arXiv subjects
Publications and source records attributed to Pier Franco Nali.
Lima and Monteiro [1] derived the buoyant force in a nonuniform gravitational field by applying a gradient version of the divergence theorem to the surface integral of the pressure forces [2]. Here it is outlined an alternate approach in the framework of fluid mechanics, based on the energy formulations of the equations of state for compressible fluids.
The purpose of this paper is to prove directly, by an elementary method, the Poisson probability law. This proof is offered as an alternative to the more usual derivation from binomial distribution in the limit of small probabilities. The same proof is then applied to the solution of a problem in statistical mechanics. --- Lo scopo di questo articolo è dimostrare direttamente, con un metodo elementare, la legge di probabilità di Poisson. Questa dimostrazione è proposta in alternativa alla più consueta derivazione dalla distribuzione binomiale nel limite delle piccole probabilità. La stessa dimostrazione viene quindi applicata alla soluzione di un problema di meccanica statistica.
Popularized explanations of the color of the sea often prove to be incomplete or oversimplified, and hence inadequate to become acquainted with the phenomenon in its whole. In this paper, after a historical review of the investigations on the subject in recent centuries and a brief account of the current state of knowledge, the topic is addressed in a more rigorous way adopting a comprehensive and multidisciplinary viewpoint. A phenomenological model providing operational results in educational context is proposed. --- Le spiegazioni del colore del mare proposte a scopo didattico o divulgativo si rivelano spesso incomplete o eccessivamente semplificate, e dunque inadeguate alla comprensione della totalità del fenomeno. In questo articolo, dopo una rassegna storica delle indagini sull'argomento negli ultimi due secoli e un accenno allo stato attuale delle conoscenze, il problema viene affrontato in modo più rigoroso adottando un punto di vista comprensivo e pluridisciplinare. Viene proposto un modello fenomenologico in grado di fornire risultati operativi in contesto didattico.
Imaginary assemblies of intercommunicating bottles-or boxes, in which marbles circulate performing random walks, can help modeling (and hence understanding) slow and long-lasting diffusion processes and enable easy evaluations of typical times involved in their dynamics. Compared to the more traditional approaches to explaining diffusion inspired by the Ehrenfest's urn problem, these simple random walk models offer a more straightforward way to illustrate irreversibility/recurrence issues.