Damage Detection Using Large-Scale Covariance Matrix

2014 ◽  
pp. 89-97 ◽  
Author(s):  
Luciana Balsamo ◽  
Raimondo Betti ◽  
Homayoon Beigi
Keyword(s):  
Damage Detection ◽  
Covariance Matrix ◽  
Large Scale ◽  
Scale Covariance

scholarly journals An Accurate Reconstruction of CMB E Mode Signal over Large Angular Scales using Prior Information of CMB Covariance Matrix in ILC Algorithm

2020 ◽  
Author(s):  
Ujjal Purkayastha ◽  
Vipin Sudevan ◽  
Rajib Saha
Keyword(s):  
Power Spectrum ◽  
Linear Combination ◽  
Covariance Matrix ◽  
Large Scale ◽  
Prior Information ◽  
Future Generation ◽  
Temperature Anisotropy ◽  
Satellite Mission ◽  
Angular Power Spectrum ◽  
Accurate Reconstruction

Abstract Recently, the internal-linear-combination (ILC) method was investigated extensively in the context of reconstruction of Cosmic Microwave Background (CMB) temperature anisotropy signal using observations obtained by WMAP and Planck satellite missions. In this article, we, for the first time, apply the ILC method to reconstruct the large scale CMB E mode polarization signal, which could probe the ionization history, using simulated observations of 15 frequency CMB polarization maps of future generation Cosmic Origin Explorer (COrE) satellite mission. We find that the clean power spectra, from the usual ILC, are strongly biased due to non zero CMB-foregrounds chance correlations. In order to address the issues of bias and errors we extend and improve the usual ILC method for CMB E mode reconstruction by incorporating prior information of theoretical E mode angular power spectrum while estimating the weights for linear combination of input maps (Sudevan & Saha 2018b). Using the E mode covariance matrix effectively suppresses the CMB-foreground chance correlation power leading to an accurate reconstruction of cleaned CMB E mode map and its angular power spectrum. We compare the performance of the usual ILC and the new method over large angular scales and show that the later produces significantly statistically improved results than the former. The new E mode CMB angular power spectrum contains neither any significant negative bias at the low multipoles nor any positive foreground bias at relatively higher mutlipoles. The error estimates of the cleaned spectrum agree very well with the cosmic variance induced error.

Acoustic Emission Source Characterisation in Large-Scale Composite Structures

2011 ◽  
Vol 70 ◽  
pp. 381-386 ◽  
Author(s):  
Mark J. Eaton ◽  
Rhys Pullin ◽  
C.A. Featherston ◽  
Karen M. Holford
Keyword(s):  
Acoustic Emission ◽  
Damage Detection ◽  
Composite Structures ◽  
Large Scale ◽  
Amplitude Ratio ◽  
Matrix Cracking ◽  
Out Of Plane ◽  
Critical Components ◽  
Observed Damage ◽  
Buckling Test

Damage detection and location in aerospace composites is currently of great interest in the research community and is being driven by the need to reduce weight of commercial aircrafts and hence make substantial environmental improvements. The increased use of composites as safety critical components has led to the need for development of structural health monitoring (SHM) systems. Acoustic Emission (AE) offers an excellent potential for delivering the necessary information of damage detection to maintenance engineers in terms of location however there are currently no methodologies that can use AE signals to characterise damage sources. This paper explores a methodology for damage characterisation based on measuring the amplitude ratio (MAR) of the two primary plate wave modes, to allow identification of in-plane (matrix cracking) and out-of-plane sources (delamination). Results from a large-scale buckling test show good correlation between signal characterization and observed damage mechanisms.

Testing and Monitoring for a Large Scale Truss Bridge Using Long-Gauge Fiber Optic Sensors

2013 ◽  
Vol 569-570 ◽  
pp. 223-229 ◽  
Author(s):  
Chun Feng Wan ◽  
Wan Hong ◽  
Zhi Shen Wu ◽  
Tadanobu Sato
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Large Scale ◽  
Fiber Optic ◽  
Fiber Optic Sensors ◽  
Structural Testing ◽  
Bragg Grating ◽  
Truss Bridges ◽  
Long Span ◽  
Truss Bridge

Fiber optic sensors become very popular for structural testing and monitoring in civil engineering nowadays, due to its advantage of high resolution and environment durability. In this paper, long-gauge fiber optic bragg grating sensors will be introduced. Structural damage detection stratagem using the micro-strain mode will be studied. Then its application to a structural testing and monitoring for a real long span truss bridge will be discussed in detail. In the testing, 23 long-gauge fiber optic bragg grating sensors were deployed on the mid span of the bridge. Testing were made under conditions either there is train on the bridge or no train on it. Corresponding dynamic characteristics were analyzed and discussed. Results of the testing show that long-gauge fiber optic sensors can work well for structural testing and also damage detection for truss bridges.

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