1,721,053 research outputs found
Photothermal coherence tomography for 3-D visualization and structural non-destructive imaging of a wood inlay
No full textThe aim of this research is to investigate the suitability of truncated correlation photothermal coherence tomography (TC-PCT) for the non-destructive imaging of a replica of a real inlay to identify subsurface features that often are invisible areas of vulnerability and damage. Defects of inlays involve glue-rich areas, glue-starved areas, termite attack, insect damage, and laminar splitting. These defects have the potential to result in extensive damage to the art design layers of inlays. Therefore, there is a need for an imaging technique to visualize and determine the location of defects within the sample. The recently introduced TC-PCT modality proved capable of providing 3-D images of specimens with high axial resolution, deep subsurface depth profiling capability, and high signal-to-noise ratio (SNR). Therefore, in this study the authors used TC-PCT to image a fabricated inlay sample with various natural and artificial defects in the middle and top layers. The inlay in question reproduces to scale a piece of art preserved in the “Mirror room” of the Castle Laffitte in France. It was built by a professional restorer following the ancient procedure named element by element. Planar TC-PCT images of the inlay were stacked coherently to provide 3-D visualization of areas with known defects in the sample. The experimental results demonstrated the identification of defects such as empty holes, a hole filled with stucco, subsurface delaminations and natural features such as a wood knot and wood grain in different layers of the sample. For this wooden sample that has a very low thermal diffusivity, a depth range of 2 mm was achieved
Physics informed neural networks for solving inverse thermal wave coupled boundary-value problems
Full text linkAs one of the essential parameters in thermophysical analysis, effective measurement of thermal diffusivity is necessary. This paper utilizes the Physics-Informed Neural Networks (PINN) framework to simulate the diffusion of thermal waves. The governing equations / boundary-value problem (BVP) for the thermal waves are expressed in a coupled partial differential form, derived using the method of separation of variables. The inverse problem associated with the coupled partial differential equations is solved using a dimensionless equation / BVP with a loss function that incorporates physical information. Even in the presence of experimental system errors, the neural network (NN) method introduced in this work (“new NN method”) was shown to be capable of robustly solving the thermal wave inverse problem without nonlinear DC components at different spatial locations, for determining the unknown thermal diffusivity of green (unsintered) metal powder compact materials. The results indicate that the coupled partial differential equations for the amplitude and phase of thermal waves within the PINN framework represent a promising strategy for determining thermophysical parameters
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Frequency domain photothermoacoustic signal amplitude dependence on the optical properties of water: turbid polyvinyl chloride-plastisol system
No full textPhotoacoustic (more precisely, photothermoacoustic) signals generated by the absorption of photons can be related to the incident laser fluence rate. The dependence of frequency domain photoacoustic (FD-PA) signals on the optical absorption coefficient (mu(a)) and the effective attenuation coefficient (mu(eff)) of a turbid medium [polyvinyl chloride-plastisol (PVCP)] with tissuelike optical properties was measured, and empirical relationships between these optical properties and the photoacoustic (PA) signal amplitude and the laser fluence rate were derived for the water (PVCP system with and without optical scatterers). The measured relationships between these sample optical properties and the PA signal amplitude were found to be linear, consistent with FD-PA theory: mu(a) = a(A/Phi) - b and mu(eff) = c(A/Phi) + d, where Phi is the laser fluence,A is the FD-PA amplitude, and a,...,d are empirical coefficients determined from the experiment using linear frequency-swept modulation and a lock-in heterodyne detection technique. This quantitative technique can easily be used to measure the optical properties of general turbid media using FD-PAs. (c) 2008 Optical Society of America.PT: J; NR: 34; TC: 0; J9: APPL OPT; PG: 10; GA: 307OBSource type: Electronic(1
Photo-Carrier Radiometric, Photovoltage and Electroluminiscence Lock-in Imaging of Silicon Solar Cells
Full text linkPhotocarrier radiometric imaging (PCR) is an effective diagnostic tool to monitor the energy conversion mechanisms affecting efficiency, transport properties and recombination processes of Si solar cells. In this paper, PCR is introduced using a near-infrared (NIR) InGaAs camera and a spread superbandgap laser beam as an optoelectronic source at low modulation frequency (10Hz) or location-by-location scanning PCR imaging with a focused laser beam at high frequency (10kHz). PCR frequency scans and simultaneous modulated photovoltage (MPV) frequency scans are produced as supplementary results to PCR images and PCR images are compared to dc electroluminescence & modulated electroluminescence images to check the correlation between the results. I-V characteristics of the solar cells are produced in darkness and shunt resistance is measured using the linear portion of the I-V curve. I-V characteristic of a solar cell is also produced using a load resistance box and by irradiating the solar cell with a laser beam. It is observed and analyzed how the experimental results vary with respect to (1) mechanical defect induced on front surface of the solar cell, (2) solar cell subjected to different temperatures, (3) variation of area of the solar cell under investigation
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Development of a Noninvasive In-Vehicle Alcohol Biosensor Using Wavelength-Modulated Differential Photothermal Radiometry
Full text linkDrunk driving is, in Canada, the leading cause of death on the roads. To reduce the number of drinking and driving incidences, new technologies were developed to accurately measure blood alcohol concentration (BAC) and overcome the limitations of current alcohol measuring technologies. In this research, a non-contacting, non-invasive in-vehicle alcohol biosensor is developed using laser-based Wavelength-Modulated Differential Photothermal Radiometry (WM-DPTR). After demonstrating the alcohol measuring capability of the WM-DPTR-based alcohol biosensor, a calibration method is developed for the biosensor using a combined theoretical and experimental approach. Evaluation of the calibrated biosensor shows that the proposed biosensor can achieve high accuracy and precision for the ethanol concentration range of 0-100 mg/dL and be incorporated in ignition interlocks that could be fitted as a universal accessory in vehicles in efforts to reduce the incidents of drunk driving.M.H.Sc
Development of a Noninvasive In-Vehicle Alcohol Biosensor Using Wavelength-Modulated Differential Photothermal Radiometry
No full textDrunk driving is, in Canada, the leading cause of death on the roads. To reduce the number of drinking and driving incidences, new technologies were developed to accurately measure blood alcohol concentration (BAC) and overcome the limitations of current alcohol measuring technologies. In this research, a non-contacting, non-invasive in-vehicle alcohol biosensor is developed using laser-based Wavelength-Modulated Differential Photothermal Radiometry (WM-DPTR). After demonstrating the alcohol measuring capability of the WM-DPTR-based alcohol biosensor, a calibration method is developed for the biosensor using a combined theoretical and experimental approach. Evaluation of the calibrated biosensor shows that the proposed biosensor can achieve high accuracy and precision for the ethanol concentration range of 0-100 mg/dL and be incorporated in ignition interlocks that could be fitted as a universal accessory in vehicles in efforts to reduce the incidents of drunk driving.M.H.Sc
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