Joaquín Fernández-Valdivia

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This paper analyzes how the natural scales of the shapes in 2D images can be extracted. Spatial information is analyzed by multiple units sensitive to both spatial and spatial-frequency variables. Scale estimates of the relevant shapes are constructed only from strongly responding detectors. The meaningful structures in the response of a detector (computed(More)
ÐThis paper describes a system for the automatically learned partitioning of ªvisual patternsº in 2D images, based on a sophisticated, band-pass, filtering operation with fixed scale and orientation sensitivity. In this scheme, the ªvisual patternsº are defined as the features which have the highest degree of alignment in the statistical structure across(More)
This paper introduces a new approach to solving the problem of representing planar curves. We describe the 2-D curve C not at all diierent scales , but each curve part C i of C, isolating a diierent structure at its single scale i. Therefore, we represent the planar curve at a scale vector (1 ; ; L) supposing that the curve is partitioned in L parts C 1 ; ;(More)
In this paper we provide the reader with a visual representation of relationships among the impact of book chapters indexed in the Book Citation Index using information gain values and published by different academic publishers in specific disciplines. The impact of book chapters can be characterized statistically by citations histograms. For instance, we(More)
ÐIt is of great benefit to have advance knowledge of human visual target acquisition performance for targets or other relevant objects. However, search performance inherently shows a large variance and depends strongly on prior knowledge of the perceived scene. A typical search experiment therefore requires a large number of observers to obtain(More)
This paper presents a method for selecting proper scale parameters for edge detection. To this aim the image is preliminarily segmented into regions with a homogeneous intensity change model, by using a clustering algorithm based on a dissimilarity measure applied on feature vectors associated to the regions. The used algorithm is a standard clustering(More)
This paper introduces a new method for clustering data using a dynamic scheme. An appropriate partitioning is obtained based on both a dissimilarity measure between pairs of entities as well as a dynamic procedure of splitting. A dissimilarity function is deened by using the cost of the optimum path from a datum to each entity on a graph, with the cost of a(More)
We present a number of autofocusing methods in lighting microscopy for its use in diatom identiica-tion. Among these, the Tenengrad method has been considered one of the best. The basic requirements for a practical autofocusing system are speed, sharpness and robustness to noise. Recently other focus measures based on a modiied Laplacian method are said to(More)
This paper presents a new method for comparing universities based on information theoretic measures. The research output of each academic institution is represented statistically by an impact-factor histogram. To this aim, for each academic institution we compute the probability of occurrence of a publication with impact factor in different intervals.(More)
In this paper we present three error measures based on feature perception models, in which pixel errors are computed on locations at which humans might perceive features in the reference image. In the rst part of this work, the three schemes of feature detection will be discussed and evaluated in terms of their performance for a simple visual(More)