Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

位屏蔽多叉树搜索射频识别防碰撞算法

针对RFID树型防碰撞算法中时隙数多、数据通行量大等问题,提出了一种改进的多叉树防碰撞算法,阅读器准确检测碰撞位并向标签反馈碰撞位信息,标签对阅读器已知的ID位进行屏蔽,把ID号转换成连续碰撞的序列号.阅读器利用屏蔽位信息和标签返回的碰撞位编码信息,对标签进行分层分类搜索.通过对标签ID进行屏蔽,阅读器和标签间仅发送对方不知道的碰撞位信息.该算法减少了碰撞时隙和识别时隙,避免了空闲时隙,减少了阅读器和标签间的数据通信量.理论分析和仿真结果表明,该算法减少了系统的时隙总数和数据通信量,提高了阅读器的识别效率.     

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.     

LTPS工艺中光刻胶与膜层粘附力的研究

本文对影响LTPS工艺中光刻胶和衬底间粘附力的4个因素进行了实验及理论分析。经实验发现:衬底的材质和粗糙度以及光刻胶中分子量的分布是影响光刻胶和衬底粘附力的最重要的两个因素。在改善粘附力方面HMDS对于电负性较强的金属衬底和光刻胶的粘附力有较好的改善效果,对于SiNX、A-Si及P-Si衬底改善效果明显,且无差异,对于ITO没有改善。光刻胶涂布后适当延长烘烤时间也可以有效改善光刻胶和衬底的粘附力。     

合成孔径雷达Mosaic模式系统性能分析

主要讨论SAR的马赛克（Mosaic）模式的系统特性。首先简述Mosaic模式的特点及与扫描（Scan）和滑动聚束模式间的差异,然后详细分析了Mosaic模式下方位扫描关系及其旋转角,推导了多普勒频率的表达式和方位分辨率的计算公式,仿真分析计算了不同方位位置目标的多普勒历程和相应的方位分辨率,为系统设计提供了技术基础。     

GaN基板上超薄阳极氧化铝的制备

在草酸溶液中对GaN基板上超薄Al膜进行阳极氧化,结合扫描电镜对阳极氧化铝形貌进行表征,系统研究了超薄Al膜的腐蚀条件和氧化过程,以及Al膜的厚度,反应变化时间和实验难度系数之间的关系。多孔状阳极氧化铝的孔径、分布及有序度等对氧化电压、氧化时间、电解液温度和溶液浓度等参数较为敏感。通过深层次的机理分析,给出了相应的合理解释。在此基础上,优化了超薄阳极氧化铝的制备参数,提升了实验的稳定性及重复性,促进了阳极氧化铝在GaN材料和器件中的应用。     

Progress in doping semiconductor nanowires during growth

The anisotropic growth of one-dimensional or filamental crystals in the form of microwires and nanowires constitutes a rich domain of epitaxy and newly enabled applications at different length and size scales. Significant progress has been accomplished in controlling the growth, morphology, and properties of semiconductor nanowires and consequently their device level performance. The objective of this review is two-fold: to highlight progress up to date in nanowire doping and to discuss the remaining fundamental challenges. We focus on the most common semiconductor nanowire growth mechanism, the vapor-liquid-solid growth, and the perturbation of its kinetic and thermodynamic aspects with the introduction of dopants. We survey the origins of dopant gradients in nanowire growth and summarize quantification techniques for dopants and free-carrier concentrations. We analyze the morphological changes due to dopants and the influence of growth droplet seeds on composition and morphology and review growth aspects and alternatives that can mitigate these effects. We then summarize some of the remaining issues pertaining to dopant control in nanowires.     

网络空间威胁狩猎的研究综述

近年来,随着网络的普及和信息化水平的不断提高,越来越多的公司把重要信息和机密文件存储在连接着网络的计算机上。但是,由于网络攻击的手段层出不穷,威胁狩猎的思想和理念孕育而生并且逐渐成熟。由此,首先对网络空间威胁的定义和攻击流程模型进行介绍,再阐述了威胁狩猎的定义和核心技术,然后描述了威胁狩猎使用的工具;最后,概括总结现有的主流威胁狩猎的框架,比较各个框架的优缺点,并阐明了下一步的发展方向。     

UAT数据链上行报文时隙实时动态分配算法研究

基于UAT数据链上行TIS-B报文和FIS-B报文时如何合理的利用时间资源,制定地面上行数据的时隙策略,避免出现报文重叠和交织的问题,提出了时隙实时动态分配的算法。重点讨论了算法中时间段划分、配置报文发射窗口、窗口轮循变换和配置报文窗口偏移,对算法进行了结果的计算和实际工程中的应用分析,表明该方法完全满足实际工程中的应用要求,并提高了系统的实时性和动态性。     

一种基于附加电池的锂电池组主动均衡方法

电动汽车使用的串联锂电池组在多次循环充放电后会出现不均衡的现象,导致电池组容量和寿命的减少。为解决这一问题,文中提出了一种基于附加电池的非能耗式充放电主动均衡方法并对均衡电路及均衡控制策略进行设计。该均衡方案在充电时将电压高的单体能量转移给附加电池,在放电时将附加电池的能量转移给电压低的单体电池,实现了能量的自由存储与转移。文中对均衡电路的原理和均衡控制策略进行了分析,并应用MATLAB/Simulink中的Simcape与Stateflow分别对均衡电路及控制策略进行建模与仿真分析。仿真结果表明,该均衡控制方法能快速实现电池组的均衡,且均衡后的电池组可用容量有明显提高。     

短距离无线通信技术综述

随着网络及通信技术的飞速发展，人们对无线通信的需求越来越大，也出现了许多的无线通信协议。文章对目前使用较广泛的蓝牙、802．11(Wi—Fi)和IrDA无线协议分别进行了阐述，比较了他们技术上的异同点。讨论了在选择、使用这些技术时应注意的问题，对较具发展潜力的新无线技术标准UWB，zigBee也进行了阐述。对他们的未来应用进行了展望。     

Rural broadband: Gaps,maps and challenges

This paper examines challenges to evidence-based decision-making in the design and implementation of rural broadband investment programs. Our focus is on Canada, and the apparent need for further intra-rural broadband research and better data and mapping for informing public investment decisions, but similar challenges are evident in the international literature. Based on proprietary telecommunication provider datasets, the Canadian Radio-television and Telecommunication Commission (CRTC) estimates that broadband services with advertised speeds that meet its basic universal service targets (50 Mbps download and 10 Mbps upload) are available to 87.4 percent of households in Canada. In rural areas however, services that meet CRTC’s speed targets are available to 45.6 percent of households. Moreover, effective speeds and service quality levels that suppliers deliver and users experience tend to fall well below the government’s aspirational targets. In response to demand for better broadband, a variety of initiatives are directing public investment to the deployment of regional and rural broadband networks, which are typically owned and operated by private companies. There remains a serious lack of relevant data and its effective use in creating rural broadband strategies and managing public investment projects. Evidence from the literature suggest that this affects the degree and quality of geo-spatial and econometric analysis that results in a limited empirical basis to allocate scarce public investments, aggregate demand of consumers/communities, and assess the outcomes of rural broadband initiatives ex post. This paper provides a historical overview of rural broadband development in Canada and questions if the body of knowledge to inform public investment initiatives has grown sufficiently to ensure their effectiveness and sustainability. With a regional case from southwestern Ontario, Canada, we discuss the findings of the literature review, characterize the broadband data challenge, and discuss the importance of proprietary provider data cross-referenced with Internet user experience data.     

5G传输网络承载方案分析

5G时代3类典型场景的业务需求对承载网络在容量、时延和组网灵活性方面提出了更高的要求,同时针对无线网和核心网架构的变化提出了网络切片、增强路由转发功能等要求。首先分析5G的承载需求,重点考虑5G的3类典型业务场景、无线和核心网的架构变化;然后结合现网100GE PTN的实际应用情况,重点围绕容量、时延等维度完成需求与网络现状的对标;最后提出了网络回传、机房配套的演进方案。     

化成箔时间电压参数的测试精度与效率研究

介绍一种化成箔上升时间(tr)、到达电压(Vt)自动测试方案,包括电压取样电路的改进、压控恒流源设计及基于Kingview实现自动测试等技术。与目前行业标准相比,该方案Vt测试精度由0.5%提高到0.5‰,测试效率提高6倍;可同时测试3片样品,自动获取tr、Vt,并实时显示升压曲线。经六年的实际应用证明,该方案在技术指标和自动化程度方面达到了国外同类产品先进水平,可确保质量控制更准确、更及时,大大降低了报废率与次品率,同时为企业节省大量人力成本。     

两种接地条件下的片上变压器的分析与建模

本文在两种接地条件（即共地情况和隔离地情况）下分别设计制作了两个片上变压器,并对这两个片上变压器的不同特性进行了相应的测试与比较。借助于电磁场仿真软件,本文分别从电场和磁场两方面对两种接地条件下片上变压器的不同性能进行深入分析。从等效电路模型的角度考虑,片上变压器在这两方面（即电场和磁场方面）的差异可以归结为集总电容和集总电感的差异。基于物理意义,本文为两种接地条件下的片上变压器提供了等效电路模型。另外,针对相应等效电路模型的简单参数提取方法同样呈现在文中。本文对模型中的所有参数均进行提取,提取结果与前文的分析相吻合。为了检验所提出模型的有效性和准确性,本文比较了模型仿真和实际测试下的散射参数,发现两者在很宽的频率范围内均吻合得很好。     

互联网动态地址命名与解析服务

命名解析机制作为互联网的核心组件，其固化的静态设计以及可扩展性的缺失是导致体系结构陷入僵化的主要原因.针对网络核心层面的创新困境，提出了一种动态的命名与解析服务，允许按需设计、构建和部署多样的地址策略，灵活支撑顶层业务需求.基于xml的通用地址描述规范通过精心抽象的元素属性以及灵活的组合方式，提供了对异构命名模型的统一表达和解释能力；动态解析服务基于预先配置的对象绑定拓扑，支持新型命名空间、协议实体以及解析机制的透明引入.试验表明，通用命名与解析服务具备良好的可扩展性和时间性能，相比传统互联网地址系统，能够赋予网络核心层面的演进能力，从而为体系结构维度的创新提供良好支撑.     

车辆状态信息显示处理系统的研究与设计

介绍了基于CAN总线的车辆状态信息显示处理系统,分析了CAN.总线的特点及在汽车中使用CAN总线的优点,并给出了其在国内外汽车中的应用现状.首重介绍了系统的总体设计方案,系统的主节点、固定节点及活动节点的硬件组成和工作原理,以及大屏幕液晶显示器的特点及其在系统中的应用.     

高效双光子引发剂及水相中制备水凝胶微结构的研究进展

对双光子引发剂的设计合成和飞秒激光双光子聚合技术的基本原理进行了简单介绍。着重介绍了用于水凝胶双光子聚合的引发剂的研究进展,主要包括通过扩大共轭链长度、引入强供/吸电子基团、加入共引发体系等来增大双光子吸收截面,引入自由基淬灭基团以降低荧光量子产率,增加引发剂的水溶性来降低微结构细胞毒性等方面。这些研究为生物相容性三维水凝胶微纳结构的制备及应用提供了科学基础,是更好地模拟体内细胞生长微环境的必要条件。接着,介绍双光子聚合制备的水凝胶微纳结构及其在组织工程领域中的应用。最后,对生物相容性水凝胶微结构在应用中存在的问题与未来发展趋势进行总结和展望。     

单相无刷直流电机的设计分析与建模仿真

文中针对单相无刷直流电机结构设计及驱动方式展开研究,推导出电机理想工况下的基本方程,根据工程实际需求并结合无刷直流电机的设计原则确定该电机的设计方案。利用设计方案设计一台额定功率38 W,额定转速750 rpm的单相无刷直流电机,并分析了渐变气隙对电机起动性能和齿槽转矩的影响,确定了最优气隙长度。通过对比单极性绕组和双极性绕组形式的优缺点确定绕组形式,结合传统电机设计公式确定绕组匝数。文中利用有限元法初步验证了设计方案的合理性。根据电机动态数学模型在Simulink环境中搭建了电机系统的模型,仿真得到电机的转速、转矩变化曲线,结果与理论分析吻合良好,验证了电机设计方案的合理性和电机模型的有效性。     

基于FPGA的导航抗干扰接收机数字变频的实现

根据卫星信号结构、频率特征设计和实现了导航抗干扰接收系统中,基于软件无线电的上下变频模块。根据系统的A/D 采样频率与转换位数、阻带衰减要求、频率选择性、增益,输入输出频率在Matlab中建模。确定了DDC和DUC的设计方案,并在硬件上实现,重点是NCO和滤波器组设计,包括梳状滤波器、半带滤波器和补偿滤波器。构建完成系统后进行了仿真验证,可满足系统设计要求。