1,721,519 research outputs found
Filosofia e tecnologie digitali: un approccio fenomenologico
No full textThe present paper assumes the phenomenological method with the aim of outlining a philosophical understanding of our symbiotic and synergetic in-teraction with current technologies by trying to reflect on both the computational and the bodily aspects inherent in the term “digital” at one and the same time. In the first section the scope of the inquiry is to be clarified, drawing on the structural and fruitful ambivalence of the digital. Furthermore, the phenomenological account of the embodiment is discussed as a suitable lead in order to understand our relationship with digital technologies. The last section, then, lists a number of issues that the philosophical research has to face while approaching the tentative interpretation of the techno-ecosystem in which such a relationship continuously evolves
A new technique for the characterization of viscoelastic materials: Theory, experiments and comparison with DMA
No full textIn this paper we present a theoretical and experimental study aimed at characterizing the hysteretic properties of viscoelastic materials. In the last decades viscoelastic materials have become a reference for new technological applications, which require lightweight, deformable but ultra-tough structures. The need to have a complete and precise knowledge of their mechanical properties, hence, is of utmost importance. The presented study is focused on the dynamics of a viscoelastic beam, which is both experimentally investigated and theoretically characterized by means of an accurate analytical model. In this way it is possible to fit the experimental curves to determine the complex modulus. Our proposed approach enables the optimal fitting of the viscoelastic modulus of the material by using the appropriate number of relaxation times, on the basis of the frequency range considered. Moreover, by varying the length of the beams, the frequency range of interest can be changed/enlarged. Our results are tested against those obtained with a well established and reliable technique as compared with experimental results from the Dynamic Mechanical Analysis (DMA), thus definitively establishing the feasibility, accuracy and reliability of the presented technique
Indenting viscoelastic thin layers: A numerical assessment
No full textNormal indentation of viscoelastic bodies is a technique widely employed to characterize the viscoelastic material properties. Here, a numerical Boundary Element methodology is developed to model the indentation process also when the solids in contact are thin layers. Specifically, two boundary conditions for the thin slabs are considered: the case of a confined layer, perfectly bonded to a rigid substrate, and that one of a free layer, supported by a constant pressure. Numerical analyses focus, firstly, on creep and relaxation indentation tests and show that finite values of the contacting layers thickness produce dramatic quantitative changes in comparison with what obtained under the half-plane (HP) assumption. Similar effects are found also in the case of loading and deformation indentation cycles: this results crucial for vibrational phenomena and confirms the opportunity of introducing the numerical technique here presented
Vibration-based identification of mechanical properties of viscoelastic materials
No full textRecent scientific advancements in field of automotive, electronics, micromechanical systems, pipe technologies, have led to new technologies where the use of lightweight, tough, soft and high deformable materials has become ubiquitous. In this scenario, viscoelastic materials have spread in many different contexts, from seals to bio-inspired adhesives, because of their superior damping and frictional properties. For an appropriate use of such materials, however, the proper knowledge of their mechanical properties is a basic requirement. In this paper we present an innovative easy-to-use approach for determining the viscoelastic modulus, based on the experimental vibrational identification of viscoelastic beams of different lengths. A very simple setup and instrumentation are utilized for acquisitions, and an accurate analytical model of the beam is considered to determine the viscoelastic modulus, which takes into account multiple relaxation times of the material
On the Role of Roughness in the Indentation of Viscoelastic Solids
Full text linkA numerical boundary element methodology is employed to understand how fractality intervenes when a 1D rigid rough profile indents a linear viscoelastic half-plane. The focus is, in particular, on the viscoelastic dissipation and how this is influenced by the profile statistical parameters, namely, the mean square roughness h(rms) of the profile, the mean square slope m(2) and the Hurst exponent H. Our numerical investigation, properly supported by a dimensional analysis, reveals that, in the one-dimensional case under investigation, the leading role is played by h(rms) and, thus, mainly by the large scales of the rough spectrum. Clearly, on an experimental level, this implies that a simple measure of the roughness parameter h(rms) is sufficient to determine the viscoelastic dissipation
La questione del mondo nei primi corsi friburghesi di Martin Heidegger
No full textI corsi che Martin Heidegger tenne dal 1919 al 1923 a Freiburg i.B. mostrano fin dal loro esordio il ruolo determinante dell’esperienza del mondo e dell’evento di significatività che ad essa corrisponde. Il libro ripercorre i documenti di questo periodo seguendo il filo conduttore del mondo della vita (Lebenswelt), tema che accompagna il lavoro di rinnovamento della fenomenologia, inteso dal giovane docente come un approfondimento critico della via tracciata da Husserl. Ambiente, collettività e ipseità sono le tre coordinate del mondo della vita prese in esame dalla ermeneutica della vita fattizia sviluppata in questi anni di intensa sperimentazione che getta le basi per "Essere e Tempo" (1927). Preparate nei primi anni friburghesi e rielaborate nel successivo periodo marburghese, l’analitica esistenziale del Dasein e la questione dell’essere che la guida si generano infatti lungo la traiettoria aperta da quella iniziale fenomenologia ermeneutica del mondo della vita, tesa tra l’evento impersonale del mondo e l’esistenza che in esso si dischiude, afferrata nella sua autenticità.The lecture courses that Martin Heidegger held from 1919 to 1923 in Freiburg i.B. demonstrate the decisive role of the experience of the world and the related event of significance. The book retraces the documents of this period, following the notion of “Life-world” (Lebenswelt). Such a theme fosters a renewal of phenomenology, understood by the young philosopher as a critical insight into the path traced by Husserl. Environment, Collectivity, and Self are the three coordinates of the Life-world, which Heidegger takes into account in order to establish the hermeneutics of the factical life. The book argues that these years of intense experimentation pave the way to “Being and Time” (1927) and that both the existential analytic of Dasein and the question of being stem from this fecund period of phenomenological inquiry into the impersonal event of the world and the existence grasped in its authenticity
Il laboratorio della regolazione dei servizi idrici, in Il regime dell’acqua e la regolazione dei servizi idrici. Annuario di diritto dell’energia 2017, a cura di L. Carbone, G. Napolitano, A. Zoppini, Bologna, il Mulino, 2017, 391-394.
No full textAdhesion and friction of an elastic half-space in contact with a slightly wavy rigid surface
No full textThe paper deals with the estimation of the pressure distribution, the shape of contact and the friction force at the interface of a flat soft elastic solid moving on a rigid half-space with a slightly wavy surface. In this case an unsymmetrical contact is considered and justified with the adhesion hysteresis. For soft solids as rubber and polymers the friction originates mainly from two different contributions: the internal friction due to the viscoelastic properties of the bulk and the adhesive processes at the interface of the two solids. In the paper the authors focus on the latter contribution to friction. It is known, indeed, that for soft solids, as rubber, the adhesion hysteresis is, at least qualitatively, related to friction: the larger the adhesion hysteresis the larger the friction. Several mechanisms may govern the adhesion hysteresis, such as the interdigitation process between the polymer chains, the local small-scale viscoelasticity or the local elastic instabilities. In the paper the authors propose a model to link, from the continuum mechanics point of view, the friction to the adhesion hysteresis. A simple one-length scale roughness model is considered having a sinusoidal profile. For partial contact conditions the detached zone is taken to be a mode I propagating crack. Due to the adhesion hysteresis, the crack is affected by two different values of the strain energy release rate at the advancing and receding edges respectively. As a result, an unsymmetrical contact and a friction force arise. Additionally, the stability of the equilibrium configurations is discussed and the adherence force for jumping out of contact and the critical load for snapping into full contact are estimated
Pensare altrimenti la storia dell’essere. Aporie dell’ontoteologia di Levinas
No full textDove possiamo rintracciare un’altra intelligibilità per Dio che non lo confonda con l’essere e la sua storia? È questa la domanda che sta alla base dell’opera decisiva di Emmanuel Lévinas Altrimenti che essere o al di là dell'essenza (1974). Come ricorda lo stesso Lévinas in quelle pagine, da un lato la ricerca non avrebbe senso se mancasse di comprendere come il sapere ontologico, traducendolo nell’essere, induce Dio a tradirsi in un tema per la filosofia stessa, dall’altro è proprio nella razionalità del discorso ontologico che l’etica – la relazione privilegiata con l’Altro – dovrà attingere per poter anche solo provare a dire l’altrimenti che essere.
Tale razionalità è rivendicata dal discorso stesso che intende relativizzarla, quello sull’al di là dell’essere. Ma di quale metodo può avvalersi l’etica di Lévinas per intendere Dio indipendentemente da ogni ontologia come da ogni teologia da questa dipendente? Propriamente e solamente del metodo fenomenologico, massima e sincera espressione del «pleonasma» della razionalità greca che domina la storia dell’ontologia. L’articolo si inserisce nel mezzo dell’aporia cui va incontro una simile scelta. Non è forse contraddittorio mettere in discussione la supremazia dell’ontologia in un discorso che, direttamente o meno, non smette e non può smettere di ricorrere all’ontologia, confermandone la sovranità? E soprattutto: quale prospettiva storica deve assumere l’etica? O, in altri termini, in che modo il tentativo di Lévinas si inserisce nel quadro della struttura ontoteologica della metafisica descritta da Heidegger?
Esattamente invertendo il rapporto tra Dio e l’essere che vige nella storia della metafisica. Al contrario di Heidegger, per Lévinas è la storia dell’essere che si svolge entro la traccia lasciata dall’assenza di Dio che – a differenza dell’essere – non si è mai fatto presenza. Questa inversione però provoca un cortocircuito, dal momento che solo a partire dalla prospettiva della Seinsgeschichte Heidegger ha potuto mettere a nudo la struttura ontoteologica della metafisica e cominciare a domandare di Dio. Di questi problemi si occupa l’ultimo lavoro di Didier Franck L’un-pour-l’autre. Levinas et la signification (ed. P.U.F., 2008). L’articolo porta al lettore italiano per la prima volta l’attenzione su questo studio (ancora inedito in Italia), che si impegna a decostruire le basi fenomenologiche dell’etica levinasiana, mettendone in luce tanto i problemi insoluti quanto le loro ragioni
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