Search results for "Microstructure"
showing 10 items of 707 documents
Multi-functional hindered amine light stabilizers-functionalized carbon nanotubes for advanced ultra-high molecular weight Polyethylene-based nanocom…
2015
Hindered Amine Light Stabilizer (HAS) molecules have been covalently linked on the outer surface of multi-walled carbon nanotubes (CNTs), and the so-obtained multi-functional fillers (HAS-f-CNTs) have been compounded with Ultra High Molecular Weight Polyethylene (UHMWPE) to get composite films. The success of the grafting reaction of the HAS molecules has been confirmed through spectroscopic and thermo-gravimetric analyses. Morphological analyses reveal a segregated microstructure, in which CNT-rich channels surround the polymer domains. This morphology results in improved mechanical properties and appreciable electrical conductive features. More importantly, the addition of only 1 wt.% of …
Evidence of Mechanisms Occurring in Thermally Induced Phase Separation of Polymeric Systems
2014
Thermally induced phase separation is a fabrication technique for porous polymeric structures. By means of easy-to-tune processing parameters, such as system composition and demixing temperature, a vast latitude of average pore dimensions, pore size distributions, and morphologies can be obtained. The relation between demixing temperature and morphology was demonstrated via cloud point curve measurement and foams fabrication with controlled thermal protocols, for the model system poly-l-lactide–dioxane–water. The morphologies obtained at a temperature lower than cloud point showed a closed-pore architecture, suggesting a “nucleation-and-growth” separation mechanism, which produced larger po…
Fracture toughness of different monolithic zirconia upon post-sintering processes
2021
Background Surface treatments are expected to be a reason for alteration in fracture resistance of zirconia. This study evaluated the effect of post-sintering processes on the fracture toughness of different types of monolithic zirconia. Material and Methods Classical- (Cz) and high-translucent (Hz) monolithic zirconia discs (1.2 mm thickness, 14 mm in Ø) were prepared, and randomly divided for surface treatments with 1) as-glazed (AG); 2) finished and polished (FP); 3) finished, polished, and overglazed (FPOG); and 4) finished, polished, and heat-treated (FPHT) technique (n=15/group). Fracture toughness (KIC) was determined with indentation fracture toughness method at load 1 kg for AG, FP…
The skeleton of the staghorn coral Acropora millepora: molecular and structural characterization.
2014
15 pages; International audience; The scleractinian coral Acropora millepora is one of the most studied species from the Great Barrier Reef. This species has been used to understand evolutionary, immune and developmental processes in cnidarians. It has also been subject of several ecological studies in order to elucidate reef responses to environmental changes such as temperature rise and ocean acidification (OA). In these contexts, several nucleic acid resources were made available. When combined to a recent proteomic analysis of the coral skeletal organic matrix (SOM), they enabled the identification of several skeletal matrix proteins, making A. millepora into an emerging model for biomi…
Assessment of lung microstructure with magnetic resonance imaging of hyperpolarized Helium-3
2005
Magnetic resonance imaging of the apparent diffusion coefficient (ADC) of hyperpolarized Helium-3 is a new technique for probing pulmonary microstructure in vivo. The aim of this study was the assessment of potential sources of systematic errors of the ADC measurement. The influence of macroscopic motion was determined by measurements at two different delays after initiating the breath-hold, and before and after cardiac arrest. An intercentre comparison was performed in two age- and lung function-matched groups of lung-healthy volunteers at two research sites. Moreover, measurements of diffusion anisotropy were performed. We found no dependency of the ADC as a function of the delay after st…
THE STATE OF FRACTIONAL HEREDITARY MATERIALS (FHM)
2014
The widespread interest on the hereditary behavior of biological and bioinspired materials motivates deeper studies on their macroscopic ``minimal" state. The resulting integral equations for the detected relaxation and creep power-laws, of exponent $\beta$, are characterized by fractional operators. Here strains in $SBV_{loc}$ are considered to account for time-like jumps. Consistently, starting from stresses in $L_{loc}^{r}$, $r\in [1,\beta^{-1}], \, \, \beta\in(0,1)$ we reconstruct the corresponding strain by extending a result in [42]. The ``minimal" state is explored by showing that different histories delivering the same response are such that the fractional derivative of their differ…
Mollusk carbonate thermal behaviour and its implications in understanding prehistoric fire events in shell middens
2018
Abstract Archaeological shell middens are particularly important for reconstructing prehistoric human subsistence strategies. However, very little is known about shellfish processing, especially when related to the use of fire for dietary and disposal purposes. To shed light on prehistoric food processing techniques, an experimental study was undertaken on modern gastropod shells (Phorcus lineatus). The shells were exposed to high temperatures (200–700 °C) to investigate subsequent mineralogy and macro- and microstructural changes. Afterwards, the three-pronged approach was applied to archaeological shells from Haua Fteah cave, Libya (Phorcus turbinatus) and from shell midden sites in the U…
Thermoelectric magnetohydrodynamic control of melt pool dynamics and microstructure evolution in additive manufacturing.
2020
Large thermal gradients in the melt pool from rapid heating followed by rapid cooling in metal additive manufacturing generate large thermoelectric currents. Applying an external magnetic field to the process introduces fluid flow through thermoelectric magnetohydrodynamics. Convective transport of heat and mass can then modify the melt pool dynamics and alter microstructural evolution. As a novel technique, this shows great promise in controlling the process to improve quality and mitigate defect formation. However, there is very little knowledge within the scientific community on the fundamental principles of this physical phenomenon to support practical implementation. To address this mu…
Statistical identification with hidden Markov models of large order splitting strategies in an equity market
2010
Large trades in a financial market are usually split into smaller parts and traded incrementally over extended periods of time. We address these large trades as hidden orders. In order to identify and characterize hidden orders we fit hidden Markov models to the time series of the sign of the tick by tick inventory variation of market members of the Spanish Stock Exchange. Our methodology probabilistically detects trading sequences, which are characterized by a net majority of buy or sell transactions. We interpret these patches of sequential buying or selling transactions as proxies of the traded hidden orders. We find that the time, volume and number of transactions size distributions of …
On the thermo-mechanical loads and the resultant residual stresses in friction stir processing operations
2008
In friction stir welding and processing both a thermal flux and a mechanical action are exerted on the material determining metallurgical evolutions, changes in the mechanical behaviour and a complex residual stress state. In the paper, the metallurgical changes are examined through numerical simulation and experiments to highlight and distinguish the effects of thermal and mechanical loadings. A particular focus is made on the residual stresses generated during the stir processing of AA7075-T6 aluminium blanks. The predictions of FE model are validated by experimental measurements. Lastly, this paper presents an in-process quenching of the processed blanks for improved mechanical propertie…