scholarly journals Optimal frequency window for Floquet engineering in optical lattices

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Gaoyong Sun ◽  
André Eckardt
Keyword(s):  
Optical Lattices ◽  
Optimal Frequency ◽  
Frequency Window

scholarly journals An Early Fault Diagnosis Method of Rolling Bearings on the Basis of Adaptive Frequency Window and Sparse Coding Shrinkage

Entropy ◽  
2019 ◽  
Vol 21 (6) ◽  
pp. 584
Author(s):  
Shuting Wan ◽  
Bo Peng
Keyword(s):  
Fault Diagnosis ◽  
Frequency Band ◽  
Sparse Coding ◽  
Optimal Frequency ◽  
Rolling Bearings ◽  
Diagnosis Method ◽  
Frequency Window ◽  
Envelope Spectrum ◽  
The Impact ◽  
Periodic Components

Early fault information of rolling bearings is weak and often submerged by background noise, easily leading to misdiagnosis or missed diagnosis. In order to solve this issue, the present paper puts forward a fault diagnosis method on the basis of adaptive frequency window (AFW) and sparse coding shrinkage (SCS). The proposed method is based on the idea of determining the resonance frequency band, extracting the narrowband signal, and envelope demodulating the extracted signal. Firstly, the paper introduces frequency window, which can slip on the frequency axis and extract the frequency band. Secondly, the double time domain feature entropy is proposed to evaluate the strength of periodic components in signal. The location of the optimal frequency window covering the resonance band caused by bearing fault is determined adaptively by this entropy index and the shifting/expanding frequency window. Thirdly, the signal corresponding to the optimal frequency window is reconstructed, and it is further filtered by the sparse coding shrinkage algorithm to highlight the impact feature and reduce the residue noise. Fourthly, the de-noised signal is demodulated by envelope operation, and the corresponding envelope spectrum is calculated. Finally, the bearing failure type can be judged by comparing the frequency corresponding to the spectral lines with larger amplitude in the envelope spectrum and the fault characteristic frequency. Two bearing vibration signals are applied to validate the proposed method. The analysis results illustrate that this method can extract more failure information and highlight the early failure feature. The data files of Case Western Reserve University for different operation conditions are used, and the proposed approach achieves a diagnostic success rate of 83.3%, superior to that of the AFW method, SCS method, and Fast Kurtogram method. The method presented in this paper can be used as a supplement to the early fault diagnosis method of rolling bearings.

Robust and Resilient Distributed Optimal Frequency Control for Microgrids Against Cyber Attacks

2021 ◽  
pp. 1-1
Author(s):  
Yun Liu ◽  
Yuanzheng Li ◽  
Yu Wang ◽  
Xian Zhang ◽  
Hoay Beng Gooi ◽  
...  
Keyword(s):  
Frequency Control ◽  
Cyber Attacks ◽  
Optimal Frequency

scholarly journals Frequency of Routine Testing for Coronavirus Disease 2019 (COVID-19) in High-risk Healthcare Environments to Reduce Outbreaks

2020 ◽  
Author(s):  
Elizabeth T Chin ◽  
Benjamin Q Huynh ◽  
Lloyd A C Chapman ◽  
Matthew Murrill ◽  
Sanjay Basu ◽  
...  
Keyword(s):  
High Risk ◽  
Simulation Modeling ◽  
Optimal Frequency ◽  
Routine Testing ◽  
Testing Strategies ◽  
Healthcare Environments ◽  
Viral Testing

Abstract Routine asymptomatic testing strategies for COVID-19 have been proposed to prevent outbreaks in high-risk healthcare environments. We used simulation modeling to evaluate the optimal frequency of viral testing. We found that routine testing substantially reduces risk of outbreaks, but may need to be as frequent as twice weekly.

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