We have implemented two analog VLSI computational sensors for sensing and encoding high dynamic range images by exploiting temporal dimension of photoreception. The first sensor is a multi-integration time photoreceptor that automatically adapts to use different integration periods depending on light intensity. It exhibits a dynamic range 128 times larger than that of a single integration period photoreceptor, approximately The second sensor is an intensity-to-time processing paradigm that is based on the notion that stronger stimuli elicit responses before weaker ones. The paradigm sorts pixels of sensed images by their intensities, thus achieving information-theoretic optimal encoding of images. It handles dynamic range of approximately 1: Both implementations can operate at standard video rate of frames 1998 Elsevier Science Ltd. All rights reserved.

This paper describes the architecture and implementation of an autonomous passenger vehicle designed to navigate using locally perceived information in preference to potentially inaccurate or incomplete map data. The vehicle architecture was designed to handle the original DARPA Urban Challenge requirements of perceiving and navigating a road network with segments defined by sparse waypoints. The vehicle implementation includes many heterogeneous sensors with significant communications and computation bandwidth to capture and process high-resolution, high-rate sensor data. The output of the comprehensive environmental sensing subsystem is fed into a kino-dynamic motion planning algorithm to generate all vehicleFigure 1: Talos in action at the National Qualifying Event. motion. The requirements of driving in lanes, three-point turns, parking, and maneuvering through obstacle fields are all generated with a unified planner. A key aspect of the planner is its use of closed-loop simulation in a Rapidly-exploring Randomized Trees (RRT) algorithm, which can randomly explore the space while efficiently generating smooth trajectories in a dynamic and uncertain environment.

We describe a robust and efficient implementation of the Bentley-Ottmann sweep line algorithm [7] based on the LEDA library of efficient data types and algorithms [7]. The program computes the planar graph G induced by a set S of straight line segments in the plane. The nodes of G are all endpoints and all proper intersection points of segments in S. The edges of G are the maximal relatively open subsegments of segments in S that contain no node of G. All edges are directed from left to right or upwards. The algorithm runs in time O((n + s) log n) where n is the number of segments and s is the number of vertices of the graph G. The implementation uses exact arithmetic for the reliable realization of the geometric primitives and it uses floating point filters to reduce the overhead of exact arithmetic.

Although direct reciprocity (Tit-for-Tat) contribution systems have been successful in reducing freeloading in peerto-peer overlays, it has been shown that, unless the contribution network is dense, they tend to be slow (or may even fail) to converge [1]. On the other hand, current indirect reciprocity mechanisms based on reputation systems tend to be susceptible to sybil attacks, peer slander and whitewashing. In this paper we present PledgeRoute, an accounting mechanism for peer contributions that is based on social capital. This mechanism allows peers to contribute resources to one set of peers and use this contribution to obtain services from a different set of peers, at a different time. PledgeRoute is completely decentralised, can be implemented in both structured and unstructured peer-to-peer systems, and it is resistant to the three kinds of attacks mentioned above. To achieve this, we model contribution transitivity as a routing problem in the contribution network of the peer-to-peer overlay, and we present arguments for the routing behaviour and the sybilproofness of our contribution transfer procedures on this basis. Additionally, we present mechanisms for the seeding of the contribution network, and a combination of incentive mechanisms and reciprocation policies that motivate peers to adhere to the protocol and maximise their service contributions to the overlay.

In this paper, we investigate an approach for creating a comprehensive textual overview of a subject composed of information drawn from the Internet. We use the high-level structure of human-authored texts to automatically induce a domainspecific template for the topic structure of a new overview. The algorithmic innovation of our work is a method to learn topicspecific extractors for content selection jointly for the entire template. We augment the standard perceptron algorithm with a global integer linear programming formulation to optimize both local fit of information into each topic and global coherence across the entire overview. The results of our evaluation confirm the benefits of incorporating structural information into the content selection process. 1

Factoring a Synchronous Context-Free Grammar into an equivalent grammar with a smaller number of nonterminals in each rule enables synchronous parsing algorithms of lower complexity. The problem can be formalized as searching for the tree-decomposition of a given permutation with the minimal branching factor. In this paper, by modifying the algorithm of Uno and Yagiura (2000) for the closely related problem of finding all common intervals of two permutations, we achieve a linear time algorithm for the permutation factorization problem. We also use the algorithm to analyze the maximum SCFG rule length needed to cover hand-aligned data from various language pairs. 1

There is growing interest in algorithms for processing and querying continuous data streams (i.e., data that is seen only once in a fixed order) with limited memory resources. Providing (perhaps approximate) answers to queries over such streams is a crucial requirement for many application environments; examples include large IP network installations where performance data from different parts of the network needs to be continuously collected and analyzed. The ability to estimate the number of distinct (sub)tuples in the result of a join operation correlating two data streams (i.e., the cardinality of a projection with duplicate elimination over a join) is an important requirement for several data-analysis scenarios. For instance, to enable real-time traffic analysis and load balancing, a network-monitoring application may need to estimate the number of distinct (source, destination) IP-address pairs occurring in the stream of IP packets observed by router R1, where the source address is also seen in packets routed through a different router R2. Earlier work has presented solutions to the individual problems of distinct counting and join-size estimation (without duplicate elimination) over streams. These solutions, however, are fundamentally different and extending or combining them to handle our more complex “Join-Distinct ” estimation problem is far from obvious. In this paper, we propose the first space-efficient algorithmic solution to the general Join-Distinct estimation problem over continuous data streams (our techniques can actually handle general update streams comprising tuple deletions as well as insertions). Our estimators are probabilistic in nature and rely on novel algorithms for building and combining a new class of hash-based synopses (termed “JD sketches”) for individual update streams. We demonstrate that our algorithms can provide low error, high-confidence Join-Distinct estimates using only small space and small processing time per update. In fact, we present lower bounds showing that the space usage of our estimators is within small factors of the best possible for the Join-Distinct problem. Preliminary experimental results verify the effectiveness of our approach. 1.

The rapid development of volume graphics offers ample scope to develop new methods and tools for computer graphics and visualisation. This paper is concerned with methods for specifying and controlling complex transformations of volumetric data. A volume distortion algorithm is presented, which allows one volume to be distorted into another under the control of two sets of disk fields. The algorithm also forms a primary module in a volume morphing process that is an extension of the feature-based image morphing technique developed by Beier and Neely [1]. For each inbetween volume, the algorithm is of time complexity O(n·m) depending on the size of the volume n and the number of disk fields m. Tests have shown that the algorithm is capable of performing complex volume transformations within an acceptable time using a small set of disk fields. The merits of the method in comparison with existing approaches for volume distortion and morphing are also discussed. Keywords --- volume visua...

Abstract – Building on the well-established form closure framework for holding rigid parts, this paper proposes a new framework for holding deformable parts. We consider the class of deformable parts that can be modeled as linearly elastic polygons with a triangular finite element mesh and given stiffness matrix. We define the D-space (deformation-space) of a part as the C-space of all its mesh nodes. Free space is the intersection of the set of topology-preserving mesh configurations with the complement of the union of all Dobstacles that represent collisions of the part with finger bodies. Consider a given set of finger bodies in frictionless contact with a part. When positive work is needed to release the part, we say that it is in deform closure. We present numerical examples and prove two results: (1) If a contact set holds a rigid part in form closure, it will hold the equivalent deformable part in deform closure and (2) deform closure is frame invariant. We then consider frictionless deform closure grasps with two contact points. We define a measure of grasp quality based on balancing the potential energy needed to release the part against the potential energy that would result in plastic deformation. Given two jaw contacts at the perimeter nodes, we develop numerical algorithms to determine the optimal jaw separation based on this metric. For a part with n mesh nodes and p perimeter nodes, we give an algorithm that computes the optimal separation in time O(n 3 p 2 + p 6 log p) and an approximation algorithm that runs in time O(n 3 p 2 + ( p 2 /ε) log p).

As small portable devices are becoming standard personal equipments, there is a great need for the adaptation of information content to small displays. Currently, no good solutions exist for viewing formatted documents, such as pdf documents, on these devices. Adapting content of web pages to small displays is usually achieved by complete redesign of a page or automatically reflowing text for small displays. Such techniques may not be applicable to documents whose format needs to be preserved. To address this problem, we propose a new document representation called Multimedia Thumbnail. Multimedia Thumbnail uses the visual and audio channels of small portable devices to communicate document information in form of a multimedia clip, which can be seen as a movie trailer for a document. Generation of such a clip includes a document analysis step, where salient document information is extracted, an optimization step, where the document information to be included in the thumbnail is determined based on display and time constraints, and a synthesis step, where visual and audible information are formed into a playable Multimedia Thumbnail. We also present user study results that evaluate an initial system design and point to further modification on analysis, optimization, and user interface components.