Nearest neighbor search algorithm for GBD tree spatial data structure

This paper describes the nearest neighbor (NN) search algorithm on the GBD(generalized BD) tree. The GBD tree is a spatial data structure suitable for two-or three-dimensional data and has good performance characteristics with respect to the dynamic data environment. On GIS and CAD systems, the R-tree and its successors have been used. In addition, the NN search algorithm is also proposed in an attempt to obtain good performance from the R-tree. On the other hand, the GBD tree is superior to the R-tree with respect to exact match retrieval, because the GBD tree has auxiliary data that uniquely determines the position of the object in the structure. The proposed NN search algorithm depends on the property of the GBD tree described above. The NN search algorithm on the GBD tree was studied and the performance thereof was evaluated through experiments.     

Nearest neighbor search algorithm forGBD tree spatial data structure

： This paper describes the nearest neighbor （NN） search algorithm on the GBD（generalized BD） tree. The GBD tree is a spatial data structure suitable for two- or three-dimensional data and has good performance characteristics with respect to the dynamic data environment. On GIS and CAD systems, the R-tree and its-successors have been used. In addition, the NN search algorithm is also proposed in an attempt to obtain good performance from the R-tree. On the other hand, the GBD tree is superior to the R-tree with respect to exact match retrieval, because the GBD tree has auxiliary data that uniquely determines the position of the object in the structure. The proposed NN search algorithm depends on the property of the GBD tree described above. The NN search algorithm on the GBD tree was studied and the performance thereof was evaluated through experiments.     

Coding of smooth eye movements in three-dimensional space by frontal cortex

Through the development of a high-acuity fovea, primates with frontal eyes have acquired the ability to use binocular eye movements to track small objects moving in space. The smooth-pursuit system moves both eyes in the same direction to track movement in the frontal plane (frontal pursuit), whereas the vergence system moves left and right eyes in opposite directions to track targets moving towards or away from the observer (vergence tracking). In the cerebral cortex and brainstem, signals related to vergence eye movements--and the retinal disparity and blur signals that elicit them--are coded independently of signals related to frontal pursuit. Here we show that these types of signal are represented in a completely different way in the smooth-pursuit region of the frontal eye fields. Neurons of the frontal eye field modulate strongly during both frontal pursuit and vergence tracking, which results in three-dimensional cartesian representations of eye movements. We propose that the brain creates this distinctly different intermediate representation to allow these neurons to function as part of a system that enables primates to track and manipulate objects moving in three-dimensional space.     

Predecessors of the giant 1960 Chile earthquake

It is commonly thought that the longer the time since last earthquake, the larger the next earthquake's slip will be. But this logical predictor of earthquake size, unsuccessful for large earthquakes on a strike-slip fault, fails also with the giant 1960 Chile earthquake of magnitude 9.5 (ref. 3). Although the time since the preceding earthquake spanned 123 years (refs 4, 5), the estimated slip in 1960, which occurred on a fault between the Nazca and South American tectonic plates, equalled 250-350 years' worth of the plate motion. Thus the average interval between such giant earthquakes on this fault should span several centuries. Here we present evidence that such long intervals were indeed typical of the last two millennia. We use buried soils and sand layers as records of tectonic subsidence and tsunami inundation at an estuary midway along the 1960 rupture. In these records, the 1960 earthquake ended a recurrence interval that had begun almost four centuries before, with an earthquake documented by Spanish conquistadors in 1575. Two later earthquakes, in 1737 and 1837, produced little if any subsidence or tsunami at the estuary and they therefore probably left the fault partly loaded with accumulated plate motion that the 1960 earthquake then expended.