1,720,984 research outputs found
Feasibility analysis and characterization of an extrusion-based AM process for a two-component and biocompatible silicone
No full textSilicone is a very widespread material with important applications especially in the medical field. Currently, Additive Manufacturing (AM) is a promising technology for the fabrication of custom products and some commercial machines are available on the market for processing biocompatible silicone. Although, no scientific literature is available on the characterization and control of the process. Given the research challenge, this work presents and investigate a novel process for 3D printing of biomedical silicone. An ad hoc equipment was realized and integrated with the Fab@Home 3D printer in order to thermally control the extrusion process of the silicone. Then, the equipment was characterized and used to study the feasibility of the process and the influence of the process parameters (Deposition Rate, Path Speed, Temperature). Quality control charts and Design of Experiments methods were used to study the stability of the process and to statistically evaluate the influence of the process parameters. Results brought to the definition of a process feasibility window and to a numerical model able to predict the dimension of the printed layer as a function of the tested parameters. A technique for the AM of biomedical silicone parts was developed and characterized. In particular, results furnish a fundamental knowledge for the control of the process. The biomedical field is one of the main target, particularly the fabrication of custom medical devices
Characterization and optimization of the hydroforming process of AISI 316L steel hydraulic tubes
No full textHydroforming is a metal forming technology that enables the fabrication of complex parts in a low cycle time. The process is based on the plastic deformation of a blank sheet using a pressurized fluid. This paper focuses on the design of a tube hydroforming (THF) process to replace the current cut-and-weld practice for components produced by a company. Specifically, the study focuses on the characterization and optimization of the THF process for stainless steel T-joint parts produced in two sizes: small and large. The new production must improve the final components’ quality and maintain the technical requirements of the previous one, especially in terms of the parts’ geometry (in particular, the third branch minimum height and thickness) and material (AISI 316L), with competitive production costs. Accordingly, the process optimization is performed in three sequential steps. Initially, the process is characterized by the material flow stress and the friction between a tube and die. Subsequently, this information is used to develop a finite element method (FEM) model, which is validated based on experimental data. The FEM is used to optimize the process parameters (pressure, stroke, and trust force of the counterpunch) to improve the final component quality and guarantee the specific dimensional requirements. Finally, further improvements of the process are implemented (initial precrash of the tube, optimal length of the blank tube, and calibration pressure to avoid wrinkles in the final component). After the THF process optimization, emphasis is placed on the punch geometry. A study is conducted to avoid stress concentrations that may cause punch breakage. The results of this study allow the minimization of tube thinning during the hydroforming process, and guarantee the target value for the third branch height with minimal material consumption. Moreover, the evaluation of different geometrical alternatives allows the stresses acting on the punches to be reduced by 45%
Design and fabrication of customized tracheal stents by additive manufacturing
No full textAdditive Manufacturing (AM) is already becoming part of our life from a technological, economic and social point of view. Nowadays, it is applied in several manufacturing sectors. In particular, AM shows huge opportunities in the medical field and for healthcare applications. Due to its capability to produce complex geometries directly working on medical 3D images and thanks to the possibility to 3D-print biocompatible materials, AM is a key technology for the fabrication both of external and internal medical devices. In particular, the use of AM for medical applications is typically articulated in three steps: 3D-scanning of the patient anatomy, segmentation the medical scan and elaboration through CAD software for the preparation of a STL file suitable for the AM process. One of the main research topic in this field is the definition and optimization of procedures that, taking precise data from an individual patient, could be applied to the design and fabrication of customized components for medical applications. Therefore, this paper presents a project aimed at the fabrication of customized tracheal stents starting from the actual patient anatomy. In particular, it follows an approach based on molds FDM fabrication followed by biocompatible silicone casting. Molds were designed to obtain a tracheal stent based the patient anatomical tracheal lumen and were fabricated using FDM technology. Moreover, since the surface roughness is one of the most critical aspects related to the FDM, the produced molds were finished with a chemical surface post-treatment based on the use of acetone vapours. Overall, the whole developed procedure results in an effective custom-made medical devices realization
A study on tool wear for micromilling process
No full textMechanical production greatly changed among the last decades. Nowadays, the need of higher accuracy and precision even for small details on the finished product makes micromachining a fundamental technology that can fulfill modern industry requirements. Micromilling is one of the most important and widespread microtechnology. This process is characterized by a great precision level even when high strength materials are machined. The understanding of tool deterioration and breakages causes is one of the main research challenges in micromilling field. Mechanisms that underlies these phenomena are different from those observed in conventional milling processes. The definition and the prediction of the tool-life are regulated by the ISO-8688 standard (part 1 and 2) for conventional milling process, but this standard actually is not referred to micromilling and a dedicated regulation has not been compiled yet. Therefore, this research work aims to investigate tool wear in micromilling process, in order to deepen the knowledge and better understand causes and mechanisms that lead to tool failure. Results are particularly focused on the correlation between flank wear and cutting force, and represents a base for a more complete study in this field aimed to provide fundamental knowledge for the development of a future standard that can fill the normative gap in tool-life criterion for micromilling processes
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
L'analisi del colloquio clinico con più strumenti di ricerca sul processo terapeutico
No full textIn questo capitolo presenteremo una integrazione di tre diversi strumenti di analisi del colloquio clinico: il Tema Relazionale Conflittuale Centrale (C.C.R.T.) di Luborsky (Luborsky & Crits-Christoph, 1992), il Triangolo Drammatico (T.D.) di Karpman (Karpman, 1968) e l’Attività Referenziale (A.R.) della Bucci (Bucci, 1997, Bucci & Kabasakalian-McKay, 1992).
Dopo una breve descrizione teorica dei metodi analizzeremo le motivazioni che ci hanno portato a sostenerne un loro utilizzo integrato.
In ultima riporteremo uno studio empirico al fine di poter valutare come l’impiego simultaneo di questi strumenti favorisca un’analisi multidimensionale del colloquio e quindi del processo psicoterapeutico
Variations 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
- …
