Effect Of High Temperature Research Articles

Electrical Conductivity of (Mg, Fe)CO3 at the Spin Crossover and Its Implication for Mid‐Mantle Geomagnetic Heterogeneities

Abstract(Mg, Fe)CO3 is an important deep carbon carrier and plays a vital role in our understanding of lower‐mantle carbon reservoirs. The electrical conductivity (EC) of FeCO3 was measured at 126−2000 K up to 83 GPa in diamond‐anvil cells using a standard four‐probe van der Pauw method. Moreover, the EC of FeCO3 increases by ∼6 orders of magnitude from 300 to 1500 K at 10−20 GPa, indicating a strong effect of high temperature. The EC of Fe0.65Mg0.35CO3 was measured up to 60 GPa at 300 K, the EC values of (Mg, Fe)CO3 are proportional to iron content and increase by 2–3 orders of magnitude at 300 K across the spin crossover. The EC values of (Mg, Fe)CO3 and FeCO3 + Fe3O4 ± C mixtures surpass that of bridgmanite, ferropericlase and davemaoite by ∼1–4 orders of magnitude at depths of 800–2,000 km. This result sheds insights into the genesis of local geomagnetic heterogeneities in the mid‐lower mantle.

Excess mortality related to high air temperature: Comparison of the periods including 1994 and 2018, the worst heat waves in the history of South Korea.

Climate change has caused extreme weather events, including frequent summer heat waves. We examined how the effects of high air temperatures on mortality have changed between the two study periods (1991-1995 and 2015-2019), including 1994 and 2018, the worst heat wave years in the meteorological history of South Korea. Temperature data from the Korea Meteorological Administration and mortality data from Statistics Korea were used in this study. We used distributed lag nonlinear models to estimate the cumulative relative risks (CRRs) to determine the association between daily maximum temperature in summer (June to September) and mortality. CRRs were estimated for each province and pooled using a random-effects meta-analysis for all provinces. Maximum temperature and annual average days in heat wave were 37.7°C and 11.8 in 1991-1995 and 38.3°C and 18.8 in 2015-2019. The slope of the CRR for mortality increases with increasing temperature and has been steeper in the past than in recent years and steeper in those over 65 than in those under 65. Excess mortality has recently declined compared with that in the past. The impact of high summer temperatures on mortality changed between the two periods, suggesting improved population resilience.

Physiological estimation of heat and drought resistance at the initial stages of winter barley ontogenesis

Drought and heat stress have significant effects on plant growth and productivity. In the natural environment, these abiotic stresses often occur simultaneously, which amplifies their negative effects. Therefore, understanding heat and drought influence on plant growth and productivity is particularly valuable. Winter barley, compared to other winter grain crops, is characterized by a relatively high resistance to moisture deficiency in soil and the effect of relatively high air temperatures. The current paper has highlighted the study of physiological indicators of winter barley resistance to moisture deficiency and high temperature effect. There have been presented the results of laboratory study for the period of 2022–2023. Identification of drought and heat resistance was carried out in the initial period of plant development on 100 winter barley samples of local selection and the VIR collection. The purpose of the study was to identify winter barley resistance to high temperatures and moisture deficiency using a set of laboratory methods. There has been studied the effect of sucrose solution of different concentrations (8, 12 and 14 atm.) and ambient temperature (52 and 54 °C) on the ability of seed germination under stress conditions. During the trials, there has been identified the best differentiation of resistance values under osmotic stress (8 atm.) and temperature (-54 °C). There have been identified the samples ‘Step’ (211.9 rel. units) and ‘HVW 36/72’ (157.9 rel. units) combining high resistance to osmotic and thermal stress, which reliably exceeded the values of the standard variety ‘Timofey’ by 25.3–79.3 rel. units.

Experimental Test and Analytical Calculation on Residual Strength of Prestressed Concrete T-Beams After Fire

High temperatures during a fire can lead to the evaporation of moisture and the degradation of hydration products within concrete, consequently compromising its mechanical properties. This paper thoroughly investigates the effect of fire-induced high temperatures on the residual load-bearing capacity of concrete structures, with a focus on prestressed concrete T-beams. By conducting constant temperature tests and residual load-bearing capacity tests, complemented by finite element modeling, this study examines the degradation of mechanical properties in prestressed concrete T-beams due to fire exposure and its impact on post-fire residual load-bearing capacity. Additionally, an equivalent concrete compressive strength method was employed to propose a calculation method for concrete material degradation under high temperatures and a corresponding concrete strength reduction factor. Simplified calculations were also performed for the high-temperature damage to reinforcement and prestressed tendons, leading to the derivation of a simplified formula for the residual load-bearing capacity of post-fire prestressed concrete T-beams. The results indicate that in prestressed concrete T-beams exposed to fire, an increase in holding time results in more severe damage modes, accelerated crack propagation, and wider crack widths during bending failure. Under the same load, a longer holding time corresponds to a more pronounced reduction in deflection. At holding times of 60 min, 120 min, and 180 min, the prestress losses were 48.17%, 85.16%, and 93.26%, respectively. The cracking load decreased by 15%, 27%, and 42%, while the residual load-bearing capacity decreased by 11%, 21%, and 28%. Comparison with experimental data demonstrates that both the finite element model and the simplified calculation formula exhibit high accuracy, offering a reliable reference for the performance evaluation of post-fire prestressed concrete T-beams.

High Temperature Effects on Global Heritage Stone Resources: A Systematic Review

Throughout history, natural stone has been a crucial building material due to its strength, durability, and aesthetic qualities. Today, it continues to be a valuable resource, representing both a cultural heritage asset and a significant economic material. However, the increasing frequency of heat waves and fires driven by climate change poses a growing threat to stone building materials. This paper reviews the scientific attention given to the effects of high temperatures on Global Heritage Stone Resources (GHSRs), an international classification designed to enhance the recognition and status of building stones. Through a systematic SCOPUS search with refined filtering criteria, the study aims to quantify the existing research on these heritage stones. The search applied the standardized lithotype terms from GHSR publications to ensure consistency, followed by the exclusion of irrelevant terms when identified. Additionally, a relevance filter was applied to restrict the number of articles per lithotype and ensure that only the most pertinent studies were considered. Key findings from the literature reveal that exposure to high temperatures (ranging from 200 °C to 900 °C) significantly affected the studied GHSRs, leading to thermal micro-fissuring, increased porosity, and changes in water absorption, which compromise the mechanical properties of the stones. Moreover, these conditions can result in irreversible chemical transformations, exacerbating the deterioration of cultural heritage assets. The study emphasizes the critical need for research to better understand how these stone materials behave when exposed to high temperatures. It also provides a relevant framework for future investigations aimed at predicting and mitigating the effects of external threats such as fires.

Study of microstructural evolution during operation of electrically connected components and analysis of failure mechanism

Abstract As a key current-carrying structure of high-voltage bushings, the reliability of electrical connection components is crucial to the safe and stable operation of power equipment. To obtain the microstructural evolution of electrical connection components with different deterioration states, CUD strap contactors were deteriorated in different ways, and electron backscatter diffraction (EBSD) technique was used to test the microstructure of strap contactors with different deterioration states. The results showed that compared to the unused contactors, the contact resistance of the contactors under the combined effect of friction and high temperature increased 203.12 times and was in a failed state. During the process from unused state to wear deterioration, high temperature deterioration, and then to eventual failure of the contactors, the average grain size gradually grows from 8.15 μm to 25 μm, the dislocation density gradually decreases from 2.38×1014 m-2 to 1.04×1014 m-2, and there are a significant proportion of the recrystallized organization. These changes are detrimental to the mechanical properties of the contactors. In addition, the distribution of grain boundaries in the contact area proves the occurrence of over-temperature phenomenon in this area, which will accelerate the deterioration of the contactors and eventually lead to the failure of the component. The relevant conclusions can provide a theoretical basis for the design of electrical connection structure of strap contacts as well as the study of deterioration mechanism.

Effect of curing temperature, silica fume, and waste tire rubber aggregate on material characterization of lightweight geopolymer composite

This study investigates the potential effect of curing temperature (80 °C and 100 °C), the effect of using waste tire rubber aggregates (WTRA), and silica fume (SF) on the properties of lightweight geopolymer (LG) composite. In LG, SF replaced 20 % of the ground granulated blast furnace slag (GGBS), and WTRA replaced pumice aggregate to varying degrees (15 %, 30 %, and 45 % by volume). The physical properties of the LG composite were assessed through apparent porosity, water absorption, and hardened density. The mechanical properties were examined by testing compressive strength (CS) and flexural strength (FS). The effect of high temperature (300 °C and 600 °C) was examined on CS and mass loss of LG composite. The durability of the LG composite was analyzed using mercury intrusion porosimetry (MIP), capillary water absorption, freeze-thaw, and thermal conductivity. The material characterization of the composite was done using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermogravimetry (DTG) curves. After 28 days, LG composites showed increased porosity and water absorption with the increased WTRA and SF, with higher values at 100 °C. Compressive and flexural strengths decreased with the increased WTRA and SF, especially at higher temperatures. The TGA-DTG curves show that the LG-0–80 mix had the lowest mass loss (15.25 % at 400°C and 19.36 % at 600 °C), while the LG-SF-45–100 mix had the highest mass loss (22.22 % and 24.53 %, respectively). XRD and TGA-DTG analyses reveal that using SF increases Ca(OH)₂ peaks and alters the geopolymer composition, improving the mechanical performance of the LG-SF-0–80 mix and enhancing the thermal stability of the composites.

Experimental Study on the Mechanical Properties of C30 Molybdenum Tailings Concrete after High-Temperature and Sulfate Corrosion

In order to study the durability of molybdenum tailings concrete after a specific period of wet-dry cycle tests and exposure to high temperatures, this paper investigates the rule of change of the mechanical properties of molybdenum tailings concrete under the coupled influence of sulfate corrosion and high-temperature environmental conditions. A total of five C30 concrete prisms with molybdenum tailings content (0%, 25%, 50%, 75%, and 100%) were considered in the tests, with sulfate solution concentrations of 0 g/L, 20 g/L, and 50 g/L, and exposure temperatures of 25° at room temperature and 400° at high temperature, respectively. The test results showed that the mass loss rate of concrete prisms with different molybdenum tailings substitution rates under sulfate corrosion and high temperature environment showed an increasing and then decreasing trend. The specimens with 25% molybdenum tailings content still maintain high mechanical properties after wet-dry cycle tests of sulfate solution and high temperature, and the reduction of peak stress in this group is only 11%, and the reduction of elastic modulus is 1%; the rest of the molybdenum tailings content has a reduction of peak stress of about 25%, and the reduction of modulus of elasticity is more than 10%. The plastic deformation capacity of molybdenum tailings concrete decreases under the single-factor effects of wet-dry cycle tests of sulfate solution and high temperature effects, but the plastic deformability capacity of the specimens is enhanced under the combined effects of multiple factors. The stress-strain curve formulas for molybdenum tailings concrete under high temperature, wet-dry cycle tests of sulfate solution, and coupled wet-dry cycle tests of sulfate solution and high temperature were fitted. The results of this study can provide experimental data and valuable references for the engineering application of molybdenum tailings concrete under wet-dry cycle tests of sulfate solution and high temperature conditions, laying a foundation for further research.

Effect of pavement layer temperature on fatigue performance of rib-to-deck weld details in orthotropic steel bridge decks

To investigate the effect of asphalt pavement layer temperature on the fatigue performance of welded details in orthotropic steel bridge deck (OSD), this study focuses on the critical fatigue crack regions of the rib-to-deck weld details. A systematic study was conducted based on the theory of linear elastic fracture mechanics (LEFM) and the finite element model (FEM). In this research, the elastic modulus of the pavement layer at different temperatures, and the initial crack shape, were considered as parameters. The maximum normal stress, stress intensity factor (SIF), and fatigue crack growth (FCG) shape and life of the weld details under the influence of these parameters were analyzed. The analysis results indicate that using a constant temperature of 20°C for the pavement layer will ignore the adverse effects of high summer temperatures. Under the influence of the pavement layer temperature effects, the weld toe of the top deck is the most critical welded detail. The FCG life and final crack shape at the weld toe of top deck are closely related to the effects of pavement layer temperature and the initial crack shape, higher pavement layer temperatures result in shorter fatigue life and larger final crack propagation sizes. Therefore, it is recommended that pavement layer and temperature effects be considered in the FCG analysis of welded details in OSDs.

Cyclic functional degradation of NiTi shape memory alloy wires in wide ranges of strain rate and ambient temperature

Shape memory alloy (SMA) dampers frequently experience cyclic loading over a broad spectrum of strain rates and ambient temperatures, resulting in a significant thermo-mechanical coupling effect during cyclic deformation. Nevertheless, the impact of this coupling effect on the functional degradation of SMAs has not been thoroughly examined, particularly in scenarios involving severe deformation. In this study, a series of strain-controlled cyclic loading–unloading tests were conducted on NiTi SMA wires utilizing various combinations of strain rates ranging from 5 × 10−4 6 × 10−2/s and different ambient temperatures (313–393 K). The functional degradation was exacerbated by increasing ambient temperature and loading rate due to the complex interactions among the inelastic deformation mechanisms and thermo-mechanical coupling effects. Furthermore, although the cyclic deformation behavior of NiTi SMA wires varied with the loading rate, this rate dependence diminished with increasing ambient temperature. The synergistic effect of elevated strain rates and high temperatures markedly accelerated the fatigue failure of NiTi SMA wires and substantially altered the underlying microstructural morphology. These findings can provide valuable support for evaluating the service performance of NiTi SMA dampers under various engineering conditions and contribute to developing a cyclic constitutive model for NiTi SMAs.

Study on the aerodynamic characteristics of reentry capsule with obtuse head inverted cone under hypersonic chemical nonequilibrium flow

Abstract During spacecraft reentry, the aerodynamic characteristics of the reentry capsule with a sizeable obtuse head inverted cone (OBHIC) in a hypersonic state are the key factors in the design of controlled reentry trajectory, the design of trim angle of attack (AoA), and the accuracy of fall point of capsules. This paper establishes a numerical simulation algorithm of a hypersonic chemical nonequilibrium flow field by considering high-temperature real gas effects. The reentry capsule’s aerodynamic and flow field characteristics are predicted and analyzed. The component transport equations for chemical reactions are added to the Navier-Stokes equations, enabling precise modeling of gas molecule vibrational excitation and ionization processes. A half-model multi-block structured mesh is employed to construct the aerodynamic profile of the reentry capsule with OBHIC. The aerodynamic characteristics and pressure distribution of the reentry capsule were calculated and analyzed under the typical conditions of flight altitude of 40~80 km, flight velocity of 6~27 Ma, and AoA of 15°~24°. The results of the aerodynamic characteristics prediction show that the aerodynamic characteristics of the reentry capsule are little affected by the incoming flow velocity in a hypersonic state but significantly affected by the AoA. As the AoA increases, the lift coefficient CL increases linearly, the drag coefficient CD decreases linearly, the lift-to-drag ratio K rises linearly, and K increases from 0.19 to 0.29. In its hypersonic state, the reentry capsule exhibits a low lift-to-drag ratio, characterized by high drag and low lift coefficients. The results of this paper play an essential role in the reentry flight dynamics and reentry trajectory design of the reentry capsule. Moreover, it can further ensure the safety and reliability of the reentry flight of spacecraft.

Effect of High Nighttime Temperatures on Growth, Yield, and Quality of Two Wheat Cultivars During the Whole Growth Period.

It is a consensus that Earth's climate has been warming. The impact of global warming is asymmetric, that is, there is more substantial warming in the daily minimum surface air temperature and lower warming in the maximum surface air temperature. Previous studies have reported diurnal temperature differences greatly affecting winter wheat yield. However, only a few studies have investigated the impact of global warming on the growth and yield of winter wheat, yet the influence of night warming on quality has not been deeply evaluated. In this study, two wheat cultivars were used as materials: Jimai 44 (JM44) with strong gluten and Jimai 22 (JM22) with medium gluten, to explore the effects of high nighttime temperatures (HNTs) on the growth, yield, and quality of wheat. The results show that HNTs significantly shortened seedling emergence and anthesis periods in both cultivars compared with ambient temperatures (ATs). In addition, HNTs increased the respiration rate at anthesis and grain-filling stages, impeding wheat pollination and grain maturity. HNTs also accelerated leaf senescence and increased the number of sterile spikelets and plant height, but decreased the effective tiller number, the number of spikes per unit area, and grains per spike. As a result, the grain yield of JM22 and JM44 was decreased by 24.6% and 21.2%, respectively. Moreover, HNTs negatively influenced the flour quality of the two wheat cultivars. The current findings provide new insights into the effects of HNTs on the growth, development, yield, and quality of different wheat genotypes during the whole growth period.

Effect of High Processing Temperature on the Rheological and Morphological Properties of Recycled Polypropylene

Effect of High Processing Temperature on the Rheological and Morphological Properties of Recycled Polypropylene

Microstructural Analysis of the Effect of Using Nano-silica on the Mechanical Properties of Cement–Sand Mortar Under the Effect of Heat

The performance of cement-based materials depends on the characteristics of solid particles at the nano-scale or nanometer porosities in the interfacial transition zone between cement particles and aggregate. Heat significantly affects the properties of these particles and the connection between them. Accordingly, the present study seeks to investigate the effect of nano-silica on the strength parameters of sand–cement mortar at high temperatures. In this regard, the sand–cement mortar was prepared by replacing 5, 10, and 15 percent of cement with nano-silica. The specimens were subjected to temperatures of 25, 100, 200, 400, 600, and 800 °C after curing at the ages of 3, 28, and 90 days. The effect of high temperatures on the physical and mechanical properties of sand–cement mortar was analyzed using macro-structural tests of compressive strength, loss in weight, and water absorption, and microstructural tests of X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that the macro-structural behavior of sand–cement mortar highly depends on the microstructure and changes in cement nanostructures during heat treatment. Primary portlandite and C–S–H nanostructure were destroyed at 600 °C, and alite, belite, and β-wollastonite were formed at 800 °C. Adding nano-silica improved the strength properties of sand–cement mortar against heat, so the compressive strength of 28-day specimens containing 15% nano-silica increased from 13.9 to 19.2 MPa at a temperature of 800 °C.

Studying the metakaolin content, fiber type, and high-temperature effects on the physico-mechanical properties of fly ash-based geopolymer composites

Studying the metakaolin content, fiber type, and high-temperature effects on the physico-mechanical properties of fly ash-based geopolymer composites

Trehalose metabolism mediates trade-offs between reproduction and survival in beet webworm, Loxostege sticticalis, under heat stress.

Temperature is an important determinant of developmental and reproductive rates in insects. Here, we investigated the physiological responses of adult beet webworm, Loxostege sticticalis L. (Lepidoptera: Crambidae), to three temperatures (16, 23 and 30 °C) focusing on trehalose metabolism. Exposure of moths to 30 °C accelerated eclosion and ovarian development, but shortened the oviposition period and adult longevity, whereas exposure to 16 °C had opposite effects. Transcriptome analysis revealed that vitellogenin (VG) and vitellogenin receptor (VR) genes were up-regulated at 30 °C, as were numerous genes related to energy metabolism, including those involved in the insulin signaling pathway, the tricarboxylic acid (TCA) cycle, and glycolysis. Expression of the trehalose transporter gene TRET1 was also induced at high temperature, primarily in the ovaries, where trehalose content increased, accompanied by lipid degradation in the fat body. Treatment with the trehalase inhibitor validamycin A reduced female fecundity and longevity at 23 °C, but enhanced the expression of genes related to stress resistance and reproduction, mimicking the effect of high temperature. Besides their practical utility for predicting the oviposition behavior and geographic distribution of L. sticticalis in the field, these results elucidate the various physiological roles of trehalose in L. sticticalis during exposure of moths to high temperature and may provide insights into the relationship between stress resistance and reproduction in insects more generally. © 2024 Society of Chemical Industry.

Dual-gate AlGaN channel HEMTs: advancements in E-mode performance with N-shaped graded composite barriers

Abstract This work evaluates the performance of dual gate AlGaN channel HEMTs on SiC substrate. The study analyzes two HEMT structures that differ only in barrier design, one design consists of fixed composite barriers (FCB-HEMT) i.e. there is fixed Aluminum composition x = 0.48 in the first Al x Ga1−x N barrier and x = 0.42 in the second Al x Ga1−xN barrier while the other design comprises N-shaped graded composite barriers (NGCB-HEMT) i.e. the Aluminum content varies gradually from 0.4 to 0.48 in the first AlGaN barrier and from 0.34 to 0.42 in the second AlGaN barrier. The paper concentrates on energy band diagrams, electron concentration profile, electric field distribution, drain and transfer characteristics, and the effects of high temperature on drain characteristics and mobility of the NGCB-HEMT. It has been reported that at zero gate bias, the FCB-HEMT has a drain current density of 0.137 A mm−1 while it decreases to 0.0058 A mm−1 in the case of NGCB-HEMT, thus presenting a novel approach towards enhancement-mode AlGaN HEMTs. Hence, grading can be optimized in the composite barriers to achieve enhancement mode operation of AlGaN channel HEMTs. Furthermore, the study reveals that the critical electric field of FCB-HEMT is 6.9975 M V cm−1, while that of NGCB-HEMT is 5.3124 M V cm−1, demonstrating their usefulness in electronic devices that operate at high voltages and harsh temperatures. Moreover, at higher temperatures, the phenomenon of optical phonon scattering leads to decreased mobilities, which in turn causes low drain currents relative to the drain voltage.

The effects of extreme temperatures on carbon total factor productivity: Evidence from China

Climate change poses a severe threat to the low-carbon and high-quality development of Chinese cities. This paper uses panel data from 2007 to 2019 for Chinese cities, which covers the transition of China's economy from high-speed growth to high-quality development. Then, this paper investigates the causal effects and mechanisms of extreme temperatures on carbon total factor productivity (CTFP). There are four main findings. First, CTFP calculated by biennial non-radial Luenberger productivity index grows by 3%, which comes from technological advances rather than efficiency gains. Second, both extremely high and low temperatures significantly reduce CTFP, and this negative effect is persistent, especially in poor and southern cities. Third, this negative effect comes from the decline in efficiency change rather than technology change and can also be explained by a decline in the productivity and efficiency of the desired output. Fourth, the forecasted outcomes for the future scenarios under the Shared Socioeconomic Pathways 1 (SSP1) and 5 (SSP5) indicate a persistent escalation in the adverse effects of extreme high temperatures. The research provides a new perspective for China to cope with climate change on low-carbon development and provides a reference for other developing countries.

Stomatal development in the changing climate.

Stomata, microscopic pores flanked by symmetrical guard cells, are vital regulators of gas exchange that link plant processes with environmental dynamics. The formation of stomata involves the multi-step progression of a specialized cell lineage. Remarkably, this process is heavily influenced by environmental factors, allowing plants to adjust stomatal production to local conditions. With global warming set to alter our climate at an unprecedented pace, understanding how environmental factors impact stomatal development and plant fitness is becoming increasingly important. In this Review, we focus on the effects of carbon dioxide, high temperature and drought - three environmental factors tightly linked to global warming - on stomatal development. We summarize the stomatal response of a variety of plant species and highlight the existence of species-specific adaptations. Using the model plant Arabidopsis, we also provide an update on the molecular mechanisms involved in mediating the plasticity of stomatal development. Finally, we explore how knowledge on stomatal development is being applied to generate crop varieties with optimized stomatal traits that enhance their resilience against climate change and maintain agricultural productivity.

Effects of load and high temperature on uniaxial compressive properties of desert sand concrete

In order to explore the influence of load and high temperature on the uniaxial compressive properties of desert sand concrete (DSC), the axial compressive strength test of desert sand concrete after different loads and temperatures was carried out, and the stress-strain curve was measured. The influence of load level, temperature grade and cooling method on the mass loss rate, ultrasonic velocity and uniaxial compressive performance of desert sand concrete after high temperature was analyzed. The results show that as the temperature increases, the mass loss rate of desert sand concrete gradually increases, the axial compressive strength gradually decreases, the peak strain increases significantly, the stress-strain curve tends to be flat, and the elastic modulus decreases continuously. The "pseudoplastic platform" near the axial compressive strength of the stress-strain curve of desert sand concrete after high temperature is more obvious. Based on the two-stage constitutive model of concrete, the constitutive model of desert sand concrete considering the influence of temperature and load level is established. The research results can provide technical support for the performance evaluation of desert sand concrete after high temperature.