基于曲线拟合的毫米波雷达安装角度校准方法

毫米波雷达的安装角度校准是雷达正常使用并与摄像头进行数据融合的重要前提,雷达安装角度偏 转过大会导致雷达数据与摄像头数据融合失败,影响高级驾驶辅助系统(Advanced Driving Assistance System,ADAS) 的正常使用。文中提出一种基于曲线拟合的毫米波雷达安装角度校准方法,当车辆在道路上行驶时辅以车辆输入 的车速和偏航角信息,通过2000 个静止点进行曲线拟合得到雷达需要补偿的角度。相较于选择有护栏的道路进行 绕行和在标定场地部署角反射器进行安装角度校准的方法,这种方法适用的场景种类更多并且校准时间从15 分钟 以上缩短为5 分钟以下。经过实验验证,在花费更短时间完成校准后,校准精度与其它自校准方法相同为±5°。     

3.705 μm紧凑型光参量振荡器

报道了一种基于工程应用的3.705 μm紧凑型高稳定性光参量振荡器。采用半导体制冷、强制气体对流冷却和热管导热技术相结合的方式,对主振荡功率放大结构的掺Yb光纤泵浦模块泵浦过程中产生的废热进行有效管理,再将经过耦合后的泵浦光注入到使用温控炉精确控温的PPMgLN晶体,在重复频率为55.56 kHz时,获得了功率不稳定度优于1.5%的1.78 W,脉冲宽度120 ns,峰值波长3.705 μm的线偏中红外激光输出,光光转换效率为12.6%。     

Adsorption of azacrown ethers at solid–liquid interface. Contact angle and neutron reflectivity study

Adsorption of two alkylated N,N′-diaza-18-crown-6 ethers (decyl- and hexadecyl-derivatives, ACE-10 and ACE-16, respectively) on solid surfaces was studied by using contact angle and neutron reflectivity measurements. The solid substrates used were (a) Si covered with a native oxide layer (Si/SiO₂) and (b) Si with sputtered Pt layer (Si/Pt). The sensitivity of neutron reflectivity was drastically improved by applying the intermediate Pt layer of 150 Å, which gave rise to several Kiessig fringes in the experimentally accessible q-range. The position of the fringes is very sensitive to slight changes of the interfacial composition induced by adsorption of a thin monolayer, otherwise very difficult to detect. Unfortunately, in the studied case this sensitivity is immediately lost due to undesired adsorption of a protonated material on the Pt surface exposed to the lab air. A decrease of surface energy (increase of contact angle) of both Si/SiO₂ and Si/Pt upon exposure to toluene solutions of ACEs suggests that the latter are attached to the surface via the hydrophilic azacrown ether head with alkyl chains standing upright towards the liquid phase.     

改进的极化SAR点散射目标扰动滤波检测方法

为完成极化合成孔径雷达(PolSAR)图像中点散射像素目标的检测,从几何扰动滤波检测点散射像素的基本原理出发,分析了经典方法存在的相干度参数阈值无法自适应获取和不同散射机制共享同一阈值两个问题,提出利用Cloude-Pottier分解结果中熵参数的分布情况计算得到阈值,利用平均阿尔法角参数完成不同散射机制的初分类,对初分类的结果排序得到的某种散射机制对应的相干度参数的比例因子,根据比例因子计算得到该类散射机制的阈值,从而完成点散射目标的检测。对机载合成孔径雷达（AIRSAR）数据集中的San Francisco Bay图像进行了实验,结果表明,改进方法在检测性能上优于经典方法。     

基于不同散射相函数的紫外光传输特性研究

为了研究三种不同散射相函数下紫外光大气传输特性,文章采用非直视紫外光通信的单次散射简化模型,对系统接收机接收到的能量及紫外光传输路径损耗随传输距离和散射角的变化情况进行分析.结果表明:三种相函数下,都表现为随传输距离的增大,接收能量减小,路径损耗增大,但三者之间存在一定的差异,对于紫外光通信系统,其传输性能的影响以前向散射为主,后向散射作用很小;随着散射角增大,后向散射作用相对明显;三种散射相函数下,紫外光通信链路的最佳散射角不同,但均随发射仰角的增大或接收仰角的增大最佳散射角增大,而接收能量减小.     

雷达罩对机载脉冲多普勒雷达的性能影响分析

雷达罩会降低机载脉冲多普勒(PD)雷达的性能。评估雷达罩对其性能影响是机载PD雷达设计过程中必不可少的环节。首先分析雷达罩对雷达天线方向图的影响,包括增益下降、波束变宽、波束偏转、副瓣抬高、产生镜像瓣和零深电平抬高等,然后分析天线性能下降对机载PD雷达的性能影响。通过仿真进一步分析了天线副瓣、镜像瓣对雷达中、低重频模式的性能影响。最后给出结论,天线罩会降低机载PD雷达的测距、测角性能。     

Preparation and Characterization of Styrene/Butyl Acrylate Emulsifier-Free Latex with 2-Acrylamido-2-Methyl Propane Sulfonic Acid as a Reactive Emulsifier

A kind of emulsifier-free latex (FL) was successfully synthesized from styrene (St) and butyl acrylate (BA) with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) as a reactive emulsifier. The particle size of latex particles, stability against electrolytes, minimum film forming temperature (MFT) and water contact angle (CA) were evaluated and compared with a conventional latex (CL). Test results show that FL has larger particle size, better stability against electrolytes and lower MFT value compared with CL; higher AMPS content leads to smaller particle size and smaller water CA.     

Alkali treatment of lignocellulosic fibers extracted from sugarcane bagasse: Composition,structure, properties

Lignocellulosic fibers extracted from sugarcane bagasse were treated with NaOH solutions of different concentration (0-40 wt%) to study the effect of alkali treatment on the composition, structure and properties of the fibers. Composition was determined by the van Soest method, structure was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while mechanical properties by tensile testing. Hemicellulose and lignin content decrease, while cellulose content goes through a maximum as a function of alkali concentration. Crystallinity changes only slightly and microfibril angle (MFA) remains constant thus structural effects and especially MFA are not the primary reasons for changing properties. The Young's modulus of the fibers shows a slight maximum at around 2-4 wt% NaOH content, while tensile strength goes through a much more pronounced one at around 5-8 wt%. Direct correlation between structure and mechanical properties was not found indicating that composition is more important in the determination of properties than structure. Regression analysis proved that the combination of several compositional variables determines mechanical properties in a non-linear manner. The improvement in fiber properties was explained with the dissolution of weak amorphous fractions and the relative increase of cellulose content.     

数字角位移传感器在航空发动机系统中的应用研究

根据某型发动机角位移传感器的工作原理,设计了一种数字角位移传感器,分析了其静态和动态特性。该传感器以角位移传感器和CMOS低频锁相环电路为核心,用于航空发动机控制系统中角位移测量。实验表明,该传感器相位移动小,干扰噪声抑制能力强,响应速度较快;测量精度可达±0.01°,可以及时有效地对角位移进行跟踪测量。     

Wide viewing optically clear adhesives using PMMA/TiO2 core-shell micro/nanoparticles

Abstract

Optically clear adhesives (OCAs) are widely used in optoelectronic displays because of their high outdoor visibility. Here, we develop new transparent adhesive films with wide-viewing-angle characteristics using poly(methyl methacrylate) (PMMA)/TiO₂ core–shell micro/nanoparticles. TiO₂ nanoparticles are embedded in the shell of PMMA microparticles, forming an organic–inorganic hybrid structure. To examine the optical transmittance of the films in the visible wavelength region, ultraviolet-visible spectroscopy is performed and light diffusion is evaluated. The TiO₂ nanoparticles in the shell of the PMMA microparticles exhibit improved light scattering, and the new functional OCAs are expected to provide wide-viewing-angle characteristics for future flexible displays.