1,720,966 research outputs found
“Influence of the forming process on the corrosion resistence of AA3103 aluminium pipes”
No full text“Frattura delle frese in chirurgia orale”
No full textObiettivo. Questo lavoro sperimentale nasce da una osservazione clinica. Lo scopo è quello di individuare eventuali fattori che possono contribuire a provocare la frattura delle frese più comunemente usate in chirurgia orale e quindi evitare eventuali rischi correlati a questa evenienza. Inoltre, si è voluto procedere anche alla caratterizzazione delle superfici di frattura al fine di ottenere dati su possibili difetti di fabbricazione o di stoccaggio, che possono alterare in qualche modo la struttura e quindi indebolirla.
Metodi. Sono stati esaminati quattro gruppi di frese chirurgiche tipo Lindemann, nuove, per un totale di 40 frese. Il primo gruppo è stato preso come controllo, gli altri tre sono stati sottoposti rispettivamente a 5, 10 e 20 cicli di sterilizzazione, preceduti da un lavaggio con disinfettante. Le frese di ciascun gruppo sono state poi sottoposte alla prova meccanica a flessione a quattro punti per provocarne la rottura. Le superfici di frattura sono state poi studiate al SEM, comparandole alle frese rotte durante gli interventi chirurgici.
Risultati. Le frese nuove non presentavano alcun difetto di lavorazione. Non è stato evidenziato alcun attacco corrosivo ad opera dei processi dei lavaggio e sterilizzazione.
Conclusioni. Le prove meccaniche e micrografiche non hanno messo in evidenza differenze significative tra i diversi gruppi
Porous titanium obtained by a new powder metallurgy technique:preliminary results of human osteoblast adhesion on surface polished substrates
No full textVacuum 3D printing of highly filled polymeric matrix composites
Get PDFIn this contribution, we have investigated how polymeric matrix composites for aerospace applications are affected, when fabricated at low pressure, by the additive manufacturing process. Commercial filaments have been selected based on their representativeness of materials derived from lunar resources. Standard samples of thermoplastic polymers reinforced by organic fibers and inorganic fillers have been printed inside a vacuum chamber, and their mechanical and thermal properties have been characterized and discussed based on the printing conditions. The reported study represents a preliminary investigation of the potential applicability of the 3D printing technology on highly filled polymers for extraterrestrial applications
Wear mechanisms and residual stresses in alumina-based laminated cutting tools
No full textThe outstanding performances of the Al2O3 cutting tools in terms of potential cutting speed can lead to substantial economies in the machining of metallic materials. Nevertheless, their widespread use is limited by some drawbacks such as the tendency to edge chipping and to the propagation of microcracks, which can lead to premature failures. These shortcomings are due to the intrinsic low toughness of the ceramic material, which is in turn related to its characteristics non-metallic bonds. A well-recognised method of increasing the toughness of brittle materials is the introduction of surface compressive stresses, which can be obtained through a suitable lamination geometry of the tools as consequence of the different coefficients of thermal expansion (CTE) of the constituent layers. The performances of an alumina/zirconia laminated cutting tool used for machining steel have been investigated and compared to those of a non-laminated commercial alumina/zirconia cutting tool. The different wear mechanisms are explained on the basis of the different microstructures and chemical compositions. We have shown that residual compressive stresses, measured by Piezo-Spectroscopy, are effective in avoiding the microchipping on the flank zone but cannot avoid larger fractures caused by the residual porosity. (c) 2004 Elsevier B.V. All rights reserved
Tailoring 3D printed cellulose acetate properties produced via direct ink writing: Densification through over-extrusion and evaporation rate control
Get PDFIn this study, we conducted a comprehensive experimental campaign aimed at controlling the final properties of 3D printed cellulose acetate. We equipped a commercial printer with a peristaltic pump to be able to print in a continuous fashion by means of the Direct Ink Writing technique. We investigated the effect of ink concentration and printing parameters on the density, mechanical and functional properties of printed objects. Furthermore, water absorption tests demonstrated the hygroscopic behavior of cellulose acetate, with higher water content in samples with lower densities. The diffusion of water within the polymer network followed Fickian diffusion, with the diffusion coefficient influenced by the density of samples. Overall, this study highlights the importance of printing conditions in achieving desired properties in 3D printed cellulose acetate. The ability to fine-tune the mechanical properties and water absorbance of 3D printed cellulose acetate makes it promising for applications in plant science and bioengineering. Highlights: Cellulose acetate has been 3D printed via Direct Ink Writing. The shear-thinning behavior allows for shape retention during printing. Density of printed samples is strongly controlled by printing parameters. Density of printed parts influences mechanical properties and water absorption
A Proof of Concept of Self Replicating Robots for Space Settlements
No full textEfficient agriculture in a hazardous environment is an essential factor for space settlement. At the same time, transporting resources for settlement is very expensive and, to a certain extent, impracticable. It is therefore necessary to find techniques and tools to exploit resources on site. The aim of the project presented in this paper consisted in realizing a partially Self Replicating mobile Robot (SRR) that can monitor and helping to cultivate plants. The fibers of the plants have been used to build the frame of another SRR. This way, except for the electronic components, it was possible to replicate the robot through cultivated plants. In particular, it was possible to replace the weight of the new robot of 30%
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
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