空间X射线通信系统误码率分析

自X射线通信的概念被提出后,大部分研究集中在发射源、收发天线和探测器等关键器件上,而关于传输理论的研究较少。文中旨在建立X射线通信的理论模型,首先建立了X射线通信的功率传输模型和链路方程;其次建立了基于泊松噪声的X射线通信误码率模型,随后建立了X射线通信中的核心参数:通信距离,通信速率,误码率与传输功率之间的关系;最后对不同阳极高压与不同调制方式下探测器端信号光子数进行实验监测,对功率传输方程及误差模型进行验证,测试了X射线通信系统的误码率,理论与实验较为符合,OOK和4 PPM的误码率可达10-4~10-5量级,为空间X射线通信研究建立了理论基础,同时有望对空间X射线通信的工程化提供一定的参考。     

X射线曝光用的掩模材料

“要使X射线曝光工艺获得成功,需要解决的关键问题有X射线源、掩模、掩模与晶片的对准、抗蚀剂、掩模的检查修正等几项工作”。本文介绍一下1984年以来日本公布的专利中有关X射线掩模的进展概况。X射线用的掩模由X射线透射层、X射线吸收体与支撑吸收体的支撑体组成。现在没有定论说氮化硼(BN)和氮化硅(SiN)作为X射线透射层的材料最好,也没有定论说金(Au)作为X射线吸收体最好,有关X射线掩模的材料问题最近提出了各种方案,预料支撑体将采用单晶硅。     

X射线荧光光谱技术在重金属检测中的应用

X射线荧光光谱技术是利用样品对X射线的吸收随样品中的成分及其多少而变化来定性或定量测定样品中成分的一种方法。它具有分析迅速、样品前处理简单、可分析元素范围广、谱线简单、光谱干扰少、试样形态多样性以及测定时的非破坏性等特点。文章概述了X射线荧光光谱仪的基本原理、分类及系统的组成,综述了X射线荧光光谱技术在土壤重金属检测和农产品重金属及微量元素检测中的应用研究,分析了X射线荧光光谱技术存在的关键问题,提出了X射线荧光光谱技术的进一步研究方向。     

X射线辐照下材料电子发射特性的模拟

稳态X射线管是一种重要的X射线辐照模拟装置,在辐照效应等研究领域有重要应用。采用蒙特卡罗模拟方法计算了50 kV,150 kV和225 kV管电压下的X射线能谱,并对X射线辐照下电子发射进行了模拟;研究了准直孔直径分别为2 mm,4 mm和6 mm条件下X射线的焦斑分布和电子发射弥散情况,以及不同能谱的X射线轰击到聚乙烯、聚酰亚胺、Si、SiO₂、Cu、Ta和W等样品上产生的电子发射能谱和电流强度等特性,为X射线辐照下材料电子发射特性的实验研究和设计提供一定的理论基础和指导。     

强电磁辐射下X射线条纹相机可靠性分析

X射线条纹相机是激光惯性约束聚变研究中的核心测量设备,用于捕获聚变反应中瞬态X射线发射。对X射线条纹相机在聚变反应中强电磁辐射下的可靠性进行研究,给出了X射线条纹相机的可靠性框图及结构,并对X射线条纹相机各功能单元进行可靠性分配,针对其故障进行了故障模式和影响分析(FMEA)。可靠性分析和FMEA显示,X射线条纹相机中变像管单元其可靠性分配值在各个分系统单元中最高,其故障能够引起严重故障和试验损失,是制约X射线条纹相机可靠性和稳定性的重要部件。通过对X射线条纹相机内各单元的可靠性以及故障模式分析,有助于研究人员开展有针对性的电磁辐射加固,提升相机在强电磁脉冲辐射环境中运行的可靠性。     

基于Contourlet变换的焊缝X射线图像增强

为了改善X射线成像对比度低、背景噪声明显、被测工件细节不易显示等缺点.针对X射线图像的特点及常规增强方法的不足,应用一种基于Contourlet变换的增强算法,对X射线图像进行图像增强,提高了原图像的对比度和像质,达到了细节区域的最佳视觉效果.实验结果表明,该算法与直方图均衡和小波域图像增强方法相比,有效的增强了对比度、抑制了背景噪声.该算法对X射线图像增强后,图像所达到的射线检测标准比前两种算法高.     

空间X射线数据信息的组织管理和提取

针对空间X射线观测的数据结构复杂、数据量庞大,难以很好地利用的问题,文章研究了空间X射线的探测原理、X射线数据信息的组织管理和数据的探测平台,提出了快速提取空间X射线的信息的方法。通过文章的研究不仅能够使空间X射线数据的有效组织管理优化,而且能快速的提取X射线源的有用信息。     

90年代多层膜软X射线反射镜的发展状况与未来动向

1　引言　　多层膜软 X射线反射镜简单地说是从E.Spiller开始 ,由 T.W.Barbee,Jr,A.V.Vinogradov,J.H.Underwood等人建立的基础 ,后来又有众多研究人员加入到此多层膜软 X射线反射镜的研究和应用研究中 ,不仅实现了反射镜的高品质化 ,而且还将其应用于分光、聚光、X射线望远镜、X射线显微镜、X射线激光器、激光核聚变等离子体观察、X射线缩小曝光 (极紫外光刻 )等 ,还开发了用于 X射线光束分离器、多层膜衍射光栅、超级反射镜、软 X射线偏光子等的元件 ,并取得了一定成果 ,到了 2 0世纪 90年代 ,多层膜软 X射线反射镜的品质 ,尤其…     

X射线分光晶体高阶衍射效率标定方法

包含高阶衍射的X射线分光晶体积分衍射效率是X射线光谱准确辨识、X射线分光晶体性能研究、X射线光谱定量测量和高分辨X射线单能成像的基础。基于X射线衍射仪,选择适当厚度的镍滤片和控制X射线管电压,极大地抑制Cu K及韧致辐射,将X射线管光源Cu K单能化。以常用的X射线分光晶体季戊四醇[PET（002）]为样品,对X射线分光晶体的高阶积分衍射效率进行标定其结果表明,在 Cu K能点,PET（002）晶体的积分衍射效率,二阶为一阶的14.36%,三阶为一阶的4.07%;Cu K1最大峰值比,二阶衍射为一阶的7.7%,三阶衍射为一阶的1.3%。基于X射线衍射仪的X射线分光晶体高阶衍射效率实验标定具有快速高效、方便灵活的特点。     

可变增益X射线象增强管

一种带可变增益SIT(硅增强靶)靶的X射线象增强管已研制成功.X射线SIT管具有的增益控制范围是300～1,低噪声,极限分辨率是1500电视线/直径,象质可与光学耦合X射线增强器-视象管结合所获得的象质相比美.利用X射线SIT管的可变内增益能制成这样一种电子X射线照像成象系统,它既可用于低曝光率X射线荧光检查,又可用作高曝光率短持续时间的X射线荧光照像记录.本文介绍了X射线SIT靶的设计构思,并且对靶噪声做了详细分析.本文还概述了6英寸和9英寸输入直径X射线SIT管的实测特性.     

Graphene‐Based Nanomaterials: Synthesis,Properties, and Optical and Optoelectronic Applications

Graphene, a two‐dimensional, single‐atom‐thick carbon crystal arranged in a honeycomb lattice, shows extraordinary electronic, mechanical, thermal, optical, and optoelectronic properties, and has great potential in next‐generation electronics, optics, and optoelectronics. Graphene and graphene‐based nanomaterials have witnessed a very fast development of both fundamental and practical aspects in optics and optoelectronics since 2008. In this Feature Article, the synthesis techniques and main electronic and optical properties of graphene‐based nanomaterials are introduced with a comprehensive view. Recent progress of graphene‐based nanomaterials in optical and optoelectronic applications is then reviewed, including transparent conductive electrodes, photodetectors and phototransistors, photovoltaics and light emitting devices, saturable absorbers for ultrafast lasers, and biological and photocatalytic applications. In the final section, perspectives are given and future challenges in optical and optoelectronic applications of graphene‐based nanomaterials are addressed.     

高速光纤综合通信网络平台研究

现代通信网络应能满足各种通信业务和通信容量日益发展的需求,实现话音、数据、视频、IP等业务的一体化综合交换和传输。在比较TDM、IP和ATM三种协议的基础上,提出"采用内置RPR和MPLS功能的MSTP平台"建设光纤综合通信网络平台的实现方法。MSTP采用SDH的数据帧结构,保持了SDH标准光接口、灵活分插低速信号、自愈环保护和功能强大的网管等优点,可对TDM、IP和ATM协议进行优化传输。     

卫星遥感温室气体的大气观测技术进展

全球、区域及城市的碳浓度、碳源汇信息是应对气候变化、达成双碳目标、完善国际谈判、支持治理政策制定与执行的重要依据。国际认可的“自上而下” 方法将卫星观测作为基础的通量计算技术, 是验证温室气体排放清单的重要手段。系统介绍了温室气体的卫星探测载荷原理、类别和发展, 以及反演、估算CO2、CH4 和N2O 的浓度和排放通量的方法, 还有探测缺失和误差存在的影响因素等; 分析了对卫星探测温室气体能力提高的迫切需求, 浓度反演和排放量估算精度不足, 以及N2O、氟化物等其他温室气体遥感研究缺乏、地基遥感验证能力薄弱等问题; 最后总结了我国温室气体卫星遥感技术的发展趋势, 主要是面向主被动高时空分辨率卫星的研制应用、高精度多尺度排放量估算(特别针对城市、小区域和点源尺度)、氟化物遥感评估等主题, 以加强对碳排放的量化观测, 并增强对碳循环的理解, 提高感知和应对气候变化的能力。     

机动6m抛物面天线车结构总体方案探讨

文章遵循策划、分解、综合及优化的总体方案研究思路,根据要求,提出了三个机动6 m抛物面天线车结构总体备选方案;针对系统结构组成,详细分析了天馈线、天线座、拖车以及系统标定等子系统所有可能的结构方案;最后综合权衡研究三个备选方案在技术、质量、成本、周期等多方面的优劣,选择了最佳结构总体方案,确保了所选方案具有合理性、可行性、经济性、先进性和科学性。实践证明,所选方案用户满意,实施效果良好。     

MATLAB在地理信息系统开发中的应用

GIS是计算机科学、地理学、测绘学、地图学等多门科学综合的技术,其核心是计算机科学,基本技术是数据库、地图可视化及空间分析。MATLAB是当前流行应用软件和编程语言,它集数学计算、可视化和编程于一体,易学易用。本文介绍了MATLAB软件的主要特点,阐述了MATLAB地图工具箱、数据库工具箱、用户图形界面及其与外部程序的接口等技术,并探讨了它们在地理信息系统开发中的应用。     

Alternative Schemes for Dynamic Secure VPN Deployment in UMTS

Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

基于声卡的虚拟示波器设计

随着现代科学和信息技术的不断进步,示波器作为一种电子测量处理仪器也在不断发展并且已经变的越来越精密,也越来越智能.传统的模拟示波器受到低频响应能力和带宽限制等多方面因素影响在很多领域已显得力不从心,虚拟示波器的出现很好的解决了这些问题.本文以LabVIEW18版本为开发平台,设计制作了一款基于声卡的虚拟示波器.重点介绍...     

法国军用电子信息技术发展研究

法国国防部于2007年6月公布《未来30年远景规划》,其中提出未来防务需要重点发展军用电子信息技术,尤其是微电子技术、光电子技术和电真空技术等基础技术,并把空间技术、信息通信技术、微纳米技术等高新技术纳入优先研究和发展领域。法国经过多年的自主研发和大型技术计划的成功推进,已具有完整独立的军用电子信息技术研制能力以及开发设施,其雷达、通信以及先进探测技术均位居世界先进水平。文中主要介绍了法国军用电子信息技术发展的现状、发展趋势和发展特点。     

A Novel Local-Dielectric-Thickening Technique for Performance Improvements of Spiral Inductors on Si Substrates

A novel local-dielectric-thickening technique is presented for performance improvements of Si-based spiral inductors.This technique employs the processes of deposition,photolithography,and wet-etching,to locally thicken the oxide layer under the inductor,which can decrease the substrate loss and improve the inductor performance.Both the structures and processes are compact,economical,and compatible with CMOS processing.Several square spiral inductors with different inductances are fabricated,and the quality factors and the self-resonant frequencies both increase clearly with this proposed technique:for the 10,5，and 2nH inductors,the peak quality factors are effectively improved by 46.7%,49.7%，and 686%,respectively;however,the improvement percents of the selfresonant frequencies are more significant,which are 92.1%,91.0%,and no less than 68.1%，respectively.     

江阴广电中心大型演播室音频处理与扩声设备的选型与应用

结合江阴广电中心大型演播室电声系统设计的实际,对系统中的扩声与制播调音台、数字音频处理器、数字功率放大器、主扩声线性阵列、台口补声、返听及监听扬声器等设备进行了具体品牌、型号的选择,对其功能参数进行了描述,并对这些设备如何进行系统整合进行了介绍。