Porous Iron–Cobalt Alloy/Nitrogen‐Doped Carbon Cages Synthesized via Pyrolysis of Complex Metal–Organic Framework Hybrids for Oxygen Reduction

Efficient and stable nonprecious metal electrocatalysts for oxygen reduction are of great significance in some important electrochemical energy storage and conversion systems. As a unique class of porous hybrid materials, metal–organic frameworks (MOFs) and their composites are recently considered as promising precursors to derive advanced functional materials with controlled structures and compositions. Here, an “MOF‐in‐MOF hybrid” confined pyrolysis strategy is developed for the synthesis of porous Fe–Co alloy/N‐doped carbon cages. A unique “MOF‐in‐MOF hybrid” architecture constructed from a Zn‐based MOF core and a Co‐based MOF hybrid shell encapsulated with FeOOH nanorods is first prepared, followed by a pyrolysis process to obtain a cage‐shaped hybrid material consisting of Fe–Co alloy nanocrystallites evenly distributed inside a porous N‐doped carbon microshell. Of note, this strategy can be extended to synthesize many other multifunctional “nanosubstrate‐in‐MOF hybrid” core–shelled structures. Benefiting from the structural and compositional advantages, the as‐derived hybrid cages exhibit superior electrocatalytic performance for the oxygen reduction reaction in alkaline solution. The present approach may provide some insight in design and synthesis of complex MOF hybrid structures and their derived functional materials for energy storage and conversion applications.     

互质阵列信号处理研究进展:波达方向估计与自适应波束成形

阵列信号处理是雷达领域各类应用的核心技术之一。近年来,互质阵列的提出打破了传统方法受限于奈奎斯特采样速率这一瓶颈,其稀疏布设的阵列结构和互质欠采样的信号处理方式大幅降低了系统所需的软硬件开销,为当前不断提升的实际应用需求提供了理论基础和技术前提。鉴于其在自由度、分辨率及计算复杂度等方面的性能优势,互质阵列信号处理的理论和技术研究受到了国内外学者的广泛关注。该文分别从波达方向估计和自适应波束成形这两个阵列信号处理领域的基本问题出发,介绍了互质阵列信号处理方向的研究进展。在互质阵列波达方向估计方面,该文总结了互质子阵分解方法和虚拟阵列信号处理方法等两类典型技术路线,并以此为基础介绍了压缩感知和无网格化技术在低复杂度和超分辨估计等方面的最新研究工作。在互质阵列波束成形方面,该文剖析了其与互质阵列波达方向估计问题的区别与联系,并介绍了面向互质阵列的高效鲁棒自适应波束成形设计方法。该文旨在通过对互质阵列信号处理研究前沿的分类归纳和总结,探讨各类方法的优势和未来的研究方向,为其在雷达等领域的产业需求和实际应用提供理论和技术参考。      

掺铒a-Si∶H,O薄膜1.54μm光致发光和微结构

采用等离子化学气相淀积方法 ,改变 Si H4 和 N2 O的流量比制备含有不同氧浓度的 a- Si∶ H,O薄膜 .用离子注入方法掺入铒 ,经 30 0— 935℃快速热退火 ,在波长 1 .54μm处观察到很强的室温光致发光 .氧的加入可以大大提高铒离子的发光强度 ,并且发光强度随氧含量的变化有一个类似于高斯曲线的分布关系 ,不是单调地随氧含量的增加而增强 .研究了掺铒 a- Si∶ H,O薄膜和微结构 ,讨论了发光强度与薄膜微结构的关系 .     

广播信号数字延时技术与实践

随着广播电视技术的迅速发展,常规的电台节目已不能满足广大听众的生活需要,因此,电台节目收听率急剧下降。为摆脱电台广播节目的困境,各地相继开播了直播节目,使听众和节目主持人直接对话,点播听众喜欢听的歌曲或节目,以及其它一些新闻直播等节目。通过开辟直播节目,一方面使广播收听率大幅度提高,另一方面也进一步活跃了整个广播节目,使电台广播节目进入了一个新的阶段,这是有利的一面。但随之而来也会出现一些弊端,如听众与主持人的对话内容是否能达到播放要求,听众和主持人的讲话是否存在诬陷他人或有政治问题的词语等。这些问题一直困…     

机载激光水下目标探测的协同搜索及其仿真

机载激光搜索水下的运动目标是一个较难的问题,因为运动目标容易跑出搜索区域使有效搜索时间缩短。为了快速有效地搜索目标。西方提出了多机在指挥控制中心指挥下的协同搜索方法;计算了在没有先验信息情况下多机搜索概率;提出了有先验信息情况下的搜索力分配方案;同时,进行了仿真实验。结果表明：协同搜索的成功率和效率与掌握目标的信息量和准确度有密切关系。     

A low-loss V-groove coplanar waveguide on an SOI substrate

eguide causes about 50% less loss than the conventional one at a high frequency of up to 40 GHz.     

Electroluminescence and Laser Emission of Soluble Pure Red Fluorescent Molecular Glasses Based on Dithienylbenzothiadiazole

Soluble molecular red emitters 1a / 1b are synthesized by Stille coupling from 2‐(3,5‐di(1‐naphthyl)phenyl)thiophene precursors. The compounds show emission maxima at ca. 610 nm in CH₂Cl₂ solution and 620 nm in solid films. Replacing the n‐hexyl substituent by 4‐sec‐butoxyphenyl produces a marked increase of glass transition temperature (T_g) from 82 °C to 137 °C and increases the solubility in toluene and p‐xylene, thus improving the film‐forming properties. Cyclic voltammetry shows that the compounds can be reversibly oxidized and reduced around +1.10 and ?1.20 V, respectively. A two‐layered electroluminescent device based on 1b produces a pure red light emission with CIE coordinates (0.646, 0.350) and a maximal luminous efficiency of 2.1 cd A^?1. Furthermore, when used as a solution‐processed red emitter in optically pumped laser devices, compound 1b successfully produces a lasing emission at ca. 650 nm.     

基于网络的移动式稳定土厂拌设备电气系统设计

介绍了由上位机、PLC、变频器组成的稳定土厂拌设备的电气控制系统。主要介绍了上位机和PLC之间的通信,及PLC和几个变频器之间的通信过程。通过PLC指令程序,该系统顺利解决了指令从上位机通过RS 232下传到PLC,再通过RS 485顺利下传到各个变频器。这对以后此类系统的实施具有借鉴作用。     

移动自组网地址配置问题的研究

MANET（Mobile Ad hoc Network）中没有一个永久的中心机构，其网络拓扑结构不断变化，所以必须有一种能够对网络主机地址动态自配置和管理的协议。给出了在MANET中动态地址自配置与管理的方法，不同方案的特点及适应情况，最后对目前Ad hoc网络地址配置研究进行总结和展望。     

Construction and performance analysis of 2-D variable-length variable-weight optical orthogonal codes

In this paper, a new generation algorithm of a two-dimensional variable-length and variable-weight optical orthogonal codes (2-D VLVWOOCs) is proposed. By analysis of the BER performance for the corresponding optical code division multiple access (OCDMA) system, it is shown that the users with different codewords have significant differences in performance. Users with heavier-weight address matrices always outperform those with lighter-weight address matrices, and shorter-length and longer-length matrices support high bit-rate and low bit-rate in OCDMA applications, respectively. Therefore, heavier-weight shorter-length matrices can accommodate high bit-rate and high-quality of services (QoS) (e.g., real-time video), and lighter-weight longer-length matrices can achieve low bit-rate and low-QoS (e.g., voice). The system performance becomes worse as the users concentrate on one type of service. Especially, a surge of the number of users with shorter-length matrices has particularly impact on system performance. Thus, the 2-D VLVWOOCs can be used to provide many different types of services with different rate-levels and different levels of QoS, and simultaneously make better use of bandwidth resources in optical networks.