IDENTIFICAZIONE DI MODELLI DI ATTRITO NELLE VALVOLE PER LA DIAGNOSTICA DI LOOPS DI REGOLAZIONE

Sviluppo di una procedura di modellazione di un loop di regolazione industriale affetto da attrito nella valvola. Identificazione dei parametri caratteristici del sistema e quantificazione dell'attrito. Applicazione su dati industriali, per la verifica e la programmazione della manutenzione degli attuatori

Stiction Quantification: A Robust Methodology for Valve Monitoring and Maintenance Scheduling

Valve stiction is one of the most common causes of poor performance in control loops. This paper presents a procedure which allows stiction quantification. The technique permits one to estimate the unknown real stem position, and moreover, it does not need any process knowledge and requires only the data normally registered in industrial plants. It is pointed out that the real problem consists of the lack of knowledge about the true value of stiction. A general methodology is proposed to discard data for which quantification is very likely to give wrong indications and to restrict its application to appropriate cases. Simulations show that several sources of perturbations can be eliminated, thus improving the reliability of stiction evaluation. Results are confirmed by application to industrial data: a significant number of valves are analyzed for repeated acquisitions before and after plant shutdown. The proposed procedure seems to be a valid methodology to monitor valve stiction and to schedule and check valve maintenance

Process of communication in public accounting; Management of an accounting practice bulletin, MAP 21

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The antidote to the fear. The rhetorical genres as a link between literature and society. Examples from Italian literature

After a brief historical-methodological overview, this study is meant to prove that the theory of rhetorical genres (deliberative, judicial and epideictic), connected to that of the literary genres, offers scholars more insightful critical opportunities. The nouvelle rhétorique, applied to the analysis of rhetorical and literary genres, permits to unveil the argumentative dimension in literature. We have evaluated some passages of the Decameron and I promessi sposi [The Betrothed], two of the great classics of Italian literature, differing by historical settings, genres and contents. The two books have been analyzed from the rhetorical perspective. I promessi sposi [The Betrothed] may be interpreted as an instance of judicial genre, while the Decameron as deliberative and epideictic genres

The Counsel of the Fox. Examples of Counsel from the Commedia, Short Stories, Letters and Treatises

If the aim of argumentation is that of increasing acceptance of the orator's thesis (Perelman and Olbrechts-Tyteca 1969, 49), then the ultimate goal of counsel, a widespread argumentative practice within the genres of discourse as well as literature, is indeed persuasion. The subject of this essay—that is, the rhetoric of counsel—allows us to observe the interpretative richness of this element of the "new rhetoric" through examples offered by Dante, Giovanni Boccaccio, Lucrezia Borgia and Niccolò Machiavelli, straddling the late Middle Ages and the Renaissance, bridging the fi elds of literature and history

Identification techniques for stiction quantification in the presence of nonstationary disturbances

The paper presents a detailed comparison of different identification techniques applied to valve stiction quantification, possibly in the presence of nonstationary unknown disturbances. The control loop with sticky valve is modeled as a Hammerstein system, in which the nonlinearity is identified using enumeration of the parameters’ space. Five different techniques for identification of the linear model are compared in terms of achievable performance. In particular, the capability to cope with the presence of nonstationary disturbances is analyzed. The techniques allow one to estimate the unknown actual valve position (MV), without requiring any process knowledge, being based only on data which are usually recorded in industrial plants: controller output (OP) and controlled variable (PV). Simulations show that external perturbations can be tolerated, thus ensuring a reliable evaluation of stiction in practical situations where external disturbances are usually present. Models which incorporate a time varying additive nonstationary disturbance grant a better process identification and a more accurate stiction estimation in the case of disturbance acting simultaneously with valve stiction. However, simpler models are the best choice when stiction happens to be the only source of loop oscillation. Results are confirmed by application to real data: pilot plant data are used to corroborate the effectiveness of the techniques

LE NUOVE RETORICHE E LA LETTURA DEI CLASSICI ITALIANI. UNA LETTURA DEL DECAMERON CON FABRIZIO FRASNEDI

Il contributo associa ricordi personali di Fabrizio Frasnedi a una discussione scientifica, non solo delle sue opere, ma anche dell’orizzonte culturale in cui sono state prodotte. In particolare, non distinguendo mai del tutto l’uomo dal maestro, si rivivono con il lettore due lezioni di retorica svolte a Bologna dall’autore e da Frasnedi. Il ricordo personale riprende vita nell’esperienza didattica, nelle comuni predilezioni critiche, nella biblioteca mentale che permetteva di riconoscersi pur nell’orizzonte sempre mutevole della critica letteraria.   New rhetoric and the reading of the Italian classics. A reading of the Decameron with Fabrizio Frasnedi The contribution associates personal memories of Fabrizio Frasnedi with a scientific discussion, not only of his works, but also of the cultural setting in which they were produced. In particular, never completely distinguishing the man from the teacher, two rhetoric lessons held in Bologna by the author and Frasnedi are relived with the reader. Personal memory comes back to life in the didactic experience, in common critical predilections, in the mental library that allowed to recognize each other, even in the ever-changing field of literary criticism