Thermal Relaxation Research Articles

Photoexcitation dynamics of azide ion bound ferric myoglobin probed by femtosecond infrared spectroscopy

AbstractThe 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.

Asymmetric thermal relaxation in driven systems: Rotations go opposite ways

Asymmetric thermal relaxation in driven systems: Rotations go opposite ways

Cattaneo-Christov heat flow model at mixed impulse stagnation point past a Riga plate: Levenberg-Marquardt backpropagation method

Applications of artificial intelligence (AI) via soft computing procedures have attracted the attention of researchers due to their effective modeling, simulation procedures, and detailed analysis. In this article, the designing of intelligence computing through a neural network that is backpropagated with the Levenberg-Marquardt method (NN-BLMM) to study the Cattaneo-Christov heat flow model at the mixed impulse stagnation point (CCHFM-MISP) past a Riga plate is investigated. The original model CCHFM-MISP in terms of PDEs is converted into non-linear ODEs through suitable similarity variables. A data set is generated for all scenarios of CCHFM-MISP through Lobatto IIIA numerical solver by varying Hartman number, velocity ratio parameter, inverse Darcy number, mixed impulse variable, non-dimensional constraint, Eckert number, heat generation variable, Prandtl number, thermal relaxation variable. To find the physical impacts of parameters of interest associated with the presented fluidic system CCHFM-MISP, the approximate solution of NN-BLMM is carried out by performing training (80 %), testing (10 %), and validation (10 %), and then the results are equated with the reference data to ensure the perfection of the proposed model. Through MSE, state transition, error histogram, and regression analysis, the outcomes of NN-BLMM are presented and analyzed. The graphical illustration and numerical outcomes confirm the authentication and effectiveness of the solver. Moreover, mean square errors for validation, training and testing data points along with performance measures lie around 10−10 and the solution plots generated through deterministic (Lobatto IIIA) approach and stochastic numerical solver are matching up to 10−6, which surely validate the solver NN-BLMM. The outcomes of M and B on velocity present the similar impacts. The velocity of material particles decreases under Da while, it increases through velocity ratio and magnetic parameters.

A comparative study on the rheological properties of upper convected Maxwell fluid along a permeable stretched sheet

The objective of this paper is to examine the flow of a non-Newtonian Maxwell fluid induced by a permeable stretching sheet in motion within a porous medium. The research incorporates the Cattaneo-Christov heat flux model to study the heat transfer process. The utilization of the Cattaneo-Christov heat flux approach becomes relevant in scenarios involving materials with high thermal conductivity or during short time intervals. Consequently, the current investigation holds significant importance. It is assumed that the viscosity of the Maxwell fluid changes exponentially as the temperature changes. The modeling of the physical phenomena being investigated takes into account the effects of a magnetic field, thermal radiation, velocity, and thermal slip conditions. In this study, the viscous dissipation phenomenon is taken into account because it can have notable impacts on the temperature and viscosity of the fluid, and is known to play a crucial role in fluid flow phenomena. The equations developed to model fluid flow are transformed into nonlinear ordinary differential equations through the use of appropriate similarity transformations. The focus of the research revolves around investigating the numerical solution of ordinary differential equations accompanied by boundary conditions using the shooting technique. The findings are then showcased via tables and graphs and scrutinized in order to arrive at conclusions. Furthermore, the precision of the present findings was evaluated by contrasting the heat transfer rate with outcomes that were previously published. Based on the obtained outcomes, it can be concluded that both the Eckert number and thermal radiation have a comparable enhancing influence, whereas the thermal relaxation parameter and thermal slip parameter exhibit opposing effects.

Effects of laser shock peening on Inconel 738LC to improve mechanical and fatigue characteristics

The effectiveness of laser shock peening at both room and elevated temperatures was examined for Inconel 738 low-carbon, a material widely used for gas turbine blades. Laser shock peening was performed with a Nd:YAG laser (wavelength = 532 nm, pulse duration = 8 ns, repetition rate = 10 Hz, top-hat profile) using aluminum foil (100 μm thick) as the protective coating at a laser intensity of 10 GW/cm2 and pass number of 10. As a result of laser shock peening, the surface hardness increased by 38%, and the compressive residual stress increased by approximately eleven times compared with that of the unpeened samples. A low cycle fatigue test was performed at room temperature and elevated temperature (850 °C) under strain control. At room temperature, the fatigue life of laser shock-peened samples increased by approximately 2.4 times that of the unpeened samples. At the high temperature of 850 °C, the fatigue life of the laser shock peened samples was overall similar to that of the unpeened samples, either slightly higher or lower depending on the applied total stress level. The results showed that laser shock peening is beneficial for enhancing fatigue strength at low temperatures, but its effectiveness largely disappears at a temperature as high as 850 °C, possibly owing to severe thermal relaxation.

Flow Dynamics of Eyring–Powell Nanofluid on Porous Stretching Cylinder under Magnetic Field and Viscous Dissipation Effects

The current paper scrutinized the flow dynamics of Eyring–Powell nanofluid on porous stretching cylinder under the effects of magnetic field and viscous dissipation by employing Cattaneo–Christov theory. In order to study impacts of thermophoretic force and Brownian motion, the two-phase (Buongiorno) model is considered. As a consequence, very nonlinear PDEs that govern flow problem were formulated, transformed into ODEs via relevant similarity variables, as well as tackled by utilizing R-K-45 integration scheme along with the shooting technique in the MATLAB R2018a software. Consequently, the numerical simulations reveal that Eyring–Powell fluid, curvature, velocity ratio parameters have the propensity to raise nanofluid velocity. Nanofluid temperature shows an increasing pattern with magnetic, curvature, dissipative heating, and thermophoresis parameters. Besides, Prandtl number, Eyring–Powell fluid, velocity ratio, thermal relaxation time, and porous parameters indicate the declining impact against the nanofluid temperature. Hence, the porous medium reasonably and successfully managed nanofluid temperature as well as the overall thermal system in terms of system cooling. The concentration profile gets fall down with escalating values of Schmidt number, magnetic, curvature, dissipative heating, thermophoresis, Brownian motion, and solutal relaxation time parameters. Moreover, coefficient of the skin friction gets rise for larger values of Eyring–Powell fluid, magnetic and curvature parameters however porous medium and velocity ratio parameters reveal the opposite trends on it. The magnetic, curvature, Eyring–Powell fluid, velocity ratio, and dissipative heating parameters indicate increasing impacts on both Nusselt N u and Sherwood S h numbers even though both N u and S h get cut down with the porous medium parameter. Moreover, an excellent and sound agreement was attained up on comparing coefficients of the skin friction for the current result against that of previously published literatures under some limiting cases.

Effect of Cattaneo-Christov heat and mass flux in Carreau-Yasuda tri-nanofluid

The Cattaneo-Christov heat and mass flux theory extends classic models to provide more accurate predictions in situations with instantaneous heat and mass transfer. Herein, an enhancement of heat and mass transfer in Carreau-Yasuda (CY) tri-nanofluid (TNF) over a stretched surface is modeled and studied via generalized conservation laws subjected to Cattaneo-Christov heat and mass flux theory. Silicon carbide (SiC), Aluminum Oxide (Al2O3), and Silver (Ag) are recruited as active nanoparticles in ethylene glycol (C2H6O2), and hired as CY fluid. Based on Finite Element Method (FEM), the code is created and validated for the formulated problems by comparing the current results to the published benchmarks. The computational findings showed that the thickness of the thermal and diffusion boundary layer decreases by increasing the thermal (δ) and diffusion relaxation (δc) parameters. The numerical analysis showed that CY-TNF exerts the largest shear stress on the wall compared to CY mono nanofluid (NF), and CY hybrid nanofluid (HNF). If CY-TNF has to flow over the specific surface, then adequate surface strength must be ensured. Moreover, comparing enhancement in thermal properties of CY-NF, CY-HNF, and CY-TNF revealed that the CY-TNF performs better than CY-HNF and CY-NF. Owing to the highest heat and mass flux, CY-TNF has an optimized ability to transport heat and mass, thus proving to be an efficient fluid for all processes requiring optimized heat and mass flux.

Cattaneo–Christov double diffusive non-Newtonian nanofluid flow over a rotating disk of variable thickness influenced by swimming microorganisms and velocity slip condition

This exploration examines the effects of the Cattaneo–Christov double diffusion in the Ostwald-de-Waele nanofluid flow on a rotating disk with varying thicknesses. The incorporation of the impacts of the bioconvection microorganisms increases the stability of the nanofluids. The slip boundary constraint is taken at the disk. The flow system is based on the Buongiorno nanofluid model. The envisioned fluid flow model incorporates heat transmission properties that are affected by nanoparticle volume fraction, Brownian motion, and thermophoresis. The numerical software bvp4c method is affianced. The presented diagrams portray the correlation of the protuberant parameters with the associated profiles given with cogent arguments. It is heeded that higher estimates of the thermal and solutal relaxation parameters dwindled the thermal and mass profiles. Furthermore, the motile microorganism distribution is diminished for larger counts of the Peclet number. A comparison table is also included to justify the truthfulness of the proposed model.

In Situ Photoisomerization of an Azobenzene-Based Triple Helicate with a Prolonged Thermal Relaxation Time.

The phosphate-coordination triple helicates A2 L3 (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.

Percutaneous laser coagulation of dilated intradermal veins: from theory to practice

Review authors consider the current possibilities of percutaneous laser coagulation for telangiectasias and reticular veins, which are the most common cosmetic defects of vascular genesis, occurring in more than 80% of women of different age groups. This vascular pathology constituting an aesthetic defect and causing local physical discomfort is one of the most common indications for phlebosclerosing therapy and percutaneous laser coagulation. The authors present the most effective and safe guidelines for percutaneous laser coagulation based on analyses of a large volume of specialized literature. Due to the use of state-of-the-art Nd:YAG lasers, percutaneous laser coagulation is increasingly used in patients with various types of intradermal vein lesions and, owing to high efficiency and safety, has advantages over compression sclerotherapy by several criteria. Nd:YAG lasers can be divided into long- and short-pulse ones according to their technical characteristics. Long-pulse lasers provide coagulation of the target vessel due to a single pulse with a high energy density (fluence), while short-pulse lasers, on the contrary, generate a series of pulses to the target vein with a running time of fractions of a millisecond, which ensures the conversion of hemoglobin into methemoglobin with a ten-fold increased ability to absorb laser energy and convert it to heat. As the duration of the pulses generated by the device is a priori shorter than the thermal relaxation time, the risk of burns to the skin and paravasal structures almost completely disappears. The authors provide clinical examples of the application of Aerolase Neo device that utilizes MicroPulse technology to confirm the effectiveness and safety of shortpulse Nd:YAG lasers.

In Situ Photoisomerization of an Azobenzene‐Based Triple Helicate with a Prolonged Thermal Relaxation Time

AbstractThe 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.

Implementation of Legendre wavelet method for the size dependent bending analysis of nano beam resonator under nonlocal strain gradient theory

The bending analysis due to thermoelastic loading in nanoscale materials is primarily determined by the physical aspect of the material and the modeling of structures. This paper examines the prediction of bending characteristics of the Euler-Bernoulli beam using Moore-Gibson-Thompson (MGT) thermoelasticity theory in conjunction with nonlocal strain gradient theory (NSGT). The coupled equations for dimensionless deflection and temperature change with ramp-type heating boundary conditions are formulated and solved using the Laplace transform method and the wavelet approximation method. The stiffness softening and hardening effects due to nonlocal and length-scale parameters are assessed, and their discrepancies are discussed. Findings further reveal that the impact of the thermal relaxation parameter on deflection and temperature is negligible. Moreover, the different aspect ratios of the beam's structure depict the prominently behavior of structural simulations in bending.

Thermodynamics of continental deformation

Continental deformation is known to be controlled by the interplay between tectonic and gravitational forces modulated by thermal relaxation-controlled lithospheric strength leading to oscillations around an equilibrium state, or to runaway extension. Using data-driven thermomechanical modelling of the Alpine Himalayan Collision Zone, we demonstrate how deviations from an equilibrium between mantle dynamics, plate-boundary forces, and the thermochemical configuration of the lithosphere control continental deformation. We quantify such balance between the internal energy of the plate and tectonic forces in terms of a critical crustal thickness, that match the global average of present-day continental crust. It follows that thicker intraplate domains than the critical crust (orogens) must undergo weakening due to their increased internal energy, and, in doing so, they dissipate the acquired energy within a diffused zone of deformation, unlike the localized deformation seen along plate boundaries. This evolution is controlled by a dissipative thermodynamic feedback loop between thermal and mechanical relaxation of the driving energy in the orogenic lithosphere. Exponentially growing energy states, leading to runaway extension are efficiently dampened by enhanced dissipation from radioactive heat sources. This ultimately drives orogens with their thickened radiogenic crust towards a final equilibrium state. Our results suggest a genetic link between the thermochemical state of the crust and the tectonic evolution of silicate Earth-like planets.

Comprehensive investigation into the thermal rheological behavior and relaxation characteristic of single/composite polymers in laminated glass

Polymeric interlayers are of significance for the structural capability of thin-walled laminated glass members both before and after glass fracture. Polymers present evident temperature and time dependence, which should be carefully assessed in the design process. To improve mechanical properties dependent on the temperature and time, novel interlayers including modified ethylene-vinyl acetate (PVE®) and composite PVE/PC (SGE®), have been developed along with the sound resistance of the interfacial adhesion to aging. In this work, dynamic mechanical thermal analysis tests were carried out to investigate the thermal rheological behavior and relaxation characteristic of polyvinyl butyral (PVB), ionomer (SentryGlas®, SG), PVE, PC and SGE. The results show that PVE and SGE follow the complex thermal rheological behavior as a result of the existence of two different types of relaxation transitions, whilst PVB, SG, and PC are thermorheologically simple materials. The arctangent function was introduced to describe the temperature dependence of PVB and SG. The relaxation modulus of polymers was subsequently derived based on the approximation equation and inverse Fourier transform. The results of the inverse Fourier transform indicate that vertical shift might need to be considered for PVE and SGE. The application of the approximation equation was assessed and its limitation was discussed. Finally, the relaxation characteristics of five polymers were described using the generalized Maxwell model based on the weighted least squares method.

Low-Temperature Heat Capacity of CsPbI3, Cs4PbI6, and Cs3Bi2I9.

The heat capacities of CsPbI3, Cs4PbI6, and Cs3Bi2I9 were studied using low-temperature thermal relaxation calorimetry in the temperature range of 1.9-300 K. The three compounds are insulators, with no electronic contribution to the heat capacity. None of them show detectable anomalies in the studied temperature window. Thermodynamic properties at standard conditions are derived. Previously reported results on Cs3Bi2I9 are not fully consistent with the present findings. Moreover, the magnetic susceptibilities of the three title compounds were measured.

Photothermal Microscopy and Spectroscopy with Nanomechanical Resonators.

In nanomechanical photothermal absorption spectroscopy and microscopy, the measured substance becomes a part of the detection system itself, inducing a nanomechanical resonance frequency shift upon thermal relaxation. Suspended, nanometer-thin ceramic or 2D material resonators are innately highly sensitive thermal detectors of localized heat exchanges from substances on their surface or integrated into the resonator itself. Consequently, the combined nanoresonator-analyte system is a self-measuring spectrometer and microscope responding to a substance's transfer of heat over the entire spectrum for which it absorbs, according to the intensity it experiences. Limited by their own thermostatistical fluctuation phenomena, nanoresonators have demonstrated sufficient sensitivity for measuring trace analyte as well as single particles and molecules with incoherent light or focused and wide-field coherent light. They are versatile in their design, support various sampling methods-potentially including hydrated sample encapsulation-and hyphenation with other spectroscopic methods, and are capable in a wide range of applications including fingerprinting, separation science, and surface sciences.

Speed limit, dissipation bound, and dissipation-time trade-off in thermal relaxation processes.

We investigate bounds on speed, nonadiabatic entropy production, and the trade-off relation between them for classical stochastic processes with time-independent transition rates. Our results show that the time required to evolve from an initial to a desired target state is bounded from below by the information-theoretical ∞-Rényi divergence between these states, divided by the total rate. Furthermore, we conjecture and provide extensive numerical evidence for an information-theoretical bound on the nonadiabatic entropy production and a dissipation-time trade-off relation that outperforms previous bounds in some cases..

Entropy analysis on EMHD 3D micropolar tri-hybrid nanofluid flow of solar radiative slendering sheet by a machine learning algorithm

The purpose of this paper is to analyze the heat transfer behavior of the electromagnetic 3D micropolar tri-hybrid nanofluid flow of a solar radiative slendering sheet with non-Fourier heat flux model. The conversion of solar radiation into thermal energy is an area of significant interest as the demand for renewable heat and power continues to grow. Due to their enhanced ability to promote heat transmission, nanofluids can significantly contribute to enhancing the efficiency of solar-thermal systems. The combination of silicon oil-based silicon (Si), magnesium oxide (MgO), and titanium (Ti) nanofluids has attracted attention for their ability to improve the performance of solar-thermal systems. The present study discloses a new approach for intelligent numerical computing solving, which utilizes an MLP feed-forward back-propagation ANN and the Levenberg-Marquard algorithm. The collection of data was conducted for the purpose of testing, certifying, and training the ANN model. The Bvp4c solver in MATLAB is utilized to solve the nonlinear equations governing the momentum, temperature, skin-friction coefficient, and Nusselt number. The characteristics of numerous dimensionless parameters such as porosity parameter left(K={0.0,2.0,4.0}right), vortex viscosity parameter left({R}_{1}={0.5,1.0,1.5}right), electric field parameter left(E={0.0,0.1,0.2}right), thermal relaxation time left(Lambda ={0.01,0.10,0.20}right), heat source/sink parameter, left(Q=-{0.3,0.0,0.3}right) thermal radiation parameter left(R={0.5,1}.{0,1.5}right), temperature ratio parameter left({theta }_{w}={0.5,1.0,1.5}right),nanoparticle volume fraction left(phi ={0.00,0.02,0.04}right) on Si + MgO + Ti/silicon oil micropolar tri-hybrid nanofluida are analyzed. The ANN model engages in a process of data selection, network construction, training, and evaluation of its effectiveness through the utilization of mean square error. Tables and graphs are used to show how essential parameters affect fluid transport properties. The velocity profile is decreased by higher values of the porosity parameter, whereas the temperature profile is increased. The temperature profile is inversely proportional to higher values of the electric field parameter. The micro-rotation profiles reduced by expanding values vortex viscosity parameter. It has been determined that entropy generation and Bejan number intensifications for enlarged nanoparticle volume fraction.

Significance of skin vasodilation for bioheat transfer within transiently heated skin tissue

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.

Convective heat and mass transfer analysis on Casson nanofluid flow over an inclined permeable expanding surface with modified heat flux and activation energy

Due to the enormous advantages of nanofluid technology, the study of various nanofluid flows under different assumptions became an important research topic. Furthermore, Fourier proposed the basic heat flux law, and it has some initial disturbances. Later, Cattaneo and Christov modified the Fourier model by including the relaxation term and rectified the conflicts in the Fourier model. Current research explores the influence of activation energy on a chemically reactive Casson nanofluid over a stretching surface. Cattaneo–Christov heat and mass flux are considered for the investigation. The governing PDEs (partial differential equations) along with the boundary constraints are transformed into ODEs (ordinary differential equations) with the aid of suitable similarity variables and then solved numerically by the bvp5c MATLAB package. We have drawn the velocity, temperature, and concentration profiles. Also, plotted the isotherms and streamlines, and analyzed the effects of all the influential parameters on the flow regime. The increasing Casson fluid parameter leads to a decrease in the fluid velocity. Larger value of the Casson fluid parameter () recovers the results for the Newtonian fluid. The results obtained from the study show that the temperature shoots up for intensifying values of the magnetic parameter, radiation parameter, Eckert number, thermal Biot number, Brownian motion parameter, and the thermophoresis parameter; meanwhile the increase in the thermal relaxation parameter drops the temperature. The positive values of the heat source parameter decreases the rate of heat transfer by 10%. Also, we noticed that the effect of the growing values of the Schmidt number and the chemical reaction parameter is to decrease the concentration field. Moreover, a rise in the Reynolds and Brinkmann numbers pushes up the entropy generation.