scholarly journals An Investigation into Error Source Identification of Machine Tools Based on Time-Frequency Feature Extraction

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Dongju Chen ◽  
Shuai Zhou ◽  
Lihua Dong ◽  
Jinwei Fan
Keyword(s):  
Machine Tool ◽  
Frequency Domain ◽  
Surface Topography ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Time Frequency ◽  
Cross Correlation Analysis ◽  
Correlation Analysis Method

This paper presents a new identification method to identify the main errors of the machine tool in time-frequency domain. The low- and high-frequency signals of the workpiece surface are decomposed based on the Daubechies wavelet transform. With power spectral density analysis, the main features of the high-frequency signal corresponding to the imbalance of the spindle system are extracted from the surface topography of the workpiece in the frequency domain. With the cross-correlation analysis method, the relationship between the guideway error of the machine tool and the low-frequency signal of the surface topography is calculated in the time domain.

Wavelet De-Noising Algorithm Based on OpenCV for Images Edge Detection

2014 ◽  
Vol 989-994 ◽  
pp. 3973-3976
Author(s):  
Yi Fan Ma ◽  
Shu Gui Liu
Keyword(s):  
Edge Detection ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Canny Edge Detection ◽  
Image Edge Detection ◽  
Canny Edge ◽  
Image Edge ◽  
Wavelet Algorithm

Image edge detection is easily affected by noise. Wavelet algorithm can divide the image into low frequency and high frequency. By the processing of high frequency signal and the reconstruction of wavelet coefficients, the purpose of removing noise can be achieved. In the environment of VC++6.0, an image de-noising algorithm based on the wavelet combined with the Canny edge detection is proposed, which obtains a good result. The above algorithms are implemented based on OpenCV, which is more efficient, providing the conditions for subsequent image analysis and recognition. Experiments are carried out and the results show that the proposed algorithm is available and has a good performance.

scholarly journals Relevance of Frequency-Domain Analyses to Relate Shoe Cushioning, Ground Impact Forces and Running Injury Risk: A Secondary Analysis of a Randomized Trial With 800+ Recreational Runners

2021 ◽  
Vol 3 ◽  
Author(s):  
Laurent Malisoux ◽  
Paul Gette ◽  
Anne Backes ◽  
Nicolas Delattre ◽  
Jan Cabri ◽  
...  
Keyword(s):  
Frequency Domain ◽  
High Frequency ◽  
Injury Risk ◽  
Peak Force ◽  
Recent Trial ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Impact Forces ◽  
Impact Peak ◽  
Force Characteristics

Cushioning systems in running shoes are used assuming that ground impact forces relate to injury risk and that cushioning materials reduce these impact forces. In our recent trial, the more cushioned shoe version was associated with lower injury risk. However, vertical impact peak force was higher in participants with the Soft shoe version. The primary objective of this study was to investigate the effect of shoe cushioning on the time, magnitude and frequency characteristics of peak forces using frequency-domain analysis by comparing the two study groups from our recent trial (Hard and Soft shoe group, respectively). The secondary objective was to investigate if force characteristics are prospectively associated with the risk of running-related injury. This is a secondary analysis of a double-blinded randomized trial on shoe cushioning with a biomechanical running analysis at baseline and a 6-month follow-up on running exposure and injury. Participants (n = 848) were tested on an instrumented treadmill at their preferred running speed in their randomly allocated shoe condition. The vertical ground reaction force signal for each stance phase was decomposed into the frequency domain using the discrete Fourier transform. Both components were recomposed into the time domain using the inverse Fourier transform. An analysis of variance was used to compare force characteristics between the two study groups. Cox regression analysis was used to investigate the association between force characteristics and injury risk. Participants using the Soft shoes displayed lower impact peak force (p < 0.001, d = 0.23), longer time to peak force (p < 0.001, d = 0.25), and lower average loading rate (p < 0.001, d = 0.18) of the high frequency signal compared to those using the Hard shoes. Participants with low average and instantaneous loading rate of the high frequency signal had lower injury risk [Sub hazard rate ratio (SHR) = 0.49 and 0.55; 95% Confidence Interval (CI) = 0.25–0.97 and 0.30–0.99, respectively], and those with early occurrence of impact peak force (high frequency signal) had greater injury risk (SHR = 1.60; 95% CI = 1.05–2.53). Our findings may explain the protective effect of the Soft shoe version previously observed. The present study also demonstrates that frequency-domain analyses may provide clinically relevant impact force characteristics.Clinical Trial Registration:https://clinicaltrials.gov/, identifier: 9NCT03115437.

Vibrational resonance in a discrete neuronal model with time delay

2014 ◽  
Vol 28 (16) ◽  
pp. 1450103 ◽  
Author(s):  
Canjun Wang ◽  
Keli Yang ◽  
Shixian Qu
Keyword(s):  
Time Delay ◽  
Input Signal ◽  
High Frequency ◽  
Phase Synchronization ◽  
Low Frequency ◽  
Neuronal Model ◽  
Vibrational Resonance ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Neuron System

The effects of time delay on the vibrational resonance (VR) in a discrete neuron system with a low-frequency signal and a high-frequency signal are investigated by numerical simulations. The results show that there exists a delay time that optimizes the phase synchronization between the low-frequency input signal and the output signal. VR is induced by the time delay. Furthermore, the time delay can improve the response to a low-frequency input signal. Therefore, the time delay plays a constructive role in the transmission of a low-frequency signal by inducing and enhancing VR.

Simulation of Secondary Equipment Lightning Protection in EHV Substation Based on ATP

2014 ◽  
Vol 543-547 ◽  
pp. 514-517
Author(s):  
Hong Bo Li ◽  
Lin Niu ◽  
Nan Nan Gao ◽  
Jie Zhan ◽  
Pei Li ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lightning Protection ◽  
Earth System ◽  
Secondary System ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Lightning Current ◽  
Grounding Grids ◽  
The One

By analyzing the two lightning accidents happening to a 500kV substation situated in the lightning-prone northeastern Guangdong Province, I conclude as follows, there should be some problem in the equipotential earthing of the secondary system of this substation. Specifically, the existing potential difference in the secondary equipment gave rise to the meltdown of it which finally caused the accident. In the context,I build the one-point earthing parallel system simulation model according to ATP graphic pretreatment program, then by using slope-ramp simulation I study the lightning current which leaked into the grounding grids of the substation.In conclusion, the application of high frequency signal mixed low frequency signal earth system in the secondary system and the equipotential bonding is key to preventing accidents.

scholarly journals Estimation of narrowband amplitude and phase from electrophysiology signals for phase-amplitude coupling studies: a comparison of methods

2018 ◽  
Author(s):  
Juan L.P. Soto ◽  
Felipe V.D. Prado ◽  
Etienne Combrisson ◽  
Karim Jerbi
Keyword(s):  
High Frequency ◽  
Brain Activity ◽  
Low Frequency ◽  
Preliminary Evidence ◽  
Visuomotor Coordination ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Electrophysiological Measurements ◽  
High Gamma ◽  
Phase Amplitude

AbstractMany functional connectivity studies based on electrophysiological measurements, such as electro- and magnetoencephalography (EEG/MEG), start their investigations by extracting a narrowband representation of brain activity time series, and then computing their envelope amplitudes and instantaneous phases, which serve as inputs to subsequent data processing. The two most popular approaches for obtaining these narrowband amplitudes and phases are: bandpass filtering followed by Hilbert transform (we call this the Hilbert approach); and convolution with wavelet kernels (the wavelet approach). In this work, we investigate how these two approaches perform in detecting the phenomenon of phase-amplitude coupling (PAC), whereby the amplitude of a high-frequency signal is driven by the phase of a low-frequency signal. The comparison of both approaches is carried out by means of simulated brain activity, from which we run receiver operating characteristic (ROC) analyses, and of experimental MEG data from a visuomotor coordination study. The ROC analyses show that both approaches have comparable accuracy, except in the presence of interfering signals with frequencies near the high-frequency band. As for the visuomotor data, the most noticeable impact of the choice of approach was observed when evaluating task-based changes in PAC between the delta (2-5 Hz) and the high-gamma (60-90 Hz) frequency bands, as we were able to identify widespread brain areas with statistically significant effects only with the Hilbert approach. These results provide preliminary evidence of the advantages of the Hilbert approach over the wavelet approach, at least in the context of PAC estimates.

scholarly journals A Facile Strategy for Visualizing and Modulating Droplet-Based Microfluidics

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 291 ◽  
Author(s):  
Zehang Gao ◽  
Huo Peng ◽  
Minjie Zhu ◽  
Lei Wu ◽  
Chunping Jia ◽  
...  
Keyword(s):  
High Throughput ◽  
High Frequency ◽  
Imaging System ◽  
Low Cost ◽  
Low Frequency ◽  
Microfluidic Chips ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Additional Signal ◽  
And Control

In droplet-based microfluidics, visualizing and modulating of droplets is often prerequisite. In this paper, we report a facile strategy for visualizing and modulating high-throughput droplets in microfluidics. In the strategy, by modulating the sampling frequency of a flash light with the droplet frequency, we are able to map a real high frequency signal to a low frequency signal, which facilitates visualizing and feedback controlling. Meanwhile, because of not needing synchronization signals, the strategy can be directly implemented on any droplet-based microfluidic chips. The only cost of the strategy is an additional signal generator. Moreover, the strategy can catch droplets with frequency up to several kilohertz, which covers the range of most high-throughput droplet-based microfluidics. In this paper, the principle, setup and procedure were introduced. Finally, as a demonstration, the strategy was also implemented in a miniaturized picoinjector in order to monitor and control the injection dosage to droplets. We expect that this facile strategy supplies a low-cost yet effective imaging system that can be easily implemented in miniaturized microfluidic systems or general laboratories.

scholarly journals Shallow crustal imaging using distant, high-magnitude earthquakes

2019 ◽  
Vol 219 (2) ◽  
pp. 1082-1091 ◽  
Author(s):  
Johno van IJsseldijk ◽  
Elmer Ruigrok ◽  
Arie Verdel ◽  
Cornelis Weemstra
Keyword(s):  
High Frequency ◽  
Structural Information ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Seismic Interferometry ◽  
Sedimentary Structure ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Midcontinent Rift ◽  
High Magnitude

SUMMARY Global phases, viz. seismic phases that travel through the Earth’s core, can be used to locally image the crust by means of seismic interferometry. This method is known as Global Phase Seismic Interferometry (GloPSI). Traditionally, GloPSI retrieves low-frequency information (up to 1 Hz). Recent studies, however, suggest that there is high-frequency signal present in the coda of strong, distant earthquakes. This research quantifies the potential of these high-frequency signals, by analysing recordings of a multitude of high-magnitude earthquakes (≥6.4 Mw) and their coda on a selection of permanent USArray stations. Nearly half of the P, PKP and PKIKP phases are recorded with a signal-to-noise ratio of at least 5 dB at 3 Hz. To assess the viability of using the high-frequency signal, the second half of the paper highlights two case studies. First, a known sedimentary structure is imaged in Malargüe, Argentina. Secondly, the method is used to reveal the structure of the Midcontinent Rift below the SPREE array in Minnesota, USA. Both studies demonstrate that structural information of the shallow crust (≤5 km) below the arrays can be retrieved. In particular, the interpreted thickness of the sedimentary layer below the Malargüe array is in agreement with earlier studies in the same area. Being able to use global phases and direct P-phases with large epicentral distances (>80°) to recover the Earth’s sedimentary structure suggests that GloPSI can be applied in an industrial context.

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