Thermal Measurements Research Articles

Topological Thermal Hall Conductance of Even-Denominator Fractional States.

The even-denominator fractional quantum Hall (FQH) states ν=5/2 and ν=7/2 have been long predicted to host non-Abelian quasiparticles. Their present energy-carrying neutral modes are hidden from customary conductance measurements and thus motivate thermal transport measurements, which are sensitive to all energy-carrying modes. While past "two-terminal" thermal conductance (k_{2t}T) measurements already proved the non-Abelian nature of the ν=5/2 FQH state, they might have been prone to a lack of thermal equilibration among the counterpropagating edge modes. Here, we report a novel thermal Hall conductance measurement of the ν=5/2 and ν=7/2 states, being insensitive to equilibration among edge modes. We verify the state's non-Abelian nature, with both states supporting a single upstream Majorana edge mode (hence, a particle-hole Pfaffian order). While current numerical works predict a different topological order, this contribution should motivate further theoretical work.

Convective Drying of Films of Polymer Solutions: Front Propagation Revealed by Thermal Measurements.

We report on the drying of films of polymer solutions under a controlled laminar air flow. Temperature measurements reveal that a drying front propagates in the film at constant velocity. Using thermal calibration, we are able to quantitatively determine the local drying rate of the film, and we find it agrees with conservation arguments. We further show that a simple mass balance allows us to relate the front velocity to the drying rate.

Labile not stable SOC fractions constitute the manageable drivers of soil health advances in carbon farming

The assessment of soil health and the determination of carbon stability in soils are current challenges that have gained momentum through initiatives at national as well as international scales. However, inferring universally valid soil health parameters that are directly linked to carbon permanence remains challenging. Our aim was to evaluate the potential of simultaneous thermal analysis (STA) for an improved monitoring of soil health advances in the context of carbon farming strategies. For this purpose, an on-farm comparison of soil health in ten conservation agricultural systems with adjacent conventional farms was performed based on STA and thermal measures were related to key biological and physical indicators for monitoring soil functions. Using an autocorrelation-based approach, we identified independent thermal indicators, revealing that carbon farming efforts predominantly increased labile soil organic matter fractions in the range of 300–400 °C, while thermally more recalcitrant fractions did not respond to farming system transformation. Similarly, most soil health indicators revealed highest correlation with temperature ranges of mass loss of labile organic matter fractions. The relation of STA with commonly used soil health indicators was highest for soil organic carbon (SOC, r=0.971) and total nitrogen (TN, r=0.981). However, also inference on microbial activity parameters such as dimethylsulfoxid reduction, microbial biomass carbon and substrate-induced respiration could be demonstrated with r>0.663. The results thus highlight key temperature ranges of organic matter stability for future soil monitoring tasks of climate change mitigation potentials of carbon farming and related advances in soil health.

MAX phases: Unexpected reactivity under impact

This study reveals that MAX phase materials can exhibit extraordinary reactivity when subjected to impact loading. This previously unknown behavior was discovered and examined in a case study of Ti3SiC2 subjected to Split Hopkinson pressure bar (SHPB) testing. The employed methodology integrated SHPB coupled with thermal measurements and ex-situ spectroscopic analysis, yielding crucial quantitative insights into MAX phase reactivity and mechanical impact response. We observed a substantial release of high energy in the form of elevated temperatures upon impact and disintegration of the MAX phase. Surprisingly, it was found that oxidation, usually the prominent contributor to reactivity, only plays a secondary role. Instead, microstructural transformation emerges as the primary source of energy release. It is postulated that the transformative kinetic mechanism involves rapid kinking, delamination, and bond breakage within the bulk material. These findings shed light on the fundamental energetics of MAX phases and highlight their potential as versatile reactive structural materials.

Development and characteristic research on new thermal insulation and anti-permeability grouting material for tunnels in cold regions

The surrounding rock of tunnels in cold regions are susceptible to the freeze–thaw cycle resulting from the combination of low temperatures and moisture during tunnel service. The phenomenon will not only lead to the expansion of pores and fissures in the surrounding rock of the initial tunnel, but also destroy the integrity of the rock. This destruction will have a serious impact on tunnel structure and rail transit operation safety. At present, the commonly used thermal insulation measures have some problems such as maintenance difficulties, low economic efficiency, and safety hazards. Therefore, it is urgent to develop a kind of tunnel maintenance grouting material with insulation and anti-permeability, which has the characteristics of simple operation, easy preparation and application. We independently developed a composite grouting material composed of polyurethane (PU), epoxy resin (E-51) and acrylic powder (PMMA). Through the material combustion test, magnesium hydroxide was selected as the flame retardant additive. Moreover, we measured the thermal conductivity, water absorption, apparent density, porosity and strength characteristic parameters. The thermal insulation and anti-permeability characteristics of the composites were also analyzed. The results indicated that the thermal conductivity of the new composite grouting material is 6.3% lower than the PU before adding flame retardant. Compared with the PU with flame retardant, the water absorption decreased by 74.4% and the ultimate strength increased by 33.3%. For the area with an average temperature lower than − 10 °C, we recommend the ratio scheme of E-51: 3%; PMMA: 15%. For the area with high water content in the surrounding rock of the tunnel, we recommend the ratio scheme of E-51: 15%; PMMA: 3%. This study provides new ideas for material preparation and tunnel insulation methods for anti-freezing measures in tunnels during their operational period in cold regions.

Large-scale characterization of drug mechanism of action using proteome-wide thermal shift assays.

In response to an ever-increasing demand of new small molecules therapeutics, numerous chemical and genetic tools have been developed to interrogate compound mechanism of action. Owing to its ability to approximate compound-dependent changes in thermal stability, the proteome-wide thermal shift assay has emerged as a powerful tool in this arsenal. The most recent iterations have drastically improved the overall efficiency of these assays, providing an opportunity to screen compounds at a previously unprecedented rate. Taking advantage of this advance, we quantified more than one million thermal stability measurements in response to multiple classes of therapeutic and tool compounds (96 compounds in living cells and 70 compounds in lysates). When interrogating the dataset as a whole, approximately 80% of compounds (with quantifiable targets) caused a significant change in the thermal stability of an annotated target. There was also a wealth of evidence portending off-target engagement despite the extensive use of the compounds in the laboratory and/or clinic. Finally, the combined application of cell- and lysate-based assays, aided in the classification of primary (direct ligand binding) and secondary (indirect) changes in thermal stability. Overall, this study highlights the value of these assays in the drug development process by affording an unbiased and reliable assessment of compound mechanism of action.

Ionic liquid regulating perovskite film for air-processed perovskite solar cells

Air-processed perovskite solar cells (PSCs) expediate its commercialization. However, since the intrinsic moisture sensitivity disturb perovskite crystallization and morphology, the photovoltaic performance and shelf stability attenuation are inevitably occurred. Herein, 1-ethy-3-methylimidazolium tetrafluoroborate ([AOEMIM][BF4]) ionic liquids (ILs) was incorporated into perovskite interior to weaken the deleterious influence of ambient moisture on perovskite crystallization. The carboxyl and imidazole from the [AOEMIM]+ moiety passivate undercoordinated Pb2+ defects through coordination bond, while hydrophobic [BF4]- incorporating into the precursor solution protects the films from moisture destruction. Consequently, the targeted PSCs fabricated in open air achieved an impressive PCE of 19.86 % with favorable shelf stability, maintaining 93 % and 89 % of their original efficiencies after 720 h under relative humidity of 80 ± 2 % and after 240 h thermal ageing measurement at 85 °C, respectively.

(Invited) Flow of Charge and Heat in Ultra-Clean Graphene

Over the past two decades our understanding of the charge and heat transport properties of graphene has evolved progressively as the quality of graphene devices improved. In this talk, I shall present some new experimental result on the electrical and thermal transport measurements in graphene devices of unprecedented electrical mobility (> 1 million cm2/V.s). We show that the transport in such graphene devices is limited by intrinsic acoustic phonons and their scattering with electrons, rather than charged impurities – which is the case in conventional disordered graphene devices. This manifests in a rather striking violation of the Wiedemann-Franz law and density-dependent variation of the effective Lorenz number over six orders of magnitude. We find that the transport properties of ultra-clean graphene are quantitatively consistent with that of a hydrodynamic Dirac fluid.

Natural Radiation Sourced Heat Stress: Thermal Comfort Depending On Color Factor In Safety Reflector Vests

Research has shown that personal protective clothing is not used by employees due to personal reasons such as lack of working comfort and heat stress. Solar (UV) radiation creates a heat effect on people working outdoors. Agricultural and construction workers are exposed to solar radiation and are known to be at high risk of heat stress, especially in arid climates. It is important for the person to individually evaluate the ambient temperature as hot or cold for the ergonomic conditions of the employee. In this study, for increasing safety and comfort expectations, heat changes in reflector vests based on colors of heating due to natural radiation were estimated with thermal camera measurements, and gained heat values ​​of vests with different fabric thicknesses were estimated using fuzzy logic modeling over time, and the effects of natural radiation on human health were examined.

Study on the Hydration Heat Effect and Pipe Cooling System of a Mass Concrete Pile Cap

Under the action of cement hydration heat, the construction environment, thermal insulation measures, and pipe cooling systems, a mass concrete pile cap is subject to a complex internal temperature field, which makes it difficult to control its internal surface temperature difference (TISTD), the internal adiabatic temperature rise (TIATR), and the surface temperature (TST). In this study, a mass concrete pile cap of a very large bridge (the length, width, and height were 26.40 m, 20.90 m, and 5.00 m, respectively, and the central-pier pile cap was constructed with C40 concrete) was taken as the research object. The control factors affecting the temperature field of the pile cap were determined by comparing the field temperature measurements with the values calculated with finite element software simulation analysis. By using Midas Civil (2022 v1.2) and Midas FEA (NX 2022) finite element software, these factors (the concrete mold temperature, the concrete surface convection coefficient, the ambient temperature, the pipe cooling system parameters, etc.) were numerically analyzed, and their influence laws and degrees were determined.

Thermal Conductivity of Nanofluid, a Mini Review

The rapid development of the world and the increasing need to increase the efficiency of devices in many applications has led to the development of fluid conductivity with more efficient heat transfer has made it necessary to enhance heat transfer to meet the cooling challenge, as is the case in the photonics, electronics, power supply and transportation industries. Nanofluids and methods for measuring them have been developed and studied to facilitate the interpretation of their behavior, including thermal behavior. The study aimed to gain a fundamental and experimental understanding of the thermal behavior of nanofluids by examining thermal conductivity, preparation techniques, stability-enhancing agents, and measurement techniques. With changes in shape, concentration, and temperature, nanofluids exhibit significantly improved thermal conductivity. In addition, efforts have been made to introduce new and accurate correlations for estimating thermal conductivity at different concentrations and temperatures.

Psychological Motivation Analysis of Farmers' Collective Energy-saving Behavior and Influence of Intervention Effect

The poor thermal performance of rural buildings in northern China and the serious pollution caused by loose coal combustion are practical problems that need to be solved urgently. In order to solve the two problems, this paper analyzed the current situation of the envelope structure of rural houses in the north of our country and the commonly used heating forms of farmers. It was found that the envelope structure of most rural houses did not take heat preservation measures and needed to be transformed to save energy. The commonly used heating systems for farmers are coal furnaces, hanging kang, earth heating, etc., and the wealthier rural areas use biogas or straw gasification for central heating, but there are still various problems to be improved in these systems. In order to improve the thermal performance of the farmers' building structure, the thermal performance measurement and energy-saving transformation of the enclosure structure of a typical farmer in Xiaoyi, Shanxi Province were carried out. Before the energy-saving transformation, Energy Plus software simulation analysis shows that the typical farmer can save 60% of the heating energy consumption after the energy-saving transformation. Before and after the energy-saving transformation, the actual measurement results show that the heat transfer coefficient of the wall, window and roof decreased by 72.7%, 61.59% and 64.99% respectively from 2.3 times, 1.43 times and 2.11 times the national requirement limit. The performance of the envelope structure after the energy-saving transformation can meet the national requirements. The actual statistics show that the biomass fuel consumption per unit temperature difference before and after the transformation is saved by 66.74%, which indicates that the energy-saving transformation has achieved good results, and shows the accuracy of the Energy Plus model. The psychological intervention of energy-saving transformation proposed in this study helps to improve people's awareness of energy-saving, reduces anxiety and fear, and has a very good effect on the psychological intervention effect.

Nanostructuring of AlSiCrMnFeNiCu High‐Entropy Alloy via Cryomilling: Exploring Structural, Magnetic, and Thermoelectric Properties

Efforts are made to understand the influence of milling intensity on structure, morphology, magnetic and thermoelectric properties of nonequiatomic nanostructured AlSiCrMnFeNiCu high‐entropy alloy (HEA) powders prepared by cryomilling. These powders are cryomilled with different ball‐to‐powder ratios (BPR) and present a dual‐phase structure containing a major B2‐type and a minor Cr5Si3‐type phase. An increase in BPR enhances the refinement of crystallite size, grain size, and particle size accompanied by a decrease in the phase fraction of the minor Cr5Si3‐type phase. Magnetic measurements revealed that at room temperature, sufficient increase in BPR leads to a transition from multi‐domain behavior to single‐domain behavior which leads to enhancement in soft magnetic properties. Thermal measurements show the presence of different magnetic phase transitions which vary with an increase in BPR. A change of charge carrier type from p to n‐type was observed as the grain size is reduced. The figure of merit decreases with the decrease in grain size from 2 × 10–5 for as‐cast powders and is lowest for the smallest grain‐sized sample due to a decrease in electrical conductivity. This study shows the possibility of exploring nonequiatomic low‐density HEAs whose functional properties can be tailored, offering flexibility in material design for specific applications.

Understanding coaxial photodiode-based multispectral pyrometer measurements at the overhang regions in laser powder bed fusion for part qualification

Coaxial photodiode monitoring sensors provide a digital signature at the melt pool level in laser powder bed fusion (L-PBF), facilitating faster part qualification. However, current signatures are plagued by significant noise and signal variation and show counterintuitive trends such as a decrease in measured temperature near overhang surfaces. This paper investigates the behavior of coaxial photodiode-based melt pool monitoring (PD-MPM) thermal measurements at overhang regions by conducting a combination of experiments and multiphysics simulations. High-speed in situ synchrotron X-ray imaging is coupled with a coaxial photodiode system to enable comparison of the observed melt pool phenomena and monitoring signals during double-track AlSi10Mg experiments. A multiphysics model is developed to simulate the melt pool dynamics and concurrent sensor signals throughout the process. We propose a surrogate model that clarifies the correlation between sensor signals and melt pool temperature. Both experimental and simulation results emphasize the significant impacts of laser energy and keyhole formation on solid-liquid interface discontinuities and PD-MPM signals. Results reveal that a boiling region with a relatively smaller projected area, as near an overhang, can lead to a decrease in the measured melt pool temperature, even when the true peak temperature remains constant, meaning that PD-MPM temperature measurements cannot be used to estimate absolute melt pool temperature. Consequently, in overhang regions, interaction between the melt pool and underlying powder results in an abruptly deforming melt pool and a pronounced decrease in both individual photodiode intensities and overall measured melt pool temperature. This work illustrates how to correctly interpret the coaxial photodiode monitoring signals in L-PBF by uncovering the intricate dynamics within the melt pool, particularly in challenging overhang regions, and pave the foundation for data-driven part qualification.

Characterization and optimization of continuous ohmic thermal sterilization based on the development of a predictive computational toolbox

Continuous thermal processing (CTP) is a common method for sterilizing food. However, it can result in an uneven temperature distribution, which can lead to a varying degree of processing intensity. Ohmic heating (OH) can be advantageous in this regard, as it enables volumetric heating for more homogenous treatments. However, evaluating the processing intensity distribution inside the equipment for OH is challenging due to the complex interaction between electrical, mechanical and thermal phenomena. Furthermore, the comparison of OH and conventional heating treatments often lack a profound basis of comparable treatment intensity considerations. To gain a deeper mechanistic understanding of the technology, a numerical computational fluid dynamics model for the OH sterilization of a clear carrot juice from the heating region to the cooling process was developed. The model was validated with thermal and electrical measurements and showed an error rate below 2.5% in its prediction capacities. Moreover, the model was implanted for the validation of the products sterilization and compared to a conventional validation approach, reviling a 33.3% underestimation of the thermal load by conventional manners, which can lead to faulty sterilization of the food product. Additionally, the model was expanded to also be able to predict the microbial inactivation ratio of the system with an average error of 1.10±0.74%. In addition, results indicate that the numerical calculation of the F0 values and their validation with the microbial inactivation ratio have a notable potential for localization and evaluation of hotspots in OH simulations. Therefore, it can be seen as a promising step for establishing a foundation for computer-assisted optimization of CTP and targeted processing.

Exploring the process-microstructure-thermal properties relationship of resin-reinforced Ag sintering material for high-power applications via 3D FIB-SEM nanotomography

Resin-reinforced Ag sintering materials represent a promising solution for die-attach applications in high-power devices requiring enhanced reliability and heat dissipation. However, the presence of resin and intricate microstructure poses challenges to its thermal performance, and improvement strategies remain unclear. This work utilizes 3D FIB-SEM nanotomography to reconstruct the microstructure of this material under various process conditions. The analysis reveals that, even with an Ag volume fraction as low as 47.3%, Ag particles form a robust 3D network. Geometric tortuosity quantifies the effect of different sintering conditions on the Ag particle network in all spatial directions. Effective thermal conductivity is simulated based on realistic microstructure models. Results show a significant negative correlation between tortuosity and effective thermal conductivity. Increasing sintering temperature in Model B notably reduces tortuosity and enhances effective thermal conductivity. Sensitivity analysis underscores the dominant role of Ag volume fraction in regulating effective thermal conductivity. Finally, transient thermal impedance measurement of this material as a thin die-attach layer in actual high-power devices demonstrated its application potential. This article strives to explore the relationship between process, microstructure, and thermal properties of this material to provide a reference for further development.

Enhancing stress assessment in sledge reindeer (Rangifer tarandus): a pilot study on infrared thermal imaging and its opportunities for advancement as a welfare assessment tool

Measuring immediate physiological stress responses in animals can be challenging; saliva and blood sampling, while invasive, may also generate confounding stress responses, and equipping animals with heart rate sensors is not always feasible. Nevertheless, emerging technologies offer a non-invasive and contactless method to measure additional body surface temperature changes induced by acute stress, using infrared thermal measurement of the eye caruncle region. Contactless temperature measurement has the potential to assess the emotional state of animals affected by human physical contact. Reindeer, being highly sensitive to touch and naturally avoiding physical contact, exemplify this case. With growing interest in safari tours involving sledging reindeer, there is a need to investigate how these animals are affected by human interactions and how they adapt to daily close contact. In this pilot experiment, we evaluated the efficacy of thermal imaging in measuring medial canthus temperature fluctuations in non-habituated sledging reindeer while being petted by unfamiliar humans. Our findings support the hypothesis that medial canthus temperature significantly decreases during petting and increases once the interaction ceases, aligning with established stress response patterns found in the literature. This pilot experiment underscores the potential of infrared thermal imaging for non-invasively monitoring physiological responses to stress in tamed reindeer. Moreover, it sets the foundation for refining methodologies and experimental designs using infrared thermal imaging in animal welfare research.

Impact of transition spaces on the indoor thermal environment: A case study of traditional dwellings in Southern Shaanxi, China

Transition space connecting internal space and external environment of buildings, which has a buffering effect on improving the indoor thermal environment and saving energy consumption. This research focuses on thermal environment regulation performance of the corridor space of traditional dwellings in hot summer and cold winter region in China was investigated. Firstly, the field investigation and thermal comfort measurement were conducted to clarify the regulating performance of corridor space in the indoor thermal comfort and human adaptability to the environment. Then, the research uses the Grasshopper and Energy plus platforms to analyze and quantitatively verify the effectiveness of the corridor space in enhancing the indoor thermal comfort. Finally, based on the multi-objective optimization by NSGA-II, the Pareto set is generated to obtain the optimal solution for the corridor space to meet the thermal comfort. The results show that corridor of dwelling has a width of 2 m, a slope of 15°, and a height of 3.9 m. The traditional dwellings with corridor space could improve the thermal comfort hours increase by 5.1 %, the energy consumption reduce by 18.7 %. This research could help inhabitants achieve the adaptive design of corridor space and improve the livability of residential habitats in southern Shaanxi.

Optimization Design Methods for Thermal Environment Problems in Chinese University Teaching Buildings at Various Periods

Chinese universities have gone through three periods of centralized construction and significant differences in the design of teaching buildings in different periods may cause various thermal environment problems. This study takes a city in a cold region in northern China as an example and selects three teaching buildings built during three concentrated construction periods: 1950s to 1960s, 1980s to 1990s, and early 21st century as common cases. Based on field research, thermal environment measurement, APMV and PMV-PPD evaluation, and DeST simulation methods, it was found that the average summer APMV of the three teaching buildings was 1.37, indicating poor thermal comfort. In winter, the ambient temperature of the classrooms was below 18 °C for about 30% to 40% of the whole year, the average PMV value was −2.36, and the PPD value was obtained as 83.28%, far exceeding the standard requirements. The obtained results form a design strategy to optimize the thermal environment of teaching buildings. By considering the teaching building of historical architecture from the 1950s to 1960s as an example, the optimization design was carried out from three aspects to improve the indoor thermal environment and reduce the building’s cooling and heating load. The cumulative load of the building throughout the year was reduced by 21%, the cumulative heat load was reduced by 28.3%, and the cumulative cooling load was reduced by 10.1%. This research is anticipated to be of great reference significance for enhancing the thermal comfort of existing buildings, promoting energy conservation, and reducing carbon emissions. At the same time, it contributes to the protection and optimal use of historical buildings.

Noncontact measurement of density and thermal properties of SS 316L powder bed through flash thermography

PurposePowder bed density is a key parameter in powder bed additive manufacturing (AM) processes but is not easily monitored. This research evaluates the possibility of non-invasively estimating the density of an AM powder bed via its thermal properties measured using flash thermography (FT).Design/methodology/approachThe thermal diffusivity and conductivity of the samples were found by fitting an analytical model to the measured surface temperature after flash of the powder on a polymer substrate, enabling the estimation of the powder bed density.FindingsFT estimated powder bed was within 8% of weight-based density measurements and the inferred thermal properties are consistent with literature findings. However, multiple flashes were necessary to ensure precise measurements due to noise in the experimental data and the similarity of thermal properties between the powder and substrate.Originality/valueThis paper emphasizes the capability of Flash Thermography (FT) for non-contact measurement of SS 316 L powder bed density, offering a pathway to in-situ monitoring for powder bed AM methods including binder jetting (BJ) and powder bed fusion. Despite the limitations of the current approach, the density knowledge and thermal properties measurements have the potential to enhance process development and thermal modeling powder bed AM processes, aiding in understanding the powder packing and thermal behavior.