On the asymptotic behavior of the quasi-static problem for a linear viscoelastic fluid

In this paper we study the quasi-static problem for a viscoelastic fluid by means of the concept of minimal state. This implies the use of a different free energy defined in a wider space of data. The existence and uniqueness is proved in this new space and the asymptotic decay for the problem with non vanishing supplies is obtained for a large class of memory kernels, including those presenting an exponential or polynomial decay.Comment: 6 page

Digital manufacturing in fiat group automobiles: virtual simulations for preliminary ergonomics optimization of workcells in the design phase of a new car model

New standards on work organization in the automotive industry, require a new concept of design methods: the human centred process. In Fiat Group Automobiles (FGA) the “Digital Manufacturing” (DM) project has started with the goal to create simulation tools and methods to improve the design of new cars’manufacturing processes giving a special attention to manual operations. The DM approach is based on a detailed “virtual plant” where virtual mannequins interact with digital models of car’s components, equipment, containers, etc. in order to simulate and improve working conditions with many benefits on ergonomics, safety, final product quality, work organization and general production costs. The key factor for this approach is that with DM methodologies, designers and engineers have, already in the design phase of a new car’s manufacturing process, a preliminary estimation of the numerical indices used in the plants to check if workcells are compliant to international standards and regional safety laws. In this way the most important ergonomic indices (like Niosh, Snook & Ciriello, EAWS, etc.) become a “design tool” that allow to change/improve project solutions (designing easy and comfortable work tasks, equipment, tools, etc.) and to distribute the work load in an optimal way between workers

Comparative assessment of strut models for the modelling of in-plane seismic response of infill walls

The influence of infills on the seismic response of frame structures has long been recognised. Typically, stiffness and strength of the infill and connections between infill and frame are such that the infill affects the global seismic behaviour of the structure. Hence, the presence of infills should be considered in the analysis and design of new buildings and in the seismic assessment of existing ones. To this aim, simple models for infill walls, such as the equivalent diagonal no-tension strut model, have been developed in the last decades. The objective of the present study is to assess the validity of different strut models. To this aim, 162 experimental tests available in the literature are considered. The data set includes both reinforced concrete and steel frames, as well as confined masonry structures. The mechanical characteristics of masonry and the boundary conditions between frames and infills of the test specimens take into account a large set of situations, reflecting the great variability in the materials and in the construction techniques adopted in different countries. Moreover, the type of tests and the related results are not uniform; in some cases monotonic experiments are performed, whereas in other cases cyclic tests are carried out. As expected, the presence of different types of infill-frame systems results in a large scatter of the data. However, the comparison between experimental results and predictions show that, on the average, the infill strength can be adequately estimated by resorting to the strut model whereas major uncertainties are found for the stiffness prediction

An investigation on the b quark mass

In this article I will review the measurements of the b quark mass performed by ALEPH and DELPHI and presented at the HEP99 Conference in Tampere. Very clean effects of the mass running are observed, even if a wide spread in the results and large systematic errors due to hadronization corrections prevent to extract an average value of the running b quark mass.Comment: 3 pages, 1 figure

TECNOLOGIE FOTOVOLTAICHE PER LO SVILUPPO SOSTENIBILE. Analisi del ciclo di vita, convenienza energetica, diffusione delle utilizzazioni, futuri scenari

Viene descritto il ciclo di vita di un’installazione fotovoltaica tipo con moduli a celle in silicio cristallino a contatti stampati. La trattazione è condotta tenendo conto della metodologia LCA (alla quale sono dedicati due paragrafi di approfondimento) ed è divisa in due parti: la prima è dedicata ai processi prettamente industriali, divisi in dieci fasi consecutive, dall’estrazione delle materie prime al riciclaggio, ed è corredata di opportuni bilanci; la seconda riguarda tematiche connesse. Vengono descritte le più importanti tecnologie FV sviluppate, ad ognuna delle quali è dedicato un paragrafo. Segue uno sguardo alle diffusione e agli impieghi del fotovoltaico, con un accenno alla sua potenzialità e possibili sviluppi. Per completezza sono inclusi una breve storia delle tecnologie FV e la descrizione dell’effetto fotovoltaico