Influence Of High Voltage Research Articles

Electrical Characterization of Epoxy Nanocomposite under High DC Voltage.

This work studies the direct current breakdown characteristics of unfilled epoxy and epoxy nonconductive nanocomposites (SiO2,MgO and Al2O3). It also examines the variation of electrical properties in epoxy nanocomposites. The novel aspect of this study is that the samples of Epoxy nanocomposite were exposed to high voltages of up to six kilo volts for three hours using field electron microscopy under high vacuum conditions (10-5 mbar). The current emitted from these samples was measured at three different intervals of time. In addition, the influence of high voltage on the permittivity, loss factor (tan(δ)), and conductivity of the epoxy nanocomposite was studied. This evaluation was conducted before and after applying the voltage at room temperature, The frequency range extends from 10-2-10-7 Hz using the Novo Control Alpha-A analyzer. Current-voltage characterization was performed through field electron microscopy. The samples were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy and Fourier Transform Infrared Spectroscopy. The unfilled epoxy exhibited structural degradation, resulting in the formation of holes when exposed to high voltages of up to six kilo volts, leading to a reduction in electrical properties. Nevertheless, the addition of nanoparticles shows a significant increase in the operational lifetime of the epoxy nanocomposite. The degree of increase in the lifetime of epoxy composite varied depending on several factors such as the type of NPs introduced and their respective sizes. The epoxy/Al2O3 nanocomposite comparing with epoxy/MgO and epoxy/SiO2 nanocomposite showed elevated resistance to direct current breakdown strength and maintaining its dielectric.

Formation of a Spray of Conducting Liquid under High Voltage and Electrical Discharge Plasma

The joint impact of an electrical discharge and a gas–droplet flow of a conducting liquid created by a centrifugal nozzle is studied. In the experiment, the electrical parameters of the discharge are recorded, and the local characteristics of the spray, namely, the droplet diameter distributions of the number of droplets and the components of their velocity vector are measured. The measurements are carried out using double shadow microphotography. The effect of a spray of a conducting liquid on the time-averaged electrical parameters of the discharge, as well as changes in the properties of the spray under the influence of high voltage and current, are studied. Additionally, the spray characteristics are measured when a high voltage of pre-breakdown value is applied. High-speed photography of a discharge in the presence of droplets of conducting liquid is carried out.

Вклад механизмов упрочнения при немонотонном изменении свойств в сплаве Cu–0,6Cr–0,1Zr при кручении под высоким давлением

Phase transformations play an important role in the formation of properties in the dispersion-hardened alloys, for example, such as the Cu–Cr–Zr system alloys. It is known that under severe plastic deformation, the diffusion conditions change significantly, which leads to a change in the phase transformation kinetics. In this work, the authors studied the Cu–0.6Cr–0.1Zr alloy in the low concentration solid solution state subjected to high pressure torsion (up to 10 cycles). In this case, due to the solid solution low concentration and the formed ensemble of large particles, the process of solid solution decomposition was excluded at the first stages. The preliminary work on the analysis of such structurally sensitive characteristics as electrical conductivity and lattice parameter made it possible to identify the nonmonotonic nature of a change in the alloying elements concentration in the solid solution during HPT. Nonmonotonicity is related to the significant changes in the characteristics of the second phase particles ensemble under the influence of high voltages. Such significant structural changes are reflected in the nature of the mechanical characteristics change. The authors identified that when increasing the number of HPT revolutions, changes in strength also have a nonmonotonic nature, which corresponds to the nonmonotonic nature of changes in the concentration of alloying elements and electrical conductivity. Various contributions to the Cu–0.6Cr–0.1Zr alloy hardening were analyzed. The analysis identified that the dispersion strengthening contribution plays the main role in the nonmonotonic change in the mechanical characteristics. The calculated data correlate with the obtained experimental results.

Low-cost perovskite detects X-rays sensitively

An inexpensive organic-inorganic combo material that can be prepared and processed via common solution-phase methods can detect X-rays more sensitively than standard costly detector materials (Sci. Adv. 2020, DOI: 10.1126/sciadv.aay0815). The hybrid material, a butylamine–methylamine lead iodide perovskite, could improve safety in X-ray-based medical and security applications by lowering the radiation levels needed to acquire high-resolution images. Commercial X-ray detectors often rely upon high-purity crystals of silicon or other semiconductors grown via energy-intensive methods. Radiation induces electrical charges in the semiconductor, which these devices convert to measurable electrical signals under the influence of high voltage. Researchers including Hsinhan Tsai and Wanyi Nie of Los Alamos National Laboratory and colleagues there and at Argonne National Laboratory knew from their earlier studies that a family of layered perovskites—including the hybrid material—responded sensitively to X-rays and could be used to make devices that work in much the same way. But these materials can

Monte-Carlo study of the MRPC prototype for the upgrade of BESIII

A GEANT4-based simulation is developed for the endcap time of flight (ETOF) upgrade based on multi-gap resistive plate chambers (MRPC) for the BESIII experiment. The MRPC prototype and the simulation method are described. Using a full Monte-Carlo simulation, the influence of high voltage and threshold on time resolution and detection efficiency are investigated. The preliminary results from simulation are presented and are compared with the experimental data taken with the prototype MRPC modules.

Space-time resolved density of helium metastable atoms in a nanosecond pulsed plasma jet: influence of high voltage and pulse frequency

Using tunable diode laser absorption spectroscopy, the spatio-temporal distributions of the helium He(23S1) metastable atoms’ density were measured in a plasma jet propagating in ambient air. The plasma jet was produced by applying short duration high voltage pulses on the electrodes of a DBD-like structure, at a repetition rate in the range 1–30 kHz. In addition to the metastable density, the spatial distribution of helium 587 nm emission intensity was also investigated to give insight into the excitation mechanisms of the He(33D) excited state inside the dielectric tube, in which no laser measurement can be performed. It is demonstrated that the shape of the radial distribution of helium He(23S1) metastable atoms strongly depends on the polarity of the applied voltage and on the repetition frequency. For positive applied voltages, a dramatic constriction of the excited species production is observed whenever the pulse repetition frequency is higher than 6 kHz, and the voltage higher than 5 kV. This shrinking of the jet structure induces an increase by one order of magnitude of the metastable atoms’ density in the jet centre which reaches values as high as 1014 cm−3. Beyond a critical distance, associated to a transition between a positive streamer and a negative one, the distribution of the excited atoms gets back to an annular structure. For the negative polarity, no shrinking effect correlated to the pulse repetition frequency was observed. The on-axis constriction of the excited species for the high repetition rate and positive polarity is attributed to a memory effect induced by the negative ions, having a lifetime of hundreds of microseconds, left between successive pulses at the periphery of the helium gas flow.

EFFECT OF HIGH VOLTAGE ON THE DEVELOPMENT OF THE PLANT TISSUE

In our experiment the electrical parameters that affect early somatic embryos (ESEs) were investigated. High voltage was generated by a special high voltage generator. High voltages ranging from 5 to 20 kV and frequency of 1 Hz were applied longitudinal and transversal directly on the Petri dish with 2 days old ESEs of Picea abies for periods of 3 hours every day. One Petri dish was placed directly on top of the high voltage generator and on the other Petri dish were fixed two copper plates for transmission of high voltage. Petri dishes were exposed to high voltage for 14 days. After this time, the influence of high voltage was evaluated. To evaluate the experiment were used biological and chemical methods, which confirmed the changes in the growth of ESEs.

Plasma decoloration of dye using dielectric barrier discharges with earthed spraying water electrodes

The plasma decoloration process of indigo carmine aqueous solution is investigated in this paper using a dielectric barrier discharge with earthed spraying water electrodes (spraying DBD). The influence of high voltage and air gaps on decoloration and the power consumption in the process are discussed. The indigo carmine aqueous solution was employed as a grounded spraying water electrode. The plate electrode was covered by a layer of glass dielectric on its inter-electrode surface and supplied with AC 50 Hz high voltage. The spraying DBD non-thermal plasma was formed in the air gap between the water electrodes and the glass dielectric plate. The experimental results have shown that the decoloration rate increases with rising high voltages and decreasing air gaps. When the air gaps were 30 mm and the voltage was 30 kV, the decoloration rate went up to 95% in 18 min. Using a lesser amount of power the higher decoloration rate could be reached when the air gaps were 30 mm and the voltage was 25 kV.

Electrospun MEH-PPV/SBA-15 composite nanofibers using a dual syringe method.

The process of electrospinning, which produces fibers in the nanometer to micron range under the influence of high voltages, has been widely studied to produce polymer and textile fibers. Mesoporous molecular sieve fibers have been produced in our lab, and this technique was extended to produce an interwoven mesh of polymer-molecular sieve composite fibers. The electroluminescent polymer MEH-PPV and molecular sieve SBA-15 were used to produce the composite fibers. An interesting aspect of these composites is that the fluorescence of MEH-PPV is blue shifted in the composites. The composites have been characterized by microscopy, vibrational spectroscopy, and fluorescence measurements.

Research Design Considerations in Studying Edema

To the Editor: I read with interest the article entitled “Influence of High Voltage Pulsed Direct Current on Edema Formation Following Impact Injury” ( Phys Ther 1990;70:219–224), authored by Bettany et al. I thought the article was very timely and well-planned, and I do not have any negative criticisms of the study. I would, however, like to comment on certain design characteristics of the study that future researchers using animal models to study edema may want to keep in mind. First, the effect of anesthesia on lymph flow should be considered. McHale and Thornbury1 found that anesthetics (ie, halothane and pentobarbitone) decreased spontaneous lymphatic contraction in bovine mesenteric lymph vessels. Pentobarbitone also reduced lymphatic vessel contraction induced by electrical stimulation, whereas ether had no effect on lymphatic contractility. Suckert2 also noted that anesthetics could alter the course of edema in rats.… [ ARTICLE][1] [1]: /lookup/volpage/70/219?iss=4

Influence of High Voltage Pulsed Direct Current on Edema Formation Following Impact Injury

Edema results in pain and may lead to reduced functional mobility. High voltage pulsed direct current (HVPC) has recently been advocated for edema control. The purpose of our study was to determine the effect of HVPC on edema formation in frogs. Hind limbs of 20 anesthetized frogs were injured by dropping a 450-g weight onto the plantar aspects of the feet. One hind limb of each frog was randomly selected to receive continuous 120-Hz HVPC at voltages 10% lower than those needed to evoke muscle contraction. Four 30-minute treatments were administered at 1.5-hour intervals beginning 10 minutes after trauma. Limb volumes were measured by water displacement. An analysis of variance for repeated measures and a Newman-Keuls post hoc test were used to determine the significance of treatment effects. The HVPC significantly (p less than .01) reduced edema formation. We hypothesize that HVPC may also be effective in controlling edema formation after impact injuries in humans. [Bettany JA, Fish DR, Mendel FC: Influence of high voltage pulsed direct current on edema formation following impact injury.