一种基于FCOS神经网络的小建筑物目标检测方法北大核心

提出了一种基于FCOS神经网络的小建筑物目标检测算法,针对FCOS模型在特征提取阶段提取到的小建筑物目标特征较少问题,引入多尺度检测和可变形卷积方式,加强网络对小建筑物目标的特征提取能力,并通过改进后的SGE注意力机制降低特征图中的干扰噪声权重。改进后的网络可以提取到更多的小建筑物目标特征,对环境干扰噪声的鲁棒性更强。在自己搭建的数据集上进行了实验测试,结果表明,在相同环境下网络改进后建筑物的整体检测准确率提升了1.7%,其中对小建筑物目标提升了3.6%,减少了小建筑物目标漏检、误检的问题。     

Co?N graphene encapsulated cobalt catalyst for H2O2 decomposition under acidic conditions

Hydrogen peroxide (H₂O₂) has been listed as one of the 100 most important chemicals in the world. However, huge amount of residual H₂O₂ is hard to timely decomposed into O₂ and H₂O under acidic condition, easily resulting in explosion hazard. Here, we reported a core–shell structure catalyst, that is graphene with Co N structure encapsulated Co nanoparticles. Co N graphene shell serves as the active site for the H₂O₂ decomposition, and Co core further enhance this decomposition. Benefiting from it, the H₂O₂ decomposition were close to 100% after 6 cycles without pH adjustment, which increased 6 orders of magnitude compared with no catalyst. At the same time, the O₂ generation reached 99.67% in 2 h with little metal leaching, and ·OH has been greatly inhibited to only 0.08%. This work can cleanly remove H₂O₂ with little deep oxidation and protect the process of H₂O₂ utilization to achieve a safer world.     

基于磁偶极子的2阶磁场梯度张量缩并方法

针对磁场定位中2阶磁场梯度张量的理论尚不够完善的现状，提出基于磁偶极子的2阶磁 场梯度张量缩并方法。给出2阶磁场梯度张量的全局模量和局部模量计算公式，分析2阶磁场梯度张量的全局模量和局部模量及相关参数的三维空间分布规律，并给出相关参数k_H、k_Hxy和k_Hz的近似计算公式，比较1阶磁场梯度张量和2阶磁场梯度张量及其模量的分布规律及与距离的关系。计算结果表明：全局模量C_H及参数k_H值在0°≤≤90°时，随着增大而减小，在=0°时最大，在=90°时最小；局部模量C_Hxy和参数k_Hxy值在0°≤≤90°时，随先增加、后减少，当=35° 时最大，当=90°时最小；局部模量C_Hz和参数k_Hz随先减少、后增加，当=0°时最大，当=71°时最小；k_H、k_Hxy和k_Hz的拟合值与理论反演值高度吻合；在距离较近时，2阶磁场梯度张量及模量更敏感；在距离较远时，1阶磁场梯度张量及模量更敏感；在实际磁场定位的应用中，可结合1阶和2阶磁场梯度张量及全局模量进行使用。     

基于Massive MIMO及频谱叠加的5G SA网络上行优化方法

大规模多输入多输出(Multiple-Input Multiple-Output, MIMO)可以有效提升5G SA网络的上行链路数据传输速率以及可靠性。针对5G SA网络上行链路速率和覆盖不均衡的情况,提出了基于大规模MIMO的分组算法,将发送信号矢量进行分组,组内采用最大似然检测,组外采用基于正交三角分解(QR分解)的干扰消除检测,并且结合5G频谱的叠加策略,在降低算法复杂度的同时,有效提升网络覆盖和速率。通过5G SA现网实测,通过MIMO降低分组数量能够提升分组检测性能,结合上行低频段频谱叠加策略能够有效提升5G SA网络上行覆盖30%,提升5G SA网络上行平均速率40%~80%,特别是弱覆盖边缘的网络速率,最高可达600%。     

Engineering A-site cation deficiency into LaCoO3 thin sheets for improved microwave absorption performance

Journal of Materials Science - Rationally designing microwave absorption materials with highly efficient and tunable bandwidth is in great demand but remains a huge challenge. In this study,...