Deriving time-varying cellular motility parameters via wavelet analysis

In the last decade, many factors, such as socio-political and econo-environmental ones, have led to a perturbation in the timeline of the worldwide development, and especially in countries and regions having political changes. This led us to introduce a new idea of risk estimation taking into account the non-uniform changes in markets by introducing a non-uniform wavelet analysis. We aim to explain the econo-political situation of Arab spring countries and the effect of the revolutions on the market beta. The main novelty is first the construction of a dynamic backward-forward model for missing data, and next the application of random non-uniform wavelets. The proposed procedure will be acted empirically on a sample corresponding to TUNINDEX stock as a representative index of the Tunisian market actively traded over the period from 14 January 2016 to 13 January 2021. The chosen 5-year period is important as it constitutes the first five years after the revolution and depends strongly on the socio-econo-political stability in the revolutionary countries. The results showed the efficiency of non-uniform wavelets in explaining the dynamics of the market well. They therefore may be good tools to explore important phenomena in the market such as the non-stationary aspect of financial series, non-constancy, and time-varying parameters. These facts in turn will have positive implications for investors as well as politicians in front of the evolution of the market. Besides, recommendations to extend the present method for other types of wavelets and markets will be of interest.

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Doubly Fed Induction Machine stator fault diagnosis under time-varying conditions based on frequency sliding and wavelet analysis

2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives ◽

10.1109/demped.2009.5292802 ◽

2009 ◽

Cited By ~ 5

Author(s):

Y. Gritli ◽

A. Stefani ◽

C. Rossi ◽

F. Filippetti ◽

A. Chatti

Keyword(s):

Fault Diagnosis ◽

Wavelet Analysis ◽

Induction Machine ◽

Time Varying ◽

Doubly Fed Induction Machine ◽

Doubly Fed ◽

Stator Fault

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Positioning and Vibration Control of Time-Varying Vibration Systems by Means of Nonstationary Optimal Regulator

Volume 5: 19th Biennial Conference on Mechanical Vibration and Noise, Parts A, B, and C ◽

10.1115/detc2003/vib-48564 ◽

2003 ◽

Cited By ~ 5

Author(s):

Susumu Hara ◽

Kenji Nakamura ◽

Tatsuo Narikiyo

Keyword(s):

Wavelet Analysis ◽

Vibration Control ◽

A Priori ◽

Gain Scheduling ◽

Time Varying ◽

Vibration System ◽

Line Measurement ◽

Time Varying Parameter ◽

On Line ◽

Optimal Regulator

This study discusses the positioning and vibration control of time-varying vibration systems whose parameters are time-varying. We assume that the time-varying parameter of a vibration system is detected by an on-line measurement or Wavelet analysis. This paper treats two control methods based on nonstationary optimal regulators (NORs) for this problem. The first method is a gain-scheduling of NORs. An actual controller is obtained by the interpolation of plural NORs designed a priori. The other one is an NOR design based on Wavelet analysis of the vibration system. In the second case, single NOR derived from the analysis result is applied. This study shows the effectiveness of these methods by numerical calculations and experiments. From the comparison of these methods, this paper suggests suitable applications of NOR according to the characteristics of each control problem.

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Structural Health Monitoring of Rotordynamic Systems by Wavelet Analysis

Materials, Nondestructive Evaluation, and Pressure Vessels and Piping ◽

10.1115/imece2006-15930 ◽

2006 ◽

Cited By ~ 1

Author(s):

Girindra Mani ◽

D. Dane Quinn ◽

Mary E. F. Kasarda

Keyword(s):

Wavelet Analysis ◽

Crack Depth ◽

Dynamical Behavior ◽

Vibration Response ◽

External Loading ◽

Time Varying ◽

External Forcing ◽

Wavelet Coefficients ◽

Combination Resonance ◽

Detection Techniques

This work describes a foundation of sophisticated diagnostic techniques for the detection of shaft cracks in rotordynamic systems, considering the dynamical behavior of a rotating cracked shaft under the application of external loads. The response is modeled as a modified Jeffcott rotor, while the crack is assumed to induce a time-varying stiffness in the model. The focus of this work is the development of external loading strategies to create damage sensitive measures of vibration response and then analyze that using advanced technologies such as wavelet analysis. This will enable the detection of the crack depth, as represented by the magnitude of the damage-induced time-varying stiffness, from vibration measurements. This entails developing external forcing functions for which features of the vibration response are sensitive to the presence of the damage. The development of such inputs is based on a multiple-scales analysis of the full equations of motion, including the time-varying stiffness. From this, a resonance (called combination resonance) is identified between the operating speed of the shaft, the fundamental frequency of the shaft, and the frequency of the external forcing. When the system is operated at this resonant condition, the translational vibrations of the shaft contain a spectral component near the fundamental shaft frequency that is proportional to the amplitude of the time-varying stiffness. The resonance bandwidth, obtained from this analysis, enables us to build a framework for the development of damage detection techniques for rotating machinery. Continuous Wavelet Transform (CWT) is applied to the vibration response of a rotordynamic system that utilizes harmonic forcing satisfying combination resonance. The variation of wavelet coefficients with respect to the variation of different system parameters is examined. Attention is focused on how the resonant bandwidth affects the variation of wavelet coefficients as crack grows.

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