基于深度学习的高频雷达射频干扰自动识别与抑制

高频地波雷达的探测性能极易受到射频干扰的影响,当前射频干扰抑制的研究主要是通过人工识别来逐一处理,鲜见实时自动识别与抑制射频干扰的研究。随着深度学习在雷达图像处理方面应用的展开,本文尝试将其引入高频雷达射频干扰抑制中,利用YOLO (You Only Look Once)模型来识别雷达距离多普勒谱图中的射频干扰,继而用高阶奇异值分解(Higher Order Singular Value Decomposition, HOSVD)方法对其进行抑制。仿真和实测数据处理结果表明,此YOLO-HOSVD联合算法实现了对高频雷达射频干扰的自动识别与抑制,单场数据处理时间不超过1.8 s。该方法可以应用于高频地波雷达常规海态观测。     

复合材料RFI成形用树脂膜的成膜工艺性研究

针对先进复合材料树脂膜渗透成形技术(RFI)中的树脂膜,分析了其成形的基本过程,在测定树脂体系的基本粘度-温度关系基础上,采用树脂膜/离型纸的拉伸剪切实验方法测定了树脂膜的拉伸剪切强度,研究了树脂膜在不同温度及速度下的剪切载荷-位移关系及内聚破坏及界面破坏的转变温度范围.结果显示,破坏形式的转化是决定剪切强度-温度依赖性的关键.确定了实验树脂体系的成膜工艺区间的下限.     

T300/QY9512复合材料的耐湿热性能

介绍了QY9512双马树脂的特性及其在RFI复合材料成型工艺中的应用，测定了树脂的流变曲线，对T300／QY9512复合材料的耐湿热性能从Tg和力学性能两个方面进行了研究。试验结果证明T300／QY9512复合材料在150℃、干态和湿态下，力学性能保持率较高，耐湿热性能好。     

GPS射频干扰浅析

论述信号噪声比和信号噪声密度比的概念，分析了射频干扰(RFI)对GPS接收的影响，最后说明了直接检测RFI的方法以及RFI源的定位。     

RFI用改性双马树脂膜的黏度特性

采用热塑性树脂改性双马来酰亚胺树脂,获得了适用于RFI成型的改性双马来酰亚胺树脂膜。采用DSC方法和黏度测试研究了该树脂的固化特性和黏度特性,并根据黏度特性建立了Arrhenius模型。结果表明,改性双马来酰亚胺树脂膜的黏度特性能够满足RFI工艺的要求,建立的Arrhenius模型能够较好地预测黏度特性,可为RFI工艺参数的制定提供理论指导。     

Correlation between electrical conductivity and manufacturing processes of nanofilled carbon fiber reinforced composites

This paper describes the difference on the electrical performance of carbon fiber reinforced composites (CFRCs) when two different Resin Film Infusion (RFI) manufacturing techniques are used. For the panel obtained by bulk infusion the measured in plane and out of plane electrical conductivities were 2.0 × 10⁴ S/m and 3.9 S/m respectively and for the panel prepared using the traditional resin film infusion the values were 1.1 × 10⁴ S/m and 1.7 S/m respectively. Morphological investigations on the sections of etched panels have highlighted that this difference in the electrical conductivity was strictly related to the different distribution of multiwall carbon nanotubes (MWCNTs) between the carbon fibers (CFs) of the plies.     

压缩感知合成孔径雷达射频干扰抑制方法

压缩感知合成孔径雷达成像技术能够利用少量采样数据恢复目标图像,大大减少数据存储系统的负担,但受到射频干扰时成像品质会严重下降;在目标场景稀疏条件下,分别构建目标回波信号原子库和射频干扰原子库,设计了压缩域合成孔径雷达成像射频干扰抑制算法,并对该算法进行理论分析,最终通过仿真实验验证了算法的有效性;仿真结果表明：该算法在较大干信比条件下,能有效抑制合成孔径雷达射频干扰,达到较好的成像效果。     

Responses of dairy cows with divergent residual feed intake as calves to metabolic challenges during midlactation and the nonlactating period

Residual feed intake (RFI) is defined as the difference between the actual and expected feed intake required to support animal maintenance and growth. Thus, a cow with a low RFI can obtain nutrients for maintenance and growth from a reduced amount of feed compared with a cow with a high RFI. Variation in RFI is underpinned by a combination of factors, including genetics, metabolism, thermoregulation and body composition; hypothalamic-pituitary-adrenal (HPA) axis responsiveness is also a possible contributor. Responses to 3 metabolic challenges were measured in lactating and nonlactating dairy cattle. Sixteen Holstein Friesian cows with phenotypic RFI measurements that were obtained during the growth period (188–220 d old) were grouped as either low-calfhood RFI (n = 8) or high-calfhood RFI (n = 8). An ACTH (2 µg/kg of body weight), insulin (0.12 U/kg), and epinephrine (a low dose of 0.1 µg/kg and a high dose of 1.6 µg/kg of epinephrine) challenge were each conducted during both midlactation (122 ± 23.4 d in milk) and the nonlactating period (dry period; approximately 38 d after cessation of milking). Cows were housed in metabolism stalls for the challenges and were fed a diet of alfalfa cubes ad libitum for at least 10 d before the experiment (lactating cows also were offered a total of 6 kg of dry matter/d of crushed wheat grain plus minerals fed as 3 kg of dry matter at each milking) and were fasted for 12 h before the challenges. The efficiency of conversion of feed into milk (the ratio of feed consumed to milk produced over the 7 d before the experiment) during midlactation was better (lower) in low-calfhood RFI cows, although dry matter intake did not differ between RFI groups. Low-calfhood RFI cows exhibited a lower plasma cortisol response to the ACTH challenge than high-calfhood RFI cows, particularly in midlactation (?15%). The low-calfhood RFI cows had a greater plasma insulin-like growth factor-1 response to the insulin challenge and plasma fatty acid response to epinephrine compared with the high-calfhood RFI cows. These data suggest that high-calfhood RFI cows exhibit a more responsive HPA axis. As divergence in RFI measured during growth is retained (although reduced) during lactation, it is possible that energy is used to respond to HPA axis activation at the expense of production in high-calfhood RFI dairy cattle during lactation and contributes to a decrease in overall feed use efficiency.     

RFI工艺成型碳NCF/环氧5228A复合材料研究

借助流变仪和差示扫描量热仪分析5228A环氧树脂膜的性能,以此为参考制定树脂膜渗透成型工艺(RFI)的固化制度;制备并测试增强材料为T700-12k碳纤维无屈曲织物(NCF)、铺层方式为[(0,90)/(±45)]s的层合板力学性能,其层间剪切强度比相应的无纬布层合板高25.3%;在层合板研究的基础上成功研制了规格为1000×200×37mm的帽形梁;利用超声波无损检测和金相显微检查等手段检测帽形梁的质量,检测结果显示,帽形梁材质致密、内部无明显缺陷,将应用于某型号卫星主承力结构。研究表明,5228A环氧树脂膜具有良好的工艺性,RFI工艺能够应用于复合材料复杂结构件的制造。     

基于分组动态帧时隙ALOHA防碰撞算法研究

为解决射频识别系统中多标签防碰撞问题,在现有ALOHA算法的基础上提出了一种改进的分组动态帧时隙ALOHA算法。当大量标签同时进入阅读器识别范围内时,算法通过设置一个阈值把要响应的标签分成两组,符合条件的一组去响应阅读器,不符合条件的暂时不响应,该算法通过分组限制响应标签数量达到较高的识别效率。仿真结果表明,该算法在标签数大于256甚至更多时识别效率也能维持在相对较高的数值。