5,270 research outputs found
On Deletion in Delaunay Triangulation
This paper presents how the space of spheres and shelling may be used to
delete a point from a -dimensional triangulation efficiently. In dimension
two, if k is the degree of the deleted vertex, the complexity is O(k log k),
but we notice that this number only applies to low cost operations, while time
consuming computations are only done a linear number of times.
This algorithm may be viewed as a variation of Heller's algorithm, which is
popular in the geographic information system community. Unfortunately, Heller
algorithm is false, as explained in this paper.Comment: 15 pages 5 figures. in Proc. 15th Annu. ACM Sympos. Comput. Geom.,
181--188, 199
The problem of the turbo-compressor
In terminating the study of the adaptation of the engine to the airplane, we will examine the problem of the turbo-compressor,the first realization of which dates from the war; this will form an addition to the indications already given on supercharging at various altitudes. This subject is of great importance for the application of the turbo-compressor worked by the exhaust gases. As a matter of fact, a compressor increasing the pressure in the admission manifold may be controlled by the engine shaft by means of multiplication gear or by a turbine operated by the exhaust gas. Assuming that the increase of pressure in the admission manifold is the same in both cases, the pressure in the exhaust manifold would be greater in the case in which the compressor is worked by the exhaust gas and there would result a certain reduction of engine power which we must be able to calculate. On the other hand , if the compressor is controlled by the engine shaft, a certain fraction of the excess power supplied is utilized for the rotation of the compressor. In order to compare the two systems, it is there-fore necessary to determine the value of the reduction of power due to back pressure when the turbine is employed
Inner and Outer Rounding of Boolean Operations on Lattice Polygonal Regions
Robustness problems due to the substitution of the exact computation on real
numbers by the rounded floating point arithmetic are often an obstacle to
obtain practical implementation of geometric algorithms. If the adoption of the
--exact computation paradigm--[Yap et Dube] gives a satisfactory solution to
this kind of problems for purely combinatorial algorithms, this solution does
not allow to solve in practice the case of algorithms that cascade the
construction of new geometric objects. In this report, we consider the problem
of rounding the intersection of two polygonal regions onto the integer lattice
with inclusion properties. Namely, given two polygonal regions A and B having
their vertices on the integer lattice, the inner and outer rounding modes
construct two polygonal regions with integer vertices which respectively is
included and contains the true intersection. We also prove interesting results
on the Hausdorff distance, the size and the convexity of these polygonal
regions
Two-hop Communication with Energy Harvesting
Communication nodes with the ability to harvest energy from the environment
have the potential to operate beyond the timeframe limited by the finite
capacity of their batteries; and accordingly, to extend the overall network
lifetime. However, the optimization of the communication system in the presence
of energy harvesting devices requires a new paradigm in terms of power
allocation since the energy becomes available over time. In this paper, we
consider the problem of two-hop relaying in the presence of energy harvesting
nodes. We identify the optimal offline transmission scheme for energy
harvesting source and relay when the relay operates in the full-duplex mode. In
the case of a half-duplex relay, we provide the optimal transmission scheme
when the source has a single energy packet.Comment: 4 pages, 3 figures. To be presented at the 4th International Workshop
on Computational Advances in Multi-Sensor Adaptive Processing, Dec. 201
Finding an ordinary conic and an ordinary hyperplane
Given a finite set of non-collinear points in the plane, there exists a line
that passes through exactly two points. Such a line is called an ordinary line.
An efficient algorithm for computing such a line was proposed by Mukhopadhyay
et al. In this note we extend this result in two directions. We first show how
to use this algorithm to compute an ordinary conic, that is, a conic passing
through exactly five points, assuming that all the points do not lie on the
same conic. Both our proofs of existence and the consequent algorithms are
simpler than previous ones. We next show how to compute an ordinary hyperplane
in three and higher dimensions.Comment: 7 pages, 2 figure
Improved Incremental Randomized Delaunay Triangulation
We propose a new data structure to compute the Delaunay triangulation of a
set of points in the plane. It combines good worst case complexity, fast
behavior on real data, and small memory occupation.
The location structure is organized into several levels. The lowest level
just consists of the triangulation, then each level contains the triangulation
of a small sample of the levels below. Point location is done by marching in a
triangulation to determine the nearest neighbor of the query at that level,
then the march restarts from that neighbor at the level below. Using a small
sample (3%) allows a small memory occupation; the march and the use of the
nearest neighbor to change levels quickly locate the query.Comment: 19 pages, 7 figures Proc. 14th Annu. ACM Sympos. Comput. Geom.,
106--115, 199
Pairwise transitive 2-designs
We classify the pairwise transitive 2-designs, that is, 2-designs such that a
group of automorphisms is transitive on the following five sets of ordered
pairs: point-pairs, incident point-block pairs, non-incident point-block pairs,
intersecting block-pairs and non-intersecting block-pairs. These 2-designs fall
into two classes: the symmetric ones and the quasisymmetric ones. The symmetric
examples include the symmetric designs from projective geometry, the 11-point
biplane, the Higman-Sims design, and designs of points and quadratic forms on
symplectic spaces. The quasisymmetric examples arise from affine geometry and
the point-line geometry of projective spaces, as well as several sporadic
examples.Comment: 28 pages, updated after review proces
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