RADIO FADING AND THE NATURAL ELECTROMAGNETIC BACKGROUND

1965 ◽  
Vol 43 (11) ◽  
pp. 1951-1961 ◽  
Author(s):  
H. J. Duffus ◽  
G. M. Boyd ◽  
J. K. Kinnear
Keyword(s):  
Radio Signal ◽  
Spectral Component ◽  
Broad Band ◽  
Auroral Zone ◽  
Frequency Range ◽  
Single Station ◽  
D Region ◽  
Radio Signals ◽  
Signal Fluctuation ◽  
The Difference

A comparison is made between the natural geomagnetic background in the frequency range 0.006–0.6 Hz and fluctuations of the difference in received signal strength between the two magnetoionic modes of vertically incident broad-band radio signals in the range 6–16 MHz, observed at a single station near Victoria, British Columbia. At this station the following points were observed:1. During the daytime there is often a spectral component common to the radio-signal fluctuations and to the natural geomagnetic background, even during quiet magnetic times. There is seldom phase coherence, however, except for a few minutes at a time.2. There is a small but highly significant (1%) linear correlation R = 0.33 between all the hourly mean amplitudes of the radio-signal fluctuation level and the hourly mean amplitudes of the natural geomagnetic background. The correlation coefficient rises as high as R = 0.71 at 1400–1500 local time, when only a particular hour of each day is considered. It is concluded that geomagnetic micropulsations in this frequency range are a better indicator of r-f. fluctuations than is the local Kp.3. At night, there is a relationship between the occurrence of Pt's and of r-f. fluctuation, although their frequency components are not usually as closely related as are those of the daytime regimes.It is suggested that geomagnetic micropulsations can couple exospheric or auroral zone fluctuations into the upper E or F regions strongly enough to produce observable radio-signal fluctuations at mid-latitudes, even during magnetically quiet times.Lack of correlation between micropulsations and phase fluctuations of 18 kHz signals observed over an E–W 100-km path, and 80 kHz observed over an E–W 3 300-km path suggests that significant coupling does not extend down to the D region during magnetically quiet times.

scholarly journals Searching for energy-resolved quasi-periodic oscillations in AGN

2021 ◽  
Author(s):  
Dominic I Ashton ◽  
Matthew J Middleton
Keyword(s):  
Power Law ◽  
Spectral Component ◽  
Broad Band ◽  
Initial Study ◽  
Periodic Oscillations ◽  
Single Observation ◽  
Curved Space ◽  
Multiple Observations ◽  
Band Noise ◽  
The Impact

Abstract X-ray quasi-periodic oscillations (QPOs) in AGN allow us to probe and understand the nature of accretion in highly curved space-time, yet the most robust form of detection (i.e. repeat detections over multiple observations) has been limited to a single source to-date, with only tentative claims of single observation detections in several others. The association of those established AGN QPOs with a specific spectral component has motivated us to search the XMM-Newton archive and analyse the energy-resolved lightcurves of 38 bright AGN. We apply a conservative false alarm testing routine folding in the uncertainty and covariance of the underlying broad-band noise. We also explore the impact of red-noise leak and the assumption of various different forms (power-law, broken power-law and lorentzians) for the underlying broad-band noise. In this initial study, we report QPO candidates in 6 AGN (7 including one tentative detection in MRK 766) from our sample of 38, which tend to be found at characteristic energies and, in four cases, at the same frequency across at least two observations, indicating they are highly unlikely to be spurious in nature.

Acceptable Levels of Tonal and Broad-Band Repetitive and Continuous Sounds during the Performance of Nonauditory Tasks

1995 ◽  
Vol 81 (3) ◽  
pp. 803-816 ◽  
Author(s):  
Ulf Landström ◽  
Anders Kjellberg ◽  
Marianne Byström
Keyword(s):  
Reaction Time ◽  
Sound Pressure ◽  
Broad Band ◽  
Reaction Time Task ◽  
Simple Reaction Time Task ◽  
Reasoning Test ◽  
Band Noise ◽  
Time Test ◽  
The Difference ◽  
Reaction Time Test

Three groups of 24 subjects were exposed to a 1000–Hz tone or broad band noise in a sound chamber. During the exposures subjects were engaged in an easy reaction time test or a difficult grammatical reasoning test. For each exposure and work subjects adjusted the noise to a tolerance level defined by its interference with task performance. During the simple reaction-time task significantly higher sound-pressure levels were accepted than during the reasoning test. At the tonal exposure, much lower levels were accepted than during the exposure to broad-band noise. For continuous sound exposures much higher levels were accepted than for noncontinuous exposures. For tonal exposures the difference was approximately 5 dB, for the broad-band exposures approximately 9 dB. In a separate study the effects of the noncontinuity of the noise and pauses were analysed. The raised annoying effect of the noncontinuous noise was not more affected by the noncontinuity of the noise periods than by the noncontinuity of the pauses. The results imply that the annoying reactions to the sound will be increased for repetitive noise and that the reaction is highly influenced by the over-all noncontinuity of the exposure.

scholarly journals Filamentary Nebulosity Surrounding M87

1987 ◽  
Vol 117 ◽  
pp. 216-217
Author(s):  
S. van den Bergh ◽  
C. J. Pritchet
Keyword(s):  
Broad Band ◽  
Integration Time ◽  
The Difference ◽  
Total Integration

Recently we have obtained both Hα + [NII] and broad-band red exposures of a number of galaxies with an RCA 320 × 512 CCD at the prime-focus of the 3.6 m CFH Telescope. Figure 1 shows the difference between Hα and red exposures (each with a total integration time of 60 min) of M87 = NGC4486.

scholarly journals THE PECULIARITIES OF THE SOUND FIELD ENERGY DECAY IN A ROOM WITH THE USE OF DIFFERENT PULSED SOUND SOURCES/GARSO LAUKO ENERGIJOS SLOPIMO PATALPOJE YPATUMAI, NAUDOJANT SKIRTINGUS IMPULSINIUS GARSO ŠALTINIUS

1999 ◽  
Vol 5 (2) ◽  
pp. 135-140
Author(s):  
Vytautas Stauskis
Keyword(s):  
Noise Level ◽  
Sound Field ◽  
Maximum Energy ◽  
Reverberation Time ◽  
Frequency Range ◽  
Sound Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Difference ◽  
Field Decay

The paper deals with the differences between the energy created by four different pulsed sound sources, ie a sound gun, a start gun, a toy gun, and a hunting gun. A knowledge of the differences between the maximum energy and the minimum energy, or the signal-noise ratio, is necessary to correctly calculate the frequency dependence of reverberation time. It has been established by investigations that the maximum energy excited by the sound gun is within the frequency range of 250 to 2000 Hz. It decreases by about 28 dB at the low frequencies. The character of change in the energy created by the hunting gun differs from that of the sound gun. There is no change in the maximum energy within the frequency range of 63–100 Hz, whereas afterwards it increases with the increase in frequency but only to the limit of 2000 Hz. In the frequency range of 63–500 Hz, the energy excited by the hunting gun is lower by 15–30 dB than that of the sound gun. As frequency increases the difference is reduced and amounts to 5–10 dB. The maximum energy of the start gun is lower by 4–5 dB than that of the hunting gun in the frequency range of up to 1000 Hz, while afterwards the difference is insignificant. In the frequency range of 125–250 Hz, the maximum energy generated by the sound gun exceeds that generated by the hunting gun by 20 dB, that by the start gun by 25 dB, and that by the toy gun—by as much as 35 dB. The maximum energy emitted by it occupies a wide frequency range of 250 to 2000 Hz. Thus, the sound gun has an advantage over the other three sound sources from the point of view of maximum energy. Up until 500 Hz the character of change in the direct sound energy is similar for all types of sources. The maximum energy of direct sound is also created by the sound gun and it increases along with frequency, the maximum values being reached at 500 Hz and 1000 Hz. The maximum energy of the hunting gun in the frequency range of 125—500 Hz is lower by about 20 dB than that of the sound gun, while the maximum energy of the toy gun is lower by about 25 dB. The maximum of the direct sound energy generated by the hunting gun, the start gun and the toy gun is found at high frequencies, ie at 1000 Hz and 2000 Hz, while the sound gun generates the maximum energy at 500 Hz and 1000 Hz. Thus, the best results are obtained when the energy is emitted by the sound gun. When the sound field is generated by the sound gun, the difference between the maximum energy and the noise level is about 35 dB at 63 Hz, while the use of the hunting gun reduces the difference to about 20–22 dB. The start gun emits only small quantities of low frequencies and is not suitable for room's acoustical analysis at 63 Hz. At the frequency of 80 Hz, the difference between the maximum energy and the noise level makes up about 50 dB, when the sound field is generated by the sound gun, and about 27 dB, when it is generated by the hunting gun. When the start gun is used, the difference between the maximum signal and the noise level is as small as 20 dB, which is not sufficient to make a reverberation time analysis correctly. At the frequency of 100 Hz, the difference of about 55 dB between the maximum energy and the noise level is only achieved by the sound gun. The hunting gun, the start gun and the toy gun create the decrease of about 25 dB, which is not sufficient for the calculation of the reverberation time. At the frequency of 125 Hz, a sufficiently large difference in the sound field decay amounting to about 40 dB is created by the sound gun, the hunting gun and the start gun, though the character of the sound field curve decay of the latter is different from the former two. At 250 Hz, the sound gun produces a field decay difference of almost 60 dB, the hunting gun almost 50 dB, the start gun almost 40 dB, and the toy gun about 45 dB. At 500 Hz, the sound field decay is sufficient when any of the four sound sources is used. The energy difference created by the sound gun is as large as 70 dB, by the hunting gun 50 dB, by the start gun 52 dB, and by the toy gun 48 dB. Such energy differences are sufficient for the analysis of acoustic indicators. At the high frequencies of 1000 to 4000 Hz, all the four sound sources used, even the toy gun, produce a good difference of the sound field decay and in all cases it is possible to analyse the reverberation process at varied intervals of the sound level decay.

Ion Beam Figuring Fabricate Effect with Different Removal Sizes

2013 ◽  
Vol 552 ◽  
pp. 142-146
Author(s):  
Yong Qiang Gu
Keyword(s):  
Spatial Frequency ◽  
Ion Beam ◽  
Influence Factors ◽  
Frequency Range ◽  
Surface Errors ◽  
Power Spectral ◽  
The Difference ◽  
Lens Surface ◽  
Ion Beam Figuring

Ion Beam Figure (IBF) is believed to be one of the most effective technics that can fabricate lens with nano or even sub-nano accuracy. For different sizes of IBF removal functions, the correct effects in different spatial frequency range are different. Power Spectral Density (PSD) curve can describe surface errors in full spatial frequency range, so it is a very convenient way to evaluate the quality of lens’ surface. In this paper, firstly, the principles of IBF and PSD are introduced briefly; Secondly, IBF removal functions with sizes from 2 mm to 15 mm are generated. A lens with surface error more than PV value 400nm is simulated with different sizes of IBF removal functions by Lucy-Richardson algorithm. Finally, experiments are done by IBF plant. A lens is fabricated by different sizes of removal functions and the fabricate results are tested by interferometer precisely and calculated to PSD curves. By the comparison of these curves, the IBF fabricate effects with different removal sizes are analyzed, which show that the smaller the removal size, the better the removal effect in higher spatial frequency range, but in the meantime, it will take a much longer time. Also the reasons of the difference between theory simulation and actual fabrication result are taken into account, and several influence factors are analyzed.

PLASMA NEW SELECTIVE PROPERTIES FOR EFFICIENT USE IN ELECTRONICS AND TELECOMMUNICATIONS

2021 ◽  
Vol 2 (64) ◽  
pp. 171-174
Author(s):  
Oleksandr Shefer ◽  
Vitalii Marchenko ◽  
Galina Cherneva
Keyword(s):  
Gaseous Medium ◽  
Charge Carriers ◽  
Practical Implementation ◽  
Large Area ◽  
Elementary Processes ◽  
Molecular Gases ◽  
Radio Signals ◽  
The Difference ◽  
Functional Purpose ◽  
Gas Pressures

In terms of active and passive electronic counteraction, detection of geophysical phenomena of artificial andnatural origin is becoming increasingly important. Discovering new properties of plasma enables to improve the informationcomponent of radio signals more effectively and use the obtained properties in related fields. Elementary processes in thelongitudinal and transverse directions of the discharge, depending on natural and artificial conditions, under different typesof gaseous medium used; at different gas pressures and different pulse-periodic application of an electric field is studied inthe article. The difference of discharge properties in inert and molecular gases with different designs and electrodes of thelaboratory device is shown. It is established that the change of functional purpose between the cathodes and the anodes doesnot change the shape of the discharge. The presence of ambipolar diffusion of charge carriers acting on a large area of plasmawas determined. Partial charge carrier homogeneity has been established, which is observed only along the plasma surface,and homogeneity is violated in the perpendicular direction. The difference in energy input in the discharge, depending on thedesign of the electrodes other things being equal is determined. The identified properties of plasma enable them to be usedmore effectively for practical implementation in the field of electronics and telecommunications and other industries.

Formation and development of the Ukrainian network of meteor radio observations

2021 ◽  
Vol 27 (3) ◽  
pp. 85-92
Author(s):  
F.I. Bushuev ◽  
◽  
M.P. Kaliuzhnyi ◽  
N.A. Kulichenko ◽  
A.V. Shulga ◽  
...  
Keyword(s):  
Remote Access ◽  
Frequency Range ◽  
Kinematic Parameters ◽  
Radio Range ◽  
Continuous Registration ◽  
Radio Signals ◽  
Current Monitoring ◽  
To Receive ◽  
E Mail ◽  
Meteor Radio

During the decade of research, the Research Institute “Mykolaiv Astronomical Observatory” (RI “MAO”) developed hardware and software for monitoring, extracting, and calculating the parameters of meteor phenomena using the forward scattering by meteor ionized trail of the signals of over-the-horizon FM-stations broadcasted in the frequency range of 88—108 MHz. This allowed creating a network of observations of meteor phenomena in the radio range, which consists of six stations located in Mykolaiv (three stations), Rivne, Lviv, and Hlukhiv. The stations have identical hardware and software. Yagi-Uda antennas with six or eight horizontal vibrators and SDR receivers based at RTR2832U microchip are used to receive radio signals. The station software performs continuous registration and analysis of received radio signals at the output of quadrature detectors of the receivers, automatic detection of moments of appearances of meteor reflections, formation, and sending by e-mail daily reports on detected meteor phenomena. Equipment setup and current monitoring of stations operations are carried out by the RI «MAO» using remote access to station computers via the Internet. Monthly reports on the number of meteor events recorded by each station are posted on the site of Radio Meteor Observation Bulletin (RMOB). The article presents the results, obtained by the network in 2017—2019, confirming a correspondence of daily variations in the number of meteors registered by network stations, to the known dependence (observation of meteors in the apex and antapex), as well as a correspondence between the expected characteristics (in time and intensity) of three meteor showers (Perseids, Geminids and Quadrantids) and that had been obtained by the network. Recommendations are also given in the article for additional research aimed at achieving the main goal, namely, expanding information about meteor phenomena, including the estimating of kinematic parameters (velocities, radiants) of meteoroids and their relationship with potentially hazardous asteroids.

scholarly journals Hydrogen Maser Support of VLBI for the NASA Crustal Dynamics Project

1988 ◽  
Vol 129 ◽  
pp. 505-506
Author(s):  
R. E. Price ◽  
M. J. Chandler ◽  
B. R. Schupler ◽  
P. R. Dachel
Keyword(s):  
Hydrogen Maser ◽  
Frequency Reference ◽  
Frequency Standards ◽  
The Pacific ◽  
Mobile Stations ◽  
Radio Signals ◽  
Crustal Dynamics ◽  
Stable Frequency ◽  
The Difference

For the NASA Crustal Dynamics Project VLBI network, signals from quasars are recorded simultaneously at widely separated antennas. It is well known that hydrogen maser frequency standards provide the stable frequency reference used to precisely measure the difference in arrival time of the radio signals at the different antennas, enabling the determination of precise distances between the antennas. This paper reviews the practical requirements for maser support of VLBI for the Crustal Dynamics Project and describes the means used to meet these requirements for a network of eight fixed and three mobile stations which participate in approximately 200 VLBI experiments per year at locations in North America and the Pacific.

SIMULATION OF RADIO SIGNALS FROM 1-10 TeV AIR SHOWERS USING EGSNRC

2006 ◽  
Vol 21 (supp01) ◽  
pp. 65-69 ◽  
Author(s):  
R. Engel ◽  
N. N. Kalmykov ◽  
A. A. Konstantinov
Keyword(s):  
Monte Carlo ◽  
Radio Emission ◽  
Monte Carlo Simulations ◽  
Frequency Spectrum ◽  
Radial Dependence ◽  
Frequency Range ◽  
Air Showers ◽  
Shower Development ◽  
Radio Signals ◽  
The Individual

Cherenkov and geosynchrotron radiation are considered as two fundamental mechanisms of the radio emission generated by extensive air showers (EAS). The code EGSnrc is used for Monte-Carlo simulations of the individual shower development. Calculations of the radial dependence and frequency spectrum of the emitted radiation are performed for the LOPES experiment frequency range.

Nanostructured Broad Band Infrared Absorber

2011 ◽  
Vol 1303 ◽  
Author(s):  
Timothy D. Corrigan ◽  
Dong Hun Park ◽  
Dennis Drew ◽  
Ray Phaneuf
Keyword(s):  
Effective Medium Theory ◽  
Scattered Light ◽  
Broad Band ◽  
Black Body ◽  
Index Of Refraction ◽  
Frequency Range ◽  
Multilayer Material ◽  
Medium Theory ◽  
Source Type ◽  
Broad Band Absorber

ABSTRACTWe describe a near perfect broad band absorber based on a laterally nanostructured multilayer material. We present calculations of the structure that demonstrates over 99% absorption of the 500 K black body spectrum. We also show the ability to manufacture an anti-reflective layer using a nanostructured metamaterial which allows us to tailor the index of refraction using effective medium theory. The absorber can be adapted for use in any frequency range and any source type. These materials may have applications in energy harvesting and scattered light control.

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