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In a series of papers we have obtained results for nonlinear heat transport when thin wires exchange heat non-linearly with the surroundings, with particular attention to propagating solitons. Here we obtain and discuss new results related to the propagation of nonlinear heat fronts and some conceptual aspects referring to the application of the second principle of thermodynamics to some nonlinear steady states related to non-propagating solitons.

We generalize the K−ϵ model of classical turbulence to superfluid helium. In a classical viscous fluid the phenomenological eddy viscosity characterizing the effects of turbulence depends on the turbulent kinetic energy K and the dissipation function ϵ, which are mainly related to the fluctuations of the velocity field and of its gradient. In superfluid helium, instead, we consider the necessary coefficients for describing the effects of classical and quantum turbulence, involving fluctuations of the velocity, the heat flux, and the vortex line density of the quantized vortex lines. By splitting the several fields into a time-average part and a fluctuating part, some expressions involving the second moments of the turbulent fluctuations appear in the evolution equations for the average quantities. As in the K−ϵ model, a practical way of closing such equations is to tentatively express such fluctuating terms as a function of the average quantities. In this context we propose how the turbulent coefficients so introduced could depend on the second moments of the fluctuations of v, q and L (respectively denoted as K, Kq and KL), and on their respective dissipation functions (related to the second moments of their gradients) ϵ, ϵq and ϵL.

In this paper we perform the first numerical comparison between the two main existing models of superfluid helium: the two-fluid model proposed by Landau and the one-fluid extended model proposed from the extended thermodynamics. The numerical experiments in this paper regard the profiles of the so-called normal and superfluid components in 2D counterflow turbulence.

In this paper we go ahead in our studies on refrigeration of nanosystems by superfluid helium, as an appealing subject for future applications to computers or astronautical precision nanodevices. We first recall the effective thermal conductivity in laminar counterflow superfluid helium through arrays of mutually parallel cylinders and we discuss the conditions for the appearance of quantum turbulence around the heat-producing cylinders. We then consider the cooling of an array of heat-producing cylindrical nanosystems by means of superfluid-helium counterflow. We discuss the upper bound on heat removal set by avoidance of quantum turbulence and avoidance of phase transition to normal He I, for arrays of cylinders placed between two infinite insulating plates and with heat flowing in the two dimensions parallel to such plates.

Gli studi organizzativi insegnano che per comprendere nel dettaglio il funzionamento di un organismo occorre oltrepassare il livello prescrittivo delle norme e delle procedure che formalmente ne governano l’azione. Le strutture organizzative, infatti, raramente nascono e si sviluppano in maniera lineare, ma spesso evolvono e si affermano seguendo traiettorie complesse, a volte imprevedibili. Sulla base di tale consapevolezza, questo saggio si propone di ricostruire e commentare il percorso che ha portato alla nascita e al progressivo sviluppo della Struttura Tecnica per l’Organizzazione (S.T.O.), staff che svolge funzioni di supporto permanente alla VII Commissione del Consiglio Superiore della Magistratura.

Nonostante nel linguaggio di tutti i giorni siano utilizzati spesso come sinonimi, “cambiamento” e “innovazione” sono due processi organizzativi distinti. Come si evince dalla letteratura su questi temi (Daft 1978; Damanpour and Evan 1984; Damanpour 1996; Catino 2012), infatti, un’organizzazione cambia quando vengono introdotte idee o comportamenti già esistenti, mentre innova nel momento in cui vengono superati l’ordine vigente e le convinzioni radicate nel corso del tempo. Innovare, dal latino novare, significa abbattere la tradizione, la sfera del “si è sempre fatto così”, per esplorare nuovi percorsi e modi di agire fino ad ora sconosciuti.