Frequency Of Applied Voltage Research Articles

Magnetoresistance and capacitance oscillations and hysteresis in type-II InAsSbP ellipsoidal quantum dots

The InAsSbP composition type-II quantum dots (QDs) are grown on a InAs(1 0 0) substrate from In-As-Sb-P quaternary liquid phase at a constant temperature in Stranski–Krastanow growth mode. Device structures in the form of photoconductive cells are prepared for investigation. Magnetospectroscopy and high-precision capacitance spectrometry are used to explore the QDs structure’s electric sheet resistance in a magnetic field and the capacitance (charge) law at lateral current flow. Aharonov–Bohm (AB) oscillations with the period of δB = 0.38 ± 0.04 T are found on the magnetoresistance curve at both room and liquid nitrogen temperatures. The influence of the QDs size distribution on the period of AB oscillations is investigated. The magnetoresistance hysteresis equals to ~50 mΩ and ~400 mΩ is revealed at room and liquid nitrogen temperature, respectively. The capacitance hysteresis (CH) and contra-directional oscillations are also detected. Behavior of the CH versus applied voltage frequency in the range f = 103–106 Hz is investigated. It is shown that the CH decreases with increasing frequency up to 106 Hz. The time constant and corresponding frequency for the QDs R–C parallel circuit (generator) equal to τ = 2.9 × 10−7 s and f 0 = 5.5 × 105 Hz, respectively, are calculated.

Dynamics of the resistive state of a narrow superconducting channel in the ac voltage driven regime

Within the framework of the time-dependent Ginzburg–Landau equations, the dynamics of the order parameter in narrow superconducting channels of different lengths is investigated in the ac voltage-driven regime. The resistive state of the system at low frequencies of the applied voltage is characterized by the formation of time-periodic groups of oscillating phase-slip centers (PSCs). Increasing the frequency reduces the lifetime of these periodic groups. Depending on the length of the channel, the ac voltage either tends to restore the state with a single central PSC in periodic groups or minimizes the number of forming PSCs and induces their ordering in the system. For relatively short channels, a further increase in frequency leads to the suppression of the order parameter without PCS formation. For the systems with the channel length exceeding the specified limit, the formation of PSC starts after a certain time delay which increases rapidly with frequency. The current-voltage characteristics of a relatively short channel at different applied voltage frequencies are calculated. It is found that the current-voltage characteristics exhibit a stepped structure, where the height of the first step is determined by the quadruple value of the Josephson frequency.

Electrohydrodynamic printing under applied pole-type nozzle configuration

A pole-type nozzle has an inserted pole that jams a contraction flow into capillary in electrohydrodynamic deposition. The jammed solution improves Taylor cone formation by shortening the hysteresis time so that pole-type nozzle is suitable for high-resolution electrohydrodynamic printing. Experimental results demonstrate a governed frequency-dividing relationship with an integral ratio of applied voltage frequency to droplet deposition frequency. It is observed that low integral frequency ratio is in favor of low voltage amplitude and duty cycle, and high voltage frequency, since polymer solution jets in a small fluidic volume per droplet under low electric force and short pulse duration.

An Integral Equation for Analysis of Partial Discharge Data Obtained with an Asymmetric IEC(b) Electrode System at Various Applied Voltage Frequency

An Integral Equation for Analysis of Partial Discharge Data Obtained with an Asymmetric IEC(b) Electrode System at Various Applied Voltage Frequency

Electromechanical behaviour of Nafion-based soft actuators.

Soft actuators based on Ionic Polymer-Metal Composites (IPMCs) are of considerable interest for applications in biomedical devices and robotics. In this work, thin commercial and thick laboratory-prepared Nafion membranes were made into model IPMC actuator devices by incorporation of Pt electrode layers. In extensive electromechanical tests the maximum average tip displacement and maximum force generated were recorded. The effect of amplitude and frequency of the applied voltage on both displacement and force was examined as were the effects of the origin of the Nafion membrane, the Pt loading, the structure of the electrode and the presence or absence of an Au overlayer. The cast samples generated much smaller displacements but much larger forces than the commercial Nafion samples. For all samples, displacement and force increased with increasing applied voltage, with increased number of Pt plating cycles and when an Au overlayer was present but decreased with increasing applied voltage frequency. Waveform analysis of applied voltage, current and force was performed by considering the capacitive nature of the IPMC actuators.

Understanding the partial discharge activity generated due to particle movement in a composite insulation under AC voltages

The UHF signals are generated due to partial discharges formed by particle movement in Gas Insulated Switchgears (GISs). It is observed that the bandwidth of UHF signals generated due to partial discharges formed by particle movement in GIS is independent of operating pressure and the applied voltage. The levitation voltage of the particle sitting on the dielectric barrier is high compared to that of it on the ground electrode. When a particle is present in between the barrier and an electrode, at certain voltage level the movement of particle will be in pseudo resonance with the applied voltage frequency. When the particle is on the barrier, on application of voltage the particle moves to the center of the electrode axis causes discharges thereby radiating UHF signals, with its dominant frequency in the range of 3–4GHz, which is much different from that of the UHF signal generated due to partial discharges formed by particle movement. When the particle moving between the high voltage electrode and the barrier, at some time its motion get collapses and the particle settles in the low field region away from the axis of the electrode and generates UHF signals having characteristics of UHF signals generated due to corona discharge.

The influence of the discharge parameters on the plasma spatial structuring in argon DBDs

The plasma parameters, discharge plasma uniformity and filamentation processes in high pressure (near atmospheric pressure) dielectric barrier discharges (DBD) in argon are studied using the developed two-dimensional 2D(r, z) model. The applied voltage frequency, the voltage shape, the dielectric layers material and its thickness are varied and the effects of such variations on plasma uniformity, discharge structure and operation are studied. The DBD discharges with different dielectric layers thickness, dielectric constants and secondary electron emission coefficients are simulated. It was shown that the dielectric layer thickness is an important parameter for producing high pressure discharges uniform over the radius. The possibility of the radially uniform discharges at atmospheric pressure was shown in the present study.

Dependence of Partial Discharge Characteristics on Applied Voltage Frequency with IEC(b) Electrode System

The significance of on-site insulation diagnosis has been increasing year by year to deal with tremendous amount of aged high voltage power apparatus in utility companies. On-site diagnostic methods based on partial discharge (PD) measurement using resonant high-voltage supply are promising technique because resonant power supplies are smaller, lighter and having higher testing capacities than those with conventional power source. However, the frequency of a resonant power supply can be different from the conventional power frequency because it depends on a capacitance of the test objects. In order to develop diagnostic methods with resonant power supply, we should clarify the PD characteristics of defects in high voltage insulation under higher power frequencies. As a first step of the development of the diagnosis, we investigated the frequency dependence of PD characteristics with an IEC(b) electrode system as a model defect for delamination between insulating materials and metallic electrodes. This paper describes the PD characteristics under the power frequencies from 25Hz to 1000Hz. As a result, we found that important PD characteristics such as the maximum apparent discharge magnitude are almost independent of the applied voltage frequency within the experimental conditions except those for frequencies higher than 500Hz.

Quantitative measurements of absolute dielectrophoretic forces using optical tweezers

Optical tweezers were used for quantitative measurement of the absolute dielectrophoresis (DEP) forces acting on polystyrene microparticles. The electrodes and tweezers were configured to create one-dimensional DEP forces acting perpendicular to the tweezers' beam. The influences of various external factors, such as applied voltage frequency, conductivity of the medium, and particle size on the measurement were estimated. By accounting for these factors, actual measurements were in close agreement with theoretical predictions. Our results show that the optical tweezers may serve as a unique tool for the measurement of DEP forces in various applications.

Investigations of electrical trees in the inner layer of XLPE cable insulation using computer-aided image recording monitoring

Using a computer-aided image recording monitoring system, extensive measurements have been performed in the inner layer of 66 kV cross-linked polyethylene (XLPE) cables. It has been found that there are three kinds of electrical trees in the samples, the branch-like tree, the bush-like tree and the mixed tree that is a mixture of the above two kinds. When the applied voltage frequency is less than or equal to 250 Hz, only the mixed tree appears in XLPE samples, when the frequency is greater than or equal to 500 Hz, only the dense branch-like tree develops, both of which are attributed to the coexistence of non-uniform crystallization and internal residual stress in semicrystalline XLPE cables during the process of manufacturing. Through the fractal analyses of these electrical trees, it has been found that both the propagation and structure characteristics can be described by fractal dimension directly or indirectly. It is suggested that the propagation and structural characteristics of electrical trees are closely related to the morphology and the residual stress in material at low frequency, i.e., the propagation characteristics of electrical trees depends upon not only the boundaries between big spherulites and amorphous region, but also the impurity, micropore concentration and the relative position of needle electrode tip with respect to spherulites or amorphous region in the low frequency range. However, at high frequency, it has nothing to do with the morphology of material. It is suggested that the injection and extraction process of charge from and to dielectrics via the needle electrode are more intense at high frequency than in low frequency. Thus, it can form relatively uniform dielectric weak region in front of needle electrode, which leads to similar initiation and propagation characteristics of electrical trees at high frequency.

Influence of the pre-ionization background and simulation of the optical emission of a streamer discharge in preheated air at atmospheric pressure between two point electrodes

This paper presents simulations of positive and negative streamers propagating between two point electrodes in preheated air at atmospheric pressure. As many discharges have occurred before the simulated one, seed charges are taken into account in the interelectrode gap. First, for a pre-ionization background of 109 cm−3, we have studied the influence of the data set used for transport parameters and reaction rates for air on the simulation results. We have compared results obtained in 1997 using input parameters from Morrow and Lowke and from Kulikovsky. Deviations as large as 20% of streamer characteristics (i.e. electric field in the streamer head and body, streamer velocity, streamer radius, streamer electron density) have been observed for this point-to-point configuration. Second, we have studied the influence of the pulsed voltage frequency on the discharge structure. For the studied discharge regime, a change in the applied voltage frequency corresponds to a change in the pre-ionization background. In this work, we have considered a wide range of pre-ionization values from 104 and up to 109 cm−3. We have noted that the value of the pre-ionization background has a small influence on the electron density, electric field and location of the negative streamer head. Conversely, it has a significant influence on the positive streamer characteristics. Finally, we have compared instantaneous and time-averaged optical emissions of the three band systems of N2 and (1PN2, 2PN2 and ) during the discharge propagation. We have shown that the emission of the 2PN2 is the strongest of the three bands, in agreement with experimental observations. It is interesting to note that even with a short time averaging of a few nanoseconds, which corresponds to currently used instruments, the structure of the time-averaged emission of the 2PN2 is different from the instantaneous one and shows negative and positive streamers with smaller radial expansions and more diffuse streamer heads.

One-dimensional simulation of low pressure xenon dielectric barrier discharge

A self-consistent one-dimensional fluid coupled model is built to describe the low pressure xenon dielectric barrier discharge (DBD). And the finite-element method is employed to investigate gas voltages, discharge currents and the time evolutions of surface charges on dielectric barrier under different applied voltage amplitudes and frequencies. The spatial and temporal distributions of electrons, ions, excited, resonance, metastable particles and spatial electrical field are also achieved. The simulation results show that the surface charges accumulated on the dielectric barriers play a key role in the ignition and the extinguishment of the discharge. And based on the variation of gas voltage, the surface charging can be divided into six stages in one discharge cycle. With the increase of applied voltage amplitude, the gas gap breakdown moves ahead of the zero-crossing point of applied voltage gradually, and the discharge becomes more and more intense. Furthermore, with the increase of applied voltage frequency, the gas voltage decreases gradually, gas gap tends to breakdown, and discharge becomes uniform. Finally, spatiotemporal distributions of particles and electric field indicate that the xenon DBD is a typical glow discharge.

Fluid modelling of an atmospheric pressure dielectric barrier discharge in cylindrical geometry

A numerical parameter study has been performed for a cylindrical atmospheric pressure dielectric barrier discharge (DBD) in helium with nitrogen impurities using a two-dimensional time-dependent fluid model. The calculated electric currents and gap voltages as a function of time for a given applied potential are presented, as well as the number densities of the various plasma species. This study shows that for the geometry under consideration the applied voltage parameters have a large impact on the electric current profiles and that the discharge current is always determined by the electron and ion conduction currents while the displacement current is nearly negligible. A relative broadening of the current profiles (compared with the duration of the half cycle of the applied voltage) with an increase in the applied frequency is obtained. Nearly sinusoidal current wave forms, usually typical for radio frequency DBDs, are observed while still operating at the frequencies of tens of kilohertz. For the setup under investigation, the Townsend mode of the DBD is observed in the entire range of applied voltage amplitudes and frequencies. It is shown that the average power density dissipated in the discharge increases with rising applied voltage and frequency. An increase in applied voltage frequency leads to an increase in the electron density and a decrease in electron energy, while increasing the voltage amplitude has the opposite effect.

The conduction characteristics of electrical trees in XLPE cable insulation

AbstractDepending on the morphology of the material and applied voltage frequency, three kinds of electrical trees can exist in cross‐linked polyethylene (XLPE) cable insulation, which are conducting, non‐conducting, and mixed trees with different growth mechanisms. It is suggested that when the needle is inserted into large spherulites, conducting trees will form in those spherulites; when it is inserted among spherulites, non‐conducting trees will appear along the boundaries of spherulites. Frequency will accelerate the growth of non‐conducting trees but have little influence on the initiation and growth processes of conducting trees. If the initiation process of non‐conducting trees is too difficult, they will grow into mixed trees. Finally, it is concluded that the space charge limited tiny breakdown around the tips of electrical trees is responsible for the propagation process of conducting trees; on the other hand, fast expansion occurs due to local high temperature and pressure along the boundaries, partial discharge in electrical tree paths and charge recombination, etc., which are the main reason for the growth of non‐conducting trees. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

S0406-1-1 エポキシ樹脂中のマイクロカーボン繊維の電界印加による方向制御に関する基礎的研究(プラスチック基複合材料の加工と評価(1))

In this research, it was tried that controlling of direction of micro-carbon-fibers in a composite material by applied electric filed could be established. In the experiment, suspension which contains the micro-carbon-fibers in uncured epoxy resin without hardener was dropped between two pairs of cathodes. The ratio of frequencies of applied sinusoidal voltages and phase angle between the voltages was changed. The micro-carbon-fiber arrangement configurations were varied with the phase angle, when the applied voltage frequencies were the same, although the configuration was not changed in the different frequency couples. The principal second moments of the electric field were calculated by deference method. Direction of the major principal second moment and intensity of difference of the second moments could show the micro-carbon-fiber arrangement configurations obtained in the experiment.

Fabrication and drive test of piezoelectric PDMS valveless micro pump

Poly‐dimethylsiloxane (PDMS) valveless micropumps with single chambers and double chambers, based on a reciprocation principle, are fabricated in this work. A drive test of a piezoelectric valveless PDMS micro pump is conducted and the influence on the flow behavior of water is investigated. Applied voltage and frequency are major factors that affect the flow rate of the micropump. The flow rate of the micropump increases with applied voltage due to the increase of piezoelectric‐disk deflection. The flow rate of the micropump is found to be when the applied voltage frequency matches the first range of the resonant frequency of the PDMS micropump filled with water at 15 to 25 Hz. The maximum flow rate and the backpressure of the micropump are about 10.51 ml/min and 274.5 Pa when applying 120 Volts at 15 Hz. The maximum flow rate of the double chamber micropump at 120 Volts and 15 Hz is 2.74 ml/min which is less than the single chamber pump. When pumping at the second range of the resonant frequency of 860–1230 Hz, the flow rate of the micropump approaches zero because a lot of air bubbles are sucked into the chamber and interfere the flow of water. Experimental measurements of generation of bubbles at a wide span of frequencies that have not previously appeared in the literature are presented and discussed.

Piezoelectric-Resonance Effect in a Radio-Frequency-Driven Ferroelectric Plasma Source

The effect of driving frequency on the minimum voltage required to form plasma in a radio-frequency ferroelectric plasma source is examined. When the driving frequency of the plasma source is less than the translational effect radial resonant frequency, the applied electric field and background pressure have an increased effect on plasma formation. Applied-voltage frequencies that are close to the radial mechanical resonance of a ferroelectric/piezoelectric disk cause plasma formation to occur at reduced voltages. In one case, a 75% reduction in the breakdown voltage is realized by altering only the frequency of the applied voltage.

Frequency-dependent light emission and extinction of electroluminescent ZnS:Cu phosphor

Alternating current thick film light emitters has been prepared by using ZnS:Cu commercial phosphors and thick film technology. The dependence of electroluminescent emission on excitation frequency and voltage applied to light emission devices was studied. Electroluminescent spectra were decomposed into four Gaussians corresponding to emission transitions and their respective peak position wavelengths and amplitudes were analyzed as a function of the applied voltage frequency. The time constants associated to every of those centres have been calculated by determining the extinction times of the related light emission. A straight relationship between electroluminescence extinction time and frequency response for each emission wavelength has been found.

Current Rectification by Spontaneous Symmetry Breaking in Coupled Nanomechanical Shuttles

We investigate the transport and the dynamical properties of tunnel-coupled double charge shuttles. The oscillation frequencies of two shuttles are mode locked to integer multiples of the applied voltage frequency omega. We show that left-right-symmetric double shuttles may generate direct net current due to bistable motions caused by parametric instability. The symmetry-broken direct current appears near omega = Omega0/(2j-1), (j = 1,2,...), where Omega0 is the dressed resonance frequency of the relative motion of the two shuttles.

Collection of submicron particles by an electrostatic precipitator using a dielectric barrier discharge

Although dielectric barrier discharge (DBD) in air has been used to clean hazardous air pollutants (HAPs) because of its high electron density and energy, its potential use as precharging dust aerosol particles is not well known. In this work, we measured the size distributions of bimodal submicron aerosol particles and estimated the collection efficiency of the particles for a hybrid two-stage electrostatic precipitator (ESP) comprised of a DBD charger as the particle charger and an ESP as charged particle collector. Nano-sized particles of NaCl (30–100 nm) and DOS (50–800 nm) were generated by evaporation–condensation and atomization, respectively. Various electrical and flow conditions were applied on the DBD charger: AC applied voltage of 9–11 kV, frequency of 60–120 Hz, and air flow rate of 60 – 180 L min - 1 ( 0.048 – 0.016 s of particle residence time). The particle collection efficiencies increased as the AC applied voltage increased at a fixed frequency–flow rate, whereas the efficiencies decreased as the frequency and flow rate increased at a fixed AC power–flow rate and a fixed AC applied voltage–frequency.