水下航行体自由表面波浪尾迹红外特征及探测

水下航行体在航行过程中,会在海面形成特性波纹尾迹,可利用这种尾迹实现红外探潜。根据势流理论和"面元"法,模拟了水下航行体在海面上产生的波浪尾迹,采用射线跟踪算法建立了表面尾迹的红外成像模型,综合考虑海面环境因素的影响,研究了多种航速和潜深下自由表面尾迹不同探测方位角的红外成像特征。结果表明:低航速下尾迹红外特征主要表现为波形较小的横波特征,高航速下尾迹表现为较为明显的纵波特征;在航行过程中,可通过控制航速和潜深来有效规避海面特性波纹的产生;探测方位位于航行体航向方向更易发现尾迹波形特征;利用自由表面尾迹波形红外特征进行探潜,主要适用于潜艇高航速航行或通气管航行状态及其他潜深不大的情况。研究结果对红外探潜及潜艇隐蔽性航行具有重要的指导意义。     

航空遥感器光学窗口光机热一体化设计

为减小光学窗口对航空光学遥感器成像质量的影响,对光学窗口的窗口玻璃厚度进行了优化设计。根据强度理论确定了窗口玻璃最小厚度。依据纵掠平壁理论计算出光学窗口外表面的平均对流换热系数;以热光学为基础,仿真了航摄时光学窗口的瞬态温度场分布;计算了光学窗口在热-力耦合作用下不同窗口玻璃厚度时的波像差(PV和RMS),最终确定了矩形光学窗口(290 mm×140 mm)的玻璃厚度为17 mm。试验结果表明:特征频率为60 lp/mm时光学系统传递函数为0.304,并获得了稳定、清晰的航摄图像。成功实现了光学窗口的光机热一体化设计,可为其他航空光学窗口设计提供参考。     

卷云有效激光雷达比反演方法研究

卷云对地球-大气系统的辐射收支平衡有着重要的影响,研究卷云的有效激光雷达比有助于了解卷云的光学特性。介绍卷云有效激光雷达比的多种反演方法,分析它们的特点和适用范围,为合理选用这些方法提供了依据。通过探测实例,对反演结果进行系统误差和随机误差分析,结果表明这些反演方法是相融的和有效的。     

基于深度学习的车联边缘网络交通事故风险预测算法研究

针对传统交通事故风险预测算法无法自动判别数据特征,且模型表达能力差等问题。该文提出一种基于深度学习的车联边缘网络交通事故风险预测算法,该算法首先针对车载自组织网络中采集的大量交通数据,采用边缘服务器中建立的卷积神经网络自主提取多维特征,经归一化、去均值等预处理后,再将得到的新变量输入卷积层、采样层进行训练,最后根据全连接层输出的判别值,得到模拟预测交通事故发生的风险性。仿真结果表明,该算法被验证能够预测交通事故发生的风险性,较传统的机器学习算法BP神经网络、逻辑回归具有更低的损失与更高的预测准确度。     

VR技术助力虚拟实验教学平台发展的策略研究

虚拟现实已成为当今时代的热点话题,并渗透很多行业、领域,无形中给人们带来了较多方便与益处。文章主要研究虚拟现实技术在货币知识教学中的应用,通过VR技术开展中国货币发展史的虚拟教学研究,也让VR技术助力于虚拟实验教学平台的发展。     

Reversible Quadruple Switching with Optical,Chiroptical, Helicity,and Macropattern in Self‐Assembled Spiropyran Gels

Enantiomeric glutamate gelators containing a spiropyran moiety are designed and found to self‐assemble into a nanohelix through gelation. Upon alternating UV and visible light irradiation, the spiropyran experiences a reversible change between a blue zwitterionic merocyanine state and a colorless closed ring state spiropyran in supramolecular gels. This photochromic switch causes a series of subsequent changes in the optical, chiroptical, morphological properties from supramolecular to macroscopic levels. While the solution of the gelator molecules does not show any circular dichroism (CD) signal in the region of 250–700 nm due to the fact that the chromophore is far from the chiral center, the gel shows chiroptical signals such as CD and circularly polarized luminescence (CPL) because of the chirality transfer by the self‐assembly. These signals are reversible upon alternating UV/vis irradiation. Therefore, a quadruple optical and chiroptical switch is developed successfully. During such process, the self‐assembled nanostructures from the enantiomeric supramolecular gels also undergo a reversible change between helices and fibers under the alternating UV and visible light trigger. Furthermore, a rewritable material fabricated from their xerogels on a glass is developed. Such rewritable material can be efficiently printed over 30 cycles without significant loss in contrast and resolution using UV and visible light.     

General Synthesis of Dual Carbon‐Confined Metal Sulfides Quantum Dots Toward High‐Performance Anodes for Sodium‐Ion Batteries

Sponge‐like composites assembled by cobalt sulfides quantum dots (Co₉S₈ QD), mesoporous hollow carbon polyhedral (HCP) matrix, and a reduced graphene oxide (rGO) wrapping sheets are synthesized by a simultaneous thermal reduction, carbonization, and sulfidation of zeolitic imidazolate frameworks@GO precursors. Specifically, Co₉S₈ QD with size less than 4 nm are homogenously embedded within HCP matrix, which is encapsulated in macroporous rGO, thereby leading to the double carbon‐confined hierarchical composites with strong coupling effect. Experimental data combined with density functional theory calculations reveal that the presence of coupled rGO not only prevents the aggregation and excessive growth of particles, but also expands the lattice parameters of Co₉S₈ crystals, enhancing the reactivity for sodium storage. Benefiting from the hierarchical porosity, conductive network, structural integrity, and a synergistic effect of the components, the sponge‐like composites used as binder‐free anodes manifest outstanding sodium‐storage performance in terms of excellent stable capacity (628 mAh g^?1 after 500 cycles at 300 mA g^?1) and exceptional rate capability (529, 448, and 330 mAh g^?1 at 1600, 3200, and 6400 mA g^?1). More importantly, the synthetic method is very versatile and can be easily extended to fabricate other transition‐metal‐sulfides‐based sponge‐like composites with excellent electrochemical performances.     

An EME blind source separation algorithm based on generalized exponential function

This letter investigates an improved blind source separation algorithm based on Maximum Entropy （ME） criteria. The original ME algorithm chooses the fixed exponential or sigmoid ftmction as the nonlinear mapping function which can not match the original signal very well. A parameter estimation method is employed in this letter to approach the probability of density function of any signal with parameter-steered generalized exponential function. An improved learning rule and a natural gradient update formula of unmixing matrix are also presented. The algorithm of this letter can separate the mixture of super-Gaussian signals and also the mixture of sub-Gaussian signals. The simulation experiment demonstrates the efficiency of the algorithm.     

一个基于PE分层技术的电子政务网络平台

电子政务网络建设的主要目标就是建立一个开放的、基于标准的统一网络平台，并在该平台上实现政府不同部门之间的信息交换和资源共享，同时保证各部门信息的独立和安全。通过介绍电子政务网络建设中的主流技术——MPLSVPN，提出了一种基于该技术原理的PE分层技术，详细讨论了基于该分层技术的电子政务网络平台的实现过程和主要技术，并对其性能参数进行了测试与分析。     

激光衍射法测量表面张力和表面压

实验上实现了低频液体表面波的激光衍射,提出了激光衍射法测量液体表面张力和表面压。当激光斜入射到几百赫兹液体表面波上,观察到反射光形成稳定的、清晰的衍射光斑。理论上导出了衍射光斑的角宽度和表面波波长的解析关系,实验上验证了液体表面波的色散关系,计算了蒸馏水的表面张力和蒸馏水中加入不溶性表面活性剂———“苯”单分子膜的表面压。根据其机理,建立起一种实时、非接触测量液体表面张力和表面压的实用方法。