On kinks and other travelling-wave solutions of a modified sine-Gordon equation

We give an exhaustive, non-perturbative classification of exact travelling-wave solutions of a perturbed sine-Gordon equation (on the real line or on the circle) which is used to describe the Josephson effect in the theory of superconductors and other remarkable physical phenomena. The perturbation of the equation consists of a constant forcing term and a linear dissipative term. On the real line candidate orbitally stable solutions with bounded energy density are either the constant one, or of kink (i.e. soliton) type, or of array-of-kinks type, or of "half-array-of-kinks" type. While the first three have unperturbed analogs, the last type is essentially new. We also propose a convergent method of successive approximations of the (anti)kink solution based on a careful application of the fixed point theorem.Comment: Latex file, 25 pages, 4 figures. Final version to appear in "Meccanica

On the photon Green functions in curved space-time

Quantization of electrodynamics in curved space-time in the Lorenz gauge and with arbitrary gauge parameter makes it necessary to study Green functions of non-minimal operators with variable coefficients. Starting from the integral representation of photon Green functions, we link them to the evaluation of integrals involving Gamma functions. Eventually, the full asymptotic expansion of the Feynman photon Green function at small values of the world function, as well as its explicit dependence on the gauge parameter, are obtained without adding by hand a mass term to the Faddeev--Popov Lagrangian. Coincidence limits of second covariant derivatives of the associated Hadamard function are also evaluated, as a first step towards the energy-momentum tensor in the non-minimal case.Comment: 22 pages, plain Tex. All sections and appendices have been improve

Error Analysis and Adaptive-Robust Control of a 6-DoF Parallel Robot with Ball-Screw Drive Actuators

Parallel kinematic machines (PKMs) are commonly used for tasks that require high precision and stiffness. In this sense, the rigidity of the drive system of the robot, which is composed of actuators and transmissions, plays a fundamental role. In this paper, ball-screw drive actuators are considered and a 6-degree of freedom (DoF) parallel robot with prismatic actuated joints is used as application case. A mathematical model of the ball-screw drive is proposed considering the most influencing sources of nonlinearity: sliding-dependent flexibility, backlash, and friction. Using this model, the most critical poses of the robot with respect to the kinematic mapping of the error from the joint- to the task-space are systematically investigated to obtain the workspace positional and rotational resolution, apart from control issues. Finally, a nonlinear adaptive-robust control algorithm for trajectory tracking, based on the minimization of the tracking error, is described and simulated

Risposta del test da carico del glucosio sul profilo metabolico e valutazione isto-patologica di campioni bioptici in bovine da latte nel periodo di transizione

Objectives of this study were to determine effects of time relative to calving and health status on blood metabolite concentrations after glucose tolerance test (GTT) and to investigate on the severity and on the distribuition of periparturient fatty change liver (FCL). Metabolic profiles were performed on plasma samples collected from 40 cows selected from 2 dairy farms. GTT and Blood sampling was carried out 7±5 d before and 7±5 d after the calving. Glucose was administrated intravenously in a 50% solution at a dose of 0,25 g/Kg. Blood samples were collected before (T0) and after the beginning of the test at different times (T2, T5, T10, T15, T20, T30, T40, T60, T80, T100, T120, T140, T160). Beta-Hydroxybutyrate (BHB), Non-Esterified Fatty Acids (NEFA), Glucose(Glu), Insuline (Ins), Aspartate Aminotransferase (AST-GOT), Alanine Transaminase (ALT-GTP), total proteins (TP), globulins(Gb), albumins(Alb) and Urea were analized. Histologic examinations by light microscopy and classifications of samples according to the severity of FCL and Inflammatory infiltrations were done. The collected data were statistically analyzed by the analysis of variance (ANOVA), using SIGMA STAT 3.7 to evaluate the effect of the period (pre-partum and post-partum) and the farm (farm A and farm B) on the hematic, clinical and productive parameters. Pearson’s coefficients were also calculated between the collected data; finally the AUC (Area Under Curve) of glucose, insulin, NEFA and BHB were calculated. The result proved that in the post-partum period cows show insulin resistance that causes a reduction of the levels of glucose and insulin (P<0,005) and a consequent increase of the levels of NEFA and BHB(P<0,05); this mechanism permits to spare glucose (and so energy) for the mammary gland for the lactation. All the cows had mild or moderate FCL degree. Results show correlations between lipidic and inflammatory infiltration of hepatocites in prepartum and levels of NEFA and AST in postpartum. NEFA and AST activity are increased from the prepartum to the postpartum period. High levels of TP and Gb are present in both periods. These data suggest statistically significant differences (P<0,05) between BHB, NEFA, AST and ALT and period. NEFA and AST are parameters of diagnostic value, also if AST is not a liver specific enzyme. Finally it was also proved that there is a correlation between hematic parameters in the pre-partum and the pathologies of the first days of lactation; imbalances in the energetic metabolism during the pre-partum predispose to developing of clinical diseas

Development of a Metaverse Platform for Tourism Promotion in Apulia

Metaverse is an engaging way to recreate in a digital environment the real world. It allows people to connect not by just browsing a website, but by using headsets and virtual reality techniques. The metaverse is actually in a rapid development phase, thanks to the advances in different topics. This paper proposes a smart tourism platform in which tourists can interact with guides and different kinds of suppliers, without the need to phisically visit the city they are in. We propose some techniques to scan the real world and transpose it in a metaverse platform, using the recreation of an Italian city, Bari, as a real life scenario

Feasibility of a magnetic suspension for second generation Gravitational Wave interferometers

This paper deals with the use of a magnetic levitation system as a part of a multi-stage seismic attenuator for gravitational wave interferometric antennas. The proposed configuration uses permanent magnets in attraction to balance the suspended weight, plus a closed loop position control to obtain a stable levitation. The system is analyzed using a MATLAB simulation code to compute the forces exerted by extended magnets. The validity of this model has been tested by a comparison with the experimental data from a levitated suspension prototype.Comment: Accepted for publication in Astroparticle Physic

sustainable reuse of disused railway

Abstract Railways, an infrastructure system consisting of 'railway lines', tunnels, toll booths and stations, are considered 'abandoned' when, for various reasons, any regular service of railway type is suspended. About 2 thousand kilometers of lines no longer active railways exist in our Italian territory, in most cases abandoned to decay. European and international examples of redevelopment of these derelict structures in bicycle lanes or otherwise dedicated to sustainable mobility foresee the transformation of old stations and toll booths in dining and reception points (youth hostels, hotels, restaurants), info points for the enhancement of the territory and care centers for bicycles maintenance. These tourism businesses may be of great impetus to the development of employment and economic exploitation, as well as be a driver of growth for tourism and economy of the country. In Italy a possible strategy for sustainable conversion of these paths necessarily has to take account not only of landscape and environmental values, but also the rich archaeological heritage which, in most cases, these routes intercept and connect. In this regard, the recovery of the railway plaza of Velia, a Focea colony of Magna Graecia is emblematic. Founded shortly after 540 BC, Velia is located inside the archaeological area (northern region), associated with an abandoned stretch of nineteenth-century galleries and ancient houses of the archaeological park. According to a view to integrated redevelopment, the project proposal is based on the idea of the "museum" structured on the historic landscape values