1,721,078 research outputs found
Two-Stage Automated Defect Recognition Algorithm for the Analysis of Infrared Images
No full textIn this article an algorithm for the analysis of raw thermal infrared images is proposed. The images are obtained by using the nondestructive evaluation method of the laser-spot thermography and aim at detecting the presence of surface defects. A laser is used to scan a test specimen through the generation of single pulses. The temperature distribution produced by this thermoelastic source is measured by an infrared camera and processed with a two-stage algorithm. In the first stage, simple mathematical and statistical parameters are used to flag the presence of damage. Then, once damage is detected, the thermal image's first and second spatial derivative and two spatial filters are computed to enhance contrast, and to locate and size the defect. Some of the advantages of the proposed method with respect to existing approaches include automation in the defect detection process and better defective area isolation through increased contrast.
The algorithm is first proven by analyzing simulated thermal images, and then it is experimentally validated by scanning the surface of a CFRP composite plate with induced defects
Use of the Electro-Mechanical Impedance Method for theAssessment of Dental Implant Stability
No full textThe robustness and reliability of the Electro-Mechanical Impedance (EMI) method to assess dental prostheses
stability is presented. The study aim at addressing an increasing need in the biomedical area where robust, reliable,
and non-invasive methods to assess the bone-interface of dental and orthopedic implants are increasingly demanded
for clinical diagnosis and direct prognosis. In this study two different dental screws were entrenched in
polyurethane foams and immersed in a solution of nitric acid to allow material degradation, inversely simulating a
bone-healing process. This process was monitored by bonding a Piezoceramic Transducer (PZT) to the implant and
measuring the admittance of the PZT over time. To simulate healing, a second set of experiments was conducted. It
consisted of placing four dental screws inside a joint compound specimen and observing the setting of the fresh
compound allocated in the alveolus containing each implant. In all cases it was found that the PZT’s conductance
and the statistical features associated with the analysis of the admittance signatures were sensitive to the degradation
or the setting process
Image processing for the laser spot thermography of composite materials
No full textThis paper describes an image processing algorithm in support of infrared based nondestructive testing. The algorithm aims at analyzing the raw thermal infrared images obtained by using the nondestructive evaluation method of the laser spot thermography. In the study presented in this paper, a laser was used to scan a test specimen through the generation of single pulses. The temperature distribution produced by this thermoelastic source was measured by an infrared camera and processed with a two-stage algorithm. In the first stage few statistical parameters were used to flag the presence of damage. In the second stage the images that revealed the presence of damage were processed computing the first and second spatial derivative. Two spatial filters were also used to enhance contrast, and to locate and size the defect. The algorithm was experimentally validated by scanning the surface of a CFRP and a GFRP composite plate with induced defects
Metrological Evaluation of New Industrial SHM Systems Based on MEMS and Microcontrollers
No full textMicrocontrollers are becoming popular in Structural Health Monitoring (SHM) systems, as they can manage sensors, process data and meet requirements compliant with the cloud and Internet of Things (IoT) paradigms. Similarly, micro electro-mechanical system (MEMS) sensors are spreading for monitoring applications, given their appealing costs. Considering the importance of data for a SHM-targeted decision-making process, a conscious use of these technologies requires a deeper analysis from a metrological point of view, to ensure reliability and robustness of the provided data. Consequently, in a multi-node sensing architecture, concepts like sensitivity of each node or data synchronization becomes of uttermost importance, especially if modal parameters extraction is sought. This paper is intended as a warning for designers of SHM monitoring architectures: can we simply replace standard sensing devices with low-cost systems and expect they perform as well as their “stronger brothers”? The answer to this question is tentatively provided by discussing results obtained in a testing campaign performed on some reinforced concrete beams, dynamically tested through two different monitoring systems: a standard, high-performance system exploiting high-sensitivity piezoelectric accelerometers and a low-cost MEMS digital accelerometers-based one, not coupled to a high performance data acqusition system, rather. Modal parameters are considered as the target measure to assess the performance of the two systems
Structural monitoring of a masonry hydraulic infrastructure in Rome: GIS integration of SAR data, geological investigation and historical surveys
No full textGreat part of the existing constructions has reached or overcome its service life. A structural assessment is not always necessary, nevertheless, it is important to monitor these structures, both for their maintenance and preservation of human lives purposes. Remote sensing techniques have proved to be useful in supporting the management process and the safety evaluation, by reducing the impact of disturbances on the construction functionality. Also, the reconstruction of the geological and stratigraphic setting of the soil beneath the construction is fundamental to evaluate any correlation between the ground movements and their causes. In this work, Differential Interferometric Synthetic Aperture Radar data are used to detect the ground movements experienced by the construction. These data are then integrated in GIS environment with the information about the engineering-geology of the area. The geometry of the structure, based on historical documents, and the subsoil stratigraphy have been modelled in 3D. The procedure is applied to the residential area of Valco San Paolo in Rome. Once the 3D model is constructed, a preliminary structural health monitoring can be performed, providing insights on critical displacement trends. The maximum deformation parameters are compared with limits derived from literature to identify the damage thresholds
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
The use of MT-DInSAR data for the safety assessment and monitoring of structures and infrastructures: the case study of “Torri Stellari” in Rome
No full textStructural Health Monitoring (SHM) field gained increasing interest during the last years, also due to the huge amount of civil structures and infrastructures near or beyond their design life, and needs to be managed, particularly in a multi-hazard prone area like Italy. In this context, the advanced multi-temporal differential interferometry synthetic aperture radar (MT-DInSAR) techniques represent a great potential for the SHM applications and future development. The exploitation of such techniques in the monitoring and structural assessment of the built environment is still an open issue even if some first applications are available in literature showing promising potentialities. In this work, after a brief description of the general framework for structural monitoring and assessment, previously proposed by the authors, the case study of the Torri Stellari buildings in Rome (Italy) is presented and critically discussed. In particular, starting from COSMO-SkyMed (CSK) ascending and descending SAR datasets and applying the Small BAseline Subset (SBAS) DInSAR processing technique, the measurement points of the investigated area are obtained for both acquisition geometries. Different techniques are applied to both the displacement time series and mean deformation velocity for assessing the structural behavior or monitoring of constructions
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
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