MATCHED FILTER DETECTION OF ELECTROMAGNETIC TRANSIENT REFLECTIONS

Geophysics ◽  
1974 ◽  
Vol 39 (5) ◽  
pp. 683-691 ◽  
Author(s):  
C. S. Clay ◽  
L. L. Greischar ◽  
T. K. Kan
Keyword(s):  
Surface Wave ◽  
Magnetic Permeability ◽  
Matched Filter ◽  
Numerical Models ◽  
Transient Signal ◽  
Matched Filters ◽  
Electromagnetic Transient ◽  
Different Depths ◽  
Aluminum Plates ◽  
Laboratory Models

An electromagnetic transient signal is distorted as it travels in the conducting earth. At vertical incidence, the signal is stretched by a time that is proportional to the magnetic permeability, conductivity, and depth squared. The stretch is a function of the travel distance, and a set of filters can be constructed to match the waveforms of signals which have traveled to different depths. Surface waves travel from the source and can overlap the reflected signals. The reflected signals were estimated by subtracting an estimate of the surface wave and then passing the estimated reflections through a set of matched filters. This method was tested by means of numerical models and laboratory models. The latter were coaxial coils on aluminum plates. In both cases, the matched filters determined the depth of the reflected signals.

scholarly journals SIMULATION MODELING OF THE INTERFERENCE IMMUNITY OF THE RADARS OPERATING WITH COMPRESSED SIGNAL

2020 ◽  
Vol 8 (12) ◽  
pp. 799-804
Author(s):  
Sevdalin Ivanov Spassov ◽  
Keyword(s):  
Simulation Modeling ◽  
Pulse Compression ◽  
Matched Filter ◽  
Chirp Signal ◽  
Interference Immunity ◽  
Matched Filters ◽  
Matlab Software ◽  
Interference Signals

The immunity to the interference of a radar operating with a pulse compression signal is an important feature. The matched filter is one of the elements of the radar, providing resistance to interference. A model of a matched filter to chirp signal has synthesized using the Simulink tool of the Matlab software. Two types of interference signals have fed to the matched filter input, and the output signals are measured. The matched filters degree of suppression against these two interference signals has been assessed. Inferences about the interference immunity of the radars operating with compressed signals have been made.

Evaluation of Digitally Coded Acoustic Surface-Wave Matched Filters

1971 ◽  
Vol 18 (1) ◽  
pp. 21-27 ◽  
Author(s):  
W.S. Jones ◽  
C.S. Hartmann ◽  
L.T. Claiborne
Keyword(s):  
Surface Wave ◽  
Matched Filters ◽  
Acoustic Surface Wave

MOSFET Ultrasonic Surface‐Wave Detectors for Programmable Matched Filters

1971 ◽  
Vol 19 (3) ◽  
pp. 58-60 ◽  
Author(s):  
L. T. Claiborne ◽  
E. J. Staples ◽  
J. L. Harris ◽  
J. P. Mize
Keyword(s):  
Surface Wave ◽  
Matched Filters

Acoustic surface-wave matched filters using a MOSFET array

1973 ◽  
Vol 61 (8) ◽  
pp. 1165-1167 ◽  
Author(s):  
G.D. O'Clock ◽  
D.A. Gandolfo ◽  
H.J. Bush
Keyword(s):  
Surface Wave ◽  
Matched Filters ◽  
Acoustic Surface Wave

scholarly journals Synthesis of matched filters.

2021 ◽  
Author(s):  
A.N. Degtyaryov ◽  
◽  
I.L. Afonin ◽  
A.L. Polyakov ◽  
A.S. Kozhemyakin ◽  
...  
Keyword(s):  
Fourier Series ◽  
Impulse Response ◽  
Correlation Functions ◽  
Matched Filter ◽  
Matched Filters ◽  
Low Pass ◽  
Pulse Characteristics ◽  
Low Pass Filters ◽  
Direct Use ◽  
Complex Transmission

Methods for approximating the impulse response of a matched, physically realizable filter with the minimum required number of functional nodes are in thei focus of the paper. Methods for approximating the pulse characteristics of a matched filter are proposed, namely: approximation by causal physically realizable functions, which are the correlation functions of the pulse characteristics of low-pass filters (LPF) Butterworth; using the Fourier series to describe the complex transmission coefficient of the filter; direct use of the Fourier series to approximate the impulse response of a matched filter. As a result, the number of elements of the matched filter is significantly reduced.

scholarly journals Composite Patch Repair for Underwater Aluminum Structures

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
R. W. Bianchi ◽  
Y. W. Kwon ◽  
E. S. Alley
Keyword(s):  
Numerical Models ◽  
Woven Fabric ◽  
Patch Repair ◽  
Shear Stresses ◽  
Curing Conditions ◽  
Composite Patch ◽  
Four Point Bending ◽  
Numerical Studies ◽  
Bending Loads ◽  
Aluminum Plates

Both experimental and numerical studies were conducted to investigate the effectiveness of composite patch repair on underwater structures, especially aluminum alloy structures. Physical samples were prepared using 5XXX aluminum plates with a premachined hole and E-glass woven fabric layers. The epoxy resin was selected such that it could be cured underwater. Test samples were prepared under different curing conditions such as dry curing and wet curing with different durations of in-water exposure. Strain gages were attached to all samples. The samples were tested for both tensile and four-point bending loads. Furthermore, numerical modeling and simulations were conducted, and the numerical models were validated against the experimental measurements. Then, the interface normal and shear stresses were determined from the numerical models so as to understand the delamination failure at the interface between the aluminum and composite patches. Underwater composite patching showed good interface strength and potential for successful usage in repairs.

Drying Shrinkage of Concrete: Experiments and Numerical Models

2017 ◽  
Vol 259 ◽  
pp. 46-51 ◽  
Author(s):  
Marek Vinkler ◽  
Jan L. Vítek
Keyword(s):  
Relative Humidity ◽  
Numerical Models ◽  
Drying Shrinkage ◽  
Shrinkage Strain ◽  
Experimental Program ◽  
Model Code ◽  
Wire Strain ◽  
Model Code 2010 ◽  
Different Depths ◽  
Pore Relative Humidity

The paper presents some results of experimental program focused on drying and shrinkage of large concrete specimens. Segments of walls with thicknesses 200, 400 and 800 mm and standard cylinders 150x300 mm were used as specimens. Each segment has embedded 4 vibrating wire strain gauges in axis plane for measurements of shrinkage strain and plastic tubes of various lengths for measurements of pore relative humidity in different depths. Relative humidity and temperature of ambient environment were not controlled, however they were recorded very closely. Measure shrinkage strains are compared with prediction based on shrinkage models. The most important predictive models are used for comparison: Model Code 2010, Eurokód 2, Model ACI 209-R92, Model B4 a Model B4s.

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