Low Current Pulses Research Articles

Synergistic Thermal and Electron Wind Force-Assisted Annealing for Extremely High-Density Defect Mitigation.

This study investigates the effectiveness of combined thermal and athermal stimuli in mitigating the extremely high-density nature of dislocation networks in the form of low-angle grain boundaries in FeCrAl alloy. Electron wind force, generated from very low duty cycle and high current density pulses, was used as the athermal stimulus. The electron wind force stimulus alone was unable to remove the residual stress (80% low-angle grain boundaries) due to cold rolling to 25% thickness reduction. When the duty cycle was increased to allow average temperature of 100 °C, the specimen could be effectively annealed in 1 min at a current density of 3300 A/mm2. In comparison, conventional thermal annealing requires at least 750 °C and 1.5 h. For specimens with 50% thickness reduction (85% low-angle grain boundaries), the electron wind force was again unable to anneal the defects even at 3300 A/mm2 current density and average temperature of 100 °C. Intriguingly, allowing average concurrent temperature of 200 °C eliminated almost all the low-angle grain boundaries at a current density of 700 A/mm2, even lower than that required for the 25% thickness reduced specimens. Comprehensive electron and X-ray diffraction evidence show that alloys with extremely high defect density can be effectively annealed in less than a minute at approximately 200 °C, offering a substantial improvement over conventional high-temperature annealing.

Women Safety Device with Shock Taser and Location Tracking

Abstract: This abstract provides an overview of a Women Safety Device. The safety and security of women continue to be a significant concern in modern society. To address this issue, we present a comprehensive Women Safety Device equipped with a Shock Taser and Location Tracking, implemented using the Arduino Uno microcontroller. The core functionalities of the proposed device include a shock taser for self- defense and a location tracking system to ensure quick response in case of emergencies. The shock taser is designed to deliver a non-lethal electric shock, acting as a deterrent against potential threats. The device utilizes high-voltage, low-current pulses generated by the Arduino Uno to create a safe and effective self-defense mechanism. Furthermore, the location tracking feature utilizes GPS and GSM technologies to continuously monitor the user's real-time position. The Arduino Uno gathers GPS data and transmits it via GSM to the predefined contacts. This allows authorized contacts, such as family members or authorities, to track the user's location and respond promptly to distress situations. By combining a shock taser for self-defense and a real-time location tracking system, this device contributes to a safer environment for women and provides peace of mind for both users and their loved ones.

Fracture Behavior of Droppers under Low Current Pulses and Stress Coupling Cyclic Fields

Fracture Behavior of Droppers under Low Current Pulses and Stress Coupling Cyclic Fields

The electroplastic effect in titanium alloys under tension

The electroplastic effect (EPE) is a phenomenon which consists in a decrease in the strain resistance and enhancing of the plasticity of metals under the effect of the electric current of a sufficiently high density [1]. The goal of the study is to compare the deformation behavior of single-phase commercially pure tita­nium Grade 4 and two-phase VT6 alloy under tension and external heating with introduction of a pulsed current. Current of various pulse ratio and density was supplied to the grips of the tensile testing machine from a pulse generator. To estimate the relative contribution of the electroplastic effect during passage of current to the reduction of flow stresses, the materials were also exposed to external heating. The microstructure of the samples in the sample head and in the vicinity of the fracture region in the longitu­dinal section was studied using optical microscopy. The electroplastic effect in the studied materials is manifested on the tensile curve through individual jumps in the downward flow stress at a high pulse ra­tio, whereas at a low current pulse ratio a decrease in the flow stress and strain hardening and increase in the plasticity are observed. It is shown that tension of the sample under the effect of current results in a greater decrease in the flow stresses than that observed under external heating at the same temperature for both materials. This confirms the athermal nature of the pulsed current effect. The critical density of the high pulse ratio current (q - 5000) capable of providing manifestation of the electroplastic effect is two times lower for a VT6 alloy than for pure titanium Grade 4. Under the same pulsed current modes, the flow stresses for VT6 decrease more than for Grade 4. Pulsed current of high pulse ratio caused an anomalous hardening effect in a VT6 alloy, but the physical nature of this effect requires an additional study. The pulsed current modes used in the study did not lead to any structural changes noticeable under optical magnification in the samples under tension, except for the disappearance of twins and separation of the impurity particles in Grade 4 and spheroidization of grains in VT6.

Transient Neurovascular Interface for Minimally Invasive Neural Recording and Stimulation

Adv. Mater. Technol. 2022, 2, 2100176 DOI: 10.1002/admt.202100176 Figure 2i in the original manuscript contained an error in the right y-axis. The error was due to an incorrect conversion while calculating the charge injection capacity. The unit originally reported was mC cm−2 instead of µC cm−2. The findings and conclusions presented in the original article are not affected. An updated version of Figure 2 is given below. Accordingly, a correction was made in the text as follows: “The average (± s.d.) maximum injectable current (always limited by the Emc) was found to be 5.2 ± 4.8 mA (n = 15 electrodes from N = 4 devices) and the respective CIC was 263.6 ± 247.5 µC cm−2 (Figure 2i). Currents used in metallic stent-electrode arrays fall within the range sustainable by the polymeric electrode presented in this article.[6]” Also, the following sentences that were added to justify an unusual CIC higher than the CSC should be removed: “It must be noted though that the CSC is usually an overestimation of the charge transfer potential of the electrodes: in fact when stimulating in vivo, at high frequencies and short pulses, only the superficial layers of the bulk PEDOT:PSS film will be active.[8] Thus, the CIC is expected to be lower than the CSC (typically CIC is 5–20% of the CSC for metals and oxides).[29] In our measurements, PEDOT:PSS electrodes reported a CIC higher than the total CSC with high variability among electrodes. A similar trend has been reported already in literature for PEDOT-coated PtIr electrodes.[38] A factor contributing to the high CIC is the positive open circuit potential reached by the electrodes after a prolonged stimulation at low current pulses to reach stabilization at the electrode-electrolyte interface. This open circuit potential was positive for all electrodes (≈0.25 V for most electrodes with a few exceptions at 0.15 V), leading most electrodes to a positive Emc value for injected currents below 1500 µA.” The authors apologize for this mistake.

The effect of electrical discharge machining parameters on the surface quality of 3D woven carbon/carbon composite

In this paper, Electrical Discharge Machining (EDM) was tested on a carbon fibre-reinforced carbon composite (C–C). The effect of three parameters of the EDM process (i.e., pulse current, pulse voltage, and pulse duration) was examined on output factors, including surface quality, heat-affected zone, dimensional accuracy, and machining speed. To this end, SEM images of the surface of cavities were taken. The best surface quality and dimensional accuracy were achieved by low pulse current and low pulse duration. However, the effect of pulse voltage on outputs was minimal and, thus, could be ignored. Experimental results showed that pulse current and pulse duration have significant impacts on outputs, and the EDM process has the capability to machine hard materials such as c-c composites.

Electrical Control of Skyrmion Density via Skyrmion-Stripe Transformation

A comprehensive understanding of numerous electrical current-induced magnetic texture transformations is necessary to ensure the reliability of skyrmionic devices during operation. Here, we present an experimental study of unipolar current-induced skyrmion-stripe transformation in a $\mathrm{Pt}/\mathrm{Co}/\mathrm{Fe}/\mathrm{Ir}$ magnetic bilayer. High current density pulses induce a densely packed skyrmion state, as commonly reported in many other studies, and skyrmion nucleation is expected to lessen with diminishing current density. However, at a lower current density where pinning effects become significant, a regime where current-induced skyrmion annihilation and skyrmion-to-stripe transformation is observed. Kerr imaging reveals that, under a low current pulse, the rapidly expanding stripes crowd out and annihilate the skyrmions before quickly decaying and leaving behind a sparse skyrmion population. Our findings establish an additional requirement of a minimum operating current density in the design of skyrmionic devices to avoid unintended skyrmion deletion. On the other hand, this skyrmion annihilation can also be strategically employed as a technique for skyrmion density control using solely current modulation in future skyrmionic devices.

An Image Reconstruction Algorithm with Experimental Validation for Electrical Impedance Tomography Imaging Applications

In the Non-Invasive Bio Impedance Technique (NIBIT) a low current pulse with high frequency inserted between two electrodes of the object while measuring voltages from the other remaining electrodes with respect to the reference electrode. The electrode arrangement is defined in the form of cylindrical shapes of the surface of the phantom. After these arrangements, it inserts the current pulse and measures the voltages according to the selected data acquisition method of bio impedance. The presented algorithm analyzes and defines each obtained data sample from the used phantoms and also allows Image Reconstruction (IR) based on developed Graphical User interface (GUI) on MATLAB. The used IR approach is based on Tikhonov regularization and FEM. The FEM and Tikhonov regularization are mathematical approaches that deal with Forward Problem (FP) and Inverse Problem (IP) of images. In our approach, the FP solution is identified first in order to reconstruct the conductivity distribution through the EIT inverse solution. Thereafter, This FP is solved through the known current pulse of a given conductivity medium. Likewise, the IP is identified and solved through the boundary potential of the object. The end of the obtained result provides a comparable result for the used phantom according to its internal structure. This proposed technique is still reliable despite having some standardization issue according to the procedure.

High-power single mode GaSb-based 2 μm superluminescent diode with double-pass gain

We report a broadband superluminescent diode operating around a 2 μm wavelength, optimized for high-power broadband operation. The high power operation is achieved by using a GaInSb/AlGaAsSb heterostructure positioned in a ridge waveguide with a J-shaped layout to form a double-pass geometry. To avoid lasing at high current while enabling high gain, a cavity suppression element is used. This combination allows demonstration of an output power as high as 120 mW for continuous-wave (CW) operation at room temperature, with a spectral full width at half maximum of about 43 nm. The maximum power spectral density was measured to be 1.8 mW/nm, which is about a fourfold increase compared to the state-of-the-art results for this wavelength range. To avoid heating, the diode was also driven with low duty-cycle current pulses; in this case, a peak power of more than 300 mW was achieved without any sign of roll-over (power was limited by the current injected). For CW operation, the central emission wavelength could be tuned by current injection between 1900 nm at 200 mA and 2027 nm at 2000 mA. Devices produce a Gaussian output beam that is suitable for coupling to single mode waveguides.

Analysis on discharge behavior and performance of As- and B-doped silicon anodes in non-aqueous Si\u2013air batteries under pulsed discharge operation

Very high theoretical specific energies and abundant resource availability have emerged interest in primary Si–air batteries during the last decade. When operated with highly doped Si anodes and EMIm(HF)2.3F ionic liquid electrolyte, specific energies up to 1660 Wh kgSi−1 can be realized. Owing to their high-discharge voltage, the most investigated anode materials are langle 100rangle oriented highly As-doped Si wafers. As there is substantial OCV corrosion for these anodes, the most favorable mode of operation is continuous discharge. The objective of the present work is, therefore, to investigate the discharge behavior of cells with langle 100rangle As-doped Si anodes and to compare their performance to cells with langle 100rangle B-doped Si anodes under pulsed discharge conditions with current densities of 0.1 and 0.3 mA cm−2. Nine cells for both anode materials were operated for 200 h each, whereby current pulse time related to total operating time ranging from zero (OCV) to one (continuous discharge), are considered. The corrosion and discharge behavior of the cells were analyzed and anode surface morphologies after discharge were characterized. The performance is evaluated in terms of specific energy, specific capacity, and anode mass conversion efficiency. While for high-current pulse time fractions, the specific energies are higher for cells with As-doped Si anodes, along with low-current pulse fractions the cells with B-doped Si anodes are more favorable. It is demonstrated, that calculations for the specific energy under pulsed discharge conditions based on only two measurements—the OCV and the continuous discharge—match very well with the experimental data.Graphic abstract

Formation of Cu/MnOx composite film by concurrent electroplating and electrophoresis in an organic solvent

A composite Cu/MnOx thin film was fabricated by conducting electroplating of Cu and electrophoresis of MnOx colloids simultaneously in an organic electrolyte. The organic electrolyte was prepared by dissolving copper (II) acetylacetonate and manganese (II) acetylacetonate in ethylene glycol, with addition of 10 vol% acetic acid to improve ionic conductivity. Since both Cu ions and MnOx colloids carry positive charges, the formation of a composite film was achieved by a pulse current mode in which a low current pulse was used for Cu2+ reduction, followed by a high current pulse for the electrophoresis of the MnOx colloids. The Cu/MnOx composite film was dense and its X-ray diffraction pattern revealed a mixture of Cu, Mn2O3, and Mn3O4. Both X-ray photoelectron spectroscopy and X-ray absorption spectroscopy show consistent results confirming the metallic nature of Cu and oxidized state of Mn.

State of health diagnosis model for lithium ion batteries based on real-time impedance and open circuit voltage parameters identification method

Impedance and open circuit voltage (OCV) parameter identification is the key technology for state of health (SOH) diagnosis of lithium ion battery (LIB) in an equivalent circuit model (ECM). The current identification methods of impedance and OCV parameter are time consuming, destructive, non-real-time and costly. It is usually difficult to identify each component from the overall impedance parameter using aforesaid impedance identification methods, which severely affects the identification precision of impedance parameter. Furthermore, fast OCV identification is another difficult issue to be resolved. In this paper, a new real-time and nondestructive method is developed to identify dynamic impedance parameter for SOH diagnosis ECM (SDEM) of LIB. This method can identify ohmic impedance and charge transfer impedance from internal impedance and realize the transformation of Warburg diffusion impedance from frequency domain to time domain. Fast determination method of OCV is proposed based on the short-time and low current pulse to realize real-time measurement and identification of the OCV. Dynamic update of the all parameters is conducted based on least squares method (LSM). SDEM with new developed impedance and OCV parameter identification method is validated with high accuracy.

The interaction of pulse width and current intensity on the extent of cortical plasticity evoked by vagus nerve stimulation

BackgroundRepeatedly pairing a tone with a brief burst of vagus nerve stimulation (VNS) results in a reorganization of primary auditory cortex (A1). The plasticity-enhancing and memory-enhancing effects of VNS follow an inverted-U response to stimulation intensity, in which moderate intensity currents yield greater effects than low or high intensity currents. It is not known how other stimulation parameters effect the plasticity-enhancing effects of VNS. ObjectiveWe sought to investigate the effect of pulse-width and intensity on VNS efficacy. Here, we used the extent of plasticity induced by VNS-tone pairing to assess VNS efficacy. MethodsRats were exposed to a 9 kHz tone paired to VNS with varying current intensities and pulse widths. Cortical plasticity was measured as changes in the percent of area of primary auditory cortex responding to a range of sounds in VNS-treated rats relative to naïve rats. ResultsWe find that a combination of low current intensity (200 μA) and short pulse duration (100 μs) is insufficient to drive cortical plasticity. Increasing the pulse duration to 500 μs results in a reorganization of receptive fields in A1 auditory cortex. The extent of plasticity engaged under these conditions is less than that driven by conditions previously reported to drive robust plasticity (800 μA with 100 μs wide pulses). ConclusionThese results suggest that the plasticity-enhancing and memory-enhancing effects of VNS follow an inverted-U response of stimulation current that is influenced by pulse width. Furthermore, shorter pulse widths may offer a clinical advantage when determining optimal stimulation current. These findings may facilitate determination of optimal VNS parameters for clinical application.

Skyrmion Sensor-Based Low-Power Global Interconnects

In this paper, we propose the use of magnetic skyrmion sensors for low-voltage, low-current global interconnects. Magnetic skyrmions have shown great potential for low-power circuit applications, since skyrmions can be generated and moved by remarkably low-current pulses. We propose the use of skyrmion-based current sensors at the receiver that allows low-current signal transmission through the line. The proposed skyrmion sensor consists of a magnetic nanotrack on top of a spin-Hall metal (SHM). The skyrmion is nucleated in the nanotrack by using spin-polarized current and, subsequently, moved along the nanotrack by using a charge current through the SHM. This charge current is the input current from a global interconnect line, which moves the skyrmion depending on the logic input to the line. The resistance of a magnetic tunnel junction (MTJ) at the receiver is based on the movement/location of the skyrmion. This resistance change is sensed using a reference MTJ and a simple complementary metal–oxide–semiconductor (CMOS) inverter. Such a receiver configuration acts as a built-in latch, and hence, expensive voltage converters or transimpedance amplifiers can be avoided, which are the bottlenecks in a conventional low-power interconnect design. Our simulation results indicate that for a 10 mm Cu-line in 45 nm CMOS technology, the energy consumption with skyrmion-based sensing is $\sim 50\times $ lower compared with full swing and $\sim 25\times $ lower compared with low-swing CMOS interconnect.

The Effect of Electrothermal Nonuniformities on Parallel Connected SiC Power Devices Under Unclamped and Clamped Inductive Switching

Nonuniformities in the electrothermal characteristics of parallel connected devices reduce overall reliability since power is not equally dissipated between the devices. Furthermore, a nonuniform rate of operational degradation induces electrothermal variations thereby accelerating the development of failure. This paper uses simulations and experiments to quantitatively and qualitatively investigate the impact of electrothermal variations on the reliability of parallel connected power devices under unclamped inductive switching (UIS) conditions. This is especially pertinent to SiC where small die areas mean devices are often connected in parallel for higher current capability. Measurements and simulations show that increasing the variation in the initial junction temperatures and switching rates between parallel connected devices under UIS reduces the total sustainable avalanche current by 10%. It is seen that the device with the lower junction temperature and lower switching rate fails. The measurements also show that the maximum sustainable avalanche energy for a given variation in junction temperature and switching rate increases with the avalanche duration, meaning that the effect of electrothermal variation is more critical with high power (high current and low inductor) UIS pulses compared with high energy (low current and high inductance) pulses. These results are important for condition monitoring and reliability analysis.

Development of a Pulse Generator for Rough Cutting of Oil-based Micro Wire-EDM

This paper aims to develop a specific pulse generator for rough cutting of oil-based micro wire electrical discharge machining (wire-EDM). A two-stage current-limiting resistance power supply was presented to suppress thermal damage on the machined surface of polycrystalline diamond (PCD) while achieving stable machining by supplying high open voltage and low discharge current pulse waveforms. Tests revealed that the two-stage resistance power supply could achieve lower thermal damaged layer, better surface quality and surface finish than a conventional pulsed power supply since the former could provide smaller peak current and shorter discharge duration than the later. Experimental results demonstrate that boron-doped polycrystalline composite diamond (BD-PCD) is superior to polycrystalline diamond in the smoothness of cutting edge, surface quality and surface roughness since the former has lower specific resistance and thermal conductivity than the later. This study has indicated that the proposed power supply could enable a prototype micro wire-EDM machine to achieve a surface finish as low as 0.45μm Ra and a thermal damaged layer as small as 6μm on the machined surface of BD-PCD after one rough machining operation.

Development of an integrated surface stimulation device for systematic evaluation of wound electrotherapy.

Ideally, all chronic wounds would be prevented as they can become life threatening complications. The concept that a wound produces a 'current of injury' due to the discontinuity in the electrical field of intact skin provides the basis for the concept that electrical stimulation (ES) may provide an effective treatment for chronic wounds. The optimal stimulation waveform parameters are unknown, limiting the reliability of achieving a successful clinical therapeutic outcome. In order to gain a more thorough understanding of ES for chronic wound therapy, systematic evaluation using a valid in vivo model is required. The focus of the current paper is development of the flexible modular surface stimulation (MSS) device by our group. This device can be programed to deliver a variety of clinically relevant stimulation paradigms and is essential to facilitate systematic in vivo studies. The MSS version 2.0 for small animal use provides all components of a single-channel, programmable current-controlled ES system within a lightweight, flexible, independently-powered portable device. Benchtop testing and validation indicates that custom electronics and control algorithms support the generation of high-voltage, low duty-cycle current pulses in a power-efficient manner, extending battery life and allowing ES therapy to be delivered for up to 7days without needing to replace or disturb the wound dressing.

Experimental Investigation of Copper-Tungsten Electrode Wear in EDM

Copper-tungsten alloy which is widely used in the field of EDM has high melting temperature and excellent electrical and thermal conductivity. Copper tungsten electrodes for electrical discharge dressing of metal-bond wheel were studied, and experiments were conducted to observe their wear performance in this paper. Orthogonal experiment was designed to explore the wear at the edge of and the bottom of electrode with the machining of holes. Thickness of the carbon layer, micro topography and experimental results were analyzed. Low current and big pulse duration can reduce the electrode wear rate. Although carbon on the electrode surface can be wiped out easily, wear rate of copper-tungsten electrode decreases with the increasing in thickness of the carbon at the initial phase. There are fewer cracks and residue presented on the machined surface by microscope.

Can we Modulate the Autonomic Nervous System to Improve the Life of Patients with Heart Failure? The Case of Vagal Stimulation.

An imbalance of the autonomic nervous system, with reduced vagal and increased sympathetic activity, contributes to pathogenesis and clinical deterioration in heart failure (HF). Experimental studies have demonstrated that vagal stimulation (VS) has an antifibrillatory effect that has proved beneficial in animal models of HF. The potential value of chronic VS in man was first investigated with an implantable neuro-stimulator capable of delivering low current pulses with adjustable parameters to stimulate the right vagus. The results of a pilot study and a small multicentre clinical trial of VS in HF patients appeared to show a favourable clinical effect, and feasibility and safety data were encouraging. An ongoing pivotal clinical trial will provide a definitive assessment of the efficacy and usefulness of chronic VS in HF patients.This approach represents a new and exciting possibility for the management of HF that will provide clinicians with a novel tool to modulate non-pharmacologically the autonomic nervous system in patients with moderate-to-advanced HF.

Time resolved tunable diode laser absoption spectroscopy of dual High Power Impulse Magnetron Sputtering discharges

Time-resolved measurements have been performed during dual High Power Impulse Magnetron Sputtering (dual-HiPIMS) with two cathodes in a closed magnetic field configuration. The dual-HiPIMS system, operated at a repetition frequency f = 100 Hz and duty cycle of 1 %, was equipped with two different metallic targets (Ti, Cu). The effect of a delay between subsequent pulses on argon excited atom density and temperature was investigated by means of tunable diode laser absorption spectroscopy. It is shown that the peak densities of pulses vary strongly with the delay. We observed an enhancement of metastable density due to pre-ionization effect but more effective than that is the contribution of metal atoms which have smaller ionization energy compare to that of buffer gas atom. Associate with the enhancement of density, the temporal variation of metastable atom temperature in the Cu pulse also transforms from those of low current pulse into the high current one.