Temperature Step Research Articles

Thermal Comfort Comparison and Cause Analysis of Low-Temperature High-Humidity Indoor Environments of Rural Houses in Gansu Province, China

Low temperatures and high humidity often occur in the northern basins and mountainous regions of China. This research reveals a common winter indoor environment in this rural areas characterized by low-temperature and high-humidity indoor thermal conditions. Improving this environment directly with equipment would inevitably result in significant energy consumption. Therefore, comprehending the thermal performance mechanisms of different structural building materials is of vital importance as it provides crucial baseline values for environmental improvement. This study conducted a survey utilizing user questionnaires, resulting in the collection of 214 valid responses. Additionally, a local experiment regarding thermal comfort was conducted. Simultaneously, this study monitored the indoor physical environments of these houses (a sample of 10 rooms was taken from earth houses and 12 rooms from brick houses). Parameters measured on site included air temperature, relative humidity, light illumination, and CO2. The results showed that the humidity inside the earth houses is more stable and regression models can be developed between thermal sensations and temperature for long-term residents. The residents of these earth houses are more sensitive to temperature step. In contrast, the residents of brick houses, experiencing greater environmental variability, demonstrated lower sensitivity and greater adaptability to temperature changes. In addition, heating from bottom to top is more comfortable and healthier for the residents of brick houses in Gansu. Moreover, it is more favorable for the inhabitants’ livelihood to regulate the temperature steps to a maximum of 4 °C. This study provides valuable reference information for the future design of houses in low-temperature and high-humidity environments.

Optical constants of germanium antimony telluride (GST) in amorphous, crystalline, and intermediate states

The optical constants of germanium antimony telluride (GST), measured by spectroscopic ellipsometry (SE), for the spectral range of 350-30,000 nm are presented. Thin films of GST with composition Ge2Sb2Te5 are prepared by sputtering. As-deposited samples are amorphous, and when heated above the phase transition temperature near 150 °C, films undergo an amorphous to face-centered cubic crystalline phase transition. The optical constants and thicknesses of amorphous and crystalline GST films are determined from multi-angle SE measurements, applying a general oscillator model in both cases. Then, in order to evaluate the optical constants at intermediate states throughout the phase transition, GST films are heated in situ on a temperature stage, and single-angle SE measurements are carried out at discrete temperature steps in a range from 120–158 °C. It is shown that ellipsometric data for partially crystallized states can be fit by treating the GST as an effective medium consisting of its amorphous and crystalline states. Its optical constants, fractional crystallinity, and thickness can be determined at intermediate crystallization states throughout the phase transition. As a practical demonstration of the usefulness of this method, samples are held at fixed temperatures near the transition temperature, and SE is performed periodically. The fraction of crystallinity is determined as a function of time, and an activation energy for the amorphous to crystalline phase transition is determined.

Hyperspectral Imaging with Active Illumination: A Theoretical Study on the Use of Incandescent Lamp and Variable Filament Temperature

In this study, we introduce a novel hyperspectral imaging approach that leverages variable filament temperature incandescent lamps for active illumination, coupled with multi-channel image acquisition, and provide a comprehensive characterization of the approach. Our methodology simulates the imaging process, encompassing spectral illumination ranging from 400 to 700 nm at varying filament temperatures, multi-channel image capture, and hyperspectral image reconstruction. We present an algorithm for spectrum reconstruction, addressing the inherent challenges of this ill-posed inverse problem. Through a rigorous sensitivity analysis, we assess the impact of various acquisition parameters on the accuracy of reconstructed spectra, including noise levels, temperature steps, filament temperature range, illumination spectral uncertainties, spectral step sizes in reconstructed spectra, and the number of detected spectral channels. Our simulation results demonstrate the successful reconstruction of most spectra, with Root Mean Squared Errors (RMSE) below 5%, reaching as low as 0.1% for specific cases such as black color. Notably, illumination spectrum accuracy emerges as a critical factor influencing reconstruction quality, with flat spectra exhibiting higher accuracy than complex ones. Ultimately, our study establishes the theoretical grounds of this innovative hyperspectral approach and identifies optimal acquisition parameters, setting the stage for future practical implementations.

Dynamic modelling of cross-flow printed circuit heat exchangers for multistage reactor intercooling

A reduced-order dynamic model of a cross-flow printed circuit heat exchanger was developed to study both steady-state and transient performance under conditions that would be encountered in multistage catalytic combustion reactors to better understand how they can be used to minimize fluctuations in heat-integrated reactors and intensified processes. Previous transient models for cross-flow heat exchangers rely on an initial steady state and apply only for changes in inlet temperature, but this work presents a model that can be applied to intermediate states or multiple concurrent upstream process changes. Steady-state simulations showed that larger channels reduce volumetric heat transfer performance and effectiveness due to convective resistance. Furthermore, larger channel spacing increases effectiveness but also reduces compactness. Operating temperature was found to have a minimal effect on the overall heat transfer coefficient and effectiveness within the range of conditions studied, and operating pressure was found to have no effect on heat transfer. Transient analyses showed that the response to a unit step in temperature matches closely with an analytical infinite gas velocity model, both for time constants and the overall thermal response, with initial variations in outlet temperatures from ideal-case models below 3.8 % of unit step magnitudes, and average differences below 0.75 %. Transient analyses also show the effects of a finite fluid velocity which is critical in the transient response of large heat exchangers. The presented numerical model can also be more easily extended to complex configurations and can be applied to other changes in inlet conditions such as changing composition and flow rates as are found in combustion applications. A three-fluid thermal management system for a multistage packed-bed microreactor using printed circuit heat exchangers is proposed and modelled to provide a method for temperature regulation and pre-heating of fresh reactor feed.

Dual effect of activity levels and temperature step-change on human comfort and recovery time: Simulated short-term commute in winter

Individuals living in a location with access to public transport and a short distance from the workplace tend to walk for short commuting. Human activity levels are affected by the rate of walking while commuting, which affects thermal comfort and response. To investigate the human thermal response in commuting, a climate chamber experiment was conducted to simulate outdoor commuting (13 °C) and indoor rest recovery (24 °C) in winter. Standing and walking at 4 and 6 km/h were used to simulate temporary rest, walking, and running, respectively. Twenty healthy participants were asked to simulate commuting (13 °C) with standing/low, 4 km/h/medium, and 6 km/h/high activity levels for 8 min and sitting (24 °C) for 32 min. The physiological parameters and subjective perceptions of the subjects were recorded. The results showed that there were differences in the sensitivity of the parameters to changes in activity levels and temperature steps. Thermal sensation and mean skin temperature responded considerably to the dual effect of activity levels and temperature up-step; however, blood pressure was exclusively sensitive to temperature step-change. The elevated activity level of 1 met may increase the recovery time by 5–10 min. Functional paradigms for psychological and physiological recovery times in a neutral environment were developed, which could provide a potential solution for improving thermal satisfaction and the assessment of recovery times. The results of this study will guide improvement strategies for physiological recovery and thermal comfort after commuting.

Developing thermal prediction models for the elderly under temperature step changes

Daily transitions between indoor and outdoor environments involving temperature step changes have been extensively studied in young people, but little attention has been given to age-related differences and the development of thermal prediction models specifically for the elderly. To address this knowledge gap, a study was conducted in a climate chamber using warm-neutral-warm experimental sessions. Twenty-four elderly participants were selected from volunteers who met the health and body shape requirements. Thermal sensation vote (TSV) and mean skin temperature (MST) responses of the elderly were collected and analyzed. The results demonstrate that temperature step changes (3–9 °C) and neutral thermal experiences significantly influence the thermal responses of the elderly. Compared to the young, the elderly exhibit lower TSV, lower MST, lower skin heat loss, and different associations between TSV and skin heat loss. Leveraging these age-related differences, an MST prediction model was established for the elderly. The predicted MST can also serve as an input for the TSV prediction model established in this study. The TSV prediction model is based on skin heat loss and applicable to both transient and steady-state conditions. This study introduces a new approach for predicting the thermal responses of the elderly and enhances understanding of age-related differences in thermal responses.

Thermo-hydro-mechanical behaviour of a deep plastic clay formation

Several applications which are framed in the energy geotechnics field, particularly the design of energy geo-structures, energy geo-storage, enhanced geothermal energy systems and radioactive waste disposal, require a thorough thermo-hydro-mechanical (THM) characterisation of their host soil/rock formation. The present study comes up from the need to investigate the THM behaviour of deep Ypresian clays (Ycs, 300 to 400 m below ground) since they are one of Belgium’s potential host rock formations for deep geological disposal of heat-emitting and long-lived radioactive waste.
 The impact of temperature on the hydro-mechanical response of deep clays has been extensively tackled for the last four decades. Nevertheless, to the authors’ knowledge, the study of the evolution of radial stresses during drained thermal paths under oedometer conditions has never been addressed. Such information would allow for drawing a better-defined stress state while accurately measuring volume changes. To this aim, the present study used a newly designed and fully instrumented temperature-controlled oedometer cell [3] combined with well-planned test protocols. The local instrumentation consisted of a pore pressure transducer embedded in the soil 3 mm from the bottom boundary, thermocouples at various positions and radial displacement transducers with a localised thin-wall system to estimate radial stress.
 Two well-preserved Ycs core samples retrieved at different depths at Kallo (Belgium) and belonging to distinct lithological units were tested (see Table 1). Both slightly overconsolidated samples (Yield Stress Ratios of Ycs between 1.2 and 1.8, [1, 2, 3]) presented high initial matric suctions induced on deep water-undrained sampling. Consequently, the first stage of the well-planned test protocol consisted of loading at constant water content to bring the samples to the large in situ stresses and diminish the induced matric suction. The remaining matric suction was then reduced by soaking with synthetic water equivalent to in situ. Afterwards, drained loading and unloading paths were followed to attain different vertical effective stresses at varying overconsolidation ratios (OCRs) before performing the main research goal of drained thermal paths. The heating-cooling (H-C) cycles consisted of slowly stepwise increase/decrease in temperature (steps of 10ºC) with intermediate stabilising periods of around 15 hours controlled by the embedded pore pressure transducer.
 Figure 1 depicts the vertical deformation in terms of the mean effective stress (p’) beyond in situ stress. Changes in radial stresses ruled the variations in p’ during heating-cooling cycles since the vertical effective stress was kept constant during non-isothermal paths. At a slightly overconsolidated (OC) state (Core-48), the drained ‘1st H-C’ cycle showed a quasi-reversible response in volume changes and radial stresses. At OC state (OCR=2) on Core-103 (‘2nd H-C’), the response was reversible. However, the induced volume change in normally consolidated (NC) states was not reversible with a contractive response dependent on the stress level. Therefore, the nature of the thermal-induced volume changes aligned with the behaviour observed on other plastic clays. Nevertheless, the stress dependence of the contractive response at NC state differed from the observations made by [4] on NC Boom Clay -the other poorly indurated clay considered as potential host rock in Belgium. As observed in ‘2nd H-C’ (NC conditions) on Core-48, a reduction of the radial effective stress was only recorded at temperatures higher than 70°C. In contrast, the radial effective stress systematically increased on heating at values < 70°C, tending the sample to lower deviatoric stress. This phenomenon might be
 associated with some change in the soil structure on heating that tends to a more isotropic stress state despite the oedometer condition. A clear transition between the elastic and elastoplastic domains was detected during the subsequent loading after each H-C cycle at NC states.
 Finally, the study included a thermo-mechanical elastoplastic interpretation: thermal expansion coefficients dependent on temperature and mean effective stress in the elastic domain and thermal softening function on post-yield drained heating.

Bestimmung der oberen Temperatur- grenze von Schmierstoffen gegen adhäsives Versagen

ASTM D8503 is a brand new tribometrical scuffing tests where adhesive failure (scuffing, scoring) is initiated by temperature step increases and not by load step increases as per FZG, 4-ball, Timken, SRV, etc.. This test method determines the upper temperature limit for operating a lubricant and can also be used to determine the upper temperature limit of non-EP lubricating oils to protect against scuffing with increasing temperature. It illuminates also the retention of frictional properties over increasing temperature. It illuminates to formulators the formation and stability of protecting tribofilms with increasing temperature. Combining the temperature step increases with the electrical contact resistance gives new insights in the “Life” of tribofilms.

Effect of temperature step on selection strategy of deposition head lift height and manufacturing stability during the direct laser deposition process

Based on the layer by layer cladding characteristics of the direct laser deposition (DLD), the optimal selection strategy of deposition head lift height is one of the effective methods to maintain the manufacturing process stability, improve product quality, and reduce complex post-process. However, owing to the temperature step caused by changeable layer residual temperature, the selection of deposition head lift height becomes extremely complex. In this paper, to clearly analyze the effect of temperature step on selection strategy of deposition head lift height for the DLD multilayer deposition process with a 1.85 kW fiber laser and a coupled coaxial four-channel nozzle, a semi-theoretical model considering the main physical phenomena involved in DLD process is proposed, validated, and applied. Here, working plane position, deposition head lift height, and step of residual and preheating temperature are considered as input process variables while manufacturing stability and error are determined as process responses. Results show that without considering the temperature influence, the final manufacturing stability can be achieved by ensuring that the distance between the deposition head and the initial working plane is less than the maximum relative distance corresponding to the selected deposition head lift height. When the layer residual temperature is considered, the single-layer cladding height steps positively, which makes the extreme working plane position positively migrated, and the manufacturing stability is also further enhanced. However, due to the migration of the finally stable working plane position, the manufacturing errors are also conditionally changed. Finally, in order to obtain an optimal manufacturing process, for any DLD process where the initial working plane position has been determined, the deposition head lift height should be selected slightly smaller than the single-layer height corresponding to that determined plane under residual temperature condition (hTr,Si), otherwise the manufacturing process will gradually lose stability and lead to fabrication failure.

Low-temperature sintering of Li0.33La0.55TiO3 electrolyte for all-solid-state Li batteries

Ceramic solid-state Li batteries have promising electrochemical properties. However, their device integration is hampered by the required high sintering temperature step to obtain good ionic conductivity. The sintering temperature often leads to thermal decomposition of the cathode active material. Advanced sintering techniques, such as field-assisted sintering technology/spark plasma sintering (FAST/SPS), utilizing applied mechanical pressure to achieve a lower sintering temperature and shorter dwell time, are helpful in overcoming thermal stability challenges. While thermal stability issues are overcome by a lower sintering temperature, new challenges in the form of surface impurities arise. Low-temperature sintering does not thermally decompose surface impurities which causes low grain boundary conductivity and thus low total ionic conductivity. In this work, a cleaning method and a low-temperature sintering process is exemplarily developed for Li0.33La0.55TiO3 (LLTO) and the impact of applied mechanical pressure during FAST/SPS on the total ionic conductivity and the phase stability of LLTO is revealed.

Soret and Dufour effects on dissipative Jeffrey nanofluid flow over a curved surface with nonlinear slip, activation energy and entropy generation

Nanofluids have potential abilities and thermal features and provide more efficient results of heat transfer when compared with common liquid. Therefore, the major novel aspect of the current analysis is to analyze the entropy production and thermal feature of the system in the presence of cross-diffusion, nonlinear radiation, endothermic/exothermic reaction, activation energy and dissipation effects. Slip factor is additionally considered to slowing down the nanomaterial velocity. Furthermore, the effects of Lorentz force and nonlinear mixed convection are accounted. The governing differential equations for considered nanofluids are first converted into dimensionless ODEs utilizing proper variables. The obtained system is then computed using NDsolve technique. The approximated results for different distributions are shown through curves and tables. The impact of dimensionless parameters is visualized on fluid velocity, temperature, concentration, Nusselt number, skin friction and entropy generation. It has been observed that velocity steps up with curvature, ratio of buoyancy, solutal mixed convection and thermal convection parameters but declines for upgrading slip parameter. The temperature step down by upgrading exothermic/endothermic parameter, Dufour number and Brownian diffusion parameter, thermophoretic parameter and radiation parameter. It is also noticed that the concentration of the nanofluid upsurges for increasing activation energy and soret number, but concentration minimizes for growing the temperature difference parameter. Numerical results show that the Nusselt number decays for rising Soret number, Dufour number, thermophoretic parameter and Brownian diffusion parameter but a reverse trend is seen for radiation parameter and activation energy. Also, skin friction coefficient declines by enhancing thermal convection parameter, solutal mixed convection parameter and slip parameter but upgrades for boosting buoyancy parameter.

Development and Characterization of Hybrid, Temperature Sensing and Heating Yarns with Color Change.

A person's body temperature is an important indicator of their health status. A deviation of that temperature by just 2 °C already has or can lead to serious consequences, such as fever or hypothermia. Hence, the development of a temperature-sensing and heatable yarn is an important step toward enabling and improving the monitoring and regulation of a person's body temperature. This technology offers benefits to several industries, such as health care and sports. This paper focuses on the characterization and development of a hybrid yarn, which can measure and visualize temperature changes through a thermoresistive and thermochromic effect. Moreover, the yarn is able to serve as a flexible heating element by connecting to a power source. The structure of the yarn is designed in three layers. Each layer and component ensures the functionality and flexibility of the yarn and additional compatibility with further processing steps. A flexible stainless steel core was used as the heat-sensitive and heat-conducting material. The layer of polyester wrapped around the stainless steel yarn improves the wearing comfort and serves as substrate material for the thermochromic coating. The resulting hybrid yarn has a reproducible sensory function and changes its resistance by 0.15 Ω between 20 and 60 °C for a length of 30 cm. In addition, the yarn has a uniform and reproducible heating power, so that temperature steps can be achieved at a defined length by selecting certain voltages. The thermochromic color change is clearly visible between 28 and 29 °C. Due to its textile structure, the hybrid sensory and actuating yarn can easily be incorporated into a woven fabric or into a textile by means of joining technology sewing.

Dot-ELISA based on recombinant Hypodermin C of Przhevalskiana silenus for field diagnosis of goat warble fly infestation.

Goat warble fly infestation (GWFI) is an economically important myiasis caused by larvae of Przhevalskiana silenus (Diptera, Oestridae), prevalent in countries of the Mediterranean Basin and Indian subcontinent. GWFI is characterized by the presence of subcutaneous warbles at the lumbar and sacral region of dorsum in the infested animal. The early larval instars (L1 and L2) remain inaccessible to physical detection due to their small size and subcutaneous presence thus causing hindrance in the diagnosis. The objective of present study was to develop a field applicable early diagnostic intervention for GWFI monitoring and prophylactic management for effective control of the disease. Recombinant Hypodermin C (rHyC) antigen of P. silenus was expressed in Escherichia coli. The purified protein was used for optimizing dot-ELISA in a checkerboard titration using goat warble fly infested serum as known positive. The optimized assay was further tested for lower temperature (18°C) and incubation time (30 min). The optimized assay was assessed for inter-rater reliability and field samples. The optimized conditions require 188 ng of protein/dot, 1:800 dilution of serum sample, 1:4000 dilution of anti-goat IgG conjugate and 5% skim milk powder in phosphate buffer saline as blocking buffer. The assay was found to have a diagnostic sensitivity and specificity of 97.3% and 95.8%, respectively. The inter-rater reliability of dot ELISA with rHyC indirect ELISA was found to be almost perfect with a Cohen's kappa index of 0.973. Further testing at ambient temperature (18°C) and shorter incubation steps (30 min) supported suitability of the assay for field diagnosis of GWFI. The present study provides the first report of a sensitive and specific dot-ELISA for early diagnosis of GWFI which is rapid and cost effective. The test may provide an effective field applicable tool for sustainable control of GWFI.

Thermal environment optimisations of cave dwellings for the elderly in heating season among cold regions of China

In the vast developing world represented by China, the unsatisfactory thermal and humidity conditions among rural built environments are extremely harmful to the elderly-health in cold regions. The cave-dwellings maintain competent thermal stability, while with current refurbishment still cannot meet their relatively demanding thermal comfort needs. In fact, few studies have highlighted the optimisation effect of passive designs engaging various buffer spaces. Through experimental field measurements of representative cave dwelling and numerical simulations based on the DesignBuilder tool for the corresponding retrofit prototypes, this study investigated in detail the hidden correlations between key buffer space design variables (sunroom, under-eave gray space, courtyard, etc.) and the resulting indoor thermal and humidity performances for the elderly. The results of the study showed that:1) The average winter room temperatures of both heated (11.2 ± 1.5 °C) and unheated (6.4 ± 2.7 °C) rooms in traditional cave-dwellings fail to meet the recommended standard by World Health Organization (18 °C) and the Chinese national standard (16 °C–24 °C). 2) For living track temperature steps reduction, the southern sunroom has obvious impact (mostly <10 °C), while enclosed courtyards with glass-top can even enhance such performance (mostly <5 °C). 3) For boosting indoor temperatures in winter, sunroom with enclosed courtyard are most effective in unheated and heated conditions. As the first systematic work to reveal the thermal-enhancing effectiveness of the south-facing buffer space for cave-dwellings in cold climates, the research findings can assist optimizing-retrofitting for cave-dwellings among similar climatic regions globally.

Direct Imaging of Surface Melting on a Single Sn Nanoparticle.

Despite previous studies, understanding the fundamental mechanism of melting metal nanoparticles remains one of the major scientific challenges of nanoscience. Herein, the kinetics of melting of a single Sn nanoparticle was investigated using in situ transmission electron microscopy heating techniques with a temperature step of up to 0.5 °C. We revealed the surface premelting effect and assessed the density of the surface overlayer on a tin particle of 47 nm size using a synergetic combination of high-resolution scanning transmission electron microscopy imaging and low electron energy loss spectral imaging. Few-monolayer-thick disordered phase nucleated at the surface of the Sn particle at a temperature ∼25 °C below the melting point and grew (up to a thickness of ∼4.5 nm) into the solid core with increasing temperature until the whole particle became liquid. We revealed that the disordered overlayer was not liquid but quasi-liquid with a density intermediate between that of solid and liquid Sn.

Enabling the Operation of Highly Compatible LiI‐3‐Hydroxypropionitrile Small‐Molecule Solid‐State Electrolytes in Lithium Metal Batteries via Stepped‐Amorphization Strategy

AbstractIntegrating the advantages of both inorganic ceramic and organic polymer solid‐state electrolytes, small‐molecule solid‐state electrolytes represented by LiI‐3‐hydroxypropionitrile (LiI‐HPN) inorganic–organic hybrid systems possess good interfacial compatibility and high modulus. However, their lack of intrinsic Li+ conduction ability hinders potential application in lithium metal batteries until now, despite containing LiI phase composition. Herein, inspired by evolution tendency of ionic conduction behaviors together with first‐principles molecular dynamics simulations, we propose a stepped‐amorphization strategy to break the Li+ conduction bottleneck of LiI‐HPN. It involves three progressive steps of composition (LiI‐content increasing), time (long‐time standing), and temperature (high‐temperature melting) regulations, to essentially construct a small‐molecule‐based composite solid‐state electrolyte with intensified amorphous degree, which realizes efficient conversion from an I− to Li+ conductor and improved conductivity. As a proof, the stepped‐optimized LiI‐HPN is successfully operated in lithium metal batteries cooperated with Li4Ti5O12 cathode to deliver considerable compatibility and stability over 250 cycles. This work not only clarifies the ionic conduction mechanisms of LiI‐HPN inorganic–organic hybrid systems, but also provides a reasonable strategy to broaden the application scenarios of highly compatible small‐molecule solid‐state electrolytes.

Enabling the Operation of Highly Compatible LiI-3-Hydroxypropionitrile Small-Molecule Solid-State Electrolytes in Lithium Metal Batteries via Stepped-Amorphization Strategy.

Integrating the advantages of both inorganic ceramic and organic polymer solid-state electrolytes, small-molecule solid-state electrolytes represented by LiI-3-hydroxypropionitrile (LiI-HPN) inorganic-organic hybrid systems possess good interfacial compatibility and high modulus. However, their lack of intrinsic Li+ conduction ability hinders potential application in lithium metal batteries until now, despite containing LiI phase composition. Herein, inspired by evolution tendency of ionic conduction behaviors together with first-principles molecular dynamics simulations, we propose a stepped-amorphization strategy to break the Li+ conduction bottleneck of LiI-HPN. It involves three progressive steps of composition (LiI-content increasing), time (long-time standing), and temperature (high-temperature melting) regulations, to essentially construct a small-molecule-based composite solid-state electrolyte with intensified amorphous degree, which realizes efficient conversion from an I- to Li+ conductor and improved conductivity. As a proof, the stepped-optimized LiI-HPN is successfully operated in lithium metal batteries cooperated with Li4 Ti5 O12 cathode to deliver considerable compatibility and stability over 250 cycles. This work not only clarifies the ionic conduction mechanisms of LiI-HPN inorganic-organic hybrid systems, but also provides a reasonable strategy to broaden the application scenarios of highly compatible small-molecule solid-state electrolytes.

Non-linear physical aging of supercooled glycerol induced by large upward ideal temperature steps monitored through cooling experiments.

The physical aging of supercooled glycerol induced by upward temperature steps of amplitude reaching 45K was studied by a new method consisting in heating a micrometer-thick liquid film at a rate of up to 60 000 K/s, holding it at a constant high temperature for a controlled duration before letting it quickly cool down to the initial temperature. By monitoring the final slow relaxation of the dielectric loss, we were able to obtain quantitative information on the liquid response to the initial upward step. The so-called TNM (Tool-Narayanaswamy-Moynihan) formalism provided a good description of our observations despite the large distance from equilibrium, provided that different values of the nonlinearity parameter were used for the cooling phase and for the (much further from equilibrium) heating phase. In this form, it allowed to precisely quantify how to design an ideal temperature step, i.e., where no relaxation occurs during the heating phase. It helped bringing a clear physical understanding of how the (kilosecond long) final relaxation is related to the (millisecond long) liquid response to the upward step. Finally, it made possible the reconstruction of the fictive temperature evolution immediately following a step, evidencing the highly non-linear character of the liquid response to such large amplitude temperature steps. This work illustrates both the strengths and limitations of the TNM approach. This new experimental device offers a promising tool to study far-from-equilibrium supercooled liquids through their dielectric response.

Infrared Spectroscopic Investigations of Calcium Oxalate Monohydrate (Whewellite) Dehydration/Rehydration

Variable-temperature infrared spectroscopy is employed to monitor molecular vibrations during dehydration of calcium oxalate monohydrate (COM) and hydration of anhydrous calcium oxalate (COA). A unique variable-temperature infrared spectroscopy approach combines precise sample temperature control and rapid (2 °C s−1) heating/cooling with high-sensitivity infrared analysis. Infrared spectra are obtained at specific isothermal sample temperatures, while applying linear temperature versus time heating and cooling ramps, and in coordination with programmed temperature steps. Spectrum vibration bands provide information regarding the symmetry and local environments of solid-state water molecules and oxalate anions. When COM is heated, water molecules liberated from different crystallographic sites are selectively detected. Subtle oxalate anion configuration changes associated with water losses are detected based on infrared vibration band shapes and wavenumber trends. Dehydration and rehydration processes occur at lower temperatures and over narrower temperature ranges than conventional thermal analysis methods because samples consist of thin layers of small particles. Reversible and irreversible sample changes are distinguished by using a step heating/cooling temperature program and spectral subtractions. COA temperature-dependent structure variations that occur while heating and cooling samples in an atmosphere with a low water vapor concentration are characterized.

Thermal Resolution of Unblocking Temperatures (TROUT): A Method for “Unmixing” Multi‐Component Magnetizations

AbstractSome rocks contain multiple remanence “components,” each of which preserves a record of a different magnetic field. The temperature ranges over which these remanence components unblock can overlap, making it difficult to determine their directions. We present a data analysis tool called Thermal Resolution Of Unblocking Temperatures (TROUT) that treats the process of thermal demagnetization as a function of temperature (or alternating field demagnetization as a function of coercivity). TROUT models the unblocking temperature/coercivity distributions of components in a demagnetization experiment, allowing these distributions to overlap. TROUT can be used to find the temperatures/coercivities over which paleomagnetic directions change and when two directional components overlap resulting in curved demagnetization trajectories. When applied to specimens given multi‐component Thermoremanent Magnetizations (TRMs) in the laboratory, the TROUT method estimates the temperature at which the partial TRMs were acquired to within one temperature step, even for specimens with significant overlap. TROUT has numerous applications: knowing the temperature at which the direction changes is useful for experiments in which the thermal history of a specimen is of interest (e.g., emplacement temperature of pyroclastic deposits, re‐heating of archaeological artifacts, reconstruction of cooling rates of igneous bodies). The ability to determine whether a single component or multiple components are demagnetizing at a given temperature is useful for choosing appropriate ranges of temperatures to use in paleodirection/intensity experiments. Finally, the width of the range of temperature overlap may be useful for inferring the composition, grain size and domain state of magnetic mineral assemblages.