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Despite the weak, van der Waals interlayer coupling, photoinduced charge transfer vertically across atomically thin interfaces can occur within surprisingly fast, sub-50 fs time scales. An early theoretical understanding of charge transfer is based on a noninteracting picture, neglecting excitonic effects that dominate optical properties of such materials. We employ an ab initio many-body perturbation theory approach, which explicitly accounts for the excitons and phonons in the heterostructure. Our large-scale first-principles calculations directly probe the role of exciton-phonon coupling in the charge dynamics of the WS2/MoS2 heterobilayer. We find that the exciton-phonon interaction induced relaxation time of photoexcited excitons at the K valley of MoS2 and WS2 is 67 and 15 fs at 300 K, respectively, which sets a lower bound to the intralayer-to-interlayer exciton transfer time and is consistent with experiment reports. We further show that electron-hole correlations facilitate novel transfer pathways that are otherwise inaccessible to noninteracting electrons and holes.

The dielectric measurements of thiamine hydrochloride (vitamin B1 hydrochloride) and dimethyl sulphoxide (DMSO) binary mixtures have been carried out in the frequency range of 10 MHz to 50 GHz at 25°C, 20°C and 15°C using the TDR technique. The dielectric parameters such as complex dielectric permittivity ɛ*(ω), static dielectric permittivity (ɛs), relaxation time (τ), and asymmetric distribution parameter (β) are obtained by using Cole-Davidson model. These parameters are used to compute thermodynamic properties, Kirkwood correlation factor (geff), and excess molar volume (VE). The heteromolecular H-bonding existing in the binary mixture is explained. [ABSTRACT FROM AUTHOR]

Due to the inherent unpredictability of geological conditions, tunnelling operations are often at risk of encountering water inrushes. Such incidents can lead to construction delays, impose financial strains and pose significant safety threats to the workers involved. Water‐bearing geological formations are the main triggers for such incidents, with factors such as the positioning, water quantity and permeability distribution of these formations being key to predicting the occurrence and severity of water inrush disasters. By leveraging the complex interplay among relaxation time, P‐wave velocity and permeability within the rock's physical properties, a series of indoor tests were conducted on 40 artificial reef limestone cores to extract the necessary parameters. Through the analysis of the data, the comprehensive permeability prediction model was established, and the correlation coefficient was 0.9420 between the model's predictions and actual measurements. At the same time, through theoretical and mechanism analysis, the relationship between permeability and relaxation time and the relationship between permeability and P‐wave velocity were analysed. Finally, 10 natural reef limestone samples were used to verify the accuracy of the model. The prediction model enables an accurate evaluation of tunnel permeability, thus providing a scientific basis for the mitigation of tunnel water inrush hazards. [ABSTRACT FROM AUTHOR]

The Time Domain Reflectometry (TDR) technique was used to analyse the complex permittivity spectra of the Pyridine-n-propyl alcohol mixture across the concentration and temperature range of 10–25°C. The Cole-Davidson model was used to match the Pyridine- n-propyl alcohol complex permittivity spectra. The nonlinear least squares fit approach has been used to obtain the Static dielectric constant (ε0), Relaxation time (τ), Effective Kirkwood correlation factor (geff) Excess permittivity$\left({\varepsilon _0^E} \right)$ε0E, Thermodynamic parameters (activation enthalpy and activation entropy), and Bruggeman factor (fB). Furthermore, the analysis of excess characteristics and the Bruggeman factor points towards the presence of hydrogen bonding between the pyridine and n-propyl alcohol molecules. [ABSTRACT FROM AUTHOR]

Molecularly crowded solutions have been used to simulate cytoplasmic fluids, but little justification is provided in the literature. This work compared three key physical properties of solutions containing polyethylene glycol and sucrose against those in the cytoplasmic fluid from bacteria Escherichia coli: fluid viscosity, relaxation time (T1 and T2) of water, and the diffusion coefficient of water. It was concluded that appropriate mixtures of sucrose and polyethylene glycol 10,000, such as 10% sucrose and 15% PEG10,000 and 7.5% sucrose and 19% PEG10,000, closely mimic these properties of cytoplasmic fluid from E. coli containing around 100 mg/mL of proteins. [ABSTRACT FROM AUTHOR]

By using the density functional theory (DFT) in combination with Boltzmann transport theory, the influence of Mg concentrations (x) doping on the thermoelectric properties of Hg 1 − x MgxSe ternary alloys was systematically investigated. The generalized gradient approximations of Perdew–Burke–Ernzerhof (GGA-PBE) have been used to illustrate the exchange correlation potential. The thermodynamic stability of the studied compounds was analyzed in terms of formation energy. Various thermoelectric transport parameters, such as the Seebeck coefficient (S), the thermal conductivity over relaxation time (k/ τ), the electrical conductivity over relaxation time (σ / τ), the power factor (PF) and the figure of merit (ZT) have been deduced and discussed. The obtained results of thermoelectric properties show that the studied materials can be useful for thermoelectric devices at room temperature. It can also be seen that Mg concentrations can increase the thermal efficiency of the HgSe alloy. [ABSTRACT FROM AUTHOR]

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (Cm) at this interface with the gate voltage Vgate ≈ 0.1 V follows approximate laws Cm~T1.2 and Cm~T0.11 (T is Vgate period) in frequency ranges (1000–50,000) Hz and (0.02–300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (Cint) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (Cm) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (Cdl) and by the graphene quantum capacitance (Cq), and it also implies that Cint is mostly charged. We have also found a voltage dependence of Cm below 10 Hz, which is likely related to the voltage dependence of Cq. The observation of this effect only at low frequencies indicates that Cq relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges. [ABSTRACT FROM AUTHOR]

AC conductivity and dielectric relaxation of MoO3 doped V2O5–ZnO–CuO glass-nanocomposites have been studied in a wide temperature and frequency ranges. Electron microscopic studies reveal that Cu3O8V2 and Cu3Mo2O9 nanophases (for higher MoO3 content) have been developed, which are expected to form various defect states. Owing to formation of such nanophases, different values of maximum barrier height have been developed, which are supposed to play vital roles in the conduction process. Electric modulus formalism has been conceived as it can exclude the electrode polarization effect at low frequency regime and suggest the transition from long-range mobility to short-range mobility assembly of polarons. Correlated barrier hopping model and its modified version have been found to be most appropriate theoretical models to explore the conduction process. It is also noteworthy that relaxation times are found to increase with higher MoO3 content, which may indicate about the slow movement of charge carriers. The nature of variation of Kohlraush Williams Watts parameters can be considered as a tool to reveal the reason for shifting of relaxation process from Debye to Non-Debye type up to a limit with more and more incorporation of MoO3 content into the previous materials. By crossing the limiting value of composition (0.08 mol% of MoO3), it becomes non-Debye type at a very slow rate. Lower values of dielectric constant at high frequencies are expected to be important for their applications in photonics and opto-electronics. Scaling method of electric modulus spectra indicates that the dielectric relaxation process in the present system leads to a common relaxation process at various temperatures, but it is strongly dependent on compositions. [ABSTRACT FROM AUTHOR]

The rheological characterization of complex liquids is of great importance in many applications. Among the properties that can be measured, the relaxation time has great relevance, as it provides a measure of fluid elasticity. In this work, we propose a novel method to estimate the longest relaxation time of viscoelastic fluids by applying machine learning to microfluidics. Specifically, we train a long-short term memory (LSTM) neural network to identify the Weissenberg number that characterizes the dynamics of trains of rigid particles suspended in a viscoelastic liquid flowing in a cylindrical microchannel. We first study the effect of the Weissenberg number on the evolution of the microstructure through numerical simulations. An in silico dataset consisting of the distributions of the interparticle distances at different channel sections is built and used to train the network. The performance of the LSTM model is tested on both classification and regression problems. The proposed method is nonintrusive, requires a simple setup, and can in principle be used to measure other properties of the fluid. [ABSTRACT FROM AUTHOR]

In this work, we investigate the viscoelastic properties of hydrogels through stress relaxation experiments to better understand the force-dependent dynamics of these materials with the aspiration of expanding their application envelope within the biomedical field and beyond. We experimentally studied the viscoelastic behavior of 4 different types of hydrogels: covalently crosslinked polyacrylamide (PAAm), covalently crosslinked PAAm network immersed in a viscous alginate solution, ionically crosslinked alginate along with crosslinked PAAm-alginate double network. Through our investigations, we demonstrate that we can tailor the viscoelasticity of a covalently bonded PAAm network by tuning the viscosity of the solution in the gel. Moreover, based on the stress relaxation test of ionically crosslinked alginate gel and the double network gel, we have revealed the quantitative correlation between the ionic bond dissociation and force-dependent viscoelastic behavior of gels containing ionic crosslinks. [ABSTRACT FROM AUTHOR]

Abstract Using smart or low salinity waters known as green processes gained increasing attention due to their unique features and their positive impacts on the environment. In light of this fact and since there is limited knowledge about the effects of salts under engineered concentrations or binary mixtures and crude oil fractions on the interfacial tension (IFT) reduction and wettability alteration of the resinous (RSO) and asphaltenic synthetic oil (ASO), the current investigation is designed and performed for the first time. Moreover, the dynamic behavior of the IFT variation was carefully investigated and the relaxation time was obtained and modeled to see the impact of mono and divalent salts individually and in binary conditions. The relaxation times revealed that the lowest adsorption times were obtained for NaCl/CaCl2 brine regardless of the examined oil types of ASO and RSO due to the high movement affinity of the polar functional groups toward the interface consequently reducing the required time for coverage and packing of active agents at the interface. Finally, the measured contact angle values revealed a significant effect of binary salts on the wettability alteration toward strongly water-wet conditions, especially for the RSO and ASO compared with crude oil.

With the accelerated development of surface well cementing technology, the engineering site has higher requirements for the early fluidity and coagulation performance of surface well cementing water slurry. In order to improve the top-off efficiency of cement injection operation in cementing engineering and improve the application of cementing engineering field operation, the method of nanoalumina particles modified cementing cement was proposed, and the NMR technique was used to study the change characteristics of the hydration reaction of nanoalumina-modified cement slurries (with the water-cement ratio of 0.44) with the mass fractions of 0.00% wt, 0.05% wt, 0.10% wt, 0.15% wt, and 0.20% wt at different hydration ages were investigated to characterize the changes in hydration reactions, and to probe the aqueous phase distribution, changes in the total signal amount of physically bound water, peak shape index, and migration rate of the nanoalumina-modified cements. The results showed that the T2 patterns of nano-alumina-modified cement pastes at the hydration stage would show three relaxation peaks, corresponding to the flocculated structure-filled water (0.1−10 ms), capillary water (10 ms), and free water (800−1000 ms), respectively; and the total signal of the physically bound water decreased gradually with the increase of the mass fraction of nanoalumina, in which the nanoalumina-modified cement pastes with the mass fraction of 0.20%wt. Alumina-modified cement paste has the fastest reduction rate of signal; the peak shape index shows the trend of increasing and then decreasing, when the hydration reaction is carried out to 600 min, the modified cement paste with mass fraction of 0.20%wt has the fastest rate of change, and the rate of the relaxation peak moving to the short relaxation direction is accelerated; the combination of the migration rate of the nanoalumina-modified cementing cement hydration reaction stage division, and the hydration mechanism of its hydration mechanism respectively acted in the four Hydration period: ① initial hydration period (5−60 min), the hydration rate did not change significantly; ② accelerated hydration period (60−600 min), nano-alumina to make the physical binding water in the cement paste into chemical binding water in a shorter period of time, the hydration process is accelerated to achieve the effect of promoting the hydration of the cement; ③ stabilized hydration period (600−1200 min), the cement system tends to stabilize; ④ Delayed hydration period (1200−1800 min), the rate of conversion of physically bonded water to chemically bonded water slows down, and the hydration process of cement slows down. It was concluded that the hydration period of nanoalumina-modified cement paste can be divided into four stages, and nanoalumina plays the roles of physical filling, accelerating, stabilizing, and retarding for the cement paste, respectively. In the accelerating period, nanoalumina promotes the early flow of cement, which is conducive to the pumping and flow of cement paste, and in the retarding period, nanoalumina retards the further hydration process of cement, which is conducive to the development of early strength. Among them, the nano-alumina modified cement paste with a mass fraction of 0.20% wt has the greatest influence on the cement hydration process, promotes the conversion of filler water to bound water, and accelerates the hydration reaction of cement paste to the greatest extent during the accelerated hydration period, which serves as the basis for providing guidance for the preparation and application of cementing cements in the field.

Using smart or low salinity waters known as green processes gained increasing attention due to their unique features and their positive impacts on the environment. In light of this fact and since there is limited knowledge about the effects of salts under engineered concentrations or binary mixtures and crude oil fractions on the interfacial tension (IFT) reduction and wettability alteration of the resinous (RSO) and asphaltenic synthetic oil (ASO), the current investigation is designed and performed for the first time. Moreover, the dynamic behavior of the IFT variation was carefully investigated and the relaxation time was obtained and modeled to see the impact of mono and divalent salts individually and in binary conditions. The relaxation times revealed that the lowest adsorption times were obtained for NaCl/CaCl2 brine regardless of the examined oil types of ASO and RSO due to the high movement affinity of the polar functional groups toward the interface consequently reducing the required time for coverage and packing of active agents at the interface. Finally, the measured contact angle values revealed a significant effect of binary salts on the wettability alteration toward strongly water-wet conditions, especially for the RSO and ASO compared with crude oil. [ABSTRACT FROM AUTHOR]

Complex permittivity spectra of propionitrile (PN) – dimethyl sulphoxide (DMSO) mixtures in the 10 MHz–30 GHz frequency range were investigated using time-domain reflectometry (TDR). The Debye model was employed to fit the measured dielectric spectra, allowing for the calculation of dielectric parameters like the static dielectric constant (ε0) and relaxation time (τ). Excess dielectric constant (ε0 E) and excess inverse relaxation time (1/τ)E were subsequently calculated from the measured ε0 and τ. The observed variations in these excess parameters provide evidence for intermolecular interactions within the PN-DMSO mixtures. Theoretical estimates of the ε0 were obtained using Luzar’s hydrogen-bonded model. [ABSTRACT FROM AUTHOR]

A usual solid-state reaction method was evolved to fabricate BaBi1.6Fe0.4TiO6 ceramic oxide at a higher calcination temperature (1000 °C). The initial crystal structure information reveals that the material has dual-phase bearing tetragonal (P4mm) and monoclinic (P121/c1). The material also possesses a tensile strain (0.915) which has been verified by using the Williamson–Hall (W–H) plot. The compound has different functional groups and vibrational modes like a usual perovskite oxide. The optical property of the compound has been studied by UV–Vis spectroscopy, and it is found 2.67-eV bandgap. The result of the UV–visible study suggests that the material can be used as source material in photovoltaic and photocatalytic applications. Complex impedance and modulus spectroscopic verification revealed a semiconducting property and non-Debye behavior. [ABSTRACT FROM AUTHOR]

The development of fast-responding electrically conductive polymers as actuators activated by low electrical current is now regarded as an urgent matter. Due to their limited electrical conductivity, actuators based on polymeric hydrogels must be activated using a high voltage (up to 200 V) and frequency (up to 500 Hz) when employing AC power. In this work, to improve the electrical conductivity of the hydrogel and decrease the required activation voltage of the hydrogel actuators, lithium chloride (LiCL) was added as a conductive filler to the polymer matrix of polyvinyl alcohol (PVA). In order to ascertain the deformation of actuators, activation and relaxation times, actuator efficiencies, and generated force under the conditions of activation, linear actuators that can be activated by extension/contraction (swelling/shrinking) cycles were prepared and investigated depending on the LiCl content, applied voltage, and frequency. Under a load of approximately 20 kPa and using a 90 V AC power at a 50 Hz frequency with a 30 wt.% LiCl content, it was found that the actuators' total contraction, reinforced by a woven mesh braided material, was about 20% with a ~2.2 s activation time, while the actuators' total extension, reinforced by a spiral weave material, was about 52% with a ~2.5 s activation time, after applying a 110 V AC at a 50 Hz frequency with a 10 wt.% LiCl content. Furthermore, as the lowest voltage, a 20 V AC power can operate these actuators by increasing the LiCl weight content to the same PVA mass content. Moreover, the PVA/LiCl hydrogels' activation force can be greater than 0.5 MPa. The actuators that have been developed have broad applications in soft robotics, artificial muscles, medicine, and aerospace fields. [ABSTRACT FROM AUTHOR]

The critical frequency and the relaxation time are analyzed through deformation and displacement during electrostriction which is induced by the electrical field at different frequencies. First, when the frequency is 50 Hz and the field strength is 2.5 kV mm−1, the electrostrictive displacement of polyethylene is 6.72 × 10−4 mm. After the data fitting, it is found that the displacement increases linearly with the square of field strength and that the proportional coefficient of 50 Hz is 1.08 × 10−4. Second, due to the influence of relaxation polarization and power loss, with the increase of frequency, the displacement and the proportional coefficient first increases then decreases, and when the frequency is 10 kHz, the displacement of 2.20 × 10−6 mm and the proportional coefficient of 3.51 × 10−7 have minimum values, which are 99.67% and 99.68% lower than that of 50 Hz, respectively. There is the critical frequency. Finally, based on the characteristic of anomalous dispersion, the relaxation time of polyethylene is 9.19 × 10−6s, which is in the time range of thermionic relaxation polarization and consistent with the actual situation. This analysis confirms the quantitative relationship between electrostrictive characteristics, field strength, and polarization. In addition, the relationship between frequency and strain is discussed, and the critical frequency in polymer and the relaxation time are confirmed. [ABSTRACT FROM AUTHOR]

The steadily growing interest in applying granular media in various novel and advanced technologies, particularly in the energy sector, entails the need to gain in-depth knowledge of their thermal and flow behaviour and develop simulation predictive tools for systems' design and optimisation. The focus of the present study is on the numerical modelling of the thermal decomposition of solid fuel grains in a packed bed while considering a non-classical description of heat transfer in such a medium. The work aims to assess the influence of the relaxation time and thermo-physical properties of the medium on the nature of the solution and highlight the factors that are the source of local non-equilibrium affecting thermal wave speed propagation. The analysis of the predicted temperature distribution was carried out based on the developed transient one-dimensional thermal and flow model, taking into account the moisture evaporation and the devolatilization of fuel particles. Obtained simulation results showed a significant increase in the temperature gradients with increased relaxation times for the case of wet granular bed. They also demonstrated the variable dynamics of thermal wave propagation due to the change in the packed bed structure with the process progress. For a relaxation time of 100 s, a several-fold increase in the temperature signal propagation speed during the fuel bed thermal decomposition was predicted. [ABSTRACT FROM AUTHOR]

Complex dielectric measurements were performed in 1-nitropropane (NTP) and DMSO mixtures at various concentrations in the frequency range of 10 MHz to 50 GHz using time domain reflectometry technique. The excess inverse relaxation time values were found to be negative, indicating that the dipoles rotated more slowly. Alenka Luzar's hydrogen-bonded theory is used to calculate theoretical estimates of the static dielectric constant. The variations in dielectric parameters such as dielectric constant, relaxation time, Kirkwood correlation factor and excess properties observed in the study confirm the existence of intermolecular interactions within the NTP-DMSO mixtures. [ABSTRACT FROM AUTHOR]

Aldous and Fill (2002) conjectured that the maximum relaxation time for the random walk on a connected regular graph with n vertices is (1 + o (1)) 3 n 2 2 π 2 . A conjecture by Guiduli and Mohar (1996) predicts the structure of graphs whose algebraic connectivity μ is the smallest among all connected graphs whose minimum degree δ is a given d. We prove that this conjecture implies the Aldous–Fill conjecture for odd d. We pose another conjecture on the structure of d -regular graphs with minimum μ , and show that this also implies the Aldous–Fill conjecture for even d. In the literature, it has been noted empirically that graphs with small μ tend to have a large diameter. In this regard, Guiduli (1996) asked if the cubic graphs with maximum diameter have algebraic connectivity smaller than all others. Motivated by these, we investigate the interplay between the graphs with maximum diameter and those with minimum algebraic connectivity. We show that the answer to Guiduli problem in its general form, that is for d -regular graphs for every d ≥ 3 is negative. We aim to develop an asymptotic formulation of the problem. It is proven that d -regular graphs for d ≥ 5 as well as graphs with δ = d for d ≥ 4 with asymptotically maximum diameter, do not necessarily exhibit the asymptotically smallest μ. We conjecture that d -regular graphs (or graphs with δ = d) that have asymptotically smallest μ , should have asymptotically maximum diameter. The above results rely heavily on our understanding of the structure as well as optimal estimation of the algebraic connectivity of nearly maximum-diameter graphs, from which the Aldous–Fill conjecture for this family of graphs also follows. [ABSTRACT FROM AUTHOR]

With the availability of efficient and sophisticated finite element analysis (FEA) and computational fluid dynamics (CFD) tools, engineering designs are becoming more software-driven and simulation-based. However, the insights relevant to engineering designs tend to be hidden within massive temporal and spatial data produced with full-fledged three-dimensional simulations. In this paper, we present a preliminary study of the controlled intermittent dispensing of a typical non-Newtonian glue employed in the manufacturing of electric vehicles (EVs). The focus of the study is on the scaling issues derived from different computational and analytical models of interest and importance to the precision control of this non-Newtonian fluid, the lowest dynamic viscosity of which at extremely high shear rates is nearly four million times that of water. More specifically, the abrupt change of the inlet pressure with a constant outlet or ambient pressure and various modeling strategies for transient viscous internal flow with both Newtonian and non-Newtonian fluids are modeled and compared. The analytical and computational results of the developing Newtonian fluid, i.e., water, are derived and computed for validation and verification purposes before the actual applications to the developing non-Newtonian fluid. The concept of a well-established relaxation time before the onset of the steady solution for Newtonian fluids has been validated with both analytical and computational approaches before its expansion and adoption to non-Newtonian fluids with complex rheological behaviors. Other issues attributed to transient operations and precision controls of non-Newtonian fluid delivery involve the pressure pulse and pressure wave propagation within the flexible pipe with compressible or almost incompressible non-Newtonian fluids with a constant pressure at the outlet and a constant mass flow rate or average axial velocity at the inlet, which will be addressed in a separate paper. [ABSTRACT FROM AUTHOR]

Herein we report the method to tailor the band gap and UV absorption of polyvinyl alcohol (PVA)/graphene oxide (GO)‐silver (Ag)/glutaraldehyde (GA) hybrid polymer nanocomposites. The modifications brought by neutron irradiation to the optical and dielectric characteristics enabled the band gap and UV absorption‐tailored polymer nanocomposites to be obtained. Neutron‐irradiated samples, compared with their unirradiated counterparts, exhibit a reduction in transmittance to 78%, rendering them opaque to UV–visible light after irradiation. The energy band gap decreases from 5.25 to 4.09 eV upon irradiation. Furthermore, upon neutron‐irradiation the relaxation time increases from 7.63 × 10−4 to 0.02 s which is evident by the shift in electric modulus imaginary part (M") peak to a lower frequency region, indicating an increase in relaxation time. The Cole–Cole plot for irradiated samples demonstrates lower fitting parameter (α) values of the modified Havriliak–Negami function, indicating a departure from pure capacitor‐like behavior. The neutron irradiation leads to a decrease in conductivity from 44.6 × 10−7 to 0.09 × 10−7 S/cm. [ABSTRACT FROM AUTHOR]

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Thin films of Ba0.8Sr0.2TiO3 were obtained by high-frequency sputtering on (100)p-Si substrates. Results of studies of frequency and temperature dependences of real and imaginary parts of dielectric permittivity of Ba0.8Sr0.2TiO3 ferroelectric film on alternating electric current are presented. It has been found that the polarization process has an activation character, the real and imaginary parts of the dielectric permeability decrease with increasing frequency, and the decrease rate is much higher at relatively low frequencies than at high frequencies. The relaxation time has been calculated and this crystal has been found to have an electron polarization mechanism due to thermal motion. [ABSTRACT FROM AUTHOR]

Using time-domain reflectometry (TDR), the complex permittivity of binary mixture of butyronitrile (BTN) and 1,4-dioxane (1,4-DX) at various temperatures and solvent proportions was determined over the frequency range of 10 MHz to 30 GHz. The complex permittivity spectra (CPS) have been fitted to the Havrilik–Negami equation. The relaxation time (τ) and static dielectric constant (ε0) have been calculated for each concentration using the least squares fit method. The nonlinear behavior of dielectric parameters suggests a change in the molecular size and intermolecular bonding of BTN–1,4-DX mixtures. Theoretical static dielectric constants (ε0) have been determined using hydrogen bonded model suggested by Luzar for all solvent proportions and compared with experimental values obtained from TDR. [ABSTRACT FROM AUTHOR]

The present paper is aimed at studying the effects of coupled thermo-hydro-mechanical dynamics on an isotropic, uniform, fully saturated, and poroviscoelastic soil whose surface is subjected to either a mechanical force or a thermal load. A formulation is first deduced in the context of the Lord-Shulman theory. The general relationships among the non-dimensional vertical displacement, excess pore water pressure, vertical stress, and temperature distribution are then deduced via normal mode analysis and depicted graphically. This study continues the authors' work of applying normal mode analysis to the derivation of theoretical results in the multi-field coupling of viscoelastic soil. Via this method, the equation can be divided into two parts without integral transformation and inverse transformation, thereby increasing the speed of decoupling and eliminating the limitation of numerical inverse transformation. Furthermore, the differences between the coupled thermo-hydro-mechanical dynamic (THMD) model and the coupled thermo-hydro-mechanical viscoelastic dynamic (THMVD) model are presented. Comparisons are made within the theory in both the presence and absence of the viscoelastic relaxation time, and the influence of the viscoelastic relaxation time on each physical variable is also discussed. This proposed derivation method can be widely applied in the geotechnical engineering field. [ABSTRACT FROM AUTHOR]

The complex dielectric permittivity spectra (CPS) of a binary mixture of 1,5-pentanediol (1,5-PD) with 1,4-dioxane (1,4-DX) were determined using time-domain reflectometry in the frequency range of 10 MHz to 30 GHz. The experimental CPS data were fitted to the Cole–Davidson equation using a nonlinear least squares fit method to determine the dielectric relaxation parameters. The intermolecular interactions in the binary liquids were studied through the Kirkwood correlation factor, excess parameters, thermodynamic parameters, and Bruggeman's factor. [ABSTRACT FROM AUTHOR]

Recently, we applied solution 2H-nuclear magnetic resonance spectroscopy (2H NMR) to analyze the water (deuterium oxide, D2O) structure in several biopolymers at ambient temperature. We established that polymers with good blood compatibility (i.e. poly(2-methoxyethyl acrylate) (PMEA)) have water observed at high magnetic fields (upfield) compared with bulk water. Polymers containing poly(propylene glycol) (PPG) or poly(propylene oxide) (PPO) exhibit good compatibility; however, the reason for this remains unclear. In addition, reports on the blood compatibility of PPO/PPG are limited. Therefore, PPG diester (PPGest) was prepared as a model polymer, and its blood compatibility and water structure were investigated. PPGest exhibited excellent blood compatibility. The water in PPGest was observed upfield by 2H NMR, and it was defined as non-freezing water via differential scanning calorimetry. Based on these observations, the relationship between the blood compatibility and water structure of PPGest is discussed by comparing with those of PMEA, and the reason for the good performance of PPG/PPO-based polymers is discussed. [ABSTRACT FROM AUTHOR]

Lignin is one of the most common biopolymers. The application of the electrophysical properties of the polymer is one of the directions of its use. The effect of impurities potassium bromide with an ionic crystal lattice on the electrophysical properties of lignin has been shown. The study of the frequency dependences of the specific electrical conductivity and the components of the complex dielectric permittivity in the frequency range from 6 × 10−2 to 6 × 107 rad s−1 was carried out. The nonadditivity of the electrophysical properties of the lignin‐potassium bromide system has been shown. It is established that the relaxation time of the π‐electrons of the aromatic rings of lignin depends on the content of potassium bromide in the mixture and varies from 1.6 × 10−7 (100% lignin) to 7.5 × 10−4 s (1% of KBr in mixture). The orientation of the positive charge of potassium atom of the KBr dipole atom to the π‐electrons of the benzene ring of lignin leads to change of high‐frequency relaxation time. This effect can be used in frequency filter to eliminate electronic polarization in the high‐frequency region. Thus, the polarization of ionic impurities has a significant effect on the dielectric properties of lignin in the region of medium and high frequencies of alternating electric field. [ABSTRACT FROM AUTHOR]

The primary focus of this study is to analyze comparative heat transfer in a two-dimensional (2D) multilayered human skin using thermal waves and Pennes' bioheat transfer models. The model comprises the epidermis, dermis, hypodermis tissue, and inner cells, and aims to understand their response to microwave (MW) power and electromagnetic (EM) frequency. The system of equations involves EM wave frequency and bioheat equations and uses the finite element method (FEM) for solving. It encompasses a range of microwave power levels (4–16 W), frequencies (0.9–4 GHz), and exposure durations (0–180 s). It examines how MW power and frequency affect temperature predictions due to different relaxation times. The results are visually represented, illustrating microwave power dissipation, isothermal profiles within the skin tissue, temperature trends at several locations, relaxation times, specific absorption rate (SAR), and the mean surface temperature of the multilayered dermal cell. Thermal analysis shows that Pennes' equation predicts higher temperatures than the thermal wave model of bioheat transfer (TWMBT). A notable disparity in temperature evolution is observed between the two models, especially in high-frequency transient heating scenarios. The TWMBT forecasts a delay in heat transfer, offering valuable insights into the more realistic short-term thermal behavior that the classical Pennes' model fails to capture. This comparative study underscores the significance of selecting an appropriate bioheat transfer model for precise thermal analysis in biomedical applications, such as hyperthermia treatment and thermal diagnostics. The findings emphasize the potential of the TWMBT to enhance the accuracy of thermal treatments in clinical settings.

This study presents a novel and corrective analysis of Dual-Phase-Lag (DPL) non-fourier heat conduction in functionally graded cylindrical materials with bi-directional property variations. For general purposes, the 2-D DPL model was employed and solved in a polar coordinate system for an FGM cylinder whose material properties vary exponentially in the axial and radial directions. The proposed model's analytical and numerical solutions were obtained through the SOV method and implicit FDM with a non-uniform grid. Moreover, the effect of the inhomogeneity parameter in the Fourier, Cattaneo–Vernotte (C–V), and DPL models has been analyzed. The results indicate that the DPL model achieves temperature stability in less time when contrasted with the C–V model. In addition, the reduced inhomogeneity parameters result in quicker attainment of a steady temperature and the induction of higher temperatures. The thermal wave propagation in the DPL model is consistently greater than that in the C–V model. In addition, an increase in time lag for heat flux enhances thermal wave properties (amplitude, wavelength, propagation speed etc.); conversely, an increase in time lag for temperature gradient counteracts wave properties and augments heat release. Nevertheless, the present outcomes offer a straightforward multivariate analytical and numerical solution for a finite cylinder's non-Fourier heat conduction equation under diverse boundary conditions.

The storage mechanisms of solid-solid supercapacitors based on graphene oxide (rGO/GO/rGO) were explored by Zhang Q et al. (Zhang et al., 2014) [1], using Density Functional Theory (DFT) and Impedance Spectroscopy (EIS) to elucidate the unusual capacitive behavior of GO sandwich films. Their study revealed alternating charged layers without diffusion zones. Analysis of complex impedance (Z*) data, ranging from 10−3 to 3.106 Hz, was conducted using an equivalent circuit, though this was limited to Nyquist plot data.To further investigate charge storage mechanisms, the current study delved deeper into complex impedance (Z*) and conductivity (σ*). A theoretical approach identified relaxation processes in the imaginary parts of (Z″) and (σ'') across frequencies. Extrapolation up to 3.10^9 Hz and deconvolution confirmed three distinct relaxation processes in Z* and σ*, similar to Cole-Cole relaxation, which describes Maxwell-Wagner-Sillars (MWS) relaxation. This reflects local electrical interactions between active sites on molecular chains and counterions, creating induced dipolar moments or diffusion processes.The identified relaxations at low, medium, and high frequencies correspond well with DFT results, attributed to specific regions: graphene oxide (GO), the (rGO/GO) interface, and reduced graphene (rGO). Key parameters extracted from each relaxation, such as relaxation time, ionic strength, and conductivity values at different frequencies, showed good correlation. This approach, based on deep conductivity (σ*) analysis, effectively highlighted the charge conduction and storage mechanisms in rGO/GO/rGO supercapacitor films.

Abstract Conventional assumptions about multiphase flow in gas condensate reservoirs often do not correlate with field production. This discrepancy stems from the various mechanisms influencing the multiphase process, which are inadequately represented in numerical models. One of the least understood mechanisms is the influence of the non-equilibrium thermodynamics on the flow in the wellbore region, where the reservoir pressure is below the dew point pressure. To address this problem, experimental and mathematical analyses were conducted using a microfluidic device designed to replicate the flow dynamics in a gas condensate system. The experimental results showed an 11% deviation from the initial pressure of condensate saturation when compared with the conventional assumption of local equilibrium in numerical models. Similarly, there is a 14% deviation between the experimental and simulated volumes of the condensate. These findings underscore the inadequacy of existing models to accurately predict the saturation profile of the condensate phase. A mathematical model based on a relaxation parameter was applied to account for non-equilibrium phase separation and the fog state of the aerosol as observed in the microfluidic experiment. Incorporating a relaxation parameter ( $$\tau$$ τ ) enhanced the accuracy of the prediction of the initial pressure of the condensate saturation and an improvement in the prediction of the condensate volumes from 76% to 97.2%. Consequently, it provides a valuable framework and insight on the non-equilibrium phase behavior of gas condensate systems under constant flow regimes.

The purpose of this paper is to demonstrate a new discovery regarding the interaction between materials and very low radio frequencies. Specifically, we observed a feedback response on an inertia active sensor when specific frequencies (around 2–4 kHz) are used to irradiate targeted pharmaceutical samples like aspirin or paracetamol drugs. The characteristics of this phenomenon, such as excitation and relaxation time, the relation between deceleration and a material's quantity, and signal amplitude, are presented and analyzed. Although the underlying physics of this phenomenon is not yet known, we have shown that it has potential applications in remote identification of compounds, detection, and location sensing, as well as identifying substances that exist in plants without the need for any processing. This method is fast, accurate, low-cost, non-destructive, and non-invasive, making it a valuable area for further research that could yield spectacular results in the future. [ABSTRACT FROM AUTHOR]

The frequency-dependent complex permittivity spectra (CPS) of the acrylonitrile (ACRN) and 1,4-dioxane (DX) binary mixture in the range from 10 MHz to 30 GHz were measured using the time domain reflectometry (TDR) technique. Experimentally obtained CPS was fitted into the Debye equation. Dielectric relaxation behaviours depend on the temperature and concentration of binary mixtures. The obtained dielectric parameters, the Kirkwood correlation, and the Bruggeman factor have been discussed to understand the molecular association and hydrogen bonding interactions in the mixture. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate a vendor‐agnostic multiparametric mapping scheme based on 3D quantification using an interleaved Look–Locker acquisition sequence with a T2 preparation pulse (3D‐QALAS) for whole‐brain T1, T2, and proton density (PD) mapping. Methods: This prospective, multi‐institutional study was conducted between September 2021 and February 2022 using five different 3T systems from four prominent MRI vendors. The accuracy of this technique was evaluated using a standardized MRI system phantom. Intra‐scanner repeatability and inter‐vendor reproducibility of T1, T2, and PD values were evaluated in 10 healthy volunteers (6 men; mean age ± SD, 28.0 ± 5.6 y) who underwent scan‐rescan sessions on each scanner (total scans = 100). To evaluate the feasibility of 3D‐QALAS, nine patients with multiple sclerosis (nine women; mean age ± SD, 48.2 ± 11.5 y) underwent imaging examination on two 3T MRI systems from different manufacturers. Results: Quantitative maps obtained with 3D‐QALAS showed high linearity (R2 = 0.998 and 0.998 for T1 and T2, respectively) with respect to reference measurements. The mean intra‐scanner coefficients of variation for each scanner and structure ranged from 0.4% to 2.6%. The mean structure‐wise test–retest repeatabilities were 1.6%, 1.1%, and 0.7% for T1, T2, and PD, respectively. Overall, high inter‐vendor reproducibility was observed for all parameter maps and all structure measurements, including white matter lesions in patients with multiple sclerosis. Conclusion: The vendor‐agnostic multiparametric mapping technique 3D‐QALAS provided reproducible measurements of T1, T2, and PD for human tissues within a typical physiological range using 3T scanners from four different MRI manufacturers. [ABSTRACT FROM AUTHOR]

The collision of drops of water and elastic liquids with a thin cylinder (fiber) has been studied. Aqueous solutions of polymers were used as elastic liquids, which simulated the rheological behavior of oral fluid—the main carrier of infections by airborne drops. Water as a Newtonian fluid was investigated to identify the elastic effects when comparing the collisions of Newtonian and non-Newtonian fluids—water and polymer solutions. The flight path of the drop and the cylinder axis are mutually perpendicular. Attention is focused on the difference between the collisions of water drops and drops of elastic liquids. In the experiments, the diameter of the drop was 3 mm, and the diameter of the horizontal stainless-steel cylinders was 0.4 and 0.8 mm. Drops were formed by the slow flow of liquid from a vertical stainless-steel capillary with an outer diameter of 0.8 mm, from which the drops were periodically separated under the influence of gravity. The velocity of the drop before the collision was determined by the distance between the end of the capillary and the target (cylinder); in the experiments, this distance was 5, 10, and 20 mm. The velocities of falling drops before impact were estimated in the range of 0.2–0.5 m/s. The collision process was monitored using high-speed video recording methods with frame rates of 240 and 960 Hz. Water and aqueous solutions of polyacrylamide with a molecular weight of 11 million and concentrations of 100 and 1000 ppm were used as test liquids. Experiments have shown that, depending on the height of the drop and the concentration of the polymer, various drop collision scenarios are possible: (1) short-term rebound of the drop from an obstacle, (2) braking and stopping the drop on the obstacle, (3) flow of the drop around a cylindrical obstacle while maintaining continuity and continuing free flight, (4) disintegration of the drop into two secondary drops, each with its own history of subsequent flight. [ABSTRACT FROM AUTHOR]

In this article, we study an electrically conductive Rosensweig model for ferrofluids, whose Bloch–Torrey regularization was studied by Hamdache and Hamroun (Appl Math Optim 81(2):479–509, 2020). We mainly prove the global existence of weak solutions to the non-regularized model under a certain smallness condition on the electric conductivity. Hence, our result not only solves a problem that was left open by Hamdache and Hamroun, but it can also serve as a confirmation that ferrofluids are naturally poor conductors of electric current. The proof, which is interesting in itself, is quite involved and relies on the Helmohltz–Leray decomposition of the magnetic fields and the use of renormalized solutions for the magnetization. We also give a rigorous and detailed description of the convergence of the global weak solutions towards the quasi-equilibrium in the relaxation time limit regime τ → 0 . [ABSTRACT FROM AUTHOR]

The present study displays a comprehensive investigation into the micro- and macrostructures of gluten and its responses to temperature-induced changes, employing various analytical techniques. The integration of time domain-nuclear magnetic resonance (TD-NMR), differential scanning calorimetry (DSC), size-exclusion high-performance liquid chromatography (SE-HPLC), field emission scanning electron microscopy (FESEM), solid-state nuclear magnetic resonance (ssNMR), and multiphoton laser microscopy (MLM) measurements facilitates the multidimensional examination of gluten's phase distribution and structure across various scales. Notably, TD-NMR helps to refine prior T2 assignments for hydrated gluten through dynamic T2 measurements at sub-zero temperatures. The innovative application of TD-NMR uncovers insights into freezable water quantities and their changes under varying temperature conditions. Through real-time analyses utilizing not only TD-NMR but also MLM techniques, along with SE-HPLC measurements, the study highlights increased lacunarities in the gluten structure, particularly between 60 and 85 °C. These structural changes are attributed to heating effects that unfold and denature proteins and culminate in aggregation and crosslinking phenomena, leading to the release of water into macropores, hence changes in the water distribution in the gluten matrix. [ABSTRACT FROM AUTHOR]

Relating the complex structures of electrodes to their charging dynamics is crucial for optimizing supercapacitors, which remains an experimental and theoretical challenge. Here, we construct a pore network model (PNM) that can be downward‐transformed into a well‐known transmission‐line model and a stack‐electrode model to describe the disordered porous structure of carbon‐based electrodes. A mathematical expression is derived using an equivalent circuit model of the PNM to quantify the relaxation times of the potential and concentration. The expression is then verified using numerical solutions based on the simplified Poisson–Nernst–Planck equations and experimental data. The structure of the PNM for experimental verification is directly extracted from a porous electrode reconstructed using a scanning electron microscopic image. A self‐driven optimization framework is proposed by coupling the derived expression with a genetic algorithm to generate an optimal porous structure that can be used to investigate the changing dynamics of the electrode. Our framework provides a general image–structure–performance optimization platform for understanding and accelerating charging dynamics in porous electrodes. [ABSTRACT FROM AUTHOR]

Between the techniques directed to studying the thermal properties of materials, we can cite the photothermal methods, including the thermal lens technique in this group. The technique of thermal lens spectroscopy has, in most cases, its temperature profile described by Fourier's Law of heat conduction. In this work, the temperature distribution was successfully represented through the hyperbolic heat conduction model. However, with the application of the hyperbolic model, the differential equation that describes the problem has no analytical solution; therefore, we used two techniques for their solution. The method of lines (purely numerical method) and the generalized integral transform technique (analytical-numerical method). Both approaches have excellent rates of convergence in their solutions. They also present the new agreement proposed solution with experimental data, thus, providing a new perspective for future work in this spectroscopic technique. [ABSTRACT FROM AUTHOR]

This study examined the usefulness of 1H T 1 relaxation measurements for evaluating the homogeneity of amorphous solid dispersion (ASD). Indomethacin and polyvinylpyrrolidone were used to prepare two kinds of ASDs. One was inhomogeneous ASD (ASD melt) prepared by a melt-quenching method, and the other was homogeneous ASD (ASD solvent) prepared by a solvent evaporation method. The T 1 relaxation was measured by the time-domain NMR (TD-NMR) technique using a low-field NMR system. Curve-fitting analysis of T 1 relaxation plots was conducted using the Akaike information criterion. This fitting analysis revealed that the T 1 relaxation of ASD melt and ASD solvent was biphasic and monophasic, respectively. ASD melt and ASD solvent were inhomogeneous and homogeneous on a nanometer scale, respectively, considering the spin diffusion of 1H nuclei. These T 1 results were consistent with the Raman mapping of ASDs. From the fitting analysis of 1H T 1 relaxation, we conclude that TD-NMR is a promising technique for evaluating ASD homogeneity. [ABSTRACT FROM AUTHOR]

The time domain nuclear magnetic resonance (TD-NMR) technique was employed to distinguish various water states, and the moisture migration during Elm wood (Ulmus rubra) heartwood vacuum drying was quantitatively analyzed. The transverse relaxation time (T2) was employed to establish the correlation between drying time and moisture migration. Additionally, the longitudinal relaxation time (T1) was utilized to identify two types of water states within the cell wall: OH bound water (B-water) and more freely bound water (C-water). Meanwhile, the changes in these two types of bound water during the drying were investigated. The results demonstrated an exponential decrease in the content of OH bound water and more freely bound water with drying time. OH bound water within the cell wall predominated, with only a small portion of more freely bound water experiencing migration loss when the moisture content (MC) dropped below 20 %. Furthermore, OH bound water exhibited higher migration rate compared to more freely bound water at 10–20 % MC, while the motion of OH bound water molecules became highly restricted and stronger binding to cell walls than more freely bound water at a MC level of below 10 %. These findings yield a theoretical foundation and empirical support for optimizing drying methods. [ABSTRACT FROM AUTHOR]

In this article, we present the results of low-temperature dielectric, magnetic and magnetodielectric properties of BiFeO3 nanoceramics prepared by auto-combustion method. Rietveld refinement results of X-ray diffraction data show that sample crystallizes in single-phase rhombohedral perovskite structure with R3c (No. 161) space group. The average crystallite size was found to be ≈ 600 Å from Williamson–Hall analysis. The temperature-dependent dielectric data have been presented in permittivity and modulus formalism to understand the relaxation dynamics. Three non-Debye-type relaxation processes were observed in the experimental window (173 to 423 K), which are explained using Kohlrausch–Williams–Watts (KWW) decay function. The temperature variation of relaxation times obeys Arrhenius's behaviour. The anomaly observed in the temperature dependence of relaxation times data near 240 K corresponds to the magnetic transition of BiFeO3. We found that single ionized oxygen vacancies with activation energy ranging from 0.4 to 0.8 eV are involved in the relaxation process. A crossover from AFM/PM to weak ferromagnetic ordering is observed at low temperature. The variation of capacitance with an applied magnetic field shows a hysteresis effect. The magnetocapacitance (MC%) changes by 3% at a magnetic field of 2 T for 200 kHz, indicating an intrinsic bulk magnetocapacitance effect in the ceramics. Hence, the above findings highlight the significance of the material as a potential candidate for device applications. [ABSTRACT FROM AUTHOR]