TMsim : an algorithmic tool for the parametric and worst-case simulation of systems with uncertainties

This paper presents a general purpose, algebraic tool—named TMsim—for the combined parametric and worst-case analysis of systems with bounded uncertain parameters.The tool is based on the theory of Taylor models and represents uncertain variables on a bounded domain in terms of a Taylor polynomial plus an interval remainder accounting for truncation and round-off errors.This representation is propagated from inputs to outputs by means of a suitable redefinition of the involved calculations, in both scalar and matrix form. The polynomial provides a parametric approximation of the variable, while the remainder gives a conservative bound of the associated error. The combination between the bound of the polynomial and the interval remainder provides an estimation of the overall (worst-case) bound of the variable. After a preliminary theoretical background, the tool (freely available online) is introduced step by step along with the necessary theoretical notions. As a validation, it is applied to illustrative examples as well as to real-life problems of relevance in electrical engineering applications, specifically a quarter-car model and a continuous time linear equalizer

Quantal Overlapping Resonance Criterion in the Pullen Edmonds Model

In order to highlight the onset of chaos in the Pullen-Edmonds model a quantal analog of the resonance overlap criterion has been examined. A quite good agreement between analytical and numerical results is obtained.Comment: 12 pages, LATEX, 2 figures available upon request to the Authors, submitted to Mod. Phys. Lett.

Changing the University System Management: a study of the Italian scenario

Over recent years, the Italian University System has been handling a phase of deep changes, which have had significant impact on its mission and on the way it operates. The most important of these changes have been to the organisation of universities, their recruitment procedures and in terms of improvements to the quality and efficiency of the university system itself. In this perspective, the objective of this research was to carry out a critical analysis of the process of change, with special reference to improving efficiency by making the transition from cash-based accounting to accrual accounting. In order to achieve this objective, the starting point was the legislation of reference that sets out the terms for the move to financial accrual accounting. A comparative analysis was then carried out at an international level, with the purpose of highlighting the strengths and weaknesses identified during the implementation of these new procedures within the public field. This was followed by an analysis of the details of the theory defining the accounting principles to be used in the process of preparing university’s financial statements. Finally, the study identified the main critical points relating to implementation of the new accounting system, offering, at the same time, several thoughts concerning possible subsequent analyses on this topic

Load distribution in small world networks

In this paper we introduce a new model of data packet transport, based on a stochastic approach with the aim of characterizing the load distribution on complex networks. Moreover we analyze the load standard deviation as an index of uniformity of the distribution of packets within the network, to characterize the effects of the network topology. We measure such index on the model proposed by Watts and Strogatz as the redirection probability is increased. We find that the uniformity of the load spread is maximized in the intermediate region, at which the small world effect is observed and both global and local efficiency are high. Moreover we analyze the relationship between load centrality and degree centrality as an approximate measure of the load at the edges. Analogous results are obtained for the load variance computed at the edges as well as at the vertices.Comment: 6 pages, 5 figures. Included in conference proceedings International Conference PhysCon 2005 August 24-26, 2005, Saint Petersburg, RUSSI

Comparison of Stochastic Methods for the Variability Assessment of Technology Parameters

This paper provides and compares two alternative solutions for the simulation of cables and interconnects with the inclusion of the effects of parameter uncertainties, namely the Polynomial Chaos (PC) method and the Response Surface Modeling (RSM). The problem formulation applies to the telegraphers equations with stochastic coefficients. According to PC, the solution requires an expansion of the unknown parameters in terms of orthogonal polynomials of random variables. On the contrary, RSM is based on a least-square polynomial fitting of the system response. The proposed methods offer accuracy and improved efficiency in computing the parameter variability effects on system responses with respect to the conventional Monte Carlo approach. These approaches are validated by means of the application to the stochastic analysis of a commercial multiconductor flat cable. This analysis allows us to highlight the respective advantages and disadvantages of the presented method

Comment on "Interaction of two solitary waves in quantum electron-positron-ion plasma" [Phys. Plasmas \textbf{18}, 052301 (2011)]

Recently, Yan-Xia Xu, et al. in the article Ref. [Phys. Plasmas \textbf{18}, 052301 (2011)] have studied the effects of various plasma parameters on interaction of two ion-acoustic solitary waves in an unmagnetized three-dimensional electron-positron-ion quantum plasma. They have used the extended reductive perturbation technique, the so-called, extended Poincare'-Lighthill-Kuo (PLK) technique, to deduce from the model governing the quantum hydrodynamics (QHD) differential equations leading to the soliton dynamical properties, namely, Korteweg-de Vries evolution equations (one for each wave) and coupled differential equations describing the phase-shift in trajectories of solitons due to the two dimensional collision. The variation of the calculated collision phase-shifts are then numerically inspected in terms of numerous plasma fractional parameters. In this comment we give some notes specific to the validity of the results of above-mentioned article and refer to important misconceptions about the use of the Fermi-temperature in quantum plasmas, appearing in this article and many other recently published ones.Comment: Accepted Journal Physics of Plasma

Pathological Behavior in the Spectral Statistics of the Asymmetric Rotor Model

The aim of this work is to study the spectral statistics of the asymmetric rotor model (triaxial rigid rotator). The asymmetric top is classically integrable and, according to the Berry-Tabor theory, its spectral statistics should be Poissonian. Surprisingly, our numerical results show that the nearest neighbor spacing distribution $P(s)$ and the spectral rigidity $\Delta_3(L)$ do not follow Poisson statistics. In particular, $P(s)$ shows a sharp peak at $s=1$ while $\Delta_3(L)$ for small values of $L$ follows the Poissonian predictions and asymptotically it shows large fluctuations around its mean value. Finally, we analyze the information entropy, which shows a dissolution of quantum numbers by breaking the axial symmetry of the rigid rotator.Comment: 11 pages, 7 figures, to be published in Phys. Rev.

The impact of the reform of the milk quota regime on the Italian dairy sector

This paper analyses the impact of the milk quota regime reform, actually under discussion, on the European countries with a detailed focus on the Italian milk and dairy sector. The dismantling of the milk quota regime is already on the EU agenda, but how and when to do it is still matter of debate. A possibility is to enlarge gradually the size of the national quotas, up to the full dismantling in 2015 (“soft landing”). Meanwhile, the discussion on Health Check of the CAP is under way. In this work we analyse the possible impacts of the reform of the milk quota regime on the basis of a Computable General Equilibrium (CGE) approach, using two models in sequence: the Global Trade Analysis Project (GTAP) model is used to evaluate the impacts of different scenarios of milk quota reform on the EU market and to compute the price changes outside Italy; these, in turn, are used as inputs for the MEG-D model, that focuses on the Italian milk and dairy market. The two models were run together with two specific objectives: the first was to avoid, in evaluating the impacts of reform of the milk sector regime in Italy, running the model with rough price estimates taken for secondary sources; the second, to have more specific results on the outcome at the national level. Particularly, the model takes in account the particular relevance of quality products (GDO) in Italian diary sector. In order to evaluate the impact of the “soft landing” reform scenario, we run a “comparison” scenario where the milk quotas are fully abolished in the 2009.Milk and dairy sector, Quota production, EU Agri-Food Market, PAC, Agricultural and Food Policy, Livestock Production/Industries,