scholarly journals Chain-stretch relaxation from low-frequency Fourier transform rheology

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
C. D. Reynolds ◽  
D. M. Hoyle ◽  
T. C. B. McLeish ◽  
R. L. Thompson
Keyword(s):  
Fourier Transform ◽  
Low Frequency ◽  
Fourier Transform Rheology

scholarly journals MULTIDIMENSIONAL REPRESENTATION OF AUTOMATIC DOSING DEVICE SIGNALS

2018 ◽  
pp. 26-32
Author(s):  
Denis Borisovich Fedosenkov ◽  
Anna Alekseevna Simikova ◽  
Boris Andreevich Fedosenkov ◽  
Stanislav Matveevich Kulakov
Keyword(s):  
Fourier Transform ◽  
Wigner Distribution ◽  
Low Frequency ◽  
Stationary Flow ◽  
Complex Model ◽  
Signal Spectrum ◽  
One Dimensional ◽  
Time Frequency ◽  
Cohen's Class ◽  
Discrete Values

The article describes the development of a special approach based on using multidimensional wavelet distributions principle to monitor and control the feed dozing processes in the mix preparation unit. As a key component, this approach uses the multidimensional time-frequency Wigner-Ville distribution, which is the part of Cohen's class distributions. The research focuses on signals characterizing mass transfer processes in the form of material flow measuring signals in relevant points of the unit. Wigner-Ville distribution has been shown in time terms as Fourier transform of products of multiplied parts of the signal under consideration for past and future time moments; corresponding distribution for the frequency spectrum is shown as Fourier transform of the products of signal parts for high-frequency and low-frequency fragments of the signal spectrum. It has been noted that when using a complex model of a dozing signal, discrete values (samples) of the latter are considered as its real values. The description of the signal parameters (amplitude, phase, frequency) has been carried out with the help of Hilbert transform. In Cohen's class distributions which represent one-dimensional non-stationary flow signals, the concept of ‘instantaneous frequency’ has been introduced. A graphical explanation for the transformation of a process flow signal from a one-dimensional time domain to a time-frequency 2 D/ 3 D -space is presented. The technology of developing a multidimensional image in the form of Wigner distribution for one-dimensional signals of continuous spiral or screw-type feeders has been examined in detail. There have been considered the features to support Wigner distribution, which allow to guess the presence or absence of time-frequency distribution elements in the interval of signal recording. There has been demonstrated how Wigner distribution can be obtained for a continuous-intermittent feeding signal. It has been concluded that for a certain types of the signal for zero fragments of the latter, non-zero time-frequency elements (i.e. virtual, anomalous ones) appear on the distribution. In addition to Wigner distribution, two other distributions - of Rihachek and Page - are considered. They display the same signal and also contain virtual elements, but in different domains of the time-frequency space. A generalized multidimensional compound signal distribution with a so-called distribution kernel available in it is presented, which includes a correction parameter that allows controlling the intensity of the virtual signal energy.

Low-Frequency Photoacoustic Spectroscopy of Solids

1988 ◽  
Vol 42 (2) ◽  
pp. 289-292 ◽  
Author(s):  
J. C. Donini ◽  
K. H. Michaelian
Keyword(s):  
Fourier Transform ◽  
Carbon Black ◽  
Low Frequency ◽  
Far Infrared ◽  
Research Quality ◽  
Signal To Noise ◽  
Single Spectrum ◽  
Mid Infrared ◽  
Infrared Spectrometer ◽  
Computational Procedures

Research-quality far-infrared photoacoustic (PA) spectra are obtainable with a Fourier transform infrared spectrometer, the only changes with respect to conventional mid-infrared PA spectroscopy being the use of (1) a caesium iodide or polyethylene window on the PA cell, and (2) a mylar beamsplitter. Far-infrared PA spectra of several solids (bentonite, Fe+3-bentonite, and asbestos), in addition to the PA reference carbon black, have been recorded in this way. In order to improve signal-to-noise ratios in one of the spectra, we recorded ten interferograms under identical conditions; it was found that the average of the ten individually calculated spectra displays less noise and fewer spurious features than the spectrum obtained by first averaging the interferograms and then calculating a single spectrum. The results of this investigation demonstrate the feasibility of far-infrared PA spectroscopy, and illustrate that both experimental and computational procedures should be optimized in order to obtain the most satisfactory spectra.

Two-dimensional Fourier transform rheology

2001 ◽  
Vol 45 (6) ◽  
pp. 1319-1339 ◽  
Author(s):  
Dagmar van Dusschoten ◽  
Manfred Wilhelm ◽  
Hans W. Spiess
Keyword(s):  
Fourier Transform ◽  
Two Dimensional ◽  
Fourier Transform Rheology

A flexible, efficient and low-cost experimental platform for FMCW radars

Sensor Review ◽  
2019 ◽  
Vol 39 (4) ◽  
pp. 495-503 ◽  
Author(s):  
Tao Wang ◽  
Ping Li ◽  
Mingfang Wang ◽  
DanDan Yang ◽  
Chaoyu Shi
Keyword(s):  
Fourier Transform ◽  
Continuous Wave ◽  
Low Cost ◽  
Low Frequency ◽  
Waveform Data ◽  
Content Type ◽  
Experimental Platform ◽  
Field Programmable ◽  
Health Care Applications ◽  
Measurement Experiment

Purpose This paper proposes a design of an efficient and automated experimental platform for frequency modulated continuous wave (FMCW) radars. The platform can quickly flexibly generate the waveform that meets measurement requirements and significantly improve experimental efficiency. Design/methodology/approach This platform not only includes radio frequency devices but also integrates a programmable transmitter based on field programmable gate array. By configuring the waveform data, the experimental platform can generate waveforms with adjustable parameters and realize automatic emission, reception and processing of signals. Different from traditional fast Fourier transform, this paper uses a discrete-time Fourier transform to process low-frequency signals to get more accurate results. Findings The authors demonstrate the effectiveness of the platform through a single-path cable experiment, an indoor ranging experiment by using different modulating waveforms and a speed measurement experiment. With complete functions and strong flexibility, the platform can operate effectively in various conditions and greatly improve the efficiency of research and study. Practical implications The platform can accelerate the research studies and applications of FMCW radars in the fields of automatic drive, through-wall detection and health-care applications. Originality/value Cost and functionality are taken into account in the platform, which can significantly improve the efficiency of research. The proposed signal processing method improves the accuracy while its computation complexity does not increase significantly.

Resonant behavior and frequency preferences of thalamic neurons

1994 ◽  
Vol 71 (2) ◽  
pp. 575-582 ◽  
Author(s):  
E. Puil ◽  
H. Meiri ◽  
Y. Yarom
Keyword(s):  
Fourier Transform ◽  
Frequency Response ◽  
Low Frequency ◽  
Wide Band ◽  
Inward Rectifier ◽  
Membrane Potentials ◽  
Resting Potential ◽  
Voltage Response ◽  
Current Input ◽  
The Fourier Transform

1. We studied the voltage responses of thalamocortical neurons to a periodic current input of variable frequency, in slices of mediodorsal thalamus (guinea pig). The ratio of the Fourier transform of the voltage response to the Fourier transform of the oscillatory current input was used to calculate the frequency response of the neurons at different resting and imposed membrane potentials. 2. Most neurons displayed a resonant hump in the frequency response curve. A narrow band of low-frequency (2-4 Hz) resonance occurred near the resting level [-66 +/- 8 mV (SD)] and at imposed membrane potentials in a range of -60 to -80 mV. An additional wide band (12-26 Hz) of peak resonant frequencies was observed at depolarized levels. 3. The low-frequency resonance was insensitive to tetrodotoxin (TTX) application in concentrations (0.5-1 microM) that blocked a depolarization activated inward rectifier and Na(+)-dependent action potentials. TTX, however, eliminated the wide-band resonant hump centered at 12-26 Hz that we observed at depolarized membrane potentials. 4. Application of Ni2+ (0.5-1 mM) reversibly blocked all slow spikes and greatly reduced the low-frequency resonant humps, without changing the resting potential. Octanol in concentrations of 50 microM had similar effects. 5. Application of Cs+ (3-5 mM), a blocker of the hyperpolarization activated inward rectifier, produced a 5- to 10-mV depolarization and completely blocked the rectification. Cs+ did not alter the low-frequency resonant hump or its dependence on membrane voltage.(ABSTRACT TRUNCATED AT 250 WORDS)

Real-time implementation of the digital Taylor–Fourier transform for identifying low frequency oscillations

2016 ◽  
Vol 140 ◽  
pp. 846-853 ◽  
Author(s):  
Mario R. Arrieta Paternina ◽  
Juan M. Ramirez ◽  
Alejandro Zamora Méndez
Keyword(s):  
Fourier Transform ◽  
Real Time ◽  
Low Frequency ◽  
Low Frequency Oscillations
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