20,414 research outputs found
Two novel evolutionary formulations of the graph coloring problem
We introduce two novel evolutionary formulations of the problem of coloring
the nodes of a graph. The first formulation is based on the relationship that
exists between a graph's chromatic number and its acyclic orientations. It
views such orientations as individuals and evolves them with the aid of
evolutionary operators that are very heavily based on the structure of the
graph and its acyclic orientations. The second formulation, unlike the first
one, does not tackle one graph at a time, but rather aims at evolving a
`program' to color all graphs belonging to a class whose members all have the
same number of nodes and other common attributes. The heuristics that result
from these formulations have been tested on some of the Second DIMACS
Implementation Challenge benchmark graphs, and have been found to be
competitive when compared to the several other heuristics that have also been
tested on those graphs.Comment: To appear in Journal of Combinatorial Optimizatio
Providing End-to-End Delay Guarantees for Multi-hop Wireless Sensor Networks over Unreliable Channels
Wireless sensor networks have been increasingly used for real-time
surveillance over large areas. In such applications, it is important to support
end-to-end delay constraints for packet deliveries even when the corresponding
flows require multi-hop transmissions. In addition to delay constraints, each
flow of real-time surveillance may require some guarantees on throughput of
packets that meet the delay constraints. Further, as wireless sensor networks
are usually deployed in challenging environments, it is important to
specifically consider the effects of unreliable wireless transmissions.
In this paper, we study the problem of providing end-to-end delay guarantees
for multi-hop wireless networks. We propose a model that jointly considers the
end-to-end delay constraints and throughput requirements of flows, the need for
multi-hop transmissions, and the unreliable nature of wireless transmissions.
We develop a framework for designing feasibility-optimal policies. We then
demonstrate the utility of this framework by considering two types of systems:
one where sensors are equipped with full-duplex radios, and the other where
sensors are equipped with half-duplex radios. When sensors are equipped with
full-duplex radios, we propose an online distributed scheduling policy and
proves the policy is feasibility-optimal. We also provide a heuristic for
systems where sensors are equipped with half-duplex radios. We show that this
heuristic is still feasibility-optimal for some topologies
Expediting TTS Synthesis with Adversarial Vocoding
Recent approaches in text-to-speech (TTS) synthesis employ neural network
strategies to vocode perceptually-informed spectrogram representations directly
into listenable waveforms. Such vocoding procedures create a computational
bottleneck in modern TTS pipelines. We propose an alternative approach which
utilizes generative adversarial networks (GANs) to learn mappings from
perceptually-informed spectrograms to simple magnitude spectrograms which can
be heuristically vocoded. Through a user study, we show that our approach
significantly outperforms na\"ive vocoding strategies while being hundreds of
times faster than neural network vocoders used in state-of-the-art TTS systems.
We also show that our method can be used to achieve state-of-the-art results in
unsupervised synthesis of individual words of speech.Comment: Published as a conference paper at INTERSPEECH 201
Obtaining Maxwell's equations heuristically
Starting from the experimental fact that a moving charge experiences the
Lorentz force and applying the fundamental principles of simplicity (first
order derivatives only) and linearity (superposition principle), we show that
the structure of the microscopic Maxwell equations for the electromagnetic
fields can be deduced heuristically by using the transformation properties of
the fields under space inversion and time reversal. Using the experimental
facts of charge conservation and that electromagnetic waves propagate with the
speed of light together with Galileo invariance of the Lorentz force allows us
to introduce arbitrary electrodynamic units naturally.Comment: 11 page
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