Search

Materials datasets usually contain many redundant (highly similar) materials due to the tinkering approach historically used in material design. This redundancy skews the performance evaluation of machine learning (ML) models when using random splitting, leading to overestimated predictive performance and poor performance on out-of-distribution samples. This issue is well-known in bioinformatics for protein function prediction, where tools like CD-HIT are used to reduce redundancy by ensuring sequence similarity among samples greater than a given threshold. In this paper, we survey the overestimated ML performance in materials science for material property prediction and propose MD-HIT, a redundancy reduction algorithm for material datasets. Applying MD-HIT to composition- and structure-based formation energy and band gap prediction problems, we demonstrate that with redundancy control, the prediction performances of the ML models on test sets tend to have relatively lower performance compared to the model with high redundancy, but better reflect models' true prediction capability. [ABSTRACT FROM AUTHOR]

In this paper, the design of a dual-band filter based on the band gap waveguide (BGW) is presented. In the low-frequency band, the TE201 mode rectangular waveguide cavity resonator was used to design the bandpass filter, which significantly reduces the impact of the high-frequency transmission line (TL). In the high-frequency band, a TE101 mode cavity resonator based on the gap waveguide (GW) structure was used to design the high-frequency band filter. A lower insertion loss can be achieved with the use of all-metal structure. A dual-band filter prototype was fabricated to verify its performance. According to the measurement results, the insertion loss is less than 1.3 dB and the return loss is better than 14 dB in the frequency range of 5.92–6.06 GHz; and the insertion loss is less than 1.77 dB and the return loss is better than 15 dB in the frequency range of 80.6–86.2 GHz. The frequency ratio is as large as 13.9, and because the high-frequency band filter is embedded in the cavity resonator of the low-frequency band filter, it saves space to a certain extent and realizes the integrated design of the dual-band filter, which is of great significance for the improvement of the performance of the dual-band communication system in higher-frequency bands. [ABSTRACT FROM AUTHOR]

CsGeI2Br-based perovskites, with their favorable band gap and high absorption coefficient, are promising candidates for the development of efficient lead-free perovskite solar cells (PSCs). However, bulk and interfacial carrier non-radiative recombination losses hinder the further improvement of power conversion efficiency and stability in PSCs. To overcome this challenge, the photovoltaic potential of the device is unlocked by optimizing the optical and electronic parameters through rigorous numerical simulation, which include tuning perovskite thickness, bulk defect density, and series and shunt resistance. Additionally, to make the simulation data as realistic as possible, recombination processes, such as Auger recombination, must be considered. In this simulation, when the Auger capture coefficient is increased to 10−29 cm6 s−1, the efficiency drops from 31.62% (without taking Auger recombination into account) to 29.10%. Since Auger recombination is unavoidable in experiments, carrier losses due to Auger recombination should be included in the analysis of the efficiency limit to avoid significantly overestimating the simulated device performance. Therefore, this paper provides valuable insights for designing realistic and efficient lead-free PSCs. [ABSTRACT FROM AUTHOR]

The utilization of lithium-ion batteries (LIBs) is increasing sharply with the increasing use of mobile phones, laptops, tablets, and electric vehicles worldwide. Technologies are required for the recycling and recovery of spent LIBs. In the context of the circular economy, it is urgent to search for new methods to recycle waste graphite that comes from the retired electrode of LIBs. The conversion of waste graphite into other products, such as new electrodes, in the field of energy devices is attractive because it reduces resource waste and processing costs, as well as preventing environmental pollution. In this paper, new electrode materials were prepared using waste anode graphite originating from a spent mobile phone battery with an xBT·0.1C12H22O11·(0.9-x)(NH4)2HPO4 composition, where x = 0–50 weight% BT from the anodic active mass of the spent phone battery (labeled as BT), using the melt quenching method. Analysis of the diffractograms shows the graphite crystalline phase with a hexagonal structure in all prepared samples. The particle sizes decrease by adding a higher BT amount in the composites. The average band gap is 1.32 eV (±0.3 eV). A higher disorder degree in the host network is the main factor responsible for lower band gap values. The prepared composites were tested as electrodes in an LIB or a fuel cell, achieving an excellent electrochemical performance. The voltammetric studies indicate that doping with 50% BT is the most suitable for applications as electrodes in LIBs and fuel cells. [ABSTRACT FROM AUTHOR]

The polymer semiconductor material known as graphitic carbon nitride (g-C3N4) has been extensively utilized for the removal of pollutants in wastewater treatment due to its notable visible photocatalytic efficiency, cost-effectiveness, straightforward synthesis, and chemical robustness. Nonetheless, unmodified g-C3N4 still exhibits deficiencies including suboptimal visible light absorption, pronounced electron-hole recombination, and wide band gaps, resulting in constrained photocatalytic efficacy. Through extensive research efforts, diverse modification approaches have been devised to enhance its photocatalytic capabilities. This paper systematically introduces the development history, preparation methods, photocatalytic mechanisms, advantages, and disadvantages of novel g-C3N4 materials, the various modification strategies including morphology control, element doping, defect construction, semiconductor coupling, and hetero-structure construction. In this paper, the preparation process, characterization results, practical applications, and performance enhancement effects of various elementally doped g-C3N4 materials in pollutant removal are discussed in detail, indicating the advantages of multielement doping modification strategy have obvious advantages in improving the photocatalytic performance of g-C3N4, highlighting the future prospects of g-C3N4 materials. [ABSTRACT FROM AUTHOR]

In this paper, a multi-layered mushroom-type electromagnetic band gap (EBG) structure is proposed. A double layer two via EBG (DLTV EBG) structure is designed at 1.65 GHz. The proposed DLTV-EBG structure consists of a two-layer dielectric substrate, which reduces the lateral sizes due to a multilayer topology. By adjusting the patch dimensions and positions of the vias, the center frequency, and equivalent L and C parameters meet design requirements. In a DLTV-EBG, layer-1 has a square ring patch; layer-2 has a circular ring; outer square ring patch with 2 edged located vias gives the additional capacitance and inductance to achieve compactness. The simulation of the DLTV-EBG structure is carried out using the Ansys high-frequency structure simulator (HFSS) and experimentally validated. The band gap of the DLTV-EBG structure is measured using suspended microstrip line (SML) method. The Experimental results agree well with simulation one. The periodic size of the proposed DLTV-EBG structure is 0.05λ1.65 GHz, which is a good candidate where compact size is highly desired. [ABSTRACT FROM AUTHOR]

This research paper reports the fabrication and evaluation of titanium dioxide (TiO2)- and zinc oxide (ZnO)-based dye-sensitized solar cells with anthocyanin dye extracted from pomegranate. TiO2 and ZnO were synthesized using the hydrothermal synthesis and chemical bath deposition techniques, respectively. The scanning electron microscopy analysis showed that TiO2 had nanopillars made up of nano rods with dimensions of 111.866, 90.521, and 81.908 nm, while ZnO had hexagonal patterned nanorods with lengths of 283.294 nm and diameters of 91.782 nm. The absorption spectra of the pomegranate dye were analysed and the strongest absorption peak was found to be at 520 nm, which corresponds to the existing anthocyanin pigment. The band gap of pomegranate dye was noted down to be 2.45 eV. The performance of the dye-sensitized solar cells was evaluated using one sun illumination (100 mW/cm2) where the dye-sensitized solar cell with TiO2 nanopillars achieved an improved efficiency of 0.46% whereas the dye-sensitized solar cell with ZnO nanorods showed a considerably reduced efficiency of 0.42%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department 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.)

The single-layer MoS2 is a highly sought-after semiconductor material in the field of photoelectric performance due to its exceptional electron mobility and narrow bandgap. However, its photocatalytic efficiency is hindered by the rapid recombination rate of internal photogenerated electron–hole pairs. Currently, the construction of heterojunctions has been demonstrated to effectively mitigate the recombination rate of photogenerated electron–hole pairs. Therefore, this paper employs the first principles method to calculate and analyze the four heterojunctions formed by MoS2/WSe2, MoS2/MoSe2, MoS2/AlN, and MoS2/ZnO. The study demonstrates that the four heterojunctions exhibit structural stability. The construction of heterojunctions, as compared to a monolayer MoS2, leads to a reduction in the band gap, thereby lowering the electron transition barrier and enhancing the light absorption capacity of the materials. The four systems exhibit II-type heterojunction. Therefore, the construction of heterojunctions can effectively enhance the optical properties of these systems. By forming heterojunctions MoS2/WSe2 and MoS2/MoSe2, the absorption coefficient in the visible light region is significantly increased, resulting in a greater ability to respond to light compared to that of MoS2/ZnO and MoS2/AlN. Consequently, MoS2-based heterojunctions incorporating chalcogenide components WSe2 and MoSe2, respectively, exhibit superior catalytic activity compared to MoS2 heterojunctions incorporating non-chalcogenide components ZnO and AlN, respectively. The absorption spectrum analysis reveals that MoS2/MoSe2 exhibits the highest light responsivity among all investigated systems, indicating its superior photoelectric performance. [ABSTRACT FROM AUTHOR]

This paper examines the influence of building characteristics, occupant demographics and behaviour on gas and electricity consumption, differentiating between family groups; homes with children; homes with elderly; and homes without either. Both regression and Lasso regression analyses are used to analyse data from a 2019 UK-based survey of 4358homes (n = 1576 with children, n = 436 with elderly, n = 2330 without either). Three models (building, occupants, behaviour) were tested against electricity and gas consumption for each group. Results indicated that homes without children or elderly consumed the least energy. Property Type emerged as the strongest predictor in the Building Model (except for homes with elderly), while Current Energy Efficiency was less significant, particularly for homes with elderly occupants. Homeownership and number of occupants were the most influential factors in the Occupants Model, though this pattern did not hold for homes with elderly. Many occupant and behaviour variables are often considered 'unregulated energy' in calculations such as SAP and are thus typically disregarded. However, this study found these variables to be significant, especially as national standards improve. The findings suggest that incorporating occupant behaviour into energy modelling could help reduce the energy performance gap. [ABSTRACT FROM AUTHOR]

The oxide and halide perovskite materials with a ABX3 structure exhibit a number of excellent properties, including a high dielectric constant, electrochemical properties, a wide band gap, and a large absorption coefficient. These properties have led to a range of applications, including renewable energy and optoelectronics, where high-performance catalysts are needed. However, it is difficult for a single structure of perovskite alone to simultaneously fulfill the diverse needs of multiple applications, such as high performance and good stability at the same time. Consequently, perovskite nanocomposites have been developed to address the current limitations and enhance their functionality by combining perovskite with two or more materials to create complementary materials. This review paper categorizes perovskite nanocomposites according to their structural composition and outlines their synthesis methodologies, as well as their applications in various fields. These include fuel cells, electrochemical water splitting, CO2 mitigation, supercapacitors, and optoelectronic devices. Additionally, the review presents a summary of their research status, practical challenges, and future prospects in the fields of renewable energy and electronics. [ABSTRACT FROM AUTHOR]

Purpose: Despite the number of quality management procedures being currently applied, construction defects in the domestic sector are acknowledged to contribute to the energy performance gap of buildings. This paper investigates the limitations and challenges to the implementation of project quality plans (PQPs) and their impact on the achievement of expected thermal performance in the UK social housing projects. Design/methodology/approach: A qualitative approach, guided by grounded theory, was used in this research. This methodology provided the structure for systematic data analysis iterations, enabling cross-case analysis. An analytic induction process was designed to seek the explanation of the targeted phenomenon and required data collection until no new ideas and concepts emerged from the research iterations. This study collected data from five social housing projects through interviews, site observations and project documentation. Findings: Multiple limitations and challenges were identified in the implementation of PQP to deliver thermal efficient social housing. Generally, there is the need for more objective quality compliance procedures based on required evidence. When investigating the root of the challenges, it was concluded that the adoption of statutory approval as the main quality compliance procedure led to the dilution of the responsibility for prevention and appraisal of defects that compromised the effectiveness of PQP devised by housing associations (HA) and contractors. Originality/value: This study identifies the shortcomings of PQP in addressing quality issues with potential to undermine the thermal performance of social housing projects. The findings could be used by HA, contractors and policymakers as steppingstones to improve the energy efficiency in the domestic sector. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to study a few advantages of bulk nanoparticles of Cu-doped SnO2 using the solid-state reaction method. Many innovative methods were employed to evaluate the special tuning of the bandgap and other structural and morphological properties of the material. X-ray diffractometer (XRD) confirmed that tin oxide has a rutile-type tetragonal-shaped structure with space group P42 / mnm. The average crystallite size was calculated which was found to increase from 53 to 80 nm by increasing the Cu-doping from x = 0 to x = 0.30. SEM images specified that nanoparticles are inhomogeneous and densely close to each other and the average particle size was found to be in the range of ~225–430 nm. Transmission electron microscopy (TEM) images showed the grains present in a few cubic and spherical shapes and grain size was increased (~20–90 nm) with doping of copper in the SnO2 lattice. UV–Vis spectroscopy showed that the band gap increased from 3.531 to 3.701 eV for pure SnO2 and Cu-doped SnO2, respectively. XPS identified the electronic state of Sn as well as Cu atoms as 4 + and 2 + , respectively. Raman spectroscopy showed that only three vibrational modes, i.e., A1g, B2g and doubly degenerate Eg, exist in a sample. [ABSTRACT FROM AUTHOR]

Nanoparticles, considered building blocks of nanotechnology, are a topic of widespread research due to their extraordinary properties that are useful in diverse sectors. Among all nanoparticle types, TiO2 (anatase) has drawn the most attention, primarily because of its superhydrophilic properties and effective antibacterial actions. Its applications include self-cleaning of solid surfaces, treatment of water and air, production of clean energy, treatment of microbial infections, pesticide management, etc. making TiO2 a focal point of research in materials science. However, the lack of photosensitivity to visible light (>390 nm) reduces the scope for utilising TiO2 in photocatalytic processes. Therefore, most studies on TiO2 nanoparticles have focused on broadening their spectral sensitivity through band gap manipulation for effective photocatalysis under visible light. Researchers have doped/co-doped metals and non-metals, such as N, C, F, S, B, Cu, Fe, V, Pt, etc. to nano-TiO2 to shorten its band gap with varying degrees of success. This review paper mainly focuses on the mechanism and effectivity of N and Fe co-doped TiO2 nanoparticles. The progress of scientific research on TiO2 photocatalysis has introduced an array of new applications using TiO2 nanoparticles, and these applications have also been discussed in this article. [ABSTRACT FROM AUTHOR]

Exploration of compounds featuring multiple anions beyond the single-oxide ion, such as oxyhalides and oxyhydrides, offers an avenue for developing materials with the prospect of novel functionality. In this paper, we present the results for a mixed anion layered material, ScHX2 (X: Br, I) based on density functional theory. The result predicted the ScHX2 (X: Br, I) monolayers to be stable and semiconducting. Notably, the electronic and mechanical properties of the ScHX2 monolayers are comparable to well-established 2D materials like graphene and MoS2, rendering them highly suitable for electronic devices. Additionally, these monolayers exhibit an ability to adjust their band gaps and band edges in response to strain and substrate engineering, thereby influencing their photocatalytic applications. [ABSTRACT FROM AUTHOR]

In the present work, Al-doped (0, 1, 2 and 3%) ZnO nanoparticles (NPs) are synthesised by green combustion method (GCM) using Terminalia Catappa seeds (TCS) extract as a novel fuel. For the synthesis Zinc nitrate and Aluminum nitrate are used as precursor and dopant respectively. The synthesised NPs are characterised by XRD, FTIR, UV-vi and impedance spectroscopy. The XRD analysis shows decrease in crystallite size varies between 40 to 26 nm as dopant increases. The FTIR spectrum reaffirms the formation of Zn-O bonding structure at 454.28 cm−1. UV-Vi spectroscopic studies show the optical band gap of 3.63, 3.53, 3.22 and 3.19 eV for Al doped (0, 1, 2 and 3%) ZnO NPs. Thermal analysis for the synthesised Al-doped (0, 1, 2 and 3%) ZnO nanoparticles are analysed using TGA/DTA studies. The Electrical characteristics are studied at various temperatures (50 to 350°C) by varying frequency (10 Hz to 8 MHz). In low frequency regions, dielectric constant and dielectric loss increases with rise in temperature. The constant AC conductivity is observed in lower frequencies and increases for higher frequencies for all doped ZnO NPs. ZnO NPs prepared with 2% of doping exhibit improved structural and electrical properties. Hence these ZnO NPs may be used as sensing material for vibration sensor. Highlights: This paper focus on green synthesis of undoped and Al-doped ZnO nanoparticles by combustion method. ZnO nanoparticles are synthesised using zinc nitrate precursor, Aluminium nitrate as dopant and Terminalia catappa seed extract as fuel. Effect of Al (0, 1,2 and 3%) doping on microstructural, optical, thermal and electrical properties of ZnO nanoparticles are investigated. The green synthesised doped and undoped ZnO nanoparticles exhibit hexagonal wruzite structure with high crystallinity. The FTIR spectrum reaffirms the formation of Zn-O bonding structure at 454.28 cm-1 The optical band gap is found to be 3.63, 3.53, 3.22 and 3.19 eV for 0, 1,2 and 3% of Al doped ZnO nanoparticles respectively. AC conductivity of ZnO nanoparticles is found to be increased with 2% of Al doped ZnO nanoparticles. Result shows an improved structural, optical and electrical performance for 2% Al doped ZnO nanoparticles and hence these nanoparticles are suitable material for sensors, organic light emitting diodes and liquid crystal displays. [ABSTRACT FROM AUTHOR]

The multiplicative first Zagreb index is the product of the square of the degree of vertices in a graph G. The multiplicative reformulated first Zagreb index is defined as Π1, e (G) = Πx12x2∈E(G) (dG(x1) +dG(x1) - 2)²,where E(G) is the edge set of a graph G and dG(x1) is the degree of a vertex x1 in a graph G. In this paper, we characterize the minimum and maximum trees and unicyclic graphs with respect to matching and perfect matching using this graph invariant Π1,e(G) among the collection of all n-vertex graphs. [ABSTRACT FROM AUTHOR]

BiOBr with different preferred growth orientation facets would show a different photocatalytic performance. When decorated in situ with metallic Bi nanoparticles, Bi/BiOBr would commonly display an enhanced photocatalytic performance. In this paper, the BiOBr nanoplates with preferred growth orientation (102) facet and (110) facet were first synthesized using a hydrothermal method. Then, some metallic Bi nanoparticles were modified in situ onto the (110)BiOBr nanoplates, which was expected to show a much more enhanced photocatalytic performance. All samples were characterized using XRD, FE-SEM, TEM, N2 adsorption–desorption, UV–vis and XPS. FE-SEM and TEM images showed that the grain size of the metallic Bi particles was about 5 nm to 10 nm. UV–vis spectra showed that, after some metallic Bi nanoparticles were modified on (110)BiOBr nanoplates, the light absorbance in the visible light region at 400–700 nm became stronger and their optical band gap became larger. N2 adsorption–desorption tests showed that the Bi(x)/(110)BiOBr nanosheets possessed larger specific surface areas than that of the (102)BiOBr and (110)BiOBr nanoplates. The XPS results showed that Bi(x)/(110)BiOBr contained more oxygen vacancies and a more negative value of the conduction band minimum. The photocatalytic performance of (102)BiOBr, (110)BiOBr and Bi(x)/(110)BiOBr were tested in the photocatalytic degradation of rhodamine B under visible light irradiation for 2 h; their photocatalytic efficiency was 45%, 75% and 80%, respectively. In comparison to (102)BiOBr, (110)BiOBr exhibited much higher photocatalytic activity, while for Bi(x)/(110)BiOBr, despite the surface Plasmon resonance effect, a larger specific surface area and more oxygen vacancies, the enhancement of the efficiency was limited, which might have resulted from the larger optical band gap. [ABSTRACT FROM AUTHOR]

In order to alleviate the structural vibrations induced by traffic loads, in this paper, a phonon crystal plate with functionally graded materials is designed based on local resonance theory. The vibration damping performance of the phonon crystal plate is studied via finite element numerical simulation and the band gap is verified via vibration transmission response analysis. Finally, the engineering application mode is simulated to make it have practical engineering application value. The results show that the phonon crystal plate has two complete bandgaps within 0~150 Hz, the initial bandgap frequency is 0.00 Hz, the cut-off frequency is 128.32 Hz, and the internal ratio of 0~100 Hz is 94.13%, which can effectively reduce the structural vibration caused by traffic loads. Finally, stress analysis of the phonon crystal plate is carried out. The results show that phonon crystals of functionally graded materials can reduce stress concentration through adjusting the band gap. The phonon crystal plate designed in this paper can effectively suppress the structural vibration caused by traffic loads, provides a new method for the vibration reduction of traffic infrastructure, and can be applied to the vibration reduction of bridges and their auxiliary facilities. [ABSTRACT FROM AUTHOR]

This paper reports the energies and charge and spin distributions of both the vertically excited and fully relaxed GR1 states of the neutral singlet vacancy in diamond obtained from direct Δ-SCF calculations used previously to describe the low-lying excited states in AFII NiO and α-Al2O3. The calculations are based on the B3LYP functional in its standard form, with a C basis set that is identical to that which was used previously in numerous calculations of the ground state properties of defective diamond. Both the vertically excited and thermally relaxed GR1 states are predicted to be excitonic and insulating, with extensive re-distribution of charge and spin density and back-donation to the donor site. The present calculations suggest that the triplet state makes no contribution to the GR1 excitation. The predicted energy of the zero phonon line (1.57 eV) compares with the observed value of 1.67 eV, which also suggests that the GR1 state is neutral. The bandgaps lead to an estimate of the next higher (GR2) excited state energy, which is close to that found in the observed spectra. Similar calculations are used to predict the energies of the higher gap states at (5.0–5.5) eV, including the bulk value of 7.3 eV, which compares with the experimental value of (7.3–7.4) eV. An explanation is suggested as to why only the GR1 luminescence is observed. This paper also suggests an alternative channel for the recovery of the ground state in photoluminescence studies. [ABSTRACT FROM AUTHOR]

Phosphates, whose obvious disadvantage is the relatively small birefringence, can be overcome by the introduction of post-transition metal cations containing stereochemically active lone-pair electrons. In this paper, two new compounds were successfully explored in the A–Sb–P–O system, i.e. Cs2Sb3O(PO4)3 (CsSbPO) and (NH4)2Sb4O2(H2O)(PO4)2[PO3(OH)]2 (NH4SbPOH). Transmission spectra show that CsSbPO has a surprising transmission range with a UV cutoff edge of 213 nm. First-principles calculations show that both compounds have a wide band gap (5.02 eV for CsSbPO and 5.30 eV for NH4SbPOH) and enlarged birefringence (Δn = 0.034@1064 nm for CsSbPO and Δn = 0.045@1064 nm for NH4SbPOH). The results of real-space atom-cutting investigations show that the distorted [SbOx] polyhedra originating from the asymmetric lone pair electrons give the main contribution to the total birefringence and overcome the disadvantage of small birefringence of phosphates but maintain wide transition windows. [ABSTRACT FROM AUTHOR]

The primary objective of this paper is to conduct a comparative analysis of diverse Electromagnetic Band Gap (EBG) antennas in terms of their suitability for Wi-Fi applications operating at 5 GHz. Wi-Fi primarily operates within the 2.4 GHz and 5 GHz frequency bands, with the 5 GHz band offering higher data rates and reduced interference compared to the 2.4 GHz band. Furthermore, its larger number of available channels makes it an optimal choice for environments with high user density. The antennas in this study are designed with dimensions of 28.11x32.40x1.6 mm³ (length x width x height) using RT/Duroid 5880 substrate, which has a thickness of 1.6 mm and a relative permittivity (εr) of 2.2. The integration of Electromagnetic Band Gap structures in antenna designs has gained substantial attention due to their unique properties that enhance antenna performance characteristics. The paper presents sixteen distinct EBG antennas, all designed using CST software. These antennas incorporate various EBG shapes, such as Fork, L-shape, C-shape, Hash, and Z-shape, positioned on a rectangular patch and in the ground plane. The study's results reveal that the Hash EBG on the patch offers superior performance compared to other EBG types. As a result, the Hash EBG on the patch, alongside various Z-shaped EBGs on the ground plane, is assessed for different antenna performance parameters, including return loss, radiation patterns, and gain. Finally, a diagonal Z-shaped EBG antenna is designed, simulated, and tested. The antenna return loss at 5.2GHz is –48 dB The proposed antenna achieved a peak gain of 7.3 dB at 5.2GHz. The proposed antenna exhibits omnidirectional properties. The antenna shows an efficiency of 90% at the resonant frequency. The experimentally measured results of the designed diagonal EBG antenna have shown satisfactory agreement and are consistent with the simulated results. The findings of this research contribute to a better understanding of EBG antennas potential for Wi-Fi applications in the 5 GHz frequency band. [ABSTRACT FROM AUTHOR]

Spray pyrolysis technique has been applied to deposit a broad range of thin films, which are used in various devices such as solar cells, sensors, and solid oxide fuel cells. Spray pyrolysis is one of the most common, inexpensive, simple, and quite versatile methods used for synthesizing submicron and sphericalshaped luminescent materials multicomponent oxide thin films. In this paper, spray pyrolysis TiO2 thin films has been deposited on glass substrates and kept at different temperature to reveal its optical properties by the help of UV-visible spectroscopy. Refractive index (n) of TiO2 thin films as wide semiconductor has been calculated using optical energy gap (Eg). The calculated values of refractive index from the new relations have been compared with the values reported by different researchers; an excellent agreement has been obtained between them. The material identification was confirmed from X-ray diffraction techniques and first derivative of transmission spectra’s has been plotted that gives band gap value of films respectively. [ABSTRACT FROM AUTHOR]

This paper studies the radial alternating material phononic crystal (RAM-PnC). By simulating the band gap structure of the phononic crystal, a complete acoustic band gap was verified at the resonant frequency of 175.14 MHz, which can prevent the propagation of elastic waves in a specific direction. The proposed alternately arranged radial phononic crystal structure is applied to the thin-film piezoelectric-on-silicon (TPOS) MEMS resonator. The finite element simulation method increases the anchor quality factor (Qanchor) from 60,596 to 659,536,011 at the operating frequency of 175.14 MHz, which is about 10,000 times higher. The motion resistance of the RAM-PnC resonator is reduced from 156.25 Ω to 48.31 Ω compared with the traditional resonator. At the same time, the insertion loss of the RAM-PnC resonator is reduced by 1.1 dB compared with the traditional resonator. [ABSTRACT FROM AUTHOR]

This paper explores the willingness-to-pay for energy efficiency by exploiting variation across products and countries within the EU market for household appliances. Based on scanner data at product-level, I use the hedonic method to estimate implicit prices for energy efficiency and derive implicit discount rates. The paper argues that the implicit price will be underestimated when energy consumption is not only a determinant of operating cost but also is positively associated with other features of a product. The empirical analysis confirms that estimates of the willingness-to-pay are higher when this effect is accounted for in the estimation. This is especially true of product types for which the heterogeneity of usage intensity is low. The results thus indicate that the energy efficiency gap is smaller than found in earlier studies. [ABSTRACT FROM AUTHOR]

The narrow gap semiconductor TlBiTe2 undergoes a solid–solid phase transformation from the rhombohedral (D3d) to the cubic (Oh) phase. The present paper deals with the study of this phase transformation combining the results of Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM). It has been found that during heating the transformation is an athermal activated process, which can be described only by a combination of more than one processes while during cooling it exhibits an expectable thermal hysteresis due to the volume difference. The results of the kinetic analysis combined with the electron microscopy findings, supported also by the Fourier Transform Infrared (FTIR) spectroscopy ones, lead to the conclusion that TlBiTe2 undergoes a multiple-step, displacive, martensitic type transformation. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, this paper reports a systematic research on HER performance enhancing of LNS-TiO2 by passivated codoping. Six codoping systems, Ti17O35CrC, Ti17O35MoC, Ti17O35WC, Ti17O35VN, Ti17O35NbN and Ti17O35TaN are studied. Results show that the energy band can be tuned by the codoping donor–acceptor pairs. The energy band performance of Ti17O35WC should be the best in HER process for its tiny CBM change and small band gap. Besides, the hydrogen adsorption ability of LNS-TiO2 in HER process can also be tuned by the codoping pairs. The hydrogen adsorption performance of Ti17O35TaN should be the best for its ∆GH* is close to zero. In a word, Ti17O35WC and Ti17O35TaN have their own advantages as catalysts in HER process, and their exact HER efficiency is waiting to be obtained in the future experiments. In general, this passivated codoping LNS-TiO2 represents a novel kind of material. Research in this paper can enrich the theoretical knowledge of HER field. [ABSTRACT FROM AUTHOR]

Over the last decade, gallium nitride (GaN) has emerged as an excellent material for the fabrication of power devices. Among the semiconductors for which power devices are already available in the market, GaN has the widest energy gap, the largest critical field, and the highest saturation velocity, thus representing an excellent material for the fabrication of high-speed/high-voltage components. The presence of spontaneous and piezoelectric polarization allows us to create a two-dimensional electron gas, with high mobility and large channel density, in the absence of any doping, thanks to the use of AlGaN/GaN heterostructures. This contributes to minimize resistive losses; at the same time, for GaN transistors, switching losses are very low, thanks to the small parasitic capacitances and switching charges. Device scaling and monolithic integration enable a high-frequency operation, with consequent advantages in terms of miniaturization. For high power/high-voltage operation, vertical device architectures are being proposed and investigated, and three-dimensional structures—fin-shaped, trench-structured, nanowire-based—are demonstrating great potential. Contrary to Si, GaN is a relatively young material: trapping and degradation processes must be understood and described in detail, with the aim of optimizing device stability and reliability. This Tutorial describes the physics, technology, and reliability of GaN-based power devices: in the first part of the article, starting from a discussion of the main properties of the material, the characteristics of lateral and vertical GaN transistors are discussed in detail to provide guidance in this complex and interesting field. The second part of the paper focuses on trapping and reliability aspects: the physical origin of traps in GaN and the main degradation mechanisms are discussed in detail. The wide set of referenced papers and the insight into the most relevant aspects gives the reader a comprehensive overview on the present and next-generation GaN electronics. [ABSTRACT FROM AUTHOR]

As a layered material with single/multi-atom thickness, two-dimensional transition metal sulfide WS2 has attracted extensive attention in the field of science for its excellent physical, chemical, optical, and electrical properties. The photoelectric properties of WS2 are even more promising than graphene. However, there are many existing preparation methods for WS2, but few reports on its direct growth on tungsten films. Therefore, this paper studies its preparation method and proposes an innovative two-dimensional material preparation method to grow large-sized WS2 with higher quality on metal film. In this experiment, it was found that the reaction temperature could regulate the growth direction of WS2. When the temperature was below 950 °C, the film showed horizontal growth, while when the temperature was above 1000 °C, the film showed vertical growth. At the same time, through Raman and band gap measurements, it is found that the different thicknesses of precursor film will lead to a difference in the number of layers of WS2. The number of layers of WS2 can be controlled by adjusting the thickness of the precursor. [ABSTRACT FROM AUTHOR]

The wave equation revealing the wave propagation in chiral phononic crystals, established through force equilibrium law, conceals the underlying physical information, such as the essence of the motion coupling and the inertial amplification effect. This has led to a controversy over the bandgap mechanism. In this article, we theoretically unveil the reason for this controversy, and put forward an alternative approach from wave behavior to formulate the wave equation, offering an alternative pathway to articulate the bandgap physics directly. Based on the physics revealed by our theory method, we identify the obstacles in coupled acoustic and optic branches to widen and lower the bandgap. Then we introduce an approach based on spherical hinges to decrease the barriers, for customizing the bandgap frequency and width. Finally, we validate our proposal through numerical simulation and experimental demonstration. The wave equation established for chiral phononic crystals based reveals only the coupling of acoustic and optic branches, hiding the complexity of the bandgap physics. The alternative method proposed in this paper allows direct observation of the essential physics, and enables to decouple acoustic and optic branches for the manipulation of band gaps. [ABSTRACT FROM AUTHOR]

Context: The key factor in designing heat-resistant energetic materials is their thermal sensitivity. Further research and prediction of thermal sensitivity remains a great challenge for us. This study is based on first-principles calculations and establishes a theoretical model, which comprehensively considers band gap, density of states, and Young's modulus to obtain a empirical parameter Ψ. A quantitative relationship was established between the new parameter and the thermal decomposition temperature. The value of Ψ is calculated for 10 energetic materials and is found to have a strong correlation with the experimental thermal decomposition temperature. This further proves the reliability of our model. Specifically, the larger the value of Ψ, the higher the thermal decomposition temperature, and the more stable the energetic material will be. Therefore, to some extent, we can use the new parameter Ψ calculated by the model to predict thermal sensitivity. Methods: Based on first-principles, this paper used the Cambridge Serial Total Energy Package (CASTEP) module of Materials Studio (MS) for calculations. The Perdew-Burke-Ernzerhof (PBE) functionals in Generalized Gradient Approximation (GGA) method as well as the Grimme dispersion correction was used in this paper. [ABSTRACT FROM AUTHOR]

The monolithic integration of gallium phosphide (GaP), with its green band gap, high refractive index, large optical non-linearity, and broad transmission range on silicon (Si) substrates, is crucial for Si-based optoelectronics and integrated photonics. However, material mismatches, including thermal expansion mismatch and polar/non-polar interfaces, cause defects such as stacking faults, microtwins, and anti-phase domains in GaP, adversely affecting its electronic properties. Our paper presents a structural and defect analysis using scanning transmission electron microscopy, high-resolution transmission electron microscopy, and scanning nanobeam electron diffraction of epitaxial GaP islands grown on Si nanotips embedded in SiO2. The Si nanotips were fabricated on 200 mm n-type Si (001) wafers using a CMOS-compatible pilot line, and GaP islands were grown selectively on the tips via gas-source molecular-beam epitaxy. Two sets of samples were investigated: GaP islands nucleated on open Si nanotips and islands nucleated within self-organized nanocavities on top of the nanotips. Our results reveal that in both cases, the GaP islands align with the Si lattice without dislocations due to lattice mismatch. Defects in GaP islands are limited to microtwins and stacking faults. When GaP nucleates in the nanocavities, most defects are trapped, resulting in defect-free GaP islands. Our findings demonstrate an effective approach to mitigate defects in epitaxial GaP on Si nanotip wafers fabricated by CMOS-compatible processes. [ABSTRACT FROM AUTHOR]

Seismic surface waves carry significant energy that poses a major threat to structures and may trigger damage to buildings. To address this issue, the implementation of periodic barriers around structures has proven effective in attenuating seismic waves and minimizing structural dynamic response. This paper introduces a framework for seismic surface wave barriers designed to generate multiple ultra-low-frequency band gaps. The framework employs the finite-element method to compute the frequency band gap of the barrier, enabling a deeper understanding of the generation mechanism of the frequency band gap based on vibrational modes. Subsequently, the transmission rates of elastic waves through a ten-period barrier were evaluated through frequency–domain analysis. The attentional effects of the barriers were investigated by the time history analysis using site seismic waves. Moreover, the influence of the soil damping and material damping are separately discussed, further enhancing the assessment. The results demonstrate the present barrier can generate low-frequency band gaps and effectively attenuate seismic surface waves. These band gaps cover the primary frequencies of seismic surface waves, showing notable attenuation capabilities. In addition, the soil damping significantly contributes to the attenuation of seismic surface waves, resulting in an attenuation rate of 50%. There is promising potential for the application of this novel isolation technology in seismic engineering practice. [ABSTRACT FROM AUTHOR]

With the development of virtual reality, the projection design of the head-mounted display (HMD) requires improvement as well. The surface relief grating (SRG) is one of the popular diffraction elements to achieve light guiding through the waveguide. Using the SRG as the coupler, incoming information light can be coupled into the waveguide by the 1-order diffraction. To increase possible design options for the HMD, SRG with complex geometry has been designed to fit more diffraction conditions. In this paper, a 2D SRG is proposed to form by periodically arranging slanted glass pillars on the surface of a glass waveguide, just like a photonic crystal. The structure can suppress all the other diffraction orders except the 0-order and the [1, 0] order. The best diffraction efficiency of the [1, 0] order can be obtained when the incident light is incident with not only an incident angle but also an azimuth angle. The geometric parameters of the pillars are investigated and optimized with the diffraction efficiency by the finite element method, and the relationship between the incident angles and the diffraction efficiency will also be discussed. The proposed structure has the potential in both the in-coupler and the out-coupler, respectively, for integrating light coming from different azimuth angles or for outputting light to different azimuth angles. [ABSTRACT FROM AUTHOR]

In this paper, a modified Josephson junction model is proposed, which splits the two-dimensional electron gas by inserting a middle superconductor strip into a conventional Josephson junction. This modification enhances the superconducting proximity effect, thus avoiding the appearance of a soft gap and inducing a stable Majorana zero-energy mode. Through numerical simulation, the impact of the middle superconductor strip with different widths on the energy band structure is studied, and a significant increase in the topological energy gap is found. In addition, the modified system maintains a robust topological gap even at a strong in-plane magnetic field. [ABSTRACT FROM AUTHOR]

An epoxy-based metamaterial plate structure with local resonance is designed in this paper. The bandgap of the bending wave ranges from 36.46Hz to 110.55Hz. Through the optimization design of the oscillators in the plate structure, the starting bandgap moves to 19.79Hz, and the band gap width is 72Hz. The dispersion curve and frequency response function were calculated by finite element method (FEM). On this basis, the plane wave expansion method formula of the structural model was derived, and the equivalent model of spring-mass model was established. The results show that the calculation results of the three methods of the epoxide metamaterial plate structure were basically consistent, and the correctness of these methods was verified mutually. The methods derived in this paper bring great convenience and diversity to the application of plate structure. The article proposes a low-frequency wide bandgap thick plate structure model. [ABSTRACT FROM AUTHOR]

Due to a wide band gap and large exciton binding energy, zinc oxide (ZnO) is currently receiving much attention in various areas, and can be prepared in various forms including nanorods, nanowires, nanoflowers, and so on. The reliability of ZnO produced by a single dopant is unstable, which in turn promotes the development of co-doping techniques. Co-doping is a very promising technique to effectively modulate the optical, electrical, magnetic, and photocatalytic properties of ZnO, as well as the ability to form various structures. In this paper, the important advances in co-doped ZnO nanomaterials are summarized, as well as the preparation of co-doped ZnO nanomaterials by using different methods, including hydrothermal, solvothermal, sol-gel, and acoustic chemistry. In addition, the wide range of applications of co-doped ZnO nanomaterials in photocatalysis, solar cells, gas sensors, and biomedicine are discussed. Finally, the challenges and future prospects in the field of co-doped ZnO nanomaterials are also elucidated. [ABSTRACT FROM AUTHOR]

This paper introduces a structural design which has superior energy harvesting ability. The proposed structure is based on the ability of most periodic structures to prohibit elastic waves from propagating in a specific frequency range of the phonon band gap. By leading into acoustic black hole (ABH) units and utilizing the energy concentration characteristics of the ABH structure, the filtering effect can be made more significant. These two characteristics can produce significant strain and energy localization, which is conducive to energy harvesting. In this paper, we obtained ABH unit capable of producing broadband gaps by adjusting the geometric parameters of the ABH structure, and chose a cantilever as the research object for energy harvesting, by applying a piezoelectric patch on the unit located near the fixed end to gain a broader application in the actual situation. The results show that the beam combining the energy concentration characteristics of band gap and ABH structure has a significant improvement in energy harvesting efficiency. Optimization on the parameters of ABH unit shows that the band gap characteristic of the periodic ABH structure can further optimize the energy harvesting efficiency of practical energy harvesters, and opens up a new possibility of energy harvesting of ABH structure. [ABSTRACT FROM AUTHOR]

Copyright of Recent Contributions to Physics is the property of Al-Farabi Kazakh National University 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.)

Copyright of Chinese Journal of Applied Chemistry is the property of Chinese Journal of Applied Chemistry 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.)

A variable-speed pump-turbine is the core component of a hydraulic storage and energy generation station. When the pump-turbine operates at a constant speed, its response to the power grid frequency is poor. In order to improve the hydraulic efficiency of the pumped storage unit, variable-speed units are used. However, there has been no numerical study on the effect of the rotational flow characteristics within the gap of a variable-speed pump-turbine. This paper calculates the flow characteristics within the gap of a variable-speed pump-turbine under three typical pump modes (maximum head minimum flow condition, minimum head maximum flow condition, and maximum speed condition). The research results indicate that the rotational speed significantly affects the pressure distribution, velocity distribution, and turbulent kinetic energy distribution within the crown and band gaps. The higher the speed, the larger the area of the high-pressure region before the runner inlet compared to other operating conditions, and similarly, the low-pressure area after the runner outlet is also larger than in other operating conditions. The change in speed mainly affects the internal flow field of the crown gap, with the most noticeable changes occurring in the pressure and flow velocity at the inlet and outlet of the crown gap. There is a clear trend of pressure drop and velocity increase within the gap as the speed increases. However, with the increase in speed, the pressure distribution and flow velocity within the band gap remain almost the same. In addition to speed changes, it is observed that the pressure within the gap and the flow velocity within the passages are also related to the head, especially in the condition of maximum head, where this relationship becomes more noticeable. [ABSTRACT FROM AUTHOR]

Iron hydroxide (Fe(OH)3) nanoparticles have garnered considerable attention for their effectiveness in water treatment. This paper reviews recent studies on the photocatalytic degradation of phenol using Fe(OH)3, detailing the synthesis procedure, photocatalytic reaction conditions under UV‐C and catalyst amount optimization. Iron hydroxide was synthesized using a facile precipitation method, and the produced catalyst was thoroughly characterized using XRD, FTIR, UV‐DRS, DTA/TGA and SEM. Characterization results indicated that the catalyst exhibited very low crystallinity, a 1.84 eV band gap, and very small particle sizes. The study investigated the degradation performance of phenol for different amounts of iron hydroxide, ranging from 0.1 g to 1 g, and determined the optimum catalyst amount to be 0.7 g. The catalyst demonstrated a degradation efficiency for phenol exceeding 90 % at the end of a 180 minute photocatalytic reaction. The paper offers a comprehensive analysis of Fe(OH)3 as a photocatalyst for phenol degradation, highlighting its potential for future applications in water treatment. [ABSTRACT FROM AUTHOR]

Context: In this paper, we systematically studied the effects of non-metallic element (B, C, N, O, F) doping and biaxial stretching on the photoelectric properties of ZrS2/ZrSe2 heterostructures by using the first-principles calculation method based on density functional theory. The results show that the p-type doping is realized by B, C, and N atom doping, and the n-type doping is realized by O and F atom doping. The doping of B and C atoms produces impurity energy levels in the band gap, which affects the conductivity of the heterostructure. The band gap of N and O atom–doped heterostructures increases under tensile strain, but it is still a direct band gap. The analysis of the optical properties of the heterostructures shows that the doping of non-metallic atoms can adjust the optical absorption rate and reflectivity of the heterostructures. Under the action of tensile strain, the optical properties of the doped heterostructures have changed significantly in the low-energy region. This article provides a theoretical basis for the future application of ZrS2/ZrSe2 heterostructures. Method: This paper uses the first-principles calculation method based on density functional theory. The PBE exchange-correlation functional based on generalized gradient approximation (GGA) is selected for the specific calculation, and the crystal structure is geometrically optimized by the ultrasoft pseudopotential method. It is verified that when the cutoff energy of the ZrS2/ZrSe2 heterostructure is 500 eV, the K-point grid is selected to be 10 × 10 × 2 with the lowest energy, so the cutoff energy is selected to be 500 eV. The K-point grid is selected to be 10 × 10 × 2. The convergence limits for structural optimization are as follows: the maximum force between atoms is 0.01 eV/Å, the convergence threshold of the maximum energy change is set to 10−9 eV/atom, and the convergence threshold of the maximum displacement is 0.001 Å. In order to avoid the influence of atomic periodic motion between different atomic layers, a vacuum layer of 20 Å is added in the vertical direction. Considering the interaction of vdW between the interfaces, the DFT-D2 method is used to verify. The optical properties were calculated by the random phase approximation method, and the K-point grid was selected as 12 × 12 × 2. [ABSTRACT FROM AUTHOR]

The conventional technique of materials design and discovery relies on experimentation and complex computational methods. The sheer number of materials present makes testing each one for specific properties and application makes the entire process time and resource intensive. This has resulted into Machine Learning (ML) to gain popularity in the domain of materials science to revolutionise and accelerate the entire process. Data-driven approaches such as these can be applied to narrow down the number of materials on which we apply the tradition methods, thus cutting down both the cost and time for development of new materials. This paper demonstrates how data-driven approach can be incorporated in materials science taking the use of band gap prediction of different materials using different machine ML algorithms. Using Random Forest Regressor, the highest R squared (r2) score of 0.685 and least root mean squared error (RMSE) of 0.87 eV were achieved. [ABSTRACT FROM AUTHOR]

A novel terahertz polarization isolator using a two-dimensional square lattice tellurium rod array is numerically investigated at the interesting band of 0.22 THz in this short paper. The isolator is designed by inserting six hexagonal tellurium rods into a fully polarized photonic crystals waveguide with high efficiency of −0.34 dB. The TE and TM photonic band gaps of the 7 × 16 tellurium photonic crystals are computed based on the plane wave expansion method, which happen to coincide at the normalized frequency domain from 0.3859(a/λ) to 0.4033(a/λ), corresponding to the frequency domain from 0.2152 to 0.2249 THz. The operating bandwidth of the tellurium photonic crystals waveguide covers 0.2146 to 0.2247 THz, calculated by the finite element method. The six hexagonal tellurium rods with smaller circumradii of 0.16a serve to isolate transverse electric waves and turn a blind eye to transverse magnetic waves. The polarization isolation function and external characteristic curves of the envisaged structure are numerically simulated, which achieves the highest isolation of −33.49 dB at the central frequency of 0.2104 THz and the maximum reflection efficiency of 98.95 percent at the frequency of 0.2141 THz. The designed isolator with a unique function and high performance provides a promising approach for implementing fully polarized THz devices for future 6G communication systems. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis of BaPbFe2O6 and modifying its photocatalytic activity by precipitation method on brilliant green (BG) dye. According to the characterization data, the UV-Vis absorption spectrum shows several peaks with an optical band gap of 5.45 eV. FESEM images showed irregular shapes of BaPbFe2O6 and EDX confirmed the presence of, Ba, Pb, Fe and O elements. The average particle size measured with maximum diffraction peak using Scherrer's equation was 12.31nm. XPS represents the different oxidation states of the elements. FTIR images show the presence of oxide film on the surface with a band gap of 500-600 cm-1 given as the characteristic stretched band of Pb-O. Maximum degradation is shown on the above optimum condition and complete degradation was held in 20 min on optimum conditions. The degradation rate of BaPbFe2O6 is 86.89% of 4*10-5 M for BG dye by exposing to sunlight for 20 minutes. Degradation of BG dye occurs due to the formation of hydroxyl radicals (.OH) on exposure to sunlight following pseudo first order kinetics. Therefore, BaPbFe2O6 synthesized in this paper can be used for the degradation of other exogenous organisms and for the treatment of wastewater and environmental polluted samples. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and characterization of a new material, (HFlucytosine)2BiCl5. The structure studied by single crystal X-ray diffraction reveals one-dimensional (1D) il [BiCl5]n2− chains surrounded by protonated flucytosine antifungal drug (HFlucytosine)+. The structure is stabilized by hydrogen bonds and non-covalent interactions. These interactions were assessed using Hirshfeld surface analysis. The optical property of the compound was studied with a focus on the band gap. Theoretical calculations on the electronic structure, band gap, and frontier molecular orbitals were performed using density functional theory (DFT) and time-dependent DFT (TD-DFT) to support our experimental findings. Our results indicate that the energy gap (Eg) and the chemical reactivity descriptors are primarily linked to the ring of the organic cation and the inorganic anion. This highlights the importance of these two components in determining the activity and antioxidant capacity of the molecule. To ascertain the efficacy of these compounds in inhibiting the proliferation of detrimental bacteria, which are prevalent environmental contaminants in the Arab region, an agar disc diffusion assay was performed. [ABSTRACT FROM AUTHOR]