Temporal Evolution Of Temperature Research Articles

Thermo-mechanical responses of rubber concrete post-exposure to elevated temperatures

This manuscript introduces a hybrid approach merging the Alternating Direction Implicit (ADI) method with the Crank Nicolson scheme, renowned for its unconditional stability, for forecasting the thermo-mechanical responses of rubber concrete experiencing thermal shock. Various proportions of rubber aggregate (0%, 10%, 20%, and 30%) are investigated under a constant humidity level (3%). The governing equation for coupled thermo-mechanical phenomena, derived from the heat conduction equation, is delineated, followed by discretization employing the proposed methodology. A comparative analysis between the analytical solution, featuring temperature and time-dependent constants, and the numerical outcomes is conducted to validate the proposed algorithm. Additionally, the impact of temperature on mechanical parameters like tensile strength, compressive strength, and elastic modulus is deliberated. The findings, including 3D contour plots and the temporal evolution of temperature and each mechanical parameter, affirm the capability of our numerical framework in anticipating and scrutinizing the thermo-mechanical dynamics of rubber concrete under fire-induced loading conditions.

Theoretical prediction model for minimum ignition energy of combustible gas mixtures

Minimum ignition energy (MIE) is a crucial parameter for identifying the hazards of combustible gases. To rapidly obtain accurate MIE values for various gases, the shape of the ignition source was simplified to cylindrical. Based on theories of heat conduction and chemical reaction kinetics, a physical model of the ignition process was established. The spatial and temporal evolution of temperature was used as a basis for judging the success of ignition. A numerical algorithm was developed and maximum flame temperatures and MIE were calculated for several combustible gases (H2, CH4, C2H6, C3H8, C4H10, C2H4, C2H2). This model accurately predicted the U-shaped trend of MIE values with concentration for CH4/air and H2/air mixtures. It found that the MIE was minimal at the stoichiometric concentration, at 0.37 mJ and 0.017 mJ, closely aligning with experimental data. This numerical model has been validated for its accuracy and promises to make relatively precise theoretical predictions for the MIE values of uncommon combustible gases or mixtures of various gases.

Precipitation and Temperature Maxima: A Study across the Southern Great Plains Winter Wheat Region

Abstract With the importance of agriculture to the southern Great Plains (SGPs), accurate knowledge of growing season (GS) temperatures and precipitation is critical. Previous research into GS precipitation and temperature maxima leads to the development of the asynchronous difference index (ADI) which identified positive and negative ADI GSs (March–September). The goal of this research is to further investigate the ADI within a specific agricultural region of the SGP, the winter wheat region, and to quantify the temporal evolution of temperature and precipitation during positive and negative ADI GSs. For this, Global Historical Climatology Network (GHCN) daily station data were analyzed across the GS (March–September) from 1900 to 2020. Results show that differences appear in the temperature and precipitation fields when comparing positive and negative GSs. Namely, positive (negative) ADI GSs show positive (negative) precipitation and negative (positive) temperature anomalies early in the GS, with these anomalies flipping in the later portion of the GS. Further, the results of this work show that the depicted changes in temperature and precipitation during positive and negative ADI GSs impact winter wheat yields. Overall, these results analyze the implications of positive and negative ADI GSs on the SGP climate, namely, the impact of the seasonal variability of daily maximum temperature and precipitation on agriculture.

Investigation of Nano-Heat-Transfer Variability of AlGaN/GaN-Heterostructure-Based High-Electron-Mobility Transistors

The aim of this work is to propose an electrothermal model for predicting the electron mobility, the effective thermal conductivity, and the operating temperature of AlGaN/GaN HEMT devices. The suggested model comprises an enhanced ballistic-diffusive model (BDE) coupled with a drift-diffusion model (D-D). Furthermore, the given model considers total electron mobility, which depends on mobility degradation caused by phonon interactions, surface imperfections, and carrier mobility inside the bulk GaN material. The model is validated based on available experimental and numerical results, and good concordance is observed. It is found that the degradation of the drain current is due to electron mobility and effective thermal conductivity degradation. The output characteristic’s degradation due to changing device temperature is analyzed. We demonstrate that for gate biases of −1 V, 0 V, and 1 V, operating temperatures of 390 K, 470 K, and 570 K are obtained when the drain currents are 0.1 A, 0.24 A, and 0.38 A, respectively. Furthermore, we demonstrate that the temperature is maximal in the active region. The temporal temperature evolution presents the same trends with the same amplitude compared to the experimental data, and the error does not exceed 5%.

Spatial–Temporal Evolution of Temperature and Gas Pressure in Soft and Hard Coal During Cryogenic Treatment: An Experimental and Theoretical Investigation

Spatial–Temporal Evolution of Temperature and Gas Pressure in Soft and Hard Coal During Cryogenic Treatment: An Experimental and Theoretical Investigation

Experimental investigation of the temperature field of a frost-penetration tunnel based on a whole life cycle laboratory test

Temperature field evolution plays an essential role in anti-freezing design of frost-penetration tunnels, for which temperature data measured throughout the whole life cycle (100 years) are lacking. The spatial and temporal temperature evolution of a frost-penetration tunnel during the whole life cycle was investigated by using a laboratory test. The test model was designed following some basic fundamental assumptions and similarity principles. The proposed test model was validated using typical cases of the long-term evolution of the temperature fields in cold region tunnels. The evolution features, formation mechanisms and influencing factors were deeply discussed. Experimental results of the model test indicate that a frost-penetration phenomenon occurs in tunnels with positive ground temperature and negative mean annual air temperature. Under negative mean annual air temperature, the freezing circle develops radially towards the surrounding rock and simultaneously develops longitudinally along the tunnel after the tunnel breakthrough. The unfrozen surrounding rock freeze yearly and can develop into permafrost. The primary impact factor of frost penetrations is the positive initial ground temperature and negative mean annual air temperature. The mean annual air temperature has an insignificant effect on the annual temperature amplitude of the surrounding rock, whereas the annual air temperature amplitude has a negligible effect on the mean annual temperature.

Temporal Temperature Evolution during the Pyrolysis of Cotton Stalks, Corn Stalk and Rice Husk Using Multifunction Family Oven for the Biochar Production

The multifunctional family oven is an oven able to produce simultaneously biochar for soil improvement and energy for cooking. However, the quality of the biochar produced depends not only on the selected biomass but especially on the pyrolysis temperature which is a very important parameter. This experimental study aims to understand the functioning of the oven with respect to its biochar production and the pyrolysis duration. To carry out our study, K-type thermocouples were used to measure the temperature on the different walls and chambers of the oven. Cotton stalks, corn stalks and rice husk were used for this study. The results obtained showed that the cotton stalks reached the maximum pyrolysis temperature at 430 °C around 1700 s. This temperature remained constant for 1500 s before decreasing to mark the end of pyrolysis. As for the corn husks, they reached their maximum average pyrolysis temperature at 470 °C after 3000 s. The rice husk reached a maximum pyrolysis temperature of 420 °C after 3500 s. A comparative study of the temperature curves of the three biomasses revealed that cotton stalks pyrolyze faster with short time than the other two biomasses. The results obtained on the pyrolysis temperature, corroborate those of the literature from which the multifunctional family oven produces a quality biochar. The maximum temperature of combustion which starts the pyrolysis is about 800 °C and can last for 1h30 min. Thus, this heat is valued by the cooking of different dishes of the country.

Temperature Profile Measurement From Radiofrequency Nasal Airway Reshaping Device.

Nasal airway obstruction (NAO) is caused by various disorders including nasal valve collapse (NVC). A bipolar radiofrequency (RF) device (VivAer®, Aerin Medical, Sunnyvale, CA) has been used to treat NAO through RF heat generation to the upper lateral cartilage (ULC). The purpose of this study is to measure temperature elevations in nasal tissue, using infrared (IR) radiometry to map the spatial and temporal evolution of temperature. Experimental and computational. Composite porcine nasal septum was harvested and sectioned (1 mm and 2 mm). The device was used to heat the cartilage in composite porcine septum. An IR camera (FLIR® ExaminIR, Teledyne, Wilsonville, OR) was used to image temperature on the back surface of the specimen. These data were incorporated into a heat transfer finite element model that also calculated tissue damage using Arrhenius rate process. IR temperature imaging showed peak back surface temperatures of 49.57°C and 42.21°C in 1 and 2 mm thick septums respectively. Temperature maps were generated demonstrating the temporal and spatial evolution of temperature. A finite element model generated temperature profiles with respect to time and depth. Rate process models using Arrhenius coefficients showed 30% chondrocyte death at 1 mm depth after 18 s of RF treatment. The use of this device creates a thermal profile that may result in thermal injury to cartilage. Computational modeling suggests chondrocyte death extending as deep as 1.4 mm below the treatment surface. Further studies should be performed to improve dosimetry and optimize the heating process to reduce potential injury. Laryngoscope, 134:1063-1070, 2024.

Optimal sensor placement and estimator-based temperature control for a deep drawing process

Deep drawing is one of the most important forming processes for the forming of flat sheet blanks, where the formation of wrinkles and the appearance of cracks can be a problem, especially in areas of high geometric complexity. The local increase of the temperature in these critical areas can help to improve the formability of the material and thus reduce defects. The present paper aims at a targeted temperature control of the die of a deep-drawing mold. For this sensors are placed systematically to develop an estimator for the spatial–temporal temperature evolution to subsequently realize tracking control using the embedded actuation devices. A continuum representation of the temperature distribution in the die is derived and transferred to a high order finite element (FE) approximation to take the complex-shaped geometry of the tool into account. Parameter identification is performed based on measurement data to improve the accuracy of the FE approximation and model order reduction (MOR) techniques are applied to determine a sufficiently low order system representation. A mixed-integer optimization problem is formulated and solved making use of different formulations of the observability Gramian to determine the optimal sensor locations and a Kalman filter is designed as an estimator based on a reduced order model. Moreover, a linear-quadratic regulator with integral part combined with the Kalman filter is developed to react efficiently towards disturbances. Finally this theoretical framework is tested in a real experiment.

Femtosecond infra-red laser carbonization and ablation of polyimide for fabrication of Kirigami inspired strain sensor

Microfabrication of polyimide (PI) with femtosecond laser of wavelength 1030 nm is studied in two process conditions. Firstly, the low power-low scan speed regime is investigated for laser carbonization producing piezoresistive laser induced graphene (LIG). The heat accumulation model is modelled to find the temporal evolution of temperature at the laser focus for a single laser scan. Secondly, the high power-high scan speed regime is studied for laser ablation where clean ablation was observed due to multiphoton absorption. To demonstrate the application of this process, a two-dimensional (2D) LIG based strain sensor is drawn on a Kapton PI sheet using laser carbonization and transformed into a three-dimensional (3D) conformal sensor by cutting into a Kirigami design using laser ablation. The strain in the sensor is calculated from finite element analysis and the gauge factor is 88.58 ± 0.16. This laser process enables the transformation of any 2D PI sheet into a 3D conformal sensor using femtosecond laser, which is useful for wearable sensors and health-monitoring applications. The fabricated sensor is demonstrated used on a knee-joint to monitor real-time tracking of bending and twisting knee movements.

Non-monotonic radial structures of fluctuating temperatures and densities associated with fishbone activities in KSTAR

General characteristics of a fishbone mode in KSTAR are investigated. Fishbone activities are observed with a Mirnov coil, an electron cyclotron emission radiometer (from the core to the edge of plasmas) and an beam emission spectroscopy system (core or edge plasmas) which are measuring fluctuations of poloidal magnetic fields, electron temperatures, and densities, respectively. Temporal evolutions of these fluctuations are similar to the observations from other tokamaks. An interesting and notable feature found in KSTAR fishbone modes is that radial coherence structures of electron temperature and density with respect to magnetic fluctuations are non-monotonic that they have a local minimum at r/a∼0.7 and a maximum at r/a∼0.9 in addition to the usual global peak near the q = 1 surface, where r/a is the normalized minor radius and q is the safety factor. Furthermore, the associated temporal evolution of the electron temperatures in slow-time scale, i.e., less than 1 kHz, with the fishbone activities show that there exist a drop in temperature or increase in temperature depending on inside or outside the q = 1 surface, respectively, from the core to the edge plasmas except that there are almost no temperature changes in the intermediate region which seems to be correlated with the non-monotonic coherence profile. Such a non-monotonic structure and the slow temporal evolution of temperatures are explained with barely trapped resonating fast ions with the banana orbit widths of the order of the minor radius, so that they transit the core and the edge regions simultaneously without trespassing the mid-plane intermediate region.

Barrow entropy and stochastic gravitational wave background generated from cosmological QCD phase transition

In this work we investigate the stochastic gravitational wave background generated during the first-order cosmological QCD phase transition of the early universe in the framework of the Barrow entropy. We first derived the Barrow corrections to the expression of stochastic gravitational wave background spectrum in presence of trace anomaly. Then, by taking account of Bubble wall collisions, sound waves and magnetohydrodynamic turbulence as the sources of stochastic gravitational wave, an analysis of the influence of Barrow entropy on the total energy density and the peak signal of stochastic gravitational wave signal is carried out. Finally, we discuss the possibility of detectors for the detection of these stochastic gravitational wave signals. Our results show that effect of Barrow entropy plays an important role in the temporal evolution of temperature of the universe as a function of the Hubble parameter, which leads to the signal of stochastic gravitational wave to shift towards the lower frequency regime, making the signal of stochastic gravitational wave possible to be probed by relevant ongoing and upcoming gravitational waves experiments.

A hybrid approach to predict vertical temperature gradient of ballastless track caused by solar radiation

• A hybrid approach combining the field test and FEM with ML technique is proposed. • Six ML techniques are used to predict spatial and temporal temperature gradient. • The key features of hybrid approach to predict temperature gradient are analyzed. • The proposed hybrid approach has excellent performance and transferability. The spatial and temporal temperature evolution of ballastless track is difficult to be determined, due to its complex thermal conditions. Accurate acquisition of vertical temperature gradient (VTG) of ballastless track is of great significance for its design, maintenance and damage control. However, few researchers have studied the predictive approach of spatial and temporal VTG evolution. In this study, a hybrid approach that combines experimental and finite element analysis with machine learning (ML) technique is proposed to automatically predict VTG of ballastless track induced by solar radiation. Six different ML techniques, i.e., multiple linear regression (MLR), polynomial regression (PR), support vector regression (SVR), random forest (RF), extreme gradient boosting (XGBOOST), and categorical boosting (CATBOOST) with fine-tuned hyperparameters are trained and validated by a dataset of 1000 cases retrieved from macroscale finite element analysis. The maximum and minimum air temperatures, latitude, average wind speed, etc., considering spatial and temporal environment actions are used as input variables to estimate the VTG of ballastless track. The results indicate that the CATBOOST-based hybrid approach demonstrates the most appropriate method for determining VTG of ballastless track among the above ML techniques. The proposed feasible and efficient hybrid approach is expected to be widely used for the identification of temperature evolution in structural engineering.

A multi modal approach to microstructure evolution and mechanical response of additive friction stir deposited AZ31B Mg alloy

Current work explored solid-state additive manufacturing of AZ31B-Mg alloy using additive friction stir deposition. Samples with relative densities ≥ 99.4% were additively produced. Spatial and temporal evolution of temperature during additive friction stir deposition was predicted using multi-layer computational process model. Microstructural evolution in the additively fabricated samples was examined using electron back scatter diffraction and high-resolution transmission electron microscopy. Mechanical properties of the additive samples were evaluated by non-destructive effective bulk modulus elastography and destructive uni-axial tensile testing. Additively produced samples experienced evolution of predominantly basal texture on the top surface and a marginal increase in the grain size compared to feed stock. Transmission electron microscopy shed light on fine scale precipitation of Mg_{17}Al_{12} within feed stock and additive samples. The fraction of Mg_{17}Al_{12} reduced in the additively produced samples compared to feed stock. The bulk dynamic modulus of the additive samples was slightly lower than the feed stock. There was a sim, 30 MPa reduction in 0.2% proof stress and a 10–30 MPa reduction in ultimate tensile strength for the additively produced samples compared to feed stock. The elongation of the additive samples was 4–10% lower than feed stock. Such a property response for additive friction stir deposited AZ31B-Mg alloy was realized through distinct thermokinetics driven multi-scale microstructure evolution.

Wavelength-modulation spectroscopy in the mid-infrared for temperature and HCl measurements in aluminum-lithium composite-propellant flames

This work presents the design, development, and application of a laser-absorption-spectroscopy diagnostic capable of providing quantitative, time-resolved measurements of gas temperature and HCl concentration in flames of metallized composite propellants containing ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB). This diagnostic utilizes a quantum-well distributed-feedback diode laser emitting near 3.27 μm to measure the absorbance spectra of HCl using a scanned-wavelength-modulation-spectroscopy technique that is insensitive to non-absorbing transmission losses caused by metal particulates in the flame. This diagnostic was applied to characterize the spatial and temporal evolution of temperature and HCl mole fraction in small-scale flames of AP-HTPB composite propellants containing either an aluminum-lithium alloy or micron-scale aluminum. Experiments were conducted at 1 and 10 atm. At both pressures, the flame temperature of the aluminum-lithium propellant, on a time-averaged basis, was 80 to 200 K higher than that of the aluminum propellant (depending on location in the flame) indicating more complete combustion. In addition, the mole fraction of HCl in the aluminum-lithium propellant flame reached values 65–70% lower than the conventional aluminum-propellant flame at the highest measurement location in the flame. The measurements at both pressures showed similar trends in the reduction of HCl in the aluminum-lithium propellant flame but at elevated pressures this occurred on a length scale nearly an order of magnitude smaller than the flame at atmospheric pressure. The results presented further support that the use of an aluminum-lithium alloy is effective at reducing HCl produced by the propellant flame without compromising performance, thereby making it an attractive additive for solid rocket propellants.

Freezing dynamics of supercooled micro-sized water droplets

The freezing of mini-sized supercooled water droplet includes two successive stages, rapid porous dendritic ice formation in recalescence stage and gradual ice growth in solidification stage. However, the freezing of supercooled micro-sized water droplet is significantly different and remains ambiguous. By implementing crystallization kinetics into heat and mass transfer analysis in the present study, a 3-dimensional numerical model is built to depict the fast freezing dynamics of micro-sized water droplets with diameters of 10 and 1 μm. The temporal evolutions of temperature and solid mass fraction during freezing process are elaborated, revealing two specific freezing patterns of the micro-sized droplets. For the water droplet with d = 10 μm, the propagation of porous ice decelerates due to strong heat conduction within the droplet. While for the water droplet with d = 1 μm, the cold energy is abundant for ice freezing due to strong heat exchange with external cold air stream, leading to the consecutive propagation of compact ice with solid mass fraction of 1.0. Furthermore, the influences of the location and number of the nucleation site on the freezing process are discussed. Limited by the external heat transfer, the freezing time is independent of the number of nucleation site for the water droplet with d = 10 μm. For the water droplet with d = 1 μm with abundant cold energy, multiple nucleation sites can accelerate the freezing of the droplet.

Kinetics of bread physical properties in baking depending on actual finely controlled temperature

Baking is a complex process involving simultaneous heat and mass transfer besides chemical reactions and structural transformations. This study built a finely controlled cavity to measure the physical changes in baking bread and correlate the process variables and bread physical properties throughout the baking process. The temporal evolution of temperature, moisture, weight loss, volume, porosity, crumb structure, and color change was assessed. The proposed experimental system showed longitudinal symmetry, ensuring greater control of the bread changes during baking. The bread lost 11, 15, and 17% of its moisture when baked at 180, 200, and 220 °C, respectively. In the baking at 200 °C, only the crust lost moisture, while the bread center gained up to 4.2% in moisture content. The bread volumetric expansion was higher at lower temperatures, i.e., 27.6% at 180 °C, 23% at 200 °C, and 23.5% at 220 °C. The color evolution presented a sigmoid profile for all CIE L*a*b* color space parameters. A proposed model described the development of color parameters as a function of temperature with good R2 and RMSE values, which allows predicting bread color throughout baking for each oven condition. The correlations obtained under controlled baking conditions accurately predict bread physical properties for each baking setup, allowing oven cavity design and optimization.

Technical assessment of phase change material thermal expansion for passive solar tracking in residential thermal energy storage applications

Phase changing materials (PCMs) have been widely investigated for Latent Heat Thermal Energy Storage (LHTES) applications in the last decades, due to their inherently high volumetric storage density and thermal control features. Nonetheless, PCMs and their related LHTES systems still require significant scientific and technical advancements and more efficient market penetration strategies, to be able to play a key role in the massive transition towards renewable energy that is expected to take place in EU in the near future. Some of the most investigated PCMs for low to medium temperature LHTES belong to the alkanes/paraffins family, which is characterized by a relatively high volumetric expansion solid-to-liquid phase transition. This is generally considered a side effect, which should be accounted for to avoid damaging the containment structure. However, it could also represent an opportunity to add extra functionalities and increase the overall efficiency of LHTES systems.In this paper, we evaluate the feasibility of using the mechanical work generated by the volumetric expansion cycles in a paraffin-based LHTES device for photovoltaic (PV) solar tracking purposes, thus assuming a novel paradigm for the efficient integration between thermal and PV solar installations. To this aim, the temporal evolution of temperature and density fields inside the PCM are modeled through a finite-difference/finite-volume numerical approach. Accurate charge/discharge profiles of the TES are implemented, considering data from a previously investigated solar-assisted heating/cooling plant for a typical residential application in southern Italy. Outcomes from this analysis allow to estimate the tracking capability of the chosen PCM in terms of number/surface of actuated PV panels.

Optical phase transition of Ge2Sb2Se4Te1 thin film using low absorption wavelength in the 1550 nm window

This paper aims to study the amorphous-to-crystalline phase transition characteristics of novel optical phase change material: Ge2Sb2Se4Te1 using excitation wavelength situated in the low absorption window of the phase change material. The GSST thin film is 300 nm thick and is coated on a glass substrate. The excitation wavelength used is situated in the 1550 nm window with absorption coefficient that is 4 orders of magnitude lower compared to the visible wavelengths typically used. Finite Element Method (FEM) is carried out to simulate the spatial distribution and temporal evolution of temperature within the GSST thin film during the laser irradiation process. Experimental verification of the simulation data is then carried out. Laser intensity between 0.45 and 0.9 GW/cm2 with pulse duration in the range of 70–190 ns, respectively, are required to induce crystallization of the GSST thin film using this excitation wavelength. This work provides useful information on implementing GSST as a functional material in current telecommunication network which uses the 1550 nm wavelength band as signal carrier.

Influence of Joule effect on thermal response of nano FinFET transistors

Integrated circuits based on FinFET nanodevices suffer from thermal processes related to heat dissipation caused by phonon transport bottlenecks. In this work, we report a numerical study of quasi-ballistic transport behavior in 20 nm FinFET transistors. Using a mathematical formulation, numerically implemented by the finite element method , we successfully validate the transfer characteristics and temporal temperature evolution compared with experimental and numerical works. We found that the proposed model, given by a calibrated charge drift-diffusion model coupled with the enhanced ballistic diffusive heat transport equation, predicts the experimental I–V characteristics and the transient temperature evolution well. The error given by this comparison is less than 10% in the I DS -V GS and T-t characteristics, respectively. We show that the proposed equations provide an improved approximation compared to the dual-phase lag and the Cattaneo-Vernotte models. From an engineering viewpoint, we found that the self-heating is concentrated at the end of the channel region at the drain side; this phenomenon was confirmed from literature by experimental results. • We report a numerical study of the quasi-ballistic transport behavior in 20 nm FinFET devices. • The model is able to predict the I(V) characteristics and heating phenomenon compared to experimental and numerical data. • The self-heating is concentrated at the end of the channel region at the drain side of the devices.