子载波个数对非对称限幅光正交频分复用误码率的影响

误码率(BER)是非对称限幅光正交频分复用(ACO-OFDM)的一项重要性能指标,子载波个数是影响这一性能指标的重要因素。通过理论推导及仿真证明的方法,分析了子载波个数对光域单边带ACO-OFDM信号在单模光纤中传输时系统误码率的影响。结果表明,在总传输速率一定时,改变子载波个数从128个到16384个,所需要的总带宽改变不超过0.775%。并在此基础上,通过实验证明了不同的传输速率下ACO-OFDM系统均存在使系统误码率最低的最优子载波个数,实验结果表明该最优子载波个数随传输速率的增加而增加。     

基于太阳能的ZigBee无线校园网络环境监测系统

本项目结合各高校的特点和供电要求,设计了一种基于太阳能供电的ZigBee无线校园网络环境监测系统,可以实现对多实验楼、多个校区的环境等信息进行实时的管理和监控功能.整个监测系统由太阳能供电系统、ZigBee模块、PM2.5传感器模块、温湿度传感器模块、Labview上位机模块等几个部分组成.经过多次测试后的实验结果表明,此系统运行可靠、稳定,具有广泛的推广价值和一定的实用性.     

用MOCVD在r面蓝宝石衬底上生长的a面GaN的独特电学性质研究

Nonpolar （1120） a-plane GaN films have been grown by low-pressure metal-organic vapor deposition on r-plane （1102） sapphire substrate. The structural and electrical properties of the a-plane GaN films are investigated by high-resolution X-ray diffraction （HRXRD）, atomic force microscopy （AFM） and van der Pauw Hall measurement. It is found that the Hall voltage shows more anisotropy than that of the c-plane samples; furthermore, the mobility changes with the degree of the van der Pauw square diagonal to the c direction, which shows significant electrical anisotropy. Further research indicates that electron mobility is strongly influenced by edge dislocations.     

磁场中准二维强耦合磁极化子的性质

采用线性组合算符和改进的LLP变分法,研究了磁场中无限势垒量子阱内电子与界面光学声子强耦合、与体纵光学声子弱耦合系统的基态,得到了磁极化子的振动频率和自陷能随量子阱宽和磁场变化的规律.对CdF2/AgCl量子阱进行了数值计算,结果表明,磁极化子的振动频率和自陷能随阱宽的增加而减小,随磁场的增加而增大,但不同支声子与电子和磁场相互作用对磁极化子的振动频率和自陷能的贡献大不相同.此外,对以上现象进行了分析和解释.     

Array公司SSL VPN夺标中石油

石油业在信息化系统建设方面一直着眼于提高效率,希望无缝满足当前和未来的业务拓展需要。其业务不断拓展和多元化,要求信息系统整体提供更高的访问,必须为勘探和生产活动的顺利进行提供全面的保障。无论从地理特性还是业务拓展的需求上,石油行业都需要高效的应用访问能力,避免     

The Heterointerface between Fe1/NC and Selenides Boosts Reversible Oxygen Electrocatalysis

The rational design and construction of efficient and inexpensive bifunctional oxygen electrocatalysts are highly desirable for the development of rechargeable Zn–air batteries (ZABs). Although single-atom Fe sites anchored on N-doped carbon catalysts (Fe₁/NC) ensure high oxygen reduction reaction activity, their unitary atomically dispersed active center faces difficult condition in catalyzing oxygen evolution reaction simultaneously. Herein, a composite catalyst containing heterointerface between Fe₁/NC and selenides ((Fe,Co)Se₂) is constructed. The obtained (Fe,Co)Se₂@Fe₁/NC exhibits extremely narrow potential gap of 0.616 V and remarkable stability in alkaline media, outperforming the benchmark catalysts (Pt/C+RuO₂: 0.720 V). Experimental results and density functional theory calculations reveal that heterointerface between Fe₁/NC and (Fe,Co)Se₂ accelerates the electron transfer and provides more moderate adsorption sites, which endow (Fe,Co)Se₂@Fe₁/NC with extremely high bifunctional oxygen catalytic activity. This study not only provides a superior bifunctional catalyst for ZABs, but also enriches the application of single-atom catalysts in multifunctional energy storage and conversion devices.     

基于延时锁定环的时间数字转换器设计

A time-to-digital converter(TDC) based on a reset-free and anti-harmonic delay-locked loop(DLL) circuit for wireless positioning systems is discussed and described. The DLL that generates 32-phase clocks and a cycle period detector is employed to avoid "false locking". Driven by multiphase clocks, an encoder detects pulses and outputs the phase of the clock when the pulse arrives. The proposed TDC was implemented in SMIC 0.18 m CMOS technology, and its core area occupies 0.7 0.55 mm2. The reference frequency ranges from 20 to 150 MHz. An LSB resolution of 521 ps can be achieved by using a reference clock of 60 MHz and the DNL is less than 0.75 LSB. It dissipates 31.5 mW at 1.8 V supply voltage.     

光学薄膜激光损伤测试平台的构建

设计构建了一光学薄膜激光损伤测试平台,通过图像检测法,激光散射法两种方法综合测试、评价损伤阈值。本系统由激光器、扩束、衰减、分光、散射探测、CCD探测等部分组成。对溶胶凝胶法制备的SiO2薄膜进行激光损伤阈值测试,实验表明,此测试平台可准确的测量损伤阈值,为研究薄膜的抗激光损伤提供了有效的测试手段。     

竞走运动员运动训练计划管理系统的设计与开发探究

随着我国经济和科技的快速发展,现代信息化技术的应用已经深入到了社会上的各个领域。在竞走运动员训练计划中建立信息化管理系统是信息化时代发展的必然需求,也是科学化、合理化运动员运动训练计划的制定。使得运动员的运动潜力得到挖掘和激发,使得运动员的竞技水平能够在比赛中得到有效的发挥。     

一种改进的保留图像细节信息的图像增强化方法

本文通过分析传统直方图均衡化的思想,得出在传统的直方图均衡化处理过程中由于图像的灰度级合并处理造成图像灰度级丢失继而使原图像细节信息损失,使增强后的图像边缘模糊,效果不理想。由此,本文给出了一种在图像经过均衡化处理后可以增加图像灰度级保留图像细节信息的方法。即先提取原目标图像中的高频细节成分,然后将其与原目标图像经直方图均衡化处理后的结果做叠加。经试验验证,与传统的直方图均衡化[1,2]算法相比,本文算法处理后的目标图像在增强了整体对比度的同时也保留了原图像的细节信息,能达到比较理想的增强效果。通过采用本文提出的改进算法,可以有效的实现图像增强的同时尽可能的保留图像细节信息的效果。