D类功放在便携式设备中的应用

采用D类放大器可延长电池供电终端产品的工作时间,并产生更少的热量,因此高效率D类音频功率放大器正越来越多地被用在移动电话、智能电话、PDA及其他类似便携式应用中,以取代AB类放大器。简单陈述了D类功放的原理,并以TI公司的芯片TPA2012D2为例,着重介绍了该芯片在便携式媒体播放器(PMP)中的应用实例。该例在实际应用中得到较好的音频播放表现。     

On designing incentive-compatible routing and forwarding protocols in wireless ad-hoc networks

In many applications, wireless ad-hoc networks are formed by devices belonging to independent users. Therefore, a challenging problem is how to provide incentives to stimulate cooperation. In this paper, we study ad-hoc games—the routing and packet forwarding games in wireless ad-hoc networks. Unlike previous work which focuses either on routing or on forwarding, this paper investigates both routing and forwarding. We first uncover an impossibility result—there does not exist a protocol such that following the protocol to always forward others' traffic is a dominant action. Then we define a novel solution concept called cooperation-optimal protocols. We present Corsac, a cooperation-optimal protocol which consists of a routing protocol and a forwarding protocol. The routing protocol of Corsac integrates VCG with a novel cryptographic technique to address the challenge in wireless ad-hoc networks that a link’s cost (i.e., its type) is determined by two nodes together. Corsac also applies efficient cryptographic techniques to design a forwarding protocol to enforce the routing decision, such that fulfilling the routing decision is the optimal action of each node in the sense that it brings the maximum utility to the node. We evaluate our protocols using simulations. Our evaluations demonstrate that our protocols provide incentives for nodes to forward packets. Additionally, we discuss the challenging issues in designing incentive-compatible protocols in ad hoc networks. Part of this paper appeared in a conference version [49]. Sheng Zhong was supported in part by NSF grants ANI-0207399 and CNS-0524030. Yang Richard Yang was supported in part by NSF grants ANI-0207399, ANI-0238038, and CNS-0435201. This work was partly done while Sheng Zhong was at Yale University; Yanbin Liu was at University of Texas at Austin. Sheng Zhong is an assistant professor in the State University of New York at Buffalo. He received his PhD (2004) from Yale University and his ME (1999), BS (1996) from Nanjing University, China, all in computer science. His research interests include economic incentives and privacy protection, particularly incentive and privacy problems in mobile computing and data mining. Li Erran Li received his B.E. in Automatic Control from Beijing Polytechnic University in 1993, his M.E. in Pattern Recognition from the Institute of Automation, Chinese Academy of Sciences, in 1996, and his Ph.D. in Computer Science from Cornell University in 2001 where Joseph Y. Halpern was his advisor. He is presently a member of the Networking Research Center in Bell Labs. His research interests are in networking with a focus on wireless networking and mobile computing. He has served as a program committee member for several conferences including ACM MobiCom, ACM MobiHoc, IEEE INFOCOM and IEEE ICNP. He is a guest editor for JSAC special issue on Non-Cooperative Behavior in Networking. He has published over 30 papers. Yanbin Liu received her B.E. degree in Computer Science and Technology from Tsinghua University (1993), Beijing, China, in 1993, and her M.S. degree in Computer Science from the University of Texas at Austin (1998), where is a Ph.D. candidate. Since 2006, he has been with IBM TJ Watson Research Center, Hawthorne, NY. Her research interests are in real-time systems, grid computing, mobile computing, and computer networks. Yang Richard Yang received his B.E. degree in Computer Science and Technology from Tsinghua University, Beijing, China, in 1993, and his M.S. and Ph.D. degrees in Computer Science from the University of Texas at Austin in 1998 and 2001, respectively. Since 2001, he has been with the Department of Computer Science, Yale University, New Haven, CT, where currently he is an Associate Professor. His current research interests are in computer networks, mobile computing, and sensor networks. He leads the Laboratory of Networked Systems (LANS) at Yale University.     

Determining correspondence in 3-D MR brain images using attribute vectors as morphological signatures of voxels

Finding point correspondence in anatomical images is a key step in shape analysis and deformable registration. This paper proposes an automatic correspondence detection algorithm for intramodality MR brain images of different subjects using wavelet-based attribute vectors (WAVs) defined on every image voxel. The attribute vector (AV) is extracted from the wavelet subimages and reflects the image structure in a large neighborhood around the respective voxel in a multiscale fashion. It plays the role of a morphological signature for each voxel, and our goal is, therefore, to make it distinctive of the respective voxel. Correspondence is then determined from similarities of AVs. By incorporating the prior knowledge of the spatial relationship among voxels, the ability of the proposed algorithm to find anatomical correspondence is further improved. Experiments with MR images of human brains show that the algorithm performs similarly to experts, even for complex cortical structures.     

A heuristic method for design of survivable WDM networks with p-cycles

We consider a new heuristic method for design of survivable wavelength-division multiplexing (WDM) networks with preconfigured protection cycles (p-cycles). Numerical studies show that the new heuristic works well for different traffic patterns, and the spare capacity obtained by the new heuristic is very close to that of the optimal solution but with much reduced computational time.     

一种基于HVS和DC分量的DCT域数字水印算法

为增强数字水印的透明性和鲁棒性,提出了一种基于人类视觉系统和直流分量的DCT变换域数字水印算法。算法依据原始图像的纹理掩蔽特性确定水印信息的嵌入位置,依据照度掩蔽特性确定水印信息的嵌入强度,将二值水印图像嵌入到原始图像在DCT域的直流分量中。在仿真实验中与同等条件下的中频嵌入做比较,实验结果表明,该算法提取的水印具有良好的透明性和鲁棒性。     

统一通信在商务领航平台上的实现

电信现网上分布着各种通信能力,在互联网上也分布多种通信能力,本文说明了如何将这些分布的通信能力进行融合,提供跨运营商、跨网络架构、跨业务平台、面向客户的统一通信业务,介绍了存商务领航企业信息化平台上的具体实现,分析了业务实现中难点和主要技术.     

基于方向性小波变换的图像稀疏修复

图像修复有着重要的应用价值,稀疏表示作为前沿的信号处理方法,也已经使用在图像修复中。但是,传统方法在稀疏图像的时候利用的是预先给定的图像基,不能自适应图像,因此稀疏表示能力有限。文中提出从参考图中估计出图像的最佳几何方向使得稀疏变换能自适应图像几何信息,提供更稀疏的图像表示方法。稀疏修复通过最小化1范数模型进行求解。实验结果表明,所提方法较传统的二维小波变换可以更好地保留图像中边缘和纹理,获得更高的峰值信噪比。     

具有e指数关联噪声的单模激光的光强关联函数和含时矩

利用线性近似方法 ,推导了由e指数关联噪声驱动的单模激光增益模型的光强关联函数和含时矩 ,利用计算机技术分析了它们随时间的演化特征 ,发现了一些奇特的现象 ,即在一定条件下 ,光强关联函数及含时矩随时间的演化曲线均会出现双极值     

高速数字设计中的反射分析

随着集成电路开关速度的提高以及PCB（Printed Circuit Board）板密度的增加,信号完整性问题已成为高速PCB设计必须关注的问题之一,对信号进行完整性分析已经成为高速数字电路设计中的一个必要环节。本文介绍了高速PCB设计中出现的信号完整性问题,对相关的时序、反射、串扰和地弹等问题进行了深入讨论,并利用Hyperlynx对其作了相应的仿真。根据以上研究的结果,比较了不同的端接策略,验证了解决方案的有效性,也进一步表明信号完整性分析对于高速PCB设计的重要性。     

Tunable Terahertz Source Based on Optics Pumped Nonlinear Crystals

Recent progresses about optical pumped tunable terahertz （THz） sources are interviewed, including THz parametric oscillation （TPO） and difference frequency generation （DFG）. We develop high efficiency and high power surface-emitted TPO, as well as DFG with nonlinear crystals. A novel scheme for the high efficiency DFG source based on the Cherenkov phase-matching technology is comprehensively investigated in both bulk crystals. The widely tunable optical THz radiation is also researched based on the organic nonlinear 4-N,N-dimethylamino-4＇-N＇- methylstilbazolium 2,4,6-trimethylbenzenesulfonate （DSTMS） crystal.