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The traceable temperature measurements using the radiation thermometers and thermal imagers above 1000 °C require blackbody fixed points and extrapolation or interpolation of Planck’s radiation law. For the realization of the ITS-90 radiance temperature scale, a radiation thermometer needs to be calibrated by using the pure metal fixed-point blackbodies (Ag or Au or Cu) and Planck’s radiation law in ratio form. At CSIR-NPL, the high-temperature radiance scale above the silver fixed-point is realized using a silicon photodiode detector-based linear pyrometer (LP4) with a 650 nm nominal wavelength. This paper presents the realization of high-temperature blackbodies of Ag (961.78 °C) and Cu (1084.62 °C), and a detailed investigation of their melting and freezing plateaus measured using LP4. The mean effective wavelength of the LP4 was evaluated using Wien’s approximation to Ag and Cu photocurrent outputs, computed to be 650.09 nm, and used in Planck’s equation to determine T90 temperatures. The characteristics of these blackbody sources and radiation thermometer, such as size-of-source effect (SSE) and distance effect (DE) were measured, and their contributions in measurement uncertainty were evaluated. Expanded uncertainties of fixed-point realization for Ag and Cu are estimated as 0.25 and 0.30 °C (k = 2), respectively. Further, photocurrents calculated using Ag fixed-point blackbody for corresponding temperatures by ratio method were employed to solve the coefficients of the Sukuma-Hattori equation for extrapolation of temperatures and measurement uncertainties up to 3000 °C. The uncertainty of scale realization is estimated to be 3.72 °C (k = 2) at 3000 °C.

The International Temperature Scale of 1990 (ITS-90) underpins much of modern thermometry, yet efforts to comprehensively characterize and improve its reproducibility have been limited. Here, a low-uncertainty data set drawn from 13 standard platinum resistance thermometers is used to quantify all three main manifestations of scale irreproducibility over the range 13.8033 K to 273.16 K. Four overlapping ITS-90 subranges are investigated, along with three prospective approaches to temperature scale improvement. The current version of the Guide to the Realization of the ITS-90 is found to overestimate scale realization uncertainties, and recommendations are made to revise the guidance provided therein. Replacing the ITS-90 deviation function of subrange 3 with a new version further improves the interpolation quality of this subrange by a factor of two, and calibrating thermometers at the triple point of xenon rather than the triple point of mercury cuts the realization uncertainty of subrange 4 in half. New linear subranges spanning from the triple point of water to the triple points of mercury or xenon could be added to the scale without compromising the performance of the existing subranges. Combining new interpolation equations with calibration at the triple point of xenon provides the basis for a much more reproducible temperature scale than the ITS-90, with magnification of fixed point uncertainties nearly eliminated for all of subranges 1–4 above the triple point of oxygen.

A dynamic model is proposed for data analysis and use in the control of heaters of three-zone electric resistance furnaces for reproducing the reference points of the temperature scale ITS-90. A software package has been developed for monitoring and controlling furnaces both in manual and automatic modes.

Heat: a measure of the total kinetic energy of a body. Measured in joules (J). It depends on the mass of the body and the specific heat capacity of the body. Temperature: a measure of the average kinetic energy within a body. It describes the potential for heat energy to move from one body to another down a gradient from an area of high temperature to an area of lower temperature. It is measured using a temperature scale which is defined against fixed physical events such as absolute zero or the triple point of water. Heat capacity: the amount of heat energy necessary to be added to an entire body to increase the temperature by one degree Kelvin (J/K). Specific heat capacity: the amount of heat energy necessary to be added to one kilogram of a body to increase the temperature by one degree Kelvin (J/K/kg). Absolute zero: a hypothetical temperature at which all molecular movement stops (zero kinetic energy). This is not possible in reality. The ice point: this is the temperature at standard pressure (101.3 kPa) at which water exists in both a solid (ice) and a liquid form. Designated as 0 oC or 32 oF. The steam point (boiling point): the temperature at standard pressure (101.3 kPa) at which water exists in botha liquid and a vapour form. Designated as 100 oC or 212 oF. Triple point of water: the temperature at a pressure of 611 Pa (0.006 atm) at which water exists in a solid (ice), liquid and a vapour form. Designated as 0.01 oC.

The paper presents a matrix approach to the propagation of uncertainties in the realization of the ITS-90 using Standard Platinum Resistance Thermometers (SPRT) calibrated at Defining Fixed Points (DFPs). The procedure allows correlations to be included between SPRT resistances measured during the calibration at the DFPs (i.e., the realization of the ITS-90) and the resistances measured during the subsequent use of the SPRT to measure temperature T 90. The example also shows the possible contribution of these correlations to the overall temperature uncertainty measured by a calibrated SPRT.

We evaluated the non-uniqueness of the temperature scale of the standard platinum resistance thermometer (SPRT) calibrated at the tripe point of sulfur hexafluoride (TPSF6), which is one of the candidates for the substitute of the triple point of mercury (TPHg). Three SPRTs calibrated at the TPSF6 were compared with a reference thermometer from 14 K to 250 K by using a precise comparison system for capsule type of thermometers. The uncertainty of the temperature scales from propagation of the uncertainties for calibrating SPRT was also evaluated. The result shows that the non-uniqueness of the temperature scale of the SPRT calibrated at the TPSF6 was almost equivalent to that of the ITS-90. This means that the triple point of TPSF6 possessed a capability for realization of the temperature scale which was equivalent to the ITS-90.

A subsecond duration pulse heating method was used to measure the melting point, the normal spectral emittance (at the melting point), and the electrical resistivity (above 1900 K) of 99.9 + percent pure titanium. The results, based on the International Practical Temperature Scale of 1968, yield a value of 1945 K for the melting point. The normal spectral emittance (at 653 nm) at the melting point is 0.40. Estimated inaccuracies are: 5 K in the melting point, 5 percent in the normal spectral emittance, and 3 percent in the electrical resistivity.

Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. We reviewed the four main formulations proposed in the literature so far and assessed how they affect the theoretical behaviour of the kinematic heat flux (H0) and the temperature scale (T*) in the stable boundary layer, as well as their consequences on the existence of critical values for both the gradient and the flux Richardson numbers. None of them turned out to be fully consistent with the literature published so far, with two of them leading to very unreliable expressions for both H0 and T*. All considered, a convincing description of flux–profile relationships still needs to be found and seems to represents a considerable challenge.

The triple points of oxygen samples sealed in miniature pressure cells were investigated by means of adiabatic calorimetry. The triple point of a 99.999 percent pure commercial oxygen sample was found to be 0.94(0) mK higher than that of an “ultra-pure” sample prepared by thermal decomposition of potassium permanganate (KMnO(4)). The higher value is attributed principally to argon impurity in the commercial oxygen. The results of eight sets of observations using six thermometers, calibrated on the International Practical Temperature Scale of 1968 as maintained at the National Bureau of Standards, and two sealed cells of the ultra-pure oxygen show a range of 0.17(8) mK. The capsule-type platinum resistance thermometers that have been used are shown to have outstanding stability and the multiple calibrations made on them at the National Bureau of Standards extending over six years are shown to be consistent to within 0.15 mK at 54.361 K. The results of measurements on an internationally circulated sealed cell of commercial oxygen show its temperature to be 0.58(1) mK higher than those of the ultra-pure oxygen.

We demonstrate that electrostatic interactions between helical electrons at the edge of a quantum spin Hall insulator and a dynamical impurity can induce quasi-elastic backscattering. Modelling the impurity as a two-level system, we show that transitions between counterpropagating Kramers-degenerate electronic states can occur without breaking time-reversal symmetry, provided that the impurity also undergoes a transition. The associated electrical resistance has a weak temperature dependence down to a non-universal temperature scale. Our results extend the range of known backscattering mechanisms in helical edge modes to include scenarios where electron tunnelling out of the system is absent., Comment: 6 + 5 pages, 3 figures

This paper presents a resonant micro-pressure sensor which was vacuum packaged by a glass-on-silicon wafer. The eigenfrequency shifts of two resonators induced under pressure measurements were susceptible to temperature disturbances. The glass-on-silicon wafer packaging can alleviate the side effect of temperature disturbances, and decrease eigenfrequency shifts of resonators. More specifically, the temperature sensitivities were quantified as 37.933 Hz/°C vs. 10.359 Hz/°C with corresponding eigenfrequency shifts measured as 10.2 Hz vs. 2.3 Hz, for the micro-pressure sensor with glass vs. glass-on-silicon packaging. Furthermore, under the pressure scale from 0.05 kPa to 10 kPa and temperature scale from -40 °C to 85 °C, the maximum measurement deviations were reduced from -11.72 Pa to -3.68 Pa with the help of the glass-on-silicon wafer packaging.

A pivotal challenge posed by unconventional superconductors is to unravel how superconductivity emerges upon cooling from the generally complex normal state. Here, we use nonlinear magnetic response, a probe that is uniquely sensitive to the superconducting precursor, to uncover remarkable universal behaviour in three distinct classes of oxide superconductors: strontium titanate, strontium ruthenate, and the cuprate high-Tc materials. We find unusual exponential temperature dependence of the diamagnetic response above the transition temperature Tc, with a characteristic temperature scale that strongly varies with Tc. We correlate this scale with the sensitivity of Tc to local stress and show that it is influenced by intentionally-induced structural disorder. The universal behaviour is therefore caused by intrinsic, self-organized structural inhomogeneity, inherent to the oxides’ perovskite-based structure. The prevalence of such inhomogeneity has far-reaching implications for the interpretation of electronic properties of perovskite-related oxides in general., The understanding of how superconductivity emerges from a complex normal state remains elusive in unconventional superconductors. Here, Pelc et al. report exponential temperature dependence of the diamagnetic response in the normal state with a characteristic temperature scale, universally existing in three classes of oxide superconductors.

Interdiffusion studies in Co-Cr-Fe-Mn-Ni, Co-Fe-Mn-Ni, Co-Cr-Fe-Ni, and Co-Cr-Mn-Ni, as well as a reevaluation of the previous results obtained for Al-Co-Cr-Fe-Ni, were conducted. In the experimental part, diffusion couples were annealed at four different temperatures: 1230, 1270, 1310 and 1350 K for each system. Then, the results were evaluated with use of the optimization-based technique, combined with the Miedema's thermodynamic description, what allowed obtaining of tracer diffusion coefficients for all elements in all considered systems. The correctness of the applied approach was tested on the example of Co-Cr-Fe-Mn-Ni system, showing very good agreement of determined tracer diffusivities with the values obtained by other authors. Obtained values of diffusivities were compared with the available data for a number of conventional binary and ternary systems. No signs of diffusion retardation were observed in the absolute temperature scale. In the case of temperature scale normalized with respect to the melting point, an abnormal behavior, previously attributed to the HEAs' sluggish diffusion effect was observed. However, it occurred only for alloys with prominent manganese content and was completely independent of the number of components, being just as likely to occur in binary systems as in HEAs. Therefore, the alleged sluggishness of diffusion in HEAs should be treated just as a result of specific compositions of the previously studied alloys and cannot be generalized for all high entropy systems.

We present the results of development of a prototype of cavity-type model of black body in the form of a graphite ampoule filled with a δMoC–C eutectic alloy of molybdenum with carbon that realizes a high-temperature reference point (HTRP) of 2856 K on the temperature scale. It is shown that the created ampoule may serve as a precision “type-A” optical radiation source. We justify the approaches to the evaluation of the uncertainty components of emissivity of the ampoule cavity equal to 0.9997 with an extended uncertainty of 0.00016 (k = 2) depending on the geometric and physical parameters with the help of numerical algorithms based on the Monte-Carlo method.

Upconversion luminescence and optical temperature sensing properties of Yb3+/Er3+/Li+ tri-doped ZnMoO4 phosphors were investigated. It has been demonstrated that Li+ doping affected not only the local symmetry of Yb3+ and Er3+ but also the distribution of them in the host lattice. As a result, the significantly improved green upconversion luminescence was obtained when excited at 980 nm. The pumping power dependent photo-thermal behavior was used to evaluate the reliability of upconversion temperature sensing. An accurate temperature scale was established by eliminating the impact of thermal effect, and the sensing ability was evaluated via a comparison with the results reported in literatures.

The thermal metrology community is considering revising the International Temperature Scale of 1990 (ITS-90), motivated by the opportunity to improve the thermodynamic accuracy, reproducibility, and ease of use of the scale, as well as health and safety concerns with the use of mercury in the current scale. This paper considers the mathematical structure of the standard platinum resistance thermometer (SPRT) interpolations of the ITS-90 and identifies (i) mathematical features that are advantageous and should be retained, (ii) opportunities for improvements, and (iii) the research required to maximise the benefits from such improvements. The improvements considered include minor adjustments that leave ITS-90 intact, numerical adjustments to reference resistance ratios that preserve the structure of ITS-90, fixed-point replacements, new subranges, and large-scale changes in the mathematical structure of the interpolations. A significant research effort will be required to implement some of the changes. Overall, an improvement in the thermodynamic accuracy by a factor of about ten is relatively easily realised, but improvements in reproducibility of the scale of even a couple of tens of percent will be hard won. For most users, the costs and inconvenience of a substantial scale revision may outweigh the benefits.

The temperature scales of screening of local magnetic and orbital moments are important characteristics of strongly correlated substances. In a recent paper X. Deng et al. using dynamic mean-field theory (DMFT) have identified temperature scales of the onset of screening in orbital and spin channels in some correlated metals from the deviation of temperature dependence of local susceptibility from the Curie law. We argue that the scales obtained this way are in fact much larger, than the corresponding Kondo temperatures, and, therefore, do not characterize the screening process. By reanalyzing the results of this paper we find the characteristic (Kondo) temperatures for screening in the spin channel $T_K\approx 100$ K for V$_2$O$_3$ and $T_K\approx 350$ K for Sr$_2$RuO$_4$, which are almost an order of magnitude smaller than those for the onset of the screening estimated in the paper ($1000$ K and $2300$ K, respectively); for V$_2$O$_3$ the obtained temperature scale $T_K$ is therefore comparable to the temperature of completion of the screening, $T^{\rm comp}\sim 25$ K, which shows that the screening in this material can be described in terms of a single temperature scale., This is a post-peer-review, pre-copyedit version of an article published in Matters Arising section of Nature Communications. The final authenticated version is available online at http://dx.doi.org/10.1038/s41467-021-21641-2

On-site thermometer calibration by the temperature scale transfer technique based on fixed points can effectively improve the calibration level of thermometers in large-diameter hot water pipes. Calibrations of contact thermometers in large-diameter hot water pipes are often carried out using dry block calibrators. Axial temperature gradients and the drift of reference thermometers are the main sources of error for the use of the traditional dry block calibrators. To overcome these disadvantages, a new dry block calibrator with small multi-fixed-point cells was designed in this work to improve the homogeneity of the inner temperature field and calibrate the reference thermometers in situ. The calibrator was based on small multi-fixed points including the melting point of Hg (234.28 K), the melting point of Ga (302.91 K), the melting point of H2O (273.15 K) and was developed for use in the temperature range from − 50 °C up to 100 °C. The calibrator was designed using thermal Finite Element simulations carried out with COMSOL Multiphysics and has an ectopic multi-fixed-point structure. The melting process of the multi-fixed points was simulated using the effective heat capacity method, and the fraction of the liquid phase for the fixed-point material was obtained at different phase-transition radius values and temperature plateaus of multiple fixed-points cells were obtained at different dT values. The simulation explored the influence of different heating temperatures on the temperature plateaus of multiple fixed-points cells, and the functional relationship between the heating temperature and the temperature plateaus of multiple fixed-points cells was obtained, calculating the error between temperature plateaus and thermometer at different heating power, providing a technical basis for the subsequent prototype experiments and the validation of the prototype design through experimental measurements in future work.

Higher land surface temperature (LST) in cities than its surrounding areas presents a major sustainability challenge for cities. Adaptation and mitigation of the increased LST require in-depth understanding of the impacts of landscape features on LST. We studied the influences of different landscape features on LST in five large cities across China to investigate how the features of a specific urban landscape (endogenous features), and neighboring environments (exogenous features) impact its LST across a continuum of spatial scales. Surprisingly, results show that the influence of endogenous landscape features (Eendo) on LST can be described consistently across all cities as a nonlinear function of grain size (gs) and neighbor size (ns) (Eendo = βnsgs-0.5, where β is a city-specific constant) while the influence of exogenous features (Eexo) depends only on neighbor size (ns) (Eexo = γ-ens0.5, where γ and e are city-specific constants). In addition, a simple relationship describing the relative strength of endogenous and exogenous impacts of landscape features on LST was found (Eendo > Eexo if ns > kgs2/5, where k is a city-specific parameter; otherwise, Eendo

We assess Scanning Thermal Microscopy (SThM) with a self-heated doped silicon nanoprobe as a method for determining the local phase transition temperature of polymeric materials by means of nano-thermomechanical analysis (nano-TA). Reference semi-crystalline samples and amorphous test samples, characterized first using differential scanning calorimetry (DSC), are studied by nano-TA in the temperature range 50–250 °C. The repeatability, the reproducibility and the reliability of nano-TA are evaluated by three laboratories by applying the same calibration protocol prior to and after the measurements. The calibration of the probe temperature scale and the variability of the sample thermomechanical response are validated by Monte Carlo uncertainty analysis, resulting in a calculated uncertainty between 3 and 5 K. The SThM probe temperature data represented as a function of DSC-measured phase-transition temperatures of the semi-crystalline samples rule out the possibility of a quadratic fit and call for a linear calibration in absence of additional information. The maximum deviation obtained between SThM and DSC temperatures with such linear calibration reaches ± 30 K for melting temperatures and 50 K for glass transition temperatures.

The Hund coupling in multiorbital Hubbard systems induces spin freezing and associated Hund metal behavior. Using dynamical mean field theory, we explore the effect of local moment formation, spin and charge excitations on the entropy and specific heat of the three-orbital model. In particular, we demonstrate a substantial enhancement of the entropy in the spin-frozen metal phase at low temperatures, and peaks in the specific heat associated with the activation of spin and charge fluctuations at high temperature. We also clarify how these temperature scales depend on the interaction parameters and filling., Comment: 19 pages, 11 figures

Recent experiments in unconventional superconductors, and in particular iron-based materials, have reported evidence of an antiferromagnetic quantum critical point (AFM-QCP) emerging inside the superconducting dome of the phase diagram. Fluctuations associated with such an AFM-QCP are expected to promote unusual temperature dependencies of thermodynamic quantities. Here, we compute the $T$ dependence of the specific heat $C(T)$ deep inside a fully gapped $s^{+-}$ superconducting state as the AFM-QCP is approached. We find that, at the AFM-QCP, the specific heat $C(T)$ vanishes quadratically with temperature, as opposed to the typical exponential suppression seen in fully-gapped BCS superconductors. This robust result is due to a non-analytic contribution to the free-energy arising from the general form of the bosonic (AFM) propagator in the SC state. Away from the AFM-QCP, as temperature is lowered, $C(T)$ shows a crossover from a $T^2$ behavior to an exponential behavior, with the crossover temperature scale set by the value of the superconducting gap and the distance to the QCP. We argue that these features in the specific heat can be used to unambiguously determine the existence of AFM-QCPs inside the superconducting domes of iron-based and other fully gapped unconventional superconductors., Comment: 10 pages, 5 figures, new Section V included

An oilfield operator relies extensively on heat exchangers (Hexs) to break heavy oil emulsions. A workhorse inhibitor worked reliably to control thermally induced scale precipitation caused by local hard waters. However, an upsurge of scale-related Hexs tubing blockage occurred during a harsh winter that coincided with a breakthrough of enhanced oil recovery (EOR) polymer into some water sources. Through comprehensive lab testing, root causes of the failure were identified. A new product was developed featuring superior tolerance to variable production parameters, especially Hexs temperatures. Scale inhibitor efficacy is strongly influenced by overall scaling conditions including water chemistry, temperature, pressure, and presence of incompatible chemicals. In this study, scale precipitates collected from Hexs were characterized using environmental scanning electron microscopy techniques. New inhibitor chemistries were screened through thermal aging; then evaluated for inhibition performance by dynamic tube blocking methods at temperatures ranging from 42°C to 171°C. An additional performance test was designed for the final candidate to further investigate adverse impacts from the EOR polymer and incumbent scale product if a dual-product treatment is required throughout the field fluid system. The incumbent effectively inhibited scale formation at ≤120°C but showed reduced performance at 160°C. This result is consistent with field records indicating most tubing blockages occurred during the coldest days when Hexs temperature was raised to 160°C to increase heat to treat fluids. Meanwhile, it also suffered antagonistic effects from the EOR polymer. A dozen new inhibitor chemistries were studied including polymers and phosphonates. Polymeric inhibitors had higher thermal aging ratings but were less compatible with the waters involved. Ideal candidates must have thermal stability, high-temperature inhibition performance, and applicability to wide ranges of operational conditions, including Hexs temperature, water hardness, bicarbonate, and foreign substances. Thus, a single product can be applied to the entire field and simple dosage adjustments can readily handle most expected scaling risks. The new product passed all the criteria and significantly reduced operating and equipment replacement cost since deployment. This paper provides a unique scaling challenge that combined ultra-high temperature and EOR polymer influence, and a systematic approach to understanding and resolving the issue.

A difference was determined between temperature defined by International Temperature Scale (ITS-90) and thermodynamic temperature measured by relative acoustic gas thermometry at 79.0000 K and at 83.8058 K. Measurement were carried out using misaligned spherical acoustic resonator filled with helium at different pressures. The isotherms were fitted for four different acoustic modes simultaneously assuming the same thermal accommodation coefficient and third acoustic virial coefficient for all modes. Our measurements yield the following differences between the thermodynamic temperature T and ITS-90 temperature $$T_{90}$$: $$T-T_{90}=-4.81 \pm 1.02$$ mK at 83.9058 K and $$T-T_{90}=-4.47 \pm 0.97$$ mK at 79.0000 K.

The reproducibility of the International Practical Temperature Scale of 1968 (IPTS-68) in the region 90.188 K to 903.89 K as maintained at the National Bureau of Standards is discussed. The realizations of the triple point of water, the freezing points of zinc and tin, and the boiling point of oxygen are described. The average of the standard deviations of the resistance measurements at the triple point of water of 213 platinum resistance thermometers received for calibration over a two-year period corresponds to ±0.15 mK. The standard deviations of the resistance ratio R(T)/R(0°C) obtained with check thermometers employed for monitoring the zinc, tin, and oxygen point measurements correspond to ±0.28 mK, ±0.30 mK, and ±0.16 mK, respectively; the results of repeated calibrations with five thermometers show comparable reproducibility at the tin and oxygen points but the reproducibility is worse by a factor of two at the zinc point. When suitably packed for protection from possible mechanical shock platinum resistance thermometers can be shipped by common carrier and retain their calibrations.

Thermoelectric devices convert thermal energy directly into electrical energy or vice versa. Analytically, the performance (efficiency and power output) of a thermoelectric generator can be quickly estimated using a Constant Properties Model (CPM) suggested by Ioffe. However, material properties in general are temperature dependent and the CPM can yield meaningful estimates only if the constant values of the TE properties used in the formulations are physically appropriate. In this study, a comparison of different averaging modes shows that a combination of integral averaging over the temperature scale for the Seebeck coefficient and spatial averages for the electrical and thermal resistivities proves to be the best among the considered approximations to represent the constant property values. However, averaging spatially requires the knowledge of the exact temperature distribution along the length of the thermoelectric leg (temperature profile), which is usually obtained by Finite Element Method (FEM) calculations. Since FEM is costly and time consuming, a fast and easy way of obtaining a well approximated self-consistent temperature profile is used in this study. The relevance, magnitude and the physical origin of the non-linearity of the temperature profile are visualised by separately plotting the individual contributions to the bending of the temperature profile (Joule, Thomson and Fourier heat contributions). On analyzing the temperature profiles for different highly efficient thermoelectric materials, it is found that the non-constancy of the temperature dependence of the thermal conductivity significantly contributes to the deflection of real temperature profiles from a linear one. This mainly explains the considerable discrepancy of CPM results from exact calculations whereas, so far, the neglect of Thomson heat has been assumed to be the main source of discrepancy and several models with Thomson correction factors have been proposed. With our current view, such models cannot completely remove the discrepancy to CPM unless the T profile is taken into account and can lead to unpredictable error for different material cases and temperatures.

High-temperature standard platinum resistance thermometers (HTSPRTs) are used to establish the International Temperature Scale of 1990 (ITS-90) for temperatures up to 960 °C. Currently available thermometers, which may differ in the design of the platinum winding of the sensor, the shape and finish of the sensor frame, the frame material, the protective sheaths, and sealing materials, need some treatments to exhibit the stabilities expected of them and some of the causes of the instability are not well understood. This paper demonstrates a novel model of commercial HTSPRT that reportedly employs a novel sensor winding construction designed to eliminate instability arising from strain on the sensor winding due to differential thermal expansion between the sensor and the sensor frame. The stability of eight different HTSPRTs, including the novel model, are compared at the triple point of water (TPW), the melting point of gallium, and the freezing points of tin, zinc, aluminum and silver. Heat treatments included annealing at 500 °C, a preheating temperature for use at the freezing points of aluminum and silver, and at 800 °C, which was selected for checking the stability of the HTSPRTs in the middle of the temperature range between the freezing points of aluminum and silver. The consistency of the resistance values at the different fixed points was also confirmed by calculating the S parameter. We found three HTSPRTs stable during the described thermal conditions within ± 0.5 mK at the TPW. The novel model of commercial HTSPRT was the best one with a stability in the resistance at the TPW of within ± 0.3 mK over the entire temperature range. These indicate that the stable three HTSPRTs are promising instruments to provide accurate temperature scale at temperatures from the freezing point of aluminum up to the freezing point of silver based on the ITS-90.

18 pags., 15 figs., 16 tabs., We report new developments in instrumentation and techniques for both acoustic (speed of sound) and radiometric primary thermometry methods. These include both new cylindrical resonators for extending acoustic gas thermometry to higher temperatures and absolute radiation thermometers incorporating InGaAs detectors to extend primary radiometry to lower temperatures than can be achieved using Si-detector based instruments. These new approaches have been established in order to determine the difference between thermodynamic temperature, T, and the International Temperature Scale of 1990 (the ITS-90), T90, over the temperature range from 430 K to 1358 K as part of the three-year EMPIR project `Implementing the new kelvin 2¿ (InK2). This paper describes the facilities and measurement methodologies for measuring T¿T90 at each of the different institutes, along with an assessment of the target uncertainties. The work is ongoing, but we anticipate that the results of these measurements will ultimately be pooled to provide consensus values of T¿T90 with associated estimated uncertainties. These consensus values will initially feed into the technical annex of the mise en pratique for the definition of the kelvin (MeP-K-19) and, if required, will be used to help to provide a foundation for any future temperature scale., This work has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 R&I programme through the InK2 project. NIM’s research was supported by the National Key R&D Program of China (number 2016YFF0200101)

Context: The effective temperature is a key parameter governing the properties of a star. For stellar chemistry, it has the strongest impact on the accuracy of the abundances derived. Since Cepheids are pulsating stars, determining their effective temperature is more complicated that in the case of non-variable stars. Aims: We want to provide a new temperature scale for classical Cepheids, with a high precision and full control of the systematics. Methods: Using a data-driven machine learning technique employing observed spectra, and taking great care to accurately phase single-epoch observations, we have tied flux ratios to (label) temperatures derived using the infrared surface brightness method. Results: We identified 143 flux ratios that allow us to determine the effective temperature with a precision of a few K and an accuracy better than 150 K, which is in line with the most accurate temperature measures available to date. The method does not require a normalization of the input spectra and provides homogeneous temperatures for low- and high-resolution spectra, even at the lowest signal-to-noise ratios. Due to the lack of a dataset of sufficient sample size for Small Magellanic Cloud Cepheids, the temperature scale does not extend to Cepheids with [Fe/H] < -0.6 dex but nevertheless provides an exquisite, homogeneous means of characterizing Galactic and Large Magellanic Cloud Cepheids. Conclusions: The temperature scale will be extremely useful in the context of spectroscopic surveys for Milky Way archaeology with the WEAVE and 4MOST spectrographs. It paves the way for highly accurate and precise metallicity estimates, which will allow us to assess the possible metallicity dependence of Cepheids' period-luminosity relations and, in turn, to improve our measurement of the Hubble constant H0., 16 pages, 13 figures, accepted in A&A

The dielectric and time co-related decay properties of Au8 and Mn-doped (Au7Mn) clusters, prepared through wet chemical technique mediated by L-Cysteine methyl ester (LCME), have been analyzed with the help of a high- precision impedance analyzer (Wayne Kerr 6500B) and Horiba Scientific time co-related single-photon counting (TCSPC) instrument. The real part of the dielectric constant varies linearly from temperature 10 – 100 K, irrespective of frequency, and it shows a substantial dielectric onset within a temperature window of 100 – 300 K, at low frequency. The dielectric onset was a shift towards higher temperature when the frequency is increased. While, for Au7Mn cluster, the RDEC value varies almost independently within a temperature scale of 10 – 200 K. A strong dielectric onset was observed from temperature 200 – 300 K, which shifted towards higher temperature value with increment in the frequency. From the frequency-dependent dielectric study, the activation energy of both Au8 and Au7Mn clusters has been estimated to be 0.0118 meV and 0.0144 meV, respectively. The decay behavior of Au7Mn cluster confirms an average life-time of ∼326 ns, whereas the average lifetime of Au8 cluster is reported to be ∼680 ps.

Within the framework of improving the state primary standard of the temperature unit in the range from 1357.7 to 2800 K, the work was carried out to study and analyze the development of methods for implementing the temperature scale, on the basis of which the structural scheme of the primary standard DETU 06.03.96 was formed.

The article introduces artificial neural network model that simulates and predicts thermal conductivity and particle size of propylene glycol - based nanofluids containing Al2O3 and TiO2 nanoparticles in a temperature rang 20 - 80oc. The experimental data indicated that the nanofluids have excellent stability over the temperature scale of interest and thermal conductivity enhancement for both nanofluid samples. The neural network system was trained on the available experimental data. The system was designed to find the optimal network that has the best training performance. The nonlinear equations which represent the relation between the inputs and output were obtained. The results of neural network model and the theoretical models of the proposed system were performed and compared with the experimental results. The neural network system appears to yield the best fit consistent with experimental data. The results of the paper demonstrate the ability of neural network model as an excellent computational tool in nanofluid field.

Flow rate mal-distribution in parallel pipes has been a common problem in all kinds of heat exchangers, which threatens the performance, even the safety of the applications. Many researches have been focusing on the control methods to achieve a rational flow distribution. However, in order to develop an effective control method, the most sensitive inputs should be located first. In this work, a numerical model of the two-parallel-pipe-system has been developed. The flow and heat transfer are considered. The properties of the hydrocarbon fuel used (RP-3) has been compared and selected. Then the sensitivity analysis on the flow rate and fuel temperature distribution of RP-3 in non-uniformly heated parallel pipes was performed using a local sensitivity analysis method. The target inputs are the thermal properties of RP-3 ( ρ , c p , λ , μ , d ρ / dT f ) and the operating condition: like thermal deviation. The results indicate that the d ρ / dT f is the most sensitive input and c p takes the second place. They are much more sensitive when the temperature exceeds pseudo-critical point. The sensitivities of ρ , λ , μ are relatively low. While the thermal deviation is also very sensitive and shows an obvious impact on temperature distribution in the whole temperature scale studied.

Approaches to deep cooling of atomic gases are discussed. The delta kick cooling and adiabatic expansion as well as the limitations of the former are considered. The applicability of hollow optical dipole traps based on radiation of near-resonance transition frequency in atoms is shown. The possibility of designing such traps with a size of ∼1 mm is analysed and the prospects for their use for cooling atoms by evaporation and adiabatic expansion are discussed.

The temperature dependence of the Er3+ green luminescence in Y3Ga5O12 crystal were analysed under ultraviolet and near-infrared laser excitations for optical sensing purposes. Changes in the relative green emission intensities from the 2H11/2 and 4S3/2 thermally-coupled multiplets to the 4I15/2 ground state were measured from room temperature up to 1000 K. The calibrated temperature scale shows a maximum in the absolute thermal sensitivity of ~23.9 × 10−4K−1 at 580 K and a relative thermal sensitivity of ~1.36%K−1 at RT, combining results for both blue and near-infrared laser excitations. The excellent results obtained, compared with other Er3+-based optical temperature sensors, are a consequence of the advantages of garnet crystals as optically efficient hosts that, apart from an impressive capability to be synthesized both as bulk and fiber forms, allow extending the long working temperature range up to 1000 K, and beyond, to the melting point limit close to 2000 K. In addition, the use of green emissions for the temperature calibration, with negligible black-body radiation disturbance, only needs a low-cost, basic setup that uses commercially available lenses, lasers and detectors. All these facts support the Er3+-doped Y3Ga5O12 garnet crystal as a potential candidate as temperature sensor, showing large sensitivity and good temperature resolution for ultra-high temperature industrial applications.

In the last few decades, theoretical and experimental studies of glass-forming liquids have revealed presence of universal regularities in the viscosity-temperature data. In the present work, we propose a viscosity model for scaling description of experimental viscosity data. A feature of this model is presence of only two adjustable parameters and high accuracy of experimental data approximation by this model for a wide temperature range. The basis of the scaling description is an original temperature scale. Within this scaling description we obtain the transformed Angell plot, in which the area separating "fragile" and "strong" glass-formers emerges. The proposed scaling procedure make it possible to reconsider belonging some liquids to the type of "fragile" glass-formers. The obtained results form basis for development of a generalized scaling description of crystallization kinetics in supercooled liquids and glasses., 18 pages, 4 figures, 1 tables

Atomic emission double-spectrum temperature measurement method was developed, and a photoelectric temperature detector based on silicon photomultiplier tube was designed. The structure and principle of the temperature measurement of the photoelectric temperature detector were introduced. The spectral radiation signal of the copper sheet excited by the laser was transmitted to the photoelectric thermometer, and Cu I 510.5 nm and Cu I 521.8 nm were used as the temperature scale spectral lines during the temperature measurement. In different acquisition delays, the ratio of the intensity of the two Cu plasma spectral lines was obtained through the LIBS system. At the same time, the ratio of the maximum voltage value of the two channels was measured using a photoelectric thermometer. At the time of 6us, and the maximum temperature of Cu plasma excited by different laser energy was calculated to be 12745 K. The results show that the atomic emission dual-spectrum temperature measurement method has the characteristics of the higher temperature measurement limit and faster response speed.

The vapour–liquid equilibrium properties of binary mixtures of R1123 and R1234yf, which are key components of the next generation of refrigerant mixtures, were measured using a recirculation-type vapour–liquid equilibrium property measurement apparatus. Two sets of measurements were conducted by two different technicians (co-authors Nishida and Saito) using the same apparatus and sample. The first set of measurements were conducted at temperatures that were close to the integer values in absolute temperature, whereas the second set of measurements was taken at temperatures that were close to the integer values in terms of degrees Celsius. Both sets of measurements were based on the ITS-90 temperature scale and were found to be in good agreement at the measurement temperatures (300 and 330 K). These data were compared with the predictions of a Helmholtz-type equation of state, and a systematic deviation of approximately 8% was observed at low temperatures. A regression analysis using the binary interaction parameter kij of the modified Peng–Robinson equation of state more accurately reproduced the experimental measurements.

The discovery of superconductivity at 203 K in highly compressed sulphur hydride validates the ideas put forward by Ashcroft 50 years ago and galvanises the quest for room-temperature superconductivity. But at such temperatures, thermal fluctuations might be expected to break up Cooper pairs. For example, in the cuprates, fluctuations reduce T c by 30% or more below the mean-field value. Similar effects are found in iron pnictides. Here, we ask: how does superconductivity survive in sulphur hydride at such high temperatures? To answer this, we examine the superfluid density which is the key parameter for quantifying fluctuations in both amplitude and phase. We show that dimensionality plays a key role in suppressing or enhancing thermal fluctuations to the benefit of hydrogen sulphide and the detriment of its more layered 2D competitors. We find that the temperature scale for phase fluctuations, T φ , in superconducting H3S exceeds 1200 K, and therefore, these are irrelevant at 200 K. But the amplitude fluctuation temperature scale, T amp, at around 300 K is much lower and this has important implications for the ongoing quest for room temperature superconductivity. Appealing to the way in which superfluid density, T φ , T amp and T c scale with each other it seems that room temperature superconductivity is nearly ruled out, but perhaps not quite. It will require 3D systems with a large Fermi velocity to achieve this goal.

Carbon thin films oxidation was investigated on-line by high-sensitivity optical transmission (OT) method. The films have been prepared by common vacuum arc discharge and subsequently air oxidized at linear heating rates until temperatures of their complete gasification. The shape of the optical curves acquired was interpreted in light of deduced partial optical changes, each of them being ascribed by simple sigmoidal dependence. The dependencies converted to their derivative form ordered respective to the temperature scale conveniently represent an inter-relationship among the sequentially evolved films’ optical events, considered as being closely related to the individual carbon-replenishing steps. The dependencies correspond well to the ones obtained on thicker films by means of the thermogravimetry (TG) measurements.

The outer part (myzoderma) of carrot was tested using dynamic mechanical analysis (DMA), in air with three different values of humidity (50, 70, and 90%) in temperature scans between 30 and 90 °C. Temperature plots of storage ( SM i.e. elastic) and loss ( LM i.e. inelastic) moduli were obtained. The DMA was combined with Dielectric thermal analysis (DETA). The tissue toughness decreased with increasing temperature; the kinetic analysis of the data led to four characteristic temperatures different for different air humidity; these characteristic temperatures divided temperature scale into temperature ranges A, B1, B2, and B3. The range A, limited for all tested cases with different humidity by 50 °C, is termed low temperature drying. With decreasing air humidity, the characteristic temperatures also decrease. The ranges B1, B2, and B3 represent the different stages of high temperature drying (initial – B1, rapid or main – B2, and final – B3). Part B2 can be understood as the temperature range where drying is most rapid and the role of plasmodesma destruction can play the fundamental role.

We present a measurement and analysis scheme for determining traceable thermodynamic temperature at cryogenic temperatures using Coulomb blockade thermometry. The uncertainty of the electrical measurement is improved by utilizing two sampling digital voltmeters instead of the traditional lock-in technique. The remaining uncertainty is dominated by that of the numerical analysis of the measurement data. Two analysis methods are demonstrated: numerical fitting of the full conductance curve and measuring the height of the conductance dip. The complete uncertainty analysis shows that using either analysis method the relative combined standard uncertainty (k = 1) in determining the thermodynamic temperature in the temperature range from 20 mK to 200 mK is below 0.5 %. In this temperature range, both analysis methods produced temperature estimates that deviated from 0.39 % to 0.67 % from the reference temperatures provided by a superconducting reference point device calibrated against the Provisional Low Temperature Scale of 2000., Comment: 11 pages

A melt of short semi-flexible polymers with hard-sphere-type non-bonded interaction undergoes a first-order crystallisation transition at lower density than a melt of hard-sphere monomers or a flexible hard-sphere chain. In contrast to the flexible hard-sphere chains, the semi-flexible ones have an intrinsic stiffness energy scale, which determines the natural temperature scale of the system. In this paper, we investigate the effect of weak additional non-bonded interaction on the phase transition temperature. We study the system using the stochastic approximation Monte Carlo (SAMC) method to estimate the micro-canonical entropy of the system. Since the density of states in the purely hard-sphere non-bonded interaction case already covers 5600 orders of magnitude, we consider the effect of weak interactions as a perturbation. In this case, the system undergoes the same ordering transition with a temperature shift non-uniformly depending on the additional interaction. Short-range attractions impede ordering of the melt of semi-flexible polymers and decrease the transition temperature, whereas relatively long-range attractions assist ordering and shift the transition temperature to higher values, whereas weak repulsive interactions demonstrate an opposite effect on the transition temperature.

The aim of this article is to describe the problem of determining measurement uncertainties in the temperature calibration, especially the calibration of the platinum resistance thermometer. Two calibration methods can be used - comparison calibration method or calibration in defined temperature points in the appropriate temperature scale. This paper describes a first calibration method that is based on comparing the value from a calibrated temperature sensor to a temperature value measured by a reference temperature sensor (standard). The uncertainty budget for platinum resistance thermometer and the calibration system is given here.

To obtain the accuracy now sought in the extragalactic distance scale through standard candles and rulers, calibration of stellar photometry must be improved. The sensitivity of the V-K color surface brightness relation is examined here by means of model atmosphere fluxes. It has previously been neglected, but is shown here to be a significant term in the error budget of a recent high precision distance of the Large Magellanic Cloud, an anchor in galaxy distances based on Cepheids., Comment: As published by PASP

A gradient theory of the coupled theory of elasticity, thermoelasticity and thermal conductivity based on a generalized model of media with fields of defects is developed. Defectiveness is defined only by free dilatation and the tensor of incompatible distortions is determined by the spherical tensor. In the general case, the unified model includes scale parameters that are responsible for mechanical and temperature scale effects. In the particular case the proposed model describes the gradient thermoelasticity, in which effects are controlled by a mechanical scale parameter, and in the limit case, it describes the classical thermoelasticity, when this parameter tends to zero. The analysis of boundary problems of the general model is given. Particular cases are considered, and it is shown that gradient thermal conductivity and thermoelasticity make it possible to simulate thermal resistance and size effects.

Directly modifying spin exchange energies in a magnetic material with light can enable ultrafast control of its magnetic states. Current approaches rely on tuning charge hopping amplitudes that mediate exchange by optically exciting either virtual or real charge-transfer transitions (CT) between magnetic sites. Here we show that when exchange is mediated by a non-magnetic ligand, it can be substantially enhanced by optically exciting a real CT transition from the ligand to magnetic site, introducing lower order virtual hopping contributions. We demonstrate sub-picosecond enhancement in a superexchange dominated ferromagnet CrSiTe3 through this mechanism using phase-resolved coherent phonon spectroscopy. This technique can also be applied in the paramagnetic phase to disentangle light induced exchange modification from other ultrafast effects that alter the magnetization. This protocol can potentially be broadly applied to engineer thermally inaccessible spin Hamiltonians in superexchange dominated magnets., Comment: 13 pages main text, 4 figures, 14 pages supplementary information

International Temperature Scale-1990 (ITS-90) is formulated based on various phase transition temperatures of high pure substances to cover the temperature range from 0.65 K to 1357.77 K (-272.5 °C to 1084.62 °C), where kelvin is defined on triple point of water (TPW) at 273.16 K and the higher defined fixed point is freezing point of copper at 1357.77 K. To extend the temperature scale at higher temperatures, metal-carbon eutectic fixed points areextensively being developedas the reference standardsupto 3000 °C for thermometry and radiometry applications. The assignment of the eutectic melting transition temperatures to these metal-carbon eutectics is challenging as the melting plateaus are not as flat and wide as the conventional high pure metal fixed points. This paper presents the method to determine eutectic melting transition temperature by calculating inflection point for Fe-C and Co-C eutectic fixed point cells developed at CSIR-NPL, the national metrology institute (NMI) of India. The noble metal Type-S thermocouple calibrated on ITS-90 fixed points was used to measure and determine the melting transition temperatures of Fe-C and Co-C cells, and the associated uncertainties in determination of transition temperatures were evaluated.

Recent changes to the SI make it possible to set up a primary temperature scale using established values for certain high-temperature fixed points. As the furnace used with the fixed points can itself have a significant impact on measurements, improving furnace temperature uniformity can help to reduce uncertainties. A thermal model was used to redesign heaters to reduce temperature gradients where the fixed-point cell is positioned in the furnace. A heater optimised for 1325 °C was compared to the standard one with a cobalt carbon high-temperature fixed-point cells, where the cell was installed in the middle, and also moved 10 mm to each end. The modified heater showed reduced melting range, improved plateau run-off and less sensitivity to fixed-point cell position. The improvements will reduce the uncertainties associated with this type of furnace.