多小区下行3D MIMO系统的传输速率分析

针对传统MIMO（多输入多输出）系统容量受限的问题,引入3D（三维）MIMO系统模型,将多小区联合传输技术应用于3D MIMO系统以提高系统容量。结合香农理论推导出采用单小区传输和多小区联合传输时的信干噪比,采用简单易实现的迫零预编码算法,分析了基站天线下倾角、用户与基站之间的距离以及小区中的用户数对系统传输速率的影响。仿真结果表明,适当调整基站天线下倾角可以提高系统传输速率,验证了采用多小区联合传输比单小区传输在提高系统传输速率方面具有更优的性能

海缆敷设过程中拉力对缆体影响的有限元分析

为获取海缆敷设过程中拉力作用下各层的机械特性,利用有限元方法建立了海缆拉伸模型。合并了机械特性相近的绝缘内外层屏蔽和阻水带,忽略了厚度和强度小的外被层,得到单芯光纤复合海底电缆的几何模型;利用等结构钢体保证了拉伸时海缆层间的位移同步;模拟实际敷设工程,对海缆施加分段力载荷;最后求解得到了海缆各层的应力、应变和塑性应变等力学数据。结果表明,海缆敷设过程中各层结构的应力和应变值随受力的增加而增大,铜导体先达到屈服状态;求解数据为海缆敷设工作提供了参考

基于小波包与神经网络的海底电缆故障诊断

针对海底电缆的故障诊断问题,提出了一种基于小波包与神经网络的诊断新方法。该方法将海缆中光纤的布里渊频移转换成温度和应变数据,首先使用六层小波分解对监测信号降噪,然后对故障数据进行三层小波包分解和重构,再通过提取能量、标准差和Shannon熵等构造特征向量并输入BP（反向传播）神经网络进行训练和测试。实验分析表明,在海底电缆故障诊断中,采用标准差作为特征向量输入BP神经网络中的诊断方法性能最佳

光纤复合海底电缆应变测量的数学建模与仿真

为了获得光纤复合海底电缆的应变与光单元应变的关系,以便用分布式光纤传感技术准确测量海底电缆本体的应变分布。在分析海缆结构的基础上,进行了海缆与光单元应变关系的数学建模和仿真。通过合理简化海缆结构,建立了海缆的有限元模型,进行了直线拉伸数值计算,对比了数值计算结果和数学模型。结果表明,数值计算结果与数学模型一致,光单元应变与海缆应变满足线性关系,且小于海缆应变值,可以利用光单元应变推算海缆的应变,这为基于分布式光纤应变测量的海缆状态监测提供了理论依据

光纤复合海底电缆故障检测与诊断方法

为及时发现并判别光纤复合海底电缆的故障,文章提出一种基于多尺度小波分析的海缆故障检测与诊断新方法。该方法先利用布里渊光时域反射计测量海缆中光纤的布里渊散射频移,然后结合双阈值法对故障点进行检测和分析。对发生接地故障的数据,用阈值法进行诊断;对非接地故障,则选用coif2小波基进行8尺度小波分解。研究结论表明,利用小波分解高频系数尺度对空间距离的敏感性可有效诊断锚害和塑料护套局部放电引发的过热故障。同时,在分析海缆故障特点的基础上,通过建立海缆故障模拟数据验证了算法的有效性

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies