Temperature Wave Research Articles

Investigation on structural, electronic and magnetic properties of Co2FeGe Heusler alloy: Experiment and theory

Experimental and computational studies are performed on Co2FeGe Heusler alloy. Significantly large saturation magnetization (Ms), Curie temperature (Tc) and spin wave stiffness constant (D) of 6.1 µB/f.u., 1073 K and 10.4 nm2-meV respectively were observed experimentally. The experimental values of Tc and D are reported first time and are among the highest reported values of the same in Heusler alloy domain. The Co2FeGe Heusler alloy strictly follows Slater-Pauling (SP) rule, however, the minor experimental deviation from its SP value is justified by doing full-potential density functional calculations, which gives more accurate result when electron–electron correlation parameter (U) is taken into account with conventional generalized gradient approximation (GGA) scheme. Effect of lattice strain and U on the total and atom-specific magnetic moments and spin-polarization is studied in detail from which we conclude that they have a key role in the deviation of the experimental results from the expected theoretical values. Dynamical stability of the alloy is studied from the phonon dispersion curve and the effect of U is found to be distinct on the phonon density of states. Role of different types of atomic site disorders on the saturation magnetization is also explored computationally and related to the experimental results. The computational results provide in-depth and detailed study followed by experimental validations.

Real-Scale Experimental Evaluation of Energy and Thermal Regulation Effects of PCM-Based Mortars in Lightweight Constructions

Lightweight construction is experiencing a significant market implementation with sustained growth both for new buildings and retrofitting purposes. Despite the acknowledged advantages of this type of construction, their reduced thermal inertia can jeopardize indoor thermal comfort levels while leading to higher energy consumption due to high indoor temperature fluctuations and overheating rates. The incorporation of phase change materials (PCMs) into constructive solutions for lightweight buildings is a promising strategy to guarantee adequate thermal comfort conditions. Particularly, the utilization of mortars embedding PCMs as an indoor wall coating for new and existing buildings represents a solution that has not been widely explored in the past and needs further development and validation efforts. This work pursues the analysis of the thermal regulation effects generated by two thermally-enhanced mortars incorporating microencapsulated PCMs with different operating temperature ranges. To that end, an experimental campaign was conducted in Valladolid (Spain) to address the investigation of the proposed solution under a real-scale relevant environment. The proposed mortars were applied as an indoor coating to the envelope of a single-zone lightweight construction that was monitored (under different weather conditions along 1-year monitoring campaign) together with an identical building unit where the mortar was not added to the constructive base layer. The analysis of indoor temperature fluctuations under free-floating operating mode as well as the energy consumption of HVAC equipment under controlled-temperature operation was specifically targeted. Results derived from the continuous monitoring campaign revealed lower temperature fluctuations during summer and shoulder seasons, reducing indoor temperature peaks by 1–2 °C, and producing a time delay of 1–1.5 h into the temperature wave. A clear reduction in energy use due to the incorporation of the PCM-based indoor coating panels is also observed. Thus, this experimental research contributes to proving that the use of innovative mortars incorporating embedded PCMs enables the development of high-end efficient building solutions with innovative materials towards a sustainable built environment.

Heat transfer performance analysis of front-end capillary heat exchanger of a subway source heat pump system

During the operation of subway systems, a significant amount of heat is stored annually in the rock surrounding the tunnel, which results in underground thermal pollution. A subway source heat pump system with a front-end capillary heat exchanger (CHE) is considered an effective technology to address this problem. However, it has not yet been employed in systematic design and operation methods. This study numerically simulates and analyses the heat transfer performance of a tunnel lining CHE for an entire year under the typical conditions of an actual project. The results are expected to provide theoretical guidance for CHE design and operation. Moreover, the proposed model was verified by comparing the simulation results with those of field experiments.The simulation results indicated that both the temperature and heat flux of the CHE and tunnel surrounding rock experienced periodic fluctuations during the heating and cooling seasons and exhibited a strong heat recovery ability in the transitional seasons. The temperature of the surrounding rock (Tmid) gradually decreased with increasing depth of the surrounding rock, and the change in Tmid at greater depths (≥15 m) was less than 0.1 and 0.13 °C during the heating and cooling seasons, respectively. However, phase delays and amplitude attenuation phenomena occurred during the harmonic temperature transfer process. The phase delay of the tunnel wall temperature (Tw) valley and peak during the heating and cooling seasons were 13 and 2.2 h from the CHE wall temperature (TC) valley and peak, respectively. It was suggested that the efficient operation of the CHE should harmonise the two temperature waves of the tunnel wall and CHE. Furthermore, the average heat flux values at the lining-CHE outer wall contact surface during the CHE operation were −16 and 22 W during the heating and cooling seasons, respectively. In addition, the CHE exhibited abnormal heat fluxes during the heating and cooling seasons along the CHE pipe (10 m), indicating that the design and operation of the CHEs must consider the influence of the pipe length.

Observation of second sound in graphite over 200\u2009K

Second sound refers to the phenomenon of heat propagation as temperature waves in the phonon hydrodynamic transport regime. We directly observe second sound in graphite at temperatures of over 200 K using a sub-picosecond transient grating technique. The experimentally determined dispersion relation of the thermal-wave velocity increases with decreasing grating period, consistent with first-principles-based solution of the Peierls-Boltzmann transport equation. Through simulation, we reveal this increase as a result of thermal zero sound—the thermal waves due to ballistic phonons. Our experimental findings are well explained with the interplay among three groups of phonons: ballistic, diffusive, and hydrodynamic phonons. Our ab initio calculations further predict a large isotope effect on the properties of thermal waves and the existence of second sound at room temperature in isotopically pure graphite.

Перенос и аккумуляция газов, растворенных в воде, в неизотермическом массиве пористой среды с учетом зон замерзания

A one-dimensional problem of gas transport through a bubbly medium under the influence of a temperature wave is investigated taking into account freezing of the near-surface layer. Such freezing means the presence of a phase transition under the action of a temperature wave on the massif of the porous medium when the temperature goes below the freezing point of water. In this case, the Stefan problem is to be solved in order to obtain a nonstationary temperature distribution. With the knowledge of the temperature distribution in the massif at each moment of time, it is possible to take into consideration the influence of the temperature wave on the gas transport process. This process is described within the framework of the bubbly medium approximation. The calculation of the solubility of gas in water is based on the scaled particle theory. It is shown that a temperature wave causes the rise of an average flow of gases generated in the porous massif toward the surface, which leads to the effect of gas accumulation in the near-surface layer. The distribution of the gas concentration in the near-surface layer is obtained and the depth of this layer is estimated. In addition, the influence of the parameters of the problem on the accumulation effect is examined. The gas accumulation rate is found to be constant if the surface of the massif is at a temperature below the freezing point all year round and to decrease with an increase in the average surface temperature. At the same time, the accumulation rate increases with the intensification of gas generation in the porous massif.

Lipid-Based Intelligent Vehicle Capabilitized with Physical and Physiological Activation.

Intelligent drug delivery system based on "stimulus-response" mode emerging a promising perspective in next generation lipid-based nanoparticle. Here, we classify signal sources into physical and physiological stimulation according to their origin. The physical signals include temperature, ultrasound, and electromagnetic wave, while physiological signals involve pH, redox condition, and associated proteins. We first summarize external physical response from three main points about efficiency, particle state, and on-demand release. Afterwards, we describe how to design drug delivery using the physiological environment in vivo and present different current application methods. Lastly, we draw a vision of possible future development.

Calculation of temperature waves in kurums

The article indicates the relevance of the study of heat transfer processes in kurums. Boundary value problems of vertical temperature change in kurums and in the underlying rock base are solved, when the temperature on the surface of kurums changes according to a given periodic law, which simulates daily and seasonal temperature fluctuations. The cases when the rock base is a heat-conducting medium and permafrost are considered. Some regularities of temperature propagation along the depth are revealed.

DEVELOPMENT OF REQUIREMENTS AND SIMULATION OF THE PROCESS OF IGNITION OF EXPLOSION-HAZARDOUS MIXTURE BY A LOW VOLTAGE MEASURING CIRCUIT

The current lack of literature on the safe use of low-voltage measuring circuits in coal mines leads to the fact that they are trying to make unreasonable demands or simply prohibit their use under any far-fetched pretext. At the same time, measuring low-voltage circuits are an important integral component of diagnostics and information content of mining equipment control systems. This is due to the fact that the theory and models of the ignition of a methane-air mine atmosphere (MMA) solve problems in a narrow setting and cannot be used in the general mine case. The article identifies the conditions and parameters for the ignition of the MMA from the low-voltage measuring circuit (NVC),developed criteria for the ignition of the form the NVC, the existing model of the possible ignition process of the MMA from the NVTs is finalized. Currently, there are two theories of ignition of the HCV: thermal and ionic. From the author's point of view, the thermal model of VSH ignition from the electric discharge of the NSC is based on the analysis of the propagation of the temperature wave from some heat source in an inert environment. The thermal ignition model of VHS does not take into account many details of the physics of the combustion mechanism, such as the chain nature of individual acts of chemical interaction, the activation energy of molecules in the formation of active centers, and it is based on postulating some electric discharge. An assessment of the intrinsic safety and the possibility of self-expansion of the NVC flame core has been carried out. The approbation of research at three foreign conferences and the interest of foreign colleagues in them are shown. The article contains links to the state budget topics of the National Academy of Sciences of Ukraine and the numbers of state registration of Ukraine.

Propagation characteristics of the overpressure waves and flame fronts of methane explosions in complex pipeline networks

The propagation characteristics of the overpressure waves and flame fronts of methane explosions in complex pipe networks under realistic conditions were studied. A custom-designed experimental platform was used, the propagation characteristics of overpressure wave and flame wave in complex pipe network were characterized by overpressure attenuation coefficient and flame mutation coefficient. The results showed that the overpressure wave propagation characteristics in complex pipe networks were more complicated and disordered than those in straight or simple branched pipes. The overpressure wave attenuation and superposition occurred many times in the propagation process, the explosion shock wave attenuation in the beveled branch pipe was faster. When the flame wave passed through all the branch tubes, the flame wave velocity increased significantly. When the flame wave passed through the same tube at different times, the flame wave mutation coefficient was different, the change of flame wave temperature had a certain lag compared with the change of flame velocity, resulting in the peak of flame wave temperature and flame wave velocity appearing in different branch tubes. The experimentally obtained data were fit to functional relationships using nonlinear multiple regression analysis, and good agreement between the functional relationships and the data was obtained.

Influence of High Temperatures and Heat Wave on Thermal Biology, Locomotor Performance, and Antioxidant System of High-Altitude Frog Nanorana pleskei Endemic to Qinghai-Tibet Plateau

Investigating how highland amphibians respond to changes in ambient temperature may be of great significance for their fate prediction and effective conservation in the background of global warming. Here, using field individuals as the control group, we investigated the influence of high temperatures (20.5 and 25.5°C) and heat wave (15–26.6°C) on the thermal preference, critical thermal limits, locomotor performance, oxidative stress, and antioxidant enzyme activities in high-altitude frog Nanorana pleskei (3,490 m) endemic to the Qinghai-Tibet Plateau (QTP). After 2 weeks of acclimation to high temperatures and heat wave, the thermal preference (Tpref), critical thermal maximum (CTmax), and range of tolerable temperature significantly increased, while the critical thermal minimum (CTmin) was significantly decreased. The total time of jump to exhaustion significantly decreased, and burst swimming speed significantly increased in frogs acclimated in the high temperature and heat wave groups compared with the field group. In the high temperature group, the level of H2O2 and lipid peroxide (malondialdehyde, MDA), as well as the activities of glutathione peroxidase (GPX), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) significantly increased in the liver or muscle. However, in the heat wave group, the MDA content significantly decreased in the liver, and antioxidants activities decreased in the liver and muscle except for CAT activities that were significantly increased in the liver. These results indicated that N. pleskei could respond to the oxidative stress caused by high temperatures by enhancing the activity of antioxidant enzymes. The heat wave did not appear to cause oxidative damage in N. pleskei, which may be attributed to the fact that they have successfully adapted to the dramatic temperature fluctuations on the QTP.

Polarization of temperature waves in a dual heat flux vector space

A new concept of a “dual” heat flux vector is advanced to phenomenologically explain the polarization of conventional temperature waves, which are known to be transverse. The paper demonstrates a novel possibility for inward spiralling in spatial elliptic polarization of these waves, in the dual heat flux vector space and for a projection for this spiralling into the realistic space of scalar temperature waves. A proposition for a related experimental verification is also reported.

Thermal dynamics and electronic temperature waves in layered correlated materials

Understanding the mechanism of heat transfer in nanoscale devices remains one of the greatest intellectual challenges in the field of thermal dynamics, by far the most relevant under an applicative standpoint. When thermal dynamics is confined to the nanoscale, the characteristic timescales become ultrafast, engendering the failure of the common description of energy propagation and paving the way to unconventional phenomena such as wave-like temperature propagation. Here, we explore layered strongly correlated materials as a platform to identify and control unconventional electronic heat transfer phenomena. We demonstrate that these systems can be tailored to sustain a wide spectrum of electronic heat transport regimes, ranging from ballistic, to hydrodynamic all the way to diffusive. Within the hydrodynamic regime, wave-like temperature oscillations are predicted up to room temperature. The interaction strength can be exploited as a knob to control the dynamics of temperature waves as well as the onset of different thermal transport regimes.

High‐Cadence Lidar Observations of Middle Atmospheric Temperature and Gravity Waves at the Southern Andes Hot Spot

AbstractThe Southern Andes are the strongest hot spot for atmospheric gravity waves (GWs) in the stratosphere. Yet, until recently, no high‐cadence measurements of GWs within the middle atmosphere were available in this region. Therefore, the COmpact Rayleigh Autonomous Lidar (CORAL) was deployed to the Estación Astrónomica Río Grande (53.7°S, 67.7°W), Argentina, to obtain temperature profiles up to 100 km altitude. CORAL operates autonomously and obtained measurements during roughly two thirds of all nights between November 2017 and October 2020. The excellent measurement coverage allows for the quantification of GW properties at the hot spot with great detail. The hot spot nature of this region is reflected in nightly mean temperature profiles showing deviations from the monthly mean in the order of 25–55 K in each winter month. This is connected to winter mean growth rates of GW potential energy (Ep), which are to our knowledge the largest ever reported in the stratosphere. The monthly mean Ep profiles show a mesospheric limit of ∼100 Jkg−1, indicating a saturated GW spectrum at altitudes above 60 km. The winter mean power spectral density also reaches the saturation limit here. Moreover, we investigated the distribution of vertical wavelengths using our novel diagnostic technique WAVELET‐SCAN. It reveals waves with vertical wavelengths that are mostly between 10 and 16 km but also can exceed 25 km in rare occasions.

Impact of light-colored paint materials on discomfort in a building for hot-dry climate

India is a tropical country with diverse climates, and thermal adaption plays a significant role in sustaining thermal comfort in non-conditioned buildings. Indoor air temperature is taken as the main parameter for thermal comfort in buildings, which is very high in western India and creates uncomfortable for occupant. Thermal comfort is a primary need inside the buildings from a human health perspective. Roof structure and the color of the exterior surface affect the thermal comfort of the buildings in a hot-dry climate. Roof contributes maximum heat gain towards the outdoor temperature wave amplitude and time lag in non-conditioned buildings during summer. Three commercially available reflective paints or coatings were selected and used in the simulation to assess the performance of a non-conditioned building. In this paper, we present the evaluation ofthe discomfort index (DI) and Tropical Summer Index (TSI) for the summer season (April and May).The comfort hours achieved using cool roof coatings were 12–17 hours more than the base case or conventional roof used in a hot-dry climate. The tropical summer index (TSI) was found adequate within its comfort range (27.5 °C) for roofs with surface coatings than a base case roof slab.

Ultrasound-Mediated Cancer Therapeutics Delivery using Micelles and Liposomes: A Review.

Existing cancer treatment methods have many undesirable side effects that greatly reduce the quality of life of cancer patients. This review will focus on the use of ultrasound-responsive liposomes and polymeric micelles in cancer therapy. This review presents a survey of the literature regarding ultrasound-triggered micelles and liposomes using articles recently published in various journals, as well as some new patents in this field. Nanoparticles have proven promising as cancer theranostic tools. Nanoparticles are selective in nature, have reduced toxicity, and controllable drug release patterns making them ideal carriers for anticancer drugs. Numerous nanocarriers have been designed to combat malignancies, including liposomes, micelles, dendrimers, solid nanoparticles, quantum dots, gold nanoparticles, and, more recently, metal-organic frameworks. The temporal and spatial release of therapeutic agents from these nanostructures can be controlled using internal and external triggers, including pH, enzymes, redox, temperature, magnetic and electromagnetic waves, and ultrasound. Ultrasound is an attractive modality because it is non-invasive, can be focused on the diseased site, and has a synergistic effect with anticancer drugs. The functionalization of micellar and liposomal surfaces with targeting moieties and the use of ultrasound as a triggering mechanism can help improve the selectivity and enable the spatiotemporal control of drug release from nanocarriers.

Evidence for melt leakage from the Hawaiian plume above the mantle transition zone

Dehydration reactions at the top of the mantle transition zone (MTZ) can stabilize partial melt in a seismic low-velocity layer (LVL), but the seismic effects of temperature, melt and volatile content are difficult to distinguish. We invert P-to-S receiver function phases converted at the top and bottom of a LVL above the MTZ beneath Hawaii. To separate the thermal and melting related seismic anomalies, we carry out over 10 million rock physics inversions. These inversions account for variations arising from the Clapeyron slope of phase transition, bulk solid composition, dihedral angle, and mantle potential temperature. We use two independent seismic constraints to evaluate the temperature and shear wave speed within the LVL. The thermal anomalies reveal the presence of a hot and seismically slow plume stem surrounded by a “halo” of cold and fast mantle material. In contrast to this temperature distribution, the plume stem contains less than 0.5vol% melt, while the surrounding LVL—within the coverage area—contains up to 1.7vol% melt, indicating possible lateral transport of the melt. When compared to the melting temperatures of mantle rocks, the temperature within the LVL, calculated from seismic observations of MTZ thickness, suggests that the observed small degrees of melting are sustained by the presence of volatiles such as CO2 and H2O. We estimate the Hawaiian plume loses up to 1.9Mt/yr H2O and 10.7Mt/yr CO2 to the LVL, providing a crucial missing flux for global volatile cycles.

Coupled porosity-fluid concentration flux-temperature waves in isotropic porous media

In this article, we study a problem on propagation of coupled porosity, fluid concentration flux, and temperature waves. We use a model formulated in previous papers for porous media saturated by a fluid flow, in the framework of non-equilibrium thermodynamics. We derive three modes of propagation in the one-dimensional and perfect isotropic case, and then we test the validity of the model. The waves propagation velocities are represented in diagrams as functions of the wave number. The derived results have applications in technological sectors such as seismology, medical sciences, geology and nanotechnology. For more information see https://ejde.math.txstate.edu/Volumes/2021/88/abstr.html

Health Risks to the Russian Population from Temperature Extremes at the Beginning of the XXI Century

Climate change and climate-sensitive disasters caused by climatic hazards have a significant and increasing direct and indirect impact on human health. Due to its vast area, complex geographical environment and various climatic conditions, Russia is one of the countries that suffers significantly from frequent climate hazards. This paper provides information about temperature extremes in Russia in the beginning of the 21st century, and their impact on human health. A literature search was conducted using the electronic databases Web of Science, Science Direct, Scopus, and e-Library, focusing on peer-reviewed journal articles published in English and in Russian from 2000 to 2021. The results are summarized in 16 studies, which are divided into location-based groups, including Moscow, Saint Petersburg and other large cities located in various climatic zones: in the Arctic, in Siberia and in the southern regions, in ultra-continental and monsoon climate. Heat waves in cities with a temperate continental climate lead to a significant increase in all-cause mortality than cold waves, compared with cities in other climatic zones. At the same time, in northern cities, in contrast to the southern regions and central Siberia, the influence of cold waves is more pronounced on mortality than heat waves. To adequately protect the population from the effects of temperature waves and to carry out preventive measures, it is necessary to know specific threshold values of air temperature in each city.

Local Nonequilibrium Electron Transport in Metals after Femtosecond Laser Pulses: A Multi-Temperature Hyperbolic Model

ABSTRACT The trend toward miniaturization of electronic devices has increased the interest in nano scale heat transport, particularly, in laser-excited solids where electron–electron thermalization and electron-phonon coupling play a key role. Using a multi-temperature hyperbolic model, which takes into account the coupling between initially non-thermalized electrons and different phonon branches, we obtain a hierarchy of heat conduction equations for the electron temperature, which arises due to multi-length and time scales nature of coupling between different excitations. The hierarchy predicts that the ultrashort laser pulse induces a multi-front temperature wave propagating into the bulk of the material, which includes various heat transport regimes, ranging from the ballistic motion of the initially non-thermalized electrons propagating on the shortest time scale without interaction with the lattice as a temperature discontinuity, to the continuous wave-like temperature fronts arising on the intermediate time scale due to coupling between various excitations, and eventually to the classical Fourier transport on the longest time scale. The model is expected to be useful for modeling heat wave propagation phenomena in heterostructures and metamaterials.

Impact of SST and Surface Waves on Hurricane Florence (2018): A Coupled Modeling Investigation

AbstractHurricane Florence (2018) devastated the coastal communities of the Carolinas through heavy rainfall that resulted in massive flooding. Florence was characterized by an abrupt reduction in intensity (Saffir–Simpson category 4 to category 1) just prior to landfall and synoptic-scale interactions that stalled the storm over the Carolinas for several days. We conducted a series of numerical modeling experiments in coupled and uncoupled configurations to examine the impact of sea surface temperature (SST) and ocean waves on storm characteristics. In addition to experiments using a fully coupled atmosphere–ocean–wave model, we introduced the capability of the atmospheric model to modulate wind stress and surface fluxes by ocean waves through data from an uncoupled wave model. We examined these experiments by comparing track, intensity, strength, SST, storm structure, wave height, surface roughness, heat fluxes, and precipitation in order to determine the impacts of resolving ocean conditions with varying degrees of coupling. We found differences in the storm’s intensity and strength, with the best correlation coefficient of intensity (r = 0.89) and strength (r = 0.95) coming from the fully coupled simulations. Further analysis into surface roughness parameterizations added to the atmospheric model revealed differences in the spatial distribution and magnitude of the largest roughness lengths. Adding ocean and wave features to the model further modified the fluxes due to more realistic cooling beneath the storm, which in turn modified the precipitation field. Our experiments highlight significant differences in how air–sea processes impact hurricane modeling. The storm characteristics of track, intensity, strength, and precipitation at landfall are crucial to predictability and forecasting of future landfalling hurricanes.