Calculation Of Absorption Coefficient Research Articles

Special-point approach for optical absorption coefficient calculations on two-dimensional self-assemblies of type-II perovskite quantum dots

All-inorganic perovskite quantum dots with the usual cubic shape have emerged as a successful and low-cost alternative to electronically functional nanomaterials motivating various fields of applications, including high-efficiency photovoltaics. Here, we present an efficient and almost analytic approach for optical absorption coefficient calculation on self-assembled perovskite quantum dot films with type-II band alignment. The approach takes advantage of the special point technique for integration over the two-dimensional Brillouin zone, which minimizes the computational cost. The set of special wave-vector points is generated using the Monkhorst and Pack method. The optical absorption spectrum for phenyl-C60-butyric acid methyl ester (PCBM)/CsPbI3quantum dot films is computed, in good agreement with the experiment assuming a homogeneous linewidth of 50 meV and considering a ten special-point set. We show that light absorption in these systems is a cooperative optoelectronic property resulting from the quantum-mechanical coupling between perovskite nanocubes, leading to extended system states. The generality of this approach makes it suitable for calculating the optical absorption coefficient in a broad class of perovskite quantum dot systems.

Random incidence absorption characteristics and parameterized design of micro-perforated panel absorbers with parallel-arranged backing cavities at different depths

Micro-perforated panel absorbers (MPAs) are recognized as efficient and environmentally friendly materials for sound absorption, prompting significant research efforts to expand their frequency ranges. This study investigates the acoustic performance of MPAs with parallel-arranged backing cavities at different depths (PCD) under random incidence conditions. Initially, an analytical model is proposed to predict the acoustic performance of PCD-MPA. The model exhibits significant consistency with finite element simulations and experimental measurements, validating its reliability in calculating absorption coefficients within the primary frequency band of concern (500~4000 Hz) in architectural acoustics applications. Subsequently, a thorough discussion of the key parameters, including the depth sequence and perforation parameters, which influence the random incidence absorption characteristics of PCD-MPA is presented based on the proposed model. These discussions lead to the development of an enhanced parameterized design method aimed at improving the absorption performance of PCD-MPA, enabling precise modulation of parameter combinations to meet specific application requirements and design nearly perfect absorbers.

Wide band gap tuning of Mg doped ZnO thin films for optoelectronic applications.

Zinc oxide (ZnO) thin films with magnesium (Mg) doping have demonstrated significant potential due to their wide band gap, which enables efficient absorption of ultraviolet (UV) radiation while maintaining transparency to visible light. Sol-gel spin coating methods were used to deposit Mg-doped ZnO thin films. The solution was made with methanol as the solvent, and the starting materials were magnesium acetate tetrahydrate and zinc acetate dihydrate. The integration of Mg content in deposited ZnO films was investigated for structural, morphological, and optical properties using an X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), and UV-VIS spectrophotometer. Mg-doped ZnO films were produced on quartz substrates and post-annealed at 400°C. According to absorption coefficient calculations, the optical band gap of Mg-doped ZnO films is in the range of 5.4 eV which is ideal for a variety of applications in the field of optoelectronic devices.

Energy gap measurements based on enhanced absorption coefficient calculation from transmittance and reflectance raw data

The absorption coefficient plays an important role in studying and characterizing semiconducting materials. It is an important parameter to study the mechanism of photons absorption within the structure of the studied material. Thus, it helps to study the several types of charge carrier transport along with the energy band structure and its defects. In literature, a formula was reported to precisely calculate the absorption coefficient from raw data of transmittance and reflectance of electromagnetic radiation. However, the reported formula has several issues limiting its validity in the literature. In this paper, we provide a more mathematically accurate form of this equation to precisely obtain the absorption coefficient from the raw data, by considering the total internal reflection at the different interfaces. Moreover, the equation is tested by simulated data and is applied to study the optical characteristics of a single-component epoxy resin from its transmittance and reflectance raw data.

Mechanism analysis and optimal design of sound-absorbing metastructure constructed by slit-embedded Helmholtz resonators

<sec>Low-frequency noise has always been a thorny problem in the field of noise control. In recent years, the development of sound-absorbing metastructures has provided new ideas for controlling low-frequency noise. In this work, we propose a low-frequency sound-absorbing metastructure constructed by Helmholtz resonators with embedded slit. Analytical and numerical models are established to analyze the sound absorption performance and mechanism of the proposed sound-absorbing metastructure, and optimization design is conducted to achieve low-frequency wideband absorption performance. The analytical modeling method and the performance of the proposed sound-absorbing metastructure are also experimentally verified. The main conclusions are summarized as follows.</sec><sec>1) By using transfer matrix method and finite element method, analytical and numerical models for calculating sound absorption coefficient are established. It is shown that analytical predictions are in good agreement with numerical calculations. It is demonstrated that a typical design of a 30-mm-thick single-cell metastructure can achieve a sound absorption coefficient of 0.88 at 404 Hz. Typical designs of two-cell parallel structure and the four-cell parallel structure (both with a thickness of 50 mm) can achieve two and four nearly perfect low-frequency sound absorption peaks in a frequency band of 200–400 Hz, respectively.</sec><sec>2) The low-frequency sound absorption mechanisms of the proposed metastructures are explained from four aspects: simplified equivalent model parameters, normalized acoustic impedance, complex-plane zero/pole distribution, and sound pressure cloud image and particle velocity field distribution. It is demonstrated that the main sound absorption mechanism is related to the thermal viscous loss of sound waves, caused by the inner wall of embedded slit.</sec><sec>3) The design for broadband low-frequency absorption performance is optimized by using differential evolution optimization algorithm. An optimized parallel-multi-cell coupled metastructure with multiple perfect sound absorption peaks below 500 Hz is realized. For a thickness of 90 mm, the sound absorption coefficient curve of an optimized metastructure exhibits 8 almost perfect sound absorption peaks and an average sound absorption coefficient of 0.86 in a frequency range of 170－380 Hz.</sec><sec>4) Experimental samples are fabricated to test sound absorption. Experimental results are basically consistent with the analytical predictions. The results from analytical model, numerical calculations and experimental measurements are mutually verified.</sec><sec>In summary, the sound-absorbing metastructures with a thickness of sub-wavelength, proposed in this work, exhibit outstanding sound absorption performance at low frequencies. We demonstrate that they are suitable for low frequency broadband sound absorption below 500 Hz. Owing to their thin thickness and relatively simple construction, they have broad application prospects in practical noise control engineering.</sec>

Optoelectronic Digital Dust Meter in Cotton Gining Manufactory

The paper discusses the problems of environmental pollution and requirements for instruments and systems for measuring dust levels. It is demonstrated that among the problems of environmental protection, the most crucial one is the protection of the air basin. Dust is one of the most common types of industrial waste. Human health is affected not only by the type of dust, particle size and mineralogical composition, but also by the duration of exposure. Therefore, high sensitivity of instruments and systems for monitoring atmospheric pollution is required. The problem of environmental pollution can only be solved with the help of automatic, continuously operating analysers. It is advisable to develop and implement portable threshold alarms that have a significantly lower cost than the cost of automatic control and measurement equipment. The operating principle of an optoelectronic device for monitoring the degree of dust in cotton ginning rooms has been developed and presented, which allows simultaneous measurement of the attenuation (extinction) and light scattering of the same passing mass of aerosol. The calculation of specific absorption and dispersion coefficients in the ginning shops of cotton gin plants has been carried out. Experimental curves of the ratio of absorption and attenuation coefficients depending on the presence of the aerosol in the optoelectronic device are presented. Methods to reduce measurement error are revealed.

Optical emission spectroscopy of fiber laser sustained Xe plasma

Laser-sustained plasma (LSP), a unique method of obtaining high brightness broadband light sources, has been used for rapid optical inspection of wafer defects and has thus attracted great interest. Then Xe plasma sustained under high pressure by a continuous fiber laser was investigated using optical emission spectroscopy (OES). Emission spectra of spatial integration diagnosis have shown that with the increase of laser power and the decrease of Gaussian beam focusing number F, the electron temperature fitted by Boltzmann plot method increased from 0.45 eV to 0.85 eV, the corresponding electron density was roughly an order of magnitude of 1016-1017 cm-3, and the calculated absorption coefficient of plasma was distributed in 0.9–1.5 cm-1. To further analyze the spatial distribution of plasma parameters, the spatial resolved OES of LSP was acquired, and the two-dimensional electron temperature and electron density were determined. The non-uniform distribution of the plasma parameters was analyzed due to the existence of thermal gravity convection and forced convection. The serious self-reversal of emission lines of 881.94 nm and 823.16 nm was observed and analyzed.

High Te discrepancies between ECE and Thomson diagnostics in high-performance JET discharges

The present paper is dedicated to the study of the discrepancies encountered in electron temperature (Te) measurements carried out with electron cyclotron emission (ECE) and Thomson scattering (TS) diagnostics in the core of the JET tokamak. A large database of discharges has been collected, including high-performance scenarios performed with deuterium only and deuterium–tritium mixtures. Discrepancies have been found between core Te measurements taken with an X-mode ECE interferometer (TECE) and a LIDAR TS system (TLID) for Te>5 keV. Depending on the plasma scenario, TECE has been found to be systematically higher or lower than TLID. Discrepancies have also been observed between the peaks of the ECE spectrum in the second (X2) and third (X3) harmonic domains, even in high optical thickness conditions. These discrepancies can be interpreted as evidence of the presence of non-Maxwellian features in the electron energy distribution function (EEDF). In order to investigate the relation between the shape of the EEDF and the measured discrepancies, a model for bipolar perturbations of Maxwellian EEDF has been developed. The model allows analytical calculations of ECE absorption and emission coefficients; hence, the comparison of modeled ECE spectra with experimental data. The different experimental results observed for the various JET scenarios have been found to be qualitatively reproducible by adapting the model parameters, suggesting that bipolar distortions of the bulk EEDF could play a role in giving rise to the reported discrepancies between ECE and TS measurements.

A study on the prediction model of water column sound absorption coefficients considering the characteristics of the East Sea of South Korea

East Sea of Korea has the deepest water depth among Korean seas, and the water column changes are distinct in space and time, resulting in a wide range of water column sound absorption coefficients. In this study, we calculate and analysis the spatiotemporal variation of water column sound absorption coefficient in the East Sea of Korea, which has unique oceanographic characteristics. Using extensive CTD data from the Korea Oceanographic Data Centre (KODC) from 1991 to 2021, we calculate the sound absorption coefficient using the widely applied Francois–Garrison model and reveal the unique absorption characteristics of the East Sea. The derived coefficients are then used to calibrate and improve past multibeam echosounder system (MBES) data, which suffered from incomplete water column information and arbitrary mean values. To facilitate the calculation and development of sound absorption coefficient, a MATLAB-based graphical user interface (GUI) was developed. The results of this study contribute to the calculation and inference of sound absorption coefficients along spatial and temporal dimensions of the water column in the East Sea and to the extraction of more accurate seafloor information from MBES data. This study developed the way for future research focusing on algorithmic advances and new methodologies for the calculation of sound absorption coefficients in the West and South Seas of Korea.

Rapid calculation of atmospheric molecular absorption characteristics in the terahertz band based on wideband K-distribution method

This paper focuses on rapidly calculating atmospheric molecular absorption properties in the 0.3–30 THz frequency range of terahertz waves. It conducts research related to spectral radiation models and fast computation model databases. Based on the latest version of the High-resolution transmission molecular absorption database-2020, in conjunction with the line-by-line (LBL) spectral radiative calculation method, the spectral absorption characteristics of nine atmospheric molecules (H2O, CO2, O3, NO, N2O, NO2, NH3, SO2, CH4) are analyzed. The relative contributions of the eight other gas molecules absorption abilities in the terahertz range are examined, with H2O molecule serving as the reference. Taking into account the non-gray absorption properties of atmospheric molecules and the need for fast computation, this study divides the frequency range of 0.3–30 THz into 24 calculation bands based on the spectral absorption distribution characteristics of atmospheric molecules. Utilizing LBL calculations with a resolution of 0.01 cm−1, a non-correlated wideband K-distribution model (WBK) is developed, which achieves nearly the same computational accuracy as LBL. Furthermore, the WBK radiation calculation model is validated under both uniform and non-uniform atmospheric conditions based on earth atmospheric environmental parameters. An exponential kernel fitting coefficient table for the rapid calculation of atmospheric molecular absorption coefficients is established based on the WBK radiation calculation model to improve computational efficiency further. This database enables fast calculation of 24 broadband absorption coefficients (corresponding to 7 Gaussian integration points) within 0–100 km altitude in earth atmosphere.

Exploring a monotonically non-decreasing behavioral function on shielding properties and transmission factors in borosilicate glasses through heavy metal oxide reinforcement

In this study, the gamma-ray attenuation properties and transmission factors of different types of glasses formed in the (B2O3)x[(ZnO)0.60-(SiO2)0.40]1-x system as a function of increasing heavy metal oxide ratio were investigated. For transmission factor and absorption coefficient calculations, the general-purpose Monte Carlo code MCNPX (2.7.0) was used. In addition, the Phy-X/PSD code is used to obtain some important gamma-ray shielding parameters. According to the obtained results, increasing the quantity of heavy metal oxide in the glass composition favorably affected the examined parameters and lowered the transmission factor and buildup factor values. Furthermore, it has been observed that parameters such as the absorption coefficient and the effective atomic number increase as a function of increasing heavy metal oxide contribution into glass configuration. The lowest half value layer values are reported for S1 sample. For example, half value layers are reported as 3.313 cm, 3.449 cm, 3.764 cm, 3.625 cm, 3.515 cm for S1, S2, S3, S4, and S5 sample at 1 MeV photon energy, respectively. According to the transmission factor values, S1 is the sample that allows the least transmission of primary photons and demonstrates the highest resistance. It was observed that the minimal exposure build-up factor and energy absorption buildup factor values for the S1 sample at 10 mean free paths. It can be concluded that the heavy metal oxide additive applied to borosilicate glasses creates a non-decreasing functional behavior effect that is monotonic in gamma-ray attenuation parameters.

Effects of Cu, Zn Doping on the Structural, Electronic, and Optical Properties of α-Ga2O3: First-Principles Calculations.

The intrinsic n-type conduction in Gallium oxides (Ga2O3) seriously hinders its potential optoelectronic applications. Pursuing p-type conductivity is of longstanding research interest for Ga2O3, where the Cu- and Zn-dopants serve as promising candidates in monoclinic β-Ga2O3. However, the theoretical band structure calculations of Cu- and Zn-doped in the allotrope α-Ga2O3 phase are rare, which is of focus in the present study based on first-principles density functional theory calculations with the Perdew-Burke-Ernzerhof functional under the generalized gradient approximation. Our results unfold the predominant Cu1+ and Zn2+ oxidation states as well as the type and locations of impurity bands that promote the p-type conductivity therein. Furthermore, the optical calculations of absorption coefficients demonstrate that foreign Cu and Zn dopants induce the migration of ultraviolet light to the visible-infrared region, which can be associated with the induced impurity 3d orbitals of Cu- and Zn-doped α-Ga2O3 near the Fermi level observed from electronic structure. Our work may provide theoretical guidance for designing p-type conductivity and innovative α-Ga2O3-based optoelectronic devices.

Cs2TiI6 (Cs2TiIxBr6-x) Halide Perovskite Solar Cell and Its Point Defect Analysis.

This work presents a comprehensive numerical study for designing a lead-free, all-inorganic, and high-performance solar cell based on Cs2TiI6 halide perovskite with all-inorganic carrier transport layers. A rigorous ab initio density-functional theory (DFT) calculation is performed to identify the electronic and optical properties of Cs2TiI6 and, upon extraction of the existing experimental data of the material, the cell is designed and optimized to the degree of practical feasibility. Consequently, a theoretical power conversion efficiency (PCE) of 21.17% is reported with inorganic TiO2 and CuI as carrier transport layers. The calculated absorption coefficient of Cs2TiI6 reveals its enormous potential as an alternative low-bandgap material for different solar cell applications. Furthermore, the role of different point defects and the corresponding defect densities on cell performance are investigated. It is found that the possible point defects in Cs2TiI6 can form both the shallow and deep defect states, with deep defect states having a prominent effect on cell performance. For both defect states, the cell performance deteriorates significantly as the defect density increases, which signifies the importance of high-quality material processing for the success of Cs2TiI6-based perovskite solar cell technology.

Submerged Photosynthesis of Molybdenum–Tungsten Nanostructures for Supercapacitor Application

Research on electrochemical energy storage devices aims to produce supercapacitors via a facile and nonpolluting method. Because of unnecessary elemental doping and disordered morphologies of nano-oxides, impurities in raw materials during the conventional fabrication process would reduce the pseudocapacitance. Herein, we propose a submerged photosynthesis crystalline method for synthesizing oxygen vacancy (Vo)-enriched Mo–W oxide hydrates and Mo-doped tungsten oxide hydrate nanocomposites at 55 °C and normal pressure. In addition, this study describes the impact of Vos on pseudocapacitance using ab initio calculations based on density functional theory. Doping the WO3·0.33H2O lattice with Mo and Vos brings the conduction band closer to the Fermi energy level. The comparison of the ultraviolet–visible–near-infrared (UV–vis–NIR) irradiation spectrum and absorption coefficient calculation suggests that Mo and Vo doping is responsible for the NIR absorption. This study concludes that enriched Vos result in the highest specific capacitance and pseudocapacitive behavior of MoxW1–xO3·0.33H2O.

Helmholtz resonator with two resonance frequencies by coupling with a mechanical resonator

This contribution presents the acoustical properties and corresponding theoretical descriptions of a Helmholtz resonator with an integrated cantilever inside the Helmholtz resonator neck. The advantage of this resonator design is a second resonance frequency, which leads to a supplemental frequency region with high sound absorption properties. An analytical model is derived to calculate the resonance frequencies and the absorption coefficient of the resonator system. This model has been verified with finite element simulations for the resonance frequencies, taking into account several geometric parameter variations. It has been validated experimentally for the calculated absorption coefficients by impedance tube measurements. In conclusion, it has been found a high influence of the geometric parameters on the resonance frequencies and a broader sound absorption performance of the coupled resonator system.

In English

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.

Discerning the crystal structure and engineering the optoelectronic properties through substitution of divalent cations (M= Zn, N = Ge) in C3H3MxN1-xI3 for solar cell applications

Herein, we identified the ground state crystal structures of C3H3ZnxGe1-xI3 hybrid perovskite materials and investigated their optoelectronic properties for the first time using van der Waals correction, included ab initio calculations with hybrid functionals. The energy difference and formation energy calculations are done to perceive the information related to their structural phase transition and stability. Chemical bonding between the atomic constituents are found from charge density distribution, projected crystal orbital Hamiltonian population (pCOHP) and its integration (IpCOHP) results. Our electronic structure calculations predict the compositions with x = 0, 0.25, 0.5, 0.833 as indirect band gap materials and x = 0.667 and 1 as direct band gap materials. Our results also predict that the composition with x = 0.833 value belongs to the classification of intermediate band gap semiconductor. The effective mass of holes and electrons are calculated at valence and conduction band edges, respectively, to realize the transport property of carriers. The absorption coefficient calculations infer that composition with x = 0.667 shows better optical absorption property in the visible region compared to other compositions. The applicability of these materials towards solar cell device performance is explored by calculations of cell parameters and it is found that the power conversion efficiency is higher for the composition with higher Ge concentration than Zn. Specifically, low PCE values in the range of 8.66–17.32% corresponds to C3H3Zn0.833Ge0.167I3 and high PCE values in the range of 16.52–33.04% corresponds to C3H3Zn0.5Ge0.5I3.

First-principles calculations of electronic structures and response functions of hexagonal BaAl2O4

Using meta generalized gradient approximations (meta-GGA) to describe the exchange–correlation functional within the framework of density functional theory, we performed first-principles calculations on the electronic structures and response functions of hexagonal BaAl2O4. The electronic structures (band structures, density of states) and response functions (dielectric function, refractive index function, extinction coefficient function and absorption coefficient function) are presented for hexagonal BaAl2O4. It is found that: (i) the bandgap value derived via the meta-GGA (6.40 eV) is in excellent agreement with the experimental value of BaAl2O4 (6.47 eV); and (ii) the calculated absorption coefficient function shows that hexagonal BaAl2O4 exhibits noticeable absorption only when the wavelength of incident photons is less than 194 nm (hν > 6.40 eV), which is consistent with the synchrotron radiation excitation spectrum. Although a complete and reliable description of the electronic structures and optical properties is still on the way, our results have demonstrated that the electronic structures and optical properties derived from the density functional theory based first-principles calculations can be used with reasonable reliability to interpret the optical features of hexagonal BaAl2O4.

Effectof annealing temperature on opticaland electrical propertiesof SnS thin films

SnS thin films have been depositedat R.T. with thickness (300 nm ± 0.01) by using a thermal evaporation technique and annealed at 200°C for 2hour.The optical band gap of the SnS film determined from optical transmittancespectrum, in the range (400-1100 nm)and the data was used to calculate absorption coefficient and optical band gap. The film as grownand annealed has shown a direct band gap ~ 2.24 eV and 2.17eV respectively.The optical constant such as extinction coefficient (k), absorption coefficient (α) and refractive index (n) have been evaluated.
 At the annealing temperature the SnS film had the best electrical properties the mobility was up to 52.35 cm².V¯¹.s ¯¹, and the resistivity was about 0.14×106(Ω.cm).

Study of Phytoextraction at Some Locations of Ajaristskali River Based of Soils and Plants Analysis

The gorge of the Ajaristskali River and its surrounding areas are important habitats for biodiversity. The territories adjacent to the gorge are a refugium of tertiary moisture-loving Colchis relic forest ecosystems, which have been awarded the status of a UNESCO World Natural Heritage Site. Ongoing work on the construction of a cascade hydroelectric power station in the gorge poses a risk of loss of the natural habitats. The article presents studies of assessing the ecological state of forest ecosystems in locations: Shuakhevi settlement, Shuakhevi water intake and Shuakhevi hydroelectric power station (HPP). In order to evaluate the current ecological state in the Ajaristskali gorge, the phytoextraction capacity of the dominant tree species forming the main natural forest in this area was studied. The alkalization of the soil samples taken from the Ajaristskali gorge was observed at the Shuakhevi HPP intake and Shuakhevi HPP. The soils are poor in total humus and nitrogen evidencing their decreased fertility. Data of the soil pollution hazard ratio show that the hazard of pollution with heavy metals, As, Ba, Cd, and Pb, exceeds 1-near Shuakhevi HPP intake and Shuakhevi HPP; pollution with Mo, Zn is observed at Shuakhevi HPP location; and Mn pollution is observed at all three locations. Based on the calculation of biological absorption coefficient of heavy metals, we have identified the dominant tree species forming the main natural forests on the study sites, whose vegetative parts have a good phyto-extraction ability for toxic elements. Such plants are: pine (needles), oak (leaves), and alder (leaves).