High Thermal Resolution Research Articles

Surface Heat Monitoring with High-Resolution UAV Thermal Imaging: Assessing Accuracy and Applications in Urban Environments

The urban heat island (UHI) effect, where urban areas experience higher temperatures than surrounding rural regions, necessitates effective monitoring to estimate and address its diverse impacts. Many existing studies on urban heat dynamics rely on satellite data with coarse resolutions, posing challenges in analyzing heterogeneous urban surfaces. Unmanned aerial vehicles (UAVs) offer a solution by providing thermal imagery at a resolution finer than 1 m. Despite UAV thermal imaging being extensively explored in agriculture, its application in urban environments, specifically for surface temperatures, remains underexplored. A pilot project conducted in Athens, Georgia, utilized a UAV with a FLIR Vue Pro R 640 thermal camera to collect thermal data from two neighborhoods. Ground data, obtained using a handheld FLIR E6-XT infrared imaging camera, were compared with UAV thermal imagery. The study aimed to assess the accuracy of the UAV camera and the handheld camera for urban monitoring. Initial testing revealed the handheld’s accuracy but tendency to underpredict, while UAV camera testing highlighted considerations for altitude in both the rjpg and tiff image pixel conversion models. Despite challenges, the study demonstrates the potential of UAV-derived thermal data for monitoring urban surface temperatures, emphasizing the need for careful model considerations in data interpretation.

High-Resolution Thermal Profiling of a High-Power Diode Laser Facet During Aging

High-Resolution Thermal Profiling of a High-Power Diode Laser Facet During Aging

Modality Conversion Meets Superresolution: A Collaborative Framework for High- Resolution Thermal UAV Image Generation

Modality Conversion Meets Superresolution: A Collaborative Framework for High- Resolution Thermal UAV Image Generation

Wide-swath and high-resolution whisk-broom imaging and on-orbit performance of SDGSAT-1 thermal infrared spectrometer

Wide-swath and high-resolution Thermal infrared (TIR) data are limited by the mutual constraint between swath and resolution. In this paper, we propose a whisk-broom imaging method with the long-linear-array (LLA) 4-stage TDI detector (a total of 2048 pixels along splicing direction) and high-precision one-dimensional scanning mirror to achieve 30 m resolution and 300 km swath. And it is being implemented in the first SDGs satellite (SATSAT-1) thermal infrared spectrometer (TIS). Specially, the integration time of whisk-broom imaging system is limited by the speed of scanning mirror, and the shorter integration time is a huge challenge to meet the requirement of high sensitivity and dynamic range. The HgCdTe detector has been improved in its annealing process to reduce dark current and noise, and the opto-mechanical system has been regulated at 195 K to reduce instrument self-emission. To address the limitations of small satellite resources, TIS is equipped with a highly integrated and lightweight design, weighing 247.5 kg and consuming 248 watts respectively. As a result of the complexity of imaging mechanisms and the low frequency of deep space observations, positioning error and radiometric calibration resources have increased, and geometric and radiometric calibration methods have been improved. On-orbit test results show that TIS is capable of detecting temperature differences with a NEdT (noise equivalent differential temperature) less than 0.08 K@300 K, an absolute radiometric accuracy of less than 1 K @ 300 K, and MTF of greater than 0.125. Presently, a collection of more than 201,856 scenes covering land and marine and some precious TIR datasets of planes and naval vessels have been obtained and provided for United Nations for the realization of SDGs goals.

Thermally boosted upconversion luminescence and high-performance thermometry in ScF3:Yb3+/Tm3+ nanorods with negative thermal expansion

Luminescence nanothermometers featuring high spatial resolution and thermal resolution have aroused extensive interest in biological and nanomedical fields. However, the challenge of thermal quenching in upconversion (UC) nanocrystals hampers achieving elevated relative temperature sensitivity (Sr). In this study, the quasi cubic nanorods of ScF3:Yb3+/Tm3+ with negative thermal expansion were prepared, and thermally boosted luminescence was found to derive from the phonon-assisted energy transfer, resulting in the emission band of 3F2,3 → 3H6 of Tm3+ ions enhanced monotonously. While the emission bands of (1G4)1D2→3F4 of Tm3+ ions first increased slightly and then decreased seriously because of the competition between phonon-assisted and cross-relaxation (CR) processes. Relying on this high-contrast thermal dependent feature, the maximum relative sensitivity of 1.60% K−1 at 523 K was achieved in the proposed luminescence intensity ratio (LIR) thermometry. These findings would open a new avenue for designing thermally boosted upconversion nanocrystals and reliable optical thermometers by using Tm3+ activated luminescent materials.

A High-Resolution Analytical Thermal Modeling Method of Capacitor Bank Considering Thermal Coupling and Different Cooling Modes

Thermal stress is of crucial importance to capacitor reliability. However, for a capacitor bank, on spatial scale, the complex heat transfer modes are not clearly illustrated; and on time scale, the ESR aging is neither fully discussed in current evaluation methods. These could lead to a glaring error in the prediction of temperature distribution and lifetime estimation. Therefore, this paper proposed an analytical thermal modeling method with high-resolution for the capacitor bank, considering the thermal coupling effect between individual capacitors, as well as different cooling conditions and the heat variation caused by ESR aging. Firstly, the improved thermal state-space modeling method is proposed to universally describe a multiple heat source system. Then, based on heat transfer and fluid mechanic theories, the characterization method of thermal coupling effect in different cooling modes is discussed. Furthermore, the ESR aging model is applied in the electro-thermal analysis of capacitor bank, aiming to improve the accuracy of thermal calculation in long time scale. Finally, to alleviate the uneven temperature distribution in an in-line designed capacitor bank, a staggered design method is proposed followed by a case study, where a nine-capacitor bank is presented to validate the corresponding modeling method and optimization.

Correction Due to Nonthermally Coupled Emission Bands and Its Implications on the Performance of Y2O3:Yb3+ /Er3+ Single-Particle Thermometers

Lanthanide-doped single dielectric nanoparticles have been exploited toward the realization of temperature sensing in the nanoscale with high spatial, temporal, and thermal resolution. However, due to the relatively small number of emitters when compared with suspensions or powders, the luminescence readouts in individual nanocrystals usually require higher excitation power densities to keep an acceptable signal-to-noise ratio. Since in numerous cases these thermometers work by exploiting upconversion excitation pathways, higher excitation powers can lead to higher-order photon emissions that can overlap with the luminescent bands used to perform the temperature measurements. This work shows that the performance and the characterization of ∼400 nm Y2O3: Yb3+/Er3+ single-particle thermometers vary depending on the excitation irradiance if higher-order spectrally overlapping bands are not properly taken into account. We apply a recently developed method to separate these bands based on their different power-law, without the need for multiple wavelength excitation, resulting in a correction procedure that reduces the temperature readout uncertainty from 0.6 to 0.3 K in the specific case of the thermometer investigated in this work. Additionally, power-excitation-related thermal artifacts on the order of 10 °C were detected and corrected with the presented method.

A New Perspective on the Diagnosis of Septic Arthritis: High-Resolution Thermal Imaging.

An increase in temperature in an area suspected of septic arthritis is a clinically important finding. The aim of this study is to evaluate temperature changes in septic arthritis with a high-resolution thermal camera. A total of 49 patients, who were evaluated with a prediagnosis of arthritis (septic or non-septic), were included in this study. A temperature increase in the knee with suspected septic arthritis was evaluated by using thermal imaging and compared with the opposite-side joint. Then, in order to confirm the diagnosis, a culture was taken using routine intra-articular aspiration. The thermal measurements were compared in 15 patients with septic arthritis and 34 patients with non-septic arthritis. The mean temperature was 37.93 °C in the septic group, while it was 36.79 °C in the non-septic group (p < 0.000 *). The mean temperature difference in both joints was 3.40 °C in the septic group, while it was 0.94 °C in the non-septic group (p < 0.000 *). While the mean temperature was 37.10 °C in the group with septic arthritis, it was measured to be 35.89 °C in the group non-septic arthritis (p < 0.020). A very strong positive correlation was found between the difference in the mean temperatures of both groups and the values of the hottest and coldest points (r = 0.960, r = 0.902). In the diagnosis of septic arthritis, thermal imagers can be used as a non-invasive diagnostic tool. A quantitative value can be obtained to indicate to a local temperature increase. In future studies, specially designed thermal devices can be developed for septic arthritis.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Urban Land Surface Temperature Retrieval From High Spatial Resolution Thermal Infrared Image Using a Modified Split-Window Algorithm

Urban Land Surface Temperature Retrieval From High Spatial Resolution Thermal Infrared Image Using a Modified Split-Window Algorithm

Spatiotemporally mapping temperature dynamics of lysosomes and mitochondria using cascade organelle-targeting upconversion nanoparticles

The intracellular metabolism of organelles, like lysosomes and mitochondria, is highly coordinated spatiotemporally and functionally. The activities of lysosomal enzymes significantly rely on the cytoplasmic temperature, and heat is constantly released by mitochondria as the byproduct of adenosine triphosphate (ATP) generation during active metabolism. Here, we developed temperature-sensitive LysoDots and MitoDots to monitor the in situ thermal dynamics of lysosomes and mitochondria. The design is based on upconversion nanoparticles (UCNPs) with high-density surface modifications to achieve the exceptionally high sensitivity of 2.7% K-1 and low uncertainty of 0.8 K for nanothermometry to be used in living cells. We show the measurement is independent of the ion concentrations and pH values. With Ca2+ ion shock, the temperatures of both lysosomes and mitochondria increased by ∼2 to 4 °C. Intriguingly, with chloroquine (CQ) treatment, the lysosomal temperature was observed to decrease by up to ∼3 °C, while mitochondria remained relatively stable. Lastly, with oxidative phosphorylation inhibitor treatment, we observed an ∼3 to 7 °C temperature increase and a thermal transition from mitochondria to lysosomes. These observations indicate different metabolic pathways and thermal transitions between lysosomes and mitochondria inside HeLa cells. The nanothermometry probes provide a powerful tool for multimodality functional imaging of subcellular organelles and interactions with high spatial, temporal, and thermal dynamics resolutions.

Thermosensitive phosphorus(V) porphyrin: Toward subcellular ratiometric optical temperature sensing

Luminescence thermometry has attracted a lot of attention due to its ability to provide temperature sensing with high spatial, temporal, and thermal resolution. This technique is the most promising for probing changes in local temperature in living cells to monitor thermogenesis and to study cellular activity. Despite rapid progress in this field, there is still a lack of optical thermometers capable of thermal sensing at the subcellular level, especially owning additional functionality. Here, cationic ( meso -mono(4-pyridyl)-triphenylporphyrinato)phosphorus(V) bromide MPyPP(OH) 2 was used as subcellular ratiometric thermal sensor in CHO-K1 and HeLa cells within the biological temperature range (30–44 o C). Introduction of porphyrin into cells resulted in its dephosphorylation and change of luminescence properties. Ratiometric sensing was performed using peak-to-peak and peak-to-valley ratios. Thermometric performance was evaluated in terms of absolute and relative sensitivities, temperature resolution. Relative thermal sensitivity and temperature resolution reached 0.61% K -1 and 0.1 o C, respectively in the case of CHO-K1 cells. • Water-soluble cationic porphyrin was successfully applied subcellular thermometry. • Introduction of porphyrin into cells leads to its dephosphorylation and change of luminescence properties. • Ratiometric sensing was realized through peak-to-peak and peak-to-valley approaches. • Thermometric performance was evaluated using relative thermal sensitivity and temperature resolution.

Measurement of thermal properties of liquid analytes using microfluidic resonators via photothermal modulation

Understanding the thermal properties of fluids at the nanoscale with high spatial, temporal, and thermal resolution are on great demand in the fields of MEMS, drug development, biomedical devices, and analytical systems. Microfluidic channel-integrated cantilevers are considered as an established benchtop sensor platform for physical and thermal characterization of materials at the picogram amount of analytes. This paper reports analysis of thermal characteristics of liquid analytes using photothermal heating effect of the microfluidic cantilever. Using real-time tracking of frequency shift of microfluidic resonator, the thermal properties of liquid samples can be estimated whilst the liquid analytes in the cantilever are locally heated by laser-induced irradiation. The heating results in the expansion of the liquid inside the channel which induces thermal stress on the walls of the channel. This thermal stress contributes to the rise of the resonance frequency of the microfluidic resonator and, therefore, the frequency shift is linearly dependent on the volumetric coefficient expansion of the liquid. A threefold improved sensitivity is observed when the second order flexural vibration mode is analyzed compared to that of the fundamental resonance. This approach, which combines photothermal heating and the dynamic mode of operation, can serve as a platform for the development of a portable, lab on a chip device for the use of real time detection of thermomechanical properties of fluids at low cost.

Invisible Thermoplasmonic Indium Tin Oxide Nanoparticle Ink for Anti-counterfeiting Applications.

In this study, we present a thermoplasmonic transparent ink based on a colloidal dispersion of indium tin oxide (ITO) nanoparticles, which can offer several advantages as anti-counterfeiting technology. The custom ink could be directly printed on several substrates, and it is transparent under visible light but is able to generate heat by absorption of NIR radiation. Dynamic temperature mapping of the printed motifs was performed by using a thermal camera while irradiating the samples with an IR lamp. The printed samples presented fine features (in the order of 75 μm) and high thermal resolution (of about 250 μm). The findings are supported by thermal finite-element simulations, which also allow us to explore the effect of different substrate characteristics on the thermal readout. Finally, we built a demonstrator comprising a QR Code invisible to the naked eye, which became visible in thermal images under NIR radiation. The high transparency of the printed ink and the high speed of the thermal reading (figures appear/disappear in less than 1 s) offer an extremely promising strategy toward low-cost, scalable production of photothermally active invisible labels.

High-Resolution Thermal Profiling of a Combustor in a Non-Dedicated Test Using Thermal History Coatings

Abstract The requirement for reduced emissions and the growing demand for gas turbine efficiency are in part met through increasing firing temperatures. However, development budgets leave only limited time for dedicated thermal testing. Consequently, manufacturers are seeking novel temperature measurement technologies to validate new engine designs. This paper will demonstrate how a new temperature mapping technology can be utilized for non-dedicated (multi-cycling) testing while still delivering high-resolution temperature data in a non-dedicated test on a combustor of an industrial gas turbine. Typically, thermocouples are used to monitor the temperature during tests, but they only provide one data point. Color-changing thermal paints are used to deliver measurements over complete surfaces, but they require dedicated testing with short-duration exposure, necessitating dismantling and re-assembling the engine for further testing. Thermal History Coatings (THC) present an alternative solution to providing high-density temperature information. This coating permanently changes consistent with the maximum temperature of exposure during the test. A laser-based instrumentation technique is then used to obtain temperatures. The maximum temperature profile of the surface can be determined through a customized calibration. Given the complex cooling system of a combustor, the high temperatures, and the long-time exposure, this case offers a unique possibility for the testing of the coating under real engine conditions. The coated region covered the external surface of the can. Highly significant is the number of measurement points above 7000 (2 × 2 mm resolution), which enables advanced analysis. This provides insight into the impact of local features, e.g., the region adjacent to a cooling hole. The temperature profile is compared to a computational fluid dynamics-conjugate heat transfer model and thermocouple measurements for the calibration of cooling pre-design methods.

Modulating the thermally coupled status of energy levels in rare earth ions for sensitive optical temperature sensing

Luminescence thermometry technique, which utilizes the rare earth ions activated luminescent nanomaterials as sensing media, has presented great potential in various fields owing to its high spatial, temporal, and thermal resolutions. Nevertheless, the development of sensitive luminescent nanothermometers working in the biological window remains a challenge. Here, Tm3+-Yb3+ codoped NaYF4 nanocrystals, the excitation and emission wavelengths of which are both located within the near-infrared region, are investigated for optical temperature measurement via the fluorescence intensity ratio (FIR) approach. The thermal population and decay rates involved in the thermally coupled levels (3F2, 3 and 3H4) are verified to play an important role in regulating the thermal coupling status. The measurement sensitivity of as-prepared nanothermometers is optimized through modulating the Tm3+ surrounding environment and a maximum sensitivity of about 2.13% K−1 is achieved in the physiological temperature range. Besides, a parameter named as thermally coupled degree is defined in this work to quantify the coupling between the thermally coupled levels. According to the conclusion of our work, special attention has to be taken for rationally constructing FIR-based optical temperature sensors.

Infrared Thermography for Monitoring of Freeze Drying Processes-Part 2: Monitoring of Temperature on the Surface and Vertically in Cuvettes during Freeze Drying of a Pharmaceutical Formulation.

The coupling of an infrared (IR) camera to a freeze dryer for monitoring of the temperature of a pharmaceutical formulation (sucrose/mannitol solution, 4:1%, m/m) during freeze-drying has been exploited further. The new development allows monitoring of temperatures simultaneously at the surface as well as vertically, (e.g., in depth) along the side using custom-made cuvettes. The IR camera was placed on the chamber roof of a process-scale freeze dryer. Monitoring of cuvettes containing the formulation took place from above where one side of each cuvette was equipped with a germanium window. The Ge-window was placed next to an IR mirror having a 45° angle. The long-wave infrared radiation (LWIR) coming from the inside of the cuvette was reflected upwards toward the IR camera. Accurate recording of the temperature along the cuvettes’ depth profile was therefore possible. Direct imaging from −40 °C to 30 °C took place every 60 s on the surface and on the side with a 2 × 2 mm resolution per IR pixel for 45 h resulting in 2700 thermograms. Results are presented for freeze-drying of a pharmaceutical formulation as a function of time and spatially for the entire side (depth) of the cuvette. As the sublimation process was progressing, the spatial resolution (84 IR pixels for the side-view and 64 pixels for the surface-view) was more than sufficient to reveal lower temperatures deeper down in the material. The results show that the pharmaceutical formulation (a true solution at the onset) dries irregularly and that the sublimation front does not progress evenly through the material. During secondary drying, potential evaporative cooling of upper layers could be detected thanks to the high thermal and spatial resolution.

CRISM‐Based High Spatial Resolution Thermal Inertia Mapping Along Curiosity's Traverses in Gale Crater

AbstractThermal inertia is a key summary property describing the thermophysical characteristics of geologic materials. Orbital estimates of thermal inertia are especially useful in conjunction with rover‐based observations to provide additional constraints on material properties and to interpret the broader region surrounding the traverse. We have developed an approach to estimate apparent thermal inertias (ATI) from observations from the Mars Reconnaissance Orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at a much higher spatial resolution than is available from any other orbital data set. We apply this method to along‐track oversampled scene FRT00021C92 over Gale Crater within Glen Torridon, where the Curiosity rover has traversed; the retrieved values are then analyzed along with remote sensing and in‐situ observations by Curiosity to characterize surface properties in and around Glen Torridon. CRISM‐based ATI estimates of basaltic sand fields indicate a correlation between higher ATI values and the abundance of large (up to 3 mm in size) grains on the crests and flanks of large ripples. On the Vera Rubin ridge, ATI estimates are used to identify a west‐to‐east increase in the abundance of rock fragments within unconsolidated surface cover. On the Greenheugh pediment, an unmixing approach is used to identify a thin layer of wind‐blown sand sourced from the nearby Sands of Forvie. Finally, within Glen Torridon, a north‐to‐south increase in the mean and width of the ATI distribution is identified as a consequence of increased bench‐like bedrock exposures.

Building a UAV Based System to Acquire High Spatial Resolution Thermal Imagery for Energy Balance Modelling

High spatial resolution and geolocation accuracy canopy evapotranspiration (ET) maps are well suited tools for evaluation of small plot field trials. While creating such a map by use of an energy balance model is routinely performed, the acquisition of the necessary imagery at a suitable quality is still challenging. An UAV based thermal/RGB integrated imaging system was built using the RaspberryPi (RPi) microcomputer as a central unit. The imagery served as input to the two-source energy balance model pyTSEB to derive the ET map. The setup’s flexibility and modularity are based on the multiple interfaces provided by the RPi and the software development kit (SDK) provided for the thermal camera. The SDK was installed on the RPi and used to trigger cameras, retrieve and store images and geolocation information from an onboard GNSS rover for PPK processing. The system allows acquisition of 8 cm spatial resolution thermal imagery from a 60 m height of flight and less than 7 cm geolocation accuracy of the mosaicked RGB imagery. Modelled latent heat flux data have been validated against latent heat fluxes measured by eddy covariance stations at two locations with RMSE of 75 W/m2 over a two-year study period.

Repeated ETRTs in a Complex Stratified Geological Setting: High-Resolution Thermal Conductivity Identification by Multiple Linear Regression

Repeated ETRTs in a Complex Stratified Geological Setting: High-Resolution Thermal Conductivity Identification by Multiple Linear Regression