15,941 research outputs found
C-essential surfaces in (3-manifold, graph) pairs
Let be a graph in a compact, orientable 3--manifold and let
be a subgraph. can be placed in bridge position with respect to a Heegaard
surface . We show that if is what we call -c-weakly
reducible in the complement of then either a "degenerate" situation occurs
or can be untelescoped and consolidated into a collection of "thick
surfaces" and "thin surfaces". The thin surfaces are c-essential
(c-incompressible and essential) in the graph exterior and each thick surface
is a strongly irreducible bridge surface in the complement of the thin
surfaces. This strengthens and extends previous results of Hayashi-Shimokawa
and Tomova to graphs in 3-manifolds that may have non-empty boundary.Comment: 33 pages, 9 figures. Accepted for publication in Communications in
Analysis and Geometr
Massively Parallel Ray Tracing Algorithm Using GPU
Ray tracing is a technique for generating an image by tracing the path of
light through pixels in an image plane and simulating the effects of
high-quality global illumination at a heavy computational cost. Because of the
high computation complexity, it can't reach the requirement of real-time
rendering. The emergence of many-core architectures, makes it possible to
reduce significantly the running time of ray tracing algorithm by employing the
powerful ability of floating point computation. In this paper, a new GPU
implementation and optimization of the ray tracing to accelerate the rendering
process is presented
Kinematic calibration of Orthoglide-type mechanisms from observation of parallel leg motions
The paper proposes a new calibration method for parallel manipulators that
allows efficient identification of the joint offsets using observations of the
manipulator leg parallelism with respect to the base surface. The method
employs a simple and low-cost measuring system, which evaluates deviation of
the leg location during motions that are assumed to preserve the leg
parallelism for the nominal values of the manipulator parameters. Using the
measured deviations, the developed algorithm estimates the joint offsets that
are treated as the most essential parameters to be identified. The validity of
the proposed calibration method and efficiency of the developed numerical
algorithms are confirmed by experimental results. The sensitivity of the
measurement methods and the calibration accuracy are also studied
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