34,809 research outputs found
Coordination of Mobile Mules via Facility Location Strategies
In this paper, we study the problem of wireless sensor network (WSN)
maintenance using mobile entities called mules. The mules are deployed in the
area of the WSN in such a way that would minimize the time it takes them to
reach a failed sensor and fix it. The mules must constantly optimize their
collective deployment to account for occupied mules. The objective is to define
the optimal deployment and task allocation strategy for the mules, so that the
sensors' downtime and the mules' traveling distance are minimized. Our
solutions are inspired by research in the field of computational geometry and
the design of our algorithms is based on state of the art approximation
algorithms for the classical problem of facility location. Our empirical
results demonstrate how cooperation enhances the team's performance, and
indicate that a combination of k-Median based deployment with closest-available
task allocation provides the best results in terms of minimizing the sensors'
downtime but is inefficient in terms of the mules' travel distance. A
k-Centroid based deployment produces good results in both criteria.Comment: 12 pages, 6 figures, conferenc
Semi-dynamic connectivity in the plane
Motivated by a path planning problem we consider the following procedure.
Assume that we have two points and in the plane and take
. At each step we add to a compact convex
set that does not contain nor . The procedure terminates when the sets
in separate and . We show how to add one set to
in amortized time plus the time needed to find
all sets of intersecting the newly added set, where is the
cardinality of , is the number of sets in
intersecting the newly added set, and is the inverse of the
Ackermann function
I/O-Efficient Dynamic Planar Range Skyline Queries
We present the first fully dynamic worst case I/O-efficient data structures
that support planar orthogonal \textit{3-sided range skyline reporting queries}
in \bigO (\log_{2B^\epsilon} n + \frac{t}{B^{1-\epsilon}}) I/Os and updates
in \bigO (\log_{2B^\epsilon} n) I/Os, using \bigO
(\frac{n}{B^{1-\epsilon}}) blocks of space, for input planar points,
reported points, and parameter . We obtain the result
by extending Sundar's priority queues with attrition to support the operations
\textsc{DeleteMin} and \textsc{CatenateAndAttrite} in \bigO (1) worst case
I/Os, and in \bigO(1/B) amortized I/Os given that a constant number of blocks
is already loaded in main memory. Finally, we show that any pointer-based
static data structure that supports \textit{dominated maxima reporting
queries}, namely the difficult special case of 4-sided skyline queries, in
\bigO(\log^{\bigO(1)}n +t) worst case time must occupy space, by adapting a similar lower bounding argument for
planar 4-sided range reporting queries.Comment: Submitted to SODA 201
Global green economy and environmental sustainability: a coopetitive model
This paper provides a coopetitive model for a global green economy taking into account the environmental sustainability. In particular we propose a differentiable coopetitive game G (in the sense recently introduced by D. Carfì) to represent a basic green economy interaction among a country c and the rest of the world w. Our game G is a linear parametric (Euclidean) perturbation of the classic Cournot duopoly. In the paper we offer the complete study of the proposed model and in particular a deep examination of its possible coopetitive solutions.environmental sustainability; global green economy; coopetitive games; infinite game
vSkyConf: Cloud-assisted Multi-party Mobile Video Conferencing
As an important application in the busy world today, mobile video
conferencing facilitates virtual face-to-face communication with friends,
families and colleagues, via their mobile devices on the move. However, how to
provision high-quality, multi-party video conferencing experiences over mobile
devices is still an open challenge. The fundamental reason behind is the lack
of computation and communication capacities on the mobile devices, to scale to
large conferencing sessions. In this paper, we present vSkyConf, a
cloud-assisted mobile video conferencing system to fundamentally improve the
quality and scale of multi-party mobile video conferencing. By novelly
employing a surrogate virtual machine in the cloud for each mobile user, we
allow fully scalable communication among the conference participants via their
surrogates, rather than directly. The surrogates exchange conferencing streams
among each other, transcode the streams to the most appropriate bit rates, and
buffer the streams for the most efficient delivery to the mobile recipients. A
fully decentralized, optimal algorithm is designed to decide the best paths of
streams and the most suitable surrogates for video transcoding along the paths,
such that the limited bandwidth is fully utilized to deliver streams of the
highest possible quality to the mobile recipients. We also carefully tailor a
buffering mechanism on each surrogate to cooperate with optimal stream
distribution. We have implemented vSkyConf based on Amazon EC2 and verified the
excellent performance of our design, as compared to the widely adopted unicast
solutions.Comment: 10 page
Dynamic similarity promotes interpersonal coordination in joint-action
Human movement has been studied for decades and dynamic laws of motion that
are common to all humans have been derived. Yet, every individual moves
differently from everyone else (faster/slower, harder/smoother etc). We propose
here an index of such variability, namely an individual motor signature (IMS)
able to capture the subtle differences in the way each of us moves. We show
that the IMS of a person is time-invariant and that it significantly differs
from those of other individuals. This allows us to quantify the dynamic
similarity, a measure of rapport between dynamics of different individuals'
movements, and demonstrate that it facilitates coordination during interaction.
We use our measure to confirm a key prediction of the theory of similarity that
coordination between two individuals performing a joint-action task is higher
if their motions share similar dynamic features. Furthermore, we use a virtual
avatar driven by an interactive cognitive architecture based on feedback
control theory to explore the effects of different kinematic features of the
avatar motion on the coordination with human players
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