273,118 research outputs found
Gradual Generalization of Nautical Chart Contours with a Cube B-Spline Snake Model
âB-spline snake methods have been used in cartographic generalization in the past decade, particularly in the generalization of navigational charts where this method yields good results with respect to the shoal-bias rules for generalization of chart contours. However, previous studies only show generalization results at particular generalization (or scale) levels, and the user can only see two conditions: before the generalization and after generalization, but nothing in between. This paper presents an improved method of using B-spline snakes for generalization in the context of nautical charts, where the generalization process is done gradually, and the user can see the complete process of the generalization
Pulsar Timing Probes of Primordial Black Holes and Subhalos
Pulsars act as accurate clocks, sensitive to gravitational redshift and
acceleration induced by transiting clumps of matter. We study the sensitivity
of pulsar timing arrays (PTAs) to single transiting compact objects, focusing
on primordial black holes and compact subhalos in the mass range from to well above . We find that the Square Kilometer
Array can constrain such objects to be a subdominant component of the dark
matter over this entire mass range, with sensitivity to a dark matter
sub-component reaching the sub-percent level over significant parts of this
range. We also find that PTAs offer an opportunity to probe substantially less
dense objects than lensing because of the large effective radius over which
such objects can be observed, and we quantify the subhalo concentration
parameters which can be constrained.Comment: 18 pages, 6 figure
A new exact closest lattice point search algorithm using linear constraints
The problem of finding the closest lattice point arises in several communications scenarios and is known to be NP-hard. We propose a new closest lattice point search algorithm which utilizes a set of new linear inequality constraints to reduce the search of the closest lattice point to the intersection of a polyhedron and a sphere. This set of linear constraints efficiently leverage the geometric structure of the lattice to reduce considerably the number of points that must be visited. Simulation results verify that this algorithm offers substantial computational savings over standard sphere decoding when the dimension of the problem is large
Any-Angle Pathfinding for Multiple Agents Based on SIPP Algorithm
The problem of finding conflict-free trajectories for multiple agents of
identical circular shape, operating in shared 2D workspace, is addressed in the
paper and decoupled, e.g., prioritized, approach is used to solve this problem.
Agents' workspace is tessellated into the square grid on which any-angle moves
are allowed, e.g. each agent can move into an arbitrary direction as long as
this move follows the straight line segment whose endpoints are tied to the
distinct grid elements. A novel any-angle planner based on Safe Interval Path
Planning (SIPP) algorithm is proposed to find trajectories for an agent moving
amidst dynamic obstacles (other agents) on a grid. This algorithm is then used
as part of a prioritized multi-agent planner AA-SIPP(m). On the theoretical,
side we show that AA-SIPP(m) is complete under well-defined conditions. On the
experimental side, in simulation tests with up to 200 agents involved, we show
that our planner finds much better solutions in terms of cost (up to 20%)
compared to the planners relying on cardinal moves only.Comment: Final version as submitted to ICAPS-2017 (main track); 8 pages; 4
figures; 1 algorithm; 2 table
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