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Keywords = high voltage electrical pulses

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20 pages, 4765 KiB  
Article
Ultrasonic EDM for External Cylindrical Surface Machining with Graphite Electrodes: Horn Design and Hybrid NSGA-II–AHP Optimization of MRR and Ra
by Van-Thanh Dinh, Thu-Quy Le, Duc-Binh Vu, Ngoc-Pi Vu and Tat-Loi Mai
Machines 2025, 13(8), 675; https://doi.org/10.3390/machines13080675 (registering DOI) - 1 Aug 2025
Viewed by 157
Abstract
This study presents the first investigation into the application of ultrasonic vibration-assisted electrical discharge machining (UV-EDM) using graphite electrodes for external cylindrical surface machining—an essential surface in the production of tablet punches and sheet metal-forming dies. A custom ultrasonic horn was designed and [...] Read more.
This study presents the first investigation into the application of ultrasonic vibration-assisted electrical discharge machining (UV-EDM) using graphite electrodes for external cylindrical surface machining—an essential surface in the production of tablet punches and sheet metal-forming dies. A custom ultrasonic horn was designed and fabricated using 90CrSi material to operate effectively at a resonant frequency of 20 kHz, ensuring stable vibration transmission throughout the machining process. A Box–Behnken experimental design was employed to explore the effects of five process parameters—vibration amplitude (A), pulse-on time (Ton), pulse-off time (Toff), discharge current (Ip), and servo voltage (SV)—on two key performance indicators: material removal rate (MRR) and surface roughness (Ra). The optimization process was conducted in two stages: single-objective analysis to maximize MRR while ensuring Ra < 4 µm, followed by a hybrid multi-objective approach combining NSGA-II and the Analytic Hierarchy Process (AHP). The optimal solution achieved a high MRR of 9.28 g/h while maintaining Ra below the critical surface finish threshold, thus meeting the practical requirements for punch surface quality. The findings confirm the effectiveness of the proposed horn design and hybrid optimization strategy, offering a new direction for enhancing productivity and surface integrity in cylindrical EDM applications using graphite electrodes. Full article
(This article belongs to the Section Advanced Manufacturing)
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21 pages, 1208 KiB  
Review
Combination of Irreversible Electroporation and Clostridium novyi-NT Bacterial Therapy for Colorectal Liver Metastasis
by Zigeng Zhang, Guangbo Yu, Qiaoming Hou, Farideh Amirrad, Sha Webster, Surya M. Nauli, Jianhua Yu, Vahid Yaghmai, Aydin Eresen and Zhuoli Zhang
Cancers 2025, 17(15), 2477; https://doi.org/10.3390/cancers17152477 - 26 Jul 2025
Viewed by 268
Abstract
Colorectal liver metastasis (CRLM) poses a significant challenge in oncology due to its high incidence and poor prognosis in unresectable cases. Current treatments, including surgical resection, systemic chemotherapy, and liver-directed therapies, often fail to effectively target hypoxic tumor regions, which are inherently more [...] Read more.
Colorectal liver metastasis (CRLM) poses a significant challenge in oncology due to its high incidence and poor prognosis in unresectable cases. Current treatments, including surgical resection, systemic chemotherapy, and liver-directed therapies, often fail to effectively target hypoxic tumor regions, which are inherently more resistant to these interventions. This review examines the potential of a novel therapeutic strategy combining irreversible electroporation (IRE) ablation and Clostridium novyi-nontoxic (C. novyi-NT) bacterial therapy. IRE is a non-thermal tumor ablation technique that uses high-voltage electric pulses to create permanent nanopores in cell membranes, leading to cell death while preserving surrounding structures, and is often associated with temporary tumor hypoxia due to disrupted perfusion. C. novyi-NT is an attenuated, anaerobic bacterium engineered to selectively germinate and proliferate in hypoxic tumor regions, resulting in localized tumor cell lysis while sparing healthy, oxygenated tissue. The synergy between IRE-induced hypoxia and hypoxia-sensitive C. novyi-NT may enhance tumor destruction and stimulate systemic antitumor immunity. Furthermore, the integration of advanced imaging and artificial intelligence can support precise treatment planning and real-time monitoring. This integrated approach holds promise for improving outcomes in patients with CRLM, though further preclinical and clinical validation is needed. Full article
(This article belongs to the Section Cancer Metastasis)
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12 pages, 1311 KiB  
Review
Modulation of Voltage-Gated Na+ Channel Currents by Small Molecules: Effects on Amplitude and Gating During High-Frequency Stimulation
by Cheng-Yuan Lin, Zi-Han Gao, Chi-Wai Cheung, Edmund Cheung So and Sheng-Nan Wu
Sci. Pharm. 2025, 93(3), 33; https://doi.org/10.3390/scipharm93030033 - 24 Jul 2025
Viewed by 325
Abstract
Cumulative inhibition of voltage-gated Na+ channel current (INa) caused by high-frequency depolarization plays a critical role in regulating electrical activity in excitable cells. As discussed in this review paper, exposure to certain small-molecule modulators can perturb INa during [...] Read more.
Cumulative inhibition of voltage-gated Na+ channel current (INa) caused by high-frequency depolarization plays a critical role in regulating electrical activity in excitable cells. As discussed in this review paper, exposure to certain small-molecule modulators can perturb INa during high-frequency stimulation, influencing the extent of cumulative inhibition and electrical excitability in excitable cells. Carbamazepine differentially suppressed transient or peak (INa(T)) and late (INa(L)) components of INa. Moreover, the cumulative inhibition of INa(T) during pulse-train stimulation at 40 Hz was enhanced by lacosamide. GV-58 was noted to exert stimulatory effect on INa(T) and INa(L). This stimulated INa was not countered by ω-conotoxin MVIID but was effectively reversed by ranolazine. GV-58′s exposure can slow down INa inactivation elicited during pulse-train stimulation. Lacosamide directly inhibited INa magnitude as well as promoted this cumulative inhibition of INa during pulse-train stimuli. Mirogabalin depressed INa magnitude as well as modulated frequency dependence of the current. Phenobarbital can directly modulate both the magnitude and frequency dependence of ionic currents, including INa. Previous investigations have shown that exposure to small-molecule modulators can perturb INa under conditions of high-frequency stimulation. This ionic mechanism plays a crucial role in modulating membrane excitability, hereby supporting the validity of these findings. Full article
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18 pages, 1587 KiB  
Article
Management of Mobile Resonant Electrical Systems for High-Voltage Generation in Non-Destructive Diagnostics of Power Equipment Insulation
by Anatolii Shcherba, Dmytro Vinnychenko, Nataliia Suprunovska, Sergy Roziskulov, Artur Dyczko and Roman Dychkovskyi
Electronics 2025, 14(15), 2923; https://doi.org/10.3390/electronics14152923 - 22 Jul 2025
Viewed by 233
Abstract
This research presents the development and management principles of mobile resonant electrical systems designed for high-voltage generation, intended for non-destructive diagnostics of insulation in high-power electrical equipment. The core of the system is a series inductive–capacitive (LC) circuit characterized by a high quality [...] Read more.
This research presents the development and management principles of mobile resonant electrical systems designed for high-voltage generation, intended for non-destructive diagnostics of insulation in high-power electrical equipment. The core of the system is a series inductive–capacitive (LC) circuit characterized by a high quality (Q) factor and operating at high frequencies, typically in the range of 40–50 kHz or higher. Practical implementations of the LC circuit with Q-factors exceeding 200 have been achieved using advanced materials and configurations. Specifically, ceramic capacitors with a capacitance of approximately 3.5 nF and Q-factors over 1000, in conjunction with custom-made coils possessing Q-factors above 280, have been employed. These coils are constructed using multi-core, insulated, and twisted copper wires of the Litzendraht type to minimize losses at high frequencies. Voltage amplification within the system is effectively controlled by adjusting the current frequency, thereby maximizing voltage across the load without increasing the system’s size or complexity. This frequency-tuning mechanism enables significant reductions in the weight and dimensional characteristics of the electrical system, facilitating the development of compact, mobile installations. These systems are particularly suitable for on-site testing and diagnostics of high-voltage insulation in power cables, large rotating machines such as turbogenerators, and other critical infrastructure components. Beyond insulation diagnostics, the proposed system architecture offers potential for broader applications, including the charging of capacitive energy storage units used in high-voltage pulse systems. Such applications extend to the synthesis of micro- and nanopowders with tailored properties and the electrohydropulse processing of materials and fluids. Overall, this research demonstrates a versatile, efficient, and portable solution for advanced electrical diagnostics and energy applications in the high-voltage domain. Full article
(This article belongs to the Special Issue Energy Harvesting and Energy Storage Systems, 3rd Edition)
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23 pages, 6645 KiB  
Article
Encapsulation Process and Dynamic Characterization of SiC Half-Bridge Power Module: Electro-Thermal Co-Design and Experimental Validation
by Kaida Cai, Jing Xiao, Xingwei Su, Qiuhui Tang and Huayuan Deng
Micromachines 2025, 16(7), 824; https://doi.org/10.3390/mi16070824 - 19 Jul 2025
Viewed by 425
Abstract
Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. [...] Read more.
Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. This approach integrates in-depth electro-thermal simulation (LTspice XVII/COMSOL Multiphysics 6.3) with micro/nano-packaging processes (sintering/bonding). Firstly, a multifunctional double-pulse test board was designed for the dynamic characterization of SiC devices. LTspice simulations revealed the switching characteristics under an 800 V operating condition. Subsequently, a thermal simulation model was constructed in COMSOL to quantify the module junction temperature gradient (25 °C → 80 °C). Key process parameters affecting reliability were then quantified, including conductive adhesive sintering (S820-F680, 39.3 W/m·K), high-temperature baking at 175 °C, and aluminum wire bonding (15 mil wire diameter and 500 mW ultrasonic power/500 g bonding force). Finally, a double-pulse dynamic test platform was established to capture switching transient characteristics. Experimental results demonstrated the following: (1) The packaged module successfully passed the 800 V high-voltage validation. Measured drain current (4.62 A) exhibited an error of <0.65% compared to the simulated value (4.65 A). (2) The simulated junction temperature (80 °C) was significantly below the safety threshold (175 °C). (3) Microscopic examination using a Leica IVesta 3 microscope (55× magnification) confirmed the absence of voids at the sintering and bonding interfaces. (4) Frequency-dependent dynamic characterization revealed a 6 nH parasitic inductance via Ansys Q3D 2025 R1 simulation, with experimental validation at 8.3 nH through double-pulse testing. Thermal evaluations up to 200 kHz indicated 109 °C peak temperature (below 175 °C datasheet limit) and low switching losses. This work provides a critical process benchmark for the micro/nano-manufacturing of high-density SiC modules. Full article
(This article belongs to the Special Issue Recent Advances in Micro/Nanofabrication, 2nd Edition)
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18 pages, 1996 KiB  
Article
Lifetime Behavior of Turn Insulation in Rotating Machines Under Repetitive Pulsed Stress
by Ousama Zidane, Rainer Haller, Pavel Trnka and Hans Bärnklau
Energies 2025, 18(14), 3826; https://doi.org/10.3390/en18143826 - 18 Jul 2025
Viewed by 286
Abstract
Insulation materials are critical for the reliability and performance of electrical power systems, particularly in high-voltage rotating machines. While failures can arise from thermal, mechanical, or electrical stress, they predominantly manifest as electrical breakdowns. Prior research has primarily concentrated on aging in straight [...] Read more.
Insulation materials are critical for the reliability and performance of electrical power systems, particularly in high-voltage rotating machines. While failures can arise from thermal, mechanical, or electrical stress, they predominantly manifest as electrical breakdowns. Prior research has primarily concentrated on aging in straight winding sections, despite evidence indicating that failures frequently occur in the bending regions of turn insulation. This study explores the influence of high-frequency pulsed electrical stress on the lifetime behavior of Type II insulation systems used in high-voltage rotating machines. Practical samples, designed with geometric configurations and technology akin to that in rotating machines, were tested under conditions characterized by voltage slew rates (dv/dt) exceeding 10 kV/μs, with variations in frequency and waveform shape. The findings reveal that the rate of electrical aging remains consistent across differing pulse widths, risetimes, and polarities, displaying a similar lifetime exponent. Nonetheless, insulation durability is markedly more compromised under pulsed conditions. At the identical times-to-failure, the sinusoidal waveform necessitated nearly twice the applied peak voltage as the bipolar pulse waveform. This finding clearly suggests that pulsed excitation exacerbates insulation degradation more effectively due to the sharp rise times and high (dv/dt) rates imposing substantial electrical stress on dielectric materials. Full article
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21 pages, 3487 KiB  
Article
Influence of Pulsed Electric Field Parameters on Electrical Conductivity in Solanum tuberosum Measured by Electrochemical Impedance Spectroscopy
by Athul Thomas, Teresa Lemainque, Marco Baragona, Joachim-Georg Pfeffer and Andreas Ritter
Appl. Sci. 2025, 15(14), 7922; https://doi.org/10.3390/app15147922 - 16 Jul 2025
Viewed by 331
Abstract
High-voltage unipolar square wave pulsed electric fields (PEFs) can cause cell membrane rupture and cell death during a process termed irreversible electroporation (IRE). PEF effects are influenced by pulse parameters like number of pulses (NP), voltage (PV), width (PW), and interval (PI). This [...] Read more.
High-voltage unipolar square wave pulsed electric fields (PEFs) can cause cell membrane rupture and cell death during a process termed irreversible electroporation (IRE). PEF effects are influenced by pulse parameters like number of pulses (NP), voltage (PV), width (PW), and interval (PI). This study systematically evaluates their effects on the conductivity and relative conductivity changes between untreated and PEF-treated regions of potato tissue across a frequency range of 1 Hz to 5 MHz by means of electrochemical impedance spectroscopy (EIS), using a custom-made four-point EIS probe with RG58/U coaxial cables. Potatoes were chosen as a plant-based PEF model to reduce animal experiments and untreated tissue showed minimal conductivity variation across regions. Relative conductivity changes were maximal at 1000 Hz. At 1000 Hz, significant conductivity differences between untreated and PEF-treated regions were observed from PV = 200 V, NP = 10, PW = 10 µs, and PI = 50 ms onwards (most significant changes occurred for PV = 700 V; NP = 70; PW = 70 µs; PI = 250 ms and 500 ms). Our results may be beneficial for multiphysics modelling of IRE with specific electrical properties, conductivity mapping with optimal contrast—such as in electrical impedance tomography—and development of IRE procedures. Full article
(This article belongs to the Special Issue Advances in Electroporation Systems and Applications)
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32 pages, 8765 KiB  
Article
Hybrid Efficient Fast Charging Strategy for WPT Systems: Memetic-Optimized Control with Pulsed/Multi-Stage Current Modes and Neural Network SOC Estimation
by Marouane El Ancary, Abdellah Lassioui, Hassan El Fadil, Yassine El Asri, Anwar Hasni, Abdelhafid Yahya and Mohammed Chiheb
World Electr. Veh. J. 2025, 16(7), 379; https://doi.org/10.3390/wevj16070379 - 6 Jul 2025
Viewed by 423
Abstract
This paper presents a hybrid fast charging strategy for static wireless power transfer (WPT) systems that synergistically combines pulsed current and multi-stage current (MCM) modes to enable rapid yet battery-health-conscious electric vehicle (EV) charging, thereby promoting sustainable transportation. The proposed approach employs a [...] Read more.
This paper presents a hybrid fast charging strategy for static wireless power transfer (WPT) systems that synergistically combines pulsed current and multi-stage current (MCM) modes to enable rapid yet battery-health-conscious electric vehicle (EV) charging, thereby promoting sustainable transportation. The proposed approach employs a memetic algorithm (MA) to dynamically optimize the charging parameters, achieving an optimal balance between speed and battery longevity while maintaining 90.78% system efficiency at the SAE J2954-standard 85 kHz operating frequency. A neural-network-based state of charge (SOC) estimator provides accurate real-time monitoring, complemented by MA-tuned PI control for enhanced resonance stability and adaptive pulsed current–MCM profiles for the optimal energy transfer. Simulations and experimental validation demonstrate faster charging compared to that using the conventional constant current–constant voltage (CC-CV) methods while effectively preserving the battery’s state of health (SOH)—a critical advantage that reduces the environmental impact of frequent battery replacements and minimizes the carbon footprint associated with raw material extraction and battery manufacturing. By addressing both the technical challenges of high-power WPT systems and the ecological imperative of battery preservation, this research bridges the gap between fast charging requirements and sustainable EV adoption, offering a practical solution that aligns with global decarbonization goals through optimized resource utilization and an extended battery service life. Full article
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17 pages, 1560 KiB  
Review
Revolutionizing Electrospinning: A Review of Alternating Current and Pulsed Voltage Techniques for Nanofiber Production
by Yasir Al Saif and Richárd Cselkó
Processes 2025, 13(7), 2048; https://doi.org/10.3390/pr13072048 - 27 Jun 2025
Viewed by 370
Abstract
Electrospinning has evolved into a vital nanofiber production technique with broad applications across biomedical, environmental, and industrial sectors. Alternating current (AC) and pulsed voltage (PV) electrospinning offer transformative alternatives by utilizing time-varying electric fields to overcome the drawbacks of DC electrospinning by employing [...] Read more.
Electrospinning has evolved into a vital nanofiber production technique with broad applications across biomedical, environmental, and industrial sectors. Alternating current (AC) and pulsed voltage (PV) electrospinning offer transformative alternatives by utilizing time-varying electric fields to overcome the drawbacks of DC electrospinning by employing an oscillating electric field that facilitates balanced charge dynamics, improved jet stability, and collectorless operation, leading to enhanced fiber alignment and significantly higher production rates, with reports exceeding 20 g/h. Conversely, PV electrospinning applies intermittent high-voltage pulses, offering precise control over jet initiation and termination. This method enables the fabrication of ultrafine, bead-free, and structurally uniform fibers, making it particularly suitable for biomedical applications such as controlled drug delivery and tissue scaffolds. Both techniques support tunable fiber morphology, reduced diameter variability, and improved structural uniformity, contributing to the advancement of high-performance nanofiber materials. This review examines the underlying electrohydrodynamic mechanisms, charge transport behavior, equipment configurations, and performance metrics associated with AC and PV electrospinning. It further highlights key innovations, current limitations in scalability and standardization, and prospective research directions. Full article
(This article belongs to the Special Issue Advances in Properties and Applications of Electrospun Fibers)
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17 pages, 3166 KiB  
Article
Power Converter Design for Pulsed Electric Field-Based Milk Processing: A Proof of Concept
by Julieta Domínguez-Soberanes, Omar F. Ruiz-Martinez and Fernando Davalos Hernandez
Foods 2025, 14(13), 2177; https://doi.org/10.3390/foods14132177 - 21 Jun 2025
Viewed by 318
Abstract
The microbiological safety of milk can be ensured through heat processing; however, this method has a negative effect on the sensory profile of this food product. Emerging technologies could be used as an alternative process for guaranteeing innocuity and maintaining sensory changes. An [...] Read more.
The microbiological safety of milk can be ensured through heat processing; however, this method has a negative effect on the sensory profile of this food product. Emerging technologies could be used as an alternative process for guaranteeing innocuity and maintaining sensory changes. An alternative is to evaluate pulsed electric field (PEF) electroporation, which is a method of processing cells using short pulses of a strong electric field. PEF has the potential to be a type of alternative low-temperature pasteurization process that consists of high-frequency voltage pulsations. Specifically, the presented work is a proof of concept for the design of a converter capable of generating a PEF to feed a load that meets the impedance characteristics of milk. The proposed converter is simulated using PLECS software (4.9.6 version) under impedance change scenarios that emulate variations in milk throughout the entire process. This research proposes the modification of a classic Vienna rectifier (adding an MBC—Multilevel Boost Converter structure) to supply a pulsating signal that could be used for low-temperature processes of milk to guarantee proper pasteurization. The characteristics of the generated high-voltage pulse make it feasible to quickly process the real sample. The control law design considers a regulation loop to achieve a voltage in the range of kV and a switching-type control law that activates switches in MMC arrays. These switches are activated randomly to avoid transients that cause significant stress on them. Full article
(This article belongs to the Special Issue Dairy Science: Emerging Trends in Research for Dairy Products)
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16 pages, 1188 KiB  
Article
Effects of Moderate Electric Field Pretreatment on the Efficiency and Nutritional Quality of Hot Air-Dried Apple Slices
by Deryanur Kalkavan and Nese Sahin Yesilcubuk
Foods 2025, 14(13), 2160; https://doi.org/10.3390/foods14132160 - 20 Jun 2025
Viewed by 344
Abstract
This study investigates the effects of electric field pretreatment parameters such as electric field strength (0.1–0.2 kV/cm), waveform (sinusoidal vs. square), and application mode (continuous vs. pulsed) on the quality attributes of dried Fuji apple slices, including ascorbic acid (vitamin C) retention, β-carotene [...] Read more.
This study investigates the effects of electric field pretreatment parameters such as electric field strength (0.1–0.2 kV/cm), waveform (sinusoidal vs. square), and application mode (continuous vs. pulsed) on the quality attributes of dried Fuji apple slices, including ascorbic acid (vitamin C) retention, β-carotene content, and hydroxymethylfurfural (HMF) formation. Electric-field-treated samples were compared to untreated controls after convective drying at 75 °C. Results revealed that vitamin C was significantly influenced by waveform, with sinusoidal waves preserving about 27% more vitamin C than square waves, likely due to reduced oxidative degradation from gentler electroporation. Conversely, square waves caused the highest β-carotene losses (25% vs. control), attributed to prolonged peak voltage destabilizing carotenoids. HMF formation was reduced by 10–23% in electric-field-treated samples compared to controls, linked to accelerated drying rates limiting Maillard reaction time. Low electric field strengths (0.1–0.15 kV/cm) enhanced antioxidant activity; however, higher intensities showed a potential decline. The square waveform had a more detrimental effect on phenolic compounds than the sinusoidal waveform. These findings suggest that low electric field pretreatment, particularly with sinusoidal waveforms at 0.2 kV/cm, enhances drying efficiency while balancing nutrient retention and HMF mitigation, offering a promising strategy for producing high-quality dried fruits. Full article
(This article belongs to the Section Food Physics and (Bio)Chemistry)
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20 pages, 3211 KiB  
Article
Three-Stage Optimization of Surface Finish in WEDM of D2 Tool Steel via Taguchi Design and ANOVA Analysis
by Thanh Tan Nguyen, Bui Phuoc Phi, Van Tron Tran, Van-Thuc Nguyen and Van Thanh Tien Nguyen
Metals 2025, 15(6), 682; https://doi.org/10.3390/met15060682 - 19 Jun 2025
Viewed by 344
Abstract
Wire electrical discharge machining (WEDM) is a standard micro-manufacturing technology. In WEDM, surface roughness (SR), deviation dimension (DD), and machining time (MT) are critical requirements that impact machining quality and are affected by various input parameters. The workpiece often performs multiple machining steps [...] Read more.
Wire electrical discharge machining (WEDM) is a standard micro-manufacturing technology. In WEDM, surface roughness (SR), deviation dimension (DD), and machining time (MT) are critical requirements that impact machining quality and are affected by various input parameters. The workpiece often performs multiple machining steps (roughing, semi-finishing, and finishing) to achieve high accuracy. Each machining step directly affects the accuracy and machining time, and the preceding machining step influences the subsequent machining step parameters. Many input control parameters regulate WEDM’s performance. Thus, optimizing process control parameters at each step is essential to achieve optimal results. This study investigates the influence of input parameters, including pulse on time (Ton), pulse off time (Toff), and servo voltage (SV), on SR, DD, and MT when machining AISI D2 mold steel through rough, semi-finish, and finish cutting. Taguchi and Analysis of Variance (ANOVA) are applied to analyze and optimize this WEDM process. The results display that the optimal surface roughness values for rough, semi-finish, and finish-cut stages are 2.03 µm, 1.77 µm, and 0.57 µm, corresponding to the parameter set of Ton = 6 μs, Toff = 10 μs, and SV = 30 V; Ton = 3 μs, Toff = 15 μs, and SV = 60 V; and Ton = 21 μs, Toff = 45 μs, and SV = 60 V, respectively. In addition, in the finish-cut stage, the parameters for optimal DD of 0.001 mm (0.04%) are Ton = 3 μs, Toff = 15 μs, and SV = 40 V. In contrast, those values for optimal MT of 218 s are Ton = 3 μs, Toff = 30 μs, and SV = 40 V. All optimal input values are confirmed by the manufacturing mold and die parts. Full article
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14 pages, 4632 KiB  
Article
Resistive Heater Element Based on a Conductive Line in AlN Ceramic Fabricated by Laser Processing
by Nikolay Nedyalkov, Nadya Stankova, Fatme Padikova, Stefan Valkov, Genoveva Atanasova, Tina Dilova and Lyubomir Aleksandrov
Materials 2025, 18(12), 2861; https://doi.org/10.3390/ma18122861 - 17 Jun 2025
Viewed by 369
Abstract
The purpose of this work is to demonstrate that laser-induced conductive tracts in AlN ceramic can be applied for fabrication of an integrated resistive heating element. Nanosecond laser processing at a wavelength of 1064 nm of ceramic in vacuum is used for a [...] Read more.
The purpose of this work is to demonstrate that laser-induced conductive tracts in AlN ceramic can be applied for fabrication of an integrated resistive heating element. Nanosecond laser processing at a wavelength of 1064 nm of ceramic in vacuum is used for a formation of conductive areas. It is demonstrated that the applied laser fluence and the number of pulses influence strongly the electrical properties of the material in the irradiated zone. The resistance value of the produced tracks with a length of about 4 mm and width of about 1 mm may vary from 17 to about 2000 Ohms, depending on the processing conditions. The material in the processed zone is characterized by means of surface composition, morphology, and electric properties. It is found that the electrical conductivity of the formed structure is based on the ceramic decomposition and formation of aluminum layer. The analysis of the influence of the temperature on the electrical resistance value shows that the material’s conductivity could be preserved after annealing, as in the present study it is confirmed up to 300 °C. The ability of the formed tracks to serve as a basis element of ceramic integrated resistive heater is studied by applying DC voltage. It is found that the fabricated element can be used with a high reliability to about 90 °C without special requirements for contact design and encapsulation. Operation at higher temperatures is also demonstrated as the maximal one achieved is about 150 °C at 10V. The performance of the heater is investigated and discussed as the operation range is defined. The proposed element can be a basis for a design of an integrated heater in ceramic with high stability and applications in everyday life and research. Full article
(This article belongs to the Special Issue Advances in Laser Processing Technology of Materials—Second Edition)
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13 pages, 2867 KiB  
Article
Characterization of Space Charge Accumulations in Alternative Gas-to-Liquid Oil-Immersed Paper Insulation Under Polarity Reversal Voltage Scenarios
by Ya Wang, Yifei Xiong, Zheming Wang and Wu Lu
Energies 2025, 18(12), 3152; https://doi.org/10.3390/en18123152 - 16 Jun 2025
Viewed by 268
Abstract
Due to its advantages, such as its corrosive sulfur-free property and high purity, gas-to-liquid (GTL) oil is regarded as an excellent alternative to conventional naphthenic mineral oil in the oil/paper composite insulation of UHV converter transformers. In such application scenarios, under the condition [...] Read more.
Due to its advantages, such as its corrosive sulfur-free property and high purity, gas-to-liquid (GTL) oil is regarded as an excellent alternative to conventional naphthenic mineral oil in the oil/paper composite insulation of UHV converter transformers. In such application scenarios, under the condition of voltage polarity reversal, charge accumulation is likely to occur along the liquid/solid interface, which leads to the distortion of the electric field, consequently reducing the breakdown voltage of the insulating material, and leading to flashover in the worst case. Therefore, understanding such space charge characteristics under polarity-reversed voltage is key for the insulation optimization of GTL oil-filled converter transformers. In this paper, a typical GTL oil is taken as the research object with naphthenic oil as the benchmark. Electroacoustic pulse measurement technology is used to study the space charge accumulation characteristics and electric field distribution of different oil-impregnated paper insulations under polarity-reversed conditions. The experimental results show that under positive–negative–positive polarity reversal voltage, the gas-impregnated pressboard exhibits significantly higher rates of space charge density variation and electric field distortion compared with mineral oil-impregnated paper. In stage B, the dissipation rate of negative charges at the grounded electrode in GTL oil-impregnated paper is 140% faster than that in mineral oil-impregnated paper. In stage C, the electric field distortion rate near the electrode of GTL oil-impregnated paper reaches 54.15%. Finally, based on the bipolar charge transport model, the microscopic processes responsible for the differences in two types of oil-immersed papers are discussed. Full article
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15 pages, 5997 KiB  
Article
Novel 3D Capacitors: Integrating Porous Nickel-Structured and Through-Glass-Via-Fabricated Capacitors
by Baichuan Zhang, Libin Gao, Hongwei Chen and Jihua Zhang
Nanomaterials 2025, 15(11), 819; https://doi.org/10.3390/nano15110819 - 28 May 2025
Viewed by 411
Abstract
In this research work, two distinct types of three-dimensional (3D) capacitors were successfully fabricated, each with its own unique features and advantages. The first type of capacitor is centered around a 3D nanoporous structure. This structure is formed on a nickel substrate through [...] Read more.
In this research work, two distinct types of three-dimensional (3D) capacitors were successfully fabricated, each with its own unique features and advantages. The first type of capacitor is centered around a 3D nanoporous structure. This structure is formed on a nickel substrate through anodic oxidation. After undergoing high-temperature thermal oxidation, a monolithic Ni-NiO-Pt metal–insulator–metal (MIM) capacitor with a nanoporous dielectric architecture is achieved. Structurally, this innovative design brings about several remarkable benefits. Due to the nanoporous structure, it has a significantly increased surface area, which can effectively store more charges. As a result, it exhibits an equivalent capacitance density of 69.95 nF/cm2, which is approximately 18 times higher than that of its planar, non-porous counterpart. This high capacitance density enables it to store more electrical energy in a given volume, making it highly suitable for applications where miniaturization and high energy storage in a small space is crucial. The second type of capacitor makes use of Through-Glass Via (TGV) technology. This technology is employed to create an interdigitated blind-via array within a glass substrate, attaining an impressively high aspect ratio of 22.5:1 (with a via diameter of 20 μm and a depth of 450 μm). By integrating atomic layer deposition (ALD), a conformal interdigital electrode structure is realized. Glass, as a key material in this capacitor, has outstanding insulating properties. This characteristic endows the capacitor with a high breakdown field strength exceeding 8.2 MV/cm, corresponding to a withstand voltage of 5000 V. High breakdown field strength and withstand voltage mean that the capacitor can handle high-voltage applications without breaking down easily, which is essential for power-intensive systems like high-voltage power supplies and some high-power pulse-generating equipment. Moreover, due to the low-loss property of glass, the capacitor can achieve an energy conversion efficiency of up to 95%. Such a high energy conversion efficiency ensures that less energy is wasted during the charge–discharge process, which is highly beneficial for energy-saving applications and systems that require high-efficiency energy utilization. Full article
(This article belongs to the Section Nanoelectronics, Nanosensors and Devices)
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