Search Results (1,514)

We demonstrate that pulsed laser annealing induces plasmonic gold nanoparticles in ZnO thin films, monitored in real-time via pulse-by-pulse spectroscopy. Initially embedded gold nanoparticles (smaller than 5 nm) in sputtered ZnO films were annealed using 532 nm pulses from a Q-switched Nd:YAG laser while monitoring transmission spectra in situ. A plasmonic resonance dip emerged after ~100 pulses in the 530–550 nm region, progressively deepening with continued exposure. Remarkably, different incident energies converged to a thermodynamically stable optical state centered near 555 nm, indicating robust nanoparticle configurations. After several hundred laser shots, the process stabilized, producing larger nanoparticles (40–200 nm diameter) with significant surface protrusion. SEM analysis confirmed substantial gold nanoparticle growth. Theoretical modeling supports these observations, correlating spectral evolution with particle size and embedding depth. The protruding gold nanoparticles can be functionalized to detect specific biomolecules, offering significant advantages for biosensing applications. This approach offers superior spatial selectivity and real-time process monitoring compared to conventional thermal annealing, with potential for optimizing uniform nanoparticle distributions with pronounced plasmonic resonances for biosensing applications. Full article

Oil–paper insulation in oil-immersed transformers undergoes a concealed degradation process that is difficult to detect during operation. To understand its discharge behavior, this study examines partial discharge characteristics under controlled moisture absorption and thermal aging. Experiments on S-PD (Surface Partial Discharge) and N-PD (Needle Partial Discharge) were carried out, and partial discharge patterns, discharge frequency, and breakdown voltage were collected to analyze discharge evolution. The results show that partial discharge develops through three stages: initiation, development, and pre-breakdown. In the initiation stage, pulses are sparse with low amplitudes and appear near the voltage peak. During development, both amplitude and discharge frequency increase, and the phase range expands. As breakdown approaches, pulse amplitude rises sharply, the phase distribution covers almost the full cycle, and conductive channels begin to form. Skewness, Peak Degree, and Maximum Steepness were extracted from statistical discharge maps to compare moisture-affected and aged samples. The findings provide experimental support for developing state-evolution-based failure warning models and diagnostic criteria, contributing to improved operational safety of oil–paper insulation systems. Full article

This work presents a highly compact and scalable 1.2-kV SiC MOSFET half-bridge building-block module enabled by a die-integrated 3D PCB packaging technology. Compared with conventional DBC-based or TO-247-based SiC half-bridge modules, the proposed design reduces the physical volume and weight by more than 90% while maintaining full compatibility with standard PCB manufacturing processes. The vertically laminated DC+/DC− conductors and symmetric PCB–die–PCB stack establish a tightly confined commutation loop, resulting in a measured power-loop inductance of 2.2 nH and a 3.8 nH gate-loop inductance—representing up to 94% and 89% reduction relative to discrete device implementations. Because the parasitic parameters are intrinsically well-balanced across replicated units and the mutual inductance between adjacent modules remains extremely small, the structure naturally supports current sharing during parallel operation. Thermal and insulation evaluations further confirm the suitability of copper filling via high-Tg laminated PCB substrates for high-power SiC applications, achieving withstand voltages exceeding twice the rated bus voltage. The proposed module is experimentally validated through finite-element parasitic extraction and 950 V double-pulse testing, demonstrating controlled dv/dt behavior and robust switching performance. This work establishes a manufacturable and parallel-friendly packaging approach for high-density SiC power conversion systems. Full article

The rapid advancement of high-performance electronics has intensified the demand for wide-bandgap semiconductor materials capable of operating under high-power and high-temperature conditions. Among these, silicon carbide (SiC) has emerged as a leading candidate due to its superior thermal conductivity, chemical stability, and mechanical strength. However, the high cost and complexity of SiC wafer fabrication, particularly in slicing and exfoliation, remain significant barriers to its widespread adoption. Conventional methods such as wire sawing suffer from considerable kerf loss, surface damage, and residual stress, reducing material yield and compromising wafer quality. Additionally, techniques like smart-cut ion implantation, though capable of enabling thin-layer transfer, are limited by long thermal annealing durations and implantation-induced defects. To overcome these limitations, ultrafast laser-based processing methods, including laser slicing and stealth dicing (SD), have gained prominence as non-contact, high-precision alternatives for SiC wafer exfoliation. This review presents the current state of the art and recent advances in laser-based precision SiC wafer exfoliation processes. Laser slicing involves focusing femtosecond or picosecond pulses at a controlled depth parallel to the beam path, creating internal damage layers that facilitate kerf-free wafer separation. In contrast, stealth dicing employs laser-induced damage tracks perpendicular to the laser propagation direction for chip separation. These techniques significantly reduce material waste and enable precise control over wafer thickness. The review also reports that recent studies have further elucidated the mechanisms of laser–SiC interaction, revealing that femtosecond pulses offer high machining accuracy due to localized energy deposition, while picosecond lasers provide greater processing efficiency through multipoint refocusing but at the cost of increased amorphous defect formation. The review identifies multiphoton ionization, internal phase explosion, and thermal diffusion key phenomena that play critical roles in microcrack formation and structural modification during precision SiC wafer laser processing. Typical ultrafast-laser operating ranges include pulse durations from 120–450 fs (and up to 10 ps), pulse energies spanning 5–50 µJ, focal depths of 100–350 µm below the surface, scan speeds ranging from 0.05–10 mm/s, and track pitches commonly between 5–20 µm. In addition, the review provides quantitative anchors including representative wafer thicknesses (250–350 µm), typical laser-induced crack or modified-layer depths (10–40 µm and extending up to 400–488 µm for deep subsurface focusing), and slicing efficiencies derived from multi-layer scanning. The review concludes that these advancements, combined with ongoing progress in ultrafast laser technology, represent research opportunities and challenges in transformative shifts in SiC wafer fabrication, offering pathways to high-throughput, low-damage, and cost-effective production. This review highlights the comparative advantages of laser-based methods, identifies the research gaps, and outlines the challenges and opportunities for future research in laser processing for semiconductor applications. Full article

Inter-turn short-circuit (ITSC) faults in motor drives can induce substantial circulating currents and localized thermal stress, ultimately degrading winding insulation and compromising torque stability. To enhance the operational reliability of open-winding (OW) five-phase fault-tolerant fractional-slot concentrated-winding interior permanent-magnet (FTFSCW-IPM) motor drive systems, this paper proposes a real-time fault-tolerant control strategy that provides current suppression and torque stabilization under ITSC conditions. Upon fault detection, the affected phase is actively isolated and connected to an external dissipative resistor, thereby limiting the fault-phase current and inhibiting further propagation of insulation damage. This reconfiguration allows the drive system to uniformly accommodate both open-circuit (OC) and ITSC scenarios without modification of the underlying control architecture. For OC operation, an equal-amplitude modulation scheme based on carrier-based pulse-width modulation (CPWM) is formulated to preserve the required magnetomotive-force distribution. Under ITSC conditions, a feedforward compensation mechanism is introduced to counteract the disturbance generated by the short-circuit loop. A principal contribution of this work is the derivation of a compensation term that can be estimated online using zero-sequence voltage (ZSV) together with measured phase currents, enabling accurate adaptation across varying ITSC severities. Simulation and experimental results demonstrate that the proposed method effectively suppresses fault-phase current, maintains near-sinusoidal current waveforms in the remaining healthy phases, and stabilizes torque production over a wide range of fault and load conditions. Full article

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed to capture the thermal propagation of the hybrid system. Synthesizing nHAp/CNT composites enables the combination of the biocompatible and piezoelectric nature of nHAp with the enhanced photothermal response introduced by CNTs. UV–Vis reflectance measurements confirmed that CNT incorporation increases the optical absorption of the ceramic matrix, resulting in more efficient photothermal conversion. The composite was irradiated with a nanosecond pulsed laser, and the resulting thermal transients were compared with CA simulations based on a D2Q9 lattice configuration. The model accurately reproduces experiments, achieving R² > 0.991 and NRMSE below 2.4% for all tested laser powers. This strong correspondence validates the CA approach for predicting spatiotemporal heat diffusion in heterogeneous nanostructured composites. Furthermore, the model revealed a sensitive thermal coupling when two heat sources were considered, indicating synergistic enhancement of local temperature fields. These findings demonstrate both the effective integration of CNTs within the nHAp matrix and the capability of CA-based modeling to describe their photothermal behavior. Overall, this study establishes a computational–experimental basis for designing controlled thermal-wave propagation and guiding future multi-frequency or multi-source photothermal mixing experiments. Full article

In the research, the effect of basaltic pumice powder on the mechanical and thermal resistance properties of alkali-activated mortars (AAM) was studied. The class F fly ash, basaltic pumice powder (BPP), and ground granulated blast furnace slag were utilized as sustainable binder materials. The BPP was incorporated instead of fly ash and slag at concentrations of 10, 20, 30, 40, and 50%. In addition, the effects of different sodium hydroxide (NaOH) molarities (8, 12, 16 M) were investigated on the thermal resistance properties. The influence of curing time and its effects on different elevated temperatures (200, 400, and 600 °C) were also studied together at 7, 28, and 56 days on the AAMs. Flexural strength, compressive strength, weight change, and ultrasonic pulse velocity tests were carried out at the macro-scale. The microstructures of the AAM samples were analyzed using SEM and EDX spectroscopy. The results showed that dissolution of basaltic pumice particles requires a longer curing time. The 50% pumice-incorporated 8 M samples at 7 d exhibited the worst, whereas 16 M samples without pumice at 56 d performed the best in terms of mechanical strength and thermal durability. The optimal formulation for the best elevated temperature resistance is the 30% BPP and 16 M NaOH molarity. Full article

The global food industry is undergoing a critical shift toward sustainability, driven by high postharvest losses—reaching up to 40% for fruits and vegetables—and the need to reduce environmental impact. Sustainable postharvest innovations focus on improving quality, extending shelf life, and minimizing waste through eco-efficient technologies. Advances in non-thermal and minimal processing, including ultrasound, pulsed electric fields, and edible coatings, support nutrient preservation and food safety while reducing energy consumption. Although integrated postharvest technologies can reduce deterioration and microbial spoilage by 70–92%, significant challenges remain, including global losses of 20–40% and the high implementation costs of certain nanostructured materials. Simultaneously, eco-friendly packaging solutions based on biodegradable biopolymers and bio-composites are replacing petroleum-based plastics and enabling intelligent systems capable of monitoring freshness and detecting spoilage. Energy-efficient storage, smart sensors, and optimized cold-chain logistics further contribute to product integrity across distribution networks. In parallel, the circular bioeconomy promotes the valorization of agro-food by-products through the recovery of bioactive compounds with antioxidant and anti-inflammatory benefits. Together, these integrated strategies represent a promising pathway toward reducing postharvest losses, supporting food security, and building a resilient, environmentally responsible fresh produce system. Full article

Temperature offers a simple yet powerful signal to program cellular behavior. Here, we engineered and characterized a set of temperature-dependent genetic circuits that integrate RNA thermometers with site-specific DNA recombinases to achieve precise, irreversible control of gene expression. Using the serine recombinase Bxb1 placed under the control of the Salmonella FourU RNA thermometer, we demonstrate how promoter strength critically defines thermal sensitivity: weak promoters’ activity clears ON/OFF transitions, while strong promoters lead to continuous, quasi-temperature-independent recombination. Furthermore, temperature pulse duration and growth phase of cell culture were found to modulate recombination efficiency, providing additional layers of control. We illustrate the potential of this framework through proof-of-concept applications, including (i) the generation of spatial expression patterns on 2D surfaces via localized heating, (ii) a paper-based device capable of recording temperature gradients as stable genetic outputs, and (iii) a temperature-triggered lysis system for controlled cellular release. Together, these results establish temperature-regulated recombinase circuits as versatile and robust tools for programmable, spatially resolved, and irreversible control of gene expression, paving the way for new applications in synthetic biology, biosensing, and bioproduction. Full article

One of the main challenges in welding aluminium concerns structural integrity and a significant reduction in mechanical properties in the region adjacent to the weld. Design provisions can result in a drastic reduction, which may exceed 50% of the base metal resistance. This research aims to evaluate the accuracy of the HAZ extent values codified in Eurocode 9 for T-connections fabricated from artificially aged 6082 aluminium alloy, which is widely used in load-bearing structures. Three plate thicknesses (6, 8 and 10 mm) and two pulsed MIG welding processes (DC-MIG-P and AC-MIG-P) were used to fabricate 20 T-connection specimens (10 different configurations) in accordance with EN 1090-3. The study focuses on characterising the welding zones through hardness testing and metallographic examination. Results show that AC-MIG-P offers better control over thermal input and may reduce structural distortion, while DC-MIG-P provides more robust fusion and metallurgical continuity. Findings related to HAZ extent (12.77 mm and 15.36 mm maximum measured for AC-MIG-P and DC-MIG-P, respectively) suggest that Eurocode 9 may be overly conservative for pulsed MIG welding processes, particularly for greater plate thicknesses where a HAZ extent of 22.50 mm or more is specified. Consequently, adopting more precise, process-specific HAZ characterisations could lead to more realistic connection design and structural behaviour. Full article

Pulsed electric field (PEF) technology represents a promising non-thermal method for enhancing the extraction of bioactive compounds from plant matrices. This study investigated the influence of PEF treatment on the bioactive compounds composition of aqueous extracts obtained after processing blackcurrant, redcurrant, chokeberry, raspberry, and blackberry seeds. The seeds were treated at 8 kV or 10 kV electrode voltage, and 50 kJ/kg energy input, and the resulting extracts were analyzed for total polyphenol content (TPC), antioxidant capacity (ABTS and DPPH assays), anthocyanin composition (HPLC-DAD), and color parameters (L*, a*, b*). The PEF treatment significantly enhanced the release of polyphenols, anthocyanins, and antioxidant compounds, particularly in chokeberry, raspberry, and blackberry seed extracts. Extracts obtained after PEF treatment exhibited higher TPC, in a range between 0.57 and 3.00 mg GAE/g, and higher radical scavenging activity in a range 2.33–35.07 µmol TE/g in ABTS assay and 1.07–12.27 µmol TE/g in DPPH assay. Also, more intense red coloration was determined, confirming that electroporation facilitated pigment and phenolic migration into the aqueous phase. These findings demonstrate that PEF is an efficient and solvent-free intensification technique for the valorization of berry by-products, generating aqueous fractions rich in natural antioxidants and colorants that support circular and sustainable fruit-processing practices. Full article

Body-contouring devices deliver controlled thermal energy to treat cellulite, reduce localized fat, and improve skin elasticity. Since the thermal effect is closely related to the delivered RF output power, precise control of the output power is critical for both efficacy and safety. In this study, we propose a 2.4 GHz CMOS pulse-mode transmitter for body-contouring device applications, featuring precise control of the average power delivered to the body. The transmitter comprises a fully integrated phase-locked loop (PLL) synthesizer, pulse modulator (PM), and 10 mW power amplifier (PA). It is fabricated in a 65 nm CMOS with a compact die area of 3.75 mm². The PA provides four-level continuous-mode output control from −0.3 dBm to 11.1 dBm, and the PM performs programmable PA switching for pulse-mode operation of the PA with a wide range of pulse rates and duty ratios. By combining the continuous-mode output power control and pulse-mode on–off time regulation, the average output power delivered to the skin is finely controlled, managing the delivered power within a safe skin temperature below 65 °C. The PLL loop filter is fully integrated with a wide programmability, improving the form factor and bill of materials for the target devices. Measurement results confirm that the designed transmitter can accurately control both the average output power and pulse profile across the 2.4 GHz ISM band, demonstrating its suitability for compact home-use RF body-contouring devices. Full article

The spoilage bacterium Acetobacter aceti poses a major threat to wine quality by causing acetification, driving the need for effective control methods. This study investigated the inactivation of A. aceti using pulsed electric field (PEF) and elucidated the multi-target mechanisms. The results demonstrated that PEF efficacy was highly dependent on the electric field intensity. PEF treatment at 30 kV/cm achieved a >3-log reduction in viable cell counts, with a Weibull model analysis indicating a critical inactivation threshold of 21.64 kV/cm. Mechanistic investigations revealed that PEF induced irreversible damage to the cell membrane, evidenced by morphological rupture (SEM) and a 4-fold increased permeability (flow cytometry), which led to a massive leakage of intracellular contents. Critically, this physical damage was correlated with profound physiological disruption, including the inactivation of key spoilage enzymes alcohol dehydrogenase (ADH, 80.0% relative activity loss) and aldehyde dehydrogenase (ALDH, 93.1% relative activity loss). Furthermore, PEF induced severe oxidative stress (4.25-fold increase in ROS and 3.30-fold increase in MDA) and a collapse in energy metabolism. Collectively, these findings reveal a synergistic inactivation mechanism, which establishes a strong theoretical foundation for the potential development of PEF as a non-thermal strategy to control acetic spoilage in winemaking. Full article

Fiber lasers operating at 1.7 μm have significant application value in fields such as gas detection and material processing due to their characteristics, including compact structure and ease of thermal management. Based on the stimulated Raman scattering (SRS) of gas molecules in hollow-core fibers (HCFs), fiber gas Raman lasers (FGRLs) are a novel and effective method for generating 1.7 μm fiber lasers. We report here, to the best of our knowledge, the first FGRL based on the anti-resonant hollow-core fiber (AR-HCF) filled with sulfur hexafluoride (SF₆) molecules. A nanosecond pulsed fiber amplifier tunable from 1540 to 1560 nm was used to pump a 17.8-m-long AR-HCF filled with SF₆ molecules. By virtue of the vibrational SRS of SF₆ molecules, laser output in the range of 1748–1774 nm was achieved. At a gas pressure of 15 bar, a maximum average power output of ~3 W was obtained, corresponding to an optical-to-optical conversion efficiency of ~22%. The output linewidth of the Raman laser was measured to be approximately 2.1 GHz using a Fabry–Pérot (F-P) scanning interferometer. The research results enriched the methods for 1.7 μm fiber laser output. Full article

Realizing the full potential of optical actuation for high-speed phase-change radio-frequency (RF) switches requires a shift to single-pulse operation. This work presents a systematic investigation of reversible phase transitions in GeTe thin films induced by single 10 ns laser pulses, utilizing spatially resolved characterization techniques, including atomic force microscopy (AFM) and micro-spectroscopy. Precise laser fluence windows for crystallization (12.7–16 mJ/cm²) and amorphization (25.44–41.28 mJ/cm²) are established. A critical finding is that the amorphization process is governed by rapid thermal accumulation, which creates a direct trade-off between achieving the phase transition and avoiding detrimental surface morphology. Specifically, we observe that excessive energy leads to the formation of laser-induced ridges and ablation craters, which are identified as primary causes of device performance degradation. This study elucidates the underlying mechanism of single-pulse-induced phase transitions and provides a practical processing window and design guidelines for developing high-performance, optically actuated GeTe-based RF switches. Full article