Voltage Amplitude Research Articles

Discharge characteristics and parameter diagnosis of brush-shaped air plasma plumes under auxiliary discharge

Atmospheric pressure plasma jet (APPJ) can produce plasma plumes rich in active species, which has a wide scope of applications. From the perspective of applications, it is one of the hot issues in APPJ research to generate a diffuse plasma plume on a large scale. At present, large-scale plasma plume has been produced by noble working gases, which is more economic and valuable if it is reproduced by air used as the working gas. In this work, an APPJ with an auxiliary discharge is proposed, with which a large-scale air plasma plume with a brush shape is produced. Results indicate that the brush-shaped air plume can exist by changing voltage amplitude (<i>V</i><sub>p</sub>) in a certain range. The length and brightness of the plasma plume increase with <i>V</i><sub>p</sub> increasing. The waveforms of voltage and light emission signalindicate that the discharge can start at most once within half a cycle of applied voltage. The probability of discharge and the intensity of light emission pulse for each half a voltage cycle increase with <i>V</i><sub>p</sub> increasing, but the voltage value at the discharge moment decreases with <i>V</i><sub>p</sub> increasing. High-speed imaging study shows that the generation mechanisms of diffuse brush-shaped air plasma plumes and small-scale air plasma are similar, both originating from the temporal superposition of bifurcated normal flow light. In addition, optical emission spectra from the brush-shaped air plasma plume are utilized to study electron temperature, electron density, molecular vibrational temperature, and gas temperature. With <i>V</i><sub>p</sub> increasing, gas temperature is low and almost unchanged, while electron density, electron temperature, and molecular vibrational temperature increase. In addition, OH concentration of the plasma plume is investigated by laser-induced fluorescence, indicating that OH is uniformly distributed, and its concentration increases with the <i>V</i><sub>p</sub> increasing. All these results mentioned above are qualitatively analyzed.

Numerical study on effects of voltage amplitude in CO2 pulsed discharges under Martian conditions by deep neural network

In recent years, non-thermal plasma (NTP) has received an increasing attention for in situ resource utilization of CO2 in the Martian atmosphere. As an important approach to exploring the underpinning physics of NTP, fluid models with tens of species and hundreds of reactions are very time-consuming in simulating CO2 plasmas under Martian conditions, especially driven by the nanosecond pulsed voltage. In this paper, a deep neural network (DNN) with multiple hidden layers is proposed as an example to replace the fluid model to accurately describe the essential discharge features of CO2 pulsed discharge under Martian conditions. After trained by the data from the experimental measurements or numerical simulation and continuously optimized to minimize the loss function, the constructed DNN can achieve a satisfied prediction performance. Compared to the fluid model, the DNN takes only a few seconds to predict the discharge characteristics and profiles of the electric field and particle density, especially to show the spatial–temporal distribution of the given products in CO2 plasmas, such as CO2+, CO3−, CO2v1. This study indicates that a DNN can efficiently yield the essential characteristics in CO2 pulsed discharge even with plenty of species involved in seconds, strongly showing the potential ability to be a highly efficient numerical tool in NTPs with multiple temporal–spatial scales.

Switched CMOS current source compared to enhanced Howland circuit for bio-impedance applications.

Bio-impedance Spectroscopy (BIS) is a technique that allows tissue analysis to diagnose a variety of diseases, such as medical imaging, cancer diagnosis, muscle fatigue detection, glucose measurement, and others under research. The development of CMOS integrated circuit front-ends for bioimpedance analysis is required by the increasing use of wearable devices in the healthcare field, as they offer key features for battery-powered wearable devices. These features include high miniaturization, low power consumption, and low voltage power supply. A key circuit in BIS systems is the current source, and one of the most common topology is the Enhanced Howland Current Source (EHCS). EHCS is also used when the current driver is driven by a pseudo-random signal like discrete interval binary sequences (DIBS), which, due to its broadband nature, requires high performance operational amplifiers. These facts lead to the need for a current source more compatible with DIBS signals, ultra-low power supply, standard CMOS integrated circuit, output current amplitude independent of input voltage amplitude, high output impedance, high load capability, high output voltage swing, and the possibility of tetra-polar BIS analysis, that is a pseudotetra-polar in the case of EHCS. The objective of this work is to evaluate the performance of the Switching CMOS Current Source (SCMOSCS) over EHCS using a Cole-skin model as a load using SPICE simulations (DC and AC sweeps and transient analysis). The SCMOSCS demonstrated an output impedance of more than 20 MΩ, a ± 2.5 V output voltage swing from a +3.3 V supply, a 275 μA current consumption, and a 10 kΩ load capacity. These results contrast with the + 1.5 V output voltage swing, the 3 kΩ load capacity, and the 4.9 mA current of the EHCS case.

Remaining useful life prediction towards cycling stability of organic electrochemical transistors

Organic electrochemical transistors (OECTs) show abundant potential in biosensors, artificial neuromorphic systems, brain-machine interfaces, etc With the fast development of novel functional materials and new device structures, OECTs with high transconductance (gm > mS) and good cycling stabilities (> 10,000 cycles) have been developed. While stability characterization is always time-consuming, to accelerate the development and commercialization of OECTs, tools for stability prediction are urgently needed. In this paper, OECTs with good cycling stabilities are realized by minimizing the gate voltage amplitude during cycling, while a remaining useful life (RUL) prediction framework for OECTs is proposed. Specifically, OECTs based on p(g2T-T) show tremendously enhanced stability which exhibits only 46.1% on-current (ION) and 33.2% peak gm decreases after 80,000 cycles (53 min). Then, RUL prediction is proposed based on the run-to-failure (RtF) aging tests (cycling stability test of OECTs). By selecting two aging parameters (ION and peak gm) as health indicators (HI), a novel multi-scale feature fusion (MFF) method for RUL prediction is proposed, which consists of a long short-term memory (LSTM) neural network based multi-scale feature generator (MFG) module for feature extraction and an attention-based feature fusion (AFF) module for feature fusion. Consequently, richer effective information is utilized to improve the prediction performance, where the experimental results show the superiority of the proposed framework on multiple OECTs in RUL prediction tasks. Therefore, by introducing such a powerful framework for the evaluation of the lifetime of OECTs, further optimization of materials, devices, and integrated systems relevant to OECTs will be stimulated. Moreover, this tool can also be extended to other relevant bioelectronics.

Numerical Simulation of Lamb Wave Propagation in Ice

Lamb wave is one of the most used ultrasonic guided waves, which has a wide application prospect in the field of aircraft icing detection. The platform of Lamb wave propagation based on piezoelectric wafer was used as the physical model, and COMSOL software was used as the numerical calculation tool to simulate the propagation of Lamb wave in different thickness, length and types of ice. The results showed that the attenuation of voltage amplitude increases with the thickness of ice in a certain range. The time delay of Lamb wave B1 mode at the receiving end increases linearly with the increase of ice length. As the mechanical parameters of ice layer decrease, the attenuation of voltage amplitude and the time delay of Lamb wave B1 mode increase gradually. The propagation characteristics of Lamb wave in ice are preliminarily proved, which provides a theoretical reference for the subsequent propagation experiments of Lamb wave in ice.

Intelligent scheduling and optimization of microenergy grid: the application and development of computer technology

Abstract For the intelligent management of micro-energy grid, the limitations of traditional scheduling optimization methods have begun to be highlighted, and computer technology has become a new generation of power system support means. This paper proposes a state estimation method based on smart grid measurement technology, and for the characteristics of micro-energy grid anomaly data, adopts the sampling value detection anti-anomaly data method based on amplitude comparison to estimate the grid dynamic process. Based on the grid state estimation dataset, a smart grid scheduling strategy based on cloud computing is constructed. The conditional value-at-risk of the penalty function of generation cost, grid cost, and motion cost is used as the objective function of the dispatch modeling, and the solution method for the optimization of the value-at-risk model is provided. Finally, an example has been built for this dispatch model to access a simulated micro-energy grid system that contains multiple nodes. The results show that the error between the voltage amplitude obtained from the dynamic state estimation of the micro-energy grid using the method of sampled-value detection against anomalous data and the real value is no more than 0.5%, and the data scheduling error rate of the cloud computing does not fluctuate significantly when dealing with a large number of scheduling data tasks, all of which are controlled to be below 0.0015. The scheduling strategy based on cloud computing has a certain degree of generalization when dealing with random and variable source and load scenarios, which can effectively improve the level of power grid business applications and complete the corresponding intelligent scheduling.

Effect of electric field on separation characteristics of oil–water–solid three phases separating device

Lubricating oil can decay as a result of the mixing of water with solid impurities in the working process, and this process can adversely affect the performance of the machinery. Therefore, desolidification and dewatering are key steps in overall oil purification. In general, a basic swirl device cannot sustain efficient dewatering and desolidification. Thus, a three-phase separating device enhanced by an electric field has been proposed. To study the performance of the oil-water-solid separation process, a numerical model of the device was conceived based on combining the governing equations of the flow field and the electric field with the particle-tracking equation giving due consideration to the population balance model. The tangential velocity and the distribution of solid particles at various voltage amplitudes were analyzed, and the effect of the electric field on the oil, water and particle separation process was studied. The results show that at 3 kV, the tangential velocity increased by 5.06%, compared with that at 12 kV. Application of an electric field to the device was found to accelerate more solid particles which assembled near the wall of the device, and where the number of the particles near the axial plane decreased. The maximum particle concentration near the wall at the z = 630 mm plane is 20.24%. Moreover, the average residence time of the solid particles initially exhibited an increasing and then a decreasing trend. Additionally, the increase in the droplet size and enhancement of the oil-water separation process are promoted through the action of the electric field. The rate for desolidification, deoiling and dewatering at 3 kV are 93.60%, 93.30% and 95.59%, respectively.

Design, Simulation, and Fabrication of a 500 kV Ultrawideband Coaxial Matched Load and Its Connectors for Fast Transient Pulse Measurement Systems

In the past few decades, Pulsed Power (PP) has been one of the fastest growing technologies, with more and more systems frequently emerging in domains such as civil, medical and military. These systems are based on high-voltage pulses, up to several hundreds of kilovolts, with temporal parameters ranging from microsecond levels to sub-nanosecond levels. One of the biggest challenges in this technology is the accurate and precise measurement of the generated PP. The PP measurement systems must possess high-voltage and wideband properties simultaneously, which is often conflicting. The central elements of a PP measurement system are a voltage divider and a termination load. The work presented in this article is dedicated to the second element of the PP measurement system. This paper describes the development of a 50 Ω coaxial termination load and its connectors for a high power ultrawideband (UWB) pulse measurement systems. The principle roles of these devices are to serve as a dummy matched load for the former and to facilitate the connections between different components of the pulse measurement system for the latter. These devices are designed to withstand pulse voltage amplitudes at least up to 500 kV with temporal parameters, such as rise time and pulse duration, varying from nanosecond to sub-nanosecond ranges. The main challenge in the development of a high-voltage UWB termination load is the tradeoff between the high-voltage and wideband characteristics, both of them requiring opposite dimensional aspects for the load device. This challenge is overcame by the special exponential geometry of the load device. The design employs a 30 cm long low-inductance tubular ceramic 50 Ω resistor, enclosed in a critically dimensioned shielding conductor of an exponential inner profile. This shrinking coaxial structure makes it possible to maintain a good level of matching all along the 50 Ω load. The results obtained through 3D electromagnetic modeling and vector network analyzer measurements show good agreement and confirm the reflection coefficient below −27 dB up to at least 2.5 GHz for the load device. Moreover, calculations demonstrate that the load device is very well adapted for nanosecond and sub-nanosecond pulses with voltage peaks as high as 500 kV. These results demonstrate the high-voltage and UWB properties of the developed load device and prove the utilization of this device in the measurement systems for the accurate and precise measurements of the PP.

Dynamic analysis of the effects of dissipative elements and modulational instability in a multicoupled nonlinear electrical transmission line with the propagation of new rogue waveforms

In this study, we consider a nonlinear multicoupled discrete electrical transmission line consisting of several modified Noguchi lines and analyze the dynamics of the effects of dissipative elements on modulated waves. This analysis shows that the dispersion element (C S ) and solution parameter (γ) strongly contribute to the increase in voltage amplitudes and to the modulation of these new rogue waveforms, unlike the dissipative element (G). Using a semi-discrete approximation, we demonstrate that the dynamics of modulated waves in such a dissipative electrical system can be governed by a system of nonlinear Schrödinger equations, the Manakov system, and system parameters. The phenomenon of modulational instability in this dissipative electrical system is studied, and areas of instability are shown. We found that the dissipative element of this system increased and decreased the areas of instability. Under the condition of this Manakov system, we determine the approximate modulated wave solutions that are then used for the dynamic analysis of the effects of dissipative elements when transmitting these new rogue waveforms through this dissipative electrical system. The effects of the parameters of this nonlinear dissipative electrical system, such as dispersive, dissipative, and solution parameters, in the dominant direction of propagation of these new rogue wave signals are presented. Based on these results, we observe that the effects of dissipative elements do exist in this nonlinear dissipative electrical system and that these dissipative elements would also impact the areas of modulational instability, which could gradually disappear in this electrical system.

High, Multiple, and Nonvolatile Polarizations in Organic-Inorganic Hybrid [(CH3)3(CH2CH2Cl)N]2InCl5·H2O for Memcapacitor.

Dielectrics with high, nonvolatile, and multiple polarizations are required for fabricating memcapacitors that enable high parallelism and low energy consumption in artificial neuromorphic computing systems as artificial synapses. Conventional ferroelectric materials based on displacive and order-disorder types generally have difficulty meeting these requirements due to their low polarization values (∼150 μC/cm2) and persistent electrical hysteresis loops. In this study, we report a novel organic-inorganic hybrid (CETM)2InCl5·H2O (CETM = (CH3)3(CH2CH2Cl)N) exhibiting an intriguing polarization vs electric field (charge vs voltage) "hysteresis loop" and a record-high nonvolatile polarization over 30 000 μC/cm2 at room temperature. The polarization is highly dependent on the period and amplitude of the ac voltage, showing multiple nonvolatile states. Electrochemical impedance spectroscopy, time-dependent current behavior, disparate resistor response in the dehydrated derivative (CETM)2InCl5, and the negative temperature dependence of ionic conductance support that the memcapacitor behavior of (CETM)2InCl5·H2O stems from irreversible long-range migration of protons. First-principles calculations further confirm this and clarify the microscale mechanism of anisotropic polarization response. Our findings may open up a new avenue for developing memcapacitors by harnessing the benefits of ion migration in organic-inorganic hybrids.

Field reversal in low pressure, unmagnetized radio frequency capacitively coupled argon plasma discharges

In general, the radio frequency (rf) electric field within a sheath points toward the metal electrode in low pressure, unmagnetized rf electropositive capacitively coupled plasma (CCP) glow discharges. This is due to the large ratio of electron to ion mobility and the formation of an ion sheath. In this work, we studied, using fully kinetic particle-in-cell simulations, a reversed electric field induced by the strong secondary electron emission during the phase of sheath collapse in a high-voltage rf-driven low pressure CCP glow discharge. We explored the transition behavior of the formation of field reversal as a function of driving voltage amplitude and found that field reversal starts to form at around 750 V, for a discharge with an electrode spacing of 4 cm at 10 mTorr argon pressure driven at 13.56 MHz. Accordingly, the energy distribution function of electrons incident on the electrode shows peaks from around 3 to 10 eV while varying the driving voltage from 150 to 2000 V, showing potentially beneficial effects in plasma material processing where relatively directional electrons are preferred to solely thermal diffusion electrons.

Effect of Oxygen Functionalities inside Carbon Micropore on Lithium-Sulfur Battery Performance

Introduction Lithium-sulfur batteries (LSB) using a sulfur cathode with a high specific capacity (1672 mAh g-1) have been regarded as one of the most promising candidates for large-scale energy storage systems, while the sulfur cathode's drawback hinders the commercial application of LSB. Soluble Li2Sx (x = 4 – 8) generated during a charge-discharge process dissolves into electrolytes, which induces LSB's self-discharge and capacity decay. The main efforts to overcome this issue have been on physical confinement of sulfur in the pores of porous carbons [1,2]; however, carbon materials, being non-polar in nature, interact weakly with the polar Li2Sx, which still leads to low cycle stability of LSB. Hence, the surface modification to porous carbon, which provides polar-polar interaction between the carbon surface and Li2Sx, has been performed, suppressing the Li2Sx dissolution and improving LSB's performance [1,3].On the other hand, we reported that polar-oxygen functionalities on microporous carbon (MC), which are generated with oxidants, significantly improve the discharge capacity of LSB [4]. The formation of Li2Sx (x = 4 – 8) is inhibited in micropores (pore diameter < 2 nm) [5]; therefore, the oxygen functional groups probably improve the discharge capacity of LSB assembled with a MC-sulfur composite cathode due to factors other than the suppression effect of Li2Sx dissolution. Our previous study revealed that oxygen functionalities on the MC surface contribute to the enhanced electrochemical performance of the LSB by preventing electrolyte decomposition and thus decreasing the resistance of the cathode electrolyte interface (Rcei) [6]. However, the ratio of Rcei to the total resistance of the LSB is small; the oxygen functional groups would improve the performance of LSB by affecting other resistance. Herein, we investigate the effect of surface oxygen functionalities on charge transfer resistance (Rct) and Li+ diffusion of LSB. Our report would provide deep insight into the surface modification of carbon materials as LSB’s cathode. Method 2.1. Preparation of Oxidized MC-Sulfur composite MC was added into 69 wt.% HNO3 and refluxed at 120ºC for 2 h (Ox MC). Washed and dried Ox MC was mixed with sulfur at a weight ratio of 48: 52. The mixture was heated at 155ºC for 5 h (Ox MC-S). 2.2. Assembling of Cells To obtain the Ox MC-S cathode, the slurry prepared by mixing the Ox MC-S, acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a weight ratio of 89: 5: 3: 3 was coated on an Al foil. The cells with the Ox MC-S cathode and Li metal anode were assembled in a glove box. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (HFE) = 10: 8: 40 (by mol) was used as the electrolyte. 2.3. Activation Energy Measurement with Electrochemical Impedance Spectroscopy (EIS) To elucidate the effect of oxidation treatment on the Rct and Warburg impedance (Rw) of Li-S batteries, activation energy measurement was carried out at 2.5 V in the 50th charging process. The temperature range was 0 – 25°C, and the alternating current voltage amplitude was 10 mV. Rw was investigated with the calculation of the Warburg coefficient (σ). Major results and conclusion The activation energy of Rct (Ect) and σ were determined to investigate the effects of oxygen functional groups formed at MC surfaces on charge transfer processes and Li+ diffusion. While Ect increased from 0.65 to 0.72 eV by oxidation treatment, the frequency factor increased from 17.7 to 20.9; this indicates that the oxygen functional groups improve the number of reaction sites where three substances (carbon, active material, and electrolyte) come into contact with each other. The σ of MC-S and Ox MC-S were 281.2 and 178.9 Ω s-1/2, respectively. Therefore, a decrease in Rw due to oxygen functional groups was suggested.The charge transfer process and Li+ diffusion occur inside the microporous carbon particles where the confined sulfur is present. We processed the Ox MC-S particle from the cathode after the 50th charging using focused ion beam (FIB) milling to obtain a cross-section and observed it with STEM-EELS. This result will also be reported in our presentation.This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING [JPMJAL1301])” from JST.[1] X. Ji et al., Nat. Mater., 8 (2009) 500.[2] T. Takahashi et al., Prog. Nat. Sci., 25 (2015) 612.[3] L. Yoshida et al., Electrochim. Acta, 429 (2022) 141000.[4] S. Okabe et al., Electrochemistry, 85 (2017) 671.[5] Y. Xiao et al., RSC Adv., 10 (2020) 39875.[6] L. Yoshida et al., 242nd ECS Meeting s, Z01-2299 (2022).

Multi-factors-regulated multi-level down-scalable and robust memristors

The memristor based on resistive switching (RS) behavior has attracted extensive attention due to its wide application prospects in artificial intelligence (AI) and information memory. In this work, a multi-factor responsive memristor based on Ag/MnO2/F-doped tin oxide (FTO) sandwich structure was fabricated by magnetic sputtering method. It was found that the RS behavior of the device was significantly improved when the diameter of the top electrode decreased from 2.0 mm to 0.5 mm, indicating that the device with Ag/MnO2/FTO structure has the down-scalable potential. Through comprehensive research, it can be concluded that the bipolar RS behavior of the memristor can be adjusted by multi-factors such as active layer thickness, top electrode size, voltage scanning rate, bias voltage amplitude and temperature. Specifically, the resistance-temperature dependence and temperature coefficient of the device in the low resistance state (LRS) indicate that the formation and disconnection of metallic Ag conductive filaments (CFs) play an important role in the RS behavior of the memristive device. Therefore, this work will lay an experimental and theoretical foundation for comprehensively understanding the mechanism of RS behavior and developing high-performance memristor with multi-level memory capacity.

Development of nanosecond spike pulse power supply for electrochemical micromachining

The use of pulse voltage can greatly improve the precision of electrochemical microfabrication, and the narrower the pulse width of the applied pulse voltage signal, the higher the machining precision. However, the commonly used chopper circuit topology of pulse power supplies is limited by the maximum switching frequency of the field-effect transistor. To address this problem, this paper proposes a nanosecond pulse electrochemical micromachining power supply based on a differential circuit. The power supply uses the STM32F103C8T6 microcontroller as the control core to output high-performance rectangular waves through a DDS device. After differential, rectification, filtering, and power amplification processing, stable, frequency, amplitude, and pulse width adjustable spike pulse voltage signals are obtained. By establishing a system mathematical model and optimizing the time constant of the differential circuit, theoretically, the sub-nanosecond pulse width can be obtained. Prototype performance tests show that the power supply has a maximum frequency of 20 MHz, a minimum pulse width of 1.8 ns, and a maximum peak voltage of 10 V. By using this power supply for microhole electrochemical machining experiments, nanometer-level machining precision has been achieved.

Temporal evolution and mechanism of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage

In this work, the temporal evolution of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage were investigated using a two-dimensional axisymmetric fluid model. The effects of voltage amplitude, polarity and oxygen concentration were analyzed. The propagation of secondary streamers is divided into two stages: fast propagation followed by slow propagation. The interior of secondary streamers is filled with positive space charges, while the exterior contains negative space charges. The reduced electric field in the secondary streamer is initially linearly proportional to the applied voltage and decreases linearly with the length of secondary streamers. The length of secondary streamers is primarily determined by the applied voltage, regardless of the oxygen concentration. A reversed propagation direction is simulated under negative applied voltage. We propose a different mechanism for secondary streamers. The high-density positive charge layer near the electrode initiates the propagation of secondary streamers, and the extension of positive charge region dominates the propagation. The distribution of electric field along the channel is mainly determined by the distribution of net space charge. The propagation direction is opposite to the direction of electron drift. The secondary streamer eventually stagnates due to the decrease in electron density in high oxygen concentration, while it is caused by the uniform current density at the front of the secondary streamer in low oxygen concentration.

Predictive direct control strategy of unified power quality conditioner based on power angle control

The unified power quality conditioner (UPQC), based on power angle control (PAC), addresses the power distribution issue and enhances equipment utilization between two active power filters (APF) of UPQC by employing conventional linear control algorithms that have complex control structures and exhibit challenges in adjusting controller parameters and control delays. This study proposes a UPQC predictive direct control strategy based on power angle control (PDCS-PAC). We combine the direct control strategy with the finite control set model predictive control (FCS-MPC) to establish the UPQC finite set model predictive direct control system model in the dq coordinate system. This approach simplifies the controller structure and alleviates the control algorithm’s complexity. Based on a detailed analysis of the PAC mechanism, an instantaneous power angle determination method is proposed based on the reactive power equalization technique, and a predictive direct control strategy given the current generation mechanism is constructed for the series and shunt sides of the UPQC, considering the active power balance of the UPQC system and the principle of constant load fundamental voltage amplitude. Finally, we construct a simulation platform and a laboratory prototype to validate the feasibility and efficacy of the proposed control strategy.

Breakdown modes in nanosecond pulsed micro-discharges at atmospheric pressure

Nanosecond pulse micro-discharges at atmospheric pressure have garnered attention because of their unique physics and numerous applications. In this study, we employed a one-dimensional particle-in-cell/Monte Carlo collision model coupled with an external circuit, using an unequal weight algorithm to investigate the breakdown processes in micro-discharges driven by pulses with voltage ranging from 1 kV to 50 kV at atmospheric pressure. The results demonstrate that nanosecond pulse-driven microplasma discharges exhibit different breakdown modes under various pulse voltage amplitudes. We present the discharge characteristics of two modes: ‘no-breakdown’ when the breakdown does not occur, and ‘runaway breakdown mode’ and ‘normal breakdown mode’ when the breakdown does happen. In the runaway breakdown mode, the presence of runaway electrons leads to a phenomenon in which the electron density drops close to zero during the pulse application phase. Within this mode, three submodes are observed: local mode, transition mode, and gap mode, which arise from different secondary electron generation scenarios. As the pulse voltage amplitude increases, a normal breakdown mode emerges, characterized by the electron density not dropping close to zero during the pulse application phase. Similarly, three sub-modes akin to those in the runaway breakdown mode exist in this mode, also determined by secondary electrons. In these modes, we find that electron loss during the pulse application phase is dominated by boundary absorption, whereas during the afterglow phase, it is dominated by recombination. Ion losses are primarily governed by recombination. These findings contribute to a better understanding of the discharge mechanisms during the breakdown process.

The Influence of Load and Speed on the Initial Breakdown of Rolling Bearings Exposed to Electrical Currents

The reason for the failure of electric vehicle drives is increasingly current-induced damage to rolling bearings. Studies show that rolling bearings are more susceptible to current pass-through after the first occurrence of unwanted bearing currents. To investigate this effect, a test plan is introduced with variations in axial and radial loads, as well as rotational speeds. A new bearing is mechanically run-in for each test point and then subjected to a realistic voltage signal of gradually increasing amplitude. After the initial breakdown, the different voltage amplitudes are applied again to investigate the behavior after the initial breakdown. During the whole test, the maximum current, the duration and the dissipated energy of each breakdown are measured. The results provide insights into the processes after the initial breakdown and the stochastic nature of the breakdown behavior.

Magnetostrictive wires-epoxy resin composite structures for human motion energy harvesting

Encapsulation of magnetostrictive alloy wires in epoxy resin has great potential for energy harvesting and can be applied to energy harvesting in human motion. In this work, a magnetostrictive wire-epoxy resin arch composite structure was proposed for harvesting energy generated by foot motion. A prestress was introduced during the resin curing process, and the relationship between the output voltage and material properties was derived based on the Villari effect. Three kinds of Fe-based magnetostrictive wires were prepared and their magnetic properties were measured, then a prototype single-layer arch composite structure was fabricated and an experimental platform was built for testing, and the amplitude of the output open-circuit voltage could reach 936 mV under an impact pressure of 750 N, which proved that the Fe–Ga alloy composite structure was superior to Fe–Co and Fe–Ni alloys in energy harvesting. The double-layer arch-shaped Fe–Ga composite structures energy harvesting prototype outputs a maximum voltage of up to 940 mV in foot energy harvesting experiments, and collected a maximum power of up to 2.45 mW at a step frequency of 3.5 Hz. Consequently, this work emphasized the feasibility of magnetostrictive alloy-epoxy composite structures for energy harvesting in human motion and the potential for developing new ways of energy harvesting.

Design, modeling and experimental research of a multi-mode, fast-response piezoelectric control valve

To realize the precise regulation and fast response of the valve, a piezoelectric control valve with a simple and compact structure, and easy control is proposed. The control valve is divided into the valve core that consists of a sandwich piezoelectric transducer and a valve body. When a single excitation signal is applied to the transducer, the longitudinal vibration mode of the valve core is excited. The valve is opened due to the liner reciprocating motion of the end of the valve core. By adjusting the frequency of the excitation signal, the vibration mode of the transducer is switched between the first three modes of longitudinal vibration, which in turn adjusts the water output of the valve. Compared with the single-mode valve, the piezoelectric control valve has three working modes. Therefore, it has different adjustment precision and range for each mode. First, the electromechanical coupling model of the valve core and the mechanical model of the valve body are established by using the transfer matrix method. By analyzing the dynamic characteristics of the piezoelectric valve, the structure parameters of the valve core and valve body are optimized. Secondly, the prototype of piezoelectric valve is manufactured and assembled, and the validity of the proposed theoretical model is verified by the vibration measurement experiments. Finally, the flow performance and response speed of the piezoelectric valve are measured by experiments. The results show that the maximum pressure of the valve is 1 MPa when the assembly pre-pressure is 983 N. A sinusoidal-signal has the best excitation effect. Under the experimental conditions of sinusoidal excitation, a driving voltage amplitude of 250 V, and pressure of 1 MPa, the optimal driving frequencies of the piezoelectric valve in the first three operating modes are 33.8 kHz, 42.2 kHz, and 83 kHz, and the corresponding maximum flow rates are 3.3 mL/min, 1.15 ml/min, and 0.445 ml/min, respectively. The response performance of the piezoelectric valve is tested, indicating that the prototype can achieve stable operation within 3.5 ms after being powered on, and stop working within 5 ms after being powered off. The piezoelectric valve has good response characteristics and flow control ability, which has potential applications in the field of biomedicine.