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Full-Text Articles in Engineering
Damage Detection In Reinforced Concrete Member Using Local Time-Frequency Transform Applied To Vibration Measurements, Ning Liu, Thomas Schumacher, Yan Li, Lina Xu, Bo Wang
Damage Detection In Reinforced Concrete Member Using Local Time-Frequency Transform Applied To Vibration Measurements, Ning Liu, Thomas Schumacher, Yan Li, Lina Xu, Bo Wang
Civil and Environmental Engineering Faculty Publications and Presentations
Signal processing and analysis of structural vibration measurements are key components of structural damage detection (SDD) in structural health monitoring (SHM). The goal of signal processing is to extract subtle changes in the measured signals, which can be used to infer changes in structural parameters and damage. Time-frequency analysis is one of the most popular characterization methods for studying non-stationary vibration signals. In this article, the local time-frequency transform (LTFT) is applied and evaluated to calculate the time-domain signals because of its excellent time-frequency energy distribution properties. The LTFT matches the input data by the Fourier basis in an inverse …
Evaluation Of Low And High Frequency Dynamic Response For Condition Assessment Of Reinforced Concrete Structures, Ali Hafiz
Dissertations and Theses
Concrete is widely used for civil infrastructure structures and they experience deterioration and degradation due to aging, increases in the traffic loads, harsher environmental conditions, use of deicing chemicals, etc. Therefore, evaluating the integrity of reinforced concrete structures has become of increasing interest for infrastructure owners and managers. A number of non-destructive testing (NDT) and structural health monitoring (SHM) methods have been developed in recent decades to aid in evaluating structures and provide input for asset management. One family of these methods uses the dynamic response of a structural member: stress waves (high frequency) and structural vibrations (low frequency). Both …
Physics-Based Signal Processing Methods For Terahertz Non-Destructive Evaluation Of Layered Media, Scott G. Schecklman
Physics-Based Signal Processing Methods For Terahertz Non-Destructive Evaluation Of Layered Media, Scott G. Schecklman
Dissertations and Theses
In recent years Terahertz (THz) time domain spectroscopy has emerged as a promising new technology with potential applications in a variety of fields, including industrial manufacturing, security screening and medical imaging. Pulsed THz systems are uniquely suited for non-destructive evaluation (NDE) of the sub-surface layers of dielectric packaging and coating materials, because they provide high dynamic range over a wide bandwidth in the far infrared portion of the electromagnetic spectrum. Often the dielectric materials of the packaging and/or surface coating layers exhibit relatively low loss and abrupt changes in the refractive index at the layer boundaries can be observed as …
Diagnostic Imaging Of Structural Concrete Using Ground Penetrating Radar And Ultrasonic Array, Sina Mehdinia, Thomas Schumacher, Eric Wan, Xubo Song
Diagnostic Imaging Of Structural Concrete Using Ground Penetrating Radar And Ultrasonic Array, Sina Mehdinia, Thomas Schumacher, Eric Wan, Xubo Song
Student Research Symposium
Structural concrete is the most widely used construction material in the world. Many structures critical to a society such as bridges, hospitals, and airports are built with concrete. While this material is well understood from a mechanical design point of view, still no accurate quantitative tools exist to assess it for damage and deterioration. This is of particular concern for an urban area like Portland with a mega-thrust earthquake waiting to occur. Non-destructive evaluation tools that can quickly and accurately give a full picture of the integrity of structural concrete elements will be key to help plan effective and safe …
Physics-Based Imaging Methods For Terahertz Nondestructive Evaluation Applications, Gabriel Paul Kniffin
Physics-Based Imaging Methods For Terahertz Nondestructive Evaluation Applications, Gabriel Paul Kniffin
Dissertations and Theses
Lying between the microwave and far infrared (IR) regions, the "terahertz gap" is a relatively unexplored frequency band in the electromagnetic spectrum that exhibits a unique combination of properties from its neighbors. Like in IR, many materials have characteristic absorption spectra in the terahertz (THz) band, facilitating the spectroscopic "fingerprinting" of compounds such as drugs and explosives. In addition, non-polar dielectric materials such as clothing, paper, and plastic are transparent to THz, just as they are to microwaves and millimeter waves. These factors, combined with sub-millimeter wavelengths and non-ionizing energy levels, makes sensing in the THz band uniquely suited for …
Oct-Based Elastography For Large And Small Deformations, Donald D. Duncan, Sean J. Kirkpatrick, Ruikang K. Wang
Oct-Based Elastography For Large And Small Deformations, Donald D. Duncan, Sean J. Kirkpatrick, Ruikang K. Wang
Electrical and Computer Engineering Faculty Publications and Presentations
We present two approaches to speckle tracking for optical coherence tomography (OCT)-based elastography, one appropriate for small speckle motions and the other for large, rapid speckle motions. Both approaches have certain advantages over traditional cross-correlation based motion algorithms. We apply our algorithms to quantifying the strain response of a mechanically inhomogeneous, bi-layered polyvinyl alcohol tissue phantom that is subjected to either small or large dynamic compressive forces while being imaged with a spectral domain OCT system. In both the small and large deformation scenarios, the algorithms performed well, clearly identifying the two mechanically disparate regions of the phantom. The stiffness …
Imaging The Mechanical Stiffness Of Skin Lesions By In Vivo Acousto-Optical Elastography, Sean J. Kirkpatrick, Donald D. Duncan, Ruikang K. Wang, Molly Kulesz-Martin, Ken Lee
Imaging The Mechanical Stiffness Of Skin Lesions By In Vivo Acousto-Optical Elastography, Sean J. Kirkpatrick, Donald D. Duncan, Ruikang K. Wang, Molly Kulesz-Martin, Ken Lee
Electrical and Computer Engineering Faculty Publications and Presentations
Optical elastography is an imaging modality that relies on variations in the local mechanical properties of biological tissues as the contrast mechanism for image formation. Skin lesions, such as melanomas and other invasive conditions, are known to alter the arrangement of collagen fibers in the skin and thus should lead to alterations in local skin mechanical properties. We report on an acousto-optical elastography (AOE) imaging modality for quantifying the mechanical behavior of skin lesions. The method relies upon stimulating the tissue with a low frequency acoustic force and imaging the resulting strains in the tissue by means of quantifying the …
Performance Analysis Of A Maximum-Likelihood Speckle Motion Estimator, Donald D. Duncan, Sean J. Kirkpatrick
Performance Analysis Of A Maximum-Likelihood Speckle Motion Estimator, Donald D. Duncan, Sean J. Kirkpatrick
Electrical and Computer Engineering Faculty Publications and Presentations
Presented herein is a performance analysis of a maximum likelihood estimator for calculating small speckle motions. Such estimators are important in a variety of speckle techniques used in non-destructive evaluation. The analysis characterizes the performance (bias and RMS deviation) of the estimator as a function of the signal-to-noise ratio. This SNR parameter is a convenient surrogate for decorrelation of sequential speckle patterns such as are seen in biological tissues. Although the particular estimator is predicated on speckle motions that are a small fraction of a pixel, accurate performance is demonstrated for instantaneous motions of up to ±0.8 pixel/record. Beyond this …