基于HLS的红外遥感图像连通域快速提取方法

连通域提取是红外遥感图像目标检测算法中的重要组成部分,包含在粗检算法中,能够筛去多数虚警,提升粗检效果,减少检测算法的运算量,降低系统功耗.现有的一些连通域提取算法基于CPU处理方式设计,不适合部署在现场可编程逻辑门阵列(FPGA)硬件端.本文采用高层次综合(HLS)的开发模式,设计了适合FPGA加速的连通域提取方法,...     

5G微基站环境下GNSS接收机性能及观测质量分析

我国已全面进入5G时代,为研究5G微基站电磁环境对全球卫星导航系统(GNSS)接收机工作性能及观测数据质量的影响,基于自主建设差分基准站的零基线观测数据,采用静态相对定位方法,通过观测数据质量分析、载波与伪距的双差残差序列、对比相对静态定位结果,综合评估5G微基站对GNSS接收机工作性能及观测数据质量的影响。实验表明：当前环境下,GNSS差分基准站及接收机处于近距离建设的5G微基站时,载波相位观测噪声变化范围为5cm,伪距观测噪声变化范围为15cm,零基线测试结果变化范围为1mm。在实验距离内,5G微基站对于GNSS接收机工作性能及数据观测质量影响较小,可以忽略。     

电帆推进在等离子体环境下推力影响因素分析和试验研究

为了分析电帆推力的影响因素，根据电帆推进原理设计了电帆地面模拟装置。首先分析了真空中带电导线和等离子作用机理，得出了电帆推力公式。利用朗缪尔探针测量了电帆模拟试验环境中等离子体参数，计算产生推力的大小，最后通过微推力测量系统测量电帆产生的推力，与计算结果进行了对比。根据推力公式和仿真结果表明，提高电压、增加带电粒子密度和速度、增加电帆长度均可增加推力。在试验中电帆上电压从300V增加到800V时，推力从9μN增加到26μN。仿真和试验结果表明，电压、带电粒子密度和速度、电帆导线长度都对推力有影响。根据试验结果，电帆推力公式的经验推力系数在1～2取值。     

Modelling of grinding mechanics: A review

Grinding is one of the most widely used material removal methods at the end of many process chains. Grinding force is related to almost all grinding parameters, which has a great influence on material removal rate, dimensional and shape accuracy, surface and subsurface integrity, thermodynamics, dynamics, wheel durability, and machining system deformation. Considering that grinding force is related to almost all grinding parameters, grinding force can be used to detect grinding wheel wear, energy calculation, chatter suppression, force control and grinding process simulation. Accurate prediction of grinding forces is important for optimizing grinding parameters and the structure of grinding machines and fixtures. Although there are substantial research papers on grinding mechanics, a comprehensive review on the modeling of grinding mechanics is still absent from the literature. To fill this gap, this work reviews and introduces theoretical methods and applications of mechanics in grinding from the aspects of modeling principles, limitations and possible future trendencies.     

节流水平对气液针栓喷注单元雾化特性的影响

为了分析气液针栓喷注单元雾化特性和雾化机制，采用背光成像技术和相位多普勒（PDA）系统进行试验研究，获得了雾化模式、体积流量分布、索泰尔平均直径（SMD）分布和速度场随节流水平的变化规律。结果表明：气液针栓喷注单元雾场形态为扇形雾场，雾化模式为剪切破碎。体积流量沿径向呈单峰形分布，随着节流水平降低，雾场外缘向中心收缩。SMD沿径向呈现递增规律，雾化最好的区域分布在雾场中心和两侧。SMD随节流水平增加而增大。当动量比不变时，节流水平对SMD的分布范围影响很小。针栓头部下方的中心回流区轴向尺寸随着节流水平降低而减小。     

Metal flow hysteresis behavior and shape control strategy during porthole die extrusion of micro heat pipe

The shape control strategy of micro grooves is still unclear and challenging during the porthole die extrusion of grooved micro heat pipe (MHP). Through the simulation and experiment of porthole die extrusion of a MHP profile, the metal flow hysteresis behavior within micro features and the effect of ram speed and extrusion temperature on it and the resulting forming integrity was elucidated. Innovatively, Taguchi design and variance analysis (ANOVA) were introduced to determine their influence magnitude on the metal flow uniformity calculated by simulation results. The main findings are given below. The metal flow hysteresis derives from part feature size effect. The negligible friction-affected area during conventional extrusion severely slows down the metal flow within micro features during the MHP profile extrusion, which is due to the surge in the area ratio of the friction-affected area to the region in which it is located. Neither ram speed nor extrusion temperature can change the distribution of the friction-affected area. However, increasing ram speed multiplies the metal flow hysteresis and severely reduces the forming integrity, whereas extrusion temperature has little effect. Following this strategy, batch extrusion of the profile with micro-grooved width of 0.27 ± 0.02 mm was achieved in industrialized conditions.     

基于可穿戴惯性测量的滑雪运动员姿态测量与水平评估方法

运动量化分析是科学化滑雪训练的重要发展方向,而滑雪过程中人体运动模式的数字化表达是科学量化分析的基础和依据.设计并搭建了基于可穿戴MEMS惯性测量单元的人体运动捕捉与姿态重构系统,结合人体多刚体运动模型实现了滑雪过程的人体重构,并应用于高山滑雪运动中回转动作的辅助训练.同时,针对基于多自由度模拟滑雪训练平台的室内训练场景,提出了一种适用于滑雪回转运动的数字化评估方法.该方法利用动作捕捉系统和姿态重构系统提取滑行者五种滑行特征数据,并通过与高水平运动员运动参数的相似性度量和线性拟合实现对滑雪运动员技术参数的评估,以辅助科学训练.最后在室内Olymp模拟滑雪训练台上进行实验,验证了该方法的有效性.     

Passive attitude stabilization of ionic-wind-powered micro air vehicles

The ionic-wind-powered Micro Air Vehicles (MAVs) can achieve a higher thrust-to-weight ratio than other MAVs. However, this kind of MAV has not yet achieved controlled flight because of the unstable thrust produced by the ionic wind and the dynamic instability related to the small size. In this paper, a passive attitude stabilization method of the ionic-wind-powered MAV using air dampers is introduced. The key factors that influence the performance of the air dampers, including the layout, position, and area of the air dampers, are theoretically studied. The appropriate optimal position of the air dampers is also obtained by Monte Carlo stochastic simulations. Then the proposed passive attitude stabilization method is applied to the ionic-wind-powered MAVs of different wingspan (2 cm and 6.3 cm). Finally, the experimental results show that using the proposed method, attitude stabilization is achieved for the first time for the ionic-wind-powered MAV. Moreover, the altitude control of an ionic-wind-powered MAV with a wingspan of 6.3 cm is also demonstrated.     

小波与BP神经网络联合反演GNSS IR高精度水库水位变化

GNSS-IR技术作为一种近地表遥感的新兴手段，在水库水位监测方面凭借其成本低、精度高等优势成为了研究热点。为了提高GNSS-IR技术反演水库水位变化的精度，提出了利用GPS、BDS双系统观测量基于小波分解与BP神经网络联合的方法反演水库水位变化。选取位于南水北调山东境内双王城水库GNSS变形观测站2017年10月1日—12月26日共87天的信噪比(SNR）数据为研究对象，分别利用小波分解和二阶多项式拟合两种方法消除其趋势项并生成SNR残差序列，然后进行Lomb-Scargle谱分析得到水库水位高度变化值，并与实测水位结果相比较。结果表明：各频段SNR利用小波分解和二阶多项式反演水位变化的平均均方根误差分别为0.1062m和 0.2245m，说明小波分解去趋势项的方法更优。最后，在小波分解去趋势项的基础上，利用阈值筛选出融合所用的频段(S1C、S2L、S5Q和S7I），分别采用均值算法、中值算法、随机森林算法和BP神经网络算法对GPS、BDS多频多模信号进行水库水位的融合反演。结果表明，对于水面较为平静的环境，以上算法均能实现厘米级的反演精度，其中BP神经网络算法用于水位反演的效果更优。     

MEMS技术中的电镀工艺及其应用

电镀已经成为MEMS(Micro-Electro-Mechanical System)技术中的一种重要加工手段,相比于传统意义的表面处理作用,MEMS技术中的电镀主要用于制作微结构。介绍了几种常用的以电镀为核心方法的微结构加工工艺和它们的应用领域。微结构加工工艺包括LIGA/UV-LIGA、EFAB、PolyStrata、TSV/TGV、Metal MUMPs等,结合设计好的光刻、镀膜、刻蚀等辅助微工艺技术,能够完成具有超高深宽比、多层堆叠、悬空、可动等特点的复杂三维金属微结构,并针对不同的使用需求,可以实现典型的微机械结构、惯性传感器、射频器件、异构集成、系统散热等功能应用,具有广泛的实用意义。