1,720,984 research outputs found
Detection of the surface coating of photovoltaic panels using drone-acquired thermal image sequences
No full textAs photovoltaic (PV) panels are installed outdoors, they are exposed to harsh environments that can degrade their performance. PV cells can be coated with a protective material to protect them from the environment. However, the coated area has relatively small temperature differences, obtaining a sufficient database for training is difficult, and detection in low-resolution thermal images is complicated. This paper proposes a method for detecting the relative temperature difference on PV panels and a method for accumulating detection results within consecutive thermal images. To verify the performance of the proposed method, we installed PV panels coated with three different materials. Subsequently, 60 infrared (IR) thermal and visible images were acquired using an IR thermal imaging camera mounted on the drone. When more than 16 out of 60 results were accumulated, the highest performance was achieved with an F1 score of 0.7178. This case study demonstrated that even low-resolution thermal images can be acquired continuously to detect areas with small temperature differences without applying machine learning, which requires a large database
Ceramics and defects: Infrared thermography and numerical simulations - A wide-ranging view for quantitative analysis
No full textThe feasibility of square-pulsed thermography nondestructive testing for the detection of defects in one ceramic material sample has been carried out by finite element (FE) analysis. In particular, a ceramic plate containing defects of different diameters, depths, locations, nature, and shapes has been numerically investigated by means of Comsol® Multiphysics computer program, taking into account the results coming from both a MATLABTM script and the infrared thermography (IRT) technique. Indeed, the FE method simulates through a 3D model the heat transfer process induced into the ceramic material by two halogen lamps that have been applied in order to provoke an optimum thermal stress. Moreover, further defects like cracks arose beneath the surface of the plate due to the shrinkage process, have been discovered, and contrasted using a non-usual segmentation algorithm that when correlated in the time to IRT data simulates the thermo-elastic effect. Following the non-direct procedure proposed, both the depth of each defect and its main dimensions have been retrieved into a satisfactory accuracy
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
Study on internal stress damage detection in long-distance oil and gas pipelines via weak magnetic method
No full textWeak magnetic stress detection is an important issue in oil–gas pipeline internal detection area. In order to verify the characteristics of weak magnetic stress internal detection signals, we built herein a magneto-mechanics equivalent model having a balanced magnetic field. First, we calculated the relationship between the stress and the weak magnetic signals; consequently, the analysis propagation laws of the weak magnetic signals with non-magnetic saturation were pointed out. Finally, the theoretical model was validated by a systematic experimental research. The analytical results show that a one-to-one linear link between the weak magnetic signals and the stress concentration is clear. Instead, the change of the weak magnetic signals with the liftoff is nonlinear, therefore we are proposing the Boltzmann liftoff correction factor whose degree of adaptability of the equivalent model can reach the value of 94%. It is possible to note that when the liftoff is in the approximate linear stage, the relevance ratio and the recognition rate of the magneto-mechanics curve show a high-quality. This conclusion is important in the engineering field for the set of the liftoff
The thermophysical behaviour of cork supports doped with an innovative thermal insulation and protective coating: A numerical analysis based on in situ experimental data
No full textIn this work, the thermal potentialities of insulation panels made of cork have been explored by means of a numerical approach based on experimental data. A comparative analysis between the panel in unaltered state, and then covered with an innovative shield coating (COIB 250®) was carried out. In addition, a defect simulating an inner detachment of the panel was fabricated to understand its behaviour during a daily solar thermal load. The site was selected ad hoc to avoid any shadow cast effect on the panel itself and any conduction phenomenon from the surrounding area. The external floor on which the panel was mounted was completely isolated from the soil. Two similar days with clear sky conditions were selected, real meteorological data recorded by a weather station installed near the inspected site and data deriving from a NASA software were used respectively for the ambient temperature and for the solar radiation, in order to provide a solid discussion of the findings. Results show how a cork panel, usually employed in civil engineering as an insulation system, may benefit a lot of a shield coating. The latter product tends also to minimize the impact of a subsurface detachment during the thermal conduction via heat transfer; this behaviour will be in-depth clarified in this work
Research on stress detection technology of long-distance pipeline applying non-magnetic saturation
No full textIn order to study the stress detection method on long-distance oil and gas pipeline, the distribution characteristics of the surface remanence signals in the stress concentration regions must be known. They were studied by using the magnetic domain model in the non magnetic saturation state. The finite element method was used herein with the aim to analyse the static and mechanical characteristics of a ferromagnetic specimen. The variation law of remanence signal in stress concentration regions was simulated. The results show that a residue signal in the stress concentration region exists. In addition, a one-to-one correspondence in the non-magnetic saturation environment is evident. In the case of magnetic saturation, the remanence signal of the stress concentration region is covered and the signal cannot be recognised
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
Improving the detection of thermal bridges in buildings via on-site infrared thermography: The potentialities of innovative mathematical tools
No full textThe detection of thermal bridges in buildings is one of the key points to be taken into account in energy saving procedures during refurbishment works. Passive infrared thermography (IRT) has been applied for years to detect thermal bridges by referring to the International Organization for Standardization (ISO) 6781:1983. However, the successfulness of this norm is strongly affected by the detection accuracy of the thermal imprint produced on the facade by a conductive material called as “defect” in this work. The drop shadow effect, also produced by the surrounding environment on the facade under inspection, plays indeed an important role during the defect evaluation procedure since it can mask/modify the natural thermal evolution due to diffusion. Many real-life signals acting in the space physics domain exhibit variations across different temporal scales. This work presents an application of a new multiscale data analysis method, the Iterative Filtering (IF), which allows to describe the multiscale nature of an electromagnetic signal working in the long-wave infrared (LWIR) region. IF appears to be a promising method minimizing the influence of the shadows projected on the facade under inspection; subsequently, it allows the optimization of the detection of thermal bridges via sparse principal component thermography (SPCT) technique. The latter inherits the advantages of PCT allowing more flexibility by introducing a penalization term. Here is shown how the accuracy of the defect detection increases after the application of the IF mathematical procedure. Results are discussed on the basis of a couple of case studies referring to dissimilar buildings. Finally, a signal-to-noise-ratio (SNR) comparison with raw data is added to the discussion of the results
Influence of insulation defects on the thermal performance of walls. An experimental and numerical investigation
No full textThe addition of insulating layers on vertical walls of buildings is a common practice for providing a higher
thermal insulation of the envelope. Workmanship defects, however, might influence the effectiveness of such
insulation strategy. Damaged materials, incorrect installation, use of aged or weathered materials might alter the
capability of reducing heat transfer through the envelope, whether vertical or sloped. In this work, drawbacks
caused by the wrong installation of insulating material and by damaged material are assessed. A specimen wall
was investigated by experimental and numerical approaches, the latter carried out by using COMSOL
Multiphysics®. Results are compared and discussed
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