scholarly journals Polarization Changes of Radio Signals in Vertical Radio-Echo Sounding of Glaciers

1975 ◽  
Vol 15 (73) ◽  
pp. 469-470 ◽  
Author(s):  
V. V. Bogorodskiy ◽  
G. V. Trepov ◽  
B. A. Fedorov
Keyword(s):  
Crystal Structure ◽  
Vertical Direction ◽  
Main Method ◽  
Receiving Antenna ◽  
Linearly Polarized ◽  
Radio Echo Sounding ◽  
Radio Signals ◽  
Interference Signals ◽  
Elliptically Polarized ◽  
Made In

An electromagnetic linearly-polarized signal transmitted through the glacier in a vertical direction, reflected from the bedrock, and received with a receiving antenna, is found to be changed into one either partially or elliptically polarized. The polarization changes are believed to be due mainly to the crystal structure of the glacier and anisotropy caused by the pressure of the upper layers. An analysis of the polarization diagrams obtained is up to the present the main method used for studies of the reflected signal polarization. Evidently using a simple dipole a partially-polarized signal is not distinguishable from one that is elliptically polarized, nor is a nonpolarized signal distinguished from circularly polarized. However, the data recently obtained are of great importance, particularly from studies of glacier crystal structure made in deep core drilling. Possible reasons for the polarization changes of the signal have been analysed. Results of the analyses of the polarization diagrams obtained both at individual points and along extended traverses are discussed. It has been found that the signal reflected from a considerable ice thickness is polarized in such a way that the parallel orientation of the receiving and transmitting dipoles can be disregarded. En route recordings of the signal fluctuations obtained by parallel and orthogonally polarized dipoles are shown. The results of polarization studies are important for practical purposes. For example, bedrock relief sounding carried out with crossed dipoles makes it possible to get rid of interference signals occurring due to scattering from inhomogeneous structures of the upper part of the glacier.

scholarly journals Polarization Changes of Radio Signals in Vertical Radio-Echo Sounding of Glaciers

1975 ◽  
Vol 15 (73) ◽  
pp. 469-470
Author(s):  
V. V. Bogorodskiy ◽  
G. V. Trepov ◽  
B. A. Fedorov
Keyword(s):  
Crystal Structure ◽  
Vertical Direction ◽  
Main Method ◽  
Receiving Antenna ◽  
Linearly Polarized ◽  
Radio Echo Sounding ◽  
Radio Signals ◽  
Interference Signals ◽  
Elliptically Polarized ◽  
Made In

An electromagnetic linearly-polarized signal transmitted through the glacier in a vertical direction, reflected from the bedrock, and received with a receiving antenna, is found to be changed into one either partially or elliptically polarized. The polarization changes are believed to be due mainly to the crystal structure of the glacier and anisotropy caused by the pressure of the upper layers.An analysis of the polarization diagrams obtained is up to the present the main method used for studies of the reflected signal polarization. Evidently using a simple dipole a partially-polarized signal is not distinguishable from one that is elliptically polarized, nor is a nonpolarized signal distinguished from circularly polarized. However, the data recently obtained are of great importance, particularly from studies of glacier crystal structure made in deep core drilling.Possible reasons for the polarization changes of the signal have been analysed. Results of the analyses of the polarization diagrams obtained both at individual points and along extended traverses are discussed. It has been found that the signal reflected from a considerable ice thickness is polarized in such a way that the parallel orientation of the receiving and transmitting dipoles can be disregarded. En route recordings of the signal fluctuations obtained by parallel and orthogonally polarized dipoles are shown. The results of polarization studies are important for practical purposes. For example, bedrock relief sounding carried out with crossed dipoles makes it possible to get rid of interference signals occurring due to scattering from inhomogeneous structures of the upper part of the glacier.

METHODS OF JAMMING INTERFERENCE

2018 ◽  
pp. 80-84
Author(s):  
A. V. Mazin ◽  
M. Yu. Aliyev
Keyword(s):  
Noise Immunity ◽  
Time Constraints ◽  
Joint Operation ◽  
Directional Diagram ◽  
Main Method ◽  
High Noise ◽  
Time Processing ◽  
Radar Systems ◽  
Interference Signals ◽  
Selection Of

The article investigates the problem of providing high noise immunity radar under the influence of passive and intentional interference. The purpose of radio operation of the radar is to create conditions that would impede the operation of systems and minimize its effectiveness. The main method of radio transmission is still creating (staging) interference. Modern radar systems must solve the tasks in terms of electronic suppression using, including intentional interference and under severe time constraints. It is shown that the most effective way to improve the noise immunity of radar systems designed to operate in multipoint space, including non-stationary, interference is adaptive space-time processing of the received signals, based on the angular selection of targets, due to the formation of zeros in the directional diagram in the direction of interference sources. This problem is solved by determining the accuracy of the direction finding of interference sources and is achieved by the joint operation of the antenna array and multi-channel signal processing devices, namely the separation of interference signals on different receiving channels.

scholarly journals Study and Analysis of Interference Signals of the LTE System of the GNSS Receiver

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4901
Author(s):  
Lucjan Setlak ◽  
Rafał Kowalik
Keyword(s):  
End User ◽  
Current Time ◽  
Gnss Receiver ◽  
System A ◽  
Telecommunication Systems ◽  
Depth Analysis ◽  
Gnss Receivers ◽  
Interference Signals ◽  
The Subject ◽  
Made In

Sometimes, it is impossible to conduct tests with the use of the GNSS system, or the obtained results of the measurements made differ significantly from the predicted accuracy. The most common cause of the problems (external factors, faulty results) are interference disturbances from other radio telecommunication systems. The subject of this paper is to conduct research, the essence of which is an in-depth analysis in the field of elimination of LTE interference signals of the GNSS receiver, that is based on the developed effective methods on counteracting the phenomenon of interference signals coming from this system and transmitted on the same frequency. Interference signals are signals transmitted in the GNSS operating band, and unwanted signals may cause incorrect processing of the information provided to the end-user about his position, speed, and current time. This article presents methods of identifying and detecting interference signals, with particular emphasis on methods based on spatial processing of signals transmitted by the LTE system. A comparative analysis of the methods of detecting an unwanted signal was made in terms of their effectiveness and complexity of their implementation. Moreover, the concept of a new comprehensive anti-interference solution was proposed. It includes, among others, information on the various stages of GNSS signal processing in the proposed system, in relation to the algorithms used in traditional GNSS receivers. The final part of the article presents the obtained research results and the resulting significant observations and practical conclusions.

scholarly journals Arctic Sea Ice of Various Ages: I. Ultimate Strength

1964 ◽  
Vol 5 (37) ◽  
pp. 93-98 ◽  
Author(s):  
M. P. Langleben ◽  
E. R. Pounder
Keyword(s):  
Crystal Structure ◽  
Tensile Strength ◽  
Sea Ice ◽  
Ultimate Strength ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
Polar Ice ◽  
Arctic Sea ◽  
Made In

AbstractA comparison of polar ice (several years old) with biennial ice (between one and two years old) was made in the field at lat. 79°N., long. 104° W. Vertical cores were extracted from the ice cover and sectioned. Their ultimate tensile strengths were measured by the ring-tensile method. Supporting measurements were made of the salinity, density, and crystal structure of the ice. Tensile strength values averaged 6 per cent higher for the polar ice and 21 per cent higher for the biennial ice than comparable results for annual sea ice. A few horizontal cores of biennial ice were analysed similarly with inconclusive results.

An automated Rayleigh-wave detection algorithm

1997 ◽  
Vol 87 (1) ◽  
pp. 157-163
Author(s):  
Eric P. Chael
Keyword(s):  
Rayleigh Wave ◽  
High Reliability ◽  
Detection Algorithm ◽  
Arrival Times ◽  
Long Period ◽  
Wave Detection ◽  
Linearly Polarized ◽  
Automated Data Processing ◽  
Component Wave ◽  
Elliptically Polarized

Abstract The desire to operate denser networks in order to monitor seismic activity at lower thresholds leads to greater emphasis on automated data processing. An algorithm for detecting and characterizing long-period Rayleigh-wave arrivals has been developed and tested. The routine continuously monitors all directions of approach to a station, in a manner similar to beamforming. The detector is based on cross-powers between the Hilbert-transformed vertical and rotated horizontal signals, so it is sensitive to both the power and polarization properties of the three-component wave field. Elliptically polarized Rayleigh arrivals are enhanced, while linearly polarized Love waves and body phases are suppressed. A test using one month of data from station ANMO demonstrated that this technique can, with high reliability, detect Rayleigh arrivals that are visible on the records. The measured arrival times and azimuths are accurate enough to permit automated association of the detections to events in a bulletin.

scholarly journals Nano-Grain Ni/ZrO2 Functional Gradient Coating Fabricated by Double Pulses Electrodeposition with Enhanced High Temperature Corrosion Performance

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 332 ◽  
Author(s):  
Wen Ge ◽  
Taisong He ◽  
Meijiao Wang ◽  
Jiamei Li
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Surface Morphology ◽  
Vertical Direction ◽  
Double Pulse ◽  
Pulse Electrodeposition ◽  
Face Centered Cubic ◽  
X Ray ◽  
Functional Gradient ◽  
Gradient Coating

Functional gradient materials (FGM) have many excellent properties, and high-performance gradient coating exhibits good prospective application. In this paper, the nano-grain Ni/ZrO2 gradient coating was prepared by double pulse electrodeposition (BP). The surface morphology, crystal structure and electrochemical corrosion resistance of the nano-grain Ni/ZrO2 coating and Ni coating, annealed at different temperatures (400–800 °C), have been compared. In the vertical direction to the substrate surface, the content of ZrO2 increases from 0% to 34.99%. X-ray diffraction (XRD) revealed that the average crystal size of Ni/ZrO2 gradient coating gradually increases from 13.75 to 27.75 nm, and the crystal structure is a face-centered cubic (FCC). The main crystal orientation faces are (111) and (200), while the (200) face exhibited a stronger preferred orientation. Compared with the Ni coating by scanning electron microscopy, the surface morphology of double pulse fabricated Ni/ZrO2 gradient coating was revealed as being smoother, denser, and having fewer pores, and the crystal particle size distribution became narrow. X-ray photoelectron spectroscopy (XPS) shows that the chemical binding states of elements Ni and Zr have been altered. The binding energies of 2p3/2 and 2p1/2 for Ni have been increased, resulting in a higher electron donor state of Ni. The binding energy of 3d5/2 and 3d3/2 of Zr4+ in ZrO2 is decreased, thus becoming better electron acceptors. Chemical bonding has been formed at the Ni/ZrO2 interface. This study demonstrated that double pulse electrodeposition is a promising fabrication method for functional gradient coatings for high temperature applications.

ON THE THEORY OF FLOW OF UNDERGROUND FLUIDS IN COMPRESSIBLE STRATA

1959 ◽  
Vol 37 (3) ◽  
pp. 276-284
Author(s):  
A. E. Scheidegger
Keyword(s):  
Porous Medium ◽  
Vertical Direction ◽  
Complex Problem ◽  
Flow Equation ◽  
Local Anisotropy ◽  
Local Isotropy ◽  
Differential Flow ◽  
Considerable Simplification ◽  
General Geometry ◽  
Made In

The problem of flow of a fluid within a compressible porous medium is investigated. It is shown that in general, the motion of the fluid cannot be separated from that of the medium. This leads to a very complex problem of consolidation. However, considerable simplification can be made in applications to the flow of underground fluids. In that case, the general geometry of the consolidation can be predicted since the latter can take place in the vertical direction only. Furthermore, in many cases it is possible to neglect the volume compressibility of the porous matrix.Two cases have been considered: that of local isotropy of stress and permeability and that of local anisotropy of these two quantities. The basic differential flow equation for the two cases is deduced.

NASA in Chile: Technology and Branding of a Satellite-Tracking Station

Design Issues ◽  
2017 ◽  
Vol 33 (2) ◽  
pp. 31-42
Author(s):  
Pedro Ignacio Alonso ◽  
Hugo Palmarola
Keyword(s):  
United States ◽  
The United States ◽  
Satellite Tracking ◽  
Global Network ◽  
Tracking Station ◽  
Radio Signals ◽  
The Subject ◽  
The U.S ◽  
Made In ◽  
Archaeological Perspective

In 1957 as part of the Minitrack Network, the U.S. Army installed a satellite-tracking station in Peldehue, Chile, intended to track radio signals from what was then the United States’ Vanguard project. With the creation of the National Aeronautics and Space Administration (NASA) in 1958, the station came under its new administration, becoming the subject of a process of rebranding that included the monumental installation of the agency insignia, a rounded slab made in concrete and tiles. By examining this object from a design and archaeological perspective - as it nowadays lays abandoned nearby its original location - this paper attempts to advance our understanding of the Chilean station in terms of its place within a much larger global network by analyzing it within the intersection of design, military economies, technologies, ideologies, and cultural and geospatial considerations.

scholarly journals Search for Strongly Polarized Radio Emission from E.T.I., and an Optimist Approach to the Great Silence (Fermi's Paradox)

1985 ◽  
Vol 112 ◽  
pp. 321-325
Author(s):  
J.P. Vallée
Keyword(s):  
Radio Emission ◽  
Linearly Polarized ◽  
Radio Signals

A summary is made of a program to scan slowly a band of sky in search of strongly linearly polarized radio signals from E.T.I. communication relays. Despite this and numerous other observational searches, no signals have been found. An optimist approach to this great silence (Fermi's Paradox) is developed.

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