Thermal Variation Research Articles

Thermal Image Analysis of Photovoltaic Panel for Condition Monitoring Using Hybrid Thermal Pixel Counting Algorithm and XGBoost Classifier

The use of thermal infrared imaging and the advancement of image processing techniques have developed fault diagnosis of Photo Voltaic (PV) panels without the need to incorporate expensive electrical detection circuitry. PV thermal image processing, supports in continuous monitoring of panels without disturbing the continuity of operation and mitigates the problem of manual inspection involved over a large area. The thermal pictures of photo voltaic panels are used to identify the nature of faults such as bypass diode, cell under fault condition, circuit which is under open condition, hot spot, polarization, Cracking, Corrosion, discoloring and delamination. An automatic PV Computer Aided Diagnosis (CAD) based condition monitoring systems with thermal image analysis is developed to identify and classify the different fault conditions such as Hotspot, Ethylene Vinyl Acetate (EVA) Discoloration, Delamination and Open Circuit. The proposed system involves a hybrid thermal pixel counting algorithm to identify the thermal patterns. The Extreme Gradient Boosting algorithm (XGBoost) is used to detect the numerical characteristics of the captured image thermal variations to support in classification. The experimental results show that the proposed Hybrid Thermal Pixel Counting (HTPC) Algorithm with XGBOOST Classifier gives better detection accuracy with improved computational speed.

Flexible simulation of animal thermoregulatory behavior in three-dimensional synthetic environments from thermal and optical images

Several animals have low metabolism and show body temperatures that are in accordance with environmental temperatures. The relationship between environmental temperature and body temperature is influenced by body size and behavior, in which that some animals accept thermal variation whereas others regulate temperature through behavior. Three-dimensional (3D) environments based on thermal imaging represent a solid tool to elucidate this thermoregulatory behavior to help understand important topics in thermal ecology such as estimating cost of thermoregulation under realistic field conditions, as well as compute the risk of overheating and thermal damage under different ecological scenarios. Although in some studies the proposed models simulate thermoregulation, the connection between thermal and optical image is not explored. This junction can offer a more useful 3D visualization, where topological structures of the landscape can be observed together with thermal information. In this article we present a computational system that is not only capable of generating 3D models by using both thermal and optical images, but is also capable of simulating the thermoregulation behaviors of several animals by means of parameter adjustments made by the user. Our system was analyzed by 22 experts in the biology area – most of them with teaching experience –, who answered objective questions based on their knowledge about the topic, as well as questions about their perception on the simulation provided by our proposal. We used a technology acceptance questionnaire and asked for their contributions through their suggestions. The objective questions reached a hit rate of 68%, which suggests that is relatively easy to use the environment, providing clear comprehension about the simulation, although there is the possibility for improvements. We also found that the hit rate is not related to the experts' level of experience nor with the volunteers' familiarity with 3D environments. Also, 95% of the volunteers indicate a high degree of perceived usefulness, suggesting a potential for using our proposal in teaching and research activities.

The Neurotoxic Effect of Environmental Temperature Variation in Adult Zebrafish (Danio rerio).

Neurotoxicity consists of the altered functionality of the nervous system caused by exposure to chemical agents or altered chemical-physical parameters. The neurotoxic effect can be evaluated from the molecular to the behavioural level. The zebrafish Danio rerio is a model organism used in many research fields, including ecotoxicology and neurotoxicology. Recent studies by our research group have demonstrated that the exposure of adult zebrafish to low (18 °C) or high (34 °C) temperatures alters their brain proteome and fish behaviour compared to control (26 °C). These results showed that thermal variation alters the functionality of the nervous system, suggesting a temperature-induced neurotoxic effect. To demonstrate that temperature variation can be counted among the factors that generate neurotoxicity, eight different protein datasets, previously published by our research group, were subjected to new analyses using an integrated proteomic approach by means of the Ingenuity Pathway Analysis (IPA) software (Release December 2022). The datasets consist of brain proteome analyses of wild type adult zebrafish kept at three different temperatures (18 °C, 26 °C, and 34 °C) for 4 days (acute) or 21 days (chronic treatment), and of BDNF+/- and BDNF-/- zebrafish kept at 26 °C or 34 °C for 21 days. The results (a) demonstrate that thermal alterations generate an effect that can be defined as neurotoxic (p value ≤ 0.05, activation Z score ≤ -2 or ≥2), (b) identify 16 proteins that can be used as hallmarks of the neurotoxic processes common to all the treatments applied and (c) provide three protein panels (p value ≤ 0.05) related to 18 °C, 34 °C, and BDNF depletion that can be linked to anxiety-like or boldness behaviour upon these treatments.

Thermal property evolution and prediction model of early-age low-heat cement concrete under different curing temperatures

The evolution of low-heat concrete thermal properties is controlled by microstructure growth and affects the early-age mass concrete structure cracking under real curing conditions from the perspective of heat transfer. In this paper, experiments were carried out to obtain the evolution of the hydration heat, thermal conductivity, specific heat capacity, and microstructure of different water-binder low-heat mortars under different curing temperatures. The results show that all the thermal property variation rates are sensitive and positive to the curing temperature. The hydration rate increases with increasing water-binder ratio, and the thermal conductivity and specific heat capacity mainly decrease with increasing hydration degree, but the thermal conductivity has a brief and rapid increase stage when the hydration degree is less than approximately 0.38. At the same curing time, the thermal conductivity is higher with a higher water-binder ratio, and the specific heat capacity is inverse. The microstructure results show that the porosity, pore size distribution curve, and threshold pore size decrease with increasing age and curing temperature and increase with increasing water-binder ratio. Meanwhile, the relations between microstructure and thermal property evolutions also show that thermal properties have an exponential positive correlation with porosity, and their variations are controlled by hydration products and pore water due to the variable hydration process. In addition, based on the results and hydration kinetics, a multiscale thermal parameter prediction model of low-heat concrete considering curing temperature and the water-binder ratio was established by the method of theoretical deduction.

Comparison between Corn and Potato Starch-Based Bioplastic: Thermal Variation

Comparison between Corn and Potato Starch-Based Bioplastic: Thermal Variation

Thermal Conductivity Variations in Frozen Hydrate-Bearing Sand upon Heating and Dissociation of Pore Gas Hydrate

High-latitude permafrost, including hydrate-bearing frozen ground, changes its properties in response to natural climate change and to impacts from petroleum production. Of special interest is the behavior of thermal conductivity, one of the key parameters that control the thermal processes in permafrost containing gas hydrate accumulations. Thermal conductivity variations under pressure and temperature changes were studied in the laboratory through physical modeling using sand sampled from gas-bearing permafrost of the Yamal Peninsula (northern West Siberia, Russia). When gas pressure drops to below equilibrium at a constant negative temperature (about −6 °C), the thermal conductivity of the samples first becomes a few percent to 10% lower as a result of cracking and then increases as pore gas hydrate dissociates and converts to water and then to ice. The range of thermal conductivity variations has several controls: pore gas pressure, hydrate saturation, rate of hydrate dissociation, and amount of additionally formed pore ice. In general, hydrate dissociation can cause up to 20% thermal conductivity decrease in frozen hydrate-bearing sand. As the samples are heated to positive temperatures, their thermal conductivity decreases by a magnitude depending on residual contents of pore gas hydrate and ice: the decrease reaches ~30% at 20–40% hydrate saturation. The thermal conductivity decrease in hydrate-free saline frozen sand is proportional to the salinity and can become ~40% lower at a salinity of 0.14%. The behavior of thermal conductivity in frozen hydrate-bearing sediments under a pressure drop below the equilibrium and a temperature increase to above 0 °C is explained in a model of pore space changes based on the experimental results.

Linking Thermal Indices, Productivity, Phenotypic Traits, and Stressors for Assessing the Health of Centennial Traditional Olive Trees

Centennial olive trees, integral components of traditional Mediterranean agroecosystems, hold immense value as repositories of biodiversity and cultural heritage due to their physiological attributes and life history, making them crucial for the conservation of High Nature Value ancient olive orchards. However, they are increasingly confronted with physiological challenges exacerbated by various biotic and abiotic stressors jeopardizing their health and productivity, underscoring the urgency for ongoing monitoring and conservation measures to secure their long-term existence. To monitor these challenges, in recent years, the adoption of non-invasive techniques like infrared thermography (IRT) has become prevalent. In this study, we aimed to comprehensively assess the health state of traditional centennial olive trees, with a particular focus on their productivity. To achieve this, we monitored 44 centennial olive trees from a traditional olive grove on the island of Naxos, Greece, a representative location for Mediterranean olive groves, during the period from 2017 to 2020. We established connections between a set of trunk and canopy thermal and humidity indices, phenotypic traits, and the two most prevalent stressors affecting olive trees not only within the context of the island but also more broadly in similar Mediterranean environments worldwide: the olive leaf spot disease (OLS) and crop water stress, assessed through the crop water stress index (CWSI). To evaluate their interrelationships, we initially assessed intraspecific thermal and humidity pattern variations, and we developed linear and logistic regression models to gain insights into the factors influencing olive tree productivity, water stress, and the OLS presence. Results indicated that combining thermal and humidity indices can substantially explain olive tree productivity, water stress, and OLS, providing a valuable tool for assessing and monitoring the health and overall state of centennial olive trees, while offering a comprehensive approach to understanding the complex interactions shaping traditional olive grove dynamics. By identifying key indicators such as tree thermal patterns and water stress levels, olive growers and conservationists can make informed decisions to enhance the vitality and longevity of these culturally and ecologically significant trees.

Eco-conscious nanofluids: exploring heat transfer performance with graphitic carbon nitride nanoparticles

Abstract The work explores the heat transfer capabilities of semiconducting graphitic carbon nitride (g-C3N4) nanofluids. Also, it presents a sustainable and eco-friendly method for synthesizing g-C3N4 nanoparticles using commercially available rice flour as a natural carbon precursor through hydrothermal treatment. The synthesized sample subjected to various characterizations, including analysis of their structure, morphology, thermal properties, and optical properties. The optical bandgap (2.66 eV) is deduced through Tauc plot analysis and reveals the semiconducting nature of the sample. The formation of g-C3N4 is confirmed by various spectroscopic techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and Raman spectroscopy. Thermogravimetric analysis (TGA) demonstrates the nanoparticles’ excellent thermal stability up to 550 °C, indicating potential applications in heat transfer fluids. The investigation of concentration-dependent thermal diffusivity variation using the sensitive mode mismatched dual beam thermal lens technique highlights the potential of g-C3N4 semiconductor nanofluid as an organic and metal-free additive in industry-demanding coolant applications.

Low lead inorganic Zn-based mixed-halide perovskites CsPb0.625Zn0.375I3−β X β (X = Cl or Br) for energy generation with 23.5% efficiency

Hybrid perovskite (HP) solar cells have garnered significant attention in recent years for their excellent light absorption, long carrier lifetime, and high diffusion length, resulting in high power conversion efficiency and superior optical performance compared to silicon solar cells. However, the organic component in HP solar cells is vulnerable to thermal variations and the presence of lead (Pb) poses a threat to the environment. To address these issues, this work proposes the use of all-inorganic halide perovskite (IHP) materials with low lead content as the absorber layer in four different perovskite solar cell configurations: CsPb0.625Zn0.375I2Br, CsPb0.625Zn0.375IBr2, CsPb0.625Zn0.375I2Cl, CsPb0.625Zn0.375ICl2. In addition, owing to the consideration novel IHP materials, it is important to identify the appropriate properties of transport layers since conventional transport layers are best suited to conventional organic–inorganic halide perovskites and may not work well with proposed IHP. Therefore, the appropriate electron transport layer (ETL) has also been investigated through optimization of electron affinity (4.0 eV − 4.23 eV), mobility (0.004 cm2/Vs to 4 cm2/Vs), and donor doping density (1015 cm−3 to 1018 cm−3). The device performance has been further analysed and optimized by varying the active layer thickness. The selected ETL is then combined with the absorber layers to evaluate performance. The effect of varying the thickness of the absorption layer is observed in all four device arrangements. Simulation results show that CsPb0.625Zn0.375ICl2 performed best among the mentioned absorber materials, with a power conversion efficiency of 23.5% with ETL parameters of 4.00 eV (electron affinity, χ), 4 cm2/Vs (electron mobility, μ n), 1×1018 cm−3 (donor doping density, Nd) and absorber layer thickness of 500 nm. Proposed work may open a window for the development of a new class of environment friendly and stable perovskite solar cells in future.

Early detection of thermal instability in railway tracks using piezo-coupled structural signatures

Rail accidents caused by rail track derailments have been a growing concern due to repetitive thermal changes resulting from high temperature stresses in rails due to rail traction and environmental thermal variation. This leads to thermal buckling, which can result in catastrophic failure. Structural health monitoring (SHM) using the electromechanical impedance (EMI) technique has emerged as a promising technology to detect structural deterioration and its severity before it leads to failure. This study used piezoelectric sensors to collect piezo-coupled structural signatures of different rail-joint bars for high-temperature repetitive thermal cycles, which were then analyzed using an impedance analyzer. The results show that the piezo-coupled signatures could identify structural changes, and the damage metric, could be employed for continuous monitoring of structural rail defects due to excessive thermal stress and residual strain. The method also derived piezo-equivalent structural parameters, such as mass, stiffness, and damping, which were very satisfactory in detecting significant changes and consequent damage. Overall, this study presents a pre-emptive experimental method that can see thermal deterioration and instability in rails and rail joints, thereby reducing the risk of rail accidents caused by derailments.

Influence and sensitivity evaluation of window thermal parameters variations on economic benefits of insulation materials for building exterior walls–a case study for traditional dwelling in China

The energy consumption intensity of rural buildings in China shows an increasing trend. Adding insulation materials for exterior walls can lower the building energy demand (ED), and evaluating its economic benefits (EB) can provide valuable references for decision-makers. Although many studies have evaluated the EB of wall insulation, the effect of window thermal parameters is rarely discussed. The variations of window thermal parameters can change the ED and the investment cost of the wall insulation, then change the final EB of the wall insulation. In this work, the impacts of four window thermal parameters (U-value, solar heat gain coefficient, window-to-wall ratio, air changes per hour) on the ED and EB of wall insulation are investigated. Then they are ordered according to the global sensitivity analysis results. Meanwhile, the effects of building orientations on these results also be discussed. Results show: (1) The optimum insulation thickness is 50 mm for traditional dwellings when considering the window system; (2) The EB of wall insulation is most sensitive to the air changes per hour, followed by window-to-wall ratio, U-value, and solar heat gain coefficient; meanwhile, the variation of building orientation cannot change this sensitivity order; (3) The insulation costs cannot be balanced out when the air changes per hour exceeds 1.3 h−1 and insulation is not thicker than 5 mm.

Nernst Equations and Concentration Chemical Reaction Overpotentials for VRFB Operation

The vanadium redox flow battery (VRFB) has been intensively examined since the 1970s, with researchers looking at its electrochemical time varying electrolyte concentration time variation equations (both tank and cells, for negative and positive half cells), its thermal time variation equations, and fluid flow equations. Chemistry behavior of the electrolyte ions have also been intensively examined too. Our focus in this treatment is a new approach to understanding the physics, chemistry, and electronics of the VRFB by looking at the equilibrium and non-equilibrium aspects of the battery. Detailed examination of the behavior inside the porous electrodes of the electrolyte concentration is done by distinguishing between the concentrations near the pore surface wall and volume elements away from the solid surface-electrolyte boundary. Relationship to the battery charging or discharging current and current density is performed allowing macroscopic overpotentials to be determined for each electrode. These are concentration overpotentials and their exact relationship to the battery potentials is developed carefully so that a rigorous basis is established. It is found that there are two overpotentials making up the negative electrode overpotential, due to the and ions. Similarly, there are two overpotentials making up the positive electrode overpotential, due to the and ions.

Analogy of spacetime as an elastic medium—Can we establish a thermal expansion coefficient of space from the cosmological constant Λ?

This paper advances the state-of-the-art by extending the study of the analogy between the fabric of spacetime and elasticity. As no prior work exists about a potential spacetime thermal expansion coefficient [Formula: see text], we explore the analogy of general relativity with the theory of elasticity by considering the cosmological constant [Formula: see text] as an additional space curvature of the structure of space due to a thermal gradient coming from the cosmic web and the cold vacuum and we propose [Formula: see text] with [Formula: see text] being the curvature radius of the space fabric. It follows from this analogy and from the supposed space model consisting of thin sheets of Planck thickness [Formula: see text] curved by this thermal gradient [Formula: see text]T a possible thermal expansion coefficient of the equivalent elastic medium modeling the space [Formula: see text] of the order of [Formula: see text][Formula: see text]K[Formula: see text]. As spacetime and not only space must be considered in general relativity, this paper also proposes an innovative approach which consists in introducing into the interval ds2 of special relativity a temperature effect [Formula: see text] (entropy variations correlated with time laps, based on temperature variations affecting always physically the clocks) based on different thermal expansion coefficients for space and time with for the flow of time [Formula: see text]. With [Formula: see text] 106[Formula: see text]K, [Formula: see text], the associate time interval is [Formula: see text][Formula: see text]s and [Formula: see text]. The consequence of this hypothesis is that dark energy potentially becomes a thermal spacetime curvature [Formula: see text] with [Formula: see text] equal to [Formula: see text] or [Formula: see text] depending of the temperature, the thermal entropy variation of the universe, the Planck thickness and time, that increases since the Big bang, depending on thermal expansion coefficients for spacetime [Formula: see text] and [Formula: see text] as a function, respectively, of [Formula: see text], [Formula: see text], in opposition to spacetime curvature gravity due to mass/energy density as described in general relativity.

High-performance magnetic thermal switch based on MnFe[formula omitted]O[formula omitted]/Ethylene Glycol:Water refrigerant dispersion

The use of magnetic nanoparticles for the remote control of heat transfer in electronic devices can overcome the current limitations of appliance engineering. In this work, we demonstrate that a thermal switch based on a low-cost and stable MnFe2O4/Ethylene Glycol:Water (MFO/EG:W) dispersion can increase the span temperatures as high as 60% in the 0.01–0.60 Hz operating frequency range under the same heat supply for different recipient filling ratios (FR). Under the optimum condition of FR = 80%, the efficiency of our new MFO/EG:W colloidal dispersion is twice the obtained for the commercial Fe3O4/paraffin oil fluid. From numerical calculation, we demonstrate that the improved heat exchange efficiency relates to the three-steps effective thermal conductivity variation during operation, expanding the contact time between the heat and cold sources. Thus, the combination of an EG:W refrigerant solution and superparamagnetic MFO nanoparticles with high saturation magnetization allows their use for heat management control of electronic systems for long operation periods.

Novel experimental technique to evaluate soil thermal conductivity in a transient state

novel experimental technique to evaluate soil thermal conductivity in a transient state

Thermal and spectroscopic profiles variation of cold-pressed raspberry seed oil studied by DSC, UV/VIS, and FTIR techniques

The characteristics of six cold-pressed raspberry seed oils, investigated by melting and crystallization phase transition analysis using differential scanning calorimetry (DSC), UV–VIS and Fourier transform infrared (FTIR) spectra, as well as the fatty acid composition, was the aim of this study. Two groups of oils samples were investigated: commercial (I-group) and laboratory-pressed (L-group). UV/VIS and FTIR spectra of raspberry seed oil revealed important wavelength and wavenumber ranges to indicate qualitative differences between I- and L-group. Regardless of the scanning rates, DSC melting curves were more suitable for detecting differences in raspberry seed oils than crystallization profiles. Based on the Principal component analysis of UV–VIS, FTIR and DSC data two groups of oils were distinguished. Fatty acids by GC analysis confirmed differences between oils, since the commercial oils exhibited a lower ratio of n-3/n-6 fatty acids than L-group oils. The obtained results provide practical information on the usefulness of DSC profiles and FTIR spectra for the comprehensive characterization of cold-pressed raspberry seed oils, especially in the field of B2B industries that need rapid and non-targeted instruments to confirm the authenticity of the purchased product.

Establishing resilience in times of climate change—a perspective on humans and buildings

With a contribution of 40% to the annual global CO2-emissions, the built environment needs to drastically reduce its impact, while also providing pleasant and healthy indoor spaces and protecting people from weather extremes. Over time, particularly in western and industrialized countries, buildings have evolved to shield occupants almost completely from outdoor conditions. As a consequence, humans have become so used to a constant, comfortable indoor environment that we struggle to cope with thermal fluctuations. The time has come to shift perspective, as the very protective character of buildings and provision of omnipresent comfort are neither feasible nor desirable any longer. An enormous amount of energy and resources are spent to provide tightly controlled thermal environments, often with the same target temperature all year round. However, being mostly exposed to constant, comfortable indoor temperatures can have negative impacts on health and deteriorate our human capability to deal with thermal challenges. Importantly, spending time outside the thermal comfort zone is known to enhance human thermoregulatory capacities and thermal resilience, while also improving metabolic and cardiovascular health. This perspective essay aims to draw attention to novel and yet underrepresented avenues of coping with climate challenges, both with respect to the built environment and humans. Allowing more thermal variation indoors will save precious resources, decrease the negative impact of building CO2-footprints, and stimulate physiological and psychological adaptation in humans, which can lead to improved resilience and health.

Innovative liquid metal strategy for real-time thermal control in additive manufacturing

Metal additive manufacturing (AM) involves rapid cycles of melting and solidification, often resulting in significant thermal stress variations, microcrack formation, and compromised structural integrity, especially for complex structures. Effective strategies are crucial for regulating temperature and stress distribution during laser-based metal AM processes; however, traditional thermal management approaches suffer from limitations in action area and response speed. In this study, the novel Liquid Metal-Assisted Additive Manufacturing (LMAAM) process is developed to enhance real-time temperature and stress control during deposition. This is the first known attempt to utilize liquid tin as an auxiliary thermal management material for AM. Numerical simulations and experimental analysis are performed to determine the relationship between LMAAM process conditions and resultant material microstructural properties. The results show that compared to AM without active thermal management, the incorporation of liquid tin yields an approximate 20 % increase in the cooling rate, a roughly 30 % reduction in residual tensile stress, a decrease in part grain size, and a roughly 30 % enhancement in microhardness. LMAAM technology opens up new possibilities for metal AM of highly reliable and intricate structures like multi-chambers, multi-channels, and deep blind holes.

THERMOELECTRIC MONITORING OF THERMAL RESISTANCE IN ELECTRONIC SYSTEMS

The article proposes to apply the method of thermoelectric testing to determine the thermophysical parameters of the thermal interface. A thermal interface is located between metal surfaces, between which, thermoelectromotive force occurs during heating at any stage of the device operation. The obtained graphs of the temperature difference dependence on the heating time, measured by thermocouples, and measured using thermoelectromotive force confirm the accuracy of the thermoelectric method of testing. Graphs visualize the heat transfer process with thermal resistance variation, temperature fluctuations and the resulting thermoelectromotive force. The proposed method makes it possible to monitor thermal resistance with an error of less than 8 %.

Evaluation of Intergranular Corrosion in 7050-T7451 Aluminum Structures Influenced by Temperature and Contact with Cutting Fluid

This research presents a practical approach to the development of the intergranular corrosion in 7050 - T7451 aluminum alloy used in the construction of manifold components of an aircraft structure. At first, it is presented what type of corrosion this is and how it develops in the crystalline structure, noting which variables contribute to the aggravation of this problem and their impacts on aviation, since this is the beginning of a number of structural defects included fatigue, which stands out even more because of the circumstances that are presented. The performance of the tests in laboratory seeks to evaluate the reactions of the material when exposed to cutting fluid and thermal variations for a long period; the development of corrosion in the microstructure has been simulated, and with this the loss of mechanical resistance of the samples could be evaluated. The results obtained indicate that the cutting fluid even slowly, showed effects in the propagation of corrosion in the alloy of aluminum studied and reduced your mechanical strength.