Search results for "dissimilar"
showing 10 items of 35 documents
Convergence and divergence in organization of phytoplankton communities under various regimes of physical and biological control
2010
The hypothesis that physical constraints may be as important, if not more important, than biological ones in shaping the structure of phytoplankton assemblage was tested by analyzing longterm (11–29 years) phytoplankton series in eight lakes and nine sites located along a latitudinal gradient in the Northern hemisphere. Phytoplankton biomass was used and similarity of assemblages in same months of the annual data sets was then calculated by subtracting the Bray–Curtis dissimilarity index from 1. The extent of biological and physical forcing was partly based on ‘‘expert evaluation’’: the importance of four physical (light availability, temperature, conductivity, and sediment stirring up) and…
Friction stir welding of dissimilar aluminium– magnesium joints: Sheet mutual position effects
2015
Friction stir welding (FSW) is a solid state welding process used to weld difficult to be welded or unweldable materials as aluminium alloys. In the last years, other materials have been successfully tested as magnesium, titanium and nickel based alloys. Dissimilar joints can be obtained by FSW, but issues arise concerning the correct choice of the process parameters. In the paper, the results of an experimental and numerical campaign aimed to produce dissimilar AZ31-AA6016-T6 butt joints are presented. The effect of sheet mutual position and main process parameters was investigated. It was found that intermetallics are the main cause of the poor quality of the joints. Sound joints can be p…
Generation and characterization of T40/A5754 interfaces with lasers
2014
Laser-induced reactive wetting and brazing of T40 titanium with A5754 aluminum alloy with 1.5 mm thickness was carried out in lap-joint configuration, with or without the use of Al5Si filler wire. A 2.4 mm diameter laser spot was positioned on the aluminum side to provoke spreading and wetting of the lower titanium sheet, with relatively low scanning speeds (0.1 to 0.6 m/min). Process conditions did not play a very significant role on mechanical strengths, which were shown to reach 250-300 N/mm on a large range of laser power and scanning speeds. In all cases considered, the fracture during tensile testing occurred next to the TiAl3 interface, but in the aluminum fusion zone. In a second st…
Friction Stir Welding as an Effective Alternative Technique for Light Structural Alloys Mixed Joints
2014
Abstract The increasing use of structural light alloys in the aeronautical, automotive and transportation industry is pushing researchers to find new solutions for the production of innovative components. Mixed joints made out dissimilar alloys represent a challenge for engineers to the difficulties arising in welding materials characterized by significantly different mechanical, thermal and chemical properties. In the paper, an overview of the most used process to produce dissimilar joints of aluminum, magnesium and titanium is given. Both fusion based and solid state welding processes can be used. Although the joining of these materials is possible, particular attention must be taken to t…
An Innovative Friction Stir Welding Based Technique to Produce Dissimilar Light Alloys to Thermoplastic Matrix Composite Joints
2016
Abstract Aluminum sheets can be joined to composite materials with different techniques. Each of them has advantages and weak points over the others. In literature, new techniques and patents are continuously developed to overcome these difficulties. In the paper a new Friction Stir Welding based approach is proposed to mechanically join AA6082-T6 to self-reinforced polypropylene. The aluminum sheet is pre-holed along both the sides of the weld line. A pinless tool generates the heat and pressure needed to activate back-extrusion of the composite. Joints have been produced with varying hole diameter and pitch. The mechanical resistance of the joint has been evaluated and the different failu…
Shape matching, shape retrieval
2016
This thesis concerns shape matching and shape retrieval. It describes four contributions to thisdomain. The first is an improvement of the k-means method, in order to find the best partition ofvoxels inside a given shape ; these best partitions permit to match shapes using an optimal matchingin a bipartite graph. The second contribution is the fusion of two descriptors, one local, the otherglobal, with the product rule. The third contribution considers the complete graph, the vertices ofwhich are the shapes in the database and the query. Edges are labelled with several distances,one per descriptor. Then the method computes, with linear programming, the convex combinationof distances which m…
On the mechanisms involved in the tensile strength of a dissimilar Ti6Al4V/316L laser welded assembly
2021
International audience; The aim of the present work is to analyze the thermomechanical behavior of dissimilar laser seams by means of FE modeling. The case of a Ti6Al4V/316L assembly with vanadium insert was considered. Effective mechanical properties of the main materials and cords were first estimated from NHT measurements. Modeling of the double pass laser welding process was performed first by considering shrinking of the two weld seams during manufacturing, to get the residual stress state in the welded assembly. Modeling of the tensile test was performed in a second step to study the assembly behavior during loading. In these modeling results, the mesh was the cross-section of the mic…
Ethnic segregation in a metropolitan area of Italy: the case of Palermo
2015
La segregazione residenziale etnica in Italia è una questione emergente, che sarà fondamentale nella definizione e attuazione di politiche urbanistiche e sociali. Questo articolo si focalizza sull’analisi del fenomeno nel comune di Palermo. Utilizziamo i dati della popolazione residente in città nel 2011 in tutti i quartieri suddivisa per etnia. Facciamo dapprima ricorso a tecniche di analisi spaziale tradizionale al fine di descrivere la segregazione residenziale degli stranieri e, tra le altre misure, calcoliamo l'indice di dissimilarità di Duncan e Duncan. Successivamente, applichiamo un approccio metodologico recentemente proposto in letteratura che consente di correggere la distorsione…
Les exercices gradués dans la méthode du Grammalessico francese a uso degl’italiani d’Arminio Wurmbrand Bianchi
2020
L’article se propose d’analyser les exercices du manuel d’Arminio Wurmbrand Bianchi, Grammalessico francese a uso degl’italiani, qui ont une forme et une structure que l’on retrouve dans de nombreux manuels s’inspirant des méthodes dites « synthétiques ». Wurmbrand, en effet, introduit dans son manuel une nouveauté pour pourvoir au caractère incomplet de la méthode synthétique : il propose, ainsi, avant chaque exercice, la traduction des seuls termes « radicalement dissemblables » des deux langues « similaires à l’origine » qui caractérisent la langue française et la langue italienne. Le but est de fournir aux élèves la maîtrise lexicale de la langue française avec une attention toute parti…
Spatiocolorimetric neighborhood hypergraph and Image Processing Applications : Noise Removal and Edge Detection.
2004
In this document, we are interested in image modeling by the means of the hypergraph theory. Our contribution is essentially centered on the determination of the properties resulting from this theory and on the analysis from their adequacy with image problems, particularly edge and noise detection.First, we study the image spatiocolorimetric neighborhood hypergraph representation. Three representations are respectively presented incorporating global properties, local properties and similarity functions. Then, we use the hypergraph properties generated by the representation in order to define the structural models of noise and edge. This enables us to deduce the algorithms of noise suppressi…