利用PtOEP掺杂改善Spiro发光器件的发光效率

为了利用有机三线态发光提高有机发光器件的发光效率,用磷光材料掺杂到聚合物主体中作为发光层,制备有机电致发光器件.在测量器件的电流-电压特性、发光亮度-电压特性和电致发光谱的基础上,计算了器件的外量子效率,研究了磷光材料的掺杂浓度对器件发光效率的影响.结果表明,对特定的材料体系,适当控制掺杂浓度,可以同时观察到荧光和磷光光谱,使掺杂器件的外量子效率在纯聚合物发光器件的基础上得到明显提高.     

iPTT: peer‐to‐peer push‐to‐talk for VoIP

This paper proposes iPTT, a peer‐to‐peer (P2P) Push‐to‐Talk (PTT) service for Voice over IP (VoIP). In iPTT, a distributed and mobile‐operator independent network architecture is presented to accelerate the deployment of the PTT service. Based on the serverless architecture, we develop two mechanisms, that is, flooding‐based floor control mechanism (FFC) and tree‐based floor control mechanism (TFC), for real‐time talk‐burst determination. The determination algorithms and the corresponding message flows for these two mechanisms are designed to show the feasibility of FFC and TFC. The performance of FFC and TFC is investigated through our analytical and simulation models in terms of the determination latency and the number of floor‐control message exchanges. Copyright © 2008 John Wiley & Sons, Ltd.     

用SystemView产生超宽带脉冲信号

本文介绍了超宽带无线通信系统(UWB)的基本原理,主要特点以及它所涉及的关键技术,目前产生UWB脉冲信号的方法。并提出了一种用SystemView产生UWB信号的方法,最后给出了结果。     

一种MQAM信号的识别算法

由于MQAM信号的概率密度函数服从莱斯分布，从而用莱斯分布来构造识别算法。在信噪比满足SNR≥13db的条件下，识别性能良好。     

基于WIFI物联网的家电智能控制系统信息控制端的研究

随着WiFi无线通信技术的发展和普及,WiFi已成为当今无线网络接入的主流标准。本文以智能家居广阔的市场需求为基础,选取家庭智能控制系统为研究对象,基于ARMS3C2440处理器和Linux嵌入式操作系统基础上,利用WiFi模块组建了家庭无线网络,采用Java技术为平台,实现一个可以在WiFi热点区域接入互联网的无线通信终端,并可以对家电设备远程控制。经测试,信息控制端可以在WiFi信号覆盖区域接入因特网,系统启动和运行正常,证明这种网络控制的方案是可行的。     

Luminescent property and energy transfer from Ce3+ to Tb3+ in YAl3(BO3)4

A series of Ce³⁺, Tb³⁺ or Ce³⁺/Tb³⁺ doped YAl₃(BO₃)₄ phosphors are synthesized by a high temperature solid-state reaction, and their luminescent properties are investigated. YAl₃(BO₃)₄:Ce³⁺ shows a broad emission band at 422 nm under the 367 nm radiation excitation. YAl₃(BO₃)₄:Tb³⁺ can be efficiently excited by the ultraviolet (UV) light, and produces green emission. The emission intensity of YAl₃(BO₃)₄:Tb³⁺ can be enhanced by adjusting Tb³⁺ doped content, and reaches the maximum at 0.06 mol Tb³⁺. When Ce³⁺ is codoped, the emission intensity of Tb³⁺ in YAl₃(BO₃)₄ can be enhanced, but the commission international del’eclairage (CIE) chromaticity coordinates of YAl₃(BO₃)₄:Tb³⁺ have almost no change. Moreover, the energy transfer from Ce³⁺ to Tb³⁺ in YAl₃(BO₃)₄ is studied.     

飞秒激光制备的全单模光纤法布里-珀罗干涉高温传感器

提出了一种全单模光纤的本征型法布里-珀罗干涉(IFPI)高温传感器。光纤IFPI传感器由飞秒激光在标准单模光纤上刻写的一对内部反射镜和腔内光纤构成,其反射光谱的干涉条纹对比度达到10dB,而插入损耗仅为0.1dB。实验结果表明,该传感器的测量温度可达1000℃,温度灵敏度为14.9pm/℃。而且在重复测量中,反射光谱具有良好的一致性,可以准确地实现高温传感。飞秒激光制备的光纤IFPI高温传感器完全由标准单模光纤构成,结构简单、成本低廉,易于连接现有的光纤器件构成光纤传感网络,在实际工程中有较大的应用价值。     

A New Lithium‐Ion Conductor LiTaSiO5: Theoretical Prediction,Materials Synthesis,and Ionic Conductivity

Owing to the nonleakage and incombustibility, solid electrolytes are crucial for solving the safety issues of rechargeable lithium batteries. In this work, a new class of solid electrolyte, acceptor‐doped LiTaSiO₅, is designed and synthesized based on the concerted migration mechanism. When Zr⁴⁺ is doped to the Ta⁵⁺ sites in LiTaSiO₅, the high‐energy lattice sites are partly occupied by the introduced lithium ions, and the lithium ions at those sites interact with the lithium ions placed in the low‐energy sites, thereby favoring the concerted motion of lithium ions and lowering the energy barrier for ion transport. Therefore, the concerted migration of lithium ions occurs in Zr‐doped LiTaSiO₅, and a 3D lithium‐ion diffusion network is established with quasi‐1D chains connected through interchain channels. The lithium‐ion occupation, as revealed by ab initio calculations, is validated by neutron powder diffraction. Zr‐doped LiTaSiO₅ electrolytes are successfully synthesized; Li_1.1Ta_0.9Zr_0.1SiO₅ shows a conductivity of 2.97 × 10^?5 S cm^?1 at 25 °C, about two orders of magnitude higher than that of LiTaSiO₅, and it increases to 3.11 × 10^?4 S cm^?1 at 100 °C. This work demonstrates the power of theory in designing new materials.     

Ultrathin Cobalt–Manganese Nanosheets: An Efficient Platform for Enhanced Photoelectrochemical Water Oxidation with Electron‐Donating Effect

An ultrathin cobalt–manganese (Co‐Mn) nanosheet, consisting of amorphous Co(OH)_x layers and ultrasmall Mn₃O₄ nanocrystals, is designed as an efficient co‐catalyst on an α‐Fe₂O₃ film for photoelectrochemical (PEC) water oxidation. The uniformly distributed Co‐Mn nanosheets lead to a remarkable 2.6‐fold enhancement on the photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) and an impressive cathodic shift (≈200 mV) of onset potential compared with bare α‐Fe₂O₃ film. Furthermore, the decorated photoanode exhibits a prominent resistance against photocorrosion with excellent stability for over 10 h. Detailed mechanism investigation manifests that incorporation of Mn sites in the nanosheets could create electron donation to Co sites and facilitate the activation of the OH group, which drastically increases the catalytic activities for water oxidation. These findings provide valuable guidance for designing high‐performance co‐catalysts for PEC applications and open new avenues toward controlled fabrication of mixed metallic composites.