Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir force

A so far not considered energy loss mechanism in suspended micro- and nanoresonators due to noncontact acoustical energy loss is investigated theoretically. The mechanism consists on the conversion of the mechanical energy from the vibratory motion of the resonator into acoustic waves on large nearby structures, such as the substrate, due to the coupling between the resonator and those structures resulting from the Casimir force acting over the separation gaps. Analytical expressions for the resulting quality factor Q for cantilever and bridge micro- and nanoresonators in close proximity to an underlying substrate are derived and the relevance of the mechanism is investigated, demonstrating its importance when nanometric gaps are involved

Anomalous quantum chaotic behavior in nanoelectromechanical structures

It is predicted that for sufficiently strong electron-phonon coupling an anomalous quantum chaotic behavior develops in certain types of suspended electro-mechanical nanostructures, here comprised by a thin cylindrical quantum dot (billiard) on a suspended rectangular dielectric plate. The deformation potential and piezoelectric interactions are considered. As a result of the electron-phonon coupling between the two systems the spectral statistics of the electro-mechanic eigenenergies exhibit an anomalous behavior. If the center of the quantum dot is located at one of the symmetry axes of the rectangular plate, the energy level distributions correspond to the Gaussian Orthogonal Ensemble (GOE), otherwise they belong to the Gaussian Unitary Ensemble (GUE), even though the system is time-reversal invariant.Comment: 4 pages, pdf forma

Alternative and extended communication for the intelectual development in children and adolescents with cerebral palsy in Brazil

Crianças e adolescentes com paralisia cerebral e privados de comunicação efetiva podem também ter seu desenvolvimento intelectual dificultado. O objetivo desta pesquisa foi avaliar o desenvolvimento intelectual de crianças e adolescentes com paralisia cerebral e necessidades complexas de comunicação em uma escola especial no Brasil, baseado no uso de comunicação alternativa e ampliada (CAA). Quinze indivíduos com paralisia cerebral (idade média: 11a3m ± 2a9m) foram avaliados: 9 usavam CAA (seis meninos, 11a9m ± 3a4m) e seis não usavam (3 meninos, 10a6m ± 1a6m). As Matrizes Progressivas Coloridas de Raven – Escala Especial (CPM) foram usadas para a avaliação intelectual. Os que utilizavam a CAA obtiveram uma média de 25.89, os que não usavam 5.83 (p=0.012). Os resultados indicam que nesse coorte existe uma diferença significativa entre o desenvolvimento intelectual dos que usam CAA e dos que não a usam.Children and adolescents with cerebral palsy and devoid of effective communication may also have their intellectual development impaired. The goal of this research was to assess the intellectual development of children and adolescents with cerebral palsy (CP) and complex communication needs in a special school in Brazil based on their reliance on augmentative and alternative communication (AAC). Fifteen individuals with cerebral palsy (mean age: 11y3m ± 2y9m) were assessed: nine of them relied on AAC (6 males, 11y9m ± 3y4m) and six did not (3 males, 10y6m ± 1y6m). Raven’s Colored Progressive Matrices – Special Scale (CPM) were used for the intellectual evaluation. Individuals who relied on AAC reached a mean of 25.89 those who did not 5.83 (p=0.012). There was a significant difference, in this cohort, between the intellectual development of those who used AAC and those who did not.Facultad de Informátic

Esercizi di matematica finanziaria: regimi finanziari, rendite e ammortamenti

Quaderno di Didattic

Dense conjugate initialization for deterministic PSO in applications: ORTHOinit+

This paper describes a class of novel initializations in Deterministic Particle Swarm Optimization (DPSO) for approximately solving costly unconstrained global optimization problems. The initializations are based on choosing specific dense initial positions and velocities for particles. These choices tend to induce in some sense orthogonality of particles’ trajectories, in the early iterations, in order to better explore the search space. Our proposal is inspired by both a theoretical analysis on a reformulation of PSO iteration, and by possible limits of the proposals reported in Campana et al. (2010); Campana et al. (2013). We explicitly show that, in comparison with other initializations from the literature, our initializations tend to scatter PSO particles, at least in the first iterations. The latter goal is obtained by imposing that the initial choice of particles’ position/velocity satisfies specific conjugacy conditions, with respect to a matrix depending on the parameters of PSO. In particular, by an appropriate condition on particles’ velocities, our initializations also resemble and partially extend a general paradigm in the literature of exact methods for derivative-free optimization. Moreover, we propose dense initializations for DPSO, so that the final approximate global solution obtained is possibly not too sparse, which might cause troubles in some applications. Numerical results, on both Portfolio Selection and Computational Fluid Dynamics problems, validate our theory and prove the effectiveness of our proposal, which applies also in case different neighborhood topologies are adopted in DPSO

Esercizi sulle funzioni: modelli lineari e non lineari con applicazioni all’economia

Quaderno di Didattic

Esercizi di algebra lineare e sistemi di equazioni lineari con applicazioni all'economia

Quaderno di Didattic

An evolutionary approach to preference disaggregation in a MURAME-based credit scoring problem

In this paper we use an evolutionary approach in order to infer the values of the parameters (weights of criteria, preference, indifference and veto thresholds) for developing the multicriteria method MURAME. According to the logic of preference disaggregation, the problem consists in finding the parameters that minimize the inconsistency between the model obtained with those parameters and that one connected with a given reference set of decisions revealed by the decision maker; in particular, two kinds of functions are considered in this analysis, representing a measure of the model inconsistency compared to the actual preferential system. In order to find a numerical solution of the mathematical programming problem involved, we adopt an evolutionary algorithm based on the Particle Swarm Optimization (PSO) method, which is an iterative heuristics grounded on swarm intelligence. The proposed approach is finally applied to a creditworthiness evaluation problem in order to test the methodology on a real data set provided by an Italian bank

Esercizi sulle funzioni di più variabili reali con applicazioni all’economia

Quaderno di Didattic

Quantum chaos in nanoelectromechanical systems

We present a theoretical study of the electron-phonon coupling in suspended nanoelectromechanical systems (NEMS) and investigate the resulting quantum chaotic behavior. The phonons are associated with the vibrational modes of a suspended rectangular dielectric plate, with free or clamped boundary conditions, whereas the electrons are confined to a large quantum dot (QD) on the plate's surface. The deformation potential and piezoelectric interactions are considered. By performing standard energy-level statistics we demonstrate that the spectral fluctuations exhibit the same distributions as those of the Gaussian Orthogonal Ensemble (GOE) or the Gaussian Unitary Ensemble (GUE), therefore evidencing the emergence of quantum chaos. That is verified for a large range of material and geometry parameters. In particular, the GUE statistics occurs only in the case of a circular QD. It represents an anomalous phenomenon, previously reported for just a small number of systems, since the problem is time-reversal invariant. The obtained results are explained through a detailed analysis of the Hamiltonian matrix structure.Comment: 14 pages, two column