Special Issue "Novel Ideas for Infrared Thermography also Applied in Integrated Approaches"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 January 2018).

Special Issue Editors

Dr. Stefano Sfarra
Website
Guest Editor
Department of Industrial and Information Engineering and Economics, University of L’Aquila, L'Aquila, Italy
Interests: Infrared thermography; image processing; terahertz; ultrasonic testing; heat transfer; innovative materials; energy saving; cultural heritage; modelling
Special Issues and Collections in MDPI journals
Prof. Dr. Dario Ambrosini
Website
Co-Guest Editor
Las.E.R. Laboratory, Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale E. Pontieri no. 1, Roio Poggio—L’Aquila (AQ), Italy
Interests: diagnostics of cultural heritage; optical metrology; infrared imaging; thermography; microclimate evaluation

Special Issue Information

Dear Colleagues,

This Special Issue is devoted to the application of the infrared thermography (IRT) method in various research fields. However, taking into account that a validation of a supposition is usually realized via a cross-check, the use of combined approaches are also welcomed. In any case, the authors should demonstrate that the part of IRT is predominant in their works, and it is direct towards the implementation of new ideas. In our humble opinion, the participation of leading scientists is really important to guide the reader and new users towards a world seen at infrared. In this way, it will be possible to see the unseen, i.e., detect anomalies without contact, otherwise indiscernible to the naked eye. This can be useful in any process temperature-dependent linked to the civil, mechanical, biomedical, aeronautical, aerospace engineering, as well as to the artistic and architectural heritage, which are the sectors at the base of this Special Issue. Particularly welcome will be works that validate, at the experimental level, preliminary numerical simulations, while mathematical explanations should forerun new processing of thermal images. In situ applications are considered on the same level as laboratory measurements, although we imagine that case studies will not be the majority of the published papers. The message that should leave your mark on, with respect to the future generations of diagnosticians, is based on IRT as a non-destructive, non-invasive, and non-intrusive method useful to analyze thermal responses coming from humans, materials, and processes.

Dr. Stefano Sfarra
Prof. Dr. Dario Ambrosini
Guest Editors

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Keywords

  • Infrared thermography

  • Non-destructive testing

  • Advanced image processing

  • Defect detection

  • Heat transfer

  • Measurement uncertainty

  • Thermographic numerical simulations

  • Infrared vision

  • Defect depth retrieval

  • Qualitative and quantitative analyses

Published Papers (19 papers)

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Research

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Open AccessFeature PaperArticle
Extraction of Independent Structural Images for Principal Component Thermography
Appl. Sci. 2018, 8(3), 459; https://doi.org/10.3390/app8030459 - 17 Mar 2018
Cited by 4
Abstract
Thermography is a powerful tool for non-destructive testing of a wide range of materials. Thermography has a number of approaches differing in both experiment setup and the way the collected data are processed. Among such approaches is the Principal Component Thermography (PCT) method, [...] Read more.
Thermography is a powerful tool for non-destructive testing of a wide range of materials. Thermography has a number of approaches differing in both experiment setup and the way the collected data are processed. Among such approaches is the Principal Component Thermography (PCT) method, which is based on the statistical processing of raw thermal images collected by thermal camera. The processed images (principal components or empirical orthogonal functions) form an orthonormal basis, and often look like a superposition of all possible structural features found in the object under inspection—i.e., surface heating non-uniformity, internal defects and material structure. At the same time, from practical point of view it is desirable to have images representing independent structural features. The work presented in this paper proposes an approach for separation of independent image patterns (archetypes) from a set of principal component images. The approach is demonstrated in the application of inspection of composite materials as well as the non-invasive analysis of works of art. Full article
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Open AccessFeature PaperArticle
Depth Retrieval Procedures in Pulsed Thermography: Remarks in Time and Frequency Domain Analyses
Appl. Sci. 2018, 8(3), 409; https://doi.org/10.3390/app8030409 - 09 Mar 2018
Cited by 7
Abstract
In the present study, a Carbon Fibre Reinforced Polymer (CFRP) sample of trapezoid shape, consisting of internal artificial delaminations of various sizes and depth locations, is investigated by means of optical pulsed thermography for the retrieval of quantitative depth information. The main objectives [...] Read more.
In the present study, a Carbon Fibre Reinforced Polymer (CFRP) sample of trapezoid shape, consisting of internal artificial delaminations of various sizes and depth locations, is investigated by means of optical pulsed thermography for the retrieval of quantitative depth information. The main objectives of this work are to evaluate the produced depth estimation accuracy from two contrast-based depth inversion procedures as well as to correlate the acquired results with characteristics such as the location and size of the detected features and with analysis parameters such as the selection of the sound area. Quantitative analysis is performed in both the temporal and frequency domains, utilising, respectively, the informative parameters of thermal contrast peak slope time and blind frequency. The two depth retrieval procedures are applied for the depth estimation of features ranging in size from 3 mm to 15 mm and in depth from 0.2 mm to 1 mm. The results of the present study showed that the two different analyses provided efficient depth estimations, with frequency domain analysis presenting a greater accuracy. Nevertheless, predicting errors were observed in both cases and the factors responsible for these errors are defined and discussed. Full article
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Open AccessArticle
Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography
Appl. Sci. 2018, 8(3), 380; https://doi.org/10.3390/app8030380 - 06 Mar 2018
Cited by 6
Abstract
This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for [...] Read more.
This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200–800 °C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 °C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further. Full article
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Open AccessFeature PaperArticle
From Thermal Inspection to Updating a Numerical Model of a Race Bicycle: Comparison with Structural Dynamics Approach
Appl. Sci. 2018, 8(2), 307; https://doi.org/10.3390/app8020307 - 21 Feb 2018
Cited by 2
Abstract
Carbon fiber bicycle frames are complex-shaped structures and are prone to delaminations and difficult to inspect. The use of finite element model updating is common in structural dynamics but not so common in active thermography inspection. However, there are many advantages to using [...] Read more.
Carbon fiber bicycle frames are complex-shaped structures and are prone to delaminations and difficult to inspect. The use of finite element model updating is common in structural dynamics but not so common in active thermography inspection. However, there are many advantages to using thermography when inspecting bicycle frames. These include the fact that the inspection can be performed in situ, can cover large areas, and is a quantitative method. In this paper, a numerical model of a bicycle frame will be updated and optimized by the surface temperature distribution captured with pulsed thermography. These results will be compared and benchmarked against frequency response function (FRF) measurement data as a reference. The chosen temperature decay measurements to be used as reference data will be of key importance. The goal of this manuscript is to compare both measurement results and model predictabilities after performing finite element model updating with respect to accuracy and speed. Full article
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Open AccessFeature PaperArticle
Infrared Thermography for Inline Monitoring of Glass/Epoxy under Impact and Quasi-Static Bending
Appl. Sci. 2018, 8(2), 301; https://doi.org/10.3390/app8020301 - 19 Feb 2018
Cited by 6
Abstract
Abstract: In this work, glass/epoxy has been chosen as case study as it represents the most-used composite material, being appropriate for a vast variety of applications and a reasonable performance/cost compromise. This material has already been inline impact-monitored with infrared thermography, mostly for [...] Read more.
Abstract: In this work, glass/epoxy has been chosen as case study as it represents the most-used composite material, being appropriate for a vast variety of applications and a reasonable performance/cost compromise. This material has already been inline impact-monitored with infrared thermography, mostly for feasibility tests. Now, impact tests are repeated by changing some parameters and by inline monitoring simultaneously with two different infrared cameras to share a high frame rate and spatial resolution at the same time. In addition, glass/epoxy is monitored also while it is under quasi-static bending tests. The aim of this paper is to show what it is possible to learn from thermal signatures developing in the same material when it is either impacted or under quasi-static bending. Full article
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Open AccessFeature PaperArticle
Multispectral Applications of Infrared Thermography in the Diagnosis and Protection of Built Cultural Heritage
Appl. Sci. 2018, 8(2), 284; https://doi.org/10.3390/app8020284 - 13 Feb 2018
Cited by 12
Abstract
Infrared thermography (IRT) is a powerful non contact imaging technique, appropriate for the protection of cultural heritage. The National Technical University of Athens research team (scientist responsible: A. Moropoulou), started to use this technique in the early 1990s, in all stages of a [...] Read more.
Infrared thermography (IRT) is a powerful non contact imaging technique, appropriate for the protection of cultural heritage. The National Technical University of Athens research team (scientist responsible: A. Moropoulou), started to use this technique in the early 1990s, in all stages of a conservation project, from decay diagnosis to assessment of conservation interventions and monitoring. The monuments investigated with the aid of this technique belonged to different historical periods, dating from antiquity to modern times. The main products of IRT, thermal maps of surfaces, were evaluated and exploited, based on the demands, special needs and requirements of each application. Additionally, in laboratory scale, many IRT measurements were performed in order to investigate the applicability and limitations of this technique for measuring a material’s thermophysical properties. All these data and accumulated knowledge and experience contributed to a set of recommendations, which enabled us to compile a protocol for the application of this technique in a more standardized way. Moreover, the added value of this practice permitted the successful application and integration of this technique in large-scale conservation projects, such as the Pythian Apollo Temple in Acropolis of Rhodes, during the diagnostic study phase, or at the Holy Aedicule, of the Holy Selphuchre in Jerusalem, during the rehabilitation works. Full article
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Open AccessArticle
Induction Thermography for Surface Crack Detection and Depth Determination
Appl. Sci. 2018, 8(2), 257; https://doi.org/10.3390/app8020257 - 09 Feb 2018
Cited by 16
Abstract
In the last few years, induction thermography has been established as a non-destructive testing method for localizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse, and the infrared camera records—during and after the [...] Read more.
In the last few years, induction thermography has been established as a non-destructive testing method for localizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse, and the infrared camera records—during and after the heating pulse—the temperature distribution at the surface. Transforming the temporal temperature development for each pixel to phase information makes not only highly reliable detection of the cracks possible but also allows an estimation of its depth. Finite element simulations were carried out to investigate how the phase contrast depends on parameters such as excitation frequency, pulse duration, material parameters, crack depth, and inclination angle of the crack. From these results, generalized functions for the dependency of the phase difference on all these parameters were derived. These functions can be used as an excellent guideline as to how measurement parameters should be optimized for a given material to be able to detect cracks and estimate their depth. Several experiments on different samples were also carried out, and the results compared with the simulations showed very good agreement. Full article
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Open AccessArticle
Multivariate Analysis of Transient State Infrared Images in Production Line Quality Control Systems
Appl. Sci. 2018, 8(2), 250; https://doi.org/10.3390/app8020250 - 07 Feb 2018
Cited by 3
Abstract
Manufacturers would like to increase production volumes while preserving the high quality of their products. The long testing times can cause a bottleneck of production processes especially taking into account the observed tendency for testing all produced devices. The main aim of this [...] Read more.
Manufacturers would like to increase production volumes while preserving the high quality of their products. The long testing times can cause a bottleneck of production processes especially taking into account the observed tendency for testing all produced devices. The main aim of this work consists in the analysis of time changes of features extracted from thermal images using the multivariate approach. The paper shows that if the principal component analysis (PCA), belonging to multivariate methods, is applied for quality control based on infrared images, then the minimum testing times can be estimated. In order to draw the final conclusions regarding testing times and, what is also very important, which principal components should be selected for classification, a detailed temporal analysis for an exemplary production line has been carried out. The future impact of the results includes higher productivity and cost-effectiveness due to the determination of an optimal decision time in production line quality control systems using the proposed approach. Full article
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Open AccessFeature PaperArticle
Thermographic Non-Destructive Evaluation for Natural Fiber-Reinforced Composite Laminates
Appl. Sci. 2018, 8(2), 240; https://doi.org/10.3390/app8020240 - 05 Feb 2018
Cited by 10
Abstract
Natural fibers, including mineral and plant fibers, are increasingly used for polymer composite materials due to their low environmental impact. In this paper, thermographic non-destructive inspection techniques were used to evaluate and characterize basalt, jute/hemp and bagasse fibers composite panels. Different defects were [...] Read more.
Natural fibers, including mineral and plant fibers, are increasingly used for polymer composite materials due to their low environmental impact. In this paper, thermographic non-destructive inspection techniques were used to evaluate and characterize basalt, jute/hemp and bagasse fibers composite panels. Different defects were analyzed in terms of impact damage, delaminations and resin abnormalities. Of particular interest, homogeneous particleboards of sugarcane bagasse, a new plant fiber material, were studied. Pulsed phase thermography and principal component thermography were used as the post-processing methods. In addition, ultrasonic C-scan and continuous wave terahertz imaging were also carried out on the mineral fiber laminates for comparative purposes. Finally, an analytical comparison of different methods was given. Full article
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Open AccessFeature PaperArticle
Evaluating the Quality of Reinforced Concrete Electric Railway Poles by Thermal Nondestructive Testing
Appl. Sci. 2018, 8(2), 222; https://doi.org/10.3390/app8020222 - 01 Feb 2018
Cited by 4
Abstract
Thermal nondestructive testing can be used to inspect reinforced concrete supports that are widely used in various industries. Corrosion damage is a typical defect found in these supports. Corrosion usually starts as a separation between the concrete and the steel rebar. Damage is [...] Read more.
Thermal nondestructive testing can be used to inspect reinforced concrete supports that are widely used in various industries. Corrosion damage is a typical defect found in these supports. Corrosion usually starts as a separation between the concrete and the steel rebar. Damage is exacerbated by pressure that is caused by the formation of corrosion products. The most logical method for using IR to detect corrosion or a disbond would be to heat up the rebar by resistive or inductive heating. In both cases, monitoring the dynamic temperature distributions on the pole allows for the evaluation of reinforcement quality. The thermal properties of steel, concrete, air, and corrosion products differ greatly. The magnitude of temperature anomalies and their behavior over time depend on the presence of corrosion products, air gaps, and the quality of contact between rebar and concrete. Full article
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Open AccessFeature PaperArticle
Numerical Model and Experimental Analysis of the Thermal Behavior of Electric Radiant Heating Panels
Appl. Sci. 2018, 8(2), 206; https://doi.org/10.3390/app8020206 - 30 Jan 2018
Cited by 5
Abstract
Electric radiant heating panels are frequently selected during the design phase of residential and industrial heating systems, especially for retrofit of existing buildings, as an alternative to other common heating systems, such as radiators or air conditioners. The possibility of saving living and [...] Read more.
Electric radiant heating panels are frequently selected during the design phase of residential and industrial heating systems, especially for retrofit of existing buildings, as an alternative to other common heating systems, such as radiators or air conditioners. The possibility of saving living and working space and the ease of installation are the main advantages of electric radiant solutions. This paper investigates the thermal performance of a typical electric radiant panel. A climatic room was equipped with temperature sensors and heat flow meters to perform a steady state experimental analysis. For the dynamic behavior, a mathematical model was created and compared to a thermographic measurement procedure. The results showed for the steady state an efficiency of energy transformation close to one, while in a transient thermal regime the time constant to reach the steady state condition was slightly faster than the typical ones of hydronic systems. Full article
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Open AccessArticle
An Examination of Thermal Features’ Relevance in the Task of Battery-Fault Detection
Appl. Sci. 2018, 8(2), 182; https://doi.org/10.3390/app8020182 - 26 Jan 2018
Cited by 8
Abstract
Uninterruptible power supplies (UPS), represented by lead-acid batteries, play an important role in various kinds of industries. They protect industrial technologies from being damaged by dangerous interruptions of an electric power supply. Advanced UPS monitoring performed by a complex battery management system (BMS) [...] Read more.
Uninterruptible power supplies (UPS), represented by lead-acid batteries, play an important role in various kinds of industries. They protect industrial technologies from being damaged by dangerous interruptions of an electric power supply. Advanced UPS monitoring performed by a complex battery management system (BMS) prevents the UPS from sustaining more serious damage due to its timely and accurate battery-fault detection based on voltage metering. This technique is very advanced and precise but also very expensive on a long-term basis. This article describes an experiment applying infrared thermographic measurements during a long term monitoring and fault detection in UPS. The assumption that the battery overheat implies its damaged state is the leading factor of our experiments. They are based on real measured data on various UPS battery sets and several statistical examinations confirming the high relevancy of the thermal features with mostly over 90% detection accuracy. Such a model can be used as a supplement for lead-acid battery based UPS monitoring to ensure their higher reliability under significantly lower maintenance costs. Full article
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Open AccessArticle
IR Reflectography and Active Thermography on Artworks: The Added Value of the 1.5–3 µm Band
Appl. Sci. 2018, 8(1), 50; https://doi.org/10.3390/app8010050 - 01 Jan 2018
Cited by 9
Abstract
Infrared Radiation (IR) artwork inspection is typically performed through active thermography and reflectography with different setups and cameras. While Infrared Radiation Reflectography (IRR) is an established technique in the museum field, exploiting mainly the IR-A (0.7–1.4 µm) band to probe for hidden layers [...] Read more.
Infrared Radiation (IR) artwork inspection is typically performed through active thermography and reflectography with different setups and cameras. While Infrared Radiation Reflectography (IRR) is an established technique in the museum field, exploiting mainly the IR-A (0.7–1.4 µm) band to probe for hidden layers and modifications within the paint stratigraphy system, active thermography operating in the IR-C range (3–5 μ m) is less frequently employed with the aim to visualize structural defects and features deeper inside the build-up. In this work, we assess to which extent the less investigated IR-B band (1.5–3 μ m) can combine the information obtained from both setups. The application of IR-B systems is relatively rare as there are only a limited amount of commercial systems available due to the technical complexity of the lens coating. This is mainly added as a so-called broadband option on regular Mid-wave infrared radiation (MWIR) (IR-C’/3–5 μ m) cameras to increase sensitivity for high temperature applications in industry. In particular, four objects were studied in both reflectographic and thermographic mode in the IR-B spectral range and their results benchmarked with IR-A and IR-C images. For multispectral application, a single benchmark is made with macroscopic reflection mode Fourier transform infrared (MA-rFTIR) results. IR-B proved valuable for visualisation of underdrawings, pencil marks, canvas fibres and wooden grain structures and potential pathways for additional applications such as pigment identification in multispectral mode or characterization of the support (panels, canvas) are indicated. Full article
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Open AccessArticle
An Efficient Numerical Approach for Field Infrared Smoke Transmittance Based on Grayscale Images
Appl. Sci. 2018, 8(1), 40; https://doi.org/10.3390/app8010040 - 29 Dec 2017
Cited by 3
Abstract
Infrared smoke screen has been playing an important role in electro-optical countermeasures on the battlefield. Smoke transmittance is one of the most important parameters which can evaluate the obscuration performance of smoke. In this paper, an efficient numerical approach for field infrared smoke [...] Read more.
Infrared smoke screen has been playing an important role in electro-optical countermeasures on the battlefield. Smoke transmittance is one of the most important parameters which can evaluate the obscuration performance of smoke. In this paper, an efficient numerical approach for field infrared smoke transmittance based on grayscale images is presented. Firstly, a field trial experimental setup is introduced. Then a grayscale smoke transmittance mathematical model is deduced and built. In addition, an image processing algorithm is used to extract the gray values of certain pixel points from grayscale images, and the positions of the selected points are discussed. Lastly, a field trial sample calculation is included to illustrate the procedure of the proposed method. The results prove to be of enough precision for engineering applications, and the method has greatly simplified the field trial process, thus improving efficiency. Full article
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Open AccessFeature PaperArticle
Non-Destructive Infrared Evaluation of Thermo-Physical Parameters in Bamboo Specimens
Appl. Sci. 2017, 7(12), 1253; https://doi.org/10.3390/app7121253 - 02 Dec 2017
Cited by 6
Abstract
The estimation of heat conduction properties has considerable importance in the characterization of bamboo with respect to its potential use as an alternative construction material. Even though traditional methods such as hot plates have successfully measured thermal parameters, like thermal diffusivity and conductivity [...] Read more.
The estimation of heat conduction properties has considerable importance in the characterization of bamboo with respect to its potential use as an alternative construction material. Even though traditional methods such as hot plates have successfully measured thermal parameters, like thermal diffusivity and conductivity in bamboo samples, it is still necessary to transform the cylindrical bamboo specimen into a piece with special geometry and size. This requirement makes this method impractical in applications where several bamboo specimens need to be measured in their original cylindrical shape. This paper presents the estimation of thermo-physical parameters k and ρ c p in Guadua angustifolia kunth (Guadua a.k.) bamboo through nonlinear least square optimization and infrared thermography. A sensitivity analysis was carried out to determine how the temperature on the bamboo surface is affected by changes in the convection coefficient h, thermal conductivity k, and volumetric heat capacity ρ c p . In spite of the nonlinearity and high correlation in the parameters of the inverse heat conduction problem (IHCP), the estimation of such parameters is robust and consistent with those reported in the literature. Full article
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Open AccessArticle
A Thermographic Measurement Approach to Assess Supercapacitor Electrical Performances
Appl. Sci. 2017, 7(12), 1247; https://doi.org/10.3390/app7121247 - 01 Dec 2017
Cited by 5
Abstract
This paper describes a proposal for the qualitative assessment of condition of supercapacitors based on the conducted thermographic measurements. The presented measurement stand was accompanied by the concept of methodology of performing tests. Necessary conditions, which were needed to minimize the influence of [...] Read more.
This paper describes a proposal for the qualitative assessment of condition of supercapacitors based on the conducted thermographic measurements. The presented measurement stand was accompanied by the concept of methodology of performing tests. Necessary conditions, which were needed to minimize the influence of disturbing factors on the performance of thermal imaging measurements, were also indicated. Mentioned factors resulted from both: the hardware limitations and from the necessity to prepare samples. The algorithm that was used to determine the basic parameters for assessment has been presented. The article suggests to use additional factors that may facilitate the analysis of obtained results. Measuring the usefulness of the proposed methodology was tested on commercial samples of supercapacitors. All of the tests were taken in conjunction with the classical methods based on capacitance (C) and equivalent series resistance (ESR) measurements, which were also presented in the paper. Selected results presenting the observed changes occurring in both: basic parameters of supercapacitors and accompanying fluctuations of thermal fields, along with analysis, were shown. The observed limitations of the proposed assessment method and the suggestions for its development were also described. Full article
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Open AccessArticle
A Non-Reference Image Denoising Method for Infrared Thermal Image Based on Enhanced Dual-Tree Complex Wavelet Optimized by Fruit Fly Algorithm and Bilateral Filter
Appl. Sci. 2017, 7(11), 1190; https://doi.org/10.3390/app7111190 - 22 Nov 2017
Cited by 6
Abstract
To eliminate the noise of infrared thermal image without reference and noise model, an improved dual-tree complex wavelet transform (DTCWT), optimized by an improved fruit-fly optimization algorithm (IFOA) and bilateral filter (BF), is proposed in this paper. Firstly, the noisy image is transformed [...] Read more.
To eliminate the noise of infrared thermal image without reference and noise model, an improved dual-tree complex wavelet transform (DTCWT), optimized by an improved fruit-fly optimization algorithm (IFOA) and bilateral filter (BF), is proposed in this paper. Firstly, the noisy image is transformed by DTCWT, and the noise variance threshold is optimized by the IFOA, which is enhanced through a fly step range with inertia weight. Then, the denoised image will be re-processed using bilateral filter to improve the denoising performance and enhance the edge information. In the experiment, the proposed method is applied to eliminate both addictive noise and multiplicative noise, and the denoising results are compared with other representative methods, such as DTCWT, block-matching and 3D filtering (BM3D), median filter, wiener filter, wavelet decomposition filter (WDF) and bilateral filter. Moreover, the proposed method is applied as pre-processing utilization for infrared thermal images in a coal mining working face. Full article
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Open AccessArticle
Infrared Small Moving Target Detection via Saliency Histogram and Geometrical Invariability
Appl. Sci. 2017, 7(6), 569; https://doi.org/10.3390/app7060569 - 01 Jun 2017
Cited by 19
Abstract
In order to detect both bright and dark small moving targets effectively in infrared (IR) video sequences, a saliency histogram and geometrical invariability based method is presented in this paper. First, a saliency map that roughly highlights the salient regions of the original [...] Read more.
In order to detect both bright and dark small moving targets effectively in infrared (IR) video sequences, a saliency histogram and geometrical invariability based method is presented in this paper. First, a saliency map that roughly highlights the salient regions of the original image is obtained by tuning its amplitude spectrum in the frequency domain. Then, a saliency histogram is constructed by means of averaging the accumulated saliency value of each gray level in the map, through which bins corresponding to bright target and dark target are assigned with large values in the histogram. Next, single-frame detection of candidate targets is accomplished by a binarized segmentation using an adaptive threshold, and their centroid coordinates with sub-pixel accuracy are calculated through a connected components labeling method as well as a gray-weighted criterion. Finally, considering the motion characteristics in consecutive frames, an inter-frame false alarm suppression method based on geometrical invariability is developed to improve the precision rate further. Quantitative analyses demonstrate the detecting precision of this proposed approach can be up to 97% and Receiver Operating Characteristic (ROC) curves further verify our method outperforms other state-of-the-arts methods in both detection rate and false alarm rate. Full article
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Review

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Open AccessReview
Pulsed Thermography Applied to the Study of Cultural Heritage
Appl. Sci. 2017, 7(10), 1010; https://doi.org/10.3390/app7101010 - 29 Sep 2017
Cited by 23
Abstract
In this paper, an overview of the recent applications of pulsed infrared thermography is presented. Pulsed infrared thermography, which provides stratigraphic information by analyzing the heat diffusion process within the sample after a thermal perturbation, is applied to the investigation of different kinds [...] Read more.
In this paper, an overview of the recent applications of pulsed infrared thermography is presented. Pulsed infrared thermography, which provides stratigraphic information by analyzing the heat diffusion process within the sample after a thermal perturbation, is applied to the investigation of different kinds of cultural heritage artefacts. In particular, it is used to analyze repairs, decorative elements, and casting faults on bronzes, to detect texts hidden or damaged in ancient books/documents, and to characterize paint decorations. Moreover, the integration of pulsed infrared thermography and three-dimensional shape recording methods is proposed in order to provide a three-dimensional representation of the thermographic results. Finally, it is shown how the obtained thermographic results may be crucial from the historical and artistic points of view for understanding the modus operandi of a specific artist and/or of a workshop and for reconstructing the manufacturing process of the analyzed artefacts. Full article
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