483,605 research outputs found
Route Swarm: Wireless Network Optimization through Mobility
In this paper, we demonstrate a novel hybrid architecture for coordinating
networked robots in sensing and information routing applications. The proposed
INformation and Sensing driven PhysIcally REconfigurable robotic network
(INSPIRE), consists of a Physical Control Plane (PCP) which commands agent
position, and an Information Control Plane (ICP) which regulates information
flow towards communication/sensing objectives. We describe an instantiation
where a mobile robotic network is dynamically reconfigured to ensure high
quality routes between static wireless nodes, which act as source/destination
pairs for information flow. The ICP commands the robots towards evenly
distributed inter-flow allocations, with intra-flow configurations that
maximize route quality. The PCP then guides the robots via potential-based
control to reconfigure according to ICP commands. This formulation, deemed
Route Swarm, decouples information flow and physical control, generating a
feedback between routing and sensing needs and robotic configuration. We
demonstrate our propositions through simulation under a realistic wireless
network regime.Comment: 9 pages, 4 figures, submitted to the IEEE International Conference on
Intelligent Robots and Systems (IROS) 201
Magpie: Automatically Tuning Static Parameters for Distributed File Systems using Deep Reinforcement Learning
Distributed file systems are widely used nowadays, yet using their default
configurations is often not optimal. At the same time, tuning configuration
parameters is typically challenging and time-consuming. It demands expertise
and tuning operations can also be expensive. This is especially the case for
static parameters, where changes take effect only after a restart of the system
or workloads. We propose a novel approach, Magpie, which utilizes deep
reinforcement learning to tune static parameters by strategically exploring and
exploiting configuration parameter spaces. To boost the tuning of the static
parameters, our method employs both server and client metrics of distributed
file systems to understand the relationship between static parameters and
performance. Our empirical evaluation results show that Magpie can noticeably
improve the performance of the distributed file system Lustre, where our
approach on average achieves 91.8% throughput gains against default
configuration after tuning towards single performance indicator optimization,
while it reaches 39.7% more throughput gains against the baseline.Comment: Accepted at The IEEE International Conference on Cloud Engineering
(IC2E) conference 202
Long-distance distribution of genuine energy-time entanglement
Any practical realization of entanglement-based quantum communication must be
intrinsically secure and able to span long distances avoiding the need of a
straight line between the communicating parties. The violation of Bell's
inequality offers a method for the certification of quantum links without
knowing the inner workings of the devices. Energy-time entanglement quantum
communication satisfies all these requirements. However, currently there is a
fundamental obstacle with the standard configuration adopted: an intrinsic
geometrical loophole that can be exploited to break the security of the
communication, in addition to other loopholes. Here we show the first
experimental Bell violation with energy-time entanglement distributed over 1 km
of optical fibers that is free of this geometrical loophole. This is achieved
by adopting a new experimental design, and by using an actively stabilized
fiber-based long interferometer. Our results represent an important step
towards long-distance secure quantum communication in optical fibers.Comment: 6 pages, 3 figures. Matches published versio
Nanomechanics of a Hydrogen Molecule Suspended between Two Equally Charged Tips
Geometric configuration and energy of a hydrogen molecule centered between
two point-shaped tips of equal charge are calculated with the variational
quantum Monte-Carlo (QMC) method without the restriction of the
Born-Oppenheimer (BO) approximation. Ground state nuclear distribution,
stability, and low vibrational excitation are investigated. Ground state
results predict significant deviations from the BO treatment that is based on a
potential energy surface (PES) obtained with the same QMC accuracy. The quantum
mechanical distribution of molecular axis direction and bond length at a
sub-nanometer level is fundamental for understanding nanomechanical dynamics
with embedded hydrogen. Because of the tips' arrangement, cylindrical symmetry
yields a uniform azimuthal distribution of the molecular axis vector relative
to the tip-tip axis. With approaching tips towards each other, the QMC sampling
shows an increasing loss of spherical symmetry with the molecular axis still
uniformly distributed over the azimuthal angle but peaked at the tip-tip
direction for negative tip charge while peaked at the equatorial plane for
positive charge. This directional behavior can be switched between both stable
configurations by changing the sign of the tip charge and by controlling the
tip-tip distance. This suggests an application in the field of molecular
machines.Comment: 20 pages, 10 figure
Distributed Reception in the Presence of Gaussian Interference
abstract: An analysis is presented of a network of distributed receivers encumbered by strong in-band interference. The structure of information present across such receivers and how they might collaborate to recover a signal of interest is studied. Unstructured (random coding) and structured (lattice coding) strategies are studied towards this purpose for a certain adaptable system model. Asymptotic performances of these strategies and algorithms to compute them are developed. A jointly-compressed lattice code with proper configuration performs best of all strategies investigated.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
Improving CO2 methanation performance by distributed feeding in a Ni-Mn catalyst fixed bed reactor
It has been successfully demonstrated the effect of feeding reactants in distributed manner for the reaction of methanation of CO2. This operation mode has improved not only the selectivity towards CH4, but also the overall process performance. A fixed bed reactor, loaded with Ni-Mn based catalyst, was operated co-feeding both CO2 and H2, but alternatively feeding one of them through several lateral inlets. Preserving the same global W/FCO2 ratio, the side distribution of CO2 allowed to clearly increase the activity of the process (e.g., at 375 °C, the conversion with distributed feeding was around 35% higher than that for the conventional one: XCO2 = 0.12 vs. XCO2 = 0.09). Furthermore, a substantially lower selectivity towards non-desired CO was obtained at any conversion level (e.g., SCO = 0.45 vs. SCO = 0.70, when XCO2 = 0.10). In addition, a more homogeneous temperature profile could be achieved in the bed without increasing the severity of hot spots appearance. On the contrary, side distribution of H2 always led to similar or worse results than for the conventional co-feeding configuration
Swarm behavior of self-propelled rods and swimming flagella
Systems of self-propelled particles are known for their tendency to aggregate
and to display swarm behavior. We investigate two model systems, self-propelled
rods interacting via volume exclusion, and sinusoidally-beating flagella
embedded in a fluid with hydrodynamic interactions. In the flagella system,
beating frequencies are Gaussian distributed with a non-zero average. These
systems are studied by Brownian-dynamics simulations and by mesoscale
hydrodynamics simulations, respectively. The clustering behavior is analyzed as
the particle density and the environmental or internal noise are varied. By
distinguishing three types of cluster-size probability density functions, we
obtain a phase diagram of different swarm behaviors. The properties of
clusters, such as their configuration, lifetime and average size are analyzed.
We find that the swarm behavior of the two systems, characterized by several
effective power laws, is very similar. However, a more careful analysis reveals
several differences. Clusters of self-propelled rods form due to partially
blocked forward motion, and are therefore typically wedge-shaped. At higher rod
density and low noise, a giant mobile cluster appears, in which most rods are
mostly oriented towards the center. In contrast, flagella become
hydrodynamically synchronized and attract each other; their clusters are
therefore more elongated. Furthermore, the lifetime of flagella clusters decays
more quickly with cluster size than of rod clusters
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