scholarly journals The Spectral Analysis of Dynamic Laser Speckle Patterns Generated by Brownian Particle Suspensions: A Stroboscopic Effect Based Filtering Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Dake Wang ◽  
James Ranger ◽  
Adam Moyer
Keyword(s):  
Power Spectrum ◽  
Brownian Particle ◽  
Modulation Frequency ◽  
Colloidal Suspensions ◽  
Frequency Component ◽  
Laser Speckle ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Full Field ◽  
Speckle Patterns

The power spectrum of the time-varying intensity in the dynamic laser speckle patterns is determined by passing the shifted power spectrum through a low-pass filter which is implemented via the signal integration. The light intensity is modulated sinusoidally to induce the stroboscopic effect which shifts the resonant frequency component of the spectrum to 0 Hz. The homodyne dynamic laser speckles generated by the quasi-inelastic scattering of the Brownian motions in colloidal suspensions are investigated. Within the frequency range from 10 Hz to 10 kHz used in this work, the bandwidth of the Lorenztian power spectrums is shown to be inversely proportional to the particle size, which is in agreement with the prediction of the dynamic light scattering theory of diffusing particle. The spatial variation observed in the full-field power spectrum maps is caused by the nonuniform distribution of average speckle intensity and varies with the modulation frequency. However, the bandwidths measured at different locations are found to be intensity independent.

Frequency-domain characteristics and filtering of blood flow following the onset of exercise: implications for kinetics analysis

2006 ◽  
Vol 100 (3) ◽  
pp. 817-825 ◽  
Author(s):  
Leonardo F. Ferreira ◽  
Allison J. Harper ◽  
Thomas J. Barstow
Keyword(s):  
Blood Flow ◽  
Power Spectrum ◽  
Time Constant ◽  
Standard Error ◽  
Phase 1 ◽  
High Signal ◽  
Parameter Estimates ◽  
Phase 2 ◽  
Pass Filter ◽  
Low Pass Filter

We examined the validity and usefulness of a low-pass filter (LPFILTER) to reduce point-to-point variability and enhance parameter estimation of the kinetics of blood flow (BF). Computer simulations were used to determine the power spectrum of simulated responses. Moreover, we studied the leg BF response to a single transition in four subjects during supine knee-extension exercise using three methods of data processing [beat-by-beat, average of 3 cardiac cycles (AVG3 BEATS), and LPFILTER]. The power spectrum of BF containing the kinetics information (≤0.2 Hz) did not overlap with the oscillations due to muscle contraction and cardiac cycle (simulations and Doppler measurements). There were no significant differences between the parameter estimates for a two-exponential model using Beat-by-Beat, AVG3 BEATS, and LPFILTER ( P > 0.05; n = 4). However, LPFILTER (cutoff = 0.2 Hz) resulted in a significantly lower standard error of the estimate for all parameters ( P < 0.05). The means ± SD for the standard error of the estimate for Beat-by-Beat, AVG3 BEATS, and LPFILTER were, respectively, time constant- phase 1 = 5.0 ± 1.1 s, 4.5 ± 2.1 s, and 0.3 ± 0.2 s; time delay- phase 2 = 17.8 ± 7.9 s, 12.8 ± 7.5 s, and 1.4 ± 1.4 s; time constant- phase 2 = 15.8 ± 4.6 s, 9.9 ± 2.9 s, and 1.1 ± 0.5 s. In conclusion, LPFILTER appeared to be a valid procedure providing a high signal-to-noise ratio and data density and thus LPFILTER resulted in the smallest confidence interval for parameter estimates of BF kinetics.

Full-Field Strain Measurement During Mechanical Testing of the Human Femur at Physiologically Relevant Strain Rates

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Lorenzo Grassi ◽  
Sami P. Väänänen ◽  
Saber Amin Yavari ◽  
Jukka S. Jurvelin ◽  
Harrie Weinans ◽  
...  
Keyword(s):  
Strain Rate ◽  
Soft Tissues ◽  
Numerical Models ◽  
Image Correlation ◽  
Field Strain ◽  
Physiological Strain ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Full Field ◽  
Principal Strains

Understanding the mechanical properties of human femora is of great importance for the development of a reliable fracture criterion aimed at assessing fracture risk. Earlier ex vivo studies have been conducted by measuring strains on a limited set of locations using strain gauges (SGs). Digital image correlation (DIC) could instead be used to reconstruct the full-field strain pattern over the surface of the femur. The objective of this study was to measure the full-field strain response of cadaver femora tested at a physiological strain rate up to fracture in a configuration resembling single stance. The three cadaver femora were cleaned from soft tissues, and a white background paint was applied with a random black speckle pattern over the anterior surface. The mechanical tests were conducted up to fracture at a constant displacement rate of 15 mm/s, and two cameras recorded the event at 3000 frames per second. DIC was performed to retrieve the full-field displacement map, from which strains were derived. A low-pass filter was applied over the measured displacements before the crack opened in order to reduce the noise level. The noise levels were assessed using a dedicated control plate. Conversely, no filtering was applied at the frames close to fracture to get the maximum resolution. The specimens showed a linear behavior of the principal strains with respect to the applied force up to fracture. The strain rate was comparable to the values available in literature from in vivo measurements during daily activities. The cracks opened and fully propagated in less than 1 ms, and small regions with high values of the major principal strains could be spotted just a few frames before the crack opened. This corroborates the hypothesis of a strain-driven fracture mechanism in human bone. The data represent a comprehensive collection of full-field strains, both at physiological load levels and up to fracture. About 10,000 points were tracked on each bone, providing superior spatial resolution compared to ∼15 measurements typically collected using SGs. These experimental data collection can be further used for validation of numerical models, and for experimental verification of bone constitutive laws and fracture criteria.

A New Method of Voltage Flicker Detection for Hilbert Vibration Decomposition

2017 ◽  
Vol 7 (1) ◽  
pp. 43
Author(s):  
Tiejun Cao
Keyword(s):  
Wavelet Transform ◽  
Instantaneous Frequency ◽  
Modulation Frequency ◽  
High Order ◽  
Synchronous Detection ◽  
Transform Method ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Power Frequency ◽  
Voltage Flicker

<p>Hilbert Vibration Decomposition (HVD) is introduced to the voltage flicker analysis. When voltage flicker accompanies with high order harmonics, the instantaneous frequency of its analytic signal in principle consists of two different parts, power frequency and a rapidly varying asymmetrical oscillating part. The important property of the instantaneous frequency offers a direct way to estimate the power frequency using a low-pass filter and remove the high order harmonics without pre-treatment procedures. Corresponding voltage flicker envelope is estimated using synchronous detection. The HVD method does not involves basic functions that the wavelet transform method needs. It can also adaptively estimate the frequency and amplitude of every modulation frequency component. Simulation results prove that the proposed method could accurately detect voltage flicker with high order harmonics. It has higher calculation efficiency and detection precision than wavelet transform method. Experimental results show that the new algorithm is feasible and efficient.</p>

Hilbert low-pass filter of non-stationary time sequence using analytical mode decomposition

2015 ◽  
Vol 23 (15) ◽  
pp. 2444-2469 ◽  
Author(s):  
Zuo-Cai Wang ◽  
Yu Xin ◽  
Jin-feng Xing ◽  
Wei-Xin Ren
Keyword(s):  
Cutoff Frequency ◽  
Low Frequency ◽  
Frequency Component ◽  
Sampling Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Mode Decomposition ◽  
Low Pass ◽  
One Step ◽  
Low Pass Filters

In this paper, the recently developed analytical mode decomposition with a constant or time-varying cutoff frequency is extended into the decomposition of a non-stationary discrete time sequence. The discretization of the signal and the selection of the cutoff frequency may cause the failure of low frequency component extraction. In this study, to eliminate the effects of the signal discretization, the one-step, two-step, and four-step low-pass filters with cutoff frequencies are proposed. Based on the theoretical derivation, the previous one-step low-pass filter is effective only when the cutoff frequency is not greater than a quarter of the sampling frequency and the maximum frequency of the signal not greater than a half of the sampling frequency. In this study, if the cutoff frequency is less than or equal to a quarter of the sampling frequency, a two-step low-pass filter is proposed to extract the low frequency component. If the cutoff frequency is greater than a quarter of the sampling frequency, a four-step low-pass filter with frequency shifting process is proposed. When the time-varying cutoff frequency is not always larger than or less than a quarter of the sampling frequency, a sufficient condition, which is the sampling frequency is greater than four times of the maximum frequency of the signal component, is provided in this study. Two numerical examples are used to validate the effectiveness of the proposed low-pass filters. Both the theoretic derivation and numerical simulations show that the proposed filters can analytical extract the discrete low frequency component with an appropriate cutoff frequency.

Modulation Frequency Analysis of 1-D Semi-Transparent Medium

2004 ◽  
Author(s):  
Joan Boulanger ◽  
Andre´ Charette ◽  
Fengshan Liu
Keyword(s):  
Frequency Analysis ◽  
Modulation Frequency ◽  
Harmonic Excitation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Optical Probing ◽  
State Tomography ◽  
Systematic Response ◽  
Analysis Models

Frequency analysis is an interesting alternative to the full transient optical probing due to its relatively simpler frame of investigation. Both frequency analysis and the full transient probing are superior to the steady-state tomography because of more information gathered per measurement point. The study of the systematic response of a semi-transparent slab to a harmonic excitation through a power modulated laser is therefore of interest and is conducted to investigate its optical properties using an accurate algorithm to solve the Radiative Transfer Equation in the frequency domain. It is found that a semi-transparent slab behaves like a low-pass filter for the power modulated light and this behaviour is mainly controlled by the scattering events occurring on the light path (dispersion). The results found are consistent with those in the literature obtained from experiments or simpler analysis models.

scholarly journals Medial Superior Olive of the Big Brown Bat: Neuronal Responses to Pure Tones, Amplitude Modulations, and Pulse Trains

2001 ◽  
Vol 86 (5) ◽  
pp. 2219-2230 ◽  
Author(s):  
Benedikt Grothe ◽  
Ellen Covey ◽  
John H. Casseday
Keyword(s):  
Interstimulus Interval ◽  
Modulation Frequency ◽  
Medial Superior Olive ◽  
Echolocation Call ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Mustached Bat ◽  
Big Brown Bat ◽  
Low Pass ◽  
Contralateral Ear

The structure and function of the medial superior olive (MSO) is highly variable among mammals. In species with large heads and low-frequency hearing, MSO is adapted for processing interaural time differences. In some species with small heads and high-frequency hearing, the MSO is greatly reduced in size; in others, including those echolocating bats that have been examined, the MSO is large. Moreover, the MSO of bats appears to have undergone different functional specializations depending on the type of echolocation call used. The echolocation call of the mustached bat contains a prominent CF component, and its MSO is predominantly monaural; the free-tailed bat uses pure frequency-modulated calls, and its MSO is predominantly binaural. To further explore the relation of call structure to MSO properties, we recorded extracellularly from 97 single neurons in the MSO of the big brown bat, Eptesicus fuscus, a species whose echolocation call is intermediate between that of the mustached bat and the free-tailed bat. The best frequencies of MSO neurons in the big brown bat ranged from 11 to 79 kHz, spanning most of the audible range. Half of the neurons were monaural, excited by sound at the contralateral ear, while the other half showed evidence of binaural interactions, supporting the idea that the binaural characteristics of MSO neurons in the big brown bat are midway between those of the mustached bat and the free-tailed bat. Within the population of binaural neurons, the majority were excited by sound at the contralateral ear and inhibited by sound at the ipsilateral ear; only 21% were excited by sound at either ear. Discharge patterns were characterized as transient on (37%), primary-like (33%), or transient off (23%). When presented with sinusoidally amplitude modulated tones, most neurons had low-pass filter characteristics with cutoffs between 100 and 300 Hz modulation frequency. For comparison with the sinusoidally modulated sounds, we presented trains of tone pips in which the pulse duration and interstimulus interval were varied. The results of these experiments indicated that it is not the modulation frequency but rather the interstimulus interval that determines the low-pass filter characteristics of MSO neurons.

Design of Programmable Wideband Low Pass Filter with Continuous-Time/Discrete-Time Hybrid Architecture

2017 ◽  
Vol E100.C (10) ◽  
pp. 858-865 ◽  
Author(s):  
Yohei MORISHITA ◽  
Koichi MIZUNO ◽  
Junji SATO ◽  
Koji TAKINAMI ◽  
Kazuaki TAKAHASHI
Keyword(s):  
Discrete Time ◽  
Continuous Time ◽  
Hybrid Architecture ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass
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