Variations of the Frequency Range of HF Signals on the Subauroral Path During Magnetic-Ionospheric Disturbances in October 2016

2021 ◽  
Vol 64 (2) ◽  
pp. 83-94
Author(s):  
V.P. Uryadov ◽  
F.I. Vybornov ◽  
A.V. Pershin
Keyword(s):  
Ionospheric Disturbances ◽  
Frequency Range

scholarly journals Combinational frequencies of HF doppler radar signals in the PC1 geomagnetic pulsation range

2020 ◽  
Keyword(s):  
Doppler Radar ◽  
Geomagnetic Pulsation ◽  
Doppler Frequency ◽  
Mhd Waves ◽  
Frequency Change ◽  
Ionospheric Disturbances ◽  
Frequency Range ◽  
Ionospheric Perturbations ◽  
Noticeable Increase ◽  
Short Period

Urgency. The urgency of this work is determined by the necessity of studying MHD waves originating from various sources within the Earth–atmosphere–ionosphere– magnetosphere system and arriving at ionospheric heights. The object of research. A matter of this study is ionospheric disturbances that accompanied geomagnetic pulsations during the dawn terminator on 23–24 March 2010. Purpose of Work. The present work was aimed at revealing short-period ionospheric disturbances in the Pc1 micropulsation frequency range (1–5-Hz) and at investigating their spectral content. Techniques and Methotology. The dynamic spectra of the variations under study were obtained with the HF Doppler radar. Results. The ionospheric disturbances have been shown to arise mainly at combinational frequencies. The durations of such disturbances have been estimated to be of the order of one minute, and the disturbance frequencies 0.7 Hz, 1.5 Hz, and 2.5 Hz. The quasi-periodic interference in the 1–5-Hz frequency band has been detected to persist for over one-half hour to a few hours. Based on the model of the signal modulated by ULF waves in the ionosphere, the appearance of constructive interference at combinational frequencies has been validated. The intercomparisons of the variations obtained using the spectrograms and the known models for the phase-modulated signals have been made. A model for the amplitude- and phase-modulated signal reflected from the ionosphere has been developed, and the signal basic parameters have been determined. Conclusions. The HF Doppler sounding can be a means for studying ionospheric disturbances in the Pc1 geomagnetic pulsation range. During the study of time variations of the Doppler frequency shift during the spring equinox, the following results were found. The period of ionospheric perturbations reached 0.2–1 s, their duration varied from 1 min to more than 10 min. A noticeable increase in the amplitude of the beat is detected, which may be a sign of the appearance of lateral maxima in the Doppler spectra. The presence of oscillations in the frequency range of the first harmonic of the spectral resonance system of the ionospheric Alfvén resonator is established. Long-term ionospheric perturbations have a linearly increasing frequency of filling the wave packet. The rate of frequency change is close to 10–3 Hz/s.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

The influence of external conditions on sound pressure in the pistonphone at the infrasound frequency range

2020 ◽  
pp. 67-72
Author(s):  
A. V. Konkov ◽  
D. V. Golovin
Keyword(s):  
Environmental Conditions ◽  
Sound Pressure ◽  
Primary Method ◽  
Frequency Range ◽  
External Conditions ◽  
Numerical Estimations

The influence of environmental conditions on a sound pressure reproduced by the primary method in the measuring chambers of the Pistonphone in the frequency range from 1 mHz to 250 Hz is estimated. Numerical estimations of influence of environmental conditions on sound pressure in pistonphone measuring chambers are given and special requirements to system of maintenance of required external conditions are specified.

The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

2020 ◽  
pp. 53-58
Author(s):  
A. V. Koudelny ◽  
I. M. Malay ◽  
V. A. Perepelkin ◽  
I. P. Chirkov
Keyword(s):  
Microwave Power ◽  
Electromagnetic Waves ◽  
Primary Standard ◽  
The State ◽  
Frequency Range ◽  
Working Standard ◽  
Extended Frequency Range ◽  
Effective Efficiency ◽  
Extended Frequency ◽  
Good Agreement

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

Portable Bioimpedance Spectrometer for Total Frequency Range of β-Dispersion

2013 ◽  
Vol 80 (11) ◽  
Author(s):  
Dhouha Bouchaala ◽  
Olfa Kanoun ◽  
Nabil Derbel
Keyword(s):  
Frequency Range ◽  
Total Frequency
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