2,182 research outputs found
Physics and Applications of Laser Diode Chaos
An overview of chaos in laser diodes is provided which surveys experimental
achievements in the area and explains the theory behind the phenomenon. The
fundamental physics underpinning this behaviour and also the opportunities for
harnessing laser diode chaos for potential applications are discussed. The
availability and ease of operation of laser diodes, in a wide range of
configurations, make them a convenient test-bed for exploring basic aspects of
nonlinear and chaotic dynamics. It also makes them attractive for practical
tasks, such as chaos-based secure communications and random number generation.
Avenues for future research and development of chaotic laser diodes are also
identified.Comment: Published in Nature Photonic
Empirical exploration of air traffic and human dynamics in terminal airspaces
Air traffic is widely known as a complex, task-critical techno-social system,
with numerous interactions between airspace, procedures, aircraft and air
traffic controllers. In order to develop and deploy high-level operational
concepts and automation systems scientifically and effectively, it is essential
to conduct an in-depth investigation on the intrinsic traffic-human dynamics
and characteristics, which is not widely seen in the literature. To fill this
gap, we propose a multi-layer network to model and analyze air traffic systems.
A Route-based Airspace Network (RAN) and Flight Trajectory Network (FTN)
encapsulate critical physical and operational characteristics; an Integrated
Flow-Driven Network (IFDN) and Interrelated Conflict-Communication Network
(ICCN) are formulated to represent air traffic flow transmissions and
intervention from air traffic controllers, respectively. Furthermore, a set of
analytical metrics including network variables, complex network attributes,
controllers' cognitive complexity, and chaotic metrics are introduced and
applied in a case study of Guangzhou terminal airspace. Empirical results show
the existence of fundamental diagram and macroscopic fundamental diagram at the
route, sector and terminal levels. Moreover, the dynamics and underlying
mechanisms of "ATCOs-flow" interactions are revealed and interpreted by
adaptive meta-cognition strategies based on network analysis of the ICCN.
Finally, at the system level, chaos is identified in conflict system and human
behavioral system when traffic switch to the semi-stable or congested phase.
This study offers analytical tools for understanding the complex human-flow
interactions at potentially a broad range of air traffic systems, and underpins
future developments and automation of intelligent air traffic management
systems.Comment: 30 pages, 28 figures, currently under revie
Equation of state of a granular gas homogeneously driven by particle rotations
We report an experimental study of a dilute "gas" of magnetic particles
subjected to a vertical alternating magnetic field in a 3D container. Due to
the torque exerted by the field on the magnetic moment of each particle, a
spatially homogeneous and chaotic forcing is reached where only rotational
motions are driven. This forcing differs significantly from boundary-driven
systems used in most previous experimental studies on non equilibrium
dissipative granular gases. Here, no cluster formation occurs, and the equation
of state displays strong analogy with the usual gas one apart from a geometric
factor. Collision statistics is also measured and shows an exponential tail for
the particle velocity distribution. Most of these observations are well
explained by a simple model which uncovers out-of-equilibrium systems
undergoing uniform "heating".Comment: Europhysics Letters (2013) in pres
Fast fixed-time synchronization of T–S fuzzy complex networks
In this paper, fast fixed-time (FDT) synchronization of T–S fuzzy (TSF) complex networks (CNs) is considered. The given control schemes can make the CNs synchronize with the given isolated system more fleetly than the most of existing results. By constructing comparison system and applying new analytical techniques, sufficient conditions are established to derive fast FDT synchronization speedily. In order to give some comparisons, FDT synchronization of the considered CNs is also presented by designing FDT fuzzy controller. Numerical examples are given to illustrate our new results
Complex scaling behavior in animal foraging patterns
This dissertation attempts to answer questions from two different areas of biology, ecology and neuroscience, using physics-based techniques. In Section 2, suitability of three competing random walk models is tested to describe the emergent movement patterns of two species of primates. The truncated power law (power law with exponential cut off) is the most suitable random walk model that characterizes the emergent movement patterns of these primates. In Section 3, an agent-based model is used to simulate search behavior in different environments (landscapes) to investigate the impact of the resource landscape on the optimal foraging movement patterns of deterministic foragers. It should be noted that this model goes beyond previous work in that it includes parameters such as spatial memory and satiation, which have received little consideration to date in the field of movement ecology. When the food availability is scarce in a tropical forest-like environment with feeding trees distributed in a clumped fashion and the size of those trees are distributed according to a lognormal distribution, the optimal foraging pattern of a generalist who can consume various and abundant food types indeed reaches the Lévy range, and hence, show evidence for Lévy-flight-like (power law distribution with exponent between 1 and 3) behavior. Section 4 of the dissertation presents an investigation of phase transition behavior in a network of locally coupled self-sustained oscillators as the system passes through various bursting states. The results suggest that a phase transition does not occur for this locally coupled neuronal network. The data analysis in the dissertation adopts a model selection approach and relies on methods based on information theory and maximum likelihood
Synchronization along quantum trajectories
We employ a quantum trajectory approach to characterize synchronization and
phase-locking between open quantum systems in nonequilibrium steady states. We
exemplify our proposal for the paradigmatic case of two quantum Van der Pol
oscillators interacting through dissipative coupling. We show the deep impact
of synchronization on the statistics of phase-locking indicators and other
correlation measures defined for single trajectories, spotting a link between
the presence of synchronization and the emergence of large tails in the
probability distribution for the entanglement along trajectories. Our results
shed new light on fundamental issues regarding quantum synchronization
providing new methods for its precise quantification.Comment: v2: 9 + 3 pages, 5 figures. v3: few typos corrected, close to the
published versio
Kalman filter based ranging and clock synchronization for ultra wide band sensor networks
This Thesis presents the design, implementation, and validation of a Kalman filterbased
range estimation technique to precisely calculate the inter-node ranges of Ultra
Wide Band (UWB) modules. In addition to that the development and validation of
an improved global clock synchronization framework is presented.
Noise characteristics of relative time measurements of a stationary UWB anchor pair
are first analyzed using an Allan deviation plot. To track the propagation of the
imprecise clocks on low cost UWB transceiver platforms, Kalman filters are used in
between every anchor pair. These filters track the variation of a remote anchor’s
hardware clock relative to it’s own hardware clock, while estimating the time of flight
between the anchor pair as a filter state. While adhering to a simple round robin
transmission schedule, both inbound and outbound message timestamp data are used
to update the filter. These measurements have made the time of flight observable in
the chosen state space. A faster relative clock filter convergence has been achieved
with the inclusion of the clock offset ratio as a measurement additional to the timestamps.
Furthermore, a modified gradient clock synchronization algorithm is used to achieve
global clock synchronization throughout the network. A correction term is used in the
gradient clock synchronization algorithm to enforce the global clock rate to converge
at the average of individual clock rates while achieving asymptotic stability in clock
rate error state. Stability of the original and modified methods for time invariant
hardware clocks are compared using eigenvalue tests. Experiments are conducted
to evaluate synchronization and ranging accuracy of the proposed range estimation
approach
Swarm dynamics may give rise to Lévy flights
“Continuous-time correlated random walks” are now gaining traction as models of scale-finite animal movement patterns because they overcome inherent shortcomings with the prevailing paradigm - discrete random walk models. Continuous-time correlated random walk models are founded on the classic Langevin equation that is driven by purely additive noise. The Langevin equation is, however, changed fundamentally by the smallest of multiplicative noises. The inclusion of such noises gives rise to Lévy flights, a popular but controversial model of scale-free movement patterns. Multiplicative noises have not featured prominently in the literature on biological Lévy flights, being seen, perhaps, as no more than a mathematical contrivance. Here we show how Langevin equations driven by multiplicative noises and incumbent Lévy flights arise naturally in the modelling of swarms. Model predictions find some support in three-dimensional, time-resolved measurements of the positions of individual insects in laboratory swarms of the midge Chironomus riparius. We hereby provide a new window on Lévy flights as models of movement pattern data, linking patterns to generative processes
Energy harvesting technologies for structural health monitoring of airplane components - a review
With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 "Optimising Design for Inspection" (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.The work of S. Zelenika, P. Gljušcic, E. Kamenar and Ž. Vrcan is partly enabled by using
the equipment funded via the EU European Regional Development Fund (ERDF) project no. RC.2.2.06-0001:
“Research Infrastructure for Campus-based Laboratories at the University of Rijeka (RISK)” and partly supported
by the University of Rijeka, Croatia, project uniri-tehnic-18-32 „Advanced mechatronics devices for smart
technological solutions“. Z. Hadas, P. Tofel and O. Ševecek acknowledge the support provided via the Czech
Science Foundation project GA19-17457S „Manufacturing and analysis of flexible piezoelectric layers for smart
engineering”. J. Hlinka, F. Ksica and O. Rubes gratefully acknowledge the financial support provided by the
ESIF, EU Operational Programme Research, Development and Education within the research project Center of
Advanced Aerospace Technology (Reg. No.: CZ.02.1.01/0.0/0.0/16_019/0000826) at the Faculty of Mechanical
Engineering, Brno University of Technology. V. Pakrashi would like to acknowledge UCD Energy Institute, Marine
and Renewable Energy Ireland (MaREI) centre Ireland, Strengthening Infrastructure Risk Assessment in the
Atlantic Area (SIRMA) Grant No. EAPA\826/2018, EU INTERREG Atlantic Area and Aquaculture Operations with
Reliable Flexible Shielding Technologies for Prevention of Infestation in Offshore and Coastal Areas (FLEXAQUA),
MarTera Era-Net cofund PBA/BIO/18/02 projects. The work of J.P.B. Silva is partially supported by the Portuguese
Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/FIS/04650/2020.
M. Mrlik gratefully acknowledges the support of the Ministry of Education, Youth and Sports of the Czech
Republic-DKRVO (RP/CPS/2020/003
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