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Convinta dell’utilità didattica del racconto autobiografico nel processo di apprendimento/insegnamento dell’italiano da parte di studenti stranieri, presento un’unità didattica di approccio alle autobiografie linguistiche, progettata per giovani apprendenti sinofoni, con una competenza dell’italiano oscillante tra i livelli A2 e B1, giunti in Italia per compiere gli studi universitari.Il percorso didattico ha come punto d’arrivo la stesura da parte di degli studenti della propria autobiografia linguistica; è organizzato in fasi e prevede attività che coinvolgono la ricezione orale e scritta, la produzione orale e scritta e l’interazione.L’unità didattica si propone di far conoscere il genere dell’autobiografia e in particolare di quella in cui chi scrive racconta la propria esperienza con le lingue; di stimolare gli studenti a riflettere su se stessi, sulle loro abitudini linguistiche, sulle esperienze pregresse di studio delle lingue e di contatto con le culture di cui le lingue sono veicolo; di incoraggiare gli allievi a parlare di sé.Si prevede, inoltre, nel corso delle attività proposte, l’introduzione di alcune nozioni di linguistica, come, ad esempio, le nozioni di lingua madre, competenza e varietà linguistica. LINGUISTIC AUTOBIOGRAPHIES: AN EXPERIENCE WITH CHINESE-SPEAKING ITALIAN L2 LEARNERS I am convinced of the utility of autobiography in the Italian L2 teaching/learning process with foreign students, and I present a teaching unit centered on linguistic autobiography, designed for young Chinese-speaking learners with A2-B1 competence in Italian, who are studying at Italian universities.The process culminates in the students’ written linguistic autobiography, organized in phases and involving oral and written activities including reception, production and interaction.The unit aims at making the students familiar with the genre of autobiography, focusing on personal experience with languages, in order to stimulate the students to reflect on themselves, their linguistic habits, their former experiences studying languages and contact with cultures where language is the vehicle, as well as encouraging the students to talk about themselves.A few linguistic notions are also introduced, including the idea of mother tongue, competence and linguistic variety., Italiano LinguaDue, Vol 4, No 1 (2012)

The paper describes a portable didactic experiment, realizing a complex network of Chua's circuits, along with its use for introducing collective dynamics in networks of nonlinear oscillators to students. The equipment enables the full configurability of the node's parameters and the network structure (topology and link impedances). An 8 nodes portable version is realized as a demonstrator, however the corresponding laboratory experiment is designed to be easily scalable to a high number of nodes. The network's control and the data acquisition are automated thanks to a USB interface board and a LabVIEW control interface. The experiment allows the student to perform some direct real time analysis of a set of networked (coupled) Chua's circuits, with the goal to give immediate impact to the discovery of collective behaviors. In particular, the proposed experiences range from the characterization of the complex dynamics of the isolated nodes to the complete synchronization, as well as the emergence of clustering and waves. It is adopted within some course on Advanced Circuit Theory at the Master Degree level.

A novel experimental set-up realized for the real time analysis of reconfigurable complex networks, with chaotic Chua’s circuits as nodes, is considered. It has been designed to easily perform large scale experiments on networks of chaotic oscillators, possibly exploring in real time the parameters space in terms of topologies, coupling strengths, nodes’ dynamics, with potential application in the area of neuro-computing and associative dynamic memories. A sample of the capabilities is given by considering diffusive coupling with a large range of coupling strengths in a set of topologies, and first experiments on a ring of 32 chaotic nodes are reported. Synchronization, chaotic waves and patterns are experimentally observed, and the potential of the realized set-up in terms of accuracy, flexibility and analysis time is fully revealed.

A time domain discrete model for nonuniform transmission lines, based on a complementary formulation of the transmission line equations, is considered. By recasting the line equations in terms of flux and charge, one has to discretize alternatively only one of the two equations, the other being exactly verified. This approach has been widely used in electromagnetics to evaluate the discretization error. With reference to simple examples, we show how the error estimation can be used for a selective meshing of the line, leading to much better approximation with the same computational effort.

In this article we present some examples of bifurcations and chaotic phenomena theoretically observed in a simple electromagnetic system. The system consists of a linear lossless, or Heaviside distorsionless, transmission line connected to a Linear resistor at one end (active branch) and to a nonlinear resistor at the other end (passive branch). The time dynamics of the backward voltage wave evaluated across the nonlinear resistor are described by a one-dimensional non linear mapping. A uniqueness theorem and the discussion of a problem with more than one solution complete the paper.

A numerical model for simulating linear lossy transmission lines ended with nonlinear resistors is described. It based on two complementary formulations of the telegrapher's equations and uses the Galerkin method. The proposed approach appears computationally less cumbersome than that based on the time-domain convolution method, especially when the analysis of multiconductor transmission lines is considered. Particular attention is paid to the uniqueness of the solution and to the convergence of the numerical approximation, Complementary formulations provide a powerfull tool to study the convergence.

The paper deals with bifurcation and chaos phenomena theoretically observed in a simple electromagnetic system consisting of a linear, distortionless transmission line connected to an active linear resistor (R < 0) at one end and to a pn-junction diode at the other end. The active resistor gives rise to the stretching phenomena and the diode the back folding one; the combination of these two mechanisms may lead to chaotic dynamics. The Poincare map of the ''backward voltage wave'' at pn-junction diode is obtained by solving a one dimensional nonlinear implicit difference equation. For R < -R(c) (R(c) is the characteristic ''impedance'' of the line) the mapping is unimodal and the dynamics follow the Feigenbaum route to chaos [1]. The nonlinear implicit difference equation is solved numerically. Spatiotemporal chaos is observed in the voltage and current waves. By replacing the pn-junction diode with a twin-pn junction diode circuit, the hopping mechanism is also met.

A composite electromagnetic system including a non-hysteretic ferromagnetic conducting body and a linear resonant circuit fed by a sinusoidal voltage source is studied. The diffusion of the magnetic field in the iron core "inductor" is described by means of a finite dimensional nonlinear dynamic system obtained by applying the Galerkin method. These equations are coupled with the circuit ones. This physical system might exhibit different nonlinear phenomena: multiple periodic oscillations and even apparently completely disordered aperiodic "chaotic" motions. In this paper multiple harmonic and subharmonic oscillations are investigated by computer-aided analysis using a static method.

The knowledge and the control of the magnetic field profile is of major importance in the application of plasma discharges as magnetic lenses for charged particles beams, because of the complex dynamics of the plasma. Since conventional field measurements are quite difficult for high current plasma discharges, we propose an inverse formulation for the identification of the field profile directly from the focusing data. The problem is shown to be ill-posed, in general; therefore a regularisation is needed. This is obtained, first, by means of a proper restriction of the observation space; second, by using an over determined data set, leading to a pseudo-inversion procedure. The numerical solution is illustrated, showing the procedure to be robust, at least for the practical applications range. In particular it is shown how the proposed method is effective in determining the amount o f distortion of the field profile as compared to the reference linear one.

The convolution method is applied to analyse lossy multiconductor lines with non-linear loads. The line is described as a time-domain m-port, through the input and transfer impulse responses. A new method is used to evaluate analytically the principal parts of these responses, i.e., the parts containing all the irregular terms, such as Dirac pulses. Once the irregular parts are known, the regular remainders are easily calculated by numerical inversion. The convolution integrals have been evaluated using two different methods, one based on crude trapezoidal rule and the other based on a fast recursive algorithm. The latter is obtained by an exponential fitting of the regular parts of the impulse responses. A comparison between the computation times of these two methods is presented.