1,720,984 research outputs found
Fatigue Prediction by Thermographic Method of Aluminum Alloy 6082 Panels: Comparison between FSW and MIG Welding
No full textThis paper is focused on the fatigue behaviour of aluminium alloy welded joints, which can represent points of weakness in the ship structure. The traditional methods of fatigue assessment of welded joints have some limitations, and are extremely time consuming. In order to overcome these difficulties, the Risitano's method, based on thermographic analysis, has been applied to predict the fatigue behaviour of welds. Experimental tests have been carried out to assess and compare the fatigue capability (S-N curves, endurance limits) of different welded joints, obtained by means of Friction Stir Welding (FSW) and Metal Inert Gas welding (MIG). Fatigue predictions obtained resorting to the Thermographic Method (TM) show a good agreement with those derived from the traditional procedure. Thus, TM proves to be a powerful tool also for the characterization of the mentioned kind of welded joints
Thermographic Method for Fatigue Prediction of Friction Stir Welded Light Alloy Panels in Shipbuilding
No full textThis paper is focused on the fatigue behaviour of aluminium alloy welded joints, which can represent regions of weakness in the ship structure. The traditional methods for fatigue assessment of welded joints have some limitations, and are extremely time consuming. In order to overcome these difficulties, the Risitano’s method, based on thermographic analysis, have been applied to predict the fatigue behaviour of welds. Experimental tests have been carried out to assess and compare the high-cycle endurance limits of different welded joints, obtained by means of Friction Stir Welding (FSW) and MIG techniques. The results obtained resorting to the Thermographic Method (TM) show a good agreement with those derived from the experimental data, represented through S-N curves
Parametric analysis of the strength in the ''Toronto'' osseous-prosthesis system
No full textAIM: The aim of this work is to analyze how the different distributions of the chewing load could be related to dental prosthesis fractures of the Toronto restoration via the fulfilment of a virtual parametric model. Moreover investigation about implant positions and perspectives in comparison with a virtual medial plane was made to evaluate the incidence of screw and prosthesis breakage. METHODS: Finite element analysis of the lower jaw was performed to underline parameters and mechanical features of dental implants connected with the fractures of the prosthetic restoration. Jaw virtual model and 3D fixtures (Global Sweden and Martina) were created by Cosmos-Solid Works. Matlab was used to recreate the distribution of an unspecific chewing phase analyzing the overall load on the fixtures of the lower jaw. RESULTS: Four virtual 3D models were performed with Matchad 14, for data analysis. The study investigated frontal and horizontal planes and vertical direction of the occlusal forces. Data results showed how position and perspective of fixtures strongly influenced the stress distribution upon the bone of the jaw; safeguard of prostheses elements like cantilever, passing screws, and dental implants are strictly related to a correct selection of the dental implant position. CONCLUSIONS: The 3D geometry of the jaw is an important condition for the choice of position, number, diameter and length of dental implants used for Toronto prostheses. This study would suggest a virtual ''method'' to help the surgeon choosing a correct model for a prosthetic rehabilitation evaluating position, perspective, and stress distribution of the chewing strengths
Cemented-retained vs screw-retained implant restorations : an investigation on 1939 dental implants
No full textAIM: The aim of this work was to present a comparison of screw-retained and cemented-retained implant prostheses based on a retrospective analysis of 1 939 dental implants. The advantages, disadvantages, and limitations of those two different types of dental restorations are discussed and compared with the recent international literature. It is important to underline the influence of the attachment mechanism on many clinical aspects of implant dentistry. METHODS: A group of 527 patients was analyzed. All of the patients required implant rehabilitation. 1 939 dental implants were positioned between January 1997 and December 2003. RESULTS: The analyzed clinical trials show the presence of several factors essential to the long-term success of any implant prosthesis. Aesthetic, retrievability, passivity of framework, occlusion, ease of fabrication and cost and retention. In this study, 762 cemented dental prostheses were used for 1 551 dental implants placed. The survival rate of this rehabilitation was 98.4 % with an average of 34.7 month follow-up; 84 screwed-dental prostheses were placed on 330 dental implants. The success percentage of this type of prostheses was 100% with an average of 44.3 month follow-up. CONCLUSION: Cemented-implant prosthesis and screw-retained implant prosthesis analyzed in this investigation, present with advantages and disadvantages. Clinicians should be aware of the limitations and disadvantages of each type of prosthesis, so as to select the one that is most appropriate for a given clinical situation
Fracture behaviour of grain refined A356 cast aluminium alloy: tensile and Charpy impact specimens
No full textThe excellent combination of high strength/weight ratio, high impact toughness, very good castability, low thermal expansion coefficient and corrosion resistance make Al-Si cast alloys suitable for the production of components like rims, engine and gear parts. Even though it is well-known that mechanical properties are closely related to secondary dendrite arm spacing (SDAS), the influence of grain size has to be considered as well. A fine and equiaxial grain structure is generally obtained through specific products, called grain refiners, which are added to the melt alloy in form of cans, bars, tabs, waffles, ingots and granulated fluxes. In this study three commercial Ti-B based grain refiners were added to the A356 (Al-Si-Mg) aluminium alloy. A number of 20 castings was obtained through permanent mould casting, n°5 for each experimental condition, named Reference (not refined), GR1, GR2 and GR3. Tensile and Charpy impact specimens were drawn by means of machining, T6 heat-treated and then tested. The influence of the grain refiners was assessed according to the experimental data of tensile and impact tests. Experimental results were compared to OM and SEM fracture observations, pointing out the effect of the different grain refiners on fracture mechanism. Although both impact and tensile specimens showed a mixed transgranular-intergranular fracture mode, it was found that impact samples were deeply influenced by the refiner added, while this effect was less pronounced for the tensile ones. Fractographic observations also revealed the role of Fe based intermetallic compounds in terms of fracture behaviour
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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