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Internet has entered in our lives in a big way, from sending mails, reading the news, to the booking of tickets on-line, it has a special role in every onepsilas life. There is a great need in the near future to take the Internet to the remote places in our country, where network infrastructure is not in place. Many efforts are made in this direction and one of the technologies enabling this is the...
Due to the increasing prices of gasoline in the world market, more and more customers and car manufacturers are looking forward to the alternate energy sources to power up their vehicles. A lot of research has been taking place and vehicles fitted with solar cells, fuel cells, battery powered vehicles as well as hybrid vehicles are becoming available in the market. Cost as well as weight of the vehicle...
Measurements of bias-dependent deflections and strain in EAPap, as well as water absorption were carried out. Model simulations have also been performed to probe the role of the various internal mechanisms. Our simulation predictions yield good agreement with the measured data on EAPap deflections. The modeling suggests that internal ion content and its migration, water absorption leading to a non-uniform...
Time-dependent, two-dimensional simulations based on random Voronoi networks have been developed to study the internal heating and related breakdown effects in ZnO varistors in response to high-voltage pulsing. Our simulations allow for dynamic predictions of internal failures and the progression of hot-spots and thermal stresses. Results show that application of high voltage pulses can lead to the...
Summary form only given. The Field Marshal electromagnetic simulation environment (FM-EMSE) is aimed at small research groups involved in electromagnetics design and analysis. Project goals include improved user interface consistency, single-geometry to drive multiple tools and inclusion of legacy codes. The FM-EMSE provides a set of tools for addressing problems in electromagnetics. All of the FM...
Summary form only given. Zinc oxide varistors are ceramic devices made by sintering ZnO powder together with small amounts of other additives such as Bi2O3, MnO2, Co3O4 etc... The presence of Bi-ions trapped at the grain-boundaries are thought to be responsible for a highly nonlinear behavior. The nonlinear current-voltage (I-V) characteristics and excellent energy absorption capabilities, make ZnO...
Optically-triggered, high-power photoconductive semiconductor switches (PCSS's) composed of semi-insulating GaAs carry current in high carrier-density filaments after the optical trigger is discontinued. This highly conductive mode of operation is called lock-on. The properties of these filaments can be explained by collective impact ionization theory in which energy redistribution by carrier-carrier...
Summary form only given. The use of very high electric fields (~500 kV/cm or higher) with pulse durations in the sub-nanosecond range has been a very recent development in bio-electrics. There appear to be inherent advantages in using short electric pulses such as: (i) negligible thermal heating, (ii) the possibility of selecting the desired time scales through pulse width manipulation, and (iii)...
With the application of pulsed electric fields of only nanosecond duration but field strengths of several megavolts per centimeter, apoptosis can be induced in tumor cells. The detailed mechanisms of this process are not yet completely understood. The accumulation of charges along the membranes in the applied electric field is likely the primary trigger. This first response is observed as a sudden...
Summary form only given. Simulation studies are presented that probe the possibility of using high field (>100 kV/cm), short-duration (~50 ns) electrical pulses for a quick-acting, localized, and reversible cessation of biological electrical signaling pathways. This would have obvious applications in neurophysiology, clinical research, neuromuscular stimulation therapies, and neuro-muscular disruption...
Summary form only given. By reducing the duration of electrical pulses from microseconds into the nanosecond range, the electric field-cell interactions shift increasingly from the plasma (cell) membrane to subcellular structures. Yet another domain of pulsed electric field interactions with cell structures and functions opens when the pulse duration is reduced to values such that membrane charging...
Electric vehicles have been around since the inception of the automobiles. But the internal combustion engines turned out to be the most suitable for automobiles due to availability of cheap fuel at that time, high energy density of gasoline, robust design, longer driving range, no battery charging requirements, rapid acceleration requirements of an automobile. Over a period of time, due to rising...
Model studies of current conduction and breakdown in TiO2 were carried out. Our simulation results indicate that electrical breakdown of TiO2 under multiple pulsed conditions can occur at lower voltages as compared to quasi-DC biasing. This is in agreement with experimental data. The results are indicative of a cumulative effect. We hypothesize that the lower breakdown voltages observed in TiO2 under...
The application of nanosecond pulses to biological cells, which has been shown to lead to electroporation of not only the cell membrane, but also the membranes of subcellular structures, has spawned a new field of research: bioelectrics. A new domain of pulsed electric field interactions with cell structures and functions opens up when the pulse duration is reduced to values such that membrane charging...
In order to study membrane charging in mammalian cells during exposure to pulsed electric fields of 60 ns duration we measured transmembrane voltage changes during and after exposure in real-time, i.e. with a resolution that is short compared to the duration of the administered electrical pulse. The applied electric field was varied between 5 kV/cm and 90 kV/cm. Under all conditions the voltage at...
The Field Marshal (FM) simulation environment is aimed at small research groups involved in electromagnetics design and analysis. Project goals include consistent user interface, single-geometry/multiple-tools and inclusion of legacy codes. A key objective is usability, maintainability, and extensibility by researchers who are not expert programmers. Four primary elements are necessary to cost-effectively...
Photoconductive semiconductor switches (PCSS's), such as optically-triggered GaAs switches, have been developed for a variety of applications. Such switches exhibit unique properties as a consequence of lock-on, a phenomenon associated with the bistable switching of these devices. In this paper, lock-on is explained in terms of collective impact ionization. Furthermore, the effect of defects on the...
An electrical breakdown model for liquids in response to a sub-microsecond (~ 100 ns) voltage pulse is presented, and quantitative evaluations carried out. It is proposed that breakdown is initiated by field emission at the interface of pre-existing micro-bubbles. Impact ionization within the micro-bubble gas then contributes to plasma development, with cathode injection having a delayed and secondary...
We studied the charging of cell membranes in response to ultrashort pulsed high electric fields with a temporal resolution on the same order as the electrical pulse, i.e. nanoseconds. The real-time resolution was achieved by using a pulsed laser (5 ns) as light source, together with a novel voltage-sensitive dye (Annine-6). The laser pulse was synchronized with the pulsed electric field to enable...
Polar liquids, especially water, offer the advantages of high permittivity, a high dielectric strength and a fast dielectric recovery. These benefits make them appealing dielectrics for use in high-energy storage systems and as high-power switching media. In certain applications, however, the use of water is limited by its relatively high freezing point of 0degC and low boiling point 100degC. In comparison,...
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