非相似元四倍频程相控阵天线

对数周期天线是一种宽带天线 ,单个天线单元的带宽可以很宽 ,但其宽带特性在组阵时将受到一定的影响 ,在相控阵中更受到扫描角的限制 ,文中采用非相似元的方法有效地解决了四倍频程相控阵天线扫描时宽带和宽角的矛盾 ,扩展了对数周期天线在相控阵中的应用     

求解非负矩阵分解的有效集BB梯度算法

非负矩阵分解是在非负限制下的一种将一个高维矩阵分解为两个低维矩阵的分解技术。目前,存在的算法大部分是基于乘性迭代算法和交替最小二乘算法。针对交替最小二乘算法的子问题,文中提出了一种有效集BB梯度法,且该算法是全局收敛的。实验结果显示,该算法比投影梯度算法更为有效。     

Nano‐Domain Pinning in Ferroelastic‐Ferroelectrics by Extended Structural Defects

Most ferroelectrics are also ferroelastics (hysteretic stress‐strain relationship and response to mechanical stresses). The interactions between ferroelastic twin walls and ferroelectric domain walls are complex and only partly understood, hindering the technological potential of these materials. Here we study via atomic force microscopy the pinning of 180‐degree ferroelectric domain walls in lead zirconate titanate (PZT). Our observations satisfy all three categories of ferroelectric‐ferroelastic domain interaction proposed by Bornarel, Lajzerowicz, and Legrand.     

Estimation and cancellation of transponder distortions in satellite forward links using memory polynomials

In this paper, a practical non‐linear equalizer with iterative distortion cancellation in a satellite receiver is studied. Assuming no prior satellite channel knowledge, distortion estimation and cancellation are performed at the receiver by means of a memory polynomial model used for channel estimation. A data packet transmission scenario over a single‐carrier satellite transponder is simulated, using the not‐linearized amplifier and onboard filter characteristics similar to the direct‐to‐home broadcast DVB‐S2X reference scenario. Varying the memory depth and the non‐linear order of the memory polynomial model trained in the receiver, we compared the packet‐error rate performance of the practical non‐linear equalizer to the standard fractionally spaced linear adaptive equalizer, as well as to an implementation of the non‐linear equalizer with ideal channel knowledge at the receiver. The improved receiver demonstrates superior performance as compared with the standard linear equalizer with up to 5.48‐dB energy efficiency gain for 64‐amplitude and phase‐shift keying for a practical memory polynomial set‐up, and it approaches consistently the packet‐error rate performance of the implementation with ideal channel knowledge when increasing the memory depth and the non‐linear order. Furthermore, it enables the use of high‐order modulation up to 256‐amplitude and phase‐shift keying in the studied scenario, improving significantly the spectral efficiency of the air interface.     

采用外调制方式产生5 Gbit/s的非归零码光脉冲

采用外调制方式得到了重复频率为５ＧＨｚ的非归零码光脉冲。采用二次谐波强度自相关法测量了光脉冲。对实验中的关键技术进行了理论和实验研究。     

长轴斜齿轮的加工

以无差动滚切法为基础 ,提出了利用花键轴铣床加工长轴斜齿轮的方法 ,为花键轴铣床扩展了加工功能。     

应力反射波法检测锚杆锚固质量的实验研究

通过应力反射波法实验分析得出 ,有效锚固长度、基频、频率比、单位动刚度 4个参数可用于衡量锚杆锚固质量的优劣和粗评锚杆锚固力的大小 ,从而证明了用应力反射波法检测锚杆的锚固质量是一种非常实用、有效的无损检测方法 .     

无底柱分段崩落法结构参数优化主要途径

分析了国内外矿山无底柱分段崩落法结构参数演变过程指出,继续增大分段高度由于诸多因素的限制,克国并不适宜推广应用,而增大进路间距却是减少采准工程量、降低采矿成本、增大一次崩矿量、提高采矿强度和劳动生产率的主要途径。     

1 000 MW超超临界锅炉分离器制造难点解析

介绍了超超临界锅炉中分离器的主要特点及制造难点,对非向心孔的加工,非向心管接头坡口的加及其装焊等问题,分别进行了论述。