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801.
Thermal properties of polypyrrole/polymethylmethacrylate (PPy/PMMA) composites were analyzed by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). A decrease in the glass transition temperatures with PPy concentration reveals the increase of segmental motion. The dielectric properties of these composites were studied for several weight concentrations of PPy in the frequency range between 500 Hz and 0.2 MHz, over the temperature range 23–110°C. Jonscher's phenomenological model has been used for modeling the dielectric response of the composite materials. This study shows that the results obtained for the dielectric response are in good agreement with the results of TGA and DSC measurements. 相似文献
802.
Ceramic KBiScNbO6 compound was synthesized for the first time. X‐ray diffraction analysis revealed that at room temperature the samples consist of a mixture of the perovskite and pyrochlore phases. The dominant phase is the perovskite one. This phase can be described as distorted pseudocubic Pm3m structure with unit‐cell parameter ac = 4.069 Å. Rhombohedral distortion leading the polar R3m phase is assumed to be one of possible structural distortions. Dielectric measurements of the compound under study demonstrated anomalies associated with relaxor ferroelectric behavior (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
803.
Feng Xiang Jeong‐Yun Sun Yong Mei Chen Hong Wang Jinxiong Zhou Zhigang Suo 《Journal of Polymer Science.Polymer Physics》2014,52(16):1055-1060
A soft ionic conductor can serve as an artificial nerve in an artificial muscle. A polyacrylamide hydrogel is synthesized containing a hygroscopic salt, lithium chloride. Two layers of the hydrogel are used as ionic conductors to sandwich a dielectric elastomer and fabricate a highly stretchable and transparent actuator. When the two layers of the hydrogels are subject to a voltage, the actuator reduces its thickness and expands. An areal strain of 134% is demonstrated. The voltage‐strain curves are calculated by using a model that accounts for the elastic constraint of the hydrogel and the inhomogeneous deformation of the actuator. For actuators fabricated with the hydrogel of various thicknesses and with the dielectric elastomer of various prestretches, excellent agreements are found between experimental data and theoretical predictions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1055–1060 相似文献
804.
Alain Delgado Lester Lavin Roberto Capote Augusto Gonzalez 《Physica E: Low-dimensional Systems and Nanostructures》2000,8(4)
A resonance behaviour of the far-infrared absorption probability at a frequency N1/4 is predicted for clusters of N electron–hole pairs (2N110) confined in disk-shaped quantum dots. For radially symmetric dots, the absorption is dominated by a giant dipole resonance, which accounts for more than 98% of the energy-weighted photoabsorption sum rule. 相似文献
805.
806.
The breakdown activity in helium atmospheric pressure dielectric barrier discharge (DBD) plasma is strongly modified by introducing small impurities (nitrogen (N2) and air in ppm), although its precise implications for the behavior of discharge plasma is not evident under several constraints. In this simulation study, we investigate the influence of gap spacing between the dielectric barriers to explore the dynamic modification in the structure of discharge plasma in distinct phases of the discharge current pulse using a two‐dimensional fluid model in He‐air gas mixture. Specifically, the impact of nitrogen and air impurities is contrasted by exploring the spatial distributions of electrons in the breakdown phase under similar operating conditions. The filamentary mode of DBD plasma in He‐N2 is transformed into uniform glow discharge in He‐air gas mixture by the dominant effect of Penning ionization. Finally, the outcomes of two‐dimensional fluid model are validated by comparing with three‐dimensional fluid model to provide the reliability of numerical simulations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
807.
将麦克斯韦方程组和简化等离子体方程耦合求解, 对介质表面附近大气击穿形成等离子体的过程进行了理论研究. 分别使用一维、二维模型对等离子体的形成过程及等离子体对电磁波的反射、吸收过程进行了模拟研究. 一维计算结果发现在ne = 0, j = 0两种边界条件下, 虽然形成的等离子体密度分布相差较大, 但二者得到的微波反射、吸收、透射波形彼此相差不大. 初始电子数密度厚度为20 mm的条件下, 得到界面附近的等离子体密度大于5 mm厚度的情况. 二维计算结果发现, 由于TE10模在波导中心位置处的微波电场最强, 电子碰撞电离首先在中心位置处形成等离子体, 当等离子体密度达到一定值(临界密度附近)时, 波导中心介质表面处微波场强减小, 等离子体区域沿着介质表面向两侧移动. TE10模在波导边缘处微波电场强度小于击穿阈值, 因此等离子体区域不可能移动到波导边缘附近. 相似文献
808.
A charged dielectric generates a series of discharges in the surrounding air when the pressure is steadily reduced from near atmospheric to fractions of a torr. The dielectrics here employed were Mylar and Teflon. With positive polarity different discharge regimes were observed as the pressure varied: spark and long streamers at relatively high pressure; diffuse cloud-like discharges below 266 Pa (2 torr). With negative polarity it is difficult to induce a discharge, due to the absence of an electron-emitting surface. Similarities between our results and some of the features of mesospheric and stratospheric discharges are discussed. 相似文献
809.
810.
在氩气空气混合气体介质阻挡放电中, 得到了同心圆环斑图. 采用高速照相机拍摄了同心圆环斑图在外加电压半周期时间尺度内的放电照片, 发现放电丝是构成同心圆环斑图的基本单元. 通过对比高速照相机拍摄的连续三个正半周期和负半周期的六张放电图像, 证实肉眼看到的同心圆环斑图是由不同半周期放电位置和不同的大量放电丝长时间积累叠加产生的. 随着外加电压升高, 同心圆环斑图会演化成螺旋波, 然后重新转变成同心圆环斑图. 通过对两种斑图的形成和转化特点进行分析, 推断该螺旋波应具有和同心圆环斑图相似的动力学机理. 计算了两种斑图的放电功率, 发现功率随外加电压增加近似满足线性增长的关系. 利用相关计算的方法计算并对比了不同延迟时间下两种斑图的互相关系数, 结果表明, 同心圆环斑图的互相关系数相对较低且无明显规律, 螺旋波的互相关系数稍高且具有随延迟时间增大呈现振荡的特点. 相似文献