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  • 1
    Publication Date: 2018-11-14
    Description: The development of new low-cost transducers and systems has been extensively aimed at in both industry and academia to promote a correct failure diagnosis in aerospace, naval, and civil structures. In this context, structural health monitoring (SHM) engineering is focused on promoting human safety and a reduction in the maintenance costs of these components. Traditionally, SHM aims to detect structural damages at the initial stage, before it reaches a critical level of severity. Numerous approaches for damage identification and location have been proposed in the literature. One of the most common damage location techniques is based on acoustic waves triangulation, which stands out as an effective approach. This method uses a piezoelectric transducer as a sensor to capture acoustic waves emitted by cracks or other damage. Basically, the damage location is defined by calculating the difference in the time of arrival (TOA) of the signals. Although it may be simple, the detection of TOA requires complex statistical and signal processing techniques. Based on this issue, this work proposes the evaluation of a low-cost piezoelectric transducer to determine damage location in metallic structures by comparing two methodologies of TOA identification, the Hinkley criterion and the statistical Akaike criterion. The tests were conducted on an aluminum beam in which two piezoelectric transducers were attached at each end. The damage was simulated by pencil lead break (PLB) test applied at four different points of the specimen and the acoustic signals emitted by the damage were acquired and processed by Hinkley and Akaike criteria. The results indicate that, although both signal processing methodologies were able to determine the damage location, Akaike presented higher precision when compared to Hinkley approach. Moreover, the experimental results indicated that the low-cost piezoelectric sensors have a great potential to be applied in the location of structural failures.
    Electronic ISSN: 2504-3900
    Topics: Technology
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1005-1009 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: When using multichannel SQUID magnetometers for biomagnetic applications, the correct measurement of the Tesla/volt calibration factor of each channel is of extreme importance, in order to avoid gross errors when analyzing the results. We propose a general calibration method valid for all kinds of gradiometer arrays. One of the main properties of this method is that the gradiometer position inside the cryogenic Dewar does not need to be known precisely. When tested, calibration factors with accuracies ranging from 0.3% to 0.8% were obtained. It is based on a spatial Fourier technique and on the fact that the gradiometer acts as a discrete spatial filter.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The erosive wear susceptibility of porous and near-fully-dense liquid-phase-sintered (LPS) alumina ceramics has been studied from dry particle impact testing. Results show that the wear rates remained relatively constant with increasing porosity to a level above which the wear degradation was accelerated markedly. Microscopic observations indicate evidence of scratching and inelastic deformation in the erosion sites of the most porous structures, while brittle fracture and grain dislodgment dominated the material removal processes in the dense material. Implications of the erosion response in the LPS aluminas are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The use of synchrotron radiation diffraction (SRD) in con-junction with conventional laboratory X-ray diffraction (XRD) for analyzing the phase assemblage of selected alu-mina-based ceramics is described. This paper outlines the benefits of synchrotron powder diffraction in resolving mi-norand impurity phases in various alumina ceramics. Laboratory XRD is shown to provide only cursory details of minor crystalline phases which are strikingly evident and clearly defined from application of SRD analysis. The po-tential of SRD techniques to characterize low-level crystal-line phases and as a check for “phase purity” in ceramic systems is considered.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 78 (1956), S. 2723-2728 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4339-4344 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Scanning optical microscopy with uncoated dielectric silica probe is used in the near field to investigate the propagation of optical modes along tapered integrated semiconductor optical amplifier devices and at larger working distances to study the electromagnetic intensity profile in the focal plane of various microlensed fibers. We show how this technique provides images of the mode structure of optoelectronic devices and profiled optical fibers with typical sizes in the range 2–10 μm, with an accuracy of 0.2 μm in beamwaist measurements. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 5899-5906 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to image the magnetic source distribution inside a flawed magnetically permeable structure, the truncated generalized inverse and singular value decomposition were used. These techniques were applied to the magnetic flux leakage generated when the structure is magnetized. The leakage field from different flaw shapes was simulated by placing magnetic dipoles at the boundary surfaces, which reduces the flux density in the flawed structure. A criterion to establish the generalized inverse truncation index is proposed, by using the two-dimensional correlation coefficient between the original image and the reconstructed image. Others aspects such as the measurement signal-to-noise ratio, and density of the model source distribution are also discussed. This imaging technique was successfully applied to a number of different model flaw sources. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2098-2101 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial discrimination of planar and axial gradiometers is compared by using a spatial filtering model. By measuring somatosensory evoked fields, equivalent current dipoles were localized with the use of planar gradiometer outputs. The planar configurations were obtained by combining, in a proper way, the outputs of a four-channel biomagnetic system. It was observed that with a proper signal-to-noise ratio, the use of the planar configurations did not significantly affect the localization precision.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3197-3199 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-frequency coupled electromagnetic field problems are analyzed using the magnetic vector potential finite element method. The two- and three-dimensional computer programs used here are extensions of previously developed static and eddy current programs. Boundary conditions are presented that enable analysis of reflected electromagnetic waves and absorbed electromagnetic waves. Calculated resonant frequencies are shown to agree closely with classical theory for reflected waves. The absorbing finite elements are shown to give low reflections.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2820-2823 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A review of the traditional method for designing gradiometers is made. A nonrecursive digital filter model for the gradiometer is presented, giving a new set of parameters for the gradiometer identification. Some designs are analyzed using the proposed set. As an example, a true differentiator is designed to be used as the SQUID input coil. It is shown that the differentiator has the same noise rejection as the conventional gradiometer but provides more signal sensitivity.
    Type of Medium: Electronic Resource
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