基于北斗的高速摄像机时间同步器设计

为了满足民用飞机在飞行试验中高速摄像机对时间同步的需求,基于国产北斗卫星导航系统设计了具有精确输出IRIG-B(AC)码的时间同步器,用于机载高速摄像机的精确时间同步。以FPGA为核心,使用直接数字频率合成技术实现了IRIG-B(AC)码的产生。实验结果表明,该同步器时间同步精度满足要求,可以实现对高速摄像机进行时间同步的功能。     

Output feedback control of discrete‐time systems with self‐triggered controllers

This paper is concerned with the self‐triggered output feedback control for discrete‐time systems, where an updating instants scheduler is implemented to determine when the controller is updated. For both the full‐order and reduced‐order observer cases, the updating instants are determined, respectively, where only the information of the estimated state at the current updating instant is required to obtain the next updating instant. It is shown that, with the proposed self‐triggered control schemes, not only the updating frequency is significantly reduced, but also the uniform ultimate boundedness of the closed‐loop system is guaranteed. Finally, a numerical example is used to verify the effectiveness and the merits of the proposed approaches. Copyright © 2014 John Wiley & Sons, Ltd.     

Design of a novel static-triggered power-rail ESD clamp circuit in a 65-nm CMOS process基于65纳米CMOS工艺的静态触发型电源钳位ESD保护电路设计

This work presents the design of a novel static-triggered power-rail electrostatic discharge (ESD) clamp circuit. The superior transient-noise immunity of the static ESD detection mechanism over the transient one is firstly discussed. Based on the discussion, a novel power-rail ESD clamp circuit utilizing the static ESD detection mechanism is proposed. By skillfully incorporating a thyristor delay stage into the trigger circuit (TC), the proposed circuit achieves the best ESD-conduction behavior while consuming the lowest leakage current (I_leak) at the normal bias voltage among all investigated circuits in this work. In addition, the proposed circuit achieves an excellent false-triggering immunity against fast power-up pulses. All investigated circuits are fabricated in a 65-nm CMOS process. Performance superiorities of the proposed circuit are fully verified by both simulation and test results. Moreover, the proposed circuit offers an efficient on-chip ESD protection scheme considering the worst discharge case in the utilized process.     

An overview of multi-antenna technologies for space-ground integrated networks

Multi-antenna technologies have already achieved a series of great successes in the development of information networks. For future space-ground integrated networks (SGINs), the traditional various kinds of separated information networks will converge to a whole fully connected information network to provide more flexible and reliable services on a world scale. Regarding their great successes in existing systems, multiantenna technologies will be of critical importance for the realization of SGINs and multi-antenna technologies are definitely one of the most important enabling technologies for future converged SGINs. In this article, a comprehensive overview on multi-antenna technologies is given. We first investigate multi-antenna technologies from a theoretical viewpoint. It is shown that we can understand multi-antenna technologies in a general and unified point of view. This fact has two-fold meanings. First, the research on multi-antennas can help us understand the relationships between different technologies e.g., OFDMA, CDMA, etc. On the other hand, multi-antenna technologies are easy to integrate into various information systems. Following that, we discuss in depth the potentials and challenges of the multi-antenna technologies on different platforms and in different applications case by case. More specifically, we investigate spaceborne multi-antenna technologies, airborne multi-antenna technologies, shipborne multi-antenna technologies, etc. Moreover, the combinations of multiantenna technologies with other advanced wireless technologies e.g., physical layer network coding, cooperative communication, etc., are also elaborated.     

基于细菌觅食算法的多线圈电- 机械转换器双模控制技术研究

针对提升电-机械转换器快速响应特性的技术需求,提出了新型三线圈结构电-机械转换器。通过建立的电-机械转换器数学模型,提出采用细菌觅食算法来寻找时间最优解,并基于此方法设计了砰-砰与比例-积分双模控制器。分析与仿真结果表明,相对于传统单线圈电-机械转换器,采用双模控制器的三线圈电-机械转换器,其响应时间从8.5 ms缩短至2.5 ms,震荡和超调不超过5%,可知该技术能够实现响应特性,前景良好。     

基于FPGA的QDPSK全数字通信电路的设计与实现

介绍了QDPSK基本原理,提出基于FPGA的全数字QDPSK通信方案。该方案对输入序列进行加扰、串并和差分运算,得到QDPSK,然后加到载波上;在接收端载波与信号分离,再进行解差分、解扰运算,还原出输入信号,实现QDPSK全数字调制与解调。整个系统采用Verilog编程,在MaxPlusⅡ环境仿真、布局和综合,最后下载到FPGA通过示波器观察输入输出信号,实验效果良好。     

故障诊断专家系统在水电厂的应用

水电机组故障诊断技术是水电厂开展状态检修的基础。水电机组作为大型旋转机械,其振动可以反映机组大部分故障。专家系统是人工智能领域应用比较成熟的技术,现在故障诊断专家系统已在国内水电厂逐步推广。本文在水电机组状态监测的基础上,针对水电机组的振动故障,提出一种基于产生式规则的专家系统。它主要由知识库、推理机、数据库、人机接口等部分组成。最后,利用实际数据进行诊断和分析,并根据机组检修情况对诊断结果进行验证,证明专家诊断系统能够给检修人员提供机组故障产生的可能原因和部位,对机组检修起到一定的指导作用。     

A novel two-box search paradigm for query disambiguation

Precision-oriented search results such as those typically returned by the major search engines are vulnerable to issues of polysemy. When the same term refers to different things, the dominant sense is preferred in the rankings of search results. In this paper, we propose a novel two-box technique in the context of Web search that utilizes contextual terms provided by users for query disambiguation, making it possible to prefer other senses without altering the original query. A prototype system, Bobo, has been implemented. In Bobo, contextual terms are used to capture domain knowledge from users, help estimate relevance of search results, and route them towards a user-intended domain. A vast advantage of Bobo is that a wide range of domain knowledge can be effectively utilized, where helpful contextual terms do not even need to co-occur with query terms on any page. We have extensively evaluated the performance of Bobo on benchmark datasets that demonstrates the utility and effectiveness of our approach.     

射阳河挡潮闸闸下冲淤特性分析

根据实测资料分析了射阳河挡潮闸建闸前后水动力条件及泥沙条件的变化,从下泄水量减少、潮波变形和潮流量变化三方面及其所引起的泥沙条件的改变分析闸下淤积原因,得到三者与河道冲淤的基本关系.从淤积的时空分布形态来描述射阳河近年闸下河道的冲淤特性:射阳河建闸初期淤积严重,之后淤积量减少并且冲淤交替,总体仍呈淤积趋势,经历裁弯取直后发展至今,冲淤总量基本达到平衡,但河道内仍存在较大幅度冲淤.     

乌梁素海污染负荷动态变化分析

地处半干旱区域的乌梁素海既是河套灌区灌排系统的重要组成部分,也是维护湖泊流域生态系统良性发展的关键所在.对乌梁素海2006-2008年气象因子和入湖污染负荷的变化规律分析结果表明:入湖水体中含有的大量氮、磷、有机物、离子等物质,是造成目前乌梁素海水体富营养化和有机物质、盐化等污染的主要原因,提高入湖水质是治理乌梁素海的关键.