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1
Kandratsyeu, Aleh, Uladzimir Sabaleuski, Luis Redondo, and Andrei G. Pakhomov. "Four Channel 6.5 kV, 65 A, 100 ns–100 µs Generator with Advanced Control of Pulse and Burst Protocols for Biomedical and Biotechnological Applications." Applied Sciences 11, no. 24 (December 11, 2021): 11782. http://dx.doi.org/10.3390/app112411782.
Повний текст джерелаАнотація:
Pulsed electric fields in the sub-microsecond range are being increasingly used in biomedical and biotechnology applications, where the demand for high-voltage and high-frequency pulse generators with enhanced performance and pulse flexibility is pushing the limits of pulse power solid state technology. In the scope of this article, a new pulsed generator, which includes four independent MOSFET based Marx modulators, operating individually or combined, controlled from a computer user interface, is described. The generator is capable of applying different pulse shapes, from unipolar to bipolar pulses into biological loads, in symmetric and asymmetric modes, with voltages up to 6.5 kV and currents up to 65 A, in pulse widths from 100 ns to 100 µs, including short-circuit protection, current and voltage monitoring. This new scientific tool can open new research possibility due to the flexibility it provides in pulse generation, particularly in adjusting pulse width, polarity, and amplitude from pulse-to-pulse. It also permits operating in burst mode up to 5 MHz in four independent channels, for example in the application of synchronized asymmetric bipolar pulses, which is shown together with other characteristics of the generator.
2
Shirokova, N., G. Pizarro, and E. Ríos. "A damped oscillation in the intramembranous charge movement and calcium release flux of frog skeletal muscle fibers." Journal of General Physiology 104, no. 3 (September 1, 1994): 449–76. http://dx.doi.org/10.1085/jgp.104.3.449.
Повний текст джерелаАнотація:
Asymmetric membrane currents and calcium transients were recorded simultaneously from cut segments of frog skeletal muscle fibers voltage clamped in a double Vaseline-gap chamber in the presence of high concentration of EGTA intracellularly. An inward phase of asymmetric currents following the hump component was observed in all fibers during the depolarization pulse to selected voltages (congruent to -45 mV). The average value of the peak inward current was 0.1 A/F (SEM = 0.01, n = 18), and the time at which it occurred was 34 ms (SEM = 1.8, n = 18). A second delayed outward phase of asymmetric current was observed after the inward phase, in those experiments in which hump component and inward phase were large. It peaked at more variable time (between 60 and 130 ms) with amplitude 0.02 A/F (SEM = 0.003, n = 11). The transmembrane voltage during a pulse, measured with a glass microelectrode, reached its steady value in less than 10 ms and showed no oscillations. The potential was steady at the time when the delayed component of asymmetric current occurred. ON and OFF charge transfers were equal for all pulse durations. The inward phase moved 1.4 nC/microF charge (SEM = 0.8, n = 6), or about one third of the final value of charge mobilized by these small pulses, and the second outward phase moved 0.7 nC/microF (SEM = 0.8, n = 6), bringing back about half of the charge moved during the inward phase. When repolarization intersected the peak of the inward phase, the OFF charge transfer was independent of the repolarization voltage in the range -60 to -90 mV. When both pre- and post-pulse voltages were changed between -120 mV and -60 mV, the equality of ON and OFF transfers of charge persisted, although they changed from 113 to 81% of their value at -90 mV. The three delayed phases in asymmetric current were also observed in experiments in which the extracellular solution contained Cd2+, La3+ and no Ca2+. Large increases in intracellular [Cl-] were imposed, and had no major effect on the delayed components of the asymmetric current. The Ca2+ transients measured optically and the calculated Ca2+ release fluxes had three phases whenever a visible outward phase followed the inward phase in the asymmetric current. Several interventions intended to interfere with Ca release, reduced or eliminated the three delayed phases of the asymmetric current.(ABSTRACT TRUNCATED AT 400 WORDS)
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Baláž, P., M. Gmitra та J. Barnaś. "Current-Pulse-Induced Switching οf Asymmetric Spin Valves". Acta Physica Polonica A 115, № 10 (січень 2009): 278–80. http://dx.doi.org/10.12693/aphyspola.115.278.
Повний текст джерела
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Duving, V. G., Ivan Alekseevich Kazarinov, and Marina Mikhailovna Burashnikova. "A Device for Charging of a Sulfated Lead-Acid Battery by Pulse Asymmetric Current." Electrochemical Energetics 12, no. 1 (2012): 21–24. http://dx.doi.org/10.18500/1608-4039-2012-12-1-21-24.
Повний текст джерелаАнотація:
The capabilities of our designed charging device for charging of lead-acid batteries with sulfated plates by pulse asymmetric current were tested experimentally. The principle of the considered charging mode is based on alternation of short high-amplitude pulses of the charging current with discharging current pulses with their sequence frequency being multiple of the alternating current frequency in Russia (50 Hz). The designed device enables effective charging of lead-acid batteries with deeply sulfated plates, and is suitable for primary battery formation of lead-acid batteries and for restoration of the initial capacity of batteries in the process of their long-term exploitation.
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Rapp, J., P. Braun, W. Hemmert, and B. Gleich. "Optimal pulse configuration for peripheral inductive nerve stimulation." Biomedical Physics & Engineering Express 8, no. 2 (February 18, 2022): 025020. http://dx.doi.org/10.1088/2057-1976/ac52d8.
Повний текст джерелаАнотація:
Abstract Peripheral magnetic stimulation is a promising technique for several applications like rehabilitation or diagnose of neuronal pathways. However, most available magnetic stimulation devices are designed for transcranial stimulation and require high-power, expensive hardware. Modern technology such as rectangular pulses allows to adapt parameters like pulse shape and duration in order to reduce the required energy. Nevertheless, the effect of different temporal electromagnetic field shapes on neuronal structures is not yet fully understood. We created a simulation environment to find out how peripheral nerves are affected by induced magnetic fields and what pulse shapes have the lowest energy requirements. Using the electric field distribution of a figure-of-8 coil together with an axon model in saline solution, we calculated the potential along the axon and determined the required threshold current to elicit an action potential. Further, for the purpose of selective stimulation, we investigated different axon diameters. Our results show that rectangular pulses have the lowest thresholds at a pulse duration of 20 μs. For sinusoidal coil currents, the optimal pulse duration was found to be 40 μs. Most importantly, with an asymmetric rectangular pulse, the coil current could be reduced from 2.3 kA (cosine shaped pulse) to 600 A. In summary, our results indicate that for magnetic nerve stimulation the use of rectangular pulse shapes holds the potential to reduce the required coil current by a factor of 4, which would be a massive improvement.
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Pizarro, G., L. Csernoch, I. Uribe, M. Rodríguez, and E. Ríos. "The relationship between Q gamma and Ca release from the sarcoplasmic reticulum in skeletal muscle." Journal of General Physiology 97, no. 5 (May 1, 1991): 913–47. http://dx.doi.org/10.1085/jgp.97.5.913.
Повний текст джерелаАнотація:
Asymmetric membrane currents and fluxes of Ca2+ release were determined in skeletal muscle fibers voltage clamped in a Vaseline-gap chamber. The conditioning pulse protocol 1 for suppressing Ca2+ release and the "hump" component of charge movement current (I gamma), described in the first paper of this series, was applied at different test pulse voltages. The amplitude of the current suppressed during the ON transient reached a maximum at slightly suprathreshold test voltages (-50 to -40 mV) and decayed at higher voltages. The component of charge movement current suppressed by 20 microM tetracaine also went through a maximum at low pulse voltages. This anomalous voltage dependence is thus a property of I gamma, defined by either the conditioning protocol or the tetracaine effect. A negative (inward-going) phase was often observed in the asymmetric current during the ON of depolarizing pulses. This inward phase was shown to be an intramembranous charge movement based on (a) its presence in the records of total membrane current, (b) its voltage dependence, with a maximum at slightly suprathreshold voltages, (c) its association with a "hump" in the asymmetric current, (d) its inhibition by interventions that reduce the "hump", (e) equality of ON and OFF areas in the records of asymmetric current presenting this inward phase, and (f) its kinetic relationship with the time derivative of Ca release flux. The nonmonotonic voltage dependence of the amplitude of the hump and the possibility of an inward phase of intramembranous charge movement are used as the main criteria in the quantitative testing of a specific model. According to this model, released Ca2+ binds to negatively charged sites on the myoplasmic face of the voltage sensor and increases the local transmembrane potential, thus driving additional charge movement (the hump). This model successfully predicts the anomalous voltage dependence and all the kinetic properties of I gamma described in the previous papers. It also accounts for the inward phase in total asymmetric current and in the current suppressed by protocol 1. According to this model, I gamma accompanies activating transitions at the same set of voltage sensors as I beta. Therefore it should open additional release channels, which in turn should cause more I gamma, providing a positive feedback mechanism in the regulation of calcium release.
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Pirc, Eva, Damijan Miklavčič, Katja Uršič, Gregor Serša, and Matej Reberšek. "High-Frequency and High-Voltage Asymmetric Bipolar Pulse Generator for Electroporation Based Technologies and Therapies." Electronics 10, no. 10 (May 18, 2021): 1203. http://dx.doi.org/10.3390/electronics10101203.
Повний текст джерелаАнотація:
Currently, in high-frequency electroporation, much progress has been made but limited to research groups with custom-made laboratory prototype electroporators. According to the review of electroporators and economic evaluations, there is still an area of pulse parameters that needs to be investigated. The development of an asymmetric bipolar pulse generator with a maximum voltage of 4 kV and minimum duration time of a few hundred nanoseconds, would enable in vivo evaluation of biological effects of high-frequency electroporation pulses. Herein, from a series of most commonly used drivers and optical isolations in high-voltage pulse generators the one with optimal characteristics was used. In addition, the circuit topology of the developed device is described in detail. The developed device is able to generate 4 kV pulses, with theoretical 131 A maximal current and 200 ns minimal pulse duration, the maximal pulse repetition rate is 2 MHz and the burst maximal repetition rate is 1 MHz. The device was tested in vivo. The effectiveness of electrochemotherapy of high-frequency electroporation pulses is compared to “classical” electrochemotherapy pulses. In vivo electrochemotherapy with high-frequency electroporation pulses was at least as effective as with “classical” well-established electric pulses, resulting in 86% and 50% complete responses, respectively. In contrast to previous reports, however, muscle contractions were comparable between the two protocols.
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Шашкин, И. С., А. Ю. Лешко, Д. Н. Николаев, В. В. Шамахов, Н. А. Рудова, К. В. Бахвалов, А. В. Лютецкий та ін. "Излучательные характеристики мощных полупроводниковых лазеров (1060 нм) с узким мезаполосковым контактом на основе асимметричных гетероструктур AlGaAs/GaAs с широким волноводом". Физика и техника полупроводников 54, № 4 (2020): 408. http://dx.doi.org/10.21883/ftp.2020.04.49149.9333.
Повний текст джерелаАнотація:
Light characteristics of narrow-stripe lasers (5.5 m) based on asymmetric AlGaAs/GaAs heterostructures are studied. It was shown that the maximum optical power achieved under continuous-wave (CW) operation is limited by thermal heating and reaches 1695 mW at a current of 2350 mA at +25°C, and the maximum efficiency reaches 54.8 %. By reducing the operating temperature to -8°C, we were able to increase the maximum power to 2 W. A peak power of 2930 mW was obtained under pulsed operation (pulse width 240 ns, amplitude 4230 mA). It is shown there is a region of an “optical dip” in the power profile with a low-efficiency lasing of a train of pulses of sub-ns duration under pulsed operation.
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Bao, Han, Aihuang Hu, and Wenbo Liu. "Bipolar Pulse-Induced Coexisting Firing Patterns in Two-Dimensional Hindmarsh–Rose Neuron Model." International Journal of Bifurcation and Chaos 29, no. 01 (January 2019): 1950006. http://dx.doi.org/10.1142/s0218127419500068.
Повний текст джерелаАнотація:
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.
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Demiyan, V. V., E. A. Zelenskaya, and N. P. Shabelskaya. "Electrolytic Behavior of Nickel in Polarization by Variable Asymmetric Rectangular Current in Alkaline Solutions." Solid State Phenomena 299 (January 2020): 1010–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.299.1010.
Повний текст джерелаАнотація:
The paper presents experimental data on nickel oxidation during electrolysis under rectangular alternating current in alkaline solutions, when the cathode pulse (Iк ) is greater than the anode pulse ( Iа ). During the process, intense nickel destruction occurs forming bivalent oxide powder. Under prolonged electrolysis, this powder deposits at the bottom of the electrolyzer in the form of a sponge. The results obtained can be used to produce active mass in the porous nickel oxide electrode of a chemical current source.
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Lin, Bor-Ren. "Soft Switching DC Converter for Medium Voltage Applications." Electronics 7, no. 12 (December 18, 2018): 449. http://dx.doi.org/10.3390/electronics7120449.
Повний текст джерелаАнотація:
A dc-dc converter with asymmetric pulse-width modulation is presented for medium voltage applications, such as three-phase ac-dc converters, dc microgrid systems, or dc traction systems. To overcome high voltage stress on primary side and high current rating on secondary side, three dc-dc circuits with primary-series secondary-parallel structure are employed in the proposed converter. Current doubler rectifiers are used on the secondary side to achieve low ripple current on output side. Asymmetric pulse-width modulation is adopted to realize soft switching operation for power switches for wide load current operation and achieve high circuit efficiency. Current balancing cells with magnetic component are used on the primary side to achieve current balance in each circuit cell. The voltage balance capacitors are also adopted on primary side to realize voltage balance of input split capacitors. Finally, the circuit performance is confirmed and verified from the experiments with a 1.44 kW prototype.
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Ezhilvannan, Parimalasundar, and Suresh Krishnan. "An Efficient Asymmetric Direct Current (DC) Source Configured Switched Capacitor Multi-level Inverter." Journal Européen des Systèmes Automatisés 53, no. 6 (December 23, 2020): 853–59. http://dx.doi.org/10.18280/jesa.530611.
Повний текст джерелаАнотація:
This paper is dealing about Switched Capacitor Multi-Level Inverter (SCMLI) circuit which is controlled by triangular multicarrier Sinewave Pulse Width Modulation (SPWM) technique. The proposed SCMLI is powered from asymmetric DC source configuration to obtain multi-level output voltage by applying switching pulse to the main circuit from control circuit for switching operation. Fourteen switches and four capacitors are employing to do the proposed inversion operation in an effective way. Switching capacitors can perform boost operation to enhance voltage from the source level to the required level. Input DC from the asymmetric sources is converted to AC voltage for the application of consumers. This proposed conversion system is applicable for mainly in industrial and renewable energy-based energy conversion system because it can carry high output voltages. This proposed method gives about more efficiency. Also reduces switching losses in lower value, low conduction losses and capacitor ripple losses. The simulation model is analyzed in MATLAB/SIMULINK platform and the same validated in hardware results. The developed SCMLI structure is witness over other topologies for the power inversion process in the multi-level.
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Xia, Zhenyuan, Viktoriia Mishukova, Szymon Sollami Delekta, Jinhua Sun, Jaime S. Sanchez, Jiantong Li, and Vincenzo Palermo. "Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors." Nanoscale 13, no. 5 (2021): 3285–94. http://dx.doi.org/10.1039/d0nr07076a.
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Paknahad, Javad, Pragya Kosta, Jean-Marie C. Bouteiller, Mark S. Humayun, and Gianluca Lazzi. "Mechanisms underlying activation of retinal bipolar cells through targeted electrical stimulation: a computational study." Journal of Neural Engineering 18, no. 6 (December 1, 2021): 066034. http://dx.doi.org/10.1088/1741-2552/ac3dd8.
Повний текст джерелаАнотація:
Abstract Objective. Retinal implants have been developed to electrically stimulate healthy retinal neurons in the progressively degenerated retina. Several stimulation approaches have been proposed to improve the visual percept induced in patients with retinal prostheses. We introduce a computational model capable of simulating the effects of electrical stimulation on retinal neurons. Leveraging this computational platform, we delve into the underlying mechanisms influencing the sensitivity of retinal neurons’ response to various stimulus waveforms. Approach. We implemented a model of spiking bipolar cells (BCs) in the magnocellular pathway of the primate retina, diffuse BC subtypes (DB4), and utilized our multiscale admittance method (AM)-NEURON computational platform to characterize the response of BCs to epiretinal electrical stimulation with monophasic, symmetric, and asymmetric biphasic pulses. Main results. Our investigations yielded four notable results: (a) the latency of BCs increases as stimulation pulse duration lengthens; conversely, this latency decreases as the current amplitude increases. (b) Stimulation with a long anodic-first symmetric biphasic pulse (duration > 8 ms) results in a significant decrease in spiking threshold compared to stimulation with similar cathodic-first pulses (from 98.2 to 57.5 µA). (c) The hyperpolarization-activated cyclic nucleotide-gated channel was a prominent contributor to the reduced threshold of BCs in response to long anodic-first stimulus pulses. (d) Finally, extending the study to asymmetric waveforms, our results predict a lower BCs threshold using asymmetric long anodic-first pulses compared to that of asymmetric short cathodic-first stimulation. Significance. This study predicts the effects of several stimulation parameters on spiking BCs response to electrical stimulation. Of importance, our findings shed light on mechanisms underlying the experimental observations from the literature, thus highlighting the capability of the methodology to predict and guide the development of electrical stimulation protocols to generate a desired biological response, thereby constituting an ideal testbed for the development of electroceutical devices.
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Kang, Heebum, Hyun Wook Kim, Eun Ryeong Hong, and Jiyong Woo. "Analog synaptic behavior of mobile ion source-limited electrochemical RAM using CuOx oxide electrode for deep learning accelerator." Applied Physics Letters 120, no. 12 (March 21, 2022): 122101. http://dx.doi.org/10.1063/5.0086164.
Повний текст джерелаАнотація:
We demonstrate the synaptic characteristics of analogously modulated channel currents in Cu-ion-actuated electrochemical RAM (ECRAM) based on an HfOx electrolyte and a WOx channel. Uncontrolled synaptic response is found as a function of the gate pulse when a Cu-rich gate electrode delivers mobile ions, presumably due to many ions injected from the infinite ion reservoir. As a result, we propose a CuOx oxide electrode to limit ion sources, which is indirectly validated by a physical examination of the degree of chemical bonding between Cu and oxygen, thereby boosting gate controllability over the channel. In addition, the HfOx electrolyte needs to be designed to facilitate the adequate migration of Cu ions, considering thickness and film quality. Using material stack engineering, the channel current of optimized CuOx/HfOx/WOx ECRAM can be steadily tuned via repeated identical gate pulses. The channel current and its change are proportional to the device area and the amount of migrated ions relevant to the gate pulse conditions, respectively. The homogeneous flow of ions across the entire area can, thus, be used to explain the obtained analog switching. The gate-controllable synaptic behavior of the ECRAM accelerates deep neural network training based on backpropagation algorithms. An improved pattern recognition accuracy of ∼88% for handwritten digits is achieved by linearly tuned multiple current states with more than 100 pulses and asymmetric gate voltage conditions in a three-layer neural network validated in simulation.
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Li, Li Qun, Jian Jun Xi, Jun Zhao, and J. Y. Chen. "Effect of Glycerin on Micro Arc Oxidation Process and Performance of Ceramic Coatings at the Surface of Magnesium Alloy AZ61." Applied Mechanics and Materials 10-12 (December 2007): 396–400. http://dx.doi.org/10.4028/www.scientific.net/amm.10-12.396.
Повний текст джерелаАнотація:
Effects of addition of glycerin in the electrolyte on the micro arc oxidation process have been investigated with a bipolar asymmetric pulse power supply, which involves peak value of pulse current, voltage, thickness and hardness of ceramic films of AZ61 magnesium alloy as well as surface roughness and structures. The results reveal that addition of a proper amount of glycerin helps to the decrease of positive pulse current peak and voltage, formation of a much dense ceramic coating with increase of the hardness, decrease of the surface roughness and good crystallization. When the amount of glycerin is more than 10ml/l, the growth of ceramic coatings begins to be inhibited and the performance of ceramic coatings seriously turns worse.
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Anusha, P., and B. V. Rajanna. "Induction drive system with DSTATCOM based asymmetric twin converter." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 4 (December 1, 2020): 1826. http://dx.doi.org/10.11591/ijpeds.v11.i4.pp1826-1834.
Повний текст джерелаАнотація:
High power demands are usually met by advanced power electronics converters in several large utility and electric drives applications. Applications from high power drives commonly uses solution based multi pulse and multilevel converters. A common DC link with atleast one voltage source converter (VSC) working with almost fundamental switching frequency are used in converters of multipulse type, and each output module is connected with the multipulse transformer in series. When compared to that of solution with single-VSC, Several VSCs generating different triggering pulses are adjused in order to achieve current injected with low specified total harmonic distortion (THD) with losses of abridged switching. Huge structure in complexity and expensive cost expenditure of the multipulse transformer is the major limitation of this scheme. DC link split capacitors in addition are eliminated by modifying the topology of the circuit. Thus, the independent voltages of the DC capacitor are controlled and decreased in number and the flow of third harmonic current component in the transformer is eliminated. The scheme of the designed controller is depending on the derived mathematical system model. Simulaion observation is used to check the scheme performance and efficiency in a detailed way with drive control technique.
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Yuniantoro, Indriarto, and Mochammad Haldi Widianto. "Novel asymmetric space vector pulse width modulation for dead-time processing in three-phase power converters." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 3 (June 1, 2022): 2346. http://dx.doi.org/10.11591/ijece.v12i3.pp2346-2352.
Повний текст джерелаАнотація:
<p>This research analyzes the asymmetric control strategies in multilevel inverters, including asymmetric techniques in space vector modulation of power converters. Modulation parameters such as reference voltage vector (Vref), switching time, and duty cycle are derived in the three-dimensional spatial vector geometry formulation. Asymmetric space vector pulse width modulation (SVPWM) is unique in specifying modulation parameters, has unequal tetrahedron patterns, accompanied by application examples for the upper and lower sector pairs of a tetrahedron. The combination of the switch in the form of an inclined cylinder produces twelve pairs of asymmetric tetrahedrons where the voltage vector positions are in the other twenty-four tetrahedrons. The calculation shows processing dead-time in switching, which is used for current compensation in three-phase power converters.</p>
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Vaivads, A., A. Retinò, Yu V. Khotyaintsev, and M. André. "The Alfvén edge in asymmetric reconnection." Annales Geophysicae 28, no. 6 (June 23, 2010): 1327–31. http://dx.doi.org/10.5194/angeo-28-1327-2010.
Повний текст джерелаАнотація:
Abstract. We show that in the case of magnetic reconnection where the Alfvén velocity is much higher in the plasma on one side of the current sheet than the other, an Alfvén edge is formed. This edge is located between the electron and ion edges on the high Alfvén velocity side of the current sheet. The Alfvén edge forms because the Alfvén wave generated near the X-line will propagate faster than the accelerated ions forming the ion edge. We discuss possible generation mechanism and the polarization of the Alfvén wave in the case when higher Alfvén speed is due to larger magnetic field and smaller plasma density, as in the case of magnetopause reconnection. The Alfvén wave can be generated due to Hall dynamics near the X-line. The Alfvén wave pulse has a unipolar electric field and the parallel current will be such that the outer current on the high magnetic field side is flowing away from the X-line. Understanding Alfvén edges is important for understanding the separatrix regions at the boundaries of reconnection jets. We present an example of Alfvén edge observed by the Cluster spacecraft at the magnetopause.
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Parker, Jessica R., Alexander N. Klishko, Boris I. Prilutsky, and Gennady S. Cymbalyuk. "Asymmetric and transient properties of reciprocal activity of antagonists during the paw-shake response in the cat." PLOS Computational Biology 17, no. 12 (December 28, 2021): e1009677. http://dx.doi.org/10.1371/journal.pcbi.1009677.
Повний текст джерелаАнотація:
Mutually inhibitory populations of neurons, half-center oscillators (HCOs), are commonly involved in the dynamics of the central pattern generators (CPGs) driving various rhythmic movements. Previously, we developed a multifunctional, multistable symmetric HCO model which produced slow locomotor-like and fast paw-shake-like activity patterns. Here, we describe asymmetric features of paw-shake responses in a symmetric HCO model and test these predictions experimentally. We considered bursting properties of the two model half-centers during transient paw-shake-like responses to short perturbations during locomotor-like activity. We found that when a current pulse was applied during the spiking phase of one half-center, let’s call it #1, the consecutive burst durations (BDs) of that half-center increased throughout the paw-shake response, while BDs of the other half-center, let’s call it #2, only changed slightly. In contrast, the consecutive interburst intervals (IBIs) of half-center #1 changed little, while IBIs of half-center #2 increased. We demonstrated that this asymmetry between the half-centers depends on the phase of the locomotor-like rhythm at which the perturbation was applied. We suggest that the fast transient response reflects functional asymmetries of slow processes that underly the locomotor-like pattern; e.g., asymmetric levels of inactivation across the two half-centers for a slowly inactivating inward current. We compared model results with those of in-vivo paw-shake responses evoked in locomoting cats and found similar asymmetries. Electromyographic (EMG) BDs of anterior hindlimb muscles with flexor-related activity increased in consecutive paw-shake cycles, while BD of posterior muscles with extensor-related activity did not change, and vice versa for IBIs of anterior flexors and posterior extensors. We conclude that EMG activity patterns during paw-shaking are consistent with the proposed mechanism producing transient paw-shake-like bursting patterns found in our multistable HCO model. We suggest that the described asymmetry of paw-shaking responses could implicate a multifunctional CPG controlling both locomotion and paw-shaking.
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Deng, Xiao Chuan, Hao Zhu, Xuan Li, Xiao Jie Xu, Kun Zhou, Zhi Qiang Li, Song Bai, You Run Zhang та Bo Zhang. "Avalanche Ruggedness Assessment of 1.2kV 45mΩ Asymmetric Trench SiC MOSFETs". Materials Science Forum 1004 (липень 2020): 837–42. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.837.
Повний текст джерелаАнотація:
In this paper, avalanche ruggedness of the commercial 1.2kV 45mΩ asymmetric silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET) is investigated by single-pulse unclamped inductive switching (UIS) test. The avalanche safe operation area (SOA) of the MOSFET is established. The impact of inductance and temperature on avalanche capability is exhibited, which is valuable for many application circuits. The variation in critical avalanche energy with peak avalanche current, peak avalanche current with avalanche time, and temperatures dependence of critical avalanche energy are confirmed.
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Li, Ying, Yu Gu, He Wang, Zhipeng Liu, Bing Song, and Tao Yin. "Electric Pulses Can Influence Galvanotaxis of Dictyostelium discoideum." BioMed Research International 2018 (August 8, 2018): 1–15. http://dx.doi.org/10.1155/2018/2534625.
Повний текст джерелаАнотація:
Galvanotaxis, or electrotaxis, plays an essential role in wound healing, embryogenesis, and nerve regeneration. Up until now great efforts have been made to identify the underlying mechanism related to galvanotaxis in various cells under direct current electric field (DCEF) in laboratory studies. However, abundant clinical research shows that non-DCEFs including monopolar or bipolar electric field may also contribute to wound healing and regeneration, although the mechanism remains elusive. Here, we designed a novel electric stimulator and applied DCEF, pulsed DCEF (pDCEF), and bipolar pulse electric field (bpEF) to the cells of Dictyostelium discoideum. The cells had better directional performance under asymmetric 90% duty cycle pDCEF and 80% duty cycle bpEF compared to DCEF, with 10 Hz frequency electric fields eliciting a better cell response than 5 Hz. Interestingly, electrically neutral 50% duty cycle bpEF triggered the highest migration speed, albeit in random directions. The results suggest that electric pulses are vital to galvanotaxis and non-DCEF is promising in both basic and clinical researches.
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Zhao, Chun Xiao, and Jun Lu. "Numerical Simulation of Atmospheric Pressure Glow Discharges in Coaxial Tube." Applied Mechanics and Materials 475-476 (December 2013): 1567–71. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.1567.
Повний текст джерелаАнотація:
The dynamics of atmospheric pressure glow discharges in coaxial tube have been numerically studied by a self-consist, one-dimensional fluid model. An asymmetric discharge current pulse, which operated in glow mode, was obtained in the cylindrical geometry. As the frequency or the voltage peak is increased, the discharge transits into a period-two state.
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Kamenev, Yurii Borisovich, Georgii Alekseevich Shtompel', and Nataliya Ivanovna Chunts. "Accelerated charge method of the lead-acid batteries. 1. Constant current stage of the charge." Electrochemical Energetics 12, no. 2 (2012): 64–71. http://dx.doi.org/10.18500/1608-4039-2012-12-2-64-71.
Повний текст джерелаАнотація:
Strategy of the accelerated mode of the charge, including constant current charge to 80 % state-of-charge and a pulse charge by asymmetric current to a full charge is offered. Results of the first investigation phase devoted to studying of influence of a mode constant current charge on a resource of lead-acid accumulators are presented in this work. Various influence of size of an initial charge current on degradation of positive and negative active materials and possibility of charge of the accumulator to 80 % state-of-charge for 0.5 h is demonstrated.
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Nescoromniy, S., E. Strizhakov, and D. Minko. "Two-stage magnetic-elasto-pulse stamping of thin sheet parts." Journal of Physics: Conference Series 2131, no. 4 (December 1, 2021): 042057. http://dx.doi.org/10.1088/1742-6596/2131/4/042057.
Повний текст джерелаАнотація:
Abstract The article substantiates the use of preliminary static loading and subsequent forging force when stamping thin sheet parts of complex shape with an elastic punch. The static load provides a relative deformation of the order of 20– 30% in the processing zone, which guarantees the stability of the position of the workpiece during subsequent pulsed loading. This technique is very important in the manufacture of asymmetric parts with a thickness of 0.01 – 0.3 mm. As a result, the accuracy of the products obtained corresponds to the 7th grade.The article provides a schematic diagram and a description of the proposed design of a double-action press, and analyzes the cyclogram of the device.It is recommended to carry out a static load with an electric drive, a pulsed one with a magnetic hammer, which is connected to a generator of impulse currents with a capacitive storage with an energy capacity of up to 40 kJ with a natural discharge frequency of the current of 20 kHz.
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Ye, Manyuan, Wei Ren, Qiwen Wei, Guizhi Song, and Zhilin Miao. "Research on Modified Hybrid Frequency Modulation Technology of Type-III Asymmetric CHB Multilevel Inverters." Electronics 9, no. 2 (February 5, 2020): 263. http://dx.doi.org/10.3390/electronics9020263.
Повний текст джерелаАнотація:
Asymmetric Cascaded H-bridge (ACHB) level inverters can output more voltage waveforms with fewer cascaded units while ensuring the quality of output voltage waveforms, so they have attracted more and more attention. Taking the topology of Type-III asymmetric CHB multilevel inverters as the research object, a Modified Hybrid Frequency Pulse Width Modulation (MHF-PWM) strategy is proposed in this paper. This modulation strategy overcomes the local overshoot of low-voltage unit in the presence of traditional Hybrid Frequency Pulse Width Modulation (HF-PWM), thus completely eliminating the low frequency harmonics in the output voltage waveform of Type-III ACHB nine-level inverters, and the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of PS-PWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage. At the same time, the strategy can also improve the problems of current backflow and energy feedback caused by the high-voltage unit pouring current to the low-voltage unit, thereby reducing the imbalance of the output power of the high-voltage and low-voltage units. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.
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Kamenev, Yury B., and Nataliya I. Chunts. "Accelerated Model of Charging of LeadAcid Batteries. 4. Pulse Charge with Asymmetrical Current, Gas Evolving and Service Life." Electrochemical Energetics 20, no. 3 (2020): 146–56. http://dx.doi.org/10.18500/1608-4039-2020-20-3-146-156.
Повний текст джерелаАнотація:
This paper is the conclusion to the series of the articles devoted to the problem of accelerated charging of a leadacid battery. In this paper we investigated the possibility of increasing the charge efficiency by applying the asymmetric current at the second stage. In addition, the effect of using admissible charging rates on the resource, the admissible number of consecutive cycles, and gas release were studied.
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Yang, Min-Kwon, and Woo-Young Choi. "High-Efficiency Full-Bridge DC-DC Converter with Current-Doubler Rectifier with Asymmetric Pulse-Width Modulation." Transactions of the Korean Institute of Power Electronics 20, no. 3 (June 20, 2015): 280–89. http://dx.doi.org/10.6113/tkpe.2015.20.3.280.
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Ryu, Hojeong, and Sungjun Kim. "Self-Rectifying Resistive Switching and Short-Term Memory Characteristics in Pt/HfO2/TaOx/TiN Artificial Synaptic Device." Nanomaterials 10, no. 11 (October 29, 2020): 2159. http://dx.doi.org/10.3390/nano10112159.
Повний текст джерелаАнотація:
Here, we propose a Pt/HfO2/TaOx/TiN artificial synaptic device that is an excellent candidate for artificial synapses. First, XPS analysis is conducted to provide the dielectric (HfO2/TaOx/TiN) information deposited by DC sputtering and atomic layer deposition (ALD). The self-rectifying resistive switching characteristics are achieved by the asymmetric device stack, which is an advantage of the current suppression in the crossbar array structure. The results show that the programmed data are lost over time and that the decay rate, which is verified from the retention test, can be adjusted by controlling the compliance current (CC). Based on these properties, we emulate bio-synaptic characteristics, such as short-term plasticity (STP), long-term plasticity (LTP), and paired-pulse facilitation (PPF), in the self-rectifying I–V characteristics of the Pt/HfO2/TaOx/TiN bilayer memristor device. The PPF characteristics are mimicked by replacing the bio-stimulation with the interval time of paired pulse inputs. The typical potentiation and depression are also implemented by optimizing the set and reset pulse. Finally, we demonstrate the natural depression by varying the interval time between pulse inputs.
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Jung, Jaehoon, Jongyoung Kim, Joonho Lee, Yeon-Wha Oh, Sanghee Jung, Il-Suk Kang, and Kiwoon Choi. "Modulation of ionic current rectification direction for biomimetic aluminum oxide membrane by surface modification." AIP Advances 12, no. 3 (March 1, 2022): 035141. http://dx.doi.org/10.1063/5.0080254.
Повний текст джерелаАнотація:
A biomimetic aluminum oxide membrane having asymmetric channels with a minimum diameter of 20 nm, a maximum diameter of 80 nm, and a length of 5 µm was prepared using square pulse anodization. The membrane effectively permitted transfer of anions only and showed an ionic current rectification characteristic with a rectification ratio of 2.4. After the sulfonic acid group was introduced by surface modification, the membrane effectively permitted transfer of cations only and showed a rectification ratio of 2.7. This modulation of the ionic current rectification direction was consistent with the theoretical prediction through the numerical analysis of 2D models. These findings present a convenient method to control ion transport for the ion exchange membrane.
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Tsai, Ming-Fa, Chung-Shi Tseng, and Po-Jen Cheng. "Implementation of an FPGA-Based Current Control and SVPWM ASIC with Asymmetric Five-Segment Switching Scheme for AC Motor Drives." Energies 14, no. 5 (March 7, 2021): 1462. http://dx.doi.org/10.3390/en14051462.
Повний текст джерелаАнотація:
This paper presents the design and implementation of an application-specific integrated circuit (ASIC) for a discrete-time current control and space-vector pulse-width modulation (SVPWM) with asymmetric five-segment switching scheme for AC motor drives. As compared to a conventional three-phase symmetric seven-segment switching SVPWM scheme, the proposed method involves five-segment two-phase switching in each switching period, so the inverter switching times and power loss can be reduced by 33%. In addition, the produced PWM signal is asymmetric with respect to the center-symmetric triangular carrier wave, and the voltage command signal from the discrete-time current control output can be given in each half period of the PWM switching time interval, hence increasing the system bandwidth and allowing the motor drive system with better dynamic response. For the verification of the proposed SVPWM modulation scheme, the current control function in the stationary reference frame is also included in the design of the ASIC. The design is firstly verified by using PSIM simulation tool. Then, a DE0-nano field programmable gate array (FPGA) control board is employed to drive a 300W permanent-magnet synchronous motor (PMSM) for the experimental verification of the ASIC.
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Lin, Bor‐Ren, and Hao‐Ping Yeh. "Analysis and implementation of a zero‐voltage switching asymmetric pulse‐width modulation converter for high load current application." IET Power Electronics 7, no. 6 (June 2014): 1435–43. http://dx.doi.org/10.1049/iet-pel.2013.0747.
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Maidul Haque, S., Pankaj R. Sagdeo, D. D. Shinde, J. S. Misal, S. N. Jha, D. Bhattacharyya, and N. K. Sahoo. "Extended x-ray absorption fine structure measurements on asymmetric bipolar pulse direct current magnetron sputtered Ta_2O_5 thin films." Applied Optics 54, no. 22 (July 24, 2015): 6744. http://dx.doi.org/10.1364/ao.54.006744.
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KONDRATYEV, Yuri, Oksana SOKOLOVA, Arkady KAMBOLOV, and Andrey MIROSHNIKOV. "Electrochemical leaching of polymetallic ore under the action of asymmetric current pulses and the addition of a surfactant." Sustainable Development of Mountain Territories 14, no. 1 (March 30, 2022): 20–26. http://dx.doi.org/10.21177/1998-4502-2022-14-1-20-26.
Повний текст джерелаАнотація:
The article presents the results of studies on the electrochemical leaching of metals from poly-metallic ores using sulfuric acid-chloride solutions under the action of a reversible infra-low-frequency direct current with varying density and the addition of a surfactant. Mathematical models of leaching indicators have been developed depending on the density, duration of the forward and reverse polarity of the current. It is revealed that the most optimal mode is the ore leaching under the action of a reversible direct current with varying density and duration of the reverse current. It is determined that the reverse current density is 6 times greater than the forward current density, and the duration of the reverse current pulse is 0.2 of the duration of the forward current. At the same time, Kazakhstan, like other countries with the transit economy, will have to overcome the risks and challenges that have emerged as a result of global digitalization. The article shows that to stimulate digitalization of geological exploration, significant investments are needed, which will require, alongside with government regulation, searching for new forms and mechanisms of public-private partnership.
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Zou, Shizan, Hengyuan Wang, Jianhang Guo, Sai Jiang, Ziqian Hao, Mengjiao Pei, Xin Xu, et al. "Asymmetric electrode geometry induced photovoltaic behavior for self-powered organic artificial synapses." Flexible and Printed Electronics 6, no. 4 (December 1, 2021): 044009. http://dx.doi.org/10.1088/2058-8585/ac442f.
Повний текст джерелаАнотація:
Abstract Opto-electronic synapses have attracted considerable attention because of their promising potential in artificial visual perception systems for neuromorphic computing. Despite remarkable progress in mimicking synaptic functions, reduction of energy consumption of artificial synapses is still a substantial obstacle that is required to be overcome to promote advanced emerging applications. Herein, we propose a zero-power artificial optoelectrical synapses using ultrathin organic crystalline semiconductors, which can be self-driven by exploiting the photovoltaic effect induced by asymmetric electrode geometry contacts. The photogenerated charge carrier collection at the two electrodes is unbalanced due to the asymmetric contacts, leading to the in-plane current without bias voltage. Our devices successfully mimic a range of important synaptic functions, such as paired-pulse facilitation and spike rate-dependent plasticity. Furthermore, we demonstrate that our devices can realize the simulation of image sharpening under self-driven optical-sensing synaptic operations, offering prospects for the development of retinomorphic visual systems.
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Joong Kyun Kim, Jin Ho Yang, Jeong Hyun Seo, and Ki-Woong Whang. "The improvement of discharge characteristics by the use of asymmetric pulse driving in an alternating current plasma display panel." IEEE Transactions on Plasma Science 29, no. 2 (April 2001): 377–82. http://dx.doi.org/10.1109/27.922749.
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Pesin, Jimy, Anna Faingersh, Dan Waisman, and Amir Landesberg. "Highly sensitive monitoring of chest wall dynamics and acoustics provides diverse valuable information for evaluating ventilation and diagnosing pneumothorax." Journal of Applied Physiology 116, no. 12 (June 15, 2014): 1632–40. http://dx.doi.org/10.1152/japplphysiol.00966.2013.
Повний текст джерелаАнотація:
Current practice of monitoring lung ventilation in neonatal intensive care units, utilizing endotracheal tube pressure and flow, end-tidal CO2, arterial O2 saturation from pulse oximetry, and hemodynamic indexes, fails to account for asymmetric pathologies and to allow for early detection of deteriorating ventilation. This study investigated the utility of bilateral measurements of chest wall dynamics and sounds, in providing early detection of changes in the mechanics and distribution of lung ventilation. Nine healthy New Zealand rabbits were ventilated at a constant pressure, while miniature accelerometers were attached to each side of the chest. Slowly progressing pneumothorax was induced by injecting 1 ml/min air into the pleural space on either side of the chest. The end of the experiment ( tPTX) was defined when arterial O2 saturation from pulse oximetry dropped <90% or when vigorous spontaneous breathing began, since it represents the time of clinical detection using common methods. Consistent and significant changes were observed in 15 of the chest dynamics parameters. The most meaningful temporal changes were noted for features extracted from subsonic dynamics (<10 Hz), e.g., tidal amplitude, energy, and autoregressive poles. Features from the high-frequency band (10–200 Hz), e.g., energy and entropy, exhibited smaller but significant changes. At 70% tPTX, identification of asymmetric ventilation was attained for all animals. Side identification of the pneumothorax was achieved at 50% tPTX, within a 95% confidence interval. Diagnosis was, on average, 34.1 ± 18.8 min before tPTX. In conclusion, bilateral monitoring of the chest dynamics and acoustics provide novel information that is sensitive to asymmetric changes in ventilation, enabling early detection and localization of pneumothorax.
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Lamping, Wiebke, John M. Deeks, Jeremy Marozeau, and Robert P. Carlyon. "The Effect of Phantom Stimulation and Pseudomonophasic Pulse Shapes on Pitch Perception by Cochlear Implant Listeners." Journal of the Association for Research in Otolaryngology 21, no. 6 (August 17, 2020): 511–26. http://dx.doi.org/10.1007/s10162-020-00768-x.
Повний текст джерелаАнотація:
Abstract It has been suggested that a specialized high-temporal-acuity brainstem pathway can be activated by stimulating more apically in the cochlea than is achieved by cochlear implants (CIs) when programmed with contemporary clinical settings. We performed multiple experiments to test the effect on pitch perception of phantom stimulation and asymmetric current pulses, both supposedly stimulating beyond the most apical electrode of a CI. The two stimulus types were generated using a bipolar electrode pair, composed of the most apical electrode of the array and a neighboring, more basal electrode. Experiment 1 used a pitch-ranking procedure where neural excitation was shifted apically or basally using so-called phantom stimulation. No benefit of apical phantom stimulation was found on the highest rate up to which pitch ranks increased (upper limit), nor on the slopes of the pitch-ranking function above 300 pulses per second (pps). Experiment 2 used the same procedure to study the effects of apical pseudomonophasic pulses, where the locus of excitation was manipulated by changing stimulus polarity. A benefit of apical stimulation was obtained for the slopes above 300 pps. Experiment 3 used an adaptive rate discrimination procedure and found a small but significant benefit of both types of apical stimulation. Overall, the results show some benefit for apical stimulation on temporal pitch processing at high pulse rates but reveal that the effect is smaller and more variable across listeners than suggested by previous research. The results also provide some indication that the benefit of apical stimulation may decline over time since implantation.
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Jiang, Fan, Cheng Li, Bin Xu, Shinichi Tashiro, Manabu Tanaka, and Shujun Chen. "Study on the Decoupled Transfer of Heat and Mass in Wire Variable Polarity Plasma Arc Welding." Materials 13, no. 5 (February 28, 2020): 1073. http://dx.doi.org/10.3390/ma13051073.
Повний текст джерелаАнотація:
A hybrid arc-wire welding method based on the variable polarity plasma arc (VPPA) and variable polarity pulse metal inert-gas (VP-PMIG) was proposed for manufacturing aluminum alloys. This paper aims to clarify the decoupling control process of heat and mass transfer in the hybrid welding process. To understand the arc physics and analyze the mass transfer behavior, the hybrid arc shape and droplet cross-sectional area with different parameters were obtained by high speed video photography. Further, the melting area of the base metal was analyzed by macro-metallography of the weld bead cross-section to study the heat transfer. It is found that the hybrid arc shape changes with time. The VPPA main arc is deflected to one side by the VP-PMIG, making the temperature distribution asymmetric, and during the VP-PMIG pulse necking occurs. The cross-sectional area of the droplet is more obviously affected by the VP-PMIG current than the VPPA current. Meanwhile, the VPPA current dominates the melting area of the base metal. Therefore, we conclude that heat transfer to the base metal is from the VPPA, while droplet transfer is mainly controlled by the VP-PMIG arc. These conclusions are confirmed by analyzing the decoupling degree of heat and mass transfer of the base metal by the VPPA and VP-PMIG arc.
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Ashcheulov, A. A., D. A. Lavrenjuk, and I. S. Romanjuk. "Vortex Express Method for Parameter Determination Thermoelectric Materials." Metrology and instruments, no. 1 (March 2, 2020): 15–20. http://dx.doi.org/10.33955/2307-2180(1)2020.15-20.
Повний текст джерелаАнотація:
The method is based on the possibility of determining the heat loss of electric power during the flow of Foucault eddy currents in the volume of a thermoelectric sample, placing in the field of action of the ferrite core an inductor through which electric currents that are symmetrical and asymmetric in nature flow sequentially in time.
Mathematical expressions are obtained for the coefficients of electrical conductivity σ, thermal conductivity ϰ, thermo-emf α and thermoelectric figure of merit Z. Minimization of the error of the proposed method, carried out by computer simulation of the physical processes occurring in the sample using appropriate programs, showed that the operating frequency of the device measuring sensors should be located in the range of 36 ÷ 250 kHz, and the electric current flowing through it — taking into account the inequality qф/П/ qф/ qϰ > 10. The magnetic field induction ratio in terms of components is selected from the condition В0/В > 8.6, which corresponds to the conditions of minimal impact on the parameters of the sample by galvanic thermomagnetic phenomena.
The block diagram of a device for non-contact measurement of symmetric σс and asymmetric σа components of the electrical conductivity of thermoelectric materials consists of: 1 — SV switch block; 2 — electronic switch; 3 — auto generator; 4 — AC amplifier; 5 — synchronous detector; 6 — DC amplifier; 7 — pulse generator; 8 — signal processing unit; 9 — indicator device; 10 — DC indicator; 11 — correction unit; FR1, FR2.
Measurement of the parameters of the thermoelectric sample based on Bi-Te-Se-Sb crystals showed that the real error of the proposed method is 2 %. This indicates that the eddy current method can be successfully used to determine the main parameters of thermoelectric materials.
The use of this method allows solving the relevant problem of avtomazation of the process of monitoring and sorting out thermoelectric ingots, billets and parts.
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Fellner, Andreas, Isabel Stiennon, and Frank Rattay. "Analysis of upper threshold mechanisms of spherical neurons during extracellular stimulation." Journal of Neurophysiology 121, no. 4 (April 1, 2019): 1315–28. http://dx.doi.org/10.1152/jn.00700.2018.
Повний текст джерелаАнотація:
Exceeding a certain stimulation strength can prevent the generation of somatic action potentials, as has been demonstrated in vitro with extracellularly stimulated dorsal root ganglion cells as well as retinal ganglion cells. This phenomenon, termed upper threshold, is currently thought to be a consequence of sodium current reversal in strongly depolarized regions. Here we analyze the contribution of membrane kinetics, using spherical model neurons that are stimulated externally with a microelectrode, in more detail. During extracellular pulse application, the electric field depolarizes one part and hyperpolarizes the other part of the cell. Strong transmembrane currents are generated only in the active depolarized region, changing the overall polarization level. The asymmetric membrane voltage distribution caused by the stimulus strongly influences the cell’s behavior during and even after the stimulus. Effects on membrane voltage and transmembrane currents during and after the stimulus are shown and discussed in detail. Aside from the sodium current reversal, two more key mechanisms were identified in causing the upper threshold: strong potassium currents and inactivation of sodium channels. The contributions of the mechanisms involved strongly depend on cell properties, stimulus parameters, and other factors such as temperature. The conclusions presented here are based on several retinal ganglion cell models of the Fohlmeister group, a model with original Hodgkin-Huxley membrane, and a pyramidal cell model. NEW & NOTEWORTHY The upper threshold phenomenon in extracellular stimulation is analyzed in detail for spherical cells. Three main mechanisms were identified that prevent the generation of action potentials at high stimulation strengths: 1) strong potassium currents, 2) inactivating sodium ion channels, and 3) sodium current reversal. Ion channel kinetics in retinal ganglion cells, pyramidal cells, and the original Hodgkin-Huxley model were investigated under the influence of an extracellular stimulus.
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Nguyen Thi Kim, Thuong, Thi Thu Bui, Anh Tuan Pham, Van Thang Duong, and Thi Huong Giang Le. "Fast Determination of Auramine O in Food by Adsorptive Stripping Voltammetry." Journal of Analytical Methods in Chemistry 2019 (March 12, 2019): 1–6. http://dx.doi.org/10.1155/2019/8639528.
Повний текст джерелаАнотація:
The electrochemical behaviour of auramine O on the hanging mercury drop electrode has been investigated by cyclic and square wave voltammetry method. Reduction peak of auramine O was irreversible and adsorptive on the hanging mercury drop electrode. The optimal conditions were chosen to be Briton–Robinson buffer pH 9.0, accumulation potential −0.5 V vs. Ag/AgCl/KCl, accumulation time 60 s, pulse amplitude 250 mV·s−1, and frequency 50 Hz. At the optimum experimental conditions, the peak of the target analyte was sharp and asymmetric. The linearity of the peak current depending on the concentration ranged from 4.0 × 10−8 to 6.4 × 10−7 mol L−1. The limit of detection and limit of quantitation were 2.46 × 10−8 mol L−1 and 8.21 × 10−8 mol L−1, respectively. The recovery and relative standard deviation were 94.9% and 2.0% (n = 5). The developed method was successfully applied to determine auramine O in chicken samples with an appropriate sample preparation.
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Malecka, Kamila, Shalini Menon, Gopal Palla, Krishnapillai Girish Kumar, Mathias Daniels, Wim Dehaen, Hanna Radecka, and Jerzy Radecki. "Redox-Active Monolayers Self-Assembled on Gold Electrodes—Effect of Their Structures on Electrochemical Parameters and DNA Sensing Ability." Molecules 25, no. 3 (January 30, 2020): 607. http://dx.doi.org/10.3390/molecules25030607.
Повний текст джерелаАнотація:
The background: The monolayers self-assembled on the gold electrode incorporated transition metal complexes can act both as receptor (“host” molecules) immobilization sites, as well as transducer for interface recognitions of “guest” molecules present in the aqueous solutions. Their electrochemical parameters influencing the sensing properties strongly depend on the transition metal complex structures. The objectives: The electrochemical characterization of the symmetric terpyridine–M2+–terpyridine and asymmetric dipyrromethene–M2+–terpyridine complexes modified with ssDNA probe covalently attached to the gold electrodes and exploring their ssDNA sensing ability were the main aims of the research presented. The methods: Two transition metal cations have been selected: Cu2+ and Co2+ for creation of redox-active monolayers. The electron transfer coefficients indicating the reversibility and electron transfer rate constant measuring kinetic of redox reactions have been determined for all SAMs studied using: Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry, and Differential Pulse Voltammetry. All redox-active platforms have been applied for immobilization of ssDNA probe. Next, their sensing properties towards complementary DNA target have been explored electrochemically. The results: All SAMs studied were stable displaying quasi-reversible redox activity. The linear relationships between cathodic and anodic current vs. san rate were obtained for both symmetric and asymmetric SAMs incorporating Co2+ and Cu2+, indicating that oxidized and reduced redox sites are adsorbed on the electrode surface. The ssDNA sensing ability were observed in the fM concentration range. The low responses towards non-complementary ssDNA sequences provided evidences for sensors good selectivity. The conclusions: All redox-active SAMs modified with a ssDNA probe were suitable for sensing of ssDNA target, with very good sensitivity in fM range and very good selectivity. The detection limits obtained for SAMs incorporating Cu2+, both symmetric and asymmetric, were better in comparison to SAMs incorporating Co2+. Thus, selection of the right transition metal cation has stronger influence on ssDNA sensing ability, than complex structures.
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Kits, K. S., J. C. Lodder, and M. J. Veerman. "Phe-Met-Arg-Phe-amide Activates a Novel Voltage-dependent K+ Current through a Lipoxygenase Pathway in Molluscan Neurones." Journal of General Physiology 110, no. 5 (November 1, 1997): 611–28. http://dx.doi.org/10.1085/jgp.110.5.611.
Повний текст джерелаАнотація:
The neuropeptide Phe-Met-Arg-Phe-amide (FMRFa) dose dependently (ED50 = 23 nM) activated a K+ current in the peptidergic caudodorsal neurones that regulate egg laying in the mollusc Lymnaea stagnalis. Under standard conditions ([K+]o = 1.7 mM), only outward current responses occurred. In high K+ salines ([K+]o = 20 or 57 mM), current reversal occurred close to the theoretical reversal potential for K+. In both salines, no responses were measured below −120 mV. Between −120 mV and the K+ reversal potential, currents were inward with maximal amplitudes at ∼−60 mV. Thus, U-shaped current–voltage relations were obtained, implying that the response is voltage dependent. The conductance depended both on membrane potential and extracellular K+ concentration. The voltage sensitivity was characterized by an e-fold change in conductance per ∼14 mV at all [K+]o. Since this result was also obtained in nearly symmetrical K+ conditions, it is concluded that channel gating is voltage dependent. In addition, outward rectification occurs in asymmetric K+ concentrations. Onset kinetics of the response were slow (rise time ∼650 ms at −40 mV). However, when FMRFa was applied while holding the cell at −120 mV, to prevent activation of the current but allow activation of the signal transduction pathway, a subsequent step to −40 mV revealed a much more rapid current onset. Thus, onset kinetics are largely determined by steps preceding channel activation. With FMRFa applied at −120 mV, the time constant of activation during the subsequent test pulse decreased from ∼36 ms at −60 mV to ∼13 ms at −30 mV, confirming that channel opening is voltage dependent. The current inactivated voltage dependently. The rate and degree of inactivation progressively increased from −120 to −50 mV. The current is blocked by internal tetraethylammonium and by bath- applied 4-aminopyridine, tetraethylammonium, Ba2+, and, partially, Cd2+ and Cs+. The response to FMRFa was affected by intracellular GTPγS. The response was inhibited by blockers of phospholipase A2 and lipoxygenases, but not by a cyclo-oxygenase blocker. Bath-applied arachidonic acid induced a slow outward current and occluded the response to FMRFa. These results suggest that the FMRFa receptor couples via a G-protein to the lipoxygenase pathway of arachidonic acid metabolism. The biophysical and pharmacological properties of this transmitter operated, but voltage-dependent K+ current distinguish it from other receptor-driven K+ currents such as the S-current- and G-protein-dependent inward rectifiers.
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Gao, Lihui, Yongkang Liu, Nan Chen, Haolin Li, Niaona Zhang, and Shengbao Yu. "A Design Method of the Transmitting Waveform of Electromagnetic Sounding Based on Selective Harmonic Elimination." Mathematical Problems in Engineering 2022 (January 10, 2022): 1–12. http://dx.doi.org/10.1155/2022/2915275.
Повний текст джерелаАнотація:
The exploration target at different depths through the ground-airborne frequency domain electromagnetic method (GAFDEM) is detected by transmitting waveforms at different frequencies. When taking these different depths into detail, arbitrarily distributed frequencies are needed. However, the current transmitting waveforms are mostly in a fixed frequency ratio or frequency difference, which fails to meet the requirements of exploration accuracy and efficiency at the same time. Therefore, as a solution to this problem, this paper proposes a transmitting waveform design method based on selective harmonic eliminated pulse width modulation (SHEPWM) technology. In the SHEPWM method, three transmitting waveforms with the desired spectrum are obtained by directly controlling the switching angles of a binary sequence with an artificial neural network algorithm. Firstly, our study puts forward the basic theories and principles of the full-periodic asymmetric SHEPWM waveform. Secondly, the study, through simulation, realizes the pseudorandom, depth-focused, and layer-identification waveform with different detection depths. Finally, the application of the proposed SHEPWM waveform to the geological survey in Kaili City, Guizhou Province, proves the correctness and feasibility of this proposed method.
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Mukherjee, P. K., and D. Chakravorty. "Growth of silver nanowires using mica structure as a template and ultrahigh dielectric permittivity of the nanocomposite." Journal of Materials Research 17, no. 12 (December 2002): 3127–32. http://dx.doi.org/10.1557/jmr.2002.0452.
Повний текст джерелаАнотація:
Fluorphlogopite mica crystallites of dimensions in the range 0.5 to 24 µm were grown within silicate glass of suitable compositions by heat treatment at 1168 K. After an ion exchange treatment (K+ ⇆ Ag+) the specimens were subjected to an electrodeposition reaction. With the optimum concentration of K+ ions in the precursor glass, electrodeposition brought about the growth of silver nanowires about 0.5 nm diameter within the nanochannels of the fluorphlogopite mica structure. By applying a voltage pulse of 20 volts of duration 3 s, break junctions could be induced in the nanowires. A high dielectric constant of around 1.0 × 107was found in the resultant specimen. This was shown to be quantum mechanical in origin and arose due to the presence of metal filaments about 1280 nm in length. An asymmetric voltage–current characteristic was recorded at 114 K in the case of the specimen containing silver nanowires grown within the mica structure. This is believed to arise due to formation of a nanojunction between the metal nanowire and silver nanoparticles with diameters of less than 3 nm. The latter were earlier shown to behave as insulators
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Yager-Elorriaga, D. A., F. W. Doss, G. A. Shipley, P. F. Knapp, D. E. Ruiz, A. J. Porwitzky, J. R. Fein, et al. "Studying the Richtmyer–Meshkov instability in convergent geometry under high energy density conditions using the Decel platform." Physics of Plasmas 29, no. 5 (May 2022): 052114. http://dx.doi.org/10.1063/5.0087215.
Повний текст джерелаАнотація:
The “Decel” platform at Sandia National Laboratories investigates the Richtmyer–Meshkov instability (RMI) in converging geometry under high energy density conditions [Knapp et al., Phys. Plasmas 27, 092707 (2020)]. In Decel, the Z machine magnetically implodes a cylindrical beryllium liner filled with liquid deuterium, launching a converging shock toward an on-axis beryllium rod machined with sinusoidal perturbations. The passage of the shock deposits vorticity along the Be/D2 interface, causing the perturbations to grow. In this paper, we present platform improvements along with recent experimental results. To improve the stability of the imploding liner to the magneto Rayleigh–Taylor instability, we modified its acceleration history by shortening the Z electrical current pulse. Next, we introduce a “split rod” configuration that allows two axial modes to be fielded simultaneously in different axial locations along the rod, doubling our data per experiment. We then demonstrate that asymmetric slots in the return current structure modify the magnetic drive pressure on the surface of the liner, advancing the evolution on one side of the rod by multiple ns compared to its 180° counterpart. This effectively enables two snapshots of the instability at different stages of evolution per radiograph with small deviations of the cross-sectional profile of the rod from the circular. Using this platform, we acquired RMI data at 272 and 157 μm wavelengths during the single shock stage. Finally, we demonstrate the utility of these data for benchmarking simulations by comparing calculations using ALEGRA MHD and RageRunner.
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Khabarov, Kirill, Maxim Urazov, Anna Lizunova, Ekaterina Kameneva, Alexey Efimov, and Victor Ivanov. "Influence of Ag Electrodes Asymmetry Arrangement on Their Erosion Wear and Nanoparticle Synthesis in Spark Discharge." Applied Sciences 11, no. 9 (May 1, 2021): 4147. http://dx.doi.org/10.3390/app11094147.
Повний текст джерелаАнотація:
For nanoparticle synthesis in a spark discharge, the influence of the degree of electrode asymmetry in the rod-to-rod configuration, using the example of silver electrodes, on the energy efficiency and nanoparticle composition is studied. The asymmetry degree was determined by the angle between electrodes’ end faces. Two types of discharge current pulses were used: oscillation-damped and unipolar, in which electrodes changed their polarities and had a constant polarity during a single discharge, respectively. A significant influence of the asymmetry degree of the electrode arrangement on the synthesized nanoparticle size, agglomeration and concentration, and on the synthesis energy efficiency, has been established. An increase in the degree of the electrode asymmetry with the oscillation-damped discharge current pulse led to an increased mass production rate and energy efficiency of nanoparticle synthesis, a significant fraction of which had large dimensions of more than 40 nm. The effect of the transfer of synthesized nanoparticles to the opposite electrode at the unipolar discharge current pulse led to the appearance of electroerosive instability, manifested in the formation of a protrusion on the anode surface, around which spark discharges, leading to its further growth and electrode gap closure.
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Milano, G., L. Boarino, I. Valov, and C. Ricciardi. "Memristive devices based on single ZnO nanowires—from material synthesis to neuromorphic functionalities." Semiconductor Science and Technology 37, no. 3 (January 28, 2022): 034002. http://dx.doi.org/10.1088/1361-6641/ac4b8a.
Повний текст джерелаАнотація:
Abstract Memristive and resistive switching devices are considered promising building blocks for the realization of artificial neural networks and neuromorphic systems. Besides conventional top-down memristive devices based on thin films, resistive switching devices based on nanowires (NWs) have attracted great attention, not only for the possibility of going beyond current scaling limitations of the top-down approach, but also as model systems for the localization and investigation of the physical mechanism of switching. This work reports on the fabrication of memristive devices based on ZnO NWs, from NW synthesis to single NW-based memristive cell fabrication and characterization. The bottom-up synthesis of ZnO NWs was performed by low-pressure chemical vapor deposition according to a self-seeding vapor-solid (VS) mechanism on a Pt substrate over large scale (∼cm2), without the requirement of previous seed deposition. The grown ZnO NWs are single crystalline with wurtzite crystal structure and are vertically aligned respect to the growth substrate. Single NWs were then contacted by means of asymmetric contacts, with an electrochemically active and an electrochemically inert electrode, to form NW-based electrochemical metallization memory cells that show reproducible resistive switching behaviour and neuromorphic functionalities including short-term synaptic plasticity and paired pulse facilitation. Besides representing building blocks for NW-based memristive and neuromorphic systems, these single crystalline devices can be exploited as model systems to study physicochemical processing underlaying memristive functionalities thanks to the high localization of switching events on the ZnO crystalline surface.
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Novickij, Vitalij, Gediminas Staigvila, Arūnas Murauskas, Nina Rembialkowska, Julita Kulbacka, and Jurij Novickij. "High Frequency Bipolar Electroporator with Double-Crowbar Circuit for Load-Independent Forming of Nanosecond Pulses." Applied Sciences 12, no. 3 (January 27, 2022): 1370. http://dx.doi.org/10.3390/app12031370.
Повний текст джерелаАнотація:
In this work, a novel electroporation system (electroporator) is presented, which is capable of forming high frequency pulses in a broad range of parameters (65 ns–100 µs). The electroporator supports voltages up to 3 kV and currents up to 40 A and is based on H-bridge circuit topology. A synchronized double crowbar driving sequence is introduced to generate short nanosecond range pulses independently of the electroporator load. The resultant circuit generates pulses with repetition frequencies up to 5 MHz and supports unipolar, bipolar, and asymmetrical pulse sequences with arbitrary waveforms. The shortest pulse duration step is hardware limited to 33 ns. The electroporator was experimentally tested on the H69AR human lung cancer cell line using 20 kV/cm bipolar and unipolar 100 ns–1 μs pulses. Based on a YO-PRO-1 permeabilization assay, it was determined that the electroporator is suitable for applied research on electroporation. The system offers high flexibility in experimental design to trigger various electroporation-based phenomena.