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The solid solutions of Ba-doped SrBi2Ta2O9 layered perovskite ceramic powders have been successfully prepared via a two-step process using BiTaO4 as a precursor. The lattice constants of the solid solutions monotonically increase with increasing barium-ion content. The sinterability of (Sr1–xBax)Bi2Ta2O9 powders is significantly improved by increasing the barium-ion content. When the specimens with high barium-ion contents are sintered at 1100°C, they thermally decompose to form rod-like grains and the matrix expands, leading to a lower density. The addition of barium ions to SrBi2Ta2O9 also results in significant variation in the morphology of the sintered specimens and the occurrence of c-axis preferred orientation which is ascribed to the anisotropic growth of plate-like grains. The precise control of the barium-ion content as well as the sintering conditions is critical for obtaining densified barium-ion doped SrBi2Ta2O9 ceramics with a pure, layered perovskite structure. 相似文献
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A novel finger‐sensing nanocomposite with remarkable and reversible piezoresistivity is successfully fabricated by dispersing homogeneously conductive graphite nanosheets (GNs) in a silicone rubber (SR) matrix. Because of the high aspect ratio of the graphite nanosheets, the nanocomposite displays a very low percolation threshold. The SR/GN nanocomposite with a volume fraction of conductive nanosheets closest to that for the percolation threshold presents a sharp positive‐pressure coefficient effect of the resistivity under very low pressure, namely, in the finger‐pressure range (0.3–0.7 MPa), whereby the abrupt transition could be attributed to compressive‐stress‐induced deformation of the conducting network. The super‐sensitive piezoresistive behavior of the nanocomposite is accounted for by an extension of the tunneling conduction theory which provides a good approximation to the piezoresistive effect. 相似文献
96.
通过电镀法制备片状磁性吸收剂,用SEM、XRD等手段对其进行表征。用网络分析仪测试了不同工艺条件下吸收剂样品2~18GHz的电磁参数,并结合晶粒尺寸因素研究了不同工艺条件下对吸收剂电磁参数的影响.结果表明,不同的工艺条件对吸收剂电磁参数的影响具有规律性,可通过合理配置工艺参数来提高吸收剂的吸波性能。 相似文献
97.
石泉水电站扩机工程自投运发电以来,一直深受机组进水口污物的困扰,致使两台机组不能正常发电,造成了严重的经济损失.本文详细介绍了机组进水口污物情况、污物处理难度以及所采取的污物处理措施,通过拦污和清污的综合方案,有效解决了污物堆积问题. 相似文献
98.
Enhancing echo cancellation via estimation of delay 总被引:2,自引:0,他引:2
Youhong Lu Fowler R. Tian W. Thompson L. 《Signal Processing, IEEE Transactions on》2005,53(11):4159-4168
The advent of packetized audio transmission, such as voice over IP (VoIP), has resulted in challenging requirements for echo cancellation technology. One key aspect of this technology is the need to characterize, quickly and accurately, the echo paths in the transmission media. Echo paths consist of a constant time delay with no echo signal and active regions in which the echo signal is present. When an adaptive filter echo cancellation algorithm is used, its performance can be greatly increased, and its complexity can be reduced if it is only applied to the active regions. This requires an algorithm to estimate the constant delay and locate the active regions. Traditionally, delay estimation has been based on direct application of cross-correlation. This method has poor performance because the input signals are highly correlated and has a high implementation cost because many cross-correlation lags have to be computed for longer time delays. The delay estimation addressed in this paper has two major advantages over the traditional methods. The first is that it has improved performance because the input signals are processed to have less correlation. The second is that the implementation cost is significantly reduced because fewer cross-correlation lags are computed, and an efficient method to estimate lags is created. 相似文献
99.
水文整编软件HDPS在佛山分局的应用 总被引:1,自引:0,他引:1
该文介绍水文资料整编软件——HDPS。该软件完全能实现过去的“微机水文资料整编软件包”和全国统一的“潮水位整编程序”的所有功能。 相似文献
100.