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Distribution of additive functions with respect to numeration systems on regular languages

THEORY OF COMPUTING SYSTEMS 2007年第3期40卷 205-223页

作者： Grabner, Peter J. Rigo, Michel Graz Univ Technol Inst Math A-8010 Graz Austria Univ Liege Inst Math B-4000 Liege Belgium

We study the distribution of values of additive functions related to numeration systems defined via regular languages.

关键词： algorithms computer programming computer algorithms MATHEMATICAL analysis FUNCTIONS (Mathematics)

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Novel data association schemes for the probability hypothesis density filter

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2007年第2期43卷 556-570页

作者： Panta, Kusha Vo, Ba-Ngu Singh, Sumeetpal Univ Melbourne Co Operat Res Ctr Sensor & Informat Proc Dept Elect & Elect Engn Melbourne Vic 3010 Australia Univ Melbourne Dept Elect & Elect Engn Cambridge CB2 1PZ England

The probability hypothesis density (PHD) filter is a practical alternative to the optimal Bayesian multi-target filter based on finite set statistics. It propagates the PHD function, a first-order moment of the full multi-target posterior density. The peaks of the PHD function give estimates of target states. However, the PHD filter keeps no record of target identities and hence does not produce track-valued estimates of individual targets. We propose two different schemes according to which PHD filter can provide track-valued estimates of individual targets. Both schemes use the probabilistic data-association functionality albeit in different ways. In the first scheme, the outputs of the PHD filter are partitioned into tracks by performing track-to-estimate association. The second scheme uses the PHD filter as a clutter filter to eliminate some of the clutter from the measurement set before it is subjected to existing data association techniques. In both schemes, the PHD filter effectively reduces the size of the data that would be subject to data association. We consider the use of multiple hypothesis tracking (MHT) for the purpose of data association. The performance of the proposed schemes are discussed and compared with that of MHT.

关键词： PROBABILITY measures TRACKING radar HYPOTHESIS STATISTICS DENSITY functionals computer algorithms GAUSSIAN processes RADIO filters ELECTRONICS

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Visual information fusion for object-based video image segmentation using unsupervised Bayesian online learning

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IET IMAGE PROCESSING 2007年第2期1卷 168-181页

作者： Jia, Z. Balasuriya, A. Challa, S. United Technol Res Ctr Shanghai 201206 Peoples R China MIT Marine Robot Lab Cambridge MA 02139 USA Univ Technol Sydney Fac Engn Sydney NSW 2007 Australia

An algorithm using the unsupervised Bayesian online learning process is proposed for the segmentation of object-based video images. The video image segmentation is solved using a classification method. First, different visual features (the spatial location, colour and optical-flow vectors) are fused in a probability framework for image pixel clustering. The appropriate modelling of the probability distribution function (PDF) for each feature-cluster is obtained through a Gaussian distribution. The image pixel is then assigned a cluster number in a maximum a posteriori probability framework. Different from the previous segmentation methods, the unsupervised Bayesian online learning algorithm has been developed to understand a cluster's PDF parameters through the image sequence. This online learning process uses the pixels of the previous clustered image and information from the feature-cluster to update the PDF parameters for segmentation of the current image. The unsupervised Bayesian online learning algorithm has shown satisfactory experimental results on different video sequences.

关键词： VISUAL learning DIGITAL video IMAGE processing PIXELS computer algorithms CLUSTER analysis (Statistics)

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RAM simulation of BGS model of abstract-state machines

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FUNDAMENTA INFORMATICAE 2007年第1-2期77卷 175-185页

作者： Seshadhri, Comandur Seth, Anil Biswas, Somenath Princeton Univ Dept Comp Sci Princeton NJ 08544 USA Indian Inst Technol Dept Comp Sci & Engn Kanpur 208016 Uttar Pradesh India

We show in this paper that the BGS model of abstract state machines can be simulated by random access machines with at most a polynomial time overhead. This result is already stated in [5] with a very brief proof sketch. The present paper gives a detailed proof of the result. We represent hereditarily finite sets, which are the typical BGS ASM objects, by membership graphs of the transitive closure of the sets. Testing for equality between BGS objects can be done in linear time in our representation.

关键词： RANDOM access memory computer simulation computerS computer algorithms computer programming

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Maximal consistent subsets

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COMPUTATIONAL LINGUISTICS 2007年第2期33卷 153-160页

作者： Malouf, Robert San Diego State Univ Dept Linguist & Asian Middle E Languages San Diego CA 92182 USA

Default unification operations combine strict information with information from one or more defeasible feature structures. Many such operations require finding the maximal subsets of a set of atomic constraints that are consistent with each other and with the strict feature structure, where a subset is maximally consistent with respect to the subsumption ordering if no constraint can be added to it without creating an inconsistency. Although this problem is NP-complete, there are a number of heuristic optimizations that can be used to substantially reduce the size of the search space. In this article, we propose a novel optimization, leaf pruning, which in some cases yields an improvement in running time of several orders of magnitude over previously described algorithms. This makes default unification efficient enough to be practical for a wide range of problems and applications.

关键词： COMPUTATIONAL linguistics -- Methodology APPLIED linguistics computer algorithms LANGUAGE & languages -- Grammars OPTIMALITY theory (Linguistics) SEMANTICS

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Approach to optical interference fringes reduction in diode laser absorption spectroscopy

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APPLIED PHYSICS B-LASERS AND OPTICS 2007年第3期87卷 523-530页

作者： Persson, L. Andersson, F. Andersson, M. Svanberg, S. Lund Univ Div Atom Phys S-22100 Lund Sweden Lund Univ Ctr Math Sci S-22100 Lund Sweden

The advantage of a new scheme for balanced detection has been investigated to reduce the influence of optical interference fringes when performing diode laser gas absorption spectroscopy employing lock-in amplifiers and pigtailed lasers. The influence of the fringes has been reduced by comparing the lock-in 2 f signal due to the gas sample with that of a reference beam. The frequency regions outside the absorption feature have been used to obtain information on the interference fringe impact on the signal of interest. We have demonstrated an efficient way to reduce the influence of such fringes by employing this technique combined with non-linear signal processing methods. The different steps of the algorithm are presented. In the experimental arrangement presented, a reduction of the optical interference fringes by about 10 times is achieved, as demonstrated in measurements on molecular oxygen around 761 nm. The new technique is compared with an analog technique for balanced detection and certain advantages of the computer algorithm are pointed out. In particular, the emerging field of gas spectroscopy in scattering solid media strongly benefits from the technique presented.

关键词： semiconductor lasers laser diodes spectroscopic techniques interference interference pattern Semiconductor lasers gas spectroscopy interference Diode Laser Light interference tunable diode laser absorption spectroscopy spectroscopic techniques reference beam computer algorithms

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Discrete-time fuzzy sliding mode control for a vehicle suspension system featuring an electrorheological fluid damper

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SMART MATERIALS AND STRUCTURES 2007年第3期16卷 798-808页

作者： Sung, Kum-Gil Han, Young-Min Lim, Kye-Hyun Choi, Seung-Bok Inha Univ Dept Mech Engn Smart Struct & Syst Lab Inchon 402751 South Korea

This paper presents real-time control characteristics of an electrorheological (ER) suspension system via a fuzzy sliding mode control algorithm which is formulated in a discrete-time manner by considering the sampling rate of an electronic control unit for a vehicle system. A quarter-vehicle system consisting of sprung mass, spring, tire and a cylindrical ER damper (shock absorber) is constructed for the real-time control. After deriving the governing equation of motion of the proposed system, a discrete-time control model with system uncertainties is formulated. A stable sliding surface is then designed and followed by the formulation of the discrete-time sliding mode controller which consists of a discontinuous part and an equivalent part. In the controller formulation, the fuzzy control algorithm is also adopted to enhance system robustness to the mass variation and reaching time to the sliding surface. The controller is then experimentally realized for the manufactured quarter-vehicle ER suspension system. Control performances such as vertical acceleration are evaluated under various road conditions and presented in both time and frequency domains.

关键词： Slip surfaces Pavement condition Suspension System normal acceleration computer algorithms time monitoring Governing equation Erbium Equations of motion Controllers fuzzy sliding mode control system uncertainties discrete-time electronic control unit Real time control

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Generating referring expressions: Making referents easy to identify

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COMPUTATIONAL LINGUISTICS 2007年第2期33卷 229-254页

作者： Paraboni, Ivandre van Deemter, Kees Masthoff, Judith Univ Sao Paulo EACH BR-05508 Sao Paulo Brazil Univ Aberdeen Dept Comp Sci Aberdeen AB9 1FX Scotland

It is often desirable that referring expressions be chosen in such a way that their referents are easy to identify. This article focuses on referring expressions in hierarchically structured domains, exploring the hypothesis that referring expressions can be improved by including logically redundant information in them if this leads to a significant reduction in the amount of search that is needed to identify the referent, Generation algorithms are presented that implement this idea by including logically redundant information into the generated expression, in certain well-circumscribed situations. To test our hypotheses, and to assess the performance of our algorithms, two controlled experiments with human subjects were conducted. The first experiment confirms that human judges have a preference for logically redundant expressions in the cases where our model predicts this to be the case. The second experiment suggests that readers benefit from the kind of logical redundancy that our algorithms produce, as measured in terms of the effort needed to identify the referent of the expression.

关键词： COMPUTATIONAL linguistics computer algorithms REDUNDANCY (Linguistics) INFORMATION science -- Study & teaching APPLIED linguistics STRUCTURAL linguistics LINGUISTICS -- Research

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Reiterative median cascaded canceler for robust adaptive array processing

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2007年第2期43卷 428-442页

作者： Picciolo, Michael L. Gerlach, Karl SAIC AMO Chantilly VA 20151 USA USN Res Lab Washington DC 20375 USA

A new robust adaptive processor based on reiterative application of the median cascaded canceler (MCC) is presented and called the reiterative median cascaded canceler (RMCC). It is shown that the RMCC processor is a robust replacement for the sample matrix inversion (SMI) adaptive processor and for its equivalent implementations. The MCC, though a robust adaptive processor, has a convergence rate that is dependent on the rank of the input interference-plus-noise covariance matrix for a given number of adaptive degrees of freedom (DOF), N. In contrast, the RMCC, using identical training data as the MCC, exhibits the highly desirable combination of: 1) convergence-robustness to outliers/targets in adaptive weight training data, like the MCC, and 2) fast convergence performance that is independent of the input interference-plus-noise covariance matrix, unlike the MCC. For a number of representative examples, the RMCC is shown to converge using similar to 2.8N samples for any interference rank value as compared with similar to 2N samples for the SMI algorithm. However, the SMI algorithm requires considerably more samples to converge in the presence of outliers/targets, whereas the RMCC does not. Both simulated data as well as measured airborne radar data from the multichannel airborne radar measurements (MCARM) space-time adaptive processing (STAP) database are used to illustrate performance improvements over SMI methods.

关键词： STOCHASTIC convergence ADAPTIVE control systems computer algorithms ARRAY processors ELECTROMAGNETIC interference SIGNAL processing FEEDBACK (Electronics) MATRICES NOISE

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An analysis of the compositional techniques in John!Chowning's Stria

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computer MUSIC JOURNAL 2007年第3期31卷 26-37页

作者： Meneghini, Matteo Univ Padua I-35131 Padua Italy

This article describes an analytic study of the process used by John Chowning for the composition of Stria. This article is intended to complete the description of the compositional process given in a previous work (Meneghini 2003), largely restated by Bossis in a subsequent paper (Bossis 2005). Stria was composed in 1977 and was fully generated by means of computer algorithms (Chowning 1977c) and the corresponding input files (Chowning 1977a, b): all the parameters of the sounds generated in Stria are determined and calculated by these algorithms on the basis of specific mathematical rules and of numerical parameters chosen by Mr. Chowning as input for the programs. For this reason, an accurate analysis of these algorithms is fundamental for a complete comprehension of the compositional process.

关键词： computer algorithms computer programming computer music ELECTRONIC music SOUND recordings PROGRAMMING languages (Electronic computers) ELECTRONIC data processing computer programmers

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