Thermal Footprint Research Articles

Investigation of the plastic zone around the crack tip in small-scale pure Titanium specimens by means of Thermal Signal Analysis and Digital Image Correlation

The local plasticity characterizing the area around the crack tip affects the elastic strain field area due to the boundary interaction between the two zones. Its effects on the SIF and on the Paris’ Law are known, hence it must be considered in the crack growth monitoring and the fatigue limit estimation. Among the different approaches developed, those focusing their attention on the interaction between the elastic stress field and the plastic area seems to be more promising in the evaluation of the crack growth behaviour. In this work, an experimental approach was adopted to identify the plastic zone around the crack. In particular the Thermal Signal Analysis was employed and the thermal footprint was compared with shape and size of the plastic zone predicted through the application of Digital Image Correlation (DIC) in combination with two theoretical models: Westergaard’s model for the stress distribution around the crack tip and the more recent Christopher–James–Patterson (CJP) model

Design and first results of a retractable 1D-CFC beam target for BATMAN upgrade

BATMAN Upgrade (BUG) is a test facility for the production of negative ion beams from an RF driven plasma ion source devoted to supporting the development of the ITER Neutral Beam Injection (NBI). BUG consists of the IPP RF prototype source and a multi-aperture grid system corresponding roughly to a beamlet group of the ITER NBI grid system, i.e. an arrangement of 14 (vertical) ×5 (horizontal) Ø14 mm apertures, meaning the ion beam is comprised of 70 individual beamlets. The beams can be extracted with up to 10 kV and accelerated up to a total voltage of 45 kV for up to 10 s (steady state operation is underway). One of the goals of BUG is a detailed study of the ion beam optics. So far, the permanently installed beam diagnostic consisted of several lines of sight of Beam Emission Spectroscopy (BES) at two different positions and thermocouple measurements on the beam dump calorimeter. Resolving the divergence and deflection of single beamlets is technically exceptionally difficult with the existing diagnostic tools, therefore, a beam target made out of a one-directional carbon fiber composite material (1D-CFC) with dimensions 376×142×20 mm³ has been installed at a distance of 851 mm from the exit of the grid system. The thermal footprints of the beamlets are observed from the back side via infrared imaging with a high spatial resolution (<0.7 mm/pixel) that allows characterization of the beamlets at low divergence. The target can be rotated out of the beam to make it compatible with long pulses and the forthcoming steady state operation. The safety analysis of the target operation for different operational scenarios is presented together with an energy-based interlock. Finally, the accuracy of estimating the shape of the heat flux on the front of the target from the temperature profile at the back is assessed, based on FEM simulations of a single beamlet.

Integrated Process Control‐Power Management System Design and Flight Performance Tests for Fuel Cell Powered Mini‐Unmanned Aerial Vehicle

Unmanned aerial vehicles (UAVs) powered by electric motors are in an advantageous position because of their properties, such as low noise and thermal footprint, high efficiency, and zero emissions. Lithium‐based batteries have restrictive factors for flight duration due to its low energy density, difficult, and expensive charging methods. It is aimed to extend flight duration of a battery powered mini‐type UAV with a combined system, which includes a 200 W polymer electrolyte membrane (PEM) fuel cell, a hydrogen generation system based on in situ hydrolysis of sodium borohydride, a hybrid power management system consisting of fuel cell and battery, and an embedded control system. It is observed that a fuel cell‐based energy system is able to extend endurance by twofolds compared with an only battery powered system. This is the first study in the literature that investigates the flight duration of UAVs in battery versus fuel cell according to actual flight data.

Decreasing Water Footprint of Electricity and Heat by Extensive Green Roofs: Case of Southern Italy

Electrical and energy production have a noticeable water footprint, and buildings′ share of global energy consumption is about 40%. This study presents a comprehensive experimental analysis of different thermal impacts and water consumption of green roofs in a Mediterranean climate. The study aims to investigate the use of water directly for green roofs and reduce the water footprint of energy in summer and winter due to its thermal impacts. The measurements were carried out for an extensive green roof with an area of 55 m2 and a thickness of 22 cm, and direct water consumption by a green roof and direct and indirect water consumption by cooling and heating systems were analyzed. According to the analysis, in summer, the maximum roof temperature on a conventional roof was 72 °C, while under the green roof it was 30.3 °C. In winter, the minimum roof temperature on a conventional roof was −8.6 °C, while under the green roof it was 7.4 °C. These results show that green roofs affect energy consumption in summer and winter, and the corresponding thermal requirements for the building have a water footprint regarding energy production. In summer, the thermal reduction in the water footprint by a green roof was 48 m3 if an evaporative air conditioner is used and 8.9 m3 for a compression air conditioner, whereas the water consumed in the green roof was 8.2 m3. Therefore, using water directly in the green roof would reduce the energy consumption in buildings, and thus less water has to be used in power plants to provide the same thermal impact. In winter, green roofs′ water consumption was higher than the thermal water footprint; however, there is no need to irrigate the green roof as the water consumed comes from precipitation. This experimental analysis determines that in the Mediterranean climate, green roofs allow the achievement of the same thermal conditions for buildings in both summer and winter, with a reduction in water consumption.

Using Thermal Springs to Quantify Deep Groundwater Flow and Its Thermal Footprint in the Alps and a Comparison With North American Orogens

AbstractThe extent of deep groundwater flow in mountain belts and its thermal effects are uncertain. Here, we use a new database of discharge, temperature, and composition of thermal springs in the Alps to estimate the extent of deep groundwater flow and its contribution to the groundwater and heat budget. The results indicate that thermal springs are fed exclusively by meteoric water and make up 0.1% of the total groundwater budget. Spring water circulates on average to a depth of at least 2 km. The net heat extracted from the subsurface equals 1% of the background heat flow, which equals an average thermal footprint of 7 km2. Cooling by downward flow and heating by upward flow are three and two times higher than the net heat flow, respectively. Comparison with North American orogens shows that hydrothermal activity is higher in areas with high relief or areas under extension.

Monopolar Radiofrequency Energy Delivered by a Conductive Endovascular Basket or Guidewire Leads to Thermal Occlusion in a Swine Model

PurposeTo assess the feasibility of inducing vascular occlusion by application of radiofrequency (RF) energy via conductive endovascular wires or baskets. Materials and MethodsA retrievable nitinol basket and stainless steel guidewire with a platinum tip were evaluated as conductors for endovascular application of RF energy. Tissue-mimicking thermochromic gel phantoms that change color with heating were cast with 2-, 5-, and 7-mm-diameter lumens and filled with 37 oC saline. After ablation, the phantoms were sectioned, and the thermal footprints were evaluated. Six castrated male domestic swine underwent endovascular ablation using the basket in iliac arteries and guidewires in renal arteries. Post-procedural angiography was performed, and postmortem arterial segments were resected for histopathologic analysis. ResultsIn the phantom, the depth of thermal change in the 5- and 7-mm lumens averaged 6.3 and 6.0 mm along the basket, respectively, and in the 2- and 5-mm lumens, the depth of thermal change averaged 1.9 and 0.5 mm along the wire, respectively. In the swine, RF energy delivery led to angiographic occlusion at 12 of 13 sites. Thermal injury and occlusion were similar at the proximal, middle, and distal basket treatment zone, whereas injury and occlusion decreased from the proximal to the distal end of the 5-cm wire treatment zone. ConclusionsEndovascular delivery of RF energy via a conductive basket in medium-sized arteries or a guidewire in small arteries led to acute angiographic and histologic occlusion. The potential to induce stasis might be useful in settings where rapid occlusion is desirable.

Thermal dynamics of deposited firebrands using phosphor thermometry

A series of experiments were carried out to identify and better understand the thermal mechanisms which govern the ignition propensity of firebrands. This work leverages the temperature-sensitive phosphorescence of YAG:Dy to non-intrusively measure and spatially resolve firebrand contact temperature along a 6.1 cm diameter area. The highly coupled firebrand heat transfer problem is studied by depositing smoldering firebrands onto a flat inert substrate and subjecting them to flow speeds of (1.5 ± 0.15) m/s. The temporal evolution of the thermal footprint is described and analyzed. Quasi-steady peak contact temperatures ranged between 500 K and 850 K while brief peaks exceeding 1150 K were also observed. The large difference in contact temperatures alludes to the significance in factors such as firebrand-fuel contact resistance, firebrand geometry, firebrand-flow orientation, fuel type (density and heat of combustion), and mass. Furthermore, the findings shed light on secondary heating events associated with shifting of the firebrand contact area and/or fragmenting, which can impart peak net heat flux equivalent to 70 % of the initial deposition. Lastly, considering the sensitivity of ignition on temperature, the work provides a brief discussion on the presence of unimodal and bimodal contact temperature distributions.

Development of Thermal Principles for the Automation of the Thermographic Monitoring of Cultural Heritage.

The continuous deterioration of elements, with high patrimonial value over time, can only be mitigated or annulled through the application of techniques that facilitate the preventative detection of the possible agents of deterioration. InfraRed Thermography (IRT) is one of the most used techniques for this task. However, there are few IRT methodologies, which can automatically monitor the cultural heritage field, and are vitally important in eliminating the subjectivity in interpreting and accelerating the analysis process. In this work, a study is performed on a tessellatum layer of a mosaic to automatically: (i) Detect the first appearance of the thermal footprint of internal water, (ii) delimit the contours of the thermal footprint of internal water from its first appearance, and (iii) classify between harmful and non-harmful internal water. The study is based on the analysis of the temperature distribution of each thermal image. Five thermal images sequences are acquired during the simulation of different real situations, obtaining a set of promising results for the optimization of the thermographic inspection process, while discussing the following recommended steps to be taken in the study for future researches.

A Lattice-Tip Temperature-Controlled Radiofrequency Ablation Catheter for Wide Thermal Lesions: First-in-Human Experience With Atrial Fibrillation.

This study sought to evaluate the safety and acute performance of the lattice tip for the treatment of atrial flutter and fibrillation (AF). A novel catheter using an expandable lattice structure with a wide thermal footprint incorporating multiple surface thermocouples/mini-electrodes has been designed for high-resolution mapping and high-current, temperature-controlled radiofrequency ablation (RFA). Patients with typical right atrial flutter or AF were prospectively enrolled in a single-arm study at 3 centers. Patients with atrial flutter underwent cavotricuspid isthmus (CTI) ablation. Patients with paroxysmal AF underwent pulmonary vein isolation (PVI) and CTI if desired, and for patients with persistent AF, mitral isthmus and left atrial roof lines were also permitted. Mapping was performed with the lattice (Sphere-9) catheter and a novel compatible electroanatomic mapping system (Prism-1). RFA was performed in a point-by-point fashion (Tmax, 73°C to 80°C; range 2 to 7s). Patients were followed for 3months. A total of 71 patients underwent ablation: 65 PVI (38% with persistent AF) and 22 mitral isthmus, 24 roof, and 48 CTI lines. PVI was achieved in 64 of 65 (98.5%) by using the lattice alone and required a mean of 2.7 ± 0.70 RFA min. Mitral block was achieved in 100% by using 11.5 ± 10.7 applications and 1.0 ± 0.92 RFA min; only 1 patient required adjunctive epicardial coronary sinus ablation. Roof line and CTI block were achieved in 95.8% and 100% of patients, using 4.9 ± 1.9 and 5.9 ± 3.1 applications for 0.4 ± 0.16 and 0.5 ± 0.24 RFA min, respectively. At 3months, there were no deaths, strokes, tamponade, or atrioesophageal fistula. This first-in-human study demonstrated clinical feasibility and safety for rapid high-current, temperature-controlled point-by-point PVI and linear ablation.

Estimating Departure Time Using Thermal Camera and Heat Traces Tracking Technique.

Advancement in science and technology is playing an increasingly important role in solving difficult cases at present. Thermal cameras can help the police crack difficult cases by capturing the heat trace on the ground left by perpetrators, which cannot be spotted by the naked eye. Therefore, the purpose of this study is to establish a thermalfoot model using thermal imaging system to estimate the departure time. To this end, in the current work, we use a thermal camera to acquire the thermal sequence left on the floor, and convert it into the heat signal via image processing algorithm. We establish the model of thermalfoot print as we observe that the residual temperature would exponentially decrease with the departure time according to Newton’s Law of Cooling. The correlation coefficients of 107 thermalfoot models derived from the corresponding 107 heat signals are basically above 0.99. In a validation experiment, a residual analysis is conducted and the residuals between estimated departure time points and ground-truth times are almost within a certain range from −150 s to +150 s. The reverse accuracy of the thermalfoot model for estimating departure time at one-third, one-half, two-thirds, three-fourths, four-fifths, and five-sixths capture time points are 71.96%, 50.47%, 42.06%, 31.78%, 21.70%, and 11.21%, respectively. The results of comparison experiments with two subjective evaluation methods (subjective 1: we directly estimate the departure time according to obtained local curves; subjective 2: we utilize auxiliary means such as a ruler to estimate the departure time based on obtained local curves) further demonstrate the effectiveness of thermalfoot model for detecting the departure time inversely. Experimental results also demonstrated that the thermalfoot model has good performance on the departure time reversal within a short time window someone leaves, whereas it is probably only approximately 15% to accurately determine the departure time via thermalfoot model within a long time window someone leaves. The influence of outliers, ROI (Region of Interest) selection, ROI size, different capture time points and environment temperature on the performance of thermalfoot model on departure time reversal can be explored in the future work. Overall, the thermalfoot model can help the police solve crimes to some extent, which in turn brings more guarantees for people’s health, social security, and stability.

Challenges and sensitivities in the modelling of Fukushima Daiichi Unit 1 unfolding with MELCOR 2.2

The accident occurred in Japan on 11 March 2011 has revived the interest for the analysis of severe accidents. The scarce and sometimes unreliable data concerning boundary conditions, effectiveness of accident management measures and equipment performance, pose a tough challenge in modelling the accident scenarios.Throughout an analysis of the challenges posed by the Fukushima Daiichi Unit 1 data recorded, this paper describes the major postulates proposed by CIEMAT concerning the equipment and component responses, the effectiveness of accident management actions and the MELCOR model applied. Among most influencing assumptions are those related to the reactor pressure vessel (RPV) leaking pathways and failure mode, the water flow rate entering the reactor, the potential leaking pathways and failure mode and location from the primary containment vessel (PCV) to the reactor building, the corium relocation from RPV to the cavity and its distribution in the PCV, the potential stratification of the suppression pool and the hypotheses made a priori concerning fission product release and transport. Based on the postulated scenario and model, a remarkable agreement of the thermal footprints in terms of RPV and PCV pressures during 500 h has been achieved, in which the RPV and PCV leaks/failures as well as venting played a determining role in the short run of the accident and water injection heavily conditioned the long one. As for the scarce data related to fission products (FP), a consistent agreement is found in the suppression chamber, but estimates in the Dry-Well are about an order of magnitude below measurements despite showing the observed trend. A number of factors might affect FP comparisons to data, from the approximate method to derive dose rates (measurements) from FP masses (MELCOR results) to the RPV and PCV postulated failures. Anyway, based on the data available the set of hypotheses and approximations made seem to make up a defensible scenario for Fukushima Daiichi Unit 1.The studies and results presented in this paper have been achieved under the frame of the OECD/BSAF projects through the CSN-CIEMAT collaboration agreement on severe accidents research.

A Lattice-Tip Temperature-Controlled Radiofrequency Ablation Catheter: Durability of Pulmonary Vein Isolation and Linear Lesion Block.

This study was designed to evaluate lesion durability on invasive electrophysiologic remapping. The lattice-tip catheter generates a large thermal footprint during temperature-controlled irrigated radiofrequency ablation. In a first-in-human study, this catheter performed rapid point-by-point pulmonary vein isolation (PVI) and other linear atrial ablations. In a prospective 3-center single-arm study, paroxysmal or persistent atrial fibrillation patients underwent PVI and, as needed, linear ablation at the cavotricuspid isthmus (CTI), mitral isthmus (MI), and/or left atrial roof; no other atrial substrate was ablated. Using the lattice catheter and a custom electroanatomic mapping system, temperature-controlled (Tmax 73° to 80°C; 2 to 7 s) point-by-point ablation was performed. Patients were followed for 12months. A total of 65 patients (61.5% paroxysmal/38.5% persistent) underwent ablation: PVI in 65, MI in 22, left atrial roof in 24, and CTI in 48 patients. At a median of 108days after the index procedure, protocol-mandated remapping was performed in 27 patients. The pulmonary veins (PVs) remained durably isolated in all but 1 reconnected PV-translating to durable isolation in 99.1% of PVs, or 96.3% of patients with all PVs isolated. Of 47 linear atrial lesions initially placed during the index procedure, durability was observed in 10 of 11 (90.9%) MI lines, all 11 (100%) roof lines, and all 25 (100%) CTI lines. After a median follow-up of 270days, the 12-month Kaplan-Meier estimate for freedom from atrial arrhythmias was 94.4 ± 3.2%. Temperature-controlled lattice-tip point-by-point ablation showed not only highly durable PVI lesion sets, but also durable contiguity of linear atrial lesions.

Inline quantification and localization of transverse matrix cracking in cross-ply CFRP during quasi-static tensile testing by a joint event-based evaluation of acoustic emission and passive IR thermography

Understanding the complex damage characteristics of fiber reinforced plastics under mechanical loading is essential for lightweight design. In this study, acoustic emission (AE)1 analysis and passive IR thermography (pIRT) are coherently combined for the quantitative characterization and localization of damage progression in cross-ply carbon fiber reinforced plastics under quasi-static tensile loading. A new evaluation methodology is presented that utilizes acoustic events as trigger for pIRT analysis. Rigourosly transferring the event-based evaluation scheme from AE to pIRT analysis allowed for the first time to extract and compare characteristic features from both: thermal and corresponding acoustic events and to correlate them to the underlying damaging event. This way, the thermal and acoustic footprint of transverse matrix cracking (TMC) in the outer 90° layers was successfully identified and used for the determination of TMC onset and density throughout the test. This highlights the potential for the inline characterization of damage progression with this new approach.

Design and development of an Allison type emittance scanner for the SPIDER ion source.

Low divergence negative ion beams are crucial for the development of ITER-like fusion reactors. SPIDER is the prototype beam source of the ITER heating neutral beam injector, and it recently started beam acceleration, up to a voltage of 30 kV. The main diagnostics used to measure beamlet divergence are a movable diagnostic calorimeter (STRIKE), which gives the thermal footprint of the beamlets; beam emission spectroscopy; and visible imaging. These systems do not allow a direct measurement of single beamlet phase-space distribution, which is useful for comparison with numerical simulations and to estimate accelerator performances. To this purpose, a movable Allison type emittance scanner for the SPIDER negative ion beam was developed and proposed for the installation on the STRIKE supporting structure. This paper describes the numerical analyses performed to dimension the mechanical and electrical components, such as the Faraday cup and the slits. An analytical approach based on the integration of an arbitrary phase-space distribution was adopted in order to simulate the device performances. The constraints due to the operation in a high heat load environment are discussed.

Dynamic Thermal Behavior of a GDI Spray Impacting on a Heated Thin Foil by Phase-Averaged Infrared Thermography

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The regulations about pollutant emissions imposed by Community’s laws encourage the investigation on the combustion optimization in modern engines and in particular in those adopting the gasoline direct injection (GDI) or direct injection spark-ignited (DISI) configuration. It is known that the piston head and cylinder surface temperatures, coupled with the fuel injection pressure, strongly influence the interaction between droplets of injected fluid and the impinged wall. In the present study, the Infrared (IR) thermography is applied to investigate the thermal footprint of an iso-octane spray generated by a multi-hole GDI injector impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50 μm in thickness) heated by Joule effect, clamped within a rigid frame, and the GDI injector located 11 mm above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays after the impact instant at two different injection pressures (10 and 20 MPa). The temperature difference distributions are employed to describe the unsteady dynamics of the impingement.&lt;/div&gt;&lt;/div&gt;

Thermal footprint of a geological disposal facility containing EURO-GANEX wasteforms

Synroc-Z is a new wasteform being developed to be specifically suited to waste from the advanced EURO-GANEX reprocessing route. This type of waste contains nuclides that release significant amounts of heat during their decay. Here, predictions for radiogenic heat generation from EURO-GANEX wasteforms based on Synroc-Z ceramic and R7T7 glass materials are presented. During reprocessing, any actinides present in the waste-stream are removed to leave only fission products. Simulation results are given demonstrating that, although initially classified as high level waste, the effects of decay mean the wasteforms effectively become intermediate level after 140 years of storage. Furthermore, many of the issues arising from alpha decay will be avoided. During the first 600 years, it is shown that the main source of self heating comes from the decay of Cs-137 and Sr-90. Our calculations show how the significant radiogenic heating by these wasteforms must be considered when defining package sizes and waste loadings. These effects are discussed for both ceramic and glass wasteforms and demonstrate that Synroc-Z provides more flexibility allowing larger packages even at higher waste loadings than R7T7.

Efficient 263 GHz magic angle spinning DNP at 100 K using solid-state diode sources

The development of new, high-frequency solid-state diode sources capable of operating at 263 GHz, together with an optimized stator design for improved millimeter-wave coupling to the NMR sample, have enabled low-power DNP experiments at 263 GHz/400 MHz. With 250 mW output power, signal enhancements as high as 120 are achieved on standard samples – approximately 1/3 of the maximal enhancement available with high-power gyrotrons under similar conditions. Diode-based sources have a number of advantages over vacuum tube devices: they emit a pure mode, can be rapidly frequency-swept over a wide range of frequencies, have reproducible output power over this range, and have excellent output stability. By virtue of their small size, low thermal footprint, and lack of facility requirements, solid-state diodes are also considerably cheaper to operate and maintain than high-power vacuum tube devices. In light of these features, and anticipating further improvements in terms of available output power, solid-state diodes are likely to find widespread use in DNP and contribute to further advances in the field.

Investigation of thermal architectures for flue-gas assisted organic rankine cycle systems: an assessment for thermodynamics and environmental performance indicators

ABSTRACTIn calculations of future energy demand and environmental pollution problems in which waste-heat recovery play a significant role, efficiency often is the primary factor. The organic Rankine cycle (ORC) continues to attract the widespread interest of researchers and/or manufacturer due to technical compatibility, feasibility, and reliability for low to medium grade waste-heat sources. This paper presents thermo-economic analysis on flue-gas assisted organic Rankine cycles (FGA-ORCs) based on both energy and exergy concepts. The heat source of the FGA-ORC system is the exhaust flue-gas of a stenter-frame which is highly used in the textile finishing process. In this study, to convert thermal energy into electrical and/or mechanical energy, an optimization study is performed using three different cycle architectures which have two turbines. Performance indicators such as thermal efficiency, exergetic efficiency, economic profit, performance ratio, and carbon footprint index were examined for the different operating conditions of three investigated thermal architectures. Finally, under the specified operating conditions, the thermal architecture with the best thermo-economic performance was determined by the reduced exergy destruction and increased economic profit due to increased net-work output.

A modal analysis of the size distribution for an hollow-cone spray in cross-flow

Studying sprays in cross-flow is a challenge as well in the design of combustion engines as for spray cooling of heat exchanger. In the latest applications, small particles with high cooling efficiency are injected in the air flow. Some studies have documented particle velocities and diameters in spray plume using Phase Doppler Analysis or photographic techniques. The present contribution focusses on the particle spatial distribution during their far-field dispersion in airflow. Size distribution measurements inside sprays were made with a high spatial resolution using a Phase Doppler Analyzer. Afterwards, the particle size in measurement planes are analysed using a statistical procedure of data analysis, which breaks down the particle cloud into groups. It uses the same concept than “Modal Models”, whose decompose the aerosol cloud into different modes or bins. This method is applied to a spray generated with an hollow-cone nozzle, in both with and without airflow. The clustering approach allows to identify a cloud of fine particles, that is spatially distinct of the coarse and intermediate groups. In a resting atmosphere, coarse particles are concentrated in the periphery of the spray whereas small droplets are confined in the centre, revealing the typical shape of hollow-cone nozzle spray. Cloud trajectories of coarse, intermediate and fine modes are dissociated in cross flow conditions. The classification facilitates the trajectory monitoring for each group and localisation of falling regions: the fall of coarse particles may be roughly approximated with the equation of motion for a single coarse particle. The fine and intermediate particles falls more rapidly than the equation’s prognostic. Noticeable lateral deviations of clouds are also observed. The kidney shape observed for the coarse cloud fits the thermal footprint of spray on heat exchanger. Other shapes, like horse-shoe and vortex-bag, are founded for intermediate and fine particles. Large particles acts as curtain and induces airflow perturbations that are associated with the particular shape of fine and intermediate clouds. The modal analysis provides an efficient tool for studying particles and should be further used with 2 or 3-dimensional measurements in order to study drift vortices.

PUGTIFs: Passively User-Generated Thermal Invariant Features

Feature detection is a vital aspect of computer vision applications, but adverse environments, distance and illumination can affect the quality and repeatability of features or even prevent their identification. Invariance to these constraints would make an ideal feature attribute. Here we propose the first exploitation of consistently occurring thermal signatures generated by a moving platform, a paradigm we define as passively user-generated thermal invariant features (PUGTIFs). In this particular instance, the PUGTIF concept is applied through the use of thermal footprints that are passively and continuously user generated by heat differences, so that features are no longer dependent on the changing scene structure (as in classical approaches) but now maintain a spatial coherency and remain invariant to changes in illumination. A framework suitable for any PUGTIF has been designed consisting of three methods: first, the known footprint size is used to solve for monocular localisation and thus scale ambiguity; second, the consistent spatial pattern allows us to determine heading orientation; and third, these principles are combined in our automated thermal footprint detector (ATFD) method to achieve segmentation/feature detection. We evaluated the detection of PUGTIFs in four laboratory environments (sand, grass, grass with foliage, and carpet) and compared ATFD to typical image segmentation methods. We found that ATFD is superior to other methods while also solving for scaled monocular camera localisation and providing user heading in multiple environments.