天线在通信系统中起着关键作用,但单一频段的天线已经无法满足如今的需求,因此多频天线的研究非常必要。文章提出了一种基于共面波导馈电的多频微带天线。该微带天线将刻蚀在基板导电表面的环形缝隙作为初始结构,之后在基板的不同位置加载电偶极子、超材料互补开口谐振环(CSRR)、交指电容加载环型谐振器(IDCLLR)及U形槽,从而实现微带天线的多频谐振。研究结果表明,天线能够同时在无线局域网(WLAN)波段(2.42~2.51 GHz)、全球微波互联网(WIMAX)波段(3.63~3.74、5.45~5.66 GHz)
K-means聚类算法全局搜索能力较低并且选择初始质心的具有盲目性,果蝇算法具有优越的全局搜素能力但寻优方向不稳定,因此对果蝇算法(FOA)进行改进并以此优化K-means。在模型基础上利用密度标准差选择初始果蝇个体,并且构建寻优目标精度高的适应度函数进性寻优,设计一种准确率高且鲁棒能力强的IFOA-K-means算法。利用4种测试函数对IFOA性能进行对比,同种测试函数下IFOA算法的迭代次数少且搜索效率高。利用UCI标准数据集对IFOA-K-means算法进行对比分析,实验结果表明改进后的算法寻优误差
The iron and steel industry in China has experienced vast changes over the past thirty years.To have a precise knowledge of the circumstances behind its evoluti
Inclusions in wrought superalloys significantly affect the stability of the alloy properties and limit their use and devel-opment in aeroengines and other appli
为实现点式感烟型火灾探测器性能的准确检测,根据火灾探测器检测标准GB4715-2005的有关规范要求,研制了一种火灾探测器标定控制系统。该系统以工控机为控制中心,采用主从模式,温控仪实现升温控制,风机变频器实现风速控制,气溶胶发生器产生烟雾浓度,光学烟密度计测量烟浓度,整个系统通过RS-485总线和Modbus-RTU协议,基于LabVIEW的VISA函数编程实现了对火灾特征参数的数据采集、参数控制以及数据处理等功能。实验结果验证了各参数指标温度0℃~100℃,湿度0%RH~100%RH,风速0~5 m/
针对风力发电的风速时间序列非平稳特性和预测精度不高的问题,提出了一种基于改进集合经验模态分解(modified ensemble empirical mode decomposition,MEEMD)-局部均值分解(l
Microstructural change,stress rupture property,deformation and fracture mechanisms of Nimonic 105 superalloy at 750℃have been studied.Experimental results show
Laboratory-scale experiments were conducted to investigate the oxygen content of Si-deoxidized H13 die steel by ferrous oxide-containing slags at 1873 K.The calculation of thermodynamics and kinetics was performed to evaluate the oxygen level of molten st
The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the
A mathematical model based on the computational fluid dynamics method,heat and mass transfer in porous media and the unreacted shrinking core model for the oxid