Current Pulse Amplitude Research Articles

Combined influence of airflows and a parallel magnetic field on the discharge characteristics of AC dielectric barrier discharge

The combined influence of airflows and a parallel magnetic field on an AC-driven dielectric barrier discharge plasma is experimentally investigated through image analyses, electrical measurements, and optical diagnoses. After applying a parallel magnetic field, more discharge filaments are generated during one discharge cycle. Besides, the electrical and optical diagnoses show that the magnetic field can increase the plasma parameters, such as the electron temperature and electron density. When airflows and a parallel magnetic field are applied in combination, the discharge uniformity presented in the long-exposure images is significantly enhanced by the airflows and slightly improved by the magnetic field. With increasing airflow velocity, the distribution of discharge filaments goes through four phases, namely, spot-like distribution, line-like distribution, cotton-like distribution, and stripe-like distribution, among which the stripe-like distribution exhibits the highest discharge uniformity. High-speed video analyses reveal that the improved discharge uniformity can be attributed to the changed breakdown positions and the increased number of filaments. Although airflow can significantly improve the macroscopic uniformity of the discharge, it leads to a decrease in the maximum current pulse amplitude, electron temperature, electron density, and gas temperature. Applying a magnetic field in flowing air can not only improve the discharge uniformity but also ensure that the discharge has high maximum current pulse amplitude intensity, electron temperature, and electron density. Based on the analyses of the electron trajectory and the estimation of the force condition of the micro-discharge remnants, the modulated charged particles, reduced electric field, and pre-ionization degree are responsible for the changed discharge uniformity and plasma parameters in the parallel magnetic field and flowing air.

Kinetics of narrow-spectrum LED glow under pulsed power

The results of experimental investigations of the glow kinetics of narrow-spectrum LEDs based on InGaN-GaN 450 and 520 nm and AlGaInP-GaAs 625 nm structures are presented. The increase and decrease of the light flux intensity under pulsed power are described by exponential dependences containing fast and slow components. The time constants of both components decrease with the increase of the pulse frequency for all three types of LED samples. The time constant of the slow component decreases with the increase of the current and voltage pulse amplitudes. The maximum light output on the frequency dependences of LED energy characteristics is observed at the frequency of 75…100 kHz. Further frequency increase results in the decrease of the LED energy efficiency. The obtained results are explained based on the LED equivalent electrical and energy circuits.

Current-induced switching of thin film α−Fe2O3 devices imaged using a scanning single-spin microscope

Electrical switching of N\'eel order in an antiferromagnetic insulator is desirable as a basis for memory applications. Unlike electrically driven switching of ferromagnetic order via spin-orbit torques, electrical switching of antiferromagnetic order remains poorly understood. Here we investigate the low-field magnetic properties of 30-nm-thick, $c$-axis-oriented $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ Hall devices using a diamond nitrogen-vacancy center scanning microscope. Using the canted moment of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ as a magnetic handle on its N\'eel vector, we apply a saturating in-plane magnetic field to create a known initial state before letting the state relax in low field for magnetic imaging. We repeat this procedure for different in-plane orientations of the initialization field. We find that the magnetic field images are characterized by stronger magnetic textures for fields along $[\overline{1}\overline{1}20]$ and $[11\overline{2}0]$, suggesting that despite the expected 3-fold magnetocrystalline anisotropy, our $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ thin films have an overall in-plane uniaxial anisotropy. We also study current-induced switching of the magnetic order in $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$. We find that the fraction of the device that switches depends on the current pulse duration, amplitude, and direction relative to the initialization field.

Study of Temperature Rise Characteristics and Voltammetry Characteristics of ZnO Varistor under 10/350μs Pulse Current

To study the effect of 10/350μs pulse current on the electrical performance of ZnO varistor, a high-current impulse experimental study was conducted in this paper. Firstly, the varistor was subjected to different amplitude impulse discharge experiments, and the temperature change of the varistor after the impulse was recorded. Then, the temperature of the varistor at the moment of 1 second after the pulse impulse was suffered by the Asymptotic function, and the Levenberg-Marquardt optimization algorithm was calculated to compare the temperature rise of the varistor under different current amplitudes. Finally, the upward shift of voltammetry characteristics in the high-current region after the impulse was explained according to the double Schottky barrier model and the linear chain aging theory. The results show that the higher the pulse current amplitude is, the higher the temperature rise of the varistor is at the 1s moment. The highest voltammetry characteristic upshift is caused by the 6.4kA pulse current. The temperature rise and the voltammetry characteristic drift in the high-current region are positively correlated. The results of the study can provide a reference for manufacturers to produce ZnO varistors for direct lightning protection of buildings.

Investigation of continuous pulse current source on the performance of phase change material-thermoelectric cooler system

In this particle, the influence of phase change materials (PCM) on the property of thermoelectric cooler (TEC) is studied by numerical simulation. The heat sink integrated with PCM is placed on the hot side of TEC to reduce the fluctuation of temperature under a continuous pulse current source. The performance of a single-layer PCM-TEC system with that of a single TEC system under continuous pulse current source is firstly compared. Based on this, the effects of current source type, PCM layer, pulse width, cooling load and pulse amplitude on the cooling performance of TEC are investigated in depth. The results show that, compared to a single TEC system, PCM is able to considerably enhance the cooling performance of the TEC during the phase transition period. Besides, increasing PCM layer or decreasing cooling load improves the phase change interval, which increases threefold when the cooling load increases from 0.02 W to 0.06 W. In addition, it is found that lower temperature can be achieved by increasing pulse width or pulse amplitude.

VESTIBULAR IMPLANT STIMULATION PAUSE DETECTION THRESHOLDS: IMPLICATIONS FOR DESIGN OF BATTERY DEPLETION ALERTS.

Vestibular implants (VI) modulate the rate and amplitude of charge-balanced current pulses to encode head angular velocity or acceleration. When the battery of a VI becomes depleted, stimulation interruptions can cause vertigo. To avoid this, VIs can use alert signals such as vibration and beeping to remind the user to replace the battery. However, in distracting and noisy environments typical of activities of daily life, some patients may fail to hear or feel those alerts, so a physiological signal can be used as an alternate channel for signaling battery depletion. Pauses in the stimulation waveform can be delivered for this purpose, with the length of the pause long enough to be detected reliably by the patient but not so long as to induce dizziness or a vertigo attack. As a guide for the design of a physiologic battery depletion alert system, this study reports the ability of nine long-term, continuous VI users to detect stimulation pauses of various durations. We also show the effect of distraction on patients' detection thresholds and response latencies for detected events.

Experimental study on positive corona discharge characteristics in plane-single/double earthed rods air gaps under negative DC voltage

In order to analyze the corona discharge characteristics at the grounding object tip under the thundercloud electric field environment, scaled simulation test has been conducted on corona discharge in the plane-single/double earthed rods air gap. Five gap configurations with three different grounding rods were built during experiments. Factors as rod tip curvature, voltage and gap configuration have been considered in detail. Corona voltage, corona current and the number of ultraviolet photons were all recorded. The grounding rod tip curvature radius can affect corona discharge processes at grounding rod tip. With increasing applied negative DC voltage, five typical corona processes of dark discharge, burst streamer corona, periodic streamer corona, glow corona and brush discharge occurred at conical and spherical grounding rod tip (r=0.75cm), but under d=5cm and d=10cm no glow corona and brush corona appeared at spherical grounding rod tip (r=1.25cm). It is much easier for grounding rod tip with smaller curvature to form glow corona phenomenon. The mean value Iav of periodic streamer corona current pulse amplitude decreases with grounding rod tip curvature radius, while the mean corona current pulse width and pulse interval increases. For grounding rod with conical tip, there is little difference of average current pulse amplitude between periodic streamer corona and brush corona; for grounding rod with spherical tip (r=0.75cm), the mean value Iav of brush corona pulse amplitude increases to 3595.8 μA which has increased by a factor of about 36. The photon number at conical grounding rod tip is larger than that at spherical grounding rod tip at low voltage but the relation reverses as the applied voltage exceeds a critical value. The shielding effect of two grounding rods in plane-double rods air gaps increased with spherical grounding rod curvature radius and decreases with the lateral gap distance between two grounding rods.

Performance assessment and optimization of a thin-film thermoelectric cooler for on-chip transient thermal management

On-demand cooling of thin-film thermoelectric cooler (TFTEC) is a promising technique for energy-saving and high efficiency. However, the transient cooling process of TFTEC is complex and systematic, involving temperature-dependent material properties, geometry factors, parasitic parameters and control parameters. In this work, a system-level optimization of the on-chip transient thermal management (TTM) performance of a Bi2Te3-based TFTEC is performed using a transient three-dimensional numerical model. The response surface method is applied to obtain a predictive model for evaluating the transient cooling performance of TFTEC in terms of four different design factors of thermoelectric leg height, electrode height, current pulse width and amplitude. The relationships between the above design factors and responses including passive cooling, active cooling, temperature overshoot, and time delay and their interactive effects are investigated. Finally, single- and multi-objective optimizations are employed to optimize these responses in different scenarios. The results show that the TFTEC with the optimal configuration enables a passive cooling of 15.57 °C and an active cooling of 5.85 °C simultaneously for a chip hotspot with a transient heat flux of 1300 W/cm2. Furthermore, the hotspot temperature can be limited to 7.15℃ lower than the predefined temperature limit, while the high-power pulse loading time can be extended by 690.2 ms.

Combined film and pulse heating of lithium ion batteries to improve performance in low ambient temperature

Low ambient temperatures significantly reduce Lithium ion batteries’ (LIBs’) charge/discharge power and energy capacity, and cause rapid degradation through lithium plating. These limitations can be addressed by preheating the LIB with an external heat source or by exploiting the internal heat generation through the LIB's internal impedance. Fast external heating generates large temperature gradients across the LIB due to the low thermal conductivity of the cell, while internal impedance heating (usually through AC or pulse charge/discharging) tends to be relatively slow, although it can achieve more uniform temperature distribution. This paper investigates the potential of combining externally sourced resistive film heating with bidirectional pulse heating to achieve fast preheating without causing steep temperature gradients. The LIB is modeled with the Doyle Fuller Newman (DFN) electrochemical model and 1D thermal model, and reinforcement learning (RL) is used to optimize the pulse current amplitude and film voltage concurrently. The results indicate that the optimal policy for maximizing the rate of temperature rise while limiting temperature gradients has the film heating dominate the initial phases and create the ideal conditions for pulse heating to take over. In addition, the pulse component shares the heating load and reduces the energy rating of the auxiliary power source.

Effect of Temperature on Current Pulse Characteristics of Negative Corona Discharge Based on Numerical Model

Temperature is an important factor affecting the dynamic processes of corona discharge, since the ionization, attachment, and mobility of charged particles are directly related to temperature. Most existing research has investigated the temperature effect on corona discharge through experimental works. However, they are hard to acquire the corona discharge microphysical processes, which are related to the formation of the current pulse and electromagnetic (EM) wave signals. This article proposes a numerical model with temperature-related transport parameters to study the temperature influence on microphysical processes and current pulses for negative corona. By comparing microphysical quantities such as the effective ionization coefficient, density, and velocity of space charges, the effect of temperature on the current pulse parameters including the rise and fall times, amplitude, and pulsewidth is systematically explained. It shows that as the temperature rises, the current pulse amplitude increases, while the other three parameters decrease. The rise time is dependent on the effective ionization coefficient. The fall time is affected by the velocities of negative and positive ions. The experimental results indicate the simulated current pulses are consistent with the measured ones, proving the effectiveness of the proposed numerical model with temperature variation.

Electrical and optical characterization of multi-hollow surface dielectric barrier discharge in configuration with the air-exposed electrode

In this paper, multi-hollow surface dielectric barrier discharge generated by a perforated ceramic substrate in a configuration with the air-exposed electrode was investigated. The electrical characteristics (discharge power, peak, and average amplitude of current pulses) and optical characteristics (emission intensity) of the discharge were evaluated under various conditions of applied voltage (peak voltage 3–6 kV, frequency 200–2000 Hz), air flow rate (0.5–2.4 L/min), and air relative humidity (0%–80%). Temperature of ceramic substrate was also monitored. Statistical analysis of current pulses was also performed, and histograms of amplitudes of current pulses were calculated. The results showed that discharge characteristics strictly depend on given working conditions. The analysis of current pulses showed opposite trends in average overall number of positive and negative pulses with an increase of discharge power: number of positive current pulses gradually increased, while number of negative current pulses slightly decreased. The highest peak currents were found at 4 kV (1.8 W). With further increase of peak voltage, peak current decreased and beginning of detection of current pulses upon a rising (declining) slope of applied voltage was slightly shifted toward earlier times. At the highest applied peak voltage, pulses appeared even before polarity of applied voltage reversed. Therefore, we suppose that a residual charge accumulated on dielectric surface plays a crucial role in characteristics of the current pulses. Significant influence on current pulses and discharge emission intensity was also found with a change of air relative humidity, while the effect of air flow rate was found weaker.

Effects of the ground-electrode temperature on the plasma physicochemical processes and biological inactivation functions involved in surface dielectric barrier discharge

In this work, a surface dielectric barrier discharge (SDBD) device coupled with power electronics technology was designed for precise control of the ground-electrode temperature to investigate the dynamic behavior of the physicochemical processes and biological inactivation functions involved in SDBD plasma. It was found that an increase of the electrode temperature from 30 to 210 °C reduced the breakdown voltage and increased the current pulse amplitude because the reduced electric field strength and average electron density of the SDBD plasma were consistently enhanced. The change in the plasma-chemistry mode (O3-dominant to NO x -dominant) was more sensitive to the ground-electrode temperature than that of the power density and gas temperature. O3 in the gas and liquid phases could not be detected at electrode temperatures above 90 °C, and the NO x mode almost immediately occurred after the plasma was turned on for ground-electrode temperatures of ⩾180 °C. The increase in the electrode temperature increased the acidity of the plasma-activated water and, more importantly, short-lived reactive species OH and NO were detected at electrode temperatures ⩾120 °C in the case of aqueous solutions treated directly with SDBD plasma. The biological inactivation function of the SDBD plasma, i.e. for bacterial suspensions and tumor cell cultures, was improved by about three orders of magnitude and 40% at the optimal electrode temperatures of 180 °C and 120 °C, respectively. This is an important breakthrough for development of SDBD-based biomedical devices for specific purposes on a commercial level by regulating the plasma chemistry through the ground-electrode temperature, overcoming the limitations of chamber heating and compressed air supply.

Short pulse-enhanced vacuum arc evaporation

The paper studies a new method in vacuum-arc deposition technology that can be called short pulse-enhanced vacuum arc evaporation (s-PEVAE). This deposition technique combines sub-microsecond high-current pulsed and direct current operation of the arc-discharge source with the pulse frequency of several kilohertz. The high pulse voltage provides a high growth rate and amplitude of discharge current pulses, i.e., over 109 А/s and 1 kА, respectively. During the s-PEVAE process, the arc discharge power can achieve several hundreds of kilowatts. According to optical and probe measurements performed during the titanium evaporation in argon gas, ionization provided by s-PEVAE is higher than that provided by direct current vacuum arc evaporation (DCVAE). In s-PEVAE, the increase in the average discharge power is accompanied by the growth in the average density of the substrate ion current. At the same time, the deposition rate of the titanium coating decreases. All this leads to a significant change in the ratio between the ions bombarding the substrate and metal atoms forming the coating. Along with the substrate bias voltage, this ratio exerts a strong effect on the structure and properties of the deposited coating and can be controlled by the pulse parameters such as amplitude, time, and frequency.

Selected Aspects of Surface Integrity of Inconel 625 Alloy after Dry-EDM in Carbon Dioxide

The dry-EDM process is environmentally neutral and enables to obtain good machining accuracy and relatively good surface quality. On the other hand, the application of dry-EDM is limited due to problems with the effective dissipation of heat from the machining zone and instability of material removal. The machining of Inconel 625 alloy was carried out in the carbon dioxide as a dielectric supplied to the machining gap through the channel in the working electrode, in the milling kinematics. In one of the investigated variants, the workpiece was submerged additionally in the deionized water during machining. The main aim of this research was to determine an influence of EDM milling in carbon dioxide with and without external workpiece cooling on the workpiece technological surface integrity ie. roughness, morphology and microhardness. The pulse time, current amplitude and gas pressure were selected as investigated parameters. Obtained results indicate significant differences in surface layer properties for both investigated machining variants.

Systematic Optimization of QW Semiconductor Laser Design for Subnanosecond Pulse Generation by Gain Switching

We have studied the basic principles of quantum well semiconductor laser design optimization and current pumping requirements for generating optical pulses with a defined width and maximum peak power by gain switching. It is shown that for a given pulse width there exist a set of optimal values of optical confinement factor, resonator length and current pulse amplitude, that ensure maximum peak output power. It is determined that the maximum output power is achieved when the optical confinement factor is as low as possible, so that the pulse width does not exceed the target value. The optimal resonator length is found to strongly depend on the target pulse width.

Transient supercooling analysis of an I-type thermoelectric cooling element by the experiment

Structure improvement and optimal operating parameters of the thermoelectric cooling component will favor obtaining a lower transient supercooling temperature. The contribution proposed a new I-type thermoelectric cooling structure by connecting the P-type arm with the N-type arm by the sandwich arrangement structure. A one-dimensional transient governing equation is constructed based on the physical model, and the finite volume method provides a numerical solving solution. Moreover, an experimental system is built to analyze the supercooling performance of the I-type cooling layout under different operating conditions. The experimental results validated that the proposed numerical simulation method is feasible and accurate for the component modeling and cooling performance analysis. Moreover, we analyzed the influences of single pulse current amplitude and reference-pulse current groups on the cold end temperature of the I-type thermoelectric cooling structure. The cold end temperature will reach the minimum when the pulse current amplitude is 20 A. Meanwhile, the combined reference-pulse current operation effectively reduces the transient subcooling temperature at the cold end. The experiments show that the minimum cold-end temperature reduces by 31.8 K when the input reference-pulse current waveform is 5 A-20A. In summary, the I-type thermoelectric cooling structure achieves better cooling performance under combined reference-pulse current operating conditions.

Transient Current Analysis of Silicon Carbide Neutron Detector Using SRIM and TCAD

Since neutrons are electrically neutral, the methods used to detect neutrons generally rely on secondary charged particles, which are produced by the interaction of neutrons and neutron conversion materials (such as <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> LiF, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B). In this report, the SRIM code has been used to analyze the ionization properties of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> particles and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> H particles traveling through the Silicon Carbide (SiC) diode, and subsequently, the final Bragg ionization distribution has been obtained. Next, according to the obtained ionization distribution of secondary particles, the linear energy transfer (LET) distribution of the secondary particles is extraced accurately. Finally, based on the distribution of LET, Technology Computer Aided Design (TCAD) simulations are utilized to analyze the transient current pulses of thin-film-coated and trench-type SiC diodes. In addition, the effects of particle energy and applied reverse bias on the output pulse characteristics of SiC diodes are also explored. Essentially, this paper augments the understanding of output response from SiC neutron detectors, and for trench-type detectors, the order of output current pulse amplitude decreases significantly and has a long-tail. Therefore, the trench-type detectors not only need a more advanced fabrication process but also require the design of dedicated readout electronics.

Dynamic rotation featured translocations of human serum albumin with a conical glass nanopore

In this paper, translocation events of single ellipsoid human serum albumin (HSA) with a solid glass nanopore have been investigated in detail by common resistive pulses. In particular, the translocation events can be classified into three main groups according to the significant difference in current pulse amplitudes. By adjusting the electric field of the nanopore upon changing applied conditions in voltage, pH, and pore size, the observation would be originally associated with dynamic rotation rather than increased size exclusion of HSA. Finally, the rotation angles of translocated HSA are determined by both experimental and theoretical studies.

Objective neuromodulation basis for intrafascicular artificial somatosensation through carbon nanotube yarn electrodes

BackgroundIntrafascicular electrical stimulation has been extensively adopted to achieve sensory feedback for limb amputees. Axon-like carbon nanotube yarn (CNTy) electrodes with both promising flexibility and spatial selectivity index (SSI) can be fascinating alternatives to generate artificial somatosensation. New methodHere we systematically disclose objective neuromodulation basis for artificial somatosensation through intrafascicular CNTy electrodes. CNTy electrodes with different exposed lengths were utilized for electrically stimulating tibial nerves in twelve rats. Somatosensory evoked potentials (SEPs) were recorded synchronously using an epidural thirty-channel electrode array. Spatiotemporal characteristics of SEPs were analyzed as current pulse amplitude (PA), pulse width (PW) and pulse frequency (PF) varied. ResultsThe current thresholds at 1 Hz exhibit the lowest means when compared with those at 4 and 8 Hz for most CNTy electrodes (20/28). For all the electrodes, amplitudes of SEPs and activated areas of perceptive fields increase with PWs and PAs rising, and decrease remarkably with PFs from 1 to 8 Hz. Latencies of P1 and N1 of SEP peaks gradually reduced with PWs and PAs advancing. Considering high SSIs, relatively stable current thresholds, wider variation ranges of sensory magnitudes and optimal stability of perceptive fields, the L-200 µm electrodes are preferable for neuromodulation with PFs of 1 – 8 Hz, PWs of 100 – 800 μs and PAs of 2 – 64 μA. Comparison with existing methodsNew-type CNTy electrodes possess both promising flexibility and SSI when compared with other neural interfaces. We systematically explore objective neuromodulation basis for artificial somatosensation through CNTy electrodes for the first time. ConclusionsSignificantly higher SSIs, lower current and charge thresholds exist for CNTy electrodes in comparison with other peripheral-nerve interfaces. This study can, for the first time, lay a solid neuromodulation foundation for CNTy electrodes to achieve fine sensory feedback.

Влияние напряжения заряда емкостного накопителя на выходные параметры ускорителя на основе импульсного трансформатора

In the modern world an electron accelerator is a tool that provides the generation of an electron beam with specified parameters. A necessary description of any tool is its functioning parameters and output characteristics. In this work, the output characteristics of a pulsed electron accelerator (diode voltage and current pulse amplitudes, current and energy of the beam extracted into the atmosphere, and the spectrum of particle kinetic energies) are studied depending on the controlled charge voltage of the primary capacitive energy storage. An analysis was made of the energy transfer efficiency in the circuits of the accelerating voltage pulse generator according to the scheme high-voltage capacitive storage - commutator - pulse transformer - vacuum electron diode.