Oxygen-related photoluminescence quenching in selectively grown GaN nanocolumns: Dependence on diameter

This work reports on the effects of air exposure on the photoluminescence intensity of GaN nanocolumns, with diameters ranging from below 40 nm up to around 230 nm, grown selectively on GaN/sapphire and GaN/Si(111). The high control of dimensions provided by selective area growth epitaxy allowed for a better study of the relationship between the observed phenomena, namely the photoluminescence intensity quenching due to oxygen photo-adsorption, and the nanocolumns properties (morphology and dimensions). For nanocolumns with diameters below 120 nm and lengths of about 300 nm, photoluminescence intensity dropped by more than 90% of the initial value, while for shorter nanocolumns a reduced drop value was found.     

机载可见光摄像机调光方法研究

针对机载光电平台可见光摄像机在执行任务时所面临的场景多样性的特点,对现有调光方法进行了研究,提出一种灰度平均值与区域信息熵相结合的调光方法.方法分为3个步骤,首先是灰度平均值法初调,获得大致清晰的图像;其次是地面人员提取感兴趣目标区域;最后是目标区域内利用信息熵法进行调光.实验结果表明,利用此方法可以获得亮度合适、目标...     

不同电镀面积计算方法探讨

电镀铜流程是印制板制造过程中非常重要的一步,孔壁镀铜厚度是影响板件可靠性的重要因素之一,PCB制造厂家和客户都十分重视孔铜的控制.在电镀生产过程中,电流密度和电镀面积是决定孔铜厚度的两个关键参数,通过这两个参数,可以利用法拉第定律来理论计算电镀铜层的厚度.但在实际运用过程中,对于全板电镀使用拼板面积(板件尺寸长x宽)做为电镀面积,而对于图形电镀使用外层线路图形面积(拼板面积减去干膜覆盖面积)做为电镀面积,往往出现实际孔铜厚度与理论计算相差甚远,这是因为没有考虑到板件上孔对电镀面积的影响.板件厚度和孔数量对实际电镀面积影响很大,本文讨论了三种电镀面积的计算方法,确定了最合适的电镀面积计算方法,并在实际生产过程中进行验证.     

基于端口的VLAN划分与信息共享的实现

为解决以太网的广播问题和安全性问题,可采用基于端口的虚拟局域网VLAN划分技术。笔者阐述了VLAN划分的意义,介绍了利用交换机进行基于端口的VLAN划分时交换机配置及PC配置的详细操作。VLAN划分后利用ping命令验证其正确性,测试表明VLAN中可以实现信息安全共享,满足实际应用要求。     

面积约束下的最优阈值法分割LED像素点阵

针对基于CCD相机采集方式的亮度校正方法需要从采集图像中分割出每颗LED像素的亮度信息的问题,提出面积约束下的最优阈值分割法。在最优阈值分割法的基础上,根据先验信息引入面积约束条件,对阈值的取值范围进行约束。与传统的最优阈值法相比可以避免分割后LED像素区域连接的情况。面积约束下的最优阈值分割法生成采集图像的灰度直方图,利用最优阈值算法结合面积约束生成最优阈值,最后通过图像的阈值分割法将采集图像分割。实验表明,该方法可以比较好地分割出采集图像中的LED像素,并可避免当LED像素点分布密集时应用最优阈值法分割LED像素造成的区域连接问题。     

An Electroabsorption Modulator Monolithically Integrated with a Semiconductor Optical Amplifier and a Dual-Waveguide Spot-Size Converter

A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spot-size converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology.A 1550～1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved.The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°×18.0°,respectively,resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.     

A novel nest-based scheduling method for mobile wireless body area networks

Wireless Body Area Networks (WBANs) comprise various sensors to monitor and collect various vital signals, such as blood pressure, pulse, heartbeat, body temperature, and blood sugar. A dense and mobile WBAN often suffers from interference, which causes serious problems, such as wasting energy and degrading throughput. In reality, not all of the sensors in WBAN need to be active at the same time. Therefore, they can be divided into different groups so that each group works in turn to avoid interference. In this paper, a Nest-Based WBAN Scheduling (NBWS) algorithm is proposed to cluster sensors of the same types in a single or multiple WBANs into different groups to avoid interference. Particularly, we borrow the graph coloring theory to schedule all groups to work using a Time Division for Multimodal Sensor (TDMS) group scheduling model. Both theoretical analysis and experimental results demonstrate that the proposed NBWS algorithm performs better in terms of frequency of collisions, transmission delay, system throughput, and energy consumption compared to the counterpart methods.     

智能建筑物综合布线系统浅析

本文主要介绍了综合布线系统的特点、设计原则及组成结构.     

基于C8051F040的高性能CAN总线节点模块设计

经过分析CAN总线节点的功能,提出了CAN总线节点模块设计方案,介绍了典型C8051F040的CAN总线网络结构和CAN控制器结构,在硬件电路设计部分中,对模块实现原理及设计要点进行了详细的介绍,软件部分阐述了CAN总线节点模块的固件程序。给出了以此芯片为核心的CAN总线节点模块的应用层软件。设计的CAN总线节点模块功能强、性能高效,目前已经运用于工业现场使用的测量系统中。     

Robust channel estimation for the OFDM-based WLAN systems with imperfect synchronization

As an effective technique for combating multipath fading and for high data rate transmission over wireless channels, orthogonal frequ- ency division multiplexing (OFDM) is extensively used in wireless local area network (WLAN) systems to support high-performance bandwidth- efficient multimedia services. In this paper, a robust channel estimation scheme is proposed for the OFDM-based WLAN systems with imperfect synchronization. The frame structure information, the preamble information, the pilot information are efficiently utilized in the proposed channel estimation scheme. Simulation results are used to illustrate the performance of the proposed scheme.