Results 1 - 10 of 36371
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[en] A novel structure for designing and fabricating a power static induction transistor (SIT) with excellent high breakdown voltage performance is presented. The active region of the device is designed to be surrounded by a deep trench to cut off the various probable parasitical effects that may degrade the device performance, and to avoid the parallel-current effect in particular. Three ring-shape junctions (RSJ) are arranged around the gate junction to reduce the electric field intensity. It is important to achieve maximum gate-source breakdown voltage BVGS, gate-drain breakdown voltage BVGD and blocking voltage for high power application. A number of technological methods to increase BVGD and BVGS are presented. The BVGS of the power SIT has been increased to 110 V from a previous value of 50-60 V, and the performance of the power SIT has been greatly improved. The optimal distance between two adjacent ring-shape junctions and the trench depth for the maximum BVGS of the structure are also presented.
[en] An out-of-plane rotational platform with in-plane electrostatic comb-drive actuators is presented in this paper. A rotational angle of ±2.87° is achieved at a static driving voltage of 105 V. The mechanical resonant frequency for torsional oscillation is ≥4750 Hz
[en] In this paper, a bipolar charging method for electrostatic vibratory energy harvester and its analysis result of electrostatic force are described. To improve the harvesting power, higher voltage charged electret with large capacitance change structures are extensively studied. However, the higher voltage also shows a higher electrostatic force, which prevents the device movement for harvesting and causes pull-in behavior. From the result of FEM analysis on bipolar charged electret, the electrostatic force for vertical and horizontal directions were reduced by 15% and 10% from negative only charged device, respectively
[en] Disclosed is a small portable extremely rugged charger for existing pocket-sized type radiation dosimeters. The charger is comprised of a rectangularly shaped housing which contains a piezoelectric charging circuit which is manually operated by a handle to produce a relatively high charging voltage. The charging voltage is coupled to a charging post mounted on a removable cover which is adapted to be selectively rotated so that the underside of the charging post is exposed to light from one of two light windows in the housing whereupon the dosimeter scale may be viewed by either direct or reflected light from any source available. The piezoelectric charging circuit is comprised of a pair of axially aligned cylinders of piezoelectric material mounted in a fulcrum type frame having a beam lever element in contact with one of the cylinders. A spring bias element is connected to the beam lever element and is actuated by a cam attached to the handle which when rotated acts upon the spring to cause an axial compressional force to be applied to the cylinders which thereby produce the required charging voltage
[en] Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude
[en] A new static induction thyristor (SITH) with a strip anode region and p- buffer layer structure (SAP-B) has been successfully designed and fabricated. This structure is composed of a p- buffer layer and lightly doped n- regions embedded in the p+-emitter. Compared with the conventional structure of a buried-gate with a diffused source region (DSR buried-gate), besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-off time decreased from 0.8 to 0.4 μs. (semiconductor integrated circuits)
[en] This paper proposes a new shallow trench and planar gate MOSFET (TPMOS) structure based on VDMOS technology, in which the shallow trench is located at the center of the n- drift region between the cells under a planar polysilicon gate. Compared with the conventional VDMOS, the proposed TPMOS device not only improves obviously the trade-off relation between on-resistance and breakdown voltage, and reduces the dependence of on-resistance and breakdown voltage on gate length, but also the manufacture process is compatible with that of the VDMOS without a shallow trench, thus the proposed TPMOS can offer more freedom in device design and fabrication. (semiconductor devices)
[en] MnO2 materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesi-um batteries due to their earth abundance and environmental friendliness. One polymorph of MnO2, α-MnO2, has 2×2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver ion containing α-MnO2 (Ag1.2Mn8O16) is examined as a candidate cathode material for Li based batteries. Electro-chemical stability of Ag1.2Mn8O16 is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7 %) and atomic distances (~4.8 %) are observed when x in LixAg1.2Mn8O16 is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn-O framework. In contrast, lattice a only expands by 2.2 % and Mn-O/Mn-Mn distances show minor changes (~1.4 %) at x <2. The structural deformation (tunnel breakage) at x >4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag0 and long term cycle stability for this silver containing α-MnO2 type material at both low and high lithiation levels.
[en] The helical micro/nanofiber arrays of polyvinylpyrrolidone (PVP) were successfully prepared by Near-field electrospinning(NFES) with different concentrations of PVP and different voltages by a gradient of per 0.5 kV from 1 kV to 2.2 kV. It is found that the morphology of the arrayed fibers evolved with regularity with the increase of the working voltage, and the uniformity of the fiber arrays also increased. The formation mechanism of the arrayed helical micro/nanofibers was analyzed. This may be a cost-effective method for the large-scale production of morphologically controllable spiral fibers, which opens up an effective way for the precise and controlled deposition of electrospun helical fibers and the integration of single or array spiral fibers with functional devices. (paper)
[en] A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves