基于多层子带匹配滤波的抗间歇采样转发干扰目标检测算法

间歇采样转发干扰(ISRJ)是一种基于欠采样原理的新型雷达干扰技术,此类干扰信号能够在雷达1维距离像(HRRP)上形成密集假目标,给目标检测带来一定挑战。针对雷达在间歇采样转发干扰背景下无法准确检测到目标的问题,一种基于多层子带匹配滤波的抗间歇采样转发干扰目标检测算法被提出。该方法首先以传统雷达匹配滤波函数为基础设计子带匹配滤波函数;随后,针对间歇采样转发干扰信号和目标回波信号的时间差异,构建子带匹配滤波信号模型,逐步分析并揭示了间歇采样转发干扰信号对子带匹配滤波函数时宽的敏感性;最后,基于此设计出基于多层子带匹配滤波的抗间歇采样转发干扰目标检测方法,并进行了仿真实验验证。实验结果表明：多层子带匹配滤波方法无需事先获得干扰的先验信息,可使雷达在受到间歇采样转发干扰且信干比大于–20 dB时,目标检测概率大于80%。     

Colloidal gel from amphiphilic heteroarm polyelectrolyte stars in aqueous media

We report on the gelation capability of polystyrene/poly(2-vinyl pyridine) amphiphilic heteroarm polyelectrolyte stars in acidic salt-free aqueous media. The star polymers associate through hydrophobic interactions, by retraction of the stretched arms under no interdigitation conditions, in the dilute regime forming colloidal soft nanoparticles comprising about 6 stars, At concentrations significantly higher than the hydrodynamic overlap concentration (c > 40c^∗), the crowding of the colloidal nanoparticles drives a jamming transition, leading to a colloidal gel. The intermediate overlap regime (c^∗ < c < 40c^∗) is characterized by a significant compaction of the polyelectrolyte entities prior interdigitation and jamming.     

TBM掘进机脱困的围岩加固技术

达坂隧洞线路全长31.92km,沿线穿越多处膨胀岩、泥质粉砂岩等不良地质洞段,施工中多次发生卡机事故并成功脱困,对其回填灌浆、固结灌浆和帷幕灌浆技术进行了系统总结,对于同类工程施工具有较强的借鉴意义。     

复杂形态管道中粗颗粒水力输送的临界条件研究

通过自行设计的管道试验系统,研究在不同流速、粒径和体积浓度条件下,粗颗粒堵管的临界条件及其安全输送的方法。试验结果表明：①颗粒的粒径和体积浓度对粗颗粒系统安全输送有重要的影响,随着粒径和体积浓度的增大,临界流速提高,且当系统的输送速度大于临界流速时方可实现系统的安全输送;②在粒径一定的条件下,随着倾角的加大,粗颗粒在弯管处发生堵管所需要的临界流速降低;③在堵管的情况下,粗颗粒高效安全输送的临界条件主要取决于体积浓度和流速。     

Models for metal hydride particle shape,packing, and heat transfer

A multiphysics modeling approach for heat conduction in metal hydride powders is presented, including particle shape distribution, size distribution, granular packing structure, and effective thermal conductivity. A statistical geometric model is presented that replicates features of particle size and shape distributions observed experimentally that result from cyclic hydride decrepitation. The quasi-static dense packing of a sample set of these particles is simulated via energy-based structural optimization methods. These particles jam (i.e., solidify) at a density (solid volume fraction) of 0.671 ± 0.009 – higher than prior experimental estimates. Effective thermal conductivity of the jammed system is simulated and found to follow the behavior predicted by granular effective medium theory. Finally, a theory is presented that links the properties of bi-porous cohesive powders to the present systems based on recent experimental observations of jammed packings of fine powder. This theory produces quantitative experimental agreement with metal hydride powders of various compositions.     

无线传感器网络中基于α-壳的射频攻击定位

传感器网络的特殊性使之易受到射频干扰攻击等各种攻击,为了下一步安全机制的实施和部署,确定攻击者的位置,利用α-壳概念及其性质提出基于α-壳的射频攻击定位算法。当1/α与最小包容圆半径相等时,节点集合的α-壳顶点可达到共圆,进而依据α-壳顶点的数目,计算最小包容圆半径。该定位算法实现了最小包容圆半径的求解和圆心位置的确定,从而实现了对射频攻击者的定位。模拟实验表明,与已有的增量算法相比较,基于α-壳的射频攻击定位算法定位误差小,且随着网络节点密度等度量值的变化,时间消耗也不会呈指数级增长,而只呈线性的略微增长。     

开关电源中的噪声及其消除方法

通过对开关电源中噪声的种类、产生的机理分析,提出了防止噪声的几种方法。     

Jamming in weakly perturbed granular media

A granular system is weakly vibrated and we observe how it reaches a static configuration when the perturbation intensity is decreased. This behavior is investigated using an immersed torsion oscillator whose angular deflections are analyzed to give information on the granular agitation. The oscillator can thus be seen as a low-frequency “thermometer” sensing the granular noise. The observed diffusive noise appears to approach the final static (or jammed) state according to the same expressions that describe the temperature dependence of viscosity or diffusivity in supercooled liquids, thus showing strong analogies with the vitrification process. We then discuss a simple model that relates the microscopic dynamics to the macroscopic rearrangements and accounts for that dependence.     

基于数字射频存储的雷达干扰环境仿真

在雷达抗干扰优化设计的研究中,针对雷达面临的干扰环境复杂、抗干扰作战训练难度大,以及当前雷达干扰环境仿真形式单一、干扰信号样式不完备等问题,设计了采用数字射频存储的雷达干扰环境仿真系统.在建立干扰环境系统结构的基础上,针对雷达干扰环境建模和系统模块化设计两个关键问题,采用数学建模方法构建了目标回波模型、欺骗干扰模型、无源杂波模型以及遮盖性干扰模型,采用数字射频存储技术,进行了系统的模块化设计,并对干扰环境平台进行了基于计算机仿真和半实物仿真的实际测试.测试结果表明,干扰仿真环境系统能够产生符合需求的各类样式的干扰信号,有效解决了干扰信号样式单一的问题,为检验雷达在复杂干扰环境下的工作性能创造了条件,改善和提高了抗干扰作战训练的效能.     

基于 MatLab的有源压制性干扰信号模拟与实现

计算机仿真是研究雷达干扰系统效能的有效方法。有源压制性干扰是雷达干扰系统中常用的一种信号,通过分析压制性干扰的原理,在 MatLab平台建立模拟和产生干扰信号的仿真模型,得到宽带阻塞式干扰、窄带瞄准干扰和扫频干扰三种典型压制性干扰信号的仿真结果,验证三种干扰信号对雷达系统的干扰效能。所搭建的仿真模型可作为雷达对抗系统效能评估的干扰信号源。