共查询到20条相似文献,搜索用时 46 毫秒
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集成电路(IC)发展到了系统芯片(SOC)时代。超深亚微米系统芯片具有规模大、复杂度高、系统时钟频率快的特点,传统的设计流程由于设计规模有限和时序难以收敛等原因,已难以适用于系统芯片的设计;常用的展平式(flat)版图设计方法,会导致工具处理能力严重不足。本文提出了一个完整的系统芯片的设计流程以及基于该流程的层次式、时间驱动的版图设计方法。设计过程采用自上而下的(top-down)的约束分配和时间驱动方式以满足时延约束,实现时序收敛;布局规划采用层次式模块分割以适应芯片规模大的要求。针对8VSB芯片采用。25um工艺在商用软件平台上对上述新方法进行了验证。实验结果表明,60万门的8VSB芯片速度可达到108Mhz。 相似文献
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Wiley Wang Ilya Pollak Tak-Shing Wong Charles A Bouman Mary P Harper Jeffrey M Siskind 《IEEE transactions on image processing》2006,15(10):3033-3052
We develop a new class of hierarchical stochastic image models called spatial random trees (SRTs) which admit polynomial-complexity exact inference algorithms. Our framework of multitree dictionaries is the starting point for this construction. SRTs are stochastic hidden tree models whose leaves are associated with image data. The states at the tree nodes are random variables, and, in addition, the structure of the tree is random and is generated by a probabilistic grammar. We describe an efficient recursive algorithm for obtaining the maximum a posteriori estimate of both the tree structure and the tree states given an image. We also develop an efficient procedure for performing one iteration of the expectation-maximization algorithm and use it to estimate the model parameters from a set of training images. We address other inference problems arising in applications such as maximization of posterior marginals and hypothesis testing. Our models and algorithms are illustrated through several image classification and segmentation experiments, ranging from the segmentation of synthetic images to the classification of natural photographs and the segmentation of scanned documents. In each case, we show that our method substantially improves accuracy over a variety of existing methods. 相似文献
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Ning An August G. Domel Jinxiong Zhou Ahmad Rafsanjani Katia Bertoldi 《Advanced functional materials》2020,30(6)
Kirigami—the Japanese art of cutting paper—has recently inspired the design of highly stretchable and morphable mechanical metamaterials that can be easily realized by embedding an array of cuts into a sheet. This study focuses on thin plastic sheets perforated with a hierarchical pattern of cuts arranged to form an array of hinged squares. It is shown that by tuning the geometric parameters of this hierarchy as well as thickness and material response of the sheets not only a variety of different buckling‐induced 3D deformation patterns can be triggered, but also the stress–strain response of the surface can be effectively programmed. Finally, it is shown that when multiple hierarchical patterns are brought together to create one combined heterogeneous surface, the mechanical response can be further tuned and information can be encrypted into and read out via the applied mechanical deformation. 相似文献
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Stefan Schwabe Robert Niemann Anja Backen Daniel Wolf Christine Damm Tina Walter Hanuš Seiner Oleg Heczko Kornelius Nielsch Sebastian Fähler 《Advanced functional materials》2021,31(7):2005715
Martensitic materials show a complex, hierarchical microstructure containing structural domains separated by various types of twin boundaries. Several concepts exist to describe this microstructure on each length scale, however, there is no comprehensive approach bridging the whole range from the nano- up to the macroscopic scale. Here, it is described for a Ni-Mn-based Heusler alloy how this hierarchical microstructure is built from scratch with just one key parameter: the tetragonal distortion of the basic building block at the atomic level. Based on this initial block, five successive levels of nested building blocks are introduced. At each level, a larger building block is formed by twinning the preceding one to minimize the relevant energy contributions locally. This naturally explains the coexistence of different types of twin boundaries. The scale-bridging approach of nested building blocks is compared with experiments in real and reciprocal space. The approach of nested building blocks is versatile as it can be applied to the broad class of functional materials exhibiting diffusionless transformations. 相似文献
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The channel routing problem is a special case of the wire routing problem when interconnections have to be performed within a rectangular strip having no obstructions, between terminals located on opposite sides of the rectangle.We present here a new channel routing algorithm, based on reduction of the problem to the case of a (2 × n) grid and on consistent utilization of a ‘divide-and-conquer’ approach. For the current implementation of the algorithm, the running time is proportional to N 1 n log(m) where N is the number of nets, n the length of the channel (number of columns) and m the width of the channel (number of tracks).Traditional technological restrictions are assumed, i.e., net terminals are located on vertical grid lines, two wiring layers are available for interconnections — one layer is used exclusively for vertical segments, another for horizontal and vias are introduced for each layer change.This algorithm consistently outperforms several known routers in quality of wiring. We tested the algorithm on several benchmark problems. One of them — Deutsch's ‘difficult example’ — was routed with only 19 horizontal wiring tracks (the absolute minimum for this case), whereas all other known routers required 20 or more tracks. 相似文献
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A hierarchical line and segment extraction algorithm, based on a pyramid, is described. Initially, lines are detected in small windows using the Hough transform. The detected lines are then merged using a distance criteria thus avoiding a reaccumulation process at each level of the pyramid. The hierarchical merging process is efficiently performed on lines rather than on segments (since there are many more segments than lines). The detected lines are broken into segments, at the top of the pyramid. The proposed approach is compared to similar approaches based on hierarchical feature extraction. The authors show that their approach combines the advantages of other works and avoids their drawbacks such as quantisation effect and lack of robustness 相似文献
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Hierarchical Error Diffusion 总被引:1,自引:0,他引:1
Zhen He 《IEEE transactions on image processing》2009,18(7):1524-1535
This paper develops a distinctive class of color error diffusion algorithm, called hierarchical error diffusion (HED). It aims to achieve perceptually pleasing color halftone through neither conventional joint quantization nor interchannel error diffusion. Instead, it explicitly controls three critical factors sequentially to yield high-quality color halftone: dot-overlapping control, dot-positioning control, and dot-coloring control. A specific implementation of HED is presented with the objective of minimum brightness variation rendering (MBVR). First, an optimal color transform is derived for dot-overlapping control to achieve minimum brightness variation color density (MBVCD). Then, the embedded monochrome error diffusion is employed in dot-positioning control. By sequentially thresholding the elements in partial density sum vector, better dot-positioning is encouraged for more visible color dots. The ldquoblue noiserdquo characteristics of dot-positioning from the monochrome error diffusion are inherited by the color halftone. The simple density priority strategy is applied in dot-coloring control. The pixel color error is diffused channel-independently with a single error filter in halftone dot color space. A comparison with the state-of-the-art color error diffusion algorithms demonstrates excellent halftone quality of HED, while without the typical artifacts of vector error diffusion. Evidence also shows that HED is closer to achieve MBVR than the minimum brightness variation quantization (MBVQ) color diffusion algorithm proposed in. 相似文献
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Tiesong Zhao Hanli Wang Sam Kwong C.-C. Jay Kuo Wolfgang A. Halang 《Journal of Visual Communication and Image Representation》2011,22(7):627-633
To enable robust video transmission over heterogeneous networks, the hierarchical B-picture prediction structure is employed in the state-of-the-art video coding standard H.264/SVC, aiming to produce scalable bitstreams with various frame rates. However, the exhaustive mode decision process with the hierarchical B-picture structure increases the computational complexity of H.264/SVC encoding dramatically. In this paper, a fast mode decision algorithm is proposed to speed up H.264/SVC encoding with the hierarchical B-picture structure, which is achieved by utilizing macroblock (MB) features, correlation of temporal–spatial neighboring MBs, and the discrepant characteristics of hierarchical layers. Extensive experimental results demonstrate that the proposed algorithm is able to reduce the encoding time of H.264/SVC significantly for video sequences with a wide range of resolutions, and meanwhile the video quality and compression ratio are well preserved. 相似文献
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Feder M. Merhav N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1996,42(5):1354-1364
In an earlier paper, we proved a strong version of the redundancy-capacity converse theorem of universal coding, stating that for “most” sources in a given class, the universal coding redundancy is essentially lower-bounded by the capacity of the channel induced by this class. Since this result holds for general classes of sources, it extends Rissanen's (1986) strong converse theorem for parametric families. While our earlier result has established strong optimality only for mixture codes weighted by the capacity-achieving prior, our first result herein extends this finding to a general prior. For some cases our technique also leads to a simplified proof of the above mentioned strong converse theorem. The major interest in this paper, however, is in extending the theory of universal coding to hierarchical structures of classes, where each class may have a different capacity. In this setting, one wishes to incur redundancy essentially as small as that corresponding to the active class, and not the union of classes. Our main result is that the redundancy of a code based on a two-stage mixture (first, within each class, and then over the classes), is no worse than that of any other code for “most” sources of “most” classes. If, in addition, the classes can be efficiently distinguished by a certain decision rule, then the best attainable redundancy is given explicitly by the capacity of the active class plus the normalized negative logarithm of the prior probability assigned to this class. These results suggest some interesting guidelines as for the choice of the prior. We also discuss some examples with a natural hierarchical partition into classes 相似文献
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Traffic restoration in case of a failure in a circuit-switched telecommunications network involves finding alternate paths for all working paths that are severed by the failure, and rerouting affected traffic on these alternate paths. A new hierarchical self-healing ring (HSHR) architecture for circuit-switched networks is proposed and the design of HSHR networks is considered. A general cost model incorporating both the installation cost and the material cost is used. It is shown that the enumeration method, which finds the optimum configuration of HSHR, can only be used for small networks due to the complexity. Heuristic algorithms to find near-optimum HSHR configurations are presented. The routing and dimensioning of HSHR are also considered. Dimensioning of an HSHR is transformed into dimensioning of single self-healing rings inside the HSHR. Numerical results show that the performance of the heuristic is satisfactory 相似文献
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文章针对网络营运环境的新变化以及网络拓扑结构的复杂性给网管带来的新要求,指出了集中式网管存在的不足,提出了层次化Mobile-Agent的实现策略,设计了层次化Mobile-Agent的定位方法。 相似文献
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Third-generation wireless communication faces the challenges of rapidly increasing mobile user demand against limited radio bandwidth. Splitting cells into smaller cells can reduce the frequency reuse distance to improve network capacity within a certain area. Other than increasing the cost of the fixed infrastructure, cell splitting also causes the problem of increasing handoff rate and event the handoff failure rate when high-speed users roam in the network. To solve this problem, larger cells are overlaid on these smaller cells, and different classes of users (usually classified by speed) are initially assigned to the proper types of cells (i.e., proper tiers). We call this kind of cellular network a hierarchical cellular network. In this study, we review the different design techniques in the hierarchical architecture and some analytical tools to study the performance of these designs. 相似文献
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《Journal of Visual Communication and Image Representation》2014,25(5):1251-1261
In this paper, a new hierarchical approach for object detection is proposed. Object detection methods based on Implicit Shape Model (ISM) efficiently handle deformable objects, occlusions and clutters. The structure of each object in ISM is defined by a spring like graph. We introduce hierarchical ISM in which structure of each object is defined by a hierarchical star graph. Hierarchical ISM has two layers. In the first layer, a set of local ISMs are used to model object parts. In the second layer, structure of parts with respect to the object center is modeled by global ISM. In the proposed approach, the obtained parts for each object category have high discriminative ability. Therefore, our approach does not require a verification stage. We applied the proposed approach to some datasets and compared the performance of our algorithm to comparable methods. The results show that our method has a superior performance. 相似文献
16.
Delay testing is used to detect timing errors in a digital circuit.In this paper, we report a tool called MODET forautomatic test generation for path delay faults in modular combinational circuits. Our technique usesprecomputed robust delay tests for individual modules to computerobust delay tests for the module-level circuit. We present alongest path theorem at the module level ofabstraction which specifies the requirements for path selectionduring delay testing. Based on this theorem, we propose a pathselection procedure in module-level circuits and report efficientalgorithms for delay test generation. MODET hasbeen tested against a number of hierarchical circuits with impressivespeedups in relation to gate-level test generation. 相似文献
17.
We present a hierarchical solution method to approximately solve the topological network design problem: given positive integers (n,d,/spl Delta/), minimize the number of arcs required to interconnect n nodes, so that the network diameter does not exceed d, the maximum node degree does not exceed /spl Delta/, and the network is single node survivable. The method uses dynamic programming to piece together small networks to create larger networks. The method was used to plan two high-speed packet networks at AT&T. 相似文献
18.
Hierarchical Threshold Secret Sharing 总被引:1,自引:0,他引:1
Tamir Tassa 《Journal of Cryptology》2007,20(2):237-264
We consider the problem of threshold secret sharing in groups with hierarchical structure. In such settings, the secret is
shared among a group of participants that is partitioned into levels. The access structure is then determined by a sequence
of threshold requirements: a subset of participants is authorized if it has at least k0 0 members from the highest level, as well as at least k1 > k0 members from the two highest levels and so forth. Such problems may occur in settings where the participants differ in their
authority or level of confidence and the presence of higher level participants is imperative to allow the recovery of the
common secret. Even though secret sharing in hierarchical groups has been studied extensively in the past, none of the existing
solutions addresses the simple setting where, say, a bank transfer should be signed by three employees, at least one of whom
must be a department manager. We present a perfect secret sharing scheme for this problem that, unlike most secret sharing
schemes that are suitable for hierarchical structures, is ideal. As in Shamir's scheme, the secret is represented as the free
coefficient of some polynomial. The novelty of our scheme is the usage of polynomial derivatives in order to generate lesser
shares for participants of lower levels. Consequently, our scheme uses Birkhoff interpolation, i.e., the construction of a
polynomial according to an unstructured set of point and derivative values. A substantial part of our discussion is dedicated
to the question of how to assign identities to the participants from the underlying finite field so that the resulting Birkhoff
interpolation problem will be well posed. In addition, we devise an ideal and efficient secret sharing scheme for the closely
related hierarchical threshold access structures that were studied by Simmons and Brickell. 相似文献
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论文阐述了程序的一种分层静态分析的模型(HSAM)。在一定的分析精度的要求下,该模型采用一种分层分析的思想:先从整体的角度对程序进行模块结构分析;然后在模块内部进行控制流的分析;最后进行数据流分析。论文提出的逆序path更新算法对于控制流的分析非常有效。 相似文献