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This paper presents the effect of sintering temperature on the structural, electrical, and dielectric properties of polycrystalline Dy0.4Sm0.6FeO3 orthoferrite prepared via the sol–gel method, and sintered at 800°C, 1000°C, and 1200°C. Rietveld refinement of XRD confirmed that the samples sintered at 800°C and 1000°C exhibit a single phase, whereas the sample sintered at 1200°C shows a small amount of Dy3Fe5O12 impurity. Room temperature Raman spectra confirmed the active vibrational modes of Dy0.4Sm0.6FeO3 and the impurity phase. FESEM images illustrate an increase in grain size with increasing sintering temperature and sintering at 1000°C shows less porosity. P-E loop data reveal the deficient ferroelectric and leaky nature of the samples. The dielectric constant and dielectric loss increase with increasing sintering temperature, and the dielectric relaxation phenomena is shifted to the high temperature side with increasing sintering temperature. The dielectric loss and activation energy are lower for the sample sintered at 1000°C compared to the other samples. The findings of this paper establish that the sample sintered at 1000°C, Dy0.4Sm0.6FeO3 , optimizes the structural, electrical, and dielectric properties. Dy0.4Sm0.6FeO3 sample prepared through the sol–gel method and sintered at 800°C, 1000°C, and 1200°C, investigated for their structural, electrical, and dielectric properties. DSFO samples sintered at 800°C and 1000°C exhibit a single phase without any impurity. [ABSTRACT FROM AUTHOR]

This article investigates the behavior of thermoelastic damping in a micro/nano beam subjected to an external magnetic field and an elastic matrix via small-scale theory. The material properties of the beam, such as Young's modulus, thermal conductivity, specific heat capacity, and coefficient of thermal expansion, are considered to analyze the physical aspects of thermoelastic damping. Further, the critical magnetic field strength of the nanobeam, which affects magnetic properties, is studied in relation to temperature, magnetic material properties, modenumber, and boundary conditions, leading to important findings for magnetomechanical systems and materials design. [ABSTRACT FROM AUTHOR]

This primary goal of this analysis is to investigate how several slips affect the flow, heat, and mass performance of Darcy–Forchheimer unstable behavior beyond a stretching sheet using a numerical analysis of the Soret effect. The novel constitutive model Cattaneo–Christov is illustrated to analyze the features of thermal relaxation time. The Cattaneo–Christov method is used to predict heat and mass transport. A surface that slanders and has varying thicknesses propels the flow. Through the use of local similarity transformations, the governing nonlinear partial differential equations reduce to the coupled ordinary differential equations and include the momentum, energy, and concentration equations. The altered ODEs are calculated numerically using the Runge–Kutta Fehlberg scheme and an efficient shooting procedure. The physical properties of the temperature, concentration, and fluid velocity profiles are shown visually and shed light on the change of several governing parameters. For example, in comparison to the classical Fourier's heat model, our result suggests that the Cattaneo–Christov heat flux constitution has lower temperature and thermal boundary layer thickness. In the meantime, a high wall thickness parameter greatly upgrades the rate of heat transfer, and thermal relaxation has the opposite effect. Discussion is held regarding the effects of various miscellaneous variables on temperature, concentration, and velocity. [ABSTRACT FROM AUTHOR]

Porous materials have been extensively used in electronic communications, aerospace, bio-medicine and petrochemical, etc. due to their attractive attributes such as low relative density, thermal and acoustical insulation and good permeability. Ultrashort laser pulses have a series of unique advantages including high energy density, ultrashort interaction time and high accuracy, which are widely used in the fields of precision machining and microelectronic manufacture. For porous materials heated by an ultrashort laser pulse, revealing the interplay between deformation field and temperature field is crucial to guide their engineering application and optimization design. The present work devotes to investigating the transient response of a porous half-space heated by a non-Gaussian laser beam on its boundary surface based on the newly established linear thermoelastic theory with strain and thermal relaxations. The coupled governing equations are formulated and solved through the Laplace transform and its numerical inversion. The distributions of the non-dimensional temperature, displacement, stress as well as volume fraction field are obtained and illustrated graphically. In calculation, the effects of the thermal relaxation factor, the strain relaxation factor on the temperature field, volume fraction field, displacement field as well as stress field are examined and discussed in detail. [ABSTRACT FROM AUTHOR]

The photoexcitation dynamics of N3−‐bound ferric myoglobin (MbN3) were investigated after exciting MbN3 in D2O at 283 K with a 575 nm pulse by probing the anti‐symmetric stretching mode of the azide. Global fitting of the overall time‐resolved spectra revealed that thermal relaxation of two stretching bands proceeded with a time constant of 6 ps, and that a new absorption band formed and decayed with time constants of 0.6 and 23 ps, respectively. The new absorption near 2040 cm−1 was attributed to the high‐spin species 2.4 kJ/mol above the low‐spin species, as the excited low‐spin relaxes thermally via the high‐spin species. However, this absorption could also arise from deligated N3̄ remaining within the protein. The decay of this absorption can be interpreted as either spin transition of the high‐spin species into the low‐spin species or geminate recombination of the dissociated N3̄. The implications of both interpretations are discussed. [ABSTRACT FROM AUTHOR]

Significance: In the photoacoustic (PA) technique, the laser irradiation in the time domain (i.e., laser pulse duration) governs the characteristics of PA imaging--it plays a crucial role in the optical-acoustic interaction, the generation of PA signals, and the PA imaging performance. Aim: We aim to provide a comprehensive analysis of the impact of laser pulse duration on various aspects of PA imaging, encompassing the signal-to-noise ratio, the spatial resolution of PA imaging, the acoustic frequency spectrum of the acoustic wave, the initiation of specific physical phenomena, and the photothermal-PA (PT-PA) interaction/conversion. Approach: By surveying and reviewing the state-of-the-art investigations, we discuss the effects of laser pulse duration on the generation of PA signals in the context of biomedical PA imaging with respect to the aforementioned aspects. Results: First, we discuss the impact of laser pulse duration on the PA signal amplitude and its correlation with the lateral resolution of PA imaging. Subsequently, the relationship between the axial resolution of PA imaging and the laser pulse duration is analyzed with consideration of the acoustic frequency spectrum. Furthermore, we examine the manipulation of the pulse duration to trigger physical phenomena and its relevant applications. In addition, we elaborate on the tuning of the pulse duration to manipulate the conversion process and ratio from the PT to PA effect. Conclusions: We contribute to the understanding of the physical mechanisms governing pulse-width-dependent PA techniques. By gaining insight into the mechanism behind the influence of the laser pulse, we can trigger the pulse-with-dependent physical phenomena for specific PA applications, enhance PA imaging performance in biomedical imaging scenarios, and modulate PT-PA conversion by tuning the pulse duration precisely. [ABSTRACT FROM AUTHOR]

The phosphate‐coordination triple helicates A2L3 (A=anion) with azobenzene‐spaced bis‐bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise "disassembly‐isomerization‐reassembly" process. This is enabled by the structural self‐adaptability of the "aniono" assembly arising from multiple relatively weak and flexible hydrogen bonds between the phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of the isomerized azobenzene unit is significantly decreased (up to 20‐fold) for the triple helicates compared to the free ligands. Moreover, the binding of chiral guest cations inside the cavity of the Z‐isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light‐activated chiroptical materials. [ABSTRACT FROM AUTHOR]

A theoretical exploration is presented for the obtaining a transfer matrix and using this technique with stiffness matrix for obtaining a solution for dispersion curves in heat conducting n–layered isotropic in the context of generalized theory of thermoelasticity This paper discusses transfer matrix technique and obtained stiffness matrix for heat conducting isotropic layered in generalized thermoelasticity with thermal relaxation. Some special cases have also been deduced and discussed from the obtained result. [ABSTRACT FROM AUTHOR]

The theory of wave propagation in non-isothermal porous rocks has been introduced in geophysics in recent years by combining the single-phase-lag (SPL) Lord-Shulman (LS) model of heat conduction with Biot's poroelasticity theory. However, the theory of SPL thermoporoelasticity is inadequate in describing the lagging behavior of thermal relaxation for wave dissipation due to fluid and heat flow effects. We address this problem by incorporating a dual-phase-lags (DPL) model of heat conduction into thermoporoelasticity, utilizing analytical solutions and numerical simulations. The DPL model involves two lagging times: the (macroscopic) heat-flux lagging time τq from the LS model and an additionally introduced lagging time τT of temperature gradient that characterizes the fluid phase. A plane-wave analysis predicts four propagation waves, namely, fast P, slow P, thermal (T), and shear (S). We calculate wavefield snapshots by using a finite-difference solver for the DPL thermoelastic equations and provide further insight into the physics of two lagging times for porous rocks. The simulations show that the DPL model induces higher thermal attenuation and larger velocity dispersion compared to the SPL model, especially at high frequencies. The influence of fluids is crucial for wave propagation within thermoporoelastic media. [ABSTRACT FROM AUTHOR]

TA15 (Ti-6Al-2Zr-1Mo-1 V) is a near-α titanium alloy widely used in aerospace applications due to its high specific strength and corrosion resistance. However, like other titanium alloys, TA15 faces significant manufacturing challenges. Selective Laser Melting (SLM), a high-precision additive manufacturing technique, enables the efficient production of complex components but also introduces issues such as tensile residual stress. This study investigates the effects of dual shot peening on the residual stress and microstructure of SLM-fabricated TA15 alloy, and analyzes the thermal relaxation behavior post-peening. The results indicate that shot peening induces a compressive residual stress (CRS) field near the material surface and significantly refines the grains in the deformed layer, resulting in the formation of nanocrystals. The introduction of low-intensity ceramic shots in dual shot peening effectively improves the surface quality and enhances CRS, although it has minimal impact on grain size and microstrain. Using the ZWA model, the activation energy for thermal relaxation of residual stress and microstrain was determined, revealing that their relaxation behavior is controlled by thermally activated diffusion of point defects, especially vacancies. Post-thermal exposure, extensive dislocation annihilation and grain growth were observed in the deformed layer, with recrystallized grain size increasing with annealing temperature and depth. • Shot peening refines grains, inducing dense dislocations, stacking faults, and nanocrystalline formation. • The trend of CRS generated by ceramic shots varies with depth, differing from that of cast steel shots. • The introduction of low-intensity ceramic shots in dual shot peening effectively improves surface quality and enhances CRS. • In SLM-TA15 alloy, residual stress relaxation occurs mostly within 60 min via thermally activated diffusion of point defects. • Microstrain relaxation, driven by the diffusion of point defects, is more pronounced than residual stress relaxation. [ABSTRACT FROM AUTHOR]

Establishing the relationship between molecular structures and mechanical properties is of great significance for the structural design of vulcanised styrene-butadiene rubber (SBR). The molecular dynamics method was used to study the mechanical properties of cross-linked SBR with controlled network topology, and the corresponding molecular mechanism was analysed by the energy contribution during the stretching process. The results showed that the tensile stress of the end-linked network sample could be up to 20 times higher than that of the sample with dangling chains at an engineering strain of 1.4. Moreover, under the same fixed cross-linking degree, the tensile stress of the long-chain network sample was significantly higher than that of the short-chain network sample. This is because the molecular chains located in the main chain network will be highly oriented during the stretching process, while the proportion of highly oriented molecular chains is high in samples with end-linked networks or a large proportion of long chains. In addition, due to the limited relaxation of structural units, the end-linked network structure has good thermal stability. [ABSTRACT FROM AUTHOR]

With the extensive applications of the micro/nano-electro-mechanical systems, a great deal of attention has been paid to explore the influences of the arising size-dependent effect and surface effect on their performance. Along with these effects, the nonlocal elasticity, strain gradient theory, and surface elasticity theory were successively proposed. Moreover, it is inevitable for MEMS/NEMS to work in a variable temperature environment, correspondingly, the thermal-induced stress or deformation becomes another issue that needs serious concern. Thermoelastic damping (TED), as a main energy dissipation source, is a major challenge in designing higher-quality factor resonators. However, considering the thermoelastic coupling effect, the aforementioned theories are not capable enough to depict the thermoelastic performance of micro/nano-resonators. To amend this deficiency, based on nonlocal strain gradient theory, a new model for assessing the TED of nanobeam resonators by incorporating the thermal relaxation effect and the surface effect is developed. The corresponding governing equations for the Euler–Bernoulli microbeam resonator model are formulated, and then, solved by means of a complex frequency method. The influences of the nonlocal parameter, strain gradient coefficients, aspect ratio, surface stress and surface elasticity on the TED are examined and discussed in detail. [ABSTRACT FROM AUTHOR]

An interesting feature that appears in the thermoelastic interaction in an orthotropic material containing cylindrical cavities is addressed in this study. For this purpose, the Finite Element Method is applied to analyze a generalized thermoelasticity theory with a relaxation time. For the development of the model, a thermal conductivity that is dependent on the temperature of the orthotropic medium was considered. The boundary condition for the internal surface of a cylindrical hollow is defined by the thermal shocks and the traction on the free surface. The nonlinear formulations of thermoelastic based on thermal relaxation time in orthotropic mediums are abbreviated using the Finite Element Method. The nonlinear equations without Kirchhoff's transformations are presented. The results are graphically represented to demonstrate how changing thermal conductivity affects all physical values. [ABSTRACT FROM AUTHOR]

In this work, the finite element technique is employed to evaluate the effects of thermal relaxation durations on temperature, displacements, and stresses in a two-dimensional, polymeric, orthotropic, elastic medium. The problem is considered in a homogeneous, polymeric, orthotropic medium in the context of the Green and Lindsay model with two thermal relaxation times. The bounding surface of the half-space was subjected to a heat flux with an exponentially decaying pulse. Finite element techniques were used to solve the governing formulations, with eight-node isoparametric rectangular elements with three degrees of freedom (DOF) per node. The developed method was calculated using numerical results applied to the polymeric, orthotropic medium. The findings were implemented and visually shown. Finally, the results were displayed to demonstrate the differences between classical dynamic coupling (CT), the Lord–Shulman (LS) and the Green and Lindsay (GL) models. [ABSTRACT FROM AUTHOR]

Understanding the thermal relaxation dynamics of photoswitches is of crucial importance when considering application scenarios. Strategies for regulating the thermal relaxation rates of photoswitches have been mostly limited to modifying the chemical structures. Herein we demonstrate a complementary method of manipulating the thermal relaxation rate of indigo‐based photoswitches that does not require chemical modification. We used indigo‐based photoswitches in aprotic solvents as a model system to demonstrate this strategy. Our method creates a deactivated pathway that extends the thermal relaxation half‐life by selectively stabilizing the parent structure of the metastable Z‐isomer via non‐covalent interaction. In addition, by establishing a quantitative kinetic model, we showed that controlling the strength of such selective stabilization enables fine‐tuning of the thermal relaxation rates to precisely access to targeted values. [ABSTRACT FROM AUTHOR]

A model of thermal relaxation in the flow of a hot vapor–gas mixture and cold water drops is presented. The cooling of vapor and gas during heating and evaporation of droplets was numerically simulated. Approximation expressions are obtained for the cooling time of vapor and gas in a given temperature range depending on the initial droplet radius, the weight fraction of droplets, and the initial composition of the vapor–gas mixture. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile (PAN) fibers which formed high-elastic deformation during the spinning process,have thermal relaxation behavior in the heat conditions, such as thermal shrinkage with disorientation. The thermal relaxation behavior of PAN fibers was investigated by thermomechanical analyzer (TMA), dynamic mechanical analyzer (DMA), wide-angle X-ray diffraction(WAXD).And PAN fibers aggregation structure changed by tension and temperature were analyzed. The results show that the forced high-elastic deformation in PAN fibers accounts for more than 10% which leads to disorientation at high temperature. With structure rearrangement under controlled conditions, the high-elastic deformation in PAN fibers can be transferred to plastic deformation by appropriate tension and temperature imposed to fibers without orientation structure loss. By imposing tension and temperature, further improvement is achieved in the regularity of aggregation structure and the orientation of the molecular chain, crystalline structure, and dimensional stability increase by more than 50%. The crystallites of PAN based carbon fibers treated by this method are more regularly arranged along the molecular chain, and the performance has been improved effectively.

We report anomalous heating in a colloidal system, an experimental observation of the inverse Mpemba effect, where for two initial temperatures lower than the temperature of the thermal bath, the colder of the two systems heats up faster when coupled to the same thermal bath. For an overdamped, Brownian colloidal particle moving in a tilted double-well potential, we find a nonmonotonic dependence of the heating times on the initial temperature of the system. Entropic effects make the inverse Mpemba effect generically weaker--harder to observe--than the usual Mpemba effect (anomalous cooling). We also observe a strong version of anomalous heating, where a cold system heats up exponentially faster than systems prepared under slightly different conditions. [ABSTRACT FROM AUTHOR]

In this study we investigated double diffusional Catteneo-Christov heat flux model to understand mass and heat transfer of liquid mix Casson nanofluid discharged over a curved shrinking/stretching channel. To govern such flow, a evenly charged force is applied in the vertical direction to the flow stream. Intensities of thermal and concentration fluxes are monitored by involving relaxations in Fourier's law. In the midst of mathematical modelling of our envisaged flow problem, we established a structure of complex partial differential equations embedded with sundry parameters. Using variable conversion procedure in vogue, these equations are transformed into simpler version of order differential equations. Numerical simulation is completed through MATLAB solver bvp4c by setting the default tolerance. The solver is applied recursively to achieve the desired accuracy in picking the best blend of the assorted parameters we entrenched in the system. We noticed thermal and concentration relaxations caused the temperature and concentration profiles to reduce, but thermophoresis enhances both fluxes. Casson and magnetic indicator parameters are responsible for slowing down the speed of the flow in case of stretching channels, moreover, adding amounts of these parameters produced less skin friction. Stretching/Shrinking and curvature of the bent channel played significant roles in behavioral modifications of various profiles and are therefore useful for future course of action.

The introduction of thermal relaxation makes non-Fourier heat transfer more effective than Pennes equation to reflect rapid bio-heat transferring during HIFU, however, the contribution of thermal relaxation in specific tissues needs to be further clarified. In this study, we first measured the thermal relaxation times of porcine muscle and porcine fat. Combining with experimental measurements, the effects of thermal relaxation on temperature elevation in the tissues were investigated by using Pennes equation, thermal wave model of bio-heat transfer (TWMBT) and dual phase-lag (DPL) bio-heat transfer. Results showed that: a) The thermal relaxation times of porcine muscle and porcine fat are experimentally determined as 5.71± 0.11 s and 5.02± 0.06 s, respectively. b) In the absence of cavitation, DPL bio-heat transfer is more accurate to predict the temperature elevation at the focus and 2 mm from the focus than Pennes equation and TWMBT. Particularly, comparing with the reported of bologna (16 s) used in most of the theoretical analysis, the utilization of the measured thermal relaxation time for a specific tissue in DPL bio-heat transfer is more effective in predicting the temperature elevation during HIFU. c) Acoustic cavitation and nonlinear propagation is easier to happen in fat, under which all bio-heat transfer models are failed to forecast the temperature elevation induced by HIFU. The results demonstrate that different tissues have different thermal relaxation, DPL bio-heat transfer with the measured thermal relaxation times of specific tissues can accurately predict the temperature elevation during HIFU without cavitation.

Nanocomposites are multiphase structures with at least one phase dimension of nanometric order size. Polymer-based materials mixed with low proportions of titanium dioxide nanoparticles (NPs-TiO2) are a versatile alternative in different industrial applications, considering the optimization of mechanical and thermal properties with respect to pure polymers and conventional materials. In this work, the synthesis and thermal characteristics measurement of a nanocomposite formed by anatase phase Nps-TiO2 of 5 nm particle size in a polyurethane matrix is reported. The polymeric matrix was obtained through the reaction between the self-condensation of castor oil and diphenylmethane diisocyanate (MDI), while sol-gel technique was used in the synthesis of NPs-TiO2, using titanium (IV)-bis(acetylacetonate) diisopropoxide as precursor. Specific heat (Cp) of the samples was measured by means of the thermal relaxation method and thermal diffusivity (α) was determined with the photoacoustic technique. Cp of the nanocomposite increased by 12.98 % due to addition of the NPs, while α decreased by 98.63 %, compared to corresponding values of the polyurethane matrix. With a concentration of 3 wt % of NPs-TiO2 in the matrix, these thermal parameters were found below average values of conventional plastics. [ABSTRACT FROM AUTHOR]

The Mpemba effect refers to systems whose thermal relaxation time is a non-monotonic function of the initial temperature. Thus, a system that is initially hot cools to a bath temperature more quickly than the same system, initially warm. In the special case where the system dynamics can be described by a double-well potential with metastable and stable states, dynamics occurs in two stages: a fast relaxation to local equilibrium followed by a slow equilibration of populations in each coarse-grained state. We have recently observed the Mpemba effect experimentally in such a setting, for a colloidal particle immersed in water. Here, we show that this metastable Mpemba effect arises from a non-monotonic temperature dependence of the maximum amount of work that can be extracted from the local-equilibrium state at the end of Stage 1.

For complex molecules, nuclear degrees of freedom can act as an environment for the electronic “system” variables, allowing the theory and concepts of open quantum systems to be applied. However, when molecular system-environment interactions are non-perturbative and non-Markovian, numerical simulations of the complete system-environment wave function become necessary. These many body dynamics can be very expensive to simulate, and extracting finite-temperature results—which require running and averaging over many such simulations—becomes especially challenging. Here, we present numerical simulations that exploit a recent theoretical result that allows dissipative environmental effects at finite temperature to be extracted efficiently from a single, zero-temperature wave function simulation. Using numerically exact time-dependent variational matrix product states, we verify that this approach can be applied to vibronic tunneling systems and provide insight into the practical problems lurking behind the elegance of the theory, such as the rapidly growing numerical demands that can appear for high temperatures over the length of computations.

In recent decades, the search for raw from renewable resources to produce polymers, elastomers, resins, foams, etc., has intensified; these materials would reduce the industrial use of petrochemical compounds. In this work, the oil extracted from the castor oil seed (Ricinus communis) was used because of ricinoleic acid content (92.3%), it is of easy production and non-edible vegetable origin. The polyurethane adhesive was synthesized through transesterification and polymerization reactions. Using the corresponding standards, this adhesive was applied to sheets of Guadua angustifolia Kunth for determining its mechanical characteristics, the compressive strength parallel to the fiber was 43±3 (MPa), and shear parallel to the fiber was 5.9±0.9 (MPa). Fourier transform infrared spectroscopy was used for determining the appropriate molar ratio and monitoring the reaction during the synthesis and final product structure was analyzed with X-ray diffraction. Through differential scanning calorimetry, the glass transition temperature of the product was estimated on -24.6 °C; the thermal relaxation technique was used to measure its specific heat, while its thermal diffusivity and thermal expansion coefficient were estimated with the photoacoustic technique. [ABSTRACT FROM AUTHOR]

Deep cold rolling (DCR) is a promising mechanical surface treatment which can be effectively used to improve the fatigue life of components by introducing deep and high beneficial compressive residual stresses on the surface and sub-surface layers. However, the application of conventional DCR on thin-walled geometries such as compressor blades can be very challenging as the applied load can damage the component. Double-sided deep rolling on thin-walled components has been proven to be a viable alternative solution as both sides of the component are treated simultaneously which thus decreases the risk of component distortion. In this study, a high-fidelity non-linear finite element model has been developed to simulate the double-sided DCR process on thin Ti-6Al-4V plate and to predict the residual stress profile introduced by the process and after thermal relaxation due to subsequent exposure to high temperature. The accuracy of the developed finite element model is validated by comparison with the experimental measurement available in the literature. Response surface method (RSM) has then been carried out on results obtained by the high-fidelity FE model to develop predictive analytical models to approximate residual stress profiles induced by the process. The developed analytical models can efficiently replace FE models to perform sensitivity analysis and design optimization of process parameters. Load distribution at high stress areas of a generic compressor blade is considered to formulate a design optimization problem of double-sided DCR process in order to achieve optimal residual stress distributions at room temperature and after thermal relaxation at elevated temperature of 450 °C. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have become one of the most promising candidates for a new class of smart structures which are widely used as sensors and actuators in control systems due to their superior electromechanical performance and high‐efficiency in electro‐mechanical energy conversion. In recent years, although there are many papers of theoretical modeling of generalized piezoelectric thermoelasticity that considered the piezoelectric‐thermoelastic coupling of piezoelectric structures serving in the extreme fast heating environment (e.g. ultra‐fast laser), the strain relaxation effect has not been considered yet. This work aims to investigate the generalized piezoelectricity problem with strain rate with the aid of extended thermodynamic principles, and corresponding generalized variational theorem is also strictly formulated to provide a complete rationale for numerical method by using semi‐inverse method. For numerical evaluation, transient thermo‐electromechanical responses of a one‐dimensional semi‐infinite piezoelectric medium with one end subjecting to a sudden thermal loading are considered and solved by applying Laplace transformation methods. Then the transient responses of temperature, displacement, strain, stress and electric potential are obtained and illustrated graphically, and the influences of strain relaxation parameters on them are also analyzed and discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We propose a laser optoacoustic method for the complex characterization of crude oil pollution of the water surface by the thickness of the layer, the speed of sound, the coefficient of optical absorption, and the temperature dependence of the Grüneisen parameter. Using a 532 nm pulsed laser and a 1–100 MHz ultra-wideband ultrasonic antenna, we have demonstrated the capability of accurate (>95%) optoacoustic thickness measurements in the 5 to 500-micron range, covering 88% of slicks observed during 2010 oil spill in the Gulf of Mexico. In the thermal relaxation regime of optoacoustic measurements, the value of optical absorption coefficient (30 mm−1) agreed with the data of independent spectrophotometric measurements, while the sound speed (1430 m/s) agreed with the tabular data. When operating in a nonlinear regime, the effect of local deformation of the surface of the oil film induced by heating laser radiation was revealed. The dose-time parameters of laser radiation ensuring the transition from the thermal relaxation regime of optoacoustic generation to nonlinear one were experimentally investigated. The developed OA method has potential for quantitative characterization of not only the volume, but also the degree and even the type of oil pollution of the water surface.

Specific heat (Cp) is a necessary thermal parameter for describing heat transport phenomena, related to adaptation to temperature changes. For this reason, it is important in the construction, glue, thermal insulator and electronic device industry. In this work, a thermal relaxation system was used to determine the Cp of Ti sheets, coated with S-TiO2 by Plasma Electrolytic Oxidation (EPO). Each sample was placed inside a vacuum chamber that reaches around 10-2 Torr and was heated by the incidence of a laser beam of 450 nm wavelength; an infrared (IR) thermometer was located at the bottom of the sample and the data obtained was sent to a computer using a programmable development card. The validation of the system was done by comparing the results with those reported by other authors for zinc, tungsten, titanium and steel. The Cp of the OEP coated Ti samples, which were obtained using an electrolyte with two concentrations of thiourea (CH4N2S) and with a voltage applied between the electrodes at 2 kHz with useful cycles of 10 %, 20 %, and 30 %, were measured and compared in order to study the influence of growth parameters on the thermal characteristics of the material. The results of the analysis of variance of the data led to find significant differences, with a confidence level of 95%, related to the variation in the concentration of CH4N2S. This is an indication of the potential use of thermal relaxation technique to determine particularities of this type of coatings. [ABSTRACT FROM AUTHOR]

Copyright of Scientia et Technica is the property of Scientia et Technica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we study the thermal relaxation features of compressive residual stresses generated during laser-shock wave processing in high-alloyed heat-resistant Iron GH2036 alloy. A finite element modeling of thermal relaxation of the generated compressive residual stresses was performed. The features of the thermal effects on the redistribution of the compressive residual stresses in the temperature range from 200 to 650°C are studied. Based on comparative analysis, the results of the finite element modeling correlated well with the experimental data known in the literature. [ABSTRACT FROM AUTHOR]

The current study presents a novel bioheat model for simulating heat transfer in skin tissue. The model, which is based on the Weinbaum–Jiji equation and incorporates the Cattaneo approach for flux in tissue, arteries, and veins, offers an improved representation of thermal dynamics in the skin compared to existing models. Numerical solutions of the model were obtained using the finite element method and were compared to experimental measurements. This study specifically highlights the incorporation of vascular inlet parameters and thermal relaxation effects in the thermal profile, which were not considered in previous models such as the Pennes model. This novel approach provides a more comprehensive understanding of heat transfer in skin tissue and has potential applications in fields such as thermal therapy and wound healing. [ABSTRACT FROM AUTHOR]

Comparative investigations are reported on poly(N-isopropylacrylamide) (PNIPA) gels of various carbon nanotube (CNT) and graphene oxide (GO) contents synthesized under identical conditions. The kind and concentration of the incorporated carbon nanoparticles (CNPs) influence the swelling and stress-strain behaviour of the composites. Practically independently of the filler content, incorporation of CNPs appreciably improves the fracture stress properties of the gels. The time constant and the swelling ratio of the shrinkage following an abrupt increase in temperature of the swelling medium from 20 to 50 °C can be adjusted by selecting both the type and the amount of nanoparticle loading. This offers a means of accurately controlling the deswelling kinetics of drug release with PNIPA systems, and could be employed in sensor applications where fast and excessive shrinkage are a significant drawback. Both CNTs and GO enhance the infrared sensitivity of the PNIPA gel, thus opening a route for the design of novel drug transport and actuator systems. It is proposed that the influence of the CNPs depends more on their surface reactivity during the gel synthesis rather than on their morphology. One of the important findings of this study is the existence of a thermally conducting network in the GO filled gels.

The α-relaxation temperatures (Tα), derived from the storage and loss moduli using dynamic mechanical analysis (DMA), were compared to methods for stickiness and glass transition determination for a selection of model whey protein concentrate (WPC) powders with varying protein contents. Glass transition temperatures (Tg) were determined using differential scanning calorimetry (DSC), and stickiness behavior was characterized using a fluidization technique. For the lower protein powders (WPC 20 and 35), the mechanical Tα determined from the storage modulus of the DMA (Tα onset) were in good agreement with the fluidization results, whereas for higher protein powders (WPC 50 and 65), the fluidization results compared better to the loss modulus results of the DMA (Tα peak). This study demonstrates that DMA has the potential to be a useful technique to complement stickiness characterization of dairy powders by providing an increased understanding of the mechanisms of stickiness.

The relevance of the researchinthe field of welded joints strength and failure is associated with the necessity of ensuring high operational reliability and safety running hazardous production facilities. Internal stresses and their relaxation as an independent cause of destruction are widely recognized nowadays. The final form of the maximum permissible state is cracks appearance, however the signs of the appeared maximum permissible state of the node or structure are not clearly defined. The aim of the researchis to establish the signs of weld zone prefracture and fracture under redistribution conditions of internal stresses during thermal relaxation. The subject of the research iswelded superheater units made of dissimilar steels. Research methods: physical modeling of operating conditions by thermal cycling of samples in the MIMP-10UE electric furnace, X-ray dosimetry of the samples, internal structural stresses evaluation on DRON- type X-ray diffractometers, morphological analysis using the «Resource S7» metallographic analyzer, including an inverted Olympus GF41 microscope with the SIAMS Photolab software, cracks morphology with a PEN SCKOPE microanalyzer, microhardness analysis using a PMT-3 microhardness tester. Results. According to the hypothesis of crack formation correlation with internal stress relaxation, crack appearance and growth and stress relaxation are interrelated processes. As a result of thermal fluctuation relaxation, the same qualitative regularities (which lead to destruction) for a single-phase and two-phase system are found. Natural aging processes occurring in the sample with an initial crack in the absence of external loads and deformations are controlled only by internal stresses that activate all mechanisms of destruction, including phase decay. Under the conditions of internal stresses thermofluctuation relaxation, the temperature limit of the stress state region is set, which determines the reliable operating temperature.