Complex Source Pulsed Beams: Propagation, Scattering and Applications

1991 ◽  
pp. 87-100
Author(s):  
Ehud Heyman
Keyword(s):  
Complex Source

scholarly journals Tutorial on seismic interferometry: Part 2 — Underlying theory and new advances

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. 75A211-75A227 ◽  
Author(s):  
Kees Wapenaar ◽  
Evert Slob ◽  
Roel Snieder ◽  
Andrew Curtis
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Seismic Interferometry ◽  
Virtual Source ◽  
Bending Waves ◽  
Complex Source ◽  
Recent Developments ◽  
Diffusion Phenomena ◽  
Quantum Mechanical Scattering ◽  
Moving Media

In the 1990s, the method of time-reversed acoustics was developed. This method exploits the fact that the acoustic wave equation for a lossless medium is invariant for time reversal. When ultrasonic responses recorded by piezoelectric transducers are reversed in time and fed simultaneously as source signals to the transducers, they focus at the position of the original source, even when the medium is very complex. In seismic interferometry the time-reversed responses are not physically sent into the earth, but they are convolved with other measured responses. The effect is essentially the same: The time-reversed signals focus and create a virtual source which radiates waves into the medium that are subsequently recorded by receivers. A mathematical derivation, based on reciprocity theory, formalizes this principle: The crosscorrelation of responses at two receivers, integrated over differ-ent sources, gives the Green’s function emitted by a virtual source at the position of one of the receivers and observed by the other receiver. This Green’s function representation for seismic interferometry is based on the assumption that the medium is lossless and nonmoving. Recent developments, circumventing these assumptions, include interferometric representations for attenuating and/or moving media, as well as unified representations for waves and diffusion phenomena, bending waves, quantum mechanical scattering, potential fields, elastodynamic, electromagnetic, poroelastic, and electroseismic waves. Significant improvements in the quality of the retrieved Green’s functions have been obtained with interferometry by deconvolution. A trace-by-trace deconvolution process compensates for complex source functions and the attenuation of the medium. Interferometry by multidimensional deconvolution also compensates for the effects of one-sided and/or irregular illumination.

Incremental theory of diffraction for complex source illumination

2006 ◽  
Author(s):  
A. Polemi ◽  
M. Albani ◽  
G. Carluccio ◽  
A. Toccafondi ◽  
S. Maci
Keyword(s):  
Incremental Theory ◽  
Source Illumination ◽  
Complex Source

Complex source pulsed beam representation of transient radiation

Wave Motion ◽  
1989 ◽  
Vol 11 (4) ◽  
pp. 337-349 ◽  
Author(s):  
Ehud Heyman
Keyword(s):  
Transient Radiation ◽  
Complex Source

Blind Complex Source Separation Based on Cyclostationary Statistics

2014 ◽  
Vol 519-520 ◽  
pp. 1051-1056
Author(s):  
Jie Guo ◽  
An Quan Wei ◽  
Lei Tang
Keyword(s):  
Blind Source Separation ◽  
Source Separation ◽  
Separation Performance ◽  
Separation Algorithm ◽  
Complex Signals ◽  
Cyclic Frequency ◽  
Complex Source ◽  
Simulation Results ◽  
Better Than ◽  
Separation Model

This paper analyzed a blind source separation algorithm based on cyclic frequency of complex signals. Under the blind source separation model, we firstly gave several useful assumptions. Then we discussed the derivation of the BSS algorithm, including the complex signals and the normalization situation. Later, we analyzed the complex WCW-CS algorithm, which was compared with NGA, NEASI and NGA-CS algorithms. Simulation results show that the complex WCW-CS algorithm has the best convergence and separation performance. It can also effectively separate mixed image signals, whose performance was better than NGA algorithm.

A “Complex Source” in the 2D Real Space

2013 ◽  
Vol 194 (1) ◽  
pp. 98-103 ◽  
Author(s):  
A. M. Tagirdzhanov
Keyword(s):  
Real Space ◽  
Complex Source

Von U-Booten, Kriegsreportern und dem Fall des Hauses Romanov

2015 ◽  
Vol 29 (1) ◽  
Author(s):  
Anna Bohn
Keyword(s):  
First World War ◽  
World War ◽  
Digital Multimedia ◽  
Balkan Wars ◽  
The First World War ◽  
Complex Source ◽  
Finding Aids ◽  
Media Types ◽  
Mass Digitization ◽  
First World

AbstractThe mass digitization of finding aids and original documents from the First World War presents a challenge in developing digital multimedia scholarly editions. Different source categories and media types such as film documents, written records, images and sound can thus be linked, annotated and contextualized. This is illustrated by describing the complex source transmission of three historical events: the submarine warfare in the Mediterranean in 1917, the murder of the Romanov family by the Bolshevik revolutionaries and the cross-border activities and professional life of the Russian born war reporter Samson Chernov (1887-1929) during the Balkan Wars and the First World War.

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