1,721,006 research outputs found
PHYSICO MECHANICAL CHARACTERISATION OF FILLERS FOR NAVAL APPLICATIONS
No full textThe term “filler” does not define a specific product, but an entire class of composite materials used to fill surface imperfec- tions. Until recently the filler was used only to treat the surface imperfections. Currently, it has several aims like sanding, filling, levelling, protecting and insulating the substrate. In the marine field its main purposes are: insulate the surface, improve the surface finish and prepare it for the next painting treatments.
The mechanical properties of fillers are fundamental to ensure the integrity of the painting systems which must be able to withstand the deformations suf- fered by the vessel.
In fact the hull undergoes different stres- ses and deformations depending on the point where it is considered (bulb, rudder, keel, topsides or superstructure), the spe- cific condition to which it is subjected (stationary or sailing) or the material of construction (aluminium, steel, wood or glass-reinforced plastic).
In the frame of the technological evolu- tion of materials, fillers underwent a remarkable development through the use of products such as epoxy resins that are, in modern formulations, very simple to use, differently from other ma- terials used in nautical field (polyester, vinylester and polyurethanes) and com- bine enhanced performance and versa- tility. Their mechanical, physical, electri- cal and thermal properties can be tailo- red with the addition of inert fillers like microfibers, phenolic microspheres, glass microspheres and colloidal silica. In particular, the glass microspheres are hollow spheres with diameters in the micrometer range.
They generally improve the hardness of the surface.
When they are mixed with epoxy resin produce a material extremely tenacious, slightly elastic and difficult to break. The phenolic microspheres are hollow spheres with diameters in the microme- ter range. They are very light and gene- rally improve the tenderness of the sur- face. The microspheres mixed with epoxy resin produce a material slightly hard, brittle, easy to work with abrasi- ves. For this reason the phenolic micro- spheres are used for the preparation of fillers particularly easy to be sanded but extremely waterproof.
The microfibers are microscopic frag- ments of a material and are able to thic- ken the resin and, once hardened, to act as “reinforcement” of the resin itself. Then the mix of epoxy resins with micro- fibers produces a tenacious, elastic material hard to break. For this reason microfibers are used for the preparation of adhesives able to join the surfaces fil- ling all the gaps between them.
The colloidal silica is a powder that has the property to make more dense the epoxy resin. It is used exclusively as a thic- kener in combination with other inert exten- ders to produce an high density filler.
In this work the evaluation of the physi- cal and mechanical properties of various commercial fillers is presented.
The morphological analysis of their structure is used to try to determine the influence of various components on their final properties
Coating a cracking concrete
No full textLe superfici in calcestruzzo si fessurano a causa della bassa resistenza a trazione del materiale: quando viene superata la sua capacità di deformazione, possono formarsi microcavillature, cavillature, fessurazioni o crepe che deturpano esteticamente il manufatto o ne riducono le caratteristiche di funzionalità, sicurezza e igiene.
La sollecitazione a trazione che è all’origine di questo fenomeno degradativo deriva da fattori relativi al calcestruzzo, quali resistenza a trazione, modulo di elasticità, scorrimento viscoso, e da fattori relativi alle condizioni di posa ed esercizio, quali grandezza della deformazione libera, grado di impedimento che si oppone alla deformazione, distribuzione delle sollecitazioni
Resinous coatings for ship decks
No full textTeak wood is known for its resistance against natural conditions. It is impervious to the effects of snow, ice, rain, sun, heat, cold, and humidity and withstands weather better than any other wood. That is one of the big reasons that teak wood is chosen for ship decks. But the increasing demand of cruises is leading to bigger ships, then lighter and cheaper materials than teak are needed for deck flooring. A valid solution is the use of resinous coatings, which, moreover, provide a range of aesthetic effects that cannot be obtained with traditional materials. The typical system is composed by a primer, an undercoat and a topcoat. Some problems may arise in the application of the different layers: 1) overcoating time for the primer and the undercoat; if too much time passes between the application of the different coats, adhesion problems can occur. 2) thixotropy-paint flow balance for the undercoat; adequate film build and ease of application are as necessary as levelling and lack of films defects. Regarding the first point, this paper reports some studies on the superficial characteristics of polyurethane primers and undercoats: the evaluation of the presence of residual –OH /–N=C=O groups as a function of application time was performed by FT-IR/ATR spectroscopy and measurements of water-contact angle. The obtained results were related to the adhesion properties of the syste
Quantitative evaluation of oxide impurities in bright annealed stainless steels for deep drawing
No full text
Resinous coatings for ship decks
No full textTeak wood is known for its resistance against natural conditions. It is impervious to the effects of snow, ice, rain, sun, heat, cold, and humidity and withstands weather better than any other wood. That is one of the big reasons that teak wood is chosen for ship decks. But the increasing demand of cruises is leading to bigger ships, then lighter and cheaper materials than teak are needed for deck flooring. A valid solution is the use of resinous coatings, which, moreover, provide a range of aesthetic effects that cannot be obtained with traditional materials. The typical system is composed by a primer, an undercoat and a topcoat. Some problems may arise in the application of the different layers: 1) overcoating time for the primer and the undercoat; if too much time passes between the application of the different coats, adhesion problems can occur. 2) thixotropy-paint flow balance for the undercoat; adequate film build and ease of application are as necessary as levelling and lack of films defects. Regarding the first point, this paper reports some studies on the superficial characteristics of polyurethane primers and undercoats: the evaluation of the presence of residual –OH /–N=C=O groups as a function of application time was performed by FT-IR/ATR spectroscopy and measurements of water-contact angle. The obtained results were related to the adhesion properties of the syste
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analisi quantitativa della presenza di impurezze sulla superficie di nastri in acciaio inox per profondo stampaggio
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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