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IEEE Digital Signal Processing Workshop

作者： G.V. Moustakides Department of Computer Engineering and Informatics University of Patras Patras Greece Computer Technology Institute CTI Patras Patras Greece

The recursive least squares (RLS) algorithm is one of the most well known algorithms used for adaptive filtering and system identification. We consider the convergence properties of the forgetting factor RLS algorithm in a stationary data environment. We study the dependence of the speed of convergence of RLS with respect to the initialization of the input sample covariance matrix and with respect to the observation noise level. By obtaining estimates of the settling time we show that RLS, in a high SNR environment, when initialized with a matrix of small norm, has a very fast convergence. The convergence speed decreases as we increase the norm of the initialization matrix. In a medium SNR environment the optimum convergence speed of the algorithm is reduced, but the RLS becomes more insensitive to initialization. Finally in a low SNR environment it is preferable to start the algorithm with a matrix of large norm.

关键词： Resonance light scattering Covariance matrix Signal to noise ratio Convergence Signal processing algorithms Time measurement Noise level Filtering algorithms Velocity measurement Noise measurement

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SILO: INTEGRATING LOGIC IN OBJECTS FOR KNOWLEDGE REPRESENTATION AND REASONING

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International Journal on Artificial Intelligence Tools 1996年第4期5卷 403-446页

作者： IOANNIS HATZILYGEROUDIS University of Patras School of Engineering Dept of Computer Engineering & Informatics 26500 Patras Greece Computer Technology Institute (CTI) P.O. Box 1122 26110 Patras Greece

There have been a large number of systems that integrate logic and objects (frames or classes) for knowledge representation and reasoning. Most of those systems give pre-eminence to logic and their objects lack the structure of frames. These choices imply a number of disadvantages, as the inability to represent exceptions and perform default reasoning, and the reduction in the naturalness of representation. In this paper, aspects of knowledge representation and reasoning in SILO, a system integrating logic in objects, are presented. SILO gives pre-eminence to objects. A SILO object comprises elements from both frames and classes. A kind of many-sorted logic is used to express object internal knowledge. Message passing, alongside inheritance, plays a significant role in the reasoning process. Control knowledge, concerning both deduction and inheritance. is separately and explicitly represented via definitions of certain functions, called meta-functions.

关键词： logic frames classes knowledge representation hybrid system meta-level system

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Wormhole versus deflection routing: A case study on the mesh 2nd

Wormhole versus deflection routing: A case study on the mesh

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Proceedings of the 1996 2nd Annual International Conference on Computing and Combinatorics, COCOON'96

作者： Karaivazoglou, Efstratios Spirakis, Paul Triantafilou, Vassilis Heinz Nixdorf Institute University of Paderborn Paderbom 33095 Germany Department of Computer Engineering and Informatics Patras University Rio Patras 265 00 Greece Computer Technology Institute P.O. Box 1122 Patras 261 10 Greece

ISBN: (纸本)9783540613329

In this paper we are comparing (via simulations) under real conditions, several routing algorithms based either on oblivious wormhole routing or deflection routing. Although these two techniques differ significally in the low level structure of information (worms, packets), we derived realistic results using an appropriate simulation model. In our experiments we compared average time, latency and throughput achieved by both deflection and wormhole routing (for both batch and continuous cases). Results show that deflection routing performs better than wormhole routing, for random traffic on the mesh, especially for large networks. Furthermore, although it is hard to analyze simple versions of wormhole routing, it seems that these versions outperform algorithms that are devised in order to simplify theoretical analysis. Finally we implemented and tested an algorithm that combines both deflection and wormhole routing. © Springer-Verlag Berlin Heidelberg 1996.

关键词： Mesh generation

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An L/sub 2/ based method for the design of one dimensional FIR digital filters

An L/sub 2/ based method for the design of one dimensional F...

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IEEE International Conference on Electronics, Circuits and Systems (ICECS)

作者： E.Z. Psarakis G.V. Moustakides Department of Computer Engineering and Informatics University of Patras Patras Greece Computer Technology Institute Patras Greece

FIR filters obtained with the classical L/sub 2/ method have performance that is very sensitive to the form of the ideal response selected for the transition region. In this paper we propose a means for selecting the unknown part of a complex ideal response optimally. By selecting a proper L/sub 2/ criterion and using variational techniques we succeed in minimizing the criterion with respect to the ideal response and thus obtain its corresponding optimum form. The complete solution to the problem can be obtained by solving a simple system of linear equations suggesting a reduced complexity for the proposed method. Using the optimum form of the ideal response we also propose a new suboptimal method for the design of weighted FIR filters. Design examples are presented to illustrate the performance of the proposed method.

关键词： Design methodology Finite impulse response filter Digital filters Nonlinear filters Least squares approximation Passband informatics Equations Approximation error Equalizers

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Transaction synchronization in multiresolation spatial databases 96

Transaction synchronization in multiresolation spatial datab...

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Proceedings of the 4th ACM international workshop on Advances in geographic information systems

作者： Eleanna Kafeza Vasilis Delis Thanasis Hadzilacos Computer Technology Institute Kolokotroni 3 26221 Patras Greece and Computer Engineering and Informatics Department University of Patras Computer Technology Institute Kolokotroni 3.26221 Patras Greece

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UNDERWATER TRACKING OF A MANEUVERING TARGET USING TIME-DELAY MEASUREMENTS

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SIGNAL PROCESSING 1995年第1期41卷 17-29页

作者： KATSIKAS, SK LEROS, AK LAINIOTIS, DG University of the Aegean Department of Mathematics Karlovassi 83200 Greece Technological Education Institute of Athens Department of Computer Science Ag. Spyridonos st. Egaleo 12210 Greece University of Patras Department of Computer Engineering and Informatics Patras 26500 Greece Florida Institute of Technology Department of Electrical and Computer Engineering Melbourne FL 32901-6988 USA

The problem of estimating the relative position of an underwater maneuvering target is treated as an estimation problem when an unknown and time varying bias is present in the plant noise process. Pilot-initiated maneuvers are modeled as impulsive unknown inputs affecting the bias term at times unknown to the observer. A new algorithm, capable of efficiently handling the problem of state estimation with time varying unknown bias, is derived by using the Lainiotis multimodel partitioning theory coupled with conventional constant bias estimation algorithms, Simulation results show that the proposed algorithm performs very well under adverse operating conditions, such as high measurement noise, long target to observer range and large-scale target maneuvers.

关键词： ADAPTIVE ESTIMATION BIAS ESTIMATION UNDERWATER TARGET TRACKING PASSIVE TARGET TRACKING

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Partiality and approximation schemes for local consistency in networks of constraints 15th

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15th Conference on Foundations of Software technology and Theoretical computer Science, FST and TCS 1995

作者： Dendris, Nick D. Kirousis, Lefteris M. Stamatiou, Yannis C. Thilikos, Dimitris M. Department of Computer Engineering and Informatics Patras University Rio Patras265 00 Greece Computer Technology Institute P.O. Box 1122 Patras261 10 Greece

ISBN: (纸本)3540606920

A constraint network is arc consistent if any value of its variables is compatible with at least one value of any other variable. The Arc Consistency Problem (ACP) consists in filtering out values of the variables of a given network to obtain one that is arc consistent, without eliminating any solution, i.e. a total value assignment that satisfies all constraints. Enforcing arc consistency, or the more general κ-consistency, in a constraint network is a widely used preprocessing step before identifying the set of solutions. ACP is known to be inherently sequential, so in this paper we examine the problem of achieving partial consistency, i.e. filtering out values from the variables so that each value in the new network is compatible with at least one value of not necessarily all, but a constant fraction of the other variables. We call such networks partially arc consistent. We give an algorithm that, for any constraint network, outputs a partially arc consistent subnetwork of it in sublin- ear [formula presented] parallel time using O(n2) processors. This is the first (to our knowledge) sublinear-time parallel algorithm with polynomially many processors that removes at least a constant fraction of the local inconsistencies of a general constraint network, without eliminating any solution. We also generalize the notion of partiality to the κ-consistency problem: We give an algorithm that is faster than the previously known κ-consistency algorithms, and which finds a partially κ-consistent sub network of any given network. Finally, we propose several approximation schemes to a total solution of ACP, and show that they are P-complete. This indicates that the approach of partial solutions, rather than that of approximation schemes, is more promising for parallelism. © Springer-Verlag Berlin Heidelberg 1995.

关键词： Parallel processing systems

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Fugitive-search games on graphs and related parameters 20th

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20th International Workshop on Graph-Theoretic Concepts in computer Science, WG 1994

作者： Dendris, Nick D. Kirousis, Lefteris M. Thilikos, Dimitris M. Department of Computer Engineering Informatics Patras University Rio Patras265 00 Greece Computer Technology Institute P.O. Box 1122 Patras261 10 Greece

ISBN: (纸本)3540590714

The goal of a fugitive-search game on a graph is to trap a fugitive that hides on the vertices of the graph by systematically placing searchers on the vertices. The fugitive is assumed to have complete knowledge of the graph and of the searchers' moves, but is restricted to move only along paths whose vertices are not guarded by searchers. The search number of the graph is the least number of searchers necessary to trap the fugitive. Variants of the fugitive-search game have been related to important graph parameters like treewidth and pathwidth. In this paper, we introduce a class of fugitive-search games where the searchers do not see the fugitive and the fugitive can only move just before a searcher is placed on the vertex it occupies. Letting the fugitive's speed (i.e. the maximum number of edges the fugitive can traverse at a single move) vary, we get different games. We show that if the speed of the fugitive is unbounded then the search number minus 1 is equal to the treewidth of the graph, while if the speed is 1 then the search number minus 1 is equal to the width, a polynomially computable graph parameter. We also show that in the above two cases, the search number remains the same even if we consider only these search strategies that at every step further restrict the fugitive's possible resorts (this monotonicity phenomenon is usually expressed as: "recontamination does not help"). Finally, we show that for any graph, if the length of any chordless cycle is bounded by a constant s (s≥3), then the treewidth of the graph plus 1 is equal to the search number for fugitive speed s−2. © Springer-Verlag Berlin Heidelberg 1995.

关键词： Graph theory

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On interval routing schemes and treewidth 21st

On interval routing schemes and treewidth

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21st International Workshop on Graph-Theoretic Concepts in computer Science, WG 1995

作者： Bodlaender, Hans L. Tan, Richard B. Thilikos, Dimitris M. Van Leeuwen, Jan Department of Computer Science Utrecht University P.O. Box 80.089 Utrecht3508 TB Netherlands Department of Computer Science University of Sciences and Arts of Oklahoma Chickasha Oklahoma73018 United States Computer Technology Institute P.O. Box 1122 Patras26110 Greece Department of Computer Engineering and Informatics University of Patras Rio Patras26500 Greece

ISBN: (纸本)3540606181

In this paper, we investigate which processor networks allow k-label Interval Routing Schemes, under the assumption that costs of edges may vary. We show that for each fixed k ≥ 1, the class of graphs allowing such routing schemes is closed under minor-taking in the domain of connected graphs, and hence has a linear time recognition algorithm. This result connects the theory of compact routing with the theory of graph minors and treewidth. We also show that every graph that does not contain K2,r as a minor has treewidth at most 2r – 2. In case the graph is planar, this bound can be lowered to r + 2. As a consequence, graphs that allow k-label Interval Routing Schemes under dynamic cost edges have treewidth at most 4k, and treewidth at most 2k + 3 if they are planar. Similar results are shown for other types of Interval Routing Schemes. © 1995, Springer-Verlag Berlin Heidelberg 1995.

关键词： Routing protocols

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Optimal synthesis of differential cascode voltage switch (DCVS) logic circuits using ordered binary decision diagrams (OBDDs)

Optimal synthesis of differential cascode voltage switch (DC...

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European Design Automation Conference

作者： T. Karoubalis G.Ph. Alexiou N. Kanopoulos Computer Technology Institute Patras Greece Department of Computer Engineering and Informatics University of Patras Patras Greece Center for Digital System Engineering RTI International Inc. NC USA

This paper presents a method for near-optimum synthesis of Differential Cascade Voltage Switch (DCVS) logic circuits using Ordered Binary Decision Diagrams (OBDD). The method presented produces efficient DCVS circuit structures in terms of transistor count which positively affects the circuit area and performance. The proposed method is also very practical because it produces results with short run-times on a design workstation. The paper presents experimental results that demonstrate the use and the efficiency of the proposed DCVS synthesis method. This method is the basis for a CAD tool that allows automatic synthesis of fault secure circuits based on the DCVS technology.

关键词： Switches Voltage Circuit synthesis Switching circuits Logic circuits Data structures Boolean functions Runtime Workstations Design automation

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