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1045 full-text articles. Page 6 of 32.

Disrupting Long-Range Polar Order With An Electric Field, Hanzheng Guo, Xiaoming Liu, Fei Xue, Long-Qing Chen, Wei Hong, Xiaoli Tan 2016 Iowa State University

Disrupting Long-Range Polar Order With An Electric Field, Hanzheng Guo, Xiaoming Liu, Fei Xue, Long-Qing Chen, Wei Hong, Xiaoli Tan

Materials Science and Engineering Publications

lectric fields are known to favor long-range polar order through the aligning of electric dipoles in relation to Coulomb's force. Therefore, it would be surprising to observe a disordered polar state induced from an ordered state by electric fields. Here we show such an unusual phenomenon in a polycrystalline oxide where electric fields induce a ferroelectric-to-relaxor phase transition. The nonergodic relaxor phase with disordered dipoles appears as an intermediate state under electric fields during polarization reversal of the ferroelectric phase. Using the phenomenological theory, the underlying mechanism for this unexpected behavior can be attributed to the slow kinetics of ...


High Resolution Time-Of-Arrival Ranging Of Wireless Sensor Nodes In Non-Homogenous Environments, Mohsen Jamalabdollahi 2016 Michigan Technological University

High Resolution Time-Of-Arrival Ranging Of Wireless Sensor Nodes In Non-Homogenous Environments, Mohsen Jamalabdollahi

Dissertations, Master's Theses and Master's Reports

Wireless Sensor Networks (WSN) have emerging applications in homogeneous environments such as free space. In addition, WSNs are finding new applications in non-homogeneous (NH) media. All referred applications entail location information of measured data or observed event. Localization in WSNs is considered as the leading remedy, which refers to the procedure of obtaining the sensor nodes relative location utilizing range measurements. Localization via Time-of-Arrival (ToA) estimation has received considerable attention because of high precision and low complexity implementation, however, the traditional techniques are not feasible in NH media due to frequency dispersion of transmitted ranging waveform.

In this work, a ...


Further Development Of Image Processing Algorithms To Improve Detectability Of Defects In Sonic Ir Nde, Omar Obeidat, Qiuye Yu, Xiaoyan Han 2016 Wayne State University

Further Development Of Image Processing Algorithms To Improve Detectability Of Defects In Sonic Ir Nde, Omar Obeidat, Qiuye Yu, Xiaoyan Han

Review of Progress in Quantitative Nondestructive Evaluation

Sonic Infrared Imaging (SIR) technology is a relatively new NDE technique that has received significant acceptance in the NDE community. SIR NDE is a super-fast, wide range NDE method. The technology uses short pulses of ultrasonic excitation together with infrared imaging to detect defects in the structures under inspection. Defects become visible to the IR camera when the temperature in the crack vicinity increases due to various heating mechanisms in the specimen. Defect detection is highly affected by noise levels as well as mode patterns in the image. Mode patterns result from the superposition of sonic waves interfering within the ...


Evaluation Of High Spatial Resolution Imaging Of Magnetic Stray Fields For Early Damage Detection, Robert Stegemann, Nadja Sonntag, Sandra Cabeza, Viktor Lyamkin, Matthias Pelkner, Giovanni Bruno, Birgit Skrotzki, Marc Kreutzbruck 2016 BAM

Evaluation Of High Spatial Resolution Imaging Of Magnetic Stray Fields For Early Damage Detection, Robert Stegemann, Nadja Sonntag, Sandra Cabeza, Viktor Lyamkin, Matthias Pelkner, Giovanni Bruno, Birgit Skrotzki, Marc Kreutzbruck

Review of Progress in Quantitative Nondestructive Evaluation

Metal magnetic memory (MMM) technique with associated ISO 24497-1:3 [1] is gaining considerable interest in the magnetic NDT community. In contrast to traditional Magnetic Flux Leakage (MFL) testing, the inspection objects are not intentionally magnetized by an external magnetic field [1,2]. Due to the physical coupling between mechanical stress and magnetization of ferromagnetic materials [3], it is assumed that the distribution of the residual MFL correspond to the internal stress of the specimen [2,4], or in the most general sense, to a degradation of the material [1,2].

Usually, MMM measurements are performed by relatively bulky magnetic ...


Electromagnetic Scattering Models For Insar Correlation Measurements Of Vegetation And Snow, Yang Lei 2016 University of Massachusetts Amherst

Electromagnetic Scattering Models For Insar Correlation Measurements Of Vegetation And Snow, Yang Lei

Doctoral Dissertations

Interferometric Synthetic Aperture Radar (InSAR) has proved successful and efficient in measuring the vertical structure of the distributed targets such as vegetation and snow, which are dominated by volume scattering. In particular, the InSAR correlation measurement has been utilized to retrieve the target vertical structural information. One existing and well-known electromagnetic scattering model of the InSAR correlation was first brought forward focusing on the single-pass InSAR observation of a sparse random medium like vegetation. However, the lack of the adaption of this InSAR scattering model for repeat-pass InSAR observation of vegetation as well as for single-pass InSAR observation of snow ...


Applications In Low-Power Phased Array Weather Radars, Robert A. Palumbo Jr 2016 University of Massachusetts Amherst

Applications In Low-Power Phased Array Weather Radars, Robert A. Palumbo Jr

Doctoral Dissertations

Low-cost X-band radars are an emerging technology that offer significant advantages over traditional systems for weather remote sensing applications. X-band radars provide enhanced angular resolution at a fraction of the aperture size compared to larger, lower frequency systems. Because of their low cost and small form factor, these radars can now be integrated into more research and commercial applications. This work presents research and development activities using a low-cost, X-band (9410 MHz) Phase-Tilt Radar. The phase-tilt design is a novel phased array architecture that allows for rapid electronic scanning in azimuth and mechanical tilting in elevation, as a compromise between ...


Multi-Classifier Fusion Strategy For Activity And Intent Recognition Of Torso Movements, Abhijit Kadrolkar 2016 University of Massachusetts - Amherst

Multi-Classifier Fusion Strategy For Activity And Intent Recognition Of Torso Movements, Abhijit Kadrolkar

Doctoral Dissertations

As assistive, wearable robotic devices are being developed to physically assist their users, it has become crucial to develop safe, reliable methods to coordinate the device with the intentions and motions of the wearer. This dissertation investigates the recognition of user intent during flexion and extension of the human torso in the sagittal plane to be used for control of an assistive exoskeleton for the human torso. A multi-sensor intent recognition approach is developed that combines information from surface electromyogram (sEMG) signals from the user’s muscles and inertial sensors mounted on the user’s body. Intent recognition is implemented ...


Monitoring Voip Speech Quality For Chopped And Clipped Speech, Andrew Hines, Jan Skoglund, Anil C. Kokaram, Naomi Harte 2016 Dublin Institute of Technology

Monitoring Voip Speech Quality For Chopped And Clipped Speech, Andrew Hines, Jan Skoglund, Anil C. Kokaram, Naomi Harte

Articles

No abstract provided.


A Novel Method For Ultrasonic Imaging Of Flaws In Coarse Grain Austenitic Stainless Steels, Govind Kumar Sharma, Purnachandra Rao Bhagi 2016 Indira Gandhi Centre for Atomic Research

A Novel Method For Ultrasonic Imaging Of Flaws In Coarse Grain Austenitic Stainless Steels, Govind Kumar Sharma, Purnachandra Rao Bhagi

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic detection and imaging of flaws in thick coarse grained austenitic stainless steel components is challenging due to very high scattering. Spectral and wavelet transform based methods have been traditionally applied to reduce the noise to detect flaws. We propose a novel ensemble empirical mode decomposition based signal processing method for adaptive detection of flaws in coarse grained austenitic stainless steel.

We have analyzed ultrasonic signals obtained from stainless steel specimens of different grain size (30-200 µm) with and without flaws. The ultrasonic signals lie in two different scattering regimes with wavelength to grain size ratio of 1.8 (near ...


Compression Of Multi-Frequency Eddy Current Data Using Principal Components Analysis For Pressure Tube To Calandria Tube Gap Measurement, Shaddy Shokralla, Jordan Morelli, Thomas W. Krause 2016 Queen’s University

Compression Of Multi-Frequency Eddy Current Data Using Principal Components Analysis For Pressure Tube To Calandria Tube Gap Measurement, Shaddy Shokralla, Jordan Morelli, Thomas W. Krause

Review of Progress in Quantitative Nondestructive Evaluation

Inspection of components with multi-variable influential parameters may result in a loss of accuracy for the measurement of the target variable. A particular example occurs in the case of a pressure tube (PT) that is contained within a calandria tube (CT) in the fuel channels of CANDU® nuclear reactors. Eddy current (EC) based measurement of gap between PT and CT, as required by nuclear regulators, is affected by variation of PT wall thickness and resistivity, which may confound the accurate gap measurement. In this work principal components analysis (PCA) is examined as a means of simplifying changes in multi-frequency EC ...


Full-Field Structural Dynamics By Video Motion Manipulations, Yongchao Yang, Charles Farrara, David Mascarenasa 2016 Los Alamos National Laboratory

Full-Field Structural Dynamics By Video Motion Manipulations, Yongchao Yang, Charles Farrara, David Mascarenasa

Review of Progress in Quantitative Nondestructive Evaluation

Structures with complex geometries, material properties, and boundary conditions, exhibit spatially local, temporally transient, dynamic behaviors. High spatial and temporal resolution vibration measurements and modeling are thus required for high-fidelity characterization, analysis, and prediction of the structure’s dynamic phenomena. For example, high spatial resolution mode shapes are needed for accurate vibration-based damage localization. Also, higher order vibration modes typically contain local structural features that are essential for high-fidelity dynamic modeling of the structure. In addition, while it is possible to build a highly- refined mathematical model (e.g., a finite element model) of the structure, it needs to be ...


Raw Data Based Image Processing Algorithm For Fast Detection Of Surface Breaking Cracks Using In-Line Laser Thermography, Sruthi Krishna, Nithin Puthiyaveettil, P. Biju, Krishnan Balasubramaniam 2016 Indian Institute of Technology Madras

Raw Data Based Image Processing Algorithm For Fast Detection Of Surface Breaking Cracks Using In-Line Laser Thermography, Sruthi Krishna, Nithin Puthiyaveettil, P. Biju, Krishnan Balasubramaniam

Review of Progress in Quantitative Nondestructive Evaluation

The aim of this work is to illustrate the contribution of signal processing techniques in the field of Non-Destructive Evaluation. A component’s life evaluation is inevitably related to the presence of flaws in it. The detection and characterization of cracks prior to damage is a technologically and economically significant task and is of very importance when it comes to safety-relevant measures. The Laser Thermography is the most effective and advanced thermography method for Non-Destructive Evaluation. High capability for the detection of surface cracks and for the characterization of the geometry of artificial surface flaws in metallic samples of laser ...


Full Matrix Capture And The Total Focusing Imaging Algorithm Using Laser Induced Ultrasonic Phased Arrays, Theodosia Stratoudaki, Matt Clark, Paul D. Wilcox 2016 University of Bristol

Full Matrix Capture And The Total Focusing Imaging Algorithm Using Laser Induced Ultrasonic Phased Arrays, Theodosia Stratoudaki, Matt Clark, Paul D. Wilcox

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasonics is a technique where lasers are used for the generation and detection of ultrasound instead of conventional piezoelectric transducers. The technique is broadband, non-contact, and couplant free, suitable for large stand-off distances, inspection of components of complex geometries and hazardous environments. In this paper, array imaging is presented by obtaining the full matrix of all possible laser generation, laser detection combinations in the array (Full Matrix Capture), at the nondestructive, thermoelastic regime. An advanced imaging technique developed for conventional ultrasonic transducers, the Total Focusing Method (TFM) [2], is adapted for laser ultrasonics and then applied to the captured ...


The Effects Of Frequency-Dependent Amplitude On The Time-Reversed Lamb Wave Based Baseline-Free Damage Detection, Liang Zeng, Jing Lin, Zhi Luo, Fei Gao 2016 Xi'an Jiaotong University

The Effects Of Frequency-Dependent Amplitude On The Time-Reversed Lamb Wave Based Baseline-Free Damage Detection, Liang Zeng, Jing Lin, Zhi Luo, Fei Gao

Review of Progress in Quantitative Nondestructive Evaluation

Time reversal is the process that a response signal recorded at a receiver location is reversed in time and emitted back to the original source transducer. In the absence of any damage, theoretically the main wave packet of the reconstructed signal could exactly resemble the original input wave form. However, since the amplitude response of Lamb wave mode is generally frequency dependent, the reconstruction is not perfect. In this study, the influences of the frequency-dependent amplitude to the spectrum of the reconstructed signal is investigated. The results show that the peak frequency shifts and the bandwidth varies due to the ...


A Novel Approach For Rapid Eddy Current Imaging Of Flaws, Ana Kumar Soni, Purnachandra Rao Bhagi 2016 Indira Gandhi Centre for Atomic Research

A Novel Approach For Rapid Eddy Current Imaging Of Flaws, Ana Kumar Soni, Purnachandra Rao Bhagi

Review of Progress in Quantitative Nondestructive Evaluation

Traditionally raster scan plan is employed in eddy current testing for imaging flaws in components. Several parallel scans using a single probe are made and the acquired data is represented in the form an image to obtain, e.g. a comprehensive picture of a flaw in the imaged region. For imaging on large surfaces time for imaging is a constraint. We present a novel probe scan plan for rapid eddy current imaging of flaws. We demonstrate the performance of this scan plan in austenitic stainless steel plates for detection of flaws using a pancake type eddy current probe. We then ...


Feasibility And Reliability Of Grain Noise Suppression In Monitoring Highly Scattering Materials Using Baseline Subtraction, Yuan Liu, Chang Liu, Peter Cawley 2016 Imperial College London

Feasibility And Reliability Of Grain Noise Suppression In Monitoring Highly Scattering Materials Using Baseline Subtraction, Yuan Liu, Chang Liu, Peter Cawley

Review of Progress in Quantitative Nondestructive Evaluation

This paper studies the feasibility and reliability of using the baseline subtraction method to suppress grain noise in monitoring highly scattering materials. Monitoring is usually done with permanently installed sensors but this is not always possible and here we investigate the feasibility of subtracting A-scans extracted from repeat C-scans. It is important that the transducer standoff and angle relative to the test piece are set consistently in the repeat scans and the influence of errors in these settings has been investigated. The successive C-scans can be registered by cross correlation and the effect of errors in the registration is illustrated ...


Data Interpolation Beyond Aliasing, Arno Volker, Paul van Neer 2016 Netherlands Organization for Applied Scientific Research

Data Interpolation Beyond Aliasing, Arno Volker, Paul Van Neer

Review of Progress in Quantitative Nondestructive Evaluation

Proper spatial sampling is critical for many applications. If the sampling criterion is not met, artifacts appear for example in images. Last year an iterative approach was presented using wave field extrapolation to interpolate spatially aliased signals. This main concept behind this approach is that after inverse wave field extrapolation the signal is concentrated in a small region with a high amplitude, while the aliasing artifacts are spread-out through the domain. Inverse wave field extrapolation focusses optimally at one depth, making the performance of the reconstruction depth dependent. Obviously the method can be repeated for several depths. This year we ...


Electromagnetic Nondestructive Evaluation Of Defects In Ferromagnetic Samples, Weiying Cheng 2016 Japan Power Engineering and Inspection Corporation

Electromagnetic Nondestructive Evaluation Of Defects In Ferromagnetic Samples, Weiying Cheng

Review of Progress in Quantitative Nondestructive Evaluation

There are increasing demands to detect and characterize defects in ferromagnetic materials. In the electromagnetic nondestructive evaluation (ENDE) of cracks in ferromagnetic materials, both the magnetic flux leakage effect and eddy current perturbation coexist and the signals may be a combination of the two effects: signals arise from flux leakage effects when the crack orients transversal to the flux, and signals arise from eddy current perturbation when the crack orients transversal to the eddy currents. The signals due to the two effects are different on signal width, signal phases, and etc. By the way, surface and back-side cracks can be ...


The Use Of Binary Quantisation For The Acquisition Of Low Snr Ultrasonic Signals: A Study Of The Input Dynamic Range, Julio Isla-Garcia, Frederic Cegla 2016 Imperial College London

The Use Of Binary Quantisation For The Acquisition Of Low Snr Ultrasonic Signals: A Study Of The Input Dynamic Range, Julio Isla-Garcia, Frederic Cegla

Review of Progress in Quantitative Nondestructive Evaluation

Several types of transducer, such as electromagnetic acoustic transducers (EMATs), piezoelectric paints or air-coupled transducers, produce weak signals that can be below the noise threshold at the receiver. In such scenarios averaging or pulse-compression is employed to increase the signal-to-noise ratio (SNR). This paper explores quantisation strategies for these weak signals. It is shown that when the SNR is low, binary (one-bit) quantisation can be used without experiencing significant losses compared to analog-to-digital converters (ADCs). Binary quantizers are simple analog comparators, which make the electronics faster, cheaper, more compact and energy efficient than ADCs. This is especially important when arrays ...


Detection Of Manufacturing Defects Via Wavefield Image Processing Techniques: An Experimental Study, Peter D. Juarez, Cara A. C. Leckey 2016 NASA Langley Research Center

Detection Of Manufacturing Defects Via Wavefield Image Processing Techniques: An Experimental Study, Peter D. Juarez, Cara A. C. Leckey

Review of Progress in Quantitative Nondestructive Evaluation

Defects that occur during the manufacturing of a composite can have drastic effects on the intended strength or durability of composite structures. These defects include gaps and overlaps in the prepreg tow-tape that can occur during Automated Fiber Placement (AFP) system operations, as well as unintended fiber waviness caused by differential thermal loading during curing cycles. Wavefield imaging offers a non-contact method of detecting various anomalies in composites, and emerging technologies can enable rapid wavefield acquisition. In this work, composite samples were created with intentional and analogous manufacturing defects such as the ones mentioned, and full guided wavefield data was ...


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