Block‐wise Alamouti schemes for OQAM‐OFDM systems with complex orthogonality

Offset quadrature amplitude modulation‐based orthogonal frequency division multiplexing (OFDM) systems cannot be directly combined with the Alamouti code because of the intrinsic imaginary interference. In this paper, we propose a block‐wise space‐frequency block coding (SFBC) scheme and a block‐wise space‐time block coding (STBC) scheme for offset quadrature amplitude modulation‐based OFDM systems, which achieve bit error rate performances that are close to OFDM systems. The proposed schemes satisfy the orthogonality condition of the Alamouti code in the complex field with guard band/intervals. To improve the spectral efficiency of the block‐wise SFBC scheme, we also consider the case without the guard band. It is observed that only the two innermost subcarriers do not satisfy the complex orthogonality condition when the guard band is removed. Then, a simple equalization scheme is proposed to independently equalize the two innermost subcarriers. Simulation results show that the block‐wise SFBC scheme works well under channels with mild‐to‐moderate frequency selectivity, and the block‐wise (STBC ) scheme suffers less than 1 dB loss under severe frequency selective channels at the bit error rate of 10 ^− 3, when only a simple one tap zero‐forcing equalizer is employed. Copyright © 2016 John Wiley & Sons, Ltd.     

游程长度受限码RLL(4,18)的研究

介绍了一种新的用于高密度光盘存储的游程长度受限码。给出RLL(4,18)码的构造方法和编解码步骤。对RLL(4,18)码的编码器和解码器进行了CPLD实现。对不同游程长度受限码的主要性能参数进行了比较。     

对多种Web语言嵌套的跨站过滤分析

由于网站服务的应用广泛性,跨站攻击已经上升为互联网中数量最多的攻击手段,对跨站代码的过滤已经成为各个网站的重中之重。网站要对跨站进行过滤就要充分了解跨站产生的机理,并且要理解数据代码在Web应用程序中的解析过程。这两点只是基本的要素,要想尽可能完全地过滤跨站代码,就要进一步针对各种语言解析模块之间的关系,研究和分析在各种模块互相嵌套下跨站的复杂性才行,这样根据各种情况才能得到降低跨站威胁的有效措施。     

Recoding the Genetic Code with Selenocysteine

Selenocysteine (Sec) is naturally incorporated into proteins by recoding the stop codon UGA. Sec is not hardwired to UGA, as the Sec insertion machinery was found to be able to site‐specifically incorporate Sec directed by 58 of the 64 codons. For 15 sense codons, complete conversion of the codon meaning from canonical amino acid (AA) to Sec was observed along with a tenfold increase in selenoprotein yield compared to Sec insertion at the three stop codons. This high‐fidelity sense‐codon recoding mechanism was demonstrated for Escherichia coli formate dehydrogenase and recombinant human thioredoxin reductase and confirmed by independent biochemical and biophysical methods. Although Sec insertion at UGA is known to compete against protein termination, it is surprising that the Sec machinery has the ability to outcompete abundant aminoacyl‐tRNAs in decoding sense codons. The findings have implications for the process of translation and the information storage capacity of the biological cell.     

苯环型化合物定量二维手性程度的研究

基于权原子和, 提出了镶嵌在二维空间的苯环型化合物的手性程度, 其中权原子和为与原子间的距离有关的原子不对称环境描述. 在描述化合物的手性时, 并没有采用简单的标记-手性或非手性, 而是采用定量的方式来表征化合物的手性程度. 定量手性程度能够区分对映体, 并且一对对映体的手性程度为相反数. 手性程度不仅仅可以采用单值,还可以采用多维向量来表示. 此外, 还将手性程度推广到三维正烷烃的旋转构象异构体描述, 即首先将正烷烃的旋转异构体转化为苯环型化合物, 然后采用手性程度描述其三维构象.     

VDSL数字用户环路的调制方法分析

首先介绍了超高速数字用户环路（VDSL）的基本构造和线路编码，然后分析了VDSL的主要两种调制方法，即时分复用（TDD）方式和频分复用（FDD）方式。     

D6122电路指令码实现剖析

本文以对红外遥控发射集成电路D6 1 2 2工作原理的介绍为基础 ,探讨了电路D6 1 2 2指令码的实现 ,着重剖析了键盘矩阵 ,用户码和功能码的实现。