156 research outputs found
Steve Freear Passes the Torch as the Editor-in-Chief of IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
No full textAs the New Year starts and after 6 years of serving as the Editor-in-Chief of the IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (UFFC), Steven Freear passes the torch to Peter A. Lewin
Compressive Sensing for Damage Detection in Composite Aircraft Wings
No full textThis work deals with an ultrasonic guided wave structural health monitoring (SHM) system for composite aircraft wing damage inspection. The main idea is to use piezoelectric discs bonded to various parts of the aircraft wing, in a form of relatively sparse arrays, to generate and receive ultrasonic guided waves aimed at detecting defects. The development of a structural monitoring system able to inspect large composite structures and to communicate remotely to the central unit is challenging due to both the huge number of piezoelectric sensors needed and the high sampling frequency of the recorded signals. To address this problem, here a low rate sampling system has been developed by using a modified version of Compressive Sensing (CS) technique that exploits the sparse representation of dispersive and anisotropic ultrasonic guided waves in the frequency warped basis. The CS framework is applied to lower the sampling frequency and to enhance defect localization performances in composite material through the analysis of anisotropic guided waves propagation. The approach is based on the inverse Warped Frequency Transform (WFT) as the sparsifying basis for the CS acquisition and to compensate the dispersive behavior of guided waves for several different directions of propagation. As a result, an automatic detection procedure to locate defect-induced reflections has been successfully tested on Comsol software simulated guided waves propagating in an composite wing specimen
Compressive sensing with frequency warped compensation for damage detection in composite plate
No full textThis work focuses on an ultrasonic guided wave structural health monitoring (SHM) system development for composite plate inspection. The development of an in situ health monitoring system that can inspect large areas and communicate remotely to the inspector is highly computational demanding due to both the huge number of piezoelectric sensors needed and the high sampling frequency. To address this problem, a general approach for low rate sampling is developed. Compressive Sensing (CS) has emerged as a potentially viable technique for the efficient acquisition that exploits the sparse representation of dispersive ultrasonic guided waves in the frequency warped basis. The framework is applied to lower the sampling frequency and to enhance defect localization performances of Lamb wave inspection systems. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested on simulated Lamb waves propagating in a carbon fiber plate using PZFlex software. The proposed method is suitable for defect detection and can be easily implemented for real application to structural health monitoring
Frequency warping compressive sensing for structural monitoring of aircraft wing
No full textThis work focuses on an ultrasonic guided wave structural health monitoring (SHM) system development for aircraft wing inspection. The performed work simulate small, low-cost and light-weight piezoelectric discs bonded to various parts of the aircraft wing, in a form of relatively sparse arrays, for cracks and corrosion monitoring. The piezoelectric discs take turns generating and receiving ultrasonic guided waves. The development of an in situ health monitoring system that can inspect large areas and communicate remotely to the inspector is highly computational demanding due to both the huge number of Piezoelectric sensors needed and the high sampling frequency. To address this problem, a general approach for low rate sampling is developed. Compressive Sensing (CS) has emerged as a potentially viable technique for the efficient acquisition that exploits the sparse representation of dispersive ultrasonic guided waves in the frequency warped basis. The framework is applied to lower the sampling frequency and to enhance defect localization performances of Lamb wave inspection systems. The approach is based on the inverse Warped Frequency Transform (WFT) as the sparsifying basis for the Compressive Sensing acquisition and to compensate the dispersive behaviour of Lamb waves. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested on simulated Lamb waves propagating in an aluminum wing specimen using PZFlex software. The proposed method is suitable for defect detection and can be easily implemented for real application to structural health monitoring
Performance Analysis of Tikhonov Regularized LS Channel Estimation for MIMO OFDM Systems with Virtual Carriers
No full textVLSI Architectures for Sliding-Window-Based Space-Time Turbo Trellis Code Decoders
No full textThe VLSI implementation of SISO-MAP decoders used for traditional iterative turbo coding has been investigated in the literature. In this paper, a complete architectural model of a space-time turbo code receiver that includes elementary decoders is presented. These architectures are based on newly proposed building blocks such as a recursive add-compare-select-offset (ACSO) unit, A-, B-, Γ-, and LLR output calculation modules. Measurements of complexity and decoding delay of several sliding-window-technique-based MAP decoder architectures and a proposed parameter set lead to defining equations and comparison between those architectures
The α — κ — μ/gamma distribution: A generalized non-linear multipath/shadowing fading model
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New analytic results for the incomplete Toronto function and incomplete Lipschitz-Hankel Integrals
No full textFractional Fourier Transform with Pulse Inversion for Second Harmonic Pulse Compression
No full textIn ultrasound harmonic imaging with chirp coded excitation, harmonic matched filtering (HMF) is required on the receiving side to perform second harmonic pulse compression to recover signal axial resolution. In the compressed signal, peak sidelobe levels will grow and the mainlobe width may increase under mismatched or overlap harmonic conditions. In this paper, fractional Fourier transform (FrFT) with pulse inversion is proposed for the second harmonic pulse compression. Experimental results are presented which show a, 13.5%, improvement in the mainlobe width, with comparable peak sidelobe levels, when compared with the conventional HMF technique
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