Structural-Damage Detection by Distributed Piezoelectric Transducers and Tuned Electric Circuits

A novel technique for damage detection of structures is introduced and discussed. It is based on purely electric measurements of the state variables of an electric network coupled to the main structure through a distributed set of piezoelectric patches. The constitutive parameters of this auxiliary network are optimized to increase the sensitivity of global measurements- as the frequency, response functions relative to selected electric degrees of freedom-with respect to a given class of variations in the structural-mechanical properties. Because the proposed method is based on purely electric input and output measurements, it allows for accurate results in the identification and localization of damages. Use of the electric frequency-response function to identify the mechanical damage leads to nonconvex optimization problems; therefore the proposed sensitivity-enhanced identification procedure becomes computationally efficient if an a priori knowledge about the damage is available.Comment: 18 page

Formal cooperation and the performance of Italian firms operating inside and outside industrial districts

none2sìopenCanello, Jacopo; Vidoli, FrancescoCanello, Jacopo; Vidoli, Francesc

Generalized Hooke's law for isotropic second gradient materials

In the spirit of Germain the most general objective stored elastic energy for a second gradient material is deduced using a literature result of Fortun\'e & Vall\'ee. Linear isotropic constitutive relations for stress and hyperstress in terms of strain and strain-gradient are then obtained proving that these materials are characterized by seven elastic moduli and generalizing previous studies by Toupin, Mindlin and Sokolowski. Using a suitable decomposition of the strain-gradient, it is found a necessary and sufficient condition, to be verified by the elastic moduli, assuring positive definiteness of the stored elastic energy. The problem of warping in linear torsion of a prismatic second gradient cylinder is formulated, thus obtaining a possible measurement procedure for one of the second gradient elastic moduli.Comment: 20 page

A comprehensive model for the evaluation of standard expenditure needs and standard level of local services

This paper addresses the problem of the simultaneous evaluation of local governments’ standard expenditure needs together with the related level of standard public services proposing a new approach to fiscal equalisation based on quantitative methods. Standard expenditure needs are estimated using quantile regression, moreover robust non-parametric methods are employed for the computation of composite indicators of demand and supply factors. Data from English local authorities over the period 1997–2006 have been used to test the internal and external validity of the model

Spatial Composite and Disaggregate Indicators: Chow-Lin Methods and Applications

The present paper aims to verify a statistical procedure that allows for the transition from aggregate indicators to disaggregate indicators, whereas in this case, the terms aggregate/disaggregate refer to territorial areas and not to categories. More specifically, an attempt was made to reconstruct the indicators of the infrastructural endowment at the provincial level (in Italy) on the basis of analogous indicators that are available at the regional level. For such purposes, Chow-Lin’s approach was followed, and some regressors representing the territorial demand for infrastructure, related to productive, demographic and tourist aspects were used. The comparison between the results obtained through the application of the mentioned approach and the “real” data (available at the provincial level) in effect allows for the verification of the coherence among factors of demand and the real distribution of the infrastructure in Italy

A class of electro-mechanical systems: linear and nonlinear dynamics

The linear and nonlinear problems of dynamics of some electro-mechanical systems, characterized by a gyroscopic internal coupling, are analyzed. Since the technical importance of this system lies in the possibility of damping and controlling structural vibrations, the interest is focused on the energy exchanges between the mechanical and electric components. In order to maximize these energy transformations, the optimal values of the system parameters and their modifications in the nonlinear case are investigated.Klasa układów elektromechanicznych: dynamika liniowa i nieliniowa. W pracy przedstawiono analizę liniowego i nieliniowego zagadnienia dynamiki układów elektromechanicznych, charakteryzujących się wewnętrznym sprzężeniem żyroskopowym. Ze względu na techniczną wartość problemu tłumienia i sterowania drganiami, główny nacisk położono na procesy wymiany energii między podzespołami mechanicznymi i elektrycznymi. W celu zmaksymalizowania przepływu i transformacji energii określono optymalne parametry układu i ich modyfikacje w przypadkku nieliniowym

Modal coupling in one-dimensional electro-mechanical structured continua

A passive continuously distributed control of mechanical vibrations is proposed. The piezoelectric actuators are interconnected by a linear electric transmission line. We introduce coupling and internal resonance criteria to determine the optimal choices for electric parameters. These criteria can be found decomposing the differential operator appearing in the linear evolutions according to a partition of the state vector into mechanical and electrical parts. The results we find allow for the design of an experimental set up