IR Thermal Imaging Research Articles

Investigation of Thermal Effect on Reliability and Chromaticity Shift in QD-LEDs Displays

In this work, thermal effect on reliability and chromaticity shift in quantum dots (QDs)-based light emitting diodes (LEDs) are investigated by long term lifetime test and IR thermal image. The results have suggested that the heat power generation during luminescence conversion process play a key role in the compatibility between QD and encapsulation resin, which is correlated to the blue luminescence intensity generated from LED chip and the QD luminescence intensity converted by QDs. The ligands detachment of QD at luminescence conversion process results in poor reliability of QDs and influence on the thermal load ability of encapsulation resin, whereas the condition of QD should be a dominant factor. It was also found that QD with thicker shell could prevented heat power generation since higher conversion efficiency and better stability, shown the better reliability of QD-LEDs and less chromaticity shift.

Modeling the Effect of Fast Charge Protocol on the Temperature Rise of a Lithium-Ion Battery during Charge

The lithium-ion battery (LIB) is a preferred power source for battery electric vehicles (BEVs),because LIBs have higher energy density, longer life and higher power density than most other practical batteries. Although there is still a plenty of room to be improved for the cost, life, and safety of the LIB in BEV applications,another important issue to be overcome for the BEV battery is searching for an appropriate fast charge protocol to enable a rapid growth of BEV market. A short charge time, however, results in a rapid temperature rise of an LIB cell during charge. Therefore, it is essential to find an optimized fast charge protocol that can keep the peak temperature of LIB cell below the maximum allowable limit recommended by the LIB manufacturer.In this work, the effect of fast charge protocol on the temperature rise of an LIB cell during charge is analyzed based on the two-dimensional thermal modeling of the LIB cell under various fast charge protocols. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperatures of the LIB cell after charge.

Ultralow Power Sensor Package for Early Warning of Wildland Fires

Ultralow Power Sensor Package for Early Warning of Wildland Fires

Understanding the growth mechanism of single vapor bubble on a hydrophobic surface: Experiments under nucleate pool boiling regime

Growth and departure characteristics of single vapor bubble on hydrophobic surfaces have been investigated under saturated bulk conditions. Nucleate pool boiling experiments, with water as the working fluid, have been carried out on two sets of hydrophobic surfaces; (1) black painted ITO-coated glass substrate, and (2) ITO-coated sapphire substrate subjected to two different levels of constant heat flux conditions. High speed camera was employed to characterize the bubble dynamics. In conjunction with the high speed camera, an IR thermal imaging camera was used to simultaneously map the spatio-temporal temperature distribution of the substrate underneath the growing vapor bubble. Compared to the black paint coated glass substrate, significantly higher transmissivity of sapphire substrate in the mid-IR spectral range ensured the authenticity of the spatio-temporal accuracy of temperature measurements of the bubble nucleation site using the employed IR camera. Results on the bubble growth clearly showed that, irrespective of the substrate employed, the bubble exhibits almost zero waiting time, leaving a small residue of vapor on the substrate after the bubble departure, which further acts as a nucleus for the next bubble. Moreover, the bubble growth process was observed to be extremely slow. The IR camera-based temperature field of the hydrophobic substrates revealed that the presence of vapor bubble does change the local temperature of the substrate underneath the vapor bubble. However, it was observed that the temperature field of the nucleation site does not change with bubble growth and its departure, which, in turn, indicated towards the possibility that the microlayer ceases to exist underneath the vapor bubble. This is in contrast to the microlayer evaporation-driven growth of single vapor bubble on a hydrophilic substrate. Based on these direct experimental observations, plausible bubble growth mechanism(s) on the given hydrophobic surfaces have been predicted and discussed.

Assessing the potential of multispectral and thermal UAV imagery from archaeological sites. A case study from the Iron Age hillfort of Villasviejas del Tamuja (Cáceres, Spain)

In recent years, the miniaturization of remote sensing equipment and the striking improvement of UAV technology has provided a new, high-resolution view of archaeological sites beyond the visible spectrum. This work explores the potential of low altitude remote sensing (multispectral and thermal infrared imaging) for the study of complex archaeological zones through the study case of an Iron Age hillfort in the southwest of the Iberian Peninsula. We describe the methodology developed in order to maximize and objectively quantify the detection of buried structures. On the one hand, we evaluate the capacity to categorize the response to varying depths of the overlying sediments, exploring the limits of the statistically significant separability between noise and signal. On the other hand, thermal IR images taken at different times of the day are compared to assess the optimal conditions for the identification of archaeological features. The results reveal that although we can only approach meaningful separability values, it was possible to identify a large number of buried structures. These results were finally validated by comparison with the data obtained by geophysical survey and excavation.

Self-heating Characteristics of Mo Electrodes and MoS2 FET Using IR Thermal Imaging Microscope

In this study, the static and transient thermal characteristics of molybdenum electrodes induced by self-heating process are reported. The corresponding local temperatures of the electrodes were measured using an infrared thermal imaging microscope system. Maximum temperature is observed to increase (80 {260 °C depending on the width of the electrode) at the narrow region of the electrodes. In addition, the measured temperature was linearly proportional to the applied power per unit width. The transient thermal measurement performed in the range between 10 Hz and 100 kHz has shown that the temperature fluctuation begins to decrease at 1 kHz and saturate to a certain level. In addition, the self-heating effect on an atomically-thin two-dimensional molybdenum disulfide field-effect transistor operating in ambient conditions was also observed.

100th Anniversary of Macromolecular Science Viewpoint: High Refractive Index Polymers from Elemental Sulfur for Infrared Thermal Imaging and Optics.

Optical technologies in the midwave and long wave infrared spectrum (MWIR, LWIR) are important systems for high resolution thermal imaging in near, or complete darkness. While IR thermal imaging has been extensively utilized in the defense sector, application of this technology is being driven toward emerging consumer markets and transportation. In this viewpoint, we review the field of IR thermal imaging and discuss the emerging use of synthetic organic and hybrid polymers as novel IR transmissive materials for this application. In particular, we review the critical role of elemental sulfur as a novel feedstock to prepare high refractive index polymers via inverse vulcanization and discuss the fundamental chemical insights required to impart improved IR transparency into these polymeric materials.

Automatic multiple moving humans detection and tracking in image sequences taken from a stationary thermal infrared camera

Several Particle Filter (PF)-based methods for human tracking in thermal IR image sequences have been proposed in the literature. Unfortunately, the majority of these methods are developed for tracking only a single human. Moreover, this human is manually pre-selected in the first frame of the image sequence, which is not practical for the real case of intelligent and efficient video surveillance system that needs tracking more than one human and without any external operator intervention. To contribute to addressing this need, in this paper, we propose a novel PF-based method that detects and tracks multiple moving humans using a thermal IR camera, without prior knowledge about their number and initial locations in the monitored scene. This method consists of three main parts. In the first one, all the moving objects are extracted from the image sequence by using the Gaussian Mixture Model (GMM) and then, for each extracted object, a combined shape, appearance, spatial and temporal-based similarity function that allows us to detect a human without any prior training of a mathematical model is calculated. The second part consists in tracking the human previously detected by using a PF and an adaptive combination of spatial, intensity, texture and motion velocity cues. In each cue, a model for the detected human is created, and when new observations arrive in the next frames, the similarity distances between each created model and the observed moving regions are calculated. The human tracking is achieved by combining individual similarity distances using adaptive weights, into a PF algorithm. The third part is devoted to detect and handle occlusions by using simple heuristic rules and grayscale Vertical Projection Histogram (VPH). Each part of the proposed method was separately tested on a set of real-world thermal IR image sequences containing background clutters, appearance and disappearance of multiple moving objects, occlusions, illumination and scales changes. A comparative study with several state-of-the-art methods has shown that the proposed method performs consistently better in terms of Center Location Error (CLE) and the Success Rate (SR), and it can also run at speed of about 15 Frame Per Second per human, which is considerably enough for real-time applications.

Electrochemical and optical studies of new symmetrical and unsymmetrical imines with thiazole and thiophene moieties

In this study new symmetrical and unsymmetrical imines based on 4-[4-(4-fluorophenyl)1,3-thiazol-2-yl]aniline and 2,2′,5′,2”-terthiophene-5,5”-dicarboxaldehyde or 2,2’:5′, 2’’-terthiophene-5-carboxaldehyde, respectively, were synthesized by melt condensation with the yield of 86% and 40%. The 5% weight loss of the imines was found in temperature range from 294 to 390 °C in nitrogen, depending on the symmetry of aldehyde used in synthesis. The band gap of symmetrical imine (PV-BLJ-SC13) is lower by about ∼0.33 eV than that of unsymmetrical PV-BLJ-SC14. For both imines the electron density of HOMO level is mainly located on thiophene moieties and is extended to imine bonds in thiazole rings and imine moieties. The theoretical calculations of their HOMO-LUMO levels by DFT methods were also provided. The UV–Vis absorption spectra and cyclic voltammograms of imines both in the form of thin films cast on the electrode as well as dissolved in 1,2-dichloromethane were studied to determine the electrochemical and optical band gap energies as well as correlate the positions of HOMO and LUMO levels obtained by DFT and electrochemical methods. The resistance of imines was approximately 113.8 Ω and 102.4 Ω for PV-BLJ-SC13 and PV-BLJ-SC14, respectively as determined by IR thermal images and have a tendency to decrease by about 17–24 Ω when mixed with PTB7 and PC71BM. Both imines showed very bright luminescence. Moreover, optical absorption, photoluminescence and IR thermal images were measured for imine:PTB7 or imine:PTB7:PC71BM composite. Finally, simple organic solar cells based on (PTB7:imine):PC71BM in weight ratio (4:1):8 and (8:1):13 w/w were constructed and characterized. The highest power conversion efficiency, which was equal to 0.42% was determined for the ITO/PEDOT:PSS/PTB7:PV-BLJ-SC13:PC71BM (4:1):8/Al device. In addition, the power conversion efficiency was strongly dependent on the weight ratio of imine in active layer.

UV-Vis Absorption Properties of New Aromatic Imines and Their Compositions with Poly({4,8-bis[(2-Ethylhexyl)oxy]Benzo[1,2-b:4,5-b']Dithiophene-2,6-diyl}{3-Fluoro-2-[(2-Ethylhexyl)Carbonyl]Thieno[3,4-b]Thiophenediyl}).

In this paper, four new aromatic imines containing at least one thiazole-based heterocycle were analyzed in detail by UV–Vis spectroscopy, taking into consideration their chemical structures and interactions with PTB7, a known polymeric electron donor widely used in bulk heterojunction organic solar cells. It is demonstrated that the absorption spectra of the investigated active compositions can be modified not only by changing the chemical structure of imine, but also via formulations with PTB7. For all investigated imines and PTB7:imine compositions, calibration curves were obtained in order to find the optimum concentration in the composition with PTB7 for expansion and optimization of absorption spectra. All imines and PTB7:imine compositions were investigated in 1,2-dichlorobenzene by UV–Vis spectroscopy in various concentrations, monitoring the changes in the π–π* and n–π* transitions. With increasing imine concentrations, we did not observe changes in absorption maxima, while with increasing imine concentrations, a hypochromic effect was observed. Finally, we could conclude that all investigated compositions exhibited wide absorptions of up to 800 nm and isosbestic points in the range of 440–540 nm, confirming changes in the macromolecular organization of the tested compounds. The theoretical calculations of their vibration spectra (FTIR) and LUMO–HOMO levels by Density Functional Theory (DFT) methods are also provided. Finally, IR thermal images were measured for organic devices based on imines and the imine:PTB7 composite.

Pulsed‐Laser‐Induced IR Stereoscopic Imaging

AbstractResearch on displays that can provide stereoscopic information for advertising, education, medical applications, and military simulations is on the rise. Because IR images are invisible to human eye, they can be used when security or privacy is required. If stereoscopic image display techniques are extended from the visible region to the IR region, they are able to provide more or selective information to humans. Therefore, a method of using laser beam steering to form IR stereoscopic images on a plain substrate is investigated in this study. A technique is developed for displaying IR stereoscopic images that can be detected by using an IR thermal imaging camera (ITIC), while remaining invisible to the human eye. This approach can be used to represent various IR patterns due to plasma generated during laser irradiation of the glass substrate. Static IR images are produced with stereoscopic contours: point‐shaped laser‐beam spots are connected to form IR‐emitting lines, and the IR‐emitting lines are further arranged to form IR‐emitting faces. IR stereoscopic video images with perspective are implemented by sequentially displaying time‐variant IR static images controlled by laser beam steering. Full‐color‐image representation on an ITIC is achieved using laser beam steering and the laser pattern formation method.

Using Thermal Imaging to Monitor Body Temperature of Koalas (Phascolarctos cinereus) in A Zoo Setting.

Simple SummaryBody temperature regulation is integral for the health and well-being of animals, especially in Zoo settings. Endothermic vertebrates such as small mammals are able to maintain a constant internal body temperature; however, extreme variation in body temperature may be reflective of underlying injuries or health issues. Thus, new technology that can enable the measurement of body temperature of small mammals without need for capture and handling can be very useful for the monitoring of animals in Zoos. In this study, we report the application of an IR thermal imaging camera for monitoring the body temperature of koalas. We found that the eye and abdomen were the most consistent body features to record body temperature. This tool will have useful application for welfare evaluation of small mammals, such as koalas in Zoos.Non-invasive techniques can be applied for monitoring the physiology and behaviour of wildlife in Zoos to improve management and welfare. Thermal imaging technology has been used as a non-invasive technique to measure the body temperature of various domesticated and wildlife species. In this study, we evaluated the application of thermal imaging to measure the body temperature of koalas (Phascolarctos cinereus) in a Zoo environment. The aim of the study was to determine the body feature most suitable for recording a koala’s body temperature (using coefficient of variation scores). We used a FLIR530TM IR thermal imaging camera to take images of each individual koala across three days in autumn 2018 at the Wildlife Sydney Zoo, Australia. Our results demonstrated that koalas had more than one reliable body feature for recording body temperature using the thermal imaging tool—the most reliable features were eyes and abdomen. This study provides first reported application of thermal imaging on an Australian native species in a Zoo and demonstrates its potential applicability as a humane/non-invasive technique for assessing the body temperature as an index of stress.

Thermographic signs of spastic type cerebral palsy in 4–7 years old children: protocol and data analysis

31 children at the age of 4–7 years with two spastic forms of cerebral palsy (G80.1 and G80.2) with the degree of motor dysfunction of levels 1 and 2 according to GMFCS were examined using IR thermal imaging. For the first time, the temperature distribution on the limbs and its dynamics in response to the dosed motor load on the spastic muscle groups are described in detail. For the group of patients with hemiparesis characterized by asymmetry of temperature on the limbs associated with the side of the lesion, and for the group with diplegia — the inversion of the normal proximal-distal gradient, most pronounced in the segments of the shin / foot and shoulder / forearm and less in the forearm / wrist, and abnormally high temperature difference on the back between the thoracic and lumbar regions. Moderate physical activity leads to the enhancement of thermal anomalies due to the additional reduction of the temperature in the projection of the affected muscles and strengthen the pathological symptoms. Knowledge of the skin thermal reactions in the projection of these muscles in response to motor tests opens up a potential opportunity to use the method in assessing the results of treatment and rehabilitation of patients with cerebral palsy.

Experimental study on the capillary performance of aluminum micro-grooved wicks with reentrant cavity array

In order to enhance the capillary performance for two-phase heat transfer apparatus, the aluminum micro-grooved wick with reentrant cavity array (MGRA) was developed by using orthogonal Ploughing-Extrusion (P-E) method. Different MGRAs with variation in the P-E pitch and depth were designed to study the effect of the fabrication parameters on the capillary performance and obtain the optimal wick structures. The IR-thermal imaging method and forced liquid flow approach were used in the capillary rise and permeability tests, respectively. It was found that the reentrant cavities became more visible and bigger with a larger pitch or smaller depth. The results manifested that the capillary rise height decreased with the increasing longitudinal P-E pitch and depth. Besides, the permeability increased with increase of pitch but decreased with increases of depth. The capillary parameter K·ΔPcap was taken as a comprehensive index to evaluate the wicks. The sample with the largest pitch and smallest depth in the tests obtained the maximal value of K·ΔPcap due to the good balance between the permeability and capillary pressure. Therefore, this sample may be the optimum structural design in this study for the application as enhanced wick for two-phase heat transfer apparatus.

IoT Based Thermal Surveillance and Security System

Security is the need in day to day life. Use of intruder detection systems were increasing year by year. IR surveillance method for the detection of illegal intruder in low light condition is more easy unlike optical camera systems. This paper presents the design and implementation of intruder detection using IR sensor based system for application in the field of security and surveillance. Presenting methods are based on use of IR thermal detection system for the intruder detection, recognition and alerting. The use of such systems has special significance in the context of security in the domain of timely detection of abnormal movements inside the buildings. IR thermal imaging has higher advantages compared to optical camera surveillance systems because thermal imaging is effected by to weather conditions and can be used any time in a day. Presenting system are mainly used for illegal intruder detection inside buildings as well as infrared thermal imagers mounted on autonomous vehicles and unmanned aerial vehicles (UAV) and Banking Security Systems for intruder detection. Thermal sensors are used to detect the hot body by IR radiation detection. Thermal sensors are combined with microwave motion detection sensors to detect abnormal movement of hot bodies. Motion sensors also helps in prevention of false alarm due to external environmental condition. After detection of intruder alert the user using IoT systems.

Study and Analysis of Exhaust Emission of Diesel Vehicles using Thermal IR Imagers

<p>Exhaust emission analysis from diesel vehicles has received a lot of attention in recent times in the context of implementation of Bharat Stage-IV norms and thermal signature analysis for civil and military applications. The exhaust emission thermal IR signatures of military diesel vehicles such as truck and bus using a gas analyser and thermal imager under idling and accelerating conditions of these vehicles is investigated. Concentration and temperature of diesel exhaust emission CO, NOx, and HC remains almost constant during engine running in idle condition and varies with the engine acceleration. Exhaust gases maximum temperature reaches in the range of 240 °C - 270 °C during engine acceleration. A detailed investigation of thermal signature in mid wave infrared, 3 µm - 5 µm waveband and long wave infrared, 8 µm - 14 µm waveband is also presented under the same engine running conditions. Thermal image analysis exhibited that the area of thermal IR image of diesel vehicles truck and bus has been increased 0.077 per cent and 0.594 per cent, respectively with the engine acceleration. It has been observed that thermal signature of exhaust gases is a good tool for vehicle exhaust emission visualisation and analysis.</p>

The Effect of Human Error on the Temperature Monitoring and Control of Freeze Drying Processes by Means of Thermocouples.

Monitoring product temperature is mandatory in a freeze-drying process, in particular in the process development stage, as final product quality may be jeopardized when its temperature trespasses a threshold value, that is a characteristic of each product being freeze-dried. To this purpose thermocouples are usually inserted in some of the vials of the batch to track product dynamics. The position of the thermocouple inside the vials strongly affects the reading of the temperature evolution during the freeze-drying process and, thus, it is necessary to place them in the right position, in such a way that correct information about product temperature is obtained. In this work, at first, the probability of the operational error resulting into a wrong positioning of the thermocouple inside the vial has been estimated experimentally. Then, the effect of this error has been assessed in terms of risk of exceeding the limit temperature in the primary drying step. Both 4R and 10R vials have been considered, and the investigation evidenced that the probability of incorrect thermocouples placement can reach 30% for 10R vials, and about 32% for 4R vials. These probability values increase, respectively, to 47 and 39% when the trays containing the vials are shifted to their final position. Then, through IR thermal imaging it has been possible to evaluate the temperature gradients in a vial, pointing out that the temperature difference between the product at the center of the vial, where the thermocouple is supposed to be, and that of the wall, that is quite often measured by the thermocouples, can be about 1°C. Therefore, associated to each thermocouple reading there is a probability distribution of product temperature. These figures can be used to assess the risk of exceeding the limit temperature in a freeze-drying process and, thus, to quantify suitable safety margins when evaluating thermocouple readings to take into account the operational errors, given a risk tolerability criteria.

Platelet-mimicking nanoparticles co-loaded with W18O49 and metformin alleviate tumor hypoxia for enhanced photodynamic therapy and photothermal therapy

W18O49-mediated photodynamic therapy (PDT) and photothermal therapy (PTT) are limited by the easily oxidized property and tumor hypoxia. Here, we report the development of platelet membranes as nanocarriers to co-load W18O49 nanoparticles (NPs) and metformin (PM-W18O49-Met NPs). Platelet membranes can protect W18O49 from oxidation and immune evasion, and increase the accumulation of W18O49 in tumor sites via the passive EPR effect and active adhesion between platelets and cancer cells. The introduction of metformin (Met), a typical anti-diabetic drug, can alleviate the tumor hypoxia through reducing oxygen consumption. As a result, ROS and heat generation are both greatly increased, as revealed by ROS/hypoxia imaging in vitro, IR thermal imaging in vivo and PET imaging in vivo. PM-W18O49-Met NPs show the improved therapeutic effects with greatly inhibited tumor growth and induced tumor cell apoptosis. Therefore, our work provides a novel strategy for simultaneous enhanced PDT and PTT, which is promising in bioapplication. Statemente of SignificanceW18O49-mediated photodynamic therapy and photothermal therapy are limited by the poor delivery of nanoparticles to tumors, the easily oxidized property, and tumor hypoxia environment, which will induce tumor treatment failure. Herein, we report the development of platelet membranes as nanocarriers to co-load W18O49 nanoparticles and metformin (PM-W18O49-Met NPs). Platelet membranes can protect W18O49 from oxidation and immune evasion, and increase the accumulation of W18O49 in tumor sites via the passive EPR effect and active adhesion. Metformin can alleviate the tumor hypoxia through reducing oxygen consumption. Hence, ROS and heat generation are both greatly increased. PM-W18O49-Met NPs show the improved therapeutic effects with greatly inhibited tumor growth and induced apoptosis. Therefore, our work provides a novel strategy in bioapplication.

Investigation on fabrication and capillary performance of multi-scale composite porous wick made by alloying-dealloying method

The multi-scale composite porous wick (MCPW) was fabricated with alloying-dealloying mehtod for the application in the two-phase heat transfer device. The nanostructures were constructed on the sintered copper powders, resulting in the change of surface topography and wettability for MCPW. The capillary rise test was conducted to study the capillary performance based on the IR thermal imaging method. In this study, the comparisons of the two kinds of copper powders and two types of corrosive solutions were conducted to explore porous structure effects and the interactions between the microstructures and nanostructures. Three different working liquids, i.e., acetone, ethanol and water were performed and compared on the MCPW and sintered wick. Test results showed that the MCPW presented hydrophilic performance, facilitating the penetration of the working fluid into the pores. Capillary performance could be significantly enhanced owing to the nanostructures, especially for the sample sintered with irregular copper powder and deallyed by NaOH solution.

Experimental and Numerical Visualization of Heat Transfer and Hydrodynamics Induced by Double Droplet Train Impingement

The objective of this study was to visualize and simulate the thermal physical process during double droplet train impingement for three different horizontal impact spacings (S = 0.65 mm, 1.2 mm and 2 mm). Two identical HFE-7100 droplet trains were produced using a piezoelectric droplet generator at a frequency of 6000 Hz with a corresponding droplet Weber number of 312. A translucent sapphire substrate with a thin film ITO coating was used as heater in the experiments. The heat transfer and hydrodynamics of double droplet train impingement have been visualized using IR thermal imaging and high speed optical imaging techniques, respectively. The double droplet train impingement process was also simulated numerically using the Coupled Level Set-Volume of Fluid (CLS-VOF) approach with dynamic mesh adaption (DMA). Humps were observed both numerically and experimentally between two adjacent impact craters due to the interactions caused by the impinging droplet trains. It was found that the hump height decreased when impact spacing increased. IR images show that higher impact spacing leads to better heat transfer performance, which could be due to the lower hump height at greater impact spacing conditions. It was also observed that higher impact spacing leads to better thermo-hydrodynamics within and outside the impingement zone. In summary, results show that horizontal impact spacing plays a significant role in double droplet train impingement cooling. This work was supported by the National Priority Research Program of the Qatar National Research Fund, Grant No.: NPRP 6-1304-2-525.