无蜂窝大规模MIMO中导频欺骗攻击检测方法

在无蜂窝大规模多输入多输出网络中，一方面，接入点（access points， APs）分布式部署导致信道硬化及利好传播现象不再显著，导频欺骗攻击（pilot spoofing attack， PSA）的恶意窃听者可以通过调整导频发送功率，得以模拟信道特性，传统依赖大尺度衰落先验信息的PSA检测技术不再适用；另一方面，基于信息论准则的PSA检测技术，需要比AP数量级高的导频样本进行观测，而信道估计阶段所耗费的时长无疑影响系统的频谱效率。针对这种情况，提出了一种基于信号子空间的欺骗检测（signal subspace based spoofing detection， SSBSD）方法。首先，在合法用户的训练序列上叠加一个随机序列，利用灵活检验准则对信源数量进行估计。其次，利用统计学中的线性收缩原理，对导频样本协方差矩阵进行优化，使观测样本的噪声特征值分布更好拟合信道噪声功率。最后，通过信号的正交补空间对观测矩阵进行投影处理，从而实现PSA检测。经仿真实验与理论分析，SSBSD方法无须大尺度衰落先验信息，也无须与AP数量级相同的导频长度，对PSA的导频发送功率十分敏感，在大尺度衰落未知、大尺度衰落时间相关或频谱资源受限的通信环境中，可以精确检测低电平功率的PSA。      

水压爆破拆除钢筋混凝土隐蔽部

水压爆破是一种控制爆破技术，它可在不动用机械设备情况下，用水作为介质，把炸药的爆炸能传递给待拆构筑物，达到破碎的目的。本文介绍采用水压爆破拆除钢筋混凝土工事的设计与实施，爆破取得圆满成功。     

Poly(4-styrenesulfonic acid) doped polypyrrole/tungsten oxide/reduced graphene oxide nanocomposite films based surface acoustic wave sensors for NO sensing behavior

Poly(4-styrenesulfonic acid) (PSSA) doped polypyrrole (PPy)/tungsten oxide (WO₃)/reduced graphene oxide (rGO) hybrid nanocomposite have been successfully synthesized using appropriate amounts of PSSA, pyrrole monomer, WO₃, and rGO dispersed in aqueous solution through in situ chemical oxidation polymerization. Here, a simple spin coating method was used to fabricate a nitric oxide (NO) gas sensor composed of the aforementioned nanocomposite on a surface acoustic wave (SAW) resonator. This sensor can detect NO gas at concentrations of 1–110 parts per billion (ppb) at room temperature in dry air, with a sensitivity of 12 Hz/ppb and response and recovery times of <2 min. Moreover, its limit of detection (LOD) is 0.31 ppb for a signal to noise ratio of 3. It demonstrates repeatability, fast response, and recovery at room temperature. Moreover, its sensory performance remains highly stable over 30 days with only a 6.3% decrease in sensitivity. In addition, the sensor is highly selective for NO, even when nitrogen dioxide, ammonia, and carbon dioxide are applied as interfering gases. The inclusion of rGO (with large specific surface area) and the synergic effect of n-type WO₃ nanoparticles in the p-type PPy matrix (leading to p-n heterojunction region formation) possibly underlie the efficient sensing performance of our sensor.     

非线性负载简化模型及其应用

为实现复杂网络电磁脉冲（electromagnetic pulse，EMP）耦合分析，针对非线性负载引起的分析效率和收敛性问题，提出了非线性负载精简建模方法，即将多项式表示的非线性关系用压控元件代替，指定器件动作时间表示开关响应时间，忽略温度等不必要参数，减少模型元器件个数等.采用该方法建立了气体放电管（gas discharge tube，GDT）和金属氧化物变阻器（metal oxide varistors，MOV）的精简SPICE（simulation program with integrated circuit emphasis）模型，并且用3种不同类型的脉冲激励端接非线性负载的传输线，进行了收敛性和仿真效率分析.结果表明，GDT和MOV的简化模型能够很好收敛，MOV的模型分析效率提高约30%，GDT的模型分析效率稍有劣化，但完全避免了理想开关元器件的使用，与实际器件的工作原理一致.这些建模方法具有较强的普适性，可以移植到其他非线性负载的建模上，例如与线缆耦合的精简计算模型相结合，从而提高超大系统的电磁兼容（electromagnetic compatibility，EMC）设计与评估效率.     

基于深度学习的人体姿态估计方法综述

基于深度学习的人体姿态估计方法旨在通过构建合适的神经网络，直接从二维的图像特征中回归出人体姿态信息。主要按照2D人体姿态估计到3D人体姿态估计的顺序，并从单人检测与多人检测、稀疏的关节点检测与密集的模型构建等方面，对近年来基于深度学习的人体姿态估计方法进行系统介绍，从而初步了解如何通过深度学习的方法得到人体姿态的各个要素，包括肢体部件的相对朝向和比例尺度、骨骼关节点的位置坐标和连接关系，甚至更为复杂的人体蒙皮模型信息。最后,对当前研究面临的挑战以及未来的热点动向进行概述，清晰地呈现出该领域的发展脉络。     

雷达目标极化散射特征提取的研究进展

极化雷达可以直接测量出雷达目标的2×2散射矩阵信息，与传统雷达相比，极化雷达的突出优点在于测量数据包含的信息量远大于传统雷达，因而在很多领域都获得了重要应用.本文将对目标极化散射特征提取的发展概况进行综述，包括基于矩阵分解的目标特征参数提取以及直接提取目标极化散射特征的方法等，并对其中存在的问题进行评论，对未来的发展进行展望.     

发用类、肤用清洁类化妆品的急性皮肤和眼刺激损害特点

分析发用类、肤用清洁类化妆品的急性皮肤刺激和急性眼刺激损害特点,了解其卫生安全状况。于2012年采用《化妆品卫生规范》(2007年版)中的急性皮肤刺激性实验和急性眼刺激性实验对发用类、肤用清洁类共计158种化妆品样品进行测试。两类受试化妆品显示出不同程度的急性皮肤刺激性和急性眼刺激性损害效应。发用类化妆品在实验中基本无皮肤刺激性损伤;肤用清洁类化妆品在实验中有少量的皮肤刺激性损伤,但大都为轻刺激性(31.0%),只有个别(3.8%)出现了皮肤红斑水肿的中刺激性损伤。发用类、肤用清洁类化妆品在急性眼刺激性实验中检出一定比例具有微刺激性及以上刺激性的样品,但引起的眼损伤都能够在观察期限内恢复。本次调查的所有化妆品中,洁面类、洗发类化妆品普遍具有急性眼刺激性和急性皮肤刺激性损害,需加强对化妆品的监督管理,进一步提升化妆品卫生安全水平,保障化妆品使用安全。     

Upgrading of cyclohexanone to hydrocarbons by hydrodeoxygenation over nickel–molybdenum catalysts

Cyclohexanone is largely generated in the direct or indirect conversion of lignin-derived bio-oils. Hence, the upgrading of cyclohexanone, i.e. deoxygenation in the presence of hydrogen is of great interest. In this regard, two nickel-molybdenum catalysts on alumina support were investigated in the temperatures up to 400 °C and pressures up to 15 bar. High activity, selectivity, and yield were achieved by utilizing these catalysts at the studied condition. The main products of the upgrading of cyclohexanone were C₆, C₇, and C₁₂ cyclic, aromatic, and bicyclic including cyclohexane, cyclohexene, benzene, and cyclohexylbenzene. The results of the present study imply that these catalysts are beneficial in producing hydrocarbon-rich products from cyclohexanone and lignin-derived bio-oils. Based on the achievements of the present study, the nickel-molybdenum catalyst composed of 1.14 wt% nickel and 14.27 wt% molybdenum showed about 87%, 100%, and 116% conversion of cyclohexanone, total hydrocarbon selectivity, and total hydrocarbon yield, respectively. The optimum condition for obtaining such results was at 400 °C and 8 bar.     

Demand aware transmission power cost optimization based on game theory and distributed learning algorithm for wireless body area network

Wireless Networks - This paper studied the issue of communication transmission power cost optimization for the personal body base station in wireless body area network (WBAN). With the limited...