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A new method of calculating the orbital angular momentum spectra of Laguerre-Gaussian beams in channels with atmospheric turbulence
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Studying orbital angular momentum(OAM) spectra is important for analyzing crosstalk in free-space optical(FSO)communication systems. This work offers a new method of simplifying the expressions for the OAM spectra of Laguerre-Gaussian(LG) beams under both weak/medium and strong atmospheric turbulences. We propose fixing the radius to the extreme point of the intensity distribution, review the expression for the OAM spectrum under weak/medium turbulence,derive the OAM spectrum expression for an LG beam under strong turbulence, and simplify both of them to concise forms.Then, we investigate the accuracy of the simplified expressions through simulations. We find that the simplified expressions permit accurate calculation of the OAM spectrum for large transmitted OAM numbers under any type of turbulence. Finally,we use the simplified expressions to analytically address the broadening of the OAM spectrum caused by atmospheric turbulence. This work should contribute to the concise theoretical derivation of analytical expressions for OAM channel matrices for FSO-OAM communications and the analytical study of the laws governing OAM spectra. 相似文献
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Silicon nanoparticles have attracted great attention in the past decades because of their intriguing physical properties,active surface state, distinctive photoluminescence and biocompatibility. In this review, we present some of the recent progress in preparation methodologies and surface functionalization approaches of silicon nanoparticles. Further, their promising applications in the fields of energy and electronic engineering are introduced. 相似文献
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为了对粗珩阶段缸套内孔表面粗糙度Rk粗糙度集中的Rk、Rpk和Rvk进行预测,进而对粗珩加工参数进行优化,以珩磨压力(P)、珩磨头旋转速度(VR)和往复速度(VRe)为决定因素,Rk粗糙度集为目标响应,进行多目标优化.建立基于广义回归神经网络(Generalized regression neural network, GRNN)与响应曲面法(Response surface methodology,RSM)的粗糙度预测模型,并采用三因素三水平的全因子珩磨试验进行验证,结果表明所建立模型的预测结果与试验结果具有很好的一致性. GRNN预测模型决定系数R2的均值为0.959,RSM多元回归预测模型决定系数R2的均值为0.963,与RSM所建立的多元回归预测模型相比,GRNN预测模型在预测Rk和Rpk时,预测精度更高,预测误差更小,R2分别提高了0.025和0.020,在预测Rvk时RSM多元回归模型更优,R2提高了0.057.进一步结合响应曲面法分析了3个决定因素对粗糙度的影响显著性并进行了排序,对于... 相似文献
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携带轨道角动量的汉克-贝塞尔(Hankel-Bessel,HB)光束具有无衍射和自聚焦特性,用来作为信息传输的载体有望增大信息传输容量.基于Rytov近似理论,推导得到了HB涡旋光束经过海洋水平弱湍流信道后的螺旋相位谱的解析表达式,并利用数值仿真方法研究了海洋湍流参数对轨道角动量模式探测概率的影响.结果表明,海洋湍流导致发射轨道角动量模式的探测概率下降,出现模式串扰和螺旋相位谱扩展.海洋湍流对HB涡旋光束的负面影响随着轨道角动量模式数、传输距离、温度方差耗散率的增加而增强,随湍流动能耗散率的增加而减弱.HB涡旋光束受以盐度波动驱动的海洋湍流的负面影响更大.另外,在弱湍流及几十米传输距离条件下,HB涡旋光束的传输性能要差于最佳束腰大小设置的拉盖尔-高斯涡旋光束.这些结果有望为海洋环境水下光通信链路的实现提供一定的参考价值. 相似文献
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<正>本文提出一种基于树莓派开发板的全自动固液料奶茶机人机交互系统,该系统可以控制多种奶茶机传感器设备同时识别语音并通过扬声器、灯带、显示屏给予顾客反馈,从而达到多层面人机交互体验。本文主要阐述了该系统的硬件设计。通过树莓派接收传感器设备传递的数据,分析处理后进行反馈控制。智能手机终端可以通过物联网云平台和本地网站服务器实时了解部分系统信息。目前市场上主流奶茶店都采用传统人工制作售卖的方式[1],这样就造成许多奶茶店高峰时期效率有限,顾客排队时间过长的问题, 相似文献
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为了提高车载视频监控系统的视频传输质量,本文基于排队论,利用多链路捆绑技术,设计了基于TD-SCDMA,WCDMA和CDMA2000的多模车载视频监控的负载均衡算法.该负载均衡算法以各个网卡在数据传输时的传输时延、信号强度、运营商因子和丢包率加权作为均衡因子,依次作为负载均衡时数据转发的依据.经实验测试,本算法能够充分利用增加用户卡来增加传输速率,并通过捆绑不同运营商的用户卡来提高数据传输的稳定性,并且该算法较常用的轮询算法的数据传输速率有了较大提高. 相似文献
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