Yolk–Shell Hybrid Materials with a Periodic Mesoporous Organosilica Shell: Ideal Nanoreactors for Selective Alcohol Oxidation

This contribution describes the preparation of multifunctional yolk–shell nanoparticles (YSNs) consisting of a core of silica spheres and an outer shell based on periodic mesoporous organosilica (PMO) with perpendicularly aligned mesoporous channels. The new yolk–shell hybrid materials were synthesised through a dual mesophase and vesicle soft templating method. The mesostructure of the shell, the dimension of the hollow space (4～52 nm), and the shell thickness (16～34 nm) could be adjusted by precise tuning of the synthesis parameters, as evidenced by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption investigations. Various metal nanoparticles (e.g., Au, Pt, and Pd) were encapsulated and confined in the void space between the core and the shell using impregnation and reduction of adequate metal precursors. The selective oxidation of various alcohol substrates was then carried out to illustrate the benefits of such an architecture in catalysis. High conversion (～100%) and excellent selectivity (～99%) were obtained over Pd nanoparticles encapsulated in the hybrid PMO yolk–shell structures.     

Network‐coded multiple‐source cooperation aided relaying for free‐space optical transmission

A network‐coded cooperative relaying aided free‐space optical (FSO) transmission scheme is designed. The resultant multiple‐source cooperation diversity is exploited by the relay to mitigate the strong turbulence‐induced fading experienced in FSO channels. At the destination, an iterative multiple source detection algorithm is proposed in conjunction with a chip‐level soft network decoding method. Our performance evaluation results using simulation analysis demonstrate that the proposed FSO multiple source detection is capable of approaching the single‐user‐bound for transmission over Gamma–Gamma turbulence channels. Also, the network‐coded cooperative FSO scheme can achieve a significant BER improvement in comparison with conventional noncooperation schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

路基设备辅助下的高速公路车辆信息方向性传输协议

针对现有VANET网络广播传输协议信道利用率低,易造成信道拥塞等问题,提出在路基设备辅助下的改进协议。利用路基设备进行车辆分簇,将簇内车辆编号加入到发送数据帧头,每个车辆节点有选择地进行数据包接收与发送。仿真结果表明,改进协议可以有效地改善传输过程中的信道使用情况,有效信息传输率可提高20%。     

基于WB的ROADM实现及光通道OSNR代价分析

文章从业务发展的需求出发,详细讨论了可重构光分插复用器(ROADM)设备的优点,提出了一种基于波长阻塞器(Wavelength Blocker,WB)的ROADM实现方案,并针对实际应用测试了该ROADM节点设备的最大光信噪比(OSNR)代价.结果表明这种ROADM节点设备满足应用的需求.     

0.22 THz回旋管渐变输出结构的设计和分析

从渐变波导耦合波方程出发,设计了0.22 THz回旋管两种渐变输出结构,上升余弦和Dolph-Chebychev渐变波导过渡器;三维电磁仿真软件HFSS对这两种波导数值模拟验证的结果表明:两种渐变波导都符合设计要求,但是改进的Dol—ph-Chebychev渐变波导要比上升余弦渐变波导短,从而得到作为传输TE_(03)模回旋管输出段的最优波导过度器。     

一种新的GPS接收机C/A码跟踪环鉴别器算法

该文分析了GPS C/A码相位估计误差与载波频率估计误差对相关函数的影响,并推导出了相关公式。从线性,对信号幅度与载波频率估计误差的敏感性和计算量等角度分析了现有的码鉴别器算法的优缺点。基于上面的分析与研究,提出了一种新的C/A码鉴别器算法。通过理论分析与仿真实验,证明该算法有良好的线性特性,能有效抑制对信号幅度与载波频率估计误差的敏感性,且计算量低,跟踪精度高,抗多经性能好,在性能上优于已有的算法。     

光纤光栅结构对磁场测量性能的影响

提出了一种基于光纤光栅的磁场测量方法.该方法主要是通过法拉第效应和对偏振相关损耗的测量来实现磁场测量.文中主要分析了不同光纤光栅结构对磁场测量性能的影响.分别通过分析普通采样光栅、啁啾采样光栅和切趾采样光栅由于透射谱的差异而导致磁场引起的透射光偏振损耗的不同,对这几种光栅结构及不同的光栅参数对测量范围、测量灵敏度的影响进行了仿真,为下一步的实验研究打下了基础.     

基于CPLD的四路数字视频光端机的设计

对输出端视频信号的处理是光端机设计的关键.文章首先简要介绍了四路数字视频光端机的系统架构和工作原理,然后详细描述了基于CPLD的四路数字视频光端机的设计过程,最后对实验结果作了分析.相比传统的光端机,本系统在硬件设计上对输出端视频信号处理方面作了改进,选择具有DirectDrive技术的MAX9530对视频信号进行处理,很好地解决了视频信号的干扰问题,同时提高了视频图像的质量.     

浅谈应用型本科学生“电工学”课程的教学

在分析应用型本科学生特点的基础上,从"电工学"课程的教学内容、教学方法和手段、考试环节几个方面提出了一些具体的改革方案,实践证明,这些改革措施对提高应用型本科学生"电工学"课程学习效果具有一定推动作用,最终取得较好的教学效果。