Efficient characterization of RF sources for the design of noise suppression filters

2008 ◽  
Author(s):  
Heinz M. Rebholz ◽  
Stefan Tenbohlen
Keyword(s):  
Noise Suppression

scholarly journals Qualitative SAR Dark Spot Analysis for Oil Anomaly Characterization

2019 ◽  
Vol 7 (5) ◽  
pp. 22-29
Author(s):  
Chituru Dike Obowu ◽  
Tamunoene Kingdom Abam ◽  
Sabastian Ngah
Keyword(s):  
Noise Suppression ◽  
Satellite Image ◽  
Primary Objective ◽  
Dark Spot ◽  
Logarithmic Scale ◽  
Physical Processes ◽  
Noise Filter ◽  
Amplitude Data

The characterization of the morphology of a dark spot event in a SAR image is crucial to determining the nature, fate and classification of a potential oil on water anomaly. Hence the need to adequately analyze SAR backscatter values from an amplitude power image were darks spots have been identified and extracted. The dark spots are potential areas of oil on water events and it is imperative that they are understood sufficiently for the purpose of assigning the level of confidence in the processing of oil analysis, understanding the type of oil on water event, classifying the extent of weathering impacting the detected anomaly and relating the oil anomaly to a potential source. In order to generate high quality datasets for anomaly characterization, it is imperative to transform satellite image amplitude data into power values in units of dB and represented on a logarithmic scale. This new power dataset is corrected radiometrically and requisite speckle to noise filter applied for data cleaning and noise suppression. Oil anomaly or darks spot extraction, representative of a potential oil on water is event which is the primary objective of the pre-processing is done. Gamma enhancement was applied on the dark spots in order to characterize their radiometric, textural and geometric properties. This is predominantly for estimating the confidence level of each anomaly detected, and their properties which are indicative of the type, fate, age and physical processes relating to each anomaly.

Design of Optimum Acoustic Treatment for Rectangular Ducts With Flow

1976 ◽  
Author(s):  
R. E. Motsinger ◽  
R. E. Kraft ◽  
J. W. Zwick
Keyword(s):  
Acoustic Pressure ◽  
Noise Suppression ◽  
Optimization Technique ◽  
Measured Data ◽  
Acoustic Velocity ◽  
Single Element ◽  
Mean Flow ◽  
Acoustic Treatment ◽  
Treatment Design

A design optimization technique for acoustic treatment in rectangular ducts with uniform mean flow is presented. The technique is based on the acoustic wave solution in terms of series of characteristic duct modes. The analysis allows multiple axial treatment sections along the length of the duct and requires a known modal characterization of the sound source. Conditions of acoustic pressure and acoustic velocity continuity are used to match modal solutions at planes of impedance discontinuity in the duct. Experimental techniques for obtaining this modal characterization are presented. Using duct modes measured at the source plane, the optimization technique is exercised to design an optimized single element liner in a case without mean flow, and optimized single and dual element liners in cases with mean flow. The validity of the program for predicting noise suppression is demonstrated by comparing analytical predictions with measured data for several (non-optimum) cases. Application to treatment design in turbomachinery exhaust ducts is considered.

Elastic Response of Flexible Polyurethane Foams in Uniaxial Tension

1996 ◽  
Vol 118 (2) ◽  
pp. 157-161 ◽  
Author(s):  
W. H. El-Ratal ◽  
P. K. Mallick
Keyword(s):  
Noise Suppression ◽  
Constitutive Models ◽  
Stretch Ratio ◽  
Industrial Applications ◽  
Polyurethane Foams ◽  
Elastic Response ◽  
Uniaxial Tensile ◽  
Tensile Data ◽  
Flexible Polyurethane

Flexible polymeric foams are used in many industrial applications, including cushioning, shock absorption, and noise suppression. There have not been many systematic studies on the characterization of their elastic response that can be used in developing their constitutive behavior. This paper presents the uniaxial tensile data of two different flexible polyurethane foams and determines the relationships between their elastic properties and the major stretch ratio. These relationships will be useful in formulating constitutive models for flexible compressible materials.

scholarly journals Characterization of the seismic field at Virgo and improved estimates of Newtonian-noise suppression by recesses

2021 ◽  
Author(s):  
Ayatri Singha ◽  
Stefan Hild ◽  
Jan Harms ◽  
Maria Concetta Tringali ◽  
Irene Fiori ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Noise Suppression ◽  
Low Frequency ◽  
Seismic Sources ◽  
Frequency Sensitivity ◽  
Gravitational Forces ◽  
Fold Reduction

Abstract Fluctuations of gravitational forces cause so-called Newtonian noise (NN) in gravitational-wave (GW) detectors which is expected to limit their low-frequency sensitivity in upcoming observing runs. Seismic NN is produced by seismic waves passing near a detector's suspended test masses. It is predicted to be the strongest contribution to NN. Modeling this contribution accurately is a major challenge. Arrays of seismometers were deployed at the Virgo site to characterize the seismic field near the four test masses. In this paper, we present results of a spectral analysis of the array data from one of Virgo's end buildings to identify dominant modes of the seismic field. Some of the modes can be associated with known seismic sources. Analyzing the modes over a range of frequencies, we provide a dispersion curve of Rayleigh waves. We find that the Rayleigh speed in the NN frequency band 10\,Hz--20\,Hz is very low ($\lesssim$100\,m/s), which has important consequences for Virgo's seismic NN. Using the new speed estimate, we find that the recess formed under the suspended test masses by a basement level at the end buildings leads to a 10 fold reduction of seismic NN.

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