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31.
CHEN XiaoJun SI JiangBo LI Zan CAI JuePing & BAI BaoMing The State Key Laboratory of Integrated Service Networks Xidian University Xi’an China The School of Microelectronics 《中国科学:信息科学(英文版)》2011,(7):1491-1499
This paper presents a new complexity metric to evaluate the unpredictability of a frequencyhopping/spread-spectrum (FH/SS) sequence based on fuzzy entropy (FuzzyEn).According to the property of the FS/SS sequence,the definition of a fuzzy membership function for a complexity metric is presented and a basic theorem for FuzzyEn complexity is proved.Simulation and analytical results show that the proposed FuzzyEn works and can effectively discern the changing complexities of the FH/SS sequences,which are compa... 相似文献
32.
Ji X Han T Shi W Zhang G 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(11):2075-2080
A promising perspective for surface acoustic wave (SAW) device applications at high temperature has been opened by langasite (LGS). The SAW properties of LGS in singly and doubly rotated cuts at 250 degrees C are investigated. Three noticeable regions for SAW-cut orientations and propagation directions at high temperature are put forward and are defined by Euler angles [0 degrees, 20 degrees --> 50 degrees, 35 degrees --> 45 degrees], [0 degrees, 85 degrees --> 110 degrees, 0 degrees --> 5 degrees], and [0 degrees, 138 degrees --> 145 degrees, 20 degrees --> 23 degrees], respectively. The first region includes zero or comparatively reduced temperature coefficient of delay (TCD) (<2 ppm) and smaller electromechanical coupling factor (K2) (0.2%-0.35%); the second one exhibits higher K2 (0.35%-0.45%) and moderate TCD (<5 ppm); and the highest K2 (>0.45%) and larger TCD (25-30 ppm) characterize the last region. For some typical orientations within the above-mentioned three regions, the temperature dependency of SAW characteristics (up to 1000 degrees C) is discussed. The second region [0 degrees, 85 degrees --> 110 degrees, 0 degrees --> 5 degrees], especially the orientation [0 degrees, 90 degrees, 0 degrees], has better comprehensive characteristics of SAW and is more suitable for high-temperature applications. Therefore, we should give a top priority to the orientation [0 degrees, 90 degrees, 0 degrees] in the design of SAW devices operating at high temperature. Comparison between published experimental results and numerical predictions based on LGS constants and their temperature coefficients available in the literature reveals that the theoretical results of TCD under 250 degrees C are in agreement with the experimental ones (the relative error of TCD is within 10%). 相似文献
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To improve the efficiency of nano-electronic device fabrication,a new method named floating electrical potential assembly is proposed to realize large-scale assembly of Cu/CuO nanowires.The simulation of floating electrical potential distribution on the micro-electrode chip is performed by COMSOL software,and the simulation result shows that the coupled electrical potential on the floating drain electrodes is very close to the original electrical potential applied on the gate electrode,which means that the method can provide di-electrophoresis(DEP)force for all the electrode pairs at one time,thus realizing large-scale assembly at one time.With Cu/CuO nanowires well dispersed and micro-electrode chip fabrication,nanowires assembly experiments are performed and the experimental results show that Cu/CuO nanowires are assembled at hundreds of micro-electrodes pairs at one time,and the success rate of nanowires assembly also reaches 90%. 相似文献
35.
汽液两相流空泡率实验与计算方法研究对于反应堆自然循环及事故分析具有重要意义,然而现有研究主要以高质量流速工况为主,已有的空泡率公式预测结果在低质量流速条件下也存在较大差异。为此,本文以单探头光学探针为主要测量手段,进行了低质量流速绝热工况空泡率实验研究,截面平均空泡率根据探针测量得出的局部空泡率在流道截面上积分计算得出。实验数据与已有空泡率计算公式进行了比较,表明低质量流速工况下多数公式预测结果偏高,而Chexal et al.、GE—Ramp以及Dix公式可得出非常满意的预测结果。综合Vijayan的研究结果,本文建议低质量流速空泡率计算中采用Chexal et al.的公式。 相似文献
36.
JIANG HongYuan REN YuKun HAN XiaoJun TAO Ye & LI ShanShan School of Mechatronics Engineering Harbin Institute of Technology Harbin China School of Chemical Engineering Technology State Key Lab of Fluid Power Transmission Control ZheJiang University Hangzhou 《中国科学:信息科学(英文版)》2011,(3)
The electrorotation of microspheres coated with conductive surface is a novel and important technology for label-free biosensors. Using the electroless plating approach, the polystyrene microspheres with 15 μm and 25 μm in diameters were coated with 50 nm gold layer in thickness. The electrorotation experiments on those gold coated polystyrene microspheres (GCPMs) were carried out. The results showed that they rotated in the opposite direction of the electric field in a low frequency range (100-100 kHz), an... 相似文献
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本文针对我国有线电视技术的应用,对有线电视系统的基本组成和发展进行了概括和总结,并提出了有线电视系统主流技术的发展方向。 相似文献
39.
网络教学中C程序设计填空题机器批改的实现 总被引:2,自引:0,他引:2
在现存的网络考试系统中,有关题型均为标准化试题,这对于需严格考察学生程序能力的程序设计考虑而言不太合适,本文从C语言的特点出发,探讨了机器自动批改C程序设计填空题的实现,提出了解决方案,并说明了需要进一步研制的问题。 相似文献
40.
铣削成型的航空发动机整体叶盘,其叶片型面为空间自由曲面,曲率变化大,严重制约了抛光表面质量均匀一致性.为掌握砂布轮柔性抛光工艺参数对材料切除深度影响规律,基于"数控机床+柔性磨头+弹性磨具(砂布轮)"的抛光工艺装备,开展了TC4试件单因素抛光试验,分析了工艺参数对材料切除深度的影响规律,开展正交试验建立了材料切除深度预测模型;计算了材料切除深度对工艺参数相对灵敏度,结果表明材料切除深度对压缩量最敏感,对转速比较敏感,对进给速度敏感度一般,对粒度敏感度最小;最后开展了抛光实验,结果表明实际测量切除轮廓和预测轮廓基本一致,证明了预测模型是可靠的,能用于材料切除深度预测,为提高抛光表面质量一致性提供依据. 相似文献