para-Selective Arylation of Arenes: A Direct Route to Biaryls by Norbornene Relay Palladation

Biaryl compounds are extremely important structural motifs in natural products, biologically active components and pharmaceuticals. Selective synthesis of biaryls by distinguishing the subtle reactivity difference of distal arene C−H bonds are significantly challenging. Herein, we describe para-selective C−H arylation, which is acheived by a unique combination of a meta-directing group and norbornene as a transient mediator. Upon direct meta-C−H palladation, one-bond relay palladation occurs in presence of norbornene and subsequently para-C−H arylation is achieved for sulfonates, phosphonates and phenols bearing 2,6-disubstitution patterns. The protocol is amenable to electron-deficient aryl iodides. Multisubstituted arenes and phenols are obtained by postsynthetic modification of the products. The protocol allows the synthesis of hexa-substituted benzene by sequential selective distal C−H functionalization.     

基于合作中继的OFDM蜂窝网络的QoS感知资源调度算法

针对基于中继的OFDM蜂窝网络,该文考虑具有不同QoS要求的混合业务场景,引入合作传输机制,提出了一种基于合作中继的QoS感知资源调度算法,解决了合作中继节点选取,子载波分配以及功率控制等问题。以最大化系统效用为目标,在考虑QoS业务的速率要求与基站功率约束的同时,针对中继结构引入了中继节点的功率约束。为降低计算复杂度,将原非线性组合优化问题分解为子载波分配与功率控制两个子问题。仿真结果表明,该文所提算法在能量节约、系统效用,吞吐量等性能方面都有显著优势。     

Error rate performance analysis of dual-hop relaying transmissions over generalized-K fading channels

In this paper we present analytical expressions for the lower bounds of the error performance of dual-hop amplify-and-forward transmissions over independent and not necessarily identical Generalized-K fading channels. Using a tight upper bound for the end-to-end SNR, a novel expression for the probability density function is derived. Based on the abovementioned formula, tight lower bounds for the average bit error probability for a variety of modulation schemes are derived. In order to validate the accuracy of the proposed mathematical analysis, various numerical and computer simulation results are presented.     

Improving amplify-and-forward relay selection algorithm based on partial relay link

This article addresses the design problem of selecting an appropriate relay in amplify-and-forward(AF) cooperative diversity systems.In this regard,this article focuses on relay selection based on partial channel knowledge only across the source and relay links.In particular,the two fundamental questions will be answered,that is,whether to cooperate and whom to cooperate with.Through answering these two questions,an improved relay selection strategy based on partial relay link,which emphasizes that cooperat...     

基于电力线载波通信的城市灯饰控制系统

介绍了城市灯饰控制系统的组成、工作原理和关键技术。基于无线接力和电力栽波通信技术的城市灯饰控制系统,通过对监控中心监控软件系统的操作,可实现城市灯饰的智能管理控制。电力线载波通信模块设计中采用意法半导体（ST）设计生产的新型电力线收发芯片ST7540,较好地解决了低压电力线载波传输中的干扰问题,稳定的试验数据和成功的小范围适用,表明本系统具有良好的应用前景。     

变压器新差动保护技术研究

变压器保护主要有瓦斯保护和纵联差动保护,纵差动是变压器必须采用的保护原理。可以反映变压器的各种内部相间和接地故障。文章提出了一种不受空投时励磁涌流影响的新方法,用阻抗继电器反应空投于内部故障．这种保护配置方式在内部故障时有很高的灵敏度,在外部故障时又有很强的制动作用,不反映空投时的励磁涌流．却能反映变压器空载合闸时有故障的情况．解决了变压器差动保护的难题。     

Editing of Chemical Exchange-Relayed NOEs in NMR Experiments for the Observation of Protein–Water Interactions

An experimental approach for the editing of exchange-relayed NOEs in water-selective NOE experiments is presented. The proposed pulse sequence is based on the application during the NOE mixing time of continuous wave irradiation, which saturates resonances of relaying labile protons in slow chemical exchange with water. The technique can efficiently reduce the contributions of exchange-relayed NOE peaks that often crowd the water-selective NOE spectra and hide direct intermolecular NOEs between water and protein protons. The present approach opens new opportunities for the characterization of hydration by NMR, even in the proximity of polar labile groups.     

一种快速蜂窝多跳网路由算法

本文提出了一种适用于蜂窝多跳网的路由算法.该算法充分考虑了蜂窝多跳小区以基站为中心的特点.将传统的分布式路由方式改为基站统一为各节点提供路由的集中处理方式,并定义了一套与之适应的信令.由于采用了集中的处理方式,在新方法中,基站能够通过处理和维护路由过程中所得到的信息,逐步获取小区的拓扑结构,提高路由的效率.仿真结果表明,相比于现有方法,本文提出的算法在寻路的时间上大大缩短,寻路的质量也有一定提高.     

Performance analysis of switch‐and‐stay combining in two‐way relay systems with analog network coding and time‐division broadcast protocols

In this paper, we consider switch‐and‐stay combining (SSC) in two‐way relay systems with two amplify‐and‐forward relays, one of which is activated to assist the information exchange between the two sources. The system operates in either analog network coding (ANC) protocol where the communication is only achieved with the help of the active relay or time‐division broadcast (TDBC) protocol where the direct link between two sources can be utilized to exploit more diversity gain. In both cases, we study the outage probability and bit error rate (BER) for Rayleigh fading channels. In particular, we derive closed‐form lower bounds for the outage probability and the average BER, which remain tight for different fading conditions. We also present asymptotic analysis for both the outage probability and the average BER at high signal‐to‐noise ratio. It is shown that SSC can achieve the full diversity order in two‐way relay systems for both ANC and TDBC protocols with proper switching thresholds. Copyright © 2014 John Wiley & Sons, Ltd.