1,721,227 research outputs found
On the usefulness of object shape coding with MPEG-4
No full textThis paper reports the results of an in-depth analysis ofthe degree of usefulness of object shape coding in videocompression. In particular, MPEG-4 is used as referencestandard. The influence of different coding parameters onthe performance is deeply examined and discussions on theresults are provided. Object shape coding is compared withclassical (MPEG-2) frame-based coding both at an objectivelevel (by comparing PSNR/quality and bitrate/filesize)and at a subjective level (asking to a set of users to expresstheir opinion on overall quality, cognitive effectiveness, andwillingness to pay). In conclusion, this paper aims at answering to the question whether it is convenient to use object shape coding instead of frame-based coding or not
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No full textMixtures of von Mises Distributions for People Trajectory Shape Analysis
No full textPeople trajectory analysis is a recurrent task in many pattern recognition applications, such as surveillance, behavior analysis, video annotation, and many others. In this paper, we propose a new framework for analyzing trajectory shape, invariant to spatial shifts of the people motion in the
scene. In order to cope with the noise and the uncertainty of the trajectory samples, we propose to describe the trajectories as a sequence of angles modeled by distributions of circular statistics, i.e., a mixture of von Mises (MovM) distributions. To deal with MovM, we define a new specific expectation-maximization (EM) algorithm for estimating the parameters and derive a closed form of the Bhattacharyya distance between single von Mises pdfs. Trajectories are then modeled with a sequence of symbols, corresponding to the most suitable distribution in the mixture,
and compared each other after a global alignment procedure to cope with trajectories of different lengths. The trajectories in the training set are clustered according to their shape similarity in an off-line phase, and testing trajectories are then classified with a specific on-line EM, based on sufficient statistics. The approach is particularly suitable for classifying people trajectories in video surveillance, searching for abnormal (i.e., infrequent) paths. Tests on synthetic and real data are provided with also a complete comparison with other circular statistical and alignment methods
Parameter tuning of a stochastic biological simulator by metaheuristics
No full textIn this paper we address the problem of tuning parameters of a biological model, in particular a simulator of stochastic processes. The task is defined as an optimisation problem over the parameter space in which the objective function to be minimised is the distance between the output of the simulator and a target one. We tackle the problem with a metaheuristic algorithm for continuous variables, Particle swarm optimisation, and show the effectiveness of the method in a prominent case-study, namely the mitogen-activated protein kinase cascade
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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