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991.
提出了一种基于电力线信道噪声的真随机数发生器的设计,即通过对电力线信道上的噪声采样的方法来产生随机数。使用EAX加密算法作为后处理算法,消除由于外部干扰产生的偏差和自相关性。通过理论分析和实验验证,可以弥补现有常用真随机数生产法的不足,获得分布均匀、相对独立的随机数。 相似文献
992.
为了进一步提高视频传输质量,充分发挥网络视频在教学中的作用,提出了一种新的基于智能数据流的传输模式,摒弃了以往单一改善网络传输环境的思路,建立更加智能的视频源服务环境,并详细阐述了智能数据流传输的几个关键技术。最后,从网络接收延时方面对基于智能数据流传输的网络视频教学系统进行仿真试验。实验表明,该系统可以有效地减少网络接收延时,提高网络视频教学的服务质量和效率。 相似文献
993.
提出一种新的传输电能的系统,即长距离磁路传输电能系统,长距离磁路是指距离在400km以上的闭合磁路。通过磁路分析的第一类方法及第二类方法对该系统的磁路结构及系统参数进行了分析,验证了该新的系统的合理性,为电能传输方式提供新的思路并进行了有益的探索。但还有诸如恒定磁场如何取电的问题有待进一步研究。 相似文献
994.
Jacek Jasielski Stanisław Kuta Witold Machowski Wojciech Kołodziejski 《Microelectronics Journal》2014
In the paper we propose a novel architecture and implementation of 11-bit Digital Pulse Width Modulator (DPWM) circuit based on previously known building blocks. Linearized Class-AD Double-sided (LADD) algorithm has been used to calculate the DPWM signals of the 11-bit resolution hybrid DPWM for a Class-AD digital audio amplifier. Noise-shaping process is used to support high fidelity with practical values of time resolution. The proposed DPWM circuit is composed of 8-bit counter and Analog Delay Locked Loop (ADLL) using 4-bit tapped delay line. A dual ADLL employing coarse and fine programmable delay element is used to adjust the delay time of delay line and lock it to required time. The coarse- as well as fine-delay lines are implemented as a cascade of variable-delay elements based on shunt capacitor delay element or single-ended Schmitt trigger. The proposed 11-bit DPWM circuit, at a switching frequency of 352.8 kHz and clock generator frequency of 90.3 MHz allows us to attain SNR of 120 dB and THD of the output signal less than 0.1% within the audio baseband and modulation index M=0.95. Basic verification of circuit manufacturability and simulation results (Monte Carlo analysis) for real CMOS process are presented. 相似文献
995.
996.
We put forward a novel single selection transmission scheme based on maximum desired signal criterion and investigate the capacity of distributed antenna systems in multicell environment. However, for most of the recent literatures, the interference plus noise is treated as Gaussian random variable with fixed variance by the central limit theorem, which ignores the effect of the short‐term fading on interference. To avoid it, non‐central limit theorem is adopted in which the variance of interference plus noise is considered as a random variable with changeable variance influenced by the short‐term fading. Moreover, channels are assumed to suffer from independent identical Rayleigh fading together with propagation path loss, and the closed‐form expression of capacity for distributed antenna systems is derived. Finally, extensive simulations are carried out to validate the theoretical analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
997.
As a memory channel, power‐line communication (PLC) channel can be modeled by the finite states Morkov model. The memory order in an finite states Morkov model is a key parameter, which is not solved in PLC systems yet. In the paper, the mutual information is used as a measure of the dependence between the different symbols, treated as the received scalar network analyzer, or amplitude of the current channel symbol or that of previous symbols. The joint distribution probabilities of the envelopes in PLC systems are computed based on the multi‐path channel model, which is commonly used in PLC. With the first‐order Markovian assumption, we confirm that given the information of the symbol immediately preceding the current one, any other previous symbol is independent of the current one in PLC systems. The field test is also performed to model the received OFDM signals with the help of autoregressive model. The results show that the first‐order autoregressive model is enough to model the fading channel in PLC systems, which means the amount of uncertainty remaining in the current symbol should be negligible, given the information corresponding to the immediately preceding one. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
998.
Alireza Alizadeh Ghosheh Abed Hodtani 《International Journal of Communication Systems》2015,28(8):1462-1474
In this paper, we consider Rayleigh fading MIMO relay channel with channel state information at the receivers. First, we extend the previously obtained results for the ergodic capacity of uncorrelated and semi‐correlated MIMO channels and derive closed‐form expressions for the capacity bounds of MIMO relay channel. Next, we study this channel from a new point of view, maximizing coverage region for a desired transmission rate, and investigate the optimal relay location in the sense of maximizing coverage region. However, in order to overcome the mathematical complexity in desired transmission rate analysis, because of the randomness of the multiple antenna channel matrices, we evaluate this rate by using an existing exact formula and also by an approximation we find in the high signal‐to‐noise ratio regime. Numerical results show a perfect match between the Monte Carlo simulations and the obtained analytical closed‐form expressions and also confirm the effectiveness of our approach in cooperative vehicular communication for determining optimal relay location at which the coverage region is maximum. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
在穿墙雷达成像领域,建筑墙体会改变电磁波的传播路径和速度,引入墙体回波延迟误差,造成建筑布局图像出现墙体位置偏移,这种现象随着穿透墙体的面数增加而加剧。并且电磁波穿透墙体时的衰减会带来前后墙体图像强度差异。对此提出了一种墙体补偿算法,该算法利用 Radon变换进行墙体距离向位置检测,实现在距离向上对成像区域进行划分,结合线段检测,实现在方位向上对成像区域进行划分,最终完成成像区域的精确划分,分别对各成像区域补偿墙体穿透延时和聚焦成像。XFDTD仿真数据验证了该算法能实现各成像区域和各面墙体的聚焦成像,有效地矫正了墙体位置,降低了前后墙体图像强度差异。 相似文献
1000.
Regulated Breathing Effect of Silicon Negative Electrode for Dramatically Enhanced Performance of Li‐Ion Battery
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Xingcheng Xiao Weidong Zhou Youngnam Kim Ill Ryu Meng Gu Chongmin Wang Gao Liu Zhongyi Liu Huajian Gao 《Advanced functional materials》2015,25(9):1426-1433
Si is an attractive negative electrode material for lithium ion batteries due to its high specific capacity (≈3600 mAh g–1). However, the huge volume swelling and shrinking during cycling, which mimics a breathing effect at the material/electrode/cell level, leads to several coupled issues including fracture of Si particles, unstable solid electrolyte interphase, and low Coulombic efficiency. In this work, the regulation of the breathing effect is reported by using Si–C yolk–shell nanocomposite which has been well‐developed by other researchers. The focus is on understanding how the nanoscaled materials design impacts the mechanical and electrochemical response at electrode level. For the first time, it is possible to observe one order of magnitude of reduction on breathing effect at the electrode level during cycling: the electrode thickness variation reduced down to 10%, comparing with 100% in the electrode with Si nanoparticles as active materials. The Si–C yolk–shell nanocomposite electrode exhibits excellent capacity retention and high cycle efficiency. In situ transmission electron microscopy and finite element simulations consistently reveals that the dramatically enhanced performance is associated with the regulated breathing of the Si in the new composite, therefore the suppression of the overall electrode expansion. 相似文献