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The structural, electronic, optical and thermodynamic properties of the halide perovskite material Cs2AgBiCl6 have been investigated using the density functional theory (DFT) method. As a first step, the structural properties of Cs2AgBiCl6 were examined to determine an optimized lattice constant, which was then used to calculate other physical properties. Analysis of the electronic band structure reveals that Cs2AgBiCl6 exhibits semiconductor characteristics. Optical properties, in particular the refractive index, have been investigated in the 1–3 eV energy range, corresponding to the bandgap region of the material. In addition, thermodynamic properties were analyzed using the quasi-harmonic Debye model over a temperature range of 0–600 K and a pressure range of 0–8 GPa. It was found that the Debye temperature decreases with increasing temperature but increases with increasing pressure. [ABSTRACT FROM AUTHOR]

Adrenal gland-induced hypertension results from underlying adrenal gland disorders including Conn's syndrome, Cushing's syndrome, and Pheochromocytoma. These adrenal disorders are a risk for cardiovascular and renal morbidity and mortality. Clinically, treatment for adrenal gland-induced hypertension involves a pharmaceutical or surgical approach. The former presents very significant side effects whereas the latter can be ineffective in cases where the adrenal disorder reoccurs in the remaining contralateral adrenal gland. Due to the limitations of existing treatment methods, minimally invasive treatment options like microwave ablation (MWA) have received significant attention for treating adrenal gland disorders. A precise comprehension of the dielectric properties of human adrenal glands will help to tailor energy delivery for MWA therapy, thus offering the potential to optimise treatments and minimise damage to surrounding tissues. This study reports the ex vivo dielectric properties of human adrenal glands, including the cortex, medulla, capsule, and tumours, based on the data obtained from four patients (diagnosed with Conn's syndrome, Cushing's syndrome, and Pheochromocytoma) who underwent unilateral adrenalectomy at the University Hospital Galway, Ireland. An open-ended coaxial probe measurement technique was used to measure the dielectric properties for a frequency range of 0.5–8.5 GHz. The dielectric properties were fitted using a two-pole Debye model, and a weighted least squares method was employed to optimise the model parameters. Moreover, the dielectric properties of adrenal tissues and tumours were compared across frequencies commonly used in MWA, including 915 MHz, 2.45 GHz, and 5.8 GHz. The study found that the dielectric properties of adrenal tumours were influenced by the presence of lipid-rich adenomas, and the dielectric properties of Cushing's syndrome tumour were lowest in comparison to the tumours in patients diagnosed with Conn's syndrome and Pheochromocytoma. Furthermore, a notable difference was observed in the dielectric properties of the medulla and cortex among patients diagnosed with Conn's syndrome, Cushing's syndrome, and Pheochromocytoma. These findings have significant implications for the diagnosis and treatment of adrenal tumours, including the optimisation of MWA therapy for precise ablation of adrenal masses. [ABSTRACT FROM AUTHOR]

Abstract Adrenal gland-induced hypertension results from underlying adrenal gland disorders including Conn’s syndrome, Cushing's syndrome, and Pheochromocytoma. These adrenal disorders are a risk for cardiovascular and renal morbidity and mortality. Clinically, treatment for adrenal gland-induced hypertension involves a pharmaceutical or surgical approach. The former presents very significant side effects whereas the latter can be ineffective in cases where the adrenal disorder reoccurs in the remaining contralateral adrenal gland. Due to the limitations of existing treatment methods, minimally invasive treatment options like microwave ablation (MWA) have received significant attention for treating adrenal gland disorders. A precise comprehension of the dielectric properties of human adrenal glands will help to tailor energy delivery for MWA therapy, thus offering the potential to optimise treatments and minimise damage to surrounding tissues. This study reports the ex vivo dielectric properties of human adrenal glands, including the cortex, medulla, capsule, and tumours, based on the data obtained from four patients (diagnosed with Conn’s syndrome, Cushing's syndrome, and Pheochromocytoma) who underwent unilateral adrenalectomy at the University Hospital Galway, Ireland. An open-ended coaxial probe measurement technique was used to measure the dielectric properties for a frequency range of 0.5–8.5 GHz. The dielectric properties were fitted using a two-pole Debye model, and a weighted least squares method was employed to optimise the model parameters. Moreover, the dielectric properties of adrenal tissues and tumours were compared across frequencies commonly used in MWA, including 915 MHz, 2.45 GHz, and 5.8 GHz. The study found that the dielectric properties of adrenal tumours were influenced by the presence of lipid-rich adenomas, and the dielectric properties of Cushing's syndrome tumour were lowest in comparison to the tumours in patients diagnosed with Conn's syndrome and Pheochromocytoma. Furthermore, a notable difference was observed in the dielectric properties of the medulla and cortex among patients diagnosed with Conn's syndrome, Cushing's syndrome, and Pheochromocytoma. These findings have significant implications for the diagnosis and treatment of adrenal tumours, including the optimisation of MWA therapy for precise ablation of adrenal masses.

The Debye model has been developed to study the pressure dependence of the extended X-ray absorption fine structure Debye–Waller factor, the Debye frequency and temperature of hexagonal close-packed (hP2) metals. The effects of the non-ideal axial ratio c/a of hP2 structure on these thermodynamic quantities at high pressures have also been considered. Additionally, based on the combination of the Debye model and the Lindemann melting law, we derive the analytic expression of melting temperature of hP2 metals as a function of pressure. Numerical calculations have been implemented for Mg and Zn metals up to 20 and 50 GPa, respectively. We have shown that Debye frequency and temperature, as well as melting temperature of these two metals increase robustly with pressure and non-ideal axial ratio plays important role in these thermodynamic quantities. The remarkable consistency observed between our calculations and various experimental results validates the reliability of the currently presented melting curve. Meanwhile, at high pressure non-ideal axial ratio gives a small contribution to pressure-dependent Debye–Waller factor of Mg (up to 20 GPa) and Zn (beyond 20 GPa), and can be safely neglected in the suggested pressure range. [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]

The current study reports the pressure-driven phase change, and electronic and thermal properties of strontium oxide (SrO) and barium oxide (BaO) under pressure in different phases via a density functional theory (DFT). The metastable phases are predicated and have not yet been perceived in the previous calculations or experimental works. The transition pressures at which various phases transform and their electronic and thermal performances are also investigated. The electronic band profiles of the compounds have been computed using different exchange-correlation functions. According to the present study, the B1 phase is the most stable phase across the phases taken into consideration. The band structure results reveal the semiconducting behavior of these compounds in all phases. Furthermore, various thermal performances are also predicted. The current study is open to experimentally verify our several predictions. [ABSTRACT FROM AUTHOR]

Research on thorium and uranium phosphides/silicides has attracted tremendous scientific and technological interest on the basic and applied prospects. This owes mainly to their enhanced melting temperature, large density, neutron abundance, and enhanced thermoelectric performance. Herein, we report on the density functional theory (DFT)-based quantum analysis of thermodynamic properties of thorium phosphides (ThP) and thorium silicides (ThSi) via ThSixP1-x (x = 0, 0.25, 0.5, 0.75, 1) alloying scheme. For the theoretical computations of the targeted properties of ThSixP1-x silicides, we employed all electron potential with linearized augmented plane wave method as implemented in DFT. To incorporate the exchange-correlations, we treated energy potential by GGA density functional. The thermodynamic properties computed via Quasi-harmonic approximations (or Debye Model) are constant volume specific heat capacity (Cv), volume thermal expansion coefficient (α), Debye temperature (θD), Gruneisen parameter (γ), and thermal entropy (S). various doping ratio in view of Si/P renders a considerable modification of the thermodynamic performance and intermetallic alloying of ThP and ThSi. As such, the reported results hold great potential for fundamental and applied prospects in view of interface thermal management and energy storage applications, thermoelectric power generation, and green nuclear energy technology. [ABSTRACT FROM AUTHOR]

In this paper, two new effective operator splitting methods (SS-MD and SM-MD) for the Maxwell's equations for dispersive media in two dimensions transverse electric polarization (the 2D Maxwell–Debye TE model) are presented and analyzed. The splitting schemes consist of two sub-stages in each time step, each of which requires solving a number of 1D discrete sub-problems. The Crank–Nicolson approach is used to solve each sub-problem's time discretization. Both splitting methods satisfy the energy decay and are unconditionally stable. The convergence result of the SS-MD scheme is shown to be of first order in time and of second order in space based on the energy technique, whereas the SM-MD scheme is of second order in both time and space. We also analyze numerical dispersion analysis to obtain two identities of the discrete numerical dispersion relations of both splitting schemes. Examples and numerical experiments are provided to demonstrate and support our theoretical results. [ABSTRACT FROM AUTHOR]

A near-morphotropic phase boundary (MPB) composition of ternary 0.49BiFeO3-0.20Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 (BF-PMN-PT) ceramic was synthesized for various dielectric, ferroelectric and piezoelectric applications using the conventional solid-state reaction method via a two-step columbite precursor technique. Powder x-ray diffraction (XRD) confirms the perovskite phase of the synthesized ceramic with a monoclinic crystal structure belonging to the P1m1 space group. The dielectric properties and the relaxation mechanisms of this ternary ceramic were studied using dielectric spectroscopy measurements for the frequency range of 10 Hz to 1 MHz over a wide range of temperature from 50°C to 400°C. A good dielectric response was observed with a high dielectric constant value (~ 800) that decreases with increasing frequency. A phase transition temperature (Tc = 275°C) and a low dielectric loss were also observed. The dielectric exhibits a clear and distinct Debye-type relaxation in the ferroelectric phase. The measured dielectric data fit quite well with the modified Debye model. Various Debye fitting parameters were obtained which show a temperature-dependent nature. The value of Debye broadening parameter α exhibits a decreasing trend from 0.136 to 0.003 as temperature increases from 50°C to 200°C, after which it increases and attains a maximum value of 0.566 at 350°C. The Cole–Cole plot obtained from the measured data reveals the distributive nature of the sample's dielectric relaxation. [ABSTRACT FROM AUTHOR]

The problem of second-harmonic generation by a plane elliptically polarized electromagnetic wave in a thin optically nonlinear surface layer of a dielectric particle shaped as an ellipsoid of revolution is solved. The generalized Rayleigh—Gans–Debye approximation is used for an analytical description with taking into account the difference in refractive indices of the medium corresponding to the frequencies of the exciting and generated radiation. The limiting forms of functions are obtained, with the use of which the electric field strength of the generated radiation is expressed. The order of dependence of these functions on the linear dimensions is found, when the lengths of the semiaxes of the particle are small compared to the wavelength of the exciting radiation and their ratio remains constant. It was found that the power density of the generated radiation in this case is determined to a greater extent by the chiral components of the nonlinear dielectric susceptibility tensor and is proportional to the fourth power of the length of the semiaxis of the particle, if the shape of the spheroidal particle differs significantly from the spherical one. The solution of this problem, obtained by other authors, is supplemented for the possibility of applying to the description of generation in the surface layer of a dielectric particle not only in the form of a prolate, but also in the form of an oblate spheroid. Corrections of inaccuracies and misprints made in similar works by other authors are proposed. The relationships between the formulas used in these works are found, taking into account the corrections and the formulas used in this work. [ABSTRACT FROM AUTHOR]

A new approach of using AC conductivity as function of frequency and temperature has been proposed for analysing ferroelectric ceramic materials, especially those having Debye-type dielectric dispersion. A theoretical model for the AC conductivity has been validated with the measurements performed on 0.64PMN–0.36PT ceramic material. It has been found that the slope of the conductivity vs. frequency curve of the material having Debye-type dielectric dispersion shows a significant change at a certain frequency, called knee frequency, which shifts towards the high-frequency side when the temperature is increased. The signature parameters of the electrical conductivity curve have been identified that can be used for a quick estimate of the dielectric dispersion behaviour of the material. The difference in the slope of the two regions, separated by the knee frequency, is found to have a strong correlation with the relaxation time distribution factor. [ABSTRACT FROM AUTHOR]

In order to investigate the electromagnetic (EM) propagation characteristics and further get the channel models for indoor environments, a modified conformal finite‐difference time‐domain (CFDTD) method is introduced in this paper. Specifically, the dispersion characteristics of media are modeled by using the auxiliary differential equation (ADE) technique of the Debye model, and the EM field iterative equation is obtained by weighted‐length of various media in the conformal cells for the curved structure. The proposed method is used to simulate the channels of 2.4 GHz wireless fidelity (Wi‐Fi) network and 5G microcellular network, respectively, for the single‐ and complex multi‐room scenarios. The impulse response, power delay profile and path loss exponent are extracted from the simulation data to analyze the effective ultra‐wideband (UWB) channel characteristics. Compared with the traditional FDTD, the proposed method has the advantage of obtaining a stable and good accuracy solution and reducing the time step without the need to solve high‐order differential equations. [ABSTRACT FROM AUTHOR]

Fractal structure investigations of materials have a recent tradition in physics with applications to the natural sciences and technology. A new approach of fractal geometry in solids is analyzed, which allows the accurate evaluation of thermodynamic quantities for various values of fractional dimensions. Based on a fractal concept, the modified Einstein–Debye model and its application of thermodynamics are presented, which contribute to the evaluation of thermal properties as well as many materials. The reliable modified analytical expressions of the energy, heat capacities, entropy, enthalpy, and Gibbs free energy are established on the basis of modified Einstein–Debye approximation. This shows the perspective of the utilizing the fractal, describing quantities and parameters that analyze properties of nature. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of alloy carbide Fe3Mo3C are studied by combining density functional theory with quasi-harmonic Debye model at high temperature and high pressure. The ranges of pressure and temperature belong to 0～40 GPa and 0～1200 K, respectively. The calculated results show that the influences of pressure on volume ratio V/V0, bulk elastic modulus B and Debye temperature θ are greater than those of temperature. When the temperature is constant, bulk elastic modulus and Debye temperature increase rapidly with the increase of pressure. Compared with the influences of the pressure on the heat capacity Cv, entropy S and thermal expansion coefficient α, the temperature provides higher priority. When the pressure remains constant, the three physical parameters（Cv, S and α） all increase monotonically with temperature increasing. The heat capacity and thermal expansion coefficient increase rapidly with the temperature at first, then tend to be flat, and finally are close to the Dulong-Petit limit. [ABSTRACT FROM AUTHOR]

Context: In this work, a comprehensive study concerning the physical properties of ternary alloys system (AlP1−xBix) at different concentrations is presented. The obtained results from our first-principle calculations are compared with previously reported studies in the literature and discussed in detail. Our computed results are found in a nice agreement where available with earlier reported results. Electronic band structures at the above-mentioned concentrations are also determined. Likewise, the impact of the varying temperature and pressure on Debye temperature, heat capacity, and entropy is analyzed as well. Furthermore, elastic constants and related elastic moduli results are also computed. Our results show that alloys are stable and found to be in brittle nature. This is the first quantitative study related to ternary alloys (AlP1−xBix) at mentioned concentrations. We soon expect the experimental confirmation of our predictions. Method: The calculations are performed, at concentrations x=0.0, 0.25, 0.5, 0.75, and 1.0 by using the "full potential (FP) linearized (L) augmented plane wave plus local orbital (APW+lo) method framed within density functional theory (DFT)" as recognized in the "WIEN2k computational code". The "quasi-harmonic Debye model" approach is employed to determine the thermal properties of the title alloys. [ABSTRACT FROM AUTHOR]

This paper delves into an examination of the structural, electronic, magnetic, thermal, and transport properties of RbNpF 3 perovskite using first-principle calculations within density functional theory (DFT). Employing the Birch Murghanan's equation of state the geometric optimization of structure confirms the cubic configuration with the Pm-3m (No. 221) space group and stability in ferromagnetic phase. Effect of high pressure on electronic and magnetic properties was also studied. Electronic band structure and density of states assessments confirm metallic character over a wide range of pressure. Furthermore, for the examined compound we have calculated the heat capacity, thermal expansion coefficients and Grüneisen parameter by using the Debye model. We have also calculated the different transport parameters like Seebeck coefficient, electrical conductivity, thermal conductivity and power factor as a function of temperature. These parameters indicate the potential application of the material for generating thermoelectric energy. [ABSTRACT FROM AUTHOR]

A first-principles method based on the density functional theory (DFT) was employed in conjunction with quasi-harmonic Debye model to investigate the structural, elastic, and thermodynamic properties of a series of AB 2 -based Laves phases alloys and their hydrides. Simulation results revealed that the studied materials possess the Laves phase structure with lattice parameters comparable to experimental findings. For the first time, to the best of our knowledge, mixing entropy determined using Debye model was used to classify alloys into (Low- Medium-High Entropy Alloys) LEA, MEA and HEA categories rather than the commonly used ideal solution model, which is often inaccurate and ignores the impact of temperature. Lattice analyses of the alloy materials indicated that cell volume increases with the addition of elements, while the enthalpy of hydride formation indicates that hydrogen absorption in these alloys is exothermic and that the 3.00 H/F.U configuration is energetically stable. The alloys and their hydrides are metallic with no band gap at the Fermi level. The thermodynamic properties were studied using the quasi-harmonic Debye model and it was found that Bulk modulus decreases with increasing volume, and the hydrides possess lower bulk modulus compared to their metallic counterparts. Moreover, Debye temperature decreases with the gradual addition of elements, indicating weaker chemical bonds in ternary and other alloys. All hydrides have lower Debye temperature than their parent alloy materials. Finally, The alloys are classified into low-, medium-, and high-entropy alloys based on mixing entropy calculated using the Debye model. TiMn 2 is classified as a low-entropy alloy, ZrMn 2 , Ti 0.5 Zr 0.5 Mn 2 , and Ti 0.5 Zr 0.5 MnFe as medium-entropy alloys, and Ti 0.5 Zr 0.5 (MnCr) 2 , Ti 0.5 Zr 0.5 Mn 2/3 Fe 2/3 Cr2/ 3 , and Ti 0.5 Zr 0.5 Mn 0.5 Fe 0.5 Cr 0.5 Ni 0.5 as high-entropy alloys. [Display omitted] • Finite-temperature thermodynamics of multi-element AB2 hydrides are explored using DFT. • The effects of substituting Mn by Cr, Fe and Ni on the thermodynamics properties Ti/ZrMn2 are evaluated. • The entropy and mixing entropy of alloys and their hydrides are found using the Debye Model. • ΔSmix of TiZr(Mn,Fe,Cr)2 or TiZr(Mn,Fe,Cr,Ni)2 is >1.78 R at room temperature. • Absolute values of ΔS of Ti-based hydride are drastically reduced from H2 configurational entropy (96–114 J/mol K). [ABSTRACT FROM AUTHOR]

A near morphotropic phase boundary (MPB) composition of PMN-PT ceramic, 0.64Pb(Mg 1/3 Nb 2/3)O 3 -0.36PbTiO 3 , has been synthesized for various piezoelectric, ferroelectric and dielectric applications. The relaxation mechanisms and dielectric characteristics of this solid solution have been investigated with dielectric spectroscopy measurements in the frequency range of 20 Hz–2 MHz. The dielectric properties have shown distinct and prominent Debye type relaxation at the temperatures corresponding to the ferroelectric phase. The peak in dielectric loss parameter has been found to be dominated by the dc conductivity in paraelectric phase. The experimentally obtained values of various parameters have been found in agreement with the values obtained by fitting of the experimental data in Debye model. An excellent agreement of the results with Debye distribution of relaxation times was obtained with the distribution parameter α showing minima around the ferro-to para-electric phase transition. Different activation energies of the relaxation time have been observed in the ferroelectric and paraelectric phases. An average relaxation time has been found to decrease from ∼10−3 s to ∼10−6 s with the increasing temperatures. [ABSTRACT FROM AUTHOR]

In this study, we have explored the structural, electronic and thermal properties of La x Sc 1 - x N ternary alloys in rock-salt structure using the full-potential linearised augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). To calculate the exchange-correlation energy and potential, we have used the Wu–Cohen generalised gradient approximation and the modified Becke–Johnson. We investigated the effect of composition on lattice parameters, bulk modulus and band gap. The variation of the calculated lattice constant with lanthanum composition is practically linear and shows a small deviation of the obtained results from Vegard's law. Moreover, the effect of thermal macroscopic properties was also investigated employing the quasiharmonic Debye model, which takes into account the lattice vibrations. We have found a good accord between our results, the experimental data and previous theoretical results available in the literature for the binary compounds which can be a support for the ternary alloys in the future. [ABSTRACT FROM AUTHOR]

Curve-fitting means the determination of the set of parameters that best fit the input data set as expressed by a given function that is usually non-linear. The paper addresses the curve fitting of Debye and Cole–Cole models to a dielectric permittivity spectrum. The success of a nonlinear curve fit heavily depends on the choice of the algorithm and how close the starting point is to the solution. For these reasons, two different algorithms, the Levenberg–Marquardt and the Variable Projection algorithms, were used for constrained optimization and compared, with particular reference to robustness with respect to the choice of the starting point of the reconstruction procedure. The dielectric spectrum of blood plasma with different glucose concentrations is taken as reference data and a Monte Carlo analysis was conducted to evaluate accuracy and precision in the two methods provided as the distance of the initial parameters from the true value's changes. In general, both algorithms with constraints on the parameters provide good results for practical situations, although the Variable Projection Algorithm has a greater computational burden for large data sets. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive examination of the τ 8-Al 2 Fe 3 Si 4 solid solution, investigating its crystal chemistry and short-range order. To do so, Density functional theory (DFT) calculations were performed, simulating partial substitutions of Al and Si on the four mixed sites of the structure. Our results indicates a negligible contribution from the SRO, allowing the Bragg–Williams approximation to be used to describe its crystal chemistry. Subsequently, systematic substitutions of Al and Si on all mixed sites generated a complete set of ordered structures, called end-members. The formation enthalpies, equation of state and elastic constants for each end-member were calculated, allowing the Gibbs free energy of the solid solution to be derived using the Debye–Wang model. On the basis of this new theoretical insights, a thermodynamic model was developed, predicting the Si occupancy factors in all the mixed sites of the structure at different temperatures, allowing the quantification of its chemical ordering. [ABSTRACT FROM AUTHOR]

The term thermal capacity appears to suggest a storable thermal quantity. However, this claim is not redeemed when thermal capacity is projected onto "heat", which, like all energy forms, exits only in transit and is not a part of internal energy. The storable thermal quantity is entropy, and entropy capacity is a well-defined physical coefficient which has the advantage of being a susceptibility. The inverse of the entropy capacity relates the response of the system (change of temperature) to a stimulus (change of entropy) such as the fluid level responses to a change in amount of fluid contained in a vessel. Frequently, entropy capacity has been used implicitly, which is clarified in examples of the low-temperature analysis of phononic and electronic contributions to the thermal capacity of solids. Generally, entropy capacity is used in the estimation of the entropy of a solid. Implicitly, the thermoelectric figure of merit refers to entropy capacity. The advantage of the explicit use of entropy capacity comes with a descriptive fundamental understanding of the thermal behaviour of solids, which is made clear by the examples of the Debye model of phonons in solids, the latest thermochemical modelling of carbon allotropes (diamond and graphite) and not least caloric materials. An electrocaloric cycle of barium titanate close to its paraelectric–ferroelectric phase transition is analysed by means of entropy capacity. Entropy capacity is a key to intuitively understanding thermal processes. [ABSTRACT FROM AUTHOR]

Complex permittivity in terms of dielectric constant (ε') and dielectric loss (ε") of medicinal compound paracetamol in dimethyl sulfoxide (DMSO) solvent was determined with different weight fractions at microwave frequency 9.85 GHz at constant temperature 27 ℃. The information on dielectric properties is related to the properties of the substance for preparation of granules while making dosage forms like tablets and capsules. Refractive index (nD), dielectricconstant (ε') and dielectric loss (ε") were used for the measurement of relaxation time (τ). The viscosity (η) and density of paracetamol in DMSO were determined using a conventional Ostwald's viscometer and specific gravity bottle respectively. The aim of the present work was to study the dielectric properties of the drugs and attempted to determine their correlations with density and viscosity to understand the behavior of the dielectric properties under different conditions like a concentration in solution. It was observed that there was a strong correlation of dielectric properties like dielectric constant, dielectric loss and dielectric relaxation time with viscosity and density. The absolute values of correlation coefficient (R) were in the range of 0.946 to 0.987 for paracetamol-DMSO system, indicating a strong correlation.

An empirical partition function, f , for polyethylene (PE) was determined based on a pressure (PV)-volume (V)-temperature (TV)-entropy (SV) isochoric equation of state where the variables of PV, TV and SV were evaluated by using the experimental P-V-T data and the isochoric heat capacity for PE. The empirical partition function is expressed by summation of the terms of T − 1 , T , T 3 and a (V) e − θ i T with i = 1 to 6 where the θ i temperatures in the Boltzmann factors were in the range of θ i = 70.5 to 423 K. The thermodynamic derivatives, such as bulk modulus, κ T , and isochoric heat capacity, CV, over a wide range of pressure were evaluated based on the two types of the partition functions derived from the isochoric equation of state and the reformed Debye partition function with θ i = i θ 1 and θ 1 = 70.5 K. The reliability of the reformed Debye partition function was checked by the partition function calculated from the empirical isochoric equation of state. [ABSTRACT FROM AUTHOR]

Multivariable component analysis is one of the most challenging topics in the area of microwave resonator based sensors. In this article, a new approach is developed for introducing new independent features for analyzing the volumetric fraction of water, ethanol, and gasoline in E85 biofuel samples. The novel features are extracted based on a multiharmonics measurement of frequency and amplitude variations of the transmission response of the resonator over multiple harmonics due to nonlinearity and uniqueness of the permittivity spectrum of different materials. For the experiments, 60 samples of biofuel mixtures are prepared with randomly chosen percentages of each of the components. An artificial neural network is trained with the extracted features from 40 of the samples and tested over the remaining 20 samples. The average relative error in determining the water concentration in the biofuel samples of as low as 0.09% is achieved. The experimental results verify the capability of the sensor for selective analysis of all the components of a multivariable mixture simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, the numerical design and simulate a biosensor to detect tumors and cancerous tissues by using metamaterial structures in the microwave regime are presented. The presented structure consists of a microstrip transmission line and a split ring resonator (SRR) that form a bandpass filter and has a unique resonance frequency. Given that cancerous tissues have larger volumes of water than healthy tissues. As a result, they have a higher dielectric coefficient and conductivity which use for healthy tissues detection. By placing biological samples on SRR, its dielectric constant changes, therefore, the resonance frequency of the system changes. We can measure the types of biological tissues by measuring these changes. We used the Debye model to simulate the muscles. Also, the benefits of this biosensor are easy to use and operation, but they have lower sensitivity than terahertz biosensors. The minimum resolution for samples under test in this biosensor is 10 MHz.

A newly-developed commercial coaxial probe kit (DAK-TL) is used to characterize the electromagnetic properties of glucose-loaded samples prepared at a range of concentrations 0.7-1.2 mg/ml similar to Type-2 normal diabetics in a broad range of frequencies from 300 MHz to 67 GHz using two different 50 Ω open-ended coaxial probes. The objective is to determine the spectrum portion of the most sensitivity to slight variations in glucose concentrations and to identify the amount of change in the dielectric permittivity and loss tangent due to different concentrations of interest. The millimeter-wave range 50-67 GHz has shown to be promising for acquiring both high sensitivity and sufficient penetration depth for the most interaction between the glucose molecules and electromagnetic waves. Subsequently, the relative permittivity of the glucose-water mimicking samples are modeled in this mm-wave band using a single-pole Debye model with independent coefficients. The fitted Debye model is used to design a simple low-cost highly-sensitive integrated mm-wave sensing structure that utilizes the travelling-wave Whispering Gallery Modes (WGMs) launched in a dielectric disc resonator (DDR) when coupled to a dielectric image waveguide (DIG). The proposed sensor is used for continuous monitoring of glucose levels in blood mimicking aquatic solutions by tracking the variations in the magnitude and phase of the WGM transmission resonances in the mm-wave spectrum. This happens in reaction to the strong interactions of the coupled WGM evanescent field with the glucose samples loaded on top of the DDR inside a container. The sensor exhibits a high sensitivity performance (2.5-7.7 dB/[mg/ml]) for the two proposed DIG layouts, straight and curved, at the lower-order modes WGH600 and WGH700 of its five pure WGH modes supported in the frequency range 50-70 GHz as demonstrated by numerical simulations in a 3D full-wave EM solver and validated through proof-of-concept measurements.

A model function of seawater, which specifies the dielectric constant of seawater as a function of salinity, temperature, and frequency, is important for the retrieval of sea surface salinity using satellite data. In 2017, a model function has been developed based on measurement data at 1.4134 GHz using a third-order polynomial expression in salinity ($S$) and temperature ($T$). Although the model showed improvements in salinity retrieval, it had an inconsistent behavior between partitioned salinities. To improve the stability of the model, new dielectric measurements of seawater have been made recently over a broad range of salinities and temperatures to expand the data set used for developing the model function. The structure of the model function has been changed from a polynomial expansion in $S$ and $T$ to a physics-based model consisting of a Debye molecular resonance term plus a conductivity term. Each unknown parameter is expressed in $S$ and $T$ based on the expanded measurement data set. Physical arguments have been used to limit the number of unknown coefficients in these expressions to improve the stability of the model function. The new model function has been employed in the retrieval algorithm of the Aquarius satellite mission to obtain a global salinity map. The retrieved salinity using a different model function is compared with in situ data collected by Argo floats to evaluate the impact and the performance of model functions. The results indicate that the new model function has significant improvements in salinity retrieval compared with other existing models. [ABSTRACT FROM AUTHOR]

In this article, the quantum dots were employed to prepare gas sensing films, whose grain size was controlled up-to twice the Debye length, which is beneficial to investigate the grain size effect within a certain range, on the sensing mechanism and sensing mechanism of the gas sensors, as Debye length is strongly related to barriers of grain boundaries. In order to clarify the relationship of gas sensing mechanism to grain size and Debye length, the grain size of ZnO films were controlled by heating conditions like reaction temperature and reaction time of Zn(OAc)2 and LiOH, while the Debye length was influenced by operating temperature. The sensing ability of ZnO films with different grain sizes were analyzed under different conditions, when employed to H2S gas. Interestingly, the best sensitivity were observed for grain size much closer to two times of the Debye length. In order to investigate this phenomenon, a Debye model of grain size effects has been derived based on the basic chemical reactions between H2S and absorbed oxygen ions on surfaces of ZnO grains. It indicated that the gas sensitivity would reach the highest sensitivity when the grain size is twice the Debye length, which is in full agreement with experiment’s results. [ABSTRACT FROM AUTHOR]

A new analytical method for the evaluation of heat capacities of semiconductors (GeS, GeSe, GeTe, and SnS) has been proposed using the Einstein-Debye approximation. These formulae differ from the Debye model representations and they involve a combination of the Einstein and Debye approximations. The proposed method allows developing an increasing accuracy for the determination of the temperature dependent heat capacities of semiconductors GeS, GeSe, GeTe and SnS. The approach suggested in this study for calculation of heat capacities is very well suitable to determine other thermodynamical properties of materials. The temperature dependence of heat capacities of GeS, GeSe, GeTe and SnS semiconductors has been evaluated and shows a good agreement with literature at different temperature ranges. [ABSTRACT FROM AUTHOR]

The dielectric properties of Maillard reaction solutions (MRSs) formed between 10 amino acids [glycine (Gly), proline (Pro), cysteine (Cys), glutamine (Gln), lysine (Lys), methionine (Met), histidine (His), arginine (Arg), tyrosine (Tyr), and tryptophan (Try)] and glucose heated for 0–5 min using microwave irradiation were studied in the frequency range of 300–3000 MHz at 25.0 ± 0.5 °C. The critical frequencies of the MRSs were in the range of 0.81–1.98 GHz and increased as the heating time increased, with the exception of the MRS formed between Gln and glucose. The color difference (ΔE) of the MRSs increased as the heating time increased; alkaline amino acids exhibited the most significant change, reaching a maximum ΔE of 12.63 compared to non-polar and neutral polar amino acids. The penetration depth of the MRSs formed between alkaline amino acids and glucose decreased at 915 and 2450 MHz upon increasing the isoelectric point (pI) (p < 0.05). However, the penetration depth of non-polar and neutral polar amino acids increased upon increasing pI (p < 0.05). Non-polar amino acids required the highest energy [20.0 (± 0.20) × 10−21 J], followed by neutral polar amino acids and alkaline amino acids [0.3 (± 0.01) × 10−21 J]. The less energy required during the Maillard reaction, the easier the reaction could start. Finally, the real and imaginary parts of the Debye model were used to calculate the dielectric constant and dielectric loss factor of the MRSs formed between the amino acids and glucose and were in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

A quantum description of the surface waves in an isotropic elastic body without the use of the semiclassical quantization is proposed. The problem about the surface waves is formulated in the Lagrangian and Hamiltonian representations. Within the framework of the generalized Debye model, the contribution of the surface phonons ("rayleighons") to thermodynamic functions is calculated. It is emphasized that the role of the surface phonons can be significant and even decisive in low-dimensional systems, granular and porous media, and that their contribution to the total heat capacity increases with decreasing temperature. [ABSTRACT FROM AUTHOR]

Electrical bioimpedance is a non-invasive and radiation-free technique that was proposed to be used in different clinical areas, however, its practical use is limited due to its low capacity to discriminate between tissues. In order to overcome this limitation, our research group proposes to incorporate the contrast media into the electrical bioimpedance procedure. The main objective of the present study was to assess the crystalloid solutions as a possible contrast media to discriminate between different tissue types in the bioimpedance technique. Two medical-grade crystalloid solutions (Hartmann and NaCl 0.9%) were injected into three biological ex vivo models: kidney, liver, and brain. BIOPAC system was used to acquire bioimpedance data before and after the injections. The data was adjusted to the Debye electrical model. The analysis of measured values showed substantial bioimpedance disparities in tissues subjected to isotonic solutions. The NaCl solution exhibited more pronounced changes in electrical parameters compared to the Hartmann solution. Similarly, NaCl solution displayed superior discriminatory capabilities among tissues, with variations of 465%, 157%, and 206%. Distinct spectral modifications were identified, with tissues demonstrating unique responses at each frequency of analysis relative to untreated tissue. Variations in bandwidth alterations were discernible among tissues, providing clear distinctions. In conclusion, the research showed that the crystalloid solution exhibited greater sensitivity and superior tissue contrast at specific frequencies. This study's findings underscore the feasibility of implementing crystalloid solutions to enhance tissue discrimination, similar to the effects of contrast agents. • Crystalloid solutions change impedance parameters in ex vivo models. • In the liver, the Hartman solution causes a decrease in bandwidth change. • The data presented acceptable adjustments to the Debye model. • Crystalloid solutions are the viable contrast media for bioimpedance applications. [ABSTRACT FROM AUTHOR]

The operation of antennas deployed in mobile terminals is affected by the presence of human tissue in their near-field region. Therefore, testing the antenna performance, when the radiator is located in close vicinity to the user, is of paramount importance for any handset. In order to conduct such a study, knowledge about the dielectric properties of relevant human tissues is needed. In this paper, the results for in vivo measured complex relative permittivity of the dry and wet human hand palm and fingertip of thumb are presented. For the sake of having a broader set of data, the palms of 22 individuals and thumbs of 16 individuals are tested at multiple points. The measurements are conducted over the frequency band of 5-67 GHz by using an open-ended coaxial probe. The single-pole Cole-Cole model is used for fitting the measured results. Furthermore, the fitting parameters for the multi-pole Debye model are extracted by using the Cole-Cole ones. The effect of the difference in the dielectric properties between dry and wet palm on the performance of a dual-element PIFA antenna array (operating in the band of 5.8-7.7 GHz) is numerically studied. Useful finding for antenna designers is that the S-parameters and radiation efficiency of the antennas are insensitive to the change in the complex permittivity of the hand.

Curve-fitting means the determination of the set of parameters that best fit the input data set as expressed by a given function that is usually non-linear. The paper addresses the curve fitting of Debye and Cole–Cole models to a dielectric permittivity spectrum. The success of a nonlinear curve fit heavily depends on the choice of the algorithm and how close the starting point is to the solution. For these reasons, two different algorithms, the Levenberg–Marquardt and the Variable Projection algorithms, were used for constrained optimization and compared, with particular reference to robustness with respect to the choice of the starting point of the reconstruction procedure. The dielectric spectrum of blood plasma with different glucose concentrations is taken as reference data and a Monte Carlo analysis was conducted to evaluate accuracy and precision in the two methods provided as the distance of the initial parameters from the true value’s changes. In general, both algorithms with constraints on the parameters provide good results for practical situations, although the Variable Projection Algorithm has a greater computational burden for large data sets.

The precise determination of diffusive properties is presented for a system described by the generalized Langevin equation. The time-dependent fractional diffusion function and the Green-Kubo relation as well as the generalized Stokes-Einstein formula, in the spirit of ensemble averages, are reconfigured. The effective friction function is introduced as a measure of the influence of frequency-dependent friction on the evolution of the system. This is applied to the generalized Debye model, from which self-oscillation emerges as indicative of ergodicity that breaks due to high finite-frequency cutoff. Moreover, several inconsistent conclusions that have appeared in the literature are revised.

Debye model is used for approximating the frequency dependent complex effective permittivity of the composite structures in filter and shielding applications at microwave frequencies. In Debye model, desired shielding effectiveness (SE) is obtained by determining the Debye parameters using trial and error method. But this may result in wasting time or not converging to an optimum solution. In this work to overcome this problem Debye parameters were optimized by using Differential Evolution (DE) algorithm. A Maxwell Garnett (MG) mixing rule was applied to these optimized parameters to obtain frequency selective surface (FSS) parameters. 12dB shielding threshold was chosen between 0.05 – 5GHz frequency range. In accordance with the obtained parameters of FSS, a structure was designed in CST simulation software and simulations had been conducted to obtain SE results. It was seen that the results obtained from analytical computations agree with those obtained from simulations. [ABSTRACT FROM AUTHOR]

The Voltage Response measurement since its introduction in the 1960s has been used successfully for the diagnostics of electrical insulation. The method is based on two quantities of decay and return voltage slopes and can be used to study the conduction and polarization processes inside the insulation. Extended Voltage Response method, being an advanced version of the Voltage Response measurement helps in further studying the polarization process by using a large polarization spectrum and hence dielectric relaxation processes. These dielectric relaxation processes can be modeled by the Debye model. Since as most of the techniques used for diagnostic purpose does not give the information about the conduction and polarization processes separately, it is difficult to determine the R-C parameters of the Debye model. The Voltage Response technique is very useful in this regard because of the two voltage slopes. The paper shows a novel experimental benchmark for testing the function fitting methodologies of the Voltage Response methodologies, which helps in determining the R-C parameters. Moreover, the problem can be used for testing the novel genetic, evolutionary algorithms, where benchmarking is an actual challenge. The proposed nonlinear function fitting method uses the genetic algorithms via the Ārtap framework, which lets it possible to select the most accurate optimization algorithm from the provided list of the algorithms and achieve better fitting precision, faster calculation time or more powerful processing ability. [ABSTRACT FROM AUTHOR]

In this paper we present a Transmission Line Matrix (TLM) algorithm for the simulation of electromagnetic wave interaction with a Debye dispersive medium. This new formulation is based on the use of the polarization currents in the medium. The auxiliary differential equation (ADE) method is considered to deal with dispersion after the classical discretization. The accuracy and efficiency of this approach were tested on 1D Debye medium by calculating the reflection coefficient on an air-dielectric interface. The potential of the developed algorithm to model the existence of tumors in a human breast is also demonstrated. The obtained results compared with the analytic model show a good agreement. The number of operations needed for each iteration has been reduced, hence the computational time in comparison with time convolution techniques, while maintaining a comparable numerical accuracy.

The term thermal capacity appears to suggest a storable thermal quantity. However, this claim is not redeemed when thermal capacity is projected onto “heat”, which, like all energy forms, exits only in transit and is not a part of internal energy. The storable thermal quantity is entropy, and entropy capacity is a well-defined physical coefficient which has the advantage of being a susceptibility. The inverse of the entropy capacity relates the response of the system (change of temperature) to a stimulus (change of entropy) such as the fluid level responses to a change in amount of fluid contained in a vessel. Frequently, entropy capacity has been used implicitly, which is clarified in examples of the low-temperature analysis of phononic and electronic contributions to the thermal capacity of solids. Generally, entropy capacity is used in the estimation of the entropy of a solid. Implicitly, the thermoelectric figure of merit refers to entropy capacity. The advantage of the explicit use of entropy capacity comes with a descriptive fundamental understanding of the thermal behaviour of solids, which is made clear by the examples of the Debye model of phonons in solids, the latest thermochemical modelling of carbon allotropes (diamond and graphite) and not least caloric materials. An electrocaloric cycle of barium titanate close to its paraelectric–ferroelectric phase transition is analysed by means of entropy capacity. Entropy capacity is a key to intuitively understanding thermal processes.

Planar microwave sensors are considered an attractive choice to noninvasively probe the dielectric attributes of biological tissues due to their low cost, simple fabrication, miniature scale, and minimum risk to human health. This paper develops and measures a novel microwave biosensor for non-invasive real-time monitoring of glucose level. The design comprises a rectangular plexiglass channel integrated on a triple-pole complementary split ring resonator (TP-CSRR). The proposed sensor operates in the centimeter-wave range 1–6 GHz and is manufactured using PCB on top of an FR4 dielectric substrate. The sensor elements are excited via a coupled microstrip transmission-line etched on the bottom side of the substrate. The integrated CSRR-based sensor is used as a near-field probe to non-invasively monitor the glucose level changes in the blood mimicking solutions of clinically relevant concentrations to Type-2 normal diabetes (70–120 mg/dL), by recording the frequency response of the harmonic reflection and transmission resonances. This indicates the sensor's capability of detecting small variations in the dielectric properties of the blood samples that are responsive to the electromagnetic fields. The proposed sensor is verified through practical measurements of the fabricated design. Experimental results obtained using a Vector Network Analyzer (VNA) demonstrate a sensitivity performance of about 6.2 dB/(mg/ml) for the developed triple-pole sensor that significantly outperforms the conventional single-pole and other proposed sensors in the literature in terms of the resonance amplitude resolution. [ABSTRACT FROM AUTHOR]

The pressure effects on atomic mean‐square relative displacement characterizing the extended X‐ray absorption fine structure (EXAFS) Debye–Waller factor of iron metal have been investigated based on the Debye model. The analytical expressions of the Debye frequency and EXAFS Debye–Waller factor have been derived as functions of crystal volume compressibility. Based on the well established equation‐of‐state including the contributions of the anharmonic and electronic thermal pressures, numerical calculations have been performed for iron up to a pressure of 220 GPa and compared with experimental data when possible. These results show that the Debye frequency increases rapidly with compression, and beyond 150 GPa it behaves as a linear function of pressure. Meanwhile the mean‐square relative displacement curve drops robustly with pressure, especially at pressures smaller than 100 GPa. This phenomenon causes the enhancement of EXAFS signals at high pressure. Reversely, the increasing of temperature will reduce the amplitude of EXAFS spectra. [ABSTRACT FROM AUTHOR]