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Turin, Italy

The Politecnico di Torino is an engineering public university based in Turin, Italy. Established in 1859, Politecnico di Torino is Italy’s oldest technical university. The university offers several courses in the fields of Engineering, Architecture and Industrial Design. Wikipedia.

Mura A.,Polytechnic University of Turin
Mechatronics | Year: 2011

Acquisition of the displacements and deformations of a loaded component is generally a not easy operation. This is especially the case as the component often presents a complex geometry and the deformations involve more degrees of freedom or a combination of them. Measurement devices used for this kind of application often allow to obtain simplified measurements. This paper presents a novel measurement device, consisting of six displacement sensors mounted as a parallel mechanism, capable to measure the global deformation of a component in terms of translations and rotations. The deformations are obtained by applying the direct kinematic equations to convert the six displacements read from the six sensors into the three translations and rotations representing the deformation of the component. The geometry of the device leads to write simplified equations for the direct kinematic that can be solved with a semi-numerical procedure implemented in a program written in Matlab environment. The results given by this procedure have been validated with the positions obtained from a 3D CAD model of the device, showing perfect agreement between the results. A prototype has been made and tested on a workbench. © 2011 Elsevier Ltd. All rights reserved.

Giustolisi O.,Polytechnic of Bari | Ridolfi L.,Polytechnic University of Turin
Journal of Hydraulic Engineering | Year: 2014

Complex and/or large size water distribution networks (WDNs) require the division of the hydraulic system into modules to simplify the analysis and the management tasks. In the modern science of networks, the modularity index has been proposed to detect communities, i.e., groups/clusters of nodes characterized by stronger interconnections. The modularity index is a measure of the strength of the network division into communities and it is maximized to identify them. Therefore, the division into modules of WDNs, also named segmentation, could be performed by using the modularity index as metric to identify cluster of nodes. Nevertheless, modularity index needs to be revised considering the specificity of the hydraulic systems, which are infrastructure networks. In fact, the division into modules for infrastructure networks, although it can be based on the identification of clusters of nodes, is not aimed at investigating network features. Differently, the aim is the practical issue of simplifying system analysis, planning and management; therefore, the division is constrained by the technical needs. Accordingly, in the present work the classic modularity index is firstly presented. Successively, it is tailored and modified for WDNs. Furthermore, a MO strategy for optimal segmentation is presented and discussed also using a real test network. The optimization framework is based on the maximization of the WDN-oriented modularity-based index versus the minimization of the cost of newly installed devices to obtain network segments. Those are a set of optimal divisions into modules of the hydraulic system which are the basis for an integrated, dynamical planning. © 2014 American Society of Civil Engineers.

Kaniadakis G.,Polytechnic University of Turin
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

The present Letter, deals with the statistical theory [G. Kaniadakis, Phys. Rev. E 66 (2002) 056125; G. Kaniadakis, Phys. Rev. E 72 (2005) 036108], which predicts the probability distribution p(E)∝expκ(-I), where, I∝βE-βμ, is the collision invariant, and expκ(x)= (1+κ2x2+κx)1/κ, with κ2<1. This, experimentally observed distribution, at low energies behaves as the Maxwell-Boltzmann exponential distribution, while at high energies presents power law tails. Here we show that the function expκ(x) and its inverse lnκ(x), can be obtained within the one-particle relativistic dynamics, in a very simple and transparent way, without invoking any extra principle or assumption, starting directly from the Lorentz transformations. The achievements support the idea that the power law tailed distributions are enforced by the Lorentz relativistic microscopic dynamics, like in the case of the exponential distribution which follows from the Newton classical microscopic dynamics. © 2010 Elsevier B.V. All rights reserved.

Xu Z.,Polytechnic University of Turin | Coors V.,Stuttgart University of Applied Sciences
Building and Environment | Year: 2012

Constructing and improving urban residential areas is an eternal critical subject in the process of the whole urban development which is connected with a series of challenges and problems. During the past decades, urban residential development has speed up extremely with massive population mobility in cities. The purpose of this study is to propose an integrated approach for sustainability assessment of urban residential development, considering sustainability indicators, housing equilibrium and building visualization. Firstly based on merging DPSIR (Driving Forces, Pressure, State, Impact and Response) framework and Analytic Hierarchy Process (AHP), the indicators were systematized for the sustainability modeling. Due to the urban activities cause impacts not only on local level but also a broader scale, a simulation model, using System Dynamics (SD) methodology, was structured to quantitatively investigate the developmental tendency of the indicators. And then the estimated results were displayed in 2D density maps in ArcGIS and 3D visualization in CityEngine. A real case study was presented for the Stuttgart Region of the state of Baden-Württemberg in Southern Germany and its Plieningen district to experience the usefulness and feasibility of the developed approach. The integration of GIS, SD model and 3D visualization, called GISSD system here, can better explain the interaction and the variation of the sustainability indicators for residential development. Hence it is able to support the Decision Maker to view the sustainable level of urban residential areas more comprehensively. © 2011 Elsevier Ltd.

Bianca C.,Polytechnic University of Turin | Guerrini L.,Marche Polytechnic University
The Scientific World Journal | Year: 2014

This paper is devoted to the existence and stability analysis of limit cycles in a delayed mathematical model for the economy growth. Specifically the Solow model is further improved by inserting the time delay into the logistic population growth rate. Moreover, by choosing the time delay as a bifurcation parameter, we prove that the system loses its stability and a Hopf bifurcation occurs when time delay passes through critical values. Finally, numerical simulations are carried out for supporting the analytical results. © 2014 Carlo Bianca and Luca Guerrini.

Sangermano M.,Polytechnic University of Turin | El Sayed H.,Leibniz Institute of Polymer Research | Voit B.,Leibniz Institute of Polymer Research
Polymer | Year: 2011

Partially ethoxysilyl-modified hyperbranched aliphatic-aromatic polyesters (HBPs) were effectively used as toughening as well as multi-site coupling agents in the preparation of organic-inorganic UV-thermal dual-cured epoxy/TEOS coatings. Through chain transfer reaction of the phenolic terminal units of the HBPs effective incorporation in the epoxy resin is achieved in the photo-initiated cationic polymerization whereas the ethoxysilane groups allow effective formation of a strongly interconnected inorganic-organics network during the in-situ sol-gel process with TEOS by binding the organic to the inorganic phase. Under those conditions, the addition of the inorganic precursor to the epoxy/HPB (20 wt%) system induced an increase of the storage modulus and more important, an improvement of the viscoelastic properties by extending the performance of the elastic modulus to higher temperatures. Thus, highly transparent hybrid coatings with enhanced thermal-mechanical and surface hardness properties resulted by the use of the partially ethoxysilyl-modified HBPs as multifunctional coupling agents. © 2011 Elsevier Ltd. All rights reserved.

Katul G.G.,Duke University | Katul G.G.,Polytechnic University of Turin | Oren R.,Duke University | Oren R.,Swedish University of Agricultural Sciences | And 3 more authors.
Reviews of Geophysics | Year: 2012

The role of evapotranspiration (ET) in the global, continental, regional, and local water cycles is reviewed. Elevated atmospheric CO 2 , air temperature, vapor pressure deficit (D), turbulent transport, radiative transfer, and reduced soil moisture all impact biotic and abiotic processes controlling ET that must be extrapolated to large scales. Suggesting a blueprint to achieve this link is the main compass of this review. Leaf-scale transpiration ( f e) as governed by the plant biochemical demand for CO 2 is first considered. When this biochemical demand is combined with mass transfer formulations, the problem remains mathematically intractable, requiring additional assumptions. A mathematical "closure" that assumes stomatal aperture is autonomously regulated so as to maximize the leaf carbon gain while minimizing water loss is proposed, which leads to analytical expressions for leaf-scale transpiration. This formulation predicts well the effects of elevated atmospheric CO 2 and increases in D on f e. The case of soil moisture stress is then considered using extensive gas exchange measurements collected in drought studies. Upscaling the f e to the canopy is then discussed at multiple time scales. The impact of limited soil water availability within the rooting zone on the upscaled ET as well as some plant strategies to cope with prolonged soil moisture stress are briefly presented. Moving further up in direction and scale, the soil-plant system is then embedded within the atmospheric boundary layer, where the influence of soil moisture on rainfall is outlined. The review concludes by discussing outstanding challenges and how to tackle them by means of novel theoretical, numerical, and experimental approaches. © 2012. American Geophysical Union.

Pandolfi L.,Polytechnic University of Turin
Annual Reviews in Control | Year: 2010

Abstract: We give an overview of a recent method we proposed for the solution of on-line deconvolution problems, which can be applied to Active Noise Cancellation (ANC). The method has been studied both for lumped parameter systems and for distributed systems in input-output and in state space form. Finally, we show that the identification algorithm can be extended to identify inputs to systems modelled by partial differential equations with infinite memory. Such class of equations are encountered in different applications: thermal processes with finite diffusion speed, viscoelasticity, nonfickian diffusion... So, this identification problem is of interest for example in thermodynamics, biology or pharmacology, when the immission of a solute - a drug for example - has to be detected. The analysis of this example will give a feeling of the methods of proof used in this kind of study. © 2010 Elsevier Ltd. All rights reserved.

Taricco G.,Polytechnic University of Turin
IEEE Journal on Selected Topics in Signal Processing | Year: 2011

Spectrum sensing is the key to coordinate the secondary users in a cognitive radio network by limiting the probability of interference with the primary users. Linear cooperative spectrum sensing consists of comparing the linear combination of the secondary users' recordings against a given threshold in order to assess the presence of the primary user signal. Simplicity is traded off for a slight suboptimality with respect to the likelihood-ratio test. Tuning the performance of linear cooperative radio sensing is complicated by the fact that optimization of the linear combining vector is required. This is accomplished by solving a nonconvex optimization problem, which is the main focus of this work. The global optimum is found by an explicit algorithm based on the solution of a polynomial equation in one scalar variable. Numerical results are reported for validation purposes and to analyze the effects of the system parameters on the complementary receiver operating characteristic. It is shown that the optimum probability of missed detection for a system with constant local signal-to-noise ratios (SNRs) and constant channel gain correlation coefficients can be expressed in closed form by a simple expression. Simulation results are also included to validate the accuracy of the Gaussian approximation. These results illustrate how large the number of sampling intervals must be in order that the Gaussian approximation holds. © 2011 IEEE.

Galleani L.,Polytechnic University of Turin
IEEE Transactions on Signal Processing | Year: 2010

The frequency spectrum is a fundamental quantity for the analysis and design of a system. When a system is turned on or off, the frequency spectrum of its output changes with time. We define the transient spectrum as the time-frequency spectrum of the system output during the transient phase. We obtain the exact transient spectrum for a wide class of random systems, and we formulate it with respect to the classical power spectrum, which is reached for large times. We apply the developed method to the case of a harmonic oscillator and of a system with two resonances. © 2010 IEEE.

Taricco G.,Polytechnic University of Turin
IEEE Signal Processing Letters | Year: 2010

Linear cooperative spectrum sensing has been proposed for cognitive radio networks which are often limited by the achievable complexity of the devices involved. The method is based on the Gaussian approximation of the summary statistics sent to the fusion center. The goodness of this approximation is investigated in this letter in the case of block Rician fading. The impact of the number of secondary users, sampling times, and the Rician factor are assessed by an analytic method proposed to calculate the false-alarm and the missed-detection probabilities. © 2010 IEEE.

Bianca C.,Polytechnic University of Turin
Nonlinear Analysis: Hybrid Systems | Year: 2010

This paper is an expository of the main dynamical properties of billiards, which depend on the shape of the walls of the container, and the recent developments like the introduction of an external field, which mimic the coupling with a thermostat.The class of dynamical system dealt with in this paper exhibits characteristics of hybrid systems as it links discrete and continuous, deterministic and stochastic dynamics.The contents are focused on applications. Specifically, transport dynamics in highly-confined regions has been of interest in the last few decades because of industrial and medical applications. Aspects of confined transport remain elusive, considering that in microporous membranes, whose size pores is about that of the molecules, the transport is sometimes ballistic, and sometimes diffusive. The classical kinetic and macroscopic approach can not be directly applied because collisions of particle fluid with walls prevail. The microscopic mathematical billiard theory can be applied as a mathematical tool since the interstices between obstacles can be considered as the pores of the membranes. © 2010 Elsevier Ltd.

Allia P.,Polytechnic University of Turin | Tiberto P.,INRIM - Istituto Nazionale di Ricerca Metrologica
Journal of Nanoparticle Research | Year: 2011

Isothermal magnetization and initial dc susceptibility of spheroidal, nearly monodisperse magnetite nanoparticles (typical diameter: 8 nm) prepared by a standard thermo-chemical route have been measured between 10 and 300 K. The samples contained magnetite nanoparticles in the form of either a dried powder (each nanoparticle being surrounded by a stable oleic acid shell as a result of the preparation procedure) or a solid dispersion in PEGDA-600 polymer; different nanoparticle (NP) concentrations in the polymer were studied. In all samples the NPs were not tightly agglomerated nor their ferromagnetic cores were directly touching. The high-temperature inverse magnetic susceptibility is always found to follow a linear law as a function of T, crossing the horizontal axis at negative temperatures ranging from 175 to about 1,000 K. The deviation from the standard superparamagnetic behavior is related to dipolar interaction among NPs; however, a careful analysis makes it hard to conclude that such a behavior originates from a dominant antiferromagnetic character of the interaction. The results are well explained considering that the studied samples are in the interacting superparamagnetic (ISP) regime. The ISP model is basically a mean field theory which allows one to straightforwardly account for the role of magnetic dipolar interaction in a NP system. The model predicts the existence of specific scaling laws for the reduced magnetization which have been confirmed in all studied samples. The interaction of each magnetic dipole moment with the local, random dipolar field produced by the other dipoles results in the presence of a large fluctuating energy term whose magnitude is comparable to the static barrier for magnetization reversal/rotation related to magnetic anisotropy. On the basis of the existing theories on thermal crossing of a barrier whose height randomly fluctuates in time it is predicted that the rate of barrier crossing is substantially driven by the rate of barrier fluctuations, which is fast (108-109 Hz) and almost independent of temperature. As a consequence, the standard picture of superparamagnetic NPs which undergo single-particle blocking by a static barrier below the blocking temperature should be substantially revised, at least in the present materials. The ISP model is perfectly matching with the view of activated magnetization rotation whose kinetics is significantly modified by barrier height fluctuations. © 2011 Springer Science+Business Media B.V.

Canuto E.,Polytechnic University of Turin
ISA transactions | Year: 2012

Robust control design guarantees closed-loop stability of a model-based control law in the presence of parametric uncertainties. Stability is guaranteed by introducing some ignorance coefficients and restricting the feedback control effort. Embedded Model Control shows that the model-based control law can be kept intact in the case of uncertainty, if the controllable dynamics is complemented by a suitable disturbance dynamics. The disturbance state must be driven by an unpredictable input vector, the noise, which can only be estimated from the model error i.e. the difference between plant and model output. The uncertainty-based design concerns the noise estimator, so as to prevent the model error from conveying uncertainty components which are command-dependent and thus prone to destabilizing the controlled plant. Separation of the components in the low and high frequency domain by the noise estimator itself allows stability recovery and guarantee, and the rejection of low frequency components. Two simple case studies help to understand the key assets of the methodology. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Bovsunovsky A.,National University of Food Technologies | Surace C.,Polytechnic University of Turin
Mechanical Systems and Signal Processing | Year: 2015

The main purpose of the present review paper is to illustrate the principal achievements of numerous researchers who have studied the non-linear effects caused by a closing crack in the most common types of structural elements such as beams, shafts and plates, the aim being to assess the potential and future prospects of using non-linear behaviour to detect damage. Indeed, for a wide range of practical applications, in order to avoid catastrophic failure, the development of diagnostics techniques which are sufficiently sensitive to incipient cracks in structures and machines is a crucial issue. The main potential advantage of using vibration diagnostics based on the use of non-linear effects is the relatively high sensitivity to the damage of the closing crack type, especially for application to beam-like structures and rotating shafts; instead the potential for application to plate-like structures has been found to be limited. After analysing the state-of-art on this subject in detail, a discussion of the respective merits, drawbacks and prospects of a range of non-linear vibration methods for structural damage detection is presented. The general conclusion which can be drawn from the highly encouraging results of recent research is that further development of these techniques for non-destructive testing of structures with closing cracks would be highly worthwhile. © 2015 Elsevier Ltd. All rights reserved.

Macia O.,Polytechnic University of Turin
Journal of Geometry and Physics | Year: 2010

It is shown that the compact Lie group SU (3) admits an Sp (2) Sp (1) structure whose distinguished 2-forms ω1, ω2, ω3 span a differential ideal. This is achieved by first reducing the structure further to a subgroup isomorphic to SO (3). © 2010 Elsevier B.V. All rights reserved.

Lucia U.,Polytechnic University of Turin
Renewable and Sustainable Energy Reviews | Year: 2013

The coefficient of performance, COP, of an adsorption cooling is theoretically obtained. It shows the influence of the thermophysical properties of the adsorbent-adsorbate media regardless of the design of the machine. These quantities require a detailed understanding of the influence of temperature on the adsorbent and the adsorbate conditions in a cycle, so that an accurate determination of the thermodynamic behaviour is developed in order to obtain the COP. © 2012 Elsevier Ltd.

Lucia U.,Polytechnic University of Turin
Renewable and Sustainable Energy Reviews | Year: 2013

Exergy and entropy generation analysis of the open systems allows to obtain a measure of how far the open real systems deviate from equilibrium with their environment. A link between entropy generation maximum principle and the exergy analysis of engineering and natural systems is suggested in order to use the exergy and entropy approach to improve the renewable energy systems. © 2012 Elsevier Ltd.

Novara C.,Polytechnic University of Turin
IEEE Transactions on Automatic Control | Year: 2012

Sparse identification can be relevant in the automatic control field to solve several problems for nonlinear systems such as identification, control, filtering, fault detection. However, identifying a maximally sparse approximation of a nonlinear function is in general an NP-hard problem. The common approach is to use relaxed or greedy algorithms that, under certain conditions, can provide sparsest solutions. In this technical note, a combined \ell 1-relaxed-greedy algorithm is proposed and conditions are given, under which the approximation derived by the algorithm is a sparsest one. Differently from other conditions available in the literature, the ones provided here can be actually verified for any choice of the basis functions defining the sparse approximation. A Set Membership analysis is also carried out, assuming that the function to approximate is a linear combination of unknown basis functions belonging to a known set of functions. It is shown that the algorithm is able to exactly select the basis functions which define the unknown function and to provide an optimal estimate of their coefficients. © 1963-2012 IEEE.

Smith M.I.,University of Edinburgh | Smith M.I.,University of Nottingham | Bertola V.,University of Edinburgh | Bertola V.,Polytechnic University of Turin
Physical Review Letters | Year: 2010

When a droplet of water impacts a hydrophobic surface, the drop is often observed to bounce. However, for about 10 years it has been known that the addition of very small quantities (∼100ppm) of a flexible polymer such as poly-(ethylene oxide) can completely prevent rebound. This effect has for some time been explained in terms of the stretching of polymer chains by a velocity gradient in the fluid, resulting in a transient increase in the so-called "extensional viscosity." Here we show, by measuring the fluid velocity inside the impacting drop, that the extensional viscosity plays no role in the antirebound phenomenon. Using fluorescently labeled λ DNA we demonstrate that the observed effect is due to the stretching of polymer molecules as the droplet edge sweeps the substrate, retarding the movement of the receding contact line. © 2010 The American Physical Society.

Cupertino F.,University of Bari | Giangrande P.,University of Bari | Pellegrino G.,Polytechnic University of Turin | Salvatore L.,University of Bari
IEEE Transactions on Industrial Electronics | Year: 2011

The sensorless position control of permanent-magnet (PM) synchronous motors can be successfully implemented by superimposing a high-frequency voltage signal on the control voltage. In this paper, the position estimation is obtained by means of a high-frequency sinusoidal voltage signal injected along the estimated d-axis. Several methods proposed in the literature obtain the position estimation by tracking the zero condition of the high-frequency q current component. We propose a new approach that also exploits the d-axis high-frequency current component and allows working with injected voltage signal of reduced amplitude, thus reducing noise and additional losses. The main contribution of this paper relies in the compensation of the motor end effects due to the finite length of the tubular motor armature. These effects must be taken into account in the motor modeling because they cause an error in the position estimation that varies with the motor position. The modeling of the phenomenon and a proper compensation technique are proposed in this paper. Last, a simplified integral-type controller is used to estimate motor position instead of the commonly adopted proportionalintegral controller plus integrator, and this requires a low-effort design. Experiments on a linear tubular PM synchronous-motor prototype are presented to validate the theoretical analysis and evidence the feasibility of the proposed sensorless technique. © 2011 IEEE.

Giacomelli R.,Polytechnic University of Turin | Ganti R.K.,University of Texas at Austin | Haenggi M.,University of Notre Dame
IEEE/ACM Transactions on Networking | Year: 2011

Outage probabilities in wireless networks depend on various factors: the node distribution, the MAC scheme, and the models for path loss, fading, and transmission success. In prior work on outage characterization for networks with randomly placed nodes, most of the emphasis was put on networks whose nodes are Poisson-distributed and where ALOHA is used as the MAC protocol. In this paper, we provide a general framework for the analysis of outage probabilities in the high-reliability regime. The outage probability characterization is based on two parameters: the intrinsic spatial contention γ of the network, introduced by Haenggi in a previous work, and the coordination level achieved by the MAC as measured by the interference scaling exponent κ introduced in this paper. We study outage probabilities under the signal-to-interference ratio (SIR) model, Rayleigh fading, and power-law path loss and explain how the two parameters depend on the network model. The main result is that the outage probability approaches γκ as the density of interferers goes to zero, and that κ assumes values in the range 1 for all practical MAC protocols, where α is the path-loss exponent. This asymptotic expression is valid for all motion-invariant point processes. We suggest a novel and complete taxonomy of MAC protocols based mainly on the value of κ. Finally, our findings suggest a conjecture that bounds the outage probability for all interferer densities. © 2011 IEEE.

Calafiore G.C.,Polytechnic University of Turin
SIAM Journal on Optimization | Year: 2010

Random convex programs (RCPs) are convex optimization problems subject to a finite number N of random constraints. The optimal objective value J* of an RCP is thus a random variable. We study the probability with which J* is no longer optimal if a further random constraint is added to the problem (violation probability V *). It turns out that this probability rapidly concentrates near zero as N increases. We first develop a theory for RCPs leading to explicit bounds on the upper tail probability of V *. Then we extend the setup to the case of RCPs with r a posteriori violated constraints (RCPVs): a paradigm that permits us to improve the optimal objective value while maintaining the violation probability under control. Explicit and nonasymptotic bounds are derived also in this case: the upper tail probability of V * is upper bounded by a multiple of a beta distribution irrespective of the distribution on the random constraints. All results are derived under no feasibility assumptions on the problem. Further the relation between RCPVs and chanceconstrained problems (CCP) is explored showing that the optimal objective J* of an RCPV with the generic constraint removal rule provides with arbitrarily high probability an upper bound on the optimal objective of a corresponding CCP. Moreover whenever an optimal constraint removal rule is used in the RCPVs then appropriate choices of N and r exist such that J* approximates arbitrarily well the objective of the CCP. © 2010 Society for Industrial and Applied Mathematics.

Nordio A.,CNR Institute of Electronics, Computer and Telecommunication Engineering | Chiasserini C.-F.,Polytechnic University of Turin
IEEE Transactions on Signal Processing | Year: 2011

Environmental monitoring is often performed through wireless sensor networks, by randomly deploying sensor nodes over the geographical region of interest. Sensors sample a physical phenomenon (the so-called field) and send their measurements to a sink, which is in charge of reconstructing the field from such irregular samples. In this work, we focus on scenarios of practical interest where the sensor deployment is unfeasible in certain areas of the geographical region (e.g., due to terrain asperities), and the delivery of sensor measurements to the sink may fail (e.g., due to fading or to transmission collisions among sensors simultaneously accessing the wireless medium). Under these conditions, we carry out an asymptotic analysis and evaluate the quality of the estimation of a field defined over a d-dimensional domain (d≥1) when the sink uses linear filtering as a reconstruction technique. Specifically, given the matrix V representing the sampling system, we let the size of V go to infinity and its aspect ratio have a finite limit bounded away from zero. Then, we provide both the moments and density of the limiting spectral distribution of VV H, in terms of those obtained when the samples collected by the sink correspond to locations that are uniformly distributed over the geographical area. By using such asymptotic results, we approximate the mean square error on the estimated field through the η-transform of VV H, and we derive the sensor network performance under the conditions described above. © 2011 IEEE.

Bianca C.,Polytechnic University of Turin
Mathematical and Computer Modelling | Year: 2010

This paper proposes an analysis of the modelling of space dynamics focused on a general class of models of the kinetic theory for active particles in space homogeneity. Various deterministic and stochastic developments are treated and referred to specific applications. These new classes of equations present different aspects of hybrid characteristic coupling deterministic and stochastic structures, as well as continuous and discrete variables, and constitute a background paradigm for the derivation of models whose qualitative properties are analyzed referring to modelling of complex systems in life and applied sciences. © 2009 Elsevier Ltd. All rights reserved.

Bellouquid A.,Cadi Ayyad University | Bianca C.,Polytechnic University of Turin
Mathematical and Computer Modelling | Year: 2010

This paper deals with the modelling of aggregation and/or fragmentation physical phenomena for large systems of interacting living entities in the framework of the mathematical kinetic theory for active particles. After introducing various mathematical structures in terms of systems of nonlinear integro-differential equations with quadratic type nonlinearities and variable number of equations, the relative qualitative analysis of the initial value problem is presented. Finally, the paper deals with the derivation of macroscopic equations based on the underlying description at the microscopic scale delivered by the kinetic theory models. © 2010 Elsevier Ltd.

Bellomo N.,Polytechnic University of Turin | Bellouquid A.,Cadi Ayyad University
Networks and Heterogeneous Media | Year: 2011

This paper presents a critical overview on the modeling of crowds and swarms and focuses on a modeling strategy based on the attempt to retain the complexity characteristics of systems under consideration viewed as an assembly of living entities characterized by the ability of expressing heterogeneously distributed strategies. © American Institute of Mathematical Sciences.

Bianca C.,Polytechnic University of Turin | Ferrara M.,University of Reggio Calabria | Guerrini L.,University of Bologna
Journal of Global Optimization | Year: 2014

Recently the thermostatted kinetic framework has been proposed as mathematical model for studying nonequilibrium complex systems constrained to keep constant the total energy. The time evolution of the distribution function of the system is described by a nonlinear partial integro-differential equation with quadratic type nonlinearity coupled with the Gaussian isokinetic thermostat. This paper is concerned with further developments of this thermostatted framework. Specifically the term related to the Gaussian thermostat is adjusted in order to ensure the conservation of even high-order moments of the distribution function. The derived framework that constitutes a new paradigm for the derivation of specific models in the applied sciences, is analytically investigated. The global in time existence and uniqueness of the solution to the relative Cauchy problem is proved. Existence and moments conservation of stationary solutions are also performed. Suitable applications and research perspectives are outlined in the last section of the paper. © 2013 Springer Science+Business Media New York.

Fernandez-Prades C.,Catalonia Technology Center of Telecomunications | Presti L.L.,Polytechnic University of Turin | Falletti E.,Navigation Signal Analysis and Simulation Group
Proceedings of the IEEE | Year: 2011

It is known that satellite radiolocalization was born in the military environment and was originally conceived for defense purposes. Nevertheless, the commercial explosion (dated to 20 years ago) of global positioning system (GPS) in the civil market (automotive, tourism, etc.) significantly changed the original perspectives of this technology. Another big change is expected when other global navigation satellite systems (GNSSs) such as the European Galileo or the Chinese COMPASS become operational and commercial. In fact, modern GNSSs are conceived principally for the civil market (at the opposite of GPS, whose civil employment is given as a sort of kind gift, with lower performance than that one granted to military users). The scope of this paper is to provide readers with a clear focus about the potentialities of current and forthcoming GNSSs and associated technologies in a renewed mass-market perspective. The paper also opens a window to the future of radiolocalization technology beyond GPS and GNSS, dealing with the role of digital signal processing and software-defined radio (SDR) in next-generation navigation systems and with the seamless integration of satellite-based navigation with other technologies in order to provide reliable position information also in hostile environments. © 2011 IEEE.

Fre P.,University of Turin | Sorin A.S.,Joint Institute for Nuclear Research | Trigiante M.,Polytechnic University of Turin
Nuclear Physics B | Year: 2014

The question whether the integrable one-field cosmologies classified in a previous paper by Fré, Sagnotti and Sorin can be embedded as consistent one-field truncations into Extended Gauged Supergravity or in N=1 supergravity gauged by a superpotential without the use of D-terms is addressed in this paper. The answer is that such an embedding is very difficult and rare but not impossible. Indeed, we were able to find two examples of integrable models embedded in supergravity in this way. Both examples are fitted into N=1 supergravity by means of a very specific and interesting choice of the superpotential W(z). The question whether there are examples of such an embedding in Extended Gauged Supergravity remains open. In the present paper, relying on the embedding tensor formalism we classified all gaugings of the N=2 STU model, confirming, in the absence on hypermultiplets, the uniqueness of the stable de Sitter vacuum found several years ago by Fré, Trigiante and Van Proeyen and excluding the embedding of any integrable cosmological model. A detailed analysis of the space of exact solutions of the first supergravity-embedded integrable cosmological model revealed several new features worth an in-depth consideration. When the scalar potential has an extremum at a negative value, the Universe necessarily collapses into a Big Crunch notwithstanding its spatial flatness. The causal structure of these Universes is quite different from that of the closed, positive curved, Universe: indeed, in this case the particle and event horizons do not coincide and develop complicated patterns. The cosmological consequences of this unexpected mechanism deserve careful consideration. © 2014 The Authors.

Galleani L.,Polytechnic University of Turin
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2010

The stability of an atomic clock can change with time due to several factors, such as temperature, humidity, radiations, aging, and sudden breakdowns. The dynamic Allan variance, or DAVAR, is a representation of the time-varying stability of an atomic clock, and it can be used to monitor the clock behavior. Unfortunately, the computational time of the DAVAR grows very quickly with the length of the analyzed time series. In this article, we present a fast algorithm for the computation of the DAVAR, and we also extend it to the case of missing data. Numerical simulations show that the fast algorithm dramatically reduces the computational time. The fast algorithm is useful when the analyzed time series is long, or when many clocks must be monitored, or when the computational power is low, as happens onboard satellites and space probes. © 2006 IEEE.

Fazzolari F.A.,City University London | Carrera E.,Polytechnic University of Turin
European Journal of Mechanics, A/Solids | Year: 2014

A fully coupled thermoelastic formulation is developed to deal with free vibration analysis of anisotropic composite plates and isotropic/sandwich FGM plates. The proposed formulation is developed by combining refined hierarchical plate models and a trigonometric Ritz method. The temperature is considered as a primary variable and allows the evaluation of the temperature field effects in the free vibration analysis. The temperature profile across the plate thickness is always modeled with a layer-wise kinematics description, nevertheless both equivalent single layer and layer-wise approaches are properly and effectively used for the displacement variables. In the 2D and quasi-3D higher-order variable-kinematics plate theories, each displacement variable, in the displacement field, is treated independently from the others. Such artifice allows to select scrupulously each expansion order for each primary variable regarding to the required accuracy and the computational cost. So-called Ritz fundamental primary nuclei related to the coupled thermal and mechanical fields are generated by virtue of an unconventional principle of virtual displacement accounting for the internal thermal virtual work to reproduce the coupling effect. Each fundamental primary nucleus is mathematically invariant with respect to the used kinematics description, the employed expansion orders and the chosen Ritz functions. The thermoelastic coupling is investigated in terms of natural frequencies and the effect of stacking sequence and length-to-thickness ratio for lower and higher modes is discussed. © 2013 Elsevier Masson SAS. All rights reserved.

Taormina R.,Hong Kong Polytechnic University | Chau K.-W.,Hong Kong Polytechnic University | Sethi R.,Polytechnic University of Turin
Engineering Applications of Artificial Intelligence | Year: 2012

Artificial Neural Networks (ANNs) have been successfully employed for predicting and forecasting groundwater levels up to some time steps ahead. In this paper, we present an application of feed forward neural networks (FFNs) for long period simulations of hourly groundwater levels in a coastal unconfined aquifer sited in the Lagoon of Venice, Italy. After initialising the model with groundwater elevations observed at a given time, the developed FNN should able to reproduce water level variations using only the external input variables, which have been identified as rainfall and evapotranspiration. To achieve this purpose, the models are first calibrated on a training dataset to perform 1-h ahead predictions of future groundwater levels using past observed groundwater levels and external inputs. Simulations are then produced on another data set by iteratively feeding back the predicted groundwater levels, along with real external data. The results show that the developed FNN can accurately reproduce groundwater depths of the shallow aquifer for several months. The study suggests that such network can be used as a viable alternative to physical-based models to simulate the responses of the aquifer under plausible future scenarios or to reconstruct long periods of missing observations provided past data for the influencing variables is available. © 2012 Elsevier Ltd. All rights reserved.

Pastrone D.,Polytechnic University of Turin
International Journal of Aerospace Engineering | Year: 2012

Hybrid rocket engines are promising propulsion systems which present appealing features such as safety, low cost, and environmental friendliness. On the other hand, certain issues hamper the development hoped for. The present paper discusses approaches addressing improvements to one of the most important among these issues: low fuel regression rate. To highlight the consequence of such an issue and to better understand the concepts proposed, fundamentals are summarized. Two approaches are presented (multiport grain and high mixture ratio) which aim at reducing negative effects without enhancing regression rate. Furthermore, fuel material changes and nonconventional geometries of grain and/or injector are presented as methods to increase fuel regression rate. Although most of these approaches are still at the laboratory or concept scale, many of them are promising. © Copyright 2012 Dario Pastrone.

D'Oca S.,Polytechnic University of Turin | Hong T.,Lawrence Berkeley National Laboratory
Building and Environment | Year: 2014

Understanding the relationship between occupant behaviors and building energy consumption is one of the most effective ways to bridge the gap between predicted and actual energy consumption in buildings. However effective methodologies to remove the impact of other variables on building energy consumption and isolate the leverage of the human factor precisely are still poorly investigated. Moreover, the effectiveness of statistical and data mining approaches in finding meaningful correlations in data is largely undiscussed in literature. This study develops a framework combining statistical analysis with two data-mining techniques, cluster analysis and association rules mining, to identify valid window operational patterns in measured data. Analyses are performed on a data set with measured indoor and outdoor physical parameters and human interaction with operable windows in 16 offices. Logistic regression was first used to identify factors influencing window opening and closing behavior. Clustering procedures were employed to obtain distinct behavioral patterns, including motivational, opening duration, interactivity and window position patterns. Finally the clustered patterns constituted a base for association rules segmenting the window opening behaviors into two archetypal office user profiles for which different natural ventilation strategies as well as robust building design recommendations that may be appropriate. Moreover, discerned working user profiles represent more accurate input to building energy modeling programs, to investigate the impacts of typical window opening behavior scenarios on energy use, thermal comfort and productivity in office buildings. © 2014 Elsevier Ltd.

Puppo G.,Polytechnic University of Turin | Semplice M.,University of Insubria
Communications in Computational Physics | Year: 2011

We propose an a-posteriori error/smoothness indicator for standard semidiscrete finite volume schemes for systems of conservation laws, based on the numerical production of entropy. This idea extends previous work by the first author limited to central finite volume schemes on staggered grids. We prove that the indicator converges to zero with the same rate of the error of the underlying numerical scheme on smooth flows under grid refinement. We construct and test an adaptive scheme for systems of equations in which the mesh is driven by the entropy indicator. The adaptive scheme uses a single nonuniform grid with a variable timestep. We show how to implement a second order scheme on such a space-time non uniform grid, preserving accuracy and conservation properties. We also give an example of a p-adaptive strategy. © 2011 Global-Science Press.

Brischetto S.,Polytechnic University of Turin
Journal of Sandwich Structures and Materials | Year: 2013

Refined two-dimensional models are proposed for the static hygrothermoleastic analysis of multilayered composite and sandwich shells. These shell models are developed in the framework of the Carrera's unified formulation (in a general and unified manner) by considering both equivalent single layer and layerwise multilayer description. The principle of virtual displacements contains elastic, thermal and hygroscopic strains. The governing equations allow mechanical, thermal and hygroscopic loads to be applied and they are solved in a closed-form solution. Thermal and hygroscopic loads are defined by means of appropriate temperature and moisture content profiles through the thickness of the shell, such profiles can 'a priori' be assumed or they can be calculated by solving the Fourier heat conduction equation and the Fick's moisture diffusion law. Such equations are solved in steady-state conditions and in curvilinear coordinates for the shell geometries. The presence of loads due to hygroscopic and thermal effects (in addition to the mechanical load) modifies the bending response of multilayered shells. Comparisons between classical and refined models, and between assumed and calculated temperature and moisture content profiles are proposed in the cases of composite and sandwich shells. The use of refined models combined with calculated temperature and moisture content profiles through the thickness is mandatory for a correct elasto-thermo-hygroscopic analysis of multilayered structures. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Petrolo M.,Polytechnic University of Turin
Composite Structures | Year: 2013

Flutter analyses of composite lifting surfaces are presented in this paper. Results were obtained through an advanced aeroelastic formulation based on higher-order 1D structural models coupled with the doublet lattice method. The g-method was used to compute flutter conditions. The Carrera Unified Formulation (CUF) was exploited to build 1D structural models. Refined theories were obtained by using Taylor-like expansions of the cross-section displacement field. In the CUF framework, the order (N) of the expansion is considered as a free-parameter, this means that N can be considered as an input of the analysis. Convergence studies on N can be straightforwardly conducted in order to establish the proper 1D theory for a given problem. Flutter analyses were conducted on several structural configurations. The effect of the stacking sequence and the effect of the sweep angle were analyzed. Results show the enhanced capabilities of CUF 1D in dealing with the flutter analysis of typical composite lifting surfaces with plate-like accuracy and low computational costs. © 2012 Elsevier Ltd.

Musso E.,Polytechnic University of Turin | Nicolodi L.,University of Parma
Nonlinearity | Year: 2010

The local motion of a null curve in Minkowski 3-space induces an evolution equation for its Lorentz invariant curvature. Special motions are constructed whose induced evolution equations are the members of the Korteweg-de Vries (KdV) hierarchy. The null curves which move under the KdV flow without changing shape are proven to be the trajectories of a certain particle model on null curves described by a Lagrangian linear in the curvature. In addition, we show that the curvature of a null curve which evolves by similarities can be computed in terms of the solutions of the second Painlevé equation. © 2010 IOP Publishing Ltd & London Mathematical Society.

Pirulli M.,Polytechnic University of Turin | Pastor M.,Technical University of Madrid
Geotechnique | Year: 2012

The entrainment of channel-path material plays an important role during runout of many rapid landslides. Such a mechanism is able to change the mobility of a flow significantly, through rapid changes of the flow volume and rheology. The purpose of this paper is to use mathematical, rheological and constitutive models to analyse the entrainment effect on runout analysis results. After a brief review and classification of some well-established erosion laws, a simple, yet effective, empirical formula for the entrainment rate has been selected, and is implemented in a continuum mechanics-based numerical model. First, some hypothetical examples are used to test the effectiveness of the implemented entrainment process, and to evidence the respective role of entrainment and topography on a flow propagation. Then a back-analysis is presented of the 2000 Tsing Shan event (Hong Kong), where a small volume of 150 m3 of material grew to 1620 m3 because of the strong erosion along the slope. From the results obtained, it emerges that the new model with erosion implemented can provide a useful contribution in describing the consequences of mass movements in which the entrainment process can play a key role.

Thai C.H.,Ton Duc Thang University | Ferreira A.J.M.,University of Porto | Ferreira A.J.M.,King Abdulaziz University | Carrera E.,Polytechnic University of Turin | Nguyen-Xuan H.,Ton Duc Thang University
Composite Structures | Year: 2013

We present an isogeometric finite element formulation for static, free vibration and buckling analysis of laminated composite and sandwich plates. The idea behind this work is to associate an isogeometric analysis (IGA) with a layerwise theory [. A.J.M. Ferreira. Analyis of composite plates using a layerwise deformation theory and multiquadrics discretization. Mech Adv Mater Struct 2005;12(2):99-112]. Isogeometric analysis based on non-uniform rational B-spline (NURBS) basic functions were recently proposed to preserve exact geometries and to enhance very significantly the accuracy of the traditional finite elements. B-splines basic function (or NURBS) is used to represent for both geometric and field variable approximations, which provide a flexible way to make refinement and degree elevation. They enable us to achieve easily the smoothness with arbitrary continuity order compared with the traditional FEM. The layerwise theory assumes a first-order shear deformation theory in each layer and the imposition of displacement continuity at the layers interfaces. This permits to remove shear correction factors and improves the accuracy of transverse shear stresses. Intensive numerical studies have been conducted to show the highly efficient performance of the proposed formulation. © 2013 Elsevier Ltd.

Sangermano M.,Polytechnic University of Turin
Pure and Applied Chemistry | Year: 2012

This review discusses cationic UV-curing processes of vinyl ethers, propenyl ethers, and epoxy monomers. Cationic photopolymerization based on photogeneration of acid from onium salts induced by UV light and consecutive polymerization initiated by photogenerated acid was first proposed at the end of the 1970s. The process engendered high interest both in academia and in industry. Cationic photoinduction presents some advantages over comparable radical-mediated processes, particularly the absence of inhibition by oxygen, low shrinkage, and good adhesion, and mechanical properties of the UV-cured materials. Moreover, the monomers employed are generally less toxic and irritant than acrylates and methacrylates, which are widely used in radical photopolymerization. In this overview, particular emphasis is given to our recent contributions to the field of cationic photopolymerization for different classes of monomers. © 2012 IUPAC.

Novara C.,Polytechnic University of Turin | Ruiz F.,Pontifical Xavierian University | Milanese M.,Modelway Srl
IEEE Transactions on Automatic Control | Year: 2013

Optimal filters for nonlinear systems are in general difficult to derive or implement. The common approach is to use approximate solutions such as extended Kalman filters, ensemble filters or particle filters. However, no optimality properties can be guaranteed by these approximations, and even the stability of the estimation error cannot often be ensured. Another relevant issue is that, in most practical situations, the system whose variables have to be estimated is not known, and a two-step procedure is adopted, based on model identification from data and filter design from the identified model. However, the designed filter may display large performance deteriorations in the case of modeling errors. In this paper, a new approach overcoming these issues is proposed, allowing the design of optimal filters for nonlinear systems in both the cases of known and unknown system. The approach is based on the direct filter design from a set of data generated by the system. Either experimental or simulated data can be used for design. A bound on the number of data necessary to ensure a given filter accuracy is also provided, showing that the proposed approach is not affected by the curse of dimensionality. © 2012 IEEE.

Galleani L.,Polytechnic University of Turin
IEEE Transactions on Signal Processing | Year: 2012

We obtain the time-frequency response of the output of a dynamical system when the input belongs to a class of common nonstationary signals, namely, an impulse, a linear chirp, a causal sinusoid, and a short duration sinusoid. The obtained results clarify how the system processes the time-varying frequencies of the input signal to generate the time-frequency spectrum of the output. All analytic results are exact. The solution is obtained by developing a method which can be used to evaluate the output of a dynamical system for complex combinations of nonstationary inputs. We show numerical examples which prove that the response of a system to a nonstationary input is made by a series of events occurring in the joint time-frequency domain. © 2012 IEEE.

Marzi T.,Polytechnic University of Turin
Construction and Building Materials | Year: 2015

The latest technological innovations in nanostructured materials for reinforcement and protection of timber structures are presented. Starting from the definition of nanotechnologies applied in the construction field, the paper briefly describes nano-materials already existing on the market, nano-coatings and their wood surface protection functions, classification and compatibility with the different wood species, focusing on their potential usage and their application in the fields of architecture, civil engineering and cultural heritage. Next-generation application fields are reviewed with a special focus on an experimental research on reinforcement of historic timber structures with the application of a polymeric resin reinforced with carbon nanotubes. © 2015 Elsevier Ltd. All rights reserved.

Torchio M.F.,Polytechnic University of Turin
Energy Conversion and Management | Year: 2015

District heating CHP (combined heat and power) and distributed generation CHP have been compared in this paper on the basis of energy, environmental and economic criteria, and a deviation index has been proposed to establish, in aggregate form, what the improvement margins are for a given design choice. Three technologies that are suitable for both district heating and distributed generation have been chosen: a mature market technology, internal combustion engines, and recent entry market technologies, that is, microturbines, and fuel cells. The calculations have been based on the real heating load curve of a town in Northern Italy at the current market conditions: power and fuel prices, tax exemptions relative to cogeneration, white certificates, etc. Two scenarios have been considered: maximum energy saving and maximum present value saving. In the first scenario, district heating obtained better energy and CO2 savings than distributed generation, but critical values have been observed for local nitrogen oxides (NOx) and particulate matter emissions, when internal combustion engines are adopted. In the second scenario, all the options offer positive energy, environmental and economic savings, and the payback times are significantly reduced compared to the previous scenario. The district heating options show the best present value savings and payback times, while distributed generation is only economically viable when internal combustion engines are adopted. Microturbines leads to the best NOx savings. Finally, the comparison with an alternative separate production of heat and power has shown that there are scenarios where none of the analysed technologies leads to a significant improvement. All this information, analysed together, provides a sort of map for policy makers through which they can better orientate themselves among the different scenarios. © 2014 Elsevier Ltd. All rights reserved.

Cimellaro G.P.,Polytechnic University of Turin | Reinhorn A.M.,State University of New York at Buffalo | Bruneau M.,State University of New York at Buffalo
Engineering Structures | Year: 2010

The concepts of disaster resilience and its quantitative evaluation are presented and a unified terminology for a common reference framework is proposed and implemented for evaluation of health care facilities subjected to earthquakes. The evaluation of disaster resilience is based on dimensionless analytical functions related to the variation of functionality during a period of interest, including the losses in the disaster and the recovery path. This evolution in time including recovery differentiates the resilience approach from the other approaches addressing the loss estimation and their momentary effects. The recovery process usually depends on available technical and human resources, societal preparedness, public policies and may take different forms, which can be estimated using simplified recovery functions or using more complex organizational and socio-political models. Losses are described as functions of fragility of systems that are determined using multidimensional performance limit thresholds. The proposed framework is formulated and exemplified for a typical Californian Hospital building using a simplified recovery model, considering direct and indirect losses in its physical system and in the population served by the system. A hospital network is also analyzed to exemplify the resilience framework. Resilience function captures the effect of the disaster, but also the results of response and recovery, the effects of restoration and preparedness. Therefore, such a function becomes an important tool in the decision process for both the policy makers and the engineering professionals. © 2010 Elsevier Ltd.

Rossani A.,Polytechnic University of Turin
Continuum Mechanics and Thermodynamics | Year: 2016

If electrons (e) and holes (h) in metals or semiconductors are heated to the temperatures (Formula presented.) and (Formula presented.) greater than the lattice temperature (Formula presented.), the electron–phonon interaction causes energy relaxation. In the nonuniform case, a momentum relaxation occurs as well. In view of such an application, a new model based on an asymptotic procedure for solving the kinetic equations of carriers and phonons is proposed, with generation–recombination of electrons and holes, which gives naturally the displaced Maxwellian at the leading order. After that, balance equations for the electron number, hole number, energy densities, and momentum densities are constructed, which constitute now a system of eight equations for the chemical potentials (carriers), the temperatures (carriers and phonons), and the drift velocities (carriers and phonons). In the drift-diffusion approximation the constitutive laws are derived and the Onsager relations recovered. © 2016 Springer-Verlag Berlin Heidelberg

Gaudino R.,Polytechnic University of Turin
Optical Fiber Communication Conference, OFC 2013 | Year: 2013

We present our recent results on coherent detection technologies applied to upstream transmission in reflective PON, comparing them to other existing architectures and showing a higher resilience to spurious reflections when compared to direct detection. © 2013 OSA.

The paper presents the most relevant and recent international guidance documents on factors affecting creep and shrinkage of concrete and on the related criteria for prediction models, giving a general summary of their scope and contents and of their status of publication. Special attention is given to ACI documents ACI 209.1R-05 and ACI 209.2R-08, specifically dedicated to these aspects and incorporating the presentation of current most widely diffused prediction models. Mention is made also of fib Structural Concrete Textbook (2009) and of fib Model Code 2010 for the parts providing the information on time-dependent deformations of concrete and presenting former CEB, now fib, shrinkage and creep prediction models. Open problems and some aspects of the related current debate in the literature and in the scientific community at the international level are also outlined. A few recommended measures are finally illustrated to counteract the effects of persisting prediction model uncertainties.

Rundo M.,Polytechnic University of Turin
SAE International Journal of Fuels and Lubricants | Year: 2010

The paper brings to evidence critical issues in the design of variable displacement vane pump controls for ICE lubrication. Tight packaging, high rotational speed and variable pressure setting are key aspects influencing the selection of pump geometric parameters as well as its displacement controls. A specific layout, where the pump displacement control is carried out by two linear actuators and a two-way pilot control valve, has been analysed. The paper focuses on the dimensioning of the front areas of the actuators considering two kinematic solutions, linear and rotational, for the external ring. Through a simulation model, validated by experimental tests, the influence of different pressure control strategies on the dimensioning has been investigated. © 2009 SAE International.

Lucia U.,Polytechnic University of Turin
Chemical Physics Letters | Year: 2013

Entropy generation is a fundamental concept in the science of complex systems as well as in engineering applications. The entropy generation approach was developed to obtain the stationary states of these systems. In this Letter, starting from these results, the entropy generation approach is presented as a powerful method useful to analyze molecular machines in relation to their role in living systems. Two examples on cancer are described: (1) the analysis of its evolution which suggests a new approach against it based on entropy generation and (2) the information obtained from the chemical interaction between anticancer drugs and microtubules. © 2012 Elsevier B.V. All rights reserved.

Serra R.,University of Twente | Canavero F.G.,Polytechnic University of Turin
IEEE Transactions on Electromagnetic Compatibility | Year: 2011

This paper presents novel theoretical probability density functions (PDFs) for the magnitude and phase of electromagnetic fields inside reverberation chambers (RC) operating in a good-but-imperfect regime. The derivation is based on considering two Gaussian random variables with mean values, variances, and correlation that are departed from the ideal assumptions. A bivariate approach using a complete joint Gaussian distribution of these variables is defined. Marginal distributions obtained by integration of a 2-D joint PDF are compared with theoretical PDFs for ideal situations, and significantly lower rejection rates are experienced for field data measured in real RCs. Additionally, these novel marginal PDFs are highly general since they are able to describe both ideal and nonideal stirred fields and reproduce other findings. © 2011 IEEE.

Diffon A.L.,University of Lyon | Samtleben H.,University of Lyon | Trigiante M.,Polytechnic University of Turin
Journal of High Energy Physics | Year: 2011

We construct maximal supergravity in four dimensions with local scaling symmetry as deformation of the original Cremmer-Julia theory. The different theories which include the standard gaugings are parametrized by an embedding tensor carrying 56+912 parameters. We determine the form of the possible gauge groups and work out the complete set of field equations. As a result we obtain the most general couplings compatible with N = 8 supersymmetry in four dimensions. A particular feature of these theories is the absence of an action and an additional positive contribution to the effective cosmological constant. Moreover, these gaugings are generically dyonic, i.e. involve simultaneously electric and magnetic vector fields.

Crovetti P.S.,Polytechnic University of Turin
Electronics Letters | Year: 2010

An operational amplifier (opamp) input stage achieving a high degree of immunity against electromagnetic interference (EMI) is presented. Unlike previously proposed topologies, the novel circuit does not show any significant penalty in baseband operation. The effectiveness of the proposed solution and its robustness to mismatch and process variations is tested by simulations performed with reference to the AMS C35 0.35m CMOS technology. © 2010 The Institution of Engineering and Technology.

Peterson A.F.,Georgia Institute of Technology | Graglia R.D.,Polytechnic University of Turin
IEEE Antennas and Wireless Propagation Letters | Year: 2010

Several families of hierarchical vector basis functions for triangular cells are reviewed, and the matrix condition numbers associated with their use are compared. Scale factors are introduced to optimize the linear independence of each set and are shown to provide substantial improvement for most families. © 2010 IEEE.

Gazzoni M.,Polytechnic University of Turin
Human Factors and Ergonomics In Manufacturing | Year: 2010

The prevention of work-related musculoskeletal disorders is one of the main goals in ergonomics. Among others, surface electromyography (sEMG) is an important tool for the evaluation of risks related to work activity. Three main issues have been approached in ergonomics via sEMG: 1) the analysis ofmuscle activation, 2) the analysis of exerted forces and torques, and 3) the analysis ofmuscle fatigue. Many studies have been carried out in static conditions. In ergonomics, however, it is more relevant to study muscle activity and fatigue during real tasks that are, in general, dynamic. From isometric to dynamic contractions, the complexity of the interpretation of sEMG signals increases considerably. Changes in sEMG signals are related to the continuous modifications in force output, muscle fiber length, and relative position of surface electrodes and sources. To increase the reliability of the information extracted from sEMG, multichannel detection systems have been applied, showing the possibility of overcoming some limits of the standard technique. Some illustrative laboratory and field studies are reported in this work to illustrate the potentialities and the open problems in the use of multichannel sEMG in ergonomics. Case 1 is a laboratory study investigating the myoelectric manifestations of fatigue in the biceps brachii (BB) during dynamic elbow flexion/extension. Case 2 is a laboratory study investigating the myoelectric manifestations of fatigue during a repetitive lifting task. Case 3 is a field study, carried out in an automotive plant, investigating muscle activation during the welding of a car door.Many factors play a leading role in the correct interpretation of information provided by sEMG. Even though multichannel sEMG provides information able to improve the estimation of force and/or fatigue duringworking tasks, many problems related to the signal acquisition and interpretation are still open. Further improvements are necessary to develop multichannel sEMG into an effective tool supporting other methodologies for the evaluation of work-related risks. © 2010 Wiley Periodicals, Inc.

Bonforte M.,Autonomous University of Madrid | Grillo G.,Polytechnic University of Turin | Vazquez J.L.,Autonomous University of Madrid
Archive for Rational Mechanics and Analysis | Year: 2010

We consider the asymptotic behaviour of positive solutions u(t, x) of the fast diffusion equation ut=Δ(um/m)=div(um-1∇u) posed for x ∈ ℝd,t > 0, with a precise value for the exponent m = (d - 4)/(d - 2). The space dimension is d ≧ 3 so that m < 1, and even m = -1 for d = 3. This case had been left open in the general study (Blanchet et al. in Arch Rat Mech Anal 191:347-385, 2009) since it requires quite different functional analytic methods, due in particular to the absence of a spectral gap for the operator generating the linearized evolution. The linearization of this flow is interpreted here as the heat flow of the Laplace- Beltrami operator of a suitable Riemannian Manifold (ℝd,g) with a metric g which is conformal to the standard ℝd metric. Studying the pointwise heat kernel behaviour allows to prove suitable Gagliardo-Nirenberg inequalities associated with the generator. Such inequalities in turn allow one to study the nonlinear evolution as well, and to determine its asymptotics, which is identical to the one satisfied by the linearization. In terms of the rescaled representation, which is a nonlinear Fokker-Planck equation, the convergence rate turns out to be polynomial in time. This result is in contrast with the known exponential decay of such representation for all other values of m. © Springer-Verlag 2009.

Pirulli M.,Polytechnic University of Turin
Rock Mechanics and Rock Engineering | Year: 2015

The large, deep-seated Rosone landslide (Western Italian Alps) has been known since the beginning of the twentieth century as an active phenomenon characterized by a slow but constant evolution. Its possible evolution, in terms of a catastrophic rock avalanche, could have serious consequences on several elements at risk, including a hydroelectric power plant. Runout estimates are needed to identify the potential impact on the territory of such an event and, when possible, to minimize hazard areas. This article analyses the evolution of three potential rock avalanche scenarios, with decreasing probability of occurrence and increasing impact on land planning. A comparison between runout results obtained by other authors and some new analyses that have been carried out with the three-dimensional continuum mechanics-based RASH3D code is made and commented on by highlighting the advantages, but also the limits, of using a more complete tool, such as RASH3D. © 2015 Springer-Verlag Wien

Thermodynamics studies the transformations of energy occurring in open systems. Living systems, with particular reference to cells, are complex systems in which energy transformations occur. Thermo-electro-chemical processes and transports occur across their border, the cells membranes. These processes take place with important differences between healthy and diseased states. In particular, different thermal and biochemical behaviours can be highlighted between these two states and they can be related to the energy transformations inside the living systems, in particular the metabolic behaviour. Moreover, living systems waste heat. This heat is the consequence of the internal irreversibility. Irreversibility is effectively studied by using the Gouy-Stodola theorem. Consequently, this approach can be introduced in the analysis of the states of living systems, in order to obtain a unifying approach to study them. Indeed, this approach allows us to consider living systems as black boxes and analyze only the inflows and outflows and their changes in relation to the modification of the environment, so information on the systems can be obtained by analyzing their behaviour in relation to the modification of external perturbations. This paper presents a review of the recent results obtained in the thermodynamics analysis of cell systems. © 2014 by the authors.

Bocchini S.,Center for Space Human Robotics Polito | Frache A.,Polytechnic University of Turin
Express Polymer Letters | Year: 2013

Polylactide (PLA) based nanocomposites of organically modified montmorillonite and micro-talc based microcomposites were prepared with different compositions and were UV-light irradiated under artificial accelerated conditions representative of solar irradiation. The chemical modifications resulting from photo-oxidation were followed by infrared (IR) and ultraviolet (UV)-visible spectroscopies. The infrared analysis of PLA photooxidation shows the formation of a band at 1847 cm-1 due to the formation of anhydrides. The filler addition provokes an increase of anhydride formation rate dependent on filler nature, amount and dispersion degree on the matrix. The main factors that influence oxidation rate are the total extension of polymer/filler interfacial area and the presence of transition metal impurities of clays. © BME-PT.

Comino E.,Polytechnic University of Turin | Ferretti V.,The London School of Economics and Political Science
Ecological Indicators | Year: 2016

Optimizing the multiple uses of land represents a challenge for today's governments and land managers. In particular, protected area planning should satisfy the demand for multiple land uses, while offering optimal protection of our natural resources. The present research aims at providing park's managers, as well as other stakeholders and decision makers, with a scientifically sound and practical approach to zoning protection levels and supporting the strategic planning phase in nature conservation. This paper thus proposes and tests the development of an indicators-based spatial Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis for a complex territorial system with exceptional multiple values. As a result, key conservation priorities and warning spots are identified to support the subsequent decision-making phase. The innovative value of the research stems not only from the integrated methodological approach based on the combination between spatial analysis, indicators systems and the traditional SWOT analysis, but also from the contextual characteristics and physical extension of the area under investigation. Moreover, the integrated and innovative framework proposed in the paper has also international significance, thanks to the possibility of replicating the research strategy and methodological approach in other contexts. © 2015 Elsevier Ltd. All rights reserved.

Mesin L.,Polytechnic University of Turin
Eurasip Journal on Advances in Signal Processing | Year: 2011

Two innovative algorithms for motion tracking and monitoring of rainy clouds from radar images are proposed. The methods are generalizations of classical optical flow techniques, including a production term (modelling formation, growth or depletion of clouds) in the model to be fit to the data. Multiple images are processed and different smoothness constraints are introduced. When applied to simulated maps (including additive noise up to 10 dB of SNR) showing formation and propagation of objects with different directions and velocities, the algorithms identified correctly the production and the flow, and were stable to noise when the number of images was sufficiently high (about 10). The average error was about 0.06 pixels (px) per sampling interval (ΔT) in identifying the modulus of the flow (velocities between 0.25 and 2 px/ΔT were simulated) and about 1° in detecting its direction (varying between 0° and 90°). An example of application to X-band radar rainfall rate images detected during a stratiform rainfall is shown. Different directions of the flow were detected when investigating short (10 min) or long time ranges (8 h), in line with the chaotic behaviour of the weather condition. The algorithms can be applied to investigate the local stability of meteorological conditions with potential future applications in nowcasting. © 2011 Mesin.

Lucia U.,Polytechnic University of Turin
Chemical Physics Letters | Year: 2013

A recent analysis of the Carnot's results has pointed out that natural systems may not convert all the inflow of energy to do work. Some energy will be used to maintain the systems' internal processes. These exergy flows appear as the heat exchanged with a second thermostat of a thermodynamic engine. In this Letter a calculus of this internal irreversibility is developed using the entropy generation approach. The obtained results are exemplified in the analysis of superconductivity. © 2013 Elsevier B.V. All rights reserved.

Recupero V.,Polytechnic University of Turin
Journal of Physics: Conference Series | Year: 2011

In some recent papers we studied how to extend to BV a hysteresis operator defined on Lipschitzian inputs, preserving suitable continuity properties. More precisely we considered the so called strict metric defined by means of the essential variation. This approach may have some drawbacks from the physical point of view, therefore in the present paper we show how to extend a general hysteresis operator with respect to a notion of convergence which takes into account of the pointwise variation rather than the essential variation. © Published under licence by IOP Publishing Ltd.

Paggi M.,Leibniz University of Hanover | Paggi M.,Polytechnic University of Turin | Barber J.R.,University of Michigan
International Journal of Heat and Mass Transfer | Year: 2011

The dependence of the contact conductance of self-affine rough surfaces on the applied pressure is studied using the electric-mechanical analogy which relates the contact conductance to the normal stiffness. According to dimensional analysis arguments, an efficient dimensionless formulation is proposed which minimizes the number of dimensionless variables governing the phenomenon. Assuming incomplete similarity in the dimensionless pressure, a power-law dependence between contact conductance and mean pressure is proposed. This is confirmed by earlier semi-empirical correlations that are recovered as special cases of the proposed formulation. To compute the exponent β of the power-law, and relate it to the morphological properties of the surfaces, we numerically test self-affine rough surfaces composed of random midpoint displacement (RMD) patches. Such patches are generated using a modified RMD algorithm in order to decouple the effect of the long wavelength cut-off from that due to microscale roughness. Numerical results show that the long wavelength cut-off has an important effect on the contact conductance, whereas the sampling interval and the fractal dimension are less important. The effect of elastic interaction between asperities has also been quantified and it significantly influences the predicted power-law exponent β. © 2011 Elsevier Ltd. All rights reserved.

Freschi F.,Polytechnic University of Turin
IEEE Transactions on Magnetics | Year: 2010

The purpose of this work is to propose and test a mixed integer linear programming formulation for the problem of brain source localization. Such technique allows the localization of the minimum number of currents that are able to reconstruct evoked potentials recorded at the scalp. The algorithm makes use of binary variables in order to be less sensible to noise on input data. Some preliminary simulation results show that the algorithm is effective in source localization and robust with respect to errors on measurement data. © 2006 IEEE.

Cimellaro G.P.,Polytechnic University of Turin | Reinhorn A.M.,State University of New York at Buffalo | Bruneau M.,State University of New York at Buffalo
Earthquake Engineering and Structural Dynamics | Year: 2011

This paper introduces an organizational model describing the response of the Hospital Emergency Department (ED). The metamodel is able to estimate the hospital capacity and the dynamic response in real time and to incorporate the influence of the damage of structural and non-structural components on the organizational ones. The waiting time is the main parameter of response and it is used to evaluate the disaster resilience index of healthcare facilities. Its behaviour is described using a double exponential function and its parameters are calibrated based on simulated data. The metamodel covers a large range of hospital configurations and takes into account hospital resources, in terms of staff and infrastructures, operational efficiency and existence of an emergency plan, maximum capacity and behaviour both in saturated and over-capacitated conditions. The sensitivity of the model to different arrival rates, hospital configurations, and capacities and the technical and organizational policies applied during and before the strike of the disaster has been investigated. This model becomes an important tool in the decision process either for the engineering profession or for the policy makers. © 2010 John Wiley & Sons, Ltd.

Calafiore G.C.,Polytechnic University of Turin
Systems and Control Letters | Year: 2010

This paper considers the problem of identification of an interval model for an unknown static function using a finite batch of stochastic inputoutput data u(i),y(i), i=1,⋯,N. The criterion used for identification is that the width of the interval output of the model should be minimized, while containing a given fraction of the observed outputs y(i). We show that, for suitable finite N, the resulting model will be reliable, that is it will explain any other unseen output, up to a given and arbitrary high probability. © 2010 Elsevier B.V.

This paper deals with the time dependent behaviour and the excavation of deep tunnels in weak rocks. Recent contributions to the formulation of a constitutive model for representing such a behaviour, advanced laboratory testing for parameters identification, and design analysis methods for use in engineering practice are discussed. The Stress Hardening ELasto VIscous Plastic constitutive model (SHELVIP), developed with the intent to analyse the rock mass behaviour of tunnels excavated in severely squeezing conditions in a relatively simple, but complete manner, is presented. Then, an innovative servo controlled triaxial apparatus (HPTA), designed and developed for testing weak rocks, with unconventional features such as accurate measurement systems, advanced mechanical set up, and a relatively high stress working range, both in terms of confining pressure, back pressure and axial load, is presented. Finally, consideration is given to numerical modelling of a tunnel excavated in a severely squeezing rock mass (the Carboniferous Formation along the Lyon-Turin Base Tunnel), where the excavation process has been closely simulated in axisymmetric conditions, and the SHELVIP constitutive model has been introduced. Numerical results are discussed and compared with in situ measurements, in terms of tunnel convergence and stresses in the lining. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Galleani L.,Polytechnic University of Turin
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2011

The dynamic Allan variance (DAVAR) is a surface which describes the stability of a high-precision clock with respect to time. When the DAVAR is evaluated from experimental data, its surface shows random fluctuations caused by the estimation process. It is fundamental to assign a statistical significance to these fluctuations, so that they can be differentiated from the variations of the surface caused by clock anomalies. First, we develop confidence surfaces to assign a statistical significance to the random fluctuations of the DAVAR estimator. Then, we introduce detection surfaces to reveal the variations of the surface caused by clock anomalies. We validate the obtained results through numerical simulations. © 2011 IEEE.

Fazzolari F.A.,City University London | Carrera E.,Polytechnic University of Turin
Composite Structures | Year: 2011

Accurate free-vibrations and linearized buckling analysis of anisotropic laminated plates with different lamination schemes and simply supported boundary condition are addressed in this paper. Approximation methods, such as Rayleigh-Ritz, Galerkin and Generalized Galerkin, based on Principle of Virtual Displacement are derived in the framework of Carrera's Unified Formulation (CUF). CUF widely used in the analysis of composite laminate beams, plates and shells, have been here formulated both for the same and different expansion orders, for the displacement components, in the thickness layer-plate direction. An extensive assessment of advanced and refined plate theories, which include Equivalent single Layer (ESL), Zig-Zag (ZZ) and Layer-wise (LW) models, with increasing number of displacement variables is provided. Accuracy of the results is shown to increase by refining the theories. Convergence studies are made in order to demonstrate that accurate results are obtained examining thin and thick plates using trigonometric approximation functions. The effects of boundary terms, upon frequency parameters and critical loads are evaluated. The effects of the various parameters (material, number of layers, fiber orientation, thickness ratio, orthotropic ratio) upon the frequencies and critical loads are discussed as well. Numerical results are compared with 3D exact solution when available from the open literature. © 2011 Elsevier Ltd.

Matekovits L.,Polytechnic University of Turin
IEEE Antennas and Wireless Propagation Letters | Year: 2010

A novel type of surface-impedance modulation mechanism for designing of microstrip-technology-based surface-wave-excited holographic antennas is proposed. The advanced radiating geometry consists of quasi-periodic arrangement of unit cells operating in the leaky-wave region. Flexible design requires a considerable numerical effort determining the dispersion characteristics of any possible unit cell present in the geometry. In this context, an analytic determination of the dispersion diagram for a unit cell with a sinusoidal modulation of the effective dielectric constant in its inside is presented. In this particular case, the solution is expressed in terms of Mathieu functions. The good agreement between numerical data and analytic solutions for an open, unbounded microstrip structure allows introducing the principle of a novel type of holographic surface obtained by cascading unit cells with different modulation parameters, where the phase of the radiating field can be geometrically controlled. © 2006 IEEE.

Novara C.,Polytechnic University of Turin
IEEE Transactions on Automatic Control | Year: 2015

An approach for the direct design of LPV controllers from data is proposed. This approach, called Direct FeedbacK (DFK) design, overcomes some relevant problems typical of the standard design methods, such as model uncertainty and complex control design and/or implementation. After a closed-loop stability analysis, an algorithm for direct control design from data is presented, completely based on convex optimization. The resulting controller is able to provide closed-loop stability when the number of data used for design is sufficiently large and is almost-optimal (in a worst-case sense) in terms of tracking accuracy. © 1963-2012 IEEE.

Baino F.,Polytechnic University of Turin
Acta Biomaterialia | Year: 2011

Treatment of orbital floor fractures and defects is often a complex issue. Repair of these injuries essentially aims to restore the continuity of the orbital floor and to provide an adequate support to the orbital content. Several materials and implants have been proposed over the years for orbital floor reconstruction, in the hope of achieving the best clinical outcome for the patient. Autografts have been traditionally considered as the "gold standard" choice due to the absence of an adverse immunological response, but they are available in limited amounts and carry the need for extra surgery. In order to overcome the drawbacks related to autografts, researchers" and surgeons" attention has been progressively attracted by alloplastic materials, which can be commercially produced and easily tailored to fit a wide range of specific clinical needs. In this review the advantages and limitations of the various biomaterials proposed and tested for orbital floor repair are critically examined and discussed. Criteria and guidelines for optimal material/implant choice, as well as future research directions, are also presented, in an attempt to understand whether an ideal biomaterial already exists or a truly functional implant will eventually materialise in the next few years. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Marchetto G.,Polytechnic University of Turin
Journal of Optical Communications and Networking | Year: 2010

The provision of service differentiation is an important aspect that has to be considered for the definition of next-generation networks due to the high heterogeneity of the traffic that will dominate networks in the near future. This is particularly important in the context of optical burst switching, which is emerging as one of the strong candidate technologies for the next-generation optical Internet. Preemptive contention resolution schemes are very effective solutions for providing service differentiation in such networks; however, they cannot be applied together with the just-in-time signaling protocol because of the great loss in efficiency in terms of wavelength utilization and maximum achieved throughput that results when the number of preemptions becomes too large. This paper presents a preemption-based service differentiation solution that is suitable for the just-in-time optical burst switching paradigm because it keeps the preemption probability (i.e., the probability of observing a preemption when a contention occurs) low. Within the proposed technique, bursts are created at their ingress node and combined into chains, arranging them in order of decreasing priority. Then, a conventional preemption scheme is adopted at core nodes to handle contentions. An analytical study is presented and some traffic scenarios are analyzed by simulation to evaluate the performance of the proposed method. © 2010 Optical Society of America.

Taricco G.,Polytechnic University of Turin
IEEE Transactions on Information Theory | Year: 2010

The error performance of different types of receivers over an arbitrarily correlated Rician fading MIMO channel is assessed by evaluating the decision metric and the pairwise error probability. The differences are in the way channel state information at the receiver (CSIR) is recovered. We consider: i) a genie-aided receiver, based on the perfect knowledge of CSIR; ii) a mismatched receiver, based on the use of pilot-aided (imperfect) CSIR in the perfect-CSIR decision metric; iii) an optimum receiver, based on perfect channel distribution information at the receiver (CDIR), which performs jointly channel and data estimation. In this paper, the decision metric of the optimum receiver is derived, and an iterative algorithm is proposed to calculate it for sequential decoding schemes. The complexity of this iterative algorithm is analyzed and compare against the complexity of the mismatched receiver. Closed-form expressions are given for the pairwise error probabilities (PEPs) of the three receivers with arbitrarily correlated Rician fading. These expressions are further processed to obtain the asymptotic (in the SNR) PEPs, the diversity order, and the asymptotic power losses. Numerical results are presented to support the validity of this analysis and to assess the impact of power efficiency and CDIR estimation errors on the PEP versus the ℰb/ N0 ratio. © 2006 IEEE.

Cristiani E.,University of Rome La Sapienza | Piccoli B.,Rutgers University | Tosin A.,Polytechnic University of Turin
Multiscale Modeling and Simulation | Year: 2011

In this paper a new multiscale modeling technique is proposed. It relies on a recently introduced measure-theoretic approach, which allows one to manage the microscopic and the macroscopic scale under a unique framework. In the resulting coupled model the two scales coexist and share information. This way it is possible to perform numerical simulations in which the trajectories and the density of the particles affect each other. Crowd dynamics is the motivating application throughout the paper. © 2011 Society for Industrial and Applied Mathematics.

Di Baldassarre G.,UNESCO-IHE Institute for Water Education | Claps P.,Polytechnic University of Turin
Hydrology Research | Year: 2011

Several hydrological studies have shown that river discharge records are affected by significant uncertainty. This uncertainty is expected to be very high for river flow data referred to flood events, when the stage-discharge rating curve is extrapolated far beyond the measurement range. This study examines the standard methodologies for the construction and extrapolation of rating curves to extreme flow depths and shows the need of proper approaches to reduce the uncertainty of flood discharge data. To this end, a comprehensive analysis is performed on a 16 km reach of the River Po (Italy) where five hydraulic models (HEC-RAS) were built. The results of five topographical surveys conducted during the last 50 years are used as geometric input. The application demonstrates that hydraulically built stage-discharge curves for the five cases differ only for ordinary flows, so that a common rating curve for flood discharges can be derived. This result confirms the validity of statistical approaches to the estimation of the so-called 'flood rating curve', a unique stage-discharge curve based on data of contemporaneous annual maxima of stage and discharge values, which appears insensitive to marginal changes in river geometry. © IWA Publishing 2011.

Asenjo F.A.,Adolfo Ibanez University | Comisso L.,Polytechnic University of Turin | Comisso L.,CNR Institute for Complex Systems
Physical Review Letters | Year: 2015

The concept of magnetic connections is extended to nonideal relativistic magnetohydrodynamical plasmas. Adopting a general set of equations for relativistic magnetohydrodynamics including thermal-inertial, thermal electromotive, Hall, and current-inertia effects, we derive a new covariant connection equation showing the existence of generalized magnetofluid connections that are preserved during the dissipationless plasma dynamics. These connections are intimately linked to a general antisymmetric tensor that unifies the electromagnetic and fluid fields, allowing the extension of the magnetic connection notion to a much broader concept. © 2015 American Physical Society.

The interest in designing nanosystems is continuously growing. Engineers apply a great number of optimization methods to design macroscopic systems. If these methods could be introduced into the design of small systems, a great improvement in nanotechnologies could be achieved. To do so, however, it is necessary to extend classical thermodynamic analysis to small systems, but irreversibility is also present in small systems, as the Loschmidt paradox highlighted. Here, the use of the recent improvement of the Gouy-Stodola theorem to complex systems (GSGL approach), based on the use of entropy generation, is suggested to obtain the extension of classical thermodynamics to nanothermodynamics. The result is a new approach to nanosystems which avoids the difficulties highlighted in the usual analysis of the small systems, such as the definition of temperature for nanosystems. © 2015 by the authors; licensee MDPI, Basel, Switzerland.

Chicco G.,Polytechnic University of Turin
Proceedings of the International Conference on Optimisation of Electrical and Electronic Equipment, OPTIM | Year: 2010

This paper deals with the evolution of distribution networks towards the smart grid paradigm, with a twofold focus. The first focus is on discussing the role of information technologies and specific aspects of data representation for generation, demand and storage patterns gathered from the field. The second focus refers to highlighting the formulation of specific objective functions for distribution system optimization incorporating new issues emerging from today's trend towards exploiting decentralized resources. ©2010 IEEE.

Mazzoli R.,University of Turin | Bosco F.,Polytechnic University of Turin | Mizrahi I.,Institute of Animal Science | Bayer E.A.,Weizmann Institute of Science | Pessione E.,University of Turin
Biotechnology Advances | Year: 2014

Lactic acid bacteria (LAB) have long been used in industrial applications mainly as starters for food fermentation or as biocontrol agents or as probiotics. However, LAB possess several characteristics that render them among the most promising candidates for use in future biorefineries in converting plant-derived biomass-either from dedicated crops or from municipal/industrial solid wastes-into biofuels and high value-added products. Lactic acid, their main fermentation product, is an attractive building block extensively used by the chemical industry, owing to the potential for production of polylactides as biodegradable and biocompatible plastic alternative to polymers derived from petrochemicals. LA is but one of many high-value compounds which can be produced by LAB fermentation, which also include biofuels such as ethanol and butanol, biodegradable plastic polymers, exopolysaccharides, antimicrobial agents, health-promoting substances and nutraceuticals. Furthermore, several LAB strains have ascertained probiotic properties, and their biomass can be considered a high-value product. The present contribution aims to provide an extensive overview of the main industrial applications of LAB and future perspectives concerning their utilization in biorefineries. Strategies will be described in detail for developing LAB strains with broader substrate metabolic capacity for fermentation of cheaper biomass. © 2014 Elsevier Inc.

Doglione R.,Polytechnic University of Turin
JOM | Year: 2012

This paper reports the results of an investigation into the damage mechanisms that occur during straining of the aluminum alloy A356-T6 using in situ tensile experiments in a scanning electron microscope. Quantitative stereological analyses of the microstructure and in situ studies of the damage mechanisms have been used to characterize the Si particles and their eutectic distribution that ultimately controls ductility. In situ testing has revealed that, at increasing applied strain, the damage begins with brittle fractures of the Si particles due to cleavage. In this way, adjacent microcracks are created. Subsequently, the joining of the Si microcracks gives rise to the nucleation of a microcrack on the dendrite boundaries. The final damage stage involves the growth of the crack along the dendrite boundaries, until instability is reached. The investigations have shown that, by means of in situ mechanical testing, it is possible to obtain quantitative data of the damage mechanisms which are useful to predict the engineering characteristics of casting alloys. © 2012 TMS.

Popescu V.A.,Polytechnic University of Bucharest | Puscas N.N.,Polytechnic University of Bucharest | Perrone G.,Polytechnic University of Turin
Journal of the Optical Society of America B: Optical Physics | Year: 2014

The propagation characteristics in a new microstructured single-core holey fiber-based plasmonic sensor are investigated using a finite element method. The fiber is specifically designed for sensing analytes with small refractive index values, like water solutions. The proposed structure is made by a silica core with a small air hole in the center, surrounded by six air holes placed at the vertices of a hexagon and four or five smaller air holes between some large air holes, and further enclosed by gold and water layers. The presence of the four small holes impedes the resonant interaction (at 0.623 μm) between one of the pair of twofold degenerate core modes with a plasmon mode and introduces two new core modes in resonance with the plasmon modes when the phase matching (at 0.618 μm) or loss matching (at 0.632 μm) conditions are satisfied. The addition of such four small air holes to a previously studied sensor structure produces a stronger transmission loss (1266.8 dB?cm) of a core guided mode at the resonant coupling due to efficient interaction with a plasmon mode near the loss matching point in the red part of the visible spectrum (0.632 μm). The advantages of the configuration with five small air holes are a better spectral resolution, a smaller value of the FWHM parameter, a higher value of the signal-to-noise ratio, and a higher amplitude sensitivity. Our sensors are capable of detecting large ranges of refractive indices with accuracy of 1.0 × 10?5 refractive index units. © 2014 Optical Society of America.

Teppati V.,Polytechnic University of Turin | Bolognesi C.R.,Wave Group
IEEE Transactions on Instrumentation and Measurement | Year: 2012

In this paper, a thorough evaluation of calibration residual uncertainty of on-wafer load-pull systems at millimeterwave frequencies, with actual comparisons between real-time and non-real-time load-pull systems, is reported for the first time. Two figures of merit for uncertainty evaluation are taken into account, showing the differences between the two methodologies. In the case of non-real-time systems, based on a simulation tool developed for the purpose, typical values of uncertainties to be expected at millimeter-wave frequencies are shown. Finally, a methodology to reduce calibration residual uncertainty of nonreal- time load-pull measurements, based on the optimization of a thru load-pull map, is for the first time introduced, and its effects on actual measurements of microwave HBTs at 40 GHz are shown. © 2012 IEEE.

Comisso L.,Polytechnic University of Turin | Comisso L.,CNR Institute for Complex Systems | Asenjo F.A.,Adolfo Ibanez University
Physical Review Letters | Year: 2014

The magnetic reconnection process is studied in relativistic pair plasmas when the thermal and inertial properties of the magnetohydrodynamical fluid are included. We find that in both Sweet-Parker and Petschek relativistic scenarios there is an increase of the reconnection rate owing to the thermal-inertial effects, both satisfying causality. To characterize the new effects we define a thermal-inertial number which is independent of the relativistic Lundquist number, implying that reconnection can be achieved even for vanishing resistivity as a result of only thermal-inertial effects. The current model has fundamental importance for relativistic collisionless reconnection, as it constitutes the simplest way to get reconnection rates faster than those accessible with the sole resistivity. © 2014 American Physical Society.

Garelli M.,HFE | Ferrero A.,Polytechnic University of Turin
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

An analytical approach to compute the uncertainty of multiport scattering parameter measurements is presented. First, the various uncertainty causes from the noise to the standard definitions are modeled and characterized, then the uncertainty propagation up to the device-under-test measurement is computed. Experiments confirm the validity of this general approach. © 2012 IEEE.

Priarone P.C.,Polytechnic University of Turin
International Journal of Advanced Manufacturing Technology | Year: 2016

The rising awareness of energy consumption and the environmental impact of manufacturing underline the need to implement structured approaches, such as a life cycle assessment, or metrics for process evaluation. Energy savings on their own are not sufficient to increase the process efficiency of industrial finishing operations, since the results, in terms of machined part quality, have to be accounted for. The research work presented in this paper applies sustainable development concepts to an industrial case study. A shaping grinding process (a flute grinding operation for tap manufacturing) has been assessed experimentally. The effects of variations in the process parameters have been discussed, with respect to processing time, energy consumption, and product quality/integrity. Whenever the optimization goals are in contrast, a trade-off between product requirements and process sustainability has to be introduced. In order to achieve energy savings, without altering the performance of the product, a specific efficiency sustainability indicator has been implemented and coupled to the life cycle inventory phase. The results provide a tool that can assist the decision-making stage and can be incorporated into a business strategy development framework. © 2016 Springer-Verlag London

Dozio L.,Polytechnic of Milan | Carrera E.,Polytechnic University of Turin
Composite Structures | Year: 2012

A variable-kinematic Ritz formulation based on two-dimensional higher-order layerwise and equivalent single-layer theories is described in this paper to accurately predict free vibration of thick and thin, rectangular and skew multilayered plates with clamped, free and simply-supported boundary conditions. The main result is the derivation at a layer level of so-called Ritz fundamental nuclei for the stiffness and mass matrices which are invariant with respect to both the assumed kinematic model and the type of Ritz functions. In this work, products of Chebyshev polynomials and boundary-compliant functions are chosen as admissible trial set. After studying the convergence of the method, its accuracy is evaluated, in terms of frequency parameters and through-the-thickness distribution of modal displacements, by comparison with some reference results available in the literature. Results for sandwich plates with soft core are given for the first time, which may serve as benchmark values for future research. © 2012 Elsevier Ltd.

Petrolo M.,Polytechnic University of Turin
International Journal of Aeronautical and Space Sciences | Year: 2012

An advanced aeroelastic formulation for flutter analyses is presented in this paper. Refined 1D structural models were coupled with the doublet lattice method, and the g-method was used for flutter analyses. Structural models were developed in the framework of the Carrera Unified Formulation (CUF). Higher-order 1D structural models were obtained by using Taylor-like expansions of the cross-section displacement field of the structure. The order (N) of the expansion was considered as a free parameter since it can be arbitrarily chosen as an input of the analysis. Convergence studies on the order of the structural model can be straightforwardly conducted in order to establish the proper 1D structural model for a given problem. Flutter analyses were conducted on several wing configurations and the results were compared to those from literature. Results show the enhanced capabilities of CUF 1D in dealing with the flutter analysis of typical wing structures with high accuracy and low computational costs. © The Korean Society for Aeronautical & Space Sciences.

Tondolo F.,Polytechnic University of Turin
Construction and Building Materials | Year: 2015

The bond between steel and concrete has a profound influence on the structural behaviour of reinforced concrete structures in both service and ultimate conditions. In the present work, bond-slip behaviour between steel and concrete has been analysed in the presence of corrosion of a steel reinforcing bar. The results of pull-out RILEM type tests are presented. The tests have been performed on specimens with and without confinement in the presence of an increasing level of corrosion up to 20% of mass loss. Corrosion has been induced by means of an electrochemical procedure with a current density of 200 μA/cm2. The local bond-slip curve between the steel and concrete, in the presence of a short embedment length between the two materials, has been obtained. The results show the influence of the corrosion level and the presence of confinement in terms of the bond-slip response. © 2015 Elsevier Ltd. All rights reserved.

Mesin L.,Polytechnic University of Turin
Computers in Biology and Medicine | Year: 2013

Models of surface electromyogram (EMG) are useful to assess the effect of geometrical or conductivity properties of the tissue on the recorded signal. This paper provides a review of structure based models describing specific volume conductors. The technique for the development of advanced analytical and numerical simulators is described. A new model is also introduced, simulating a layered volume conductor including a subcutaneous tissue with variable thicknesses, providing an approximate analytical solution in the Fourier transform domain. Note that volume conductors are described using Poisson equation, fundamental model of Mathematical Physics, which applies also to mechanics, diffusion, electrostatics problems. © 2013 Elsevier Ltd.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2016

The balance of forces and processes between the system and the environment and the processes inside the system are the result of the flows of the quanta. Moreover, the transition between two thermodynamic states is the consequence of absorption or emission of quanta, but, during the transition, the entropy variation due to the irreversibility occurs and it breaks any symmetry of time. Consequently, the irreversibility is the result of a transition, a process, an interaction between the system and its environment. This interaction results completely time-irreversible for any real process because of irreversibility. As a consequence, a proof of the third law is obtained proving that the zero temperature state can be achieved only for an infinite work lost for dissipation or in an infinite time. The fundamental role of time both in equilibrium and in non equilibrium analysis is pointed out. Moreover, the non equilibrium temperature is related to the entropy generation and its fluctuation rate; indeed, non-stationary temperature means that the system has not yet attained free energy minimum state, i.e., the maximum entropy state; the consequence is that the zero temperature state can be achieved only for an infinite work lost for dissipation or in an infinite time. In engineering thermodynamics the efficiency is always obtained without any consideration on time, while, here, just the time is introduced as a fundamental quantity of the analysis of non equilibrium states. © 2015 Elsevier B.V. All rights reserved.

Taricco G.,Polytechnic University of Turin | Riegler E.,Vienna University of Technology
IEEE Transactions on Information Theory | Year: 2011

An asymptotic approach to derive the ergodic capacity achieving covariance matrix for a multiple-input multiple-output (MIMO) channel is presented. The method is applicable to MIMO channels affected by separately correlated Rician fading and co-channel interference. It is assumed that the number of transmit, receive and interfering antennas grows asymptotically while their ratios, as well as the SNR and the SIR, approach finite constants. Nevertheless, it is shown that the asymptotic results represent an accurate approximation in the case of a finitely many antennas and can be used to derive the ergodic channel capacity. This is accomplished by using an iterative power allocation algorithm based on a water-filling approach. The convergence of a similar algorithm (nicknamed frozen water-filling) was conjectured in a work by Dumont Here, we show that, in the Rayleigh case, the frozen water-filling algorithm may not converge while, in those cases, our proposed algorithm converges. Finally, numerical results are included in order to assess the accuracy of the asymptotic method proposed, which is compared to equivalent results obtained via Monte-Carlo simulations. © 2011 IEEE.

The fascination of a leaning tower actually hides some problems related to the interaction with the foundation soil, sometime not so evident at first glance. At the same time we can notice how the observer, even if not aware of scientific knowledge, has the ability of capturing the essence of the problem, because, when asking himself about the reaction of the tower if perturbed by any external action, he is just disputing about the stability of equilibrium. The danger of a leaning instability increases if there is lack of stiffness of the soil, and in this respect the leaning tower of Pisa represents a powerful example, because the preservation of the tower was recognised as being a problem of leaning instability [HAMBLEY, 1985; LANCELLOTTA, 1993; COMO, 1993; DESIDERI and VIGGIANI, 1994; NOVA and MONTRASIO, 1995; PEPE, 1995; BURLAND et al., 2003; MARCHI et al., 2011].

Xia J.,Polytechnic University of Turin | Xia J.,INRIM - Istituto Nazionale di Ricerca Metrologica | Rossi A.M.,INRIM - Istituto Nazionale di Ricerca Metrologica | Murphy T.E.,University of Maryland University College
Optics Letters | Year: 2012

We report that low-loss ridge waveguides are directly written on nanoporous silicon layers by using an argon-ion laser at 514 nm up to 100 mW. Optical characterization of the waveguides indicates light propagation loss lower than 0.5 dB/cm at 1550 nm after oxidation. A Mach-Zehnder interferometer sensor is experimentally demonstrated using the waveguide in its sensing branch, and analytical results indicate that very high sensitivity can be achieved. With large internal surface area, versatile surface chemistry, and adjustable index of refraction of porous silicon, the ridge waveguides can be used to configure Mach-Zehnder interferometers, Young's interferometers, and other photonic devices for highly sensitive optical biosensors and chemical sensors as well as other applications. © 2012 Optical Society of America.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2016

Nature can be considered the "first" engineer! For scientists and engineers, dynamics and evolution of complex systems are not easy to predict. A fundamental approach to study complex system is thermodynamics. But, the result is the origin of too many schools of thermodynamics with a consequent difficulty in communication between thermodynamicists and other scientists and, also, among themselves. The solution is to obtain a unified approach based on the fundamentals of physics. Here we suggest a possible unification of the schools of thermodynamics starting from two fundamental concepts of physics, interaction and flows. © 2015 Elsevier B.V.

Asadi M.S.,Baker Hughes Inc. | Rasouli V.,Curtin University Australia | Barla G.,Polytechnic University of Turin
Rock Mechanics and Rock Engineering | Year: 2012

Different failure modes during fracture shearing have been introduced including normal dilation or sliding, asperity cut-off and degradation. Attempts have been made to study these mechanisms using analytical, experimental and numerical methods. However, the majority of the existing models simplify the problem, which leads to unrealistic results. With this in mind, the aim of this paper is to simulate the mechanical behaviour of synthetic and rock fracture profiles during direct shear tests by using the twodimensional particle flow computer code PFC2D. Correlations between the simulated peak shear strength and the fracture roughness parameter DR1 recently proposed by Rasouli and Harrison (2010) are developed. Shear test simulations are carried out with PFC2D and the effects of the geometrical features as well as the model micro-properties on the fracture shear behaviour are studied. The shear strength and asperity degradation processes of synthetic profiles including triangular, sinusoidal and randomly generated profiles are analysed. Different failure modes including asperity sliding, cut-off, and asperity degradation are explicitly observed and compared with the available models. The DR1 parameter is applied to the analysis of synthetic and rock fracture profiles. Accordingly, correlations are developed between DR1 and the peak shear strength obtained from simulations and by using analytical solutions. The results are shown to be in good agreement with the basic understanding of rock fracture shear behaviour and asperity contact degradation. © Springer-Verlag 2012.

Dall'agata G.,University of Padua | Dall'agata G.,National Institute of Nuclear Physics, Italy | Inverso G.,University of Rome Tor Vergata | Inverso G.,National Institute of Nuclear Physics, Italy | And 2 more authors.
Physical Review Letters | Year: 2012

In this note we discuss the classification of duality orbits of N=8 gauged supergravity models. Using tensor classifiers, we show that there is a one-parameter family of inequivalent SO(8) gauged supergravity theories. We briefly discuss the couplings of such models and show that, although the maximally symmetric vacuum has the same quadratic spectrum, the supersymmetry transformations, the couplings, and the scalar potential are parameter dependent. We also comment on the possible M theory uplift and on the meaning of the parameter for the dual gauge theories. © 2012 American Physical Society.

Gioannini M.,Polytechnic University of Turin
Journal of Applied Physics | Year: 2012

The paper analyses theoretically the quenching of the ground state (GS) power observed in InAs/GaAs quantum dot lasers when emitting simultaneously from both ground state and excited state. The model, based on a set of rate equations for the electrons, holes, and photons, shows that the power quenching is caused by the different time scales of the electron and hole intra-level dynamic, as well as by the long transport time of the holes in the GaAs barrier. The results presented also evidence how the very different dynamics of electrons and holes have other important consequences on the laser behavior; we show for example that the electron and hole carrier densities of the states resonant with lasing modes are never clamped at the threshold value, and that the damping of relaxation oscillations is strongly influenced by the hole dynamics. © 2012 American Institute of Physics.

Mukhopadhyay S.,University of Calgary | Banerjee S.,Polytechnic University of Turin
Expert Systems with Applications | Year: 2012

The control and estimation of unknown parameters of chaotic systems are a daunting task till date from the perspective of nonlinear science. Inspired from ecological co-habitation, we propose a variant of Particle Swarm Optimization (PSO), known as Chaotic Multi Swarm Particle Swarm Optimization (CMS-PSO), by modifying the generic PSO with the help of the chaotic sequence for multi-dimension unknown parameter estimation and optimization by forming multiple cooperating swarms. This achieves load balancing by delegating the global optimizing task to concurrently operating swarms. We apply it successfully in estimating the unknown parameters of an autonomous chaotic laser system derived from Maxwell-Bloch equations. Numerical results and comparison demonstrate that for the given system parameters, CMS-PSO can identify the optimized parameters effectively evolving at each iteration to attain the pareto optimal solution with small population size and enhanced convergence speedup. © 2011 Elsevier Ltd. All rights reserved.

Angelini A.,Polytechnic University of Turin
Optics Letters | Year: 2015

Complex light fields, including evanescent Bessel beams, can be generated at dielectric interfaces by means of oilimmersion optics operating in total internal reflection conditions. Here we report on the observation of evanescent complex fields produced on a dielectric multilayer through the interference of surface modes resonantly sustained by the multilayer itself. The coupling to surface modes is attained by modifying the wavefront of an incident laser beam in such a way that the resulting intensity distribution in k-space matches the dispersion of the surface mode. The phase of surface modes can be further controlled, and twodimensional vortex beams can also be produced according to the same working principle. © 2015 Optical Society of America.

Chiampi M.,Polytechnic University of Turin | Zilberti L.,INRIM - Istituto Nazionale di Ricerca Metrologica
IEEE Transactions on Biomedical Engineering | Year: 2011

A computational procedure, based on the boundary element method, has been developed in order to evaluate the electric field induced in a body that moves in the static field around an MRI system. A general approach enables us to investigate rigid translational and rotational movements with any change of motion velocity. The accuracy of the computations is validated by comparison with analytical solutions for simple shaped geometries. Some examples of application of the proposed procedure in the case of motion around an MRI scanner are finally presented. © 2011 IEEE.

Paggi M.,Polytechnic University of Turin
International Journal of Solids and Structures | Year: 2010

The engineering response of metamaterials has a dramatic impact on the physics, optics and engineering communities, because they offer electromagnetic properties that are difficult or impossible to achieve with conventional materials. In this paper, an asymptotic analysis of the electromagnetic fields at multi-material wedges composed of metamaterials is proposed. This is made possible by removing the assumption of positive electric permittivities and magnetic permeabilities, an hypothesis which usually applies to conventional materials. Exploring the whole range of variability of these electromagnetic properties, it is shown that, in addition to the classical real eigenvalues 0 ≤ λ < 1 leading to power-law singularities of the type O(r λ-1) as r → 0, it is also possible to find imaginary eigenvalues leading to hypersingular solutions, as well as nonsingular configurations for a suitable choice of the negative electric permittivities and magnetic permeabilities of the media. Moreover, to fully characterize the asymptotic fields, the analysis is not only restricted to the determination of the lowest real and complex eigenvalues, but is also extended to the evaluation of the higher-order nonsingular ones. The obtained analytical results collected in synthetic diagrams are expected to have impact on the design of micro- and nano-electro-mechanical systems. © 2010 Elsevier Ltd. All rights reserved.

Vallone M.E.,Polytechnic University of Turin
Journal of Applied Physics | Year: 2013

A quantum model is developed to obtain electron capture and hot electron intraband relaxation times in a quantum well, for electron-longitudinal optic (LO) phonon scattering. In particular, we have investigated the effect of carrier density and electron energy, obtaining semi-analytic expressions as function of carrier density, a topic often neglected in literature, despite its fundamental interest in semiconductor physics. We demonstrated that the usual approximation of constant scattering time in modeling applications is often not adequate, because these parameters vary considerably with the injected or photogenerated carrier density. Furthermore we show that the scattering through the emission of pure LO-phonons is not a good approximation when the population increases, whereas the interplay between LO-phonon and collective plasma modes must be considered. We obtained novel semi-analytic expressions in the single plasmon pole dynamical form of the random phase approximation, without making use of the more usual static limit of it. © 2013 AIP Publishing LLC.

Cimellaro G.P.,Polytechnic University of Turin | Lopez-Garcia D.,University of Santiago de Chile
Structural Control and Health Monitoring | Year: 2011

This paper presents a versatile and robust algorithm for the optimal design of adjacent structural systems linked by passive energy dissipation devices. The algorithm works both with stationary and nonstationary force input. It is a two-stage design procedure that (i) determines an active control law, and then (ii) adds damper and stiffness coefficients that are computed based on the minimization of the difference between the response of the actively controlled system and an equivalent passive control system. The algorithm is an iterative procedure that leads to a close form global optimal solution for the damping and stiffness coefficients in such a way to obtain a response as close as possible to the active control. The method is tested for two adjacent ten-degree-of-freedom spring-dashpot-mass systems. Sensitivity analysis is carried out studying the effects of period variation, the number of DOFs variation and link location using a stationary band-limited white noise input as ground acceleration. Results show that the same performance can be achieved with less amount of damping when the linear damper is located at the last mass of the system. When dampers are located in one of the node of the mode shape, the total amount of damping is higher to achieve the same performance. © 2009 John Wiley & Sons, Ltd.

Calafiore G.C.,Polytechnic University of Turin | Dabbene F.,CNR Institute of Electronics, Computer and Telecommunication Engineering | Tempo R.,CNR Institute of Electronics, Computer and Telecommunication Engineering
Automatica | Year: 2011

A novel approach based on probability and randomization has emerged to synergize with the standard deterministic methods for control of systems with uncertainty. The main objective of this paper is to provide a broad perspective on this area of research known as "probabilistic robust control", and to address in a systematic manner recent advances. The focal point is on design methods, based on the interplay between uncertainty randomization and convex optimization, and on the illustration of specific control applications. © 2011 Elsevier Ltd. All rights reserved.

Mancini S.,Polytechnic University of Turin
Transportation Research Part C: Emerging Technologies | Year: 2015

In this paper, a new rich Vehicle Routing Problem that could arise in a real life context is introduced and formalized: the Multi Depot Multi Period Vehicle Routing Problem with a Heterogeneous Fleet. The goal of the problem is to minimize the total delivery cost. A heterogeneous fleet composed of vehicles with different capacity, characteristics (i.e. refrigerated vehicles) and hourly costs is considered. A limit on the maximum route duration is imposed. Unlike what happens in classical multi-depot VRP, not every customer may/will be served by all the vehicles or from all the depots. The planning horizon, as in most real life applications, consists of multiple periods, and the period in which each route is performed is a variable of the problem. The set of periods, within the time horizon, in which the delivery may be carried out is known for each customer. A Mixed Integer Programming (MIP) formulation for MDMPVRPHF is presented in this paper, and an Adaptive Large Neighborhood Search (ALNS) based Matheuristic approach is proposed, in which different destroy operators are defined. Computational results, pertaining to realistic instances, which show the effectiveness of the proposed method, are provided. © 2015 Elsevier Ltd.

Montagna F.,Polytechnic University of Turin
Research in Engineering Design | Year: 2011

The complexity and uncertainty that exist in New Product Development (NPD) processes require a comprehensive approach to deal with a problem that involves people, technology and organisations. An effective approach should integrate tools that facilitate communication, the interpretation of different individualvisions and collective problem structuring with tools that analytically study the process activities of NPD. This paper presents the results of a study that began from an observation of the phenomena involved in an NPD process and from the analysis of some tools from different domains (Product Lifecycle Management, Management Science/ Operation Research, and Knowledge Management). The analysis of the benefits and drawbacks of the tools suggested a general framework, the Hybrid Approach, for the systematic integration of tools, from different perspectives, where typological decision-aiding situations are recognised and modelled and where context and communication in design are considered. © Springer-Verlag London Limited 2011.

High speed rotors are usually operated above the critical speed to achieve a good self-centring and to reduce the reactions of bearings. Damping associated to the rotating parts induces some dynamic instability, when the system rotates faster than an angular velocity defined as 'instability threshold'. To increase the range between the critical speed and the instability threshold the designer usually applies to the stator a suitable amount of non-rotating damping, being always stabilizing. In some application there is no stator available (spacecrafts, satellites) and in rotors suspended on active magnetic bearings the control current may be fairly large, if the dynamic stability has to be assured at a high spin speed. A new kind of active magnetic stabilisation is therefore proposed to overcome those limits. The damping action of the stator is here rotating, but its vector and the rotor spin speed are just opposite. Therefore that action appears as 'contra-rotating'. This approach provides an asymptotic dynamic stability of both the forward and backward whirling motions, even in the high supercritical regime. Design issues, implementation and results obtained in case of a semi-active system based on permanent magnets as well as of an active magnetic device are herein discussed. © 2014 Elsevier Ltd. All rights reserved.

Lin J.,New York University | Gueudre T.,Polytechnic University of Turin | Rosso A.,University Paris - Sud | Wyart M.,Ecole Polytechnique Federale de Lausanne
Physical Review Letters | Year: 2015

Failure of amorphous solids is fundamental to various phenomena, including landslides and earthquakes. Recent experiments indicate that highly plastic regions form elongated structures that are especially apparent near the maximal shear stress Σmax where failure occurs. This observation suggested that Σmax acts as a critical point where the length scale of those structures diverges, possibly causing macroscopic transient shear bands. Here, we argue instead that the entire solid phase (Σ<Σmax) is critical, that plasticity always involves system-spanning events, and that their magnitude diverges at Σmax independently of the presence of shear bands. We relate the statistics and fractal properties of these rearrangements to an exponent θ that captures the stability of the material, which is observed to vary continuously with stress, and we confirm our predictions in elastoplastic models. © 2015 American Physical Society.

Daniele V.G.,Polytechnic University of Turin
Electromagnetics | Year: 2010

The diffraction by a dielectric wedge of an arbitrary aperture angle is studied by means of the generalized Wiener-Hopf technique. Generalized Wiener-Hopf equations are deduced that apparently cannot be solved in closed form. The factorization of the kernels can be reduced to Fredholm equations of the second kind by using a standard procedure (Fredholm factorization). The solutions of the Fredholm equations are obtained through a simple quadrature technique that very quickly yields a numerically stable evaluation of the unknowns of the generalized Wiener-Hopf equations. The generalized Wiener-Hopf technique provides a representation of the fields only in certain regions of the spectral domain. To obtain valid solutions everywhere, a process of analytical continuation is required. This latter task is accomplished in the companion article. Copyright © Taylor & Francis Group, LLC.

Fracastoro G.V.,Polytechnic University of Turin | Serraino M.,Clivet S.p.A.
Energy and Buildings | Year: 2011

From energy statistics (primary energy consumption) and a few Census data (residential buildings floor area) the average specific primary energy use (kWh/m2) of a territorial (Regional or National) building stock may be easily evaluated. However, can we achieve a deeper insight on this building stock using basically the same data bases? This is the question which this paper is aiming at, and the results is an analytical methodology to determine the Statistical Distribution Of residential Buildings according to primary Energy consumption for heating purposes (E-SDOB) at a Regional or National scale. This tool may allow the legislator to define a performance scale for building energy certification, to introduce mandatory measures and incentives for building energy retrofits, to evaluate the potential of new technologies, etc. The main source of data required for determining E-SDOB is still the National Census, but it has to be integrated by energy standards and laws, literature and a few data taken from the authors' experience and in situ analysis. The results obtained have been compared with those derived from two Italian Regional (Piedmont and Lombardy) energy statistics, with excellent agreement. © 2010 Elsevier B.V. All rights reserved.

Fiori F.,Polytechnic University of Turin
IEEE Electromagnetic Compatibility Magazine | Year: 2015

In this paper the main causes of failures induced by radio frequency interference in elementary integrated circuits (ICs) are summarized, then more complex devices like smart power ICs are considered and a method to evaluate their susceptibility to such disturbances is presented. The weakness of smart power ICs against radio frequency interference is highlighted referring to the results of measurements carried out on a test chip composed of a power MOS and an analog block both integrated in the same silicon die but electrically isolated one to each other. © 2012 IEEE.

Noel J.P.,University of Liege | Marchesiello S.,Polytechnic University of Turin | Kerschen G.,University of Liege
Mechanical Systems and Signal Processing | Year: 2014

The objective of the present paper is to address the identification of a strongly nonlinear satellite structure. To this end, two nonlinear subspace identification methods formulated in the time and frequency domains are exploited, referred to as the TNSI and FNSI methods, respectively. The modal parameters of the underlying linear structure and the coefficients of the nonlinearities will be estimated by these two approaches based on periodic random measurements. Their respective merits will also be discussed in terms of both accuracy and computational efficiency and the use of stabilisation diagrams in nonlinear system identification will be introduced. The application of interest is the SmallSat spacecraft developed by EADS-Astrium, which possesses an impact-type nonlinear device consisting of eight mechanical stops limiting the motion of an inertia wheel mounted on an elastomeric interface. This application is challenging for several reasons including the non-smooth nature of the nonlinearities, high modal density and high non-proportional damping. © 2013 Elsevier Ltd. All rights reserved.

Mazzucco M.,Polytechnic University of Turin
Computer Methods in Applied Mechanics and Engineering | Year: 2014

Structural engineering practice often involves tasks, such as design, optimization or statistical analysis, where iterative solutions of dynamical systems are required varying some parameter which affect the system matrices in a generally non-linear way. The approach of interpolating among matrices of reduced-order models (ROMs) is not new in the literature and it is very promising in order to speed up the calculations. In particular, the method shows a great potential since it is applicable to any kind of FE model and of geometry, with no restrictions regarding the element type constituting the full-order model or the range of parameter variability. Yet, dealing with symmetric positive definite (SPD) full-order matrices, the SPD nature of the reduced matrices must be preserved. To this end, a special mathematical framework must be used, which allows to linearize the curved space of SPD matrices. In the literature of ROMs interpolation, the common choice is to rely on the principles of Riemannian geometry through the concept of the tangent plane to the SPD manifold. Although mathematically robust, this approach brings a marked distortion in the space of SPD matrices. Also, it shows numerical instabilities when dealing with strongly anisotropic matrices. In this work, a polynomial fitting of the reduced matrices is proposed with Log-Euclidean metrics. These metrics were obtained by giving the SPD manifold the structure of a Lie group. While maintaining the already proposed approach of interpolating between a number of sampling ROMs, the advantages of using Log-Euclidean metrics are illustrated in details. In particular, a great improvement is shown in case of a unique reduction matrix whose columns span the solution of the parameter space of interest in an accurate enough way, and in case of substructuring reduction techniques. The reported examples of applications show excellent accuracy, while maintaining the dramatic decrease in the computational time of the interpolatory scheme. © 2013 Elsevier B.V.

McGill K.C.,Rehabilitation Research and Development Center | Marateb H.R.,Polytechnic University of Turin
IEEE Transactions on Neural Systems and Rehabilitation Engineering | Year: 2011

If electromyography (EMG) decomposition is to be a useful tool for scientific investigation, it is essential to know that the results are accurate. Because of background noise, waveform variability, motor-unit action potential (MUAP) indistinguishability, and perplexing superpositions, accuracy assessment is not straightforward. This paper presents a rigorous statistical method for assessing decomposition accuracy based only on evidence from the signal itself. The method uses statistical decision theory in a Bayesian framework to integrate all the shape- and firing-time-related information in the signal to compute an objective a posteriori measure of confidence in the accuracy of each discharge in the decomposition. The assessment is based on the estimated statistical properties of the MUAPs and noise and takes into account the relative likelihood of every other possible decomposition. The method was tested on 3 pairs of real EMG signals containing 47 active MUAP trains per signal that had been decomposed by a human expert. It rated 97% of the identified MUAP discharges as accurate to within ± 0.5 ms with a confidence level of 99%, and detected six decomposition errors. Cross-checking between signal pairs verified all but two of these assertions. These results demonstrate that the approach is reliable and practical for real EMG signals. © 2010 IEEE.

Giannini V.,Polytechnic University of Turin
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2010

Automatic segmentation of the breast and axillary region is an important preprocessing step for automatic lesion detection in breast MR and dynamic contrast-enhanced-MR studies. In this paper, we present a fully automatic procedure based on the detection of the upper border of the pectoral muscle. Compared with previous methods based on thresholding, this method is more robust to noise and field inhomogeneities. The method was quantitatively evaluated on 31 cases acquired from two centers by comparing the results with a manual segmentation. Results indicate good overall agreement within the reference segmentation (overlap=0.79 ± 0.09, recall=0.95 ± 0.02, precision=0.82 ± 0.1).

Novara C.,Polytechnic University of Turin
International Journal of Adaptive Control and Signal Processing | Year: 2016

The problem of approximating an unknown function from data and deriving reliable interval estimates is important in many fields of science and technology. In this paper, an algorithm is proposed to solve this problem, based on a sparsification technique and a nonparametric set membership analysis. Assuming that the noise affecting the data is bounded and the unknown function satisfies a mild regularity assumption, it is shown that the algorithm provides an approximation with suitable optimality properties, together with tight interval estimates. An innovative approach to fault detection, based on the derived interval estimates, is then proposed, overcoming some relevant problems proper of the 'classical' techniques. The approach is applied in a simulation study to solve the challenging problem of fault detection for a new class of wind energy generators, which uses kites to capture the power from high-altitude winds. © Copyright 2015 John Wiley & Sons, Ltd.

Bertoluzzi L.,Jaume I University | Ma S.,Polytechnic University of Turin
Physical Chemistry Chemical Physics | Year: 2013

The charge collection efficiency is one of the most critical parameters of photovoltaic devices. In this paper we provide the analysis and comparison between several approaches for the calculation of the collection efficiency of dye-sensitized solar cells. In addition, we point out that although it is reasonable to correlate transit time and recombination lifetime with respect to diffusion length, it is less physical to directly calculate collection efficiency only based on characteristic time constants. © 2013 the Owner Societies.

Ruggeri B.,Polytechnic University of Turin | Tommasi T.,Italian Institute of Technology
International Journal of Hydrogen Energy | Year: 2012

Two energy conversion parameters that are able to evaluate and score the pre-treatments and biohydrogen conversion processes of organic waste refuses have been introduced and applied using original experimental data. The parameters can be considered a suitable tool to score and select processes using rich lignocelluloses materials. The first efficiency (ξ) takes into account the quantity of energy that the process is able to extract as hydrogen, compared to the available amount of energy embedded in the refuse; the second efficacy (η) compares the energy conversion efficiency of the bioprocess using the refuse with the same energy conversion parameter obtained using glucose as a lignin-cellulose free substrate. Both the efficiency and efficacy have been applied in several experimental tests carried out with different kinds of experimental apparatus: an Erlenmeyer flask and bench bioreactor (2 L stirred-batch reactor STR), using mechanical (kitchen blade mixer) and chemical (HCl or NaOH for 24 h at 30 °C) pre-treated Organic Waste Market (OWM) refuse. The alkaline pre-treatment is the most efficient. A comparison of OWM efficiency with that of a glucose test under the same bench bioreactor experimental conditions, shows that the efficacy of energy production is 45%, which is equivalent to 7.3 L H2/kg as the gross material i.e. at its original undiluted strength. The paper shows that the two parameters are able to quantify the efficacy of energy production of such a bioprocess, including the pretreatment, using lignin-cellulose refuses, and to score different processes against glucose. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Grivet-Talocia S.,Polytechnic University of Turin
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

This paper provides a theoretical framework for passivity characterization of symmetric rational macromodels. These may be obtained for linear and time-invariant reciprocal structures if structural symmetry is preserved during the rational fitting stage of the macromodel generation. Standard Hamiltonian-based methods can be used to characterize any passivity violation of such macromodels. Recent developments have suggested, however, that the same results may be obtained at a reduced computational cost, using so-called "half-size"passivity test matrices. In this paper, we generalize such results by providing a complete theoretical framework. In addition to imaginary Hamiltonian eigenvalues, we present a complete characterization of associated eigenvectors, allowing for precise localization of passivity violations. Since half-size matrices are also used for computing the eigenvectors, the overall computational cost is reduced up to a factor of eight. Several numerical examples validate and confirm the theoretical developments. Copyright © 2010 IEEE.

Dalla Chiara B.,Polytechnic University of Turin
IET Intelligent Transport Systems | Year: 2010

This study concerns the application of automatic vehicle location systems (AVLSs) for the control and management of fleet of vehicles whose regular routes are random, that is, with origins and destinations so numerous and variable that they cannot be predefined. Typical examples include road shipments, pick-up and delivery services and express couriers, demand responsive transport services and public utility services (gas, water etc.). Specific reference is made to transport of goods but analogous observations may be valid for passenger transport. The average response time of the mobile unit depends on (i) the accuracy of the AVLS adopted; (ii) the configuration of the fleet within the territory where it operates; (iii) a number of operative parameters, among which are the size of the operative area, the number of vehicles employed, the average time that they are in use, their average speed and the average time taken to perform the service. The results of two specific models provide average response times which can be compared in transport operations carried out with and without the use of an AVLS. If we abstract the equations derived from these, we obtain a quantity Δt, which measures the reduction in response time resulting from the adoption of an AVLS. The relevance of the results is related to the role of accuracy, integrity and continuity of the future Galileo system for transport location services. © 2010 The Institution of Engineering and Technology.

The paper presents a comparison between two existing zigzag functions that are used to improve equivalent single layer (ESL) theories for the analysis of multilayered composite and sandwich beams. ESL theories are easy to implement and computationally affordable but, in order to correctly describe the mechanical behavior of laminated structures (especially those exhibiting high transverse anisotropy or high thickness-to-side length ratios), the displacement field needs to be enriched by a through-the-thickness piecewise linear contribution denoted as "zigzag." The zigzag term of the displacement field is used to model the local distortion of the cross section in each lamina of multilayered structures and is related to the continuity of transverse stresses. The paper considers two zigzag functions that have been proposed in the open literature (namely Murakami's zigzag function and the refined zigzag function) and compares their performances when they are used to improve the classical Timoshenko beam theory; both displacement-based and mixed formulations are considered. To the best of the author's knowledge, such a comparative study has never been published. The problem of a simply supported beam subjected to a transverse distributed load is considered as a test case. Several stacking sequences, ranging from monolithic to sandwich-like and from symmetric to arbitrary, are considered. The special case of laminates with external weak layers is also investigated and the effects of these lay-ups on the derivation of the refined zigzag function are analyzed for the first time. The capability of the tested zigzag functions to help evaluate the overall deflection and model the through-the-thickness distribution of the axial displacement and stress is investigated. It has been recognized that the refined zigzag function is more accurate, especially for unsymmetric and arbitrary lay-ups and can be adopted to efficiently introduce zigzag kinematics into any ESL theory. Copyright © 2013 by ASME.

Tiranti D.,Agency Systems | Deangeli C.,Polytechnic University of Turin
Frontiers in Earth Sciences | Year: 2015

A method to predict the most probable flow rheology in Alpine debris flows is presented. The methods classifies outcropping rock masses in catchments on the basis of the type of resulting unconsolidated deposits. The grain size distribution of the debris material and the depositional style of past debris flow events are related to the dominant flow processes: viscoplastic and frictional/collisional. Three catchments in the upper Susa Valley (Western Alps), characterized by different lithologies, were selected for numerical analysis carried out with a Cellular Automata code with viscoplastic and frictional/collisional rheologies. The obtained numerical results are in good agreement with in site evidences in terms of depositional patterns, confirming the possibility of choosing the rheology of the debris flow based on the source material within the catchment. © 2015 Tiranti and Deangeli.

Oreste P.P.,Polytechnic University of Turin | Dias D.,Joseph Fourier University
Rock Mechanics and Rock Engineering | Year: 2012

Stability of the excavation face in shallow tunnels excavated in poor rock is at present a relevant problem in tunnelling. Even though face reinforcement with fibreglass dowels has proved to be efficient, there is still no reliable routine design method available. A new calculation procedure is illustrated in this paper for the analysis of face reinforcement with fibreglass dowels in shallow tunnels. The procedure is based on the limit equilibrium method applied to the rock core ahead of the face, and it offers a detailed evaluation of the interaction between each reinforcement element and the surrounding rock. The main calculation result concerns the safety factor of the excavation face with dowel reinforcement. On the basis of this safety factor, it is possible to identify the appropriate dowel lengths and the number of dowels. The procedure has been applied to two real cases, and satisfactory results have been obtained. © 2012 Springer-Verlag.

Graglia R.D.,Polytechnic University of Turin | Peterson A.F.,Georgia Institute of Technology | Andriulli F.P.,Telecom Bretagne
IEEE Transactions on Antennas and Propagation | Year: 2011

A new family of hierarchical vector bases is proposed for triangles and tetrahedra. These functions span the curl-conforming reduced-gradient spaces of Nédélec. The bases are constructed from orthogonal scalar polynomials to enhance their linear independence, which is a simpler process than an orthogonalization applied to the final vector functions. Specific functions are tabulated to order 6.5. Preliminary results confirm that the new bases produce reasonably well-conditioned matrices. © 2010 IEEE.

Jepps O.G.,Griffith University | Rondoni L.,Polytechnic University of Turin
Journal of Physics A: Mathematical and Theoretical | Year: 2010

Deterministic 'thermostats' are mathematical tools used to model nonequilibrium steady states of fluids. The resulting dynamical systems correctly represent the transport properties of these fluids and are easily simulated on modern computers. More recently, the connection between such thermostats and entropy production has been exploited in the development of nonequilibrium fluid theories. The purpose and limitations of deterministic thermostats are discussed in the context of irreversible thermodynamics and the development of theories of nonequilibrium phenomena. We draw parallels between the development of such nonequilibrium theories and the development of notions of ergodicity in equilibrium theories. © 2010 IOP Publishing Ltd.

Surace C.,Polytechnic University of Turin | Worden K.,University of Sheffield
Mechanical Systems and Signal Processing | Year: 2010

In the recent past, there have been a number of engineering studies motivated by analogies with the human immune system. The immune system has provided a rich source of inspiration for pattern recognition, machine learning and data mining analyses. One of the properties of the immune system which proves particularly useful for novelty detection is that of self/non-self discrimination and this forms the basis of the negative selection algorithm which has previously been applied by other researchers to the problem of time-series novelty detection. The object of the current paper is to apply the negative selection algorithm to more general feature sets and also to consider the case of novelty detection where the normal condition set is significantly non-Gaussian or varies with operational or environmental conditions. © 2009 Elsevier Ltd.

De Biagi V.,Polytechnic University of Turin
International Journal of Solids and Structures | Year: 2016

Modern requirements on constructions impose that proper design strategies must be adopted in order to obtain a robust structure: in this sense, consequence-based design focuses the attention on the structural response to damage. The behavior of statically indeterminate structural systems under damage is nonlinear because the load paths intertwine each other, even if each component behaves linearly. The paper aims both to highlight the behavior of a metallic truss under progressive damage and to define a possible strategy for designing a truss that is able to sustain damage acting at random on one of its elements. Structural complexity is used as a leading parameter. Following the results of a parametric analysis, it emerges that, as much as the Normalized Structural Complexity Index increases, the efficacy of the load paths is spread such that the impact of random damage decreases, making the approach feasible. © 2015 Elsevier Ltd. All rights reserved.

Bergel I.,Bar - Ilan University | Benedetto S.,Polytechnic University of Turin
IEEE Transactions on Information Theory | Year: 2012

The analysis of the channel capacity in the absence of prior channel knowledge (noncoherent channel) has gained increasing interest in recent years. Yet, the noncoherent channel capacity is still unknown for the general case. In this paper, we derive bounds on the capacity of the noncoherent, underspread complex Gaussian, orthogonal frequency division multiplexing, wide sense stationary channel with uncorrelated scattering, under a peak power constraint or a constraint on the second and fourth moments of the transmitted signal. These bounds are characterized only by the system signal-to-noise ratio (SNR) and by a newly defined quantity termed effective coherence time. Intuitively, the effective coherence time can be interpreted as the length of a block in the block-fading model in which a system with the same SNR will achieve the same capacity as in the analyzed channel. Unlike commonly used coherence time definitions, it is shown that the effective coherence time depends on the SNR, and is a nonincreasing function of it. We show that for low SNR, the capacity is proportional to the effective coherence time, while for higher SNR, the coherent channel capacity can be achieved provided that the effective coherence time is large enough. © 1963-2012 IEEE.

Lavagno A.,Polytechnic University of Turin | Lavagno A.,National Institute of Nuclear Physics, Italy
Physical Review C - Nuclear Physics | Year: 2010

We investigate the equation of state of hadronic matter at finite values of baryon density and temperature reachable in high-energy heavy-ion collisions. The analysis is performed by requiring the Gibbs conditions on the global conservation of baryon number, electric charge fraction, and zero net strangeness. We consider an effective relativistic mean-field model with the inclusion of Δ isobars, hyperons, and the lightest pseudoscalar and vector meson degrees of freedom. In this context, we study the influence of the Δ-isobar degrees of freedom in the hadronic equation of state and, in connection, the behavior of different particle-antiparticle ratios and strangeness production. © 2010 The American Physical Society.

Brischetto S.,Polytechnic University of Turin
CMES - Computer Modeling in Engineering and Sciences | Year: 2015

This paper proposes the free vibration analysis of Double-Walled Carbon NanoTubes (DWCNTs). A continuum elastic three-dimensional shell model is used for natural frequency investigation of simply supported DWCNTs. The 3D shell method is compared with beam analyses to show the applicability limits of 1D beam models. The effect of van der Waals interaction between the two cylinders is shown for different Carbon NanoTube (CNT) lengths and vibration modes. Results give the van der Waals interaction effect in terms of frequency values. In order to apply the 3D shell continuum model, DWCNTs are defined as two concentric isotropic cylinders (with an equivalent thickness and Young modulus) which can be linked by means of the interlaminar continuity conditions or by means of an infinitesimal fictitious layer which represents the van der Waals interaction. Copyright © 2015 Tech Science Press.

Montorsi G.,Polytechnic University of Turin
IEEE Communications Letters | Year: 2012

We introduce a message passing belief propagation (BP) algorithm for factor graph over linear models that uses messages in the form of Gaussian-like distributions. With respect to the regular Gaussian BP, the proposed algorithm adds two operations to the model, namely the wrapping and the discretization of variables. This addition requires the derivation of proper modifications of message representations and updating rules at the BP nodes. We named the new algorithm Analog-Digital-Belief-Propagation (ADBP). The ADBP allows to construct iterative decoders for mod-M ring encoders that have a complexity independent from the size M of the alphabets, thus yielding efficient decoders for very high spectral efficiencies. © 2012 IEEE.

Surace C.,Polytechnic University of Turin
Key Engineering Materials | Year: 2013

Damage to many structural systems (including bridges, offshore platforms, airplanes and aerospace systems) can occur during normal service due to fatigue loading, a corrosive environment, collisions with extraneous objects, etc. For such structures, in order to guarantee safety, periodic inspections and maintenance are essential: Since undetected damage may result in catastrophic structural failure, the realisation of an accurate and trustworthy damage detection technique is fundamental. Vibration-based inspection offers the potential for detecting faults by monitoring the dynamic response of a structure, exploiting the fundamental principle that structural damage affects the stiffness distribution and hence the presence of the fault will change the dynamic properties of the structure under investigation. Many vibration-based inspection techniques have been developed over recent years which require knowledge of the baseline modal responses of the structure in the original undamaged state. However, for the vast majority of existing structures in operation, such data are simply not available. This keynote presentation reviews past and present research studies in which the author has been involved that aim to detect the presence of structural damage and identify its approximate location, using only post-damage vibration measurements. The techniques presented analyse either the mode shapes, operating deflection shapes or principal orthogonal modes and their corresponding derivatives. These features have been found to be good indicators of damage due to the spatial information that can be provided with respect to location of damage. The methodologies proposed are applied to isotropic/orthotropic uni/bi-dimensional structures and corresponding numerical and experimental results are presented. © (2013) Trans Tech Publications.

Zn phosphinate, organo-modified sepiolite and poly(ethylene terephthalate) (PET) have been melt blended to develop a new flame retardant system for PET plastics and textiles. The combination of Zn phosphinate and sepiolite have been exploited in order to enhance the flame retardancy of PET for both plastics and textiles. The thermal stability of PET blends evaluated by thermogravimetric analysis and differential scanning calorimetry results remarkably affected by the loaded fillers. The combustion tests by cone calorimetry reveal a relevant decrease of combustion rate and a high increase of fire performance index for both plastics and textiles due to the presence of this novel flame retardant mixture. Analogously, limiting oxygen index has been found increased in a remarkable way. © 2011 The Korean Fiber Society and Springer Netherlands.

Bedda C.,Polytechnic University of Turin
Nuclear and Particle Physics Proceedings | Year: 2016

Heavy quarks (charm and beauty) are produced in hard parton scattering processes in the initial stages of hadronic collisions. The study of their production can give us different information in each type of collisions. In pp collisions at the LHC it provides a test of perturbative QCD calculations at the highest collision energy. In p-Pb collisions it allows one to characterise the nuclear modification of the parton distribution functions and the kT-broadening effect due to soft scatterings of the partons in the incoming nuclei. Moreover, it provides insight into possible final state effects that could occur in p-Pb collisions, like energy loss of heavy quarks in the cold nuclear matter and their collective behaviour. In Pb-Pb collisions, heavy-flavour production can be used to study the properties of the high energy-density and strongly-interacting medium created in heavy-ion collisions. Passing through all the phases of the system evolution, heavy quarks lose energy via gluon radiation and elastic collisions in the medium. Therefore, the study of their production can be used to test parton energy-loss models. In these proceedings we will focus on the ALICE results of prompt D mesons measured via the full reconstruction of their hadronic decays. We will present results on open-charm production in pp collisions at √s = 7 TeV, p-Pb collisions at √sNN=5.02 TeV and Pb-Pb collisions at √sNN=2.76 TeV. © 2016 Elsevier B.V.

Sterpone L.,Polytechnic University of Turin
Microelectronics Reliability | Year: 2013

Space missions require extremely high reliable components that must guarantee correct functionality without incurring in catastrophic effects. When electronic devices are adopted in space applications, radiation hardened technology should be mandatorily adopted. In this paper we propose a novel method for analyzing the sensitivity with respect to Single Event Latch-up (SEL) in radiation hardened technology. Experimental results obtained comparing heavy-ion beam campaign demonstrated the feasibility of the proposed solution. © 2013 Elsevier Ltd. All rights reserved.

Lucia U.,Polytechnic University of Turin
Medical Hypotheses | Year: 2013

The recent developments in thermodynamic analysis of irreversibility for open systems represent an important result useful in the study of brain, both in relation to its neurobiology and to its diseases. In this paper the extrema entropy generation principle is suggested as a new powerful approach to the study of brain. © 2012 Elsevier Ltd.

Lucia U.,Polytechnic University of Turin
Medical Hypotheses | Year: 2013

Entropy generation approach has been developed in order to use it for the analysis of complex systems with particular regards to biological systems in order to evaluate their stationary states. The entropy generation is related to the transport processes related to energy flows. Moreover, cancer can be described as an open complex dynamic and self-organizing system. Using the entropy generation approach it is possible to point out different chemical reaction time between normal and solid cancer cells. © 2013 Elsevier Ltd.

Peila D.,Polytechnic University of Turin
KSCE Journal of Civil Engineering | Year: 2014

The use of conditioning agents that change the mechanical and hydraulic behavior of a cohesionless soil into an impervious and plastic paste is the key point for the correct management of EPB (Earth Pressure Balance) shield tunneling. The design of soil conditioning sets and the choice of the best products to be used require special laboratory tests. These tests should be carried out already at the design stage to allow to check if the needed results can be achieved in the soil to be excavated. In the paper an overview of the different type of laboratory tests that can be used on cohesionless soils are presented and the most important results that can be obtained are discussed. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.

Mura A.,Polytechnic University of Turin
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2014

Object of this paper is the performance analysis of a six degrees of freedom measuring device based on a modified Stewart platform structure. Because of the device studied in this work represents a novel application of a Stewart like platform, an investigation about its performance has been done, in order to evaluate both behaviour and characteristics of this device in different geometrical configurations. In particular, sensitivity analysis has been carried on about geometrical characteristics and displacements amplitude. To calculate the sensitivity, the inverse kinematic equations of the device have been obtained. © IMechE 2013.

Rossi M.,University of Camerino | Rocco V.M.,Polytechnic University of Turin
Energy and Buildings | Year: 2014

Recent studies have shown that considering the values of superficial mass (Ms) and periodic thermal transmittance (Ymn) of external walls is not sufficient to achieve energy savings, particularly in summer. For this reason experimental reference values of the internal areal heat capacity (k1) were introduced. This study aims to understand the interdependency between some thermal parameters (U, Ms, φ, F a, Ymn, k1) of massive and lightweight walls with respect to their energy performance in use in office buildings in Southern Europe. The study has analyzed eight walls with Italian standard U and Y mn values. These walls have been then modified in order to reach k1 values corresponding to the reference ones. The energy demand to ensure a defined level of indoor thermal comfort has been verified with thermodynamic simulations on a virtual test-room localized in two Italian cities, characterized by different climate conditions. The research results are: to develop design change strategies for external walls to achieve the k 1 reference values; to quantify the thermal annual energy demand of a virtual test-room equipped with the sample walls and then equipped with the improved walls; to compare the energetic and economic impact for the improved walls against the sample ones. © 2012 Elsevier B.V.

Pastore S.,University of Trieste | Ponta L.,Polytechnic University of Turin | Cincotti S.,University of Genoa
New Journal of Physics | Year: 2010

In this paper, an information-based artificial stock market is considered. The market is populated by heterogeneous agents that are seen as nodes of a sparsely connected graph. Agents trade a risky asset in exchange for cash. Besides the amount of cash and assets owned, each agent is characterized by a sentiment. Moreover, agents share their sentiments by means of interactions that are identified by the graph. Interactions are unidirectional and are supplied with heterogeneous weights. The agent's trading decision is based on sentiment and, consequently, the stock price process depends on the propagation of information among the interacting agents, on budget constraints and on market feedback. A central market maker (clearing house mechanism) determines the price process at the intersection of the demand and supply curves. Both closedand open-market conditions are considered. The results point out the validity of the proposed model of information exchange among agents and are helpful for understanding the role of information in real markets. Under closed market conditions, the interaction among agents' sentiments yields a price process that reproduces the main stylized facts of real markets, e.g. the fat tails of the returns distributions and the clustering of volatility. Within open-market conditions, i.e. with an external cash inflow that results in asset price inflation, also the unitary root stylized fact is reproduced by the artificial stock market. Finally, the effects of model parameters on the properties of the artificial stock market are also addressed. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

This study describes an experimental analysis of energy dissipation due to damping sources in microstructures and micro-electromechanical systems (MEMS) components using interferometric microscopy techniques. Viscous damping caused by the surrounding air (squeeze film damping) and material damping are measured using variable geometrical parameters of samples and under different environmental conditions. The equipment included a self-made climatic chamber which was used to modify the surrounding air pressure. Results show the relationship between damping coefficients and sample geometry caused by variation in airflow resistance and the relationship between quality factor and air pressure. The experimental results will provide a useful data source for validating analytic models and calibrating simulations. A thorough discussion about interferometry applied to experimental mechanics of MEMS will also contribute to the reduction of the knowledge gap between specialists in optical methods and microsystem designers. © 2013 Elsevier B.V. All rights reserved.

Vipiana F.,Polytechnic University of Turin | Vipiana F.,Antenna and EMC Laboratory LACE | Wilton D.R.,University of Houston
IEEE Transactions on Antennas and Propagation | Year: 2013

In this paper, we present a purely numerical procedure to evaluate strongly near-singular integrals involving the gradient of Helmholtz-type potentials for observation points at finite, arbitrarily small distances from the source domain. In the proposed approach the source domain is subdivided into a disc plus truncated subtriangles, and proper variable transformations are applied in each integration domain to exactly cancel the kernel singularity. A novel feature of the proposed angular transform is that required discrete values of the inverse transform, which is transcendental, are determined via a root-finding procedure; the same idea can also be applied to other transforms that arise in singularity cancellation methods. The resulting integral may then evaluated via a low order Gauss-Legendre quadrature scheme. © 2012 IEEE.

Giaccone L.,Polytechnic University of Turin
Electric Power Systems Research | Year: 2016

This paper deals with three-phase power lines operated by parallel power cables. In these systems each phase is made up of several parallel subconductors and it is well known that the sequence of the subconductors influences the magnetic field generated by the power line. This paper proposes a new approach to identify the optimal arrangement of the power cables that minimizes the stray magnetic field. Unlike the design methods covered by the literature, this paper proposes a deterministic procedure that is based mainly on a simple geometrical indicator. This geometrical quantity makes it possible to analyze all the configurations in order to create a small subset of candidate solutions. From this subset the optimal solution is then identified quickly and easily by computing and comparing the stray field. A full validation of the proposed approach is performed by comparing it with a standard method based on genetic algorithm. The results of the validation also provide a useful table that covers all the cases from 2 to 6 subconductors for each phase. Furthermore, it is shown that the geometrical indicator makes it possible to obtain a good cable arrangement in a direct way, without performing any magnetic field evaluations. © 2016 Elsevier B.V. All rights reserved.

German G.,Yale University | Bertola V.,Polytechnic University of Turin
Physics of Fluids | Year: 2010

The process of growth and detachment of drops from a capillary nozzle is studied experimentally by high-speed imaging. Newtonian drops are compared to shear-thinning and viscoplastic drops. Both Newtonian and shear-thinning fluid drops grow on the end of the capillary until a maximum supportable tensile stress is reached in the drop neck, after which they become unstable and detach. The critical stress is not influenced by variations in viscosity or in the degree of shear thinning. Viscoplastic fluids show a different behavior: at low values of the yield stress, the critical stability behavior is similar to that of Newtonian and shear-thinning drops. Above a threshold value, characterized in terms of the drop size, surface tension and tensile yield-stress magnitude, yield-stress forces are larger than surface forces, and the maximum tensile stress achievable in the drop neck at the point of critical stability is governed by the von Mises criterion. © 2010 American Institute of Physics.

Ceria A.,Polytechnic University of Turin | Hauser P.J.,North Carolina State University
Surface and Coatings Technology | Year: 2010

In this study, the influence of an atmospheric plasma treatment on the durability of a commercial water and oil repellent finish was tested. Acrylic fabrics were processed with a RF atmospheric pressure plasma generator and afterwards a fluorocarbon finish was applied through a traditional pad-dry-cure method. Two gas mixtures were tested (helium and helium/oxygen) with different plasma treatment times. The ageing of the finishing was simulated through repeated accelerated laundry cycles. The water and oil repellencies were measured through standard test methods. While the initial water and oil repellency did not change, the plasma treatment improved the durability of the finish after artificial ageing. Scanning electron microscopy analyses were carried out to highlight morphological changes. © 2009 Elsevier B.V. All rights reserved.

Hodson-Tole E.F.,Manchester Metropolitan University | Loram I.D.,Manchester Metropolitan University | Vieira T.M.M.,Polytechnic University of Turin
Journal of Electromyography and Kinesiology | Year: 2013

It has recently been shown that motor units in human medial gastrocnemius (MG), activated during standing, occupy relatively small territories along the muscle's longitudinal axis. Such organisation provides potential for different motor tasks to produce differing regional patterns of activity. Here, we investigate whether postural control and nerve electrical stimulation produce equal longitudinal activation patterns in MG. Myoelectric activity, at different proximal-distal locations of MG, was recorded using a linear electrode array. To ensure differences in signal amplitude between channels did not result from local, morphological factors two experimental protocols were completed: (i) quiet standing; (ii) electrical stimulation of the tibial nerve. Averaged, rectified values (ARVs) were calculated for each channel in each condition. The distribution of signals along electrode channels was described using linear regression and differences between protocols at each channel determined as the ratio between mean ARV from standing: stimulation protocols. Ratio values changed systematically across electrode channels in seven (of eight) participants, with larger values in distal channels. The distribution of ARV along MG therefore differed between experimental conditions. Compared to fibres of units activated during MG nerve stimulation, units activated during standing may have a tendency to be more highly represented in the distal muscle portion. © 2012 Elsevier Ltd.

Pugno N.M.,Polytechnic University of Turin | Pugno N.M.,National Institute of Nuclear Physics, Italy | Pugno N.M.,National Institute of Metrological Research
Journal of the Mechanics and Physics of Solids | Year: 2010

The study reported in this paper suggests that the influence of the surrounding nanotubes in a bundle is nearly identical to that of a liquid having surface tension equal to the surface energy of the nanotubes. This surprising behaviour is supported by the calculation of the polygonization and especially of the self-collapse diameters, and related dog-bone configurations, of nanotubes in a bundle, in agreement with atomistic simulations and nanoscale experiments. Accordingly, we have evaluated the strength of the nanotube bundle, with or without collapsed nanotubes, assuming a sliding failure: the self-collapse can increase the strength up to a value of about ∼30%, suggesting the design of self-collapsed super-strong nanotube bundles. Other systems, such as peapods and fullerites, can be similarly treated, including the effect of the presence of a liquid, as reported in the appendices. © 2010 Elsevier Ltd. All rights reserved.

Heiselberg P.,University of Aalborg | Perino M.,Polytechnic University of Turin
Indoor Air | Year: 2010

Abstract: The need to improve the energy efficiency of buildings requires new and more efficient ventilation systems. It has been demonstrated that innovative operating concepts that make use of natural ventilation seem to be more appreciated by occupants. Among the available ventilation strategies that are currently available, buoyancy driven, single-sided natural ventilation has proved to be very effective and can provide high air change rates for temperature and Indoor Air Quality (IAQ) control. However, to promote a wider distribution of these systems an improvement in the knowledge of their working principles is necessary. The present study analyses and presents the results of an experimental evaluation of airing performance in terms of ventilation characteristics, IAQ and thermal comfort. It includes investigations of the consequences of opening time, opening frequency, opening area and expected airflow rate, ventilation efficiency, thermal comfort and dynamic temperature conditions. A suitable laboratory test rig was developed to perform extensive experimental analyses of the phenomenon under controlled and repeatable conditions. The results showed that short-term window airing is very effective and can provide both acceptable IAQ and thermal comfort conditions in buildings. © 2010 The Authors. Journal compilation © John Wiley & Sons A/S 2010.

Caviggioli F.,Polytechnic University of Turin
Technovation | Year: 2016

The concepts of technology convergence or technology fusion describe the phenomenon of technology overlap. Despite evidence of the higher value associated to interdisciplinary research and cross-industry innovation, few studies have investigated the characteristics of technology fusion based on patent data. This study identifies new cases of convergence relying on the International Patent Classification (IPC) of patents filed at the European Patent Office between 1991 and 2007: the first occurrence of a patent incorporating a combination of IPC subclasses signals a new instance of fusion. Duration models are employed to investigate the impact of field level characteristics derived from patent bibliometrics on the likelihood of identifying a new fusion. The results show that merges are more frequent if the focal technology fields are closely related (based on a higher number of cross citations), are characterized by wide technological scope, and are the result of an inter-firm collaboration. In contrast to previous findings, the results show that the more complex the technologies involved, the less the likelihood of their convergence or fusion. The correlation between fusion likelihood and the characteristics of the merging fields could help managers and policymakers to predict the emergence of new technology areas. © 2016 Elsevier Ltd.

Bianca C.,Polytechnic University of Turin
The Scientific World Journal | Year: 2013

This paper is concerned with the derivation of hybrid kinetic partial integrodifferential equations that can be proposed for the mathematical modeling of multicellular systems subjected to external force fields and characterized by nonconservative interactions. In order to prevent an uncontrolled time evolution of the moments of the solution, a control operator is introduced which is based on the Gaussian thermostat. Specifically, the analysis shows that the moments are solution of a Riccati-type differential equation. © 2013 Carlo Bianca.

Galleani L.,Polytechnic University of Turin
IEEE Transactions on Signal Processing | Year: 2013

Many deterministic and random physical signals can be modeled as the output of a multi-input-multi-output (MIMO) dynamical system. Since physical signals are typically nonstationary, their frequency content changes with time. To understand this time variation, we transform the MIMO system to the time-frequency domain. The result is a time-frequency MIMO dynamical system, whose input and output are the time-frequency spectra of the original input and output signals in the time domain. The time-frequency system reveals the spectral mechanisms involved in the generation of nonstationary signals. We apply our method to the case of a MIMO system with two vibrational modes and a nonstationary noise at the input. We obtain the time-frequency spectrum of the output, which shows how the spectrum of the modes changes with time. This result cannot be achieved with classical spectral techniques, because they require the input random process to be wide sense stationary. © 1991-2012 IEEE.

Rossani A.,Polytechnic University of Turin
Journal of Physics A: Mathematical and Theoretical | Year: 2010

A new model, based on an asymptotic procedure for solving the generalized kinetic equations of electrons and phonons, is proposed, which gives naturally the displaced Maxwellian at the leading order. The balance equations for the electron number, total energy density and total momentum for the whole system constitute now, together with Poisson equation, a system of four equations for the electron chemical potential, the temperature of the system, the drift velocity and the electric potential. In the drift-diffusion approximation the constitutive laws are derived and the Onsager relations recovered. © 2010 IOP Publishing Ltd.

Graglia R.D.,Polytechnic University of Turin | Peterson A.F.,Georgia Institute of Technology
IEEE Transactions on Antennas and Propagation | Year: 2011

New curl-conforming hierarchical vector basis functions are developed for quadrilateral and hexahedral cells. These bases are constructed from orthogonal polynomials and are shown to maintain superior linear independence as their polynomial order is increased. The procedure for constructing these basis functions is described and general expressions are provided for an arbitrary order. © 2011 IEEE.

In this study a method based on dual-well step drawdown test (i.e. a combination of an aquifer and a well performance test) for the determination of hydrodynamic parameters (namely storage coefficient and hydraulic conductivity), mechanical wellbore finite thickness skin factor, non-linear wellbore and non-linear aquifer parameters in an homogeneous confined aquifer is presented in order to put together aquifer and well tests. The interpretation procedure is based on the application of superposition principle to a large time logarithmic approximation of the solution.The advantages of this method, that can be considered an extension of Jacob step-test (1947) and Cooper-Jacob approximation (1946), are that: (I) it is possible to determine simultaneously aquifer and well properties in a single test; (II) the method is based on a large time approximation and it is therefore independent from wellbore storage; (III) if the well skin is absent, the aquifer parameters (storage coefficient and hydraulic conductivity) can be derived just from a single-well test; (IV) the interpretation procedure is easy to apply and robust and does not require any specific numeric code or software. The same procedure can be easily adapted to gas well testing.It is also shown that, even in the presence of linear and non-linear flow, skin effect and wellbore storage, the hydraulic conductivity (and not the storage coefficient) of the aquifer can be correctly estimated by the Cooper and Jacob (1946) method applied to a single-rate pumping test, using exclusively the large time drawdown data measured at the pumping well. © 2011 Elsevier B.V.

Deflorio F.P.,Polytechnic University of Turin
IET Intelligent Transport Systems | Year: 2011

In a demand responsive transport system (DRTS), vehicles follow routes and timetables automatically scheduled by a travel dispatch centre to match the trip requests and to associate as many users as possible to the same vehicle, while guaranteeing the quality standards in terms of pickup/delivery time and travel duration. How efficient the system is in combining user requests on vehicles depends on the dispersion of travel demand, both space-wise and time-wise. This study describes and analyses a trips simulation method that aims at generating users'requests by recreating an actual demand structure of a study area divided into zones. It has been assumed that trip requests are sampled looking at specific features, such as the ability of attracting and generating trips assigned to the zones of the area, the information on minimum distance for trips and the time profile of the requests. Travel requests are then processed by a trip-planning tool, in order to assess the resources needed for the service operations (number of vehicles, travel times). The demand scenarios explored show the influence of the assumed criteria on the random minimum distance for DRTS trips, both on the characteristics of the generated demand and on the consequent trip-plans. © 2011 The Institution of Engineering and Technology.

Osgoui R.R.,GEODATA S.p.A Corso Duca degli Abruzzi | Oreste P.,Polytechnic University of Turin
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2010

This paper presents an elasto-plastic analytical solution of an axi-symmetrical problem for a circular tunnel reinforced by grouted bolts. Considered as the improved model of Indraratna and Kaiser (Int. J. Rock. Mech. Min. Sci. Geomech. Abstr. 1990; 27:269-281; Int. J. Numer. Anal. Meth. Geomech. 1990; 14:227-251), in proposed solution the rock mass obeys the non-linear Hoek-Brown yield criterion (version 2002) in terms of its peak and residual strength parameters (the most spread strength criterion for the rock masses). The proposed approach considers a≥0.5 for the rock mass and is based on the assumption that after the peak strength of the rock is reached, the material loses its strength, as dictated by a strength loss parameter. The strength loss parameter makes it possible to model either elastic-perfectly plastic or elastic-brittle-plastic behaviour. Because of the mathematical complexity, numerical treatments have been used to assist the solution in order to evaluate the equilibrium and compatibility equations. The concept of equivalent material for Hoek-Brown strength parameters is introduced to describe the rock mass improvement due to bolting effect. The results of the numerical analyses reveal a linear relation between the improved Hoek-Brown strength parameters and residual ones, taking into consideration the bolt density parameter (β). The proposed solution is able to analyse the stress and displacement state in the presence of a bolting intervention with the objective of improving the degree of stability of the rock around the tunnel. Descriptive applications of the derived elasto-plastic solutions are also presented to explain the effectiveness of the grouted bolts in convergence reduction. Evidences obtained by numerical analysis verify the analytical solution. © 2009 John Wiley & Sons, Ltd.

Ali M.,University of Manchester | Ilie I.-S.,University of Edinburgh | Milanovic J.V.,University of Manchester | Chicco G.,Polytechnic University of Turin
IEEE Transactions on Power Systems | Year: 2013

The paper proposes an innovative probabilistic clustering concept for aggregate modeling of wind farms (WFs). The proposed technique determines the number of equivalent turbines that can be used to represent large WF during the year in system studies. Support vector clustering (SVC) technique is used to cluster wind turbines (WTs) based on WF layout and incoming wind. These clusters are then arranged into groups, and finally through analysis of wind at the site, equivalent number of WTs for WF representation is determined. The method is demonstrated on a WF consisting of 49 WTs connected to the grid through two transmission lines. Dynamic responses of the aggregate model of the WF are compared against responses of the full WF model for various wind scenarios. © 2012 IEEE.

Bruno G.,Polytechnic University of Turin
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

In recent years, research in the field of business processes has shown a shift of interest from the activity-centric perspective to the artifact-centric one. The benefits, such as improved communication among the stakeholders and higher potential for flexibility, come from the focus on the key business entities (called artifacts) and on the distribution of the control flow in the life cycles of the artifacts. However, this perspective also entails a number of challenges, such as the coordination between the life cycles of the artifacts. This paper proposes an approach based on correlated transitions, i.e., transitions that belong to different life cycles and must be performed jointly. A new notation called Acta is illustrated with the help of two motivating examples. © 2013 Springer-Verlag.

Bacciotti A.,Polytechnic University of Turin
International Journal of Robust and Nonlinear Control | Year: 2013

Recently, it has been enlightened the interest of a class of switching rules with good properties, which are called eventually periodic: more precisely, it has been proven that a finite family F of linear vector fields of Rd can be stabilized by means of eventually periodic switching rules provided that it is asymptotically controllable and satisfies an additional finite time controllability condition. Unfortunately, simple examples point out that in general, eventually periodic switching rules are not robust with respect to state measurement errors.In this paper, we introduce a new type of switching rules with improved robustness properties, which are called recurrent switching rules. They are subject to the construction of a finite sequence of complete cones Γ1, ...,ΓH of ℝd. We shown that, if a stabilizing eventually periodic switching rule for F is known, then Γ1, ...,ΓH can be constructed in such a way that F is stabilized by any recurrent switching rule subject to Γ1, ...,ΓH. Copyright © 2012 John Wiley & Sons, Ltd.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2012

The thermodynamic analysis of open systems is fundamental in engineering. For the open systems at their steady state, two apparently opposed principles for the rate of entropy production have been used: the minimum entropy production rate derived by Prigogine, used in the description of various processes in physics, chemistry and biology, and the maximum entropy production, used in many other cases and now considered more general. Both principles involve an extreme value of the rate of entropy production in an open system at the steady state under non-equilibrium conditions. In this paper, a link between these two approaches is developed and their synthesis with the constructal law is proposed. An application to ATP synthesis in anaerobic fermentation for biogas production is presented. © 2012 Elsevier B.V. All rights reserved.

Pirulli M.,Polytechnic University of Turin
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010

A numerical model set up to simulate rapid flowlike landslide motion across three-dimensional terrain has been used to investigate the capability of various constitutive relationships to model the dynamics of complex events characterized by a changing type of substrate and morphology (e.g., glacier, bends). The numerical procedure is based on a continuum mechanics approach and on depth-averaged St. Venant equations for shallow flows. The developed RASH3D code includes the possibility of using several rheological laws, whose parameter values can vary along the runout path. Two rock avalanche cases, with some morphological peculiarities along the propagation path, have been numerically back-analyzed with both a frictional and a Voellmy rheology. Of the two considered rheologies, the Voellmy model produces the most consistent results in terms of runout area as well as velocity values. The main drawbacks of the frictional model are the tendency to predict excessive spreading of the mass and to overestimate the velocities. The results show that, when a complex problem of runout of rapid flowlike landslides has to be analyzed, it is necessary to have detailed knowledge of the geological and morphological features and to resort to increasingly complex rheologies. © 2010 ASCE.

Mancini S.,Polytechnic University of Turin
European Transport - Trasporti Europei | Year: 2013

In the last decades, the increasing quality of services requested by the customer, yields to the necessity of optimizing the whole distribution process. This goal may be achieved through a smart exploitation of existing resources other than a clever planning of the whole distribution process. For doing that, it is necessary to enhance goods consolidation. One of the most efficient way to implement it is to adopt Multi-Echelon distribution systems which are very common in City Logistic context, in which they allow to keep large trucks from the city center, with strong environmental advantages. The aim of the paper is to review routing problems arising in City Logistics, in which multi-echelon distribution systems are involved: the Two Echelon Location Routing Problem (2E-LRP), the Two Echelon Vehicle Routing Problem (2E-VRP) and Truck and Trailer Routing Problem (TTRP), and to discuss literature on optimization methods, both exact and heuristic, developed to address these problems.

Calafiore G.C.,Polytechnic University of Turin
Automatica | Year: 2013

This paper proposes a novel methodology for optimal allocation of a portfolio of risky financial assets. Most existing methods that aim at compromising between portfolio performance (e.g.; expected return) and its risk (e.g.; volatility or shortfall probability) need some statistical model of the asset returns. This means that: (i) one needs to make rather strong assumptions on the market for eliciting a return distribution, and (ii) the parameters of this distribution need be somehow estimated, which is quite a critical aspect, since optimal portfolios will then depend on the way parameters are estimated. Here we propose instead a direct, data-driven, route to portfolio optimization that avoids both of the mentioned issues: the optimal portfolios are computed directly from historical data, by solving a sequence of convex optimization problems (typically, linear programs). Much more importantly, the resulting portfolios are theoretically backed by a guarantee that their expected shortfall is no larger than an a-priori assigned level. This result is here obtained assuming efficiency of the market, under no hypotheses on the shape of the joint distribution of the asset returns, which can remain unknown and need not be estimated. © 2012 Elsevier Ltd. All rights reserved.

Ceravolo R.,Polytechnic University of Turin | Abbiati G.,University of Trento
Journal of Engineering Mechanics | Year: 2013

The focus of this work is on methods for modal identification of civil structures using output data only. An important family of time domain methods uses autoregressive time series models and exploits formulations developed in the field of system control. Another strategy consists of using methods well tested in the identification of structures on the basis of impulse response or free decay and extending them to the analysis of response signals generated by excitations of a more general nature. A third option refers to the Ho-Kalman minimal realization algorithm, which was extended by Akaike and Aoki to stochastic systems. These approaches, or their combinations, include a sizable proportion of the methods actually used in output-only identification of civil structures subjected to natural excitation, and most of them are based on stationarity assumptions. The question that prompted this study was as follows: what degrees of reliability and accuracy can such methods ensure when they are used, as is often the case in actual practice, in nonstationary conditions An answer to this question was sought numerically by focusing on nonstationary conditions deemed typical of the actions naturally applied to civil structures. © 2013 American Society of Civil Engineers.

Bianca C.,Polytechnic University of Turin
Mathematical Methods in the Applied Sciences | Year: 2013

The thermostatted kinetic framework has been recently proposed in [C. Bianca, Nonlinear Analysis: Real World Applications 13 (2012) 2593-2608] for the modeling of complex systems in the applied sciences under the action of an external force field that moves out of equilibrium the system. The framework consists in an integro-differential equation with quadratic nonlinearity coupled with the Gaussian isokinetic thermostat. This paper is concerned with the existence of stationary solutions proof. The main result is gained by fixed point and measure theory arguments. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd.

Frasca P.,Polytechnic University of Turin | Hendrickx J.M.,Catholic University of Louvain
Automatica | Year: 2013

This paper considers randomized discrete-time consensus systems that preserve the average "on average". As a main result, we provide an upper bound on the mean square deviation of the consensus value from the initial average. Then, we apply our result to systems in which few or weakly correlated interactions take place: these assumptions cover several algorithms proposed in the literature. For such systems we show that, when the network size grows, the deviation tends to zero, and that the speed of this decay is not slower than the inverse of the size. Our results are based on a new approach, which is unrelated to the convergence properties of the system. © 2013 Elsevier Ltd. All rights reserved.

Guglieri G.,Polytechnic University of Turin
Aeronautical Journal | Year: 2013

Great attention is focused on the development of both remotely controlled and unmanned flying vehicles. As a matter of fact, the design of such vehicles is a topical direction of development for modern aeronautics. Among such promising flying vehicles, micro- and mini-UAVs play a leading role. The present paper proposes a method to validate the inclusion of the relevant modelling elements in a comprehensive simulation tool reproducing some of the flight phases of a mini-UAV. The energy balance budget and the dynamic response of the aircraft during the automatic flight are investigated, assessing the impact of autopilot configuration, such as altitudeairspeed holding modes and suggesting a setting guideline for flight mode selection compatible with the features of commercial autopilots.

Lazarescu M.T.,Polytechnic University of Turin
IEEE Journal on Emerging and Selected Topics in Circuits and Systems | Year: 2013

The Internet of Things (IoT) provides a virtual view, via the Internet Protocol, to a huge variety of real life objects, ranging from a car, to a teacup, to a building, to trees in a forest. Its appeal is the ubiquitous generalized access to the status and location of any 'thing' we may be interested in. © 2011 IEEE.

Brischetto S.,Polytechnic University of Turin
Journal of Zhejiang University: Science A | Year: 2013

The principle of virtual displacements (PVDs) extended to elasto-thermo-electric problems includes virtual internal elastic, thermal and electric works. The governing equations have displacement vector, temperature and electric potential as primary variables of the problem, and the elasto-thermal, elasto-electric and pure elastic problems are obtained as particular cases by deleting the appropriate contributions in the general elasto-thermo-electric variational statement. The most sensitive issue is given by thermal coupling because the thermo-elastic and thermo-electric effects change depending on the type of load and analysis considered (mechanical load, temperature or electric potential imposed and free vibration analysis). This feature means that the form of the virtual internal thermal work in such variational statements changes depending on the analysis performed and the load applied. Results about multilayered plates and shells suggest the appropriate extension of the variational statement for each analysis, and they give an exhaustive explanation for several forms of the PVD proposed. © 2013 Zhejiang University and Springer-Verlag Berlin Heidelberg.

Calafiore G.C.,Polytechnic University of Turin | Fagiano L.,ETH Zurich | Fagiano L.,University of California at Santa Barbara
Automatica | Year: 2013

A stochastic receding-horizon control approach for constrained Linear Parameter Varying discrete-time systems is proposed in this paper. It is assumed that the time-varying parameters have stochastic nature and that the system's matrices are bounded but otherwise arbitrary nonlinear functions of these parameters. No specific assumption on the statistics of the parameters is required. By using a randomization approach, a scenario-based finite-horizon optimal control problem is formulated, where only a finite number M of sampled predicted parameter trajectories ('scenarios') are considered. This problem is convex and its solution is a priori guaranteed to be probabilistically robust, up to a user-defined probability level p. The p level is linked to M by an analytic relationship, which establishes a tradeoff between computational complexity and robustness of the solution. Then, a receding horizon strategy is presented, involving the iterated solution of a scenario-based finite-horizon control problem at each time step. Our key result is to show that the state trajectories of the controlled system reach a terminal positively invariant set in finite time, either deterministically, or with probability no smaller than p. The features of the approach are illustrated by a numerical example. © 2013 Elsevier Ltd. All rights reserved.

Crovetti P.S.,Polytechnic University of Turin
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2013

A novel, digital-in-concept approach in the design of analog differential circuits, suitable to very low voltage, aggressively scaled, pure digital integrated circuit technologies, is explored in this paper. A differential stage based on the proposed technique is presented and its operation as a voltage comparator and as an operational amplifier in negative feedback configurations is discussed and demonstrated on the basis of theory and simulations. The practical feasibility of the proposed approach is finally verified by experiments carried out on a proof-of-concept prototype. © 2013 IEEE.

Palmero P.,Polytechnic University of Turin | Esnouf C.,CNRS Laboratory for Materials: Engineering and Science
Journal of the European Ceramic Society | Year: 2011

Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing Al 2O 3-Y 3Al 5O 12 (YAG) composite powders. DTA analysis allowed to highlight the role of yttrium on the α-phase crystallization path. Systematic XRD and HRTEM analyses were carried out in parallel on powders calcined in a wide temperature range (600-1300°C) in order to follow phase and microstructural evolution. A thin, homogeneous yttrium-rich layer was yielded on the alumina particles surface; yttrium diffusion into the alumina matrix was negligible up to 1150°C whereas, starting from 1200°C, aggregates of partially sintered alumina particles appeared, stuck together by yttrium-rich thin films. Moreover, in the yttrium-richer zones, such as alumina grain boundaries and triple joints, yttrium-aluminates precipitated at alumina particles surface. Finally, at 1300°C, alumina-YAG composite powders were produced, in which YAG was homogenously distributed among the alumina grains. © 2010 Elsevier Ltd.

Pirulli M.,Polytechnic University of Turin
Natural Hazards and Earth System Science | Year: 2010

In the present paper the problem of modeling the propagation of potential debris flows is tackled resorting to a numerical approach. In particular, numerical analyses are carried out with the RASH3D code, based on a single-phase depth-averaged continuum mechanics approach. Since each numerical analysis requires the selection of a rheology and the setting of the rheological input parameters, a calibration-based approach, where the rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of full-scale events, has been assumed. The back-analysis of a 1000 m3 debris flow, located at Tate's Cairn, Hong Kong, and the forward-analysis of a 10 000 m 3 potential debris flow, located in the same basin have been used to investigate the transferability of back-calculated rheological parameters from one case to another. Three different rheologies have been tested: Frictional, Voellmy and Quadratic. From obtained results it emerges that 1) the back-calculation of a past event with different rheologies can help in selecting the rheology that better reproduces the runout of the analysed event and, on the basis of that selection, can give some indication about the dynamics of the investigated flow, 2) the use of back-calculated parameters for forward purposes requires that past and potential events have similar characteristics, some of which are a function of the assumed rheology. Among tested rheologies, it is observed that the Quadratic rheology is more influenced by volume size than Frictional and Voellmy rheologies and consequently its application requires that events are also similar in volume. © Author(s) 2010. CC Attribution 3.0 License.

Pugno N.M.,Polytechnic University of Turin | Elliott J.A.,University of Cambridge
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

In this paper, the buckling under an applied external pressure and the self-buckling of nanostructures, such as peapods, nanotubes and fullerenes, is numerically treated with Molecular Dynamics simulations and compared with theoretical calculations. The self-buckling is due to the interaction among the nanostructures caused by the surface energy; it is peculiar to the nanoscale and does not have a macroscopiic counterpart. Atomistic simulations confirm that the influence on a single nanostructure from the surrounding nanostructures in a crystal, is nearly identical to that of a liquid with surface tension equal to the surface energy of the solid. © 2012 Elsevier B.V. All rights reserved.

Ramezanpour A.,Polytechnic University of Turin
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

A local and distributive algorithm is proposed to find an optimal trial wave function minimizing the Hamiltonian expectation in a quantum system. To this end, the quantum state of the system is connected to the Gibbs state of a classical system with the set of couplings playing the role of variational parameters. The average energy is written within the replica-symmetric approximation, and the optimal parameters are obtained by a heuristic message-passing algorithm based on the Bethe approximation. The performance of this approximate algorithm depends on the structure and quality of the trial wave functions, starting from a classical system of isolated elements, i.e., mean-field approximation, and improving on that by considering the higher-order many-body interactions. The method is applied to some disordered quantum Ising models in transverse fields, and the results are compared with the exact ones for small systems. © 2012 American Physical Society.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2012

Entropy generation is analysed and obtained from the entropy balance for open systems, considering the lifetime of the natural real process. The Lagrangian approach is discussed in order to develop an analytical method to obtain the stationary states of the open irreversible systems. The stationary conditions of the open systems are obtained in relation to the entropy generation and its maximum principle. An analysis of both minimum and maximum entropy generation is proposed, suggesting that they are two different viewpoints of the same aspect: the first is related to the system, while the second is related to the interaction between the system and the environment. © 2012 Elsevier B.V. All rights reserved.

Sereno M.,Polytechnic University of Turin | Sereno M.,National Institute of Nuclear Physics, Italy | Paraficz D.,Aix - Marseille University
Monthly Notices of the Royal Astronomical Society | Year: 2013

Time delays between multiple images of lensed sources can probe the geometry of the universe. We propose a novel method based on free-form modelling of gravitational lenses to estimate time delay distances and, in turn, cosmological parameters. This approach does not suffer from the degeneracy between the steepness of the profile and the cosmological parameters. We apply the method to 18 systems having time delay measurements and find H0 = 69 ± 6(stat.) ± 4(syst.) km s-1Mpc-1. In combination with Wilkinson Microwave Anisotropy Probe 9, the constraints on dark energy are ωw = 0.68 ± 0.05 and w =-0.86 ± 0.17 in a flat model with constant equation of state. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Traversa F.L.,Autonomous University of Barcelona | Bonani F.,Polytechnic University of Turin
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems | Year: 2013

We present a mixed time-frequency domain algorithm for the approximate computation of the Floquet quantities (exponents and both direct and adjoint eigenvectors) resulting from the linearization of index-1 differential-algebraic equations around a periodic limit cycle. The approach allows to select the number of Floquet exponents to be calculated approximating the matrix of the obtained eigenvalue problem. The error in the evaluation (for both exponents and eigenvectors) is proved to tend to zero along with the ratio between the norms of the neglected and retained rows of the relevant matrix. © 2013 IEEE.

Scalerandi M.,Polytechnic University of Turin
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

Nonlinear ultrasonic methods have been widely used to characterize the microstructure of damaged solids and consolidated granular media. Besides distinguishing between materials exhibiting classical nonlinear behaviors from those exhibiting hysteresis, it could be of importance the discrimination between ultrasonic indications from different physical sources (scatterers). Elastic hysteresis could indeed be due to dislocations, grain boundaries, stick-slip at interfaces, etc. Analyzing data obtained on various concrete samples, we show that the power law behavior of the nonlinear indicator vs. the energy of excitation could be used to classify different microscopic features. In particular, the power law exponent ranges between 1 and 3, depending on the nature of nonlinearity. We also provide a theoretical interpretation of the collected data using models for clapping and hysteretic nonlinearities. © 2015 Elsevier B.V. All rights reserved.

Tartaglia A.,Polytechnic University of Turin
International Journal of Modern Physics A | Year: 2016

Starting from some relevant facts concerning the behavior of the universe over large scale and time span, the analogy between the geometric approach of General Relativity and the classical description of an elastic strained material continuum is discussed. Extending the elastic deformation approach to four dimensions it is shown that the accelerated expansion of the universe is recovered. The strain field of space-time reproduces properties similar to the ones ascribed to the dark energy currently called in to explain the accelerated expansion. The strain field in the primordial universe behaves as radiation, but asymptotically it reproduces the cosmological constant. Subjecting the theory to a number of cosmological tests confirms the soundness of the approach and gives an optimal value for the one parameter of the model, i.e. the bulk modulus of the space-time continuum. Finally various aspects of the Strained State Cosmology (SSC) are discussed and contrasted with some non-linear massive gravity theories. The possible role of structure topological defects is also mentioned. The conclusion is that SSC is at least as good as the ACDM standard cosmology, giving a more intuitive interpretation of the physical nature of the phenomena.

Bella F.,Polytechnic University of Turin
Electrochimica Acta | Year: 2015

Photoelectrochemical devices for the conversion of sunlight into electricity are experiencing a period of fervour due to the use of new solid-state materials capable of ensuring a durability higher than that of liquid electrolytes-based cells. Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) are currently contending for the role of leader in the field of third-generation photovoltaic technologies. In particular, such success is attributed to the introduction of polymer electrolytes and perovskites, which have recently contributed to obtaining high conversion efficiencies. This review summarizes the most important results in this field and the strategies developed to maximize DSSCs and PSCs performance. In addition, limitations and disadvantages of polymer electrolytes and perovskites are presented, together with possible strategies aimed at improving the photovoltaic efficiency, reducing the cost and limiting the use of toxic and rare materials. © 2015 Elsevier Ltd. All rights reserved.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2016

Exergy is a fundamental quantity because it allows us to obtain information on the useful work obtainable in a process. The analyses of irreversibility are important not only in the design and development of the industrial devices, but also in fundamental thermodynamics and in the socio-economic analysis of municipality. Consequently, the link between entropy and exergy is discussed in order to link econophysics to the bio-chemical engineering thermodynamics. Last, this link holds to the fundamental role of fluxes and to the exergy exchanged in the interaction between the system and its environment. The result consists in a thermodynamic approach to the analysis of the unavailability of the economic, productive or social systems. The unavailability is what the system cannot use in relation to its internal processes. This quantity result is interesting also as a support to public manager for economic decisions. Here, the Alessandria Municipality is analyzed in order to highlight the application of the theoretical results. © 2016 Elsevier B.V.

Lucia U.,Polytechnic University of Turin
Physica A: Statistical Mechanics and its Applications | Year: 2016

Cells are complex thermodynamic systems. Their energy transfer, thermo-electro-chemical processes and transports phenomena can occur across the cells membranes, the border of the complex system. Moreover, cells can also actively modify their behaviours in relation to any change of their environment. All the living systems waste heat, which is no more than the result of their internal irreversibility. This heat is dissipated into their environment. But, this wasted heat represents also a sort of information, which outflows from the cell towards its environment, completely accessible to any observer. The analysis of irreversibility related to this wasted heat can represent a new useful approach to the study of the cells behaviour. This approach allows us to consider the living systems as black boxes and analyse only the inflows and outflows and their changes in relation to any environmental change. This analysis allows also the explanation of the effects of electromagnetic fields on the cell behaviour. © 2016 Elsevier B.V.

Badugu R.,University of Maryland Baltimore County | Descrovi E.,Polytechnic University of Turin | Lakowicz J.R.,University of Maryland Baltimore County
Analytical Biochemistry | Year: 2014

There is a continuing need to increase the brightness and photostability of fluorophores for use in biotechnology, medical diagnostics, and cell imaging. One approach developed during the past decade is to use metallic surfaces and nanostructures. It is now known that excited state fluorophores display interactions with surface plasmons, which can increase the radiative decay rates, modify the spatial distribution of emission, and result in directional emission. One important example is surface plasmon-coupled emission (SPCE). In this phenomenon, the fluorophores at close distances from a thin metal film, typically silver, display emission over a small range of angles into the substrate. A disadvantage of SPCE is that the emission occurs at large angles relative to the surface normal and at angles that are larger than the critical angle for the glass substrate. The large angles make it difficult to collect all of the coupled emission and have prevented the use of SPCE with high-throughput and/or array applications. In the current article, we describe a simple multilayer metal-dielectric structure that allows excitation with light that is perpendicular (normal) to the plane and provides emission within a narrow angular distribution that is normal to the plane. This structure consists of a thin silver film on top of a multilayer dielectric Bragg grating, with no nanoscale features except for the metal or dielectric layer thicknesses. Our structure is designed to support optical Tamm states, which are trapped electromagnetic modes between the metal film and the underlying Bragg grating. We used simulations with the transfer matrix method to understand the optical properties of Tamm states and localization of the modes or electric fields in the structure. Tamm states can exist with zero in-plane wavevector components and can be created without the use of a coupling prism. We show that fluorophores on top of the metal film can interact with the Tamm state under the metal film and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S or P polarization. The TSCE angle is highly sensitive to wavelength, which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications.

Carbone A.,Polytechnic University of Turin | Kiyono K.,Osaka University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

The Detrending Moving Average (DMA) algorithm has been widely used in its several variants for characterizing long-range correlations of random signals and sets (one-dimensional sequences or high-dimensional arrays) over either time or space. In this paper, mainly based on analytical arguments, the scaling performances of the centered DMA, including higher-order ones, are investigated by means of a continuous time approximation and a frequency response approach. Our results are also confirmed by numerical tests. The study is carried out for higher-order DMA operating with moving average polynomials of different degree. In particular, detrending power degree, frequency response, asymptotic scaling, upper limit of the detectable scaling exponent, and finite scale range behavior will be discussed. © 2016 American Physical Society.

Garetto M.,University of Turin | Leonardi E.,Polytechnic University of Turin
IEEE Transactions on Information Theory | Year: 2010

In this paper, we analyze asymptotic delay-throughput tradeoffs in mobile ad hoc networks comprising heterogeneous nodes with restricted mobility. We show that node spatial heterogeneity has the ability to drastically improve upon existing scaling laws established under the assumption that nodes are identical and uniformly visit the entire network area. In particular, we consider the situation in which each node moves around its own home-point according to a restricted mobility process which results into a spatial stationary distribution that decays as a power law of exponent δ with the distance from the home-point. For such restricted mobility model, we propose a novel class of scheduling and routing schemes, which significantly outperforms all delay-throughput results previously obtained in the case of identical nodes. In particular, for δ = 2 it is possible to achieve almost constant delay and almost constant per-node throughput (except for a polylogarithmic factor) as the number of nodes increases, even without resorting to sophisticated coding or signal processing techniques. © 2010 IEEE.

Asinari P.,Polytechnic University of Turin
Computer Physics Communications | Year: 2010

The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many applications in thermodynamics, econophysics and sociodynamics. Despite recent hardware improvements, the solution of the Boltzmann equation remains extremely challenging from the computational point of view, in particular by deterministic methods (free of stochastic noise). This work aims to improve a deterministic direct method recently proposed [V.V. Aristov, Kluwer Academic Publishers, 2001] for solving the HIBE with a generic collisional kernel and, in particular, for taking care of the late dynamics of the relaxation towards the equilibrium. Essentially (a) the original problem is reformulated in terms of particle kinetic energy (exact particle number and energy conservation during microscopic collisions) and (b) the computation of the relaxation rates is improved by the DVM-like correction, where DVM stands for Discrete Velocity Model (ensuring that the macroscopic conservation laws are exactly satisfied). Both these corrections make possible to derive very accurate reference solutions for this test case. Moreover this work aims to distribute an open-source program (called HOMISBOLTZ), which can be redistributed and/or modified for dealing with different applications, under the terms of the GNU General Public License. The program has been purposely designed in order to be minimal, not only with regards to the reduced number of lines (less than 1000), but also with regards to the coding style (as simple as possible). © 2010 Elsevier Ltd. All rights reserved.

Ohwada T.,Kyoto University | Asinari P.,Polytechnic University of Turin
Journal of Computational Physics | Year: 2010

The artificial compressibility method for the incompressible Navier-Stokes equations is revived as a high order accurate numerical method (fourth order in space and second order in time). Similar to the lattice Boltzmann method, the mesh spacing is linked to the Mach number. An accuracy higher than that of the lattice Boltzmann method is achieved by exploiting the asymptotic behavior of the solution of the artificial compressibility equations for small Mach numbers and the simple lattice structure. An easy method for accelerating the decay of acoustic waves, which deteriorate the quality of the numerical solution, and a simple cure for the checkerboard instability are proposed. The high performance of the scheme is demonstrated not only for the periodic boundary condition but also for the Dirichlet-type boundary condition. © 2009 Elsevier Inc. All rights reserved.

Doria P.,Institute For Quanteninformationsverarbeitung | Doria P.,Polytechnic University of Turin | Calarco T.,Institute For Quanteninformationsverarbeitung | Montangero S.,Institute For Quanteninformationsverarbeitung
Physical Review Letters | Year: 2011

We present an efficient strategy for controlling a vast range of nonintegrable quantum many-body one-dimensional systems that can be merged with state-of-the-art tensor network simulation methods such as the density matrix renormalization group. To demonstrate its potential, we employ it to solve a major issue in current optical-lattice physics with ultracold atoms: we show how to reduce by about 2 orders of magnitude the time needed to bring a superfluid gas into a Mott insulator state, while suppressing defects by more than 1 order of magnitude as compared to current experiments. Finally, we show that the optimal pulse is robust against atom number fluctuations. © 2011 American Physical Society.

Stassi S.,Center for Space Human Robotics Polito | Stassi S.,Polytechnic University of Turin | Canavese G.,Center for Space Human Robotics Polito
Journal of Polymer Science, Part B: Polymer Physics | Year: 2012

This work presents a comprehensive investigation of the piezoresistive response of a composite material based on conductive nickel filler in a silicone-insulating matrix. In the absence of a deformation, the prepared composite shows no electric conductivity, even though the metal particle content is well above the expected percolation threshold. Upon samples deformation (compressive or tensile stress), the composite exploits a variation of electrical resistance up to nine orders of magnitude. This huge variation can be explained with the quantum tunnelling mechanism where the probability of an electron to tunnel from a particle to the next one is exponentially proportional to the thickness of the insulating layer between them and strongly enhanced by the morphology of the nickel particles, showing spiky nanostructured tips. Two different conduction theoretical models are proposed and compared with the experimental results. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 A huge piezoresistive response upon compressive or tensile stress is achieved in a composite material based on nickel conductive filler in a polydimethylsiloxane (PDMS) insulating matrix. The conduction mechanism, enhanced by the spiky nanostructured morphology of the particles inside the composite, is based on a quantum tunneling effect as confirmed by theoretical models. The huge variation in resistance upon a small deformation of the composite material makes it a good candidate for sensor applications. Copyright © 2012 Wiley Periodicals, Inc.

Galleani L.,Polytechnic University of Turin
European Signal Processing Conference | Year: 2014

The dynamic Allan variance (DAVAR) is a tool for the characterization of precise clocks. Monitoring anomalies of precise clocks is essential, especially when they are employed onboard the satellites of a global navigation satellite system (GNSS). When an anomaly occurs, the DAVAR changes with time, its shape depending on the type of anomaly occurred. We obtain the analytic DAVAR for a change of variance in the clock noise, an anomaly with critical effects on the clock performances. This result is helpful when the clock health is monitored by observing the DAVAR. © 2014 EURASIP.

Tran P.D.,Nanyang Technological University | Wong L.H.,Nanyang Technological University | Barber J.,Nanyang Technological University | Barber J.,Imperial College London | And 2 more authors.
Energy and Environmental Science | Year: 2012

Converting solar energy into fuel via photo-assisted water splitting to generate hydrogen or drive CO 2 reduction is an attractive scientific and technological goal to address the increasing global demand for energy and to reduce the impact of energy production on climate change. Engineering an efficient, low-cost photocatalyst is necessary to achieve this technological goal. A photocatalyst combines a photosensitiser and an electrocatalyst to capture light and accelerate the chemical reactions in the same device. In this perspective paper, we first describe the recent developments of some families of semiconductors that are attractive candidates for engineering photocatalysts. We then discuss the use of semiconductors as light harvesting agents, combined with a bio-catalyst, synthetic bio-mimetic molecular catalyst or synthetic all-inorganic catalyst, in photocatalytic hybrid systems for water splitting and CO 2 reduction. To highlight the advantages of semiconductors for engineering efficient and robust photocatalysts, we compare these systems to examples of homogeneous photocatalytic systems constructed from molecular photosensitisers (dyes). We conclude that all-inorganic catalysts coupled to appropriate semiconductors look more promising for the construction of robust photocatalytic hybrid systems for producing solar fuels. © 2012 The Royal Society of Chemistry.

Bourreau M.,Telecom ParisTech | Cambini C.,Polytechnic University of Turin
Telecommunications Policy | Year: 2012

Investments in next generation access networks (NGANs) ask for a new set of regulatory remedies. This paper contributes to this debate by focusing on three issues: the migration from the legacy copper network to the NGA infrastructure, and how wholesale pricing regulation might affect this process; the introduction of differentiated wholesale remedies according to geographical differences in NGAN deployment; the impact of co-investment decisions on market outcomes and their interplay with access regulation. Using the recent economic literature, arguments and possible guidelines are proposed, which might be useful to regulators and policy makers. © 2011 Elsevier Ltd.

Allia P.,Polytechnic University of Turin
Journal of Physics: Conference Series | Year: 2014

Magnetic dipolar interaction plays a major role in systems of ferrimagnetic Fe-oxide nanoparticles. Dipolar interaction plays a role over a wide range of temperatures above blocking temperature and results in the onset of the Interacting Superparamagnetic (ISP) regime. In this paper, distinctive aspects and basic issues of the ISP model are discussed by exploiting the experimental data obtained in well-characterized magnetite nanoparticles. © Published under licence by IOP Publishing Ltd.

Shi X.,Brown University | Cheng Y.,Institute of High Performance Computing of Singapore | Pugno N.M.,Polytechnic University of Turin | Gao H.,Brown University
Small | Year: 2010

Molecular dynamics simulations and theoretical analyses are performed to show that the flow rate of water through the core of carbon nanoscrolls (CNSs) can be adjusted over a broad range through the effective surface energy, which in turn can be tuned by an applied DC or AC electric field. The results suggest that the CNSs hold great promise for applications such as tunable water and ion channels, nanofluidic devices, and nanofilters, as well as tunable gene- and drug-delivery systems. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graglia R.D.,Polytechnic University of Turin | Peterson A.F.,Georgia Institute of Technology
IEEE Transactions on Antennas and Propagation | Year: 2012

New curl-conforming hierarchical vector basis functions are developed for triangular-prism cells. These bases are constructed by taking the product of base vectors with scalar orthogonal polynomials and are shown to maintain linear independence as their polynomial order is increased. The procedure for constructing these basis functions is described and specific functions are tabulated for orders up to 6.5. These bases are compatible with recently-proposed hierarchical bases for tetrahedral and hexahedral cells and will maintain tangential continuity with those bases if used in a mesh containing multiple cell shapes. © 1963-2012 IEEE.

Chiavazzo E.,Polytechnic University of Turin
Journal of Computational Physics | Year: 2012

In this paper, we introduce a fictitious dynamics for describing the only fast relaxation of a stiff ordinary differential equation (ODE) system towards a stable low-dimensional invariant manifold in the phase-space (slow invariant manifold - SIM). As a result, the demanding problem of constructing SIM of any dimensions is recast into the remarkably simpler task of solving a properly devised ODE system by stiff numerical schemes available in the literature. In the same spirit, a set of equations is elaborated for local construction of the fast subspace, and possible initialization procedures for the above equations are discussed. The implementation to a detailed mechanism for combustion of hydrogen and air has been carried out, while a model with the exact Chapman-Enskog solution of the invariance equation is utilized as a benchmark. © 2011 Elsevier Inc.

Cimellaro G.P.,Polytechnic University of Turin
Earthquake Engineering and Structural Dynamics | Year: 2013

The shape of a uniform hazard spectrum has been criticized to be unrealistic for a site where the spectral ordinates of the uniform hazard spectrum at different periods are governed by different scenario events and conservative for long-return-period earthquake shaking. The conditional mean spectrum considering epsilon (CMS-ε) takes into account the correlation of spectral demands (represented by values of ε) at different periods, to address these issues. This paper proposes new prediction models for the correlation coefficient ρεT1εT2 of ε(T1) and ε(T2), a key component for developing a CMS, using Pan-European earthquake records from a European ground motion database. Epsilon (ε) for each record is computed using the 2005 Ambraseys ground-motion prediction equation. The model can be used to develop CMS for European sites, and it can be incorporated in the European seismic standards. © 2012 John Wiley & Sons, Ltd..

Mantelero A.,Polytechnic University of Turin
Computer Law and Security Review | Year: 2013

The EU Proposal for a General Data Protection Regulation has caused a wide debate between lawyers and legal scholars and many opinions have been voiced on the issue of the right to be forgotten. In order to analyse the relevance of the new rule provided by Article 17 of the Proposal, this paper considers the original idea of the right to be forgotten, pre-existing in both European and U.S. legal frameworks. This article focuses on the new provisions of Article 17 of the EU Proposal for a General Data Protection Regulation and evaluates its effects on court decisions. The author assumes that the new provisions do not seem to represent a revolutionary change to the existing rules with regard to the right granted to the individual, but instead have an impact on the extension of the protection of the information disseminated on-line. © 2013 Alessandro Mantelero. Published by Elsevier Ltd. All rights reserved.

Andriulli F.P.,Telecom Bretagne | Vecchi G.,Polytechnic University of Turin
IEEE Transactions on Antennas and Propagation | Year: 2012

A new fast matrix-vector multiplication scheme for the solution of the electric field integral equation is presented in this work. Similarly to other fast methods, our approach reduces the matrix-vector multiplication cost from O(N 2) to O(N log N). Differently from other fast solvers, however, the effectiveness of EFIE preconditioning techniques such as quasi-Helmholtz decompositions or Caldern approaches is maintained by our method even for very high matrix compression rates. This is thanks to the fact that, in the scheme we are proposing, the contribution from the scalar potential when applied to or tested with solenoidal functions is always zero independent of the compression error. In addition, the new method will take advantage of the redundancies of the EFIE matrix in the low-frequency/dense discretization regime, and it will further decrease both the memory storage and the multiplication cost with respect to currently available fast solvers. Numerical results will show the effectiveness of our approach and its impact on the solution of realistic problems. © 2012 IEEE.

In the first part of this work, combined heat and power (CHP) criteria pertaining to energy, exergy, environmental (pollutant emission) and economic aspects, have been investigated and compared. Although the constraints in legislation usually refer to energy efficiency, primary energy savings and greenhouse gas savings, other criteria should also be taken into account in order to obtain a better evaluation of a cogeneration plant. Here particular attention has been paid to saving indexes for both an individual CHP-unit and for a CHP-system, that is the complete system with all the cogeneration units and the auxiliary plants necessary to cover the users' demand. Five indexes, named potential indexes, have been introduced to evaluate the cogeneration potential: one for energy saving, one for exergy, two for environmental aspects (global and local scale) and one for economic aspects. Finally, some indexes analysed in the paper have been applied to a case study concerning a district heating cogeneration system, and the different behaviour of the energy-exergy, environmental and economic aspects has been discussed. © 2013 by the authors.

Battezzati M.,Polytechnic University of Turin
Archives of Mechanics | Year: 2012

A classical mechanical system subjected to frictional forces is considered in the limit of large frictional coefficient. Random white noise is also introduced in confor-mity to the fluctuation-dissipation theorem. The velocity is split into a deterministic component plus a random stochastic component consequently, the evolution operator (generator) for the probability density in configuration space is evaluated recalling previous work by the same author, by stochastically averaging the flux of particles. The averages depend upon the history of the system, but memory may be eliminated by suitably defining the drift, in the limit of large time. The fundamental solution of the diffusion equation is recast into the form of a Feynman path integral, and subsequently transformed into an Onsager-Machlup path integral, whose regressive stationary solutions satisfy the minimum entropy pro-duction principle. It is focused upon the role played by the appropriate definition of drift velocity adopted in this approach, allowing for interpretation of the Onsager-Machlup potential.Copyright © 2012 by IPPT PAN.

Taricco G.,Polytechnic University of Turin
IEEE Wireless Communications Letters | Year: 2012

This letter addresses the calculation of the ergodic beamforming capacity of a multiple-input single-output (MISO) communication channel in the presence of additive Gaussian noise and known channel distribution information at the transmitter (CDIT). Necessary conditions to achieve the ergodic beamforming capacity are presented in the general case and derived explicitly when the CDIT is Gaussian. This case is commonly addressed in the literature as the joint channel mean information (CMI) and channel covariance information (CCI) case. An iterative algorithm based on the projected gradient approach is derived in order to find the beamforming capacity and the corresponding capacity-achieving beamforming vector. © 2012 IEEE.

Graglia R.D.,Polytechnic University of Turin | Peterson A.F.,Georgia Institute of Technology
IEEE Transactions on Antennas and Propagation | Year: 2014

A new family of hierarchical divergence-conforming vector bases is proposed for tetrahedral, prism and brick cells. These functions span the divergence-conforming reduced-curl spaces of Nédélec. The bases are constructed from orthogonal scalar polynomials to enhance their linear independence, which is a simpler process than an orthogonalization applied to the final vector functions. Specific functions are tabulated to order 6.5. These basis are intended for use with numerical solutions of volume integral equations or differential equations containing divergence operators. © 2012 IEEE.

Araque Quijano J.L.,National University of Colombia | Vecchi G.,Polytechnic University of Turin
IEEE Transactions on Antennas and Propagation | Year: 2012

This paper presents a novel ultra-compact (0.17× 0.17×0.05 wavelengths) reconfigurable antenna equipped with shunt switches at the edges of the radiating elements; in addition to wide-band frequency-reconfigurability, the antenna can also adapt to different environments. The challenging task of designing a compact antenna for multi-band and multi-environment operation is tackled by a hierarchical optimization process consisting of the genetic algorithm (GA) and local search for geometry optimization, and exhaustive search for computation of the optimum switch patterns for a fixed geometry. Both tunability and environment robustness were confirmed in simulation and measurements on a proof-of-concept prototype where switches were simulated by soldering. Numerical analysis of the impact of commercial MEMS devices is also reported, including a case study of practical interest: a compact antenna that can operate at different locations around a simplified model of a laptop PC without performance degradation. © 2012 IEEE.

Cagliero L.,Polytechnic University of Turin
IEEE Transactions on Knowledge and Data Engineering | Year: 2013

Frequent itemset mining is a widely exploratory technique that focuses on discovering recurrent correlations among data. The steadfast evolution of markets and business environments prompts the need of data mining algorithms to discover significant correlation changes in order to reactively suit product and service provision to customer needs. Change mining, in the context of frequent itemsets, focuses on detecting and reporting significant changes in the set of mined itemsets from one time period to another. The discovery of frequent generalized itemsets, i.e., itemsets that 1) frequently occur in the source data, and 2) provide a high-level abstraction of the mined knowledge, issues new challenges in the analysis of itemsets that become rare, and thus are no longer extracted, from a certain point. This paper proposes a novel kind of dynamic pattern, namely the History Generalized Pattern (HiGen), that represents the evolution of an itemset in consecutive time periods, by reporting the information about its frequent generalizations characterized by minimal redundancy (i.e., minimum level of abstraction) in case it becomes infrequent in a certain time period. To address HiGen mining, it proposes HiGen Miner, an algorithm that focuses on avoiding itemset mining followed by postprocessing by exploiting a support-driven itemset generalization approach. To focus the attention on the minimally redundant frequent generalizations and thus reduce the amount of the generated patterns, the discovery of a smart subset of HiGens, namely the Non-redundant HiGens, is addressed as well. Experiments performed on both real and synthetic datasets show the efficiency and the effectiveness of the proposed approach as well as its usefulness in a real application context. © 1989-2012 IEEE.

The integration between Geographic Information Systems (GIS) and Multicriteria Decision Aiding (MCDA) has attracted increasing attention since the nineteen's and represents nowadays a very important research field. The main objective of this contribution is to highlight the heterogeneity of the fields in which spatial multicriteria evaluation is applied by developing a survey and classification of the scientific literature published between 2005 and 2011. In particular through the literature classification the contribution aims at identifying current trends in GIS-MCDA research and applications, with reference to the fundamental characteristics of the models as for instance, the MCDA techniques being used, the application domain, and the typology of decision problems being solved. The results highlight the flexibility of the methodological approach as well as the increasing interest toward it from different research domains.

Filippi M.,Polytechnic University of Turin
Energy and Buildings | Year: 2015

Latest European Union programs related to energy efficiency underline the need for retrofitting existing buildings, which are responsible for 40% of EU final energy consumption. Although new buildings can be constructed with high performance levels, the majority of the building stock, characterized by a low energy performance, still needs renovation. Thanks to its potential to deliver high energy and CO2 savings, green retrofitting of existing buildings can thus play a pivotal role in creating a sustainable future. In this context, interventions on buildings constructed before 1945 (commonly defined as "historic buildings") mean a higher benefit/cost ratio, because, in many cases, green retrofitting can be linked to unavoidable refurbishment works and renovated buildings can take on an interesting market value. However, an important part of these historic buildings in Italy is composed of cultural heritage buildings; these buildings require a specific design approach, and green retrofitting is often not attractive from an economic point of view. The remarks reported in this work aim to stimulate a discussion on operational procedures, barriers and challenges that investors, professional figures and supervisory authorities can encounter when they are engaged in the green retrofitting of historic buildings belonging to Italian cultural heritage. © 2014 Elsevier B.V. All rights reserved.

D'Oca S.,Lawrence Berkeley National Laboratory | D'Oca S.,Polytechnic University of Turin | Hong T.,Lawrence Berkeley National Laboratory
Energy and Buildings | Year: 2015

Building occupancy is a paramount factor in building energy simulations. Specifically, lighting, plug loads, HVAC equipment utilization, fresh air requirements and internal heat gain or loss greatly depends on the level of occupancy within a building. Developing the appropriate methodologies to describe and reproduce the intricate network responsible for human-building interactions are needed. Extrapolation of patterns from big data streams is a powerful analysis technique which will allow for a better understanding of energy usage in buildings. A three-step data mining framework is applied to discover occupancy patterns in office spaces. First, a data set of 16 offices with 10 min interval occupancy data, over a two year period is mined through a decision tree model which predicts the occupancy presence. Then a rule induction algorithm is used to learn a pruned set of rules on the results from the decision tree model. Finally, a cluster analysis is employed in order to obtain consistent patterns of occupancy schedules. The identified occupancy rules and schedules are representative as four archetypal working profiles that can be used as input to current building energy modeling programs, such as EnergyPlus or IDA-ICE, to investigate impact of occupant presence on design, operation and energy use in office buildings. © 2014 Elsevier B.V. All rights reserved.

Banchero M.,Polytechnic University of Turin
Coloration Technology | Year: 2013

Supercritical fluid dyeing is an interesting alternative to the conventional aqueous process because of its environmental benefits. The aim of the paper is to provide the reader with an up-to-date overview of this subject, covering various aspects, such as the solubility and equilibrium partitioning of the dyes, mass transfer phenomena and solvent-polymer interactions occurring during coloration, up to the most recent reports on the technology of the dyeing process. Even though the best results have been obtained in the coloration of synthetic textiles, particular attention is given to the dyeing of natural textiles, which is, at the moment, the limiting step of this technology. © 2012 The Authors. Coloration Technology © 2012 Society of Dyers and Colourists.

Bellomo N.,Polytechnic University of Turin | Carbonaro B.,University of Naples
Physics of Life Reviews | Year: 2011

This review paper is devoted to present a personal perspective, based on a critical analysis of the existing literature, about the conceptual difficulties that mathematics meets when attempting to describe the complexity of living matter focusing on the challenging goal of developing a mathematical theory for living systems. The authors propose a personal path, starting from the identification of a number of common features of living systems that can be viewed as sources of complexity, firstly in general, and subsequently focusing specifically on evolution problems. Further, three key questions are posed addressing to a mathematical theory. Finally, the tools of the kinetic theory of active particles are critically analyzed to understand how far this approach still is from the achievement of the afore said ambitious objective. © 2010 Elsevier B.V.

Musso G.,Polytechnic University of Turin | Romero E.,Polytechnic University of Catalonia | della Vecchia G.,Polytechnic of Milan
Geotechnique | Year: 2013

This work presents an insight into double-structure effects on the coupled chemo-hydro-mechanical behaviour of a compacted active clay. In the first part, selected pore size distribution curves are introduced, to highlight the influence of solute concentration on the evolution of the microstructure of compacted samples. An aggregated structure with dual-pore network is induced by compaction even at relatively high water contents. This structural arrangement is enhanced by salinisation, and has a notable influence on transient volume change behaviour - that is, the occurrence of different stages of swelling upon pore water dilution and higher volume change rates upon salinisation. A coupled chemo-hydro-mechanical model, taking into consideration double-structural features from a chemo-mechanical viewpoint, is described and then used to interpret these behavioural responses and present complementary information on local transient processes. The model is designed to identify an intra-aggregate and an inter-aggregate domain, and assigns different values of hydraulic pressure and osmotic suction to each domain. Distinct constitutive laws for both domains are formulated, and the flow of salt and water between the two domains is accounted for by a physically based mass exchange term. The model is used to simulate salt diffusion tests run in an oedometer at constant vertical stress. Parameters used in the formulation are calibrated based on separate experimental evidence, both through direct test results and through back-analyses of laboratory experiments. © 2013 Thomas Telford Ltd.

Fais A.,Polytechnic University of Turin
Journal of Materials Processing Technology | Year: 2010

A powder processing technique is here presented. The process consists in a single short impulse (5-40 ms) of electric current (with current densities greater than 108 A/m2) combined with mechanical pressure and allows for nearly complete to complete densification of powders (>90% of theoretical density) with energy inputs from 1 to 4.5 kJ/g. The fundamental process parameter known as SEI is analyzed and is correlated with other known electro-discharge sintering techniques which present analogous values. An experimental equation correlating SEI and densities is proposed. Theoretical physical considerations on the amplification of mechanical and electrical energies during the process are made to explain the sintering process and the experimental evidence. © 2010 Elsevier B.V. All rights reserved.

Bertuch T.,Fraunhofer Institute for High Frequency Physics and Radar Techniques | Vipiana F.,Antenna and EMC Laboratory LACE | Vecchi G.,Polytechnic University of Turin
IEEE Transactions on Antennas and Propagation | Year: 2012

We present an approach for the method of moments (MoM) analysis of antennas of arbitrary shape printed on a cylindrical substrate. We propose several key components of a code to perform this analysis, with the explicit goal of adapting MoM codes devised for planar stratified structures. For that purpose, the background medium Green's function is expressed in the mixed-potential (MP) format to allow for efficient numerical integration; the spectral dyadic Green's function is first recast in the spectral counterpart of the spatial mixed-potential form. The convergence of the spectral-to-spatial transform is accelerated by extraction of spectral asymptotic functions and exploitation of the azimuthal periodicity. Several important issues of implementation, numerical stability, and accuracy are addressed with a view to incorporate the spatial MP Green's function into the MoM analysis of printed structures of arbitrary shape using RWG basis functions. The numerical results are in good agreement with those obtained by other methods and with measured data. © 2006 IEEE.

Fiori F.,Polytechnic University of Turin
IEEE Transactions on Electromagnetic Compatibility | Year: 2012

This paper deals with the susceptibility to RF interference (RFI) of common CMOS voltage comparators. Approximate nonlinear analysis and time-domain computer simulations are carried out to highlight the causes of the false commutations induced by the disturbances superimposed onto the nominal input signals. Through these investigations, it is shown that the response of voltage comparators to RFI depends on the comparator initial state. This effect is also confirmed by the results of measurements carried out on a CMOS voltage comparator embedded in a test chip. Based on this, a new voltage comparator that avoids false commutations induced by high-frequency disturbances is proposed. © 2012 IEEE.

Paggi M.,Polytechnic University of Turin | Wriggers P.,Leibniz University of Hanover
Journal of the Mechanics and Physics of Solids | Year: 2012

In this study we investigate the effect of imperfect (not perfectly bonded) interfaces on the stiffness and strength of hierarchical polycrystalline materials. As a case study we consider a honeycomb cellular polycrystal used for drilling and cutting tools. The conclusions of the analysis are, however, general and applicable to any material with structural hierarchy. Regarding the stiffness, generalized expressions for the Voigt and Reuss estimates of the bounds to the effective elastic modulus of heterogeneous materials are derived. The generalizations regard two aspects that are not included in the standard Reuss and Voigt estimates. The first novelty consists in considering finite thickness interfaces between the constituents undergoing damage up to final debonding. The second generalization consists of interfaces not perpendicular or parallel to the loading direction, i.e., when isostress or isostrain conditions are not satisfied. In this case, approximate expressions for the effective elastic modulus are obtained by performing a computational homogenization approach. In the second part of the paper, the homogenized response of a representative volume element (RVE) of the honeycomb cellular polycrystalline material with one or two levels of hierarchy is numerically investigated. This is put forward by using the cohesive zone model (CZM) for finite thickness interfaces recently proposed by the authors and implemented in the finite element program FEAP. From tensile tests we find that the interface nonlinearity significantly contributes to the deformability of the material. Increasing the number of hierarchical levels, the deformability increases. The RVE is tested in two different directions and, due to different orientations of the interfaces and Mixed Mode deformation, anisotropy in stiffness and strength is observed. Stiffness anisotropy is amplified by increasing the number of hierarchical levels. Finally, the interaction between interfaces at different hierarchical levels is numerically characterized. A condition for scale separation, which corresponds to the independence of the material tensile strength from the properties of the interfaces in the second level, is established. When this condition is fulfilled, the material microstructure at the second level can be efficiently replaced by an effective homogeneous continuum with a homogenized stressstrain response. From the engineering point of view, the proposed criterion of scale separation suggests how to design the optimal microstructure of a hierarchical level to maximize the material tensile strength. An interpretation of this phenomenon according to the concept of flaw tolerance is finally presented. © 2012 Elsevier Ltd. All rights reserved.

Elcrat A.,Wichita State University | Zannetti L.,Polytechnic University of Turin
Journal of Fluid Mechanics | Year: 2012

Closed and open hollow wakes are considered as analytic models for the two-dimensional inviscid steady flow past a plate normal to the stream. It is shown that only open configurations which satisfy the Kutta condition exist. The main argument is based on considering a plate located on the edge of a step with varying height. It is shown that solutions for open wakes exist for backward-, null and forward-facing steps, while closed wakes only exist for backward-facing steps. The occurrence of secondary separation has been modelled by adding a hollow region attached to the downstream corner. Peculiar accuracy issues of the problem are pointed out which may explain other contradictory results from the literature. It is shown how the Kirchhoff wake is a limiting solution for certain values of the governing parameters. © 2012 Cambridge University Press.

Crovetti P.S.,Polytechnic University of Turin
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

The possibility of reproducing the effects on an electronic equipment of an arbitrary electromagnetic (EM) field excitation for effective EM interference susceptibility assessment is explored in this paper. To this purpose, a method to recreate the effects of a given EM field over an equipment under test by proper RF current injection on its reference conductor is derived from EM theory. The effectiveness and the practical feasibility of this approach is discussed on the basis of full-wave EM simulations and experimental results. © 2012 IEEE.

Taricco G.,Polytechnic University of Turin
IEEE Wireless Communications Letters | Year: 2015

The gain of a multipath propagation scenario is addressed by this work and it is shown that the convergence to the Rayleigh distribution depends on some conditions on the path gains, which are not always satisfied. These conditions confirm the convergence to the Rayleigh distribution for some well known scenarios. However, counter-examples are also exhibited where this convergence does not hold. Furthermore, the role of the Central Limit Theorem (often advocated in the literature to prove convergence to the Rayleigh distribution) is critically discussed by showing that the Lindeberg condition may not hold. Finally, it is shown that the amplitude and phase of the asymptotic gain are independent and the phase is uniformly distributed over [0, 2π]. © 2015 IEEE.

Tkindt V.,University of Tours | Della Croce F.,Polytechnic University of Turin
Computers and Operations Research | Year: 2012

In a recent paper by Shabtay and Gasper Two-machine flow-shop scheduling with rejection, Computers and Operations Research, forthcoming, doi:10.1016/j.cor.2011.05.023, several complexity and approximation results are proposed for a two-criteria two-machine flow-shop scheduling problem with rejection. The two criteria to be minimized are the makespan the total rejection cost. This note positions the contribution of such results with respect to the contributions of the literature on common due date assignment and flow-shop scheduling not considered in the work of Shabtay and Gasper. © 2012 Elsevier Ltd. All rights reserved.

Brischetto S.,Polytechnic University of Turin
CMES - Computer Modeling in Engineering and Sciences | Year: 2012

The paper analyzes the hygrothermal loading effects in the bending of multilayered composite plates. Refined two-dimensional models are used to evaluate these effects, they are implemented in the framework of the Carrera's Unified Formulation (CUF) which also allows classical models to be obtained. Hygroscopic and thermal effects are evaluated by means of hygroscopic and thermal load applications, respectively. Such loads can be determined via a priori linear or constant moisture content and temperature profiles through the thickness of the plate, or by calculating them via the solution of the Fick moisture diffusion law and the Fourier heat conduction equation, respectively. These equations are solved in steady-state conditions and in a range of moisture content and temperature variations which requires constant material properties to be considered. Comparisons between assumed linear and calculated moisture content and temperature profiles are also made for different thickness ratios and lamination sequences. The presence of hygroscopic and thermal effects modifies the bending response in composite structures by increasing the maximum deflection and the discontinuity values of in-plane stresses at the layer interfaces. Copyright © 2012 Tech Science Press.

Khalili S.M.R.,K. N. Toosi University of Technology | Botshekanan Dehkordi M.,K. N. Toosi University of Technology | Carrera E.,Polytechnic University of Turin | Shariyat M.,K. N. Toosi University of Technology
Composite Structures | Year: 2013

In the present work a non-linear dynamic response of a continuous sandwich beam with SMA hybrid composite face sheets and flexible core is analyzed taking into account the phase transformation and also the material non-linearity effects, for every point along the face sheets. The one-dimensional constitutive equation of SMA proposed by Brinson is employed. Equations of motion are derived using Hamilton's principle and a new finite element is proposed based on a higher order sandwich panel theory. Due to the phase transformation, the equations of motion are coupled with the phase transformation's kinetic equations of SMA wires. A new finite-element-based approach along with an iterative incremental method is developed to study the dynamic response of sandwich beam with SMA hybrid composite face sheets and flexible core. A damped response of the sandwich beam is observed, which is due to the hysteresis behavior of SMA wires. The influence of the SMA wires on the vibration suppression related to the resonance phenomena of a sandwich beam as well as the effect of the through thickness location of the SMA wires inside the composite face sheets and also the effect of different boundary conditions on the dynamic response are analyzed. © 2012 Elsevier Ltd.

Giustolisi O.,Polytechnic of Bari | Ridolfi L.,Polytechnic University of Turin
Water Resources Research | Year: 2014

The search for suitable segmentations is a challenging and urgent issue for the analysis, planning and management of complex water distribution networks (WDNs). In fact, complex and large size hydraulic systems require the division into modules in order to simplify the analysis and the management tasks. In the complex network theory, modularity index has been proposed as a measure of the strength of the network division into modules and its maximization is used in order to identify community of nodes (i.e., modules) which are characterized by strong interconnections. Nevertheless, modularity index needs to be revised considering the specificity of the hydraulic systems as infrastructure systems. To this aim, the classic modularity index has been recently modified and tailored for WDNs. Nevertheless, the WDN-oriented modularity is affected by the resolution limit stemming from classic modularity index. Such a limit hampers the identification/design of small modules and this is a major drawback for technical tasks requiring a detailed resolution of the network segmentation. In order to get over this problem, we propose a novel infrastructure modularity index that is not affected by the resolution limit of the classic one. The rationale and good features of the proposed index are theoretically demonstrated and discussed using two real hydraulic networks. Key Points A general quantitative approach for water distribution network segmentation No resolution limit Proposed approach is discussed and tested on real water networks © 2014. American Geophysical Union. All Rights Reserved.

Minetola P.,Polytechnic University of Turin
International Journal of Precision Engineering and Manufacturing | Year: 2012

Nowadays products having complex freeform custom-made shapes can be fabricated without any tool by means of additive manufacturing processes. Additive manufactured parts must be inspected for quality to verify that they meet dimensional and geometrical specifications among other requirements just as any other product. Contactless inspection carried out with optical 3D scanners is preferred to traditional pointwise measurements because of the higher amount of data retrieved in short times. A key step of the contactless inspection process is the definition of the part reference frame for the alignment of scan data. This paper considers different 3-2-1 alignments and analyze their influence on the inspection results, putting in evidence that an inattentive or inaccurate definition of the part reference frame can lead to incorrect evaluations of real part deviations. © KSPE and Springer 2012.

Fiori F.,Polytechnic University of Turin | Merlin M.,North China Electrical Power University
IEEE Transactions on Power Electronics | Year: 2012

This paper focuses on the electromagnetic emissions of smart-power integrated systems that include analog, digital, and power sections. With reference to common high-voltage CMOS technology processes, it is shown that the switching noise of digital core blocks can propagate to the power sections through the silicon substrate they share. Such disturbances feed the printed circuit board traces and cables connected to the IC power section, which behave like parasitic antennas, and unwanted electromagnetic emissions are experienced. A generic integrated system fabricated with a planar CMOS technology process is considered and the propagation of digital switching noise is analyzed referring to a system level equivalent circuit, which comprises a substrate model and an IC package model. Based on this, the circuit parameters that affect the propagation of the switching noise are highlighted and a new grounding scheme, which reduces the substrate parasitic coupling in smart-power system-on-chip, is proposed. Its effectiveness is proved through computer simulations and experimental tests. © 2011 IEEE.

Boria S.,University of Camerino | Belingardi G.,Polytechnic University of Turin
International Journal of Crashworthiness | Year: 2012

Nowadays, there is increasing interest in lightweight automotive structures capable of absorbing large quantities of energy in case of a crash phenomenon. These requirements are satisfied by composite devices, provided they are properly designed. The aim of the present paper is the investigation of the crashworthy behaviour of composite material tubes with woven laminae subjected to dynamic axial compression. The research was done by combining experimental and numerical analysis; without any experimental feedback, in fact, engineers might not accurately design an innovative structure. After the numerical characterisation of the used CFRP (carbon fibre-reinforced polymer) material, different simulations with the non-linear explicit dynamic code LS-DYNA have been done in order to understand how the structure absorbs energy by varying its geometrical and material parameters. In particular, circular and square tubes have been investigated with different resistant section, wall thickness, fibres orientation and staking sequence. The numerical analysis has been carried out taking into account different composite material models present in the LS-DYNA library, where each of them implements a different damage criterion. The choice of model to be used was made only after performing crash tests on the same tubes using a drop tower, appropriately instrumented in order to measure the main impact characteristics. The comparison between numerical and experimental results gave satisfactory outcomes, providing the basis for the design methodology of impact attenuators that are geometrically more complex. © 2012 Taylor & Francis.

Crovetti P.S.,Polytechnic University of Turin
Electronics Letters | Year: 2012

A new method to achieve immunity to EMI in a front-end for baseband analogue signal acquisition, avoiding the adverse effects of electromagnetic interference on operational amplifier-based conditioning amplifiers, is proposed. Unlike previous solutions, the presented novel system-level approach is based on standard hardware and does not require microelectronic optimisation. The validity of the proposed technique has been verified by computer simulations. © 2012 The Institution of Engineering and Technology.

Boccardo P.,Polytechnic University of Turin
Rendiconti Lincei | Year: 2015

In recent years an increasing number of extreme meteorological events have been recorded. Geomatics techniques have been historically adopted to support the different phases of the Emergency Management cycle with a main focus on emergency response, initial recovery and preparedness through the acquisition, processing, management and dissemination of geospatial data. In the meantime, the increased availability of geospatial data in terms of reference topographic datasets, made available by authoritative National Mapping Cadastre Agencies or by Collaborative Mapping initiatives like OpenStreetMap, as well as of remotely sensed imagery, poses new challenges to the Geomatics role in defining operational tools and services in support of emergency management activities. This paper is mainly focused on the role of Geomatics in supporting the response phase of the Emergency Management cycle through Rapid Mapping activities, which can be defined as “the on-demand and fast provision (within hours or days) of geospatial information in support of emergency management activities immediately following an emergency event” (source: European Union, http://emergency.copernicus.eu/mapping/ems/service-overview). Management of geospatial datasets (both reference and thematic), Remote Sensing sensors and techniques and spatial information science methodologies applied to Rapid Mapping will be described, with the goal to highlight the role that Geomatics is currently playing in this domain. The major technical requirements, constraints and research opportunities of a Rapid Mapping service will be discussed, with a specific focus on: the time constraints of the service, the data quality requirements, the need to provide replicable products, the need for consistent data models, the advantages of data interoperability, the automation of feature extraction procedures to reduce the need for Computer Aided Photo Interpretation, the dissemination strategies. © 2015, The Author(s).

Marano V.,Ohio State University | Rizzo G.,University of Salerno | Tiano F.A.,Polytechnic University of Turin
Applied Energy | Year: 2012

A model for thermo-economic analysis and optimization of a hybrid power plant consisting of compressed air energy storage (CAES) coupled with a wind farm and a photovoltaic plant is presented. This kind of plant is aiming to overcome some of the major limitations of renewable energy sources, represented by their low power density and intermittent nature, largely depending upon local site and unpredictable weather conditions. In CAES, energy is stored in the form of compressed air in a reservoir during off-peak periods, while it is used on demand during peak periods to generate power with a turbo-generator system. Such plants can offer significant benefits in terms of flexibility in matching a fluctuating power demand, particularly when coupled with renewable sources, characterized by high and often unpredictable variability. A mathematical model, validated in a previous study over the CAES plant in Alabama, US, is coupled with a dynamic programming algorithm to achieve the optimal management of the plant, in order to minimize operational costs while satisfying constraints related to the operation of reservoir, compressors and turbines, also considering their off-design performance. The potential benefits of such plant in terms of energy consumption and CO2 emission are analyzed and discussed, for different configurations and scenarios. © 2012 Elsevier Ltd.

Barber J.,Imperial College London | Barber J.,Nanyang Technological University | Barber J.,Polytechnic University of Turin | Tran P.D.,Nanyang Technological University
Journal of the Royal Society Interface | Year: 2013

Demand for energy is projected to increase at least twofold by mid-century relative to the present global consumption because of predicted population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of carbon dioxide (CO2) emissions demands that stabilizing the atmospheric CO 2 levels to just twice their pre-anthropogenic values by mid-century will be extremely challenging, requiring invention, development and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable and exploitable energy resources, nuclear fusion energy or solar energy are by far the largest. However, in both cases, technological breakthroughs are required with nuclear fusion being very difficult, if not impossible on the scale required. On the other hand, 1 h of sunlight falling on our planet is equivalent to all the energy consumed by humans in an entire year. If solar energy is to be a major primary energy source, then it must be stored and despatched on demand to the end user. An especially attractive approach is to store solar energy in the form of chemical bonds as occurs in natural photosynthesis. However, a technology is needed which has a year-round average conversion efficiency significantly higher than currently available by natural photosynthesis so as to reduce land-area requirements and to be independent of food production. Therefore, the scientific challenge is to construct an 'artificial leaf' able to efficiently capture and convert solar energy and then store it in the form of chemical bonds of a high-energy density fuel such as hydrogen while at the same time producing oxygen from water. Realistically, the efficiency target for such a technology must be 10 per cent or better. Here, we review the molecular details of the energy capturing reactions of natural photosynthesis, particularly the water-splitting reaction of photosystem II and the hydrogen-generating reaction of hydrogenases. We then follow on to describe how these two reactions are being mimicked in physico-chemical-based catalytic or electrocatalytic systems with the challenge of creating a large-scale robust and efficient artificial leaf technology. © 2013 The Authors.

Yassami H.,Shahrood University of Technology | Darabi A.,Shahrood University of Technology | Rafiei S.M.R.,Polytechnic University of Turin
Electric Power Systems Research | Year: 2010

Power system stabilizers (PSSs) are the most well-known and effective tools to damp power system oscillation caused by disturbances. To gain a good transient response, the design methodology of the PSS is quite important. The present paper, discusses a new method for PSS design using the multi-objective optimization approach named Strength Pareto approach. Maximizations of the damping factor and the damping ratio of power system modes are taken as the goals or two objective functions, when designing the PSS parameters. The program generates a set of optimal parameters called Pareto set corresponding to each Pareto front, which is a set of optimal results for the objective functions. This provides an excellent negotiation opportunity for the system manager, manufacturer of the PSS and customers to pick out the desired PSS from a set of optimally designed PSSs. The proposed approach is implemented and examined in the system comprising a single machine connected to an infinite bus via a transmission line. This is also done for two familiar multi-machine systems named two-area four-machine system of Kundur and ten-machine 39-bus New England system. Parameters of the Conventional Power System Stabilizer (CPSS) are optimally designed by the proposed approach. Finally, a comparison with famous GAs is given. © 2009 Elsevier B.V. All rights reserved.

Bourreau M.,Telecom ParisTech | Cambini C.,Polytechnic University of Turin | Dogan P.,Harvard University
International Journal of Industrial Organization | Year: 2012

In this paper, we analyze the incentives of an incumbent and an entrant to migrate from an old technology to a new technology, and discuss how the terms of wholesale access affect this migration. We show that the coverage of the new technology varies non-monotonically with the access price of the old technology: a higher access charge on the legacy network pushes the entrant firm to invest more, but has an ambiguous effect on the incumbent's investments, due to two conflicting effects: the wholesale revenue effect, and the retail-level migration effect. When the new technology is also subject to access provision, we find that migration from the old to the new generation network at the wholesale level can be incentivized if a positive correlation between the access prices (to the two old and new generation networks) is maintained. © 2012 Elsevier B.V.

Lombardi G.,Polytechnic University of Turin
IEEE Antennas and Wireless Propagation Letters | Year: 2012

The diffraction of a plane wave at skew incidence by an arbitrary-angled concave wedge with anisotropic impedance faces is studied. Concave wedges are of interest in wireless propagation models, in particular on modeling buildings and reflectors. The solution is obtained via the generalized Wiener-Hopf technique for arbitrary impedance wedges using a numerical-analytical approach. The numerical results show the spectral properties of the fields, GTD/UTD diffraction coefficients, and total fields. © 2011 IEEE.

Baino F.,Polytechnic University of Turin
Medical Engineering and Physics | Year: 2010

Scleral buckling is a widely used surgical procedure that aims at repairing retinal detachments. Many materials and procedural techniques have been variously proposed and tested in an attempt to find the best combination for providing optimal results to the patient. This review highlights the evolution of scleral buckling implants and chronicles the main advances that have been made in such a context. Specifically, the limitations of the materials and implants fallen in disuse, as well as the advantages of currently adopted devices are critically examined and discussed. Future directions for the research are considered, underlining in particular the great potential carried by the development of accurate mathematical models for describing the postoperative evolution of buckled eye. These analytical models, supported by a comprehensive data set provided by advanced techniques of medical investigations, may become useful tools for helping surgeons to choose, and to design if necessary, the best buckling material and configuration to be used in each specific clinical case. © 2010 IPEM.

Blengini G.A.,Polytechnic University of Turin | Blengini G.A.,CNR Institute of Environmental Geology and Geoengineering | Garbarino E.,Provincia di Turin
Journal of Cleaner Production | Year: 2010

The ever increasing quantity of construction and demolition waste (C&DW) in Italy is presently challenging public administrators, which strive to ensure that collection and recycling are sustainably managed and need to understand whether and to what extent recycled aggregates can complement natural aggregates in a sustainable supply mix (SSM) for the construction industry. The paper presents a research aimed at analysing energy and environmental implications of the C&DW recycling chain in the administrative territory of Provincia di Torino in Northern Italy, with 2.25 million inhabitants and yearly generation of 1.8 million tons of C&DW. A combined Geographical Information System (GIS) and Life Cycle Assessment (LCA) model was developed using site-specific data and paying particular attention to land use, transportation and avoided landfill: crucial issues for sustainable planning and management. A GIS was used to handle data and information about 89 recycling plants, including technological features, output and physical-mechanical characteristics of recycled aggregate. The LCA methodology was used to identify and quantify energy and environmental loads, under different assumptions relevant to delivery distances, quality of recycled aggregates, local availability of natural aggregates and geographical coverage of market demand. The C&DW recycling chain was proved to be eco-efficient, as avoided impacts were found to be higher than the induced impacts for 13 out of 14 environmental indicators. It was also estimated that the transportation distance of recycled aggregate should increase 2-3 times before the induced impacts outweigh the avoided impacts. © 2010 Elsevier Ltd.

Acemoglu D.,Massachusetts Institute of Technology | Como G.,Lund University | Fagnani F.,Polytechnic University of Turin | Ozdaglar A.,Massachusetts Institute of Technology
Mathematics of Operations Research | Year: 2013

We study a tractable opinion dynamics model that generates long-run disagreements and persistent opinion fluctuations. Our model involves an inhomogeneous stochastic gossip process of continuous opinion dynamics in a society consisting of two types of agents: (1) regular agents who update their beliefs according to information that they receive from their social neighbors and (2) stubborn agents who never update their opinions and might represent leaders, political parties, or media sources attempting to influence the beliefs in the rest of the society. When the society contains stubborn agents with different opinions, the belief dynamics never lead to a consensus (among the regular agents). Instead, beliefs in the society fail to converge almost surely, the belief profile keeps on fluctuating in an ergodic fashion, and it converges in law to a nondegenerate random vector. The structure of the graph describing the social network and the location of the stubborn agents within it shape the opinion dynamics. The expected belief vector is proved to evolve according to an ordinary differential equation coinciding with the Kolmogorov backward equation of a continuous-time Markov chain on the graph with absorbing states corresponding to the stubborn agents, and hence to converge to a harmonic vector, with every regular agent's value being the weighted average of its neighbors' values, and boundary conditions corresponding to the stubborn agents' beliefs. Expected cross products of the agents' beliefs allow for a similar characterization in terms of coupled Markov chains on the graph describing the social network. We prove that, in large-scale societies, which are highly fluid, meaning that the product of the mixing time of the Markov chain on the graph describing the social network and the relative size of the linkages to stubborn agents vanishes as the population size grows large, a condition of homogeneous influence emerges, whereby the stationary beliefs' marginal distributions of most of the regular agents have approximately equal first and second moments. ©2013 INFORMS.