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

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

A statistical model analysis of K/πK/\pi fluctuations in heavy ion collisions

We briefly describe two statistical hadronization models, based respectively on the presence and absence of light quark chemical equilibrium, used to analyze particle yields in heavy ion collisions. We then try to distinguish between these models using $K/\pi$ fluctuations data. We find that while the non-equilibrium model provides an acceptable description of fluctuations at top SPS and RHIC energies, both models considerably under-estimate fluctuations at low SPS energies.Comment: References updated Poster in QM2006 conference, Shangha

Deformation patterns in a second-gradient lattice annular plate composed of "Spira mirabilis" fibers

In this paper, we aim to explore the mechanical potentialities of a material made of an orthogonal net of fibers arranged in logarithmic spirals. Therefore, an annular plate described with a second-gradient model is envisaged to evaluate the behavior of such material in a nonlinear elastic regime when large displacements and deformations occur. Several mechanical tests are performed numerically under the finite element method approximation obtained directly with a weak formulation based on the elastic energy that it is assumed to be predictive for this kind of network system of fibers. Plots reporting the mechanical characteristics in all the considered tests are provided to illustrate the overall mechanical behavior of the evaluated system

Hadron Resonances and Phase Threshold in Heavy Ion Collisions

We show that a measurement of the reaction energy dependence of relative hadron resonance yields in heavy ion collisions can be used to study the phase structure of the dense QCD matter created in these collisions, and investigate the origin of the trends observed in the excitation functions of certain soft hadronic observables. We show that presence of chemical nonequilibrium in light quark abundance imparts a characteristic signature on the energy dependence of resonance yields, that differs considerably from what is expected in the equilibrium picture.Comment: In press, Phys. Rev.

A two-dimensional continuum model of pantographic sheets moving in a 3D space and accounting for the offset and relative rotations of the fibers

Recently growing attention has been paid to the particular class of metamaterials which has been called pantographic. Pantographic metamaterials have the following peculiar features: (i) their continuum model, at the macroscale, has to include a term of the deformation energy depending on the second gradient of placement, (ii) they can show an elastic behavior in large deformation regimes, and (iii) they are resilient and tough during rupture phenomena (dell'Isola et al. 2015). In order to predict pantographic metamaterials' mechanical behavior, it is possible to introduce a three-dimensional continuum micromodel, in which their internal geometrical microstructure is described in detail. However, the computational costs of this choice are presently prohibitive. In this paper, we introduce a reduced order model for pantographic sheets-which are an example of an elastic surface-whose kinematics include, for each of the two constituting families of fibers fully independent three-dimensional (i) placement and (ii) rotation fields. In this way it is possible to include, also in the reduced order model, (i) the initial and the actual offset between the fibers and (ii) the deformation energy of the interconnecting pivots. By postulating a simplified expression for the deformation energy we prove that also a reduced order model can describe some experimental observed buckling and postbuckling phenomena. The promising results which we present here motivate the quest of more general expressions for deformation energy capable of capturing the fully nonlinear behavior exhibited by pantographic sheets

An Approach to the Simulation of a Batch-respirometer

Dynamic models in activated sludge processes have demonstrated to be a reliable and useful instrument in design and management of wastewater treatment plants. The biochemical nature of the processes involved the models which need a specific calibration to local conditions. A common method to determine kinetic and stoichiometric parameters of the biomass or wastewater/sludge fractionations is respirometry. Theoretically, nearly all biomass parameters and fractions can be estimated by respirometry, but a lot of difficulties rise when some parameters, such as saturation and hydrolysis rate constants, have to be drawn from experimental data. The aim of our work is the setting up of a simple method to calibrate Activated Sludge Model No. 1 applying traditional batch respirometric tests together with dynamic simulations of the respirometer itself

Particle yield fluctuations and chemical non-equilibrium at RHIC

We study charge fluctuations within the statistical hadronization model. Considering both the particle yield ratios and the charge fluctuations we show that it is possible to differentiate between chemical equilibrium and non-equilibrium freeze-out conditions. As an example of the procedure we show quantitatively how the relative yield ratio $\Lambda/K^-$ together with the normalized net charge fluctuation v(Q)=\ave{\Delta Q^2}/\ave{\Nch} constrain the chemical conditions at freeze-out. We also discuss the influence of the limited detector acceptance on fluctuation measurements, and show how this can be accounted for within a quantitative analysis.Comment: Accepted for publication by Physical Review

Thermodynamic Field Theory with the Iso-Entropic Formalism

A new formulation of the thermodynamic field theory (TFT) is presented. In this new version, one of the basic restriction in the old theory, namely a closed-form solution for the thermodynamic field strength, has been removed. In addition, the general covariance principle is replaced by Prigogine's thermodynamic covariance principle (TCP). The introduction of TCP required the application of an appropriate mathematical formalism, which has been referred to as the iso-entropic formalism. The validity of the Glansdorff-Prigogine Universal Criterion of Evolution, via geometrical arguments, is proven. A new set of thermodynamic field equations, able to determine the nonlinear corrections to the linear ("Onsager") transport coefficients, is also derived. The geometry of the thermodynamic space is non-Riemannian tending to be Riemannian for hight values of the entropy production. In this limit, we obtain again the same thermodynamic field equations found by the old theory. Applications of the theory, such as transport in magnetically confined plasmas, materials submitted to temperature and electric potential gradients or to unimolecular triangular chemical reactions can be found at references cited herein.Comment: 35 page

The mean field theory of spin glasses: the heuristic replica approach and recent rigorous results

The mathematically correct computation of the spin glasses free energy in the infinite range limit crowns 25 years of mathematic efforts in solving this model. The exact solution of the model was found many years ago by using a heuristic approach; the results coming from the heuristic approach were crucial in deriving the mathematical results. The mathematical tools used in the rigorous approach are quite different from those of the heuristic approach. In this note we will review the heuristic approach to spin glasses in the light of the rigorous results; we will also discuss some conjectures that may be useful to derive the solution of the model in an alternative way.Comment: 12 pages, 1 figure; lecture at the Flato Colloquia Day, Thursday 27 November, 200