Mario A. López

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In this paper we present the results from an extensive comparison study of three R-tree packing Mgorithms, including a new easy to implement Mgorithm. The algorithms are evaluated using both synthetic and actual data from various application domains including VLSI design, GIS (tiger), and computational fluid dynamics. Our studies also consider the ilnpact(More)
CM-line loading of R-trees is useful to improve node utilization and query performance. WTepresent an algorithm for bulk loading R-trees -r&id diifers horn previous ones in two aspects (a) it partitions input data into subtrees in a top-down fashion (based on the fact that splits close to the root are likely to have a greater impact on performance), (b) at(More)
We present a new approach for approximate nearest neighbor queries for sets of high dimensional points under any L t-metric, t = 1; : : : ; 1. The proposed algorithm is eecient and simple to implement. The algorithm uses multiple shifted copies of the data points and stores them in up to (d + 1) B-trees where d is the dimensionality of the data, sorted(More)
BACKGROUND AND PURPOSE In hemiparetic individuals, low endurance to exercise may compound the increased energy cost of movement and contribute to poor rehabilitation outcomes. The purpose of this investigation was to describe how hemiparetic stroke patients responded to intense exercise and aerobic training. METHODS Forty-two subjects were randomly(More)
ÐPast R-tree studies have focused on the number of nodes visited as a metric of query performance. Since database systems usually include a buffering mechanism, we propose that the number of disk accesses is a more realistic measure of performance. We develop a buffer model to analyze the number of disk accesses required for spatial queries using R-trees.(More)
A method for constructing hierarchical in terconnection networks is presented. The method is based on connecting isomorphic clusters using a complete graph as the higher level network. Applying it to various classes of graphs, including hypercubes and meshes, results in networks with optimal connectivity, high bisection width, low degree, diameter and cost.(More)