Search Results (629)

Periodically supported beams are widely employed in engineering structures, where effective control of low-frequency vibration and noise is often required. To achieve broadband elastic wave manipulation, an inertial amplification (IA) mechanism was introduced to generate low-frequency and ultra-wide bandgaps. Based on the Timoshenko beam theory, analytical models for flexural wave propagation in periodically supported beams with IA structures were established using the generalized state transfer matrix method and the Floquet transform method, respectively. The validity of the analytical models was verified by vibration transmission analysis using a finite element model. The results demonstrate that the Floquet transform method enables rapid and accurate solution of the wave model. The introduction of the IA mechanism can generate low-frequency bandgaps, which are most sensitive to the amplification angle and amplification mass. The bandgap formation mechanism arises from the modulation of Bragg scattering in the periodically supported beam by the IA structure. This modulation causes the standing wave mode frequencies to shift to lower frequencies, thereby widening the bandgaps. Furthermore, hybrid IA structure configuration can achieve broader bandgaps, facilitating elastic wave control in the ultra-wide low-frequency range. These findings provide valuable insights for low-frequency vibration and noise attenuation in engineering structures. Full article

The global clean energy transition requires power conversion technologies that combine high efficiency, operational flexibility, and reduced environmental impact over their entire service life. Solid-state transformers (SSTs) have emerged as a promising alternative to conventional line-frequency transformers, offering bidirectional power flow, high-frequency isolation, and advanced control capabilities that support renewable integration and electrified infrastructures. This paper presents a comparative life cycle assessment (LCA) of conventional transformers and SSTs across representative power-system applications, including residential and industrial distribution networks, electric vehicle fast-charging infrastructure, and transmission–distribution interface substations. The analysis follows a cradle-to-grave approach and is based on literature-derived LCA data, manufacturer specifications, and harmonized engineering assumptions applied consistently across all case studies. The results show that, under identical assumptions, SST-based solutions are associated with indicative lifecycle CO₂ emission reductions of approximately 10–30% compared to conventional transformers, depending on power rating and operating profile (≈90–1000 t CO₂ over 25 years across the four cases). These reductions are primarily driven by lower operational losses and reduced material intensity, while additional system-level benefits arise from enhanced controllability and compatibility with renewable-rich and hybrid AC/DC grids. The study also identifies key challenges that influence the sustainability performance of SSTs, including higher capital cost, thermal management requirements, and the long-term reliability of power-electronic components. Overall, the results indicate that SSTs represent a relevant enabling technology for future low-carbon power systems, while highlighting the importance of transparent assumptions and lifecycle-oriented evaluation when comparing emerging grid technologies. Full article

The calculation of the limiting efficiency and structural optimization of solar cells based on the detailed balance principle is systematically investigated in this study. Through modeling and numerical simulations of various cell architectures, the theoretical efficiency limits of these structures under AM1.5G (Air Mass 1.5 Global) spectrum were quantitatively evaluated. Through a comprehensive consideration of the effects of bandgap and composition, the Al_0.03Ga_0.97As/Ge (1.46 eV/0.67 eV) cell configuration was determined to achieve a high theoretical efficiency of 43.0% for two-junction cells while maintaining satisfactory lattice matching. Furthermore, the study proposes that incorporating a Ga_0.96In_0.04As (8.3 nm)/GaAs_0.77P_0.23 (3.3 nm) strain-balanced multiple quantum wells (MQWs) structure enables precise bandgap engineering, modulating the effective bandgap to the optimal middle-cell value of 1.37 eV, as determined by graphical analysis for triple junctions. This approach effectively surpasses the efficiency constraints inherent in conventional bulk-material III–V semiconductor solar cells. The results demonstrate that an optimized triple-junction solar cell with MQWs can theoretically achieve a conversion efficiency of 51.5%. This study provides a reliable theoretical foundation and a feasible technical pathway for the design of high-efficiency solar cells, especially for the emerging MQW-integrated III–V semiconductor tandem cells. Full article

At an ultra-thin 3 nm SnO₂ channel thickness, a record-high effective mobility (µ_eff) of 301 cm²/V·s, field-effect mobility (µ_FE) of 304 cm²/V·s, and a sharp subthreshold swing (SS) of 201 mV/decade are achieved at a high carrier density (N_e) of 5 × 10¹² cm⁻². These excellent transport properties are attributed to ultraviolet (UV) light annealing. The resulting µ_eff is significantly higher than that of Molybdenum Disulfide (MoS₂) and Tungsten Diselenide (WSe₂), and is more than twice that of single-crystalline Si channel transistors at the same quasi-two-dimensional (2D) thickness of 3 nm (equivalent to five monolayers of MoS₂). UV annealing not only enhances µ_eff and µ_FE but also sharpens the SS, which is crucial for low-power operation. This improved SS is attributed to reduced scattering from charged interface traps, as supported by µ_eff-N_e analysis, thereby increasing the transistor’s mobility. The realization of such high-mobility devices at a quasi-2D thickness of only 3 nm is of particular importance for the further downscaling of ultra-thin-body transistors for high-speed computing and monolithic three-dimensional (M3D) integration. Furthermore, the wide bandgap of SnO₂ (3.7 eV) enables operation at relatively high voltages, paving the way for pioneering ternary logic applications. Full article

The current–voltage characteristics (IVCs) of anodic TiO₂ films in a thin-film structure (Carbon paste/TiO₂/Ti/Al) were investigated in the temperature range of T = 80–300 K with bias voltages from −0.5 V to +0.5 V. Anodic oxide film, with a thickness of 14 nm, was obtained by electrochemical oxidation of Ti at a voltage of 10 V. The obtained data for various temperatures showed that the IVCs in the forward (negative on the Ti electrode) and reverse (positive on the Ti electrode) bias of the thin film structure are not symmetrical. Based on the analysis, three temperature ranges (sections) were identified in which the IVCs differ in their behavior. Examination of the IVCs revealed that the conductivity mechanism in Section I (temperature range from 298 to 263 K) is determined by the Space Charge Limited Current (SCLC). Section II, in the temperature range from 243 to 203 K, is characterized by the onset of conductivity involving donor centers, in the case where the concentration of electrons on traps is significantly higher than the concentration of electrons in the conduction band. In Section III, within the temperature range from 183 to 90 K, the conduction mechanism is the Poole–Frenkel process involving donor centers. These donor centers are located below the level of traps in the forbidden band. The results obtained indicate that anodic TiO₂ is an n-type semiconductor, in the bandgap of which there are both electron traps and donor centers formed by anionic (oxygen) vacancies. The different behavior of the characteristic energy with different sample biasing in the case of the Poole–Frenkel mechanism indicates a two-layer structure of anodic TiO₂. Full article

The increasing presence of pharmaceutical residues such as ibuprofen in aquatic environments represents a growing concern due to their persistence and limited biodegradability. In this study, selenium-doped tin oxide (SnO₂:Se) nanoparticles covered with glycerol were synthesized via a microwave-assisted method to evaluate their photocatalytic performance in the degradation of ibuprofen under ultraviolet (UV) and visible light. Optimal synthesis parameters were determined at pH 7.5–8.0 and 130 °C, yielding stable, dark-brown colloidal suspensions. HRTEM analysis revealed a coexistence of one-dimensional (1D) nanowires and zero-dimensional (0D) quantum dots, confirming nanoscale morphology with crystallite sizes between 8 and 100 nm. EDS analysis confirmed the presence of Sn, O, and trace Se (0.1 wt%), indicating Se incorporation as a dopant. UV–Vis spectroscopy showed strong absorption near 324 nm and slight band-gap narrowing in the Se-doped samples, suggesting enhanced visible-light responsiveness. Photocatalytic experiments demonstrated an ibuprofen degradation efficiency of ~60% under visible light and 80% under UV irradiation with aeration, compared to only 5% removal using commercial SnO₂. The enhanced performance was attributed to Se-induced band-gap modulation, effective charge-carrier separation, and singlet oxygen generation. Full article

Wide-bandgap (WBG) semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) are key enablers of power-electronics converters for aerospace platforms, where high efficiency, weight reduction, and thermal robustness are critical requirements. This paper presents the main challenges associated with the use of these technologies, including protection requirements, electromagnetic compatibility, and thermal management, as well as the material advantages that enable higher switching frequencies and lower losses compared to conventional Si technologies. A comparative analysis of semiconductor technologies and suitable power-conversion topologies for the aerospace context is provided. Representative laboratory-scale experimental validation is presented, including the development of a DC–DC boost converter and a DC–AC full-bridge inverter, which are linked through the common DC-link and are used for interfacing batteries and an electrical motor, both based on GaN and SiC diodes. The results demonstrated the correct operation, with stable high-frequency performance under controlled laboratory conditions, supporting aerospace-oriented development, although evaluated in a laboratory environment, confirming the potential of WBG technologies for future power-conversion architectures. Full article

We report the synthesis and multifunctional characterization of copper-reinforced Ba_0.85Sr_0.15TiO₃ (BST) ceramic composites with Cu contents ranging from 0 to 40 wt%, prepared by a sol–gel route and densified using spark plasma sintering (SPS). X-ray diffraction and FT-IR analyses confirm the coexistence of cubic and tetragonal BST phases, while Cu remains as a chemically separate metallic phase without detectable interfacial reaction products. Microstructural observations reveal abnormal grain growth induced by localized liquid-phase-assisted sintering and progressive Cu agglomeration at higher loadings. Scanning electron microscopy reveals abnormal grain growth, with the average BST grain size increasing from approximately 3.1 µm in pure BST to about 5.2 µm in BST–Cu40% composites. Optical measurements show a continuous reduction in the effective optical bandgap (apparent absorption edge) from 3.10 eV for pure BST to 2.01 eV for BST–Cu40%, attributed to interfacial electronic states, defect-related absorption, and enhanced scattering rather than Cu lattice substitution. Electrical characterization reveals a percolation threshold at approximately 30 wt% Cu, where AC conductivity and dielectric permittivity reach their maximum values. Impedance spectroscopy and equivalent-circuit analysis demonstrate strong Maxwell–Wagner interfacial polarization, yielding a maximum permittivity of ~1.2 × 10⁵ at 1 kHz for BST–Cu30%. At higher Cu contents, conductivity and permittivity decrease due to disrupted Cu connectivity and increased porosity. These findings establish BST–Cu composites as tunable ceramic–metal systems with enhanced dielectric and optical responses, demonstrating potential for specialized high-capacitance decoupling applications where giant permittivity is prioritized over low dielectric loss. Full article

Wireless Power Transfer (WPT) has become a pivotal technology, enabling the battery-free operation of Internet of Things (IoT) and biomedical devices while supporting environmental sustainability. This review provides a comprehensive analysis of microstrip patch antennas (MPAs) operating at the 5.8 GHz Industrial, Scientific, and Medical (ISM) band, emphasizing their advantages over the more commonly used 2.4 GHz band. A detailed and systematic classification framework for MPA architectures is introduced, covering single-element, multi-band, ultra-wideband, array, MIMO, wearable, and rectenna systems. The review examines advanced optimization methodologies, including Defected Ground Structures (DGS), Electromagnetic Bandgap (EBG) structures, Metamaterials (MTM), Machine Learning (ML), and nanomaterials, each contributing to improvements in gain, bandwidth, efficiency, and device miniaturization. Unlike previous surveys, this work offers a performance-benchmarked classification specifically for 5.8 GHz MPAs and provides a quantitative assessment of key trade-offs, such as efficiency versus substrate cost. The review also advocates for a shift toward Power Conversion Efficiency (PCE)-centric co-design strategies. The analysis identifies critical research gaps, particularly the ongoing disparity between simulated and experimental performance. The review concludes by recommending multi-objective optimization, integrated antenna-rectifier co-design to maximize PCE, and the use of advanced materials and computational intelligence to advance next-generation, high-efficiency 5.8 GHz WPT systems. Full article

The increasing discharge of recalcitrant organic dyes from the textile industry necessitates the development of efficient and sustainable wastewater treatment technologies. This study reports the successful eco-friendly fabrication of magnetically separable cerium–manganese ferrite (Ce-MnFe₂O₄) nanocatalysts via a one-pot green synthesis route, utilizing an aqueous extract of Brachychiton populneus leaves. The structural, morphological, magnetic, and optical properties of the synthesized nanocatalysts were systematically investigated. X-ray diffraction (XRD) analysis confirmed the formation of a phase-pure cubic spinel structure, with evidence of Ce³⁺ ion incorporation leading to lattice expansion and the formation of beneficial oxygen vacancies. The composite material exhibited superparamagnetic behavior with a high saturation magnetization of 38.7 emu/g, which facilitates efficient magnetic separation and recovery. Optical studies revealed a direct bandgap of 2.33 eV, enabling significant photocatalytic activity under visible light irradiation. The Ce-MnFe₂O₄ nanocatalyst demonstrated superior performance, achieving degradation efficiencies of 96% for methylene blue and 98% for Congo Red within 90 min. Furthermore, the catalyst demonstrated good operational stability, maintaining 62% of its initial degradation efficiency for CR and 51% for MB after five consecutive reuse cycles. These results underscore the potential of this green-synthesized, magnetically recoverable nanocatalyst as a highly effective and sustainable solution for the remediation of dye-contaminated industrial effluents. Full article

In this present study, sodium- and strontium-modified bismuth titanate—Bi_0.5Na_0.5TiO₃ (BNT) and Bi_0.5Sr_0.5TiO₃ (BST)—were synthesized using the auto-combustion technique with citric acid (C₆H₈O₇) and glycine (C₂H₅NO₂) as fuels in an optimized ratio of 1.5:1. The resulting powders were characterized using X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, UV–Visible diffuse reflectance spectroscopy (DRS), and Fourier-transform infrared (FT-IR) spectroscopy. The electrical behavior of the samples was studied using an LCR meter. XRD analysis confirmed the formation of a single-phase perovskite structure with average crystallite sizes of 18.60 nm for BNT and 22.03 nm for BST, attributed to the difference in ionic radii between Na⁺ and Sr²⁺. An increase in crystallite size was accompanied by a corresponding increase in lattice parameters and unit-cell volume. The Williamson–Hall analysis further validated the strain-size contributions. EDX (Energy-Dispersive X-ray analysis) results confirmed successful incorporation of Na⁺ and Sr²⁺ without detectable impurity phases. Optical studies revealed distinct absorption peaks at 341 nm for BNT and 374 nm for BST, and the optical bandgap (E_g), calculated using Tauc’s relation, was found to be 2.6 eV and 2.0 eV, respectively. FT-IR spectra exhibited characteristic Ti-O vibrational bands in the range of 420–720 cm⁻¹, consistent with the perovskite structure. For electrical characterization, the powders were pelletized under 3-ton pressure and sintered at 1000 °C for 3 h. The dielectric constant (ε_r), dielectric loss (tan δ), and ac conductivity (σ) of both samples increased with frequency. The combined structural, optical, and electrical results indicate that the optimized compositions of BNT and BST possess properties suitable for use in capacitors and other energy-storage applications. Full article

Defect engineering in semiconductor heterojunctions offers a promising route for enhancing the selectivity of photocatalytic CO₂ conversion. In this work, a ZnS/gel-derived TiO₂ photocatalyst featuring sulfur vacancies introduced via hydrazine hydrate (N₂H₄) treatment is developed. XRD, HRTEM, and XPS analyses confirm the formation of a crystalline heterointerface and a defect-rich ZnS surface, enabling effective interfacial electronic modulation. The optimized ZnS/gel-derived TiO₂-0.48 composite achieves CH₄ and CO yields of 6.76 and 14.47 μmol·g⁻¹·h⁻¹, respectively, with a CH₄ selectivity of 31.8% and an electron selectivity of 65.1%, clearly outperforming pristine TiO₂ and the corresponding single-component catalysts under identical conditions. Photoluminescence quenching, enhanced photocurrent response, and reduced charge-transfer resistance indicate significantly improved interfacial charge separation. Mott–Schottky analysis combined with optical bandgap measurements reveals pronounced interfacial charge redistribution in the composite system. Considering the intrinsic band structure of ZnS and gel-derived TiO₂, a Z-scheme-compatible interfacial charge migration model is proposed, in which photogenerated electrons with strong reductive power are preferentially retained on ZnS, while holes with strong oxidative capability remain on gel-derived TiO₂. This charge migration pathway preserves high redox potentials, facilitating multi-electron CO₂ methanation and water oxidation. Density functional theory calculations further demonstrate that sulfur vacancies stabilize *COOH and *CO intermediates and reduce the energy barrier for *COOH formation from +0.51 eV to +0.21 eV, thereby promoting CO₂ activation and CH₄ formation. These results reveal that sulfur vacancies not only activate CO₂ molecules but also regulate interfacial charge migration behavior. This work provides a synergistic strategy combining defect engineering and interfacial electronic modulation to enhance selectivity and mechanistic understanding in CO₂-to-CH₄ photoconversion. Full article

Rb₂KWO₃F₃ elpasolite was synthesized via the solid-state reaction route. The phase purity of the obtained sample was verified by the XRD analysis with Rietveld refinement in space group Fm-3m, yielding the unit cell parameter a = 8.92413 (17) Å. The electronic structure and chemical states of the constituent elements were investigated using X-ray photoelectron spectroscopy. The binding energy of the W 4f_7/2 core level (34.95 eV) was found to be characteristic of the W⁶⁺ oxidation state, while the values for Rb 3d, K 2p, O 1s and F 1s levels were consistent with those reported for related oxide and oxyfluoride compounds. First-principles density functional theory calculations were performed to model the electronic structure. The fac-configuration of the WO₃F₃ octahedra was identified as the most energetically favorable. The calculations revealed a direct band gap of 4.38 eV, with the valence band maximum composed primarily of O 2p orbitals and the conduction band minimum formed by W 5d orbitals. This combined experimental/theoretical study shows that the electronic structure and wide bandgap of Rb₂KWO₃F₃ are governed by the WO₃F₃ units and are largely insensitive to the Rb/K substitution. The wide bandgap identifies this class of oxyfluorides as a promising platform for developing new UV-transparent materials. Full article

The present study targets key limitation ‘separation after the process’ that is responsible for the loss of the photocatalyst in water treatment during heterogeneous photocatalysis. Therefore, eco-friendly nanostructured ZnO coatings were engineered by the doctor blade technique through the immobilization of green ZnO nanomaterials onto alumina substrate. ZnO/BPE 30 and ZnO/BPE 60 coatings were obtained from banana peel extract-based ZnO powder (ZnO/BPE). Likewise, ZnO/GTE 30 and ZnO/GTE 60 were prepared using green tea extract-based ZnO powder (ZnO/GTE). XRD characterization verified hexagonal wurtzite ZnO phase, while HRSEM analysis revealed that the flat surface of ZnO/BPE had rod-like nanostructures below 120 nm, and ZnO/GTE had spherical, porous nanoparticle networks with less than 70 nm. According to UV–vis spectrometry, all four coatings have bandgaps of ~5 eV. The highest efficiency for the solar-driven photocatalytic degradation of emerging organic pollutants was for ciprofloxacin (among pesticides clomazone and tembotrione; pharmaceuticals ciprofloxacin and 17α-ethinylestradiol; and mycotoxin zearalenone) in ultrapure water with the presence of all studied ZnO-based coatings, after 60 min of simulated solar irradiation. Its highest removal (89.1%) was achieved with ZnO/GTE 30, also having good reusability across three consecutive cycles in river water, thus supporting the application of eco-friendly, immobilized ZnO nanomaterials for wastewater treatment and environmental remediation. Full article

In this article, the authors present an in-depth analysis of a PTAT sensor and its role as one of the analogue blocks in a test ASIC. The authors propose some modifications to the PTAT sensor to reduce output signal non-linearities observed following measurements that are more accurate than those in their previous article on a PTAT sensor. The obtained PTAT sensor linearity ranges from R² = 0.9990 to R² = 0.9999 in a temperature range from −40 °C to 150 °C for the entire set of measured specimens, and the details of these test sessions are discussed in this manuscript. Moreover, it is demonstrated that at least some of the implemented circuits may have a discernible impact on the operation of the others. This is particularly evident regarding the bandgap reference, whose operation is also presented and analysed. The integrated circuit specimens containing all analysed circuits were manufactured using custom 3 µm CMOS technology on an n-type wafer. Measurements showed that some circuits containing p-diff resistors behave differently compared to those consisting solely of MOS transistors in symmetrical and matched configurations. The spread of resistor values is approximately 20%, thus requiring their skilful operation in this technology. The likely cause of the bandgap reference’s operation modification has been identified, and promising results have been obtained by recreating its malfunction via simulation. The authors found that in this technology, analogue circuits should be designed with a large margin for component dimensions, especially those implanted in p-wells. Full article