2,427 research outputs found
Online Distributed Sensor Selection
A key problem in sensor networks is to decide which sensors to query when, in
order to obtain the most useful information (e.g., for performing accurate
prediction), subject to constraints (e.g., on power and bandwidth). In many
applications the utility function is not known a priori, must be learned from
data, and can even change over time. Furthermore for large sensor networks
solving a centralized optimization problem to select sensors is not feasible,
and thus we seek a fully distributed solution. In this paper, we present
Distributed Online Greedy (DOG), an efficient, distributed algorithm for
repeatedly selecting sensors online, only receiving feedback about the utility
of the selected sensors. We prove very strong theoretical no-regret guarantees
that apply whenever the (unknown) utility function satisfies a natural
diminishing returns property called submodularity. Our algorithm has extremely
low communication requirements, and scales well to large sensor deployments. We
extend DOG to allow observation-dependent sensor selection. We empirically
demonstrate the effectiveness of our algorithm on several real-world sensing
tasks
Complete classification of stationary flows with constant total pressure of ideal incompressible infinitely conducting fluid
The exhaustive classification of stationary incompressible flows with
constant total pressure of ideal infinitely electrically conducting fluid is
given. By introduction of curvilinear coordinates based on streamlines and
magnetic lines of the flow the system of magnetohydrodynamics (MHD) equations
is reduced to a nonlinear vector wave equation extended by the
incompressibility condition in a form of a generalized Cauchy integral. For
flows with constant total pressure the wave equation is explicitly integrated,
whereas the incompressibility condition is reduced to a scalar equation for
functions, depending on different sets of variables. The central difficulty of
the investigation is the separation of variables in the scalar equation, and
integration of the resulting overdetermined systems of nonlinear partially
differential equations. The canonical representatives of all possible types of
solutions together with equivalence transformations, that extend the canonical
set to the whole amount of solutions are represented
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