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31.
本文对采用区内C/I平衡的多区蜂窝CDMA系统下行链路的性能进行分析,给出两种区内C/I平衡算法并比较它们的性能,考虑呈对数正态分布的阴影和R^-4规律的路径损失的综合影响,采用与传统不同的小区平均中断概率来评价系统的性能。 相似文献
32.
W. F. Flanagan Lijun Zhong B. D. Lichter 《Metallurgical and Materials Transactions A》1993,24(3):553-559
A model is proposed to explain transgranular-stress corrosion cracking (T-SCC) in face-centered cubic (fcc) materials. Crack
propagation is shown to be anisotropic, in that growth near {110} < 001> is discontinuous due to crack arrest by dislocation
blunting whereas growth away from this growth orientation is continuous. For the former case, renucleation of arrested cracks
involves active dissolution of shear bands at the crack tip, which changes the stress state at Lomer-Cottrell locks, causing
them to fail by cleavage. Once the crack is nucleated, its instantaneous macroscopic crack-growth velocity is considered to
be comprised of multiple nucleation of microcracks with intervening arrests. This microcracking results from the interaction
of the stress fields from neighboring cracks which are forming simultaneously, the crack-opening constraint due to ligaments
which act as “bridges” behind the crack front, and the localized dissolution at the microcrack tip which affectsK
IC and leads to the “cobblestone” appearance. Experimental evidence and theoretical considerations are presented to support
the model. The system studied was Cu-25 at. pct Au in 0.6 M NaCl solution at potentials between 300 and 400 mV (sce), which
precludes hydrogen embrittlement.
This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting,
Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and
Fracture Committee. 相似文献
33.
Juey H. Lai Curtis Knudson Leander Hallgren Richard B. Douglas Patrick Griffin 《Polymer Engineering and Science》1985,25(12):778-781
This paper reports the effect of humidity and temperature on the adhesive strength of a pressure sensitive adhesive (Flexbond 150) used to bond Mylar films. It has been found that, ill general, the adhesive strength decreases significantly with an increase in temperature. The effect of humidity on the bonding strength, however, was found to be process dependent. The sample preparation conditions, e.g., press weight for the bonding and the press time, are important in determining the humidity effect. The water sorption isotherm A 24°C for the adhesive was also determined. The amount of water sorbed by the adhesive at 95 percent relative pressure was found to be less than one weight percent. 相似文献
34.
电潜泵中压变频调速系统的改进 总被引:1,自引:0,他引:1
电潜泵中压变频器输出端产生高次谐波和脉冲电流 ,对电潜泵电动机的绝缘性能和轴承寿命造成不利影响。为此 ,提出 3项改进对策 :①采用谐振软性开关逆变电路 ,使功率开关器件在零电压条件下导通 ;②在变频器逆变输出端设置电抗滤波器抑制高次谐波电流 ;③改变电动机内部结构 ,如加大定子槽宽 ,增加转子导条尺寸 ,变星接法为星 角接法 ,采用绝缘轴承等。实践证明 ,采取改进对策后 ,不仅提高了电潜泵的产量 ,而且变频器滤波后电动机端的过电压明显减小 ,电潜泵和电缆的寿命延长 相似文献
35.
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37.
企业成功的道路有许多条,成功的模式有很多种,但成功的企业都走出了一条适合自己企业的发展道路。北新集团亦是如此。多年来,面对风云变幻的市场环境,北新集团立足现实,着眼未来,兼顾历史,在坚持企业发展愿景和整体价值观的基础上,审时度势,精准出击,以无比的气魄完成了一次次堪称完美的战略转型,走出了一条虽有波折但却辉煌的发展道路。古人云:以史为鉴,可以知兴替。今天,在我们回眸北新20多年的发展历程时,除了自豪并骄傲于她的光荣外,我们更愿意从更大的时空范围,理性的眼光来审视北新历次成功转型背后的深刻原因和基本支撑,从中汲取智慧。 相似文献
38.
镍氢电池负极用低成本储氢合金的研究 总被引:1,自引:0,他引:1
研究了ABS型储氢合金在低Co含量条件下,随B组元替代元素Co,Al,Si等含量的变化对合金电化学性能的影响规律,同时研究了A组元中不同La/Ce比对合金电化学性能的影响情况。结果表明,随合金中Co含量的降低,合金的活化性能和放电容量得以改善,但合金的循环寿命下降也比较明显;在试验范围内,随Al元素的加入,合金的循环寿命得以改善,但材料的放电容量和活化性能均有所下降;随合金La/Ce比的降低,合金的放电容量略有下降,但其循环寿命和放电电压平台有较大提高。 相似文献
39.
Effect of Thickness of the p-AlGaN Electron Blocking Layer on the Improvement of ESD Characteristics in GaN-Based LEDs 总被引:1,自引:0,他引:1
Chung-Hsun Jang Sheu J.K. Tsai C.M. Shei S.C. Lai W.C. Chang S.J. 《Photonics Technology Letters, IEEE》2008,20(13):1142-1144
The following letter presents a study regarding GaN-based light-emitting diodes (LEDs) with p-type AlGaN electron blocking layers (EBLs) of different thicknesses. The study revealed that the LEDs could endure higher electrostatic discharge (ESD) levels as the thickness of the AlGaN EBL increased. The observed improvement in the ESD endurance ability could be attributed to the fact that the thickened p-AlGaN EBL may partly fill the dislocation-related pits that occur on the surface of the InGaN-GaN multiple-quantum well (MQW) and that are due to the strain and the low-temperature-growth process. If these dislocation-related pits are not partly suppressed, they will eventually result in numerous surface pits associated with threading dislocations that intersect the InGaN-GaN (MQW), thereby reducing the ESD endurance ability. The results of the experiment show that the ESD endurance voltages could increase from 1500 to 6000 V when the thickness of the p-AlGaN EBL in the GaN LEDs is increased from 32.5 to 130 nm, while the forward voltages and light output powers remained almost the same. 相似文献
40.
A wavelet-based multisensor data fusion algorithm 总被引:7,自引:0,他引:7
Lijun Xu Jian Qiu Zhang Yong Yan 《IEEE transactions on instrumentation and measurement》2004,53(6):1539-1545
This paper presents a wavelet transform-based data fusion algorithm for multisensor systems. With this algorithm, the optimum estimate of a measurand can be obtained in terms of minimum mean square error (MMSE). The variance of the optimum estimate is not only smaller than that of each observation sequence but also smaller than the arithmetic average estimate. To implement this algorithm, the variance of each observation sequence is estimated using the wavelet transform, and the optimum weighting factor to each observation is obtained accordingly. Since the variance of each observation sequence is estimated only from its most recent data of a predetermined length, the algorithm is self-adaptive. This algorithm is applicable to both static and dynamic systems including time-invariant and time-varying processes. The effectiveness of the algorithm is demonstrated using a piecewise-smooth signal and an actual time-varying flow signal. 相似文献