用Encounter实现Mesh-Local-Tree结构的时钟设计流程

提出了一种实用的设计流程,即在Cadencd公司的Encounter环境中去实现对网格 本地树(MLT)时钟结构的综合与分析方法.对一个实际工业设计试验的数据表明:运用Clockmesh CRS的综合方式,MLT的时钟架构相对于单一的树结构能够实现更小的时钟偏差(114ps、 171ps).同时,将这种设计流程运用于其他设计中,以比较MLT和CTS不同的设计流程.结果显示,MLT的时钟架构可以实现更小的时钟偏差,同时还可以降低缓冲器的数量,这样也弥补了单一网格结构的功耗问题.     

Planar clock routing for high performance chip and packageco-design

A new concept of chip and package co-design for the clock network is presented in this paper. We propose a two level clock distribution scheme which partitions the clock network into two levels. First, the clock terminals are partitioned into a set of clusters. For each cluster, a local on-chip clock tree is used to distribute the clock signal from a locally inserted buffer to terminals inside this cluster. The clock signal is then distributed from the main clock driver to each of local buffers by means of a global clock tree, which is a planar tree with equal path lengths. With the flip chip area I/O attachment, the planar global clock tree can be put on a dedicated package layer. The interconnect on the package layer has two to four order smaller resistance than that on the chip layer. The main contribution of this paper is a novel algorithm to construct a planar clock tree with equal path lengths-the length of the path from the clock source to each destination is exactly the same. In addition, the path length from the source to destinations is minimized     

SMART: a many-to-many multicast protocol for ATM

We present a protocol for controlling a shared ATM multicast tree supporting many-to-many communication. The protocol supports one or several ATM virtual channel connections (VCCs) of the many-to-many type. The number of VCCs is independent of the number of endpoints. The protocol guarantees that there is no interleaving on any VCC of the tree. The protocol also guarantees that the traffic contract associated with the VCCs is respected, thus making it possible to use ordinary VCCs of the constant bit rate (CBR), variable bit rate (VBR), or unspecified bit rate (UBR) class. No resequencing server or cell buffering inside the network is required, and all cell forwarding is performed at the ATM layer. We describe the protocol both informally and formally     

利用车载激光点云的分车带识别及单木分割方法

提出了一种基于车载激光点云数据的城区分车带识别及单木点云分割方法,首先通过布料模拟算法进行点云滤波去除地面点,然后利用基于八叉树连通性分析对非地面点进行聚类并构建聚类单元的最小包围矩形,基于先验知识和高差约束进行分车带识别,最后根据单木的空间几何特征,引入基于局部最高点的区域生长算法实现分车带内点云单木分割。选取北京市某道路的车载激光点云数据进行实验,结果表明:该方法能够从车载激光点云中快速识别出分车带点云并完成单木分割,能达到较好的识别和分割效果,具有抗噪性强和提取精度高的特点。     

An active networking based service for media transcoding in multicast sessions

Active networking is one of the suggested technologies to introduce additional intelligence and programmability in the network and its services. In this paper, the use of active networking to support advanced multicast services providing media transcoding inside the network is investigated. In the multicast service different versions of the streamed data are made available and customers can select a specific version according to their wishes or their capabilities. Based on the active networking facilities of the underlying framework the different versions of the streamed data can be created inside the network, through transformations or transcodings of the original data. Both design and performance issues of the detailed service are discussed. A new multicast tree set-up protocol, taking into account the required transcodings, is introduced. A number of different strategies are discussed optimizing the location of the transcodings as well as the use of bandwidth in the network, while considering the availability of sufficient processing power in the nodes. The performance analysis is done for a voice stream multicast service, addressing the efficiency of the tree set-up strategies, the optimization of network resource utilization, the use of processing power for transcodings, and the resulting quality of streamed voice signals after multiple transcodings.     

支持空间迷你时槽重用的IEEE 802.16Mesh网络多播调度算法

In this paper, we propose a mechanism for multicast data transmission in IEEE 802.16 mesh networks aimed at increasing the throughput by incorporating mini-slot spatial reuse. The proposed mechanism includes two novel algorithms: a source-based multicast tree topology construction algorithm followed by an interference-aware multicast scheduling algorithm. The proposed multicast interfer-ence-aware scheduling algorithm can be ap-plied to both source-based and rendez-vous-based multicast tree topologies. Results of our simulation study show that in compari-son to the mechanism used for the IEEE 802.16’s standard, the proposed multicast tree generation algorithm reduces the number of consumed mini-slots by 64% on average. Moreover, using the proposed interfer-ence-aware scheduling algorithm decreases the number of required mini-slots by a further 22% on average. Therefore, the proposed multicast scheduling mechanism shows a higher throughput than the previous ap-proaches and it is more scalable with respect to increasing the number of multicast groups as well as increasing the number of members inside each multicast group.     

A waveguide irradiation chamber for destruction of red palm weevils (Rhynchophorus ferrugineus) inside a block sample of a palm tree trunk.

A simple waveguide irradiation chamber at 2.45 GHz. was locally constructed for controlled laboratory experiments to assess the potentiality of using microwave heating for irradiation of weevils (RPW) inside healthy and infected palm tree trunks. The chamber consists of an aluminum rectangular waveguide with one of its broad sides removed for easy insertion of the block samples of the palm tree trunk. A rectangular aluminum plate, with the same dimensions as the removed wall section was made to slide-in and cover the tree block sample after its insertion in the waveguide to insure continuity of metallic walls. Temperature rise in the samples were monitored by thermocouples inserted through holes drilled at different positions along one of the waveguide side walls. Results showed that 100% mortality rate could be obtained with the RPW samples at distances not more than 2-3 cm from the leading edge of healthy tree block samples and 4-5 cm from leading edge of infected samples. Hot spots were observed at the leading edge of the tree samples due to high absorption of microwave at these regions.     

Ant colony optimisation for tree-searching-based synthesis of monopulse array antenna

The design of simple feed networks is of great interest in synthesising monopulse radar array antennas in order to reduce the complexity of the antenna architecture, the costs as well as the occupied physical space (e.g. on aircraft). Sub-arraying techniques have been proposed to properly address such a task. Starting from the formulation of the sub-arraying problem in terms of a combinatorial one, the final compromise solution is obtained by looking for the minimum cost path inside a binary tree graph through an ant colony optimiser.     

Polarimetric channel characterization of foliage for performanceassessment of GPS receivers under tree canopies

The attenuation, depolarization, and fluctuation of a microwave signal going through a tree canopy are investigated by developing a Monte Carlo based coherent scattering model. In particular, the model is used to analyze the performance of Global Positioning System (GPS) receivers under tree canopies. Also the frequency and time-domain channel characteristics of a forest are investigated when a transmitter is outside and a receiver is inside a forest. A fractal algorithm (Lindenmayer system) is used to generate the structure of coniferous or deciduous trees whose basic building blocks are arbitrarily oriented finite cylinders, thin dielectric needles, and thin dielectric disks. Attenuation and phase change of the mean field through foliage is accounted for using Foldy's approximation. Scattering of the mean field from individual tree components and their images in the underlying ground plane are computed analytically and added coherently. Since tree trunks and some branches are large compared to the wavelength and may be in the close proximity of the receiver, a closed-form and uniform expression for the scattered near-field from dielectric cylinders is also developed. Monte Carlo simulation of field calculation is applied to a cluster of trees in order to estimate the statistics of the channel parameters, such as the probability density function (pdf) of the polarization state of the transmitted field, path loss, and the incoherent scattered power (the second moment of the scattered field), as a function of the observation point above the ground     

M×N Booth encoded multiplier generatorusing optimized Wallace trees

The architecture of a design method for an M-bit by N -bit Booth encoded parallel multiplier generator are discussed. An algorithm for reducing the delay inside the branches of the Wallace tree section is explained. The final step of adding two N±M-1-bit numbers is done by an optimal carry select adder stage. The algorithm for optimal partitioning of the N ±M-1-bit adder is also presented     

Second-Order Greedy Algorithms for Centralized Teleprocessing Network Design

We consider the problem of designing a centralized telecommunication network comprised of multipoint lines given a set of terminal locations, traffic requirements, and a common central site. The optimal solution to this problem is a capacitated minimal spanning tree. We develop a class of heuristic algorithms for the solution of this problem by imbedding existing heuristics, referred to as first-order greedy algorithms, inside a loop where small, carefully chosen sets of arcs are alternately forced in and out of the solution. The resultant procedure is shown to be superior to existing techniques, producing solutions typically 2 percent better, while requiring only a modest amount of additional computer time.     

Hybrid FDTD and single-scattering theory for simulation of scattering from hard targets camouflaged under forest canopy

A hybrid target-foliage model is developed to investigate the scattering behavior of hard targets embedded inside a forest canopy. The proposed model is composed of two existing electromagnetic-scattering models, one for the foliage and the other for the hard targets that are coupled in a computationally efficient manner. The connection between these two models, which accounts for the interaction between the foliage scatterers and the target, is accomplished through the application of Huygens' principle. Wave penetration through the forest canopy and near-field and far-field scattering from its constituents is calculated using a coherent single-scattering theory, which makes use of realistic tree structures. Defining a Huygens' surface enclosing the hard target and calculating the illuminating field (the scattered fields from the nearby vegetation scatterers and reduced incident field), the interaction between the foliage and the hard target is accounted for. Computing the scattered field from target on the Huygens' surface and using a reciprocity theorem target-foliage interaction is captured very efficiently. Calculation of scattering from a hard target is carried out using a finite-difference time-domain (FDTD) technique. For a typical vehicle dimensions, the required time and memory for the FDTD computation and exact field calculation inside the foliage limits the simulation frequency to upper very high frequency (VHF) band.     

短语统计机器翻译的句法调序模型

为了处理统计机器翻译中的长距离调序,在基于短语的统计翻译模型的基础上提出了句法调序模型.该模型按照短语切分来分割句法树结构,从而能够避免短语和句法结构的不一致性.在该模型中依据短语对齐和短语内词对齐确定句法树部分结构的调序顺序,依据各个节点上的调序概率计算子结构的调序概率,作为对数线性模型的特征函数.该模型的实验结果比经典的短语统计翻译模型的BLEU评分有明显提高.结果表明句法调序模型对于基于短语的统计机器翻译是有效的,能够较好地将句法知识和短语翻译过程结合起来.     

Radar modeling of a boreal forest

The authors report on the use of microwave modeling, ground truth, and synthetic aperture radar (SAR) data to investigate the characteristics of forest stands. A mixed coniferous forest stand has been modeled at SAR frequencies (P-, L-, and C-bands). The extensive measurements of ground truth and canopy geometry parameters were performed in a 200 m-square hemlock-dominated plot inside a forest. Hemlock trees in the forest are modeled by characterizing tree trunks, branches, and needles (leaves) with randomly oriented, lossy dielectric cylinders whose area and orientation distributions are prescribed. The distorted Born approximation is used to compute the backscatter at P-, L-, and C-SAR frequencies     

利用局域网构建安全的信息化高校实验室

探讨了如何利用局域网技术开发信息资源,促进信息交流和知识共享,提高资源设备利用率和教学科研效率,改变实验室内部信息孤岛的状况,构建一个安全的信息化实验室。具体讨论了局域网的树形拓扑结构设计、网络和信息安全设计、IP地址规划以及部署在其上的服务和功能。该局域网方案实现了实验室内的软硬件资源的共享、点对点通讯、仪器设备远程化操作、分布式实验数据库系统、分布式存储和计算、团队协作式开发、信息化管理、Web服务、Email和传真服务等一系列功能,提高了实验室信息化水平,取得了良好的应用效果。     

Route Optimization Using Tree Information Option for Nested Mobile Networks

Mobile IP is the basic solution to provide host mobility, whereas network mobility refers to the concept of collective mobility of a set of nodes. In the simplest scenario, a mobile network moves as a single unit with one mobile router (MR) that connects it to the global Internet. Also, multiple mobile networks can be nested in a hierarchical form, e.g., a wireless personal area network (PAN) in a vehicular network. In a nested mobile network, multiple MRs form a tree hierarchy in which the root MR is called the top-level mobile router (TLMR). Nested mobile networks exhibit the pinball routing problem, which becomes worse in proportion to the number of nested levels in the hierarchy. To solve this problem, we propose a routing optimization scheme using a tree information option (ROTIO) that extends the NEMO basic support protocol. In the ROTIO scheme, each MR in the nested mobile network sends two binding updates (BUs): one to its home agent and the other to the TLMR. The former BU contains the TLMR's home address, while the latter contains routing information between the issuing MR and the TLMR. This alleviates the pinball routing problem significantly. Now, a packet from a correspondent node only needs to visit two transit nodes (the home agents of the MR and the TLMR), regardless of the degree of nesting. Moreover, the ROTIO scheme provides location privacy and mobility transparency. We also extend ROTIO to perform routing between two mobile network nodes inside the same nested mobile network more efficiently and to substantially reduce the disruption when a mobile network hands off.     

Restricted dynamic Steiner trees for scalable multicast in datagramnetworks

The paper addresses the issue of minimizing the number of nodes involved in routing over a multicast tree and in the maintenance of such a tree in a datagram network. It presents a scheme where the tree routing and maintenance burden is laid only upon the source node and the destination nodes associated with the multicast tree. The main concept behind this scheme is to view each multicast tree as a collection of unicast paths and to locate only the multicast source and destination nodes on the junctions of their multicast tree. The paper shows that despite this restriction, the cost of the created multicast trees is not necessarily higher than the cost of the trees created by other algorithms that do not impose the restriction and therefore require all nodes along the data path of a tree to participate in routing over the tree and in the maintenance of the tree     

共享路径优先组播路由算法

求解开销最小组播树在数学上归结为Steiner树问题,但由于寻找最优的Steiner树问题是NP-Complete问题,因此在组播应用中,采用启发式算法获得次优的组播树是常见的方法。该文提出了一种新的的启发式组播路由算法(Shared Path First Heuristic,SPFH)该算法在选择目的节点加入组播树时,既考虑到目的节点到树上的距离,又考虑到先加入的节点对后续加入节点的影响。算法从距离当前组播树近的目的节点中挑选节点加入组播树,选择的规则是,把能够减小其它目的节点加入组播树开销的节点先加入树。仿真结果表明,SPFH算法能找到开销接近于最优解的组播树。     

一种改进的多播路由算法

低代价最短路径树是一种广泛使用的多播树,它能够在保证传送时延最小的同时尽量降低带宽消耗。DDSP(Destination-Driven Shortest Path)算法是一个性能较好,计算效率较高的低代价最短路径树算法,在该算法基础上,通过改进结点的搜索过程,提出一种改进的快速低代价最短路径树算法。由算法分析和实验比较得出,改进算法的计算效率高于DDSP算法,且算法构造的最短路径树的性能也优于DDSP算法构造的树．     

一种并行决策树学习方法研究

提出一种并行的决策树学习方法。该方法首先将数据库分为若干个子部分,针对每个子部分分别进行决策树学习,优选分裂属性,再对各个决策树学习的结果综合,生成最终的树。在树上剪枝以降低分类错误率。通过在变压器绝缘故障诊断中的应用表明该方法有很强的学习能力和诊断速度,是一种有效的决策树学习方法。