一种超宽带印刷单极天线的研究

提出并研究了一种平面印刷单极天线,采用共面波导馈电,天线辐射体采用椭圆和带有对称枝节环的组合结构。着重研究如何通过调整内、外圆环枝节的长度,改变天线的谐振特性,从而实现天线在3.1～10.6GHz频率范围内回波损耗S11<-10dB,满足超宽带通信的要求。制作了实验模型,用矢量网络分析仪进行测试,与仿真结果比较取得较好一致性。     

Electrically and Sunlight‐Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite

Designing multistimuli responsive soft actuators which can mimic advanced and sophisticated biological movements through simple configuration is highly demanded for the biomimetic robotics application. Here, inspired by the human's flick finger behavior which can release large force output, a soft jumping robot mimicking the gymnast's somersault is designed based on the rolled carbon nanotube/polymer bilayer composite actuator. This new type of rolled bilayer actuator with tubular shape is fabricated and shows electrically and sunlight‐induced actuation with remarkable performances including ultralarge deformation from tubular to flat (angel change >200° or curvature >2 cm^?1), fast response (<5 s), and low actuation voltage (≤10 V). Besides jumping, the uniquely reversible rolling–unrolling actuation can lead to other smart soft robots with versatile complex biomimetic motions, including light‐induced tumbler with cyclic wobbling, electrically/light‐induced crawling‐type walking robots and grippers, electrically induced mouth movement, and ambient‐sunlight‐induced blooming of a biomimetic flower. These results open the way for using one simple type of actuator structure for the construction of various soft robots and devices toward practical biomimetic applications.     

High‐Energy‐Density Dielectric Polymer Nanocomposites with Trilayered Architecture

The development of advanced dielectric materials with high electric energy densities is of crucial importance in modern electronics and electric power systems. Here, a new class of multilayer‐structured polymer nanocomposites with high energy and power densities is presented. The outer layers of the trilayered structure are composed of boron nitride nanosheets dispersed in poly(vinylidene fluoride) (PVDF) matrix to provide high breakdown strength, while PVDF with barium strontium titanate nanowires forms the central layer to offer high dielectric constant of the resulting composites. The influence of the filler contents on the electrical polarization, breakdown strength, and energy density is examined. Simulations are carried out to model the electrical tree formation in the layered nanocomposites and to verify the experimental breakdown results. The trilayered polymer nanocomposite with an optimized filler content displays a discharged energy density of 20.5 J cm^?3 at Weibull breakdown strength of 588 MV m^?1, which is among the highest discharged energy densities reported so far. Moreover, the nanocomposite exhibits a superior power density of 0.91 MW cm^?3, more than nine times that of the commercially available biaxially oriented polypropylene. The findings of this research provide a new design paradigm for high‐performance dielectric polymer nanocomposites.     

短时傅里叶变换在线性调频信号时频滤波中的应用

将短时傅里叶变换（STFT）的时频分析方法应用到线性调频（LFM）信号的滤波中, 突破了传统匹配滤波方法基于平稳假设的限制,将信号分析空间从一维频率域扩展到二维的 时间-频率域。利用自滤波的时频滤波方法进行LFM信号的滤波,然后分别采用时域和时频域 的均方误差（MSE）标准,分析了时频滤波的性能。仿真结果表明,基于STFT的时频滤波方 法能有效实现对LFM信号的滤波。     

电子轰击型有源像素传感器在激光雷达的应用

激光雷达技术是成像前沿技术之一,在红外波段尤为重要。由于大面阵激光成像雷达回波很弱,且红外波段探测器灵敏度等技术指标较低,导致成像距离有限,制约了其应用范围。美国Intevac公司发明并生产的电子轰击型有源像素传感器(EBAPS)适用于微光探测,且其响应谱段为950～1650 nm。美国陆军实验室等单位将EBAPS用于激光雷达。本文简述了EBAPS的工作原理及其三代相机产品的特性,重点介绍了EBAPS在激光雷达中的应用情况。旨在为我国激光雷达的发展及微光成像中探测器的选择提供参考。     

电脑连锁店维修管理系统的设计与实现

电脑连锁店维修管理系统能实现连锁店的信息化管理,帮助企业将更多信息通过现代信息技术进行统计、分析,以指导企业各方面工作。在需求分析过程中,将整个系统分为采购管理模块、维修管理模块、库存管理模块、系统管理等八个模块,使用统一建模语言UML对系统进行面向对象的分析和建模,创建了系统的静态模型。系统采用B/S结构开发,在企业内部网上进行测试,实现了预期目标。     

Multi-authority ABS supporting dendritic access structure

Attribute-based signature (ABS),which could realize fine-grained access control,was considered to be an important method for anonymous authentication in cloud computing.However,normal ABS only provided simple access control through threshold structure and thus could not cope with the large-scale attribute sets of users in the cloud.Moreover,the attribute sets were supervised by only one attribute authority,which increased the cost of computation and storage.The whole system was in danger of collapsing once the attribute authority was breached.Aiming at tackling the problems above,a novel scheme,was proposed called multi-authority ABS supporting dendritic access structure which supported any AND,OR and threshold gates and affords more flexible access control.Meanwhile,the attribute sets of users were classified by diverse attribute authorities which reduced the overhead and the risk of systems.Besides,the scheme is proved to be selective predicate chosen message attack secure in the random oracle model.     

一种低电源电压灵敏度RC振荡器的设计

基于传统RC振荡器的理论分析,采用电阻串分压提供参考电压的方式,设计了一种低电源电压灵敏度的振荡器。基于HHNEC 0.5μm BiCMOS工艺,完成了HSPICE仿真。仿真结果显示,该振荡器输出一个频率为63kHz、占空比为50%的方波信号,当电源电压在4.5～5.5V之间变化时,频率变化范围在±0.52%内,有效降低了电源电压对振荡频率的影响。该振荡器可应用于开关电源芯片。     

激光熔覆同轴送粉喷嘴研制

针对现有送粉喷嘴粉末汇聚性差、出粉口容易堵塞以及受热变形的缺点,设计了一种四孔式同轴送粉喷嘴。喷嘴中央为激光束及保护气通道,沿中心锥孔轴向均布的4个小孔,为粉末通道。建立了数值计算模型,应用FLUENT软件对粉末通道不同出口形状和不同倾角条件下粉末流场情况进行数值模拟,选择最优方案。计算结果表明,在其他工艺参数一定的前提下,采用收缩出口与粉末通道倾角为70°时有利于改善熔覆成形效果。最后利用研制的送粉喷嘴进行粉末汇聚、激光熔覆成形等实验,验证该送粉喷嘴的实验效果。     

隐藏物的连续太赫兹反射扫描成像实验

太赫兹成像的优势在于能够穿透大多数非金属、非极性物质进行隐藏物的探测,而且不会对生物体造成伤害。其中太赫兹反射成像具有更为广泛的应用空间。由于对常见包装品和衣物的穿透能力在太赫兹反射成像系统的评估中十分重要,故利用CO2抽运太赫兹激光器所搭建的2.52THz反射扫描成像系统对剃须刀、铅笔字、5角硬币、金属纪念币和星卡等多种物体进行了穿透力实验;以纸、纸质快递信封和实验服为遮挡物,进行了成像对比分析。实验结果表明,该成像装置可以穿透单层实验服或单层纸制信封对目标成反射像,最大插入损耗近42dB。