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A New PopulationBased Method for Satisfiability Problems
 Proceedings of the ECAI Workshop on Applied Genetic and other Evolutionary Algorithms
, 1994
"... . This paper presents the mask method (MASK), a new populationbased, evolutionary search procedure for finding models for satisfiability problems (SAT). In this method, a partial truth assignment for a given boolean expression containing N variables is represented by a partially instantiated 0/1 st ..."
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Cited by 15 (3 self)
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. This paper presents the mask method (MASK), a new populationbased, evolutionary search procedure for finding models for satisfiability problems (SAT). In this method, a partial truth assignment for a given boolean expression containing N variables is represented by a partially instantiated 0/1 string with N positions (called mask), with each position coding one variable. The mask method begins with a population of masks. An iteration process follows to evaluate each mask in the population using an evaluation mechanism, then to discard half of them, and finally to divide each remaining mask into two new ones by fixing a free position in the mask to 0 and 1 respectively. This process continues until all the positions in the mask have a fixed value. The method is compared with a class of genetic algorithms (GAs) on a set of SAT instances and proves to be much more efficient. 1 INTRODUCTION The satisfiability problem or SAT [5] is of great importance in Artificial Intelligence both in...
Automating the Assembly of Presentations from Multimedia Databases
, 1996
"... A multimedia presentation refers to the presentation of multimedia data using output devices such as monitors for text and video, and speakers for audio. Each presentation consists of multimedia segments which are obtained from a multimedia data model. In this paper, we propose to express semantic c ..."
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Cited by 11 (3 self)
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A multimedia presentation refers to the presentation of multimedia data using output devices such as monitors for text and video, and speakers for audio. Each presentation consists of multimedia segments which are obtained from a multimedia data model. In this paper, we propose to express semantic coherency of a multimedia presentation in terms of presentation inclusion and exclusion constraints that are incorporated into the multimedia data model. Thus, when a user specifies a set of segments for a presentation, the DBMS adds segments into and/or deletes segments from the set in order to satisfy the inclusion and exclusion constraints. To automate the assembly of a presentation with concurrent presentation streams, we also propose presentation organization constraints that are incorporated into the multimedia data model, independent of any presentation. We give two algorithms for automated presentation assembly and discuss their complexity. We discuss the satisfiability of inclusion a...
DSpace and Deform Closure Grasps of Deformable Parts
"... Abstract – Building on the wellestablished 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 sti ..."
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Cited by 11 (1 self)
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Abstract – Building on the wellestablished 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 Dspace (deformationspace) of a part as the Cspace of all its mesh nodes. Free space is the intersection of the set of topologypreserving 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).
Temporal Photoreception for Adaptive Dynamic Range Image Sensing and Encoding
, 1998
"... 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 multiintegration time photoreceptor that automatically adapts to use different integration periods depending on lig ..."
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Cited by 10 (1 self)
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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 multiintegration 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 intensitytotime 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 informationtheoretic 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.
JoinDistinct aggregate estimation over update streams
 In Proc. ACM PODS
, 2005
"... 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 environme ..."
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Cited by 10 (1 self)
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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 dataanalysis scenarios. For instance, to enable realtime traffic analysis and load balancing, a networkmonitoring application may need to estimate the number of distinct (source, destination) IPaddress 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 joinsize estimation (without duplicate elimination) over streams. These solutions, however, are fundamentally different and extending or combining them to handle our more complex “JoinDistinct ” estimation problem is far from obvious. In this paper, we propose the first spaceefficient algorithmic solution to the general JoinDistinct 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 hashbased synopses (termed “JD sketches”) for individual update streams. We demonstrate that our algorithms can provide low error, highconfidence JoinDistinct 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 JoinDistinct problem. Preliminary experimental results verify the effectiveness of our approach. 1.
A Sybilproof Indirect Reciprocity Mechanism for PeertoPeer Networks
"... Although direct reciprocity (TitforTat) contribution systems have been successful in reducing freeloading in peertopeer 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 reciproc ..."
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Cited by 10 (3 self)
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Although direct reciprocity (TitforTat) contribution systems have been successful in reducing freeloading in peertopeer 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 peertopeer 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 peertopeer 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.
Factorization of synchronous contextfree grammars in linear time
 In NAACL Workshop on Syntax and Structure in Statistical Translation (SSST
, 2007
"... Factoring a Synchronous ContextFree 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 treedecomposition of a given permutation with the minimal branchi ..."
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Cited by 9 (5 self)
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Factoring a Synchronous ContextFree 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 treedecomposition 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 handaligned data from various language pairs. 1
Implementation of a Sweep Line Algorithm for the Straight Line Segment Intersection Problem
 TR MPII94105, MAXPLANCKINSTITUT FUR INFORMATIK, SAARBRUCKEN
, 1994
"... We describe a robust and efficient implementation of the BentleyOttmann 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 ..."
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Cited by 9 (2 self)
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We describe a robust and efficient implementation of the BentleyOttmann 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.
Multimedia thumbnails for documents
 In Proceedings of ACM Multimedia
, 2006
"... 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 ..."
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Cited by 9 (2 self)
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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.