Optical simulation of phosphor layer of white LEDs

A Matlab(2009a) program was developed to simulate the photons emitted by the LED chips.The photons’transmission,reflection,and refraction in phosphor layers with different shapes were calculated in this program.The CCT was calculated at different emergent angles with different layer profiles,such as planar layer, hemispherical layer(with different diameters),half ellipsoid layer and other irregular shapes.As a consequence of optimization of angular color uniformity,the trend of configuration of the phosphor layer was discussed and analyzed.     

Milcom 2009 Gears up to Solve "The Challenge of Convergence"

MILCOM, now in its 28th year, is the world?s premier international communications and networking technical conference bringing together the best of academia and commercial enterprise with military applications. Attracting over 5000 attendees from industry, academia, and government, MILCOM provides an unparalleled program of presentations of both government classified and unclassified papers, panels, tutorials, and keynote presentations. In addition to the technical program, MILCOM 2009 will include exhibits from more than 200 of the world?s leading providers of high-tech solutions and communications technologies.     

张海涛在BIRTV2009主题报告会上的讲话

一年一度的北京广播电影电视设备展览会（BIRTV）就要开幕了．我代表国家广电总局和王太华同志对BIRTV的举办表示热烈祝贺,对前来参加展会的各位来宾、各位同行表示热烈欢迎．对多年来关心支持参与我国广播影视建设发展的国内外厂商和各界朋友表示衷心感谢!BIRTV自1987年举办以来．参展厂商不断增加．参展面积不断扩大,服务水平不断提高．     

Report on First International Summer School on Radar/SAR

In the picturesque Rhine Valley close to Bonn, more than 30 young students and scientists from all corners of the world congregated from July 24 to 31, 2009, to participate in the 1st International Summer School on Radar/SAR. The summer school was the initiative of Prof. Dr. Joachim Ender, director of one of Europe's foremost radar research establishments: the Fraunhofer Institute for High Frequency Physics and Radar (formerly, FGAN-FHR). Fraunhofer-FHR, in cooperation with renowned experts from across Europe and Canada, combined their creativity and scientific prowess to put together a program that would appeal to young scientists (particularly PhD candidates) across the globe.     

671例高血压住院患者用药状况分析

目的：分析2009年成医附院高血压住院患者降压达标时的用药状况及临床意义。方法：对住院的671例高血压患者在血压达标时所用降压药的情况进行分析。结果：671例患者中联合用药者521例,占用药例数的77.65%,其中两药合用者262例,占用药例数的39.05%,以CCB＋ARB（89例）最常见;三药合用者201例,占用药...     

基于K-L变换和平均近邻法的人脸识别

首先介绍了K-L变换和近邻法判别的原理;然后以MATLAB R2009b为实验平台,分别利用类间散布矩阵和总体散布矩阵作为K-L变换的的产生矩阵,对ORL人脸库的400幅图片进行K-L变换,一部分作为训练样本,一部分作为待识别样本,训练样本以产生特征脸空间;接着计算出待识别图片在特征脸空间的坐标,采用平均近邻法进行人脸识别.最终的实验结果给出了基于两种产生矩阵的算法时间和正确识别率,实验证明采用K-L变换对人脸提取特征很有效,本文基于K-L变换和平均近邻判别法的人脸识别的方法正确率最高可达到95％.     

Ultraviolet ZnO Nanorod/P-GaN-Heterostructured Light-Emitting Diodes

Both i-ZnO and n-ZnO : In nanorod arrays were grown on a p-GaN layer with an anodic alumina membrane template using a vapor cooling condensation method. Electroluminescence emissions were observed from the resulting p-n (p-GaN/n-ZnO : In nanorod array) and p-i-n (p-GaN/i-ZnO nanorod array/n-ZnO : In nanorod array) heterostructured light-emitting diodes (LEDs). The ultraviolet emission peak at 386 nm observed in the p-i-n heterostructured LEDs was attributed to radiative recombination of the near-band edge in the i-ZnO nanorods. Using power-law fitted current–voltage relationships, it was shown that a space-charge-limited current and associated effects occurred in the p-n and p-i-n nanorod heterostructured LEDs.      

Simpler and more accurate throughput analysis of a DS CDMA/unslotted ALOHA system with two user classes based on M/M/infinity queueing model

We propose that the throughput performance of the DS CDMA unslotted ALOHA system with two user classes is analyzed by the M/M/infinity queueing model without the death rate approximation. The previous scheme uses the M/D/infinity queueing model with the death rate approximation. The new analysis method is simpler than the previous one because four‐dimensional summation is replaced by two‐dimensional summation in the packet success probability calculation. The speed of new analysis program is 250 times faster than that of the previous one. In the numerical results, we consider the cases when the message arrival rates of the two classes are equal or not equal, and the access control is present or not. It shows that the proposed scheme has more accurate analyzed throughput than the previous one does. Copyright © 2009 John Wiley & Sons, Ltd.     

InGaAs–GaAs Quantum-Dot Mode-Locked Laser Diodes: Optimization of the Laser Geometry for Subpicosecond Pulse Generation

The effect of cavity geometry on both pulsewidth and pulse output power is systematically investigated for a monolithic mode-locked quantum-dot laser diode. Subpicosecond pulse generation is demonstrated, and trends in pulsewidth and pulse output power are correlated to the ratio of the gain-to-absorber section lengths. A three-fold reduction in the pulsewidth, from 2.3 ps to 800 fs, is observed for a change in the gain-to-absorber section length ratio of 14 : 1 to 3 : 1. In addition, an associated five-fold increase in average power and 14-fold increase in peak power are also observed.      

Three-Band White Light-Emitting Diodes Based on Hybridization of Polyfluorene and Colloidal CdSe–ZnS Quantum Dots

The authors have demonstrated the hybridization of polyfluorene (PFO) polymer light-emitting diodes with CdSe–ZnS core/shell quantum dots (QDs) in different device structures. To achieve white light emission, the green and red QDs have been incorporated into the PFO as the single emissive layer. Furthermore, the whole structures were also optimized to engineer the emission spectra. Accordingly, the incorporation of QDs increased the turn-on voltage from 10 to 23 V in device with the blend ratio of PFO : green QD : red QD being 6 : 1 : 1, while the maximum brightness was dramatically decreased.      

Electrically Controlled Liquid Crystal Phase Grating for Terahertz Waves

This work demonstrates the feasibility of electrically controlled liquid-crystal-based phase grating for manipulating the terahertz (THz) waves. This device can be utilized as a THz beam splitter and the beam splitting ratio of the zeroth- to the first-order diffractions can be tuned from 10 : 1 to 1 : 1.      

The $hbox{1}/f$ Noise and Random Telegraph Noise Characteristics in Floating-Gate nand Flash Memories

We have characterized low-frequency noise (LFN) such as $hbox{1}/f$ noise and random telegraph noise (RTN) in a nand Flash memory cell string for the first time and shown its fundamental properties. The nand Flash memory cells showed specific LFN characteristics under various conditions such as bit-line bias, word-line bias of a selected cell, and pass bias of the unselected cells in the nand string. Also, LFN was investigated with the program/erase (P/E) cycling of a cell or all cells in a string, and maximum threshold voltage fluctuation of several tens of millivolts after $sim$100 000 cycles at the 70-nm technology node was shown. Finally, we predicted the effects of LFN in sub-70-nm nand Flash memories.      

Density‐adaptive network reprogramming protocol for wireless sensor networks

Network reprogramming is a process used to update program codes of sensor nodes that are already deployed. To deal with potentially unstable link conditions of wireless sensor networks, the epidemic approach based on 3‐way advertise‐request‐data handshaking is preferred for network reprogramming. Existing epidemic protocols, however, require a long completion period and high traffic overhead in high‐density networks, mainly due to the hidden terminal problem. In this paper, we address this problem by dynamically adjusting the frequency of advertisement messages in terms of the density of sensor nodes, which is the number of sensor nodes in a certain area. We compare the performance of the proposed scheme, called DANP (Density‐Adaptive Network Reprogramming Protocol), with a well‐known epidemic protocol, Deluge. Simulations indicate that, in the grid topologies, DANP outperforms Deluge by about 30% in terms of the completion time and about 50% in terms of the traffic overhead. Significant performance gain is observed in random topologies as well. The performance of DANP is further confirmed via measurements in an experimental test bed. Copyright © 2009 John Wiley & Sons, Ltd.     

现代层次化可编程逻辑器件软件系统FDE2009

本文提出并实现了适用于现代层次化结构的FPGA芯片的CAD软件系统:FDE2009(FPGA Development Environment).该软件系统不但由工艺映射,布局布线,位流生成,编程下载等功能模块构成了一套完整的FPGA CAD流程,并且根据现代FPGA芯片层次化的结构特点,提出了逻辑分层的布局思想及由底至上逐层构建布线资源图的算法,提高了硬件资源的利用率及程序的运行效率.此外,本软件自定义了一套使用扩展性标志语言的文件系统,从而使其具有一定的通用性及良好的扩展性.软硬件协同测试结果表明该软件系统各模块功能正确,并能配合硬件高效的实现各类功能电路,是一套实用的FPGA软件系统.     

Efficient Access Control for Wireless Sensor Data

Although very developed in many sectors (databases, filesystems), access control schemes are still somewhat elusive when it comes to wireless sensor networks. However, it is clear that many WSN systems—such as healthcare and automotive ones—need a controlled access to data that sensor nodes produce, given its high sensitivity. Enforcing access control in wireless sensor networks is a particularly difficult task due to the limited computational capacity of wireless sensor nodes. In this paper we present a full-fledged access control scheme for wireless sensor data. We enforce access control through data encryption, thus embedding access control in sensor data units. We also propose a lightweight key generation mechanism, based on cryptographic hash functions, that allows for hierarchical key derivation. The suggested protocol only relies on simple operations, does not require interactions between nodes and data consumers and has minimal storage requirements.

The land of pixels hosts ICIP 2009 [Conference Spotlight]

Cairo, Egypt, will host the 2009 IEEE International Con ference on Image Processing (ICIP) 7?11 November 2009. This is the first time that ICIP will be held in the Middle East and only the second time that any major IEEE Signal Processing Society conference, ICASSP or ICIP, is taking place in this region (the first conference was ICASSP, which took place in Istanbul). ICIP 2009 is one of the main Society initiatives to reach out and have a signal processing global impact.     

2009电子封装技术和高密度封装国际会议（ICEPT—HDP）暨电子封装技术国际会议十届庆典 2009年8月10日-13日·北京·中国

我代表中国电子学会生产技术学分会和电子封装专委会,诚挚地邀请各位封装界的朋友参加将于2009年8月10日～13日在北京举行的电子封装技术和高密度封装国际会议（ICEPT-HDP 2009）,踊跃提交论文。     

宽带无线应用发展推动产业升级

2009年,全球通信行业的呈现平稳发展的态势,用户数增量呈现放缓的趋势。截至2009年底,全球移动用户达到了45．9亿,全年新增用户达到了5．9亿,但同比2008年增长量减少4000万,这其中有金融危机的影响,但和全球用户的普及率已经达到66％这一比较高的水平不无关系。     

2009电子封装技术和高密度封装国际会议（ICEPT—HDP）暨电子封装技术国际会议十届庆典

我代表中国电子学会生产技术学分会和电子封装专委会,诚挚地邀请各位封装界的朋友参加将于2009年8月10日～13日在北京举行的电子封装技术和高密度封装国际会议（ICEPT-HDP2009）,踊跃提交论文。     

Energy Efficient Reliable Data Collection in Wireless Sensor Networks with Asymmetric Links

Field measurements reveal that radio link asymmetry has a severe impact on reliable data delivery. We analyze the energy efficiencies of selected reliability schemes for asymmetric radio links using theoretical models. The analysis provides guidelines for retransmission control so as to balance between reliability and energy consumption. We also design two enhancements to the “implicit” ARQ scheme addressing the negative effects of asymmetric radio links. The energy efficiencies of these algorithms are explicitly derived using our theoretical model and validated by simulations and field trials. Based on the analysis of the two enhanced algorithms, we propose an improvement, referred to as Energy Efficient Reliable Data Collection (EERDC) that controls the retransmissions of the enhanced ARQ schemes. Simulations and field trials confirm our theoretical findings and demonstrate that our proposed EERDC algorithm alleviates the impact of link asymmetry and achieves energy savings.