1,721,149 research outputs found
Kinetic model for international trade allowing transfer of individuals
Full text linkWe propose a kinetic model to describe trade among different populations, living in different countries. The interaction rules are assumed depending on the trading propensity of each population and also on non-deterministic (random) effects. Moreover, the possible transfers of individuals from one country to another are also taken into account, by means of suitable Boltzmann-type operators. Consistent macroscopic equations for number density and mean wealth of each country are derived from the kinetic equations, and the effects of transfers on their equilibrium values are commented on. Finally, a suitable continuous trading limit is considered, leading to a simpler system of Fokker-Planck-type kinetic equations, with specific contributions accounting for transfers.This article is part of the theme issue 'Kinetic exchange models of societies and economies'
A BGK model for mixtures of monoatomic and polyatomic gases with discrete internal energy
No full textWe generalize the BGK model proposed in Bisi and Cáceres (2016) to a mixture constituted by both monoatomic and polyatomic gas species with each polyatomic one being characterized by its own number of discrete internal energy levels, to model its non-translational degrees of freedom. We prove that all disposable parameters appearing in the Maxwellian attractors may be determined in terms of the actual macroscopic fields in such a way that correct Maxwellian equilibria and collision invariants are preserved, as well as the validity of the H-theorem. Evolution equations for species densities, velocities and temperatures are also derived, and some numerical examples are shown in space homogeneous conditions
Erratum: "Fluid-dynamic equations for granular particles in a host medium" [J. Math. Phys. 46, 113301 (2005)]
No full textHuman motor control: Is a subject-specific quantitative assessment of its multiple characteristics possible? A demonstrative application on children motor development
Full text linkIn synergy with the musculoskeletal system, motor control is responsible of motor performance, determining joint kinematics and kinetics as related to task and environmental constraints. Multiple metrics have been proposed to quantify motor control from kinematic measures of motion, each index quantifying a different specific aspect, but the characterization of motor control as related to a specific subject or population during the execution of a specific task is still missing. In the present work, the performance of a novel approach for quantitative parametrization of motor control is tested over 86 primary school children: 36 I grade, 50 II grade; 40 females, 46 males. Children were assessed performing natural and tandem gait using 3 inertial measurement units, and gait variability, regularity, and complexity indexes were calculated from gait temporal parameters and trunk acceleration. Standard Test of Motor Competence and Developmental Coordination Disorder Questionnaire were used to assess reference motor competence. The proposed set of parameters allowed to discriminate the level of motor competence as related to age and standardised scales, while differences related to sex resulted negligible. The proposed method can effectively integrate musculoskeletal dynamic models, allowing the parametric characterization of motor control of specific subjects and/or populations
A ‘Fingerprint’ of locomotor maturation: Motor development descriptors, reference development bands and data-set
No full textBackground: When aiming at studying and monitoring locomotor development in childhood, innovative indexes for the characterization of motor control performance and wearable technologies have highlighted the potential of significant advances. In particular, quantitative assessment of motor performance during natural walking (NW) and tandem walking (TW) has been proposed to highlight manifestations of motor automaticity and complexity, respectively. Research question: This work aims at providing a quantitative overview of metrics characterizing locomotor maturation in a typically developing population, by analysing NW and TW. The final goal is to propose a novel graphical representation of motor development from childhood to adulthood, providing metrics for quantitative assessment with reference bands and data-set, supporting data interpretation and longitudinal assessment. Methods: 112 typically developing participants (age groups: 6-, 7-, 8-, 9-, 10-, 15-, and 25 years) walked in NW and in TW at self-selected speed. 3D acceleration and angular velocity of lower trunk and shanks were collected. Temporal parameters, their variability, and nonlinear metrics characterizing human movement (harmonic ratio, short-term Lyapunov exponents, multiscale entropy, and recurrence quantification analysis) were calculated. Effect of age was analysed on the different parameters and a graphical polar plot was defined to represent parameters that showed age effect in at least one of the two tasks. Results: Age effect was shown on temporal parameters, their variability, multiscale entropy and recurrence quantification analysis. These parameters were selected for monitoring locomotor development and presented on an ad-hoc designed polar plot showing age-group reference bands. Significance: Graphic results outline locomotor differences with maturation at first glance. The patterns in NW and TW allow to characterize specific aspects of locomotor maturation, to evaluate in which area changes occur and towards which direction, depending on the task. The novel database containing participants’ raw collected data is made available as additional result of the present study
Kinetic models of conservative economies with wealth redistribution
No full textKinetic models for wealth distribution in a simple market
economy are introduced, to reproduce the salient features of the wealth distribution by including taxes to each trading process and redistributing the collected money among the population according to a given criterion. Our analysis gives a theoretical basis to some recent research that analyzed discrete simplified models for the exploitation of finite resources by interacting agents, where each agent receives a random fraction of the available resources. It is shown that in general the redistribution is able to modify the Pareto index, and that this modification can be quantified in terms of the redistribution operator
- …
