Voltage Reduction Research Articles

Abstract 4114716: Concurrent Ethanol Infusion with Pulsed Field Ablation Augments Electroporation of Porcine Atria

Background: Pulsed field ablation (PFA) is a promising modality for treatment of cardiac arrhythmias. PFA increases cell permeability, thereby promoting cell apoptosis. Although greater PFA energy may produce larger lesions, it also carries risks of side effects such as arcing, hemolysis, and microbubbles. Chemical ablation using ethanol (EtOH), such as with injection of the Vein of Marshall, has been used to treat atrial myocardium for refractory atrial arrhythmias. Hypothesis: We hypothesize that PFA in the atria can increase EtOH uptake through PFA-generated pores, thereby augmenting ablation efficacy by utilizing the cell permeability effects of PFA. Aim: The aim of this study is to investigate the effects of local EtOH infusion after PFA on lesion size in porcine atria. Methods: The atria of five porcine subjects were ablated in vivo with low PFA power settings (250V, at 20μs for 50 pulses separated by 200 ms) using a focal bipolar irrigated ablation catheter and BTX 830 electroporation generator (Harvard Apparatus). After PFA, 2 ml of 90 % EtOH vs. saline (control) was infused through the catheter tip to the site of ablation. We compared electrogram voltage amplitude reduction and ablation lesion parameters before and after PFA. Results: A total of 14 control lesions and 14 EtOH lesions were analyzed. There was significant difference in voltage reduction between two groups ( Figure 1A-B ). On gross pathology, there were significant differences in ablation lesion maximum surface diameter, lesion depth, and volume between the 2 lesion sets ( Figure 1C ). Conclusion: Concurrent EtOH infusion after PFA enhanced acute efficacy of electroporation in porcine atria. Adjuvant therapy has the potential to improve efficacy without requiring higher energy parameters, thereby reducing PFA risks. Further studies to assess chronic efficacy are warranted.

Parameter Identification of Solid Oxide Fuel Cell Using Elman Neural Network and Dynamic Fitness Distance Balance-Manta Ray Foraging Optimization Algorithm

An accurate solid oxide fuel cell model is a prerequisite for optimizing the operation and state estimation of subsequent cell systems. Hence, this work aimed to utilize a vigoroso algorithmic tool, i.e., Elman neural network, for data prediction to enrich cell measurement data and employ the trained network model for noise reduction of voltage–current data. Furthermore, to obtain reliable cell parameters, a novel parameter identification model based on the dynamic fitness distance balance-manta ray foraging optimization (dFDB-MRFO) algorithm is proposed. Two datasets were applied to extract the electrochemical model and simple electrochemical model parameters of the solid oxide fuel cell model. To verify adequately the superiority of this method, which is compared with another seven conventional heuristic algorithms, four performance indicators were selected as evaluation criteria. Comprehensive case studies demonstrated that through data processing, the precision and robustness of identification could be effectively heightened. In general, the model fitting data obtained via parameter identification using dFDB-MRFO have excellent fitting precision contrast with the measured voltage–current data. Notably, the fitting degree obtained by dFDB-MRFO in the simple electrochemical model reached 99.95% and 99.91% under the two datasets, respectively.

Exploring LGE areas in the atria: Insights from electroanatomical voltage mapping in AF patients

Abstract Introduction Late gadolinium enhancement MRI (LGE MRI) is a common method for the evaluation of the atrial substrate in atrial fibrillation (AF) patients. The extent of LGE is associated with atrial cardiomyopathy and ablation outcomes. However, previous studies have yielded inconsistent results in detecting low voltage areas (LVA) using bipolar electroanatomical mapping (EAM) in LGE regions. Objective Conduct a thorough analysis of the bipolar and unipolar voltage in LGE areas and its relationship with the voltage in non-LGE areas, utilizing high-density (HD) EAM generated by a multipolar HD-mapping catheter. Methods In this study, 20 patients undergoing AF ablation were examined using LGE-MRI. A 3D mesh integrating LGE data was generated. HD-EAM (> 4000 points) was performed in sinus rhythm. The EAM map and MRI mesh underwent manual alignment and registration. Using a nearest neighbor algorithm, EAM points nearest to LGE areas were identified, and the corresponding unipolar and bipolar voltage values, along with LGE voxel intensity, were exported for analysis. Results LGE areas exhibited a median bipolar voltage amplitude of 0.93 mV, median unipolar voltage of 1.73 mV. In contrast, areas without enhancement displayed median bipolar voltage of 2.33 mV, unipolar voltage of 3.58 mV. We observed a variation in voltage amplitudes across the different LGE areas: bipolar voltage ranged from 0.04 to 2.51 mV and unipolar voltage from 0.22 to 3.75 mV. This variation strongly correlated with voxel intensity in LGE areas (correlation coefficient r = -0.86 [p <0.001]). Irrespective of the voltage amplitude in the examined LGE areas, a significant voltage drop was observed, with an average reduction of 54% in bipolar and 51% in unipolar voltages, compared to the amplitudes in non-LGE areas within the same atria. Conclusion Variations in bipolar and unipolar voltage within LGE areas are significantly correlated with local voxel intensity. Despite the inconsistent overlap with the predefined bipolar threshold for LVA, LGE regions exhibit a pronounced and consistent reduction in both bipolar and unipolar voltage compared to non-LGE areas. This pattern suggests notable electrophysiological changes in these areas. These insights underscore the need for further investigation to better understand the implications and mechanisms underlying these alterations in LGE regions.

Experimental study of voltage uniformity and stability of H2/O2 PEM fuel cell stack with dead-end anode and recirculation cathode

Dead-end anode and recirculation cathode is an operating mode effectively improving the gas reactant utilization of hydrogen–oxygen proton exchange membrane fuel cell (H2/O2 PEMFC) stack. However, the difference of single cells in the stack, will be further expanded due to the flooding and impurities and necessary purge for removing them. In this work, the voltage uniformity and stability of H2/O2 PEMFC under different operating conditions are investigated based on a dead-end anode and recirculation cathode PEMFC stack. Research indicates that enhancing the current density and temperature, lowering the inlet gas pressure will diminish the uniformity in stack voltage. The analysis of the experimental pattern reveals a positive correlation between the voltage uniformity and stability. This is due to the water flooding or membrane dehydration phenomenon of the single-cell leading to a reduction of the single-cell voltage and the voltage uniformity of the stack, while the water flooding or membrane drying phenomenon makes the stack more unstable and the purge interval shorter. Based on these experimental results, the best operating scheme for the designed stack is proposed, which is of some guidance and reference value for the practical application of air-cooled PEMFC in the hundred-watt class.

Highwall mining productivity enhancement with energy conservation: A case study

ABSTRACT Open-cast mining in India is transitioning from closing existing mines to extracting remaining coal seams from dormant sites. Highwall machines are key to this efficient extraction process. To meet international safety and environmental standards, audits are essential. This article evaluates the power quality of the substation’s incomer, transformer, and feeder, and proposes energy-efficient changes to boost production. Tests on the main substation transformers included voltage, current, power, power factor, harmonics, and AC waveform analysis. Thermal imaging of electrical equipment was conducted to verify operating temperatures. Results were graphed for each test. The study recommends installing an Automatic Power Factor Correction (APFC) unit and lowering the tap value from 5 to 4 to improve the transformer’s power factor. It is estimated that a 4% voltage reduction will save 1% energy, while a 5% reduction will save 1.25% energy.

Local calcium chloride infusion after pulsed field ablation enhances acute efficacy of cardiac electroporation.

Pulsed field ablation (PFA) has emerged as an innovative therapy for cardiac arrhythmias. Drawing parallels with PFA's application in solid tumors, calcium chloride (CaCl2) as an adjuvant therapy, known as calcium electroporation, may amplify PFA's apoptotic effects. We propose that PFA in the atrium could enhance calcium uptake through PFA-created pores, thereby increasing ablation efficacy even at reduced power levels by exploiting PFA's permeabilization effects. We conducted in vivo ablations on the atria of seven pigs using low PFA power (250 V, 20 μs for 50 pulses at 200 ms intervals). Post-PFA, we randomly administered an infusion of either 200 mg/2 ml CaCl2 (calcium group) or saline (control) directly to the ablation site via the catheter tip. We evaluated reduction in electrogram voltage amplitude, electrocardiography (ECG) parameters, ablation lesion parameters, and histology after PFA. Nineteen lesions from control and calcium groups were examined. Control lesions showed no voltage decrease post-PFA, whereas calcium-treated lesions exhibited a significant voltage reduction. Gross pathology indicated marked differences in maximum lesion surface diameter, depth, and volume between the lesion groups. Histologically, calcium group lesions were characterized by a more severe acute PFA response with contraction band necrosis, myocytolysis and nuclear pyknosis in adjacent myocardium, in addition to microhemorrhages. Infusing calcium chloride locally after PFA markedly improves the immediate efficacy of electroporation in porcine atria. This study suggests that calcium electroporation could bolster PFA outcomes without higher energy levels, potentially diminishing associated risks. These preliminary findings warrant further research into the long-term efficacy and potential clinical application of calcium electroporation in PFA.

Electromagnetic plasma micro actuator for active airflow control

This study presents a novel electromagnetic plasma micro actuator capable of generating ionic wind at an extremely low voltage. Ionic and electron movements, driven by the Lorentz force, introduce a lateral injection of initiation carriers, resulting in a significant reduction in discharge onset voltage. Straight ionic wind was demonstrated using a tapered gap electrode, which allowed continuous movement of plasma filament along the electrode at the speed of 4m/s when a DC pulse of 900V was applied. The results suggest that the proposed device may address key challenges faced by current ionic wind generators, such as high voltage requirements and limited device lifespans. In addition, a notable change in the airflow was observed when the direction of ionic wind was altered, indicating the feasibility of active airflow control with stable plasma formation and fast response times.

Enhanced performance of cyclone separator through coupling of centrifugal force, electrostatic force and particle pre-charge

The electrostatic enhancement can effectively improve the performance of cyclone separator at low load or high-temperature, but its application is limited owing to the reduction of spark voltage in high-temperature. Aiming at this question, a new technology coupling centrifugal force, electrostatic force and particle pre-charge was proposed. The characteristics of particles charging and agglomeration were analyzed, and the influence of different factors on the change of particle partition number concentration and total removal efficiency of cyclone separator were studied. The results showed that, increasing the charge generator voltage and decreasing the main pipe gas velocity can increase the particles charge quantity and improve agglomeration, which is benefit for the efficiency improvement of either cyclone separator or electrostatic cyclone separator, especially at low inlet gas velocity. Higher charge generator voltage and lower inlet gas velocity, more obvious efficiency improvement. The total removal efficiency can be increased by up to 10 % and 9 % respectively for the cyclone separator and electrostatic cyclone separator because of particle pre-charge at 10 m/s of inlet gas velocity, and the removal efficiency of fine particles can also be effectively improved. Comparing with the electrostatic cyclone separator, achieving the same total removal efficiency, the internal voltage can be reduced 16 kV through particle pre-charge. The electrostatic force and centrifugal force were the main factor of the small particles and big particles removal, respectively.

Solving Optimal Power Flow Using New Efficient Hybrid Jellyfish Search and Moth Flame Optimization Algorithms

This paper presents a new optimization technique based on the hybridization of two meta-heuristic methods, Jellyfish Search (JS) and Moth Flame Optimizer (MFO), to solve the Optimal Power Flow (OPF) problem. The JS algorithm offers good exploration capacity but lacks performance in its exploitation mechanism. To improve its efficiency, we combined it with the Moth Flame Optimizer, which has proven its ability to exploit good solutions in the search area. This hybrid algorithm combines the advantages of both algorithms. The performance and precision of the hybrid optimization approach (JS-MFO) were investigated by minimizing well-known mathematical benchmark functions and by solving the complex OPF problem. The OPF problem was solved by optimizing non-convex objective functions such as total fuel cost, total active transmission losses, total gas emission, total voltage deviation, and the voltage stability index. Two test systems, the IEEE 30-bus network and the Mauritanian RIM 27-bus transmission network, were considered for implementing the JS-MFO approach. Experimental tests of the JS, MFO, and JS-MFO algorithms on eight well-known benchmark functions, the IEEE 30-bus, and the Mauritanian RIM 27-bus system were conducted. For the IEEE 30-bus test system, the proposed hybrid approach provides a percent cost saving of 11.4028%, a percent gas emission reduction of 14.38%, and a percent loss saving of 50.60% with respect to the base case. For the RIM 27-bus system, JS-MFO achieved a loss percent saving of 50.67% and percent voltage reduction of 62.44% with reference to the base case. The simulation results using JS-MFO and obtained with the MATLAB 2009b software were compared with those of JS, MFO, and other well-known meta-heuristics cited in the literature. The comparison report proves the superiority of the JS-MFO method over JS, MFO, and other competing meta-heuristics in solving difficult OPF problems.

The Design and Construction of Overcurrent Soft Starting on ESP32 Microcontroller Based Water Machine

The advancement of household water pump technology utilizing induction motors provides numerous benefits, such as efficiency and low cost, but also faces challenges like high inrush current. This study demonstrates the necessity of voltage reduction methods to address high inrush currents that can impact home electrical systems. Testing reveals that the device's error percentage is 0.31%, indicating good performance. The DHT22 and PZEM sensors operate optimally in detecting temperature and current, and controlling relays and water pumps according to the specified thresholds, achieving a 100% system success rate. These results confirm that the system operates as expected according to the specifications.

Influence of electrodes on the resistive switching characteristics of Al/Gd2Zr2O7/E (E=Al or ITO) RRAM devices

Sol-gel derived amorphous Gd2Zr2O7 (GZO) thin films with Al/GZO/E (E = ITO or Al) structures were prepared to demonstrate the effect of electrode material on the switching behavior of resistive random access memory (RRAM) devices. All devices exhibit bipolar resistive switching (BRS) mode. After the post-metal annealing (PMA) treatment, the AlOx interfacial layer contributes to enhancing oxygen ion storage capacity and limiting the electromigration of aluminum metal. The forming-free Al/GZO/ITO device exhibits a switching cycle of 3027, a Vset/Vreset ratio of −1.83 V/0.56 V, a Ron/Roff ratio of approximately 10, and a retention time of 104 s. And the Al/GZO/Al device features a dual-layer AlOx structure, significantly improving the integrity of filament rupture to reduce leakage current and increase the switching window. Its switching cycle is 1946, with a Vset/Vreset ratio of −3.47 V/0.29 V, a Ron/Roff ratio of approximately 102, and a retention time of 104 s. The oxygen storage capacity of the dual-layer AlOx interfacial layer in the Al/GZO/Al device surpasses that of the Al/GZO/ITO device, allowing for a reduction in the reset voltage and ensuring more complete filament rupture, thereby enhancing the RHRS. Accordingly, GZO thin films can be applied to achieve the desired RS characteristics on different electrodes, making them promising candidates for RRAM applications.

The HVDC commutation failure mechanism impacted by harmonics and its suppression method

Harmonics are an important cause of voltage distortion, and voltage reduction and voltage distortion are the main causes of commutation failure. But most of the current research studies on commutation failure are based on the drop in fundamental voltage after a fault, and there are few reports on the impact of voltage distortion on commutation failure. Aiming to solve the above problem, this article first analyzes the generation and transmission characteristics of harmonics in AC and DC systems, as well as the coupling degree of harmonics in DC systems. Then, starting from the mechanism of the commutation process, a commutation failure analysis method based on the harmonic voltage time area is proposed. This method can quantitatively analyze the impact of different harmonics on commutation failure. On this basis, the harmonic criteria for causing commutation failure are established, and the harmonic characteristics of AC voltage when harmonics cause subsequent commutation failure are quantitatively analyzed. Finally, a preventive controller is proposed to suppress commutation failure caused by different harmonics, where the above analysis is verified by the simulations.

An Ultrasensitive Programmable 2D Photoelectric Synaptic Transistor

AbstractThe burgeoning advancement of information technology has engendered a discernible surge in the examination of neuromorphic devices, notably drawing broader attention to artificial vision systems endowed with sensory recognition capabilities. Current photoelectric synapse devices employed in artificial vision systems are generally well‐suited for well‐illuminated conditions, yet exhibit diminished sensitivity in weak‐light scenarios, resulting in a pronounced deterioration of recognition accuracy. Here, an ultrasensitive photoelectric synaptic transistor based on negative quantum capacitance effect resulted from the 2D semi‐metallic graphene layer that partially enclosed within the gate dielectric layer, which manifests a noteworthy reduction in device control voltage and exhibits perception and storage capabilities for weak light of 39.4 nW cm−2 with detectivity above 1016 cm Hz1/2 W−1 is demonstrated. The voltage amplification effect and the concomitant formation of an equivalent local electrostatic field induced by the negative quantum capacitance effect engenders a robust programmable synaptic plasticity for extremely weak light by modifying the control gate. These results represent the inaugural integration of the negative quantum capacitance effect into optoelectronic devices and furnish a robust hardware foundation for developing vision systems in weak‐light environments.

Operational Characteristics of AlGaN/GaN High-Electron-Mobility Transistors with Various Dielectric Passivation Structures for High-Power and High-Frequency Operations: A Simulation Study.

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by employing various passivation materials with different dielectric constants and passivation structures. To ensure the simulation reliability, the parameters were calibrated based on the measured data from the fabricated basic Si3N4 passivation structure of the HEMT. The Si3N4 passivation material was replaced with high-k materials, such as Al2O3 and HfO2, to improve the breakdown voltage. The Al2O3 and HfO2 passivation structures achieved breakdown voltage improvements of 6.62% and 17.45%, respectively, compared to the basic Si3N4 passivation structure. However, the increased parasitic capacitances reduced the cut-off frequency. To mitigate this reduction, the operational characteristics of hybrid and partial passivation structures were analyzed. Compared with the HfO2 passivation structure, the HfO2 partial passivation structure exhibited a 7.6% reduction in breakdown voltage but a substantial 82.76% increase in cut-off frequency. In addition, the HfO2 partial passivation structure exhibited the highest Johnson's figure of merit. Consequently, considering the trade-off relationship between breakdown voltage and frequency characteristics, the HfO2 partial passivation structure emerged as a promising candidate for high-power and high-frequency AlGaN/GaN HEMT applications.

Multi-objective Harris Hawks optimization algorithm for selecting best location and size of distributed generation in radial distribution system

Distributed Generating Units (DGUs) are widely used in backup power, renewable energy integration, voltage regulation, and energy storage applications. The DGUs are small-scale power-generating units located near the load centers of a power system, as opposed to large, centralized power plants located far away. However, the DGUs must reduce power losses and environmental impacts and improve the voltage profile. This was achieved by effective optimization of the position and rating of DGU. However, the conventional optimization methods failed to optimize the power losses, voltage-current balancing issues, and harmonic distortions. So, this article presents the selection of the best location and size of DGU in radial distribution systems using a nature-inspired multi-objective Harris Hawks optimization (HHO) algorithm while considering improvements in the voltage profile and reductions in active power losses. The HHO algorithm is inspired by the supportive actions of intelligent birds, such as Harris Hawks, while searching for prey. The distinguished hunting process of Harris Hawks using other family members makes it unique, which is useful for searching for better quality solutions while optimizing multi-objective fitness functions. Fitness function is determined by considering each bus's voltage profile and branches' active power losses. The proposed method is tested on two circle distribution systems (69 bus and 118 bus). The results are compared to those obtained using some of the more well-known optimization techniques given by scholars in recent years. The optimization of seven DGU in 118 bus radial distribution systems resulted in 405.32 kW of active power losses, a 68.78% decrease in losses, and 0.9723 Vs of minimum voltage.

Generalized Modulation of Common Mode Voltage Reduction for Current Source Inverter in Balanced and Unbalanced Load Cases

Generalized Modulation of Common Mode Voltage Reduction for Current Source Inverter in Balanced and Unbalanced Load Cases

A Carrier-Based Discontinuous Space-Vector PWM for Common-Mode Voltage Reduction in Dual-Input Three-Level T-Type Inverters With Unbalanced Neutral-Point Voltages

A Carrier-Based Discontinuous Space-Vector PWM for Common-Mode Voltage Reduction in Dual-Input Three-Level T-Type Inverters With Unbalanced Neutral-Point Voltages

Performance analysis of high voltage disc insulators with different profiles in clean and polluted environments using flashover, withstand voltage tests and finite element analysis

Severe pollution-induced flashovers on insulators present a pressing challenge to power system safety. The frequent failure of high-voltage insulators, particularly in the polluted environments of Pakistan, poses a critical concern. This paper investigates the impact of insulator profile on reducing pollution flashovers, testing two designs as per IEC standard 60383 and simulated using the Finite Element Method in COMSOL Multiphysics®. The test results revealed that deep under-ribs insulators exhibited a 5.008% reduction in flashover voltage, while alternating shed insulators experienced a 3.233% decrease in polluted conditions compared to clean conditions. Notably, under both clean and polluted conditions, alternating shed insulators consistently outperformed deep under-ribs insulators, with a 25.377% higher flashover voltage in clean conditions and a 27.400% superiority in polluted conditions. Computational analysis through the Finite Element Method in COMSOL Multiphysics shows a consistent pattern in potential distribution with increasing insulator count, but the presence of a pollution layer introduces spikes in the electric field distribution, validating experimental results. These findings highlight the superior performance of alternating shed insulators, especially in polluted environments.

Effect of moisture on breakdown strength and glass transition temperature of bio-polyamide reinforced with glass or basalt fiber

In this study we investigate the effect of moisture content on the dielectric breakdown strength and glass transition temperature (Tg) of bio-polyamide 4.10 reinforced with glass or basalt fiber (15, 30, 50 wt%). Moisture absorption decreased with increasing fiber content, regardless of fiber type. The reduction in breakdown voltage (BDV) was more pronounced in the composites with higher moisture content reinforced with basalt fiber. This may be due to weaker interactions at the interface. The presence of moisture decreased the glass transition temperature of the composites. PA 4.10, especially reinforced with glass fiber, is characterized by better performance properties than PA 6.6 reinforced with 50 wt% glass fiber in applications requiring both stability of mechanical properties and dielectric properties.

Emission of Trapped Electrons from the 4H-SiC/SiO<sub>2</sub>-Interface via Photon-Irradiance at Cryogenic Temperatures

For a reliable MOSFET performance it is crucial to identify and reduce device performance limiting 4H-SiC/SiO2 interface defects. Previous studies have focused on the quantification of the interface states density, however, the atomic defect structure is still to be investigated. Here, we introduce a new approach based on opto-electrical measurements, which allow to determine the energetic position of interface defects. The measurement routine is performed at cryogenic temperatures to suppress the thermal emission of electrons, which were trapped at interface states during the cooldown processed (from 300 K to 15 K) while a positive gate voltage of 50 V was applied. At 15 K the photon-assisted emission of trapped electrons is measured in dependence on the photon’s energy (1.8 eV-3 eV). The reduction of the threshold voltage is taken as an indicator for the amount of released charges after each photon irradiation. We found an enhanced emission efficiency at certain photon energies, especially at 2.8 eV. Near-interface-traps (NITs), reported by Afanasev et al. are located close to the measuredtrap level with ENIT = EC, SiO2−2.77(5) eV. Recently, El-Sayed et al. suggested wide-angle O-Si-Obonds as defect configuration, that act as electron traps and have a similar energy as the measure traplevel.