Search Results (9,898)

This study investigates the effects of laser power and scanning rate on the surface morphology, relative density, microhardness and microstructure of pure tungsten fabricated by laser powder bed fusion (LPBF). Increasing the laser power or decreasing the scanning rate effectively suppresses spheroidisation and enhances densification, achieving a maximum relative density of ~98%. However, excessive laser power intensifies Marangoni convection, leading to surface protrusions that reduce density. Microstructural analysis reveals that the laser-scanned surface is dominated by fine columnar grains (390–480 HV), whereas the side surface comprises coarser columnar grains with lower hardness (~390 HV). Electron backscatter diffraction analysis confirms that the side surface contains a high proportion of grains exceeding 100 μm and reveals a significant peak (~41.8%) at ~3.5° for low-angle grain boundaries, indicating substantial internal stress and microstrain. Pole figures show a weak preferred orientation (maximum texture intensity of 3.161). Phase analysis shows no significant phase transformation after LPBF, while internal stress and microstrain increase notably. Full article

Compact wireless electronic devices require charging interfaces that can support different receiver positions and orientations within limited spaces. In this context, a double-sided mixed-coupling structure can provide independent magnetic- and electric-field power-transfer paths by combining coil-based and plate-based coupling mechanisms. This paper proposes a double-sided mixed-coupling wireless power transfer (DMPT) coupler for compact wireless electronic devices related to the Internet of Things (IoT) and the Internet of Drones (IoD). The proposed coupler integrates an upper coil-based magnetic-field coupling path and a lower stacked-plate-based electric-field coupling path within a single transmitter structure. Through this configuration, inductive wireless power transfer (IPT) and capacitive wireless power transfer (CPT) are implemented as independent double-sided power-transfer paths. To analyze the resonant behavior, a three-port equivalent circuit including mutual inductance and mutual capacitance is developed, and the resonance splitting under the uncompensated condition is investigated using even/odd mode decomposition. The predicted resonant frequencies agree with the ANSYS HFSS results with errors of 0.16% and 1.12%. After series-L compensation, the 60 × 60 × 7.31 mm³ coupler operates at the 6.78 MHz industrial, scientific, and medical band, showing S₁₁ ≈ 0.042, S₂₁ ≈ 0.68, and S₃₁ ≈ 0.64 under the double-sided aligned condition. Field and transient waveform analyses further verify that the upper H-coupling region and lower E-coupling region operate simultaneously while being spatially separated. The proposed DMPT coupler provides a coupler-level design framework for implementing IPT and CPT as independent double-sided coupling paths. Full article

Accurate fault location is essential for improving the reliability and service restoration capability of distribution networks. With the increasing penetration of distributed generation, power electronic devices, and flexible loads, fault transient signals become increasingly nonlinear and nonstationary, posing challenges to conventional impedance-based, traveling-wave-based, and feature-engineering-based methods. To improve transient fault feature representation, this paper proposes a wavelet-embedded residual attention convolutional neural network (CNN) for distribution network fault location. The task is formulated as a multi-class classification problem, in which each predefined line section is treated as a candidate fault location class. The proposed method embeds discrete wavelet decomposition into the convolutional feature extraction process, enabling low-frequency trend components and high-frequency transient components to be jointly represented and fused by subsequent trainable network modules. Residual connections improve deep feature propagation, and an attention mechanism enhances fault-sensitive representations. Simulation studies on the IEEE 33-bus distribution system show that the proposed method outperforms multi-layer perceptron (MLP), support vector machine (SVM), standard CNN, ResNet, and Attention-CNN, achieving 98.27% accuracy and a 98.33% F1-score. The class-wise results and robustness tests under different transition resistances, noise levels, and fault types further verify the effectiveness and adaptability of the proposed method. Full article

Lycopene is a highly significant carotenoid in daily life, exhibiting potent antioxidant properties and recognized as one of the most powerful natural antioxidants identified in plants to date. Its functionality originates from electronic and vibrational states that exhibit a high sensitivity to environmental perturbations. Nevertheless, exclusively experimental methodologies face challenges in delivering a comprehensive molecular-level comprehension of the influence exerted by particular environmental factors on the vibronic characteristics. This deficiency in understanding hinders the accurate prediction of its behavior and functional performance within complex systems. The first principle computational investigation enables a precise elucidation of the coupling mechanisms between electronic excitations and vibrational modes under diverse solvation and interaction environments. The results indicate that the local environment significantly influences the charge distribution and orbital energies of lycopene, altering its vibrational and electronic state properties. This provides a fundamental theoretical framework for predicting their photophysical behavior and biological functions within complex matrices. Full article

One of the latest and innovative areas of research in energy is the development of thermoelectric generators (TEGs). A novel family of soft, sustainable energy harvesters, hydrogel-based renewable flexible thermoelectric generators use linked ionic, electronic, and redox processes to transform heat gradients into electrical energy. According to recent research, a hydrogel-based TEG has ionic Seebeck coefficients (S) of the order 10–40 mV K⁻¹, which are tens to hundreds of times greater than those of electronic polymers. Thermal conductivities are modest (~0.3–0.6 W/m·K), ionic conductivities typically vary from 10⁻³ to 10⁻¹ S cm⁻¹, and water-rich gels are naturally soft with elastic moduli ~10³–10⁶ Pa and elongations > 100–800%. Recent developments in the concepts, properties, working mechanism, and potential applications of hydrogel-based thermoelectric generators are the focus of this review paper. We investigate the basic transport processes, such as ionic thermodiffusion, thermoelectric ion–electron coupling, and redox-mediated potential production, that allow thermoelectric conversion in hydrogels. This review identifies bottlenecks such as poor output power under minor gradients, summarize performance parameters, and assess methods to improve efficiency. Wearable and implanted power sources, low-grade waste heat collection, and environmental monitoring are examples of promising applications. Lastly, we describe the research avenues that must be pursued in order to expedite the transition of hydrogel-based thermoelectric generators from lab tests to useful, sustainable energy sources. Therefore, the review can provide fundamental knowledge on hydrogel-based TEGs along with their working principles. Full article

A significant amount of mechanical and thermal energy is lost when typing on a laptop keyboard. To address this, hybrid energy harvesters must increase the generated power density and mitigate energy fluctuation issues. This paper explores the potential enhancement of energy harvesting by combining thermoelectric and piezoelectric effects within a multilayered structure integrated into a laptop keyboard button. Through numerical simulation, the study assesses how these two behaviors can synergistically increase the power density generated by the hybrid device. The focus is on optimizing energy efficiency by harnessing the heat losses from integrated circuits and the mechanical stresses due to the act of typing. The point is to refine the design of such a system to maximize the conversion of ambient energy into electricity. The findings indicate that the hybrid structure combining both piezoelectric and thermoelectric effects, effectively captures energy from a laptop keyboard, producing a substantial amount of electricity. This investigation shows that the generator can produce up to 2.07 mW of power using PU-40%PZT as piezoelectric material and an additional 71.93 μW through the PEDOT: PSS as thermoelectric material from a single keystroke when pressed and heated. This study underscores the potential for improving energy-harvesting efficiency in laptop keyboards, contributing to more sustainable and energy-efficient electronic devices. Full article

This work reports the results of a study on the optical, morphological, and structural properties of cesium lead bromide iodide mixed perovskite thin films (CsPbBr_3−xI_x), synthesized by sequential evaporation of precursors (CsBr, PbBr₂, PbI₂). First, the deposition conditions were optimized to obtain thin films predominantly composed of the pure CsPbBr₃ phase. Subsequently, the influence of partial substitution of Br⁻ by I⁻ on the film properties was investigated. Particular emphasis was placed on evaluating the effect of partial Pb²⁺ substitution by Zn²⁺ on the optical, morphological, electronic, and structural properties using optical transmittance, photoluminescence, scanning electron microscopy (SEM), X-ray diffraction (XRD), Urbach energy analysis, and density functional theory (DFT) calculations. Zn²⁺-doped CsPbBr_3−xI_x films were prepared by evaporating a ZnBr₂ layer onto the pre-deposited PbBr₂/PbI₂ precursor layers. It was found that Zn²⁺-doped inorganic CsPbBr_3−xI_x perovskite films exhibit enhanced crystallinity and improved surface morphology. Additionally, photoluminescence characterization confirms that non-radiative recombination decreases significantly, apparently due to a reduction in intrinsic defect density. The effect of Zn²⁺ doping on the power conversion efficiency of carbon-based planar solar cells was also evaluated. Collectively, Urbach energy, photoluminescence, and SEM analyses revealed that the optimal Zn²⁺ doping range for CsPbBr_3−xI_x perovskite films is ≤5%. Full article

Gamma-ray bursts (GRBs) represent the most powerful explosions in the Universe, releasing extreme fluxes of non-thermal radiation across the electromagnetic spectrum. A central enigma in GRB physics remains the mechanism responsible for accelerating electrons, positrons, and hadrons to the required ultra-relativistic energies. Conventional theories primarily invoke diffusive shock acceleration (DSA), magnetic reconnection, and relativistic turbulence. This short review first examines these canonical acceleration methods, then discusses the principles and successes of plasma wakefield acceleration as a powerful future technique for ground-based applications. Finally, we critically analyze the feasibility of applying this mechanism to the cosmological environment of GRBs, exploring why the terrestrial success of wakefield acceleration has not yet been definitively confirmed “on the sky”. Full article

Optimizing the carrier concentration across the entire operating temperature range is crucial for maximizing the power factor in n-type PbTe. However, conventional shallow donors produce a nearly temperature-invariant electron concentration, leading to an increasingly large deviation from the optimal carrier concentration at elevated temperatures. Herein, we implement a dynamic deep-shallow co-doping strategy by combining iodine (a shallow donor) with gallium (a deep-level donor) in PbTe. The Ga-related deep impurity states thermally ionize at elevated temperatures, providing additional electrons and driving the Hall carrier concentration above ~563 K toward its temperature-dependent optimum. Concurrently, our optimized synthesis preserves a high carrier mobility, which synergistically sustains a remarkable peak power factor of 30 μW·cm⁻¹·K⁻² for the optimal composition, Ga_0.02Pb_0.98Te_0.996I_0.004. Combined with a strongly suppressed lattice thermal conductivity, this results in a maximum figure of merit (ZT) of 1.41 at 803 K and an average ZT of 1.00 within 400–773 K for Ga_0.02Pb_0.97Te_0.996I_0.004—a 25% improvement over the I-only doped baseline. These findings establish deep-shallow co-doping as a robust and broadly applicable carrier-engineering paradigm for thermoelectric optimization. Full article

Pyroelectric nanogenerators (PyNGs) have attracted extensive attention for converting thermal energy into electricity, yet their low output power remains a critical bottleneck hindering practical use. This review summarizes various pyroelectric materials and device structures, elucidates the working principle, and discusses their output performances and application scenarios. The correlation between device output and key factors, including intrinsic material properties, electrode dimensions, and external thermal excitation, is systematically examined. Hybrid nanogenerators (HNGs) that couple pyroelectric with piezoelectric, triboelectric, and photovoltaic effects are also reviewed. In addition, the evaluation criteria for pyroelectric energy conversion efficiency are examined, highlighting the need for more systematic studies in this aspect. Finally, key challenges and corresponding strategies are discussed to facilitate the practical deployment of PyNGs in areas such as wearable electronics and self-powered sensors. Full article

Gated transistors in the form of MOSFET, FinFET, or IGBT are capable of controlling and transferring either signals or powers. These capabilities are closely associated with applied biases on Gates, which surpass the respective threshold voltages. Source/Drain bias, V_DS, then establishes the electric field, E_DS, driving carriers to flow with a speed which is proportional to E_DS with the proportionality, termed mobility, μ. The mobility somewhat addresses the electrical performances of the specific transistor, and is V_GS-dependent, where the generated electric field is perpendicular to the interface in between the Gate and the Gate oxide and is directed across the channel. The mobility may be treated as the collective quantum statistical behaviors of carriers, i.e., electrons or fermions. It is worth analyzing the electrical performances by way of quantum statistics. Nevertheless, the threshold voltages are surprisingly negative on FinFETs as the fitting is performed, which means that I_DS would flow even without applied voltage on the Gate. I_DS-V_DS characteristic curves with negative threshold voltage intriguingly perform just like the other ones with positive threshold voltages. Therefore, there might exist some kind of mechanism enhancing strong inversion layers that is responsible for the characteristics. In this paper, characteristic curves of FinFETs may be well fitted by using both modified characteristic formulas and the proposed kink effects. The extracted parameters (k_N, Vth, λ) thus provide information on mobility, concentration of p (1/cm³), or even leakage current. Also, the mobility, μ, here is analyzed by using Fermion statistics. Furthermore, trivial solutions for the specific boundary conditions, V_GS = 0 V, surrounding the channel are presented, where one of the possibilities proposed is the mass plasma oscillation of electrons, which might be an option for addressing the negative threshold voltage. Full article

Magnetoresistive random-access memory (MRAM), as a promising non-volatile memory technology, has attracted extensive research interest owing to its unique combination of high operating speed, exceptional endurance, low standby power consumption, and CMOS process compatibility. In this review, we provide a comprehensive overview of the technological evolution of MRAM, spanning from Toggle-MRAM to spin-transfer torque (STT)-MRAM and then to spin–orbit torque (SOT)-MRAM. The working mechanisms, performance trade-offs, and integration potential of each generation are systematically summarized. Furthermore, the diverse applications of MRAM—including embedded systems-on-chip (SoCs), edge computing, aerospace and automotive electronics, artificial intelligence accelerators, neuromorphic computing, and hardware-level security—are thoroughly discussed. We also identify key challenges hindering large-scale commercialization, such as the trade-off between write energy and speed, process complexity, storage density constraints, and cost competitiveness. Finally, emerging research directions are proposed, emphasizing short-term priorities such as write current reduction and yield improvement, as well as long-term development strategies focusing on material–device–algorithm co-optimization and ecosystem establishment. Full article

The κ-phase gallium oxide (κ-Ga₂O₃) has emerged as a promising material for next-generation electronic devices owing to its ultra-wide band gap, remarkable spontaneous polarization and unique ferroelectricity. We have investigated the two-dimensional electron gas (2DEG) characteristics and device performance of κ-Ga₂O₃/GaN HEMTs via numerical simulations. The κ-Ga₂O₃/GaN heterostructure exhibits a significantly enhanced 2DEG density (~1.05 × 10¹⁴ cm⁻²), which is nearly an order of magnitude higher than that of conventional AlGaN/GaN HEMTs, due to the strong polarization effect. For a barrier thickness of 25 nm, the κ-Ga₂O₃/GaN HEMT exhibits a maximum drain current density (I_D,max) of 4.40 A/mm at V_GS = 2 V and a peak transconductance (g_m,max) of 0.45 S/mm, accompanied by a steep subthreshold swing (SS) of 63.2 mV/decade. Furthermore, we find that the absolute value of threshold voltage increases with the barrier thickness and the peak transconductance decreases with the increase in barrier thickness. When the thickness reaches 40 nm, the 2DEG density becomes saturated with a value of 1.12 × 10¹⁴ cm⁻². Moreover, by incorporating a p-type GaN cap layer into the κ-Ga₂O₃/GaN heterostructure, a normally off operation is achieved, with a positive threshold voltage as the acceptor concentration exceeds 8.0 × 10¹⁷ cm⁻³. These results highlight the potential of κ-Ga₂O₃/GaN heterostructures for high-performance power electronic applications. Full article

A methodology for the development of nonlinear model predictive control for thermal management of a 40-ton fuel-cell heavy-duty truck is presented, using the medium-temperature cooling circuit as a case study. The approach integrates control-oriented modeling, parameter estimation, and experimental validation based on drivetrain test bench measurements under controlled high-temperature ambient conditions. A lumped-parameter model of the medium-temperature circuit, including coolant, oil, electric motors, and power-electronics auxiliaries, is derived and implemented in a Simulink environment, with heat-transfer parameters calibrated from test bench data and radiator air-side resistance and fan characteristics derived from CFD simulations and manufacturer specifications, respectively. Model parameters are identified using a systematic estimation procedure and the resulting model is validated against long-duration roller test measurements, achieving coefficients of determination above R² = 0.9 and normalized RMSE values below 10% for all key temperatures. The validated model is then used as the prediction model in a model predictive controller that manipulates radiator fan and coolant-pump speeds, while treating component heat losses, vehicle speed and ambient temperature as measured disturbances. The controller is evaluated in a model-in-the-loop environment for representative long-haul and urban driving cycles and different ambient temperatures, and its performance is benchmarked against conventional rule-based and PI-based control strategies. Depending on the driving cycle and ambient conditions, the proposed NMPC reduces cooling system energy consumption by up to 39.6% compared to a PI controller (VECTO Urban Delivery cycle, 35 °C ambient), with an average reduction of 16.6% across all investigated driving cycles and ambient conditions, without a significant increase in average or maximum coolant temperature. The proposed methodology provides a transferable workflow for developing predictive thermal management control in fuel-cell heavy-duty vehicles and other complex automotive cooling systems. Full article