Rectangular Current Pulses Research Articles

A numerical study of a single isolated human ventricular cell response to a periodic pulse stimulus current using the Rogers–McCulloch model

Among the primary causes of cardiac arrhythmias are abnormalities in the generation of action potentials (APs) by the cardiac cells, which may be induced by alterations in the electrophysiological properties of the cells as well as the stimuli delivered to them. Through numerical simulations using the phenomenological model of Rogers–McCulloch, this study examined how external stimuli modulate the electrical activity of a single isolated human ventricular cell functioning under normal conditions. First, we investigated how the initial conditions of the two model state variables affect how the cell responds to a single rectangular current pulse. This allows for the determination of a critical curve, which separates the initial conditions that allow for AP activation from those that inhibit it. This critical curve can be used to predict AP activation not only when the cell is stimulated by a single current pulse but also by a periodic stimulus. Then, we examined the cell response to a periodic train of rectangular current pulses, with a focus on the effects of the stimulus pacing length and amplitude. Our findings demonstrated that, despite not considering any alteration in the dynamics of ionic currents through the cell membrane, the Rogers–McCulloch model was capable of reproducing some of the most common activation patterns that have been widely identified in several clinical, experimental, and numerical studies. Depending on the stimulus properties, the following activation patterns were identified: (1) AP activation in synchrony with the stimulus, with one AP activation per pulse; (2) quasi-periodic and periodic Wenckebach-like patterns, in which successive AP activations are interrupted by a skipped beat; (3) completely irregular patterns; (4) abnormal potential oscillations that interrupt the repolarization of a previously activated AP, followed or not by a skipped beat; and (5) abnormal potential oscillations that completely inhibit cell repolarization.

An All-Solid-State Rectangular Current Pulse Generator Based on Coupling Inductor

To explore the application of pulsed current in biomedicine, an all-solid-state rectangular pulse current generator (RCPG) is proposed. The RCPG uses a field programmable gate array (FPGA) as the control system and a solid-state semiconductor switching metal–oxide–semiconductor field-effect transistor (MOSFET) as the control switch. The RCPG is modular in design, with each module consisting of a diode, a switch, and a coupled inductor. Each inductor of the RCPG is coupled to each other, increasing the energy storage density of the system. When the switch is on, the inductors are charged in series. And when the switch is off, the inductors are discharged in parallel to the load. The energy on the inductor can be superimposed on the load in the form of a current. Through simulation, the principle of RCPG topology and its feasibility is verified. Finally, a five-stage RCPG miniaturized prototype was developed. The experiments show that the RCPG can be adjusted by adjusting the inductor parameters to meet different load requirements, such as biomedical. In addition, the number of modules can be increased to achieve higher current output.

Metallization system as a part of thermal memory

This study aims to substantiate the potential of using “classical” metallization systems as microelectronic thermal memory cells. An experimental simulation is used to demonstrate that thermal information can be stored in memory for a certain time and then read without distortion. The possibility of using thin metal films on single-crystal silicon wafers as thermal memory cells is discussed. An experimental parametric study of “recording” thermal pulses and the temperature dynamics after their interruption is performed. This study uses rectangular current pulses with an amplitude of (1 … 6) × 1010 A/m2 and a duration of up to 1 ms. The temperature dynamics of a “thermal cell” are oscillographically studied up to the critical conditions when the contact area and metal film start degrading. The conditions of interconnections overheating up to the circuit break are considered.

準定常作動2cm級自己誘起磁場型MPDスラスタの推力特性評価

In order to understand the characteristics of the Self-field MPD thruster with a discharge chamber diameter of 2cm, a ground experiment system was constructed and the thrust characteristics were obtained. For the power supply system, a capacitor bank using an electric double-layer capacitor and IGBTs was adopted, and it was confirmed that rectangular discharge current pulses could be output at arbitrary times. In the operation check of the experimental system, the discharge current, discharge voltage, and ion saturation current remained constant during 2ms, confirming the quasi-steady operation of the small MPD thruster for 2ms. Thrust measurement experiments were conducted using argon as the propellant, and a thrust force of 0.9N was confirmed at a maximum discharge current of 2.2kA. The measured thrust was proportional to the square of the discharge current. Therefore, it was confirmed that electromagnetic acceleration was dominant. As the highest propulsive characteristics, a specific impulse of 1800s and a propulsive efficiency of 2.3% were confirmed.

Radiation Power of a Short High-Current Vacuum Arc at High Current Densities

The radiation of a vacuum arc was measured in the spectral region <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\text {nm} \le \lambda \le 1100$ </tex-math></inline-formula> nm. The arc was initiated in the center of the cathode by breaking the current in the auxiliary circuit and was fed by the rectangular current pulse with a duration of 10 ms. The interelectrode gap was fixed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h = 4$ </tex-math></inline-formula> mm, and the butt <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2r =30$ </tex-math></inline-formula> -mm CuCr30 electrodes were used. The arc was stabilized by an external uniform axial magnetic field (AMF). The radiation was coming out of the vacuum chamber through quartz ultraviolet (KU)-1 quartz window. The radiation detector was a silicon photodiode with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d =1.2$ </tex-math></inline-formula> mm. It was located on an axis intersecting the axis of symmetry of the discharge in the center of the interelectrode gap. The distance from the diode to the axis of symmetry was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L =1340$ </tex-math></inline-formula> mm. After amplification, the signal from the diode was recorded on an oscilloscope. The measurements were made in a range of currents from 10 to 25 kA in order to cover the modes with the anodic activity. It was found that under the conditions of these experiments, the anode activity begins to manifest itself at the end of the pulse, starting with currents exceeding 15 kA. As the current increases, the activity begins closer to the beginning of the pulse. Considering the type of the spectral sensitivity of the diode, two series of measurements were made—measurements without a filter and through a yellow filter ZhS-10 that cuts off radiation with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \le400$ </tex-math></inline-formula> nm. The results obtained made it possible to analyze the dependence of the radiation power on the arc current. The results showed that at high current densities in the developed vacuum arc with anodic activity, a significant part of the power is transferred by radiation. At the end of a pulse with a current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 25$ </tex-math></inline-formula> kA, the radiation power is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {uv}}~\approx ~150$ </tex-math></inline-formula> kW, while in the discharge, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{a} ~\approx ~800$ </tex-math></inline-formula> kW is released. That is, at high current densities at the end of the pulse, the radiation power reaches almost 20% of the power released in the arc at this time. Estimates of lateral losses due to radiation are made.

Perception thresholds and qualitative perceptions for electrocutaneous stimulation

Our long-term goal is the development of a wearable warning system that uses electrocutaneous stimulation. To find appropriate stimulation parameters and electrode configurations, we investigate perception amplitude thresholds and qualitative perceptions of electrocutaneous stimulation for varying pulse widths, electrode sizes, and electrode positions. The upper right arm was stimulated in 81 healthy volunteers with biphasic rectangular current pulses varying between 20 and 2000,upmu hbox {s}. We determined perception, attention, and intolerance thresholds and the corresponding qualitative perceptions for 8 electrode pairs distributed around the upper arm. For a pulse width of 150,upmu hbox {s}, we find median values of 3.5, 6.9, and 13.8 mA for perception, attention, and intolerance thresholds, respectively. All thresholds decrease with increasing pulse width. Lateral electrode positions have higher intolerance thresholds than medial electrode positions, but perception and attention threshold are not significantly different across electrode positions. Electrode size between 15 times 15,hbox {mm}^{2} and 40times 40,hbox {mm}^{2} has no significant influence on the thresholds. Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between 150,upmu hbox {s} and 250,upmu hbox {s} are suitable for electric warning wearables. Within the given practical limits at the upper arm, electrode size, inter-electrode distance, and electrode position are flexible parameters of electric warning wearables. Our investigations provide the basis for electric warning wearables.

Dynamics of the transition resistance of Al–(Ti, Ni, Mo)–Si type contacts under conditions of non-stationary electrical loads

This paper analyses the behavioral features of ohmic contacts under the conditions of traditional isothermal annealing. The purpose of this paper is to study the value change of the semiconductor contact resistance when applying electric current pulses of different powers. For the experiments, structures were formed of metal-sublayer-semiconductor wafer Al–(Ti, Ni, Mo)–Si. The quality control of the deposited films was carried out microscopically by the four-probe method. The presented results indicate the solid-phase interaction of components during diffusion annealing Si–Me–Al thin-film systems. This rearrangement of atoms, which occurs with grain-boundary diffusion, significantly affects the electrical and thermal characteristics of the formed contacts. The novelty of the paper is that the optimal parameters of a rectangular current pulse were selected, which made it possible to reduce the value of the transition resistance by 1.6 times.

Analysis of the process of aluminium destruction on the surface of silicon during the electrical explosion of the conductor

The work considers the processes of formation of aluminium melt drops, dispersion of aluminium melts and dynamics along the surface of the semiconductor during the electrical explosion of the metal film. It has been shown that in conditions of flow of rectangular high-density current pulses (amplitude jmax=2· 1011 A/m2 and duration up to 2.0 ms), an electrical explosion of a conductor occurs through a test structure based on aluminium film (thickness 5 μm). Dispersion of up to 30% of the mass of the aluminium film is observed. It has been established that the main parameter characterizing the dispersion during the destruction of an aluminium film is the energy of an electrical pulse. The distribution of rounded aluminium particles by size (diameter) has been determined experimentally. It has been found that the largest number of particles in the conditions considered are 1-3 μm in size. Keywords: non-stationary states, heat shock, formation of drops on the surface, non-stationary surface mass transfer.

Анализ процесса разрушения алюминия на поверхности кремния при электрическом взрыве проводника

The work considers the processes of formation of aluminium melt drops, dispersion of aluminium melts and dynamics along the surface of the semiconductor during the electrical explosion of the metal film. It has been shown that in conditions of flow of rectangular high-density current pulses (amplitude j=8.1010 A/m2 and duration up to 2.5 ms), an electrical explosion of a conductor occurs through a test structure based on aluminium film (thickness 3 μm). Dispersion of up to 30% of the mass of the aluminium film is observed. It has been established that the main parameter characterizing the dispersion during the destruction of an aluminium film is the energy of an electrical pulse. The distribution of rounded aluminium particles by size (diameter) has been determined experimentally. It has been found that the largest number of particles in the conditions considered are 1-3 µm in size.

Low-Frequency Intravesical Electrical Stimulation for the Treatment of Acute Urinary Retention: A Promising Therapeutic Approach.

Acute urinary retention (AUR) is a troublesome urological disease, which causes various lower urinary tract symptoms. However, only few studies explored and evaluated the effective treatments to improve AUR. We aimed to find an effective approach to cure AUR through comparing the efficacy of existing classical low-frequency transcutaneous electrical nerve stimulation (TENS) and novel intravesical electrical stimulation (IVES). A total of 24 AUR female rats were divided into 3 groups as follows: control, TENS, and IVES groups. Rats in the control group had no fake stimulation. Rats in the TENS and IVES groups underwent transcutaneous or intravesical stimulation of a symmetrical biphasic rectangular current pulse with a frequency of 35 Hz, 30 min per day, for seven consecutive days. IVES significantly reduced the actin expression in the submucosal layer but increased its expression in the detrusor layer (p = 0.035, p = 0.001). The neovascularization in the submucosal layer in the IVES group was significantly increased than in the other 2 groups (p = 0.006). Low-frequency IVES performed better than TENS in terms of simultaneously relieving bladder hyperactivity, accelerating epithelial recovery, and strengthening detrusor muscle. IVES may be a promising therapeutic approach for bladder dysfunction, specifically for AUR and overactive bladder in clinical practice.

Rectangular current pulse generator to test varistors with pulsed electrical load

A brand-new circuit of a rectangular pulse current generator is presented. As a rule, generators consisting of 6-10 LC cells connected in series are used to obtain rectangular current pulses. Such units are very cumbersome and complicated in the selection of element parameters and adjustment, so a new scheme of pulse current generator was proposed. The main difference from the classical circuit is the method of generating a rectangular current pulse, i.e. by adding the currents from two parallel circuits connected to the load. The first circuit at discharge generates an aperiodic current pulse, the second generates an oscillatory current pulse. The total current pulse flowing through varistor has constant amplitude for some time. In a specified period of time, while the current pulse has a constant amplitude, there is an interruption of current with the help of a switching device. The given circuit solution is possible to implement when using fundamentally new switching devices of the IGBT module. A connection diagram of a pulse current generator for testing varistors with a classification voltage to 1200 V with adjustable pulse duration of 50, 1000, 2000 µs is proposed. The parameters of the generator circuit elements are determined. The measures aimed at suppression of overvoltages arising at break of current in circuits with high inductance as well as the tests confirming the operability of the designed circuit are carried out.

Моделирование температурного режима, мониторинг и прогнозирование перегрева болтовых контактных соединений токоведущих шин

The widely used infrared imaging control of bolted connections in live rectangular buses is performed without direct access to the object being diagnosed. This gives only an approximate idea of the contact state, whereas the contact layer condition remains poorly known. The high thermal conductivity of the live bus material makes the thermal field pattern near the contact connection rather soft, which significantly adds complexity to the diagnostics. Therefore, it is important to develop diagnostics of contact connections by dynamic methods based on analyzing the thermal effect of rectangular test or quasi-rectangular operational current pulses in the busbars of electrical installations. By analyzing the temperature field dynamics in the flat contact zone it becomes possible to establish a functional relationship between the contact zone temperature and the bus free surface temperature, and also the relationship between the temperature recorded on the bus surface and the transition resistance, which is the contact quality characteristic. It has been shown, by simulating the contact surface temperature control in the dynamic monitoring mode, that it is possible to determine the rectangular bus bolted connection overheating protection response time. It is proposed to use the obtained dependence as a conversion function for an intelligent electrical contact temperature sensor.

State of Stress in the Near-Contact Region of a Semiconductor during Metallization Track Electrodegradation

Heating of a thin metal film on a semiconductor surface and the corresponding state of stress of the near-contact region are considered. The stress estimation procedure in case of the local pulsed heating of a metallized region on the semiconductor surface is described. The theoretical and experimental sizes of the deformed silicon substrate region are compared with each other. An experiment is carried out using rectangular current pulses. The stress–strain region, which depends on the electric pulse duration and amplitude, is estimated. Experimental evidence shows a strong heterogeneity of the metallization track after pulse passage.

Sensation thresholds in electrocutaneous stimulation

Abstract Acoustic or visual warning signals for workers in hazardous situations might fail under loud and/or lowvisibility work situations. A warning system should be developed that uses electrocutaneous stimulation through textile electrodes. Previous work investigated suitable stimulation parameters using TENS electrodes. The aim of this study was to compare TENS and textile cuff electrodes in terms of sensation thresholds, qualitative and spatial sensation. A study on 30 healthy volunteers (f=13, m=17) of mean age of 26.7 years was conducted applying bi-phasic rectangular current pulses to electrodes attached to the upper right arm. The study revealed that perception, attention and intolerance thresholds, qualitative and spatial perception are comparable indicating that future studies with the textile cuff electrodes can be generally based on the previous results with TENS electrodes.

Pulse power supply of diode-pumped solid-state lasers

Recently, solid-state pumped semiconductor lasers have become increasingly widespread. Lasers of this type have several advantages over solid-state lasers with lamp pumping. First of all, this is high efficiency, long service life, small dimensions and weight. The use of semiconductor laser diodes for pumping solid-state active media imposes a number of rather stringent requirements on the power sources of laser diodes. The power source should provide rectangular current pulses with a flat top, a steep leading edge of the pulses and the absence of reverse current surges at the trailing edge.A pulsed power source for a diode pump system of a ytterbium-erbium laser was developed, manufactured and studied. In this source, the control unit provides functions for protecting the load in emergency conditions, controlling the charge of the storage capacitors to the required voltage and generating current pulses to power the laser diode line. The current is regulated by a field effect transistor operating in a linear mode. The load is included in the source circuit of the field-effect transistor, and the reference signal is generated by the DAC of the microcontroller. Such an approach made it possible to create a relatively simple, reliable and small-sized laser power source with a wide range of adjustment of the duration and amplitude of current pulses. This makes it possible to select the optimal operating mode depending on the characteristics of the active medium of the laser. Particular attention is paid to solving the problems of protecting expensive rulers of laser diodes from failure. The developed source can be used to pump other solid-state lasers with shorter lifetimes of the upper laser level than erbium.

Contactless galvano-magnetics transducers of monitoring and control systems in agricultural energy

The paper provides information on the state of the use of direct current energy in the electric power industry of agriculture and water resource, hydraulic engineering, industry and metallurgy, irrigation, and land reclamation. Identified the need for contactless non-destructive testing of large constant currents in high-power electrical installations in irrigation, land reclamation, and hydraulic engineering. The basic requirements for contactless transducers and meters of large direct currents in circuits without breaking them are shown. Identified priority areas in the development of these transducers. The general principles of constructing contactless ferromagnetic transducers of large direct currents also the basic requirements for them and the results of the development of one of the options for the development of effective innovative galvano-magnetic contactless transducers of large direct currents with an expanded range of monitoring and control systems for powerful pumping stations in water supply and land reclamation are presented. To increase the sensitivity of galvanomagnetic contactless transducers of large direct currents, Hall transducers have supplied with short-term rectangular current pulses from a special generator. When measuring the amplitude values of the rectified current, in this case of galvanomagnetic contactless transducers, the supply of pulses of the control current of the Hall transducers with the converted current in the bus synchronization is provided. This is achieved by supplying galvano-magnetic contactless transducers of large direct currents with a magnetically controlled contact located near the bus with the converted current and included in the circuit of the current electrodes of the Hall transducers.A static characteristic of the developed galvano-magnetic contactless transducer of high currents obtained and its main technical characteristics and parameters are given. It is shown that the developed transducer, unlike the known ones, has increased accuracy and sensitivity, a technological design, and low weight and dimensions at low material consumption and cost. It can be widely used in electrical systems in land reclamation and irrigation, in water supply, industry, rail transport, science, technology, and for checking electric meters at the installation site.

Demonstration of a 1 MJ XRAM Generator Supplying a Medium Caliber Railgun

The electric power supply for an electromagnetic launcher has to provide energy in the mega-joule range within an acceleration time which only lasts for milliseconds. Today’s giga-watt pulsed power generators are based on large capacitor banks and are therefore unsuitable for most mobile applications. Thus, power supply research focuses on size reduction by means of alternative technologies like inductive storage. The XRAM topology, where several inductors are charged in a series and discharged in a parallel connection, is a concept for inductive current multiplication. This technique requires simultaneous switching of closing and opening switches and was realized by using thyristors turned off by a counter-current pulse (inverse current commutation with semiconductor devices - ICCOS). At the French-German Research Institute of Saint-Louis (ISL), several aspects of this technology have been investigated and several demonstrators for different energies have been developed. Nowadays, the development of inductive pulsed power generators advances towards energy levels relevant for future applications. This paper presents the development of a 1 MJ XRAM generator which demonstrates the suitability of this technology by supplying the medium-caliber ISL railgun RAFIRA during dynamic experiments. The results of the latest experiment are reported, where the XRAM generator was charged to 842 kJ. A current of 40 kA was successfully interrupted by the ICCOS opening switches and an 80 g brush projectile was accelerated to 1120 m/s. The railgun current was switched off at the time of the projectile’s bore-exit, thus approximating a rectangular current pulse shape. Experimental results are compared to outcomes achieved with capacitor banks as railgun power supply.

Soft magnetic amorphous alloys in X-ray light: Insights from ultra-fast Joule heating experiments

In this contribution a novel setup for studying rapid crystallization of metallic glasses using a time resolved in situ X-ray diffraction combined with a direct current fast Joule heating (flash-annealing) is presented. The setup was implemented and successfully tested at the P02.1 beamline of the PETRA III storage ring (DESY Hamburg, Germany). Its potential use is demonstrated by studying rapid crystallization of soft magnetic Fe73.5Cu1Nb3Si15.5B7 (at.%) metallic glass prepared by melt spinning technique. Flash-annealing experiment is realized by bursting 20 rectangular current pulses with a fixed amplitude of 1.5 A and pulse length δ is varied (30, 40 and 50 ms). A single pulse with duration of 30 ms causes temperature to rise to 770 °C with an average heating rate of 4200 K/s. Phase composition of crystallized material consist of major Fe3Si phase and small traces of boride phase Fe23B6. Consecutive pulses result in cyclic thermal expansion of a crystal lattice, which appears fully reversible. Increasing pulse width to 50 ms causes temperature to increase up to 1020 °C with an average heating rate of 5600 K/s. Differentiation of the temperature profile yields exceptionally high value of heating rate 10800 ± 2400 K/s.

The propagation of temperature pulsations along the free surface of a liquid layer from a linear heat source

The evolution of the temperature field on the free surface of a fluid near a periodically heated wire is experimentally investigated. The wire was heated by rectangular current pulses with specified duration and pulse repetition period. The data on the spatial characteristics of thermal waves and the propagation velocity of a thermal wave are presented. Using digital video of the visualized fluid flow, the structure of the unsteady convective fluid flow was studied

Recording of pulsed currents by a fibre-optic Faraday effect-based sensor with limited frequency band

We have studied, experimentally and theoretically, the dependence of the amplitude and noise response parameters of a fibre-optic Faraday effect-based current sensor on the photodetector frequency band in recording rectangular current pulses, the duration of which does not exceed the time of light propagation through the sensing fibre. The presence of an optimal band at which the signal-to-noise ratio has a pronounced maximum is demonstrated. It is shown that the optimal bandwidth is close in magnitude to the inverse time of light passage through the fibre. The revealed feature is explained by the difference in dependences of the response amplitude and the white noise level of optical radiation on the frequency band of the photodetector. A technique for amplitude error correction at the optimal band is proposed.