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Perovskite solar cells (PSCs) are advancing swiftly due to their remarkable increase in power conversion efficiency (PCE) compared to traditional photovoltaic technologies. The main purpose of this study is to investigate the efficiency of two distinct PSCS structures that use as an inorganic perovskite active layer. The calculations are based on the optoelectronic model of the solar cell and the use of the finite element method to solve the continuity equations for current and charge density. Therefore, the layer thicknesses of different materials (as ETL and Active layer) are modified to find the better power conversion efficiency of these solar cells. The obtained results of simulation calculations illustrate that the first structure FTO/ITO/ /PEDOT: PSS/Au exhibits a maximum power conversion efficiency of 11.37%, with a short circuit current of 14.47 (mA/cm^2) and an open circuit voltage of 0.96 (V) and while the FTO/TiO2/ /Spiro- OMETAD/Au structure shows a maximum power conversion efficiency of 10.57%. The greatest power conversion efficiency for the aforementioned designs is 80 nm for the electron transporting layer is 80 nm and 200 nm for the inorganic active layer, respectively. The results of this article can be useful in the design of new-generation solar cells based on inorganic perovskite layers.

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]

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]

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

Different types of resonators are used to create acoustic metamaterials and metasurfaces. Recent studies focused on the use of multiple resonators of the dipole, quadrupole, octupole, and even hexadecapole types. This paper considers the theory of an acoustic metasurface, which is a flat surface with a periodic arrangement of multipole resonators. The sound field reflected by the metasurface is determined. If the distance between the resonators is less than half the wavelength of the incident plane wave, the far field can be described by a reflection coefficient that depends on the angle of incidence. This allows us to characterize the acoustic properties of the metasurface by a homogenized boundary condition, which is a high-order tangential impedance boundary condition. The tangential impedance depending on the multipole order of the resonators is introduced. In addition, we analyze the sound absorption properties of these metasurfaces, which are a critical factor in determining their performance. The paper presents a theoretical model for the subwavelength case that accounts for the multipole orders of resonators and their impact on sound absorption. The maximum absorption coefficient for a diffuse sound field, as well as the optimal value for the homogenized impedance, are calculated for arbitrary multipole orders. The examples of the multipole resonators, which can be made from a set of Helmholtz resonators or membrane resonators, are discussed as well. [ABSTRACT FROM AUTHOR]

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

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]

The present paper deals with the evaluation of the impact of newly developed biofuels together with a comparison with conventionally produced fuel, diesel, in terms of their impact on the technical and emission condition of a studied vehicle. The main energy and emission parameters of the internal combustion diesel engine were evaluated. For laboratory experiments, a discrete test method was used for comprehensive assessment, the procedure of which is described in the methodology of the paper together with a description of the measurement chain designed to achieve the determined results. The paper deals with the evaluation of the measured results of power, torque, consumption, and emissions such as CO2 and absorption coefficient. Among the technical parameters, the power and torque drop were observed for each biofuel. The decrease is attributed to lower values of calorific value, viscosity, and density. A positive effect was observed for the CO2 and absorption coefficient emission parameters, i.e., a decrease for each of the newly developed biofuels studied. [ABSTRACT FROM AUTHOR]

An attempt has been made to study the effect of thickness and compactness of natural fibre assembly in the reduction of noise. Fourteen available natural fibres i.e. banana, bhimal, roselle, coconut, cotton, wool, flax, hemp, jute, nettle, okra, pineapple, ramie, sisal and two synthetic sound absorbers i.e. rockwool, glass wool have been tested for sound absorption coefficient. Depending on availability and sound absorbency property, jute fibre (Corchorus olitorius), has been selected for detailed study. Test probe has been designed to test the fibre bundle in impedance tube principle. It is observed that there are significant absorption and transmission loss of sound energy through the jute fibre bundle either alone or covered with paper laminate. Statistical models based on second-order standard polynomial and Box and Benken factorial design, have been suggested to predict the sound transmission loss and absorption with respect to thickness and density in different frequency level of sound for stuffed fibre and paper panel stuffed with fibre. The correlation coefficients between observed and predicted values are above 0.95. Stuffed jute fibre shows maximum sound absorption with 30 mm thickness, 1.0 g/cm3 density in the application of 5000 Hz sound frequency. In case of transmission loss for below 18 mm thickness, jute fibre stuffed paper laminate panel shows increase up to 1.0 g/cm2 and then decrease. The sound loss reaches the maximum in the application of 1500 Hz frequency and then remains constant. Therefore, it can be effectively used as sound absorber or barrier protecting the environment from sound pollution, if designed properly. The knowledge from this study can help to design sound insulator or barrier from an industrial crop like jute. [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]

The article considers methods for measuring grain moisture. The authors carried out the analysis and selected significant parameters that affect the measurement of grain moisture. Methods and ways of grain moisture control are investigated. Modern technological methods of production of agricultural products are largely related to moisture content. The excess or lack of moisture in the material affects its physico-chemical, physico-mechanical and operational properties, as well as quality indicators. Quick and accurate determination of water content in a particular material, both in the production process and during operation, is the most important task. The accuracy and measurement errors of moisture content of moisture meters significantly depend on the density of materials and the parameters of the measurement medium. The optimal method for the most accurate measurement of humidity has been determined. Growing requirements for the quality and competitiveness of domestic agricultural products put forward new requests for the devices and facilities for express moisture control in most technological processes. Modern technological processes require universal devices that control the moisture content of a wide range of agricultural materials. Having analyzed in detail and determined the significant parameters that affect the measurement of grain moisture, the paper proposes mathematical model of ultra-high-frequency measuring transformation of the moisture of grain crops, the essence of which is to measure the power of this signal at the output of the waveguide when the grain moisture changes by using a traveling wave. By means of the analysis, carried out, the authors suggested the structural diagram of ultra-high-frequency humidity meter of cereal crops which realizes the mathematical model, proposed in the paper. [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.

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]

In a recent paper [J. Electron. Mater., 48, 7915 (2019)], Karnan et al. studied the physical properties of the cadmium chloride-doped L-alanine (LACC) single crystal. It is shown in this comment that the authors used a wrong approach to calculate the reflection coefficient. Erroneous values of the reflection coefficient were used to calculate the refractive index. Consequently, the reported values of the mentioned parameters, as well as other optical parameters that were calculated based on them, i.e. the real and imaginary parts of the third-order nonlinear optical susceptibility, are incorrect. [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]

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]

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]

Knowledge of the optical parameters of tumors is important for choosing the correct laser treatment parameters. In this paper, optical properties and refraction indices of breast tissue in healthy mice and a 4T1 model mimicking human breast cancer have been measured. A significant decrease in both the scattering and refractive index of tumor tissue has been observed. The change in tissue morphology has induced the change in the slope of the scattering spectrum. Thus, the light penetration depth into tumor has increased by almost 1.5–2 times in the near infrared "optical windows." Raman spectra have shown lower lipid content and higher protein content in tumor. The difference in the optical parameters of the tissues under study makes it possible to reliably differentiate them. The results may be useful for modeling the distribution of laser radiation in healthy tissues and cancers for deriving optimal irradiation conditions in photodynamic therapy. [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]

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 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]

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]

Terahertz (THz) frequency generation via nonlinear optical techniques is of particular interest due to the immense potential of this type of radiation in various scientific fields, ranging from medicine to telecommunications. Selecting suitable nonlinear media for laser frequency down-conversion presents a challenging task. Considering an approach that uses nonlinear crystals with high radiation resistance, pumped by intense laser pulses near their damage threshold, we suggest the crystal of bismuth triborate (BiB3O6, BIBO). Compared to other borate-class crystals, BIBO exhibits relatively high coefficients of quadratic susceptibility. In this paper, we have studied the optical properties of BIBO samples in a wide spectral range from 0.1 to 2.1 THz at temperatures of 473, 383, 295, and 77 K using Terahertz Time-Domain Spectroscopy (THz-TDS). Furthermore, we simulated collinear three-wave interactions with nonzero efficiency for difference frequency generation (DFG) in the THz range. For the pump wavelengths of about 800 nm, we determined phase-matching (PM) conditions and compared the generation efficiency for different crystal cuts. The potential of utilizing BIBO crystal for terahertz frequency generation is discussed. [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]

Different types of resonators are used to create acoustic metamaterials and metasurfaces. Recent studies focused on the use of multiple resonators of the dipole, quadrupole, octupole, and even hexadecapole types. This paper considers the theory of an acoustic metasurface, which is a flat surface with a periodic arrangement of multipole resonators. The sound field reflected by the metasurface is determined. If the distance between the resonators is less than half the wavelength of the incident plane wave, the far field can be described by a reflection coefficient that depends on the angle of incidence. This allows us to characterize the acoustic properties of the metasurface by a homogenized boundary condition, which is a high-order tangential impedance boundary condition. The tangential impedance depending on the multipole order of the resonators is introduced. In addition, we analyze the sound absorption properties of these metasurfaces, which are a critical factor in determining their performance. The paper presents a theoretical model for the subwavelength case that accounts for the multipole orders of resonators and their impact on sound absorption. The maximum absorption coefficient for a diffuse sound field, as well as the optimal value for the homogenized impedance, are calculated for arbitrary multipole orders. The examples of the multipole resonators, which can be made from a set of Helmholtz resonators or membrane resonators, are discussed as well.

• 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]

This paper presents the design and characterization of DENORMS (Designs for Noise‐Reducing Materials and Structures) cell‐based acoustic metamaterial developed using a 3D printing technique. The metamaterial's acoustic absorption properties were investigated through experimental testing and numerical simulations. The experimental testing of the acoustic metamaterial was conducted in an impedance tube using a two‐microphone method. The numerical simulations were carried out using a thermoviscous module. The simulations allowed for a deeper understanding of the influence of geometric parameters on the absorption coefficient, providing valuable insights for optimizing the design. It was observed that upon increasing the spherical diameter while maintaining the same cylindrical diameter and cylindrical length resulted in an increase in the absorption coefficient throughout the frequency range. It was also observed that upon increasing the cylindrical diameter, there was a significant decrement of absorption coefficient, and upon increasing the length of the cylinder, there was a shift of response toward lower frequency. The augmentation in cell count from 9 to 24 led to a rise in the absorption coefficient and a shift of the response toward lower frequencies. The findings highlight the significance of photopolymer 3D printing in tailoring complex geometries for enhanced performance of the acoustic metamaterial. Highlights: Photopolymeric resin used for DENORMS cell‐based acoustic metamaterial.High cleanability and accuracy of digital light processing 3D printing technique.Usage of thermoviscous model for simulation of sound absorption behavior.Use of two microphone impedance tube to determine sound absorption coefficient.Geometric parameters significantly affect the absorption coefficient. [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]

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]

In recent years, the possibility of combining graphene and carbon nanotubes has attracted much attention from researchers attempting to obtain new multifunctional hybrid materials with promising properties. Optoelectronics shows potential as a field of application for such hybrid structures. The variety of existing structural configurations of graphene-nanotube hybrids requires preliminary detailed studies of their optical properties by computer simulation methods. In this paper, we consider island-type graphene-nanotube hybrid films formed by AB-stacked bilayer graphene and single-walled carbon nanotubes (SWCNTs). In this case, bilayer graphene is located above the surface of the nanotube, forming areas with an increased density of carbon atoms, creating so-called "islands." To meet the conditions of a real experiment, we chose chiral SWCNTs (12,6) with a diameter of 1.2 nm, which are most often synthesized in real experiments. All constructed atomistic models of bilayer graphene-chiral SWCNT films were tested for thermodynamic stability at room temperature and proved their suitability for research. Using Kubo-Greenwood formalism, we calculated the complex optical conductivity tensor and absorbance coefficient in the wavelengths of ultraviolet, visible, and near-infrared radiations. The photocurrent spectra are calculated based on the obtained absorption spectra and solar radiation spectra on the earth's surface (AM1.5) and outside the earth's atmosphere (AM0). The results of calculations revealed regularities in the influence of structural parameters (nanotube diameter, graphene width) on the optical and optoelectronic properties of graphene-chiral SWCNT (12,6) with an island structure. [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]

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]

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 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]

Over the last few decades, research works have focused on elucidating the optical properties of semiconductor materials. Despite remarkable progress in the measurement and calculation of the absorption coefficient for semiconductor materials, there is a lack of comprehensive review on the comparative study of absorption coefficient properties for different types of bulk semiconductor materials and their methods for calculating the absorption coefficient. Hence, this paper summarizes the fundamentals of the various methods used to determine the absorption coefficient properties of bulk growth semiconductor crystals, and discusses their advantages and disadvantages. Furthermore, this review provides comprehensive results from recent studies and findings on the absorption properties of near- to mid-infrared (wavelengths from 800 to 7300 nm) group III-V semiconductor materials. In addition, the absorption coefficient of the conventional group IV semiconductors (silicon and Ge) were included for performance comparison. Critical analysis was done for the reviewed materials concerning their material properties, such as band gap structure, crystal quality, and the structural design of the device. The related studies on the methods to determine the absorption coefficients of semiconductors and to improve the likelihood of absorption performance were well highlighted. This review also provides an in-depth discussion on the knowledge of absorption coefficient based on a wide range of semiconductor materials and their potential for sensors, photodetectors, solar and photovoltaic application in the near to mid infrared region. Lastly, the future prospects for research on absorption coefficients are discussed and the advancement in the determination of absorption coefficients for new ternary and quaternary materials is proposed using artificial intelligence such as neural networks and genetic algorithm. [ABSTRACT FROM AUTHOR]

In a recent paper [J Am Ceram Soc. 2018;101:5335‐5345], Pakizeh and Moradi studied the structural, morphological, and optical properties of lead zirconate titanate nanopowders. The refractive index and extinction coefficient of samples were calculated based on reflectance and phase angle between the incident and reflected signals for a particular wavenumber. The authors used the Beer‐Lamber equation to calculate the reflectance spectra. It is shown in this comment that they have used a wrong relation to calculate the reflectance, and consequently, calculated results based on the reflectance, such as refractive index, extinction coefficient, real and imaginary parts of dielectric constant, LO and TO phonon modes are incorrect. [ABSTRACT FROM AUTHOR]

The paper presents the sound absorption coefficient of acoustic absorbers fabricated from natural durian husk fibers, which are currently still considered as agricultural wastes, especially in Malaysia. Samples were fabricated with different fiber densities and thicknesses and the sound absorption performance was measured using the impedance tube method. The results reveal that the durian husk fibers can have absorption coefficient of more than 0.5 above 1 kHz for a minimum thick sample of 20 mm and with minimum density of 160 kg/m3. The optimised macroscopic parameters for various densities were calculated using the inverse method employing the well-known Johnson-Champoux-Allard (JCA) model for porous 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]