The method is applicable to high modal density fields, but not restricted to the usual low-absorption, diffuse, and quasi-uniform assumptions. The approach can accommodate fully specular reflection, or any combination of diffuse and specular reflection. This boundary element method differs from the classical version in that element size is large compared to an acoustic wavelength and equations are not solved on a frequency-by-frequency basis. In the earlier EIBEM, the source strength and directivity associated with the energy sources, distributed over enclosure boundaries, were determined in an iterative manner and the directivity was limited to three terms of a Fourier expansion. Here, the original method is improved by eliminating the iteration and allowing for an unlimited number of terms in the Fourier expansion of the directivity function. For verification, the improved EIBEM is compared to experimental measurements and exact analytical solutions; excellent agreement is obtained.

scholarly journals Experimentelles FMCW-Radar zur hochfrequenten Charakterisierung von Windenergieanlagen

2017 ◽  
Vol 15 ◽  
pp. 1-9
Author(s):  
Karsten Schubert ◽  
Jens Werner ◽  
Fabian Schwartau
Keyword(s):  
Renewable Energy ◽  
High Frequency ◽  
Renewable Energy Sources ◽  
Cost Effective ◽  
Energy Sources ◽  
Interference Effects ◽  
Fmcw Radar ◽  
Weather Radars ◽  
Radar Systems ◽  
Radar Echoes

Abstract. During the increasing dissemination of renewable energy sources the potential and actual interference effects of wind turbine plants became obvious. Turbines reflect the signals of weather radar and other radar systems. In addition to the static radar echoes, in particular the Doppler echoes are to be mentioned as an undesirable impairment Keränen (2014). As a result, building permit is refused for numerous new wind turbines, as the potential interference can not be reliably predicted. As a contribution to the improvement of this predictability, measurements are planned which aim at the high-frequency characterisation of wind energy installations. In this paper, a cost-effective FMCW radar is presented, which is operated in the same frequency band (C-band) as the weather radars of the German weather service. Here, the focus is on the description of the hardware design including the considerations used for its dimensioning.

scholarly journals Review of a Disruptive Vision of Future Power Grids: A New Path Based on Hybrid AC/DC Grids and Solid-State Transformers

2021 ◽  
Vol 13 (16) ◽  
pp. 9423
Author(s):  
Vitor Monteiro ◽  
Julio S. Martins ◽  
João Carlos Aparício Fernandes ◽  
Joao L. Afonso
Keyword(s):  
Solid State ◽  
Power Quality ◽  
High Frequency ◽  
Universal Access ◽  
Renewable Energy Sources ◽  
Low Frequency ◽  
Power Grids ◽  
Energy Sources ◽  
Solid State Transformers ◽  
Port Systems

Power grids are evolving with the aim to guarantee sustainability and higher levels of power quality for universal access to electricity. More specifically, over the last two decades, power grids have been targeted for significant changes, including migration from centralized to decentralized paradigms as a corollary of intensive integration of novel electrical technologies and the availability of derived equipment. This paper addresses a review of a disruptive vision of future power grids, mainly focusing on the use of hybrid AC/DC grids and solid-state transformers technologies. Regarding hybrid AC/DC grids in particular, they are analyzed in detail in the context of unipolar and bipolar DC grids (i.e., two-wire or three-wire DC grids), as well as the different structures concerning coupled and decoupled AC configurations with low-frequency or high-frequency isolation. The contextualization of the possible configurations of solid-state transformers and the different configurations of hybrid transformers (in the perspective of offering benefits for increasing power quality in terms of currents or voltages) is also analyzed within the perspective of the smart transformers. Additionally, the paper also presents unified multi-port systems used to interface various technologies with hybrid AC/DC grids, which are also foreseen to play an important role in future power grids (e.g., the unified interface of renewable energy sources and energy storage systems), including an analysis concerning unified multi-port systems for AC or DC grids. Throughout the paper, these topics are presented and discussed in the context of future power grids. An exhaustive description of these technologies is made, covering the most relevant and recent structures and features that can be developed, as well as the challenges for the future power grids. Several scenarios are presented, encompassing the mentioned technologies, and unveiling a progressive evolution that culminates in the cooperative scope of such technologies for a disruptive vision of future power grids.

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