Search

A series of low‐carbon fly ash cenosphere plates was prepared using solid waste based cementitious material as binder through a simple process; meanwhile, effects of cenosphere's particle size and size distribution on microstructure and properties were investigated. In the range of 20–200 mesh, as particle size decreases, sound absorption performance decreases while strength improves. Appropriate particle grading can effectively improve the compressive strength, but it will lead to a significant decrease in sound absorption performance. Samples prepared from fly ash cenosphere with a particle size of 20–40 mesh show good sound absorption performance: when the cavity size is 0 mm, the maximum sound absorption coefficient is 0.64 and the average value is 0.36 in the range of 50–1 600 Hz; when the cavity size is 100 mm, sound absorption coefficient at 100 Hz is 0.47, the maximum sound absorption coefficient in the range of 50–1 600 Hz is 0.90, and the average value is 0.57 in the range of 100–500 Hz. The prepared low‐carbon fly ash cenosphere plates show excellent sound absorption performance at low‐frequency and are expected to have broad application prospects in low‐frequency noise reduction and absorption. [ABSTRACT FROM AUTHOR]

This study uses computational analysis to comprehensively investigate lead‐free organic–inorganic CH3NH3SnI3 (MASnI3)‐based perovskite solar cells (PSCs). The optoelectronic properties of MASnI3 are investigated using density functional theory with first‐principles calculations, highlighting its potential for photovoltaic applications. Key findings include the determination of a crucial bandgap (0.97 eV), identification of the onset of photon absorption at energies exceeding 2 eV, and characterization of material properties, such as the absorption and extinction coefficients, reflectivity, and refractive index. Device optimization through simulations explores parameters such as layer thickness, defect density, and different charge transport layers, resulting in a remarkable enhancement in the power conversion efficiency to 16.72%. Additionally, this study focuses on the influence of the working temperature, series resistance (Rs), and shunt resistance (Rsh) on the photovoltaic device performance. Hence, a high photovoltaic efficiency in MASnI3‐based PSCs can be achieved by carefully optimizing the device performance parameters and effectively managing the defect densities. [ABSTRACT FROM AUTHOR]

In the bioinformation photoplethysmography (PPG) measurement, the precision and repeatability could be impacted by the contact pressure between the optical sensor and the measurement site. Taking the finger's geometrical, mechanical, and optical characteristics into consideration, finite element models and Monte Carlo (MC) simulation methods were used to quantitatively analyze the effects of the deformation of different finger layers under contact pressure on its optical parameters and PPG signals during fingertip spectroscopic detection. Firstly, a 3D axisymmetric finger model was established, pelican optimization was used to find the parameter lamp that caused the simulation to best match the finger pressing behavior, modeled the deformation of each layer, and quantified the changes in their absorption and scattering coefficient. Then, before and after pressure application, photon propagation in the reflectance and transmittance modalities within the diastolic and systolic finger tissues at 660 nm and 940 nm were studied by MC simulation. The result shows that contact pressure significantly altered the thickness of the dermis and subcutaneous tissues, a decrease in tissue thickness caused an increase in optical coefficient, which resulted in a reduction in normalized pulsatile reflectance and a boost in transmittance, and the change was dependent on wavelength. [ABSTRACT FROM AUTHOR]

The coupling effects between the stage house and the auditorium in opera houses make the sound field very complex. In the present study, the effects of stage absorption on the primary monaural objective room acoustic parameters in the seating area of an opera house in China were investigated by means of computer simulation and scaled model measurement. In computer simulations, the absorption coefficient of the ceiling and walls of the stage house was changed across several steps, and then a series of experiments were conducted in a 1:20 scaled hall with and without curtains and wall absorption on the stage to verify the simulation results. It was found that stage absorption has a significant influence on early decay time (EDT), reverberation time (RT) and clarity (C80) in the seating area, while the effect on sound strength (G) is much smaller. The values of EDT and RT decrease with an increase in sound absorption on the stage, while C80 displays an opposite trend. In addition, when the average absorption coefficient of the stage walls and ceiling is over 0.5, the variations in these four parameters due to the increase in stage absorption can be constrained within an acceptable range. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation on compacted natural and stabilized tufa sourced from the Beni-Saf region (Algeria). The main objective was to investigate the influence of the hydric parameters (water content (w) and degree of saturation (Sr)) on the capillary absorption coefficient (Aw), thermal diffusivity (D), and thermal effusivity (E). In addition, particular attention was dedicated to the assessment of lime stabilization and different drying periods on the aforementioned properties. The conducted tests involved the examination of samples that were statically compacted under a vertical stress of 4 MPa at a speed rate of 1 mm/min. The results showed an inverse relationship between the capillary absorption coefficient and both the water content and the degree of saturation. Furthermore, the thermal properties (diffusivity and effusivity) displayed a linear relationship with w and Sr. A comparative analysis revealed that samples subjected to lime stabilization exhibited an increase in the coefficient Aw accompanied by a decrease in the thermal properties D and E when compared to natural tufa samples. [ABSTRACT FROM AUTHOR]

Current research efforts in the field of the semiconducting chalcogenide perovskites are directed towards the fabrication of thin films and subsequently determine their performance in the photovoltaic application. These efforts are motivated by the outstanding properties of this class of materials in terms of stability, high absorption coefficient near the band edge and no significant health concerns compared to their halide counterparts. The approach followed here is to use stacked precursor layers and is adopted from other chalcogenide photovoltaic materials like the kesterites and chalcopyrites. The successful synthesis of BaZrS3 from stacked layers of BaS and Zr and annealing at high temperatures (~1100 °C) with the addition of elemental sulfur is demonstrated. However, the film shows the presence of secondary phases and a flawed surface. As an alternative to this, BaS3 could be used as precursor due to its low melting point of 554 °C. Previously, the fabrication of BaS3 films was demonstrated, but in order to utilize them in the fabrication of BaZrS3 thin films, their microstructure and processing are further improved in this work by reducing the synthesis temperature to 300 °C, resulting in a smoother surface. This work lays the groundwork for future research in the fabrication of chalcogenide perovskites utilizing stacked layers and BaS3. [ABSTRACT FROM AUTHOR]

X-ray Absorption Fine Structure Spectroscopy (XAFS) has proven instrumental for the study of atomic-scale structures across diverse materials. This study conducts a meticulous comparative analysis between total electron yield (TEY) and absorption coefficients at the K absorption edge of polycrystalline Fe and Zr60Cu20Fe20 alloy. Our findings not only highlight differences between TEY and transmission XAFS measurements but also demonstrate the capabilities and limitations inherent in these measurement modes within the context of XAFS. This article provides an experimental exploration of widely used X-ray absorption spectroscopy methods, shedding light on the nuances of TEY and transmission XAFS. Through presenting experimental results, we aim to offer insights crucial to the material science community, guiding experimentalists in optimizing measurements while raising awareness about potential misinterpretations. [ABSTRACT FROM AUTHOR]

Background: The background of the study involves the characterization of porous media using an innovative acoustic method. The researchers focus on determining specific parameters related to wave propagation in porous materials. They utilize the equivalent fluid model, a special case of Biot's theory, to understand how sound waves travel through these materials. Purpose: The purpose of the study is to introduce a novel acoustic method for characterizing porous media and determining four important low-frequency non-acoustic parameters. These parameters are viscous permeability, thermal permeability, Norris' inertial factor (viscous tortuosity), and Lafarge's thermal tortuosity. The researchers aim to achieve this characterization by utilizing impedance measurements, numerical solutions for the inverse problem, and experimental data from polyurethane foam samples. Results: The researchers successfully developed and applied the innovative acoustic method to estimate the aforementioned parameters for polyurethane foam samples. The method's accuracy is demonstrated by showing consistent results with direct measurement techniques. Additionally, the absorption coefficients calculated through simulations closely match the experimental data. Importantly, the study's key contribution is its simultaneous measurement of various parameters solely based on low-frequency experimental absorption coefficients. This approach offers a cost-effective and promising alternative to existing methods for characterizing porous media. Conclusion: The study presents a new acoustic method that effectively characterizes porous media and determines key parameters related to wave propagation. This method has been applied to polyurethane foam samples and provides accurate results, offering a cost-effective alternative for characterizing porous materials with potential applications in noise control, acoustic insulation, and environmental acoustics. [ABSTRACT FROM AUTHOR]

Purpose: The low-frequency noise radiated by ships has a significant impact on marine animals; however, traditional ship sound-absorbing materials are not optimal for low-frequency noise control. Therefore, an acoustic metasurface suitable for low-frequency noise control is devised using a spatial folding structure, which is composed of folded channels and perforated structural units. Methods: Numerical methods are used to investigate the acoustic characteristics and absorption mechanism of the metasurface, and the impact of common structural factors on the acoustic performance of the metasurface is studied. An experimental model is produced with 3D printing technology, and the structure's absorption coefficient is examined. Results: A composite acoustic metasurface is designed by coupling multiple cells, and the designed metasurface structure achieves continuous broadband sound absorption in the range of 125–200 Hz. The structure exhibits subwavelength absorption characteristics and has an average absorption coefficient of 0.886 in the target frequency range, with a thickness of 1/27 of the wavelength. Conclusion: Folded channels extend the propagation path of acoustic waves, lead to lower absorption frequencies, and the coupled multicell design broadens the absorption bandwidth. The proposed coupled multicell folded low-frequency acoustic metasurface structure has excellent sound absorption performance and provides new ideas for the design of marine low-frequency broadband acoustic absorbers. [ABSTRACT FROM AUTHOR]

Purpose: Development a new combined material, nanomembrane and melamine foam, for noise attenuation at mid-range frequency to reduce noise inside an airplane cabin. Methods: To be able to investigate how acoustic properties of acoustic foams are affected by nanomaterials, a new type of Helmholtz resonator based on a combination melamine foam and nanomembranes is proposed. Its performance was evaluated experimentally based on ASTM C384 and ASTM C522. Results: The Helmholtz resonator based on an association of nanomembranes doped with carbon nanotubes and melamine foams provided an effective sound absorption coefficient peak (α), ranging from 0.94 to 0.99, in the range of 1200–1600 Hz, a drastic shift from the high frequency range (5500–6000 Hz) commonly detected for melamine foam. The new system sound absorption peak performance at mid-range frequencies (1200–1600 Hz) was obtained with an increase in thickness between 0.05 and 0.09%, a virtual no weight addition to the soundproof material. Moreover, the analytical model based on Langmuir air flow resistivity and the Delany–Bazley equations captured the experimental trend with accuracy. Conclusion: The new material proposed is a valuable option for noise attenuation inside airplane cabin, in special, regional jets. [ABSTRACT FROM AUTHOR]

We present a red light-activated zincII bis(dipyrrin) symmetry breaking charge transfer (SBCT) architecture, showing a large molar absorption coefficient (ε = 15.4 × 104 M−1 cm−1), high reactive singlet oxygen generation efficiency (ΦΔ ≈ 0.8) and long-lived triplet state (τT = 150 μs) compared to the donor–acceptor analogue dipyrrin-BF2 complex, highlighting the superiority of the SBCT approach. For the first time, we demonstrated the potential of a SBCT scaffold in red-light-induced methyl methacrylate (MMA) polymerization, using a dual photocatalyst excitation approach. [ABSTRACT FROM AUTHOR]

Lanthanum titanate glasses (17 La2O3-83 TiO2) are fabricated via aerodynamic levitation melting. Nonlinear refraction and absorption were measured with the Z scan technique using ∼ 550 ps optical pulses at 532 nm wavelength with peak intensities in the range of 0.25–2.5 GW/cm2. The two-photon absorption coefficient (β) and the effective nonlinear refraction coefficient ( n 2 eff ) are found to be, respectively, 2.19 cm/GW and 152 × 10−16 cm2/W (85 × 10−13 esu). The Raman gain is measured to be 106 × 10−11 cm/W. The nonlinearity strength is found to be nearly 60 times larger in lanthanum titanate glasses relative to silica. [ABSTRACT FROM AUTHOR]

In this paper, we formed two graphene/C2P4 van der Waals (vdW) heterostructures (HSs) by stacking the graphene and the C2P4 monolayer which have been predicted by us. First, we investigated the stability of C2P4 monolayer, and calculated the binding energies and flat average differential charge density of two vdW-HSs. Second, we found that two graphene/C2P4 vdW-HSs are all direct semiconductors with bandgap as 0.051/0.064 eV and 0.536/0.697 eV under GGA-PBE/HSE06 functional, respectively, which provides a way to unfold the zero bandgap of graphene or let an indirect monolayer to be a relevant direct semiconductor. Additionally, two graphene/C2P4 vdW-HSs possess high absorption coefficients (16%∼18%) for the visible light and higher absorption coefficients (22%) for the near ultraviolet light, respectively. These admirable properties make two vdW-HSs as novel and potential two-dimensional materials applied on optoelectronic, electronic and photovoltaics devices. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) is a crucial component of continental aquatic ecosystems. It plays a vital role in the carbon cycle by serving as a significant source and reservoir of carbon in water. DOM provides energy and nutrients to organisms, affecting primary productivity, organic composition, and the food chain. This study presents empirical bio-optical models for estimating the absorption of colored dissolved organic matter (aCDOM) in the Negro River using in situ remote sensing reflectance (Rrs) data. Physical–chemical data (TSS, DOC, and POC) and optical data (aCDOM and Rrs) were collected from the Negro River, its tributaries, and lakes and empirical relationships between aCDOM at 440 nm, single band, and the ratio bands of Rrs were assessed. The analysis of spectral slope shows no statistically significant correlations with DOC concentration or aCDOM absorption coefficient. However, strong relationships were observed between DOC and aCDOM (R2 = 0.72), aCDOM and Rrs at 650 nm (R2 > 0.80 and RMSE < 1.75 m−1), as well as aCDOM and the green/red band ratio (R2 > 0.80 and RMSE < 2.30 m−1). aCDOM displayed large spatial and temporal variations, varying from 1.9 up to 20.1 m−1, with higher values in rivers of the upper course of the Negro basin and lower values in rivers with total solids suspended > 10 mg·L−1. Environmental factors that influence the production of dissolved organic matter include soil type, dense forest cover, high precipitation, and low erosion rates. This study demonstrated that aCDOM can serve as an indicator of DOC, and Rrs can serve as an indicator of aCDOM in the Negro basin. Our findings offer a starting point for future research on the optical properties of Amazonian black-water rivers. [ABSTRACT FROM AUTHOR]

In this paper, multi-source observation, such as aircraft, ground-based remote sensing, and satellite-retrieved data, has been utilized to compare and analyze the vertical characteristics of aerosol optical properties and the planetary boundary layer height (HPBL) over the North China Plain (NCP) region during May–June 2016. Aircraft observations show the vertical profiles of aerosol absorption coefficients (σabs), scattering coefficients (σsca), and extinction coefficients (σext) gradually decrease with altitude, with their maximum values near HPBL. The vertical profiles of σext depended most on the vertical distribution of measured σsca, indicating a significant contribution of scattering aerosols. In addition, the prominent characteristic of the inverse relationship between σext and moisture profile could serve as a reference for predicting air quality in the NCP region. The lower layer pollution during the field experiment was likely caused by the accumulation of fine-mode aerosols, characterized by the vertical distribution of the Ångström exponent and the Aerosol Robotic Network (AERONET) products. Typically, HPBL derived from aircraft and surface Micro Pulse Lidar (MPL) was approximate, while the predicted HPBL by meteorological data indicates an underestimation of ~192 m. Aerosol optical depth (AOD) calculated from aircraft and ground-based remote sensing (such as MPL and AERONET) experienced a strong correlation, and both of them exhibited a similar tendency. However, the AOD retrieved from satellites was significantly larger than that from aircraft and ground-based remote sensing. Overall, the inversion algorithm, cloud identification algorithm, representativeness of the space, and time of the observation may lead to an overestimation or underestimation of AOD under certain circumstances. This study may serve as a re-evaluation of AOD retrieved from multi-source observations and provide a reference to uncover the actual atmospheric environment in the NCP regions. [ABSTRACT FROM AUTHOR]

The photoluminescence spectra of the dominant H3 and H4 centers in a natural diamond sample, which is preliminarily characterized by optical and infrared spectrophotometry, are excited by femtosecond laser pulses with a wavelength of 470 nm and varying intensity. Saturation of the photoluminescence intensity of the H3 and H4 centers normalized by the intensity of laser radiation is observed and attributed to the saturation of the resonance transition responsible for the excitation. This makes it possible for the first time to estimate the absorption cross sections of H3 and H4 centers, which can be compared with values known from the literature and those determined from photoluminescence kinetics. The total concentration of H3 and H4 centers can then be found. Taking into account the known absorption coefficient of the sample at a wavelength of 470 nm and the previously established ratio of the contributions from H3 and H4 centers, their concentrations have been estimated separately for the first time. [ABSTRACT FROM AUTHOR]

Instruments measuring aerosol light absorption, such as the Aethalometer and the Multi-Wavelength Absorbance Analyzer (MWAA), have been extensively used to characterize optical absorption of atmospheric particulate matter. Data retrieved with such instruments can be analysed with mathematical models to apportion different aerosol sources (Aethalometer model) and components (MWAA model). In this work we present an upgrade to the MWAA optical apportionment model. In addition to the apportionment of the absorption coefficient babs in its components (black carbon and brown carbon) and sources (fossil fuels and wood burning), the extended model allows for the retrieval of the absorption Ångström exponent of each component and source, thereby avoiding initial assumptions regarding these parameters. We also present a new open-source software toolkit, the MWAA model toolkit (MWAA_MT), written in both Python and R, that performs the entire apportionment procedure. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting, a process aimed at hydrogen production, is considered a pivotal clean energy sources to achieve environmental friendliness and high energy efficiency in the future. The crux of achieving this objective lies in the design of stable and efficient catalysts. Herein, we proposed a novel type-II band alignment GaSe/YAlS 3 van der Waals heterostructure with robust stability for photocatalytic water splitting. The intrinsic electric field of YAlS 3 monolayer can break the requirement of band gap (>1.23 eV) in traditional photocatalytic water splitting theory and significantly enhancing the utilization of solar energy. Encouragingly, compared to individual monolayers GaSe or YAlS 3 , the optical absorption coefficients of the GaSe/YAlS 3 heterostructure are significantly improved and the corrected solar-to-hydrogen (STH) efficiency is improved by 406% and 132%, respectively, reaching an impressive 29.73% efficiency. Furthermore, the heterostructure demonstrates exceptional overall water splitting performance across a broad pH range and maintains a consistently high STH efficiency (25.41%∼34.71%) under a wide range biaxial strain (−6%–5%). In addition, the designed GaSe/YAlS 3 heterostructure showcases enhanced absorption of visible as well as partial absorption of infrared light for photocatalytic water splitting. These compelling findings unequivocally establish GaSe/YAlS 3 heterostructure as an excellent and promising candidate for photocatalytic water splitting. [Display omitted] • The GaSe/YAlS 3 heterostructure is a stable type-II van der Waals semiconductor with large intrinsic electric field. • The GaSe/YAlS 3 heterostructure has a high STH efficiency of 29.73% and can be further enhanced by biaxial tensile strain. • The optical absorption intensity of GaSe/YAlS 3 heterostructure has greatly enhanced in infrared and visible light range. • The GaSe/YAlS 3 heterostructure is a promising water-splitting photocatalyst. [ABSTRACT FROM AUTHOR]

Indole (ind) is a nitrogen-containing heterocyclic volatile organic compound commonly emitted from animal husbandry and from different plants like maize with global emissions of 0.1 Tg yr -1. The chemical composition and optical properties of indole secondary organic aerosol (SOA) and brown carbon (BrC) are still not well understood. To address this, environmental chamber experiments were conducted to investigate the oxidation of indole at atmospherically relevant concentrations of selected oxidants (OH radicals and O 3) with or without NO 2. In the presence of NO 2 , the SOA yields decreased by more than a factor of 2, but the mass absorption coefficient at 365 nm (MAC 365) of ind-SOA was 4.3 ± 0.4 m 2 g -1 , which was 5 times higher than that in experiments without NO 2. In the presence of NO 2 , C 8 H 6 N 2 O 2 (identified as 3-nitroindole) contributed 76 % to all organic compounds detected by a chemical ionization mass spectrometer, contributing ∼ 50 % of the light absorption at 365 nm (Abs 365). In the absence of NO 2 , the dominating chromophore was C 8 H 7 O 3 N, contributing to 20 %–30 % of Abs 365. Indole contributes substantially to the formation of secondary BrC and its potential impact on the atmospheric radiative transfer is further enhanced in the presence of NO 2 , as it significantly increases the specific light absorption of ind-SOA by facilitating the formation of 3-nitroindole. This work provides new insights into an important process of brown carbon formation by interaction of two pollutants, NO 2 and indole, mainly emitted by anthropogenic activities. [ABSTRACT FROM AUTHOR]

We investigated long-term changes using a harmonised 22-year data set of aerosol light absorption measurements, in conjunction with air mass history and aerosol source analysis. The measurements were performed at Zeppelin Observatory, Svalbard, from 2002 to 2023. We report a statistically significant decreasing long-term trend for the light absorption coefficient. However, the last 8 years of 2016–2023 showed a slight increase in the magnitude of the light absorption coefficient for the Arctic haze season. In addition, we observed an increasing trend in the single-scattering albedo from 2002 to 2023. Five distinct source regions, representing different transport pathways, were identified. The trends involving air masses from the five regions showed decreasing absorption coefficients, except for the air masses from Eurasia. We show that the changes in the occurrences of each transport pathway cannot explain the reductions in the absorption coefficient observed at the Zeppelin station. An increase in contributions of air masses from more marine regions, with lower absorption coefficients, is compensated for by an influence from high-emission regions. The proportion of air masses en route to Zeppelin, which have been influenced by active fires, has undergone a noticeable increase starting in 2015. However, this increase has not impacted the long-term trends in the concentration of light-absorbing aerosol. Along with aerosol optical properties, we also show an increasing trend in accumulated surface precipitation experienced by air masses en route to the Zeppelin Observatory. We argue that the increase in precipitation, as experienced by air masses arriving at the station, can explain a quarter of the long-term reduction in the light absorption coefficient. We emphasise that meteorological conditions en route to the Zeppelin Observatory are critical for understanding the observed trends. [ABSTRACT FROM AUTHOR]

Recent huge progress in the field of chemical doping for modifying the physical properties of nano-materials has inspired us to perform this investigation on the electronic and optical properties of GeSe/SnSe vertical heterojunction via P-doping. The calculated results indicate that the pristine GeSe/SnSe vertical heterojunction is a semiconductor and shows a type-II band alignment. After P-doping, all doped heterojunctions have good structural stability due to the negative binding energies. Interestingly, the typical p-type and n-type degenerate semiconductors can be found. In addition, the optical properties including the absorption coefficient, reflectivity and loss function of P-doped GeSe/SnSe vertical heterojunction are discussed. Particularly, in the ultraviolet light range, the optical absorption coefficient of P-doped systems can reach up to 1 4 × 1 0 5 cm − 1 , which suggests that P-doping GeSe/SnSe vertical heterojunctions can serve as a promising material for ultraviolet light detecting. Meanwhile, the absorption and the loss peaks of doped cases exhibit an apparent trend of blue shift with respect to the pristine heterojunction. All these interesting results show that the P-doping gives GeSe/SnSe heterojunction the possibility to tune its electronic and optical properties. [ABSTRACT FROM AUTHOR]

The production of hydrogen through photocatalytic water splitting offers a secure and eco-friendly approach. In this study, the application of GaTe/SnS 2 heterojunction in the field of photocatalysis was studied in depth by using the first-principles calculation method. Based on single-layer GaTe and SnS 2 , a novel two-dimensional GaTe/SnS 2 van der Waals heterojunction (vdwH) was constructed. Through analytical calculations, it is obvious that the GaTe/SnS 2 heterojunction has an indirect bandgap of 0.85eV. Furthermore, its type-II band alignment facilitates efficient separation of photogenerated electrons and holes across different layers. The application of Bader charge analysis revealed an intriguing observation: the GaTe layer transferred a charge of 0.058e to the SnS 2 layer. This charge transfer led to the creation of a robust built-in electric field, which played a pivotal role in efficiently inhibiting the recombination of photogenerated electrons and holes. Under the condition of pH = 0, GaTe/SnS 2 heterojunction can promote redox reaction and realize water splitting. In addition, when the biaxial strain of -3%–3 % is applied to the GaTe/SnS 2 heterojunction, the band edge position and light absorption properties are effectively changed, and more photons participate in the water splitting process. More importantly, the solar-to-hydrogen (STH) efficiency of GaTe/SnS 2 heterojunction reaches 56.6 %, and when ε = 3 %, ηSTH increases to 58.21 %. Hence, our research showcases the GaTe/SnS 2 heterojunction's potential as a highly efficient Z-scheme photocatalyst for water splitting, offering promising prospects for hydrogen production. [Display omitted] • The direct Z-scheme GaTe/SnS 2 heterojunction can effectively promote the separation of electrons and holes. • The GaTe/SnS 2 heterojunction has a built-in electric field from the GaTe to the SnS2 layer. • The absorption coefficient of GaTe/SnS 2 heterojunction is as high as 3.53 × 105cm-1. • The GaTe/SnS 2 van der Waals heterojunction is a highly efficient photocatalyst that can be used for photolysis of water. • The solar-to-hydrogen efficiency of GaTe/SnS 2 van der Waals heterojunction can reach 56.6 %, and can reach 58.21 % when ε = 3 %. [ABSTRACT FROM AUTHOR]

Mixed Sn–Pb perovskites with narrow bandgaps and high optical absorption coefficients are promising photovoltaic materials. However, the easy oxidation of Sn2+ and fast crystallization of mixed Sn–Pb perovskites still limit the efficiency of mixed Sn–Pb perovskite solar cells (PSCs). Here, an imidazole derivative 2‐(Aminomethyl)imidazole dihydrochloride (2‐AD) to suppress the oxidation of Sn2+ and improve the perovskite film quality through coordination with Sn2+/Pb2+ ions is introduced. The optimized devices show a high power conversion efficiency of 22.31% with outstanding long‐term illumination stability. This work provides an effective strategy to achieve efficient and stable mixed Sn–Pb PSCs. [ABSTRACT FROM AUTHOR]

In this article, we have investigated an electron energy spectrum, optical absorption coefficients (OACs) and polarizability under the effect of the co-directed electric and magnetic fields in the multilayer spherical quantum antidot (MSQAD) Al0.3 Ga0.7 As/GaAs/Al0.3Ga0.7 As with off-center impurity. The calculations were done for different dot sizes within the effective mass approximation using the matrix method. The dependence of the total, linear, and nonlinear OACs on the incident photon energy is calculated considering the intraband electron quantum transitions. The donor polarizability and impurity binding energy as function of electric field intensity are obtained at different values of the magnetic field induction. [ABSTRACT FROM AUTHOR]

Sound-absorbing panels are widely used in the acoustic design of aircraft parts, buildings and vehicles as well as in sound insulation and absorption in areas with heavy traffic. This paper studied the acoustic properties of sound-absorbing panels manufactured with three nozzle diameters (0.4 mm, 0.6 mm and 0.8 mm) by 3D printing from three types of polylactic acid filaments (Grey Tough PLA; Black PLA Pro; Natural PLA) and with six internal configurations with labyrinthine zigzag channels (Z1 and Z2). The absorption coefficient of the sample with the Z2 pattern, a 5.33 mm height, a 0.6 mm nozzle diameter and with Black PLA Pro showed the maximum value (α = 0.93) for the nozzle diameter of 0.6 mm. Next in position were the three samples with the Z1 pattern (4 mm height) made from all three materials used and printed with a nozzle diameter of 0.4 mm with a sound absorption coefficient value (α = 0.91) at 500 Hz. The highest value of the sound transmission loss (56 dB) was found for the sample printed with a nozzle size of 0.8 mm with the Z2 pattern (8 mm height) and with Black PLA Pro. The extruded material, the nozzle diameter and the internal configuration had a significant impact on the acoustic performance of the 3D-printed samples. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is the most important staple crop feeding more than half of the world's population. Extensive effort currently undertaken to develop new and improve existing rice cultivars calls for high-throughput, ideally non-invasive methods for monitoring the phenology and performance of rice plants in the field. We report on the results of systematic application of canopy-level reflectance-derived absorption coefficients to the monitoring of rice stands with unmanned aerial vehicle multispectral sensors. The proposed approach was tested in the field on 39 rice varieties. It was capable of assessing rice phenology and physiology traits such as canopy absorption in different spectral regions, biomass productivity, panicle weight and, eventually, crop yield. Importantly, the proposed approach reflected the pigment transformation patterns accompanying the progression of rice phenological phases. Based on this information, our results showed it was possible to resolve with confidence the three key phases of rice phenology regardless of cultivar-specific variation in stand optical properties. The absorption coefficient in photosynthetically active radiation spectral range was significantly related to rice final yield. To the best of our knowledge, for the first time the absorption coefficients at blue and red bands were used to indicate panicle ripening, thus estimating panicle biomass accurately in the tested 39 varieties with the determination coefficient above 0.8. We argue that the proposed approach gives valuable insights into the rice phenology and physiology in the field, so it will become a useful complement to the traditional plant monitoring techniques welcomed by plant physiologists and practitioners, especially those involving in accelerated rice breeding. [ABSTRACT FROM AUTHOR]

The area-averaged effective sound absorption coefficient (SAC) of a rigid-backed homogeneous porous material subjected to a monopole excitation is calculated as the absorbed-to-incident sound power ratio. Using Allard's model to describe the sound propagation above the porous material, an analytical model for this power-based SAC is proposed and proves to give a good approximation of the sound absorption performance under monopole excitation of sufficiently large areas of material. The impact of factors on the power-based SAC, such as monopole height, material radial dimension used to calculate the sound powers, and material properties is discussed. The power-based SAC frequency-dependent behavior is analyzed through sound intensity field assessments at the material surface and is compared to normal incident plane wave and diffuse field SACs. The sound absorption behavior of sound absorbers under monopole excitation exhibits notable distinctions and peculiar results compared to those observed under plane wave and diffuse fields, particularly at low frequencies and for sources close to the material. [ABSTRACT FROM AUTHOR]

The nonlinear absorption of high power cosh-Gaussian laser beam in arrays of vertically aligned carbon nanotube is theoretically investigated. Herein, the cosh-Gaussian (ChG) laser beam propagates perpendicular to the length of carbon nanotube arrays and is mounted on a planer surface. As the high-power laser beam interacts with the carbon nanotube, the electrons associated with it might be excited, undergo the ionized state, and formed the preformed plasma. By the result, the electron cylinder is displaced with respect to ion cylinder. The laser electric field produces the electrostatic restoration force due to the excursion of electrons with respect to ions. This restoration force causes to arise of nonlinearity. An analytical expression of effective nonlinear absorption coefficient of the cosh-Gaussian laser beam is derived. The absorption coefficient is resonantly enhanced as the laser beam frequency approaches near the surface plasmons frequency ω ∼ ω pe / 2 . The presence of collisional frequency between electrons and ions leads to strengthen the absorption process. The laser beam decentered parameter associated with hyperbolic cosine term is a sensitive and effective parameter. This parameter much affects the effective absorption coefficient. The graphical results reveal that the absorption coefficient is strongly dependent on laser beam parameters and carbon nanotube array parameters. This enhanced and tunable absorption process of the cosh-Gaussian laser beam might be applicable in electron heating, self-focusing, and high harmonic generation process. [ABSTRACT FROM AUTHOR]

Photosensitive resin is a kind of polymer gel material. Due to its excellent UV curing performance, it is widely used in the emerging 3D printing industry. This article combines terahertz technology with microfluidic chip technology to study the terahertz spectral characteristics of liquid and solid photosensitive resins under different electric fields. In the experiment, it was found that an electric field can also cause polymerization of photosensitive resin monomers to form cross-linked polymers, increasing their curing degree. For solid photosensitive resins, the orientation of polymer molecules is enhanced under an electric field, and the molecular arrangement changes from a disordered state to an ordered state. Meanwhile, it was found that both liquid and solid photosensitive resins subjected to electric fields exhibit absorption coefficients below zero within a very small frequency range. We explain this from two aspects: energy and the Fabry Pérot effect. This article uses terahertz spectra to study the curing and structural changes in photosensitive resins under an electric field, laying a foundation for further improving 3D printing technology. [ABSTRACT FROM AUTHOR]

Particle size ratio, tablet thickness, and compaction pressure are three important tableting parameters that affect the obtained tablet spectrum. In this study, the single-factor test and response surface analysis (RSM) were adopted to examine how these three parameters and their interactions affect the analytical measurements performed over terahertz time-domain spectroscopy (THz-TDS). Tablet samples were composed of a different percent (wt-%) of acetylsalicylic acid within microcrystalline cellulose. Results indicate that change in absorption coefficient was found to be more obvious for a larger particle size ratio. Thinner tablets were sensitive to absorption coefficient effects created as the transmitted THz radiation propagates through the tablet interfaces. Compression pressure has a limited effect on the absorption coefficient. The particle size ratio had the largest effect on the coefficient of correlation of the quantitative regression model, followed by the compaction pressure, and the tablet thickness. In this study, the optimized tableting parameters were determined: tablet thickness of 0.48 mm, particle size ratio of about 1:1, and compaction pressure of 30 MPa. Under this condition, the R2 of the quantitative regression model of acetylsalicylic acid content was 0.971 and 0.998 at the range of acetylsalicylic acid mass fraction between 10 and 90 wt-%, 1 and 30 wt-%, respectively. This study provides a method to effectively reduce the scattering effect of spectral detection of tablets by improving the sample's properties, to provide a reference for enhancing the reliability and accuracy of quantitative measurements. [ABSTRACT FROM AUTHOR]

Context: The study investigates the impact of Hubbard U correction and spin-orbit coupling (SOC) on the structural, mechanical, electronic, and optical properties of Ti 2 O 3 and SrTiO 3 compounds. The research is motivated by the potential applications of these materials in photovoltaics, with a focus on understanding their properties for such use. The ductility, ionicity, and mechanical stability of both compounds at zero pressure are assessed, indicating their potential as resilient materials. Also, the compounds display high refractive indices and absorption coefficients, indicating their suitability for solar harvesting applications. The predicted bandgaps align primarily with the UV–Vis areas of the electromagnetic spectrum, highlighting their potential in this domain. Methods: Computational techniques employed in this study are density functional theory (DFT) with and without spin-orbit coupling, as well as DFT+U methods, implemented using the Quantum ESPRESSO (QE) package. The study adopts the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, while employing a plane-wave basis set with an energy cutoff of 50 Ry for wavefunctions and 500 Ry for charge density. [ABSTRACT FROM AUTHOR]

Quantum Dots have shown a significant potential as a top candidate for infrared photodetection at higher temperatures. In the presented work, a theoretical model for estimating the coefficient of optical absorption of self-assembled truncated conical quantum dot is developed. This model considers both bound-to-continuum and bound-to-bound absorption mechanisms that increase the accuracy of the absorption coefficient estimation. The developed model is based on estimating the bound states by diagonalizing the Hamiltonian matrix, where the density of states is computed using the Non-Equilibrium Greens function and the effective mass theory to obtain the unbound states. The kinetic equation of Green's function is solved numerically by finite difference method. Besides, the effects of quantum dot size, height, aspect ratio, and density on the coefficient of the optical absorption are investigated. The results of the developed model are contrasted with those of other alternative QD structures where the truncated conical QD structure results in a higher absorption coefficient in infrared range than semispherical and conical QD structures. [ABSTRACT FROM AUTHOR]

Phytoplankton respond to physical and hydrographic forcing on time and space scales up to and including those relevant to climate change. Quantifying changes in phytoplankton communities over these scales is essential for predicting ocean food resources, occurrences of harmful algal blooms, and carbon and other elemental cycles, among other predictions. However, one of the best tools for quantifying phytoplankton communities across relevant time and space scales, ocean color sensors, is constrained by its own spectral capabilities and availability of adequately vetted and relevant optical models. To address this later shortcoming, greater than fifty strains of phytoplankton, from a range of taxonomic lineages, geographic locations, and time in culture, alone and in mixtures, were grown to exponential and/or stationary phase for determination of hyperspectral UV-VIS absorption coefficients, multi-angle and multi-spectral backscatter coefficients, volume scattering functions, particle size distributions, pigment content, and fluorescence. The aim of this publication is to share these measurements to expedite their utilization in the development of new optical models for the next generation of ocean color satellites. [ABSTRACT FROM AUTHOR]

We explored imaging methods to perform in situ field measurements of physical correlates of the visual appearance of snow. Measurements were performed at three locations in Norway between February and March 2023. We used a method to estimate the absorption and scattering coefficients of snow using only one measurement of reflectance captured by the Dia-Stron© TLS850 translucency meter. We also measured the sparkle indicators (contrast and density of sparkle spots) from digital images of snow. The contrast of sparkle spots can be defined as the median value of all the pixels identified as sparkle spots by an algorithm, and the density of sparkle spots is the number of sparkle spots in a selected area of the image. In the case of the sparkle of the snow surface, we found that there is a potential to use the sparkle indicators for classifying the grain types, but it requires a larger data set coupled with expert labelling to define the type of snow. For the absorption and scattering properties, the measurements confirm the fact that snow is a weakly absorptive and highly scattering material when modelling light interactions in the snow. No correlation between the optical properties and sparkle could be found in our data. [ABSTRACT FROM AUTHOR]

Extracting the microscopic parameters of a porous material is a complex task, and attempts have been made to develop models that can simulate their characteristics, gathering the least amount of information possible. As a case in point, tests to evaluate macroscopic behaviors such as tortuosity, which depends directly on the microscopic fluid velocities, are highly susceptible to generate errors if the precision of the measurement devices is not correct, and the same goes for the other parameters. For this reason, in this paper, a sound propagation model in porous materials with a rigid frame is presented based on a local theory, which tries to simplify, even more, the way to obtain the basic characteristics of porous materials, such as their absorption coefficient at normal and random incidence, and their normal surface impedance. The proposed linearized equivalent fluid model presents four phenomenological coefficients, which characterize acoustic propagation trough the material. Their values are obtained from the material thickness and a measurement in an impedance tube following the ISO 10534 standard. Thus, what is only required is the measured absorption coefficient, either on one third or one octave bands, to fully represent the acoustic behavior in the finite different in time domain (FDTD) method. The model has been simulated with FDTD in porous and fibrous kernels, and the results show a strong agreement with the laboratory measurements and with the analytical results calculated with well-established semi-phenomenological models. [ABSTRACT FROM AUTHOR]

Porous materials have emerged as one of the most widely employed sound-absorbing materials in practical applications, owing to their excellent sound absorption properties and lightweight nature. Unsaturated porous materials have the potential to achieve superior sound absorption effects and significantly reduce mass. However, current research on the sound absorption performance of unsaturated porous materials is limited. This paper used a modified transfer matrix method (MTMM), which relies on matrix dimensionality reduction, to analyze the sound absorption characteristics of unsaturated porous materials under various boundary conditions. The study also examines the impact of different parameters, such as material thickness and saturation, on sound absorption performance and compares the results. The findings indicate that when a solid elastic plate is attached to an unsaturated porous elastic plate, the absorption coefficient decreases while the transmission loss increases. Additionally, reducing the thickness of the plate and increasing its porosity and saturation levels lead to an increase in the absorption coefficient and a decrease in the transmission loss. [ABSTRACT FROM AUTHOR]

To investigate the interaction mechanism between a laser, water jet, and substrate, a model is developed to simulate the temperature field evolution and removal process during water jet-guided laser (WJGL) cutting of silicon. The model accounted for the temperature-dependent properties of the silicon absorption coefficient, as well as the physical processes of solid-liquid-gas phase change. A three-dimensional finite volume model of WJGL cutting of silicon is created, incorporating laser energy input, water jet impact-cooling, and silicon phase transition and removal. The volume of fluid (VOF) method is employed to trace the interphase interface and obtain the groove shape. The validity of the model is verified by comparing simulation results with experimental data. The simulation results show that the groove cross section is characterized by a "V" shape. The groove depth nonlinearly increases from 52 to 385 μm with an increasing number of cuts. Additionally, the residual temperature of the silicon substrate rises from 837 to 1345 K as the number of scans increases from 1 to 10. The findings offer valuable insights into WJGL cutting research, specifically shedding light on the intricate details of the laser-water jet-substrate interaction mechanism. [ABSTRACT FROM AUTHOR]

This research analyzes the field enhancement properties of a subwavelength metallic groove working at 0.4 terahertz (THz), which is potentially applicable as a receiver to enhance THz signals in integrated circuits. We derive the analytic formulation of the field magnification by utilizing the distinctive characteristics of the electromagnetic (EM) field inside and above the groove with the EM field continuity on the upper and lower surfaces of the groove. This method, known as the Bruijn theory, has been applied in acoustics and optics to obtain reflection and absorption coefficients. Then, the dependence of these field enhancement properties on both the groove width and depth is examined by theoretical analysis and numerical simulations consistently. Results show that the field enhancement varies periodically with the groove depth in a period of 0.5 λ , featuring the typical Fabry–Perot resonance. The field enhancement is inversely proportional to the groove width due to the cavity effect. Besides, the field intensity can be further enhanced by 10 % via appropriately rounding the sharp vertices at the inlet of the groove. Moreover, the incident angle effect on the field enhancing property is explored. An enhancement of >32 dB can be realized at any incident angle with a groove of dimensions 158 × 225 μ m 2. These results are helpful for understanding the field enhancement mechanism and designing novel THz plasmonic devices, such as an easily manufactured antenna receiver or sensor with simple and compact configuration, as well as offering a feasible solution for the high attenuation problem of THz communications. [ABSTRACT FROM AUTHOR]

We set up an analytical optical model to emulate the absorptance spectra of light scattering, sulfur-hyperdoped silicon that we fabricate by using femtosecond laser pulses. The model allows us to distinguish between contributions to the absolute sub-bandgap absorptance from the path length enhancement of photons due to laser-induced surface roughness, on the one hand, and from the actual hyperdoped layer, on the other hand. Both effects are quantified via the two free parameters of the model. By varying the laser fluence and the areal pulse density, we create a range from almost planar to heavily structured hyperdoped Si samples that we show to behave almost like a Lambertian scatterer. The optical depth a1, i.e., the product of the absorption coefficient close to the Si bandgap energy and the effective thickness of the hyperdoped layer, scales with the surface area enhancement, which we identify as the main driving force for large sub-bandgap absorptances of this material type. It reaches maximum values of nearly a1 = 0.4, which refers to an absolute absorptance of 82% at a wavelength of 1450 nm. We furthermore discuss, quantify, and reduce possible error sources when determining the absorptance of such optically rough, hyperdoped samples with a spectrophotometer. [ABSTRACT FROM AUTHOR]

The development of inkjet-printed 2D crystal inks offers the ability to print different 2D materials on various substrates to form vertical heterostructures. However, the detailed characterization of the atomic structures of the inkjet-printed MoTe2 nanosheets has been rarely reported. In this work, water-based 2D crystal inks of MoTe2, WS2, and graphene have been prepared and printed to obtain the flexible photodetectors. The absorption coefficient of MoTe2 has been estimated as α (500 nm) = 925 ± 47 lg−1 m−1 using the gravimetric method. Intriguingly, the inkjet-printed MoTe2 nanosheets down to 4 nm show both the semiconducting 2H and metallic 1T′ phases. The responsivities of the photodetectors based on MoTe2/graphene and WS2/graphene heterostructures can reach 120 mA/W and 2.5 A/W at 532 nm, respectively. Moreover, the inkjet-printed MoTe2/graphene shows a responsivity of 7.7 mA/W at 940 nm. The fabrication technique of inkjet printing will help design flexible optoelectronic devices based transition metal dichalcogenide–graphene heterostructures for the near-infrared photo detection. [ABSTRACT FROM AUTHOR]

Essential Climate Variables (ECVs) like ocean colour provide crucial information on the Optically Active Constituents (OACs) of seawater, such as phytoplankton, non-algal particles, and coloured dissolved organic matter (CDOM). The challenge in estimating these constituents through remote sensing is in accurately distinguishing and quantifying optical and biogeochemical properties, e.g., absorption coefficients and the concentration of chlorophyll a (Chla), especially in complex waters. This study evaluated the temporal and spatial variability of bio-optical properties in the coastal waters of the Western Iberian Coast (WIC), contributing to the assessment of satellite retrievals. In situ data from three oceanographic cruises conducted in 2019–2020 across different seasons were analyzed. Field-measured biogenic light absorption coefficients were compared to satellite estimates from Ocean-Colour Climate Change Initiative (OC-CCI) reflectance data using semi-analytical approaches (QAA, GSM, GIOP). Key findings indicate substantial variability in bio-optical properties across different seasons and regions. New bio-optical coefficients improved satellite data retrieval, reducing uncertainties and providing more reliable phytoplankton absorption estimates. These results highlight the need for region-specific algorithms to accurately capture the unique optical characteristics of coastal waters. Improved comprehension of bio-optical variability and retrieval techniques offers valuable insights for future research and coastal environment monitoring using satellite ocean colour data.

Monitoring and protecting flowing watercourses is a complex and challenging task that requires the collaboration and coordination of various stakeholders such as governments, industries, farmers, consumers and environmental groups. The study of the dynamics of the concentration of polluting factors and especially the concentrations of heavy metals and highlighting a seasonal variation is a necessary element from this point of view. In this article, we present the results of our analyses carried out in two measurement campaigns executed in 10 monitoring points along the Danube River, between Braila city and Isaccea city in the pre-deltaic area, during the summer season and autumn season 2022. The importance of this area is given by the fact that the Danube Delta is part of the UNESCO heritage, and the monitoring of polluting factors is a necessity in the desire to protect this area. The data measured during the July and August 2022 campaign cover a wide range of chemical species: Phosphate, CCO, CBO5, NH4+, N-NO2, N-NO3−, N-Total, P-PO4 3−, SO42−, Cl−, phenols, as well as metals with a harmful effect: Al, As, Cd, Cr, Fe. The study includes an evaluation based on the statistical approach of the results to highlight the significant correlations and differences identified between the two data sets. Next, to highlight the obtained results, a numerical model was considered using HEC-RAS and ESRI ArcGIS applications in a two-dimensional unsteady flow model in order to obtain the non-homogenous concentrations’ distributions in the studied area. These two-dimensional models have been less studied in the specialized literature. In this way, interesting results could be obtained, and prediction methods regarding the dynamics of metal concentrations could be structured. The data obtained were used for the terrain model from the USGS service, and the flows of the Danube and its two tributaries were simulated using the data provided by the national services. In this work, we present the results obtained for the dynamics of the concentrations of the metals Al, As, Cd, Cr and Fe and the evaluation of the specific absorption coefficients for the explanation and correlation with the results of the measurements. Except for the numerical model presented, we would like to highlight the existence of some contributions of the main tributaries of the Danube in the study area. Such a systematic study has not been carried out due to conditions imposed by the border authorities. From this point of view, this study has an element of originality. The study is part of a more complex project in which the spatio-temporal distribution of the polluting factors in the water was evaluated, and the habitats in the study area were inventoried—especially those of community interest. In this way, we were able to expose the self-purification capacity of the Danube and highlight the existence of a concentration reduction gradient along the course of the river. The aspects related to the influence of the distribution of polluting factors on the state of health will be the subject of another article.

A compact, highly sensitive, and cost-effective photoacoustic spectroscopic sensor for multiple trace gas detection was reported with a self-designed compact distributed feedback laser array and a 2-channel dual phase field programmable gate array based digital lock-in amplifier, only twentieth in size and weight of the commercial instruments. The capability of the portable sensor was verified by measuring CH4 and C2H2 simultaneously. With an integrated nonlocal means algorithm denoising, noise-equivalent concentrations were achieved as 6.89 ppb for CH4 and 2.74 ppb for C2H2, respectively, corresponding to a normalized noise equivalent absorption coefficient of 1.1 × 10-10 cm-1 W/Hz-1/2, a 79 folds higher than the original data. The results demonstrate that the developed minimized sensor has the potential for sensitive and portable measurement of multiple trace gases. [ABSTRACT FROM AUTHOR]