5,372 research outputs found
Energy-based trajectory tracking and vibration control for multilink highly flexible manipulators
In this paper, a discrete model is adopted, as proposed by Hencky for elastica based on rigid bars and lumped rotational springs, to design the control of a lightweight planar manipulator with multiple highly flexible links. This model is particularly suited to deal with nonlinear equations of motion as those associated with multilink robot arms, because it does not include any simplification due to linearization, as in the assumed modes method. The aim of the control is to track a trajectory of the end effector of the robot arm, without the onset of vibrations. To this end, an energy-based method is proposed. Numerical simulations show the effectiveness of the presented approach
Darboux Integrability of Trapezoidal and Families of Lattice Equations II: General Solutions
In this paper we construct the general solutions of two families of
quad-equations, namely the trapezoidal equations and the
equations. These solutions are obtained exploiting the properties of the first
integrals in the Darboux sense, which were derived in [Gubbiotti G., Yamilov
R.I., J. Phys. A: Math. Theor. 50 (2017), 345205, 26 pages, arXiv:1608.03506].
These first integrals are used to reduce the problem to the solution of some
linear or linearizable non-autonomous ordinary difference equations which can
be formally solved
Heuristic Ranking in Tightly Coupled Probabilistic Description Logics
The Semantic Web effort has steadily been gaining traction in the recent
years. In particular,Web search companies are recently realizing that their
products need to evolve towards having richer semantic search capabilities.
Description logics (DLs) have been adopted as the formal underpinnings for
Semantic Web languages used in describing ontologies. Reasoning under
uncertainty has recently taken a leading role in this arena, given the nature
of data found on theWeb. In this paper, we present a probabilistic extension of
the DL EL++ (which underlies the OWL2 EL profile) using Markov logic networks
(MLNs) as probabilistic semantics. This extension is tightly coupled, meaning
that probabilistic annotations in formulas can refer to objects in the
ontology. We show that, even though the tightly coupled nature of our language
means that many basic operations are data-intractable, we can leverage a
sublanguage of MLNs that allows to rank the atomic consequences of an ontology
relative to their probability values (called ranking queries) even when these
values are not fully computed. We present an anytime algorithm to answer
ranking queries, and provide an upper bound on the error that it incurs, as
well as a criterion to decide when results are guaranteed to be correct.Comment: Appears in Proceedings of the Twenty-Eighth Conference on Uncertainty
in Artificial Intelligence (UAI2012
Wrinkling in engineering fabrics: a comparison between two different comprehensive modelling approaches
We consider two ‘comprehensive’ modelling approaches for engineering fabrics. We distinguish the two approaches using the terms ‘semi-discrete’ and ‘continuum’, reflecting their natures. We demonstrate a fitting procedure, used to identify the constitutive parameters of the continuum model from predictions of the semi-discrete model, the parameters of which are in turn fitted to experimental data. We, then, check the effectiveness of the continuum model by verifying the correspondence between semi-discrete and continuum model predictions using test cases not previously used in the identification process. Predictions of both modelling approaches are compared against full-field experimental kinematic data, obtained using stereoscopic digital image correlation techniques, and also with measured force data. Being a reduced order model and being implemented in an implicit rather than an explicit finite-element code, the continuum model requires significantly less computational power than the semi-discrete model and could therefore be used to more efficiently explore the mechanical response of engineering fabrics
Universal microstructure and mechanical stability of jammed packings
Jammed packings' mechanical properties depend sensitively on their detailed
local structure. Here we provide a complete characterization of the pair
correlation close to contact and of the force distribution of jammed
frictionless spheres. In particular we discover a set of new scaling relations
that connect the behavior of particles bearing small forces and those bearing
no force but that are almost in contact. By performing systematic
investigations for spatial dimensions d=3-10, in a wide density range and using
different preparation protocols, we show that these scalings are indeed
universal. We therefore establish clear milestones for the emergence of a
complete microscopic theory of jamming. This description is also crucial for
high-precision force experiments in granular systems.Comment: 11 pages, 7 figure
Universal non-Debye scaling in the density of states of amorphous solids
At the jamming transition, amorphous packings are known to display anomalous
vibrational modes with a density of states (DOS) that remains constant at low
frequency. The scaling of the DOS at higher densities remains, however,
unclear. One might expect to find simple Debye scaling, but recent results from
effective medium theory and the exact solution of mean-field models both
predict an anomalous, non-Debye scaling. Being mean-field solutions, however,
these solutions are only strictly applicable to the limit of infinite spatial
dimension, and it is unclear what value they have for finite-dimensional
systems. Here, we study packings of soft spheres in dimensions 3 through 7 and
find, far from jamming, a universal non-Debye scaling of the DOS that is
consistent with the mean-field predictions. We also consider how the soft mode
participation ratio converges to the mean-field prediction as dimension
increases.Comment: 5 pages, 4 figure
Oral health knowledge in pre-school children: a survey among parents in central Italy
Background: The aim of this survey was to evaluate the knowledge and awareness of parents about potential oral
health risk factors and correct management of oral hygiene of their preschool children.
Material and Methods: The participation to the survey was proposed to all parents of 3-5 year aged children attending a kindergarten in Campobasso. A self-administered questionnaire was completed to obtain information regarding demographic and education variables, knowledge about caries and its transmission, infant feeding practice,
maternal oral health during pregnancy, parents and children’s oral hygiene habits and risk behaviors (e.g., sharing
cutlery, tasting of baby food, nightly using of baby bottles or pacifier), oral health prevention and role of school.
Results: Overall, the parents of 101 children consented to fill the questionnaire. Data analysis showed that only
24% of respondents was aware of the potential vertical transmissibility of cariogenic bacteria through contaminated
saliva. It is still a common trend from61% of parents tasting food of their child. On 101 children, 30% used pacifier
and 17% used baby bottle with milk during night and among these children 41% for more than 2 years. Parents
reported no toothbrushing for 57% of the children in their first 3 years of life.
Conclusions: From this survey, independently on parents education, it emerges as still nowadays parents are not
fully trained and informed about the management of their child’s oral hygiene and as it’s necessary a parental oral
health promoting program to control children oral health risk status, starting from school
Experimental Quantum Imaging exploiting multi-mode spatial correlation of twin beams
Properties of quantum states have disclosed new and revolutionary
technologies, ranging from quantum information to quantum imaging. This last
field is addressed to overcome limits of classical imaging by exploiting
specific properties of quantum states of light. One of the most interesting
proposed scheme exploits spatial quantum correlations between twin beams for
realizing sub-shot-noise imaging of the weak absorbing objects, leading ideally
to a noise-free imaging. Here we discuss in detail the experimental realization
of this scheme, showing its capability to reach a larger signal to noise ratio
with respect to classical imaging methods and, therefore, its interest for
future practical applications
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