11,931 research outputs found
The maximum disjoint paths problem on multi-relations social networks
Motivated by applications to social network analysis (SNA), we study the
problem of finding the maximum number of disjoint uni-color paths in an
edge-colored graph. We show the NP-hardness and the approximability of the
problem, and both approximation and exact algorithms are proposed. Since short
paths are much more significant in SNA, we also study the length-bounded
version of the problem, in which the lengths of paths are required to be upper
bounded by a fixed integer . It is shown that the problem can be solved in
polynomial time for and is NP-hard for . We also show that the
problem can be approximated with ratio in polynomial time
for any . Particularly, for , we develop an efficient
2-approximation algorithm
Power Aware Routing for Sensor Databases
Wireless sensor networks offer the potential to span and monitor large
geographical areas inexpensively. Sensor network databases like TinyDB are the
dominant architectures to extract and manage data in such networks. Since
sensors have significant power constraints (battery life), and high
communication costs, design of energy efficient communication algorithms is of
great importance. The data flow in a sensor database is very different from
data flow in an ordinary network and poses novel challenges in designing
efficient routing algorithms. In this work we explore the problem of energy
efficient routing for various different types of database queries and show that
in general, this problem is NP-complete. We give a constant factor
approximation algorithm for one class of query, and for other queries give
heuristic algorithms. We evaluate the efficiency of the proposed algorithms by
simulation and demonstrate their near optimal performance for various network
sizes
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