Quadrature Oscillators with Grounded Capacitors and Resistors Using FDCCIIs

Two current‐mode and/or voltage‐mode quadrature oscillator circuits each using one fully‐differential second‐generation current conveyor (FDCCII), two grounded capacitors, and two (or three) grounded resistors are presented. In the proposed circuits, the current‐mode quadrature signals have the advantage of high‐output impedance. The oscillation conditions and oscillation frequencies are orthogonally (or independently) controllable. The current‐mode and voltage‐mode quadrature signals can be simultaneously obtained from the second proposed circuit. The use of only grounded capacitors and resistors makes the proposed circuits ideal for integrated circuit implementation. Simulation results are also included.     

ZBO(ZnO∶B)靶材烧结机理与特征的研究

用常压烧结方法，在1200℃-1350℃烧结不同含B量的掺硼氧化锌（ZBO）靶材。研究了掺杂量、烧结温度对ZBO靶材微观结构的影响。实验表明，随着烧结温度的增加。ZBO陶瓷的晶粒大小和密度逐渐增大。指出了由于B2O3的挥发，造成ZBO靶材的剩余含B量与掺B量的不符，要获得含定量B的ZBO就必须掺入大约2倍所需量的B2O3。     

A scalable, power-efficient broadcast algorithm for wireless networks

Scalability and power-efficiency are two of the most important design challenges in wireless ad hoc networks. In this paper, we present a scalable, power-efficient broadcast algorithm for wireless ad hoc networks. We first investigate the trade-off between (i) reaching more nodes in a single hop using higher transmission power and (ii) reaching fewer nodes using lower transmission power and relaying messages through multiple hops. Our analysis indicates that multi-hop broadcast is more power-efficient if α ≥ 2.2, where α is the path loss exponent in the power consumption model P(r,α) = c₀⋅ r^α+c₁. Based on the analysis, we then propose Broadcast over Local Spanning Subgraph (BLSS). In BLSS, an underlying topology is first constructed by a localized topology control algorithm, Fault-Tolerant Local Spanning Subgraph (FLSS). FLSS can preserve k-connectivity of the network, where the value of k determines the degree of fault tolerance. Broadcast messages are then simply relayed through the derived topology in a constrained flooding fashion. BLSS is fully localized, scalable, power-efficient, and fault-tolerant. Simulation results show that the performance of BLSS is comparable to that of centralized algorithms. Ning Li received the B.E. and M.E. degrees from Department of Automation, Tsinghua University, Beijing, PR China, in 1998 and 1999, respectively, and the M.S. degree in Computer Engineering from The Ohio State University, Columbus, OH, in 2001 and the Ph.D. degree in Computer Science from University of Illinois at Urbana-Champaign, Urbana, IL. His research interests include design and analysis of wireless mobile ad hoc networks and sensor networks, large-scale network simulation and emulation, and distributed and mobile computing. Jennifer C. Hou received her Ph.D. from The University of Michigan, Ann Arbor, MI in 1993. She is currently a professor in the Department of Computer Science at University of Illinois at Urbana-Champaign, Urbana, IL. Dr. Hou has been supervising several federally and industry funded projects in the areas of network modeling and simualtion, network measurement and diagnostics, enabling communication software for assisted living, and both the theoretical and protocol design aspects of wireless sensor networks. She has published (with her former advisor, students, and colleagues) over 125 papers and book chapters in archived journals and peer-reviewed conferences, and released a truly extensible, reusable, component-based, compositional network simulation and emulation package, J-Sim. She has also served on the TPC of several major networking, real-time, and distributed systems conferences/symposiums, such as IEEE INFOCOM, IEEE ICNP, IEEE ICDCS, IEEE RTSS, IEEE ICC, IEEE Globecome, ACM Mobicom, and ACM Sigmetrics. She is the Technical Program Co-chair of 27th IEEE INFOCOM 2008, First International Wireless Internet Conference 2005, ACM 3rd Information Processing in Sensor Networks (IPSN 2004) and IEEE Real-time Technology and Application Symposium (RTAS 2000). She is severing on the editorial board of IEEE Trans. on Wireless Communications, IEEE Trans. on Parallel and Distributed Systems, IEEE Wireless Communication Magazine, ACM/Kluwer Wireless Networks, Kluwer Computer Networks, and ACM Trans. on Sensor Networks. Dr. Hou was a recipient of an ACM Recognition of Service Award in 2004, a Lumley Research Award from The Ohio State University in 2001, a NSF CAREER award in 1996–2000 and a Women in Science Intiative Award from The University of Wisconsin—Madison in 1993–1995.     

Automated passive filter synthesis using a novel tree representation and genetic programming

This paper proposes a novel tree representation which is suitable for the analysis of RLC (i.e., resistor, inductor, and capacitor) circuits. Genetic programming (GP) based on the tree representation is applied to passive filter synthesis problems. The GP is optimized and then incorporated into an algorithm which can automatically find parsimonious solutions without predetermining the number of the required circuit components. The experimental results show the proposed method is efficient in three aspects. First, the GP-evolved circuits are more parsimonious than those resulting from traditional design methods in many cases. Second, the proposed method is faster than previous work and can effectively generate parsimonious filters of very high order where conventional methods fail. Third, when the component values are restricted to a set of preferred values, the GP method can generate compliant solutions by means of novel circuit topology.     

北京及邻区荒漠化动态演化的遥感综合研究

在研究区野外实际调研和地质、水文、气象、人文环境、土壤质地等荒漠化相关多源信息研究的基础上，对1987、1996年TM及2000年CBERS－1的CCD三个时相遥感影像的处理和分析，提取了研究区荒漠化轻、中、重三个级别的面积，实现了不同时相遥感图像的数据融合与动态对比分析，结合研究区DEM影像分析获得了北京及邻区荒漠化分布和动态演化的时空信息，并由此得出研究区荒漠化存在两种演化类型：在相对干旱的研究区北部（康保至多伦）以面蚀为主体，荒漠化主要受风蚀作用呈面状分布与演化；研究区的西南部以沟蚀为主体，主要受水蚀作用沿洋河、大洋河和永定河呈线状分布与演化。研究区荒漠化总体表现为北强南弱，荒漠化主要发展及演化趋势位于距北京以北百余公里以外的康保至多伦地区，其方向为由西向东，因此，北京地区的荒漠化程度总体低于以北周边地区。     

一种视觉增强环境中的快速目标定位映射算法

文章对在视觉增强的交互系统中所面临的利用图像校正数据进行定位和映射的问题进行了研究,针对交互系统应用的实时性特征,提出了一种快速高效的双四边形定位和映射算法。该算法克服了采用传统方法所可能引起的耗时低效的缺点,利用一定的近似性原理,较好地满足了交互系统定位过程中的高效性和精确性需求。该算法应用于人机交互系统VIPwin中,实践证明达到了很好的效果。     

野战防空CGF系统的构造与建模

首先阐述了构造计算机生成兵力CGF的意义和特点,然后介绍野战防空CGF的组成结构,最后叙述了野战防空CGF系统中的重要对象:雷达、地对空导弹和高炮等的建模方法及特点,并给出仿真评论。     

复杂背景图像中检测动目标的一种方法

该文研究了基于Kalman滤波理论的渐消记忆递归最小二乘法,探讨了渐消记忆递归最小二乘法在重建图像背景中的应用,并用于实现在复杂背景下视频图像动目标的检测。首先用该算法对复杂背景进行更新预测,然后用当前帧图像与预测背景差分提取动目标,最后用灰度投影算法计算出目标的质心。整个目标检测方法简单、有效,便于用硬件快速实现。文中给出了实验结果。     

基于XML的“虚拟购物Agent”的系统设计研究

XML在电子商务的两个重要方面起到重要作用:内容定义和信息交换。文章所提出的“虚拟购物Agent”模型充分利用了XML的这两大新特性,是对新的电子商务发展的有益探讨。该模型通过帮助用户搜索各种型号、价格的商品并代理用户提交订单,使得在用户方看来,整个Internet就象一个单一的数据库,无须明确具体商家和相关服务站点,整个选购过程简单、明晰。并且有效地减少了服务器间的连接次数,优化网络特性,还能真正地实现客户端的个人化。     

基于耦合边界条件的发电机定子非线性温度场计算

介绍了求解大型同步发电机的定子温度场的三维等参元法 ,利用径向通风沟壁面温度、径向通风沟表面散热系数和风沟中风速三者耦合关系 ,解决了流体与构件耦合场的数值求解问题 ,并用有限元法对影响定子温度场的进风口风速进行了数值模拟 ,得出了相应的结论