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1.
Electric nanogenerators that directly convert the energy of moving drops into electrical signals require hydrophobic substrates with a high density of static electric charge that is stable in “harsh environments” created by continued exposure to potentially saline water. The recently proposed charge-trapping electric generators (CTEGs) that rely on stacked inorganic oxide–fluoropolymer (FP) composite electrets charged by homogeneous electrowetting-assisted charge injection (h-EWCI) seem to solve both problems, yet the reasons for this success have remained elusive. Here, systematic measurements at variable oxide and FP thickness, charging voltage, and charging time and thermal annealing up to 230 °C are reported, leading to a consistent model of the charging process. It is found to be controlled by an energy barrier at the water-FP interface, followed by trapping at the FP-oxide interface. Protection by the FP layer prevents charge densities up to −1.7 mC m−2 from degrading and the dielectric strength of SiO2 enables charge decay times up to 48 h at 230 °C, suggesting lifetimes against thermally activated discharging of thousands of years at room temperature. Combining high dielectric strength oxides and weaker FP top coatings with electrically controlled charging provides a new paradigm for developing ultrastable electrets for applications in energy harvesting and beyond. 相似文献
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Magnus Fredriksson Niels Saabye Ottosen 《International journal for numerical methods in engineering》2004,61(11):1809-1834
An accurate and variationally consistent 4‐node quadrilateral element is introduced where high coarse mesh accuracy and low mesh distortion sensitivity are characteristic qualities, even when incompressibility is approached for plane strain. One‐point quadrature integration procedure is adopted and a new improved stabilization technique is developed. Orthogonality conditions are utilized so that the patch test is satisfied for arbitrary quadrilaterals. Several numerical examples including a convergence rate study are presented which confirm the excellent performance of this element. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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F. Goschenhofer J. Gerschütz A. Pfeuffer-Jeschke R. Hellmig C. R. Becker G. Landwehr 《Journal of Electronic Materials》1998,27(6):532-535
N-type Hg1−xCdxTe layers with x values of 0.3 and 0.7 have been grown by molecular beam epitaxy using iodine in the form of CdI2 as a dopant. Carrier concentrations up to 1.1 × 1018 cm−3 have been achieved for x = 0.7 and up to 7.6 × 1017 cm−3 for x=0.3. The best low temperature mobilities are 460 cm2/(Vs) and 1.2 × 105 cm2/(Vs) for x=0.7 and x=0.3, respectively. Using CdI2 as the dopant modulation doped HgTe quantum well structures have been grown. These structures display very pronounced Shubnikov-de
Haas oscillations and quantum Hall plateaus. Electron densities in the 2D electron gas in the HgTe quantum well could be varied
from 1.9 × 1011 cm−2 up to 1.4 × 1012 cm−2 by adjusting the thicknesses of the spacer and doped layer. Typical mobilities of the 2D electron gas are of the order of
5.0 × 104 cm2/(Vs) with the highest value being 7.8 × 104 cm2/(Vs). 相似文献
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The scope of the magazine is being expanded to incorporate reliability and dependability concerns and its readership will include members of the IEEE Reliability Society. This expansion is appropriate because the requirements for a system to be reliable, safe, secure (i.e. its dependability or trustworthiness attributes) often need to be considered together in order to achieve the desired result. 相似文献
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Jeffrey E. Marchese Matteo Cirillo Niels Grøch-Jensen 《Open Systems & Information Dynamics》2007,14(2):189-196
We present evidence for a close analogy between the nonlinear behaviour of a pulsed microwave-driven Josephson junction at
low temperature and the experimentally observed behaviour of Josephson systems operated below the quantum transition temperature
under similar conditions. We specifically address observations of Ramsey-type fringe oscillations, which can be understood
in classical nonlinear dynamics as results of slow transient oscillations in a pulsed microwave environment. Simulations are
conducted to mimic experimental measurements by recording the statistics of microwave-induced escape events from the anharmonic
potential well of a zero-voltage state. Observations consistent with experimentally obtained Ramsey-type oscillations are
found in the classical model.
An erratum to this article can be found at 相似文献