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介绍了光纤陀螺的磁敏感性机理并进行了实验研究。利用亥姆霍兹线圈装置和光纤陀螺测试平台,研究了光纤陀螺在直流磁场中的磁敏感性,得到光纤陀螺数据输出与磁感应强度基本呈线性关系,以及轴向磁场和径向磁场影响系数的大小和光纤陀螺磁敏感轴的方向。主要针对50Hz的交流磁场研究交流磁场对光纤陀螺零偏和零漂的影响及其交流磁敏感性,得到交流磁场对零偏的影响可以忽略,但磁感应强度与陀螺零漂值的大小基本呈线性关系。研究了不同频率交流磁场对光纤陀螺输出的影响,说明了光纤陀螺数据输出主要与瞬态的磁感应强度成正比,不同频率交流磁场对光纤陀螺零漂值的影响不同,存在一个频率(或频率范围)对光纤陀螺零漂的影响较大,其频率范围与光纤陀螺输出带宽有关。 相似文献
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光纤陀螺对温度比较敏感,由于温度引起的零偏漂移是光纤陀螺工作尤其是启动过程中的一种较大误差。文中为了减小光纤陀螺启动过程的零偏漂移、缩短启动时间,提出了对光纤陀螺启动过程进行补偿的方案。该方案以光纤陀螺温度和温度变化率为输入、光纤陀螺漂移为输出建立二输入单输出的RBF神经网络,用于陀螺启动过程补偿。在室温下对某型号光纤陀螺启动漂移进行了补偿,试验结果表明该方法能有效减小陀螺的启动温度漂移,缩短陀螺启动时间。将该方案运用到某型号的光纤陀螺寻北仪上,常温试验表明,该方案大大缩短了寻北仪的准备时间,提高了寻北精度。 相似文献
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在光纤陀螺中,保偏光纤性能的优劣直接影响陀螺的输出精度和温度特性.理论分析了光纤参数,特别是光纤涂层与陀螺稳定性的关系,通过改善特定的光纤涂层指标,光纤在时变温度场下的可靠性得到提高,并最终保证了陀螺具有更强的抗环境干扰能力.将理论预测与实际工程应用相结合,采用改进后的保偏光纤绕制的陀螺,表现出了更好的温度性能,基于对保偏光纤特性的理论和初步实验研究,强调了一直以来被忽视的保偏光纤参数在光纤陀螺应用中的重要性. 相似文献
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David C. Look 《Journal of Electronic Materials》2006,35(6):1299-1305
ZnO is a wide-band-gap semiconductor material that is now being developed for many applications, including ultraviolet (UV)
light-emitting diodes, UV photodetectors, transparent thin-film transistors, and gas sensors. It can be grown as boules, as
thin films, or as nanostructures of many types and shapes. However, as with any useful semiconductor material, its electrical
and optical properties are controlled by impurities and defects. Here, we consider various important donor-type impurities,
such as H, Al, Ga, and In, and acceptor-type impurities, such as N, P, As, and Sb. We also examine the effects of a few common
point defects, including Zn interstitials, Zn vacancies, O vacancies, and complexes of each. The main experimental techniques
of interest here include temperature-dependent Hall-effect and low-temperature photoluminescence measurements, because they
alone can provide donor and acceptor concentrations and donor energies. The important topic of p-type ZnO is also considered
in some detail. 相似文献
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植物园(含树木园)以科学研究、保护、展示和教育为目的,收集保存活植物并保有其档案记录。其主要任务是迁地保护植物多样性、实现其资源的可持续利用,开展相应的植物展示、科普教育和科学研究。全世界现有约2 000个各种类型的植物园和树木园,保存了80 000种植物,包括许多珍稀、濒危的植物种类。中国的植物园目前已达约160个,在植物引种、驯化、开发利用、保护方面取得了巨大成绩,在科普教育、旅游服务方面的重要性得到承认。植物园工作者在相关研究领域取得了理论和技术的创新成果,在管理、政策、培训和植物记录系统计算机化方面也在和世界接轨。面临生物多样性保护与可持续发展的挑战和机遇,我们期待中国的植物园在建园、植物收集保存、科普旅游、能力建设、科学研究等领域取得更大成绩,更好地满足经济和社会发展、环境和资源保护利用的需求,与世界植物园同步前进。 相似文献
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Yang Li Guangze Yang Lukas Gerstweiler San H. Thang Chun-Xia Zhao 《Advanced functional materials》2023,33(7):2210387
Stimuli-responsive peptides and proteins are an exciting class of smart biomaterials for various applications and have received significant attention over the past decades. A wide variety of stimuli such as temperature, pH, ions, enzymes, magnetic field, redox, etc., are explored. This article provides a review of five intensively studied types of stimuli-responsive peptides and proteins, their design principles and applications, including temperature-, pH-, light-, metal ion-, and enzyme-responsive with an emphasis on the key design concepts and switch function. Moreover, typical examples of their applications are discussed to provide a better understanding of the design concept and underlying methodology. This review will facilitate and inspire future innovation toward new peptide- and protein-based materials and their diverse applications. 相似文献
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ARX(Addition,Rotation,Xor)算法基于模整数加,异或加和循环移位三种运算,便于软硬件的快速实现.不可能差分分析和零相关分析是攻击ARX的有效方法,攻击的关键是搜索更长轮数、更多数量的不可能差分和零相关区分器.目前很多的搜索方法都没有充分考虑非线性组件的性质,往往不能搜索得到更好、更准确的区分器.本文提出了基于SAT(Satisfiability)的ARX不可能差分和零相关区分器的自动化搜索算法.通过分析ARX算法组件的性质,特别是常规模加和密钥模加这两种非线性运算差分和线性传播的特性,给出了高效简单的SAT约束式.在此基础上,建立SAT模型进行区分器的搜索.作为应用,本文首次给出了Chaskey算法13条4轮不可能差分和1条4轮零相关区分器;首次给出了SPECK32算法10条6轮零相关区分器和SPECK48算法15条6轮零相关区分器;在较短的时间内,给出了HIGHT算法17轮的不可能差分和零相关区分器.与现有结果相比,无论是区分器的条数,还是搜索区分器的时间均有明显的提升.此外,通过重新封装求解器STP的输出接口,建立了自动化的SAT\\SMT分析模型,能够给出ARX算法在特殊输入输出差分和掩码集合下,不可能差分和零相关区分器轮数的上界. 相似文献
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《Digital Communications & Networks》2017,3(4):260-273
At present, big data is very popular, because it has proved to be much successful in many fields such as social media, E-commerce transactions, etc. Big data describes the tools and technologies needed to capture, manage, store, distribute, and analyze petabyte or larger-sized datasets having different structures with high speed. Big data can be structured, unstructured, or semi structured. Hadoop is an open source framework that is used to process large amounts of data in an inexpensive and efficient way, and job scheduling is a key factor for achieving high performance in big data processing. This paper gives an overview of big data and highlights the problems and challenges in big data. It then highlights Hadoop Distributed File System (HDFS), Hadoop MapReduce, and various parameters that affect the performance of job scheduling algorithms in big data such as Job Tracker, Task Tracker, Name Node, Data Node, etc. The primary purpose of this paper is to present a comparative study of job scheduling algorithms along with their experimental results in Hadoop environment. In addition, this paper describes the advantages, disadvantages, features, and drawbacks of various Hadoop job schedulers such as FIFO, Fair, capacity, Deadline Constraints, Delay, LATE, Resource Aware, etc, and provides a comparative study among these schedulers. 相似文献
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VoIP技术--语音和数据的集成 总被引:2,自引:0,他引:2
介绍了VoIP(Voice over IP)的基本组成构件即网关(Gateway)、网守(Gatekeeper)的概念和用途。讲述了语音在IP网上传输的基本原理,语音和数据、数据和IP包之间的转换和传送过程。在H.323协议栈的基础上详细讲述了H.248,H.225,H.245等通信协议和语音编码G.729,G.23l,G.7ll等协议。最后对VoIP的语音服务质量作了较为详细的阐述。 相似文献
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Nonaqueous conversion‐reaction sulfur chemistry has been attracting increasing attention over the past decade for the development of next‐generation lithium‐based batteries. Li–S batteries are currently approaching a nexus stage from lab‐scale experiments to possible pragmatic applications. Inspired by the success of Li–S chemistry, other metal–sulfur batteries with a variety of metallic anodes, such as sodium, potassium, magnesium, calcium, and aluminum, have also started to attract attention. In comparison to lithium, Na, Mg, Al, K, and Ca are naturally more abundant and affordable. The Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S battery systems provide a great potential for improving the volumetric energy density of sulfur‐based batteries. The multivalent metal‐sulfur systems, Mg‐S, Al‐S, and Ca‐S, offer better safety features as well. However, the research and development on Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S batteries is far behind the Li–S system due to many critical challenges. In this progress report, the fundamental principles of various metal–sulfur chemistries are first presented and compared. Then, the historical progress, recent advances, and key challenges of the Li–S, Na‐S, Mg‐S, Al‐S, K‐S, and Ca‐S systems are summarized and discussed. Finally, future efforts and directions for both the fundamental and practical research are prospected. 相似文献
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In this paper, we investigate the Multiple-Input Multiple-Output (MIMO) channel capacity in indoor Ricean channels based on MIMO channel measurements at 2.45 GHz. The measured data is analysed using a super resolution parameter estimation algorithm. Our results demonstrate that the line-of-sight (LOS) component in a Ricean scenario influences indoor MIMO performance through increased spatial correlation between array elements. We found that indoor channels with higher values of Ricean K factor have smaller numbers of effective multipath components and increased spatial correlation. Measurement results also showed that, the effect of varying antenna height on indoor MIMO capacity is also due to the spatial correlation of multipath propagation and has a close relationship with the separation between the transmitter and receiver.
Zhongwei Tang is currently with the Wireless Technologies Laboratory at CSIRO. He was with Microwave and Wireless Technology Research Laboratory (MWTRL), Information and Communication Group, Faculty of Engineering of the University of Technology Sydney, Australia, where he pursued his Ph.D. Degree. His current research interests include RF propagation, MIMO Space-Time channel measurements, characterization and channel modelling, smart antennas, MIMO systems and array signal processing.
Ananda S. Mohan is currently a member of the Faculty of Engineering, University of Technology, Sydney (UTS), Australia where he leads research on antennas, microwaves, wave propagation, and wireless technology. He received a Ph.D. degree in electrical communication engineering from the Indian Institute of Technology, Kharagpur, India and was a Scientist and Senior Scientist at the Research and Training Unit for Navigational Electronics, Hyderabad, India. At UTS, he directed the Sydney microwave design resource centre and was the associate program leader of the co-operative research centre for satellite systems. He currently directs the microwave and wireless technology research laboratory and a core member of the university research centre on health technologies. His current teaching and research interests include wireless mobile communications, microwaves and antennas, smart antennas and applications of microwave and wireless technology in medicine and has obtained many competitive research grants in these areas. Dr. Mohan was a co-recipient of the Priestly memorial award from the Institute of Radio and Electronic Engineers (IREE), Australia. He was a member of the organizing and technical Program Committees of the IEEE Globecom'98, APMC 2000, and International Symposium on Wireless Systems and Networks, 2003 and IASTED International Conference on Antennas, Radar, and Wave Propagation, for 2004 and 2005. 相似文献
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为推动城市智能建筑管理新技术的开发和应用,针对工程实际问题,提出了一种支持冗余和兼容设计的城市智能建筑综合管理系统的设计方案.系统设计内容包括为楼宇控制、照明控制和停车引导控制设计的同一架构的CPU模块及软件、通信网关模块及软件、集中控制模块及软件、I/O模块及软件、无线模块、超声波检测模块及内部总线等,并阐述和分析了总线冗余、设备兼容性和集成监控软件等系统关键技术.系统具有先进的分布式系统、开放的网络化通信和标准化程序设计等多项新特性,可以显著提升大型城市建筑的智能化和节能管理水平. 相似文献
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在数字化中国的大背景下,在公司个人宽带与互动电视在线交费用户均突破300万户的情况下,为解决我们的用户总找不到自己喜欢看的节目,记不住频道名称和喜欢的节目,提升公司竞争力。通过对前端的点播系统、AAA系统、EPG系统、PORTAL系统、ISMP系统、媒资系统、机顶盒终端的功能进行剥离、整合和详细设计,最后完成终端用户语音操控电视直播、点播、时移、回看、页面操控、系统设置,并支持普通话和四川话方言的目的。达到提升用户体验,增加公司竞争力,促进业务的发展。系统试运行后,用户体验效果得到很大提升,完全达到预期设计目的。 相似文献