scholarly journals Applicability of the ultra-high radio frequency band (UHF) for hydrometeor detection by phase difference method

2021 ◽  
Vol 51 (2) ◽  
pp. 109-127
Author(s):  
Peter FABO ◽  
Pavol NEJEDLÍK ◽  
Michal KUBA ◽  
Milan ONDERKA ◽  
Dušan PODHORSKÝ
Keyword(s):  
Frequency Band ◽  
Cell Phone ◽  
Signal Amplitude ◽  
Ice Crystals ◽  
Spatial Density ◽  
First Results ◽  
Primary Advantage ◽  
Electromagnetic Signals ◽  
Novel Concept ◽  
Phase Differences

Hydrometeors (rain, fog and ice crystals) affect the transmission of electromagnetic signals. Previous research showed that alterations in the signal (amplitude and phase) are affected by the composition of the atmosphere, e.g. the presence of hydrometeors. The majority of hydrometeorological detecting methods are based on the attenuation of electromagnetic signals as they penetrate the atmosphere. Novel methods based on monitoring of parameters of the signal appeared in recent time. This article presents the first results from our investigation of how hydrometeors affect the phase differences in signals transmitted by BTS stations. Cell phone operators transmit electromagnetic signals in the 1 GHz frequency band. This paper describes a novel concept of how phase differences between two signals arriving at two different antennas can be used to detect hydrometeors. Although the described concept is assumed to be independent from the signal strength, the analysed signal must be detectable. The primary advantage of the proposed passive method is that the signal is almost ubiquitous and does not require demodulation. In densely populated areas, the network of BTS stations reaches a spatial density of 1 station per 1 km2 which gives excellent opportunity to use the signal for detection purposes.

scholarly journals Multisite spectroscopic and photometric observations of the pulsating sdB star PG 1605+072

2004 ◽  
Vol 193 ◽  
pp. 230-233
Author(s):  
S.J. O’Toole ◽  
S. Falter ◽  
U. Heber ◽  
C.S. Jeffery ◽  
S. Dreizier ◽  
...  
Keyword(s):  
Amplitude Ratios ◽  
Data Set ◽  
Velocity Amplitude ◽  
Mode Identification ◽  
Horizontal Branch Stars ◽  
Massive Data Set ◽  
Photometric Observations ◽  
First Results ◽  
Formation And Evolution ◽  
Phase Differences

AbstractWe present the first results from the MultiSite Spectroscopic Telescope (MSST) observations of the sdBV star PG 1605+072. Pulsating sdB stars (V361 Hya stars) offer the chance to gain new insights into the formation and evolution of extreme Horizontal Branch stars using the tools of asteroseismology. PG 1605+072 is an outstanding object in its class, with the richest frequency spectrum, the longest periods, and the largest variations. The MSST campaign took place in 2002 May/June and we present here the massive data set, made up of 399 hr of photometry and 151 hr of spectroscopy. The overall aims of the project are to examine light/velocity amplitude ratios and phase differences, changes in equivalent width/line index, and λ-dependence of photometric amplitudes, and to use these properties for mode identification.

scholarly journals Researching of quasiperiodic variations in the amplitude of VLF electromagnetic signals from lightning discharges passing over strong earthquakes

2019 ◽  
Vol 127 ◽  
pp. 03005
Author(s):  
Vyacheslav Argunov ◽  
Mikhail Gotovtsev
Keyword(s):  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Cross Sectional ◽  
Epicentral Area ◽  
F Region ◽  
Signal Characteristics ◽  
Lightning Discharges ◽  
Electromagnetic Signals ◽  
Wave Phenomena ◽  
Shallow Focus

The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results of azimuthal scanning, cross sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter. Quasi-periodic variations of signal amplitude of lightning discharges passing over earthquake epicenters are in details considered. It has been obtained that the period of amplitude modulation makes up 2-3 hours, i.e. in the ionosphere D-layer the same values of the periods of wave phenomena are registered as which are observed in a higher F-region of the ionosphere. The results obtained during the work specify that, at least, in the part of events the seismic disturbances in the ionosphere can be caused by AGW, propagating upwards from the epicentral area.

scholarly journals Electromagnetic field measurements in ULF-ELF-VLF [0.001 Hz–100 KHz] bands

2008 ◽  
Vol 14 ◽  
pp. 69-73 ◽  
Author(s):  
P. Palangio ◽  
F. Masci ◽  
M. Di Persio ◽  
C. Di Lorenzo
Keyword(s):  
Electromagnetic Field ◽  
Electromagnetic Fields ◽  
Frequency Band ◽  
Seismic Activity ◽  
Central Italy ◽  
Field Measurements ◽  
Wide Band ◽  
The Earth ◽  
Innovative Technique ◽  
Electromagnetic Signals

Abstract. We are reporting the technological and scientific objectives of the MEM project. The MEM project has been activated in the INGV Observatory of L'Aquila to create in Central Italy a network of observatories in order to monitoring the electromagnetic signals in the frequency band [0.001 Hz–100 kHz]. Some examples of the instrumentation developed in the frame of the project are reported. An innovative technique, based on the wide band interferometry is proposed to obtain detailed information concerning the several detected electromagnetic sources. Moreover, data from each station will be elaborated to investigate different sectors as the structure of ground electric conductibility, the electromagnetic phenomena connected with seismic activity, the separation of the electromagnetic fields originated in the Earth's interior and the electromagnetic phenomena originated in the magnetosphere, in the ionosphere and in the Earth-ionosphere cavity.

Two-Dimension Fault Line Selection Method Based on Transient Signal Features of Fault Phase

2011 ◽  
Vol 354-355 ◽  
pp. 1289-1292
Author(s):  
Wen Hai Zhang ◽  
Jian Wen Yang ◽  
Xian Yong Xiao ◽  
Ying Wang
Keyword(s):  
Frequency Band ◽  
Signal Amplitude ◽  
Selection Method ◽  
Transient Signal ◽  
Initial Angle ◽  
Signal Energy ◽  
Two Dimension ◽  
Fault Resistance ◽  
Signal Features ◽  
Line Selection

When single-line-to-ground fault happen in neutral non-effectively earthed system, there is a big difference between the fault feeder and un-fault feeder in transient signal energy centralized frequency band and signal amplitude of fault phase. The transient signal energy in fault feeder’s fault phase is bigger, and it centralizes in lower frequency band. But the transient signal in un-fault feeders’ has the contrary features. And this feature is affected little by the fault initial angle. So the paper proposed a method that using the gravity frequency and transient signal energy to form a two-dimension line selection method that using the signal overall distribution characteristics. It can be applied in neutral unearthed and resonant system simultaneously. And the method is effectively to different fault initial angle and fault resistance. The method is proved correctly, effectively and adaptively by actual simulation in different fault cases.

Investigations on the band-gap characteristics of one-dimensional flexural periodic structures with varying geometries

2021 ◽  
pp. 107754632110368
Author(s):  
Sachchidanand Das ◽  
Murtaza Bohra ◽  
Sabareesh Geetha Rajasekharan ◽  
Yendluri Venkata Daseswara Rao
Keyword(s):  
Band Gap ◽  
Frequency Band ◽  
Periodic Structures ◽  
Band Gaps ◽  
One Dimensional ◽  
Vibration Attenuation ◽  
Gap Characteristics ◽  
Novel Concept ◽  
Selection Of ◽  
Shape And Size

Periodic structures have been studied extensively for their wave-filtering capabilities as they exhibit frequency band-gaps. The band-gap characteristics of flexural periodic structures, consisting of periodic cavities, depend on the geometry (shape and size) of cavities. The present work brings out experimental and numerical investigation of the effect of geometry of periodicity on the vibration characteristics of one-dimensional periodic structures. A procedure for prediction of the experimentally observed frequency band-gaps, with the help of eigenfrequency analysis, has been presented. Further, a novel concept of ‘real’ and ‘pseudo’ band-gaps has been theorized. Based on the experimental and numerical results, the best configuration of a periodic structure for maximum vibration attenuation has been arrived at. The work can find application in the design of frames and channels, made of periodic structures, where periodicity can be introduced to reduce vibration transmission in desired frequency bands. It can also reduce the requirement of extensive prototype trials for the selection of suitable periodic geometry.

scholarly journals The study of the electromagnetic anomalies linked with the Earth's crustal activity in the frequency band [0.001 Hz–100 kHz]

2007 ◽  
Vol 7 (5) ◽  
pp. 507-511 ◽  
Author(s):  
P. Palangio ◽  
C. Di Lorenzo ◽  
F. Masci ◽  
M. Di Persio
Keyword(s):  
Electric Fields ◽  
Frequency Band ◽  
Central Italy ◽  
Tectonic Activity ◽  
Normal Behaviour ◽  
Know How ◽  
Single Station ◽  
Lower Frequency Band ◽  
Electromagnetic Signals

Abstract. The technological and the scientific objectives of the MEM (Magnetic and Electric fields Monitoring) project concerning to the study of the electromagnetic signals linked with the Earth's crustal activity are reported. The MEM project has been activated in Central Italy to create a network of observatories so as to monitoring the electromagnetic signals, both natural and artificial, in the frequency band [0.001 Hz–100 kHz]. Some examples of the developed instrumentation and the know-how transfer to the industry are reported. We also report some results obtained in the first MEM station installed in the area of the INGV (Italian Istituto Nazionale di Geofisica e Vulcanologia) Observatory of L'Aquila. Using the single station magnetotelluric approach we have obtained some valuables information about the underground resistivity structure in the area of the measurement station. Concerning to the study of the magnetic signals linked with the tectonic activity we have reported an example of the long term behaviour of the magnetic induction vectors characteristics in the lower frequency band [0.001–0.5] Hz, showing their normal behaviour when no large crustal changes due to geodynamical processes are present.

Discussion of the Oblique Rotator Model Cases Of 108 Aqr and x Serp.

1976 ◽  
Vol 32 ◽  
pp. 577-588
Author(s):  
C. Mégessier ◽  
V. Khokhlova ◽  
T. Ryabchikova
Keyword(s):  
Mathematical Formulation ◽  
The Other ◽  
Rotator Model ◽  
Oblique Rotator ◽  
First Results

My talk will be on the oblique rotator model which was first proposed by Stibbs (1950), and since received success and further developments. I shall present two different attempts at describing a star according to this model and the first results obtained in the framework of a Russian-French collaboration in order to test the precision of the two methods. The aim is to give the best possible representation of the element distributions on the Ap stellar surfaces. The first method is the mathematical formulation proposed by Deutsch (1958-1970) and applied by Deutsch (1958) to HD 125248, by Pyper (1969) to α2CVn and by Mégessier (1975) to 108 Aqr. The other one was proposed by Khokhlova (1974) and used by her group.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Reconstruction of Objects from their Projections Using Orthogonal Functions

1973 ◽  
Vol 31 ◽  
pp. 268-269
Author(s):  
Elrnar Zeitler
Keyword(s):  
Unit Area ◽  
Three Dimensional ◽  
One Dimension ◽  
Spatial Density ◽  
Dimensional Representation ◽  
Orthogonal Functions ◽  
Object A ◽  
Plane Normal ◽  
Dimensional Object ◽  
Spatial Density Distribution

Considering any finite three-dimensional object, a “projection” is here defined as a two-dimensional representation of the object's mass per unit area on a plane normal to a given projection axis, here taken as they-axis. Since the object can be seen as being built from parallel, thin slices, the relation between object structure and its projection can be reduced by one dimension. It is assumed that an electron microscope equipped with a tilting stage records the projectionWhere the object has a spatial density distribution p(r,ϕ) within a limiting radius taken to be unity, and the stage is tilted by an angle 9 with respect to the x-axis of the recording plane.

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