Propagation of high-frequency harmonic elastic waves from an axially symmetric cavity

1991 ◽  
Vol 56 (6) ◽  
pp. 2787-2793
Author(s):  
Yu. K. Rubtsov ◽  
P. N. Soroka
Keyword(s):  
Elastic Waves ◽  
High Frequency ◽  
Axially Symmetric ◽  
Symmetric Cavity ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

scholarly journals Early Fault Detection Method for Rotating Machinery Based on Harmonic-Assisted Multivariate Empirical Mode Decomposition and Transfer Entropy

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 873 ◽  
Author(s):  
Zhe Wu ◽  
Qiang Zhang ◽  
Lixin Wang ◽  
Lifeng Cheng ◽  
Jingbo Zhou
Keyword(s):  
Fault Detection ◽  
Empirical Mode Decomposition ◽  
High Frequency ◽  
Rotating Machinery ◽  
Transfer Entropy ◽  
Multivariate Empirical Mode Decomposition ◽  
Mode Decomposition ◽  
Coupling Characteristics ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

It is a difficult task to analyze the coupling characteristics of rotating machinery fault signals under the influence of complex and nonlinear interference signals. This difficulty is due to the strong noise background of rotating machinery fault feature extraction and weaknesses, such as modal mixing problems, in the existing Ensemble Empirical Mode Decomposition (EEMD) time–frequency analysis methods. To quantitatively study the nonlinear synchronous coupling characteristics and information transfer characteristics of rotating machinery fault signals between different frequency scales under the influence of complex and nonlinear interference signals, a new nonlinear signal processing method—the harmonic assisted multivariate empirical mode decomposition method (HA-MEMD)—is proposed in this paper. By adding additional high-frequency harmonic-assisted channels and reducing them, the decomposing precision of the Intrinsic Mode Function (IMF) can be effectively improved, and the phenomenon of mode aliasing can be mitigated. Analysis results of the simulated signals prove the effectiveness of this method. By combining HA-MEMD with the transfer entropy algorithm and introducing signal processing of the rotating machinery, a fault detection method of rotating machinery based on high-frequency harmonic-assisted multivariate empirical mode decomposition-transfer entropy (HA-MEMD-TE) was established. The main features of the mechanical transmission system were extracted by the high-frequency harmonic-assisted multivariate empirical mode decomposition method, and the signal, after noise reduction, was used for the transfer entropy calculation. The evaluation index of the rotating machinery state based on HA-MEMD-TE was established to quantitatively describe the degree of nonlinear coupling between signals to effectively evaluate and diagnose the operating state of the mechanical system. By adding noise to different signal-to-noise ratios, the fault detection ability of HA-MEMD-TE method in the background of strong noise is investigated, which proves that the method has strong reliability and robustness. In this paper, transfer entropy is applied to the fault diagnosis field of rotating machinery, which provides a new effective method for early fault diagnosis and performance degradation-state recognition of rotating machinery, and leads to relevant research conclusions.

scholarly journals Double Pendulum Induced Stability

2015 ◽  
Vol 07 (06) ◽  
pp. 1550088
Author(s):  
Bezdenejnykh Nikolai ◽  
Andres Mateo Gabin ◽  
Raul Zazo Jimenez
Keyword(s):  
Theoretical Analysis ◽  
Potential Energy ◽  
High Frequency ◽  
Relative Equilibrium ◽  
Double Pendulum ◽  
Harmonic Vibrations ◽  
Hamilton Equations ◽  
High Frequency Harmonic ◽  
Good Agreement ◽  
Frequency Harmonic

In this work, a study of the relative equilibrium of a double pendulum whose point of suspension performs high frequency harmonic vibrations is presented. In order to determine the induced positions of equilibrium of the double pendulum at different gravity and vibration configurations, a set of experiments has been conducted. The theoretical analysis of the problem has been developed using Kapitsa’s method and numerical method. The method of Kapitsa allows to analyze the potential energy of a system in general and to find the values of the parameters of the problem that correspond to the relative extreme of energy — positions of stable or unstable equilibrium. The results of numerical and theoretical analysis of Hamilton equations are in good agreement with the results of the experiments.

scholarly journals NORMAL FORM AND ENERGY CONSERVATION OF HIGH FREQUENCY SUBSYSTEMS WITHOUT NONRESONANCE CONDITIONS

2013 ◽  
Author(s):  
Dario Bambusi ◽  
Antonio Giorgilli ◽  
Simone Paleari ◽  
Tiziano Penati
Keyword(s):  
Normal Form ◽  
Energy Conservation ◽  
High Frequency ◽  
Harmonic Oscillators ◽  
Fast System ◽  
System Changes ◽  
High Frequency Harmonic ◽  
Slow System ◽  
Frequency Harmonic

We consider a system in which some high frequency harmonic oscillators are coupled with a slow system. We prove that up to very long times the energy of the high frequency system changes only by a small amount. The result we obtain is completely independent of the resonance relations among the frequencies of the fast system. More in detail, denote by ϵ-1 the smallest high frequency. In the first part of the paper we apply the main result of [1] to prove almost conservation of the energy of the high frequency system over times exponentially long with ϵ-1/n (n being the number of fast oscillators). In the second part of the paper we give a new self-contained proof of a similar result which however is valid only over times of order ϵ-N with an arbitrary N. Such a second result is very similar to the main result of the paper [4], which actually was the paper which stimulated our work.

P3P-2 Dual Element Transducers for High Frequency Harmonic Imaging

2006 ◽  
Author(s):  
R. H. Silverman ◽  
K. K. Shung ◽  
R. Liu ◽  
L. Sun ◽  
J. M. Cannata ◽  
...  
Keyword(s):  
High Frequency ◽  
Harmonic Imaging ◽  
High Frequency Harmonic ◽  
Frequency Harmonic
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