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51.
Ying Ding Chunqing Wang Yanhong Tian Binbin Zhang 《Metallurgical and Materials Transactions A》2006,37(12):1017-1025
in-situ transmission electron microscopy (TEM) tensile tests on as-cast and aged 63Sn37Pb solder alloys were conducted, and the fracture
behavior in nanometer scale ahead of the crack tip was inspected and discussed. Results show that the fracture was completed
by connecting the discontinuous cracks or voids. Dislocation behavior was concentrated along the grain boundaries for as-cast
samples, and displayed mainly as dislocation climb. The crack was intergranular dominated under the lower strain rate. While
remarkable mutual dislocation emission was detected in the aged solder. Transgranular cracks were dominant in the fractured
area, and they propagated by linking up with the nanometer scale cracks ahead of the crack tips under the effective promotion
of the inverse dislocation emission. At the same time, the partial interphase or intergranular cracks in the thinned area
were also found. Under this condition, a new critical stress intensity factor K
c
′ to define the mutual dislocation emission was proposed. 相似文献
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55.
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
56.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
57.
An experimental study of an optical burst switching network based on wavelength-selective optical switches 总被引:1,自引:0,他引:1
Li Xinwan Chen Jianping Wu Guiling Wang Hui Ye Ailun 《Communications Magazine, IEEE》2005,43(5):S3-10
In this article we report the system structure and test results of an experimental optical burst switching network with three edge router's and one core node. Wavelength-selective switches developed for this system and their characteristics are depicted. The implementation and performance of our new scheme for the just-in-time protocol are described. We also report experimental results of FTP and VOD services on this system. Some parameters, including traffic rate, average burst data length, and assembly time, are studied. 相似文献
58.
Methylated-β-cyclodextrin (Me-β-CD) was used to complex the photoinitiator, 2,2-dimethoxy-2-phenyl acetophenone (DMPA), yielding a water-soluble host/guest complex. The comparative studies demonstrated that the Me-β-CD complexed DMPA exhibited a high photoreactivity identical to the uncomplexed DMPA, while the CD complex obviously influenced the products of primary photolysis of DMPA and the photopolymerization kinetics due to the steric effect of CD on the subsequent initiation reactions. The photopolymerization rate of acrylamide can be described by the equation: Rp=K[2a]0.62[M]1.37[I]0.5[Me-β-CD]0. The mechanism of polymerization was also discussed. 相似文献
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