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Purpose: Experimental results and numerical simulations are presented, concerning effects of microwave generation in coaxial transmission lines which are fed with unipolar, high voltage electric pulses. The work is aimed at clarifying the relative importance of several mechanisms that could be responsible for the appearance of microwave-frequency oscillations in the course of pulse propagation through the guiding structure. Design/methodology/approach: Dispersive and filtering properties of coaxial waveguides that involve three structural sections are discussed. These latter follow one another along the axis of symmetry. Two identical sections at the input and output are filled with an isotropic liquid dielectric, while the middle part may, in addition, be either partially or fully filled with a non-conductive gyrotropic material. The inserted core represents a set of ferrite rings showing a nonlinear response to the initial high voltage, pulsed excitation. Throughout the series of measurements, the diameters of the inner conductor and of the ferrite core were kept constant. The outer conductor’s diameter was varied to permit analysis of the effect of that size proper and of the degree to which the cross-section is fi lled with ferrite. The gyrotropic properties of the ferrimagnetic material were realized through application of a magnetic bias field from an external coil. The measurements were made for a variety of pulsed voltage magnitudes from the range of hundreds of kilovolts, and magnetic bias fields of tens kiloamperes per meter. Findings: As observed in our experiments, as well as in papers by other writers, a unipolar pulse coming from the radially uniform front-end section, further on gives rise to quasi-monochromatic voltage oscillations. These appear as soon as the pulse has advanced a sufficient distance into the radially nonuniform portion of the guide. The oscillations may consist of a small number of quasi-periods, which suggests a large spectral line width. However, by properly selecting geometric parameters of the wave guiding line and the characteristics of the initial pulsed waveform it proves possible to obtain output frequencies of about units of gigahertz and pulse powers at subgigawatt levels. Conclusions: The frequencies and amplitudes of the appearing oscillations, as well as their spectral widths, are governed by the complex of dispersive and non-linear properties of the guiding structure. The diameters of the inner and outer coaxial conductors in the line, diameter of the ferrimagnetic insert and its intrinsic linear dispersion determine the set of waveguide modes capable of propagating through the line. An oscillating part of the waveform may appear and get separated from the main body of the pulse if it has originated at a higher frequency than the cut-off value for a different mode than the initial TEM. Key words: unipolar pulse, coaxial transmission line, microwave frequency oscillations, dispersion laws, waveguide modes

A novel hexagonal prism Copper (II) metal organic framework (Cu-BTC) was first synthesized by using a facile unipolar pulse electropolymerization method. It has been found that the morphology of Cu-BTC crystals can be changed from octahedron to hexagonal prism with the increase of pulse cycles. The XRD pattern confirms that the crystal structure of Cu-BTC was slightly affected by the change of the crystal morphology. Furthermore, the growth mechanism of hexagonal prism Cu-BTC crystals was proposed. This method provides valuable guidelines for the design of other MOFs and opens up new opportunities for exploring their application.

The most typical way to optically control population of atomic and molecular systems is to illuminate them with radiation, resonant to the relevant transitions. Here we consider a possibility to control populations with the subcycle and even unipolar pulses, containing less than one oscillation of electric field. Despite the spectrum of such pulses covers several levels at once, we show that it is possible to selectively excite the levels of our choice by varying the driving pulse shape, duration or time delay between consecutive pulses. The pulses which are not unipolar, but have a peak of electric field of one polarity much higher (and shorter) than of the opposite one, are also capable for such control. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Multilevel inverters (MLIs) are an imperative solution for high power and high voltage applications. The MLIs can be classified into two categories such as symmetric and asymmetric. The asymmetric type MLIs has large number of output voltage steps with less number of input DC voltage sources and switching devices. In this paper, a single phase asymmetric (trinary sequence DC source) Cascaded H-Bridge MLI has been developed using unipolar PWM control schemes. The topology can produce 27-level output voltage with the help of 12 switches and 3 DC sources. It has been examined with a diverse combination of multicarrier unipolar PWM control. The PWM control includes Phase Disposition (PDPWM), Alternative Opposition Disposition (APODPWM), Carrier overlapping (COPWM), and Variable Frequency (VFPWM). The harmonic content of output voltage for each technique has been observed with different modulation indices. The demonstration of proposed topology for generating 27-level output voltage has been tested through simulation in MATLAB-SIMULINK and verified with laboratory-based experimental setup. From the results, it is evident that the APODPWM offers quality output voltage with relatively low harmonic distortion. Also, it has been observed that COPWM performance is superior since it delivers relatively higher fundamental RMS output voltage.

The National Aeronautics and Space Administration (NASA) has spent years studying magnetic therapy and has built their own pulse electromagnetic field apparatus (PEMF). The concept of unipolar pulsed electromagnetic field (UPEMF) devices is presented; this device is an improved medical apparatus for magnetic therapy based on PEMF. A concentrator is designed to strengthen the magnetic field on the north pole and weaken the opposite field. The UPEMF device provides an approximate unipolar electromagnetic field and meets the medical requirements of magnetic therapy in terms of frequency, shape, and intensity.

This paper describes the influence of gas pressure on the conversion of O2 to O3 and the ozone production efficiency in a multichannel dielectric barrier discharge (DBD) reactor utilizing positive and negative pulses. Results show that conversion of O2 to O3 is continuously enhanced by the increase of gas pressure (0.1–0.24 MPa) while the rising speed of oxygen conversion with the increasing gas pressure at fixed specific input energy is reduced above 0.15 MPa. The maximum ozone generation efficiency is increased with increasing gas pressure (0–0.2 MPa) while positive pulse exhibits higher energy efficiency. The maximum ozone generation efficiency is suppressed with further increase of gas pressure (0.2–0.24 MPa) while no significant difference in ozone generation efficiency is observed for two unipolar pulse modes. Results also show that 0.2 MPa is the optimal working gas pressure to obtain the maximum ozone generation efficiency and increasing gas pressure would lead to remarkable increase of oz...

Since the baseline of the unipolar pulse shaper have the direct-current (DC) offset and drift, an additional baseline estimator is need to obtain baseline values in real-time. The bipolar zero-area (BZA) pulse shapers can be used for baseline restoration, but they cannot restrain the baseline drift due to their asymmetrical shape. In this study, three trapezoids are synthesized as a symmetrical zero-area (SZA) shape, which can remove the DC offset and restrain the baseline drift. This baseline restoration technique can be easily implemented in digital pulse processing (DPP) systems base on the recursive algorithm. To strengthen our approach, the iron's characteristic x-ray was detected using a Si-PIN diode detector. Compared with traditional trapezoidal pulse shapers, the SZA trapezoidal pulse shaper improved the energy resolution from 237 eV to 216 eV for the 6.403 keV Kα peak.

A unique aspect of electrostimulation (ES) with nanosecond electric pulses (nsEP) is the inhibition of effects when the polarity is reversed. This bipolar cancellation feature makes bipolar nsEP less efficient at biostimulation than unipolar nsEP. We propose to minimize stimulation near pulse-delivering electrodes by applying bipolar nsEP, whereas the superposition of two phase-shifted bipolar nsEP from two independent sources yields a biologically-effective unipolar pulse remotely. This is accomplished by electrical compensation of all nsEP phases except the first one, resulting in the restoration of stimulation efficiency due to cancellation of bipolar cancellation (CANCAN-ES). We experimentally proved the CANCAN-ES paradigm by measuring YO-PRO-1 dye uptake in CHO-K1 cells which were permeabilized by multiphasic nsEP (600 ns per phase) from two generators; these nsEP were synchronized either to overlap into a unipolar pulse remotely from electrodes (CANCAN), or not to overlap (control). Enhancement of YO-PRO-1 entry due to CANCAN was observed in all sets of experiments and reached ~3-fold in the center of the gap between electrodes, exactly where the unipolar pulse was formed, and equaled the degree of bipolar cancellation. CANCAN-ES is promising for non-invasive deep tissue stimulation, either alone or combined with other remote stimulation techniques to improve targeting.

Here we numerically investigate the propagation of unipolar half-cycle attosecond pulses with a duration much shorter than the period of the proper oscillations T 0 of the medium and its relaxation times T 1 and T 2 in a two-level resonant absorbing and amplifying medium. We find that despite breaking down of the famous McCall and Hahn area theorem, some phenomena described by this theorem are still qualitatively preserved. In particular, it is shown that pulses with small initial electric pulse area become sign-alternating upon the propagation, similar to the traditional 0 π pulses; pulses with 4 π , 5 π , and 6 π area are unstable and split into lower-order pulses, exactly as in the long-pulse case. The electric pulse area conservation rule and limitations of unipolar pulse amplification in two-level gain media, which follows from this rule, are discussed.

Multilevel inverters (MLIs) are gaining familiarity in industries for high-voltage applications. This study is a comparison of symmetric and asymmetric reduced switch MLI topologies which require a lesser number of switches for generating the desired number of voltage levels. In both symmetric and asymmetric conditions, output voltage levels are generated using the same number of switches with different DC source magnitudes. Unipolar pulse width modulation strategy is adapted in these topologies to generate the switching pulses. Three different unipolar references (sine, trapezoidal, 60°) and three different carrier arrangements (phase disposition, alternative phase opposition and disposition and variable frequency) are taken and each reference is compared with three different carrier signals. The performance parameters such as total harmonic distortion (THD), crest factor and distortion factor are evaluated for different modulation indices and compared with both conditions. The proposed topology in symmetric and asymmetric conditions can generate 9-level and 31-level output voltages, respectively, which are simulated using MATLAB/Simulink and verified with the experimental setup. The calculation of %THD using analytical asymptotic formula is also carried out. The theoretical value of %THD is verified to match closely with the simulation and experimental results.

The extended or dynamic harmonic domain method is used to obtain harmonic Analysis during steady dynamic states for static shunt compensation (STATCOM). Firing pulses used for voltage source converter (VSC) are based on unipolar pulse width modulation and space vector pulse width modulation PWM, and SVPWMs and the simulation results obtained during steady state are validated by prototype panel experiments. The voltage and current harmonics are reduced considerably when space vector modulation is used for STATCOM VSC switching.

Nickel hexacyanoferrate (NiHCF) film was successfully deposited on carbon fibers by unipolar pulse electrodeposition (UPED) method. The effects of pulse potential and cycle number during the film deposition on the composition, regeneration ability and cycle stability of the film were investigated.The morphology, composition and electrochemical behavior of the as-fabricated NiHCF film were varied with the deposition conditions, and two structural analogues, i.e., soluble and insoluble NiHCFs, could be appeared together or alone in the finally obtained films. Especially, it is found that higher pulse potential was necessary to obtain high-quality NiHCF film on the carbon fiber than on metal electrode. In this study, when the pulse potential during the unipolar deposition of NiHCF film was set at a condition of 0.8 V with 0.5 s on-time, 0.5 s off-time and 3000 cycles, a film with insoluble structural analogue was obtained and it showed large ion exchange capacity, good regeneration ability and long-term cycle stability.

A high reliable amorphous silicon gate driver with shared dual pull-down units is proposed and fabricated for large-sized TFT-LCD applications. A special unit in the driver is designed to generate bipolar pulse bias for low-level holding TFTs to suppress the threshold voltage shift, which achieves 40.5% and 34.8% improvement compared with conventional DC and unipolar pulse bias respectively according to measurement results.

Crystallographic phases of Plasma electrolytic oxidized Al alloy, A1050, were investigated. The electrolyte of PEO was and KOH. Unipolar pulse, with impulse, were applied for 2 min, 5 min, 15 min, and 30 min. , as well as , was main crystal phase. was appeared in the beginning, then the amount of was increased with time, but the amount of remained constant without any increasing. So, it is concluded that plasma gas produce at the first, and then transform finally. During the transformation, high temperature of micro plasma gives transformation energy.

The article explores the ways to use multiconductor strip lines (SL) for solving the problems of generating a bipolar and unipolar pulse oscillations packet. Reflection-symmetric and five-conductor microstrip structures, as well as their various configurations, which are cascade-connections of these SLs are considered. The maximum conversion efficiency of a unipolar nanosecond pulse into high-frequency oscillations is estimated to be less than 1–2%. The results are important for further research and the possibility of using SLs for such tasks.

This paper describes how copper plating is influenced by modulated current. By unipolar pulse plating smooth, compact and fine grained structures can be obtained, but the macro throwing power is worse than by direct current plating. The best throwing power is obtained by pulse reverse plating. In additive containing solutions, excellent throwing power has been obtained at the following parameters: T c/T a=20, i a/i c=1–3·5 and Q a/Q c

The effect of pulse switching on the piezoelectric response of 10-μm-thick Pb(Zr0.53Ti0.47)O3 films was investigated. The amount of the longitudinal displacement related with piezoelectric response decreases when the bipolar pulse switching count is greater than 107. This degradation tendency is consistent with the “fatigue” profile for remanent polarization of the PZT films. However, longitudinal displacement degradation was not observed for unipolar pulse switching. These experimental results suggest that the unipolar drive of the high electrical field does not affect the displacement endurance property of the PZT thick films for micro-actuator application.

Muscle contraction is one of puzzles for clinicians most eager to solve in the treatment of tumors during electroporation. The current measures to reduce muscle contraction, such as injection of muscle relaxation agents have certain side effects. Some studies suggest that bipolar pulse can effectively reduce muscle contraction, but the mechanism of this phenomenon is still unclear. Most exciting simulation studies concerning electrical activation of human muscles are based on the modeling approach of Hodgkin-Huxley model. For the study of bipolar pulse effect on action potential firing of myocytes from the point of excitability of myocytes, Simulink model of myocytes was established based on Hodgkin-Huxley model with Matlab. By comparing the different results that whether the action potential of myocytes is firing or not with the different conditions of myocytes that applying bipolar or unipolar pulses which both have the same duration of high level, we analyze the weakened effect of bipolar pulse on muscle contraction in the terms of the generation of the action potential of the myocytes. The results showed that for the same high level time for the two different pulses, the amplitude needed to fire the action potential of myocytes with bipolar pulses is significantly higher than the unipolar pulses, and this indicate that bipolar pulse can inhibit the firing of the action potential of myocytess. And in this way, the bipolar pulse can achieve the effect of weakening muscle contraction in terms of inhibition of transmembrane potential. In addition, we also find that when we apply bipolar pulses with short duration like 40us or 5us, there will be an incubation period before the potential appears. Through the preliminary animal experiments with tunable bipolar pulse source developed by our group, muscle contraction with bipolar pulses is weaken compared with unipolar pulse in the same amplitude of the two different pulses. Even in some cases, muscle contracts occur with unipolar pulses, while no shrinkage with bipolar pulses.

Electric fatigue of piezoelectric ceramics is very important for piezoelectric actuator applications in strong field. In order to classify the fatigue of ferroelectric and piezoelectric properties, the electric fatigue behavior of piezoelectric ceramics of PZT-PMN-PNN was investigated under bias and unipolar pulse cycling field. The bias and unipolar polarization hysteresis loops are measured before and after cycling. The polarization measurements after cycling show a much smaller decrease than bipolar fatigue, but the piezoelectric coefficient d33 still suffers relatively higher deterioration, which indicates different characteristics for piezoelectric and ferroelectric fatigues. A possible mechanism of the partial pining of switching domains responsible for the difference is discussed in this paper.

Проведен анализ схемных решений по подключению инструмента магнитно-импульсного воздействия к источнику мощности. Раскрыты особенности построения системы контроля и управления магнитно-импульсной установки в режиме многократных токовых импульсов. Приведено описание структурных схем системы контроля и управления., An analysis of circuit designs as to connecting a magnetic pulse action tool to a power source has been carried out. Design features of a magnetic pulse installation control and monitoring system in a multiple current pulse mode have been revealed. The description of the control and monitoring system block diagrams has been presented., Проведено аналіз схемних рішень по підключенню інструменту магнітно-імпульсного впливу до джерела потужності. Розкрито особливості побудови системи контролю і управління магнітно-імпульсної установки в режимі багаторазових струмових імпульсів. Наведено опис структурних схем системи контролю та управління.

Проведен анализ схемных решений по подключению инструмента магнитно-импульсного воздействия к источнику мощности. Раскрыты особенности построения системы контроля и управления магнитно-импульсной установки в режиме многократных токовых импульсов. Приведено описание структурных схем системы контроля и управления. An analysis of circuit designs as to connecting a magnetic pulse action tool to a power source has been carried out. Design features of a magnetic pulse installation control and monitoring system in a multiple current pulse mode have been revealed. The description of the control and monitoring system block diagrams has been presented.

Electromigration (EM) of Copper interconnects is studied under unipolar pulse current (UPC) at 1.25 kHz ∼ 1.25 MHz and bipolar pulse current (BPC) at 100 kHz ∼ 5.0 MHz. For symmetric BPC, where a time-averaged current density (J avg ) is 0, we found interconnect failures by EM-induced void formation. This means EM is not fully recovered during the opposite-polarity pulse current. The degree of EM recovery is found to be 0.7 ∼ 0.9, where 1 is for full-recovery. Also, the short lead EM effect is investigated under UPC. We found short lead EM lifetimes are modeled by peak current density (J peak ), instead of J avg . Also, we observed, during the off-time between low frequency pulse currents, mechanical back-stress may reduce the stress gradient built by UPC and increase the EM lifetimes of the short leads.

Photon counting statistics with pulse pileup effects (PPE) have been investigated for detection schemes with two assumptions: a fixed deadtime (i.e., non-paralyable and paralyzable detection schemes) and a delta pulse shape. Analytical expressions have been developed which shed light on interesting findings: (1) the variance becomes smaller than mean with PPE; and (2) the variance-to-mean ratio (VMR) of narrow energy windows remains very close to 1. In this study, we experimentally investigate VMR with PPE with a variable deadtime (i.e., pulse height analysis) and bipolar and unipolar pulse shapes with a long tail in addition to the above cases. We will use Monte Carlo simulation for a systematic study and a physical photon counting detector to confirm the results.