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In this paper, the authors report rationally designed, innovative tri-layer flexible transparent conductive electrodes (TCEs) fabricated via thermal deposition. The proposed structure improves transparency compared with that of the traditional tri-layer electrode (dielectric/metal film/dielectric) by using metallic grid patterns (dielectric/metal grids/dielectric). The obtained MoO3/Ag grids/MoO3 TCEs show low sheet resistance and good mechanical properties. The sheet resistance of the proposed electrodes is 5.88 Ω/square and the transmittance reaches 76.5%, which are better than those of conventional MoO3/Ag film/MoO3 electrodes (6.12 Ω/square, <70%). The mechanical properties are significantly improved compared with those of MoO3/Ag film/MoO3 in the bending test under both tensile and compressive stress. The surface features of the MoO3/Ag grids/MoO3 TCEs were measured using the contact angle method to calculate the surface energy and polarity. The polarity is 0.5-0.26, which is better than those of indium tin oxide (0.35) and MoO3/Ag film/MoO3 (0.5-0.0058) electrodes for 0-800 bending cycles. The proposed flexible transparent electrodes show good optical, electrical, and mechanical characteristics and have potential for application in optoelectronics. [ABSTRACT FROM AUTHOR]

Preparation and characteristics of conductive-bridge random access memory devices containing Ge2Sb2Te5 (GST) chalcogenide as the solid-state electrolyte, Ag as the active electrode, and W-Ti as the counter electrode are presented. As revealed by the electrical measurement, only the samples containing crystalline GST exhibited the resistive switching behaviors. With an insertion of ZnS-SiO2 dielectric layer at the Ag/GST interface and a postannealing at 100?°C for 1?min, the sample exhibited the best electrical performance with satisfactory cycleability and retention properties. Moreover, the forming-free and bi-directional polarity features were observed in such a sample type. Microstructure and composition analyses found the finely dispersed nano-scale Ag clusters in GST and, when electrical bias is applied, the migrating Ag ions may build up the connections in between neighboring Ag clusters. Moreover, grain boundaries in polycrystalline GST might be the main paths for Ag migration. The thread-like conduction channels in GST hence form, leading to the low resistance state of sample. On the contrary, the depletion of Ag in GST broke the connections in between Ag clusters when the electrical bias is reversed. This led to the rupture of conduction channels and, hence, the high resistance state of sample. The low operational voltage, forming-free, and bi-directional polarity features observed in (AZGW)T sample might also originated from the fine dispersion of Ag clusters in GST electrolyte. [ABSTRACT FROM AUTHOR]

In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20K lower than the unipolar discharge plasma. [ABSTRACT FROM AUTHOR]

We develop a criterion for spark-breakdown in non-uniform field geometries with positive polarity and small electrode separations so that breakdown evolves without the formation of a leader. We arrive at the spark-breakdown criterion by framing it in terms of gain and instability conditions, whose relative importance is established from an analysis of the experimental breakdown characteristics and correlations with streamer behavior in short gaps. Results are presented in the context of two generic geometries having coaxial and point-plane electrodes. For nearly uniform field situations, we re-confirm that the breakdown criterion obtained by the usual extension of either the Townsend or Meek criteria satisfactorily predicts the experimental results. On the other hand, for increasing non-uniformity, the results for the corona and spark branches of the breakdown characteristics are shown inconsistent with a breakdown criterion solely based on either the Townsend or streamer mechanisms. In particular, the avalanche gain factor, the primary component of the Townsend and streamer criteria, does not determine the spark breakdown criterion. Streamers can cross the gap for a significantly wide range of applied voltages without triggering a spark. We find that it is the instability condition, derived from a relation between the minimum Laplacian field in the gap and the local streamer body field (which we relate to the streamer sustaining field), that is sufficient for determining the spark threshold thereby yielding a breakdown criterion. [ABSTRACT FROM AUTHOR]

The aim of this research was to determine in which areas of the bovine body surface the electrodes should be placed to record T waves with stable polarity and morphology by using bipolar and unipolar leads to detect alterations in the conduction of the ventricular repolarization impulse. One hundred animals of both sexes from different age groups were used. Each T-wave form was numerically coded and its polarity was classified. Sixteen different forms of T waves were observed, presenting four types of polarity: positive, negative, biphasic +/- and biphasic -/+. In the bipolar shoulder lead IH, the T wave was largely negative or biphasic +/-; and it was positive or biphasic -/+ in the remaining bipolar leads. The T-wave was negative or in some cases biphasic +/- in the unipolar basal leads of the heart. Positive or biphasic polarity was always obtained in the apical leads -/+ and four to six different forms were recorded. It is concluded that, in the areas located towards the base or the apex of the heart, leads can be used originating electrocardiographic records with great stability in the polarity of the T wave and in which the quantity of different forms detected is very reduced, with great predominance of the pointed one, so that they become a very useful reference to diagnose the alterations in the conduction of the repolarization impulse through the cardiac ventricles. [ABSTRACT FROM AUTHOR]

This paper presents experimental results on electrical explosions of thin tungsten wires at wire currents of 0.04–0.4 kA and current rise times of several tens of nanoseconds. The experiment was performed for both negative and positive polarity of the high-voltage electrode. In addition to conventional current and voltage measurements, the current to a grounded cylindrical collector placed between the exploded wire and the return conductor was measured. The collector current was observed only for a 6 μm wire exploded with the high-voltage electrode being at a negative potential. In all other test modes (a 6 μm wire exploded with electrode positive polarity, 6 μm wire exploded with electrodes enclosed in ceramic tubes, 30 μm wires exploded with electrode negative and positive polarities) no collector current was detected. A model of the discharge initiation during a wire explosion (WE) in vacuum has been proposed which is based on the supposition that a surface discharge develops over the electrodes. The presence of plasma-emitted electrons at the cathode surface makes it possible to interpret the experimental results on WEs at different electrode polarities reported both in this paper and in previous publications. [ABSTRACT FROM AUTHOR]

The utilization of charged domain walls (CDWs) as nanoelectronic devices requires three technological aspects to be developed: (1) controllable CDW creation, (2) tuning of CDW geometry, and (3) CDW removal. We have studied CDW formation in lithium niobate single crystals during polarization reversal using liquid and solid-state electrodes, as well as their combination. It was shown that CDW can be formed by two alternative procedures: (1) by forward switching for the liquid electrode at the Z+ polar surface and solid at the Z− one, (2) by backward switching for solid at the Z+ polar surface and liquid at the Z− one. The created CDW can be transformed to an almost neutral domain wall by the application of the field pulse of the reverse polarity for both procedures. As a result, the tilt of the formed CDW can be tuned reversibly in the range from 0.2° to 1.2° resulting in a change between isolated and highly conductive states. We have demonstrated that the created CDW can be used as a nanoelectronic channel for local electrolysis opening the additional possibilities for ferroelectric lithography. [ABSTRACT FROM AUTHOR]

Neuronal excitability is determined in a complex way by several interacting factors, such as membrane dynamics, fibre geometry, electrode configuration, myelin impedance, neuronal terminations[Formula: see text] This study aims to increase understanding in excitability, by investigating the impact of these factors on different models of myelinated and unmyelinated fibres (five well-known membrane models are combined with three electrostimulation models, that take into account the spatial structure of the neuron). Several excitability indices (rheobase, polarity ratio, bi/monophasic ratio, time constants[Formula: see text]) are calculated during extensive parameter sweeps, allowing us to obtain novel findings on how these factors interact, e.g. how the dependency of excitability indices on the fibre diameter and myelin impedance is influenced by the electrode location and membrane dynamics. It was found that excitability is profoundly impacted by the used membrane model and the location of the neuronal terminations. The approximation of infinite myelin impedance was investigated by two implementations of the spatially extended non-linear node model. The impact of this approximation on the time constant of strength-duration plots is significant, most importantly in the Frankenhaeuser-Huxley membrane model for large electrode-neuron separations. Finally, a multi-compartmental model for C-fibres is used to determine the impact of the absence of internodes on excitability. Graphical Abstract Electrostimulation models, obtained by combining five membrane models with three representations of the neuronal cable equation, are fed with electrode and stimulus input parameters. The dependency of neuronal excitability on the interaction of these input parameters is determined by deriving excitability indices from the spatiotemporal model response. The impact of the myelin impedance and the fibre diameter on neural excitability is also considered. [ABSTRACT FROM AUTHOR]

This study examined the interaction between polarity and electrode-activation order on loudness in cochlear implant users. Pulses were presented with the polarity of the leading phase alternating or constant across channels. Electrode-activation order was either consecutive or staggered. Staggered electrode-activation orders required less current for equal loudness than consecutive orders with constant polarity. Consecutive electrode-activation orders required less current than staggered orders with alternating polarity. The results support the hypothesis that crosstalk between channels can interfere with or facilitate neuronal activation depending on polarity. [ABSTRACT FROM AUTHOR]

A thorough understanding of the governing concepts of polarity behavior within electroencephalograph (EEG) promotes analytical and thus technical proficiency of the technologist by providing a skill set to logically resolve the myriad of waveform presentations that are expected across all montage derivations. In addition to avoiding a reliance on cursory conceptualization techniques, a solid grasp of the underlying theory of EEG polarity permits a fundamental realization of the cause-effect relationships between the various directions of eye movement and the resulting multitude of wave deflection presentations observed across all montages. Such wisdom can logically account for the futility of using a particular bipolar montage to localize discharges of interest that are located at end-of-chain. Further, it provides a logical template from which to make sense of physiological and nonphysiological contamination within referential electrodes. Regardless of montage formatting, an EEG epoch can be deconstructed into discrete components; all of the left-sided electrodes within each pair of leads, or channel, are classified as input 1, whereas the right-sided ones are termed input 2. The Polarity Rule states that if input 1 is more negative with respect to input 2, there will be an upward deflection of the associated wave. All wave deflections within any montage arrangement can be explained from this core rule. For those expected to take examinations that include EEG polarity questions, this deeper appreciation may assist by shifting away from the need to memorize a plethora of scenario-dependent wave behaviors. [ABSTRACT FROM AUTHOR]

It is well known that after current interruptions, a fine Cu-Cr melted layer is formed on the electrode surface, and the vacuum insulation between electrodes is improved. However, the influence of the depth of the arc-melted layer on the vacuum insulation is still not clear. The objective of this paper is to determine the influence of the depth of the arc-melted layer of the cathode on the vacuum insulation. A 12 kV vacuum interrupter with a pair of rod-plane electrodes was designed. A DC current source was applied to the vacuum interrupter, and the rod electrode was chosen as the anode. A drawn vacuum arc in the anode spot mode was used to generate melted layers with different depths on the rod electrode. The arcing time was controlled to 0, 10, 46 or 73 ms. Then, the vacuum gap was adjusted to 1 mm to measure the basic lightning impulse breakdown voltage. Standard positive-polarity 1.2/50 μs lightning impulses were applied by a basic up-down method, in which the rod electrode was the cathode. Experimental results revealed that the breakdown probability followed a Weibull distribution when the breakdown voltage reached saturation. The 50% breakdown voltage U50 with arcing times of 0, 10, 46 and 73 ms was 55.6, 73.3, 75.5 and 77.9 kV, respectively. Next, a cross section of the rod electrode was analyzed using an electron microscope, and the average depths of the arc-melted layers were 0, 5, 35 and 65 μm at current arcing times of 0, 10, 46 and 73 ms, respectively. The depth of the arc-melted layer varied approximately linearly with the arcing time. The U50 values of the vacuum gaps with the arc-melted layers were significantly larger than that without a melted layer but very close to each other for all arc-melted layer depths. Thus, the melted layer did improve the breakdown voltage, but the depth of the arc-melted layer had little influence on the breakdown voltage. [ABSTRACT FROM AUTHOR]

One of the main reasons of metal film capacitors failure in pulse modes is a degradation of contacts between film metallization and solid electrodes—contact edges. This paper presents the results of experimental investigations of modeled contact edges behavior under current pulses of varying amplitude, duration, and quantity. It was found that the contact edge degradation is caused only by metallization destruction and independent on metal of the solid electrodes (“shoopage”). Depending on pulse parameters and dissipated energy in the contact edge, the contact erosion rate is in the range of (0.4– 2.7) \times 10^-3 g/J. Current pulse polarity effect on contact edge degradation was found: mean time to failure (MTTF) of the contact edge depends on its polarity, i.e., on the direction of the current flow through the contact during charge or discharge of capacitor. For different contacts polarities the difference between MTTFs reaches 20%–60% depending on pulse parameters. Based on these facts, one makes a supposition that the timely changing of the capacitor’s terminals polarity can lead to the increasing of capacitor lifetime. [ABSTRACT FROM PUBLISHER]

Electrical tree propagation is a precursor to dielectric failure in high voltage polymeric insulation. Tree growth has been widely studied under AC conditions, but its behavior under DC is not well understood. The aim of this work was to examine the importance of polarity and initiating defect size on DC tree propagation. Electrical tree propagation in epoxy resin under constant DC voltages of +60 kV and −60 kV was measured in samples with classical needle-plane electrodes, but with small initial trees (< 100 μm) incepted under lower AC voltages before the DC tests. Experimental results showed strong polarity dependence. In either polarity, the length of the initial AC tree had a major influence on the inception of the subsequent DC tree. The effect was attributed to the defect being influential if it is larger than the space charge injection region. As a consequence, there is a critical defect size that will accelerate failure of DC insulation dependent on space charge injection behavior of the polymer/electrode system in question — a critical finding for high voltage asset management. [ABSTRACT FROM PUBLISHER]

For the safe design and operation of wet-mate (WM) DC power connector, a time-dependent full thermo-electrodynamic model comprised of Poisson's equation, three charge continuity equations-one each for the positive and negative ions and one for the electrons-, and a thermal diffusion equation is developed to study the streamer initiation and propagation in the oil portion of a WM DC chamber. The electric field dependent molecular ionization mechanism accounts for the source term for free charge carriers, and positive ion/electron recombination, positive/negative ion recombination and electron attachment represent sink terms in the oil section. The solid portion of the WM DC connector is modeled as a perfect insulator. Considering a needle-sphere electrode geometry with electrodes covered by a dielectric solid and oil enclosed by the dielectric solid, it is approached the complicated solid-liquid insulation system envisaged in a WM DC connector after mating. By using the model, the influence of three parameters including magnitude and rise time of applied voltage as well as the type of oil on streamer initiation and propagation is investigated. It is found that the shorter rise time the more prominent streamer growth in the oil portion. For oil comprising only aromatics, an electric field magnitude larger than about 2×108 V/m is needed to propagate streamers, while this value for the oil comprising naphthenics/paraffinics will be exceeding 4×108 V/m. [ABSTRACT FROM PUBLISHER]

Purpose: Microchambers demonstrate anomalous voltage-dependent polarity effects. Existing polarity and ion recombination correction factors do not account for these effects. As a result, many commercial microchamber models do not meet the specification of a reference-class ionization chamber as defined by the American Association of Physicists in Medicine. The purpose of this investigation is to determine the cause of these voltage-dependent polarity effects. Methods: A series of microchamber prototypes were produced to isolate the source of the voltagedependent polarity effects. Parameters including ionization-chamber collecting-volume size, stem and cable irradiation, chamber assembly, contaminants, high-Z materials, and individual chamber components were investigated. Measurements were performed with electrodes coated with graphite to isolate electrode conductivity. Chamber response was measured as the potential bias of the guard electrode was altered with respect to the collecting electrode, through the integration of additional power supplies. Ionization chamber models were also simulated using COMSOL Multiphysics software to investigate the effect of a potential difference between electrodes on electric field lines and collecting volume definition. Results: Investigations with microchamber prototypes demonstrated that the significant source of the voltage-dependent polarity effects was a potential difference between the guard and collecting electrodes of the chambers. The voltage-dependent polarity effects for each prototype were primarily isolated to either the guard or collecting electrode. Polarity effects were reduced by coating the isolated electrode with a conductive layer of graphite. Polarity effects were increased by introducing a potential difference between the electrodes. COMSOL simulations further demonstrated that for a given potential difference between electrodes, the collecting volume of the chamber changed as the applied voltage was altered, producing voltage-dependent polarity effects in the chamber response. Ionization chamber measurements and COMSOL simulations demonstrated an inverse relationship between the chamber collecting volume size and the severity of voltage-dependent polarity effects on chamber response. The effect of a given potential difference on chamber polarity effects was roughly ten times greater for microchambers as compared to Farmer-type chambers. Stem and cable irradiations, chamber assembly, contaminants, and high-Z materials were not found to be a significant source of the voltage-dependent polarity effects. Conclusions: A potential difference between the guard and collecting electrodes was found to be the primary source of the voltage-dependent polarity effects demonstrated by microchambers. For a given potential difference between electrodes, the relative change in the collecting volume is smaller for larger-volume chambers, illustrating why these polarity effects are not seen in larger-volume chambers with similar guard and collecting electrode designs. Thus, for small-volume chambers, it is necessary to reduce the potential difference between the guard and collecting electrodes in order to reduce polarity effects for reference dosimetry measurements. [ABSTRACT FROM AUTHOR]

A comparative study of electrical breakdown properties of deionized water (H2O) and heavy water (D2O) is presented with two different electrode materials (stainless steel (SS) and brass) and polarity (positive and negative) combinations. The pulsed (~a few tens of nanoseconds) discharges are conducted by applying high voltage (~a few hundred kV) pulse between two hemisphere electrodes of the same material, spaced 3 mm apart, at room temperature (~26-28 °C) with the help of Tesla based pulse generator. It is observed that breakdown occurred in heavy water at lesser voltage and in short duration compared to deionized water irrespective of the electrode material and applied voltage polarity chosen. SS electrodes are seen to perform better in terms of the voltage withstanding capacity of the liquid dielectric as compared to brass electrodes. Further, discharges with negative polarity are found to give slightly enhanced discharge breakdown voltage when compared with those with positive polarity. The observations corroborate well with conductivity measurements carried out on original and post-treated liquid samples. An interpretation of the observations is attempted using Fourier transform infrared measurements on original and post-treated liquids as well as in situ emission spectra studies. A yet another important observation from the emission spectra has been that even short (nanosecond) duration discharges result in the formation of a considerable amount of ions injected into the liquid from the electrodes in a similar manner as reported for long (microseconds) discharges. The experimental observations show that deionised water is better suited for high voltage applications and also offer a comparison of the discharge behaviour with different electrodes and polarities. [ABSTRACT FROM AUTHOR]

Inverted polarity effect was studied at the breakdown of point-to-plane discharge gap filled with air at a pressure range of 0.013–0.3 MPa. High-voltage nanosecond pulses were applied to the electrode with a small radius of curvature. Pulser was operated at both negative and positive polarities in the single-pulse mode. Waveforms of voltage pulse, discharge current, and intensity of the discharge plasma radiation near the electrode with a small radius of curvature were registered. It was obtained that at the breakdown of point-to-plane discharge gap filled with air, the breakdown voltage at positive polarity of the pointed electrode was higher than that at negative one. The inverted polarity effect was shown to come to naught with an increasing of air pressure up to 0.3 MPa. It is suggested that the inverted polarity effect is related to the impeded formation of the explosive emission centers on the flat electrode (cathode) after arrival of the ionization wave front to the one. In addition, both the inverted and the ordinary polarity effects were not observed at the breakdown of nitrogen at pressures of 0.4 and 0.7 MPa. [ABSTRACT FROM PUBLISHER]

In this study, investigation of the unipolar resistive switching (RS) of InGaZnO film indicates that the reset voltage polarity can strongly affect the RS region. The dependence of the RS characteristics on the top electrode (Pt, Al, or Cu) was investigated. Asymmetrical electrodes (Cu/InGaZnO/Al) were chosen and the dependence of the RS parameters (e.g., high and low resistance states, set and reset voltages) on these two diverse electrodes can provide two indicators to trace the location of the RS region. The RS region is usually located near the anode when the applied set and reset voltages have the same polarity. In comparison, when the reset voltage has the opposite polarity to the set voltage, the RS region prefers to be located near the anode of the reset process rather than the cathode (which is used as the anode in the set process), indicating the movement of the RS region during the reset process. With the aid of joule heating, oxygen ions can overcome the energy barrier during the reset process under small voltage, resulting in the CFs restructuring and having the inverse shape, which is responsible for the drift mechanism of the RS region. [ABSTRACT FROM AUTHOR]

Breakdown characteristics of air gaps under negative switching impulse are complicated. To better understand the nonlinear discharge characteristics of long air gaps, the 50% breakdown characteristics of rod-rod gaps, rod-plane gaps and rod-conductor gaps, with air gap distance ranged from 1 m to 10 m, are studied thoroughly, with two waveforms of negative switching surges. Saturating characteristics have been obtained for the above three typical gaps. For air gaps exceed 4 m, the 50% breakdown voltage appears to be lower for rod-plane gaps than that for rod-rod gaps, while the average breakdown electric field decreases with the length of air gaps. Gap factors under negative impulses tend to level off with gap spacing. Furthermore, new knowledge is obtained indicating that, the 50% breakdown voltage for rod-conductor gaps may be lower with conductor grounded than that with conductor ungrounded. Finally, it also indicates that the wave front of the applied voltage has great influence on the breakdown time of rod-rod air gaps. [ABSTRACT FROM AUTHOR]

Electrophoretic manipulation of multiple-emulsion oil-in-water-in-oil (O/W)/O and water-in-oil-inwater- in-oil (W/O/W)/O core-shell droplets is shown. It was found that the electrophoretic mobility of the droplets is determined solely by the outer water shell, regardless of size or composition of the inner droplets. It was observed that the surface charge of the outer water shell can be changed and the polarity can be reversed through contact with a biased electrode in a similar way as with simple W/O droplets. Furthermore, addition of the anionic surfactant, sodium dodecyl sulfate to the outer water shell reverses the initial polarity and hence, electrophoretic mobility of the core-shell droplets before contact with an electrode. The results have practical implications for the manipulation of oil droplets in a continuous oil phase. [ABSTRACT FROM AUTHOR]

Thin ZrO2 films and ZrO2/TiO2 bilayers grown by atomic layer deposition (ALD) are integrated into metal-oxide-metal (MOM) structures for investigation of resistive switching (RS) properties. The films have different microstructure depending on the used ALD oxygen source and stacking sequence for the bilayers. Pt/ZrO2/Ti/Pt devices show unipolar RS for oxide thicknesses of 11-18 nm. The devices with O3 grown ZrO2 show higher yield in comparison to the ones with H2O processed oxide. The switching polarity of the Pt/ZrO2/Ti/Pt cells depends on the thickness of the Ti electrode layer. The increase of the Ti layer thickness leads to a change in switching polarity from unipolar to bipolar. The formation of ZrO2/TiO2 bilayers results in changes in the RS behavior of the MOM cells depending on the stacking sequence. [ABSTRACT FROM AUTHOR]

Abstract: We report polarity-switchable polymer solar cells that use poly [(9,9-bis((6′-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-(2-methoxy-ethoxy)ethoxy)ethyl)-9-fluorene))dibromide polyelectrolyte (WPF-6-oxy-F). By introducing WPF-6-oxy-F as a polarity-controlling layer, we selectively achieved polarity switching in the device operation. When we deposited the WPF-6-oxy-F film on the top of an active polymer layer, the device operated conventionally; holes moved to the transparent indium tin oxide (ITO) electrode. However, the device showed switched polarity when we changed the position of insertion of the WPF-6-oxy-F film to the top of the transparent ITO electrode. Then, the electrons moved to the transparent ITO electrode, leading to an inverted device. [Copyright &y& Elsevier]

Tonpilz acoustic transducers for use underwater often include a stack of piezoelectric material pieces polarized along the length of the stack and having alternating polarity. The pieces are interspersed with electrodes, bonded together, and electrically connected in parallel. The stack is normally much shorter than a quarter wavelength at the fundamental resonance frequency so that the mechanical behavior of the transducer is not affected by the segmentation. When the transducer bandwidth is less than a half octave, as has conventionally been the case, for example, with lead zircon ate titan ate (PZT) material, stack segmentation has no significant effect on the mechanical behavior of the device in its normal operating band near the fundamental resonance. However, when a high coupling coefficient material such as lead magnesium niobate-lead titan ate (PMN-PT) is used to achieve a wider bandwidth with the tonpilz, the performance difference between a segmented stack and a similar piezoelectric section with electrodes only at the two ends can be significant. This paper investigates the effects of stack segmentation on the performance of wide band underwater tonpilz acoustic transducers. Included is a discussion of a particular tonpilz transducer design using single crystal piezoelectric material with high coupling coefficient compared with a similar design using more traditional PZT ceramics. [ABSTRACT FROM AUTHOR]

Abstract: Space charge is a key insulation problem of HVDC equipment. In this paper, the influence of voltage polarity and electrode material were studied by the pulse electroacoustic (PEA) method. It had been found that the type of space charge accumulating at the interface was the same with the voltage polarity. With different electrode materials, the space charge injection was consequently different, but not evident. The interface made the drift velocity slower in two-layer samples. It suggested that the interface had a significant impact on space charge distribution and the contact state was complex, so a modified Maxwell–Wagner model was proposed. [Copyright &y& Elsevier]

Abstract: In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by nanosecond pulsed high voltage are investigated. The goal is to experimentally characterize the surface DBD actuators in terms of electrical and geometrical parameters. The actuators are made of two conducting electrodes separated by a thin dielectric (Kapton films) and arranged asymmetrically. The active electrode is connected to a pulsed high voltage power supply (voltage up to ±10 kV, rise and fall times of 50 ns and pulse width of 250 ns) and the second electrode is grounded. The experimental results show that the energy per pulse (normalized by the length of the active electrode) is smaller when one increases the inter-electrode spacing between 1 and 3 mm, the thickness of the dielectric barrier between 120 and 360 μm or the length of the electrodes between 10 and 50 cm, for both applied voltage polarities. Optical characterization of the plasma layer for different electrode gaps has been investigated by using an ICCD camera. Results indicate that the plasma produced by positive and negative rising voltage propagates in a streamer-like regime with numerous and well-distributed channels, for any electrode gap distance. However, the positive and negative falling voltage produces similar discharges only for large electrode gaps. In this case, the plasma layer starts from a corona spot in contact with the active electrode and expands in the direction of the grounded electrode in a plume shape. [Copyright &y& Elsevier]

The results from an experimental measurement of the interelectrode gap filling with plasma channels in a pulsed sliding multichannel discharge of opposite polarities in Ne, Ar and Xe are presented and discussed. The experiments are performed at submicrosecond pulse duration (50-800 ns current pulse FWHM) and gas pressures of 30 and 100 kPa, with two discharge cavities of different alumina ceramic substrate thicknesses (0.4 and 0.17 cm) and interelectrode gap lengths (4 and 10.3cm).A comparative measurement at opposite polarities is aimed at getting additional information on the discharge formation mechanism and optimal mode for quasi-uniform plasma sheet generation. The discharge features common for the three gases are revealed. In particular, the index of interelectrode gap filling with plasma channels is shown to depend at each gas type/pressure/cavity on the peak current, along with the discharge voltage, in such a manner that the greater the peak current at a fixed discharge voltage, the greater the gap filling index, independent of the voltage polarity. For the practical purpose of generating a quasi-uniform discharge structure, the lower of the two gas pressures, the positive discharge polarity and the lowest impedance of the power supply chain are preferable. [ABSTRACT FROM AUTHOR]

An electrothermal hydrodynamic model is presented to evaluate effects of the applied lightning impulse voltage parameters such as polarity, magnitude, and rise time on the initiation and propagation of the streamers formed in an IEC defined needle-sphere electrode geometry filled with transformer oil. Instantaneous velocity, column diameter, head curvature, maximum electric field, and the volume charge density have been investigated as the main characteristics of the streamer. Modeling results indicate that greater applied voltage peak amplitudes form streamers with higher velocity, greater head curvatures, and thicker columns. The bushy negative streamers usually initiate at almost twice the applied voltage magnitude and propagate slower than filamentary positive streamers. Results also show that in transformer oil at the same impulse voltage peak amplitude, shorter rise times create thicker positive and negative streamers. [ABSTRACT FROM PUBLISHER]

The contribution of the electrode material to the formation of the plasma of a low-inductive high-current vacuum spark and its influence on the process of discharge micropinching were studied using X-ray spectroscopy and laser diagnostics. Electrode system configurations are determined in which the contributions of the materials of both electrodes to the plasma emitting X-rays are comparable and in which the contribution of one electrode is dominating. It is found that discharge pinching occurs primarily in the vapor of the pointed electrode independently of its polarity. The experimental results indicate the formation of a suprathermal electron beam in the micropinch region. [ABSTRACT FROM AUTHOR]

The focus of this work has been on the pre-breakdown phenomena and the breakdown characteristics of N gas in a sphere-plane gap under various impulse voltages. Both electrical and optical experimental investigation methods were used. Following parameters were considered: gas pressure range from 0.2 to 0.6 MPa, electric field utilization factor of the electrode configuration 71%, positive and negative impulse waveforms with the rise time of 500 ns, 1.2 μs and 180 μs. The observed discharge processes before the breakdown through the light emission images by the ICCD camera are in good agreement with the streamer mechanism. Under both polarity stresses, discharges are initially concentrated around the tip of the sphere and later pointing towards the earth electrode. However, negative streamers are thinner and more diffuse. As expected, the breakdown voltages for negative polarity are lower than those for positive polarity regardless of the gas pressure and shape of the applied impulse voltage. The breakdown voltage is increased with shortening the rise time of pulse waveforms. As a substitute for SF, N gas under pressures above 0.3 MPa can reach the standard rated withstand voltage for 24 kV C-GIS. [ABSTRACT FROM AUTHOR]

The electrical properties of metal-dielectric-metal (MDM) structures with the dielectric layer representing a monolayer of spherical AlO or ZrO oxide nanoparticles have been studied. It is established that these heterogeneous structures exhibit electric conductivity according to the mechanism for which the differential resistance dU/dI is negative and reversibly approaches zero with increasing current I. The electric conductivity strongly depends on the polarity of the applied voltage U, provided that electrodes are made of basically different metals or the same metal with different surface conditions. The mechanism of the electric conductivity in the given MDM structure depends on the diameter of nanoparticles in the dielectric layer. [ABSTRACT FROM AUTHOR]

This study reports a droplet-based microfluidic device for on-demand electrostatic droplet charging and sorting. This device combines two independent modules: one is a hydrodynamic flow focusing structure to generate water-in-oil droplets, and the other is the two paired-electrodes for charging and sorting of the droplets. Depending on the polarity on charging electrodes, water-in-oil droplets can be electrostatically charged positively or negatively, followed by automatic real-time electric sorting. This approach will be useful when preformed droplets, with a positive, a negative, or with no charge, need to be manipulated for further on-chip droplet manipulation. [ABSTRACT FROM AUTHOR]

A fast-response vertical alignment liquid crystal display with a positive dielectric liquid crystal is described. The adjacent pixel electrodes in the bottom substrate are driven by opposite voltage polarity to the low operating voltage, and the grating common electrodes are set in the upper substrate and at the centre of the gap of the pixel electrodes. This gives a faster response speed, with an improvement of more than double in rise time compared with that of the normal vertical alignment mode without common electrodes. [ABSTRACT FROM AUTHOR]

An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases are recorded photographically to provide more information on the physical mechanisms of the corona discharge in the investigated gases. The obtained results have been discussed in the light of gas discharge physics and its applications. [ABSTRACT FROM AUTHOR]

It has long been known that there is a sustained electrical potential (voltage) difference between the xylem of many plants and their surrounding soil, but the mechanism behind this voltage has remained controversial. After eliminating any extraneous capacitive or inductive couplings and ground-mediated electric current flows, we have measured sustained differences of 50-200 mV between the xylem region of a Faraday-caged, intact, potted Ficus benjamina tree and its soil, as well as between its cut branches and soils and ionic solutions standardized to various pH values. Using identical platinum electrodes, no correlation between the voltage and time of day, illumination, sap flow, electrode elevation, or ionic composition of soil was found, suggesting no direct connection to simple dissimilar-metal redox reactions or transpirational activity. Instead, a clear relationship between the voltage polarity and magnitude and the pH difference between xylem and soil was observed. We attribute these sustained voltages to a biological concentration cell likely set up by the homeostatic mechanisms of the tree. Potential applications of this finding are briefly explored. [ABSTRACT FROM AUTHOR]

This paper aims to extensively review, discuss, and compare the published studies on soil behavior under high currents, based on field tests, laboratory tests, and computational methods, conducted by previous authors from 1928 to 2003. The paper presents an informative review on soil electrical characteristics under high impulse currents as well as a useful list of references for researchers on nonlinear soil behavior. [ABSTRACT FROM AUTHOR]

Negative discharge induction experiments were performed with a rod-to-rod electrode configuration having a gap length of 0.8 m using a high-power XeCl excimer laser of maximum output energy of 2 J/pulse and an impulse generator of maximum voltage of 1.2 MV. Development of a leader in the laser-ionized plasma channel was observed by using an image converter camera. When a XeCl excimer laser is applied at a carefully controlled instant, the guiding effect for an impulse discharge is optimized. Three main results were obtained. First, the discharge started near the focal point and then developed bidirectionally toward the high-voltage electrode and the grounded electrode. Midgap leaders were frequently observed. Second, it was observed that the lifetime of the laser-ionized plasma channel was about 1 Ps. Third, the discharge processes were classified into six stages. The mechanism of the streamer and leader propagation is discussed. [ABSTRACT FROM AUTHOR]

We report on the experimental observation of reciprocal phase-locking in stacked Nb-AlO/sub x/-Nb Josephson junctions having overlap geometry. When the junctions are independently biased in zero external magnetic field, they each exhibit several Zero Field Steps. Biasing both the junctions on the Zero Field Steps, one with constant current while the other is swept along the step, we have observed phase-locking between the fluxons in the two junctions and measured the phase-locking range. We have found that the bound state can be very stable, and that the stack exhibits the same features reversing either the polarity of the bias current or the role of the junctions. An analogous investigation of the effect of the magnetic field on the stability of the bound state has been performed. Numerical simulations have shown that the underlying dynamics corresponding to this situation is a bound state of a fluxon-antifluxon pair. Finally, the effect of rf radiation on the junctions has been investigated. [ABSTRACT FROM PUBLISHER]

Part of the reason for the failure of magnetically controlled Abrikosov vortex flow devices has been low magnetic coupling coefficients, combined with pinning: control currents tend to drive the control electrode normal before sufficient flux is coupled to the flux flow channel to overcome pinning. We have observed that interesting devices may use direct injection of flux, without an isolated control electrode. Experimental studies using opposite polarity currents show dramatic effects in device characteristics; simulations show that these effects are manifestations of vortex interactions. [ABSTRACT FROM PUBLISHER]

This paper reports an experimental study of the optical emission characteristics of the surface dielectric barrier discharge plasma excited by nanosecond pulsed voltage. N2(C3Пu) rotational and vibrational temperatures are almost the same with upper electrode powered with positive polarity and lower electrode grounded or upper electrode grounded and lower electrode powered with positive polarity. While the electron temperature is 12% higher with upper electrode powered with positive polarity and lower electrode grounded. When the frequency is below 2000 Hz, there is almost no influence of applied voltage amplitude and frequency on N2(C3Пu) rotational, vibrational temperature and electron temperature. As the pressure decreases from 760 Torr to 5 Torr, N2(C3Пu) rotational temperature remains almost unchanged, while its vibrational temperature decreases initially and then increases. The discharge mode changes from a filamentary type to a glow type around 80 Torr. In the filamentary mode, the electron temperature remains almost unchanged. In the glow mode, the electron temperature increases while the pressure decreases. [ABSTRACT FROM AUTHOR]

We design the A-R rectifier based on the D-σ-A molecules to examine the rectifying performances by the first-principles method. The calculated results show that the electronic structures for all of our systems perfectly match the A-R rectifier, as expected, but their rectifying direction is very strikingly opposite and working mechanism is completely different. This behavior can be rationalized through an asymmetrical shift of molecular levels under bias of different polarities, which is because of always-existing intrinsic asymmetrical coupling effects of molecular levels to electrodes. Detailed analysis demonstrates that the rectifying direction induced by this mechanism is always in opposition to that induced by the A-R mechanism. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an ink-jet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change in surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors. [ABSTRACT FROM AUTHOR]

Electric switching and memory effects were observed on devices composed of a RbAg4I5 film sandwiched between Ag and Pt electrodes. The RbAg4I5 films were prepared by pulsed laser deposition and the lateral size of devices was scaled down to 300 nm by focused ion beam lithography. The device can be switched between high- and low-resistance states with a ratio of ∼103 by applying voltage with opposite polarities. The read-write cycles could be repeated at 1 kHz and for 104 times. The switching characters are attributed to the formation or breakdown of Ag filaments in RbAg4I5 films induced by electrochemical reactions. [ABSTRACT FROM AUTHOR]

The authors introduced a concept of self-sensing neutralization system by means of automatically ejected charged particles from alternative current microhollow cathode discharge. When the positive bias was applied to the third electrode, a real current flow was only detected during negative polarity period of voltage applied to the first electrode. On the other hand, in the case of negative bias, there was only the real current during positive polarity period. These results mean that our system shows simultaneously the self-sensing and then neutralizing characteristics in a period. [ABSTRACT FROM AUTHOR]

We measured the impact of the thermoelectric effect, especially the Peltier effect, upon the operation of phase change memory (PCM) in which the contact resistance between the phase change material and the electrode dominates the total resistance. A PCM device having a pillar structure of diameter 500 nm was fabricated using GeCu2Te3 (GCT) material. During read operation, the set state (with crystalline PCM) showed ohmic contact between the PCM and the electrode, whereas the reset state (with amorphous PCM) showed Schottky contact. The Schottky contact between the amorphous GCT and the electrode showed a bias polarity dependence of set operation owing to the Peltier effect, which is one of the thermoelectric effects. As PCM devices scale down to the nanometre scale, research on contact resistance and various related effects will become more important. [ABSTRACT FROM AUTHOR]

This paper investigates the factors affecting the impulse characteristics of purposely built grounding systems. We installed 2 m × 2 m grounding systems in four different sites with different soil resistivity values. The effect of impulse polarity on soil characteristics was also investigated for different soil resistivity. A circular ring electrode was used as a return electrode in all four sites. For one of the sites, different configurations of grounding systems were installed to allow the study of the effect of ground electrode configurations on soil characteristics. The aim of this study was to quantify the effects of soil resistivity, impulse polarity, and earth electrode configurations on soil electrical properties under high impulse conditions by field measurements. The new data could be useful in understanding the characteristics of grounding systems in various factors under high impulse conditions. It is hoped that by considering these factors, it can help optimize the design of earthing systems. [ABSTRACT FROM AUTHOR]

The nanosecond single-pulse voltage was employed here to generate a large-volume discharge between the wire-plane electrodes in nitrogen. In order to find out the effect of pulse polarity on the propagation of a large-volume discharge, both the positive and negative pulses were applied to the wire-plane electrodes, respectively. Images presented here reveal that the discharge channels are more homogeneous under the negative pulse, and the propagation speed of the discharge channels is faster under the positive pulse. [ABSTRACT FROM AUTHOR]

The dynamics of an atmospheric pressure air discharge in a point-to-plane geometry with a dielectric layer obstacle on the discharge path is investigated numerically for different applied voltages. Whatever the polarity of the voltage applied, first, a streamer discharge of the same polarity ignites at the point and propagates towards the dielectric layer. After the impact on the dielectric surface, the streamer discharge spreads along the upper dielectric surface and charges it positively or negatively depending on its polarity. On the bottom surface of the dielectric layer, charges with an opposite polarity are deposited. Surface charges on both faces of the dielectric layer are shown to have a significant influence on the discharge reignition for a negative applied voltage, but not for a positive one. Furthermore, it is shown that the dynamics of the discharge reignition below the dielectric layer depends on the polarity of the applied voltage at the point electrode. For a positive applied voltage, the reignited discharge is a positive ionization wave propagating towards the grounded plane. For a negative applied voltage, a double headed discharge is observed with positive and negative fronts propagating in opposite directions. Finally, the minimal value of the ionization integral to have a discharge reignition below the dielectric obstacle is found to be less for a negative applied voltage than for a positive one. [ABSTRACT FROM AUTHOR]

A volatile switching of conductive filament (CF) in a Cu/TaOx/δ-Cu/Pt device has been observed. The device differs from a conventional Cu/TaOx/Pt device by the insertion of a thin Cu-layer (δ-Cu) between the electrolyte and the inert electrode. The Cu CF is formed the same way as in the conventional nonvolatile devices. However, when applied voltage becomes zero, CF ruptures spontaneously. The dynamic balance between Cu+ field-supported hopping transport and the Cu self-diffusion explains the effect of CF volatility. The device can operate reliably in volatile and nonvolatile modes. [ABSTRACT FROM AUTHOR]

Very fast transient overvoltage (VFTO) in gas insulated switchgear (GIS) is of great concern at the higher rated voltages because the difference between the rated lightning impulse (LI) and the VFTO withstand voltage decreases. In order to clarify VFTO withstand level of 1100 kV GIS, a simulation system was designed for generation of VFTO. The breakdown characteristics of sphere-plane gap and rod-plane gap in SF6 under VFTO and LI were investigated for different gas pressures. Experimental results show that the breakdown voltages in slightly inhomogeneous field gaps under VFTO are higher than that under LI. However, for the rod-plane gaps, the breakdown voltages and voltage-time curves under VFTO fall below that of LI at higher pressure in the case of negative polarity. The polarity effect of rod-plane gaps under LI is reversed at a certain pressure. Based on the analyses, it is concluded that the different breakdown characteristics of SF6 gaps may be attribute to the difference between space charge behaviors during the discharge development under the impulse with different wave front and oscillation tail of VFTO and LI. [ABSTRACT FROM PUBLISHER]