1,090 research outputs found
Fault-tolerant formation driving mechanism designed for heterogeneous MAVs-UGVs groups
A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper
Signatures of Star-planet interactions
Planets interact with their host stars through gravity, radiation and
magnetic fields, and for those giant planets that orbit their stars within
10 stellar radii (0.1 AU for a sun-like star), star-planet
interactions (SPI) are observable with a wide variety of photometric,
spectroscopic and spectropolarimetric studies. At such close distances, the
planet orbits within the sub-alfv\'enic radius of the star in which the
transfer of energy and angular momentum between the two bodies is particularly
efficient. The magnetic interactions appear as enhanced stellar activity
modulated by the planet as it orbits the star rather than only by stellar
rotation. These SPI effects are informative for the study of the internal
dynamics and atmospheric evolution of exoplanets. The nature of magnetic SPI is
modeled to be strongly affected by both the stellar and planetary magnetic
fields, possibly influencing the magnetic activity of both, as well as
affecting the irradiation and even the migration of the planet and rotational
evolution of the star. As phase-resolved observational techniques are applied
to a large statistical sample of hot Jupiter systems, extensions to other
tightly orbiting stellar systems, such as smaller planets close to M dwarfs
become possible. In these systems, star-planet separations of tens of stellar
radii begin to coincide with the radiative habitable zone where planetary
magnetic fields are likely a necessary condition for surface habitability.Comment: Accepted for publication in the handbook of exoplanet
Development of the Prevent for Work questionnaire (P4Wq) for assessment of musculoskeletal risk in the workplace: part 1-literature review and domains selection
Objective This study aims to define appropriate domains and items for the development of a self-administered questionnaire to assess the risk of developing work-related musculoskeletal disorder (WMSD) and the risk of its progression to chronicity. Design Literature review and survey study. Setting and participants A literature review and a two-round interview with 15 experts in musculoskeletal pain were performed to identify the available domains for WMSD assessment. Interventions and outcome To ensure quality, only validated questionnaires were included for the Delphi process. A three-round Delphi method, with three round steps, was used to select the most pertinent and relevant domains and items. Results Nine questionnaires were identified through the expert discussion and literature review, comprising 38 candidate domains and 504 items. In the first round of the Delphi group, 17 domains reached more than 70% agreement and were selected. In the second round, 10 domains were rejected, while 11 were selected to complete the pool of domains. In the third and final round, 89 items belonging to 28 domains were defined as significant to develop a WMSDs risk assessment questionnaire. Conclusions No specific risk assessment questionnaires for WMSDs were identified from the literature. WMSD risk of presence and chronicity can be defined by an assessment tool based on the biopsychosocial model and the fear-avoidance components of chronic pain. The present study provides the formulation and operationalisation of the constructs in domains and items needed for developing and validating the questionnaire
Interaction Between Convection and Pulsation
This article reviews our current understanding of modelling convection
dynamics in stars. Several semi-analytical time-dependent convection models
have been proposed for pulsating one-dimensional stellar structures with
different formulations for how the convective turbulent velocity field couples
with the global stellar oscillations. In this review we put emphasis on two,
widely used, time-dependent convection formulations for estimating pulsation
properties in one-dimensional stellar models. Applications to pulsating stars
are presented with results for oscillation properties, such as the effects of
convection dynamics on the oscillation frequencies, or the stability of
pulsation modes, in classical pulsators and in stars supporting solar-type
oscillations.Comment: Invited review article for Living Reviews in Solar Physics. 88 pages,
14 figure
Is the incidence of meningiomas underestimated? A regional survey
We assessed the undercount of meningiomas in a population-based cancer registry. A comprehensive material was formed by compiling hospital sources with the Finnish Cancer Registry database. The completeness of each source ranged 62–69%. The corrected age-standardised meningioma incidence was 2.9/100 000 for men and 13.0/100 000 for women, a third higher than the cancer registry figures
Crossing media boundaries: adaptations and new media forms of the book
t is necessary to continuously review the definition of the book moving from one bound by its material form to one determined by its function as a means of communication. The book’s social function as the high status vehicle for communicating new ideas and cultural expressions is being challenged by sophisticated systems of conveying meaning in other media. In this article, we report on two projects: electronic book (e-book) publication and reader forum for Nature Mage and the transmedia augmented reality (AR) fiction Sherwood Rise, which investigate these issues. Claudio Pires Franco’s work is based on the adaptation of a source work: Duncan Pile’s Nature Mage. The project aims to develop the book from e-book to a fan-produced enhanced digital book. Through this practice-based research, Franco investigates the definitions and classification of the e and i forms of the book and adaptation in new media; the role of the author in creative collaboration with readers through online forums; the extension of the story world through creative collaboration and reader participation while respecting and safeguarding creative properties. One remove from the traditional book, David Miller’s Sherwood Rise, research the user experience with AR to examine narrative problems and explore new storytelling aesthetics. These new media forms define the outer borders of the book system within which content is formed and moulded, and around which society is shaped
Asteroseismology
Asteroseismology is the determination of the interior structures of stars by
using their oscillations as seismic waves. Simple explanations of the
astrophysical background and some basic theoretical considerations needed in
this rapidly evolving field are followed by introductions to the most important
concepts and methods on the basis of example. Previous and potential
applications of asteroseismology are reviewed and future trends are attempted
to be foreseen.Comment: 38 pages, 13 figures, to appear in: "Planets, Stars and Stellar
Systems", eds. T. D. Oswalt et al., Springer Verla
Presynaptic partner selection during retinal circuit reassembly varies with timing of neuronal regeneration in vivo
Whether neurons can restore their original connectivity patterns during circuit repair is unclear. Taking advantage of the regenerative capacity of zebrafish retina, we show here the remarkable specificity by which surviving neurons reassemble their connectivity upon regeneration of their major input. H3 horizontal cells (HCs) normally avoid red and green cones, and prefer ultraviolet over blue cones. Upon ablation of the major (ultraviolet) input, H3 HCs do not immediately increase connectivity with other cone types. Instead, H3 dendrites retract and re-extend to contact new ultraviolet cones. But, if regeneration is delayed or absent, blue-cone synaptogenesis increases and ectopic synapses are made with red and green cones. Thus, cues directing synapse specificity can be maintained following input loss, but only within a limited time period. Further, we postulate that signals from the major input that shape the H3 HC's wiring pattern during development persist to restrict miswiring after damage
A Complete Model of Low-Scale Gauge Mediation
Recent signs of a Standard Model-like Higgs at 125 GeV point towards large
A-terms in the MSSM. This presents special challenges for gauge mediation,
which by itself predicts vanishing A-terms at the messenger scale. In this
paper, we review the general problems that arise when extending gauge mediation
to achieve large A-terms, and the mechanisms that exist to overcome them. Using
these mechanisms, we construct weakly-coupled models of low-scale gauge
mediation with extended Higgs-messenger couplings that generate large A-terms
at the messenger scale and viable mu/B_mu-terms. Our models are simple,
economical, and complete realizations of supersymmetry at the weak scale.Comment: 33 pages; v2: refs added, minor change
The effect of web based depression interventions on self reported help seeking: randomised controlled trial [ISRCTN77824516]
BACKGROUND: To date, there has been very little work investigating behaviour changes induced by interventions that are designed to increase help seeking. The present paper examines the effects of two Internet depression websites on help seeking. METHODS: 414 individuals with elevated scores on a depression assessment scale were randomly allocated to a depression information website, a cognitive-behavioural skills training website (CBT) or an attention control condition. Reports of help seeking for specific treatments, from specific sources and for categories of treatments were assessed. RESULTS: Relative to the control, the depression information site was associated with decreases in seeking support from friends and family, the use of music and of everyday treatments and no increase in seeking evidence based interventions. The CBT site was associated with the report of help seeking for CBT, massage and exercise. CONCLUSION: Methods to encourage the use of evidence-based treatments need further research to determine whether the assistance sought is evidence based and whether there are unintended effects
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