Unipolar Pulse Research Articles

Электрофизические и тепловые параметры плазменной струи атмосферного давления в гелии при возбуждении синусоидальным и импульсным напряжением

Comparative studies of generation of cold plasma jet of atmospheric pressure in helium when excited by sinusoidal voltage and unipolar positive pulses at 2-6 kV for medical applications have been conducted. It is shown that the achieved parameters are identical, but the absence of the effect of frequency self-organization of streamer breakdown leading to irregularity in streamer propagation under pulse excitation makes it preferable in biophysical experiments. A limiting factor for plasma jet exposure is the achievable target temperature, which can be reduced by limiting the duration of the current.

Selective pumping of a nonlinear quantum oscillator

Selective pumping of a quantum system under the influence of unmodulated short-range pulses of large amplitude is studied using the example of a weakly nonlinear Josephson oscillator. An exact solution is obtained in the case of small parameter anharmonicity for changes in the system energy and population of levels after impact. It is shown that due to the interference of state amplitudes, it is possible to stabilize the system and prevent undesirable excitations (energy growth). When anharmonicity is taken into account, the system stability conditions are studied numerically. The obtained results are important when analyzing leakage to high-lying levels in a transmon-qubit under the influence of short unipolar control pulses.

Получение униполярных импульсов в дальней зоне источника

Under the pulses with non-harmonic waveform, propagate in free space, the time dependence of the field strength changes. In the far field or when the radiation is focused on the focal point, the field strength becomes proportional to the time derivative of the source field. If the field in any near zone is unipolar, then differentiation will lead to unipolarity lost. Based on these considerations, it is usually concluded that the practical use of radiation from unipolar sources is extremely limited. Since any propagation and attempts to focusing will lead to the loss of radiation unipolarity. However, this limitation does not effect situations when the field is depended on time in a near zone having a special form. In this note, conditions are given when it is possible to obtain unipolar pulses in the far field zone.

Coupled mechano-electrokinetic Burridge-Knopoff model of fault sliding events and transient geoelectric signals

We introduce the first fully self-consistent numerical model combining seismic micro-ruptures, occurring within a generalized Burridge-Knopoff spring-block model, with the nucleation and propagation of electric charge pulses within a coupled mechano-electrokinetic system. This model provides a general theoretical framework for modeling and analyzing geoelectric anomalies to earthquakes. In particular, it is able to reproduce the unipolar pulses that have often been reported before large seismic events, as well as various previously reported anomalies in the statistical moments of the ambient electric fields and the shape of their power spectra.

2-ns Electrostimulation of Ca2+ Influx into Chromaffin Cells: Rapid Modulation by Field Reversal

Cellular effects of nanosecond-pulsed electric field exposures can be attenuated by an electric field reversal, a phenomenon called bipolar pulse cancellation. Our investigations of this phenomenon in neuroendocrine adrenal chromaffin cells show that a single 2-ns, 16 MV/m unipolar pulse elicited a rapid, transient rise in intracellular Ca2+ levels due to Ca2+ influx through voltage-gated calcium channels. The response was eliminated by a 2-ns bipolar pulse with positive and negative phases of equal duration and amplitude and fully restored (unipolar-equivalent response) when the delay between each phase of the bipolar pulse was 30 ns. Longer interphase intervals evoked Ca2+ responses that were greater in magnitude than those evoked by a unipolar pulse (stimulation). Cancellation was also observed when the amplitude of the second (negative) phase of the bipolar pulse was half that of the first (positive) phase but progressively lost as the amplitude of the second phase was incrementally increased above that of the first phase. When the amplitude of the second phase was twice that of the first phase, there was stimulation. By comparing the experimental results for each manipulation of the bipolar pulse waveform with analytical calculations of capacitive membrane charging/discharging, also known as accelerated membrane discharge mechanism, we show that the transition from cancellation to unipolar-equivalent stimulation broadly agrees with this model. Taken as a whole, our results demonstrate that electrostimulation of adrenal chromaffin cells with ultrashort pulses can be modulated with interphase intervals of tens of nanoseconds, a prediction of the accelerated membrane discharge mechanism not previously observed in other bipolar pulse cancellation studies. Such modulation of Ca2+ responses in a neural-type cell is promising for the potential use of nanosecond bipolar pulse technologies for remote electrostimulation applications for neuromodulation.

Optical diagnostics of the characteristics of a square unipolar nanosecond pulse-driven atmospheric pressure helium plasma jet

Compared with the traditional sinusoidal voltage source, a short rising nanosecond voltage source can generate a high electron current for a short rising time. This paper investigates how the nanopulse parameters such as the voltage amplitude, pulse duration, and repetition frequency affect the radical generation and the plasma bullet propagation in an atmospheric pressure helium plasma jet. An intensified charge-coupled device was used to observe the bullet propagation in the nanosecond gate mode. The plasma bullet’s propagation speed is mainly affected by the applied voltage and externally biased electrodes rather than the pulse duration or the driving frequency. In contrast, optical emission spectroscopy diagnostics estimate that the radical density inside the atmospheric pressure plasma jet mainly increases with the repetition frequency. At the same time, the population of high-energy electrons can be controlled with the unipolar voltage amplitude. Thus, unipolar nanosecond pulses make it possible to control the emitting charges and the generated radicals independently.

Sub-waveform optimization for producing water window single-order harmonic

Through the sub-waveform optimization of the laser field, a potential method to produce the water window single-order harmonic (SOH) has been proposed. First, by properly introducing the chirps of two-color field, the SOHs from 303th order to 616th order can be obtained. Theoretical analyses show that the folding region on the harmonic emission process, caused by the multiple accelerations, is responsible for the enhanced SOH. Moreover, the folding region is dependent on the neighbor two half-cycle profiles. Thus, through further controlling the sub-waveform of the folding region by using the unipolar pulse, the folding region on the harmonic emission process will be extended to the higher photon energy region, including the water window region. Finally, by properly choosing the combinations of chirps and unipolar pulses, the water window SOH from 446th order to 833th order (from 345 eV to 645 eV) can be obtained.

Design of a Multichannel Pulser/Receiver and Optimized Damping Resistor for High-Frequency Transducer Applied to SAM System

Scanning acoustic microcopy (SAM) is widely used in biomedical and industrial applications in dermatology, ophthalmology, intravascular imaging, and small animal images, owing to SAM’s ability to photograph small structures with a good spatial resolution. One of the most important devices of this system is the pulser/receiver (P/R) (PRN-300, Ohlabs Corporation, Nam-gu Busan, Republic of Korea), which generates pulses to trigger a high-frequency transducer. This article presents the design of a pulse generator to excite high-frequency transducers with four channels. The characteristics of the pulses, such as time and frequency, can be reconfigured by using a high-speed field programmable gate array (FPGA). The configuration software was developed for communicating with the P/R device via a USB connector for easy, feasible pulse selection and real-time pulse management. Besides that, during the design and implementation of the hardware, we optimized the damping resistor value to reduce the overshoot and undershoot part of the signal, ensuring the best effect on the transducer signal. The test results show that unipolar pulses worked with transducers with frequencies over 100 MHz. The SAM systems can work simultaneously with multiple transducers, and the resulting images have different resolutions of regions.

Difference by Frequencies on Cell Killing Effect by Superposing Low Frequency on High-Frequency Bipolar Burst Pulse

An ultrashort pulse high electric field provides new biological applications, such as sterilization of a packaged food. In this study, we investigate the effect on yeast cells by a high-frequency and high-intensity burst pulse for the purpose of killing cells in packaged food. Previously, we showed that applying a burst pulse to cells was more effective in causing cell death than repeatedly supplying a single pulse. However, in case of a unipolar burst pulse, a low-frequency component caused by a burst pulsewidth was included in addition to the high-frequency component to be investigated. Therefore, it was not clear which frequency was effective in killing cells. Here, we investigate how the low-frequency component superposed on the high-frequency burst pulse affects cell death by comparing the unipolar burst pulse having the-low frequency component, the bipolar burst pulse not having the low-frequency component, and a single pulse that was the low-frequency component of the unipolar burst pulse. As a result, the cell death ratio was higher by applying 150-MHz band unipolar burst pulses including 150-MHz band as a high-frequency component and 15-MHz band as a low-frequency component to the cells than by applying bipolar burst pulses with only frequency component of 150-MHz band to the cells. Also, the cell death ratio was higher by applying the 150-MHz band unipolar burst pulses to the cells than by applying the 15-MHz band single pulse that was the low-frequency component of the 150-MHz band unipolar burst pulse to the cells. These results show that the burst pulse is possible in causing cell death more effectively by superposing low frequency on high frequency.

Electromechanical installation based on high power current pulse generator

Electromechanical installation containing electromagnetic s noid with a piston operating in reciprocating motion mode has been developed. Technologies with similar operating modes are widely used in various industries (mechanical engineering, metallurgy, mining, mechanics, robotics, as presses for forging and stamping, as well as jack-hammers in crushing devices for coal, ore and rock). An economically effective generator of high power unipolar current pulses (with unique systems that allow adjustment of the main parameters in a wide range and with high speed: the frequency of pulse reproduction, amplitude) was used as a power source for electromechanical installation. The principle of operation of the generator is based on periodic discharge of pre-charged capacitors to a low-resistance active-inductive load. Generator contains power unit, consisting of a capacitor discharge unit for load; a generator control system (GCS), consisting of a capacitor charging unit (reversible thyristor converter with counter-parallel connected thyristor bridges); a recharge unit and an automatic control system of the ACS. According to the known equations, parameters of mechanical and electrical parts of the electromechanical installation were calculated: initial coordinate of the piston; magnetomotive force arising from change in inductance L(x) ; spring force; the force of resistance to the piston, proportional to the speed of its movement; force action on the piston; amplitude, duration and frequency of reproduction of current pulses. A simulation model of the installation has been developed in the MATLAB-SIMULINK environment. The graphs of transient processes during operation of the installation at idle and under load were built. Analysis of the operating modes of the installation was carried out. Developed electromechanical installation for influencing load with the aim of its destruction or deformation with a system of automatic control of parameters makes it possible to regulate process parameters with high speed: force and distance traveled by the piston.

Topology and Control of Four-Quadrant Dual-DC-Port Dual-Buck Inverters For Semi-Two-Stage DC–AC Power Conversion

A method to derive topologies of four-quadrant dual-dc-port dual-buck inverter (DDP-DBI) is proposed in this article. A new family of DDP-DBIs is obtained by replacing one of the switching legs in a four-quadrant dual-buck half-bridge switching cell with a dual-input buck type switching leg. With the proposed DDP-DBIs, both the low voltage dc source and the high voltage intermediate dc-bus can be used as the inputs of the inverter. Therefore, in comparison with the conventional two-stage dc-ac power system, a semi-two-stage dc-ac power conversion system with reduced power losses and enhanced conversion efficiency is achieved. A unipolar sinusoidal pulse width-modulation strategy is presented for the DDP-DBI. In each line cycle, all the power devices and filter inductors only operate within half line cycle, and only one active switch is operated at high frequency. Moreover, no freewheeling current flows through the body diodes of the active switches. As a result, the conversion efficiency of the overall dc-ac power conversion system is improved. Operation principles, characteristics, modulation and control strategies of one of the proposed DDP-DBI are analyzed in detail. Effectiveness and feasibility of the proposed DDP-DBI are verified with experimental results.

Population Gratings Created by a Pair of Unipolar Attosecond Pulses in a Three-Level Atomic Medium

The possibility of inducing population gratings in a three-level resonant medium using a pair of unipolar attosecond pulses that do not overlap in the medium has been studied theoretically. It has been shown that the results of the approximate solution of the Schrodinger equation agree with the results of the numerical solution of the system of equations for the density matrix of a three-level medium whose parameters are close to the parameters of atomic vapors of rubidium.

Generation of an Attosecond Pulse Based on Collective Spontaneous Radiation Emission of a Layer of Three-Level Atoms Excited by a Pair of Unipolar Pulses

A method of coherent controlling the polarization of a medium has been proposed recently for the generation of extremely short pulses. The method is based on the excitation of atomic polarization oscillations and their subsequent stop using a pair of ultrashort pulses. The so-called stopped pulse of the polarization of a medium, which arises in the interval between its excitation and deexcitation, can be a source of an extremely short radiation pulse. In this work, the above-indicated possibility of generation of an isolated attosecond ultraviolet pulse in a three-level resonant medium whose parameters correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses is considered theoretically. In this case, the generation mechanism is of the antenna-type, that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization.

New modular high‐voltage pulse generator based on SEPIC converter for electroporation applications

High-voltage (HV) pulses are widely used in many applications. This study proposes a new HV unipolar pulse generator based on Single-Ended Primary-Inductance Converter (SEPIC) for electroporation applications. The converter in the proposed pulse generator operates in discontinuous conduction mode with continuous input current. The proposed structure uses voltage-boosting modules that are fed from a relatively low voltage DC source with a reduced number of semiconductors. The number of semiconductor devices and the voltage stress across them are important issues for HV pulse generators. The proposed approach does not have any chopping switches at the output stage, which greatly affects cost, efficiency, and system control. The employed semiconductor switches and diodes in the proposed topology have low voltage and current stresses, so the structure can be implemented with the market-available semiconductor technology. Mathematical analysis is presented along with a full design of the system components. Finally, simulation and experimental results are presented to validate the proposed concept.

Flexible all-solid-state supercapacitor based on polyhedron C-ZIF-8/PANI composite synthesized by unipolar pulse electrodeposition method

In this work, the unipolar pulse electrodeposition (UPED) method is used to electrodeposit the conductive polyaniline (PANI) on the carbonized polyhedron zeolitic imidazole particles (C-ZIF-8). The composite film of C-ZIF-8/PANI coated on the flexible substrate stainless steel wire mesh (SSWM) offers large contact area between the electrode material and the electrolyte, which provides enough active sites for charge storage. The obtained flexible electrode exhibits efficient-specific capacity of 363 F g−1 with 300° stretching angle and excellent long-term cycling stability after 10,000 cycles at 5 mA g−1 in 1 M H2SO4 electrolyte. It is found that the flexible electrode shows obvious improvement in the electrochemical properties when it was bent or stretched. Asymmetrical all-solid-state supercapacitor device is fabricated by using polyvinyl alcohol (PVA) solid gel as electrolyte and separator, which shows general gravimetric capacitance of 147, 156, and 156 F g−1 with energy densities of 8.66, 9.16, and 9.16 W kg−1 at stretching angle of 0°, 120°, and 300°, respectively, and stable power density of 162.5 W kg−1 in the different conditions. It indicates that such a composite C-ZIF-8/PANI/SSWM is a favorable material for portable and flexible energy storage.

RETRACTED: A hybrid technique used in grid integration of photovoltaic system for maximum power point tracking with multilevel inverter

A new hybrid technique for grid integration of solar photovoltaic system using modified incremental conductance maximum power point tracking algorithm with multi-output converter and multilevel inverter is proposed in the paper. The proposed hybrid technique is the joint execution of improved dolphin echolocation algorithm and gradient boosting decision trees and this way the proposed technique is named as IDE-GBDT technique. The novelty of the proposed work is the dolphin echolocation algorithm, which is integrated by the crossover and the mutation function so it is named as IDE. In the proposed technique, the multi-output converter is the combination of boost converter and switched capacitor function to generate different self-balanced output voltages. The utilization of multilevel inverter in the proposed system provides better quality of output voltage and current waveform thereby reducing the size of passive filters. Also, eliminates the requirement of bulky transformers for grid integration. Multicarrier unipolar phase disposition pulse width modulation technique is employed for triggering the switches of the multilevel inverter. The maximum power point tracking algorithm uses the estimated active power output of the generator as its input and generates command speed so that maximum power is transferred to the dc link. This control system also incorporates a loss minimization approach to minimize the losses in the generator and hence to improve the efficiency of the photovoltaic system. Finally, the performance of the proposed maximum power point tracking control of wind and photovoltaic power generation schemes is executed in Matrix Laboratory/Simulink working platform and the execution is assessed with the existing techniques. The proposed technique is compared with the existing techniques and the observed total harmonic distortion of the proposed technique in all the cases is 0.67%, 0.51%, 0.58%, 0.63%, 0.92%, and 1.03% and the total harmonic distortion is found to be very less compared with existing techniques.

High-speed wide dynamic range linear mode time-of-flight receiver based on zero-crossing timing detection

We present an accurate laser radar receiver with a wide dynamic range intended for ranging applications based on an event-based approach, in which a receiver-time-to-digital converter is used to extract the timing information from the reflected echo. The receiver is based on LC resonance pulse shaping at the input so that the unipolar pulse detected by the avalanche photodiode is converted to a bipolar signal, and the first zero-crossing of this converted signal is marked as the only timing point. One important aspect of the proposed scheme is that it does not need any postcompensation or gain control for achieving a wide dynamic range. The receiver chip was fabricated in a 0.35-μm standard CMOS technology, and a laser radar platform was developed to verify the functionality of the proposed receiver channel. The measured accuracy of the receiver is ±3.5 cm within a dynamic range of more than 1:250,000 using 3-ns FWHM pulses when target materials with different reflectivities are used in the measurements. The single-shot precision of the receiver (σ value) is ∼5 cm for a minimum SNR of ∼10.

AN APPLICATION OF R-HiPIMS METHOD FOR TiO2- AND TiO2:Cu-BASED MEMRISTORS: CONTROLLING Cu DOPING USING DC PULSE METHOD

Nowadays, the High-Power Impulse Magnetron Sputtering (HiPIMS) as an additional technique to plasma-based sputtering, is applied to depositing or coating of thin films. HiPIMS is based on applying high-power and low-duty-cycle unipolar pulses to the magnetron target by a low repetition frequency, which are produced from the high ionization part of sputtered atoms by high discharge power. By applying voltage to substrate and bombarding it in the presence of an inert gas such as Ar, the growth of the film is controlled by the acceleration of the sputtered material across the highly dense plasma. To deposit compound materials, metal targets are sputtered with gases such as CH4, N2, O2, etc. or by Reactive HiPIMS (R-HiPIMS) techniques. The transparent metal oxide (TiO[Formula: see text] film depositions by R-HiPIMS are denser and have flatter surfaces due to a higher degree of crystallinity than other sputtering methods. The applicable potential of TiO2thin films and similar metal oxides on the ultra-high-density electronic devices due to the presence of oxygen deficiency, leads them to be chosen for memristor devices. As theory predicted, a current-controlled memristor is possible with metal–TiO2–metal structures. But stability and repeatability with high ON/OFF ratios remain as problems. A high ON/OFF ratio due to filament formation is revealed by Cu doping of TiO2thin films which leads to two state functions to be applicable for the traditional digital electronics. On the other hand, an ideal memristor has a potential for gray scale with no limitation. This approach has a big potential impact on data storage and computation in electronics. A new spotlight for this prediction is recognized by the high mobility of transition elements such as Cu in semiconductors. In this work, a nano-scale memristor based on Cu-doped TiO2is fabricated from metallic targets (i.e. Ti and Cu) by the R-HiPIMS method. Cu doping is synchronously controlled by using pulsed DC sputtering onto the TiO2structure. DC pulse duration and its frequency are used for adjusting the Cu doping concentration during the growth time of TiO2. The memristor properties of Cu–Pt–TiO2–p[Formula: see text]Si–Al and Cu–Pt–TiO2:Cu–p[Formula: see text]Si–Al devices are considered. The electrode change effect on the memristive properties and performance of Cu-doped memristor is investigated. The [Formula: see text]–[Formula: see text] characteristic of the Cu-doped memristor with Cu top electrode is recognized to be asymmetric in comparison with Cu-doped TiO2-based memristor with Pt top electrode. The structural, optical and electrical characterizations are carried out and preliminary findings are given in detail.

Probabilistically Shaped 4-PAM for Short-Reach IM/DD Links With a Peak Power Constraint

Probabilistic shaping for intensity modulation and direct detection (IM/DD) links is discussed and a peak power constraint determined by the limited modulation extinction ratio (ER) of optical modulators is introduced. The input distribution of 4-ary unipolar pulse amplitude modulation (PAM) symbols is optimized for short-reach transmission links without optical amplification nor in-line dispersion compensation. The resulting distribution is symmetric around its mean allowing to use probabilistic amplitude shaping (PAS) to generate symbols that are protected by forward error correction (FEC) and that have the optimal input distribution. The numerical analysis is confirmed experimentally for both an additive white Gaussian noise (AWGN) channel and a fiber channel, showing gains in transmission reach and transmission rate, as well as rate adaptability.

Tomography of Qubit States and Implementation of Quantum Algorithms by Unipolar Pulses

The conventional technique for controlling the states of individual qubits and quantum registers is based on the use of high-frequency modulated pulses whose carrier frequency is close to the transition frequency between the ground states of “artificial atoms” and “molecules” (the Rabi technique). In this paper, an alternative concept for controlling superconducting qubits is developed that is based on the idea of fast excitation of a quantum system by solitary unmodulated pulses. The formation of entangled Bell states in a two-qubit superconducting register under the action of field pulses obtained by rapid single flux quantum (RSFQ) devices is demonstrated by numerical simulation. The tomography of quantum states is performed by solving the density matrix equation. It is shown that the technique of “unipolar pulses” allows one to speed up the formation of entangled states (at picosecond times) with a fidelity of 95–98%. The execution of the basic quantum algorithms is demonstrated: the Deutsch–Jozsa algorithm with an accuracy of more than 98% and Grover’s algorithm with an accuracy of 93%.