Bipolar Current Pulses Research Articles

Braiding Operations for a Topological Josephson Junction Array Using a Bipolar Current Pulse Generator Controlled by SFQ Logic Circuits

Braiding Operations for a Topological Josephson Junction Array Using a Bipolar Current Pulse Generator Controlled by SFQ Logic Circuits

A Finite Element Approach for Forearm Neuromodulation: Impact of Electrode Size on the Current Density

Electrical impedance myography is a transcutaneous neuromodulation method for assessing muscle conditions through the application of a high-frequency, low-intensity current to the muscle region of interest (ROI). It has been shown that the mechanisms underpinning these findings are controversial as studies showed that the current reaching the target structure may not be enough to activate tissue due to various factors. It has been shown that anatomical properties as well as non-anatomical factors including electrode shape and size, inter-electrode distance may affect the outcome. This study was conducted to investigate the impact of the different sizes of the electrodes on the current density of the ROI. It may not be feasible to investigate these parameters impact on the outcome using experimental procedures. Alternatively, the computational methos have been used as a tool to study electrical stimulation of bio-computational models. The neuromodulators can be designed and developed using such advanced methods. This study investigates the impact of the electrode size on the current distributions. The fundamental anatomical layers of the human forearm were generated based on standard dimensions using concentric shapes. A sinusoidal bipolar current pulse was applied on the different sizes of electrodes to simulate current distribution within the associated anatomical layers. It was shown that the electrode size has a significant impact on the induced current density of the target anatomical layer.

Semi-Airborne UAV-TEM System Data Inversion with S-Plane Method—Case Study over Lake Baikal

The article presents the results of transient electromagnetic (TEM) prospecting surveys using an unmanned aerial system carried out at Lake Baikal, which is a unique geoelectrical setting where low-resistivity lacustrine sediments are located under a relatively isotropic water body. The task was to investigate the possibility of using a drone-based TEM survey to delineate the electrical stratigraphy of the subsurface at depths between 50 and 300 m, separated into layers and blocks. A new version of the SibGIS UAV-TEM unmanned system was used, significantly improved compared to the prototype previously described in the literature. The current switch providing bipolar current pulses connected to a grounded electrical line was the source of the electromagnetic field in the geological environment. The hexacopter carrying a measuring system consisting of 18-bit ADC and sensor—analog of 50 × 50 loop, was the receiving system. We measured survey data of 16 traverses over the Baikal going from the shore to the depths. Significant attention is being paid to a new approach to data inversion. For fast interpretation of the TEM data, we used the Sτ-method, which allows for tracing the change in the apparent longitudinal conductivity with depth. It is shown that thanks to the new sensor and current switch, the data quality has increased significantly; now, the UAV system can register sounding curves up to 1 ms. As a result, new data on the geological structure of the shelf zone of Lake Baikal were obtained. They had a good fundamental agreement with the predecessor data obtained from terrestrial measurements (from ice cover), allowing us to conclude that the UAV-TEM technology can already replace conventional ground-based electromagnetic surveys.

High versus low frequency transcutaneous acupoint electrical stimulation as an adjunct therapy to prevent nausea and vomiting in the first 24 hours after infusion of high-grade emetic chemotherapy: A randomized controlled trial

Background: Transcutaneous acupoint electrical stimulation (TAES) has been tested as antiemetic therapy. Objective: Evaluation of the effectiveness of two different frequencies of the electrical current as adjunctive therapy in the prevention of nausea and vomiting. Methods: This placebo-controlled clinical trial compared the incidence of nausea and vomiting (within the first 24 hours after high-grade emetic chemotherapy infusion) of 61 women (54 ± 11 years) with breast cancer undergoing three modes of TAES: high frequency (HF:150 Hz), low frequency (LF:10 Hz), and placebo (P). Electrodes were fixed at the acupuncture point PC6 and a symmetric bipolar current (pulse width 200 μs) was applied in a single 30-minute session prior to the start of chemotherapy infusion. All patients receive fixed antiemetic treatment infusions (ondansetron 8 mg) and rescue medication instructions, if necessary, according to the routine for infusions of cyclophosphamide associated with anthracycline. Results: The incidence of nausea was 47% in P, 45% in HF and 26% in LF. Although not significant, the intervention with LF-TAES at PC6 acupoint reached relevant values in reducing the relative risk of developing nausea (RR = 0.51; CI 95% = 0.18 to 1.44; p = 0.18) and a trend toward improved reported well-being (p = 0.06) and a lower Edmonton Symptom Rating Scale score (p = 0.08). The incidence of vomiting and the consumption of rescue antiemetic doses were very similar between the groups. Conclusion: New studies with LF and HF of TAES as adjuvant therapy for the prevention of nausea and vomiting should be carried out to confirm this hypothesis.

The use of the combined anesthesia method using local anesthesia and percutaneous electroneurostimulation for dental implantation

The purpose of the work: to conduct a comparative assessment of the adequacy of pain relief based on the study of the dynamics of pain indicators, the autonomic nervous system and the psycho-emotional status of patients with a combination of local anesthesia and percutaneous electroneurostimulation.
 Materials and methods. 40 patients aged 38 to 63 years took part in the study. The number of patients in the first group amounted to 20 people aged 38 to 63 years, and they all completed the study. In the first group, only local anesthesia (MA) was used by a 4% solution of articaine with epinephrine in a concentration of 1: 200000. In the second group, the number of patients was 20 people aged 38 to 60 years, and all of them also completed the study. In the second group — a combination of percutaneous electroneurostimulation (Chens) with subsequent local anesthesia (Chens+Ma); Electroneurostimulation was carried out using the EPB50-01 Electronics device (Russia), which generates bipolar asymmetric current pulses of 20 s and a frequency of 10 imp/s. The intensity of electroneurostimulation was selected individually until the patient achieve intense non -pain sensations.
 Results. The use of percutaneous electroneurostimulation potentiates the analgesic effect of local anesthesia in the intraoperative period and has a prolonged analgesic effect, which manifests itself in a decrease in the intensity of pain throughout the postoperative period. Analysis of the features of the action of percutaneous electroneurostimulation indicates that this effect is due to exacerbation of not pain sensitivity, but by sensitization (exacerbation of sensitivity) of non -column peripheral nerves and oral trigeminal core, transmitting signals from receptors that are excited with no damaging effects (touches, displacement of tissues). This sensitization can develop as a result of prolonged preliminary electroneurostimulation, which was carried out before the injection. Against the background of sensitization of sensation from any mechanical effects on the tissue, more acute will be perceived, which was evaluated by patients as more intense pain. This feature of the action of percutaneous electroneurostimulation must be taken into account when compiling methods of its application in clinical practice.
 Conclusion. The use of percutaneous electroneurostimulation creates favorable conditions for the period of adaptation and integration of implants in the early stages of the postoperative period.

Characterization of the initial stage in upward lightning at the Gaisberg Tower: 2. Electric field signatures

• Near and far electric field signatures of IS current pulses were analyzed. • Electric field signatures of early-stage-IS bipolar current pulses were characterized. • Such bipolar pulses could be associated with upward leader inception. We examined the characteristics of electric field signatures occurring during the initial stage of 58 flashes measured simultaneously at near (170 m) and far (79 or 109 km) distances from the Gaisberg Tower located near Salzburg, Austria. Of the 340 field signatures measured at the near station, 68 (20%) were associated with current pulses occurring during the initiation and propagation phase (IPP) of the upward leader, and 272 (80%) were associated with pulses that occurred during the mature phase (MP) of the upward leader. Of the 68 field signatures of IPP pulses, 40 were associated with bipolar (IPP-B type) current pulses and 28 were associated with unipolar (IPP-U type) current pulses. Field signatures of IPP-B pulses were only detected at the near measurement station and appear to be associated with currents in relatively short (meter-scale) channel segments formed during the upward leader inception. At the far stations, field signatures of 84 IS pulses were recorded and analyzed. There was modest correlation between the background-to-peak current of IS pulses and near and far electric radiation field changes as well as between radiation field changes recorded at near and far distances.

Characterization of the initial stage in upward lightning at the Gaisberg Tower: 1. Current pulses

• Upward-flash IS current is comprised of slowly varying and impulsive components. • 60% of IS current pulses were bipolar and 40% were unipolar. • Bipolar current pulses only occurred at early times (within first 15% of IS duration). We examined current waveforms for 58 upward flashes occurring in 2006–2014 initiated from the Gaisberg Tower located near Salzburg, Austria. The initial stage (IS) of these flashes comprised of relatively slowly varying “background” current, with faster, more impulsive current variations overlaid on this background current. In 46 of the 58 flashes (79%) the background continuing current was negative, and in the other 12 flashes (21%) it was bipolar. 1180 current pulses occurred during the IS of these 58 flashes, of which 708 (60%) were positive bipolar (positive initial polarity with a negative opposite polarity overshoot), 28 (2.4%) were positive unipolar (positive initial polarity with no opposite polarity overshoot), 440 (37%) were negative unipolar, and four (0.3%) were negative bipolar pulses. We found that bipolar current pulses only occurred in the IS at early times. We divided the IS current into two phases: (1) upward leader initiation and propagation phase (IPP) and (2) upward leader mature phase (MP). 901 or 76% (712 bipolar and 189 unipolar) pulses occurred during the IPP, and 279 or 21% (unipolar) pulses occurred during the MP. The median background-to-peak current was 134 A for IPP pulses and 687 A for MP pulses.

Bipolar Waveform Synthesis With an Optically Driven Josephson Arbitrary Waveform Synthesizer

An array of Josephson junctions (JJs) was driven with photonically generated current pulses to synthesize a high-fidelity 1 kHz bipolar voltage waveform with a quantum-based amplitude that can be directly related to fundamental constants. A photodiode capable of producing high average photocurrent was used to generate large-amplitude current pulses that were ac-coupled to a JJ array. The resulting bipolar current pulses have enabled the first demonstration of quantum-based bipolar waveform synthesis with an optical drive. We measured the quantum locking range with respect to several operating parameters, including 1.2 mA with respect to a dc bias current applied to the array, confirming the robust synthesis of bipolar waveforms.

Research of micro EDM/ECM method in same electrolyte with running wire tool electrode

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C1, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.

Precision electrochemical machining of tungsten micro-rods using wire electrochemical turning method

The novel wire electrochemical turning (WECT) method has been proposed to machine tungsten with neutral electrolyte and bipolar pulse current in the authors’ previous research. The influence of tool wear caused by the bipolar pulse current, which is needed to remove the oxide layer generated on tungsten surface when using a neutral electrolyte, was eliminated by the WECT method because the wire tool electrode was kept being wound during the machining process. In this paper, the influences of the most important process parameters, such as the kind of electrolyte, wire material, wire diameter, rotation speed of the workpiece rod, and frequency of the pulse voltage, were studied to understand the fundamental aspects of the WECT method and improve the machining efficiency of tungsten micro-rods. The experimental results showed that the NaCl electrolyte and the NaNO3 electrolyte had higher machining efficiency and better machining accuracy, respectively. The machining accuracy was improved with the SUS304 stainless steel wire used as tool electrode than the brass wire tool electrode. It was also found that the machining efficiency and accuracy were improved with decreasing the wire diameter and increasing the rotation speed of workpiece because the influence of stray current flowing through the side and end surface of machined micro-rod was reduced. The machinable length of micro-rod peaked at an optimum feed speed of the workpiece, and the optimum speed increased with increasing the frequency of pulse voltage. As a result, a minimum rod diameter of 11 μm was fabricated with a high aspect ratio of 36. Compared with the previous method using a platinum film as tool electrode, the aspect ratio was increased significantly because the influence of tool wear was eliminated.

Effects of basal forebrain stimulation on the vibrotactile responses of neurons from the hindpaw representation in the rat SI cortex.

Basal forebrain (BF) cholinergic system is important for attention and modulates sensory processing. We focused on the hindpaw representation in rat primary somatosensory cortex (S1), which receives inputs related to mechanoreceptors identical to those in human glabrous skin. Spike data were recorded from S1 tactile neurons (n = 87) with (ON condition: 0.5-ms bipolar current pulses at 100Hz; amplitude 50μA, duration 0.5s at each trial) and without (OFF condition) electrical stimulation of BF in anesthetized rats. We expected that prior activation of BF would induce changes in the vibrotactile responses of neurons during sinusoidal (5, 40, and 250Hz) mechanical stimulation of the glabrous skin. The experiment consisted of sequential OFF-ON conditions in two-time blocks separated by 30min to test possible remaining effects. Average firing rates (AFRs) and vector strengths of spike phases (VS) were analyzed for different neuron types [regular spiking (RS) and fast spiking (FS)] in different cortical layers (III-VI). Immediate effect of BF activation was only significant by increasing synchronization to 5-Hz vibrotactile stimulus within the second block. Regardless of frequency, ON-OFF paired VS differences were significantly higher in the second block compared to the first, more prominent for RS neurons, and in general for neurons in layers III and VI. No such effects could be found on AFRs. The results suggest that cholinergic activation induces some changes in the hindpaw area, enabling relatively higher increases in synchronization to vibrotactile inputs with subsequent BF modulation. In addition, this modulation depends on neuron type and layer, which may be related to detailed projection pattern from BF.

Electromagnetic soundings of the earth crust and deformation processes in geosphere of the Bishkek geodynamic polygon (BGP)

A new processing of materials on variations of seismicity of the Bishkek geodynamic polygon (BGP) under effect of electromagnetic (EM) soundings of geological medium has been carried out. The revision of these materials is topical due to following issue. During the period of 1983-1989 the disharges of the capacitor battery (so-called cold runs) were used for supply for EM soundings in addition to the MHD generator launchs (hot, or fire runs). Moreover, alternative source of EM soundings by bipolar current pulses (namely, the ERGU-600-2 equip) was used in the times of 90s. But previous studies paid low attention to electric injection to Earth Crust besides MHD generator hot runs. Motivated by such state of the art we have analysed temporal dependence of Benioff strain on the territory of the BGP in the overall period of EM soundings (from 1983 up to now). The alterations of EM soundings sources and operational modes have been taken into account. But our approach has reveal no no noticeable change seismic regime (by the Benioff strain data) during the nineties in close surrounding of the injecting dipole.

Bipolar Pulse-Induced Coexisting Firing Patterns in Two-Dimensional Hindmarsh–Rose Neuron Model

In this paper, a bipolar pulse (BP) current is taken to mimic a periodic stimulus effect on the membrane potential in the axon of a neuron. By introducing the BP current to substitute the externally applied constant current, a BP-forced two-dimensional Hindmarsh–Rose (HR) neuron model is proposed. Based on the proposed neuron model, the BP-switched equilibrium point and its stability evolution with the periodic variation in time are explored. Furthermore, coexisting asymmetric attractors (or coexisting firing patterns) with bistability are revealed by phase plane orbits, time sequences, and attraction basins, as well as the BP-induced coexisting asymmetric attractors’ behaviors are then elaborated through bifurcation analysis. The research results exhibit that, with the increase of the time, the stabilities of the neuron model are continually switched between an unstable node-focus and a stable point, resulting in the coexisting behaviors of numerous asymmetric attractors under the specified initials. Consequently, the newly introduced BP current stimulus, instead of the original constant current stimulus, allows the two-dimensional HR neuron model to possess complex dynamical behaviors for the membrane potential. Additionally, a hardware breadboard is fabricated and circuit experiments are carried out to validate the numerical simulations.

Interplay of the photon drag and the surface photogalvanic effects in the metal-semiconductor nanocomposite

Photon drag effect (PDE) and surface photogalvanic effect (SPGE) can be observed in centrosymmetric media and manifest themselves in photocurrents, the magnitude and polarity of which depend on wavevector and polarization of the excitation laser beam. PDE photocurrent originates from the transfer of the photon momentum to a free charge carrier, while SPGE photocurrent is due to diffuse scattering of the photoexcited carriers in the subsurface layer. However, despite the different underlying physical mechanisms, these photocurrents have almost indistinguishable dependencies on the polarization and the angle of incidence of the excitation laser beam. In this paper, we observe for the first time a competition between PDE and SPGE in the film containing metal (Ag-Pd) and semiconductor (PdO) nanocrystallites. We show that, depending on the angle of incidence, polarization azimuth and wavelength of the excitation laser beam, the interplay of the PDE and SPGE leads to the generation of either monopolar or bipolar nanosecond current pulses. The experiments performed allow us to visualize the contributions both these effects and obtain light-to-current conversion efficiency in a wide spectral range. Our experimental findings can be employed to control the magnitude and polarity of the light-induced current by polarization of the excitation laser beam.

Bipolar Triangular Wave Current Pulse Inverter for Shallow TEM Survey

A bipolar triangular wave current pulse inverter for shallow TEM survey is described. It can generate a peak current more than 10A and the PRF of the bipolar current pulse is between 1Hz and 10kHz. The proposed inverter contains a high voltage source circuit for the rising edge and a Zener diodes circuit with constant voltage clamping for the falling edge. Measurement results are presented, which show the high quality triangular wave current pulse with linear rising edge and rapidly turnoff falling edge.

Control systems of high-voltage transistor switches

Control systems of high-voltage transistor switches are described. Possible ways to develop these systems are considered. A control system of the transistors of a high-voltage switch on the basis of a current loop is considered in detail. Signals for turning the transistors on and off arrive to their control boards from their common conductor with bipolar current pulses. A positive pulse turns the transistors on, while a negative pulse turns them off. The time interval between these pulses sets the time during which the switch is in the conducting state. The minimum duration of the conducting state is several microseconds, while the maximum duration is not limited. The results of tests of a switch prototype with an operating voltage of up to 4 kV are presented. The operation of the switch was demonstrated when obtaining rectangular pulses in the microsecond range across a resistive load. We also verified the possibility of forming pulses of damped oscillations at a frequency of 1 MHz by this device. The positive test results make it possible to develop switches for operating voltages of tens of kilovolts using the considered approach.

A DC voltage converter with a series resonant inverter and asymmetric control of power transistors

The interest in dc converters with a series resonant inverter (resonant converters) is due to the fact that they easily realize switching of semiconductor devices at zero current and zero voltage in a device. This makes it possible to significantly reduce power losses during switching of semiconductor devices and to realize the operation of a dc–dc converter at higher frequencies with a high efficiency. In the foreign literature, many circuits of resonant converters are described and many results of experimental studies are presented. However, the theory of such converters has not been sufficiently developed and theoretical studies are conducted using approximate methods, for example, fundamental-harmonic method. This paper describes the operating principle of the power part of a dc–dc converter with a series resonant inverter with asymmetric control in the discontinuous conduction mode (DCM), when the switching frequency is less than the resonance frequency of the LC circuit. The features of symmetric and asymmetric control of the inverter’s power transistors are described, in which bipolar current pulses are formed in half of the switching period. An algorithm for asymmetric control of transistors is proposed, and a scheme for implementing this algorithm on discrete components in the form of a virtual model in the Matlab–Simulink environment is presented. The results of modeling (transient and steady-state conditions, external characteristics, and other dependences), as well as the results of a comparison of the taken and theoretical (constructed from analytical relationships) characteristics, are presented.

Application of a duplex diffusion layer model to pulse reverse plating

The application of Ibl’s duplex diffusion layer model to the analysis of mass transport in pulse reverse plating with bipolar current pulses has been investigated. Although originally proposed to describe normal pulse plating, Yin has recently extended Ibl’s model to include pulse reverse plating. Using the expressions derived by Yin the pulse limiting current density was determined over a wide range of pulse plating conditions, and then compared to values calculated using more accurate numerical solutions. In general, there was good agreement between the two approaches which demonstrated the essential validity of Yin’s extension to Ibl’s original model. The simplified model is most accurate at long duty cycles, small dimensionless pulse times and for low values of the dimensionless pulse reverse current where its underlying assumptions are most likely to be valid. At very long dimensionless pulse times (i.e. T* > 1) the model becomes increasingly inaccurate and its use in these circumstances cannot be justified.

Fabrication of Micro Rods of Cemented Carbide by Electrolyte Jet Turning

Electrolyte jet turning system was developed to machine cemented tungsten carbide rods. Use of flat electrolyte jet enabled easy positioning of the jet relative to the workpiece rod and higher material removal rate than cylindrical jets. Using a bipolar current pulse, both cobalt binder and tungsten carbide were dissolved evenly. Influence of pulse conditions on the current efficiency and machining accuracy was investigated to obtain the optimum pulse conditions. Finer grain size of tungsten carbide resulted in higher material removal and smoother surface. A micro rod of 36μm in diameter and aspect ratio of 20 was successfully machined.

Four-Leg Current-Source Inverter With a New Space Vector Modulation for Common-Mode Voltage Suppression

Common-mode voltage (CMV) is one of the most important issues for the power electronics inverters. An interesting space vector modulation of the three-leg current-source inverter has been reported for the CMV reduction recently. However, it has the disadvantages of the bipolar current pulses and modulation index range limitation. In order to solve these problems, a four-leg current-source inverter with a new space vector modulation is proposed in this paper. With the proposed method, the system CMV can be significantly reduced without bipolar current pulses and modulation index range limitation. Finally, the experimental tests are carried out on a four-leg current-source inverter, and the experimental results verify the effectiveness of the proposed method.