Heat Measurements Research Articles

Investigation of the Microenvironment, Land Cover Characteristics, and Social Vulnerability of Heat-Vulnerable Bus Stops in Knoxville, Tennessee

The urban heat island is a climate, public health, and environmental justice issue. Sustainable urban infrastructure needs improvements in public transport to protect citizens’ health from the urban heat island. This case study investigates the local microenvironment and social vulnerability of heat-vulnerable bus stops in Knoxville, Tennessee, using publicly available data from a variety of sources. These included ground and satellite measurements of heat and humidity from the Knoxville Heat Mapping Campaign, characteristics of land surface from the National Land Cover Dataset 2019 of the United States Geological Survey, and the 2018 Social Vulnerability Index from the U.S. Centers for Disease Control and Prevention. A geographic information system and a principal component analysis were used to identify social vulnerability in areas where the bus stops are located. The results show that most heat-vulnerable bus stops are poor microenvironments without trees and shelters. The hottest bus stops are concentrated in the highly developed and densely populated areas of West Knoxville and downtown Knoxville and in South, North, Northeast, and Northwest Knoxville, which are relatively high vulnerability clustered and have poor public infrastructure. The findings provide the foundation for mitigation strategies to better prepare local communities for climate change by identifying public transportation areas negatively impacted by the urban heat island.

Design of an Adiabatic Calorimeter for Cementitious Mixtures by Multi-Objective Optimization

This study aims to design an adiabatic calorimeter for cementitious mixtures using NSGA-II and the Pareto optimal solution set. In this multi-objective optimization, the controller effort and heating time are selected as objective functions. Likewise, the volume and the material to be heated were chosen as decision variables. The optimal solution was selected using Nash bargaining methods. After implementing the optimal solution, the Wilcoxon test was applied to statistically validate the developed work. The measurements performed were compared with other research and it was observed an improvement in the measurement of heat of hydration in cementitious mixtures. Also, it was noted a decrease in the error in the temperature measurement.

Synthesis, Structure, and Physicochemical Characteristics of Zn1−xRexCr2Se4 Single Crystals

This study aimed to obtain and investigate ZnCr2Se4 single crystals doped with rhenium. The single crystals were obtained by applying chemical vapour transport. An X-ray study confirmed the cubic (Fd3¯m) structure of the tested crystals. Thermal, magnetic, electrical, and specific heat measurements accurately determined the physicochemical characteristics, which revealed that the obtained single crystals are p-type semiconductors with antiferromagnetic order below the Néel temperature TN = 21.7 K. The Debye temperature had a value of 295 K. The substitution of Re-paramagnetic ions, possessing a screened 5d-shell, in place of Zn-diamagnetic ions, caused an increase in the activation energy, Fermi energy, and Fermi temperature compared to the pure ZnCr2Se4. The boost of the dc magnetic field induced a shift of TN towards lower temperatures and a spin fluctuation peak visible at Hdc = 40 and 50 kOe. The obtained single crystals are thermally stable up to 1100 °C.

Role of electron correlation and disorder on the electronic structure of layered nickelate (La0.5Sr0.5)2NiO4

We investigate the role of electron correlation and disorder on the electronic structure of layered nickelate ${({\mathrm{La}}_{0.5}{\mathrm{Sr}}_{0.5})}_{2}{\mathrm{NiO}}_{4}$ using core level and valence band photoemission spectroscopy in conjunction with density functional theory (DFT) and dynamical mean-field theory (DMFT) calculations. Sr $3d$ and La $4d$ core level spectra exhibit multiple features associated with photoemission final-state effects. An increase of unscreened features in the Sr $3d$ and La $4d$ core level spectra with lowering temperature suggests the reduction in density of states (DOS) at the Fermi level, ${E}_{F}$. Valence band spectra collected using different photon energies reveal finite intensity at ${E}_{F}$ and overall spectra are well captured by $\mathrm{DFT}+\mathrm{DMFT}$. Strong renormalization of partially filled ${e}_{g}$ bands in $\mathrm{DFT}+\mathrm{DMFT}$ result indicates strong correlation in this system. Mass enhancement factor, ${m}^{*}/{m}_{\text{DFT}}\ensuremath{\sim}$ 3, agrees well with values obtained from specific heat measurements. High-resolution spectra in the vicinity of ${E}_{F}$ show monotonically decreasing spectral intensity with lowering temperature, which evolves to exhibit a Fermi cutoff at low temperatures indicating metallic character in contrast to insulating transport, suggesting Anderson insulating state. $|E\ensuremath{-}{E}_{F}{|}^{1/2}$ dependence of the spectral DOS and square-root temperature dependence of spectral DOS at ${E}_{F}$ evidences the role of disorder in the electronic structure of ${({\mathrm{La}}_{0.5}{\mathrm{Sr}}_{0.5})}_{2}{\mathrm{NiO}}_{4}$.

High-strength and high-toughness weld of S690QL HSLA steel via a high-speed high frequency electric cooperated arc welding without additional heating measures

Problems in balancing joint strength and toughness, caused by the strict requirements of welding heat, have been a long-troubling problem that attracts close attention in the High Strength Low alloy (HSLA) steel welding field. Additional heating measures have been considered as an only and necessary solution with limited effect to deal with the above issue, which not only complicate the welding process but also have some incidental impacts. In this paper, a novel method named High Frequency Electric Cooperated Arc Welding (HFAW) was employed to join typical HSLA steel S690QL without additional pre- or post-heating measures. Relationships between the welding thermal characteristics, microstructure and mechanical properties of different parts in the joint were revealed and compared. Results showed that sound HFAW joint was achieved with a welding heat input and speed of 3630.6 J/cm and 2.3 cm/s, while that in conventional GMAW was 7077.1 J/cm and 0.5 cm/s, respectively. The width of the softening zone in the optimal HFAW joint was narrow to 0.95 mm. Lath Martensite and Bainite were generated in the coarse grain zone with an average grain size of 14.9 μm, rather than coarse feathery Bainite in the GMAW joint (with doubled grain size). Benefitted from the fine grain size, better phase composition, narrow and slight softening, the HFAW joints exhibited excellent tensile strength, moreover, the impact toughness at hardened zone and softening zone reached 0.87 J/mm2 and 1.15 J/mm2, which were at least 60% higher than that in the GMAW joint (0.58 J/mm2 and 0.61 J/cm2).

Magnetic and transport properties in metallic and disordered Ru2VAl and Ru2VGa

In this work, we report an elaborate study on the structural, magnetic and thermoelectric properties of two Ru-based Heusler alloys, viz., Ru2VAl and Ru2VGa, having valence electron count 24. While Ru2VGa exhibits a nonmagnetic ground state, in Ru2VAl a short range ferromagnetic interaction is developed below 10 K due to the structural antisite defects and disorder, that also manifests its signature in the specific heat and electrical resistivity measurements at low temperatures. Both the Seebeck coefficient (S) and Hall measurements suggest the dominance of hole-type carrier for electronic transport in Ru2VAl whereas Ru2VGa is found to be a n-type material. The linear nature and small absolute values of S, as well as non-zero values of electronic contribution to specific heat γS (γSRu2VAl = 4.9 mJ/mol-K2 and γSRu2VGa = 5.5 mJ/mol-K2) point towards a metallic ground state for both these alloys. Both the compounds exhibit lower thermal conductivity at room temperature in comparison to Fe-based Heusler alloys due to the presence of heavier element Ru.

The magnetic ground state of Ba(Fe1/2Sn1/2)O3-δ: A potential giant dielectric material for technological applications

Ba(Fe1/2Sn1/2)O3-δ (BFSO) is a potential environmental friendly compound for miniaturization of electronic devices as it exhibits giant dielectric constant at room temperature. However, its magnetic ground state is not settled. We present here comprehensive investigation of the as-sintered and oxygen-annealed BFSO samples using x-ray diffraction, dielectric, x-ray photoelectron spectroscopy (XPS), dc magnetization (M(T, H, t)) and specific heat measurements. Both samples crystallize in a cubic Pm-3m symmetry. At room temperature, both samples show a giant dielectric constant of the order of ε' ∼104 and two low-temperature dielectric relaxations resulting from polaron-hoping and Maxwell-Wagner effect, respectively. The temperature-dependent dc magnetization and specific heat measurements on as-sintered and oxygen-annealed BFSO samples confirm the absence of long-range ordered antiferromagnetic transition at TN ∼55 K. Further, both samples show history-dependent irreversibility of zero-field cooled warming (ZFCW) and field cooled warming (FCW) M(T) curves at the irreversibility temperature (Tirr ∼18 K) with a peak in the ZFCW M(T) curve at the spin-glass freezing temperature Tf ∼16 K. In addition, the FCW M(T) curve of both samples show plateauing over a small temperature range before it starts increasing below Tf, a characteristic typically observed in cluster/spin-glass systems. The presence of long-time magnetic relaxation and aging effect in both samples further support the spin-glass behavior. We also discussed the impact of oxygen vacancies on the physical and magnetic properties and possible origin of the glassy ground state in BFSO.

Phonon-mediated superconductivity in the Sb square-net compound LaCuSb2

We investigated the electronic structure and superconducting properties of single-crystalline LaCuSb$_2$. The resistivity, magnetization, and specific heat measurements showed that LaCuSb$_2$ is a bulk superconductor. The observed Shubnikov-de Haas oscillation and magnetic field dependence of the Hall resistivity can be reasonably understood assuming a slightly hole-doped Fermi surface. Electron-phonon coupling calculation clarified the difference from the isostructural compound LaAgSb$_2$ indicating that (i) low-frequency vibration modes related to the interstitial layer sandwiched between the Sb-square nets significantly contribute to the superconductivity and (ii) carriers with sizable electron--phonon coupling distribute isotropically on the Fermi surface. These are assumed to be the origin of higher superconducting transition temperature compared with LaAgSb$_2$. We conclude that the superconducting properties of LaCuSb$_2$ can be understood within the framework of conventional phonon-mediated mechanism.

High-pressure synthesis and magnetic properties of tetragonal R2BaCuO5 (R = Sm and Eu).

We report the experimental discovery of a new structural phase of well-known orthorhombic R 2BaCuO5 (R = Sm and Eu), exhibiting a tetragonal crystal structure with space group . The high-pressure tetragonal phase is isostructural with the brown phase R 2BaCuO5 (R = La, Pr, and Nd). In this structure, the Cu ions form an isolated square planar environment, contrary to the orthorhombic phase, where the Cu ions are located in a distorted square pyramid. Magnetization and specific heat measurements reveal the long-range antiferromagnetic order of the Cu2+ and/or Sm3+ moments for the Sm-sample, with the magnetic specific heat accounting for only 35% of the magnetic entropy. Interestingly, the Eu-sample remains paramagnetic down to the lowest temperature. The high Curie-Weiss temperature of -140K and magnetic entropy of 3% of the expected value indicates that the system is highly frustrated. We estimated the isothermal entropy change and investigated the magnetocaloric effect for Eu2BaCuO5, and the maximum entropy change detected at a field of 70kOe at 3K reaches 5.6Jkg-1K-1.

Effect of Clean Heating on Carbonaceous Aerosols in PM2.5 During the Heating Period in Baoding

In order to study the effects of clean heating measures on the concentration and source of carbonaceous aerosols in PM2.5 in Baoding, we collected PM2.5 samples in Baoding during the winter heating periods of 2014 and 2019. The concentrations of OC and EC in the samples were determined by using a DRI Model 2001A thermo-optical carbon analyzer.The results showed that the average values of ρ(OC) and ρ(EC) in the heating period in 2014 were 60.92 μg·m-3 and 18.15 μg·m-3, and the average values of ρ(OC) and ρ(EC) in the heating period in 2019 were 36.63 μg·m-3 and 6.07 μg·m-3. Compared with those in 2014, the concentrations of OC and EC decreased by 39.87% and 66.56%, respectively, in 2019; the decrease in EC was larger than that in OC, and the meteorological conditions in 2019 were more severe than those in 2014, which was not conducive to the spread of pollutants.The correlation analysis and SOC estimation of OC and EC indicated that the correlation R2 of OC and EC in Baoding in 2014 and 2019 were 0.874 and 0.811, respectively, indicating that OC and EC in Baoding had relatively consistent sources. The average values of ρ(SOC) in 2014 and 2019 were 16.59 μg·m-3 and 11.31 μg·m-3, respectively, and the contribution rates to OC were 27.23% and 30.87%, respectively. This showed that in 2019, compared with that in 2014, the primary pollution decreased, but the secondary pollution increased, and the atmospheric oxidation increased.The analysis of the pollution sources of carbonaceous aerosols revealed that in 2014 and 2019 before and after the implementation of clean heating, the carbonaceous aerosols in the atmosphere were mainly from biomass combustion, coal combustion, and vehicle exhaust emissions. However, the contribution from biomass burning and coal burning decreased in 2019 compared to that in 2014. The decrease in OC and EC concentrations was attributed to the control of coal-fired and biomass-fired sources by clean heating. At the same time, the implementation of clean heating measures reduced the contribution of primary emissions to carbonaceous aerosols in PM2.5 in Baoding City.

Composition dependence of the specific heat of FeSi

Recently, a high-mobility surface conduction channel and in-gap states were identified in the correlated small-gap semiconductor FeSi using electrical transport measurements and high-resolution tunneling spectroscopy. The mobility of the charge carriers in the surface channel is quantitatively reminiscent of topological insulators, but displays a lack of sensitivity to the presence of ferromagnetic impurities as studied by means of a series of single crystals with slightly different starting compositions. Here, we report measurements of the specific heat of these crystals. At low temperatures, a shallow maximum is observed in the specific heat divided by temperature. This maximum is suppressed under magnetic field, characteristic of a Schottky anomaly associated with magnetic impurities. In comparison, the height of this maximum decreases with increasing initial iron content.

Transport and magnetic properties in the Nd diluted system Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$

We report the electrical resistivity, specific heat, and magnetization measurements of Y_{1-x}1−xNd_{x}xCo_{2}2Zn_{20}20 for 0.017 \leq x \leq 0.950.017≤x≤0.95. The Schottky-type specific heat peak at around 13 K for all the samples is reproduced by the crystalline electric field model with the \Gamma_{6}Γ6 doublet ground state of a Nd^{3+}3+ ion. The magnetization and magnetic susceptibility data of the samples for x \leq 0.06x≤0.06 are well reproduced by the calculation without intersite magnetic interactions among Nd moments. Therefore, the dilute Nd system Y_{1-x}1−xNd_{x}xCo_{2}2Zn_{20}20 for x \leq 0.06x≤0.06 is a good candidate to study on-site interaction of the \Gamma_{6}Γ6 doublet ground state of 4ff electrons with conduction electrons.

New Nabokoite-like Phases ACu7 TeO4 (SO4 )5 Cl (A=Na, K, Rb, Cs) with Decorated and Distorted Square Kagome Lattices.

A new family of compounds ACu7 TeO4 (SO4 )5 Cl (A=Na, K, Rb, Cs) isostructural to mineral Nabokoite (K species) was synthesized by solid state and gas transport reactions in sealed ampoules and characterized in measurements of magnetization and specific heat in a wide temperature range. These complex compounds are of the utmost interest as a testing playground to study the properties of quasi-two-dimensional magnets with a square kagome lattice geometry. A quantum ground state of such a corner-sharing network is a spin liquid. Unlike idealized grid analyzed in numerous models, the square kagome lattice in nabokoites is wavy and distorted being composed of versatile triangles. Moreover, it contains "excessive" decorating magnetic ions, which makes magnetism of these objects even more complicated. The interaction of these decorating ions through virtual excitations of the square kagome lattice is accompanied by the formation of a long-range magnetic order coexisting with the spin liquid.

Particle filter algorithms for on-line prediction of transient heat flux of participating medium

The particle filter (PF) and corresponding improved algorithm (unscented particle filter (UPF)) are introduced to solve the on-line prediction of transient heat flux (q(t)) on the boundary of participating medium for the first time. The temperature-dependent thermophysical properties of the medium result in a highly nonlinear heat transfer system. The graded index medium (caused by the temperature-varying refractive index) is also taken into account, in which the radiation transfer is more complex than that in the uniform refractive index medium. The finite volume method is employed to address the transient coupled radiative and conductive heat transfer in medium. The impacts of particle number, process error covariance, measurement error covariance, sampling time interval, forms of heat flux and measurement errors on prediction results are researched in detail. The UPF algorithm, in which unscented Kalman filter technique is applied to pick an appropriate proposal density function to ameliorate the degradation phenomenon in original PF algorithm, outperforms the PF algorithm in terms of stability and accuracy of estimation results. All the prediction results demonstrate that UPF method is effective and reliable to solve the real-time reconstruction of q(t) even with measurement errors.

Random singlets in the s=5/2 coupled frustrated cubic lattice Lu3Sb3Mn2O14

We combine thermodynamic, electron spin resonance (ESR), and muon spin-relaxation ($\mathrm{\ensuremath{\mu}}\mathrm{SR}$) measurements with density functional theory (DFT) and classical Monte Carlo calculations toward understanding a disorder-driven behavior of the 3D coupled frustrated cubic lattice $\mathrm{Lu}{}_{3}\mathrm{Sb}{}_{3}\mathrm{Mn}{}_{2}{\mathrm{O}}_{14}$ with $s=5/2$. The classical Monte Carlo calculations based on exchange interactions extracted from DFT predict that $\mathrm{Lu}{}_{3}\mathrm{Sb}{}_{3}\mathrm{Mn}{}_{2}{\mathrm{O}}_{14}$ undergoes a transition to magnetic ordering. In sharp contrast, our specific heat measurements evince a weak magnetic anomaly at 0.5 K while $\mathrm{\ensuremath{\mu}}\mathrm{SR}$ detects neither long-range magnetic order nor spin freezing down to 0.3 K. For temperatures above 2 K, our $\mathit{ac}$ susceptibility, magnetization, and specific heat data obey temperature-magnetic field scalings, indicative of the formation of 3D random singlets. The development of multiple ESR lines with decreasing temperature below 80 K supports the notion of inhomogeneous magnetism. Our results extend random-singlet physics to 3D frustrated classical magnets with a large spin number $s=5/2$.

Performance and uncertainty of the all-wave net radiation space-time integrators by treetops

The quantification of electromagnetic energy exchanged between plants and their environment is important for ecophysiological studies. Measurement techniques have been developed for the determination of these changes in different spatial scales. In the literature are found some studies describing the use of devices carrying radiometers rotating around isolated trees. Otherwise, when it comes to plantations with spatial arrangement of trees in hedgerows, it is more convenient to use a notional cylindrical geometry of measurement. In this paper we described technical details of assembling devices moving along a stretch of the planting line, generating a notional cylindrical geometry for space-time integration of the all-wave radiation absorbed by the trees in hedgerow. Throughout the experiments it was verified the need for minor modifications which led to the improvement of mobile systems of measurement. Tests with the device free of plants indicated that the errors arising from the null deviation in this condition were sufficiently small. Analyses of measurements of each net radiometer over several days and, also comparison with measurement of daily latent heat calculated from sap flow in 24-hr period indicated that the proposed system gives accurate measurements, being reliable for testing the results of physical-mathematical models.

Emergence of a Non-Van der Waals Magnetic Phase in a Van der Waals Ferromagnet.

Manipulation of long-range order in 2D van der Waals (vdW) magnetic materials (e.g., CrI3 , CrSiTe3 ,etc.), exfoliated in few-atomic layer, can be achieved via application of electric field, mechanical-constraint, interface engineering, or even by chemical substitution/doping. Usually, active surface oxidation due to the exposure in the ambient condition and hydrolysis in the presence of water/moisture causes degradation in magnetic nanosheets that, in turn, affects the nanoelectronic /spintronic device performance. Counterintuitively, the current study reveals that exposure to the air at ambient atmosphere results in advent of a stable nonlayered secondary ferromagnetic phase in the form of Cr2 Te3 (TC2 ≈160K) in the parent vdW magnetic semiconductor Cr2 Ge2 Te6 (TC1 ≈69K). The coexistence of the two ferromagnetic phases in the time elapsed bulk crystal is confirmed through systematic investigation of crystal structure along with detailed dc/ac magnetic susceptibility, specific heat, and magneto-transport measurement. To capture the concurrence of the two ferromagnetic phases in a single material, Ginzburg-Landau theory with two independent order parameters (as magnetization) with a coupling term can be introduced. In contrast to the rather common poor environmental stability of the vdW magnets, the results open possibilities of finding air-stable novel materials having multiple magnetic phases.

Human migration on a heating planet: A scoping review

Whilst people’s migration outcomes may be influenced by climate change, the interaction of heat with migration and migrants is little understood. This scoping review explores the relationship between heat and human migration, focusing on i) whether and how heat functions as a driver of migration, and ii) how migrants are impacted by heat across the migratory journey. Four databases were searched for peer-reviewed literature to identify studies reporting on the heat-migration nexus through 18 June 2021, alongside a grey literature search. Of 12,149 peer-reviewed and 476 grey literature records, 187 articles were screened in full, resulting in the inclusion of 50 records (47 peer-reviewed, 3 grey). Publications assessed the impact of heat on human migration (n = 32), or the experience of heat among migrants (n = 18). In the former, 16/32 report a significant positive association where exposure to heat increases the likelihood of migration or intention to migrate. Moderating factors in the heat-migration pathway include other climatic factors, agricultural productivity, economic opportunities, age, and gender. The vast majority of studies assessing the impact of heat on migrants reported negative impacts of heat (such as heat related illness, heat stress and premature mortality) among migrants compared to non-migrants. Heat impacts were aggravated by poor infrastructure, insufficient workplace adaptations, lower educational level, and socio-economic factors. Findings suggest heat may influence migratory patterns in terms of people’s intention to move, risk when on the move, and consequences of heat for settled migrants. However, the heterogeneous results suggest heat may not be a driver of migration in all contexts. No literature reported on a so-called ‘temperature threshold’ above which migration is certain. Developing comparability in measurements of heat, heat impacts, and definitions of environmentally-induced migration and migrants may support future research on, risk reduction for, and response to the impact of heat on migration and migrants.

Thermal and magnetic properties of Fe7Se8 studied on single crystals

Specific heat, thermal expansion and magnetic measurements on single crystalline samples have been employed to study the interplay between the lattice and the magnetic state in the layered iron selenide compound Fe7Se8, which exhibits a ferrimagnetic order below TN ≈ 440 K and a spin reorientation transition upon cooling below Tsr ∼ 115 K. Thermal expansion measurements performed on single-crystal samples revealed significant anisotropic deformations of the crystal lattice with decreasing temperature below TN, an increase in the c/a ratio, and negative volume spontaneous magnetostriction (ωs ∼ −5.3⋅10−3 at 120 K). The first-order spin reorientation transition in Fe7Se8 is found to be accompanied by a hysteretic behavior of the specific heat and thermal expansion, and an anomaly in the ωs vs T dependence. The results obtained are indicative of a strong influence of the magnetoelastic interactions on the properties of Fe7Se8.

Spin density wave and antiferromagnetic transition in EuFe2As2: a high field transport and heat capacity study

Abstract Here we reported structural, electrical, magnetic, and thermal transport properties of ternary pnictide bulk iron based compound EuFe2As2 (Eu-122). This compound (Eu-122) crystallized in ThCr2Si2-type tetragonal phase structure with space group I4/mmm at ambient temperature. A promising divalent state (Eu2+) of Eu-ions was observed in the studied EuFe2As2. Magnetic ordering of Eu2+ ions takes place at very low temperature at around T N = 20 K in EuFe2As2. The ferromagnetic interactions between Fe–Fe ions were established at higher temperature which was revealed from magnetic susceptibility measurements with negative value of the paramagnetic Curie temperature. Both magnetic phase transitions (20 K and 190 K) were clearly established the intrinsic magnetic nature revealed by both electrical transport and specific heat measurement. However the phase transition at low temperature corresponds to the magnetic ordering of Eu2+ ions while the high transition temperature is due to the itinerant moment of Fe. EuFe2As2 is the only compound among various parent compounds of iron pnictide superconductor’s family, in which both spin density wave (SDW) of Fe and A-type antiferromagnetic (AFM) ordering of the localized Eu2+ magnetic moments take place simultaneously. We observed here that the localized character of Eu anti-ferromagnetism dominated via RKKY interactions, despite the largely itinerant nature of Fe magnetic interactions. The resistivity with applied magnetic field revealed that the AFM ordering temperature of Eu2+ ions suppress with applied magnetic field. Also resistivity under hydrostatic pressure measurements shows the T SDW (Fe) transition of the Fe moments shifts towards the lower temperatures while AFM ordering of Eu2+ decreases with pressure and the same is completely disappears at 2 GPa.