Search results for "Microstructure"
showing 10 items of 707 documents
Identification of Clusters of Investors from Their Real Trading Activity in a Financial Market
2011
We use statistically validated networks, a recently introduced method to validate links in a bipartite system, to identify clusters of investors trading in a financial market. Specifically, we investigate a special database allowing to track the trading activity of individual investors of the stock Nokia. We find that many statistically detected clusters of investors show a very high degree of synchronization in the time when they decide to trade and in the trading action taken. We investigate the composition of these clusters and we find that several of them show an over-expression of specific categories of investors.
Influence of process parameters for thixotropic alloys
2007
With reference to a metallic alloy, the attribute thixotropic is utilized to indicate the behaviour of it in the semi-solid state when its microstructure consists of spheroids in a liquid matrix. Such alloys are characterized by very low values of viscosity under shearing stress in the semi-solid state, while after solidification they show relevant mechanical properties. Actually a structural change from a dendritic structure to a globular one, with the globular grains finely dispersed in a liquid matrix, is observed after particular thermo-mechanical treatments. In the present paper the authors present the results of a wide experimental campaign on the AA 7075 aluminium alloy that shows a …
Numerical prediction of Biphasic Titanium Alloys Microstructure in Hot Forging Operations.
2012
Modern transportation industries shall comply with two demanding requirements: reducing operational consumption together with production costs coming from materials and labour. Current trend of engineering is oriented to meet both requirements increasing the rate of polymer matrix composites which implies association with structures made of titanium alloys. Hot forming can be used to reduce the production costs of titanium components: forging in closed dies of billets or semi finished form, in the temperature range where the Beta phase of titanium is stable, grants an adequate plasticity of the Ti-6Al-4V alloy, the most commercially used, allowing production of complex shapes with limited a…
An Automated Visual Inspection System for the Classification of the Phases of Ti-6Al-4V Titanium Alloy
2013
Metallography is the science of studying the physical properties of metal microstructures, by means of microscopes. While traditional approaches involve the direct observation of the acquired images by human experts, Com-puter Vision techniques may help experts in the analysis of the inspected mate-rials. In this paper we present an automated system to classify the phases of a Titanium alloy, Ti-6Al-4V. Our system has been tested to analyze the final products of a Friction Stir Welding process, to study the states of the micro-structures of the welded material.
Influence of the metallurgy and the microstructure on the strength of titanium-steel laser welded assemblies
2021
The dissimilar laser welding of titanium alloys with stainless steel is of high interest for different industrial applications. However, the joining of these materials by direct fusion is hardly achievable because of the presence of brittle intermetallic phases in the Ti-Fe system that produce spontaneous cracking of the welds. The scientific aim of this thesis is to identify a reliable criterion that allows identifying the possible conditions allowing obtaining a durable dissimilar titanium/steel joints, in terms of mechanical strength in service conditions. The determination of this criterion is necessary for the comprehension of the relation between the microstructure of the melted zone …
Efficacity of SMAT and laser shock-peening process for enhancement of titanium alloys high temperature oxidation resistance
2017
The aim of this thesis is to determine the influence of two mechanical surface treatments, the shot- peening performed with several type of balls (WC, alumina and glass) and the laser shock peening, on the high temperature oxidation resistance of two titanium alloys : alpha alloy with commercially purity (Grade 1) and aeronautical beta metastable alloy (TIMETAL-21S).After different treatments, the pieces are oxidized with different conditions: of time (between 5 hours to study the firsts times of oxidation and 3000 hours to compare with a classical aeronautical test), of temperature (600°C to 700°C) and atmosphere (dry air or oxygen).The pieces are analyzed before and after oxidation exposu…
Mechanical, thermal and electrical properties of nanostructured CNTs/SiC composites
2018
International audience; Dense SiC-based nanostructured composites reinforced by well-distributed carbon nanotubes (CNTs) were elaborated for the first time by spark plasma sintering (SPS) without sintering additive. Microstructures of materials containing different amounts of CNTs – up to 8.0 vol% – were correlated with their mechanical, electrical and thermal properties. A continuous decrease of the SiC grain size was observed when the amount of CNT was increased, while the evolution of density showed a different behavior that could be explained by the particular combination of SPS technique with the electrical resistivity evolution of the green bodies. Optimal effect of CNTs addition on h…
Environmental and depositional controls on laminated freshwater carbonates: An example from the Roman aqueduct of Patara, Turkey
2013
Carbonate deposits in aqueducts are a new high-resolution data source for environmental changes during the time of the Roman Empire, notably in the fields of palaeoclimate and spring hydrology. In order to distinguish environmental effects from those related to depositional setting, laminated carbonate deposits were compared along the entire length of an ancient aqueduct channel at Patara, Turkey. The carbonate deposits, up to 80mm in thickness, are composed of lamina couplets up to 1mm thick of alternating porous microspar and dense, columnar sparite. The former formed in the dry, warm season and the latter in the wet, cool season. The presence of biofilms seems to play a role in the devel…
Inverse Thermogelation of Aqueous Triblock Copolymer Solutions into Macroporous Shear-Thinning 3D Printable Inks
2020
Amphiphilic block copolymers that undergo (reversible) physical gelation in aqueous media are of great interest in ditIerent areas including drug delivery, tissue engineering, regenerative medicine, and biofabrication. We investigated a small library of ABA-type triblock copolymers comprising poly(2-methyl-2-oxazoline) as the hydrophilic shell A and different aromatic poly(2-oxazoline)s and poly(2-oxazine)s cores B in an aqueous solution at different concentrations and temperatures. Interestingly, aqueous solutions of poly(2-methyl-2-oxazoline)-block-poly(2-phenyl-2-oxazine)-block-poly(2-methyl-2-oxazoline) (PMeOx-b-PPheOzi-b-PMeOx) undergo inverse thermogelation below a critical temperatur…
Nestandartu interneta vārdnīcu struktūra
2015
Spēja noteikt strukturālos elementus, kuri ir nepieciešami vārdnīca ssastādīšanai, ir būtiska leksikogrāfa prasme. Maģistra darba mērķis ir izanalizēt nestandarta vārdnīcas autoru un atbalstītāju strukturālās izvēles, kuras ir izmantotas individuālo projektu vārdnīcu saradīšanai. Mērķa sasniegšanai izmantotās metodes ir literatūras apraksts, lai formulētu teorētisko bāzi, un manuāla datu vākšana un aprakstoša analīze. Analīzes rezultāti atļāva identificēt defektus izvēlētajos struktūras elementos un apsvērt defektu ietekmi uz vispārējo vārdnīcas kvalitāti. Tomēr rezultāti arī liecināja, ka, neskatoties uz kļūdām, vārdnīcu autoriem ir dažas atkārtojošās izvēles struktūru organizācijā, lai ga…