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This paper presents sound absorbing structure constructed using multiple layers of fibrous papers. Sound absorbing materials converts sound wave into thermal energy due to the porosity. The proposed sound absorbing structure has helical-like shapes in layered format with cyclic winding of the mulberry papers and coconut fibers. The acoustic properties changes depending on the thickness of the air cavity between the thin layers and porosity of the layers themselves. Sound absorption coefficients were measured using two-microphone impedance tube in order to investigate the acoustic property variations with porosity. The measured results were compared to predictions utilizing wave propagations through a slit for verification of the sound absorbing mechanism. A simple method for improving the sound absorption with less material by composite structure is proposed and verified through the experiment. Dynamic stiffness and loss factor of the helical-shaped sound absorbers were measured and compared by analyzing supporting properties to the vibrating beam. Depending on the construction method, the frame dynamic properties showed variation even when the sound absorption was identical. This information is required for optimal design of absorbing layers for specific noise control applications. [ABSTRACT FROM AUTHOR]

Knowledge of the optical properties of blood plays important role in medical diagnostics and therapeutic applications in laser medicine. In this paper, we present a very rapid and accurate artificial intelligent approach using Dragonfly Algorithm/Support Vector Machine models to estimate the optical properties of blood, specifically the absorption coefficient, and the scattering coefficient using key parameters such as wavelength (nm), hematocrit percentage (%), and saturation of oxygen (%), in building very highly accurate Dragonfly Algorithm-Support Vector Regression models (DA-SVR). 1000 training and testing sets were selected in the wavelength range of 250-1200 nm and the hematocrit of 0-100%. The performance of the proposed method is characterized by high accuracy indicated in the correlation coefficients (R) of 0.9994 and 0.9957 for absorption and scattering coefficients, respectively. In addition, the root mean squared error values (RMSE) of 0.972 and 2.9193, as well as low mean absolute error values (MAE) of 0.2173 and 0.2423, this result showed a strong match with the experimental data. The models can be used to accurately predict the absorption and scattering coefficients of blood, and provide a reliable reference for future studies on the optical properties of human blood. [ABSTRACT FROM AUTHOR]

The massless Dirac electron shows a linear energy dispersion in topological insulators (TIs) and these materials posses interesting properties such as high mobility, tuneable density and protection against backscattering over the time reversal symmetry and strong spin-orbit interaction. The flexibility is also an important parameter for development of wearable devices specially THz detector for imaging and quantum devices for optoelectronics applications. In this research work first time Bi 2 Te 3 TIs thin film is fabricated on inhouse develop metallic multi wall carbon nanotubes flexible paper (MWCNT-FP) and characterized by terahertz-time domain spectroscopy acquired at room temperature. This research work delivers exclusive opportunities to explore interesting phenomena in topological surface states and topological phase transition in Bi 2 Te 3 TIs thin film. Here, we measured terahertz absorption, optical density conductance and conductivity. An excellent broad band absorption is observed between 0.02 and 3.0 THz. The real conductance level is scientifically quite linear below 3.0 meV and thereafter certain increase. Similar trend is observed for the study of an imaginary conductance with respect to photon energy. The optical conductivity is observed in the range of 0.02–2.0 THz. • The Bi 2 Te 3 TIs thin film on multi wall carbon nanotubes flexible paper (MWCNT-FP) is developed and examine by using THz spectroscopy. • The sample is measured over a wide frequency band ranging from 0.02 to 3.0. • A very good broad band absorption is observed between 0.02 and 3.0 THz. • We measured quantize optical density, conductance and conductivity. • The real and imaginary conductance are measured with respect to photon energy. [ABSTRACT FROM AUTHOR]

The paper investigates the possibility of fabricating a carbon nanotubes (CNT)-modified nanocomposite based on pyrolyzed polyacrylonitrile (PPAN). The layered structure of PPAN ensures the attachment of nanotubes (NT) to the polymer matrix, forming enhanced PPAN/CNT nanocomposites. We synthesized a PPAN/CNT polymer nanocomposite and investigated its mechanical, conductive, and electronic properties. Using the quantum chemical method density functional theory (DFT), we studied an interaction mechanism between PPAN and single-walled carbon nanotubes. We described the structural features and electron energy structure of the obtained systems. We found that the attachment of a CNT to the PPAN matrix increases tensile strength, electrical conductivity, and thermal stability in the complex. The obtained materials were exposed to electromagnetic radiation and the dielectric constant, reflection, transmission, and absorption coefficients were measured. The study demonstrates the possibility of using carbon nanotubes for reinforcing polyacrylonitrile polymer matrix, which can result in the development of an enhanced class of materials possessing the properties of both polymers and CNTs. [ABSTRACT FROM AUTHOR]

Considering the green transformation, more and more attention must be paid to reducing noise pollution, which is one of the most important environmental problems today. Internal combustion engine (ICE) powered hand tools and small appliances, such as leaf blowers, brush cutters, chainsaws, and lawn mowers, are examples of the most undesirable sources of noise in today's human environment. This paper discusses the acoustic properties of a novel and compact silencer for a small twostroke ICE and proposes a novel concept with corresponding acoustic properties. The proposed solution has been measured on a test bench, and its properties, including transmission loss (TL) and reflection and absorption properties, have been experimentally determined. Using 3D printing technology and technological advantages, an innovative silencer with up to two microperforated (MP) panels, integrated into the expansion chamber of the original silencer, has been applied for rapid prototyping. As a result, noise reduction has been increased by at least 20 dB in the frequency range 800-4000 Hz. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the design and characterization of a 3D printed tetrakaidecahedron cell-based acoustic metamaterial. At present, the mitigation of low-frequency noise involves the utilization of spatially demanding materials for the absorption of sound. These materials lack the ability for targeted frequency control adjustments. Hence, there is a requirement for an approach that can effectively manage low-frequency noise using lightweight and durable materials. Design/methodology/approach: The CAD model was created in SolidWorks and was manufactured using the Digital Light Processing (DLP) 3D printing technique. Experimental study and numerical simulations examined the metamaterial's acoustic absorption. An impedance tube with two microphones was used to determine the absorption coefficient of the metamaterial. The simulations were run in a thermoviscous module. Findings: The testing of acoustic samples highlighted the effects of geometric parameters on acoustic performance. Increment of the strut length by 0.4 mm led to a shift in response to a lower frequency by 500 Hz. Peak absorption rose from 0.461 to 0.690 as the strut diameter was increased from 0.6 to 1.0 mm. Increasing the number of cells from 8 to 20 increased the absorption coefficient and lowered the response frequency. Originality/value: DLP 3D printing technique was used to successfully manufacture tetrakaidecahedron-based acoustic metamaterial samples. A novel study on the effects of geometric parameters of tetrakaidecahedron cell-based acoustic metamaterial on the acoustic absorption coefficient was conducted, which seemed to be missing in the literature. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the electronic and optical properties of CdSe/ZnS quantum dots (QDs) of varying sizes. We calculate the energy eigenvalues and wave functions dependence on QD dimensions, temperature, and pressure using a combination of coordinate transformation and the finite difference method. We analyze the oscillator strength, transition lifetime, absorption coefficients (AC), and refractive index changes (RIC) for various values of dot sizes, temperature, hydrostatic pressure, and incident photon intensity. The results obtained indicate a strong dependence of electronic and optical properties on temperature, hydrostatic pressure, and the size of the nanostructure. The oscillator strength decreased with increasing hydrostatic pressure, but increased with rising temperature. Conversely, the transition lifetime exhibits an opposite trend. Furthermore, the total AC and RIC increase as incident optical intensity decreases. Linear, nonlinear, and total AC and RIC display a red shift with increasing hydrostatic pressure and a blue shift with rising temperature. [ABSTRACT FROM AUTHOR]

In this paper, we show and analyse the results of morphological characterisations of Dy2O3 layer deposited on an n-type GaAs substrate using atomic force microscopy (AFM). For structural measurement, the surface morphology of the elaborated layer was revealed as a nano-conical event. The global experimental ellipsometric results Ψ and Δ versus emission wavelength of the Dy2O3/n-GaAs structure have been presented and discussed. Using these results and a Matlab code in which we assumed the structure had three layers, we have calculated several linear and nonlinear optical constants of the Dy2O3 thin layer. Dysprosium oxide has high optical conductivity and a noticeable increase in nonlinear optical parameters, making it a promising candidate for various applications. This is especially true in the field of optoelectronics. [ABSTRACT FROM AUTHOR]

Context: This research paper investigates the properties and potential applications of antiperovskite materials. Antiperovskites are a class of materials with a unique crystal structure, where the central atom is surrounded by a cage of anions. We review recent research on antiperovskite-based materials for energy storage, photovoltaics, catalysis, and sensors. We discovered that these materials display direct band gap semiconductors, strong absorption in the visible (VIS), ultra-violet (UV), and near infrared regions (NIR) based on their fundamental features, which is the most admirable quality that may be found in many optoelectronic devices. Both mechanical and thermodynamic stability have been confirmed for these materials. We discovered that these materials exhibit high figures of merit through the calculation of transport properties, which makes them a promising candidate for thermoelectric devices. It is anticipated that the proposed material BiPMg3, which has a theoretical efficiency of 11.5%, will make a suitable photovoltaic absorber. This paper highlights the potential of these materials for future technological advancements. Methods: Herein, we have used most authentic techniques to compute fundamental physical properties of these antiperovskites. Full-potential linear augmented plane wave (FP-LAPW) method has been used to investigate electronic, magnetic, optical properties, and make antiperovskites attractive for a variety of applications. In light of its implementation, we have checked the theoretical power conversion efficiency by first principles spectroscopic screening methodology, and inspect the fundamental physical parameters of antiperovskites, focusing on their potential as functional materials for energy and information technologies. [ABSTRACT FROM AUTHOR]

Measuring the optical properties of highly diffuse materials is a challenge as it could be related to the white colour or an oversaturation of pixels in the acquisition system. We used a spatially resolved method and adapted a nonlinear trust-region algorithm to the fit Farrell diffusion theory model. We established an inversion method to estimate two optical properties of a material through a single reflectance measurement: the absorption and the reduced scattering coefficient. We demonstrate the validity of our method by comparing results obtained on milk samples, with a good fitting and a retrieval of linear correlations with the fat content, given by R 2 scores over 0.94 with low p-values. The values of absorption coefficients retrieved vary between 1 × 10 − 3 and 8 × 10 − 3 mm − 1 , whilst the values of the scattering coefficients obtained from our method are between 3 and 8 mm − 1 depending on the percentage of fat in the milk sample, and under the assumption of the anisotropy factor g > 0.8 . We also measured and analyzed the results on white paint and paper, although the paper results were difficult to relate to indicators. Thus, the method designed works for highly diffuse isotropic materials. [ABSTRACT FROM AUTHOR]

In this paper, we have performed a study on the optical properties of single crystals ZnGa2S4 by method of density functional theory (DFT) and ellipsometry measurements. The calculated results for the real ε r and imaginary ε i parts of the dielectric function are compared with the measured experimental spectroscopic ellipsometry (SE) spectra in the 0.7–6.5 eV spectral region. Absorption coefficient-photon energy dependency revealed the existence of direct bandgap transitions with energy 3.5 eV. This result is very close to bandgap obtained from our theoretical calculation. [ABSTRACT FROM AUTHOR]

The paper considers the problem of light absorption by a nanocomposite with randomly oriented metal spheroidal particles-inclusions, provided that the volume content of such inclusions is small. Expressions for the frequency dependences of the effective dielectric function and the absorption coefficient of the metal-dielectric nanocomposite are obtained within the effective medium model taking into account the axial symmetry of spheroidal inclusions. The effective relaxation rate of electrons is introduced using the kinetic approach. Numerical calculations are performed for the cases when inclusion particles have the form of prolate and oblate nanospheroids. The results of the calculations indicate the presence of two maxima of the absorption coefficient, which correspond to longitudinal and transverse surface plasmon resonance. The change in the position and magnitude of the maxima of the frequency dependences of the effective dielectric function and the absorption coefficient with varying the size and shape of the spheroidal particles-inclusions is analyzed. It is shown that the greater the difference in the lengths of the semi-axes of the spheroids, the greater the distance between the maxima of the effective dielectric function and the absorption coefficient, and the shape of the curves depends on the eccentricity of spheroidal inclusions. It has been found that the position of the maxima is significantly influenced by the choice of the material of the inclusion particles and the matrix medium, while the height of the maxima is largely influenced by the shape of the nanoparticles, as well as their volume content in the composite medium. It is proved that, dependent on the material of nanoparticles-inclusions, both maxima of the absorption coefficient can be found in the visible part of the spectrum (for Au inclusions) or in the ultraviolet (for Al inclusions). It is also possible that one maximum lies in the visible part of the spectrum, and the other in the ultraviolet, which is the case for inclusions of Pd, Pt, Cu, Ag. [ABSTRACT FROM AUTHOR]

In this paper, we study the optical properties of a two-dimensional quantum ring with a diluted magnetic semiconductors structure. The Volcano model was chosen as the confinement potential of a quantum system. For interband optical transitions, the behavior of the absorption coefficient of a quantum ring as a function of the incident photon energy is numerically studied as a function of various values of such parameters as temperature, magnetic field, ring radius, and inner ring radius. In addition, the change in the threshold frequency as a function of the magnetic field and temperature for an interband optical transition is numerically studied. According to the results obtained, the considered parameters change the optical properties of the quantum ring. [ABSTRACT FROM AUTHOR]

• Demonstration of the efficacy of FT-IR in characterizing materials. • Usage of FT-IR considering of thickness and absorption coefficient effects. • Explanation of dipolar electric moment, overtone bands, and Fermi resonance. • Vibrational modes in 1D, 2D, and 3D systems and IR spectrum representation. • Criteria for the correct FT-IR band identification. This paper investigates the application of Fourier-transform infrared (FT-IR) spectroscopy by analyzing a commercially available plastic bag as an example. The study investigates the vibrational modes, mechanical properties, and structural changes of a bare sample during a tensile test. By measuring the absorption bands and their intensities, valuable information about the chemical composition and the concentration of certain components in the plastic bag is obtained. The behavior of vibrational modes in one, two, and three-dimensional systems is studied, with a focus on their representation in the IR spectrum. The concept of the dipolar electric moment and phenomena such as overtone bands and Fermi resonance are also explained. The X-ray patterns of the bag show talc and polyethylene crystalline phases. Scanning electron microscopy (SEM) determines the thickness of the sample. Tensile tests are performed to investigate the mechanical behavior of the plastic bags. This study demonstrates the informative and educational capabilities of FT-IR spectroscopy in studying the vibrational, mechanical, and structural properties of materials, with an emphasis on the correct application of this technique. The study highlights the importance of considering the effects of thickness and absorption coefficient and applying the Beer-Lambert law to understand the changes in vibrational modes during tensile testing. The results contribute to a deeper understanding of the structural behavior of plastic bags and demonstrate the effectiveness of FT-IR spectroscopy in characterizing such materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper focuses on the area of experimental measurements for monitoring the impact of decarbonization on the technical and environmental parameters of the ICE. The condition for the implementation of the measurements was the selection of an ICE that had driven more than 300,790 km. During the laboratory tests, several test methods were used to assess the technical and emission conditions of the tested ICE with the code designation ALH, which is used in VOLKSWAGEN BORA vehicles. The technical parameters of the tested ICE (corrected power PNorm and torque MMom), emission parameters (absorption coefficient k and NOx emission) and fuel consumption parameters (specific fuel consumption bsfc) were compared and evaluated in the results. The results show that the decarbonization process on the tested vehicle VOLKSVWAGEN BORA 1.9 TDi affected the emission parameters but did not affect the technical parameters and specific fuel consumption. [ABSTRACT FROM AUTHOR]

Lithium terbium fluoride (LTF) crystal is a good kind of magneto-optical material with high Verdet constant and low absorption coefficient, which is suitable to be used in magnetic-optical devices for high-power and large energy laser systems. In this paper, large size and high optical quality LTF crystal with a diameter of 2 inch was prepared by resistance heating Czochralski method, under the conditions of a protective atmosphere mixed with Ar and CF4. During this process, high-purity TbF3 and LiF were adopted as the raw materials. The optical properties of the LTF crystal were analyzed in detail. This crystal boule exhibits a complete appearance, good optical uniformity, and low residual stress, with no visible scattering particles under He-Ne laser irradiation. The LTF crystal elements with a diameter of 10 mm were processed from this boule. The parameters of the crystal elements such as the single-pass loss coefficient, extinction ratio, wavefront distortion, and weak absorption coefficient were tested. The results show that the grown LTF crystal have good optical quality. The magneto-optical performance of the LTF crystal was also researched, and its Verdet constant is about 98% of that of the commercial TGG crystals. [ABSTRACT FROM AUTHOR]

In this paper, the optical properties of two-dimensional coupled concentric double quantum rings with a parabolic confinement potential are studied theoretically. The optical absorption coefficient for the transition from the ground state to the first excited state is calculated. The effects of inter-ring coupling, internal or external ring width variation, and on-center donor and acceptor impurities are investigated. The peak value of the absorption coefficient decreases when the width of the internal ring is decreased, but reducing the width of the external ring causes the absorption coefficient to first increase and then decrease. In addition, concentric double quantum rings with a wider internal (external) ring absorb the photons with higher (lower) energies. An increment of the inter-ring coupling causes the concentric double quantum rings to absorb photons with higher energies. Although the on-center impurity reduces the magnitude of the absorption coefficient, the decrement is considerable for the donor impurity rather than the acceptor impurity. It is shown that the peak value position of the absorption coefficient has an obvious blue-shift (red-shift) in the presence of donor (acceptor) impurity. [ABSTRACT FROM AUTHOR]

GaxIn1−xAs–GaAsySb1−y type-II superlattices (T2SLs) have recently received broad attention as an InP-based optical absorption layer in short-wavelength infrared detectors. However, the cut-off wavelength of a GaInAs–GaAsSb T2SL detector is ordinarily around 2.4 µm at room temperature. This paper proposes extending the cut-off wavelength using a GaAs/InAs digital alloy instead of a GaxIn1-xAs random alloy layer in a GaxIn1−xAs–GaAsySb1−y T2SL. The calculation result employing an empirical sp3d5s* tight-binding method has revealed that a (GaAs/InAs)–GaAsySb1−y digital alloy T2SL on an InP substrate possesses a band gap corresponding to a wavelength of 2.9 µm which is over 0.4 µm longer than that in a conventional GaInAs–GaAsSb T2SL at a temperature of 200 K. Figured optical absorption coefficient spectra of certain digital alloy T2SLs, e.g., a [(GaAs)4(InAs)4]2–(GaAs0.53Sb0.47)17 structure, present a considerable polarization-direction dependence—originating from the asymmetrical shape of the wavefunction in the quantum well. Yet, by altering the atomic layer configuration in the growth direction of the digital alloy T2SL to have such a quantum well structure with a reflection symmetry as in [(GaAs)4(InAs)4]2(GaAs)3–(GaAs0.45Sb0.55)17, the polarization dependency can be dramatically decreased due to the symmetry improvement of the wavefunction. [ABSTRACT FROM AUTHOR]

Present study focuses on analyzing the role of magnetic field on electronic spectra and absorption coefficients for the transitions 1 s → 2 p of G a A s / Ga 1 - x Al x A s / G a A s spherical multilayer quantum dot (MLQD) and Ga 1 - x Al x A s / G a A s / Ga 1 - x Al x A s spherical multilayer quantum anti-dot (MLQAD) with hydrogenic impurity, via a comparative view. These nano structure systems have been studied both theoretically (Perturbation Theory), and numerically (Finite Difference Method). The wave functions and energy eigenvalues have been calculated using the finite difference method. In this paper it will be shown that a new degeneracy in presence of the uniform magnetic field in the MLQAD model will be appeared. Furthermore, the effects of the magnetic field, core radius size and potential confinement on 1 s → 2 p 0 absorption coefficient and also on 1 s and 2 p energy states of these nano spherical structures have been discussed. [ABSTRACT FROM AUTHOR]

The creation of new nanomaterials for absorbtion of electromagnetic radiation microwave range is an important direction in consequence of electromagnetic pollution of the environment. The aim of the paper was to develop and synthesize the polymer-filled systems based on the polychlorotrifluoroethylene and tin dioxide modified by nickel ferrite in order to study their electrophysical properties as potential materials absorbing electromagnetic radiation. NiFe2O4/SnO2 nanocomposites with a volume content of nickel ferrite on the surface of tin dioxide from 0.62 to 0.8 were synthesized by co-precipitation. Size of SnO2 and NiFe2O4 nanoparticles was determined by a transmission electron microscope and its about 30–50 nm and 15–30 nm, respectively. For the NiFe2O4/SnO2 nanocomposites the values of complex permittivity and complex permeability in the microwave range, values of conductivity at low frequencies were investigated. Maximum values of complex permittivity and complex permeability were found for NiFe2O4/SnO2 nanocomposites at the volume content of nickel ferrite 0.62. An increase was observed in the complex permittivity for the NiFe2O4/SnO2–polychlorotrifluoroethylene system, 2–3 times greater than the values related to the NiFe2O4/SnO2 nanocomposites. The electrical conductivity at low frequencies (100 Hz) of polymer composites increases by an order of magnitude with a decrease of the concentration of nickel ferrite on the surface of tin dioxide. It was found that the calculated absorption coefficient of an electromagnetic wave in the frequency range 1–41 GHz for NiFe2O4/SnO2 nanocomposites is about 2 times greater than that for nickel ferrite. It is shown that the creation of nanocomposites based on a conductive component modified by a magnetic component is more efficient for the processes of absorption of electromagnetic waves in the microwave range at optimal ratios of the values of the permittivity and permeability than pure ferrite. [ABSTRACT FROM AUTHOR]

The paper presents promising models of onboard black bodies based on phase transitions of high-purity substances or eutectic compositions and carbon nanotubes used in aerospace vehicles for the radiometric calibration measurements of the equipment to observe the Earth. Their design and technical specifications, advantages and disadvantages as well as the examples of their use and tests are described. [ABSTRACT FROM AUTHOR]

The paper presents promising models of onboard black bodies based on phase transitions of high-purity substances or eutectic compositions and carbon nanotubes used in aerospace vehicles for the radiometric calibration measurements of the equipment to observe the Earth. Their design and technical specifications, advantages and disadvantages as well as the examples of their use and tests are described. [ABSTRACT FROM AUTHOR]

The concentration of fibers and fillers in the pulp suspension is an important parameter in the monitoring process. This paper proposes a versatile optical measurement system to estimate the concentration of a solids mixture in water. The geometry used in a multispectrophotometer (MSM) enables the controlled observation of transmission, and forward scattering light from the suspension in the UV-visible spectral range. We have developed the new fibers mixing system which gives a homogenous distribution of the fines and fillers making it possible to increase the reproducibility and accuracy of the measurement. The data analysis is based on the Beer- Lambert law and CIELAB color space equations. The results show that the proposed method is accurate for measuring the fines and filler concentrations in multicomponent suspensions.

One of the most vulnerable issues in the technical protection of information is to obtain data via leakage through the opto-electronic channel. In this paper, studies of the protective capabilities of glass from laser sounding depending on its elemental composition were carried out using such indicators as the coefficients of reflection and absorption of the laser beam by the window glass. As a result of the work, an experimental installation based on a continuous solid-state laser was assembled. The study of the elemental composition of window glass, which is produced by modern industry, X-ray fluorescence method and the study of the coefficients of reflection and absorption of glass samples in the experimental setup showed that the studied window glass chemically belongs to quartz (silicate). All chemical elements involved in its formation can be divided into 3 groups: glass-forming, transitional, modifiers, which affects the optical properties of the studied glasses, as the elements used have different not only qualitative but also quantitative parameters. Absorption increases if the number of chemical elements that exhibit amphoteric and non-metallic properties and have (-charge) decreases, and increases if the number of chemical elements in the glass that exhibit the most alkaline, alkaline earth properties and in which the radius of cations (+ions) increases. Systematization of the elemental and quantitative composition of the studied window glass in accordance with the periods and groups of the periodic table of chemical elements, enabled the relationship between the electronic structure of chemical elements and the protective properties of glass. [ABSTRACT FROM AUTHOR]

In this paper, we study the electromagnetically induced transparency (EIT) of a quantum ring by considering both interband and intraband transitions, under the influence of external electric and magnetic fields, as well as Rashba spin–orbit interaction (RSOI). Four band k ⋅ p model along with effective mass one band approximation were respectively employed to compute valence and conduction bands energy eigenvalues. We investigate the effects of applied electric and magnetic fields, as well as RSOI and the ring dimensions, on EIT. Our results reveal that the external magnetic field and the ring dimensions have a great influence on the EIT phenomenon. Ultimately, our numerical results will be used to develop devices with controllable nonlinear optical absorption and refraction. • Kohn-Luttinger Hamiltonian for holes is derived within the cylindrical coordinates. • Fields effect as well as RSOI on interband EIT in a QR are investigated. • Magnetic field has a great influence on EIT and the transparency window. • The ring size considerably changes the transparency window. [ABSTRACT FROM AUTHOR]

Herein, we propose that the commonly used methylammonium cation (CH 3 NH 3 +) in CH 3 NH 3 PbI 3 (MAPbI 3) be replaced with ethyl-phosphonium cation CH 3 CH 2 PH 3 + (EP+), allowing stronger electronic coupling between the PbI 6 octahedra and the organic cation and thereby increasing its stability. This paper will examine EP + based hybrid perovskite (CH 3 CH 2 PH 3 PbI 3 or EPPbI 3) as an alternative absorber material for photovoltaic cells of high efficiency and that too at affordable processing costs. By using FP-LAPW + lo methodology as used in density functional theory (DFT), we have examined physical features such as the bandgap energy, distribution of valence electron density, DOS, and optical and thermodynamical coefficients. We also simulated the performance of solar cells by employing EPPbI 3 as PVA material using SCAPS-1D. The findings of the current study viz. an absorption coefficient surpassing 10 4 cm−1, a direct forbidden energy gap of 1.388 eV and simulated PCE of 31.8%, is enough to support applicability EPPbI 3 perovskite as a PVA material. [ABSTRACT FROM AUTHOR]

In this paper, the first‐principles calculations based on the Density Functional Theory (DFT) have been used to study the effect of strain on the structural, electronic, optical and thermoelectric properties of the puckered Si2SeS monolayer. Our calculations show that the puckered Si2SeS monolayer has an indirect band gap of 1.30 eV at the equilibrium state, which can be tuned by biaxial strain and the semiconductor–metal phase transition occurs at −10%. Interestingly, a high absorption coefficient exceeds 107 cm−1 in the visible light region under compression biaxial strain was predicted. The electronic Figure of merit (ZTe) of puckered Si2SeS monolayer reaches 2.55 under the tensile biaxial strain of +6%. The presented results show the promising potential of puckered Si2SeS monolayer for optoelectronic and energy conversion applications. [ABSTRACT FROM AUTHOR]

In this paper, a micro-perforated panel (MPP) composite structure consisting of an inhomogeneous MPP (IMPP) backed with J-shaped cavities of different depths for low-frequency sound absorption is proposed. The goal is to increase the low-frequency (≤ 500 Hz) sound absorption performance of the IMPP. Sound absorption in a frequency range of 300–480 Hz was achieved with parallel-arranged IMPPs backed by J-shaped cavities, with average absorption of greater than 90%. A parametric analysis was used to optimize the structure's geometric parameters for the specified frequency range. The results show that when the length and volume of the back cavity depths increase, the low-frequency sound absorption peaks shift to a lower frequency. Similarly, the sound absorption curves are enhanced and move towards lower frequencies as the thickness of the IMPP increases. The structure was studied using an electro-acoustic equivalent circuit model (ECM) and finite element method (FEM) simulation. Model prototypes were then made using stereolithography (SLA) and verified by a square-shaped impedance tube-based experimental study to determine the normal absorption coefficient. The results revealed that the three types of curves, namely theoretical, FEM simulation, and experimental, were in good agreement. [ABSTRACT FROM AUTHOR]

There are some adverse reactions in dye-sensitized solar cells (DSSC), such as dye relaxation, electrons in semiconductor films react with oxidized dye molecules and electron recombination with oxidized ions in electrolyte. It is very important to use a more sophisticated DSSC carrier transport model to simulate the photoelectric performance of the battery. Therefore, this paper is based on the carrier transport model including electron, dye cation, iodide and triiodide in DSSC established by multiple capture theory. The J-V curves of DSSC with different TiO2 film thickness, different incident light intensity and different dye molecular absorption coefficient were obtained by numerical simulation. The results show that with the increase of TiO2 film thickness, the short-circuit current density of solar cells increases, the open circuit voltage decreases, and the photoelectric conversion efficiency first increases and then decreases. When the TiO2 film thickness of DSSC is 20 μm, the photoelectric conversion efficiency reaches the maximum value of 7. 41%. At the same time, the photoelectric conversion efficiency increases with the increase of incident light intensity and dye molecular absorption coefficient. When the absorption coefficient is 4 500 cm-1, the photoelectric conversion efficiency is 6. 73%. The above analysis and research results can provide theoretical guidance for improving the photoelectric performance of DSSC. [ABSTRACT FROM AUTHOR]

In this paper, we studied the effects of the annealing temperature of nickel oxide (NiO x) thin films on the structural, optical, and electrical transport properties. Thin NiO x was synthesized by the sol-gel method, followed by annealing at different temperatures varying from 200 to 450 °C. From the obtained AFM image data, an increase in the surface Ra value is observed with rising film annealing temperature. The decrease in film thickness with increasing annealing temperature is associated with significant densification of NiO x. During thermal annealing, a change in the redistribution of Ni/O elements is seen in the films. The increase in the intensity of the (1P)LO scattering peak in NiO x with rising annealing temperature is associated with a growth in the density of defects due to Ni vacancies. When the annealing temperature reaches 250 °C, an increase in Eg = 3.49 eV is detected; a further rise of the annealing temperature leads to a decrease in Eg = 2.92 eV. The increase in the index n of films with rising annealing temperature is associated with the formation of a denser and more ordered NiO x film. A rise in the annealing temperature of NiO x films leads to an increase in the value of the total resistance of the films, a decrease in the resistance of hole recombination at the NiO x /electrode interface, and the value of the conditional mobility of holes. • An increase in the RMS value of films with increasing annealing temperature is associated with an increase in grain size on the surface. • At an annealing temperature of 250 °C, an increase in Eg is observed; a further increase in the annealing temperature leads to a decrease in Eg. • An increase in the extinction coefficient and dispersion index is associated with the densification of the NiO x film with increasing annealing temperature. • An increase in film density with increasing annealing temperature leads to an increase in the NiO x resistance and a decrease in the value of the conditional hole mobility. [ABSTRACT FROM AUTHOR]

Space launch vehicles experience severe dynamic loadings throughout the flight. Acoustic loads are one such load which are very critical to the launch vehicle at the time of ignition and take off. The amplitudes of acoustic loadings are generally very high and required to be diminished to save electronic components. Typically, one of the most common and efficient insulating material is Melamine Foam (MF). In this paper, the acoustic and environmental noise reduction MF panels of variable thicknesses (25, 50 and 75mm) are analyzed. Commercial FEA software is used to estimate the acoustic parameters which are experimentally validated using impedance tube based on transfer matrix method. The impedance tube can measure the normal incident sound absorption coefficient and transmission loss for frequency range of 64 Hz to 6.2 kHz. A conventional, twomicrophone impedance tube, is connected to a sample holder downstream of the first microphone pair and a section downstream of the sample holder that accommodates a second pair of microphones. Two separate arrangements of impedance tube are used to measure the absorption coefficient and transmission loss. The FEA and experimental results are compared and found in good agreements Furthermore, the optimized insulation foam thickness is obtained based on required acoustic parameters. [ABSTRACT FROM AUTHOR]

The relevance of the study is conditioned by the need to determine the state and residual life duration of high-voltage cable lines to identify faulty and maintainable cables. The aim of the article is to determine a reliable scientifically grounded criterion for assessment of insulation characteristics of the cables in use and to perform a comparative analysis of the results obtained by the traditional method of diagnosing insulation with the results of a new method of assessment by the return voltage. In this regard, the article deals with the issues related to the testing of cables having oil-impregnated paper insulation, as well as with the issue of switching from planned replacement of cables to assessment of their actual state and period of residual life. The authors propose to use the method of examining the cables by the return voltage using the device for testing electrical insulation "UDEI-1" developed at the department of Electrification and Automation of the Nizhny Novgorod State University of Engineering and Economics. The article presents the results of measuring the return voltage of three cables that operated under different conditions. The cables had different technical state. The analysis of the estimation of the residual life of cables by the return voltage was carried out using such criteria as the PIRV polarization index, the LIRV electrical conductivity index, and the P-factor. The P-factor is the physical criterion demonstrating the aging of paper-oil insulation by the shape of the return voltage curve. It represents such characteristics of insulation aging as moistening. To compare the results of testing the cables by the return voltage with the conventional methods of diagnostics and to determine the actual technical condition of power cables, the authors applied the method of spatiotemporal reflectometry and the method of measuring insulation resistance with the determination of such indicators of state as insulation resistance normalized per one kilometer, absorption coefficient, and polarization index. The results of this article confirm that the return voltage gives a qualitative assessment of the state and degree of aging of cables with impregnated paper insulation. The authors proposed a new system for evaluation of cable condition by weighting coefficients. In this approach, the determination of residual life of cables with impregnated paper insulation is based on the values of the return voltage. Application of the new system gives opportunity to improve reliability of the power lines. Recommendations for the further operation of the studied cables are given. The materials of the article are of practical value for carrying out complex assessment of the technical condition of power cables by the return voltage and can be useful for drawing up a schedule for replacement or repair of cable lines depending on their actual state. [ABSTRACT FROM AUTHOR]

Diagnosis in the early stage of breast cancer is crucial for the onset of preliminary treatment. Non-radiative bioimpedance measurement in the microwave frequency range can contribute to electrode-medium interface error and the malaise of electrode placement on the patient to take measurements. These reasons account for alternate diagnosis procedure and improved reliability of retrieved mensuration. Non-invasive optical diagnosis in the near infra-red (NIR) and visible light of the electromagnetic range is the shifting paradigm for healthcare diagnosis. An accurate quantitative measurement is unparalleled to circumvent false positives. The focus of this paper is to perform quantitative mathematical analysis for bioimpedance and optical properties for sample breast cancer cells for meticulous interpretation of malignant cell diagnosis. The analytical solution of the Cole–Cole plot, relaxation frequency, and capacitance measurement showed reliability with previous experimental findings. The dissimilitude of the frequency-dependent refractive index measurement of the malignant and healthy cell can be used by clinicians for pronouncement. The diffusion theory is also used to interpret the pathlength of the source light particle and the absorption property of the malignant cell. The synergistic analytical solutions of the bioimpedance and optical parameters can be used by licensed Physicians or Clinical Practitioners (CP) to meticulously interpret the diagnosis result. The quantitative parameters obtained from the dispersed bandwidth range from microwave to visible light offers a comprehensive understanding of the biophysical properties of the malignant cell. [ABSTRACT FROM AUTHOR]

In this paper, the plasmonic property of triple layered ZnO@M@Au (M = spacer) spherical core-shell nanostructures embedded in a dielectrics host medium is investigated by varying core size, spacer thickness, shell thickness and dielectrics function of the host medium within the framework of the qausi-static approximation method. The absorption coefficient of ZnO@M@Au spherical triple layered core-shell nanostructures is effectively studied by optimizing the parameters with range of nano-inclusion size mainly in between 18 and 23 nm. In this triple layered core-shell nanostructure two plasonic resonances are found associated with spacer@Au and Au@medium interfaces. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from near-UV to nearinfrared spectral region. [ABSTRACT FROM AUTHOR]

Electrically-pumped AlGaN-based edge-emitting laser diodes with a buried tunnel junction (TJ) for sub-300 nm emission are designed in this paper. Hole injection is one of the major concerns for the design of ultraviolet (UV) lasers based on this material system. The use of a low-resistive TJ as an intracavity contact within the devices will offer an opportunity to replace highly resistive p-type AlGaN-based cladding and contact layers by their n-doped counterparts. This advanced polarization-engineered interband TJs will lead to improved hole injection and a significantly reduced threshold voltage. The thermal properties of the tunnel-injected devices are thoroughly studied theoretically. For the demonstration of continuous-wave operating lasers, possible improvements in terms of better thermal management of the device are also discussed. Our improved design allows CW-operating AlGaN lasers with a threshold current density of <8 kA/cm2 and maximum optical output power of > 220 mW, yielding a wall-plug efficiency of > 2.8%. [ABSTRACT FROM AUTHOR]

Recently, a large variety of photothermal agents have been developed and are currently under study, owing to their wide range of applications. Nonetheless, a comparison of their relative performances remains a challenge, and it appears that no tool is yet available for rationalizing the data reported in the literature. Indeed, we demonstrate in this paper that neither the temperature increase (ΔT) nor the photothermal efficiency (η) are sufficient to account for the performance of a photothermal agent. From this observation, we propose that a new index, IPTmax, could be used, in order to properly rank molecular photothermal agents according to their efficacy for converting light into heat, in a similar fashion that brilliance is used to compare luminescence properties. [ABSTRACT FROM AUTHOR]

The paper presents the morphological, structural, and optical properties of nanostructured SnO (x) films obtained by molecular beam epitaxy using deposition of tin in an oxygen flux on an oxidized silicon substrate as a function of the annealing temperature of the synthesized structure. The effect of annealing temperature on the structural and phase state of the films is established. The orthorhombic phase of SnO2 was observed after annealing in air at 500°C. An increase in the annealing temperature up to 800°C leads to the appearance of small fraction of the tetragonal phase of SnO2. The effect of the crystal structure on the optical properties of tin oxide films is shown. Ellipsometry revealed a sharp change in the optical constants of the film near the annealing temperature of 500°C. The observed wide absorption band in the range 1.9–3.4 eV is apparently associated with small (approximately 1%) amount of unoxidized metal Sn clusters. Photoluminescence in a wide range of 450–850 nm with a maximum at ~600 nm is observed. An increase in the annealing temperature from 500 to 800°С leads to an increase in the PL intensity by almost a factor of 6. [ABSTRACT FROM AUTHOR]

In this research paper, we studied the optical and nuclear shielding efficiency of newly developed BGO glasses with the following compositions (in wt%): 32Bi 2 O 3 –68GeO 2 , 42Bi 2 O 3 –58GeO 2 , 47Bi 2 O 3 –53GeO 2 , 52Bi 2 O–48GeO 2 , 62Bi 2 O 3 –38GeO 2. BGO glasses were prepared by traditional melt quenching method. To obtain the band gap values of fabricated BGO glasses, optical absorption spectra were used for evaluation of optical properties. The mass attenuation coefficients (μ/ρ) were achieved for prepared glasses at 0.015–15 MeV photon energies employing MCNPX Monte Carlo code and WinXcom program. Moreover, broad-range of nuclear shielding parameters for gamma ray, neutrons and charged particles such as mass attenuation coefficient, half value layer, effective atomic number, buildup factors, mass stopping powers, projected ranges, fast neutron removal cross sections and damage factors were calculated. The refractive index is calculated from E opt , As Bi 2 O 3 concentration is enhanced, E opt is also increased as well as the optical electronegativity and consequently the refractive index. In addition, the results showed that BIGE5 glass sample with highest Bi 2 O 3 contribution has excellent nuclear radiation shielding ability among the other fabricated glass samples. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to calculate an accurate sound absorption coefficient for a micro-perforated panel absorber (MPPA). When the sound absorption coefficient is calculated, there is a difference between the measurement and the calculation. In the calculation, a resistive end correction coefficient (β) of 2 or 4 and a reactive end correction coefficient (δ) of 0.85 are generally applied. However, using an impedance tube test, we confirm that end correction coefficients change depending on the specification of the micro-perforated panel. The resistive end correction coefficient is in the range of 2–4 and increases when the hole diameter and the porosity decrease and the panel thickness increases. The reactive end correction coefficient is less than 0.85 and increases when the hole diameter and the panel thickness increase and the porosity decreases. Based on our experimental results, we derive new coefficient formulas expressed by the hole diameter (d), the hole spacing (b), the porosity (p) and the panel thickness (t). To verify the proposed formulas, the sound absorption coefficient calculation is compared with the measurement, which confirms that the absorption coefficient is affected by the ratio between the air mass inside the hole and the added air mass outside the hole. The relation between the two masses can be confirmed by the ratio of the panel thickness (t) to the hole diameter (d). In a single-layer MPPA, when t/d is greater than or equal to about 2, the absorption peak level of calculations, no matter what β is applied, is similar to the measurement. On the other hand, when t/d is less than about 2, the calculation is greatly affected by β. The sound absorption coefficients for both single- and double-layer MPPAs are compared according to the proposed formulas and coefficients of other researchers. The calculation of the proposed formulas among calculations is in good agreement with the measurement. [ABSTRACT FROM AUTHOR]

Nowadays, micro-perforated absorbers are one of the structures that are widely used. The sound absorption mechanism is performed by viscous energy losses in the cavities on the plate. This paper was examined the effect of the surface shape on the micro-perforated absorber performance at low frequencies (less than 500 Hz). The three-dimensional finite element method was used to predict the absorption coefficient of this group of adsorbents. Also, the results obtained from the shaped absorbers were compared with the flat micro-perforated absorbers. After validating the numerical results, six different designs were defined as the surface shape of the micro-perforated plates in the COMSOL Multiphysics, Ver. 5.3a software. The results reflected the fact that the factor of the surface shape can be used as a contributing factor in some frequencies. In general, the dented or concave shapes provided better outcomes than other flat designs and shapes and the convex or outward shapes bring the weakest results. [ABSTRACT FROM AUTHOR]

• The underwater low-frequency sound absorption performance and mechanism of membrane-type acoustic metamaterials (MAM) are investigated by numerical simulation. • The effects of key parameters on absorption performance are explored by numerical simulation, and these are used to optimize the underwater sound absorption performance. • A parallel combination design of multiple MAM units is proposed to achieve broadband and efficient absorption of underwater low-frequency sound by the acoustical siphon effect, and the accuracy of numerical simulation is verified by the experiment. The underwater low-frequency sound absorption performance of membrane-type acoustic metamaterials (MAM) is investigated in this paper. The MAM unit is composed of a tensioned membrane, an upper cavity frame, a lower cavity frame, a steel backing and a cylindrical mass block located at the geometric center of the membrane. The sound absorption mechanism of MAM and the influence of critical structural parameters are analyzed by numerical simulation. The absorption performance of MAM is further optimized by the parallel combination design of multiple MAM units and the acoustical siphon effect. A design of MAM with 19 units is proposed to improve the absorption bandwidth. The calculation result demonstrates that the structure can effectively absorb sound in the low-frequency range of 250–750 Hz, and the average absorption coefficient is above 0.6. Lastly, the corresponding sample is fabricated, and the underwater sound absorption performance is tested in the standing wave tube. The accuracy of numerical simulation is validated by experiment. [ABSTRACT FROM AUTHOR]

The authors of recently published "Materials Science and Engineering B 281(2022)115754" try to estimate the optical conductivity (σ) using the refractive index (n) and the absorption coefficient (α) values through this relationship (σ = αn/4π). Unfortunately, this equation in this form is incorrect whether in Gaussian (G) or Standard International (SI) units due to the dimensions are not the same on the two sides of this relation. Such relationship must be corrected to the following form (σ = αnc/4π where c is the light velocity), which agree with that published in textbooks and research papers. According to the Gaussian system σ is measured by s - 1 while the authors use S c m - 1 units (see the Y-axis units of Figure 5) which corresponding standard international (SI) units. Such Scm−1 units should be corrected to s - 1 or multiplied by the term (4 π ε o where ε o = 8.85 × 10 - 12 F m - 1 ) which is the transformation factor form Gaussian to SI units. [ABSTRACT FROM AUTHOR]

The highly absorptive acoustic element studied in this paper is constituted by two mating plates provided with slots and a number of micro-channels engraved on the contact surface. This fibre-less element has been first presented in a previous work, with the name of micro-grooved element (MGE), as a potential substitute of the well-known micro-perforated element (MPE) (Auriemma et al. in SAE Int J Mater Manuf 6(3), 2013). Compared to MPE, it offered advantages in terms of cost-effectiveness of the production process, but similar acoustic behaviour. In this paper, MGEs with improved design are presented. The new geometry of the outer layers results in inner micro-channels with smaller overall dimensions, while still keeping adequate porosity. As a result, the acoustic behaviour is enhanced and the sound absorption of traditional MPEs is finally overcome. The transfer impedances of several MGE and MPE samples are measured, modelled and compared. The impedance end corrections are extrapolated with a completely experimental procedure and the behaviour in nonlinear regime is studied and described by means of a semi-empirical formulation. [ABSTRACT FROM AUTHOR]

• Creation of three transparency windows. • Absorption and refractive index depend on the length of quantum dot for z-polarization. • Absorption and refractive index depend on the radius of quantum dot for x-polarization. • Transparency window and FWHM do no depend on the size of quantum dot. • By increasing Rabi frequency, transparency window is increased. In this paper, electromagnetically induced transparency (EIT) is investigated in a four-level C-model of GaAs cylindrical quantum dot (QD) with parabolic potential. In these system three transparency windows is created. By solving the Schrӧdinger equation in effective mass, eigenfunctions and eigenvalues of QD are found. By obtained eigenfunctions, eigenvalues and with solving the density matrix equations in steady-state, susceptibility of cylindrical QD is found. Dependence of EIT, refractive index and absorption coefficient on control laser fields, radius and height of cylindrical QD, decay rates, control laser detuning and polarization of probe and control lasers are investigated. [ABSTRACT FROM AUTHOR]

The present paper reports the optical and spectral properties of amorphous Se58Ge42 – xPbx (x = 6, 12, 18, 20) thin films deposited onto pre-cleaned glass substrate under a vacuum of 10–5 Torr. The amorphous samples have been prepared using melt quenching method. The structural characterization of the samples has been done using XRD and EDXA. The optical absorption and transmission spectra were recorded using UV-Vis spectrophotometer in the wavelength range 400–2500 nm. The study of absorption spectra shows that sample exhibits indirect optical band gap which decreases on increase of Pb content in Se–Ge system. This decrease in band gap has been explained in terms of chemical bond approach and density of state model. Transmission spectra have been utilized to obtain refractive index, dielectric constant and thickness of films. It is found that refractive index increases with increase in Pb content in Se–Ge system. [ABSTRACT FROM AUTHOR]

Abstract Acoustic impedance is typically measured using an impedance tube, which requires a material sample physically fitted to the tube. However, the impedance can vary greatly between the material mounted in the tube and the material located in a real environment, where the mounting conditions are likely to be different. Also, oblique incidence cannot be measured in an impedance tube. In this paper, we investigate the use of a double-layer microphone array for in-situ measurement of surface impedance and absorption coefficient. With the array positioned near the material surface, a source emits broad-band sound towards the array and the material. A measurement is taken, and the sound pressure and the surface-normal particle velocity at the material surface are calculated using Statistically Optimized Near-field Acoustical Holography (SONAH). From the surface pressure and velocity, the impedance across a selected area is calculated, and finally the absorption coefficient is calculated from the impedance. A set of tests has been performed on porous material samples in an anechoic chamber as well as in a fitted room. Different sample sizes and different sound incidence angles have been considered. The results show consistency between the measurements in the anechoic room and the ordinary room as well as good agreement with Miki's model up to large oblique incidence angles. [ABSTRACT FROM AUTHOR]

Abstract This paper presents results of investigations of Fe+, Ge+, Mn+ ions implanted silicon samples with the use of the modulated free carrier absorption (MFCA) technique. These ions are significant in a modern electronics. The nondestructive character of the MFCA method makes it very useful for characterization of implanted materials. Spatial distributions and profiles of the amplitudes of the modulated free carrier absorption signal of the implanted silicon samples were measured and analyzed. The amplitude and phase frequency characteristics of the MFCA signal for the ion implanted regions have been measured and interpreted for different wavelengths of the illuminating light. The dependence of the amplitude of the MFCA signal on the lifetime of carriers and the optical absorption coefficient of the implanted layer has been analyzed theoretically and discussed. The influence of the ion implantation process on the values of the optical absorption coefficient and the lifetime of carriers of the implanted layers has been determined. Highlights • The influence of Fe+, Ge+, Mn+ ion implantation into silicon has been presented. • Frequency domain nondestructive MFCA method has been applied for investigations. • Changes of the optical and recombination parameters have been explained. [ABSTRACT FROM AUTHOR]

In this paper, the modified Biot’s equations based on nonlocal elasticity theory are presented for modeling nanocomposite porous media. The analytical solution of modified Biot’s equations is obtained by using the recently developed potential function method. By doing some mathematical manipulation, the coupled modified Biot’s equations are converted to two decoupled equations. Consequently, the variations of field variables and acoustical properties of a considered nanocomposite foam are studied by changing the nonlocal parameter. The obtained results show that the local Biot’s results are in good agreement with the nonlocal modified Biot’s results for very small values of the nonlocal parameter. In addition, the values of field variables (i.e. pressure) in the thickness direction are decreased by increasing the nonlocal parameter for frequencies below 5000 Hz. Furthermore, by increasing the nonlocal parameter, the differences between local and nonlocal values of field variables and the absorption coefficient increase. Also, the nonlocal parameter has no considerable effect on the absorption coefficient for frequencies lower than 2000 Hz, whereas by increasing the nonlocal parameter the differences between corresponding results of local and nonlocal theories increase for frequencies above 2000 Hz. [ABSTRACT FROM AUTHOR]