太赫兹时间分辨系统研究有机卤化物钙钛矿薄膜的超快太赫兹调制

研究了利用太赫兹时间分辨系统研究有机卤化物钙钛矿薄膜(CH_3NH_3PbI_3 and CH_3NH_3PbI_(3-x)Cl_x)的皮秒尺度的超快太赫兹调制特性.在光激发作用下出现了太赫兹透射波的瞬时下降.相比于CH_3NH_3PbI_3薄膜,在光激发作用下CH_3NH_3PbI_(3-x)Cl_x薄膜展现了更高的调制深度(10%).通过测算材料的电导率及载流子浓度,其调制机理为瞬态光激发载流子浓度上升.实验结果表明,CH_3NH_3PbI_(3-x)Cl_x薄膜可作为一种高效超快太赫兹调制器件.     

Tuning the Charge Transfer Dynamics of the Nanostructured GaN Photoelectrodes for Efficient Photoelectrochemical Detection in the Ultraviolet Band

The intriguing surface sensitivity of the single-crystalline semiconductor nanowires offers tremendous opportunity in tuning the physical properties of nanophotonic and nanoelectronic devices for versatile applications. Particularly, in the pursuit of emerging photoelectrochemical (PEC)-type devices, significant efforts have been devoted to understanding the charge transfer dynamics between the nanowires and the electrolyte. Here, a PEC-type ultraviolet photodetector consisting of GaN p-n junction nanowires as photoelectrodes is constructed. It is found that two competing charge transport processes at the nanowires’ surface as well as in the p-n junction co-determine the photoresponsive behavior of the device. Furthermore, the surface platinum (Pt) decoration has successfully tuned the charge transfer dynamics by enhancing the charge transport efficiency at the surface, resulting in a twenty-fold increase of the photocurrent compared to the pristine GaN nanowires. Theoretical calculations reveal that the newly formed electronic states at the Pt/GaN interface account for the improved charge transfer at the surface, and the optimal hydrogen adsorption energy contributes to the boosted PEC reaction rate. The synergy of these two effects uncover the underlying mechanism of the high photoresponse of the constructed Pt/GaN-nanowires-based PEC photodetectors.     

CCD相机调制传递函数的测试分析

调制传递函数(MTF)是评价CCD相机成像系统质量的重要参数,它能真实地反映相机拍摄时的空间频率与图像对比度的关系。CCD相机的MTF测试中最关键的是靶标的选择,它决定了整个系统的测量精度和操作过程的复杂程度。理想的靶标函数是正弦函数,但制作光出射度随正弦波规律变化的分辨率板是非常困难的,因此利用明暗相间、相互平行的黑白条纹分辨率板来代替正弦波分辨率板,提出了测量MTF的方法。重点对CCD相机在奈奎斯特频率处的MTF测试结果进行了分析与评价。     

一种DC-DC开关电源的简单高效软启动电路

提出了一种简单而高效的新型软启动电路,实现了输出电压平稳、快速的上升.该电路有效抑制了DC-DC开关电源启动过程中出现的浪涌电流,同时避免了传统软启动电路在软启动结束时出现的输出电压过冲.电路完全集成在芯片内部,避免使用额外电容而占用过多面积和增加功耗.经过对电路的Hspice仿真以及芯片样品的测试,在输入电压为3.3V的升压型开关电源芯片中,输出电压在500 μs内分两步平稳上升,避免了浪涌电流和过冲电压,符合设计指标.     

An efficient and provably‐secure certificateless signature scheme without bilinear pairings

Certificateless public key cryptography simplifies the complex certificate management in the traditional public key cryptography and resolves the key escrow problem in identitybased cryptography. The certificateless signature scheme is studied widely as an important primitive. Following the pioneering work done by Al‐Riyami et al., many certificateless signature schemes using bilinear pairings have been proposed ever since. However, the relative computation cost of the pairing is approximately 20 times higher than that of the scalar multiplication over the elliptic curve group. To improve the performance we propose a certificateless signature scheme without bilinear pairings. With the running time being reduced greatly, our scheme is more practical than the previous related schemes for practical application. Copyright © 2011 John Wiley & Sons, Ltd.     

无线局域网

本文介绍了无线局域网的概念、结构、技术优势、ＣＳＭＡ／ＣＡ协议和标准化工作，并简介了目前主要产品以及作者一些建议。     

开放式网络管理及其实现问题

开放式网络管理是开放系统研究和实现的重要组成部分。本文在分析现有几种典型开放式网络管理体系结构的基础上，结合出了开放式网络管理的较为确切的定义，另外，本文还讨论了开放式网络管理的实现问题。     

日本的广播电视事业

本文较详细地介绍了日本广播电视事业的管理体制，覆盖手段，东京广播电视发射塔的设置情况，以及新媒体实验情况和计划等。并结合我国国情，笔者提出了一些看法。